NIMP| Mihaela Stegarescu, Author at NIMP

Publications

Open Access

1. Thermal Stability and Irradiation Resistance of (CrFeTiTa)70W30 and VFeTiTaW High Entropy Alloys

Authors: Pereira, A; Martins, R; Monteiro, B; Correia, JB; Galatanu, A; Catarino, N; Belec, PJ; Dias, M

Published: MAR 2025, MATERIALS, 18, 1030, DOI: 10.3390/ma18051030

Nuclear fusion is a promising energy source. The International Thermonuclear Experimental Reactor aims to study the feasibility of tokamak-type reactors and test technologies and materials for commercial use. One major challenge is developing materials for the reactor's divertor, which supports high thermal flux. Tungsten was chosen as the plasma-facing material, while a CuCrZr alloy will be used in the cooling pipes. However, the gradient between the working temperatures of these materials requires the use of a thermal barrier interlayer between them. To this end, refractory high-entropy (CrFeTiTa)70W30 and VFeTiTaW alloys were prepared by mechanical alloying and sintering, and their thermal and irradiation resistance was evaluated. Both alloys showed phase growth after annealing at 1100 degrees C for 8 days, being more pronounced for higher temperatures (1300 degrees C and 1500 degrees C). The VFeTiTaW alloy presented greater phase growth, suggesting lower microstructural stability, however, no new phases were formed. Both (as-sintered) alloys were irradiated with Ar+ (150 keV) with a fluence of 2.4 x 1020 at/m2, as well as He+ (10 keV) and D+ (5 keV) both with a fluence of 5 x 1021 at/m2. The morphology of the surface of both samples was analyzed before and after irradiation showing no severe morphologic changes, indicating high irradiation resistance. Additionally, the VFeTiTaW alloy presented a lower deuterium retention (8.58%) when compared to (CrFeTiTa)70W30 alloy (14.41%).

2. Structural Analysis of Colloidal Titania-Based Ribbons and Their Self-Assembly upon Drying

Authors: Boukhris, S; Iacoban, AC; Ibrahim, M; Badr, H; Kuncser, AC; Neatu, S; Neatu, F; Barsoum, MW; Florea, M; Constantin, D

Published: 2025 APR 22 2025, SMALL STRUCTURES, DOI: 10.1002/sstr.202500017

Synchrotron-based small- and wide-angle X-ray scattering is used to elucidate the structure of low-dimensional lepidocrocite-titanate-based nanofilaments. In the colloidal state, they consist of quantum-confined 1D NFs, loosely associated into nanoribbons, one lepidocrocite sheet thick (about 4 & Aring;), 30-40 & Aring; wide (5-8 NFs), and more than 300 & Aring; long. In the dry state, they reach a final state of extended sheets, stacked three to about twenty high, whose crystallinity increases with stack height, in parallel with a decrease in photocatalytic activity. These findings suggest a kinetic pathway for the self-assembly of initially 1D titanate nanoribbons into 2D and ultimately 3D structures, providing context for a recent body of work on these low-dimensional materials.

Open Access

3. Catalytic behaviour of CuOx and VOx on Ti3SiC2 support for direct oxidation of methane

Authors: Iacoban, AC; Haldar, T; Neatu, F; Chirica, IM; Mirea, AG; Neatu, S; Barsoum, MW; Florea, M

Published: JAN 1 2025, CATALYSIS TODAY, 443, 114959, DOI: 10.1016/j.cattod.2024.114959

Herein we show that the Ti3SiC2 MAX phase can be used as a support for deposition of different amounts of metal oxides (MOx, M = Cu or V) (5, 10 and 20 wt%) for the direct oxidation of methane to formaldehyde using molecular oxygen, at relatively low temperatures and atmospheric pressure. The oxides were deposited using a hydrothermal method at 180 degrees C without affecting the bulk MAX phase structure. However, during the hydrothermal treatment (HT) a thin oxide layer - found to play an important role in the reaction's selectivity- was evidenced by X-ray photoelectron spectroscopy. We thus conclude that the MOx species are responsible for the CH4 activation, while the Ti3SiC2 surface is responsible for the high selectivity to formaldehyde indicating that, Ti3SiC2 has great potential for designing innovative catalysts for direct oxidation of methane using molecular oxygen and at atmospheric pressure.

4. Bilayered metallic cathodes consisting of pure Mg and Zn:Al thin films optimized by Laser-induced Thermionic Vacuum Arc (LTVA) technology

Authors: Mandes, A; Vladoiu, R; Dinca, V; Tichy, M; Kudrna, P; Matei, E; Polosan, S

Published: AUG 2025, APPLIED SURFACE SCIENCE ADVANCES, 28, 100787, DOI: 10.1016/j.apsadv.2025.100787

Bilayer metallic electrodes of magnesium and zinc-aluminum alloys Mg/Zn:Al were prepared using combined laser-thermionic vacuum arc methods. Plasma diagnosis suggests laser-plasma interaction by increasing the discharge voltage when the laser is on, which is converted by thermal annealing of plasma ions. A magnesium thin film with a lower work function, covered with a Zn:Al (4:1) layer was successfully used for efficient charge injection into electroluminescent diodes. The zinc-aluminum combination preserved the electrical conductivity of the thin magnesium film and protected it against oxidation. The capacitance-voltage measurements confirmed the integrity of the magnesium layer, whereas the work function was not affected. The zinc-aluminum alloy obtained through a thermionic vacuum arc exhibits good conductivity compared to pure zinc layers and better stability against degradation.

5. Comparative study of the Cu-TiO2 nanostructures obtained by sol-gel and microwave assisted sol-gel methods

Authors: Predoana, L; Pandele-Cusu, J; Atkinson, I; Petrescu, S; Mocioiu, OC; Culiba, DC; Karajz, DA; Odhiambo, VO; Lemago, HH; Gomes, APB; Varady, ZI; Bohus, M; Costescu, RM; Szilágyi, IM; Pokol, G; Zaharescu, M

Published: JUN 2025, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 114, DOI: 10.1007/s10971-025-06757-x

In this study, pristine TiO2 and Copper (Cu)-doped TiO2 nanopowders were synthesized using two sol-gel methods: conventional sol-gel (SG) and microwave-assisted sol-gel (MW). The aim was to investigate the effect of the synthesis route and Cu doping on the structural, optical, and photocatalytic properties of TiO2. X-ray diffraction (XRD) analysis confirmed the formation of anatase TiO2 in all samples, with a minor presence of rutile observed in the samples obtained by the MW method. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis (EDX) showed that the nanopowders obtained by the MW method exhibited a greater tendency for particle aggregation compared to those obtained through the SG method. The presence of Cu2+/Cu+ species in the samples was confirmed by X-ray photoelectron spectroscopy (XPS). UV-Vis reflectance measurements revealed a shift in the absorption edge of the 5% Cu-doped samples toward the visible light range, significantly reducing the band gap. Evaluation of photocatalytic activity demonstrated that doping TiO2 with 5% Cu enhanced the degradation of Congo Red dye under visible light. [GRAPHICS] .

6. Beneficial role of silicotungstic acid presence on the WO3-modified boron-doped diamond substrate on the electrocatalytic activity for methanol anodic oxidation of supported platinum

Authors: Spataru, N; Preda, L; Matei, E; Satulu, V; Mihai, MA; Radu, MM; Donath, C; Moga, OG

Published: APR 17 2025, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 120, DOI: 10.1016/j.ijhydene.2025.03.327

The present paper evidences the beneficial effect that the combination of Pt with WO3 and silicotungstic acid (STA) brings to the methanol oxidation electroactivity. To avoid substrate interferences boron doped diamond (BDD) was used as the electrocatalysts support. SEM measurements have shown that the use of a STA/WO3/BDD substrate allows the electrodeposition of smaller Pt clusters, exhibiting better dispersion, higher homogeneity in terms of size and enhanced electrochemically active surface area. Cyclic voltammetry, polarization and EIS experiments demonstrated than STA addition on the WO3/BDD support induces to the deposited Pt higher activity and improved resistance to fouling during methanol anodic oxidation. Based on the XPS results such behavior was tentatively ascribed to the higher surface concentration of Pt(OH)2 species and adsorbed water that STA presence enables, which may assist in the oxidative desorption of reaction intermediates.

Open Access

7. Ultra-Sensitive, Self-powered, CMOS-Compatible Near-Infrared Photodetectors for Wide-Ranging Applications

Authors: Silva, NE; Jayakrishnan, AR; Kaim, A; Gwozdz, K; Domingues, L; Kim, JS; Istrate, MC; Ghica, C; Pereira, M; Marques, L; Gomes, MJM; Hoye, RLZ; MacManus-Driscoll, JL; Silva, JPB

Published: APR 2025, ADVANCED FUNCTIONAL MATERIALS, 35, DOI: 10.1002/adfm.202416979

Self-powered near-infrared (NIR) photodetectors are essential for surveillance systems, sensing in IoT electronics, facial recognition, health monitoring, optical communication networks, night vision, and biomedical imaging. However, silicon commercial detectors need external power to operate and cooling to suppress large dark currents. This work demonstrates a new class of CMOS-compatible self-powered NIR photodetector based on ferroelectric 5-nm thick ZrO2 films which do not require cooling and therefore have two key advantages over Si, and at the same time have comparable performance metrics. At room-temperature, under 940 nm wavelength illumination (1.4 mW cm-2 power density, 10 Hz repetition rate), and without any power applied, fast rise and fall times of approximate to 2 and 4 mu s, respectively, are achieved in Al/Si/SiOx/ZrO2/ITO devices, along with responsivity, detectivity and sensitivity values of up to approximate to 3.4 A W-1, 1.2 x 1010 Jones and 4.2 x 103, respectively, far exceeding all other emerging self-powered systems. Furthermore, dual-band NIR detection is shown for different NIR wavelengths, proof-of-concept feasibility being demonstrated for the smart identification of NIR targets. Therefore, it is demonstrated, for the first time, that coupling together the pyroelectric effect, the photovoltaic effect, and the ferroelectric effect is a novel method to significantly enhance the performance of CMOS-compatible ZrO2-based self-powered photodetectors in the NIR region.

8. Synthesis of dynamic N-acylhydrazone-based macrocycles

Authors: Sandu, N; Hanganu, A; Popescu, C; Demeter, AM; Mirea, AG; Kuncser, A; Tablet, C; Hadade, ND; Florea, M; Funeriu, DP; Matache, M

Published: APR 1 2025, JOURNAL OF MATERIALS CHEMISTRY A, 13, DOI: 10.1039/d4ta09035g

We present herein the synthesis of novel [2 + 2] and [3 + 3] N-acylhydrazone-based macrocycles using a pool of dialdehydes and dihydrazides, under thermodynamic control. The resulting macrocycles, which were assigned triangular and rectangular shapes, were characterised in the solid state. The rectangular macrocycle was further investigated in solution by absorption and emission spectroscopy. Additionally, the rectangular macrocycle was used in various assays to investigate the hosting capacity towards various guests using NMR, HRMS, UV-visible and fluorescence spectroscopy. Theoretical calculations regarding structure and properties of the novel compounds were in agreement with the experimental details. The experimental data showed intriguing results toward tetra-n-butylammonium fluoride.

Open Access

9. Influence of Electron Beam Irradiation and RPMI Immersion on the Development of Magnesium-Doped Hydroxyapatite/Chitosan Composite Bioactive Layers for Biomedical Applications

Authors: Groza, A; Hurjui, ME; Yehia-Alexe, SA; Staicu, C; Bleotu, C; Iconaru, SL; Ciobanu, CS; Ghegoiu, L; Predoi, D

Published: FEB 2025, POLYMERS, 17, 533, DOI: 10.3390/polym17040533

Magnesium-doped hydroxyapatite/chitosan composite coatings produced by the radio-frequency magnetron sputtering technique were exposed to 5 MeV electron beams of 8 and 30 Gy radiation doses in a linear electron accelerator. The surfaces of unirradiated layers are smooth, while the irradiated ones exhibit nano-structures with sizes that increase from 60 nm at a 8 Gy dose to 200 nm at a 30 Gy dose. Young's modulus and the stiffness of the layers decrease from 58.9 GPa and 10 mu N/nm to 5 GPa and 2.2 mu N/nm, respectively, when the radiation doses are increased from 0 to 30 Gy. These data suggest the diminishing of the contribution of the chitosan to the elasticity of the magnesium-doped hydroxyapatite/chitosan composite layers after electron beam irradiation. The biological capabilities of the coatings were assessed before and after their immersion in RPMI-1640 cell culture medium for 7 and 14 days, respectively, and further cultured with a MG63 cell line (ATCC CRL1427) in Dulbecco's Modified Eagle Medium supplemented with fetal bovine serum, penicillin-streptomycin, and L-glutamine. Thus, 1 mu m spherical structures were developed on the surfaces of the layers exposed to a 30 Gy radiation dose and immersed for 14 days in the RPMI-1640 biological medium. The molecular structures of all the RPMI-1640 immersed samples were modified by the growth of a carbonated hydroxyapatite layer characterized by a B-type substitution, as Fourier Transform Infrared Spectroscopy revealed. The biological assay proved the increased biocompatibility of the layers kept in RPMI-1640 medium and enhanced MG63 cell attachment and proliferation. Atomic force microscopy analysis indicated the elongated fibroblastic cell morphology of MG63 cells with minor alteration at 30 Gy irradiation doses as a result of layer biocompatibility modifications.

10. Non-destructive ultrasonic inspections of small-scale mock-ups provided with advanced tungsten armours for DEMO divertor target

Authors: De Luca, R; Cacciotti, E; Cerocchi, M; Crea, F; Roccella, S; Greuner, H; Hunger, K; Bonnekoh, C; Galatanu, A; Ivekovic, A; Jenus, P; Wirtz, M

Published: JUN 2025, FUSION ENGINEERING AND DESIGN, 215, 115007, DOI: 10.1016/j.fusengdes.2025.115007

Within the framework of the EUROfusion Consortium, the Characterization of armour, heat sinks materials and joints sub-project of the Work Package Material (WP-MAT) has been dedicated to the development of different tungsten (W) monoblock mock-ups equipped with advanced materials for divertor target applications in the EUDEMO fusion reactor. Assessing the status of the relevant joining interfaces of these mock-ups, not only after fabrication but throughout the whole component lifetime, plays a key role in the qualification process. At the ENEA Special Technologies Laboratory (TES), a number of facilities have been built to perform non-destructive inspections of plasma-facing components for fusion applications by ultrasonic testing (UT). The present work reports on the results of the UT inspections assessing the structural integrity of the relevant joining interfaces of three small-scale mock-ups provided with advanced W armour materials, specifically W-matrix with W2C inclusions consolidated by Spark Plasma Sintering (SPS), K-doped rolled W and K-doped laminated W. The UT examinations are carried out after fabrication and after the high heat flux tests (HHFT) at the neutral beam facility GLADIS. All results confirm the high-quality joining achieved by HIP and HRP. During the HHF tests of mock-ups, after a few hundred HHFT cycles defects are detected at the joining interfaces, due to debonding, delamination and W material cracks mainly affecting the loaded zone. The ultrasonic pulse-echo technique provides not only the size and position of the defects in the plane orthogonal to the ultrasonic beam, but also their depth in the material. During the analysis, the probe is inserted inside the pipe and the mock-up is examined in a cylindrical configuration. The coupling medium (demineralized water) is poured only inside the pipe. The main inspection parameters and the piezoelectric probes are chosen to obtain the maximum resolution in accordance with the thickness and joining interfaces to be analyzed.

11. Composite Films Based on Poly(3-hexylthiophene):Perylene Diimide Derivative:Copper Sulfide Nanoparticles Deposited by Matrix Assisted Pulsed Laser Evaporation on Flexible Substrates for Photovoltaic Applications

Authors: Socol, M; Preda, N; Costas, A; Petre, G; Stochioiu, A; Popescu-Pelin, G; Iftimie, S; Catargiu, AM; Socol, G; Stanculescu, A

Published: APR 1 2025, JOURNAL OF COMPOSITES SCIENCE, 9, 172, DOI: 10.3390/jcs9040172

Today, flexible and lightweight electronics are regarded as a viable alternative to conventional rigid and heavy devices in various application fields. In the optoelectronic area, organic semiconductors offer advantages such as high absorption coefficients, low processing temperatures, mechanical flexibility and compatibility with plastic substrates, while inorganic nanostructures provide good electronic properties and high thermal stability. Thus, composite films with enhanced properties can be achieved by inserting inorganic nanostructures within organic layers. In this research work, CuS nanoparticles were prepared by wet chemical precipitation and then added to an organic mixture containing poly(3-hexylthiophene) (P3HT) and N,N-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14), a chemically synthesized semiconductor, for fabricating hybrid composite films by matrix assisted pulsed laser evaporation (MAPLE) on indium tin oxide/poly(ethylene terephthalate) (ITO/PET) flexible substrates. A comparative assessment of the morphological, compositional, optical and electrical properties of the composite (P3HT:AMC14:CuS) and organic (P3HT:AMC14) layers was performed to evaluate their applicability in the photovoltaic cells. The transmission and emission spectra of the composite films are dominated by the optical features of AMC14, a perylene diimide derivative compound used as acceptor. In the case of devices based on MAPLE deposited composite layer fabricated on ITO/PET substrates, the electrical measurements carried under illumination revealed an improvement in the open circuit voltage parameter emphasizing their potential applications in the flexible device area.

Open Access

12. Cobalt oxyhydroxide co-catalyst loaded onto Al:SrTiO3 surface to boost photocatalytic performance

Authors: Radu, I; Borhan, AI; Gherca, D; Dirtu, AC; Dirtu, D; Popescu, DG; Husanu, MA; Pui, A

Published: FEB 15 2025, MATERIALS CHEMISTRY AND PHYSICS, 332, 130274, DOI: 10.1016/j.matchemphys.2024.130274

In photocatalysis, a common challenge is the rapid recombination of photogenerated electrons and holes, coupled with low surface reaction efficiency in aqueous environments. This study addresses these issues by improving the photocatalytic performance of Al3+-doped SrTiO3 perovskite through the strategic loading of CoOOH onto its surface. We successfully demonstrated that the combined approach of Al3+ doping and CoOOH co-catalyst functionalization significantly enhances the photocatalytic performance of SrTiO3. The Al3%:SrTiO3 was functionalized with CoOOH using a two-step process. This process involved the oxidation of Co2+ ions to Co3+ ions, followed by the precipitation of cobalt oxyhydroxide (CoOOH) onto the surface of Al3%:SrTiO3, resulting in the formation of an Al3%:SrTiO3@CoOOH composite heterostructure. The UV-Vis data shows an enhanced light absorption capabilities into the visible spectrum with a direct band gap of 1.73 eV in contrast to 3.24 eV for the pristine perovskite. XPS analysis confirms the surface functionalization with CoOOH co-catalyst and the determined 1:1 Sr:Ti stoichiometry, the reduced state of Al, and the absence of oxygen vacancies were identified as beneficial properties for photocatalytic applications, as shown in DFT calculations. The oxacillin photodegradation was tested at three different concentrations of Al3%:SrTiO3@CoOOH photocatalyst (0.25 g/L; 0.5 g/L and 1 g/L) and we observed that the removal efficiency significantly varies from 99 % for 1 g/L Al3%: SrTiO3@CoOOH to 78 % and 44 % for 0.5 g/L and, respectively 0.25 g/L. Additionally, under visible light irradiation, the Al3%:SrTiO3@CoOOH composite achieved an exceptional degradation rate of the (3-lactam antibiotic oxacillin of up to 99 %, with holes identified as key players in the photocatalytic process. This study highlights that effective surface modification using a well-chosen co-catalyst can substantially boost the photocatalytic efficiency of semiconductor-based materials, offering a promising strategy for developing advanced photocatalysts for environmental remediation applications.

13. Development of Chrome-Doped Hydroxyapatite in a PVA Matrix Enriched with Amoxicillin for Biomedical Applications

Authors: Ciobanu, SC; Predoi, D; Iconaru, SL; Rokosz, K; Raaen, S; Bleotu, C; Predoi, MV

Published: APR 30 2025, ANTIBIOTICS-BASEL, 14, 455, DOI: 10.3390/antibiotics14050455

Background/Objectives: In this paper, we report the development of the first chrome-doped hydroxyapatite in a poly (vinyl alcohol) (PVA) matrix enriched with amoxicillin for biomedical applications. The development of chromium-doped hydroxyapatite coatings in a PVA matrix enriched with amoxicillin aims to provide new biomaterials with improved physico-chemical and biological properties, making them promising candidates for biomedical applications. Methods: Through ultrasound studies, we obtained valuable information on the stability of the samples. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, metallographic microscopy (MM), and atomic force microscopy (AFM) were employed for the characterization of the samples. The biocompatibility of the CrHApAPV and CrHApAPV-Ax coatings was assessed using the MG63 human osteoblast-like cell line. To evaluate the cytotoxic potential of these coatings, the cell viability was quantified using the MTT assay after 24 h of incubation. The antibacterial activity of the coatings was evaluated with the aid of the reference strain Pseudomonas aeruginosa ATCC 27853 (P. aeruginosa). Results: The XRD patterns of CrHApAPV and CrHApAPV-Ax samples were examined to evaluate the effects of PVA and amoxicillin on the lattice parameters, unit cell volume, and average crystallite sizes. The results of the in vitro antibacterial assay demonstrated that both the CrHApAPV and CrHApAPV-Ax coatings exhibited very good antibacterial properties for all the tested time intervals. Conclusions: Our results underline the stability of the analyzed samples. Moreover, our physico-chemical and biological studies highlight that CrHApAPV and CrHApAPV-Ax coatings could be considered promising materials for biomedical uses.

Open Access

14. Phase evolution in low Fe concentration V1 _xFexO2compounds: Phase diagram and annealing effects

Authors: Manousou, DK; Atata, SB; Sohn, YJ; Tsipas, P; Grzechnik, A; Calamiotou, M; Friese, K; Gardelis, S

Published: APR 20 2025, JOURNAL OF ALLOYS AND COMPOUNDS, 1024, 180081, DOI: 10.1016/j.jallcom.2025.180081

We present a comprehensive investigation into the synthesis, phase evolution and valence state of vanadium (V) in V1_xFexO2 (x = 0 %, 0.5 %, 0.75 %, 1.0 %) compounds. Polycrystalline samples have been synthesized with solid-state reaction method, followed by thermal annealing. X-Ray Powder Diffraction (XRPD) analyzed by Le Bail method revealed the transformation from monoclinic (M1) phase (space group: P21/c) to triclinic (T) one with increasing Fe concentration. Additionally, a monoclinic (M2) phase (space group: C2/m) emerged at 1.0 % Fe doping. Temperature-dependent XRPD and diffuse reflectance measurements elucidated the phase transitions during heating cycles, showing the impact of Fe doping on the system's behavior. The construction of a complete phase diagram for the V1_xFexO2 system (x <= 1.0 %) was achieved, addressing ambiguities in the low-Fe concentration region. X-ray Photoelectron Spectroscopy (XPS) further confirmed the influence of Fe doping on the vanadium valence states, indicating an increase of V5+ sites and therefore a lattice distortion and stabilization of the triclinic phase. The metal-insulator transition temperature (TMIT) appears to be almost constant. Post-annealing led to the reinstatement of the M1 phase in all samples, and a modified phase diagram was constructed. The accompanied decrease of V5+ ions contributed to the destabilization of the T and M2 phases, favoring the thermodynamically stable M1 phase. The findings provide valuable insights into the complex phase behavior of V1_xFexO2 compounds, showcasing a significant interplay between charge redistribution, the vanadium valence state, and the oxygen defects of the system.

Open Access

15. Ensemble Machine Learning for the Prediction and Understanding of the Refractive Index in Chalcogenide Glasses

Authors: Belciu, MI; Velea, A

Published: APR 14 2025, MOLECULES, 30, 1745, DOI: 10.3390/molecules30081745

Chalcogenide glasses (ChGs) are a class of amorphous materials presenting remarkable mechanical, optical, and electrical properties, making them promising candidates for advanced photonic and optoelectronic applications. With the increasing integration of artificial intelligence in modern materials design, we are able to systematically select, prepare, and optimize appropriate compositions for desired applications in a manner that was unachievable before. This study employs various machine learning models to reliably predict the refractive index at 20 degrees C using a small dataset of 541 samples extracted from the SciGlass database. The input for the algorithms consists of a selected set of physico-chemical features computed for the chemical composition of each entry. Additionally, these algorithms served as inner models for an ensemble logistic regression estimator that achieved a superior R2 value of 0.8985. SHAP feature analysis of the second-best model, CatBoostRegressor (R2 = 0.8920), revealed the importance of elemental density, atomic weight, ground state atomic gap, and fraction of p valence electrons in tuning the value of the refractive index of a chalcogenide compound.

16. Modeling of potential field data for detecting structural and tectonic framework of Esh El Mellaha area, Red Sea, Egypt

Authors: Abudeif, AM; Hamimi, Z; Gaber, GM; Kotb, A; Alarifi, N; Bellucci, S; Masoud, MM

Published: JUN 20 2025, SCIENTIFIC REPORTS, 15, 20131, DOI: 10.1038/s41598-025-04674-1

The main objective of this research is to get a comprehensive view on the subsurface geological data on the Esh El Mellaha area and environs, Red Sea, Egypt. This includes determining the depth and structural characteristics of the basement surface beneath the region, as well as identifying additional gravity and magnetic sources and potential structures within the sedimentary cover. To achieve this goal, Bouguer gravity and aeromagnetic data were used, processed and analyzed. Various depth estimation techniques were employed to analyze subsurface structures, each offering distinct advantages. Euler Deconvolution effectively delineates structural discontinuities and fault systems, while the Source Parameter Imaging (SPI) method improves depth accuracy through wavenumber analysis. The Analytical Signal method enhances resolution, providing detailed depth variations. Across these methods, the estimated depth ranges from 300 to 5000 m, with an average depth of approximately 2380 m, offering critical insights into the subsurface geological framework. Two-dimensional (2.5D) modeling was conducted on two selected gravity and magnetic profiles to estimate the depth, dip, density, and magnetic susceptibility of the source bodies. Additionally, three-dimensional (3D) modeling was applied to Bouguer gravity and Reduced-to-the-Pole (RTP) magnetic profiles, providing a detailed representation of the causative source structures. The results of the 3D inversion of gravity and magnetic data reveal the subsurface distribution of density and magnetic susceptibility, aiding in the identification of major geological structures. The sectional maps and 3D models illustrate the vertical and horizontal variations in subsurface formations, highlighting distinct anomaly zones that may correspond to faults and lithological changes. The obtained results indicate that the sedimentary succession thickness is ranging from 1.0 to 2.2 km, a finding corroborated by the borehole data. Positive structural features identified in these models suggest promising targets for potential hydrocarbon reservoirs.

Open Access

17. Annealing temperature, a key factor in shaping Ag-decorated TiO2 aerogels as efficient visible-light photocatalysts

Authors: Rostas, AM; Suciu, RC; Rosu, MC; Turza, A; Cosma, DV; Tripon, S; Fort, CI; Danciu, V; Baia, M; Bocirnea, A; Indrea, E

Published: JUN 1 2025, MATERIALS CHEMISTRY AND PHYSICS, 337, 130557, DOI: 10.1016/j.matchemphys.2025.130557

Ag-decorated TiO2 aerogels were synthesized using an acid-catalyzed sol-gel method, followed by drying under supercritical CO2 and annealing within the temperature range of 350-500 degrees C, with 50 degrees C increments. This study explores the preparation-structure-performance relationships of Ag-TiO2 aerogels influenced by the annealing process, focusing on their morphological, (micro)structural, optical, and textural properties and surface defects concerning photocatalytic activity. X-ray diffraction (XRD) and Raman spectroscopy confirmed that all aerogels exhibited a single anatase phase of TiO2, while electron microscopy (SEM/TEM) and XPS analysis demonstrated the presence of components. Increasing the annealing temperature resulted in particle size and pore structure changes, reducing the aerogel's overall surface area and porosity, as observed by SEM and nitrogen (N2) sorption analysis. Additionally, according to the Williamson-Hall (W-H) analysis based on the X-ray peak profile, the lattice microstrain value decreased while the crystallite size increased with rising annealing temperature. Optical investigation showed a strong UV light absorption characteristic of TiO2 and a visible light absorption band attributed to the plasmonic effect of silver nanoparticles. Moreover, a gradual photoluminescence (PL) quenching trend was observed with decreasing annealing temperature, indicating a reduction in the recombination rate of photo-induced electrons and holes in Ag-TiO2, alongside the formation of oxygen vacancies and structural defects, consistent with electron paramagnetic resonance (EPR) measurements. The Ag-decorated TiO2 aerogels demonstrated enhanced visible-light photocatalytic activity for methylene blue (MB) degradation, with the Ag-TiO2 aerogel annealed at 500 degrees C exhibiting the highest photocatalytic performance. This improvement can be attributed to the synergistic effects of chemical composition, plasmonic enhancement, morphological properties, and light absorption characteristics.

18. Electrochemical assay for the quantification of anticancer drugs and their inhibition mechanism

Authors: Leote, RJB; Sanz, CG; Diculescu, VC; Barsan, MM

Published: SEP 2025, METHODS, 241, DOI: 10.1016/j.ymeth.2025.05.002

Overexpression of pyruvate kinase (PyK) is linked to many kinds of malignant tumors, representing therefore one of the most promising therapeutic targets for cancer treatment. Inhibition of PyK slows down tumor growth or causes tumor cell death, minimizing cancer cell proliferation, and understanding inhibitor mechanism of action can significantly improve cancer therapy. The present work describes the use of an amperometric bienzymatic biosensor, based on PyK and pyruvate oxidase (PyOx), in enzyme inhibition studies of four kinase inhibitors, CPG77675, Nilotinib, Ruxolitinib, Cerdulatinib. Their inhibition mechanism is studied and discussed in detail, with a thorough evaluation of their enzyme-inhibitor complex binding constants (Ki) and the inhibitor concentration required for 50% inhibition (IC50), employing standard inhibition procedure graphical methods. The biosensor is successfully applied for the quantification of the inhibitors by fixed potential amperometry, with excellent detection limit values in the pM range. It is the first detection method reported for the anticancer drugs CPG77675 and Cerdulatinib. The electrochemical assay based on the biosensor brings several advantages over the available assay kits for high-throughput screening (HTS) of kinase inhibitors, namely: low cost, easy operability and robustness demonstrated by biosensor high reproducibility and both operational and storage stability, offering an opportunity to discover new inhibitors and optimize their therapeutic index.

Open Access

19. Electrochemical bienzymatic biosensor for pyruvate kinase activity evaluation and inhibitor screening

Authors: Leote, RJB; Barsan, MM; Sanz, CG; Diculescu, VC

Published: AUG 15 2025, TALANTA, 291, 127886, DOI: 10.1016/j.talanta.2025.127886

This study describes the development of a pyruvate kinase (PyK)-biosensor for the evaluation of PyK activity, as a diagnostic tool for early cancer screening and detection of kinase inhibitors used in cancer treatment, with the evaluation of the inhibition mechanism. The biosensor was constructed by co-immobilizing the enzymes PyK and pyruvate oxidase (PyOx) on Au film electrodes by crosslinking with glutaraldehyde (GA) and evaluated electrochemically by cyclic voltammetry (CV) and fixed potential amperometry (CA). First, the experimental conditions were optimized in terms of applied potential, enzyme ratio PyK:PyOx and enzyme substrate concentration: phosphoenolpyruvate (PEP) and adenosine diphosphate (ADP). The biosensor sensitivity towards PEP detection was 2.11 +/- 0.08 mu A mM- 1 cm- 2, with very high reproducibility and repeatability, which made it suitable for inhibition studies of PyK inhibitor. The inhibition mechanism of shikonin was determined in relation to both PEP and ADP, with the calculation of IC50 values and binding constants (Ki). Detection of shikonin was possible at very low concentrations in the linear range of 0.1-4.0 pM. The electrochemical results were validated by UV-Vis spectrophotometry. The developed biosensor is a valuable tool for drug screening by enabling enzyme catalytic function examination with applicability to identify inhibitors, estimate their affinity, inhibition mechanism linked to their molecular mechanisms of action and evaluate selectivity, of great interest in both pharmaceutical and medical domains.

Open Access

20. Chrome Doped Hydroxyapatite Enriched with Amoxicillin Layers for Biomedical Applications

Authors: Ciobanu, CS; Predoi, D; Iconaru, SL; Rokosz, K; Raaen, S; Negrila, CC; Ghegoiu, L; Bleotu, C; Predoi, MV

Published: FEB 2025, COATINGS, 15, 233, DOI: 10.3390/coatings15020233

In the last decade, it has been observed that the field of biomaterials has gained the attention of the researchers. This study presents the physicochemical and biological properties of coatings based on chromium-doped hydroxyapatite (CrHAp) and chromium-doped hydroxyapatite enriched with amoxicillin (CrHApAx). The coatings were obtained for the first time using the dip coating technique, beginning from dense suspensions of CrHAp and CrHApAx. The obtained layers were then analyzed by various methods in order to have a comprehensive overview of their physicochemical properties. Stability studies performed using ultrasound measurements showed that the CrHAp suspension has very good stability (S = 6.86<middle dot>10-6 s-1) compared to double-distilled water. The CrHApAx suspension (S = 0.00025 s-1) shows good but weaker stability compared to that of the CrHAp suspension. Following XRD studies, a single hydroxyapatite-specific phase was observed in the CrHAp sample, while in the case of the CrHApAx sample, an amoxicillin-specific peak was also observed. The AFM results showed that the CrHAp coatings had a surface topography of a homogenous and uniform layer, with no significant cracks and fissures, while the CrHApAx coatings exhibited a surface morphology of homogenous layers formed of particles conglomerates. The biocompatibility of CrHAp and CrHApAx coatings was assessed using the MG63 cell line. The cytotoxicity of the coatings was evaluated by measuring cell viability with the aid of an MTT assay after 24, 48, and 72 h of incubation with the CrHAp and CrHApAx coatings. The results demonstrated that both CrHAp and CrHApAx coatings exhibited good biocompatibility for all the tested time intervals. The in vitro antibacterial activity of the coatings was also assessed against Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa) bacterial cells. The potential of P. aeruginosa bacterial cells to adhere and develop on the surfaces of CrHAp and CrHApAx coatings was also investigated using AFM analysis. The findings of the biological assays suggest that CrHAp and CrHApAx coatings could be considered as promising candidates for biomedical applications, including the development of novel antimicrobial materials.

Open Access

21. Phosphorothioated oligonucleotides on gold-coated electrospun polymeric fibers for electrochemical genosensors

Authors: Aldea, A; Onea, M; Matei, E; Apostol, N; Botta, D; Enculescu, I; Diculescu, VC

Published: JUN 1 2025, ELECTROCHIMICA ACTA, 524, 146006, DOI: 10.1016/j.electacta.2025.146006

This study investigates the development of electrochemical genosensors using gold-coated electrospun polymeric fibers electrodes, Au/PMMA/PET and immobilized phosphorothioated oligonucleotides. Scanning electron microscopy (SEM) with energy-dispersive X-rays spectroscopy (EDS) revealed a uniform distribution of oligonucleotides on the fibers, contrary to planar gold electrodes Au/Ti/SiO2/Si, where network-like films were observed. X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the phosphorothioated oligonucleotides via strong covalent gold-sulfur bonds, while surface plasmon resonance (SPR) indicated superior binding affinity, with significantly lower equilibrium dissociation constants, when compared to unmodified probes. The detection of BCR/ABL fusion gene of chronic myeloid leukemia using differential pulse voltammetry and methylene blue as electroactive indicator, showed that the Au/PMMA/PET electrodes achieved a sensitivity of 379 +/- 12 mu A cm(-)(2) pM(-)(1) and a limit of detection of similar to 5.00 +/- 0.01 fM, outperforming the Au/Ti/SiO2/Si planar electrodes. Reduced non-specific adsorption was observed on the Au/PMMA/PET electrodes and attributed to the inherent charges introduced during the electrospinning process, which created localized electrostatic fields that repelled weakly adsorbing molecules. These findings demonstrate the potential of Au/PMMA/PET electrodes as a robust platform for further development of high-performance clinical diagnostic devices.

Open Access

22. Influence of flexible substrate nature covered with ITO on the characteristics of organic heterostructures fabricated by laser deposition techniques

Authors: Socol, M; Preda, N; Costas, A; Petre, G; Stanculescu, A; Stavarache, I; Popescu-Pelin, G; Iftimie, S; Stochioiu, A; Catargiu, AM; Socol, G

Published: JAN 2025, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 131, 17, DOI: 10.1007/s00339-024-08149-4

Laser thin layer deposition technologies were applied to develop organic heterostructures on flexible transparent conductive electrode (TCE). Flexible substrates such as flexible glass (FG), polyethersulfone (PES), amorphous polyethylene terephthalate (PET-A) and biaxially-oriented polyethylene terephthalate (PET-B) were employed to assess the influence of the substrate type on the optical and electrical characteristics of the organic devices. For comparison reason, the organic heterostructures were fabricated on rigid glass substrate and commercially available indium tin oxide (ITO)-coated PET. Hence, flexible and rigid glass substrates were coated with ITO film by pulsed laser deposition (PLD) at low fluence, subsequently a blend layer based on zinc phthalocyanine (ZnPc) and N, N '-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide (AMC14) being deposited by matrix assisted pulsed laser evaporation (MAPLE) on the TCE film. The investigations evidenced that the roughness and the substrate type can strongly influence the properties of the ITO layer deposited by PLD as well as the optical and electrical characteristics of the organic heterostructures based on the blend layer deposited by MAPLE. Thus, the lowest roughness (0.8 nm) and the best Hall mobility (41.9 cm2/V center dot s) were achieved for ITO coatings deposited on flexible glass substrate. Also, the highest current density value (9.3 x 10- 4 A/cm2 at 0.5 V) was reached for the organic heterostructures fabricated on this type of flexible substrate.

23. Exploring the fabrication, properties, and morphology of fluorine substituted hydroxyapatite coatings

Authors: Predoi, D; Iconaru, SL; Ciobanu, SC; Rokosz, K; Talu, S; Predoi, SA; Raaen, S; Motelica-Heino, M

Published: JAN 2025, CERAMICS INTERNATIONAL, 51, DOI: 10.1016/j.ceramint.2024.11.168

Hydroxyapatite (HAp), resembling human bone tissue, is a promising biomaterial for dental and hip prosthetics. Incorporating fluorine ions enhances HAp properties, particularly in dental restoration. This new study examines the physicochemical and biological properties of fluorine substituted hydroxyapatite (FHAp) coatings. Structural and morphological properties of the coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental composition of the FHAp coatings was studied using energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy. Fourier Transform Infrared spectroscopy (FTIR) investigations were also conducted. The typical peaks identified in XRD patterns of the FHAp were associated with pure hydroxyapatite with hexagonal structure. The general XPS spectrum of FHAp coatings shows peaks corresponding to the constituent elements of stoichiometric HAp as well as the presence of F that was used as a substituent. Consequently, the FTIR studies results underlined the presence of hydroxyapatite in the FHAp coatings. The SEM images reveal the presence of a uniform and continuous layer of particle conglomerates evenly distributed across the FHAp surface. Valuable information about the FHAp coating's wettability, adhesion and coating thickness were also obtained. Also, the AFM images suggest the absence of the significant irregularities from the surface of the FHAp coatings. Investigations of FHAp coatings reveal promising outcomes for cell viability and proliferation. Detailed analysis of FHAp's 3D surface characteristics and roughness, following ISO 25178-2:2012 standards, highlights their favorable biocompatibility, supporting MG63 cell proliferation. The surface roughness parameters of FHAp coatings were found to vary, with Sa values spanning from 0.029 +/- 0.004 mu m to 0.778 +/- 0.007 mu m, while Sq ranged from 0.035 +/- 0.005 mu m to 0.907 +/- 0.011 mu m. Furthermore, FHAp exhibits skewness (Ssk) from -0.048 +/- 0.006 to 0.195 +/- 0.009, kurtosis (Sku) from -0.600 +/- 0.011 to -1.050 +/- 0.021, and fractal dimension from 2.14 +/- 0.01 to 2.19 +/- 0.01, indicating consistent surface complexity and favorable properties. The Minkowski Functionals mirror the morphological observations from AFM images, emphasizing their dynamic influence on the samples' surfaces.

24. Monophasic Titanate-Based Photocatalyst with Heteroatom Mixed Iso-Aliovalency Enabling Water Oxidation

Authors: Gherca, D; Borhan, AI; Popescu, DG; Husanu, MA; Borca, CN; Stoian, G; Chiriac, H; Ababei, G; Lupu, N

Published: MAY 16 2025, ACS APPLIED MATERIALS & INTERFACES, 17, DOI: 10.1021/acsami.5c03417

Rhodium-doped SrTiO3 perovskite as a monophasic titanate-based catalyst (SrTi1-xRhxO3) showed photocatalytic activity for oxygen evolution reaction (OER) from water under solar light irradiation with an instant induction period, although Rh4+ in SrTiO3 introduces deep trap states thereby diminishing the efficiency of the hydrogen evolution reaction (HER). Despite its potential, the exact crystal structure of Rh:SrTiO3 has not been yet completely investigated. Overcoming these challenges, here, we synthesized a monophasic SrTi0.95Rh0.05O3 (RSTO) perovskite oxide with a precisely determined crystal structure and highlighted an unconsidered pivotal role of the Rh iso-aliovalency reversibility that enables excellent photocatalytic water oxidation. With structural, morphological, optical, and electronic insights from XRD, FE-SEM, HR-TEM, XPS, and advanced XAS measurements in both total electron yield (TEY) and fluorescence yield (TFY), the oxygen evolution reaction (OER) process is attributed to the redox dynamics of Rh4+ <-> Rh3+ synergistic interplay.

25. Martensitic transformation dynamics and mechanical properties investigation in spark plasma sintered Ni-Mn-Ga shape memory alloys

Authors: Popescu, B; Bartha, C; Enculescu, M; Tolea, F; Grigoroscuta, MA; Tolea, M; Badica, P; Sofronie, M

Published: MAY 1 2025, SMART MATERIALS AND STRUCTURES, 34, 055012, DOI: 10.1088/1361-665X/add19d

The Ni49+xMn32-2xGa19+x (x = 0; 2) Heusler ferromagnetic shape memory alloys were prepared using spark plasma sintering using raw flake-type powders obtained by soft grinding melt-spun ribbons. Samples were characterized using x-ray diffraction, electron microscopy, thermal analysis, and bending tests. Although the properties of ribbons and corresponding powders show similar properties' tendencies, they are opposite in the bulk sintered alloys when compared with precursor powders. Namely, Ni49Mn32Ga19 bulk shows a higher enthalpy (5.8 J g-1), an increased martensitic transformation (MT) temperature (by 9 K), and a reduced hysteresis span (5 K). Conversely, for the Ni51Mn28Ga21 sintered sample, a lower enthalpy (2 J g-1), a significant decrease (by 40 K) in the MT starting temperature, and a broadening of the hysteresis range (26 K) were observed. This difference is analyzed versus specific features of the microstructure. Moreover, the activation energy and the pre-exponential factor of the MT, extracted through kinetic analysis within two non-isothermal models, Kissinger and Friedman, complement and sustain these findings. Fractography details of the sintered samples are discussed in relation to the stress-strain curves from the bending tests. The Ni49Mn32Ga19 bulk sample exhibits a higher bending strength (260 MPa) and a lower strain (0.55%) than the Ni51Mn28Ga21 sample (177 MPa and 0.61%). The observed dependence of functional characteristics on preparation enables the possibility of property control required for various applications and suggests that the proposed route is promising in this regard for further investigations.

26. Comprehensive Physicochemical and Biological Analysis of Hydroxyapatite/Dextran Powders before and after Immersion in Kokubo Solution

Authors: Predoi, D; Ciobanu, CS; Iconaru, SL; Rokosz, K; Raaen, S; Predoi, SA; Talu, S; Motelica-Heino, M

Published: 2025 JUN 26 2025, LANGMUIR, DOI: 10.1021/acs.langmuir.5c01585

Understanding the behavior of biomaterials under physiological conditions is essential for the development of new materials for implants and bone regeneration. This study addresses the critical need to evaluate how exposure to simulated body fluid (SBF) affects hydroxyapatite (HAp) and dextran-coated hydroxyapatite (HApDx) nanoparticles, which are widely considered for biomedical applications due to their bioactivity and biocompatibility. Structural, morphological, and surface property changes induced by SBF immersion were systematically investigated for the first time using advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and fractal and Minkowski functional analyses. The results revealed that SBF immersion significantly influenced both HAp and HApDx, leading to reduced crystallite sizes, surface smoothening, and enhanced structural homogeneity. FTIR and FT-Raman spectra indicated subtle structural modifications, while SEM and AFM analyses confirmed the formation of a biomimetic apatite layer and a decrease in surface roughness. These changes are indicative of improved bioactivity, suggesting enhanced potential for osteoconductivity and cellular interaction. Biological evaluations using MG63 osteoblast-like cells demonstrated favorable cell viability and adhesion across 24, 48, and 72 h, particularly for the samples immersed in SBF. AFM further confirmed that surface modifications supported the cell attachment and proliferation. Overall, our findings underscore the importance of SBF exposure in enhancing the physicochemical and biological performance of HAp-based materials, reinforcing their promise for biomedical applications.

Open Access

27. Enhancement of luminescence of ZnS:Ag treated in low power radio frequency argon plasma and excited with an electron beam at 13 keV

Authors: Scurtu, A; Dumitru, M; Garoi, P; Banici, AM; Radu, C; Ticos, D; Udrea, N; Mitu, ML; Ticos, CM

Published: MAR 15 2025, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 188, 109259, DOI: 10.1016/j.mssp.2024.109259

We report on the increase of luminescence of ZnS:Ag after exposure to a radio-frequency (RF) argon plasma at low powers ranging from 5W to 50W. The best luminescence enhancement was achieved at 5W RF power, when the increase was approximately 57.02 % over a 35-min exposure. The luminescence is measured in-situ by excitation with an electron beam with energy 13 keV and a fiber coupled to a spectrometer. The increase in luminescence is attributed to the cleaning effect of surface defects of the crystal caused by argon ions accelerated in the plasma sheath. Surface impurities were highlighted by TEM and XPS analysis. Zn2p(3/2), Zn2p(1/2) and S2p(3/2) peaks show initially high oxidation state and after plasma treatment they shifted to lower value which indicated a decontamination of trapped oxygen. At higher RF powers up to 50W, the trend of increased luminescence continues, but it is mitigated by the thermal quenching effect and sulfur depletion observed in EDS analysis. Calculations based on power deposition indicate a thermoquenching point of approximately 130-150 degrees C.

Open Access

28. New Nanobioceramics Based on Hydroxyapatite for Biomedical Applications: Stability and Properties

Authors: Ciobanu, CS; Predoi, D; Iconaru, SL; Negrila, CC; Leduc, D; Ghegoiu, L; Bleotu, C; El Kettani, MEC; Trusca, R; Zelmar, P; Predoi, MV

Published: FEB 2025, NANOMATERIALS, 15, 224, DOI: 10.3390/nano15030224

In this work, we report for the first time the development and complex characterization of new bioceramics based on hydroxyapatite (HAp, Ca10(PO4)6(OH)2). On the other hand, the lyophilization process was used for the first time in this research. The samples were obtained by a modified coprecipitation method and were dried by lyophilization (lyophilized hydroxyapatite (HApLF) and lyophilized zinc-doped hydroxyapatite (5ZnHApLF)). Valuable information about the HApLF and 5ZnHApLF stability was obtained through nondestructive ultrasound measurements. The X-ray diffraction (XRD) studies revealed the phase and the effects of the incorporation of Zn ions into the HAp structure. The chemical composition of the samples was evaluated by energy dispersive X-ray analysis (EDS) and X-ray photoelectron spectroscopy (XPS). Information about the functional groups present in the HApLF and 5ZnHApLF was obtained using Fourier Transform Infrared Spectroscopy (FTIR) studies. The morphology of HApLF and 5ZnHApLF pellets was observed by scanning electron microscopy (SEM). The surface topography of HApLF and 5ZnHApLF pellets was studied with the aid of atomic force microscopy (AFM). Details regarding the roughness of the samples were also obtained using AFM topographies and SEM images. A complementary study was also carried out on a larger analysis surface using a Scanning Acoustic Microscope (SAM). The SAM was used for the first time to analyze the surface of HAp and 5ZnHAp pellets. The biological properties of the HApLF and 5ZnHApLF pellets was investigated with the aid of MG63 and human gingival fibroblasts (HGF-1) cell lines. The results of the cell viability assay highlighted that both the HApLF and 5ZnHApLF pellets exhibited good biological activity. Moreover, SEM and AFM studies were conducted in order to emphasize the development of MG63 and HGF-1 cells on the pellet's surface. Both SEM and AFM images depicted that the pellets' surface favored the cell attachment and development of MG63 and HGF-1 cells. Furthermore, the antimicrobial properties of the HApLF and 5ZnHApLF were evaluated against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and Candida albicans ATCC 10231. The results of the antimicrobial assays highlighted that the 5ZnHApLF exhibited a strong antimicrobial activity against the tested microbial strains. The results of the biological assays suggested that the samples show great potential for being used in the development of novel materials for biomedical applications.

Open Access

29. Effect of molecular adsorption on the conductivity of selectively grown, interconnected 2D-MoS2 atomically thin flake structures

Authors: Stavarache, I; Palade, C; Slav, A; Dascalescu, I; Lepadatu, AM; Matei, E; Besleaga, C; Ciurea, ML; Kardynal, BE; Stoica, T

Published: APR 8 2025, NANOSCALE ADVANCES, 7, DOI: 10.1039/d5na00138b

The gas sensitivity of field-effect structures with 2D-MoS2 channels selectively grown between Mo electrodes using the Mo-CVD method was investigated by measuring the effect of molecular adsorption from air on the device source-drain current (Isd). The channels were composed of interconnected atomically thin MoS2 grains, with their density and average thickness varied by choosing two different distances (15 and 20 mu m) between the Mo contacts. A high response to the tested stimuli, including molecule adsorption, illumination and gate voltage changes, was observed. A significant, persistent photoconduction was induced by positive charge accumulation on traps, most likely at grain boundaries and associated defects. Isd increased under high vacuum, both in the dark and under illumination. The relative dark current response to the transition from air to high vacuum reached up to 1000% at the turn-on voltage. When monitored during the gradual change in air pressure, Isd exhibited a non-monotonic function, sharply peaking at about 10-2 mbar, suggesting molecular adsorption on different defect sites and orientations of adsorbed H2O molecules, which were capable of inducing electron accumulation or depletion. Despite the screening of disorder by extra electrons, the #20 mu m sample remained more sensitive to air molecules on its surface. The high vacuum state was also investigated by annealing devices at temperatures up to 340 K in high vacuum, followed by measurements down to 100 K. This revealed thermally stimulated currents and activation energies of trapping electronic states assigned to sulfur vacancies (230 meV) and other shallow levels (85-120 meV), possibly due to natural impurities, grain boundaries or disorder defects. The results demonstrate the high sensitivity of these devices to molecular adsorption, making the technology promising for the easy fabrication of chemical sensors.

Open Access

30. Composites Based on Poly(ortho-toluidine) and WS2 Sheets for Applications in the Supercapacitor Field

Authors: Burlanescu, T; Smaranda, I; Androne, A; Florica, CS; Cercel, M; Paraschiv, M; Udrescu, A; Lorinczi, A; Palade, P; Galatanu, A; Negrila, C; Matei, E; Dinescu, M; Cercel, R; Baibarac, M

Published: JAN 2025, BATTERIES-BASEL, 11, 37, DOI: 10.3390/batteries11010037

In this work, three methods for the synthesis of composites based on poly(ortho-toluidine) (POT) and WS2 are reported: (a) the solid-state interaction (SSI) of POT with WS2 nanoparticles (NPs); (b) the in situ chemical polymerization (ICP) of ortho-toluidine (OT); and (c) the electrochemical polymerization (ECP) of OT. The preparation of WS2 sheets was performed by the ball milling of the WS2 NPs followed by ultrasonication in the solvent N,N'-dimethyl formamide. During the synthesis of the POT/WS2 composites by SSI and ICP, an additional exfoliation of the WS2 NPs was reported. In this work, we demonstrated the following: (a) the ICP method leads to POT/WS2 composites, which contain repeating units of POT in the leucoemeraldine salt (LS) state, while (b) the ECP method leads to POT/WS2 composites, which contain repeating units of POT in the emeraldine salt (ES) state. Capacitances equal to 123.5, 465.76, and 751.6 mF cm-2 in the cases of POT-ES/WS2 composites, synthesized by SSI, ICP, and ECP, respectively, were reported.

Open Access

31. Exploring the Synthesis of Cu2(Zn,Cd)SnS4 at High Temperatures as a Route for High-Efficiency Solar Cells

Authors: El Khouja, O; Gong, YC; Jimenez-Arguijo, A; Guerra, MJ; Medaille, AG; Scaffidi, R; Basak, A; Radu, C; Flandre, D; Vermang, B; Giraldo, S; Placidi, M; Li-Kao, ZJ; Galca, AC; Saucedo, E

Published: MAY 2025, PROGRESS IN PHOTOVOLTAICS, 33, DOI: 10.1002/pip.3899

The present research explores for the first time the intricate relationship between sulfurization temperature at unusual high temperatures (up to 700 degrees C) and the structural/optoelectronic properties of Cu-2(Zn,Cd)SnS4 (CZCTS) thin films, synthesized via a two-step sequential process involving the precursor film deposition using aprotic molecular ink followed by thermal treatment in sulfur atmosphere. X-ray diffraction patterns confirms the tetragonal structure. Scanning Electron Micrographs revealed significant grain growth, with grain sizes increasing from similar to 0.3 mu m at 620 degrees C to similar to 1.5 mu m at 680 degrees C, effectively reducing grain boundary recombination. Energy dispersive X-ray spectroscopy demonstrated a Cu-poor and Zn-rich composition, with a consistent Cd incorporation of similar to 3.7 at%. Raman spectroscopy showcases the homogeneity and purity of the CZCTS crystalline structure. Precise control of the sulfurization temperature plays a crucial role in determining the photovoltaic characteristics of CZCTS-based solar cells. By increasing the grain size and preventing the thermal decomposition of the CZTS phase, the photovoltaic performance peaked at a sulfurization temperature of 680 degrees C, achieving a power conversion efficiency (PCE) of 10.4%, with an open-circuit voltage of 0.701 V, a short-circuit current density of 24.3 mA/cm(2) and a fill factor of 60.8%. External quantum efficiency reached a maximum of 83.3% at 580 nm. The bandgap of the CZCTS absorber was determined to be 1.48 eV, optimal for photovoltaic applications. However, further increasing the sulfurization temperature to 700 degrees C resulted in a lower PCE of 8.5%, attributed to interface degradation and secondary phase formation. Temperature-dependent current-voltage measurements revealed a reduction in recombination losses, with an activation energy of 1.24 eV at the CZCTS/CdS interface, indicating effective defect passivation by Cd incorporation. The optimized films, sulfurized at 680 degrees C, displayed an absorber thickness of similar to 1.2 mu m after sulfurization, providing efficient light absorption and charge transport. The findings not only emphasize the critical role of sulfurization temperature in engineering CZCTS film and subsequently their functionality but also provide valuable insights for fine tuning their performance in the field of photovoltaic applications.

32. Large-scale synthesis of monolayer WS2 by low-temperature sulfurization of oxidized magnetron sputtered monolayer W precursors in a microreactor

Authors: Velea, A; Simandan, ID; Mihai, C; Baibarac, M; Vaduva, M; Udrescu, A; Smaranda, I; Bocirnea, AE; Tite, T; Zaki, MY; Kuncser, A; Sava, F

Published: JUN 30 2025, NANOTECHNOLOGY, 36, 265601, DOI: 10.1088/1361-6528/ade25f

We report large-scale synthesis of monolayer WS2 films obtained by sulfurization of oxidized magnetron sputtered monolayer W precursors. Literature routes typically require similar to 800 degrees C, well above the 400 degrees C limit imposed by back-end-of-line (BEOL) integration. Here, using an enhanced chemical vapor deposition (CVD) approach, the magnetron sputtered ultrathin W precursor (a W monolayer film, 0.27 nm thick, which in ambient air becomes a WOx monolayer) is sulfurized at the lowest possible temperature (450 degrees C) within a microreactor, which consists of a sandwich-like structure formed by the precursor and a clean Si substrate. The obtained WS2 material has a good crystallinity and uniform morphology across the entire growth substrate, as confirmed by detailed characterization. These results highlight the versatility of the method combining magnetron sputtering and microreactor-CVD, facilitating its applications to wafer-scale synthesis of monolayer WS2, heterogeneously integrated into electronic circuits (a major objective for next-generation electronics and optoelectronics). Additionally, we investigate in detail the properties of WS2 films synthesized from a bilayer W precursor (0.43 nm thick), under the same conditions, and we calculated the frequencies of the second-order Raman scattering modes. For electrical measurements, we fabricated WS2/few-layer-graphene heterostructures, whose atomically clean interface yields reliable, low-resistance contacts. These devices exhibit resistive switching behavior, likely governed by vacancy migration, making it a promising candidate for memristive applications. Our results demonstrate that electronics-grade monolayer WS2 can be synthesized at 450 degrees C, approaching the BEOL requirement of 400 degrees C.

33. Synthesis, characterization, and photocatalytic efficiency of Mg-doped ZnO nanoparticles for basic Fuchsin dye degradation: Experimental and theoretical insights

Authors: Khammar, F; Boukerche, S; Djaber, S; Boublia, A; Messabhia, A; Gharbi, A; Ferkous, H; Gomez, CV; Bellucci, S; Albrahim, M; Alam, M; Benguerba, Y

Published: JUN 2025, INORGANIC CHEMISTRY COMMUNICATIONS, 176, 114274, DOI: 10.1016/j.inoche.2025.114274

This study synthesized Mg-doped ZnO nanoparticles using the co-precipitation method with doping concentrations ranging from 2 % to 8 %. The structural, morphological, and optical properties of the synthesized nanoparticles were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and UV-Visible spectroscopy. XRD analysis confirmed the successful incorporation of Mg2+ ions into the ZnO lattice, evidenced by lattice parameter shifts and a significant reduction in crystallite size from 30.91 nm (pure ZnO) to 18.10 nm (6 % Mg doping). SEM images showed uniform morphology with reduced particle agglomeration at optimal doping levels, while FTIR analysis identified characteristic Zn-O and Mg-O bonding vibrations, confirming structural integrity. UV-Vis spectroscopy revealed strong absorbance in the UV region, with the band gap energy decreasing from 3.68 eV (pure ZnO) to 3.16 eV (6 % Mg doping), indicating enhanced optical properties conducive to improved photocatalytic performance. The photocatalytic activity of Mg-doped ZnO nanoparticles was evaluated by degrading Basic Fuchsin (BF) dye under UV light irradiation. The Mg-doped ZnO nanoparticles exhibited significantly enhanced photocatalytic performance compared to undoped ZnO, achieving a maximum degradation efficiency of 99.38 % at 6 % Mg doping within 100 min. Optimal photocatalytic conditions were observed at pH 6, using 0.1 g of catalyst and an initial dye concentration of 10 ppm. These enhancements were attributed to improved electron-hole pair separation and increased generation of reactive oxygen species (ROS), facilitated by the strategic incorporation of Mg. To complement the experimental findings, Density Functional Theory (DFT) simulations were performed, integrating the Conductor-like Screening Model for Realistic Solvation (COSMO-RS), Reduced Density Gradient (RDG), and Quantum Theory of Atoms in Molecules (QTAIM). The DFT analysis revealed enhanced charge separation, optimized electron transfer dynamics, and stronger adsorption interactions at Mg-doped sites, which promoted efficient ROS generation. The calculated valence band (VB) and conduction band (CB) edge potentials supported the formation of a Z-scheme heterojunction mechanism, enhancing charge separation and minimizing recombination. These theoretical insights aligned with the experimental observations, confirming that Mg doping effectively enhances photocatalytic efficiency by optimizing electronic interactions and promoting reactive surface dynamics. This integrated experimental and theoretical investigation demonstrates that Mgdoped ZnO nanoparticles exhibit superior photocatalytic properties, making them highly effective for environmental remediation applications, particularly in degrading organic pollutants in wastewater treatment. The study highlights the potential of Mg-doped ZnO as a promising photocatalyst for sustainable environmental solutions.

34. Influence of Cr on the quaternary FeTaTiW medium entropy alloy

Authors: Martins, R; Monteiro, B; Goncalves, AP; Correia, JB; Galatanu, A; Alves, E; Tejado, E; Pastor, JY; Dias, M

Published: APR 9 2025, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ENGINEERING, 20, 52, DOI: 10.1186/s40712-025-00256-1

The search for advanced materials has been growing, and high entropy alloys (HEAs) are emerging as promising candidates for application in the fusion domain. This work investigates the effect of Cr on the FeTaTiW medium entropy alloy to form (CrFeTaTi)70W30 high entropy alloy, comparing the experimental production and characterization with the simulation (molecular dynamics and hybrid molecular dynamics-Monte Carlo) of the phases formed. The alloys were produced by mechanical alloying and sintered by spark plasma sintering. Both simulations have shown that a body-centered cubic structure is formed for both compositions. Monte Carlo simulation provides a more precise prediction of microstructural formation and element segregation. Microstructural examination of the consolidated material revealed the presence of a W-rich phase and a Ti-rich phase, consistent with the phase separation observed in the MC simulations. Moreover, X-ray diffraction analysis of the milled powder for FeTaTiW and (CrFeTaTi)70W30 confirmed the formation of a bcc (body-centered cubic)-type structure with a low fraction of intermetallic phases. Mechanical testing showed ductile behavior at 1000 degrees C where (CrFeTaTi)70W30 showed a stress magnitude almost double that of FeTaTiW. Additionally, the thermal diffusivity between 20 and 1000 degrees C of both alloys increases as the temperature rises. (CrFeTaTi)70W30 exhibits an increase from 3 to 5 mm2/s, while FeTaTiW increases from 4 to 9 mm2/s. Still, both system's thermal diffusivity values are lower than those of CuCrZr and pure tungsten. Despite this, the study underscores the promising attributes of HEAs and highlights areas for further optimization to enhance its suitability for extreme conditions.

Open Access

35. Ultrasound-assisted synthesis of (3-cyclodextrin/hydroxyapatite composites as a green and safe additive for enhancing leather properties

Authors: Quaratesi, I; Calinescu, I; Chipurici, P; Dumbrava, EG; Cucos, A; Zaki, MY; La Manna, P; Bercea, A; Stan, MS; Michalik, S; Pearce, C; Odlyha, M; Burca, G; Badea, E

Published: APR 25 2025, JOURNAL OF MOLECULAR STRUCTURE, 1328, 141299, DOI: 10.1016/j.molstruc.2024.141299

This study presents an ultrasound-assisted synthesis of (3-cyclodextrin/hydroxyapatite composites to be used as green and safe auxiliaries in the tanning process. A combination of spectroscopic and non-spectroscopic techniques such as DLS (dynamic light scattering), ZP (zeta potential), XRD (X-ray diffraction), SEM (scanning electron microscopy) and ATR-FTIR (attenuated total reflectance-Fourier transform infrared spectroscopy) were used to thoroughly characterize the eight composites obtained by varying the ultrasound process parameters. While not cytotoxic, all composites had strong antibacterial action against Brevibacterium lines, Staphylococcus aureus, Escherichia coli, and Staphylococcus epidermis. All composites underwent lab-scale tanning tests, but only those exhibiting the most suitable set of tanning abilities underwent pilot-scale testing. The composites' interaction with the collagen matrix was assessed by micro-DSC (micro-differential scanning calorimetry), TG/DTG/ DTA (thermal analysis), 1H unilateral NMR (proton nuclear magnetic resonance), ATR-FTIR, in-situ temperature synchrotron-based XRD and standard tests (UNI EN ISO 3380: 2015, UNI EN ISO 2589: 2016, UNI EN ISO 105B02:2014). Thermal stability, dye penetration, thickness, colour fastness, surface appearance and microbiological protection were all improved for the leather treated with a small amount of composite added to the wet finish float. These findings demonstrate the benefits of (3-cyclodextrin/hydroxyapatite composites as safe and sustainable tanning additives.

Open Access

36. Phase Transitions in Dimer/Layered Sb-Based Hybrid Halide Perovskites: An In-Depth Analysis of Structural and Spectroscopic Properties

Authors: Ciobotaru, IC; Ciobotaru, CC; Bartha, C; Enculescu, M; Secu, M; Polosan, S; Besleaga, C

Published: FEB 2025, ADVANCED OPTICAL MATERIALS, 13, DOI: 10.1002/adom.202402242

When used as the active layers-either as a light absorber in photovoltaic devices or as an electroluminescent material in light-emitting devices-lead-free perovskites significantly impact the performance of optoelectronic devices. This study focuses on antimony-based perovskites, which are promising for lighting applications. These types of perovskites enable the formation of self-trapped excitons (STEs) with higher dissociation energy than lead-based perovskites, which generate excitons with lower dissociation energy. The (CH3NH3)3Sb2I9 crystals are synthesized using two methods, resulting in distinct spatial configurations - dimer and dimer/layered mixtures, each exhibiting unique structural and spectroscopic properties, as revealed by comprehensive multi-parametric complementary analyses. Their emissive properties underscore the efficiency of the STE photoluminescence, driven by electron-phonon interactions and influenced by Sb-Sb distances in (CH3NH3)3Sb2I9 powder, whether dispersed in polymethyl-methacrylate or solution. The phase transition from monoclinic to hexagonal (dimer) and trigonal (layered) structures enabled the tuning of the optical properties in direct correlation with the structural and electrical features. The photoluminescence behavior of the STEs, analyzed in conjunction with the Raman spectroscopy, elucidates the dynamic process of the electron-phonon coupling effects in the dimer (face-capping Sb-I octahedra) and layered (corner-sharing Sb-I octahedra) crystallographic structures.

Open Access

37. Ru/Beta Zeolite Catalysts for Levulinic Acid Hydrogenation: The Importance of Catalyst Synthesis Methodology

Authors: Petcuta, OA; Guzo, NC; Bordeiasu, M; Nicolaev, A; Parvulescu, VI; Coman, SM

Published: JAN 2025, CATALYSTS, 15, 80, DOI: 10.3390/catal15010080

Ruthenium-based catalysts were prepared through a deposition-precipitation approach, taking beta zeolites with Si/Al ratios of 12.5, 18.5, and 150, respectively, as supports, and 1-3 wt% loadings of metal. Their activation was performed in the presence of either H2 or NaBH4. The dispersion of the Ru species and the acid-base properties were influenced by both the preparation method and the activation protocol. The catalysts reduced under H2 flow presented well-dispersed Ru(0) and RuOx nanoparticles, while the reduction with NaBH4 led to larger RuOx crystallites and highly dispersed Ru(0). These characteristics exerted an important role in the hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). The H2 dissociation occurred via a heterolytic mechanism involving Lewis acid-base pairs associated with RuOx and the framework oxygen (Si-O-Al) located near the zeolite pore edge. The Ru(0) nanoparticles activated the -C=O bond of the LA substrate, while the presence of the carrier zeolite Br & oslash;nsted acid sites promoted the ring-closure esterification of the 4-hydroxyvaleric acid (4-HVA) intermediate to GVL. An optimal combination of these features was achieved for the catalyst with 3 wt% Ru and a Si/Al ratio of 150, which selectively converted LA (XLA = 96.5%) to GVL (SGVL = 97.8%) at 130 degrees C and 10 bars of H2.

38. Recent highlights from INDRA and FAZIA

Authors: Gruyer, D; Baldesi, L; Barlini, S; Borderie, B; Bougault, R; Camaiani, A; Casini, G; Chbihi, A; Ciampi, C; Dueñas, JA; Fable, Q; Fabris, D; Frankland, JD; Frosin, C; Génard, T; Gramegna, F; Henri, M; Hong, B; Kim, S; Kordyasz, A; Kozik, T; Kweon, MJ; LE Neindre, N; Lombardo, I; Lopez, O; Marchi, T; Mazurek, K; Nam, SH; Park, J; Parlog, M; Pasquali, G; Piantelli, S; Poggi, G; Rebillard-Soulié, A; Stefanini, AA; Upadhyaya, S; Valdre, S; Verdé, G; Vient, E; Vigilante, M

Published: MAR-APR 2025, NUOVO CIMENTO C-COLLOQUIA AND COMMUNICATIONS IN PHYSICS, 48, 43, DOI: 10.1393/ncc/i2025-25043-0

In this contribution, we review the recent results from the INDRA and FAZIA Collaborations. It will cover the results from INDRA-VAMOS experiments at GANIL, the first two INDRA-FAZIA campaigns at GANIL and FAZIA experiments at LNS Catania. Recent detector upgrades and developpements will also be discussed. Those results are better explained and more detailed in the following report presentations of this issue and just a brief overview will be mentionned here, with mostly the main conclusions addressed.

Open Access

39. 2025 roadmap on 3D nanomagnetism

Authors: Gubbiotti, G; Barman, A; Ladak, S; Bran, C; Grundler, D; Huth, M; Plank, H; Schmidt, G; van Dijken, S; Streubel, R; Dobrovoloskiy, O; Scagnoli, V; Heyderman, L; Donnelly, C; Hellwig, O; Fallarino, L; Jungfleisch, MB; Farhan, A; Maccaferri, N; Vavassori, P; Fischer, P; Tomasello, R; Finocchio, G; Clérac, R; Sessoli, R; Makarov, D; Sheka, DD; Krawczyk, M; Gallardo, R; Landeros, P; d'Aquino, M; Hertel, R; Pirro, P; Ciubotaru, F; Becherer, M; Gartside, J; Ono, T; Bortolotti, P; Fernández-Pacheco, A

Published: APR 7 2025, JOURNAL OF PHYSICS-CONDENSED MATTER, 37, 143502, DOI: 10.1088/1361-648X/ad9655

The transition from planar to three-dimensional (3D) magnetic nanostructures represents a significant advancement in both fundamental research and practical applications, offering vast potential for next-generation technologies like ultrahigh-density storage, memory, logic, and neuromorphic computing. Despite being a relatively new field, the emergence of 3D nanomagnetism presents numerous opportunities for innovation, prompting the creation of a comprehensive roadmap by leading international researchers. This roadmap aims to facilitate collaboration and interdisciplinary dialogue to address challenges in materials science, physics, engineering, and computing. The roadmap comprises eighteen sections, roughly divided into three blocks. The first block explores the fundamentals of 3D nanomagnetism, focusing on recent trends in fabrication techniques and imaging methods crucial for understanding complex spin textures, curved surfaces, and small-scale interactions. Techniques such as two-photon lithography and focused electron beam-induced deposition enable the creation of intricate 3D architectures, while advanced imaging methods like electron holography and synchrotron x-ray tomography provide nanoscale spatial resolution for studying magnetization dynamics in three dimensions. Various 3D magnetic systems, including coupled multilayer systems, artificial spin-ice, magneto-plasmonic systems, topological spin textures, and molecular magnets are discussed. The second block introduces analytical and numerical methods for investigating 3D nanomagnetic structures and curvilinear systems, highlighting geometrically curved architectures, interconnected nanowire systems, and other complex geometries. Finite element methods are emphasized for capturing complex geometries, along with direct frequency domain solutions for addressing magnonic problems. The final block focuses on 3D magnonic crystals and networks, exploring their fundamental properties and potential applications in magnonic circuits, memory, and spintronics. Computational approaches using 3D nanomagnetic systems and complex topological textures in 3D spintronics are highlighted for their potential to enable faster and more energy-efficient computing.

Open Access

40. Induced antibacterial activity of printable composite materials: Influence of the conjoined modulation of ampicillin/hydroxyapatite/graphene nanoplatelets ratios

Authors: Mocanu, AC; Miculescu, F; Dondea, ES; Pandele, MA; Voicu, SI; Dobre, AA; Stan, GE; Ghebaur, A; Ciocan, LT

Published: FEB 2025, CERAMICS INTERNATIONAL, 51, DOI: 10.1016/j.ceramint.2024.11.492

Biodegradable templates are sought for targeted antibiotic administration/delivery in bone infections to avoid detrimental reactions during bone regeneration. We investigated two key-aspects in this direction: 1) the optimal antibiotic delineation, with thermal stability equivalent to the temperature involved for templates preparation and 2) the antibacterial templates development by a two-step homogenization process. The selected antibiotic - ampicillin (AMP) was mechanically and then thermally mixed with the prime materials: poly(lactic acid) (PLA) - the polymeric matrix, biogenic bovine bone-derived hydroxyapatite (HA, particles <40 mu m), and graphene nanoplatelets (GnP, micrometric range). For the first time, all materials were used in simultaneous modulated ratios for the synthesis of PLA/AMP (1-5 wt.%)/HA (0-30 wt.%)/GnP (0-3 wt.%) composites. The influence of the concomitant materials modulation was surveyed through several assays. The FTIR-ATR spectroscopy depicted a three-level model of overlapping structures asserting the solid molecular cross-linking between all materials, without structural alterations induced to any material (XRD analysis). The addition of AMP to the PLA matrix caused a slight particle conglomeration, alleviated through GnP addition. The microporous HA particles supported the adhesion to the PLA matrix and promoted the AMP particles' entrapment/attachment. Linked to the enhanced wettability of the composite materials, the phosphate buffered saline solution (PBS) degradation profiles revealed a pronounced burst during the first 14-28 days of incubation and a long-term, low-level process hereafter. Thus, the formation of pores and cavities were signalled along with the HA particles' fragmentation. The released AMP (percentage) pictured an ascending trendline during the 24 h of analysis, at all targeted ratios. The preservation of AMP features at 200 degrees C was endorsed by the strong antibacterial activity of composite materials against Staphylococcus aureus (S. Aureus) growth and the medium response against Escherichia coli (E. Coli) - the higher the drug release, the higher the inhibitory effect on bacteria evolution.

41. Optical, structural and electrical proprieties of composites based on MoS2, WS2 and poly(ortho-toluidine)

Authors: Burlanescu, T; Cercel, M; Smaranda, I; Androne, A; Zgura, I; Ganea, CP; Negrila, C; Lorinczi, A; Bartha, C; Baibarac, M

Published: JUN 2025, MATERIALS TODAY COMMUNICATIONS, 46, 112469, DOI: 10.1016/j.mtcomm.2025.112469

In this work a method in two steps for the preparation of the composites based on poly(ortho-toluidine) (POT) and the MoS2 and WS2 sheets was reported. In the first step, by ball-milling of mixtures of MoS2 and WS2 particles, the sheets of MoS2 and WS2 (MoS2: WS2) with weight ratio equal to 3:1, 1:1 and 1:3 were prepared. In the second step, the interaction in solid-state of the MoS2: WS2 samples with POT in emeraldine-base (POT-EB) and emeraldine-salt (POT-ES) was used to obtain composites of the type MoS2: WS2/POT-EB and MoS2: WS2/ POT-ES. Using X-ray diffraction (XRD), FTIR spectroscopy, Raman scattering and X-ray photoelectron spectroscopy (XPS), we demonstrate that: i) the ball-milling method can allow the preparation of the MoS2 and WS2 sheets with different stacking order, ii) the interaction of POT-EB with the MoS2: WS2 samples involves the transformation of some repeating units of the type EB into ES; and iii) the interaction of POT-ES with the MoS2: WS2 samples leads to the appearance of new positive charges onto macromolecular chains which are compensated by S2- ions. According to thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), all samples are demonstrated to be stable up to 230 degrees C. Dielectric spectroscopy data reveal a complex dependence of DC electrical conductivity on frequency, temperature, and composite concentration. We use the apparent activation energy, defined as the derivative of the logarithm of conductivity with respect to the inverse temperature. The obtained results indicate that apparent activation energy is influenced by system composition via filling factors. The electrical properties of these heterogeneous materials are described using Lichtenecker's mixing laws. For components with similar electrical properties, the effective conductivity and apparent activation energy were determined as linear combinations of the individual conductivities and activation energies, respectively, weighted by the component concentrations. Our findings align with experimental data, offering a framework for understanding conductivity and activation energy in multi-component systems.

42. Electrochemical detection of superoxide anion in living systems: Recent trends and clinical implications

Authors: Sanz, CG; Aldea, A; Barsan, MM

Published: OCT 2025, BIOELECTROCHEMISTRY, 165, 108998, DOI: 10.1016/j.bioelechem.2025.108998

Superoxide plays a significant role in maintaining physiological states of living systems, with major roles in eradicating invading microorganisms and in cell signaling. It is regulated intricately by the enzyme superoxide dismutase (SOD), and when not properly regulated it can lead to cascade biological pathways with severe and irreversible damage to biofilms, tissue, and organs, being linked with many neurodegenerative diseases, atherosclerotic and cardiovascular diseases. Therefore, superoxide anion (O center dot-2 ) detection has a tremendous potential in clinical diagnostics to assess oxidative stress in living cells. This comprehensive review aims to explore, discuss, and analyze recent trends in the electrochemical detection of O center dot-2 in living systems, focusing not only on the recognition mechanism for in vitro assays (living cell cultures/tissues) but also on the importance of the electrode design and operational parameters for in vivo measurements (implantable sensors). By analyzing current in vitro/in vivo electrochemical strategies we gather information that is helpful to overcome existing limitations in the dynamic monitoring of O center dot-2 , and further improve electrochemical strategies that can be adopted and applied to prevent its negative effect, with an insight into the pathophysiology of neurodegenerative disorders and even cellular malignancies that derive from its accumulation in living systems.

43. Electrical properties of epitaxial PZT-LSMO magnetoelectric heterostructures: the effect of the interface with the electrodes

Authors: Hrib, LM; Trupina, L; Botea, MI; Chirila, CF; Boni, AG; Istrate, MC; Pintilie, L

Published: JUN 9 2025, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 58, 235304, DOI: 10.1088/1361-6463/add542

Ferroelectric-ferromagnetic heterostructures with well-defined polarization orientation are the focus of many research studies owing to their interesting interface-driven phenomena such as magnetoelectric coupling. In most practical electronic applications, capacitor geometry is often used, and in the case of ferroelectric-ferromagnetic heterostructures this can bring additional challenges regarding the overall functionality due to the physical phenomena from the ferroelectric-electrode interface. In this study, it is presented the influence of the top and bottom electrode on the electrical properties of Pb(Zr0,2Ti0,8)O3-La1-xSrxMnO3/SrTiO3(001) epitaxial heterostructures. This was done by growing the thin films with different layer stacking sequences by changing the Sr doping level from the bottom electrode. It was found that both the ferroelectric polarization orientation and tetragonality of the PZT films were significantly affected by the layer stacking sequence and Sr doping level of the bottom electrode. The ferroelectric polarization was oriented either towards or away from the Pb(Zr0,2Ti0,8)O3-La1-xSrxMnO3 interface depending on the layer stacking sequence, and the tetragonality increased when the Sr doping increases from x = 0.3 to x = 0.33. The materials used as the top electrode were Pt and Au/SrRuO3. Electric measurements performed in capacitor geometry show that the hysteresis curves start to be affected by leakage currents, which have a direct impact on the estimation of the ferroelectric polarization values and on the internal built in field. The most severely affected were the measurements performed with top Pt electrodes. The conduction mechanisms and leakage current values obtained by using the top Au/SrRuO3 electrode were found to be dependent on the Sr doping level, despite the fact that the electrical resistivity values and microstructures of the individual La1-xSrxMnO3 films were similar.

44. Experimental study on thermal evolution from precursor gel to crystallized MgO for biomedical applications

Authors: Hattab, M; Oprea, OC; Cernea, M

Published: MAR 2025, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 150, DOI: 10.1007/s10973-024-13951-6

Magnesium and its alloys, pure or doped MgO and its solid solutions show an increasing interest for future applications in the field of biomaterials. In this paper, MgO nanoparticles were prepared by sol-gel route starting from magnesium acetylacetonate and 2-methoxyethanol. A complex thermal analysis was used to investigate in situ the decomposition reactions, the gaseous products evolved from the gel precursor of MgO during the thermal treatment procedure, in the temperature range of 293.2-1123.2 K (20-850 degrees C), and crystallization of cubic MgO phase. We found 5 steps for the pyrolysis of the precursor gel and, as gaseous products removed: water, carbon dioxide and fragments of acetylacetone and 2-methoxyethanol. The structure and morphology of the resulting MgO powder were also investigated by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The results of these analyses demonstrated that as-prepared MgO powder show a microstructure consisting of particles with rounded shape and size ranging from 7 to 12 nm and, a structure of cubic phase by heating the gel precursor at 773.2 K (500 degrees C), 1 h in 5%H2/Ar.

Open Access

45. α-MoO3 Micro- and Nanoparticles as Catalysts for Biofuel Production

Authors: de Medeiros, SASL; de Oliveira, ALM; Duarte, TM; Kennedy, BJ; Rostas, AM; Negrila, CC; Galca, AC; Maia, AD; Sambrano, JR; Dantas, MC; Farias, AF; dos Santos, IMG

Published: MAR 7 2025, ACS APPLIED NANO MATERIALS, 8, DOI: 10.1021/acsanm.4c01239

Herein, alpha-MoO3 micro- and nanoparticles were synthesized by a modified Pechini method, and the impact of the crystal structure and crystal growth orientation on the formation of ionic defects and, consequently, on the catalytic performance of the materials in the ethylic transesterification reaction for biodiesel production was investigated. Structural refinements from X-ray diffraction data and Raman spectra revealed the formation of alpha-MoO3 in a Pbnm orthorhombic phase, with nanoplate-like morphology at 500 degrees C (thickness between 100 and 260 nm) or ribbon-like morphology at 700 degrees C (thickness between 400 and 900 nm). An anisotropic crystal orientation along the [010] direction was observed with an increase of the calcination temperature. We emphasize the dependence of the orientation change with the elimination of ionic-type defects (oxygen vacancies and reduced Mo5+ centers) by the temperature using complementary techniques such as X-ray photoelectron and electron paramagnetic resonance spectroscopies. The catalytic activity of the samples depends on the orientation process and the presence of defects that act as acid-active sites on the catalyst surface and therefore play an important role in biodiesel production. This effect was confirmed by surface stability and reactivity simulated by density functional theory calculations, suggesting that the Mo and O surface terminals greatly impacted the interface catalytic reaction. The highest catalytic performance toward the biodiesel conversion (89% of conversion at 150 degrees C for 2 h) was achieved for the polycrystalline catalyst calcined at 500 degrees C, which was correlated with random crystal orientation and the presence of reduced Mo5+ and oxygen vacancy centers on the different facets exposed on the surface. The biodiesel production was confirmed by H-1 and C-13 NMR spectroscopy and gas chromatography analysis.

Open Access

46. Aluminum doped zinc oxide nanoplatelets based sensor with enhanced hydrogen sulfide detection

Authors: Ydir, B; Ajdour, A; Antohe, I; Socol, G; Socol, M; Toderascu, LI; Saadaoui, D; Choulli, I; Leghrib, R; Lahlou, H

Published: MAR 13 2025, SCIENTIFIC REPORTS, 15, 8633, DOI: 10.1038/s41598-025-93252-6

This study explores the development of highly sensitive hydrogen sulfide (H2S) gas sensors employing hierarchical aluminum-doped zinc oxide (AZO) nanostructures. Vertically oriented AZO nanoplatelets with Al/ZnO molar ratios of 4% and 6% were successfully synthesized using an automated successive ionic layer adsorption and reaction (SILAR) technique. The morphological features of the AZO films significantly changed with the Al content. The AZO thin films exhibited a polycrystalline wurtzite structure and an increase in crystallite size with increasing Al concentrations. This work demonstrates that our AZO sensor structures achieved a maximum response at 150 ppm H2S and 573 K of 23.3%, being characterized by fast response and recovery times of 28 and 464 s, respectively. Notably, the 6% AZO samples exhibited an augmented selective sensitivity to H2S, demonstrating stable detection performance. Additionally, the significant improvement in detection capabilities can be attributed to the synergistic effects of electronic and chemical sensitization. These effects enhance the formation of active sites and create doping-induced defects while providing shorter and more efficient diffusion paths for the electrons, significantly improving the sensor's sensitivity and response speed.

Open Access

47. Development of new scaffolds for bone substitution by electrospinning and laser ablation

Authors: Oprica, IMA; Beregoi, M; Popescu-Pelin, GF; Constantinoiu, I; Bacalum, M; Draghici, CI; Jinga, SI; Busuioc, C

Published: MAR-APR 2025, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 35, DOI: 10.1016/j.jmrt.2025.02.225

The present study aims to develop and investigate the biological response of a bone substitute based on electrospun polyvinylidene fluoride (PVDF) fibres, which are either embedded or coated with a silicate bioglass belonging to SiO2-P2O5-CaO-Na2O oxide system. This bioglass is substituted with antibacterial agents, silver (Ag) and cerium (Ce), while deposition methods utilized include pulsed laser deposition (PLD) and matrixassisted pulsed laser evaporation (MAPLE). The results showed the inhomogeneous distribution of the glassy particulate phase in the polymer fibres when using electrospinning as single processing technique. In contrast, the materials achieved by combining the electrospinning with laser ablation displayed a continuous coating of glass at the polymer fibres surface. The thickness and roughness of this layer can be easily tuned as a function of deposition conditions, as it was demonstrated when changing the dispersion medium or working pressure. Good results were obtained for all coated PVDF fibres, but especially in the case of PLD processing with a thicker layer of silicate glass, the imaging evaluation suggested a superior beneficial impact on cellular metabolism. Such scaffolds, with controlled porosity, engineered surface and potential piezoelectric properties represent important candidates for the field of personalized bone substitutes.

48. Boosting poly(ε-caprolactone) with oleic acid: a green catalyst-driven approach for high-performance antioxidant and antibacterial biodegradable polymers

Authors: Bezzekhami, MA; Belkhir, NL; Zaoui, S; Harrane, A; Sid, ANE; Mostefai, A; Belalia, M; Bellucci, S

Published: 2025 JUN 16 2025, JOURNAL OF MACROMOLECULAR SCIENCE PART A-PURE AND APPLIED CHEMISTRY, DOI: 10.1080/10601325.2025.2518214

Biodegradable polymers like poly(epsilon-caprolactone) (PCL) are widely studied for their potential applications in biomedical and environmental fields. To enhance PCL's thermal, and bioactive properties, researchers have explored composite formulations with other polymers or bioactive compounds. Oleic acid (OA), a naturally occurring fatty acid, has been identified as a promising modifier. This study investigates the modification of PCL with OA using an eco-friendly catalyst to improve its functional properties. PCL was grafted with OA using Maghnite-H+, a heterogeneous solid catalyst clay activated via sulfuric acid treatment. A response surface methodology with a central composite design was applied to optimize synthesis parameters, including reaction temperature, duration, and catalyst concentration. The resulting composite was characterized using FTIR and NMR to confirm structural modifications, while its thermal stability was evaluated. Antioxidant activity was assessed using the DPPH radical scavenging assay, and antimicrobial potential was tested against various microorganisms. The PCL-OA composite exhibited enhanced antioxidant activity, with increased radical scavenging efficiency compared to unmodified PCL. Antimicrobial tests revealed strain-dependent effects, with improved inhibition observed in specific combinations of caprolactone, OA, and PCL-OA. The findings suggest that OA incorporation enhances PCL's bioactivity, making it a promising material for biomedical and packaging applications.

Open Access

49. Supercapacitor devices based on multiphase MgTiO3 perovskites doped with Mn²⁺ ions

Authors: Aleinawi, MH; Saritas, E; Stefan, M; Ammar, AU; Hroub, A; Misirlioglu, FB; Bocirnea, A; Macavei, S; Tripon, S; Erdem, E; Mihai, RA

Published: JAN 1 2025, MATERIALS CHEMISTRY AND PHYSICS, 329, 130016, DOI: 10.1016/j.matchemphys.2024.130016

Recently, perovskites have become a hotspot for researchers attempting to exploit metal and oxygen vacancies in structures of the form MTiO3, facilitating the convenient electron/hole migration, thus displaying interesting properties. Magnesium Titanate (MgTiO3) is a prominent part of the perovskite class, exhibiting remarkable electrical, thermal, and chemical properties. Undoped and Mn-doped MgTiO3 samples were obtained using a solid-state reaction starting from previously synthesized MgO and TiO2 powders, which were separately doped with different Mn ion concentrations. The resulting multiphase materials with a major MgTiO3 phase were thoroughly morpho-structurally analyzed employing XRD, STEM, Raman, PL, XPS, and EPR spectroscopy. The electrochemical results indicate that they show superior performance when used as electrode materials for supercapacitor application due to the high defect concentration as shown in EPR and PL spectroscopy and the ferroelectric behavior observed in XPS and XRD. When used in symmetric and asymmetric supercapacitor devices, they show promising results, with specific capacity values reaching up to 109 F/g for the symmetric and 609 F/g for the asymmetric devices, while energy and power density values reached 84.7 Wh/kg and 90.8 kW/kg respectively, proving a great potential in the energy storage field.

50. Fast charging and high-efficiency sputter-deposited silicon thin film anodes for Li-ion batteries

Authors: Elomari, G; Larhlimi, H; Oubaki, R; Elmaataouy, E; Aqil, M; Samih, Y; Makha, M; Negrila, C; Alami, J; Dahbi, M

Published: JUN 30 2025, JOURNAL OF POWER SOURCES, 642, 236967, DOI: 10.1016/j.jpowsour.2025.236967

In this study, we investigate the electrochemical performance and stability of silicon thin films, deposited by magnetron sputtering, as anodes for lithium-ion batteries (LIBs). The conventional direct current magnetron sputtering and the highly ionized technique high power impulse magnetron sputtering HiPIMS, known to produce high-density thin films, were used for the purpose. Silicon films with thicknesses of 50, 75, 124, 600 and 1000 nm were prepared and the morphology, density, and electrochemical performances of the films produced using both techniques were compared. Characterization of the prepared electrodes showed that the DCMSdeposited films exhibited lower density and large grain sizes, while the HiPIMS-deposited films exhibited higher density and relatively smaller grain sizes. The electrochemical tests revealed that the DCMS-deposited electrodes exhibited discharge capacities of 800 mAh g- 1 and 406 mAh g- 1 at a current density of 5 A g- 1 for electrode thicknesses of 600 nm and 1000 nm , respectively, demonstrating their high potential for fast charging applications. Additionally, these electrodes showed remarkable initial coulombic efficiency (ICE), with the 1000 nm thick electrode achieving an ICE of 96.08 %, outperforming traditional graphite anodes, which was attributed to a larger particle size and a lower SEI resistance. Furthermore, DCMS-deposited Si electrodes showed higher resistance to plastic deformation, which enhanced capacity retention and mitigated volume expansion, demonstrating their potential for high-performance anodes.

51. Two decades of continuous progresses and breakthroughs in the field of bioactive ceramics and glasses driven by CICECO-hub scientists (vol 40, pg 104, 2024)

Authors: Fernandes, HR; Kannan, S; Alam, M; Stan, GE; Popa, AC; Buczynski, R; Globebiewski, PG; Ferreira, JMF

Published: JUL 2025, BIOACTIVE MATERIALS, 49, DOI: 10.1016/j.bioactmat.2025.02.044

Open Access

52. Physicochemical and Preliminary Biological Properties of Thin Films Based on Fluoride-Doped Hydroxyapatite in a Dextran Matrix for Biomedical Applications

Authors: Ghegoiu, L; Predoi, D; Iconaru, SL; Ciobanu, CS; Rokosz, K; Raaen, S; Badea, ML; Predoi, MV

Published: MAY 9 2025, COATINGS, 15, 565, DOI: 10.3390/coatings15050565

A spin-coating technique was used to produce new thin films of fluoride-doped hydroxyapatite (HApF) and fluoride-doped hydroxyapatite in a dextran matrix (HApF-Dx) with the potential to be used as nanocoatings for various biomedical implants. The stability of the suspensions used in obtaining the thin films was confirmed by ultrasonic measurements with double-distilled water as a reference. The HApF and HApF-Dx thin films obtained by spin-coating showed diffraction patterns corresponding to hexagonal hydroxyapatite. The X-ray photoelectron spectroscopy studies confirmed the partial substitution of hydroxyl groups (-OH) by fluoride ions. The FTIR studies were conducted in order to highlight the presence of the functional group specific for the HAp in the samples and the influence of the dextran addition on the vibrational characteristics. The surface morphologies of the HApF and HApF-Dx thin films were explored using scanning electron microscopy (SEM), atomic force microscopy (AFM), and metallographic microscopy (MM). The surfaces of the HApF and HApF-Dx thin films were found to be smooth, homogenous, and nanostructured. The biocompatibility assays on HGF-1 cells confirmed that both coatings exhibited good cell viability for all the tested time intervals (24 and 48 h). The findings highlighted the potential of HApF and HApF-Dx coatings for biomedical applications. Additional information about the HGF-1 adherence and development on the surface of the HApF and HApF-Dx coatings was obtained using metallographic microscopy, scanning electron microscopy, and atomic force microscopy techniques. This research demonstrates that the spin-coating method can be successfully used to fabricate HApF and HApF-Dx nanocoatings for potential biomedical applications.

53. A general algorithm for determining the conductivity zeros in large molecular nanostructures: applications to rectangular graphene sheets

Authors: Nita, M; Tolea, M; Marinescu, DC

Published: JUN 9 2025, JOURNAL OF PHYSICS-CONDENSED MATTER, 37, 235301, DOI: 10.1088/1361-648X/add77f

We propose an algorithm for determining the zeros of the electric conductivity in large molecular nanonstructures such as graphene sheets. To this end, we employ the inverse graph method, whereby non-zeros of the Green's functions are represented graphically by a segment connecting two atomic sites, to visually signal the existence of a conductance zero as a line that is missing. In rectangular graphene structures the topological properties of the inverse graph determine the existence of two types of Green's function zeros that correspond to absolute conductance cancellations with distinct behavior in the presence of external disorder. We discuss these findings and their potential applications in some particular cases.

54. Induced Effects of Nano-Patterned Substrates on the Electrical and Photo-Electrical Properties of PTB7-Th:ICBA (1:1, wt.%) Bulk-Heterojunction Solar Cells

Authors: Suteu, T; Antohe, VA; Antohe, S; Stavarache, I; Balasin, MC; Socol, G; Socol, M; Rasoga, O; Iftimie, S

Published: MAY 1 2025, SURFACES, 8, 30, DOI: 10.3390/surfaces8020030

In this study, we detailed the fabrication and characterization of photovoltaic structures based on PTB7:ICBA (1:1, wt.%) bulk-heterojunction on optical glass substrates by spin-coating. Some samples were deposited on a flat substrate, and others were placed on a patterned substrate obtained by nano-imprinting lithography; the induced effects were analyzed. We demonstrated that using a patterned substrate enhanced the maximum output power, primarily because the short-circuit current density increased. This can be considered a direct consequence of reduced optical reflection and improved optical absorption. The topological parameters evaluated by atomic force microscopy, namely, the root mean square, Skewness, and Kurtosis, had small values of around 2 nm and 1 nm, respectively. This proves that the mixture of a conductive polymer and a fullerene derivative creates a thin film network with a high flatness degree. The samples discussed in this paper were fabricated and characterized in air; we can admit that the results are encouraging, but further optimization is needed.

Open Access

55. High-Entropy Ti, Zr, Hf, Ta Multiphase Diboride with Deformation Resistance up to 2000 °C

Authors: Badica, P; Grigoroscuta, MA; Kuncser, AC; Vasylkiv, O

Published: MAY 2025, ADVANCED ENGINEERING MATERIALS, 27, DOI: 10.1002/adem.202402723

A multiphase high-entropy diboride (Ti0.25Ta0.25Hf0.25Zr0.25)B2 is obtained by spark plasma sintering from a mixture of single-metal diborides. The as-prepared material at the microscale can be defined as a composite where grains of a Ta-rich/Ti-poor complex diboride phase are the reinforcement and grains of Ta-poor/Ti-rich complex diboride are the matrix. However, at the nanoscale, the grains are heterogeneous, composed of regions with a multitude of complex diboride compositions. The interface between nanoregions is compositionally graded and has an irregular shape. The four-metal diboride shows a deformation-resistant mechanism under bending load. A strengthening process is active, increasing the room temperature bending strength (326 MPa) by approximate to 50% at 1800 degrees C (488 MPa). A ductile behavior with a deformation strain of approximate to 7.5% is observed at 2000 degrees C while bending strength (407 MPa) is approximate to 25% above the value at room temperature. At 2000 degrees C, observation of dislocations propagating from one compositional nanoregion to another and with a different density suggests dislocation contribution, first of all, to plasticity. The peculiar heterogeneity of this material at nano- and microscales is considered the reason for the remarkable mechanical response to bending load at different temperatures.

Open Access

56. Electron transporting bilayers for perovskite solar cells: Spray coating deposition of c-TiO2/m-SnO2-quantum dots

Authors: Mirea, AG; Vlaicu, ID; Derbali, S; Neatu, F; Tomulescu, AG; Besleaga, C; Enculescu, M; Kuncser, AC; Iacoban, AC; Filipoiu, N; Cuzminschi, M; Nemnes, GA; Manolescu, A; Florea, M; Pintilie, I

Published: JAN 20 2025, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 705, 135508, DOI: 10.1016/j.colsurfa.2024.135508

Herein we present a comparative study among different spray-coated nanometric mesoporous electron transporting layers (ETLs) in perovskite solar cells (PSC), namely m-TiO2, 2 , m-SnO2 2 and m-SnO2 2 quantum dots (mSnO2QDs). 2 QDs). The solutions used for deposition were prepared from commercial pastes and colloidal suspensions for m-TiO2 2 and m-SnO2. 2 . For m-SnO2QDs 2 QDs in-house QDs solutions were prepared. The formamidiniummethylamonium-potassium (FAMA@10 K) has been used as light absorber material in the fabricated PSCs. The structural, compositional and morphological studies, correlated with the photovoltaic performance of PSCs, indicate that the m-SnO2 2 QDs layer is the best candidate among the three investigated mesoporous ETLs. Compared with the suspensions used for the other two ETLs, the in-house prepared SnO2 2 QDs solution presents smaller agglomerates of nanoparticles and results in the formation of a thinner, more uniform and compact mesoporous ETL. The FAMA@10 K perovskite deposited on m-SnO2 2 QDs ETL presents a lower roughness, better uniformity and a higher amount of PbI2. 2 . Our work unveils that the SnO2 2 QDs solution can be easily produced in laboratory and when is deposited as mesoporous scaffold in a PSC with FAMA@10 K perovskite, the power conversion efficiency increases up to 14.90 %, being with up to 27 % larger than in the PSCs with m-TiO2 2 and mSnO2 2 ETLs prepared from commercial solutions. By modeling the J-V dynamic hysteresis with more than 90 % match between the calculated and experimental J-V data, for all three types of mesoporous ETLs, the relevant parameters that explain the hysteresis magnitude and account for ionic-induced recombination processes in PSCs were determined.

57. Enhanced photocatalytic performance of V2O5 NRs/RGO nanocomposites for Rhodamine-B decolorization under solar irradiation: Experimental and theoretical study

Authors: Boukhoubza, I; Achehboune, M; El Khouja, O; Basyooni-M Kabates, MA; Mindroc, M; Derkaoui, I; Enculescu, M; Matei, E

Published: JUN 2025, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 201, 112654, DOI: 10.1016/j.jpcs.2025.112654

In the present work, an essential advance in the preparation of novel nanocomposites based on functionalized V2O5 nanostructures with reduced graphene oxide by hydrothermal method, which has great potential for use in photocatalytic processes related to environmental remediation. XRD analysis confirmed V2O5 in an orthorhombic structure. SEM images showed transparent RGO layers well anchored onto the surface of the V2O5 with a homogeneous distribution. Raman spectroscopy further explained the hybridization and interaction between the components. The photocatalytic activity of Rhodamine-B in aqueous solutions has been studied upon irradiation with visible light. A high RhB degradation was obtained using the V2O5/RGO photocatalyst (82 %), compared to the degradation obtained with only V2O5 (60 %). First-principles Density Functional Theory (DFT) simulations reveal a strong interaction between V2O5 molecules and graphene surfaces, with an adsorption energy of -1.673 eV and a significant charge transfer of 0.367 e- to RGO. This interaction modifies the electronic structure, creating semi-metallic behavior near the Fermi level and enhancing catalytic activity through improved charge carrier dynamics and active sites for photocatalytic applications.

Open Access

58. Strain engineering of epitaxial perovskite-type LaFeO3/ BiFeO3 heterostructures for photoelectrochemical water splitting

Authors: Andrei, F; Ion, V; Birjega, R; Ghitiu, I; Zamfir, M; Moldovan, A; Teodorescu, VS; Dinescu, M; Marcu, IC; Scarisoreanu, ND

Published: APR 1 2025, SURFACES AND INTERFACES, 62, 106234, DOI: 10.1016/j.surfin.2025.106234

Following the approach of inducing structural constrains for the creation of polar nanodomains/nanoregions in the perovskite thin films, the photoelectrochemical properties of complex heterostructures based on LaFeO3 and BiFeO3 materials have been studied in correlation with the imposed structural strain and polarization orientation anisotropy conditions. The LFO/BFO thin film heterostructures have been tested using photoelectrochemical (PEC) technique. The recorded photocurrent values for the heterostructure with the LFO layer on top- LFO/BFO/STON- in the potentiodinamic regime are considerably higher (similar to 1.64 mA/cm(2) at 2 V vs RHE) than those obtained for BFO/LFO/STON heterostructure where the BFO layer is acting as the surface layer (similar to 0.32 mA/cm(2) at 2 V vs RHE). Moreover, the LFO/BFO/STON heterostructure exhibits both photocathodic and photoanodic behavior. The atomic resolution STEM data demonstrate the polarization orientation anisotropy in LFO/BFO/STON heterostructure, due to the cooperative effects of competing surface chemistry and polarization of the LFO/BFO interface over the magnitude and orientation of the Fe3+ cations displacement within the La3+ cages. For the BFO/LFO/STON heterostructure however, robust single-oriented domains with large Fe3+ cations displacement characteristics for long-range ferroelectric order, has been revealed also. Taking into account the possibility to control the PEC features such as charge distribution/transport characteristics for both photocathodic/photoanodic reactions, as well as the control of the polarization direction without a pre-poling process, this work is of relevance for applications where the use of a top electrode is not possible.

Open Access

59. Reduced graphene oxide- based multilayer transparent conductive electrodes

Authors: Socol, M; Preda, N; Costas, A; Stanculescu, A; Rasoga, O; Stavarache, I; Petre, G; Popescu-Pelin, G; Toderascu, I; Breazu, C; Socol, G

Published: MAR 2025, VACUUM, 233, 113943, DOI: 10.1016/j.vacuum.2024.113943

In this work, we investigated the influence of reduced graphene oxide (RGO) on the electrical performances of ZnO/Ag multilayer transparent conductive electrodes. RGO flakes were successfully laser transferred by matrix assisted pulsed laser evaporation (MAPLE) using frozen targets obtained from suspensions of commercially chemically RGO powder dispersed in dimethyl sulfoxide (DMSO). The main deposition parameters such as RGO concentration, laser fluence, number of the laser pulses and deposition pressure were varied to identify the optimal morphological and optical characteristics. The laser transfer conditions for the RGO structures with the best transmittance were further employed in preparation of RGO/Ag/ZnO multilayer transparent conductive electrodes (MTCE). Thus, the MAPLE deposited RGO structures were covered with metal (Ag) by vacuum thermal evaporation (VTE) and subsequently with metal oxide (ZnO) by radio frequency magnetron sputtering (RF-MS). In comparison to the optical and electrical properties of a ZnO/Ag/ZnO reference structure, the results emphasize that the RGO/Ag/ZnO are featured by a similar transmittance (similar to 82-85 %) and improved sheet resistance (similar to 10.6 Omega/square, meaning up to 2-fold smaller).

60. Tailoring Structural Distortions and Ionic Defects as Alternative Strategy to Modulate Reactive Oxygen Species and Photocatalytic Activity in SnO2 Nanoparticles

Authors: do Nascimento, JLA; Rostas, AM; Silva, A; Kennedy, BJ; Barbu-Tudoran, L; Bocirnea, AE; dos Santos, IM; Alves, MCF; de Oliveira, ALM

Published: 2025 MAY 20 2025, CHEMISTRY OF MATERIALS, DOI: 10.1021/acs.chemmater.4c03146

This study presents annealing time variation as an alternative approach for tuning structural and ionic defects in SnO2 nanoparticles (NPs) synthesized by a modified Pechini method, to modulate charge transfer and the formation of reactive oxygen species (ROS), enabling a correlation of these with photocatalytic activity. Structural refinements of the X-ray diffraction (XRD) data, combined with Raman and infrared (IR) spectroscopy, revealed that the samples adopted a tetragonal P42/mnm symmetry, with a distinct short-range structural order (associated with intraoctahedral [SnO6] distortions), which strongly depends on the annealing time. Field emission scanning electron microscopy (FE-SEM), scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (STEM/EDX), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) analyses showed the formation of homogeneous NPs smaller than 50 nm in the SnO2 samples, with a surface area between 12.072 and 14.102 m2 g-1. The presence of unusual reduced Sn3+ species associated with oxygen vacancies (VO) was evidenced by electron paramagnetic resonance (EPR) spectroscopy, and Sn2+ was characterized by Sn MNN Auger electron emission. The amount of these defects also depends on the annealing time. The synergistic effect and the photocatalytic mechanism were then elucidated. The degree of intraoctahedral [SnO6] distortions and the amounts of Sn3+:VO defects play a fundamental role in the charge transfer mechanism to modulate ROS generation during photoexcitation, as indicated by the photohydroxylation of terephthalic acid (TA) and in situ spin-trapping EPR measurements. Specifically, we show the formation of two main ROS, center dot OOH and center dot OH, which leads to a different photocatalytic pathway in SnO2 NPs. In conclusion, our study enlightens and uncovers the importance of choosing appropriate conditions for materials processing to fine-tune structural and electronic properties to design other functional materials.

61. Detection and Selective Sorption of Copper Ions by a COF-Modified Melamine Sponge

Authors: Bika, P; Ioannidis, N; Tsipas, P; Papagiannis, S; Gatou, MA; Pavlatou, EA; Karydas, AG; Stergiopoulos, T; Dallas, P

Published: MAY 21 2025, ACS OMEGA, 10, DOI: 10.1021/acsomega.5c01393

Commercial melamine sponges were modified with a functional covalent organic framework (COF), and they were evaluated as adsorbents of divalent copper cations from aqueous solutions. A phosphazene unit successfully covered the surface of the melamine sponge, and the organic framework was subsequently formed through the nucleophilic substitution with 4,4 ' bipyridine. The covalent organic framework functionalized on the melamine sponge can detect and effectively adsorb copper compounds in aqueous solutions. Its selectivity toward the adsorption of copper was demonstrated through the presence of different metal salts. Four competitive metal cations, i.e., copper, nickel, iron, and calcium, were selected to confirm the preferential binding of copper on the COF-functionalized sponge. The outcome was determined through the studies of X-Ray Fluorescence elemental analysis, X-Ray Photoelectron Spectroscopy (XPS), and Electron Paramagnetic Resonance experiments. XRF reported a copper sorption capacity of 293 mu g cm-2, which is nearly nine times higher than the performance of the pristine sponge. Q-band EPR measurements demonstrated the presence of different coordination sites with different substituents for copper on the modified sponges, when the adsorption took place in an aqueous solution containing exclusively copper cations, while only one coordination, the favorable trigonal bipyramidal geometry, was obtained in the presence of additional metals.

Open Access

62. Experimental and theoretical perspective on band gap modulation in Sr modified BaTiO3 capacitors ²⁺

Authors: Zidi, Y; Khaldi, O; Patru, RE; Leonat, LN; Enculescu, M; Toma, V; Stepanova, A; Ben Younes, R; Galca, AC

Published: MAY 2025, CERAMICS INTERNATIONAL, 51, DOI: 10.1016/j.ceramint.2025.01.591

The present study investigates the influence of strontium (Sr) content on the intrinsic properties of barium strontium titanate (Ba1-xSrxTiO3, BST) which was successfully prepared by the conventional solid-state reaction with different concentrations of strontium (x = 0, 0.3, 0.5, 0.6, 0.7, 1). The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and diffuse reflectance spectroscopy, the dielectric properties being also investigated. Structural and vibrational analyses reveal a structural phase transition from tetragonal to cubic at x = 0.4, with a linear decline of the tetragonality ratio as well as a shrinkage in the unit cell volume that occur with increasing Sr content. The morphological study shows that the grain size decreases as the Sr content increases in the tetragonal phase. Yet, upon the phase transition from tetragonal to cubic, the grain size initially increases, followed by a subsequent decrease with further Sr addition. It has been found that the band gap shows a decrease as Sr content increases. The temperature dependence of the dielectric parameters reveals that the Curie temperature as well as the dielectric constant and the loss tangent are strongly affected by the addition of Sr. The activation energy derived from the dielectric response, was found to be in the range 0.685-1.065eV, suggesting the dominance of doubly ionized oxygen vacancy for conduction and relaxation mechanism. Ab initio calculations were done employing the Linear Combination of Atomic Orbitals (LCAO) method. The bandgap energy (Eg) and the structural parameters were calculated using various types of exchange-correlation functionals (PWGGA, PBE, B3LYP and PBE0). A good agreement with the experimental results is achieved using the PBE0 functional. This study contributes to a better understanding of the structure-property relationship in BaSrTiO3 and provides valuable insights for optimizing its performance in various technological applications.

Open Access

63. Microwave surface resistance in MgB2: Effect of Te and cubic-BN addition on flux flow and pinning

Authors: Alimenti, A; Silva, E; Torokhtii, K; Garcia, PV; Badica, P; Crisan, A; Grigoroscuta, MA; Pompeo, N

Published: JUN 2025, SUPERCONDUCTIVITY, 14, 100170, DOI: 10.1016/j.supcon.2025.100170

MgB2 is a perspective superconductor for many power applications. How this potential refers also to microwave or radiofrequency applications is still to be determined. Although its ultimate surface resistance in zero field is not competitive with conventional metallic superconductors, its strong pinning properties can favor RF applications in a dc magnetic field. Nonetheless, the RF response in the vortex state has been relatively less studied, as well as the effect of artificial pinning centers on the microwave surface resistance in the mixed state. In this paper we study the surface resistance of spark-plasma-sintered MgB2, with and without Te and cubic-BN (cBN) addition, in a dc magnetic field up to 1.2 T. We summarize previous results on pure MgB2, and we present new data on Te-and cBN-added MgB2. We use a two-tone dielectric-loaded resonator to measure the field-dependent surface resistance at 16.5 and 26.7 GHz in the temperature range from 10 K to T. By exploiting the simultaneous measurements at two frequencies, we extract the flux-flow resistivity, the pinning constant kp and the depinning frequency fp. The two-band nature of MgB2 affects the field dependence of the flux-flow resistivity. The microscopic superconducting state is not affected by the addition of artificial pinning centers, indicating that Te and cBN do not affect interband or intraband scattering. Pinning shows a measurable trend towards an increase in the Te-and cBN-added samples at higher temperatures and fields. We finally compare the results to those obtained in bulk Nb3Sn, also in view of possible in-field RF applications such as microwave cavity-based haloscopes.

64. APPLICATION OF SPECTRAL GAMMA-RAY LOGS TO DETERMINE THE LITHOFACIES AND DEPOSITIONAL ENVIRONMENT OF THE LAM MEMBER, HABBAN OILFIELD, SAB'ATAYN BASIN (Yemen)

Authors: Al-Azazi, NAS; Abudeif, AM; Mohammed, MA; Albaroot, MA; Alarifi, N; Bellucci, S; Basrada, FMQ; Masoud, MM

Published: 2025 MAY 25 2025, RUSSIAN GEOLOGY AND GEOPHYSICS, DOI: 10.2113/RGG20254854

The study of spectral gamma-ray logs plays a critical role in understanding the lithofacies and depositional environments of subsurface geologic formations. This research focuses on the Lam Member within the Habban oilfield, located in the Sab'atayn Basin, Yemen. By integrating spectral gamma-ray data with core analysis and other geological datasets, this study aims to provide insights into the stratigraphic distribution, mineral composition, and depositional processes of the Lam Member. Key parameters, such as thorium, uranium, and potassium concentrations, recorded from two wells were analyzed to infer sedimentary characteristics and environmental conditions. The results reveal significant lithologic heterogeneity and suggest a complex interplay of fluvial and marine depositional systems, enhancing the understanding of the basin petroleum potential. The Lam Member comprises interbedded carbonate (dolomite) and claystone with intercalated sandstone. Spectral gamma-ray results indicate that clay minerals primarily consist of mixed-layer clays, chlorite, kaolinite, and minor illite. Based on the Th/U ratio (less than 2), the depositional environment is identified as marine.

65. Thermally Interpenetrated Co-Ni Mixed Oxide as Efficient Oxygen Evolution Electrodes

Authors: Mihai, MA; Preda, L; Negrila, C; Somacescu, S; Becherescu, ND; Velea, A; Zaki, MY; Spataru, N

Published: JUL 2025, ELECTROCATALYSIS, 16, DOI: 10.1007/s12678-025-00956-4

Electrochemical water splitting is regarded as a viable solution to future energy demands. Considering this, an innovative method to produce efficient oxygen evolution electrodes based on Co and Ni was proposed and successfully developed, where the metal atoms are intimately mixed before the calcination treatment. Electrochemical measurements demonstrated the high oxygen evolution activity and stability of the thus synthesized electrodes, EDX, and XPS revealing that the surface exhibits a remarkable oxidation resistance, allowing the active phase to better maintain its state when subjected to the aggressive positive potential required for oxygen evolution. Moreover, low electrical resistivity was recorded as a result of reduced thickness of the catalytic layer, further increasing the efficiency. These findings provide new insights into the design of durable and high-performance OER electrodes.

Open Access

66. Influence of in-situ hydrogenation on photoelectrical properties of amorphous and nanocrystalline GeSn deposited by magnetron sputtering

Authors: Dascalescu, I; Palade, C; Lungu, GA; Lepadatu, AM; Teodorescu, VS; Braic, M; Ciurea, ML; Stoica, T; Slav, A

Published: JAN 5 2025, JOURNAL OF ALLOYS AND COMPOUNDS, 1010, 177065, DOI: 10.1016/j.jallcom.2024.177065

This study investigates the fabrication of short-wavelength infrared (SWIR) photosensitive amorphous and nanocrystalline Ge1-xSnx:H thin films by magnetron sputtering from separate Ge and Sn targets using different Ar: H mixing ratios as working gas. Amorphous Ge1-xSnx:H films have been obtained on both c-Si and fused quartz substrates at ambient temperature, while dynamic nanocrystallization occurs in-situ when the substrate temperature during deposition is raised to 200 degrees C. Fourier-transform infrared spectroscopy has shown the hydrogen incorporation by detecting an absorption line at 1873 cm(-1), close to the value corresponding to Ge-H bonding, only in the room temperature amorphous films. Based on that, we infer that the hydrogen concentration is very low in the films deposited at high temperature. The higher concentration of hydrogen in the amorphous samples is associated with an increase of the absorption gap to 0.5 eV compared to 0.3 eV in the 200 degrees C samples. In-situ (during deposition) and ex-situ (by subsequent rapid thermal annealing) nanocrystallization have been analyzed by high-resolution transmission electron microscopy, X-ray diffraction and micro-Raman spectroscopy. SWIR spectral photosensitivity up to 2.4 mu m was found to be more than two orders of magnitude improved in hydrogenated amorphous films with high hydrogen content, compared to the nanocrystalline ones that are weakly hydrogenated. These findings demonstrate the potential of hydrogenation to enhance the photoelectric properties of GeSn sputtering films for optoelectronic SWIR infrared applications.

67. Influence of Shale on Petrophysical Properties and Reservoir Quality: Insights from the Matulla Formation, Saqqara Field, Gulf of Suez, Egypt

Authors: Abudeif, AM; Mohammed, MA; Masoud, MM; Radwan, AE; Alarifi, N; Bellucci, S; Tawfik, FA

Published: 2025 APR 23 2025, PURE AND APPLIED GEOPHYSICS, DOI: 10.1007/s00024-025-03711-4

This study examines the impact of shale volume (Vsh) and clay mineral distribution on the petrophysical properties and reservoir quality of the Matulla Formation in the Gulf of Suez, a critical factor in global hydrocarbon exploration and production. Understanding how shale affects porosity, permeability, and fluid saturation enhances reservoir characterization, optimizing recovery techniques such as hydraulic fracturing and sustainable resource management. The evaluation process involved calculating shale volume using the neutron-density method, with values ranging from 1.9% to 11% across four wells (GS323-1, GS323-2A, GS323-3, GS323-4A). Clay minerals have been identified through Potassium-Thorium (K-Th) cross-plot include chlorite, illite, kaolinite, montmorillonite, and mixed-layer clays. Montmorillonite and chlorite negatively impact porosity and permeability, while kaolinite and illite improve hydrocarbon retention. Shale distribution analysis using the Thomas and Stieber model showed both laminated and dispersed forms, where laminated shales had minimal blockage, and dispersed clays significantly reduced the reservoir quality. Results reveal that wells with low Vsh (GS323-1 and GS323-4A) which ranges from 1.5 to 2% exhibit excellent reservoir quality, with high porosity (14%), high permeability (317-320.7 mD), and low water saturation (32-44%). Moderate Vsh wells (GS323-2A) show reduced porosity (13%), permeability (220 mD), and increased water saturation (46%), reflecting good but diminished quality. High Vsh well (GS323-3) display lower porosity (12%), permeability (140 mD), and moderate water saturation (37%), indicating challenges in fluid flow. This study highlights the need for tailored strategies to mitigate high shale content and swelling clays, offering valuable insights into optimizing hydrocarbon exploration and production in shale-influenced reservoirs worldwide.

Open Access

68. Cells proliferation on surfaces functionalized with amyloid beta peptide fibrils

Authors: Beregoi, M; Nistor, S; Ciobotaru, IC; Nitescu, A; Zgura, I; Bunea, MC; Enculescu, M; Nedelcu, L; Busuioc, C; Enache, TA

Published: MAY 2025, INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES, 309, 143160, DOI: 10.1016/j.ijbiomac.2025.143160

Amyloid beta (A(3) peptide aggregates are well-established biomarkers for Alzheimer's disease, though the complete etiology of this disorder remains elusive. Developing biointerfaces to elucidate the physiological roles of these peptides is essential. This study investigates the aggregation, fibrillation, and interaction of A(3 peptides with conductive, biocompatible nanostructured materials designed for applications involving neuronal cells. Various conductive, rigid, and flexible surfaces, both functionalized and non-functionalized with A(340 fibrils, were fabricated. These included glass substrates and poly(methyl methacrylate) electrospun fiber networks coated with gold via magnetron sputtering. The substrates were also functionalized through physical adsorption with poly-L-lysine and collagen, known to support cell proliferation, as well as with the inverse-A(340 peptide and an Amyloid Protein Non-A(3 Component, and the results were compared. The scaffolds were characterized using scanning electron microscopy, X-ray diffraction, atomic force microscopy, contact angle and electrical measurements, while their biological interactions were assessed using MTS assays, fluorescence imaging, and scanning electron microscopy. Fibroblast L929 and neuroblastoma SH-SY5Y cell lines were used as models, with results indicating an elevated cell viability, comparable to the control. The developed nanostructured surfaces are highly promising for integration into advanced neuromorphic engineering devices, as they have proven capable of maintaining their structural integrity when exposed to proteases.

69. Synthesis and photocatalytic activity of WO3 nanocomposites incorporating GO and MWCNTs for enhanced Rhodamine-B degradation

Authors: Hatel, R; Boukhoubza, I; Derkaoui, I; Kabatas, MABM; Matei, E; Enculescu, M; Baitoul, M

Published: APR 20 2025, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 711, 136395, DOI: 10.1016/j.colsurfa.2025.136395

In this study, we developed a ternary nanocomposite using graphene oxide (GO), multiwalled carbon nanotubes (MWCNTs), and tungsten trioxide (WO3), nanostructures, synthesized via a straightforward chemical process with ultrasound assistance. The initial composition was GO/MWCNT, later combined with WO3 to form the GO/ MWCNT: WO3 (25/25:50) structure. Characterization was performed using X-ray diffraction, which revealed the multiphase nature of the WO3 nanostructures. Scanning Electron Microscopy showed the one-dimensional CNTs interwoven with graphene oxide sheets decorated with densely populated WO3 nanopetals. Fourier transform infrared and Raman spectroscopy confirmed the chemical composition of the system. The photocatalytic degradation of Rhodamine-B in water under visible light irradiation was significantly enhanced using the GO/

Open Access

70. Charge Transfer-Driven Conversion of Molecular Oxygen to Doublet State on Vanadium Diselenide (VSe2) Surface at Room Temperature

Authors: Boukhvalov, DW; Stefan, M; Joita, AC; Kuo, CN; Lue, CS; Politano, A

Published: MAR 2025, ADVANCED MATERIALS INTERFACES, 12, DOI: 10.1002/admi.202400656

Oxygen in the excited state is essential for organic synthesis and medical treatment. Herein, a novel phenomenon is reported in which the magnetic ground state of molecular oxygen undergoes a transition at room temperature from S = 1 to S = 1/2, corresponding to the transition of O2 from a triplet to a doublet state after stable physical adsorption on the defect-free surface of bulk VSe2. This density functional theory (DFT) calculations demonstrate the stable physical adsorption of O2 on both 1T- and 2H-VSe2 surfaces without further decomposition. Electron spin resonance (ESR) measurements confirm the spin state transition. Theoretical simulations reveal the charge transfer from entangled V-3d and Se-4p bands to oxygen as the leading cause of the spin state transition. This mechanism has not been previously proposed and offers multiple potential applications, from organic synthesis to medicine. Moreover, this approach can be extended to reveal new aspects of known catalytic materials and to design novel catalysts.

Open Access

71. Distortion of charge carrier trapping centers during incipient phase transformations in TiO2 can enhance its photocatalytic performance

Authors: Iacoban, AC; Rostas, AM; Mihalcea, CG; Vlaicu, ID; Culita, D; Ilas, MC; Florea, M; Neatu, S; Neatu, F; Secu, M; Popescu, T

Published: MAR 5 2025, JOURNAL OF ALLOYS AND COMPOUNDS, 1018, 179097, DOI: 10.1016/j.jallcom.2025.179097

Most photocatalytic processes involve physicochemical phenomena occurring at the semiconductor-water interface. The interfacial charge transfer strongly depends on the charge carrier self-trapping or defect-based trapping mechanisms active in the crystal lattice of the photocatalyst. Thus, the crystal lattice distortion is expected to influence the photocatalytic efficiency during polymorphic phase transformations (PPT). A simple synthesis method involving the ultrasound-assisted excess hydrolysis of titanium tetra-isopropoxide (TTIP) (hydrolysis ratio (number of moles of water/number of moles of TTIP) r = 245) was used to obtain multiphase titanium dioxide (TiO2) nanomaterials with complex defect structures. Electron paramagnetic resonance (EPR) spectroscopy was employed to characterize the paramagnetic centers in the synthesized TiO2 and their behavior during incipient PPT. The calcined samples showed a complex defect structure comprising three types of paramagnetic centers: F+-centers (an electron trapped in an oxygen vacancy (Ov)), V-centers (oxygen ions with trapped holes) and paramagnetic centers involving Ti3+ such as Ti3+- Ov. The sample obtained at 600 degrees C, temperature marking the onset of a massive mixed transformation of anatase into rutile and brookite, composed of approximately 81 % anatase, 10 % brookite, and 9 % rutile, exhibited an intense and broadened EPR signal and enhanced photocatalytic activity for hydroxyl radical generation and hydrogen production by water splitting, despite its rather low specific surface area of 34 m2/g. The results revealed the synergistic effects of charge carrier trapping mechanisms in the early stages of PPT, boosting the photocatalytic performance of TiO2. The present study supports the design of facile synthesis methods for better TiO2 photocatalysts and promotes the development of further studies regarding lattice defect engineering during phase transformations in nanomaterials.

72. Ce-doped ZnO photoanode with enhanced photoelectrochemical performance

Authors: Sima, M; Preda, N; Negrila, C; Matei, E; Sima, A; Stancu, V

Published: MAR 31 2025, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 114, DOI: 10.1016/j.ijhydene.2025.03.048

Photoanodes based Ce-doped ZnO nanorods arrays were prepared by hydrothermal method in order to improve photoelectrochemical efficiency of ZnO photoanodes in water splitting process. Scanning electron microscopy investigation showed ZnO based nanorods with length of around 500 nm and different thicknesses and growth directions. Some morphological changes were noted following the thermal treatment. Energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy measurements proved the presence of cerium species both in bulk and on the surface of ZnO nanorods. A current density of 2.44 mA/cm(2) at 1.23 V against the reversible hydrogen electrode (0.265 V vs. Ag/AgCl) was obtained for Ce-doped ZnO sample, which is >162% increase over that of ZnO sample. The increased photocurrent value obtained for this sample was correlated with the passivation of surface defects evidenced by photoluminescence study and the increased concentration of Ce3+ on the surface. Also, the electrochemical impedance spectroscopy measurements suggested that Ce doping improves the charge transfer in bulk.

73. Growth of pyramidal nanostructures in CeO2-x thin films: Characterization and morphology modeling

Authors: Craciun, C; Bercea, A; Radu, C; Stîngescu, ML; Bonciu, A; Satulu, V; Filipescu, M

Published: OCT 1 2025, APPLIED SURFACE SCIENCE, 705, 163499, DOI: 10.1016/j.apsusc.2025.163499

Cerium dioxide (CeO2) thin films with pyramidal nanostructures exhibiting a fractal aspect are suitable for various applications that require a large surface area. An accurate model of these films is valuable not only for optimizing the properties for specific applications but also for predicting and understanding the growth mechanism. In this paper, we present the foundation of a simulation for the growth of CeO2-x nanostructured thin films. We propose a 3-dimensional model of the surface nanostructures and link the morphology with crystallographic orientations and growth modes. To validate our model, we fabricated CeO2_ x thin films with different thicknesses using pulsed laser deposition (PLD) and characterized their morphological and structural properties. The evolution of our films shows the representative features of the Stranski-Krastanov model. The morphology changes from compact and smooth to dendritic with pyramidal nanostructures. The texture of our film also changes with thickness, and the preferential orientations are (111) and (220). Additionally, we characterize the CeO2_ x thin films from the chemical and optical points of view. The stoichiometry of CeO2 is not fully achieved, our thin films present the Ce3+ oxidation state at the surface. The formation of C-type Ce2O3 with fluorite structure can be associated with a small refractive index and small band gap.

Open Access

74. Composites of Titanium-Molybdenum Mixed Oxides and Non-Traditional Carbon Materials: Innovative Supports for Platinum Electrocatalysts for Polymer Electrolyte Membrane Fuel Cells

Authors: Ayyubov, I; Talas, E; Borbáth, I; Pászti, Z; Silva, C; Szegedi, A; Kuncser, A; Yazici, MS; Sajó, IE; Szabó, T; Tompos, A

Published: JUN 2024, NANOMATERIALS, 14, 1053, DOI: 10.3390/nano14121053

TiO2-based mixed oxide-carbon composite support for Pt electrocatalysts provides higher stability and CO tolerance under the working conditions of polymer electrolyte membrane fuel cells compared to traditional carbon supports. Non-traditional carbon materials like graphene nanoplatelets and graphite oxide used as the carbonaceous component of the composite can contribute to its affordability and/or functionality. Ti(1-x)MoxO2-C composites involving these carbon materials were prepared through a sol-gel route; the effect of the extension of the procedure through a solvothermal treatment step was assessed. Both supports and supported Pt catalysts were characterized by physicochemical methods. Electrochemical behavior of the catalysts in terms of stability, activity, and CO tolerance was studied. Solvothermal treatment decreased the fracture of graphite oxide plates and enhanced the formation of a reduced graphene oxide-like structure, resulting in an electrically more conductive and more stable catalyst. In parallel, solvothermal treatment enhanced the growth of mixed oxide crystallites, decreasing the chance of formation of Pt-oxide-carbon triple junctions, resulting in somewhat less CO tolerance. The electrocatalyst containing graphene nanoplatelets, along with good stability, has the highest activity in oxygen reduction reaction compared to the other composite-supported catalysts.

Open Access

75. The Effect of Loading W&V:TiO2 Nanoparticles with Noble Metals for CH4 Detection

Authors: Scarisoreanu, M; Constantinoiu, I; Goncearenco, E; Morjan, IP; Teodorescu, VS; Viespe, C

Published: AUG 2024, CHEMOSENSORS, 12, 160, DOI: 10.3390/chemosensors12080160

TiO2 nanoparticles (NPs) doped with W (W:TiO2), double-doped with W and V (W&V:TiO2), and loaded with noble metals (W:TiO2 @Pt/Pd/Ag and W&V:TiO2@Pt/Pd/Ag) were synthesized by laser pyrolysis followed by chemical impregnation and reduction. Due to its exceptional properties, TiO2 is considered a key material being used in a wide range of applications. To improve its detection activity, the increase in the specific surface of the material, and the presence of defects in its structure play a decisive role. Doped and double-doped TiO2 nanoparticles with dimensions in the range of 25-30 nm presented a mixture of phases corresponding to titania, with the anatase phase accounting for the majority (95%). By loading these nanoparticles with small particles of noble metals, a significant increase in the specific surface area by three or even five times the original values was achieved. Sensitive thin films for surface acoustic wave (SAW) sensors were made with the NPs, embedded in polyethyleneimine (PEI) polymer and deposited by spin-coating. Each sensor was tested at CH4 concentrations between 0.4 and 2%, at room temperature, and the best results were obtained by the sensor with NPs doped with V and decorated with Pd, with a limit of detection (LOD) of 17 ppm, due to the strong catalytic effect of Pd.

76. Tri-layered Si/Co3O4/ZnO heterojunction for high-performance visible photodetection

Authors: Domingues, L; Jayakrishnan, AR; Kaim, A; Gwozdz, K; Istrate, MC; Ghica, C; Pereira, M; Castro, A; Marques, L; Hoye, RLZ; MacManus-Driscoll, JL; Silva, JPB

Published: JUN 20 2024, JOURNAL OF MATERIALS CHEMISTRY C, 12, DOI: 10.1039/d4tc01624f

Tri-layered heterojunction devices based on oxide thin films are attracting significant attention for ultra-fast visible photodetection. However, the responsivity of these devices is still low. In this work, high performance photodetectors based on a tri-layered heterojunction of n-Si/p-Co3O4/n-ZnO were fabricated. Under no applied bias, a maximum responsivity and detectivity of 14.2 mA W-1 and 1.34 x 10(12) Jones were achieved respectively, for a power density of 9.35 mW cm(-2). Remarkably, a significant increase in the responsivity of approximately 864% was found when the device was biased at -2 V. This effect is understood based on the coupling of the photovoltaic and pyroelectric effects. Also, upon applying an external bias of -2 V, at a laser power density of 9.35 mW cm(-2) and at a chopper frequency of 10 Hz, the device exhibits a detectivity and sensitivity of 3.4 x 10(11) Jones and 2.2, respectively, together with a rise and fall time of 4 and 2 mu s, respectively. Compared to high performance Al/Si/SnO/ZnO/ITO and Au/pCuI/ZnO devices, our voltage-biased Al/Si/Co3O4/ZnO/ITO devices exhibit a >40% increase in R and >10x higher D*. Furthermore, an important advantage of our PDs is the p-type component, Co3O4, which is more stable and stoichiometric than CuI and SnO, ensuring PD performance that is stable with time. Therefore, n-Si/p-Co3O4/n-ZnO heterojunction devices shows great promise for ultrafast visible photodetection.

77. Enhancing Short-Wave Infrared Photosensitivity of SiGe Nanocrystals-Based Films through Embedding Matrix-Induced Passivation, Stress, and Nanocrystallization

Authors: Lepadatu, AM; Stavarache, I; Palade, C; Slav, A; Dascalescu, I; Cojocaru, O; Maraloiu, VA; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: MAR 4 2024, JOURNAL OF PHYSICAL CHEMISTRY C, 128, DOI: 10.1021/acs.jpcc.3c06996

The development of new materials for short-wavelength infrared (SWIR) optical sensors is of high importance for the fast development of different applications, as, for example, Internet of Things, road safety, and pollution monitoring. Group IV SiGe provides more sustainable As-, Cd-, and Pb-free nanomaterials that are cheaper and ecologic and offer easy integration with CMOS technology. This Review is on Ge and SiGe quantum dots/nanocrystals (QDs/NCs) embedded in dielectrics for VIS-SWIR photodetection, in which we highlight and discuss photocurrent mechanisms, correlation of photodetection parameters and characteristics with crystalline structure, morphology and energy bandgap, and applications as photodetectors, optical sensors, phototransistors, and solar cells. The embedding matrix induces NC surface passivation, stress field, and nanocrystallization effects and brings specific advantages depending on the matrix material. SiGe NCs in oxides for VIS-SWIR sensing represents a niche domain, showing high photosensitivity (photocurrent) in SWIR up to 1.8 mu m at room temperature and 2 mu m at 100 K, deeper in SWIR than Ge. By alloying Ge with a small content of Si, NC thermal stability is much improved as the detrimental Ge fast diffusion in oxides is hindered and SWIR photosensing is enhanced due to light absorption in Ge-rich SiGe NCs.

78. Nitrogen-Doped WO3 Nanoparticles as Electrode Materials in All-in-One Supercapacitor Devices

Authors: Ammar, AU; Popa, A; Toloman, D; Macavei, S; Ciorita, A; Bocirnea, AE; Stan, M; Erdem, E; Rostas, AM

Published: JAN 10 2024, ACS APPLIED ENGINEERING MATERIALS, 2, DOI: 10.1021/acsaenm.3c00654

The effect of the annealing temperature on 1% nitrogen-doped WO3 materials was studied, which were then used as electrode materials for high-performance supercapacitor (SC) devices. The supercapacitive performance of the proposed materials was strongly influenced by the doping element and the annealing temperature by directly changing the defect structure of the host material. The 1% N-doped WO3 materials annealed at different temperatures were thoroughly characterized through various characterization techniques, including electron paramagnetic resonance and photoluminescence spectroscopy, giving insight into the effect of N-doping on the defect structure and optical properties of WO3. When the WO3:N materials were used as electrode material in symmetric SCs, the doping element and the annealing temperature improved the electrochemical performance. No booster materials (such as carbon black) were used in the symmetric SC designs, showing increased specific capacitance (102 F/g) and energy density (14.6 W h/kg) values.

Open Access

79. Controlling the optoelectronic properties of nitrogen-doped carbon quantum dots using biomass-derived precursors in a continuous flow system

Authors: Nguyen, KG; Hus, M; Baragau, IA; Puccinelli, E; Bowen, J; Heil, T; Nicolaev, A; Andrews, D; Sajjad, MT; Dunn, S; Kellici, S

Published: NOV 2024, CARBON, 230, 119623, DOI: 10.1016/j.carbon.2024.119623

The synthesis of carbon quantum dots (CQDs) from high molecular weight biomass-derived precursors poses a significant challenge due to the complex molecular structures and low conversion efficiency. This work demonstrates a green, rapid, and sustainable continuous hydrothermal flow synthesis (CHFS) approach for nitrogen-doped carbon quantum dots (NCQDs) from various biomass-derived precursors, including high molecular weight polymeric sources like chitosan, lignin, and humic acid. We find that the precursor structure significantly impacts the size of the fabricated NCQDs and their optical properties. Citric acid, a low molecular weight precursor, yields NCQDs with excitation-independent emission, higher quantum yields, and low non-radiative losses, while NCQDs derived from polymeric precursors exhibit excitation-dependent, red-shifted, and lower efficiency emission. Theoretical calculations, performed to understand the configuration and distribution of nitrogen dopants within the NCQD structure, show that pyridinic and graphitic nitrogen atoms exhibit a strong preference to aggregate near the centre of the edge of the NCQD and not in the vertices nor in the graphitic core, thus affecting the HOMO and LUMO, bandgap, and light absorption and emission wavelengths. The life cycle assessment (LCA) analysis highlights the green and scalable advantages of the CHFS process for producing NCQDs compared to batch methods, making it a sustainable and economically viable approach for large-scale NCQD synthesis from high molecular weight biomass-derived precursors. Hence, the combination of experimental data and theoretical calculations provides a comprehensive understanding of the structure-property relationships in these NCQDs.

80. Ce-doped MgO films on AZ31 alloy substrate for biomedical applications: preparation, characterization and testing

Authors: Hattab, M; Ben Hassen, S; Spriano, S; Ferraris, S; Cernea, M; Ben Amor, Y

Published: MAR 1 2024, BIOMEDICAL MATERIALS, 19, 025013, DOI: 10.1088/1748-605X/ad1dfa

Magnesium ions, MgO nanoparticles and thin films, magnesium alloys and cerium compounds are materials intensively studied due to their corrosion protection, antibacterial and pharmacological properties. In this work, we have designed, prepared and investigated, novel thin films of MgO doped with cerium, deposited on Mg alloy (AZ31) for temporary implants, in order to enhance their life time. More precisely, we report on microstructure and corrosion behavior of MgO pure and doped with 0.1 at % Ce films, fabricated by sol-gel route coupled with spin-coating technique, on AZ31 alloy substrate. A modified sol-gel method that start from magnesium acetylacetonate, cerium nitrate and 2-methoxyethanol (as a stabilizer for the sol) was been used successfully for cerium doped MgO sol precursor preparation. The structure and morphology of the surface of the coatings, before and after immersion for 7-30 d in Hank's solution at 37 degrees C, were characterized by x-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscope, x-ray photoelectron spectroscopy and Fourier infrared transmittance spectrum (FT-IR). A comparison between the corrosion protection of undoped MgO and MgO doped with 0.1 at % Ce coatings on the AZ31 alloy substrate is performed by electrochemical tests and immersion tests using open circuit potential and electrochemical impedance spectroscopy in Hank's solution, at 37 degrees C. The electrochemical results showed that the protection of the AZ31 alloy substrate against corrosion was better with the doped with 0.1 at % Ce MgO film deposited than with pure MgO coting. The investigations of the films after immersion in Hank's solution, at 37 degrees C, for 7, 21 and 30 d indicated that the grown layer on the film is bone like apatite that suggests a good bioactivity of 0.1 at % Ce-doped MgO coating. Our work demonstrates that the performance corrosion protection of the biodegradable magnesium alloys used for orthopedic applications, in simulated physiological environments (Hank and Ringer) can be enhanced through coating with Ce3+ doped MgO sol-gel thin film.

81. ASSESSING THE COMBINED EFFECTS OF CHEMICAL AND MECHANICAL PARAMETERS ON SILAR-GROWN NANOSTRUCTURED ZnO THIN FILMS

Authors: Ydir, B; Ajdour, A; Soumane, M; Achouch, S; Ben Hmamou, D; Antohe, I; Socol, G; Toderascu, LI; Socol, M; Luculescu, C; Leghrib, R; Lahlou, H

Published: 2024, ROMANIAN REPORTS IN PHYSICS, 76, 508, DOI: 10.59277/RomRepPhys.2024.76.508

In the literature, a comprehensive assessment of the combined impacts of chemical and mechanical parameters on the properties of thin films grown by SILAR is missing. In this work, ZnO film formation is investigated under variable precursor concentration, pH, withdrawal speed and number of cycles. Interestingly, the produced ZnO films displayed remarkable aspect ratio and morphological variability, ranging from the commonly obtained nanograins shape towards hexagonal nanorods, flowerlike rods and nanoneedles, which to our knowledge have not yet been achieved by using single step SILAR process. More particularly, low concentration and intermediate pH and withdrawal rates were favorable for nanorods formation. In addition, increasing the withdrawal speed from 26 to 30 cm<middle dot>min(-1 )resulted in a thinner film with improved rod uniformity and reduced crystallite size. This is the first study on the impact of substrate withdrawal speed on SILAR films. Among all studied parameters, the number of cycles was particularly useful for tuning film thickness, while preserving its target shape. In addition, the films grown under a higher number of cycles showed improved film crystallinity and rod orientation with reduced dislocation density, microstrain and bandgap energy. In our conditions, the most suitable combination of parameters required for exhibiting optimized nanorod-shaped coating are: a concentration of 0.07 M, pH of 10.5, speed of 30 cm<middle dot>min(-1 ) and 40 cycles. In this case, XRD, XPS, Raman and FTIR spectra displayed typical features of hexagonal Wurtzite structure of ZnO with no impurities within the film surface, whereas AFM measured a thickness of 1.4 mu m with 243 nm surface roughness.

82. Insights into Large-Scale Synthesis of Benfotiamine

Authors: Hanganu, A; Maximov, M; Maximov, OC; Popescu, CC; Sandu, N; Florea, M; Mirea, AG; Gârbea, C; Matache, M; Funeriu, DP

Published: OCT 14 2024, ORGANIC PROCESS RESEARCH & DEVELOPMENT, 28, DOI: 10.1021/acs.oprd.4c00351

There has been increased interest in the synthesis of benfotiamine during the past few years, most likely as a direct consequence of growing market demand. It has much higher bioavailability than thiamine (vitamin B1) and therefore is more suitable for therapeutic purposes, especially in oral form. We report herein our research in an academic-private R&D project in which we investigate all aspects of the process on small and large scales. The procedure involves two labor-intensive steps, starting from thiami3ne chloride hydrochloride with the key intermediate thiamine monophosphate phosphate (TMP-the phosphate ester of thiamine monophosphate). We obtained the crystalline form of benfotiamine directly from the synthesis in the crystalline form required on the market, as proven by XRD powder spectroscopy, IR, and RAMAN.

Open Access

83. Strategies to improve CO tolerance and corrosion resistance of Pt electrocatalysts for polymer electrolyte membrane fuel cells: Sn-doping of the mixed oxide-carbon composite support

Authors: Borbáth, I; Salmanzade, K; Pászti, Z; Kuncser, A; Radu, D; Neatu, S; Tálas, E; Sajó, IE; Olasz, D; Sáfrán, G; Szegedi, A; Florea, M; Tompos, A

Published: AUG 1 2024, CATALYSIS TODAY, 438, 114788, DOI: 10.1016/j.cattod.2024.114788

Design of composite support materials based on Sn-doped TiO2 and carbon is one of the strategies to develop corrosion-resistant and CO-tolerant Pt electrocatalysts for polymer electrolyte membrane (PEM) fuel cells. As the synthesis methodology may have crucial influence on the structural and functional properties of the composites, different preparation routes for the novel support materials are explored and compared. Ti(1-x)SnxO2-C (x: 0.1-0.3) composites with different mixed oxide/carbon ratios were prepared by two sol-gel-based synthesis routes, namely (i) the introduction of a Sn precursor after the formation of the TiO2-rutile nuclei on the carbon backbone (route A), and (ii) simultaneous introduction of Ti and Sn precursors, resulting in good mixing of the Sn- and Ti-sol before the addition of the carbon (route B). The bulk and surface microstructure of the composites and the electrocatalysts obtained by their Pt-loading were investigated in detail. The incorporation of tin into the TiO2-rutile unit cell was confirmed by X-ray powder diffraction and Raman spectroscopy; the results indicated doping levels in good accordance with the amount of tin precursor. The advantages of composites and Pt electrocatalysts obtained via synthesis route B were that they do not contain segregated Sn-0 or SnO2 phases, have a more homogeneous/uniform mixed oxide distribution over the carbon backbone, and the electrochemically active surface area values (similar to 60-80 m(2)/g(Pt)) are twice as high as those of catalysts with similar compositions synthesized by method A. A common feature of the composites prepared by routes A and B was the presence of a tin oxide-rich overlayer identified by X-ray photoelectron spectroscopy. As a consequence, the electrocatalytic behavior of the catalysts was not influenced by the Ti/Sn ratio and was mainly dependent on the synthesis method used in the preparation of composite support materials. Elemental maps confirmed the formation of areas where Pt and the Sn doping element were in atomic proximity to each other, which means a favorable interaction either for the bifunctional mechanism or the electronic ligand effect. An increase in carbon content in composite materials led to an increase in both catalytic activity and long-term stability. The results of electrochemical studies showed that Sn-containing Pt catalysts with a high carbon content (75 wt%) are the most promising for potential use both as an anode and a cathode for PEM fuel cells.

84. Optical characterization of Sm3+doped phosphate glasses for potential orange laser applications

Authors: Bayoudhi, D; Bouzidi, C; Matei, E; Secu, M; Galca, AC

Published: JAN 2024, JOURNAL OF LUMINESCENCE, 265, 120204, DOI: 10.1016/j.jlumin.2023.120204

Undoped and Sm3+doped 45P2O5-45Na2O-2Al2O3-8BaO glasses were synthesized by the melt-quenching technique. The glass structure and luminescence properties were investigated by using Raman spectroscopy, scanning electron microscopy (SEM), spectroscopic ellipsometry, Judd-Ofelt theory and photoluminescence. Electron microscopy showed the homogeneity of samples. Raman spectroscopy revealed that the overall struc-ture of the glass was unaffected by the doping of Sm3+ and ellipsometry was used to measure the optical constants. Judd-Ofelt (JO) analysis was performed on the absorption bands of Sm3+ (4f5) and the three phenomenological parameters (omega 2, omega 4, and omega 6) were computed and then used to determine radiative properties such as the radiative transition probability (Ar), the fluorescent branching ratio (beta r), the stimulated emission cross-section (sigma e) and the radiative lifetime (tau rad). Photoluminescence (PL) spectrum showed the typical four transitions of Sm3+ at wavelengths of 564, 600, 645 and 703 nm corresponding to 4G5/2 -> 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The spectroscopic quality factors omega 4/omega 6, the predicted lifetime (tau rad) calculated using the JO method and the experimentally lifetime (tau exp) for the 4G5/2level were calculated and discussed. The glass color purity is as high as 98%, which makes it a potential candidate for laser emission.

85. Magnetocaloric properties of La0.9K0.1MnO3 and La0.8K0.1Pb0.1MnO3 bulk perovskite manganites

Authors: Bouzid, SA; Elhamouchi, N; Sajieddine, M; Aitmellal, O; Kuncser, V; Galca, AC; Iacob, N; Enculescu, M; Essoumhi, A

Published: NOV 2024, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 35, 2138, DOI: 10.1007/s10854-024-13873-x

In the present work, we report the synthesis and investigations of La0.9K0.1MnO3 and La0.8K0.1Pb0.1MnO3 bulk samples which could be potential magnetocaloric materials for magnetic refrigeration close to room temperature. A flash combustion reaction and sintering at 1200 degrees C for 10 h are used to prepare the bulk materials. Both compounds crystallized into a rhombohedral structure with R3<overline>\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{3 }$$\end{document}c space group confirmed by X-ray powder diffraction results. Scanning electron microscopy analysis, combined with XRD peak profiles is performed to estimate the particle/crystallite size of the samples. Moreover, the Curie temperature, TC, is found to be higher in lead-rich sample due to the enhancement of the grain size and the Mn3+-O-Mn4+ double exchange (DE) interaction. Therefore, the bulk sample La0.8K0.1Pb0.1MnO3 shows a room temperature phase transition of 289 K as well as a higher saturation magnetization. The La0.8K0.1Pb0.1MnO3 bulk compound exhibits a high and sharp peak in magnetic entropy change up to 5.5 Jkg-1 K-1 under 5 T at the magnetic transition temperature TC. To compare the magnetocaloric performances of the studied compounds, relative cooling power (RCP) was employed. The obtained experimental results revealed that the increase in particle size influences severely the magnetocaloric properties.

86. The influence of the functionalization of polystyrene and graphene oxide composites on the flammability characteristics: modeling with artificial intelligence tools

Authors: Anghel, I; Lisa, C; Curteanu, S; Preda, DM; Sofran, IE; Baia, M; Stroe, M; Paraschiv, M; Baibarac, M; Danciu, V; Cotet, LC; Baia, L

Published: APR 2024, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 149, DOI: 10.1007/s10973-023-12869-9

This paper tackles the influence of the functionalization of polystyrene and graphene oxide (GO) composites on the flammability characteristics. A microscale combustion calorimeter (MCC) was used to experimentally determine the heat release capacity (HRC), the specific heat release rate (HRR) and the total heat released (THR). Neural models were designed that correlate the THR with a number of parameters related to the composition and type of flame retardant used, the heating rate, the amount of residue, the HRC, the peak heat release rate (PHRR), the temperature at the peak pyrolysis rate (TPHRR) and the time elapsed until the occurrence of the peak heat release rate (Time). The best results in the training, validation and testing stages were achieved with the neural model with 9 neurons in the input layer, 40 neurons in the hidden layer and one neuron in the output layer. This model was incorporated into an optimization procedure, based on a genetic algorithm, to establish the values of the input parameters used in the training of the neural networks, in order to generate a minimum THR value, which is the output parameter. Since the synthesis of polystyrene particles with different GO concentrations is costly, this research helps to reduce the number of experimental tests and allows to determine the best GO concentration by means of neural models and genetic algorithms.

87. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbáth, I; Pászti, Z; Sebestyén, Z; Mihály, J; Szabó, T; Illés, E; Domján, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Tálas, E

Published: NOV 2024, TOPICS IN CATALYSIS, 67, DOI: 10.1007/s11244-021-01513-1

TiO2-C (carbon) hybrid materials are promising electrocatalyst supports because the presence of TiO2 results in enhanced stability. Use of new types of carbonaceous materials such as reduced graphene oxide instead of traditional active carbon provides certain benefits. Although the rutile polymorph of TiO2 seems to have the most beneficial properties in these hybrid materials, the anatase type is more frequent in TiO2-rGO composites, especially in graphite oxide (GO) derived ones, as GO has several properties which may interfere with rutile formation. To explore and evaluate these peculiarities and their influence on the composite formation, we compared TiO2-C systems formulated with GO and Black Pearls (BP) carbon. Various physicochemical methods, such as attenuated total reflection infrared (ATR-IR)-, solid state NMR-, Raman- and X-ray photoelectron spectroscopy, X-ray powder diffraction (XRD), electron microscopy, etc. were used to characterize the samples from the different stages of our multistep sol-gel synthesis. Our experiments demonstrated that utilization of GO is indeed feasible for composite preparation, although its sodium contamination has to be removed during the synthesis. On the other hand, high temperature treatment and/or solvothermal treatment during composite synthesis resulted in decomposition of the functional groups of the GO and the functional properties of the final product were similar in case of both composites. However, Pt/TiO2-GO derived sample showed higher oxygen reduction reaction activity than Pt/TiO2-BP derived one. Based on the decrease of electrochemical surface area, the stability order was the following: Pt/C (commercial) < Pt/TiO2-BP derived C < Pt/TiO2-GO derived C.

Open Access

88. Biocompatibility and Osteogenic Activity of Samarium-Doped Hydroxyapatite-Biomimetic Nanoceramics for Bone Regeneration Applications

Authors: Balas, M; Badea, MA; Ciobanu, SC; Piciu, F; Iconaru, SL; Dinischiotu, A; Predoi, D

Published: JUN 2024, BIOMIMETICS, 9, 309, DOI: 10.3390/biomimetics9060309

In this study, we report on the development of hydroxyapatite (HAp) and samarium-doped hydroxyapatite (SmHAp) nanoparticles using a cost-effective method and their biological effects on a bone-derived cell line MC3T3-E1. The physicochemical and biological features of HAp and SmHAp nanoparticles are explored. The X-ray diffraction (XRD) studies revealed that no additional peaks were observed after the integration of samarium (Sm) ions into the HAp structure. Valuable information regarding the molecular structure and morphological features of nanoparticles were obtained by using Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The elemental composition obtained by using energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of the HAp constituent elements, Ca, O, and P, as well as the presence and uniform distribution of Sm3+ ions. Both HAp and SmHAp nanoparticles demonstrated biocompatibility at concentrations below 25 mu g/mL and 50 mu g/mL, respectively, for up to 72 h of exposure. Cell membrane integrity was preserved following treatment with concentrations up to 100 mu g/mL HAp and 400 mu g/mL SmHAp, confirming the role of Sm3+ ions in enhancing the cytocompatibility of HAp. Furthermore, our findings reveal a positive, albeit limited, effect of SmHAp nanoparticles on the actin dynamics, osteogenesis, and cell migration compared to HAp nanoparticles. Importantly, the biological results highlight the potential role of Sm3+ ions in maintaining cellular balance by mitigating disruptions in Ca2+ homeostasis induced by HAp nanoparticles. Therefore, our study represents a significant contribution to the safety assessment of both HAp and SmHAp nanoparticles for biomedical applications focused on bone regeneration.

89. GRAPHENE FOR ELECTRONIC DEVICES - SYNTHESIS AND CHARACTERIZATION

Authors: Apostol, M; Enache, A; Diculescu, V; Tite, T; Onea, M; Enculescu, I; Matei, E; Andronescu, E

Published: 2024, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 86, DOI:

In this paper, graphene was obtained on a copper substrate using the CVD method, and then it was transferred to various substrates such as glass and SiO2/Si patterned with metallic interdigitated electrodes. The graphene thus obtained was characterized using Raman spectroscopy, scanning electron microscopy (SEM), current-voltage measurements, and electrochemical methods, in order to be used for sensing applications.

Open Access

90. Copper doped hydroxyapatite nanocomposite thin films: synthesis, physico-chemical and biological evaluation

Authors: Ciobanu, CS; Predoi, D; Iconaru, SL; Predoi, MV; Ghegoiu, L; Buton, N; Motelica-Heino, M

Published: DEC 2024, BIOMETALS, 37, DOI: 10.1007/s10534-024-00620-2

Cu-doped hydroxyapatite (CuHAp) thin films were obtained using spin coating method. To make these thin films, CuHAp suspensions obtained by sol-gel method were used. The coatings obtained were thermally treated at 500 degrees C. After the thermal treatment, the thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Moreover, the stability of the suspensions before being used to obtain the thin films was certified by dynamic light scattering (DLS), zeta potential methods and ultrasound measurements. In the XRD patterns, the peaks associated with hexagonal hydroxyapatite were identified in accordance with JCPDS no. 09-0432. EDS and XPS results confirmed the presence of Cu ions in the samples. Data about the morphological features and chemical composition of CuHAp thin films were obtained by performing scanning electron microscopy (SEM) measurements. Our results suggest that the CuHAp thin films surface is continuous and homogenous. The presence of the functional groups in the CuHAp thin films was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy studies. Information about the surface topography of the CuHAp thin films has been obtained using atomic force microscopy (AFM). The AFM images determined that the surface topography of the CuHAp thin layer is homogenous and continuous without presenting any unevenness or fissures. The cytotoxicity of CuHAp thin films was assessed using human gingival fibroblasts (HGF-1) cells. The results of the cell viability assays demonstrated that the thin films presented good biocompatible properties towards the HGF-1 cells. Additionally, the adherence and development of HGF-1 cells on the surface of CuHAp thin films were determined using AFM. The AFM surface topographies highlighted that the CuHAp thin film's surface favored the attachment and proliferation of HGF-1 cells on their surface.

Open Access

91. Phase transitions in ferroelectric ZrO2 thin films

Authors: Pereira, RMP; Istrate, MC; Figueiras, FG; Lenzi, V; Silva, BM; Benamara, M; Romanyuk, KN; Ghica, C; Almeida, BG; Marques, L; Pereira, M; Silva, JPB

Published: MAR 15 2024, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 172, 108102, DOI: 10.1016/j.mssp.2023.108102

In this work, the formation of the orthorhombic phase of ZrO2 together with the minor monoclinic phase were elucidated by X-ray diffraction and transmission electron microscopy. Moreover, oxidized W can be responsible for the formation of oxygen vacancies in the ZrO2 through oxygen scavenging. The ferroelectric properties of the W/ZrO2/W film capacitors were investigated through piezoresponse force microscopy (PFM) and polarizationvoltage measurements. A second-order phase transition from the polar orthorhombic phase to the non-polar tetragonal phase was observed. Density functional theory calculations confirm our experimental results and propose that oxygen vacancies are responsible for the Curie-Weiss temperature of 130 degrees C, significantly lower than the theoretical value for the bulk.

Open Access

92. Electronic Synapses Enabled by an Epitaxial SrTiO3-δ / Hf0.5Zr0.5O2 Ferroelectric Field-Effect Memristor Integrated on Silicon

Authors: Siannas, N; Zacharaki, C; Tsipas, P; Kim, DJ; Hamouda, W; Istrate, C; Pintilie, L; Schmidbauer, M; Dubourdieu, C; Dimoulas, A

Published: FEB 2024, ADVANCED FUNCTIONAL MATERIALS, 34, DOI: 10.1002/adfm.202311767

Synapses play a vital role in information processing, learning, and memory formation in the brain. By emulating the behavior of biological synapses, electronic synaptic devices hold the promise of enabling high-performance, energy-efficient, and scalable neuromorphic computing. Ferroelectric memristive devices integrate the characteristics of both ferroelectric and memristive materials and present a far-reaching potential as artificial synapses. Here, it is reported on a new ferroelectric device on silicon, a field-effect memristor, consisting of an epitaxial ultrathin ferroelectric Hf(0.5)Z(r0.5)O(2) film sandwiched between an epitaxial highly doped oxide semiconductor SrTiO3-delta and a top metal. Upon a low voltage of less than 2 V, the field-effect modulation in the semiconductor enables to access multiple states. The device works in a large time domain ranging from milliseconds down to tens of nanoseconds. By gradually switching the polarization by identical pulses, the ferroelectric diode devices can dynamically adjust the synaptic strength to mimic short- and long-term memory plasticity. Ionic contributions due to redox processes in the oxide semiconductor beneficially influence the device operation and retention.

93. Dielectric characterization of polymer dispersed liquid crystal film with chitosan biopolymer

Authors: Manaila-Maximean, D; Ilis, M; Ganea, PC; Micutz, M; Boscornea, C; Circu, V

Published: JAN 1 2024, JOURNAL OF MOLECULAR LIQUIDS, 393, 123552, DOI: 10.1016/j.molliq.2023.123552

Polymer Dispersed Liquid Crystals (PDLC) systems were obtained using chitosan as a biopolymer matrix and the nematic liquid crystal (LC) mixture E7 in various concentrations (30, 40 and 50% E7 in chitosan). Several techniques were used to analyze the obtained films: polarizing optical microscopy (POM), IR spectroscopy (FTIR), differential scanning calorimetry (DSC) and dielectric spectroscopy (DS). FTIR spectroscopy revealed minor changes for all PDLC films, suggesting weak interactions between LC and chitosan matrix. For each sample a clear segregation of the nematic droplets could be observed by POM. DSC measurements show that the phase transitions have shifted to lower temperature values for PDLC samples with approximately 2.7 degrees C compare to pure E7. The values of alpha (fraction of LC in the droplets) for compositions of 30, 40 and 50 wt% E7 in Chitosan were 0.48, 0.55 and 0.61 respectively, that are lower than for E7/PMMA system. The qualitative and quantitative analysis of the permittivity spectra obtained by DS reveals the fact that there are no significant changes in the molecular dynamics attributed to pure LC E7 compared to the PDLC composites, leading to the conclusion of the existence of a weak interaction between the two components, fact confirmed by the findings from the FTIR results.

94. A new porous composite hydroxyapatite/chitosan/microcrystalline-cellulose: synthesis, characterization and application to the adsorption of Eriochrome Black T

Authors: Benali, Y; Mabrouki, N; Agougui, H; Jabli, M; Majdoub, H; Predoi, D; Ciobanu, S; Iconaru, SL; Talu, S; Boughzala, K

Published: DEC 2024, POLYMER BULLETIN, 81, DOI: 10.1007/s00289-024-05496-3

In the current study, a porous composite material, hydroxyapatite/chitosan/microcrystalline-cellulose (CaHAp-CS-MCC), was successfully prepared and used for the adsorption of Eriochrome Black T (EBT) from water. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), specific surface area (SSA), and atomic force microscope (AFM) were used to evaluate the physicochemical properties of the prepared adsorbents. CaHAp-CS-MCC exhibited a decrease in crystallinity and reduction in crystallite size. CaHAp-CS-MCC surface exhibited cracks and pores. AFM displayed changes in surface micro-texture of CaHAp, formation of new surface structures, and variations in particle size and distribution. Upon grafting CaHAp with CS and MCC, its specific surface area decreased from 139.224 to 11.775 m2/g. BET suggested that filling CaHAp pores by CS and MCC contributed to the reduction in surface area. The pore volume values decreased from 2.56 x 10-1 (CaHAp) to 3.91 x 10-2 cm3/g (CaHAp-CS-MCC). Adsorption equilibrium was reached at about 40 min. The adsorption capacities values of CaHAp-CS-MCC and CaHAp were equal to 248 mg/g and 92 mg/g, respectively. The pseudo-second order and the Langmuir equations fitted well the adsorption phenomenon. The calculated thermodynamic parameters showed an exothermic and non-spontaneous system.

Open Access

95. Magnetic Shape Memory Nanocomposites Assembled with High Speed High Pressure Torsion

Authors: Gurau, C; Tolea, F; Cimpoesu, N; Sofronie, M; Ceoromila, AC; Stefanescu, C; Gurau, G

Published: MAR 2024, NANOMATERIALS, 14, 405, DOI: 10.3390/nano14050405

When a severe plastic deformation (SPD) process is performed at high temperatures, it becomes more versatile. Designed originally for the bulk nanoconstruction of hard-to-deform alloys, high-speed high-pressure torsion (HSHPT) is an SPD method used in this research for assembling multiple layers of shape memory nanocomposites. Three hard-to-deform magnetic alloys in the cast state were used. Soft magnetic shape memory alloys, NiFeGa and FePdMn, and a potentially hard magnetic alloy, CoZr, were assembled in various composites. Both grain refinement and strong layer bonding were achieved in ZrCo/FePdMn and ZrCo/NiFeGa composites in seconds. The very short SPD time is specific to HSHPT because of the intense friction that occurs under high pressures, which generates huge amounts of heat. After SPD, the temperature rises in bulk material like a pulse, being dissipated mostly through heat conduction. The SPD parameters were carefully controlled with an advanced automation system using a programmable logic controller. Nevertheless, the major drawbacks of high-pressure torsion were overcome, and large SPD discs were obtained. Various investigation techniques (optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and atomic force microscopy) show well-defined interfaces as well as a fine and ultrafine structure.

96. The interface structural, electronic and optical properties of ZnO nanowires/Graphene nanohybrid (ZnO NWs/G): Experimental and theoretical DFT investigations

Authors: Boukhoubza, I; Achehboune, M; Derkaoui, I; Apostol, MM; Basyooni, MA; Khenfouch, M; Nedelcu, L; Enculescu, I; Matei, E

Published: MAR 5 2024, JOURNAL OF ALLOYS AND COMPOUNDS, 976, 173109, DOI: 10.1016/j.jallcom.2023.173109

In this work, a ZnO nanowires/graphene nanohybrid was synthesized by a three steps approach. Copper substrates were covered with graphene by chemical vapor deposition, further ZnO nanowires were electrochemically deposited on the as grown graphene on copper and finally a transfer process was employed for moving the heterostructure onto a different substrate. A comprehensive structural analysis which included scanning electron microscopy, X-ray diffraction and Raman measurements revealed that the ZnO nanowires crystallize in wurtzite structure perpendicular to graphene, the process leading to the formation of a nanohybrid heterostructure. The band gap energy of the ZnO nanowires deposited on graphene was estimated to be 3.11 eV, as calculated from the reflectance spectrum analysis. The GGA-PBE+U within Grimme (DFT-D) approach was used to provide an accurate description of the interface structure in terms of electronic and optical properties, confirming that the decrease in the band gap energy of ZnO nanowires is caused by the interaction with the graphene surface. The findings of this study could serve as an experimental and theoretical reference for upcoming studies on ZnO NWs/Graphene nanohybrid-based optoelectronic applications.

Open Access

97. Electrospun fibrillary scaffold for electrochemical cell biomarkers detection

Authors: Beregoi, M; Oprea, D; Bunea, MC; Enculescu, M; Enache, TA

Published: JUL 2024, MICROCHIMICA ACTA, 191, 435, DOI: 10.1007/s00604-024-06523-w

A novel scaffold for in situ electrochemical detection of cell biomarkers was developed using electrospun nanofibers and commercial adhesive polymeric membranes. The electrochemical sensing of cell biomarkers requires the cultivation of the cells on/near the (bio)sensor surface in a manner to preserve an appropriate electroactive available surface and to avoid the surface passivation and sensor damage. This can be achieved by employing biocompatible nanofiber meshes that allow the cells to have a normal behavior and do not alter the electrochemical detection. For a better mechanical stability and ease of handling, nylon 6/6 nanofibers were collected on commercial polymeric membranes, at an optimal fiber density, obtaining a double-layered platform. To demonstrate the functionality of the fabricated scaffold, the screening of cellular stress has been achieved integrating melanoma B16-F10 cells and the (bio)sensor components on the transducer whereas the melanin exocytosis was successfully quantified using a commercial electrode. Either directly on the surface of the (bio)sensor or spatially detached from it, the integration of cell cultures in biosensing platforms based on electrospun nanofibers represents a powerful bioanalytical tool able to provide real-time information about the biomarker release, enzyme activity or inhibition, and monitoring of various cellular events.

Open Access

98. Anticorrosion Protection of New Composite Coating for Cobalt-Based Alloy in Hydrochloric Acid Solution Obtained by Electrodeposition Methods

Authors: Branzoi, F; Mihai, AM; Zaki, MY; Xu, JY

Published: JAN 2024, COATINGS, 14, 106, DOI: 10.3390/coatings14010106

In this work, electrochemical deposition techniques (galvanostatic and potentiostatic) were used to obtain coatings of a new composite polymer, 3-methylpyrrole-sodium dodecyl sulfate/poly 2-methythiophene (P3MPY-SDS/P2MT), on cobalt-based alloy samples for anti-corrosion safety. The use of sodium dodecyl sulfate as a dopant ion in electrosynthesis can have a relevant effect on the anticorrosive property of the composite polymer layer by blocking the entry of corrosive ions. The cobalt alloy specimen had an important impact on the electrochemical performance of the composite coating and this together with the presence of the polymeric layer was achieved by simultaneously constitution of a complex oxides film and polymeric layers. The polymeric coatings were analyzed using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and cyclic voltammetry (CV) methods. The corrosion protection of the P3MPY-SDS/P2MT-covered cobalt-based alloy was explored using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization procedures in a 1 M HCl solution. The corrosion speed of the P3MPY-SDS/P2MT-covered cobalt-based alloy was observed to be similar to 10 times less than an uncovered specimen, and the effectiveness of the composite layers of this coating is greater than 91%. This superior efficaciousness was obtained by the electropolymerization of P3MPY-SDS/P2MT at current densities of 1 mA/cm(2) and 0.5 mA/cm(2), applied potentials of 0.9 V and 1.0 V, and a molar ratio of 5:1. Corrosion test results indicate that the P3MPY-SDS/P2MT coatings provide a good result: protection against the corrosion of a cobalt-based alloy in aggressive solutions.

99. Enhancement of SrTiO3 photocatalytic efficiency by Al doping: Answers from the structure, morphology and electronic properties contributions

Authors: Radu, I; Borhan, AI; Gherca, D; Popescu, DG; Borca, CN; Huthwelker, T; Bulai, G; Stoian, G; Husanu, MA; Pui, A

Published: JUN 1 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2024.03.188

Our study focuses on disclosing the mechanisms standing behind the improved photocatalytic performance of SrTiO3, where Al modification of the perovskite structure boosts the photocatalytic O2 evolution activity of the Al:SrTiO3 system. By adapting the synthesis method that produces well-crystallized materials with low defect density and employing surface modification techniques, we aim to enhance the photocatalytic efficiency of SrTiO3 via Al2O3 nanoceramic oxide doping at concentrations ranging from 0 to 10% and further examining of the relationship between doping process and the changes in the electronic and crystalline structure of SrTiO3. The prepared Al-based SrTiO3 perovskite samples (Al3%:SrTiO3, Al7%:SrTiO3, Al10%:SrTiO3) were thoroughly characterized to understand their structural, electronic, and morphological properties. Complementary X-ray techniques were employed to assess the stoichiometry (X-ray photoelectron spectroscopy - XPS), local environment, and chemical state (X-ray absorption spectroscopy - XAS in both total electron yield (TEY) and fluorescence yield (TFY). The comprehensive characterization enables us to understand the changes in the electronic properties and morphological features of the modified samples elucidating the surface formation mechanism while providing insights into the structural modifications induced by Al doping in the SrTiO3 perovskite lattice. Our findings give new perspectives for the development of Al-modified SrTiO3 perovskite materials with enhanced photocatalytic performance providing rich insights into the optimization of photocatalytic processes for applications in environmental remediation and sustainable energy production.

Open Access

100. Simulation and study of the milling parameters on CuFeTaTiW multicomponent alloy

Authors: Martins, R; Conçalves, AP; Correia, JB; Galatanu, A; Alves, E; Dias, M

Published: MAR 2024, NUCLEAR MATERIALS AND ENERGY, 38, 101568, DOI: 10.1016/j.nme.2023.101568

The CuFeTaTiW multicomponent alloy has been devised as an interlayer thermal barrier in nuclear fusion re-actors. In order to predict the phase constitution of this alloy, two different lines of work were performed: (a) simulation using Molecular dynamics and Monte Carlo and (b) study of the influence of mechanical alloying parameters on the structures formed. The simulation results show that the most stable structure is achieved starting from a bcc type-structure and using Monte Carlo simulation. In fact, in these conditions the separation into two bcc phases Fe-Ta-W and Cu-Ti is predicted at room temperature. However, the experimental preparation of the materials with mechanical alloying revealed that from 2 h of milling a single bcc phase is formed. The structure of the milled powder was not much influenced by the amount of the process control agent and the by the size of the W starting particles, but generally there was formation of Ta2H from the reaction between the powders and the process control agent.

101. Self-Powered UV Photodetector Utilizing Plasmonic Hot Carriers in 2D α-MoO3/Ir/Si Schottky Heterojunction Devices

Authors: Basyooni, MA; Zaki, SE; Tihtih, M; Boukhoubza, I; En-nadir, R; Derkaoui, I; Attia, GF; Ates, S; Eker, YR

Published: JAN 2024, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 18, DOI: 10.1002/pssr.202300175

Self-powered UV sensing has enormous potential in military and civilian applications. However, achieving high responsivity and fast response/recovery time presents significant challenges. Self-powered photodetectors (PDs) have several advantages over traditional PDs, including higher sensitivity, lower power consumption, and simpler design. This study introduces a breakthrough self-powered PD that uses a Schottky junction of 2D alpha-MoO3/iridium (Ir)/Si ultrathin film to detect 365 nm light at 0 V bias through using atomic layer deposition (ALD) and sputtering systems. The PD response is enhanced by plasmonic Ir-induced hot carriers, enabling detection in a mere 0.1 ms. Incorporating a 4 nm Ir layer boosts the responsivity from 0 to 34 A W-1, and the external quantum efficiency is elevated from 0 to 7E11 under 365 nm light illumination. It also has a high I-ON/I-OFF ratio of 11.22E4 at 0 V. These results make the MoO3/4 nm Ir/Si structure an interesting option for self-powered PDs with high efficiency, and the use of a simple ALD system for large-scale fabrication of 2D alpha-MoO3 on hot carrier Ir plasmonic layer. The findings of this research hold tremendous promise in the field of UV sensing and can lead to exciting developments in military and civilian technology.

Open Access

102. Reticulated mesoporous TiO2 scaffold for self-cleaning surfaces

Authors: Besleaga, C; Tomulescu, AG; Zgura, I; Stepanova, A; Galca, AC; Laafar, S; Zorila, FL; Alexandru, M; Pintilie, I; Iliescu, M

Published: NOV 1 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2024.08.072

Interest in self-cleaning coatings is rising due to their potential to enhance comfort and quality of life in polluted urban environments, driving the search for materials with optimal physical properties. Convergent with this goal, this study investigates the wetting properties and photo-catalytic efficiency of reticulated TiO2 layers. It shows that these properties are significantly influenced by the topographical characteristics of the TiO2 surface, which can be precisely controlled through variations in pulverization pressure and low-temperature post-annealing treatments. Post-deposition annealing of the TiO2 layers achieves 100 % self-cleaning efficiency for both thick and thin films, with optical transmission ranging from approximately 60 %-80 % in the visible spectrum. Additionally, the TiO2 layers exhibited promising capabilities for eliminating pathogenic microorganisms and disinfecting surfaces. The underlying causal factors of these remarkable and technologically promising surface features are explored and discussed.

Open Access

103. Pinning Energy and Evidence of Granularity in the AC Susceptibility of an YBa2Cu3O7-x Superconducting Film (vol 14, 4379, 2024)

Authors: Galluzzi, A; Crisan, A; Ionescu, AM; Ivan, I; Leo, A; Grimaldi, G; Polichetti, M

Published: SEP 2024, APPLIED SCIENCES-BASEL, 14, 7664, DOI: 10.3390/app14177664

Open Access

104. Improving the control of the electroforming process in oxide-based memristive devices by X-ray nanopatterning

Authors: Mino, L; Bonino, V; Alessio, A; Picollo, F; Kuncser, A; Mercioniu, I; Vlaicu, AM; Badica, P; Brescia, R; Fretto, M; Goss, K; Dittmann, R; Truccato, M

Published: JUL 25 2024, JOURNAL OF MATERIALS CHEMISTRY C, 12, DOI: 10.1039/d4tc01815j

We explored the possibility to guide the forming process in a Ta/TiO2/Pt memristive device using an X-ray nanopatterning procedure, which enables the manipulation of the oxygen content at the nanoscale. The irradiation of selected areas of the sample by a 65 x 58 nm2 synchrotron X-ray nanobeam locally generated oxygen vacancies which resulted in the formation of a conductive filament in the desired position in the material. The subsequent application of an electric field between the electrodes was exploited to achieve reversible bipolar resistive switching. A multitechnique characterization was then performed, highlighting a local increase in the height of the crystal and the formation of a dislocation network, associated with the presence of Wadsley defects. Our results show that X-ray nanopatterning could open new avenues for a more deterministic implementation of electroforming in oxide-based memristive devices. We tuned the oxygen content in a Ta/TiO2/Pt memristive device at the nanoscale by a synchrotron X-ray nanobeam. We obtained a conductive filament of oxygen vacancies in the desired position in the material to achieve a controlled resistive switching.

Open Access

105. Insulin loaded iron magnetic nanoparticle-graphene oxide composites: synthesis, characterization and application for in vivo delivery of insulin

Authors: Turcheniuk, K; Khanal, M; Motorina, A; Subramanian, P; Barras, A; Zaitsev, V; Kuncser, V; Leca, A; Martoriati, A; Cailliau, K; Bodart, JF; Boukherroub, R; Szunerits, S

Published: DEC 3 2024, RSC ADVANCES, 14, DOI: 10.1039/d4ra90136c

Open Access

106. Pinning Energy and Evidence of Granularity in the AC Susceptibility of an YBa2Cu3O7-x Superconducting Film

Authors: Galluzzi, A; Crisan, A; Ionescu, AM; Ivan, I; Leo, A; Grimaldi, G; Polichetti, M

Published: JUN 2024, APPLIED SCIENCES-BASEL, 14, 4379, DOI: 10.3390/app14114379

The study of granularity in superconducting films by using AC susceptibility has a crucial role in the development of and improvement in the ReBCO-coated conductors, which are a constantly evolving reality in the modern power applications of superconductivity. Specifically, the study of the granularity is essential because the ReBCO superconducting wires and tapes are far from the regularity of a single crystal while they often present an inter- and intragranular contribution to the critical current density. On the other hand, the AC susceptibility is a key part of the characterization of a granular sample because this technique is very sensitive to the presence of granularity in the superconductors and, moreover, the study of its first harmonic allows for determining pivotal properties such as the pinning energy as well as the dissipation processes acting in the sample. The pinning energy values and the granularity of an YBCO thin film have been studied by means of AC susceptibility measurements as a function of the AC amplitude, temperature, and DC field. In particular, the first harmonic imaginary component of the AC susceptibility chi 1 '' related to the dissipation processes of the sample has been studied. First, starting from the Brandt approach, the critical current density J(c) and the pinning energy U of the sample have been extracted at 77 K by using the chi 1 '' measurements as a function of the AC amplitude at different AC frequencies and DC fields. From these measurements, a first signal of granularity appears. In order to confirm it, the temperature dependence of the chi 1 '' at different DC fields has been studied and a contribution deriving from the inter- and intragranular part of the sample has emerged. By taking the temperature corresponding to the crossover between the two contributions at the different DC fields, the intergranular and intragranular response has been separated. Successively, the temperature has been fixed to 77 K, together with an AC frequency equal to 1597.9 Hz, and the chi 1 '' as a function of the DC field at different AC amplitudes has been analyzed showing a clear presence of granularity in all the curves. By drawing the contour plot of the chi 1 '' with the DC and AC values, it was possible to determine the best parameters to put at 77 K in order to exploit the material for applications.

107. Ex-situ spark plasma sintered MgB2 with Ge-based organometallic additions: Key ingredients for superconductivity enhancement

Authors: Batalu, D; Nakamura, T; Burdusel, M; Pasuk, I; Bezergheanu, A; Badica, P

Published: FEB 2024, SOLID STATE SCIENCES, 148, 107429, DOI: 10.1016/j.solidstatesciences.2023.107429

Dense samples of MgB2, with a relative density of 98.3-99.1 %, were prepared by ex-situ spark plasma sintering using a raw powder supplied by Alfa Aesar. Samples were added with Ge-based organometallics (repagermanium/RGe, propagermaniu/PGe, linear Ge-based organometallic/GeSP, and Na-doped octamer/8THGP-Na) for the starting composition (MgB2)(Ge-based organometallics)0.0014. Except for the 8THGP-Na, they have a similar chemical composition in respect to Ge and C, while the crystal structure differs. Below 20 K, all studied additions increased the critical current density, Jc, and the irreversibility field, Hirr. Samples added with GeSP and 8THGPNa have marginal differences regarding superconducting characteristics. The best Jc and Hirr are obtained for the sample added with RGe. This sample has the highest amount of carbon in the crystal lattice of MgB2. Results point out that there is a complex influence of the additive on carbon behaviour. Although in general it is accepted that a higher amount of carbon produces higher Jc and Hirr, a comparison with the literature indicates that C-rich raw MgB2 powders (e.g. the C-enhanced MgB2 nanopowder produced by Pavezyum) are not suitable to promote strong superconductivity enhancement in the samples added with indicated organometallics, and the origin, states, and evolution of carbon should to be carefully assessed.

108. Iridium/Silicon Ultrathin Film for Ultraviolet Photodetection: Harnessing Hot Plasmonic Effects

Authors: Basyooni, MA; Tihtih, M; Boukhoubza, I; Ibrahim, JEFM; En-nadir, R; Abdelbar, AM; Rahmani, K; Zaki, SE; Ates, S; Eker, YR

Published: JAN 2024, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 18, DOI: 10.1002/pssr.202300257

The phenomenon of hot carriers, which are generated through the nonradiative decay of surface plasmons in ultrathin metallic films, offers an intriguing opportunity for subbandgap photodetection even at room temperature. These hot carriers possess sufficient energy to inject into the conduction band of a semiconductor material. The groundbreaking use of iridium (Ir) ultrathin film as an ultraviolet (UV) plasmonic material on silicon (Si) for high-performance photodetectors (PHDs) has been successfully demonstrated. Elevating the thickness of the sputtered Ir film to 4 nm yields a notable surge in photocurrent, registering an impressive 600 & mu;A under 365 nm UV illumination with electron mobility of 1.37E3 cm2 V-1 s. This PHD exhibits excellent OFF-ON photoresponses at various applied voltages ranging from 0 to 5 V, maintaining a stable photocurrent. Under UV illumination, it displays exceptional performance, achieving a high detectivity of 1.25E14 Jones and a responsivity of 1.28 A W-1. These outstanding results underscore the significant advantages of increasing the thickness of the Ir film in PHDs, leading to improvements in conductivity, detectivity, external quantum efficiency, responsivity, as well as superior sensitivity for light detection. Exploring hot plasmon effects in iridium/silicon ultrathin films: This study delves into a remarkable ultrasmooth iridium thin film's application in hot electron plasmonic photodetectors. Exciting strides in optoelectronic devices are anticipated, owing to their capability for efficient light modulation, absorption, and conversion, with implications for photodetection and solar energy transformation.image & COPY; 2023 WILEY-VCH GmbH

Open Access

109. The Inhibition Action of Some Brij-Type Nonionic Surfactants on the Corrosion of OLC 45 in Various Aggressive Environments

Authors: Branzoi, F; Baran, A; Mihai, MA; Zaki, MY

Published: MAR 2024, MATERIALS, 17, 1378, DOI: 10.3390/ma17061378

The corrosion protection property of three Brij-type surfactants, namely, Brij 35, Brij 56 and Brij 58P, was considered on OLC 45 carbon steel in a 0.5 M H2SO4 medium. The efficacy for these organic compounds was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods, scanning electron microscopy (SEM) procedures, and Fourier transform infrared (FT-IR) spectroscopy. We hypothesized that these surfactants hinder the corrosion for OLC 45 samples through a protecting mechanism owing to the adsorption of organic molecules that form an inhibitive film or through the formation of complex oxides. These surfactants exhibited an appreciable protective effect against OLC 45 corrosion, operating as mixed inhibitors, as could be demonstrated by their influence on the electrochemical characteristics of the metallic substrates. The adsorption of surfactants over the substrates zone conformed to the representation of the Langmuir isotherm. The effect of temperature on the electrochemical comportment of the OLC 45 specimens in H2SO4 without and with Brij at 800 ppm was examined in the temperature interval of 293 to 333 K. The negative estimate of thermodynamic attributed as Gibbs free energy of adsorption presented the spontaneity of the adsorption activity. The investigation with FT-IR and SEM established the adsorption of Brij and the constitution of the corrosive components on the OLC 45 surface. Electrochemical determinations of these surfactants indicated its anticorrosion inhibition performance and the highest inhibition of 96% was reached when the Brij 35 concentration was at 800 or 1000 ppm, while for Brij 56 and Brij 58P, the highest inhibition was obtained when their concentrations were 500, 800, or 1000 ppm.

Open Access

110. Microstructure and coupling mechanisms in MnBi-FeSiB nanocomposites obtained by spark plasma sintering

Authors: Alexandru-Dinu, A; Locovei, C; Bartha, C; Grigoroscuta, MA; Burdusel, M; Kuncser, A; Palade, P; Schinteie, G; Iacob, N; Lu, W; Batalu, D; Badica, P; Kuncser, V

Published: JUL 24 2024, SCIENTIFIC REPORTS, 14, 17029, DOI: 10.1038/s41598-024-67353-7

Fabrication and extensive characterization of hard-soft nanocomposites composed of hard magnetic low-temperature phase LTP-MnBi and amorphous Fe70Si10B20 soft magnetic phase for bulk magnets are reported. Samples with compositions Mn55Bi45 + x center dot(Fe70Si10B20) (x = 0, 3, 5, 10, 20 wt.%) were prepared by spark plasma sintering of powder mixtures. Characterization has been performed by X-ray diffraction, scanning and transmission electron microscopy, magnetometry and Fe-57 Mossbauer spectroscopy. It was shown that samples contain crystallized and nanometric LTP-MnBi phases with various elemental compositions depending on the degree of Bi clustering. Complex correlations between starting compositions, processes during fabrication, and functional magnetic characteristics were observed. Unexpected special situations of the relation between microstructure and magnetic coupling mechanisms are discovered. Exchange spring effects of different strengths occur, being very sensitive to morpho-structural and compositional features, which in turn are controlled by processing conditions. An in-depth analysis of related microscopic characteristics is provided. Results of this work suggest that fabrication by powder metallurgy routes, such as spark plasma sintering of hard and soft magnetic powder mixtures, of MnBi-based composites with exchange spring phenomena have a high potential in designing and optimization of suitable materials with tunable magnetic properties towards rare-earth-free permanent magnet applications.

Open Access

111. The Influence of Cyclic Thermal Shocks at High Temperatures on the Microstructure, Hardness and Thermal Diffusivity of the Rene 41 Alloy

Authors: Arva, ERU; Negrea, DA; Galatanu, A; Galatanu, M; Moga, SG; Anghel, DC; Branzei, M; Stoica, L; Jinga, AI; Petrescu, MI; Munteanu, C; Abrudeanu, M

Published: MAY 2024, MATERIALS, 17, 2262, DOI: 10.3390/ma17102262

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 degrees C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks.

Open Access

112. Engineering Nitrogen-Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors

Authors: Nguyen, KG; Hus, M; Baragau, IA; Bowen, J; Heil, T; Nicolaev, A; Abramiuc, LE; Sapelkin, A; Sajjad, MT; Kellici, S

Published: JUN 2024, SMALL, 20, DOI: 10.1002/smll.202310587

The process of N-doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high-quality N-doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco- friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention-related issues. Citric acid is used as the carbon source, and urea, trizma base, beta-alanine, L-arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation-independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time-dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs' electronic structure than nitrogen-containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single-layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications. This manuscript highlights continuous hydrothermal flow synthesis (CHFS) that directly obtains luminescent nitrogen doped carbon quantum dots using a simple precursor, citric acid, whilst varying the N-dopants to systematically engineer carbon dots with varied but controllable optical characteristics. It reports that a common approach of modelling single-layer structures is insufficient, but two layers suffice to reproduce the experimental data. image

Open Access

113. Organic Heterostructures with Dendrimer Based Mixed Layer for Electronic Applications

Authors: Rasoga, O; Yonkeu, ALD; Breazu, C; Socol, M; Preda, N; Stanculescu, F; Stanculescu, A; Iwuoha, E

Published: SEP 2024, MOLECULES, 29, 4155, DOI: 10.3390/molecules29174155

Recently, much research has focused on the search for new mixed donor-acceptor layers for applications in organic electronics. Organic heterostructures with layers based on the generation 1 poly(propylene thiophenoimine) (G1PPT) dendrimer, N,N '-diisopropylnaphthalene diimide (MNDI), and a combination of the two were prepared and their electrical properties were investigated. Single layers of G1PPT and MNDI and a mixed layer (G1PPT:MNDI) were obtained via spin coating on quartz glass, silicon, and glass/ITO substrates, using chloroform as a solvent. The absorption mechanism was investigated, the degree of disorder was estimated, and the emission properties of the layers were highlighted using spectroscopic methods (UV-Vis transmission and photoluminescence). The effects of the concentration and surface topographical particularities on the properties of the layers were analyzed via atomic force microscopy. All of the heterostructures realized with ITO and Au electrodes showed good conduction, with currents of the order of mA. Additionally, the heterostructure with a mixed layer exhibited asymmetry in the current-voltage curve between forward and reverse polarization in the lower range of the applied voltages, which was more significant at increased concentrations and could be correlated with rectifier diode behavior. Consequently, the mixed-layer generation 1 poly(propylene thiophenoimine) dendrimer with N,N '-diisopropylnaphthalene diimide can be considered promising for electronic applications.

114. Biocompatible and antimicrobial chitosan/PVP/PEO/PAA/AgNP composite hydrogels synthesized by e-beam cross-linking

Authors: Demeter, M; Calina, I; Scarisoreanu, A; Mitran, V; Popa, M; Cîmpean, A; Chifiriuc, MC; Micutz, M; Matei, E; Mitu, B

Published: MAR 2024, RADIATION PHYSICS AND CHEMISTRY, 216, 111391, DOI: 10.1016/j.radphyschem.2023.111391

Novel biocompatible composite hydrogels with good elastic and antimicrobial properties have been fabricated by e-beam cross-linking using chitosan and water-soluble polymers mixed with commercial silver nanoparticles (AgNP). Hydrogels having different formulations were characterized by rheological, swelling, FTIR, SEM, and biodegradation measurements. The network structure, biocompatibility, and antimicrobial properties were evaluated as well. The composite hydrogels showed higher stability and absorb large amounts of fluids specific to an infected wound without losing structural integrity. The rheological, SEM, and network structure results demonstrate that at above 0.1 mg/mL AgNP, hydrogels with high cross-linking density are obtained. The in vitro response of fibroblasts proved the high biocompatibility of the hydrogel's composites. The antimicrobial activity is directly influenced by the amount of AgNP and cross-linking degree of the hydrogel. Significant antimicrobial activity was recorded against Gram-negative bacteria, while for the Gram-positive ones, the growth inhibition seems to require a decrease of the cross-linking degree.

Open Access

115. Hydrothermal carbonization and pyrolysis in wetland engineering: Carbon sequestration, phosphorus recovery, and structural characterization of willow-based chars with X-ray μ-computed tomography

Authors: Acosta, AC; Arias, CA; Biller, P; Wittig, NK; Baragau, IA; Alhnidi, MJ; Ravenni, G; Sárossy, Z; Benedini, L; Abramiuc, LE; Popescu, DG; Negassa, W; Marulanda, VF; Müller-Stöver, DS; Brix, H

Published: JUL 15 2024, CHEMICAL ENGINEERING JOURNAL, 492, 151916, DOI: 10.1016/j.cej.2024.151916

Willows from engineered wetland systems (EWS) offer a sustainable approach to wastewater treatment and biomass production. Our study assesses their potential for nutrient recovery and carbon sequestration using slow pyrolysis (600 degrees C) and hydrothermal carbonization (250 degrees C). Here, we propose EWS-pyrochars as a ready-to integrate opportunity for soil amendment, as they exhibit a predominant CO2 2 release and the absence of harmful compounds in pyrolysis-chromatograms, indicating higher stability than hydrochars. Using sequential Pextractions, we observed a high bioavailability in the willow-woodchips and a significant P-retention in EWSchars-up to 92 % in pyrochars and near-complete retention in hydrochars, along with a higher labile-P fraction of 21 % in hydrochars than 5 % in pyrochars. Utilizing X-ray-based techniques, Raman spectroscopy, scanning electron microscopy, and gas physisorption, we characterized the EWS-chars' structures. We revealed innovative 3D-visualizations, which transcend previous literature by providing insights into the chars' internal porosity and quantifying, for the first time, their carbonaceous structural thickness via a meshing algorithm and the mean Feret diameter. EWS-pyrochars exhibit remarkable aromaticity with a higher concentration of overall sp2 2 Catoms at 63 % vs. 43 % in hydrochars. Moreover, unlike hydrochars, which depict occluded porosity, EWSpyrochars exhibited 92 % water storage-like pores. Although hydrochars indicated lower carbonization and thermal stability than pyrochars, their higher carbon retention (55 vs. 41 % in pyrochar) suggest superior annual benefits-on a 10 ha EWS scale-of 80-tons of carbon sequestration and 334 kg of phosphorus recovery versus 60-tons of carbon and 298 kg of phosphorus with pyrochars. Our findings suggest innovative materials for resource recovery, advancing the engineered wetland systems field, shifting their traditional use, and opening the opportunity for future integration into biorefineries.

116. Layered double hydroxides matrix as host for curcumin loading: structural and spectroscopic investigations

Authors: Todan, L; Voicescu, M; Culita, DC; Atkinson, I; Soare, EM; Ionita, S; Radu, D

Published: JUN 2024, CHEMICAL PAPERS, 78, DOI: 10.1007/s11696-024-03488-1

Curcumin, an important bioactive compound and natural photosensitizer, which exhibits various biological properties, was loaded into inorganic carriers MgAl/ZnAl layered double hydroxides (LDH). The supporting matrices were obtained by co-precipitation, and a surfactant was used for including the organic drug. The structural, morphological, and spectral properties of the obtained composites were followed by X-ray diffraction, FTIR, SEM, UV-Vis, and fluorescence spectroscopy in solid state and in different solvents. The prepared formulations, the curcumin-loaded carriers, were introduced in alcohol-aqueous mixtures and the effect of solvent on the spectral properties of the formulations was investigated. Interactions between the keto-enol group of the pigment and the metals in LDHs laminates as well as inter-molecular bonds between alcohols and curcumin were evidenced. As a consequence, it was concluded that the composition of the carrier as well as the nature of the solvent determine the structural changes of the formulations. MgAl-LDH in powder has better spectral characteristics in the low-energy range (UV-Vis and fluorescence) than ZnAl-LDH. Their spectra are altered when methanol and water are present in the solvent mixture. The released curcumin concentration is in the range for photosensitization applications. The results have potential utilizations in many fields such as food, pharmaceutical, and biology.

Open Access

117. Physico-Chemical and Antimicrobial Features of Magnesium Doped Hydroxyapatite Nanoparticles in Polymer Matrix

Authors: Ciobanu, SC; Iconaru, SL; Predoi, MV; Ghegoiu, L; Badea, ML; Predoi, D; Jiga, G

Published: AUG 2024, MACROMOLECULAR SYMPOSIA, 413, 2400022, DOI: 10.1002/masy.202400022

Magnesium doped hydroxyapatite nanoparticles in dextran matrix (7MgHApDx) with average size diameter of 18.2 +/- 0.5 nm are synthesized by co-precipitation. The surface morphology and shape of 7MgHApDx particles are established by scanning electron microscopy (SEM). The stability that is evaluated by ultrasound measurements and zeta potential reveals a good stability. More than that, the functional groups present in the studied samples are identified by Fourier transform infrared spectroscopy studies. The antimicrobial properties of 7MgHApDx suspensions are determined against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231 microbial strains.

118. Influence of synthesis method and processing on the thermoelectric properties of CoSb3 skutterudites

Authors: Kumar, MU; Swetha, R; Sahana, BV; Kuri, RS; Popescu, B; Assahsahi, I; Kumari, L

Published: MAR 2024, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 35, 514, DOI: 10.1007/s10854-024-12277-1

In the present work, single phase CoSb3 skutterudite nanomaterials were prepared via a ball milling method, and their thermoelectric characteristics were compared with the samples synthesized by the solvo-hydrothermal method. Thermoelectric transport properties were recorded in the temperature regime of 300-830 K. Both samples exhibit p-type conduction behavior with a positive sign of Seebeck coefficient. CoSb3 ball mill sample exhibit higher resistivity of 127 x 10(-5)Omega.m at 300 K as compared to CoSb3 solvo-hydrothermal sample with 4.85 x 10(-5)Omega.m. However, CoSb3 ball mill sample show enhanced Seebeck coefficient of 183 mu V/K at 473 K where CoSb3 solvo-hydrothermal sample depict 98 mu V/K at 650 K. Furthermore, the total thermal conductivity of sintered CoSb3 ball mill and CoSb3 solvo-hydrothermal samples was found to be 3.02 Wm(-1)K(-1) and 3.23 W m(-1)K(-1) at room temperature and reaches a significantly lower value of 2.47 W m(-1)K(-1) and 2.46 W m(-1)K(-1) at 580 and 670 K, respectively. The dimensionless figure of merit ZT values of CoSb3 ball mill and CoSb3 solvo-hydrothermal obtained are 0.053 and 0.060 at 650 and 700 K, respectively. A systematic tuning of processing parameters by ball milling method can lead to better thermoelectric efficiency.

Open Access

119. Synthesis of WS2 Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space

Authors: Sava, F; Simandan, ID; Buruiana, AT; Bocirnea, AE; El Khouja, O; Tite, T; Zaki, MY; Mihai, C; Velea, A

Published: MAR 2024, SURFACES, 7, DOI: 10.3390/surfaces7010008

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications.

Open Access

120. High-performance and self-powered visible light photodetector using multiple coupled synergetic effects

Authors: Silva, JPB; Vieira, EMF; Gwozdz, K; Silva, NE; Kaim, A; Istrate, MC; Ghica, C; Correia, JH; Pereira, M; Marques, L; MacManus-Driscoll, JL; Hoye, RLZ; Gomes, MJM

Published: FEB 6 2024, MATERIALS HORIZONS, 11, DOI: 10.1039/d3mh01725g

In this work, we demonstrate, for the first time, that coupling together the pyroelectric effect, the photovoltaic effect and the plasmonic effect is a novel method to significantly enhance the performance of self-powered photodetectors in the visible region. Photodetectors based on tri-layered heterojunction of n-Si/p-SnO/n-ZnO through the inclusion of silver (Ag) nanoparticles (NPs) at the SnO/ZnO interface were fabricated. The photo-response of the device, with excitation from a chopped 650 nm wavelength laser, was carefully investigated, and it was shown that the photodetector performance is enhanced the most with the inclusion of spheroidal Ag NPs with similar to 70 nm diameter. The Al/Si/SnO/Ag NPs/ZnO/ITO device exhibited an optimum responsivity, detectivity and sensitivity of 210.2 mA W-1, 5.47 x 109 Jones and 15.0 x 104, respectively, together with a rise and fall time of 2.3 and 51.3 mu s, respectively, at a laser power density of 317 mW cm-2 and at a chopper frequency of 10 Hz. The present photodetectors are more than twice as responsive as the current best-performing ZnO-based pyro-phototronic photodetectors and they also exhibit other competitive features, such as detectivity, and fall and rise times. Therefore, by exploiting the plasmonic effect of the Ag NPs together with the pyroelectric effect in a ZnO film, and the photovoltaic effect at a Si/SnO junction, all in a single device, photodetectors were developed with state-of-the-art performance for the visible region. Coupling together the pyroelectric effect, the photovoltaic effect and the plasmonic effect is a novel method to significantly enhance the performance of self-powered photodetectors in the visible region.

Open Access

121. Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation

Authors: Stoian, MC; Romanitan, C; Neubauer, K; Atia, H; Negrila, CC; Popescu, I; Marcu, IC

Published: SEP 2024, CATALYSTS, 14, 625, DOI: 10.3390/catal14090625

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 degrees C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H2-TPR) and nitrogen adsorption-desorption at -196 degrees C. XRD analysis revealed in all the samples the presence of Co3O4 crystallites together with periclase-like and CeO2 phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts' preparation. The redox properties studied by H2-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T50, of 489 degrees C, which is ca. 40 degrees C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe-Co-Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed.

Open Access

122. Critical advances in the field of magnetron sputtered bioactive glass thin-films: An analytical review

Authors: Stan, GE; Montazerian, M; Shearer, A; Stuart, BW; Baino, F; Mauro, JC; Ferreira, JMF

Published: FEB 15 2024, APPLIED SURFACE SCIENCE, 646, 158760, DOI: 10.1016/j.apsusc.2023.158760

Bioactive glasses (BGs) are known for their selective ability to (i) form a mechanically strong interfacial bond with hard (bone) or soft tissues (gingivae or cartilages) (i.e., silica-, silica-phosphate-, phosphate-, boratephosphate-, or silica-phosphate-borate-based BGs); or (ii) serve as reservoirs for fast-release of therapeutic (osteogenic, angiogenic, anticarcinogenic, or antimicrobial) ions (i.e., phosphate-based BGs and mesoporous BGs). The strength of the bone bond yielded by the osteoproductive-capable BGs is generally equivalent to, or higher than the bone strength. The resorbability of phosphate-based BG is dependent on the content of network formers and cross-linkers. All BGs elicit excellent biochemical compatibility. However, their fracture toughness is typically less than and the elastic modulus is greater than those of bone, indicating that most BGs have suboptimal biomechanical compatibility when used in load-bearing applications. One promising approach to overcome this problem is the development of BGs in coating form, applied to the surface of load-bearing endosseous implants. This work critically assesses BG thin-layers fabricated by the radio-frequency magnetron sputtering method, an industry-ready large-scale physical vapour deposition technology. It is demonstrated that, despite the relative lack of attention paid to this technology, it enables the development of unique BG coatings with efficacious therapeutic capabilities. Here, we present an overview of the most relevant developments achieved thus far, along with the remarkable advantages, drawbacks to overcome, and future perspectives with the intention of highlighting the vast possibilities of this specific field of research.

Open Access

123. Antimicrobial and Antioxidant Properties of Polyvinyl Alcohol Biocomposite Films Containing Ferulic Acid and Cellulose Extracted from Robinia Pseudoacacia Pods

Authors: Marinas, IC; Oprea, E; Gaboreanu, DM; Matei, E; Nedelcu, L; Zgura, I; Angheloiu, M; Chifiriuc, MC

Published: DEC 31 2024, JOURNAL OF NATURAL FIBERS, 21, 2355297, DOI: 10.1080/15440478.2024.2355297

Capitalizing on invasive plant species and stopping their aggressive spread might be achieved by using them as a renewable source of useful products such as cellulose. The study aimed to develop new cellulose-based food packaging materials with antioxidant and antimicrobial activity. The cellulose was extracted from the invasive plant species Robinia pseudoacacia pods, crosslinked with citric acid, used as reinforcement for polyvinyl alcohol (PVA) and functionalized with ferulic acid (FA). The obtained materials were characterized by XRD, ATR-FTIR, contact angle and SEM. The materials exhibited low solubility in water and the swelling degree was proportional to the FA content. The FA release from the matrix was assessed by HPLC and the antioxidant profile by CUPRAC, FRAP, and TEAC methods. The obtained materials inhibited the growth of bacteria, yeasts and molds, being especially active on Gram-positive bacteria and yeasts. Overall, the most promising formulation for further developing new packaging materials for products with water activity less than 0.95 was the one with the highest FA content.

Open Access

124. Editorial for Special Issue: "Thin Films Based on Nanocomposites (2nd Edition)"

Authors: Socol, M; Preda, N

Published: DEC 2024, NANOMATERIALS, 14, 2049, DOI: 10.3390/nano14242049

Open Access

125. Development and Characterization of Silver Doped Hydroxyapatite/Chitosan Nanobiocomposites

Authors: Iconaru, SL; Ciobanu, SC; Predoi, MV; Ghegoiu, L; Badea, ML; Trusca, R; Predoi, D; Jiga, G

Published: AUG 2024, MACROMOLECULAR SYMPOSIA, 413, 2400023, DOI: 10.1002/masy.202400023

The aim of this study is to develop a new nanobiocomposite based on silver doped hydroxyapatite (AgHAp)/chitosan (CH), AgHAp-CH (x(Ag) = 0.15) by an adapted method. The obtained nanobiocomposites are studied by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) studies. The good stability of AgHAp-CH suspension is established by ultrasound and zeta potential measurements. More than that, the antimicrobial activity of AgHAp-CH nanobiocomposites against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231 microbial strains is evaluated. AgHAp-CH nanobiocomposites demonstrate an effective antibacterial effect against the studied microbial strains. Considering the facile method involved in the development of these nanobiomaterials and their excellent properties, it is suggested that they can be suitable candidates for applications in the biomedical field.

Open Access

126. Unlocking superior NO2 sensitivity and selectivity: the role of sulfur abstraction in indium sulfide (InS) nanosheet-based sensors

Authors: D'Olimpio, G; Boukhvalov, DW; Galstyan, V; Occhiuzzi, J; Vorochta, M; Amati, M; Milosz, Z; Gregoratti, L; Istrate, MC; Kuo, CN; Lue, CS; Ghica, C; Comini, E; Politano, A

Published: APR 30 2024, JOURNAL OF MATERIALS CHEMISTRY A, 12, DOI: 10.1039/d4ta01287a

To advance gas sensor technologies, it is essential to identify materials that exhibit both high selectivity and sensitivity. Here, we unravel the gas-sensing capabilities of indium sulfide (InS) nanosheets, particularly in relation to nitrogen dioxide (NO2) detection. Utilizing a synergistic approach that combines in situ and operando experimental methodologies with density functional theory calculations, we demonstrate that these nanosheets offer outstanding sensitivity toward NO2, characterized by a remarkably low detection threshold of 180 ppb at an operational temperature of 350 degrees C. This remarkable sensitivity is ascribed to the electronic charge redistribution around the Fermi level, facilitated by an oxygen-deficient In2O3-x surface layer that forms naturally when the InS surface is exposed to ambient conditions. A pivotal aspect of our investigation was the exploration of the influence of sulfur abstraction on these surface modifications. We demonstrate that sulfur abstraction plays a critical role in the formation and operational efficacy of the In2O3-x layer, thereby acting as a key element in the sensor mechanism. This unique surface chemistry not only amplifies the sensitivity to NO2 but also confers unparalleled selectivity over other gases and volatile organic compounds. Notably, this level of performance exceeds that of other 2D semiconductors and metal oxides, thus establishing InS nanosheets as an ideal platform for high-performance gas sensors suitable for demanding environments. Moreover, unlike many state-of-the-art sensor materials, InS-based sensors can withstand a wider variety of environmental conditions due to their superior water adsorption resistance.

127. PEDOT:PSS based electrospun nanofibres used as trigger for fibroblasts differentiation

Authors: Beregoi, M; Enache, TA; Oprea, D; Enculescu, M; Ciobotaru, IC; Busuioc, C; Enculescu, I

Published: JAN 1 2024, SMART MATERIALS AND STRUCTURES, 33, 015009, DOI: 10.1088/1361-665X/ad10bf

Electrospun nanofibres based on poly(styrene sulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) were fabricated using a straightforward procedure which combines electrospinning, sputtering deposition and electrochemical synthesis. In general, electrospun fibre meshes based on conducting polymers are prepared by mixing the conducting polymer with a carrier polymer or chemically coverage of the fibres. In contrast, freestanding nylon 6/6 nanofibre webs were prepared through electrospinning and were coated by sputtering with gold in order to make them conductive. Further, a PEDOT:PSS layer was electrochemically deposited onto the metalized nanofibre meshes and the synthesis parameters were chosen in such a way to preserve the high active area of the fibres. The prepared material was morphologically characterized and the formation of PEDOT:PSS was also demonstrated. The PEDOT:PSS coated nanofibres revealed remarkable electrical properties (sheet resistance of about 3.5 Omega cm(-2)), similar to those of metalized nanofibres (sheet resistance around 3 Omega cm2). The in vitro studies using L929 fibroblast mouse cells showed that the bioactive material has no cytotoxic effect and allows proliferation. Moreover, after 72 h of incubation, the fibroblasts shrunk their nuclei and spread suggesting that a differentiation in myofibroblast occurs without application of any kind of external stimuli. These results will be helpful for developing efficient materials for wound healing applications that work without energy consumption.

Open Access

128. Sodium bicarbonate-hydroxyapatite used for removal of lead ions from aqueous solution

Authors: Predoi, SA; Ciobanu, SC; Chifiriuc, CM; Iconaru, SL; Predoi, D; Negrila, CC; Marinas, IC; Raaen, S; Rokosz, K; Motelica-Heino, M

Published: JAN 1 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2023.10.273

This study reports the development of a novel biocomposite for potential applications in the environmental remediation. The hydroxyapatite/sodium bicarbonate (HAp-SB) biocomposite obtained by a cheap method could offer promising characteristics to be used in environmental applications. The obtaining of HAp-SB ceramic composites was studied with the aim of increasing the adsorption efficiency of lead ions from contaminated waters. A composite material (HAp-SB) with good crystallinity that preserves the hexagonal structure of pure hydroxyapatite was obtained. For the powder recovered after decontamination of the lead solution (PbHAp-SB), the XRD model highlighted additional maxima belonging to Ca10(PO4)5(OH)2, Ca0.805Pb4.195(PO4)(OH) and PbH2P2O7. The FTIR spectra of PbHAp-SB are similar to those of HAp-SB composites showing a broadening of the vibration peaks and a slight shift. The XPS and EDS studies illustrated the purity of the HAp-SB sample. Moreover, the presence of lead in the powder recovered after decontamination was also highlighted by XPS and EDS studies. The efficiency of HAp-SB in the adsorption of Pb2+ ions from the contaminated solution was also highlighted by ultrasound studies using double-distilled water as the reference liquid. The adsorption kinetics were investigated with the aid of Langmuir and Freundlich theoretical models. The results demonstrated that the HAp-SB ceramic composite has a strong affinity for the adsorption of Pb2+ ions from contaminated solutions. The removal efficiency of Pb2+ ions was about 92% for the initial Pb2+ concentration above 50 mg/L. The results of the cell viability and cytotoxicity studies demonstrated that HAp-SB nanoparticles did not influence negatively the HeLa cell's viability and did not induce any significant changes of the morphological features of HeLa cells after 24 h of incubation. The batch adsorption results as well as the cytotoxicity assay results suggested that the HAp-SB powder could be successfully used for the removal of Pb2+ from contaminated water.

129. Optimization of CZTSe Thin Films Using Sequential Annealing in Selenium and Tin-Selenium Environments

Authors: Zaki, MY; Sava, F; Simandan, ID; Stavarache, I; Velea, A; Pintilie, L

Published: DEC 26 2024, INORGANIC CHEMISTRY, 64, DOI: 10.1021/acs.inorgchem.4c04082

Cu2ZnSnSe4 (CZTSe) is a promising material for thin-film solar cells due to its suitable band gap, high absorption coefficient, and composition of earth-abundant and nontoxic elements. In this study, we prepared CZTSe thin films from Cu/SnSe2 and ZnSe stacks using a two-step annealing process. Initially, Cu-Sn-Se (CTSe) films were synthesized by sequential deposition and annealing of Cu and SnSe2 precursors in either a selenium (Se) or tin-selenium (Sn+Se) atmosphere. After the deposition of a ZnSe layer on top of CTSe films, the stack underwent a second annealing process, again in either a Se or Sn+Se atmosphere, resulting in four distinct annealing combinations: Se -> Se, Sn+Se -> Se, Se -> Sn+Se, and Sn+Se -> Sn+Se. The first annealing step enabled the formation of CTSe, while the second annealing step, performed after ZnSe deposition, led to the formation of the CZTSe phase. Comprehensive characterization including grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrical measurements was conducted. GIXRD and Raman analysis revealed kesterite CZTSe phase peaks, with some samples showing a split in the main peak at similar to 27 degrees (2 theta), indicating the presence of Cu x Se and ZnSe secondary phases. SEM analysis showed the impact of Sn and Se annealing on grain size, with larger grains observed in films annealed in Sn+Se atmospheres, particularly in the second heat treatment process. EDS results displayed consistent elemental composition across samples, with varying Cu/(Zn+Sn), Zn/Sn and Se/metal ratios influencing the band gap values from 1.09 to 1.63 eV. Hall measurements indicated p-type conductivity with carrier concentrations between 1016 and 1023 cm-3. These results highlight the effectiveness of our two-step annealing process, particularly the Sn+Se atmosphere, in optimizing CZTSe thin films for potential use in high-efficiency thin-film solar cells.

Open Access

130. Physico-Chemical Properties of Copper-Doped Hydroxyapatite Coatings Obtained by Vacuum Deposition Technique

Authors: Benali, Y; Predoi, D; Rokosz, K; Ciobanu, CS; Iconaru, SL; Raaen, S; Negrila, CC; Cimpeanu, C; Trusca, R; Ghegoiu, L; Bleotu, C; Marinas, IC; Stan, M; Boughzala, K

Published: AUG 2024, MATERIALS, 17, 3681, DOI: 10.3390/ma17153681

The hydroxyapatite and copper-doped hydroxyapatite coatings (Ca10-xCux(PO4)6(OH)2; xCu = 0, 0.03; HAp and 3CuHAp) were obtained by the vacuum deposition technique. Then, both coatings were analyzed by the X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and water contact angle techniques. Information regarding the in vitro antibacterial activity and biological evaluation were obtained. The XRD studies confirmed that the obtained thin films consist of a single phase associated with hydroxyapatite (HAp). The obtained 2D and 3D SEM images did not show cracks or other types of surface defects. The FTIR studies' results proved the presence of vibrational bands characteristic of the hydroxyapatite structure in the studied coating. Moreover, information regarding the HAp and 3CuHAp surface wettability was obtained by water contact angle measurements. The biocompatibility of the HAp and 3CuHAp coatings was evaluated using the HeLa and MG63 cell lines. The cytotoxicity evaluation of the coatings was performed by assessing the cell viability through the MTT assay after incubation with the HAp and 3CuHAp coatings for 24, 48, and 72 h. The results proved that the 3CuHAp coatings exhibited good biocompatible activity for all the tested intervals. The ability of Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa) cells to adhere to and develop on the surface of the HAp and 3CuHAp coatings was investigated using AFM studies. The AFM studies revealed that the 3CuHAp coatings inhibited the formation of P. aeruginosa biofilms. The AFM data indicated that P. aeruginosa's attachment and development on the 3CuHAp coatings were significantly inhibited within the first 24 h. Both the 2D and 3D topographies showed a rapid decrease in attached bacterial cells over time, with a significant reduction observed after 72 h of exposure. Our studies suggest that 3CuHAp coatings could be suitable candidates for biomedical uses such as the development of new antimicrobial agents.

Open Access

131. Recent Progress and Challenges in Controlling Secondary Phases in Kesterite CZT(S/Se) Thin Films: A Critical Review

Authors: Zaki, MY; Velea, A

Published: APR 2024, ENERGIES, 17, 1600, DOI: 10.3390/en17071600

Kesterite-based copper zinc tin sulfide (CZTS) and copper zinc tin selenide (CZTSe) thin films have attracted considerable attention as promising materials for sustainable and cost-effective thin-film solar cells. However, the successful integration of these materials into photovoltaic devices is hindered by the coexistence of secondary phases, which can significantly affect device performance and stability. This review article provides a comprehensive overview of recent progress and challenges in controlling secondary phases in kesterite CZTS and CZTSe thin films. Drawing from relevant studies, we discuss state-of-the-art strategies and techniques employed to mitigate the formation of secondary phases. These include a range of deposition methods, such as electrodeposition, sol-gel, spray pyrolysis, evaporation, pulsed laser deposition, and sputtering, each presenting distinct benefits in enhancing phase purity. This study highlights the importance of employing various characterization techniques, such as X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, for the precise identification of secondary phases in CZTS and CZTSe thin films. Furthermore, the review discusses innovative strategies and techniques aimed at mitigating the occurrence of secondary phases, including process optimization, compositional tuning, and post-deposition treatments. These approaches offer promising avenues for enhancing the purity and performance of kesterite-based thin-film solar cells. Challenges and open questions in this field are addressed, and potential future research directions are proposed. By comprehensively analyzing recent advancements, this review contributes to a deeper understanding of secondary phase-related issues in kesterite CZT(S/Se) thin films, paving the way for enhanced performance and commercial viability of thin-film solar cell technologies.

132. Microwave post-treated activated carbons for capacitance boosted non-aqueous supercapacitors

Authors: Fasahat, S; Khosravi, M; Dini, G; del Pino, AP; Logofatu, C

Published: MAY 15 2024, JOURNAL OF ALLOYS AND COMPOUNDS, 984, 173948, DOI: 10.1016/j.jallcom.2024.173948

Herein, as a novel idea, a microwave (MW) post-treatment strategy is proposed to modify the structure and surface characteristics of already prepared activated carbons (ACs) for application in non-aqueous Electric Double-Layer Capacitors. Pistachio nutshell-derived carbon is first KOH-activated and then subjected to MW irradiation for 0, 2, 5, and 10 minutes. X-ray Diffraction and Raman analyses show that MW post-treatment leads to structural modifications, and FTIR and XPS analyses reveal relative elimination of surface functional groups which results in subsequent enhancement in water contact angle and renders more favorable surface wetting of carbon by non-aqueous organic electrolyte. The performance characteristics of symmetrical non-aqueous supercapacitors incorporated with the prepared ACs show a significant positive effect of MW irradiation in such a way that 0 and 10-minute-irradiated ACs demonstrate 152 and 392 F g-1 capacities, respectively, at 1.75 A g-1, with the corresponding specific energies and powers of 340 Wh kg-1 and 11 kW kg-1 for AC-10, respectively. This remarkable enhancement in the electrochemical performance is attributed to the effective role of the MW post-treatment in modifying the AC structure as well as providing AC surfaces that have better wettability with less polar non-aqueous electrolyte. Moreover, this strategy is additionally applicable to make hydrophobic activated carbons for other applications as the absorption of less polar contaminants from liquid or gaseous environments.

Open Access

133. Honey-Derived Hydrochar Containing 2,2,6,6-tetramethylpiperidine-1-oxyl Free Radical for Degradation of Aqueous Organic Pollutants

Authors: Patrinoiu, G; Musuc, AM; Calderon-Moreno, JM; Florea, M; Neatu, F; Ionita, P

Published: DEC 2024, ENVIRONMENTAL PROCESSES-AN INTERNATIONAL JOURNAL, 11, 60, DOI: 10.1007/s40710-024-00731-5

The increasing demand for greener technologies in environmental remediation makes carbon materials from biomass and its derivatives some of the most attractive resources for a sustainable future. However, integrating these materials with stable free radicals remains challenging. This study presents a straightforward one-pot hydrothermal route using raw honey as the carbon source and 4-amino 2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) as the free radical. The addition of TEMPO derivative initiates Maillard reactions between its amino group and the carbonyl groups of the carbohydrates in honey, resulting in the formation of a functionalized hydrochar with a spherical morphology (similar to 8 mu m). The presence of free radicals within the carbonaceous matrix was confirmed by electron spin resonance spectroscopy, supported by infrared spectroscopy, elemental analysis, thermal analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The free radical content was estimated at 0.4 mmol center dot g(-1). The material effectively removed methylene blue, fluorescein, and doxorubicin from water in the presence of green oxidants like hydrogen peroxide and sodium hypochlorite. After 24 h, removal efficiencies reached 92% for doxorubicin, 73% for methylene blue, and 23% for fluorescein. Moreover, the hydrochar demonstrated good regeneration capability, maintaining its dye removal efficiency over several cycles.

Open Access

134. Evaluation of thermal properties of CuCrFeV (Ti, Ta, W, Mo) for nuclear fusion applications

Authors: Rodríguez-López, A; Savoini, B; Monge, MA; Galatanu, A; Galatanu, M

Published: DEC 2024, NUCLEAR MATERIALS AND ENERGY, 41, 101767, DOI: 10.1016/j.nme.2024.101767

This work investigates the influence of composition on the thermal properties of the high entropy alloy family Cu5Cr35Fe35V20-X-5 (at. %), where X = Ti, Ta, W or Mo in the framework of acting as a thermal barrier between the W-based plasma-facing elements and the CuCrZr or Cu-based heat sink components of the fusion reactor. The alloys were produced by arc melting and their microstructure and mechanical properties were previously characterized by XRD, SEM, and Vickers hardness measurements. Thermal properties have been measured on as-cast at thermally treated alloys using the laser flash method in the temperature range 25 degrees C to 600 degrees C to determine the thermal diffusivity, alpha, thermal conductivity, lambda, and specific heat, C-p. Dilatometry experiments were also carried out to obtain the linear thermal expansion coefficient, CTE, as a function of temperature. For all materials, the thermal conductivity increases with temperature from 15 W/m<middle dot>K at RT to 28 W/m<middle dot>K at 600 degrees C and does not significantly depend on the thermal treatment for the Mo-HEA and W-HEA, but increases after aging for the Ta-HEA and Ti-HEA. These values are lower than those of W (similar to 122 W/m<middle dot>K at 600 degrees C) and much lower than for CuCrZr-IG (similar to 354 W/m<middle dot>K at 400 degrees C). The thermal expansion coefficients of these HEAs, similar to 10 x 10(-6) degrees C-1 at RT and similar to 2 x 10(-6) degrees C-1 at 650 degrees C are between those of CuCrZr and the W for the entire operative temperature range. These results indicate that the Cu5Cr35Fe35V20-X-5 (X = Ti, Ta, W, Mo) HEAs have a promising combination of the thermophysical properties, lambda, C-p and CTE, to act as thermal barrier in plasma-facing components that require the union of W- and Cu-based materials.

Open Access

135. Investigation of kesterite to stannite phase transition and band gap engineering in Cu2Zn1-xCoxSnS4 thin films prepared by sol-gel spin coating

Authors: El Mahboub, E; El Khouja, O; Bocirnea, AE; Zakaria, S; Galca, AC; Mansori, M; El Hichou, A

Published: NOV 1 2024, APPLIED SURFACE SCIENCE, 672, 160848, DOI: 10.1016/j.apsusc.2024.160848

In this study, the Cu2Zn1-xCoxSnS4 (CZn1-xCoxTS) films with partial cation substitution of cobalt are synthetized by sol gel spin coating, followed by sulfurization treatment. The incorporation of cobalt cation in the CZTS crystalline lattice as well as the phase transition from kesterite to stannite were confirmed by the X-ray diffraction (XRD) and Raman spectroscopy data. The XRD pattern shows peak-shifting toward higher 2 theta by increasing the Co concentration, indicating a decrease in lattice parameters. The red shift of Raman peaks by increasing x from 0 to 0.6, confirms the phase transition. The CZn1-xCoxTS morphology was observed by scanning electron microscopy, showing large grain size as x increases and a good distribution of elements for all films. Xray photoelectron spectroscopy was employed to study the valence of cations/anions and to probe the chemical bonds. The optical band gap showed a parabolic behavior versus the molar ratio Co/(Co + Zn), this deviation from Vegard's law being induced by the difference in electronegativity between cobalt and zinc. The pure CZTS has a band gap of 1.47 eV, while for CZn0.6Co0.4TS the gap is 1.17 eV, which indicates that the incorporation of cobalt cation produces a red-shift of the band to band transition energy.

Open Access

136. Adsorption-catalysis synergy in the visible-light-driven removal of 17 β-estradiol by (Au)TiO 2 nanotubes-graphene composites

Authors: Cosma, DV; Rosu, MC; Socaci, C; Rostas, AM; Urda, A; Radu, T; Turza, A; Dan, MNC; Costescu, R; Gustavsen, KR; Dobroliubov, O; Wang, KY

Published: JUN 2024, JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, 12, 112885, DOI: 10.1016/j.jece.2024.112885

Visible light-mediated photodegradation offers a sustainable and environmentally friendly solution for removing emerging contaminants from water sources. Herein, we report on the synergy effect between adsorption and visible-light-driven photo-degradation of 17 fl - estradiol using (Au)TiO 2 nanotubes-graphene composites. The graphene structures (graphene oxide - GO or thermally reduced graphene oxide - trGO) provide a platform for strong adsorption of 17 fl -estradiol molecules and facilitate the charge transfer between plasmonic Au nanoparticles and TiO 2 , leading to an improvement of the overall degradation process. To better understand the effect of Au nanoparticles and TiO 2 separately, three different concentrations of Au (1 %, 2.5 %, and 5 %) were prepared and characterized. The estrogenic molecules preferred GO over trGO, suggesting that hydrogen bonds govern the interaction between GO and 17 fl -estradiol. Consequently, a higher photocatalytic efficiency of GOcontaining composites was observed when removing estrogenic molecules. The role of adsorption proved crucial for capturing and retaining more contaminant molecules on the composite surface, thus increasing the odds of surface reactions with the photogenerated carriers. A total removal of 17 fl -estradiol has been obtained for Au (1 %, 2.5 %, and 5 %) TiO 2 nanotubes-GO. The mechanism behind the adsorption and photo-degradation processes has been discussed.

137. In-depth insight into the structural properties of nanoparticulate NiO for CO sensing

Authors: Mihalcea, CG; Stefan, M; Ghica, C; Florea, OG; Stanoiu, A; Simion, CE; Somacescu, S; Ghica, D

Published: APR 1 2024, APPLIED SURFACE SCIENCE, 651, 159252, DOI: 10.1016/j.apsusc.2023.159252

The outstanding properties exhibited by the p-type NiO nanostructures can be greatly affected by morpho-structural and defect characteristics with constructive or competing effects. We have conducted an in-depth study on NiO nanoparticles obtained by hydrothermal synthesis and submitted to various thermal treatments, to monitor the evolution of their structural properties and the effect of the thermal history on their CO sensing. Correlated electron paramagnetic resonance and analytical transmission electron microscopy investigations evidenced an amount of up to 1 % metallic nickel clusters close to surface in the NiO nanoparticles calcined at 400 degrees C and 500 degrees C for 8 h. Subsequent annealing in vacuum and in air of the sample calcined at 400 degrees C resulted in different size distributions and morphology of the NiO nanoparticles and an increase/decrease of the nickel phase, respectively. Comparative CO sensing tests on the two pristine samples and on the sample calcined at 400 degrees C and further annealed in air at 500 degrees C for 2 h showed an increase in the baseline resistance of the later due to the decrease of free charge carriers induced by the dissolution of the nickel clusters. The overall CO sensing results show a strong dependence on the samples thermal history.

Open Access

138. MAPLE deposition of hybrid PLGA-Fe3O4-Cypress-PEDOT: PSS coatings

Authors: Stefan, N; Visan, AI; Grumezescu, V; Kuncser, V; Kuncser, A; Iacob, N; Schinteie, G; Socol, M; Florica, C; Zgura, I; Popescu, RC; Holban, AM; Socol, G

Published: JUN 2024, GIANT, 18, 100250, DOI: 10.1016/j.giant.2024.100250

We report on the Matrix Assisted Pulsed Laser Evaporation, laser technology for depositing biocompatible, antimicrobial, hydrophilic, and biodegradable complex hybrid polymeric system loaded with essential cypress-oil and magnetite nanoparticles as resorbable implants, capable of targeting possible hyperthermia applications, an anticancer moderate field heating therapy. Magnetite nanoparticles based on iron oxide (Fe3O4) coated with Cypress essential oil (denoted: Fe3O4- Cypress) and embedded in PLGA (poly(lactic-co-glycolic acid) (denoted: PLGA-Fe3O4- Cypress-) and PLGA - poly(3,4ethylene dioxythiophene) doped with poly(styrene sulfonate) anions) (PEDOT: PSS) mixture (denoted: PLGA-Fe3O4- Cypress- PEDOT: PSS) were used as MAPLE targets. The controlled drug delivery of the active Cypress oil, an antimicrobial therapeutic agent from Fe3O4- Cypress nanoparticles could be possible by applying an external radio frequency (RF) magnetic field. The Fe3O4-Cypress-based powders as well as the final hybrid coatings have been characterized in terms of stoichiometry, morphology, magnetic, antimicrobial properties, biocompatibility, and response to external physical stimuli. FTIR analyses confirmed the quasi-stoichiometric laser transfer of organic compounds while the XRD evidenced the semicrystalline structure of deposited thin films. SEM and AFM images evidence that conductive polymer addition led to the films' relief flattening and a decrease in the coatings' thickness and roughness by changing the polymeric packaging. The samples containing conductive polymer exhibited 3 times higher current and corrosion rate values. All coatings are hydrophilic and revealed enhanced cellular viability when cultured with osteoblast-like MG-63 cells. The composite structures exhibited significant antimicrobial activity against Gram-positive (Staphylococcus aureus), and Gram -negative (Escherichia coli ) bacteria, as well as to the opportunistic yeast Candida albicans.

139. Influence of molybdenum incorporation on the structural, chemical, and catalytic properties of iron cobaltite and cobalt ferrite catalysts

Authors: Mitran, G; Pavel, OD; Urda, A; Mirea, AG; Neatu, F; Neatu, S; Florea, M

Published: JUN 2 2024, APPLIED CATALYSIS A-GENERAL, 679, 119739, DOI: 10.1016/j.apcata.2024.119739

In this study, molybdenum doped iron cobaltite and cobalt ferrite catalysts were prepared by coprecipitation, and their structural, morphological, and optical, properties were evaluated by XRD, BET, SEM, FTIR, Raman, XPS and UV-VIS techniques. Their catalytic behavior evaluated in the malic acid oxidative decarboxylation reaction underlined the importance of the incorporation of Mo into the structure of iron cobaltite and cobalt ferrite catalysts. The catalysts with the highest molybdenum content forming cobaltite and iron molybdate phases showed better activity, with cobaltite-based catalysts being more active than ferrite-based ones.

Open Access

140. Two decades of continuous progresses and breakthroughs in the field of bioactive ceramics and glasses driven by CICECO-hub scientists

Authors: Fernandes, HR; Kannan, S; Alam, M; Stan, GE; Popa, AC; Buczynski, R; Golebiewski, P; Ferreira, JMF

Published: OCT 2024, BIOACTIVE MATERIALS, 40, DOI: 10.1016/j.bioactmat.2024.05.041

Over the past two decades, the CICECO-hub scientists have devoted substantial efforts to advancing bioactive inorganic materials based on calcium phosphates and alkali-free bioactive glasses. A key focus has been the deliberate incorporation of therapeutic ions like Mg, Sr, Zn, Mn, or Ga to enhance osteointegration and vascularization, confer antioxidant properties, and impart antimicrobial effects, marking significant contributions to the field of biomaterials and bone tissue engineering. Such an approach is expected to circumvent the uncertainties posed by methods relying on growth factors, such as bone morphogenetic proteins, parathyroid hormone, and platelet-rich plasma, along with their associated high costs and potential adverse side effects. This comprehensive overview of CICECO-hub ' s significant contributions to the forefront inorganic biomaterials across all research aspects and dimensionalities (powders, granules, thin films, bulk materials, and porous structures), follows a unified approach rooted in a cohesive conceptual framework, including synthesis, characterization, and testing protocols. Tangible outcomes [injectable cements, durable implant coatings, and bone graft substitutes (scaffolds) featuring customized porous architectures for implant fixation, osteointegration, accelerated bone regeneration in critical-sized bone defects] were achieved. The manuscript showcases specific biofunctional examples of successful biomedical applications and effective translations to the market of bone grafts for advanced therapies.

Open Access

141. The Influence of SnO2 and Noble Metals on the Properties of TiO2 for Environmental Sustainability

Authors: Goncearenco, E; Morjan, IP; Fleaca, C; Dutu, E; Criveanu, A; Viespe, C; Galca, AC; Maraloiu, AV; Stan, MS; Fort, CI; Scarisoreanu, M

Published: APR 2024, SUSTAINABILITY, 16, 2904, DOI: 10.3390/su16072904

In order to find solutions to current worldwide environmental problems, it is crucial to develop sustainable nanomaterials, ideally with multifunctional properties. Considering this, novel TiO2-SnO2@NMs (noble metals: Au and Ag) composites, for use as sustainable nanomaterials, were successfully prepared via a two-step synthesis process consisting of laser pyrolysis followed by the chemical impregnation of the collected materials with noble metals. The addition of SnO2 favors the transformation of TiO2 from a mixture with a majority Anatase phase to one with a Rutile phase majority. With consideration for their level of environmental toxicity, the features of the synthesized nanomaterials were structurally, morphologically, and optically described and assessed for environmental protection applications as gas sensors and photocatalysts. In the case of the Surface Acoustic Wave sensor, based on a pure TiO2 nanopowder, a notable difference in the frequency shift was detected in comparison to the other examined sensors. All sensors responded to the CH4 concentrations tested (0.02-0.1%). On the other hand, when methyl orange was photodegraded under visible light, the results obtained using NMs for decoration revealed that the photocatalytic activity of TiO2-SnO2@NMs was significantly improved compared to the TiO2-SnO2 binary composite, which already has an enhanced photocatalytic activity, compared to pure TiO2. Overall, this work produces nanoparticles that exhibit better sensory and photocatalytic features, as well as higher levels of biocompatibility with skin cells, for use as eco-friendly nanomaterials for a sustainable future.

Open Access

142. Structural and Compositional Analysis of CZTSSe Thin Films by Varying S/(S plus Se) Ratio

Authors: Zaki, MY; Sava, F; Simandan, ID; Mihai, C; Velea, A

Published: AUG 2024, ENERGIES, 17, 3684, DOI: 10.3390/en17153684

The development of kesterite (Cu2ZnSn(S,Se)4, CZTSSe) thin films for photovoltaic applications is highly necessary, given their composition of Earth-abundant, environmentally friendly elements and their compatibility with established photovoltaic technologies. This study presents a novel synthesis approach for CZTSSe films with varied S/(S+Se) ratios, ranging from 0.83 to 0.44, by a two-step magnetron sputtering deposition/annealing process. The first step consists in an initial deposition of stacked Mo/SnS2/Cu layers, which, upon thermal treatment in a sulfur atmosphere, were transformed into Cu2SnS3 (CTS) films. In the second step, further deposition of ZnSe and subsequent annealing in a tin and selenium atmosphere resulted in the formation of a CZTSSe phase. These processes were optimized to fabricate high-quality and single-phase CZTSSe films, thereby mitigating the formation of secondary phases. Characterization techniques, including scanning electron microscopy, demonstrated a clear correlation between decreased S/(S+Se) ratios and enhanced film densification and grain size. Moreover, grazing incidence X-ray diffraction and Raman spectroscopy confirmed a compositional and structural transition from close to CZTS to nearly a CZTSe phase as the S/(S+Se) ratios decreased. This study advances kesterite-based solar cell technology by enhancing the structural properties and crystallinity of the absorber layer, necessary for improving photovoltaic performance.

Open Access

143. Effects of Ti and Sn Substitutions on Magnetic and Transport Properties of the TiFe2Sn Full Heusler Compound

Authors: Popescu, B; Assahsahi, I; Galatanu, M; Galatanu, A

Published: DEC 2024, INORGANICS, 12, 322, DOI: 10.3390/inorganics12120322

The synthesis of polycrystalline TiFe2Sn samples by a route including arc melting and spark plasma sintering with Hf, Y, and In substitutions at the Ti and Sn sites is investigated. For a reduced amount of substitution, around 2 at%, the samples are single phase, while for increased amounts, secondary phases segregate. As is characteristic of these compounds, the Fe-Ti atomic disorder generates a weak ferromagnetic ordering, which is also influenced by the type of substitutional atoms and the secondary phases in the samples with a higher Hf content. The Seebeck coefficient values show an increase for Ti0.98Hf0.02Fe2Sn and for samples with an adjusted Sn content, resulting in slightly increased power factor values. These values reach a maximum for Ti0.98Hf0.02Fe2Sn at approximately 300 K and for TiFe2Sn1.05 at approximately 325 K, namely, 2.69 x 10(-)(4) Wm(-1)K(-2) and 2.52 x 10(-)(4) Wm(-1)K(-2), respectively. The thermal conductivity of all the samples with substitutions increases with respect to the pristine sample. The highest figure of merit value of 0.016 is also obtained for Ti0.98Hf0.02Fe2Sn at 325 K.

Open Access

144. Investigation of high resistivity p-type FZ silicon diodes after 60Co y-irradiation

Authors: Liao, C; Fretwurst, E; Garutti, E; Schwandt, J; Pintilie, I; Nitescu, A; Himmerlich, A; Moll, M; Gurimskaya, Y; Li, Z

Published: APR 2024, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1061, 169103, DOI: 10.1016/j.nima.2024.169103

In this work, the effects of 60Co y -ray irradiation on high resistivity p -type diodes have been investigated. The diodes were exposed to dose values of 0.1, 0.2, 1, and 2 MGy. Both macroscopic (I-V, C-V) and microscopic investigations, by means of Thermally Stimulated Current (TSC) and Deep Level Transient Spectroscopy (DLTS) techniques, were conducted to characterize the radiation -induced changes. The investigated diodes were manufactured on high resistivity p -type Float Zone (FZ) silicon and were further classified into two types based on the isolation technique between the pad and guard ring: p -stop and p -spray. After irradiation, the macroscopic results of current-voltage and capacitance-voltage measurements were obtained and compared with existing literature data. Additionally, the microscopic measurements focused on the development of the concentration of different radiation -induced defects, including the Boron interstitial -Oxygen interstitial (BiOi) complex, the Carbon interstitial -Oxygen interstitial (CiOi) defect, the H40K, and the so-called I*P. To investigate the thermal stability of induced defects in the bulk, isochronal annealing studies were performed in the temperature range of 100 degrees C to 300 degrees C. These annealing processes were carried out on diodes irradiated with doses of 1 and 2 MGy. Furthermore, in order to investigate the unexpected results observed in the C-V measurements after irradiation with high dose values, the surface conductance between the pad and guard ring was measured as a function of both dose and annealing temperature.

Open Access

145. Simulation, Structural, Thermal and Mechanical Properties of the FeTiTaVW High Entropy Alloy

Authors: Martins, R; Gonçalves, AP; Correia, JB; Galatanu, A; Alves, E; Tejado, E; Pastor, JY; Dias, M

Published: APR 2024, METALS, 14, 436, DOI: 10.3390/met14040436

Developing new materials to be applied in extreme environments is an opportunity and a challenge for the future. High entropy alloys are new materials that seem promising approaches to work in nuclear fusion reactors. In this work, FeTaTiVW high entropy alloys were developed and characterized with Molecular Dynamic and Hybrid Molecular Dynamic Monte Carlo simulations. The simulation results show that phase separation originates a lower potential energy per atom and a high level of segregation compared to those of a uniform solid solution. Moreover, the experimental diffractogram of the milled powder shows the formation of a body-centred cubic-type structure and the presence of TiO2. In addition, the microstructure of the consolidated material evidenced three phases: W-rich, Ti-rich, and a phase with all the elements. This phase separation observed in the microstructure agrees with the Hybrid Molecular Dynamic Monte Carlo simulation. Moreover, the consolidated material's thermal conductivity and specific heat are almost constant from 25 degrees C to 1000 degrees C, and linear expansion increases with increasing temperature. On the other hand, specific heat and thermal expansion values are in between CuCrZr and W values (materials chosen for the reactor walls). The FeTaTiVW high entropy alloy evidences a ductile behaviour at 1000 degrees C. Therefore, the promising thermal properties of this system can be attributed to the multiple phases and systems with different compositions of the same elements, which is exciting for future developments.

Open Access

146. Spin asymmetry of O 2p-related states in SrTiO3(001)

Authors: Popescu, DG; Nicolaev, A; Costescu, RM; Borcan, LE; Lungu, GA; Tache, CA; Husanu, MA; Teodorescu, CM

Published: OCT 1 2024, PHYSICA SCRIPTA, 99, 105925, DOI: 10.1088/1402-4896/ad732c

Atomically clean SrTiO3(001) is characterized by low energy electron diffraction, core level and valence band photoelectron spectroscopy, the latter also with spin resolution. Samples prepared by a sputtering-annealing procedure exhibited in-gap states in the valence band spectra, Ti3+ components in Ti 2p core level spectra and a noticeable spin asymmetry in the 3-9 eV binding energy range, which corresponds to valence states of mainly O 2p character. Upon annealing in oxygen, the spin asymmetry vanishes, accompanied by the intensity decrease of the contribution of titanium low ionization states and of in-gap states, indicating that these three phenomena are mutually connected. The observed spin asymmetry may be generated by indirect exchange mediated by the in-gap states between O 2p orbitals, or by the partial Ti 3d character of these states, which acquire non-zero spin in case of incomplete oxygen coordination.

Open Access

147. Functionalization of Carbon Nanotubes and Graphene Derivatives with Conducting Polymers and Their Applications in Dye-Sensitized Solar Cells and Supercapacitors

Authors: Vaduva, M; Burlanescu, T; Baibarac, M

Published: JAN 2024, POLYMERS, 16, 53, DOI: 10.3390/polym16010053

Recent progress concerning the development of counter electrode material (CE) from the dye-sensitized solar cells (DSSCs) and the electrode material (EM) within supercapacitors is reviewed. From composites based on carbon nanotubes (CNTs) and conducting polymers (CPs) to their biggest competitor, namely composites based on graphene or graphene derivate (GD) and CPs, there are many methods of synthesis that influence the morphology and the functionalization inside the composite, making them valuable candidates for EM both inside DSSCs and in supercapacitors devices. From the combination of CPs with carbon-based materials, such as CNT and graphene or GD, the perfect network is created, and so the charge transfer takes place faster and more easily. Inside composites, between the functional groups of the components, different functionalizations are formed, namely covalent or non-covalent, which further provide the so-called synergic effect. Inside CPs/CNTs, CNTs could play the role of template but could also be wrapped in a CP film due to pi-pi coupling enhancing the composite conductivity. Active in regenerating the redox couple I-/I3-, the weakly bound electrons play a key role inside CPs/GD composites.

Open Access

148. Albumin-Rutin Nanoparticles: Design, Characterization, and Biophysical Evaluation

Authors: Chilom, CG; Balan, AE; Enache, TA; Oprea, D; Enculescu, M; Florescu, M; David, M

Published: FEB 2024, COATINGS, 14, 220, DOI: 10.3390/coatings14020220

The bioavailability of the administered drugs that reach the systemic circulation is the first point in resolving the pathology of patients. Albumin-based nanoparticles represent an increasingly used strategy to deliver cancer drugs into cells that otherwise cannot overcome biological barriers. In this work, rutin (Ru), a flavonoid with anticancer and antioxidant potential, was incorporated into bovine serum albumin nanoparticles (BSA-Ru NPs), developed using the desolvation method, and the entire system was characterized and evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis absorption spectroscopy. The results showed that BSA and BSA-Ru NPs are uniformly distributed, have relatively large sizes, and have a time stability of more than 60%. Furthermore, the effect of these nanohybrids on the thermal stability of liposomal membranes was evaluated by surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The viability evaluation was assessed by the tetrazolium salt (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) protocol in the fibroblast L929 line and a high level of biocompatibility, confirmed by SEM results, was found.

Open Access

149. EFFLORESCENT COMPOUNDS - CHARACTERIZATION AND INTERACTIONS WITH LITHIC MATERIAL. INSIGHTS FROM THE EXTERIOR WALL OF THE EPISCOPAL CATHEDRAL - CURTEA DE ARGES

Authors: Buruiana, AT; Zaki, MY; Sava, F; Velea, A; Marin, M; Ispas, E; Petre, A; Simion, CA; Luca, A

Published: 2024, ROMANIAN REPORTS IN PHYSICS, 76, 803, DOI: 10.59277/RomRepPhys.2024.76.803

. The study on efflorescence in salts collected from Curtea de Arges cathedral's exterior wall during restorations aimed to characterize compounds and lithic material using SEM-EDX, XRD, Raman, FTIR. Radiocarbon measurements using AMS method and FTIR results demonstrate decarbonation/recarbonation at the compound-lithic interface but further research is required.

Open Access

150. Crystallization processes of rare-earth doped GdF3 nanocrystals in silicate glass matrix: Dimorphism and photoluminescence properties

Authors: Secu, CE; Bartha, C; Radu, C; Secu, M

Published: OCT 15 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2024.06.335

Rare-earth doped GdF3 nanocrystals embedded in silica glassy matrix have been prepared by controlled crystallization of the xerogel; the influence of rare-earth ion (Pr, Sm, Eu, Tb, Dy, Er, Yb) and additional Li-codopant on structural and optical properties was discussed. The precipitation of RE-doped GdF3 nanocrystalline phase is the result of Gd-trifluoracetate thermolysis revealed as a strong exothermic peak at around 300 degrees C. Structural analysis of RE-doped SiO2-GdF3 glass-ceramic sample calcined at 525 degrees C showed the occurrence of GdF3 nanocrystals of about 25 nm size, showing hexagonal or orthorombic structure depending on the RE-ion. Under UV-light excitation at 273 nm of Gd3+ ions (S-8(7/2) -> I-6(13/2,15/2) transition), photoluminescence spectra showed characteristic RE3+ luminescence due to the non-radiative energy transfer between the excited Gd3+ and acceptor RE ions; the highest energy transfer (congruent to 80 %) was observed for Tb3+ and lowest (congruent to 21 %) for Sm3+.

Open Access

151. Experimental Research on the Influence of Repeated Overheating on the Thermal Diffusivity of the Inconel 718 Alloy

Authors: Arva, ERU; Abrudeanu, M; Negrea, DA; Galatanu, A; Galatanu, M; Rizea, AD; Anghel, DC; Branzei, M; Jinga, AI; Petrescu, MI

Published: SEP 2024, APPLIED SCIENCES-BASEL, 14, 8574, DOI: 10.3390/app14188574

The Inconel 718 superalloy, a precipitation-hardenable material, is of particular interest for applications involving components operating under extreme conditions due to its excellent mechanical properties, high corrosion resistance at temperatures up to 700 degrees C, and good workability. At high temperatures, thermal transfer processes are crucial for temperature distribution across the component's section, structural transformations, and variations in the alloy's properties. The history of accidental overheating events is critical for the microstructure and properties of the alloy. Studies on thermal transfer in the Inconel 718 alloy available in the literature typically focus on the alloy in its as-delivered state. The experimental research presented in this paper examines the influence of repeated overheating history on the thermal diffusivity of the alloy.

Open Access

152. Synthesis of Wrinkled MoS2 Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space

Authors: Mihai, C; Simandan, ID; Sava, F; Buruiana, AT; Bocirnea, AE; Tite, T; Zaki, MY; Velea, A

Published: MAY 2024, SUSTAINABILITY, 16, 3819, DOI: 10.3390/su16093819

Considering the increasing need for sustainable and economical energy storage solutions, the integration of layered materials such as MoS2 into these systems represents an important step toward enhancing energy sustainability and efficiency. Exploring environmentally responsible fabrication techniques, this study assesses wrinkled MoS2 thin films synthesized from distinct Mo and MoS2 targets, followed by sulfurization conducted in a graphite box. We utilized magnetron sputtering to deposit precursor Mo and MoS2 films on Si substrates, achieving thicknesses below 20 nm. This novel approach decreases sulfur by up to tenfold during sulfurization due to the confined space technique, contributing also to avoiding the formation of toxic gases such as SO2 or the necessity of using H2S, aligning with sustainable materials development. Thinner MoS2 layers were obtained post-sulfurization from the MoS2 precursors, as shown by X-ray reflectometry. Raman spectroscopy and grazing X-ray diffraction analyses confirmed the amorphous nature of the as-deposited films. Post-sulfurization, both types of films exhibited crystalline hexagonal MoS2 phases, with the sulfurized Mo showing a polycrystalline nature with a (100) orientation and sulfurized MoS2 displaying a (00L) preferred orientation. The X-ray photoelectron spectroscopy results supported a Mo:S ratio of 1:2 on the surface of the films obtained using the MoS2 precursor films, confirming the stoichiometry obtained by means of energy dispersive X-ray spectroscopy. Scanning electron microscopy and atomic force microscopy images revealed micrometer-sized clusters potentially formed during rapid cooling post-sulfurization, with an increased average roughness. These results open the way for the further exploration of wrinkled MoS2 thin films in advanced energy storage technologies.

Open Access

153. Fractal Behavior of Nanostructured Pt/TiO2 Catalysts: Synthesis, Characterization and Evaluation of Photocatalytic Hydrogen Generation

Authors: Vasile, A; Dobrescu, G; Bratan, V; Teodorescu, M; Munteanu, C; Atkinson, I; Negrila, C; Papa, F; Balint, I

Published: SEP 2024, CATALYSTS, 14, 619, DOI: 10.3390/catal14090619

The fractal characterization of supported nanoparticles is a useful tool for obtaining structural and morphological information that strongly impacts catalytic properties. We have synthesized and characterized Pt supported on TiO2 nanostructures. Triblock copolymers with thermosensitive properties were used as templating agents during the synthesis process. In addition to the several techniques used for the characterization of the materials, we carried out fractal analysis. The prepared materials showed a reduction in the band gap of TiO2 from 3.44 to 3.01 eV. The extended absorption in the 500-700 nm regions is mostly attributed to the presence of supported Pt nanoparticles. The ability of the nanostructured Pt/TiO2 catalysts to generate H-2 in an aqueous solution was evaluated. The test reaction was carried out in the presence of methanol, as a hole scavenger, under simulated solar light. Pt/TiO2-3TB shows the highest rate of H-2 (4.17 mmol h(-1) g(cat)(-1)) when compared to Pt/TiO2-0TB (3.65 mmol h(-1) g(cat)(-1)) and Pt/TiO2-6TB (2.29 mmol h(-1) g(cat)(-1)) during simulated solar light irradiation. Pt/TiO2-3TB exhibits a more structured organization (fractal dimensions of 1.65-1.74 nm at short scales, 1.27-1.30 nm at long scales) and a distinct fractal behavior. The generation of hydrogen via photocatalysis can be linked to the fractal characteristics.

Open Access

154. Bioactive Hybrids Containing Artificial Cell Membranes and Phyto-Gold-Silver Chloride Bio-Nanoparticles

Authors: Barbinta-Patrascu, ME; Nichita, C; Enculescu, M; Maraloiu, VA; Bacalum, M; Ungureanu, C; Negrila, CC; Zgura, I

Published: NOV 2024, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 25, 11929, DOI: 10.3390/ijms252211929

This research targets the need for eco-friendly strategies in the synthesis of bioactive materials, addressing the importance of valorization of vegetal waste. This study focuses on developing biohybrids containing biomimetic lipid vesicles and phytosynthesized gold-silver chloride nanoparticles (AuAgCl NPs) derived from Achillea millefolium L. extract. By leveraging the natural antioxidant and antimicrobial properties of the plant, the research proposes a sustainable approach to creating materials with potential biomedical applications. The biomimetic membranes were loaded with chlorophyll a, a natural spectral marker. Three types of bioactive materials (biohybrids) were developed by varying the lipid vesicle/AuAgCl NP ratio. Optical (UV-Vis, fluorescence emission, FTIR), structural (XRD), elemental (EDX, XPS), and morphological (TEM) studies were performed to characterize the bio-developed materials. The hydrophobic/hydrophilic characteristics of the samples were investigated by measuring the water contact angle, and their size was estimated by DLS and TEM. Zeta potential measurements were used to evaluate the physical stability of phyto-developed particles. Antioxidant properties of phyto-particles were investigated through the chemiluminescence technique. The obtained biomaterials exhibited high antioxidant activity and antiproliferative activity against HT-29 and B-16 cancer cells. Therapeutic index values were calculated for each biohybrid. Additionally, the bio-prepared hybrids revealed biocidal action against Staphylococcus aureus and Enterococcus faecalis. The phyto-developed biomaterials are promising in biomedical applications, particularly as adjuvants in cancer therapy.

155. Downscaling grain size toward the nanometre range - A key-factor for tuning the crystalline structure, phase transitions, dielectric and ferroelectric behaviour in Ba 0.8 Sr 0.2 TiO 3 ceramics

Authors: Patru, RE; Stanciu, CA; Surdu, VA; Soare, EM; Trusca, RD; Vasile, BS; Nicoara, AI; Trupina, L; Pasuk, I; Botea, M; Horchidan, N; Mitoseriu, L; Pintilie, L; Pintilie, I; Ianculescu, AC

Published: JUN 2024, PROGRESS IN SOLID STATE CHEMISTRY, 74, 100457, DOI: 10.1016/j.progsolidstchem.2024.100457

The present study aims to describe the role of the grain size on the properties of submicron- and nano-structured Ba0.8Sr0.2TiO3 (BST) ceramics. Dense (1 - 2% porosity) ceramics with average grain sizes in the range of (77 234) nm were consolidated under different spark plasma sintering conditions starting from nanopowders with a mean particle size of 70 nm, synthesized via the acetate variant of the sol-gel method. The structural analysis based on XRD data revealed a mixture of cubic and tetragonal modifications at room temperature for the precursor powders and for all the investigated ceramics. The structural heterogeneity of the individual ceramic grains with coexistence of cubic and tetragonal polymorphs was confirmed by HR-TEM investigations. Accordingly, a "brick-wall" model with cubic grain boundary regions and tetragonal grain cores is proposed. By increasing the grain size, from 77 to 234 nm, a decrease of the phase transitions diffuseness accompanied by an increase of the permittivity maxima (from 650 to 4500) and dielectric losses (from 5 to 7.5%, at 100 Hz), was detected by broadband dielectric spectroscopy. No variation of the Curie temperature in the investigated Ba0.8Sr0.2TiO3 ceramics was detected, unlike typically reported for BaTiO3 ceramics with similar grain sizes. The Curie-Weiss temperature and the Curie constant decrease when grain size is diminished, indicating an overall reduction of the ferroelectric active volume, as a scaling effect. The ferroelectric switching was demonstrated for all the selected fine-grained BST ceramics, either at nanoscale or macroscopically, with an increased ferroelectric character for the coarser submicron-structured ceramics, with respect to the nanocrystalline one. The observed properties of the fine-grained Ba0.8Sr0.2TiO3 ceramics are explained in the frame of multiphase coexistence and ferroelectricity "dilution" due to the increasing role of non-ferroelectric grain boundaries when reducing grain size and complete the knowledge on the scale-dependent properties of dense fine-grained BaTiO3-based ceramics.

156. A green way for pyruvic acid synthesis from biomass-derived L-malic acid on tetrahedral versus octahedral cobalt sites/hematite

Authors: Mitran, G; Urda, A; Pavel, OD; Neatu, S; Florea, M; Neatu, F

Published: JAN 2024, BIOMASS CONVERSION AND BIOREFINERY, 14, DOI: 10.1007/s13399-022-02513-1

A series of cobalt-iron mixed oxides, CoxFe3-xO4 (x = 0; 0.05; 0.1; 0.15), were synthesized by coprecipitation and tested for oxidative decarboxylation of malic acid to pyruvic or malonic acid. The characterization of catalysts was performed by different techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT) and Ultraviolet-visible spectroscopy (UV-Vis). Among studied catalysts, Co0.15Fe2.85O4 sample (denoted Co3Fe) showed the highest malic acid conversion in oxidative decarboxylation reaction as well as the highest pyruvic acid yield. This behavior can be due to the fact that this sample has the highest content of tetrahedral Co2+ that replaces Fe3+ from octahedral position that determine an increased number of defects that play a crucial role for the malic acid conversion.

Open Access

157. Customized flexible platform - starting point for the development of wearable sensor for the direct electrochemical detection of kynurenic acid in biological samples

Authors: Irimes, MB; Tertis, M; Bogdan, D; Diculescu, V; Matei, E; Cristea, C; Oprean, R

Published: DEC 1 2024, TALANTA, 280, 126684, DOI: 10.1016/j.talanta.2024.126684

Kynurenic acid (KA) is an active metabolite of tryptophan with notable biological effects, such as antioxidant, neuroprotective, and anti-inflammatory properties. It often undergoes changes of the concentration in biological fluids in chronic diseases. Thus, detecting KA is of great importance for diagnosing inflammatory and neurodegenerative conditions, monitoring disease progression, and assessing responses to pharmacological treatment. This study aimed to design a tailored, flexible platform for sensitive and direct electrochemical detection of KA in biological fluids. Carbon-based electrodes were custom-printed in the lab using specialized inks and flexible substrates. The working electrodes were further functionalized with graphene oxide and subsequently electrochemically reduced to increase the sensitivity toward the analyte. An optimized differential pulse voltammetry protocol was developed for KA detection. The elaborated platform was firstly characterized and then evaluated regarding the analytical performances. It showed a good limit of detection (3 nM and demonstrated the capability to detect KA across a broad concentration range (0.01-500 mu M). Finally, the elaborated flexible platform, was succesfully applied for KA determination in serum and saliva samples, in comparison with an optimized HPLC-UV method. The developed platform is the first example of in-lab printed flexible platform reported in literature so far for KA detection. It is also the first study reported in the literature of detection of KA in raw saliva collected from 10 subjects. The sensitivity towards the target analyte, coupled with the adaptability and portability, showcases the potential of this platform for thus illustrating great potential for further development of wearable sensors and biomedical applications.

158. Electron paramagnetic resonance signature of rock-forming blue quartz from the Albesti (Romania) granite

Authors: Joita, AC; Ghica, D; Stefan, M; Bulat, S; Pantia, AI

Published: SEP 2024, MINERALOGY AND PETROLOGY, 118, DOI: 10.1007/s00710-024-00868-z

The ca. 480 Ma Albesti granite (Southern Carpathians, Romania) is characterized by the presence of color zoned blue quartz grains, and is part of the rather extensive European Cambro-Ordovician blue quartz landscape. The color is heat sensitive, fading at temperatures as low as 300degree celsius, inconsistent with the thermally stable, light scattering, nanometric rutile/ilmenite inclusions cited in literature. Extensive X- and Q-band electron paramagnetic resonance (EPR) investigations were carried out, searching for distinctive features of the Albesti quartz that are directly or indirectly involved in the generation of the blue coloration. The analyzed quartz grains were extracted from three granite samples of varying coloration and anisotropy, and the quartz from each rock sample was further separated into colored and colorless fractions. The paramagnetic E' and [AlO4]0 centers, as well as Mn2+ ions localized in traces of amorphous associated minerals at grain boundaries or fissure planes, were observed in all quartz samples. Broad EPR lines associated with the presence of magnetic clusters were observed in the spectra of the white quartz sample and the corresponding colorless one. Isochronal annealing up to 500degree celsius induced the correlated recombination of the E' and [AlO4]0 centers, the strong decrease of the Mn2+ spectrum and the formation of a minority iron oxide phase at the grain boundaries and/or fissure planes. The EPR signature was similar for the colored and the corresponding colorless quartz samples, before and after annealing, showing that the heat sensitive coloration of the Albesti quartz does not directly involve the presence of paramagnetic defects and/or minority magnetic phases.

Open Access

159. MAPLE-Deposited Perylene Diimide Derivative Based Layers for Optoelectronic Applications

Authors: Breazu, C; Girtan, M; Stanculescu, A; Preda, N; Rasoga, O; Costas, A; Catargiu, AM; Socol, G; Stochioiu, A; Popescu-Pelin, G; Iftimie, S; Petre, G; Socol, M

Published: NOV 2024, NANOMATERIALS, 14, 1733, DOI: 10.3390/nano14211733

Nowadays, the development of devices based on organic materials is an interesting research challenge. The performance of such devices is strongly influenced by material selection, material properties, design, and the manufacturing process. Usually, buckminsterfullerene (C60) is employed as electron transport material in organic photovoltaic (OPV) devices due to its high mobility. However, considering its low solubility, there have been many attempts to replace it with more soluble non-fullerene compounds. In this study, bulk heterojunction thin films with various compositions of zinc phthalocyanine (ZnPc), a perylene diimide derivative, or C60 were prepared by matrix-assisted pulsed laser evaporation (MAPLE) technique to assess the influence of C60 replacement on fabricated heterostructure properties. The investigations revealed that the optical features and the electrical parameters of the organic heterostructures based on this perylene diimide derivative used as an organic acceptor were improved. An increase in the JSC value (4.3 x 10-4 A/cm2) was obtained for the structures where the perylene diimide derivative acceptor entirely replaced C60 compared to the JSC value (7.5 x 10-8 A/cm2) for the heterostructure fabricated only with fullerene. These results are encouraging, demonstrating the potential of non-fullerene compounds as electron transport material in OPV devices.

Open Access

160. Physicochemical Characterization of Ca- and Cu-Decorated TiO2 Microparticles and Investigation of Their Antimicrobial Properties

Authors: Neacsu, A; Chihaia, V; Bucuresteanu, R; Ficai, A; Trusca, RD; Surdu, VA; Nicolaev, A; Cojocaru, B; Ionita, M; Calinescu, I; Parvulescu, V; Ditu, LM

Published: SEP 2024, MATERIALS, 17, 4483, DOI: 10.3390/ma17184483

Ca- and Cu-decorated TiO2 microparticles are titanium dioxide nanoparticles that have been decorated with calcium and copper ions. TiO2, CaO, and CuO are low-cost, non-toxic, and non-hazardous materials. The aim of the present study was the physicochemical characterization of Ca- and Cu-decorated TiO2 microparticles and the evaluation of their antimicrobial activity. Thus, Ca2+ and Cu2+ species were incorporated onto TiO2 surfaces by a two-step wet method. The obtained TiO2-CaO-CuO composites were characterized by several experimental techniques. The electronic structure and charge properties of the composites were investigated by density functional theory calculations. Furthermore, the composites were successfully tested for inhibitory effects on Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans standard strains. The zeta potential data indicate that the physiological condition of investigated microbial strains was strongly affected in presence of a dispersion of 10 mu g/L of composites in a saline phosphate buffer also, the recorded SEM images show a damaged microbial cell surface in the presence of composites.

161. Atomically Thin MoS2 Layers Selectively Grown on Mo Patterned Substrates for Field-Effect-Controlled Photosensors

Authors: Stavarache, I; Palade, C; Slav, A; Dascalescu, I; Lepadatu, AM; Trupina, L; Matei, E; Ciurea, ML; Stoica, T

Published: FEB 28 2024, ACS APPLIED NANO MATERIALS, 7, DOI: 10.1021/acsanm.3c05809

Selective growth of 2D MoS2 layers on patterned substrates is highly desired for easy fabrication of devices. Selectively grown 2D MoS2 on Mo patterned substrates for the formation of intimate metallic contact was obtained by a Mo-CVD method in which MoO2 from an oxidized Mo pattern and S powder are the growth precursors. Mo films were deposited by magnetron sputtering on SiO2(300 nm)/c-Si substrates and patterned by photolithography techniques for obtaining Mo strips and finger contact structures, with the gap between the strips and finger varied from 5 to 20 mu m. The filling of the gap by selectively grown atomically thin MoS2 plates of 1-2 monolayers (MLs) was demonstrated by scanning electron microscopy and atomic force microscopy imaging. Field effect devices for the characterization of the photosensitivity of selectively grown MoS2 have been fabricated from finger contact structures. The dark current is drastically reduced from 10(-9) to 10(-13)-10(-14) A by varying the gate voltage from +7 to -7 V, showing the n-type semiconductor behavior of the selectively grown 2D MoS2. High photosensitivity of 10(5) (%) was obtained for 4.5 x 10(-4) mW/cm(2) at 650 nm wavelength illumination. The spectral responsivity reaches values of 15-25 A/W at 600 nm wavelength and shows an energy onset of 1.72-1.77 eV corresponding to about 2 ML MoS2. The carrier-trapping effect responsible for the slow part of the device response can be caused by structural defects and also by adsorbed molecules like in gas sensors.

Open Access

162. Vortex-Mixing Microfluidic Fabrication of Micafungin-Loaded Magnetite-Salicylic Acid-Silica Nanocomposite with Sustained-Release Capacity

Authors: Mercan, DA; Niculescu, AG; Birca, AC; Cristea, DE; Morosan, A; Tudorache, DI; Purcareanu, B; Vasile, BS; Radu, D; Grigoroscuta, MA; Hadibarata, T; Mihaiescu, DE; Grumezescu, AM

Published: DEC 2024, MATERIALS, 17, 5816, DOI: 10.3390/ma17235816

Iron oxide nanoparticles were synthesized using a vortex microfluidic system and subsequently functionalized with a primary shell of salicylic acid, recognized for its ability to increase the stability and biocompatibility of coated materials. In the second stage, the vortex platform was placed in a magnetic field to facilitate the growth and development of a porous silica shell. The selected drug for this study was micafungin, an antifungal agent well regarded for its effectiveness in combating fungal infections and identified as a priority compound by the World Health Organization (WHO). The resulting nanocomposite system was characterized using various techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), Brunauer-Emmett-Teller (BET) analysis, UV-Vis spectroscopy, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The synthesis method produced nanoparticles with dimensions of 5-7 nm, highlighting the advantages of the chosen approach. A desorption profile was established using a continuous-flow, UV-Vis analysis system, indicating that the bioactive compound was released slowly; after two hours, approximately 50% of the loaded micafungin was detected in the release medium. Furthermore, the results obtained from the FT-ICR MS analysis provided molecular-level confirmation, thereby supporting the release mechanism of micafungin from the nanosystem.

163. Growth and optimization of spray coated Cu 2 BaSnS 4 thin films for solar photovoltaic application

Authors: Kadari, AS; Ech-Chergui, AN; Ghediya, PR; Guendouz, A; Guezzoul, M; El Khouja, O; Bocirnea, AE; Driss-Khodja, K; Amrani, B; Galca, AC

Published: AUG 2024, MATERIALIA, 36, 102178, DOI: 10.1016/j.mtla.2024.102178

Quaternary multicomponent Cu2BaSnS4 (CBTS) has emerged as a potential absorber material due to its abundant and nontoxic constituents, high absorption coefficient (10-4 cm-1) and suitable bandgap (1.5-2.0 eV) for the solar photovoltaic application. In this study, polycrystalline CBTS thin layers have been deposited by a typical spray pyrolysis technique on glass substrates using different substrate temperatures (Ts = 200, 250, 300 and 350 degrees C) followed by annealing in a sulfur-rich atmosphere at 550 degrees C under an argon flow. The (micro-)structural, compositional, and optical properties of both types of films have been studied. Analysis of x-ray diffractogram (XRD) patterns for all acquired films showed the presence of polycrystalline CBTS alongside various secondary phases, including Cu2SnS3 being predominant. Nonetheless, the XRD of the films deposited at 250 degrees C and annealed at 550 degrees C showed only the CBTS phase. Raman spectroscopy confirm the formation of the trigonal phase of CBTS. The presence of Cu, Ba, Sn and S in CBTS thin films was confirmed by X-ray photoelectron spectroscopy and Energy-dispersive X-ray spectroscopy. Scanning electron micrographs show a smooth and dense structure with enhanced crystallinity and improved uniformity. Overall, the physical properties of CBTS thin films were found to be spray deposition temperature dependent. An appropriate optical band gap of 1.6 to 1.8 eV and a compact structure indicate their prospective for solar cell applications.

Open Access

164. Expression of concern: Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

Authors: Mazur, M; Barras, A; Kuncser, V; Galatanu, A; Zaitzev, V; Turcheniuk, KV; Woisel, P; Lyskawa, J; Laure, W; Siriwardena, A; Boukherroub, R; Szunerits, S

Published: DEC 19 2024, NANOSCALE, 17, DOI: 10.1039/d4nr90209b

Expression of concern for 'Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors' by Mykola Mazur et al., Nanoscale, 2013, 5, 2692-2702, https://doi.org/10.1039/C3NR33506B.

Open Access

165. Nanocomposites Based on Iron Oxide and Carbonaceous Nanoparticles: From Synthesis to Their Biomedical Applications

Authors: Vaduva, M; Nila, A; Udrescu, A; Cramariuc, O; Baibarac, M

Published: DEC 2024, MATERIALS, 17, 6127, DOI: 10.3390/ma17246127

Nanocomposites based on Fe3O4 and carbonaceous nanoparticles (CNPs), including carbon nanotubes (CNTs) and graphene derivatives (graphene oxide (GO) and reduced graphene oxide (RGO)), such as Fe3O4@GO, Fe3O4@RGO, and Fe3O4@CNT, have demonstrated considerable potential in a number of health applications, including tissue regeneration and innovative cancer treatments such as hyperthermia (HT). This is due to their ability to transport drugs and generate localized heat under the influence of an alternating magnetic field on Fe3O4. Despite the promising potential of CNTs and graphene derivatives as drug delivery systems, their use in biological applications is hindered by challenges related to dispersion in physiological media and particle agglomeration. Hence, a solid foundation has been established for the integration of various synthesis techniques for these nanocomposites, with the wet co-precipitation method being the most prevalent. Moreover, the dimensions and morphology of the composite nanoparticles are directly correlated with the value of magnetic saturation, thus influencing the efficiency of the composite in drug delivery and other significant biomedical applications. The current demand for this type of material is related to the loading of a larger quantity of drugs within the hybrid structure of the carrier, with the objective of releasing this amount into the tumor cells. A second demand refers to the biocompatibility of the drug carrier and its capacity to permeate cell membranes, as well as the processes occurring within the drug carriers. The main objective of this paper is to review the synthesis methods used to prepare hybrids based on Fe3O4 and CNPs, such as GO, RGO, and CNTs, and to examinate their role in the formation of hybrid nanoparticles and the correlation between their morphology, the dimensions, and optical/magnetic properties.

166. Optimizing photocurrent intensity in layered SiGe heterostructures

Authors: Sultan, MT; Ciurea, ML; Stavarache, I; Thórarinsdóttir, KA; Arnalds, UB; Teodorescu, ; Manolescu, A; Ingvarsson, S; Svavarsson, HG

Published: OCT 1 2024, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 39, 105007, DOI: 10.1088/1361-6641/ad70d4

We study the dependence of photo-spectral intensity on tri- and multilayers of SiO2/[SiGe [ dSiGe]/SiO2]N with repetitions N = 1 to 10 and thicknesses dSiGe=5-100 nm. Photocurrent analysis reveals a bimodal spectral feature. A comparison of the photocurrent analysis between tri- and multilayers shows that in the multilayer structures, the photo-spectral intensity increases with increasing repetition N. The change in intensity could then be further tuned by changing the thickness of the SiGe layers dSiGe. We attribute the change in intensity to an increase in tensile strain, along with increased Ge atomic concentration and reduced SiGe-nano cluster size.

167. A Synthetic Approach for Oxadiazole-Decorated Azobenzene Photoswitches

Authors: Dobre, AF; Hanganu, A; Nicolau, I; Popescu, CC; Paun, A; Madalan, AM; Tablet, C; Mirea, AG; Matache, M

Published: FEB 2024, CHEMPLUSCHEM, 89, DOI: 10.1002/cplu.202300504

This work reports the design and synthesis of novel oxadiazole-decorated azobenzenes, structural analysis of the resulting compounds and behavior under light irradiation. The synthetic strategy involved constructing amino functionalized heterocyclic key intermediates which were used either to yield electrophilic diazonium salts able to react with phenol moieties or as nucleophilic partners in Bayer-Mills reaction with nitroso-substituted derivatives. The amino-derived oxadiazole intermediates were investigated by absorption and emission spectroscopy providing blue and green emitted light. The target oxadiazole-decorated azobenzenes were structurally characterized, including solid-state structures, and subsequently used in irradiation experiments in order to take advantage of the azo group known to provide photoswitching abilities. We noticed quenching of the emissive properties in presence of the azo group; however, all compounds were very stable to repeated cycles of light irradiation. In addition, according to structural diversification we could obtain half-lives of the meta stable isomers within hours to hundreds of hours range. The experimental results were very well correlated with DFT calculations. The synthesis of novel oxadiazole-decorated azobenzenes using amino functionalised heterocyclic intermediates used either to provide electrophilic diazonium salts able to react with phenols or as nucleophilic partners in Bayer-Mills reaction is reported in this work. The oxadiazole-decorated azobenzenes were used in irradiation experiments to determine the parameters that characterize a photoswitch, yielding appealing results. The experimental results were very well correlated with DFT calculations.+image

Open Access

168. Functionalization of graphene oxide surface by conjugation with glucosamine and analysis of interactions occurring in nanoceramic-graphene heterostructures

Authors: Kukielski, M; Kasprzak, A; Zurowski, R; Tanska, J; Wiecinska, P; Wieclaw-Midor, A; Zygmuntowicz, J; Grigoroscuta, MA; Wiecinski, P

Published: JAN 1 2024, POWDER TECHNOLOGY, 431, 119089, DOI: 10.1016/j.powtec.2023.119089

The paper describes the chemical modification of the graphene oxide (GO) surface with glucosamine, which was conjugated to GO via a carbodiimide-mediated amidation-type reaction. The efficiency of the reaction was confirmed by FT-IR and Raman spectroscopy and elemental analysis. The elaborated functionalization significantly reduces the agglomeration of graphene oxide platelets. The interactions at the interface of GO and two types of ceramic nanoparticles (ZrO2 and Al2O3 with particle sizes of 58 nm and 158 nm, respectively) were examined by zeta potential measurements at different pH values. The viscosity of ZrO2 suspensions (35 vol% of solid loading) at 1.5 s- 1 increases from 24.8 Pas to 170.7 Pas and 142.7 Pas with the addition of GO and f-GO, respectively. The interfaces at ceramic-graphene heterostructures obtained by slip casting method have been analyzed by SEM. The investigations revealed the presence of multilayer graphene oxide and flexible single-layer f-GO within the ceramic matrix.

Open Access

169. Enhancing SiGeSn nanocrystals SWIR photosensing by high passivation in nanocrystalline HfO2 matrix

Authors: Dascalescu, I; Palade, C; Slav, A; Stavarache, I; Cojocaru, O; Teodorescu, VS; Maraloiu, VA; Lepadatu, AM; Ciurea, ML; Stoica, T

Published: FEB 12 2024, SCIENTIFIC REPORTS, 14, 3532, DOI: 10.1038/s41598-024-53845-z

SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500-800 degrees C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and beta-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices.

Open Access

170. Biologically Synthesized Gold Nanoparticles with Enhanced Antioxidant and Catalytic Properties

Authors: David, M; Enache, TA; Barbu-Tudoran, L; Bala, C; Florescu, M

Published: SEP 2024, PHARMACEUTICALS, 17, 1105, DOI: 10.3390/ph17091105

Increasing levels of reactive oxygen species generate oxidative stress in the human body that can lead to various medical conditions. The use of nanomaterials exhibiting antioxidant properties may prevent these effects. The biological synthesis of metallic nanoparticles using plant extracts with antioxidant properties can offer benefits due to their active compounds. The used extracts contained reducing and stabilizing agents, which were shown to be transferred onto the gold nanoparticles, functionalizing them. Herin, we report a gold nanoparticle synthesis by eco-friendly biological methods (b-AuNPs) using extracts of sea buckthorn, lavender, walnuts, and grapes, obtained through ultrasound-assisted extraction and pressure-enhanced extraction. The obtained b-AuNPs were characterized by UV-Vis and FTIR spectroscopies and visualized using transmission electron microscopy. The catalytic and scavenging effect of the b-AuNPs towards H2O2 (as reactive oxygen species) was evaluated electrochemically, highlighting the protective behavior of b-AuNPs towards lipid peroxidation. All experiments demonstrated the stability and reproducibility of prepared b-AuNPs with enhanced antioxidant and catalytic properties, opening a new perspective for their use in biomedical applications.

171. Formation of skyrmion phase in the Fe-Co-Si system by mechanochemical activation

Authors: Sorescu, M; Tolea, F; Sofronie, M; Kuncser, V; Craig, AJ; Aitken, JA

Published: SEP 1 2024, PHYSICA B-CONDENSED MATTER, 688, 416153, DOI: 10.1016/j.physb.2024.416153

Fe, Co and Si powders were exposed to mechanochemical activation by high-energy ball milling for 0, 2, 4, 8 and 12 h. The samples were subsequently characterized by Mo<spacing diaeresis>ssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. The room temperature Mo<spacing diaeresis>ssbauer measurements were consistent with the occurrence of FeCo2Si and Fe0.5Co0.5Si crystalline phases. The low temperature Mo<spacing diaeresis>ssbauer spectra confirmed the absence of superparamagnetism up to 44 K in the milled system. XRPD patterns supported the phase sequence derived from Mo<spacing diaeresis>ssbauer spectroscopy. The coercive field was found to increase with the ball milling time (BMT). Zero-field-cooling-field-cooling (ZFC-FC) measurements performed at 200 Oe in the temperature range 5-300 K evidenced the transition to the skyrmion phase of the Fe0.5Co0.5Si material below the critical temperature of 44 K. The optical absorption in the UV-Vis-NIR region of the spectrum was found to increase with BMT.

Open Access

172. Investigation of the Effect of the Third Cation M (M = Mg, Al, Mn, and Fe) on the Properties and Catalytic Behavior in Ethane Oxidative Dehydrogenation of M-NiNbO Mixed Oxides

Authors: Ivan, SB; Trandafir, MM; Papa, F; Negrila, CC; Loridant, S; Florea, M; Popescu, I; Marcu, IC

Published: OCT 25 2024, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 63, DOI: 10.1021/acs.iecr.4c02682

This work examines the effect of incorporating a third cation M (M = Mg, Al, Mn, or Fe) into Nb-promoted NiO catalysts (Ni0.85Nb0.15O) on their physicochemical properties and catalytic performance in the oxidative dehydrogenation (ODH) of ethane into ethylene. Therefore, a series of mixed oxides with the composition Ni0.765Nb0.135M0.1O was synthesized, characterized, and analyzed for catalytic behavior. The addition of the third cation markedly modified the redox and semiconductive properties of the catalysts, thus affecting their ODH performance. The selectivity toward ethylene was strongly dependent on the cation modifier, as it modulated the density of nonselective sites on the catalyst surface. In the low-temperature region, Mn-NiNbO demonstrated the highest conversion rates but with the lowest ethylene selectivity, whereas Fe-NiNbO, despite being less active than the undoped NiNbO, exhibited the highest ethylene selectivity. Overall, undoped NiNbO emerged as the best catalyst in terms of both activity and selectivity at isoconversion. All catalysts underwent partial reduction under reaction conditions, with the degree of reduction inversely correlated with the specific reaction rates. Although none of the catalysts remained stable at 400 degrees C, Al-NiNbO showed the least deactivation over time. The deactivation was linked to a reduction in p-type conductivity and a loss of redox functionality during operation.

Open Access

173. Hindrances and solutions on the path towards adjoined barium titanate-hydroxyapatite ceramics with uncompromised piezoelectric and biological responses

Authors: Cioangher, M; Amarande, L; Stan, GE; Nedelcu, L; Pasuk, I; Leonat, L; Popa, AC; Miclea, LC; Savopol, T; Moisescu, MG; Tivig, I

Published: SEP 1 2024, CERAMICS INTERNATIONAL, 50, DOI: 10.1016/j.ceramint.2024.05.268

The synergistic piezoelectric and osteoconductive properties of barium titanate (BT) and hydroxyapatite (HA) could stir the development of a new generation of synthetic bone graft substitutes, with capability for rapid and safe osseointegration. The research focused on two concurrent approaches for coupling the BT and HA materials: (i) conventional sintering of BT-HA powder mixtures; and (ii) functionalization of pre-sintered BT with HA coatings using magnetron sputtering (MS). Irrespective of the BT/HA ratios ranging from 95/5 to 80/20 wt%, nanocrystalline or highly-crystallized nature of the powders, sub-micron- or micron-sized particle dimensions, and sintering temperature, it was observed that the BT-HA reactivity cannot be prevented above 800 degrees C. At higher temperatures in the range of 1000-1300 degrees C, HA undergoes decomposition and extensively reacts with BT, leading to the formation of several secondary phases such as CaTiO3, Ba2Ca(PO4)2, BaCa6(PO4)4O, BaCa(PO3)4, and beta-Ca2P2O7. As a consequence, the cytocompatibility assessed in fibroblast and osteoblast cell cultures, as well as the piezoelectric response, were significantly altered. Applying HA coatings by MS to the sintered BT ceramics successfully preserved their piezoelectric properties, while also providing an unaltered cytocompatible and osteogenic-prone surface. The HA coatings were fully crystallized at post-deposition annealing temperatures of 550 and 700 degrees C, achieving crystalline qualities comparable to HA powders sintered at 1100 and 1200 degrees C, respectively. No reactivity events between BT and HA were observed. Partial reactivity was only noticeable upon annealing at 1000 degrees C. Therefore, it is suggested that the HA coating of BT is effective in seamlessly coupling the piezoelectric and osteogenic properties of the two constituents without compromise.

Open Access

174. Novel Antimicrobial Agents Based on Zinc-Doped Hydroxyapatite Loaded with Tetracycline

Authors: Iconaru, SL; Predoi, D; Ciobanu, CS; Negrila, CC; Trusca, R; Raaen, S; Rokosz, K; Ghegoiu, L; Badea, ML; Cimpeanu, C

Published: SEP 2024, ANTIBIOTICS-BASEL, 13, 803, DOI: 10.3390/antibiotics13090803

In this paper, we present for the first time the development of zinc-doped hydroxyapatite enriched with tetracycline (ZnHApTe) powders and provide a comprehensive evaluation of their physico-chemical and biological properties. Various techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used for the sample's complex evaluation. Moreover, the biocompatibility of zinc-doped hydroxyapatite (ZnHAp) and ZnHApTe nanoparticles was evaluated with the aid of human fetal osteoblastic cells (hFOB 1.19 cell line). The results of the biological assays suggested that these nanoparticles hold great promise as potential candidates for the future development of novel biocompatible and antimicrobial agents for biomedical applications. The antimicrobial properties of the ZnHAp and ZnHApTe nanoparticles were assessed using the standard reference microbial strains Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231. The results of the in vitro antimicrobial assay demonstrated that both tested materials exhibited good antimicrobial activity. Additionally, these data also indicated that the antimicrobial effects of the ZnHAp nanoparticles were intensified by the presence of tetracycline (Te). Furthermore, the results also suggested that the antimicrobial activity of the samples increased with the incubation time.

175. Annealing Effects on the Charging-Discharging Mechanism in Trilayer Al2O3/Ge/Al2O3 Memory Structures

Authors: Stavarache, I; Palade, C; Maraloiu, VA; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: JAN 17 2024, ACS APPLIED ELECTRONIC MATERIALS, 6, DOI: 10.1021/acsaelm.3c01454

For the development of memory devices for the continuous advancement of IT engineering, a good understanding of the charging-discharging mechanisms in nanocrystalline floating gate memories is crucial to overcoming the current limitations. The charging-discharging mechanism in Al2O3/Ge/Al2O3 trilayer memory structures obtained by magnetron sputtering deposition is investigated as a function of the postdeposition annealing temperature, up to 900 degrees C. The change by annealing of C-V hysteresis curves from a clockwise type at low temperatures to counterclockwise one in a sample annealed within the intermediary temperature range of 550 to 650 degrees C, and then, a return to a clockwise type for annealing within the higher temperature range of 800-900 degrees C was observed. Up to 700 degrees C, memory performances are constantly improved reaching for 600 degrees C annealed samples, a memory window of 5.6 V for voltage sweep in the range -1 to +15 V, and good retention characteristics for 650 degrees C annealed structures, in which the charge loss is only similar to 2% after 10(8) s. When the annealing temperature was increased above 700 degrees C, a rapid decrease in the memory performance takes place. The annealing-induced changes are explained based on the Ge fast diffusion and nanocrystallization process, in correlation with morphological and structural high-resolution transmission electron microscopy results.

176. Probing geometry-induced magnetic defects in cylindrical modulated nanowires with optically detected spin resonance in nitrogen-vacancy center in diamond

Authors: Celano, U; Rickhaus, P; Bran, C; Marqués-Marchán, J; Borrás, VJ; Korytov, M; Asenjo, A; Vazquez, M

Published: SEP 19 2024, NANOSCALE, 16, DOI: 10.1039/d4nr01064g

Cylindrical magnetic nanowires (NWs) have gained significant interest as building-blocks of spintronics devices and magnetic sensors thanks to their geometry-tunable magnetic properties and anisotropy. While the synthesis and compositional control of NWs have seen major improvements in recent years, considerable challenges remain for the characterization of local magnetic features at the nanoscale. Here, we demonstrate non-perturbative field distribution mapping and minimally invasive magnetic imaging with scanning nitrogen-vacancy magnetometry. This enables a sensitivity down to 3 mu T Hz-1/2 used to localize ultra-scaled magnetic defects with lateral dimensions below 50 nm. The imaging reveals the presence of magnetic inhomogeneities in correspondence of periodical geometrical modulations/anti-notches in axial magnetized nanowires that are largely undetectable with standard metrology. The features induce local fluctuations of the NWs' magnetization orientation that are sensed by SNVM and compared with magnetic force microscopy. Finally, the strong magnetic field confinement in the nanowires is leveraged to study the interaction between the stray magnetic field and the fluorescence generated by two nitrogen-vacancies contained in the probe sensor, thus clarifying the contrast formation mechanisms. We report on magnetic imaging capability with non-perturbative field distribution mapping and minimally invasive magnetic sensing using scanning nitrogen-vacancy magnetometry in axial magnetized nanowires.

Open Access

177. Fs Laser Patterning of Amorphous As2S3 Thin Films

Authors: Mihai, C; Jipa, F; Socol, G; Kiss, AE; Zamfirescu, M; Velea, A

Published: FEB 2024, MATERIALS, 17, 798, DOI: 10.3390/ma17040798

This study investigates the morphological changes induced by femtosecond (fs) laser pulses in arsenic trisulfide (As2S3) thin films and gold-arsenic trisulfide (Au\As2S3) heterostructures, grown by pulsed laser deposition (PLD). By means of a direct laser writing experimental setup, the films were systematically irradiated at various laser power and irradiation times to observe their effects on surface modifications. AFM was employed for morphological and topological characterization. Our results reveal a clear transition threshold between photoexpansion and photoevaporation phenomena under different femtosecond laser power regimes, occurring between 1 and 1.5 mW, irrespective of exposure time. Notably, the presence of a gold layer in the heterostructure minimally influenced this threshold. A maximum photoexpansion of 5.2% was obtained in As2S3 films, while the Au\As2S3 heterostructure exhibited a peak photoexpansion of 0.8%. The study also includes a comparative analysis of continuous-wave (cw) laser irradiation, confirming the efficiency of fs laser pulses in inducing photoexpansion effects.

Open Access

178. Development of Novel Biocomposites with Antimicrobial-Activity-Based Magnesium-Doped Hydroxyapatite with Amoxicillin

Authors: Cimpeanu, C; Predoi, D; Ciobanu, CS; Iconaru, SL; Rokosz, K; Predoi, MV; Raaen, S; Badea, ML

Published: OCT 2024, ANTIBIOTICS-BASEL, 13, 963, DOI: 10.3390/antibiotics13100963

Background/Objectives: A biocomposite based on magnesium-doped hydroxyapatite and enriched with amoxicillin (MgHApOx) was synthesized using the coprecipitation method and is presented here for the first time. Methods: The stability of MgHAp and MgHApOx suspensions was evaluated by ultrasound measurements. The structure of the synthesized MgHAp and MgHApOx was examined with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The crystalline structure was determined by X-ray diffraction. The FTIR data were collected in the range of 4000-400 cm-1. The morphology of the nanoparticles was evaluated by scanning electron microscopy (SEM). Furthermore, the biocompatible properties of MgHAp, MgHApOx and amoxicillin (Ox) suspensions were assessed using human fetal osteoblastic cells (hFOB 1.19 cell line). The antimicrobial properties of the MgHAp, MgHApOx and Ox suspension nanoparticles were assessed using the standard reference microbial strains Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Candida albicans ATCC 10231. Results: X-ray studies have shown that the biocomposite retains the characteristics of HAp and amoxicillin. The SEM assessment exhibited that the apatite contains particles at nanometric scale with acicular flakes morphology. The XRD and SEM results exhibited crystalline nanoparticles. The average crystallite size calculated from XRD analysis increased from 15.31 nm for MgHAp to 17.79 nm in the case of the MgHApOx sample. The energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis highlighted the presence of the constituent elements of MgHAp and amoxicillin. Moreover, XPS confirmed the substitution of Ca2+ ions with Mg2+ and the presence of amoxicillin constituents in the MgHAp lattice. The results of the in vitro antimicrobial assay demonstrated that MgHAp, MgHApOx and Ox suspensions exhibited good antimicrobial activity against the tested microbial strains. The results showed that the antimicrobial activity of the samples was influenced by the presence of the antibiotic and also by the incubation time. Conclusions: The findings from the biological assays indicate that MgHAp and MgHApOx are promising candidates for the development of new biocompatible and antimicrobial agents for biomedical applications.

179. Acid-Modified, Ti3C2-Based MXene as Catalysts for Upcycling Polyethylene Terephthalate

Authors: Chirica, IM; Mirea, AG; Suteu, T; Kuncser, A; Neatu, S; Florea, M; Barsoum, MW; Neatu, F

Published: JUN 14 2024, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 12, DOI: 10.1021/acssuschemeng.4c01920

Plastics are indispensable materials for packaging and many products from our daily life, and their recycling is essential to ensure a circular economy. In this study, -SO3H-modified, Ti3C2-MXene was used as a recoverable solid acid catalyst for upcycling of polyethylene terephthalate (PET) to terephthalic acid (TPA) and ethylene glycol by hydrolysis. For the grafting of -SO3H groups to the Ti3C2Tx surface (where T-x represents the surface moieties, such as -OH or -O), sulfonation with an aryl diazonium salt obtained from sulfanilic acid was employed. X-ray photoelectron and Fourier transform infrared spectroscopy analyses provided a direct indication that sulfonation of the Ti3C2Tx was successfully performed, while X-ray diffraction and transmission electron microscopy analyses evidence the presence of -SO3H groups between the Ti3C2Tx layers due to the increases of the interlayer spacing through the intercalation of functional groups. The higher the concentration of acid groups, the higher the interlayer spacing. The depolymerization of PET in water occurred with a very good isolated yield in TPA (99%) for the MXene with the highest amount of sulfonic acid groups. We conclude that the acidity is mandatory to perform the hydrolysis reaction, in agreement with the acidity measurements, which show that the MXenes modified with the highest amount of derived sulfonic acids are the most active. Nevertheless, the accessibility to the acidic sites is a key factor that promotes the 2D acid-modified MXene materials as important catalysts for PET upcycling to TPA.

Open Access

180. Mock-ups fabrication by HRP technology with advanced W-alloy monoblocks for DEMO divertor target

Authors: Crea, F; Böswirth, B; Cacciotti, E; Galatanu, A; Greuner, H; García-Rosales, C; Lorusso, P; Roccella, S; Sal, E; Verdini, L; Wirtz, M

Published: APR 2024, FUSION ENGINEERING AND DESIGN, 201, 114232, DOI: 10.1016/j.fusengdes.2024.114232

Tungsten is the primary candidate armour material for the divertor target of the European demonstration fusion power plant. During operation at high temperature, pure tungsten is subject to fracture and recrystallization which results in a loss of strength and worsening of the thermal properties. Additionally, loss-of-coolant accidents with simultaneous air ingress can generate volatile and radioactive tungsten oxides. Advanced W-alloys were developed as alternative and upgrading armour materials of pure tungsten, such as potassium-doped tungsten laminates and self-passivating tungsten alloys. Three mock-ups were manufactured using potassium-doped tungsten laminates, W-10Cr-0.5Y and W-10Cr-0.5Y-0.5Zr as armour materials, each of them consisting of n degrees 4 blocks. The fabrication required optimization and upscaling of the ITER-like process which foresees oxygen-free high conductivity copper as interlayer joined to W-alloy armour block and CuCrZr ITER grade pipe welded to the Cu/W-alloy blocks by hot radial pressing. For quality control of the fabrication steps, non-destructive examination by ultrasonic testing was done on the monoblocks as received, after casting, after hot radial pressing and after high heat flux testing. The results demonstrated that these W-alloys can be used as armour materials of the European demonstration fusion power plant divertor target.

181. In vitro and in vivo investigations of citric acid functionalized magnetic iron oxide nanoparticles for intra-tumoral melanoma treatment

Authors: Sima, L; Toderascu, LI; Tudor, M; Florian, P; Icriverzi, M; Ionita, F; Maraloiu, V; Iacob, N; Kuncser, V; Antohe, I; Stanciu, G; Trif, M; Roseanu, A; Coman, C; Socol, G

Published: JUN 2024, FEBS OPEN BIO, 14, DOI:

182. SWIR photosensing of GeSn-HfO2 films with small Si amount

Authors: Palade, C; Slav, A; Stavarache, I; Dascalescu, I; Cojocaru, O; Stoica, T; Ciurea, ML; Lepadatu, AM

Published: 2024, 2024 INTERNATIONAL SEMICONDUCTOR CONFERENCE, CAS 2024, DOI: 10.1109/CAS62834.2024.10736731

In this paper, short-wave infrared (SWIR) photosensing of GeSn-HfO2 films with small Si amount is studied in correlation with structure and composition of films. SiGeSnHfO2 films are deposited by magnetron sputtering and nanostructured by subsequent rapid thermal annealing. XRD and Raman spectroscopy investigations are carried out revealing the SiGeSn nanocrystallization in annealed films. Spectral responsivity shows enhanced sensitivity up to 2 mu m due to SiGeSn nanocrystals (NCs) and clusters with contribution from disorder.

183. Bioactive Carbon@CeO2 Composites as Efficient Antioxidants with Antiamyloid and Radioprotective Potentials

Authors: Shlapa, Y; Siposova, K; Sarnatskaya, V; Drajnova, M; Silvestre-Albero, J; Lykhova, O; Maraloiu, VA; Solopan, SO; Molcan, M; Musatov, A; Belous, A

Published: SEP 25 2024, ACS APPLIED BIO MATERIALS, 7, DOI: 10.1021/acsabm.4c00912

Blending carbon particles (CPs) and nanoscale bioactive cerium dioxide is a promising approach for designing composites for biomedical applications, combining the sorption and antioxidant potentials of each individual component. To address this issue, it is crucial to assess the correlation between the components' ratio, physicochemical parameters, and biofunctionality of the composites. Thus, the current research was aimed at fabricating C@CeO2 composites with different molar ratios and the examination of how the parameters of the composites affect their bioactivity. XRD, X-ray photoelectron spectroscopy, and electron microscopy data verified the formation of C@CeO2 composites. CeO2 nanoparticles (NPs) of 4-6 nm are highly dispersed on the surfaces of amorphous CPs. The presence of CeO2 NPs on the carbon surface decreased its adsorption potential in a dose-dependent manner. Besides, the coexistence of carbon and CeO2 in a single composite promotes some redox interactions between O-functionalities and Ce3+/Ce4+ species, resulting in changes in the chemical state of the surface of the composites. These observations suggest the strong connection between these parameters and the biofunctionality of the composites. The presence of CeO2 NPs on the surface of carbon led to a significant increase in the stability of the prepared composites in their aqueous suspensions. The enhancement of bioactivity of the newly prepared C@CeO2 compared to bare carbon and CeO2 was validated by testing their pseudomimetic (catalase/peroxidase-like and superoxide dismutase-like), antiamyloid, and radioprotective activities.

Open Access

184. Physico-Chemical and Biological Features of Fluorine-Substituted Hydroxyapatite Suspensions

Authors: Ciobanu, CS; Predoi, D; Iconaru, SL; Predoi, MV; Rokosz, K; Raaen, S; Negrila, CC; Buton, N; Ghegoiu, L; Badea, ML

Published: JUL 2024, MATERIALS, 17, 3404, DOI: 10.3390/ma17143404

Infections related to orthopedic/stomatology surgery are widely recognized as a significant health concern. Therefore, the development of new materials with superior biological properties and good stability could represent a valuable alternative to the classical treatments. In this paper, the fluorine-substituted hydroxyapatite (FHAp) suspension, with the chemical formula Ca10(PO4)6(OH)2-2xF2x (where x = 0.05), was prepared using a modified coprecipitation technique. Stability studies were conducted by zeta potential and ultrasound measurements for the first time. The X-ray diffraction (XRD) patterns of FHAp powders displayed a hexagonal structure akin to that of pure hydroxyapatite (HAp). The XPS general spectrum revealed peaks corresponding to the constituent elements of fluorine-substituted hydroxyapatite such as calcium, phosphorus, oxygen, and fluorine. The purity of the obtained FHAp samples was confirmed by energy-dispersive X-ray spectroscopy (EDS) studies. The FHAp morphology was evaluated by scanning electron microscopy (SEM) measurements. Fourier-transform infrared spectroscopy (FTIR) studies were performed in order to study the vibrational properties of the FHAp samples. The FHAp suspensions were tested for antibacterial activity against reference strains such as Staphylococcus aureus 25923 ATCC, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231. Additionally, the biocompatibility of the FHAp suspensions was assessed using human fetal osteoblastic cells (hFOB 1.19 cell line). The results of our biological tests suggest that FHAp suspensions are promising candidates for the future development of new biocompatible and antimicrobial agents for use in the biomedical field.

185. Interaction of Low-Density Polyethylene Nanofragments with Autotrophic and Chemotrophic Bacteria

Authors: Ciorita, A; Suciu, M; Rostas, AM; Tarta, A; Popovici, G; Bocaneala, M; Nekvapil, F; Macavei, SG; Potara, M; Marica, I; Kacso, I; Moldovan, CS; Stiufiuc, RI; Tuta, CS; Cinta-Panzaru, S; Barbu-Tudoran, L

Published: JUL 11 2024, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 12, DOI: 10.1021/acssuschemeng.4c02440

Plastics are omnipresent in the environment and degrade into smaller fragments in time. This study shows how plastics could reach nanometer sizes under specific conditions and the interaction of the nanofragments with prokaryotic cells. Imaging and spectroscopy techniques were employed to determine the modifications induced in artificially aged low-density polyethylene (LDPE). Scanning electron microscopy indicated that nanometer-scale LDPE could be obtained after ultraviolet-C (UVC) exposure for 10 days. Raman and Fourier-transformed infrared spectroscopy confirmed the chemical changes within the UVC-exposed LDPE are consistent with the increase of crystallinity. Moreover, the interaction between the degraded LDPE and chemo- and photosynthetic organisms was observed through fluorescence, confocal, electron microscopy techniques, and electron paramagnetic resonance spectroscopy. The results showed how micro/nano-LDPE could influence the development of Escherichia coli and Arthrospira platensis after only 72 h of interaction. This fundamental study indicates the environmental presence and effects of nanometer-sized LDPE resulting from light exposure.

Open Access

186. Optimizing SiGe-SiO2 Visible-Short-Wave Infrared Photoresponse by Modulating Interplay Between Strain and Defects Through Annealing

Authors: Sultan, MT; Stavarache, I; Manolescu, A; Arnalds, UB; Teodorescu, VS; Svavarsson, HG; Ingvarsson, S; Ciurea, ML

Published: AUG 2024, ADVANCED PHOTONICS RESEARCH, 5, DOI: 10.1002/adpr.202300316

SiGe-SiO2-based structures present high interest for their high photosensitivity from visible to short-wavelength infrared. Herein, two postdeposition annealing procedures, that is, rapid thermal annealing (RTA) and rapid-like furnace annealing (FA), are compared. Both RTA and FA are performed at 600 degrees C for 1 min for SiGe nanocrystals (NCs) formation in SiO2 matrix in Si/SiO2/SiGe/SiO2 structures deposited by magnetron sputtering. The FA imitates RTA resulting in enhanced spectral response. X-ray diffraction, transmission electron microscopy, and Raman spectroscopy are carried out showing Ge-rich SiGe NCs with 11.3 +/- 1.2 nm size for RTA and 9.4 +/- 0.8 nm for FA. Photocurrent spectra for both structures show several peaks that are annealing dependent. The photocurrent intensity for FA samples is approximate to 7 times higher than RTA samples while cutoff wavelengths are slightly different, that is, 1365 nm for FA and 1375 nm for RTA. The FA structures show (at -1.5 V) over 4 A W-1 responsivity at 730 nm, 6.4 x 10(7) Jones detectivity at 735 nm, and 2.2 x 10(7) Jones at about 1210 nm. FA structures contain small SiGe NCs with incorporated residual strain, while RTA ones are formed of columnar SiGe NCs separated by SiGeOx amorphous regions and show increased tensile strain in the SiGe.

Open Access

187. Exploring FAST Technique for Diffusion Bonding of Tungsten to EUROFERE97 in DEMO First Wall

Authors: Sánchez, M; de Prado, J; Izaguirre, I; Galatanu, A; Ureña, A

Published: JUN 2024, MATERIALS, 17, 2624, DOI: 10.3390/ma17112624

The European Fusion Reactor (DEMO, Demonstration Power Plant) relies significantly on joining technologies in its design. Current research within the EUROfusion framework focuses on developing materials for the first wall and divertor applications, emphasizing the need for suitable joining processes, particularly for tungsten. The electric field-assisted sintering technique (FAST) emerges as a promising alternative due to its high current density, enabling rapid heating and cooling rates for fast sintering or joining. In this study, FAST was employed to join tungsten and EUROFERE97 steel, the chosen materials for the first wall, using 50-mu m-thick Cu foils as interlayers. Three distinct joining conditions were tested at 980 degrees C for 2, 5, and 9 min at 41.97 MPa to optimize joint properties and assess FAST parameters influence. Hardness measurements revealed values around 450 HV0.1 for tungsten, 100 HV0.1 for copper, and 390 HV0.1 for EUROFER97 under all joining conditions. Increasing bonding time improved joint continuity along the EUROFER97/Cu and W/Cu interfaces. Notably, the 5 min bonding time resulted in the highest shear strength, while the 9 min sample exhibited reduced strength, possibly due to Kirkendall porosity accumulation at the EUROFER97/Cu interface. This porosity facilitated crack initiation and propagation, diminishing interfacial adhesion properties.

Open Access

188. Magnetic Memory Effects in BaFe2(As0.68P0.32)2 Superconducting Single Crystal

Authors: Badea, AM; Ivan, I; Miclea, CF; Crisan, DN; Galluzzi, A; Polichetti, M; Crisan, A

Published: NOV 2024, MATERIALS, 17, 5340, DOI: 10.3390/ma17215340

Among many iron-based superconductors, isovalently substituted BaFe2(As1-xPx)2 displays, for x approximate to 0.3, apart from the quite usual Second Magnetization Peak (SMP) in the field dependence of the critical current density, an unusual peak effect in the temperature dependence of the critical current density in the constant field, which is related to the rhombic-to-square (RST) structural transition of the Bragg vortex glass (BVG). By using multi-harmonic AC susceptibility investigations in three different cooling regimes-field cooling, zero-field cooling, and field cooling with measurements during warming up-we have discovered the existence of a temperature region in which there is a pronounced magnetic memory effect, which we attributed to the direction of the structural transition. The observed huge differences in the third harmonic susceptibility at low and high AC frequencies indicates the difference in the time-scale of the structural transition in comparison with the timescale of the vortex excitations. Our findings show that the RST influence on the vortex dynamics goes beyond the previously observed influence on the onset of the SMP.

189. Influence of Ge concentration and deposition temperature on the photoresponse characteristics of Ge:SiO2 nanocomposite thin films

Authors: Stavarache, I; Prepelita, P; Cojocaru, O; Ciurea, ML

Published: 2024, 2024 INTERNATIONAL SEMICONDUCTOR CONFERENCE, CAS 2024, DOI: 10.1109/CAS62834.2024.10736851

This study examines the opto-electric characteristics of Ge:SiO2 composite films produced via magnetron sputtering at substrate temperatures of 300 degrees C, 400 degrees C, and 500 degrees C, with varying Ge concentrations. We employed x-ray diffraction, current-voltage measurements, and spectral photocurrent analysis to investigate the films structural, optical, and opto-electrical properties. Illumination of the samples resulted in a marked increase in current compared to dark conditions. Spectral photocurrent measurements revealed cutoff wavelengths of 1300 nm for films with 25:75 vol% Ge:SiO2 ratio, extending to 1320 nm for compositions with higher Ge content (60:40 vol%). These findings align with observations from I-V curve analyses. Our research highlights the potential of Ge:SiO2 composites for enhancing optoelectronic device performance. The results underscore the importance of continued investigation and innovative applications in this field to drive technological advancements.

190. A-site K-doped lanthanum manganite nanocrystalline La0.67Ba0.33MnO3 for room-temperature micro-scale magnetic cooling

Authors: Oumezzine, M; Rostas, AM; Bocirnea, AE; Hlil, E; Galca, AC

Published: MAR 5 2024, JOURNAL OF ALLOYS AND COMPOUNDS, 976, 173257, DOI: 10.1016/j.jallcom.2023.173257

Bulk nanocrystalline La0.67Ba0.33_xKxMnO3 (with x = 0, 0.05, 0.1, and 0.2) manganites have been prepared by the modified sol-gel method (Pechini). The single-phase rhombohedral crystal structure with the R-3c (no. 167) space group was verified by X-ray diffraction (XRD) and sustained by Rietveld refinement. As follows from the results of XRD structural analyses, the increase in K-doping triggers an increase in the distortion of the MnO6 octahedra, which eventually causes the narrowing of the eg bandwidth. Mn is in a mixed valence state of Mn4+/ Mn3+ as inferred by X-ray photoelectron spectroscopy. Magnetic measurements confirm that the Curie tem-perature decreases from 348 K for La0.67Ba0.33MnO3 to 316 K for La0.67Ba0.13K0.20MnO3. The increasing of the Mn4+ ion concentration at the B-site sublattice and A-site ionic disorder (sigma 2) breaks up the double exchange interaction between the Mn3+ and Mn4+ ions. The ferromagnetic to paramagnetic second-order magnetic phase transition at TC is also confirmed by electron paramagnetic resonance. According to magnetic field-dependent magnetization isotherms at different temperatures, La0.67Ba0.13K0.20MnO3 shows a relatively large magneto -caloric effect (1400 mJ cm_ 3 K_ 1 at 316 K under 5 T applied magnetic field), which raises the possibility of using this material for room-temperature micro-scale magnetic cooling.

Open Access

191. Highly Efficient Ru-Based Catalysts for Lactic Acid Conversion to Alanine

Authors: Podolean, I; Dogaru, M; Guzo, NC; Petcuta, OA; Jacobsen, EE; Nicolaev, A; Cojocaru, B; Tudorache, M; Parvulescu, VI; Coman, SM

Published: FEB 2024, NANOMATERIALS, 14, 277, DOI: 10.3390/nano14030277

The primary objective of this research was to develop efficient solid catalysts that can directly convert the lactic acid (LA) obtained from lignocellulosic biomass into alanine (AL) through a reductive amination process. To achieve this, various catalysts based on ruthenium were synthesized using different carriers such as multi-walled carbon nanotubes (MWCNTs), beta-zeolite, and magnetic nanoparticles (MNPs). Among these catalysts, Ru/MNP demonstrated a remarkable yield of 74.0% for alanine at a temperature of 200 degrees C. This yield was found to be superior not only to the Ru/CNT (55.7%) and Ru/BEA (6.6%) catalysts but also to most of the previously reported catalysts. The characterization of the catalysts and their catalytic results revealed that metallic ruthenium nanoparticles, which were highly dispersed on the external surface of the magnetic carrier, significantly enhanced the catalyst's ability for dehydrogenation. Additionally, the -NH2 basic sites on the catalyst further facilitated the formation of alanine by promoting the adsorption of acidic reactants. Furthermore, the catalyst could be easily separated using an external magnetic field and exhibited the potential for multiple reuses without any significant loss in its catalytic performance. These practical advantages further enhance its appeal for applications in the reductive amination of lactic acid to alanine.

192. Structural and magneto-optical investigations of citrate sol-gel derived barium hexaferrite nanocrystalline powder

Authors: Secu, M; Secu, CE; Matei, E; Negrilla, C; Turchenko, V; Radu, C; Polosan, S

Published: MAY 5 2024, JOURNAL OF ALLOYS AND COMPOUNDS, 983, 173897, DOI: 10.1016/j.jallcom.2024.173897

Magneto-optical measurements enable the identification of Fe2+ and Fe3+ in the R and S blocks of BaFe12O19 Mhexaferrite powder obtained by sol -gel processing, followed by thermal annealing at 900 C for 3 hours. The ferromagnetic phase is evidenced by the spin-majority configuration (Fe3+) due to their unpaired electrons between d -d orbitals, while the Fe2+ in the low spin possesses diamagnetic behavior strongly dependent on the surrounded crystal field. Additionally, the irradiation with gamma rays changes the ratio between Fe2+/Fe3+, mainly on the surface of BaFe12O19 nanocrystals. These changes were confirmed by X-ray Photoelectron Spectroscopy measurements, in which the concentration of Fe2+ increased from 69% to 82%, while the one of Fe3+ decreased from 31% to 18%. he thermoluminescent measurements reveal the same changes of Fe3+ in Fe2+ by electron capturing during irradiation, which is released as a red emission after recombination processes. The changes are explained by the increasing of some Fe-O bonds along the c-axis, mainly due to breaking a part of these bonds. The X-ray analysis confirms the changing of the parameters for the BaFe12O19 hexagonal structure.

193. Possible reduction of lattice thermal conductivity in n-type CoSb2.875Te0.125 skutterudite originating from collaborative adjustment between Indium micro and α-WC nano inclusions

Authors: Kumar, MU; Swetha, R; Sahana, BV; Kuri, RS; Popescu, B; Assahsahi, I; Kumari, L

Published: OCT 2024, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 35, 1960, DOI: 10.1007/s10854-024-13713-y

In this work, single-phase Te-doped CoSb3 polycrystalline bulk (Indium powder) and nanocomposites (alpha-WC nanopowder) were synthesized via a ball milling, hand-grinding and consolidated by spark plasma sintering technique. The thermoelectric and mechanical characteristics of as-synthesized composites were studied. The electrical resistivity varies between 11.82 and 12.82 mu Omega-m for CoSb2.875Te0.125 + x (x = 0.33% In, 1% In, 2% In, 4% In and 1% In + 0.33% alpha-WC, respectively) composites. At temperature of 300 K, composite with x = 1% In exhibit the lowest resistivity of 11.82 mu Omega-m. Also, negative values of Seebeck coefficients confirm that electrons are the predominant charge carriers. The maximum power factor of 2566 and 2482 mu Wm-1 K-2 are observed from x = 1% In and x = 1% In + 0.33% alpha-WC composites at 673 K, respectively. Notably, the power factor of 1% In and 1% In + 0.33% alpha-WC composites is slightly higher (1.05 times) than the CoSb2.875Te0.125 sample. The composites with lowest weight percent of 1% In and 1% In + 0.33% alpha-WC have a considerably improved power factor. For the composite with x = 1% In + 0.33% alpha-WC, the minimum thermal conductivity of 2.32 W/m-K at 300 K was achieved through a combination of doping and dispersion in the CoSb2.875Te0.125 matrix. It is possible that the multi-scale size distributions of grains will reduce the lattice thermal conductivity by scattering phonons over a large wavelength range. As a result, an increased figure of merit of 0.82 was achieved for CoSb2.875Te0.125 + 1% In + 0.33% alpha-WC composites at 823 K. The results suggest that the doping with composite approach could boost thermoelectric efficiency in n-type CoSb3-based materials.

Open Access

194. Versatile techniques based on the Thermionic Vacuum Arc (TVA) and laser-induced TVA methods for Mg/Mg:X thin films deposition-A review

Authors: Vladoiu, R; Mandes, A; Dinca, V; Tichy, M; Kudrna, P; Ciobotaru, CC; Polosan, S

Published: AUG 2024, JOURNAL OF MAGNESIUM AND ALLOYS, 12, DOI: 10.1016/j.jma.2024.08.012

Magnesium and magnesium thin alloy films were deposited using a thermionic vacuum arc (TVA), which has multiple applications in the field of metallic electrodes for diodes and batteries or active corrosion protection. An improved laser-induced TVA (LTVA) method favors the crystallization processes of the deposited magnesium-based films because the interaction between laser and plasma discharge changes the thermal energy during photonic processes due to the local temperature variation. Plasma diagnosis based on current discharge measurements suggests an inelastic collision between the laser beam and the atoms from the plasma discharge. The morphology and surface properties of the obtained thin films differ between these two methods. While the amorphous character is dominant for TVA thin films, enabling a smooth surface, the LTVA method produces rough surfaces with prominent crystallinity, less hydrophobic character and lower surface energy. The smooth surfaces obtained by the TVA methods produce metallic electrodes with good electrical contact, ensuring better diodes and battery charge transport. Both methods allow uniform magnesium alloys to be obtained, but the laser used in the LTVA on the discharge plasma controls the added metal or element ratio. (c) 2024 Chongqing University. Publishing services provided by Elsevier B.V.

195. Electrodeposition mechanism of Cu 2 CoSnS 4 thin films onto FTO-coated glass: Effect of some additives

Authors: Layachi, OA; Moujib, A; El Khouja, O; Galca, AC; Boudouma, A; Azmi, S; Nini, M; Nohair, M; Khoumri, E

Published: APR 15 2024, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 959, 118177, DOI: 10.1016/j.jelechem.2024.118177

In this study, we synthesized thin films of semiconductor Cu 2 CoSnS 4 (CCTS). We investigated the mechanism of CCTS electrodeposition precursor onto fluorine -doped tin oxide (FTO) surface. This investigation utilized various mixed additives (Trisodium citrate, Glycine, and Boric acid) through voltammetric and chronoamperometric techniques. The polarization cathodic indicated that the additives narrowing the potential range for electrodeposition of the four elements. The reduction of S 2 O 3 2- was mainly induced by the effect of metal ions. The current transient was analyzed using the Astley and Scharifker-Hills models. Trisodium citrate electrolyte showed an instantaneous model followed by 3D diffusion -limited growth. Both trisodium citrate mixed with glycine and trisodium citrate mixed with boric acid shifted towards the progressive nucleation model. Trisodium citrate with tartaric acid showed a strong agreement with progressive nucleation. In -situ electrochemical impedance spectroscopy (EIS) evaluated a low charge transfer resistance for CCTS precursor electrodeposition in trisodium citrate electrolyte. The X-ray diffraction and Raman analysis study revealed the stannite structure of the obtained Cu 2 CoSnS 4 thin film. The morphological properties and thickness of the films were investigated using a scanning electron microscope (SEM). The compositions were determined using energy dispersive spectroscopy which indicated different atomic ratios of Cu-Co-Sn-S. The maximum absorption was observed within the 1.5 eV range for the film deposited in the Trisodium citrate bath, as determined by spectroscopic ellipsometry.

196. Growth and spectroscopic properties of Ca3(Ta,Ga)5O12:Pr³⁺ single crystal as a promising new laser material in the visible domain

Authors: Gheorghe, C; Hau, S; Gheorghe, L; Broasca, A; Greculeasa, M; Voicu, F; Stanciu, G; Enculescu, M

Published: APR 2024, OPTICAL MATERIALS, 150, 115286, DOI: 10.1016/j.optmat.2024.115286

Structurally disordered Pr3+-doped Ca-3(Ta,Ga)(5)O-12 - Pr:CTGG single crystal was grown by the Czochralski technique for the first time and its spectroscopic properties were investigated. Modified Judd-Ofelt analysis was applied to determine spectroscopic and laser emission characteristics. Based on low-temperature absorption and emission spectra, the partial energy levels of Pr3+ ions have been obtained and a multicenter structure of the optical spectra was highlighted. The electron-phonon interactions were also observed in the emission spectra corresponding to the P-3(0) -> H-3(4) transition under different excitation wavelengths. The fluorescence decays of the P-3(0) and D-1(2) levels were measured. The emission cross-sections corresponding to the P-3(0) -> H-3(4) (486.5 nm) and P-3(0) -> F-3(2) (652.7 nm) transitions were found to be sigma(em) = 19 x 10(-20) cm(2) and crem = 15 x 10(-20) cm(2), respectively. The values for other parameters that may predict the possibility of achieving efficient laser emission, especially at 486.5 nm, such as quantum efficiency (eta = 50 %), gain bandwidth (sigma(em) x Iota lambda(eff), = 32.2 x 10(-26) cm(3)), and optical gain (sigma(em) x tau(meas) = 12.86 x 10(-25) cm(2) s) were determined. The obtained results indicate that the Pr:CTGG crystal has a high potential for obtaining efficient laser emission in the blue domain.

Open Access

197. USE OF ENERGY DISPERSIVE X-RAY SPECTROSCOPY AS A CONVENIENT TECHNIQUE FOR ESTIMATION OF QUARTZ PURITY IN GEOLOGICAL SAMPLES SUBJECT TO SURFACE EXPOSURE DATING WITH 10Be AND 26Al

Authors: Pascal, D; Enachescu, M; Mereuta, P; Petre, AR; Grigoroscuta, M; Badica, P

Published: 2023, ROMANIAN REPORTS IN PHYSICS, 75, 205, DOI: 10.59277/RomRepPhys.2023.75.205

Accelerator Mass Spectrometry (AMS) and cosmogenic nuclides techniques are used in quantitative geomorphological studies on large time scale. In order to accurately date surface exposure to cosmic rays, the amount of pure quartz taken into account, needs to be well determined. Depending on the particularity of the rocks, sometimes the presence of feldspar in geological samples hinders the accurate determination of 26Al and 10Be by AMS. To overcome this problem, our paper proposes the assessment of quartz purity by SEM-EDX analysis, in an objective and facile way, compared to ICP-MS method. The proposed methodology is not only effective, but it shows features that save time and excessive consumption of reagents that often are not environment and health friendly.

Open Access

198. Revolutionizing n-type Co3O4 Nanowire for Hydrogen Gas Sensing

Authors: Kumarage, GWC; Zappa, D; Mihalcea, CG; Maraloiu, VA; Stefan, M; Comini, E

Published: OCT 2023, ADVANCED ENERGY AND SUSTAINABILITY RESEARCH, 4, DOI: 10.1002/aesr.202300067

This study presents conductometric sensors based on Co3O4 nanowires for hydrogen detection at ppb levels. The nanowires are synthesized through thermal oxidation of a 50 nm cobalt layer, exhibiting diameters between 6-50 nm and lengths of 1-5 & mu;m, primarily growing along the (311) direction of spinal Co3O4. Raman investigation reveals five characteristic peaks at 195, 482, 521, 620, and 692 cm(-1), corresponding to symmetric phonon modes of crystalline Co3O4. Electron paramagnetic resonance measurements confirm the presence of a ferromagnetic phase, attributed to incomplete cobalt oxidation, which disappears after 8 h of thermal aging at 400 & DEG;C. Conductometry measurements are performed in the temperature range of 300-500 & DEG;C. At temperatures above 300 & DEG;C, sensors exhibit abnormal n-type semiconducting behavior due to lattice oxygen's involvement in the hydrogen sensing mechanism. Operating at 450 & DEG;C in dry air, the sensor shows a higher 232% response to 100 ppm H-2 compared to ethanol, acetone, methane, carbon monoxide, and nitrogen dioxide. Remarkably, the sensor maintains a consistent conductance baseline even under high humidity (90%) for 25 d, with three-cycle repeatability. This distinctive gas-sensing capability is attributed to the catalytic activity and elevated operating temperature.

Open Access

199. Microemulsions of Nonionic Surfactant with Water and Various Homologous Esters: Preparation, Phase Transitions, Physical Property Measurements, and Application for Extraction of Tricyclic Antidepressant Drugs from Aqueous Media

Authors: Racovita, RC; Ciuca, MD; Catana, D; Comanescu, C; Ciocirlan, O

Published: AUG 2023, NANOMATERIALS, 13, 2311, DOI: 10.3390/nano13162311

Microemulsions are nanocolloidal systems composed of water, an oil, and a surfactant, sometimes with an additional co-surfactant, which have found a wide range of practical applications, including the extractive removal of contaminants from polluted water. In this study, microemulsion systems, including a nonionic surfactant (Brij 30), water, and esters selected from two homologous series of C-1-C-6 alkyl acetates and ethyl C-1-C-4 carboxylates, respectively, were prepared by the surfactant titration method. Phase transitions leading to the formation of Winsor II and Winsor IV microemulsions were observed and phase diagrams were constructed. The dependences of phase transitions on the salinity and pH and the addition of isopropanol as a co-surfactant were also investigated. Some physical properties, namely density, refractive index, electrical conductivity, dynamic viscosity, and particle size, were measured for a selection of Winsor IV microemulsions, providing further insight into some other phase transitions occurring in the monophasic domains of phase diagrams. Finally, Winsor II microemulsions were tested as extraction solvents for the removal of four tricyclic antidepressant drugs from aqueous media. Propyl acetate/Brij 30/H2O microemulsions provided the best extraction yields (>90%), the highest Nernst distribution coefficients (similar to 40-88), and a large volumetric ratio of almost 3 between the recovered purified water and the resulting microemulsion extract. Increasing the ionic strength (salinity) or the pH of the aqueous antidepressant solutions led to an improvement in extraction efficiencies, approaching 100%. These results could be extrapolated to other classes of pharmaceutical contaminants and suggest ester- and nonionic surfactant-based microemulsions are a promising tool for environmental remediation.

200. Organic heterostructures based on thermal evaporated phthalocyanine and porphyrin as mixed (ZnPc:TPyP) or stacked (ZnPc/TPyP) films

Authors: Petre, G; Socol, M; Preda, N; Breazu, C; Rasoga, O; Stanculescu, F; Costas, A; Antohe, S; Iftimie, S; Socol, G; Stanculescu, A

Published: DEC 31 2023, THIN SOLID FILMS, 787, 140140, DOI: 10.1016/j.tsf.2023.140140

A metallic phthalocyanine (zinc phthalocyanine - ZnPc) and a non-metallic porphyrin (10,15,20-tetra(4-pyridyl) 21H,23H-porphyne -TPyP) were used to deposit mixed and stacked organic thin films by vacuum thermal evaporation method. The obtained layers were analyzed in a comparative manner from optical, structural, morphological and electrical point of view. The ultraviolet-visible spectra of the deposited layers showed that both organic components have absorption bands in the visible part of the solar spectrum, which means that the acceptor TPyP also contributes to absorption together with the donor. The photoluminescence spectra revealed only the emission bands associated to the porphyrin, especially in the single and stacked layers, while a quenching effect of the photoluminescence was noted in the mixed ones. The X-ray diffraction showed that the prepared layers are in general amorphous. The constituent materials in the single layers and the ratio between the two organic components in the mixed layers affect the morphology of the deposited films as was emphasized by scanning electron microscopy and atomic force microscopy analysis. The current density-voltage characteristics plotted under illumination revealed that the highest short-circuit current value was achieved in the case of the structure based on the layer showing the lowest roughness and thickness emphasizing the significant role played by these parameters of the layers considered for possible applications in the optoelectronic device area.

Open Access

201. In vitro analysis of the cytotoxic effect of two different sizes ITER-like tungsten nanoparticles on human dermal fibroblasts

Authors: Carpen, LG; Acasandrei, MA; Acsente, T; Matei, E; Lungu, I; Dinescu, G

Published: MAR 2023, HELIYON, 9, e13849, DOI: 10.1016/j.heliyon.2023.e13849

Background: Based on the current configuration of the International Thermonuclear Experimental Reactor, tungsten (W) was chosen as the armour material. Nevertheless, during operation, the expected power and temperature of plasma can trigger the formation of W dust in the plasma chamber. According to the scenario for a Loss Of Vacuum Accident (LOVA), in the case of confinement failure dust is released, which can lead to occupational or accidental exposure.Methods: For a first evidence of potential risks, fusion devices relevant W dust has been produced on purpose, using a magnetron sputtering gas aggregation source. We aimed to assess the in vitro cytotoxicity of synthesized tungsten nanoparticles (W-NPs) with diameters of 30 and 100 nm, on human BJ fibroblasts. That was systematically investigated using different cytotoxic endpoints (metabolic activity, cellular ATP, AK release and caspase-3/7 activity) and by direct observation with optical and scanning electron microscopy.Results: Increasing concentrations of W-NPs of both sizes induced cell viability decrease, but the effect was significantly higher for large W-NPs, starting from 200 mu g/mL. In direct correlation with the effect on the cell membrane integrity, high concentrations of large W-NPs appear to increase AK release in the first 24 h of treatment. On the other hand, activation of the cellular caspase 3/7 was found significantly increased after 16 h of treatment solely for low concentra-tions of small W-NPs. SEM images revealed an increased tendency of agglomeration of small W -NPs in liquid medium, but no major differences in cells development and morphology were observed after treatment. An apparent internalization of nanoparticles under the cell membrane was also identified.Conclusion: These results provide evidence for different toxicological outputs identified as mechanistic responses of BJ fibroblasts to different sizes of W-NPs, indicating also that small W -NPs (30 nm) display lower cytotoxicity compared to larger ones (100 nm).

202. COMPARATIVE STUDY ON TiO2 NANOPARTICLES OBTAINED BY PRECIPITATION AND SOL-GEL

Authors: Alecu, AE; Girjoaba, SA; Enculescu, MM; Busuioc, C

Published: 2023, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 85, DOI:

The purpose of the work is the synthesis and characterization of TiO2 nanoparticles. These were obtained by two different methods, precipitation and sol-gel, starting from titanium(IV) isopropoxide and calcining at 500 degrees C for 2 h. The compositional, structural, morphological and optical properties of the resulting powders were investigated by energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, reflectance spectroscopy and photoluminescence spectroscopy. The thermally treated samples contain TiO2 as single phase with tetragonal structure, known as anatase. SEM analysis showed quasi-spherical particles with a diameter of few nanometres for the calcined samples, while the optical studies revealed band gap values of 3.04 and 3.17 eV, as a function of the preparation route.

203. Hybrid nanostructures based on vertically graphenes decorated with tungsten oxide nanoparticles for enhanced capacitive performance

Authors: Coman, LG; Marcu, M; Acsente, T; Vizireanu, S; Satulu, V; Dinescu, G; Matei, E; Spataru, T; Spataru, N; Preda, L

Published: NOV 2023, DIAMOND AND RELATED MATERIALS, 139, 110316, DOI: 10.1016/j.diamond.2023.110316

Herewith, we investigated the capacitive properties of hybrid nanometric architectures consisting of tungsten oxide nanoparticles deposited on graphite (WOx/G) and graphite coated with highly-porous carbon nanowall layers (WOx/CNW/G). The deposition of the nanostructured oxide was performed by a plasma-assisted sublimation, vapor transport and condensation technique. The samples containing the CNW interlayer show superior areal capacitances making this architecture and its fabrication route promising approaches for supercapacitor applications. Thus, areal capacitances of WOx/CNW/G and WOx/G, estimated from galvanostatic chargedischarge tests (GCD) at an applied density current of 1 mA cm-2, are 1247.2 mF cm-2 and 527.3 mF cm-2, respectively. From SEM and XPS investigations, it was observed that CNW promotes the formation of a high amount of small tungsten oxide particles, homogeneously distributed on electrode surface, and facilitates the formation of highly conductive tungsten nitride species, resulting in electrodes with remarkable charge-storage capacity.

204. Design of Magnetic Fe3O4/CeO2 "Core/Shell"-Like Nanocomposites with Pronounced Antiamyloidogenic and Antioxidant Bioactivity

Authors: Shlapa, Y; Siposova, K; Veltruska, K; Maraloiu, VA; Garcarova, I; Rajnak, M; Musatov, A; Belous, A

Published: OCT 12 2023, ACS APPLIED MATERIALS & INTERFACES, 15, DOI: 10.1021/acsami.3c10845

Core/shell nanocomposites based on magnetic magnetite (Fe3O4) and redox-active cerium dioxide (CeO2) nanoparticles (NPs) are promising in the field of biomedical interests because they can combine the ability of magnetic NPs to heat up in an alternating magnetic field (AMF) with the pronounced antioxidant activity of CeO2 NPs. Thus, this report is devoted to Fe3O4/CeO2 nanocomposites (NCPs) synthesized by precipitation of the computed amount of "CeO2-shell" on the surface of prefabricated Fe3O4 NPs. The X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy data validated the formation of Fe3O4/CeO2 "core/shell"-like NCPs, in which ultrafine CeO2 NPs with an average size of approximately 3-3.5 nm neatly surround Fe3O4 NPs. The presence of a CeO2 "shell" significantly increased the stability of Fe3O4/CeO2 NCPs in aqueous suspensions: Fe3O4/CeO2 NCPs with "shell thicknesses" of 5 and 7 nm formed highly stable magnetic fluids with zeta-potential values of >+30 mV. The magnetization values of Fe3O4/CeO2 NCPs decreased with a growing CeO2 "shell" around the magnetic NPs; however, the resulting composites retained the ability to heat efficiently in an AMF. The presence of a CeO2 "shell" generates a possibility to precisely regulate tuning of the maximum heating temperature of magnetic NCPs in the 42-50 degrees C range and stabilize it after a certain time of exposure to an AMF by changing the thickness of the "CeO2-shell". A great improvement was observed in both antioxidant and antiamyloidogenic activities. It was found that inhibition of insulin amyloid formation, expressed in IC50 concentration, using NCPs with a "shell thickness" of 7 nm was approximately 10 times lower compared to that of pure CeO2. For these NCPs, more than 2 times higher superoxide dismutase-like activity was observed. The coupling of both Fe3O4 and CeO2 results in higher bioactivity than either of them individually, probably due to a synergistic catalytic mechanism.

Open Access

205. Microengineering Design for Advanced W-Based Bulk Materials with Improved Properties

Authors: Galatanu, M; Enculescu, M; Galatanu, A; Ticos, D; Dumitru, M; Ticos, C

Published: MAR 2023, NANOMATERIALS, 13, 1012, DOI: 10.3390/nano13061012

In fusion reactors, such as ITER or DEMO, the plasma used to generate nuclear reactions will reach temperatures that are an order of magnitude higher than in the Sun's core. Although the plasma is not supposed to be in contact with the reactor walls, a large amount of heat generated by electromagnetic radiation, electrons and ions being expelled from the plasma will reach the plasma-facing surface of the reactor. Especially for the divertor part, high heat fluxes of up to 20 MW/m(2) are expected even in normal operating conditions. An improvement in the plasma-facing material (which is, in the case of ITER, pure Tungsten, W) is desired at least in terms of both a higher recrystallization temperature and a lower brittle-to-ductile transition temperature. In the present work, we discuss three microengineering routes based on inclusions of nanometric dispersions, which are proposed to improve the W properties, and present the microstructural and thermophysical properties of the resulting W-based composites with such dispersions. The materials' behavior after 6 MeV electron irradiation tests is also presented, and their further development is discussed.

206. NANOSTRUCTURED LAYERS DEPOSITION FOR SELF-CLEANING GLASS

Authors: Iliescu, M; Besleaga, C; Nitu, C; Tomulescu, A; Pintilie, I; Melinte, O; Rosu, MM

Published: OCT 2023, ACTA TECHNICA NAPOCENSIS SERIES-APPLIED MATHEMATICS MECHANICS AND ENGINEERING, 66, DOI:

This paper evidences research results on a new technology for deposition of TiO2 nanostructured layers on glass. Air pollution, industrialization and everyday life activities are factors that point towards the need for efficient and ergonomic cleaning process of the impressive glazing surfaces that surround people in modern offices, leisure places and not the least, in houses. The design of equipment, the innovative technique based on pneumatically spraying a suspension of TiO2 nanocrystals, the process parameters and preliminary test results for the obtained layers stand as main topics for the article. Integration of the system into industry 4.0 virtual intelligent platform is also presented. Further research development in order to validate the nanostructured TiO2 coating on glazed surfaces is aimed.

Open Access

207. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption

Authors: Borca, B; Michnowicz, T; Aguilar-Galindo, F; Petuya, R; Pristl, M; Schendel, V; Pentegov, I; Kraft, U; Klauk, H; Wahl, P; Arnau, A; Schlickum, U

Published: 2023 FEB 17 2023, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, DOI: 10.1021/acs.jpclett.2c03575

The changes of properties and preferential interactions based on subtle energetic differences are important characteristics of organic molecules, particularly for their functionalities in biological systems. Only slightly energetically favored interactions are important for the molecular adsorption and bonding to surfaces, which define their properties for further technological applications. Here, prochiral tetracenothiophene molecules are adsorbed on the Cu(111) surface. The chiral adsorption configurations are determined by Scanning Tunneling Microscopy studies and confirmed by first-principles calculations. Remarkably, the selection of the adsorption sites by chemically different moieties of the molecules is dictated by the arrangement of the atoms in the first and second surface layers. Furthermore, we have investigated the thermal effects on the direct desulfurization reaction that occurs under the catalytic activity of the Cu substrate. This reaction leads to a product that is covalently bound to the surface in chiral configurations.

Open Access

208. Multiparticle quantum walk: A dynamical probe of topological many-body excitations

Authors: Ostahie, B; Sticlet, D; Moca, CP; Dóra, B; Werner, MA; Asboth, JK; Zaránd, G

Published: JUL 13 2023, PHYSICAL REVIEW B, 108, 035126, DOI: 10.1103/PhysRevB.108.035126

Recent experiments demonstrated that single-particle quantum walks can reveal the topological properties of single-particle states. Here, we generalize this picture to the many-body realm by focusing on multiparticle quantum walks of strongly interacting fermions. After injecting N particles with multiple flavors in the interacting SU(N) Su-Schrieffer-Heeger chain, their multiparticle continuous-time quantum walk is monitored by a variety of methods. We find that the many-body Berry phase in the N-body part of the spectrum signals a topological transition upon varying the dimerization, similarly to the single-particle case. This topological transition is captured by the single- and many-body mean chiral displacement during the quantum walk and remains present for strong interaction as well as for moderate disorder. Our predictions are well within experimental reach for cold atomic gases and can be used to detect the topological properties of many-body excitations through dynamical probes.

209. First Sharp Diffraction Peak features of the intermediate phase glasses and amorphous thin films in the non-stoichiometric (GeS4)x(AsS3)1-x system

Authors: Ciobanu, M; Galca, AC; Sava, F; Zaki, MY; Velea, A; Tsiulyanu, D

Published: MAY 31 2023, THIN SOLID FILMS, 773, 139828, DOI: 10.1016/j.tsf.2023.139828

Grazing incidence X-ray scattering (GIXRS) patterns of thin solid films based on non-stoichiometric chalcogenide glasses (ChG) from the pseudo - binary system (GeS4)x(AsS3)1-x were studied with a focus on the First Sharp Diffraction Peak (FSDP), assigned to the middle range order (MRO) of the glassy material. The films were grown using explosive thermal evaporation in vacuum (10-4 Pa) of pulverized ChG, prepared from previously synthesized bulk glasses, onto mono-crystalline silicon substrates. Scanning Electron Microscopy (SEM) and EnergyDispersive X-ray (EDX) spectroscopy were used to examine the morphology and elemental composition of the films, which were found to have similar composition to the bulk glasses. However, it was revealed that the molecular structure of the grown amorphous films differs from that of the initial ChG bulk material, as indicated by changes in the composition-dependent position and width of the FSDP. Additionally, the intensities of the FSDP in the films were higher compared to those of the bulk samples, suggesting that the molecular-like structure of ChGs is more pronounced in the form of thin films grown from the vapor phase.

Open Access

210. Partial replacement of Pb²⁺ in MAPbI2.6Cl0.4 perovskite films and their photovoltaic performance

Authors: Derbali, S; Nouneh, K; Leonat, LN; Stancu, V; Tomulescu, AG; Galca, AC; Touhami, ME; Pintilie, I; Florea, M

Published: APR 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 903, DOI: 10.1007/s10854-023-10318-9

Replacing lead atoms in halide perovskite materials is of significant importance for the development of environmentally friendly perovskite solar cells. In this paper, we investigated the effect of doping the MAPbI(2.6)Cl(0.4) hybrid perovskite (MA-methyl ammonium) with non-toxic elements, such as alkaline earth metal ions (Mg2+) and transition metal ions (Zn2+). The structural, morphological, and optical properties of the prepared samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV-Vis. spectroscopy. Finally, the doped films were used as photoactive layers in solar devices in order to evaluate their photovoltaic performance. Zn proved to be more appropriate to replace partially Pb and films with higher quality were obtained. As a result, the MAPb1(-x)Zn(x)I(2.6)Cl(0.4) based solar cells have demonstrated a slight improvement of the photovoltaic performances, resulting in a uniform and narrower PCEs (power conversion efficiency) range, compared to pristine MAPbI(2.6)Cl(0.4) based devices.

Open Access

211. Salvia officinalis-Hydroxyapatite Nanocomposites with Antibacterial Properties

Authors: Ciobanu, SC; Predoi, D; Chifiriuc, MC; Iconaru, SL; Predoi, MV; Popa, M; Rokosz, K; Raaen, S; Marinas, IC; Huang, HM

Published: DEC 2023, POLYMERS, 15, 4484, DOI: 10.3390/polym15234484

In the present study, sage-coated zinc-doped hydroxyapatite was incorporated into a dextran matrix (7ZnHAp-SD), and its physico-chemical and antimicrobial activities were investigated. A 7ZnHAp-SD nanocomposite suspension was obtained using the co-precipitation method. The stability of the nanocomposite suspension was evaluated using ultrasound measurements. The stability parameter calculated relative to double-distilled water as a reference fluid highlights the very good stability of the 7ZnHAp-SD suspension. X-ray diffraction (XRD) experiments were performed to evaluate the characteristic diffraction peak of the hydroxyapatite phase. Valuable information regarding the morphology and chemical composition of 7ZnHAp-SD was obtained via scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) studies. Fourier-transform infrared spectroscopy (FTIR) measurements were performed on the 7ZnHAp-SD suspensions in order to evaluate the functional groups present in the sample. Preliminary studies on the antimicrobial activity of 7ZnHAp-SD suspensions against the standard strains of Staphylococcus aureus 25923 ATCC, Enterococcus faecalis 29212 ATCC, Escherichia coli 25922 ATCC, and Pseudomonas aeruginosa 27853 ATCC were conducted. More than that, preliminary studies on the biocompatibility of 7ZnHAp-SD were conducted using human cervical adenocarcinoma (HeLa) cells, and their results emphasized that the 7ZnHAp-SD sample did not exhibit a toxic effect and did not induce any noticeable changes in the morphological characteristics of HeLa cells. These preliminary results showed that these nanoparticles could be possible candidates for biomedical/antimicrobial applications.

Open Access

212. Columnar Liquid Crystals of Copper(I) Complexes with Ionic Conductivity and Solid State Emission

Authors: Circu, V; Ganea, CP; Secu, M; Manaila-Maximean, D; Marinescu, GC; Popescu, RG; Pasuk, I

Published: MAY 19 2023, MOLECULES, 28, 4196, DOI: 10.3390/molecules28104196

Two neutral copper(I) halide complexes ([Cu(BTU)(2)X], X = Cl, Br) were prepared by the reduction of the corresponding copper(II) halides (chloride or bromide) with a benzoylthiourea (BTU, N-(3,4-diheptyloxybenzoyl)-N '-(4-heptadecafluorooctylphenyl)thiourea) ligand in ethanol. The two copper(I) complexes show a very interesting combination of 2D supramolecular structures, liquid crystalline, emission, and 1D ionic conduction properties. Their chemical structure was ascribed based on ESI-MS, elemental analysis, IR, and NMR spectroscopies (H-1 and C-13), while the mesomorphic behavior was analyzed through a combination of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and powder X-ray diffraction (XRD). These new copper(I) complexes have mesomorphic properties and exhibit a hexagonal columnar mesophase over a large temperature range, more than 100 K, as evidenced by DSC studies and POM observations. The thermogravimetric analysis (TG) indicated a very good thermal stability of these samples up to the isotropization temperatures and over the whole temperature range of the liquid crystalline phase existence. Both complexes displayed a solid-state emission with quantum yields up to 8% at ambient temperature. The electrical properties of the new metallomesogens were investigated by variable temperature dielectric spectroscopy over the entire temperature range of the liquid crystalline phase. It was found that the liquid crystal phases favoured anhydrous proton conduction provided by the hydrogen-bonding networks formed by the NH horizontal ellipsis X moieties (X = halide or oxygen) of the benzoylthiourea ligand in the copper(I) complexes. A proton conductivity of 2.97 x 10(-7) S.cm(-1) was achieved at 430 K for the chloro-complex and 1.37 x 10(-6) S.cm(-1) at 440K for the related bromo-complex.

213. Cu2SnSe3 phase formation from different metallic and binary chalcogenides stacks using magnetron sputtering

Authors: Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Mihai, C; Velea, A; Galca, AC

Published: JAN 2023, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 153, 107195, DOI: 10.1016/j.mssp.2022.107195

Cu2SnSe3 (CTSe) is a polyvalent material that can be used as an absorber layer for thin film solar cells or as a starting layer for the synthesis of CZTSe or CZTSSe compounds. Obtaining CTSe single phase films with opti-mized properties for thin film solar cells is a difficult task. A systematic study using both metallic and binary chalcogenides precursors for the formation of the CTSe phase was not performed. The films consisting of four different stacks (Sn\Cu, SnSe2\Cu, Sn\Cu2Se, and SnSe2\Cu2Se) were prepared by magnetron sputtering on soda lime glass (SLG) and molybdenum (Mo) coated SLG substrates, followed by annealing at 550 degrees C under Sn + Se atmosphere. X-ray diffraction and Raman spectroscopy results indicated the formation of a single CTSe phase in most of the stacks deposited on both substrates. Scanning electron microscopy images showed compact surfaces with large grains in the films deposited on Mo substrate, while the films on SLG have more voids on their sur-faces. The elemental analysis measured by energy dispersive spectroscopy revealed stoichiometric films on Mo, and copper and tin rich compositions on SLG substrates. The band gap values inferred by conventional spec-troscopy are between 0.81 and 1.95 eV. It was found that the SnSe2\Cu and Sn\Cu2Se stacks are preferred for the formation of a single CTSe phase, with dense surface morphology, a stoichiometric composition, and an optimal absorber layer band gap. This study opens the way to comprehend the formation reactions during the seleni-zation of metallic and binary chalcogenides precursors towards the optimization of kesterite absorber for photovoltaic device fabrication.

Open Access

214. Optoelectronic and stability properties of quasi-2D alkylammonium based perovskites

Authors: Filipoiu, N; Mirea, AG; Derbali, S; Pantis-Simut, CA; Anghel, DV; Manolescu, A; Pintilie, I; Florea, M; Nemnes, GA

Published: JAN 27 2023, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 25, DOI: 10.1039/d2cp04748a

Electronic and stability properties of quasi-2D alkylammonium perovskites are investigated using density functional theory (DFT) calculations and validated experimentally on selected classes of compounds. Our analysis is focused on perovskite structures of formula (A)(2)(A ')(n-1)PbnX3n+1, with large cations A = butyl-, pentyl-, hexylammonium (BA, PA, HXA), small cations A ' = methylammonium, formamidinium, ethylammonium, guanidinium (MA, FA, EA, GA) and halogens X = I, Br, Cl. The role of the halogen ions is outlined for the band structure, stability and defect formation energies. Two opposing trends are found for the absorption efficiency versus stability, the latter being assessed with respect to possible degradation mechanisms. Experimental validation is performed on quasi-2D perovskites based on pentylammonium cations, namely: (PA)(2)PbX4 and (PA)(2)(MA)Pb2X7, synthesized by antisolvent-assisted vapor crystallization. Structural and optical analysis are inline with the DFT based calculations. In addition, the thermogravimetric analysis shows an enhanced stability of bromide and chloride based compounds, in agreement with the theoretical predictions.

Open Access

215. Bio-Entities Based on Albumin Nanoparticles and Biomimetic Cell Membranes: Design, Characterization and Biophysical Evaluation

Authors: Barbinta-Patrascu, ME; Iftimie, S; Cazacu, N; Stan, DL; Costas, A; Balan, AE; Chilom, CG

Published: APR 2023, COATINGS, 13, 671, DOI: 10.3390/coatings13040671

Protein-based particles are one of the most important research topics in nanomedicine, being used especially as drug delivery systems. From the wide variety of proteins, albumins offer several advantages in biomedical applications due to their special properties. Albumin nanoparticles play an important role as carriers in the drug delivery of chemical and biomolecular drugs, such as anticancer drugs; offer many advantages, such as biocompatibility and biodegradability; and are well-tolerated, without any side effects. In this work, various types of bovine serum albumin nanoparticles (BSA NPs), with or without ascorbic acid or glucose, were prepared via different nanoprecipitation methods. The obtained BSA NPs were characterized by UV-Vis absorption spectroscopy. Their size and morphology were studied by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The stability in time of the developed BSA NPs was spectrally monitored. Three types of bio-entities containing BSA NPs and chlorophyll-labeled artificial cell membranes were "green" developed. The designed biohybrids were characterized by UV-Vis absorption and fluorescence emission spectroscopy, and their three-dimensional topography was investigated by AFM. Both the size and shape of the developed bio-entities were monitored through SEM analysis. These results could be exploited in the development of novel drug carrier systems or as bio-coatings to be used in the biomedical field.

Open Access

216. Macrocyclic Compounds: Metal Oxide Particles Nanocomposite Thin Films Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Costas, A; Rasoga, O; Petre, G; Popescu-Pelin, G; Iftimie, S; Stochioiu, A; Socol, G; Stanculescu, A

Published: MAR 2023, MATERIALS, 16, 2480, DOI: 10.3390/ma16062480

Nanocomposite films based on macrocyclic compounds (zinc phthalocyanine (ZnPc) and 5,10,15,20-tetra(4-pyridyl) 21H,23H-porphyrin (TPyP)) and metal oxide nanoparticles (ZnO or CuO) were deposited by matrix-assisted pulsed laser evaporation (MAPLE). 1,4-dioxane was used as a solvent in the preparation of MAPLE targets that favor the deposition of films with a low roughness, which is a key feature for their integration in structures for optoelectronic applications. The influence of the addition of ZnO nanoparticles (similar to 20 nm in size) or CuO nanoparticles (similar to 5 nm in size) in the ZnPc:TPyP mixture and the impact of the added metal oxide amount on the properties of the obtained composite films were evaluated in comparison to a reference layer based only on an organic blend. Thus, in the case of nanocomposite films, the vibrational fingerprints of both organic compounds were identified in the infrared spectra, their specific strong absorption bands were observed in the UV-Vis spectra, and a quenching of the TPyP emission band was visible in the photoluminescence spectra. The morphological analysis evidenced agglomerated particles on the composite film surface, but their presence has no significant impact on the roughness of the MAPLE deposited layers. The current density-voltage (J-V) characteristics of the structures based on the nanocomposite films deposited by MAPLE revealed the critical role played by the layer composition and component ratio, an improvement in the electrical parameters values being achieved only for the films with a certain type and optimum amount of metal oxide nanoparticles.

217. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe0@Ni0@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics

Authors: Borhan, AI; Ghemes, AI; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUN 15 2023, APPLIED SURFACE SCIENCE, 622, 156987, DOI: 10.1016/j.apsusc.2023.156987

We reported on the sequential development of a high-operative photocatalyst with penta-component inorganic bulk heterojunction for improved charge trapping characteristics at particle-particle interfaces for enhanced solar light-driven photocatalytic degradation of active tetracycline antibiotic. Structural, morphological, optical, and electronic properties of the synthesized samples were investigated using a series of complementary char-acterization techniques, such as XRD, FE-SEM, HR-TEM, XPS, as well as hard and soft XAS in both total electron yield (TEY) and fluorescence yield (TFY). For the case of the carbon composite material, SrTiO3@NiFe2O4@-Fe0@Ni0@CNTs, a reduced crystallinity when compared to the starting support material was noticed, although this translated into a significant improvement of the morphology and the photocatalytic performance. The SrTiO3@NiFe2O4@Fe0@Ni0@CNTs fibrous photocatalyst can efficiently achieve a high-to-total degradation of tetracycline antibiotic under visible light irradiation in less than two hours, following a non-linear PFO kinetic model with an apparent reaction rate of about 0.0606 min-1 and an 98% photodegradation activity. The XPS and XAS analysis demonstrated unequivocally the appearance of nanoscale zero-valent iron (Fe0) and zero-valent nickel (Ni0) on the photocatalyst surface, which facilitates the separation of photogenerated e+ and h+ pairs, and the appearance of more active sites.

Open Access

218. In situ Electrochemical Evaluation of the Interaction of dsDNA with the Proteasome Inhibitor Anticancer Drug Bortezomib

Authors: Bunea, MC; Enache, TA; Diculescu, VC

Published: APR 2023, MOLECULES, 28, 3277, DOI: 10.3390/molecules28073277

Bortezomib is an inhibitor of proteasomes and an anti-cancer drug. Although bortezomib is considered a safe drug, as confirmed by cytotoxicity assays, recent reports highlighted the possibility of interaction between bortezomib and cellular components, with detrimental long-term effects. The evaluation of the interaction between bortezomib and dsDNA was investigated in bulk solution and using a dsDNA electrochemical biosensor. The binding of bortezomib to dsDNA involved its electroactive centers and led to small morphological modifications in the dsDNA double helix, which were electrochemically identified through changes in the guanine and adenine residue oxidation peaks and confirmed by electrophoretic and spectrophotometric measurements. The redox product of bortezomib amino group oxidation was electrochemically generated in situ on the surface of the dsDNA electrochemical biosensor. The redox product of bortezomib was shown to interact primarily with guanine residues, preventing their oxidation and leading to the formation of bortezomib-guanine adducts, which was confirmed by control experiments with polyhomonucleotides electrochemical biosensors and mass spectrometry. An interaction mechanism between dsDNA and bortezomib is proposed, and the formation of the bortezomib redox product-guanine adduct explained.

Open Access

219. Silver Nanoparticle Synthesis via Photochemical Reduction with Sodium Citrate

Authors: Pascu, B; Negrea, A; Ciopec, M; Duteanu, N; Negrea, P; Bumm, LA; Grad, O; Nemes, NS; Mihalcea, C; Duda-Seiman, DM

Published: JAN 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 255, DOI: 10.3390/ijms24010255

The aim of this paper is to provide a simple and efficient photoassisted approach to synthesize silver nanoparticles, and to elucidate the role of the key factors (synthesis parameters, such as the concentration of TSC, irradiation time, and UV intensity) that play a major role in the photochemical synthesis of silver nanoparticles using TSC, both as a reducing and stabilizing agent. Concomitantly, we aim to provide an easy way to evaluate the particle size based on Mie theory. One of the key advantages of this method is that the synthesis can be "activated" whenever or wherever silver nanoparticles are needed, by premixing the reactants and irradiating the final solution with UV radiation. UV irradiance was determined by using Keitz's theory. This argument has been verified by premixing the reagents and deposited them in an enclosed space (away from sunlight) at 25 degrees C, then checking them for three days. Nothing happened, unless the sample was directly irradiated by UV light. Further, obtained materials were monitored for 390 days and characterized using scanning electron microscopy, UV-VIS, and transmission electron microscopy.

220. Structural, Frequency and Temperature Dependent Dielectric Properties of Zn²⁺ Substituted Ni-Co Based Spinel Ferrite (ZnxNi0.8-xCo0.2Fe2O4)

Authors: Oumezzine, M; Iuga, A; Enculescu, M; Galca, AC

Published: MAY 1 2023, ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY, 12, 053008, DOI: 10.1149/2162-8777/acd6bb

Zinc substituted nickel-cobalt ferrites, i.e., ZnxNi0.8-xCo0.2Fe2O4 (x = 0.0, 0.05, 0.10 and 0.20) with average crystallite size 100 nm were synthesized by citrate-gel auto-combustion method to investigate effects of Zn2+ substitution on the structural and dielectric properties. Both X-ray diffraction (XRD) and IR spectroscopy studies confirms the formation of pure cubic spinel structure. Variation of lattice parameter infers Vegard's law linear dependence with the addition of Zn2+ concentration. The temperature-dependent behavior of dielectric and modulus spectra has been studied within the frequency range 100 Hz-100 kHz for different temperatures between 100 K and 400 K. It was concluded that the dielectric responses of ZnxNi0.8-xCo0.2Fe2O4 are found to be frequency dependent and thermally activated. Also, In the Zn doped ferrites variations of dielectric loss (tan d) and the imaginary part of electric modulus (M") show the presence of the non-Debye type of dielectric relaxation. Rise in Zinc concentration leads to a decrease in dielectric constant (e (r)) due to the declining of Fe3+-O-M2+ conducting network (M is Co or Ni). Here, we report a low loss tangent factor of the order of 8x10-3 0.6Zn(0.2)Co(0.2)Fe(2)O(4) make this composition suitable for high frequency-applications at room temperature. The activation energy is calculated from electric modulus formalism and DC electrical conductivity and found to increase with further substitution of Zn2+ concentration.

Open Access

221. FORMATION AND DETECTION OF SECONDARY CRYSTALLINE PHASES IN Cu2SnS3 THIN FILMS FOR PHOTOVOLTAIC APPLICATIONS

Authors: Catana, D; Parloaga, CA; Zaki, MY; Simandan, D; Buruiana, AT; Sava, F; Velea, A

Published: 2023, ROMANIAN REPORTS IN PHYSICS, 75, 504, DOI: 10.59277/RomRepPhys.2023.75.504

Cu2SnS3 thin films emerged as promising materials for sustainable photovoltaics due to their earth-abundant constituents and great optoelectronic properties. The formation of secondary phases during synthesis poses challenges to achieving efficient performances. This study investigates the impact of secondary on the of CTS films.

Open Access

222. Pulsed laser deposited V2O3 thin-films on graphene/aluminum foil for micro-battery applications

Authors: Tite, T; Ungureanu, C; Buga, M; Stavarache, I; Matei, E; Negrila, CC; Trupina, L; Spinu-Zaulet, A; Galca, AC

Published: MAR 15 2023, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 933, 117290, DOI: 10.1016/j.jelechem.2023.117290

The development of new thin-film cathodes triggered a recent research interest in energy storage applications. Over the past years, vanadium oxides have been extensively explored as promising electrodes for batteries owing to their rich valence states and remarkable electrochemical properties. Herein, we report on the synthe-sis of undoped and Sn doped V2O3 thin-films on graphene (G)/Al foil by pulsed laser deposition followed by rapid thermal annealing in N2 at low temperature (similar to 430 degrees C). The obtaining V2O3 phase on graphene/Al foil (G/Al) has been confirmed by X-ray diffraction and Raman and X-ray photoelectron spectroscopy analyses. The synthesized vanadium oxide films were tested as cathodes in coin cells. The electrochemical properties have been systematically investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge discharge (GCD) measurements. A superior electrochemical performance was observed for the V2O3 on G/Al structures, with an initial capacity of around 300 mAh g-1, with respect to the bare G/Al electrode. The use of the Sn-doped (5 mol%) V2O3 thin-films improved slightly the initial capac-ity up to a value of ca. 311 mAh g-1. Both V2O3/G/Al and Sn-doped V2O3/G/Al exhibited excellent cycling performances after 40 cycles with a capacity maintenance at a C-rate C/20 of 317 mAh g-1. Long-term cycling test (up to 200 cycles) showed that the Sn doping could be an excellent strategy to improve the stability of the electrodes, which yielded a capacity loss of only 0.128% per cycle. Possible mechanisms are presented and dis-cussed. This work could serve as point of reference for future developments in the field of batteries employing vanadium oxide-based thin-films deposited by physical vapor deposition techniques.

Open Access

223. TiO2 Phase Ratio's Contribution to the Photocatalytic Activity

Authors: Stepanova, A; Tite, T; Ivanenko, I; Enculescu, M; Radu, C; Culita, DC; Rostas, AM; Galca, AC

Published: OCT 25 2023, ACS OMEGA, 8, DOI: 10.1021/acsomega.3c05890

Photocatalysis is one of the approaches for solving environmental issues derived from extremely harmful pollution caused by industrial dyes, medicine, and heavy metals. Titanium dioxide is among the most promising photocatalytic semiconductors; thus, in this work, TiO2 powders were prepared by a hydrothermal synthesis using titanium tetrachloride TiCl4 as a Ti source. The effect of the hydrochloric acid (HCl) concentration on TiO2 formation was analyzed, in which a thorough morpho-structural analysis was performed employing different analysis methods like XRD, Raman spectroscopy, SEM/TEM, and N-2 physisorption. EPR spectroscopy was employed to characterize the paramagnetic defect centers and the photogeneration of reactive oxygen species. Photocatalytic properties were tested by photocatalytic degradation of the rhodamine B (RhB) dye under UV light irradiation and using a solar simulator. The pH value directly influenced the formation of the TiO2 phases; for less acidic conditions, the anatase phase of TiO2 crystallized, with a crystallite size of approximate to 9 nm. Promising results were observed for TiO2, which contained 76% rutile, showing a 96% degradation of RhB under the solar simulator and 91% under UV light after 90 min irradiation, and the best result showed that the sample with 67% of the anatase phase after 60 min irradiation under the solar simulator had a 99% degradation efficiency.

Open Access

224. Carbon-based heterostructure from multi-photo-active nanobuilding blocks SrTiO3@NiFe2O4@Fe⁰@Ni⁰@CNTs with derived nanoreaction metallic clusters for enhanced solar light-driven photodegradation of harmful antibiotics (vol 622, 156987, 2023)

Authors: Borhan, AI; Ghemes, IA; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Radu, I; Dirtu, AC; Dirtu, D; Bulai, G; Lupu, N; Palamaru, MN; Iordan, AR; Gherca, D

Published: JUL 1 2023, APPLIED SURFACE SCIENCE, 624, 157067, DOI: 10.1016/j.apsusc.2023.157067

Open Access

225. New Insights into the Biological Response Triggered by Dextran-Coated Maghemite Nanoparticles in Pancreatic Cancer Cells and Their Potential for Theranostic Applications

Authors: Balas, M; Predoi, D; Burtea, C; Dinischiotu, A

Published: FEB 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 3307, DOI: 10.3390/ijms24043307

Iron oxide nanoparticles are one of the most promising tools for theranostic applications of pancreatic cancer due to their unique physicochemical and magnetic properties making them suitable for both diagnosis and therapy. Thus, our study aimed to characterize the properties of dextran-coated iron oxide nanoparticles (DIO-NPs) of maghemite (gamma-Fe2O3) type synthesized by co-precipitation and to investigate their effects (low-dose versus high-dose) on pancreatic cancer cells focusing on NP cellular uptake, MR contrast, and toxicological profile. This paper also addressed the modulation of heat shock proteins (HSPs) and p53 protein expression as well as the potential of DIO-NPs for theranostic purposes. DIO-NPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering analyses (DLS), and zeta potential. Pancreatic cancer cells (PANC-1 cell line) were exposed to different doses of dextran-coated gamma-Fe2O3 NPs (14, 28, 42, 56 mu g/mL) for up to 72 h. The results revealed that DIO-NPs with a hydrodynamic diameter of 16.3 nm produce a significant negative contrast using a 7 T MRI scanner correlated with dose-dependent cellular iron uptake and toxicity levels. We showed that DIO-NPs are biocompatible up to a concentration of 28 mu g/mL (low-dose), while exposure to a concentration of 56 mu g/mL (high-dose) caused a reduction in PANC-1 cell viability to 50% after 72 h by inducing reactive oxygen species (ROS) production, reduced glutathione (GSH) depletion, lipid peroxidation, enhancement of caspase-1 activity, and LDH release. An alteration in Hsp70 and Hsp90 protein expression was also observed. At low doses, these findings provide evidence that DIO-NPs could act as safe platforms in drug delivery, as well as antitumoral and imaging agents for theranostic uses in pancreatic cancer.

226. Structural and flame retardancy properties of GO-DOPO-HAK composite

Authors: Mihis, AG; Cotet, LC; Cadar, C; Pop, LC; Todea, M; Rusu, MM; Vulpoi, A; Székely, I; Salagean, CA; Magyari, K; Muresan-Pop, M; Cadar, O; Baia, M; Sofran, IE; Lisa, G; Anghel, I; Baibarac, M; Danciu, V; Baia, L

Published: APR 2023, JOURNAL OF MATERIALS SCIENCE, 58, DOI: 10.1007/s10853-023-08456-w

In the view of the advantages of using P, N, Si and graphene oxide (GO) for the development of flame retardants materials, a multi-structure synergistic composite was synthesized by grafting a novel nitrogen-containing polyhedral oligomeric silsesquioxane (HAK) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) on the surface of GO nanosheet. In the first step, 2-hydroxyethyl acrylate was selectively reacted, and then, HAK was synthetized by the condensation of the aza-Michael addition product with 3-(methacryloyloxy)propyltrimethoxysilane. Finally, the GO obtained by an innovative variant of Marcano-Tour improved exfoliation method was functionalized, first with DOPO, and then with HAK. The structural, morphological and surface properties of GO and GO-DOPO-HAK were investigated by means of XRD, TEM-EDX, FT-IR, Raman, zeta potential and XPS techniques, and it was evidenced the functionalization of GO with DOPO, and then with HAK. The performed microscale combustion calorimetry (MCC) and TG measurements indicated a great potential of the GO-DOPO-HAK as flame retardant material as the obtained residual weight for this sample was found to be the highest one compared to the other investigated samples. MCC analyses further revealed a major decrease in heat release capacity (HRC) and a significant increase in char yield, results that confirm the great potential of GO-DOPO-HAK as flame retardancy material. [GRAPHICS] .

227. Bulk MgB2 superconductor for levitation applications fabricated with boron processed by different routes

Authors: Savaskan, B; Ozturk, UK; Guner, SB; Abdioglu, M; Bahadir, MV; Acar, S; Somer, M; Ionescu, AM; Locovei, C; Enculescu, M; Badica, P

Published: OCT 25 2023, JOURNAL OF ALLOYS AND COMPOUNDS, 961, 170893, DOI: 10.1016/j.jallcom.2023.170893

Bulk MgB2 discs were prepared by an in situ route from mixtures of magnesium and boron powders. The boron powders were produced by two methods. The first one consisted of a self-propagating high tem-perature magnesiothermic synthesis (SHS) process followed by acid and fluorine cleaning and a heat treatment in inert atmosphere. This approach produced boron with purities between 86 % and 97 %, where the main impurity was Mg. Depending on the final heat treatment, these boron powders were amorphous or crystalline. In the second route, high purity nano powders (99 %) of boron were obtained by a diborane pyrolysis process. Bulks of MgB2 were characterized by structural, microstructural, and magnetic mea-surements. Critical current density, pinning force aspects and levitation force (including guiding force) details were assessed. Amorphous lower purity boron (86-97 %) obtained by the first processing route was found to promote the largest levitation forces of the MgB2 bulks and, among these samples, the best le-vitation results were recorded when using boron with a purity of 95-97 %. Use of a lower purity boron that decreases the cost of MgB2 promotes large scale production at industrial level of bulk MgB2 super-conducting magnets for levitation applications and enhances the applicability potential of MgB2 super-conductor. The relationship between levitation force and specific features of the samples such as pinning force details are discussed.& COPY; 2023 Elsevier B.V. All rights reserved.

228. Unravelling the role of nickel incorporation on the physical properties of CuO thin films deposited by spray pyrolysis and theoretical analysis of nanostructured ZnO/Ni:CuO-based heterojunction solar cells

Authors: Daoudi, O; Jellal, I; Haddout, A; Zimou, J; EL Khouja, O; Nouneh, K; Lharch, M; Fahoume, M; Bendoumou, A

Published: MAR 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 819, DOI: 10.1007/s10854-023-10167-6

Whereas solar photovoltaic cells are promising for proper power production, their wide deployment is hampered by production costs, material availability and toxicity. One of these materials is CuO, which has great chemical stability as well as interesting physical properties, including a direct band gap, a high absorption coefficient, and p-type conductivity. These properties indicate CuO as an exciting semiconducting material to use an absorber layer in thin films solar cells. For this specific reason, this paper focuses on the synthesis of pristine and Ni-incorporated CuO thin films by spray pyrolysis process. Several techniques such as; X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) and UV-Visible spectroscopy have been employed to characterize the synthesized samples. The XRD analysis indicated the formation of polycrystalline CuO thin films and the average crystallite size was decreased from 35 to 20 nm for the samples with x = 0-8 at%, respectively. Furthermore, Raman spectroscopy also confirms the single-phase formation of CuO films. The SEM images demonstrated that the incorporation of Ni in the CuO matrix improved the films surface. The EDX analysis and the elemental mapping belay the homogeneous distribution of the elements. Moreover, UV-Visible spectroscopy has shown a significant expansion in optical energy band gap from 1.45 to 1.53 eV with an increase of Ni concentration. On the other hand, to investigate the impact of Ni-incorporated CuO on nanostructure Ni:CuO/ZnO-NRs heterojunction solar cell performance, SCAPS-1D software is used. It has been found that, 8% Ni:CuO layer has been revealed as better for nanostructured solar cells. The results of this contribution will provide some vital guidelines for fabricating higher-efficiency solar cells.

Open Access

229. Response of the Endogenous Antioxidant Defense System Induced in RAW 264.7 Macrophages upon Exposure to Dextran-Coated Iron Oxide Nanoparticles

Authors: Balas, M; Iconaru, SL; Dinischiotu, A; Buton, N; Predoi, D

Published: FEB 2023, PHARMACEUTICS, 15, 552, DOI: 10.3390/pharmaceutics15020552

Presently, iron oxide nanoparticles are the only ones approved for clinical use as contrast agents in magnetic resonance imaging (MRI). Even though there is a high demand for these types of nanoparticles both for clinical use as well as for research, there are difficulties in obtaining stable nanoparticles with reproducible properties. In this context, in this study, we report the obtaining by an adapted coprecipitation method of dextran-coated maghemite nanoparticles (gamma-Fe2O3 NPs). The morphology and structure of the dextran-coated maghemite nanoparticles (gamma-Fe2O3 NPs) were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The TEM and SEM micrographs highlighted the obtaining of particles of nanometric size and spherical shape morphology. Furthermore, the high-resolution transmission electron microscopy (HRTEM), as well as selected area diffraction (SAED), revealed that the obtained samples presented the structure of cubic maghemite. In this study, we also explored the effects of the co-precipitation synthesized dextran-coated maghemite nanoparticles (gamma-Fe2O3 NPs) on the redox status of macrophages. For cytotoxicity evaluation of these NPs, murine macrophages (RAW 264.7 cell line) were exposed to different concentrations of dextran-coated maghemite nanoparticles (gamma-Fe2O3 NPs) corresponding to 0-500 mu g Fe3+/mL and incubated for 24, 48, and 72 h. Intracellular iron uptake, changes in the oxidative stress parameters (reactive oxygen species production and malondialdehyde level), and the activity of antioxidant enzymes, as well as GSH concentration in cells, were evaluated after incubation with a lower (50 mu g Fe3+/mL) and higher (500 mu g Fe3+/mL) dose of NPs. The results indicated a significant decrease in RAW 264.7 cell viability after 72 h in the presence of NPs at concentrations above 25 mu g Fe3+/mL. An important accumulation of NPs, dependent on dose and exposure time, was detected in macrophages, but it induced only a limited raise in the oxidative status. We showed here that the antioxidant capacity of RAW 264.7 macrophages was efficient in counteracting dextran-coated maghemite nanoparticles (gamma-Fe2O3 NPs) toxicity even at higher doses.

230. DATA ANALYSIS FOR GRAVITATIONAL WAVES USING NEURAL NETWORKS ON QUANTUM COMPUTERS

Authors: Isfan, MC; Caramete, LI; Caramete, A; Basceanu, VA; Popescu, T

Published: 2023, ROMANIAN REPORTS IN PHYSICS, 75, 113, DOI:

In this study, we evaluate the feasibility of using quantum neural networks for classifying gravitational waveforms, using both simulators and quantum computers. The analysis is quite interdisciplinary in its nature, combining knowledge involving astrophysics, quantum information as well as quantum and classical machine learning. We showed that the quantum classifiers and hybrid classical-quantum layers give highly accurate results when tested on a simple dataset and ran on a simulator; also, adding a quantum layer to poorly performing classical neural network can highly improve its accuracy. When running on a real quantum computer, error minimizing algorithms need to be implemented in order to obtain a satisfying accuracy.

231. Surface species of the nematic mixture E7 obtained by electrochemical insertion of Li⁺ ions

Authors: Baibarac, M; Zgura, I; Ganea, CP; Frunza, L

Published: APR 2023, EUROPEAN PHYSICAL JOURNAL E, 46, 26, DOI: 10.1140/epje/s10189-023-00280-z

We studied here the influence of Li+ ions on the benzene rings of nematic mixture E7, which is electrochemically adsorbed onto gold electrode surface, to highlight the ability of this mixture for the applications in the field of the rechargeable Li+-ion batteries. Raman spectra support the changes observed in electrochemical analyses while contact angle measurements show that wetting properties of E7 layer were modified after deposition of this mixture onto gold support and the doping with Li+ ions.

232. Liquid phase oxidation of alkenes and glycerol with molecular oxygen over mixed-ligand copper(II) complexes grafted on GO as catalysts

Authors: Rizescu, C; El Fergani, M; Eftemie, DI; Cojocaru, B; Popescu, D; Andruh, M; Parvulescu, VI

Published: AUG 5 2023, APPLIED CATALYSIS A-GENERAL, 663, 119302, DOI: 10.1016/j.apcata.2023.119302

[Cu(acac)(phen)(H2O)](ClO4) and [Cu(acac)(bipy)(H2O)](ClO4) catalysts were prepared by the immobilization of mixed-ligand complexes on graphene oxide derivatized with monochloroacetic acid. These catalysts were characterized through an ensemble of techniques including XRD, FTIR, Raman, and XPS while the catalytic behavior has been investigated in the oxidation of cyclohexene, 1-octene and glycerol in the presence of molecular oxygen. Cyclohexanone was the dominant product in the oxidation of cyclohexene resulting in selectivities higher than 50% for a conversion of 14.5%. The turnover frequencies were pretty high, namely, 4.5 h(-1) for [Cu(acac)(phen)(H2O)](ClO4) and 2.3 h(-1) for Cu(acac)(bipy)(H2O)](ClO4). The oxidation of 1-octene also occurred with a pretty high selectivity in 2-octanol as the main product. The role of copper in the oxidative dehydrogenation of glyceric acid towards tartronic acid was as well confirmed. Noteworthy, these catalysts were stable and their recycling occurred with no change in the conversion or selectivity.

233. Reduced graphene oxide-functionalized zinc oxide nanorods as promising nanocomposites for white light emitting diodes and reliable UV photodetection devices

Authors: Boukhoubza, I; Derkaoui, I; Basyooni, MA; Achehboune, M; Khenfouch, M; Belaid, W; Enculescu, M; Matei, E

Published: SEP 15 2023, MATERIALS CHEMISTRY AND PHYSICS, 306, 128063, DOI: 10.1016/j.matchemphys.2023.128063

We present a breakthrough in the development of novel nanocomposites based on reduced graphene oxide (RGO)-functionalized zinc oxide (ZnO) nanorods that hold exceptional promise for their use in white light emitting diodes (LEDs) and reliable UV photodetection. The nanorods had a pristine hexagonal wurtzite struc-ture, as confirmed by XRD analysis. SEM images revealed sandwich-like nanocomposites with ZnO nanorods coated in reduced graphene oxide and embedded between two layers of RGO. The study also confirmed the hybridization and interactions between the layers using Raman measurements. The resulting nanocomposites displayed a lower band gap energy than ZnO and exhibited unique photoluminescence spectra with a white PL light. The photodetector based on RGO/ZnO/RGO sandwich structures demonstrated exceptional photoresponse, with higher photocurrent under UV illumination, making it highly promising for a wide range of optoelectronic applications. Overall, this study offers a novel and powerful approach to create nanocomposite structures with enhanced optical characteristics.

Open Access

234. Iron-doped Co3O4 catalysts prepared by a surfactant-assisted method as effective catalysts for malic acid oxidative decarboxylation

Authors: Mitran, G; Neatu, S; Pavel, OD; Urda, A; Mirea, AG; Florea, M; Neatu, F

Published: JUL 31 2023, CATALYSIS SCIENCE & TECHNOLOGY, 13, DOI: 10.1039/d3cy00121k

Iron-doped Co3O4 oxides prepared by a surfactant-assisted method exhibited good catalytic activity in malic acid conversion, and the oxygen defects associated with the presence of Co2+ played a key role in catalyst activation for pyruvic acid production. The most active catalyst, for which the malic acid conversion was 70% and the pyruvic acid yield was 24%, has an inverse spinel type structure (Fe3+ replaces Co2+ from tetrahedral sites, while Fe2+ replaces Co3+ from octahedral sites) as well as a small energy difference between the highest occupied orbital and the lowest unoccupied orbital (low band-gap, E-g). The catalyst with the highest Co2+ loading showed the highest yield of pyruvic acid.

235. WO3 layer sensitized with BiVO4 and MIL-101(Fe) as photoanode for photoelectrochemical water oxidation

Authors: Sima, M; Vasile, E; Preda, N; Matei, E; Sima, A; Negrila, C

Published: OCT 2023, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 181, 111472, DOI: 10.1016/j.jpcs.2023.111472

Thick tungsten oxide layers were prepared electrophoretically in order to be used as photoanodes in photoelectrochemical water oxidation applications. The highest photocurrent density was obtained for a WO3 layer with thickness of similar to 900 nm. Additionally, WO3/BiVO4 and WO3/BiVO4/MIL-101(Fe) heterojunctions have been fabricated using WO3 layer as substrate. WO3/BiVO4 shows an increased value of the electrochemical active surface area indicating that more sites of this photoanode are activated through the formation of the heterojunction. The small V5+ signals observed in the V 2p XPS spectra of these heterojunctions were attributed to the substitution of V5+ atoms with W6+ atoms on the surface of BiVO4. Excessive W doping of the BiVO4 film determined the decrease of the photoelectrochemical performance of WO3/BiVO4 photoanode. The significant improvement of the photoconversion efficiency of the sample decorated with MIL-101(Fe) indicated that this cocatalyst provides sites more efficiently in the photoelectrochemical process. This performance was correlated with the reduced value of the charge transfer resistance at electrode/electrolyte interface obtained from electrochemical impedance spectroscopy investigation.

Open Access

236. Hydroxyapatite Thin Films of Marine Origin as Sustainable Candidates for Dental Implants

Authors: Dorcioman, G; Grumezescu, V; Stan, GE; Chifiriuc, MC; Gradisteanu, GP; Miculescu, F; Matei, E; Popescu-Pelin, G; Zgura, I; Craciun, V; Oktar, FN; Duta, L

Published: APR 2023, PHARMACEUTICS, 15, 1294, DOI: 10.3390/pharmaceutics15041294

Novel biomaterials with promising bone regeneration potential, derived from rich, renewable, and cheap sources, are reported. Thus, thin films were synthesized from marine-derived (i.e., from fish bones and seashells) hydroxyapatite (MdHA) by pulsed laser deposition (PLD) technique. Besides the physical-chemical and mechanical investigations, the deposited thin films were also evaluated in vitro using dedicated cytocompatibility and antimicrobial assays. The morphological examination of MdHA films revealed the fabrication of rough surfaces, which were shown to favor good cell adhesion, and furthermore could foster the in-situ anchorage of implants. The strong hydrophilic behavior of the thin films was evidenced by contact angle (CA) measurements, with values in the range of 15-18 degrees. The inferred bonding strength adherence values were superior (i.e., similar to 49 MPa) to the threshold established by ISO regulation for high-load implant coatings. After immersion in biological fluids, the growth of an apatite-based layer was noted, which indicated the good mineralization capacity of the MdHA films. All PLD films exhibited low cytotoxicity on osteoblast, fibroblast, and epithelial cells. Moreover, a persistent protective effect against bacterial and fungal colonization (i.e., 1- to 3-log reduction of E. coli, E. faecalis, and C. albicans growth) was demonstrated after 48 h of incubation, with respect to the Ti control. The good cytocompatibility and effective antimicrobial activity, along with the reduced fabrication costs from sustainable sources (available in large quantities), should, therefore, recommend the MdHA materials proposed herein as innovative and viable solutions for the development of novel coatings for metallic dental implants.

Open Access

237. Investigation of the Boron removal effect induced by 5.5 MeV electrons on highly doped EPI- and Cz-silicon

Authors: Liao, C; Fretwurst, E; Garutti, E; Schwandt, J; Makarenko, L; Pintilie, I; Filip, LD; Himmerlich, A; Moll, M; Gurimskaya, Y; Li, Z

Published: NOV 2023, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1056, 168559, DOI: 10.1016/j.nima.2023.168559

This study focuses on the properties of the BiOi (interstitial Boron-interstitial Oxygen) and CiOi (interstitial Carbon-interstitial Oxygen) defect complexes by 5.5MeV electrons in low resistivity silicon. Two different types of diodes manufactured on p-type epitaxial and Czochralski silicon with a resistivity of about 10 Omega center dot cm were irradiated with fluence values between 1x10(15) cm(-2) and 6x10(15) cm(-2). Such diodes cannot be fully depleted and thus the accurate evaluation of defect concentrations and properties (activation energy, capture cross-section, concentration) from Thermally Stimulated Currents (TSC) experiments alone is not possible. In this study we demonstrate that by performing Thermally Stimulated Capacitance (TS-Cap) experiments in similar conditions to TSC measurements and developing theoretical models for simulating both types of BiOi signals generated in TSC and TS-Cap measurements, accurate evaluations can be performed. The changes of the position-dependent electric field, the effective space charge density N-eff profile as well as the occupation of the BiOi defect during the electric field dependent electron emission, are simulated as a function of temperature. The macroscopic properties (leakage current and..eff) extracted from current-voltage and capacitance-voltage measurements at 20 degrees C are also presented and discussed.

238. Straightforward FeOOH nanografting of Al-based SrTiO3 perovskite material as core-shell nanoflower-like heteronanostructure with enhanced solar light-driven photodegradation capability

Authors: Borhan, AI; Herea, DD; Husanu, MA; Popescu, DG; Borca, CN; Huthwelker, T; Bulai, G; Radu, I; Dirtu, AC; Dirtu, D; Mita, C; Stoian, G; Ababei, G; Lupu, N; Pui, A; Gherca, D

Published: MAR 30 2023, APPLIED SURFACE SCIENCE, 614, 156247, DOI: 10.1016/j.apsusc.2022.156247

Extensive attention and considerable efforts have been made to construct efficient heterogeneous nano -particulate systems for surface chemical reactions to be active in solar light-driven photodegradation. This work addresses current deficiencies of the nanoparticles-focused systems intended for visible light photodegradation by developing a newly-formulated innovative chemically-engineered multi-component system that functions as a recyclabe, nontoxic, active and inexpensive catalyst for photodegradation of tetracyclne antibiotic. Here, we show a straightforward FeOOH nanografting of Al-based SrTiO3 perovskite material as core-shell nanoflower-like heteronanostructure with enhanced solar light-driven photodegradation capability over harmful antibi-otics. A persuasive surface formation mechanism is proposed based on systematic investigation of the assembly process. In-depth caracterization of structural, optical and morphological properties of the prepared samples was investigated using a series of complementary analytical techniques, such as XRD, FE-SEM, HR-TEM, synchrotron XPS, as well as hard and soft XAS in both total electron yield (TEY) and fluorescence yield (TFY). The oxygen -deficient nature of core and shell interface indicates its n-doping and the availability of free charges in core which can be either transferred to the shell or create localized absorption levels into the valence band. This study provides a real opportunity to rationally photocatalysts design with very promising performance in water treatment.

Open Access

239. Biological Response of Human Gingival Fibroblasts to Zinc-Doped Hydroxyapatite Designed for Dental Applications-An In Vitro Study

Authors: Badea, MA; Balas, M; Popa, M; Borcan, T; Bunea, AC; Predoi, D; Dinischiotu, A

Published: JUN 2 2023, MATERIALS, 16, 4145, DOI: 10.3390/ma16114145

This study aimed to investigate the biological response induced by hydroxyapatite (HAp) and zinc-doped HAp (ZnHAp) in human gingival fibroblasts and to explore their antimicrobial activity. The ZnHAp (with xZn = 0.00 and 0.07) powders, synthesized by the sol-gel method, retained the crystallographic structure of pure HA without any modification. Elemental mapping confirmed the uniform dispersion of zinc ions in the HAp lattice. The size of crystallites was 18.67 +/- 2 nm for ZnHAp and 21.54 +/- 1 nm for HAp. The average particle size was 19.38 +/- 1 nm for ZnHAp and 22.47 +/- 1 nm for HAp. Antimicrobial studies indicated an inhibition of bacterial adherence to the inert substrate. In vitro biocompatibility was tested on various doses of HAp and ZnHAp after 24 and 72 h of exposure and revealed that cell viability decreased after 72 h starting with a dose of 31.25 mu g/mL. However, cells retained membrane integrity and no inflammatory response was induced. High doses (such as 125 mu g/mL) affected cell adhesion and the architecture of F-actin filaments, while in the presence of lower doses (such as 15.625 mu g/mL), no modifications were observed. Cell proliferation was inhibited after treatment with HAp and ZnHAp, except the dose of 15.625 mu g/mL ZnHAp at 72 h of exposure, when a slight increase was observed, proving an improvement in ZnHAp activity due to Zn doping.

240. The electrochemical behavior of methionine residues oxidation

Authors: Bunea, MC; Enache, TA

Published: JUL 2023, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, 52, DOI:

Open Access

241. Experimental Band Structure of Pb(Zr,Ti)O3: Mechanism of Ferroelectric Stabilization

Authors: Popescu, DG; Husanu, MA; Constantinou, PC; Filip, LD; Trupina, L; Bucur, CI; Pasuk, I; Chirila, C; Hrib, LM; Stancu, V; Pintilie, L; Schmitt, T; Teodorescu, CM; Strocov, VN

Published: FEB 2023, ADVANCED SCIENCE, 10, DOI: 10.1002/advs.202205476

Pb(Zr,Ti)O-3 (PZT) is the most common ferroelectric (FE) material widely used in solid-state technology. Despite intense studies of PZT over decades, its intrinsic band structure, electron energy depending on 3D momentum k, is still unknown. Here, Pb(Zr0.2Ti0.8)O-3 using soft-X-ray angle-resolved photoelectron spectroscopy (ARPES) is explored. The enhanced photoelectron escape depth in this photon energy range allows sharp intrinsic definition of the out-of-plane momentum k and thereby of the full 3D band structure. Furthermore, the problem of sample charging due to the inherently insulating nature of PZT is solved by using thin-film PZT samples, where a thickness-induced self-doping results in their heavy doping. For the first time, the soft-X-ray ARPES experiments deliver the intrinsic 3D band structure of PZT as well as the FE-polarization dependent electrostatic potential profile across the PZT film deposited on SrTiO3 and LaxSrMn1-xO3 substrates. The negative charges near the surface, required to stabilize the FE state pointing away from the sample (P+), are identified as oxygen vacancies creating localized in-gap states below the Fermi energy. For the opposite polarization state (P-), the positive charges near the surface are identified as cation vacancies resulting from non-ideal stoichiometry of the PZT film as deduced from quantitative XPS measurements.

242. Integration of cell cultures in electrochemical (bio)sensing platforms

Authors: Enache, A; Sanz, C; Oprea, D; Beregoi, M; Barsan, M

Published: JUL 2023, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, 52, DOI:

243. Analysis and characterization of magneto-structural transformations and critical exponent analysis of La0.8Ca0.2-xPbxMnO3

Authors: Bouzid, SA; Sajieddine, M; Hlil, E; Boubekri, AE; Rostas, AM; Essoumhi, A

Published: NOV 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 2166, DOI: 10.1007/s10854-023-11475-7

Because of their significant magnetocaloric properties, Ca and Pb-doped LaMnO3 can be employed in magnetic refrigeration systems. The partial substitution effect of Ca2+ by Pb2+ cations on the structural, magnetocaloric properties, and critical behavior of mixed valence perovskites La0.8Ca0.2-xPbxMnO3 (0 <= x <= 0.15), synthesized by the flash combustion route, was studied in this work. The presence of structural transformations of the prepared ceramics from an orthorhombic structure (Pbnm space group) for samples with x <= 0.05 to a rhombohedral system (R (3) over barc space group) for x >= 0.1 was detected by X-ray diffraction analysis, which is related to the A-site disorder. The field-cooled (FC) magnetization indicated a second-order ferromagnetic-paramagnetic transition for the investigated samples when the temperature was increased. Due to the change in the Mn3+/Mn4+ ratio, substituting Ca2+ with larger Pb2+ ions increases the Curie temperature (T-C) by increasing Pb doping content from 90 K for x = 0 to 205 K for x = 0.15. The magnetization isotherms of all samples showing a second-order phase transition were studied, where an applied magnetic field of 5 T, the value of maximum magnetic entropy variation /Delta S-M(max)/ for the sample with x = 0.15 was estimated to be 2.73 Jkg(-1) K-1. In addition, it has a significant relative cooling power of about 276 Jkg(-1) under the same applied magnetic field strength. The critical behavior of the samples was investigated close to T-C. The exponent values were identical to the mean-field method, indicating a large disorder of spin magnetic moments in the perovskite compounds.

Open Access

244. Organic Light-Emitting Diodes with Electrospun Electrodes for Double-Side Emissions

Authors: Ciobotaru, IC; Enculescu, M; Polosan, S; Enculescu, I; Ciobotaru, CC

Published: MAR 2023, MICROMACHINES, 14, 543, DOI: 10.3390/mi14030543

Transparent conductive electrodes (TCE) obtained by the electrospinning method and gold covered were used as cathodes in the organic light-emitting diodes (OLEDs) to create double side-emission. The electro-active nanofibers of poly(methyl methacrylate) (PMMA) with diameters in the range of several hundreds of nanometers, were prepared through the electrospinning method. The nanofibers were coated with gold by sputtering deposition, maintaining optimal transparency and conductivity to increase the electroluminescence on both electrodes. Optical, structural, and electrical measurements of the as-prepared transparent electrodes have shown good transparency and higher electrical conductivity. In this study, two types of OLEDs consisting of indium tin oxide (ITO)/ poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT-PSS)/ Ir(III) complex (8-hydroxyquinolinat bis(2-phenylpyridyl) iridium-IrQ(ppy)(2) 20 wt% embedded in N, N '-Dicarbazolyl-4,4 '-biphenyl (CBP) sandwich structure and either gold-covered PMMA electrospun nanoweb (OLED with electrospun cathode) were fabricated together with a similar structure containing thin film gold cathodes (OLED with thin film cathode). The luminance-current-voltage characteristics, the capacitance-voltage, and the electroluminescence properties of these OLEDs were investigated.

Open Access

245. Microscopic mechanism of ferroelectric properties in barium hexaferrites

Authors: Turchenko, V; Bondyakov, AS; Trukhanov, S; Fina, I; Korovushkin, VV; Balasoiu, M; Polosan, S; Bozzo, B; Lupu, N; Trukhanov, A

Published: JAN 10 2023, JOURNAL OF ALLOYS AND COMPOUNDS, 931, 167433, DOI: 10.1016/j.jallcom.2022.167433

The microscopic mechanism of the occurrence of ferroelectric properties in M-type barium hexaferrites is investigated by experimental and first-principle computation methods. The analysis of magnetic, X-ray, and Mossbauer measurements of BaFe12O19 samples ascertains the correlation between the thermal factor in the process of annealing samples and their functional properties. The occurrence of the remnant polarization in barium hexaferrites at room temperature contradicts the description of their crystal structure in the fra-mework of centrosymmetric space group P63/mmc (No. 194), in which one of the symmetry operations is inversion center. Therefore, the crystal structure of BaFe12O19 was analyzed in the frameworks of SG P63/mmc (No. 194) and non-centrosymmetric SG P63mc (No. 186). The computed value of polarization for a non-centrosymmetric unit cell is similar to 3.5 mu C/cm2. The analysis of polarization was carried out on a path connecting the polar P63mc and non-polar P63/mmc structures and considered in terms of the total energy barrier. Our result allows ascertaining a direct relationship between the remnant polarization of the unit cell and the broken spatial-inversion symmetry in the crystal structure of M-type barium hexaferrite.(c) 2022 Elsevier B.V. All rights reserved.

246. On the electrochemical oxidation of methionine residues of proteins

Authors: Bunea, MC; Oprescu, C; Enache, TA

Published: FEB 15 2023, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 931, 117209, DOI: 10.1016/j.jelechem.2023.117209

The oxidation of methionine side chain residues in proteins provides a great diversity of possible oxidation mechanisms dictated, among others, by the oxidizing species, solvent properties, and protein structure. The oxidation behavior of a series of short acetylated synthetic peptides, Ac-GMG, Ac-GGMGG and Ac-GGGMGGG, was investigated by differential pulse and square wave voltammetry, in a wide pH range, at glassy carbon electrode. It was found that always the first oxidation step represents the one-electron oxidation of thioether moiety with the formation of a radical cation. Following this, depending on the experimental condi-tions and side chain position of methionine, the radical is stabilized by the nucleophilic attack of water or by catalytic support of the neighboring carbonyl and amide groups in an intermediate structure, finally converted in methionine sulfoxide which can be further oxidized, at more positive potential, into methionine sulfone. For Ac-GGGMGGG, at pH 8.0, the amino and amide groups are active involved in the oxidation process and the electrode reaction takes place with proton transfer

Open Access

247. Ferroelectricity and negative piezoelectric coefficient in orthorhombic phase pure ZrO2 thin films

Authors: Sliva, JPB; Istrate, MC; Hellenbrand, M; Jan, AT; Becker, MT; Symonowicz, J; Figueiras, FG; Lenzi, V; Hill, MO; Ghica, C; Romanyuk, KN; Gomes, MJM; Di Martino, G; Marques, L; MacManus-Driscoll, JL

Published: FEB 2023, APPLIED MATERIALS TODAY, 30, 101708, DOI: 10.1016/j.apmt.2022.101708

A new approach for epitaxial stabilisation of ferroelectric orthorhombic (o-) ZrO2 films with negative piezoelectric coefficient in - 8nm thick films grown by ion-beam sputtering is demonstrated. Films on (011)-Nb: SrTiO3 gave the oriented o-phase, as confirmed by transmission electron microscopy and electron backscatter diffraction mapping, grazing incidence x-ray diffraction and Raman spectroscopy. Scanning probe microscopy techniques and macroscopic polarization-electric field hysteresis loops show ferroelectric behavior, with saturation polarization of -14.3 mu C/cm2, remnant polarization of -9.3 mu C/cm2 and coercive field -1.2 MV/cm. In contrast to the o-films grown on (011)-Nb:SrTiO3, films grown on (001)-Nb:SrTiO3 showed mixed monoclinic (m) and o-phases causing an inferior remnant polarization of -4.8 mu C/cm2, over 50% lower than the one observed for the film grown on (011)-Nb:SrTiO3. Density functional theory (DFT) calculations of the SrTiO3/ZrO2 interfaces support the experimental findings of a stable polar o-phase for growth on (011) Nb:SrTiO3, and they also explain the negative piezoelectric coefficient.

248. Hydrogen Production Mechanism in Low-Temperature Methanol Decomposition Catalyzed by Ni3Sn4 Intermetallic Compound: A Combined Operando and Density Functional Theory Investigation

Authors: Mauri, S; D'Olimpio, G; Ghica, C; Braglia, L; Kuo, CN; Istrate, MC; Lue, CS; Ottaviano, L; Klimczuk, T; Boukhvalov, DW; Politano, A; Torelli, P

Published: FEB 9 2023, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 14, DOI: 10.1021/acs.jpclett.2c03471

Hydrogen production from methanol decomposition to syngas (H2 + CO) is a promising alternative route for clean energy transition. One major challenge is related to the quest for stable, cost-effective, and selective catalysts operating below 400 degrees C. We illustrate an investigation of the surface reactivity of a Ni3Sn4 catalyst working at 250 degrees C, by combining density functional theory, operando X-ray absorption spectroscopy, and high-resolution transmission electron microscopy. We discovered that the catalytic reaction is driven by surface tin-oxide phases, which protects the underlying Ni atoms from irreversible chemical modifications, increasing the catalyst durability. Moreover, we found that Sn content plays a key role in enhancing the H2 selectivity, with respect to secondary products such as CO2. These findings open new perspectives for the engineering of scalable and low-cost catalysts for hydrogen production.

249. Characterization of defect structures in nanoscaled W-doped TiO2 tested as supercapacitor electrode materials

Authors: Ammar, AU; Stefan, M; Macavei, SG; Tripon, S; Pana, O; Leostean, C; Vlaicu, ID; Rostas, AM; Erdem, E

Published: JAN 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 8, DOI: 10.1007/s10854-022-09540-8

In this work, Tungsten(W)-doped TiO2 nanoparticles were synthesized using the sol-gel method and were used as electrode materials in supercapacitor applications. The structural and morphological properties of the prepared samples were analyzed by means of XRD, STEM, TEM, and XPS. The analysis of the defect centers was carried out using EPR spectroscopy. The electrochemical analysis of the assembled supercapacitor was done using cyclic voltammetry, galvanostatic cycling with potential limitation technique, potentiostatic electrochemical impedance spectroscopy, and voltage-holding experiments. All the presented samples showed paramagnetic defects in the EPR analysis, while 0.5% W-doped TiO2 showed a maximum signal intensity. The supercapacitor performance from the synthesized electrode material showed highly encouraging results. The equivalent series resistance (R-s) value for all the designs showed values under "1 omega,' which reflects high conductivity. As the maximum EPR intensity comes from TiO2 doped with 0.5% W, the supercapacitor performance of this sample was tested with a newly designed five-electrode system. This design showed superior performance compared to any other used designs with a specific capacitance of 25.5 F g(-1), with an energy density of 14.16 Wh kg (-1 )at 302 kW kg (-1).

Open Access

250. Fermiology of Chiral Cadmium Diarsenide CdAs2, a Candidate for Hosting Kramers-Weyl Fermions

Authors: Mazzola, F; Zhang, YX; Olszowska, N; Rosmus, M; D'Olimpio, G; Istrate, MC; Politano, GG; Vobornik, I; Sankar, R; Ghica, C; Gao, JF; Politano, A

Published: MAR 23 2023, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 14, DOI: 10.1021/acs.jpclett.3c00005

Nonmagnetic chiral crystals are a new class of systems hosting Kramers-Weyl Fermions, arising from the combination of structural chirality, spin- orbit coupling (SOC), and time-reversal symmetry. These materials exhibit nontrivial Fermi surfaces with SOC-induced Chern gaps over a wide energy range, leading to exotic transport and optical properties. In this study, we investigate the electronic structure and transport properties of CdAs2, a newly reported chiral material. We use synchrotron-based angle-resolved photoelectron spectroscopy (ARPES) and density functional theory (DFT) to determine the Fermiology of the (110)-terminated CdAs2 crystal. Our results, together with complementary magnetotransport measurements, suggest that CdAs2 is a promising candidate for novel topological properties protected by the structural chirality of the system. Our work sheds light on the details of the Fermi surface and topology for this chiral quantum material, providing useful information for engineering novel spintronic and optical devices based on quantized chiral charges, negative longitudinal magnetoresistance, and nontrivial Chern numbers.

Open Access

251. Mesoporous Composite Bioactive Compound Delivery System for Wound-Healing Processes

Authors: Purcareanu, B; Ene, MD; Morosan, A; Mihaiescu, DE; Florea, MA; Ghica, A; Nita, RA; Drumea, V; Grigoroscuta, MA; Kuncser, A; Badica, P; Olariu, L

Published: SEP 2023, PHARMACEUTICS, 15, 2258, DOI: 10.3390/pharmaceutics15092258

Currently, the treatment of wounds is still a challenge for healthcare professionals due to high complication incidences and social impacts, and the development of biocompatible and efficient medicines remains a goal. In this regard, mesoporous materials loaded with bioactive compounds from natural extracts have a high potential for wound treatment due to their nontoxicity, high loading capacity and slow drug release. MCM-41-type mesoporous material was synthesized by using sodium trisilicate as a silica source at room temperature and normal pressure. The synthesized mesoporous silica was characterized by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), N2 absorption-desorption (BET), Dynamic Light Scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR), revealing a high surface area (BET, 1244 m2/g); pore diameter of approx. 2 nm; and a homogenous, ordered and hexagonal geometry (TEM images). Qualitative monitoring of the desorption degree of the Salvia officinalis (SO) extract, rich in ursolic acid and oleanolic acid, and Calendula officinalis (CO) extract, rich in polyphenols and flavones, was performed via the continuous recording of the UV-VIS spectra at predetermined intervals. The active ingredients in the new composite MCM-41/sage and marigold (MCM-41/SO & CO) were quantified by using HPLC-DAD and LC-MS-MS techniques. The evaluation of the biological composites' activity on the wound site was performed on two cell lines, HS27 and HaCaT, naturally involved in tissue-regeneration processes. The experimental results revealed the ability to stimulate collagen biosynthesis, the enzymatic activity of the main metalloproteinases (MMP-2 and MMP-9) involved in tissue remodeling processes and the migration rate in the wound site, thus providing insights into the re-epithelializing properties of mesoporous composites.

252. Role of the Dopants in Improving the Piezoelectric Properties of Bi0.5Na0.5TiO3

Authors: Belgacem, K; Stanciu, C; Perju, S; Cernea, M

Published: JUL 2023, JOURNAL OF ELECTRONIC MATERIALS, 52, DOI: 10.1007/s11664-023-10407-9

Despite the high coercive field (E-c = 7.3 kV/mm) and the high conductivity (2.1 x 10(-7) (omega m)(-1)) of (Bi0.5Na0.5)TiO3 (BNT) ceramics, their microstructure and electric properties can be tailored by appropriate substitutions at the A and/or B-sites. In this paper, we offer a comprehensive review of the up-to-date advances on doped lead-free BNT ceramics, highlighting the role of the nature and concentration of dopants on the stoichiometry, microstructure, density, dielectric properties, and piezoelectric properties of the solid solutions obtained after doping. For each composition presented in this review, the synthesis method and the sintering technique of the ceramics are also given because of the well-known connection between powder processing (its morphology), ceramics densification (its density), and the macroscopic properties of the final product. A substitution mechanism for each dopant that explains the role of the dopant on the structure and electrical properties of the BNT matrix is also described in detail. Our review provides knowledge for the development of new solid solutions of BNT.

Open Access

253. Cost-effective, high-performance Ni3Sn4 electrocatalysts for methanol oxidation reaction in acidic environments

Authors: Boukhvalov, DW; D'Olimpio, G; Liu, JZ; Ghica, C; Istrate, MC; Kuo, CN; Politano, GG; Lue, CS; Torelli, P; Zhang, LX; Politano, A

Published: MAY 16 2023, CHEMICAL COMMUNICATIONS, 59, DOI: 10.1039/d3cc01623d

Methanol (CH3OH) oxidation offers a promising avenue for transitioning to clean energy, particularly in the field of direct methanol fuel cells (DMFCs). However, the development of efficient and cost-effective catalysts for the methanol oxidation reaction (MOR) remains a critical challenge. Herein, we report the exceptional electrocatalytic activity and stability of Ni3Sn4 toward MOR in acidic media, achieving a performance comparable to that of commercial Pt/C catalysts. Our catalyst design incorporates Earth-abundant Ni and Sn elements, resulting in a material that is 1800 times more cost-effective than Pt/C. Density functional theory (DFT) modeling substantiates our experimental findings, shedding light on the favorable reaction mechanisms and kinetics on the Ni3Sn4 surface. Additionally, the as-synthesized Ni3Sn4 electrocatalyst demonstrates commendable durability, maintaining its electrocatalytic activity even after prolonged exposure to harsh acidic conditions.

254. Nickel Species-Modified Mesoporous SnO2 as a Non-Platinum Electrocatalyst for Bioethanol Anodic Oxidation

Authors: Spataru, T; Somacescu, S; Osiceanu, P; Culita, DC; Mihai, MA; Florea, M; Kuncser, A; Spataru, N

Published: DEC 1 2023, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 170, 124518, DOI: 10.1149/1945-7111/ad1557

The effectiveness of mesoporous SnO2 nickel-decoration as a method for obtaining active electrode materials for bioethanol electrochemical oxidation and the way in which the embedment of a small amount of Black Pearls (BP) affects the electrocatalytic performances of Ni/SnO2 systems were investigated. XPS analysis reveals the presence of NiO, Ni(OH)(2) and Ni2O3 chemical species which favors the oxidation of bioethanol and improves the COx tolerance. Nickel deposition in a reducing environment does not affect the Sn chemistry and the mesoporosity but significantly increases S-BET. A slight amount of BP enhances the S-BET value and a induces a small contribution of larger pores appears. Tafel slopes of 80 mV decade(-1) were estimated for bioethanol oxidation at Ni/SnO2, which favorably compare to those reported in the literature. It was also found that BP incorporation leads to a decrease of the Tafel slope to 70 mV decade(-1), without deleteriously affecting the stability of the electrocatalyst during long-term polarization. EIS results suggested that this improvement might be the combined effect of a lower electrical resistance, a higher specific surface area and a certain contribution from larger pores, which could lead to a better access of the bioethanol species to the electrocatalyst surface.

Open Access

255. Influence of on-off pulsed current pattern on processes during spark plasma sintering of MgB2 superconductor

Authors: Aldica, G; Sandu, V; Popa, S; Pasuk, I; Enculescu, M; Ionescu, AM; Badica, P

Published: DEC 2023, OPEN CERAMICS, 16, 100441, DOI: 10.1016/j.oceram.2023.100441

High density samples (92-94.5 %) of MgB2 were prepared by Spark Plasma Sintering (SPS). The on-off pulsed current patterns of SPS processing were 8-4, 12-2, 24-2, 99-1. Patterns with more on pulses favor formation of a higher amount of the secondary MgB4 phase through the decomposition of MgB2. They also promote enhancement of larger MgO crystallites without a strong increase in the amount of this phase. Densification rate and pressure in the SPS chamber show a similar behavior, but their amplitude varies and the temperatures defining different stages present some shifts. As-revealed differences induced by pulsed patterns impact superconducting properties in a complex manner. An attempt to assess correlations between the pattern and different superconducting parameters is presented.

Open Access

256. Up-Conversion Luminescence and Magnetic Properties of Multifunctional Er³⁺/Yb³⁺-Doped SiO2-GdF3/LiGdF4 Glass Ceramics

Authors: Secu, C; Bartha, C; Radu, C; Secu, M

Published: JAN 2023, MAGNETOCHEMISTRY, 9, 11, DOI: 10.3390/magnetochemistry9010011

Glassy nanocomposites containing Yb3+/Er3+-doped GdF3 and LiGdF4 nanocrystals have been prepared by controlled crystallization of the xerogel and the structural, up-conversion luminescence, and magnetic properties were analyzed and discussed. Structural and morphological analysis showed uniform distribution of both GdF3 and LiGdF4 nanocrystals (tens of nm size), embedded in silica glass matrix as the result of thermal decomposition of the trifluoracetates, revealed as a strong exothermic peak at about 300 degrees C; the Li-ions co-doping showed a strong influence on the GdF3 and LiGdF4 nanocrystalline fraction. The energy dispersive spectrometry mapping showed Gd, F and Yb, Er within the nanocrystals but not in the silica glass matrix. X-ray diffraction pattern analysis indicated the crystalline lattice distortion consistent with the Yb/Er incorporation in both fluoride nanocrystals. The "green" ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and "red" (F-4(9/2)-> I-4(15/2)) up-conversion luminescences at 525, 545, and 660 nm observed under 980 nm laser light pumping were assigned to the Er3+ ions deexcitation through a two-photon process. The magnetic properties of the nanocomposite are strongly temperature dependent. The magnetization hysteresis loops show a ferromagnetic behavior at low temperatures (5K) related to the rare-earth ions contribution and the saturation magnetization of 39 emu/g. At 300 K a paramagnetic behavior was observed that was ascribed to the non-interacting localized nature of the magnetic moment of the rare-earth ions. Hence, such novel, multifunctional magnetic and optical materials can allow the intertwining between magnetism and photonics and might offer new opportunities for new magneto-optical device development.

257. Development of ceramic coatings on titanium alloy substrate by laser cladding with pre-placed natural derived-slurry: Influence of hydroxyapatite ratio and beam power

Authors: Mocanu, AC; Miculescu, F; Stan, GE; Tite, T; Miculescu, M; Tierean, MH; Pascu, A; Ciocoiu, RC; Butte, TM; Ciocan, LT

Published: APR 1 2023, CERAMICS INTERNATIONAL, 49, DOI: 10.1016/j.ceramint.2022.11.227

The attraction towards Ti and its alloys reside in their superior mechanical and tribological features, as compared to CaPs, which are renowned for their compositional and structural features similar to those of natural bones. However, Ti-based materials suffer from limited biocompatibility and inertness when implanted for extended periods. As such, surface modification with ceramic coatings is required in order to achieve proper biomedical features and enhance their overall behavior in the human body. Hence, this study outlined for the first time the prospect of coating several Ti6Al4V substrates (disks) with bovine-bone derived hydroxyapatite (HA) by laser cladding technique with pre-placed slurry. During laser processing the input materials merge depending on the heating rate/temperature and clad materials. The proposed sample preparation set-up, followed for the first time in this study, involved the concomitant modulation of two parameters: the natural HA ratio (100 wt%, and 50 wt % HA + 50 wt% Ti blends) and laser beam power (500-1000 W range). The laser beam was applied after the ceramic slurries (prepared HA/HA-based blends mixed with polyvinyl alcohol) were placed inside the priorly machined channels on the metallic Ti disks. Partially overlapped cladding tracks (similar to 30% overlapping ratio) resulted and the investigations were further performed in cross-section view. The structural analyses confirmed the formation of calcium titanate as main phase for all samples and the arrest of HA only for those prepared with 100% HA ratio at low to medium laser powers. In addition, the morpho-compositional evaluation revealed the formation of a fully ceramic coating only for the latter sample sets. Further, the surface wettability (contact angle and surface free energy) and Vickers micro-hardness results led to the selection of the optimal technological parameters for the development of ceramic cladded layers with prospect compatibility with regenerative med-icine applications.

Open Access

258. Solution-processed In2Se3 nanosheets for ultrasensitive and highly selective NO2 gas sensors

Authors: D'Olimpio, G; Galstyan, V; Ghica, C; Vorokhta, M; Istrate, MC; Kuo, CN; Lue, CS; Boukhvalov, DW; Comini, E; Politano, A

Published: JUN 13 2023, JOURNAL OF MATERIALS CHEMISTRY A, 11, DOI: 10.1039/d3ta01390a

In this work, we demonstrate that solution-processed In2Se3 nanosheets exhibit exceptional selectivity and sensitivity to NO2 gas, making them a promising candidate for gas detection systems. Theoretical simulations and surface-science experiments reveal the unique surface properties of In2Se3 nanosheets, which prevent physisorption of oxygen, carbon monoxide, and carbon dioxide, making them remarkably stable towards oxidation and CO-poisoning. Moreover, we show that NO2 molecules adsorb stably on In2Se3 nanosheets, particularly on Se vacancies, even at high temperatures. The coadsorption of water further enhances NO2 sticking on the In2Se3 surface, making it an ideal material for gas sensing applications in humid and harsh environments. The fabricated In2Se3 gas sensors exhibit excellent and reversible sensing response to NO2 gas, with a limit of detection of 5 ppb at 300 degrees C, and a highly selective response to NO2 compared to other gases and volatile organic compounds. Our sensors outperform other two-dimensional (2D) semiconductors, metal oxides, and their heterostructures, thanks to the unique surface properties of In2Se3 nanosheets. Importantly, the number of layers and termination of the surface almost have no impact on the sensing performance of In2Se3, which is advantageous for practical applications. The high sensitivity, selectivity, and stability of In2Se3 nanosheets make them an exciting platform for the fabrication of high-performance gas sensors, particularly in harsh environments, such as industrial settings or outdoor monitoring. Moreover, our solution processing approach enables scalable production of the sensors. Additionally, their unique surface properties make them an attractive candidate for developing complex composite nanostructures with tailored gas sensing characteristics for various applications.

Open Access

259. Outstanding visible light photocatalysis using nano-TiO2 hybrids with nitrogen-doped carbon quantum dots and/or reduced graphene oxide

Authors: Baragau, IA; Buckeridge, J; Nguyen, KG; Heil, T; Sajjad, MT; Thomson, SAJ; Rennie, A; Morgan, DJ; Power, NP; Nicolae, SA; Titirici, MM; Dunn, S; Kellici, S

Published: MAY 9 2023, JOURNAL OF MATERIALS CHEMISTRY A, 11, DOI: 10.1039/d2ta09586f

Historically, titanium dioxide (TiO2) has been one of the most extensively studied metal oxide photocatalysts; however, it suffers from a large bandgap and fast charge recombination. We report the use of green, rapid, single-step continuous hydrothermal flow synthesis for the preparation of TiO2, and TiO2 hybrids with reduced graphene oxide (rGO) and/or N-doped carbon quantum dots (NCQDs) with significant enhancement in photocatalytic activity. Using a solar light generator under ambient conditions with no extra oxygen gas added, we observed the evolution reaction of the model pollutant (methylene blue) in real time. Tailoring of the light absorption to match that of the solar spectrum was achieved by a combination of materials of nano-TiO2 hybrids of nitrogen-doped carbon quantum dots and graphene in its reduced form with a photocatalytic rate constant of ca. 25 x 10(-5) s(-1). Using a diversity of state-of-the-art techniques including high-resolution transmission electron microscopy, transient photoluminescence, X-ray photoelectron spectroscopy and high accuracy, sophisticated hybrid density functional theory calculations we have gained substantial insight into the charge transfer and modulation of the energy band edges of anatase due to the presence of graphene or carbon dots, parameters which play a key role in improving drastically the photocatalytic efficiencies when compared to pristine titania. More importantly, we prove that a combination of features and materials displays the best photocatalytic behaviour. This performance is delivered in a greener synthetic process that not only produces photocatalytic materials with optimised properties and tailored visible light absorption and efficiency but also provides a path to industrialization.

Open Access

260. Molecular sensitised probe for amino acid recognition within peptide sequences

Authors: Wu, X; Borca, B; Sen, S; Koslowski, S; Abb, S; Rosenblatt, DP; Gallardo, A; Mendieta-Moreno, JI; Nachtigall, M; Jelinek, P; Rauschenbach, S; Kern, K; Schlickum, U

Published: DEC 14 2023, NATURE COMMUNICATIONS, 14, 8335, DOI: 10.1038/s41467-023-43844-5

The combination of low-temperature scanning tunnelling microscopy with a mass-selective electro-spray ion-beam deposition established the investigation of large biomolecules at nanometer and sub-nanometer scale. Due to complex architecture and conformational freedom, however, the chemical identification of building blocks of these biopolymers often relies on the presence of markers, extensive simulations, or is not possible at all. Here, we present a molecular probe-sensitisation approach addressing the identification of a specific amino acid within different peptides. A selective intermolecular interaction between the sensitiser attached at the tip-apex and the target amino acid on the surface induces an enhanced tunnelling conductance of one specific spectral feature, which can be mapped in spectroscopic imaging. Density functional theory calculations suggest a mechanism that relies on conformational changes of the sensitiser that are accompanied by local charge redistributions in the tunnelling junction, which, in turn, lower the tunnelling barrier at that specific part of the peptide. Chemical identification of the building blocks of biopolymers often considerably relies on the presence of markers, extensive simulations, or is not possible at all. Here, the authors report a molecular probe-sensitisation approach addressing the identification of a specific amino acid within different peptides.

Open Access

261. The Depairing Current Density of a Fe(Se,Te) Crystal Evaluated in Presence of Demagnetizing Factors

Authors: Galluzzi, A; Buchkov, K; Tomov, V; Nazarova, E; Leo, A; Grimaldi, G; Crisan, A; Polichetti, M

Published: DEC 2023, CONDENSED MATTER, 8, 91, DOI: 10.3390/condmat8040091

The effect of the demagnetizing factor, regarding the determination of the de-pairing current density Jdep, has been studied in the case of a Fe(Se,Te) crystal, using DC magnetic measurements as a function of a magnetic field (H) at different temperatures (T). First, the lower critical field Hc1(T) values were obtained, and the demagnetization effects acting on them were investigated after calculating the demagnetizing factor. The temperature behaviors of both the original Hc1 values and the ones obtained after considering the demagnetization effects (Hc1demag) were analyzed, and the temperature dependence of the London penetration depth lambda L(T) was obtained in both cases. In particular, the lambda L(T) curves were fitted with a power law dependence, indicating the presence of low-energy quasiparticle excitations. Furthermore, by plotting lambda L-2 as a function of T, we found that our sample behaves as a multigap superconductor, which is similar to other Fe-11 family iron-based compounds. After that, the coherence length xi values were extracted, starting with the Hc2(T) curve. The knowledge of lambda L and xi allowed us to determine the Jdep values and to observe how they are influenced by the demagnetizing factor.

262. Impact of thickness on optoelectronic properties of α-MoO3 film photodetectors: Integrating first-principles calculations with experimental analysis

Authors: Basyooni, MA; Achehboune, M; Boukhoubza, I; Gaballah, AEH; Tihtih, M; Belaid, W; En-nadir, R; Derkaoui, I; Abdelbar, AM; Zaki, SE; Ates, S; Eker, YR

Published: DEC 1 2023, PHYSICA B-CONDENSED MATTER, 670, 415373, DOI: 10.1016/j.physb.2023.415373

This study focused on investigating the optoelectronic properties of molybdenum trioxide (alpha-MoO3) thin films using the atomic layer deposition (ALD) technique through different cycle numbers and theoretical investigation. Initial band gap calculations using standard DFT with GGA-PBE resulted in a value of 1.19 eV, which deviated significantly from experimental measurements. The GGA + U method with Hubbard U corrections was applied for the first time to improve the accuracy. This refinement led to a more precise band gap value of 3.09 eV, closely matching previously reported experimental data. The electronic parameters of the alpha-MoO3 photodetector, such as ideality factor (n), barrier height (phi 0), and series resistance (Rs), were analyzed using the thermionic emission theory and confirmed by Cheung and Nord's methods. The results demonstrated that the sample deposited with 100 pulses exhibited higher photodetector performance under UV illumination, despite having a lower Rs.

Open Access

263. A Nanocomposite Sol-Gel Film Based on PbS Quantum Dots Embedded into an Amorphous Host Inorganic Matrix

Authors: Elisa, M; Sava, BA; Eftimie, M; Nicoara, AI; Vasiliu, IC; Rusu, MI; Bartha, C; Enculescu, M; Kuncser, AC; Oane, M; Aguado, CE; López-Torres, D

Published: NOV 2023, MATERIALS, 16, 7105, DOI: 10.3390/ma16227105

In this study, a sol-gel film based on lead sulfide (PbS) quantum dots incorporated into a host network was synthesized as a special nanostructured composite material with potential applications in temperature sensor systems. This work dealt with the optical, structural, and morphological properties of a representative PbS quantum dot (QD)-containing thin film belonging to the Al2O3-SiO2-P2O5 system. The film was prepared using the sol-gel method combined with the spin coating technique, starting from a precursor solution containing a suspension of PbS QDs in toluene with a narrow size distribution and coated on a glass substrate in a multilayer process, followed by annealing of each deposited layer. The size (approximately 10 nm) of the lead sulfide nanocrystallites was validated by XRD and by the quantum confinement effect based on the band gap value and by TEM results. The photoluminescence peak of 1505 nm was very close to that of the precursor PbS QD solution, which demonstrated that the synthesis route of the film preserved the optical emission characteristic of the PbS QDs. The photoluminescence of the lead sulfide QD-containing film in the near infrared domain demonstrates that this material is a promising candidate for future sensing applications in temperature monitoring.

264. From non-stoichiometric CTSe to single phase and stoichiometric CZTSe films by annealing under Sn plus Se atmosphere

Authors: Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Bocirnea, AE; Stavarache, I; Velea, A; Galca, AC; Pintilie, L

Published: NOV 1 2023, CERAMICS INTERNATIONAL, 49, DOI: 10.1016/j.ceramint.2023.08.056

One of the new materials for next-generation thin film solar cells is Cu2ZnSnSe4 (CZTSe). However, achieving a single-phase CZTSe compound remains a challenge. This study describes the development of Cu2ZnSnSe4 thin films through the sequential deposition of stacked films of non-stoichiometric Cu2SnSe3 (CTSe) and ZnSe by magnetron sputtering. The structural, morphological, and electrical properties as well as the surface chemistry of the films were investigated and compared depending on the growth sequence of the thin films. By using Raman spectroscopy and grazing incidence X-ray diffraction, the tetragonal CZTSe structure was confirmed. Scanning electron microscopy and energy-dispersive spectroscopy measurements of the morphological and compositional properties indicated large grains and dense surfaces with an elemental composition close to the desired stoichiometry in SLG\SnSe2\Cu\ZnSe and SLG\SnSe2\Cu2Se\ZnSe stacks. To ascertain the surface chemistry and unique characteristics of the produced films, additional X-ray photoemission spectroscopy experiments were carried out. The optimal band gap values for the absorber layers were found using conventional spectroscopy, and they ranged from 0.88 to 1.47 eV. According to the electrical measurements, all the films were p-type and have high carrier concentrations between 1016 and 1020 cm-3. Our findings demonstrate that employing a sequential deposition approach and annealing in different atmospheres can yield CZTSe absorber layers with desirable properties, overcoming the challenge of non-stoichiometric CTSe precursors.

Open Access

265. Burdock-Derived Composites Based on Biogenic Gold, Silver Chloride and Zinc Oxide Particles as Green Multifunctional Platforms for Biomedical Applications and Environmental Protection

Authors: Zgura, I; Badea, N; Enculescu, M; Maraloiu, VA; Ungureanu, C; Barbinta-Patrascu, ME

Published: FEB 2023, MATERIALS, 16, 1153, DOI: 10.3390/ma16031153

Green nanotechnology is a rapidly growing field linked to using the principles of green chemistry to design novel nanomaterials with great potential in environmental and health protection. In this work, metal and semiconducting particles (AuNPs, AgClNPs, ZnO, AuZnO, AgClZnO, and AuAgClZnO) were phytosynthesized through a "green" bottom-up approach, using burdock (Arctium lappa L.) aqueous extract. The morphological (SEM/TEM), structural (XRD, SAED), compositional (EDS), optical (UV-Vis absorption and FTIR spectroscopy), photocatalytic, and bio-properties of the prepared composites were analyzed. The particle size was determined by SEM/TEM and by DLS measurements. The phytoparticles presented high and moderate physical stability, evaluated by zeta potential measurements. The investigation of photocatalytic activity of these composites, using Rhodamine B solutions' degradation under solar light irradiation in the presence of prepared powders, showed different degradation efficiencies. Bioevaluation of the obtained composites revealed the antioxidant and antibacterial properties. The tricomponent system AuAgClZnO showed the best antioxidant activity for capturing ROS and ABTS center dot(+) radicals, and the best biocidal action against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The "green" developed composites can be considered potential adjuvants in biomedical (antioxidant or biocidal agents) or environmental (as antimicrobial agents and catalysts for degradation of water pollutants) applications.

266. Temperature Dependence of the Conductivity of InSb Measured by Terahertz Time-Domain Spectroscopy

Authors: Liu, S; Agulto, VC; Iwamoto, T; Kato, K; Mag-Usara, VK; Ota, M; Dolas, S; Newman, N; Nedelcu, L; Tani, M; Yoshimura, M; Nakajima, M

Published: 2023, 2023 48TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES, IRMMW-THZ, DOI: 10.1109/IRMMW-THz57677.2023.10299341

In this study, we characterized the temperature-dependent electrical conductivity properties of undoped and lightly doped bulk InSb samples using terahertz time-domain spectroscopy. We obtained the permittivity spectra at low temperatures and analyzed the carrier density and mobility by fitting the spectra to the Drude model. Based on our analysis, we show the temperature dependence of the optical constants and explain the underlying physical mechanisms for the observed behavior. Our results provide important insights into the electronic properties of InSb.

Open Access

267. Defect structures and (ferro)magnetism in Zn1-xFexO nanoparticles with the iron concentration level in the dilute regime (x = 0.001 - 0.01) prepared from acetate precursors

Authors: Mihalache, V; Negrila, C; Secu, M; Mercioniu, I; Iacob, N; Kuncser, V

Published: AUG 2023, RESULTS IN PHYSICS, 51, 106644, DOI: 10.1016/j.rinp.2023.106644

Zn1-xFexO nanoparticles with the iron concentrations level in the dilute regime (x = 0.001---0.01) were produced by a sol-gel route from acetate precursors along with an un-doped and 3 at.% Fe-doped reference. The X-ray diffraction of the un-doped and 0.1-1 at.% Fe-doped samples reveal the reflections for only the ZnO wurtzite structure. Fe doping enhances the a-axis lattice constant, the unit cell volume and the microstrain. Iron doping reduces the average crystallite/particle size (confirmed by Scanning Electron Microscopy), improving the surface-to-volume ratio or the concentration of defective surface sites. XPS identifies the iron in both Fe3+ and Fe2+ states. XPS and Fe-57 Mossbauer spectroscopy indicate a broad distribution (distortion) of Fe3+ sites on the surface of ZnO nanoparticles. The blue shift and broadening of the UV emission, and quenching of defect-related photoluminescence in the Fe-doped samples verify the presence of iron in the ZnO lattice and surface intrinsic defects. 0.1-1 at.% Fe-doped ZnO show room temperature ferromagnetism, RTFM, characteristic of dilute magnetic semiconductors, DMS. The magnetization measurements with temperature evidence an antiferromagnetic alignment and an increase of ferromagnetic contribution with Fe doping up to 1 at.%. Zn0.97Fe0.3O reference is a superparamagnetic ZnO/ZnFe2O4 nanocomposite with a blocking temperature of 20 K; HRTEM shows (ultra)fine ZnFe2O4 particles at the surface of ZnO nanoparticles. The analysis of experimental data of 0.1-1 at.% Fe-doped ZnO was done in terms of iron coupling with intrinsic defects, which can generate surface Fe3+ states with geometries similar to the Fe3+ in inverse spinel ZnFe2O4. The superexchange interaction (resembling that in the inverse spinel ZnFe2O4) between the Fe3+ sites with distorted configuration resulting in ferrimagnetism was hypothesised as a possible mechanism of RTFM. Experimental (structural, local chemical, magnetic, optical) and interpretation results can be used to optimize the processing conditions for Fe-doped ZnO to serve as an effective DMS, e.g. for spintronic applications.

268. Multicationic LDH-derived Co(x)CeMgAlO mixed oxide catalysts for the total oxidation of methane

Authors: Stoian, MC; Romanitan, C; Craciun, G; Culita, DC; Papa, F; Badea, M; Negrila, C; Popescu, I; Marcu, IC

Published: JAN 25 2023, APPLIED CATALYSIS A-GENERAL, 650, 119001, DOI: 10.1016/j.apcata.2022.119001

Several Co(x)CeMgAlO mixed oxides with different cobalt contents x between 7 and 50 at% with respect to cations, but with fixed 10 at% Ce and Mg/Al atomic ratio of 3, were obtained by the calcination of layered double hydroxide (LDH) precursors at 750 degrees C. The mixed oxide catalysts were characterized by XRD, nitrogen adsorption, DRIFT, DR-UV-Vis, SEM-EDX, including elemental mapping, XPS, H2-TPR and O2-TPO techniques. XRD analysis indicated the coexistence of Co3O4 crystallites with periclase-like and ceria phases, distributed homogeneously as shown by EDX measurements. The surface composition determined by XPS and the redox properties studied by H2-TPR and O2-TPO were shown to be key factors controlling the catalytic behavior of the investigated materials. Their catalytic performance was evaluated in the total oxidation of methane, used as a volatile organic compound (VOC) model molecule. Co(40)CeMgAlO mixed oxide showed the highest catalytic activity for methane combustion with a T50 of 528 degrees C, associated with its greatest Co/Ce surface atomic ratio and the best redox properties in the Co(x)CeMgAlO series. In addition, the influence of the contact time on the catalytic activity of the Co(40)CeMgAlO mixed oxide has been examined and its good stability was evidenced from combustion tests with prolonged time on stream. Nevertheless, the addition of water vapors to the reaction mixture induces textural and structural changes of the mixed oxide with negative consequences on its performance.

Open Access

269. Nanostructured Al2O3/graphene additive in bio-based lubricant: A novel approach to improve engine performance

Authors: Hettiarachchi, SJ; Bowen, J; Kershaw, M; Baragau, IA; Nicolaev, A; Kellici, S

Published: AUG 2023, TRIBOLOGY INTERNATIONAL, 186, 108619, DOI: 10.1016/j.triboint.2023.108619

Personal and industrial use of internal combustion engines (ICEs) is projected to continue until 2050 and beyond. Yet demands to reduce global dependence on petrochemicals and fossil fuel-derived lubricants are increasing and environmentally necessary. New strategies for maintaining and enhancing ICE performance by reducing friction, wear, fuel consumption, and exhaust emissions will reduce the depletion of mineral and fossil fuel reserves and environmental pollution. This paper reports the tribological enhancement of nano-bio lubricants formulated using 2D nanocomposites of Al2O3/graphene as novel additives in coconut oil, whose performance as a lubricant compares favorably with the mineral-based engine oil 15W40. Structural, compositional, and morphological characterization of the Al2O3/graphene nanocomposite revealed an ultra-fine particle size (< 10 nm) with spherical/laminar morphology and a rich sp2 domain, exhibiting a consistent colloidal stability when formulated as nanofluid. Through the use of various characterization techniques, including friction and wear analysis we gained valuable insight into the tribological mechanism. Our optimization of this 2D tribological system using coconut oil formulation resulted significant reductions in the coefficient of friction (28 %), specific fuel con-sumption (8 %), and exhaust pollutant emissions (CO, SO2, and NOx). This work demonstrates the benefits of using nano-bio lubricant formulated using coconut oil and 2D-based hybrids as base stock and additives, delivering solutions to global challenges such as improving fuel consumption while reducing environmental pollution; solutions that can be transferred to other areas where lubricants are a necessity.

270. Synthetic peptide array on gold for the electrochemical assessment of the 20S proteasome activity and effect of inhibitory compounds

Authors: Barsan, MM; Serban, A; Onea, M; Wysocka, M; Lesner, A; Diculescu, VC

Published: FEB 1 2023, APPLIED SURFACE SCIENCE, 610, 155620, DOI: 10.1016/j.apsusc.2022.155620

A sensor for the enzymatic activity and inhibition of the 20S proteasome was developed by immobilizing the synthetic peptide ABZ-VVSYAMG-(O2Oc)2-OH at Au electrodes. The detection principle is based on the elec-troactivity of ABZ, part of the ABZ-VVSY-OH moiety released from the peptide upon 20S proteasome chymo-trypsin action. The peptide was immobilized on a para-amino thiophenol (PATP) self-assembled monolayer on Au electrode by cross-linking its amino group to the -(O2Oc)2-OH moiety of the peptide (Au/PATP/peptide). The immobilization of the peptide and its interaction with 20S proteasome was investigated by SEM, QCM, SPR, ATR-FTIR and electrochemistry. The activity of 20S proteasome was assessed electrochemically by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) after the immersion Au/PATP/peptide in 20S proteasome solution. CV study showed a decrease in both capacitive and faradaic currents corresponding to the ABZ-VVSY-OH removal, allowing the quantification of the 20S proteasome activity. The EIS study revealed that the resis-tance corresponding to charge transfer reactions at the peptide/solution interface correlated to the ABZ redox reaction, decreased linearly with increasing the incubation time in 20S proteasome solution. The perfected assay was applied for the investigation of the inhibitory effect of one synthetic, bortezomib, and two naturally occurring, epoxomicin, and lactacystin inhibitors.

Open Access

271. Synthesis and Anti-Melanoma Activity of L-Cysteine-Coated Iron Oxide Nanoparticles Loaded with Doxorubicin

Authors: Toderascu, LI; Sima, LE; Orobeti, S; Florian, PE; Icriverzi, M; Maraloiu, VA; Comanescu, C; Iacob, N; Kuncser, V; Antohe, I; Popescu-Pelin, G; Stanciu, G; Ionita, P; Mihailescu, CN; Socol, G

Published: FEB 2023, NANOMATERIALS, 13, 621, DOI: 10.3390/nano13040621

In this study, we report on the synthesis of L-Cysteine (L-Cys)-coated magnetic iron oxide nanoparticles (NPs) loaded with doxorubicin (Dox). The Fe3O4-L-Cys-Dox NPs were extensively characterized for their compositional and morpho-structural features using EDS, SAED, XRD, FTIR and TEM. XPS, Mossbauer spectroscopy and SQUID measurements were also performed to determine the electronic and magnetic properties of the Fe3O4-L-Cys-Dox nanoparticles. Moreover, by means of a FO-SPR sensor, we evidenced and confirmed the binding of Dox to L-Cys. Biological tests on mouse (B16F10) and human (A375) metastatic melanoma cells evidenced the internalization of magnetic nanoparticles delivering Dox. Half maximum inhibitory concentration IC50 values of Fe3O4-L-Cys-Dox were determined for both cell lines: 4.26 mu g/mL for A375 and 2.74 mu g/mL for B16F10, as compared to 60.74 and 98.75 mu g/mL, respectively, for unloaded controls. Incubation of cells with Fe3O4-L-Cys-Dox modulated MAPK signaling pathway activity 3 h post-treatment and produced cell cycle arrest and increased apoptosis by 48 h. We show that within the first 2 h of incubation in physiological (pH = 7.4) media, similar to 10-15 mu M Dox/h was released from a 200 mu g/mL Fe3O4-L-Cys-Dox solution, as compared to double upon incubation in citrate solution (pH = 3), which resembles acidic environment conditions. Our results highlight the potential of Fe3O4-L-Cys-Dox NPs as efficient drug delivery vehicles in melanoma therapy.

Open Access

272. Photocatalytic Activity of the Blends Based on TiO2 Nanoparticles and Reduced Graphene Oxide for Degradation of Acetaminophen

Authors: Daescu, M; Chivu, M; Matei, E; Negrila, C; Cramariuc, O; Baibarac, M

Published: JUN 4 2023, MOLECULES, 28, 4546, DOI: 10.3390/molecules28114546

The aim of this work is to highlight the influence of blends based on TiO2 nanoparticles and reduced graphene oxide (RGO) on the photodegradation of acetaminophen (AC). To this end, the catalysts of TiO2/RGO blends with RGO sheet concentrations equal 5, 10, and 20 wt. % were prepared by the solid-state interaction of the two constituents. The preferential adsorption of TiO2 particles onto the RGO sheets' surfaces via the water molecules on the TiO2 particle surface was demonstrated by FTIR spectroscopy. This adsorption process induced an increase in the disordered state of the RGO sheets in the presence of the TiO2 particles, as highlighted by Raman scattering and scanning electron microscopy (SEM). The novelty of this work lies in the demonstration that TiO2/RGO mixtures, obtained by the solid-phase interaction of the two constituents, allow an acetaminophen removal of up to 95.18% after 100 min of UV irradiation. This TiO2/RGO catalyst induced a higher photodegradation efficiency of AC than TiO2 due to the presence of RGO sheets, which acted as a capture agent for the photogenerated electrons of TiO2, hindering the electron-hole recombination. The reaction kinetics of AC aqueous solutions containing TiO2/RGO blends followed a complex first-order kinetic model. Another novelty of this work is the demonstration of the ability of PVC membranes modified with Au nanoparticles to act both as filters for the removal of TiO2/RGO blends after AC photodegradation and as potential SERS supports, which illustrate the vibrational properties of the reused catalyst. The reuse of the TiO2/RGO blends after the first cycle of AC photodegradation indicated their suitable stability during the five cycles of pharmaceutical compound photodegradation.

273. Nitrite anodic oxidation at Ni(ii)/Ni(iii)-decorated mesoporous SnO2 and its analytical applications

Authors: Mihai, MA; Spataru, T; Somacescu, S; Moga, OG; Preda, L; Florea, M; Kuncser, A; Spataru, N

Published: NOV 20 2023, ANALYST, 148, DOI: 10.1039/d3an01249b

Hydrothermally formed mesoporous SnO2 was used as a support for nickel chemical deposition and, after subsequent thermal treatment, a high specific surface area (36 m(2) g(-1)) Ni/SnO2 material was obtained. XPS analysis has shown that in the Sn 3d region the spectrum is similar to that of pristine SnO2, whereas Ni species are present on the surface as NiO, Ni2O3 and Ni(OH)(2). Mixing Ni/SnO2 with a small amount of Black Pearls (BP) leads to a significant enhancement of the resulting Ni/SnO2-BP composite activity for nitrite anodic oxidation, presumably due to the higher surface area (115 m(2) g(-1)), to better electrical conductivity and to a certain contribution of the BP to an increase in surface density of the active sites. Ni/SnO2-BP also outperforms pristine BP (in terms of Tafel slopes and electron-transfer rates), most likely due to the fact that the Ni(ii)/Ni(iii) couple can act as an electrocatalyst for nitrite oxidation. A voltammetric method is proposed for the determination of nitrite, over a concentration range of three orders of magnitude (0.05 to 20 mM), with good reproducibility, high stability and excellent sensitivity. The high upper limit of the dynamic range of the analytically useful response might provide a basis for the reliable quantification of nitrite in wastewater.

Open Access

274. Design of electrocatalysts with reduced Pt content supported on mesoporous NiWO4 and NiWO4-graphene nanoplatelets composite for oxygen reduction and hydrogen oxidation in acidic medium

Authors: Somacescu, S; Osiceanu, P; Moreno, JMC; Culita, DC; Neatu, F; Trandafir, MM; Neatu, S; Kuncser, A; Szijjártó, GP; Tálas, E; Tompos, A; Borbáth, I; Florea, M

Published: FEB 22 2023, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 48, DOI: 10.1016/j.ijhydene.2022.04.270

Herein, a new direct synthesis route leading to a mesoporous NiWO4 with crystalline framework and NiWO4 -graphene nanoplatelets (GNP) composite is reported. Ni and W assembled into a mesoporous tungstate type of symmetry by co-precipitation synthesis route and its composite with GNP were used as supports for electrocatalysts, with reduced Pt content (8 wt.%), in oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) in acidic medium. A comprehensive assessment of the modifications related to the crystalline and porous structures, morphological aspects as well as the surface chemistry aiming to explain the electrochemical properties was performed. It was found that the presence of GNP during the synthesis process leads, mainly, to the enhanced growth of NiWO4 nanocrystallites, as well as induces changes in the surface chemistry. The elec-trochemical results show that the introduction of GNPs into the NiWO4 composite support leads to a significant improvement in the activity of the Pt electrocatalyst in ORR and HOR compared to both initial NiWO4 and Pt/NiWO4 samples, as well as mechanical mixtures of these catalysts with carbon. Mass activity for hydrogen oxidation, determined in a mixed kinetic-diffusion controlled region, obtained on the 8 wt.% Pt/NiWO4-GNP catalyst was significantly higher compared to the commercial 20 wt.% Pt/C Quintech catalyst. Our comprehensive structural and surface chemistry assessments indicate this composite material as a viable electrocatalyst for PEMFCs using a broader type of fuels.& COPY; 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Open Access

275. Kinetics and the Effect of Thermal Treatments on the Martensitic Transformation and Magnetic Properties in Ni49Mn32Ga19 Ferromagnetic Shape Memory Ribbons

Authors: Tolea, F; Popescu, B; Bartha, C; Enculescu, M; Tolea, M; Sofronie, M

Published: JAN 2023, MAGNETOCHEMISTRY, 9, 7, DOI: 10.3390/magnetochemistry9010007

In our work, the kinetics of martensitic transformations and the influence of thermal treatments on martensitic transformations, as well as the related magnetic properties of the Ni49Mn32Ga19 ferromagnetic shape memory melt-spun ribbons, have been investigated. Thermal treatments at 673 K for 1, 4 and 8 h can be considered an instrument for fine-tuning the performance parameters of alloys. One-hour thermal treatments promote an improvement in the crystallinity of these otherwise highly textured ribbons, reducing internal defects and stress induced by the melt-spinning technique. Longer thermal treatments induce an important magnetization rise concomitantly with a slight and continuous increase in martensitic temperatures and transformation enthalpy. The activation energy, evaluated from differential scanning calorimeter experimental data with a Friedman model, significantly increases after thermal treatments as a result of the multi-phase coexistence and stabilization of the non-modulated martensitic phase, which increases the reverse martensitic transformation hindrance.

Open Access

276. Understanding the Effects of Post-Deposition Sequential Annealing on the Physical and Chemical Properties of Cu2ZnSnSe4 Thin Films

Authors: Catana, DS; Zaki, MY; Simandan, ID; Buruiana, AT; Sava, F; Velea, A

Published: DEC 2023, SURFACES, 6, DOI: 10.3390/surfaces6040031

Cu2ZnSnSe4 thin films have been synthesized by employing two magnetron-sputtering depositions, interlaced with two sequential post-deposition heat treatments in low vacuum, Sn+Se and Se-rich atmospheres at 550 degrees C. By employing successive structural analysis methods, namely Grazing Incidence X-Ray Diffraction (GIXRD) and Raman Spectroscopy, secondary phases such as ZnSe coexisting with the main kesterite phase have been identified. SEM peered into the surface morphology of the samples, detecting structural defects and grain profiles, while EDS experiments showed off-stoichiometric elemental composition. The optical bandgaps in our samples were calculated by a widely used extrapolation method from recorded transmission spectra, holding values from 1.42 to 2.01 eV. Understanding the processes behind the appearance of secondary phases and occurring structural defects accompanied by finding ways to mitigate their impact on the solar cells' properties is the prime goal of the research beforehand.

Open Access

277. Optical and Structural Properties of Composites Based on Poly(urethane) and TiO2 Nanowires

Authors: Stroe, M; Burlanescu, T; Paraschiv, M; Lorinczi, A; Matei, E; Ciobanu, R; Baibarac, M

Published: FEB 2023, MATERIALS, 16, 1742, DOI: 10.3390/ma16041742

This article's objective is the synthesis of new composites based on thermoplastic polyurethane (TPU) and TiO2 nanowires (NWs) as free-standing films, highlighting their structural and optical properties. The free-standing TPU-TiO2 NW films were prepared by a wet chemical method accompanied by a thermal treatment at 100 degrees C for 1 h, followed by air-drying for 2 h. X-ray diffraction (XRD) studies indicated that the starting commercial TiO2 NW sample contains TiO2 tetragonal anatase (A), cubic Ti0.91O (C), and orthorhombic Ti2O3 (OR), as well as monoclinic H2Ti3O7 (M). In the presence of TPU, an increase in the ratio between the intensities of the diffraction peaks at 43.4 degrees and 48 degrees belonging to the C and A phases of titanium dioxide, respectively, is reported. The increase in the intensity of the peak at 43.4 degrees is explained to be a consequence of the interaction of TiO2 NWs with PTU, which occurs when the formation of suboxides takes place. The variation in the ratio of the absorbance of the IR bands peaked at 765-771 cm(-1) and 3304-3315 cm(-1) from 4.68 to 4.21 and 3.83 for TPU and the TPU-TiO2 NW composites, respectively, with TiO2 NW concentration equal to 2 wt.% and 17 wt.%, indicated a decrease in the higher-order aggregates of TPU with a simultaneous increase in the hydrogen bonds established between the amide groups of TPU and the oxygen atoms of TiO2 NWs. The decrease in the ratio of the intensity of the Raman lines peaked at 658 cm(-1) and 635 cm(-1), which were assigned to the vibrational modes E-g in TiO2 A and E-g in H2Ti3O7 (ITiO2-A/I-H2Ti3O7), respectively, from 3.45 in TiO2 NWs to 0.94-0.96 in the TPU-TiO2 NW composites, which indicates that the adsorption of TPU onto TiO2 NWs involves an exchange reaction of TPU in the presence of TiO2 NWs, followed by the formation of new hydrogen bonds between the -NH- of the amide group and the oxygen atoms of TixO2x-mn, Ti2O3, and Ti0.91O. Photoluminescence (PL) studies highlighted a gradual decrease in the intensity of the TPU emission band, which is situated in the spectral range 380-650 nm, in the presence of TiO2 NW. After increasing the TiO2 NW concentration in the TPU-TiO2 NW composite mass from 0 wt.% to 2 wt.% and 17 wt.%, respectively, a change in the binding angle of the TPU onto the TiO2 NW surface from 12.6 degrees to 32 degrees and 45.9 degrees, respectively, took place.

Open Access

278. Obtaining and characterisation of thermoelectric Mg2Si compound via wet and dry mechanical alloying and spark plasma sintering

Authors: Cebotari, V; Popa, F; Marinca, TF; Neamtu, BV; Sechel, NA; Galatanu, M; Galatanu, A; Chicinas, I

Published: SEP-OCT 2023, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 26, DOI: 10.1016/j.jmrt.2023.09.167

Mg2Si thermoelectric compound was obtained by dry and wet (isohexane and benzene) mechanical alloying route. The Mg2Si compound was characterised by X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), laser particle size analysis and thermoelectric measurements. After 14 h of milling, the complete reaction of the elements is achieved by both routes. The powders particle size distribution obtained after 14 h of dry or wet milling (using benzene) reveals a bimodal curve. The wet milling moves the particle size distribution towards smaller particle sizes. The SEM analysis confirms the results of particles size analysis. DSC analyses performed for samples milled up to 14 h present stress relief and recrystallisation thermal events. For the benzene wet-milled sample, the DSC curve shows an additional thermal event at 350'C, associated with benzene removal. Thermoelectric properties were determined on spark plasma sintered compacts. The milling process with benzene leads to a higher value of Seebeck coefficient (z580 mV/K). The electrical conductivity is low at room temperature and increases exponentially with temperature. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Open Access

279. Behavior of Cu-Y2O3 and CuCrZr-Y2O3 composites before and after irradiation

Authors: Martins, R; Antao, F; Correia, JB; Tejado, E; Pastor, J; Galatanu, A; Carvalho, PA; Alves, E; Dias, M

Published: JUN 2023, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 539, DOI: 10.1016/j.nimb.2023.03.011

The Cu-Y2O3 and CuCrZr-Y2O3 materials have been devised as thermal barriers in nuclear fusion reactors. It is expected that in the nuclear environments, the materials should be working on extreme conditions of irradiation. In this work the Cu-Y2O3 and CuCrZr-Y2O3 were prepared and then irradiated in order to understand the surface irradiation resistance of the material. The composites were prepared in a glove box and consolidated with spark plasma sintering. The microstructures revealed regions of Y2O3 dispersion and Y2O3 agglomerates both in the Cu matrix and in the CuCrZr. The irradiated samples did not show any surface modification indicating that the materials seem to be irradiation resistant in the present situation. The thermal conductivity values for all the samples measured are lower than pure Cu and higher than pure W, however are higher than those expected, and therefore, the application of these materials as thermal barriers is compromised.

Open Access

280. Sub-Stochiometric Nickel Oxide Hole-Selective Contacts in Solar Cells: Comparison of Simulations and Experiments with Sputtered Films

Authors: Nayak, M; Bergum, K; Stan, GE; Lee, IH; Kuznetsov, A

Published: MAY 2023, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 220, DOI: 10.1002/pssa.202200651

Sub-stochiometric nickel oxide (NiOx) films were investigated as a hole selective contact option in silicon (Si) heterojunction solar cells. Numerical simulations were carried out to evaluate the impacts of the NiOx electronic properties variations and the NiOx/Si interface defect density (D-it) on device performance. Simulation data suggest that the best performance is achievable for wide bandgaps (E-g) and corresponding high valence band edge (E-VB) positions in the NiOx films. Overall, in simulations, the performance remains practically unchanged for the nickel vacancy concentrations [V-Ni] = 10(17)-10(21 )cm(-3), assuming high E-VB and low D-it. The experimental data measured using NiOx films prepared by radio-frequency magnetron sputtering reveal that the increase in [V-Ni] lifts the conductivity, concurrently decreasing E-g and E-VB. As a result, we concluded that the performance of the fabricated sputtered NiOx/Si heterojunction solar cell is limited by high D-it as well as narrow E-g and low E-VB.

281. Novel cells integrated biosensor based on superoxide dismutase on electrospun fiber scaffolds for the electrochemical screening of cellular stress

Authors: Sanz, CG; Aldea, A; Oprea, D; Onea, M; Enache, AT; Barsan, MM

Published: JAN 15 2023, BIOSENSORS & BIOELECTRONICS, 220, 114858, DOI: 10.1016/j.bios.2022.114858

A novel electrochemical biosensor was developed to monitor fibroblast cells stress levels for the first time in situ under external stimuli based on the recognition of superoxide anion released upon cell damage. The biosensor comprised metallized polycaprolactone electrospun fibers covered with zinc oxide for improved cell adhesion and signal transduction, whilst stable bioconjugates of mercaptobenzoic acid-functionalized gold nanoparticles/ superoxide dismutase were employed as recognition bioelements. Biosensors were first tested and optimized for in situ generated superoxide detection by fixed potential amperometry at +0.3 V, with minimal interferences from electroactive species in cell culture media. L929 fibroblast cells were then implanted on the optimized biosensor surface and the biosensor morphologically characterized by scanning electron microscopy (SEM) and fluorescence microscopy, which illustrated the network-type pattern of fibroblasts adjacent to the fiber scaffold. Fibroblast stress was induced by zymosan and monitored at the cells integrated biosensor using fixed potential amperometry (CA) with a sensitivity of 26 nA cm-2 mu g mL-1 zymosan and electrochemical impedance spectros-copy (EIS), with similar sensitivity of the biosensor considering the Rs and Z' parameters of around 0.13 omega cm2 mu g-1 mL and high correlation factors R2 of 0.9994. The obtained results underline the applicability of the here developed biosensor for the electrochemical screening of the fibroblast cells stress. The concept in using low-cost biocompatible polymeric fibers as versatile scaffolds for both enzyme immobilization and cell adhesion, opens a new path in developing biosensors for the in-situ investigation of a variety of cellular events.

Open Access

282. Atomic scale insight into the decomposition of nanocrystalline zinc hydroxynitrate toward ZnO using Mn²⁺ paramagnetic probes

Authors: Vlaicu, ID; Stefan, M; Radu, C; Culita, DC; Radu, D; Ghica, D

Published: APR 6 2023, FRONTIERS IN CHEMISTRY, 11, 1154219, DOI: 10.3389/fchem.2023.1154219

Layered zinc hydroxynitrate (ZHN), with the chemical formula Zn-5 (OH)(8) (NO3)(2)center dot 2H(2)O, exhibits a range of special properties such as anion-exchange and intercalation capacity, as well as biocompatibility, making it attractive for a large variety of applications in fields from nanotechnology to healthcare and agriculture. In this study nanocrystalline ZHN doped with 1,000 ppm Mn2+ was prepared by two synthesis methods (coprecipitation and solid state reaction) using similar environment-friendly precursors. The complex morpho-structural [X-ray diffraction, scanning and transmission electron microscopy, textural analysis] and spectroscopic [Fourier transform infrared and electron paramagnetic resonance (EPR)] characterization of the two ZHN nanopowders showed similar crystalline structures with Mn2+ ions localized in the nanocrystals volume, but with differences in their morphological and textural characteristics, as well as in the doping efficiency. ZHN obtained by coprecipitation consists of larger nanoplatelets with more than two times larger specific surface area and pore volume, as well as a dopant concentration than in the ZHN sample obtained by solid state reaction. The thermal stability and the on-set of the structural phase transformation have been investigated at atomic scale with high accuracy by EPR, using Mn2+ as paramagnetic probes. The on-set of the ZHN structural phase transformation toward ZnO was observed by EPR to take place at 110 degrees C and 130 degrees C for the samples prepared by coprecipitation and solid state reaction, respectively, evidencing a manganese induced local decrease of the transformation temperature. Our results contribute to the selection of the most appropriate ZHN synthesis method for specific applications and in the development of new green, cost-effective synthesis routes for Mn2+ doped nano-ZnO.

283. Aminocoumarin derivatives grafted on graphene oxide - new antimicrobial agents to combat the resistance of Mycobacterium tuberculosis and ESKAPE pathogens

Authors: Müuk, GR; Popa, M; Chifiriuc, MC; Voicu, SN; Florea, M; Neatu, F; Mihalache, I; Stoian, M; Anghel, EM; Culita, DC; Mitran, RA; Petrescu, S; Tudose, M

Published: DEC 1 2023, APPLIED SURFACE SCIENCE, 639, 158224, DOI: 10.1016/j.apsusc.2023.158224

Two hybrid materials, based on 7-amino-4-(trifluoromethyl)coumarin and 7-amino-4-methyl-coumarin that attach covalently to graphene oxide (GO) have been synthesized in two steps: i) increasing the number of carboxyl groups required for functionalization with aminocoumarin derivatives by derivatization of the hydroxyls groups with chloroacetic acid, transforming GO into GO-COOH material; ii) activation of carboxylic groups using the carbodiimide-promoted reaction. The obtained composites were characterized by numerous methods that highlighted their successful obtaining. The antimicrobial activity was evaluated on resistant Mycobacterium tuberculosis strains, as well as on ESKAPE pathogens ((Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) in planktonic and biofilm growth states. The biocompatibility of the materials has been assayed using 3-(4, 5-dimethylthiazol-2-yl)2, 5-diphenyltetrazolium bromide assay as well as by measuring the level of nitric oxide/total reactive oxygen species and superoxide release in treated cells. The results have shown that materials exhibited improved inhibitory activity against resistant M. tuberculosis strains in comparison with GO, but also against planktonic and adherent strains. Also, the tested composites have been proved to be biocompatible on the MRC-5 fibroblast cells, demonstrating their promising potential to develop novel agents effective against multidrug resistant pathogens, including M. tuberculosis, as well as by the activation of a pro-inflammatory and of an oxidative response in the mammalian cells.

284. Surface charge dynamics on air-exposed ferroelectric Pb(Zr,Ti)O3(001) thin films

Authors: Abramiuc, LE; Tanase, LC; Prieto, MJ; Caldas, LD; Tiwari, A; Apostol, NG; Husanu, MA; Chirila, CF; Trupina, L; Schmidt, T; Pintilie, L; Teodorescu, CM

Published: AUG 10 2023, NANOSCALE, 15, DOI: 10.1039/d3nr02690f

Probing of the free surface ferroelectric properties of thin polar films can be achieved either by estimating the band bending variance under the top-most layer or by studying the extent of the extrinsic charge accumulated outside the surface. Photoemitted or incoming low-energy electrons can be used to characterize locally both properties in a spectromicroscopic approach. Thin ferroelectric lead zirco-titanate (PZT) is investigated by combining low energy/mirror electron microscopy (LEEM/MEM) with photoemission electron microscopy (PEEM) and high-resolution photoelectron spectroscopy (XPS). Significant extrinsic negative compensation charge is proven to accumulate on the surface of the outward polarized thin film, indicated by high MEM-LEEM transition values, up to 15.3 eV, and is correlated with the surface electrostatic potential, which can be partially screened either by electrons interacting with the sample or by soft X-rays through the ejection of secondary electrons and generation of positive charge under the surface. A radiation-induced surface charge compensation effect is observed. The study indicates that air-exposed high quality ferroelectric thin films show large negative surface potentials, determined locally on the surface, which are nevertheless sensitive to beam damage and molecular desorption. These values represent a confirmation of previously estimated surface potential energy values determined from the LEED data on clean surfaces.

285. Structural and Electrical Properties of Novel Cr/Fe Mixed Transition-Metal Phosphates

Authors: Mighri, Z; Souiwa, K; Rostas, AM; Patru, RE; Bocirnea, AE; Iacob, N; Kuncser, V; El Khouja, O; Leonat, LN; Hidouri, M; Nasri, H; Galca, AC

Published: MAY 24 2023, INORGANIC CHEMISTRY, 62, DOI: 10.1021/acs.inorgchem.2c04389

The phosphate KCoCr-(PO4)(2) and iron-substitutedvariants KCoCr1-x Fe x (PO4)(2) (x =0.25, 0.5, and 0.75) were synthesized by a solid-state reaction route,while a high substitution level of Fe was achieved. Their structureswere refined using powder X-ray diffraction and indexed in a monoclinicsystem with a P2(1)/n spacegroup. A 3D framework with six-sided tunnels parallel to the [101]direction was formed in which the K atoms are located. Mo''ssbauerspectroscopy confirms the exclusive presence of octahedral paramagneticFe(3+) ions, with isomer shifts increasing slightly with x substitution. Electron paramagnetic resonance spectroscopyconfirmed the presence of paramagnetic Cr3+ ions. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present higher ionic activity. Relative to the electrochemicalactivity of K, these materials could be good candidates for positiveand/or negative electrode materials for energy storage applications. The synthesized phosphate KCoCr-(PO4)(2) and Fe-substituted variants KCoCr1-x Fe x (PO4)(2) (x = 0.25, 0.5, and 0.75) present a 3D frameworkwith six-sided tunnels in which the K atoms are located. The activationenergy, determined by dielectric measurements, shows that the iron-containingsamples present improved ionic activity, making these materials goodcandidates for positive and/or negative electrode materials for energystorage applications.

286. Green synthesis of aminated hyaluronic acid-based silver nanoparticles on modified titanium dioxide surface: Influence of size and chemical composition on their biological properties

Authors: Stoian, M; Kuncser, A; Neatu, F; Florea, M; Popa, M; Voicu, SN; Chifiriuc, MC; Hanganu, A; Anghel, ME; Tudose, M

Published: DEC 31 2023, INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES, 253, 127445, DOI: 10.1016/j.ijbiomac.2023.127445

This is the first report on an efficient, "environmentally friendly" chemical reduction method for the synthesis of aminated hyaluronic acid-based silver nanoparticles on the modified surface of titanium dioxide nanoparticles aimed for biological applications. Silver nanoparticles exhibit well-known physical-chemical and optical prop-erties appropriate for different biological applications. Modifying the nanoparticles leads to a change in their expected bioactivity. This represents an important topic for the current research. We have developed a novel aminated hyaluronic acid (HA-EDA)-based protocol to obtain silver nanoparticles, in which HA-EDA was used for the first time as a reducing and stabilizing agent. The effect of the size of silver nanoparticles on the titanium dioxide surface and the chemical composition of the obtained materials were investigated by TEM, XRD, XPS, ATR-FTIR, Raman spectroscopy, NMR and H2-TPR analyses. The antioxidant, in vitro biocompatibility, and antimicrobial activity of the fabricated composites have been evaluated. The results prove that the prepared materials exhibit antimicrobial, antioxidant, and anti-inflammatory activity, thus providing protection against infection and supporting tissue regeneration, these two key effects being of paramount importance for promoting wound healing.

Open Access

287. Dextran-Coated Iron Oxide Nanoparticles Loaded with 5-Fluorouracil for Drug-Delivery Applications

Authors: Predoi, D; Balas, M; Badea, MA; Ciobanu, SC; Buton, N; Dinischiotu, A

Published: JUN 2023, NANOMATERIALS, 13, 1811, DOI: 10.3390/nano13121811

This study aims to design and test different formulations composed of dextran-coated iron oxide nanoparticles (IONPs) loaded with 5-Fluorouracil (5-FU) with varying nanoparticle:drug ratios on colorectal cancer cells. The stable suspension of IONPs s was synthesized by the adapted co-precipitation method. The stable suspension of IONPs was mixed with a solution of dextran and 5-FU solubilized in a saline solution. The final suspensions with optimized ratios of IONP:5-FU in the final suspension were 0.5:1, 1:1, and 1.5:1. The information on the morphology and size distribution of the IONPs suspension and IONP loads with 5-FU was obtained using scanning electron microscopy (SEM). The presence of 5-FU and dextran on the surface of the IONPs was highlighted by energy-dispersive X-ray spectroscopy (EDS) studies. The determination of the surface charge of the nanoparticles in the final suspensions of IONP:5-FU was achieved by measuring the zeta potential (& zeta;). The hydrodynamic diameter of the resulting suspensions of IONP:5-FU was determined by dynamic light scattering (DLS). A cytocompatibility analysis was performed using Caco-2 (human epithelial colorectal adenocarcinoma) cells. In this research, our goal was to find a relationship between the formulation ratio of nanoparticles and drug, and the cellular response after exposure, as a strategy to increase the efficacy of this drug-delivery system. The nanoparticle uptake and antitumor activity, including modulation of oxidative stress, apoptosis, and proliferation biomarkers, were analyzed. The present study showed that the nanoformulation with the ratio IONP:5-FU 1.5:1 had the highest anti-tumor efficiency. Moreover, decreased MCM-2 expression in Caco-2 cells exposed to dextran-coated iron oxide nanoparticles loaded with 5-FU was demonstrated for the first time.

288. Memory of incomplete phase transitions from a random squares model

Authors: Tolea, F; Sofronie, M; Nita, M; Tolea, M

Published: DEC 26 2023, PHYSICAL REVIEW E, 108, 064134, DOI: 10.1103/PhysRevE.108.064134

We present a simple two-dimensional model for a phase transition, then study its predictions, in particular the memory properties. The direct transformation is modeled by randomly placing small squares, "nuclei", on an initially empty surface. Then, the nuclei expand ("grow") up to finite final sizes which are randomly chosen in a given range, while keeping their square shape. An important issue is the "interaction" which forces some squares to remain at smaller sizes if the surrounding squares get in the way of their growth. Interestingly, this naturally leads to quasiequal total area covered by the squares of each size after a complete direct transformation. Next, it is shown that the system "remembers" incomplete ("arrested") reverse transformations taking place in reversed order of the squares sizes. The memory is "encrypted" in the distribution of the squares sizes after a next direct transformation and manifests as a significant imbalance between the areas covered by the "big" and "small" (relative to the arrest size) squares. We are able to also reproduce the so-called "hammer effect" and the memorizing of multiple arrest points. Our model is particularly relevant for the thermal memory effect in shape memory alloys, and we actually borrowed many features from existing thermodynamic models addressing this effect. However, here we eliminate the explicit thermodynamics and end up with a statistical geometry model, presumably easier to reproduce.

Open Access

289. Synthesis of CoFe2O4 through Wet Ferritization Method Using an Aqueous Extract of Eucalyptus Leaves

Authors: Gingasu, D; Culita, DC; Moreno, JMC; Marinescu, G; Bartha, C; Oprea, O; Preda, S; Chifiriuc, MC; Popa, M

Published: JUL 2023, COATINGS, 13, 1250, DOI: 10.3390/coatings13071250

This study explored a new green approach of the wet ferritization method to obtain magnetic cobalt ferrite (CoFe2O4) by using eucalyptus leaves aqueous extract as a reducing/chelating/capping agent. The spinel single cubic phases of prepared samples were proved by powder X-ray diffraction (XRD), Fourier-Transform Infrared (FTIR) and Raman spectroscopy. The average crystallite size is in the range between 3 and 20 nm. The presence of the functional groups coating the obtained material is confirmed from FTIR and thermal analysis. The scanning electron microscopy (SEM) analysis showed a morphology consisting of nanoparticle aggregates. Raman spectroscopy detects the characteristic bands of spinel-type CoFe2O4. Magnetic investigations reveal the formation of ferromagnetic compounds with cubic magnetic anisotropy and a blocking temperature around 140 K, specific for this type of material. The biosynthesized CoFe2O4 could be an attractive candidate for biomedical applications, exhibiting promising antimicrobial and antibiofilm activity, particularly against Gram-negative bacteria and fungal strains.

Open Access

290. Nanohybrid Composites Based on TiO2 and Single-Walled Carbon Nanohorns as Promising Catalysts for Photodegradation of Amoxicillin

Authors: Cercel, R; Androne, A; Florica, CS; Lorinczi, A; Serbschi, C; Baibarac, M

Published: OCT 2023, MOLECULES, 28, 6958, DOI: 10.3390/molecules28196958

In this work, applications of nanohybrid composites based on titanium dioxide (TiO2) with anatase crystallin phase and single-walled carbon nanohorns (SWCNHs) as promising catalysts for the photodegradation of amoxicillin (AMOX) are reported. In this order, TiO2/SWCNH composites were prepared by the solid-state interaction of the two chemical compounds. The increase in the SWCNH concentration in the TiO2/SWCNH composite mass, from 1 wt.% to 5 wt.% and 10 wt.% induces (i) a change in the relative intensity ratio of the Raman lines located at 145 and 1595 cm(-1), which are attributed to the E-g(1) vibrational mode of TiO2 and the graphitic structure of SWCNHs; and (ii) a gradual increase in the IR band absorbance at 1735 cm(-1) because of the formation of new carboxylic groups on the SWCNHs' surface. The best photocatalytic properties were obtained for the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.%, when approx. 92.4% of AMOX removal was achieved after 90 min of UV irradiation. The TiO2/SWCNH composite is a more efficient catalyst in AMOX photodegradation than TiO2 as a consequence of the SWCNHs' presence, which acts as a capture agent for the photogenerated electrons of TiO2 hindering the electron-hole recombination. The high stability of the TiO2/SWCNH composite with a SWCNH concentration of 5 wt.% is proved by the reusing of the catalyst in six photodegradation cycles of the 98.5 mu M AMOX solution, when the efficiency decreases from 92.4% up to 78%.

Open Access

291. 3D Porous Collagen Matrices-A Reservoir for In Vitro Simultaneous Release of Tannic Acid and Chlorhexidine

Authors: Brazdaru, L; Staicu, T; Kaya, MGA; Chelaru, C; Ghica, C; Cîrcu, V; Leca, M; Ghica, MV; Micutz, M

Published: JAN 2023, PHARMACEUTICS, 15, 76, DOI: 10.3390/pharmaceutics15010076

The treatment of wounds occurring accidentally or as a result of chronic diseases most frequently requires the use of appropriate dressings, mainly to ensure tissue regeneration/healing, at the same time as treating or preventing potential bacterial infections or superinfections. Collagen type I-based scaffolds in tandem with adequate antimicrobials can successfully fulfill these requirements. In this work, starting from the corresponding hydrogels, we prepared a series of freeze-dried atelocollagen type I-based matrices loaded with tannic acid (TA) and chlorhexidine digluconate (CHDG) as active agents with a broad spectrum of antimicrobial activity and also as crosslinkers for the collagen network. The primary aim of this study was to design an original and reliable algorithm to in vitro monitor and kinetically analyze the simultaneous release of TA and CHDG from the porous matrices into an aqueous solution of phosphate-buffered saline (PBS, pH 7.4, 37 degrees C) containing micellar carriers of a cationic surfactant (hexadecyltrimethylammonium bromide, HTAB) as a release environment that roughly mimics human extracellular fluids in living tissues. Around this central idea, a comprehensive investigation of the lyophilized matrices (morpho-structural characterization through FT-IR spectroscopy, scanning electron microscopy, swelling behavior, resistance against the collagenolytic action of collagenase type I) was carried out. The kinetic treatment of the release data displayed a preponderance of non-Fickian-Case II diffusion behavior, which led to a general anomalous transport mechanism for both TA and CHDG, irrespective of their concentrations. This is equivalent to saying that the release regime is not governed only by the gradient concentration of the releasing components inside and outside the matrix (like in ideal Fickian diffusion), but also, to a large extent, by the relaxation phenomena of the collagen network (determined, in turn, by its crosslinking degree induced by TA and CHDG) and the dynamic capacity of the HTAB micelles to solubilize the two antimicrobials. By controlling the degree of physical crosslinking of collagen with a proper content of TA and CHDG loaded in the matrix, a tunable, sustainable release profile can be obtained.

Open Access

292. Magnetoelectric properties of CoFe2O4/BNT-BT0.08 biphasic nanocomposites, with 0-3 connectivity, prepared by sol-gel method

Authors: Cernea, M; Radu, R; Amorín, H; Vasile, BS; Surdu, VA; Trusca, R; Gavrila, R; Galassi, C

Published: AUG 15 2023, JOURNAL OF ALLOYS AND COMPOUNDS, 952, 170041, DOI: 10.1016/j.jallcom.2023.170041

Motivated by the goal of developing ultralow power, smart and multifunctional nano (micro) electronic devices, research has shown unwavering interest in synthesis methods, architectures and interphase connectivity of composites containing magnetostrictive and piezoelectric phases, known as magnetoelectric (ME) materials. Herein we report on CoFe2O4/0.92Bi0.5Na0.5TiO3-0.08BaTiO3 biphasic ME composites, obtained by sol-gel chemistry, by mixing the precursor sols of the two phases into one precursor sol and further transforming it into gel, with the goal of obtaining homogeneous nanocomposites with magnetoelectric properties. The structural properties, the temperature dependance of dielectric properties, the magnetic and magnetoelectric properties of these biphasic mixtures, with various molar ratios CoFe2O4/ BNT-BT0.08 = 0.5:1, 1:1 and 1.5:1, are investigated. It is observed that the amount of CoFe2O4 and the synthesis in situ of these composites influences their macroscopic properties showing a high difficulty of carrying out an efficient poling resulting in small piezoelectric and magnetoelectric response. It was concluded that the synthesis procedure, the type of architecture and the interphase connectivity are of outmost importance for magnetoelectric properties based on lead-free materials. (c) 2023 Published by Elsevier B.V.

Open Access

293. Effects of Solvent Additive and Micro-Patterned Substrate on the Properties of Thin Films Based on P3HT:PC70BM Blends Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Petre, G; Stanculescu, A; Stavarache, I; Popescu-Pelin, G; Stochioiu, A; Socol, G; Iftimie, S; Thanner, C; Rasoga, O

Published: JAN 2023, MATERIALS, 16, 144, DOI: 10.3390/ma16010144

Lately, there is a growing interest in organic photovoltaic (OPV) cells due to the organic materials' properties and compatibility with various types of substrates. However, their efficiencies are low relative to the silicon ones; therefore, other ways (i.e., electrode micron/nanostructuring, synthesis of new organic materials, use of additives) to improve their performances are still being sought. In this context, we studied the behavior of the common organic bulk heterojunction (P3HT:PC70BM) deposited by matrix-assisted pulsed laser evaporation (MAPLE) with/without 0.3% of 1,8-diiodooctane (DIO) additive on flat and micro-patterned ITO substrates. The obtained results showed that in the MAPLE process, a small quantity of additive can modify the morphology of the organic films and decrease their roughness. Besides the use of the additive, the micro-patterning of the electrode leads to a greater increase in the absorption of the studied photovoltaic structures. The inferred values of the filling factors for the measured cells in ambient conditions range from 19% for the photovoltaic structures with no additive and without substrate patterning to 27% for the counterpart structures with patterning and a small quantity of additive.

Open Access

294. Defect characterization studies on irradiated boron-doped silicon pad diodes and Low Gain Avalanche Detectors

Authors: Himmerlich, A; Castello-Mor, N; Rivera, EC; Gurimskaya, Y; Maulerova-Subert, V; Moll, M; Pintilie, I; Fretwurst, E; Liao, C; Schwandt, J

Published: MAR 2023, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1048, 167977, DOI: 10.1016/j.nima.2022.167977

High-energy physics detectors with internal charge multiplication, like Low Gain Avalanche Detectors (LGADs), that will be used for fast timing in the High Luminosity LHC experiments, have to exhibit a significant radiation tolerance. In this context, the impact of radiation on the highly boron-doped gain layer is of particular interest, since due to the so-called Acceptor Removal Effect (ARE) a radiation-induced deactivation of active boron dopants takes place, that is causing a progressive loss in the gain with increasing irradiation level. In this paper we present defect-spectroscopy measurements (Deep-Level Transient Spectroscopy and Thermally Stimulated Current technique) on neutron, proton and electron irradiated p-type silicon pad diodes of different resistivity as well as LGADs neutron irradiated at fluences up to 1 x 1015 neq/cm2. We show that compared to silicon pad diodes the determination of LGAD defect introduction rates is less straightforward as they are strongly influenced by the impact of the gain layer. The measured gain layer capacitance has a strong frequency and temperature dependence which makes DLTS measurements challenging to perform with results difficult to interpret. With the TSC technique the defects formed in the LGADs are nicely observed and can be compared to the defects formed in the silicon pad diodes. However, the exact assignment of defects to the gain layer or bulk region remains challenging and the charge amplification effect of the LGADs impacts the exact determination of defect concentrations. We also demonstrate that, depending on the TSC measurement conditions, defect induced internal electric fields are built up in the irradiated LGADs which impact the signal current.

295. Shifting emission of oxadiazoles via inter- or intramolecular hydrogen bonding

Authors: Anghel, CC; Mirea, AG; Popescu, CC; Madalan, AM; Hanganu, A; Bende, A; Hadade, ND; Matache, M; Andruh, M

Published: FEB 2023, DYES AND PIGMENTS, 210, 111023, DOI: 10.1016/j.dyepig.2022.111023

Light-emissive compounds able to transfer protons, either intra-or intermolecularly in the excited state, have increasingly attracted attention, especially by structural diversification of recognized fluorophores. We report herein synthesis and structural characterization of novel 1,3,4-oxadiazole-based compounds functionalised by salicylaldehyde or o-vanillin moieties. Solution absorption and emission spectroscopy performed on the resulted compounds indicated the essential influence of the established (intra and/or intermolecular) hydrogen bonds onto the optical properties. Theoretical calculations positively contributed to the effort of understanding the emissive behaviour of the compounds and the calculated data correlated very well to experiments. Occurrence of hydrogen bond interactions has been also observed in solid state and we discuss their molecular structures and the effects on the luminescent behaviour. The phenol groups in close proximity of the oxadiazole core were further exploited in cocrystallization experiments with pyridine-based co-partners. Hydrogen bonding were also found responsible for the supramolecular recognition between the two components. One type of the resulted co -crystals preserved the luminescence of the starting compound.

Open Access

296. High-Entropy Lead-Free Perovskite Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 Powders and Related Ceramics: Synthesis, Processing, and Electrical Properties

Authors: Surdu, VA; Marinica, MA; Patru, RE; Oprea, OC; Nicoara, AI; Vasile, BS; Trusca, R; Ianculescu, AC

Published: NOV 2023, NANOMATERIALS, 13, 2974, DOI: 10.3390/nano13222974

A novel high-entropy perovskite powder with the composition Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 was successfully synthesized using a modified Pechini method. The precursor powder underwent characterization through Fourier Transform Infrared Spectroscopy and thermal analysis. The resultant Bi0.2K0.2Ba0.2Sr0.2Ca0.2TiO3 powder, obtained post-calcination at 900 C-degrees, was further examined using a variety of techniques including X-ray diffraction, Raman spectroscopy, X-ray fluorescence, scanning electron microscopy, and transmission electron microscopy. Ceramic samples were fabricated by conventional sintering at various temperatures (900, 950, and 1000 C-degrees). The structure, microstructure, and dielectric properties of these ceramics were subsequently analyzed and discussed. The ceramics exhibited a two-phase composition comprising cubic and tetragonal perovskites. The grain size was observed to increase from 35 to 50 nm, contingent on the sintering temperature. All ceramic samples demonstrated relaxor behavior with a dielectric maximum that became more flattened and shifted towards lower temperatures as the grain size decreased.

297. Growth and characterization of Cu-Ni-Sn-S films electrodeposited at different applied potentials

Authors: El Khouja, O; Nouneh, K; Touhami, ME; Matei, E; Stancu, V; Enculescu, M; Galca, AC

Published: MAR 2023, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 34, 760, DOI: 10.1007/s10854-023-10173-8

Cu2NiSnS4 (CNTS) absorber layers are elaborated by electrodeposition at various applied potentials followed by sulfurization treatment at 450 degrees C under sulfur atmosphere. The microstructural investigations revealed the presence of Cu4SnS4 secondary phases which can be reduced using an applied potential of -1.15 V vs. Ag/AgCl. Using the corresponding cathodic potential for Ni2+, the competing detrimental hydrogen evolution regresses the morphology and composition. The film with the highest Ni concentration has a band gap of 1.44 eV as inferred from diffuse reflectance data. The Randles cell model is probed by electrochemical impedance spectroscopy.

Open Access

298. Measurements of Surface Impedance in MgB2 in DC Magnetic Fields: Insights in Flux-Flow Resistivity

Authors: Alimenti, A; Torokhtii, K; García, PV; Silva, E; Grigoroscuta, MA; Badica, P; Crisan, A; Pompeo, N

Published: JAN 2023, MATERIALS, 16, 205, DOI: 10.3390/ma16010205

We present the multifrequency measurements of the surface resistance of spark-plasma-sintered MgB2 performed through a dielectric loaded resonator operating at 16.5 and 26.7 GHz. By normally applying magnetic fields <= 1.2 T to the sample surface, we drove it in the mixed state. By means of data-rooted analysis, we found that the sample vortex dynamics could be fully described within a single-component approach. Pinning phenomena were present and characterized by a depinning frequency smaller than the measurement ones. The multiband nature of the superconductor emerged in the flux-flow resistivity, whose field dependence could be interpreted well within theoretical models. By exploiting them, the upper critical field was extracted in the low-temperature range, which exhibited a consistent temperature trend with the values obtained at the onset of the resistive transition near Tc, and was well in line with literature data on other polycrystalline samples.

Open Access

299. Physico-chemical and pro-wound healing properties of microporous cellulosic sponge from Gleditsia triacanthos pods functionalized with Phytolacca americana fruit extract

Authors: Marinas, IC; Pircalabioru, GG; Oprea, E; Geana, EI; Zgura, I; Romanitan, C; Matei, E; Angheloiu, M; Brincoveanu, O; Georgescu, M; Chifiriuc, MC

Published: NOV 2023, CELLULOSE, 30, DOI: 10.1007/s10570-023-05491-3

This study aimed to exploit two invasive plant species to develop a novel, multifunctional, bioactive wound dressing based on a microporous cellulosic sponge (CS) from Gleditsia triacanthos pods and functionalizing them with Phytolacca americana fruit extract. The CS was functionalized, lyophilized, and characterized by Attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, contact angle, water absorption, and retention capacity. In addition, two parameters were evaluated in temporal dynamics: controlled release of phenolic compounds and antioxidant activities. The hemolytic index, blood clotting kinetics, lactate dehydrogenase release, and wound scratch assays proved their hemo- and bio-compatibility, as well as their ability to promote cell proliferation and migration promoting-activity and to inhibit microbial growth. Furthermore, the obtained spongious material exhibited an anti-inflammatory effect by modulating the macrophages' secretion profile of IL-6 and IL-10. In conclusion, the microporous cellulosic sponge obtained from G. triacanthos could be used as a vehicle to ensure the controlled release of bioactive principles with pro-wound healing activities extracted from invasive plants. [GRAPHICS] .

300. I APLICAII SYNTHESIS AND EVALUATION OF COMPOSITE SCAFFOLDS BASED ON PVDF FIBRES AND MINERAL POWDERS FOR MEDICAL APPLICATIONS

Authors: Alecu, AE; Gîrjoaba, SA; Beregoi, M; Bacalum, M; Raileanu, M; Jinga, SI; Busuioc, C

Published: 2023, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 53, DOI:

In this work, polyvinylidene fluoride (PVDF) fibres loaded with mineral powders, such as titanium dioxide (TiO2), barium titanate (BaTiO3), and calcium magnesium silicate (CaxMgSi2Oy), were prepared by electrospinning polymeric suspensions containing 20 wt.% PVDF and 3 wt.% powder. The piezoelectric polymer was combined with powders having antibacterial, piezoelectric, or bioactive properties, respectively, in the desire to obtain multifunctional materials compatible with the requirements of the medical field. All powders were characterized in terms of morphology and crystalline structure, which confirmed the nanometric character of TiO2 samples and micrometric one for the other two, as well as the lower crystallite size for TiO2 specimens as against BaTiO3 and CaxMgSi2Oy. The final fibrous scaffolds were homogeneous, composed of individual fibres with a diameter below 1 mu m and decorated with aggregates of inorganic particles, placed either inside the fibres or attached to their surface. The biological evaluation demonstrated the superiority of the composites towards the plain polymer in terms of cell viability.

Open Access

301. Effects of mechanochemical activation on the structural, magnetic and optical properties of yttrium iron garnet-graphene nanoparticles

Authors: Glasser, S; Tolea, F; Craig, AJ; Sofronie, M; Aitken, JA; Sorescu, M

Published: FEB 1 2023, PHYSICA B-CONDENSED MATTER, 650, 414501, DOI: 10.1016/j.physb.2022.414501

Yttrium iron garnet nanoparticles were exposed to mechanochemical activation by high-energy ball milling for 0, 2, 4, 8 and 12 h, with and without graphene nanoparticles. The samples were subsequently characterized by Mo center dot ssbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflec-tance spectroscopy. Examination of the quadrupole doublet's abundance as function of ball milling time indi-cated that graphene slowed down the precipitation of the yttrium iron perovskite (yttrium orthoferrite) phase. The increased linewidth of the doublet showed that the carbon from graphene preferentially entered the lattice of the yttrium orthoferrite. The saturation magnetization decreased with decreasing particle size for prolonged milling due to the occurrence of the antiferromagnetic hematite phase. The enhanced absorption in the infrared region could be associated with the incorporation of carbon from graphene in the lattice of the yttrium ortho-ferrite. The results are interesting for sensing and microwave applications.

Open Access

302. Effect of P2O5 Content on Luminescence of Reduced Graphene-Oxide-Doped ZnO-P2O5 Nano-Structured Films Prepared via the Sol-Gel Method

Authors: Vasiliu, IC; Filip, AV; Chilibon, I; Elisa, M; Bartha, C; Kuncser, V; Leca, A; Boroica, L; Sava, BA; Trusca, R; Eftimie, M; Nicoara, A

Published: SEP 2023, MATERIALS, 16, 6156, DOI: 10.3390/ma16186156

A convenient and low-cost sol-gel approach for the one-step synthesis of ZnO-P2O5-rGO nanostructures with tuned bandgap and fluorescence was investigated. The obtained hybrid nanostructures exploit the properties of zinc oxide, graphene oxide and phosphorous oxide as promising candidates for a wide range of optoelectronic applications. A predominant amorphous structure, ZnO-P2O5-rGO, containing ZnO nanorods was evidenced by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The estimated size of the ZnO nanorods in nanostructures with P2O5 was noticed to decrease when the P2O5/ZnO ratio was increased. The presence of ZnO, P2O5 and rGO was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman investigation. P2O5 was noticed to tune the bandgap and the fluorescence emissions of the nanostructured films, as estimated by UV-Vis-NIR and fluorescence spectroscopy, respectively. The electrical measurements performed at room temperature showed that the main influence on the film's resistivity does not come from the 1% rGO doping but from the P2O5/ZnO ratio. It was found that a 10/90 molar ratio of P2O5/ZnO decreases the resistivity almost seven-fold compared with rGO-doped ZnO films.

Open Access

303. Multi-Parametric Exploration of a Selection of Piezoceramic Materials for Bone Graft Substitute Applications

Authors: Nedelcu, L; Ferreira, JMF; Popa, AC; Amarande, L; Nan, B; Balescu, LM; Geambasu, CD; Cioangher, MC; Leonat, L; Grigoroscuta, M; Cristea, D; Stroescu, H; Ciocoiu, RC; Stan, GE

Published: FEB 2023, MATERIALS, 16, 901, DOI: 10.3390/ma16030901

This work was devoted to the first multi-parametric unitary comparative analysis of a selection of sintered piezoceramic materials synthesised by solid-state reactions, aiming to delineate the most promising biocompatible piezoelectric material, to be further implemented into macro-porous ceramic scaffolds fabricated by 3D printing technologies. The piezoceramics under scrutiny were: KNbO3, LiNbO3, LiTaO3, BaTiO3, Zr-doped BaTiO3, and the (Ba0.85Ca0.15)(Ti0.9Zr0.1)O-3 solid solution (BCTZ). The XRD analysis revealed the high crystallinity of all sintered ceramics, while the best densification was achieved for the BaTiO3-based materials via conventional sintering. Conjunctively, BCTZ yielded the best combination of functional properties-piezoelectric response (in terms of longitudinal piezoelectric constant and planar electromechanical coupling factor) and mechanical and in vitro osteoblast cell compatibility. The selected piezoceramic was further used as a base material for the robocasting fabrication of 3D macro-porous scaffolds (porosity of similar to 50%), which yielded a promising compressive strength of similar to 20 MPa (higher than that of trabecular bone), excellent cell colonization capability, and noteworthy cytocompatibility in osteoblast cell cultures, analogous to the biological control. Thereby, good prospects for the possible development of a new generation of synthetic bone graft substitutes endowed with the piezoelectric effect as a stimulus for the enhancement of osteogenic capacity were settled.

304. Photo-stable, 1D-nanofilaments TiO2-based lepidocrocite for photocatalytic hydrogen production in water-methanol mixtures

Authors: Badr, HO; Natu, V; Neatu, S; Neatu, F; Kuncser, A; Rostas, AM; Racey, M; Barsoum, MW; Florea, M

Published: SEP 6 2023, MATTER, 6, DOI: 10.1016/j.matt.2023.05.026

Water and sunlight are the cleanest, most renewable, and abundant resources on Earth. Developing inexpensive, scalable photocatalysts that are highly stable for hydrogen (H-2) production has long been a cherished dream of humanity. Herein, we report on one-dimensional lepidocrocite-based sub-nanofilaments (NFs), approximate to 5 x 7 & Aring;(2) in cross-section, that generate H-2 from 80:20 v/v water/methanol mixtures when illuminated by simulated sunlight. The NFs were stable in the mixtures for times >4,300 h, 300 h of which were under irradiation. Apparent quantum yields as high as 11.7% were obtained. Based on deuterated water results, we conclude that water is the H-2 source. Further, no carbon dioxide (CO2) due to photocatalytic degradation of methanol was detected. Therefore, the NFs have strong green credentials and lucrative economic prospects for large scale up. We expect these NFs will lead to new lines for developing cheap and ultra-stable materials to produce H-2 photochemically for a long time.

Open Access

305. Three-Dimensional Printable Flexible Piezoelectric Composites with Energy Harvesting Features

Authors: Aradoaei, M; Ciobanu, RC; Schreiner, C; Paulet, M; Caramitu, AR; Pintea, J; Baibarac, M

Published: MAY 31 2023, POLYMERS, 15, 2548, DOI: 10.3390/polym15112548

The purpose of this work was to obtain an elastic composite material from polymer powders (polyurethane and polypropylene) with the addition of BaTiO3 until 35% with tailored dielectric and piezoelectric features. The filament extruded from the composite material was very elastic but had good features to be used for 3D printing applications. It was technically demonstrated that the 3D thermal deposition of composite filament with 35% BaTiO3 was a convenient process for achieving tailored architectures to be used as devices with functionality as piezoelectric sensors. Finally, the functionality of such 3D printable flexible piezoelectric devices with energy harvesting features was demonstrated, which can be used in various biomedical devices (as wearable electronics or intelligent prosthesis), generating enough energy to make such devices completely autonomous only by exploiting body movements at variable low frequencies.

Open Access

306. Ferroelectric Orthorhombic ZrO2 Thin Films Achieved Through Nanosecond Laser Annealing

Authors: Crema, APS; Istrate, MC; Silva, A; Lenzi, V; Domingues, L; Hill, MO; Teodorescu, VS; Ghica, C; Gomes, MJM; Pereira, M; Marques, L; MacManus-Driscoll, JL; Silva, JPB

Published: MAY 2023, ADVANCED SCIENCE, 10, DOI: 10.1002/advs.202207390

A new approach for the stabilization of the ferroelectric orthorhombic ZrO2 films is demonstrated through nanosecond laser annealing (NLA) of as-deposited Si/SiOx/W(14 nm)/ZrO2(8 nm)/W(22 nm), grown by ion beam sputtering at low temperatures. The NLA process optimization is guided by COMSOL multiphysics simulations. The films annealed under the optimized conditions reveal the presence of the orthorhombic phase, as confirmed by X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Macroscopic polarization-electric field hysteresis loops show ferroelectric behavior, with saturation polarization of 12.8 mu C cm(-2), remnant polarization of 12.7 mu C cm(-2) and coercive field of 1.2 MV cm(-1). The films exhibit a wake-up effect that is attributed to the migration of point defects, such as oxygen vacancies, and/or a transition from nonferroelectric (monoclinic and tetragonal phase) to the ferroelectric orthorhombic phase. The capacitors demonstrate a stable polarization with an endurance of 6.0 x 10(5) cycles, demonstrating the potential of the NLA process for the fabrication of ferroelectric memory devices with high polarization, low coercive field, and high cycling stability.

307. Multi-analytical characterization of the white inlaid decoration on the prehistoric pottery from southern Romania

Authors: Secu, M; Matei, E; Secu, C; Bartha, C; Buruiana, T; Rostas, AM; Popescu, AD; Boroneant, A; Bajenaru, R

Published: JUN 2023, SOLID STATE SCIENCES, 140, 107193, DOI: 10.1016/j.solidstatesciences.2023.107193

Complex physico-chemical investigations have been performed on white inlaid substance used in the orna-mentation of prehistoric clay artefacts from southern Romania ceramics from the Early Chalcolithic, up to the Middle/Late Bronze Age. Structural and morphological investigations of the white pigments have showed hundreds of nm up to microns size particles with calcite and hydroxyapatite (ash bone) as dominant components. The calcite was found on Early Chalcolithic pigment vessels while those where hydroxyapatite was dominant from the Middle/Late Bronze Age. FTIR spectra revealed the biogenic source of the hydroxyapatite (i.e. cremated animal bone) and the crystallinity degree values agrees with the expected temperatures of firing of the ancient furnaces; the calcite-based pigments were supposed to be filled post firing. The EPR was not able to able to provide a clear assignment of the cremated animal bones but thermoluminescence showed various sources of calcite.

Open Access

308. Deciphering the role of water and a zinc-doping process in a polyol-based approach for obtaining Zn/Co/Al-based spinels: toward "green" mesoporous inorganic pigments

Authors: Alexandru, MG; Ianculescu, AC; Carp, O; Culita, DC; Preda, S; Ene, CD; Vasile, BS; Surdu, VA; Nicoara, AI; Neatu, F; Pintilie, I; Visinescu, D

Published: AUG 1 2023, DALTON TRANSACTIONS, 52, DOI: 10.1039/d3dt00972f

Two new families of zinc/cobalt/aluminum-based pigments, with a unique composition, were obtained through the polyol method. The hydrolysis process of a mixture of Co(CH3COO)(2), Zn(acac)(2) and Al(acac)(3) (acac(-) = acetylacetonate ion) in 1,4-butanediol afforded dark blue gels (wPZn(x)Co(1-x)Al), in the presence of a supplementary amount of water, and light green powders (PZnxCo1-xAl), respectively, for the water-free procedure (x = 0, 0.2, 0.4). The calcination of the precursors yielded dark green (wZn(x)Co(1-x)Al) and blue (ZnxCo1-xAl) products. XRD measurements and Rietveld refinement indicate the co-existence of three spinel phases, in different proportions: ZnxCo1-xAl2O4, Co3O4 and the defect spinel, ?-Al2.67O4. The Raman scattering and XPS spectra are in agreement with the compositions of the samples. The morphology of wZn(x)Co(1-x)Al consists of large and irregular spherical particle aggregates (ca. 5-100 mm). Smaller agglomerates (ca. 1-5 mm) with a unique silkworm cocoon-like hierarchical morphology composed of cobalt aluminate cores covered with flake-like alumina shells are formed for ZnxCo1-xAl. TEM and HR-TEM analyses revealed the formation of crystalline, polyhedral particles of 7-43 nm sizes for wZn(x)Co(1-x)Al, while for ZnxCo1-xAl, a duplex-type morphology, with small (7-13 nm) and larger (30-40 nm) particles, was found. BET assessment showed that both series of oxides are mesoporous materials, with different pore structures, with the water-free samples exhibiting the largest surface areas due, most likely, to the high percent of aluminum oxide. A chemical mechanism is proposed to highlight the role of the water amount and the nature of the starting compounds in the hydrolysis reaction products and, further, in the morpho-structural features and composition of the resulting spinel oxides. The CIE L*a*b* and C* colorimetric parameters indicate that the pigments are bright, with a moderate degree of luminosity, presenting an outstanding high blueness.

Open Access

309. Complex Spectroscopy Studies of Nifedipine Photodegradation

Authors: Paraschiv, M; Daescu, M; Bartha, C; Chiricuta, B; Baibarac, M; Ioele, G

Published: NOV 2023, PHARMACEUTICS, 15, 2613, DOI: 10.3390/pharmaceutics15112613

The aim of this work is to highlight the influence of UV light on the hydrolysis reaction of nifedipine (NIF) in the presence of alkaline solutions. In this context, the photodegradation of NIF in the absence of alkaline solutions caused (a) a change in the ratio between the absorbances of three bands in the UV-VIS spectra localized at 224-240 nm, 272-276 nm and 310-340 nm, assigned to the electronic transitions of -COOCH3 groups, -NO2 groups and a heterocycle with six atoms; (b) a red-shift of the photoluminescence (PL) band from 458 nm to 477 nm, simultaneous with an increase in its intensity; (c) a decrease in the ratio of the Raman line intensities, which peaked at 1224 cm-1 and 1649 cm-1, associated with the vibrational modes of -C-C-O in the ester group and C=C stretching; and (d) a decrease in the ratio between the absorbances of the IR bands, which peaked at 1493 cm-1 and 1223 cm-1, associated with the vibrational modes of the -NO2 group and C-N stretching. These changes were explained considering the NIF photodegradation reaction, which leads to the generation of the compound 4-(2-nitrosophenyl)-2.6-dimethyl-3.5-dimethoxy carbonyl pyridine. The interaction of NIF with NaOH in the absence of UV light was demonstrated to induce changes in the vibrational mode of the -C-C-O bond in the ester group. The photodegradation of NIF after its reaction with NaOH induces significant changes highlighted in its (a) UV-VIS spectra, by the shift of the absorption band at 238 nm; (b) PL spectra, by the supraunitary value of the ratio between the emission band intensities at 394-396 nm and 450 nm; (c) Raman spectra, by the change in the ratio between the intensities of the lines that peaked at 1224 cm-1 and 1649 cm-1 from 0.61 to 0.49; and (d) FTIR spectra, by the lowered absorbance of the IR band at 1493 cm-1 assigned to the vibrational mode of the -NO2 group as a result of the generation of the nitroso compound. These changes were explained considering the hydrolysis reaction products of NIF, as the nitroso compound is converted to a lactam-type compound. The photodegradation reaction rate constants of NIF and NIF after interaction with NaOH were also reported. The decrease in thermal stability of NIF samples after interaction with NaOH, as well as of NIF after exposure to UV light compared to NIF prior to exposure to UV light, was demonstrated by thermogravimetry, and the key fragments were confirmed by mass spectrometry.

Open Access

310. Development and Characterization of Electrospun Composites Built on Polycaprolactone and Cerium-Containing Phases

Authors: Plocon, C; Evanghelidis, A; Enculescu, M; Isopencu, G; Oprea, O; Bacalum, M; Raileanu, M; Jinga, S; Busuioc, C

Published: SEP 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 14201, DOI: 10.3390/ijms241814201

The current study reports on the fabrication of composite scaffolds based on polycaprolactone (PCL) and cerium (Ce)-containing powders, followed by their characterization from compositional, structural, morphological, optical and biological points of view. First, CeO2, Ce-doped calcium phosphates and Ce-substituted bioglass were synthesized by wet-chemistry methods (precipitation/coprecipitation and sol-gel) and subsequently loaded on PCL fibres processed by electrospinning. The powders were proven to be nanometric or micrometric, while the investigation of their phase composition showed that Ce was present as a dopant within the crystal lattice of the obtained calcium phosphates or as crystalline domains inside the glassy matrix. The best bioactivity was attained in the case of Ce-containing bioglass, while the most pronounced antibacterial effect was visible for Ce-doped calcium phosphates calcined at a lower temperature. The scaffolds were composed of either dimensionally homogeneous fibres or mixtures of fibres with a wide size distribution and beads of different shapes. In most cases, the increase in polymer concentration in the precursor solution ensured the achievement of more ordered fibre mats. The immersion in SBF for 28 days triggered an incipient degradation of PCL, evidenced mostly through cracks and gaps. In terms of biological properties, the composite scaffolds displayed a very good biocompatibility when tested with human osteoblast cells, with a superior response for the samples consisting of the polymer and Ce-doped calcium phosphates.

Open Access

311. Gd-Er interaction promotes NaGdF4:Yb, Er as a new candidate for high-power density applications (vol 11, pg 10409, 2023)

Authors: Avram, D; Patrascu, AA; Istrate, MC; Tiseanu, C

Published: AUG 24 2023, JOURNAL OF MATERIALS CHEMISTRY C, 11, DOI: 10.1039/d3tc90168h

312. Physico-chemical characterization and in vitro biological study of manganese doped β-tricalcium phosphate-based ceramics for bone regeneration applications

Authors: Arpak, MC; Daglilar, S; Kalkandelen, C; Balescu, LM; Sasmazel, HT; Pasuk, I; Stan, GE; Durukan, K; Gunduz, O

Published: SEP 2023, JOURNAL OF THE AUSTRALIAN CERAMIC SOCIETY, 59, DOI: 10.1007/s41779-023-00889-5

This work evaluates the effects of manganese (Mn) doping on the morpho-structural features, mechanical performance, and in vitro biological response of beta-tricalcium phosphate (beta-TCP) derived bioceramics for bone tissue engineering applications. Five different Mn doping levels (i.e., 0.01%, 0.05%, 0.1%, 0.5%, and 1 wt.%) were investigated, with the beta-TCP-based bioceramics being sintered at four temperatures (i.e., 1000, 1100, 1200, and 1300 degrees C). A densification improvement was induced when using Mn in excess of 0.05 wt.%; the densification remained stationary in the sintering temperature range of 1200 - 1300 degrees C. The structural analyses evidenced that all samples sintered at 1000 and 1100 degrees C were composed of beta-TCP as major phase and hydroxyapatite (HA) as a minor constituent (similar to 4-6 wt.%). At the higher temperatures (1200 and 1300 degrees C), the formation of alpha-TCP was signalled at the expense of both beta-TCP and HA. The Mn doping was evidenced by lattice parameters changes. The evolution of the phase weights is linked to a complex inter-play between the capacity of the compounds to incorporate Mn and the thermal decomposition kinetics. The Mn doping induced a reduction in the mechanical performance (in terms of compressive strength, Vickers hardness and elastic modulus) of the beta-TCP-based ceramics. The metabolic activity and viability of osteoblastic cells (MC3T3-E1) for the ceramics were studied in both powder and compacted pellet form. Ceramics with Mn doping levels lower than 0.1 wt.% yielded a more favorable microenvironment for the osteoblast cells with respect to the undoped beta-TCP. No cytotoxic effects were recorded up to 21 days. The Mn-doped beta-TCPs showed a significant increase (p < 0.01) in alkaline phosphatase activity with respect to pure beta-TCP.

Open Access

313. Phytochemical Synthesis of Silver Nanoparticles and Their Antimicrobial Investigation on Cotton and Wool Textiles

Authors: Lite, MC; Constantinescu, R; Tanasescu, EC; Kuncser, A; Romanitan, C; Mihaiescu, DE; Lacatusu, I; Badea, N

Published: MAY 24 2023, MATERIALS, 16, 3924, DOI: 10.3390/ma16113924

The use of bio-based reagents for silver nanoparticle (AgNP) production has gained much attention among researchers as it has paved the way for environmentally friendly approaches at low cost for synthesizing nanomaterials while maintaining their properties. In this study, Stellaria media aqueous extract was used for silver nanoparticle phyto-synthesis, and the resulting treatment was applied to textile fabrics to test its antimicrobial properties against bacteria and fungi strains. The chromatic effect was also established by determining the L*a*b* parameters. For optimizing the synthesis, different ratios of extract to silver precursor were tested using UV-Vis spectroscopy to observe the SPR-specific band. Moreover, the AgNP dispersions were tested for their antioxidant properties using chemiluminescence and TEAC methods, and the phenolic content was evaluated by the Folin-Ciocalteu method. For the optimal ratio, values of average size, 50.11 +/- 3.25 nm, zeta potential, 27.10 +/- 2.16 mV, and polydispersity index, 0.209, were obtained via the DLS technique and zeta potential measurements. AgNPs were further characterized by EDX and XRD techniques to confirm their formation and by microscopic techniques to evaluate their morphology. TEM measurements revealed cvasi-spherical particles with sizes in the range of 10-30 nm, while SEM images confirmed their uniform distribution on the textile fiber surface.

Open Access

314. Influence of the Biological Medium on the Properties of Magnesium Doped Hydroxyapatite Composite Coatings

Authors: Predoi, D; Ciobanu, SC; Iconaru, SL; Predoi, MV

Published: FEB 2023, COATINGS, 13, 409, DOI: 10.3390/coatings13020409

In this paper, the stability of magnesium-doped hydroxyapatite/chitosan (MHC) suspension obtained with the sol-gel approach was evaluated using nondestructive ultrasound measurements. The MHC coatings obtained by the spin-coating technique were characterized before and after immersion for 7 and 14 days, respectively, in Dulbecco's modified eagle medium (DMEM) by scanning electron microscopy, equipped with an EDAX detector. Also, the functional groups present on the MHC coatings surface were analyzed with the aid of attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The surface microstructure was evaluated using two commentary techniques, namely atomic force microscopy (AFM) and metallographic microscopy (MM). The influence of immersion in DMEM on the biological properties was studied with in vitro studies using primary osteoblast and HCT-8 cell lines. Our results revealed that both surface morphology and chemical composition of the MHC coatings allow rapid development of a new apatite layer on their surface after immersion in DMEM. Preliminary in vitro biological studies underlined the noncytotoxic effect of the studied samples on the proliferation of primary osteoblast and HCT-8 cell lines, which makes them a promising candidate for applications in fields such as orthopedics or dentistry. The antifungal assay of the MHC coatings was assessed using Candida albicans ATCC 10231 and their results showed a good inhibitory effect. The coatings made on the basis of the MHC composite could contribute to increasing the degree of success of implants by decreasing the risk of infections and postoperative inflammation.

Open Access

315. Obtaining and conductive properties of a vanadate-borate-phosphate glass

Authors: Eftimie, M; Filip, AV; Danescu, CB; Nitescu, A; Sava, BA

Published: SEP 25 2023, SCIENTIFIC REPORTS, 13, 16054, DOI: 10.1038/s41598-023-43302-8

Vanadate glasses exhibit semiconducting property at certain temperatures. This work demonstrates the conductivity of the composition 45V(2)O(5)-25B(2)O(3)-30P(2)O(5), which is a new glass in the vanadium-boron-phosphorus ternary system that expands the glass forming area reported in literature data. The glass was obtained through a classical melt-quenching technique. The structural composition of the obtained glass was revealed with Raman spectroscopy and the amorphous characteristic has been highlighted with X-ray diffraction. The characteristic temperatures and the thermal expansion coefficient were determined by dilatometry. Based on the experimental measurements of electrical resistance, mathematical calculations were performed, resulting in a conductivity of 2.04.10(-6) S/cm at 125 degrees C, and an activation energy of 42.91 kJ/mol for this glass. Impedance spectroscopy in DC and AC at 100 V and 100 Hz to 2 MHz, respectively, showed a lower activation energy of about 0.166 eV and transition temperatures of 24 degrees C and 11 degrees C, respectively. These results were compared with those from the literature considering the temperatures at which the reported conductivities were measured. This glass has potential applications in electronic devices and temperature sensors.

Open Access

316. Studies of New Layer Formation on the Surface of Zinc Doped Hydroxyapatite/Chitosan Composite Coatings in Biological Medium

Authors: Motelica-Heino, M; Predoi, MV; Ciobanu, SC; Iconaru, SL; Predoi, D

Published: FEB 2023, COATINGS, 13, 472, DOI: 10.3390/coatings13020472

Usually, before being used in biomedical applications, a biomaterials' bioactivity is tested by in vitro methods that simulate similar conditions to those found in the human body. In this work, we report on the synthesis of zinc-doped hydroxyapatite-chitosan (ZnHApC) composite coatings by the vacuum deposition method. The surface microstructure and the chemical and molecular modification of the coatings before and after soaking in DMEM (Dulbecco's Modified Eagle's Medium) were studied. For this objective, techniques such as attenuated total reflection (ATR), Fourier transform infrared (FTIR) spectroscopy, metallographic microscopy (MM), and scanning electron microscopy (SEM) were applied used. Also, water contact angle measurements and swelling studies were made on ZnHApC composite coatings before and after soaking in a biological medium. The coatings' adherence to the substrate was also studied. The results of antifungal studies on ZnHApC composite coatings against the Candida albicans microbial strain reveal their good antifungal activity. The biocompatibility of the composite coatings was tested using a primary osteoblast cell line. Our results suggest that zinc-doped hydroxyapatite-chitosan samples could be used as a bioimplant material due to their enhanced bioactivity and biocompatibility.

Open Access

317. A comparative overview of MXenes and metal oxides as cocatalysts in clean energy production through photocatalysis

Authors: Nair, MM; Iacoban, AC; Neatu, F; Florea, M; Neatu, S

Published: JUN 20 2023, JOURNAL OF MATERIALS CHEMISTRY A, 11, DOI: 10.1039/d2ta08983a

Photocatalytic conversion of H2O, CO2 and N-2 represents one promising approach to harvest and store solar energy, for which efficient visible light responsive semiconductors are inevitable. Often, the presence of a small amount of an additional component called a "cocatalyst", is required to synergistically enhance the performance of the photocatalyst. Tremendous efforts were made in the past to identify inexpensive materials to be used as cocatalysts, for which metal oxides (MOs) are one of the traditional choices. Among alternative categories of materials investigated, the recently discovered MXenes display enormous potential owing to their unique 2D layered structure, tuneable composition, abundant surface functionalities and superior electronic conductivity. Specifically, MOs and MXenes encompass a variety of distinct as well as analogous characteristics that allows them to be tailored to different extents. Unfortunately, a comprehensive overview covering the synthetic, structural and photocatalytic aspects of MOs and MXenes is not available as of now. Herein, we intend to summarize the progress achieved so far in these two families of materials to be used as cocatalysts for the photoconversion of H2O, CO2 and N-2. Followed by a general introduction, we briefly outline the fundamental principles and the role of cocatalysts in photocatalytic reactions. A discussion regarding the use of MOs and MXenes as cocatalysts for the conversion of H2O, CO2 and N-2 is then provided in separate sections. Critical assessment regarding structure and morphology control, surface properties and stability concerns can not only help to recognize the challenges that limit further advancement, but can also highlight the future research directions of these materials for the effective transformation of H2O, CO2 and N-2.

Open Access

318. Complex Evaluation of Nanocomposite-Based Hydroxyapatite for Biomedical Applications

Authors: Predoi, D; Iconaru, SL; Ciobanu, SC; Buton, N; Predoi, MV

Published: NOV 2023, BIOMIMETICS, 8, 528, DOI: 10.3390/biomimetics8070528

A magnesium-doped hydroxyapatite in chitosan matrix (MgHApC) sample was developed as a potential platform for numerous applications in the pharmaceutical, medical, and food industries. Magnesium-doped hydroxyapatite suspensions in the chitosan matrix were obtained by the coprecipitation technique. The surface shape and morphological features were determined by scanning electron microscopy (SEM). The hydrodynamic diameter of the suspended particles was determined by Dynamic light scattering (DLS) measurements. The stability of MgHApC suspensions was evaluated by ultrasonic measurements. The hydrodynamic diameter of the MgHApC particles in suspension was 29.5 nm. The diameter of MgHApC particles calculated from SEM was 12.5 +/- 2 nm. Following the SEM observations, it was seen that the MgHApC particles have a spherical shape. The Fourier-transform infrared spectroscopy (FTIR) studies conducted on MgHApC proved the presence of chitosan and hydroxyapatite in the studied specimens. In vitro antimicrobial assays were performed on Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231 microbial strains. The antimicrobial experiments showed that MgHApC exhibited very good antimicrobial properties against all the tested microorganisms. More than that, the results of the in vitro studies revealed that the antimicrobial properties of the samples depend on the incubation time. The evaluation of the sample's cytotoxicity was performed using the human colon cancer (HCT-8) cell line. Our results suggested the great potential of MgHApC to be used in future applications in the field of biomedical applications (e.g., dentistry, orthopedics, etc.).

Open Access

319. Lead-Free Perovskite Thin Films with Tailored Pockels-Kerr Effects for Photonics

Authors: Ion, V; Teodorescu, V; Birjega, R; Dinescu, M; Mitterbauer, C; Alexandrou, I; Ghitiu, I; Craciun, F; Scarisoreanu, ND

Published: JUL 27 2023, ACS APPLIED MATERIALS & INTERFACES, 15, DOI: 10.1021/acsami.3c06499

Pockels and Kerr effects are linear and nonlinear electro-opticaleffects, respectively, used in many applications. The modulation ofthe refractive index is employed in different photonic circuits. However,the greatest challenge is in photonic elements for quantum computingat room temperature. For this aim, materials with strong Pockels/Kerreffects and & chi;((2))/& chi;((3)) nonlinearsusceptibilities are necessary. Here, we demonstrate composition-modulatedstrong electro-optical response in epitaxial films of (Ba,Ca)(Ti,Zr)O-3 perovskite titanate. These films are grown by pulsed laserdeposition on SrTiO3. Depending on the ratios of Ca/Baand Ti/Zr, films show high Pockels or Kerr optical nonlinearities.We relate the variable electro-optic response to the occurrence ofnanopolar domains with different symmetries in a selected compositionrange. These findings open the route to easily implement nonlinearoptical elements in integrated photonic circuits.

Open Access

320. Functionalization of Graphene Derivatives with Conducting Polymers and Their Applications in Uric Acid Detection

Authors: Vaduva, M; Baibarac, M; Cramariuc, O

Published: JAN 2023, MOLECULES, 28, 135, DOI: 10.3390/molecules28010135

In this article, we review recent progress concerning the development of sensorial platforms based on graphene derivatives and conducting polymers (CPs), alternatively deposited or co-deposited on the working electrode (usually a glassy carbon electrode; GCE) using a simple potentiostatic method (often cyclic voltammetry; CV), possibly followed by the deposition of metallic nanoparticles (NPs) on the electrode surface (ES). These materials have been successfully used to detect an extended range of biomolecules of clinical interest, such as uric acid (UA), dopamine (DA), ascorbic acid (AA), adenine, guanine, and others. The most common method is electrochemical synthesis. In the composites, which are often combined with metallic NPs, the interaction between the graphene derivatives-including graphene oxide (GO), reduced graphene oxide (RGO), or graphene quantum dots (GQDs)-and the CPs is usually governed by non-covalent functionalization through pi-pi interactions, hydrogen bonds, and van der Waals (VW) forces. The functionalization of GO, RGO, or GQDs with CPs has been shown to speed up electron transfer during the oxidation process, thus improving the electrochemical response of the resulting sensor. The oxidation mechanism behind the electrochemical response of the sensor seems to involve a partial charge transfer (CT) from the analytes to graphene derivatives, due to the overlapping of pi orbitals.

Open Access

321. Up-conversion emission in transition metal and lanthanide co-doped systems: dimer sensitization revisited

Authors: Avram, D; Colbea, C; Patrascu, AA; Istrate, MC; Teodorescu, V; Tiseanu, C

Published: FEB 7 2023, SCIENTIFIC REPORTS, 13, 2165, DOI: 10.1038/s41598-023-28583-3

Lanthanide (Ln) co-doped transition metal (TM) upconversion (UC) co-doped systems are being intensively investigated for their exciting applications in photonics, bioimaging, and luminescence thermometry. The presence of TM, such as Mo6 + /W6 +, Mn2 +, or Fe3 + determines significant changes in Ln UC emission, such as intensity enhancement, colour modulation, and even the alteration of the photon order. The current mechanism assumes a ground-state absorption/excited-state absorption (ESA/GSA) in TM-Yb dimer followed by direct energy transfer to Er/Tm excited states. We revisit this mechanism by addressing two issues that remain ignored: a dynamical approach to the investigation of the upconversion mechanism and the intrinsic chemical complexity of co-doped TM, Ln systems. To this aim, we employ a pulsed, excitation variable laser across a complete set of UC measurements, such as the emission and excitation spectra and emission decays and analyze multiple grains with transmission electron microscopy (TEM). In the Mo co-doped garnet, the results sustain the co-existence of Mo-free garnet and Mo oxide impurity. In this Mo oxide, the Er upconversion emission properties are fully explained by a relatively efficient sequential Yb to Er upconversion process, with no contribution from Yb-Mo dimer sensitization.

Open Access

322. Effect of Pressure on the Dynamics of Iodide Defects in Methylammonium Lead Iodide: An Atomistic Simulation

Authors: Brophy, RE; Kateb, M; Torfason, K; Nemnes, GA; Svavarsson, HG; Pintilie, I; Manolescu, A

Published: APR 21 2023, JOURNAL OF PHYSICAL CHEMISTRY C, 127, DOI: 10.1021/acs.jpcc.3c00657

The diffusion of iodide defects has been considered the most important degradation mechanism of methylammonium lead iodide (MAPI) in solar cells. The present study demonstrates the importance of the pressure inside this material on the dynamics of iodide defects, using molecular dynamics simulations. It is known that the diffusion coefficient of an iodide vacancy is an order of magnitude higher than that of interstitial iodide. We show that this difference systematically increases with increased tensile strain and that both diffusion coefficients tend to zero when a compressive strain is applied. This result suggests that compression of the MAPI can be a good solution to reduce its degradation rate. Besides, the statistical aspect of deriving the diffusion coefficient from the mean squared displacement (MSD) is discussed in terms of the initial conditions (positions and velocities) of the atoms and the simulation time, considering different seeds of the pseudorandom number generator used in the simulations performed with the LAMMPS software.

323. Thermoelectric properties of p-type Mg2Si0.3Sn0.7 doped with silver and gallium

Authors: Assahsahi, I; Popescu, B; El Bouayadi, R; Zejli, D; Enculescu, M; Galatanu, A

Published: MAY 25 2023, JOURNAL OF ALLOYS AND COMPOUNDS, 944, 169270, DOI: 10.1016/j.jallcom.2023.169270

Structure, composition, and transport properties of Mg2-xAgx(Si0.3Sn0.7)1-yGay (x = {0, 0.021, y = {0, 0.02, 0.04, 0.061) solid solutions produced by melting followed by spark plasma sintering are investigated. The preparation method is adjusted to control sample stoichiometry and phase composition. Doping with two types of dopants at different sites, while employing synthesis methods which generate a small amount of secondary phase, is an uncommon approach in this materials, expected to enhance their thermoelectric performance. An enhanced carrier concentration but diminished mobility is observed in the samples with higher amounts of dopant, which leads to the highest values of the power factor, for Mg1.98Ag0.02Si0.27Sn0.67Ga0.06 in a narrow temperature range (575-675 K) around the peak value, of 9.10-4 Wm-1 K-2 at 625 K. The two types of dopants have opposing effects on the thermal conductivity, with Ag promoting strong phonon scattering and decreasing its values while Ga increases them because of its en-hanced carrier concentration. The rather high thermal conductivity values of the double doped compounds produce low values of the ZT without exceeding 0.29 at 627 K for Mg1.98Ag0.02Si0.3Sn0.7 sample.(c) 2023 Elsevier B.V. All rights reserved.

324. The use of a new selective AB3 aptamer for the hematologic tumor cells' detection

Authors: Rus, I; Tertis, M; Pop, A; Fizesan, I; Bogdan, D; Matei, E; Oprea, D; Diculescu, V; Sandulescu, R; Cristea, C

Published: NOV 1 2023, SENSORS AND ACTUATORS B-CHEMICAL, 394, 134389, DOI: 10.1016/j.snb.2023.134389

Hematologic malignancies represent cancer diseases that affect the bone marrow and blood cells and include various subtypes depending mostly on the morphology of the cells. It is well known that an early diagnosis could be very useful for increasing survival rates in cancer, especially in the aggressive forms which can quickly progress to untreatable forms. The development of an easy, fast, and sensitive analytical tool with indicative applications in diagnosis and follow-up care, that could bring benefits in the discovery of new malignant diseases or relapses is reported. Oncofetal antigen/immature laminin receptor protein (OFA/iLRP) is an immunogenic protein found in fetal cells as well as overexpressed on the surface of some malignant tumors, including some hematologic malignancies. An aptamer, AB3, was selected and reported in the literature, having as a target the immature laminin receptor protein. Using the AB3 aptamer and its affinity to immature laminin receptor protein-positive cells an aptasensor was developed and tested on Jurkat cells. For the immobilization of the aptamer, graphene oxide modified screen printed electrodes were used and subjected to an activation procedure. The aptasensor development and cell caption were evaluated using electrochemical methods as well as microscopic techniques. The limit of detection of the developed aptasensor was 3.3 x 10(3) cells mL(-1), meaning 16 cells in the 5 mu L of suspension tested.

Open Access

325. Development of Novel Tetracycline and Ciprofloxacin Loaded Silver Doped Hydroxyapatite Suspensions for Biomedical Applications

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Buton, N

Published: JAN 2023, ANTIBIOTICS-BASEL, 12, 74, DOI: 10.3390/antibiotics12010074

The objective of this study consisted of the development of new materials with antimicrobial properties at the nanometric scale that could lead to an increase in therapeutic efficacy and reduction of toxic side effects. This work focuses on obtaining and characterizing stable suspensions with narrow size distribution with antimicrobial properties. The stability of the suspensions obtained by an adapted co-precipitation method was evaluated by ultrasonic measurements. The size and size distribution of the particle populations were determined using scanning electron microscopy (SEM), and dynamic light scattering (DLS). Both methods of analysis showed a narrow distribution of particles. DLS gave a monomodal distribution with hydrodynamic diameters around 38 nm for ciprofloxacin embedded in silver doped hydroxyapatite (AgHA-C) and 45.7 nm for tetracycline embedded in silver doped hydroxyapatite (AgHA-T). The average diameters calculated from SEM were 17 nm for AgHA-C and 19 nm for AgHA-T. Both Ciprofloxacin and Tetracycline influenced the hydroxyapatite structure, which led to the appearance of new vibrational bands characteristic of the specific chemical composition in the FTIR spectrum. The antimicrobial properties of the AgHA-C and AgHA-T suspensions were assessed using the most common reference microbial strains Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231. The results of the in vitro antimicrobial assays determined that the AgHA-C and AgHA-T suspensions exhibited exceptional antimicrobial activity. Moreover, the data revealed that the antimicrobial activity increased with the increase of the incubation time.

326. Two Roman Glass Furnaces Discovered at Resca-Romula (Romania)

Authors: Negru, M; Badica, P; Alexandru-Dinu, A; Galatanu, M; Kuncser, A; Patroi, D; Artene, I

Published: OCT 1 2023, AMERICAN JOURNAL OF ARCHAEOLOGY, 127, DOI: 10.1086/726009

Romula (today Resca, Dobrosloveni Village, Romania) was the largest urban and economic center of Dacia Inferior (Malvensis), a Roman province located in the north of the Lower Danube region. In this context, the city market included workshops for the production of ceramic, metal, stone, bone, and glass objects. In 2013, 2015, and 2018, during excavations of the former Roman city, two rectangular glass furnaces were discovered. One has only one chamber, the other has two chambers. A melted glass layer was found on the walls of furnace no. 1, as well as in one room of furnace no. 2. Broken fragments of glass were also found in both. The furnaces are located in the central area of the Roman city. The evidence suggests that the furnaces belong to secondary glass workshops. The glass may have arrived in raw form, where it was remelted and processed. The discovery of these furnaces contributes to the growing body of evidence for Roman glass production around the empire.1

327. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

Authors: Padurariu, L; Horchidan, N; Ciomaga, CE; Curecheriu, LP; Lukacs, VA; Stirbu, RS; Stoian, G; Botea, M; Florea, M; Maraloiu, VA; Pintilie, L; Rotaru, A; Mitoseriu, L

Published: 2023 JAN 18 2023, ACS APPLIED MATERIALS & INTERFACES, DOI: 10.1021/acsami.2c15641

The paper presents a study concerning the role of ferroelectric filler size and clustering in the dielectric properties of 20%BaTiO3-80%PVDF and of 20% (2%Ag-98%BaTiO3)-PVDF hybrid nanocomposites. By finite element calculations, it was shown that using fillers with epsilon > 103 does not provide a permittivity rise in the composites and the effective dielectric constant tends to saturate to specific values determined by the filler size and agglomeration degree. Irrespective of the ferroelectric filler sizes, the addition of metallic ultrafine nanoparticles (Ag) results in permittivity intensification and the effect is even stronger if the metallic nanoparticles are connected to a higher degree with the ferroelectric particles' surfaces. When using coarse ferroelectric fillers, the probability of clustering is higher, thus favoring the permittivity increase by field concentration in small regions close to the interfaces separating dissimilar materials. The modeling results were validated by an experimental dielectric analysis performed in a series of PVDF-based thick films with the same amount of BaTiO3 fillers or with Ag-BaTiO3 hybrid fillers. Similar trends as predicted by simulations were found experimentally but with slightly higher permittivity values which were assigned to the modifications of the polymer phase composition due to the presence of nanofillers and the local sample inhomogeneity (the presence of clustering, in particular for coarse BaTiO3 grains), which create regions with enhanced local fields.

Open Access

328. Anticoagulant Properties of Coated Fe-Pd Ferromagnetic Shape Memory Ribbons

Authors: Bunge, A; Chiriac, A; Sofronie, M; Craciunescu, I; Porav, AS; Turcu, R

Published: FEB 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 2452, DOI: 10.3390/ijms24032452

Shape memory alloys, especially ferromagnetic shape memory alloys, are interesting new materials for the manufacturing of stents. Iron-palladium alloys in particular can be used to manufacture self-expanding temporary stents due to their optimum rate of degradation, which is between that of magnesium and pure iron, two metals commonly used in temporary stent research. In order to avoid blood clotting upon the introduction of the stent, they are often coated with anticoagulants. In this study, sulfated pectin, a heparin mimetic, was synthesized in different ways and used as coating on multiple iron-palladium alloys. The static and dynamic prothrombin time (PT) and activated partial thromboplastin time (APTT) of the prepared materials were compared to samples uncoated or coated with polyethylene glycol. While no large differences were observed in the prothrombin time measurements, the activated partial thromboplastin time increased significantly with all alloys coated with sulfated pectin. Aside from that, sulfated pectin synthesized by different methods also caused slight changes in the activated partial thromboplastin time. These findings show that iron-palladium alloys can be coated with anticoagulants to improve their utility as material for temporary stents. Sulfated pectin was characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy, and the coated alloys by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Open Access

329. An improved balanced replicated sampling design for preliminary screening of the tailings ponds aiming at zero-waste valorization. A Romanian case study

Authors: Pencea, I; Turcu, RN; Popescu-Arges, AC; Timis, AL; Priceputu, A; Ungureanu, C; Matei, E; Nedelcu, L; Petrescu, MI; Niculescu, F

Published: APR 1 2023, JOURNAL OF ENVIRONMENTAL MANAGEMENT, 331, 117260, DOI: 10.1016/j.jenvman.2023.117260

The scope of this study consists of setting up of an integrated cost-effective sampling & laboratory analyses procedure which delineates sampling, sub-sampling and analytical uncertainties in case of fine-grained extractive waste deposits. This procedure is designed to support the decision makers towards fine-grained waste deposits upcycling and land reclamation. This procedure consists of a balanced replicated sampling design (BRSD) coupled with a three split levels ANOVA data processing. The paper provides the readership with the mathematical backgrounds of the three split level ANOVA analysis (3L-ANOVA) and an Excel algorithm for its implementation. Also, the paper presents an example of implementation of the developed methods in the case of a Romanian iron ore tailings (IOT) old pond. The findings of the paper consist of: a) argues, based on OM, SEM-EDS, XRFS and XRD observations, that classical TOS is ineffective for fine-grained waste deposits; b) BRSD in conjunction with 3L-ANOVA analysis is the only approach fit for reliable characterization of the fine-grained stockpiles; c) sampling uncertainty is the critical factor of the uncertainty budget of the analyte concentration; d) Lilliefors approach is adequate for the hypothesis testing where or not the measurand is normal distributed; e) The outcomes of the BRDSD&3L-ANOVA investigations carried on Teliuc tailings, estimated at circa 5.5* 106 m3, consist mainly of mineral quantification at lot level i.e. quartz-54% (+/- 7%), hematite-15% (+/- 3%), calcite-11% (+/- 3%), MgO 3% (+/- 1%), Al2O3 9% (+/- 2%). The concentrations of some CRMs like Ti, V, Ba, Y, W were found at ACE limits and their associated relative expanded uncertainties overpass 50%. Thus, the expanded uncertainties clearly depict the reliability of acquired data for the decision makers regarding waste valorization. f) The IOT into Teliuc can be upcycled as minerals for cement and ceramic industries as well as for geopolymer manufacture. Also, IOT can be downcycles as filler in road construction and mine closure. Finally, the Teliuc yard can be rehabilitated with zero-waste left behind. The data exactness provided by this procedure can be increased to any desirable level through increasing the number of collected items, but the cost of sampling and analyses increases proportionally. In such circumstances, the posted approach can be tailored at the stakeholder request as to safely underpin the decision to turn fine-grained by-products into valuable secondary resources, facilitating a greater circularity of the mining industry.

Open Access

330. Antibacterial Activity of PVA Hydrogels Embedding Oxide Nanostructures Sensitized by Noble Metals and Ruthenium Dye

Authors: Pelinescu, D; Anastasescu, M; Bratan, V; Maraloiu, VA; Negrila, C; Mitrea, D; Calderon-Moreno, J; Preda, S; Gifu, IC; Stan, A; Ionescu, R; Stoica, I; Anastasescu, C; Zaharescu, M; Balint, I

Published: AUG 2023, GELS, 9, 650, DOI: 10.3390/gels9080650

Nanostructured oxides (SiO2, TiO2) were synthesized using the sol-gel method and mod-ified with noble metal nanoparticles (Pt, Au) and ruthenium dye to enhance light harvesting and promote the photogeneration of reactive oxygen species, namely singlet oxygen (O-1(2)) and hydroxyl radical (center dot OH). The resulting nanostructures were embedded in a transparent polyvinyl alcohol (PVA) hydrogel. Morphological and structural characterization of the bare and modified oxides was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), UV-Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Additionally, electrokinetic potential measurements were conducted. Crystallinity data and elemental analysis of the investigated systems were obtained through X-ray diffraction and X-ray fluorescence analyses, while the chemical state of the elements was determined using XPS. The engineered ma-terials, both as simple powders and embedded in the hydrogel, were evaluated for their ability to generate reactive oxygen species (ROS) under visible and simulated solar light irradiation to establish a correlation with their antibacterial activity against Staphylococcus aureus. The generation of singlet oxygen (O-1(2)) by the samples under visible light exposure can be of significant importance for their potential use in biomedical applications.

Open Access

331. Surface properties, chemical reactivity, and ambient stability of cadmium diarsenide CdAs2, a topological chiral material hosting Kramers-Weyl fermions

Authors: Zhang, YX; D'Olimpio, G; Bondino, F; Nappini, S; Istrate, MC; Sankar, R; Ghica, C; Ottaviano, L; Gao, JF; Politano, A

Published: JUL 15 2023, APPLIED SURFACE SCIENCE, 625, 157132, DOI: 10.1016/j.apsusc.2023.157132

Chiral materials showing Kramers-Weyl fermions represent a suitable platform for quantum technology, i.e., for engineering quantum solenoids, spin-torque devices, polarization-sensitive photodetectors based on quantized circular photogalvanic effect, etc. Accordingly, the stability of this class of materials in oxidative environments, such as the ambient atmosphere, should be carefully investigated to succeed in technology transfer. Here, taking as case-study example the well-recognized topological chiral system cadmium diarsenide (CdAs2), we assess its chemical reactivity towards ambient gases (oxygen and water) and air by density functional theory and experiments. The surface of CdAs2 evolves into an oxide skin, but its thickness remains nanometric even after one year in air, as directly imaged by high-resolution transmission electron microscopy. Accordingly, it is evident that future quantum devices based on Kramers-Weyl fermions could be stable in air, as the oxide layer formed on chiral quantum materials only represents a native oxide, which actually protects bulk features, including Kramers-Weyl fermions (correlated to bulk band structure), from degradation in air.

Open Access

332. Vortex Dynamics and Pinning in CaKFe4As4 Single Crystals from DC Magnetization Relaxation and AC Susceptibility

Authors: Ionescu, AM; Ivan, I; Miclea, CF; Crisan, DN; Galluzzi, A; Polichetti, M; Crisan, A

Published: DEC 2023, CONDENSED MATTER, 8, 93, DOI: 10.3390/condmat8040093

Among various "families" of iron-based superconductors, the quite recently discovered AeAFe(4)As(4) (where Ae is an alkali-earth metal and A is an alkali metal) has high critical current density, a very high upper critical field, and a low anisotropy, and has recently received much interest for the possibility of high magnetic field applications at the liquid hydrogen temperature. We have performed DC magnetization relaxation and frequency-dependent AC susceptibility measurements on high-quality single crystals of CaKFe4As4 with the aim of determining the pinning potential U*. The temperature dependence of U* displays a clear crossover between elastic creep and plastic creep. At temperatures around 27-28 K, U* has a very high value, up to 1200 K, resulting in an infinitesimally small probability of thermally activated flux jumps. From the dependence of the normalized pinning potential on irreversible magnetization, we have determined the creep exponents in the two creep regimes, which are in complete agreement with theoretical models. The estimation of the pinning potential from multifrequency AC susceptibility measurements was possible only near the critical temperature due to equipment limitations, and the resulting value is very close to the one that resulted from the magnetization relaxation data. Magnetic hysteresis loops revealed a second magnetization peak and very high values of the critical current density.

Open Access

333. Studies of the Tarragon Essential Oil Effects on the Characteristics of Doped Hydroxyapatite/Chitosan Biocomposites

Authors: Predoi, D; Iconaru, SL; Ciobanu, CS; Raita, MS; Ghegoiu, L; Trusca, R; Badea, ML; Cimpeanu, C

Published: APR 2023, POLYMERS, 15, 1908, DOI: 10.3390/polym15081908

Due to the emergence of antibiotic-resistant pathogens, the need to find new, efficient antimicrobial agents is rapidly increasing. Therefore, in this study, we report the development of new biocomposites based on zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L. with good antimicrobial activity. Techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) were used in order to evaluate their physico-chemical properties. Our studies revealed that biocomposite materials with nanometric dimension and homogeneous composition could be obtained through an economic and cost-effective synthesis method. The biological assays demonstrated that ZnHA (zinc-doped hydroxyapatite), ZnHACh (zinc-doped hydroxyapatite/chitosan) and ZnHAChT (zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L.) did not exhibit a toxic effect on the cell viability and proliferation of the primary osteoblast culture (hFOB 1.19). Moreover, the cytotoxic assay also highlighted that the cell morphology of the hFOB 1.19 was not altered in the presence of ZnHA, ZnHACh or ZnHAChT. Furthermore, the in vitro antimicrobial studies emphasized that the samples exhibited strong antimicrobial properties against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231 microbial strains. These results are encouraging for the following development of new composite materials with enhanced biological properties that could promote the osteogenic process of bone healing and also exhibit good antimicrobial properties.

Open Access

334. Efficient Sintering of Mo Matrix Composites-A Study of Temperature Dependences and the Use of the Sinter Additive Ni

Authors: Solodkyi, I; Petrusha, V; Grigoroscuta, MA; Schmelzer, J; Hasemann, G; Betke, U; Badica, P; Krüger, M

Published: OCT 2023, METALS, 13, 1715, DOI: 10.3390/met13101715

Mo matrix composites (MMC) with Mo-9Si-8B inclusions were fabricated by pressure-less sintering (PLS) and spark plasma sintering (SPS) techniques at temperatures between 1200-1500 degrees C using 1 wt.% Ni sinter additive. The positive impact of the addition Ni addition on the sinterability and formation of a continuous Mo matrix of MMC with randomly distributed Mo3Si and Mo5SiB2 inclusions was determined. The Ni addition increased the shrinkage of MMC during PLS by almost a third. The continuous Mo matrix of MMC and a relative density of more than 98% was obtained after SPS at 1400-1500 degrees C. The composite with the maximum relative density of 98% showed a Vickers hardness of 482 +/- 9 (HV20). The potential of using Ni-activated PLS and SPS to produce high-density MMC is shown.

Open Access

335. Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids

Authors: Enache, TA; Enculescu, M; Bunea, MC; Zubillaga, EA; Tellechea, E; Aresti, M; Lasheras, M; Asensio, AC; Diculescu, VC

Published: JAN 2023, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 24, 1129, DOI: 10.3390/ijms24021129

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field.

336. From interface to interphase

Authors: Chipara, M; Baibarac, M; Compagnini, G; Gao, JW

Published: NOV 2023, SURFACES AND INTERFACES, 42, 103435, DOI: 10.1016/j.surfin.2023.103435

A critical brief review of the evolution of the ideas describing the matter, with emphasis on concepts relevant to the journal's goals: surfaces, interfaces, and interphases is presented. The complex relationship between interphase and interface, including the role of the submicron confinement on the physical and chemical properties of matter are analyzed from both theoretical and experimental standpoints. The most important consequences triggered by the recognition of interphases are briefly discussed. Most matter (at a macroscopic scale) is dominated by bulk behavior. The rapid advances in materials and especially the accelerated progress in the synthesis and characterization of submicron materials and associated technologies, labeled as the "nano revolution", revived the research on interfaces and interphases at atomic and molecular scales. It is suggested that interphase ignites a new kind of material, whose "bulk physical features" have been distorted by the submicron confinement. Such an "interphase surface" (for example a drop of gold with a diameter smaller than a few nanometers, or a few layers of graphene), may exist free standing and be stable. These materials, which no more exhibit the bulk properties will be tentatively referred to as "Sutter" ("Sutter" defines an abbreviation that involves both surface and matter concepts). Sutter is characterized by the fact that its physical and chemical properties are controlled by the interphase. It is concluded that Sutter is essentially a submicron phase of the matter, that exhibits size-dependent features. Sutter materials may be embedded in various materials (such as polymers, metals, and alloys) as nanocomposites, thus projecting specific features at the macroscopic scale. Most free standing interphases may be considered as Sutter materials or phases. The interface does not qualify as a Sutter material.

337. Preparation of 82Se thin films with trigonal hexagonal crystal structure for in-beam nuclear structure experiments

Authors: Florea, NM; Nita, CR; Sotty, C; Marginean, RM; Bacalum, M; Enculescu, M; Marginean, N; Matei, E; Mereuta, P; Mihai, C; Vasilca, S

Published: SEP 2023, VACUUM, 215, 112250, DOI: 10.1016/j.vacuum.2023.112250

We report a novel approach in producing and characterizing enriched isotopic selenium-82 (82Se) thin films with trigonal hexagonal crystal structure (t-82Se), the most thermodynamically stable form of the element. The ob-tained t-82Se thin films are used as targets in accelerator based nuclear structure experiments. Several 82Se thin films with thicknesses around 5 mg/cm2 (10.4 & mu;m) were deposited on 5 mg/cm2 (3 & mu;m) tantalum (Ta) foils by vacuum evaporation-condensation method. The condensed 82Se films exhibit unstable amorphous structure (a-82Se), therefore were converted to t-82Se by means of an appropriate vacuum heat treatment developed in the target laboratory of IFIN-HH. After the thermal treatment, the microstructure, morphology and composition of the 82Se films were evaluated before and after the vacuum thermal treatment using Fourier Transform Raman Spectroscopy (FT-Raman), X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Mi-croscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) techniques. Furthermore, an in-beam & gamma;-spectroscopy experiment performed at the 9-MV tandem accelerator of IFIN-HH confirmed that the ther-mally treated t-82Se films possess high durability and high purity with no detectable contamination and no mass loss.

Open Access

338. Titania nanoparticles for photocatalytic degradation of ethanol under simulated solar light

Authors: Goncearenco, E; Morjan, IP; Fleaca, CT; Dumitrache, F; Dutu, E; Scarisoreanu, M; Teodorescu, VS; Sandulescu, A; Anastasescu, C; Balint, I

Published: MAY 22 2023, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 14, DOI: 10.3762/bjnano.14.51

TiO2 nanoparticles were synthesized by laser pyrolysis from TiCl4 vapor in air in the presence of ethylene as sensitizer at different working pressures (250-850 mbar) with and without further calcination at 450 degrees C. The obtained powders were analyzed by energydispersive X-ray spectroscopy, X- ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. Also, specific surface area and photoluminescence with optical absorbance were evaluated. By varying the synthesis parameters (especially the working pressure), different TiO2 nanopowders were obtained, whose photodegradation properties were tested compared to a commercial Degussa P25 sample. Two series of samples were obtained. Series "a" includes thermally treated TiO2 nanoparticles (to remove impurities) that have different proportions of the anatase phase (41.12-90.74%) mixed with rutile and small crystallite sizes of 11-22 nm. Series "b" series represents nanoparticles with high purity, which did not require thermal treatment after synthesis (ca. 1 atom % of impurities). These nanoparticles show an increased anatase phase content (77.33-87.42%) and crystallite sizes of 23-45 nm. The TEM images showed that in both series small crystallites form spheroidal nanoparticles with dimensions of 40-80 nm, whose number increases with increasing the working pressure. The photocatalytic properties have been investigated regarding the photodegradation of ethanol vapors in Ar with 0.3% O2 using P25 powder as reference under simulated solar light. During the irradiation H-2 gas production has been detected for the samples from series "b", whereas the CO2 evolution was observed for all samples from series "a".

339. Gd-Er interaction promotes NaGdF4:Yb, Er as a new candidate for high-power density applications

Authors: Avram, D; Patrascu, AA; Istrate, MC; Tiseanu, C

Published: AUG 3 2023, JOURNAL OF MATERIALS CHEMISTRY C, 11, DOI: 10.1039/d3tc01391j

High-power density applications using up-conversion (UC) systems rely mostly on the Yb, Tm lanthanide couple. Herein, we investigate the extent to which Gd high energy levels can enhance the four-order UC process in NaGdF4:Yb, Er under pulsed excitation, making the Yb, Er UC system suitable for high power density applications. Unlike cw excitation, pulsed laser excitation enables higher equivalent power densities with reduced local heating effects. We found that Gd upholds the saturation level by one order of magnitude in NaGdF4:Yb, Er@NaYF4 compared to NaYF4:Yb, Er@NaYF4 nanoparticles, i.e., from 5 x 10(6) to 5 x 10(7) W cm(-2). Such an effect is determined by efficient two-step Er-Gd energy transfer, in which the Gd levels, populated by four-order Yb-Er processes, act further as the long(est)-lived reservoir level for Er UC emissions. Notably, above 10(8) W cm(-2), NaGdF4:Yb, Er@NaYF4 shows similar performance to NaGdF4:Yb, Tm@NaYF4 in terms of UC photon order, which is considered a direct indicator of spatial resolution in high power density applications. Our results showcase the promise of the Yb, (Gd) Er UC system for high power density applications, thus stimulating research for expanding the presently limited range of applicable UC systems.

Open Access

340. Hydroxyapatite Nanopowders for Effective Removal of Strontium Ions from Aqueous Solutions

Authors: Predoi, SA; Ciobanu, SC; Chifiriuc, MC; Motelica-Heino, M; Predoi, D; Iconaru, SL

Published: JAN 2023, MATERIALS, 16, 229, DOI: 10.3390/ma16010229

Drinking water contamination has become a worldwide problem due to the highly negative effects that pollutants can have on human organisms and the environment. Hydroxyapatite (HAp) has the appropriate properties for the immobilization of various pollutants, being considered amongst the most cost-effective materials for water decontamination. The main objective of this study was to use synthesized hydroxyapatite for the elimination of Sr2+ ions from contaminated solutions. The hydroxyapatite used in the decontamination process was synthesized in the laboratory using an adapted method. The hydroxyapatite powder (HAp) resulting from the synthesis was analyzed both before and after the elimination of Sr2+ ions from contaminated solutions. The efficiency of the HAp nanoparticles in removing Sr2+ ions from contaminated solution was determined by batch adsorption experiments. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to study the HAp samples before and after the removal of Sr2+ ions. The ability of HAp nanoparticles to eliminate strontium ions from contaminated solutions was established. Moreover, the removal of Sr2+ ions from the contaminated aqueous solutions was highlighted by ultrasound measurements. The value of the stability parameter calculated by ultrasonic measurements after the removal of Sr2+ ions from the contaminated solution was similar to that of double distilled water whose stability was used as reference. The outcomes of the batch experiments and the parameters obtained from Langmuir and Freundlich models indicated that the HAp nanoparticles had a strong affinity for the elimination of Sr2+ ions from polluted solutions. These results emphasized that HAp nanoparticles could be excellent candidates in the development of new technologies for water remediation. More than that, the outcomes of the cytotoxic assays proved that HAp nanoparticles did not induce any noticeable harmful effects against HeLa cells and did not affect their proliferation after 1 day and 7 days of incubation.

341. Molecular OR and AND logic gates: A theoretical proposal

Authors: Nita, M; Tolea, M; Marinescu, DC

Published: DEC 11 2023, PHYSICAL REVIEW B, 108, 235307, DOI: 10.1103/PhysRevB.108.235307

A conductance zero that results from the destructive quantum interference of the electron states in quantum transport between two given sites of a molecular system persists or disappears depending on the location of an externally applied perturbation. The a priori knowledge of the perturbation site that destroys or preserves a zero is the basis of an algorithm that outlines the creation of logic gates having external perturbations as inputs and a given conductance as output. Using a graph of the possible conductance paths between the various sites, we showcase the several different scenarios that correspond to AND/OR/XOR logical functions for a given set of contacts. This setup is shown to be independent of the strength of the coupling to the leads and magnitude of the perturbation. We illustrate this approach in the case of bipartite and nonbipartite single carbon cycle molecules (fulvene and benzene) and double carbon cycle molecules (naphthalene and biphenyl).

Open Access

342. Electrochemical Deposition of ZnO Nanowires on CVD-Graphene/Copper Substrates

Authors: Boukhoubza, I; Matei, E; Jorio, A; Enculescu, M; Enculescu, I

Published: AUG 2022, NANOMATERIALS, 12, 2858, DOI: 10.3390/nano12162858

ZnO nanostructures were electrochemically synthesized on Cu and on chemical vapor deposited (CVD)-graphene/Cu electrodes. The deposition was performed at different electrode potentials ranging from -0.8 to -1.2 V, employing a zinc nitrate bath, and using voltametric and chronoamperometric techniques. The effects of the electrode nature and of the working electrode potential on the structural, morphological, and optical properties of the ZnO structures were investigated. It was found that all the samples crystallize in hexagonal wurtzite structure with a preferential orientation along the c-axis. Scanning electron microscopy (SEM) images confirm that the presence of a graphene covered electrode led to the formation of ZnO nanowires with a smaller diameter compared with the deposition directly on copper surface. The photoluminescence (PL) measurements revealed that the ZnO nanowires grown on graphene/Cu exhibit stronger emission compared to the nanowires grown on Cu. The obtained results add another possibility of tailoring the properties of such nanostructured films according to the specific functionality required.

343. THE INFLUENCE OF ELECTROSPINNING PARAMETERS ON THE MORPHOLOGICAL FEATURES OF PVDF FIBRES

Authors: Alecu, AE; Girjoaba, SA; Beregoi, M; Jinga, SI; Busuioc, C

Published: 2022, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 52, DOI:

In this work, polyvinylidene fluoride was obtained in the form of one-dimensional structures with the help of electrospinning technique. Several types of precursor solutions were tested to find the optimal experimental conditions to produce smooth, continuous and beadless fibres, morphologically suitable for the development of piezoelectric scaffolds dedicated to tissue engineering applications. Thus, the influence of solvent type, polymer concentration, as well as electrospinning parameters (feeding rate, spinneret-collector distance, and applied voltage) was assessed and the best situation was the one with a 2:3 ratio between dimethylformamide and acetone, 20 % polymer concentration, 1 mL/h flow, 20 cm distance and 18 kV voltage. In the end, the fibres were loaded with barium titanate commercial particles, as first attempt to produce a piezoelectric composite with potential in the medical field.

Open Access

344. Epoxy Coatings Containing Modified Graphene for Electromagnetic Shielding

Authors: Bontas, MG; Diacon, A; Calinescu, I; Necolau, MI; Dinescu, A; Toader, G; Ginghina, R; Vizitiu, AM; Velicu, V; Palade, P; Istrate, M; Rusen, E

Published: JUN 2022, POLYMERS, 14, 2508, DOI: 10.3390/polym14122508

This study presents the functionalization and characterization of graphene and electromagnetic interference (EMI) attenuation capacity in epoxy-nanocomposites. The modification of graphene involved both small molecules and polymers for compatibilization with epoxy resin components to provide EMI shielding. The TGA and RAMAN analyses confirmed the synthesis of graphene with a different layer thickness of the graphene sheets. Graphene samples with different layer thicknesses (monolayer, few layers, and multilayer) were selected and further employed for epoxy coating formulation. The obtained nanocomposites were characterized in terms of EMI shielding effectiveness, SEM, micro-CT, magnetic properties, and stress-strain resistance. The EMI shielding effectiveness results indicated that the unmodified graphene and hexamethylene diamine (HMDA) modified graphene displayed the best EMI shielding properties at 11 GHz. However, the epoxy nanocomposites based on HMDA modified graphene displayed better flexibility with an identical EMI shielding effectiveness compared to the unmodified graphene despite the formation of aggregates. The improved flexibility of the epoxy nanocomposites and EMI shielding characteristics of HMDA functionalized graphene offers a practical solution for textile coatings with microwave absorbing (MA) capacity.

345. Luminescent heteroleptic copper(I) complexes with phosphine and N-benzoyl thiourea ligands: Synthesis, structure and emission properties

Authors: Tudor, CA; Ilis, M; Secu, M; Ferbinteanu, M; Cîrcu, V

Published: JAN 1 2022, POLYHEDRON, 211, 115542, DOI: 10.1016/j.poly.2021.115542

The reactions between [CuX(PPh3)](4) or [CuX(PPh3)(3)], X = Cl or Br, and N-benzoyl-N'-(4-methoxyphenyl)thio-urea (BTU-OMe), N-benzoyl-N'-(4-methylphenyl)thiourea (BTU-Me) in toluene gave new four-coordinated tetrahedral copper(I) complexes of two types: [CuX(BTU)(PPh3)(2)] (1, 2) and [CuX(BTU)(2)(PPh3)] (3,4) [BTU = N-benzoyl-N'-(4-methoxy/methyl phenyl)thiourea derivatives, X = Cl (a) and Br (b)]. These complexes were fully characterized by several analytical and spectroscopic (IR, UV/VIS, H-1, C-13 and P-31 NMR) techniques. The molecular structure of a representative complex, [Cu(BTU-OMe)(PPh3)(2)Cl] (3a), was determined by the single crystal X-ray diffraction method which reveals a distorted tetrahedral geometry where the Cu(I) ion is surrounded by one BTU ligand molecule, two PPh3 groups and one chloride anion. These eight heteroleptic complexes were found to emit in solid state with lifetimes in the 12-99 mu s range and with the highest quantum yield of 4.0% for 3b. The reaction between [CuBr(PPh3)](4) and N-benzoyl-N',N'-(di-n-butyl)thiourea (BTU-Bu-2) ligand gave the simple [CuBr(BTU-Bu-2)(3)] complex (5), when the PPh3 molecules were completely removed by the BTU derivative. The spectroscopic data indicated a distorted tetrahedral geometry produced by three BTU ligand molecules and one bromide anion. Complex 5 has the highest quantum yield (11%) with the lifetime of 29 mu s in solid-state.

Open Access

346. Insights into Structure and Biological Activity of Copper(II) and Zinc(II) Complexes with Triazolopyrimidine Ligands

Authors: Argaseala, A; Maxim, C; Badea, M; Ionita, L; Chifiriuc, MC; Rostas, AM; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Iorgulescu, EE; Olar, R

Published: FEB 2022, MOLECULES, 27, 765, DOI: 10.3390/molecules27030765

In an attempt to increase the biological activity of the 1,2,4-triazolo[1,5-a]pyrimidine scaffold through complexation with essential metal ions, the complexes trans-[Cu(mptp)(2)Cl-2] (1), [Zn(mptp)Cl-2(DMSO)] (2) (mptp: 5-methyl-7-phenyl-1,2,4-triazolo[1,5-a]pyrimidine), [Cu-2(dmtp)(4)Cl-4]center dot 2H(2)O (3) and [Zn(dmtp)(2)Cl-2] (4) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized as new antiproliferative and antimicrobial species. Both complexes (1) and (2) crystallize in the P2(1)/n monoclinic space group, with the tetrahedral surroundings generating a square-planar stereochemistry in the Cu(II) complex and a tetrahedral stereochemistry in the Zn(II) species. The mononuclear units are interconnected in a supramolecular network through pi-pi interactions between the pyrimidine moiety and the phenyl ring in (1) while supramolecular chains resulting from C-H center dot center dot center dot pi interactions were observed in (2). All complexes exhibit an antiproliferative effect against B16 tumor cells and improved antibacterial and antifungal activities compared to the free ligands. Complex (3) displays the best antimicrobial activity against all four tested strains, both in the planktonic and biofilm-embedded states, which can be correlated to its stronger DNA-binding and nuclease-activity traits.

Open Access

347. SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors

Authors: Palade, C; Slav, A; Cojocaru, O; Teodorescu, VS; Stoica, T; Ciurea, ML; Lepadatu, AM

Published: MAR 2022, COATINGS, 12, 348, DOI: 10.3390/coatings12030348

Group IV quantum dots (QDs) in HfO2 are attractive for non-volatile memories (NVMs) due to complementary metal-oxide semiconductor (CMOS) compatibility. Besides the role of charge storage centers, SiGeSn QDs have the advantage of a low thermal budget for formation, because Sn presence decreases crystallization temperature, while Si ensures higher thermal stability. In this paper, we prepare MOS capacitors based on 3-layer stacks of gate HfO2/floating gate of SiGeSn QDs in HfO2/tunnel HfO2/p-Si obtained by magnetron sputtering deposition followed by rapid thermal annealing (RTA) for nanocrystallization. Crystalline structure, morphology, and composition studies by cross-section transmission electron microscopy and X-ray diffraction correlated with Raman spectroscopy and C-V measurements are carried out for understanding RTA temperature effects on charge storage behavior. 3-layer morphology and Sn content trends with RTA temperature are explained by the strongly temperature-dependent Sn segregation and diffusion processes. We show that the memory properties measured on Al/3-layer stack/p-Si/Al capacitors are controlled by SiGeSn-related trapping states (deep electronic levels) and low-ordering clusters for RTA at 325-450 degrees C, and by crystalline SiGeSn QDs for 520 and 530 degrees C RTA. Specific to the structures annealed at 520 and 530 degrees C is the formation of two kinds of crystalline SiGeSn QDs, i.e., QDs with low Sn content (2 at.%) that are positioned inside the floating gate, and QDs with high Sn content (up to 12.5 at.%) located at the interface of floating gate with adjacent HfO2 layers. The presence of Sn in the SiGe intermediate layer decreases the SiGe crystallization temperature and induces the easier crystallization of the diamond structure in comparison with 3-layer stacks with Ge-HfO2 intermediate layer. High frequency-independent memory windows of 3-4 V and stored electron densities of 1-2 x 10(13) electrons/cm(2) are achieved.

Open Access

348. Investigating the effect of N-doping on carbon quantum dots structure, optical properties and metal ion screening

Authors: Nguyen, KG; Baragau, IA; Gromicova, R; Nicolaev, A; Thomson, SAJ; Rennie, A; Power, NP; Sajjad, MT; Kellici, S

Published: AUG 15 2022, SCIENTIFIC REPORTS, 12, 13806, DOI: 10.1038/s41598-022-16893-x

Carbon quantum dots (CQDs) derived from biomass, a suggested green approach for nanomaterial synthesis, often possess poor optical properties and have low photoluminescence quantum yield (PLQY). This study employed an environmentally friendly, cost-effective, continuous hydrothermal flow synthesis (CHFS) process to synthesise efficient nitrogen-doped carbon quantum dots (N-CQDs) from biomass precursors (glucose in the presence of ammonia). The concentrations of ammonia, as nitrogen dopant precursor, were varied to optimise the optical properties of CQDs. Optimised N-CQDs showed significant enhancement in fluorescence emission properties with a PLQY of 9.6% compared to pure glucose derived-CQDs (g-CQDs) without nitrogen doping which have PLQY of less than 1%. With stability over a pH range of pH 2 to pH 11, the N-CQDs showed excellent sensitivity as a nano-sensor for the highly toxic highly-pollutant chromium (VI), where efficient photoluminescence (PL) quenching was observed. The optimised nitrogen-doping process demonstrated effective and efficient tuning of the overall electronic structure of the N-CQDs resulting in enhanced optical properties and performance as a nano-sensor.

Open Access

349. Effect of the Cadmium Telluride Deposition Method on the Covering Degree of Electrodes Based on Copper Nanowire Arrays

Authors: Panaitescu, AM; Antohe, I; Locovei, C; Iftimie, S; Antohe, S; Piraux, L; Suchea, MP; Antohe, VA

Published: AUG 2022, APPLIED SCIENCES-BASEL, 12, 7808, DOI: 10.3390/app12157808

In this work, we report the preparation of nanostructured electrodes based on dense arrays of vertically-aligned copper (Cu) nanowires (NWs) to be subsequently covered by cadmium telluride (CdTe) thin films, with great potential to be used within "substrate"-type photovoltaic cells based on A(II)-BVI heterojunctions. In particular, the multi-step preparation protocol presented here involves an electrochemical synthesis procedure within a supported anodic aluminum oxide (AAO) nanoporous template for first generating a homogeneous array of vertically-aligned Cu NWs, which are then further embedded within a compact CdTe thin film. In a second stage, we tested three deposition methods (vacuum thermal evaporation, VTE; radio-frequency magnetron sputtering, RF-MS; and electrochemical deposition, ECD) for use in obtaining CdTe layers potentially able to consistently penetrate the previously prepared Cu NWs array. A comparative analysis was performed to critically evaluate the morphological, optical, and structural properties of the deposited CdTe films. The presented results demonstrate that under optimized processing conditions, the ECD approach could potentially allow the cost-effective fabrication of absorber layer/collecting electrode CdTe/Cu nanostructured interfaces that could improve charge collection mechanisms, which in turn could allow the fabrication of more efficient solar cells based on A(II)-BVI semiconducting compounds.

Open Access

350. Nanoporous Membranes for the Filtration of Proteins from Biological Fluids: Biocompatibility Tests on Cell Cultures and Suggested Applications for the Treatment of Alzheimer's Disease

Authors: Schreiner, TG; Tamba, BI; Mihai, CT; Lorinczi, A; Baibarac, M; Ciobanu, RC; Popescu, BO

Published: OCT 2022, JOURNAL OF CLINICAL MEDICINE, 11, 5846, DOI: 10.3390/jcm11195846

Background: Alzheimer's disease has a significant epidemiological and socioeconomic impact, and, unfortunately, the extensive research focused on potential curative therapies has not yet proven to be successful. However, in recent years, important steps have been made in the development and functionalization of nanoporous alumina membranes, which might be of great interest for medical use, including the treatment of neurodegenerative diseases. In this context, the aim of this article is to present the synthesis and biocompatibility testing of a special filtrating nano-membrane, which is planned to be used in an experimental device for Alzheimer's disease treatment. Methods: Firstly, the alumina nanoporous membrane was synthesized via the two-step anodizing process in oxalic acid-based electrolytes and functionalized via the atomic layer deposition technique. Subsequently, quality control tests (spectrophotometry and potential measurements), toxicity, and biocompatibility tests (cell viability assays) were conducted. Results: The proposed alumina nanoporous membrane proved to be efficient for amyloid-beta filtration according to the permeability studies conducted for 72 h. The proposed membrane has proven to be fully compatible with the tested cell cultures. Conclusions: The proposed alumina nanoporous membrane model is safe and could be incorporated into implantable devices for further in vivo experiments and might be an efficient therapeutic approach for Alzheimer's disease.

Open Access

351. Europium (II)-Doped CaF2 Nanocrystals in Sol-Gel Derived Glass-Ceramic: Luminescence and EPR Spectroscopy Investigations

Authors: Secu, C; Rostas, AM; Secu, M

Published: SEP 2022, NANOMATERIALS, 12, 3016, DOI: 10.3390/nano12173016

The remarkable properties of Eu2+-activated phosphors, related to the broad and intense luminescence of Eu2+ ions, showed a high potential for a wide range of optical-related applications. Oxy-fluoride glass-ceramic containing Europium (II)-doped CaF2 nanocrystals embedded in silica matrix were produced in two steps: glass-ceramization in air at 800 degrees with Eu3+-doped CaF2 nanocrystals embedded followed by Eu3+ to Eu2+ reduction during annealing in reducing atmosphere. The broad, blue luminescence band at 425 nm and with the long, weak tail in the visible range is assigned to the d -> f type transition of the Eu2+ located inside the CaF2 nanocrystals in substitutional and perturbed sites, respectively; the photoluminescence quantum yield was about 0.76. The X-ray photoelectron spectroscopy and Electron paramagnetic spectroscopy confirmed the presence of Eu2+ inside the CaF2 nanocrystals. Thermoluminescence curves recorded after X-ray irradiation of un-doped and Eu2+-doped glass-ceramics showed a single dominant glow peak at 85 degrees C related to the recombination between F centers and Eu2+ related hole within the CaF2 nanocrystals. The applicability of the procedure can be tested to obtain an oxy-fluoride glass-ceramic doped with other divalent ions such as Sm2+, Yb2+, as nanophosphors for radiation detector or photonics-related applications.

352. Persistent destructive quantum interference in the inverted graph method

Authors: Nita, M; Marinescu, DC

Published: APR 8 2022, PHYSICAL REVIEW B, 105, 155303, DOI: 10.1103/PhysRevB.105.155303

We formulate a general criterion that underlies the persistence of conductance zeros induced by destructive quantum interference under the application of external perturbations in physical systems described by a discrete nonsingular Hamiltonian H. Our approach uses nonzero matrix elements of H???1 between two lattice points as edges of a graph to indicate the existence of a nonzero conductance between the same points. A given conductance zero, or a missing edge in the inverted graph, is preserved when the perturbation, in the form of on-site or additional interpoint hopping energies, is applied only to points outside the set of first-order graph neighbors of either the entry lead or the exit lead. We discuss the application of these results to a study of the robustness of the conductance zeros in the fulvene and benzene molecules.

353. Electron Irradiation of Titanium-Doped Chromium Nanostructured Thin Films for Higher Conductive Electrodes

Authors: Polosan, S; Ciobotaru, CC; Ciobotaru, IC; Enculescu, M; Iosub, D; Mandes, A; Vladoiu, R

Published: 2022, IEEE TRANSACTIONS ON NANOTECHNOLOGY, 21, DOI: 10.1109/TNANO.2022.3227366

The low-energy electron irradiation improves the electrical properties of the Ti-doped chromium thin films obtained by Laser-assisted Thermionic Vacuum Arc (LTVA). The irradiation doses, between 0.6 C/m(2) and 326.4 C/m(2), operate as a nanozonal melting effect, decreasing the metallic alloy's roughness, and increasing the electrical conductivity at a depth up to 8 nm. Therefore, the grain sizes of the surface nanostructures are increased after irradiation, but the surface roughness is substantially improved. By tailoring the surface parameters like crystallinity and roughness of the metallic thin films used as electrodes in the OLED technologies, a reduction of the Schottky contacts between the metal and semiconductor contact is expected. This fact minimizes the contact resistance between the metallic and semiconductor thin films and increases the charge injection across the OLED sandwich structures.

354. Effect of growth temperature on the physical properties of Spray pyrolysis deposited CZTS films

Authors: Khaaissa, Y; Talbi, A; Nouneh, K; El Khouja, O; Ahmoum, H; Fahoume, M

Published: SEP 2022, MATERIALS TODAY-PROCEEDINGS, 66, DOI: 10.1016/j.matpr.2022.04.893

Cu2ZnSnS4 (CZTS) functional thin films have been successfully synthesized using the spray pyrolysis method in a single deposition process and under atmospheric pressure. The samples have been deposited on glass substrates under different growth temperatures ranging from 350 ? to 450 ?. The solution has been prepared using Copper chloride dihydrate, Zinc chloride, Tin chloride dihydrate, and Thiourea as Copper, Zinc, Tin and Sulfur sources respectively. The structural, optical, morphological and electrical properties of CZTS films have been investigated. X-ray diffraction (XRD) and Raman spectroscopy have confirmed the kesterite structure of all samples without any secondary phase. The surface morphology and topography of the samples have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Data from UV-Vis spectroscopy analysis and Hall effect measurement showed that CZTS films elaborated at 400 ? have an optimum band gap (Eg = 1.5 eV), low resistivity (1.7239 x 10(-2) omega.cm), and high conductivity (58.00 (omega.cm)(-1)). Copyright (c) 2022 Elsevier Ltd. All rights reserved.

355. Screening of magnetic fields by superconducting and hybrid shields with a circular cross-section

Authors: Gozzelino, L; Fracasso, M; Solovyov, M; Gömöry, F; Napolitano, A; Gerbaldo, R; Ghigo, G; Laviano, F; Torsello, D; Grigoroscuta, MA; Aldica, G; Burdusel, M; Badica, P

Published: APR 1 2022, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 35, 044002, DOI: 10.1088/1361-6668/ac4ad0

The use of superconducting (SC) materials is crucial for shielding quasi-static magnetic fields. However, the need for space-saving solutions with high shielding performance requires the development of a three-dimensional (3D) modelling procedure capable of predicting the screening properties for different orientations of the applied field. In this paper, we use a 3D numerical model based on a vector potential formulation to investigate the shielding ability of SC screens with cylindrical symmetry and a height/diameter aspect ratio close to unity, without and with the superimposition of a ferromagnetic (FM) circular shell. The chosen materials were MgB2 and soft iron. First, the outcomes of the calculations were compared with the experimental data obtained with different shielding arrangements, achieving a notable agreement in both axial field (AF) and transverse field (TF) orientations. Then, we used this validated modelling approach to investigate how the magnetic mitigation properties of a cup-shaped SC bulk can be improved by the superimposition of a coaxial FM cup. Calculations highlighted that the FM addition is very efficient in enhancing the shielding factors (SFs) in the TF orientation. Assuming a working temperature of 30 K and using a layout with the FM cup protruding over the SC one, SFs up to eight times greater than those with a single SC cup were attained at applied field up to 0.15 T, reaching values equal to or higher than 10(2) in the inner half of the shield. In the AF orientation, the addition of the same FM cup incurs a modest worsening at low fields, but at the same time it widens the applied field range where SF > 10(4) occurs near the close extremity of the shield to over 1 T.

356. Ferroelectric properties of ZrO2 films deposited on ITO-coated glass

Authors: Silva, JPB; Sekhar, KC; Negrea, RF; Ghica, C; Dastan, D; Gomes, MJM

Published: MAR 1 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2021.11.152

In this work, the ferroelectric characteristics of ZrO2 thin films grown on ITO-coated glass have been investigated. The ferroelectric nature of the ZrO2 films has been studied by polarization-electric field (P-E) hysteresis loops and found to be optimum for the films processed by rapid thermal annealing at 600 degrees C. The increase in the annealing temperature improves the ferroelectric properties through the increase of the in-plane strain that causes the formation of the ferroelectric orthorhombic phase. The formation of the orthorhombic phase was confirmed through high-resolution transmission electron microscopy. The effect of the electric field on the polarization switching kinetics of ZrO2 films has been investigated revealing that the switching kinetics follows the nucleation limited switching (NLS) model. The activation fields estimated from the peak values of the polarization currents (im) and the time (tm) at which im occurs are in good agreement with the values obtained from the switching characteristic time of the NLS model. This work paves the way towards the integration of (pseudo)binary oxide thin films on cheap substrates like glass for the next-generation of non-volatile memories.

Open Access

357. Band-Gap Engineering of Layered Perovskites by Cu Spacer Insertion as Photocatalysts for Depollution Reaction

Authors: Raciulete, M; Anastasescu, C; Papa, F; Atkinson, I; Bradu, C; Negrila, C; Eftemie, DI; Culita, DC; Miyazaki, A; Bratan, V; Pandele-Cusu, J; Munteanu, C; Dobrescu, G; Sandulescu, A; Balint, I

Published: DEC 2022, CATALYSTS, 12, 1529, DOI: 10.3390/catal12121529

A multi-step ion-exchange methodology was developed for the fabrication of Cu(LaTa2O7)(2) lamellar architectures capable of wastewater depollution. The (001) diffraction line of RbLaTa2O7 depended on the guest species hosted by the starting material. SEM and TEM images confirmed the well-preserved lamellar structure for all intercalated layered perovskites. The UV-Vis, XPS, and photocurrent spectroscopies proved that Cu intercalation induces a red-shift band gap compared to the perovskite host. Moreover, the UV-Vis spectroscopy elucidated the copper ions environment in the Cu-modified layered perovskites. H-2-TPR results confirmed that Cu species located on the surface are reduced at a lower temperature while those from the interlayer occur at higher temperature ranges. The photocatalytic degradation of phenol under simulated solar irradiation was used as a model reaction to assess the performances of the studied catalysts. Increased photocatalytic activity was observed for Cu-modified layered perovskites compared to RbLaTa2O7 pristine. This behavior resulted from the efficient separation of photogenerated charge carriers and light absorption induced by copper spacer insertion.

358. New superdielectric materials: (1-x) SrFe12O19 - x BNT-BT nanocomposites

Authors: Greculeasa, SG; Comanescu, C; Iacob, N; Kuncser, A; Smaranda, I; Amarande, L; Cioangher, M; Burdusel, M; Teodorescu, V

Published: OCT 1 2022, PHYSICA B-CONDENSED MATTER, 642, 414139, DOI: 10.1016/j.physb.2022.414139

Novel (1-x) SrFe12O19 - x BNT-BT0.08 (x = 0; 0.5; 0.8; 1) nanocomposites were explored in this study. The samples were produced by sol-gel method and compacted by conventional sintering. The composition, morphology, local structure, dielectric and magnetic properties were investigated by X-ray diffraction, Transmission Electron Microscopy, Impedance Analysis, Mossbauer spectroscopy, and SQUID magnetometry. The desired composition and the presence of the magnetoplumbite SrFe12O19 and perovskite BNT-BT structures were verified by X-ray diffraction. Irregular morphology and large size distributions are evidenced in the electron microscopy micrographs. The reported room temperature dielectric constants in this study are the highest values obtained in multiferroic composites at room temperature: giant dielectric constants (similar to 1.3 x 10(6)) were obtained, relative to 0.13 x 10(4) in BNT-BT. The hyperfine parameters allowed the identification of the Wyckoff positions of the Fe ions corresponding closely to the theoretical case. The hard magnetic character of the SrFe12O19 phase is evidenced from the magnetic measurements. For the first time in multifermic composites, superdielectric characteristics are evidenced at room temperature.

Open Access

359. Charge State Effects in Swift-Heavy-Ion-Irradiated Nanomaterials

Authors: Luketic, KT; Hanzek, J; Mihalcea, CG; Dubcek, P; Gajovic, A; Siketic, Z; Jaksic, M; Ghica, C; Karlusic, M

Published: JUN 2022, CRYSTALS, 12, 865, DOI: 10.3390/cryst12060865

The aim of this experimental work was to investigate the influence of the ion beam charge state on damage production in nanomaterials. To achieve this, we employed Raman spectroscopy, atomic force microscopy, and transmission electron microscopy to investigate nanomaterials irradiated by a 23 MeV I beam. We found a significant influence of the ion charge state on damage production in monolayer graphene, but found no evidence of this effect in bilayer and trilayer graphene, nor in graphite. Furthermore, we found no evidence of this effect in CaF2 and SiO2 nanocrystals irradiated with the same ion beam.

360. Structural properties and near-infrared light from Ce³⁺/Nd³⁺-co-doped LaPO4 nanophosphors for solar cell applications

Authors: AitMellal, O; Oufni, L; Messous, MY; Tahri, M; Neatu, S; Florea, M; Neatu, F; Secu, M

Published: MAR 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 33, DOI: 10.1007/s10854-021-07615-6

To enhance the spectral response of solar cells, an experimental study on LaPO4:0.01Ce(3+)/xNd(3+) (x = 0, 2, 4 mol%) was carried out, where structural and morphological properties of the prepared samples were well characterized by the means of X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electronic microscope. Additionally, the photoluminescence behavior of phosphors in ultraviolet-visible (UV-VIS) and Near-infrared (NIR) regions were investigated to confirm the energy transfer (ET) from Ce3+ to Nd3+. Moreover, the quantum efficiency of Ce3+/Nd3+-co-doped samples was estimated as high as similar to 172% and the possible ET process was described. Accordingly, the LaPO4:Ce3+/Nd3+ phosphors can convert the UV light (275 nm) into NIR photons (approx. 1059 nm) through the possible two-pathway energy transfer processes from Ce3+ sensitizer ions to Nd3+ activators. Obtained NIR down-conversion emissions are suitable for improving the conversion efficiency of c-Si solar cells.

Open Access

361. C-doped TiO2 nanotubes with pulsed laser deposited Bi2O3 films for photovoltaic application

Authors: Bjelajac, A; Petrovic, R; Stan, GE; Socol, G; Mihailescu, A; Mihailescu, IN; Veltruska, K; Matolin, V; Siketic, Z; Provatas, G; Jaksic, M; Janackovic, D

Published: FEB 15 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2021.10.251

Anodization was used to obtain a nanotubular TiO2 photoanode on F-SnO2 glass. Subsequent annealing in the CH4 atmosphere promoted the C-doping and improved the crystallinity of the TiO2 nanotubes. The pulsed laser deposition was applied to cover the nanotubes with Bi2O3, serving as a hole transport material. X-ray photoelectron spectroscopy analyses of the doped samples reveal a shift in the valence band's maximum position towards lower binding energy as compared to those observed for the undoped samples (annealed in the air). The doping positively affects the absorption by shifting the absorption edge to 567 nm. I-V measurements under illumination show that the C-doping of TiO2 increases the current density following the absorbance results. The highest open circuit voltage was reached for the samples with the 300 degrees C-deposited Bi2O3 layer, pointing to better quality of the p-n junction, hence of the contact between Bi2O3 and TiO2. This in situ annealing provided the formation of close contact between Bi2O3 and TiO2, which enabled a faster charge transport as compared to the contact obtained with no annealing or even with post annealing.

362. Effect of dopants on the optical properties of benzil crystals

Authors: Stanculescu, F; Socol, M; Rasoga, O; Preda, N; Ionita, I; Petre, G; Breazu, C; Stanculescu, A

Published: APR 15 2022, JOURNAL OF CRYSTAL GROWTH, 584, 126577, DOI: 10.1016/j.jcrysgro.2022.126577

Single-doped [Ag, Na, iodine, naphthalene (Naph), meta-dintrobenzene (m-DNB)] and double-doped, organic-inorganic (Naph + iodine; m-DNB + iodine) benzil (Bz) crystals have been grown from melt in a Bridgman-Stockbarger configuration. All crystals have been grown in the same experimental conditions, temperature variation at the growth interface = 30 K and moving speed of the growth ampoule = 1 mm/h. These conditions have been estimated from the theoretical analysis involving the solution of the classical (conventional) Stefan problem for flat solid-liquid interface in the boundary conditions imposed by our growth system. The effect of doping on the disorder degree, photoluminescence and dielectric constant of the Bz matrix has been investigated. The disorder in the crystals increased with the increase of dopant concentration. The highest disorder was induced by the organic dopant m-DNB, whose molecules does not show an adequate geometrical similarity with Bz molecules. The position of the photoluminescence peak, both at excitation with 335 nm and 435 nm, has not been affected by the presence of dopant(s). All doped samples show Second Harmonic Generation, even those with a significant degree of disorder. The effect of the single and double-doping on the second-order ONL co-efficient was analyzed by comparison with the second-order ONL coefficient of pure Bz crystals. In the case of the double-doping, the highest second-order optical nonlinear coefficient has been evidenced in the Bz crystals simultaneously doped with m-DNB and iodine in the same concentration (1%).

363. Monodispersed nanoplatelets of samarium oxides for biosensing applications in biological fluids

Authors: Leote, RJB; Matei, E; Apostol, NG; Enculescu, M; Enculescu, I; Diculescu, VC

Published: JAN 10 2022, ELECTROCHIMICA ACTA, 402, 139532, DOI: 10.1016/j.electacta.2021.139532

A nanostructured samarium oxide electrode was constructed by electrodeposition onto the surface of a gold electrode on SiO2/Si wafer. The samarium oxides electrode's surface morphology was investigated by scanning electron microcopy showing a quasi-monodispersed nanoplatelets like structure. X-rays diffraction analysis demonstrated a mixture of monoclinic and hexagonal phases while the X-rays photoelectron spectroscopy indicated the co-existence of both Sm2+ and Sm3+ species in a 1:3 proportion. Cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the charge transfer processes at the surface of the samarium oxide electrode in the absence and in the presence of redox probes. A roughness factor of 2.5 was determined from the samarium oxide electrode while the charge transfer constant was almost double when compared to the planar gold electrode. Then, the samarium oxide electrode was used for the H2O2 detection by fixed potential amperometry at -0.20 V (vs. Ag/AgCl) with a linear region between 0.01 and 1.00 mM, a sensitivity of 153 mu A cm(-2) mM(-1) and a LoD = 2.70 mu M. Glucose oxidase was used as a model enzyme in order to test the capacity of the samarium oxides electrode for biosensing. The enzyme was immobilized by physical adsorption and the optimum conditions for glucose analysis investigated. The biosensor showed a linear range for glucose detection between 0.10 and 1.20 mM with a sensitivity of 8.40 mu A cm(-2) mM(-1) and a LoD = 8.00 mu M. Selectivity was tested toward common interfering species, and the results revealed the lack of biosensor response. The glucose biosensor on samarium oxides was tested for glucose detection in serum samples with a recovery factor of 90%, and the result validated with a commercial glucometer. (C) 2021 Elsevier Ltd. All rights reserved.

Open Access

364. Surface, Structural, and Mechanical Properties Enhancement of Cr2O3 and SiO2 Co-Deposited Coatings with W or Be

Authors: Lungu, M; Cristea, D; Baiasu, F; Staicu, C; Marin, A; Pompilian, OG; Butoi, B; Locovei, C; Porosnicu, C

Published: AUG 2022, NANOMATERIALS, 12, 2870, DOI: 10.3390/nano12162870

Direct current (DC) and radio frequency (RF) magnetron sputtering methods were selected for conducting the deposition of structural materials, namely ceramic and metallic co-depositions. A total of six configurations were deposited: single thin layers of oxides (Cr2O3, SiO2) and co-deposition configurations (50:50 wt.%) as structural materials (W, Be)-(Cr2O3, SiO2), all deposited on 304L stainless steel (SS). A comprehensive evaluation such as surface topology, thermal desorption outgassing, and structural/chemical state was performed. Moreover, mechanical characterization evaluating properties such as adherence, nano indentation hardness, indentation modulus, and deformation relative to yielding, was performed. Experimental results show that, contrary to SiO2 matrix, the composite layers of Cr2O3 with Be and W exhibit surface smoothing with mitigation of artifacts, thus presenting a uniform and compact state with the best microstructure. These results are relevant in order to develop future dense coatings to be used in the fusion domain.

365. Asymmetric microstrip line feed multimode cylindrical dielectric resonator antenna

Authors: Avadanei, OG; Banciu, MG; Nedelcu, L; Avadanei, M

Published: JUL-AUG 2022, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 24, DOI:

The aim of this work is the development of a cylindrical dielectric resonator antenna with multimodal operation. In order to use modes with different radiation patterns, the field distributions were investigated. Using a feeding solution with the resonator placed asymmetrically above a wide microstrip feeding line, we managed to excite and identify 17 operating modes in the 1.8-4.5 GHz frequency band. In dissimilarity with the symmetric configuration, the proposed feeding allows excitation of new modes, which exhibit a magnetic dipole radiation pattern. The new added modes enhance the antenna pattern diversity and increase the antenna capacity to mitigate the multipath effects.

366. Evaluation of quinoxaline-2(1H)-one, derivatives as corrosion inhibitors for mild steel in 1.0 M acidic media: Electrochemistry, quantum calculations, dynamic simulations, and surface analysis

Authors: Ech-chebab, A; Missioui, M; Guo, L; El Khouja, O; Lachhab, R; Kharbouch, O; Galai, M; Ouakki, M; Ejbouh, A; Dahmani, K; Dkhireche, N; Touhami, ME

Published: DEC 16 2022, CHEMICAL PHYSICS LETTERS, 809, 140156, DOI: 10.1016/j.cplett.2022.140156

The evaluation of corrosion inhibition of mild steel (M-S) in 1.0 M HCl solution in the absence and the presence of different concentrations of (E)-3-(5-bromo-2-hydroxystyryl)quinoxalin-2(1H)-one (FR178) and (E)-3-(5-fluoro-2-hydroxystyryl)quinoxalin-2(1H)-one (FR179) was studied by electrochemical,and theoretical measurements. These organic inhibitors have proven to be effective corrosion inhibitors for the protection of mild steel. Increasing concentrations of inhibitors contributed to high inhibition efficiencies, which were attributed to the simple blocking action of the anodic and cathodic sites by adsorption of the inhibitors molecules onto the M-S surface. Their inhibition efficiencies can reach about 90.9 % and 91.5 % when the optimal concentration is 10-3M for the two inhibitors FR178 and FR179 respectively.On the other hand, as the temperature rises, the anticorrosion capability of both FR178 and FR179 diminishes slightly and attains 82 % and 84 % respectively at the temperature of 328 K.Potentiodynamique polarization (PDP) and electrochemical impedance spectroscopy (EIS) demonstrated that both inhibitors examined act as mixed-type inhibitors.Furthermore, X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectroscopy (SEM/EDS) measurements indicated the formation of a protective layer adsorbed on the mild steel surface. The density functional theory (DFT) and molecular dynamics (MD) simulations were carried out to examine the correlation between molecular and chemical reactivity. The obtained results were found to be consistent with the experimental findings.

Open Access

367. Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers

Authors: Bucuresteanu, R; Ionita, M; Chihaia, V; Ficai, A; Trusca, RD; Ilie, CI; Kuncser, A; Holban, AM; Mihaescu, G; Petcu, G; Nicolaev, A; Costescu, RM; Husch, M; Parvulescu, V; Ditu, LM

Published: JUL 2022, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 23, 6888, DOI: 10.3390/ijms23136888

The ability of TiO2 to generate reactive oxygen species under UV radiation makes it an efficient candidate in antimicrobial studies. In this context, the preparation of TiO2 microparticles coated with Ca- and Cu-based composite layers over which Cu(II), Cu(I), and Cu(0) species were identified is presented here. The obtained materials were characterized by a wide range of analytical methods, such as X-ray diffraction, electron microscopy (TEM, SEM), X-ray photoelectron (XPS), and UV-VIS spectroscopy. The antimicrobial efficiency was evaluated using qualitative and quantitative standard methods and standard clinical microbial strains. A significant aspect of this composite is that the antimicrobial properties were evidenced both in the presence and absence of the light, as result of competition between photo and electrical effects. However, the antibacterial effect was similar in darkness and light for all samples. Because no photocatalytic properties were found in the absence of copper, the results sustain the antibacterial effect of the electric field (generated by the electrostatic potential of the composite layer) both under the dark and in light conditions. In this way, the composite layers supported on the TiO2 microparticles' surface can offer continuous antibacterial protection and do not require the presence of a permanent light source for activation. However, the antimicrobial effect in the dark is more significant and is considered to be the result of the electric field effect generated on the composite layer.

Open Access

368. Memory Properties of Zr-Doped ZrO2 MOS-like Capacitor

Authors: Palade, C; Slav, A; Stavarache, I; Maraloiu, VA; Negrila, C; Ciurea, ML

Published: SEP 2022, COATINGS, 12, 1369, DOI: 10.3390/coatings12091369

The high-k-based MOS-like capacitors are a promising approach for the domain of non-volatile memory devices, which currently is limited by SiO2 technology and cannot face the rapid downsizing of the electronic device trend. In this paper, we prepare MOS-like trilayer memory structures based on high-k ZrO2 by magnetron sputtering, with a 5% and a 10% concentrations of Zr in the Zr-ZrO2 floating gate layer. For crystallization of the memory structure, rapid thermal annealing at different temperatures between 500 degrees C and 700 degrees C was performed. Additionally, Al electrodes were deposited in a top-down configuration. High-resolution transmission electron microscopy reveals that ZrO2 has a polycrystalline-columnar crystallization and a tetragonal crystalline structure, which was confirmed by X-ray diffraction measurements. It is shown that the tetragonal phase is stabilized during the crystallization by the fast diffusion of oxygen atoms. The capacitance-voltage characteristics show that the widest memory window (Delta V = 2.23 V) was obtained for samples with 10% Zr annealed at 700 degrees C for 4 min. The charge retention characteristics show a capacitance decrease of 36% after 10 years.

Open Access

369. Direct and remote induced actuation in artificial muscles based on electrospun fiber networks

Authors: Bunea, MC; Beregoi, M; Evanghelidis, A; Galatanu, A; Enculescu, I

Published: JUL 29 2022, SCIENTIFIC REPORTS, 12, 13084, DOI: 10.1038/s41598-022-16872-2

The present work reports a new configuration of soft artificial muscle based on a web of metal covered nylon 6/6 micrometric fibers attached to a thin polydimethylsiloxane (PDMS) film. The preparation process is simple and implies the attachment of metalized fiber networks to a PDMS sheet substrate while heating and applying compression. The resulting composite is versatile and can be cut in different shapes as a function of the application sought. When an electric current passes through the metallic web, heat is produced, leading to local dilatation and to subsequent controlled deformation. Because of this, the artificial muscle displays a fast and ample movement (maximum displacement of 0.8 cm) when applying a relatively low voltage (2.2 V), a consequence of the contrast between the thermal expanse coefficients of the PDMS substrate and of the web-like electrode. It was shown that the electrical current producing this effect can originate from both direct electric contacts, and untethered configurations i.e. radio frequency induced. Usually, for thermal activated actuators the heating is produced by using metallic films or conductive carbon-based materials, while here a fast heating/cooling process is obtained by using microfiber-based heaters. This new approach for untethered devices is an interesting path to follow, opening a wide range of applications were autonomous actuation and remote transfer of energy are needed.

370. The effect of noble metal addition on the properties of oxide semiconductors nanoparticles

Authors: Goncearenco, E; Morjan, IP; Dutu, E; Scarisoreanu, M; Fleaca, C; Gavrila-Florescu, L; Dumitrache, F; Banici, AM; Teodorescu, VS; Anastasescu, C; Sandulescu, A; Balint,

Published: MAR 2022, JOURNAL OF SOLID STATE CHEMISTRY, 307, 122817, DOI: 10.1016/j.jssc.2021.122817

This work presents the preparation of W and V co-doped TiO2 nanoparticles (W:TiO2 and W:V:TiO2) using laser pyrolysis technique subsequently modified with noble metals Pt or Pd using chemical impregnation method. By using well defined TiO2 nanoparticles, the enhancement of catalytic activity is expected mainly due to their higher surface area and density defects relative to bulk material. Structural, morphological and optical properties of the as-obtained nanopowders have been characterized by transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, UV-VIS diffuse reflectance spectroscopy and photoluminescence techniques. The phase composition analysis reveals the preponderance of anatase (95%) in addition to ruffle phase, its particle average size ranging from 25 to 30 nm. The TiO 2 based nanomaterials were supplementary modified by noble metals deposition (Pt particles with dimensions of 3-4 nm and spherical Pd crystallites with a diameter between 3 and 9 nm) and their photocatalytic activity was tested in oxidative photo degradation of CH3OH, under simulated solar light. The metal modified samples displayed higher specific surface areas (3-6 times) and improved photocatalytic properties, the W:V:TiO2@Pt material showing better conversion efficiency of CH3OH to CH2O than the reference Degussa P25 sample (1.54 versus 0.90%).

Open Access

371. Physicochemical and Biological Evaluation of Chitosan-Coated Magnesium-Doped Hydroxyapatite Composite Layers Obtained by Vacuum Deposition

Authors: Predoi, D; Ciobanu, CS; Iconaru, SL; Raaen, S; Badea, ML; Rokosz, K

Published: MAY 2022, COATINGS, 12, 702, DOI: 10.3390/coatings12050702

In the present work, the effectiveness of vacuum deposition technique for obtaining composite thin films based on chitosan-coated magnesium-doped hydroxyapatite Ca10-xMgx(PO4)(6) (OH)(2) with x(Mg) = 0.025 (MgHApCh) was proved for the first time. The prepared samples were exposed to three doses (0, 3, and 6 Gy) of gamma irradiation. The MgHApCh composite thin films nonirradiated and irradiated were evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies. The biological evaluation of the samples was also presented. All the results obtained from this study showed that the vacuum deposition method allowed for obtaining uniform and homogeneous layers. Fine cracks were observed on the MgHApCh composite thin films' surface after exposure to a 6 Gy irradiation dose. Additionally, after gamma irradiation, a decrease in Ca, P, and Mg content was noticed. The MgHApCh composite thin films with doses of 0 and 3 Gy of gamma irradiation showed a cellular viability similar to that of the control. Samples with 6 Gy doses of gamma irradiation did not cause significantly higher fibroblast cell death than the control (p > 0.05). On the other hand, the homogeneous distribution of pores that appeared on the surface of coatings after 6 Gy doses of gamma irradiation did not prevent the adhesion of fibroblast cells and their spread on the coatings. In conclusion, we could say that the thin films could be suitable both for use in bone implants and for other orthopedic and dentistry applications.

372. BaTiO3 nanocubes-Gelatin composites for piezoelectric harvesting: Modeling and experimental study

Authors: Ciomaga, CE; Horchidan, N; Padurariu, L; Stirbu, RS; Tiron, V; Tufescu, FM; Topala, I; Condurache, O; Botea, M; Pintilie, I; Pintilie, L; Rotaru, A; Caruntu, G; Mitoseriu, L

Published: SEP 15 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2022.05.264

Flexible composites containing BaTiO3 nanoparticles into Gelatin bio-polymer matrix were designed and investigated. Following the idea that the electric field concentration in corners/edges at the interfaces between dissimilar materials give rise to enhanced effective permittivity in composites, cuboid-like BaTiO3 nanoparticles have been employed as nanofillers into Gelatin matrix by using an inexpensive solution-based processing method. As predicted by finite element method simulations developed for cubic-like inclusions into a homogeneous polymer matrix, the experimental permittivity of xBT-(1-x)Gelatin composites increases when increasing the high-permittivity filler addition. For the composition x = 40 wt% (corresponding to 12 vol% BaTiO3 addition), permittivity reaches epsilon r -15.7 with respect to epsilon r -9.8 of pure Gelatine (measured at 105 Hz), while the average piezoelectric coefficient d33 as determined by piezoelectric force microscopy shows a remarkable increase up to 21 pm/V in composites with x = 40 wt%, in comparison to -7 pm/V in pure Gelatin. By using the experimentally determined material constants, the simulated piezoelectric voltage output vs. time has shown a similar increase (about a doubling of its amplitude) of the harvesting signal in the composite with x = 40 wt% BT, with respect to one of the polymer matrix, thus demonstrating the beneficial role of embedding BT nanoparticles into the biopolymer for increasing the mechanical harvesting response.

373. MICROSTRUCTURE, MAGNETIC AND MAGNETOSTRICTIVE BEHAVIOUR IN RAPIDLY QUENCHED OFF-STOICHIOMETRIC Ni-Mn-Ga FERROMAGNETIC SHAPE MEMORY ALLOYS

Authors: Sofronie, M; Tolea, F; Enculescu, M; Pasuk, I; Popescu, B

Published: 2022, ROMANIAN REPORTS IN PHYSICS, 74, 503, DOI:

This work reports the effect of the rapid solidification technique and thermal treatment on the martensitic transformation (MT), magnetic and magnetostrictive properties on the off-stoichiometric Ni49Mn31Ga20 and Ni51Mn28Ga21 ferromagnetic shape memory ribbons. The samples were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, magnetic and magnetostrictive measurements. The temperature dependence of the X-ray phases analysis shows the presence of martensite structures, both tetragonal and monoclinic, at room temperature and allowed to study their evolution through MT. The thermal treatment induces changes in the microstructure with implications in MT and Curie temperatures evolution. The competition between the magnetization orientation and twin boundary motion within martensitic variants under magnetic field evidenced in the magnetic-strain curves was discussed and correlated with the magnetic data.

Open Access

374. Robust Electronic Structure of Manganite-Buffered Oxide Interfaces with Extreme Mobility Enhancement

Authors: Li, H; Gan, YL; Husanu, MA; Dahm, RT; Christensen, DV; Radovic, M; Sun, JR; Shi, M; Shen, BG; Pryds, N; Chen, YZ

Published: APR 26 2022, ACS NANO, 16, DOI: 10.1021/acsnano.2c00609

The electronic structure as well as the mechanism underlying the high-mobility two-dimensional electron gases (2DEGs) at complex oxide interfaces remain elusive. Herein, using soft X-ray angle-resolved photoemission spectroscopy (ARPES), we present the band dispersion of metallic states at buffered LaAlO3/SrTiO3 (LAO/STO) heterointerfaces where a single-unit-cell LaMnO3 (LMO) spacer not only enhances the electron mobility but also renders the electronic structure robust toward X-ray radiation. By tracing the evolution of band dispersion, orbital occupation, and electron-phonon interaction of the interfacial 2DEG, we find unambiguous evidence that the insertion of the LMO buffer strongly suppresses both the formation of oxygen vacancies as well as the electron-phonon interaction on the STO side. The latter effect makes the buffered sample different from any other STO-based interfaces and may explain the maximum mobility enhancement achieved at buffered oxide interfaces.

Open Access

375. Novel Antitumor Agents Based on Fluorescent Benzofurazan Derivatives and Mesoporous Silica

Authors: Tudose, M; Culita, DC; Baratoiu-Carpen, RD; Mitran, RA; Kuncser, A; Romanitan, C; Popescu, RC; Savu, DI

Published: DEC 2022, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 23, 15663, DOI: 10.3390/ijms232415663

Two novel fluorescent mesoporous silica-based hybrid materials were obtained through the covalent grafting of [4-hydrazinyl-7-nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and N-1-(7-nitrobenzo[c][1,2,5]-oxadiazol-4-yl) benzene-1,2-diamine (NBD-PD), respectively, inside the channels of mesoporous silica SBA-15. The presence of fluorescent organic compounds (nitrobenzofurazan derivatives) was confirmed by infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermal analysis (TG), and fluorescence spectroscopy. The nitrogen physisorption analysis showed that the nitrobenzofurazan derivatives were distributed uniformly on the internal surface of SBA-15, the immobilization process having a negligible effect on the structure of the support. Their antioxidant activity was studied by measuring the ability to reduce free radicals DPPH (free radical scavenging activity), in order to formulate potential applications of the materials obtained. Cytotoxicity of the newly synthesized materials, SBA-NBDH and SBA-NBD-PD, was evaluated on human B16 melanoma cells. The morphology of these cells, internalization and localization of the investigated materials in melanoma and fibroblast cells were examined through fluorescence imaging. The viability of B16 (3D) spheroids after treatment with SBA-NBDH and SBA-NBD-PD was evaluated using MTS assay. The results showed that both materials induced a selective antiproliferative effect, reducing to various degrees the viability of melanoma cells. The observed effect was enhanced with increasing concentration. SBA-NBD-PD exhibited a higher antitumor effect compared to SBA-NBDH starting with a concentration of 125 mu g/mL. In both cases, a significantly more pronounced antiproliferative effect on tumor cells compared to normal cells was observed. The viability of B16 spheroids dropped by 40% after treatment with SBA-NBDH and SBA-NBD-PD at 500 mu g/mL concentration, indicating a clear cytotoxic effect of the tested compounds. These results suggest that both newly synthesized biomaterials could be promising antitumor agents for applications in cancer therapy.

Open Access

376. PC-12 Cell Line as a Neuronal Cell Model for Biosensing Applications

Authors: Oprea, D; Sanz, CG; Barsan, MM; Enache, TA

Published: JUL 2022, BIOSENSORS-BASEL, 12, 500, DOI: 10.3390/bios12070500

PC-12 cells have been widely used as a neuronal line study model in many biosensing devices, mainly due to the neurogenic characteristics acquired after differentiation, such as high level of secreted neurotransmitter, neuron morphology characterized by neurite outgrowth, and expression of ion and neurotransmitter receptors. For understanding the pathophysiology processes involved in brain disorders, PC-12 cell line is extensively assessed in neuroscience research, including studies on neurotoxicity, neuroprotection, or neurosecretion. Various analytical technologies have been developed to investigate physicochemical processes and the biosensors based on optical and electrochemical techniques, among others, have been at the forefront of this development. This article summarizes the application of different biosensors in PC-12 cell cultures and presents the modern approaches employed in neuronal networks biosensing.

377. ZnS stacking order influence on the formation of Zn-poor and Zn-rich Cu2ZnSnS4 phase

Authors: Zaki, MY; El Khouja, O; Nouneh, K; Touhami, ME; Matei, E; Azmi, S; Rusu, MI; Grigorescu, CEA; Briche, S; Boutamart, M; Badica, P; Burdusel, M; Secu, M; Pintilie, L; Galca, AC

Published: MAY 2022, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 33, DOI: 10.1007/s10854-022-08160-6

This paper reports the synthesis and characterization of Cu2ZnSnS4 (CZTS) absorber films, prepared by a two-step electrodeposition of a ZnS (zinc sulfide) binary and a CZT (copper, zinc and tin) ternary precursors on Mo/Ti/Si substrates. The as-electrodeposited ZnS/CZT and CZT/ZnS stacks were thermally treated in a tubular furnace in sulfur environment at 550 degrees C. The role of the ZnS buffer layer is to provide a zinc and sulfur reservoir, needed to complete the formation of kesterite phase. X-ray diffraction and Raman analyses revealed the formation of the CZTS phase. The surface morphology and chemical composition of the films were studied using a scanning electron microscope. The bandgap values inferred from diffuse reflectance data, are discussed with respect to the stoichiometry which is considerably affected by the order of the stacks. Room-temperature photoluminescence of the CZT/ZnS sample showed a board PL band of 1.51 eV. It was found that the film with a ZnS layer on top is preferred for the formation of a Zn-rich single CZTS phase.

Open Access

378. Comparative characterization study of LYSO:Ce crystals for timing applications

Authors: Addesa, FM; Barria, P; Bianco, R; Campana, M; Cavallari, F; Cemmi, A; Cipriani, M; Dafinei, I; D'Orsi, B; del Re, D; Diemoz, M; D'Imperio, G; Di Marco, E; Di Sarcina, I; Enculescu, M; Longo, E; Lucchini, MT; Marchegiani, F; Meridiani, P; Nisi, S; Organtini, G; Pandolfi, F; Paramatti, R; Pettinacci, V; Quaranta, C; Rahatlou, S; Rovelli, C; Santanastasio, F; Soffi, L; Tramontano, R; Tully, CG

Published: AUG 2022, JOURNAL OF INSTRUMENTATION, 17, P08028, DOI: 10.1088/1748-0221/17/08/P08028

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce) is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce ([Lu((1-x))Y-x](2)SiO5 : Ce) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers. The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

Open Access

379. Mud and burnt Roman bricks from Romula

Authors: Badica, P; Alexandru-Dinu, A; Grigoroscuta, MA; Burdusel, M; Aldica, GV; Sandu, V; Bartha, C; Polosan, S; Galatanu, A; Kuncser, V; Enculescu, M; Locovei, C; Porosnicu, I; Tiseanu, I; Ferbinteanu, M; Savulescu, I; Negru, M; Batalu, ND

Published: SEP 23 2022, SCIENTIFIC REPORTS, 12, 15864, DOI: 10.1038/s41598-022-19427-7

Sesquipedalian mud and burnt bricks (second to third century AD) were excavated from the Roman city of Romula located in the Lower Danube Region (Olt county, Romania). Along with local soils, bricks are investigated by petrographic analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), electron microscopy (SEM/EDX), X-ray microtomography (XRT), thermal analysis (DTA-TG), M.ssbauer spectroscopy, magnetometry, colorimetry, and mechanical properties assessment. The results correlate well with each other, being useful for conservation/restoration purposes and as reference data for other ceramic materials. Remarkably, our analysis and comparison with literature data indicate possible control and wise optimization by the ancient brickmakers through the recipe, design (size, shape, and micro/ macrostructure), and technology of the desired physical-chemical-mechanical properties. We discuss the Roman bricks as materials that can adapt to external factors, similar, to some extent, to modern "smart" or "intelligent" materials. These features can explain their outstanding durability to changes of weather/climate and mechanical load.

380. Electrochemical quantification of levothyroxine at disposable screen-printed electrodes

Authors: David, M; Serban, A; Enache, TA; Florescu, M

Published: APR 15 2022, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 911, 116240, DOI: 10.1016/j.jelechem.2022.116240

The concentration of thyroxine hormone is linked to a large variety of medical conditions, where the best therapy is hormone substitution, through administration of levothyroxine (LT4) medication. Herewith, the detection of these biomolecules still lacks a simple, reliable tool, such as label-free sensors.In this work, the performances of commercial screen-printed carbon electrodes, containing different nanostructured materials (carbon nanotubes, graphene, and gold nanoparticles), used as sensors for LT4 detection, were described and compared. Electrochemical methods were used for the characterization of the nanostructure-based sensors. Several optimization steps were undertaken to achieve optimum performances for selective LT4 quantification. The redox behaviour of LT4 at sensors surface together with the interfacial changes, which occur due to the interaction between nanostructures and LT4, were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) was used for LT4 detection, where best performances were obtained in the presence of carbon nanotubes, with a detection limit of 30 nM.

381. Pyruvate Oxidase Biosensors Based on Glassy Carbon Electrodes Modified with Carbon Nanotubes and Poly(Neutral Red) Synthesized in Ethaline Deep Eutectic Solvent

Authors: Leote, RJB; Ghica, ME; Brett, CMA

Published: APR 2022, ELECTROANALYSIS, 34, DOI: 10.1002/elan.202100164

A novel nanostructured platform for pyruvate oxidase biosensors comprises poly(neutral red) (PNR) prepared by electropolymerization of NR in ethaline deep eutectic solvent (DES) with acid dopant, on a multiwalled carbon nanotubes (MWCNT) modified glassy carbon electrode (GCE). Characterization was by cyclic voltammetry and electrochemical impedance spectroscopy and morphology was examined by scanning electron microscopy. Ascorbate and H2O2 gave a better response at PNRDES/GCE than at PNRaq/GCE. Biosensors for pyruvate and phosphate, immobilizing pyruvate oxidase onto PNRDES/MWCNT/GCE enabled selective determination of pyruvate and phosphate, with micromolar limits of detection. Pyruvate was determined in onion samples and phosphate in water samples.

Open Access

382. Evidence of Counterion Size Effect on the Stability of Columnar Phase of Ionic Liquid Crystals Based on Pyridinium Salts Derived from N-3,4,5-Tri(alkyloxy)-benzyl-4-pyridones

Authors: Dumitru, I; Chiriac, FL; Ilis, M; Pasuk, I; Manaila-Maximean, D; Micutz, M; Staicu, T; Cîrcu, V

Published: MAY 2022, CRYSTALS, 12, 715, DOI: 10.3390/cryst12050715

The synthesis and characterization of novel ionic liquid crystals based on pyridinium salts with Br- and PF6- counterions are described in this work. These pyridinium salts were derived from 4-hydroxypyridine, both by N- and O-alkylation. The 3,4,5-tri(alkyloxy)-benzyl mesogenic unit was attached to the nitrogen atom of the pyridinium ring. Alkyl chains with a different number of carbon atoms (6, 8, 10, 12 and 14) were employed in order to show the effect on the stability of mesophase. The POM (polarizing optical microscopy) and XRD (powder X-ray diffraction) studies indicated that bromide salts with shorter chains C-6, C-8 and C-10 do not show mesomorphic properties, while longer chain analogues with C-12 and C-14 exhibit two enantiotropic columnar phases. Surprisingly, the pyridinium salts with the larger size PF6- counterion do not exhibit liquid crystal properties.

Open Access

383. Multifunctional Zn-Doped ITO Sol-Gel Films Deposited on Different Substrates: Application as CO2-Sensing Material

Authors: Gartner, M; Anastasescu, M; Calderon-Moreno, JM; Nicolescu, M; Stroescu, H; Hornoiu, C; Preda, S; Predoana, L; Mitrea, D; Covei, M; Maraloiu, VA; Teodorescu, VS; Moldovan, C; Petrik, P; Zaharescu, M

Published: SEP 2022, NANOMATERIALS, 12, 3244, DOI: 10.3390/nano12183244

Undoped and Zn-doped ITO (ITO:Zn) multifunctional thin films were successfully synthesized using the sol-gel and dipping method on three different types of substrates (glass, SiO2/glass, and Si). The effect of Zn doping on the optoelectronic, microstructural, and gas-sensing properties of the films was investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), spectroscopic ellipsometry (SE), Raman spectroscopy, Hall effect measurements (HE), and gas testing. The results showed that the optical constants, the transmission, and the carrier numbers were correlated with the substrate type and with the microstructure and the thickness of the films. The Raman study showed the formation of ITO films and the incorporation of Zn in the doped film (ITO:Zn), which was confirmed by EDX analysis. The potential use of the multifunctional sol-gel ITO and ITO:Zn thin films was proven for TCO applications or gas-sensing experiments toward CO2. The Nyquist plots and equivalent circuit for fitting the experimental data were provided. The best electrical response of the sensor in CO2 atmosphere was found at 150 degrees C, with activation energy of around 0.31 eV.

384. Metallized electrospun polymeric fibers for electrochemical sensors and actuators

Authors: Leote, RJB; Beregoi, M; Enculescu, I; Diculescu, VC

Published: AUG 2022, CURRENT OPINION IN ELECTROCHEMISTRY, 34, 101024, DOI: 10.1016/j.coelec.2022.101024

Electrospun polymeric fibers present an emerging alternative for the development of flexible electronics, enabling applications in wearable sensors and biosensors for continuous monitoring, and actuators for tissue engineering. The possibility to prepare sub-micrometric polymeric scaffolds, their processing for increasing the conductivity, their modification with different materials, conductive polymers and biomolecules in order to obtain functional flexible electrodes, allows the development of innovative devices for healthcare, and biomedical applications. In this review, the impact of metallized electrospun polymeric fibers in electrochemical (bio)sensors and actuators is discussed. A relation between their structure and functionality is provided, alongside with an overview of the different methods to obtain functional conductive fibers.

385. Effect of chlorine and bromine on the perovskite crystal growth in mesoscopic heterojunction photovoltaic device

Authors: Mehdi, H; Leonat, LN; Stancu, V; Saidi, H; Enculescu, M; Tomulescu, AG; Toma, V; Pintilie, I; Bouazizi, A; Galca, AC

Published: JUN 1 2022, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 143, 106558, DOI: 10.1016/j.mssp.2022.106558

Organic-inorganic hybrid perovskite solar cells are within the emerging photovoltaic technologies. The combination of different halogen ions, in certain fill fractions, is one of the methods to improve the perovskite film properties. Herein, fabrication and characterization of perovskite cells in standard mesoscopic architecture using one-step deposition method has been done. The role of the halogen ions (Chlorine or Bromine) on crystal structure growth and photoelectric performance has been investigated. X-ray diffraction, scanning electron microscopy, atomic force microscopy and optical microscopy analysis were performed. The microstructure, composition and morphology of CH3NH3PbI1.8Br1.2 and CH3NH3PbI1.8Cl1.2 films are dissimilar, although identical fabrication method was used. Same holds for optical properties, band gap energies of 1.84 eV and 1.63 eV, respectively, being obtained. Integrated in solar cells, the maximum power conversion efficiency of the Br based devices is beyond 10%, while for those based on Cl, the efficiency drops around 5%.

Open Access

386. Capacitive and Inductive Effects in Perovskite Solar Cells: The Different Roles of Ionic Current and Ionic Charge Accumulation

Authors: Filipoiu, N; Preda, AT; Anghel, DV; Patru, R; Brophy, RE; Kateb, M; Besleaga, C; Tomulescu, AG; Pintilie, I; Manolescu, A; Nemnes, GA

Published: DEC 28 2022, PHYSICAL REVIEW APPLIED, 18, 064087, DOI: 10.1103/PhysRevApplied.18.064087

Dynamic hysteresis effects have been long known to occur in the current density-voltage characteristics of perovskite solar cells, with the ionic migration being identified as the primary factor. The hysteretic effects impacted early studies by the uncertainty in the evaluation of the power conversion efficiency, while currently, potential links to degradation mechanisms are the focus. Therefore, understanding ion migration is a central goal, typically addressed by performing a combined large and small signal analysis. The reported large capacitive and inductive effects created controversies with respect to the underlying mechanisms, yielding essentially two classes of models, one based on the large accumulation capacitances and the other based on the ionic modulation of the collected current. We introduce here an equivalent circuit model and interpret these phenomena in terms of recombination current modulation, identifying the distinct contributions from ion current and ionic charge accumulations. These contributions to the recombination current are associated with capacitive and inductive effects, respectively, and we corroborate the numerical simulations with electrochemical impedance spectroscopy measurements. These show the role of the recombination currents of photogenerated carriers in producing both capacitive and inductive effects as the illumination is varied. Moreover, we provide a bridging point between the two classes of models and suggest a framework of investigation of defect states based on the observed inductive behavior, which would further aid the mitigation of the degradation effects.

387. Disposable superoxide dismutase biosensors based on gold covered polycaprolactone fibers for the detection of superoxide in cell culture media

Authors: Sanz, CG; Onea, M; Aldea, A; Barsan, MM

Published: MAY 1 2022, TALANTA, 241, 123255, DOI: 10.1016/j.talanta.2022.123255

A novel and disposable biosensor based on superoxide dismutase (SOD) immobilized on gold metallized polycaprolactone electrospun polymeric fibers (PCl/Au) has been developed for the determination of superoxide (O-2(center dot-)) in cell culture media. SOD biosensors were constructed employing three immobilization methods: crosslinking with EDC/NHS at a cysteine self-assembled monolayer (PCl/Au/SODCYS), biopolymer encapsulation with chitosan (PCl/Au/SODCHI) and cross-linking with glutaraldehyde (PCl/Au/SODGA). Scanning electron microscopy was performed at the three different biosensors to evaluate their surface morphologies. Biosensors were employed for the electrochemical detection of superoxide by fixed potential amperometry at different applied potentials, with two distinct enzymatic mechanisms being proposed: i) the reduction of the enzymatically generated peroxide, at -0.3 V, for which the PCl/Au/SODCHI biosensor presented the highest value of sensitivity of 40.1 mu A mM(-1) cm(-2), and ii) the regeneration of the enzyme catalytic copper centre, at +0.3 V, for which the PCl/Au/SODCYS biosensor had the highest sensitivity value of 16.1 mu A mM(-1) cm(-2). The proposed recognition mechanisms were further confirmed by cyclic voltammetric measurements, which enabled also to determine the amount of immobilized electroactive SOD, with highest value corresponding to the PCl/Au/SODCYS biosensor. The biosensors with best analytical performance, PCl/Au/SODCYS and PCl/Au/SODCHI, were further investigated for stability and selectivity, with best results for the PCl/Au/SODCYS, chosen for superoxide monitoring in cell culture media. The study is promising for future application of PCl/Au/SODCYS for the on-line superoxide monitoring of superoxide in cell cultures, grown directly on the biosensor itself.

388. The inclusion of ceramic carbides dispersion in In and Yb filled CoSb3 and their effect on the thermoelectric performance

Authors: Popescu, B; Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 10 2022, JOURNAL OF ALLOYS AND COMPOUNDS, 893, 162400, DOI: 10.1016/j.jallcom.2021.162400

In this work, thermoelectric properties of the nanocomposite materials produced via ball milling followed by spark plasma sintering from In0.2Yb0.2Co4Sb12 double filled skutterudite (SKT) with silicon and tungsten carbide inclusions are investigated. The nanocomposites with low volume ratios of beta-SiC and '-WC have a significantly increased power factor, while the lattice thermal conductivity is lowered only for beta-SiC composites. The power factor enhancement in '-WC/SKT composite compensates the increase of its thermal conductivity, and as a consequence, the maximum value of the figure of merit, 0.97, is attained for 0.33 v% 'WC at 450 degrees C, with 15% higher than that of the simple skutterudite sample. (c) 2021 Elsevier B.V. All rights reserved.

Open Access

389. Soft Chemistry Synthesis and Characterization of CoFe1.8RE0.2O4 (RE³⁺ = Tb³⁺, Er³⁺) Ferrite

Authors: Gingasu, D; Mindru, I; Ianculescu, AC; Diamandescu, L; Surdu, VA; Marinescu, G; Bartha, C; Preda, S; Popa, M; Chifiriuc, MC

Published: FEB 2022, MAGNETOCHEMISTRY, 8, 12, DOI: 10.3390/magnetochemistry8020012

Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), Fourier transform infrared spectroscopy (FTIR), Mossbauer spectroscopy and magnetic measurements. The XRD results revealed that the average crystallite size is 5.77 nm for CoFe1.8Tb0.2O4 and 6.42 nm for CoFe1.8Er0.2O4. Distribution of metal cations in the spinel structure estimated from X-ray diffraction data showed that the Tb3+ and Er3+ ions occupy the octahedral sites. TEM images indicated the presence of polyhedral particles with average size 5.91 nm for CoFe1.8Tb0.2O4 and 6.80 nm for CoFe1.8Er0.2O4. Room temperature Mossbauer spectra exhibit typical nanoscaled cobalt ferrite spectra in good agreement with XRD and TEM data. The saturation magnetization value (M-s) is 60 emu/g for CoFe1.8Tb0.2O4 and 80 emu/g for CoFe1.8Er0.2O4. CoFe1.8RE0.2O4 nanoparticles showed similar antimicrobial efficacy against the five tested microbial strains, both in planktonic and biofilm state. The results highlight the promising potential of these types of nanoparticles for the development of novel anti-biofilm agents and materials.

Open Access

390. Calcium Phosphates-Chitosan Composite Layers Obtained by Combining Radio-Frequency Magnetron Sputtering and Matrix-Assisted Pulsed Laser Evaporation Techniques

Authors: Zarif, ME; Yehia-Alexe, SA; Bita, B; Negut, I; Locovei, C; Groza, A

Published: DEC 2022, POLYMERS, 14, 5241, DOI: 10.3390/polym14235241

In this work, we report the synthesis of calcium phosphate-chitosan composite layers. Calcium phosphate layers were deposited on titanium substrates by radio-frequency magnetron sputtering technique by varying the substrate temperature from room temperature (25 degrees C) up to 100 and 300 degrees C. Further, chitosan was deposited by matrix-assisted pulsed laser evaporation technique on the calcium phosphate layers. The temperature at the substrate during the deposition process of calcium phosphate layers plays an important role in the embedding of chitosan, as scanning electron microscopy analysis showed. The degree of chitosan incorporation into the calcium phosphate layers significantly influence the physico-chemical properties and the adherence strength of the resulted layers to the substrates. For example, the decreases of Ca/P ratio at the addition of chitosan suggests that a calcium deficient hydroxyapatite structure is formed when the CaP layers are generated on Ti substrates kept at room temperature during the deposition process. The Fourier transform infrared spectroscopy analysis of the samples suggest that the PO43-/CO32- substitution is possible. The X-ray diffraction spectra indicated that the crystalline structure of the calcium phosphate layers obtained at the 300 degrees C substrate temperature is disturbed by the addition of chitosan. The adherence strength of the composite layers to the titanium substrates is diminished after the chitosan deposition. However, no complete exfoliation of the layers was observed.

Open Access

391. Structural and Optical Characterization of Silica Nanospheres Embedded with Monodisperse CeO2-Eu³⁺ Nanocrystals

Authors: Secu, C; Bartha, C; Matei, E; Radu, C; Secu, M

Published: FEB 2022, MAGNETOCHEMISTRY, 8, 22, DOI: 10.3390/magnetochemistry8020022

Luminescent nanocrystals embedded into silica microspheres were shown to be useful for silica labeling for biological applications, ensuring mechanical and chemical stability, nontoxicity, biocompatibility and optical properties. We used sol-gel technology to prepare silica nanospheres embedded with fluorescent and magnetic Eu3+(1 mol%)-doped CeO2 nanocrystals. The X-ray diffraction pattern analysis and transmission electron microscopy investigations showed CeO2:Eu3+(1 mol%) nanocrystals of about 9 nm size and Ce3+ ions substitution by the Eu3+ ions; the nanocrystals dispersed inside the nanosized silica spheres of about 400 nm diameters. The photoluminescence spectra recorded under UV-light excitation showed Eu3+ ions luminescence peaks (D-5(0)-F-7(J), J = 0-4) accompanied by a weaker 425 nm luminescence due to the silica matrix; the quantum yield was 0.14. The weak hysteresis loop and magnetization curves recorded up to 20,000 Oe showed dominantly paramagnetic behavior associated with the silica matrix; a slight opening of the hysteresis loop to a very small magnetic field (about 0.005 Oe) was due to the presence of the two rare earth ions. The photonic crystal properties of SiO2-CeO2:Eu3+(1 mol%) silica nanospheres deposited as films on quartz plates were revealed by the two weak attenuation peaks at 420 and 500 nm and were associated with the reflection from different planes. The SiO2-CeO2:Eu3+(1 mol%) nanospheres are attractive potential candidates for photonics-related applications or for multifunctional bio-labels by combining the luminescence and magnetic properties of the nanocrystals.

Open Access

392. Composite Fibers Based on Polycaprolactone and Calcium Magnesium Silicate Powders for Tissue Engineering Applications

Authors: Busuioc, C; Alecu, AE; Costea, CC; Beregoi, M; Bacalum, M; Raileanu, M; Jinga, SI; Deleanu, IM

Published: NOV 2022, POLYMERS, 14, 4611, DOI: 10.3390/polym14214611

The present work reports the synthesis and characterization of polycaprolactone fibers loaded with particulate calcium magnesium silicates, to form composite materials with bioresorbable and bioactive properties. The inorganic powders were achieved through a sol-gel method, starting from the compositions of diopside, akermanite, and merwinite, three mineral phases with suitable features for the field of hard tissue engineering. The fibrous composites were fabricated by electrospinning polymeric solutions with a content of 16% polycaprolactone and 5 or 10% inorganic powder. The physico-chemical evaluation from compositional and morphological points of view was followed by the biological assessment of powder bioactivity and scaffold biocompatibility. SEM investigation highlighted a significant reduction in fiber diameter, from around 3 mu m to less than 100 nm after the loading stage, while EDX and FTIR spectra confirmed the existence of embedded mineral entities. The silicate phases were found be highly bioactive after 4 weeks of immersion in SBF, enriching the potential of the polymeric host that provides only biocompatibility and bioresorbability. Moreover, the cellular tests indicated a slight decrease in cell viability over the short-term, a compromise that can be accepted if the overall benefits of such multifunctional composites are considered.

393. Enhanced magnetocaloric properties of La0.8K0.2-xPbxMnO3 nanoparticles by optimizing Pb doping concentrations

Authors: Bouzid, SA; Essoumhi, A; Rostas, AM; Kuncser, AC; Negrila, CC; Iacob, N; Galatanu, A; Popescu, B; Sajieddine, M; Galca, AC; Kuncser, V

Published: JUN 15 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2022.02.239

Polycrystalline La(0.8)K(0.2-x)Pb(x)MnO3 (x = 0.05, 0.10, 0.15, 0.20) ceramics were successfully prepared by flash combustion route and their structural, morphological, magnetic and magnetocaloric properties were investi-gated. Structural analyses using X-ray diffraction reveal that all samples are crystallized in the rhombohedral structure and belong to R <(3) over bar > c space group. The increase of Pb doping does not modify the crystalline structure but changes the grain size and lattice parameters. X-ray photoelectron spectroscopy (XPS) fitting results of Mn 2p peaks confirmed the coexistence of Mn3+ and Mn4+ ions which contribute to the double exchange interactions improving the ferromagnetic order in the samples. The magnetization's temperature and magnetic field de-pendences indicate a second-order ferromagnetic-paramagnetic transition of the ceramics. A significant mag-netic entropy change near room temperature was observed for La0.8K0.1Pb0.1MnO3, showing considerable magnetocaloric properties. Furthermore, electron paramagnetic resonance spectroscopy (EPR) was also used to examine the ferromagnetic-paramagnetic transition.

Open Access

394. New solutions for combatting implant bacterial infection based on silver nano-dispersed and gallium incorporated phosphate bioactive glass sputtered films: A preliminary study

Authors: Stuart, BW; Stan, GE; Popa, AC; Carrington, MJ; Zgura, ; Necsulescu, M; Grant, DM

Published: FEB 2022, BIOACTIVE MATERIALS, 8, DOI: 10.1016/j.bioactmat.2021.05.055

Ag/Ga were incorporated into resorbable orthopaedic phosphate bioactive glasses (PBG, containing P, Ca, Mg, Na, and Fe) thin films to demonstrate their potential to limit growth of Staphylococcus aureus and Escherichia coli in post-operative prosthetic implantation. Dual target consecutive co-sputtering was uniquely employed to produce a 46 nm Ag:PBG composite observed by high resolution TEM to consist of uniformly dispersed similar to 5 nm metallic Ag nano-particles in a glass matrix. Ga3+ was integrated into a phosphate glass preform target which was magnetron sputtered to film thicknesses of similar to 400 or 1400 nm. All coatings exhibited high surface energy of 75.4-77.3 mN/m, attributed to the presence of hydrolytic P-O-P structural surface bonds. Degradation profiles obtained in deionized water, nutrient broth and cell culture medium showed varying ion release profiles, whereby Ga release was measured in 1400 nm coating by ICP-MS to be similar to 6, 27, and 4 ppm respectively, fully dissolving by 24 h. Solubility of Ag nanoparticles was only observed in nutrient broth (similar to 9 ppm by 24 h). Quantification of colony forming units after 24 h showed encouraging antibacterial efficacy towards both S. aureus (4-log reduction for Ag:PBG and 6-log reduction for Ga-PBG approximate to 1400 nm) and E. coli (5-log reduction for all physical vapour deposited layers) strains. Human Hs27 fibroblast and mesenchymal stem cell line in vitro tests indicated good cytocompatibility for all sputtered layers, with a marginal cell proliferation inertia in the case of the Ag:PBG composite thin film. The study therefore highlights the (i) significant manufacturing development via the controlled inclusion of metallic nanoparticles into a PBG glass matrix by dual consecutive target co-sputtering and (ii) potential of PBG resorbable thin-film structures to incorporate and release cytocompatible/antibacterial oxides. Both architectures showed prospective bio-functional performance for a future generation of endo-osseous implant-type coatings.

395. X-ray tomography assessment of the heat treatment effect on Nb3Sn wires with different architectures

Authors: Sima, A; Lungu, M; Ionescu, AM; Badica, P; Zani, L; Tiseanu, I

Published: NOV 2022, MATERIALS CHARACTERIZATION, 193, 112316, DOI: 10.1016/j.matchar.2022.112316

Two unreacted commercially available Nb3Sn precursor wires with different architecture were subject to a two-temperature heat treatment in vacuum at 650 degrees C for 72 h and at 700 degrees C for 168 h. Evolution of wires towards formation of the superconducting phase was assessed by the non-invasive X-ray computed microtomography (micro XRT) with a spatial resolution of similar to 2 mu m on the samples before and after the heat treatments. Statistical image analysis quantified the defects and quantitatively revealed the deviation of the geometrical perfection of the wire components comparative to designed parameters depending on the wire architecture and heat treatment conditions. Our results position XRT as a tool to evaluate the quality of Nb3Sn, also promoting it as a method capable for providing new insights that could be used in the optimization processes of Nb3Sn wires design, technology, and during operation.

396. Temperature-induced phase transition and tunable luminescence properties of Ce³⁺-Mn²⁺-Zr⁴⁺ tri-doped LaPO4 phosphor

Authors: AitMellal, O; Oufni, L; Messous, MY; Matei, E; Rostas, AM; Galca, AC; Secu, M

Published: JUL 2022, OPTICAL MATERIALS, 129, 112567, DOI: 10.1016/j.optmat.2022.112567

Tunable blue-white-orange emitting LaPO4:Ce3+/Mn2+/Zr4+(LPCMZ) phosphors have been synthesized by co precipitation followed by calcination. The X-ray diffraction (XRD) shows the phase transition from hexagonal to monoclinic between 600 and 700 ?C, accompanied by the increase of average nanocrystallites size from 8 to 64 nm. The Raman measurements revealed the vibrational modes associated with the LPCMZ crystalline phases, where the band positions and the full width at half maximum values depend on the structural parameters and nanocrystals size. For low-temperature calcination of 500 ?C, scanning electron microscopy (SEM) revealed nanoclusters composed of thinner nanoneedles, which developed into a rod-like self-assembly shape for higher calcination temperatures at around 900 ?C. Electron paramagnetic resonance (EPR) spectroscopy reveals a broad isotropic EPR signal, assigned to agglomerated/clustered Mn2+ ions, which are dispersed only at high temperatures above 900 ?C. The photoluminescence spectra recorded under UV-excitation of Ce3+ ions showed the Mn2+ green/red (546, 630 nm) emissions due to an energy transfer (ET) between Ce3+ and Mn2+. Depending on the calcination temperature, the Mn2+ emission color can be finely adjusted from blue to white and orange.

397. Growth and characterization of 3.5 at.% Nd:LGSB bifunctional crystal

Authors: Broasca, A; Greculeasa, M; Voicu, F; Stanciu, G; Hau, S; Gheorghe, C; Brandus, CA; Pavel, N; Enculescu, M; Gheorghe, L

Published: JAN 2022, OPTICAL MATERIALS, 123, 111832, DOI: 10.1016/j.optmat.2021.111832

The performances of 3.5 at.% Nd:LGSB bifunctional laser and nonlinear optical (NLO) crystal were investigated. A high-quality single crystal with incongruent melting, having dimensions of about 12 mm in diameter and 35 mm in length, was grown along the c-axis by the Czochralski technique. The phase-matching curve for type I second harmonic generation (SHG) was determined. Efficient laser emission at 1062 nm, along the phase-matching direction for SHG of 1062 nm radiation, was obtained under the pump at 807 nm with a fiber-coupled laser diode. The Nd:LGSB laser operated with a high slope efficiency of eta(sa) = 0.56 (with respect to the absorbed pump power), delivering the highest output power of 2.1 W for 4.04 W of absorbed pump power. Preliminary SFD experiments resulted in achieving a maximum green output power of 48 mW at 3.94 W absorbed pump power.

398. Nanocrystalline rhenium-doped TiO2: an efficient catalyst in the one-pot conversion of carbohydrates into levulinic acid. The synergistic effect between Bronsted and Lewis acid sites

Authors: Avramescu, S; Ene, CD; Ciobanu, M; Schnee, J; Devred, F; Bucur, C; Vasile, E; Colaciello, L; Richards, R; Gaigneaux, EM; Verziu, MN

Published: JAN 4 2022, CATALYSIS SCIENCE & TECHNOLOGY, 12, DOI: 10.1039/d1cy01450a

Catalytic activity of TiO2, 2%Re-TiO2 and 10%Re-TiO2 in the conversion of carbohydrates into levulinic acid under autoclave conditions was evaluated. These materials were prepared by aerogel method, for the first time to the best of our knowledge, and characterized by XPS, SEM-EDX, DRIFTS, DR UV-vis, Raman, N-2 adsorption/desorption isotherms, TGA and XRD. Further, the surface acidity was probed by NH3-TPD and pyridine-FT-IR where it was observed that increasing the amount of rhenium doped into TiO2 led to an increase in the total number of acid sites (Lewis + Bronsted) but with an overall lower strength. The presence of both Bronsted and Lewis acid sites led to the hypothesis that these materials may be well suited for conversion of carbohydrates into levulinic acid. Indeed a levulinic acid yield of 57% was reached over 10%Re-TiO2 for a low mass ratio catalyst to glucose (1 : 5). Moreover, the 10%Re-TiO2 catalyst was reused in the conversion of glucose for four catalytic cycles without a significant loss of the catalytic activity.

399. Effects of the Severe Plastic Deformation on the Magnetic Properties of Zr13Co87 Ribbons

Authors: Popescu, B; Palade, P; Sofronie, M; Kuncser, A; Gurau, C; Gurau, G; Tolea, F

Published: JAN 2022, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 53, DOI: 10.1007/s11661-021-06507-y

The influence of the severe plastic deformation via high-speed high-pressure torsion (HSHPT) on the structural and magnetic properties of the Zr13Co87 alloys is investigated. Moderate applied deformation promotes the growth of the rhombohedral hard magnetic phase leading to the increase of the sample's hardness and magnetic coercivity. A higher degree of deformation affects the samples morphology leading to a critical value of the grain size under which the exchange coupling of the soft phase is less effective. Additionally, it produces a random alignment of the anisotropy axes, which are both detrimental to the hard magnetic properties.

Open Access

400. Editorial for Special Issue: "Thin Films Based on Nanocomposites"

Authors: Socol, M; Preda, N

Published: OCT 2022, NANOMATERIALS, 12, 3301, DOI: 10.3390/nano12193301

401. MgB2 with Addition of Cubic BN and Ge2C6H10O7 Obtained by Spark Plasma Sintering Technique

Authors: Ionescu, AM; Aldica, G; Popa, S; Enculescu, M; Sandu, V; Pasuk, I; Burdusel, M; Grigoroscuta, MA; Miu, L; Badica, P

Published: DEC 2022, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 35, DOI: 10.1007/s10948-022-06350-1

High density (94-98% of the theoretical density) MgB2 samples added with C6H10Ge2O7 and cubic BN with compositions (MgB2)(1-x)(Ge2C6H10O7)(0.0028)(cBN)(x) (x = 0.003, 0.005, 0.007, 0.01) and (MgB2)(1-y)(Ge2C6H10O7)(y)(cBN)(0.005) (y = 0.0014, 0.0028, 0.005, 0.0075) were obtained by spark plasma sintering technique. For optimum doped samples with x = 0.005-0.007 and y = 0.0028-0.005, a weak enhancement of zero-field critical current density J(c0), irreversibility field H-irr, and volume pinning force F-p,F-max was determined. This behavior is very different from similar samples added with a single additive for which H-irr has a large enhancement. Consequently, it suggests the presence of opposite structural and microstructural effects induced by the additives. These effects, on the one hand, are discussed to decrease the sensitivity of MgB2 superconducting properties in the co-added samples comparative to samples added with C6H10Ge2O7, and, on the other hand, they contribute to anomalies that were found when assessing the pinning force-related parameters by the universal scaling law.

402. Re-entrant ferromagnetism at ultrahigh temperatures in epsilon-iron as possible origin of the geomagnetic field

Authors: Teodorescu, CM; Husanu, MA

Published: MAY 2022, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 326, 106856, DOI: 10.1016/j.pepi.2022.106856

A recent theory of band ferromagnetism in 3d metals predicts 're-entrant' ferromagnetism at temperatures far above the boiling point of these metals in normal conditions (Teodorescu, C.M., 2021. Spin asymmetry originating from densities of states: Criterion for ferromagnetism, structures and magnetic properties of 3d metals from crystal field based DOSs. Results in Physics 25, 104,241). Metals, and in particular iron rich alloys, are still solid at such extremal temperatures in the Earth's inner solid core. It follows that this piece of the Earth may become ferromagnetic. This hypothesis is investigated in this work in more details, by using densities of states derived by ab initio density functional theory calculations for hexagonal close-packed iron and applying the basic theory of band ferromagnetism derived in the above Reference. The temperature for 're-entrant' ferromagnetism increases with the pressure, ranging between about 6530 and 6640 K for pressures between 330 and 360 GPa; these temperatures are in the range of most estimates for the temperature of the inner solid core of our planet. The dimension of the ferromagnetic "innermost inner core" (IMIC) derived from the estimated Fe magnetic moment are within the dimensions of a IMIC with different anisotropy in the propagation of seismic waves. For body centered cubic Fe no 're-entrant' ferromagnetism is predicted based on the actual model. It follows that the Earth's inner solid core with hexagonal close-packed structure is the main responsible for the geomagnetic field, and also most probably the reversal of this field proceeds by simple rotation of the magnetization of this core, while keeping a non-vanishing magnetic field during the reversal. This might prevent the Earth's surface bombardment with energetic charged particles during the reversals, with beneficial effects for complex lifeforms and for mankind civilization.

403. Dielectric, piezoelectric and magnetic behavior of CoFe2O4/BNT-BT0.08 monolayer thin films composites

Authors: Cernea, M; Radu, R; Craciun, F; Gavrila, R; Surdu, VA; Trusca, R; Mihalache, V

Published: AUG 2022, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 282, 115770, DOI: 10.1016/j.mseb.2022.115770

We report in this paper on the monolayer composites thin films that have the magnetic spinel CoFe2O4 and the piezoelectric perovskite BNT-BT0.08 as constituent phases. Composite thin films of CoFe2O4 and BNT-BT0.08, with molar ratios of 0.5:1, 1:1 and 1.5:1, have been deposited by spin coating method from a sol precursor, mixture type, of CoFe2O4 and BNT-BT0.08. The monolayer thin films, deposited on Si/SiO2/TiO2/Pt substrate, were characterized using selected methods, such as: X-ray diffraction, scanning electron microscopy, atomic force microscopy/piezoelectric force microscopy, dielectric spectroscopy, and vibrating sample magnetometer. X-ray diffraction demonstrated the two phases: cubic CoFe2O4 and rhombohedral BNT-BT0.08. Furthermore, the Si/ SiO2/TiO2/Pt/BNT-BT0.08/CoFe2O4 monolayers show a simultaneous enhancement of both the magnetization and coercivity with the increase of the magnetic phase, accompanied by a decrease of the dielectric constant. The obtained results reveal that the investigated monolayer structures present superior properties compared to those of bilayer composites.

Open Access

404. Structural, Optical, and Sensing Properties of Nb-Doped ITO Thin Films Deposited by the Sol-Gel Method

Authors: Nicolescu, M; Mitrea, D; Hornoiu, C; Preda, S; Stroescu, H; Anastasescu, M; Calderon-Moreno, JM; Predoana, L; Teodorescu, VS; Maraloiu, VA; Zaharescu, M; Gartner, M

Published: NOV 2022, GELS, 8, 717, DOI: 10.3390/gels8110717

The aim of the present study was the development of Nb-doped ITO thin films for carbon monoxide (CO) sensing applications. The detection of CO is imperious because of its high toxicity, with long-term exposure having a negative impact on human health. Using a feasible sol-gel method, the doped ITO thin films were prepared at room temperature and deposited onto various substrates (Si, SiO2/glass, and glass). The structural, morphological, and optical characterization was performed by the following techniques: X-ray diffractometry (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV/Vis/NIR spectroscopic ellipsometry (SE). The analysis revealed a crystalline structure and a low surface roughness of the doped ITO-based thin films. XTEM analysis (cross-sectional transmission electron microscopy) showed that the film has crystallites of the order of 5-10 nm and relatively large pores (around 3-5 nm in diameter). A transmittance value of 80% in the visible region and an optical band-gap energy of around 3.7 eV were found for dip-coated ITO/Nb films on SiO2/glass and glass supports. The EDX measurements proved the presence of Nb in the ITO film in a molar ratio of 3.7%, close to the intended one (4%). Gas testing measurements were carried out on the ITO undoped and doped thin films deposited on glass substrate. The presence of Nb in the ITO matrix increases the electrical signal and the sensitivity to CO detection, leading to the highest response for 2000 ppm CO concentration at working temperature of 300 degrees C.

Open Access

405. Impact of band-bending on the k-resolved electronic structure of Si-doped GaN

Authors: Lev, LL; Maiboroda, IO; Grichuk, ES; Chumakov, NK; Schröter, NBM; Husanu, MA; Schmitt, T; Aeppli, G; Zanaveskin, ML; Valeyev, VG; Strocov, VN

Published: MAR 4 2022, PHYSICAL REVIEW RESEARCH, 4, 013183, DOI: 10.1103/PhysRevResearch.4.013183

Band bending at semiconductor surfaces and interfaces is the key to applications ranging from classical transistors to topological quantum computing. A semiconductor particularly important for optical as well as microwave devices is GaN. What makes the material useful is not only its large bandgap but also that it can be heavily doped to become metallic. Here, we apply soft-x-ray angle-resolved photoelectron spectroscopy (ARPES) to metallic Si-doped GaN to explore the electron density and momentum-resolved band dispersions of the valence and conduction electrons varying through the surface band-bending region. We find an upward band bending, where the measured band occupation reduces toward the surface, as probed with low photon energies <0.5 keV. The band occupation approaches the bulk value, matching Hall effect measurements, as the photon energy increases to >1.4 keV, where the photoelectron mean free path exceeds the spatial extent of the band-bending region. Our quantitative analysis of the experimental data describes the potential variation in the band-bending region via self-consistent Poisson-Schrodinger equations. We put forward an insightful model to simulate the ARPES spectra from this region through summing up the contribution from all atomic layers, weighted by the photoelectron mean free path, under in-phase conditions achieved at particular values of the photoelectron out-of-plane momentum. The model adequately describes the peculiarities of the ARPES spectra caused by the surface band bending, including the photon-energy dependence of the apparent band occupation and Fermi-surface area, and allows accurate determination of the band-bending profile and values of the photoelectron mean free path. Finally, comparison of our data with supercell density functional theory calculations reveals the preferential location of Si atoms as substitutional for Ga, with the doped electrons entering the GaN conduction bands without formation of separate impurity states as would occur for Si interstitials. Our theoretical and experimental results resolve fundamental questions underpinning device performance of the GaN-based and other semiconductor materials in general and demonstrate a general methodology for quantitative studies of electron states in the band-bending region.

406. Pseudo-dielectric function spectra of the near surface layer of GaAs implanted with various fluence of Xe⁺ ions

Authors: Tuan, PL; Kulik, M; Phuc, TV; Madadzada, AI; Zelenyak, TY; Turek, M; Zuk, J; Mita, C; Stanculescu, A; Doroshkevich, AS; Jasinska, B; Khiem, LH; Anh, NN; My, NTB

Published: AUG 31 2022, THIN SOLID FILMS, 756, 139376, DOI: 10.1016/j.tsf.2022.139376

Monocrystalline (100) semi-insulating gallium arsenide (GaAs) samples were irradiated with a 250-keV Xe+ ion beam at room temperature. To investigate the effect of ion irradiation on GaAs samples, the ion fluence was varied from 1 x 1012 to 3 x 1016 ions/cm2. The spectroscopic ellipsometry (SE) method and the Rutherford backscattering spectrometry (RBS) with nuclear reaction (NR) method were used to determine the properties of the virgin and implanted samples. The SE approach reveals that the pseudo-dielectric function of implanted GaAs samples varies with ion fluence. The RBS approach, which exposes the depth-profile of As, Ga, and Xe in the implanted samples, allows us to correlate changes in the pseudo-dielectric function with structural modifications caused by the ion irradiation. The NR approach points out the existence of an oxygen-enriched layer on the surface of implanted GaAs samples. Lastly, the optical study involving the Cauchy and Urbach dispersion model measures the refractive index n and extinction coefficient k of the native oxide layer on the surface of GaAs samples.

Open Access

407. Influence of Post-Deposition Thermal Treatments on the Morpho-Structural, and Bonding Strength Characteristics of Lithium-Doped Biological-Derived Hydroxyapatite Coatings

Authors: Duta, L; Stan, GE; Popescu-Pelin, G; Zgura, I; Anastasescu, M; Oktar, FN

Published: DEC 2022, COATINGS, 12, 1883, DOI: 10.3390/coatings12121883

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and bonding strength standpoints of as-deposited (NTT) and post-deposition thermal-treated (TT) coatings at temperatures ranging from 400 to 700 degrees C (i.e., TT400-TT700), was performed. Structural investigations indicated a complete crystallization of the initially amorphous HA-based layers at temperatures in excess of 500 degrees C. The morphological analyses emphasized the rough appearance of the film surfaces, consisting of particulates whose dimensions increased at higher temperatures, with an emphasis on LiC coatings. AFM investigations evidenced rough surfaces, with a clear tendency to increase in corrugation with the applied temperature, in the case of LiC coatings. A hydrophobic behavior was observed for control, NTT and TT400 samples, whilst a radical shift towards hydrophilicity was demonstrated for both types of structures at higher temperatures. In the case of TT500-TT700 coatings, the pull-out adherence values increased considerably compared to control ones. Taking into consideration the obtained results, the positive influence of post-deposition thermal treatments (performed at higher temperatures) on the physical-chemical and mechanical properties of LiC and LiP coatings was indicated. Alongside these improved characteristics observed at elevated temperatures, the sustainable nature of the used BioHA materials should recommend them as viable alternatives to synthetic HA ones for bone implant applications.

Open Access

408. A Two-Step Magnetron Sputtering Approach for the Synthesis of Cu2ZnSnS4 Films from Cu2SnS3\ZnS Stacks

Authors: Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Stavarache, I; Bocirnea, AE; Mihai, C; Velea, A; Galca, AC

Published: 2022 JUN 27 2022, ACS OMEGA, DOI: 10.1021/acsomega.2c02475

Cu2ZnSnS4 (CZTS) is regarded as one of the emerging materials for next-generation thin film solar cells. However, its synthesis is complex, and obtaining a single-phase CZTS thin film is difficult. This work reports the elaboration of Cu2ZnSnS4 thin films by a sequential magnetron sputtering deposition of Cu2SnS3 (CTS) and ZnS as stacked films. Initially, the CTS films were prepared on a soda lime glass substrate by annealing Cu and SnS2 stacked layers. Second, ZnS was deposited by magnetron sputtering on the CTS films. The CTS\ZnS stacks were then annealed in Sn + S or S atmospheres. The tetragonal CZTS structure was obtained and confirmed by grazing incidence X-ray diffraction and Raman spectroscopy. The morphological and compositional characteristics, measured by scanning electron microscopy and energy-dispersive spectroscopy, revealed large grains and dense surfaces with the elemental composition close to the intended stoichiometry. Additional X-ray photoemission spectroscopy measurements were performed to determine the surface chemistry and particularities of the obtained films. The optical properties, determined using conventional spectroscopy, showed optimal absorber layer band gap values ranging between 1.38 and 1.50 eV. The electrical measurements showed that all the films are p-type with high carrier concentrations in the range of 10(15) to 10(20) cm(-3). This new synthesis route for CZTS opens the way to obtain high-quality films by an industry-compatible method.

Open Access

409. Iron-Oxide-Nanoparticles-Doped Polyaniline Composite Thin Films

Authors: Butoi, B; Ciobanu, CS; Iconaru, SL; Negrila, CC; Badea, MA; Balas, M; Dinischiotu, A; Predoi, G; Bita, B; Groza, A; Predoi, D

Published: MAY 2022, POLYMERS, 14, 1821, DOI: 10.3390/polym14091821

Iron-oxide-doped polyaniline (PANI-IO) thin films were obtained by the polymerization of aniline monomers and iron oxide solutions in direct current glow discharge plasma in the absence of a buffer gas for the first time. The PANI-IO thin films were deposited on optical polished Si wafers in order to study surface morphology and evaluate their in vitro biocompatibility. The characterization of the coatings was accomplished using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), metallographic microscopy (MM), and X-ray photoelectron spectroscopy (XPS). In vitro biocompatibility assessments were also conducted on the PANI-IO thin films. It was observed that a uniform distribution of iron oxide particles inside the PANI layers was obtained. The constituent elements of the coatings were uniformly distributed. The Fe-O bonds were associated with magnetite in the XPS studies. The surface morphology of the PANI-IO thin films was assessed by atomic force microscopy (AFM). The AFM topographies revealed that PANI-IO exhibited the morphology of a uniformly distributed and continuous layer. The viability of Caco-2 cells cultured on the Si substrate and PANI-IO coating was not significantly modified compared to control cells. Moreover, after 24 h of incubation, we observed no increase in LDH activity in media in comparison to the control. In addition, our results revealed that the NO levels for the Si substrate and PANI-IO coating were similar to those found in the control sample.

Open Access

410. Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3

Authors: Zaki, MY; Sava, F; Simandan, ID; Buruiana, AT; Mihai, C; Velea, A; Galca, AC

Published: MAY 13 2022, SCIENTIFIC REPORTS, 12, 7958, DOI: 10.1038/s41598-022-12045-3

Cu2SnS3 (CTS) is emerging as a promising absorber for the next generation thin film solar cells (TFSC) due to its excellent optical and electronic properties, earth-abundance and eco-friendly elemental composition. In addition, CTS can be used as precursor films for the Cu2ZnSnS4 (CZTS) synthesis. The optical properties of CTS are influenced by stoichiometry, crystalline structure, secondary phases and crystallite size. Routes for obtaining CTS films with optimized properties for TFSC are still being sought. Here, the CTS thin films synthesized by magnetron sputtering on soda lime glass (SLG) using Cu and SnS2 targets in two different stacks, were studied. The SLG\Cu\SnS2 and SLG\SnS2\Cu stacks were annealed in S and Sn + S atmospheres, at various temperatures. Both stacks show a polymorphic structure, and higher annealing temperatures favor the monoclinic CTS phase formation. Morphology is influenced by the stacking order since a SnS2 top layer generates several voids on the surface due to the evaporation of SnS, while a Cu top layer provides uniform and void-free surfaces. The films in the copper-capped stack annealed under Sn + S atmosphere have the best structural, morphological, compositional and optical properties, with tunable band gaps between 1.18 and 1.37 eV. Remarkably, secondary phases are present only in a very low percent (< 3.5%) in samples annealed at higher temperatures. This new synthesis strategy opens the way for obtaining CTS thin films for solar cell applications, that can be used also as intermediary stage for CZTS synthesis.

411. A curcumin-loaded silica carrier with NH3 sensitivity and antimicrobial properties

Authors: Todan, L; Voicescu, M; Culita, DC; Lincu, D; Ion, RM; Calin, M; Raut, I; Kuncser, AC

Published: MAY 2022, CHEMICAL PAPERS, 76, DOI: 10.1007/s11696-022-02090-7

In this study curcumin was immobilized in a silica matrix to overcome its poor aqueous solubility and rapid degradation profile. Two kinds of sol-gel powders based on colloidal silica were synthesized and characterized, one prepared with an ethanolic solution of curcumin and the other using cethyltrimethylammonium bromide (CTAB) to solubilize the dye. The successful integration of curcumin in the matrix as well as the interaction with the components of the composite powders was validated by different analysis methods (DSC, FTIR). The samples morphology was evaluated by SEM. UV-Vis and fluorescence studies showed that curcumin was stable, in its enol configuration in both matrices. The sensitivity to ammonia was proved by exposing the powders to NH3 vapors in a sealed vessel. Color changes were measured with a colorimeter. UV-Vis spectra showed that the enol form of the dye in EtOH/CTAB based SiO2 matrices was energetically stable under NH3 atmosphere, even after being kept a few days at low temperature. A fluorescence quenching of both samples was noticed due to interaction curcumin-ammonia. Both samples have antimicrobial properties, the CTAB containing one being more efficient. The EtOH/CTAB based SiO2 powders may represent a novel signaling and antimicrobial system, useful for food or pharmaceutical applications. [GRAPHICS] .

Open Access

412. Impact of Gamma Irradiation on the Properties of Magnesium-Doped Hydroxyapatite in Chitosan Matrix

Authors: Predoi, D; Ciobanu, CS; Iconaru, SL; Predoi, SA; Chifiriuc, MC; Raaen, S; Badea, ML; Rokosz, K

Published: AUG 2022, MATERIALS, 15, 5372, DOI: 10.3390/ma15155372

This is the first report regarding the effect of gamma irradiation on chitosan-coated magnesium-doped hydroxyapatite (x(Mg) = 0.1; 10 MgHApCh) layers prepared by the spin-coating process. The stability of the resulting 10 MgHApCh gel suspension used to obtain the layers has been shown by ultrasound measurements. The presence of magnesium and the effect of the irradiation process on the studied samples were shown by X-ray photoelectron spectroscopy (XPS). The XPS results obtained for irradiated 10 MgHApCh layers suggested that the magnesium and calcium contained in the surface layer are from tricalcium phosphate (TCP; Ca-3(PO4)(2)) and hydroxyapatite (HAp). The XPS analysis has also highlighted that the amount of TCP in the surface layer increased with the irradiation dose. The energy-dispersive X-ray spectroscopy (EDX) evaluation showed that the calcium decreases with the increase in the irradiation dose. In addition, a decrease in crystallinity and crystallite size was highlighted after irradiation. By atomic force microscopy (AFM) we have obtained images suggesting a good homogeneity of the surface of the non-irradiated and irradiated layers. The AFM results were also sustained by the scanning electron microscopy (SEM) images obtained for the studied samples. The effect of gamma-ray doses on the Fourier transform infrared spectroscopy (ATR-FTIR) spectra of 10 MgHApCh composite layers was also evaluated. The in vitro antifungal assays proved that 10 MgHApCh composite layers presented a strong antifungal effect, correlated with the irradiation dose and incubation time. The study of the stability of the 10 MgHApCh gel allowed us to achieve uniform and homogeneous layers that could be used in different biomedical applications.

Open Access

413. Could Iron-Nitrogen Doping Modulate the Cytotoxicity of TiO2 Nanoparticles?

Authors: Nica, IC; Miu, BA; Stan, MS; Diamandescu, L; Dinischiotu, A

Published: MAR 2022, NANOMATERIALS, 12, 770, DOI: 10.3390/nano12050770

Titanium dioxide nanoparticles (TiO2 NPs) are found in several products on the market that include paints, smart textiles, cosmetics and food products. Besides these, TiO2 NPs are intensively researched for their use in biomedicine, agriculture or installations to produce energy. Taking into account that several risks have been associated with the use of TiO2 NPs, our aim was to provide TiO2 NPs with improved qualities and lower toxicity to humans and the environment. Pure TiO2 P25 NPs and the same NPs co-doped with iron (1%) and nitrogen atoms (P25-Fe(1%)-N NPs) by hydrothermal treatment to increase the photocatalytic activity in the visible light spectrum were in vitro evaluated in the presence of human lung cells. After 24 and 72 h of incubation, the oxidative stress was initiated in a time- and dose-dependent manner with major differences between pure P25 and P25-Fe(1%)-N NPs as revealed by malondialdehyde and reactive oxygen species levels. Additionally, a lower dynamic of autophagic vacuoles formation was observed in cells exposed to Fe-N-doped P25 NPs compared to the pure ones. Therefore, our results suggest that Fe-N doping of TiO2 NPs can represent a valuable alternative to the conventional P25 Degussa particles in industrial and medical applications.

414. Effect of annealing on the structural, optical and electrical properties of (F, Zn) double doped SnO2 nanoparticles obtained by the laser pyrolysis method

Authors: Morjan, IP; Dutu, E; Fleaca, CT; Dumitrache, F; Morjan, I; Mihailescu, N; Demian, M; Teodorescu, VS; Scarisoreanu, M

Published: MAY 2022, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 142, 106511, DOI: 10.1016/j.mssp.2022.106511

SnO2 nanoparticles have a great potential in photocatalytic and optoelectronic applications by extending their absorbtion and emission from UV to the visible domain. The effect of annealing at 750 degrees C and 1000 degrees C for 3 h in ambient conditions on structural, optical and electrical properties of F&Zn double doped SnO2 nanoparticles synthesized by continuous wave CO2 laser pyrolysis method were investigated for the first time. X-Ray diffraction studies confirmed the expected crystallite size increasing and also the vanishing of divalent tin phases (SnF2, SnO) upon air annealing. Detailed X ray photoelectron spectroscopy (XPS) analysis confirmed that fluorine disappears completely from SnO2 structure at 1000 degrees C. The annealing also induced a reduction in oxygen vacancies as confirmed by Raman spectroscopy and XPS. Transmission FTIR spectroscopy was used for revealing the existence of Sn-O, O-Sn-O, O-H and H-O-H vibrational modes. The optical band gap energies of all annealed samples are in the visible region, decreasing for those that were initially doped with F, and increasing for the only Zn doped sample. Photoluminescence (PL) measurements showed a broad dominant peak in green visible region, around 530 nm. For the sample with the highest content of Zn, PL spectrum shifted to higher wavelengths, respectively to the orange and red regions. The oxygen vacancies concentrations after annealing are correlated with the electrical conductivity of F, F&Zn, and Zn doped SnO2 samples.

415. The influence of Zr⁴⁺ doping on the structural and photoluminescence properties of LaPO4:Ce³⁺/Mn²⁺ phosphors

Authors: AitMellal, O; Oufni, L; Messous, MY; Rostas, AM; Galca, AC; Toma, ; Matei, E; Secu, M

Published: NOV 2022, JOURNAL OF LUMINESCENCE, 251, 119226, DOI: 10.1016/j.jlumin.2022.119226

A series of LaPO4:Ce3+/Mn2+/xZr(4+) (LPOCM:xZr(4+)) (0% <= x <= 30%) emission-tunable phosphors were synthesized by a cost-efficient co-precipitation method. The samples presented a monoclinic phase structure and a macroscopic rod-like shape. Photoluminescence (PL) and electron paramagnetic resonance spectroscopy were employed, the Zr4+ concentration-dependent excitation, emission, decay time, and energy transfer (Ce3+ -> Mn2+) being discussed in detail. Under UV-excitation of Ce3+, typical green-red PL emission is observed for the LPOCM:xZr(4+) phosphors, which is attributed to the T-4(1)(G) -> (6)A(1)(S) transition of the Mn2+ ion. The charge compensation strategy achieved the Mn2+ PL-enhancement and color-tuning effect in LPOCM:xZr(4+) phosphors. A strong blue emission with color purity of up to 97% is observed in the Ce3+ singly-doped sample. Cold white light emission can be obtained by doping 5% Zr4+ in LPOCM phosphor under UV irradiation. The corresponding CIE 1931 coordinates were inferred to be (0.309, 0.329), close to the standard white emission (0.330, 0.330). The color was tuned towards whitish-orange/red emissions for higher Zr4+ concentrations (15% and 30%). These findings indicate that the charge compensation approach can greatly improve the PL and color-tunable properties of LPOCM:xZr(4+) phosphors.

Open Access

416. Processing Effects on the Martensitic Transformation and Related Properties in the Ni55Fe18Nd2Ga25 Ferromagnetic Shape Memory Alloy

Authors: Sofronie, M; Popescu, B; Enculescu, M; Tolea, M; Tolea, F

Published: OCT 2022, NANOMATERIALS, 12, 3667, DOI: 10.3390/nano12203667

The influence of processing on the martensitic transformation and related magnetic properties of the Ni55Fe18Nd2Ga25 ferromagnetic shape memory alloy, as bulk and ribbons prepared by the melt spinning method and subjected to different thermal treatments, is investigated. Structural, calorimetric, and magnetic characterizations are performed. Thermal treatment at 1173 K induces a decrease in both the Curie and the martensitic transformation temperatures, while a treatment at 673 K produces the structural ordering of the ribbons, hence an increase in T-C. A maximum value of the magnetic entropy variation of -5.41 J/kgK was recorded at 310 K for the as quenched ribbons. The evaluation of the magnetoresistive effect shows a remarkable value of -13.5% at 275 K on the bulk sample, which is much higher than in the ribbons.

Open Access

417. Influence of the Photodegradation of Azathioprine on DNA and Cells

Authors: Bunea, MC; Diculescu, VC; Enculescu, M; Oprea, D; Enache, TA

Published: NOV 2022, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 23, 14438, DOI: 10.3390/ijms232214438

Azathioprine (AZA) is a pharmacologic immunosuppressive agent administrated in various conditions such as autoimmune disease or to prevent the rejection of organ transplantation. The mechanism of action is based on its biologically active metabolite 6-mercaptopurine (6-MP), which is converted, among others, into thioguanine nucleotides capable of incorporating into replicating DNA, which may act as a strong UV chromophore and trigger DNA oxidation. The interaction between azathioprine and DNA, before and after exposure to solar simulator radiation, was investigated using UV-vis spectrometry and differential pulse voltammetry at a glassy carbon electrode. The results indicated that the interaction of AZA with UV radiation was pH-dependent and occurred with the formation of several metabolites, which induced oxidative damage in DNA, and the formation of DNA-metabolite adducts. Moreover, the viability assays obtained for the L929 cell culture showed that both azathioprine and degraded azathioprine induced a decrease in cell proliferation.

Open Access

418. Bioinspired polypyrrole based fibrillary artificial muscle with actuation and intrinsic sensing capabilities

Authors: Beregoi, M; Beaumont, S; Evanghelidis, A; Otero, TF; Enculescu, I

Published: SEP 2 2022, SCIENTIFIC REPORTS, 12, 15019, DOI: 10.1038/s41598-022-18955-6

A non-conventional, bioinspired device based on polypyrrole coated electrospun fibrous microstructures, which simultaneously works as artificial muscle and mechanical sensor is reported. Fibrous morphology is preferred due to its high active surface which can improve the actuation/sensing properties, its preparation still being challenging. Thus, a simple fabrication algorithm based on electrospinning, sputtering deposition and electrochemical polymerization produced electroactive aligned ribbon meshes with analogous characteristics as natural muscle fibers. These can simultaneously generate a movement (by applying an electric current/potential) and sense the effort of holding weights (by measuring the potential/current while holding objects up to 21.1 mg). Electroactivity was consisting in a fast bending/curling motion, depending on the fiber strip width. The amplitude of the movement decreases by increasing the load, a behavior similar with natural muscles. Moreover, when different weights were hung on the device, it senses the load modification, demonstrating a sensitivity of about 7 mV/mg for oxidation and - 4 mV/mg for reduction. These results are important since simultaneous actuation and sensitivity are essential for complex activity. Such devices with multiple functionalities can open new possibilities of applications as e.g. smart prosthesis or lifelike robots.

Open Access

419. Improving the Efficiency of Gallium Telluride for Photocatalysis, Electrocatalysis, and Chemical Sensing through Defects Engineering and Interfacing with its Native Oxide

Authors: Bondino, F; Duman, S; Nappini, S; D'Olimpio, G; Ghica, C; Mazzola, F; Istrate, MC; Jugovac, M; Vorokhta, M; Santoro, S; Gürbulak, B; Locatelli, A; Boukhvalov, DW; Politano, A

Published: OCT 2022, ADVANCED FUNCTIONAL MATERIALS, 32, 2205923, DOI: 10.1002/adfm.202205923

Gallium telluride (GaTe) is a van der Waals semiconductor, currently adopted for photonic and optoelectronic devices. However, the rapid degradation of GaTe in air, promoted by Te vacancies, is detrimental for device applications. Here, it is demonstrate that the surface oxidation of GaTe can be unexpectedly exploited for expanding the breadth of applications of GaTe. Specifically, the formation of a nanoscale sub-stoichiometric wide-band-gap Ga2O3 skin, promoted by Te vacancies, over narrow-band-gap GaTex upon air exposure is beneficial for electrocatalysis, photocatalysis, and gas sensing . In particular, the Heyrovsky step (H-ads + H+ + e(-) -> H-2) of hydrogen evolution reaction in an acidic medium is barrier-free for the sub-stoichiometric gallium-oxide/gallium-telluride heterostructure, which also enables a significant reduction of costs with respect to state-of-the-art Pt/C electrodes. In the photocatalytic process, the photo-generated electrons migrate from GaTe to Ga2Ox skin, which acts as the chemically active side of the interface. Moreover, the Ga2O3/GaTe heterostructure is a suitable platform for sensing of H2O, NH3, and NO2 at operational temperatures extended up to 600 degrees C (useful for gas detection in combustion processes), mainly due to the increased area of charge redistribution after adsorption achieved upon oxidation of GaTe.

Open Access

420. Catalytic Hydrotreatment of Humins Waste over Bifunctional Pd-Based Zeolite Catalysts

Authors: El Fergani, M; Candu, N; Podolean, I; Cojocaru, B; Nicolaev, A; Teodorescu, CM; Tudorache, M; Parvulescu, VI; Coman, SM

Published: OCT 2022, CATALYSTS, 12, 1202, DOI: 10.3390/catal12101202

The catalytic hydrotreatment of humins, the solid byproduct produced from the conversion of C6 sugars (glucose, fructose) to 5-hydroxymethylfurfural (HMF), using supported Pd@zeolite (Beta, Y, and USY) catalysts with different amounts of Pd (i.e., 0.5, 1.0 and 1.5 wt%) was investigated under molecular hydrogen pressure. The highest conversion of humins (52.0%) was obtained on 1.5Pd@USY catalyst while the highest amount of humins oil (27.3%) was obtained in the presence of the 1Pd@Beta zeolite sample, at P-H2 = 30 bars and T = 250 degrees C. The major compounds in the humins oil evidenced by GC-MS are alcohols, organic acids, ethers, and alkyl-phenolics. However, although all these classes of compounds are obtained regardless of the nature of the catalyst used, the composition of the mixture differs from one catalyst to another. Furanic compounds were not identified in the reaction products. A possible explanation may be related to their high reactivity under the reaction conditions, in the presence of the Pd-based catalysts these compounds lead to alkyl phenolics, important intermediates in the petrochemical industry.

421. Intrinsic losses in microwave dielectrics investigated by THz-TDS: A comparison between conventional and spark plasma sintered Zr0.8Sn0.2TiO4 ceramics

Authors: Nedelcu, L; Banciu, MG; Geambasu, CD; Burdusel, M; Grigoroscuta, MA; Enculescu, M; Badica, P

Published: 2022, 2022 47TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ 2022), DOI: 10.1109/IRMMW-THz50927.2022.9895934

Zr0.8Sn0.2TiO4 powders synthesized by solid state reaction route have been consolidated by conventional and spark plasma sintering methods. Single-phase ceramics with various microstructures and, consequently, different extrinsic absorption were investigated by terahertz time-domain spectroscopy. The results showed that the terahertz spectroscopy can be used for tailoring in the " synthesis - microstructure - properties" cycle.

Open Access

422. Pinning Potential of the Self-Assembled Artificial Pinning Centers in Nanostructured YBa2Cu3O7-x Superconducting Films

Authors: Ivan, I; Ionescu, AM; Crisan, DN; Andrei, A; Galluzzi, A; Polichetti, M; Mosqueira, J; Crisan, A

Published: MAY 2022, NANOMATERIALS, 12, 1713, DOI: 10.3390/nano12101713

For high-field power applications of high-temperature superconductors, it became obvious in recent years that nano-engineered artificial pinning centers are needed for increasing the critical current and pinning potential. As opposed to the artificial pinning centers obtained by irradiation with various particles, which is a quite expensive approach, we have studied superconducting samples having self-assembled defects, created during the sample fabrication, that act as effective pinning centers. We introduced a simple, straight-forward method of estimating the frequency-dependent critical current density by using frequency-dependent AC susceptibility measurements, in fixed temperatures and DC magnetic fields, from the positions of the maxima in the dependence of the out-of-phase susceptibility on the amplitude of AC excitation magnetic field. The results are compatible with a model that stipulates a logarithmic dependence of the pinning potential on the probing current. A mathematical derivation allowed us to estimate from the experimental data the pinning potentials in various samples, and in various DC magnetic fields. The resulted values indicate large pinning potentials, leading to very small probability of magnetic flux escaping the pinning wells, hence, leading to very high critical currents in high magnetic fields.

Open Access

423. Electrochemical evaluation of proton beam radiation effect on the B16 cell culture

Authors: Onea, M; Bacalum, M; Radulescu, AL; Raileanu, M; Craciun, L; Esanu, TR; Enache, TA

Published: FEB 10 2022, SCIENTIFIC REPORTS, 12, 2261, DOI: 10.1038/s41598-022-06277-6

The interaction of radiation with matter takes place through energy transfer and is accomplished especially by ionized atoms or molecules. The effect of radiation on biological systems involves multiple physical, chemical and biological steps. Direct effects result in a large number of reactive oxygen species (ROS) within and outside and inside of the cells as well, which are responsible for oxidative stress. Indirect effects are defined as alteration of normal biological processes and cellular components (DNA, protein, lipids, etc.) caused by the reactive oxygen species directly induced by radiation. In this work, a classical design of an electrochemical (EC) three-electrodes system was employed for analyzing the effects of proton beam radiation on melanoma B16 cell line. In order to investigate the effect of proton radiation on the B16 cells, the cells were grown on the EC surface and irradiated. After optimization of the experimental set-up and dosimetry, the radiobiological experiments were performed at doses ranging between 0 and 2 Gy and the effect of proton beam irradiation on the cells was evaluated by the means of cyclic voltammetry and measuring the open circuit potential between working and reference electrodes.

424. Effect of polysilane addition on spark plasma sintering and superconducting properties of MgB2 bulks

Authors: Sandu, V; Aldica, G; Grigoroscuta, MA; Burdusel, M; Pasuk, ; Ching, YC; Ionescu, AM; Badica, P

Published: NOV 1 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2022.07.127

Polycrystalline MgB2 bulk samples were produced by ex-situ spark plasma sintering (SPS) using the oxygen-free preceramic polymer additive poly(dimethylsilane) as a source for carbon doping and as a sintering aid. Two major effects were identified. One is the significant enhancement of the densification kinetics during sintering for all tested compositions. The second one is the improvement of the high field critical current density for a certain level of the poly(dimethylsilane) addition.

Open Access

425. Biological and Physico-Chemical Properties of Composite Layers Based on Magnesium-Doped Hydroxyapatite in Chitosan Matrix

Authors: Iconaru, SL; Ciobanu, CS; Predoi, G; Rokosz, K; Chifiriuc, MC; Bleotu, C; Stanciu, G; Hristu, R; Raaen, S; Raita, SM; Ghegoiu, L; Badea, ML; Predoi, D

Published: OCT 2022, MICROMACHINES, 13, 1574, DOI: 10.3390/mi13101574

In the present study, we report the development and characterization of composite layers (by spin coating) based on magnesium-doped hydroxyapatite in a chitosan matrix, (Ca10-xMgx(PO4)(6)(OH)(2); x(Mg) = 0, 0.08 and 0.3; HApCh, 8MgHApCh and 30MgHApCh). The MgHApCh composite layers were investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The in vitro biological evaluation included the assessment of their cytotoxicity on MG63 osteoblast-like cells and antifungal activity against Candida albicans ATCC 10231 fungal cell lines. The results of the physico-chemical characterization highlighted the obtaining of uniform and homogeneous composite layers. In addition, the biological assays demonstrated that the increase in the magnesium concentration in the samples enhanced the antifungal effect but also decreased their cytocompatibility. However, for certain optimal magnesium ion concentrations, the composite layers presented both excellent biocompatibility and antifungal properties, suggesting their promising potential for biomedical applications in both implantology and dentistry.

426. Bioconjugates of mercaptocarboxylic acids functionalized AuNP and superoxide dismutase for superoxide electrochemical monitoring

Authors: Sanz, CG; Crisan, DN; Leote, RJB; Onea, M; Barsan, MM

Published: JUL 2022, MICROCHIMICA ACTA, 189, 245, DOI: 10.1007/s00604-022-05352-z

The use of gold nanoparticles/superoxide dismutase (AuNP/SOD) bioconjugates is described as building blocks in SOD biosensor development for the quantification of superoxide in cell culture media. AuNP functionalization with 11-mercaptoundecanoic acid (MUA) and 4-mercaptobenzoic acid (MBA) (AuNPMUA and AuNPMBA) was used to improve SOD immobilization through EDC/NHS coupling using their -COOH terminus, leading to the formation of more stable bioconjugates. AuNP and AuNP/SOD bioconjugates were characterized by SEM to determine their size and morphology, UV-Vis for optical properties, FT-IR, and Raman spectroscopies for chemical functional group analysis and EDX for elemental analysis. Electrochemical methods were used to characterize the Au/AuNP-modified electrodes. For the optimization of the biosensor architecture, different AuNP/enzyme bioconjugates were prepared by varying the amount of both enzyme and AuNP, as well as their incubation time. Finally, the biosensors incorporating the bioconjugates were characterized by fixed potential amperometry and voltammetric analysis in order to establish the enzymatic mechanism and to elucidate the best biosensor architecture for monitoring superoxide in cell culture media. The best sensitivity value for superoxide detection corresponded to 41.2 nA mu M cm(-2), achieved by a biosensor based on AuNPMBA/SOD bioconjugates monitored through fixed potential amperometry at 0.3 V vs. Ag/AgCl, with a limit of detection of 1.0 mu M, and overall very good operational stability, maintaining 91% of the initial sensitivity after 30 days. Finally, the optimized biosensor was employed for the quantification of successive additions of superoxide in cell culture media, with excellent recovery values.

Open Access

427. Photodegradation of Azathioprine in the Presence of Sodium Thiosulfate

Authors: Toulbe, N; Smaranda, I; Negrila, C; Bartha, C; Manta, CM; Baibarac, M

Published: APR 2022, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 23, 3975, DOI: 10.3390/ijms23073975

The effect of sodium thiosulfate (ST) on the photodegradation of azathioprine (AZA) was analyzed by UV-VIS spectroscopy, photoluminescence (PL), FTIR spectroscopy, Raman scattering, X-ray photoelectron (XPS) spectroscopy, thermogravimetry (TG) and mass spectrometry (MS). The PL studies highlighted that as the ST concentration increased from 25 wt.% to 75 wt.% in the AZA:ST mixture, the emission band of AZA gradual downshifted to 553, 542 and 530 nm. The photodegradation process of AZA:ST induced: (i) the emergence of a new band in the 320-400 nm range in the UV-VIS spectra of AZA and (ii) a change in the intensity ratio of the photoluminescence excitation (PLE) bands in the 280-335 and 335-430 nm spectral ranges. These changes suggest the emergence of new compounds during the photo-oxidation reaction of AZA with ST. The invoked photodegradation compounds were confirmed by studies of the Raman scattering, the FTIR spectroscopy and XPS spectroscopy through: (i) the downshift of the IR band of AZA from 1336 cm(-1) to 1331 cm(-1), attributed to N-C-N deformation in the purine ring; (ii) the change in the intensity ratio of the Raman lines peaking at 1305 cm(-1) and 1330 cm(-1) from 3.45 to 4.57, as the weight of ST in the AZA:ST mixture mass increased; and (iii) the emergence of a new band in the XPS O1s spectrum peaking at 531 eV, which was associated with the C=O bond. Through correlated studies of TG-MS, the main key fragments of ST-reacted AZA are reported.

Open Access

428. Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO3 Nanofillers

Authors: Horchidan, N; Ciomaga, CE; Curecheriu, LP; Stoian, G; Botea, M; Florea, M; Maraloiu, VA; Pintilie, L; Tufescu, FM; Tiron, V; Rotaru, A; Mitoseriu, L

Published: MAR 2022, NANOMATERIALS, 12, 934, DOI: 10.3390/nano12060934

The role of Ag addition on the structural, dielectric, and mechanical harvesting response of 20%(xAg - (1 - x)BaTiO3) - 80%PVDF (x = 0, 2, 5, 7 and 27 vol.%) flexible composites is investigated. The inorganic fillers were realized by precipitating fine (similar to 3 nm) silver nanoparticles onto BaTiO3 nanoparticles (similar to 60 nm average size). The hybrid admixtures with a total filling factor of 20 vol.% were embedded into the PVDF matrix. The presence of filler enhances the amount of beta-PVDF polar phase and the BaTiO3 filler induces an increase of the permittivity from 11 to 18 (1 kHz) in the flexible composites. The addition of increasing amounts of Ag is further beneficial for permittivity increase; with the maximum amount (x = 27 vol.%), permittivity is three times larger than in pure PVDF (epsilon(r) similar to 33 at 1 kHz) with a similar level of tangent losses. This result is due to the local field enhancement in the regions close to the filler-PVDF interfaces which are additionally intensified by the presence of silver nanoparticles. The metallic addition is also beneficial for the mechanical harvesting ability of such composites: the amplitude of the maximum piezoelectric-triboelectric combined output collected in open circuit conditions increases from 0.2 V/cm(2) (PVDF) to 30 V/cm(2) for x = 27 vol.% Ag in a capacitive configuration. The role of ferroelectric and metallic nanoparticles on the increasing mechanical-electric conversion response is also been explained.

Open Access

429. Electric Energy Storage Effect in Hydrated ZrO2-Nanostructured System

Authors: Doroshkevich, AS; Lyubchyk, AI; Oksengendler, BL; Zelenyak, TY; Appazov, NO; Kirillov, AK; Vasilenko, TA; Tatarinova, AA; Gorban, OO; Bodnarchuk, VI; Nikiforova, NN; Balasoiu, M; Mardare, DM; Mita, C; Luca, D; Mirzayev, MN; Nabiyev, AA; Popov, EP; Stanculescu, A; Konstantinova, TE; Aleksiayenak, YV

Published: JUN 2022, NANOMATERIALS, 12, 1783, DOI: 10.3390/nano12111783

The dimensional effect of electric charge storage with a density of up to 270 mu F/g by the hydrated ZrO2-nanoparticles system was determined. It was found that the place of localization of different charge carriers is the generalized heterophase boundary-nanoparticles surface. The supposed mechanism of the effect was investigated using the theory of dispersed systems, the band theory, and the theory of contact phenomena in semiconductors, which consists of the formation of localized electronic states in the nanoparticle material due to donor-acceptor interaction with the adsorption ionic atmosphere. The effect is relevant for modern nanoelectronics, microsystem technology, and printed electronics because it allows overcoming the basic physical restrictions on the size, temperature, and operation frequency of the device, caused by leakage currents.

430. Charge transport mechanisms in free-standing devices with electrospun electrodes

Authors: Ciobotaru, IC; Polosan, S; Enculescu, M; Nitescu, A; Enculescu, I; Beregoi, M; Ciobotaru, CC

Published: SEP 24 2022, NANOTECHNOLOGY, 33, 395203, DOI: 10.1088/1361-6528/ac7ac1

Embedding electronic and optoelectronic devices in common, daily use objects is a fast developing field of research. New architectures are needed for migrating from the classic wafer- based substrates. Novel types of flexible PMMA/Au/Alq(3)/LiF/Al structures were obtained starting from electrospun polymer fibers. Thus, using an electrospinning process poly (methyl metacrylate) (PMMA) nanofibers were fabricated. A thin Au layer deposition rendered the fiber array conductive, this being further employed as the anode. The next steps consisted of the thermal evaporation of tris(8-hydroxyquinolinato) aluminum (Alq(3)) and aluminum deposition as the cathode. The Au covered PMMA nanofiber layer had a similar behavior with an indium tin oxide film i.e. low sheet resistance 10.6 omega/sq and high transparency. The low electrode resistivities allow an electron drift mobility of about 10(-6) cm(2) V-1 s(-1) at a low applied field, similar to the counterpart structures based on thin films. Concerning the relaxation processes in these structures, the Cole-Cole plots exhibit a slightly deformed semicircle, indicating a more complex equivalent circuit for the processes between metal electrodes and the active layer. This equivalent circuit includes reactance equivalent processes at the anode, cathode, in the active layer and most probably originates from the roughness of the metallic electrodes.

431. Water denitration over titania-supported Pt and Cu by combined photocatalytic and catalytic processes: Implications for hydrogen generation properties in a photocatalytic system

Authors: Vasile, A; Papa, F; Bratan, V; Munteanu, C; Teodorescu, M; Atkinson, I; Anastasescu, M; Kawamoto, D; Negrila, C; Ene, CDD; Spataru, T; Balint, I

Published: APR 2022, JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, 10, 107129, DOI: 10.1016/j.jece.2022.107129

The present work provides a new approach to the water denitration process and a facile strategy of catalyst preparation for the efficient hydrogen generation. The main focus of the research reported here was nitrate removal from aqueous solutions and simultaneous hydrogen generation under UV-Vis-light irradiation. This is a very important aspect in case of practical applications, eliminating the external source of hydrogen. Aiming to get a deeper understanding on the role of surface structures (size and shape of nanoparticles) towards the reduction mechanism and to establish basic principles for an efficient process, Pt-Cu/TiO2 and Pt-Cu/TiO2 modified with well-defined Pt nanoparticles were employed. The synthesized materials were characterized using various physicochemical techniques and tested comparatively for: (i) nitrate catalytic reduction by hydrogen (dark reaction) and (ii) nitrate photocatalytic reduction by in-situ generated solar hydrogen. In order to enhance overall denitration reaction by combined photocatalytic and catalytic processes, photo-generated charges and in-situ generated H-2 as reducing agent were used. Improvement of catalytic performances of nitrate hydrogenation reaction (~100% NO3 over line conversion) related to intimate contact between Pt and Cu was obtained. The in-situ generated H-2 by water splitting over the studied catalysts reduces efficiently NO3 over line ions. Enhanced photo-catalytic activity toward solar H-2 production by deposited well-defined Pt nanoparticles (~10 nm) was achieved. In order to make possible decontamination of polluted waters using in-situ generated H-2 under light exposure, the future optimization of such photo-catalytic systems looks promising.

Open Access

432. Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose

Authors: Bartos, D; Burducea, C; Burducea, I; Caragheorgheopol, G; Constantin, F; Craciun, L; Dorobantu, D; Ghena, M; Iancu, D; Marcu, A; Mateescu, G; Mereuta, P; Moise, V; Negrila, C; Negut, D; Petris, M; Petrovici, M; Radulescu, L; Aprodu, V; Prodan, L; Radu, A; Stoian, G

Published: FEB 1 2022, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1024, 166122, DOI: 10.1016/j.nima.2021.166122

Detailed tests and analysis of ageing effects of high irradiation dose on Multi-Strip Multi-Gap Resistive Plate Counters (MSMGRPC) based on low resistivity glass electrodes, foreseen to be used for the most forward polar angles covered by the Time-of Flight (ToF) sub-detector of the Compressed Baryonic Matter (CBM) experiment at Facility for Antiprotons and Ion Research (FAIR) - Darmstadt are reported. The tests were performed at a multi-purpose irradiation facility of IFIN-HH based on Co-60 source. MSMGRPC efficiency, cluster size, surface and volume resistivity of the glass electrodes after irradiation are measured and compared with their values before irradiation. The results of a comprehensive analysis of the composition and properties of the deposited layers on the glass electrodes, based on different methods, i.e. Scanning Electron Microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), foil Elastic Recoil Detection Analysis (ERDA), Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM) and Terahertz Time Domain Spectroscopy (THz-TDS), are presented.

Open Access

433. Thermal Fluctuations and Electromagnetic Noise Spectra in Quantum Statistical Mechanics

Authors: Banyai, LA; Bundaru, M; Gartner, P

Published: JUN 9 2022, INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS, 61, 164, DOI: 10.1007/s10773-022-05124-8

We derive the thermal noise spectrum of the longitudinal and transverse electric field operator of a given wave vector starting from the quantum-statistical definitions and relate it to the frequency and wave vector dependent complex conductivity in a homogeneous, isotropic system of electromagnetic interacting charged particles in the frame of the non-relativistic QED. No additional assumptions except the validity of linear response are used in the proof. The Nyquist formula for vanishing frequency, as well as the noise spectral density of Callen-Welton follow as byproduct. Furthermore we discuss also the noise of the photon occupation numbers.

434. Copper(II) species with 1-(o-tolyl)biguanide: Structural characterization, ROS scavenging, antibacterial activity, biocompatibility and in silico studies

Authors: Maxim, C; Badea, M; Rostas, AM; Chifiriuc, MC; Pircalabioru, GG; Avram, S; Olar, R

Published: JAN 2022, APPLIED ORGANOMETALLIC CHEMISTRY, 36, e6471, DOI: 10.1002/aoc.6471

The species cis-[Cu(tbg)(2)](ClO4)(2) (CuTP) (tbg: 1-(o-tolyl)biguanide) was designed as a novel antimicrobial and biocompatible agent. The single-crystal X-ray diffraction revealed a mononuclear species with a very interesting structure consisting of two tautomeric forms of tbg arranged in a cis-configuration. A complex hydrogen bond network with perchlorate anions involved in different interactions leads to a supramolecular structure. The EPR data indicated the formation of a stable cis-trans mixture in dimethylsulfoxide. Moreover, the EPR experiments evidenced no activity against the superoxide radical (O-2 center dot(-)) but scavenging ability of the hydroxyl radical (HO center dot). This complex exhibited excellent antibacterial properties against planktonic and biofilm embedded gram-negative (Klebsiella pneumoniae, Enterobacter cloacae) and gram-positive (Bacillus subtilis, Lysteria monocytogenes) bacteria. The best efficiency was noticed against E. cloacae and L. monocytogenes with minimal inhibitory concentration and minimal biofilm eradication for a concentration value of 1.95 mu g/ml. One of the possible mechanisms of antimicrobial activity is represented by reactive oxygen species (ROS) generation. The complex was not cytotoxic on L929 fibroblasts. The in silico analysis confirmed the drug-likeness and safety profile of the tested compound and its potential for developing novel antimicrobial and therapeutic tools, targeting other clinical conditions besides infectious diseases.

Open Access

435. Photocatalytic and Antibacterial Properties of Doped TiO2 Nanopowders Synthesized by Sol-Gel Method

Authors: Preda, S; Pandele-Cusu, J; Petrescu, SV; Ciobanu, EM; Petcu, G; Culita, DC; Apostol, NG; Costescu, RM; Raut, I; Constantin, M; Predoana, L

Published: OCT 2022, GELS, 8, 673, DOI: 10.3390/gels8100673

For environmental applications, nanosized TiO2-based materials are known as the most important photocatalyst and are intensively studied for their advantages such as their higher activity, lower price, and chemical and photoresist properties. Zn or Cu doped TiO2 nanoparticles with anatase crystalline structure were synthesized by sol-gel process. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent, and a hydrolysing agent (ammonia-containing water) was added to obtain a solution with pH 10. The gels were characterized by TG/DTA analysis, SEM, and XPS. Based on TG/DTA results, the temperature of 500 degrees C was chosen for processing the powders in air. The structure of the samples thermally treated at 500 degrees C was analysed by XRD and the patterns show crystallization in a single phase of TiO2 (anatase). The surface of the samples and the oxidation states was investigated by XPS, confirming the presence of Ti, O, Zn and Cu. The antibacterial activity of the nanoparticle powder samples was verified using the gram-positive bacterium Staphylococcus aureus. The photocatalytic efficiency of the doped TiO2 nanopowders for degradation of methyl orange (MO) is here examined in order to evaluate the potential applications of these materials for environmental remediation.

Open Access

436. The Rectifying Contact of Hydrated Different Size YSZ Nanoparticles for Advanced Electronics

Authors: Doroshkevich, AS; Zakharova, AS; Oksengendler, BL; Lyubchyk, AI; Lyubchyk, SI; Lyubchyk, SB; Tatarinova, AA; Kirillov, AK; Vasilenko, TA; Gorban, OO; Bodnarchuk, VI; Nikiforova, NN; Zakharova, EA; Balasoiu, M; Mardare, DM; Mita, C; Stanculescu, A; Mirzayev, MN; Nabiyev, AA; Popov, EP; Khiem, L; Donkov, AA; Teofilovic, V; Jasinska, B; Chicea, D; Konstantinova, TY

Published: DEC 2022, NANOMATERIALS, 12, 4493, DOI: 10.3390/nano12244493

The paper considers the new effects of the nanoscale state of matter, which open up prospects for the development of electronic devices using new physical principles. The contacts of chemically homogeneous nanoparticles of yttrium-stabilized zirconium oxide (ZrO2-x mol% Y2O3, x = 0, 3, 4, 8; YSZ) with different sizes of 7.5 nm and 9 nm; 7.5 nm and 11 nm; and 7.5 nm and 14 nm, respectively, was studied on direct current using nanostructured objects in the form of compacts obtained by high-hydrostatic pressure (HP-compacts of 300MPa). A unique size effect of the nonlinear (rectifying-type contact) dependence of the electrical properties (in the region U < 2.5 V, I <= 2.7 mA) of the contact of different-sized YSZ nanoparticles of the same chemical composition is revealed, which indicates the possibility of creating semiconductor structures of a new type (homogeneous electronics). The electronic structure of the near-surface regions of nanoparticles of studied oxide materials and the possibility of obtaining specifically rectifying properties of the contacts were studied theoretically. Models of surface states of the Tamm-type are constructed considering the Coulomb long-range action. The discovered energy variance and its dependence on the curvature of the surface of nanoparticles made it possible to study the conditions for the formation of a contact potential difference in cases of nanoparticles of the same radius (synergistic effect), different radii (doped and undoped variants), as well as to discover the possibility of describing a group of powder particles within the Anderson model. The determined effect makes it possible to solve the problem of diffusion instability of semiconductor heterojunctions and opens up prospects for creating electronic devices with a fundamentally new level of properties for use in various fields of the economy and breakthrough critical technologies.

Open Access

437. Nanostructured PbS-Doped Inorganic Film Synthesized by Sol-Gel Route

Authors: Nicoara, AI; Eftimie, M; Elisa, M; Vasiliu, IC; Bartha, C; Enculescu, M; Filipescu, M; Aguado, CE; Lopez, D; Sava, BA; Oane, M

Published: SEP 2022, NANOMATERIALS, 12, 3006, DOI: 10.3390/nano12173006

IV-VI semiconductor quantum dots embedded into an inorganic matrix represent nanostructured composite materials with potential application in temperature sensor systems. This study explores the optical, structural, and morphological properties of a novel PbS quantum dots (QDs)-doped inorganic thin film belonging to the Al2O3-SiO2-P2O5 system. The film was synthesized by the sol-gel method, spin coating technique, starting from a precursor solution deposited on a glass substrate in a multilayer process, followed by drying of each deposited layer. Crystalline PbS QDs embedded in the inorganic vitreous host matrix formed a nanocomposite material. Specific investigations such as X-ray diffraction (XRD), optical absorbance in the ultraviolet (UV)-visible (Vis)-near infrared (NIR) domain, NIR luminescence, Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and atomic force microscopy (AFM) were used to obtain a comprehensive characterization of the deposited film. The dimensions of the PbS nanocrystallite phase were corroborated by XRD, SEM-EDX, and AFM results. The luminescence band from 1400 nm follows the luminescence peak of the precursor solution and that of the dopant solution. The emission of the PbS-doped film in the NIR domain is a premise for potential application in temperature sensing systems.

Open Access

438. The sustainable materials roadmap

Authors: Titirici, M; Baird, SG; Sparks, TD; Yang, SM; Brandt-Talbot, A; Hosseinaei, O; Harper, DP; Parker, RM; Vignolini, S; Berglund, LA; Li, YY; Gao, HL; Mao, LB; Yu, SH; Díez, N; Ferrero, GA; Sevilla, M; Szilágyi, PA; Stubbs, CJ; Worch, JC; Huang, YP; Luscombe, CK; Lee, KY; Luo, H; Platts, MJ; Tiwari, D; Kovalevskiy, D; Fermin, DJ; Au, H; Alptekin, H; Crespo-Ribadeneyra, M; Ting, VP; Fellinger, TP; Barrio, J; Westhead, O; Roy, C; Stephens, IEL; Nicolae, SA; Sarma, SC; Oates, RP; Wang, CG; Li, ZB; Loh, XJ; Myers, RJ; Heeren, N; Grégoire, A; Périssé, C; Zhao, XY; Vodovotz, Y; Earley, B; Finnveden, G; Björklund, A; Harper, GDJ; Walton, A; Anderson, PA

Published: JUL 1 2022, JOURNAL OF PHYSICS-MATERIALS, 5, 032001, DOI: 10.1088/2515-7639/ac4ee5

Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently 'critical materials' are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as 'critical' by the European Union and Department of Energy. Except in sustainable energy, materials are also key components in packaging, construction, and textile industry along with many other industrial sectors. This roadmap authored by prominent researchers working across disciplines in the very important field of sustainable materials is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the sustainable materials community. In compiling this roadmap, we hope to aid the development of the wider sustainable materials research community, providing a guide for academia, industry, government, and funding agencies in this critically important and rapidly developing research space which is key to future sustainability.

439. Tuning the acidity by addition of transition metal to Mn modified hollow silica spheres and their catalytic activity in ethanol dehydration to ethylene

Authors: Florea, M; Bocirnea, A; Neatu, S; Kuncser, AM; Trandafir, MM; Neatu, F

Published: SEP 25 2022, APPLIED CATALYSIS A-GENERAL, 646, 118860, DOI: 10.1016/j.apcata.2022.118860

Due to the currently worldwide petrochemical feedstock shortage, the ethylene synthesis from renewable non-oil sources becomes of high interest. The catalysts were prepared in two steps: (i) formation of spheres containing the carbon-coated Mn core by hydrothermal method, (ii) formation of the Si-Zr oxide shell by sol-gel method. The prepared catalysts were characterized by N2 physisorption, SEM-EDX, XRD, XPS, and NH3-TPD. The catalytic results have shown that Fe, Zn or Ni modified Mn core exhibited superior activity compared to the catalysts containing only Mn in the core. With 75% yield and 98% ethanol conversion at 350 degrees C and WHSV of 1.4 h-1, MnNi@SiZr was the best catalyst. These results are due to an increased number of acid sites compared to the other materials and an optimal ratio of weak/medium acid sites. Our findings suggest new lines for developing active and stable catalysts for ethylene synthesis from ethanol.

Open Access

440. Green Epoxidation of Olefins with ZnxAl/MgxAl-LDH Compounds: Influence of the Chemical Composition

Authors: Zavoianu, R; Cruceanu, A; Pavel, OD; Bradu, C; Florea, M; Bîrjega, R

Published: FEB 2022, CATALYSTS, 12, 145, DOI: 10.3390/catal12020145

This contribution concerns the effect of the chemical composition of the brucite-type layer of bi-cationic LDH materials ZnxAl and MgxAl (x = 2-5) and tri-cationic LDH MgyZnzAl (y + z = 4, y = 1, 2, 3) on their catalytic activity for olefin epoxidation with H2O2 in the presence of acetonitrile. LDH materials were prepared by the standard method of co-precipitation at constant pH 10, using an aqueous solution of the corresponding metal nitrates and a basic solution containing NaOH and Na2CO3. The fresh LDHs were calcined to yield the corresponding mixed oxides and then the recovery of the LDH structure by hydration of the mixed oxides was performed. The resulting samples were characterized by AAS, XRD, DRIFT, DR-UV-Vis, BET and determination of basic sites. The results of the catalytic tests for olefin epoxidation were well correlated with the basicity of the samples, which was in turn related to the M2+/Al3+ ratio and the electronegativity of different bivalent metals in the brucite-type layer.

Open Access

441. Damage threshold of CuCrFeTiV high entropy alloys for nuclear fusion reactors

Authors: Dias, M; Magalha, S; Antao, F; da Silva, RC; Gonsalves, AP; Carvalho, PA; Correia, JB; Galatanu, A; Alves, E

Published: OCT 15 2022, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 529, DOI: 10.1016/j.nimb.2022.09.003

A CuCrFeTiV high entropy alloy was prepared and irradiated with swift heavy ions in order to check its adequacy for use as a thermal barrier in future nuclear fusion reactors. The alloy was prepared from the elemental powders by ball milling, followed by consolidation by spark plasma sintering at 1178 K and 65 MPa. The samples were then irradiated at room temperature with 300 keV Ar+ ions with fluences in the 3 x 1015 to 3 x 1018 Ar+/cm2 range to mimic neutron-induced damage accumulation during a duty cycle of a fusion reactor. Structural changes were investigated by X-ray diffraction, and scanning electron microscopy and scanning transmission electron microscopy, both coupled with X-ray energy dispersive spectroscopy. Surface irradiation damage was detected for high fluences (3 x 1018 Ar+/cm2) with formation of blisters of up to 1 mu m in diameter. Cross-sectional scanning transmission electron microscopy showed the presence of intergranular cavities only in the sample irradiated with 3 x 1018 Ar+/cm2, while all irradiation experiments produced intragranular nanometric-sized bubbles with increased density for higher Ar+ fluence. The Williamson-Hall method revealed a decrease in the average crystallite size and an increase in residual strain with increasing fluence, consistent with the formation of Ar+ bubbles at the irradiated surface.

Open Access

442. Microwave and Terahertz Properties of Spark-Plasma-Sintered Zr0.8Sn0.2TiO4 Ceramics

Authors: Nedelcu, L; Burdusel, M; Grigoroscuta, MA; Geambasu, CD; Enculescu, M; Badica, P; Banciu, MG

Published: FEB 2022, MATERIALS, 15, 1258, DOI: 10.3390/ma15031258

Zr0.8Sn0.2TiO3 (ZST) powders synthesized by solid-state reaction were subject to processing by spark plasma sintering (SPS). A single-phase ceramic with a high relative density of 95.7% and 99.6% was obtained for sintering temperatures of 1150 degrees C and 1200 degrees C, respectively, and for a dwell time of 3 min. In order to reduce the oxygen vacancies, as-sintered discs were annealed in air at 1000 degrees C. The dielectric loss of the annealed samples, expressed by the Q x f product, measured in the microwave (MW) domain, varied between 35 THz and 50 THz. The intrinsic losses (Q x f ~ 60 THz) were derived by using terahertz time-domain spectroscopy (THz-TDS).

Open Access

443. The Effects of Electron Beam Irradiation on the Morphological and Physicochemical Properties of Magnesium-Doped Hydroxyapatite/Chitosan Composite Coatings

Authors: Bita, B; Stancu, E; Stroe, D; Dumitrache, M; Ciobanu, SC; Iconaru, SL; Predoi, D; Groza, A

Published: FEB 2022, POLYMERS, 14, 582, DOI: 10.3390/polym14030582

This work reports on the influence of 5 MeV electron beam radiations on the morphological features and chemical structure of magnesium-doped hydroxyapatite/chitosan composite coatings generated by the magnetron sputtering technique. The exposure to ionizing radiation in a linear electron accelerator dedicated to medical use has been performed in a controllable manner by delivering up to 50 Gy radiation dose in fractions of 2 Gy radiation dose per 40 s. After the irradiation with electron beams, the surface of layers became nano-size structured. The partial detachment of irradiated layers from the substrates has been revealed only after visualizing their cross sections by scanning electron microscopy. The energy dispersive X-ray spectral analysis of layer cross-sections indicated that the distribution of chemical elements in the samples depends on the radiation dose. The X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction analysis have shown that the physicochemical processes induced by the ionizing radiation in the magnesium doped hydroxyapatite/chitosan composite coatings do not alter the apatite structure, and Mg remains bonded with the phosphate groups.

Open Access

444. MgB2-based biodegradable materials for orthopedic implants br

Authors: Badica, P; Batalu, ND; Balint, E; Tudor, N; Barbuceanu, F; Peteoaca, A; Micsa, C; Eremia, AD; Trancau, OI; Burdusel, M; Grigoroscuta, MA; Aldica, GV; Radu, D; Porosnicu, I; Tiseanu, I

Published: SEP-OCT 2022, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 20, DOI: 10.1016/j.jmrt.2022.07.164

Bulk high density MgB2 and a composite material made of a PLA matrix and MgB2 powder inclusions were in vivo tested as candidates for biodegradable materials for orthopedic implants. A rat model was used. Implants were introduced into femoral bone, in transversal and longitudinal directions. Assessment of the implant-tissue interaction was performed by X-ray imaging, X-ray computer tomography, electron microscopy, cytology, and histopathology on samples at 40 and 90 days after surgery. Both materials are biocompatible, bone and adjacent soft tissue showing good tolerance of implants. Biodegradation of MgB2 is faster than for PLA-MgB2 composite, but in both cases, it is accompanied by bone regeneration. Results suggest that use of MgB2-containing composites can promote space and time control of degradation and promotes MgB2 as a promising material for fracture repair. (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Open Access

445. Ferroelectricity modulates polaronic coupling at multiferroic interfaces

Authors: Husanu, MA; Popescu, DG; Bisti, F; Hrib, LM; Filip, LD; Pasuk, I; Negrea, R; Istrate, MC; Lev, L; Schmitt, T; Pintilie, L; Mishchenko, A; Teodorescu, CM; Strocov, VN

Published: AUG 15 2022, COMMUNICATIONS PHYSICS, 5, 209, DOI: 10.1038/s42005-022-00983-3

A deeper understanding of the coupling at the interface of multiferroics heterostructures is being achieved by the use of synchrotron radiation techniques. Here, the authors use k-resolved soft X-ray photoemission spectroscopy and first principles calculations to investigate the band structure of several multiferroic heterostructures, isolating the distinct signature of the interface. Physics of the multiferroic interfaces is currently understood mostly within a phenomenological framework based on screening of the polarization field and depolarizing charges. Additional effects still unexplored are the band dependence of the interfacial charge modulation and the associated changes of the electron-phonon interaction, coupling the charge and lattice degrees of freedom. Here, multiferroic heterostructures of the colossal-magnetoresistance manganite La1-xSrxMnO3 buried under ferroelectric BaTiO3 and PbZrxTi1-xO3 are investigated using soft-X-ray angle-resolved photoemission. The experimental band dispersions from the buried La1-xSrxMnO3 identify coexisting two-dimensional hole and three-dimensional electron charge carriers. The ferroelectric polarization modulates their charge density, affecting the coupling of the 2D holes and 3D electrons with the lattice which forms large Frohlich polarons inherently reducing mobility of the charge carriers. Our k-resolved results on the orbital occupancy, band filling and electron-lattice interaction in multiferroic oxide heterostructures modulated by the ferroelectric polarization disclose most fundamental physics of these systems needed for further progress of beyond-CMOS ferro-functional electronics.

446. Sonogashira Synthesis of New Porous Aromatic Framework-Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling

Authors: Cata, L; Terenti, N; Cociug, C; Hadade, ND; Grosu, I; Bucur, C; Cojocaru, B; Parvulescu, V; Mazur, M; Cejka, J

Published: MAR 2 2022, ACS APPLIED MATERIALS & INTERFACES, 14, DOI: 10.1021/acsami.1c24429

Palladium nanoparticles entrapped in porous aromatic frameworks (PAFs) or covalent organic frameworks may promote heterogeneous catalytic reactions. However, preparing such materials as active nanocatalysts usually requires additional steps for palladium entrapment and reduction. This paper reports as a new approach, a simple procedure leading to the self-entrapment of Pd nanoparticles within the PAF structure. Thus, the selected Sonogashira synthesis affords PAF-entrapped Pd nanoparticles that can catalyze the C-C Suzuki-Miyaura cross-coupling reactions. Following this new concept, PAFs were synthesized via Sonogashira cross-coupling of the tetraiodurated derivative of tetraphenyl aLam an tan e or spiro-9,9'-bifluorene with 1,6-diethynylpyrene, then characterized them using powder X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, high-resolution scanning transmission electron microscopy, and textural properties (i.e., adsorption-desorption isotherms). The PAF-entrapped Pd nanocatalysts showed high catalytic activity in Suzuki-Miyaura coupling reactions (demonstrated by preserving the turnover frequency values) and stability (demonstrated by palladium leaching and recycling experiments). This new approach presents a new class of PAFs with unique structural, topological, and compositional complexities as entrapped metal nanocatalysts or for other diverse applications.

Open Access

447. Microstructure and Conduction Electron Quantum Properties of Small Diamond Cubic α-Sn Nanocrystals Embedded in Cubic Boron Nitride Crystals

Authors: Nistor, SV; Nistor, LC; Stefan, M; Joita, AC

Published: 2022 NOV 11 2022, ACS OMEGA, DOI: 10.1021/acsomega.2c03785

The morphology, structure, composition, and con-duction electron properties of quasi-spherical tin nanocrystals (NCs) of 2.5 nm average diameter, with unstrained, bulk-like alpha-Sn diamond cubic structure, observed in dark cubic boron nitride (cBN) crystallites, were determined by correlated analytical high-resolution scanning transmission electron microscopy and multifrequency electron spin resonance (ESR) investigations. The narrow Lorentzian ESR line with g = 2.0028 is attributed to the conduction ESR of the alpha- Sn NCs, consistent with the temperature-and frequency-independent small g-shift and intensity reduction under high temperature (950 degrees C) vacuum annealing when the alpha-Sn NCs are thermally dissolved in the host cBN crystallites. The ESR linewidth and line intensity vs temperature dependences recorded in the 20 to 295 K range are quantitatively described considering the presence of discrete, quantum confinement-induced conduction electron energy levels with Delta QC/kB = 125 K separation, close to the theoretical value for conductive alpha-Sn NCs of 2.5 nm in diameter. The observed properties are tentatively explained with the predicted nanosize induced band-gap opening and change of band ordering from bulk alpha-Sn to small unstrained alpha-Sn NCs, resulting in a topological phase transition that also explains the predominantly s-like character of the conduction band electron orbitals.

Open Access

448. Novel Green Nanotechnologies Applied in Environmental Protection and Health

Authors: Barbinta-Patrascu, ME; Badea, N; Zgura, I

Published: AUG 2022, MATERIALS, 15, 5297, DOI: 10.3390/ma15155297

Open Access

449. The Photoluminescence and Vibrational Properties of Black Phosphorous Sheets Chemically/Electrochemically Functionalized in the Presence of Diphenylamine

Authors: Baibarac, M; Burlanescu, T; Stroe, M; Smaranda, I; Negrila, C

Published: NOV 2022, POLYMERS, 14, 4479, DOI: 10.3390/polym14214479

In this work, new information concerning the optical properties of black phosphorus (BP) sheets chemically/electrochemically functionalized with diphenyl amine (DPA) and its macromolecular compound (poly(diphenylamine) (PDPA)) in the absence/presence of phosphotungstic acid (PTA) is reported. Raman scattering and FTIR spectroscopy studies indicate that the interaction of BP with PTA leads to the elimination of the PxOy layer onto the surface of the BP sheets. In the case of the chemical interaction of BP with DPA, the reaction product corresponds to DPA chemically functionalized BP sheets having an imino-phosphorane (IP) structure. The electrochemical oxidation of BP sheets chemically functionalized with DPA in the presence of PTA leads to an increase in the weight of P-N bonds as a consequence of the generation of PDPA doped with the PTA heteropolyanions, as shown by FTIR spectroscopy and Raman scattering. This process is evidenced by a shift of the Raman line from 362 cm(-1) to 378 cm(-1), assigned to the A(1g) mode. This change was explained by taking into account the compression of the layers containing P atoms, which is induced by PDPA macromolecular chains. The decrease in the intensity of the PL spectra of DPA as well as PDPA, in the presence of BP, indicates that BP acts as a PL quenching agent for these compounds. A preferential orientation of the PDPA doped with the PTA heteropolyanions on the surface of BP sheets is highlighted by the variation of the binding angle of the PDPA on the surface of BP sheets from 44.7 degrees to 39.9 degrees.

450. Enhanced photoelectrochemical activity of WO3-decorated native titania films by mild laser treatment

Authors: Spataru, T; Mihai, MA; Preda, L; Marcu, M; Radu, MM; Becherescu, ND; Velea, A; Zaki, MY; Udrea, R; Satulu, V; Spataru, N

Published: SEP 15 2022, APPLIED SURFACE SCIENCE, 596, 153682, DOI: 10.1016/j.apsusc.2022.153682

The effectiveness of the electrochemical WO3-modification as a method for improving the photoactivity of native air-formed TiO2 layers was assessed. The way in which a mild laser treatment influences the photo-electrochemical performances of the thus obtained WO3/TiO2 systems was also investigated. At laser-treated electrodes (L-WO3/TiO2), the melting-solidification process induced by the treatment led to a smaller size of the deposited WO3 particles and to their better dispersion on the surface. The treatment also enhanced the surface oxygen deficiency and ensured better relative absorptivity of the oxygenated species on the surface. These features, together with the intrinsic narrower bandgap of the WO3/TiO2 composites, the higher donor density and the lower flat band potential of L-WO3/TiO2 enabled faster kinetic of the oxygen photoanodic evolution. Importantly, the same process exhibited a cathodic shift of its onset potential. The laser treatment also strongly enhanced the photoelectrocatalytic performances for UV-assisted methanol anodic oxidation.

Open Access

451. New Aspects Concerning the Ampicillin Photodegradation

Authors: Cercel, R; Paraschiv, M; Florica, CS; Daescu, M; Udrescu, A; Ciobanu, RC; Schreiner, C; Baibarac, M

Published: APR 2022, PHARMACEUTICALS, 15, 415, DOI: 10.3390/ph15040415

New aspects concerning the photodegradation (PD) of ampicillin are reported by photoluminescence (PL), Raman scattering and FTIR spectroscopy. The exposure of ampicillin in the absence (AM) and in the presence of the excipient (AMP) to UV light leads to an intensity diminution of the photoluminescence excitation (PLE) and photoluminescence (PL) spectra and the emergence of a new IR band at 3450 cm(-1). The photoluminescence studies demonstrate that the AM PD is amplified in the presence of excipients and an alkaline medium. In this last case, the PD process of AM involves the emergence of new compounds, whose presence is highlighted by: (i) the emergence of the isosbestic point at 300 nm in the UV-VIS spectra; (ii) a change in the ratio between the absorbance of IR bands situated in the spectral ranges 1200-1660 and 3250-3450 cm(-1); and (iii) a change in the ratio between the intensities of the Raman lines localized in the spectral ranges 1050-1800 and 2750-3100 cm(-1). A chemical mechanism of the PD processes of AM in an alkaline medium is proposed.

452. Quantification of cell oxygenation in 2D constructs of metallized electrospun polycaprolactone fibers encapsulating human valvular interstitial cells

Authors: Sanz, CG; Mihaila, AC; Evanghelidis, A; Diculescu, VC; Butoi, E; Barsan, MM

Published: JAN 15 2022, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 905, 116005, DOI: 10.1016/j.jelechem.2021.116005

The present study brings developments in the area of tissue engineering of heart valves, with the design and application of a new 2D model for human heart valve. This model contains valvular interstitial cells (VIC) encapsulated in gold covered electrospun polycaprolactone (PCL/Au) fibers, the latter serving also as an electrochemical sensor that enables the monitoring of oxygen levels of cellular media. The biocompatibility of PCL and PCL/Au with VIC was evaluated after the encapsulation of VIC in both scaffolds using the lactate dehydrogenase assay. Fluorescence microscopy of the encapsulated cells was used for the investigation of cell morphology, by employing phalloidin labelled F-actin (red) and DAPI nuclear staining (blue). The electrochemical techniques allowed to investigate the effect of cell encapsulation within the PCL/Au 2D constructs and to quantify the dissolved oxygen levels in cell culture media at both PCL/Au and PCL/Au with encapsulated cells (PCL/ Au/cells). Experiments were performed in a hypoxistation, which allowed a fine control on the cellular media oxygenation. Electrochemical impedance spectroscopy (EIS) was used to evaluate the electrochemical behavior of the 2D constructs, PCL/Au and PCL/Au/cells, in cellular media at different O-2 concentration. Results were analyzed and both impedance values at a fixed frequency and values of the equivalent circuit elements were used to construct calibration curves for dissolved O-2 determination. The second electrochemical technique used to monitor the levels of O-2 at PCL/Au and PCL/Au/cells in the cellular media was square wave voltammetry with sensitivities of 1.5 and 2.5 mu A cm(-2) mu M-1, for PCL/Au and PCL/Au/cells, respectively.

Open Access

453. New Chalcogenide Glass-Ceramics Based on Ge-Zn-Se for IR Applications

Authors: Velea, A; Sava, F; Badica, P; Burdusel, M; Mihai, C; Galca, AC; Matei, E; Buruiana, AT; El Khouja, O; Calvez, L

Published: JUL 2022, MATERIALS, 15, 5002, DOI: 10.3390/ma15145002

The consumer market requests infrared (IR) optical components, made of relatively abundant and environmentally friendly materials, to be integrated or attached to smartphones. For this purpose, three new chalcogenides samples, namely Ge23.3Zn30.0Se46.7 (d_GZSe-1), Ge26.7Zn20.0Se53.3 (d_GZSe-2) and Ba4.0Ge12.0Zn17.0Se59.0I8.0 (d_GZSe-3) were obtained by mechanical alloying and processed by spark plasma sintering into dense bulk disks. Obtaining a completely amorphous and homogeneous material proved to be difficult. d_GZSe-2 and d_GZSe-3 are glass-ceramics with the amount of the amorphous phase being 19.7 and 51.4 wt. %, while d_GZSe-1 is fully polycrystalline. Doping with barium and iodine preserves the amorphous phase formed by milling and lowers the sintering temperature from 350 degrees C to 200 degrees C. The main crystalline phase in all of the prepared samples is cubic ZnSe or cubic Zn0.5Ge0.25Se, while in d_GZSe-3 the amorphous phase contains GeSe4 clusters. The color of the first two sintered samples is black (the band gap values are 0.42 and 0.79 eV), while d_GZSe-3 is red (E-g is 1.37 eV) and is transparent in IR domain. These results are promising for future research in IR materials and thin films.

454. DIELECTRIC AND ELECTRIC PROPERTIES OF NOVEL CORE-SHELL NANOCOMPOSITE: SrFe12O19 - BNT-BT

Authors: Greculeasa, SG; Comanescu, C; Cioangher, M

Published: 2022, ROMANIAN REPORTS IN PHYSICS, 74, 504, DOI:

The dielectric and electric properties of a core-shell SrFe12O19 - BNT-BT nanocomposite were explored in this study. The desired composition and the existence of the magnetoplumbite SrFe12O19 and perovskite BNT-BT structures were verified by X-ray diffraction. The dielectric constant values approached the case of BNT-BT due to the small amount of hexaferrite content. The electric properties were also derived.

455. The effect of cation distribution and heat treatment temperature on the structural, surface, morphological and magnetic properties of MnxCo1-xFe2O4@SiO2 nanocomposites

Authors: Dippong, T; Lazar, MD; Deac, IG; Palade, P; Petean, I; Borodi, G; Cadar, O

Published: FEB 25 2022, JOURNAL OF ALLOYS AND COMPOUNDS, 895, 162715, DOI: 10.1016/j.jallcom.2021.162715

This paper presents the effect of Mn2+ substitution for Co2+, in CoFe2O4 embedded in SiO2 matrix, on the structural, surface, morphological and magnetic properties. X-ray diffraction (XRD) and Mossbauer spectroscopy indicate the presence of a nanocrystalline mixed cubic spinel. In all cases, for the nanocomposites (NCs) heat-treated at 200 degrees C, a single, low crystalline ferrite phase was remarked, while for the other heat-treatment temperatures up to 1200 degrees C and with increasing Mn content, the secondary phase of alpha-Fe2O3 appears, accompanied also by the secondary phase of SiO2 at 1200 degrees C. The Fourier transform infrared (FT-IR) spectroscopy confirms the consumption of starting metallic nitrates, the formation of Co-O, Mn-O, Fe-O bonds in ferrites@SiO2 matrix. The Mossbauer spectra show the characteristic magnetic patterns of Co and Mn spinels. According to the atomic force microscopy (AFM) analysis, the particle size increases from 15 to 80 nm with the increase of Mn content. The specific surface area varies in the range 150-450 m(2)/g due to the substitution of Co2+ ion with Mn2+ ion and decreases with increasing heat treatment temperature, reaching values below 1 m(2)/g at 1200 degrees C. All NCs have pores within the mesoporous range, with high dispersion of pores' sizes. Furthermore, the release of fine nanoparticles in aqueous environment is facilitated by the powders' mesoporous structure preserved at 200, 500 and 800 degrees C heat treatment temperatures. The porous network collapse after heat treatment at 1200 degrees C leads to releasing of bigger nanoparticles, in good agreement with AFM observation. Magnetization, coercivity and anisotropy evolve proportionally with the particle size for the NCs heat-treated at 800 degrees C (M-s = 18.9-36.3 emu/g; M-R = 3.05-14.1 emu/g, H-c = 31.83-53.2 kA/m, K= 0.378.10(-3) -1.21.10(-3) erg/cm(-1)) and inverse proportionally for those heat-treated at 1200 degrees C (M-s = 30.7-19.4 emu/g; M-R = 11.60 7.20 emu/g, H-c= 127.3-15.9 kA/m, K= 2.45.10(-3)-0.19.10(-3) erg/cm(-1)). The NCs with high Mn content heat-treated at 1200 degrees C show superparamagnetic behavior, while those with low Mn content display ferrimagnetic behavior. (C) 2021 Elsevier B.V. All rights reserved.

456. Layered SnSe nanoflakes with anharmonic phonon properties and memristive characteristics

Authors: Buruiana, AT; Bocirnea, AE; Kuncser, AC; Tite, T; Matei, E; Mihai, C; Zawadzka, N; Olkowska-Pucko, K; Kipczak, L; Babinski, A; Molas, MR; Velea, A; Galca, AC

Published: OCT 15 2022, APPLIED SURFACE SCIENCE, 599, 153983, DOI: 10.1016/j.apsusc.2022.153983

Understanding the phonon anharmonicity and temperature-dependent behavior of phonons that affect the thermal transport properties in 2D materials is crucial for developing efficient thermoelectric and memristor devices. SnSe has attracted significant interest because of its potential applications for developing such novel devices. Here, orthorhombic SnSe nanoflakes with a thickness of less than 100 nm and oriented along the [100] crystal axis were obtained using physical vapor transport at atmospheric pressure. Polarization-resolved Raman spectroscopy of SnSe nanoflakes was performed at a temperature of 5 K. Temperature-dependent frequencies and linewidths of Raman modes in tin selenide were fitted according to the anharmonic phonon coupling theory. The results indicate that both two and three order processes are responsible for the phonon decay in tin selenide. The memristive property was confirmed by electrical measurements of SnSe devices. SnSe memristors have an operating current of 10-4 A, similar to other transition-metal dichalcogenide memristors, but are more energy efficient than memristors based on defect migration, with a threshold voltage of 3 V.

457. Textile Materials Treatment With Mixture of TiO2:N and SiO2Nanoparticles for Improvement of Their Self-Cleaning Properties

Authors: Mateescu, AO; Mateescu, G; Burducea, I; Mereuta, P; Chirila, L; Popescu, A; Stroe, M; Nila, A; Baibarac, M

Published: JUL 3 2022, JOURNAL OF NATURAL FIBERS, 19, DOI: 10.1080/15440478.2020.1818349

This study addresses the deposition with improved adhesion of TiO2:N/SiO(2)mixture, with different concentrations of the nano-powders (NPs) (1:0,5; 1:1 and 1:1,5) on 100% cotton fabrics. The characteristics of the deposited thin films were investigated by scanning electron microscopy (SEM), Rutherford backscattering spectrometry (RBS), Raman scattering, FTIR, and UV-VIS absorption spectroscopy. To improve the treatment durability to the external factors, the different crosslinking methods were used. Photocatalytic activity of functionalized textile fabrics was evaluated by determining the photodegradation efficiency of the methylene blue (MB) dye and forest juice, measuring the color difference of the irradiated samples compared with non-irradiated samples. Washing durability of the samples was achieved qualitatively by determining the photocatalytic activity remaining on the textile fabrics after 1 and 5 washing cycles. The samples treated with the mixture of TiO2:N/SiO(2)have demonstrated improved self-cleaning properties, the highest photocatalytic activity being obtained for the highest value of TiO2:N/SiO(2)NPs molar concentrations equal to 1:1.

Open Access

458. Synthesis and Characterization of Hematite-Based Nanocomposites as Promising Catalysts for Indigo Carmine Oxidation

Authors: Kuncser, AC; Rostas, AM; Zavoianu, R; Pavel, OD; Vlaicu, ID; Badea, M; Culita, DC; Tirsoaga, A; Olar, R

Published: JUL 2022, NANOMATERIALS, 12, 2511, DOI: 10.3390/nano12142511

The hematite-based nanomaterials are involved in several catalytic organic and inorganic processes, including water decontamination from organic pollutants. In order to develop such species, a series of bimetallic hematite-based nanocomposites were obtained by some goethite composites-controlled calcination. Their composition consists of various phases such as alpha-FeOOH, alpha-Fe2O3 or gamma-Fe2O3 combined with amorphous (Mn2O3, Co3O4, NiO, ZnO) or crystalline (CuO) oxides of the second transition ion from the structure. The component dimensions, either in the 10-30 or in the 100-200 nm range, together with the quasi-spherical or nanorod-like shapes, were provided by Mossbauer spectroscopy and powder X-ray diffraction as well as transmission electron microscopy data. The textural characterization showed a decrease in the specific area of the hematite-based nanocomposites compared with corresponding goethites, with the pore volume ranging between 0.219 and 0.278 cm(3)g(-1). The best catalytic activity concerning indigo carmine removal from water in hydrogen peroxide presence was exhibited by a copper-containing hematite-based nanocomposite sample that reached a dye removal extent of over 99%, which correlates with both the base/acid site ratio and pore size. Moreover, Cu-hbnc preserves its catalytic activity even after four recyclings, when it still reached a dye removal extent higher than 90%.

459. Two are better than one-Synthesis of novel blue and green emissive hydroxy-oxadiazoles

Authors: Anghel, CC; Badescu, C; Mirea, AG; Paun, A; Hadade, ND; Madalan, AM; Matache, M; Popescu, CC

Published: JAN 2022, DYES AND PIGMENTS, 197, 109927, DOI: 10.1016/j.dyepig.2021.109927

We describe herein synthesis of novel hydroxy-bis-2,5-disubstituted-1,3,4-oxadiazoles and their ability to emit green light, through ESIPT mechanism. Unlike previous reports, our compounds exhibit very good quantum yields, most likely avoiding the presumed intramolecular fluorescence quenching in presence of the second oxadiazole moiety. Studies regarding behaviour of the compounds in polar and non-polar solvents are also described, indicating the possibility to modulate the emission according to the environment. The solid-state structural analysis, corroborated with fluorescence data, suggest the importance of the tert-butyl group in preservation of the luminescent properties. The corresponding benzyl-protected compounds, precursors to the target hydroxy-bis-2,5-disubstituted-1,3,4-oxadiazoles were also investigated for their optical properties and found to display very intense blue emission, with quantum yields values in dichloromethane (between 0.423 and 0.499) almost equal to the standard quinine sulfate.

Open Access

460. 'Put variety in White': Multi-analytical investigation of the white pigments inlaid on Early Chalcolithic pottery from Southern Romania

Authors: Opris, V; Velea, A; Secu, M; Rostas, AM; Buruiana, AT; Simion, CA; Mirea, DA; Matei, E; Bartha, C; Dimache, M; Lazar, C

Published: APR 2022, JOURNAL OF ARCHAEOLOGICAL SCIENCE-REPORTS, 42, 103402, DOI: 10.1016/j.jasrep.2022.103402

The current study aims to present and discuss the results obtained by complementary archaeometric methods applied for the first time on white pigments inlaid on excised pottery of the Boian-Vidra tradition (Early Chalcolithic, c. 4900-4600 BCE). The samples came from three settlements located in Southern Romania (Sultana-Ghetarie, Vidra, and Vladiceasca). They were selected considering that the pottery was produced in approximately contemporary sites, located relatively close to each other in the same geographical region, namely the Romanian Plain. The experimental part included the analysis of local samples of carbonate concretions and prehistoric animal bone ash as reference materials. Archaeometric investigations consisted in applying "in-air" PIXE and EDX methods for the chemical composition, XRD and FTIR for mineralogical data, SEM for microstructure observation, and EPR for the characterisation of the paramagnetic centres. Calcite, bone ash, and silica rich sediments were identified as the primary decorating pigments. The mixtures of calcite and bone-ash observed in 13 samples were specific to the sites at Vidra and Vladiceasca. Silica-rich sediments from distant sources were the main whitening materials in two samples from Vladiceasca, while for the samples from Sultana-Ghetarie, calcite was the only whitening mineral. The results show with a high degree of confidence the use of both local (i.e., carbonate neo-formations and bone ash) and exotic (silica-rich sediments) raw materials to obtain the white pigment applied to Boian-Vidra pottery. Thus, the current data show the adaptability of the potters with respect to the surrounding resources and also provide new evidence for a vast trade network of raw materials and/or finished products in the Lower Danube area during the Early Chalcolithic. The deliberate mixing of two whitening materials from different sources could be a technological choice and may highlight complex symbolic behaviours.

461. Radiation-induced point- and cluster-related defects in epitaxial p-type silicon diodes

Authors: Gurimskaya, Y; Suau, IM; Moll, M; Fretwurst, E; Makarenko, L; Pintilie, I; Schwandt, J

Published: 2022, 2019 19TH EUROPEAN CONFERENCE ON RADIATION AND ITS EFFECTS ON COMPONENTS AND SYSTEMS (RADECS), DOI: 10.1109/RADECS47380.2019.9745686

A consistent quantitative description of radiation-induced degradation on p-type Silicon detectors is conducted within CERN RD50 collaboration. The present contribution summarizes the first obtained results for epitaxial 50 mu m thin pad diodes irradiated with protons, neutrons and gamma rays. Microscopic and Macroscopic damage-driven effects are analyzed.

Open Access

462. Antiproliferative Copper(II) Complexes Bearing Mixed Chelating Ligands: Structural Characterization, ROS Scavenging, In Silico Studies, and Anti-Melanoma Activity

Authors: Olar, R; Maxim, C; Badea, M; Bacalum, M; Raileanu, M; Avram, S; Korosin, NC; Burlanescu, T; Rostas, AM

Published: AUG 2022, PHARMACEUTICS, 14, 1692, DOI: 10.3390/pharmaceutics14081692

Melanoma is a skin cancer characterized by rapid growth and spread for which current therapies produce both resistance and increased risk of infection. To develop new anti-melanoma biocompatible species, the series of complexes Cu(N-N)(bzac)(X)center dot nH(2)O (N-N: 1,10-phenanthroline/2,2 '-bipyridine, Hbzac: 1-phenyl-1,3-butanedione, X: NO3/ClO4, and n = 0, 1) was studied. Single-crystal X-ray diffraction revealed a mononuclear structure for all complexes. The ability of the complexes to scavenge or trap reactive oxygen species such as O-2 center dot(-) and HO center dot was proved by EPR spectroscopy experiments. All complexes inhibited B16 murine melanoma cells in a dose-dependent and nanomolar range, but the complexes with 1,10-phenanthroline were more active. Moreover, comparative activity on B16 and healthy BJ cells revealed a therapeutic index of 1.27-2.24. Bioinformatic methods were used to calculate the drug-likeness, pharmacokinetic, pharmacogenomic, and pharmacodynamic profiles of the compounds. The results showed that all compounds exhibit drug-likeness features, as well as promising absorption, distribution, metabolism, and excretion (ADME) properties, and no toxicity. The pharmacodynamics results showed that the neutral species appear to be good candidates for antitumor molecular targets (Tyrosyl-DNA phosphodiesterase 1, DNA-(apurinic or apyrimidinic site) lyase or Kruppel-like factor 5). Furthermore, the pharmacogenomic results showed a good affinity of the copper(II) complexes for the human cytochrome. These results recommend complexes bearing 1,10-phenanthroline as good candidates for developing drugs to melanoma alternative treatment.

Open Access

463. Correlated studies of photoluminescence, vibrational spectroscopy and mass spectrometry concerning the pantoprazole sodium photodegradation

Authors: Baibarac, M; Paraschiv, M; Cercel, R; Smaranda, I; Bartha, C; Trandabat, A

Published: JUN 9 2022, SCIENTIFIC REPORTS, 12, 9515, DOI: 10.1038/s41598-022-13648-6

In this work, new optical evidences concerning the changes induced of the UV light on pantoprazole sodium (PS), in solid state and as aqueous solution, are reported by UV-VIS spectroscopy, photoluminescence (PL), Raman scattering and FTIR spectroscopy. New evidences concerning the products of the PS photodegradation pathways are reported by the correlated studies of thermogravimetry and mass spectrometry. The influence of the excipients and alkaline medium on the PS photodegradation is also studied. New aspects regarding the chemical mechanism of the PS photodegradation in the presence of the water vapor and oxygen form air and the alkaline medium are shown. Our results confirm that the PS photodegradation induced of the water vapors and oxygen from air leads to the generation of 5-difluoromethoxy-3H-benzimidazole-2-thione sodium, 5-difluoromethoxy-3H-benzimidazole sodium, 2-thiol methyl-3, 4-dimethoxypyridine and 2-hydroxymethyl-3, 4-dimethoxypyridine, while in the alkaline medium, compounds of the type of the 2-oxymethyl-3,4-dimethoxypyridine sodium salts are resulted.

Open Access

464. Physicochemical Characterization of Europium-Doped Hydroxyapatite Thin Films with Antifungal Activity

Authors: Ciobanu, CS; Predoi, MV; Buton, N; Megier, C; Iconaru, SL; Predoi, D

Published: MAR 2022, COATINGS, 12, 306, DOI: 10.3390/coatings12030306

Owing to its unique biological and physicochemical properties, hydroxyapatite (HAp) represents one of the most extensively studied biomaterials for biomedical applications. It is well known that Candida is currently one of the fungi frequently involved in the onset and development of post-implant infections and, owing to the appearance of antifungal resistance, it is quite difficult to treat despite all the tremendous efforts made in this regard by the scientific world. Therefore, in this context, we report for the first time in this paper, the development and characterization of europium-doped thin films (5EuHAp, x(Eu) = 0.05) on a Si substrate by a spin-coating method. The results of ultrasound (US), zeta (zeta) potential, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) studies are presented. The XRD studies conducted on 5EuHAp suspension revealed the nanometric dimensions of the particles and sample purity. In addition, a moderate stability of the 5EuHAp suspension was observed. XPS measurements revealed the presence of Eu 3d in the 5EuHAp thin films. In the SEM micrographs, the surface uniformity and the absence of the surface defects could be observed. Moreover, the results of the FTIR studies showed the presence of the vibrational bands specific to the HAp structure in the studied sample. The antifungal activity of the HAp and 5EuHAp suspensions and coatings was evaluated using the Candida albicans ATCC 10231 (C. albicans) fungal strain. The qualitative assays of the antifungal properties of HAp and 5EuHAp coatings were also visualized by SEM and CLSM. The antifungal studies revealed that both 5EuHAp suspensions and coatings exhibited noticeable antifungal activity against C. albicans cells.

465. Structural and transport properties of Cu2CoSnS4 films prepared by spray pyrolysis

Authors: El Khouja, O; Assahsahi, I; Nouneh, K; Touhami, ME; Secu, M; Talbi, A; Khaaissa, Y; Matei, E; Stancu, V; Galatanu, A; Galca, AC

Published: NOV 1 2022, CERAMICS INTERNATIONAL, 48, DOI: 10.1016/j.ceramint.2022.07.185

In the present work, stannite Cu2CoSnS4 (CCTS) films were elaborated using spray pyrolysis method on soda-lime glass, at different deposition temperatures (T-d = 250, 300, and 350 degrees C), followed by different chosen sulfurization temperatures (T-s = 450, 500, and 550 degrees C). X-ray diffraction (XRD) revealed the nearly single-phase formation of CCTS films at 300 degrees C deposition temperature. After sulfurization in argon flow, the XRD lines become narrower, the average crystallite size expanding above 70 nm. The Raman spectroscopy analysis confirmed the stannite structure formation, as well as the presence CoS2 secondary phases, which reduces at higher sulfurization temperature (550 degrees C). The energy dispersive spectroscopy results indicated atomic ratios of Cu/Co/Sn/S close to the ideal stoichiometric ratio 2:1:1:4. The room temperature photoluminescence emission is recorded with maximum in the 1.35-1.40 eV range. Thermoelectric properties are measured up to 130 degrees C, the films show poor power factor as a result of small positive Seebeck coefficients 10-45 Of K -1 and low electrical conductivity despite of having relatively high carrier concentration (similar to 10(20) cm(-3)).

466. Effect of disubstitution pattern of the terminal alkyl chains on the mesophase of liquid crystals based on lanthanide(III) complexes: A study of the thermal, emission and dielectric behavior

Authors: Ilinca, TA; Chiriac, LF; Ilis, M; Manaila-Maximean, D; Ganea, PC; Pasuk, I; Cîrcu, V

Published: AUG 15 2022, JOURNAL OF MOLECULAR LIQUIDS, 360, 119425, DOI: 10.1016/j.molliq.2022.119425

In the present work, new luminescent lanthanide complexes with extended mesomorphic range were prepared by coordination to lanthanide ions (Eu3+, Sm3+ and Tb3+) of the new 4-pyridone based organic ligands (L) with 3,4-(7-n) and 3,5-di(alkyloxy)benzyl (8-n) mesogenic groups and variable length (n = 12 or 14 carbon atoms) onto the benzyl unit. The cumulative results of the elemental analyses as well as the H-1, C-13 NMR and IR spectroscopies support the structure of the organic derivatives and their lanthanide complexes [LnL(3)(NO3)(3)] (9-n/Ln and 10-n/Ln) described in this work. These complexes show characteristic lanthanide solid state emission, both at room and elevated temperatures corresponding to crystalline, glassy or liquid crystal states. The long range SmA phases displayed by all complexes were supported by a combination of characterization methods, including: differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and variable-temperature powder X-ray diffraction (XRD). This work shows that the number, substitution pattern and length of flexible alkoxy chains are important parameters to control the phase-transition characteristics of the lanthanide complexes. Complexes with 3,4-disubstituted pattern (9-n/Ln) show higher clearing temperatures (nearly 60 degrees C for Eu3+, 70 degrees C for Sm3+ and 85 degrees C for Tb3+ complexes) compared to their counterparts with 3,5-disubstituted pattern (10-n/Ln). Moreover, complexes 9-n/Ln crystallize when cooling their LC phase while complexes 10-n/Ln are stable in glassy state at room temperature as a consequence of the different close interdigitated molecular packing evidenced by XRD measurements. Dielectric spectroscopy was employed to detect the changes of order degree specific to each phases (crystalline, LC or isotropic). The variation of dielectric constant and the electrical conductivity versus temperature shows three transition intervals for selected complexes 10-14/Sm and 10-14/Tb, which delimit the main intervals: 45-60 degrees C, 90-110 degrees C; 140-160 degrees C corresponding to the Cr-1-Cr-2, Cr-2 - SmA and SmA-Iso transitions, and agree very well with the DSC results. The change of characteristic time, obtained by Havriliak-Negami fit function, with temperature also provides a very good correlation with the DSC and POM results. (C) 2022 Elsevier B.V. All rights reserved.

467. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: AUG 2022, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 219, 2100521, DOI: 10.1002/pssa.202100521

Herein, the properties of the organic heterostructures with triple-layer ZnO/Ag/ZnO as a replacement for ITO and mixed layer containing arylenevinylene oligomer (based on triphenylamine or carbazole) donor and nonfullerene (perylene diimide) acceptor mixed in the ratio 1:2 and the effect of a buffer layer of PEDOT-PSS intercalated between triple layer and mixed organic layer are discussed. The UV-vis transmission and photoluminescence (PL) properties are investigated in correlation with the surface topography and reveal a good match between the absorption and emission domain, which can favor the generation of the charge carriers. The heterostructure with the mixed layer based on triphenylamine oligomer shows the widest absorption domain, and the PL spectra of the heterostructures realized with either triphenylamine or carbazole oligomer show peaks corresponding to the radiative decay of the donor and acceptor. The I-V characteristics in the dark indicate a slightly nonlinear behavior and the current is affected by the charge carriers recombination on the defects present in the thick mixed layer deposited by matrix-assisted pulsed laser evaporation. The effect of the PEDOT-PSS buffer layer on the electrical properties of the organic heterostructure with ZnO/Ag/ZnO electrode is also investigated.

Open Access

468. Ligand-Promoted Surface Solubilization of TiO2 Nanoparticles by the Enterobactin Siderophore in Biological Medium

Authors: Laisney, J; Chevallet, M; Fauquant, C; Sageot, C; Moreau, Y; Predoi, D; Herlin-Boime, N; Lebrun, C; Michaud-Soret, I

Published: OCT 2022, BIOMOLECULES, 12, 1516, DOI: 10.3390/biom12101516

Titanium dioxide nanoparticles (TiO2-NPs) are increasingly used in consumer products for their particular properties. Even though TiO2 is considered chemically stable and insoluble, studying their behavior in biological environments is of great importance to figure their potential dissolution and transformation. The interaction between TiO2-NPs with different sizes and crystallographic forms (anatase and rutile) and the strong chelating enterobactin (ent) siderophore was investigated to look at a possible dissolution. For the first time, direct evidence of anatase TiO2-NP surface dissolution or solubilization (i.e., the removal of Ti atoms located at the surface) in a biological medium by this siderophore was shown and the progressive formation of a hexacoordinated titanium-enterobactin (Ti-ent) complex observed. This complex was characterized by UV-visible and Fourier transform infrared (FTIR) spectroscopy (both supported by Density Functional Theory calculations) as well as electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS). A maximum of ca. 6.3% of Ti surface atoms were found to be solubilized after 24 h of incubation, releasing Ti-ent complexes in the micromolar range that could then be taken up by bacteria in an iron-depleted medium. From a health and environmental point of view, the effects associated to the solubilization of the E171 TiO2 food additive in the presence of enterobactin and the entrance of the Ti-enterobactin complex in bacteria were questioned.

Open Access

469. Effect of Aluminum Nanostructured Electrode on the Properties of Bulk Heterojunction Based Heterostructures for Electronics

Authors: Rasoga, O; Breazu, C; Socol, M; Solonaru, AM; Vacareanu, L; Petre, G; Preda, N; Stanculescu, F; Socol, G; Girtan, M; Stanculescu, A

Published: DEC 2022, NANOMATERIALS, 12, 4230, DOI: 10.3390/nano12234230

The properties of organic heterostructures with mixed layers made of arylenevinylene-based polymer donor and non-fullerene perylene diimide acceptor, deposited using Matrix Assisted Pulsed Laser Evaporation on flat Al and nano-patterned Al electrodes, were investigated. The Al layer electrode deposited on the 2D array of cylindrical nanostructures with a periodicity of 1.1 mu m, developed in a polymeric layer using UV-Nanoimprint Lithography, is characterized by an inflorescence-like morphology. The effect of the nanostructuring on the optical and electrical properties was studied by comparison with those of the heterostructures based on a mixed layer with fullerene derivative acceptor. The low roughness of the mixed layer deposited on flat Al was associated with high reflectance. The nano-patterning, which was preserved in the mixed layer, determining the light trapping by multiple scattering, correlated with the high roughness and led to lower reflectance. A decrease was also revealed in photoluminescence emission both at UV and Vis excitation of the mixed layer, with the non-fullerene acceptor deposited on nano-patterned Al. An injector contact behavior was highlighted for all Al/mixed layer/ITO heterostructures by I-V characteristics in dark. The current increased, independently of acceptor (fullerene or non-fullerene), in the heterostructures with nano-patterned Al electrodes for shorter conjugation length polymer donors.

470. Influence of erbium doping on the structural, magnetic and optical properties of hematite (?-Fe2O 3) nanorods

Authors: Popov, N; Ristic, M; Kuncser, V; Zadro, K; Velinov, N; Badica, P; Alexandru-Dinu, A; Iacob, N; Krehula, LK; Music, S; Krehula, S

Published: OCT 2022, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 169, 110857, DOI: 10.1016/j.jpcs.2022.110857

Pure and Er-doped hematite (alpha-Fe2O3) nanorods were prepared by a two-step method involving hydrothermal synthesis and calcination of pure and Er-doped goethite (alpha-FeOOH) nanorods. Substitution of Fe3+ by Er3+ in the crystal structure of hematite caused morpho-structural changes such as expansion of the unit cell and gradual shortening and rounding of hematite nanorods towards formation of nanoellipsoids. These changes induced modification of magnetic and optical properties suggesting the possibility of a systematic control of physical properties via rare earth substitution. A decrease in the hyperfine magnetic field, coercive field and Morin transition temperature, as well as an increase of the magnetic susceptibility and a narrowing of the optical band gap were observed by substitution. Intimate mechanisms related to the formation of more and more defect-like hematite phases with decreased temperatures for the transition to the low temperature antiferromagnetic phase at increased doping level were evidenced via temperature dependent Mo center dot ssbauer spectroscopy.

471. Mechanochemical synthesis and Mossbauer characterization of neodymium oxide-hematite magnetic ceramic nanoparticles: Phase sequence and recoilless fraction

Authors: Sorescu, M; Diamandescu, L; Sofronie, M; Pratt, C; Jubeck, J

Published: FEB 1 2022, MATERIALS CHEMISTRY AND PHYSICS, 277, 125511, DOI: 10.1016/j.matchemphys.2021.125511

Magnetic ceramic nanoparticles system xNd(2)O(3)-(1-x)alpha-Fe2O3 (x = 0.1, 0.3 and 0.5) was synthesized by mechanochemical activation starting from hematite and neodymium oxide precursors and characterized by X-ray diffraction (XRD) and Mossbauer spectroscopy. Rietveld refinement of XRD data evidenced the formation of neodymium orthoferrite NdFeO3 as an end-product with a particle size of about 22 nm, determined using the Scherrer method for x = 0.5. The Mossbauer spectra were typically analyzed considering 2 sextets, corresponding to hematite and neodymium orthoferrite and a doublet, representing superparamagnetic particles (SPM). The recoilless fractions were determined using our dual absorber method and were found consistent with a decrease in particle size as consequence of the ball milling process performed.

472. Bulk and surface characteristics of co-electrodeposited Cu2FeSnS4 thin films sulfurized at different annealing temperatures

Authors: El Khouja, O; Negrila, CC; Nouneh, K; Secu, M; Touhami, ME; Matei, E; Stancu, V; Enculescu, M; Kuncser, V; Galca, AC

Published: JUN 15 2022, JOURNAL OF ALLOYS AND COMPOUNDS, 906, 164379, DOI: 10.1016/j.jallcom.2022.164379

In this study, stannite, Cu2FeSnS4 (CFTS), absorber films were obtained by electrodeposition on Molybdenum-coated soda-lime substrates, followed by sulfurization treatment at certain temperatures in the 400-550 degrees C range. The purposes of this work were to control the manufacturing of CFTS films with good stoichiometry, high crystallinity and to study the annealing temperature impact on CFTS films properties. The X-ray diffraction and the Raman spectroscopy measurement distinguished the CFTS phase formation, with a presence of SnS2 secondary phase. The energy dispersive spectroscopy results reveal compositional differences between samples as well as the in-depth gradients. The photoluminescence emission band around 1.35-1.40 eV is slightly below the direct bandgap inferred from the conventional spectroscopy (diffuse reflectance). X-ray photoelectron spectroscopy results indicate clearly a high amount of Sn on the surface. The Conversion Electron Mossbauer unveiled the presence of Fe in the chalcogenide unit cell. The electrochemical characteristics of the synthesized films are also given. (c) 2022 Elsevier B.V. All rights reserved.

473. Influence of the synthesis parameters on the transport properties of Mg2Si0.4Sn0.6 solid solutions produced by melting and spark plasma sintering

Authors: Assahsahi, I; Popescu, B; Enculescu, M; Galatanu, M; Galca, AC; El Bouayadi, R; Zejli, D; Galatanu, A

Published: APR 2022, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 163, 110561, DOI: 10.1016/j.jpcs.2021.110561

In this work, the influence of the preparation route on the structural, morphological, and thermoelectric properties of the Mg2Si0.4Sn0.6 solid solutions is investigated. The synthesis based on melting the constituent elements in a closed graphite crucible followed by spark plasma sintering allows mixing elements with a large difference of their melting temperatures and a good control of sample stoichiometry. The optimized synthesis route is validated by the doped V and Sb samples, which yield good thermoelectric performance. The n-type doping leads to two orders of magnitude increase of the carrier concentration, and thus a subsequent increase of the electrical conductivity, which, in turn, augments greatly the power factor of the Mg1.98V0.02Si0.385Sn0.6Sb0.015 to 42.61 x10(-4) Wm(-1)K 2 at 650K. Although doping slightly enlarges the thermal conductivity, a peak value of the figure of merit ZT similar to 1.15 is obtained at 723K, which is 20 times higher than the ZT of un-doped material.

Open Access

474. Pinning potential in highly performant CaKFe4As4 superconductor from DC magnetic relaxation and AC multi-frequency susceptibility studies

Authors: Ionescu, AM; Ivan, I; Crisan, DN; Galluzzi, A; Polichetti, M; Ishida, S; Iyo, A; Eisaki, H; Crisan, A

Published: NOV 9 2022, SCIENTIFIC REPORTS, 12, 19132, DOI: 10.1038/s41598-022-23879-2

We have investigated the pinning potential of high-quality single crystals of superconducting material CaKFe4As4 having high critical current density and very high upper critical field using both magnetization relaxation measurements and frequency-dependent AC susceptibility. Preliminary studies of the superconducting transition and of the isothermal magnetization loops confirmed the high quality of the samples, while temperature dependence of the AC susceptibility in high magnetic fields show absolutely no dependence on the cooling conditions, hence, no magnetic history. From magnetization relaxation measurements were extracted the values of the normalized pinning potential U*, which reveals a clear crossover between elastic creep and plastic creep. The extremely high values of U*, up to 1200 K around the temperature of 20 K lead to a nearly zero value of the probability of thermally-activated flux jumps at temperatures of interest for high-field applications. The values of the creep exponents in the two creep regimes resulted from the analysis of the magnetization relaxation data are in complete agreement with theoretical models. Pinning potentials were also estimated, near the critical temperature, from AC susceptibility measurements, their values being close to those resulted (at the same temperature and DC field) from the magnetization relaxation data.

475. NaMn0.2Fe0.2Co0.2Ni0.2Ti0.2O2 high-entropy layered oxide - experimental and theoretical evidence of high electrochemical performance in sodium batteries

Authors: Walczak, K; Plewa, A; Ghica, C; Zajac, W; Trenczek-Zajac, A; Zajac, M; Tobo, J; Molenda, J

Published: MAY 2022, ENERGY STORAGE MATERIALS, 47, DOI: 10.1016/j.ensm.2022.02.038

Li-ion batteries, widely used in portable electronics, electric vehicles, and energy storage systems, are an integral element of our daily life. However, the limitation of lithium sources, which leads to high prices, prompts the search for alternatives. Recently there has been noticed a rapid interest in Na-ion batteries technology. Especially, suitable cathode structures are investigated to accumulate larger sodium ions. In this paper, the high entropy layered oxide NaMn0.2Fe0.2Co0.2Ni0.2Ti0.2O2 is presented which achieves superior electrochemical properties with a stable capacity of ca. 180 mAh g(-1). The understanding of its high performance is based on a complex study of the multiphase intercalation mechanism. The combination of advanced structural analysis by XAS, in situ XRD, TEM, and computational DFT modelling gives a new concept on the nature of O3-P3 structure reorganization. The presented experimental and theoretical evidence indicates that the P3 phase of layered oxides is energetically favourable for a lower sodium content for specific transition metal-oxide pair distance. Fundamental understanding of the nature of phase transformation is crucial for tailoring structural composition, where the desirable O3-P3 reorganization will occur, resulting in achieving high-performance cathodes.

476. Chemical sensing and actuation properties of polypyrrole coated fibers

Authors: Beregoi, M; Beaumont, S; Jinga, SI; Otero, TF; Enculescu, I

Published: OCT 1 2022, SMART MATERIALS AND STRUCTURES, 31, 105012, DOI: 10.1088/1361-665X/ac83ff

Designing complex electrochemical artificial muscles aims towards novel devices which besides excellent actuation capabilities should also present the ability to self-sense the modification of environmental parameters. In order to improve efficiency, mimicking the structure of natural muscles, synthetic actuators should have a similar fibrillary morphology. The importance of using materials based on fiber building blocks in actuators aimed at soft robotics field was demonstrated in the present report by comparing a fibrillary artificial muscle with one based on a classical film structure. Nylon electrospun fiber meshes and films were covered in the same conditions with a thin polypyrrole (PPy) layer. The fibrillary electrospun web morphology mimics that of natural muscles and the structure performs a fast, ample bending movement in liquid electrolyte when switching an applied electric potential between -0.6 and +0.6 V. Using the same actuation conditions, no movement of a film based artificial muscle was observed. In order to check the sensing ability of both fibrillary and film like electroactive architectures, their response i.e. PPy reaction when potential cycles were applied in different concentrations of LiClO4 electrolyte were recorded. The obtained results suggest that the ion exchange of the fibrillary artificial muscle is more efficient due to its higher active surface and such devices could work also as dual device (sensor/artificial muscle).

Open Access

477. Graphene/Ferroelectric (Ge-Doped HfO2) Adaptable Transistors Acting as Reconfigurable Logic Gates

Authors: Dragoman, M; Dinescu, A; Dragoman, D; Palade, C; Teodorescu, VS; Ciurea, ML

Published: JAN 2022, NANOMATERIALS, 12, 279, DOI: 10.3390/nano12020279

We present an array of 225 field-effect transistors (FETs), where each of them has a graphene monolayer channel grown on a 3-layer deposited stack of 22 nm control HfO2/5 nm Ge-HfO2 intermediate layer/8 nm tunnel HfO2/p-Si substrate. The intermediate layer is ferroelectric and acts as a floating gate. All transistors have two top gates, while the p-Si substrate is acting as a back gate. We show that these FETs are acting memtransistors, working as two-input reconfigurable logic gates with memory, the type of the logic gate depending only on the values of the applied gate voltages and the choice of a threshold current.

Open Access

478. Visible-Light-Active Black TiO2 Nanoparticles with Efficient Photocatalytic Performance for Degradation of Pharmaceuticals

Authors: Andronic, L; Ghica, D; Stefan, M; Mihalcea, CG; Vlaicu, AM; Karazhanov, S

Published: AUG 2022, NANOMATERIALS, 12, 2563, DOI: 10.3390/nano12152563

Special attention has recently been paid to surface-defective titanium dioxide and black TiO2 with advanced optical, electrical, and photocatalytic properties. Synthesis of these materials for photodegradation and mineralization of persistent organic pollutants in water, especially under visible radiation, presents interest from scientific and application points of view. Chemical reduction by heating a TiO2 and NaBH4 mixture at 350 degrees C successfully introduced Ti3+ defects and oxygen vacancies at the surface of TiO2, with an increase in the photocatalytic degradation of amoxicillin-an antibiotic that is present in wastewater due to its intense use in human and animal medicine. Three TiO2 samples were prepared at different annealing temperatures to control the ratio between anatase and rutile and were subjected to chemical reduction. Electron paramagnetic resonance investigations showed that the formation of surface Ti3+ defects in a high concentration occurred mainly in the anatase sample annealed at 400 degrees C, contributing to the bandgap reduction from 3.32 eV to 2.92 eV. The reduced band gap enhances visible light absorption and the efficiency of photocatalysis. The nanoparticles of similar to 90 m(2)/g specific surface area and 12 nm average size exhibit similar to 100% efficiency in the degradation of amoxicillin under simulated solar irradiation compared with pristine TiO2. Mineralization of amoxicillin and by-products was over 75% after 48 h irradiation for the anatase sample, where the Ti3+ defects were present in a higher concentration at the catalyst's surface.

Open Access

479. Electrocatalytic Properties of Mixed-Oxide-Containing Composite-Supported Platinum for Polymer Electrolyte Membrane (PEM) Fuel Cells

Authors: Ayyubov, I; Tálas, E; Salmanzade, K; Kuncser, A; Pászti, Z; Neatu, S; Mirea, AG; Florea, M; Tompos, A; Borbáth, I

Published: MAY 2022, MATERIALS, 15, 3671, DOI: 10.3390/ma15103671

TiO2-based mixed oxide-carbon composite supports have been suggested to provide enhanced stability for platinum (Pt) electrocatalysts in polymer electrolyte membrane (PEM) fuel cells. The addition of molybdenum (Mo) to the mixed oxide is known to increase the CO tolerance of the electrocatalyst. In this work Pt catalysts, supported on Ti1-xMoxO2-C composites with a 25/75 oxide/carbon mass ratio and prepared from different carbon materials (C: Vulcan XC-72, unmodified and functionalized Black Pearls 2000), were compared in the hydrogen oxidation reaction (HOR) and in the oxygen reduction reaction (ORR) with a commercial Pt/C reference catalyst in order to assess the influence of the support on the electrocatalytic behavior. Our aim was to perform electrochemical studies in preparation for fuel cell tests. The ORR kinetic parameters from the Koutecky-Levich plot suggested a four-electron transfer per oxygen molecule, resulting in H2O. The similarity between the Tafel slopes suggested the same reaction mechanism for electrocatalysts supported by these composites. The HOR activity of the composite-supported electrocatalysts was independent of the type of carbonaceous material. A noticeable difference in the stability of the catalysts appeared only after 5000 polarization cycles; the Black Pearl-containing sample showed the highest stability.

Open Access

480. Degradation of Losartan Potassium Highlighted by Correlated Studies of Photoluminescence, Infrared Absorption Spectroscopy and Dielectric Spectroscopy

Authors: Paraschiv, M; Smaranda, I; Zgura, I; Ganea, P; Chivu, M; Chiricuta, B; Baibarac, M

Published: NOV 2022, PHARMACEUTICS, 14, 2419, DOI: 10.3390/pharmaceutics14112419

In this paper, new results on the degradation of losartan potassium (LP, (1)), in the absence and presence of excipients, which was induced by UV light, the acid character of phosphate buffer solution (PBS) and alkaline medium, respectively, are reported through correlated studies of FTIR spectroscopy, photoluminescence and dielectric spectroscopy. The photoluminescence (PL) spectra of LP and the drug marked under the name Lorista (LO) are characterized by intense emission bands, peaking at 378 nm and 380 nm, respectively, accompanied by low intensity bands with a maximum at similar to 450-460 nm. Photodegradation of LO in a solid state is evidenced by a decrease in the intensity of the PL band at 380 nm, a variation that originates both in the adsorption of water vapors from the air and in the interaction of LP with excipients such as cornstarch, silicon dioxide and cellulose. The LP-water interaction is described, taking into account the main electrical parameters, i.e., complex dielectric permittivity and electrical conductivity. Photodegradation of LP and LO also induces an increase in the intensity of the emission band, at similar to 450-460 nm. The influence of acid and alkaline medium on the LO degradation is analyzed using phosphate buffer (PBS) and NaOH solutions, respectively. In both cases, a decrease in the intensity of the PL band, at 380 nm, is reported. The intensity diminution of the PL spectra of NaOH-reacted LP and LO is the result of the formation of the photodegradation product N-methanolamide-{[2'-(1H-tetrazol-5-yl)(1,1'-biphenyl)-4-yl]methyl} (2). This compound was proven by the studies of FTIR spectroscopy achieved on LP and NaOH-reacted LP. The appearance of the IR band at 1740 cm(-1) and the increase in the absorbance in the IR band at 1423 cm(-1) indicate that the photodegradation product (2) contains the C=O and C-OH functional groups.

481. Glutathione-capped gold nanoclusters as near-infrared-emitting efficient contrast agents for confocal fluorescence imaging of tissue-mimicking phantoms

Authors: Hada, AM; Craciun, AM; Focsan, M; Vulpoi, A; Borcan, EL; Astilean, S

Published: SEP 2022, MICROCHIMICA ACTA, 189, 337, DOI: 10.1007/s00604-022-05440-0

An innovative research has been conducted focused on demonstrating the ability of novel dual-emissive glutathione-stabilized gold nanoclusters (GSH-AuNCs) to perform bright near-infrared (NIR)-emitting contrast agents inside tissue-mimicking agarose-phantoms via two complementary confocal fluorescence imaging techniques. First, using a new and fast microwave-assisted approach, we synthesized photostable dual-emitting GSH-AuNCs with an average size of 3.2 +/- 0.4 nm and NIR emission quantum yield of 9.9%. Steady-state fluorescence measurements coupled with fluorescence lifetime imaging microscopy (FLIM) assays performed on lyophilized GSH-AuNCs revealed that the obtained GSH-AuNCs exhibit PL emissions at 610 nm (red PL) and, respectively, 800 nm (NIR PL) in both solution and powder solid-state. Time-resolved fluorescence measurements showed that the two PL components are characterized by average lifetimes of 407 ns (red PL) and 1821 ns (NIR PL), respectively. Additionally, due to a partial overlap between the red PL and the absorption of the NIR PL, an energy transfer between the two coexisting emissive centers was discovered and confirmed via steady-state and time-resolved fluorescence measurements. Furthermore, the FLIM analysis performed on powder GSH-AuNCs under 640 nm, an excitation more suitable for bioimaging applications, revealed a homogeneous and photostable NIR PL signal from GSH-AuNCs. Finally, the ability of GSH-AuNCs to operate as reliable NIR-emitting contrast agents inside tissue-mimicking agarose-phantoms was demonstrated here for the first time via complementary FLIM and re-scan confocal fluorescence imaging techniques. In consequence, GSH-AuNCs show great promise for future in vivo imaging applications via confocal fluorescence microscopy.

Open Access

482. Analysis of Functionalized Ferromagnetic Memory Alloys from the Perspective of Developing a Medical Vascular Implant

Authors: Nan, A; Turcu, R; Tudoran, C; Sofronie, M; Chiriac, A

Published: APR 2022, POLYMERS, 14, 1397, DOI: 10.3390/polym14071397

Durable biocompatible metal vascular implants are still one of the significant challenges of contemporary medicine. This work presents the preparation of ferromagnetic biomaterials with shape memory in metal strips based on FePd (30 at% Pd) that is either not doped or doped with Ga and Mn, coated with poly(benzofuran-co-arylacetic acid) or polyglutamic acid. The coating of the metal strips with polymers was achieved after the metal surface had been previously treated with open-air cold plasma. The final functionalization was performed to induce anti-thrombogenic/thrombolytic properties in the resulting materials. SEM-EDX microscopy and X-ray photoelectron microscopy (XPS) determined the morphology and composition of the metal strips covered with polymers. In vitro tests of standardized thromboplastin time (PTT) and prothrombin time (PT) were performed to evaluate the thrombogenicity of these biofunctionalized materials for future possible monitoring of the implant in patients.

Open Access

483. Electrochemical and In Vitro Biological Evaluation of Bio-Active Coatings Deposited by Magnetron Sputtering onto Biocompatible Mg-0 .8Ca Alloy

Authors: Bita, AI; Antoniac, I; Miculescu, M; Stan, GE; Leonat, L; Antoniac, A; Constantin, B; Forna, N

Published: MAY 2022, MATERIALS, 15, 3100, DOI: 10.3390/ma15093100

The use of resorbable magnesium alloys in the design of implants represents a new direction in the healthcare domain. Two main research avenues are currently explored for developing or improving metallic biomaterials: (i) increase of their corrosion resistance by designed compositional and structural modifications, and (ii) functionalization of their surfaces by coating with ceramic or polymeric layers. The main objective of this work was to comparatively assess bio-functional coatings (i.e., highly-crystallized hydroxyapatite and silica-rich glass) deposited by radio-frequency magnetron sputtering (RF-MS) on a biodegradable Mg-0.8Ca alloy (0.8 wt.% of Ca). After probing their morphology (by scanning electron microscopy) and structure (by Fourier transform infrared spectroscopy and grazing incidence X-ray diffraction), the corrosion resistance of the RF-MS coated Mg-0.8Ca substrates was electrochemically tested (in synthetic biological media with different degrees of biomimicry), and their cytocompatibility was assessed in osteoblast and fibroblast cell cultures. By collective assessment, the most promising performances, in terms of mass loss (similar to 7% after 12 days), hydrogen release rate (similar to 6 mL/cm(2) after 12 days), electrochemical corrosion parameters and cytocompatibility, were obtained for the crystalline HA coating.

484. BIOPHYSICAL INSIGHTS ON JACK BEAN UREASE IN THE PRESENCE OF SILVER CHLORIDE PHYTONANOPARTICLES GENERATED FROM MENTHA PIPERITA L. LEAVES

Authors: Barbinta-Patrascu, ME; Chilom, C; Nichita, C; Zgura, I; Iftimie, S; Antohe, S

Published: 2022, ROMANIAN REPORTS IN PHYSICS, 74, 605, DOI:

Recent progress in "Green" Nanotechnology is trying to fight against many diseases, a special interest being given to silver-based nanoparticles biogenerated from plants. In this study, phytogenic silver chloride nanoparticles (m-AgClNPs) were "green" synthesized by using an aqueous extract of Mentha piperita L. leaves, and then examined against urease activity. Urease, a nickel-containing enzyme, has been reported to contribute to the pathogenesis of many diseases (hepatic coma, encephalopathy, gastritis, gastric ulcer, and others). The obtained m-AgClNPs presented good physical stability (checked by zeta potential measurements) and high antioxidant activity (evaluated by chemiluminescence technique). Their size was estimated by Dynamic Light Scattering (DLS) measurements. UV-Vis absorption and fluorescence emission spectroscopy were used to study the impact of bio-AgNPs on urease. Our bio-developed m-AgClNPs exhibited good urease inhibitory activity and no destabilization of urease structure against thermal denaturation. These findings could be exploited in the development of novel inhibitors of urease for agronomic and biomedical applications.

Open Access

485. Structural evolution of carbon dots during low temperature pyrolysis

Authors: Luo, H; Lari, L; Kim, H; Hérou, S; Tanase, LC; Lazarov, VK; Titirici, MM

Published: JAN 20 2022, NANOSCALE, 14, DOI: 10.1039/d1nr07015k

Carbon dots (CDs) are an emerging class of photoluminescent material. Their unique optical properties arise from the discrete energy levels in their electronic states, which directly relate to their crystalline and chemical structure. It is expected that when CDs go through structural changes via chemical reduction or thermal annealing, their energy levels will be altered, inducing unique optoelectronic properties such as solid-state photoluminescence (PL). However, the detailed structural evolution and how the optoelectronic characteristics of CDs are affected remain unclear. Therefore, it is of fundamental interest to understand how the structure of CDs prepared by hydrothermal carbonisation (HTC) rearranges from a highly functionalised disordered structure into a more ordered graphitic structure. In this paper, detailed structural characterisation and in situ TEM were conducted to reveal the structural evolution of CDs during the carbonisation process, which have demonstrated a growth in aromatic domains and reduction in oxidation sites. These structural features are correlated with their near-infrared (NIR) solid-state PL properties, which may find a lot of practical applications such as temperature sensing, solid-state display lighting and anti-counterfeit security inks.

Open Access

486. Investigations Regarding the Addition of ZnO and Li2O-TiO2 to Phosphate-Tellurite Glasses: Structural, Chemical, and Mechanical Properties

Authors: Elisa, M; Iordache, SM; Iordache, AM; Stefan, CR; Vasiliu, IC; Cristea, D; Ursutiu, D; Samoila, C; Sava, BA; Boroica, L; Dinca, MC; Filip, AV; Eftimie, M; Enculescu, M

Published: MAR 2022, MATERIALS, 15, 1644, DOI: 10.3390/ma15051644

Phosphate and tellurite glasses can be used in optics, optoelectronics, magneto-optics, and nuclear and medical fields. Two series of phosphate-tellurite glasses, (50-x)ZnO-10Al(2)O(3)-40P(2)O(5)-xTeO(2) and (40-x)Li2O-10Al(2)O(3)-5TiO(2)-45P(2)O(5)-xTeO(2) (x = 5, 10), were synthesized by a non-conventional wet-route, and the mechanical properties as key performance measures for their application in optoelectronics were investigated. X-ray Diffraction (XRD) measurements revealed the vitreous nature of the investigated materials. Instrumented indentation tests allowed the calculation of hardness (H) and Young's modulus (E) using the Oliver and Pharr model. The influence of increasing the TeO2 content, as well as the substitution of ZnO by Li2O-TiO2, on the variation of hardness, Young's modulus, penetration depth (PD), and fracture toughness (FT) was evaluated in both series. As a general trend, there is a decrease in the hardness and Young's modulus with increasing penetration depth. The addition of Li2O and TiO2 instead of ZnO leads to improved hardness and elastic modulus values. Regarding the H/E ratio, it was found that the samples with lower TeO2 content should be significantly more crack-resistant compared to the higher TeO2 content samples. The H-3/E-2 ratio, being lower than 0.01, revealed a poor resistance of these glasses to plastic deformation. At the same time, a decrease of the fracture toughness with increasing TeO2 content was noticed for each glass series. Based on dilatometry measurements, the thermal expansion coefficient as well as the characteristic temperatures of the glasses were measured. Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray analysis (FESEM-EDX) revealed a uniform distribution of the elements in the bulk samples. The mechanical properties of these vitreous materials are important in relation to their application as magneto-optical Faraday rotators in laser cavities.

Open Access

487. Development of Silver Doped Hydroxyapatite Thin Films for Biomedical Applications

Authors: Iconaru, SL; Predoi, D; Ciobanu, CS; Motelica-Heino, M; Guegan, R; Bleotu, C

Published: MAR 2022, COATINGS, 12, 341, DOI: 10.3390/coatings12030341

Silver doped hydroxyapatite [AgHAp, Ca10-xAg(PO4)(6)(OH)(2)], due to its antimicrobial properties, is an advantageous material to be used for various coatings. The AgHAp thin films with x(Ag) = 0.05 and x(Ag) = 0.1 were achieved using the spin-coating method. The resulting samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XRD analysis revealed that the particles of both samples are ellipsoidal. Also, in agreement with the results obtained by XRD measurements, the results of the SEM studies have shown that the particles shape is ellipsoidal. Optical properties of silver doped hydroxyapatite thin films deposited on Si substrate were investigated through Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The results obtained by the two complementary techniques highlighted that the molecular structure of the studied samples is not influenced by the increase of the silver concentration in the samples. Our studies revealed that the surface morphology of the obtained samples consist of uniform and continuous layers. The biocompatibility of the obtained thin films was also evaluated with the aid of human osteosarcoma MG63 (ATCC CRL 1427) cell line. Moreover, the in vitro antifungal activity against Candida albicans fungal strain of the AgHAp thin films was studied and the obtained results revealed their antifungal effect. The results of the biological assays showed that the AgHAp thin films are a very promising material for biomedical applications.

Open Access

488. Irradiation of W and K-Doped W Laminates without or with Cu, V, Ti Interlayers under a Pulsed 6 MeV Electron Beam

Authors: Ticos, D; Galatanu, M; Galatanu, A; Dumitru, M; Mitu, ML; Udrea, N; Scurtu, A; Ticos, CM

Published: FEB 2022, MATERIALS, 15, 956, DOI: 10.3390/ma15030956

Small multilayered laminated samples consisting of stacks of W (or K-doped W) foils without an interlayer or with interlayers from Cu, V, and Ti were exposed to a pulsed electron beam with an energy of 6 MeV in several irradiation sessions. All samples maintained their macroscopic integrity, suggesting that the W-metal laminate concept is compatible with high heat flux applications. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after each irradiation session. The experimental results indicate that electron beam irradiation induces obvious modifications on the surface of the samples. Morphological changes such as the appearance of nanodroplets, nanostructures, and melting and cracking, depending on the sample type and the electron beam fluence, are observed. The irradiation is carried out in a vacuum at a pressure of 2 to 4 x 10(-2) torr, without active cooling for the samples. The structures observed on the surface of the samples are likely due to electron beam heating and vaporization followed by vapor condensation in the volume adjacent to the surface.

Open Access

489. Synthesis and characterization of some C-Ti based multilayer and composite nanostructures

Authors: Ciupina, V; Lungu, CP; Vladoiu, R; Prodan, GC; Porosnicu, C; Vasile, E; Prodan, M; Nicolescu, V; Dinca, V; Cupsa, O; Velea, A; Manu, R

Published: MAR-APR 2022, JOURNAL OF OVONIC RESEARCH, 18, DOI: 10.15251/JOR.2022.182.177

Carbon-Titanium multilayer and composite thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisted by a carbon base layer and seven alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. By changing of substrate temperature, and on the other hand the bias potential up to ???700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Grazing Incidence X-ray Diffraction (GIXRD) and Electron Microscopy technique (TEM). The measurements show that increase of the substrate temperature reveal the changes in TixCy lattice parameters. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively and a Bruker Hystrion TI 980 TriboIndenter. Was found that the coefficient of friction depends on the synthesis temperature, bias voltage and also by the C content, Ti content and amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedeman-Frantz law was obtained the thermal conductivity.

Open Access

490. Unidirectional Magnetic Anisotropy in Molybdenum Dioxide-Hematite Mixed-Oxide Nanostructures

Authors: Tolea, F; Sorescu, M; Diamandescu, L; Iacob, N; Tolea, M; Kuncser, V

Published: MAR 2022, NANOMATERIALS, 12, 938, DOI: 10.3390/nano12060938

MoO2-Fe2O3 nanoparticle systems were successfully synthesized by mechanochemical activation of MoO2 and alpha-Fe2O3 equimolar mixtures throughout 0-12 h of ball-milling. The role of the long-range ferromagnetism of MoO2 on a fraction of more defect hematite nanoparticles supporting a defect antiferromagnetic phase down to the lowest temperatures was investigated in this work. The structure and the size evolution of the nanoparticles were investigated by X-ray diffraction, whereas the magnetic properties were investigated by SQUID magnetometry. The local electronic structure and the specific phase evolution in the analyzed system versus the milling time were investigated by temperature-dependent Mossbauer spectroscopy. The substantially shifted magnetic hysteresis loops were interpreted in terms of the unidirectional anisotropy induced by pinning the long-range ferromagnetic order of the local net magnetic moments in the defect antiferromagnetic phase, as mediated by the diluted magnetic oxide phase of MoO2, to those less defect hematite nanoparticles supporting Morin transition. The specific evolutions of the exchange bias and of the coercive field versus temperature in the samples were interpreted in the frame of the specific phase evolution pointed out by Mossbauer spectroscopy. Depending on the milling time, a different fraction of defect hematite nanoparticles is formed. Less nanoparticles supporting the Morin transition are formed for samples exposed to a longer milling time, with a direct influence on the induced unidirectional anisotropy and related effects.

Open Access

491. Ferromagnetism and Superconductivity in CaRuO3/YBa2Cu3O7-δ Heterostructures

Authors: Ionescu, AM; Ivan, I; Locovei, C; Onea, M; Crisan, A; Soltan, S; Schütz, G; Albrecht, J

Published: APR 2022, MATERIALS, 15, 2345, DOI: 10.3390/ma15072345

The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. We investigated the influence of ferromagnetic CaRuO3 on the properties of YBa2Cu3O7-x (YBCO) superconducting thin films when the layers are either in direct contact or separated by a barrier layer of 5 nm SrTiO3. Detailed measurements of the magnetic moment of the superconductor and ferromagnet as a function of temperature and magnetic field have been performed using SQUID magnetometry. Magnetometry and relaxation measurements show that the modification of the superconducting properties of YBCO strongly depends on the interaction with the ferromagnetic layer on top. The barrier layer has a significant impact on both the supercon-ducting properties of the YBCO film and the ferromagnetic ordering of CaRuO3. The physical properties mentioned above were discussed in correlation with the materials' structure determined by XRD analysis.

Open Access

492. Facile synthesis of low toxicity iron oxide/TiO2 nanocomposites with hyperthermic and photo-oxidation properties

Authors: Popescu, T; Matei, CO; Culita, DC; Maraloiu, VA; Rostas, AM; Diamandescu, L; Iacob, N; Savopol, T; Ilas, MC; Feder, M; Lupu, AR; Iacoban, AC; Vlaicu, ID; Moisescu, MG

Published: APR 27 2022, SCIENTIFIC REPORTS, 12, 6887, DOI: 10.1038/s41598-022-11003-3

The present study aimed to assess the feasibility of developing low-cost multipurpose iron oxide/TiO2 nanocomposites (NCs) for use in combined antitumor therapies and water treatment applications. Larger size (approximate to 100 nm) iron oxide nanoparticles (IONPs) formed magnetic core-TiO2 shell structures at high Fe/Ti ratios and solid dispersions of IONPs embedded in TiO2 matrices when the Fe/Ti ratio was low. When the size of the iron phase was comparable to the size of the crystallized TiO2 nanoparticles (approximate to 10 nm), the obtained nanocomposites consisted of randomly mixed aggregates of TiO2 and IONPs. The best inductive heating and ROS photogeneration properties were shown by the NCs synthesized at 400 degrees C which contained the minimum amount of alpha-Fe2O3 and sufficiently crystallized anatase TiO2. Their cytocompatibility was assessed on cultured human and murine fibroblast cells and analyzed in relation to the adsorption of bovine serum albumin from the culture medium onto their surface. The tested nanocomposites showed excellent cytocompatibility to human fibroblast cells. The results also indicated that the environment (i.e. phosphate buffer or culture medium) used to disperse the nanomaterials prior to performing the viability tests can have a significant impact on their cytotoxicity.

Open Access

493. TiO2 Nanotubes Film/FTO Glass Interface: Thermal Treatment Effects

Authors: Vujancevic, J; Bjelajac, A; Veltruska, K; Matolin, V; Siketic, Z; Provatas, G; Jaksic, M; Stan, GE; Socol, G; Mihailescu, IN; Pavlovic, VB; Janackovic, D

Published: 2022, SCIENCE OF SINTERING, 54, DOI: 10.2298/SOS2202235V

Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO samples were sintered at 450, 550 and 630 degrees C, in ambient air. The thermal treatment did not influence the crystal phase composition, preserving in all cases the anatase single phase. As expected, the crystalline anatase quality improved with the annealing temperature. Nevertheless, slight differences in nanotubular morphology, such as the appearance of grains inside the walls, were observed in the case of the sample sintered at 630 degrees C. Chemical analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the substrate to TiO2. For the substrate was used FTO glass whose top layer consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and Time-of-Flight Elastic Recoil Detection Analysis were carried out to study the elemental depth profile of the films. It was found that the temperature of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse towards the TiO2 NTs surface for the samples annealed at 450 and 550 degrees C. The diffusion is however hindered in the case of the heat treatment at 630 degrees C. Besides, the Ti diffusion into the SnO2 underlayer was observed, together with the formation of TiO2/SnO2 interfaces. One then expected but not a great difference in absorption between samples, since all contained anatase phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of Sn was however detected for the sample annealed at 550 degrees C, which accounts for a slight red absorption shift. The importance of controlling the annealing parameters of the anodized TiO2/FTO structures was highlighted through the formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can play an essential role in increasing the photoperformances of TiO2 NTs/FTO based structures of photovoltaic cells.

Open Access

494. Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O2, N2, He, or Ar for Dye-Sensitized Solar Cells

Authors: Albu, DF; Lungu, J; Popescu-Pelin, G; Mihailescu, CN; Socol, G; Georgescu, A; Socol, M; Banica, A; Ciupina, V; Mihailescu, IN

Published: MAR 2022, COATINGS, 12, 293, DOI: 10.3390/coatings12030293

Active semiconductor layers of TiO2 were synthesized via pulsed laser deposition in He, N-2, O-2, or Ar to manufacture DSSC structures. As-prepared nanostructured TiO2 coatings grown on FTO were photosensitized by the natural absorption of the N719 (Ruthenium 535-bis TBA) dye to fabricate photovoltaic structures. TiO2 photoanode nanostructures with increased adsorption areas of the photosensitizer (a combination with voluminous media) were grown under different deposition conditions. Systematic SEM, AFM, and XRD investigations were carried out to study the morphological and structural characteristics of the TiO2 nanostructures. It was shown that the gas nature acts as a key parameter of the architecture and the overall performance of the deposited films. The best electro-optical performance was reached for photovoltaic structures based on TiO2 coatings grown in He, as was demonstrated by the short-circuit current (Isc) of 5.40 mA, which corresponds to the higher recorded roughness (of 44 +/- 2.9 nm RMS). The higher roughness is thus reflected in a more efficient and deeper penetration of the dye inside the nanostructured TiO2 coatings. The photovoltaic conversion efficiency (eta) was 1.18 and 2.32% for the DSSCs when the TiO2 coatings were deposited in O-2 and He, respectively. The results point to a direct correlation between the electro-optical performance of the prepared PV cells, the morphology of the TiO2 deposited layers, and the crystallinity features, respectively.

Open Access

495. Dimensionality of mobile electrons at x-ray-irradiated LaAlO3/SrTiO3 interfaces

Authors: Strocov, VN; Lechermann, F; Chikina, A; Alarab, F; Lev, LL; Rogalev, VA; Schmitt, T; Husanu, MA

Published: MAR 1 2022, ELECTRONIC STRUCTURE, 4, 015003, DOI: 10.1088/2516-1075/ac4e74

Electronic structure of LaAlO3/SrTiO3 (LAO/STO) samples, grown at low oxygen pressure and post-annealed ex situ, was investigated by soft-x-ray ARPES focussing on the Fermi momentum (k (F)) of the mobile electron system (MES). X-ray irradiation of these samples at temperatures below 100 K creates oxygen vacancies (V(O)s) injecting Ti t (2g)-electrons into the MES. At this temperature the oxygen out-diffusion is suppressed, and the V(O)s should appear mostly in the top STO layer. The x-ray generated MES demonstrates, however, a pronounced three-dimensional (3D) behavior as evidenced by variations of its experimental k (F) over different Brillouin zones. Identical to bare STO, this behavior indicates an unexpectedly large extension of the x-ray generated MES into the STO depth. The intrinsic MES in the standard LAO/STO samples annealed in situ, in contrast, demonstrates purely two-dimensional (2D) behaviour. The relevance of our ARPES data analysis is supported by model calculations to compare the intensity vs gradient methods of the k (F) determination as a function of the energy resolution ratio to the bandwidth. Based on self-interaction-corrected DFT calculations of the MES induced by V(O)s at the interface and in STO bulk, we discuss possible scenarios of the puzzling 3D-ity. It may involve either a dense ladder of quantum-well states formed in a long-range interfacial potential or, more likely, x-ray-induced bulk metallicity in STO accessed in the ARPES experiment through a short-range interfacial barrier. The mechanism of this metallicity may involve remnant V(O)s and photoconductivity-induced metallic states in the STO bulk, and even more exotic mechanisms such as x-ray induced formation of Frenkel pairs.

Open Access

496. Ferrofluids and bio-ferrofluids: looking back and stepping forward

Authors: Socoliuc, V; Avdeev, M; Kuncser, ; Turcu, R; Tombácz, E; Vékás, L

Published: MAR 31 2022, NANOSCALE, 14, DOI: 10.1039/d1nr05841j

Ferrofluids investigated along for about five decades are ultrastable colloidal suspensions of magnetic nanoparticles, which manifest simultaneously fluid and magnetic properties. Their magnetically controllable and tunable feature proved to be from the beginning an extremely fertile ground for a wide range of engineering applications. More recently, biocompatible ferrofluids attracted huge interest and produced a considerable increase of the applicative potential in nanomedicine, biotechnology and environmental protection. This paper offers a brief overview of the most relevant early results and a comprehensive description of recent achievements in ferrofluid synthesis, advanced characterization, as well as the governing equations of ferrohydrodynamics, the most important interfacial phenomena and the flow properties. Finally, it provides an overview of recent advances in tunable and adaptive multifunctional materials derived from ferrofluids and a detailed presentation of the recent progress of applications in the field of sensors and actuators, ferrofluid-driven assembly and manipulation, droplet technology, including droplet generation and control, mechanical actuation, liquid computing and robotics.

Open Access

497. Magnetocaloric and Giant Magnetoresistance Effects in La-Ba-Mn-Ti-O Epitaxial Thin Films: Influence of Phase Transition and Magnetic Anisotropy

Authors: Oumezzine, M; Chirila, CF; Pasuk, I; Galca, AC; Leca, A; Borca, B; Kuncser, V

Published: NOV 2022, MATERIALS, 15, 8003, DOI: 10.3390/ma15228003

Magnetic perovskite films have promising properties for use in energy-efficient spintronic devices and magnetic refrigeration. Here, an epitaxial ferromagnetic La0.67Ba0.33Mn0.95Ti0.05O3 (LBMTO-5) thin film was grown on SrTiO3(001) single crystal substrate by pulsed laser deposition. High-resolution X-ray diffraction proved the high crystallinity of the film with tetragonal symmetry. The magnetic, magnetocaloric and magnetoresistance properties at different directions of the applied magnetic field with respect to the ab plane of the film were investigated. An in-plane uni-axial magnetic anisotropy was evidenced. The LBMTO-5 epilayer exhibits a second-order ferromagnetic-paramagnetic phase transition around 234 K together with a metal-semiconductor transition close to this Curie temperature (T-C). The magnetic entropy variation under 5 T induction of a magnetic field applied parallel to the film surface reaches a maximum of 17.27 mJ/cm(3) K. The relative cooling power is 1400 mJ/cm(3) K (53% of the reference value reported for bulk Gd) for the same applied magnetic field. Giant magnetoresistance of about 82% under 5 T is obtained at a temperature close to T-C. Defined as the difference between specific resistivity obtained under 5 T with the current flowing along the magnetic easy axis and the magnetic field oriented transversally to the current, parallel and perpendicular to the sample plane, respectively, the in-plane magneto-resistance anisotropy in 5 T is about 9% near the T-C.

Open Access

498. Towards high degree of c-axis orientation in MgB2 bulks

Authors: Grigoroscuta, MA; Aldica, G; Burdusel, M; Sandu, ; Kuncser, A; Pasuk, ; Ionescu, AM; Suzuki, TS; Vasylkiv, O; Badica, P

Published: AUG 2022, JOURNAL OF MAGNESIUM AND ALLOYS, 10, DOI: 10.1016/j.jma.2021.10.013

The paper presents fabrication and characterization of spark plasma sintered textured (001) MgB2 with a record degree of orientation of about 40% and 16% by high-energy ultra-sonication and slip casting in high magnetic field (12 T) and 0 T magnetic field, respectively. Structural characterization was performed by X-ray diffraction, and electron microscopy. The analysis revealed unexpected preferred orientation also in the MgO secondary phase due to the epitaxial growth of (111) MgO on (001) MgB2. The influence of oriented microstructure on the superconducting characteristics expressed by critical current density (Jc), irreversibility field ( H irr), and on the pinning properties were assessed. High anisotropy versus sample orientation in applied magnetic field, H , was observed for Jc, Hirr, pinning activation energy ( U *) extracted from relaxation measurements. The zero-field critical current, Jc0 and Fp,maxare weakly or not dependent on the direction of H , while the other indicated parameters are significantly influenced. Results enable control of superconducting parameters by further optimization of microstructure through MgB2 texturing as a novel and viable strategy for development of bulk MgB2 with enhanced properties when taking advantage of its anisotropy.(c) 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Open Access

499. The Boron-Oxygen (BiOi) Defect Complex Induced by Irradiation With 23 GeV Protons in p-Type Epitaxial Silicon Diodes

Authors: Liao, C; Fretwurst, E; Garutti, E; Schwandt, J; Moll, M; Himmerlich, A; Gurimskaya, Y; Pintilie, ; Nitescu, A; Li, Z; Makarenko, L

Published: MAR 2022, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 69, DOI: 10.1109/TNS.2022.3148030

In this work, the thermally stimulated current (TSC) technique has been used to investigate the properties of the radiation-induced interstitial boron and interstitial oxygen defect complex by 23-GeV (E-kin) protons, including activation energy, defect concentration, as well as the annealing behavior. At first isothermal annealing (at 80 degrees C for 0-180 min) followed by isochronal annealing (for 15 min between 100 degrees C and 190 degrees C in steps of 10 degrees C), studies had been performed in order to get information about the thermal stability of the interstitial boron and interstitial oxygen defect in 50-Omega cm material after irradiation with 23-GeV protons to a fluence of 6.91 x 10(13) p/cm(2). The results are presented and discussed. Furthermore, the extracted data from TSC measurements are compared with the macroscopic properties derived from current-voltage and capacitance-voltage characteristics. In addition, the introduction rate of interstitial boron and interstitial oxygen defect as a function of the initial doping concentration was determined by exposing diodes with different resistivities (10, 50, 250, and 2 k Omega cm) to 23-GeV protons. These results are compared with data from TSC and deep-level transient spectroscopy measurements achieved by the team of the CERN-RD50 "Acceptor removal project."

Open Access

500. Hierarchical Flax Fibers by ZnO Electroless Deposition: Tailoring the Natural Fibers/Synthetic Matrix Interphase in Composites

Authors: Preda, N; Costas, A; Sbardella, F; Seghini, MC; Touchard, F; Chocinski-Arnault, L; Tirillò, J; Sarasini, F

Published: AUG 2022, NANOMATERIALS, 12, 2765, DOI: 10.3390/nano12162765

Hierarchical functionalization of flax fibers with ZnO nanostructures was achieved by electroless deposition to improve the interfacial adhesion between the natural fibers and synthetic matrix in composite materials. The structural, morphological, thermal and wetting properties of the pristine and ZnO-coated flax fibers were investigated. Thus, the ZnO-coated flax fabric discloses an apparent contact angle of similar to 140 degrees immediately after the placement of a water droplet on its surface. An assessment of the interfacial adhesion at the yarn scale was also carried out on the flax yarns coated with ZnO nanostructures. Thus, after the ZnO functionalization process, no significant degradation of the tensile properties of the flax yarns occurs. Furthermore, the single yarn fragmentation tests revealed a notable increase in the interfacial adhesion with an epoxy matrix, reductions of 36% and 9% in debonding and critical length values being measured compared to those of the pristine flax yarns, respectively. The analysis of the fracture morphology by scanning electron microscopy and X-ray microtomography highlighted the positive role of ZnO nanostructures in restraining debonding phenomena at the flax fibers/epoxyresin matrix interphase.

501. A nanoscale continuous transition from the monoclinic to ferroelectric orthorhombic phase inside HfO2 nanocrystals stabilized by HfO2 capping and self-controlled Ge doping

Authors: Palade, C; Lepadatu, AM; Slav, A; Cojocaru, O; Iuga, A; Maraloiu, VA; Moldovan, A; Dinescu, M; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: SEP 28 2021, JOURNAL OF MATERIALS CHEMISTRY C, 9, DOI: 10.1039/d1tc02921e

Orthorhombic HfO2 exhibits nanoscale ferroelectricity that opens the perspective of ultra-scalable CMOS integration of ferroelectric memories. However, many aspects of the metastable orthorhombic crystallization mechanisms still need to be elucidated and new fabrication methods are of high interest. In this paper, the atomically resolved crystal structure of HfO2 is a 3-layer structure with a Ge-rich HfO2 intermediate layer capped by a top (cap) HfO2 layer and cladded by a bottom HfO2 layer. There is a continuity of crystal growth from the top and bottom HfO2 layers into the intermediate layer. A spatial transition from a monoclinic phase to an orthorhombic phase was revealed within a region of a few atomic layers at the interface between capped and intermediate HfO2 layers. This result suggests the mechanism of orthorhombic and monoclinic phase formation by a martensitic-like transformation of the initially grown tetragonal phase. The sample fabrication method we used involved magnetron sputtering deposition of the 3-layer structures, i.e. a stack of top HfO2/Ge-rich HfO2 intermediate/bottom HfO2 layers, followed by rapid thermal annealing. It results in self-optimized orthorhombic crystallization of HfO2 by Ge nanoparticle segregation in the intermediate layer. The ferroelectric effects are revealed by polarization-voltage hysteresis loops and piezoresponse force microscopy measurements. The atomistic computations performed by using the density functional theory support the experimental results by showing that the Ge doping of HfO2 leads to orthorhombic phase stabilization and increased Berry phase polarization.

Open Access

502. Antimicrobial Activity of MgB2 Powders Produced via Reactive Liquid Infiltration Method

Authors: Padhi, SK; Baglieri, N; Bonino, V; Agostino, A; Operti, L; Batalu, ND; Chifiriuc, MC; Popa, M; Burdusel, M; Grigoroscuta, MA; Aldica, GV; Radu, D; Badica, P; Truccato, M

Published: AUG 2021, MOLECULES, 26, 4966, DOI: 10.3390/molecules26164966

We report for the first time on the antimicrobial activity of MgB2 powders produced via the Reactive Liquid Infiltration (RLI) process. Samples with MgB2 wt.% ranging from 2% to 99% were obtained and characterized, observing different levels of grain aggregation and of impurity phases. Their antimicrobial activity was tested against Staphylococcus aureus ATCC BAA 1026, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. A general correlation is observed between the antibacterial activity and the MgB2 wt.%, but the sample microstructure also appears to be very important. RLI-MgB2 powders show better performances compared to commercial powders against microbial strains in the planktonic form, and their activity against biofilms is also very similar.

Open Access

503. Investigation of Opto-Electronic Properties and Stability of Mixed-Cation Mixed-Halide Perovskite Materials with Machine-Learning Implementation

Authors: Filipoiu, N; Mitran, TL; Anghel, DV; Florea, M; Pintilie, I; Manolescu, A; Nemnes, GA

Published: SEP 2021, ENERGIES, 14, 5431, DOI: 10.3390/en14175431

The feasibility of mixed-cation mixed-halogen perovskites of formula A(x)A'1-xPbXyXz'X3-y-z '' is analyzed from the perspective of structural stability, opto-electronic properties and possible degradation mechanisms. Using density functional theory (DFT) calculations aided by machine-learning (ML) methods, the structurally stable compositions are further evaluated for the highest absorption and optimal stability. Here, the role of the halogen mixtures is demonstrated in tuning the contrasting trends of optical absorption and stability. Similarly, binary organic cation mixtures are found to significantly influence the degradation, while they have a lesser, but still visible effect on the opto-electronic properties. The combined framework of high-throughput calculations and ML techniques such as the linear regression methods, random forests and artificial neural networks offers the necessary grounds for an efficient exploration of multi-dimensional compositional spaces.

Open Access

504. Thermoelectric Efficiency of Epitaxial GeSn Alloys for Integrated Si-Based Applications: Assessing the Lattice Thermal Conductivity by Raman Thermometry

Authors: Spirito, D; Driesch, NV; Manganelli, CL; Zoellner, MH; Corley-Wiciak, AA; Ikonic, Z; Stoica, T; Grützmacher, D; Buca, D; Capellini, G

Published: JUL 26 2021, ACS APPLIED ENERGY MATERIALS, 4, DOI: 10.1021/acsaem.1c01576

Energy harvesting for Internet of Things applications, comprising sensing, life sciences, wearables, and communications, requires efficient thermoelectric (TE) materials, ideally semiconductors compatible with Si technology. In this work, we investigate the potential of GeSn/Ge layers, a group IV material system, as TE material for low-grade heat conversion. We extract the lattice thermal conductivity, by developing an analytical model based on Raman thermometry and heat transport model, and use it to predict thermoelectric performances. The lattice thermal conductivity decreases from 56 W/(m.K) for Ge to 4 W/(m.K) by increasing the Sn atomic composition to 14%. The bulk cubic Ge0.86Sn0.14 alloy features a TE figure of merit of ZT similar to 0.4 at 300 K and an impressive 1.04 at 600 K. These values are extremely promising in view of the use of GeSn/Ge layers operating in the typical on-chip temperature range.

505. Properties of Ni0.5Zn0.5Fe2O4 nanoparticles with the spinel structure synthesized via cryo-chemical method

Authors: Timashkov, I; Shlapa, Y; Maraloiu, VA; Rajnak, M; Timko, M; Belous, A

Published: SEP 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, 650, DOI: 10.1007/s00339-021-04795-0

Ni0.5Zn0.5Fe2O4 nanoparticles (NPs) with the spinel structure were synthesized by the cryo-chemical method with further heat treatment in the temperature range of 200-800 degrees C. Crystalline NPs began to form in one-stage and the degree of crystallinity grew with the increase of the heating temperature. Particles sizes, their size distributions and magnetization also tended to growth directly with the increasing the heating temperature of NPs. Magnetic fluids based on the obtained Ni0.5Zn0.5Fe2O4 NPs demonstrated effective and self-controlled heating up to the certain temperatures under the effect of an alternating magnetic field in contrast to known in literature Fe3O4 NPs with the spinel structure, which heated up uncontrolled to the extremely high phase transition temperature.

Open Access

506. New Phenotype and Mineralization of Biogenic Iron Oxide in Magnetotactic Bacteria

Authors: Baaziz, W; Ghica, C; Cypriano, J; Abreu, F; Anselme, K; Ersen, O; Farina, M; Werckmann, J

Published: DEC 2021, NANOMATERIALS, 11, 3189, DOI: 10.3390/nano11123189

Many magnetotactic bacteria (MTB) biomineralize magnetite crystals that nucleate and grow inside intracellular membranous vesicles originating from invaginations of the cytoplasmic membrane. The crystals together with their surrounding membranes are referred to as magnetosomes. Magnetosome magnetite crystals nucleate and grow using iron transported inside the vesicle by specific proteins. Here, we tackle the question of the organization of magnetosomes, which are always described as constituted by linear chains of nanocrystals. In addition, it is commonly accepted that the iron oxide nanocrystals are in the magnetite-based phase. We show, in the case of a wild species of coccus-type bacterium, that there is a double organization of the magnetosomes, relatively perpendicular to each other, and that the nanocrystals are in fact maghemite. These findings were obtained, respectively, by using electron tomography of whole mounts of cells directly from the environment and high-resolution transmission electron microscopy and diffraction. Structure simulations were performed with the MacTempas software. This study opens new perspectives on the diversity of phenotypes within MTBs and allows to envisage other mechanisms of nucleation and formation of biogenic iron oxide crystals.

507. Morpho-structural properties of ZnSe, TiO2-ZnSe materials and enzymatic activity of their bioinorganic hybrids with lysozyme

Authors: Anastasescu, C; Gifu, IC; Negrila, C; Socoteanu, R; Atkinson, I; Calderon-Moreno, JM; Munteanu, C; Plavan, G; Strungaru, SA; Cheatham, B; Malaroiu, AV; Teodorescu, VS; Anastasescu, M; Zaharescu, M; Balint, I; Lazarescu, V

Published: OCT 2021, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 272, 115350, DOI: 10.1016/j.mseb.2021.115350

Structural and functional changes induced by TiO2 addition to spherical zinc selenide together with lysozyme adsorption lead to valuable bioinorganic catalysts with enhanced activity. Spherical zinc selenide and its composite with TiO2 were obtained by hydrothermal method and subsequently modified by lysozyme adsorption. Morphological, structural and functional characteristics of zinc selenide based materials (ZnSe, TiO2-ZnSe) and their hybrids with lysozyme (Lys/ZnSe, Lys/TiO2-ZnSe) were investigated. TiO2 addition to ZnSe results in significant changes of surface composition, electrochemical behavior and lysozyme retention capacity. The lysozyme modified ZnSe and TiO2-ZnSe surfaces doubles the biocatalysts efficiency for 4-Methylumbelliferyl p-D-N,N',N ''-triacetylchitotrioside hydrolysis reaction compared to free lysozyme.

Open Access

508. Advancements on Basic Working Principles of Photo-Driven Oxidative Degradation of Organic Substrates over Pristine and Noble Metal-Modified TiO2. Model Case of Phenol Photo Oxidation

Authors: Sandulescu, A; Anastasescu, C; Papa, F; Raciulete, M; Vasile, A; Spataru, T; Scarisoreanu, M; Fleaca, C; Mihailescu, CN; Teodorescu, VS; Spataru, N; Zaharescu, M; Balint, I

Published: APR 2021, CATALYSTS, 11, 487, DOI: 10.3390/catal11040487

The specific roles played by both support and noble metals in light absorption, charge separation, and the formation of center dot OH and O-2(-) (ROS) are analyzed for light-triggered oxidation of phenol (Ph) over pristine and over noble metal (Ag, Au, Pt) -loaded TiO2. Experiments show that the supported noble metals act as a light visible absorber, assist the separation of photo-charges and reduction of O-2 to O-2(-). The O-2(-) oxidizes mildly Ph to oxygenated products (hydroquinone, benzoquinone, and 1,2-dihydroxibenzene). In a parallel process, center dot OH radicals, yielded by TiO2, mineralize Ph to CO2 by fast reaction sequences. Radical quenching and photo electrochemical measurements (surface photovoltage) confirm independently that the production of center dot OH and O-2(-) scale with oxidative conversion of Ph. The selectivity to CO2 and mild oxidation products is the result of the interplay between catalyst activity for center dot OH and for O-2(-) production.

509. Hard/soft effects of multivalence co-dopants in correlation with their location in PZT ceramics

Authors: Amarande, L; Cioangher, MC; Toma, V; Miclea, CF; Stefan, M; Pasuk, I; Iuga, AR; Negrila, C; Matei, E; Palici, AM; Joita, AC

Published: DEC 1 2021, CERAMICS INTERNATIONAL, 47, DOI: 10.1016/j.ceramint.2021.08.243

Piezoelectric hard/soft effects of multivalence co-dopants (Sb and Mn) in correlation with their location in the lattice, were investigated in PZT ceramics, prepared by conventional ceramic technology, with the following compositions: Pb0.98Sr0.02 ((Ti0.49Zr0.51)(1-0.015-x)Mn0.015Sbx)O-3 with x = 0, 0.005, 0.01, 0.02, 0.03, where antimony was initially assumed to substitute for Ti/Zr ions. The antimony valence state was found to be +3 in all samples by X-ray Photoelectron Spectroscopy investigations. The Electron Paramagnetic Resonance spectra evidenced a steep enhancement of the Mn2+ concentration upon increasing antimony doping level, explained by a charge compensation mechanism, between the Sb3+ ions substituting Pb2+ at the A-sites and the Mn2+ ions, localized at the B-sites. The incorporation of Sb3+ at the A-site of the PZT lattice is also supported by the variation of the lattice parameters, determined by X-ray Diffraction, with the increasing Sb concentration. The investigation of the dielectric, electromechanical and ferroelectric properties evidenced a hard piezoelectric behavior, mainly attributed to the presence of large sized Mn2+ ions, localized at B-sites. Our results prove that the piezoelectric hard/soft response is decisively influenced by the interplay between multiple valence states and locations of the co-dopants, on one hand, and the charge compensation mechanisms, on the other hand. This provides indirect information about the location of some co-dopants which can substitute for both cationic sites in the PZT based ceramics.

Open Access

510. The Influence of the Ceramic Nanoparticles on the Thermoplastic Polymers Matrix: Their Structural, Optical, and Conductive Properties

Authors: Smaranda, I; Nila, A; Ganea, P; Daescu, M; Zgura, I; Ciobanu, RC; Trandabat, A; Baibarac, M

Published: AUG 2021, POLYMERS, 13, 2773, DOI: 10.3390/polym13162773

This paper prepared composites under the free membranes form that are based on thermoplastic polymers of the type of polyurethane (TPU) and polyolefin (TPO), which are blended in the weight ratio of 2:1, and ceramic nanoparticles (CNs) such as BaSrTiO3 and SrTiO3. The structural, optical, and conductive properties of these new composite materials are reported. The X-ray diffraction studies highlight a cubic crystalline structure of these CNs. The main variations in the vibrational properties of the TPU:TPO blend induced by CNs consist of the following: (i) the increase in the intensity of the Raman line of 1616 cm(-1); (ii) the down-shift of the IR band from 800 to 791 cm(-1); (iii) the change of the ratio between the absorbance of IR bands localized in the spectral range 950-1200 cm(-1); and (iv) the decrease in the absorbance of the IR band from 1221 cm(-1). All these variations were correlated with a preferential adsorption of thermoplastic polymers on the CNs surface. A photoluminescence (PL) quenching process of thermoplastic polymers is demonstrated to occur in the presence of CNs. The anisotropic PL measurements have highlighted a change in the angle of the binding of the TPU:TPO blend, which varies from 23.7 degrees to approximate to 49.3 degrees and approximate to 53.4 degrees, when the concentration of BaSrTiO3 and SrTiO3 CNs, respectively, is changed from 0 to 25 wt. %. Using dielectric spectroscopy, two mechanisms are invoked to take place in the case of the composites based on TPU:TPO blends and CNs, i.e., one regarding the type of the electrical conduction and another specifying the dielectric-dipolar relaxation processes.

511. Functionalization of basalt fibers with ZnO nanostructures by electroless deposition for improving the interfacial adhesion of basalt fibers/epoxy resin composites

Authors: Preda, N; Costas, A; Lilli, M; Sbardella, F; Scheffler, C; Tirillò, J; Sarasini, F

Published: OCT 2021, COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, 149, 106488, DOI: 10.1016/j.compositesa.2021.106488

Basalt fibers were functionalized by ZnO electroless deposition for obtaining a nanostructured interphase for enhancing the interfacial strength with an epoxy resin matrix. The structural, morphological and wetting properties of the pristine basalt fabrics and ZnO-coated basalt fabrics were evaluated. The fabrics were uniformly coated with ZnO nanostructures featuring a wurtzite structure and a twin hexagonal prism morphology. The contact angle measurements revealed that ZnO prisms transformed the hydrophilic basalt fabric into a hydrophobic one (similar to 130 degrees). ZnOs were also grown on the basalt fibers as yarns to evaluate their interfacial adhesion by single fiber pull-out tests. The results emphasize significant improvement in the apparent interfacial shear strength (similar to 42%) with limited degradation of the pristine basalt fiber tensile strength (a reduction of similar to 17%). Therefore, ZnO electroless deposition can be regarded as an effective mute to improve the mechanical performance of basalt/epoxy composites expanding their potential range of applications as structural materials.

512. Potassium-containing triple-cation mixed-halide perovskite materials: Toward efficient and stable solar cells

Authors: Derbali, S; Nouneh, K; Florea, M; Leonat, LN; Stancu, V; Tomulescu, AG; Galca, AC; Secu, M; Pintilie, L; Touhami, ME

Published: MAR 25 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 858, 158335, DOI: 10.1016/j.jallcom.2020.158335

In this paper, potassium based triple cation mixed-halide perovskite films were explored in order to enhance the stability and photovoltaic performance of perovskite based solar cells. It was found that adding potassium (K+) to a double cation mixed halide perovskite (FA(0.80)MA(0.20)PbI(2.8)Cl(0.2)), structural, morphological and optoelectronic properties of perovskites are improved. The perovskite films were prepared by one-step spin coating method with and without K+ and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). The results indicate that potassium incorporation reduces significantly the yellow non-perovskite delta-phase formation and improves the perovskite film quality, thus contributing to the reduction of hysteresis, improves the stability and increases the PCE up to 12.51%. Furthermore, the doped devices exhibit reduced hysteresis and provide remarkable shelf stability by retaining more than 70% of the initial efficiency with low humidity over 850 h. (C) 2020 Elsevier B.V. All rights reserved.

513. Water oxidation at photoanodes based on hematite films and nanowire arrays

Authors: Sima, M; Matei, E; Vasile, E; Sima, A; Preda, N; Logofatu, C

Published: APR 30 2021, THIN SOLID FILMS, 724, 138626, DOI: 10.1016/j.tsf.2021.138626

In this paper we report the results of a photoelectrochemical study performed on photoanodes based on hematite nanowire arrays and films prepared on fluoride-doped tin oxide coated glass (FTO) and FTO/TiO2 substrates, respectively by hydrothermal and spray pyrolysis methods. The hematite nanowires grown on FTO/TiO2 substrate are more stable mechanically, longer (1 ?m) and their density on substrate is higher. Hematite film obtained on FTO substrate has a thickness of 92 nm covering uniformly the substrate. X-ray photoelectron spectroscopy measurements showed that hematite samples synthesized on FTO/TiO2 substrate have lower content of oxygen vacancies. The photoelectrochemical performances of the prepared photoanodes are in close connection with the presence or absence of the TiO2 underlayer, with oxygen vacancies content and with their morphological characteristics. Electrochemical impedace spectroscopy was used to investigate the charge transfer kinetics at electrode/electrolyte interface and Mott-Schottky analysis was performed to estimate the flatband potential and the carrier density. TiO2 underlayer led to the formation of defects on the samples surface which induced a positive shift of the flatband potentials compared to that of the bare hematite film. The results showed that the best density photocurrent was obtained with a photoanode of hematite nanowires grown on FTO/TiO2 substrate.

Open Access

514. MgB2 powders and bioevaluation of their interaction with planktonic microbes, biofilms, and tumor cells

Authors: Badica, P; Batalu, ND; Chifiriuc, MC; Burdusel, M; Grigoroscuta, MA; Aldica, G; Pasuk, I; Kuncser, A; Enculescu, M; Popa, M; Marutescu, LG; Gheorghe, I; Thamer, O; Bleotu, C; Pircalabioru, GG; Operti, L; Bonino, V; Agostino, A; Truccato, M

Published: MAY-JUN 2021, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 12, DOI: 10.1016/j.jmrt.2021.04.003

Commercial nanopowders of MgB2 were characterized from the viewpoint of granulometric distribution, structure, microstructure, and pH behavior in water. The powders are very different: a higher amount of the MgB2 phase with a lower tendency for agglomeration determines a higher rate of pH-increase. A higher rate of pH-increase usually produces a stronger antimicrobial activity against Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Candida parapsilosis reference strains. The variation of the pH-increase rate suggests the possibility of temporo-spatial control of MgB2 bioactivity, although the contribution of other factors should not be neglected. Remarkably, the efficiency of the MgB2 powders is higher against biofilms than on microbes in the planktonic state. Further, our experiments confirm the antimicrobial efficiency of MgB2 in the in vitro tests against 29 methicillin resistant clinical S. aureus isolates and 33 vancomycin resistant E. faecium/faecalis strains, but in this case the biofilms are more resistant than planktonic cells. The MgB2 treatment of infected mice led to a significant decrease of E. coli colonization in liver, spleen and peritoneal liquid and it also caused changes in the intestinal microbiota. The activity of powders on HeLa and HT-29 tumor cell lines was assessed by inverted microscopy, flow cytometry, and evaluation of the cellular cycle. MgB2 inhibits tumor cell growth influencing DNA synthesis (S-phase). The obtained results indicate that the tested powders could provide promising solutions for the development of large-spectrum multifunctional antimicrobial and anti-biofilm agents, and/or for anti-cancer therapies. (C) 2021 The Authors. Published by Elsevier B.V.

515. Operation of a magnetron sputtering gas aggregation cluster source in a plasma jet regime for synthesis of core-shell nanoparticles

Authors: Acsente, T; Istrate, MC; Satulu, V; Bita, B; Dinescu, G

Published: JAN 14 2021, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 54, 02LT01, DOI: 10.1088/1361-6463/abbb05

Operation of a magnetron sputtering gas aggregation cluster source in a plasma jet regime is presented. In specific experimental conditions, the plasma extends from the inside of the cluster source in the deposition chamber as a plasma jet, transporting also the nanoparticles (NPs) produced in the cluster source. The chemistry of the NP surface is modified in-flight by injecting a chemical precursor in the plasma jet, resulting in core-shell NPs. Also, the plasma jet presents a low gas temperature, safely interacting with materials sensitive to thermal degradation (like polymers). These findings prove the potential of the presented plasma jet for applications in nanotechnology.

516. Recent progress in electrocatalysts and electrodes for portable fuel cells

Authors: Neatu, S; Neatu, F; Chirica, IM; Borbath, I; Tálas, E; Tompos, A; Somacescu, S; Osiceanu, P; Folgado, MA; Chaparro, AM; Florea, M

Published: AUG 28 2021, JOURNAL OF MATERIALS CHEMISTRY A, 9, DOI: 10.1039/d1ta03644k

Fuel cells are devices that transform efficiently the chemical energy of hydrogen or another fuel into clean electricity. The fuel cell technology is attractive for its high-energy efficiency and expanded fuel flexibility and it became very relevant in the last decade. Moreover, the utilization of fuel cells for portable electronic devices has seen remarkable increase in the last few years. Performances of fuel cells, among others, strongly depend on the types of electrocatalysts and membrane, anion exchange or cation exchange, used in the system. Therefore, a status report about the latest advances in electrocatalysts and electrodes for portable fuel cells is the objective of this review paper. Herein, the recent progress in designing electrocatalysts for producing high performance fuel cells with truly potential applicability to be used in portable devices is highlighted.

517. BIOPHYSICAL ASPECTS OF BIO-NANOSILVER GENERATED FROM URTICA DIOICA LEAVES AND VITIS VINIFERA FRUITS' EXTRACTS

Authors: Barbinta-Patrascu, ME; Nichita, C; Badea, N; Ungureanu, C; Bacalum, M; Zgura, I; Iosif, L; Antohe, S

Published: 2021, ROMANIAN REPORTS IN PHYSICS, 73, 601, DOI:

Green chemistry principles were used to phytosynthesis of three types of silver nanoparticles (AgNPs) from aqueous extracts of: nettle (Urtica dioica) leaves, black grapes (Vitis vinifera fruits), and their mixture. The combination of these extracts proved to be the most potent bioreductant for Ag+, as compared to each extract alone. UV-Vis absorption and FT-IR spectroscopy proved the formation of silver nanoparticles. Total polyphenols' quantification of vegetal extracts and "green" AgNPs was carried out by Folin-Ciocalteu analysis. Structural (XRD) analysis revealed crystalline nature of bio-developed AgNPs. Morphological studies (AFM) showed spherical shape and the nano-scale dimensions of the obtained metallic nanoparticles. Physical stability of "green" developed nanoparticles was estimated by zeta potential measurements, and their biological activity was checked by evaluating the antimicrobial and the antioxidant potency. AgNPs phyto-generated from a combination of two extracts (nettle and grapes) proved to be the most bio-active, combining in a synergistic manner, the properties of nettle and grapes. These nanoparticles exhibited high antioxidant activity (AA = 89.4%) evaluated through chemiluminescence method, and strong antibacterial effect (showing an inhibition zone diameter of 20 mm) against Escherichia coli.

518. pH-triggered intracellular release of doxorubicin by a poly(glycidyl methacrylate)-based double-shell magnetic nanocarrier

Authors: Zohreh, N; Rastegaran, Z; Hosseini, SH; Akhlaghi, M; Istrate, C; Busuioc, C

Published: JAN 2021, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 118, 111498, DOI: 10.1016/j.msec.2020.111498

Two core-double-shell pH-sensitive nanocarriers were fabricated using Fe3O4 as magnetic core, poly(glycidyl methacrylate-PEG) and salep dialdehyde as the first and the second shell, and doxorubicin as the hydrophobic anticancer drug. Two nanocarriers were different in the drug loading steps. The interaction between the first and the second shell assumed to be pH-sensitive via acetal cross linkages. The structure of nanocarriers, organic shell loading, magnetic responsibility, morphology, size, dispersibility, and drug loading content were investigated by IR, NMR, TG, VSM, XRD, DLS, HRTEM and UV-Vis analyses. The long-term drug release profiles of both nanocarriers showed that the drug loading before cross-linking between the first and second shell led to a more pH-sensitive nanocarrier exhibiting higher control on DOX release. Cellular toxicity assay (MTT) showed that DOX-free nanocarrier is biocompatible having cell viability greater than 80% for HEK-293 and MCF-7 cell lines. Besides, high cytotoxic effect observed for drug-loaded nanocarrier on MCF-7 cancer cells. Cellular uptake analysis showed that the nanocarrier is able to transport DOX into the cytoplasm and perinuclear regions of MCF-7 cells. In vitro hemolysis and coagulation assays demonstrated high blood compatibility of nanocarrier. The results also suggested that low concentration of nanocarrier have a great potential as a contrast agent in magnetic resonance imaging (MRI).

Open Access

519. Hybrid Nanocomposite Platform, Based on Carbon Nanotubes and Poly(Methylene Blue) Redox Polymer Synthesized in Ethaline Deep Eutectic Solvent for Electrochemical Determination of 5-Aminosalicylic Acid

Authors: Hosu, O; Barsan, MM; Sandulescu, R; Cristea, C; Brett, CMA

Published: FEB 2021, SENSORS, 21, 1161, DOI: 10.3390/s21041161

A novel hybrid composite of conductive poly(methylene blue) (PMB) and carbon nanotubes (CNT) was prepared for the detection of 5-aminosalicylic acid (5-ASA). Electrosynthesis of PMB with glassy carbon electrode (GCE) or with carbon nanotube modified GCE was done in ethaline deep eutectic solvent of choline chloride mixed with ethylene glycol and a 10% v/v aqueous solution. Different sensor architectures were evaluated in a broad range of pH values in a Britton-Robinson (BR) buffer using electrochemical techniques, chronoamperometry (CA), and differential pulse voltammetry (DPV), to determine the optimum sensor configuration for 5-ASA sensing. Under optimal conditions, the best analytical performance was obtained with CNT/PMBDES/GCE in 0.04 M BR buffer pH 7.0 in the range 5-100 mu M 5-ASA using the DPV method, with an excellent sensitivity of 9.84 mu A cm(-2) mu M-1 (4.9 % RSD, n = 5) and a detection limit (LOD) (3 sigma/slope) of 7.7 nM, outclassing most similar sensors found in the literature. The sensitivity of the same sensor obtained in CA (1.33 mu A cm(-2) mu M-1) under optimal conditions (pH 7.0, E-app = +0.40 V) was lower than that obtained by DPV. Simultaneous detection of 5-ASA and its analogue, acetaminophen (APAP), was successfully realized, showing a catalytic effect towards the electro-oxidation of both analytes, lowering their oxidation overpotential, and enhancing the oxidation peak currents and peak-to-peak separation as compared with the unmodified electrode. The proposed method is simple, sensitive, easy to apply, and economical for routine analysis.

Open Access

520. Development of Iron-Doped Hydroxyapatite Coatings

Authors: Predoi, D; Iconaru, SL; Ciobanu, SC; Predoi, SA; Buton, N; Megier, C; Beuran, M

Published: FEB 2021, COATINGS, 11, 186, DOI: 10.3390/coatings11020186

It is known that iron is found as a trace element in bone tissue, the main inorganic constituent of which is hydroxyapatite. Therefore, iron-doped hydroxyapatite (HApFe) materials could be new alternatives for many biomedical applications. A facile dip coating process was used to elaborate the iron-doped hydroxyapatite (HApFe) nanocomposite coatings. The HApFe suspension used to prepare the coatings was achieved using a co-precipitation method, which was adapted in the laboratory. The quality of the HApFe suspension was assessed through dynamic light scattering (DLS), ultrasonic measurements, and zeta potential values. The hydroxyapatite XRD patterns were observed in the HApFe nanocomposite with no significant shifting of peak positions, thus suggesting that the incorporation of iron did not significantly modify the hydroxyapatite structure. The morphology of the HApFe nanoparticles was evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used in order to investigate the morphologies of HApFe particles and coatings, while their chemical compositions were assessed using energy-dispersive X-ray spectroscopy (EDS). The SEM results suggested that the HApFe consists mainly of spherical nanometric particles and that the surfaces of the coatings are continuous and homogeneous. Additionally, the EDS spectra highlighted the purity of the samples and confirmed the presence of calcium, phosphorous, and iron in the analyzed sample. The in vitro cytotoxicity of the HApFe suspensions and coatings was evidenced using osteoblast cells. The MTT assay showed that both the HApFe suspensions and coatings exhibited biocompatible properties.

Open Access

521. Preparation of Porous Hydroxyapatite Using Cetyl Trimethyl Ammonium Bromide as Surfactant for the Removal of Lead Ions from Aquatic Solutions

Authors: Predoi, SA; Ciobanu, CS; Motelica-Heino, M; Chifiriuc, MC; Badea, ML; Iconaru, SL

Published: MAY 2021, POLYMERS, 13, 1617, DOI: 10.3390/polym13101617

In the present study, a new low-cost bioceramic nanocomposite based on porous hydroxyapatite (HAp) and cetyl trimethyl ammonium bromide (CTAB) as surfactant was successfully obtained by a simple chemical co-precipitation. The composition and structure of the HAp-CTAB were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) spectrometer, and N-2 adsorption/desorption analysis. The capacity of HAp-CTAB nanocomposites to remove the lead ions from aqueous solutions was studied by adsorption batch experiments and proved by Langmuir and Freundlich models. The Pb2+ removal efficiency of HAp-CTAB biocomposite was also confirmed by non-destructive ultrasound studies. The cytotoxicity assays showed that the HAp-CTAB nanocomposites did not induce any significant morphological changes of HeLa cells after 24 h of incubation or other toxic effects. Taken together, our results suggests that the obtained porous HAp-CTAB powder could be used for the decontamination of water polluted with heavy metals, such as Pb2+.

522. Optical, microstructural and vibrational properties of sol-gel ITO films

Authors: Nicolescu, M; Anastasescu, M; Calderon-Moreno, JM; Maraloiu, AV; Teodorescu, VS; Preda, S; Predoana, L; Zaharescu, M; Gartner, M

Published: APR 2021, OPTICAL MATERIALS, 114, 110999, DOI: 10.1016/j.optmat.2021.110999

The aim of this paper is to prepare multi-layered ITO thin films by a low cost and environmental-friendly method for different applications (optoelectronics, sensors, etc.). ITO films with 15 layers were obtained by successive depositions using the sol-gel & dip-coating method on three different substrates: glass, SiO2/glass and SiO2/Si. Comparative structural, morphological and optical characterization were performed by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Cross Section Transmission Electron Microscopy (XTEM) coupled with Selected Area Electron Diffraction (SAED), Infrared Spectroscopic Ellipsometry (IRSE) and Raman spectroscopy analyses. The optical constants (refractive index n and extinction coefficient k) were determined in a large spectral range (300-27500 cm-1) by spectroscopic ellipsometry (SE). The thicknesses determined by SE were confirmed by HRTEM (High Resolution TEM) measurements which also presents in detail the textural properties of the ITO films at nanometric level. A comparison between IRSE and Raman analysis in the infrared active region was presented.

Open Access

523. Nanocrystallized Ge-Rich SiGe-HfO2 Highly Photosensitive in Short-Wave Infrared

Authors: Palade, C; Lepadatu, AM; Slav, A; Teodorescu, VS; Stoica, T; Ciurea, ML; Ursutiu, D; Samoila, C

Published: NOV 2021, MATERIALS, 14, 7040, DOI: 10.3390/ma14227040

Group IV nanocrystals (NCs), in particular from the Si-Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron sputtering deposition followed by rapid thermal annealing at 600 & DEG;C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, mu-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3-7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs-HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600-2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.

524. The effect of fullerene layer on the aggregates formation in amyloid beta Langmuir-Blodgett films

Authors: Breazu, C; Rasoga, O; Socol, M; Ganea, P; Tite, T; Matei, E; Stanculescu, F; Stanculescu, A

Published: JAN 30 2021, APPLIED SURFACE SCIENCE, 537, 147800, DOI: 10.1016/j.apsusc.2020.147800

The investigation of the effect of carbon nanomaterials and lipids on the aggregation particularities of the amyloid beta/A beta(1-42) layers is important for understanding the generation mechanism of neuronal disorder and how it can be inhibited. Additionally, amyloids are nanomaterials with a wide area of potential applications from nanotechnology to biotechnology. This paper presents a study about the preparation of A beta(1-42) layer by two different methods, Langmuir-Blodgett (L-B) and drop cast (DC), on Si and Si covered by a layer of Buckminster fullerene, C-60, and on the effect of fullerene layer or/and cholesterol (Ch) on the generation of A beta(1-42) secondary structure forms, relevant for specific applications. AFM, SEM FTIR and Raman analysis offered details about the layer surface topography, morphology and particularities of the secondary structure generated in the process of A beta(1-42) molecules aggregation. This study showed that the presence of Ch inhibited the formation of fibrils in A beta(1-42) film deposited by L-B on Si covered by C-60 The structures developed during aggregation were correlated with the topography and roughness of the films. The presence of Ch determined a decrease in roughness for L-B film and increase in roughness for DC film deposited on Si covered by C-60 layer.

Open Access

525. Cytotoxicity, Antioxidant, Antibacterial, and Photocatalytic Activities of ZnO-CdS Powders (vol 13, 182, 2020)

Authors: Zgura, I; Preda, N; Enculescu, M; Diamandescu, L; Negrila, C; Bacalum, M; Ungureanu, C; Barbinta-Patrascu, ME

Published: DEC 2021, MATERIALS, 14, 7713, DOI: 10.3390/ma14247713

526. Effects of Ge-related storage centers formation in Al2O3 enhancing the performance of floating gate memories

Authors: Stavarache, I; Cojocaru, O; Maraloiu, VA; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: MAR 15 2021, APPLIED SURFACE SCIENCE, 542, 148702, DOI: 10.1016/j.apsusc.2020.148702

In this paper, we report studies on Al2O3/Ge/Al2O3 trilayer memory structures deposited by magnetron sputtering at room temperature on p-Si substrates coated with 3 nm SiO2. The changes of the structure, morphology and memory properties induced by rapid thermal annealing (RTA) in a broad temperature range 550-900 degrees C have been carefully investigated. High resolution transmission electron microscopy (HRTEM) revealed the existence of distinct RTA effects for different temperature ranges, in correlation with memory properties measured on Al/Al2O3/Ge/Al2O3/SiO2/p-Si/Al devices. Thus, at temperatures smaller than 650 degrees C, Ge diffuses into adjacent Al2O3, the layers remaining amorphous. The memory window increases from as-deposited samples to those annealed at 600 degrees C reaching the maximum of 5.4 V. After RTA at 700 degrees C, Ge nanocrystals (NCs) in intermediate Ge layer and Ge-rich amorphous nanoparticles in Al2O3 tunnel oxide are formed. Increasing RTA temperature to 800 and 900 degrees C, Ge NCs are no longer formed due to Ge strong diffusion. Instead, Ge-rich mixed GeAl oxide NCs of unknown crystalline structure are evidenced by HRTEM. The memory window continuously decreases with annealing temperature in the range 650-900 degrees C. The ON (OFF) charge loss of only 11% (9.8%) was found by extrapolation to 10 years.

Open Access

527. Strippable Polymeric Nanocomposites Comprising "Green" Chelates, for the Removal of Heavy Metals and Radionuclides

Authors: Toader, G; Pulpea, D; Rotariu, T; Diacon, A; Rusen, E; Moldovan, A; Podaru, A; Ginghina, R; Alexe, F; Iorga, O; Bajenaru, SA; Ungureanu, M; Dirloman, F; Pulpea, B; Leonat, L

Published: DEC 2021, POLYMERS, 13, 4194, DOI: 10.3390/polym13234194

The issue of heavy metal and radionuclide contamination is still causing a great deal of concern worldwide for environmental protection and industrial sites remediation. Various techniques have been developed for surface decontamination aiming for high decontamination factors (DF) and minimal environmental impact, but strippable polymeric nanocomposite coatings are some of the best candidates in this area. In this study, novel strippable coatings for heavy metal and radionuclides decontamination were developed based on the film-forming ability of polyvinyl alcohol, with the remarkable metal retention capacity of bentonite nanoclay, together with the chelating ability of sodium alginate and with "new-generation" "green" complexing agents: iminodisuccinic acid (IDS) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC). These environmentally friendly water-based decontamination solutions are capable of generating strippable polymeric films with optimized mechanical and thermal properties while exhibiting high decontamination efficiency (DF approximate to 95-98% for heavy metals tested on glass surface and DF approximate to 91-97% for radionuclides Am-241, Sr-90-Y and Cs-137 on metal, painted metal, plastic, and glass surfaces).

528. Alternative lignopolymer-based composites useful as enhanced functionalized support for enzymes immobilization

Authors: Lite, C; Ion, S; Tudorache, M; Zgura, I; Galca, AC; Enache, M; Maria, GM; Parvulescu, VI

Published: NOV 1 2021, CATALYSIS TODAY, 379, DOI: 10.1016/j.cattod.2020.05.060

Amino-derivatized lignocomposite (ADL-composite) has been designed as an artificial lignin polymer (P1) of monolignol (coniferyl alcohol, CA) enhanced by aniline insertion (P2). The derivatized lignopolymeric (P2) layer covered the surface of a methacrylate particles (SC2/SC6) functionalized previously with amino phenolic crosslinker (p-phenylenediamine (p-Ph-2-NH2) or p-amino-2-hydroxybenzoic acid (p-NH2-SalA)). One-pot biocatalytic approach allowed to combine the preparation of the polymeric materials and also its attachment on the particles surface. Thus, the monolignol (CA) will be oxi-copolymerized together with aniline on the amino prefunctionalized support surface. The oxidation process was performed using H2O2 reagent and catalyzed by peroxidase enzyme (horseradish peroxidase, HRP). The biocatalytic process was evaluated in term of aromatic monomers (CA and aniline) conversion. The chemical structure and properties of the resulted ADL-composites were investigated using specific techniques (e.g. FTIR, TPD, TGA, static contact angle, elemental analysis, and gel permeation chromatography). Attachment of P1/P2 polymer on the particles improved the hydrophobicity and also the basicity of the composite surface. Lipase enzyme was immobilized on the ADL-composites for testing the applicability of ADL-composites for biocatalyst preparation. SEM analysis allowed to notice the modification of ADL-composites surface after enzyme immobilization. Immobilized lipase exhibited better activity compared with free lipase demonstrating the efficiency of ADL-composite as support for enzyme immobilization.

529. Magnesium-silver cathodes for efficient charge injection into Organic Light Emitting Diodes deposited by LTVA method

Authors: Vladoiu, R; Mandes, A; Dinca, V; Kudrna, P; Tichy, M; Polosan, S

Published: JUL 15 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 869, 159364, DOI: 10.1016/j.jallcom.2021.159364

The Laser-induced Thermionic Vacuum Arc method was applied to optimize magnesium-silver (Mg:Ag) alloys, which can be potentially used as stable metallic cathodes for optoelectronic devices. Besides lowering the cathode work function given by the magnesium that improves the electron injection, Mg:Ag alloys induce a higher electrical conductivity, estimated here to be 3.42 x 10(7) S m(-1) for AgMg3, compared with 2.64 x 10(7) S m(-1), estimated here for Mg thin films. Mg:Ag alloys avoid the critical issue of Mg oxidation for better charge injection in optoelectronic active layers. By improving the Thermionic Vacuum Arc technique with the laser beam, this method enables the control of the silver concentration in these alloys due to photonic processes. The uniformity of metallic thin films, compactness, and high purity are the primary advantages of the Laser-induced Thermionic Vacuum Arc method. (C) 2021 Elsevier B.V. All rights reserved.

Open Access

530. Beyond Nitrogen in the Oxygen Reduction Reaction on Nitrogen-Doped Carbons: A NEXAFS Investigation

Authors: Tanasa, E; Maxim, FI; Erniyazov, T; Iacob, MT; Skála, T; Tanase, LC; Ianasi, C; Moisescu, C; Miron, C; Ardelean, I; Antohe, VA; Fagadar-Cosma, E; Stamatin, SN

Published: MAY 2021, NANOMATERIALS, 11, 1198, DOI: 10.3390/nano11051198

Polymer electrolyte membrane fuel cells require cheap and active electrocatalysts to drive the oxygen reduction reaction. Nitrogen-doped carbons have been extensively studied regarding their oxygen reduction reaction. The work at hand looks beyond the nitrogen chemistry and brings to light the role of oxygen. Nitrogen-doped nanocarbons were obtained by a radio-frequency plasma route at 0, 100, 250, and 350 W. The lateral size of the graphitic domain, determined from Raman spectroscopy, showed that the nitrogen plasma treatment decreased the crystallite size. Synchrotron radiation photoelectron spectroscopy showed a similar nitrogen chemistry, albeit the nitrogen concentration increased with the plasma power. Lateral crystallite size and several nitrogen moieties were plotted against the onset potential determined from oxygen reduction reaction curves. There was no correlation between the electrochemical activity and the sample structure, as determine from Raman and synchrotron radiation photoelectron spectroscopy. Near-edge X-ray absorption fine structure (NEXAFS) was performed to unravel the carbon and nitrogen local structure. A difference analysis of the NEXAFS spectra showed that the oxygen surrounding the pyridinic nitrogen was critical in achieving high onset potentials. The work shows that there were more factors at play, other than carbon organization and nitrogen chemistry.

Open Access

531. Transient increase of Tc and Jc in superconducting/metallic heterostructures

Authors: Ionescu, AM; Bihler, M; Simmendinger, J; Miksch, C; Fischer, P; Cristiani, G; Rabinovich, KS; Schütz, G; Albrecht, J

Published: APR 15 2021, MATERIALS CHEMISTRY AND PHYSICS, 263, 124390, DOI: 10.1016/j.matchemphys.2021.124390

The presence of a metallic layer can influence the properties of high-temperature superconductors underneath. We investigate the influence of metallic structures deposited in form of nanoparticles or continuous layers by electron beam evaporation or ion beam sputtering on the properties of Y1Ba2Cu3O7-x (YBCO) thin films. To generally avoid diffusion of metal atoms an additional barrier layer is introduced. Detailed measurements of the magnetic moment of the superconductor as a function of temperature and magnetic field have been performed using SQUID magnetometry. It is found that the modification of the superconducting properties of coated YBCO strongly depends on the deposition method of the metal on top rather than the type of metal (Ni or Ag), its magnetic properties (ferromagnetic or paramagnetic) or its morphology (nanoparticles or thin film). The main result is a transient increase of the critical temperature T-c and critical current density J(c) that was observed for samples prepared by electron beam evaporation.

532. Effect of ferroelectric poling on the photoelectrochemical activity of hematite-BaTiO3 nanowire arrays

Authors: Sima, M; Vasile, E; Preda, N; Sima, A; Matei, E; Logofatu, C

Published: OCT 22 2021, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 46, DOI: 10.1016/j.ijhydene.2021.08.152

Ferroelectric alpha-Fe2O3/BaTiO3 photoanodes (hematite/BT) were fabricated on FTO and FTO/TiO2 substrates using a hydrothermal process and spin coating along with thermal treatments. The prepared hematite nanowires had length under 1 mu m and the BT film was about 18 nm thick. SEM, TEM and XPS investigations prove the formation of alpha-Fe2O3/BaTiO3 heterojunction structure. The ferroelectric poling of hematite/BT heterojunction was conducted both in propylene carbonate and in air. The photoelectrochemical performance of hematite/BT photoanodes is strongly influenced by the direction of ferroelectric polarization. The positive poling of the hematite/BT prepared on FTO/TiO2 substrate produces a 40.4% photocurrent density enhancement, in comparison with not poled version of the sample. Electrochemical impedance spectroscopy measurements provided usefull information regarding the effect of ferroelectric polarization on the charge transfer kinetics at the photoanode/electrolyte interface. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

533. Electro-active properties of nanostructured films of cytosine and guanine nucleobases

Authors: Socol, M; Trupina, L; Galca, AC; Chirila, C; Stan, GE; Vlaicu, AM; Stanciu, AE; Boni, AG; Botea, M; Stanculescu, A; Pintilie, L; Borca, B

Published: OCT 8 2021, NANOTECHNOLOGY, 32, 415702, DOI: 10.1088/1361-6528/ac10e4

The discovery of multifunctional properties related to electro-activity of organic systems of biomolecules is important for a variety of applications, especially for devices in the realm of biocompatible sensors and/or bioactuators. A further step towards such applications is to prepare thin films with the required properties. Here, the investigation is focused on the characterization of films of guanine and cytosine nucleobases, prepared by thermal evaporation-an industrial accessible deposition technique. The cytosine films have an orthorhombic non-centrosymmetric structure and grow in two interconnected nanostructured fractal patterns, of nearly equal proportion. Piezoresponse force microscopy images acquired at room temperature on the cytosine films display large zones with antiparallel alignment of the vertical components of the polarization vector. Guanine films have a dense nano-grained morphology. Our studies reveal electrical polarization switching effects which can be related to ferroelectricity in the films of guanine molecules. Characteristic ferroelectric polarization-electric-field hysteresis loops showing large electrical polarization are observed at low temperatures up to 200 K. Above this temperature, the guanine films have a preponderant paraelectric phase containing residual or locally induced nano-scopic ferroelectric domains, as observed by piezoresponse force microscopy at room temperature.

Open Access

534. Investigation of Spin Coating Cerium-Doped Hydroxyapatite Thin Films with Antifungal Properties

Authors: Iconaru, SL; Predoi, MV; Chapon, P; Gaiaschi, S; Rokosz, K; Raaen, S; Motelica-Heino, M; Predoi, D

Published: APR 2021, COATINGS, 11, 464, DOI: 10.3390/coatings11040464

In this study, the cerium-doped hydroxyapatite (Ca10-xCex(PO4)(6)(OH)(2) with x(Ce) = 0.1, 10Ce-HAp) coatings obtained by the spin coating method were presented for the first time. The stability of the 10Ce-HAp suspension particles used in the preparation of coatings was evaluated by ultrasonic studies, transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The surface morphology of the 10Ce-HAp coating was studied by SEM and atomic force microscopy (AFM) techniques. The obtained 10Ce-HAp coatings were uniform and without cracks or unevenness. Glow discharge optical emission spectroscopy (GDOES) and X-ray photoelectron spectroscopy (XPS) were used for the investigation of fine chemical depth profiling. The antifungal properties of the HAp and 10Ce-HAp suspensions and coatings were assessed using Candida albicans ATCC 10231 (C. albicans) fungal strain. The quantitative antifungal assays demonstrated that both 10Ce-HAp suspensions and coatings exhibited strong antifungal properties and that they successfully inhibited the development and adherence of C. albicans fungal cells for all the tested time intervals. The scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) visualization of the C. albicans fungal cells adherence to the 10Ce-HAp surface also demonstrated their strong inhibitory effects. In addition, the qualitative assays also suggested that the 10Ce-HAp coatings successfully stopped the biofilm formation.

Open Access

535. Fabrication of Novel Chitosan-Hydroxyapatite Nanostructured Thin Films for Biomedical Applications

Authors: Ciobanu, CS; Iconaru, SL; Predoi, D; Trusca, RD; Prodan, AM; Groza, A; Chifiriuc, MC; Beuran, M

Published: DEC 2021, COATINGS, 11, 1561, DOI: 10.3390/coatings11121561

In this study, we develop chitosan-hydroxyapatite (CS-HAp) composite layers that were deposited on Si substrates in radio frequency (RF) magnetron sputtering discharge in argon gas. The composition and structure of CS-HAp composite layers were investigated by analytical techniques, such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), metallographic microscopy (MM), and atomic force microscopy (AFM). On the other hand, in the present study the second order derivative of FT-IR-ATR spectra, for compositional analyses of CS-HAp, were used. The SEM, MM, and AFM data have shown the formation of CS-HAp composite layers. The surface of CS-HAp composite layers showed uniform growth (at an Ar gas working pressure of p = 2 x 10(-3) mbar). The surface of the CS-HAp composites coatings became more nanostructured, becoming granular as the gas pressure increased from 5 x 10(-3) to 1.2 x 10(-2) mbar. However, our studies revealed that the surface morphology of the CS-HAp composite layers varies with the Ar gas working pressure. At the same time, optical properties are slightly influenced by Ar pressure. Their unique physicochemical properties make them suitable for various applications in the biomedical field, if we consider the already proven antimicrobial properties of chitosan. The antifungal properties and the capacity of the CS-HAp composite layers to inhibit the development of fungal biofilms were also demonstrated using the Candida albicans ATCC 10231 (C. albicans) fungal strain.

Open Access

536. Cyclophane with eclipsed pyrene units enables construction of spin interfaces with chemical accuracy

Authors: Metzelaars, M; Schleicher, S; Hattori, T; Borca, B; Matthes, F; Sanz, S; Bürgler, DE; Rawson, J; Schneider, CM; Kögerler, P

Published: JUN 28 2021, CHEMICAL SCIENCE, 12, DOI: 10.1039/d1sc01036k

Advanced functionality in molecular electronics and spintronics is orchestrated by exact molecular arrangements at metal surfaces, but the strategies for constructing such arrangements remain limited. Here, we report the synthesis and surface hybridization of a cyclophane that comprises two pyrene groups fastened together by two ferrocene pillars. Crystallographic structure analysis revealed pyrene planes separated by similar to 352 pm and stacked in an eclipsed geometry that approximates the rare configuration of AA-stacked bilayer graphene. We deposited this cyclophane onto surfaces of Cu(111) and Co(111) at submonolayer coverage and studied the resulting hybrid entities with scanning tunnelling microscopy (STM). We found distinct characteristics of this cyclophane on each metal surface: on non-magnetic Cu(111), physisorption occurred and the two pyrene groups remained electronically coupled to each other; on ferromagnetic Co(111) nanoislands, chemisorption occurred and the two pyrene groups became electronically decoupled. Spin-polarized STM measurements revealed that the ferrocene groups had spin polarization opposite to that of the surrounding Co metal, while the pyrene stack had no spin polarization. Comparisons to the non-stacked analogue comprising only one pyrene group bolster our interpretation of the cyclophane's STM features. The design strategy presented herein can be extended to realize versatile, three-dimensional platforms in single-molecule electronics and spintronics.

Open Access

537. Composite Drug Delivery System Based on Amorphous Calcium Phosphate-Chitosan: An Efficient Antimicrobial Platform for Extended Release of Tetracycline

Authors: Visan, AI; Ristoscu, C; Popescu-Pelin, G; Sopronyi, M; Matei, CE; Socol, G; Chifiriuc, MC; Bleotu, C; Grossin, D; Brouillet, F; Le Grill, S; Bertrand, G; Zgura, I; Cristescu, R; Mihailescu, IN

Published: OCT 2021, PHARMACEUTICS, 13, 1659, DOI: 10.3390/pharmaceutics13101659

One major warning emerging during the first worldwide combat against healthcare-associated infections concerns the key role of the surface in the storage and transfer of the virus. Our study is based on the laser coating of surfaces with an inorganic/organic composite mixture of amorphous calcium phosphate-chitosan-tetracycline that is able to fight against infectious agents, but also capable of preserving its activity for a prolonged time, up to several days. The extended release in simulated fluids of the composite mixture containing the drug (tetracycline) was demonstrated by mass loss and UV-VIS investigations. The drug release profile from our composite coatings proceeds via two stages: an initial burst release (during the first hours), followed by a slower evolution active for the next 72 h, and probably more. Optimized coatings strongly inhibit the growth of tested bacteria (Enterococcus faecalis and Escherichia coli), while the drug incorporation has no impact on the in vitro composite's cytotoxicity, the coatings proving an excellent biocompatibility sustaining the normal development of MG63 bone-like cells. One may, therefore, consider that the proposed coatings' composition can open the prospective of a new generation of antimicrobial coatings for implants, but also for nosocomial and other large area contamination prevention.

Open Access

538. Effect of starting materials and sintering temperature on microstructure and optical properties of Y2O3:Yb³⁺5 at% transparent ceramics

Authors: Yavetskiy, RP; Balabanov, AE; Parkhomenko, SV; Kryzhanovska, OS; Doroshenko, AG; Mateychenko, PV; Tolmachev, AV; Li, J; Jiang, N; Gheorghe, L; Enculescu, M

Published: FEB 2021, JOURNAL OF ADVANCED CERAMICS, 10, DOI: 10.1007/s40145-020-0416-3

Y2O3:Yb(3+)5 at% ceramics have been synthesized by the reactive sintering method using different commercial yttria powders (Alfa-Micro, Alfa-Nano, and ITO-V) as raw materials. It has been shown that all Y(2)O(3)starting powders consist from agglomerates up to 5-7 mu m in size which are formed from 25-60 nm primary particles. High-energy ball milling allows to significantly decreasing the median particle sizeD(50)below 500 nm regardless of the commercial powders used. Sintering experiments indicate that powder mixtures fabricated from Alfa-Nano yttria powders have the highest sintering activity, while (Y0.86La0.09Yb0.05)(2)O(3)ceramics sintered at 1750 degrees C for 10 h are characterized by the highest transmittance of about 45%. Y2O3:Yb(3+)ceramics have been obtained by the reactive sintering at 1750-1825 degrees C using Alfa-Nano Y(2)O(3)powders and La2O3+ZrO(2)as a complex sintering aid. The effects of the sintering temperature on densification processes, microstructure, and optical properties of Y2O3:Yb(3)(+)5 at% ceramics have been studied. It has been shown that Zr(4)(+)ions decrease the grain growth of Y2O3:Yb(3+)ceramics for sintering temperatures 1750-1775 degrees C. Further increasing the sintering temperature was accompanied by a sharp increase of the average grain size of ceramics referred to changes of structure and chemical composition of grain boundaries, as well as their mobility. It has been determined that the optimal sintering temperature to produce high-dense yttria ceramics with transmittance of 79%-83% and average grain size of 8 mu m is 1800 degrees C. Finally, laser emission at similar to 1030.7 nm with a slope efficiency of 10% was obtained with the most transparent Y2O3:Yb(3+)5 at% ceramics sintered.

Open Access

539. Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles

Authors: Jinga, LI; Popescu-Pelin, G; Socol, G; Mocanu, S; Tudose, M; Culita, DC; Kuncser, A; Ionita, P

Published: JUN 2021, NANOMATERIALS, 11, 1605, DOI: 10.3390/nano11061605

Gold nanoparticles (similar to 10 nm) were deposited on titanium dioxide nanoparticles (similar to 21 nm) and the material obtained was characterized using IR, UV-Vis, N-2 adsorption-desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded in the presence of this material when using hydrogen peroxide as the oxidant. Tests were performed at 2, 4, 6, and 24 h, with hydrogen peroxide contents varying from 1 to 5 mg/mL. Longer exposure time and a higher content of oxidant led to the degradation of methylene blue dye at up to 90%. The material can be reused several times with no loss of activity.

Open Access

540. Raman investigations of the radiation-induced modifications in iPP-VGCNF nanocomposites: The nanofillers' tale

Authors: Chipara, DM; Secu, M; Lozano, K; Secu, C; Chipara, M

Published: OCT 2021, CARBON TRENDS, 5, 100119, DOI: 10.1016/j.cartre.2021.100119

Nanocomposites of isotactic polypropylene loaded by various amounts of vapor-grown carbon nanotubes ranging from 0 to 20% wt. were obtained by extrusion. Raman investigations on these nanocomposites are reported. The nanocomposites were irradiated using a Co-60, with an integral dose of 1 kGy/h up to integral doses of 9 kGy, 18 kGy, and 27 kGy, in air, at room temperature. Raman measurements were performed by using a Bruker Senterra confocal Raman spectrometer operating at 785 nm. The research is focused on the information contained within the D and G Raman lines of these nanocomposites as a function of nanotube loading for various integral doses. The experimental data revealed the graduate silencing of the molecular motions assigned to the polymeric matrix due to the nanofiller and ionizing radiation. Based on experimental data, it is concluded that the positions of the D and G lines exhibit faint shifts due to the irradiation and that (on average) these shifts are consistent with the changes of the positions of D and G lines upon the increase of the loading with vapor-grown carbon nanofibers. Raman data suggest that the irradiation relaxes the pressure exerted on the nanofiller by the polymeric matrix, indicating a path to improve the physical features of polymer-carbon nanostructure nanocomposites. The research demonstrates the capability of Raman spectroscopy to sense the modifications of molecular vibrations in polymer-based nanocomposites, for both the polymeric matrix and the nanofiller. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Open Access

541. Immobilized Antibodies on Mercaptophenylboronic Acid Monolayers for Dual-Strategy Detection of 20S Proteasome

Authors: Barsan, MM; Sanz, CG; Onea, M; Diculescu, VC

Published: APR 2021, SENSORS, 21, 2702, DOI: 10.3390/s21082702

A dual strategy for the electrochemical detection for 20S proteasome (20S) is proposed, based on the oriented immobilization of a capture monoclonal antibody (Ab beta) on a self-assembled monolayer of 4-mercaptophenylboronic acid (4-MPBA) on gold electrodes, which led to the Au/4-MPBA/Ab beta immunosensor. The methodology comprises the correlation of 20S concentration with (i) its proteolytic activity toward the Z-LLE-AMC substrate, using the Au/4-MPBA/Ab beta/20S, and (ii) the enzymatic activity of an alkaline phosphatase (AlkP) from the AlkP-labeled secondary antibody (Ab(core)-AlkP), which involves the conversion of aminophenylphosphate to the electroactive aminophenol using Au/4-MPBA/Ab beta/20S/Ab(core)-AlkP. The step-by-step construction of the immunosensor and the interactions at its surface were evaluated by surface plasmon resonance and gravimetric analysis with quartz crystal microbalance, showing a high affinity between both antibodies and 20S. Morphological analysis by scanning electron microscopy demonstrated a pattern of parallel lines upon immobilization of Ab beta on 4-MPBA and morphological changes to a well-organized granular structure upon binding of 20S. A voltametric and impedimetric characterization was performed after each step in the immunosensor construction. The two detection strategies were evaluated. It was shown that the immunosensor responds linearly with 20S concentration in the range between 5 and 100 mu g mL(-1), which corresponds to proteasome levels in serum in the case of diverse pathological situations, and LoD values of 1.4 and 0.2 mu g mL(-1) were calculated for the detection strategies. The immunosensor was applied to the detection of 20S in serum samples with recovery values ranging from 101 to 103%.

Open Access

542. In Vitro Evaluation of MgB2 Powders as Novel Tools to Fight Fungal Biodeterioration of Heritage Buildings and Objects

Authors: Gheorghe, I; Avram, I; Corbu, VM; Marutescu, L; Popa, M; Balotescu, I; Blajan, I; Mateescu, V; Zaharia, D; Dumbrava, AS; Zetu, OE; Pecete, I; Cristea, VC; Batalu, D; Grigoroscuta, MA; Burdusel, M; Aldica, GV; Badica, P; Datcu, AD; Ianovici, N; Bleotu, C; Lazar, V; Ditu, LM; Chifiriuc, MC

Published: JAN 13 2021, FRONTIERS IN MATERIALS, 7, 601059, DOI: 10.3389/fmats.2020.601059

The 17th-19th century wooden and stone churches are an iconic symbol for the Romanian national heritage, raising urgent needs for the development of efficient and ecofriendly restoration and preservation solutions. Nanotechnology has a great but largely unexplored potential in this field, providing new tools and methods to achieve higher consolidation and protection efficiency, mainly due to the ability of nanoparticles to inhibit the growth and metabolic activity of different biodeteriorating agents, including fungi. The purpose of the present study was to report for the first time on the efficiency of MgB2 materials, mainly prized for their practical superconducting properties, against a large collection of filamentous fungal strains recently isolated from biodeteriorated wooden and stone heritage objects. Four types of MgB2 powders, with a crystallite size of 42-113 nm, were tested by qualitative (on 149 strains) and quantitative (on 87 strains) assays. The cytotoxicity was evaluated by the microscopic analysis of SiHa cells morphology and Hep2 cell cycle analysis and the ecotoxicity by the Allium test. The tested filamentous fungal strains belonged to 11 different genera, and those isolated from mural paintings and wooden objects exhibited the best capacity to colonize the inert substratum. All MgB2 powders exhibited similar and relatively low minimal inhibitory concentrations (MIC) values against the Aspergillus and Penicillium isolates, which were predominated among isolates. From the tested powders, PVZ and CERAC proved to be more efficient against the strains isolated from stone and wood materials, while LTS was active against the fungal strains colonizing the mural paintings and museum objects. The cytotoxicity results indicated that the tested powders are toxic for the human cells at concentrations higher than 50 mu g/ml, but, however, the very short lifetime of these NPs prevents their accumulation in the natural environment and, thus, the occurrence of toxic effects. The tested powders proved to be ecofriendly at the active antifungal concentrations, as suggested by the phytotoxicity test results. Taken together, our results suggest the potential of the MgB2 materials for the development of environmentally safe antifungal substances, which can be used in the control of the material cultural heritage biodeterioration process.

Open Access

543. Intrinsic Dielectric Loss in Zr0.8Sn0.2TiO4 Ceramics Investigated by Terahertz Time Domain Spectroscopy

Authors: Nedelcu, L; Geambasu, CD; Enculescu, M; Banciu, MG

Published: JAN 2021, MATERIALS, 14, 216, DOI: 10.3390/ma14010216

Terahertz time-domain spectroscopy (THz-TDS) was employed for estimation of intrinsic dielectric loss of Zr0.8Sn0.2TiO4 (ZST) ceramics. Single-phase ZST dielectric resonators (DRs) with various synthesis parameters and, consequently, different extrinsic losses, were prepared by conventional ceramic technology. Even though the DRs exhibit a similar microstructure, their quality factor (Q is the inverse of dielectric loss tangent) measured in microwave (MW) domain at 6 GHz varies between 2500 and 8400. On the other hand, it was found that the THz dielectric loss is less sensitive to the sample preparation. The intrinsic losses (Q x f similar to 60 THz) of the ZST ceramics have been derived from THz data.

Open Access

544. Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

Authors: Cojocaru, O; Lepadatu, AM; Nemnes, GA; Stoica, T; Ciurea, ML

Published: JUN 30 2021, SCIENTIFIC REPORTS, 11, 13582, DOI: 10.1038/s41598-021-92936-z

We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1-x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by Delta E(eV)=0.651(1-x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d(1.25) for 2-4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1-x NC surface reaches the total number atoms of the Ge+Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.

Open Access

545. Structural, functional properties and enhanced thermal stability of bulk graded (Ba,Sr)TiO3 structures obtained by spark plasma sintering

Authors: Botea, M; Pintilie, I; Surdu, VA; Stanciu, CA; Trusca, RD; Vasile, BS; Patru, R; Ianculescu, AC; Pintilie, L

Published: MAY-JUN 2021, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 12, DOI: 10.1016/j.jmrt.2021.04.011

Graded structures with different architectures were obtained by spark plasma sintering from (Ba1-xSrx)TiO3 (BST, x = 0.10; 0.20; 0.30) powders. The presence of the composition gradient was confirmed by structural and compositional investigations using X-ray diffraction and electron microscopy combined with energy dispersive X-ray spectroscopy. The concentration gradient was either asymmetric (3 layers, starting with x = 0.10 and ending with x = 0.30) or symmetric (5 or 6 layers, starting and ending with x = 0.10, and with a single or double x = 0.30 layer in the middle, respectively). Electrical measurements reveal a decrease of the dielectric constant with increasing the number of the layers. It was found that the symmetric graded structure with 6 layers has the best thermal stability of both, the dielectric constant (variation of only 8% between zero and 100 degrees C) and the py-roelectric coefficient (6% variation between zero and 80 degrees C). In addition, an enhancement of the pyroelectric signal for frequencies above 100 Hz is obtained in symmetric structures, an effect that is attributed to the additive contributions of the signals originated from the layers with different Sr content. (C) 2021 The Author(s). Published by Elsevier B.V.

Open Access

546. Nitrogen and Bromide Co-Doped Hydroxyapatite Thin Films with Antimicrobial Properties

Authors: Iconaru, SL; Ciobanu, CS; Predoi, D; Motelica-Heino, M; Negrila, CC; Badea, ML; Predoi, MV; Chifiriuc, CM; Popa, M

Published: DEC 2021, COATINGS, 11, 1505, DOI: 10.3390/coatings11121505

Hydroxyapatite (Ca-10(PO4)(6)(OH)(2), HAp), due to its high biocompatibility, is widely used as biomaterial. Doping with various ions of hydroxyapatite is performed to acquire properties as close as possible to the biological apatite present in bones and teeth. In this research the results of a study performed on thin films of hydroxyapatite co-doped with nitrogen and bromine (NBrHAp) are presented for the first time. The NBrHAp suspension was obtained by performing the adapted co-precipitation method using cetyltrimethylammonium bromide (CTAB). The thin layers of NBrHAp were obtained by spin-coating. The stability of the NBrHAp suspension was examined by ultrasound measurements. The thin layers obtained by the spin-coating method were examined by scanning electron microscopy (SEM), optical microscopy (OM), and metallographic microscopy (MM). The presence of nitrogen and bromine were highlighted by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) studies. Fourier transform infrared spectroscopy (FTIR) was used to highlight the chemical status of nitrogen and bromine. In addition, the powder obtained from the NBrHAp suspension was analyzed by XRD. Moreover, the in vitro antimicrobial activity of the NBrHAp suspensions and coatings was investigated using the reference microbial strains Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231. The results highlighted the successful obtainment of N and Br co-doped hydroxyapatite suspension for the first time by an adapted co-precipitation method. The obtained suspension was used to produce pure NBrHAp composite thin films with superior morphological properties. The NBrHAp suspensions and coatings exhibited in vitro antimicrobial activity against bacterial and fungal strains and revealed their good antimicrobial activity.

Open Access

547. Optical Properties of Transparent Rare-Earth Doped Sol-Gel Derived Nano-Glass Ceramics

Authors: Secu, M; Secu, C; Bartha, C

Published: NOV 2021, MATERIALS, 14, 6871, DOI: 10.3390/ma14226871

Rare-earth doped oxyfluoride glass ceramics represent a new generation of tailorable optical materials with high potential for optical-related applications such as optical amplifiers, optical waveguides, and white LEDs. Their key features are related to the high transparency and remarkable luminescence properties, while keeping the thermal and chemical advantages of oxide glasses. Sol-gel chemistry offers a flexible synthesis approach with several advantages, such as lower processing temperature, the ability to control the purity and homogeneity of the final materials on a molecular level, and the large compositional flexibility. The review will be focused on optical properties of sol-gel derived nano-glass ceramics related to the RE-doped luminescent nanocrystals (fluorides, chlorides, oxychlorides, etc.) such as photoluminescence, up-conversion luminescence, thermoluminescence and how these properties are influenced by their specific processing, mostly focusing on the findings from our group and similar ones in the literature, along with a discussion of perspectives, potential challenges, and future development directions.

548. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

Authors: Olar, R; Badea, M; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Rostas, AM; Vlaicu, ID; Popa, M; Chifiriuc, MC

Published: OCT 2021, BIOMETALS, 34, DOI: 10.1007/s10534-021-00334-9

In an attempt to propose new applications for the biomedical field, complexes with mixed ligands {[Cu(bpy)(2)(mu 2OClO3)]ClO4}n (1) and [Cu(phen)(2)(OH2)](ClO4)(2) (2) (bpy: 2,2'-biyridine; phen and 1,10-phenantroline) were evaluated for their antibacterial and cytotoxicicity features and for the elucidation of some of the mechanisms involved. Complex (2) proved to be a very potent antibacterial agent, exhibing MIC and MBEC values 2 to 54 times lower than those obtained for complex (1) against both susceptible or resistant Gram-positive and Gram-negative strains, in planktonic or biofilm growth state. In exchange, complex (1) exhibited selective cytotoxicity against melanoma tumor cells (B16), proving a promising potential for developing novel anticancer drugs. The possible mechanisms of both antimicrobial and antitumor activity of the copper(II) complexes is their DNA intercalative ability coupled with ROS generation. The obtained results recommend the two complexes for further development as multipurpose copper-containing drugs.

549. NANOMAGNETIC IRON OXIDE SOLUTION FOR FERTILIZATION ON WHEAT PLANTS

Authors: Cimpeanu, C; Badea, ML; Ciobanu, CS; Savulescu, E; Badulescu, L; Petcu, E; Mustatea, P; Raita, SM; Barbuceanu, F; Furnaris, F; Predoi, G

Published: 2021, ROMANIAN AGRICULTURAL RESEARCH, 38, DOI:

Wheat is the most cultivated plant and an important source of carbohydrates in the world. The Fe deficiency reduces quality of grain wheat leading to Fe deficiency in human. The purpose of this study was to investigate the effects of foliar and ground application of iron oxide nanoparticles (made in Romania) on growth components, yield and morphological and anatomical modifications of wheat plants. The ground application of iron oxide decreased height of plant, length of root and increased root volume and chlorophyll content more than foliar application. For the wheat plants fertilized with iron oxide nanoparticles, the decrease of root length was compensated by an increase of radicular density, which led to the development of new adventitious roots that could help the plants have a better uptake of water and nutrients. This meant that the production was not negatively influenced by the treatments performed, regardless of the application method. Our studies revealed that the fertilized wheat plants (foliar and root zone) presented anatomical changes in relation to control plants. The studies presented in this paper can contribute to achieve the necessary framework for the innovative development strategy regarding the efficiency of magnetic nanoparticles in foliar and ground fertilization of different crops.

Open Access

550. Engineering hydrogenation active sites on graphene oxide and N-doped graphene by plasma treatment

Authors: Magureanu, M; Mandache, NB; Rizescu, C; Bucur, C; Cojocaru, B; Man, IC; Primo, A; Parvulescu, V; Garcia, H

Published: JUN 15 2021, APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY, 287, 119962, DOI: 10.1016/j.apcatb.2021.119962

Graphene oxide (GO) and N-doped graphene [(N)G] graphenes were submitted to H-2 glow discharge under different discharge regimes, in both the negative glow and positive column plasma regions. The resulted catalysts were fully characterized using several techniques such as Raman, DRIFT and XPS spectroscopy, powder X-ray diffraction, H-2 pulse chemisorption and H-2-, CO2- and NH3-TPD experiments. Density functional theory calculations were performed taking a slab model of graphene sheet with an optimized C-C bond length (1.426 angstrom) and a 16 angstrom vacuum layer between sheets. An overview of these characterizations showed that the O/C atomic ratio of GO is influenced by the plasma regime, indicating the occurrence of O removal, as also predicted by DFT calculations. In the case of (N)G, the plasma treatment also removes pyridinic N with an increase of the C/N ratio. The efficiency of the plasma modification has been checked through catalytic tests in hydroisomerization of 1-octene and hydrogenation of alpha-methyl-styrene. Contrarily to classical thermal activation requiring high temperatures, the generation of the defects by treating with plasma occurs at voltages in the range of 2 5 kV. In consequence, the hydrogenation and isomerization of alkenes resulted with high yields and good selectivities. Graphene prepared from sodium alginate from brown algae was considered as reference in these investigations.

Open Access

551. Nucleobases thin films deposited on nanostructured transparent conductive electrodes for optoelectronic applications

Authors: Breazu, C; Socol, M; Preda, N; Rasoga, O; Costas, A; Socol, G; Petre, G; Stanculescu, A

Published: APR 6 2021, SCIENTIFIC REPORTS, 11, 7551, DOI: 10.1038/s41598-021-87181-3

Environmentally-friendly bio-organic materials have become the centre of recent developments in organic electronics, while a suitable interfacial modification is a prerequisite for future applications. In the context of researches on low cost and biodegradable resource for optoelectronics applications, the influence of a 2D nanostructured transparent conductive electrode on the morphological, structural, optical and electrical properties of nucleobases (adenine, guanine, cytosine, thymine and uracil) thin films obtained by thermal evaporation was analysed. The 2D array of nanostructures has been developed in a polymeric layer on glass substrate using a high throughput and low cost technique, UV-Nanoimprint Lithography. The indium tin oxide electrode was grown on both nanostructured and flat substrate and the properties of the heterostructures built on these two types of electrodes were analysed by comparison. We report that the organic-electrode interface modification by nano-patterning affects both the optical (transmission and emission) properties by multiple reflections on the walls of nanostructures and the electrical properties by the effect on the organic/electrode contact area and charge carrier pathway through electrodes. These results encourage the potential application of the nucleobases thin films deposited on nanostructured conductive electrode in green optoelectronic devices.

Open Access

552. Carbon-Coated SiO2 Composites as Promising Anode Material for Li-Ion Batteries

Authors: Buga, MR; Spinu-Zaulet, AA; Ungureanu, CG; Mitran, RA; Vasile, E; Florea, M; Neatu, F

Published: AUG 2021, MOLECULES, 26, 4531, DOI: 10.3390/molecules26154531

Porous silica-based materials are a promising alternative to graphite anodes for Li-ion batteries due to their high theoretical capacity, low discharge potential similar to pure silicon, superior cycling stability compared to silicon, abundance, and environmental friendliness. However, several challenges prevent the practical application of silica anodes, such as low coulombic efficiency and irreversible capacity losses during cycling. The main strategy to tackle the challenges of silica as an anode material has been developed to prepare carbon-coated SiO2 composites by carbonization in argon atmosphere. A facile and eco-friendly method of preparing carbon-coated SiO2 composites using sucrose is reported herein. The carbon-coated SiO2 composites were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetry, transmission and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, cyclic voltammetry, and charge-discharge cycling. A C/SiO2-0.085 M calendered electrode displays the best cycling stability, capacity of 714.3 mAh center dot g(-1), and coulombic efficiency as well as the lowest charge transfer resistance over 200 cycles without electrode degradation. The electrochemical performance improvement could be attributed to the positive effect of the carbon thin layer that can effectively diminish interfacial impedance.

Open Access

553. Micrometer Sized Hexagonal Chromium Selenide Flakes for Cryogenic Temperature Sensors

Authors: Buruiana, AT; Sava, F; Iacob, N; Matei, E; Bocirnea, AE; Onea, M; Galca, AC; Mihai, C; Velea, A; Kuncser, V

Published: DEC 2021, SENSORS, 21, 8084, DOI: 10.3390/s21238084

Nanoscale thermometers with high sensitivity are needed in domains which study quantum and classical effects at cryogenic temperatures. Here, we present a micrometer sized and nanometer thick chromium selenide cryogenic temperature sensor capable of measuring a large domain of cryogenic temperatures down to tenths of K. Hexagonal Cr-Se flakes were obtained by a simple physical vapor transport method and investigated using scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy measurements. The flakes were transferred onto Au contacts using a dry transfer method and resistivity measurements were performed in a temperature range from 7 K to 300 K. The collected data have been fitted by exponential functions. The excellent fit quality allowed for the further extrapolation of resistivity values down to tenths of K. It has been shown that the logarithmic sensitivity of the sensor computed over a large domain of cryogenic temperature is higher than the sensitivity of thermometers commonly used in industry and research. This study opens the way to produce Cr-Se sensors for classical and quantum cryogenic measurements.

Open Access

554. Nitrogen Functionalization of CVD Grown Three-Dimensional Graphene Foam for Hydrogen Evolution Reactions in Alkaline Media

Authors: Ion-Ebrasu, D; Andrei, RD; Enache, S; Caprarescu, S; Negrila, CC; Jianu, C; Enache, A; Boerasu, I; Carcadea, E; Varlam, M; Vasile, BS; Ren, JW

Published: SEP 2021, MATERIALS, 14, 4952, DOI: 10.3390/ma14174952

Three-dimensional graphene foam (3D-GrFoam) is a highly porous structure and sustained lattice formed by graphene layers with sp(2) and sp(3) hybridized carbon. In this work, chemical vapor deposition (CVD)-grown 3D-GrFoam was nitrogen-doped and platinum functionalized using hydrothermal treatment with different reducing agents (i.e., urea, hydrazine, ammonia, and dihydrogen hexachloroplatinate (IV) hydrate, respectively). X-ray photoelectron spectroscopy (XPS) survey showed that the most electrochemically active nitrogen-doped sample (GrFoam3N) contained 1.8 at % of N, and it exhibited a 172 mV dec(-1) Tafel plot associated with the Volmer-Heyrovsky hydrogen evolution (HER) mechanism in 0.1 M KOH. By the hydrothermal process, 0.2 at % of platinum was anchored to the graphene foam surface, and the resultant sample of GrFoamPt yielded a value of 80 mV dec(-1) Tafel associated with the Volmer-Tafel HER mechanism. Furthermore, Raman and infrared spectroscopy analysis, as well as scanning electron microscopy (SEM) were carried out to understand the structure of the samples.

Open Access

555. Preliminary Study on Light-Activated Antimicrobial Agents as Photocatalytic Method for Protection of Surfaces with Increased Risk of Infections

Authors: Bucuresteanu, R; Ditu, LM; Ionita, M; Calinescu, I; Raditoiu, V; Cojocaru, B; Cinteza, LO; Curutiu, C; Holban, AM; Enachescu, M; Enache, LB; Mustatea, G; Chihaia, V; Nicolaev, A; Borcan, EL; Mihaescu, G

Published: SEP 2021, MATERIALS, 14, 5307, DOI: 10.3390/ma14185307

Preventing and controlling the spread of multidrug-resistant (MDR) bacteria implicated in healthcare-associated infections is the greatest challenge of the health systems. In recent decades, research has shown the need for passive antibacterial protection of surfaces in order to reduce the microbial load and microbial biofilm development, frequently associated with transmission of infections. The aim of the present study is to analyze the efficiency of photocatalytic antimicrobial protection methods of surfaces using the new photocatalytic paint activated by light in the visible spectrum. The new composition is characterized by a wide range of analytical methods, such as UV-VIS spectroscopy, electron microscopy (SEM), X-ray powder diffraction (PXRD) or X-ray photoelectron spectroscopy (XPS). The photocatalytic activity in the UV-A was compared with the one in the visible light spectrum using an internal method developed on the basis of DIN 52980: 2008-10 standard and ISO 10678-2010 standard. Migration of metal ions in the composition was tested based on SR EN1186-3: 2003 standard. The new photocatalytic antimicrobial method uses a type of photocatalytic paint that is active in the visible spectral range and generates reactive oxygen species with inhibitory effect against all tested microbial strains.

Open Access

556. Multifunctional leather surfaces coated with nanocomposites through conventional and unconventional methods

Authors: Alexe, CA; Gaidau, C; Stanca, M; Radu, A; Stroe, M; Baibarac, M; Mateescu, G; Mateescu, A; Stanculescu, IR

Published: 2021, INTERNATIONAL CONFERENCES & EXHIBITION ON NANOTECHNOLOGIES, ORGANIC ELECTRONICS & NANOMEDICINE, NANOTEXNOLOGY 2020, PT 1, 54, DOI: 10.1016/j.matpr.2021.09.377

In this paper we present the results obtained by depositing the nanocomposite materials based on nano TiO2/TiO2:N, Ag, SiO2, single-walled carbon nanotube (SWCNTs), single-walled functionalized carboxylic acid, (SWCNT-COOH), poly(2,2' bithiophene) (PBTh) and poly(dipheylamine) (PDPA) by conventional and unconventional methods on the surface of sheepskin leathers. The nanocomposite materials were integrated in film forming polymers and were applied on sheepskin leather surfaces by spraying (conventional method) or by activating the surface with cold atmospheric plasma followed by electrospraying (unconventional methods). The leather surfaces were tested for antimicrobial properties against Grampositive and Gram-negative bacteria and fungi according to ISO 20743: 2007. The photocatalytic properties under visible light exposure were also tested using two organic stain models (methylene blue and orange II). The stain discoloring was evaluated by measuring the color differences between the blank and the samples with DATA Color Check Plus II portable device assisted by CIELab color management software. The evaluation of the physical-mechanical resistance and comfort properties for the sheepskin leathers was determined by measuring the water vapor permeability, rubbing tests and abrasion resistance. The results showed that the sheepskin leather surfaces treated with nanocomposite materials have improved antibacterial, self-cleaning, physical-mechanical and comfort properties as compared to untreated samples, with potential applications for added value multifunctional products. (c) 2021 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conferences & Exhibition on Nanotechnologies, Organic Electronics & Nanomedicine - NANOTEXNOLOGY 2020. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/

Open Access

557. Structural Details of BaTiO3 Nano-Powders Deduced from the Anisotropic XRD Peak Broadening

Authors: Pasuk, I; Neatu, F; Neatu, S; Florea, M; Istrate, CM; Pintilie, I; Pintilie, L

Published: MAY 2021, NANOMATERIALS, 11, 1121, DOI: 10.3390/nano11051121

In this study, nano-BaTiO3 (BTO) powders were obtained via the solvothermal method at different reaction times and were investigated using transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results were compared with those obtained for a larger crystallite size BTO powder (BTO-m). The sizes of the cuboid crystallites (as determined by XRD and TEM) ranged from about 18 to 24 nm, depending on the reaction time. The evolution with temperature of the structure parameters of nano-BTO was monitored by means of X-ray diffraction and Raman spectroscopy and no signs of phase transition were found up to 170 degrees C. Careful monitoring of the dependence of the XRD peak widths on the hkl indices showed that the effect of the cubic crystallite shape upon the XRD peak widths was buried by the effect of hidden tetragonal line splits and by anisotropic microstrain. The good correlation of the line widths with the tetragonal split amplitudes, observed especially for BTO-m above the transition temperature, indicates tetragonal deformations, as also revealed by Raman spectroscopy. The large anisotropic microstrain shown by the nano-powders, which had a maximum value in the directions, was considered evidence of the phenomenon of surface relaxation of cubic crystallites edged by {100} faces. The observed behavior of the nano-BTO structures with increasing temperature may suggest a correlation between the surface relaxation and tetragonal deformation in the nano-cubes. The experimental results for both nano-BTO and mezoscale-BTO are in agreement with the core-shell model.

558. The impact of having an oxygen-rich microporous surface in carbon electrodes for high-power aqueous supercapacitors

Authors: Hérou, S; Ribadeneyra, MC; Schlee, P; Luo, H; Tanase, LC; Rossberg, C; Titirici, M

Published: FEB 2021, JOURNAL OF ENERGY CHEMISTRY, 53, DOI: 10.1016/j.jechem.2020.04.068

The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply. Supercapacitors are high-power devices, particularly suitable for public transportation since they can easily store breaking energy due to their high-rate charging ability. Additionally, they can function with two carbon electrodes, which is an advantage due to the abundance of carbon in biomass and other waste materials (i.e., plastic waste). Newly developed supercapacitive nanocarbons display extremely narrow micropores (0.8 nm), as it increases drastically the capacitance in aqueous electrolytes. Here, we present a strategy to produce low-cost flexible microporous electrodes with extremely high power density (100 kW kg(-1)), using fourty times less activating agent than traditionnal chemically activated carbons. We also demonstrate that the affinity between the carbon and the electrolyte is of paramount importance to maintain rapid ionic diffusion in narrow micropores. Finally, this facile synthesis method shows that low-cost and bio-based free-standing electrode materials with reliable supercapacitive performances can be used in electrochemistry. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Open Access

559. Fe-N Co-Doped Titanium Dioxide Nanoparticles Induce Cell Death in Human Lung Fibroblasts in a p53-Independent Manner

Authors: Nica, IC; Stan, MS; Popescu, RG; Nicula, N; Ducu, R; Diamandescu, L; Dinischiotu, A

Published: SEP 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 9627, DOI: 10.3390/ijms22179627

The advancement of nanotechnology in the last decade has developed an abundance of novel and intriguing TiO2-based nanomaterials that are widely used in many sectors, including industry (as a food additive and colorant in cosmetics, paints, plastics, and toothpaste) and biomedicine (photoelectrochemical biosensing, implant coatings, drug delivery, and new emerging antimicrobial agents). Therefore, the increased use of engineered nanomaterials in the industry has raised serious concern about human exposure and their unexpected cytotoxic effects. Since inhalation is considered the most relevant way of absorbing nanomaterials, different cell death mechanisms induced in MRC-5 lung fibroblasts, following the exposure to functionalized TiO2 NPs, were investigated. Long-term exposure to TiO2 nanoparticles co-doped with 1% of iron and nitrogen led to the alteration of p53 protein activity and the gene expression controlled by this suppressor (NF-kB and mdm2), DNA damage, cell cycle disruptions at the G2/M and S phases, and lysosomal membrane permeabilization and the subsequent release of cathepsin B, triggering the intrinsic pathway of apoptosis in a Bax- and p53-independent manner. Our results are of major significance, contributing to the understanding of the mechanisms underlying the interaction of these nanoparticles with in vitro biological systems, and also providing useful information for the development of new photocatalytic nanoparticles that are active in the visible spectrum, but with increased biocompatibility.

Open Access

560. Soft synthesis and characterization of goethite-based nanocomposites as promising cyclooctene oxidation catalysts

Authors: Kuncser, AC; Vlaicu, ID; Pavel, OD; Zavoianu, R; Badea, M; Radu, D; Culita, DC; Rostas, AM; Olar, R

Published: AUG 24 2021, RSC ADVANCES, 11, DOI: 10.1039/d1ra04211d

Goethite based nanocomposites with a different composition such as 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite), xFeO(OH)center dot M(OH)(2)center dot yH(2)O (Co-composite (M: Co, x = 12, y = 3), Ni-composite (M: Ni, x = 7, y = 2)) and xFeO(OH)center dot MO center dot yH(2)O (Cu-composite (M: Cu, x = 5.5, y = 3), Zn-composite (M: Zn, x = 6, y = 1.5)) have been prepared by a soft chemical synthesis consisting in acetate hydrolysis. The data provided by Fourier transform infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), electron paramagnetic resonance (EPR) and Mossbauer spectra account for a slight modification of all composites' physicochemical properties compared to the starting material. Powder X-ray diffraction and transmission electron microscopy (TEM) investigations revealed the secondary phase nature and presence along with that of goethite. The TEM data are also consistent with a nano rod-like morphology with a 5-10 nm width and an average length of 40 nm. The catalytic oxidation of cyclooctene with O-2 using isobutyraldehyde as reductant and acetonitrile as a solvent was performed in batch conditions for 5 h at room temperature. The selectivity for the epoxide was higher than 99% for all tested solids. The conversion of cyclooctene decreased from 55% to 4% following the same order of variance as the base/acid sites ratio: Mn-composite > Fe-composite > Co-composite > Ni-composite > Zn-composite > Cu-composite. The 6FeO(OH)center dot MnO(OH)center dot 0.5H(2)O (Mn-composite) exhibited the most promising catalytic activity in cyclooctene oxidation, which can be correlated with the redox ability of Mn(iii) combined with the increased base character of this solid. The catalytic activity of this sample decreases by 10% after several successive reaction cycles.

Open Access

561. From useless humins by-product to Nb@graphite-like carbon catalysts highly efficient in HMF synthesis

Authors: El Fergani, M; Candu, N; Tudorache, M; Bucur, C; Djelal, N; Granger, P; Coman, SM

Published: MAY 25 2021, APPLIED CATALYSIS A-GENERAL, 618, 118130, DOI: 10.1016/j.apcata.2021.118130

Highly dispersed supported NbOx species were prepared via a deposition precipitation-carbonization (DPC)-like method. As precursors for niobium species and carrier ammonium niobate(V) oxalate hydrate and humins were used. Characterization of the resulted catalysts indicated bi-functional acid-base niobium species anchored onto a highly hydrophobic graphite-like carbon structure. These catalysts were investigated in the one-pot conversion of glucose to 5-hydroxymethylfurfural (HMF) in a biphasic system consisting of a mixture of a 20 wt% NaCl aqueous solution phase and an organic extracting phase (methyl-isobutyl-ketone (MIBK), 2-tert-butylphenol (TBP) or 2sec-butylphenol (SBP)). The optimization conditions afforded the highest yield to HMF (96 %) for the GHNb1.2 catalyst (with 2.5 wt%Nb), the base/acid sites ratio of 1.76, in biphasic TBP/water system, at 180 ?C after 8 h.

Open Access

562. Low Blue Dose Photodynamic Therapy with Porphyrin-Iron Oxide Nanoparticles Complexes: In Vitro Study on Human Melanoma Cells

Authors: Nistorescu, S; Udrea, AM; Badea, MA; Lungu, I; Boni, M; Tozar, T; Dumitrache, F; Maraloiu, VA; Popescu, RG; Fleaca, C; Andronescu, E; Dinischiotu, A; Staicu, A; Balas, M

Published: DEC 2021, PHARMACEUTICS, 13, 2130, DOI: 10.3390/pharmaceutics13122130

The purpose of this study was to investigate the effectiveness in photodynamic therapy of iron oxide nanoparticles (gamma-Fe2O3 NPs), synthesized by laser pyrolysis technique, functionalized with 5,10,15,20-(Tetra-4-sulfonatophenyl) porphyrin tetraammonium (TPPS) on human cutaneous melanoma cells, after only 1 min blue light exposure. The efficiency of porphyrin loading on the iron oxide nanocarriers was estimated by using absorption and FTIR spectroscopy. The singlet oxygen yield was determined via transient characteristics of singlet oxygen phosphorescence at 1270 nm both for porphyrin functionalized nanoparticles and rose bengal used as standard. The irradiation was performed with a LED (405 nm, 1 mW/cm(2)) for 1 min after melanoma cells were treated with TPPS functionalized iron oxide nanoparticles (gamma-Fe2O3 NPs_TPPS) and incubated for 24 h. Biological tests revealed a high anticancer effect of gamma-Fe2O3 NPs_TPPS complexes indi-cated by the inhibition of tumor cell proliferation, reduction of cell adhesion, and induction of cell death through ROS generated by TPPS under light exposure. The biological assays were combined with the pharmacokinetic prediction of the porphyrin.

Open Access

563. On the pinning force in high density MgB2 samples

Authors: Sandu, V; Ionescu, AM; Aldica, G; Grigoroscuta, MA; Burdusel, M; Badica, P

Published: MAR 15 2021, SCIENTIFIC REPORTS, 11, 5951, DOI: 10.1038/s41598-021-85209-2

An analysis of the field dependence of the pinning force in different, high density sintered samples of MgB2 is presented. The samples were chosen to be representative for pure MgB2, MgB2 with additives, and partially oriented massive samples. In some cases, the curves of pinning force versus magnetic field of the selected samples present peculiar profiles and application of the typical scaling procedures fails. Based on the percolation model, we show that most features of the field dependence of the critical force that generate dissipation comply with the Dew-Hughes scaling law predictions within the grain boundary pinning mechanism if a connecting factor related to the superconducting connection of the grains is used. The field dependence of the connecting function, which is dependent on the superconducting anisotropy, is the main factor that controls the boundary between dissipative and non-dissipative current transport in high magnetic field. Experimental data indicate that the connecting function is also dependent on the particular properties (e.g., the presence of slightly non-stoichiometric phases, defects, homogeneity, and others) of each sample and it has the form of a single or double peaked function in all investigated samples.

Open Access

564. Tetragonal-Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

Authors: Patru, RE; Khassaf, H; Pasuk, I; Botea, M; Trupina, L; Ganea, CP; Pintilie, L; Pintilie, I

Published: AUG 2021, MATERIALS, 14, 4215, DOI: 10.3390/ma14154215

The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes' interfaces.

Open Access

565. Multi-Level Evaluation of UV Action upon Vitamin D Enhanced, Silver Doped Hydroxyapatite Thin Films Deposited on Titanium Substrate

Authors: Negrila, CC; Predoi, D; Ghita, RV; Iconaru, SL; Ciobanu, SC; Manea, M; Badea, ML; Costescu, A; Trusca, R; Predoi, G; Stanciu, GA; Hristu, R; Dragu, LD; Bleotu, C; Groza, A; Marinas, IC; Chifiriuc, MC

Published: FEB 2021, COATINGS, 11, 120, DOI: 10.3390/coatings11020120

Hydroxyapatite Ca-10(PO4)(6)(OH)(2) (HAp) is an important bioactive material for bone tissue reconstruction, due to its highly thermodynamic stability at a physiological pH without bio-resorption. In the present study, the Ag:HAp and the corresponding Ag:HAp + D-3 thin films (similar to 200 nm) coating were obtained by vacuum deposition method on Ti substrate. The obtained samples were exposed to different UV irradiation times, in order to investigate the UV light action upon thin films, before considering this method for the thin film's decontamination. The effects of UV irradiation upon Ag:Hap + D-3 are presented for the first time in the literature, marking a turning point for understanding the effect of UV light on composite biomaterial thin films. The UV irradiation induced an increase in the initial stages of surface roughness of Ag:HAp thin film, correlated with the modifications of XPS and FTIR signals. The characteristics of thin films measured by AFM (RMS) analysis corroborated with XPS and FTIR investigation highlighted a process of recovery of the thin film's properties (e.g., RMS), suggesting a possible adaptation to UV irradiation. This process has been a stage to a more complicated UVA rapid degradation process. The antifungal assays demonstrated that all the investigated samples exhibited antifungal properties. Moreover, the cytotoxicity assays revealed that the HeLa cells morphology did not show any alterations after 24 h of incubation with the Ag:HAp and Ag:HAp + D-3 thin films.

Open Access

566. Hybrid Nanocomposite Thin Films for Photovoltaic Applications: A Review

Authors: Socol, M; Preda, N

Published: MAY 2021, NANOMATERIALS, 11, 1117, DOI: 10.3390/nano11051117

Continuing growth in global energy consumption and the growing concerns regarding climate change and environmental pollution are the strongest drivers of renewable energy deployment. Solar energy is the most abundant and cleanest renewable energy source available. Nowadays, photovoltaic technologies can be regarded as viable pathways to provide sustainable energy generation, the achievement attained in designing nanomaterials with tunable properties and the progress made in the production processes having a major impact in their development. Solar cells involving hybrid nanocomposite layers have, lately, received extensive research attention due to the possibility to combine the advantages derived from the properties of both components: flexibility and processability from the organic part and stability and optoelectronics features from the inorganic part. Thus, this review provides a synopsis on hybrid solar cells developed in the last decade which involve composite layers deposited by spin-coating, the most used deposition method, and matrix-assisted pulsed laser evaporation, a relatively new deposition technique. The overview is focused on the hybrid nanocomposite films that can use conducting polymers and metal phthalocyanines as p-type materials, fullerene derivatives and non-fullerene compounds as n-type materials, and semiconductor nanostructures based on metal oxide, chalcogenides, and silicon. A survey regarding the influence of various factors on the hybrid solar cell efficiency is given in order to identify new strategies for enhancing the device performance in the upcoming years.

567. Wake-up Free Ferroelectric Rhombohedral Phase in Epitaxially Strained ZrO2 Thin Films

Authors: Silva, JPB; Negrea, RF; Istrate, MC; Dutta, S; Aramberri, H; Iñiguez, J; Figueiras, FG; Ghica, C; Sekhar, KC; Kholkin, AL

Published: NOV 3 2021, ACS APPLIED MATERIALS & INTERFACES, 13, DOI: 10.1021/acsami.1c15875

Zirconia- and hafnia-based thin films have attracted tremendous attention in the past decade because of their unexpected ferroelectric behavior at the nanoscale, which enables the downscaling of ferroelectric devices. The present work reports an unprecedented ferroelectric rhombohedral phase of ZrO2 that can be achieved in thin films grown directly on (111)-Nb:SrTiO3 substrates by ion-beam sputtering. Structural and ferroelectric characterizations reveal (111)-oriented ZrO2 films under epitaxial compressive strain exhibiting switchable ferroelectric polarization of about 20.2 mu C/cm(2) with a coercive field of 1.5 MV/cm. Moreover, the time-dependent polarization reversal characteristics of Nb:SrTiO3/ZrO2/Au film capacitors exhibit typical bell-shaped curve features associated with the ferroelectric domain reversal and agree well with the nucleation limited switching (NLS) model. The polarization-electric field hysteresis loops point to an activation field comparable to the coercive field. Interestingly, the studied films show ferroelectric behavior per se, without the need to apply the wake-up cycle found in the orthorhombic phase of ZrO2. Overall, the rhombohedral ferroelectric ZrO2 films present technological advantages over the previously studied zirconia- and hafnia-based thin films and may be attractive for nanoscale ferroelectric devices.

568. Insight on spectral, thermal and biological behaviour of some Cu(II) complexes with saturated pentaazamacrocyclic ligands bearing amino acid residues

Authors: Patrascu, E; Badea, M; Korosin, NC; Korosec, RC; Ruta, LL; Farcasanu, IC; Grecu, MN; Guillaumet, G; Olar, R

Published: JAN 2021, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 143, DOI: 10.1007/s10973-020-09259-w

A novel series of Cu(II) complexes with formula M(HLn)(ClO4)(2)center dot mH(2)O [HLn: 13-membered pentaazamacrocyclic ligand resulted from condensation ofN,N '-bis(2-aminoethyl)ethane-1,2-diamine,l-tyrosine (HL1)/l-tryptophan (HL2)/l-phenylalanine (HL3) and formaldehyde] were synthesized by one-pot method. Techniques such as ESI-MS, IR, UV-Vis and EPR spectroscopy provided data characterizing the complexes as mononuclear species. The course of thermal decomposition was followed using TG/DSC-MS analysis in air atmosphere. The TG curves showed a gradual decomposition in several stages that comprise dehydration, decomposition of perchlorate ions as well as fragmentation and oxidative degradation of the organic part. The intermediates formed after first stage of water elimination are stable on 40, 15 and 80 degrees C interval for complexes (1), (2) and (3), respectively. The compounds were tested on the eukaryotic unicellular organismSaccharomyces cerevisiae, showing variable actions in terms of toxicity, cellular uptake and capacity to alleviate growth defects associated with Cu, Zn-superoxide dismutase (SOD1) depletion.

Open Access

569. Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Authors: Alfè, M; Gargiulo, V; Amati, M; Maraloiu, VA; Maddalena, P; Lettieri, S

Published: JUL 2021, CATALYSTS, 11, 795, DOI: 10.3390/catal11070795

Metal-organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O-2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O-2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

570. EPR spectroscopy and structural investigations, of Eu²⁺-doped chloroborate glass-ceramic

Authors: Secu, M; Kuncser, A; Negrila, C; Rostas, AM

Published: DEC 15 2021, CERAMICS INTERNATIONAL, 47, DOI: 10.1016/j.ceramint.2021.09.051

Europium doped (0.1% and 1%) chlomborate BaO-B2O3-BaCl2 glass and glass-ceramic with embedded BaCl2 nanocrystals have been synthesised, investigated, and compared with the corresponding nanocrystalline powder. The structural analysis of the glass evidenced ionic bonds characteristic to the glass host structure and compositional changes during the melting. X-ray diffraction and transmission electron microscopy revealed the formation of orthorhombic BaCl2 nanocrystals of about tens on nm in size and a smaller amount of BaB2O4 nanocrystals. Structural analysis of the Eu2+-doped BaCl2 nanocrystals has shown a distortion of the crystalline cell assigned to the growth process, affected by defects and ionic impurities. Photoluminescence spectra of the glass-ceramic revealed Eu3+ and Eu2+ luminescent ion species, but only Eu2+ is incorporated within the BaCl2 nanocrystalline phase. Electron paramagnetic resonance measurements in X-band sustain the presence of Eu2+ ions. The EPR parameters (g values and hyperfine constants) resulting from the Q-band EPR spectra simulations recorded on glass-ceramic are similar to those in Eu2+-doped BaCl2 and confirmed the partial incorporation of Eu2+ ions within the BaCl2:Eu2+ nanocrystals in the glass-ceramics.

571. Spectroscopic Ellipsometry of InSb in the Terahertz Region

Authors: Agulto, VC; Iwamoto, T; Toya, K; Mag-usara, VK; Dolas, S; Newman, N; Nedelcu, L; Tani, M; Nakajima, M

Published: 2021, 2021 46TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ), DOI: 10.1109/IRMMW-THz50926.2021.9567607

Herein we show the terahertz (THz) time-domain ellipsometry investigation of the InSb semiconductor. At room temperature, the carriers of InSb are thermally excited to the conduction band due to its narrow bandgap. We, nevertheless, show that THz ellipsometry can detect subtle differences between carrier densities of undoped and lightly doped InSb bulk semiconductors. The advantage of THz ellipsometry over other THz time-domain spectroscopy techniques is that it does not require reference measurements through an aperture or standard mirrors.

Open Access

572. Physicochemical Characterization and Drug Release Properties of Methyl-Substituted Silica Xerogels Made Using Sol-Gel Process

Authors: Len, A; Paladini, G; Románszki, L; Putz, AM; Almásy, L; László, K; Bálint, S; Krajnc, A; Kriechbaum, M; Kuncser, A; Kalmár, J; Dudás, Z

Published: SEP 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 9197, DOI: 10.3390/ijms22179197

In this work, a multi-analytical approach involving nitrogen porosimetry, small angle neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy was applied to organically modified silica-based xerogels obtained through the sol-gel process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane (MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5) producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences in the structure were revealed in terms of the chemical composition of the silica network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and surface characteristics. The combined use of structural characterization methods allowed us to reveal a relation between the cavity dimensions, the synthesis pH value and the grade of methyl substitution. The effect of the structural properties on the controlled Captopril release efficiency has also been tested. This knowledge facilitates tailoring the pore network for specific usage in biological/medical applications. Knowledge on structural aspects, as reported in this work, represents a key starting point for the production of high-performance silica-based hybrid materials showing enhanced efficacy compared to bare silica prepared using only TEOS.

Open Access

573. Magnetic and Magnetostrictive Properties of Ni50Mn20Ga27Cu3 Rapidly Quenched Ribbons

Authors: Sofronie, M; Tolea, M; Popescu, B; Enculescu, M; Tolea, F

Published: SEP 2021, MATERIALS, 14, 5126, DOI: 10.3390/ma14185126

The influence of the rapid solidification technique and heat treatment on the martensitic transformation, magnetic properties, thermo- and magnetic induced strain and electrical resistivity is investigated for the Cu doped NiMnGa Heusler-based ferromagnetic shape memory ribbons. The martensitic transformation temperatures are unexpectedly low (below 90 K-which can be attributed to the disordered texture as well as to the uncertainty in the elements substituted by the Cu), preceded by a premartensitic transformation (starting at around 190 K). A thermal treatment slightly increases the transformation as well as the Curie temperatures. Additionally, the thermal treatment promotes a higher magnetization value of the austenite phase and a lower one in the martensite. The shift of the martensitic transformation temperatures induced by the applied magnetic field, quantified from thermo-magnetic and thermo-magnetic induced strain measurements, is measured to have a positive value of about 1 K/T, and is then used to calculate the transformation entropy of the ribbons. The magnetostriction measurements suggest a rotational mechanism in low fields for the thermal treated samples and a saturation tendency at higher magnetic fields, except for the temperatures close to the phase transition temperatures (saturation is not reached at 5 T), where a linear volume magnetostriction cannot be ruled out. Resistivity and magnetoresistance properties have also been measured for all the samples.

Open Access

574. Preliminary Studies on Graphene-Reinforced 3D Products Obtained by the One-Stage Sacrificial Template Method for Bone Reconstruction Applications

Authors: Mocanu, AC; Miculescu, F; Stan, GE; Ciocoiu, RC; Corobea, MC; Miculescu, M; Ciocan, LT

Published: MAR 2021, JOURNAL OF FUNCTIONAL BIOMATERIALS, 12, 13, DOI: 10.3390/jfb12010013

The bone remodeling field has shifted focus towards the delineation of products with two main critical attributes: internal architectures capable to promote fast cell colonization and good mechanical performance. In this paper, Luffa-fibers and graphene nanoplatelets were proposed as porogen template and mechanical reinforcing agent, respectively, in view of framing 3D products by a one-stage polymer-free process. The ceramic matrix was prepared through a reproducible technology, developed for the conversion of marble resources into calcium phosphates (CaP) powders. After the graphene incorporation (by mechanical and ultrasonication mixing) into the CaP matrix, and Luffa-fibers addition, the samples were evaluated in both as-admixed and thermally-treated form (compact/porous products) by complementary structural, morphological, and compositional techniques. The results confirmed the benefits of the two agents' addition upon the compact products' micro-porosity and the global mechanical features, inferred by compressive strength and elastic modulus determinations. For the porous products, overall optimal results were obtained at a graphene amount of <1 wt.%. Further, no influence of graphene on fibers' ability to generate at high temperatures internal interconnected-channels-arrays was depicted. Moreover, its incorporation led to a general preservation of structural composition and stability for both the as-admixed and thermally-treated products. The developed CaP-reinforced structures sustain the premises for prospective non- and load-bearing biomedical applications.

Open Access

575. Band-Order Anomaly at the γ-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

Authors: Chikina, A; Christensen, D; Borisov, V; Husanu, MA; Chen, YZ; Wang, XQ; Schmitt, T; Radovic, M; Nagaosa, N; Mishchenko, AS; Valentí, R; Pryds, N; Strocov, VN

Published: MAR 23 2021, ACS NANO, 15, DOI: 10.1021/acsnano.0c07609

The rich functionalities of transition-metal oxides and their interfaces bear an enormous technological potential. Its realization in practical devices requires, however, a significant improvement of yet relatively low electron mobility in oxide materials. Recently, a mobility boost of about 2 orders of magnitude has been demonstrated at the spinel-perovskite gamma-Al2O3/SrTiO3 interface compared to the paradigm perovskite-perovskite LaAlO3/SrTiO3 interface. We explore the fundamental physics behind this phenomenon from direct measurements of the momentum-resolved electronic structure of this interface using resonant soft-X-ray angle-resolved photoemission. We find an anomaly in orbital ordering of the mobile electrons in gamma-Al2O3/SrTiO3 which depopulates electron states in the top SrTiO3 layer. This rearrangement of the mobile electron system pushes the electron density away from the interface, which reduces its overlap with the interfacial defects and weakens the electron-phonon interaction, both effects contributing to the mobility boost. A crystal-field analysis shows that the band order alters owing to the symmetry breaking between the spinel gamma-Al2O3 and perovskite SrTiO3. Band-order engineering, exploiting the fundamental symmetry properties, emerges as another route to boost the performance of oxide devices.

576. Structural, magnetic and magnetostrictive properties of the ternary iron-palladium-silicon ferromagnetic shape memory ribbons

Authors: Sofronie, M; Popescu, B; Enculescu, M

Published: FEB 5 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, 168, DOI: 10.1007/s00339-021-04315-0

The influence of the partial substitution of Fe by Si and thermal treatments on the structural, magnetic and magnetostrictive properties of the Fe67.5Pd30.5Si2 rapidly solidified ribbons has been investigated. A remarkable decrease in the martensite transformation temperature, with similar to 65 K lower than that of the Fe-Pd archetype alloy, is observed in the as-prepared ribbons. The thermal treatments shift the martensite transformation temperatures upward, with approximately 13 K for the higher thermal treatment. Also, these induce an improvement in the crystallinity in these ribbons with high texture and an increase in the crystallite size as a result of reducing the internal defects and stress. The thermodynamic considerations discussed in the frame of the Clapeyron-Clausius relation by using the calorimetric and thermomagnetic measurements (up to 7 T) reveal a weak influence of the magnetic fields on the martensitic transformation temperatures (similar to 0.5 K/T). The magnetostriction decrease with temperature under small magnetic fields was discussed, beside an unusual behaviour in the technically saturated domain. This behaviour is based on the coexistence of the ordinary and forced magnetostrictions, the last one increasing faster with the temperature decreasing.

577. Structural features, magnetic and ferroelectric properties of SrFe10.8In1.2O19 compound

Authors: Turchenko, V; Kostishin, VG; Trukhanov, S; Damay, F; Balasoiu, M; Bozzo, B; Fina, I; Burkhovetsky, VV; Polosan, S; Zdorovets, MV; Kozlovskiy, AL; Astapovich, KA; Trukhanov, A

Published: JUN 2021, MATERIALS RESEARCH BULLETIN, 138, 111236, DOI: 10.1016/j.materresbull.2021.111236

The effect of temperature on the features of the crystal and magnetic structures, as well as the magnetic properties of the solid solution of SrFe10.8In1.2O19 hexaferrite was investigated. The appearance of ferroelectric properties was detected at room temperature, which contradicts the generally accepted opinion on the description of the crystal structure of hexaferrites within the framework of the centrosymmetric P6(3)/mmc (No. 194) space group. The reasons of spontaneous polarization in solid solutions of hexaferrites remain controversial. No deviation from the collinear magnetic structure was found in the investigated temperature range from 1.5 to 350 K, while the thermal expansion of the unit cell was practically absent in the range from 1.5 to 50 K. The crystal structure of hexaferrites was considered in the framework of both centrosymmetric P6(3)/mmc and non-centrosymmetric P6(3)mc space groups, which allowed us to associate the emerging spontaneous polarization with unequal distortions of neighboring oxygen polyhedra.

578. Nd-doped ZnO films grown on c-cut sapphire by pulsed-electron beam deposition under oblique incidence

Authors: Nistor, M; Millon, E; Cachoncinlle, C; Ghica, C; Hebert, C; Perrière, J

Published: OCT 15 2021, APPLIED SURFACE SCIENCE, 563, 150287, DOI: 10.1016/j.apsusc.2021.150287

Nd-doped ZnO thin films were grown by pulsed-electron beam deposition (PED) on c-cut sapphire substrates under oblique angle incidence, at 10-2 mbar oxygen pressure and for a substrate temperature of 500 degrees C. The films were smooth, compact and constituted with columnar grains inclined at about 17 degrees +/- 4 degrees from the normal to the substrate surface. From X-ray diffraction and transmission electron microscopy experiments, it was found that the wurtzite phase of Nd-doped ZnO thin films is observed with the c-axis inclined around 35 degrees with respect to the normal axis of the substrate, with a three-fold azimuthal symmetry. Epitaxial relationships between Nd-doped ZnO films and sapphire substrate were determined from the asymmetric X-ray diffraction and are presented compared with those obtained for the films grown by non-oblique PED. The tilt of the ZnO c-axis has been explained by the epitaxy of the (2 2 9) ZnO plane on the (0 0 l) sapphire plane, such particular epitaxial growth having never been reported previously.

579. The origin of the dual ferroic properties in quasi-centrosymmetrical SrFe12-xInxO19 hexaferrites

Authors: Trukhanov, AV; Turchenko, VA; Kostishin, VG; Damay, F; Porcher, F; Lupu, N; Bozzo, B; Fina, I; Polosan, S; Silibin, MV; Salem, MM; Tishkevich, DI; Trukhanov, SV

Published: DEC 15 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 886, 161249, DOI: 10.1016/j.jallcom.2021.161249

The local crystal/magnetic structures of the SrFe12-xInxO19 solid solutions (x = 0.1; 0.3; 0.6 and 1.2) were investigated using neutron powder diffraction. The measurements of the electric polarization for all investigated samples were carried out as a function of the external electric field. The presence of the ferroelectric and ferromagnetic ordering (dual ferroic ordering) in the SrFe12-xInxO19 hexaferrites at 300 K was found. This appearance contradicts to the conventional opinion describing their crystal structure (centrosymmetric space group P6(3)/mmc (No. 194)). The reason for the existence of a spontaneous polarization (nonzero dipole moment) in the SrFe12-xInxO19 hexaferrites continues controversial. The crystal structure of the hexaferrites was considered both the centrosymmetric P6(3)/mmc and non-centrosymmetric P6(3)mc space groups. This fact made it possible to find a connection between the emerging dipole moment and not equal distortions of the neighbor oxygen polyhedral. The nature description of the nonzero dipole moment formation in a quasi-centrosymmetrical system of the In-substituted SrFe12-xInxO19 hexaferrites was presented based on the neutron diffraction data. (C) 2021 Elsevier B.V. All rights reserved.

580. School - University - Industry Cooperation "Cypress - National Instruments CLUB"

Authors: Ursutiu, D; Samoila, C; Kane, P; Ciurea, M; Stremtan, M; Ravariu, C

Published: 2021, INTERNET OF THINGS, INFRASTRUCTURES AND MOBILE APPLICATIONS, 1192, DOI: 10.1007/978-3-030-49932-7_92

In this paper we introduce a model of cooperation between High School-University-Industry sustained by activities and results obtained in "Cypress - National Instruments Club" started at "Transilvania" University of Brasov - Romania. This strategic collaboration between High School-University-Industry was become necessary because technology is evolving at a rate that is quickly outpacing traditional engineering teaching methods. New methods such as hands-on learning labs, industry-centric curriculum, permanent updating of facilities, and using new adaptive learning software are being adopted. "Transilvania" University is targeting education at the industries of the future rather than industries of the past and for this reason we must apply the same strategies inside the high school in order to well prepare the children's, future students and the new engineers.

581. Preparation of isocyanate-free composite coating with controlled molecular architecture: A new convergent approach to functional macromolecules

Authors: Haniffa, MAM; Chee, CY; Illias, HA; Halil, A; Munawer, K; Sandu, V; Chuah, CH

Published: FEB 2021, PROGRESS IN ORGANIC COATINGS, 151, 106039, DOI: 10.1016/j.porgcoat.2020.106039

Isocyanate-free composite coating can improve radiative cooling, energy storage and harvesting applications. This study reports the development and use of a isocyanate-free green surface coating(GSC) matrix derived from (2,2,6,6-tetramethylpiperidin-1-yl)oxy radical (TEMPO)-oxidized cellulose-(3-Aminopropyl)trimethoxysilane (APTMS)-ZnO nanoparticles-green polymer matrix that possesses upto similar to 220 degrees C thermal stability. The GSC exhibited excellent UV block and IR active capacity while achieving good coating hardness. The NMR, TGA-DTG and Pencil hardness studies revealed that this attribute by GSC was due to the formation of uniform crosslinking and reinforcement network. Using electrochemical impedance spectroscopy, the GSC had a low resistance. A high charge transfer resistance of similar to 15.826 k Omega was measured using electrochemical impedance spectroscopy for the GSC, high enough to attenuate photon radiation, making GSC material stable for application. Also, UV-weathering study was performed to investigate coating stability of the GSC. This is the first time application of TEMPO-cellulose based reinforcement of the green polymer matrix for the development of GSC through convergent approach to functional macromolecules. The study opens an opportunity of utilizing green material in energy applications, especially in windows shielding by a sufficient attenuation of photon radiations.

Open Access

582. Carbon Xerogel Nanostructures with Integrated Bi and Fe Components for Hydrogen Peroxide and Heavy Metal Detection

Authors: Fort, CI; Rusu, MM; Cotet, LC; Vulpoi, A; Florea, I; Tuseau-Nenez, S; Baia, M; Baibarac, M; Baia, L

Published: JAN 2021, MOLECULES, 26, 117, DOI: 10.3390/molecules26010117

Multifunctional Bi- and Fe-modified carbon xerogel composites (CXBiFe), with different Fe concentrations, were obtained by a resorcinol-formaldehyde sol-gel method, followed by drying in ambient conditions and pyrolysis treatment. The morphological and structural characterization performed by X-ray diffraction (XRD), Raman spectroscopy, N-2 adsorption/desorption porosimetry, scanning electron microscopy (SEM) and scanning/transmission electron microscopy (STEM) analyses, indicates the formation of carbon-based nanocomposites with integrated Bi and Fe oxide nanoparticles. At higher Fe concentrations, Bi-Fe-O interactions lead to the formation of hybrid nanostructures and off-stoichiometric Bi2Fe4O9 mullite-like structures together with an excess of iron oxide nanoparticles. To examine the effect of the Fe content on the electrochemical performance of the CXBiFe composites, the obtained powders were initially dispersed in a chitosan solution and applied on the surface of glassy carbon electrodes. Then, the multifunctional character of the CXBiFe systems is assessed by involving the obtained modified electrodes for the detection of different analytes, such as biomarkers (hydrogen peroxide) and heavy metal ions (i.e., Pb2+). The achieved results indicate a drop in the detection limit for H2O2 as Fe content increases. Even though the current results suggest that the surface modifications of the Bi phase with Fe and O impurities lower Pb2+ detection efficiencies, Pb2+ sensing well below the admitted concentrations for drinkable water is also noticed.

Open Access

583. CuWO4 with CuO and Cu(OH)2 Native Surface Layers for H2S Detection under in-Field Conditions

Authors: Somacescu, S; Stanoiu, A; Dinu, IV; Calderon-Moreno, JM; Florea, OG; Florea, M; Osiceanu, P; Simion, CE

Published: JAN 2021, MATERIALS, 14, 465, DOI: 10.3390/ma14020465

The paper presents the possibility of detecting low H2S concentrations using CuWO4. The applicative challenge was to obtain sensitivity, selectivity, short response time, and full recovery at a low operating temperature under in-field atmosphere, which means variable relative humidity (%RH). Three different chemical synthesis routes were used for obtaining the samples labeled as: CuW1, CuW2, and CuW3. The materials have been fully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). While CuWO4 is the common main phase with triclinic symmetry, different native layers of CuO and Cu(OH)(2) have been identified on top of the surfaces. The differences induced into their structural, morphological, and surface chemistry revealed different degrees of surface hydroxylation. Knowing the poisonous effect of H2S, the sensing properties evaluation allowed the CuW2 selection based on its specific surface recovery upon gas exposure. Simultaneous electrical resistance and work function measurements confirmed the weak influence of moisture over the sensing properties of CuW2, due to the pronounced Cu(OH)(2) native surface layer, as shown by XPS investigations. Moreover, the experimental results obtained at 150 degrees C highlight the linear sensor signal for CuW2 in the range of 1 to 10 ppm H2S concentrations and a pronounced selectivity towards CO, CH4, NH3, SO2, and NO2. Therefore, the applicative potential deserves to be noted. The study has been completed by a theoretical approach aiming to link the experimental findings with the CuW2 intrinsic properties.

Open Access

584. Bistability of the BiOi complex and its implications on evaluating the "acceptor removal"process in p-type silicon

Authors: Besleaga, C; Kuncser, A; Nitescu, A; Kramberger, G; Moll, M; Pintilie, I

Published: NOV 21 2021, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 1017, 165809, DOI: 10.1016/j.nima.2021.165809

The dependencies of the BiOi defect concentration on doping, irradiation fluence and particle type in p-type silicon diodes have been investigated. We evidenced that large data scattering occurs for fluences above 10(12) 1 MeV neutrons/cm(2), becoming significant larger for higher fluences. We show that the BiOi defect is metastable, with two configurations A and B, of which only A is detected by Deep Level Transient Spectroscopy and Thermally Stimulated Currents techniques. The defect' electrical activity is influenced by the inherent variations in ambient and procedural experimental conditions, resulting not only in a large scattering of the results coming from the same type of measurement but making correlation between different types of experiments difficult. It is evidenced that the variations in [BiOiA] are triggered by subjecting the samples to an excess of carriers, by either heating or an inherent short exposure to ambient light when manipulating the samples prior to experiments. For the samples investigated in this work both, the [BiOiA] as determined from electrical spectroscopic measurements and the full depletion voltage as measured from Current-Voltage characteristics reach a steady state in similar to 7h. Any electrical measurement performed before will give a different result. The bi-stable behavior of the BiOi defect fully accounts for these variations.

585. A novel composite based on pyrene thiazole grafted on graphene oxide: physico-chemical characterization and electrochemical investigations

Authors: Tudose, M; Baratoiu-Carpen, RD; Anghel, EM; Voicescu, M; Somacescu, S; Culita, DC; Hanganu, A; Kuncser, A; Radoi, A

Published: APR 1 2021, MATERIALS CHEMISTRY AND PHYSICS, 262, 124315, DOI: 10.1016/j.matchemphys.2021.124315

We report the obtaining of a new composite starting from pyrene thiazole, a compound certified by nuclear magnetic resonance and its covalent grafting on the surface of graphene oxide. Novel material was synthesized in two stages: the first involving transformation of carboxyl groups of graphene oxide into acid chlorides and the second the amide reaction between acid chloride and amine group of pyrene thiazole (PTC). Numerous characterization methods have been used to certify this material, such as: Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Their results show the successful covalent functionalization of graphene oxide with pyrene thiazole through the formation of amide bonds. The electrochemical investigation consisted of evaluating the redox behavior of the carbon screen printed electrodes modified with the new composite (GO-PTC) using caffeic acid, as analyte. From analytical point of view, it is relevant to be able to quantify the presence of caffeic acid and for such reason we used as analytical method the square wave voltammetry. The results showed that the GO-PTC modified carbon screen printed electrodes were able to detect the caffeic acid over more than one order of magnitude (linear working range: 0.005-0.1 mM) and GO-PTC modified electrodes can be considered promising for other analytical investigations.

Open Access

586. Deposition, Morphological, and Mechanical Evaluation of W and Be-Al2O3 and Er2O3 Co-Sputtered Films in Comparison with Pure Oxides

Authors: Lungu, M; Staicu, C; Baiasu, F; Marin, A; Butoi, B; Cristea, D; Pompilian, OG; Locovei, C; Porosnicu, C

Published: NOV 2021, COATINGS, 11, 1430, DOI: 10.3390/coatings11111430

Compact and defect-free high melting point oxide strengthened metallic matrix configurations are promising to resolve the hydrogen permeation and brittleness issues relevant to the fusion research community. Previous studies on oxide addition to metallic matrix demonstrated a mitigation in brittleness behavior, while deposition techniques and material configurations are still to be investigated. Thus, here, we report the structural, morphological, and mechanical characterization of metal-oxides thin layers co-deposited by radio frequency (RF)and direct current (DC) magnetron sputtering. A total of six configurations were deposited such as single thin layers of oxides (Al2O3, Er2O3) and co-deposition configurations as metal-oxides (W, Be)-(Al2O3, Er2O3). The study of films roughness by atomic force microscopy (AFM) method show that for Al2O3 metallic-oxides is increased to an extent that could favor gaseous trapping, while co-depositions with Be seem to promote an increased roughness and defects formation probability compared to Wco-depositions. Lower elastic modulus on metal-oxide co-depositions was observed, while the indentation hardness increased for Be and decreased for W matrix configurations. These outputs are highly relevant for choosing the proper compact and trap-free configuration that could be categorized as a permeation barrier for hydrogen and furtherly studied in laborious permeation yield campaigns.

Open Access

587. Fiber-Templated 3D Calcium-Phosphate Scaffolds for Biomedical Applications: The Role of the Thermal Treatment Ambient on Physico-Chemical Properties

Authors: Mocanu, AC; Miculescu, F; Stan, GE; Pandele, AM; Pop, MA; Ciocoiu, RC; Voicu, SI; Ciocan, LT

Published: MAY 2021, MATERIALS, 14, 2198, DOI: 10.3390/ma14092198

A successful bone-graft-controlled healing entails the development of novel products with tunable compositional and architectural features and mechanical performances and is, thereby, able to accommodate fast bone in-growth and remodeling. To this effect, graphene nanoplatelets and Luffa-fibers were chosen as mechanical reinforcement phase and sacrificial template, respectively, and incorporated into a hydroxyapatite and brushite matrix derived by marble conversion with the help of a reproducible technology. The bio-products, framed by a one-stage-addition polymer-free fabrication route, were thoroughly physico-chemically investigated (by XRD, FTIR spectroscopy, SEM, and nano-computed tomography analysis, as well as surface energy measurements and mechanical performance assessments) after sintering in air or nitrogen ambient. The experiments exposed that the coupling of a nitrogen ambient with the graphene admixing triggers, in both compact and porous samples, important structural (i.e., decomposition of beta-Ca-3(PO4)(2) into alpha-Ca-3(PO4)(2) and alpha-Ca2P2O7) and morphological modifications. Certain restrictions and benefits were outlined with respect to the spatial porosity and global mechanical features of the derived bone scaffolds. Specifically, in nitrogen ambient, the graphene amount should be set to a maximum 0.25 wt.% in the case of compact products, while for the porous ones, significantly augmented compressive strengths were revealed at all graphene amounts. The sintering ambient or the graphene addition did not interfere with the Luffa ability to generate 3D-channels-arrays at high temperatures. It can be concluded that both Luffa and graphene agents act as adjuvants under nitrogen ambient, and that their incorporation-ratio can be modulated to favorably fit certain foreseeable biomedical applications.

588. Martensitic Transformation and Magnetic Properties of Ni57Fe18Ga25 Shape Memory Alloy Subjected to Severe Plastic Deformation

Authors: Popescu, B; Gurau, C; Gurau, G; Tolea, M; Sofronie, M; Tolea, F

Published: OCT 2021, TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS, 74, DOI: 10.1007/s12666-021-02293-8

The effects of severe plastic deformation (SPD) process via high-speed high-pressure torsion technique on martensitic transformation of Ni-Fe-Ga Heusler shape memory alloy are the subject of this work. The results show that moderate degrees of deformation lead to a decrease in the martensitic transformation temperatures, while the heat of reaction is enhanced only for the sample processed with the lowest degree of deformation. The results are explained by the interplay between the constituent tetragonal L10 and the cubic gamma crystal structures and the evolution of the samples morphology with the severity of deformation. The reduction in the samples granulation due to the progressive increase in the SPD is reflected by the magnetic properties of the samples with decreasing coercivity and Curie temperatures. At the highest applied degree of deformation, sample nanostructuring and a possible amorphization might explain the vanishing of MT.

Open Access

589. The Effect of the In-Situ Heat Treatment on the Martensitic Transformation and Specific Properties of the Fe-Mn-Si-Cr Shape Memory Alloys Processed by HSHPT Severe Plastic Deformation

Authors: Gurau, C; Gurau, G; Tolea, F; Popescu, B; Banu, M; Bujoreanu, LG

Published: AUG 2021, MATERIALS, 14, 4621, DOI: 10.3390/ma14164621

This work focuses on the temperature evolution of the martensitic phase epsilon (hexagonal close packed) induced by the severe plastic deformation via High Speed High Pressure Torsion method in Fe57Mn27Si11Cr5 (at %) alloy. The iron rich alloy crystalline structure, magnetic and transport properties were investigated on samples subjected to room temperature High Speed High Pressure Torsion incorporating 1.86 degree of deformation and also hot-compression. Thermo-resistivity as well as thermomagnetic measurements indicate an antiferromagnetic behavior with the Neel temperature (T-N) around 244 K, directly related to the austenitic gamma-phase. The sudden increase of the resistivity on cooling below the Neel temperature can be explained by an increased phonon-electron interaction. In-situ magnetic and electric transport measurements up to 900 K are equivalent to thermal treatments and lead to the appearance of the bcc-ferrite-like type phase, to the detriment of the epsilon(hcp) martensite and the gamma (fcc) austenite phases.

Open Access

590. Preparation and Characterization of Dextran Coated Iron Oxide Nanoparticles Thin Layers

Authors: Predoi, G; Ciobanu, CS; Iconaru, SL; Predoi, D; Dreghici, DB; Groza, A; Barbuceanu, F; Cimpeanu, C; Badea, ML; Barbuceanu, SF; Furnaris, CF; Belu, C; Ghegoiu, L; Raita, MS

Published: JUL 2021, POLYMERS, 13, 2351, DOI: 10.3390/polym13142351

In the present study, we report the synthesis of a dextran coated iron oxide nanoparticles (DIO-NPs) thin layer on glass substrate by an adapted method. The surface morphology of the obtained samples was analyzed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), optical, and metallographic microscopies. In addition, the distribution of the chemical elements into the DIO-NPs thin layer was analyzed by Glow Discharge Optical Emission Spectrometry (GDOES). Furthermore, the chemical bonds formed between the dextran and iron oxide nanoparticles was investigated by Fourier Transform Infrared Spectroscopy (FTIR). Additionally, the HepG2 viability incubated with the DIO-NPs layers was evaluated at different time intervals using MTT (3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The goal of this study was to obtain a DIO-NPs thin layer which could be used as a coating for medical devices such as microfluidic channel, microchips, and catheter. The results of the surface morphology investigations conducted on DIO-NPs thin layer suggests the presence of a continuous and homogeneous layer. In addition, the GDOES results indicate the presence of C, H, Fe, and O signal intensities characteristic to the DIO-NPs layers. The presence in the IR spectra of the Fe-CO metal carbonyl vibration bonds prove that the linkage between iron oxide nanoparticles and dextran take place through carbon-oxygen bonds. The cytotoxicity assays highlighted that HepG2 cells morphology did not show any noticeable modifications after being incubated with DIO-NPs layers. In addition, the MTT assay suggested that the DIO-NPs layers did not present any toxic effects towards HEpG2 cells.

591. Effect of strain and stoichiometry on the ferroelectric and pyroelectric properties of the epitaxial Pb(Zr0.2Ti0.8)O3 films deposited on Si wafers

Authors: Chirila, C; Boni, GA; Filip, LD; Husanu, M; Neatu, S; Istrate, CM; Le Rhun, G; Vilquin, B; Trupina, L; Pasuk, I; Botea, M; Pintilie, I; Pintilie, L

Published: APR 2021, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 266, 115042, DOI: 10.1016/j.mseb.2021.115042

Properties of epitaxial PbZr0.2Ti0.8O3 (PZT) films deposited on Si substrates were investigated for integration in the present CMOS technology. Polarization is downward oriented, in association with the presence of an internal electric field, and has a lower value compared to the PZT films deposited on single crystal perovskite SrTiO3 (STO) substrates (40 mu C/cm(2) versus 80 mu C/cm(2)), while the dielectric constant is larger (180 versus 120). Large value for the pyroelectric coefficient was also found, 1.22 x 10(-3)C/m(2)K, as for PZT grown on single crystal STO. The macroscopic ferroelectric and pyroelectric properties appear to be affected by the structural quality and stoichiometry of the PZT film. The changes in the electric properties are an effect of the strain gradients induced by the large difference between the thermal expansion coefficients of PZT and Si substrate, leading in turn to Pb oxidation and antisite defect formation compared to PZT films deposited on STO substrates.

592. New photoactive mesoporous Ce-modified TiO2 for simultaneous wastewater treatment and electric power generation

Authors: Mureseanu, M; Chivu, V; Osiac, M; Ciobanu, M; Bucur, C; Parvulescu, V; Cioatera, N

Published: APR 15 2021, CATALYSIS TODAY, 366, DOI: 10.1016/j.cattod.2020.09.035

In the present paper is presented an efficient strategy for synthesis of mesoporous TiO2 modified with different Ce concentrations through a sol-gel process in the presence of triblock Pluronic P123 as structure directing agent, integrated with evaporation-induced self- assembly (EISA) approach. The nanocomposite consisted mostly of small crystallite of anatase. The presence of a new crystal phase corresponding to cerium titanate was evidenced in Ce-modified powder samples. All materials were characterized by SEM and TEM microscopies, UV-vis, XPS and N-2 adsorption-desorption isotherms in order to examine the textural and structural characteristics and the chemical nature of their surface. Furthermore, the photoelectrochemical characterization evidenced the effect of the TiO2 mesoporous structure, the amount of cerium and the oxidation state of Ti and Ce in the new photocatalysts on the enhanced photovoltaic performance. The photocatalytic activity of the as-synthesized materials was evaluated for phenol photodegradation in aqueous media and the reactive species involved in photocatalytic process were established by using some radical scavengers in the photodegradation experiments. Based on the obtained results, these new Ce-modified mesoporous TiO2 photocatalysts could be considered for degradation of organic compounds from wastewaters by advanced oxidation processes or for photoanodes construction for efficient photoelectrochemical fuel cell (PFC) systems.

Open Access

593. Rhodamine B Photodegradation in Aqueous Solutions Containing Nitrogen Doped TiO2 and Carbon Nanotubes Composites

Authors: Udrescu, A; Florica, S; Chivu, M; Mercioniu, I; Matei, E; Baibarac, M

Published: DEC 2021, MOLECULES, 26, 7237, DOI: 10.3390/molecules26237237

In this work, new results concerning the potential of mixtures based on nitrogen doped titanium dioxide (TiO2:N) and carbon nanotubes (CNTs) as possible catalyst candidates for the rhodamine B (RhB) UV photodegradation are reported. The RhB photodegradation was evaluated by UV-VIS absorption spectroscopy using samples of TiO2:N and CNTs of the type of single-walled carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNT-COOH) having various concentrations of CNTs. The best photocatalytic performance was obtained for sample containing TiO2:N and 2.5 wt.% SWNTs-COOH, when approx. 85% of dye removal was achieved after 300 min. of UV irradiation. The reaction kinetics of RhB aqueous solutions containing TiO2:N/CNT mixtures followed a complex first-order kinetic model. The TiO2:N/CNTs catalyst induced higher photodegradation efficiency of RhB than TiO2:N due to the presence of CNTs, which act as adsorbent and dispersing agent and capture the photogenerated electrons of TiO2:N hindering the electron-hole recombination.

594. Comprehensive analysis of compatible natural fibre as sacrificial porogen template for tailored ceramic 3D bioproducts destined for hard tissue reconstruction

Authors: Mocanu, AC; Miculescu, F; Miculescu, M; Ciocoiu, RC; Pandele, AM; Stan, GE; Cîmpean, A; Voicu, SI; Ciocan, LT

Published: FEB 15 2021, CERAMICS INTERNATIONAL, 47, DOI: 10.1016/j.ceramint.2020.10.113

For successful bone remodelling, the implantable 3D structures require suitable internal architectures which can be achieved by the use of fibres as natural templates. The ability of fibres to generate complex configurations for 3D bioceramic products was preliminary reported by sacrificial fibrous-porogen method. This study aims to demonstrate the safe-prospect of repurposing natural-fibres (i.e. luffa, hemp, wool) for embedment into a calcium phosphate (CaPs) matrix prepared through a completely reproducible route, and the beneficial influence of fibres upon structural, topographic and mechanical features of CaPs-products, since a complete assessment of the fibres-combustion-products resulted after thermal treatment was not yet disclosed. The complex investigation program based on i) thermo-gravimetric (TGA-DTG), ii) structural (XRD, FTIR-ATR), iii) morpho-compositional (SEM/EDS) and, most importantly, iv) biological cytotoxicity assays of fibres-derived chars, clearly indicated that luffa-fibres are the safest (>95% cell-survival) to be considered for bioceramic porous-orthopaedic-implants. Further, as exposed by nano-CT, the high temperature pyrolysis of luffa-fibres led to 3D interconnected channels inside the products, which allows a suitable vascularization and osteointegration. The topographic reconstruction of channels-inside-surface revealed a secondary 3D network of micro-pores. Along with the mechanical features, the novel bioceramic porous structures stand as reliable bone-repair alternatives.

595. Benzofurazan derivatives modified graphene oxide nanocomposite: Physico-chemical characterization and interaction with bacterial and tumoral cells

Authors: Tudose, M; Anghel, EM; Hristea, EN; Voicescu, M; Somacescu, S; Culita, DC; Musuc, AM; Dumitrascu, F; Hanganu, A; Kuncser, A; Zorila, FL; Alexandru, M; Acasandrei, MA; Savu, DI

Published: APR 2021, MATERIALS SCIENCE AND ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 123, 112028, DOI: 10.1016/j.msec.2021.112028

Two novel graphene oxide-benzofuran derivatives composites were obtained through the covalent immobilization of [4-hydrazinyl-7nitrobenz-[2,1,3-d]-oxadiazole (NBDH) and respectively, N1-(7-nitrobenzo[c][1,2,5] oxadiazol-4-yl)benzene-1,2-diamine (NBD-PD), on graphene oxide. This covalent functionalization was achieved by activating the carboxylic groups on the surface of graphene oxide by the reaction with thionyl chloride followed by coupling with the amino group of benzofurazane derivatives to obtain the NBD derivatives grafted on graphene oxide. The formation of new materials was check by Raman spectroscopy, fluorescence, infrared spectroscopy and X-ray photoelectron spectroscopy, thermal analysis, scanning electron microscopy, and elemental mapping. The antimicrobial effect of the new composites was evaluated on Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, both on planktonic and adherent biofilm populations. The cytotoxic effects of the materials on human colon cancer HCT-116 cell line and the normal human fibroblast BJ cell line were evaluated by investigating cell viability and membrane integrity. Apoptosis and colony forming ability of tumor cells were also investigated following exposure to new materials. The biological results of this study have shown that the new materials have potential in combating biofilm formation and also, the tested materials induced cytotoxicity in human colon cancer HCT-116 cell line with limited effects on normal BJ fibroblasts, suggesting their antitumor potential.

Open Access

596. Fabrication of ZnO and TiO2 Nanotubes via Flexible Electro-Spun Nanofibers for Photocatalytic Applications

Authors: Enculescu, M; Costas, A; Evanghelidis, A; Enculescu, I

Published: MAY 2021, NANOMATERIALS, 11, 1305, DOI: 10.3390/nano11051305

Web-like architectures of ZnO and TiO2 nanotubes were fabricated based on a three-step process of templating polymer nanofibers produced by electrospinning (step 1). The electrospun polymer nanofibers were covered by radio-frequency magnetron sputtering with thin layers of semiconducting materials (step 2), with FESEM observations proving uniform deposits over their entire surface. ZnO or TiO2 nanotubes were obtained by subsequent calcination (step 3). XRD measurements proved that the nanotubes were of a single crystalline phase (wurtzite for ZnO and anatase for TiO2) and that no other crystalline phases appeared. No other elements were present in the composition of the nanotubes, confirmed by EDX measurements. Reflectance spectra and Tauc plots of Kubelka-Munk functions revealed that the band gaps of the nanotubes were lower than those of the bulk materials (3.05 eV for ZnO and 3.16 eV for TiO2). Photocatalytic performances for the degradation of Rhodamine B showed a large degradation efficiency, even for small quantities of nanotubes (0.5 mg/10 mL dye solution): similar to 55% for ZnO, and similar to 95% for TiO2.

Open Access

597. Structural, functional properties and enhanced thermal stability of bulk graded (Ba,Sr) TiO3 structures obtained by spark plasma sintering (vol 12, pg 2085, 2021)

Authors: Botea, M; Pintilie, I; Surdu, VA; Stanciu, CA; Trusca, RD; Vasile, BS; Patru, R; Udrea, M; Ianculescu, AC; Pintilie, L

Published: JUL-AUG 2021, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 13, DOI: 10.1016/j.jmrt.2021.06.001

Open Access

598. Thickness-Dependent Photoelectrochemical Water Splitting Properties of Self-Assembled Nanostructured LaFeO3 Perovskite Thin Films

Authors: Andrei, F; Ion, V; Bîrjega, R; Dinescu, M; Enea, N; Pantelica, D; Mihai, MD; Maraloiu, VA; Teodorescu, VS; Marcu, IC; Scarisoreanu, ND

Published: JUN 2021, NANOMATERIALS, 11, 1371, DOI: 10.3390/nano11061371

Tuning the intrinsic structural and stoichiometric properties by different means is used for increasing the green energy production efficiency of complex oxide materials. Here, we report on the formation of self-assembled nanodomains and their effects on the photoelectrochemical (PEC) properties of LaFeO3 (LFO) epitaxial thin films as a function of layer's thickness. The variation with the film's thickness of the structural parameters such as in-plane and out-of-plane crystalline coherence length and the coexistence of different epitaxial orientation-SrTiO3// LFO, SrTiO3// LFO and [110] LFO//[10] STO, as well as the appearance of self-assembled nanodomains for film's thicknesses higher than 14 nm, is presented. LFO thin films exhibit different epitaxial orientations depending on their thickness, and the appearance of self-assembled nanopyramids-like domains after a thickness threshold value has proven to have a detrimental effect on the PEC functional properties. Using Nb:SrTiO3 as conductive substrate and 0.5 M NaOH aqueous solution for PEC measurements, the dependence of the photocurrent density and the onset potential vs. RHE on the structural and stoichiometric features exhibited by the LFO photoelectrodes are unveiled by the X-ray diffraction, high-resolution transmission electron microscopy, ellipsometry, and Rutherford backscattering spectroscopy results. The potentiodynamic PEC analysis has revealed the highest photocurrent density J(photocurrent) values (up to 1.2 mA/cm(2)) with excellent stability over time, for the thinnest LFO/Nb:SrTiO3 sample, both cathodic and anodic behavior being noticed. Noticeably, the LFO thin film shows unbiased hydrogen evolution from water, as determined by gas chromatography in aqueous 0.5 M NaOH solution under constant illumination.

599. An antibody-based amperometric biosensor for 20S proteasome activity and inhibitor screening†

Authors: Barsan, MM; Diculescu, VC

Published: MAY 21 2021, ANALYST, 146, DOI: 10.1039/d0an02426k

The 20S proteasome enzyme complex is involved in the proteolytic degradation of misfolded and oxidatively damaged proteins and is a focus of medical research for the development of compounds with pharmaceutical properties, which are active in cancer cells and/or neurodegenerative diseases. The present study aims to develop a biosensor for investigating the 20S proteasome activity and inhibition by means of electrochemical methods. The 20S proteasome is best immobilized at the electrode surface through bio-affinity interactions with antibodies that target different subunits on the 20S proteasome, enabling the investigation of the effect of an enzyme's orientation on biosensor response. The enzymatic activity is analyzed by fixed potential amperometry with the highest sensitivity of 24 mu A cm(-2) mM(-1) and a LOD of 0.4 mu M. The detection principle involves the oxidation of an electroactive probe that is released from the enzyme's substrates upon proteolysis. The most sensitive biosensor is then used to study the multicatalytic activity of the 20S proteasome, i.e. the caspase-, trypsin- and chymotrypsin-like activity, by analyzing the biosensor's sensitivity towards different substrates. The behavior of the immobilized 20S proteasome is investigated as a function of substrate concentration. The kinetic parameters are derived and compared with those obtained when the enzyme was free in solution, with K-0.5 values being one to two orders of magnitude lower in the present case. Two 20S inhibitors, epoxomicin and bortezomib, are investigated by analyzing their influence on the 20S biosensor response. The proposed analytical method for proteasome activity and inhibitor screening has the main advantage of being cost-effective compared to the ones typically employed.

600. Comparative investigation of structural, EPR, optical and photoluminescence properties of nanostructured LaPO4:Ce/RE/Me and LaPO4:Yb/Er phosphors prepared by co-precipitation method

Authors: AitMellal, O; Oufni, L; Messous, MY; Trandafir, MM; Chirica, IM; Florea, M; Neatu, S; Rostas, AM; Secu, M; Neatu, F

Published: SEP 2021, JOURNAL OF SOLID STATE CHEMISTRY, 301, 122310, DOI: 10.1016/j.jssc.2021.122310

In this work, the structural, thermal, vibrational, morphological, magnetic and optical properties of LaPO4:Ce/RE/Me (RE=Nd3+, Tb3+; Me-Cr3+, Mn2+) and LaPO4:Yb3+/Er3+ phosphors prepared by the co-precipitation method are presented. The obtained materials crystallized in monoclinic structure with the P2(1)/n space group and the particles were of nanorod shape with about 200 nm in length and the diameter approximately 19 nm. The presence of dopant ions was confirmed by both electron paramagnetic resonance (EPR) and UV-visible spectroscopies. In addition, the down-conversion (DC) and up-conversion (UC) of the LaPO4 nanophosphors via the 275 and 980 nm excitations, respectively, were considered, and a wide range of electronic transitions was observed. Based on the photoluminescence (PL) spectra, there is an efficient energy transfer (ET) process from Ce3+ donors to Nd3+ and Tb3+ acceptors, and the computed ET efficiency was 70% and 88%, respectively. The Ce3+/Cr3+ and Ce3+/Mn2+ doped LaPO4 showed weak far-red and green luminescence with much smaller ET efficiency of about 3.7 and 0.4%, respectively. LaPO4:Yb3+/Er3+ showed UC luminescence under the 980 nm laser radiation, and the resulted red and green light was attributed to the Er3+ transitions.

601. Photoluminescence study of Si1-xGex nanoparticles in various oxide matrices

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Ciurea, ML; Svavarsson, HG; Ingvarsson, S

Published: 2021, 2021 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), DOI: 10.1109/CAS52836.2021.9604131

We investigate the photoluminescence properties of structures comprising of Si1-xGex nanoparticles (NPs) within SiO2, GeO2, TiO2 and Ta2O5 oxide matrices. Of the investigated structures, it was observed that the structures with GeO2 and TiO2 matrices provide increased spectral response (at similar to 907 and 844 nm respectively) and increased PL intensity. The improved PL characteristic have been attributed to increased diffusion barrier against oxygen which otherwise would result in formation of unwanted oxide at the film-oxide interface, thereby deteriorating the optical properties.

Open Access

602. Peculiarities of the structural and optical properties of rare-earth-doped phosphate glasses for temperature sensing applications

Authors: Elisa, M; Iordache, SM; Iordache, AM; Vasiliu, IC; Grigorescu, CEA; Sava, BA; Boroica, L; Filip, AV; Dinca, MC; Bartha, C; de Acha, N; Aguado, CE

Published: MAR 15 2021, JOURNAL OF NON-CRYSTALLINE SOLIDS, 556, 120569, DOI: 10.1016/j.jnoncrysol.2020.120569

Eu, Er, Yb-Er, and Dy-doped phosphate glasses were prepared by a wet-route processing of chemical precursors followed by melt-quenching and annealing. XRD measurements highlighted the amorphous nature of the investigated glasses. UV-Vis absorption spectra revealed peaks specific to f-f electronic transitions of the doping ions whereas FTIR and Raman spectroscopy proved the vitreous network forming role of phosphorous pentoxide. Luminescence spectra in the Vis domain, at RT, showed emission bands characteristic to the ion transitions from the excited states to the ground state. The luminescence spectra collected in the 25-160 degrees C range exhibited a decrease of the emission intensity with temperature rise. In the case of Eu and Dy-doped glasses a relatively small decrease of the emission intensity with temperature is observed by comparison with Er and, respectively, Yb-Er-doped glass where a significant change of the emission intensity is noticed, which recommends the latter as promising candidate for sensing devices.

Open Access

603. NiO/Sr doped Ce0.85Pr0.10 Er0.05O2-δ mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H2

Authors: Navarrete, L; Florea, M; Osiceanu, P; Calderon-Moreno, JM; Trandafir, MM; Somacescu, S; Serra, JM

Published: AUG 2021, MICROPOROUS AND MESOPOROUS MATERIALS, 323, 111171, DOI: 10.1016/j.micromeso.2021.111171

Our study focuses on an advanced exploratory research based on the development of the new IT-SOFCs anode compositions in conjunction with surfactants as template to obtain mesoarchitectured catalysts. We designed NiO/Sr doped Ce0.85Pr0.10 Er0.05O2-o (2.5 and 5 mol.% Sr) mesoarchitectures with robust crystalline framework following a hydrothermal synthesis route. NiO was deposited by wet impregnation and calcined in air at 900.C, in order to assure a good interaction between Ni and mesoporous matrix. The obtained materials exhibit a cubic CeO2 fluorite phase with Pr2O3 and SrCeO3 as secondary phase traces and these were assessed as catalyst for the partial oxidation of CH4 over time and IT-SOFCs anode under reducing atmosphere. The electrochemical behavior as anode fed by wet H2 (2.5% vol. H2O) was investigated in the NiO/CPS/YSZ/GDC/Pt electrochemical cells. The compositional effect on the structural properties, surface chemistry, catalytic and electrochemical performance were highlighted. Sr incorporated in the lattice, proved by X-ray Photoelectron Spectroscopy, guarantees an excellent stability of the catalysts over time for 20h, during partial oxidation of CH4 with high CH4 conversion and CO selectivity (90% in the range 700-800.C) as well as a better performance as IT-SOFCs anode.

604. New superconductor/ferromagnet heterostructure formed by YBa2Cu3O7-x and CaRuO3

Authors: Ivan, I; Pasuk, I; Crisan, A; Sandu, V; Onea, M; Leca, A; Cosar, C; Burdusel, M

Published: NOV 2021, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 34, 115009, DOI: 10.1088/1361-6668/ac2622

Almost all proposed configurations and practical achievements based on superconductor/ferromagnet (S/F) heterostrucutres focus on s-wave superconductors. However, several attempts targeted also high temperature superconductors, most of them using manganite ferromagnets LaXMnO3 (X: Ca or Sr) and Y1Ba2Cu3O7-x (YBCO). Here we propose a new ferromagnetic material that can be used with YBCO for the fabrication of S/F hybrid structures. We show that a ferromagnetic order can be induced in a thin layer (similar to 130 nm thickness) of CaRuO3 grown by pulsed laser deposition on epitaxial YBCO film. Detailed magnetic and structural investigations show that the observations of the weak ferromagnetism are consistent with the magnetic order induced by in-plane tensile strain of about 1.7% and the easy-magnetization axis forms an angle of similar to 180o with the layer plane. The value of the Curie temperature T (Curie) estimated using the Curie-Weiss law was 340 K. An unusual temperature dependence of the magnetic moment around the superconducting transition was observed in both field-cooled and zero-field-cooled configurations which is attributed to the paramagnetic Meissner effect.

Open Access

605. The effects of mechanical alloying on the physical and thermal properties of CuCrFeTiV alloy

Authors: Antao, F; Dias, M; Correia, JB; Galatanu, A; Galatanu, M; Mardolcar, UV; Myakush, A; Cruz, MM; Casaca, A; da Silva, RC; Alves, E

Published: JAN 2021, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 263, 114805, DOI: 10.1016/j.mseb.2020.114805

The present work reports the production and key properties of the CuCrFeTiV high entropy alloy synthetized mechanical alloying and spark plasma sintering. The milled powders and the as-sintered samples were analysed through scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy and particle induced X-ray emission. Magnetic properties together with electrical resistivity, thermal conductivity, specific heat differential thermal analysis were also evaluated on the consolidated samples. The powders reveal an increasing content in iron as the millings are prolonged up to 20 h. The elemental composition of the sintered alloy, determined through particle induced X-ray emission, confirms the final composition after mechanical alloying with an increase of iron and a decrease in the remaining elements. Furthermore, although the alloy presents electrical resistivity typical of a high entropy alloy, a ferromagnetic behaviour was found, consistently with major Fe content as detected in prior observations. Finally, thermal measurements show that this CuCrFeTiV entropy alloy possesses thermal properties suitable for its potential use as thermal barriers.

Open Access

606. Multifunctional GaFeO3 Obtained via Mechanochemical Activation Followed by Calcination of Equimolar Nano-System Ga2O3-Fe2O3

Authors: Diamandescu, L; Tolea, F; Feder, M; Vasiliu, F; Mercioniu, I; Enculescu, M; Popescu, T; Popescu, B

Published: JAN 2021, NANOMATERIALS, 11, 57, DOI: 10.3390/nano11010057

The equimolar oxide mixture beta-Ga2O3-alpha-Fe2O3 was subjected to high-energy ball milling (HEBM) with the aim to obtain the nanoscaled GaFeO3 ortho-ferrite. X-ray diffraction, Fe-57 Mossbauer spectroscopy, and transmission electron microscopy were used to evidence the phase structure and evolution of the equimolar nano-system beta-Ga2O3-alpha-Fe2O3 under mechanochemical activation, either as-prepared or followed by subsequent calcination. The mechanical activation was performed for 2 h to 12 h in normal atmosphere. After 12 h of HEBM, only nanoscaled (similar to 20 nm) gallium-doped alpha-Fe2O3 was obtained. The GaFeO3 structure was obtained as single phase, merely after calcination at 950 degrees C for a couple of hours, of the sample being subjected to HEBM for 12 h. This temperature is 450 degrees C lower than used in the conventional solid phase reaction to obtain gallium orthoferrite. The optical and magnetic properties of representative nanoscaled samples, revealing their multifunctional character, were presented.

607. Structural and Optical Investigations of Ce³⁺/Mn²⁺-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: APR 2021, JOURNAL OF ELECTRONIC MATERIALS, 50, DOI: 10.1007/s11664-020-08678-7

Lanthanum orthophosphate (LaPO4) and La0.95-xCe0.05MnxPO4 (x = 0.00, 0.03, 0.10) phosphors were synthesized by a simple and cost-efficient co-precipitation method and the formation of LaPO4 nanorods with a monoclinic P21/n crystal structure was observed. X-ray diffraction pattern analysis indicated a slight distortion of the LaPO4 crystalline structure and an increase of the lattice strain as a consequence of the Mn2+ and Ce3+ dopants incorporation in the host matrix. Scanning electron microscopy revealed that the microstructure of all powders consists of agglomerations of nanorods, which are around 17 +/- 3 nm in diameter and length ranging from 100 nm to 300 nm. Electron paramagnetic resonance measurements have indicated the presence of Mn2+ in isolated species, but also as agglomerates. Ce3+ and Mn2+ doping of LaPO4 resulted also in a decrease of the band gap up to 4.70 eV compared to the un-doped sample. Because of an energy transfer effect from Ce3+ to Mn2+ ions, green emission of Mn2+ ions at around 550 nm was observed upon 275 nm excitation.

Open Access

608. Poly(Vinyl Chloride) Spheres Coated with Graphene Oxide Sheets: From Synthesis to Optical Properties and Their Applications as Flame-Retardant Agents

Authors: Baibarac, M; Stingescu, L; Stroe, M; Negrila, C; Matei, E; Cotet, LC; Anghel, I; Sofran, IE; Baia, L

Published: FEB 2021, POLYMERS, 13, 565, DOI: 10.3390/polym13040565

A new method to obtain poly(vinyl chloride) (PVC) spheres, which consists of an interaction between commercial PVC grains and hexyl ethyl cellulose and lauroyl peroxide at a temperature of 60 degrees C, is reported. The addition of the graphene oxide (GO) sheets dispersed in dimethylformamide to the reaction mixture leads to the generation of composites made of PVC spheres coated with GO sheets. Scanning electron microscopy studies have demonstrated that this method allows for the transformation of PVC grains with sizes between 75 and 227 mu m into spheres with sizes varying from 0.7 to 3.5 mu m when the GO concentration in the PVC/GO composite mass increases from 0.5 to 5 wt.%. Our studies of Raman scattering and FTIR spectroscopy highlight a series of changes that indicate the appearance of ClCH=CH-, CH2=CCl-, and/or -CH=CCl- units as a result of PVC partial dehydrogenation. New -COO- and C-OH bonds on the GO sheet surfaces are induced during the preparation of PVC spheres coated with GO sheets. A photoluminescence (PL) band with a maximum at 325 nm is reported to characterize the PVC spheres. A PVC PL quenching process is demonstrated to be induced by the increase in the concentration of the GO sheets in the PVC/GO composite mass. The perspectives regarding the use of this composite as a flame-retardant material are also reported.

609. Comparison between lead free BaTio3/PDMS and doped- PZT/PDMS composite on ferroelectric characteristics

Authors: Amarande, L; Stancu, V; Botea, M; Toma, V; Ciobanu, R; Pintilie, L

Published: JUL-SEP 2021, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 16, DOI:

Composites of BaTiO3 (BT) and doped-PZT (d-PZT) micro-particles randomly dispersed in a PDMS matrix were prepared by a molding process. The morpho-structural characterization, performed by SEM and XRD, showed ceramic micro-grains of cubic BT and orthorhombic d-PZT, randomly dispersed in the PDMS matrix. Polarization (P) as a function of the applied field (E) was measured for composite samples, as well as for polymer samples. Hysteresis loops typical for a dielectric material were obtained, but also atypical ones, especially for higher fraction of polymer in composite, lower fields and shorter measuring periods, as a result of the dielectric relaxation in polymer and the presence of interfacial polarization charges at the contact between polymer and ferroelectric. All these composites show very low polarizations (less than 0.2 mu C/cm(2) and 0.05 mu C/cm(2) the maximum and remnant polarization, respectively), caused by the very low dielectric constant of the polymer (less than 10), which drastically reduces, up to 100 times, the electric field effectively applied to the ferroelectric. Weak pyroelectric response was recorded on BT/PDMS, but a typical behavior of a pyroelectric detector was observed. A figure of merit of the material which exceeds 10(-4) m(2) /C was estimated.

Open Access

610. Optical Evidence for the Assembly of Sensors Based on Reduced Graphene Oxide and Polydiphenylamine for the Detection of Epidermal Growth Factor Receptor

Authors: Baibarac, M; Daescu, M; Fejer, SN

Published: FEB 2021, COATINGS, 11, 258, DOI: 10.3390/coatings11020258

Using Raman scattering and FTIR spectroscopy, new optical evidence for the assembly of sensors based on reduced graphene oxide (RGO) and polydiphenylamine (PDPA) for the electrochemical detection of the epidermal growth factor receptor (EGFR) are reported. The assembly process of the RGO sheets electrochemical functionalized with PDPA involves the chemical adsorption of 1,4-phenylene diisothiocyanate (PDITC), followed by an incubation with protein G in phosphate buffer (PB) solution and after that the interaction with EGFR antibodies solution. Taking into account the changes reported by Raman scattering and FTIR spectroscopy, a chemical mechanism of the assembling process for this sensor is proposed. The preliminary testing of the electrochemical activity of the sensors based on RGO and PDPA was reported by cyclic voltammetry.

Open Access

611. The Physico-Chemical Properties and Exploratory Real-Time Cell Analysis of Hydroxyapatite Nanopowders Substituted with Ce, Mg, Sr, and Zn (0.5-5 at.%)

Authors: Chirica, IM; Enciu, AM; Tite, T; Dudau, M; Albulescu, L; Iconaru, SL; Predoi, D; Pasuk, I; Enculescu, M; Radu, C; Mihalcea, CG; Popa, AC; Rusu, N; Nita, S; Tanase, C; Stan, GE

Published: JUL 2021, MATERIALS, 14, 3808, DOI: 10.3390/ma14143808

Cation-substituted hydroxyapatite (HA), standalone or as a composite (blended with polymers or metals), is currently regarded as a noteworthy candidate material for bone repair/regeneration either in the form of powders, porous scaffolds or coatings for endo-osseous dental and orthopaedic implants. As a response to the numerous contradictions reported in literature, this work presents, in one study, the physico-chemical properties and the cytocompatibility response of single cation-doped (Ce, Mg, Sr or Zn) HA nanopowders in a wide concentration range (0.5-5 at.%). The modification of composition, morphology, and structure was multiparametrically monitored via energy dispersive X-ray, X-ray photoelectron, Fourier-transform infrared and micro-Raman spectroscopy methods, as well as by transmission electron microscopy and X-ray diffraction. From a compositional point of view, Ce and Sr were well-incorporated in HA, while slight and pronounced deviations were observed for Mg and Zn, respectively. The change of the lattice parameters, crystallite size, and substituting cation occupation factors either in the Ca(I) or Ca(II) sites were further determined. Sr produced the most important HA structural changes. The in vitro biological performance was evaluated by the (i) determination of leached therapeutic cations (by inductively coupled plasma mass spectrometry) and (ii) assessment of cell behaviour by both conventional assays (e.g., proliferation-3-(4,5-dimethyl thiazol-2-yl) 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay; cytotoxicity-lactate dehydrogenase release assay) and, for the first time, real-time cell analysis (RTCA). Three cell lines were employed: fibroblast, osteoblast, and endothelial. When monophasic, the substituted HA supported the cells' viability and proliferation without signs of toxicity. The RTCA results indicate the excellent adherence of cells. The study strived to offer a perspective on the behaviour of Ce-, Mg-, Sr-, or Zn-substituted HAs and to deliver a well-encompassing viewpoint on their effects. This can be highly important for the future development of such bioceramics, paving the road toward the identification of candidates with highly promising therapeutic effects.

Open Access

612. Spectroscopic studies on photodegradation of atorvastatin calcium

Authors: Oprica, M; Iota, M; Daescu, M; Fejer, SN; Negrila, C; Baibarac, M

Published: JUL 28 2021, SCIENTIFIC REPORTS, 11, 15338, DOI: 10.1038/s41598-021-94693-5

In this work, the photodegradation process of atorvastatin calcium (ATC) is reported as depending on: (1) the presence and the absence of excipients in the solid state; (2) the chemical interaction of ATC with phosphate buffer (PB) having pH equal to 7 and 8; and (3) hydrolysis reaction of ATC in the presence of aqueous solution of NaOH. The novelty of this work consists in the monitoring of the ATC photodegradation by photoluminescence (PL). The exposure of ATC in solid state to UV light induces the photo-oxygenation reactions in the presence of water vapors and oxygen from air. According to the X-ray photoelectron spectroscopic studies, we demonstrate that the photo-oxygenation reaction leads to photodegradation compounds having a high share of C=O bonds compared to ATC before exposure to UV light. Both in the presence of PB and NaOH, the photodegradation process of ATC is highlighted by a significant decrease in the intensity of the PL and photoluminescence excitation (PLE) spectra. According to PLE spectra, the exposure of ATC in the presence of NaOH to UV light leads to the appearance of a new band in the spectral range 340-370 nm, this belonging to the photodegradation products. Arguments concerning the chemical compounds, that resulted in this last case, are shown by Raman scattering and FTIR spectroscopy.

Open Access

613. Biocompatibility and Antibiofilm Properties of Samarium Doped Hydroxyapatite Coatings: An In Vitro Study

Authors: Nica, IC; Popa, M; Marutescu, L; Dinischiotu, A; Iconaru, SL; Ciobanu, SC; Predoi, D

Published: OCT 2021, COATINGS, 11, 1185, DOI: 10.3390/coatings11101185

The implant-related infection as a consequence of bacterial adherence and biofilm formation remains one of the main causes of implant failure. Grace to recent advances in materials science, their great mechanical properties and their biocompatibility (both in vitro and in vivo), antibacterial coatings have gradually become a primary component of the global strategy for preventing microbial colonization. In the present work, novel antibacterial coatings containing hydroxyapatite nanoparticles doped with two different concentrations of samarium (5SmHAp and 10SmHAp) were obtained on Si substrates using the dip coating method. The morphology and physicochemical properties of these modified surfaces were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). In addition, their antimicrobial effects and biocompatibility were assessed. The results showed a continuous and homogeneous layer, uniformly deposited, with no cracks or impurities. 5SmHAp and 10SmHAp surfaces exhibited significant antibiofilm activity and good biocompatibility without inducing cytotoxic effects in human gingival fibroblasts. All these findings indicate that samarium doped hydroxyapatite coatings could be great candidates for the development of new antimicrobial strategies.

Open Access

614. Valorization of Gleditsia triacanthos Invasive Plant Cellulose Microfibers and Phenolic Compounds for Obtaining Multi-Functional Wound Dressings with Antimicrobial and Antioxidant Properties

Authors: Marinas, IC; Oprea, E; Geana, EI; Tutunaru, O; Pircalabioru, GG; Zgura, I; Chifiriuc, MC

Published: JAN 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 33, DOI: 10.3390/ijms22010033

Gleditsia triacanthos is an aggressive invasive species in Eastern Europe, producing a significant number of pods that could represent an inexhaustible resource of raw material for various applications. The aim of this study was to extract cellulose from the Gleditsia triacanthos pods, characterize it by spectrophotometric and UHPLC-DAD-ESI/MS analysis, and use it to fabricate a wound dressing that is multi-functionalized with phenolic compounds extracted from the leaves of the same species. The obtained cellulose microfibers (CM) were functionalized, lyophilized, and characterized by ATR-FTIR and SEM. The water absorption and retention capacity as well as the controlled release of phenolic compounds with antioxidant properties evaluated in temporal dynamics were also determined. The antimicrobial activity against reference and clinical multi-drug-resistant Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Enterobacter cloacae, Candida albicans, and Candida parapsilosis strains occurred immediately after the contact with the tested materials and was maintained for 24 h for all tested microbial strains. In conclusion, the multi-functionalized cellulose microfibers (MFCM) obtained from the reproductive organs of an invasive species can represent a promising alternative for the development of functional wound dressings with antioxidant and antimicrobial activity, as well as being a scalable example for designing cost-effective, circular bio-economy approaches to combat the accelerated spread of invasive species.

Open Access

615. Physico-chemical properties of two anhydrous azathioprine forms and their interaction with typical pharmaceutical excipients: highlighting new findings in drug formulation development

Authors: Barbatu, A; Lungan, MA; Toulbe, N; Smaranda, I; Daescu, M; Baibarac, M; Manta, CM

Published: OCT 3 2021, DRUG DEVELOPMENT AND INDUSTRIAL PHARMACY, 47, DOI: 10.1080/03639045.2022.2032131

The physico-chemical properties of two anhydrous AZA forms and their interaction with typical pharmaceutical excipients were assessed by applying various methods (such as PXRD, HPLC, TG/DSC, IR, Raman, PL or UV-Vis) in order to highlight new directions for drug formulation. The stability assessment of AZA anhydrous forms I and II was performed in order to determine the risk of degradation of the active ingredient by accidental exposure to nonstandard conditions in the industrial environment, under different storage, transport or processing conditions. The benefits of form II include increased resistance to chemical degradation over a wide range of pH, but further control of storage and processing conditions is necessary to avoid polymorphic transformation into form I. The solubility assessment on the AZA solid forms in different environments that simulate the conditions of the gastrointestinal tract has the advantage of a significantly increased solubility of form II compared with the commercial form I due to the modification of the crystalline structure. In the case of capsules compared to AZA form I or II as powder, an improvement in their solubility was observed, promoted by the presence of one or more excipients in the formulation mixture.

Open Access

616. Anisotropic Photoluminescence of Poly(3-hexyl thiophene) and Their Composites with Single-Walled Carbon Nanotubes Highly Separated in Metallic and Semiconducting Tubes

Authors: Baibarac, M; Arzumanyan, G; Daescu, M; Udrescu, A; Mamatkulov, K

Published: JAN 2021, MOLECULES, 26, 294, DOI: 10.3390/molecules26020294

In this work, the effect of the single-walled carbon nanotubes (SWNTs) as the mixtures of metallic and semiconducting tubes (M + S-SWNTs) as well as highly separated semiconducting (S-SWNTs) and metallic (M-SWNTs) tubes on the photoluminescence (PL) of poly(3-hexyl thiophene) (P3HT) was reported. Two methods were used to prepare such composites, that is, the chemical interaction of the two constituents and the electrochemical polymerization of the 3-hexyl thiophene onto the rough Au supports modified with carbon nanotubes (CNTs). The measurements of the anisotropic PL of these composites have highlighted a significant diminution of the angle of the binding of the P3HT films electrochemical synthetized onto Au electrodes covered with M + S-SWNTs. This change was attributed to metallic tubes, as was demonstrated using the anisotropic PL measurements carried out on the P3HT/M-SWNTs and P3HT/S-SWNTs composites. Small variations in the angle of the binding were reported in the case of the composites prepared by chemical interaction of the two constituents. The proposed mechanism to explain this behavior took into account the functionalization process of CNTs with P3HT. The experimental arguments of the functionalization process of CNTs with P3HT were shown by the UV-VIS-NIR and FTIR spectroscopy as well as surface-enhanced Raman scattering (SERS). A PL quenching process of P3HT induced both in the presence of S-SWNTs and M-SWNTs was reported, too. This process origins in the various de-excitation pathways which can be developed considering the energy levels diagram of the two constituents of each studied composite.

617. Pyrolysis and combustion of polystyrene composites based on graphene oxide functionalized with 3-(methacryloyloxy)-propyltrimethoxysilane

Authors: Anghel, I; Lisa, G; Sofran, IE; Mitroi-Symeonidis, FC; Rusu, MM; Baia, M; Baia, L; Magyari, K; Danciu, V; Cotet, LC; Stroe, M; Baibarac, M

Published: 2021, JOURNAL OF POLYMER ENGINEERING, 41, DOI: 10.1515/polyeng-2021-0071

In this study, polystyrene composites (PS-GO(f)) with variable concentration (0.5; 1; 2; 3; 4; and 5 wt%) of GO(f) were obtained through the in-situ polymerisation of the styrene in the presence of benzoyl peroxide and graphene oxide(GO) functionalized with 3-(methacryloyloxy)-propyltrimethoxysilane(gamma-MPTS). For determining the morphological and structural particularities of polymeric composites transmission electron microscopy (TEM) measurements were performed. The influence of functionalized GO on thermal and combustion properties of polystyrene (PS)-based composite materials was determined through several methods: Thermogravimetry (TGA); derived thermogravimetry (DTG); microscale combustion calorimetry analysis (MCC); and chemical kinetic studies through TGA and MCC determinations at similar heating rates.

Open Access

618. Influences of Dispersions' Shapes and Processing in Magnetic Field on Thermal Conductibility of PDMS-Fe3O4 Composites

Authors: Stancu, V; Galatanu, A; Enculescu, M; Onea, M; Popescu, B; Palade, P; Aradoaie, M; Ciobanu, R; Pintilie, L

Published: JUL 2021, MATERIALS, 14, 3696, DOI: 10.3390/ma14133696

Composites of magnetite (Fe3O4) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (alpha-FeOOH) and spherical hematite (alpha-Fe2O3), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe3O4 composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.

619. Antioxidant activity of thirty-six peppers varieties and vasorelaxant of selected varieties

Authors: Machado, FB; de Mace, IYL; Campos, HM; Moreno, EKG; Silva, MFB; de Oliveira, JR; Ramalho, RRF; Nascimento, AD; Vaz, BG; da Cunha, LC; Ghedini, PC; Diculescu, VC; Gil, ED

Published: JUN 2021, FOOD BIOSCIENCE, 41, 100989, DOI: 10.1016/j.fbio.2021.100989

Peppers are consumed all over the world, have several benefits to human health, such as antioxidant properties that can prevent diseases related to free radicals such as cardiovascular, inflammatory diseases, cancer, among others. This work aimed to evaluate the antioxidant capacity (AOC) of 36 varieties of peppers through ABTS and DPPH radical scavenging, electroanalytical assays, and to verify the vasorelaxant properties of selected samples. The greater the amount of capsaicin found in the extracts, the higher the AOC the greater the vasorelaxation. Naga had the highest scoring for antioxidant capacity, pout showed the lowest antioxidant capacity, vase pyramid intermediate level, whereas the capsaicin content followed the same trend. Extracts from all pepper varieties studied presented vasorelaxant properties in independent and dependent endothelial pathways.

620. Ecological formulation for improving resveratrol stability and release in aqueous environment

Authors: Todan, L; Voicescu, M; Culita, DC; Pandele-Cusu, J; Albu, C; Kuncser, AC

Published: MAY 2021, CHEMICAL PAPERS, 75, DOI: 10.1007/s11696-020-01409-6

Resveratrol (RES) is a naturally occurring product with numerous biological activities. Despite its potential benefits, its use is limited due to its low aqueous stability and solubility in its native form. The porous sol-gel silica materials which are able to entrap different organic molecules represent new studied release carriers. The aim of this work was to generate a solid matrix to encapsulate RES ensuring protection, increased solubility and release in solutions. A non-toxic ingredient, namely beta-cyclodextrin (beta-CD), able to form inclusion complexes (ICs) with RES has been used. Ecological formulations have been processed by entrapping the RES containing ICs in silica matrices obtained from a silica colloidal sol by the aqueous route of the sol-gel method. Characterization methods (DSC, FTIR, UV-Vis, fluorescence studies, SEM) have evidenced the presence of RES-beta-CD inclusion complex in the silica powder, RES stability in the matrix and its release in aqueous and organic solutions, and the morphology of the carrier. An evaluation of the antioxidant activity of RES in the present formulation was performed by the chemiluminescence assay and RES release profile in aqueous solutions was obtained by HPLC-MS. The resulted materials can find applications in different domains. Graphic abstract

621. In-situ magnetron sputtering co-deposition of Ge nanoparticles in Si3N4 films for near infrared detection

Authors: Stavarache, I; Palade, C; Prepelita, P; Teodorescu, VS; Ciurea, ML

Published: 2021, 2021 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), DOI: 10.1109/CAS52836.2021.9604124

Deposition of Ge nanoparticles in Si3N4 films by heating Si and quartz substrates at 500 degrees C were obtained using co-sputtering Ge, and Si3N4. Their structure and photo-electrical behaviour were investigated by transmission electron microscopy, current - voltage and spectral photo-current investigations, respectively. The spectral photoresponse were correlated with microscopy results. Depending on the measuring temperature, the current under illumination increases with about five orders of magnitude compared with the dark one. The photo-current spectra measured in photovoltaic regime and at -1 V show a single cut-off wavelength in near infrared domain at about 1362 nm.

Open Access

622. The Influence of the Structural and Morphological Properties of WO3 Thin Films Obtained by PLD on the Photoelectrochemical Water-Splitting Reaction Efficiency

Authors: Andrei, F; Andrei, A; Birjega, R; Sirjita, EN; Radu, AI; Dinescu, M; Ion, V; Maraloiu, VA; Teodorescu, VS; Scarisoreanu, ND

Published: JAN 2021, NANOMATERIALS, 11, 110, DOI: 10.3390/nano11010110

Due to its physical and chemical properties, the n-type tungsten oxide (WO3) semiconductor is a suitable photoanode for water decomposition reaction. The responses of the photoelectrochemical PEC water-splitting properties as an effect of structural and optical changes of WO3 thin films, as well as the nature of electrolyte solutions, were studied in this work. The WO3 thins films have been obtained by pulsed laser deposition (PLD) on silicon (Si(001)) covered with platinum substrates using three different laser wavelengths. As the XRD (X-ray diffraction) and XTEM (cross-section transmission electron microscopy) analysis shows, the formation of highly crystalline monocline WO3 phase is formed for the film deposited at 1064 nm wavelength and poor crystalline phases with a large ordering anisotropy, characteristic of 2D structures for the films deposited at 355 nm and 193 nm wavelengths, respectively. The photogenerated current densities J(ph) depend on the laser wavelength, in both alkaline and acidic electrolyte. The maximum values of the photocurrent density have been obtained for the sample prepared with laser emitting at 355 nm. This behavior can be correlated with the coherent crystallized atomic ordering that appear for long distances (10-15 nm) in the (001) plane of the monoclinic WO3 phase structure films obtained at 355 nm laser wavelength. All the samples show poor current density in dark conditions and they are very stable in both acidic and alkaline solutions. The highest photocurrent density value is obtained in acidic solution for the WO3 thin film prepared by 355 nm laser (29 mA/cm(2) at 1.6 V vs. RHE (1.35 V vs. Ag/AgCl)).

623. A comparative investigation of hetero-epitaxial TiC thin films deposited by magnetron sputtering using either hybrid DCMS/HiPIMS or reactive DCMS process

Authors: Zoita, NC; Dinu, M; Kiss, AE; Logofatu, C; Braic, M

Published: JAN 30 2021, APPLIED SURFACE SCIENCE, 537, 147903, DOI: 10.1016/j.apsusc.2020.147903

A hybrid direct current magnetron sputtering/high-power impulse magnetron sputtering (DCMS/HiPIMS) technique was used to improve the structural and electrical properties of single-crystal titanium carbide (TiC) thin films. The hetero-epitaxial TiC films, similar to 60 nm thick, were grown on MgO (001) substrates at temperatures ranging from 200 degrees C to 800 degrees C, by co-sputtering of Ti and C targets powered by DCMS and HiPIMS, respectively. Films' composition and the structural, morphological, and electrical properties were comparatively investigated to those of a set of samples deposited at same temperatures by reactive-DCMS (R-DCMS) in Ar/CH4 atmosphere. The composition and the FWHM of rocking curves of the films deposited by R-DCMS varied from TiC0.84 to TiC0.94 and from 1.38 degrees to 0.64 degrees, respectively, as the growth temperature increased. TiC0.94 - TiC0.96 layers were deposited by hybrid DCMS/HiPIMS method at temperatures higher than 400 degrees C, fully strained over their full thickness, with FWHM of rocking curves of about 0.13 degrees. Electrical resistivity values measured for these films were of about 155 mu Omega cm, significantly close to those corresponding to bulk TiC0.95 single crystals. The resistivity of R-DCMS films is higher by 6% to 23% in comparison with that of the DCMS/HiPIMS grown samples, depending on the growth temperature.

Open Access

624. Experimental tuning of AuAg nanoalloy plasmon resonances assisted by machine learning method

Authors: Koziol, R; Lapinski, M; Syty, P; Sadowski, W; Sienkiewicz, JE; Nurek, B; Maraloiu, VA; Koscielska, B

Published: NOV 30 2021, APPLIED SURFACE SCIENCE, 567, 150802, DOI: 10.1016/j.apsusc.2021.150802

Plasmonic nanostructures based on AuAg nanoalloys were fabricated by thermal annealing of metallic films in an argon atmosphere. The nanoalloys were chosen because they can extend the wavelength range in which plasmon resonance occurs and thus allow the design of plasmonic platforms with the desired parameters. The influence of initial fabrication parameters and experimental conditions on the formation of nanostructures was investigated. For the surface morphology studies, chemical composition analysis and nanograin structure, Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-Ray Spectroscopy (EDS) and High-Resolution Transmission Electron Microscopy (HR TEM) measurements were performed. The position of the resonance band was successfully tuned in the 100 nm range. The EDS together with the XPS analysis confirmed the formation of an alloy with the aspect ratio of individual metals in a single nanoisland similar to the ratio of the thicknesses of the initially sputtered layers. The experimental research was complemented by the neural network model, which enables the calculation of the absorbance peak depending on the thickness of Au and Ag layers and the annealing time. The proposed model of machine learning makes it possible to fine-tune the desired position of the plasmon resonance.

Open Access

625. Organic Thin Films Deposited by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) for Photovoltaic Cell Applications: A Review

Authors: Socol, M; Preda, N; Socol, G

Published: NOV 2021, COATINGS, 11, 1368, DOI: 10.3390/coatings11111368

Human society's demand for energy has increased faster in the last few decades due to the world's population growth and economy development. Solar power can be a part of a sustainable solution to this world's energy need, taking into account that the cost of the renewable energy recently dropped owed to the remarkable progress achieved in the solar panels field. Thus, this inexhaustible source of energy can produce cheap and clean energy with a beneficial impact on the climate change. The considerable potential of the organic photovoltaic (OPV) cells was recently emphasized, with efficiencies exceeding 18% being achieved for OPV devices with various architectures. The challenges regarding the improvement in the OPV performance consist of the selection of the adequate raw organic compounds and manufacturing techniques, both strongly influencing the electrical parameters of the fabricated OPV devices. At the laboratory level, the solution-based techniques are used in the preparation of the active films based on polymers, while the vacuum evaporation is usually involved in the deposition of small molecule organic compounds. The major breakthrough in the OPV field was the implementation of the bulk heterojunction concept but the deposition of mixed films from the same solvent is not always possible. Therefore, this review provides a survey on the development attained in the deposition of organic layers based on small molecules compounds, oligomers and polymers using matrix-assisted pulsed laser evaporation (MAPLE)-based deposition techniques (MAPLE, RIR-MAPLE and emulsion-based RIR-MAPLE). An overview of the influence of various experimental parameters involved in these laser deposition methods on the properties of the fabricated layers is given in order to identify, in the forthcoming years, new strategies for enhancing the OPV cells performance.

626. Memory properties of GeZrO2 based trilayer structure

Authors: Palade, C; Slav, A; Ciurea, ML

Published: 2021, 2021 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), DOI: 10.1109/CAS52836.2021.9604154

The memory properties of a trilayer structure of ZrO2/Ge-ZrO2/ZrO2/Si-p were investigated. The trilayer was prepared by magnetron sputtering deposition followed by a rapid thermal annealing process for obtaining Ge nanocrystals embedded in ZrO2 matrix. The X-ray diffraction patterns obtained on annealed structures show that both trilayer structures are cristallized, with narrow diffraction peaks. Ge as a separated phase is not evidenced in the diffractograms, instead is possible that Ge atoms enters in ZrO2 lattice structure and form a compound of ZrO3GeO8 crystallized in the tetragonal phase. In the case of ZrO2 control structure, the diffractograms show that the ZrO2 layer is crystallized in tetragonal phase. The memory properties are evidenced by C-V characteristics with counterclockwise hysteresis loop and a memory window of Delta V=1.1V for the structure annealed at 570 degrees C and Delta V=0.8 V for the structure annealed at 650 degrees C. The influence of the interface SiO2 layer on the frequency dependence of capacitance was evidenced by C-f characteristics.

Open Access

627. The Influence of UV Light on Photodegradation of Acetylsalicylic Acid

Authors: Daescu, M; Iota, M; Serbschi, C; Ion, AC; Baibarac, M

Published: APR 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 4046, DOI: 10.3390/ijms22084046

Photodegradation of the aqueous solutions of acetylsalicylic acid, in the absence (ASA) and the presence of excipients (ASE), is demonstrated by the photoluminescence (PL). A shift of the PL bands from 342 and 338 nm to 358 and 361-397 nm for ASA and ASE in solid state and as aqueous solutions was reported. By exposure of the solution of ASA 0.3 M to UV light, a decrease in the PL band intensity was highlighted. This behavior was revealed for ASA in the presence of phosphate buffer (PB) having the pH equal to 6.4, 7, and 8 or by the interaction with NaOH 0.3 M. A different behavior was reported in the case of ASE. In the presence of PB, an increase in the intensity of the PL band of ASE simultaneously with a change of the ratio between the intensities of the bands at 361-364 and 394-397 nm was highlighted. The differences between PL spectra of ASA and ASE have their origin in the presence of salicylic acid (SAL). The interaction of ASE with NaOH induces a shift of the PL band at 405-407 nm. Arguments for the reaction of ASA with NaOH are shown by Raman scattering and FTIR spectroscopy.

Open Access

628. Redox Mechanism of Azathioprine and Its Interaction with DNA

Authors: Bunea, MC; Diculescu, VC; Enculescu, M; Iovu, H; Enache, TA

Published: JUL 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 6805, DOI: 10.3390/ijms22136805

The electrochemical behavior and the interaction of the immunosuppressive drug azathioprine (AZA) with deoxyribonucleic acid (DNA) were investigated using voltammetric techniques, mass spectrometry (MS), and scanning electron microscopy (SEM). The redox mechanism of AZA on glassy carbon (GC) was investigated using cyclic and differential pulse (DP) voltammetry. It was proven that the electroactive center of AZA is the nitro group and its reduction mechanism is a diffusion-controlled process, which occurs in consecutive steps with formation of electroactive products and involves the transfer of electrons and protons. A redox mechanism was proposed and the interaction of AZA with DNA was also investigated. Morphological characterization of the DNA film on the electrode surface before and after interaction with AZA was performed using scanning electron microscopy. An electrochemical DNA biosensor was employed to study the interactions between AZA and DNA with different concentrations, incubation times, and applied potential values. It was shown that the reduction of AZA molecules bound to the DNA layer induces structural changes of the DNA double strands and oxidative damage, which were recognized through the occurrence of the 8-oxo-deoxyguanosine oxidation peak. Mass spectrometry investigation of the DNA film before and after interaction with AZA also demonstrated the formation of AZA adducts with purine bases.

Open Access

629. Optical, Structural, and Dielectric Properties of Composites Based on Thermoplastic Polymers of the Polyolefin and Polyurethane Type and BaTiO3 Nanoparticles

Authors: Baibarac, M; Nila, A; Smaranda, I; Stroe, M; Stingescu, L; Cristea, M; Cercel, RC; Lorinczi, A; Ganea, P; Mercioniu, I; Ciobanu, R; Schreiner, C; Garcia, RG; Bartha, C

Published: FEB 2021, MATERIALS, 14, 753, DOI: 10.3390/ma14040753

In this work, new films containing composite materials based on blends of thermoplastic polymers of the polyurethane (TPU) and polyolefin (TPO) type, in the absence and presence of BaTiO3 nanoparticles (NPs) with the size smaller 100 nm, were prepared. The vibrational properties of the free films depending on the weight ratio of the two thermoplastic polymers were studied. Our results demonstrate that these films are optically active, with strong, broad, and adjustable photoluminescence by varying the amount of TPU. The crystalline structure of BaTiO3 and the influence of thermoplastic polymers on the crystallization process of these inorganic NPs were determined by X-ray diffraction (XRD) studies. The vibrational changes induced in the thermoplastic polymer's matrix of the BaTiO3 NPs were showcased by Raman scattering and FTIR spectroscopy. The incorporation of BaTiO3 NPs in the matrix of thermoplastic elastomers revealed the shift dependence of the photoluminescence (PL) band depending on the BaTiO3 NP concentration, which was capable of covering a wide visible spectral range. The dependencies of the dielectric relaxation phenomena with the weight of BaTiO3 NPs in thermoplastic polymers blends were also demonstrated.

Open Access

630. Optical Properties of Composites Based on Poly(o-phenylenediamine), Poly(vinylenefluoride) and Double-Wall Carbon Nanotubes

Authors: Baibarac, M; Daescu, M; Matei, E; Nastac, D; Cramariuc, O

Published: AUG 2021, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 22, 8260, DOI: 10.3390/ijms22158260

In this work, synthesis and optical properties of a new composite based on poly(o-phenylenediamine) (POPD) fiber like structures, poly(vinylidene fluoride) (PVDF) spheres and double-walled carbon nanotubes (DWNTs) are reported. As increasing the PVDF weight in the mixture of the chemical polymerization reaction of o-phenylenediamine, the presence of the PVDF spheres onto the POPD fibers surface is highlighted by scanning electron microscopy (SEM). The down-shift of the Raman line from 1421 cm(-1) to 1415 cm(-1) proves the covalent functionalization of DWNTs with the POPD-PVDF blends. The changes in the absorbance of the IR bands peaked around 840, 881, 1240 and 1402 cm(-1) indicate hindrance steric effects induced of DWNTs to the POPD fiber like structures and the PVDF spheres, as a consequence of the functionalization process of carbon nanotubes with macromolecular compounds. The presence of the PVDF spheres onto the POPD fiber like structures surface induces a POPD photoluminescence (PL) quenching process. An additional PL quenching process of the POPD-PVDF blends is reported to be induced in the presence of DWNTs. The studies of anisotropic PL highlight a change of the angle of the binding of the PVDF spheres onto the POPD fiber like structures surface from 50.2 degrees to 38 degrees when the carbon nanotubes concentration increases in the POPD-PVDF/DWNTs composites mass up to 2 wt.%.

631. Secondary phases and their influence on optical and electrical properties of electrodeposited Cu2FeSnS4 films

Authors: El Khouja, O; Galca, AC; Zaki, MY; Talbi, A; Ahmoum, H; Nouneh, K; Touhami, ME; Taibi, M; Matei, E; Enculescu, M; Pintilie, L

Published: NOV 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, 887, DOI: 10.1007/s00339-021-05038-y

Cu-Fe-Sn-S have been electrodeposited on indium tin oxide coated glass (ITO/glass) substrates, varying only the deposition time, followed by sulfurization in argon atmosphere at a temperature of 500 degrees C. X-ray diffraction patterns confirmed the formation of polycrystalline CFTS and other secondary phases. The Raman spectroscopy results confirm the formation of stannite phase, by the existence of the most intense peak at 330 cm(-1) corresponding to A-symmetry vibrational mode, while the SnS2 surface phase reduces upon increasing deposition time. The inferred bandgaps by specular transmission are in 1.4-1.7 eV range, influenced by the detected orthorhombic Cu4SnS4 and rhodostannite secondary phases. The electrical measurements confirm the p-type nature of the films, while density of free carriers is relatively high (similar to 10(19) cm(-3)), leading to extremely low resistivity in the Omega cm range.

Open Access

632. Silicon Metalens Fabrication from Electron Beam to UV-Nanoimprint Lithography

Authors: Baracu, AM; Avram, MA; Breazu, C; Bunea, MC; Socol, M; Stanculescu, A; Matei, E; Thrane, PCV; Dirdal, CA; Dinescu, A; Rasoga, O

Published: SEP 2021, NANOMATERIALS, 11, 2329, DOI: 10.3390/nano11092329

This study presents the design and manufacture of metasurface lenses optimized for focusing light with 1.55 mu m wavelength. The lenses are fabricated on silicon substrates using electron beam lithography, ultraviolet-nanoimprint lithography and cryogenic deep reactive-ion etching techniques. The designed metasurface makes use of the geometrical phase principle and consists of rectangular pillars with target dimensions of height h = 1200 nm, width w = 230 nm, length l = 354 nm and periodicity p = 835 nm. The simulated efficiency of the lens is 60%, while the master lenses obtained by using electron beam lithography are found to have an efficiency of 45%. The lenses subsequently fabricated via nanoimprint are characterized by an efficiency of 6%; the low efficiency is mainly attributed to the rounding of the rectangular nanostructures during the pattern transfer processes from the resist to silicon due to the presence of a thicker residual layer.

633. Magneto-optical properties of borophosphate glasses co-doped with Tb³⁺ and Dy³⁺ions

Authors: Dinca, MC; Sava, BA; Galca, AC; Kuncser, V; Iacob, N; Stan, GE; Boroica, L; Filip, AV; Elisa, M

Published: SEP 15 2021, JOURNAL OF NON-CRYSTALLINE SOLIDS, 568, 120967, DOI: 10.1016/j.jnoncrysol.2021.120967

Glasses from lithium-aluminum-zinc-boron-phosphorous oxide system co-doped with terbium (Tb3+) and dysprosium (Dy3+) oxides were studied for magneto-optical applications in lasers. The Fourier Transform Infrared and Raman Spectroscopy complementary analysis suggested the depolymerization of the borophosphate glass network by adding and increasing the rare-earth (RE) oxide content. Main UV-vis absorption maxima of Tb and Dy ions were identified at 348 and 1266 nm. Spectroscopic ellipsometry indicated a maximum refractive index of 1.56, at 400 nm, for the highest RE content. The Verdet constant amplified by increasing the RE content, reaching for the 9 mol% RE co-doped sample a value of -0.075 min/Oe/cm at 630 nm. The Faraday rotation angle was additionally confirmed by using a Faraday Cell Device, being also related to the specific paramagnetic behavior evidenced by Superconducting Quantum Interference Device magnetometry. The magneto-optical properties recommend such vitreous co-doped materials for magneto-optical devices.

634. Structural, electrical properties and photoluminescence analyses of the terbium doped barium titanate

Authors: Cernea, M; Secu, M; Radu, R; Ganea, P; Surdu, VA; Trusca, R; Vasile, ET; Secu, EC

Published: OCT 15 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 878, 160380, DOI: 10.1016/j.jallcom.2021.160380

Multifunctional materials integrating optical and electric properties into a composite or into a doped single-phase material have attracted much attention from scientists for future optoelectronic devices. In this work, polycrystalline Ba1-xTbxTiO3, x = 0.00, 0.01 and 0.05 materials were synthesized by hydrothermal route and their photoluminescence and dielectric properties were studied. The as-prepared powders showed a microstructure consisting of grains with the shape of cube; and average particle size ranging from 75 nm to 150 nm. The investigated temperature dependence of dielectric permittivity of Ba1-xTbxTiO3 ceramics revealed a decrease of the Curie temperature (Tc) with increasing terbium content, and a more pronounced degree of diffuseness of phase transition. The resistivity at room temperature was discussed in terms of positive temperature coefficient of resistance (PTRC) effect. UV-vis reflectance spectra of Ba1-xTbxTiO3 samples showed a decrease of the band gap energy with the increase of Tb amount, due to the band-gap narrowing effect. The photoluminescence spectra recorded for Tb doped BaTiO3 materials, at 80 K, evidenced the typical f-f luminescence lines of the Tb3+ accompanied the broad luminescence band at about 425 nm due to self-trapped exciton recombination. These results demonstrated that the terbium enhances the dielectric properties and photoluminescence simultaneously, being suitable for electronic applications. (C) 2021 Elsevier B.V. All rights reserved.

Open Access

635. Applications of MAX phases and MXenes as catalysts

Authors: Chirica, IM; Mirea, AG; Neatu, S; Florea, M; Barsoum, MW; Neatu, F

Published: SEP 21 2021, JOURNAL OF MATERIALS CHEMISTRY A, 9, DOI: 10.1039/d1ta04097a

MAX phases and MXenes are important materials that have recently gained great popularity due to their special properties, which render them particularly useful in many applications, including catalytic ones. This can be seen in the large number of publications that appear annually on these materials and their applications. This review aims to evaluate MAX phases and MXenes as materials for heterogeneous, non-electrocatalytic, catalytic applications. The review begins with a brief introduction to the MAX phase and MXene properties that recommend them as potential materials for heterogeneous catalytic applications, followed by four sections grouped according to the processes in which they have already proven effective. These include supports to activate the C-H or C-O bonds in applications such as dehydrogenation of light or aromatic alkanes, methanol formation from CH4, dry reforming, and CO oxidation or the water gas shift reaction (Section 2), and their use in fine chemical reactions (Section 3) and in chemical degradation (Section 4). The last section deals with photocatalytic applications (Section 5). The review ends by highlighting the huge potential of these materials for a wide range of heterogeneous catalytic applications as well as the challenges ahead.

Open Access

636. THERMAL BEHAVIOR OF Cu-DOPED TiO2 GELS SYNTHESIZED BY THE SOL-GEL METHOD

Authors: Pandele-Cusu, J; Atkinson, I; Rusu, A; Apostol, N; Teodorescu, V; Predoana, L; Szilágyi, IM; Pokol, G; Zaharescu, M

Published: MAR 2021, REVUE ROUMAINE DE CHIMIE, 66, DOI: 10.33224/rrch.2021.66.3.01

The thermal behavior of Cu-doped TiO2 gels obtained by the sol-gel method was investigated by thermogravimetric and differential thermal analysis (TG/DTG/DTA) and differential scanning calorimetry (DSC) measurements. The comparative investigation of the structure and morphology of the as-prepared gels and of the nanopowders obtained by annealing them was realized by transmission electron microscopy (TEM), Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Significant differences were noticed depending on the amount of dopant (0.5 or 2.0 mol % CuO). A higher dopant concentration resulted in a more complex decomposition of the sample. This behavior was associated with the formation of various molecular species in the sol-gel solutions before gelation, determined by the different amount of the dopant used.

637. Insight on Ni(II) and Cu(II) complexes of biguanide derivatives developed as effective antimicrobial and antitumour agents

Authors: Badea, M; Grecu, MN; Chifiriuc, MC; Bleotu, C; Popa, M; Iorgulescu, EE; Avram, S; Uivarosi, V; Munteanu, AC; Ghica, D; Olar, R

Published: APR 2021, APPLIED ORGANOMETALLIC CHEMISTRY, 35, e6155, DOI: 10.1002/aoc.6155

Six compounds of the types [M(dmbg)(2)]center dot nH(2)O ((1) M: Ni, n = 0; (4) M: Cu, n = 1; Hdmbg: N,N '-dimethylbiguanide) and, respectively, [ML]center dot nH(2)O (where (2) M: Ni, L: L-1, n = 0; (3) M: Ni, L: L-2, n = 0; (5) M: Cu, L: L-1, n = 0 and (6) M: Cu, L: L-2, n = 3, H2L1: ligand resulted from the condensation of (1) with ammonia and formaldehyde and H2L2: ligand resulted from the condensation of (4) with hydrazine and formaldehyde) were characterized as mononuclear species through information provided by NMR, electronic paramagnetic resonance (EPR) and UV-Vis spectroscopy as well as cyclic voltammetry. All data are consistent with macrocyclic formation by condensation. The complexes adopt a distorted square planar geometry resulting from the chelating behaviour of the corresponding ligands. The EPR spectra recorded after the addition of Cu(II) complexes into the corresponding Ni(II) complexes show a well resolved hyperfine structure with the superhyperfine pattern corresponding to four nitrogen atom donors. The cathodically shift of E-pc2 for both series can be correlated with the increased stability of the M(I) species through macrocyclic ligands. Geometry optimization studies for complexes (2), (3), (5) and (6) have further confirmed the experimental data. The pharmacokinetic computational results indicate that the complexes exhibit medium to low intestinal absorption and slow blood-brain barrier permeability but low toxicity. Their predictive pharmacodynamic profiles show that the compounds present the ability to inhibit protease activity. By corroborating the results of the in silico analysis with the experimental ones, the most promising complexes for antimicrobial applications are (1) and (2) and, respectively, (4) and (6) for the development of novel antitumour strategies.

Open Access

638. Biological Activity of Triazolopyrimidine Copper(II) Complexes Modulated by an Auxiliary N-N-Chelating Heterocycle Ligands

Authors: Ruta, LL; Farcasanu, IC; Bacalum, M; Raileanu, M; Rostas, AM; Daniliuc, C; Chifiriuc, MC; Marutescu, L; Popa, M; Badea, M; Iorgulescu, EE; Olar, R

Published: NOV 2021, MOLECULES, 26, 6772, DOI: 10.3390/molecules26226772

Novel complexes of type [Cu(N-N)(dmtp)(2)(OH2)](ClO4)(2)& BULL;dmtp ((1) N-N: 2,2 & PRIME;-bipyridine; (2) L: 1,10-phenantroline and dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine) were designed in order to obtain biologically active compounds. Complexes were characterized as mononuclear species that crystallized in the space group P-1 of the triclinic system with a square pyramidal geometry around the copper (II). In addition to the antiproliferative effect on murine melanoma B16 cells, complex (1) exhibited low toxicity on normal BJ cells and did not affect membrane integrity. Complex (2) proved to be a more potent antimicrobial in comparison with (1), but both compounds were more active in comparison with dmtp-both against planktonic cells and biofilms. A stronger antimicrobial and antibiofilm effect was noticed against the Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). Both electron paramagnetic resonance (EPR) and Saccharomyces cerevisiae studies indicated that the complexes were scavengers rather than reactive oxygen species promoters. Their DNA intercalating capacity was evidenced by modifications in both absorption and fluorescence spectra. Furthermore, both complexes exhibited nuclease-like activity, which increased in the presence of hydrogen peroxide.

639. STUDIES ABOUT STRUCTURAL AND THERMAL INVESTIGATIONS ON Ti50Ni30Cu20 ALLOYS OBTAINED BY DIFFERENT TECHNOLOGICAL PROCESSES

Authors: Cirstea, CD; Lucaci, M; Valeanu, M; Sofronie, M; Bujoreanu, LG; Lungu, MV; Tsakiris, V; Cucos, A; Talpeanu, D; Enescu, E

Published: 2021, ROMANIAN JOURNAL OF PHYSICS, 66, 601, DOI:

The paper presents the research results in the field of TiNiCu shape memory alloys processed by powder metallurgy techniques. The powders mixtures used to synthesize Ti50Ni30Cu20 alloys were obtained by blended constitutive elemental powders or by mechanical alloying of powder mixtures for 10 and 20 hours, respectively. Finally, a subsequent annealing process was carried out, followed by a rapid cooling in ice water. All experiments were performed under 99.9% argon atmosphere. At room temperature, the obtained materials contained monoclinic and orthorhombic martensite type. The structural and thermal investigation of these materials were discussed in view of the potential development of actuators.

640. Kaolin clay pottery discovered in the Roman city of Romula (Olt County, Romania)

Authors: Badica, P; Alexandru-Dinu, A; Grigoroscuta, M; Locovei, C; Kuncser, A; Bartha, C; Aldica, G; Negru, M; Batalu, D; Cruceru, N; Savulescu, I

Published: APR 2021, JOURNAL OF ARCHAEOLOGICAL SCIENCE-REPORTS, 36, 102899, DOI: 10.1016/j.jasrep.2021.102899

Pottery vessels made of kaolin clay from the Roman Period (2nd, 3rd centuries CE) found in Romula (Re?ca village, Olt County, Romania) from Dacia Inferior (Malvensis) were investigated by petrographic, X-ray diffraction, X-ray fluorescence, thermal analysis, electron microscopy, and mechanical tests. Our results are compared with available data on kaolin clays and pottery vessels from other sites located along the lower course of Danube river and near the Black Sea, namely in Moesia Superior, Moesia Inferior, and Thracia. Archeological and geographical contexts are addressed. Results of our analysis suggest a local production of ceramics in Romula, by using raw materials from the north of Lower Danube, in opposition to the idea that kaolin ware was imported from the provinces south of the Danube.

Open Access

641. Antibacterial composite coatings of MgB2 powders embedded in PVP matrix

Authors: Badica, P; Batalu, ND; Burdusel, M; Grigoroscuta, MA; Aldica, G; Enculescu, M; Pircalabioru, GG; Popa, M; Marutescu, LG; Dumitriu, BG; Olariu, L; Bicu, A; Purcareanu, B; Operti, L; Bonino, V; Agostino, A; Truccato, M; Chifiriuc, MC

Published: MAY 5 2021, SCIENTIFIC REPORTS, 11, 9591, DOI: 10.1038/s41598-021-88885-2

Three commercial powders of MgB2 were tested in vitro by MTS and LDH cytotoxicity tests on the HS27 dermal cell line. Depending on powders, the toxicity concentrations were established in the range of 8.3-33.2 mu g/ml. The powder with the lowest toxicity limit was embedded into polyvinylpyrrolidone (PVP), a biocompatible and biodegradable polymer, for two different concentrations. The self-replenishing MgB2-PVP composite materials were coated on substrate materials (plastic foil of the reservoir and silicon tubes) composing a commercial urinary catheter. The influence of the PVP-reference and MgB2-PVP novel coatings on the bacterial growth of Staphylococcus aureus ATCC 25923, Enterococcus faecium DMS 13590, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, in planktonic and biofilm state was assessed in vitro at 6, 24, and 48 h of incubation time. The MgB2-PVP coatings are efficient both against planktonic microbes and microbial biofilms. Results open promising applications for the use of MgB2 in the design of anti-infective strategies for different biomedical devices and systems.

642. Improving the University - Industry Environment by Adopting the Remote Experiment as a Pedagogical Method

Authors: Samoila, C; Ursutiu, D; Ciurea, M; Müller, R

Published: 2021, EDUCATING ENGINEERS FOR FUTURE INDUSTRIAL REVOLUTIONS, ICL2020, VOL 2, VOL. 1329, 1329, DOI: 10.1007/978-3-030-68201-9_61

Context: The work shows the alignment of virtual environment to the needs of the industrial revolution of level 4. Purpose or Goal: The work insists on the qualities that remote experiment offers for the global engineer creation and on the skills for hiring and rapid adaptation to the industry needs. Approach: In the university environment the remote experiment plays a decisive role in facilitating e-learning development for specialties that cannot exist without an experimental-applying part. Remote experiment must to satisfy both the needs of evolution in education and those from the industry (i.e. globalization, digitalization, socio-economic world). It is noted the emergence of new skills namely: "Cognitive flexibility" and "Emotional intelligence". After us, the most important trend, derived from the application of remote experiment and its use is "acceptance of failure". Until recently, the failure was penalized with bad marks. Acceptance is defined as a succession of failures by whose gradual removal, the amount of accumulated knowledge increases. It was concluded that failure is an important part of the road to innovation and creativity. Actual or Anticipated Outcomes: Technology progresses exponentially and the society linear. Over time, it can create a gap between technology and society. It was found from practice that the remote experiment is much more connected to the needs of industry than classical laboratories. Conclusions/Recommendations: Remote experiments can create skills and competencies faster than those achieved through classical learning systems for immediate necessity in industry.

643. Phase and structural characterization of phosphate-tellurite crystalline materials

Authors: Elisa, M; Vasiliu, IC; Sava, BA; Boroica, L; Filip, AV; Dinca, MC; Bartha, C

Published: MAY-JUN 2021, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 23, DOI:

Phosphate-tellurite crystalline materials containing titanium and aluminum oxide as well as a tellurite crystalline material containing lithium, barium and aluminum oxide were synthesized and investigated by X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. XRD analysis shows peaks specific to the crystalline phases Al(PO3)(3) and TiP2O7. FTIR analysis revealed absorption bands specific to the bending and stretching vibration modes of the phosphate and tellurite crystalline networks.

Open Access

644. Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties

Authors: Badica, P; Batalu, ND; Chifiriuc, MC; Burdusel, M; Grigoroscuta, MA; Aldica, GV; Pasuk, I; Kuncser, A; Popa, M; Agostino, A; Operti, L; Padhi, SK; Bonino, V; Truccato, M

Published: OCT 2021, MOLECULES, 26, 6045, DOI: 10.3390/molecules26196045

Pristine high-density bulk disks of MgB2 with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB2 powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible.

645. Influence of Ce addition and Pt loading upon the catalytic properties of modified mesoporous PtTi-SBA-15 in total oxidation reactions

Authors: Ciobanu, M; Petcu, G; Anghel, EM; Papa, F; Apostol, NG; Culita, DC; Atkinson, I; Todorova, S; Shopska, M; Naydenov, A; Velinova, R; Parvulescu, V

Published: JUN 5 2021, APPLIED CATALYSIS A-GENERAL, 619, 118123, DOI: 10.1016/j.apcata.2021.118123

A series of PtCeTi-SBA-15 catalysts, with different concentrations of Pt (0.25 %, 0.5 %, 1.0 %), were synthesized. New Ti-SBA-15 material was obtained by direct synthesis and used as support in successive immobilization of Pt and Ce precursors, changing their order of addition. The characterization of the catalysts has been achieved taking an ensemble of techniques which showed preservation of the support porous structure, high dispersion of the amorphous metal oxides and Pt?, the formation of metal crystals for samples with 1wt% Pt and variation of Pt? content on surface in condition of ceria addition. The best conversion (100 %) was obtained in oxidation of hydrocarbons (CH4, C3H8 and C6H14) for the samples with 1% Pt and a significant diminish of activity was obtained for catalyst in which Ce was added on PtTi-SBA-15 sample. Differently of these, CO oxidation was totally irrespective of the catalyst composition.

646. Enhancing stability of hybrid perovskite solar cells by imidazolium incorporation

Authors: Tomulescu, AG; Leonat, LN; Neatu, F; Stancu, V; Toma, V; Derbali, S; Neatu, S; Rostas, AM; Besleaga, C; Patru, R; Pintilie, I; Florea, M

Published: AUG 1 2021, SOLAR ENERGY MATERIALS AND SOLAR CELLS, 227, 111096, DOI: 10.1016/j.solmat.2021.111096

Hybrid perovskites based solar cells have demonstrated high conversion efficiency but poor long-term stability. This study reports on the results obtained after doping the CH3NH3PbI2.6Cl0.4 mixed halide perovskite with imidazolium (C3N2H5+, denoted IM) on the "A site" position of a perovskite, to improve photovoltaic performances and stability of hybrid perovskite solar cells. The perovskite films were investigated exhaustively by different characterization techniques: X-ray diffraction, Atomic Force Microscopy, Scanning Electron Microscopy, UV-Vis, X-ray Photoelectron Electron Paramagnetic Resonance spectroscopies, Impedance Spectroscopy and Incident Photon-to-Electron Conversion Efficiency. The photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The amount of IM inserted in the perovskite play a key role on the film properties. The calculated new tolerance factors according to the "globularity factor" are experimentally proved and thus at doping concentrations greater than 20% for CH3NH3PbI2.6Cl0.4 perovskite the 3D structure is no longer obtained. However, below this value, the IM substituted perovskite film possesses an improved film quality and crystallinity as compared to the pristine film. Substituting MA+ with IM+ provides a favorable way to reduce recombination processes and shows great potential to achieve high stability, and an improved charge generation, resulting in increased PCE values. We find that the optimal percentage of imidazolium incorporation to achieve better stability of solar cells is 6%.

647. CO adsorption, reduction and oxidation on Pb(Zr,Ti)O3(001) surfaces associated with negatively charged gold nanoparticles

Authors: Apostol, NG; Husanu, MA; Lizzit, D; Hristea, IA; Chirila, CF; Trupina, L; Teodorescu, CM

Published: APR 15 2021, CATALYSIS TODAY, 366, DOI: 10.1016/j.cattod.2020.02.042

Gold is deposited on atomically clean, inwards polarized, ferroelectric lead zirco-titanate deposited by pulsed laser deposition on strontium titanate (001) single crystal, then carbon monoxide adsorption and desorption experiments are investigated by in situ fast photoelectron spectroscopy using synchrotron radiation. Atomic force microscopy and high resolution photoelectron spectroscopy are consistent with the formation of 50?100 nm nanoparticles, and their Au 4f core levels point to a negative charge state of gold. As compared with a similar experiment performed on ferroelectric lead zirco-titanate with similar polarization state and without gold, the saturation coverage after exposure to carbon monoxide increases by about 68 %, and also most of the additional carbon is found in oxidized state. Desorption experiments with in situ follow-up by photoelectron spectroscopy are performed as function of temperature, and the neutral carbon intensity decreases when the ferroelectric polarization decreases, while the components corresponding to oxidized carbon remain unchanged. It looks that neutral carbon adsorption is strictly related to the polarization of the ferroelectric film, while carbon still found in molecular form is related to its carbonyl bonding on metal nanoparticles, independent of the polarization state of the substrate. Desorbed carbon at higher temperature uptakes oxygen from the substrate.

Open Access

648. Conductance zeros in complex molecules and lattices from the interference set method

Authors: Nita, M; Tolea, M; Marinescu, DC

Published: MAR 23 2021, PHYSICAL REVIEW B, 103, 125307, DOI: 10.1103/PhysRevB.103.125307

Destructive quantum interference (DQI) and its effects on electron transport are studied in chemical molecules and finite physical lattices that can be described by a discrete Hamiltonian. Starting from a bipartite system whose conductance zeros are known to exist between any two points of a specially designated set, the interference set, we use the Dyson equation to develop a general algorithm for determining the zero conductance points in complex systems, which are not necessarily bipartite. We illustrate this procedure as it applies to the fulvene molecule. The stability of the conductance zeros is analyzed with respect to external perturbations.

649. Argon pressure dependent optoelectronic characteristics of amorphous tin oxide thin films obtained by non-reactive RF sputtering process

Authors: Ziani, N; Galca, AC; Belkaid, MS; Stavarache, I

Published: MAY 2021, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 32, DOI: 10.1007/s10854-021-05861-2

In this work, amorphous tin oxide thin films were deposited by non-reactive radio frequency magnetron sputtering. A ceramic SnO2 target was used, while different working pressures were employed. The target to substrate distance was fixed to 17 cm, and the substrate was not intentionally heated. The properties of SnO2 (thickness, refractive index dispersion, optical band gap, resistivity, free carriers concentration, carriers mobility, carriers majority type and their scattering time) have been inferred from spectroscopic ellipsometry, conventional UV-Vis spectroscopy and specific Hall electrical measurements. Thickness and refractive index are slightly dependent on the deposition conditions, while the optical band gap, free carriers concentration and their mobilities are changing from sample to sample. The evolution of the optical band gap and carriers concentration is correlated to the active defects concentration. Amorphous SnO2 films grown at 0.4 Pa have the lowest resistivity of 0.86 Omega cm, a carrier concentration of 1.05x10(18)cm(-3) Vs. The average optical transmittance in visible spectrum is 76%.

Open Access

650. Thermal and Emission Properties of a Series of Lanthanides Complexes with N-Biphenyl-Alkylated-4-Pyridone Ligands: Crystal Structure of a Terbium Complex with N-Benzyl-4-Pyridone

Authors: Chiriac, FL; Ilis, M; Madalan, A; Manaila-Maximean, D; Secu, M; Cîrcu, V

Published: APR 2021, MOLECULES, 26, 2017, DOI: 10.3390/molecules26072017

This work focuses on the investigation of the liquid crystalline behavior and luminescence properties of the lanthanide complexes of Eu(III), Sm(III) and Tb(III) with N-biphenyl-alkylated-4-pyridone ligands. The organic ligands having a biphenyl group attached via a long flexible spacer with either 9 or 10 carbon atoms were synthesized by the reaction between 4-hydroxypyridine and the corresponding bromide compounds. The chemical structures of the organic and lanthanide complexes were assigned based on elemental analysis, single-crystal X-ray diffraction, H-1, C-13 NMR and IR spectroscopies, and thermogravimetric analysis (TGA). The X-ray diffraction analysis of a parent compound shows that the lanthanide ions are surrounded by three monodentate pyridone ligands and three bidentate nitrate ions, giving a 9-coordinate environment. The mesogenic behavior and the type of liquid crystalline phases exhibited by the new complexes were analyzed by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), and powder X-ray diffraction (XRD) studies. Only the lanthanide complexes with longer spacer (10) display a monotropic SmA phase, typically on a short thermal range (less than 10 degrees C). The complexes with shorter flexible chains (9) show no liquid crystalline properties with melting temperatures lower than their analogs with longer spacers. The emission spectra recorded in solid state at room temperatures show typical emission bands for each lanthanide ion employed (Eu(III), Tb(III) and Sm(III)).

651. Partially-oriented MgB2 superconducting bulks with addition of B4C and cubic BN obtained by slip casting under high magnetic field and spark plasma sintering

Authors: Grigoroscuta, MA; Aldica, G; Pasuk, I; Burdusel, M; Sandu, V; Kuncser, A; Suzuki, TS; Vasylkiv, O; Badica, P

Published: FEB 2021, MATERIALS RESEARCH BULLETIN, 134, 111103, DOI: 10.1016/j.materresbull.2020.111103

Partially-oriented MgB2 bulk discs (13 and 9 %) with the starting compositions of (MgB2)(0.99)(B4C)(0.01) and (MgB2)(0.99)(c-BN)om were fabricated by slip casting under an H-0 = 12 T magnetic field (perpendicular to the disc surface) and subsequent spark plasma sintering. The maximum critical current density and irreversibility field are for H//H-0 (H=applied field). These values are higher or similar to the randomly-oriented samples with the same composition. The maximum volume pinning force (F-p) is lower in the partially-oriented ones than in the randomly-oriented samples. The pinning-force-related parameters depend on the additive and orientation. Assessment of the major pinning mechanism within the scaling and percolation models considering these parameters shows significant limitations. A method to scale F-p is proposed; for the randomly and partially-oriented samples (that show an extra peak in F-p), the single and double Gaussian functions fit well. The results suggest an anisotropic influence of carbon substituting for boron in the MgB2.

Open Access

652. Synthesis and Characterization of Cu2ZnSnS4 Thin Films Obtained by Combined Magnetron Sputtering and Pulsed Laser Deposition

Authors: Zaki, MY; Sava, F; Buruiana, AT; Simandan, ID; Becherescu, N; Galca, AC; Mihai, C; Velea, A

Published: SEP 2021, NANOMATERIALS, 11, 2403, DOI: 10.3390/nano11092403

Cu2ZnSnS4 (CZTS) is a complex quaternary material, and obtaining a single-phase CZTS with no secondary phases is known to be challenging and dependent on the production technique. This work involves the synthesis and characterization of CZTS absorber layers for solar cells. Thin films were deposited on Si and glass substrates by a combined magnetron sputtering (MS) and pulsed laser deposition (PLD) hybrid system, followed by annealing without and with sulfur powder at 500 degrees C under argon (Ar) flow. Three different Cu2S, SnS2, and ZnS targets were used each time, employing a different target for PLD and the two others for MS. The effect of the different target arrangements and the role of annealing and/or sulfurization treatment were investigated. The characterization of the absorber films was performed by grazing incidence X-ray diffraction (GIXRD), X-ray reflectometry (XRR), Raman spectroscopy, scanning electron microscopy, and regular transmission spectroscopy. The film with ZnS deposited by PLD and SnS2 and Cu2S by MS was found to be the best for obtaining a single CZTS phase, with uniform surface morphology, a nearly stoichiometric composition, and an optimal band gap of 1.40 eV. These results show that a new method that combines the advantages of both MS and PLD techniques was successfully used to obtain single-phase Cu2ZnSnS4 films for solar cell applications.

Open Access

653. Arylenevinylene Oligomer-Based Heterostructures on Flexible AZO Electrodes

Authors: Stanculescu, A; Socol, M; Rasoga, O; Breazu, C; Preda, N; Stanculescu, F; Socol, G; Vacareanu, L; Girtan, M; Doroshkevich, AS

Published: DEC 2021, MATERIALS, 14, 7688, DOI: 10.3390/ma14247688

We investigated the optical and electrical properties of flexible single and bi-layer organic heterostructures prepared by vacuum evaporation with a p-type layer of arylenevinylene oligomers, based on carbazole, 3,3 ' bis(N hexylcarbazole)vinylbenzene = L13, or triphenylamine, 1,4 bis [4 (N,N' diphenylamino)phenylvinyl] benzene = L78, and an n-type layer of 5,10,15,20-tetra(4-pyrydil)21H,23H-porphyne = TPyP. Transparent conductor films of Al-doped ZnO (AZO) with high transparency, >90% for wavelengths > 400 nm, and low resistivity, between 6.9 x 10(-4) ohm center dot cm and 23 x 10(-4) ohm center dot cm, were deposited by pulsed laser deposition on flexible substrates of polyethylene terephthalate (PET). The properties of the heterostructures based on oligomers and zinc phthalocyanine (ZnPc) were compared, emphasizing the effect of the surface morphology. The measurements revealed a good absorption in the visible range of the PET/AZO/arylenevinylene oligomer/TPyP heterostructures and a typical injection contact behavior with linear (ZnPc, L78) or non-linear (L13) J-V characteristics in the dark, at voltages < 0.4 V. The heterostructure PET/AZO/L78/TPyP/Al showed a current density of similar to 1 mA/cm(2) at a voltage of 0.3 V. The correlation between the roughness exponent, evaluated from the height-height correlation function, grain shape, and electrical behavior was analyzed. Consequently, the oligomer based on triphenylamine could be a promising replacement of donor ZnPc in flexible electronic applications.

Open Access

654. Fabrication and Physico-Chemical Properties of Antifungal Samarium Doped Hydroxyapatite Thin Films

Authors: Ciobanu, CS; Predoi, D; Chapon, P; Predoi, MV; Iconaru, SL

Published: DEC 2021, COATINGS, 11, 1466, DOI: 10.3390/coatings11121466

Samarium doped hydroxyapatite (Ca10-xSmx(PO4)(6)(OH)(2), x(Sm) = 0.5, 50SmHAp) is a very promising candidate to be used for different coatings in various dental and orthopedic implants. We report, for the first time, the obtaining of 50SmHAp thin films by a cost-effective method, namely spin coating. Thin films of 50SmHAp on silicon substrate have been analyzed by various techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), Metallographic microscopy and Glow Discharge Optical Emission Spectroscopy (GDOES). The stability of 50SmHAp suspension was evaluated by ultrasound measurements. Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were also used to evaluate the 50SmHAp suspension. The antifungal activity of 50SmHAp suspension and coatings was assessed using Candida albicans ATCC 10231 fungal strain (C. albicans). The results of the antifungal assays depicted that both 50SmHAp suspensions and coatings were effective in inhibiting the development of C. albicans fungal cells, thus making them ideal candidates for the development of novel antifungal agents. The obtained results give new perspective for possible applications of 50SmHAp thin films in various medical applications due to their antifungal properties.

655. Pulsed Laser Deposition Films Based on CdSe-Doped Zinc Aluminophosphate Glass

Authors: Elisa, M; Iordache, SM; Iordache, AM; Rusu, MI; Socol, G; Filipescu, M; Bartha, C; Enculescu, M

Published: FEB 2021, JOM, 73, DOI: 10.1007/s11837-020-04150-3

A composite material with applications in optoelectronics has been investigated. Pulsed laser deposition CdSe-doped glass film was prepared by the combinatorial deposition from two targets, namely pure CdSe and glass belonging to the 20Li(2)O-10Al(2)O(3)-7BaO-2La(2)O(3)-2ZnO-59P(2)O(5)system. Exciton peaks in the Vis domain, related to electron-hole pairs transitions from the valence band to the conduction band, were revealed in the optical absorption spectra of the CdSe-doped film. CdSe quantum dots (QDs) band gap energy depends on the CdSe quantum confinement effect. CdSe-doped film photoluminescence exhibits peaks in the red domain assigned to CdSe transitions from the excited state to the ground state. The size of CdSe nanoclusters, determined from x-ray diffraction is correlated with scanning electron microscopy-energy dispersive x-ray spectroscopy and atomic force microscopy results. Vibration modes specific both to CdSe QDs and to the vitreous network have been evidenced by Fourier transform infrared and Raman spectroscopy.

Open Access

656. Impact of Iridium Oxide Electrodes on the Ferroelectric Phase of Thin Hf0.5Zr0.5O2 Films

Authors: Mittmann, T; Szyjka, T; Alex, H; Istrate, MC; Lomenzo, PD; Baumgarten, L; Müller, M; Jones, JL; Pintilie, L; Mikolajick, T; Schroeder, U

Published: MAY 2021, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 15, 2100012, DOI: 10.1002/pssr.202100012

Thin film metal-ferroelectric-metal capacitors with an equal mixture of hafnium oxide and zirconium oxide as the ferroelectric material are fabricated using iridium oxide as the electrode material. The influence of the oxygen concentration in the electrodes during crystallization anneal on the ferroelectric properties is characterized by electrical, chemical, and structural methods. Forming gas, O-2, and N-2 annealing atmospheres significantly change the ferroelectric performance. The use of oxygen-deficient electrodes improves the stabilization of the ferroelectric orthorhombic phase and reduces the wake-up effect. It is found that oxygen-rich electrodes supply oxygen during anneal and reduce the amount of oxygen vacancies, but the nonferroelectric monoclinic phase is stabilized with a negative impact on the ferroelectric properties.

657. Structural, morphological and optical properties of Cu-Fe-Sn-S thin films prepared by electrodeposition at fixed applied potential

Authors: El Khouja, O; Galca, AC; Nouneh, K; Zaki, MY; Touhami, ME; Taibi, M; Matei, E; Negrila, CC; Enculescu, M; Pintilie, L

Published: MAR 1 2021, THIN SOLID FILMS, 721, 138547, DOI: 10.1016/j.tsf.2021.138547

Cu-Fe-Sn-S films were obtained on indium tin oxide / glass substrates by a low-cost electrodeposition using an aqueous solution of CuSO4, FeSO4, SnSO4, and Na2S2O3 at room temperature followed by high-temperature sulfurization (500 degrees C) in argon flow. A range of cathodic potentials have been used for electrodeposition, those being chosen after a preliminary cyclic voltammetry study. The coatings were characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray Photoelectron Spectroscopy and conventional spectroscopy (diffuse reflectance and specular transmission). The results are discussed with respect to the used applied potential.

658. Lanthanide doped TiO2: Coexistence of discrete and continuous dopant distribution in anatase phase

Authors: Avram, D; Patrascu, AA; Istrate, MC; Cojocaru, B; Tiseanu, C

Published: JAN 15 2021, JOURNAL OF ALLOYS AND COMPOUNDS, 851, 156849, DOI: 10.1016/j.jallcom.2020.156849

Despite extensive studies on lanthanide (Ln) doped TiO2 nanoparticles, there is still considerable uncertainty as to whether Ln reside in the bulk (either as substitutional or interstitial dopant) or on the surface. Herein, new Ln (Eu, Sm, Nd and Er) discrete substitutional centers are identified in the anatase phase using low temperature, site selective time-gated luminescence spectroscopy. The excitation wavelength spanned UV (TiO2 host absorption) to visible excitation range into Ln f-f absorption transitions. The Ln multisite distribution is described in terms of fingerprint emission/excitation spectra and emission decays. The emission of Ln centers cover the visible (Eu, Sm) to near-infrared range (Nd, Er) and display narrow emission with full width at half maximum (FWHM) as small as 0.2 nm. The role of TiO2 host in sensitization of Ln emission is emphasized for each center. We have also found that besides discrete distribution, Ln distribute continuously on closely related anatase lattice sites. In this case, the Ln emission is significantly broader, with FWHM around 20 nm and change continuously in spectral shape and intensity with the excitation wavelength. The challenges encountered while identifying the Ln centers in TiO2 and comparison with case of CeO2 and SnO2 are also discussed. (C) 2020 Elsevier B.V. All rights reserved.

Open Access

659. Biocompatible Silver Nanoparticles: Study of the Chemical and Molecular Structure, and the Ability to Interact with Cadmium and Arsenic in Water and Biological Properties

Authors: Bertelà, F; Marsotto, M; Meneghini, C; Burratti, L; Maraloiu, VA; Iucci, G; Venditti, I; Prosposito, P; D'Ezio, V; Persichini, T; Battocchio, C

Published: OCT 2021, NANOMATERIALS, 11, 2540, DOI: 10.3390/nano11102540

In the field of research for designing and preparing innovative nanostructured systems, these systems are able to reveal the presence of heavy metals in water samples, and can efficiently and selectively interact with them, allowing for future applications in the field of water remediation. We investigated the electronic and molecular structure, as well as the morphology, of silver nanoparticles stabilized by mixed biocompatible ligands (the amino acid L-cysteine and the organic molecule citrate) in the presence of cadmium and arsenic ions. The molecular, electronic, and local structure at the ligands/silver nanoparticles interface was probed by the complementary synchrotron radiation-induced techniques (SR-XPS, NEXAFS and XAS). The optical absorption (in the UV-Vis range) of the nanosystem was investigated in the presence of Cd(II) and As(III) and the observed behavior suggested a selective interaction with cadmium. In addition, the toxicological profile of the innovative nanosystem was assessed in vitro using a human epithelial cell line HEK293T. We analyzed the viability of the cells treated with silver nanoparticles, as well as the activation of antioxidant response.

Open Access

660. Physico-Chemical Properties and In Vitro Antifungal Evaluation of Samarium Doped Hydroxyapatite Coatings

Authors: Ciobanu, SC; Iconaru, SL; Predoi, D; Prodan, AM; Predoi, MV

Published: SEP 2020, COATINGS, 10, 827, DOI: 10.3390/coatings10090827

Hydroxyapatite (HAp) and samarium doped hydroxyapatite, Ca10-xSmx(PO4)(6)(OH)(2),x(Sm)= 0.05, (5SmHAp), coatings were prepared by sol-gel process using the dip coating method. The stability of 5SmHAp suspension was evaluated by ultrasound measurements. Fourier transform infrared spectroscopy (FTIR) was used to examine the optical characteristics of HAp and 5SmHAp nanoparticles in suspension and coatings. The FTIR analysis revealed the presence of the functional groups specific to the structure of hydroxyapatite in the 5SmHAp suspensions and coatings. The morphology of 5SmHAp nanoparticles in suspension was evaluated by transmission electron microscopy (TEM). Moreover, scanning electron microscope (SEM) was used to evaluate the morphology of nanoparticle in suspension and the morphology of the surface on the coating. The SEM and TEM studies on 5SmHAp nanoparticles in suspension showed that our samples consist of nanometric particles with elongated morphology. The SEM micrographs of HAp and 5SmHAp coatings pointed out that the coatings are continuous and homogeneous. The surface morphology of the 5SmHAp coatings was also assessed by Atomic Force Microscopy (AFM) studies. The AFM results emphasized that the coatings presented the morphology of a uniformly deposited layer with no cracks and fissures. The crystal structure of 5SmHAp coating was characterized by X-ray diffraction (XRD). The surface composition of 5SmHAp coating was analyzed by X-ray photoelectron spectroscopy (XPS). The XRD and XPS analysis shown that the Sm(3+)ions have been incorporated into the 5SmHAp synthesized material. The antifungal properties of the 5SmHAp suspensions and coatings were studied usingCandida albicansATCC 10231 (C. albicans) fungal strains. The quantitative results of the antifungal assay showed that colony forming unity development was inhibited from the early phase of adherence in the case of both suspensions and coatings. Furthermore, the adhesion, cell proliferation and biofilm formation of theC. albicanswere also investigated by AFM, SEM and Confocal Laser Scanning Microscopy (CLSM) techniques. The results highlighted that theC. albicansadhesion and cell development was inhibited by the 5SmHAp coatings. Moreover, the data also revealed that the 5SmHAp coatings were effective in stopping the biofilm formation on their surface. The toxicity of the 5SmHap was also investigated in vitro using HeLa cell line.

Open Access

661. Image potential states of germanene

Authors: Borca, B; Castenmiller, C; Tsvetanova, M; Sotthewes, K; Rudenko, AN; Zandvliet, HJW

Published: JUL 2020, 2D MATERIALS, 7, 035021, DOI: 10.1088/2053-1583/ab96cf

We have measured the two-dimensional image potential states (IPS) of a germanene layer synthesized on a Ge2Pt crystal using scanning tunnelling microscopy and spectroscopy. The IPS spectrum of germanene exhibits several differences as compared to the IPS spectrum of pristine Ge(001). First, then = 1peak of the Rydberg series of the IPS spectrum of germanene has two contributions, labelledn = 1(-)andn = 1(+), respectively. The peak at the lower energy side is weaker and is associated to the mirror-symmetric state with opposite parity. The appearance of this peak indicates that the interaction between the germanene layer and the substrate is very weak. Second, the work function of germanene is about 0.75 eV lower in energy than the work function of Ge(001). This large difference in work function of germanene and pristine Ge(001) is in agreement with first-principles calculations.

Open Access

662. Fabrication of Silver- and Zinc-Doped Hydroxyapatite Coatings for Enhancing Antimicrobial Effect

Authors: Predoi, D; Iconaru, SL; Predoi, MV

Published: SEP 2020, COATINGS, 10, 905, DOI: 10.3390/coatings10090905

This study develops, for the first time, composite coatings based on silver and zinc doped hydroxyapatite in chitosan matrix (AgZnHApCs). The AgZnHApCs composite coatings were prepared by dip coating method. The hydroxyapatite (HAp), biocompatible material for regenerating and strengthening damaged bones were doped with silver and zinc ions and coated with chitosan in order to produce a uniform and homogenous coating with biocompatibility and antimicrobial properties. The stability of AgZnHApCs suspensions was evaluated by ultrasound measurements. The value of stability parameters of AgZnHApCs suspension is in good agreement with the value of bidistilled water used as reference fluid. Homogeneously dispersed solutions of AgZnHApCs were synthesized to endeavor to optimize the physico-chemical and biological characteristics of the coatings obtained at room temperature. The AgZnHApCs composite suspension and coatings were analyzed using various investigation techniques, such as X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenylte-2H-tetrazolium bromide) assay and antimicrobial studies. The optical spectroscopy, atomic force microscopy (AFM), metallographic examination and X-ray photoelectron spectroscopy (XPS) on AgZnHApCs composite coatings were also conducted. Cell culture and MTT assays demonstrate that AgZnHApCs composite suspension and coatings have no negative effect on the cell viability and proliferation. The cell morphology was not affected in presence of AgZnHApCs composite suspension and coatings. The antimicrobial assays conducted againstStaphylococcus aureusATCC 25923,Escherichia coliATCC 25922, andCandida albicansATCC 90029 microbial strains revealed that both the AgZnHApCs composite suspension and coatings exhibited great antimicrobial properties.

Open Access

663. SnSe2-Zn-Porphyrin Nanocomposite Thin Films for Threshold Methane Concentration Detection at Room Temperature

Authors: Lorinczi, A; Fagadar-Cosma, E; Socol, G; Mihailescu, A; Matei, E; Sava, F; Stefan, M

Published: DEC 2020, CHEMOSENSORS, 8, 134, DOI: 10.3390/chemosensors8040134

Nanocomposite thin films, sensitive to methane at the room temperature (25-30 degrees C), have been prepared, starting from SnSe2 powder and Zn(II)-5,10,15,20-tetrakis-(4-aminophenyl)- -porphyrin (ZnTAPP) powder, that were fully characterized by XRD, UV-VIS, FT-IR, Nuclear Magnetic Resonance (H-1-NMR and C-13-NMR), Atomic Force Microscopy (AFM), SEM and Electron Paramagnetic Resonance (EPR) techniques. Film deposition was made by drop casting from a suitable solvent for the two starting materials, after mixing them in an ultrasonic bath. The thickness of these films were estimated from SEM images, and found to be around 1.3 mu m. These thin films proved to be sensitive to a threshold methane (CH4) concentration as low as 1000 ppm, at a room temperature of about 25 degrees C, without the need for heating the sensing element. The nanocomposite material has a prompt and reproducible response to methane in the case of air, with 50% relative humidity (RH) as well. A comparison of the methane sensing performances of our new nanocomposite film with that of other recently reported methane sensitive materials is provided. It is suitable for signaling gas presence before reaching the critical lower explosion limit concentration of methane at 50,000 ppm.

664. GeSn/SiO2 Multilayers by Magnetron Sputtering Deposition for Short-Wave Infrared Photonics

Authors: Slav, A; Dascalescu, I; Lepadatu, AM; Palade, C; Zoita, NC; Stroescu, H; Iftimie, S; Lazanu, S; Gartner, M; Buca, D; Teodorescu, VS; Ciurea, ML; Braic, M; Stoica, T

Published: DEC 16 2020, ACS APPLIED MATERIALS & INTERFACES, 12, DOI: 10.1021/acsami.0c15887

The development of short-wave infrared (SWIR) photonics based on GeSn alloys is of high technological interest for many application fields, such as the Internet of things or pollution monitoring. The manufacture of crystalline GeSn is a major challenge, mainly because of the low miscibility of Ge and Sn. The use of embedded GeSn nanocrystals (NCs) by magnetron sputtering is a cost-effective and efficient method to relax the growth conditions. We report on the use of GeSn/SiO2 multilayer deposition as a way to control the NC size and their insulation. The in situ prenucleation of NCs during deposition was followed by ex situ rapid thermal annealing. The nanocrystallization of 20X(11nm_Ge0.865S0.135/1.5nm_SiO2) multilayers leads to formation of GeSn NCs with similar to 16% Sn concentration and similar to 9 nm size. Formation of GeSn domes that are vertically correlated contributes to the nanocrystallization process. The absorption limit of similar to 0.4 eV in SWIR found by ellipsometry is in agreement with the spectral photosensitivity. The ITO/20x(GeSn NC/SiO2)/p-Si/Al diodes show a maximum value of the SWIR photosensitivity at a reverse voltage of 0.5 V, with extended sensitivity to wavelengths longer than 2200 nm. The multilayer diodes have higher photocurrent efficiency compared to diodes based on a thick monolayer of GeSn NCs.

665. DEPOSITION AND CHARACTERIZATION OF THIN FILMS BASED ON NANOSTRUCTURED WO3 AS SENSORIAL ELEMENTS FOR DETECTION O F H2S

Authors: Sobetkii, A; Olaru, MT; Cindemir, U; Österlund, L; Stanoiu, A; Simion, CE; Bejan, SE; Irimescu, RE

Published: 2020, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 50, DOI:

Thin nanostructured films are the state-of-the-art materials for detection of very low limits of toxic gases. The work presents a comparison between the properties of WO3 thin films obtained by two different deposition techniques: Advanced Gas Deposition (AGD) and DC Reactive Sputtering. Films have been characterized by XRD, SEM and XPS. WO3-based sensors have selective sensitivity in H2S detection at operating temperature of 200 degrees C and relative humidity specific to field applications. The potential interferences with CO2, SO2 and NH3 are negligible, highlighting the application potential of WO3.

Open Access

666. Enhanced critical current density at high magnetic fields in MgB2 with Ga/In acetylacetonate processed by spark plasma sintering

Authors: Batalu, D; Aldica, G; Burdusel, M; Grigoroscuta, M; Pasuk, I; Kuncser, A; Ionescu, AM; Badica, P

Published: MAY-JUN 2020, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 9, DOI: 10.1016/j.jmrt.2020.01.109

Dense samples (94-96%) with starting composition (MgB2)(0.99)(X-acac)(0.01) (X-acac denotes Ga or In acetylacetonate) were obtained by spark plasma sintering. The resulting material is a superconducting composite, where carbon substitutes for boron in the crystal structure of MgB2. Added samples show enhanced critical current density at high magnetic fields and this is reflected in high values of irreversibility field (H-irr) at temperatures below 25 K when compared to a pristine sample. More efficient is In-acac addition and it promotes a H-irr of similar to 12.4T (100 A/cm(2) criterion) at 5 K. Carbon substitution for boron in the crystal structure of MgB2 has a strong influence on the pinning force and its related parameters and promotes in the added samples a grain boundary pinning mechanism as the dominant one, whereas the pristine sample with a low amount of carbon shows a major mechanism of point pinning type. However, our analysis indicates on the synergetic effects of the carbon substituting for boron and of the microstructural details on pinning and critical current density. The result strongly emphasizes the significantly different behavior of the additive during processing of the MgB2 samples, although thermal analysis experiments on both additives show very similar decomposition patterns. (C) 2020 The Authors. Published by Elsevier B.V.

667. Hybrid organic-inorganic thin films based on zinc phthalocyanine and zinc oxide deposited by MAPLE

Authors: Socol, M; Preda, N; Costas, A; Breazu, C; Stanculescu, A; Rasoga, O; Popescu-Pelin, G; Mihailescu, A; Socol, G

Published: FEB 15 2020, APPLIED SURFACE SCIENCE, 503, 144317, DOI: 10.1016/j.apsusc.2019.144317

Hybrid organic-inorganic thin films based on zinc phthalocyanine (ZnPc) and ZnO nanoparticles were deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE). Synthesized by a simple wet chemical precipitation method, the ZnO nanoparticles were featured by a hexagonal wurtzite structure, a band-gap value of similar to 3.3 eV and emission bands typical for this semiconductor. The hybrid films containing ZnPc and various amounts of ZnO nanoparticles were evaluated from morphological, compositional, structural, optical and electrical point of view. No chemical decomposition of the organic compound was observed in the FTIR spectra of the deposited layers. The transmittance and photoluminescence spectra recorded on hybrid films disclose the optical signature of both organic (ZnPc) and inorganic (ZnO) components. The electrical measurements carried out under illumination emphasized the importance of the quantity of the inorganic component on the performance parameters of the structures prepared with the hybrid films. Our study provides new insight in the MAPLE deposition of the organic-inorganic hybrid films with potential applications in the photovoltaic cells area.

668. SWIR photoresponse of SiGe/TiO2 multilayers with Ge-rich SiGe nanocrystals

Authors: Lepadatu, AM; Palade, C; Slav, A; Dascalescu, I; Cojocaru, O; Iftimie, S; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: 2020, CAS 2020 PROCEEDINGS: 2020 INTERNATIONAL SEMICONDUCTOR CONFERENCE, DOI:

The 1600 nm-extended SWIR photoresponse of SiGe/TiO2 multilayers with Ge-rich SiGe nanocrystals (NCs) is demonstrated. The SiGe NCs based multilayers are obtained by magnetron sputtering deposition of TiO2/ 6x(Ge/SiGe/Ge/TiO2) layers on heated p-Si substrate followed by rapid thermal annealing (RTA). Grazing incidence X-ray diffraction and Raman spectroscopy evidence the formation of cubic Ge-rich SiGe NCs and anatase TiO2. ITO/Ge-rich SiGe NCs based multilayer /p-Si heterostructure diodes, fabricated by depositing top ITO and bottom Al contacts, show n-p behavior. Photocurrent-voltage characteristics measured at 100 K under integral light illumination of reverse biased diode present a photocurrent higher with up to 2 orders of magnitude than the dark current. Spectral photocurrent increases with bias voltage increase and presents a bandgap-related cutoff wavelength of similar to 1600 nm due to the high Ge content of SiGe NCs.

669. Multidisciplinary characterization of melanin pigments from the black fungus Cryomyces antarcticus

Authors: Pacelli, C; Cassaro, A; Maturilli, A; Timperio, AM; Gevi, F; Cavalazzi, B; Stefan, M; Ghica, D; Onofri, S

Published: JUL 2020, APPLIED MICROBIOLOGY AND BIOTECHNOLOGY, 104, DOI: 10.1007/s00253-020-10666-0

Melanin is a natural pigment present in almost all biological groups, and is composed of indolic polymers and characterized by black-brown colorization. Furthermore, it is one of the pigments produced by extremophiles including those living in the Antarctic desert, and is mainly involved in their protection from high UV radiation, desiccation, salinity and oxidation. Previous studies have shown that melanized species have an increased capability to survive high level of radiation compared with the non-melanized counterpart. Understanding the molecular composition of fungal melanin could help to understand this peculiar capability. Here, we aimed to characterize the melanin pigment extracted from the Antarctic black fungus Cryomyces antarcticus, which is a good test model for radioprotection researches, by studying its chemical properties and spectral data. Our results demonstrated that, in spite of having a specific type of melanin as the majority of fungi, the fungus possesses the ability to produce both 1,8-dihydroxynaphthalene (DHN) and l 3-4 dihydroxyphenylalanine (L-DOPA) melanins, opening interesting scenarios for the protection role against radiation. Researches on fungal melanin have a huge application in different fields, including radioprotection, bioremediation, and biomedical applications.

Open Access

670. Nonisocyanate Poly(Hydroxyl Urethane)-Based Green Polymer Hybrid Coating Systems: Tailoring of Biomacromolecular Compound Architecture Using APTMS-ZnO/TEMPO-Oxidized Cellulose Nanoparticles

Authors: Haniffa, MAM; Illias, HA; Chee, CY; Ibrahim, S; Sandu, V; Chuah, CH

Published: MAY 12 2020, ACS OMEGA, 5, DOI: 10.1021/acsomega.9b04388

Hybrid bionanocomposite coating systems (HBCSs) are green polymer materials consisting of an interface between a coating matrix and nanoparticles. The coating matrix was prepared by using a nonisocyanate poly(hydroxyl urethane) (NIPHU) prepolymer crosslinked via 1,3-diaminopropane and epoxidized Jatropha curcas oil. TEMPO-oxidized cellulose nanoparticles (TARC) were prepared from microcrystalline cellulose, and (3-aminopropyl)trimethoxysilane (APTMS)-coated ZnO nanoparticles (APTMS-ZnO) and their suspensions were synthesized separately. The suspensions at different weight ratios were incorporated into the coating matrix to prepare a series of HBCSs. FT-IR, H-1-NMR, C-13-NMR, XRD, SEM, and TEM were used to confirm the chemical structures, morphology, and elements of the coating matrix, nanomaterials, and HBCSs. The thermomechanical properties of the HBCSs were investigated by TGA-DTG and pencil hardness analyses. The UV and IR absorption spectra of the HBCSs were obtained using UV-vis spectroscopy and FTIR spectroscopy, respectively. The HBCSs exhibited good thermal stability at about 200 degrees C. The degradation temperature at 5% mass loss of all samples was over around 280 degrees C. The HBCSs exhibited excellent UV block and IR active properties with a stoichiometric ratio of the NIPHU prepolymer and EJCO of 1:1 (wt/wt) containing 5 wt % TARC and 15 wt % APTMS-ZnO nanoparticles. It was observed that the sample with 5 wt % TARC and 15 wt % APTMS-ZnO (HBCS-2) exhibited a uniform crosslinking and reinforcement network with a T-onset of 282 degrees C. This sample has successfully achieved good coating hardness and excellent UV and IR absorption.

671. Radiation damage in p-type EPI silicon pad diodes irradiated with protons and neutrons

Authors: Gurimskaya, Y; de Almeida, PD; Garcia, MF; Suau, IM; Moll, M; Fretwurst, E; Makarenko, L; Pintilie, I

Published: APR 1 2020, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 958, 162221, DOI: 10.1016/j.nima.2019.05.062

In view of the HL-LHC upgrade, radiation-tolerant silicon sensors containing low-resistivity p-type implants or substrates, like LGAD or HV-CMOS devices, are being developed in the framework of ATLAS, CMS, RD50 and other sensor R&D projects. These devices are facing a particular problem - the apparent deactivation of the doping due to the irradiation, the so-called acceptor removal effect. In the present work proton and neutron fluence-dependent radiation damage effects, including the change in leakage current and effective doping concentration, space charge sign-inversion, but also introduction and annealing of point- and cluster-like defects have been studied in Si pad diodes fabricated from p-type EPI material of different resistivity (10-1000 Omega cm). Standard electrical characterisations (IV, CV), TCT (Transient Current Technique) and TSC (Thermally Stimulated Current) techniques were applied. A correlation between effective doping concentration obtained from CV measurements and defect concentration N-t extracted from TSC measurements for both - neutron and proton - irradiations was observed pointing towards the microscopic origin of the acceptor removal. A detailed analysis of the dominant TSC peaks - E(30), BiOi and three main deep acceptor levels H(116), H(140) and H(152) - responsible for the changes in the effective space charge is performed. The origin and annealing behaviour of E(30) and H(40) and other cluster-related defects are discussed as well.

672. Antimicrobial and Cytocompatible Bovine Hydroxyapatite-Alumina-Zeolite Composite Coatings Synthesized by Pulsed Laser Deposition from Low-Cost Sustainable Natural Resources

Authors: Popescu-Pelin, G; Ristoscu, C; Duta, L; Stan, GE; Pasuk, I; Tite, T; Stan, MS; Bleotu, C; Popa, M; Chifiriuc, MC; Oktar, FN; Nicarel, A; Mihailescu, IN

Published: MAR 16 2020, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 8, DOI: 10.1021/acssuschemeng.9b05031

Bovine hydroxyapatite (BHA) and BHA blended with clinoptilolite (CLIN) and alumina (Al2O3) coatings were synthesized using pulsed laser deposition (PLD) with a KrF* excimer laser source (lambda = 248 nm, tau(FWHM) <= 25 ns). Physical-chemical characteristics and the potential use of coatings for preventing bacteria adhesion and biofilm formation were investigated. Optimized PLD conditions were selected for coatings with rough morphologies, suitable for good cell adhesion and implant anchorage and good replication of the source target composition. The crystallinity of composite coatings was progressively decreasing with the augment of the Al2O3 and CLIN contents, which in turn can facilitate an efficacious release of active components. Al2O3- and CLIN-containing coatings exhibited high cytocompatibility and specific antibiofilm profiles, preventing the initiation and maturation of bacterial biofilms. Optimum biological activity profiles associated with the use of sustainable and/or inexpensive materials are, in our opinion, of key importance for the future development of performant implant coatings, which should he perfectly compatible with the surrounding tissue while preventing postsurgical endogenous or nosocomial infections.

673. Crown-ether functionalized graphene oxide for metal ions sequestration

Authors: Petrescu, S; Avramescu, S; Musuc, AM; Neatu, F; Florea, M; Ionita, P

Published: FEB 2020, MATERIALS RESEARCH BULLETIN, 122, 110643, DOI: 10.1016/j.materresbull.2019.110643

Graphene oxide has been synthesized, additionally derivatized with chloroacetic acid for increase the number of available carboxylic groups and further functionalized with crown-ether moieties. The thus obtained material was characterized by IR, thermal analysis, SEM, Raman, and XPS. Tests on adsorption of several metal cations showed that cooper and iron are more retained than potassium.

Open Access

674. Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation

Authors: Socol, M; Preda, N; Costas, A; Borca, B; Popescu-Pelin, G; Mihailescu, A; Socol, G; Stanculescu, A

Published: MAR 2020, NANOMATERIALS, 10, 468, DOI: 10.3390/nano10030468

Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet-visible (UV-Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.

Open Access

675. Lead-Free BNT-BT0.08/CoFe2O4 Core-Shell Nanostructures with Potential Multifunctional Applications

Authors: Cernea, M; Radu, R; Amorín, H; Greculeasa, SG; Vasile, BS; Surdu, VA; Ganea, P; Trusca, R; Hattab, M; Galassi, C

Published: APR 2020, NANOMATERIALS, 10, 672, DOI: 10.3390/nano10040672

Herein we report on novel multiferroic core shell nanostructures of cobalt ferrite (CoFe2O4) bismuth, sodium titanate doped with barium titanate (BNT-BT0.08), prepared by a two step wet chemical procedure, using the sol gel technique. The fraction of CoFe2O4 was varied from 1:0.5 to 1:1.5 = BNT-BT0.08/CoFe2O4 (molar ratio). X-ray diffraction confirmed the presence of both the spinel CoFe2O4 and the perovskite Bi0.5Na0.5TiO3 phases. Scanning electron microscopy analysis indicated that the diameter of the core shell nanoparticles was between 15 and 40 nm. Transmission electron microscopy data showed two phase composite nanostructures consisting of a BNT-BT0.08 core surrounded by a CoFe2O4 shell with an average thickness of 4-7 nm. Cole-Cole plots reveal the presence of grains and grain boundary effects in the BNT-BT0.08/CoFe2O4 composite. Moreover, the values of the dc conductivity were found to increase with the amount of CoFe2O4 semiconductive phase. Both X-ray photoelectron spectroscopy (XPS) and Mossbauer measurements have shown no change in the valence of the Fe3+, Co2+, Bi3+ and Ti4+ cations. This study provides a detailed insight into the magnetoelectric coupling of the multiferroic BNT-BT0.08/CoFe2O4 core shell composite potentially suitable for magnetoelectric applications.

676. TiO2/Fe2O3 photoanodes for solar water oxidation prepared via electrodeposition of amorphous precursors

Authors: Vasile, E; Sima, M; Sima, A; Logofatu, C

Published: JAN 2020, MATERIALS RESEARCH BULLETIN, 121, 110623, DOI: 10.1016/j.materresbull.2019.110623

Hematite-titania thin films with various ratios of Ti/Fe have been prepared on FTO substrate via cathodic and anodic deposition of amorphous Ti oxyhydroxide gel (TiOx) and iron oxyhydroxide (FeOOH) films, respectively followed by annealing processes. TiOx underlayer behaved as a template for FeOOH electrodeposition. The photocatalytic behavior of the photoanodes based on the prepared structures was studied. An increased photocurrent density was obtained without anodic shifting of the photocurrent onset potential. Mott-Schottky studies showed that Ti contributes little to donor density in hematite-titania photoanodes prepared by this technique. The impedance measurements suggest that both separation and transfer of charge carriers are promoted in these hematite-titania photoanodes. For comparative studies, hematite-titania photoanodes have been prepared from TiOx and FeOOH precursors formed by spin-coating technique and anodic deposition method, respectively. The photoelectrochemical performance of these photoanodes in the presence of cobalt-phosphate catalyst was also evaluated.

Open Access

677. Photoluminescence as a Complementary Tool for UV-VIS Spectroscopy to Highlight the Photodegradation of Drugs: A Case Study on Melatonin

Authors: Daescu, M; Toulbe, N; Baibarac, M; Mogos, A; Lorinczi, A; Logofatu, C

Published: SEP 2020, MOLECULES, 25, 3820, DOI: 10.3390/molecules25173820

In this work, a complementary ultraviolet-visible (UV-VIS) spectroscopy and photoluminescence (PL) study on melatonin (MEL) hydrolysis in the presence of alkaline aqueous solutions and the photodegradation of MEL is reported. The UV-VIS spectrum of MEL is characterized by an absorption band with a peak at 278 nm. This peak shifts to 272 nm simultaneously with an increase in the band absorbance at 329 nm in the presence of an NaOH solution. The isosbestic point localized at 308 nm indicates the generation of some chemical compounds in addition to MEL and NaOH. The MEL PL spectrum is characterized by a band at 365 nm. There is a gradual decrease in the MEL PL intensity as the alkaline solution concentration added at the drug solution is increased. In the case of the MEL samples interacting with an alkaline solution, a new photoluminescence excitation (PLE) band at 335 nm appears when the exposure time to UV light reaches 310 min. A down-shift in the MEL PLE band, from 321 to 311 nm, as a consequence of the presence of excipients, is also shown. These changes are explained in reference to the MEL hydrolytic products.

678. Highly Efficient Ultralow Pd Loading Supported on MAX Phases for Chemoselective Hydrogenation

Authors: Trandafir, MM; Neatu, F; Chirica, IM; Neatu, S; Kuncser, AC; Cucolea, EI; Natu, V; Barsoum, MW; Florea, M

Published: MAY 15 2020, ACS CATALYSIS, 10, DOI: 10.1021/acscatal.0c00082

Palladium is one of the most efficient metals for the hydrogenation of organic compounds. However, when molecules, such as nitroaromatics, with several reducible functionalities, are hydrogenated, Pd, like any other very active metal, such as nickel or platinum, often behaves unselectively. One strategy to render Pd more selective is to choose the proper support. Herein, we show that MAX phase powders of Ti3SiC2, Ti2AlC, or Ti3AlC2 can chemoselectively hydrogenate 4-nitrostyrene to 4-aminostyrene, with 100% selectivity, at around 3-4% conversion. To boost the latter, we loaded Ti3SiC2 with 0.0005 wt % Pd and increased the conversion to 100% while maintaining the 4-AS selectivity at >90%. By optimizing the Pd loading, we were also able to increase the turnover frequency 100-fold relative to previous literature results. The identification of this highly efficient and chemoselective system has broad implications for the design of cost-effective, earth-abundant, nontoxic, metal catalysts, with ultralow noble metal loadings.

679. Stimulated Raman scattering and defect-based photoconductivity in mixtures of CdS/TiO2

Authors: Nila, A; Baibarac, M

Published: DEC 14 2020, JOURNAL OF APPLIED PHYSICS, 128, 225704, DOI: 10.1063/5.0030301

Stimulated Raman scattering (SRS) is studied in polycrystalline CdS/TiO2 mixtures based on laser power and temperature dependences in Raman investigation. Our Raman analysis reveals several features of nonlinear behavior, such as nonlinear laser power dependencies or high enhancement of Raman lines at a low temperature due to the intrinsic nonlinear nature of CdS, a high light scattering inside the matter, and a trap-based diffusive medium in a grain-boundary system. In particular, building up experimental evidence of conductivity at various temperatures, it is shown that the samples exhibit thermally activated conductivity due to potential local barriers revealed by a considerable fraction of the grain-boundaries in a diffusive medium. Taking into account the defect-based conductivity, a double Poole-Frenkel barrier is established within the grain-boundaries of CdS/TiO2 mixtures, and their barrier energies are investigated considering the temperature-dependent dark current of the grain-boundary model. We thus demonstrate that diffusive medium-based defects in a grain-boundary model makes CdS/TiO2 mixtures behave efficiently in nonlinear processes such as SRS. These features are of particular interest for optical communication technology, and the fundamental application of the SRS effect is semiconductor optical amplifiers.

Open Access

680. Influence of surfactant-tailored Mn-doped ZnO nanoparticles on ROS production and DNA damage induced in murine fibroblast cells

Authors: Popescu, T; Matei, CO; Vlaicu, ID; Tivig, I; Kuncser, AC; Stefan, M; Ghica, D; Miclea, LC; Savopol, T; Culita, DC; Moisescu, MG

Published: OCT 22 2020, SCIENTIFIC REPORTS, 10, 18062, DOI: 10.1038/s41598-020-74816-0

The present study concerns the in vitro oxidative stress responses of non-malignant murine cells exposed to surfactant-tailored ZnO nanoparticles (NPs) with distinct morphologies and different levels of manganese doping. Two series of Mn-doped ZnO NPs were obtained by coprecipitation synthesis method, in the presence of either polyvinylpyrrolidone (PVP) or sodium hexametaphosphate (SHMTP). The samples were investigated by powder X-ray Diffraction, Transmission Electron Microscopy, Fourier-Transform Infrared and Electron Paramagnetic Resonance spectroscopic methods, and N-2 adsorption-desorption analysis. The observed surfactant-dependent effects concerned: i) particle size and morphology; ii) Mn-doping level; iii) specific surface area and porosity. The relationship between the surfactant dependent characteristics of the Mn-doped ZnO NPs and their in vitro toxicity was assessed by studying the cell viability, intracellular reactive oxygen species (ROS) generation, and DNA fragmentation in NIH3T3 fibroblast cells. The results indicated a positive correlation between the specific surface area and the magnitude of the induced toxicological effects and suggested that Mn-doping exerted a protective effect on cells by diminishing the pro-oxidative action associated with the increase in the specific BET area. The obtained results support the possibility to modulate the in vitro toxicity of ZnO nanomaterials by surfactant-controlled Mn-doping.

681. Adsorption, wicking behavior and photodegradation tests of Rhodamine B solution upon wool substrates

Authors: Frunza, L; Cotorobai, VF; Enculescu, M; Zgura, I; Ganea, CP; Birzu, M; Manaila-Maximean, D

Published: 2020, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS AND NANOTECHNOLOGIES X, 11718, 117182W, DOI: 10.1117/12.2572130

Behavior of some wool fabrics as such or functionalized with semiconductor nanoparticles against the photodegradation of Rhodamine B was investigated. The wool samples were commercially purchased, they were chosen to differ by the chemical nature of the yarns, by the size of the 2D texture elements and by the applied pretreatment. The samples were routinely characterized both in the original form and in the form coated with the oxide particles as well to consider the structure, the surface morphology and their changes due to dye deposition. Several techniques were routinely applied: optical microscopy, XRD, SEM, TGA, UV-Vis spectroscopy and FTIR-ATR. Data have shown that TiO2 layer has either an amorphous structure or is highly dispersed. Drops of Rhodamine B solution were deposited by sessile drop method. We have obtained optical images of the wet/colored spot during the radial wicking, collected with a usual camera. Image comparison was made by direct visualisation. The optical images of the spot on fabrics were taken immediately after the dye was applied, after the fabric was dried and afterwards, after the system illumination by UV-vis light as function of the time. The obtained final spots speak about the dye photodegradation in the studied cases.

682. Structural Changes in Palladium Nanofilms during Thermal Oxidation

Authors: Samoylov, AM; Ivkov, SA; Pelipenko, D; Sharov, MK; Tsyganova, VO; Agapov, BL; Tutov, EA; Badica, P

Published: OCT 2020, INORGANIC MATERIALS, 56, DOI: 10.1134/S0020168520100131

Nanocrystalline PdO films have been characterized by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The results demonstrate that thermal oxidation in an O-2 atmosphere causes similar to 35-nm-thick nanocrystalline Pd films on SiO2/Si(100) substrates to undergo a sequence of phase transformations resulting in PdO formation, followed by PdO decomposition into metallic Pd atT > 1120 K. In the range 670-970 K, theaandctetragonal cell parameters of the nanocrystalline PdO films increase monotonically with increasing temperature. The present and previously reported data have been used to construct a model for the unit cell in the crystal structure of palladium(II) oxide. Based on the quasi-chemical approach, we propose a model that accounts for the observed increase in the tetragonal cell parameters and thep-type conductivity of the nanocrystalline PdO films in terms of the formation of excess interstitial oxygen atoms.

Open Access

683. Texture and interface characterization of iridium thin films grown on MgO substrates with different orientations

Authors: Trupina, L; Nedelcu, L; Banciu, MG; Crunteanu, A; Huitema, L; Constantinescu, C; Boulle, A

Published: FEB 2020, JOURNAL OF MATERIALS SCIENCE, 55, DOI: 10.1007/s10853-019-04004-7

Iridium thin films are grown by direct-current plasma magnetron sputtering, on MgO single-crystal substrates with various surface orientations, i.e. (100), (111), and (110). The surface morphology, the crystalline properties of the films, and the substrate-thin-film interface are investigated by atomic force microscopy, X-ray diffraction (XRD), focused ion beam scanning electron microscopy, and high-resolution transmission electron microscopy, respectively. The results reveal that hetero-epitaxial thin films with different crystallographic orientation and notable atomic scale smooth surface are obtained. From the XRD analysis, the following epitaxial relations are obtained: (1) (100)(Ir)||(100)(MgO) out-of-plane and [001](Ir)||[001](MgO) in-plane for Ir grown on MgO(100), (2) (110)(Ir)||(110)(MgO) out-of-plane and [1-10](Ir)||[1-10](MgO) in-plane for Ir grown on MgO(110), and (3) (111)(Ir)||(111)(MgO) out-of-plane and two variants for in-plane orientation [1-10](Ir)||[1-10](MgO) and [1-10](Ir)||[10-1](MgO), respectively, for Ir grown on MgO(111). Because of the large misfit strain (9.7%), the thin films are found to grow in a strain-relaxed state with the formation of geometrical misfit dislocations with a similar to 2.8-nm spacing, whereas thermal strain is stored upon cooling down from the growth temperature (600 degrees C). The best structural characteristics are obtained for the (111)-oriented films with a mosaicity of 0.3 degrees and vanishingly small lattice distortions. The (100)- and (110)-oriented films exhibit mosaicities of similar to 1.2 degrees and lattice distortions of similar to 1% which can be explained by the larger surface energy of these planes as compared to (111).

684. Effect of Cr and V coatings on W base material in W-Eurofer brazed joints for fusion applications

Authors: de Prado, J; Sánchez, M; Stan, G; Galatanu, A; Ureña, A

Published: OCT 2020, FUSION ENGINEERING AND DESIGN, 159, 111748, DOI: 10.1016/j.fusengdes.2020.111748

Titanium diffusion in tungsten is an undesirable phenomenon that may cause the drop of mechanical and thermal fatigue properties of tungsten base material and components in future fusion reactors. To avoid such as problematic, the effectiveness of two different diffusion coatings, deposited onto W base materials by means of RF magnetron sputtering (Cr and V layers), has been studied to analyze its impact on the operative brazing aspects of the W-Eurofer joints. Coatings with two different thicknesses were deposited over tungsten base material prepared using different surface roughness (0.08 and 0.09 mu m). The results indicated that Ti diffusion into tungsten base material after the brazing process was suppressed in all cases while the consecution of full metallic continuity was reached. However, both Cr and V layers were dissolved during the brazing process due to the high solubility of both elements into beta-Ti. Mechanical properties of the joints dropped especially when Cr is used but a strength higher than 100 MPa was obtained in the case of using V layers.

685. Polarization-dependent magnetism of the Ni/BaTiO3 interface

Authors: Bocirnea, AE; Popescu, DG; Chirila, C; Costescu, RM; Kuncser, V; Stancu, V; Trupina, L; Pasuk, I; Vlaicu, AM; Husanu, MA

Published: MAR 4 2020, PHYSICAL REVIEW MATERIALS, 4, 034402, DOI: 10.1103/PhysRevMaterials.4.034402

We explore the cross coupling between the ferroelectric and ferromagnetic phases in Ni/BaTiO3(001) heterostructures and demonstrate the modulation of the magnetism and incidence of exchange bias in the ultrathin metallic Ni overlayer, depending on the ferroelectric state of the bottom layer. We establish that 5-nm-thick monocrystalline Ni film deposited on BaTiO3 with ferroelectric polarization pointing towards the surface (P+) favors the organization of Ni into uniform ferromagnetic domains. Ni grown on BaTiO3 with opposite ferroelectric polarization is featured by emerging exchange-bias coupling between the ferromagnetic Ni top layers and the antiferromagnetic reacted interface, as theoretically explained by first-principles calculations. We explicitly obtain the morphology of the magnetic domains of the crystalline Ni layer in atomic and magnetic force microscopy measurements (AFM/MFM). The resemblance of AFM and MFM images indicate that, although with radically different morphologies, in both cases all spins orient in the Ni plane. Consequently, the distinct signature of the ferroelectric-ferromagnetic coupling extracted from the magneto-optical Kerr effect measurements encodes all the information of sample magnetism. The peculiar magnetic coupling depending on the ferroelectric state indicates new ways of engineering the functionality of metal/ferroelectric interfaces.

686. The interplay of work function and polarization state at the Schottky barriers height for Cu/BaTiO3 interface

Authors: Popescu, DG; Husanu, MA; Chirila, C; Pintilie, L; Teodorescu, CM

Published: FEB 1 2020, APPLIED SURFACE SCIENCE, 502, 144101, DOI: 10.1016/j.apsusc.2019.144101

The emerging field of electronics based on ferro-functional materials relies on driving effectively and predictably a ferroelectric system between different polarization states through bias applied to metallic contacts. This requires detailed understanding of the growth mechanisms and electronic properties of the interface, including ferroelectric and material - dependent band alignment and Schottky barrier heights. Whether the major contribution at the interface band alignment comes from the work function difference or from the ferroelectric state is still under debate. Here, using X-ray photoemsion and ab-initio calculations, we derive the complex microscopic picture of metal/ferroelectric interface formation, including growth mechanism, valence alteration, ferroelectric-dependent electrostatic potential and thickness - dependent compensation mechanisms of ferroelectricity, starting from the ultrathin growth of Cu up to 100 angstrom on BaTiO3. One establishes the evolution of the band bending and of the build-in potential from the initial probed thickness of the ferroelectric in the range of 3 lambda (lambda - the inelastic mean free path) while gradually approaching the contact region with the metal at higher thickness of the top layer. We find that the well-defined orientation of the ferroelectric polarization lead to a band bending at the interface, which add at the bending expected from the work function difference of the two joining materials.

Open Access

687. Cytotoxicity, Antioxidant, Antibacterial, and Photocatalytic Activities of ZnO-CdS Powders

Authors: Zgura, I; Preda, N; Enculescu, M; Diamandescu, L; Negrila, C; Bacalum, M; Ungureanu, C; Barbinta-Patrascu, ME

Published: JAN 1 2020, MATERIALS, 13, 182, DOI: 10.3390/ma13010182

In this work, ZnO-CdS composite powders synthesized by a simple chemical precipitation method were thoroughly characterized. The morphological, structural, compositional, photocatalytical, and biological properties of the prepared composites were investigated in comparison with those of the pristine components and correlated with the CdS concentration. ZnO-CdS composites contain flower-like structures, their size being tuned by the CdS amount added during the chemical synthesis. The photocatalytic activity of the composites was analyzed under UV irradiation using powders impregnated with methylene blue; the tests confirming that the presence of CdS along the ZnO in composites can improve the dye discoloration. The biological properties such as antioxidant capacity, antibacterial activity, and cytotoxicity of the ZnO, CdS, and ZnO-CdS composites were evaluated. Thus, the obtained composites presented medium antioxidant effect, biocidal activity against Escherichia coli, and no toxicity (at concentrations less than 0.05 mg/mL for composites with a low CdS amount) for human fibroblast cells. Based on these results, such composites can be used as photocatalytic and/or biocidal additives for photoactive coatings, paints, or epoxy floors, which in their turn can provide a cleaner and healthier environment.

688. Oxidation of chalcopyrite in air-equilibrated acidic solution: Inhibition with phenacyl derivatives

Authors: Chirita, P; Duinea, MI; Sarbu, LG; Birsa, LM; Baibarac, M; Sava, F; Matei, E

Published: JUL 2020, TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA, 30, DOI: 10.1016/S1003-6326(20)65351-1

The effects of 4-(2-hydroxyphenyl)-2-(morpholin-4-yl)-1,3-thiazole (Pr02), 1-(3,5-dibromo-2-hydroxyphenyl)-1-oxoethan-2-yl-N,N-diethyldithiocarbamate (Pr04) and 1-(5-bromo-2-hydroxy-3-methylphenyl)-1-oxoethan-2-yl-O- ethyl xanthate (Pr06) on the aqueous oxidation of chalcopyrite (CuFeS2) in air-equilibrated solution at a temperature of 25 degrees C and a pH of 2.5 were studied. The effects were investigated by using potentiodynamic polarization, electro-chemical impedance spectroscopy (EIS), scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, aqueous batch experiments, Fourier transform infrared (FTIR) spectroscopy, Raman scattering and quantum chemical calculations. It is found that the anodic current densities decrease in the order of EtOH Pr02 > Pr04 > Pr06. These results, along with those of the EIS measurements, show that Pr02, Pr04 and Pr06 are effective anodic inhibitors of chalcopyrite aqueous oxidation. Both Raman scattering and FTIR spectroscopy indicate that the elemental sulfur, polysulfide and ferric oxyhydroxides that form on the surface of the mineral are not responsible when it comes to the aqueous oxidation inhibition of chalcopyrite. Quantum chemical calculations show that the adsorption of the tested compounds on the chalcopyrite surface is energetically favorable and so, it can explain the inhibiting effects that were observed.

689. Biomorphic 3D fibrous networks based on ZnO, CuO and ZnO-CuO composite nanostructures prepared from eggshell membranes

Authors: Preda, N; Costas, A; Enculescu, M; Enculescu, I

Published: JAN 15 2020, MATERIALS CHEMISTRY AND PHYSICS, 240, 122205, DOI: 10.1016/j.matchemphys.2019.122205

Three-dimensional (3D) fibrous networks based on metal oxides were obtained by a bio-inspired approach: the replication of an ecological daily-waste, the eggshell membrane (ESM). The biomorphic process consists in the immersion of the ESM into aqueous solutions containing the metal salt precursors followed by the calcination of the metal ions impregnated ESM. Biomorphic ZnO, CuO and ZnO-CuO composite networks were obtained, their morphological, structural, compositional, optical, photocatalytical and electrical properties being evaluated. The scanning electron microscopy investigations proved that the hierarchical structure of the original organic template is perfectly replicated into inorganic architectures consisting of interconnected fibers containing metal oxide nanoparticles as building blocks. The photocatalytical properties of the metal oxide networks under solar simulator irradiation were tested through the degradation of methylene blue. Using Si/SiO2 patterned with interdigitated metallic electrodes as substrates during the calcination step, the electrical properties of the selfcontacted metal oxide networks were investigated. Thus, by replicating the unique architecture of the ESM, 3D metal oxide interwoven meshwork can be easily developed for various applications in fields such as photocatalysis, sensing, optoelectronic devices, etc.

690. Investigation of Ba0.6Sr0.4TiO3 thick films by means of a novel THz-TDS approach

Authors: Nedelcu, L; Annino, G; Chirila, C; Trupina, L; Galca, AC; Banciu, MG

Published: MAR 15 2020, APPLIED SURFACE SCIENCE, 506, 144807, DOI: 10.1016/j.apsusc.2019.144807

Ba0.6Sr0.4TiO3 (BST) ferroelectric thick films were grown on MgO(001) and Al2O3 (0 0 0 1) single-crystal substrates by using a pulsed laser deposition method. Structural, morphological, optical, and terahertz characterization of the BST films were performed by X-ray Diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry (SE), and Terahertz Time-Domain Spectroscopy (THz-TDS). Single-phase samples with strong preferred (1 1 1) orientation and surface roughness lower than 1.5% of their thicknesses have been obtained for both types of substrates. SE was employed to extract the thickness and optical properties by using a 3-layer optical model (substrate/thin film/roughness). The inferred refractive index @630 nm is around 2.05, while the optical interference is visible until 3.3 eV. The THz-TDS measurements in transmission set-up were carried out one after the other on substrates before and after the BST film deposition. The standard THz-TDS analysis of double-layer samples proved difficult to complete in the cases in which a thin or thick film is deposited on a much thicker substrate of known dielectric properties. However, we have been able to extract the complex dielectric permittivity in the THz domain for BST samples with thicknesses of few microns, by developing a specific procedure of data analysis.

691. One-dimensional coordination polymers constructed from copper(II) ions and chromato bridges: Synthesis, crystal structures and thermal analysis

Authors: Dumbrava, A; Maxim, C; Olar, R; Badea, M; Stefan, M; Grecu, MN; Andruh, M

Published: SEP 1 2020, INORGANICA CHIMICA ACTA, 509, 119663, DOI: 10.1016/j.ica.2020.119663

692. PVDF-ferrite composites with dual magneto-piezoelectric response for flexible electronics applications: synthesis and functional properties

Authors: Gheorghiu, F; Stanculescu, R; Curecheriu, L; Brunengo, E; Stagnaro, P; Tiron, V; Postolache, P; Buscaglia, MT; Mitoseriu, L

Published: MAR 2020, JOURNAL OF MATERIALS SCIENCE, 55, DOI: 10.1007/s10853-019-04279-w

In the present work, a magnetodielectric flexible thick film composite with a quaternary Ba12Fe28Ti15O84 ferrite filler (<= 9 vol%) embedded into PVDF polymer matrix was investigated. The role of filler volume on the macroscopic dielectric, magnetic and ferroelectric properties as well as on the nanoscale magnetic and piezoelectric response was analyzed. The formation of small amounts of polar phases besides the majority alpha-phase of PVDF was shown by XRD and FTIR combined analysis. The electrical properties are dominated by the polymer response, while magnetic order is derived as sum property from the ferrite ones, having a predominant soft magnetic character with small coercivity of H-c similar to 60 Oe and high saturation magnetization of M-s = 2.6 emu/g for the highest concentration of 9 vol%. Permittivity and losses slightly increase with ferrite filler addition, and the composite maintains a dielectric character for all the compositions. Local PFM and MFM investigations have shown a combined ferro/piezoelectric character and magnetic order, with magnetoelectric coupling demonstrated by the reorientation of filler particles and modifications of local piezoresponse when applying a static magnetic field.

693. Nanostructures based detection of pharmaceuticals and other contaminants of emerging concern

Authors: Baibarac, M; Toulbe, N

Published: 2020, ADVANCED NANOSTRUCTURES FOR ENVIRONMENTAL HEALTH, DOI: 10.1016/B978-0-12-815882-1.00003-3

694. Estimation of the pyroelectric coefficient for ceramic Pb(Zr,Ti)O3 samples: Comparison of the results obtained by two easy to implement methods

Authors: Pintilie, L; Iuga, A; Stancu, V; Botea, M

Published: MAY 2020, INFRARED PHYSICS & TECHNOLOGY, 106, 103269, DOI: 10.1016/j.infrared.2020.103269

The pyroelectric coefficient of some Pb(Zr,Ti)O-3 type ceramics was estimated using two methods: a direct method, based on the temperature dependence of the charge/current generated by pyroelectric effect; an indirect method based on the frequency dependence of the pyroelectric signal generated by a pyroelectric element under modulated irradiation with infrared light. The purpose was to compare the results and to assess if the indirect method is enough accurate for rapid estimation of the pyroelectric coefficient of a material envisaged for infrared detection. The direct method is more accurate and requires accurate control of temperature and heating rate, while the indirect method is less accurate, with an error up to 20%, and requires the knowledge of quantities such as dielectric constant, electric conductance, and incident power. However, the indirect method can be more easily implemented and can provide a rapid assessment on the pyroelectric quality of a material with potential use in infrared detectors.

Open Access

695. Graphene Oxide Concentration Effect on the Optoelectronic Properties of ZnO/GO Nanocomposites

Authors: Boukhoubza, I; Khenfouch, M; Achehboune, M; Leontie, L; Galca, AC; Enculescu, M; Carlescu, A; Guerboub, M; Mothudi, BM; Jorio, A; Zorkani, I

Published: AUG 2020, NANOMATERIALS, 10, 1532, DOI: 10.3390/nano10081532

In this work, the effects of graphene oxide (GO) concentrations (1.5 wt.%, 2.5 wt.%, and 5 wt.%) on the structural, morphological, optical, and luminescence properties of zinc oxide nanorods (ZnO NRs)/GO nanocomposites, synthesized by a facile hydrothermal process, were investigated. X-ray diffraction (XRD) patterns of NRs revealed the hexagonal wurtzite structure for all composites with an average coherence length of about 40-60 nm. A scanning electron microscopy (SEM) study confirmed the presence of transparent and wrinkled, dense GO nanosheets among flower-like ZnO nanorods, depending on the GO amounts used in preparation. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) absorption spectroscopy, and photoluminescence (PL) measurements revealed the impact of GO concentration on the optical and luminescence properties of ZnO NRs/GO nanocomposites. The energy band gap of the ZnO nanorods was independent of GO concentration. Photoluminescence spectra of nanocomposites showed a significant decrease in the intensities in the visible light range and red shifted suggesting a charge transfer process. The nanocomposites' chromaticity coordinates for CIE 1931 color space were estimated to be (0.33, 0.34), close to pure white ones. The obtained results highlight the possibility of using these nanocomposites to achieve good performance and suitability for optoelectronic applications.

Open Access

696. Multifunctional Hydroxyapatite Coated with Arthemisia absinthium Composites

Authors: Raita, MS; Iconaru, SL; Groza, A; Cimpeanu, C; Predoi, G; Ghegoiu, L; Badea, ML; Chifiriuc, MC; Marutescu, L; Trusca, R; Furnaris, CF; Turculet, CS; Enache, DV; Predoi, D

Published: JAN 2 2020, MOLECULES, 25, 413, DOI: 10.3390/molecules25020413

There is significant research showing that essential oils extracted from the plants have antibacterial effects. The purpose of this study was to develop a biocomposite based on hydroxyapatite coated with Artemisia absinthium essential oil and to highlight its antibacterial activity. Therefore, present studies are aimed at developing new materials combining hydroxyapatite with Artemisia absinthium essential oil, in order to avoid postoperative infections. The purpose of this work is to highlight the antimicrobial properties of the Artemisia absinthium essential oil-hydroxyapatite composites obtained by a simple method and at low costs. The structural properties and antimicrobial efficiency of the Artemisia absinthium essential oil-hydroxyapatite composite have been studied. The samples based on Artemisia absinthium essential oil analyzed in this study showed that wormwood essential oil presented the highest efficacy against the fungal strain of C. parapsilosis. It has been shown that wormwood essential oil has a strong antimicrobial effect against the microbial strains tested in this study. Furthermore, the antimicrobial properties of the biocomposites based on hydroxyapatite and essential oil are due to the presence of the essential oil in the samples.

697. THICKNESS INFLUENCE ON THE PYROELECTRIC SIGNAL OF DOPPED PZT CERAMIC PELLETS

Authors: Stancu, V; Botea, M; Amarande, L; Pintilie, L

Published: JUL-SEP 2020, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 15, DOI:

Pb0.98Bi0.02Zr0.5Fe0.1Nb0.09Ti0.31O3 (PBiZFNT) powder obtained by a solid state reaction technique was uniaxial pressed and sintered at 1200 degrees C in order to fabricate dense thin disk ceramics with different thickness (200 mu up to 600 mu m). The pyroelectric response was influenced by the thickness of the ceramics. The thin ceramic disks of 250 mu m thickness show better pyroelectric signal (approximate to 35 mV) which recommend them for potential use in laser energy meters.

Open Access

698. Organic Thin Films Based on DPP-DTT:C60 Blends Deposited by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Costas, A; Petre, G; Stanculescu, A; Popescu-Pelin, G; Mihailescu, A; Socol, G

Published: DEC 2020, NANOMATERIALS, 10, 2366, DOI: 10.3390/nano10122366

The matrix-assisted pulsed laser evaporation (MAPLE) technique was used for depositing thin films based on a recently developed conjugated polymer, poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPP-DTT) and fullerene C60 blends. The targets used in the MAPLE process were obtained by freezing chloroform solutions with different DPP-DTT:C60 weight ratios, with the MAPLE deposition being carried at a low laser fluence, varying the number of laser pulses. The structural, morphological, optical, and electrical properties of the DPP-DTT:C60 blend layers deposited by MAPLE were investigated in order to emphasize the influence of the DPP-DTT:C60 weight ratio and the number of laser pulses on these features. The preservation of the chemical structure of both DPP-DTT and C60 during the MAPLE deposition process is confirmed by the presence of their vibrational fingerprints in the FTIR spectra of the organic thin films. The UV-VIS and photoluminescence spectra of the obtained organic layers reveal the absorption bands attributed to DPP-DTT and the emission bands associated with C60, respectively. The morphology of the DPP-DTT:C60 blend films consists of aggregates and fibril-like structures. Regardless the DPP-DTT:C60 weight ratio and the number of laser pulses used during the MAPLE process, the current-voltage characteristics recorded, under illumination, of all structures developed on the MAPLE deposited layers evidenced a photovoltaic cell behavior. The results proved that the MAPLE emerges as a viable technique for depositing thin films based on conjugated polymers featured by a complex structure that can be further used to develop devices for applications in the solar cell area.

Open Access

699. MAPLE Deposition of Binary and Ternary Organic Bulk Heterojunctions Based on Zinc Phthalocyanine

Authors: Socol, M; Preda, N; Petre, G; Costas, A; Rasoga, O; Popescu-Pelin, G; Mihailescu, A; Stanculescu, A; Socol, G

Published: OCT 2020, COATINGS, 10, 956, DOI: 10.3390/coatings10100956

Organic bulk heterojunctions (BHJ) based on zinc phthalocyanine (ZnPc), fullerene compounds (C60 fullerene and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM)), and 5,6,11,12-tetraphenylnaphthacene (rubrene) were fabricated through the matrix-assisted pulsed-laser evaporation (MAPLE) technique. Thus, ZnPc:C60 and ZnPc:PC70BM binary BHJ and ZnPc:rubrene:PC70BM ternary BHJ were deposited as thin films on various substrates. The preservation of the chemical structure of the organic compounds during the MAPLE deposition was confirmed by infrared spectroscopy. The structural, optical, and morphological properties of the deposited layers were investigated by X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence (PL), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM), respectively. Further, the electrical properties of the developed structures based on ZnPc:C60, ZnPc:PC70BM, and ZnPc:rubrene:PC70BM were evaluated. The J-V characteristics of the organic structures, recorded under illumination, show that an increase in the open-circuit voltage (V-OC) is achieved in the case of the ternary blend in comparison with that obtained for the binary blends. The results evidenced that MAPLE-deposited thin films containing binary and ternary organic bulk heterojunctions can find applications in the field of photovoltaic devices.

Open Access

700. Second magnetization peak, rhombic-to-square Bragg vortex glass transition, and intersecting magnetic hysteresis curves in overdoped BaFe2(As1-xPx)2 single crystals

Authors: Miu, L; Ionescu, AM; Miu, D; Burdusel, M; Badica, P; Batalu, D; Crisan, A

Published: OCT 14 2020, SCIENTIFIC REPORTS, 10, 17274, DOI: 10.1038/s41598-020-74156-z

The second magnetization peak (SMP) in the fourfold symmetric superconducting single crystals (such as iron pnictides and tetragonal cuprates) has been attributed to the rhombic-to-square transition (RST) of the quasi-ordered vortex solid (the Bragg vortex glass, BVG). This represents an alternative to the pinning-induced BVG disordering as the actual SMP mechanism. The analysis of the magnetic response of BaFe2(As1-xPx)(2) specimens presented here shows that the SMP is not generated by the RST. However, the latter can affect the pinning-dependent SMP onset field if this is close to the (intrinsic) RST line, through the occurrence of a "shoulder" on the magnetic hysteresis curves m(H), and a maximum in the temperature variation of the DC critical current density. These features disappear in AC conditions, where the vortex system is dynamically ordered in the RST domain, emphasizing the essential role of vortex dislocations for an efficient accommodation of the vortex system to the pinning landscape and the SMP development. The m(H) shoulder is associated with a precipitous pinning-induced proliferation of dislocations at the RST, where the BVG elastic "squash" modulus softens. The DC magnetization relaxation indicates that the pinning-induced vortex system disordering continues above the RST domain, as the basic SMP mechanism.

701. PHOTOELECTROCHEMICAL WATER OXIDATION ON HEMATITE FILMS IN NEUTRAL AND ALKALINE ELECTROLYTES

Authors: Vasile, E; Sima, M; Sima, A

Published: JUL-SEP 2020, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 15, DOI:

Nanostructured hematite prepared via anodic deposition has been studied as photoanode in neutral and alkaline electrolytes. The morphology of the nanostructures was characterized by SEM, XRD analysis was performed to verify the phase of the films, absorption coefficient and band gap were determined from spectrophotometric measurements and the atomic concentration of Sn in hematite film was estimated from XPS measurements. EIS measurements and photocurrent responses showed the different behavior of hematite photoanode in alkaline and neutral electrolytes. The alkaline medium favors the chemisorption of the water molecules on hematite photoanode, contributing to the diminishing of the charge transfer resistance.

Open Access

702. Dextran-Thyme Magnesium-Doped Hydroxyapatite Composite Antimicrobial Coatings

Authors: Iconaru, SL; Predoi, MV; Motelica-Heino, M; Predoi, D; Buton, N; Megier, C; Stan, GE

Published: JAN 2020, COATINGS, 10, 57, DOI: 10.3390/coatings10010057

The dextran-thyme magnesium-doped hydroxyapatite (10MgHAp-Dex-thyme) composite layers were prepared by a dip-coating procedure from stable suspensions and further analyzed for the first time. Different characterization techniques were employed to explore the physical-chemical features of the 10MgHAp-Dex-thyme suspensions and derived coatings. Information regarding the 10MgHAp-Dex-thyme suspensions was extracted on the basis of dynamic light scattering, zeta potential, and ultrasound measurements. The crystalline quality of the biocomposite powders-resulting after the centrifugation of suspensions-and the layers deposited on glass was assessed by X-ray diffraction in symmetric and grazing incidence geometries, respectively. The chemical structure and presence of functional groups were evaluated for both powder and coating by Fourier transform infrared spectroscopy in attenuated total reflectance mode. The extent of the antimicrobial effect range of the biocomposite suspensions and coatings was tested against different Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa) and fungus (Candida albicans) strains with promising results.

703. UV Light Effect on Cationic Photopolymerization of the SU8 Photoresist and Its Composites with Carbon Nanotubes: New Evidence Shown by Photoluminescence Studies

Authors: Baibarac, M; Radu, A; Cristea, M; Cercel, R; Smaranda, I

Published: APR 2 2020, JOURNAL OF PHYSICAL CHEMISTRY C, 124, DOI: 10.1021/acs.jpcc.9b11925

The effect of UV light on the cationic photopolymerization of the SU8 negative photoresist is shown by photoluminescence (PL) studies. Our results demonstrate that the cationic photopolymerization reaction of the SU8 photoresist takes place predominantly under the influence of the UVA light. Using UVA light, the influence of carbon nanotubes [of the types single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), multiwalled carbon nanotubes (MWNTs), and SWNTs functionalized with carboxyl groups (SWNTs-COOH)] on the cationic photopolymerization process of the SU8 photoresist is shown by PL studies. The cationic photopolymerization of the SU8 photoresist is monitored by the variations of the two emission bands with maxima at similar to 400-429 nm and 523-556 nm. The increase in the relative intensity of the PL band at similar to 523-556 nm is dependent on (i) the carbon nanotube concentration in the SU8 photoresist matrix; (ii) the type of carbon nanotubes, i.e., SWNTs, DWNTs, and MWNTs; and (iii) the nonfunctionalized and functionalized state of SWNTs. The results reported in this work demonstrate that PL can be used as a complementary method to Raman scattering and IR spectroscopy in the investigation of the cationic photopolymerization reaction of the SU8 negative photoresist. A decrease in the wrapping angle of carbon nanotubes with the SU8 photoresist is highlighted by anisotropic PL studies.

Open Access

704. Sn-doped TiO2 nanotubular thin film for photocatalytic degradation of methyl orange dye

Authors: Bjelajac, A; Petrovic, R; Vujancevic, J; Veltruska, K; Matolin, V; Siketic, Z; Provatas, G; Jaksic, M; Stan, GE; Socol, G; Mihailescu, IN; Janackovic, D

Published: DEC 2020, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 147, 109609, DOI: 10.1016/j.jpcs.2020.109609

We fabricated Sn-doped TiO2 nanotubular film via annealing of anodized TiO2 nanotubes grown on F-SnO2 (FTO) glass. Annealing was carried out at 500 degrees C in ambient air. Anatase crystal structure was achieved with no change in nanotubular morphology in respect to as-anodized amorphous TiO(2 )nanotubes. The X-ray photoelectron spectroscopy analysis revealed Sn on the surface of TiO2 film, following the thermal treatment, probably caused by the diffusion from FTO glass. Depth profile examination of the film chemical composition was conducted by elastic recoil detection analysis, which showed that in addition to the diffusion of Sn from FTO, diffusion of Ti to FTO concurrently occurred. Thus, a higher concentration of Sn was found at the bottom of the tubes, while a lower concentration was present on the tubes' surface top. This explains the improved optical response revealed by a diffuse reflectance spectroscopy. The absorption enhancement demonstrated that Sn-doped TiO2 film was efficient in the degradation of methyl orange dye under visible light.

Open Access

705. Functionalization of eggshell membranes with CuO-ZnO based p-n junctions for visible light induced antibacterial activity against Escherichia coli

Authors: Preda, N; Costas, A; Beregoi, M; Apostol, N; Kuncser, A; Curutiu, C; Iordache, F; Enculescu, I

Published: DEC 1 2020, SCIENTIFIC REPORTS, 10, 20960, DOI: 10.1038/s41598-020-78005-x

Biopolymers provide versatile platforms for designing naturally-derived wound care dressings through eco-friendly pathways. Eggshell membrane (ESM), a widely available, biocompatible biopolymer based structure features a unique 3D porous interwoven fibrous protein network. The ESM was functionalized with inorganic compounds (Ag, ZnO, CuO used either separately or combined) using a straightforward deposition technique namely radio frequency magnetron sputtering. The functionalized ESMs were characterized from morphological, structural, compositional, surface chemistry, optical, cytotoxicity and antibacterial point of view. It was emphasized that functionalization with a combination of metal oxides and exposure to visible light results in a highly efficient antibacterial activity against Escherichia coli when compared to the activity of individual metal oxide components. It is assumed that this is possible due to the fact that an axial p-n junction is created by joining the two metal oxides. This structure separates into components the charge carrier pairs promoted by visible light irradiation that further can influence the generation of reactive oxygen species which ultimately are responsible for the bactericide effect. This study proves that, by employing inexpensive and environmentally friendly materials (ESM and metal oxides) and fabrication techniques (radio frequency magnetron sputtering), affordable antibacterial materials can be developed for potential applications in chronic wound healing device area.

706. RETRACTION: Synthesis and properties of Ba(Zn1/3Ta2/3)O3 for microwave and millimeter-wave applications (Retraction of Vol 516, Pg 1558, 2007)

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Alexandru, HV; Antohe, S; Andronescu, E; Jinga, S; Nita, P

Published: MAR 31 2020, THIN SOLID FILMS, 698, 137898, DOI: 10.1016/j.tsf.2020.137898

Open Access

707. Obtaining and Characterizing Thin Layers of Magnesium Doped Hydroxyapatite by Dip Coating Procedure

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Motelica-Heino, M; Buton, N; Megier, C

Published: JUN 2020, COATINGS, 10, 510, DOI: 10.3390/coatings10060510

A simple dip coating procedure was used to prepare the magnesium doped hydroxyapatite coatings. An adapted co-precipitation method was used in order to obtain a Ca25-xMgx(PO4)(6)(OH)(2), 25MgHAp (x(Mg)= 0.25) suspension for preparing the coatings. The stabilities of 25MgHAp suspensions were evaluated using ultrasound measurements, zeta potential (ZP), and dynamic light scattering (DLS). Using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) information at nanometric resolution regarding the shape and distribution of the 25MgHAp particles in suspension was obtained. The surfaces of obtained layers were evaluated using SEM and atomic force microscopy (AFM) analysis. The antimicrobial evaluation of 25MgHAp suspensions and coatings on various bacterial strains and fungus were realized. The present study presents important results regarding the physico-chemical and antimicrobial studies of the magnesium doped hydroxyapatite suspensions, as well as the coatings. The studies have shown that magnesium doped hydroxyapatite suspensions prepared withx(Mg)= 0.25 presented a good stability and relevant antimicrobial properties. The coatings made using 25MgHAp suspension were homogeneous and showed remarkable antimicrobial properties. Also, it was observed that the layer realized has antimicrobial properties very close to those of the suspension. Both samples of the 25MgHAp suspensions and coatings have very good biocompatible properties.

Open Access

708. Development of Cerium-Doped Hydroxyapatite Coatings with Antimicrobial Properties for Biomedical Applications

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Groza, A; Gaiaschi, S; Rokosz, K; Raaen, S; Negrila, CC; Prodan, AM; Costescu, A; Badea, ML; Chapon, P

Published: JUN 2020, COATINGS, 10, 516, DOI: 10.3390/coatings10060516

Antibacterial cerium-doped hydroxyapatite (Ce-HAp) layers have been researched sparingly in recent years. The Ce-HAp powder, Ca10-xCex(PO4)(6)(OH()2)with x(Ce)= 0.05, was obtained by an adapted chemical co-precipitation method at room temperature. The target was prepared using the Ce-HAp (x(Ce)= 0.05) powder sintered in air at 600 degrees C. The coatings on the Ti substrate were generated in plasma using a radio frequency (RF) magnetron sputtering discharge in an Ar gas flow in a single run. To collect the most complete information regarding the antimicrobial activity of cerium-doped hydroxyapatite with x(Ce)= 0.05, (5Ce-HAp), antimicrobial studies were carried out both on the final suspensions and on the coated surfaces. The target was tested using ultrasound measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), glow-discharge optical emission spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The present study exhibited for the first time results of the homogeneous coatings of hydroxyapatite doped with cerium using a radio frequency magnetron sputtering technique. In addition, this study highlighted for the first time the stability of the cerium-doped hydroxyapatite gels used in the creation of the coating. Ultrasound measurements on the concentrated suspension of 5Ce-HAp showed a good stability compared to double distilled, water which was chosen as the reference fluid. Particles with spherical shape were observed by both TEM and SEM analysis. The broadening of the IR bands in the IR spectrum of the 5Ce-HAp film in comparison with the IR spectrum of the precursor target indicate the formation of interlinked bonds into the layer bulk. XPS analysis revealed that the mixture of Ce(3+)and Ce(4+)ions in the hydroxyapatite (HAp) structure of the coatings could be due to the deposition process. The surface of 5Ce-HAp coatings was homogenous with particles having a spherical shape. A uniform distribution of all the constituent elements on the surface the 5Ce-HAp layer was revealed. The antimicrobial assays proved that both 5Ce-HAp suspensions and 5Ce-HAp coatings effectively inhibited the development of colony forming units (CFU) for all the tested microbial strains. Moreover, the antimicrobial assays emphasized that the 5Ce-HAp suspensions had a biocide effect against Escherichia coli (E. coli) andCandida albicans(C. albicans)microbial strains after 72 h of incubation.

Open Access

709. Long-Term Evaluation of Dip-Coated PCL-Blend-PEG Coatings in Simulated Conditions

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Mihailescu, A; Socol, M; Zgura, I; Chiritoiu, M; Sima, LE; Antohe, F; Ivan, L; Vranceanu, DM; Cotrut, CM; Cristescu, R; Socol, G

Published: MAR 2020, POLYMERS, 12, 717, DOI: 10.3390/polym12030717

Our study focused on the long-term degradation under simulated conditions of coatings based on different compositions of polycaprolactone-polyethylene glycol blends (PCL-blend-PEG), fabricated for titanium implants by a dip-coating technique. The degradation behavior of polymeric coatings was evaluated by polymer mass loss measurements of the PCL-blend-PEG during immersion in SBF up to 16 weeks and correlated with those yielded from electrochemical experiments. The results are thoroughly supported by extensive compositional and surface analyses (FTIR, GIXRD, SEM, and wettability investigations). We found that the degradation behavior of PCL-blend-PEG coatings is governed by the properties of the main polymer constituents: the PEG solubilizes fast, immediately after the immersion, while the PCL degrades slowly over the whole period of time. Furthermore, the results evidence that the alteration of blend coatings is strongly enhanced by the increase in PEG content. The biological assessment unveiled the beneficial influence of PCL-blend-PEG coatings for the adhesion and spreading of both human-derived mesenchymal stem cells and endothelial cells.

Open Access

710. Strategy for Modifying Layered Perovskites toward Efficient Solar Light-Driven Photocatalysts for Removal of Chlorinated Pollutants

Authors: Raciulete, M; Papa, F; Negrila, C; Bratan, V; Munteanu, C; Pandele-Cusu, J; Culita, DC; Atkinson, I; Balint, I

Published: JUN 2020, CATALYSTS, 10, 637, DOI: 10.3390/catal10060637

We have explored an efficient strategy to enhance the overall photocatalytic performances of layered perovskites by increasing the density of hydroxyl group by protonation. The experimental procedure consisted of the slow replacement of interlayer Rb(+)cation of RbLaTa(2)O(7)Dion-Jacobson (DJ) perovskite by H(+)via acid treatment. Two layered perovskites synthesized by mild (1200 degrees C for 18 h) and harsh (950 and 1200 degrees C, for 36 h) annealing treatment routes were used as starting materials. The successful intercalation of proton into D-J interlayer galleries was confirmed by FTIR spectroscopy, thermal analyses, ion chromatography and XPS results. In addition, the ion-exchange route was effective to enlarge the specific surface area, thus enhancing the supply of photocharges able to participate in redox processes involved in the degradation of organic pollutants. HLaTa_01 protonated layered perovskite is reported as a efficient photocatalyst for photomineralization of trichloroethylene (TCE) to Cl(-)and CO(2)under simulated solar light. The enhanced activity is attributed to combined beneficial roles played by the increased specific surface area and high density of hydroxyl groups, leading to an efficiency of TCE mineralization of 68% moles after 5 h of irradiation.

711. Synthesis and characterization of a titanium phosphate-tellurite glass for Faraday rotators

Authors: Elisa, M; Boroica, L; Sava, BA; Iordache, SM; Iordache, AM; Vasiliu, IC; Stefan, RC; Galca, AC; Kuncser, V; Eftimie, M

Published: JUL 2020, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 103, DOI: 10.1111/jace.17071

This work is focused on investigation of thermal, structural, optical, magnetic, and magneto-optical properties of novel titanium phosphate-tellurite glass applied as Faraday rotators. The glass belonging to the system 35Li(2)O-10Al(2)O(3)-5TiO(2)-45P(2)O(5)-5TeO(2) was prepared by a nonconventional wet route of raw materials processing, followed by melting-quenching-annealing steps. Some important physical properties of the investigated glass have been measured and calculated, providing knowledge related to glass compactness, electronic structure, glass forming capability, etc. XRD analysis evidenced an amorphous network structure of the investigated glass. The optical absorption in the Vis domain is mainly due to Ti3+ ions and Te-2 clusters formed during the glass melting process. A relatively low optical absorption is noticed over 600 nm that activates a significant Faraday magneto-optical effect. Photoluminescence bands in the blue, red, and infrared domains are observed, caused by Te-2 clusters formed during the glass melting process. The magnetization in dependency on applied magnetic field reveals a complex behavior of the glass, depending on temperature. Thus, it is found a ferromagnetic behavior up to 2000 Oe, a paramagnetic component up to 40 000 Oe, followed by a diamagnetic one over 40 000 Oe. Faraday rotation angle and Verdet constant values in the visible domain are correlated with the reduced TeO2 content of the glass.

Open Access

712. The Beneficial Mechanical and Biological Outcomes of Thin Copper-Gallium Doped Silica-Rich Bio-Active Glass Implant-Type Coatings

Authors: Stan, GE; Tite, T; Popa, AC; Chirica, IM; Negrila, CC; Besleaga, C; Zgura, I; Sergentu, AC; Popescu-Pelin, G; Cristea, D; Ionescu, LE; Necsulescu, M; Fernandes, HR; Ferreira, JMF

Published: NOV 2020, COATINGS, 10, 1119, DOI: 10.3390/coatings10111119

Silica-based bioactive glasses (SBG) hold great promise as bio-functional coatings of metallic endo-osseous implants, due to their osteoproductive potential, and, in the case of designed formulations, suitable mechanical properties and antibacterial efficacy. In the framework of this study, the FastOs(R)BG alkali-free SBG system (mol%: SiO2-38.49, CaO-36.07, P2O5-5.61, MgO-19.24, CaF2-0.59), with CuO (2 mol%) and Ga2O3 (3 mol%) antimicrobial agents, partially substituting in the parent system CaO and MgO, respectively, was used as source material for the fabrication of intentionally silica-enriched implant-type thin coatings (similar to 600 nm) onto titanium (Ti) substrates by radio-frequency magnetron sputtering. The physico-chemical and mechanical characteristics, as well as the in vitro preliminary cytocompatibility and antibacterial performance of an alkali-free silica-rich bio-active glass coating designs was further explored. The films were smooth (R-RMS < 1 nm) and hydrophilic (water contact angle of similar to 65 degrees). The SBG coatings deposited from alkali-free copper-gallium co-doped FastOs(R)BG-derived exhibited improved wear performance, with the coatings eliciting a bonding strength value of similar to 53 MPa, Lc3 critical load value of similar to 4.9 N, hardness of similar to 6.1 GPa and an elastic modulus of similar to 127 GPa. The Cu and Ga co-doped SBG layers had excellent cytocompatibility, while reducing after 24 h the Staphylococcus aureus bacterial development with 4 orders of magnitude with respect to the control situations (i.e., nutritive broth and Ti substrate). Thereby, such SBG constructs could pave the road towards high-performance bio-functional coatings with excellent mechanical properties and enhanced biological features (e.g., by coupling cytocompatibility with antimicrobial properties), which are in great demand nowadays.

713. Perovskite ferroelectric thin film as an efficient interface to enhance the photovoltaic characteristics of Si/SnOxheterojunctions

Authors: Silva, JPB; Vieira, EMF; Silva, JMB; Gwozdz, K; Figueiras, FG; Veltruská, K; Matolín, V; Istrate, MC; Ghica, C; Sekhar, KC; Kholkin, AL; Goncalves, LM; Chahboun, A; Pereira, M

Published: JUN 14 2020, JOURNAL OF MATERIALS CHEMISTRY A, 8, DOI: 10.1039/d0ta02198a

The photovoltaic (PV) response of SnOx/Si heterojunctions (HJs) through the change of the SnO and SnO(2)ratio in the samples that allows us to obtain p- or n-type SnO(x)films is investigated in this work. The values of short-circuit photocurrent density (J(sc)), open-circuit voltage (V-OC), fill factor (FF) and power conversion efficiency (PCE) are found to be 12.6 mA cm(-2), 0.23 V, 27% and 8.3%, for the p-SnOx/n-Si HJ and 10.3 mA cm(-2), 0.20 V, 20% and 4.5% for the n-SnOx/p-Si HJ. The enhanced PV effect observed in the p-SnOx/n-Si HJs can be attributed to a small band offset between SnO(x)and Si, which lowers the diffusion length that can contribute to higher recombination rate and smaller series resistance. Furthermore, the values ofJ(sc),V-OC, FF and PCE were enhanced up to 30.9 mA cm(-2), -2.0 V, 19% and 10.9%, respectively, through the insertion of a 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3(BCZT) ferroelectric layer between n-Si and p-SnOx. The built-in field developed at the Si/BCZT/SiOx/SnO(x)interfaces together with the depolarizing field, provides a favorable electric potential for the separation and further transport of photo generated electron-hole (e-h) pairs. This work provides a viable approach by combining ferroelectrics with p-SnOx/n-Si HJs for building efficient ferroelectric-based solar cells.

Open Access

714. Silver-Doped Hydroxyapatite Thin Layers Obtained by Sol-Gel Spin Coating Procedure

Authors: Prodan, AM; Iconaru, SL; Predoi, MV; Predoi, D; Motelica-Heino, M; Turculet, CS; Beuran, M

Published: JAN 2020, COATINGS, 10, 14, DOI: 10.3390/coatings10010014

The main objective of this paper is to develop silver-doped hydroxyapatite suspensions (HApAg) with different concentrations of silver (x(Ag) = 0.05 and x(Ag) = 0.2) in order to obtain uniform and homogenous layers by spin-coating procedure. The colloidal properties of HApAg suspensions are evaluated by dynamic light scattering (DLS) analysis, zeta-potential (ZP), and ultrasound measurements. The ultrasound studies show that the HApAg20 sample revealed better stability than the HApAg5 sample. The structural and morphological analysis on suspensions and thin layers is also conducted. It is observed that the particles of the two samples have a similar shape and are uniform. The layers obtained present a homogeneous appearance of the surface without evidence of cracks or interruption of the coatings. The in vitro antifungal studies conducted on the two thin layers at two different time intervals (24 and 48 h) show that both HApAg5 (x(Ag) = 0.05) and HApAg20 (x(Ag) = 0.05) nanoparticles suspensions and composite layers inhibit the development of colony forming units (CFU) even after 24 h of incubation comparative to the control, represented by the Candida albicans (C. albicans) culture in a proper medium. The fungicidal effect was evident after 48 h of incubation in the case of both HApAg20 nanoparticles suspensions and composite layers.

Open Access

715. Synthesis of Core-Double Shell Nylon-ZnO/Polypyrrole Electrospun Nanofibers

Authors: Beregoi, M; Preda, N; Costas, A; Enculescu, M; Negrea, RF; Iovu, H; Enculescu, I

Published: NOV 2020, NANOMATERIALS, 10, 2241, DOI: 10.3390/nano10112241

Core-double shell nylon-ZnO/polypyrrole electrospun nanofibers were fabricated by combining three straightforward methods (electrospinning, sol-gel synthesis and electrodeposition). The hybrid fibrous organic-inorganic nanocomposite was obtained starting from freestanding nylon 6/6 nanofibers obtained through electrospinning. Nylon meshes were functionalized with a very thin, continuous ZnO film by a sol-gel process and thermally treated in order to increase its crystallinity. Further, the ZnO coated networks were used as a working electrode for the electrochemical deposition of a very thin, homogenous polypyrrole layer. X-ray diffraction measurements were employed for characterizing the ZnO structures while spectroscopic techniques such as FTIR and Raman were employed for describing the polypyrrole layer. An elemental analysis was performed through X-ray microanalysis, confirming the expected double shell structure. A detailed micromorphological characterization through FESEM and TEM assays evidenced the deposition of both organic and inorganic layers. Highly transparent, flexible due to the presence of the polymer core and embedding a semiconducting heterojunction, such materials can be easily tailored and integrated in functional platforms with a wide range of applications.

716. Wafer-scale graphene-ferroelectric HfO2/Ge-HfO2/HfO2 transistors acting as three-terminal memristors

Authors: Dragoman, M; Dinescu, A; Dragoman, D; Palade, C; Moldovan, A; Dinescu, M; Teodorescu, VS; Ciurea, ML

Published: DEC 4 2020, NANOTECHNOLOGY, 31, 495207, DOI: 10.1088/1361-6528/abb2bf

In this paper we report a set of experiments at the wafer level regarding field-effect transistors with a graphene monolayer channel transferred on the ferroelectric HfO2/Ge-HfO2/HfO(2)three-layer structure. This kind of transistor has a switching ratio of 10(3)between on and off states due to the bandgap in graphene induced by the ferroelectric structure. Both top and back gates effectively control the carriers' charge flow in graphene. The transistor acts as a three-terminal memristor, termed a memtransistor, with applications in neuromorphic computation.

717. Spectroscopic investigations on PVDF-Fe2O3 nanocomposites

Authors: Chipara, D; Kuncser, V; Lozano, K; Alcoutlabi, M; Ibrahim, E; Chipara, M

Published: AUG 10 2020, JOURNAL OF APPLIED POLYMER SCIENCE, 137, 48907, DOI: 10.1002/app.48907

Polyvinylidene fluoride-iron oxide (PVDF-Fe2O3) nanocomposites have been obtained my melt mixing of PVDF with Fe2O3 nanoparticles. The interactions between the polymeric matrix and the nanofiller have been investigated by wide angle X-ray scattering (WAXS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, using both red and green excitations (lasers). WAXS, FTIR, and Raman spectra confirm that all samples contain alpha PVDF as the major crystalline form of the polymeric matrix. Experimental data revealed small changes in the positions of X-ray lines as well as modifications of the width of X-ray lines upon loading by Fe2O3 nanoparticles. FTIR and Raman spectra are dominated by the lines of the polymeric matrix. Within the experimental errors, the positions of Raman lines are not affected by the wavelength of the incoming electromagnetic radiation, although they are sensitive to the strain of the polymeric matrix induced by addition of the nanofiller. The loading of the polymeric matrix with nanoparticles stretches the macromolecular chains, affecting their vibrational spectra (FTIR and Raman). A complex dependence of the positions of some Raman and FTIR lines on the loading with Fe2O3 is reported. The manuscript provides a detailed analysis of the effects of nanofiller on the position of WAXS, FTIR, and Raman lines. (c) 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48907.

718. A sensitive near infrared to near-infrared luminescence nanothermometer based on triple doped Ln -Y2O3

Authors: Porosnicu, I; Colbea, C; Baiasu, F; Lungu, M; Istrate, MC; Avram, D; Tiseanu, C

Published: JUL 2020, METHODS AND APPLICATIONS IN FLUORESCENCE, 8, 035005, DOI: 10.1088/2050-6120/ab8c20

In recent years, luminescence nanothermometers with near infrared light (NIR) emission excited in the NIR range have attracted much attention due to their potential in bio applications. Here, we propose a new nanothermometer based on triple doped 1%Ho, 1%Er, 1%Yb - Y(2)O(3)that operates in the second and third biological windows around 1200 and 1530 nm under pulsed excitation at 905 nm. The NIR emissions were analysed in the temperature range of 298-473 K in terms of intensity, shape and dynamics. The nanothermometer performances were described using the luminescent intensity ratio (LIR) corresponding to the(5)I(6)-(5)I(8)and(4)I(13/2)-(4)I(15/2)emissions transitions of Ho and Er, respectively. A maximum relative sensitivity of 1.5% K(-1)was achieved at 309 K, which is among the highest five values reported so far for the NIR to NIR downconversion nanothermometers. The thermometer performance for biological application was assessed in terms of nanothermometer reliability and stability as well as emission shape changes induced by water and custom designed optical phantoms. Combination between use of pulsed excitation and identification of Ln doping configuration offering both excitation and emission in the biological windows represent a solid approach that can be easily translated to other hosts to develop a new class of near infrared nanothermometers.

Open Access

719. Processing and Optical Properties of Eu-Doped Chloroborate Glass-Ceramic

Authors: Secu, M; Secu, CE

Published: DEC 2020, CRYSTALS, 10, 1101, DOI: 10.3390/cryst10121101

An europium doped BaO-B2O3-BaCl2 chloroborate glass-ceramic containing a BaCl2 nanocrystalline phase was produced by melt-quenching followed by glass crystallization during annealing. Structural and morphological investigations using x-ray diffraction and scanning electron microscopy have shown fvBaCl(2) nanocrystals of about tens of nm size accompanied by a smaller amount of the BaB2O4 crystalline phase. Photoluminescence spectra have indicated the reduction of Eu3+ to Eu2+ during processing in air or a reducing atmosphere. The spectra analysis showed the presence of Eu3+ ions in the borate glass matrix, while the Eu2+ were incorporated in both the BaCl2 nanocrystals and glass matrix. Thermoluminescence properties were due to the recombination of F(Cl) centers and Eu2+ related hole centers produced by irradiation within the BaCl2 nanocrystals. The color impression of the samples and the photoluminescence quantum efficiency were influenced by the glass processing.

Open Access

720. Beneficial effects of a WC addition in FAST-densified tungsten

Authors: Novak, S; Kocen, M; Zavagnik, AS; Galatanu, A; Galatanu, M; Tarancón, S; Tejado, E; Pastor, JY; Jenus, P

Published: JAN 20 2020, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 772, 138666, DOI: 10.1016/j.msea.2019.138666

The particle reinforcement of fusion-relevant tungsten through the incorporation of tungsten sub-carbide W2C particles at the grain boundaries is demonstrated as an effective way of eliminating the harmful W oxide, enhancing densification and stabilising the composite's microstructure and flexural strength at room and high temperatures. The W2C particles are formed in situ during the sintering by carbon diffusion from WC nano-particles added as a precursor to the W matrix. Even in an extremely fast sintering process using Field-Assisted Sintering Technology (FAST, 1900 degrees C, 5 min), the added WC completely transforms to W2C, resulting in a W-W2C composite. While at least 5 vol % of WC nanoparticles are needed to eliminate the oxide, approximately 10 vol % result in a W-W2C composite with favourable characteristics: high density, high flexural strength at RT (>1200 MPa) as well as at elevated temperatures, and high thermal conductivity, which remains above 100 W/mK up to 1000 degrees C.

Open Access

721. Magnetic and ferroelectric properties, crystal and magnetic structures of SrFe11.9In0.1O19

Authors: Turchenko, VA; Trukhanov, A; Trukhanov, S; Damay, F; Porcher, F; Balasoiu, M; Lupu, N; Chiriac, H; Bozzo, B; Fina, I; Waliszewski, J; Kostishyn, VG; Recko, K; Polosan, S

Published: APR 2020, PHYSICA SCRIPTA, 95, 044006, DOI: 10.1088/1402-4896/ab60fb

The structural investigations of SrFe11.9In0.1O19 compound synthesized by solid-state method have been carried by neutron diffraction method in a wide temperature range. The appearace of spontaneous polarization that coexists with ferrimagnetic ordering has been found out at room temperature in strontium hexaferrite partially substituted with In ions. In order to explaine the presence of ferroelectric properties in SrFe11.9In0.1O19 compound, its crystal structure has been refined within the framework of both centrosymmetric P6(3)/mmc (No. 194) and non-centrosymmetric P6(3)mc (No. 186) space groups. The analysis of refinement results allows to understand microscopic mechanism of appearance ferroelectric properties in strontium hexaferrites.

722. Electron Small Polaron and Magnetic Interactions Direct Anisotropic Growth of Silicon-Doped Hematite Nanocrystals

Authors: Allieta, M; Beranová, K; Marelli, M; Coduri, M; Stefan, M; Ghica, D; Morello, G; Malara, F; Naldoni, A

Published: JUL 1 2020, CRYSTAL GROWTH & DESIGN, 20, DOI: 10.1021/acs.cgd.0c00496

Hematite (alpha-Fe2O3) is a promising and Earth-abundant material for solar fuel production, and Si-doping has been employed as a general strategy to improve its performance. However, an atomistic description that reconciles the modifications that Si-doping induces on the morphology, crystalline lattice, and electronic and magnetic properties of alpha-Fe2O3 has remained elusive. Here we report on the role of electron small polarons in driving the morphological transition from nearly rounded-shaped to nanowire nanocrystals in Si-doped hematite alpha-Fe2O3. Electron small polaron formation is evidenced by the formation of Fe2+ and the increase of FeO6 distortion at increasing Si content. Local analysis via pair distribution function highlights an unreported crossover from small to large polarons, which affects the correlation length of the polaronic distortion from short to average scales. Ferromagnetic double exchange interactions between Fe2+/Fe3+ species are found to be the driving force of the crossover, constraining the chaining of chemical bonds along the [110] crystallographic direction. This promotes the increase in the reticular density of Fe atoms along the hematite basal plane only, which boosts the anisotropic growth of nanocrystals with more extended [110] facets. Our results show that magnetic and electronic interactions drive preferential crystallographic growth in Si-doped alpha-Fe2O3, thus providing new insights for the nanoscale structural design of efficient solar fuel devices.

Open Access

723. Crystal and magnetic structures, magnetic and ferroelectric properties of strontium ferrite partially substituted with in ions

Authors: Turchenko, V; Kostishyn, VG; Trukhanov, S; Damay, F; Porcher, F; Balasoiu, M; Lupu, N; Bozzo, B; Fina, I; Trukhanov, A; Waliszewski, J; Recko, K; Polosan, S

Published: APR 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 821, 153412, DOI: 10.1016/j.jallcom.2019.153412

The influence of temperature factor to crystal structure as well as magnetic and electric properties of strontium hexaferrite partially substituted with diamagnetic indium ions has been investigated. Ferroelectric properties have been found out in SrFe11.9In0.1O19 compound that contradicts to conventional opinion, which describe its crystal structure within the framework of centrosymmetric space group P6(3)/mmc (No. 194). For determination features of the crystal structure, which are responsible for ferroelectric properties of strontium hexaferrite, have been carried out neutron diffraction measurements with high resolution in temperature range from 1.5 to 740 K. The analysis of hexaferrite structure has been executed within the framework both centrosymmetric and non-centrosymmetric space group. Values of coefficients of magneto crystalline anisotropy at 5 and 300 K and influence of ambient temperature to linear size of magnetic regions have been determined from magnetic measurements. (C) 2019 Elsevier B.V. All rights reserved.

724. Simple and clean method for obtaining Sn nanoparticles for hydrophobic coatings

Authors: Buruiana, AT; Sava, F; Matei, E; Zgura, I; Burdusel, M; Mihai, C; Velea, A

Published: NOV 1 2020, MATERIALS LETTERS, 278, 128419, DOI: 10.1016/j.matlet.2020.128419

Sn nanoparticles (NPs) are usually obtained by difficult chemical routes in several steps followed by thermal treatments. Here, a simple and clean method, to obtain Sn NPs directly on the substrate, is developed based on a vapor transport technique. The method is versatile, thus can be easily adjusted to obtain Sn NPs of different size, areal density and morphology, by controlling the deposition conditions. NPs are grown on Si/SiO2 substrate and characterized. Water contact angle measurements show that Sn nanoparticles increase the surface hydrophobicity by 20%. Thus, NPs cleanly obtained from a low-cost, earth-abundant, and environmentally friendly material, can be used to modulate the wettability of surfaces. (C) 2020 Elsevier B.V. All rights reserved.

Open Access

725. Structure of Kα1,2- and Kβ1,3-emission x-ray spectra for Se, Y, and Zr

Authors: Ito, Y; Tochio, T; Yamashita, M; Fukushima, S; Vlaicu, AM; Marques, JP; Sampaio, JM; Guerra, M; Santos, JP; Syrocki, L; Slabkowska, K; Weder, E; Polasik, M; Rzadkiewicz, J; Indelicato, P; Ménesguen, Y; Lépy, MC; Parente, F

Published: NOV 20 2020, PHYSICAL REVIEW A, 102, 052820, DOI: 10.1103/PhysRevA.102.052820

The K alpha and K beta x-ray spectra of Se, Y, and Zr were studied experimentally and theoretically in order to obtain information on the K alpha(1) line asymmetry and the spin doublet in K beta(1,3) diagram lines. Using a high-resolution antiparallel double-crystal x-ray spectrometer, we obtained the line shapes, that is, asymmetry index and natural linewidths. We found that the corrected full width at half maximum of the K alpha(1) and K alpha(2) lines as a function of Z is in good agreement with the data in the literature. Furthermore, satellite lines arising from shake-off appear in the low-energy side of the K alpha(1) and K alpha(2) lines in Se but, in Y and Zr, it was very difficult to identify the contribution of the shake process to the overall lines. The K beta(1,3) natural linewidth of these elements was also corrected using the appropriate instrumental function for this type of x-ray spectrometer, and the spin doublet energies were obtained from the peak positions. The corrected full width at half maximum (FWHM) of the K alpha(1) x-ray lines increases linearly with Z, but this tendency was found to be, in general, not linear for K alpha(3) x-ray lines. This behavior may be due to the existence of satellite lines originated from shake processes. Simulated line profiles, obtained using the multiconfiguration Dirac-Fock formalism, accounting for radiative and radiationless transitions and shake-off processes, show a very good agreement with the high-resolution experimental spectra.

726. Temperature dependence and defect related structure, photoluminescence, (ferro)magnetism and ammonia sensitivity of un-doped nanocrystalline ZnO

Authors: Mihalache, V; Secu, M; Negrila, C; Bercu, V; Mercioniu, I; Leca, A

Published: DEC 2020, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 262, 114748, DOI: 10.1016/j.mseb.2020.114748

ZnO nanostructures with intrinsic and extended defects were prepared by rapid decomposition of zinc-propio-nate and annealing at 400 degrees C-970 degrees C. The correlation between the structure/morphology, type of native defects (photoluminescence (PL), EPR) and ferromagnetism was investigated, together with ammonia adsorption capacity. All the samples show room temperature ferromagnetism (RTFM). Crystallite size increases while the unit cell volume, c-axis constant, microstrain and saturation magnetization relax with increasing temperature; morphology varies from aggregated nanoparticles to frameworks of well-welded crystals. 400 degrees C-800 degrees C annealed samples show a broad visible and/or a prominent violet-blue PL emission and, two narrow g = 2.0065 and g = 1.9632 EPR signals. 800 degrees C-970 degrees C annealed samples exhibit very intense green-yellow photoluminescence. The intrinsic defects in conjunction with a deformed lattice and/or pinned by grain-boundaries appear responsible for RTFM and Curie temperature exceeding 700 degrees C. Tuning the morphology, PL intensity and ferromagnetic signal by choice of annealing temperature can find applications in (gas) sensing, photonic/optoelectronic and spintronic devices.

Open Access

727. Electron-polaron dichotomy of charge carriers in perovskite oxides

Authors: Husanu, MA; Vistoli, L; Verdi, C; Sander, A; Garcia, V; Rault, J; Bisti, F; Lev, LL; Schmitt, T; Giustino, F; Mishchenko, AS; Bibes, M; Strocov, VN

Published: APR 2 2020, COMMUNICATIONS PHYSICS, 3, 62, DOI: 10.1038/s42005-020-0330-6

The underlying mechanisms of the metal-insulator transition in correlated oxides are a rich source of interesting physics and a topic of long-standing investigation. Here, the authors use angle-resolved photoelectron spectroscopy to investigate changes in charge carrier properties and electron-phonon interactions as a function of Ce-doping across the metal-insulator transition in CaMnO3. Many transition metal oxides (TMOs) are Mott insulators due to strong Coulomb repulsion between electrons, and exhibit metal-insulator transitions (MITs) whose mechanisms are not always fully understood. Unlike most TMOs, minute doping in CaMnO3 induces a metallic state without any structural transformations. This material is thus an ideal platform to explore band formation through the MIT. Here, we use angle-resolved photoemission spectroscopy to visualize how electrons delocalize and couple to phonons in CaMnO3. We show the development of a Fermi surface where mobile electrons coexist with heavier carriers, strongly coupled polarons. The latter originate from a boost of the electron-phonon interaction (EPI). This finding brings to light the role that the EPI can play in MITs even caused by purely electronic mechanisms. Our discovery of the EPI-induced dichotomy of the charge carriers explains the transport response of Ce-doped CaMnO3 and suggests strategies to engineer quantum matter from TMOs.

728. Investigation of the effect of sodium azide on the coordination mode of flexible ONO-donor hydrazone ligand in preparing manganese coordination compounds

Authors: Bikas, R; Darvishvand, M; Kuncser, V; Schinteie, G; Siczek, M; Lis, T

Published: NOV 1 2020, POLYHEDRON, 190, 114751, DOI: 10.1016/j.poly.2020.114751

Mononuclear Mn(II) coordination compound, [Mn(H2L)Cl-2] (1), was synthesized by the reaction of H2L and MnCl2 center dot 4H(2)O in methanol where H2L is tridentate ONO-donor hydrazone ligand [H2L = (E)-N'-(2-hydroxy-5-iodobenzylidene)isonicotinohydrazide]. The reaction of H2L with MnCl2 center dot 4H(2)O in the presence of excess amount of NaN3 in methanol gave an azido bridged dinuclear Mn(III) coordination compound, [Mn-2(L)(mu-N-3)(2)(CH3OH)(2)] (2), whereas in the presence of low amount of NaN3, a phenolate bridged dinuclear Mn(II) coordination compound, [Mn-2(HL)(2)(CH3OH)(2)Cl-2]center dot CH3OH (3), was obtained. These compounds were characterized by elemental analysis, spectroscopic methods, single crystal X-ray analysis and magnetic measurements. The structural studies indicated that the ligand is coordinated as ONO-donor ligand in 1-3 and behave as a neutral, dianionic and monoanionic ligand in compounds 1, 2 and 3, respectively. There is a good agreement between spectroscopic properties and structures of the compounds. Several synthetic attempts indicated that the azide anion has considerable effect on the formation of phenolate bridged dinuclear Mn(II) coordination compound which attributed to its general basic properties. Magnetic measurements indicate the formation of dinuclear molecules with ferromagnetic intramolecular couplings in the case of 2 and 3 as well as with much weaker and distributed antiferromagnetic interactions among the dinuclear units of these compounds. (C) 2020 Elsevier Ltd. All rights reserved.

Open Access

729. Controlling Single Molecule Conductance by a Locally Induced Chemical Reaction on Individual Thiophene Units

Authors: Michnowicz, T; Borca, B; Pétuya, R; Schendel, V; Pristl, M; Pentegov, I; Kraft, U; Klauk, H; Wahl, P; Mutombo, P; Jelínek, P; Arnau, A; Schlickum, U; Kern, K

Published: APR 6 2020, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 59, DOI: 10.1002/anie.201915200

Among the prerequisites for the progress of single-molecule-based electronic devices are a better understanding of the electronic properties at the individual molecular level and the development of methods to tune the charge transport through molecular junctions. Scanning tunneling microscopy (STM) is an ideal tool not only for the characterization, but also for the manipulation of single atoms and molecules on surfaces. The conductance through a single molecule can be measured by contacting the molecule with atomic precision and forming a molecular bridge between the metallic STM tip electrode and the metallic surface electrode. The parameters affecting the conductance are mainly related to their electronic structure and to the coupling to the metallic electrodes. Here, the experimental and theoretical analyses are focused on single tetracenothiophene molecules and demonstrate that an in situ-induced direct desulfurization reaction of the thiophene moiety strongly improves the molecular anchoring by forming covalent bonds between molecular carbon and copper surface atoms. This bond formation leads to an increase of the conductance by about 50 % compared to the initial state.

730. Third-order optical nonlinearity properties of CdCl2-modifed Ge-Sb-S chalcogenide glasses

Authors: Lu, XS; Li, JH; Yang, L; Zhang, RN; Zhang, YD; Ren, J; Galca, AC; Secu, M; Farrell, G; Wang, PF

Published: JAN 15 2020, JOURNAL OF NON-CRYSTALLINE SOLIDS, 528, 119757, DOI: 10.1016/j.jnonerysol.2019.119757

We developed a new type of chalcohalide glasses with physicochemical and nonlinear optical properties that are tunable by composition. It is found that more than 60 mol.% CdCl2 heavy metal halide can be dissolved into the ternary Ge Sb S system and forming stable glasses. The visible-light transparency range is extended to shorter wavelengths with the addition of CdCl2, which is beneficial for the optical quality control and infra-red (IR) system alignment. The third-order optical nonlinearity (TONL) is studied using the femtosecond Z-scan method. The results show that both the nonlinear refractive index and two photon absorption co-efficient decrease with CdCl2. Benefiting from the favorable property-tailoring effects of CdCl2, the TONL figure of merit (FOM) can be improved to meet the requirement (FOM < 1) for all-optical switching and IR photonic applications.

Open Access

731. Electrospun conductive gold covered polycaprolactone fibers as electrochemical sensors for O2 monitoring in cell culture media

Authors: Serban, A; Evanghelidis, A; Onea, M; Diculescu, V; Enculescu, I; Barsan, MM

Published: FEB 2020, ELECTROCHEMISTRY COMMUNICATIONS, 111, 106662, DOI: 10.1016/j.elecom.2020.106662

This work reports the use of electrospun conductive gold covered polycaprolactone fibers for the quantification of dissolved O-2. The morphologies of the electrospun fibers obtained at a static and a dynamic drum collector were investigated by scanning electron microscopy. The reduction process of O-2 at negative potentials is analyzed by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) in sodium phosphate buffer (NaPB) pH 7.0 and in cellular media pH 7.4. The electrochemical sensing performance of Au/PCL towards O-2 quantification in NaPB and cellular media is compared by using three electrochemical techniques: cyclic and linear sweep voltammetry and EIS. Measurements are done in a two electrode configuration, using a silver wire as reference, to show the applicability of the method for O-2 quantification in cellular culture media.

732. Optical spectroscopy and dielectric properties of phosphate-tellurite glasses

Authors: Polosan, S; Nitescu, A; Secu, M

Published: MAR 2020, PHYSICA SCRIPTA, 95, 034005, DOI: 10.1088/1402-4896/ab5263

Tellurium metallic colloids were evidence in the phosphate tellurite glasses obtained by the melt quenching method over 1000 degrees C. The concentration and subsequent color of these glasses strongly depend on the preparation conditions due to the significant differences among the melting point of the component oxides. The presence of Te metallic colloids was evidenced by the magneto-optical measurements at different temperatures, by the shift of the emissions spectra with the excitation wavelength and the thermoluminescence spectra as a result of recombination between the hole centers, created during x-ray irradiation, with the quasi coupled electrons from the surface of the metallic colloids. The peak position in the absorption spectra of these metallic colloids was modeled based on generalized Mie light scattering theory on these metallic structures, taking into account the size and shape of colloids but also the dielectric constant of the phosphate tellurite glasses in which these colloids are embedded.

Open Access

733. Quantum dot exciton dephasing by Coulomb interaction: A fermionic analog of the independent boson model

Authors: Dinu, IV; Tolea, M; Gartner, P

Published: FEB 18 2020, PHYSICAL REVIEW B, 101, 085304, DOI: 10.1103/PhysRevB.101.085304

The time evolution of a quantum dot exciton in Coulomb interaction with wetting layer carriers is treated using an approach similar to the independent boson model. The role of the polaronic unitary transform is played by the scattering matrix, for which a diagrammatic, linked cluster expansion is available Similarities and differences to the independent boson model are discussed. A numerical example is presented.

734. Simple Ethanol Refluxing Method for Production of Blue-Colored Titanium Dioxide with Oxygen Vacancies and Visible Light-Driven Photocatalytic Properties

Authors: Lettieri, S; Gargiulo, V; Alfe, M; Amati, M; Zeller, P; Maraloiu, VA; Borbone, F; Pavone, M; Muñoz-García, AB; Maddalena, P

Published: FEB 13 2020, JOURNAL OF PHYSICAL CHEMISTRY C, 124, DOI: 10.1021/acs.jpcc.9b08993

We show that a simple ethanol (EtOH) refluxing treatment at mild temperature (120 degrees C) allows producing blue-colored and reduced titanium dioxide (TiO2-x) exhibiting improved visible-light (VIS) photocatalytic properties. The treatment causes an increase in the density of Ti(III) species and the appearance of two optical absorption features: a broad absorption band-responsible for the blue coloration- extending from the green region (similar to 2.3 eV) up to the near-infrared and a subgap absorption tail close to the band gap energy. The experimental results combined with a computation of the density of states via hybrid Hartree-Fock density functional support the hypothesis that the EtOH reflux treatment leads to formation of surface and subsurface oxygen (O) vacancies. We also show that the excitation-resolved photoluminescence technique allows a high-contrast detection of a subgap optical excitation band peaked at about 430 nm (similar to 2.9 eV), associated with anatase photoluminescence, whose intensity increases after the EtOH reflux treatment. This result gives a very direct support to the debated hypothesis identifying O vacancy states as the energy levels involved in the radiative transition of anatase TiO2. Improved photocatalytic degradation by the processed TiO2 under VIS illumination is demonstrated, and the possible mechanism involved in the formation of surface O vacancies is discussed. The method outlines a very simple, low-cost, and fast procedure to target the formation of O vacancies in the TiO2 surface region.

735. EFFECT OF Mn SUBSTITUTION ON THE STRUCTURAL, MAGNETIC AND MAGNETOSTRICTIVE PROPERTIES OF Fe-Pd FERROMAGNETIC SHAPE MEMORY RIBBONS

Authors: Sofronie, M; Enculescu, M; Crisan, AD; Tolea, F

Published: 2020, ROMANIAN REPORTS IN PHYSICS, 72, 502, DOI:

This work reports the effect of the Mn substitution, rapid solidification technique and heat treatments on the martensitic transformation, magnetic and magnetostrictive properties on the Fe70-xPd30Mnx (x = 1, 3) ferromagnetic shape memory ribbons. The samples were investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, magnetic and magnetostrictive measurements. The thermal treatments induce significant changes in the microstructure and magnetocrystalline anisotropy of the martensitic phase, for Fe67Pd30Mn3 compared to Fe69Pd30Mn1. The competition between the magnetization orientation and twin boundary motion within martensitic variants under magnetic field evidenced in the magnetic-strain curves was discussed and correlated with the magnetic data.

Open Access

736. Soft-magnetic coatings as possible sensors for magnetic imaging of superconductors

Authors: Ionescu, AM; Simmendinger, J; Bihler, M; Miksch, C; Fischer, P; Soltan, S; Schütz, G; Albrecht, J

Published: JAN 2020, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 33, 015002, DOI: 10.1088/1361-6668/ab5984

Magnetic imaging of superconductors typically requires a soft-magnetic material placed on top of the superconductor to probe local magnetic fields. For reasonable results the influence of the magnet onto the superconductor has to be small. Thin YBCO films with soft-magnetic coatings are investigated using SQUID magnetometry. Detailed measurements of the magnetic moment as a function of temperature, magnetic field and time have been performed for different heterostructures. It is found that the modification of the superconducting transport in these heterostructures strongly depends on the magnetic and structural properties of the soft-magnetic material. This effect is especially pronounced for an inhomogeneous coating consisting of ferromagnetic nanoparticles.

737. Magneto-functionalities of La 1-x A x MnO 3 (A = K; Ba) synthesized by flash combustion method

Authors: Bouzid, SA; Galca, AC; Sajieddine, M; Kuncser, V; Rostas, AM; Iacob, N; Enculescu, M; Amarande, L; Pasuk, I; Essoumhi, A

Published: OCT 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 839, 155546, DOI: 10.1016/j.jallcom.2020.155546

Open Access

738. A New Zinc Phosphate-Tellurite Glass for Magneto-Optical Applications

Authors: Elisa, M; Stefan, RC; Vasiliu, IC; Iordache, SM; Iordache, AM; Sava, BA; Boroica, L; Dinca, MC; Filip, AV; Galca, AC; Bartha, C; Iacob, N; Rusu, MI; Eftimie, M; Kuncser, V

Published: SEP 2020, NANOMATERIALS, 10, 1875, DOI: 10.3390/nano10091875

This work investigates the structural, magnetic and magneto-optical properties of a new zinc phosphate-tellurite glass belonging to the 45ZnO-10Al(2)O(3)-40P(2)O(5)-5TeO(2)system. The glass was prepared by a wet method of processing the starting reagents followed by suitable melting-stirring-quenching-annealing steps. Specific parameters such as density, average molecular mass, molar volume, oxygen packaging density, refractive index, molar refractivity, electronic polarizability, reflection loss, optical transmission, band gap and optical basicity have been reported together with thermal, magnetic and magneto-optical characteristics. Absorption bands appear in the blue and red visible region, while over 600 nm the glass becomes more transparent. FTIR and Raman spectra evidenced phosphate-tellurite vibration modes proving the P(2)O(5)and TeO(2)network forming role. Magnetic measurements reveal the diamagnetic character of the Te-doped glass with an additional weak ferromagnetic signal, specific to diluted ferromagnetic oxides. Positive Faraday rotation angle with monotonous decreasing value at increasing wavelength was evidenced from magneto-optical measurements. The final product is a composite material comprising of a non-crystalline vitreous phase and Te-based nanoclusters accompanied by oxygen vacancies. The metallic-like Te colloids are responsible for the dark reddish color of the glass whereas the accompanying oxygen vacancies might be responsible for the weak ferromagnetic signal persisting up to room temperature.

739. Undoped SnO2 as a Support for Ni Species to Boost Oxygen Generation through Alkaline Water Electrolysis

Authors: Neatu, S; Neatu, F; Diculescu, VC; Trandafir, MM; Petrea, N; Somacescu, S; Krumeich, F; Wennmacher, JTC; Knorpp, AJ; van Bokhoven, JA; Florea, M

Published: APR 22 2020, ACS APPLIED MATERIALS & INTERFACES, 12, DOI: 10.1021/acsami.9b19541

In this study, the synergistic behavior of Ni species and bimodal mesoporous undoped SnO2 is investigated in oxygen evolution reactions (OERs) under alkaline conditions without any other modification of the compositional phases or using noble metals. An efficient and environmentally friendly hydrothermal method to prepare bimodal mesoporous undoped SnO2 with a very high surface area (>130 m(2) g(-1)) and a general deposition-precipitation method for the synthesis of well-dispersed Ni species on undoped SnO2 are reported. The powders were characterized by adsorption-desorption isotherms, TG-DTA, XRD, SEM, TEM, Raman, TPRH2, and XPS. The best NiSn composite generates, under certain experimental conditions, a very high TOF value of 1.14 s(-1) and a mass activity higher than 370 A g(-1), which are remarkable results considering the low amount of Ni deposited on the electrode (3.78 ng). Moreover, in 1 M NaOH electrolyte, this material produces more than 24 mA cm(-2) at an overpotential value of approximately +0.33 V, with only 5 wt % Ni species. This performance stems from the dual role of undoped SnO2, on the one hand, as a support for active and well-dispersed Ni species and on the other hand as an active player through the oxygen vacancies generated upon Ni deposition.

Open Access

740. VAlPOs as Efficient Catalysts for Glycerol Conversion to Methanol

Authors: Mitran, G; Neatu, F; Neatu, S; Trandafir, MM; Florea, M

Published: JUL 2020, CATALYSTS, 10, 728, DOI: 10.3390/catal10070728

The catalytic activity of a series of vanadium aluminophosphates catalysts prepared by sol-gel method followed by combustion of the obtained gel was evaluated in glycerol conversion towards methanol. The materials were characterized by several techniques such as X-ray diffraction (XRD), UV-vis, Fourier-transform infrared (FTIR), Raman and X-ray photoelectron (XPS) spectroscopies. The amount of vanadium incorporated in aluminophosphates framework played an important role in the catalytic activity, while in the products distribution the key role is played by the vanadium oxidation state on the surface. The sample that contains a large amount of V(4+)has the highest selectivity towards methanol. On the sample with the lowest vanadium loading the oxidation path to dihydroxyacetone is predominant. The catalyst with higher content of tetrahedral isolated vanadium species, such V5APO, is less active in breaking the C-C bonds in the glycerol molecule than the one containing polymeric species.

Open Access

741. Secondary Crystalline Phases Influence on Optical Properties in Off-Stoichiometric Cu2S-ZnS-SnS2 Thin Films

Authors: Sava, F; Diagne, O; Galca, AC; Simandan, ID; Matei, E; Burdusel, M; Becherescu, N; Becherescu, V; Mihai, C; Velea, A

Published: OCT 2020, MATERIALS, 13, 4624, DOI: 10.3390/ma13204624

Cu2ZnSnS4 (CZTS) is an economically and environmentally friendly alternative to other toxic and expensive materials used for photovoltaics, however, the variation in the composition during synthesis is often followed by the occurrence of the secondary binary and ternary crystalline phases. These phases produce changes in the optical absorption edge important in cell efficiency. We explore here the secondary phases that emerge in a combinatorial Cu2S-ZnS-SnS2 thin films library. Thin films with a composition gradient were prepared by simultaneous magnetron sputtering from three binary chalcogenide targets (Cu2S, SnS2 and ZnS). Then, the samples were crystallized by sulfurization annealing at 450 degrees C under argon flow. Their composition was measured by energy dispersive X-ray spectroscopy (EDX), whereas the structural and optical properties were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and optical transmission measurements. As already known, we found that annealing in a sulfur environment is beneficial, increasing the crystallinity of the samples. Raman spectroscopy revealed the presence of CZTS in all the samples from the library. Secondary crystalline phases such as SnS2, ZnS and Cu-S are also formed in the samples depending on their proximity to the binary chalcogenide targets. The formation of ZnS or Cu-S strongly correlates with the Zn/Sn and Cu/Zn ratio of the total sample composition. The presence of these phases produces a variation in the bandgap between 1.41 eV and 1.68 eV. This study reveals that as we go further away from CZTS in the composition space, in the quasi-ternary Cu2S-ZnS-SnS2 diagram, secondary crystalline phases arise and increase in number, whereas the bandgap takes values outside the optimum range for photovoltaic applications.

742. Degenerated TiO2 Semiconductor Modified with Ni and Zn as Efficient Photocatalysts for the Water Splitting Reaction

Authors: Neatu, F; Abramiuc, LE; Trandafir, MM; Negrea, RF; Florea, M; Teodorescu, CM; Neatu, S

Published: SEP 17 2020, CHEMCATCHEM, 12, DOI: 10.1002/cctc.202000691

The development of robust, safe, cost-effective and efficient photocatalytic systems for water splitting should take into account the presence of a proper and powerful photon absorber and an efficient, low-cost and earth-abundant electrocatalyst to perform the reaction at high conversions. In this study, Ni-Zn/TiO(2)ternary composites with high photocatalytic activity for water splitting under UV irradiation were successfully prepared via a simple and low-cost deposition-precipitation route. Thus, different Ni : Zn molar ratios (1 : 0, 1 : 1, 3 : 1, 6 : 1, 9 : 1, and 0 : 1) were deposited on TiO(2)in order to reach a total metal loading of 50 wt. %. The obtained composites were characterized using several techniques, such as: X-ray diffraction, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The most active synthesized composite, namely Ni-Zn/TiO2(9 : 1), exhibits H(2)generation rate above 17 mmols g(-1) h(-1), which is nearly one thousand times higher than that obtained with TiO(2)Evonik P25. Our study demonstrates that TiO(2)becomes a degenerated semiconductor in the presence of Ni and ZnO, with remarkable photocatalytic properties. Thus, the obtained results can open new opportunities in the preparation of very active materials for hydrogen production based on the optimization of three-component structures.

Open Access

743. About detecting very low mass black holes in LAr detectors

Authors: Lazanu, I; Lazanu, S; Pârvu, M

Published: OCT 2020, JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS, 046, DOI: 10.1088/1475-7516/2020/10/046

The nature of dark matter is still an open problem. The simplest assumption is that gravity is the only force certainly coupled to dark matter and thus the micro black holes could be a viable candidate. We investigated the possibility of direct detection of charged micro black holes with masses around and upward the Planck scale (10(-5) g), ensuring a classical gravitational treatment of these objects in the next generation huge LAr detectors. We show that the signals (ionization and scintillation) produced in LAr enable the discrimination between micro black holes and other particles. It is expected that the trajectories of these micro black holes will appear as crossing the whole active medium, in any direction, producing uniform ionization and scintillation on the whole path.

744. Chalcogenide Science in Romania

Authors: Lorinczi, A; Badica, P; Botila, T; Ciurea, M; Velea, A; Popescu, A; Socol, G; Antohe, S; Nedelcu, N; Sobetkii, A

Published: NOV 2020, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 257, 2000284, DOI: 10.1002/pssb.202000284

Almost six decades ago, in Romania a small group of physicists begun to study chalcogenide compositions, motivated primarily by the desire to understand the phase-change phenomenon in these materials, discovered recently, at that time, by Stanford R. Ovshinsky. It took not too long for them to realize the challenges these materials set to the research. With newcomers to the field, the research was broadened. In some cases just for basic research, to model, and to understand the chalcogenide materials, whereas in other cases, the applicative potential was revealed and used. Herein, the evolution of the field of these somewhat exotic materials is followed, listing the main contributions done in Romania, both in basic and applied research.

745. Correlation of native point defects and photocatalytic activity of annealed ZnO nanoparticle studied by electron spin resonance and photoluminescence emission

Authors: Nguyen, XS; Nguyen, MQ; Trinh, XT; Joita, AC; Nistor, SV

Published: SEP 2020, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 35, 095035, DOI: 10.1088/1361-6641/aba168

In this paper, we investigate the origin of point defects revealed by electron spin resonance (ESR) and photoluminescence (PL) emission in correlation with the photocatalytic activity of ZnO nanocrystals subjected to thermal annealing at various temperatures. Two ESR signals at g similar to 1.96 and similar to 2.003 were consistently observed in all annealed ZnO samples. However, their relative intensities have changed, indicating that the point defect densities were influenced by the annealing temperature. Interestingly, when doping nanoZnO with Cr3+, the Q-band ESR measurements at T = 100 K did show that the g similar to 1.96 signal was completely passivated, suggesting that the origin of the signal lies in the electrons located near the conduction band, i.e. at a shallow-donor level. The intensity of the g similar to 2.003 signal decreased by rising the annealing temperature, and this is attributed to the depopulation of zinc interstitials through the thermally induced migration process and/or recombination with the zinc vacancies. The green PL emission line at similar to 520 nm, which is dominant in the 700 degrees C annealed ZnO sample, shows a correlation with the ESR signal at g similar to 1.96, whose origin is attributed to the radiative transition of the electron from the shallow donor level to the singly ionized zinc vacancy. Furthermore, the high density of the shallow donor electron states was found to be primarily responsible for the high photocatalytic activity in the degradation of methylene blue.

Open Access

746. Towards a Correlation between Structural, Magnetic, and Luminescence Properties of CeF3:Tb³⁺Nanocrystals

Authors: Bartha, C; Secu, C; Matei, E; Negrila, C; Leca, A; Secu, M

Published: JUL 2020, MATERIALS, 13, 2980, DOI: 10.3390/ma13132980

In this study, we report on the structural, magnetic, and optical properties of Tb3+-doped CeF(3)nanocrystals prepared via a polyol-assisted route, followed by calcination. X-ray diffraction analysis and electron microscopy investigations have shown the formation of a dominant Ce(0.75)F(3)nanocrystalline phase (of about 99%), with a relatively uniform distribution of nanocrystals about 15 nm in size. Magnetization curves showed typical paramagnetic properties related to the presence of Ce(3+)and Tb(3+)ions. The magnetic susceptibility showed a weak inflexion at about 150 K, assigned to the cerium ions' crystal field splitting. Under UV light excitation of the Ce(3+)ions, we observed Tb(3+)green luminescence with a quantum yield of about 20%.

747. Magnetic and magnetostrictive properties of the ternary Fe67.5Pd30.5Ga2 ferromagnetic shape memory ribbons

Authors: Sofronie, M; Tolea, F; Tolea, M; Popescu, B; Valeanu, M

Published: JUL 2020, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 142, 109446, DOI: 10.1016/j.jpcs.2020.109446

Specific functional characteristics of the ferromagnetic shape memory alloy Fe67.5Pd30.5Ga2 prepared as ribbons by rapid quenching technique are reported. The shift of the martensitic transformation temperature induced by the applied magnetic field was determined from the thermomagnetic measurements at various fields up to 5T being proved to be in good agreement with the result obtained from calorimetric data via the Clapeyron - Claussius relation. Magnetostriction measurements reveal a pure spin rotation mechanism under low applied magnetic fields, allowed by the reduced magnetic anisotropy. In high magnetic fields and at temperatures close to martensitic transformation, the magnetostriction has a linear increase up to the maximum considered magnetic induction of 3T. This behavior has been discussed in connection with the forced magnetostiction aspects.

Open Access

748. Fish Bone Derived Bi-Phasic Calcium Phosphate Coatings Fabricated by Pulsed Laser Deposition for Biomedical Applications

Authors: Popescu-Pelin, G; Ristoscu, C; Duta, L; Pasuk, I; Stan, GE; Stan, MS; Popa, M; Chifiriuc, MC; Hapenciuc, C; Oktar, FN; Nicarel, A; Mihailescu, IN

Published: DEC 2020, MARINE DRUGS, 18, 623, DOI: 10.3390/md18120623

We report on new biomaterials with promising bone and cartilage regeneration potential, from sustainable, cheap resources of fish origin. Thin films were fabricated from fish bone-derived bi-phasic calcium phosphate targets via pulsed laser deposition with a KrF * excimer laser source (lambda = 248 nm, tau(FWHM) <= 25 ns). Targets and deposited nanostructures were characterized by SEM and XRD, as well as by Energy Dispersive X-ray (EDX) and FTIR spectroscopy. Films were next assessed in vitro by dedicated cytocompatibility and antimicrobial assays. Films were Ca-deficient and contained a significant fraction of beta-tricalcium phosphate apart from hydroxyapatite, which could contribute to an increased solubility and an improved biocompatibility for bone regeneration applications. The deposited structures were biocompatible as confirmed by the lack of cytotoxicity on human gingival fibroblast cells, making them promising for fast osseointegration implants. Pulsed laser deposition (PLD) coatings inhibited the microbial adhesion and/or the subsequent biofilm development. A persistent protection against bacterial colonization (Escherichia coli) was demonstrated for at least 72 h, probably due to the release of the native trace elements (i.e., Na, Mg, Si, and/or S) from fish bones. Progress is therefore expected in the realm of multifunctional thin film biomaterials, combining antimicrobial, anti-inflammatory, and regenerative properties for advanced implant coatings and nosocomial infections prevention applications.

749. Towards phase pure kesterite Cu2ZnSnS4 absorber layers growth via single step free sulfurization electrodeposition under a fix applied potential on Mo substrate

Authors: Azmi, S; Moujib, A; Layachi, OA; Matei, E; Galca, AC; Zaki, MY; Secu, M; Rusu, MI; Grigorescu, CEA; Khoumri, EM

Published: NOV 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 842, 155821, DOI: 10.1016/j.jallcom.2020.155821

This work presents a new synthesis and characterization of Kesterite Cu2ZnSnS4 films by one step electrodeposition with free sulfurization annealing treatment at different applied potentials. This study highlights the effect of applied potential and annealing treatment on the properties of CZTS deposited films. X-ray Diffraction and Raman spectroscopy were employed to assess the structure and composition of the films elaborated at -1V, -1.1V, and -1.2V vs Saturated Calomel Electrode (SCE). The morphological and optical properties were studied using Scanning Electron microscopy and photoluminescence spectroscopy (PL), respectively. The structural properties are improved by annealing treatment, while -1.1V vs SCE was found to be the optimum applied potential to prepare the Kesterite CZTS thin film with a bandgap around 1.5 eV. (C) 2020 Elsevier B.V. All rights reserved.

Open Access

750. Sol-Gel Processing of Bismuth Germanate Thin-Films

Authors: Secu, M; Secu, CE; Tite, T; Polosan, S

Published: MAR 2020, COATINGS, 10, 255, DOI: 10.3390/coatings10030255

This study aims to obtain uniform and homogeneous bismuth germanate oxides thin films by spin coating and using the sol-gel technique with different precursors, followed by low-temperature annealing at 560 degrees C. By using Bi(NO3)(3) precursors, we have obtained transparent, yellowish thin films with a 200 nm thickness. The structural analysis of the initial sol-gel powder has shown the presence of two crystalline structures, the cubic Bi4Ge3O12 (BGO) and monoclinic Bi2GeO5 crystallites, which evolves towards the BGO structure after annealing. The elemental analysis confirmed the composition of the desired compound Bi4Ge3O12 with 60 wt % GeO2 and 40 wt % Bi2O5. On the other hand, by changing the precursor to (Bi(CH3COO)(2), the film thickness increased to 500 nm thicker due to the high viscosity of the sol, and a dominant monoclinic Bi2GeO5 crystalline structure appeared. The elemental analysis revealed a nonstoichiometric composition with 38 wt % GeO2 and 62 wt % Bi2O3. Due to the low GeO2 phase content that reacted with metastable Bi2GeO5, we obtained cubic Bi4Ge3O12 as a secondary phase, with Bi2GeO5 as a dominant crystalline phase. The redshifts of both absorptions and emissions spectra peaks confirmed a different disorder structure as an interplay between the cubic Bi4Ge3O12 (BGO) and monoclinic Bi2GeO5 phases.

751. The enhancement mechanism of dielectric properties of Pb(Zr,Ti)O3 via (Mg²⁺,Sb³⁺) incorporation for supercapacitors

Authors: Craciun, F; Dimitriu, E; Vasile, BS; Negrila, CC; Trusca, R; Birjega, R; Cernea, M

Published: DEC 2020, MATERIALS TODAY CHEMISTRY, 18, 100350, DOI: 10.1016/j.mtchem.2020.100350

Due to the extraordinary versatility of the perovskite structure in accommodating different dopant ions in its structure, in recent years a huge number of multifunctional perovskite materials have been developed. In this work we aim to obtain high temperature-stable and huge dielectric constant materials for supercapacitors by doping divalent Mg2+ and trivalent Sb3+ ions into the octahedral sites, and divalent Sr2+ ions into the dodecahedral sites of lead zirconate-titanate perovskite. The resulting (Pb0.95Sr0.05)(Zr0.425Ti0.45Mg0.042Sb0.083)O3-delta is examined by X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), dielectric spectroscopy (DS) and resonance dielectric spectroscopy (RDS) in order to correlate composition, local structure, ion valence and chemical environment of the doped material with the dielectric properties. HRTEM evidences that a composite structure, with co-existent ferroelectric domains and relaxor nanodomains, is formed by doping. XPS shows that Sb3+ and Mg2+ substitute for the Ti4+/Zr4+ ions, pointing to these strong defects as the main cause for the appearance of the relaxor phase. DS and RDS found that the ferroelectric lead zirconate-titanate transforms into a re-entrant relaxorferroelectric composite with a huge dielectric constant of about 10(4) which remains stable (within +/- 10%) in the high temperature range up to 250 degrees C, pointing to this mechanism of relaxor phase re-entrance below the normal ferroelectric phase transition, as being responsible for the enhancement. (C) 2020 Elsevier Ltd. All rights reserved.

Open Access

752. Surface states mediated charge transfer in redox behavior of hemin at GaAs(100) electrodes

Authors: Enache, M; Negrila, C; Lazarescu, V

Published: MAR 29 2020, RSC ADVANCES, 10, DOI: 10.1039/d0ra01508c

EIS and XPS investigations on the interaction of hemin with p- and n-doped GaAs(100) electrodes in PBS solution revealed significant differences concerning both the adsorbed species and the mechanism of the redox process caused by dopant nature. XPS data show that hemin is adsorbed on p-GaAs(100) by its carboxyl groups and adopts a vertical position favorable to a polymeric film formation whereas on n-GaAs(100), the adsorbed hemin is monomeric and has a rather planar configuration involving mainly the OH groups of the organic molecule. Hemin gives rise to a reversible redox process at the p-GaAs(100) electrode whereas at n-GaAs(100), there is only one reduction wave of a considerably lower current density appearing at a more negative potential. The effects of the applied potential on the phase angle measured at p-GaAs(100) point out major changes not only in the insulating properties of the adsorbed layer, as found at n-GaAs(100), but also in the electronic properties of the semiconductor triggered by the hemin redox process. Analysis of the experimental data points to a mechanism of charge transfer through surface states, the observed differences being related to the location of the surface states with respect to the formal potential of the hemin redox couple.

Open Access

753. CeO2:Mn3O4 Catalytic Micro-Converters Tuned for CH4 Detection Based on Catalytic Combustion under Real Operating Conditions

Authors: Simion, CE; Florea, OG; Florea, M; Neatu, F; Neatu, S; Trandafir, MM; Stanoiu, A

Published: MAY 2020, MATERIALS, 13, 2196, DOI: 10.3390/ma13092196

Mesoporous CeO2:Mn3O4 materials (3:7 and 7:3 molar ratio) were prepared by co-precipitation and deposited as porous thick films over alumina (Al2O3) planar substrate provided with Pt meander. The aim was oriented towards detecting low levels methane (CH4) at moderate operating temperatures. Herein we demonstrated that the sensitivity of catalytic micro-converters (CMCs) towards a given peak of CH4 concentration corresponds to specific gas-surface interaction phenomena. More precisely, a transition from thermal conductivity to combustion rate is likely to occur when CMCs are operated under real atmospheric conditions (normal pressure, presence of relative humidity, and constant operating temperature). The response to CH4 was analyzed over different gas flows and different gas concentrations under the same operating regime. The materials were fully characterized by adsorption-desorption isotherms, H-2-Temperature Programmed Reduction (H-2-TPR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Raman spectroscopies. Thus, the applicative aspect of using CeO2:Mn3O4 as moderate temperature CMC for CH4 detection is brought to the fore.

754. Magnetic properties and thermal stability of polyvinylidene fluoride-Fe2O3 nanocomposites

Authors: Kuncser, V; Chipara, D; Martirosyan, KS; Schinteie, GA; Ibrahim, E; Chipara, M

Published: JAN 28 2020, JOURNAL OF MATERIALS RESEARCH, 35, DOI: 10.1557/jmr.2019.375

Nanocomposites of polyvinylidene fluoride loaded with various amounts of gamma-Fe2O nanoparticles, with an average size ranging between 20 and 40 nm, have been obtained by melt mixing and investigated using various experimental techniques [Superconducting Quantum Interference Device, Mossbauer, and Thermogravimetric Analysis]. Magnetic and Mossbauer measurements confirmed the presence of maghemite and a trace of a paramagnetic iron compound. Magnetic data are consistent with a blocking temperature close to room temperature (RT), showing a decrease in the coercive field as the temperature is increased. A weak exchange bias was noticed in all nanocomposites investigated at all temperatures and tentatively ascribed to surface spin disorder. The temperature dependence of the coercive field obeys the Kneller law. The nanocomposites exhibit superparamagnetic behavior near RT. Most magnetic measurements have been performed below the blocking temperature, revealing thus a complex behavior. The dependence of the mass loss derivative versus temperature, as obtained by thermogravimetric analysis, exhibits a single peak due to the thermal degradation of the polymeric matrix. A weak increase in the thermal stability of the polymeric matrix upon loading with maghemite is reported.

Open Access

755. Microwave investigation of pinning in Te- and cubic-BN- added MgB2

Authors: Alimenti, A; Torokhtii, K; Grigoroscuta, M; Badica, P; Crisan, A; Silva, E; Pompeo, N

Published: 2020, 14TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS2019), 1559, 012039, DOI: 10.1088/1742-6596/1559/1/012039

MgB2 has great potential for many applications, thanks to its relatively high critical temperature and low fabrication cost. Large efforts are done to improve the current carrying capabilities of bulks and tapes in view of different application fields, e.g. with the addition of Te and cubic-BN to MgB2. To elucidate the vortex pinning physics exploiting a different dynamic regime, we present here a microwave study of the pinning properties of spark plasma sintered bulk MgB2 with and without the addition of 0.01 % at. Te or cubic-BN. We show the surface resistance R-s of the MgB2 samples measured with a dielectric-loaded resonator at similar to 16.5 GHz and similar to 26.7 GHz in the 10 K-Tc temperature range at fields up to 1.0 T. Then, the MgB2 R., is studied with high frequency vortex motion models in order to obtain the pinning constant (Labusch parameter) and the depinning frequency. Finally, the microwave behavior of MgB2 in the mixed state is compared with the recent results obtained on Nb3Sn.

756. Therapeutic Use of Inorganic Nanomaterials in Malignant Diseases

Authors: Lupu, AR; Popescu, T; Stojanovic, M

Published: 2020, ENVIRONMENTAL NANOTECHNOLOGY, VOL 3, 27, DOI: 10.1007/978-3-030-26672-1_2

Neoplastic disease has multifactorial etiology and insidious evolution which make it unlikely to be detected in early stages and very difficult to treat at later times. The effectiveness of standard therapeutic approaches is limited by severe adverse effects, metastasis, and tumor capacity to develop multidrug resistance. The success of inorganic nanomaterial-based therapeutic agents depends on the degree to which these nanostructures satisfy general requirements for drug safety regarding biocompatibility, biodegradability, and stability and on their antitumor efficacy. Fabrication of such nanomedicines requires adequate assessment and engineering of nanomaterial physicochemical characteristics like particle size, specific surface area, surface charge, hydrodynamic size, and magnetic, optical, and photocatalytic properties. Together with surface functionalization and delivery method, these properties dictate the in vivo "biological identity" of the nanomaterial and its fate with respect to cellular uptake and distribution/accumulation inside the body. We reviewed recent literature on interdisciplinary studies regarding applications of inorganic nanomaterials in the treatment of cancer. The major functions that inorganic nanomaterials can play in cancer therapy are: 1. Nanocarriers for therapeutic agents and active targeting ligands for molecules overexpressed on tumor tissues as well as for altered signal transduction pathways. Inorganic nanomaterial-based therapeutic agents are able to reduce tumor growth acting on neoplastic vasculature (by inhibiting angiogenesis, vasculogenesis, and vasculogenic mimicry) or on malignant cells (blocking activation of overexpressed receptors and their specific signaling pathways, inducing oxidative stress, and reducing multidrug resistance). Moreover, inorganic nanomaterials are able to inhibit tumor invasiveness and metastasis by reducing degradation of extracellular matrix, exosome secretion, and cell proliferation at the secondary site. 2. Contrast agents and medical adhesives in cancer surgery: (i). Vital staining of sentinel lymph nodes (SLNs) where the first metastasis appears - the use of carbon nanoparticles, single-walled and multilayer carbon nanotubes, or superparamagnetic iron oxide nanoparticles was associated with a significantly higher number of harvested SLNs in breast and cervical tumors, lung cancer, papillary thyroid carcinoma, and prostate carcinoma. (ii). Nanoparticle-based medical adhesives used for surgical wound closure aqueous suspensions of iron oxide and silicon dioxide nanoparticles were shown to rapidly connect highly vascularized tissues (e.g., liver). 3. Inorganic sensitizers for radiotherapy - gold nanoparticles were reported to significantly enhance the efficiency of ionizing radiation and induce targeted cancer cell apoptosis, tumor growth inhibition, and increases of survival rates in tumor-bearing mice. 4. Antitumor agents based on specific material properties like surface plasmon resonance (photothermal heating), magnetic responsiveness (magnetic hyperthermia), and photocatalysis (photodynamic therapy) - heat generated by plasmonic (gold-based) or magnetic (iron oxide-based) nanomaterials exposed to laser light or alternating magnetic fields, respectively, was shown to efficiently destroy tumors in mouse models or leads to promising results in clinical trials; the antitumor action of photoactivated TiO2-based nanomedicines was assessed in numerous in vitro and several in vivo studies. 5. Adjuvant therapy (iron replacement therapy) - iron oxide colloids (IOC) are more efficient than free iron in treating iron-deficient anemia associated with cancer. Overall, inorganic-organic therapeutic nanoplatforms provide enhanced treatment efficiency, reduced adverse effects, multiple antitumor action mechanisms, facile cell internalization, and diminished multidrug resistance.

757. EFFECTS OF ANNEALING ON THE PHYSICAL PROPERTIES OF ITO THIN FILMS GROWN BY RADIO FREQUENCY MAGNETRON SPUTTERING

Authors: Radu, A; Locovei, C; Antohe, VA; Socol, M; Coman, D; Manica, M; Dumitru, A; Dan, L; Radu, C; Raduta, AM; Ion, L; Iftimie, S; Antohe, S

Published: JUL-SEP 2020, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 15, DOI:

Indium-doped tin oxide (ITO) thin films were fabricated by radio frequency magnetron sputtering and were subjected to in-situ and ex-situ annealing, at 200 degrees C, 300 degrees C and 400 degrees C, respectively. The in-situ thermal treatment consisted to intentionally heating the samples' substrates, while the ex-situ annealing was performed using an oven, under ambient atmosphere. For the ITO samples subjected to ex-situ annealing, the density of oxygen vacancies increased leading to the decrease of the electrical resistivity. No significant changes were noticed in terms of transmission spectroscopy after the thermal treatment; while by evaluating the Skewness parameter was determined that the annealing improves the planarity of samples' surface.

Open Access

758. Methane Combustion Using Pd Deposited on CeOx-MnOx/La-Al2O3 Pellistors

Authors: Florea, OG; Stanoiu, A; Gheorghe, M; Cobianu, C; Neatu, F; Trandafir, MM; Neatu, S; Florea, M; Simion, CE

Published: NOV 2020, MATERIALS, 13, 4888, DOI: 10.3390/ma13214888

Pd deposited on CeOx-MnOx/La-Al2O3 has been prepared as a sensitive material for methane (CH4) detection. The effect of different amounts (1.25%, 2.5% and 5%) of Pd loading has been investigated. The as prepared materials were deposited on Pt microcoils using a drop-coating method, as a way of developing pellistors operated using a Wheatstone bridge configuration. By spanning the operating temperature range between 300 degrees C and 550 degrees C, we established the linearity region as well as the maximum sensitivity towards 4900 ppm of CH4. By making use of the sigmoid dependence of the output voltage signal from the Wheatstone bridge, the gas surface reaction and diffusion phenomena have been decoupled. The pellistor with 5% Pd deposited on CeOx-MnOx/La-Al2O3 exhibited the highest selective-sensitivity in the benefit of CH4 detection against threshold limits of carbon monoxide (CO), sulfur dioxide (SO2) and hydrogen sulfide (H2S). Accordingly, adjusting the percent of Pd makes the preparation strategies of pellistors good candidates towards CH4 detection.

Open Access

759. Investigation of flux jumps during pulsed field magnetization in graphene-added MgB2 bulks

Authors: Yokoyama, K; Oka, T; Berger, K; Dorget, R; Koblischka, M; Grigoroscuta, M; Burdusel, M; Batalu, D; Aldica, G; Badica, P; Sakai, N; Muralidhar, M; Murakami, M

Published: 2020, 14TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS2019), 1559, 012080, DOI: 10.1088/1742-6596/1559/1/012080

MgB2 bulk superconductors are expected to be utilized as rare-earth-free and lightweight trapped field magnets. However, the flux jumps frequently happen during the magnetizing processes, and heavily degrade the field-trapping performances. We have investigated the effect of additives to the MgB2 bulk samples prepared by spark plasma sintering process, and observed various flux jumps during the pulsed field magnetizing processes, which were carried out at 14 K which was obtained by the 2-stage GM cryocooler. The authors classified the flux motions as three categories as "no flux flow", "fast flux flow", and "flux jump" regions, and investigated the conditions where the flux jumps happen. We observed some drastic flux jumps in the pristine and clarified the effect of graphene addition to the flux jumps. The experimental results showed us a possible expansion of no flux jump region, and suggested us the improvement of field trapping capability.

Open Access

760. HRTEM analysis of the high-temperature phases of the newly developed high-temperature Ni-base superalloy VDM 780 Premium

Authors: Ghica, C; Solís, C; Munke, J; Stark, A; Gehrmann, B; Bergner, M; Rösler, J; Gilles, R

Published: JAN 25 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 814, 152157, DOI: 10.1016/j.jallcom.2019.152157

VDM 780 Premium is a recently developed Ni-based superalloy designed for working at high service temperatures (above 650 degrees C) while keeping the good workability of alloy 718. VDM 780 Premium is based on the austenitic matrix (gamma phase) strengthened by intermetallic Ni3Al-like precipitates (gamma' phase, fcc L1(2) structure). Other co-precipitates may be formed in function of the applied heat treatment, such as Ni3Nb-based (delta phase, orthorhombic DOa structure) or Ni3Ti-based (eta phase, hexagonal DO24 structure) precipitates. The amount as well as the size and morphology of the different precipitates depend on the heat treatments performed on the alloy, playing an important role in improving the creep properties or the behavior during forging and recrystallization. This work contains a complex study using various techniques of analytical electron microscopy and synchrotron diffraction intended to clarify the structure of the high-temperature phase formed in the newly developed VDM 780 Premium alloy. The atomic structure of the high-temperature plate-like precipitates formed in VDM 780 Premium after two different thermal treatments has been investigated in relation with the surrounding matrix lattice, proving the stacked delta/eta structure of the precipitates. (C) 2019 Published by Elsevier B.V.

Open Access

761. Copper(II) Complexes with Mixed Heterocycle Ligands as Promising Antibacterial and Antitumor Species

Authors: Rostas, AM; Badea, M; Ruta, LL; Farcasanu, IC; Maxim, C; Chifiriuc, MC; Popa, M; Luca, M; Korosin, NC; Korosec, RC; Bacalum, M; Raileanu, M; Olar, R

Published: SEP 2020, MOLECULES, 25, 3777, DOI: 10.3390/molecules25173777

Complexes with mixed ligands [Cu(N-N)(2)(pmtp)](ClO4)(2)((1) N-N: 2,2 '-bipyridine; (2) L: 1,10-phenanthroline and pmpt: 5-phenyl-7-methyl-1,2,4-triazolo[1,5-a]pyrimidine) were synthesized and structurally and biologically characterized. Compound (1) crystallizes into space groupPaand (2) inP-1. Both complexes display an intermediate stereochemistry between the two five-coordinated ones. The biological tests indicated that the two compounds exhibited superoxide scavenging capacity, intercalative DNA properties, and metallonuclease activity. Tests on various cell systems indicated that the two complexes neither interfere with the proliferation ofSaccharomyces cerevisiaeor BJ healthy skin cells, nor cause hemolysis in the active concentration range. Nevertheless, the compounds showed antibacterial potential, with complex (2) being significantly more active than complex (1) against all tested bacterial strains, both in planktonic and biofilm growth state. Both complexes exhibited a very good activity against B16 melanoma cells, with a higher specificity being displayed by compound (1). Taken together, the results indicate that complexes (1) and (2) have specific biological relevance, with potential for the development of antitumor or antimicrobial drugs.

Open Access

762. Novel Ecogenic Plasmonic Biohybrids as Multifunctional Bioactive Coatings

Authors: Barbinta-Patrascu, ME; Ungureanu, C; Badea, N; Bacalum, M; Lazea-Stoyanova, A; Zgura, I; Negrila, C; Enculescu, M; Burnei, C

Published: JUL 2020, COATINGS, 10, 659, DOI: 10.3390/coatings10070659

The objective of the present study is the valorization of natural resources and the recycling of vegetal wastes by converting them into novel plasmonic bio-active hybrids. Thus, a "green" approach was used to design pectin-coated bio-nanosilver. Silver nanoparticles were generated from two common garden herbs (Mentha piperitaandAmaranthus retroflexus), and pectin was extracted from lemon peels. The samples were characterized by the following methods: Ultraviolet-visible (UV-Vis) absorption spectroscopy, Fourier Transform Infrared (FT-IR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), dynamic light scattering (DLS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM)-Energy-dispersive X-ray Spectroscopy (EDX), and zeta potential measurements. Microscopic investigations revealed the spherical shape and the nano-scale size of the prepared biohybrids. Their bioperformances were checked in terms of antioxidant and antibacterial activity. The developed plasmonic materials exhibited a strong ability to scavenge short-life (96.1% divided by 98.7%) and long-life (39.1% divided by 91%) free radicals. Microbiological analyses demonstrated an impressive antibacterial effectiveness of pectin-based hybrids againstEscherichia coli. The results are promising, and the obtained biomaterials could be used in many bio-applications, especially as antioxidant and antimicrobial biocoatings.

763. Effect of ITO electrode patterning on the properties of organic heterostructures based on non-fullerene acceptor prepared by MAPLE

Authors: Stanculescu, A; Breazu, C; Socol, M; Rasoga, O; Preda, N; Petre, G; Solonaru, AM; Grigoras, M; Stanculescu, F; Socol, G; Popescu-Pelin, G; Girtan, M

Published: APR 15 2020, APPLIED SURFACE SCIENCE, 509, 145351, DOI: 10.1016/j.apsusc.2020.145351

This paper presents some studies on the organic heterostructures realized by Matrix Assisted Pulsed Laser Evaporation in both bi-layer and mixed layer configurations on glass substrates covered by flat or nano-patterned ITO. The donor, a star-shaped arylenevinylene compound, 4,4',4 ''-tris[(4'-diphenylamino) styryl] triphenylamine, and acceptor, a non-fullerene compound, N,N'-bis-(1-dodecyl)perylene-3,4,9,10 tetracarboxylic diimide, were blended in three weight ratios: 1:2, 1:3 and 1:4. A grating of cylindrical pillars with a periodicity of 1.1 mu m has been developed by UV-Nanoimprint Lithography in a polymer layer. The shape of the nanostructures changed to cone trunk by the Pulsed Laser Deposition of ITO on this nanostructured surface. The effect of the nanostructures and composition on the optical and electrical properties of the heterostructures was analyzed. The nano-patterning affected both the UV-Vis transmission and photoluminescence through the multiple reflections inside the cavities and at interfaces and the particularities of the molecular arrangement. The patterning was preserved independently of composition, but the roughness increased with increasing acceptor amount. The I-V characteristics drawn at room temperature in dark revealed an ohmic contact behavior for all heterostructures. The nano-patterning had a similar effect on the current in the heterostructures with mixed layer (1:2) and stacked bi-layer.

764. TESTING AND VERIFICATION METHODS FOR DIELECTRIC MIRRORS USED IN FEMTOSECOND REGIME LASER SYSTEMS

Authors: Ghita, I; Rizea, A; Zamfirescu, M; Oancea, D; Naziru, A; Georgescu, M; Lachapelle, A; Cojocaru, G; Ungureanu, R; Cotirlan-Seviioniuc, C

Published: 2020, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 82, DOI:

This paper presents the methodology and reports the results concerning the Laser Induced Damage Threshold (LIDT), surface quality and group delay dispersion (GDD) measurements of large aperture femtosecond laser mirrors, achieved in a project funded by IFA under the contract number 02 ELI/18.10.20.17., having, as a main goal, the manufacturing of large aperture mirrors (150mm effective diameter) and tests performing for use in high energy ultra-short pulse laser systems, such as ELI-NP and CETAL infrastructures. The manufacturing process of the mirror substrates was described in a previous paper [1] and the coating technology will be presented in a future article. The novelty of this paper consists, mainly, in the method, experimental arrangement and test procedure to determine the Laser Induced Damage Threshold (LIDT) but also in the entire testing protocol, including Group Delay Dispersion (GDD) and other measurements presented here.

Open Access

765. Optical Properties of Composites Based on Graphene Oxide and Polystyrene

Authors: Stroe, M; Cristea, M; Matei, E; Galatanu, A; Cotet, LC; Pop, LC; Baia, M; Danciu, V; Anghel, I; Baia, L; Baibarac, MA

Published: MAY 2020, MOLECULES, 25, 2419, DOI: 10.3390/molecules25102419

In this work, new optical properties of composites based on polystyrene (PS) microspheres and graphene oxide (GO) are reported. The radical polymerization of styrene in the presence of benzoyl peroxide, pentane and GO induces the appearance of new ester groups in the PS macromolecular chains remarked through an increase in the absorbance of the infrared (IR) band at 1743 cm(-1). The decrease in the GO concentration in the PS/GO composites mass from 5 wt.% to 0.5 wt.% induces a diminution in the intensities of the D and G Raman bands of GO simultaneous with a down-shift of the D band from 1351 to 1322 cm(-1). These variations correlated with the covalent functionalization of the GO layers with PS. For the first time, the photoluminescent (PL) properties of PS/GO composites are reported. The PS microspheres are characterized by a PL band at 397 nm. Through increasing the GO sheets' concentration in the PS/GO composite mass from 0.5 wt.% to 5 wt.%, a PS PL quenching process is reported. In addition, in the presence of ultraviolet A (UVA) light, a photo-degradation process of the PS/GO composite having the GO concentration equal to 5 wt.% is demonstrated by the PL studies.

766. Obtaining SiGe nanocrystallites between crystalline TiO2 layers by HiPIMS without annealing

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Teodorescu, VS; Ciurea, ML; Svavarsson, HG

Published: MAY 1 2020, APPLIED SURFACE SCIENCE, 511, 145552, DOI: 10.1016/j.apsusc.2020.145552

Formation of SiGe nanocrystals in an oxide matrix via deposition and subsequent annealing is a widely applied approach as it gives good control over optical properties by varying the Ge atomic fraction, the size, shape and crystallinity of the nanocrystals. A common drawback of annealing is a strain relaxation in the structure creating dislocations, point defects, dangling bonds, Ge clustering and altered interface morphology. All these phenomena are well-known to degrade the optoelectronic and electrical properties of the structure. As a proof of concept, in this study we have utilized a modern technique of high impulse power magnetron sputtering (HiPIMS) to obtain a crystalline TiO2/SiGe/TiO2 structure without any pre-/post-annealing. It is furthermore demonstrated how a control of the nano-crystallite size is obtained by altering the HiPIMS discharge power alone. Grazing incidence X-ray diffraction analysis was carried out for the structural characterization, while photocurrent measurements were utilized to access the role of TiO2 structural morphology over interface integrity in determining spectral feature and sensitivity. An increase of 1 - 2 orders magnitude in spectral intensity was achieved for as-grown structures fabricated via HiPIMS in comparison to annealed structure, sputtered with conventional direct current magnetron sputtering.

767. Influence of doping the inorganic cation with Eu or Sb on the properties of perovskite films

Authors: Stancu, V; Leonat, LN; Tomulescu, AG; Derbali, S; Pintilie, L; Besleaga, C; Galca, AC; Neatu, F; Neatu, T; Florea, M; Pintilie, I

Published: JUL 2020, PHYSICA SCRIPTA, 95, 075707, DOI: 10.1088/1402-4896/ab90be

This study reports on the results obtained after doping the [CH3NH3](0.94)[C3N2H5](0.06)PbI2.6Cl0.4 mixt halide perovskite with europium or antimony (Eu3+/Sb3+) at the 'B site'. This way two new complex compounds were obtained, [CH3NH3](0.94)[C3N2H5](0.06)Pb1-yByI2.6Cl0.4 (B = Eu or Sb and y = 0-0.05) as perovskite precursor solutions and deposited as thin films. The properties of the perovskite films were investigated by various characterization techniques: x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. We find that doping the mixt halide perovskite with very small quantities of Sb improves the quality of the perovskite films and further improves the stability of perovskite solar cells.

Open Access

768. Photoluminescence as a Valuable Tool in the Optical Characterization of Acetaminophen and the Monitoring of Its Photodegradation Reactions

Authors: Daescu, M; Matea, A; Negrila, C; Serbschi, C; Ion, AC; Baibarac, M

Published: OCT 2020, MOLECULES, 25, 4571, DOI: 10.3390/molecules25194571

In this work, new evidence for the photodegradation reactions of acetaminophen (AC) is reported by photoluminescence (PL), Raman scattering and FTIR spectroscopy. Under excitation wavelength of 320 nm, AC shows a PL band in the spectral range of 340-550 nm, whose intensity decreases by exposure to UV light. The chemical interaction of AC with the NaOH solutions, having the concentration ranging between 0.001 and 0.3 M, induces a gradual enhancement of the photoluminescence excitation (PLE) and PL spectra, when the exposure time of samples at the UV light increases until 140 min, as a result of the formation of p-aminophenol and sodium acetate. This behavior is not influenced by the excipients or other active compounds in pharmaceutical products as demonstrated by PLE and PL studies. Experimental arguments for the obtaining of p-aminophenol and sodium acetate, when AC has interacted with NaOH, are shown by Raman scattering and FTIR spectroscopy.

769. Magnetic properties of BaNi x Fe 12-x O 19 (x=0.0-1.0) hexaferrites, synthesized by citrate -gel auto -combustion and sintered by conventional and spark plasma methods

Authors: Cernea, M; Greculeasa, SG; Radu, R; Aldica, G; Ganea, P; Surdu, VA; Tanasa, ET; Cioangher, M; Iacob, N; Costescu, RM

Published: AUG 5 2020, JOURNAL OF ALLOYS AND COMPOUNDS, 831, DOI:

Open Access

770. On the Physical Properties PEDOT:PSS Thin Films

Authors: Girtan, M; Mallet, R; Socol, M; Stanculescu, A

Published: MAR 2020, MATERIALS TODAY COMMUNICATIONS, 22, 100735, DOI: 10.1016/j.mtcomm.2019.100735

A complete characterization from optical, morphological, electrical, photo-electrical and thermo-electrical point of view was done for PEDOT:PSS thin films and DMSO and EG sensitized PEDOT:PSS films. The studies on the electrical conductivity and electrical photoconductivity allowed the calculation of different relaxation times. The relaxation time of the electrical conductivity is of order of femtosecond and is multiplied by a factor 10 when PEDOT: PSS thin films were deposited on surfaces sensitized with DMSO and EG. Besides, the photoconduction excitation and relaxation times are of order of seconds. An increase in the relaxation photoconduction time by 2 was observed for films deposited on surfaces sensitized with DMSO and by 1.2 for films deposited on surfaces sensitized with EG. The time response of electrical conductivity after exposure to light adds supplementary knowledge for the understanding of the inertial processes, or hysteresis behavior of organic or perovskite solar cells involving PEDOT:PSS films. The electrical conductivity increases with the temperature and the use of DMSO and EG as surfactants lead to higher values of electrical conductivity and Seebeck coefficient. A better stability of the electrical conductivity with the temperature increase, was noticed for films deposited on surfaces sensitized with DMSO.

Open Access

771. Assessment of Potential of the High-Voltage Anodic Plasma Source to Deposit Multilayer Structures Relevant to X-ray Mirror Applications

Authors: Vlaicu, AM; Anghel, A; Badulescu, M; Surdu-Bob, C

Published: JUN 2020, COATINGS, 10, 531, DOI: 10.3390/coatings10060531

(1) Background: The high-voltage anodic-plasma (HVAP) coating technique has a series of specificities that are not simultaneously met in other deposition methods. This paper aimed at assessing the potential of HVAP to synthesize quality multilayers for X-ray optics. (2) Methods: Nanolayers of W, Ta, B, and Si were deposited as mono-, bi-, and multilayers onto very smooth glass substrates by HVAP, and their thickness and density were analyzed by X-ray reflectometry. The minimal film thickness needed to obtain continuous nanolayers was also investigated. (3) Results: Nanolayer roughness did not increase with layer thickness, and could be lowered via deposition rate, with values as low as 0.6 for the W nanolayer. Minimal film thickness for continuous films for the studied metals was 4 nm (W), 6 nm (Ta), 2.5 nm (B), and 6 nm (Si). (4) Conclusions: The investigation revealed the range of parameters to be used for obtaining quality nanolayers and multilayers by HVAP. Advantages and possible improvements are discussed. This deposition technique can be tailored for demanding applications such as X-ray mirrors.

Open Access

772. Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5T

Authors: Badica, P; Aldica, G; Grigoroscuta, MA; Burdusel, M; Pasuk, ; Batalu, D; Berger, K; Koblischka-Veneva, A; Koblischka, MR

Published: JUN 29 2020, SCIENTIFIC REPORTS, 10, 10538, DOI: 10.1038/s41598-020-67463-y

Bulk discs (20 mm diameter and 4.3 mm thickness) of MgB2 added with Ge2C6H10O7 were obtained by Spark Plasma Sintering. Six samples with composition Mg B 2 (Ge2C6H10O7)(0.0014) and one undoped sample were fabricated under similar conditions and were magnetically characterized in order to determine the scattering of properties and reproducibility. The main source of the scattering of the properties is the decomposition of the additive due to elimination of the organic part in gas form, which occurs stepwise with intensive vacuum drops at around similar to 560 and similar to 740 degrees C. A third drop, which is sometimes not well resolved being part of the second peak at 740 degrees C, occurs at similar to 820 degrees C. The critical temperature at the midpoint of the transition, T-C, shows only a relatively small variation between 37.4 and 38 K, and the irreversibility field at a low temperature of 5 K takes values between 8 and 10 T. The pinning force and pinning force related parameters do not correlate with the carbon substituting for boron in MgB2 and suggest a synergetic influence of the microstructural details and carbon. Overall, despite the superconducting properties scattering, the samples are of high quality. Stacked into a column of six samples, they can trap at the center and on the surface of the column a magnetic field of 6.78 and 5.19 Tat 12 K, 5.20 and 3.98 Tat 20 K and 2.39, and 1.96 Tat 30 K. These promising values, combined with facile fabrication of the samples with relatively high quality and reproducibility, show the feasibility of their use in building complex and large compound arrangements for bulk magnets and other applications.

Open Access

773. Influence of Reduced Graphene Oxide on the Electropolymerization of 5-Amino-1-naphthol and the Interaction of 1,4-Phenylene Diisothiocyanate with the Poly(5-Amino-1-naphtol)/Reduced Graphene Oxide Composite

Authors: Baibarac, M; Daescu, M; Socol, M; Bartha, C; Negrila, C; Fejer, SN

Published: JUN 2020, POLYMERS, 12, 1299, DOI: 10.3390/polym12061299

A new composite base on reduced graphene oxide (RGO) and poly(5-amino-1-naphthol) (P5A1N) was synthesized by the electrochemical polymerization of 5-amino-1-naphthol (5A1N) in the presence of HClO(4)and H(4)SiW(12)O(40)onto the surface of Au electrode covered with the RGO sheets. The linear dependence of the current densities of the anodic and cathodic peaks with the scan rate of the potential range (0; 0.8) V vs. SCE, reported during electropolymerization of 5A1N, indicates an electron transfer that is controlled by diffusion. A covalent functionalization of the RGO sheets with P5A1N is argued by: (i) the simultaneous disappearance of the IR band at 1584 cm(-1)and the appearance of the new IR bands at 812, 976 and 3744 cm(-1), and (ii) the appearance of two Raman lines at 738 and 1428 cm(-1). An application of the RGO sheets covalently functionalized with P5A1N is demonstrated to support 1,4-phenylene diisothiocyanate (PDITC), a compound used as a cross-linking agent for various biological applications. The chemical adsorption of PDITC onto the RGO sheets covalently functionalized with P5A1N, which involves the appearance of new functional groups of the type thiourea, was proven by Raman scattering and IR spectroscopy.

774. Exploring the effect of aliovalent substitution of Pb²⁺ by Eu³⁺ on structural, morphological and optical properties of CH3NH3PbI3 perovskite films

Authors: Derbali, S; Nouneh, K; Florea, M; Neatu, F; Neatu, S; Leonat, LN; Secu, M; Tomulescu, AG; Stancu, V; Pintilie, L; Touhami, ME; Galca, AC

Published: APR 2020, PHYSICA SCRIPTA, 95, 044003, DOI: 10.1088/1402-4896/ab5baa

In this work, the effect of aliovalent substitution of Pb2+ by Eu3+ on structural, morphological and optical properties of CH3NH3PbI3 (MAPbI(3)) was studied, aiming to improve the properties of perovskite films used in solar cells application. The surface morphology, the microstructure and the optical properties of the obtained films containing different Europium (Eu) concentrations were characterized by atomic force microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, UV-vis spectroscopy and photoluminescence spectroscopy.

Open Access

775. SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

Authors: Stavarache, I; Logofatu, C; Sultan, MT; Manolescu, A; Svavarsson, HG; Teodorescu, VS; Ciurea, ML

Published: FEB 24 2020, SCIENTIFIC REPORTS, 10, 3252, DOI: 10.1038/s41598-020-60000-x

Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NC s composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 degrees C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 10(3) times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 degrees C annealed films to 1210 nm for those at 1000 degrees C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 degrees C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW(-1).

776. HfO2-Al2O3 Dielectric Layer for a Performing Metal-Ferroelectric-Insulator-Semiconductor Structure with a Ferroelectric 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Thin Film

Authors: Silva, JPB; Sekhar, KC; Veltruská, K; Matolín, V; Negrea, RF; Ghica, C; Oliveira, MJS; Moreira, JA; Pereira, M; Gomes, MJM

Published: SEP 22 2020, ACS APPLIED ELECTRONIC MATERIALS, 2, DOI: 10.1021/acsaelm.0c00480

In this work, the ferroelectric and fatigue characteristics of Au/0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3(BCZT)/Si metal-ferroelectric-semiconductor (MFS) structures are investigated. Moreover, the effect of introducing a thin dielectric HfO2-Al2O3 (HAO) layer with different thicknesses between the BCZT layer and the Si substrate on the ferroelectric characteristics in the metal-ferroelectric-insulator-semiconductor (MFIS) configuration is evaluated. It is evidenced that the insertion of the HAO layer with a thickness of 8 nm improves the memory window of the capacitance-voltage (C-V) curves by 106% compared to the value obtained in the MFS structure and reduces the leakage currents. Furthermore, the Au/BCZT/HAO (8 nm)/Si structure shows a remarkable remnant polarization (P-r) of 7.8 mu C/cm(2), with a coercive voltage of 1.9 V. The obtained value for P-r corresponds to a six times enhancement when compared to the value obtained in the Au/BCZT/Si structure. In addition, the fatigue studies reveal that the P-r obtained in the Au/BCZT/HAO/Si structure slightly decreases (3%) with continuous cycling, up to 10(9) cycles. The present work evidences that Au/BCZT/HAO/Si structures are promising for nonvolatile memory applications.

Open Access

777. MORPHOLOGICAL AND STRUCTURAL INVESTIGATION OF THE POLY(VINYL CHLORIDE)/GRAPHENE OXIDE COMPOSITES

Authors: Stingescu, L; Cadar, C; Cotet, LC; Baia, L; Saszet, K; Magyari, K; Mihis, AG; Fort, CI; Stroe, M; Matei, E; Nila, A; Anghel, I; Baia, M; Baibarac, M; Danciu, V

Published: 2020, STUDIA UNIVERSITATIS BABES-BOLYAI CHEMIA, 65, DOI: 10.24193/subbchem.2020.3.19

The morphological and structural properties of the poly(vinyl chloride)/graphene oxide (PVC/GO) composites are reported. By the mixture of the two constituents, the PVC/GO composite membranes with a concentration of the GO sheets varying from 0 wt.% to 0.5, 1, 2, 3, 4 and 5 wt.% were prepared. Using scanning electron microscopy (SEM) and the analysis of the atomic force microscopy (AFM) images we observed that as increasing the GO concentration in the PVC mass from 0 wt.% to 5 wt.%, the average surface roughness decreases from 235 mu m to 227 mu m. Using Raman scattering, we report that as increasing the GO concentration in the PVC mass, the ratio between the relative intensities of the Raman lines situated in the spectral ranges 600-650 and 2850-3000 cm(-1) (I600-650/I2850-3000) increases as a consequence of the change of GO carbon atoms hybridization from sp(2) to sp(3). An increase in the number of C-C bonds, simultaneous with the appearance of O-C=O bonds and the decrease of the chlorine concentration, when the GO concentration increases in the PVC weight is reported by X-ray photoelectron spectroscopy (XPS). The down-shift of the main diffraction signal from 24 degrees to 26 degrees when the GO concentration increases in the PVC/GO composite mass from 0 wt.% to 5 wt.%, confirms the incorporation of GO in the polymeric matrix and the modification of the original PVC sample structure. Using transmission electron microscopy (TEM), no agglomerations of the GO structures within the PVC/GO matrix contrast limit were observed.

778. Energy storage performance of ferroelectric ZrO2film capacitors: effect of HfO2:Al2O3dielectric insert layer

Authors: Silva, JPB; Silva, JMB; Sekhar, KC; Palneedi, H; Istrate, MC; Negrea, RF; Ghica, C; Chahboun, A; Pereira, M; Gomes, MJM

Published: JUL 28 2020, JOURNAL OF MATERIALS CHEMISTRY A, 8, DOI: 10.1039/d0ta04984k

The present work reports for the first time, the employment of ferroelectric ZrO(2)films as energy storage capacitors utilized in pulsed power systems. Furthermore, the effect of insertion of a low permittivity dielectric HfO2:Al2O3(HAO) layer, with a thickness ranging from 2 to 8 nm, on the tunability of ferroelectric and energy storage characteristics of ZrO(2)films is assessed. The increase in thickness of the HAO layer gave rise to distorted ferroelectric loops with decreased polarization, coercive field, and hysteresis loss of the films. These results are correlated with the depolarization field induced by the insertion of the dielectric HAO layer. An optimum combination of high energy density of 54.3 J cm(-3)and good storage efficiency of 51.3% are obtained for the ZrO(2)film capacitors with 2 nm-thick HAO insert layer. These values correspond to an increase of similar to 55% and similar to 92%, from the respective values of pure ZrO(2)film capacitors. In addition, the HAO/ZrO(2)films showed a good fatigue endurance of energy storage performance over 10(9)electric field cycles. The energy storage density obtained from HAO(2 nm)/ZrO(2)film capacitor is found to be higher than that reported for several Pb-based as well as Pb-free ferroelectric ceramic films with complex compositions. The present study demonstrates that simple binary oxides such as ZrO(2)with ferroelectric behavior could be potential candidates for developing high performance energy storage capacitors.

Open Access

779. Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles

Authors: Toulbe, N; Stroe, MS; Daescu, M; Cercel, R; Mogos, A; Dragoman, D; Socol, M; Mercioniu, I; Baibarac, M

Published: NOV 2020, NANOMATERIALS, 10, 2238, DOI: 10.3390/nano10112238

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of alpha-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines' position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets.

780. Influence of SiGe Nanocrystallization on Short-Wave Infrared Sensitivity of SiGe-TiO2 Films and Multilayers

Authors: Lepadatu, AM; Palade, C; Slav, A; Cojocaru, O; Maraloiu, VA; Iftimie, S; Comanescu, F; Dinescu, A; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: NOV 12 2020, JOURNAL OF PHYSICAL CHEMISTRY C, 124, DOI: 10.1021/acs.jpcc.0c06290

Continuous development of Si photonics requires ecological and cost-effective materials. In this work, SiGe nanocrystals (NCs) embedded in TiO2 are investigated as a photosensitive material for visible (VIS) to short-wave infrared (SWIR) broad-range detection. The TiO2 matrix has the advantage of a lower band gap than SiO2, facilitating transport of photogenerated carriers in NCs. The advantage of SiGe NCs over Ge NCs is emphasized by elucidating the mechanisms involved in rapid thermal annealing (RTA)-induced nanocrystallization. An efficiently increased NC stabilization is achieved by avoiding the detrimental fast Ge diffusion. For this, the structure, morphology, and composition were carefully characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. Two types of structures were investigated, a film of SiGe-TiO2 alloy and a multilayer of a stack of six SiGe/TiO2 pairs. The layers have been deposited on Si wafers using magnetron sputtering of Si, Ge, and TiO2 followed by RTA in an inert atmosphere. The stabilization of SiGe NCs is achieved by the formation during RTA of protective SiO2 thin layers through Si oxidation at the SiGe NC surface, acting as a barrier for Ge diffusion. Thus, embedded Ge-rich SiGe NCs are obtained, resulting in the SWIR extension of the spectral photocurrent up to 1700 nm for films and 1600 nm for multilayers. This study has shown that in multilayers, the local anisotropy of crystallization is compensated by the stress field developed in the SiGe lattice, highly visible in the bottom part. Also, SiGe crystallizes faster than TiO2 in the rutile phase, and therefore, TiO2 remains mainly amorphous.

781. Influence of boric acid concentration on the properties of electrodeposited CZTS absorber layers

Authors: Zaki, MY; Nouneh, K; Touhami, ME; Matei, E; Badica, P; Burdusel, M; Negrila, CC; Baibarac, M; Pintilie, L; Galca, AC

Published: MAY 2020, PHYSICA SCRIPTA, 95, 054001, DOI: 10.1088/1402-4896/ab6afd

This work involves the synthesis and characterization of Cu2ZnSnS4 (CZTS) layers. The films were prepared on Mo/glass substrates by single-step electrodeposition method followed by sulfurization at 500 degrees C under argon flow. The effect of boric acid concentration on the crystallographic structure, compositional and morphological properties of CZTS films was investigated, with the objective to understand the growth behavior and to enhance the film properties. Cyclic Voltammetry was used in order to estimate the adequate deposition potential for the CZT alloy. The x-ray diffraction analysis showed the formation of the kesterite phase in all the samples. The Raman and x-ray photoelectron spectroscopy studies confirmed the existence of the CZTS phase. The scanning electron microscopy was employed to inspect the films structure. The results indicated that increasing the concentration of boric acid affects the physico-chemical properties of the films.

782. Reusable on-plate immunoprecipitation method with covalently immobilized antibodies on a protein G covered microtiter plate

Authors: Korodi, M; Rákosi, K; Baibarac, M; Fejer, SN

Published: AUG 2020, JOURNAL OF IMMUNOLOGICAL METHODS, 483, 112812, DOI: 10.1016/j.jim.2020.112812

Covalent immobilization of antibodies to protein G beads is a basic molecular biology method, although the beads present poor recovery results. Our aim was to reuse the immobilized antibody-protein G complex on a very small scale, therefore we optimized the crosslinking procedure to be used on the wells of a standard 96-well microplate. The method used involves the affinity binding of the antibody to the protein G surface, followed by the immobilization step using different crosslinking reagents, DMP and BS3, quenching the crosslinking reaction, and binding the antibody-specific antigen. By scaling down the procedure, we were able to reuse the anti-EGFR crosslinked wells more than 20 times. This method can be used to perform assays on a wide range of solid supports containing the protein G in an immobilized form, including functionalized nanosensors, for immunoprecipitation, protein and cell lysate purification, target protein enrichment.

Open Access

783. Robust conductance zeros in graphene quantum dots and other bipartite systems

Authors: Nita, M; Tolea, M; Marinescu, DC

Published: JUN 30 2020, PHYSICAL REVIEW B, 101, 235318, DOI: 10.1103/PhysRevB.101.235318

Within the Landauer transport formalism we demonstrate that conductance zeros are possible in bipartite systems at half-filling when leads are contacted to different sublattice sites. In particular, we investigate the application of this theory to graphene quantum dots with leads in the armchair configuration. The obtained conductance cancellation is robust in the presence of any single-site impurity.

784. Aminopropyl-silica functionalized with halogen-reactive compounds for antimicrobial applications

Authors: Zarafu, I; Al Taweel, AAJ; Limban, C; Popa, M; Marutescu, L; Chifiriuc, MC; Pircalabioru, GG; Culita, D; Ghica, C; Ionita, P

Published: FEB 1 2020, MATERIALS CHEMISTRY AND PHYSICS, 241, 122353, DOI: 10.1016/j.matchemphys.2019.122353

Aminopropyl-silica nanoparticles S0 were obtained and further functionalized with eight halogen-reactive organic compounds 1-8, leading to the S1-S8 hybrid organic-inorganic materials, with spherical morphology and having a 50-200 nm size, as showed TEM analysis. These were further characterized by IR and DLS. Biological assays were performed using five microbial strains, belonging to species frequently encountered in the aetiology of human infections (Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia toll and Candida albicans). The obtained materials exhibited promising antimicrobial properties, being active against planktonic, but particularly on biofilm-embedded cells. Among the tested hybrid nanomaterials, S6 seemed to exhibit the most promising antimicrobial profile.

785. High magnetic shielding properties of an MgB2 cup obtained by machining a spark-plasma-sintered bulk cylinder

Authors: Gozzelino, L; Gerbaldo, R; Ghigo, G; Torsello, D; Bonino, V; Truccato, M; Grigoroscuta, MA; Burdusel, M; Aldica, GV; Sandu, V; Pasuk, I; Badica, P

Published: APR 2020, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 33, 044018, DOI: 10.1088/1361-6668/ab7846

Superconductors are key materials for shielding quasi-static magnetic fields. In this work, we investigated the shielding properties of an MgB2 cup-shaped shield with small aspect-ratio of height/outer radius. Shape and aspect-ratio were chosen in order to address practical requirements of both high shielding factors (SFs) and space-saving solutions. To obtain large critical current densities (J(c)), which are crucial for achieving high magnetic-mitigation performance, a high-purity starting MgB2 powder was selected. Then, processing of the starting MgB2 powder into high density bulks was performed by spark plasma sintering. The as-obtained material is fully machinable and was shaped into a cup-shield. Assessment of the material by scaling of the pinning force showed a non-trivial pinning behaviour. The MgB2 powder selection was decisive in enlarging the range of external fields where efficient shielding occurs. The shield's properties were measured in both axial- and transverse-field configurations using Hall probes. Despite a height/outer radius aspect ratio of 2.2, shielding factors higher than 10(4) at T = 20 K up to a threshold field of 1.8 T were measured in axial-field geometry at a distance of 1 mm from the closed extremity of the cup, while SFs > 10(2) occurred in the inner half of the cup. As expected, this threshold field decreased with increased temperature, but SFs still exceeding the above mentioned values were found up to 0.35 T at 35 K. The shield's shape limits the SF values achievable in transverse-field configuration. Nevertheless, the in-field J(c) of the sample supported SFs over 40 at T = 20 K up to a field of 0.8 T, 1 mm away from the cup closure.

Open Access

786. Bound and stable vortex-antivortex pairs in high-Tc superconductors

Authors: Simmendinger, J; Bihler, M; Ionescu, AM; Weigand, M; Schütz, G; Albrecht, J

Published: DEC 2020, NEW JOURNAL OF PHYSICS, 22, 123035, DOI: 10.1088/1367-2630/abd123

787. Synthesis and characterization of conducting aniline and o-anisidine nanocomposites based on montmorillonite modified clay

Authors: Kenane, A; Galca, AC; Matei, E; Yahiaoui, A; Hachemaoui, A; Benkouider, AM; Bartha, C; Istrate, MC; Galatanu, M; Rasoga, O; Stanculescu, A

Published: JAN 2020, APPLIED CLAY SCIENCE, 184, 105395, DOI: 10.1016/j.clay.2019.105395

A study on clay mineral polymer nanocomposites (CPN), namely polyaniline/montmorillonite-cetyltrimethylammonium bromide (PANI/Mt-CTAB), poly o-anisidine/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS)/Mt-CTAB) and poly o-anisidine-co-aniline/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS-co-ANI)/Mt-CTAB), synthesized by oxidative chemical polymerization method is presented. The nanocomposites have been characterized by Fourier transform infrared spectroscopy, UV-vis spectroscopy, and cyclic voltammetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and thermogravimetry and differential scanning calorimetry analysis. By UV-vis measurements different electronic transitions for the CPNs were pointed out. The voltammograms indicate that the synthetized materials are electroactive. The FTIR analysis reveals the characteristic bands of the polymers and of the Mt-CTAB. The shift of the bands to higher/lower wavenumbers demonstrate the interaction between the pristine polymers macromolecular chains and the montmorillonite (Mt). The intercalation of the polymers inside the mineral clay was confirmed by the increased interlayer distance connected with the position of the 011 diffraction plane of the Mt., and the intercalation and exfoliation states were highlighted in the scanning and transmission electron microscopy images. The obtained results are encouraging in respect with the purpose to use them in the field of photovoltaic applications.

Open Access

788. Removal and Oxidation of As(III) from Water Using Iron Oxide Coated CTAB as Adsorbent

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Motelica-Heino, M

Published: AUG 2020, POLYMERS, 12, 1687, DOI: 10.3390/polym12081687

Iron oxides such as magnetite and maghemite coated with cetyltrimethylammonium bromide (CTAB) are very promising materials for wastewater treatment because iron oxide can be easily separated from solutions using the magnetic separation procedure Iron oxide (IO) coated CTAB was synthesized by an adapted co-precipitation method. In the present study, the IO-CTAB was used for removing arsenic from water for the first time. In the present study, the performance of iron oxide coated CTAB biocomposites as an adsorbent for arsenic removal from aqueous solutions was examined. X-ray diffraction (XRD) analysis and the results revealed a cubic phase Fd-3 m of Fe(3)O(4)with lattice a = 8.40 angstrom and average crystal size equal to 17.26 +/- 3 nm. The mean particle size calculated from transmission electron microscopy (TEM) was 19.86 +/- 1.7 nm. The results of the adsorption batch experiments and the data determined using the Langmuir and Freundlich models emphasized that IO-CTAB nanoparticles were favorable for the adsorption of As(III) ions from aqueous solutions. Ultrasound measurements have shown that IO-CTAB is a cost-effective biocomposite for removing arsenic from contaminated solutions. Moreover, x-ray photoelectron spectroscopy (XPS) has shown that during the process of arsenic absorption, there is oxidation from As(III) to As(V), which leads to a decrease in toxicity during this process. The results of the cytotoxic assays confirmed that the IO-CTAB nanoparticles did not induce any morphological changes in the HeLa cells and did not affect their proliferation after 24 h of incubation.

789. Epitaxial GeSn Obtained by High Power Impulse Magnetron Sputtering and the Heterojunction with Embedded GeSn Nanocrystals for Shortwave Infrared Detection

Authors: Dascalescu, I; Zoita, NC; Slav, A; Matei, E; Iftimie, S; Comanescu, F; Lepadatu, AM; Palade, C; Lazanu, S; Buca, D; Teodorescu, VS; Ciurea, ML; Braic, M; Stoica, T

Published: JUL 29 2020, ACS APPLIED MATERIALS & INTERFACES, 12, DOI: 10.1021/acsami.0c06212

GeSn alloys have the potential of extending the Si photonics functionality in shortwave infrared (SWIR) light emission and detection. Epitaxial GeSn layers were deposited on a relaxed Ge buffer on Si(100) wafer by using high power impulse magnetron sputtering (HiPI-MS). Detailed X-ray reciprocal space mapping and HRTEM investigations indicate higher crystalline quality of GeSn epitaxial layers deposited by Ge HiPI-MS compared to commonly used radio frequency magnetron sputtering (RF-MS). To obtain a rectifying heterostructure for SWIR light detection, a layer of GeSn nanocrystals (NCs) embedded in oxide was deposited on the epitaxial GeSn one. Embedded GeSn NCs are obtained by cosputtering deposition of (Ge1-xSnx)(1-y)(SiO2)(y) layers and subsequent rapid thermal annealing at a low temperature of 400 degrees C. Intrinsic GeSn structural defects give p-type behavior, while the presence of oxygen leads to the n-character of the embedded GeSn NCs. Such an embedded NCs/epitaxial GeSn p-n heterostructure shows superior photoelectrical response up to 3 orders of magnitude increase in the 1.2-2.5 mu m range, as compared to performances of diode based only on embedded NCs.

Open Access

790. Fundamental studies of hafnia-hematite nanoparticles

Authors: Ferris, L; Allwes, M; Diamandescu, L; Perrin, A; McHenry, M; Sorescu, M

Published: OCT 2020, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 145, 109567, DOI: 10.1016/j.jpcs.2020.109567

xHfO(2)-(1-x)alpha-Fe2O3 (x = 0.1, 0.3, 0.5 and 0.7) nanoparticles system was obtained using mechanochemical activation by high energy ball milling for time periods ranging from 0 to 12 h. X-ray diffraction patterns revealed the presence of two phases, a hafnium-doped hematite and an iron-doped hafnia, which competed with each other to form a solid solution. The trend observed in the lattice parameters using Rietveld refinement was consistent with differences in ionic radii between Hf and Fe. Crystallite sizes for both hematite and hafnia were analyzed as function of milling time using the Scherrer method and found to decrease down to similar to 15 nm for all molar concentrations used. Mossbauer spectroscopy revealed the presence of 1-5 sextets corresponding to different numbers of Hf nearest neighbors of Fe in the hematite structure. The different hyperfine magnetic fields could be resolved in the model of local atomic environment. Substitutions of Fe in hafnia gave rise to a nonmagnetic phase represented by a quadrupole split doublet, whose abundance was found to increase with ball milling time. Hysteresis loops recorded at 5 K showed that the Hf-doped system does not saturate in an applied magnetic field of 5 T. The Morin transition was observed during zero-field-cooling-field cooling (ZFC-FC) in an external magnetic field of 200 Oe. Differential scanning calorimetry with thermal gravimetric analysis (DSC-TGA) evidenced an exothermic peak for the starting oxides and an endothermic peak for the solid solution.

791. Synthesis and characterization of antibacterial drug loaded β-tricalcium phosphate powders for bone engineering applications

Authors: Topsakal, A; Ekren, N; Kilic, O; Oktar, FN; Mahirogullari, M; Ozkan, O; Sasmazel, HT; Turk, M; Bogdan, IM; Stan, GE; Gunduz, O

Published: JAN 21 2020, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 31, 16, DOI: 10.1007/s10856-019-6356-1

Powders of beta-tricalcium phosphate [beta-TCP, beta-Ca-3(PO4)(2)] and composite powders of beta-TCP and polyvinyl alcohol (PVA) were synthesized by using wet precipitation methods. First, the conditions for the preparation of single phase beta-TCP have been delineated. In the co-precipitation procedure, calcium nitrate and diammonium hydrogen phosphate were used as calcium and phosphorous precursors, respectively. The pH of the system was varied in the range 7-11 by adding designed amounts of ammonia solution. The filtered cakes were desiccated at 80 degrees C and subsequently calcined at different temperatures in the range between 700-1100 degrees C. Later on, rifampicin form II was used to produce drug-loaded beta-TCP and PVA/beta-TCP powders. All the synthesized materials have been characterized from morphological (by scanning electron microscopy) and structural-chemical (by X-ray diffraction and Fourier transform infrared spectroscopy) point of view. The drug loading capacity of the selected pure beta-TCP powder has been assessed. The biological performance (cytocompatibility in fibroblast cell culture and antibacterial efficacy against Escherichia coli and Staphylococcus aureus) has been tested with promising results. Application perspectives of the designed drug-bioceramic-polymer blends are advanced and discussed. [GRAPHICS] .

Open Access

792. GeSi Nanocrystals Photo-Sensors for Optical Detection of Slippery Road Conditions Combining Two Classification Algorithms

Authors: Palade, C; Stavarache, I; Stoica, T; Ciurea, ML

Published: NOV 2020, SENSORS, 20, 6395, DOI: 10.3390/s20216395

One of the key elements in assessing traffic safety on the roads is the detection of asphalt conditions. In this paper, we propose an optical sensor based on GeSi nanocrystals embedded in SiO2 matrix that discriminates between different slippery road conditions (wet and icy asphalt and asphalt covered with dirty ice) in respect to dry asphalt. The sensor is fabricated by magnetron sputtering deposition followed by rapid thermal annealing. The photodetector has spectral sensitivity in the 360-1350 nm range and the signal-noise ratio is 10(2)-10(3). The working principle of sensor setup for detection of road conditions is based on the photoresponse (photocurrent) of the sensor under illumination with the light reflected from the asphalt having different reflection coefficients for dry, wet, icy and dirty ice coatings. For this, the asphalt is illuminated sequentially with 980 and 1064 nm laser diodes. A database of these photocurrents is obtained for the different road conditions. We show that the use of both k-nearest neighbor and artificial neural networks classification algorithms enables a more accurate recognition of the class corresponding to a specific road state than in the case of using only one algorithm. This is achieved by comparing the new output sensor data with previously classified data for each algorithm and then by performing an intersection of the algorithms' results.

Open Access

793. Performant Composite Materials Based on Oxide Semiconductors and Metallic Nanoparticles Generated from Cloves and Mandarin Peel Extracts

Authors: Zgura, I; Enculescu, M; Istrate, C; Negrea, R; Bacalum, M; Nedelcu, L; Barbinta-Patrascu, ME

Published: NOV 2020, NANOMATERIALS, 10, 2146, DOI: 10.3390/nano10112146

In this work, the metal and semiconducting nanoparticles (AgNPs, ZnONPs and AgZnONPs) were phyto-synthesized using aqueous vegetal extracts from: Caryophyllus aromaticus L. (cloves) and Citrus reticulata L. (mandarin) peels. The morphological, structural, compositional, optical and biological properties (antibacterial activity, and cytotoxicity) of the prepared composites were investigated. The most effective sample proved to be AgZnONPs, derived from cloves, with a minimum inhibitory concentration (MIC) value of 0.11 mg/mL and a minimum bactericidal concentration (MBC) value of 2.68 mg/mL. All the other three composites inhibited bacterial growth at a concentration between 0.25 mg/mL and 0.37 mg/mL, with a bactericidal concentration between 3 mg/mL and 4 mg/mL. The obtained composites presented biocidal activity against Staphylococcus aureus, and biocompatibility (on human fibroblast BJ cells) and did not damage the human red blood cells. Additionally, an important result is that the presence of silver in composite materials improved the bactericidal action of these nanomaterials against the most common nosocomial pathogen, Staphylococcus aureus.

794. Characterization of C-Ti multilayer thin films obtained by TVA technology

Authors: Ciupina, V; Lungu, CP; Vladoiu, R; Prodan, GC; Porosnicu, C; Vasile, E; Prodan, M; Nicolescu, V; Dinca, V; Manu, R; Cupsa, O; Velea, A

Published: 2020, NANOENGINEERING: FABRICATION, PROPERTIES, OPTICS, THIN FILMS, AND DEVICES XVII, 11467, 114671R, DOI: 10.1117/12.2567927

Carbon-Titanium multilayer thin films were obtained by Thermionic Vacuum Arc (TVA) method. The nanostructured films consisting by 100nm Carbon base layer and seven 40nm alternatively Titanium and Carbon layers were deposed on Silicon substrate. As well, to give C-Ti multilayer films with different percentages in Ti and C of layers, a 100nm thick Carbon base layer was deposed on Si substrate, and then seven Ti-C layers, each of these having thickness of 40nm. In order to achieve the successively layers with C, and Ti different percentages, were adjusted the discharge parameters of C and Ti plasma sources to obtain the desired composition of layers. Also, were obtained composite films having a variable C: Ti atomic ratio 9:1 at interface to 1:9 at the surface. By changing of substrate temperature from room temperature to 100 degrees C, 200 degrees C, 300 degrees C, 400 degrees C respectively, and on the other hand the bias potential up to -700V, different batches of samples were obtained. Characterization of structural properties of films was achieved by Electron Microscopy technique (TEM, STEM) and GIXRD techniques. The measurements show that increase of the substrate temperature reveal changes in TixCy lattice parameters. Thus, according to GIXRD analysis it was found out that the Ti:C atomic ratio changes with increase of synthesis temperature. Also, in the case of composite films an increase of amount and sizes of TiC nanocrystals with the increase of energy of Ti ions determined by increase of bias voltage was observed. The tribological measurements were performed using a ball-on-disk system with normal forces of 0.5, 1, 2, 3N respectively. Was found that the coefficient of friction depends on the synthesis temperature and on the bias voltage. It is also noted that the friction coefficient depends on the pure C content, Ti content and amount of TiC nanocrystallites. These results are due to atomic diffusion at Ti/C interfaces and also are associated with amount of TiC nanocrystallites. To characterize the electrical conductive properties, the electrical surface resistance versus temperature have been measured, and then the electrical conductivity is calculated. Using the Wiedemann-Frantz law was obtained the thermal conductivity.

Open Access

795. Highly Active Transition Metal-Promoted CuCeMgAlO Mixed Oxide Catalysts Obtained from Multicationic LDH Precursors for the Total Oxidation of Methane

Authors: Al-Aani, HMS; Trandafir, MM; Fechete, I; Leonat, LN; Badea, M; Negrila, C; Popescu, I; Florea, M; Marcu, IC

Published: JUN 2020, CATALYSTS, 10, 613, DOI: 10.3390/catal10060613

To improve the catalytic performance of an active layered double hydroxide (LDH)-derived CuCeMgAlO mixed oxide catalyst in the total oxidation of methane, it was promoted with different transition-metal cations. Thus, two series of multicationic mixed oxides were prepared by the thermal decomposition at 750 degrees C of their corresponding LDH precursors synthesized by coprecipitation at constant pH of 10 under ambient atmosphere. The first series of catalysts consisted of four M(3)CuCeMgAlO mixed oxides containing 3 at.% M (M = Mn, Fe, Co, Ni), 15 at.% Cu, 10 at.% Ce (at.% with respect to cations), and with Mg/Al atomic ratio fixed to 3. The second series consisted of four Co(x)CuCeMgAlO mixed oxides withx= 1, 3, 6, and 9 at.% Co, while keeping constant the Cu and Ce contents and the Mg/Al atomic ratio. All the mixed oxides were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with X-ray energy dispersion analysis (EDX), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption at -196 degrees C, temperature-programmed reduction under hydrogen (H-2-TPR), and diffuse reflectance UV-VIS spectroscopy (DR UV-VIS), while thermogravimetric and differential thermal analyses (TG-DTG-DTA) together with XRD were used for the LDH precursors. The catalysts were evaluated in the total oxidation of methane, a test reaction for volatile organic compounds (VOC) abatement. Their catalytic performance was explained in correlation with their physicochemical properties and was compared with that of a reference Pd/Al(2)O(3)catalyst. Among the mixed oxides studied, Co(3)CuCeMgAlO was found to be the most active catalyst, with a temperature corresponding to 50% methane conversion (T-50) of 438 degrees C, which was only 19 degrees C higher than that of a reference Pd/Al(2)O(3)catalyst. On the other hand, this T(50)value was ca. 25 degrees C lower than that observed for the unpromoted CuCeMgAlO system, accounting for the improved performance of the Co-promoted catalyst, which also showed a good stability on stream.

796. Multilayer protective coatings obtained by pulsed laser deposition

Authors: Ion, V; Scarisoreanu, ND; Bonciu, A; Moldovan, A; Ghenescu, V; Ghenescu, M; Banciu, MG; Andrei, A; Dinescu, M

Published: JUN 15 2019, APPLIED SURFACE SCIENCE, 479, 1131, DOI: 10.1016/j.apsusc.2019.02.186

Devices developed for the aeronautic or space industries must be able to operate in harsh environments. In order to protect devices such as microstrip antennae, various coatings have to be used. Herein, we present the results of obtaining YSZ/Al2O3 heterostructures by Pulsed Laser Deposition (PLD) for the protection of planar monopole antennas without changing their performances after the deposition process. The theoretical SRIM-TRIM simulation code results on the effects of ionized radiations incident on a YSZ/Al2O3 heterostructure, as well as the physical properties of the YSZ/Al2O3 thin films obtained by the PLD technique are also presented. The SRIM studies show that at the same energy range the proton penetration depth is higher than the alpha penetration depth, giving insights about the penetration depth of proton and alpha particles in the studied targets. Our goal is to obtain a multilayer structure able to enhance the endurance of the antenna and microwave circuitry in harsh space environment without reducing the performances under nominal operation conditions.

797. Peppermint Essential Oil-Doped Hydroxyapatite Nanoparticles with Antimicrobial Properties

Authors: Badea, ML; Iconaru, SL; Groza, A; Chifiriuc, MC; Beuran, M; Predoi, D

Published: JUN 1 2019, MOLECULES, 24, DOI: 10.3390/molecules24112169

This study aimed at developing an antimicrobial material based on hydroxyapatite (HAp) and peppermint essential oil (P-EO) in order to stimulate the antimicrobial activity of hydroxyapatite. The molecular spectral features and morphology of the P-EO, HAp and hydroxyapatite coated with peppermint essential oil (HAp-P) were analyzed using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The coating of the HAp with the P-EO did not affect the ellipsoidal shape of the nanoparticles. The overlapping of IR bands of P-EO and HAp in the HAp-P spectrum determined the formation of the broad molecular bands that were observed in the spectral regions of 400-1000 cm(-1) and 1000-1200 cm(-1). The antibacterial activity of the P-EO, HAp and HAp-P were also tested against different Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) 388, S. aureus ATCC 25923, S. aureus ATCC 6538, E. faecium DSM 13590), Gram-negative bacteria (Escherichia coli ATCC 25922, E. coli C5, P. aeruginosa ATCC 27853, P. aeruginosa ATCC 9027) and a fungal strain of Candida parapsilosis. The results of the present study revealed that the antimicrobial activity of HAp-P increased significantly over that of HAp.

798. Multiferroic (Nd,Fe)-doped PbTiO3 thin films obtained by pulsed laser deposition

Authors: Dumitru-Grivei, M; Ion, V; Birjega, R; Moldovan, A; Craciun, F; Cernea, M; Galassi, C; Dinescu, M

Published: FEB 2019, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 125, DOI: 10.1007/s00339-019-2403-5

We report the successful growth of multiferroic (Nd,Fe)-doped PbTiO3 thin films with the composition (Pb0.88Nd0.08)(Ti0.93Fe0.05Mn0.02)O-3 (PNFT) using pulsed laser deposition. The deposited films have been investigated by XRD, SEM, energy-dispersive X-ray spectroscopy (EDS), secondary-ion mass spectroscopy (SIMS), atomic force microscopy, magnetic force microscopy, piezoforce microscopy, spectroscopic ellipsometry (SE) and dielectric spectroscopy measurements. PNFT films deposited on different substrates (MgO, SrTiO3 and Nb:SrTiO3) are (001) oriented, preserving the orientation of the single-crystal substrates. EDS mapping and SIMS across the film thickness probed the uniform distribution of all the elements. The refractive index and extinction coefficient have been obtained with the SE software package and refined with an optical-graded model. Magnetic domains and ferroelectric domains have been evidenced at microscopic scale. Good dielectric properties and low loss, comparable to those of bulk materials, have been obtained.

799. Fabrication of graphene-based electrochemical capacitors through reactive inverse matrix assisted pulsed laser evaporation

Authors: del Pino, AP; Ramadan, MA; Lebiere, PG; Ivan, R; Logofatu, C; Yousef, I; Gyorgy, E

Published: AUG 1 2019, APPLIED SURFACE SCIENCE, 484, 256, DOI: 10.1016/j.apsusc.2019.04.127

Electrodes constituted by nitrogen-doped reduced graphene oxide (NrGO) in combination with NiO nanostructures were fabricated by means of reactive inverse matrix assisted pulsed laser evaporation technique. The structure-composition of the electrode composites was tailored by laser-inducing chemical reactions of graphene oxide (GO) flakes with different precursor molecules (citric acid, ascorbic acid and imidazole) during GO deposition. Structural characterizations reveal the formation of wrinkles and nanoholes in the NrGO sheets, besides their coating with NiO nanostructures. Compositional studies disclose that imidazole precursor promotes the synthesis of NrGO with the largest degree of reduction and nitrogen doping (mainly with graphitic and pyridinic N). Electrochemical analyses of the obtained electrodes reveal that NiO nanostructures increase surface charge storage processes (double layer - pseudocapacitive) over diffusive ones, being the imidazole-based electrodes the ones exhibiting the best performance (up to 114 F cm(-3) at 10 mV s(-1)). Symmetric and asymmetric electro-chemical capacitors were also fabricated showing excellent robustness over 10,000 charge-discharge cycles at high specific currents.

800. The Effect of the Ionizing Radiation on Hydroxyapatite-Polydimethylsiloxane Layers

Authors: Groza, A; Iconaru, SL; Jiga, G; Chapon, P; Gaiaschi, S; Verga, N; Beuran, M; Prodan, AM; Matei, M; Marinescu, SA; Trusca, R; Predoi, D

Published: DEC 2019, POLYMER ENGINEERING AND SCIENCE, 59, 2412, DOI: 10.1002/pen.25247

The bio hydroxyapatite (HAp) was used from a long time in different medical and environmental applications. The HAp layers with a uniform surface were used for various medical applications such as orthopedic and dental metal implants. In this work, we reported on the influence of X-ray radiation on the structural and morphological properties of composite layers based on HAp and polydimethylsiloxane (PDMS) deposited on titanium substrates. The HAp:PDMS layers were investigated by different complementary methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and glow discharge optical emission spectrometry (GDOES). FTIR spectral analysis showed that the molecular structure of the coatings was not changed after their irradiation even though, the depth profile analysis performed by GDOES indicated a depletion of Ca and P elements from the HAp:PDMS irradiated samples. By SEM, we showed that the morphological features of the coatings were also changed, as the irradiated layers are delaminated. The biological assays confirmed that the antibacterial activity of HAp:PDMS composite layers increased after irradiation. The results obtained in this study highlighted that the biological properties of HAp:PDMS layers could be influenced by irradiation. (C) 2019 Society of Plastics Engineers.

801. Probing single-unit-cell resolved electronic structure modulations in oxide superlattices with standing-wave photoemission

Authors: Yang, W; Chandrasena, RU; Gu, M; dos Reis, RMS; Moon, EJ; Arab, A; Husanu, MA; Nemsak, S; Gullikson, EM; Ciston, J; Strocov, VN; Rondinelli, JM; May, SJ; Gray, AX

Published: SEP 9 2019, PHYSICAL REVIEW B, 100, DOI: 10.1103/PhysRevB.100.125119

Control of structural coupling at complex-oxide interfaces is a powerful platform for creating ultrathin layers with electronic and magnetic properties unattainable in the bulk. However, with the capability to design and control the electronic structure of such buried layers and interfaces at a unit-cell level, a new challenge emerges to be able to probe these engineered emergent phenomena with depth-dependent atomic resolution as well as element- and orbital selectivity. Here, we utilize a combination of core-level and valence-band soft x-ray standing-wave photoemission spectroscopy, in conjunction with scanning transmission electron microscopy, to probe the depth-dependent and single-unit-cell resolved electronic structure of an isovalent manganite superlattice [Eu0.7Sr0.3MnO3/La0.7Sr0.3MnO3] x 15 wherein the electronic-structural properties are intentionally modulated with depth via engineered oxygen octahedra rotations/tilts and A-site displacements. Our unit-cell resolved measurements reveal significant transformations in the local chemical and electronic valence-band states, which are consistent with the layer-resolved first-principles theoretical calculations, thus opening the door for future depth-resolved studies of a wide variety of heteroengineered material systems.

802. k-resolved electronic structure of buried heterostructure and impurity systems by soft-X-ray ARPES

Authors: Strocov, VN; Lev, LL; Kobayashi, M; Cancellieri, C; Husanu, MA; Chikina, A; Schroter, NBM; Wang, X; Krieger, JA; Salman, Z

Published: OCT 2019, JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 236, 8, DOI: 10.1016/j.elspec.2019.06.009

Angle-resolved photoelectron spectroscopy (ARPES) is the main experimental tool to explore electronic structure of solids resolved in the electron momentum k. Soft-X-ray ARPES (SX-ARPES), operating in a photon energy range around 1 keV, benefits from enhanced probing depth compared to the conventional VUV-range ARPES, and elemental/chemical state specificity achieved with resonant photoemission. These advantages make SX-ARPES ideally suited for buried heterostructure and impurity systems, which are at the heart of current and future electronics. These applications are illustrated here with a few pioneering results, including buried quantum-well states in semiconductor and oxide heterostructures, their bosonic coupling critically affecting electron transport, magnetic impurities in diluted magnetic semiconductors and topological materials, etc. High photon flux and detection efficiency are crucial for pushing the SX-ARPES experiment to these most photon-hungry cases.

803. Enhancement of the supercapacitive properties of laser deposited graphene-based electrodes through carbon nanotube loading and nitrogen doping

Authors: del Pino, AP; Lopez, MR; Ramadan, MA; Lebiere, PG; Logofatu, C; Martinez-Rovira, I; Yousef, I; Gyorgy, E

Published: DEC 7 2019, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 21, 25186, DOI: 10.1039/c9cp04237g

Several technological routes are being investigated for improving the energy storage capability and power delivery of electrochemical capacitors. In this work, ternary hybrid electrodes composed of conducting graphene/reduced graphene oxide (rGO), which store charge mainly through electric double-layer mechanisms, covered by NiO nanostructures, for adding pseudocapacitance, were fabricated through a matrix assisted pulsed laser evaporation technique. The incorporation of multiwall carbon nanotubes (MWCNTs) provokes an increase of the porosity and thus, a substantial enhancement of the electrodes' capacitance (from 4 to 20 F cm(-3) at 10 mV s(-1)). Volumetric capacitances of 34 F cm(-3) were also obtained with electrodes containing just carbon nanotubes coated with NiO nanostructures. Moreover, the use of nitrogen containing precursors (ammonia, urea) for laser-induced N-doping of the nanocarbons also provokes a notable increase of the capacitance. Remarkably, N-containing groups in rGO-MWCNTs mainly add electric double layer charge storage, pointing to an increase of electrode porosity, whereas redox reactions contribute with a minor diffusion fraction. It was also observed that the loading of carbon nanotubes leads to an increase of diffusion-controlled charge storage mechanisms versus capacitive ones in rGO-based electrodes, the opposite effect being observed in graphene electrodes.

804. Preparations of Silver/Montmorillonite Biocomposite Multilayers and Their Antifungal Activity

Authors: Iconaru, SL; Groza, A; Stan, GE; Predoi, D; Gaiaschi, S; Trusca, R; Chifiriuc, CM; Marutescu, L; Tite, T; Stanciu, GA; Hristu, R; Ghegoiu, L; Badea, ML; Turculet, CS; Ganciu, M; Chapon, P

Published: DEC 2019, COATINGS, 9, DOI: 10.3390/coatings9120817

In this study, the results about the influence of the surface morphology of layers based on montmorillonite (MMT) and silver (Ag) on antimicrobial properties are reported. The coating depositions were performed in the plasma of a radio frequency (RF) magnetron sputtering discharge. The studied layers were single montmorillonite layers (MMT) and silver/montmorillonite multilayers (MMT-Ag) obtained by magnetron sputtering technique with a different surface thickness. The resultant MMT-Ag biocomposite multilayers exhibited a uniform distribution of constituent elements and enhanced antimicrobial properties against fungal biofilm development. Glow-discharge optical emission spectroscopy (GDOES) analysis revealed the formation of MMT-Ag biocomposite multilayers following the deposit of a silver layer for an MMT layer that was initially deposited on a Si substrate. The surface morphology and thickness evaluation of deposited biocomposite layers were performed by scanning electron microscopy (SEM). A qualitative analysis of the chemical composition of thin layers was performed and the elements O, Ag, Mg, Fe, Al, and Si were identified in the MMT-Ag biocomposite multilayers. The in vitro antifungal assay proved that the inhibitory effect against the growth of Candida albicans ATCC 101231 CFU was more emphasized in the case of MMT-Ag biocomposite multilayers that in the case of the MMT layer. Cytotoxicity studies performed on HeLa cells showed that the tested layers did not show significant toxicity at the time intervals during which the assay was performed. On the other hand, it was observed that the MMT layers exhibited slightly higher biocompatible properties than the MMT-Ag composite layers.

805. The Quality of Fe14Cr ODS Powder Alloys During Milling and Upon Heating and Its Impact on the Mechanical Properties of Consolidated Steels

Authors: Mihalache, V; Walter, M; Mercioniu, I; Ordas, N

Published: JUL 2019, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 50A, 3294, DOI: 10.1007/s11661-019-05264-3

Oxide dispersion-strengthened ferritic steels (ODSFSs) are promising structural materials for applications in fusion and fission power reactors, but further improvement in their (high-temperature) mechanical properties and ferrite phase stability is required. This work demonstrates that an approach to produce Fe14Cr ODSFSs with a stable ferrite phase and improved strength could involve grain size strengthening by long-term milling with a tiny amount of nitrogen. Fe-14Cr-3W-0.4Ti-0.25Y(2)O(3) powders were ball-milled up to 170 hours under an argon atmosphere. In addition to X-ray diffraction, the change in product quality during milling and upon heating was thoroughly investigated by more sensitive magnetic and thermal analysis by measuring the saturation magnetization sigma(s), coercivity H-c, Curie temperature T-c, and temperature of ferrite-austenite (alpha ->gamma) transition T-alpha ->gamma. A pronounced modification of magnetic and microstructure parameters was observed when milling over 70 hours and upon heating above 800 degrees C and was found to be generated by long-term milling with a tiny amount of nitrogen. Upon heating, the nitrogen, incorporated during milling, developed a transition region, with the decomposition of nitrides precipitated at the earlier stage of heating followed by austenite decomposition, nitrogen degassing, and microstructure refinement to a grain size of a few tenths of a nm (e.g., 28 nm by heating at 910 degrees C of 100-hour milled powder). The resulting ferrite phase with refined grains is highly stable to (further) heating. The powders milled for 70 and 100 hours containing 0.175 and 0.500 wt pct nitrogen, respectively, were consolidated at 1100 degrees C with subsequent annealing at 1050 degrees C and subjected to Vickers hardness and 3-point bending tests. The steel produced from the powder milled for 70 hours shows lower hardness, higher density (close to the theoretical value of 7.8 g/cm(3)), and fracture strain. The ductility of this ODS alloy (0.075 fracture strain) is comparable with Eurofer97 (0.075 fracture strain), whereas its strength (2070 MPa ultimate stress) is significantly higher than that of Eurofer97 (1222 MPa ultimate stress). This improvement was attributed to grain size strengthening-the refined grains (promoted by milling with nitrogen) could be effectively pinned by Y-Ti-O dispersoids.

806. Direct Immobilization of Biomolecules through Magnetic Forces on Ni Electrodes via Ni Nanoparticles: Applications in Electrochemical Biosensors

Authors: Barsan, MM; Enache, TA; Preda, N; Stan, G; Apostol, NG; Matei, E; Kuncser, A; Diculescu, VC

Published: JUN 5 2019, ACS APPLIED MATERIALS & INTERFACES, 11, 19877, DOI: 10.1021/acsami.9b04990

The present work describes a new simple procedure for the direct immobilization of biomolecules on Ni electrodes using magnetic Ni nanoparticles (NiNPs) as biomolecule carriers. Ni electrodes were fabricated by electroplating, and NiNPs were chemically synthesized. The chemical composition, crystallinity, and granular size of Ni electrodes, NiNP, and NiNP-modified Ni electrodes (NiNP/Ni) were determined by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of Ni electrodes by cyclic voltammetry and electrochemical impedance spectroscopy confirmed the existence of nickel oxides, hydroxides, and oxohydroxide films at the surface of Ni. Magnetic characterization and micromagnetic simulations were performed in order to prove that the magnetic force is responsible for the immobilization process. Further, Ni electrodes were employed as amperometric sensors for the detection of hydrogen peroxide because it is an important performance indicator for a material to be applied in biosensing. The working principle for magnetic immobilization of the enzyme-functionalized NiNP, without the use of external magnetic sources, was demonstrated for glucose oxidase (GOx) as a model enzyme. XPS results enabled to identify the presence of GOx attached to the NiNP (GOx-NiNP) on Ni electrodes. Finally, glucose detection and quantification were evaluated with the newly developed GOx-NiNP/Ni biosensor by amperometry at different potentials, and control experiments at different electrode materials in the presence and absence of NiNP demonstrated their importance in the biosensor architecture.

807. Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH4 Catalytic Combustion

Authors: Neatu, S; Trandafir, MM; Stanoiu, A; Florea, OG; Simion, CE; Leonat, LN; Cobianu, C; Gheorghe, M; Florea, M; Neatu, F

Published: JUN 1 2019, MATERIALS, 12, DOI: 10.3390/ma12111771

This study presents the synthesis and characterization of lanthanum-modified alumina supported cerium-manganese mixed oxides, which were prepared by three different methods (coprecipitation, impregnation and citrate-based sol-gel method) followed by calcination at 500 degrees C. The physicochemical properties of the synthesized materials were investigated by various characterization techniques, namely: nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and H-2-temperature programmed reduction (TPR). This experimental study demonstrated that the role of the catalytic surface is much more important than the bulk one. Indeed, the incipient impregnation of CeO2-MnOx catalyst, supported on an optimized amount of 4 wt.% La2O3-Al2O3, provided the best results of the catalytic combustion of methane on our catalytic micro-convertors. This is mainly due to: (i) the highest pore size dimensions according to the Brunauer-Emmett-Teller (BET) investigations, (ii) the highest amount of Mn4+ or/and Ce4+ on the surface as revealed by XPS, (iii) the presence of a mixed phase (Ce2MnO6) as shown by X-ray diffraction; and (iv) a higher reducibility of Mn4+ or/and Ce4+ species as displayed by H-2-TPR and therefore more reactive oxygen species.

808. Extrinsic absorption in spark plasma sintered Zr0.8Sn0.2TiO4 ceramics investigated by terahertz time-domain spectroscopy

Authors: Nedelcu, L; Burdusel, M; Grigoroscuta, MA; Geambasu, CD; Banciu, MG; Badica, P

Published: 2019, 2019 44TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ), DOI:

Solid-state reaction synthesized Zr0.8Sn0.2TiO3 powders have been compacted by spark plasma sintering. In order to reduce the oxygen vacancies, the sintered samples were annealed ex-situ in air. Single-phase ceramics with different amount of oxygen vacancies and, consequently, different extrinsic absorption were investigated by terahertz time-domain spectroscopy. The results showed that the terahertz spectroscopy could be a suitable technique for tailoring the absorption properties of the spark plasma sintered materials.

809. Efficacy of annealing and fabrication parameters on photo-response of SiGe in TiO2 matrix

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Teodorescu, VS; Ciurea, ML; Svavarsson, HG

Published: SEP 6 2019, NANOTECHNOLOGY, 30, DOI: 10.1088/1361-6528/ab260e

SiGe nanoparticles dispersed in a dielectric matrix exhibit properties different from those of bulk and have shown great potential in devices for application in advanced optoelectronics. Annealing is a common fabrication step used to increase crystallinity and to form nanoparticles in such a system. A frequent downside of such annealing treatment is the formation of insulating SiO2 layer at the matrix/SiGe interface, degrading the optical properties of the structure. An annealing process that could bypass this downside would therefore be of great interest. In this work, a short-time furnace annealing of a SiGe/TiO2 system is applied to obtain SiGe nanoparticles without formation of the undesired SiO2 layer between the dielectric matrix (TiO2) and SiGe. The structures were prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A wide range spectral response with a response-threshold up to similar to 1300 nm was obtained, accompanied with an increase in photo-response of more than two-orders of magnitude. Scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy and grazing incidence x-ray diffraction were used to analyze the morphological changes in respective structures. Photoconductive properties were studied by measuring photocurrent spectra using applied dc-voltages at various temperatures.

810. Charge separation and ROS generation on tubular sodium titanates exposed to simulated solar light

Authors: Preda, S; Anastasescu, C; Balint, I; Umek, P; Sluban, M; Negrila, CC; Angelescu, DG; Bratan, V; Rusu, A; Zaharescu, M

Published: MAR 15 2019, APPLIED SURFACE SCIENCE, 470, 1063, DOI: 10.1016/j.apsusc.2018.11.194

The research focuses on a few key points concerning the light-driven processes taking place on TiO2 anatase and sodium titanates with tubular morphology, such as the relationship between the morphology and activity for H-2 and CO2 production, density of surface hydroxyl groups, ROS (center dot OH and center dot O-2(-)) production and photocatalytic activity, and charge separation at the interface of semiconducting domains and enhancement of activity. One key point discussed is whether the materials with peculiar morphologies (i.e. tubular) are superior to the conventional ones. The experimental evidences show that the main advantage of the tubular morphology of sodium titanate is given by its significantly higher surface area compared to parental anatase. FTIR and XPS progressive analyses evidence that the density of surface hydroxyl groups decreases with the development of the tubular morphology. The radical trapping experiments show that the variation of surface hydroxyl density is, generally, followed by activities for center dot OH and center dot O-2(-) generation, as well as by the photocatalytic production of H-2 and CO2 from water/methanol mixture. Consequently, the ROS, formed by action of photogenerated electrons and holes on adsorbed O-2 and hydroxyl groups, respectively, play an important role in determining the photocatalytic activity of titania-based materials. The other major aspect revealed by this research is that the charge separation at the interfaces formed between anatase and sodium titanate crystalline phases has remarkable effect on the activity formation rates of H-2 and CO2.

811. Antibacterial efficiency of alkali-free bio-glasses incorporating ZnO and/or SrO as therapeutic agents

Authors: Popa, AC; Fernandes, HR; Necsulescu, M; Luculescu, C; Cioangher, M; Dumitru, V; Stuart, BW; Grant, DM; Ferreira, JMF; Stan, GE

Published: MAR 2019, CERAMICS INTERNATIONAL, 45, 4380, DOI: 10.1016/j.ceramint.2018.11.112

A series of seven alkali-free silica-based bioactive glasses (SBG) with ZnO and/or SrO additives (in concentrations of 0-12 mol%) were synthesized by melt-quenching, aiming to delineate a candidate formulation possessing (i) a coefficient of thermal expansion (CTE) similar to the one of titanium (Ti) and its medical grade super alloys (crucial for the future development of mechanically adherent implant-type SBG coatings) and (ii) antibacterial efficiency, while (iii) conserving a good cytocompatibility. The SBGs powders were multi-parametrically evaluated by X-ray diffraction, Fourier transform infrared and micro-Raman spectroscopy, dilatometry, inductively coupled plasma mass spectrometry, antibacterial (against Staphylococcus aureus and Escherichia coli strains) suspension inhibition and agar diffusion tests, and human mesenchymal stem cells cytocompatibility assays. The results showed that the coupled incorporation of zinc and strontium ions into the parent glass composition has a combinatorial and additive benefit. In particular, the "Z6S4" formulation (mol%: SiO2-38.49, CaO-32.07, P2O5-5.61, MgO-13.24, CaF2-0.59, ZnO-6.0, SrO-4.0) conferred strong antimicrobial activity against both types of strains, minimal cytotoxicity combined with good stem cells viability and proliferation, and a CTE (similar to 8.7 x 10(-6) x degrees C-1) matching well those of the Ti-based implant materials.

812. Raman investigations on gamma irradiated iPP-VGCNF nanocomposites: The polymer's tale

Authors: Chipara, DM; Secu, C; Lozano, K; Secu, M; Chipara, M

Published: DEC 2019, SURFACES AND INTERFACES, 17, DOI: 10.1016/j.surfin.2019.100351

Raman investigations on nanocomposites obtained by loading various amounts of vapor grown carbon nanofibers within an isotactic polypropylene matrix, and gamma irradiated in air, at various integral doses ranging between 0 and 27 kGy, are reported. The analysis is focused on the polymer's answers as revealed by Raman spectroscopy and investigate in detail the effect of ionizing radiation on the position of the Raman line originating from the polymer. The as-obtained data are correlated to the elastic features of the nanocomposites. A competition between gamma irradiation and loading by carbon nanofiber, resulting in the stretching of the polymeric matrix and revealed as a displacement of Raman lines towards smaller wavenumber is reported. It is concluded that side groups (CH3) are less affected by the loading with carbon nanofibers,

813. Passively mode-locked self-frequency doubling Yb:LGSB laser

Authors: Porebski, M; Kowalczyk, M; Gheorghe, L; Greculeasa, M; Broasca, A; Voicu, F; Sotor, J

Published: 2019, 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), DOI:

814. Electrochemical assay for 20S proteasome activity and inhibition with anticancer drugs

Authors: de Jesus, CSH; Chiorcea-Paquim, AM; Barsan, MM; Diculescu, VC

Published: JUL 1 2019, TALANTA, 199, 39, DOI: 10.1016/j.talanta.2019.02.052

The majority of eukaryotic regulated protein turnover is performed by the proteasome, a multi-catalytic enzyme. Due to the fact that proteasome enzyme abnormal functioning was observed in different malignant cells, the proteasome is becoming a target for medical treatment. In order to evaluate the mechanisms of action of pharmaceutical compounds on proteasome enzyme inhibition, detecting and characterizing its activity is essential. An electrochemical assay that allows the monitoring of the chymotrypsin-like activity and inhibition of the 20S proteasome enzyme, based on the electrochemical detection of an electroactive compound released upon proteolysis of an adequate chymotrypsin-substrate is described. By employing differential pulse voltammetric measurement, the activity of the 20S proteasome enzyme was investigated for different incubation times of 20S with oligopeptide substrate as well as for different concentrations of substrate. Enzyme kinetic parameters were determined by voltammetry and the electrochemical assay compared with fluorescence spectroscopy. Electrochemical quartz crystal microbalance and atomic force microscopy were also used to investigate substrate interaction with the 20S proteasome and their adsorption at the electrode surface. Finally, the new electrochemical assay allowed to investigate the mechanisms of two different proteasome inhibitor drugs, bortezomib and oprozomib, underlying the applicability of the assay for understanding proteasome inhibitor action.

815. Next frontiers in cleaner synthesis: 3D printed graphene-supported CeZrLa mixed -oxide nanocatalyst for CO2 utilisation and direct propylene carbonate production

Authors: Middelkoop, V; Slater, T; Florea, M; Neatu, F; Danaci, S; Onyenkeadi, V; Boonen, K; Saha, B; Baragau, LA; Kellici, S

Published: MAR 20 2019, JOURNAL OF CLEANER PRODUCTION, 214, 614, DOI: 10.1016/j.jclepro.2018.12.274

A rapidly-growing 3D printing technology is innovatively employed for the manufacture of a new class of heterogenous catalysts for the conversion of CO2 into industrially relevant chemicals such as cyclic carbonates. For the first time, directly printed graphene-based 3D structured nanocatalysts have been developed combining the exceptional properties of graphene and active CeZrLa mixed-oxide nano particles. It constitutes a significant advance on previous attempts at 3D printing graphene inks in that it does not merely explore the printability itself, but enhances the efficiency of industrially relevant reactions, such as CO2 utilisation for direct propylene carbonate (PC) production in the absence of organic solvents. In comparison to the starting powder, 3D printed GO-supported CeZeLa catalysts showed improved activity with higher conversion and no noticeable change in selectivity. This can be attributed to the spatially uniform distribution of nanoparticles over the 2D and 3D surfaces, and the larger surface area and pore volume of the printed structures. 3D printed GO-supported CeZeLa catalysts compared to unsupported 3D printed samples exhibited higher selectivity and yield owing to the great number of new weak acid sites appearing in the supported sample, as observed by NH3-TPD analysis. In addition, the catalyst's facile separation from the product has the capacity to massively reduce materials and operating costs resulting in increased sustainability. It convincingly shows the potential of these printing technologies in revolutionising the way catalysts and catalytic reactors are designed in the general quest for clean technologies and greener chemistry. 2019 Elsevier Ltd. All rights reserved.

816. The influence of UV light on the azathioprine photodegradation: New evidences by photoluminescence

Authors: Smaranda, I; Nila, A; Manta, CM; Samohvalov, D; Gherca, D; Baibarac, M

Published: SEP 2019, RESULTS IN PHYSICS, 14, DOI: 10.1016/j.rinp.2019.102443

In this work, we report a photodegradation process of azathioprine (AZA) highlighted by correlated studies of photoluminescence (PL) and the UV-VIS and IR absorption spectroscopy. The photodegradation process of AZA is observed by the gradual increasing in the intensity of the PL spectrum recorded under the excitation wavelength of 300 nm. This behaviour is accompanied, in the photoluminescence excitation (PLE) spectra, by a gradual intensity decreasing of the PLE band situated in the 250-320 nm spectral range simultaneous with the intensity increasing of the PLE band localized in the 325-425 nm spectral range. Regardless if the immunosuppressive compound is in the state of powder, tablet or solution, the PL and UV-VIS absorption spectroscopy studies have demonstrated that a photodegradation process under UV light takes place. According to the PL studies carried out in ambient and vacuum condition, the photodegradation process of AZA was demonstrated to be influenced by the oxygen from air. The presence of a new IR band with maximum at 1745 cm(-1) confirms the AZA photodegradation pathway proposed in this work.

817. Isospin dynamics and nuclear dipolar degree of freedom

Authors: Papa, M; Barcenau, I; Acosta, L; Cardella, G; Gnoffo, B; Lanzalone, J; Lombardo, I; Maiolino, C; Pagano, A; Pagano, EV; Pirrone, S; Politi, G; Porto, F; Russotto, P; Trifiro, A; Trimarchi, M; Verde, G; Vigilante, M

Published: MAR-JUN 2019, NUOVO CIMENTO C-COLLOQUIA AND COMMUNICATIONS IN PHYSICS, 42, DOI: 10.1393/ncc/i2019-19103-1

The strong connection between the dipolar signal as obtained from the measured velocities and charge of all fragments produced in a heavy collision and the dynamics of the isospin equilibration processes is illustrated. Effects due to both statistical and dynamical mechanisms are shortly discussed. Experimental data related to semi-peripheral collisions induced on the Ca-48 + Al-27 at 40 MeV/nucleon system are also shown and compared with CoMD-III calculations.

818. Laser Processed Antimicrobial Nanocomposite Based on Polyaniline Grafted Lignin Loaded with Gentamicin-Functionalized Magnetite

Authors: Visan, AI; Popescu-Pelin, G; Gherasim, O; Grumezescu, V; Socol, M; Zgura, I; Florica, C; Popescu, RC; Savu, D; Holban, AM; Cristescu, R; Matei, CE; Socol, G

Published: FEB 2019, POLYMERS, 11, DOI: 10.3390/polym11020283

Composite thin coatings of conductive polymer (polyaniline grafted lignin, PANI-LIG) embedded with aminoglycoside Gentamicin sulfate (GS) or magnetite nanoparticles loaded with GS (Fe3O4@GS) were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. The aim was to obtain such nanostructured coatings for titanium-based biomedical surfaces, which would induce multi-functional properties to implantable devices, such as the controlled release of the therapeutically active substance under the action of a magnetic and/or electric field. Thus, the unaltered laser transfer of the initial biomaterials was reported, and the deposited thin coatings exhibited an appropriate nanostructured surface, suitable for bone-related applications. The laser processing of PANI-LIG materials had a meaningful impact on the composites' wettability, since the contact angle values corresponding to the composite laser processed materials decreased in comparison with pristine conductive polymer coatings, indicating more hydrophilic surfaces. The corrosion resistant structures exhibited significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans strains. In vitro cytotoxicity studies demonstrated that the PANI-LIG-modified titanium substrates can allow growth of bone-like cells. These results encourage further assessment of this type of biomaterial for their application in controlled drug release at implantation sites by external activation.

819. Biocompatible Layers Obtained from Functionalized Iron Oxide Nanoparticles in Suspension

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Buton, N; Megier, C; Motelica-Heino, M

Published: DEC 2019, COATINGS, 9, DOI: 10.3390/coatings9120773

Iron oxide nanoparticles have been extensively studied for challenges in applicable areas such as medicine, pharmacy, and the environment. The functionalization of iron oxide nanoparticles with dextran opens new prospects for application. Suspension characterization methods such as dynamic light scattering (DLS) and zeta potential (ZP) have allowed us to obtain information regarding the stability and hydrodynamic diameter of these suspended particles. For rigorous characterization of the suspension of dextran-coated iron oxide nanoparticles (D-MNPs), studies have been performed using ultrasound measurements. The results obtained from DLS and ZP studies were compared with those obtained from ultrasound measurements. The obtained results show a good stability of D-MNPs. A comparison between the D-MNP dimension obtained from transmission electron microscopy (TEM), X-ray diffraction (XRD), and DLS studies was also performed. A scanning electron spectroscopy (SEM) image of a surface D-MNP layer obtained from the stable suspension shows that the particles are spherical in shape. The topographies of the elemental maps of the D-MNP layer showed a uniform distribution of the constituent elements. The homogeneity of the layer was also observed. The morphology of the HeLa cells incubated for 24 and 48 h with the D-MNP suspension and D-MNP layers did not change relative to the morphology presented by the control cells. The cytotoxicity studies conducted at different time intervals have shown that a slight decrease in the HeLa cell viability after 48 h of incubation for both samples was observed.

820. GeSn Nanocrystals in GeSnSiO2 by Magnetron Sputtering for Short-Wave Infrared Detection

Authors: Slav, A; Palade, C; Logofatu, C; Dascalescu, I; Lepadatu, AM; Stavarache, I; Comanescu, F; Iftimie, S; Antohe, S; Lazanu, S; Teodorescu, VS; Buca, D; Ciurea, ML; Braic, M; Stoica, T

Published: JUN 2019, ACS APPLIED NANO MATERIALS, 2, +, DOI: 10.1021/acsanm.9b00571

Detection in short-wave infrared (SWIR) has become a very stringent technology requirement for developing fields like hyperspectral imaging or climate changes. In a market dominated by III-V materials, GeSn, a Si compatible semiconductor, has the advantage of cost efficiency and inerrability by using the mature Si technology. Despite the recent progress in material growth, the easy fabrication of crystalline GeSn still remains a major challenge, and different methods are under investigation. We present the formation of GeSn nanocrystals (NCs) embedded in oxide matrix and their SWIR characterization. The simple and cost-effective fabrication method is based on thermal treatment of amorphous (Ge1-xSnx)(y)(SiO2)(1-y) layers deposited by magnetron sputtering. The nanocrystallization for Ge1-xSnx with 9-22 at. % Sn composition in SiO2 matrix with 9% to 15% mole percent was studied under low thermal budget annealing in the 350-450 degrees C temperature range. While the Sn at.% content is the main parameter influencing the band-structure of the NCs, the SWIR sensitivity can be optimized by SiO2 content and H-2 gas component in the deposition atmosphere. Their role is not only changing the crystallization parameters but also to reduce the carrier recombination by passivation of NCs defects. The experiments indicate a limited composition dependent temperature range for GeSn NCs formation before beta-Sn phase segregation occurs. NCs with an average size of 6 nm are uniformly distributed in the film, except the surface region where larger GeSn NCs are formed. Spectral photovoltaic current measured on SiO2 embedded GeSn NCs deposited on p-Si substrate shows extended SWIR sensitivity up to 2.4 mu m for 15 at. % Sn in GeSn NCs. The large extension of the SWIR detection is a result of many factors related to the growth parameters and also to the in situ or ex situ annealing procedures that influence the uniformity and size distribution of NCs.

821. Impact on Ferroelectricity and Band Alignment of Gradually Grown Au on BaTiO3

Authors: Popescu, DG; Husanu, MA; Chirila, C; Pintilie, L; Teodorescu, CM

Published: JUL 2019, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 13, DOI: 10.1002/pssr.201900077

The competition between interface barrier in the Schottky-Mott limit and polarization driven mechanism is established during gradual formation of metal (Au) - ferroelectric (BaTiO3) interface. X-ray photoelectron spectroscopy provides core level energies and valence band positions in the contact region, to monitor the band alignment from the very first stages of metal deposition on BaTiO3. The band bending at metal/ferroelectric (FE) interface is extracted from the shift of core levels (Ba 3d, Ti 2p) as a function of the metal thickness. It is shown that the interface band alignment mechanism involves a well-defined polarization orientation washing out the bending expected from the work function difference. The sudden modification of the binding energies within ferroelectric at the first 2 angstrom Au indicates that the ferroelectric compensation mechanism triggered by the metal overlayer initiates already at ultrathin top layer, while subsequent growth contributes only at a gradual correction of the potential in the FE. The emerging picture is confirmed in first-principle calculation indicating the preferences of Au to grow preferentially to different terminated regions and to stabilize distinct ferroelectric polarization.

822. Conductance Model for Single-Crystalline/Compact Metal Oxide Gas-Sensing Layers in the Nondegenerate Limit: Example of Epitaxial SnO2(101)

Authors: Simion, CE; Schipani, F; Papadogianni, A; Stanoiu, A; Budde, M; Oprea, A; Weimar, U; Bierwagen, O; Barsan, N

Published: SEP 2019, ACS SENSORS, 4, 2428, DOI: 10.1021/acssensors.9b01018

Semiconducting metal oxide (SMOX)-based gas sensors are indispensable for safety and health applications, for example, explosive, toxic gas alarms, controls for intake into car cabins, and monitor for industrial processes. In the past, the sensor community has been studying polycrystalline materials as sensors where the porous and random microstructure of the SMOX does not allow a separation of the phenomena involved in the sensing process. This led to conduction models that can model and predict the behavior of the overall response, but they were not capable of giving fundamental information regarding the basic mechanisms taking place. The study of epitaxial layers is a definite improvement, allowing clarifying the different aspects and contributions of the sensing mechanisms. A detailed analytical model of the transduction function for n- and p-type single-crystalline/compact metal oxide gas sensors was developed that directly relates the conductance of the sample with changes in the surface electrostatic potential. Combined dc resistance and work function measurements were used in a compact SnO2(101) layer in operando conditions that allowed us to check the validity of our model in the region where Boltzmann approximation holds to determine the surface and bulk properties of the material.

823. Effect of dilute doping and non-equilibrium synthesis on the structural, luminescent and magnetic properties of nanocrystalline Zn1-xNixO (x=0.0025-0.03)

Authors: Mihalache, V; Negrila, C; Bercu, V; Secu, M; Vasile, E; Stan, GE

Published: JUL 2019, MATERIALS RESEARCH BULLETIN, 115, 48, DOI: 10.1016/j.materresbull.2019.03.001

We report on the influence of dilute doping combined with the processing conditions on the morphological, structural, chemical states, photoluminescence and magnetic properties of Zn1-xNixO nanopowders. Ni doping changes the ZnO powder morphology from randomly-aggregated nanocrystals to densely-packed nanocrystals arranged in columnar particles, modifies the high-energy-component of O1 s spectrum and increases the modified Auger parameter in XPS, enhances the blue photoluminescence (PL) emission, suppresses the green PL emission and the intensity of the g = 1.997 EPR signal. Ni-ZnO nanostructures show room-temperature ferro-magnetism (implying they can serve as dilute magnetic semiconductors). The saturation magnetization, crystallite size and microstrain increase with the doping level; the c-axis constant and unit cell volume decrease, however, being unexpectedly higher with respect to a (reference) ZnO powder with a relaxed lattice. We demonstrate that the investigated properties were controlled by both (dilute) doping level and donor native defects produced by non-equilibrium (oxygen-deficiency and high rate of) ZnO formation.

824. Nanoclustered Pd decorated nanocrystalline Zn doped SnO2 for ppb NO2 detection at low temperature

Authors: Somacescu, S; Ghica, C; Simion, CE; Kuncser, AC; Vlaicu, AM; Stefan, M; Ghica, D; Florea, OG; Mercioniu, IF; Stanoiu, A

Published: SEP 1 2019, SENSORS AND ACTUATORS B-CHEMICAL, 294, 156, DOI: 10.1016/j.snb.2019.05.033

Nanoclustered Pd (2 mol%) was used to decorate Zn doped SnO2 (10 mol% Zn) in order to increase its sensing performances. Zn doped SnO2 built from nanoparticles was prepared by a hydrothermal method using a nonionic surfactant -Brij52 and Tripropylamine (TPA) as co-templates. The presence of well-dispersed Zn2+ ions in the SnO2 matrix leads to a nonstoichiometric surface. Pd was deposited by subsequent wet impregnation using hydrazine as reducing agent. The as obtained powders were deposited as thick layers onto commercial substrates, in order to obtain the sensitive structures. The coexistence of a mixture of valence states (Pd-0, Pd2+ and Pd4+) was highlighted on the surface of the as prepared layers. Several aspects have been followed regarding the Zn and Pd dispersion into the SnO2 matrix: the large scale and low scale morphology (SEM and TEM/HRTEM) in relation with the synthesis route, the obtained crystallographic phases (XRD, SAED) and the way in which the Zn2+ ions are inserted into the SnO2 structure (XRD, XPS, EPR), the spatial distribution of the added chemical elements, Zn and Pd (SEM, STEM, EDS). All these morphological and structural aspects, as well as the Pd surface chemistry, have been correlated with the sensing properties of the nanostructured materials under controlled gas atmosphere. Through this study, we could harvest the specific role of the aforementioned loadings towards selective detection of low NO2 concentrations, between 350 ppb to 5 ppm, at low operating temperature of 100 degrees C, for infield conditions.

825. CuxCeMgAlO mixed oxide catalysts derived from multicationic LDH precursors for methane total oxidation

Authors: Al-Aani, HMS; Iro, E; Chirra, P; Fechete, I; Badea, M; Negrila, C; Popescu, I; Olea, M; Marcu, IC

Published: SEP 25 2019, APPLIED CATALYSIS A-GENERAL, 586, DOI: 10.1016/j.apcata.2019.117215

A series of five Cu(x)CeMgAlO mixed oxides with different copper contents (x) ranging from 6 to 18 at. % with respect to cations, but with fixed 10 at. % Ce and Mg/Al atomic ratio of 3, were prepared by thermal decomposition of layered double hydroxide (LDH) precursors at 750 degrees C. The solid containing 15 at. % Cu, i.e. Cu (15)CeMgAlO, was also calcined at 550 and 650 degrees C. Powder XRD was used to characterize the crystalline structure and SEM-EDX was used to monitor the morphology and chemical composition of both as prepared and calcined materials. Additionally, the textural properties and the reducibility of the mixed oxide catalysts were studied by nitrogen adsorption/desorption and temperature programmed reduction with hydrogen (H-2-TPR) techniques, respectively. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical state of the elements on the catalyst surface and the diffuse reflectance UV-vis spectroscopy, to obtain information about the stereochemistry and aggregation of copper in the Cu-containing mixed oxides. Their catalytic properties in the total oxidation of methane, used as a volatile organic compound (VOC) model molecule, were evaluated and compared with those of an industrial Pd/Al2O3 catalyst. Their catalytic behavior was explained in correlation with their physicochemical properties. Cu(15)CeMgAlO mixed oxide was shown to be the most active catalyst in this series, with a T-50 (temperature corresponding to 50% methane conversion) value of only ca. 45 degrees C higher than that of a commercial Pd/Al2O3 catalyst. This difference becomes as low as ca. 25 degrees C for the Cu(15)CeMgAlO system calcined at 550 degrees C. The influences of the contact time and of the methane concentration in the feed gas on the catalytic performances of the Cu(15)CeMgAlO catalyst have been investigated and its good stability on stream was evidenced.

826. Unveiling the double-well energy landscape in a ferroelectric layer

Authors: Hoffmann, M; Fengler, FPG; Herzig, M; Mittmann, T; Max, B; Schroeder, U; Negrea, R; Pintilie, L; Slesazeck, S; Mikolajick, T

Published: JAN 24 2019, NATURE, 565, +, DOI: 10.1038/s41586-018-0854-z

The properties of ferroelectric materials, which were discovered almost a century ago(1), have led to a huge range of applications, such as digital information storage(2), pyroelectric energy conversion(3) and neuromorphic computing(4,5). Recently, it was shown that ferroelectrics can have negative capacitance(6-11), which could improve the energy efficiency of conventional electronics beyond fundamental limits(12-14). In Landau-Ginzburg-Devonshire theory(15-17), this negative capacitance is directly related to the double-well shape of the ferroelectric polarization-energy landscape, which was thought for more than 70 years to be inaccessible to experiments(18). Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric Hf0.5Zr0.5O2. To achieve this, we integrated the ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has its origin in the energy barrier in a double-well landscape. Furthermore, we demonstrate that ferroelectric negative capacitance can be fast and hysteresis-free, which is important for prospective applications(19). In addition, the Hf0.5Zr0.5O2 used in this work is currently the most industry-relevant ferroelectric material, because both HfO2 and ZrO2 thin films are already used in everyday electronics(20). This could lead to fast adoption of negative capacitance effects in future products with markedly improved energy efficiency.

827. Mineralization-Inspired Synthesis of Magnetic Zeolitic Imidazole Framework Composites

Authors: Terzopoulou, A; Hoop, M; Chen, XZ; Hirt, AM; Charilaou, M; Shen, Y; Mushtaq, F; del Pino, AP; Logofatu, C; Simonelli, L; de Mello, AJ; Doonan, CJ; Sort, J; Nelson, BJ; Pane, S; Puigmarti-Luis, J

Published: SEP 16 2019, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 58, 13555, DOI: 10.1002/anie.201907389

Metal-organic frameworks (MOFs) capable of mobility and manipulation are attractive materials for potential applications in targeted drug delivery, catalysis, and small-scale machines. One way of rendering MOFs navigable is incorporating magnetically responsive nanostructures, which usually involve at least two preparation steps: the growth of the magnetic nanomaterial and its incorporation during the synthesis of the MOF crystals. Now, by using optimal combinations of salts and ligands, zeolitic imidazolate framework composite structures with ferrimagnetic behavior can be readily obtained via a one-step synthetic procedure, that is, without the incorporation of extrinsic magnetic components. The ferrimagnetism of the composite originates from binary oxides of iron and transition metals such as cobalt. This approach exhibits similarities to the natural mineralization of iron oxide species, as is observed in ores and in biomineralization.

828. Spectroscopic investigations of Pr3+ ions doped CNGG and CLNGG single crystals

Authors: Hau, S; Gheorghe, C; Gheorghe, L; Voicu, E; Greculeasa, M; Stanciu, G; Broasca, A; Enculescu, M

Published: AUG 30 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 799, 301, DOI: 10.1016/j.jallcom.2019.05.154

Spectroscopic characteristics of Pr3+ ions doped CNGG and CLNGG single crystals were investigated in order to assess their potential as laser materials for visible emission. The Judd-Ofelt intensity parameters for the f-f transitions of Pr3+ ions were used to determine spectroscopic and laser emission features. The temperature dependence of the absorption spectra for the H-3(4) -> P-3(0) transition was used to highlight the multicenter structure, different Stark levels, hot bands, and also the connection between the vibronic and electronic lines. The presence of electron-phonon interaction was also observed in the emission spectra corresponding to the P-3(0) -> H-3(4) transition under different excitation wavelengths. Based on low temperature absorption and emission spectra, partial energy level diagrams of Pr3+ ions doped in CNGG and CLNGG single crystals were obtained. The emission cross-sections for different transitions of Pr3+ ions were evaluated by the Fuchtbauer-Ladenburg formula. The fluorescence decay curve of the D-1(2) level was measured under selective excitation at different concentrations and temperatures. The concentration quenching process for the D-1(2) state was also studied. (C) 2019 Elsevier B.V. All rights reserved.

829. Theoretical and Experimental Study of (Ba,Sr)TiO3 Perovskite Solid Solutions and BaTiO3/SrTiO3 Heterostructures

Authors: Rusevich, LL; Zvejnieks, G; Kotomin, EA; Krzmanc, MM; Meden, A; Kunej, S; Vlaicu, ID

Published: JAN 31 2019, JOURNAL OF PHYSICAL CHEMISTRY C, 123, 2036, DOI: 10.1021/acs.jpcc.8b09750

The results of experimental and theoretical ab initio study of structural and piezoelectric properties of (Ba,Sr)TiO3 perovskite solid solutions are discussed and compared. Experimentally, plate-like (Ba,Sr)TiO3 particles were synthesized by the topochemical conversion in the molten salt from Bi4Ti3O12 template plates. All dimensions (side length approximate to 1 mu m, thickness approximate to 200-400 nm) were well above the critical size necessary for observation of piezo- and ferroelectricity. The first-principles computations of the structural and electromechanical properties of solid solutions were performed with the CRYSTAL14 computer code within the linear combination of atomic orbitals approximation, using three advanced hybrid functionals of density functional theory. Different chemical compositions are considered for the ferroelectric and paraelectric phases. The calculated structural properties of solid solutions in tetragonal and cubic phases are in very good agreement with experimental data. Experimentally obtained and calculated band gaps are compared for cubic SrTiO3 and tetragonal BaTiO3. BaTiO3/SrTiO3 heterostructures were considered theoretically for different chemical compositions. The calculated piezoelectric properties of solid solutions and heterostructures in the ferroelectric phase are compared. It is predicted that both solid solutions and heterostructures improve the piezoelectric properties of bulk BaTiO3, but solid solutions are more preferable for equal Sr concentrations.

830. Passive magnetic shielding by machinable MgB2 bulks: measurements and numerical simulations

Authors: Gozzelino, L; Gerbaldo, R; Ghigo, G; Laviano, F; Torsello, D; Bonino, V; Truccato, M; Batalu, D; Grigoroscuta, MA; Burdusel, M; Aldica, GV; Badica, P

Published: MAR 2019, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 32, DOI: 10.1088/1361-6668/aaf99e

We report on a combined experimental and modelling approach towards the design and fabrication of efficient bulk shields for low-frequency magnetic fields. To this aim, MgB2 is a promising material when its growing technique allows the fabrication of suitably shaped products and a realistic numerical modelling can be exploited to guide the shield design. Here, we report the shielding properties of an MgB2 tube grown by a novel technique that produces fully machinable bulks, which can match specific shape requirements. Despite a height/radius aspect ratio of only 1.75, shielding factors higher than 175 and 55 were measured at temperature T = 20 K and in axially-applied magnetic fields mu H-0(appl) = 0.1 and 1.0 T, respectively, by means of cryogenic Hall probes placed on the tube's axis. The magnetic behaviour of the superconductor was then modelled as follows: first we used a two-step procedure to reconstruct the macroscopic critical current density dependence on magnetic field, J(c)(B), at different temperatures from the local magnetic induction cycles measured by the Hall probes. Next, using these J(c)(B) characteristics, by means of finite-element calculations we reproduced the experimental cycles remarkably well at all the investigated temperatures and positions along the tube's axis. Finally, this validated model was exploited to study the influence both of the tube's wall thickness and of a cap addition on the shield performance. In the latter case, assuming the working temperature of 25 K, shielding factors of 10(5) and 10(4) are predicted in axial applied fields it mu H-0(appl) = 0.1 and 1.0 T, respectively.

831. Spirobifluorene-based Porous Organic Polymers as Efficient Porous Supports for Pd and Pt for Selective Hydrogenation

Authors: Trandafir, MM; Pop, L; Hadade, ND; Hristea, I; Teodorescu, CM; Krumeich, F; van Bokhoven, JA; Grosu, I; Parvulescu, VI

Published: JAN 9 2019, CHEMCATCHEM, 11, 549, DOI: 10.1002/cctc.201801247

Spirobifluorene-based porous organic polymers (POP) were synthesized following two different protocols; the acetylenic coupling reaction conditions and the Sonogashira cross-coupling reaction. These were utilized as support for the hydrogenation of a series of species containing unsaturated C=C and C=O bonds (4-nitrostyrene, 4-bromobenzophenone, acetophenone, 7-nitro-1-tetralone and 1,2-naphtoquinone confirmed their efficiency). POP1 prepared via a copper-catalysis protocol was completely inactive, while POP2-4 containing residual Pd exhibited different activities in accordance to the accessibility of the substrates to the metal. Further deposition of 0.5wt% Pd led to active and stable catalysts. They were easily separated by filtration, and after re-dispersion, afforded the same performances for ten successive cycles. This study also evidenced the specific role of the support in these reactions by comparing the behavior of Pd/POP with that of a Pd/C catalyst with the same loading of palladium. The deposition of Pt on these supports led to sub-nanometric particles and, in accordance, to a different catalytic behavior reflected merely by differences in the selectivity.

832. TAILORING SP2/SP3 RATIO IN DIAMOND-LIKE CARBON FILMS VIA DEPOSITION PARAMETERS IN A HIGH VOLTAGE ANODIC VACUUM PLASMA

Authors: Badulescu, M; Anghel, A; Surdu-Bob, CC; Logofatu, C; Luculescu, C

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

Tailoring sp(2)/sp(3) ratio in diamond-like carbon thin films offers new surface engineering solutions for the continuously increasing devices requirements in various fields. We report here the control of sp(2)/sp(3) carbon content using the high voltage anodic plasma in vacuum. Correlation of data obtained by visible Raman Spectroscopy and XPS spectra of our DLC films with deposition parameters showed an increase in sp(3) bonding of about 10% when decreasing the discharge voltage from 600 V to 200 V or increasing the anode-substrate distance from 15 cm to 36 cm.

833. Novel anhydrous solid-state form of Azathioprine: The assessing of crystal structure by powder X-Ray diffraction, Infrared Absorption Spectroscopy and Raman scattering

Authors: Covaci, OI; Samohvalov, D; Manta, CM; Buhalteanu, L; Barbatu, A; Baibarac, M; Daescu, M; Matea, A; Gherca, D

Published: FEB 15 2019, JOURNAL OF MOLECULAR STRUCTURE, 1178, 710, DOI: 10.1016/j.molstruc.2018.10.065

Azathioprine (Imuran), one of the oldest immunosuppressants, having been used in transplantation since the early 1960's, is known to have only two crystal forms: an anhydrous form and a dihydrate phase. We report the crystal structure of a new anhydrous solid-state form of Azathioprine, determined directly form powder X-Ray diffraction data, employing the direct-space genetic algorithm technique for structure solution, followed by Rietveld refinement. The new anhydrous polymorph is accessible only by a solid-state dehydration process of the readily obtained monohydrate form of Azathioprine, the form for which a crystal structure has not previously been reported. The IR and Raman spectra confirmed the results obtained from X-Ray diffraction indicating the presence of all functional groups involved in intermolecular hydrogen bonding which dictates different arrangement of molecules in the structural packing. (C) 2018 Elsevier B.V. All rights reserved.

834. Manipulating the Optical Properties of Carbon Dots by Fine-Tuning their Structural Features

Authors: Luo, H; Papaioannou, N; Salvadori, E; Roessler, MM; Ploenes, G; van Eck, ERH; Tanase, LC; Feng, JY; Sun, YW; Yang, Y; Danaie, M; Jorge, AB; Sapelkin, A; Durrant, J; Dimitrov, SD; Titirici, MM

Published: OCT 8 2019, CHEMSUSCHEM, 12, 4441, DOI: 10.1002/cssc.201901795

As a new class of sustainable carbon material, "carbon dots" is an umbrella term covering many types of materials. Herein, a broad range of techniques was used to develop the understanding of hydrothermally synthesized carbon dots, and it is shown how fine-tuning the structural features by simple reduction/oxidation reactions can drastically affect their excited-state properties. Structural and spectroscopic studies found that photoluminescence originates from direct excitation of localized fluorophores involving oxygen functional groups, whereas excitation at graphene-like features leads to ultrafast phonon-assisted relaxation and largely quenches the fluorescent quantum yields. This is arguably the first study to identify the dynamics of photoluminescence including Stokes shift and allow the relaxation pathways in these carbon dots to be fully resolved. This comprehensive investigation sheds light on how understanding the excited-state relaxation processes in different carbon structures is crucial for tuning the optical properties for any potential commercial applications.

835. Core-shell nanowire arrays based on ZnO and CuxO for water stable photocatalysts

Authors: Florica, C; Costas, A; Preda, N; Beregoi, M; Kuncser, A; Apostol, N; Popa, C; Socol, G; Diculescu, V; Enculescu, I

Published: NOV 21 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-53873-0

Staggered gap radial heterojunctions based on ZnO-CuxO core-shell nanowires are used as water stable photocatalysts to harvest solar energy for pollutants removal. ZnO nanowires with a wurtzite crystalline structure and a band gap of approximately 3.3 eV are obtained by thermal oxidation in air. These are covered with an amorphous CuxO layer having a band gap of 1.74 eV and subsequently form core-shell heterojunctions. The electrical characterization of the ZnO pristine and ZnO-CuxO core-shell nanowires emphasizes the charge transfer phenomena at the junction and at the interface between the nanowires and water based solutions. The methylene blue degradation mechanism is discussed taking into consideration the dissolution of ZnO in water based solutions for ZnO nanowires and ZnO-CuxO core-shell nanowires with different shell thicknesses. An optimum thickness of the CuxO layer is used to obtain water stable photocatalysts, where the ZnO-CuxO radial heterojunction enhances the separation and transport of the photogenerated charge carriers when irradiating with UV-light, leading to swift pollutant degradation.

836. Development of W-monoblock divertor components with embedded thermal barrier interfaces

Authors: Galatanu, M; Cioca, M; Ighigeanu, A; Ruiu, G; Enculescu, M; Popescu, B; Galatanu, A

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 1354, DOI: 10.1016/j.fusengdes.2019.02.074

In the case of DEMO fusion reactor, the divertor should be able to extract a steady heat flux of about 10 MW/m(2). A promising concept is the W-monoblock which should be connected to a CuCrZr or an advanced Cu ODS alloy pipe passing through the W component. Taking into account the optimum operating temperature windows for W and existing Cu-based alloys and the thermal expansion coefficients mismatch of these two materials, a "thermal barrier" interface material is inserted in between in order to mitigate the thermal stresses and to optimize the heat flow through divertor components. In this work we investigate the feasibility to realize such divertor components using materials produced by FAST (field assisted sintering technology). This powder metallurgy technique was used firstly to produce W or W-based composites and the thermal barriers in an almost final shape and then to join the materials in realistic divertor mock-ups. The thermal barrier materials are various Cu-based composites which are included both as single material or as functionally graded components. The interface quality between different materials is investigated by scanning electron microscopy and the heat flow through components is evaluated using simulations.

837. Deposition temperature influence on the wear behaviour of carbon-based coatings deposited on hardened steel

Authors: Feldiorean, D; Cristea, D; Tierean, M; Croitoru, C; Gabor, C; Jakab-Farkas, L; Cunha, L; Barradas, NP; Alves, E; Craciun, V; Marin, A; Moura, C; Leme, J; Socol, M; Craciun, D; Cosnita, M; Munteanu, D

Published: MAY 1 2019, APPLIED SURFACE SCIENCE, 475, 773, DOI: 10.1016/j.apsusc.2019.01.028

This paper presents an evaluation regarding the influence of substrate material characteristics and deposition parameters on the tribological behaviour of carbon-based coatings. Chromium nitride ceramic interlayers and carbon-based thin films were deposited by magnetron sputtering on hardened AISI 5115 (16MnCr5) case hardening steel. The physical vapour deposition (PVD) deposition was performed at three different temperatures: 180 degrees C, 200 degrees C and 250 degrees C. The chemical composition of the samples was assessed by Rutherford Backscattering Spectroscopy (RBS), the structure by X-ray Diffraction (XRD), and the surface morphology by Atomic Force Microscopy (AFM). The surface chemistry was analysed by X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. The coatings are homogeneous, amorphous, with a smooth surface. The mechanical behaviour has been assessed on a pin-on disk rotational tribometer (wear characteristics), on a micro scratch tester (adhesion to the substrate), by ball-cratering (film thickness) and by nanoindentation (hardness and the modulus of elasticity). A strong correlation has been observed between the substrate characteristics and, more importantly, the deposition temperature, and the mechanical properties of the assembly. The fracture toughness is positively influenced by the presence of the ceramic chromium nitride interlayer. The modulus of elasticity and friction coefficient (both in dry and lubricated conditions) are decreased for higher deposition temperatures, however the higher deposition temperature negatively affects the mechanical characteristics of the steel substrate.

838. Efficient glucose dehydration to HMF onto Nb-BEA catalysts

Authors: Candu, N; El Fergani, M; Verziu, M; Cojocaru, B; Jurca, B; Apostol, N; Teodorescu, C; Parvulescu, VI; Coman, SM

Published: MAR 15 2019, CATALYSIS TODAY, 325, 116, DOI: 10.1016/j.cattod.2018.08.004

The one-pot production of HMF from glucose was investigated in pure hot water and biphasic water/methyli-sobutylketone (MIBK) solvent using mesoporous Nb(0.02 and 0.05 mol%)-Beta zeolites obtained by a post synthesis methodology. The mesoporous Nb-Beta zeolites present residual framework Al-acid sites, extra-framework isolated Nb(V) and Nb2O5 pore-encapsulated clusters in which Nb(V) O-H exhibit moderate strength Bronsted acidity. After optimization, the dehydration of glucose onto the Nb-modified Beta-zeolites occurred with a selectivity of 84.3% in HMF for a glucose conversion of 97.4%. This result has been obtained in a biphasic water/ MIBK solvent and in the presence of NaCl, at 180 degrees C, after 12 h.

839. Comparison between dielectric and pyroelectric properties of PZFNT and BST type ceramics

Authors: Stancu, V; Amarande, L; Botea, M; Iuga, A; Leonat, LN; Tomulescu, AG; Cioangher, M; Balescu, LM; Pintilie, L

Published: 2019, PROCESSING AND APPLICATION OF CERAMICS, 13, 276, DOI: 10.2298/PAC1903269S

Ba0.75Sr0.25TiO3 (BST) and PbZr0.68Fe0.14Nb0.14Ti0.04O3 (PZFNT) ceramic pellets were obtained by ceramic technology and their structural, ferroelectric and pyroelectric properties were investigated. The relative density of BST and PZFNT is about 93% and 90%, respectively, with an average grain size of 102 mu m and 6.45 mu m. Both materials have similar room temperature dielectric constants (similar to 2000), but PZFNT shows higher remnant polarization (similar to 15 mu C/cm(2)) and better pyroelectric properties (similar to 1.69 . 10(-4) C/m(2)K), which recommend it for pyroelectric detectors, infrared radiation- and laser pulse energy-meters.

840. Formation of a Bistable Interstitial Complex in Irradiated p-Type Silicon

Authors: Makarenko, LF; Lastovski, SB; Yakushevich, HS; Gaubas, E; Pavlov, J; Kozlovski, VV; Moll, M; Pintilie, I

Published: SEP 2019, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 216, DOI: 10.1002/pssa.201900354

The influence of the injection of minority charge carriers on the formation of a divalent bistable defect (DBH) having two energy levels of E-v + 0.44 eV and E-v + 0.53 eV in its metastable configuration is investigated. Using forward current injection, the formation temperature of this defect in p-type silicon can be lowered by about 50 degrees C. The production of such bistable defect is enhanced in materials with a high ratio of boron to carbon concentrations. This allows one to conclude that the boron atom is one of the constituents of the defect under study. There is also a correlation between the behavior of the bistable hole traps and a metastable electron trap observed earlier. It is concluded that these traps are related to metastable and stable configurations of the DBH defect, which has inverse occupancy level ordering in its stable configuration.

841. Internal and external surface features of newly developed porous ceramics with random interconnected 3D channels by a fibrous sacrificial porogen method

Authors: Mocanu, AC; Miculescu, M; Machedon-Pisu, T; Maidaniuc, A; Ciocoiu, RC; Ionita, M; Pasuk, J; Stan, GE; Miculescu, F

Published: SEP 30 2019, APPLIED SURFACE SCIENCE, 489, 238, DOI: 10.1016/j.apsusc.2019.05.354

The bone remodeling research field has shifted focus towards sustainable, eco-friendly and reproducible manufacturing technologies of 3D structures. It is now accepted that a suitable internal architecture and an active interface between the 3D structure and host bone-tissue constitute the two most critical traits for a successful bone tissue engineering application. A completely reproducible synthesis set-up was recently developed for calcium phosphate (CaP) bioceramics preparation from natural highly available marble and seashells. The influence of the pressing force in the fabrication process of porous 3D scaffolds derived from such CaPs by a sacrificial porogen method using natural fibers is here investigated. The fiber-ceramic based-products underwent thermal processing, followed by surface and volume features characterization. After fibers' thermal removal, interconnected 3D channels were obtained, which could allow a suitable in vivo irrigation and implant-associated negative side-effects prevention. This method provides the prospect of tunable HA/beta-TCP content in the case of both precursors' derived-scaffolds. The morphological results revealed the internal and external pores dimensions, modulated through different pressing forces that led to a controlled total porosity, evidenced by computed tomography techniques. Further, the wettability and mechanical features supported the advance of the novel porous-ceramic-structure designs as reliable bone reconstruction alternatives.

842. Very large remanent polarization in ferroelectric Hf1-xZrxO2 grown on Ge substrates by plasma assisted atomic oxygen deposition

Authors: Zacharaki, C; Tsipas, P; Chaitoglou, S; Fragkos, S; Axiotis, M; Lagoyiannis, A; Negrea, R; Pintilie, L; Dimoulas, A

Published: MAR 18 2019, APPLIED PHYSICS LETTERS, 114, DOI: 10.1063/1.5090036

Plasma assisted atomic oxygen deposition was used to grow polycrystalline ferroelectric Hf1-xZrxO2 (x = 0.5-0.7) on technologically important (100) Germanium substrates showing sharp crystalline interfaces free of interfacial amorphous layers and strong evidence for the presence of a predominately orthorhombic phase. The electrical properties, evaluated using metal-ferroelectric-semiconductor (MFS) capacitors, show symmetric and robust ferroelectric hysteresis with weak or no wake-up effects. The MFS capacitors with x = 0.58 show very large remanent polarization up to 34.4 mu C/cm(2) or 30.6 mu C/cm(2) after correction for leakage and parasitics, combined with good endurance reaching 10(5) cycles at a cycling field of 2.3 MV/cm. The results show good prospects for the fabrication of Ge ferroelectric field effect transistors (FeFETs) for use in 1 T FeFET embedded nonvolatile memory cells with improved endurance. (C) 2019 Author(s).

843. Carbon-based sprayed electrodes for pyroelectric applications

Authors: Chirila, C; Botea, M; Iuga, A; Tomulescu, AG; Balescu, L; Galca, AC; Boni, AG; Leonat, L; Pintilie, I; Pintilie, L

Published: AUG 15 2019, PLOS ONE, 14, DOI: 10.1371/journal.pone.0221108

A carbon-based layer was deposited by spraying on top of a ferroelectric layer grown by sol-gel on Si (001) substrate and its properties as electrode and absorber for pyroelectric detection were tested. It was found that the electric properties of the ferroelectric capacitor with top carbon-based sprayed electrode (CBSE) are comparable with those of the capacitors with standard top SrRuO3 (SRO)/Au electrode. Pyroelectric measurements show that the pyroelectric signal recorded on ferroelectric capacitors with top CBSE electrode is 2.5 times greater than for top SRO/Au electrode for low frequency range. The value of the pyroelectric coefficient was estimated to 9.73.10(-4) C/m(2)K for CBSE electrodes and 3.36.10(-4) C/m(2)K for SRO/Au respectively. The fabrication process of CBSE is of low cost, easy to implement and with high throughput making it attractive for manufacturing various devices like pyroelectric detector, thermal imaging, solar cells, etc.

844. High performance NIR photosensitive films of Ge nanoparticles in Si3N4

Authors: Stavarache, I; Prepelita, P; Lalau, I; Cojocaru, O; Teodorescu, VS; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 228, DOI:

Films of amorphous Ge nanoparticles in Si3N4 on heated Si and quartz substrates at 300 degrees C were obtained by co-sputtering Ge, and Si3N4. The films structure and photo-electrical behaviour were studied through transmission electron microscopy and, current voltage and spectral photo-current investigations, respectively. The spectral photo-current were correlated with results obtained from transmission electron microscopy. Under illumination the current present a high increase with about one order of magnitude compared with the dark one. The photo-current spectra show a widening in near infrared to 0.97eV. Internal quantum efficiency values for -1V and 0V were determined.

845. Electronic Structure of a Graphene-like Artificial Crystal of NdNiO3

Authors: Arab, A; Liu, XR; Koksal, O; Yang, WB; Chandrasena, RU; Middey, S; Kareev, M; Kumar, S; Husanu, MA; Yang, ZZ; Gu, L; Strocov, VN; Lee, TL; Minar, J; Pentcheva, R; Chakhalian, J; Gray, AX

Published: NOV 2019, NANO LETTERS, 19, 8317, DOI: 10.1021/acs.nanolett.9b03962

Artificial complex-oxide heterostructures containing ultrathin buried layers grown along the pseudocubic [111] direction have been predicted to host a plethora of exotic quantum states arising from the graphene-like lattice geometry and the interplay between strong electronic correlations and band topology. To date, however, electronic-structural investigations of such atomic layers remain an immense challenge due to the shortcomings of conventional surface-sensitive probes with typical information depths of a few angstroms. Here, we use a combination of bulk-sensitive soft X-ray angle-resolved photoelectron spectroscopy (SX-ARPES), hard X-ray photoelectron spectroscopy (HAXPES), and state-of-the-art first-principles calculations to demonstrate a direct and robust method for extracting momentum-resolved and angle-integrated valence-band electronic structure of an ultrathin buckled graphene-like layer of NdNiO3 confined between two 4-unit cell-thick layers of insulating LaAlO3. The momentum-resolved dispersion of the buried Ni d states near the Fermi level obtained via SX-ARPES is in excellent agreement with the first-principles calculations and establishes the realization of an antiferro-orbital order in this artificial lattice. The HAXPES measurements reveal the presence of a valence-band bandgap of 265 meV. Our findings open a promising avenue for designing and investigating quantum states of matter with exotic order and topology in a few buried layers.

846. Fluorescent coumarin-modified mesoporous SBA-15 nanocomposite: Physico-chemical characterization and interaction with prokaryotic and eukaryotic cells

Authors: Tudose, M; Culita, DC; Voicescu, M; Musuc, AM; Kuncser, AC; Bleotu, C; Popa, M; Marutescu, L; Chifiriuc, MC; Nicolescu, M; Deleanu, C

Published: NOV 1 2019, MICROPOROUS AND MESOPOROUS MATERIALS, 288, DOI: 10.1016/j.micromeso.2019.109583

Three novel fluorescent mesoporous silica composites were obtained through the covalent immobilization of 7-amino-4-(trifluoromethyl)coumarin, 6-amino-chromen-2-one and 7-amino-4-methyl-3-coumarinylacetic acid, respectively, inside the channels of mesoporous silica SBA-15. Presence of fluorescent moieties was assessed by elemental analysis, thermal analysis, infrared, UV-Vis, Si-29- and C-13-CP/MAS NMR, and fluorescence spectroscopy. Reduction of specific surface area of the composites by 50-60% and also the average pore size diameter by 0.5-0.55 nm compared to unfunctionalized SBA-15 was evidenced by N-2 adsorption desorption analysis. Their antioxidant, antimicrobial activity and cytotoxicity on HeLa-2 cells were evaluated in order to formulate some potential applications of the obtained compounds. The obtained results recommend the obtained fluorescent mesoporous nanocomposites as potential candidates for the development of novel probes for the in situ tracking of oxidative stress, as well as for antimicrobial applications.

847. Prototype Orthopedic Bone Plates 3D Printed by Laser Melting Deposition

Authors: Chioibasu, D; Achim, A; Popescu, C; Stan, GE; Pasuk, I; Enculescu, M; Iosub, S; Duta, L; Popescu, A

Published: MAR 19 2019, MATERIALS, 12, DOI: 10.3390/ma12060906

Laser melting deposition is a 3D printing method usually studied for the manufacturing of machine parts in the industry. However, for the medical sector, although feasible, applications and actual products taking advantage of this technique are only scarcely reported. Therefore, in this study, Ti6Al4V orthopedic implants in the form of plates were 3D printed by laser melting deposition. Tuning of the laser power, scanning speed and powder feed rate was conducted, in order to obtain a continuous deposition after a single laser pass and to diminish unwanted blown powder, stuck in the vicinity of the printed elements. The fabrication of bone plates is presented in detail, putting emphasis on the scanning direction, which had a decisive role in the 3D printing resolution. The printed material was investigated by optical microscopy and was found to be dense, with no visible pores or cracks. The metallographic investigations and X-ray diffraction data exposed an unusual biphasic alpha+beta structure. The energy dispersive X-ray spectroscopy revealed a composition very similar to the one of the starting powder material. The mapping of the surface showed a uniform distribution of elements, with no segregations or areas with deficient elemental distribution. The in vitro tests performed on the 3D printed Ti6Al4V samples in osteoblast-like cell cultures up to 7 days showed that the material deposited by laser melting is cytocompatible.

848. Sintering and irradiation of copper-based high entropy alloys for nuclear fusion

Authors: Dias, M; Antao, F; Catarino, N; Galatanu, A; Galatanu, M; Ferreira, P; Correia, JB; da Silva, RC; Goncalves, AP; Alves, E

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 1828, DOI: 10.1016/j.fusengdes.2019.03.044

In this study, CuxCrFeTiV (x = 0.21, 0.44, 1 and 1.7 M ratio) high entropy alloys have been devised for thermal barriers between the plasma facing tungsten tiles and the copper-based heat sink in the first wall of nuclear fusion reactors. The high entropy alloys were produced by ball milling the elemental powders, followed by consolidation with spark plasma sintering. Irradiation of the equiatomic CuCrFeTiV sample was carried out at room temperature with Ai(+) (300 keV) beams with a fluence of 3 x 10(20) at/m(2). Structural changes prior and after irradiation were investigated by scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy, X-ray diffraction and thermal diffusivity. Preliminary results showed the presence of heterogenous and multiphasic microstructures in all samples. Moreover, with the increase of the Cu content it is possible to observe the formation of Cu-rich structures. The diffractogram of the CuCrFeTiV sample revealed major peaks of a BCC crystal structure and minor peaks of a FCC crystal structure. In addition, after irradiation no modifications in the CuCrFeTiV microstructure or in the diffractogram were observed.

849. Controlling SWIR photosensitivity limit by composition engineering: from Ge to GeSi nanocrystals embedded in TiO2

Authors: Dascalescu, I; Cojocaru, O; Lalau, I; Palade, C; Slav, A; Lepadatu, AM; Lazanu, S; Stoica, T; Ciurea, ML

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 40, DOI:

The VIS-SWIR photosensing properties of Ge and GeSi NCs embedded in TiO2 films are investigated. For this, we deposit GeTiO2 and GeSiTiO2 films, respectively by magnetron sputtering and then we perform rapid thermal annealing (RTA) for Ge NCs and GeSi NCs formation, respectively. Raman studies and spectral photocurrent measurements were carried out. Ge NCs formation is evidenced in the Raman spectrum of GeTiO2 film annealed at 550 degrees C. The photocurrent spectra measured on the Ge NCs-TiO2 film present four peaks separated by deconvolution. The broad peaks at similar to 700, 890, 1010 nm are due to photo-effects in the Ge NCs-TiO2 film. More than that, the photocurrent increases exponentially with the increase of bias voltage. The cut-off wavelength is similar to 1240 nm. We achieve the extension of the photosensitivity limit to similar to 1310 nm in GeSi NCs-TiO2 films (800 degrees C RTA).

850. Bimodal mesoporous NiO/CeO2-delta-YSZ with enhanced carbon tolerance in catalytic partial oxidation of methane-Potential IT-SOFCs anode

Authors: Somacescu, S; Cioatera, N; Osiceanu, P; Calderon-Moreno, JM; Ghica, C; Neatu, F; Florea, M

Published: FEB 2019, APPLIED CATALYSIS B-ENVIRONMENTAL, 241, 406, DOI: 10.1016/j.apcatb.2018.09.065

In the present study we report on the activity, selectivity and stability of the bimodal mesoporous NiO/CeO2-delta-YSZ anodes for IT-SOFCs applications. These materials present high concentration of C3+ ions stably retained in the lattice, which proved to be efficient for the catalytic partial oxidation of CH4 to syngas in the temperature range 600-800 degrees C. The excellent carbon tolerance was proved by a comprehensive XPS analysis, which monitored the amount of carbon before and after catalytic partial oxidation of methane (CPOM) tests. The mesoporous anodes templated by hexadecyltrimethylammonium bromide (CTAB) and tripropylamine (TPA) were obtained using a hydrothermal synthesis route. The effect of Ni and Ce incorporation on the yttria stabilized zirconia (YSZ) structure, texture, morphology and surface chemistry was discussed and correlated with catalytic and electrochemical behavior. The exhaustive characterization of the bulk and surface properties of the catalysts have been accomplished by means of complementary methods: XRD, SEM / EDX / HR TEM, TGA / TPR, XPS. The electrochemical and catalytic performance were improved when the surface contains more reduced ceria and NiO was formed as secondary phase. These features lead to a large number of vacancies and consequently a better oxygen migration, which facilitate the carbon removal.

851. Structural and optical properties of ZnO thin films grown by rapid atmospheric mist chemical vapor technique

Authors: Derbali, S; Nouneh, K; Galca, AC; Touhami, ME; Secu, M; Matei, E; Leonat, LN; Pintilie, L; El Harfaoui, N; Fahoume, M

Published: JUL 2019, OPTICAL AND QUANTUM ELECTRONICS, 51, DOI: 10.1007/s11082-019-1937-2

In this work, the effect of deposition time on the structural and optical properties of ZnO films deposited by Ultrasonic Spray Mist-CVD was studied aiming the application in perovskite solar cells, as holes blocking layer. Crystallinity, surface morphology and optical properties of the ZnO films were investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), conventional and Photoluminescence (PL) spectroscopies, respectively. The XRD measurement proves the existence of the hexagonal wurtzite phase and a high degree of crystallinity with [001] preferential orientation. The SEM study shows that the films possess a compact structure. Smooth and homogenous surface was confirmed also by AFM. The obtained results indicate that ZnO films deposited by a simple, safe and cost-effective method present a great potential for application in perovskite solar cells.

852. Pulsed Laser Deposition of Indium Tin Oxide Thin Films on Nanopatterned Glass Substrates

Authors: Socol, M; Preda, N; Rasoga, O; Costas, A; Stanculescu, A; Breazu, C; Gherendi, F; Socol, G

Published: JAN 2019, COATINGS, 9, DOI: 10.3390/coatings9010019

Indium tin oxide (ITO) thin films were grown on nanopatterned glass substrates by the pulsed laser deposition (PLD) technique. The deposition was carried out at 1.2 J/cm(2) laser fluence, low oxygen pressure (1.5 Pa) and on unheated substrate. Arrays of periodic pillars with widths of similar to 350 nm, heights of similar to 250 nm, and separation pitches of similar to 1100 nm were fabricated on glass substrates using UV nanoimprint lithography (UV-NIL), a simple, cost-effective, and high throughput technique used to fabricate nanopatterns on large areas. In order to emphasize the influence of the periodic patterns on the properties of the nanostructured ITO films, this transparent conductive oxide (TCO) was also grown on flat glass substrates. Therefore, the structural, compositional, morphological, optical, and electrical properties of both non-patterned and patterned ITO films were investigated in a comparative manner. The energy dispersive X-ray analysis (EDX) confirms that the ITO films preserve the In2O3:SnO2 weight ratio from the solid ITO target. The SEM and atomic force microscopy (AFM) images prove that the deposited ITO films retain the pattern of the glass substrates. The optical investigations reveal that patterned ITO films present a good optical transmittance. The electrical measurements show that both the non-patterned and patterned ITO films are characterized by a low electrical resistivity (<2.8 x 10(-4)). However, an improvement in the Hall mobility was achieved in the case of the nanopatterned ITO films, evidencing the potential applications of such nanopatterned TCO films obtained by PLD in photovoltaic and light emitting devices.

853. Graphitic carbon nitride based photoanodes prepared by spray coating method

Authors: Sima, M; Vasile, E; Sima, A; Preda, N; Logofatu, C

Published: SEP 20 2019, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 44, 24440, DOI: 10.1016/j.ijhydene.2019.07.243

Controlled deposition of g-C3N4 films, used as photoelectrodes in PEC water splitting is still considered a challenge. In this paper, nanosheets of g-C3N4 were deposited on FTO and FTO/TiO2 substrates via spray coating method. This method allows the preparation of g-C3N4 films with a better exposure of nanosheet edges to the solution and light, favoring the photocatalytic process. The morphology, chemical composition and optical properties of these films were investigated, their behavior as photoanodes in photoelectrochemical water splitting being also evaluated. The results evidenced the formation of g-C3N4 films with an enhanced visible light absorption and improved photocatalytic activity. The interaction of these films with TiO2 substrate consists in the insertion of nitrogen species in the TiO2 lattice. A significant increase in bulk donor densities value correlated with a longer lifetime of photogenerated electrons was observed for TiO2/g-C3N4 photoanode. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

854. Palladium/palladium oxide coated electrospun fibers for wearable sweat pH-sensors

Authors: Diculescu, VC; Beregoi, M; Evanghelidis, A; Negrea, RF; Apostol, NG; Enculescu, I

Published: JUN 20 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-45399-2

The work describes the development of a flexible, hydrogel embedded pH-sensor that can be integrated in inexpensive wearable and non-invasive devices at epidermal level for electrochemical quantification of H+ ions in sweat. Such a device can be useful for swift, real time diagnosis and for monitoring specific conditions. The sensors' working electrodes are flexible poly(methyl methacrylate) electrospun fibers coated with a thin gold layer and electrochemically functionalized with nanostructured palladium/palladium oxide. The response to H+ ions is investigated by cyclic voltammetry and electrochemical impedance spectroscopy while open circuit potential measurements show a sensitivity of aprox. -59 mV per pH unit. The modification of the sensing interface upon basic and acid treatment is characterized by scanning and transmission electron microscopy and the chemical composition by X-ray photoelectron spectroscopy. In order to demonstrate the functionality of the pH-sensor at epidermal level, as a wearable device, the palladium/palladium oxide working electrode and silver/silver chloride reference electrode are embedded within a pad of polyacrylamide hydrogel and measurements in artificial sweat over a broad pH range were performed. Sensitivity up to -28 mV/pH unit, response time below 30 s, temperature dependence of approx. 1 mV/degrees C as well as the minimum volume to which the sensor responses of 250 nanoliters were obtained for this device. The proposed configuration represents a viable alternative making use of low-cost and fast fabrication processes and materials.

855. PCL-ZnO/TiO2/HAp Electrospun Composite Fibers with Applications in Tissue Engineering

Authors: Jinga, SI; Zamfirescu, AI; Voicu, G; Enculescu, M; Evanghelidis, A; Busuioc, C

Published: NOV 2019, POLYMERS, 11, DOI: 10.3390/polym11111793

The main objective of the tissue engineering field is to regenerate the damaged parts of the body by developing biological substitutes that maintain, restore, or improve original tissue function. In this context, by using the electrospinning technique, composite scaffolds based on polycaprolactone (PCL) and inorganic powders were successfully obtained, namely: zinc oxide (ZnO), titanium dioxide (TiO2) and hydroxyapatite (HAp). The novelty of this approach consists in the production of fibrous membranes based on a biodegradable polymer and loaded with different types of mineral powders, each of them having a particular function in the resulting composite. Subsequently, the precursor powders and the resulting composite materials were characterized by the structural and morphological point of view in order to determine their applicability in the field of bone regeneration. The biological assays demonstrated that the obtained scaffolds represent support that is accepted by the cell cultures. Through simulated body fluid immersion, the biodegradability of the composites was highlighted, with fiber fragmentation and surface degradation within the testing period.

856. The influence of the nanocrystals size and surface on the Yb/Er doped LaF3 luminescence properties

Authors: Secu, CE; Matei, E; Negrila, C; Secu, M

Published: JUN 30 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 791, 1104, DOI: 10.1016/j.jallcom.2019.03.267

Up-conversion luminescence and thermoluminescence properties of LaF3 nanocrystals, with sizes of about 20 nm, were studied and discussed in relation to -size and surface related effects. XPS spectra have evidenced the presence of oxidized Er and La ions within a thin layer (of about 1 nm thickness) at the nanocrystals surface, as well as Yb ions bonded with fluorine ions. The green ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and red (F-4(9/2) -> I-4(15/2)) up-conversion emissions of Er3+ ions are influenced by the relative dominance of Erions that reside within the thin oxidized layer. The broad thermoluminescence curves are assigned to the recombination of trap defects associated with surface states and within the oxidized surface layer. (C) 2019 Elsevier B.V. All rights reserved.

857. Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Authors: Albulescu, R; Popa, AC; Enciu, AM; Albulescu, L; Dudau, M; Popescu, ID; Mihai, S; Codrici, E; Pop, S; Lupu, AR; Stan, GE; Manda, G; Tanase, C

Published: NOV 2 2019, MATERIALS, 12, DOI: 10.3390/ma12223704

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

858. Coordination polymers and a dinuclear complex constructed from zinc(II) ions and fluorescein: iodine adsorption and optical properties

Authors: Raduca, M; Ene, CD; Ionescu, S; Florea, M; Madalan, AM

Published: APR 18 2019, JOURNAL OF COORDINATION CHEMISTRY, 72, 1237, DOI: 10.1080/00958972.2019.1605442

1-D coordination polymers, (1)(infinity)[Zn(fl)(2)]center dot 2EtOH and (1)(infinity)[Zn(fl)(2)]center dot 2MeOH, and a dinuclear complex, [{Zn(fl)(2)}(2)(dienpip)]center dot 4H(2)O center dot 4EtOH (dienpip= N,N '-bis(2-aminoethyl)piperazine), were obtained using Zn(II) ions and fluorescein anions (fl). Thermal analysis shows stability of the polymers after solvent removal up to more than 400 degrees C. Crystallization solvent molecules were removed under reduced pressure with the preservation of the polymeric structure, (1)(infinity)[Zn(fl)(2)]. Desolvated crystals were exposed to I-2 vapors and the crystal structure determination by X-ray diffraction confirmed the presence of I-2 molecules in the channels generated in crystals by the metal-organic framework. The iodine content, evaluated by X-ray diffraction, corresponds to the overall formula (1)(infinity)[Zn(fl)(2)]center dot 0.3I(2). The optical properties of the coordination polymers and the dinuclear complex have been investigated. [GRAPHICS] .

859. Structural, Compositional, and Mechanical Characterization of WxCryFe1-x-y Layers Relevant to Nuclear Fusion, Obtained with TVA Technology

Authors: Lungu, M; Porosnicu, I; Dinca, P; Velea, A; Baiasu, F; Butoi, B; Pompilian, OG; Staicu, C; Constantina, PA; Porosnicu, C; Lungu, C; Tiseanu, I

Published: DEC 2 2019, MATERIALS, 12, DOI: 10.3390/ma12244072

Reduced activation ferritic and martensitic steel like EUROFER (9Cr-1W) are considered as potential structural materials for the first wall of the future next-generation DEMOnstration Power Station (DEMO) fusion reactor and as a reference material for the International Thermonuclear Experimental Reactor (ITER) test blanket module. The primary motivation of this work is to study the re-deposition of the main constituent materials of EUROFER, namely tungsten (W), iron (Fe), and chromium (Cr), in a DEMO type reactor by producing and analyzing complex WxCryFe1-x-y layers. The composite layers were produced in laboratory using the thermionic vacuum arc (TVA) method, and the morphology, crystalline structure, elemental composition, and mechanical properties were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-X-ray fluorescence (micro-XRF), and glow discharge optical emission spectrometry (GDOES), as well as nanoindentation and tribology measurements. The results show that the layer morphology is textured and is highly dependent on sample positioning during the deposition process. The formation of polycrystalline WxCryFe1-x-y was observed for all samples with the exception of the sample positioned closer to Fe anode during deposition. The crystalline grain size dimension varied between 10 and 20 nm. The composition and thickness of the layers were strongly influenced by the in-situ coating position, and the elemental depth profiles show a non-uniform distribution of Fe and Cr in the layers. The highest hardness was measured for the sample positioned near the Cr anode, 6.84 GPa, and the lowest was 4.84 GPa, measured for the sample positioned near the W anode. The tribology measurements showed an abrasive sliding wear behavior for most of the samples with a reduction of the friction coefficient with the increase of the normal load.

860. Evaluating the biological potential of some new cobalt (II) complexes with acrylate and benzimidazole derivatives

Authors: Vlaicu, ID; Olar, R; Maxim, C; Chifiriuc, MC; Bleotu, C; Stanica, N; Scaeteanu, GV; Dulea, C; Avram, S; Badea, M

Published: JUL 2019, APPLIED ORGANOMETALLIC CHEMISTRY, 33, DOI: 10.1002/aoc.4976

This paper presents the synthesis, physico-chemical and biological properties of four new coordination compounds with mixed ligands: acrylate ion (acr) and benzimidazole/benzimidazole derivatives with the general formula [Co(L)(2)(acr)(2)]center dot nH(2)O [(1) L: benzimidazole (HBzIm), n: 0.5; (2) L: 2-methylbenzimidazole (2-MeBzIm), n: 0.5; (3) L: 5-methylbenzimidazole (5-MeBzIm), n: 0; (4) L: 5,6-dimethylbenzimidazole (5,6-Me(2)BzIm), n: 0]. Their chemical formulae were achieved correlating the chemical analysis with mass spectrometry data, the ligands coordination modes were assigned by Fourier transform-infrared measurements, and the trigonal bipyramidal geometry of cobalt ion in complexes was assigned by data correlation of UV-Vis-NIR spectra and magnetic moments measurements. Single-crystal X-ray diffraction reveals a mononuclear structure with a pentacoordinated cobalt (II) ion, connected to two acrylato coordinated in different modes and two unidentate 5,6-dimethylbenzimidazole ligands for compound (4). The biological tests were performed against several microbial strains, the cytotoxicity was evaluated on HCT8 cellular lines and the cell cycle analysis was performed on HT29 cellular lines. Microbiological assays indicated that Co (II) complexes present a very good to good activity against Candida albicans 1760, Enterococcus faecium E5, Bacillus subtilis ATCC 6683 and Escherichia coli ATCC 25922. Predictive pharmacokinetic (ADME), toxicity and drug-likeness profiles were evaluated for Co (II) complexes. Our results highlight that Co (II) complexes depicted in the present study are suitable to be used as efficient pharmacological agents.

861. Frequency selective surfaces with hexagonal elements for millimeter waves applications

Authors: Banciu, MG; Geambasu, DC; Nedelcu, L; Trupina, L

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 64, DOI:

Numerical investigations on a frequency selective surface using metalized strips deposited on high resistive silicon in a millimeter waves are presented in this paper. High resistivity Si substrate was chosen due to the very good transparence in millimeter waves. For simulations, normal incidence of millimeter waves alongside Floquet modes and ports are considered. Dependence of the frequency response with the geometrical parameters of the unit cell is discussed.

862. Annealing of preexisting defects in silicon single crystals by ion irradiation

Authors: Mihai, MD; Ionescu, P; Pantelica, D; Petrascu, H; Craciun, D; Craciun, V; Vasiliu, F; Vasile, BS; Mercioniu, I

Published: JUL 1 2019, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 450, 89, DOI: 10.1016/j.nimb.2018.09.005

The annealing of crystalline defects in Si single crystals created by ion implantation at room temperature was investigated. Silicon single crystals were firstly implanted at room temperature with 1.345 MeV Au1+ ions at fluences from 1 x 10(13) to 1 x 10(14) at/cm(2) to induce damage. A second implantation at room temperature was afterwards performed with 10 MeV Co3+ ions at a fluence of 3 x 10(14) at/cm(2). All samples were analyzed afterwards by Rutherford backscattering in random and channeling geometry to assess the crystalline damage present in the surface region. The results showed a significant reduction of the degree of damage or a reduction of the size of damaged region. The morphology and local atomic structure, studied using high -resolution electron microscopy, selected area electron diffraction and high resolution X-ray diffraction confirmed the reduction of damage degree and volume caused by Au implantation after Co implantation.

863. Properties of textile and leather materials treated with new hybrid SiO2/TiO2/poly(2,2 '-bithiophene) nanocomposites

Authors: Chirila, L; Gaidau, C; Stroe, M; Baibarac, M; Stanca, M; Radulescu, DM; Radulescu, DE; Alexe, CA

Published: 2019, , DOI: 10.35530/IT.070.03.1634

The aim of this study was to investigate the influence of new hybrid composites of TiO2 or SiO2 nanoparticles with poly(2,2'-bithiophene) on 50% cotton/50% polyester fabric and sheep skin leather surface properties. The dispersion-based newly made nanocomposites were analyzed to determine conductivity, particle size, polydispersity and Zeta potential. The finished textile and leather materials were characterized in terms of functionalization treatments performance by: surface resistivity, water contact behaviour, physical-mechanical characteristics and photocatalytic properties. SEM analysis was used to investigate the distribution of nanoparticles on the textile and leather materials surface. Textile materials treated with SiO2/poly(2,2'-bithiophene) nanocomposite with concentration 98 wt% nanoparticles of SiO2 and leather treated with poly SiO2/poly(2,2'-bithiophene) nanocomposite with concentration of 95 wt% nanoparticles of SiO2 showed lower resistivity values, confirming the conductive properties of silica. The higher photodegradation efficiency of functionalized materials has been obtained for textile material treated with poly TiO2/(2,2'-bithiophene) with concentration of 95 wt% nanoparticles of TiO2 and for leather material treated with TiO2/poly(2,2'-bithiophene) with concentration of 98 wt% nanoparticles of TiO2, respectively.

864. Photoluminescence and structural properties of the nitrogen doped TiO2 and the influence of SiO2 and Ag nanoparticles

Authors: Nila, A; Baibarac, M; Udrescu, A; Smaranda, I; Mateescu, A; Mateescu, G; Mereuta, P; Negrila, CC

Published: SEP 18 2019, JOURNAL OF PHYSICS-CONDENSED MATTER, 31, DOI: 10.1088/1361-648X/ab2692

Mixtures of nitrogen-doped titanium dioxide (TiO2:N) with different concentrations of Ag and/or SiO2 particles (0.5, 1 and 2 wt.%) were prepared in solid state by mechanico-chemical interactions. Using UV-VIS spectroscopy, Raman scattering, photoluminescence (PL) and photoluminescence excitation (PLE), the influence of the particles on the host material is evaluated. UV-VIS spectroscopy studies indicate a TiO2:N band gap shift to the UV range with increasing concentrations of SiO2 and Ag particles. PL intensities decrease with increasing concentrations of Ag and/or SiO2 particles in the TiO2:N host matrix, which in turn could effectively restrict the electron and hole recombination. To explain these processes, the different de-excitation ways will be advanced, taking into account the energy levels diagram of TiO2:N/Ag, TiO2:N/SiO2 and TiO2:N/Ag/SiO2 systems. PLE spectra show a gradual decrease in their relative intensities after 165 min of continuous irradiation due to photosensitivity of TiO2:N. The plasmonic effect of Ag particles in the TiO2:N/Ag system is highlighted for the first time by PLE studies.

865. New electrochemical sensor based on CoQ(10) and cyclodextrin complexes for the detection of oxidative stress initiators

Authors: Barsan, MM; Diculescu, VC

Published: APR 10 2019, ELECTROCHIMICA ACTA, 302, 448, DOI: 10.1016/j.electacta.2019.02.060

The development of coenzyme Q(10) (CoQ(10)) based electrochemical sensor for the detection of oxidative stress initiators is described for the first time. The sensor relies on CoQ(10) redox properties. CoQ(10) was immobilized at the surface of glassy carbon electrodes (GCE) in combination with cyclodextrins (CD), alpha-CD or beta-CD, that ensure the formation of a well dispersed CoQ(10) film. Nanostructured thin films of CoQ(10) alone and in complexes with alpha-CD or beta-CD at the electrode surface were characterized by scanning electron microscopy (SEM) and Fourier-transformed infrared spectroscopy (FTIR), enabling to identify the morphology of the films and the interactions between the CoQ(10) and CD. Nafion (R) was used to ensure sensor stability. The optimization of the CoQ(10) sensor configuration was made by assessing CoQ(10) redox properties through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), correlated with the results obtained from SEM and FTIR characterization. Next, the sensor in the optimized configuration, GCE/alpha-CD + CoQ(10)/Nafion (R), was applied for the detection of oxidant molecules, hydrogen peroxide and the superoxide radical, through the evaluation of the CoQ(10) redox properties monitored by fixed potential chronoamperometry and square wave voltammetry (SWV). (C) 2019 Elsevier Ltd. All rights reserved.

866. Antireflective coatings with high damage threshold prepared by laser ablation

Authors: Filipescu, M; Palla-Papavlu, A; Bercea, A; Rusen, L; Cernaianu, MO; Ion, V; Calugar, A; Nistor, LC; Dinescu, M

Published: DEC 2019, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 125, DOI: 10.1007/s00339-019-3110-y

Latest developments in the field of high power ultra-short pulse lasers have led to intensive studies dedicated to the fabrication possibility of new antireflective coatings which exhibit high damage threshold. Therefore, this study is focused on the deposition and characterization of metal oxide heterostructures followed by laser-induced damage threshold tests which evidence their application in high power laser optics. Al2O3, SiO2, and HfO2 layers are combined to obtain different heterostructures, i.e. HfO2/Al2O3/HfO2/Al2O3/HfO2 and HfO2/SiO2/HfO2/SiO2/HfO2. The metal oxide heterostructures are deposited in a controllable oxygen atmosphere, either at room temperature or high temperatures (600 degrees C) by pulsed laser deposition (PLD). The morphological, structural and optical properties of the as-deposited heterostructures are first investigated. Atomic force microscopy and spectroscopic ellipsometry investigations reveal a lower roughness of the heterostructures based on HfO2/Al2O3 layers grown at 600 degrees C as compared to those grown at room temperature. Furthermore, following the laser-induced damage threshold (LIDT) tests carried out with a Ti-Sapphire laser, higher LIDT values are obtained for the HfO2/Al2O3-based heterostructures than for the HfO2/SiO2-based heterostructures. The ability to control the morphological and structural properties of the antireflective coatings by modifying the deposition parameters of the metal oxide heterostructures demonstrates that PLD is a suitable technique for the manufacturing of antireflective coatings for high power ultra-short laser systems.

867. Adsorption of 1,4-phenylene diisothiocyanate onto the graphene oxide sheets functionalized with polydiphenylamine in doped state

Authors: Baibarac, M; Daescu, M; Fejer, SN

Published: AUG 19 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-48314-x

Adsorption processes of 1,4-phenylene diisothiocyanate (PDITC) on two new platforms of the type graphene oxide (GO) sheets and GO layers functionalization with polydiphenylamine (PDPA) are studied by Raman scattering and photoluminescence (PL). An interaction in solid state phase of the two constituents, i.e. PDITC and GO sheets, and a deposition of PDITC onto the PDPA functionalized GO layers, respectively, by the drop casting method, were performed. In the first case, it is shown that interaction in solid state phase of GO with PDITC leads to an intercalation of the organic compound between GO sheets simultaneously with the appearance of the o-thiocarbamate groups, that induces: (i) an enhancement of the PDITC Raman lines situated in the 400-800 and 1000-1300 cm(-1) spectral ranges, (ii) a change in the ratio between the relative intensities of the two Raman lines peaked at 1585 and 1602 cm(-1) accompanied by an up-shift in the case of the second line and (iii) a down-shift of the PDTIC PL band from 502 to 491 nm. Using cyclic voltammetry, an electrochemical functionalization of the GO layers with PDPA doped with H3PMo12O40 heteropolyanions takes place, as demonstrated by Raman scattering and FTIR spectroscopy. The presence of the amine groups in the molecular structure of the doped PDPA functionalized GO layers induces a chemical adsorption of PDITC on this platform, when the thiourea groups appear simultaneously with o-thiocarbamate groups. A chemical mechanism is proposed to take place at the interface of the GO sheets and the doped PDPA functionalized GO layers, respectively, with PDITC.

868. Naturally-Derived Biphasic Calcium Phosphates through Increased Phosphorus-Based Reagent Amounts for Biomedical Applications

Authors: Mocanu, AC; Stan, GE; Maidaniuc, A; Miculescu, M; Antoniac, IV; Ciocoiu, RC; Voicu, SI; Mitran, V; Cimpean, A; Miculescu, F

Published: FEB 1 2019, MATERIALS, 12, DOI: 10.3390/ma12030381

Calcium carbonate from marble and seashells is an eco-friendly, sustainable, and largely available bioresource for producing natural bone-like calcium phosphates (CaPs). Based on three main objectives, this research targeted the: (i) adaptation of an indirect synthesis route by modulating the amount of phosphorus used in the chemical reaction, (ii) comprehensive structural, morphological, and surface characterization, and (iii) biocompatibility assessment of the synthesized powdered samples. The morphological characterization was performed on digitally processed scanning electron microscopy (SEM) images. The complementary 3D image augmentation of SEM results also allowed the quantification of roughness parameters. The results revealed that both morphology and roughness were modulated through the induced variation of the synthesis parameters. Structural investigation of the samples was performed by Fourier transform infrared spectroscopy and X-ray diffraction. Depending on the phosphorus amount from the chemical reaction, the structural studies revealed the formation of biphasic CaPs based on hydroxyapatite/brushite or brushite/monetite. The in vitro assessment of the powdered samples demonstrated their capacity to support MC3T3-E1 pre-osteoblast viability and proliferation at comparable levels to the negative cytotoxicity control and the reference material (commercial hydroxyapatite). Therefore, these samples hold great promise for biomedical applications.

869. Fabrication and characterization of Si1-xGex nanocrystals in as-grown and annealed structures: a comparative study

Authors: Sultan, MT; Maraloiu, AV; Stavarache, I; Gudmundsson, JT; Manolescu, A; Teodorescu, VS; Ciurea, ML; Svavarsson, HG

Published: SEP 17 2019, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 10, 1882, DOI: 10.3762/bjnano.10.182

Multilayer structures comprising of SiO2/SiGe/SiO2 and containing SiGe nanoparticles were obtained by depositing SiO2 layers using reactive direct current magnetron sputtering (dcMS), whereas, Si and Ge were co-sputtered using dcMS and high-power impulse magnetron sputtering (HiPIMS). The as-grown structures subsequently underwent rapid thermal annealing (550-900 degrees C for 1 min) in N-2 ambient atmosphere. The structures were investigated using X-ray diffraction, high-resolution transmission electron microscopy together with spectral photocurrent measurements, to explore structural changes and corresponding properties. It is observed that the employment of HiPIMS facilitates the formation of SiGe nanoparticles (2.1 +/- 0.8 nm) in the as-grown structure, and that presence of such nanoparticles acts as a seed for heterogeneous nucleation, which upon annealing results in the periodically arranged columnar self-assembly of SiGe core-shell nanocrystals. An increase in photocurrent intensity by more than an order of magnitude was achieved by annealing. Furthermore, a detailed discussion is provided on strain development within the structures, the consequential interface characteristics and its effect on the photocurrent spectra.

870. Behavior of Molybdenum-Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene

Authors: Mitran, G; Neatu, F; Pavel, OD; Trandafir, MM; Florea, M

Published: MAR 1 2019, MATERIALS, 12, DOI: 10.3390/ma12050748

This study deals with the behavior of molybdenum-vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several techniques: nitrogen adsorption-desorption isotherms, X-Ray diffraction (XRD), ammonia temperature-programmed desorption (TPD-NH3), temperature-programmed reduction by hydrogen (H-2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared-spectroscopy (FTIR) and ultraviolet-visible spectroscopies (UV-VIS). The XRD results evidenced the presence of orthorhombic -MoO3 and V2O5 phases, as well as monoclinic -MoO3 and V2MoO8 phases, their abundance depending on the Mo to V ratio, while the TPD-NH3 emphasized that, the total amount of the acid sites diminished with the increase of the Mo loading. The TPR investigations indicated that the samples with higher Mo/V ratio possess a higher reducibility. The main findings of this study led to the conclusion that the presence of strong acid sites afforded a high conversion in toluene disproportionation (Mo/V = 1), while a higher reducibility is a prerequisite to accomplishing high conversion in toluene oxidation (Mo/V = 2). The catalyst with Mo/V = 1 acquires the best yield to xylenes from the toluene disproportionation reaction, while the catalyst with Mo/V = 0.33 presents the highest yield to benzaldehyde.

871. 3D Superparamagnetic Scaffolds for Bone Mineralization under Static Magnetic Field Stimulation

Authors: Paun, IA; Calin, BS; Mustaciosu, CC; Mihailescu, M; Moldovan, A; Crisan, O; Leca, A; Luculescu, CR

Published: SEP 2019, MATERIALS, 12, DOI: 10.3390/ma12172834

We reported on three-dimensional (3D) superparamagnetic scaffolds that enhanced the mineralization of magnetic nanoparticle-free osteoblast cells. The scaffolds were fabricated with submicronic resolution by laser direct writing via two photons polymerization of Ormocore/magnetic nanoparticles (MNPs) composites and possessed complex and reproducible architectures. MNPs with a diameter of 4.9 +/- 1.5 nm and saturation magnetization of 30 emu/g were added to Ormocore, in concentrations of 0, 2 and 4 mg/mL. The homogenous distribution and the concentration of the MNPs from the unpolymerized Ormocore/MNPs composite were preserved after the photopolymerization process. The MNPs in the scaffolds retained their superparamagnetic behavior. The specific magnetizations of the scaffolds with 2 and 4 mg/mL MNPs concentrations were of 14 emu/g and 17 emu/g, respectively. The MNPs reduced the shrinkage of the structures from 80.2 +/- 5.3% for scaffolds without MNPs to 20.7 +/- 4.7% for scaffolds with 4 mg/mL MNPs. Osteoblast cells seeded on scaffolds exposed to static magnetic field of 1.3 T deformed the regular architecture of the scaffolds and evoked faster mineralization in comparison to unstimulated samples. Scaffolds deformation and extracellular matrix mineralization under static magnetic field (SMF) exposure increased with increasing MNPs concentration. The results are discussed in the frame of gradient magnetic fields of similar to 3 x 10(-4) T/m generated by MNPs over the cells bodies.

872. STRUCTURAL, DIELECTRIC AND PYROELECTRIC PROPERTIES OF Nb AND Fe DOPED PZT CERAMICS

Authors: Stancu, V; Amarande, L; Botea, M; Cioangher, M; Tomulescu, A; Iuga, A; Pintilie, L

Published: JAN-MAR 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 230, DOI:

Lead zirconate titanate doped with iron and niobium (PZFNT) was prepared by conventional processing technique, solid state synthesis method. The influence of dopants on the microstructure, ferroelectric and pyroelectric properties was investigated. XRD data reveals a perovskite structure near to the lead zirconate phase. The relative density of PZFNT is approximate 90%, with average grains size of 6.45 mu m.

873. Effect of slow charged 90 keV Ne8+ ions on zinc ferrite nanoparticles

Authors: Trandafir, EV; Caltun, OF; Ciocarlan, R; Pui, A; Hempelmann, R; Diamandescu, L; Cervera, S; Trassinelli, M; Vernhet, D

Published: SEP 2019, MATERIALS RESEARCH EXPRESS, 6, DOI: 10.1088/2053-1591/ab3174

The present work reports on the effect of slow charged ions irradiation on the structural and magnetic properties of zinc ferrite nanoparticles obtained by coprecipitation method. Results from both the x-ray and Fourier Transform Infrared Spectroscopies confirm the formation of the spinel phase. The structural investigation using x-rays reveals no significant impurity peak and a crystallite size of 9 nm. Particle size of pristine sample is determined to be around 9 nm. Crystallinity and magnetic properties of ferrite sample investigated before and after irradiation process show that electronic excitations inside the material alter the magnetic parameters. Mossbauer Spectroscopy measurements indicate that a fluence of 3*10(14) ions cm(-2) Ne8+ ions of 90 keV are sufficient to induce cation redistribution into zinc ferrite nanoparticles.

874. EXPERIMENTAL STUDY OF TERAHERTZ RESPONSE FROM SOME FERROELECTRIC AND DIELECTRIC MATERIALS

Authors: Banciu, MG; Nedelcu, L; Furuya, T; Hrib, L; Geambasu, DC; Trupina, L; Pantelica, D; Mihai, MD; Tani, M

Published: OCT-DEC 2019, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 20, 360, DOI:

Barium strontium titanate (BST) ferroelectric layers were deposited on high resistivity Si substrates by Pulsed Laser Deposition and Radio Frequency sputtering. The stoichiometry was measured by using the Rutherford Backscattering technique at 3.041 MeV. For sub-THz measurements of Si samples, a new resonant method placing the sample between two flanged waveguides is proposed. In the THz range, the Time Domain Spectroscopy proved to be a reliable method. Both methods show effects due to the dielectric losses of BST in that frequency range.

875. Thermophysical and mechanical properties of W-Cu laminates produced by FAST joining

Authors: Galatanu, A; Galatanu, M; Enculescu, M; Reiser, J; Sickinger, S

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 2374, DOI: 10.1016/j.fusengdes.2019.03.193

W-laminates are multi layered composites realized from alternately stacked W and a second metal foils. Such materials are promising candidates for W-based structural materials for fusion reactors like DEMO or beyond concepts, due to the fact that cold-rolled ultrafine-grained thin W foils show exceptional properties in terms of ductility, toughness and ductile to brittle transition (DBT), in contrast to classic bulk W materials. Therefore, different routes to transfer the W foils properties to bulk materials have been investigated. In this work we present the results obtained for W-Cu laminates produced via a FAST (Field Assisted Sintering Technique) joining route. The main advantages of FAST resides in the short processing time, with subsequent lower recrystallization detrimental effects. Structural and thermophysical properties show that the best materials are obtained for about 100 mu m thick W foils and 50-100 mu m thick Cu foils, while tensile and Charpy impact tests results show that the FAST processed W-Cu laminates are similar to the W-Cu laminates obtained by diffusion bonding.

876. Effect of high gamma radiations on physical properties of In2S3 thin films grown by chemical bath deposition for buffer layer applications

Authors: Souli, M; Bensalem, Y; Secu, M; Bartha, C; Enculescu, M; Mejri, A; Kamoun-Turki, N; Badica, P

Published: JUN 2019, RESULTS IN PHYSICS, 13, DOI: 10.1016/j.rinp.2019.02.051

Polycrystalline In2S3 thin films have been grown on SnO2/glass substrates by chemical bath deposition technique and irradiated at different high gamma doses 3, 7, 15 and 40 kGy. X-ray diffraction, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Spectrophotometer, Photoluminescence and Thermoluminescence were used to investigate physical properties of In2S3 thin films induced by gamma irradiation. After being irradiated, structural properties of In2S3 thin films have shown that preferred orientation has been moved from (4 0 0) plan at 2 theta(1)=33.42 degrees to a new created orientation at 2 theta(2)=38.06 degrees for 40 kGy gamma dose. EDS analysis has shown that atomic percentage (S/In) has been strongly varied for 40 kGy which indicate significant changes in stoichiometry. Thermoluminescence of irradiated In2S3 thin films has revealed a good sensitivity toward absorbed gamma dose. After irradiation, optical transmittance of In2S3 thin films has been increased from 50% to a maximum value of 70% in the visible range for 15 kGy dose. Band gap energy E-g has been slightly decreased. Other optical parameters such absorption and extinction coefficients, refractive index and permittivity have been determined. These experimental results show that gamma radiations can be used for tuning physical properties of In2S3 thin films for photovoltaic applications.

877. UV-vis light induced photocatalytic activity of TiO2/graphene oxide nanocomposite coatings

Authors: Datcu, A; Mendoza, ML; del Pino, AP; Logofatu, C; Luculescu, C; Gyorgy, E

Published: FEB 1 2019, CATALYSIS TODAY, 321, 86, DOI: 10.1016/j.cattod.2018.02.026

Titanium dioxide (TiO2) and TiO2 - graphene oxide (GO) composite layers were deposited by spin coating technique onto SiO2 quartz substrates. TiO2 NPs and GO platelets were used as base materials for the preparation of the starting water/acetone dispersions. Polystyrene (PS) buffer layers were deposited by drop-cast method onto the substrates surface to ensure the adherence of the pure TiO2/PS and TiO2-GO/PS composite layer. The surface morphology and physico-chemical properties of the layers have been determined and correlated with their photocatalytic properties. It was found that GO oxygen functional groups are reduced by the presence of TiO2 NPs in the composite materials. Photodegradation activity under UV-visible light irradiation was studied by measuring the concentration changes in time of organic methylene blue dye in aqueous solutions as well as the chemical oxygen demand for real wastewater samples. The obtained results revealed that the photocatalytic properties of the spin coated composites are determined by the graphene oxide concentration. The effect of the spontaneous reduction of GO in the presence of TiO2 NPs on the photocatalytic activity of the TiO2-GO/PS composites is discussed in detail.

878. Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

Authors: Vasylkiv, O; Borodianska, H; Demirskyi, D; Li, P; Suzuki, TS; Grigoroscuta, MA; Pasuk, I; Kuncser, A; Badica, P

Published: DEC 20 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-55888-z

Mixtures of B4C, alpha-AlB12 and B powders were reactively spark plasma sintered at 1800 degrees C. Crystalline and amorphous boron powders were used. Samples were tested for their impact behavior by the Split Hopkinson Pressure Bar method. When the ratio R = B4C/alpha-AlB12 >= 1.3 for a constant B-amount, the major phase in the samples was the orthorhombic AlB24C4, and when R < 1 the amount of AlB24C4 significantly decreased. Predictions that AlB24C4 has the best mechanical impact properties since it is the most compact and close to the ideal cubic packing among the Al-B-C phases containing B-12-type icosahedra were partially confirmed. Namely, the highest values of the Vickers hardness (32.4 GPa), dynamic strength (1323 MPa), strain and toughness were determined for the samples with R = 1.3, i.e., for the samples with a high amount of AlB24C4. However, the existence of a maximum, detectable especially in the dynamic strength vs. R, indicated the additional influence of the phases and the composite's microstructure in the samples. The type of boron does not influence the dependencies of the indicated mechanical parameters with R, but the curves are shifted to slightly higher values for the samples in which amorphous boron was used.

879. The Influence of Heteroatom Dopants Nitrogen, Boron, Sulfur, and Phosphorus on Carbon Electrocatalysts for the Oxygen Reduction Reaction

Authors: Preuss, K; Siwoniku, AM; Bucur, CI; Titirici, MM

Published: MAY 2019, CHEMPLUSCHEM, 84, 464, DOI: 10.1002/cplu.201900083

A hard templating method, using SBA-15 in combination with glucose solution and different heteroatom precursors, has been employed to investigate the influence of the different heteroatom dopants nitrogen, boron, sulfur, and phosphorus on carbon electrocatalysts for the oxygen reduction reaction. Samples were synthesized under the same conditions and resulted in a similar morphology and surface areas around 1000 m(2)/g. Incorporating nitrogen into the carbon matrix was found to be easier than for boron or phosphorus, while sulfur doping proved problematic and only yielded 2 at% of sulfur or less. Different dopant concentrations as well as a combination of dopants suggested that nitrogen was the only heteroatom exerting an actual influence on the catalytic activity, resulting in higher electron transfer numbers. The other dopants exhibited a similar performance regardless of the dopant content, though slightly improved when compared to an undoped control sample. These findings indicate that incorporated nitrogen can act as catalytic sites, while boron, sulfur and phosphorus can enhance the catalytic activity by possibly creating defects in the carbon matrix.

880. On the development of a robust cyber security system for Internet of Things devices

Authors: Ionescu, O; Dumitru, V; Pricop, E; Buiu, O; Cobianu, C; Raneti, M; Pircalabu, S; Marica, C

Published: 2019, PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTERS AND ARTIFICIAL INTELLIGENCE (ECAI-2019), DOI:

Cyber security threats have escalated dramatically in the past few years, this being the main reason why the development of Internet of Things (IoT) devices was hindered and the full potential of their utility was not reached. A major step forward could be taken only by providing reliable and cheap protection against unauthorized interference from malicious users and other threats so that people can feel safe keeping their devices connected to the cloud. This paper is focused on the development of a robust cyber security solution for IoT. The device developed and presented in this paper has the capability of solving cyber security problem by using a simple and low-cost solution, that comes with the advantage of being less intrusive and easily adaptable to any Ethernet connected IoT device. The developed device has two embodiments, the first one being a simple hardware control of the communication line using a parallel channel, and the second one extending the features of the first by using the physical unclonable functions (PUF) generated by a controlled memristor for securing the data sent over the communication channel.

881. Rhodium-Catalyzed Annulation of ortho-Alkenyl Anilides with Alkynes: Formation of Unexpected Naphthalene Adducts

Authors: Seoane, A; Comanescu, C; Casanova, N; Garcia-Fandino, R; Diz, X; Mascarenas, JL; Gulias, M

Published: FEB 4 2019, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 58, 1704, DOI: 10.1002/anie.201811747

o-Alkenyl N-triflylanilides underwent rhodium(III)-catalyzed oxidative annulations with alkynes to produce different types of naphthylamides in a process which involves the cleavage of two C-H bonds. Remarkably, besides formal dehydrogenative (4C+2C) cycloadducts, the reaction also produces variable amounts of isomeric naphthylamides, whose formation requires a formal migration of the alkenyl moiety from the ortho to the meta position of the anilide. The annulation reaction can be efficiently carried out in the absence of external oxidants, such as Cu(OAc)(2).

882. Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Authors: Strocov, VN; Chikina, A; Caputo, M; Husanu, MA; Bisti, F; Bracher, D; Schmitt, T; Granozio, FM; Vaz, CAF; Lechermann, F

Published: OCT 7 2019, PHYSICAL REVIEW MATERIALS, 3, DOI: 10.1103/PhysRevMaterials.3.106001

Electronic phase separation is crucial for the fascinating macroscopic properties of the LaAlO3/SrTiO3 (LAO/STO) paradigm oxide interface, including the coexistence of superconductivity and ferromagnetism. We investigate this phenomenon using angle-resolved photoelectron spectroscopy (ARPES) in the soft-x-ray energy range, where the enhanced probing depth combined with resonant photoexcitation allow us access to fundamental electronic structure characteristics - momentum-resolved spectral function, dispersions and ordering of energy bands, Fermi surface - of buried interfaces. Our experiment uses x-ray irradiation of the LAO/STO interface to tune its oxygen deficiency, building up a dichotomic system where mobile weakly correlated Ti t(2g) electrons coexist with localized strongly correlated Ti e(g) ones. The ARPES spectra dynamics under x-ray irradiation shows a gradual intensity increase under constant Luttinger count of the Fermi surface. This fact identifies electronic phase separation (EPS) where the mobile electrons accumulate in conducting puddles with fixed electronic structure embedded in an insulating host phase, and allows us to estimate the lateral fraction of these puddles. We discuss the physics of EPS invoking a theoretical picture of oxygen-vacancy clustering, promoted by the magnetism of the localized Ti e(g) electrons, and repelling of the mobile t(2g) electrons from these clusters. Our results on the irradiation-tuned EPS elucidate the intrinsic one taking place at the stoichiometric LAO/STO interfaces.

883. Physical properties of the ferroelectric capacitors based on Al-doped HfO2 grown via Atomic Layer Deposition on Si

Authors: Vulpe, S; Nastase, F; Dragoman, M; Dinescu, A; Romanitan, C; Iftimie, S; Moldovan, A; Apostol, N

Published: JUL 31 2019, APPLIED SURFACE SCIENCE, 483, 333, DOI: 10.1016/j.apsusc.2019.03.166

Ferroelectric capacitors based on aluminium (Al) doped hafnium oxide (HfO2) thin films grown on silicon substrates were fabricated by Atomic Layer Deposition (ALD), taking into account two methods. The first one involved the growth of a binary oxide, in a laminar way, by alternating the ALD cycles of HfO2 and Al2O3, and the second, the two precursors were sequentially mixed on the surface. The composition and structure of deposited aluminium doped hafnium oxide (Al: HfO2) thin films have been studied using X-ray photoelectron spectroscopy (XPS) and grazing incidence X-ray diffraction (GIXRD). XPS measurements show the formation of opposite ferroelectric polarization areas. Via GIXRD, it was found that the Al: HfO2 films deposited on Si have a structure with polycrystalline domains. Recording and investigation of ferroelectric domains were performed by Piezoresponse Force Microscopy (PFM), while the electrical performances of obtained devices were analysed by capacitance-voltage (C-V) and current-voltage (I-V) characteristics. The PFM measurements show there is a mechanical non-zero response even outside the written area and for an appropriate value of the electrical stress the difference in phase between successive areas is saturated to a value close to 180 degrees. The atomic force microscopy (AFM) analyses indicate a very low value of roughness average, for all grown thin films, similar to 0.2 nm, for a thickness of similar to 7 nm. From C-V characteristics, the memory window was extracted and the calculated values were found to be 0.8 V for the device obtained by the first ALD method, and 0.44 V for the second one, respectively. Moreover, in the case of the device based on the ferroelectric layer grown by the second ALD method, the memory window extends over a much wider applied voltage domain, in the range (+/- 4 V; +/- 8 V), at a signal of 100 kHz.

884. Addition of carbon fibers into B4C infiltrated with molten silicon

Authors: Solodkyi, I; Bezdorozhev, O; Vterkovskiy, M; Bogomol, I; Bolbut, V; Kruger, M; Badica, P; Loboda, P

Published: JAN 2019, CERAMICS INTERNATIONAL, 45, 174, DOI: 10.1016/j.ceramint.2018.09.148

Boron carbide added with 0-20 wt% carbon fibers was subject to Si infiltration. Samples mainly consist of B13C2, beta-SiC and unreacted Si. Some amount of SiB6 and alpha-SiC was also detected, while formation of B-12(B,C,Si)(3) phase was suppressed due to short infiltration time. The carbon fibers react with Si and result in formation of a composite core-shell fiber with SiC-shell and C-core. Theoretical estimations suggest that these composite fibers have a strong influence on the enhancement of the bending strength. Although apparently in good agreement with experimental data showing an increase of bending strength up to 510 +/- 27 MPa in the sample with 10 wt% carbon fiber, the implications of phase changes with the carbon fiber amount has to be carefully considered. At higher amounts of carbon fibers, bending strength decreases.

885. Tailoring the Dopant Distribution in ZnO:Mn Nanocrystals

Authors: Ghica, D; Vlaicu, ID; Stefan, M; Maraloiu, VA; Joita, AC; Ghica, C

Published: MAY 3 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-43388-z

The synthesis of semiconductor nanocrystals with controlled doping is highly challenging, as often a significant part of the doping ions are found segregated at nanocrystals surface, even forming secondary phases, rather than incorporated in the core. We have investigated the dopant distribution dynamics under slight changes in the preparation procedure of nanocrystalline ZnO doped with manganese in low concentration by electron paramagnetic resonance spectroscopy, paying attention to the formation of transient secondary phases and their transformation into doped ZnO. The acidification of the starting solution in the co-precipitation synthesis from nitrate precursors lead to the decrease of the Mn2+ ions concentration in the core of the ZnO nanocrystals and their accumulation in minority phases, until similar to 79% of the Mn2+ ions were localized in a thin disordered shell of zinc hydroxynitrate (ZHN). A lower synthesis temperature resulted in polycrystalline Mn-doped ZHN. Under isochronal annealing up to 250 degrees C the bulk ZHN and the minority phases from the ZnO samples decomposed into ZnO. The Mn2+ ions distribution in the annealed nanocrystals was significantly altered, varying from a uniform volume distribution to a preferential localization in the outer layers of the nanocrystals. Our results provide a synthesis strategy for tailoring the dopant distribution in ZnO nanocrystals for applications ranging from surface based to ones involving core properties.

886. Synthesis, Characterization, and Antimicrobial Activity of Magnesium-Doped Hydroxyapatite Suspensions

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Stan, GE; Buton, N

Published: SEP 2019, NANOMATERIALS, 9, DOI: 10.3390/nano9091295

Obtaining nanoscale materials has allowed for the miniaturization of components, which has led to the possibility of achieving more efficient devices with faster functions and much lower costs. While hydroxyapatite [HAp, Ca-10(PO4)(6)(OH)(2)] is considered the most widely used material for medical applications in orthopedics, dentistry, and general surgery, the magnesium (Mg) is viewed as a promising biodegradable and biocompatible implant material. Furthermore, Mg is regarded as a strong candidate for developing medical implants due to its biocompatibility and antimicrobial properties against gram-positive and gram-negative bacteria. For this study, magnesium-doped hydroxyapatite (Ca10-xMgx (PO4)(6) (OH)(2), x(Mg) = 0.1), 10MgHAp, suspensions were successfully obtained by an adapted and simple chemical co-precipitation method. The information regarding the stability of the nanosized 10MgHAp particles suspension obtained by zeta-potential analysis were confirmed for the first time by a non-destructive ultrasound-based technique. Structural and morphological studies of synthesized 10MgHAp were conducted by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy in attenuated total reflectance (ATR) mode and scanning electron microscopy (SEM). The XRD analysis of the 10MgHAp samples confirmed that a single crystalline phase associated to HAp with an average grain size about 93.3 nm was obtained. The FTIR-ATR spectra revealed that the 10MgHAp sample presented broader IR bands with less visible peaks when compared to a well-crystallized pure HAp. The SEM results evidenced uniform MgHAp nanoparticles with spherical shape. The antimicrobial activity of the 10MgHAp suspension against gram-positive strains (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212), gram-negative strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853), as well as a fungal strain (Candida albicans ATCC 90029) were evaluated.

887. Vibrational and photoluminescence properties of polydiphenylamine doped with silicotungstic acid heteropolyanions and their composites with reduced graphene oxide

Authors: Baibarac, M; Stroe, M; Fejer, SN

Published: MAY 15 2019, JOURNAL OF MOLECULAR STRUCTURE, 1184, 35, DOI: 10.1016/j.molstruc.2019.02.014

In this work, the influence of silicotungstic acid concentration on the diphenylamine (DPA) electro-polymerization in the absence and the presence of reduced graphene oxide (RGO) is studied. The optical properties of the composites based on polydiphenylamine (PDPA) doped with the H4SiW12O40 heteropolyanions and RGO are investigated by Raman scattering, IR absorption spectroscopy and photoluminescence (PL). The presence of RGO induces an up-shift of the oxidation maximum of the DPA, as a result of a covalent functionalization process of graphene sheets with the polymer in the doped state. The deposition of PDPA onto RGO sheets surface is confirmed by the Raman scattering studies. Regardless of the H4SiW12O40 concentration, an up-shift of the IR bands from 910 to 1014 cm(-1) to similar to 920 and 1022 cm(-1) is reported as a consequence of the compensation of positive charges of PDPA macromolecular chains with of the H4SiW12O40 heteropolyanions. An enhancement in the absorbance of the IR bands situated in the spectral range 750-1050 cm(-1) accompanied of a decrease in the relative intensity of the PL bands of PDPA and their composites with RGO, as increasing the H4SiW12O40 concentration, is reported. In the presence of RGO, a change in the PDPA PL spectra profile is also highlighted. (C) 2019 The Authors. Published by Elsevier B.V.

888. Molecular scale biophysical methodologies for levo-thyroxine interaction with DNA

Authors: David, M; Enache, A; Moga, M; Florescu, M

Published: JUL 2019, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, 48, S241, DOI:

889. Fe3O4/BaTiO3 COMPOSITES WITH CORE-SHELL STRUCTURE

Authors: Tanasa, E; Andronescu, E; Cernea, M; Oprea, OC

Published: 2019, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 81, 180, DOI:

This paper demonstrates the possibility of the preparation of Fe3O4/BaTiO3 core-shell composites. BaTiO3-coated Fe3O4 (Fe3O4/BaTiO3) with 5-15 nm Fe3O4 nanoparticles as cores and 2.5-4 nm BaTiO3 shell thickness, was successfully prepared through coprecipitation method and sol-gel deposition technique. High-Resolution Transmission Electron Microscopy (HRTEM), Energy Dispersive X-ray Spectrometry (EDXS) and Selected-Area Electron Diffraction (SAED) showed the formation of the core-shell structure with face centered cubic Fe3O4 and tetragonal BaTiO3 phases.

890. Optical properties of folic acid in phosphate buffer solutions: the influence of pH and UV irradiation on the UV-VIS absorption spectra and photoluminescence

Authors: Baibarac, M; Smaranda, I; Nila, A; Serbschi, C

Published: OCT 3 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-50721-z

Using UV-VIS absorption spectroscopy, photoluminescence (PL) and photoluminescence excitation (PLE), the photodegradation reactions of folic acid (FA) in phosphate buffer (PB) solutions were studied. Regardless of the PB solution's pH, the UV-VIS spectra showed a gradual decrease in absorbance at 284 nm simultaneous with an increase in the absorbance of another band in the spectral range of 320-380 nm, which was downshifted under UV irradiation. The relative intensity of the FA PL band, situated in the spectral range 375-600 nm, was dependent on the pH of the PB solution. The FA PL intensity increased as increasing UV irradiation time up to 281 min. in PB solutions with pH values of 6.4 and 5.4. Under an emission wavelength of 500 nm, the position of the FA PLE spectrum changed as the PB solution pH varied from 7 to 5.4 and the irradiation time increased to 317 min. These changes were correlated with the formation of two photodegradation products, namely, pterine-6-carboxylic acid and p-amino-benzoyl-L-glutamic acid. According to UV-VIS spectroscopy and PL and PLE studies, the presence of various excipients in commercial pharmaceutical tablets does not affect the photodegradation of FA in PB solutions. Using IR spectroscopy, new evidences for the formation of the two photodegradation products of FA in PB solutions are shown.

891. Thermal, structural, magnetic and magneto-optical properties of dysprosium-doped phosphate glass

Authors: Elisa, M; Stefan, R; Vasiliu, IC; Rusu, MI; Sava, BA; Boroica, L; Sofronie, M; Kuncser, V; Galca, AC; Beldiceanu, A; Volceanov, A; Eftimie, M

Published: OCT 1 2019, JOURNAL OF NON-CRYSTALLINE SOLIDS, 521, DOI: 10.1016/j.jnoncrysol.2019.119545

The work is dedicated to the investigation of optical, structural, magnetic and magneto-optical properties of an aluminophosphate glass doped with Dy3+ ions, for specific applications as Faraday rotators in the visible spectral domain. The vitreous material belongs to the 16Li(2)O-8Al(2)O(3)-6BaO center dot 60P(2)O(5)-10Dy(2)O(3) system. Optical homogeneity measured by a polariscopic method, as well as by polarimetry and interferometry revealed an optical quality glass. Time dependent electrical conductance measurements have shown a high chemical strength of the glass. Optical absorption of the doped glass in the visible domain evidenced the specific absorption lines of dysprosium ions, whereas structural investigations made by FTIR and Raman spectroscopy put in evidence the vitreous network forming role of phosphorous pentoxide. Magnetic and magneto-optical measurements demonstrated paramagnetic features of the doped glass, as well as a Verdet constant of about -0.05 min/Oe/cm at 600 nm wavelength.

892. Zinc Doped Hydroxyapatite Thin Films Prepared by Sol-Gel Spin Coating Procedure

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Buton, N; Motelica-Heino, M

Published: FEB 28 2019, COATINGS, 9, DOI: 10.3390/coatings9030156

In this study, ZnHAp layers deposited on a Si substrate were obtained by a sol-gel spin-coating procedure. The ZnHAp solutions used to obtain the ZnHAp coatings were investigated by dynamic light scattering (DLS) analysis, zeta-potential, ultrasound measurements, and flame atomic absorption spectrometry (AAS). The average measured hydrodynamic diameter from the DLS analysis, zeta-potential, and ultrasound measurements were analyzed so as to characterize and estimate the stability of the ZnHAp nanoparticles. The AAS results confirmed the presence of zinc in the gels used in the preparation of the ZnHAp layers. The layers were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed the diffraction peaks of the hexagonal hydroxyapatite in all of the investigated samples. The morphology of the ZnHAp coatings annealed at 500 degrees C (ZnHAp-500) and 700 degrees C (ZnHAp-700), which evidenced that no fissures or cracks formed on the surface of the coatings. The biocompatibility assays indicated that the ZnHAp coatings did not present any toxicity towards the HeLa cells. Furthermore, the study regarding the cytotoxicity of the ZnHAp layers against microorganisms emphasized that ZnHAp coatings exhibited an inhibitory effect towards S. aureus bacterial cells and also towards C. albicans fungal cells.

893. Tryptophan/Dextran70 Based-Fluorescent Silver Nanoparticles: Synthesis and Physicochemical Properties

Authors: Voicescu, M; Ionescu, S; Calderon-Moreno, JM; Teodorescu, VS; Anastasescu, M; Culita, DC

Published: JUL 2019, JOURNAL OF FLUORESCENCE, 29, 992, DOI: 10.1007/s10895-019-02411-2

Nano-size and shape of fluorescent silver nanostructures are important for a wide range of bio-applications, especially as drug delivery systems, imaging and sensing. The aim of the work is to develop a fluorescent silver nano-structured system, synthesized by chemical reduction of aqueous AgNO3 solution by Tryptophan using Dextran 70 as stabilizing agent (SNPs(FL)). The formed fluorescent nano-system was analyzed by UV-Vis absorption, DLS, SEM, TEM, AFM, steady-state and time resolved fluorescence spectroscopy. TEM analysis showed multi-twined nanoparticle, with the size within 15-40 nm. SNPs(FL) shows the fluorescence emission at 346 nm, the fluorescence quantum yield, phi = 0.034 and the integrated fluorescence lifetime, = 1.82 ns. Riboflavin fluorescence behaviour in the RF/SNPs(FL) system, has been also studied. The results have relevance in using SNPs(FL) as a potential marker/emissive system to solve various biological barriers in humans, like drug release and protein structure.

894. NiTi coated with oxide and polymer films in the in vivo healing processes

Authors: Batalu, D; Nastase, F; Militaru, M; Gherghiceanu, M; Badica, P

Published: JAN-MAR 2019, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 8, 922, DOI: 10.1016/j.jmrt.2018.06.015

Plates of NiTi chemically etched, electro-polished, and sol gel coated with XO2 (X =Ti, Si, Zr), or coated with oxides and dip-coated polymers of Dextro-Levo-lactide-co-glycolide (DL-PLG, 0.4 mu m thickness), Dextro-Levo-lactic acid (DL-PLA, 1.3 mu m) or poly methyl methacrylate polymer (PMMA, 1.7 mu m) were obtained. Smooth and uniform NiTi surfaces without significant pitting, as revealed by AFM, were prepared for chemical etching of 120 s in HF:HNO3:H2O = 1:5:4, followed by electropolishing 120 s in H2SO4:CH3OH:H2O = 1:4:5 electrolyte and using a potential of 9 V. Dip-coated layer of PMMA has shown cracks and large pores and was eliminated from further experiments. Samples of pristine and coated NiTi were in vivo implanted into rabbits and extracted after 10 and 60 days. Clinically, all implants are biocompatible; all rabbits survived and a recovery process was observed for all cases. NiTi covered with SiO2, DL-PLG and SiO2/DL-PLG have shown the best healing evolution. For 10 and 60 days good recovery was found also for NiTi coated with TiO2. Coatings of ZrO2 and ZrO2/DL-PLG have shown the poorest results. The oxide coating and the roughness R-ZJIS that contains information on the 'deep' large areas in the coatings show the strongest influence on the healing processes. Work indicates the possibility of space- and time- scale controlled variation of the functional properties. (C) 2018 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.

895. Growth of SrTiO3 Single Crystals with a Diameter of about 30 mm by the Verneuil Method

Authors: Tateno, Y; Endo, K; Arisawa, S; Vlaicu, AM; Nedelcu, L; Preda, N; Secu, M; Iordanescu, R; Kuncser, AC; Badica, P

Published: FEB 2019, CRYSTAL GROWTH & DESIGN, 19, 612, DOI: 10.1021/acs.cgd.8b01004

The work demonstrates growth by the Verneuil method of SrTiO3 single crystals of 30 mm in diameter. Experiments are performed under an industrial environment. Growth was for 4.75 h, i.e., within one production shift. The optimum growth conditions for which the length of the region with bubbles D is zero and the effective length EL (i.e., the crystal length of commercial value) is maximized are for the amount of SrCO3 additive of similar to 3 wt % and for H-2 outer flow rate of similar to 35 L/min. These two parameters show the strongest influence on the bubble-free growth, but other growth parameters (H-2 inner flow rate, O-2 flow rate increase, rotation speed) were also optimized. Selected crystals are characterized from the structural, microstructural, optical, and THz spectroscopy viewpoints, and they are compared with a commercial substrate and with crystals reported in the literature. This work opens the possibility for the industrial growth of large SrTiO3 single crystals and commercialization of large area substrates.

896. Evaluation of Antibacterial Activity of Zinc-Doped Hydroxyapatite Colloids and Dispersion Stability Using Ultrasounds

Authors: Predoi, D; Iconaru, SL; Predoi, MV; Motelica-Heino, M; Guegan, R; Buton, N

Published: APR 2019, NANOMATERIALS, 9, DOI: 10.3390/nano9040515

This study proves that the new developed zinc-doped hydroxyapatite (ZnHAp) colloids by an adapted sol-gel method can be widely used in the pharmaceutical, medical, and environmental industries. ZnHAp nanoparticles were stabilized in an aqueous solution, and their colloidal dispersions have been characterized by different techniques. Scanning Electron Microscopy (SEM) was used to get information on the morphology and composition of the investigated samples. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the elemental compositions of ZnHAp colloidal dispersions. The homogeneous and uniform distribution of constituent elements (zinc, calcium, phosphorus, oxygen) was highlighted by the obtained elemental mapping results. The X-ray diffraction (XRD) results of the obtained samples showed a single phase corresponding to the hexagonal hydroxyapatite. The characteristic bands of the hydroxyapatite structure were also evidenced by Fourier-transform infrared spectroscopy (FTIR) analysis. For a stability assessment of the colloidal system, -potential for the ZnHAp dispersions was estimated. Dynamic light scattering (DLS) was used to determine particles dispersion and hydrodynamic diameter (D-HYD). The goal of this study was to provide for the first time information on the stability of ZnHAp particles in solutions evaluated by non-destructive ultrasound-based technique. In this work, the influence of the ZnHAp colloidal solutions stability on the development of bacteria, such as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), was also established for the first time. The antimicrobial activity of ZnHAp solutions was strongly influenced by both the stability of the solutions and the amount of Zn.

897. Photoluminescence and thermoluminescence properties of the Sr3Al2O6:Eu3+/Eu2+,Tb3+ persistent phosphor

Authors: Gingasu, D; Mindru, I; Ianculescu, A; Preda, S; Negrila, C; Secu, M

Published: OCT 2019, JOURNAL OF LUMINESCENCE, 214, DOI: 10.1016/j.jlumin.2019.116540

Eu3+,Tb3+-doped Sr3Al2O6 powder phosphor was synthesized via a precursor route and subjected to a subsequent thermal treatment in reducing atmosphere. Photoluminescence and thermoluminescence properties of Sr3Al2O6:Eu3+/Eu2+,Tb3+ were investigated. The structure and morphology of oxides were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used for the nanocrystals surface composition analysis. X-ray diffraction patterns confirmed the formation of the cubic structure specific to Sr3Al2O6 with space group Pa3 and lattice parameter a = 15.8322 angstrom, while SEM investigations revealed equiaxial, polycrystalline particles, with sizes in the submicronic range, for both Sr3Al2O6:Eu3+,Tb3+ and Sr3Al2O6:Eu3+/Eu2+,Tb3+ samples. The photoluminescence spectra showed the typical f-f luminescence lines of the Tb(3+ )and Eu3+ - ions, accompanied by a broad Eu2+ luminescence band at 510 nm (after calcination in reducing atmosphere). The "after-glow" luminescence signal and the thermoluminescence were assigned to the recombination of close neighbor partners (electron and Eu2+ - hole centers) within the same complex of defects.

898. Structural, electric and pyroelectric properties of up and down graded PZT multilayers

Authors: Botea, M; Hrib, L; Pasuk, I; Iuga, A; Trupina, L; Negrea, R; Becherescu, N; Pintilie, L

Published: JUL 2019, CURRENT APPLIED PHYSICS, 19, 810, DOI: 10.1016/j.cap.2019.04.010

Multi-layered structures, composed of thin films from materials with different compositions or physical properties, represents a way to obtain enhanced properties or even new functionalities. In this work, lead zirconate titanate PbZrxTi1-xO3 (PZT; x = 0.20, 0.52, 0.80) multilayers were grown by pulsed laser deposition (PLD) on a single crystal strontium titanate (SrTiO3, STO) substrate, using a strontium ruthenate (SrRuO3, SRO) film as buffer layer for epitaxial growth, and also as back electrode. Up and down multi-layers were grown and their physical and structural properties were compared, up being the structure in which Zr concentration was varied from 20% near the STO substrate to 80% at the surface, while down is for the structure in which the Zr concentration starts with 80% near the substrate and ends with 20% at the surface. It was found that the electric and pyroelectric properties of the two graded structures are significantly different. The up structure presents electric properties that are comparable with those of single composition PZT films while the properties of the down structure are deteriorated, especially in terms of the leakage current magnitude. Pyroelectric signal could be measured only for the up structure. These differences were attributed to larger density of structural defects in the down structure compared to the up one. This is due to the different growth sequence: Lop structure starts with tetragonal PZT on cubic substrate (lower lattice mismatch, 1.1%) while down structure starts with rhombohedral PZT on cubic substrate (larger lattice mismatch, almost 5%).

899. La0.75Sr0.25XO3 (X = Fe, Mn or Cr) with coking tolerance for CH4/H2O reaction: effect of H2S on catalytic performance

Authors: Florea, M; Somacescu, S; Postole, G; Urda, A; Neatu, F; Neatu, S; Massin, L; Gelin, P

Published: MAY 7 2019, CATALYSIS SCIENCE & TECHNOLOGY, 9, 2366, DOI: 10.1039/c9cy00065h

The influence of the B type cation from the ABO(3) perovskite formulation La0.75Sr0.25XO3 (LSX, where X is Fe, Mn or Cr) on the C and H2S tolerance and its catalytic activity for the methane/water reaction has been studied. The samples were prepared by a simple and cost-efficient citrate method. The exhaustive characterization of the bulk and surface properties of the catalysts has been accomplished by means of complementary methods: nitrogen adsorption-desorption isotherm measurements, XRD, TPR and XPS. Their catalytic properties in CH4/H2O reactions (CH4/H2O molar ratios of 10 and 1) were studied in the presence and absence of H2S in order to evaluate their potential use as anode materials in solid oxide fuel cells operated on natural gas. Before addition and upon suppression of H2S, the activity varied in the following order: LSF > LSM >> LSC. This correlates with the oxygen mobility determined by TPR. A strong promoting effect of H2S on the catalytic activity is observed for LSC, which makes this sample the most active of the series, while H2S has a weak influence on the other perovskites. The oxygen vacancies and the presence of S2- were identified as being responsible for the enhanced catalytic activity upon H2S addition.

900. Photoconductive Behavior of the PPV/RGO Composites: Insights of Charge Transfer Process

Authors: Ilie, M; Dragoman, D; Baibarac, M

Published: JUL 2019, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 256, DOI: 10.1002/pssb.201800392

The paper deals with a study of composites based on poly(p-phenylenevinylene) (PPV) and reduced graphene oxide (RGO) in terms of photoconductivity and photocurrent (PC) dynamics in charge-discharge cyclic processes. The explanation for the photoconductive behavior is built with the support of DeVore and Onsager theories. Scanning samples in both directions involves charge transport, to and from, available energy states called defect centers. The existence of these centers is confirmed by a decrease in the composite bandgap caused by the RGO localized states which are situated slightly above the first HOMO level in the PPV bandgap. The contribution of RGO to the photoconductive properties of PPV is revealed through a photocurrent value with two orders of magnitude higher than for PPV.

901. Reduced graphene oxide/TiO2 nanocomposites coating of cotton fabrics with antibacterial and self-cleaning properties

Authors: Stan, MS; Nica, IC; Popa, M; Chifiriuc, MC; Iordache, O; Dumitrescu, I; Diamandescu, L; Dinischiotu, A

Published: SEP 2019, JOURNAL OF INDUSTRIAL TEXTILES, 49, 293, DOI: 10.1177/1528083718779447

Textile materials can be easily used as a support for the nano-decoration with active particles in order to gain new features such as self-cleaning, antimicrobial efficiency, water repellency, mechanical strength, color change and protection against ultraviolet radiations. In this context, our present research reports the fabrication and characterization (physico-chemical analysis and surface morphology) of cotton fabrics treated with reduced graphene oxide decorated with two types of TiO2 nanoparticles co-doped with 1% iron and nitrogen atoms (TiO2/rGO NPs) and synthesized in different hydrothermal conditions by a simultaneous precipitation of Ti3+ and Fe3+ ions to achieve their uniform distribution or after a sequential precipitation of these two cations for obtaining a higher concentration of iron on the surface of Ti4+ oxyhydroxide. Further, the antimicrobial efficiency of these TiO2/rGO-treated textiles and their influence on human cells were assessed. We demonstrated the successful development of TiO2/rGO coating of cotton fabrics which are harmless for human skin cells and inhibit the growth of Staphylococcus aureus and Enterococcus faecalis. These findings confirm their great potential as novel graphene-based materials for biomedical and photocatalytic applications and this approach could be used for the large-scale fabrication of innovative self-cleaning and antimicrobial textiles.

902. Broadband Y-type Divider in Ku-band Using Substrate Integrated Waveguide

Authors: Fu, Y; Chan, KY; Banciu, MG; Ramer, R

Published: 2019, 2019 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2019), 42ND EDITION, 60, DOI:

This paper presents the study and analyses on substrate integrated waveguide (SIW) Y-type power dividers. In traditional configurations, a potential stop peak exists and separates the dominant frequency band. To overcome this drawback, a Y-type power divider with an enhanced bandwidth is proposed, where the reflection at the stop peak is reduced. The broadband characteristic relies on the adjustment of the TE10 and TE30 modes in the coupling region. The symmetric topology could ensure balanced phase and amplitude properties at two output ports. For the demonstration, the prototype is fabricated by the printed circuit board (PCB) process. Measurements agree well with simulations, and a fractional bandwidth of 50.26% around the centre frequency of 15 GHz is measured with 10 dB return loss.

903. Ge nanoparticles in SiO2 for near infrared photodetectors with high performance

Authors: Stavarache, I; Teodorescu, VS; Prepelita, P; Logofatu, C; Ciurea, ML

Published: JUL 16 2019, SCIENTIFIC REPORTS, 9, DOI: 10.1038/s41598-019-46711-w

In this work we prepared films of amorphous germanium nanoparticles embedded in SiO2 deposited by magnetron sputtering on Si and quartz heated substrates at 300, 400 and 500 degrees C. Structure, morphology, optical, electrical and photoconduction properties of all films were investigated. The Ge concentration in the depth of the films is strongly dependent on the deposition temperature. In the films deposited at 300 degrees C, the Ge content is constant in the depth, while films deposited at 500 degrees C show a significant decrease of Ge content from interface of the film with substrate towards the film free surface. From the absorption curves we obtained the Ge band gap of 1.39 eV for 300 degrees C deposited films and 1.44 eV for the films deposited at 500 degrees C. The photocurrents are higher with more than one order of magnitude than the dark ones. The photocurrent spectra present different cutoff wavelengths depending on the deposition temperature, i.e. 1325 nm for 300 degrees C and 1267 nm for 500 degrees C. These films present good responsivities of 2.42 AW(-1) (52 mu W incident power) at 300 degrees C and 0.69 AW(-1) (57 mW) at 500 degrees C and high internal quantum efficiency of similar to 445% for 300 degrees C and similar to 118% for 500 degrees C.

904. The hysteresis-free behavior of perovskite solar cells from the perspective of the measurement conditions

Authors: Nemnes, GA; Besleaga, C; Tomulescu, AG; Leonat, LN; Stancu, V; Florea, M; Manolescu, A; Pintilie, I

Published: MAY 14 2019, JOURNAL OF MATERIALS CHEMISTRY C, 7, 5274, DOI: 10.1039/c8tc05999c

We investigate how far the hysteresis-free behavior of perovskite solar cells can be reproduced using particular pre-conditioning and measurement conditions. As there are currently more and more reports of perovskite solar cells without J-V hysteresis it is crucial to distinguish between genuine performance improvements and measurement artifacts. We focus on two of the parameters that influence the dynamic J-V scans, namely the bias scan rate and the bias poling voltage, and point out measurement conditions for achieving a hysteresis-free behavior. In this context we discuss the suitability of defining a hysteresis index (HI) for the characterization of dynamic J-V scans. Using HI, aging effects are also investigated, establishing a potential connection between the sample degradation and the variation of the maximal hysteresis on one hand, and the relaxation time scale of the slow process on the other hand. Pre-poling induced recombination effects are identified. In addition, our analysis based on sample pre-biasing reveals potential indications regarding two types of slow processes, with two different relaxation time scales, which provides further insight regarding ionic migration.

905. Particularities of trichloroethylene photocatalytic degradation over crystalline RbLaTa2O7 nanowire bundles grown by solid-state synthesis route

Authors: Raciulete, M; Papa, F; Kawamoto, D; Munteanu, C; Culita, DC; Negrila, C; Atkinson, I; Bratan, V; Pandele-Cusu, J; Balint, I

Published: FEB 2019, JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING, 7, DOI: 10.1016/j.jece.2018.11.034

This is the first report on synthesis and photocatalytic activity for trichloroethylene (TCE) degradation under simulated solar light over RbLaTa2O7 layered perovskites with predominant nanowire or platelet morphologies. SEM images witnessed that the one step thermal treatment at 1200 degrees C lead to formation of RbLaTa2O7 nanowires with diameter of 80-320 nm and several microns in length associated in bundles and sharp-edged, merged platelets (minor phase). The two-step annealing at 950 degrees C and 1200 degrees C resulted in decrease of wires bundle population and increase in that of platelets merged in facetted particles. The RbLaTa2O7 nanowires are made of by well-aligned atomic rows with preferred orientation toward the c-axis, relatively free of defect. High density of hydroxyl groups on the sample calcined in mild conditions (RbLaTa_01) favors the photo mineralization of TCE. In contrast, the activity of RbLaTa_02 annealed in harsh conditions (950 and 1200 degrees C), poor in surface hydroxyl groups, remained modest. The weak surface basicity directed the reaction mainly to generation of intermediate chlorinated compounds. Pd and Au were supported on RbLaTa2O7 perovskites as an alternative strategy to boost the removal of chlorinated pollutants by combining photocatalytic (mineralization) and catalytic (hydrodechlorination, HDC) processes. The mineralization of TCE to Cl- was drastically hindered in presence of methanol due to quenching of -OH radicals by alcohol. The results suggested that the density of RbLaTa2O7 surface hydroxyl groups is essential for photo mineralization of TCE whereas the surface carbonate is beneficial for the formation of intermediate chlorinated product.

906. Influence of Sintering Strategy on the Characteristics of Sol-Gel Ba1-xCexTi1-x/4O3 Ceramics

Authors: Stanciu, CA; Pintilie, I; Surdu, A; Trusca, R; Vasile, BS; Eftimie, M; Ianculescu, AC

Published: DEC 2019, NANOMATERIALS, 9, DOI: 10.3390/nano9121675

Single-phase Ce3+-doped BaTiO3 powders described by the nominal formula Ba1-xCexTi1-x/4O3 with x = 0.005 and 0.05 were synthesized by the acetate variant of the sol-gel method. The structural parameters, particle size, and morphology are strongly dependent on the Ce3+ content. From these powders, dense ceramics were prepared by conventional sintering at 1300 degrees C for 2 h, as well as by spark plasma sintering at 1050 degrees C for 2 min. For the conventionally sintered ceramics, the XRD data and the dielectric and hysteresis measurements reveal that at room temperature, the specimen with low cerium content (x = 0.005) was in the ferroelectric state, while the samples with significantly higher Ce3+ concentration (x = 0.05) were found to be in the proximity of the ferroelectric-paraelectric phase transition. The sample with low solute content after spark plasma sintering exhibited insulating behavior, with significantly higher values of relative permittivity and dielectric losses over the entire investigated temperature range relative to the conventionally sintered sample of similar composition. The spark-plasma-sintered Ce-BaTiO3 specimen with high solute content (x = 0.05) showed a fine-grained microstructure and an almost temperature-independent colossal dielectric constant which originated from very high interfacial polarization.

907. INVESTIGATION OF THE PHOTOELECTROCHEMICAL BEHAVIOR OF NANOCARBON/MESOPOROUS TiO2 FILMS

Authors: Sima, M; Vasile, E; Sima, A

Published: OCT-DEC 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 941, DOI:

In this work, we report the influence of nanocarbon deposited on mesoporous TiO2 by spray method on photoelectrochemical performance of the formed photoanodes. Scanning electron microscopy and transmission electron microscopy images confirmed presence of carbon nanoparticles on the surface of anatase TiO2 films. Nanocarbon decorated TiO2 photoanodes were characterized by electrochemical impedance spectroscopy and Mott-Schottky analysis. Charge recombination process was evaluated by measurement of open-circuit voltage decay after interruption the illumination Only a small enhancement of photoelectrochemical performance of these photoanodes was observed. It was attributed to increasing of charge carrier density as a result of nanocarbon deposition on TiO2 film.

908. Gd3+ co-doping influence on the morphological, up-conversion luminescence and magnetic properties of LiYF4:Yb3+/Er3+ nanocrystals

Authors: Secu, CE; Bartha, C; Matei, E; Negrila, C; Crisan, A; Secu, M

Published: JUL 2019, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 130, 241, DOI: 10.1016/j.jpcs.2019.03.003

The influence of the Gd3+ co-dopant on the structure, morphology and up-conversion luminescence/magnetic properties of the LiYF4:Gd3+/Yb3+/Er3+ nanocrystals was investigated and compared to those of Gd-free samples. Electron microscopy has indicated an inhibiting effect of the agglomeration and collapsing process of the nanocrystals compared to the Gd-free powder samples. The surface analysis of nanocrystals have not shown oxygen-metal bonds related to the metal oxidation within the surface nanometric layer. The paramagnetic properties are related to the magnetic moment of the Gd3+ ions. The up-conversion luminescence of the LiYF4:Gd3+/Yb3+/Er3+ nanocrystals is about six times stronger than in LiYF4:Yb3+/Er3+ nanocrystals; the enhancement effect is most probably due to the lattice distortion induced by the Gd co-doping.

909. Designing cotton fibers impregnated with photocatalytic graphene oxide/Fe, N-doped TiO2 particles as prospective industrial self-cleaning and biocompatible textiles

Authors: Stan, MS; Badea, MA; Pircalabioru, GG; Chifiriuc, MC; Diamandescu, L; Dumitrescu, I; Trica, B; Lambert, C; Dinischiotu, A

Published: JAN 1 2019, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 94, 332, DOI: 10.1016/j.msec.2018.09.046

Our study reports the fabrication and characterization (surface morphology, hydrophobicity/hydrophilicity, photocatalytic efficiency) of cotton fibers treated by various methods with graphene oxide decorated with Fe, N-doped TiO2 nanoparticles. Designed as prospective industrial self-cleaning, antimicrobial and biocompatible textiles, microbiological and cytotoxicity tests were performed on these particles-treated fibers to validate their qualities. The photocatalytic effect was dependent on chemicals used to disperse the nanoparticles, the parameters of the treatment, the fiber structure and composition of the material. The double and triple treatment of the textiles with the same particle dispersion resulted in a relatively uniform coverage of cotton fibers with relatively large amounts of particles. A larger amount of doped TiO2 particles demonstrated a better photo - catalytic effect under visible light. The material's hydrophobicity increased with the number of treatments due to the deposition of successive layers of reduced graphene, ensuring self-cleaning properties. The photocatalyst-treated cotton fabrics exhibited an increased resistance to Enterococcus faecalis and Escherichia coli colonization, and also high biocompatibility, as they did not affect the cell viability, membrane integrity and morphology, nor induce inflammation. All these data confirm the improved properties of cotton fibers treated with graphene oxide decorated with Fe, N-doped TiO2 particles in order to be used as industrial self-cleaning and biocompatible textiles.

910. Highly transparent Yb:Y2O3 ceramics obtained by solid-state reaction and combined sintering procedures

Authors: Stanciu, G; Gheorghe, L; Voicu, F; Hau, S; Gheorghe, C; Croitoru, G; Enculescu, M; Yavetskiy, RP

Published: FEB 15 2019, CERAMICS INTERNATIONAL, 45, 3222, DOI: 10.1016/j.ceramint.2018.10.224

(Y0.87-xLa0.1Zr0.03Ybx)(2)O-3 (x = 0.02, 0.04, 0.05) transparent ceramics were obtained by solid-state reaction and combined sintering procedures with La2O3 and ZrO2 as sintering additives. A method based on two-step intermediate sintering in air followed by vacuum sintering was applied in order to control the densification and grain growth of the samples during the final sintering process. The results indicate that La2O3 and ZrO2 co-additives can improve the microstructure and optical properties of Yb:Y2O3 ceramics at relatively low sintering temperature. On the other hand, the addition of Zr4+ ions leads to the formation of dispersed scattering volumes in the ceramic bodies. Transmittance of 78.8% was measured for the 2.0 at% Yb:Y2O3 ceramic sample at the wavelength of 1100 nm. The spectroscopic properties of Yb:Y2O3 ceramics were investigated at room temperature. The obtained results show that the absorption cross-section at 978 nm is in the range of 2.08 x 10(-20) to 2.36 x 10(-20) cm(2), whereas the emission cross-section at 1032 nm is similar to 1.0 x 10(-20) cm(2).

911. Do topology and ferromagnetism cooperate at the EuS/Bi2Se3 interface?

Authors: Krieger, JA; Ou, Y; Caputo, M; Chikina, A; Dobeli, M; Husanu, MA; Keren, I; Prokscha, T; Suter, A; Chang, CZ; Moodera, JS; Strocov, VN; Salman, Z

Published: FEB 19 2019, PHYSICAL REVIEW B, 99, DOI: 10.1103/PhysRevB.99.064423

We probe the local magnetic properties of interfaces between the insulating ferromagnet EuS and the topological insulator Bi2Se3 using low energy muon spin rotation (LE-mu SR). We compare these to the interface between EuS and the topologically trivial metal, titanium. Below the magnetic transition of EuS, we detect strong local magnetic fields which extend several nm into the adjacent layer and cause a complete depolarization of the muons. However, in both Bi(2)Se(3 )and titanium we measure similar local magnetic fields, implying that their origin is mostly independent of the topological properties of the interface electronic states. In addition, we use resonant soft x-ray angle resolved photoemission spectroscopy (SX-ARPES) to probe the electronic band structure at the interface between EuS and Bi2Se3. By tuning the photon energy to the Eu antiresonance at the Eu M-5 pre-edge we are able to detect the Bi2Se3 conduction band, through a protective Al2O3 capping layer and the EuS layer. Moreover, we observe a signature of an interface-induced modification of the buried Bi2Se3 wave functions and/or the presence of interface states.

912. Superconducting MgB2 textured bulk obtained by ex situ spark plasma sintering from green compacts processed by slip casting under a 12T magnetic field

Authors: Grigoroscuta, MA; Sandu, V; Kuncser, A; Pasuk, I; Aldica, G; Suzuki, TS; Vasylkiv, O; Badica, P

Published: DEC 2019, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 32, DOI: 10.1088/1361-6668/ab4620

MgB2 green bodies were prepared by magnetic field slip casting in ethyl alcohol with added polyethyleneimine dispersing agent under a high magnetic field, mu H-0(0) = 12 T. Samples were further processed by spark plasma sintering (SPS) and characterized for superconducting properties. Slip casting provides texturing of MgB2 (the degree of c-axis orientation is approximately 3.5%), which is further increased significantly (to about 21%) in the SPSed sample. The critical current density (J(c)) displays anisotropy relative to the orientation of the measuring magnetic field. Specific features of J(c)(H, T) and of the pinning force extracted from magnetic measurements with the field parallel and perpendicular to H-0 are discussed.

913. Dextran-Coated Zinc-Doped Hydroxyapatite for Biomedical Applications

Authors: Predoi, D; Iconaru, SL; Predoi, MV

Published: MAY 2019, POLYMERS, 11, DOI: 10.3390/polym11050886

Dextran-coated zinc-doped hydroxyapatite (ZnHApD) was synthesized by an adapted sol-gel method. The stability of ZnHApD nanoparticles in an aqueous solution was analyzed using ultrasonic measurements. The analysis of the evolution in time of the attenuation for each of the frequencies was performed. The X-ray diffraction (XRD) investigations exhibited that no impurity was found. The morphology, size and size distribution of the ZnHApD sample was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The TEM and SEM results showed that the ZnHApD particles have an ellipsoidal shape and a narrow distribution of sizes. The cell growth and toxicity of HEK-293 cells were investigated on the ZnHApD solution for four different concentrations and analyzed after 24 and 48 h. The ZnHApD solution presented a non-toxic activity against HEK-293 cells for all analyzed concentrations. The antibacterial assay revealed that all the tested microorganisms were inhibited by the ZnHApD dispersion after 24 and 48 h of incubation. It was observed that the effect of the ZnHApD solution on bacteria growth depended on the bacterial strain. The Porphyromonas gingivalis ATCC 33277 bacterial strain was the most sensitive, as a growth inhibition in the presence of 0.075 mu g/mL ZnHApD in the culture medium was observed.

914. Multiferroic (Nd,Fe)-doped PbTiO3 ceramics with coexistent ferroelectricity and magnetism at room temperature

Authors: Craciun, F; Cordero, F; Cernea, M; Fruth, V; Atkinson, I; Stanica, N; Vasile, BS; Trusca, R; Iuga, A; Galizia, P; Galassi, C

Published: MAY 2019, CERAMICS INTERNATIONAL, 45, 9396, DOI: 10.1016/j.ceramint.2018.08.147

We report the structural, dielectric, elastic, ferroelectric and ferromagnetic properties of multiferroic (Nd, Fe)doped PbTiO3 perovskite ceramics with composition (Pb-0.88 Nd-0.08 )(Ti-0.94 Fe-0 .04 Mn-0.02)O-3, prepared by different solid state reaction methods: the first one based on a single-stage calcination (Method I) and the second based on a double-stage calcination (Method II). Structural, dielectric and anelastic measurements evidenced a double phase transition for samples prepared by Method I, which has been attributed to phase separation. This phase separation has been confirmed also by TEM and HRTEM investigations. Samples prepared by Method II showed a single phase transition from paraelectric to ferroelectric phase. We found coexistent ferroelectric and ferromagnetic properties, also at room-temperature, but only for ceramics prepared by Method II. The crucial role of calcination process for avoiding phase separation and obtaining homogeneous structures with ferroelectric and ferromagnetic order is underlined.

915. Composite BNT-BT0.08/CoFe2O4 with core-shell nanostructure for piezoelectric and ferromagnetic applications

Authors: Cernea, M; Vasile, BS; Ciuchi, IV; Surdu, VA; Bartha, C; Iuga, A; Galizia, P; Galassi, C

Published: JAN 2019, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 240, 15, DOI: 10.1016/j.mseb.2019.01.001

In this work, we report on the synthesis and characterization of BNT-BT0.08/CoFe2O4 biphasic composite with core-shell structure. This artificial core (BNT-BT0.08/shell (CoFe2O4) heterostructure was prepared by sol-gel method and the resulting composite was characterized in term of microstructure, dielectric, piezoelectric and magnetic properties. BNT-BT0.08/CoFe2O4 sintered ceramic shows high permittivity (epsilon' >= 30) and high dielectric losses (tan delta >= 10) in the low frequency range (nu <= 10(4) Hz), remnant polarization (Pr) of similar to 7.7 mu C/cm(2) and, remanent magnetization (Mr) of 24 emu/g at 5 K and of 14 emu/g, at room temperature. The present study reveals that the ferroelectric, piezoelectric and magnetic properties of this new architectured composite depend on the amount of each component and, can be tailored by adjusting their synthesis conditions. BNT-BT0.08/CoFe2O4 core-shell material investigated in this work provides a novel way to exploit new applications for the multifunctional composite, such as piezoelectric sensor, magnetoelectronic sensors and data storage devices.

916. Sub-lattice polarization states in anti-ferroelectrics and their relaxation process

Authors: Vopson, MM; Tan, X; Namvar, E; Belusky, M; Thompson, SP; Kuncser, V; Plazaola, F; Unzueta, I; Tang, CC

Published: MAY 2019, CURRENT APPLIED PHYSICS, 19, 656, DOI: 10.1016/j.cap.2019.03.009

We report studies of quasi-remanent polarization states in Pb0.99Nb0.02[(Zr0.57Sn0.43)(0.94)Ti-0.06](0.98)O-3 (PNZST) anti-ferroelectric ceramics and investigation of their relaxation effects using unique in-situ electrically activated time-resolved Synchrotron X-ray powder diffraction (SXPD) and Sn-119 Mossbauer Spectroscopy (MS). The SXPD patterns are consistent with a phase transition from quasi-tetragonal perovskite in 0 V relaxed anti-ferroelectric state to rhombohedral distortion in ferroelectric state under saturating applied voltages of +/- 2 kV. The observed quasi-remanent polarization relaxation processes are due to the fact that tetragonal to rhombohedral distortion does not occur at the applied voltage required to access the quasiremanent polarization states, and the tetragonal symmetry restored after the removal of the applied electric field is preserved. Since these quasi-remanent polarization states were seen as possibly suitable for memory applications, the implications of this study are that anti-ferroelectrics are more feasible for multi-state dynamic random access memories (DRAM), while their application to non-volatile memories requires development of more sophisticated "read-out" protocols, possibly involving dc electrical biasing.

917. USING RADIOMETRIC AND NON RADIOMETRIC METHODS FOR A COMPLEX CHARACTERIZATION OF A HISTORICAL MONUMENT ENSEMBLE; OTETELESANU EX-MANSION FROM MAGURELE TOWN, ROMANIA, CASE STUDY

Authors: Simion, CA; Sava, TB; Gaza, O; Pacesila, DG; Florea, NM; Ghita, DG; Manea, MM; Straticiuc, M; Andrei, RF; Calin, MR; Radulescu, I; Lukacs, A; Ionescu, DD; Nemteanu, R; Sabo, EE

Published: 2019, ROMANIAN JOURNAL OF PHYSICS, 64, DOI:

Radiometric methods aimed the use of liquid scintillation counting for tritium evaluation in different environmental compartments, alpha-beta and high resolution gamma spectrometry in determining radionuclides in soils, sediments and building materials. The non radiometric methods were focused on radiocarbon dating by accelerator mass spectrometry of bones, on FTIR and TGA analyzes of raw bone material vs. extracted collagen, and on the PIXE compositional analysis of archaeological materials.

918. Pulsed Laser Fabrication of TiO2 Buffer Layers for Dye Sensitized Solar Cells

Authors: Lungu, J; Socol, G; Stan, GE; Stefan, N; Luculescu, C; Georgescu, A; Popescu-Pelin, G; Prodan, G; Girtu, MA; Mihailescu, IN

Published: MAY 2019, NANOMATERIALS, 9, DOI: 10.3390/nano9050746

We report on the fabrication of dye-sensitized solar cells with a TiO2 buffer layer between the transparent conductive oxide substrate and the mesoporous TiO2 film, in order to improve the photovoltaic conversion efficiency of the device. The buffer layer was fabricated by pulsed laser deposition whereas the mesoporous film by the doctor blade method, using TiO2 paste obtained by the sol-gel technique. The buffer layer was deposited in either oxygen (10 Pa and 50 Pa) or argon (10 Pa and 50 Pa) onto transparent conducting oxide glass kept at room temperature. The cross-section scanning electron microscopy image showed differences in layer morphology and thickness, depending on the deposition conditions. Transmission electron microscopy studies of the TiO2 buffer layers indicated that films consisted of grains with typical diameters of 10 nm to 30 nm. We found that the photovoltaic conversion efficiencies, determined under standard air mass 1.5 global (AM 1.5G) conditions, of the solar cells with a buffer layer are more than two times larger than those of the standard cells. The best performance was reached for buffer layers deposited at 10 Pa O-2. We discuss the processes that take place in the device and emphasize the role of the brush-like buffer layer in the performance increase.

919. Highly -sensitive near infrared luminescent nanothermometers based on binary mixture

Authors: Avram, D; Colbea, C; Florea, M; Tiseanu, C

Published: MAY 15 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 785, 259, DOI: 10.1016/j.jallcom.2019.01.162

We propose a simple strategy to obtain a luminescence intensity ratio nanothermometer operating in the near infrared range (1000-1700 nm) by use of binary mixtures of lanthanide doped Y2O3 selected as 1% Ho - Y2O3 + 1%Er - Y2O3 and 1%Ho - Y2O3 + 1%Nd - Y2O3. All nanoparticles were synthetized by citrate complexation method and thermally annealed at 800 degrees C. The temperature evolution of the emission properties was monitored in the range of 297-472 K and analyzed in terms of emission shape, intensity, dynamics, excitation wavelength, acquisition mode and weight ratio of the binary mixture. A maximum relative sensitivity of 1%K-1 at 297 K was recorded for the 3/1 weight ratio Ho - Y2O3 + Er - Y2O3 binary mixture upon excitation at 536.8 nm. For the more appropriate excitation wavelength for bioimaging applications at 649.7 nm, a relative sensitivity of 0.55-0.6% K-1 was recorded in the relevant physiological temperature range (300-320 K) for the 3/1 weight ratio Ho - Y2O3 + Er - Y2O3 binary mixture. To the best of our knowledge, our study also represents a first report on the near -infrared luminescence (around 1200 nm) lifetime thermometry for a Ho doped nanoparticle. Comparison with the literature demonstrates that our system represents a promising near-infrared thermometer, with a non-sophisticated and reproducible configuration that is open to multiple optimization routes. (C) 2019 Elsevier B.V. All rights reserved.

920. Physical properties investigation of samarium doped calcium sulfate thin films under high gamma irradiations for space photovoltaic and dosimetric applications

Authors: Souli, M; Reghima, M; Secu, M; Bartha, C; Enculescu, M; Mejri, A; Kamoun-Turki, N; Badica, P

Published: FEB 2019, SUPERLATTICES AND MICROSTRUCTURES, 126, 119, DOI: 10.1016/j.spmi.2018.12.021

This research work is dedicated to study structural, morphological, optical and photoluminescence properties of samarium doped calcium sulfate (CaSO4) thin films after exposure to high gamma radiations. Polycrystalline doped CaSO4 thin films have been grown on glass substrates by spray pyrolysis technique and irradiated at different high gamma doses 3, 7, 15 and 40 kGy. Physical characterization of irradiated thin films has been made by X-ray diffraction, Spectrophotometer, Scanning Electron Microscope, Energy Dispersive Spectroscopy, Fluorescence Spectrometer and Thermoluminescence. The most remarkable result, as shown by structural analysis, is the increase of grain size from 52 to a maximum value of 93 nm for 15 kGy gamma dose which indicates a clear enhancement in crystal structure by gamma irradiation. Moreover, the preferred orientation has been immediately changed from (102) plan to (100) just after the first 3 kGy gamma dose. SEM micrographs of irradiated thin layers show deep modifications in surface morphology. Optical transmission spectra have shown a sharp and intense peak at 350 nm wavelength. Band gap energy has been slightly decreased from 3.9 eV before irradiation to 3.6 eV for 40 kGy. A new and strong energy level noted E r , has been emerged and created due to high gamma irradiations in addition to the principal one relative to band gap energy. Other parameters like absorption and extinction coefficients and refractive index have been determined. Thermoluminescence data show a high sensibility to gamma radiations doses which offer opportunities for dosimetry applications. These experimental results suggest the use of irradiated samarium doped calcium sulfate as optical window for space photovoltaic devices where gamma rays are abundant. These results are also helpful for researchers using CaSO4 thin films near nuclear apparatus (nuclear reactors and particle accelerators) or those interested in studying interaction between radiations and condensed matter.

921. Nanostructured palladium doped nickel electrodes for immobilization of oxidases through nickel nanoparticles

Authors: Barsan, MM; Matei, E; Enculescu, M; Costescu, R; Preda, N; Enache, TA; Enculescu, I; Diculescu, VC

Published: AUG 20 2019, ELECTROCHIMICA ACTA, 315, 113, DOI: 10.1016/j.electacta.2019.04.143

The present investigation deals with the development, characterization and application of nano-structured Pd doped Ni electrodes (Pd@Ni), which uses the electrochemical properties of Pd in synergy with the magnetic properties of Ni for biosensors development. The Pd@Ni electrodes have been characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It has been shown that palladium presented spherical assemblies ranging 150-200 nm medium diameter size that covers large areas of the electrode surface while metallic nickel, which confers magnetic properties, showed a uniform granular structure with sizes between 20 and 50 nm. Cyclic voltammetry and electrochemical impedance spectroscopy were performed to understand the electrochemical process at the Pd@Ni electrodes in neutral media. The Pd@Ni electrodes were applied for the electrochemical detection of H2O2. Finally, Ni nanoparticles (NiNP) functionalized with the model enzyme glucose oxidase (GOx-NiNP) have been attached to the Pd@Ni electrode solely through magnetic interactions, and the obtained GOx-NiNP/Pd@Ni biosensor applied for glucose determination in aqueous solutions by fixed potential amperometry at -0.05 V (vs Ag/AgCl) with reduced interferences. (C) 2019 Elsevier Ltd. All rights reserved.

922. Enhanced photoconductivity of embedded SiGe nanoparticles by hydrogenation

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Stoica, T; Ciurea, ML; Svavarsson, HG

Published: JUN 15 2019, APPLIED SURFACE SCIENCE, 479, 409, DOI: 10.1016/j.apsusc.2019.02.096

We investigate the effect of room-temperature hydrogen-plasma treatment on the photoconductivity of SiGe nanoparticles sandwiched within SiO2 layers. An increase in photocurrent intensity of more than an order magnitude is observed after the hydrogen plasma treatment. The enhancement is attributed to neutralization of dangling bonds at the nanoparticles and to passivation of nonradiative defects in the oxide matrix and at SiGe/matrix interfaces. We find that increasing the partial pressure of hydrogen to pressures where H-3(+) and H-2(+) were the dominant ions results in increased photocurrent.

923. Orthorhombic HfO2 with embedded Ge nanoparticles in nonvolatile memories used for the detection of ionizing radiation

Authors: Palade, C; Slav, A; Lepadatu, AM; Stavarache, I; Dascalescu, I; Maraloiu, AV; Negrila, C; Logofatu, C; Stoica, T; Teodorescu, VS; Ciurea, ML; Lazanu, S

Published: NOV 1 2019, NANOTECHNOLOGY, 30, DOI: 10.1088/1361-6528/ab352b

Trilayer memory capacitors of control HfO2/floating gate of Ge nanoparticles in HfO2/tunnel HfO2/Si substrate deposited by magnetron sputtering and subsequently annealed are investigated for the first time for applications in radiation dosimetry. In the floating gate (FG), amorphous Ge nanoparticles (NPs) are arranged in two rows inside the HfO2 matrix. The HfO2 matrix is formed of orthorhombic/tetragonal nanocrystals (NCs). The adjacent thin films to the FG are also formed of orthorhombic/tetragonal HfO2 NCs. This phase is formed during annealing, in samples with thick control HfO2, in the presence of Ge, being induced by the stress. In the rest of the control oxide, HfO2 NCs are monoclinic. Orthorhombic HfO2 has ferroelectric properties and therefore enhances the memory window produced by charge storage in Ge NPs to above 6 V. The high sensitivity of 0.8 mV Gy(-1) to a particle irradiation from a Am-241 source was measured by monitoring the flatband potential during radiation exposure after electrical writing of the memory.

924. Stable Hall voltages in presence of dynamic quasi-continuum bands in poly (3,4-ethylene-dioxythiophene)

Authors: Stadler, P; Leonat, LN; Menon, R; Coskun, H; van Frank, S; Rankl, C; Scharber, MC

Published: FEB 2019, ORGANIC ELECTRONICS, 65, 418, DOI: 10.1016/j.orgel.2018.12.001

Topological and thermal disorder complicate the mobility characterization in poly(3,4-ethylenedioxythiophene) systems and presently leaves the exact transport mechanisms not fully understood. Here we show that ac-Hall measured by lock-in amplifier is able to resolve the Hall voltage in semimetallic polymers between room temperature and 32 K. These results are evaluated using an organic random phase model. This accounts for the role of tail states and, particularly, for thermal disorder of molecular semiconductors. We report band mobilities up to 3.7 cm(2) V-1 s(-1) in semimetallic polymers occurring in delocalized bands that originate from significant electron coherence across the polymer chains.

925. Imaging dopant distribution across complete phase transformation by TEM and upconversion emission

Authors: Avram, D; Colbea, C; Florea, M; Lazar, S; Stroppa, D; Tiseanu, C

Published: SEP 28 2019, NANOSCALE, 11, 16754, DOI: 10.1039/c9nr04345d

Correlating dopant distribution to its optical response represents a complex challenge for nanomaterials science. Differentiating the "true" clustering nature from dopant pairs formed in statistical distribution complicates even more the elucidation of doping-functionality relationship. The present study associates lanthanide dopant distribution, including all significant events (enrichment, depletion and surface segregation), to its optical response in upconversion (UPC) at the ensemble and single-nanoparticle level. A small deviation from the Er nominal concentration of a few percent is able to induce clear differences in Er UPC emission color, intensity, excited-state dynamics and ultimately, UPC mechanisms, across tetragonal to monoclinic phase transformation in rationally designed Er doped ZrO2 nanoparticles. Rare evidence of a heterogeneous dopant distribution leading to the coexistence of two polymorphs in a single nanoparticle is revealed by Z- and phase contrast transmission electron microscopy (TEM). Despite their spatial proximity, Er in the two polymorphs are spectroscopically isolated, i.e. they do not communicate by energy transfer. Segregated Er, which is well imaged in TEM, is absent in UPC, while the minor phase content overlooked by X-ray diffraction and TEM is revealed by UPC. The outstanding sensitivity of combined TEM and UPC emission to subtle deviations from uniform doping in the diluted concentration regime renders such an approach relevant for various functional oxides supporting lanthanide dopants as emitters.

926. Hybrid layered double hydroxides-curcumin thin films deposited via Matrix Assisted Pulsed Laser Evaporation-MAPLE with photoluminescence properties

Authors: Andrei, F; Vlad, A; Birjega, R; Tozar, T; Secu, M; Urzica, I; Dinescu, M; Zavoianu, R

Published: JUN 1 2019, APPLIED SURFACE SCIENCE, 478, 761, DOI: 10.1016/j.apsusc.2019.02.011

Curcumin (CR) is a natural compound with a well-known antioxidant and therapeutic activity. Its stability may be enhanced when incorporated in different matrices as a layered double hydroxides (LDH) matrix. Curcumin intercalated layered double hydroxide nanohybrid is a potential drug delivery system for effective photodynamic therapy in human breast cancer or skin cancer. The synthesis of the hybrid LDH-CR powder implies the dissolution of CR in water or in another organic solvent which is miscible with water. Since the solubility of curcumin in water is very weak, the aim of this study is to investigate the effect of the solvent employed for its dissolution on the structural and physico-chemicalphotoluminescent properties of the resulting hybrid materials. Four powders of curcumin (CR)-containing Mg2.5Al-LDH hybrids (Mg/Al molar ratio of 2.5) were prepared by co-precipitation (P) and reconstruction (R) using two different solvents for the dissolution of curcumin: (i) an alkaline aqueous solution (A), and (ii) ethanol (E). The reconstruction used the calcinated (460 degrees C for 18 h) form of the parent Mg2.5Al-LDH powder. All the solids were characterized by X-ray diffraction (XRD), and FTIR spectroscopy. The FTIR-ATR spectra of the all the powders except the powder prepared via reconstruction in ethanol exhibit LDH characteristics, consistent with the XRD results. Matrix Assisted Pulsed Laser Evaporation (MAPLE) was employed for the deposition of hybrid LDH-CR thin films. Aqueous solutions of the as prepared hybrid LDH-CR powders were frozen and used as targets for MAPLE depositions. The films were deposited using a nanosecond laser emitting at 266 nm. MAPLE is considered a "soft" deposition technique suitable to conserve the CR stability. XRD, scanning electron microscopy, FT-IR spectroscopy and fluorescence measurements were used to characterize the deposited films in order to evidence the influence of the preparation methods on the structural and photophysical characteristics of the hybrid LDH-CR films.

927. Study of the Structure and Antimicrobial Activity of Ca-Deficient Ceramics on Chlorhexidine Nanoclay Substrate

Authors: Pazourkova, L; Reli, M; Hundakova, M; Pazdziora, E; Predoi, D; Martynkova, GS; Lafdi, K

Published: SEP 2019, MATERIALS, 12, DOI: 10.3390/ma12182996

Novel biomedical composites, based on organically modified vermiculite and montmorillonite with deposited Ca-deficient hydroxyapatite (CDH), were prepared. The monoionic sodium forms of vermiculite and montmorillonite were intercalated with chlorhexidine diacetate (CA). The surfaces of organoclays were used for the precipitation of Ca-deficient hydroxyapatite. The composites with Ca-deficient hydroxyapatite showed very good antibacterial effects, similar to the antimicrobial activity of pure organoclay samples. Better antibacterial activity was shown in the organically modified montmorillonite sample with Ca-deficient hydroxyapatite compared with the vermiculite composite, but, in the case of Staphylococcus aureus, both composites showed the same minimum inhibitory concentration (MIC) value. The antimicrobial effect of composites against bacteria and fungi increased with the time of exposure. The structural characterization of all the prepared materials, performed using X-ray diffraction and FT infrared spectroscopy analysis, detected no changes in the original clay or CDH during the intercalation or precipitation process, therefore we expect the strength of the compounds to be in the original power.

928. 3D hybrid structures based on biomimetic membranes and Caryophyllus aromaticus - "green" synthesized nano-silver with improved bioperformances

Authors: Barbinta-Patrascu, ME; Badea, N; Bacalum, M; Ungureanu, C; Suica-Bunghez, IR; Lordache, SM; Pirvu, C; Zgura, I; Maraloiu, VA

Published: AUG 2019, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 101, 137, DOI: 10.1016/j.msec.2019.03.069

The paper describes an innovative bio-design of some hybrid nanoarchitectures containing bioartificial membranes and silver nanoparticles phytogenerated by using a natural extract Caryophyllus aromaticus (cloves) that contains many bioactive compounds. Two kinds of liposomes with and without chlorophyll a (Chla) obtained through thin film hydration method were used to achieve bio-green-generated hybrids by a simple, cost effective bottom-up approach. The characteristic peaks of CE-nAg monitored by UV-Vis absorption have firstly demonstrated the biohybrids formation. The slightly blue shift and fluorescence quenching observed by fluorescence emission spectra highlighted the formation of hybrid systems by biointeraction between lipid vesicles and silver nanoparticles. The incorporation of silver nanoparticles in lipid vesicles resulted in significant changes of FT-IR spectra of liposomes, indicating a reorganization of biomimetic membranes. All the microscopic methods (SEM, AFM and TEM) confirmed the biosynthesis of "green" AgNPs together with associated biohybrids, their spherical and quasi-spherical shapes with nano-scaled size. By TEM assay it was shown that CE-nAg are surrounded by petal like cloud structures that consist of biopolymers like proteins or polysaccharides and other phytochemicals arising from clove extract. EDS spectra confirmed the formation of phyto-nanoAg and also the presence of silver in the biohybrids. In addition, Selected Area Electron Diffraction showed characteristic polycrystalline ring patterns for a cubic structure of the clove-generated AgNPs. The hybrid materials showed efficient physical stability, ie. xi value of - 28.0 mV (for biohybrids without Chla, BH) and of - 31.7 mV (for biohybrids labelled with Chla, Chla-BH), assured by strong electrostatic repulsive forces between particles. The "green" nano-silver particles (CE-nAg) showed remarkable antioxidant activity (AA = 90.2%). The biohybrids loaded with clove-AgNPs proved to be more effective, scavenging about 98.8% of free radicals (in case of ChlaBH), and of 92.6% (in case of BH). The antibacterial effectiveness showed that green AgNPs combine in a synergistic manner the antibacterial properties of clove extract with those of silver, resulting in an enhancement of inhibition diameter, by 20%. Chla-BH proved to be more potent against Escherichia coli, than BH, exhibiting an inhibition diameter of 42 mm. Regarding the in vitro cytotoxicity against tumour cells, the CE-nAg concentration significantly influenced the cell viability, ie. IC50 was 3.6% (v/v) for HT-29 cells. Chla-BH was more effective against HT-29 cancer cells at the concentrations ranging from 0 to 18% (v/v), when the normal cells were not affected. Clove-generated AgNPs exhibited haemolytic activity against hRBCs, while the biohybrids were haemocompatible. The action mechanism on the two cell lines (mouse fibroblast L929 cells and human colorectal adenocarcinoma HT-29 cells) investigated by fluorescence microscopy demonstrated that CE-nAg killed almost all the cells (94%) through necrosis at a concentration of 33.4% (v/v). The treatment of HT-29 cells with BH resulted in: 71.5% viable cells, 19.5% apoptotic and only 9% necrotic cells, while in the case of Chla-BH treatment, only 77.5% cells were viable, 16% cells were apoptotic and 6.5% were necrotic. In this way, the developed silver-based nanoparticles can represent viable promoters to develop new biohybrids with improved features, e.g. antioxidant and antibacterial effectiveness, haemolytic activity and greater specificity towards tumour cells.

929. Enhanced photoconductivity of SiGe nanocrystals in SiO2 driven by mild annealing

Authors: Sultan, MT; Manolescu, A; Gudmundsson, JT; Torfason, K; Nemnes, GA; Stavarache, I; Logofatu, C; Teodorescu, VS; Ciurea, ML; Svavarsson, HG

Published: MAR 1 2019, APPLIED SURFACE SCIENCE, 469, 878, DOI: 10.1016/j.apsusc.2018.11.061

Photosensitive films based on finely dispersed semiconductor nanocrystals (NCs) in dielectric films have great potential for sensor applications. Here we report on preparation and characterization of photosensitive Si1-xGex NCs sandwiched between SiO2 matrix. A radio-frequency magnetron sputtering was applied to obtain a multilayer-structures (MLs) by depositing SiO2/SiGe/SiO2 films on Si (0 0 1) substrate. The Si1-xGex NCs were formed by a post-deposition annealing at 100-700 degrees C for 1-5 min. The effect of annealing temperature and time on MLs morphology and NCs size and density was studied using grazing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and measurements of spectral distribution of photocurrent. It is demonstrated how the photoconductive properties of the MLs can be enhanced and tailored by controlling the NCs formation conditions and the presence of stress field in MLs and defects acting as traps and recombination centers. All these features can be adjusted/controlled by altering the annealing conditions (temperature and time). The MLs photosensitivity was increased of more than an order of magnitude by the annealing process. A mechanism, where a competition between crystallization process (NCs formation and evolution i.e. size and shapes) and stress field appearance determines the peak position in the photocurrent spectra, was identified.

930. Commercial Hydroxyapatite Powders for Lead Removal from Aqueous Solution

Authors: Negrila, CC; Iconaru, SL; Motelica-Heino, M; Guegan, R; Predoi, G; Barbuceanu, F; Ghita, RV; Petre, CC; Jiga, G; Badea, ML; Prodan, AM; Predoi, D

Published: 2018, 9TH INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1981, DOI: 10.1063/1.5045983

Nowadays, the advances materials science have created the possibility of using nanomaterials as adsorbents in environmental technologies. This study is focused on the evaluation of C-HAp powders capacity in lead ions removal from contaminated solutions. The C-HAp powders after removal of lead (Pb2+) ions from contaminated water were characterized by X-Ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray analysis (EDX). The presence of lead in the hydroxyapatite powders after removal experiments was observed in the XPS general spectrum and also in the EDX spectra. In addition, the AAS studies revealed that the C-HAp powders possess a high affinity towards lead ions with an effective removal rate of 80% for an initial lead concentration of 20 mg.L-1.

931. Structure and magnetic behavior of unpredictable EE-azide bridged tetranuclear Mn(II) complex with ONO-donor hydrazone ligand and its transformation to dinuclear Mn(III) complex

Authors: Bikas, R; Kuncser, V; Sanchiz, J; Schinteie, G; Siczek, M; Hosseini-Monfared, H; Lis, T

Published: JUN 1 2018, POLYHEDRON, 147, 151, DOI: 10.1016/j.poly.2018.03.019

The reaction of manganese(II) chloride tetrahydrate with sodium azide and ONO-donor hydrazone ligand, (H2L = (E)-3-hydroxy-N'-((2)-4-hydroxy-4-phenylbut-3-en-2-ylidene)-2-naphthohydrazide), in methanol gives rise to the formation of red crystals which are stable out of the solvent. The red crystals slowly transform to brown crystals in the methanolic solution. In the last case, the rate of the transformation from red to brown crystals mainly depends on the presence of molecular oxygen and reaction temperature. Both compounds are characterized by elemental analysis, spectroscopic methods and single crystal X-ray diffraction studies. The X-ray analysis indicates that the red crystals consist of a tetranuclear Mn(II) complex molecules, [Mn-4(H0.5L)(4) (mu(1.3)-N-3)(2)(CH3OH)(4)] (1), while the brown crystals consist of dinucelar Mn(III), [Mn2L2(mu(1.1)-OCH3)(1.5)(mu(1.1)-N-3)(0.5)] (2) molecules. In complex 1 with molecules of D2 (222) point symmetry, four Mn(II) ions are connected together by four ONO-donor hydrazone ligands and two end-to-end (EE) bridging azide anions. In complex 2 two Mn(III) ions are connected together by azide or methoxy bridging groups. Magnetic susceptibility measurements on complex 1 reveal the occurrence of antiferromagnetic couplings through azide ligands and enolate oxygen atom of the ligand in which the magnetic coupling constants have been determined. (C) 2018 Elsevier Ltd. All rights reserved.

932. Hysteretic Characteristics of Pulsed Laser Deposited 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3/ZnO Bilayers

Authors: Silva, JPB; Wang, J; Koster, G; Rijnders, G; Negrea, RF; Ghica, C; Sekhar, KC; Moreira, JA; Gomes, MJM

Published: MAY 2 2018, ACS APPLIED MATERIALS & INTERFACES, 10, 15249, DOI: 10.1021/acsami.8b01695

In the present work, we study the hysteretic behavior in the electric-field-dependent capacitance and the current characteristics of 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3 (BCZT)/ZnO bilayers deposited on 0.7 wt % Nb-doped (001)-SrTiO3 (Nb:STO) substrates in a metal-ferroelectric-semiconductor (MFS) configuration. The X-ray diffraction measurements show that the BCZT and ZnO layers are highly oriented along the c-axis and have a single perovskite and wurtzite phases, respectively, whereas high-resolution transmission electron microscopy revealed very sharp Nb:STO/ BCZT/ZnO interfaces. The capacitance-electric field (C-E) characteristics of the bilayers exhibit a memory window of 47 kV/cm and a capacitance decrease of 22%, at a negative bias. The later result is explained by the formation of a depletion region in the ZnO layer. Moreover, an unusual resistive switching (RS) behavior is observed in the BCZT films, where the RS ratio can be 500 times enhanced in the BCZT/ZnO bilayers. The RS enhancement can be understood by the barrier potential profile modulation at the depletion region, in the BCZT/ZnO junction, via ferroelectric polarization switching of the BCZT layer. This work builds a bridge between the hysteretic behavior observed either in the C-E and current-electric field characteristics on a MFS structure.

933. ORGANIC HETEROSTRUCTURES DEPOSITED BY MAPLE ON PATTERNED AZO ELECTRODES

Authors: Socol, M; Preda, N; Breazu, C; Rasoga, O; Stanculescu, A; Popescu-Pelin, G; Gherendi, F; Socol, G; Vacareanu, L

Published: OCT-DEC 2018, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 13, 1053, DOI:

The paper is focused on the investigation of the properties of some organic heterostructures deposited on patterned AZO electrodes. In the first step, 2D patterned arrays based on commercially photoresist were fabricated on glass substrates using nanoimprint litography. Next, on these periodic nanostructures, the transparent AZO layers were deposited by pulsed laser deposition. Further, heterostructures consisting in organic thin films such as 4,7 diphenyl-1,10-phenanthroline (BPhen) (electron transport layer), N,N'-di(1-naftalenil)-N,N'-diafenil-(1,1'-bifenil)-4,4'-diamina (alpha-NPD) (hole transport layer) and arylenevinylene oligomers (3,3-bis (N-hexylcarbazole)vinylbenzene (P13) and 1,4-bis [4-(N,N-diphenylamino)phenylvinyl] benzene (P78)) were obtained by matrix assisted pulsed laser evaporation. The fabricated multilayer organic structures have been investigated from optical (UV-VIS spectroscopy), morphological (scanning electron microscopy and atomic force microscopy) and electrical (I-V characteristics) point of view. An improvement in the current value recorded on the samples prepared on nanostructured electrode was recorded. The results evidence the possibility to integrate these heterostructures in organic electronic devices.

934. Structural, Magnetic and Hyperfine Properties of Molybdenum Dioxide-Hematite Mixed Oxide Nanostructures

Authors: Trotta, R; Tolea, F; Valeanu, M; Diamandescu, L; Grabias, A; Sorescu, M

Published: 2018, MRS ADVANCES, 3, 2892, DOI: 10.1557/adv.2018.420

MoO2-Fe2O3 nanoparticle system was successfully synthesized by mechanochemical activation of MoO2 and alpha-Fe2O3 equimolar mixtures for 0-12 hours of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale. X-ray powder diffraction (XRD), Mossbauer spectroscopy and magnetic measurements were used to study the phase evolution of MoO2-Fe2O3 nanoparticle system under the mechanochemical activation process. The Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextet and a doublet upon duration of the milling process with molybdenum dioxide. Recoilless fraction was determined using our dual absorber method and was found to decrease with increasing ball milling time. Magnetic measurements recorded at 5 and 300 K in an applied magnetic field of 50,000 Oe showed the magnetic properties in the antiferromagnetic and canted ferromagnetic states. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in 200 Oe and the transformation characteristic temperatures were shifted to lower values.

935. Antimicrobial Studies on Iron Oxide-Dextran Colloidal Suspension

Authors: Predoi, D; Iconaru, SL; Buton, N; Predoi, G; Barbuceanu, F; Petre, CC; Jiga, G; Badea, ML; Prodan, AM

Published: 2018, 9TH INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1981, DOI: 10.1063/1.5045967

Iron oxide-dextran nanoparticle suspensions (IOD-NPsS) have attracted attention for their considerable applications in various biomedical area such as cosmetics, water remediation, hyperthermia, drug delivery or magnetic resonance imaging (MRI) contrast enhancement. In these research we report the antimicrobial studies on iron oxide-dextran colloidal suspension against prokaryotic cells such as Escherichia coli (E. coli). The ultrasound studies and dynamic light scattering (DLS) of iron oxide-dextran nanoparticle suspensions. According colloidal studies of the iron oxide suspension, the nanoparticles was in dispersed state.

936. k-space imaging of anisotropic 2D electron gas in GaN/GaAlN high-electron-mobility transistor heterostructures

Authors: Lev, LL; Maiboroda, IO; Husanu, MA; Grichuk, ES; Chumakov, NK; Ezubchenko, IS; Chernykh, IA; Wang, X; Tobler, B; Schmitt, T; Zanaveskin, ML; Valeyev, VG; Strocov, VN

Published: JUL 11 2018, NATURE COMMUNICATIONS, 9, DOI: 10.1038/s41467-018-04354-x

Nanostructures based on buried interfaces and heterostructures are at the heart of modern semiconductor electronics as well as future devices utilizing spintronics, multiferroics, topological effects, and other novel operational principles. Knowledge of electronic structure of these systems resolved in electron momentum k delivers unprecedented insights into their physics. Here we explore 2D electron gas formed in GaN/AlGaN high-electron-mobility transistor heterostructures with an ultrathin barrier layer, key elements in current high-frequency and high-power electronics. Its electronic structure is accessed with angle-resolved photoelectron spectroscopy whose probing depth is pushed to a few nanometers using soft-X-ray synchrotron radiation. The experiment yields direct k-space images of the electronic structure fundamentals of this system-the Fermi surface, band dispersions and occupancy, and the Fourier composition of wavefunctions encoded in the k-dependent photoemission intensity. We discover significant planar anisotropy of the electron Fermi surface and effective mass connected with relaxation of the interfacial atomic positions, which translates into nonlinear (high-field) transport properties of the GaN/AlGaN heterostructures as an anisotropy of the saturation drift velocity of the 2D electrons.

937. Hierarchical functionalization of electrospun fibers by electrodeposition of zinc oxide nanostructures

Authors: Matei, E; Busuioc, C; Evanghelidis, A; Zgura, I; Enculescu, M; Beregoi, M; Enculescu, I

Published: NOV 15 2018, APPLIED SURFACE SCIENCE, 458, 563, DOI: 10.1016/j.apsusc.2018.06.143

Electrospun sub-micrometer polymer fiber mats represent an interesting substrate which can be employed as a transparent conducting electrode. Functionalization by using nanostructures represents a convenient way of increasing the range of applications. The present paper describes an electrodeposition process which can be applied for preparing ZnO nanostructures covered fibers in a straightforward manner. Poly(methyl methacrylate) fiber mats were obtained by electrospinning using metal frame collectors. Subsequent metallization by DC sputtering was used, these microstructured electrodes being thermally transferred onto glass substrates and further employed as working electrodes for the electrochemical deposition of ZnO. The transparency of the metal covered webs, a function of fiber density, is comparable to that of conventional transparent conductive oxides electrodes such as ITO. The same enhanced control of the ZnO electrodeposition process was observed for the case of the web electrodes as for the classic case of deposition on transparent conducting oxides or on metallic substrates. Structural, optical, morphological and wetting properties were investigated and correlated with the electrodeposition conditions. The photocatalytic properties of ZnO covered fibers were tested through the decomposition of methylene blue thin films under UV irradiation.

938. One-Pot Enzymatic Production of Lignin-Composites

Authors: Ion, S; Opris, C; Cojocaru, B; Tudorache, M; Zgura, I; Galca, AC; Bodescu, AM; Enache, M; Maria, GM; Parvulescu, VI

Published: APR 20 2018, FRONTIERS IN CHEMISTRY, 6, DOI: 10.3389/fchem.2018.00124

A novel and efficient one-pot system for green production of artificial lignin bio-composites has been developed. Monolignols such as sinapyl (SA) and coniferyl (CA) alcohols were linked together with caffeic acid (CafAc) affording a polymeric network similar with natural lignin. The interaction of the dissolved SA/CA with CafAc already bound on a solid support (S-C2/S-C6 CafAc) allowed the attachment of the polymeric product direct on the support surface (S-C2/S-C6-CafAc-L-1 and S-C2/S-C6-CafAc-L-2, from CA and SA, respectively). Accordingly, this procedure offers the advantage of a simultaneous polymer production and deposition. Chemically, oxi-copolymerization of phenolic derivatives (SA/CA and CAfAc) was performed with H2O2 as oxidation reagent using peroxidase enzyme (2-1B mutant of versatile peroxidase from Pleurotus eryngii) as catalyst. The system performance reached a maximum of conversion for SA and CA of 71.1 and 49.8%, respectively. The conversion is affected by the system polarity as resulted from the addition of a co-solvent (e.g., MeOH, EtOH, or THF). The chemical structure, morphology, and properties of the bio-composites surface were investigated using different techniques, e.g., FTIR, TPD-NH3, TGA, contact angle, and SEM. Thus, it was demonstrated that the SA monolignol favored bio-composites with a dense polymeric surface, high acidity, and low hydrophobicity, while CA allowed the production of thinner polymeric layers with high hydrophobicity.

939. X-ray Crystal Structure, Geometric Isomerism, and Antimicrobial Activity of New Copper(II) Carboxylate Complexes with Imidazole Derivatives

Authors: Vlaicu, ID; Borodi, G; Scaeteanu, GV; Chifiriuc, MC; Marutescu, L; Popa, M; Stefan, M; Mercioniu, IF; Maurer, M; Daniliuc, CG; Olar, R; Badea, M

Published: DEC 2018, MOLECULES, 23, DOI: 10.3390/molecules23123253

Five new copper(II) acrylate complexes (acr is the acrylate anion: C3H3O2) with imidazole derivatives (2-methylimidazole/2-MeIm, 5-methylimidazole/5-MeIm, 2-ethylimidazole/2-EtIm) of type: cis-[Cu(2-RIm)(2)(acr)(2)]xH(2)O ((1): R = -CH3, x = 2; (4): R = -CH2-CH3, x = 0), trans-[Cu(2-RIm)(2)(acr)(2)] ((2): R = -CH3; (5): R = -CH2-CH3) and trans-[Cu(5-RIm)(2)(acr)(2)] ((3): R = -CH3) have been prepared and characterized by elemental analysis, Fourier Transform Infrared spectrometry (FTIR), Electron Paramagnetic Resonance (EPR), electronic reflectance spectroscopy, scanning electron microscopy, and mass spectrometry. The single crystal X-ray diffraction study of complexes (2) and (5) reveals that the copper(II) ion is located on an inversion center and show elongated octahedral geometry completed by two coplanar bidentate acrylates and two unidentate imidazole derivatives displayed in trans positions. For complex (4) the single crystal X-ray diffraction shows that the copper(II) ion is in a distorted octahedral environment which can be easily confused with a trigonal prism completed by two bidentate acrylates and two unidentate imidazole derivatives displayed in cis positions. These results indicate the fact that complexes (4) and (5) are the geometric isomers of the same compound bis(acrylate)-bis(2-ethylimidazole)-copper(II). Complexes (1) and (2), as well as (4) and (5), were produced simultaneously in the reaction of the corresponding copper(II) acrylate with imidazole derivatives in methanol solution. Furthermore, in order to be able to formulate potential applications of the obtained compounds, our next goal was to investigate the in vitro antimicrobial activity of the synthesized complexes against Gram-positive and Gram-negative bacteria, as well as fungal strains, of both clinical and ecological importance (biodeterioration of historical buildings). The trans isomers (2) and (5), followed by (4) have shown the broadest range of antimicrobial activity. In case of (1) and (2) isomers, the trans isomer (2) was significantly more active than cis (1), while the cis isomer (4) proved to be more active than trans (5). Taken together, the biological evaluation results indicate that the trans (2) was the most active complex, demonstrating its potential for the development of novel antimicrobial agents, with potential applications in the biomedical and restoration of architectural monuments fields.

940. Physico-Chemical Characteristics and Antimicrobial Studies of Silver Doped Hydroxyapatite

Authors: Predoi, D; Predoi, MV; El Kettani, MEC; Leduc, D; Iconaru, SL; Ciobanu, CS; Buton, N; Petre, CC; Prodan, AM

Published: 2018, 7TH INTERNATIONAL CONFERENCE ON STRUCTURAL ANALYSIS OF ADVANCED MATERIALS (ICSAAM 2017), 1932, DOI: 10.1063/1.5024184

The present research is focused on the synthesis, structural and morphological characterization and antimicrobial evaluation of silver doped hydroxyapatite (AgHAp) in water. The preliminary ultrasonic characterizations of the AgHAp in water synthesized by an adapted co-precipitation method are also presented. X-ray diffraction result showed that silver ions were substituted in the hydroxyapatite structure. The lattice parameters increased when the silver substitution increased. The morphology of AgHAp were evaluated by Scanning Electron Microscopy (SEM). By EDX analysis the constituents elements of hydroxyapatite were detected in all analyzed samples. The silver was also found in the samples with x(Ag) = 0.5 and 0.2. The colloidal properties of the resulted AgHAp (x(Ag) = 0.0, 0.05 and 0.2) in water were analyzed by Dynamic Light Scattering (DLS) and zeta potential. On the other hand, the novelty of our research consists of preliminary ultrasonic measurements (US) conducted on AgHAp in water. Furthermore, the antimicrobial activity of AgHAp was evaluated and a decrease in the number of surviving cells was established.

941. Epitaxial growth of single-orientation high-quality MoS2 monolayers

Authors: Bana, H; Travaglia, E; Bignardi, L; Lacovig, P; Sanders, CE; Dendzik, M; Michiardi, M; Bianchi, M; Lizzit, D; Presel, F; De Angelis, D; Apostol, N; Das, PK; Fujii, J; Vobornik, I; Larciprete, R; Baraldi, A; Hofmann, P; Lizzit, S

Published: JUL 2018, 2D MATERIALS, 5, DOI: 10.1088/2053-1583/aabb74

We present a study on the growth and characterization of high-quality single-layer MoS2 with a single orientation, i.e. without the presence of mirror domains. This single orientation of the MoS2 layer is established by means of x-ray photoelectron diffraction. The high quality is evidenced by combining scanning tunneling microscopy with x-ray photoelectron spectroscopy measurements. Spin-and angle-resolved photoemission experiments performed on the sample revealed complete spin-polarization of the valence band states near the K and -K points of the Brillouin zone. These findings open up the possibility to exploit the spin and valley degrees of freedom for encoding and processing information in devices that are based on epitaxially grown materials.

942. Zinc incorporation in marine bivalve shells grown in mine-polluted seabed sediments: a case study in the Malfidano mining area (SW Sardinia, Italy)

Authors: Medas, D; Carlomagno, I; Meneghini, C; Aquilanti, G; Araki, T; Bedolla, DE; Buosi, C; Casu, MA; Gianoncelli, A; Kuncser, AC; Maraloiu, VA; De Giudici, G

Published: DEC 2018, ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH, 25, 36660, DOI: 10.1007/s11356-018-3504-y

Zinc incorporation into marine bivalve shells belonging to different genera (Donax, Glycymeris, Lentidium, and Chamelea) grown in mine-polluted seabed sediments (Zn up to 1% w/w) was investigated using x-ray diffraction (XRD), chemical analysis, soft x-ray microscopy combined with low-energy x-ray fluorescence (XRF) mapping, x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). These bivalves grew their shells, producing aragonite as the main biomineral and they were able to incorporate up to 2.0-80mg/kg of Zn, 5.4-60mg/kg of Fe and 0.5-4.5mg/kg of Mn. X-ray absorption near edge structure (XANES) analysis revealed that for all the investigated genera, Zn occurred as independent Zn mineral phases, i.e., it was not incorporated or adsorbed into the aragonitic lattice. Overall, our results indicated that Zn coordination environment depends on the amount of incorporated Zn. Zn phosphate was the most abundant species in Donax and Lentidium genera, whereas, Chamelea shells, characterized by the highest Zn concentrations, showed the prevalence of Zn-cysteine species (up to 56% of total speciation). Other Zn coordination species found in the investigated samples were Zn hydrate carbonate (hydrozincite) and Zn phosphate. On the basis of the coordination environments, it was deduced that bivalves have developed different biogeochemical mechanisms to regulate Zn content and its chemical speciation and that cysteine plays an important role as an active part of detoxification mechanism. This work represents a step forward for understanding bivalve biomineralization and its significance for environmental monitoring and paleoreconstruction.

943. Large positive linear magnetoresistance in the two-dimensional t(2g) electron gas at the EuO/SrTiO3 interface

Authors: Kormondy, KJ; Gao, LY; Li, X; Lu, SR; Posadas, AB; Shen, SD; Tsoi, M; McCartney, MR; Smith, DJ; Zhou, JS; Lev, LL; Husanu, MA; Strocov, VN; Demkov, AA

Published: MAY 16 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-26017-z

The development of novel nano-oxide spintronic devices would benefit greatly from interfacing with emergent phenomena at oxide interfaces. In this paper, we integrate highly spin-split ferromagnetic semiconductor EuO onto perovskite SrTiO3 (001). A careful deposition of Eu metal by molecular beam epitaxy results in EuO growth via oxygen out-diffusion from SrTiO3. This in turn leaves behind a highly conductive interfacial layer through generation of oxygen vacancies. Below the Curie temperature of 70 K of EuO, this spin-polarized two- dimensional t(2g) electron gas at the EuO/SrTiO3 interface displays very large positive linear magnetoresistance (MR). Soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) reveals the t(2g) nature of the carriers. First principles calculations strongly suggest that Zeeman splitting, caused by proximity magnetism and oxygen vacancies in SrTiO3, is responsible for the MR. This system offers an as-yet-unexplored route to pursue proximity-induced effects in the oxide two- dimensional t(2g) electron gas.

944. The adsorption of silicon on an iridium surface ruling out silicene growth

Authors: Satta, M; Lacovig, P; Apostol, N; Dalmiglio, M; Orlando, F; Bignardi, L; Bana, H; Travaglia, E; Baraldi, A; Lizzit, S; Larciprete, R

Published: APR 21 2018, NANOSCALE, 10, 7094, DOI: 10.1039/c8nr00648b

The adsorption of Si atoms on a metal surface might proceed through complex surface processes, whose rate is determined differently by factors such as temperature, Si coverage, and metal cohesive energy. Among other transition metals, iridium is a special case since the Ir(111) surface was reported first, in addition to Ag(111), as being suitable for the epitaxy of silicene monolayers. In this study we followed the adsorption of Si on the Ir(111) surface via high resolution core level photoelectron spectroscopy, starting from the clean metal surface up to a coverage exceeding one monolayer, in a temperature range between 300 and 670 K. Density functional theory calculations were carried out in order to evaluate the stability of the different Si adsorption configurations as a function of the coverage. Results indicate that, at low coverage, the Si adatoms tend to occupy the hollow Ir sites, although a small fraction of them penetrates the first Ir layer. Si penetration of the Ir surface can take place if the energy gained upon Si adsorption is used to displace the Ir surface atoms, rather then being dissipated differently. At a Si coverage of similar to 1 monolayer, the Ir 4f spectrum indicates that not only the metal surface but also the layers underneath are perturbed. Our results point out that the Si/Ir(111) interface is unstable towards Si-Ir intermixing, in agreement with the silicide phase formation reported in the literature for the reverted interface.

945. Properties of Basil and Lavender Essential Oils Adsorbed on the Surface of Hydroxyapatite

Authors: Predoi, D; Groza, A; Iconaru, SL; Predoi, G; Barbuceanu, F; Guegan, R; Motelica-Heino, MS; Cimpeanu, C

Published: MAY 2018, MATERIALS, 11, DOI: 10.3390/ma11050652

The research conducted in this study presented for the first time results of physico-chemical properties and in vitro antimicrobial activity of hydroxyapatite plant essential oil against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA) and S. aureus 0364) and Gram-negative bacteria (Escherichia coli ATCC 25922). The samples were studied by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to determine the morphology and structure of the nanocomposites of hydroxyapatite coated with basil (HAp-B) and lavender (HAp-L) essential oils (EOs). The values of the BET specific surface area (S-BET), total pore volume (V-P) and pore size (D-P) were determined. The results for the physico-chemical properties of HAp-L and HAp-B revealed that lavender EOs were well adsorbed on the surface of hydroxyapatite, whereas basil EOs showed a poor adsorption on the surface of hydroxyapatite. We found that the lavender EOs hydroxyapatite (HAp-L) exhibited a very good inhibitory growth activity. The value of the minimum inhibitory concentration (MIC) related to growth bacteria was 0.039 mg/mL for MRSA, 0.02 mg/mL for S. aureus and 0.039 mg/mL E. coli ATCC 25922. The basil EO hydroxyapatite (HAp-B) showed poor inhibition of bacterial cell growth. The MIC value was 0.625 mg/mL for the HAp-B sample in the presence of the MRSA bacteria, 0.313 mg/mL in the presence of S. aureus and 0.078 mg/mL for E. coli ATCC 25922.

946. Performant silver-based biohybrids generated from orange and grapefruit wastes

Authors: Barbinta-Patrascu, ME; Ungureanu, C; Suica-Bunghez, IR; Iordache, AM; Petrovic, SM; Ispas, A; Zgura, I

Published: SEP-OCT 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 557, DOI:

Clean technologies using the principles of green chemistry have attracted the attention of scientists in the last decade. Our work was focused on building advanced silver-based materials using an eco-friendly and convenient method. Two types of silver nanoparticles were synthesized using aqueous extracts of orange (Citrus sinensis) and grapefruit (Citrus paradisi) peels. Hybrid entities consisting of these bionanosilver particles and biomimetic membranes were "green" prepared and studied by spectral methods (UV-Vis absorption and emission, and FTIR-ATR spectroscopy). The morphology of silver-containing materials was analyzed by AFM images and their physical stability was checked by zeta potential measurements. Also, their antioxidant and antimicrobial properties were evaluated.

947. Effect of electron injection on defect reactions in irradiated silicon containing boron, carbon, and oxygen

Authors: Makarenko, LF; Lastovskii, SB; Yakushevich, HS; Moll, M; Pintilie, I

Published: APR 28 2018, JOURNAL OF APPLIED PHYSICS, 123, DOI: 10.1063/1.5010965

Comparative studies employing Deep Level Transient Spectroscopy and C-V measurements have been performed on recombination-enhanced reactions between defects of interstitial type in boron doped silicon diodes irradiated with alpha-particles. It has been shown that self-interstitial related defects which are immobile even at room temperatures can be activated by very low forward currents at liquid nitrogen temperatures. Their activation is accompanied by the appearance of interstitial carbon atoms. It has been found that at rather high forward current densities which enhance BiOi complex disappearance, a retardation of C-i annealing takes place. Contrary to conventional thermal annealing of the interstitial boron-interstitial oxygen complex, the use of forward current injection helps to recover an essential part of charge carriers removed due to irradiation. Published by AIP Publishing.

948. New bio-active, antimicrobial and adherent coatings of nanostructured carbon double-reinforced with silver and silicon by Matrix-Assisted Pulsed Laser Evaporation for medical applications

Authors: Duta, L; Ristoscu, C; Stan, GE; Husanu, MA; Besleaga, C; Chifiriuc, MC; Lazar, V; Bleotu, C; Miculescu, F; Mihailescu, N; Axente, E; Badiceanu, M; Bociaga, D; Mihailescu, IN

Published: MAY 31 2018, APPLIED SURFACE SCIENCE, 441, 883, DOI: 10.1016/j.apsusc.2018.02.047

We report on Matrix-Assisted Pulsed Laser Evaporation (MAPLE) deposition of Carbon thin films, simple or reinforced with intended concentrations of Ag and Si. A KrF* (lambda = 248 nm, tau(FWHM) < 25 ns, v = 10 Hz) excimer laser was used for irradiation. The effect of a post-deposition thermal treatment in vacuum was studied. Besides detailed morphological, compositional, structural and pull-out adherence characterizations, the potential of the carbonaceous films for medical applications was investigated in vitro by anti-biofilm and cytocompatibility assays. The microscopic images evidenced no delaminations. Micro-Raman spectroscopy revealed a graphitization tendency depending on preparation conditions, thermal treatment and reinforcing agents' presence. Adherence values improved considerably after thermal treatment. In vitro biological evaluation showed that the films containing similar to 1.85 at.% Ag were non-cytotoxic for MG63 cells, while eliciting a limited antimicrobial activity. The increase of Ag content to 3.6 at.% results in a significant enhancement of antimicrobial activity, whilst maintaining the cytotoxic action and adherence characteristics at acceptable levels. We propose a new class of metamaterials based on C reinforced with Ag and Si obtained by MAPLE for medical applications, i.e. the prevention and treatment of various infections associated with biofilms developed on implants and other medical equipments. (C) 2018 Elsevier B.V. All rights reserved.

949. Hydrogenolysis of lignin over Ru-based catalysts: The role of the ruthenium in a lignin fragmentation process

Authors: Verziu, M; Tirsoaga, A; Cojocaru, B; Bucur, C; Tudora, B; Richel, A; Aguedo, M; Samikannu, A; Mikkola, JP

Published: MAY 2018, MOLECULAR CATALYSIS, 450, 76, DOI: 10.1016/j.mcat.2018.03.004

The catalytic performances of two different classes of catalysts containing nickel or/and ruthenium as the active sites were studied in the depolymerisation of lignin isolated from Miscanthus x giganteus. The catalysts were prepared either by coprecipitation (ie, (RuNiMgAlO)x, (RuNiAlO)x, (NiAlO)x, (NiMgAlO)x) or by wet impregnation (ie, Ru/Al2O3) and characterized by nitrogen physisorption (BET), XRD, XPS, NH3-TPD, Raman and H-2-TPR techniques. The experimental results indicate that the presence of ruthenium led to dimers as dominant products.

950. Bioceramic Layers with Antifungal Properties

Authors: Predoi, D; Iconaru, SL; Predoi, MV

Published: AUG 2018, COATINGS, 8, DOI: 10.3390/coatings8080276

The sol-gel method was used to synthesize the silver doped hydroxyapatite (Ag:HAp) gels in order to produce the antifungal composite layers. The pure Ti disks were used as the substrate for the composite layers. Important information about suspensions used to make Ag:HAp composite layers were obtained from an ultrasonic technique. The identification of the phase composition of the Ag:HAp composite layers was accomplished X-ray diffraction (XRD). The morphology and the thickness of the layers was evaluated using scanning electron microscopy (SEM). The uniform distribution of the constituent elements (Ag, Ca, P, and O) in both analyzed samples was observed. The antifungal activity of the samples against Candida albicans ATCC 10231 microbial strain were investigated immediately after their preparation and six months later. SEM and confocal laser scanning microscopy (CLSM) images showed that the composite layers at the two time intervals exhibited a strong antifungal activity against Candida albicans ATCC 10231 and completely inhibited the biofilm formation.

951. Intrinsic losses in dielectrics investigated by terahertz spectroscopy

Authors: Nedelcu, L; Geambasu, CD; Banciu, MG; Mogildea, G; Mogildea, M

Published: 2018, 2018 43RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER, AND TERAHERTZ WAVES (IRMMW-THZ), DOI:

Low-loss dielectrics with various microstructure and, consequently, different extrinsic losses were investigated by using terahertz time-domain spectroscopy. The losses have been extrapolated and compared with those measured at microwave frequencies. The results showed that extrinsic factors have a considerably contribution in microwave domain. The intrinsic limit of dielectric loss of low absorption polycrystalline materials have been estimated by terahertz spectroscopy.

952. Selective catalytic oxidation reaction of p-xylene on manganese-iron mixed oxide materials

Authors: Nicolae, S; Neatu, F; Florea, M

Published: MAR-APR 2018, COMPTES RENDUS CHIMIE, 21, 361, DOI: 10.1016/j.crci.2017.06.005

Mixed manganese iron oxides (Mn/Fe/O) as heterogeneous catalysts were prepared by hydrothermal treatment and citrate methods to be tested in the oxidation of p-xylene (PX) using as oxidation agent molecular oxygen, hydrogen peroxide, and tert-butyl hydroperoxide. Preparation of mixed Mn-Fe oxide by the citrate method releases materials with smaller particle size and lower degree of crystallinity as compared with the hydrothermal one, which further leads to a higher activity toward the oxidation of PX. A conversion of PX of 98% and a yield in p-toluic acid of 93% were obtained in the presence of Mn/Fe/O prepared by the citrate method using tert-butyl hydroperoxide as an oxidizing agent. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

953. Fabrication and Characterization of Iron Oxide Dextran Composite Layers

Authors: Iconaru, SL; Predoi, SA; Beuran, M; Ciobanu, CS; Trusca, R; Ghita, R; Negoi, I; Teleanu, G; Turculet, SC; Matei, M; Badea, M; Prodan, AM

Published: 2018, 7TH INTERNATIONAL CONFERENCE ON STRUCTURAL ANALYSIS OF ADVANCED MATERIALS (ICSAAM 2017), 1932, DOI: 10.1063/1.5024169

Super paramagnetic iron oxide nanoparticles such as maghemite have been shown to exhibit antimicrobial properties [1-5]. Moreover, the iron oxide nanoparticles have been proposed as a potential magnetically controllable antimicrobial agent which could be directed to a specific infection [3-5]. The present research has focused on studies of the surface and structure of iron oxide dextran (D-IO) composite layers surface and structure. These composite layers were deposited on Si substrates. The structure of iron oxide dextran composite layers was investigated by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while the surface morphology was evaluated by Scanning Electron Microscopy (SEM). The structural characterizations of the iron oxide dextran composite layers revealed the basic constituents of both iron and dextran structure. Furthermore, the in vitro evaluation of the antifungal effect of the complex layers, which have been shown revealed to be active against C. albicans cells at distinct intervals of time, is exhibited. Our research came to confirm the fungicidal effect of iron oxide dextran composite layers. Also, our results suggest that iron oxide dextran surface may be used for medical treatment of biofilm associated Candida infections.

954. Removal of Zinc Ions Using Hydroxyapatite and Study of Ultrasound Behavior of Aqueous Media

Authors: Iconaru, SL; Motelica-Heino, M; Guegan, R; Predoi, MV; Prodan, AM; Predoi, D

Published: AUG 2018, MATERIALS, 11, DOI: 10.3390/ma11081350

The present study demonstrates the effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions. The synthesized hydroxyapatites before (HAp) and after the adsorption of zinc (at a concentration of 50 mg/L) in solution (HApD) were characterized using X-ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM, respectively). The effectiveness of hydroxyapatite nanopowders in the adsorption of zinc in aqueous solutions was stressed out through ultrasonic measurements. Both Langmuir and Freundlich models properly fitted on a wide range of concentration the equilibrium adsorption isotherms, allowing us to precisely quantify the affinity of zinc to hydroxyapatite nanopowders and to probe the efficacy of hydroxyapatite in removal of zinc ions from aqueous solutions in ultrasonic conditions.

955. Zinc Oxide Spherical-Shaped Nanostructures: Investigation of Surface Reactivity and Interactions with Microbial and Mammalian Cells

Authors: Visinescu, D; Hussien, MD; Moreno, JC; Negrea, R; Birjega, R; Somacescu, S; Ene, CD; Chifiriuc, MC; Popa, M; Stan, MS; Carp, O

Published: NOV 13 2018, LANGMUIR, 34, 13651, DOI: 10.1021/acs.langmuir.8b02528

Two ZnO materials of spherical hierarchical morphologies, with hollow (ZnOHS) and solid cores (ZnOSS), were obtained through the hydrolysis of zinc acetylacetonate in 1,4-butanediol. The nature of the defects and surface reactivity for the two ZnO materials were investigated through photoluminescence, X-ray photoelectron spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy proving the coexistence of shallow and deep defects and, also, the presence of polyol byproducts adsorbed on the outer layers of the ZnO samples. The EPR spectroscopy coupled with the spin-trapping technique showed that the surface of the ZnO samples generates reactive oxygen species (ROS) like hydroxyl (OH) and singlet oxygen (O-1(2)) as well as carbon-centered radicals. The ZnO materials exhibited a wide spectrum of antimicrobial activity, being active against Gram-positive, Gram-negative, and fungi strains, both in planktonic and, more importantly, adherent groywth states. The decrease of antimicrobial efficiency in the presence of a ROS scavenger (mannitol) and the decrease of the cell viability with the ROS level suggest that one of the mechanisms that governs both the antimicrobial and cytotoxic activities on human liver cells is ROS-mediated. However, at active antimicrobial concentrations, the biocompatibility of the tested materials is very good.

956. Near infrared emission properties of Er doped cubic sesquioxides in the second/third biological windows

Authors: Avram, D; Tiseanu, I; Vasile, BS; Florea, M; Tiseanu, C

Published: DEC 21 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-36639-y

In the recent years, there is an extensive effort concentrated towards the development of nanoparticles with near-infrared emission within the so called second or third biological windows induced by excitation outside 800-1000 nm range corresponding to the traditional Nd (800 nm) and Yb (980 nm) sensitizers. Here, we present a first report on the near-infrared (900-1700 nm) emission of significant member of cubic sesquioxides, Er-Lu2O3 nanoparticles, measured under both near-infrared up-conversion and low energy X-ray excitations. The nanoparticle compositions are optimized by varying Er concentration and Li addition. It is found that, under ca. 1500 nm up-conversion excitation, the emission is almost monochromatic (>93%) and centered at 980 nm while over 80% of the X-ray induced emission is concentrated around 1500 nm. The mechanisms responsible for the up-conversion emission of Er - Lu2O3 are identified by help of the up-conversion emission and excitation spectra as well as emission decays considering multiple excitation/emission transitions across visible to near-infrared ranges. Comparison between the emission properties of Er-Lu2O3 and Er-Y2O3 induced by optical and X-ray excitation is also presented. Our results suggest that the further optimized Er-doped cubic sesquioxides represent promising candidates for bioimaging and photovoltaic applications.

957. Effect of green body annealing on laser performance of YAG:Nd3+ ceramics

Authors: Yavetskiy, RP; Parkhomenko, SV; Vorona, IO; Tolmachev, AV; Kosyanov, DY; Kuryavyi, VG; Mayorov, VY; Gheorghe, L; Croitoru, G; Enculescu, M

Published: MAR 2018, CERAMICS INTERNATIONAL, 44, 4490, DOI: 10.1016/j.ceramint.2017.11.192

Annealing temperature of green bodies has been shown to influence greatly the optical properties and laser characteristics of Y3Al5O12:Nd3+ (1 at%) ceramics. Increase the annealing temperature above some critical one (800 degrees C) results in appearance of submicron pores due to Y4Al2O9 phase formation accompanied by specific volume expansion. The energy changes associated with the chemical reaction can lead to the development of microstructures that possess lower sinterability. As a result, Y3Al5O12:Nd3+ ceramics prepared from unannealed green bodies and those annealed at 600 and 800 degrees C possess higher optical transmittance and enhanced slope efficiency (63-67%) compared with that obtained using green bodies annealed at 1000 degrees C (41%). Further investigations are necessary in order to explain this behavior.

958. Combined use of Mossbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy for estimating incipient phase separation in lead titanate-based multiferroics

Authors: Craciun, F; Cordero, F; Vasile, BS; Fruth, V; Zaharescu, M; Atkinson, I; Trusca, R; Diamandescu, L; Tanase, LC; Galizia, P; Cernea, M; Galassi, C

Published: JUN 7 2018, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 20, 14663, DOI: 10.1039/c8cp01456f

The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O-3 (x = 0.00, 0.03, 0.04, 0.05) by means of a combination of Mossbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy. We found that Fe ions are substituted as Fe3+ at Ti sites and preferentially exhibit pentahedral coordination, whereas Ti ions have coexisting valences of Ti4+/Ti3+. Fe3+ ions are preferentially ordered in clusters, and there exists a transition temperature T-C1, below which phase separation occurs between a tetragonal phase T1 free of magnetic clusters and a cubic phase, and a lower transition temperature T-C2, below which the cubic phase rich in magnetic clusters is transformed into a tetragonal phase T2. The phase separation persists at the nanoscale level down to room temperature and is visible in HRTEM images as a mixing of nanodomains with different tetragonality ratios. This phase separation was observed over the whole studied concentration range of x(Fe) values. It occurs progressively with the value of x(Fe), and the transition temperature T-C2 decreases with the concentration from about 620 K (x(Fe) = 0.03) to about 600 K (x(Fe) = 0.05), while T-C1 remains nearly constant.

959. Flexible Delivery Patch Systems based on Thermoresponsive Hydrogels and Submicronic Fiber Heaters

Authors: Evanghelidis, A; Beregoi, M; Diculescu, VC; Galatanu, A; Ganea, P; Enculescu, I

Published: DEC 3 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-35914-2

This paper proposes a novel, flexible, low cost administration patch which could be used as a non-invasive, controlled transdermal drug delivery system. The fabricated device consists in a flexible microfiber architecture heater covered with a thermoresponsive hydrogel, namely poly(N-isopropylacrylamide), as a matrix for the incorporation of active molecules. The manufacturing process consists of two main steps. First, the electrospun poly(methyl methacrylate) fiber networks are sputter coated with a thin gold layer and attached to flexible poly(ethylene terephthalate) substrates to obtain the heating platforms. Second, the heaters are encapsulated in poly(ethylene terephthalate) foils and covered with poly(N-isopropylacrylamide) hydrogel sheets. In order to illustrate the functionality of the fabricated patch, the hydrogel layer is loaded with methylene blue aqueous solution and is afterwards heated via Joule effect, by applying a voltage on the metalized fibers. The methylene blue releasing profiles of the heated patch are compared with those of the unheated one and the influence of parameters such as hydrogel composition and morphology, as well as the applied voltage values for microheating are investigated. The results indicate that the fabricated patch can be used as a drug administration instrument, while its performance can be tuned depending on the targeted application.

960. Enhanced photoconductivity of SiGe-trilayer stack by retrenching annealing conditions

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Ciurea, ML; Palade, C; Maraloiu, AV; Svavarsson, HG

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 64, DOI:

We studied the effect of short term furnace annealing over the photoconductive properties of tristacked layer i.e. TiO2/(SiGe/TiO2)(3). The structure was prepared by depositing alternate layers of TiO2 and SiGe films, using direct-current magnetron sputtering technique. A transmission electron microscopy and grazing incidence spectroscopy was used to analyze the morphology of the structure. Photoconductive properties were studied by measuring photocurrent spectra at different applied voltages and temperatures. Tristack layers were obtained with 5-10 nm SiGe nanocrystals (NCs) by annealing at 600 degrees C for 5 min. No sign of SiO2 formation was found inside stacked layers. A maximum in the photocurrent spectra was observed at 994 nm at 300 K but it red-shifted gradually to 1045 nm with decrease in temperature to 100 K. This transition in peak maxima is attributed to SiGe NCs, due to lattice vibration and to contribution of non-radiative recombination at low temperatures.

961. Influence of Ionizing Radiations on Structural and Antibacterial Properties of Hydroxyapatite-Polydimethylsiloxane Layers

Authors: Groza, A; Iconaru, SL; Petre, CC; Jiga, G; Badea, ML; Prodan, AM; Beuran, M; Chapon, P; Gaianschi, S; Ganciu, M; Verga, N; Trusca, R; Vineticu, N; Predoi, D

Published: 2018, 9TH INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1981, DOI: 10.1063/1.5045985

In the recent years a special attention has been granted to the generation and characterization of hydroxyapatite-polydimethylsiloxane layers especially due to their biomedical applications. In this context, in this paper, we analyzed the influence of X ray radiation delivered in medical dose on the morphological mid chemical structure of hydroxyapatite-polydimethylsiloxane layers deposited on Ti substrates. The damage effects produced by the ionizing radiation on the surface and structure of hydroxyapatite-polydimethylsiloxane layers were identified by Scanning Electron Microscopy (SEM) and Glow Discharge Optical Emission Spectroscopy (GDOES). The antibacterial activity of the irradiated and non irradiated samples was also evaluated.

962. Influence of In-Gap States on the Formation of Two-Dimensional Election Gas at ABO(3)/SrTiO3 Interfaces

Authors: Li, CJ; Xue, HX; Qu, GL; Shen, SC; Hong, YP; Wang, XX; Liu, MR; Jiang, WM; Badica, P; He, L; Dou, RF; Xiong, CM; Lu, WM; Nie, JC

Published: JAN 9 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-017-18583-5

We explored in-gap states (IGSs) in perovskite oxide heterojunction films. We report that IGSs in these films play a crucial role in determining the formation and properties of interfacial two-dimensional electron gas (2DEG). We report that electron trapping by IGSs opposes charge transfer from the film to the interface. The IGS in films yielded insulating interfaces with polar discontinuity and explained low interface carrier density of conducting interfaces. An ion trapping model was proposed to explain the physics of the IGSs and some experimental findings, such as the unexpected formation of 2DEG at the initially insulating LaCrO3/SrTiO3 interface and the influence of substitution layers on 2DEG.

963. Ex Situ Spark Plasma Sintering of Short Powder-in-Tube MgB2 Tapes with Open and Closed Ends

Authors: Aldica, G; Burdusel, M; Popa, S; Pasuk, I; Ionescu, AM; Kuncser, A; Badica, P

Published: NOV 2018, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 31, 3432, DOI: 10.1007/s10948-018-4616-9

Short powder-in-tube tapes of MgB2 in the Fe sheath were fabricated by ex situ route from a commercial powder containing some free Mg and MgO impurity phases. The final heat treatment was performed by spark plasma sintering (SPS). Tapes were with open (OT) or closed (CT) endings. Closed endings were made by folding and pressing. The MgB2 core of the OT sample has shown a higher low-field critical current density, a higher maximum pinning force, a slightly higher disorder, smaller average MgB2 crystallite size, a weak contact between Fe and MgB2 core, and more macro-flux jumps. The upper and irreversibility fields were similar for OT and CT samples. In the center of the MgB2 cores, the detected impurity phase is MgO, while at the interface with Fe, MgB4 also occurs. Impurity phases found at interface, MgO and MgB4, are present in the center of the bulk SPSed samples. Reactions and pinning-force-related parameters are discussed with respect to Mg behavior influenced by condition of endings. It is inferred that the presence of free Mg in the raw MgB2 powder has an important contribution to observed differences, and its removal or control is recommended.

964. Application of Biocompatible Magnetite Nanoparticles for the Removal of Arsenic and Copper from Water

Authors: Iconaru, SL; Beuran, M; Turculet, CS; Negoi, I; Teleanu, G; Prodan, AM; Motelica-Heino, M; Guegan, R; Ciobanu, CS; Jiga, G; Predoi, D

Published: 2018, 7TH INTERNATIONAL CONFERENCE ON STRUCTURAL ANALYSIS OF ADVANCED MATERIALS (ICSAAM 2017), 1932, DOI: 10.1063/1.5024168

The progress of nanotechnology made possible the use of nanomaterials as adsorbents and magnetic iron oxides represents one of the first generations of nanoscale materials used in environment technologies [1]. A systematic characterization of commercial magnetite (Fe3O4) is presented in this research. The commercial (Fe3O4) magnetic adsorbents were characterized by various characterizations methods such as X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). This study was also focused on the study of adsorption isotherms and the kinetics evaluation. X-ray studies indicated that As3+ and Cu2+ removed by Fe3O4 did not seem to alter the structure of Fe3O4 but they were highlighted in the EDX analysis. In addition, the SEM studies were consistent with the XRD results. The rate of adsorption of contaminants, in contaminated solutions decreases when the amount of contaminant increases in all experiments performed. The results revealed that Fe3O4 nanoparticles are promising candidates which could be used as sorbents for the removal of arsenic from the marine environment, for site remediation and groundwater treatment.

965. Piezoelectric ferromagnetic BNT-BT0.08/CoFe2O4 coaxial core-shell composite nanotubes for nanoelectronic devices

Authors: Cernea, M; Vasile, BS; Surdu, VA; Trusca, R; Sima, M; Craciun, F; Galassi, C

Published: JUL 5 2018, JOURNAL OF ALLOYS AND COMPOUNDS, 752, 388, DOI: 10.1016/j.jallcom.2018.04.146

In this paper we report on a novel 1-D piezoelectric/ferroelectric nanostructure. Composites of piezoelectric (0.92Na(0.5)Bi(0.5)TiO(3)-0.08BaTiO(3) abbreviated as BNT-BT0.08) and ferromagnetic (CoFe2O4) nanotubes were assembled and studied in order to envisage new multifunctional applications. Using a polycarbonate membrane template and sols precursors of BNT-BT(0.08 )and CoFe2O4, heterostructured BNT-BT0.08/CoFe2O4 core-shell composite nanotubes were created. Selective methods such as SEM, TEM, AFM, PFM and MFM were used for the characterization of the as-prepared hybrid piezoelectric/ferromagnetic coaxial nanotubes structure. This composite shows two crystalline phases: rhombohedral BNT-BT0.08 and cubicCoFe(2)O(4). The piezoelectric and ferromagnetic properties have been characterized. Piezo force microscopy (PFM) images evidenced ferroelectric domains with opposite polarity due to lead free piezoelectric BNT-BT0.08 outer tube. Magnetic force microscopy (MFM) images evidenced magnetic domains attributed to the CoFe2O4 inner tube. Magnetic hysteresis curves demonstrate a weak ferromagnetic behavior, accompanied by a linear variation of the magnetization at higher magnetic fields, especially at room temperature. From dielectric measurements, high tunability values reaching about 70% at 0.5 kHz and E = 80 kV/cm have been obtained. An effective dielectric constant epsilon(r) = 32 has been measured. The results obtained from this work provide a base for the design of tubular multi-layered materials with novel functionalities and applications in various multifunctional electronic devices such as actuators, transducers, and energy storage microsystems. (C) 2018 Elsevier B.V. All rights reserved.

966. Particularities of photocatalysis and formation of reactive oxygen species on insulators and semiconductors: cases of SiO2, TiO2 and their composite SiO2-TiO2

Authors: Anastasescu, C; Negrila, C; Angelescu, DG; Atkinson, I; Anastasescu, M; Spataru, N; Zaharescu, M; Balint, I

Published: NOV 7 2018, CATALYSIS SCIENCE & TECHNOLOGY, 8, 5668, DOI: 10.1039/c8cy00991k

Highly defected tubular SiO2 is found to outperform the activity of TiO2-P25 and the SiO2-TiO2 composite in photocatalytic H-2 generation from methanol-water solution under simulated solar light AM 1.5. The enhanced performances of SiO2 come from the particularities of the reaction mechanism and ROS (reactive oxygen species) generation. The SiO2 exposed to light generates solely O-1(2) (singlet oxygen). The TiO2-P25 produces uniquely large quantities of OH radicals whereas the formation of O-2(-) is evidenced only over SiO2-TiO2, along with small amounts of OH. The TiO2 works as a photocatalyst by intermediation of OH radicals. In contrast, the organic substrate is activated on the surface of SiO2 by the intra-band gap, isolated, surface quantum defects. Distinct reaction mechanisms, involving the participation of photogenerated charges and ROS, are proposed. The material-related ROS production can be of great practical importance in fields such as biology (germ inactivation), medicine (photodynamic therapy by O-1(2)), and synthesis of oxygenated organic compounds of great added value.

967. High temperature thermo-physical properties of SPS-edW-Cu functional gradient materials

Authors: Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 2018, MATERIALS RESEARCH EXPRESS, 5, DOI: 10.1088/2053-1591/aaa860

The divertor of a fusion reactor like DEMO requires materials able to withstand high heat fluxes and neutron irradiation for several years. For the water cooling concept of this essential part of the reactor, the most likely plasma facing material will be W, while the heatsink material considered is CuCrZr or an improved version of such a Cu-based alloy. To realize W-Cu alloy joints able to withstand thousands of thermal cycles can be difficult due to the difference between the thermal expansion coefficients of these materials. In this work we investigate the possibility to realize such joints by using W-Cu functional gradient materials (FGMs) produced from nanometric and micrometric metallic powders mixtures and consolidated by spark plasma sintering at about 900 degrees C. Morphological and thermal properties investigations, performed for typical compositions, shows that the best results are obtained using powders with micrometric dimensions. A resulting 1 mm thick, 3 layers W-Cu FGM produced by this simple method shows a remarkable almost constant thermal conductivity value of 200 W m(-1) K-1, from room temperature up to 1000 degrees C.

968. Adsorption of Pb (II) Ions onto Hydroxyapatite Nanopowders in Aqueous Solutions

Authors: Iconaru, SL; Motelica-Heino, M; Guegan, R; Beuran, M; Costescu, A; Predoi, D

Published: NOV 2018, MATERIALS, 11, DOI: 10.3390/ma11112204

Contamination of water with heavy metals such as lead is a major worldwide problem because they affect the physiological functions of living organisms, cause cancer, and damage the immune system. Hydroxyapatite, (Ca-5(PO4)(3)OH) is considered one of the most effective materials for removing heavy metals from contaminated water. The hydroxyapatite nanopowders (N-HAp) obtained by a co-precipitation method were used in this research to determine the effectiveness in removing lead ions from contaminated solutions. In this study, we have investigated the structure and morphology of N-HAp nanopowders using X-ray diffraction (XRD), electronic transmission microscopy (TEM), and scanning electron microscopy (SEM). The structure information was also obtained by spectroscopy measurements. The Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy measurements revealed the presence of peaks corresponding to the phosphate and hydroxyl groups. The ability of N-HAp nanopowders to adsorb lead ions from aqueous solutions were established. The results of the kinetic and equilibrium studies on the removal of Pb (II) from aqueous solution revealed that the adsorption of lead (II) cations is due to the surface reaction with the hydroxyl terminal groups on the adsorbent and the combination of the positive charges of the metal cations with the negative charges on the adsorbent surfaces. These observations could validate the use of these ceramic nanopowders in ecological remediation strategies.

969. White-Light Emission of Dye-Doped Polymer Submicronic Fibers Produced by Electrospinning

Authors: Enculescu, M; Evanghelidis, A; Enculescu, I

Published: JUL 2018, POLYMERS, 10, DOI: 10.3390/polym10070737

Lighting and display technologies are evolving at tremendous rates nowadays; new device architectures based on new, microscopic building blocks are being developed. Besides high light-emission efficiencies, qualities including low cost, low environmental impact, flexibility, or lightweightness are sought for developing new types of devices. Electrospun polymer fibers represent an interesting type of such microscopic structures that can be employed in developing new functionalities. White-light-emitting fiber mats were prepared by the electrospinning of different dye-doped polymer solutions. Two approaches were used in order to obtain white-light emissions: the overlapping of single-dye-doped electrospun fiber mats, and the electrospinning of mixtures of different ratios of single-dye-doped polymer solutions. Scanning electron microscopy (SEM) was used to investigate the morphologies of the electrospun fibers with diameters ranging between 300 nm and 1 mu m. Optical absorption and photoluminescence (PL) were evaluated for single-dye-doped submicronic fiber mats, for overlapping mats, and for fiber mats obtained from different compositions of mixtures. Depending on the ratios of the mixtures of different dyes, the luminance was balanced between blue and red emissions. Commission Internationale de L'Eclairage (CIE) measurements depict this fine-tuning of the colors' intensities, and the right composition for white-light emission of the submicronic fiber mats was found.

970. Charge carrier traps in tris-(8-hydroxyquinoline) aluminum

Authors: Secu, M; Polosan, S

Published: FEB 2018, JOURNAL OF LUMINESCENCE, 194, 95, DOI: 10.1016/j.jlumin.2017.10.003

Thermoluminescent measurements between 40 and 300 C revealed two traps in the irradiated Alq(3) powder synthetized from Al(OH)(3), at 0.8 and 1.1 eV below the conduction band. These two traps have been assigned with the Alq(3) facial and meridional isomers and the trapping process stand for a long time after the switching off the irradiation source. The spectra recorded an hour after switching recover 60% from the photoluminescence and also decreasing the TL signals. A theoretical model was proposed in order to explain the trapping and detrapping processes in both meridional and facial Alq(3) isomers based on the XPS measurements for the HOMO, LUMO, ionization potential and optical bandgap, completed with the DFT calculated parameters and similar experimental results concerning the evidences of the triplet states in Alq(3) compound.

971. Surface States- and Field-Effects at GaAs(100) Electrodes in Sodium Dodecyl Sulfate Acid Solution

Authors: Enache, M; Negrila, C; Anastasescu, M; Dobrescu, G; Lazarescu, MF; Lazarescu, V

Published: 2018, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 165, H3017, DOI: 10.1149/2.0031804jes

Sodium dodecyl sulfate (SDS) effects at the electrified p- and n-GaAs(100)/H2SO4 interfaces were investigated by EIS, XPS and AFM. XPS data revealed that under the open circuit conditions, SDS adsorption on GaAs(100) results in a protective overlayer which prevents the further oxidation in air of both types of semiconductor surfaces. The dopant nature is, however, decisive for the way of bonding the surfactant molecule to the surface. At the p-doped substrate, SDS adsorbs mainly at As sites by its hydrocarbon tail and by the anion head to the Ga sites at the n-doped one. Although the surfactant behaves as a dipole under the applied potential control, the dopant type plays a key role in the SDS interaction with GaAs(100) electrodes too. EIS data evidenced that SDS interaction with n-GaAs(100) electrode brings a pronounced decrease of the capacitive contribution of the surface states and a shift of the flatband potential to less negative values, unlike the p-doped one, where no significant change in its electronic properties was observed. These results were rationalized in terms of surface states- and field-effects operating at the electrified interfaces under discussion. (C) The Author(s) 2017. Published by ECS.

972. Synthesis and characterization of CoFe2O4/BNT-BT0.08 core shell nanotubes by a template based sol-gel method

Authors: Cernea, M; Vasile, BS; Surdu, VA; Trusca, R; Craciun, F; Galassi, C

Published: JUN 15 2018, CERAMICS INTERNATIONAL, 44, 10819, DOI: 10.1016/j.ceramint.2018.03.123

In this work we report on a new 1-1 composite coaxial nanostructure containing nanotubes of CoFe2O4 and BET-BT0.08 prepared by a template-based fabrication technique using the sol-gel chemistry. In this regard, CoFe2O4/BNT-BT0.08 core-shell nanotubes were prepared using a polycarbonate membrane template and sols precursors of CoFe2O4 and BNT-BT0.08. The deposition of nanotubes was performed by pore wetting of the porous membranes via capillary action and subsequent pyrolysis. The studies with scanning electron microscopy and transmission electron microscopy (TEM) revealed that the composite material is characterized by the 1-D tubular structure. Analysis by X-ray diffraction, high-resolution TEM imaging and selected-area electron diffraction pattern demonstrated that the synthetic composite nanotube CoFe2O4/BNT-BT0.08 has crystalline structure with cubic CoFe2O4 and rhombohedral BNT-BT0.08 phases. CoFe2O4/BNT-BT0.08 coaxial nanotubes show dielectric properties, piezoelectric and ferromagnetic behavior.

973. Edge-state mechanism for the anomalous quantum Hall effect in a diatomic square lattice

Authors: Ostahie, B; Nita, M; Aldea, A

Published: SEP 4 2018, PHYSICAL REVIEW B, 98, DOI: 10.1103/PhysRevB.98.125403

We investigate the spectral and transport properties of a diatomic square lattice with hopping to the next-nearest-neighbors and broken time-reversal symmetry, which behaves as a Chern insulator. In a finite-size approach, the attention is paid to the formation of chiral edge states in the topological insulating phase, but also in the semimetallic one. The edge states are revealed in the ribbon and plaquette geometries by analytical and numerical methods, significant differences being produced by the specific atomic connectivity at the boundary. The Hall resistance R-H is calculated in the plaquette geometry using the Landauer-Mittiker approach. The chiral edge states located in the unique gap of the energy spectrum manifest themselves by quantized values R-H = +/- h/e(2) specific to the Chern insulator. The semimetallic system containing chiral edge states embedded in the quasicontinuum of bulk states shows a disorder-driven AQHE as a consequence of the Anderson localization process.

974. Effect of Li doping on the electric and pyroelectric properties of ZnO thin films

Authors: Trinca, LM; Galca, AC; Boni, AG; Botea, M; Pintilie, L

Published: JAN 1 2018, APPLIED SURFACE SCIENCE, 427, 37, DOI: 10.1016/j.apsusc.2017.08.009

Un-doped ZnO (UDZO) and Li-doped ZnO (LZO) polycrystalline thin films were grown on platinized silicon by pulsed laser deposition (PLD). The electrical properties were investigated on as-grown and annealed UDZO and LZO films with capacitor configuration, using top and bottom platinum electrodes. In the case of the as-grown films it was found that the introduction of Li increases the resistivity of ZnO and induces butterfly shape in the C-V characteristic, suggesting ferroelectric-like behavior in LZO films. The properties of LZO samples does not significantly changes after thermal annealing while the properties of UDZO samples show significant changes upon annealing, manifested in a butterfly shape of the C-V characteristic and resistive-like switching. However, the butterfly shape disappears if long delay time is used in the C-V measurement, the characteristic remaining non-linear. Pyroelectric signal could be measured only on annealed films. Comparing the UDZO results with those obtained in the case of Li: ZnO, it was found that the pyroelectric properties are considerably enhanced by Li doping, leading to pyroelectric signal with about one order of magnitude larger at low modulation frequencies than for un-doped samples. Although the results of this study hint towards a ferroelectric-like behavior of Li doped ZnO, the presence of real ferroelectricity in this material remains controversial. (C) 2017 Elsevier B.V. All rights reserved.

975. Magneto-optical properties of Ce3+ and Tb3+-doped silico-phosphate sol-gel thin films

Authors: Stefan, CR; Elisa, M; Vasiliu, IC; Sava, BA; Boroica, L; Sofronie, M; Tolea, F; Enculescu, M; Kuncser, V; Beldiceanu, A; Volceanov, A; Eftimie, M

Published: AUG 1 2018, APPLIED SURFACE SCIENCE, 448, 480, DOI: 10.1016/j.apsusc.2018.04.067

Ce3+ and Tb3+-doped silico-phosphate films were obtained by using the sol-gel method, followed by the spin-coating deposition on silicon substrate. The homogeneity of the films was investigated by the conoscopy method. It was observed that the analysed films are isotropic but relatively inhomogeneous due to the specificity of the deposition technique. The morphology of the sol-gel films was investigated by Scanning Electron Microscopy and Atomic Force Microscopy. The elemental composition was determined by Energy Dispersive X-ray analysis. The magneto-optical investigations evidenced the capability of Ce and Tb-doped films of less than 2 mu m thickness to produce measurable Kerr rotations of 1 mdeg/T and 0.28 mdeg/T, respectively. (C) 2018 Elsevier B.V. All rights reserved.

976. Improved Optical and Morphological Properties of Vinyl-Substituted Hybrid Silica Materials Incorporating a Zn-Metalloporphyrin

Authors: Dudas, Z; Fagadar-Cosma, E; Len, A; Romanszki, L; Almasy, L; Vlad-Oros, B; Dascalu, D; Krajnc, A; Kriechbaum, M; Kuncser, A

Published: APR 2018, MATERIALS, 11, DOI: 10.3390/ma11040565

This work is focused on a novel class of hybrid materials exhibiting enhanced optical properties and high surface areas that combine the morphology offered by the vinyl substituted silica host, and the excellent absorption and emission properties of 5,10,15,20-tetrakis(N-methyl-4-pyridyl) porphyrin-Zn(II) tetrachloride as a water soluble guest molecule. In order to optimize the synthesis procedure and the performance of the immobilized porphyrin, silica precursor mixtures of different compositions were used. To achieve the requirements regarding the hydrophobicity and the porous structure of the gels for the successful incorporation of porphyrin, the content of vinyltriacetoxysilane was systematically changed and thoroughly investigated. Substitution of the silica gels with organic groups is a viable way to provide new properties to the support. An exhaustive characterization of the synthesized silica samples was realised by complementary physicochemical methods, such as infrared spectroscopy (FT-IR), absorption spectroscopy (UV-Vis) and photoluminescence, nuclear magnetic resonance spectroscopy (Si-29-MAS-NMR) transmission and scanning electron microscopy (TEM and SEM), nitrogen absorption (BET), contact angle (CA), small angle X ray and neutron scattering (SAXS and SANS). All hybrids showed an increase in emission intensity in the wide region from 575 to 725 nm (Q bands) in comparison with bare porphyrin. By simply tuning the vinyltriacetoxysilane content, the hydrophilic/hydrophobic profile of the hybrid materials was changed, while maintaining a high surface area. Good control of hydrophobicity is important to enhance properties such as dispersion, stability behaviour, and resistance to water, in order to achieve highly dispersible systems in water for biomedical applications.

977. Photoelectrochemical response of carbon dots (CDs) derived from chitosan and their use in electrochemical imaging

Authors: Zhang, DW; Papaioannou, N; David, NM; Luo, H; Gao, H; Tanase, LC; Degousee, T; Samori, P; Sapelkin, A; Fenwick, O; Titirici, MM; Krause, S

Published: MAY 1 2018, MATERIALS HORIZONS, 5, 428, DOI: 10.1039/c7mh00784a

We report a direct photoelectrochemical response from low cost carbon dots (CDs) prepared from chitosan via a solvothermal method. The carbon dots were covalently linked to an indium tin oxide (ITO) surface through a self-assembled silane monolayer. We attribute the photocurrent of the ITO-silane-CD surface to a photogenerated electron-transfer process by CDs under illumination with a wavelength of 420 nm to 450 nm. The self-assembled monolayer of CDs was used for ac-photocurrent imaging of the surface with micron scale lateral resolution. This discovery opens up new applications for CDs as biocompatible, light-addressable electrochemical sensors in bioanalytical and bioimaging applications.

978. Enhanced photocurrent in GeSi NCs/TiO2 multilayers

Authors: Palade, C; Slav, A; Cojocaru, O; Teodorescu, VS; Lazanu, S; Stoica, T; Sultan, MT; Svavarsson, HG; Ciurea, ML

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 76, DOI:

GeSi NCs / TiO2 multilayers with enhanced photocurrent properties were prepared and studied. Multilayers of TiO2 /(GeSi/TiO2)x2 /Si-p were deposited by magnetron sputtering and annealed by RTA at 700 degrees C for GeSi NCs formation. A post-annealing hydrogenation in plasma was performed on multilayers for healing of defects acting as traps and/or recombination centers and consequently producing the photocurrent enhancement. We studied the electrical and photoconductive properties of multilayers annealed by RTA and post-annealing hydrogenated. The current - temperature dependence reveals the conduction mechanisms in GeSi NCs / TiO2 multilayers RTA annealed, i.e. thermal activation of carriers to extended states (0.31 eV activation energy), the electron tunneling mechanism to nearest neighbors (T-1/2 behavior) and Mott variable range hopping (T-1/4 dependence). The photocurrent spectra made on multilayers structures hydrogenated for 10, 20 and 30 min evidence the photocurrent increasing up to 50%, showing that the hydrogenation is a suitable treatment for enhancing photocurrent. All photocurrent spectra present a dominant maximum (920 nm) and two shoulders (similar to 770 and similar to 1060 nm).

979. Magnetism and magnetoresistance of single Ni-Cu alloy nanowires

Authors: Costas, A; Florica, C; Matei, E; Toimil-Molares, ME; Stavarache, I; Kuncser, A; Kuncser, V; Enculescu, I

Published: AUG 30 2018, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 9, 2355, DOI: 10.3762/bjnano.9.219

Arrays of magnetic Ni-Cu alloy nanowires with different compositions were prepared by a template-replication technique using electrochemical deposition into polycarbonate nanoporous membranes. Photolithography was employed for obtaining interdigitated metallic electrode systems of Ti/Au onto SiO2/Si substrates and subsequent electron beam lithography was used for contacting single nanowires in order to investigate their galvano-magnetic properties. The results of the magnetoresistance measurements made on single Ni-Cu alloy nanowires of different compositions have been reported and discussed in detail. A direct methodology for transforming the magnetoresistance data into the corresponding magnetic hysteresis loops was proposed, opening new possibilities for an easy magnetic investigation of single magnetic nanowires in the peculiar cases of Stoner-Wohlfarth-like magnetization reversal mechanisms. The magnetic parameters of single Ni-Cu nanowires of different Ni content have been estimated and discussed by the interpretation of the as derived magnetic hysteresis loops via micromagnetic modeling. It has been theoretically proven that the proposed methodology can be applied over a large range of nanowire diameters if the measurement geometry is suitably chosen.

980. Modeling issues regarding thermal conductivity of graphene-based nanocomposites

Authors: Sandu, T; Gologanu, M; Voicu, R; Boldeiu, G; Moagar-Poladian, V

Published: 2018, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 21, 92, DOI:

Modeling thermal conductivity of graphene-based nanocomposites is analyzed from an effective medium approximation point of view, where interfacial thermal resistance and arbitrary shape of the fillers are considered. Two approximations, Maxwell-Garnett and coherent potential approximation, are used to show that the usual oblate spheroidal shape approximation of graphene nanodots is not satisfactory to model thermal conductivity in graphene-based composites.

981. Synthesis and characterization of novel ferrite-piezoelectric multiferroic core-shell-type structure

Authors: Cernea, M; Vasile, BS; Ciuchi, IV; Surdu, VA; Bartha, C; Iuga, A; Galizia, P; Galassi, C

Published: JUL 2018, JOURNAL OF MATERIALS SCIENCE, 53, 9661, DOI: 10.1007/s10853-018-2264-x

Hybrid ferromagnetic/piezoelectric core-shell nanoparticles and ceramics have potential for a wide range of applications due to their tunability, electronic and magnetic properties. In this study, we designed a core-shell-type nanostructure of composition CoFe2O4/BNT-BT0.08, where BNT-BT0.08 is the abbreviation of bismuth, sodium titanate (Bi0.5Na0.5TiO3, BNT) doped with 8 mol% barium titanate (BaTiO3, BT). This multiferroic composite was prepared by covering CoFe2O4 nanoparticles with a shell of BNT-BT0.08 using the sol-gel technique. Scanning and transmission electron microscopy confirmed formation of a core-shell structure. The results of microstructure, dielectric, piezoelectric and magnetic investigations demonstrated that this heterostructure shows simultaneously electrical and magnetic behavior, at room temperature. XRD pattern of core-shell composite CoFe2O4/BNT-BT0.08 powder reveals only cubic CoFe2O4 and rhombohedral Bi0.5Na0.5TiO3 phases. CoFe2O4/BNT-BT0.08 core-shell nanostructure sample shows high values of permittivity (epsilon >= 600) together with high dielectric losses (tan delta >= 1) in the low-frequency range (nu <= 10(4) Hz). PFM and polarization hysteresis indicated a ferroelectric domains structure and remnant polarization of similar to 2.6 A mu C/cm(2) for the ceramics pellets samples of CoFe2O4/BNT-BT0.08. The present study reveals the possibility of coating nanoparticles onto nanometer-sized core particles, using controlled sol-gel process, in order to prepare multifunctional core-shell composites for piezoelectric and magnetoelectronic sensors.

982. Yellow laser potential of cubic Ca-3(Nb,Ga)(5)O-12:Dy3+ and Ca-3(Li,Nb,Ga)(5)O-12:Dy3+ single crystals

Authors: Gheorghe, C; Hau, S; Gheorghe, L; Voicu, F; Greculeasa, M; Enculescu, M; Belikov, KN; Bryleva, EY; Gaiduk, OV

Published: MAR 30 2018, JOURNAL OF ALLOYS AND COMPOUNDS, 739, 816, DOI: 10.1016/j.jallcom.2017.12.259

Spectroscopic investigation of Dy3+ doped Ca-3(Nb,Ga)(5)O-12 (CNGG) and Ca-3(Li,Nb,Ga)(5)O-12 (CLNGG) single crystals were performed in order to assess their potential as laser materials for yellow emission. Dy: CNGG and Dy: CLNGG single crystals were grown by the Czochralski method and investigated by high-resolution spectroscopic measurements for the first time. The Judd-Ofelt intensity parameters for the f-f transitions of Dy3+ in CNGG and CLNGG single crystals, were used to determine radiative transition rates A(r), branching ratios beta, and radiative lifetime tau(r) of the fluorescent Dy3+ levels. Based on low temperature absorption and emission spectra, partial energy levels diagram of Dy3+ doped CNGG and CLNGG single crystals were obtained. The emission cross-sections for the F-4(9/2) -> H-6(13/2) transition of special interest for laser application were determined. The room temperature decay curves were analyzed through the framework of Inokuti-Hirayama (I-H) model and the results shows that electric dipole-dipole interaction are responsible for the energy transfer processes between Dy3+ ions in CNGG and CLNGG single crystals. (c) 2017 Elsevier B.V. All rights reserved.

983. Structure of high-resolution K beta(1,3) x-ray emission spectra for the elements from Ca to Ge

Authors: Ito, Y; Tochio, T; Yamashita, M; Fukushima, S; Vlaicu, AM; Syrocki, L; Slabkowska, K; Weder, E; Polasik, M; Sawicka, K; Indelicato, P; Marques, JP; Sampaio, JM; Guerra, M; Santos, JP; Parente, F

Published: MAY 11 2018, PHYSICAL REVIEW A, 97, DOI: 10.1103/PhysRevA.97.052505

The K beta x-ray spectra of the elements from Ca to Ge have been systematically investigated using a high resolution antiparallel double-crystal x-ray spectrometer. Each K beta(1,3) natural linewidth has been corrected using the instrumental function of this type of x-ray spectrometer, and the spin doublet energies have been obtained from the peak position values in K beta(1,3) x-ray spectra. For all studied elements the corrected K beta(1) x-ray lines FWHM increase linearly as a function of Z. However, for K beta(3) x-ray lines this dependence is generally not linear in the case of 3d elements but increases from Sc to Co elements. It has been found that the contributions of satellite lines are considered to be [KM] shake processes. Our theoretically predicted synthetic spectra of Ca, Mn, Cu, and Zn are in very good agreement with our high-resolution measurements, except in the case of Mn, due to the open-shell valence configuration effect (more than 7000 transitions for diagram lines and more than 100 000 transitions for satellite lines) and the influence of the complicated structure of the metallic Mn.

984. Wet chemical synthesis of ZnO-CdS composites and their photocatalytic activity

Authors: Zgura, I; Preda, N; Socol, G; Ghica, C; Ghica, D; Enculescu, M; Negut, I; Nedelcu, L; Frunza, L; Ganea, CP; Frunza, S

Published: MAR 2018, MATERIALS RESEARCH BULLETIN, 99, 181, DOI: 10.1016/j.materresbull.2017.11.013

The present study is focused on the wet chemical synthesis and the characterization of ZnO-CdS composites. The X-ray diffraction shows that the composites contain ZnO in hexagonal wurtzite structure and CdS in cubic phase. The scanning/transmission electron microscopy images reveal flower-like structures with different sizes depending on the CdS content. The optical investigations on composites reveal that the reflectance spectra disclose two thresholds of similar to 370 nm and similar to 460 nm associated with the ZnO and CdS, respectively. The photocatalytic activity measurements evidenced that the degradation efficiency of RhB in the presence of composites is higher comparatively with pristine ZnO, depending on the catalyst morphology, which varies with CdS content and the pH value of RhB solution. The electron paramagnetic resonance revealed the presence of the paramagnetic point defects in the samples. Thus, the wet chemical approaches are suitable for a large scale production of such ZnO-CdS composites having enhanced photocatalytic activity.

985. Flexible organic heterostructures obtained by MAPLE

Authors: Socol, M; Preda, N; Breazu, C; Stanculescu, A; Costas, A; Stanculescu, F; Girtan, M; Gherendi, F; Popescu-Pelin, G; Socol, G

Published: SEP 2018, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 124, DOI: 10.1007/s00339-018-1960-3

Organic heterostructures based on zinc phthalocyanine (ZnPc) and perylene tetracarboxylic dianhydride (PTCDA) were deposited by matrix-assisted pulsed laser evaporation (MAPLE) technique on conductive flexible substrate (ITO/PET) in three configurations: ZnPc/PTCDA (stacked layers), ZnPc:PTCDA (blend) and ZnPc/ZnPc:PTCDA/PTCDA. The effect of the configuration on the optical and electrical properties of the obtained heterostructures was investigated. For all heterostructures was observed an improved optical absorption in visible domain. The I-V characteristics recorded under illumination, revealed higher short circuit current (I (SC)) values for the ZnPc:PTCDA and ZnPc/ZnPc:PTCDA/PTCDA structures in comparison with that of the ZnPc/PTCDA structure. The results proved that by MAPLE can be obtained flexible organic heterostructures (in different configurations) with properties adequate for applications in flexible electronics and solar cell fields.

986. 1532 nm sensitized luminescence and up-conversion in Yb,Er:YAG transparent ceramics

Authors: Vorona, I; Yavetskiy, RP; Dobrotvorskaya, MV; Doroshenko, AG; Parkhomenko, SV; Tolmachev, AV; Kosyanov, DY; Gheorghe, L; Gheorghe, C; Hau, S; Enculescu, M

Published: MAR 2018, OPTICAL MATERIALS, 77, 225, DOI: 10.1016/j.optmat.2018.01.038

Luminescent properties of Yb,Er:YAG transparent ceramics containing 5 at% Yb3+ and 0.5, 1 and 1.5 at%, respectively, Er3+ ions have been studied. It has been found that increasing of erbium ions concentration increases both efficiency of nonradiative energy transfer Yb3+ -> Er3+ (which reaches 72% for 1.5 at% Er3+) and the luminescence in the range of 650-700 nm associated with F-4(9/2), (11/2) -> I-4(15/2) transitions of Er3+ ions. It was also determined that the concentration quenching of sensitized luminescence of Er3+ ions at 1532 nm is associated with secondary excitation of metastable energy level of Er3+ followed by up conversion emission. (C) 2018 Elsevier B.V. All rights reserved.

987. Synthesis and Characterization of Chitosan-Coated Cobalt Ferrite Nanoparticles and Their Antimicrobial Activity

Authors: Gingasu, D; Mindru, I; Patron, L; Ianculescu, A; Vasile, E; Marinescu, G; Preda, S; Diamandescu, L; Oprea, O; Popa, M; Saviuc, C; Chifiriuc, MC

Published: SEP 2018, JOURNAL OF INORGANIC AND ORGANOMETALLIC POLYMERS AND MATERIALS, 28, 1941, DOI: 10.1007/s10904-018-0870-3

Chitosan-coated cobalt ferrites were synthesized by wet ferritization method through two different approaches. The nanostructured chitosan-coated cobalt ferrites were characterized by: X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), thermal analysis, infrared spectroscopy (IR) and Mossbauer spectroscopy. X-ray diffraction patterns confirmed the formation of CoFe2O4 cubic spinel structure with an average crystallite size of 1.75 and 5.5 nm, respectively. Mossbauer spectra consist in a central quadrupole pattern. The deconvolution in the hypothesis of Lorentzian line shape evidences the prevailing presence of Fe3+ ions at the nanoparticle surface. The antimicrobial activity of chitosan-coated cobalt ferrites against Gram-positive and Gram-negative bacteria, as well as fungal strains was investigated. Based on the results, chitosan-coated cobalt ferrites are thought to be suitable candidates for the development of novel anti-biofilm agents.

988. Alternative valorization of red mud waste as functional materials with catalytic activity for sulfide oxidation in wastewater

Authors: Cruceanu, A; Zavoianu, R; Pavel, OD; Florea, M; Mara, L

Published: APR 2018, INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY, 15, 908, DOI: 10.1007/s13762-017-1449-1

This work investigates the catalytic properties toward sulfide oxidation in wastewater for three composites which are functional materials obtained from red mud waste following its neutralization, chemical activation and functionalization of the iron by treatment with disodium salt of ethylenediaminetetraacetic acid, trisodium citrate or a combination of these two organic ligands. X-ray diffraction and diffuse reflectance Fourier transformed infrared spectroscopy characterizations indicated the coexistence of the corresponding iron chelates phases along with hematite the main crystallographic phase from red mud. The most active catalyst was the red mud-derived material obtained by functionalization with the mixture of ethylenediaminetetraacetate and citrate ligands. The results obtained after its testing in multiple reaction cycles showed that the decrease in conversion after 10 reaction cycles was less than 5%. Considering the results of diffuse reflectance ultraviolet visible narrow infrared spectroscopical analysis which revealed that this solid contains species with lower bond strength, it has been inferred that both the higher catalytic activity, as well as the enhanced stability, is directly related to the versatility of the active species.

989. Effects of a surfactant on the morphology and photocatalytic properties of polycrystalline Fe-doped ZnO powders

Authors: Diamandescu, L; Cernea, M; Trusca, R; Enculescu, M; Tanase, L; Baibarac, M; Feder, M; Nicoara, AI; Popescu, T

Published: OCT 2018, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 121, 328, DOI: 10.1016/j.jpcs.2018.05.041

In this study, we compared the structural, morphological, and optical properties of a series of Zn1-xFexO (x = 0.00, 0.01, and 0.03) powders synthesized via a hydrothermal route with and without cetyltrimethylammonium bromide as a cationic surfactant. Our results highlighted the critical effects of the surfactant and the iron concentration on the structure, morphology, and optical properties of ZnO. X-ray diffraction, Mossbauer spectroscopy, and X-ray photoelectron spectroscopy analyses indicated the presence of a single phase comprising ZnO with a hexagonal wurtzite structure in all samples and a single oxidation state (+3) for the iron (Fe3+) that replaced Zn2+ in the ZnO structure. Morphological investigations by scanning electron microscopy showed that the surfactant and Fe3+ dopant greatly affected the shape of the ZnO grains, which varied between sheets and rod-like flowers. We found that the morphological and photocatalytic properties of the two series of samples comprising iron-doped ZnO with and without the surfactant were in opposition. We propose a possible growth mechanism for the ZnO polycrystalline grains in the presence of the Fe dopant and/or surfactant. The photocatalytic properties increased for the samples prepared with surfactant as the iron content increased, which was confirmed by ultraviolet-visible reflection measurements. The photocatalytic activities of the samples prepared without surfactant decreased in both the ultraviolet and visible spectral regions as the iron content increased in the samples.

990. Electrochemical Synthesis of the Composites Based on Multi-Wall Carbon Nanotubes and Polypyrrole Doped with Phosphomolybdic Acid Heteropolyanions and Their Vibrational Properties

Authors: Baibarac, M; Serbschi, C; Stroe, M

Published: NOV 2018, INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE, 13, 10526, DOI: 10.20964/2018.11.07

Using cyclic voltammetry, Raman scattering and infrared (IR) spectroscopy, new findings concerning the electrochemical synthesis of composites based on multi-wall carbon nanotubes (MWNTs) and polypyrrole (PPY) doped with H3PMo12O40 heteropolyanions are described in this report. To better understand the electrochemical mechanism behind the synthesis of these composites, the influence of the concentrations of pyrrole and the electrolytes of H3PMo12O40 and H2SO4 on the cyclic voltammogram profile is studied. The formation of PPY doped with H3PMo12O40 heteropolyanions onto the MWNT surface is demonstrated by complementary studies of Raman scattering and IR spectroscopy.

991. A Comparative Study of Ge-Based Organometallic Additions to MgB2

Authors: Batalu, D; Nakamura, T; Enculescu, M; Popa, S; Pasuk, I; Aldica, G; Ionescu, AM; Badica, P

Published: JUN 2018, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 28, DOI: 10.1109/TASC.2018.2808366

Four Ge-based organometallic (OM = C6H10 Ge2O7) polymers with similar chemical composition were used as additions for MgB2. MgB2 (OM) 0.0014 dense samples with a relative density higher than 97% were obtained by ex situ spark plasma sintering. The critical current density and the irreversibility magnetic field of the added samples are slightly improved at high magnetic fields by repagermanium (Alfa Aesar) addition when compared to the pristine reference sample. Addition of Ge-straight-chain polymer shows some improvement of the maximum volume pinning force, F-p (max). There is no significant Ge substitution in the crystal lattice of MgB2, while C substitutes for B. Pinning mechanism is mainly of a point pinning type, with the grain boundary pinning mechanism strengthening at lower temperatures and when additives are not used. A relatively high amount of carbon in the samples washes out the Ge effects on pinning-force-related parameters. The structure and morphology of the polymer additive play an important role in dispersion when mixing, impacting the quality of the superconducting properties. The nanosize dimension of the pristine MgB2 powder shows also some drawbacks in mixing and sintering.

992. Doped ceria prepared by precipitation route for steam reforming of methane

Authors: Florea, M; Matei-Rutkovska, F; Postole, G; Urda, A; Neatu, F; Parvulescu, VI; Gelin, P

Published: MAY 15 2018, , DOI: 10.1016/j.cattod.2016.12.006

993. Influence of the modulated two-step synthesis of biogenic hydroxyapatite on biomimetic products' surface

Authors: Miculescu, F; Mocanu, AC; Stan, GE; Miculescu, M; Maidaniuc, A; Cimpean, A; Mitran, V; Voicu, SI; Machedon-Pisu, T; Ciocan, LT

Published: APR 30 2018, APPLIED SURFACE SCIENCE, 438, 157, DOI: 10.1016/j.apsusc.2017.07.144

Processing calcium-rich natural resources, such as marble and mussel seashells, into biomimetic products could constitute an environmentally-friendly and economically sustainable alternative given their geographical widespread. Hitherto, their value for biomedicine was demonstrated only for seashells, with the technological exploitation approaches still facing challenges with respect to the identification of generic synthesis parameters capable to allow the reproducible and designed synthesis of calcium phosphate at an industrial-ready level. In this study was targeted the optimization of Rathje synthesis method for the fabrication of biogenic calcium phosphates, by conveniently adjusting the chemical composition of employed reagents. It was shown that post-synthesis heat-treatment of compacted powders is the key step for inducing structural transformations suitable to attain biomimetic products for reconstructive orthopedic applications. The sintered materials have been multi-parametricallyevaluated from morpho-compositional, structural, wettability, mechanical and cytocompatibility points of view and the results have been cross-examined and discussed. Convenient and efficient preparation routes to produce biogenic hydroxyapatite have been identified. The functional performances of the as-prepared biogenic ceramics endorse their use as a solid and inexpensive alternative source material for the fabrication of various bone regenerative products and implant coatings. (C) 2017 Elsevier B.V. All rights reserved.

994. Thermophysical properties of Cu-ZrO2 composites as potential thermal barrier materials for a DEMO W-monoblock divertor

Authors: Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 2018, FUSION ENGINEERING AND DESIGN, 127, 184, DOI: 10.1016/j.fusengdes.2018.01.011

DEMO fusion reactor divertor is expected to extract a heat flux of about 10 MW/m(2). One of the most promising concept design for it is the W-monoblock, which should be connected to a CuCrZr or an advanced Cu ODS alloy pipe passing through the W component. Since the optimum operating temperature windows for W and existing Cu alloys are far away from overlapping, a suited interface is needed to keep the adjacent materials as close as Possible to their respective temperature operating windows. The interface material should therefore have a low enough thermal conductivity to act as a thermal barrier and a thermal expansion coefficient suited to protect the W-pipe joint from stresses induced by the different thermo-mechanical properties of W and Cu-alloys. As interface materials we have considered Cu-ZrO2 composites produced by powder metallurgy route. Such materials can be realized in an unexpected large compositional range (up to at least 90% ZrO2 volume concentration) and be easily further joined to both W and Cu-alloys by an electrical field assisted technology. We analyse their microstructure and thermo-physical properties both as single materials and included in W-thermal barrier-CuCrZr 3-layers systems in comparison to those of previously produced Cu-ased composites and commercially available Cu foams.

995. Localization Properties of Zig-Zag Edge States in Disordered Phosphorene

Authors: Nita, M; Ostahie, B; Tolea, M; Aldea, A

Published: JUL 2018, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 12, DOI: 10.1002/pssr.201800051

Herein, the spectral and transport properties in the finite phosphorene lattice are investigated using the tight-binding model in the presence of Anderson disorder potential. The focus is on the zig-zag edge states localization, provided by the numerically calculated inverse participation number. At low disorder, the zig-zag states undergo a localization process, keeping their 1D character, while further increasing the disorder leads to delocalization due to hybridization with the extended 2D states. The disorder-induced changes in the electronic conductance, from one zig-zag edge to the other, are also discussed.

996. Inhibitory effect of three phenacyl derivatives on the oxidation of sphalerite (ZnS) in air-equilibrated acidic solution

Authors: Chirita, P; Duinea, MI; Sandu, AM; Birsa, LM; Sarbu, LG; Baibarac, M; Sava, F; Popescu, M; Matei, E

Published: JUL 1 2018, CORROSION SCIENCE, 138, 162, DOI: 10.1016/j.corsci.2018.04.017

Three phenacyl derivatives have been investigated as potential inhibitors for the aqueous oxidation of sphalerite (ZnS) in air-equilibrated solutions of HCl (pH 2.5 and 25 degrees C) using potentyodynamic polarization, aqueous batch experiments, scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) analysis, Fourier transform infrared (FTIR) spectroscopy, Raman scattering and quantum chemical calculations. Findings show that the studied phenacyl derivatives are inhibitors of sphalerite aqueous oxidation. Quantum chemical calculations indicate that the adsorption of phenacyl derivatives on ZnS is energetically favorable and accounts for the observed inhibiting effects.

997. CERAMIC THIN FILMS DEPOSITED BY SPIN COATING AS COATINGS FOR METALLIC IMPLANTS

Authors: Busuioc, C; Constantinoiu, I; Enculescu, M; Beregoi, M; Jinga, SI

Published: 2018, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 48, 406, DOI:

Ceramic thin films belonging to SiO2-P2O5-CaO-MgO-ZnO-CaF2 system were obtained by combining the sol-gel approach with the spin coating technique. Titanium plates were employed as substrates. The deposited coatings were characterized in terms of composition, structure and morphology with the help of the following methods: X-ray diffraction, Fourier - transform infrared spectroscopy and scanning electron microscopy coupled with energy - dispersive X-ray spectroscopy. In order to assess the bioactivity of a potential metallic implant covered with such layers, the samples were immersed in simulated body fluid for 14 days and their surface was investigated. The results showed that the thin films calcined at a lower temperature have a better biological response due to the vitroceramic nature.

998. Thermal behaviour of sym-octahydroacridines and their corresponding N(10)-oxides

Authors: Marinescu, M; Potmischil, F; Florea, M; Constantinescu, C

Published: JAN 2018, , DOI: 10.1007/s10973-016-5862-3

999. Investigation of the interactions of PVDF shell films with Ni core submicron wires and AAO matrix

Authors: Sima, M; Baibarac, M; Vasile, E; Sima, M; Schinteie, GA; Kuncser, V

Published: SEP 15 2018, PHYSICA B-CONDENSED MATTER, 545, 509, DOI: 10.1016/j.physb.2018.07.015

Arrays of Ni submicron wires surrounded by poly (vinylidene fluoride) (PVDF) submicron tubes were prepared via solution-processed polymer and Ni electrodeposition into anodic aluminum oxide template. The PVDF solution was filtered in vacuum through the template and the resulting dried structure was used for the electrodeposition of Ni wires. The obtained core-shell submicron wire structure consists of a metallic magnetic nanowire core of about 50 mu m in length and about 300 nm diameter surrounded by a polymer tube shell with thickness less than 10 nm. The specific ferroelectric beta-phase of the polymer was obtained whereas the magnetic behavior of the Ni-cores was proven to be specific to an array of ferromagnetic Ni cylindrical wires (about 0.62 mu(B)/Ni atom) with magnetization reversal mechanisms dominated by dipolar interactions and domain wall displacements. No significant differences of the magnetization reversal mechanism were observed in case of Ni submicron wires surrounded by PVDF tubes and similar Ni wires without PVDF shell, suggesting that magneto-coupling effects in such systems might be observed only by measuring the perturbation of the electric state of the polymer shell under a magnetic excitation of the Ni cores.

1000. Branch-like NiO/ZnO heterostructures for VOC sensing

Authors: Kaur, N; Zappa, D; Ferroni, M; Poli, N; Campanini, M; Negrea, R; Comini, E

Published: JUN 1 2018, SENSORS AND ACTUATORS B-CHEMICAL, 262, 485, DOI: 10.1016/j.snb.2018.02.042

We report for the first time on the synthesis of NiO/ZnO one-dimensional (1D) nanowire (NW) based heterostructures by applying a suitable methodology of transport and condensation. The synthesis involves, firstly the growth of NiO NWs on gold (Au) catalyzed alumina substrates using the vapor-liquid-solid (VLS) mechanism and then the formation of ZnO NWs directly on the NiO NWs using the vapor-solid (VS) mechanism. Sequential evaporation-condensation over Au-seeded alumina promotes the formation of NiO NWs, driven by the VLS growth mechanism. These NiO NWs act as backbones for the condensation of epitaxial ZnO nanostructures. The detailed morphological study of these heterostructures reveals that ZnO nanowires completely cover the whole NiO nanowires completely and growing out in the form of flat leaves from the NiO nanowire branches. The diameters of the NiO NWs have been found to vary from 15 nm to 60 nm. Selected area electron diffraction data (SAED) indicate an epitaxial growth of ZnO nanowires along (101)-planes on the strongly oriented NiO nanowires along (200) crystallographic planes. Finally, NiO NW and NiO/ZnO heterostructure based conductometric gas sensing devices have been fabricated and the comparison between their sensing performances have been compared. Interestingly, NiO/ZnO NWs heterostructure based sensing devices shows superior performance compared to NiO sensors toward volatile organic compounds (VOC). (C) 2018 Elsevier B.V. All rights reserved.

1001. Antimicrobial Activity of New Materials Based on Lavender and Basil Essential Oils and Hydroxyapatite

Authors: Predoi, D; Iconaru, SL; Buton, N; Badea, ML; Marutescu, L

Published: MAY 2018, NANOMATERIALS, 8, DOI: 10.3390/nano8050291

This study presents, for the first-time, the results of a study on the hydrodynamic diameter of essential oils (EOs) of basil and lavender in water, and solutions of EOs of basil (B) and lavender (L) and hydroxyapatite (HAp). The possible influence of basil and lavender EOs on the size of hydroxyapatite nanoparticles was analyzed by Scanning Electron Microscopy (SEM). We also investigated the in vitro antimicrobial activity of plant EOs and plant EOs hydroxyapatite respectively, against Gram-positive bacteria (methicillin-resistant Staphylococcus aureus1144 (MRSA 1144) and S. aureus 1426) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Escherichia coli ESBL 4493). From the autocorrelation function, obtained by Dynamic Light Scattering (DLS) measurements it was observed that basil yielded one peak at an average hydrodynamic diameter of 354.16 nm, while lavender yielded one peak at an average hydrodynamic diameter of 259.76 nm. In the case of HAp nanoparticles coated with basil (HApB) and lavender (HApL) essential oil, the aggregation was minimal. We found that the lavender EO exhibited a very good inhibitory growth activity (MIC values ranging from <0.1% for E. coli reference strain to 0.78% for S. aureus strains). The biological studies indicated that HapL material displayed an enhanced antimicrobial activity, indicating the potential use of HAp as vehicle for low concentrations of lavender EO with antibacterial properties. Flow cytometry analysis (FCM) allowed us to determine some of the potential mechanisms of the antimicrobial activities of EOs, suggesting that lavender EO was active against E. coli by interfering with membrane potential, the membrane depolarization effect being increased by incorporation of the EOs into the microporous structure of HAp. These findings could contribute to the development of new antimicrobial agents that are urgently needed for combating the antibiotic resistance phenomena.

1002. CdS/ZnS-doped silico-phosphate films prepared by sol-gel synthesis

Authors: Rusu, MI; Stefan, CR; Elisa, M; Feraru, ID; Vasiliu, IC; Bartha, C; Trusca, RD; Vasile, E; Peretz, S

Published: FEB 1 2018, JOURNAL OF NON-CRYSTALLINE SOLIDS, 481, 440, DOI: 10.1016/j.jnoncrysol.2017.11.025

Silico-phosphate films doped with CdS/ZnS quantum dots (QDs) for luminescence temperature sensing devices, were deposited on silicon substrate by sol-gel method, spin coating technique. Optical absorption and photoluminescence emission of CdS/ZnS-doped silico-phosphate films were investigated. CdS/ZnS nano-crystalline particles were put into evidence by X-Ray Diffraction (XRD) spectroscopy. The specific vibration modes of the constituents were evidenced by structural analysis carried out by Raman and Fourier Transform Infrared spectroscopy (FTIR). The characteristic fluorescence emission of CdS/ZnS nanoparticles was noticed in the visible domain. The morphology of the films was investigated by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Clusters of hexagonal crystalline CdS/ZnS QDs were put into evidence.

1003. On the properties of organic heterostructures prepared with nano-patterned metallic electrode

Authors: Breazu, C; Socol, M; Preda, N; Matei, E; Rasoga, O; Girtan, M; Mallet, R; Stanculescu, F; Stanculescu, A

Published: JUN 15 2018, APPLIED SURFACE SCIENCE, 443, 602, DOI: 10.1016/j.apsusc.2018.02.103

This paper presents a comparative study between the properties of the heterostructures realized with single/multi layer organic (zinc phthalocyanine or/and fullerene) prepared on Si substrate between flat or patterned aluminum (Al) layer metallic electrode and multi layer ZnO/Au/ZnO transparent conductor electrode (TCE). The UV-Nanoimprint Lithography was used for the realization of a 2D array of nanostructures (holes/pillars) characterized by a periodicity of 1.1 mu m and cylindrical shape: diameter = 400 nm and depth/height = 300 nm. The effect of the electrode patterning on the properties of the organic heterostructures was analyzed. For the samples with patterned Al electrode was remarked a slight red shift of the peaks in the reflection spectra determined by an increased interaction between the organic molecules in the delimited region of the patterned holes. The shape of the emission spectra at excitation with UV light showed a narrow intense peak around 500 nm associated with the intense resonance phenomena between the energy of the incident light and the surface plasmons in the patterned Al layer. The TCE followed the morphology of the organic film on which it was deposited. The significant differences between the morphology of the top layer in the heterostructures realized on flat and patterned Al are correlated with the total thickness of the successively deposited layers and with the particularities of the molecular arrangement, leading to the preservation or deleting of patterning. An injection contact behavior was evidence for most heterostructures built on flat and patterned Al. The slight increase in current at an applied bias <1 V in the heterostructure Si/Al/ZnPc/TCE is attributed to the larger interfacial area between the patterned Al electrode and ZnPc layer compared to the interface area between flat Al and ZnPc. A buffer layer of 1,4,5,8-naphthalen-tetracarboxylic dianhydride (NTCDA), sandwiched between the flat metallic electrode and organic film in the heterostructure Si/Al/C60/ZnPc/TCE has determined an increase in the current at low applied voltages. (C) 2018 Elsevier B.V. All rights reserved.

1004. On the hydrophilicity of Ni-doped TiO2 thin films. A study by X-ray absorption spectroscopy

Authors: Macovei, D; Tiron, V; Adomnitei, C; Luca, D; Dobromir, M; Antohe, S; Mardare, D

Published: JUL 1 2018, THIN SOLID FILMS, 657, 49, DOI: 10.1016/j.tsf.2018.04.045

Undoped and Ni-doped TiO2 thin films, with Ni concentration in the range 3-9 at.%, were obtained by reactive magnetron co-sputtering. A combined analysis by X-ray photoelectron spectroscopy and extended X-ray absorption-edge fine structure shows that Ni2+ substitutes for Ti4+ in the TiO2 lattice and promotes, at higher Ni amounts, a structural transition of the host from anatase to rutile. Several difficulties of the extended X-ray absorption-edge fine structure analysis, in the case of Ni-doped TiO2, are also discussed. X-ray diffraction data revealed that a large amount of the films material is in amorphous state. The films are very smooth, with root mean square roughness values (below 1.5 nm) decreasing with the increase of the Ni content. The hydrophilic properties of TiO2, modified by Ni doping, are also investigated.

1005. Dense Ge nanocrystals embedded in TiO2 with exponentially increased photoconduction by field effect

Authors: Lepadatu, AM; Slav, A; Palade, C; Dascalescu, I; Enculescu, M; Iftimie, S; Lazanu, S; Teodorescul, VS; Ciurea, ML; Stoica, T

Published: MAR 20 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-23316-3

Si and Ge nanocrystals in oxides are of a large interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in nanocrystals. In this work, dense Ge nanocrystals suitable for enhanced photoconduction were fabricated from 60% Ge in TiO2 amorphous layers by low temperature rapid thermal annealing at 550 degrees C. An exponential increase of the photocurrent with the applied voltage was observed in coplanar structure of Ge nanocrystals composite films deposited on oxidized Si wafers. The behaviour was explained by field effect control of the Fermi level at the Ge nanocrystals-TiO2 layer/substrate interfaces. The blue-shift of the absorption gap from bulk Ge value to 1.14 eV was evidenced in both photocurrent spectra and optical reflection-transmission experiments, in good agreement with quantum confinement induced bandgap broadening in Ge nanocrystal with sizes of about 5 nm as found from HRTEM and XRD investigations. A nonmonotonic spectral dependence of the refractive index is associated to the Ge nanocrystals formation. The nanocrystal morphology is also in good agreement with the Coulomb gap hopping mechanism of T-1/2 -type explaining the temperature dependence of the dark conduction.

1006. The improvement of SiO2 nanotubes electrochemical behavior by hydrogen atmosphere thermal treatment

Authors: Spataru, N; Anastasescu, C; Radu, MM; Balint, I; Negrila, C; Spataru, T; Fujishima, A

Published: JUN 30 2018, APPLIED SURFACE SCIENCE, 444, 223, DOI: 10.1016/j.apsusc.2018.03.074

Highly defected SiO2 nanotubes (SiO2-NT) were obtained by a simple sol-gel procedure followed by calcination. Boron-doped diamond (BDD) polycrystalline films coated with SiO2-NT were used as working electrodes and, unexpectedly, cyclic voltammetric experiments have shown that the concentration of both positive and negative defects at the surface is high enough to enable redox processes involving positively charged Ru(bpy)(3)(2+/3+) to occur. Conversely, no electrochemical activity was put into evidence for Fe (CN)(6)(3/4) species, most likely as a result of the strong electrostatic repulsion exerted by the negatively charged SiO2 surface. The concentration of surface defects was further increased by a subsequent thermal treatment in a hydrogen atmosphere which, as EIS measurements have shown, significantly promotes Ru (bpy)(3)(2+) anodic oxidation. Digital simulation of the voltammetric responses demonstrated that this treatment does not lead to a similar increase of the number of electron-donor sites. It was also found that methanol anodic oxidation at hydrogenated SiO2-NT-supported platinum results in Tafel slopes of 116-220 mV decade(-1), comparable to those reported for both conventional PtRu and Pt-oxide catalysts. (C) 2018 Elsevier B.V. All rights reserved.

1007. Thermal, spectral and biological investigation of new nickel complexes with imidazole derivatives

Authors: Vlaicu, ID; Olar, R; Scaeteanu, GV; Silvestro, L; Maurer, M; Stanica, N; Badea, M

Published: OCT 2018, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 134, 512, DOI: 10.1007/s10973-018-7133-y

Four new Ni(II) complexes with acrylate and imidazole (Him) or imidazole derivatives [2-methylimidazole(2-MeIm)/5-methylimidazole(5-MeIm)/2-ethylimidazole(2-EtIm)] as ligands were prepared and characterized. All coordination compounds were characterized by elemental analysis, infrared (FTIR) and ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy, mass spectroscopy, magnetic moments measurements and thermal analysis (TG). The resulted complexes were formulated as follows: [Ni(HIm)(2)(acr)(2)] (1), [Ni(2-MeIm)(2)(acr)(2)(H2O)] center dot H2O (2), [Ni(5-MeIm)(2)(acr)(2)]center dot H2O. (3), [Ni(2-EtIm)(2)(acr)(2)(H2O)] center dot H2O (4). On the basis of magnetic moments measurements and on UV-Vis-NIR spectra, for all Ni(II) complexes was proposed an octahedral stereochemistry. Acrylate ions act as bidentate in complexes (1) and (3); meanwhile, in (2) and (4) they behave as bidentate and unidentate. Antimicrobial activity of complexes was investigated on ATCC reference and clinical microbial strains. The MIC (minimum inhibitory concentration) values revealed moderate antimicrobial activity of complex (1) against Enterococcus faecium and of complex (2) against Pseudomonas aeruginosa and Bacillus subtilis.

1008. Structural, dielectric and piezoelectric properties of the ferroelectric PZT-BT ceramic compounds

Authors: Miclea, C; Miclea, CF; Amarande, L; Miclea, CT; Cioangher, M

Published: SEP-OCT 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 565, DOI:

Ceramic compounds of ferroelectric lead zirconate titanate (PZT) and ferroelectric barium titanate (BT) were prepared from nanopowders corresponding to the formula (1-x)PZT.xBT with x = 0; 0.1; 0.2 ... 0.9; 1. The samples were investigated by X-ray diffraction and electron microscopy and the piezoelectric properties were determined by means of an impedance analyzer. The sintering process is complex since samples densify at different temperatures depending on the composition resulting in different morphostructures. Accordingly, the piezoelectric properties show unusual behavior discussed in terms of different grain size and composition. A remarkably high enhancement of the relative dielectric constant, epsilon(r) coupled with maxima in both, piezoelectric charge constant d(33) and the piezoelectric voltage constant g(33), is observed for x = 0.4 while the values of the coupling coefficient kp are still high similar to those of pure PZT.

1009. Engineering active sites on reduced graphene oxide by hydrogen plasma irradiation: mimicking bifunctional metal/supported catalysts in hydrogenation reactions

Authors: Primo, A; Franconetti, A; Magureanu, M; Mandache, NB; Bucur, C; Rizescu, C; Cojocaru, B; Parvulescu, VI; Garcia, H

Published: JUN 7 2018, GREEN CHEMISTRY, 20, 2623, DOI: 10.1039/c7gc03397d

H2 plasma has been used to generate carbon vacancies on reduced graphene oxide to increase its catalytic activity as a hydrogenation catalyst. A relationship between the power of the plasma treatment and the exposure time with the activity of the material was observed for CvC double bond hydrogenation. The activity data in the case of 1-octene, showing skeletal isomerization besides hydrogenation, indicate that H2 plasma treatment can introduce hydrogenating and acid sites rendering a bifunctional catalyst that is reminiscent of the activity of noble metals supported on acid supports.

1010. Polyaniline photoluminescence quenching induced by single-walled carbon nanotubes enriched in metallic and semiconducting tubes

Authors: Baibarac, M; Matea, A; Daescu, M; Mercioniu, I; Quillard, S; Mevellec, JY; Lefrant, S

Published: JUN 22 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-27769-4

The influence of single-walled carbon nanotubes enriched in semiconductor (S-SWNTs) and metallic (M-SWNTs) tubes on the photoluminescence (PL) of polyaniline (PANI), electrosynthesized in the presence of the H2SO4 and HCl solutions, is reported. The emission bands peaked at 407-418 and 440-520 nm indicate that the electropolymerization of aniline (ANI) leads to the formation of short and longer macromolecular chains (MCs), respectively. We demonstrate that the reaction product consists of ANI tetramers (TT) and trimers (TR) as well as PANI-salt. Using Raman scattering and IR absorption spectroscopy, a covalent functionalization of SWNTs with shorter and longer MCs of PANI-salt is demonstrated. The presence of S-SWNTs and M-SWNTs induces a decrease in ANI TT weight in the reaction product mass consisting in S-SWNTs and M-SWNTs covalently functionalized with PANI-emeraldine salt (ES) and PANI-leucoemeraldine salt (LS), respectively. A PANI PL quenching is reported to be induced of the S-SWNTs and M-SWNTs. A de-excitation mechanism is proposed to explain PANI PL quenching.

1011. Palladium pincer complex incorporation onto the Fe3O4-entrapped cross-linked multilayered polymer as a high loaded nanocatalyst for oxidation'

Authors: Zohreh, N; Hosseini, SH; Tavakolizadeh, M; Busuioc, C; Negrea, R

Published: SEP 15 2018, JOURNAL OF MOLECULAR LIQUIDS, 266, 404, DOI: 10.1016/j.molliq.2018.06.076

Pd nanoparticles are stabilized onto the surface of Fe3O4-entrapped poly(aminoethyl acrylamide) via functionalization of polymer with a new class of NNN-pincer ligand providing a high loading and stable catalyst for aerobic oxidation of alcohols to aldehydes. Varieties of alcohols are oxidized to the corresponding aldehydes with good selectivity using 0.95 mol% Pd catalyst. The catalyst is reusable (5 runs) without loss of activity and leaching or agglomeration of Pd nanoparticles while structural regularity of the catalyst is preserved. Oxidation of benzyl alcohol is also scaled up to a few grams. (C) 2018 Elsevier B.V. All rights reserved.

1012. (Fe, Nd) codoped ZnO micro- and nanostructures with multifunctional characteristics like photocatalytic activity, optical and ferromagnetic properties

Authors: Diamandescu, L; Cernea, M; Tolea, F; Secu, EC; Trusca, R; Secu, M; Enculescu, M

Published: DEC 1 2018, CERAMICS INTERNATIONAL, 44, 21975, DOI: 10.1016/j.ceramint.2018.08.310

Zn1-x-yFexNdyO, x = 0.02 and y = 0.00-0.05 were successfully synthesized via a hydrothermal method at 200 degrees C. XRD and Mossbauer spectroscopy indicated that (Fe, Nd) codoped ZnO, calcined at 700 degrees C, 3 h in air, contains hexagonal ZnO phase as main phase and traces of ZnFe2O4; no phase containing neodymium was observed. In this study, a strong powder morphology dependence on Nd concentration and calcination temperature was evidenced by SEM. The photocatalytic properties were found to depend on the sample morphology and Nd content. Thermoluminescence signal is weak compared to the undoped ZnO and the curves shape was almost independent on the doping level and dependent on the calcination temperature and was related to the structural defects induced by the synthesis and calcination. Photoluminescence spectra showed that the green-yellow band due to the oxygen related defects, decreases by Fe and Nd-codoping. Thermo-magnetization curves measured in low applied fields and the magnetic hysteresis loops recorded in the temperature range 5-380 K, indicate two superimposed magnetic regimes, one predominant above 100 K the other below 100 K. The observed magnetic order is not directly related to the dopant Fe or Nd ions, but to different type of defects.

1013. Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

Authors: Ticos, CM; Galatanu, M; Galatanu, A; Luculescu, C; Scurtu, A; Udrea, N; Ticos, D; Dumitru, M

Published: MAR 15 2018, APPLIED SURFACE SCIENCE, 434, 1128, DOI: 10.1016/j.apsusc.2017.11.057

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 mu m. The plasma power load to the sample surface was estimated to be 4.7 MJ m(-2) s(-1/2) per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 x 10(22) m(-3), respectively. (C) 2017 National Institute for Laser, Plasma, and Radiation Physics (INFLPR). Published by Elsevier B.V. All rights reserved.

1014. Functional properties improvement of Ag-ZnO thin films using Inconel 600 interlayer produced by electron beam evaporation technique

Authors: Lungu, MV; Sobetkii, A; Sobetkii, AA; Patroi, D; Prioteasa, P; Ion, I; Negrila, CC; Chifiriuc, MC

Published: DEC 1 2018, THIN SOLID FILMS, 667, 87, DOI: 10.1016/j.tsf.2018.09.055

500 nm thick silver-zinc oxide (Ag-ZnO) films were grown by electron beam evaporation on 316 L stainless steel (SS) substrate and on 150 nm thick Inconel 600 (IN600) interlayer. The films were annealed in air at 500 degrees C for 1 h. The morphological and structural analyses confirmed smooth, uniform, homogeneous and crack-free surfaces with nanocrystalline grain size for all films. The elemental composition analysis yielded up to 0.6 wt% Ag in Ag-ZnO/IN600 films. The ultraviolet-visible spectroscopy and Raman spectroscopy along with mechanical and electrochemical tests revealed improved optical, scratch resistance and electrochemical properties of Ag-ZnO/IN600 films than Ag-ZnO films. Ag-ZnO/IN600 and Ag-ZnO films exhibited higher antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans pathogens, comparatively with IN600 films and SS substrate. The superior functional properties of Ag-ZnO/IN600 films suggest their potential for practical applications as antimicrobial and robust coatings on SS surface-contacting medical devices with limited exposure.

1015. Rolling dopant and strain in Y-doped BiFeO3 epitaxial thin films for photoelectrochemical water splitting

Authors: Haydous, F; Scarisoreanu, ND; Birjega, R; Ion, V; Lippert, T; Dumitrescu, N; Moldovan, A; Andrei, A; Teodorescu, VS; Ghica, C; Negrea, R; Dinescu, M

Published: OCT 25 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-34010-9

We report significant photoelectrochemical activity of Y-doped BiFeO3 (Y-BFO) epitaxial thin films deposited on Nb: SrTiO3 substrates. The Y-BFO photoanodes exhibit a strong dependence of the photocurrent values on the thickness of the films, and implicitly on the induced epitaxial strain. The peculiar crystalline structure of the Y-BFO thin films and the structural changes after the PEC experiments have been revealed by high resolution X-ray diffraction and transmission electron microscopy investigations. The crystalline coherence breaking due to the small ionic radius Y-addition was analyzed using Willliamson-Hall approach on the 2 theta-omega scans of the symmetric (00l) reflections and confirmed by high resolution TEM (HR-TEM) analysis. In the thinnest sample the lateral coherence length (L-parallel to) is preserved on larger nanoregions/ nanodomains. For higher thickness values L-parallel to is decreasing while domains tilt angles (alpha(tilt)) is increasing. The photocurrent value obtained for the thinnest sample was as high as J(ph) = 0.72 mA/cm(2), at 1.4 V(vs. RHE). The potentiostatic scans of the Y-BFO photoanodes show the stability of photoresponse, irrespective of the film's thickness. There is no clear cathodic photocurrent observation for the Y-BFO thin films confirming the n-type semiconductor behavior of the Y-BFO photoelectrodes.

1016. Organic heterostructures obtained on ZnO/Ag/ZnO electrode

Authors: Socol, M; Preda, N; Breazu, C; Florica, C; Costas, A; Istrate, CM; Stanculescu, A; Girtan, M; Gherendi, F

Published: AUG 2018, VACUUM, 154, 370, DOI: 10.1016/j.vacuum.2018.05.039

This work is focused on the use of multilayer transparent conductive electrode (TCE) based on ZnO/Ag/ZnO in the fabrication of the organic heterostructures. The ZnO/Ag/ZnO obtained combining sputtering/thermal evaporation/sputtering techniques is featured by a good optical transmittance, a low electrical resistivity and a reduced roughness. All these characteristics recommend it as a viable alternative to indium tin oxide (ITO) for different applications. The organic materials, N,N' - diphenyl N,N' - bis (1 - aphthyl) 1,1' - biphenyl 4,4' - diamine (alpha-NPD), 5,12-Dihydro-5-12-dimethylquino [2,3-b]acridine-7,14dione (DMQA) and 4,7 diphenyl-1,10-phenanthroline (BPhen) were deposited by vacuum thermal evaporation (VTE) method, the properties of the obtained layers being investigated by FTIR, UV-VIS and PL) spectroscopy. The I-V characteristic (recorded in dark) of the organic heterostructure fabricated on the ZnO/Ag/ZriO electrode shows diode behavior, revealing its potential applications in the organic light emitting devices (OLED).

1017. ESR Study of Irradiated Polysaccharides ESR investigation of gamma irradiated pectin

Authors: Slave, RM; Grecu, MN; Grecu, VV

Published: 2018, 4TH INTERNATIONAL SCIENTIFIC CONFERENCE SEA-CONF 2018, 172, DOI: 10.1088/1755-1315/172/1/012003

Polysaccharides irradiation is usually used for their decontamination of fungi, pathogenic bacteria, toxigenic molds, parasitic organisms. ESR studies are performed just to evidence their irradiation. Therefore the accent is put on radical stability in time and ESR signal intensity dependence on irradiation dose. Less attention is given to radical nature and their dependence on plant nature. In this report a study of gamma irradiated pectin is given. Dose dependence of double integrated ESR signal is analyzed in terms of a recombination reaction during the radiation period. Radical stability dependence on water content is put in evidence.

1018. Enhanced photocurrent in GeSi NCs / TiO2 multilayers

Authors: Palade, C; Slav, A; Cojocaru, O; Teodorescu, VS; Lazanu, S; Stoica, T; Sultan, MT; Svavarsson, HG; Ciurea, ML

Published: 2018, , DOI:

1019. An X-ray photoelectron spectroscopy depth profile study on the InGeNi/(110) cleaved GaAs structure

Authors: Negrila, CC; Lazarescu, MF; Logofatu, C; Ghita, RV; Cotirlan, C

Published: AUG 1 2018, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 82, 66, DOI: 10.1016/j.mssp.2018.02.022

InGeNi ohmic contacts on n-type semi-insulating GaAs(110) cleaved surfaces were fabricated. Cleaving semiconductor single crystal ensures the obtaining of semiconductor surfaces almost ideal in terms of chemical purity and stoichiometry. The chemical depth profile of metallic layer was investigated and revealed through multiple alternating steps of Ar+ etchings and XPS (x-ray photoelectron spectroscopy) measurements. The metallic layers made of alloy of Ge, In and Ni (60 nm Ge, 60 nm In and 10 nm Ni), were obtained by thermal evaporation on cleaved surfaces in a high vacuum facility, followed by a thermal annealing at 430-450 degrees C for 5 min. Twelve etching sessions were required until the metal/semiconductor interface has been reached. A total of 14 etchings steps were performed during the experiment, a layer with a thickness of 140 nm being removed from the surface. The atomic concentrations of the constituent chemical elements were determined. In3d, In4d, Ga3d, Ga2p, As3d, As2p, Ni2p(3/2), Ge3d, O1s and C1s spectral lines were recorded and chemical bonds within the layer were analyzed from the fittings. The formation of InxGa1-xAs type compounds and of an intermediate semiconductor layer rich in Ge atoms at the interface was highlighted. X-ray detectors InGeNi/GaAs/Al and InGeNi/GaAs/Ti were fabricated with ohmic contacts based on this contacting scheme and Schottky interfaces prepared also by evaporation on cleaved edges. Electrical characteristics have been investigated and key diode parameters determined - ideality factor, Schottky barrier height, series resistance. Detection capabilities of these devices were studied in an x-rays flux, provided by a Co anode x-ray source.

1020. Annealing-Induced High Ordering and Coercivity in Novel L1(0) CoPt-Based Nanocomposite Magnets

Authors: Crisan, AD; Vasiliu, F; Mercioniu, I; Bartha, C; Enculescu, M; Crisan, O

Published: JUN 2018, METALS, 8, DOI: 10.3390/met8060466

A novel class of quaternary intermetallic alloys based on CoPt is investigated in view of their interesting magnetic properties induced by the presence of hard magnetic L1(0) phase. A Co48Pt28Ag6B18 alloy has been prepared by rapid solidification from the melt and subjected to various isothermal annealing procedures. The structure and magnetism of both as-cast and annealed samples as well as the phase evolution with temperature are investigated by means of thermal analysis, X-ray, and selected area electron diffraction, scanning and high-resolution electron microscopy, and magnetic measurements. The X-ray diffraction (XRD) analysis shows that both the as-cast alloy and the sample annealed at 400 degrees C (673 K) have a nanocrystalline structure where fcc CoPt phase predominates. Annealing at 473 degrees C promotes the formation of L1(0) phase triggered by the disorder-order phase transformation as documented in the differential scanning calorimetry results. The sample annealed at 670 degrees C (943 K) shows full formation of L1(0) CoPt as revealed by XRD. Magnetic measurements showed coercivity values ten times increased compared to the as-cast state. This confirms the full formation of L1(0) CoPt in the annealed samples. Moreover, detailed atomic resolution HREM images and SAED patterns show the occurrence of the rarely seen (003) superlattice peaks, which translated into a high ordering of the L1(0) CoPt superlattice. Such results spur more interest in finding novel classes of nanocomposite magnets based on L1(0) phase.

1021. Millimeter wave and Terahertz investigations on some dielectric materials

Authors: Banciu, MG; Furuya, T; Geambasu, DC; Nedelcu, L; Pantelica, D; Dracea, MD; Ionescu, P; Iuga, A; Chirila, C; Hrib, L; Trupina, L; Tani, M

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 290, DOI:

Investigations of barium strontium titanate (BST) layers deposited on MgO and Si substrates are presented. Since the Sr content determines the dielectric and optical properties of the BST layers at room temperature, accurate compositional analysis was performed by using Rutherford Backscattering technique at 3.041 Mev.

1022. Osteoblast Cell Response to Naturally Derived Calcium Phosphate-Based Materials

Authors: Mitran, V; Ion, R; Miculescu, F; Necula, MG; Mocanu, AC; Stan, GE; Antoniac, IV; Cimpean, A

Published: JUL 2018, MATERIALS, 11, DOI: 10.3390/ma11071097

The demand of calcium phosphate bioceramics for biomedical applications is constantly increasing. Efficient and cost-effective production can be achieved using naturally derived materials. In this work, calcium phosphate powders, obtained from dolomitic marble and Mytilus galloprovincialis seashells by a previously reported and improved Rathje method were used to fabricate microporous pellets through cold isostatic pressing followed by sintering at 1200 degrees C. The interaction of the developed materials with MC3T3-E1 pre-osteoblasts was explored in terms of cell adhesion, morphology, viability, proliferation, and differentiation to evaluate their potential for bone regeneration. Results showed appropriate cell adhesion and high viability without distinguishable differences in the morphological features. Likewise, the pre-osteoblast proliferation overtime on both naturally derived calcium phosphate materials showed a statistically significant increase comparable to that of commercial hydroxyapatite, used as reference material. Furthermore, evaluation of the intracellular alkaline phosphatase activity and collagen synthesis and deposition, used as markers of the osteogenic ability of these bioceramics, revealed that all samples promoted pre-osteoblast differentiation. However, a seashell-derived ceramic demonstrated a higher efficacy in inducing cell differentiation, almost equivalent to that of the commercial hydroxyapatite. Therefore, data obtained demonstrate that this naturally sourced calcium-phosphate material holds promise for applications in bone tissue regeneration.

1023. Versatile Actuators Based on Polypyrrole-Coated Metalized Eggshell Membranes

Authors: Beregoi, M; Preda, N; Evanghelidis, A; Costas, A; Enculescu, I

Published: AUG 2018, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 6, 10181, DOI: 10.1021/acssuschemeng.8b01489

Eggshell membranes were employed as biological scaffolds for developing soft and versatile actuators. A particular architecture, consisting of eggshell membrane coated with polypyrrole, has been fabricated and has been found to be a green, inexpensive, lightweight, and easy to handle class of actuators. The polypyrrole-coated eggshell membrane devices were tested in liquid, ambient atmosphere and controlled humidity environment, with the recorded movements proving their versatility. In 1 M NaCl aqueous solution, by applying successive potential pulses, the actuator contracts/expands owing to the expulsion/insertion of the electrolyte ions out/into polypyrrole film, producing a displacement of similar to 0.1 cm. In air, upon application of voltages from 2 to 5 V on a V-shaped geometry actuator, it bends due to water desorption from its structure induced by Joule heating, generating a displacement which reaches similar to 0.4 cm at 5 V. In a chamber with controlled humidity, the decrease of humidity stimulates a bending/curling motion of the actuator, achieving a displacement of similar to 2.1 cm at 50% relative humidity. Upon modification of the humidity, these actuators move, hold, and release delicate and lightweight objects. Such polypyrrole-coated eggshell membrane actuators which operate in different environments and respond to multiple stimuli can have potential applications in biomimetic micromanipulators or artificial muscle fields.

1024. Networked mesoporous SnO2 nanostructures templated by Brij (R) 35 with enhanced H2S selective performance

Authors: Stanoiu, A; Simion, CE; Sackmann, A; Baibarac, M; Florea, OG; Osiceanu, P; Teodorescu, VS; Somacescu, S

Published: NOV 1 2018, MICROPOROUS AND MESOPOROUS MATERIALS, 270, 101, DOI: 10.1016/j.micromeso.2018.05.008

Sensors based networked mesoporous SnO2 nanostructures templated by non-ionic surfactant - Brij (R) 35 were prepared via hydrothermal chemistry route. Specific patterns of the structure, morphology, surface chemistry and sensing properties were obtained by pH and autogenous pressure tuning. Consequently, the as-obtained SnO2 powders were subjected to extensive BET, Raman, TEM, HRTEM and XPS complementary investigations. The sensitive films were obtained by screen printing deposition of the powders onto commercial Al2O3 substrates. The gas sensing properties were assessed towards different hazardous gas species: CO, CH4, NH3, NO2, SO2 and H2S over a wide range of operating temperatures. Our particular SnO2 HP sensor synthesized at high autogenous pressure showed the highest selective-sensitivity to H2S (< 5 ppm) under 50% relative humidity (RH). The enhancement in the H2S sensitivity at low operating temperature under infield conditions was found to be closely connected to the morphological aspects and surface chemistry, peculiarities that can be assessed as consequences of the chemical tuning.

1025. Highly Efficient, Easily Recoverable, and Recyclable Re-SiO2-Fe3O4 Catalyst for the Fragmentation of Lignin

Authors: Tudorache, M; Opris, C; Cojocaru, B; Apostol, NG; Tirsoaga, A; Coman, SM; Parvulescu, VI; Duraki, B; Krumeich, F; van Bokhoven, JA

Published: AUG 2018, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 6, 9618, DOI: 10.1021/acssuschemeng.7b04294

A series of Fe3O4@SiO2@Re catalysts were prepared by deposition of rhenium by means of the precipitation-deposition and impregnation procedures. Characterization of the catalysts confirmed that the deposition of silica protected the magnetite nanoparticles, resulting in a stable SiO(2)pFe(3)O(4) composite, which was not affected by the treatments during the further deposition of rhenium. Rhenium was silent in XRD over the range of concentrations, at which it was deposited. Furthermore, XPS detected rhenium, only in the impregnation series; this may confirm that dispersion was high. As expected, rhenium was not reduced to the metallic state and generated weakly acidic Bronsted-type centers as detected by NH3-TPD. H-2-TPD and chemisorption experiments demonstrate the capacity of these catalysts to chemisorb hydrogen. In line with these properties, rhenium catalyzed both C-C hydrogenolysis and C-O hydrolysis in successive steps. The performance of these catalysts was checked for a series of lignins of different origin and by means of different separation procedures. A very important finding is that these catalysts were highly stable and easy to recover.

1026. Influence of Mn content on the catalytic properties of Cu(Mn)-Zn-Mg-Al mixed oxides derived from LDH precursors in the total oxidation of methane

Authors: Raciulete, M; Layrac, G; Papa, F; Negrila, C; Tichit, D; Marcu, IC

Published: MAY 15 2018, CATALYSIS TODAY, 306, 286, DOI: 10.1016/j.cattod.2017.01.013

Cu-(Mn)-Zn-Mg-Al mixed oxides with Cu/Zn atomic ratio of 1 and different Mn contents were synthesized by thermal decomposition of layered double hydroxides (LDHs) precursors. They were characterized using X-ray diffraction, textural measurements, EDX, TEM, H-2-TPR and XPS techniques, and their catalytic properties in the total oxidation of methane were evaluated. The precursors consisted in nitrate-interlayered multicationic LDH phase with additional Mn3O4 side phase for Mn-containing systems. Their thermal decomposition resulted in complex mixed oxides containing periclase-like, CuO and different spinel (Cu1.5Mn1.5O4, CuMn2O4, and MnAl2O4) phases. XPS analysis confirmed the existence of copper and manganese with different valence states in the Cu,Mn-containing mixed oxides. The catalytic activity expressed as the intrinsic rate of CH4 conversion increased by adding Mn to the CuZnMgAl mixed oxide calcined at 650 degrees C and by increasing its content. The intrinsic activity also strongly increased when the calcination temperature increased from 650 to 800 degrees C. The increased activity was correlated to enhanced catalyst reducibility due to the favorable Cu-Mn interaction. Among the different catalytic active phases, i.e. CuO, Cu1.5Mn1.5O4 and CuMn2O4, the Cu1.5Mn1.5O4 spinel seems to be the most active one. (C) 2017 Elsevier B.V. All rights reserved.

1027. Enhanced near-infrared response of a silicon solar cell by using an up-conversion phosphor film of Yb/Er - co-doped CeO2

Authors: Grigoroscuta, M; Secu, M; Trupina, L; Enculescu, M; Besleaga, C; Pintilie, I; Badica, P

Published: SEP 1 2018, SOLAR ENERGY, 171, 46, DOI: 10.1016/j.solener.2018.06.057

Co-doped CeO2 thin films were grown from a bulk target with starting composition Ce0.95Yb0.04Er0.01O2 by pulsed laser deposition (PLD) on a p(+)-n-n(+) single crystal silicon diode. The PLD laser fluence was varied between 1.7 J/cm(2) and 3.7 J/cm(2). The device with the film grown for a laser fluence of 2.3 J/cm(2) delivers the highest performance taking advantage of the up conversion (UC) effect provided by this film. Namely, the increase in the relative power conversion efficiency of the device is 12.1% and 39.2% for illumination under 1 and 2.1 sun, respectively, and its relative external quantum efficiency is 8.2% when illuminated with 980 nm light. The film grown for the optimum 2.3 J/cm(2) fluence shows good target-film composition transfer and a granular morphology with a low roughness. The UC mechanism consists of efficient energy transfer between spatially separated Yb3+ and Er3+ ions, i.e. the absorption of infrared light photons by the Yb3+ ions (F-2(7/2) -> F-2(5/2) transition) is followed by a two-step energy transfer process to neighboring Er3+ ions and by their characteristic luminescent emissions ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and (F-4(9/2) -> I-4(15/2)).

1028. Synthesis and Mechanical Properties of Polyurea-Based Hybrid Composites for Ballistic Individual Protection

Authors: Petre, R; Zecheru, T; Petrea, N; Ginghina, R; Sandu, S; Muresan, M; Matache, LC; Sava, AC; Neatu, F

Published: SEP 2018, MATERIALE PLASTICE, 55, 319, DOI:

During conflict situations, the combat staff is exposed to a wide variety of aggressions, such as temperature and pressure variations and dynamic impacts (from ammunition or fragments). Textiles used in the manufacture of the military uniforms and devices have always played an important role in defending the military against these hazards, and an adequate level of individual protection equipment is required. In this respect, novel fibre-reinforced polymer composite materials for military application, such as reducing blunt trauma for ballistic protection equipment, have been studied in terms of thermal and mechanical properties and ballistic protection, obtaining very good results.

1029. Development of Zinc-Doped Hydroxyapatite by Sol-Gel Method for Medical Applications

Authors: Negrila, CC; Predoi, MV; Iconaru, SL; Predoi, D

Published: NOV 2018, MOLECULES, 23, DOI: 10.3390/molecules23112986

Zinc- (Zn) doped hydroxyapatite (HAp) were prepared by sol-gel method. Zinc-doped hydroxyapatite (ZnHAp) and HAp were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Rietveld analysis revealed that the HAp and 7ZnHAp powders obtained by sol-gel method have a monophasic hydroxyapatite structure belonging to the P6(3/m) spatial group. The results obtained from the ultrasound characterization of HAp and ZnHAp are also presented in this study. The effect of zinc concentration on properties that were deduced from ultrasonic measurements are studied in the case of a significant zinc concentration (x(Zn) = 0.07). From the values of the ultrasonic waves velocities were determined by the pairs of elastic coefficients of the suspensions (Young modulus E, Poisson coefficient nu), which have proven to be similar to those determined by other authors.

1030. Material parameters from frequency dispersion simulation of floating gate memory with Ge nanocrystals in HfO2

Authors: Palade, C; Lepadatu, AM; Slav, A; Lazanu, S; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: JAN 15 2018, APPLIED SURFACE SCIENCE, 428, 702, DOI: 10.1016/j.apsusc.2017.09.038

Trilayer memory capacitors with Ge nanocrystals (NCs) floating gate in HfO2 were obtained by magnetron sputtering deposition on p-type Si substrate followed by rapid thermal annealing at relatively low temperature of 600 degrees C. The frequency dispersion of capacitance and resistance was measured in accumulation regime of Al/HfO2 gate oxide/Ge NCs in HfO2 floating gate/HfO2 tunnel oxide/SiOx/p-Si/Al memory capacitors. For simulation of the frequency dispersion a complex circuit model was used considering an equivalent parallel RC circuit for each layer of the trilayer structure. A series resistance due to metallic contacts and Si substrate was necessary to be included in the model. A very good fit to the experimental data was obtained and the parameters of each layer in the memory capacitor, i.e. capacitances and resistances were determined and in turn the intrinsic material parameters, i.e. dielectric constants and resistivities of layers were evaluated. The results are very important for the study and optimization of the hysteresis behaviour of floating gate memories based on NCs embedded in oxide. (C) 2017 Published by Elsevier B.V.

1031. Physical-chemical characterization and biological assessment of simple and lithium-doped biological-derived hydroxyapatite thin films for a new generation of metallic implants

Authors: Popescu, AC; Florian, PE; Stan, GE; Popescu-Pelin, G; Zgura, I; Enculescu, M; Oktar, FN; Trusca, R; Sima, LE; Roseanu, A; Duta, L

Published: MAY 1 2018, APPLIED SURFACE SCIENCE, 439, 735, DOI: 10.1016/j.apsusc.2018.01.008

We report on the synthesis by PLD of simple and lithium-doped biological-origin hydroxyapatite (HA) films. The role of doping reagents (Li2CO3, Li3PO4) on the morphology, structure, chemical composition, bonding strength and cytocompatibility of the films was investigated. SEM investigations of the films evidenced a surface morphology consisting of particles with mean diameters of (5-7) mu m. GIXRD analyses demonstrated that the synthesized structures consisted of HA phase only, with different degrees of crystallinity, mainly influenced by the doping reagent type. After only three days of immersion in simulated body fluid, FTIR spectra showed a remarkable growth of a biomimetic apatitic film, indicative of a high biomineralization capacity of the coatings. EDS analyses revealed a quasi-stoichiometric target-to-substrate transfer, the values inferred for the Ca/P ratio corresponding to a biological apatite. All synthesized structures displayed a hydrophilic behavior, suitable for attachment of osteoblast cells. In vitro cell viability tests showed that the presence of Li2CO3 and Li3PO4 as doping reagents promoted the hMSC growth on film surfaces. Taking into consideration these enhanced characteristics, corroborated with a low fabrication cost generated by sustainable resources, one should consider the lithium-doped biological-derived materials as promising prospective solutions for a next generation of coated implants with rapid osteointegration. (C) 2018 Elsevier B.V. All rights reserved.

1032. GeSi nanocrystals in SiO2 matrix with extended photoresponse in near infrared

Authors: Stavarache, I; Nedelcu, L; Teodorescu, VS; Maraloiu, VA; Dascalescu, I; Ciurea, ML

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 256, DOI:

The films of SiGe nanocrystals in SiO2 on Si substrate were obtained by co-sputtering Si, Ge, and SiO2 followed by rapid thermal annealing. The films structure and morphology together with electrical and photoelectrical properties were studied by x-ray diffraction, transmission electron microscopy, current - voltage and spectral photocurrent measurements. The photocurrent spectra at 300, 200 and 100 K were correlated with results obtained from X-ray diffractograms and transmission electron microscopy. The photocurrent spectra show an extension in near infrared due to the enriching SiGe nanocrystals in Ge.

1033. Hydroxyapatite coatings on Mg-Ca alloy prepared by Pulsed Laser Deposition: Properties and corrosion resistance in Simulated Body Fluid

Authors: Rau, JV; Antoniac, I; Filipescu, M; Cotrut, C; Fosca, M; Nistor, LC; Birjega, R; Dinescu, M

Published: OCT 1 2018, CERAMICS INTERNATIONAL, 44, 16687, DOI: 10.1016/j.ceramint.2018.06.095

Magnesium (Mg) alloys are very promising biocompatible materials for biodegradable biomedical implants, however, the main problem in using them is their fast degradation in the conditions of human body. In this work, we coated Mg-Ca (calcium) alloy substrate with hydroxyapatite (HA) to improve its resistance to corrosion and to control the in vitro degradation. Pulsed Laser Deposition technique was applied to deposit HA coatings. Their properties were investigated by X-ray diffraction, atomic force microscopy, scanning electron microscopy, high resolution transmission electron microscopy, Vickers microhardness, and Tafel plot electrochemical technique. The substrate temperature was ranged in the interval from room up to 400 degrees C. According to the obtained results, the recommended substrate temperatures are 200-300 degrees C, since higher ones lead to the HA decomposition. Furthermore, the HA films deposited at 200 and 300 degrees C show good corrosion resistance in Simulated Body Fluid. The obtained coatings are promising for a perspective use in biomedical implant applications.

1034. Production and Structural Characterization of Some Magnesium Matrix Composites Reinforced with Amorphous/Nanocrystalline NiTi Particulates

Authors: Ciurdas, M; Necsulescu, DA; Pantilimon, CM; Ion, V; Galatanu, M; Ruiu, G; Dumitrescu, RE

Published: DEC 2018, REVISTA DE CHIMIE, 69, 3507, DOI:

Two mixtures of elemental nickel and titanium powders in atomic proportions of 50% Ni + 50% Ti and 32% Ni + 68% Ti, respectively, were ground for 40 hours in a high energy planetary mill. In the case of the first mixture, the mechanical alloying was totally produced, while for the second, the alloying was partial. In both mixtures, qualitative X-ray diffraction phase analysis revealed the presence of metastable phases, such as Ni HC and NiTi- R-phase. Also, the equiatomic mixture is characterized by a partially amorphous structure. 10% of each type of mixture submitted to milling was used as reinforcing element in the form of particulates for two magnesium matrix composites. They were obtained by sintering in the plasma at 590 degrees C. In the case of the reinforced with the second mixture composite, the production of new phases other than the matrix and those present in the mixture of nickel and titanium powders after milling were recorded. The electron microscopy images of the two composites have resistant, free of micropores or microcracks matrix / particulates interfaces. The Mg-10% (32 at% Ni + 68 at% Ti) composite is characterized by Vickers hardness higher than that of the composite reinforced with the equiatomic mixture.

1035. The Cu- and Zn-complex-catalyzed methanolysis of the chemical warfare nerve agents soman, sarin, and VX

Authors: Petrea, N; Petre, R; Pretorian, A; Toader, C; Somoghi, V; Neatu, F; Florea, M; Neatu, S

Published: MAR-APR 2018, COMPTES RENDUS CHIMIE, 21, 345, DOI: 10.1016/j.crci.2017.08.006

The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

1036. Photocatalytic activity of wool fabrics deposited at low temperature with ZnO or TiO2 nanoparticles: Methylene blue degradation as a test reaction

Authors: Frunza, L; Diamandescu, L; Zgura, I; Frunza, S; Ganea, CP; Negrila, CC; Enculescu, M; Birzu, M

Published: MAY 15 2018, CATALYSIS TODAY, 306, 259, DOI: 10.1016/j.cattod.2017.02.044

Different amounts of TiO2 and ZnO particles were deposited upon wool fabrics, which are among the less studied textiles. The materials were get from industry or were home made. Model samples for these oxide deposition and properties were also considered. Either sputtering or chemical sol-gel/electro less technique was respectively applied. The coated samples were then characterized structurally and morphologically, by XRD, SEM and XPS and were checked for photocatalytic properties. Both UV and vis light beams were used for irradiation. The photocatalytic experiments were performed by photodegradation of methylene blue in the PCC2 checker apparatus. The fabrics were firstly impregnated with the dye solution and then dried: self cleaning of the wool fabric samples took in fact place. Reflectance data in the visible spectral range of highest absorption band served for direct analysis of MB degradation. The photocatalytic properties of the coated fabrics increased much in comparison with the raw materials. The photocatalytic decolorization of methylene blue follows up a simple apparently first order kinetic equation in many studied cases. Thus it was demonstrated that MB decolorization can serve as a test reaction at least for self cleaning of fabrics. (C) 2017 Elsevier B.V. All rights reserved.

1037. OPTICAL COATINGS FOR ELI EXPERIMENTS PREPARED BY LASER ABLATION

Authors: Bercea, A; Filipescu, M; Moldovan, A; Brajnicov, S; Colceag, D; Ion, V; Nistor, LC; Zorila, A; Dinescu, M

Published: 2018, ROMANIAN JOURNAL OF PHYSICS, 63, DOI:

Dielectric materials (HfO2, A1(2)O(3), SiO2 and Ta2O5) processed as thin films have been studied extensively for applications in microelectronics, biology, medicine, etc. In the last decade, antireflection coatings based on these types of materials have received considerable attention for applications in the field of high power laser optics. In this paper we report on multi-layers from materials with low and high refractive indices deposited on quartz substrates by laser ablation. Damage tests performed with a Ti-Sapphire laser (775 nm wavelength, 220 fs pulse duration) evidenced higher threshold values for hafnia based heterostructures than for the others heterostructures.

1038. Spectroscopic Characterisation of Multiferroic Interfaces

Authors: Husanu, MA; Vaz, CAF

Published: 2018, SPECTROSCOPY OF COMPLEX OXIDE INTERFACES: PHOTOEMISSION AND RELATED SPECTROSCOPIES, 266, 281, DOI: 10.1007/978-3-319-74989-1_10

In this chapter we discuss the capabilities of X-ray photoemission and absorption spectroscopies for the investigation of the electronic, magnetic and electric properties of multiferroic materials and heterostructures. As complementary techniques providing element selective information on both occupied and empty states, their combination delivers a comprehensive picture of the chemical state of individual species, magnetic moments, bulk and surface band structure, and local atomic environment at the interface between dissimilar materials. By directly probing the electronic structure at the atomic level, unique insights can be learned about the mechanisms responsible for the magnetoelectric couplings in this fascinating class of materials.

1039. Exploiting surface plasmon resonance in Au/ZnO photocatalysts for the selective oxidation of phenols

Authors: Lin, F; Cojocaru, B; Colaciello, LW; Cadigan, C; Tian, CX; Grecu, M; Xin, HL; Vyas, S; Parvulescu, V; Richards, R

Published: MAR 18 2018, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 255, DOI:

1040. Influence of Gd and Pr doping on the properties of ceria: texture, structure, redox behaviour and reactivity in CH4/H2O reactions in the presence of H2S

Authors: Florea, M; Postole, G; Matei-Rutkovska, F; Urda, A; Neatu, F; Massin, L; Gelin, P

Published: MAR 7 2018, CATALYSIS SCIENCE & TECHNOLOGY, 8, 1348, DOI: 10.1039/c7cy02192e

Ceria materials doped by Gd and/or Pr were prepared by a precipitation route and calcined in air at 500 and 900 degrees C. The effects of doping and thermal treatment on the materials' surfaces were studied by X-ray photoelectron and Raman spectroscopies. The redox properties were investigated using temperature-programmed reduction experiments in H-2 and CH4 followed by temperature-programmed oxidation in O-2. The catalytic properties of these materials in CH4/H2O reaction in the absence/presence of H2S were evaluated at 750 degrees C in a large excess of CH4 with respect to H2O. The materials were classified by order of reactivity as follows: CPO > CGPO > CeO2 > CGO, which can be primarily related to the surface area variation. Comparing the activity per m(2) of various samples indicates that the catalytic activity is correlated with the Ce3+ concentration at the surface as measured by XPS. Gd-doped and undoped samples exhibit the highest surface Ce3+ concentration as well as the highest activity in SMR per m(2), while Pr-doped samples are the least active (activity per m(2)) with the lowest surface Ce3+ concentrations. H2S has a sharp promoting effect on the catalytic behavior of ceria-based materials, improving the production of H-2 by almost one order of magnitude.

1041. ZnHAp Thin Films for Medical Applications

Authors: Iconaru, SL; Groza, A; Chapon, P; Gaianschi, S; Petre, CC; Jiga, G; Beuran, M; Prodan, AM; Lupescu, O; Trusca, R; Predoi, D

Published: 2018, 9TH INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1981, DOI: 10.1063/1.5045984

The research regarding the properties of thin films of hydroxyapatite doped with various ions such as zinc elaborated by spin-coating technique have rarely been fabricated and studies in recent years. In the present study Zn doped hydroxyapatite (ZrHAp) synthesized by a sol-gel method were coated on Ti substrates using a spin-coating technique. The thin films was characterized by Scanning Electron Microscopy (SEM) and Glow Discharge Optical Emission Spectroscopy (GDOES). The structural characterizations of ZnHAp thin films showed the presence of Zn and apatitic structure. The GD depth profiles revealed the successful embedding of the Zn ions in HAp structure. In addition, in vitro evaluation of the antifungal properties of ZnHAp demonstrated the potential antifungal effect of ZnHAp thin films against Staphylococcus aureus 0364 biofilm.

1042. Heavy doping of ceria by wet impregnation: a viable alternative to bulk doping approaches

Authors: Florea, M; Avram, D; Maraloiu, VA; Cojocaru, B; Tiseanu, C

Published: OCT 7 2018, NANOSCALE, 10, 18054, DOI: 10.1039/c8nr03695k

To avoid the deleterious effects of dopant segregation, synthesis methods that facilitate a homogenous dopant distribution in the ceria lattice were employed. Though doping ceria by wet impregnation was also credited to induce a homogeneous solid solution even in the heavy regime (concentration >= 20%, A. Corma, P. Atienzar, H. Garcia and J. Chane-Ching, Nat. Mater., 2004, 3, 394-397), no follow up investigation has been reported. Herein, we investigated ceria nanoparticles (1% Tm-CeO2 and 1% Eu-CeO2) wetimpregnated with trivalent rare-earth (Yb, 20%), bivalent (Ca, 20%) and isovalent (Zr, 30%) metals, followed by annealing in air. Homogeneity of the solid solutions of Yb-impregnated ceria was confirmed by a two-feature characterization toolbox that included X-ray diffraction, Raman spectroscopy, transmission electron microscopy, as well as up-conversion emission as a probe tool. Since the up-conversion emission of Tm was not detectable in the absence of Yb while its efficiency depends on the average distance between Yb and Tm ions, the Yb incorporation and its migration from the surface to the lattice bulk sites in wet-impregnated ceria can be "visualized" and compared with that of the Yb bulk-doped counterpart. The use of Eu luminescence as a local probe confirmed the homogeneity of solid solutions of Ca and Zr-impregnated ceria and also sustained the opposite roles of Ca and Zr as the repeller and the scavenger of oxygen vacancies, respectively. All these results suggested that heavy doping of ceria by wet impregnation with metals with +2, +3 and +4 valencies represent a facile alternative to conventional doping approaches. Therefore, the effects of the amount and the type of metal dopant on the structural properties of CeO2 could be investigated in a more systematic and probably a more reproducible manner, which would significantly increase the potential of ceria in catalysis and other applications.

1043. Photoanode for solar water oxidation based on titania and hematite films

Authors: Sima, M; Vasile, E; Sima, A

Published: JUL 31 2018, THIN SOLID FILMS, 658, 11, DOI: 10.1016/j.tsf.2018.05.019

Nanostructured hematite (alpha-Fe2O3) film deposited on mesoporous titania (TiO2) underlayer was described as a photoanode for photoelectrochemical water splitting. Mesoporous TiO2 layers were prepared by spin coating a paste on conductive fluorine-doped tin oxide glass followed by an annealing process. Hematite film was prepared after electrochemical and annealing processes. The TiO2/Fe2O3 photoanodes achieve photocurrent densities up to 0.5 mA/cm(2) at 1.23 V versus reversible hydrogen electrode. This value is greater than that for photocurrent density obtained with pristine hematite photoanode. Impedance measurements showed that prepared heterostructure TiO2/Fe2O3 contributes to diminution of electron-hole recombination process.

1044. Dwell Time Influence on Spark Plasma-Sintered MgB2

Authors: Aldica, G; Popa, S; Enculescu, M; Pasuk, I; Ionescu, AM; Badica, P

Published: FEB 2018, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 31, 325, DOI: 10.1007/s10948-017-4236-9

Samples of MgB2 with relative density above 95% were obtained by spark plasma sintering (SPS) at 1150 A degrees C for a heating time of 100 A degrees C/min and a maximum pressure of 95 MPa. Dwell time was of 1, 4, 7, 10, and 20 min. Samples show that dwell time has a low influence on superconducting characteristics. However, small differences were observed and they are discussed from the viewpoint of density, structural, microstructural, critical current density, irreversibility field, and pinning type. The dominant contribution for all investigated samples is given by point and delta T (c) pinning.

1045. Bismuth and lead oxides codoped boron phosphate glasses for Faraday rotators

Authors: Sava, BA; Boroica, L; Elisa, M; Shikimaka, O; Grabco, D; Popa, M; Barbos, Z; Iordanescu, R; Niculescu, AM; Kuncser, V; Galca, AC; Eftimie, M; Monteiro, RCC

Published: APR 15 2018, CERAMICS INTERNATIONAL, 44, 6025, DOI: 10.1016/j.ceramint.2017.12.205

New magneto-optical vitreous materials were obtained by melting-quenching technique comprising wet route raw materials preparation. The glass has the following composition in oxide mol. % 10 Li2O, 9 Al2O3, 5 ZnO, (35; 20; 50) B2O3,,(35; 50; 20) P2O5, 3 Bi2O3, 3 PbO, phosphorus and boron oxide being the vitreous network formers. It was also prepared a similar reference glass composition but without Bi2O3 and PbO. Optical and structural characterization by ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FTIR) and Raman Spectroscopy of the bulk glasses showed a transmission over 90%, metaphosphate structure of glass together with Q(2) boron oxide units and P-O-B bonds. The mechanical parameters, hardness (H), Youngs modulus (E) and fracture toughness (KO of boron phosphate glasses, evaluated by micro- and nanoindentation techniques, demonstrated mostly higher values in comparison with those for alumino-phosphate glasses due to mixed borophosphate network. Thermal behavior was investigated by Differential Scanning Calorimetry (DSC) putting in evidence the vitreous transition temperature which decreases with about 45 degrees C when Bi and Pb oxides were added and two crystallization effects. The diamagnetic character of a highly transparent Bi and Pb oxide co doped boron phosphate glass was confirmed by ellipsometry, and the glass presented high magneto-optical properties at the top of the commercial bulk products.

1046. Crystal growth and structural characterization of Sm3+, Pr3+ and Dy3+ - doped CNGG and CLNGG single crystals

Authors: Gheorghe, L; Greculeasa, M; Voicu, F; Gheorghe, C; Hau, S; Vlaicu, AM; Belikov, KN; Bryleva, EY; Gaiduk, OV

Published: OCT 2018, OPTICAL MATERIALS, 84, 338, DOI: 10.1016/j.optmat.2018.07.029

Sm3+, Pr3+ and Dy3+-doped Ca3Nb1.6875Ga3.1875O12 - CNGG and Ca3Li0.275Nb1.775Ga2.95O12 - CLNGG crystals are of interest as solid-state laser materials emitting in the yellow-orange spectral range, especially for diode pumping due to their partially disordered nature. In this work, for the first time to our knowledge, single crystals of Sm, Pr and Dy-doped CNGG and CLNGG crystals were grown by the Czochralski method. For the doping of CNGG and CLNGG crystals, five new stoichiometric garnets were synthesised by solid-state reaction method: praseodymium-gallium-garnet (PrGG), dysprosium-gallium-garnet (DyGG) and praseodymium-lithium-niobium gallium-garnet (PrLNGG), samarium-lithium-niobium-gallium-garnet (SmLNGG), and dysprosium-lithium-niobium-gallium-garnet (DyLNGG). Samarium-gallium-garnet (SmGG) was also sintered and used for the doping of Sm:CNGG crystal. Structural properties of sintered materials and grown crystals were investigated by X-ray diffraction and the chemical compositions of the grown crystals were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) method. The spectroscopic investigations of the grown crystals have shown that they are promising laser materials in the yellow-orange spectral range.

1047. Defect states and room temperature ferromagnetism in cerium oxide nanopowders prepared by decomposition of Ce-propionate

Authors: Mihalache, V; Secu, M; Grivel, JC

Published: APR 15 2018, MATERIALS CHEMISTRY AND PHYSICS, 209, 133, DOI: 10.1016/j.matchemphys.2018.01.053

Four batches of cerium oxide powders (with nanocrystallite size of 6.9 nm-572 nm) were prepared from four precursor nanopowders by thermal decomposition of Ce-propionate and annealing in air between 250 degrees C-1200 degrees C for 10 min-240 min. Ceria formation reactions, structure, vibrational, luminescence and magnetic properties were investigated by differential scanning calorimetry, x-ray diffraction, electron microscopy, infrared spectroscopy, photoluminescence and SQUID. All the samples exhibit room temperature ferromagnetism, RTFM, (with coercivity, H-c, of 8 Oe - 121 Oe and saturation magnetization, M-s, of up to 6.7*10(-3) emu/g) and a broad defect-related photoluminescence, PL, emission in the visible range. The samples derived from the same precursor show M-s proportional to the peak area of defect-related PL emission whereas this is not valid for the samples derived from the different precursors. An improvement of ferromagnetism and intensity of defect-related PL emission was observed when annealing the products in which nanocrystalline cerium oxide coexists with Ce - oxicarbonate traces, Ce2O2CO3. The experimental results were explained based on the following considerations: room temperature ferromagnetism was induced by the defective ceria with high concentration of oxygen vacancies generated by decomposition of Ce-propionate; oxygen vacancies of the starting precursor nanopowders could be redistributed (at the surfaces/grain boundaries, GBs) upon heating under conditions that promote an inert local environment; the decomposition of Ce2O2CO3 residues can provide an excess of oxygen vacancies at the nanoparticles surfaces or GBs, which can induce or enhance ferromagnetism; surfaces/GBs rather than bulk defects appear responsible for RTFM - this can explain the (often reported in literature) inconsistency between oxygen vacancies concentration and M-s. (C) 2018 Elsevier B.V. All rights reserved.

1048. Optoelectric charging-discharging of Ge nanocrystals in floating gate memory

Authors: Palade, C; Slav, A; Lepadatu, AM; Maraloiu, AV; Dascalescu, I; Iftimie, S; Lazanu, S; Ciurea, ML; Stoica, T

Published: NOV 19 2018, APPLIED PHYSICS LETTERS, 113, DOI: 10.1063/1.5039554

Photo-induced effects on charging and discharging of nanocrystals (NCs) in capacitor memories with Ge NCs in an HfO2 matrix as a floating gate layer are studied. The sequence of layers HfO2/Ge-HfO2/ HfO2 was deposited on a p-Si substrate using magnetron sputtering. Well separated Ge NCs are obtained after rapid thermal annealing at 600 degrees C. The optoelectric capacitor memories were fabricated with a semi-transparent electrode on top of the structure and an Al electrode on the back side of the Si substrate. Light illumination effects on hysteresis curves were investigated using different operation modes. The hysteresis window increases by increasing the light exposure time. The spectral dependence of the hysteresis window shows the maximum contribution of the light in the wavelength range of 950-1000 nm, corresponding to both contributions from the Si substrate and from Ge NCs. The stored information about the electrical and optical pulses is also investigated in the regime of the flat band potential measurements (retention measurements). It is shown that in our memory structure, the photo-effect on the memory retention corresponds to a tunnelling transfer of negative charges from the Si substrate to Ge NCs, up to a mean value of 1.6 electrons per NC. Published by AIP Publishing.

1049. Effect of mixing complexing agents on the properties of electrodeposited CZTS thin films

Authors: Zaki, MY; Nouneh, K; Touhami, ME; Belakhmima, RA; Galca, AC; Pintilie, L; Enculescu, M; Baibarac, M; Taibi, M

Published: SEP 2018, OPTICAL MATERIALS, 83, 256, DOI: 10.1016/j.optmat.2018.06.030

This work involves the synthesis and characterization of Cu2ZnSnS4 (CZTS) layers. The films were prepared on ITO/glass substrate by ecofriendly and simple single-step electrodeposition method followed by sulfurization and annealing at 500 degrees C under Argon flow. By using two different complexing agents, the electrodeposition process can give better results. Therefore, the effect of combining the trisodium citrate - TC to multiple cornplexing agents (cetyl trimethyl ammonium bromide - CTAB, ethylene diamine tetra acetic acid - EDTA, Boric Acid - BA, Glutamic Acid - GA and Tartaric Acid - TA) is investigated. The characterization of the absorber films was done by X-ray diffraction (XRD) analysis, Raman spectroscopy, Scanning Electron Microscopy and Diffuse Reflectivity. The combination of TC and CTAB is suggested to be the best pair of complexing agents within the combinations used in this work.

1050. Limits and Particularities of the Synthesis of Ba1-xCaxTiO3 for Piezoelectric Applications, by Topochemical Conversion from Molten Salt Solutions

Authors: Vlaicu, ID; Maraloiu, AV; Ghica, D; Mercioniu, IF; Stefan, M; Vlaicu, AM; Negrea, RF; Kuncser, AC; Bulat, S; Krzmanc, MM; Ciobanu, R; Plopa, O

Published: 2018, 2018 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE), 1050, DOI:

Because of the unique properties of the ferroelectric perovskite particles with a well-defined anisotropic form like shape-and size dependent at low dimensions they have all the attention of the scientific world. Extensive morphostructural techniques will be used to characterize the piezoelectric material.

1051. Probing the dielectric, piezoelectric and magnetic behavior of CoFe2O4/BNT-BT0.08 composite thin film fabricated by sol-gel and spin-coating methods

Authors: Cernea, M; Vasile, BS; Surdu, VA; Trusca, R; Bartha, C; Craciun, F; Galassi, C

Published: DEC 14 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-36232-3

We investigated in this paper a novel bilayer composite obtained by sol-gel and spin coating of the ferroelectric 0.92Na(0.5)Bi(0.5)TiO(3)-0.08BaTiO(3) (abbreviated as BNT-BT0.08) and ferromagnetic CoFe2O4 phases, for miniature low-frequency magnetic sensors and piezoelectric sensors. This heterostructure, deposited on Si-Pt substrate (Si-Pt/CoFe2O4/BNT-BT0.08), was characterized using selected method such as: X-ray diffraction, dielectric spectroscopy, piezoelectric force microscopy, SQUID magnetometry, atomic force microscopy/magnetic force microscopy, and advanced methods of transmission electron microscopy. CoFe2O4/BNT-BT0.08 ferromagnetic-piezoelectric thin films show good magnetization, dielectric constant and piezoelectric response. The results of analyses and measurements reveal that this heterostructure can have applications in high-performance magnetoelectric devices at room temperature.

1052. Impact of thickness variation on structural, dielectric and piezoelectric properties of (Ba, Ca) (Ti, Zr)O-3 epitaxial thin films

Authors: Ion, V; Craciun, F; Scarisoreanu, ND; Moldovan, A; Andrei, A; Birjega, R; Ghica, C; Di Pietrantonio, F; Cannata, D; Benetti, M; Dinescu, M

Published: FEB 1 2018, SCIENTIFIC REPORTS, 8, DOI: 10.1038/s41598-018-20149-y

It is shown that the dielectric and piezoelectric properties of Ba(Ti0.8Zr0.2)O-3-x(Ba0.7Ca0.3)TiO3 (x = 0.45) (BCTZ 45) epitaxial thin films have a nontrivial dependence on film thickness. BCTZ 45 epitaxial films with different thicknesses (up to 400 nm) have been deposited on SrTiO3 by pulsed laser deposition and investigated by different combined techniques: conventional and off-axis X-ray diffraction, high resolution transmission electron microscopy and dielectric and piezoforce microscopy. The changes occurring in epitaxial films when their thickness increases have been attributed to a partial relaxation of misfit strain, driving the induced tetragonal symmetry in very thin films to the original rhombohedral symmetry of the bulk material in the thickest film, which influences directly and indirectly the dielectric and piezoelectric properties.

1053. Irradiation of nuclear materials with laser-plasma filaments produced in air and deuterium by terrawatt (TW) laser pulses

Authors: Avotina, L; Lungu, M; Dinca, P; Butoi, B; Cojocaru, G; Ungureanu, R; Marcu, A; Luculescu, C; Hapenciuc, C; Ganea, PC; Petjukevics, A; Lungu, CP; Kizane, G; Ticos, CM; Antohe, S

Published: JAN 17 2018, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 51, DOI: 10.1088/1361-6463/aa9b0f

Be-C-W mixed materials with variable atomic ratios were exposed to high power (TW) laser induced filamentation plasma in air in normal conditions and in deuterium at a reduced pressure of 20 Torr. Morphological and structural investigations were performed on the irradiated zones for both ambient conditions. The presence of low-pressure deuterium increased the overall ablation rate for all samples. From the elemental concentration point of view, the increase of the carbon percentage has led to an increase in the ablation rate. An increase of the tungsten percentage had the opposite effect. From structural spectroscopic investigations using XPS, Raman and FT-IR of the irradiated and non-irradiated sample surfaces, we conclude that deuterium-induced enhancement of the ablation process could be explained by preferential amorphous carbon removal, possibly by forming deuterated hydrocarbons which further evaporated, weakening the layer structure.

1054. Orbital Ordering of the Mobile and Localized Electrons at Oxygen-Deficient LaAlO3/SrTiO3 If Interfaces

Authors: Chikina, A; Lechermann, F; Husanu, MA; Caputo, M; Cancellieri, C; Wang, XQ; Schmitt, T; Radovic, M; Strocov, VN

Published: AUG 2018, ACS NANO, 12, 7935, DOI: 10.1021/acsnano.8b02335

Interfacing different transition-metal oxides opens a route to functionalizing their rich interplay of electron, spin, orbital, and lattice degrees of freedom for electronic and spintronic devices. Electronic and magnetic properties of SrTiO3-based interfaces hosting a mobile two-dimensional electron system (2DES) are strongly influenced by oxygen vacancies, which form an electronic dichotomy, where strongly correlated localized electrons in the in-gap states (IGSs) coexist with noncorrelated delocalized 2DES. Here, we use resonant soft-X-ray photoelectron spectroscopy to prove the e(g) character of the IGSs, as opposed to the t(2g) character of the 2DES in the paradigmatic LaAlO3/SrTiO3 interface. We furthermore separate the d(xy) and d(xz)/d(xz) orbital contributions based on deeper consideration of the resonant photoexcitation process in terms of orbital and momentum selectivity. Supported by a self-consistent combination of density functional theory and dynamical mean field theory calculations, this experiment identifies local orbital reconstruction that goes beyond the conventional e(g)-vs-t(2g) band ordering. A hallmark of oxygen-deficient LaAlO3/SrTiO3 is a significant hybridization of the e(g) and t(2g) orbitals. Our findings provide routes for tuning the electronic and magnetic properties of oxide interfaces through "defect engineering" with oxygen vacancies.

1055. The effect of H-2/Ar plasma treatment over photoconductivity of SiGe nanoparticles sandwiched between silicon oxide matrix

Authors: Sultan, MT; Gudmundsson, JT; Manolescu, A; Ciurea, ML; Svavarsson, HG

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 260, DOI:

The effect of room temperature hydrogen plasma treatment on the photoconductive properties of the SiO2 matrix containing SiGe nanoparticles is investigated. A considerable increase in photocurrent intensity is observed after plasma treatment. The increase is partly attributed to neutralization of dangling bonds around the nanoparticles and partly to passivation of non-radiative centers and defects in the matrix and at the nanoparticles-matrix interfaces.

1056. Electric and magnetic properties of ferromagnetic/piezoelectric bilayered composite

Authors: Cernea, M; Vasile, BS; Surdu, VA; Trusca, R; Bartha, C; Craciun, F; Galassi, C

Published: OCT 2018, JOURNAL OF MATERIALS SCIENCE, 53, 14171, DOI: 10.1007/s10853-018-2673-x

One of the most promising ways for the realization of multi-functional materials is the integration of oxides with different properties in artificial heterostructures. In this paper, a novel piezoelectric-ferromagnetic heterostructure consisting of 0.92Na(0.5)Bi(0.5)TiO(3)-0.08BaTiO(3) (abbreviated as BNT-BT0.08) and CoFe2O4 layers is fabricated on Si-Pt substrate, by sol-gel method coupled with spin-coating technique. The composite thin film shows only perovskite Bi0.5Na0.5TiO3-like rhombohedral phase and CoFe2O4 cubic phase. The thickness of CoFe2O4 and BNT-BT0.08 layers is similar to 280 and similar to 400 nm, respectively. BNT-BT0.08/CoFe2O4 heterostructure thin film shows a saturation magnetization of 0.11 emu/g at 5 K and 0.07 emu/g at 295 K, dielectric constant of 235 at 1 kHz and tunability of 70% at 1 kHz and an electric field E = 110 kV/cm. The results reveal that the investigated hybrid piezoelectric/ferromagnetic structure shows piezoelectric behavior, good ferroelectric and ferromagnetic properties. This bilayer composite can be used in miniature low-frequency magnetic sensor and piezoelectric sensor for biomedical domain.

1057. Investigation of sol-gel derived BaCl2:Eu2+ luminescent nanophosphor and the corresponding PVP@BaCl2:Eu2+ polymer nanocomposite

Authors: Secu, CE; Negrila, C; Secu, M

Published: AUG 1 2018, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 51, DOI: 10.1088/1361-6463/aace7c

We have prepared Eu2+ (1%) doped BaCl2 nanopowders by using a hybrid sol-gel/thermal decomposition route using barium acetate and trichloracetic acid as in situ chlorination agent. Structural and thermal analysis data have shown that orthorhombic BaCl2 phase crystallization occurs at 260 degrees C. BaCl2:Eu2+ nanocrystals of about 100-200 nm in size were produced after annealing (in air) at 500 degrees C and they displayed Eu2+ d -> f type luminescence at 396 nm. X-ray photoelectron spectroscopy indicated the presence of both Eu2+, Eu3+ ions species and a BaO passivating layer at the surface of the nanocrystals. A polymer nanocomposite (PVP@BaCl2:Eu2+) was also processed and its optical response under x-ray irradiation was found to be similar to that of the nanopowder. X-ray excited luminescence showed Eu2+ luminescence at 396 nm, whereas the thermoluminescence peak at 130 degrees C was assigned to the F(Cl)-center recombination with Eu2+ related hole centers.

1058. Lincomycin-embedded PANI-based coatings for biomedical applications

Authors: Popescu-Pelin, G; Fufa, O; Popescu, RC; Savu, D; Socol, M; Zgura, I; Holban, AM; Vasile, BS; Grumezescu, V; Socol, G

Published: OCT 15 2018, APPLIED SURFACE SCIENCE, 455, 666, DOI: 10.1016/j.apsusc.2018.06.016

We report on the successful laser transfer of biocompatible composite coatings based on polyaniline (PANI) embedded with magnetite (PANI-Fe3O4) and Lincomycin hydrochloride (PANI-Lincomycin) or Lincomycin-functionalized magnetite (PANI-Fe3O4@Lincomycin) by matrix assisted pulsed laser evaporation (MAPLE) technique. The physico-chemical investigations revealed relevant data regarding the stoichiometric deposition, morphology and topography of the as-deposited coatings. Regarding the MAPLE coatings, the FTIR studies evidenced the vibrational bands characteristic to pristine PANI material, while the SEM investigations unveiled a preferential particulate morphology (with aggregates shape and size depending on the deposited material). Additionally, the AFM measurements indicated variations of RMS value, following the Lincomycin and magnetite incorporation. The wettability measurements displayed a hydrophilic behavior of the synthesized coatings, while the electrochemical studies emphasized an enhanced resistance against corrosion in simulated body fluid when compared with bare Ti. Cellular viability, immunofluorescence and SEM results proved that the MAPLE coatings were suitable materials for beneficial adhesion, spreading and proliferation of osteoblast-like cells (MG-63). Moreover, an increased efficiency was evidenced against Staphylococcus aureus biofilm development. The multifunctional properties of the laser processed composite coatings - confirmed by cumulative biocompatible, antimicrobial and anticorrosive behaviors - recommend them as promising solutions for biomedical applications.

1059. Compressive properties of pristine and SiC-Te-added MgB2 powders, green compacts and spark-plasma-sintered bulks

Authors: Badica, P; Batalu, D; Burdusel, M; Grigoroscuta, MA; Aldica, GV; Enculescu, M; Gabor, RA; Wang, ZY; Huang, RX; Li, PF

Published: JUN 15 2018, CERAMICS INTERNATIONAL, 44, 10191, DOI: 10.1016/j.ceramint.2018.03.008

Pristine and (SiC + Te)-added MgB2 powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC + Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB2 show very similar compressive parameters (tan delta, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static K-IC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB2 blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data.

1060. Martensitic transformation and related properties of Fe69.4Pd30.6 ferromagnetic shape memory ribbons

Authors: Tolea, F; Sofronie, M

Published: NOV-DEC 2018, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 20, 706, DOI:

Ferromagnetic shape memory alloys (FSMA) have attained strong interest over the last years and Fe-Pd alloys seems to be more suited for engineering and medical applications, due to their improved ductility and biocompatibility compared to the well-known Ni2MnGa alloy. The shape memory effect in disordered Fe-Pd (30 at.% Pd) is associated with FCC-FCT thermoelastic martensitic transformation. The melt-spinning technique enables to get ribbons with the FCC meta-stable structure preventing the precipitation of undesirable BCT irreversible phase and subsequent proper thermal treatments could improve the characteristic parameters of the martensitic transformation. The present work reports the effect of the rapid solidification (via melt-spinning technique) and the different thermal treatments on the microstructure, martensitic transformation and magnetic properties of the Fe69.4Pd30.6 ribbons. The samples were investigated by calorimetry, X-ray diffractometry, scanning electron microscopy and magnetometry. Two different structures induced by the distinct thermal treatments and responsible for the characteristic behavior of the martensitic transformation, were noticed and discussed in details. The high temperature treatment for short time stabilized the FCC phase and slightly decrease the martensitic transformation temperature, while the annealing at low temperature for longer time promotes the reduction of the amount of transforming FCC phase by its partial decomposition in the stable phases, causing the fall of the heat of transformation.

1061. Wide-Range Columnar and Lamellar Photoluminescent Liquid-Crystalline Lanthanide Complexes with Mesogenic 4-Pyridone Derivatives

Authors: Chiriac, LF; Pasuk, I; Secu, M; Micutz, M; Circu, V

Published: SEP 12 2018, CHEMISTRY-A EUROPEAN JOURNAL, 24, 13522, DOI: 10.1002/chem.201801781

A series of liquid crystals with various lanthanide ions (Eu-III, Sm-III, and Tb-III) was designed and prepared starting from the corresponding lanthanide nitrates and N-alkylated 4-pyridone derivatives bearing mesogenic 3,4,5-tris(alkyloxy)-benzyl moieties (alkyl=hexyl, octyl, decyl, dodecyl, tetradecyl, or hexadecyl). These new lanthanidomesogens were investigated for their mesogenic properties by a combination of differential scanning calorimetry, polarizing optical microscopy, and temperature-dependent powder X-ray diffraction (XRD). Their thermal stability was assessed by thermogravimetric analysis. All of these complexes show enantiotropic liquid-crystalline behavior with lamellar (SmA) phases in the case of shorter-chain complexes (C-6 and C-8) or hexagonal columnar phases (Col(h)) for complexes with longer alkyl chains (C-12, C-14, and C-16), which were assigned on the basis of their characteristic textures and XRD studies. For complexes with an intermediate number of carbon atoms in the side chains (C-10), both a lamellar phase at lower temperatures and a Col(h) phase at higher temperatures were evidenced. In the solid state, all these complexes show characteristic emissions assigned to the corresponding lanthanide ion. In addition, the luminescence decay curves showed single-exponential decays with characteristic times in the millisecond range (0.75-0.90 ms for Eu-III, 0.045-0.060 ms for Sm-III, and 0.75-1.05 ms for Tb-III).

1062. Ferroelectric switching dynamics in 0.5Ba(Zr0.2Ti0.8)O-3-0.5( Ba0.7Ca0.3)TiO3 thin films

Authors: Silva, JPB; Kamakshi, K; Negrea, RF; Ghica, C; Wang, J; Koster, G; Rijnders, G; Figueiras, F; Pereira, M; Gomes, MJM

Published: AUG 20 2018, APPLIED PHYSICS LETTERS, 113, DOI: 10.1063/1.5044623

In this work, the ferroelectric characteristics of 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) thin films grown on 0.7 wt. % Nb-doped (001)-SrTiO3 (Nb:STO) single-crystal have been investigated. High-resolution transmission electron microscopy and electron energy loss spectroscopy revealed a very sharp Nb:STO/BCZT interface, while selected area electron diffraction revealed the epitaxial growth of the BCZT layer on the Nb:STO substrate. The ferroelectric nature of the BCZT films have been investigated by piezoresponse force microscopy and hysteresis loops. The effect of electric field on polarization switching kinetics has been investigated and has been analyzed by the nucleation limited switching model with a Lorentzian distribution function. The local field variation was found to decrease with the increase in the electric field, and thus, the switching process becomes faster. The peak value of the polarization current and the logarithmic characteristic switching time exhibited an exponential dependence on the inverse of electric field. This model gave an excellent agreement with the experimental polarization reversal transients throughout the whole time range. Published by AIP Publishing.

1063. Strain induced magnetism and superexchange interaction in Cr substituted nanocrystalline cobalt ferrite

Authors: Kumar, L; Kumar, P; Kuncser, V; Greculeasa, S; Sahoo, B; Kar, M

Published: JUN 1 2018, MATERIALS CHEMISTRY AND PHYSICS, 211, 64, DOI: 10.1016/j.matchemphys.2018.02.008

Distribution of magnetic relaxation time using Mossbauer spectroscopy has been observed for CoFe2-xCrxO4 (0.1 <= x <= 0.4) annealed at lower temperature (<= 400 degrees C). The estimated cation distribution over A and B sites observed by Mossbauer spectroscopy is consistent with that obtained by the Rietveld analysis of the X-ray diffraction patterns. Saturation magnetization and magnetocrystalline anisotropy constant increase up to 20% of Cr (x = 0.2) substitution and, decrease with further increase of x. However, the coercive field as well as the Neel temperature decreases with increase in Cr3+ concentration, i.e., a crossover from the hard magnetic to soft magnetic nature by Cr substitution at the Fe site of CoFe2O4 has been observed. This behavior is attributed to the competition between strain induced magnetism and superexchange interaction between cations. (C) 2018 Elsevier B.V. All rights reserved.

1064. A straightforward route to obtain organic/inorganic hybrid network from bio-waste: Electroless deposition of ZnO nanostructures on eggshell membranes

Authors: Preda, N; Costas, A; Beregoi, M; Enculescu, I

Published: AUG 16 2018, CHEMICAL PHYSICS LETTERS, 706, 30, DOI: 10.1016/j.cplett.2018.05.073

Bio-waste eggshell membranes (ESM) present a unique micro-architecture consisting in an interwoven fibrous network which can be functionalized with metal oxides resulting in hybrid materials. ESM were covered with ZnO nanostructures by electroless deposition using Au as catalyst. The structural, optical, morphological and wetting properties of the pristine ESM and ESM/ZnO were evaluated. The ESM fibers were uniformly coated by ZnO hexagonal prisms, the hybrid ESM/ZnO preserving the water absorption characteristic of the pristine ESM. Combining an abundant bio-waste with a simple wet chemical synthesis method, flexible organic/inorganic hybrid networks based on ZnO-functionalized ESM can be designed for various applications. (C) 2018 Elsevier B.V. All rights reserved.

1065. Synthesis and Characterization of Jellified Composites from Bovine Bone-Derived Hydroxyapatite and Starch as Precursors for Robocasting

Authors: Miculescu, F; Maidaniuc, A; Miculescu, M; Batalu, ND; Ciocoiu, RC; Voicu, SI; Stan, GE; Thakur, VK

Published: JAN 2018, ACS OMEGA, 3, 1349, DOI: 10.1021/acsomega.7b01855

Hydroxyapatite-starch composites solidify rapidly via jellification, making them suitable candidates for robocasting. However, many aspects related to hydroxyapatite powder characteristics, hydroxyapatite-starch interaction, and composites composition and properties need to be aligned with robocasting requirements to achieve a notable improvement in the functionality of printed scaffolds intended for bone regeneration. This article presents a preliminary evaluation of hydroxyapatite-starch microcomposites. Thermal analysis of the starting powders was performed for predicting composites' behavior during heat-induced densification. Also, morphology, mechanical properties, and hydroxyapatite-starch interaction were evaluated for the jellified composites and the porous bodies obtained after conventional sintering, for different starch additions, and for ceramic particle size distributions. The results indicate that starch could be used for hydroxyapatite consolidation in limited quantities, whereas the composites shall be processed under controlled temperature. Due to a different mechanical behavior induced by particle size and geometry, a wide particle size distribution of hydroxyapatite powder is recommended for further robocasting ink development.

1066. MOS DOSIMETER BASED ON Ge NANOCRYSTALS IN HfO2

Authors: Palade, C; Slav, A; Lepadatu, AM; Stavarache, I; Dascalescu, I; Cojocaru, O; Stoica, T; Ciurea, ML; Lazanu, S

Published: 2018, CAS 2018 PROCEEDINGS: 2018 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 90, DOI:

Trilayer MOS capacitors gate HfO2 / floating gate of Ge nanocrystals in HfO2 / tunnel HfO2 / Si substrate were prepared in the aim to be used for the detection of ionizing radiation. Magnetron sputtering and rapid thermal annealing were used for their fabrication. Capacitance-voltage measurements showed that Ge nanocrystals are the most important charge storage centres in our structure. The possibility to use these trilayer MOS capacitors as dosimeters was investigated, and the sensitivity to alpha particle irradiation was extracted.

1067. Titanium implants' surface functionalization by pulsed laser deposition of TiN, ZrC and ZrN hard films

Authors: Floroian, L; Craciun, D; Socol, G; Dorcioman, G; Socol, M; Badea, M; Craciun, V

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 182, DOI: 10.1016/j.apsusc.2017.03.068

Thin films of TiN, ZrC, and ZrN were deposited at room temperature on highly polished Ti and Si samples using the pulsed laser deposition technique. Grazing incidence X-ray diffraction investigations showed that films were nanocrystalline, with grain sizes from 5 to 12 nm and under compression. Simulations of X-ray reflectivity curves acquired from the samples indicated that the deposited layers were dense and smooth. Electrochemical tests performed in simulated body fluid showed that the deposited coatings significantly improved the corrosion resistance of Ti samples. The comparative study found out that the best sample was ZrN/Ti, its corrosion current after 32 days immersion in simulated body fluids being half of that measured for the bare Ti sample and in the same time almost unchanged from the initial value. (C) 2017 Elsevier B.V. All rights reserved.

1068. Lanthanum influence on the structure, dielectric properties and luminescence of BaTiO3 ceramics processed by spark plasma sintering technique

Authors: Stanciu, CA; Cernea, M; Secu, EC; Aldica, G; Ganea, P; Trusca, R

Published: JUN 5 2017, JOURNAL OF ALLOYS AND COMPOUNDS, 706, 545, DOI: 10.1016/j.jallcom.2017.02.258

Nano-sized lanthanum doped barium titanate Ba1-xLaxTiO3 (0.00 <= x <= 0.08) powders were prepared by sol-gel method. These powders with perovskite BaTiO3 cubic single phase structure, obtained after calcinations of gels precursors at 1100 degrees C, 3 h in air, were pressed and sintered by spark plasma technique in order to obtain dense ceramics. The optimal sintering temperatures used for Ba1-xLaxTiO3 powders were dependent on lanthanum amount added to barium titanate and decrease from 1300 degrees C to 1160 degrees C when the La concentration increases from 0 to 8 at.% La. An additional annealing treatment was made in air at 900 degrees C for all the sintered pellets for oxidize and remove the contaminant graphite which migrated in ceramics from the graphite die during the sintering process. The effect of lanthanum concentration on the densification behavior, structure, microstructure, photoluminescence and dielectric properties of the Ba1-xLaxTiO3 ceramics was investigated in this work. The results shown that as the lanthanum content increases, the grain size of the powders and ceramics increases accompanied by decrease of density of the samples. Also, increase of La amount inserted in BaTiO3 lattice leads to significant decrease of the dielectric losses and Curie temperature and, increase of dielectric permittivity but the luminescence properties seem to be less affected. (C) 2017 Elsevier B. V. All rights reserved.

1069. Biocomposite coatings based on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/calcium phosphates obtained by MAPLE for bone tissue engineering

Authors: Rasoga, O; Sima, L; Chiritoiu, M; Popescu-Pelin, G; Fufa, O; Grumezescu, V; Socol, M; Stanculescu, A; Zgura, I; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 212, DOI: 10.1016/j.apsusc.2017.01.205

The aim of our research was to synthesize and investigate the physico-chemical and biological features of composite coatings based on poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and commercial calcium phosphates (CaPs), hydroxyapatite and beta-tricalcium phosphate, obtained by means of matrix assisted pulsed laser evaporation (MAPLE) technique. In this respect, laser fluence and dropcast studies were performed for pristine polymer and PHBV-CaPs composites. The microstructure of the synthesized coatings was investigated by scanning electron microscopy, while for the chemical structure and functional integrity we performed Fourier transform infrared spectroscopy comparative analysis. By using the X-ray diffraction measurements we experimentally evaluated the crystalline nature of the obtained composite materials, while relevant data regarding the hydrophilic/hydrophobic behavior of the synthesized coatings were obtained by performing static CA measurements. The biocompatibility of PHBV/CaPs coatings was evaluated by performing cellular adhesion and differentiation in vitro assays on mesenchymal stem cells. (C) 2017 Elsevier B.V. All rights reserved.

1070. Lipoic acid functionalized SiO2@Ag nanoparticles. Synthesis, characterization and evaluation of biological activity

Authors: Tudose, M; Culita, DC; Musuc, AM; Somacescu, S; Ghica, C; Chifiriuc, MC; Bleotu, C

Published: OCT 1 2017, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 79, 506, DOI: 10.1016/j.msec.2017.05.083

A novel nanocomposite was obtained through the covalent immobilization of lipoic acid on the surface of silver nanoparticles-decorated silica nanoparticles (SiO2@Ag). The hybrid organic inorganic material obtained was characterized by Fourier transform infrared spectroscopy, thermal analysis, scanning and transmision electron microscopy, X-ray photoelectron spectroscopy and UV-Visible spectroscopy. Its antioxidant, cytotoxic, antimicrobial activity and influence on mammalian cells cycle were evaluated. The results of this study have shown that the functionalization of SiO2@Ag with lipoic acid resulted in a composite with increased specificity of interaction with different mammalian cell lines and antioxidant activity, but with decreased cytotoxicity and antimicrobial properties. Therefore, the SiO2@Ag functionalized with lipoic acid could be successfully used in certain concentrations to modulate the cell cycle, in order to obtain the desired anti-proliferative or stimulatory therapeutic effect. (C) 2017 Elsevier B.V. All rights reserved.

1071. Magnetic and magneto-optical properties of Bi and Pb-containing aluminophosphate glass

Authors: Elisa, M; Iordanescu, R; Vasiliu, C; Sava, BA; Boroica, L; Valeanu, M; Kuncser, V; Galca, AC; Volceanov, A; Eftimie, M; Melinescu, A; Beldiceanu, A

Published: JUN 1 2017, JOURNAL OF NON-CRYSTALLINE SOLIDS, 465, 58, DOI: 10.1016/j.jnoncrysol.2016.11.010

Bi3+, Pb2+ and Bi3+-Pb2+-containing aluminophosphate glasses were obtained by unconventional wet method, the molar formula of the glasses being: i) 58LiPO(3), 29Al(PO3)(3), 10Ba(PO3)(2), 3Bi(2)O(3); ii) 58LiPO(3), 29Al(PO3)(3), 10Ba(PO3)(2), 3PbO and iii) 6LiPO(3), 3Al(PO3)(3), 1Ba(PO3)(2), 10Bi(PO3)(3), 80Pb(PO3)(2). The glass samples were investigated to determine the density, the thermal expansion coefficients and the chemical stability. The magnetic measurements for Bi and Pb-single doped glasses revealed a diamagnetic behavior and those of Bi-Pb-containing glass disclosed a diamagnetic behavior superposed a small paramagnetic contribution, observed in low magnetic fields that can be attributed to the impurities presented in the matrix. The Verdet constant for the analyzed glasses appeared to have positive values proving a diamagnetic behavior of the investigated material. (C) 2016 Published by Elsevier B.V.

1072. Structure-property relationships for Eu doped TiO2 thin films grown by a laser assisted technique from colloidal sols

Authors: Camps, I; Borlaf, M; Colomer, MT; Moreno, R; Duta, L; Nita, C; del Pino, AP; Logofatu, C; Serna, R; Gyorgy, E

Published: 2017, RSC ADVANCES, 7, 37653, DOI: 10.1039/c7ra05074g

Photoactive europium doped titanium dioxide (Eu: TiO2) thin films were grown by a matrix assisted pulsed laser evaporation technique. TiO2 and Eu cation-adsorbed TiO2 nanoparticles (NPs) sols were used as starting materials. The sols were synthesized by a colloidal sol-gel route. In order to obtain solid targets, the sols were cooled down until solidification in liquid nitrogen. The irradiation of the solid targets was performed in a controlled oxygen atmosphere using an UV KrF* (lambda = 248 nm, tau(FWHM) nu 25 ns, n = 10 Hz) excimer laser source. The NPs were transferred and deposited onto solid substrates placed in the front of the frozen targets, forming continuous thin films. The as-grown undoped and Eu: TiO2 thin films were submitted to post-deposition thermal treatments. The surface morphology, crystalline structure, and chemical composition of the thin films were characterized by field emission scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Functional optical properties of the films were investigated by UV-VIS-NIR spectroscopy, spectroscopic ellipsometry, and photoluminescence as a function of dopant concentration in the TiO2 host and annealing temperature. A direct correlation was established between the processing conditions, films structure, chemical composition and oxidation states studied both at the top surface and in-depth as well as their functional, optical properties. Eu doping induces a blue-shift of the absorption edge with respect to the as-grown samples. Under visible light excitation (lambda = 488 nm, emitted by an Ar+ laser source), the Eu: TiO2 samples show characteristic photoluminescence corresponding to the D-5(0) -> F-7(i) (i = 0, 1, 2, 3, 4) transitions of Eu+ ions in the visible spectral range. The samples treated at the highest annealing temperature are characterized by strong photoluminescence emission, high transmittance in the VIS-NIR spectral regions, and high refractive index.

1073. Influence of preparation conditions on structure and photosensing properties of GeSi/TiO2 multilayers

Authors: Slav, A; Palade, C; Stavarache, I; Teodorescu, VS; Ciurea, ML; Muller, R; Dinescu, A; Sultan, MT; Manolescu, A; Gudmundsson, JT; Svavarsson, HG

Published: 2017, 2017 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 40TH EDITION, 66, DOI:

The photosensing properties related to the structure of GeSi/TiO2 multilayers prepared under different conditions are studied. TiO2 cap/(GeSi/TiO2)(2) multilayers (ML) were deposited by magnetron sputtering (MS) and annealed by rapid thermal annealing. Trilayers of TiO2 cap/GeSi/TiO2 (TL) were also deposited using reactive high power impulse MS (HiPIMS) for TiO2 layers and dc MS for the GeSi layer. For TL samples a two-step annealing was employed, one before and the second after depositing TiO2 cap. Structure and morphology characterization (X-ray diffraction, scanning and transmission electron microscopy) was carried out and photocurrent measurements (voltage dependences, spectral curves) were performed. The annealed ML samples are formed of GeSi NCs with 5 - 10 nm sizes, while in the annealed TL samples, the GeSi NCs are larger (20 - 30 nm). These morphologies determine the multilayers photosensing properties in VIS-NIR of ML structures and in UV in TL ones, respectively.

1074. IZO deposited by PLD on flexible substrate for organic heterostructures

Authors: Socol, M; Preda, N; Stanculescu, A; Breazu, C; Florica, C; Rasoga, O; Stanculescu, F; Socol, G

Published: MAY 2017, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 123, DOI: 10.1007/s00339-017-0992-4

In: ZnO (IZO) thin films were deposited on flexible plastic substrates by pulsed laser deposition (PLD) method. The obtained layers present adequate optical and electrical properties competitive with those based on indium tin oxide (ITO). The figure of merit (9 X 10(-3) Omega(-1)) calculated for IZO layers demonstrates that high quality coatings can be prepared by this deposition technique. A thermal annealing (150 degrees C for 1 h) or an oxygen plasma etching (6 mbar for 10 min.) were applied to the IZO layers to evaluate the influence of these treatments on the properties of the transparent coatings. Using vacuum evaporation, organic heterostructures based on cooper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited on the untreated and treated IZO layers. The optical and electrical properties of the heterostructures were investigated by UVVis, FTIR and current-voltage (I-V) measurements. For the heterostructure fabricated on IZO treated in oxygen plasma, an improvement in the current value with at least one order of magnitude was evidenced in the I-V characteristics recorded in dark conditions. Also, an increase in the current value for the heterostructure deposited on untreated IZO layer can be achieved by adding an organic layer such as tris-8-hydroxyquinoline aluminium (Alq(3)).

1075. On the threshold for ion track formation in CaF2

Authors: Karlusic, M; Ghica, C; Negrea, RF; Siketic, Z; Jaksic, M; Schleberger, M; Fazinic, S

Published: FEB 10 2017, NEW JOURNAL OF PHYSICS, 19, DOI: 10.1088/1367-2630/aa5914

There is an ongoing debate regarding the mechanism of swift heavy ion (SHI) track formation in CaF2. The objective of this study is to shed light on this important topic using a range of complementary experimental techniques. Evidence of the threshold for ion track formation being below 3 keV nm(-1) is provided by both transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy in the channelling mode, which has direct consequences for the validity of models describing the response of CaF2 to SHI irradiation. Furthermore, information about the elemental composition within the ion tracks is obtained using scanning TEM, electron energy loss spectroscopy, and with respect to the stoichiometry of the materials surface by in situ time of flight elastic recoil detection analysis. Advances in the analyses of the experimental data presented here pave the way for a better understanding of the ion track formation.

1076. Laser deposition of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) - lysozyme microspheres based coatings with anti-microbial properties

Authors: Grumezescu, V; Holban, AM; Sima, LE; Chiritoiu, MB; Chiritoiu, GN; Grumezescu, AM; Ivan, L; Safciuc, F; Antohe, F; Florica, C; Luculescu, CR; Chifiriuc, MC; Socol, G

Published: APR 15 2017, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 521, 195, DOI: 10.1016/j.ijpharm.2017.01.069

The purpose of this study was to obtain, characterize and evaluate the cytotoxicity and antimicrobial activity of coatings based on poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) -Lysozyme (P(3HB3HV)/ Lys) and P(3HB-3HV) -Polyethylene glycol -Lysozyme (P(3HB-3HV)/PEG/Lys) spheres prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique, in order to obtain functional and improved Ti-based implants. Morphological investigation of the coatings by Infrared Microscopy (IRM) and SEM revealed that the average diameter of P(3HB-3HV)/Lys spheres is around 2 mm and unlike the drop cast samples, IRM recorded on MAPLE films revealed a good distribution of monitored functional groups on the entire scanned surface. The biological evaluation of MAPLE structured surfaces revealed an improved biocompatibility with respect to osteoblasts and endothelial cells as compared with Ti substrates and an enhanced anti-biofilm effect against Gram positive (Staphylococcus aureus) and Gram negative (Pseudomonas aeruginosa) tested strains. Thus, we propose that the fabricated P(3HB-3HV)/PEG/Lys and P(3HB-3HV)/Lys microspheres may be efficiently used as a matrix for controlled local drug delivery, with practical applications in developing improved medical surfaces for the reduction of implant-associated infections. (C) 2017 Elsevier B. V. All rights reserved.

1077. Development and Biocompatibility Evaluation of Photocatalytic TiO2/Reduced Graphene Oxide-Based Nanoparticles Designed for Self-Cleaning Purposes

Authors: Nica, IC; Stan, MS; Popa, M; Chifiriuc, MC; Pircalabioru, GG; Lazar, V; Dumitrescu, I; Diamandescu, L; Feder, M; Baibarac, M; Cernea, M; Maraloiu, VA; Popescu, T; Dinischiotu, A

Published: SEP 2017, NANOMATERIALS, 7, DOI: 10.3390/nano7090279

Graphene is widely used in nanotechnologies to amplify the photocatalytic activity of TiO2, but the development of TiO2/graphene composites imposes the assessment of their risk to human and environmental health. Therefore, reduced graphene oxide was decorated with two types of TiO2 particles co-doped with 1% iron and nitrogen, one of them being obtained by a simultaneous precipitation of Ti3+ and Fe3+ ions to achieve their uniform distribution, and the other one after a sequential precipitation of these two cations for a higher concentration of iron on the surface. Physico-chemical characterization, photocatalytic efficiency evaluation, antimicrobial analysis and biocompatibility assessment were performed for these TiO2-based composites. The best photocatalytic efficiency was found for the sample with iron atoms localized at the sample surface. A very good anti-inhibitory activity was obtained for both samples against biofilms of Gram-positive and Gram-negative strains. Exposure of human skin and lung fibroblasts to photocatalysts did not significantly affect cell viability, but analysis of oxidative stress showed increased levels of carbonyl groups and advanced oxidation protein products for both cell lines after 48 h of incubation. Our findings are of major importance by providing useful knowledge for future photocatalytic self-cleaning and biomedical applications of graphene-based materials.

1078. Single layer of Ge quantum dots in HfO2 for floating gate memory capacitors

Authors: Lepadatu, AM; Palade, C; Slav, A; Maraloiu, AV; Lazanu, S; Stoica, T; Logofatu, C; Teodorescu, VS; Ciurea, ML

Published: APR 28 2017, NANOTECHNOLOGY, 28, DOI: 10.1088/1361-6528/aa66b7

High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO2 were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO2/floating gate of single layer of Ge QDs in HfO2/tunnel HfO2/p-Si wafers. Both Ge and HfO2 are nanostructured by RTA at moderate temperatures of 600-700 degrees C. By nanostructuring at 600 degrees C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 x 1015 m(-2) is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO2 nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO2 NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO2 NCs boundaries, while another part of the Ge atoms is present inside the HfO2 lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8. +/-. 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO2, distanced from the Si substrate by the tunnel oxide layer with a precise thickness.

1079. Electrochemically shape-controlled transformation of magnetron sputtered platinum films into platinum nanostructures enclosed by high-index facets

Authors: Khalakhan, I; Lavkova, J; Matolinova, I; Vorokhta, M; Potin, V; Kus, P; Vaclavu, M; Maraloiu, VA; Kuncser, AC; Matolin, V

Published: JAN 15 2017, SURFACE & COATINGS TECHNOLOGY, 309, 11, DOI: 10.1016/j.surfcoat.2016.11.017

A new method based on transformation of magnetron sputtered platinum thin films into platinum nanostructures enclosed by high-index facets, using electrochemical potential cycling in a twin working electrode system is reported. The controllable formation of various Pt nanostructures, described in this paper, indicates that this method can be used to control a selective growth of high purity Pt nanostructures with specific shapes (facets or edges). The method opens up new possibilities for electrochemical preparation of nanostructured Pt catalysts at high yield. (C) 2016 Elsevier B.V. All rights reserved.

1080. Microwave antenna array using new dielectric resonator antenna elements

Authors: Banciu, MG; Militaru, N; Martian, A; Nicolaescu, I; Tuta, L; Geambasu, DC; Nedelcu, L; Trupina, L; Ramer, R

Published: 2017, 2017 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 40TH EDITION, 132, DOI:

Investigations on antenna array for 5.8 GHz frequency band applications are presented in this paper. In order to enhance the characteristics of the dielectric resonator antenna elements, a pair of resonators with different sizes and dielectric constants is used. The antenna elements are connected to four daughter-boards of Universal Software Radio Peripherals, which perform the signal processing required by the sources detection and beamforming.

1081. Advances in Functionalized Materials Research 2016

Authors: Predoi, D; Motelica-Heino, M; Guegan, R; Le Coustumer, P

Published: 2017, JOURNAL OF NANOMATERIALS, 2017, DOI: 10.1155/2017/1269319

1082. Optimized silicon reinforcement of carbon coatings by pulsed laser technique for superior functional biomedical surfaces fabrication

Authors: Mihailescu, IN; Bociaga, D; Popescu-Pelin, G; Stan, GE; Duta, L; Socol, G; Chifiriuc, MC; Bleotu, C; Lazar, V; Husanu, MA; Zgura, I; Miculescu, F; Negut, I; Hapenciuc, C

Published: JUN 1 2017, BIOFABRICATION, 9, DOI: 10.1088/1758-5090/aa7076

We report on the fabrication of silicon-reinforced carbon (C: Si) structures by combinatorial pulsed laser deposition to search for the best design for a new generation of multi-functional coated implants. The synthesized films were characterized from the morphological, structural, compositional, mechanical and microbiological points of view. Scanning electron microscopy revealed the presence, on top of the deposited layers, of spheroid particulates with sizes in the micron range. No microcracks or delaminations were observed. Energy dispersive x-ray spectroscopy and grazing incidence x-ray diffraction pointed to the existence of aC to Si compositional gradient from one end of the film to the other. Raman investigation revealed a relatively high sp(3) hybridization of up to 80% at 40-48 mm a part from the edge with higher Ccontent. Si addition was demonstrated to significantly increase C: Si film bonding to the substrate, with values above the ISO threshold for coatings to be used in high-loading biomedical applications. Surface energy studies pointed to an increase in the hydrophilic character of the deposited structures along with Si content up to 52 m Nm(-1'). In certain cases, the Si-reinforced Ccoatings elicited an antimicrobial biofilm action. The presence of Si was proven to be benign to HEp-2 cells of human origin, without interfering with their cellular cycle. On this basis, reliable C: Si structures with good adherence to the substrate and high efficiency against microbial biofilms can be developed for implant coatings and other advanced medical devices.

1083. Structure and magnetic properties of CoFe2O4/SiO2 nanocomposites obtained by sol-gel and post annealing pathways

Authors: Dippong, T; Cadar, O; Levei, EA; Bibicu, I; Diamandescu, L; Leostean, C; Lazar, M; Borodi, G; Tudoran, LB

Published: FEB 1 2017, CERAMICS INTERNATIONAL, 43, 2122, DOI: 10.1016/j.ceramint.2016.10.192

The influence of the CoFe2O4 nanoparticles concentration in silica matrix on the structural and magnetic properties of xCoFe(2)O(4)/(100-x)SiO2 nanocomposites with x=10, 30, 50, 70 and 90 was studied. Magnetic CoFe2O4 nanoparticles dispersed in silica matrix was obtained by sol-gel method, followed by annealing at 1100 degrees C. The X-ray diffraction pattern and FT-IR spectra revealed the single spinel ferrite structure for all samples. The FT-IR spectra also suggested the formation of the amorphous silica matrix. The results showed that the increase of cobalt ferrite concentration (x) in the silica matrix leads to high crystallinity, specific surface area and particle size. The magnetic CoFe2O4 nanoparticles have spherical shapes and size in the 6-35 nm range. The Mossbauer measurements were fitted with two Zeeman sextets, indicating that all the samples were completely magnetically ordered. The vibrating sample magnetometer studies showed that the saturation magnetization (Ms) and coercivity (Hc) of the CoFe2O4 nanocrystals embedded in silica matrix possessed a linear relationship with the mean crystallite size. Also, the saturation magnetization of the studied nanocomposites increases with the increase of cobalt ferrite concentration (x) in the silica matrix.

1084. Melt infiltrated tungsten-copper composites as advanced heat sink materials for plasma facing components of future nuclear fusion devices

Authors: Von Muller, A; Ewert, D; Galatanu, A; Milwich, M; Neu, R; Pastor, JY; Siefken, U; Tejado, E; You, JH

Published: NOV 2017, FUSION ENGINEERING AND DESIGN, 124, 459, DOI: 10.1016/j.fusengdes.2017.01.042

The exhaust of power and particles is regarded as a major challenge in view of the design of a magnetic confinement nuclear fusion demonstration power plant (DEMO). In such a reactor, highly loaded plasma facing components (PFCs), like the divertor targets, have to withstand both severe heat flux loads and considerable neutron irradiation. Existing divertor target designs make use of monolithic tungsten (W) and copper (Cu) material grades that are combined in a PFC. Such an approach, however, bears engineering difficulties as W and Cu are materials with inherently different thermomechanical properties and their optimum operating temperature windows do not overlap. Against this background, W Cu composite materials are promising candidates regarding the application to the heat sink of highly loaded PFCs. The present contribution summarises recent results regarding the manufacturing and characterisation of such W Cu composite materials produced by means of liquid Cu melt infiltration of open porous W preforms. On the one hand, this includes composites manufactured by infiltrating powder metallurgically produced W skeletons. On the other hand, W Cu composites based on textile technologically produced fibrous reinforcement preforms are discussed. (C) 2017 The Author(s). Published by Elsevier B.V.

1085. Magnetite-based glass-ceramics prepared by controlled crystallization of borosilicate glasses: Effect of nucleating agents on magnetic properties and relaxation

Authors: Sandu, V; Cimpoiasu, E; Greculeasa, S; Kuncser, A; Nicolescu, MS; Kuncser, V

Published: FEB 15 2017, CERAMICS INTERNATIONAL, 43, 3413, DOI: 10.1016/j.ceramint.2016.11.188

The specific magnetic structure and magnetic relaxation phenomena in magnetite nanoentities grown in a glassy matrix by controlled crystallization of Fe-containing borosilicate and boroaluminosilicate glasses in the presence of two types of nucleating agents, Cr2O3 and P2O5, were investigated. The structure, morphology and magnetic properties are strongly influenced by the nucleating agents. Cr2O3 generates magnetite-based glass ceramics with magnetite configurations showing an upward relaxation of magnetization at low and high temperatures but downward at intermediate temperatures. The magnetite grown with P2O5 displays only downward relaxation but with different signs of the temperature derivative of the relaxation rate S in different temperature ranges. The observed effects are discussed with respect to the following factors: i) the existence of a multimodal size distribution of the magnetite (nano)particles as revealed by high resolution electron microscopy; ii) the degree of occupation of different sublattices of the magnetite structure with Fe3+ and Fe2+ ions; and the interplay between the relaxation mechanisms in different temperature ranges.

1086. Effect of in-plane ordering on dielectric properties of highly {111}-oriented bismuth-zinc-niobate thin films

Authors: Le Febvrier, A; Deputier, S; Demange, V; Bouquet, V; Galca, AC; Iuga, A; Pintilie, L; Guilloux-Viry, M

Published: OCT 2017, JOURNAL OF MATERIALS SCIENCE, 52, 11313, DOI: 10.1007/s10853-017-1297-x

Bi1.5-xZn0.92-yNb1.5O6.92-delta (BZN) thin films were grown by pulsed laser deposition on two different Pt-covered substrates, namely textured {111} Pt/TiO2/SiO2/(100) Si substrate (Pt/Si) and epitaxial {111} Pt/R-plane sapphire substrate (Pt/sapphire). In both cases, the BZN films present {111} and {100} out-of-plane orientations, in relative ratios of 65: 35 on Pt/Si and 80: 20 on Pt/sapphire, respectively. The film grown on Pt/Si is textured, while the film deposited on Pt/sapphire presents epitaxial-like relationships with the substrate, for both out-of-plane orientations. Dielectric measurements were taken on both types of thin films, using Pt/BZN/Pt planar capacitor structures. The BZN/Pt/sapphire film presents higher dielectric constant (245 at 100 kHz) and higher tunability (12% at 600 kV/cm) than the BZN/Pt/Si film (200; 6%), while the dielectric losses values are nearly same (similar to 0.05).

1087. Combined Electrochemical Impedance Spectroscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy study of the distinct behavior of L-cysteine-thiolate formed at p- and n-GaAs(100) electrodes in Sodium Dodecyl Sulfate solution

Authors: Lazarescu, V; Enache, M; Anastasescu, M; Dobrescu, G; Negrila, C; Lazarescu, MF

Published: JAN 20 2017, ELECTROCHIMICA ACTA, 225, 558, DOI: 10.1016/j.electacta.2016.12.156

Electrochemical impedance spectroscopy (EIS), X-ray spectroscopy (XPS), and atomic force microscopy (AFM) have been used to investigate the effects of the sodium dodecyl sulfate (SDS) interaction with the L-cysteine-thiolate covered p- and n-GaAs(100) electrodes in H2SO4 solution. The potential-induced reversible proton transfer found to occur within the L-cysteine-thiolate layer in the simple acid solution during the cathodic as well as the anodic potential scans at the p-doped semiconductor electrode and only in the anodic scan at the n-doped one is suppressed in both cases. XPS data revealed that the anionic surfactant has a complex interaction with the L-cysteine-thiolate covered GaAs(100) electrodes, which implicates both electrostatic and chemical forces. The SO42 head group interacts electrostatically with the NH3+ group of the cysteine-thiolate but it is also chemically involved in a chemisorption bond with the available Ga atoms. The amount of Ga-bound SDS species is much more pronounced at the L-cysteine-thiolate/p-GaAs(100) than at the L-cysteine thiolate/n-doped GaAs(100) electrodes meaning that cysteine-thiolate is mainly formed at As sites in the first case and at Ga sites in the latter one. This outcome strengthens the previous conclusions concerning the role of the dopant in determining the bonding way of the L-cysteine on GaAs(100) surfaces. (C) 2016 Elsevier Ltd. All rights reserved.

1088. The influence of single-walled carbon nanotubes on optical properties of the poly[(2,5-bisoctyloy)-1, 4-phenylenevinylene] evidenced by infrared spectroscopy and anti-Stokes photoluminescence

Authors: Baibarac, M; Smaranda, I; Baltog, I; Lefrant, S; Mevellec, JY

Published: MAY 2017, OPTICAL MATERIALS, 67, 58, DOI: 10.1016/j.optmat.2017.03.039

Significant differences are reported for the IR spectra of poly[(2,5-bisoctyloy)-1, 4-phenylenevinylene] (BO-PPV) recorded onto the KBr, Ag and Au supports. In this work, a decrease in the absorbance of the IR spectra of the BO-PPV films deposited onto Au and Ag supports as increasing the macromolecular compound film thickness is reported. A preferential orientation of the BO-PPV molecules and its composite with single-walled carbon nanotubes (SWNTs) versus metallic supports of Ag and Au is assessed using the IR absorption spectroscopy under s and p polarized light. An anti-Stokes photoluminescence (ASPL) is reported to characterize the BO-PPV macromolecular compound. The BO-PPV ASPL spectra intensity dependent both of the thickness of the macromolecular compound layer deposited onto the metallic supports and the SWNTs weight in the BO-PPV/SWNTs composite mass. (C) 2017 Elsevier B.V. All rights reserved.

1089. Intrinsic and extrinsic effects near orthorhombic-tetragonal phase transition in barium titanate ceramics doped with small amounts of zirconium

Authors: Amarande, L; Miclea, C; Cioangher, M; Pasuk, I; Iuga, A; Pintilie, I

Published: APR 15 2017, CERAMICS INTERNATIONAL, 43, 4925, DOI: 10.1016/j.ceramint.2016.12.143

Pure BT and BT doped with 1 and 2 mol% Zr, with orthorhombic-tetragonal (O-T) phase transitions near room temperature were prepared, with different grain sizes, by conventional ceramic method, at various sintering temperatures. Intrinsic and extrinsic effects of Zr addition on structural, dielectric, piezoelectric and ferroelectric properties of BT ceramics, near O-T phase transition were studied. In coarse grained ceramics, the intrinsic effects manifested in low field measurements (dielectric and piezoelectric constants), were reduced by Zr addition, while the extrinsic effects which control the high field response (remanent polarization and coercive field) were significantly enhanced. Instead, in fine grains ceramics, of either pure or doped BT, the extrinsic effects related to increased domain wall and grain boundaries density were dominant in both low and high field measurements, overlapping Zr effects. The results were explained in terms of crystal anisotropy correlated with grain size effects.

1090. Double band inversion in alpha-Sn: Appearance of topological surface states and the role of orbital composition

Authors: Rogalev, VA; Rauch, T; Scholz, MR; Reis, F; Dudy, L; Fleszar, A; Husanu, MA; Strocov, VN; Henk, J; Mertig, I; Schafer, J; Claessen, R

Published: APR 27 2017, PHYSICAL REVIEW B, 95, DOI: 10.1103/PhysRevB.95.161117

The electronic structure of alpha-Sn (001) thin films strained compressively in-plane was studied both experimentally and theoretically. A new topological surface state (TSS) located entirely within the gapless projected bulk bands is revealed by ab initio-based tight-binding calculations as well as directly accessed by soft x-ray angle-resolved photoemission. The topological character of this state, which is a surface resonance, is confirmed by unravelling the band inversion and by calculating the topological invariants. In agreement with experiment, electronic structure calculations show the maximum density of states in the subsurface region, while the already established TSS near the Fermi level is strongly localized at the surface. Such varied behavior is explained by the differences in orbital composition between the specific TSS and its associated bulk states, i.e., their hybridization, respectively.

1091. Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

Authors: Schutz, P; Di Sante, D; Dudy, L; Gabel, J; Stubinger, M; Kamp, M; Huang, Y; Capone, M; Husanu, MA; Strocov, VN; Sangiovanni, G; Sing, M; Claessen, R

Published: DEC 22 2017, PHYSICAL REVIEW LETTERS, 119, DOI: 10.1103/PhysRevLett.119.256404

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr2IrO4 opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating.

1092. Sol-gel preparation and structural investigations of silico-phosphate glasses doped with Fe ions

Authors: Sava, BAC; Elisa, M; Boroica, L; Kuncser, V; Valeanu, M; Vasiliu, IC; Feraru, I; Iordanescu, R

Published: JAN 2017, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 81, 302, DOI: 10.1007/s10971-016-4192-z

Different aspects related to the sol-gel preparation and structural investigation of silico-phosphate glasses (SiO2-P2O5 system) doped with Fe ions are reported. During the preparation process, tetraethoxysilane was used as a precursor for SiO2 and phosphoric acid (H3PO4-HP) for P2O5. Ferric chloride was used as precursor for Fe ions, water as reagent for hydrolysis reaction and ethylic alcohol as solvent. The pH of the sols was modified by adding hydrochloric acid and ammonia. It was observed that a slight increase of the solution temperature (up to 40 degrees C) allows a drastic decrease of the gelation time (from days to hours). The structure of the obtained powders dried in air at room temperature and at 100 degrees C for 10 h and subsequently thermally treated at different temperatures was investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy. Vibration modes specific to Si-O-Et, Si-OH, PO-P, P-O-Si, hydrogen bonds and H2O, as well as combined modes have been observed. The local structure and electron configurations of the doping Fe ions have been investigated by Fe-57 Mossbauer spectroscopy.

1093. Bioglass implant-coating interactions in synthetic physiological fluids with varying degrees of biomimicry

Authors: Popa, AC; Stan, GE; Husanu, MA; Mercioniu, I; Santos, LF; Fernandes, HR; Ferreira, JMF

Published: 2017, INTERNATIONAL JOURNAL OF NANOMEDICINE, 12, 707, DOI: 10.2147/IJN.S123236

Synthetic physiological fluids are currently used as a first in vitro bioactivity assessment for bone grafts. Our understanding about the interactions taking place at the fluid-implant interface has evolved remarkably during the last decade, and does not comply with the traditional International Organization for Standardization/final draft International Standard 23317 protocol in purely inorganic simulated body fluid. The advances in our knowledge point to the need of a true paradigm shift toward testing physiological fluids with enhanced biomimicry and a better understanding of the materials' structure-dissolution behavior. This will contribute to "upgrade" our vision of entire cascades of events taking place at the implant surfaces upon immersion in the testing media or after implantation. Starting from an osteoinductive bioglass composition with the ability to alleviate the oxidative stress, thin bioglass films with different degrees of polymerization were deposited onto titanium substrates. Their biomineralization activity in simulated body fluid and in a series of new inorganic-organic media with increasing biomimicry that more closely simulated the human intercellular environment was compared. A comprehensive range of advanced characterization tools (scanning electron microscopy; grazing-incidence X-ray diffraction; Fourier-transform infrared, micro-Raman, energy-dispersive, X-ray photoelectron, and surface-enhanced laser desorption/ionization time-of-flight mass spectroscopies; and cytocompatibility assays using mesenchymal stem cells) were used. The information gathered is very useful to biologists, biophysicists, clinicians, and material scientists with special interest in teaching and research. By combining all the analyses, we propose herein a step forward toward establishing an improved unified protocol for testing the bioactivity of implant materials.

1094. Textural, Structural and Biological Evaluation of Hydroxyapatite Doped with Zinc at Low Concentrations

Authors: Predoi, D; Iconaru, SL; Deniaud, A; Chevallet, M; Michaud-Soret, I; Buton, N; Prodan, AM

Published: MAR 2017, MATERIALS, 10, DOI: 10.3390/ma10030229

The present work was focused on the synthesis and characterization of hydroxyapatite doped with low concentrations of zinc (Zn: HAp) (0.01 < x(Zn) < 0.05). The incorporation of low concentrations of Zn2+ ions in the hydroxyapatite (HAp) structure was achieved by co-precipitation method. The physico-chemical properties of the samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), zeta-potential, and DLS and N2-BET measurements. The results obtained by XRD and FTIR studies demonstrated that doping hydroxyapatite with low concentrations of zinc leads to the formation of a hexagonal structure with lattice parameters characteristic to hydroxyapatite. The XRD studies have also shown that the crystallite size and lattice parameters of the unit cell depend on the substitutions of Ca2+ with Zn2+ in the apatitic structure. Moreover, the FTIR analysis revealed that the water content increases with the increase of zinc concentration. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) and XPS analyses showed that the elements Ca, P, O, and Zn were found in all the Zn: HAp samples suggesting that the synthesized materials were zinc doped hydroxyapatite, Ca10-Zn-x(x)(PO4) (6)(OH), with 0.01 <= x(Zn) <= 0.05. Antimicrobial assays on Staphylococcus aureus and Escherichia coli bacterial strains and HepG2 cell viability assay were carried out.

1095. In-gap corner states in core-shell polygonal quantum rings

Authors: Sitek, A; Tolea, M; Nita, M; Serra, L; Gudmundsson, V; Manolescu, A

Published: JAN 10 2017, SCIENTIFIC REPORTS, 7, DOI: 10.1038/srep40197

We study Coulomb interacting electrons confined in polygonal quantum rings. We focus on the interplay of localization at the polygon corners and Coulomb repulsion. Remarkably, the Coulomb repulsion allows the formation of in-gap states, i.e., corner-localized states of electron pairs or clusters shifted to energies that were forbidden for non-interacting electrons, but below the energies of corner-side-localized states. We specify conditions allowing optical excitation to those states.

1096. Synthesis and liquid crystalline properties of novel fluorinated N-benzoyl thiourea compounds. Effect of perfluoroalkyl chains on the thermal behavior and smectic phases stability

Authors: Ilis, M; Micutz, M; Pasuk, I; Staicu, T; Circu, V

Published: DEC 2017, JOURNAL OF FLUORINE CHEMISTRY, 204, 89, DOI: 10.1016/j.jfluchem.2017.10.008

A series of novel N-benzoyl-N'-aryl thiourea derivatives (BTU) bearing different number of alkoxy groups in terminal positions of benzoyl unit and a perfluorooctyl group on the other side have been designed and prepared. Their liquid crystalline properties were investigated by a combination of three techniques: polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and variable-temperature powder X-ray diffraction (XRD). Their thermal stability was studied by thermogravimetric analysis (TG). It was found that only the compounds which have only one alkoxy chain attached to benzoyl unit, 1a and 1b, show calamitic mesomorphic behavior, with smectic A and C phases being displayed. The type and stability of these mesophases are greatly influenced by the alkyl chain length as well as by the presence of perfluorooctyl group. The clearing and the mesophase ranges are significantly increased with the incorporation of perfluoroalkyl chains when compared to non-fluorinated analogues, with almost 40 degrees C. The attachment of additional alkoxy groups on the benzoyl moiety led to a significant decrease of the clearing points and suppression of the mesogenic character.

1097. Effect of heavy ions irradiation on the properties of benzil crystals

Authors: Stanculescu, F; Socol, M; Matei, E; Stanculescu, A

Published: AUG 2017, CRYSTAL RESEARCH AND TECHNOLOGY, 52, DOI: 10.1002/crat.201700047

Thick slices mechanically polished cut from a pure benzil ingot grown from melt in a modified Bridgman-Stockbarger configuration were irradiated with Ni ions having a specific energy of 11.4 MeV/u at different fluences. The effect of radiation on the properties of bulk benzil has been investigated. The chemical structure was not substantially affected as shown by infrared spectrum. The changes induced on the disorder degree have been evaluated from the Urbach law and X Ray Diffraction measurements. The morphology and surface topography have been analyzed emphasising a decrease in the size of granules and an increase in the surface roughness by irradiation. No effect of irradiation on the photoluminescence emission and optical nonlinear properties has been evidenced. These results recommend benzil as candidate for applications in space technology.

1098. Ultrasound studies on magnetic fluids based on maghemite nanoparticles

Authors: Predoi, D; Popa, CL; Predoi, MV

Published: JUN 2017, POLYMER ENGINEERING AND SCIENCE, 57, 490, DOI: 10.1002/pen.24501

In the last decades, the study of magnetic fluids with different biomedical applications such as targeted delivery of a chemotherapeutic solution to the tumor site has been of high interest. For this purpose, ultrasonic and antimicrobial studies were used to characterize the aqueous solutions based on maghemite nanoparticles. The maghemite (-Fe2O3) and dextran-coated maghemite nanoparticles (DMNp) were synthesized by coprecipitation method. The spherical shape of the nanoparticles and uniform size with an average diameter around 9.5 +/- 0.5nm for -Fe2O3 were observed in transmission electron microscopy micrographs. Dynamic light scattering was used to determine the hydrodynamic size of -Fe2O3 nanoparticles and DMNp in suspensions. The hydrodynamic diameter obtained of -Fe2O3 and DMNp was 17 and 21nm, respectively. Moreover, a noninvasive method based on ultrasounds was used to characterize the aqueous solutions. The preliminary results showed the attainable accuracy in determining acoustic wave velocity and attenuation in various solutions. These data could be correlated with particle density and size. More than that, velocity and attenuation can be used as characteristic parameters of a given solution. A finite element model of the dispersed particles, correlated with measured velocity, allowed to solve for the elastic properties of the particles. POLYM. ENG. SCI., 57:485-490, 2017. (c) 2017 Society of Plastics Engineers

1099. Mn2+ ions distribution in doped sol-gel deposited ZnO films

Authors: Stefan, M; Ghica, D; Nistor, SV; Maraloiu, AV; Plugaru, R

Published: FEB 28 2017, APPLIED SURFACE SCIENCE, 396, 1889, DOI: 10.1016/j.apsusc.2016.02.167

The localization and distribution of the Mn2+ ions in two sol-gel deposited ZnO films doped with different manganese concentrations were investigated by electron paramagnetic resonance spectroscopy and analytical transmission electron microscopy. In the lightly doped sample the Mn2+ ions are mainly localized substitutionally at isolated tetrahedrally coordinated Zn2+ sites in both crystalline ZnO nanograins (34%) and surrounding disordered ZnO (52%). In the highly doped ZnO film, a much smaller proportion of manganese substitutes Zn2+ in the crystalline and disordered ZnO (10%). The main amount (85%) of manganese aggregates in a secondary phase as an insular-like distribution between the ZnO nanograins. The remaining Mn2+ ions (14% and 5% at low and high doping levels, respectively) are localized at isolated, six-fold coordinated sites, very likely in the disordered intergrain region. Annealing at 600 degrees C induced changes in the Mn2+ ions distribution, reflecting the increase of the ZnO crystallization degree, better observed in the lightly doped sample. (C) 2016 Elsevier B.V. All rights reserved.

1100. Te-based chalcogenide materials for selector applications

Authors: Velea, A; Opsomer, K; Devulder, W; Dumortier, J; Fan, J; Detavernier, C; Jurczak, M; Govoreanu, B

Published: AUG 14 2017, SCIENTIFIC REPORTS, 7, DOI: 10.1038/s41598-017-08251-z

The implementation of dense, one-selector one-resistor (1S1R), resistive switching memory arrays, can be achieved with an appropriate selector for correct information storage and retrieval. Ovonic threshold switches (OTS) based on chalcogenide materials are a strong candidate, but their low thermal stability is one of the key factors that prevents rapid adoption by emerging resistive switching memory technologies. A previously developed map for phase change materials is expanded and improved for OTS materials. Selected materials from different areas of the map, belonging to binary Ge-Te and Si-Te systems, are explored. Several routes, including Si doping and reduction of Te amount, are used to increase the crystallization temperature. Selector devices, with areas as small as 55 x 55 nm(2), were electrically assessed. Sub-threshold conduction models, based on Poole-Frenkel conduction mechanism, are applied to fresh samples in order to extract as-processed material parameters, such as trap height and density of defects, tailoring of which could be an important element for designing a suitable OTS material. Finally, a glass transition temperature estimation model is applied to Te-based materials in order to predict materials that might have the required thermal stability. A lower average number of p-electrons is correlated with a good thermal stability.

1101. The exciton-phonon interaction as stimulated Raman scattering effect supported by the excitonic photoluminescence in BiI3 layered crystal structure

Authors: Nila, A; Matea, A; Baibarac, M; Baltog, I

Published: FEB 2017, JOURNAL OF LUMINESCENCE, 182, 171, DOI: 10.1016/j.jlumin.2016.10.028

Raman enhancement in a layered structure of Bib was studied under optical excitation near the edge of the fundamental absorption band. This phenomenon simultaneously appears at a low temperature with the generation of the excitonic photoluminescence (PL) band, unequally across the Raman spectrum, i.e. in the Stokes and anti-Stokes Raman branches, being dependent on the superposition of the excitation laser line to the excitonic emission band. Performed with the use of different resonant laser light excitations, this effect is regarded as a signature of the exciton-phonon interaction, which is interpreted in terms of a stimulated Raman scattering process (SRS), resulting from the mixing inside of the sample to two optical fields, the pump laser light and the excitonic PL light. (C) 2016 Elsevier B.V. All rights reserved.

1102. Strong light-matter coupling in the presence of lasing

Authors: Gies, C; Gericke, F; Gartner, P; Holzinger, S; Hopfmann, C; Heindel, T; Wolters, J; Schneider, C; Florian, M; Jahnke, F; Hofling, S; Kamp, M; Reitzenstein, S

Published: AUG 3 2017, PHYSICAL REVIEW A, 96, DOI: 10.1103/PhysRevA.96.023806

The regime of strong light-matter coupling is typically associated with weak excitation. With current realizations of cavity-QED systems, strong coupling may persevere even at elevated excitation levels sufficient to cross the threshold to lasing. In the presence of stimulated emission, the vacuum-Rabi doublet in the emission spectrum is modified and the established criterion for strong coupling no longer applies. We provide a generalized criterion for strong coupling and the corresponding emission spectrum, which includes the influence of higher Jaynes-Cummings states. The applicability is demonstrated in a theory-experiment comparison of a few-emitter quantum-dot-micropillar laser as a particular realization of the driven dissipative Jaynes-Cummings model. Furthermore, we address the question if and for which parameters true single-emitter lasing can be achieved and provide evidence for the coexistence of strong coupling and lasing in our system in the presence of background emitter contributions.

1103. Synthesis and up-conversion luminescence properties of BaFBr-Er3+ @SiO2 core/shell heterostructures

Authors: Secu, CE; Secu, M; Cernea, M

Published: AUG 2017, JOURNAL OF LUMINESCENCE, 188, 100, DOI: 10.1016/j.jlumin.2017.04.015

BaFBr:Er3+ @SiO2 core-shell composites were synthesized starting from BaFBr:Er3+ phosphor core grains (BaFBr doped with 1 at% Er3+) prepared by coprecipitation method. A sol-gel process was used to obtain the outer Si02 layer shell from silica sol precursor. The polycrystalline BaFBr:Er3+ @SiO2 heterostructures were formed following calcination at 700 degrees C, in air. The resulting material was characterized in terms of microstructure, photoluminescence and up-conversion luminescence properties. The results indicate that the as-obtained composite has a core-shell structure and shows good luminescence properties. The BaFBr:Er3+ @SiO2 heterostructure is made of BaFBr:Er3+ square sheets encased in a SiO2 shell layer with thickness values between 100 and 400 nm. Under 810 nm laser light pumping, the core-shell heterostructure exhibits Er3+ green up conversion luminescence bands ((H-2(11/2),S-4(3/2)) -> I-4(15/2)) at 525 and 545 nm, ascribed to a two-photon process.

1104. Thermal memory fading by heating to a lower temperature: Experimental data on polycrystalline NiFeGa ribbons and 2D statistical model predictions

Authors: Tolea, F; Tolea, M; Valeanu, M

Published: MAY 2017, SOLID STATE COMMUNICATIONS, 257, 41, DOI: 10.1016/j.ssc.2017.04.003

Shape memory alloys are known to memorise one -or several-temperatures at which the martensite-austenite transformation was stopped before completion in the past, the memory manifesting as specific dips in subsequent calorimetric scans. Previous studies have shown that this memory can be erased by heating to higher temperatures than the ones previously recorded. In this paper, we study a distinct memory fading effect which takes place by heating to a lower temperature. This effect is reported in NiFeGa as polycrystalline ribbons, the alloy being initially studied as bulk for which the thermal memory effect was not found. If, after an initial incomplete heating up to T-1 one performs a second incomplete heating up to T-2 < T-1, a new calorimetric dip appears at T-2, as expected, while less expected was that the dip corresponding to T-1 reduces in amplitude or even vanishes ( if the arrest at T-2 is repeated). The memory fading effect is more clear for small differences T-1-T-2 and less obvious or absent for large ones. The second part of the paper employs a statistical 2D model, which associates the memorized temperatures with a depletion of certain martensite plates sizes, and also supports the memory fading effect.

1105. Electronic band structure of the buried SiO2/SiC interface investigated by soft x-ray ARPES

Authors: Woerle, J; Bisti, F; Husanu, MA; Strocov, VN; Schneider, CW; Sigg, H; Gobrecht, J; Grossner, U; Camarda, M

Published: MAR 27 2017, APPLIED PHYSICS LETTERS, 110, DOI: 10.1063/1.4979102

The electronic structure of the SiO2/SiC (0001) interface, buried below SiO2 layers with a thickness from 2 to 4 nm, was explored using soft X-ray angle-resolved photoemission spectroscopy with photon energies between 350 and 1000 eV. The measurements have detected the characteristic k-dispersive energy bands of bulk Silicon Carbide (SiC) below the SiO2 layer without any sign of additional dispersive states, up to an estimated instrumental sensitivity of approximate to 5 x 10(9) cm 2 eV. This experimental result supports the physical picture that the large density of interface traps observed in macroscopic measurements results from dangling bonds randomized by the SiO2 rather than from Shockley-Tamm surface derived states extending into the bulk SiC. Published by AIP Publishing.

1106. Exciton-phonon interactions in the Cs3Bi2I9 crystal structure revealed by Raman spectroscopic studies

Authors: Nila, A; Baibarac, M; Matea, A; Mitran, R; Baltog, I

Published: APR 2017, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 254, DOI: 10.1002/pssb.201552805

The enhancement of the Raman scattering in Cs3Bi2I9 is evaluated by the ratio I-T/I-300K between the relative intensities of the Raman line peaked at 146cm(-1), when the spectra are recorded in the temperature range of 88-300K, as a signature of exciton-phonon interactions. In the resonant and nonresonant conditions, excitation wavelengths 476, 561, and 660nm, respectively, are used in order to overlap with great accuracy the bands disclosed by diffuse reflection, photoconductivity (PC), photoluminescence (PL), and photoluminescence excitation (PLE) spectra. Based on the experimental analyses, the strength of exciton-phonon interaction is dependent on the defects in the crystal and the type-range interaction of the excitations in an independent Bi2I93- cluster. The noticeable PL band, attributed to excitons trapped on different stacking faults, manifests some defects in crystal that diminish the movement of excitons. This effect significantly decreases the overlaps of excitons with the phonons, resulting in a reduced exciton-phonon coupling.

1107. Normal and Inverted Hysteresis in Perovskite Solar Cells

Authors: Nemnes, GA; Besleaga, C; Stancu, V; Dogaru, DE; Leonat, LN; Pintilie, L; Torfason, K; Ilkov, M; Manolescu, A; Pintilie, I

Published: JUN 1 2017, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 11214, DOI: 10.1021/acs.jpcc.7b04248

Hysteretic effects are investigated in perovskite solar cells in the standard FTO/TiO2/CH3NH3PbI3-xClx/spiro-OMeTAD/Au configuration. We report normal (NH) and inverted hysteresis (IH) in the J-V characteristics occurring for the same device structure, and the behavior strictly depends on the prepoling bias. NH typically appears at prepoling biases larger than the open circuit bias, while pronounced IH occurs for negative bias prepoling. The transition from NH to IH is marked by an intermediate mixed hysteresis behavior characterized by a crossing point in the J-V characteristics. The measured J-V characteristics are explained quantitatively by the dynamic electrical model. Furthermore, the influence of the bias scan rate on the NH/IH hysteresis is discussed based on the time evolution of the accumulated ionic and electronic polarization charge at the interfaces. Introducing a three-step measurement protocol, which includes stabilization, prepoling, and measurement, we put forward the difficulties and possible solutions for a correct photoconversion efficiency evaluation.

1108. Hydrothermal route to (FE, N) codoped titania photocatalysts with increased visible light activity

Authors: Diamandescu, L; Feder, M; Vasiliu, F; Tanase, L; Sobetkii, A; Dumitrescu, I; Teodorescu, M; Popescu, T

Published: 2017, INDUSTRIA TEXTILA, 68, 308, DOI: 10.35530/IT.068.04.1438

Iron and nitrogen doped TiO2 nanoparticles were synthesized and investigated with the aim to obtain photocatalytic systems with enhanced visible light efficiency. In a first step, commercially available Degussa P25 was impregnated with iron (0.3, 0.5, and 1 at. %) and nitrogen under hydrothermal conditions. In the second step, Fe-N doped TiO2 was synthesized by a hydrothermal route starting with TiCl3, FeCl3 center dot 6H(2)O and Urea, at 200 degrees C for 2 h. All samples were post annealed at 400 degrees C for 2h. The X-ray diffraction (XRD) revealed a two phase nanoscaled composition (Anatase and Rutile) of Degussa P25 and a single phase-nanoscaled Anatase content of the hydrothermally synthesized (1at.%) Fe-N doped TiO2 sample. The presence of Fe and nitrogen in samples was confirmed by Mossbauer and X-ray photoelectron spectroscopy measurements (XPS). Transmission electron microscopy (TEM) revealed the structure, particle dimension and morphology. The photocatalytic measurements (based on degradation of Methylene Blue) evidenced the most efficient composition in TiO2 Degussa P25 series as corresponding to 1 at.% Fe, in both UV and visible spectrum. At the same time, the hydrothermal synthesized sample (1at.%) Fe-N doped TiO2 exhibits the best activity in visible spectral region. The nanoscaled systems were synthesized in view of tests on textile materials.

1109. Origin and chemical composition of the amorphous material from the intergrain pores of self-assembled cubic ZnS:Mn nanocrystals

Authors: Stefan, M; Vlaicu, ID; Nistor, LC; Ghica, D; Nistor, SV

Published: DEC 31 2017, APPLIED SURFACE SCIENCE, 426, 350, DOI: 10.1016/j.apsusc.2017.07.172

We have shown in previous investigations that the low temperature collective magnetism observed in mesoporous cubic ZnS:Mn nanocrystalline powders prepared by colloidal synthesis, with nominal doping concentrations above 0.2 at.%, is due to the formation of Mn2+ clusters with distributed antifer romagnetic coupling localized in an amorphous phase found between the cubic ZnS:Mn nanocrystals. Here we investigate the composition, origin and thermal annealing behavior of this amorphous phase in such a mesoporous ZnS:Mn sample doped with 5 at.% Mn nominal concentration. Correlated analytical transmission electron microscopy, multifrequency electron paramagnetic resonance and Fourier transform infrared spectroscopy data show that the amorphous nanomaterial consists of unreacted precursor hydrated zinc and manganese acetates trapped inside the pores and on the surface of the cubic ZnS nanocrystals. The decomposition of the acetates under isochronal annealing up to 270 degrees C, where the mesoporous structure is still preserved, lead to changes in the nature and strength of the magnetic inter actions between the aggregated Mn2+ ions. These results strongly suggest the possibility to modulate the magnetic properties of such transition metal ions doped II-VI mesoporous structures by varying the synthesis conditions and/or by post-synthesis thermochemical treatments. (C) 2017 Elsevier B.V. All rights reserved.

1110. Optical properties of Sm3+ doped Ca-3(Nb,Ga)(5)O-12 and Ca-3(Li,Nb,Ga)(5)O-12 single crystals

Authors: Gheorghe, C; Hau, S; Gheorghe, L; Voicu, F; Greculeasa, M; Achim, A; Enculescu, M

Published: JUN 2017, JOURNAL OF LUMINESCENCE, 186, 182, DOI: 10.1016/j.jlumin.2017.02.036

Sm3+ doped partially disordered calcium-niobium-gallium -garnet (CNGG) and calcium-lithium-niobium-gallium -garnet (CLNGG) single crystals were grown by the Czochralski method. Spectroscopic characteristics of Sm:CNGG and Sm:CLNGG single crystals were obtained by high-resolution absorption and emission spectra and emission dynamics measurements. Partial energy levels of Sm3+ doped CNGG and CLNGG were extracted from the measured spectra. The Judd-Ofelt theory has been applied to evaluate the Omega(t)(t=2,4, 6) intensity parameters, radiative transition rates A(r) branching ratios beta, and radiative lifetime tau(r), of the fluorescent Sm3+ (4)G(5/2) level. The emission cross-sections for the (4)G(5/2)-> H-6(J) (J=5/2, 7/2, 9/2) transitions of special interest for visible laser application were obtained by the Fucht-bauer - Ladenburg equation. The interaction between Sm3+ ions is dipole-dipole type and the C-DA, microparameter for both crystals was calculated based on Inokuti-Hirayama model. (C) 2017 Elsevier B.V. All rights reserved.

1111. Electric-Field-Driven Direct Desulfurization

Authors: Borca, B; Michnowicz, T; Petuya, R; Pristl, M; Schendel, V; Pentegov, I; Kraft, U; Klauk, H; Wahl, P; Gutzler, R; Arnau, A; Schlickum, U; Kern, K

Published: MAY 2017, ACS NANO, 11, 4709, DOI: 10.1021/acsnano.7b00612

The ability to elucidate the elementary steps of a chemical reaction at the atomic scale is important for the detailed understanding of the processes involved, which is key to uncover avenues for improved reaction paths. Here, we track the chemical pathway of an irreversible direct desulfurization reaction of tetracenothiophene adsorbed on the Cu(111) closed-packed surface at the submolecular level. Using the precise control of the tip position in a scanning tunneling microscope and the electric field applied across the tunnel junction, the two carbon-sulfur bonds of a thiophene unit are successively cleaved. Comparison of spatially mapped molecular states close to the Fermi level of the metallic substrate acquired at each reaction step with density functional theory calculations reveals the two elementary steps of this reaction mechanism. The first reaction step is activated by an electric field larger than 2 V nm(-1), practically in absence of tunneling electrons, opening the thiophene ring and leading to a transient intermediate. Subsequently, at the same threshold electric field and with simultaneous injection of electrons into the molecule, the exergonic detachment of the sulfur atom is triggered. Thus, a stable molecule with a bifurcated end is obtained, which is covalently bound to the metallic surface. The sulfur atom is expelled from the vicinity of the molecule.

1112. Up-conversion luminescence of Er(Yb)-CeO2: Status and new results

Authors: Porosnicu, I; Avram, D; Cojocaru, B; Florea, M; Tiseanu, C

Published: JUL 15 2017, JOURNAL OF ALLOYS AND COMPOUNDS, 711, 636, DOI: 10.1016/j.jallcom.2017.04.043

We investigate the down- and up-conversion properties of Er (0.3, 1 and 3%)-CeO2 and Er(1%)Yb(20%)-CeO2 nanoparticles by use of ns pulsed monochromatic excitation. The emission spectra were recorded in the visible to near-infrared range (500-1100 nm) under ultraviolet, visible (490 and 650 nm) and near infrared (790, 971/977 and 1470 nm) up-conversion excitations as well as X-ray excitation. The structural properties were characterized by X-ray diffraction, Raman, Diffuse Reflectance UV/Vis and Diffuse Reflectance Fourier Transform Infrared spectroscopies. The role of CeO2 charge transfer band as a level selective antenna sensitizer, the dopant induced oxygen vacancies and the effect of Er concentration on the overall emission properties are highlighted. The mechanisms involved in the up-conversion emission in Er-CeO2 and Er,Yb-CeO2 are analysed in terms of up-conversion excitation spectra, up-conversion emission decays and evolution of the red to green emission ratio with Er concentration and delay after the laser pulse. Our findings are also discussed in the context of a comprehensive literature survey regarding the actual stage of research on the luminescence of Er and Er,Yb doped CeO2 and their possible applications. (C) 2017 Elsevier B.V. All rights reserved.

1113. Laser processing of Yb3+/Er3+ co-doped LiYF4 thin films with up-conversion properties

Authors: Secu, CE; Secu, M; Stokker-Cheregi, F; Ion, V; Brajnicov, S; Dinescu, M

Published: MAR 1 2017, THIN SOLID FILMS, 625, 10, DOI: 10.1016/j.tsf.2017.01.057

We present a comparative study between the properties of Yb3+/Er3+ co-doped LiYF4 thin films obtained by pulsed laser deposition (PLD) and matrix-assisted pulsed evaporation (MAPLE) growth techniques, respectively. We performed structural, morphological, and optical analyses in order to draw a conclusion about the potential of MAPLE as a growth technique used for the obtaining of RE-doped fluoride thin films having up-conversion properties. For both techniques the surface morphology is typical for laser processed thin films of RE-doped fluorides, with roughness values of the order of few hundreds of nanometers and a higher density of defects in the sample obtained by MAPLE. Up-conversion properties do not exhibit major differences between the thin film samples and the pressed target. Under 980 nm laser light pumping, both Yb3+/Er3+ co-doped LiYF4 thin film samples, obtained by PLD and MAPLE, show green ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and red (F-4(9/2) -> I-4(15/2)) up-conversion luminescence explained by a two-photon processes. Therefore MAPLE is a viable growth technique for the fundamental study of RE-doped fluoride thin films and their respective functional properties. (C) 2017 Elsevier B.V. All rights reserved.

1114. Structural, morphological, ferromagnetic and photoluminescence properties of Fe-doped ZnO, prepared by hydrothermal route

Authors: Cernea, M; Mihalache, V; Secu, EC; Trusca, R; Bercu, V; Diamandescu, L

Published: APR 2017, SUPERLATTICES AND MICROSTRUCTURES, 104, 373, DOI: 10.1016/j.spmi.2017.02.048

Fe doped ZnO particles of flower-like shape, hexagonal prisms and hybrid structures flower-prisms have been synthesized by hydrothermal technique, and their luminescence and magnetic properties have been investigated as a function of the morphology changes due to iron dopant (0-0.03 at.% Fe3+). The X-ray diffractograms of Zn1-xFexO powders indicated a hexagonal wurtzite polycrystalline structure. SEM images reveal the change of Zn1-xFexO grains shape from flower-like to hexagonal prisms as the Fe concentration (x) increases from 0 to 3 at.% Fe. Undoped ZnO shown weak room temperatures ferromagnetism, with high coercivity (H-c = 107 Oe) and saturation magnetization M-s of 1.5-10(-3) emu/g. ZnO doped with 1 and 3 at.% Fe presented a significant increase of the magnetization in comparison with the undoped ZnO. For ZnO doped with 3 at.% Fe, Ms = 32.5-10(-3) emu/g and M-rem = 0.78-10(-3) emu/g. Compared with other reports on magnetic properties of undoped and Fe doped ZnO, these results indicated higher coercivity and smaller magnetizations. The drop in the intensity of characteristic green-yellow photoluminescence band of ZnO at about 550-600 nm was attributed to the decrease of the number of oxygen vacancies and interstitial oxygen. By increasing the Fe concentration, the electron paramagnetic resonance (EPR) signal of undoped ZnO decreases due to the decrease of defects concentration. (C) 2017 Elsevier Ltd. All rights reserved.

1115. Specific Changes in the Magnetoresistance of Ni-Fe-Ga Heusler Alloys Induced by Cu, Co, and Al Substitutions

Authors: Tolea, F; Tolea, M; Sofronie, M; Popescu, B; Crisan, A; Leca, A; Valeanu, M

Published: APR 2017, IEEE TRANSACTIONS ON MAGNETICS, 53, DOI: 10.1109/TMAG.2016.2628386

In this paper, we investigate the influence of Cu, Co, and Al substitutions on the transport properties, and in particular, the magnetoresistive effect in Ni-Fe-Ga ferromagnetic shape memory alloys (FSMAs) prepared as ribbons by melt spinning method and subjected to different thermal treatments. X-ray diffraction, differential scanning calorimetry, magnetometry, and magnetoresistive characterizations were performed. In the range of the martensitic transformation (MT), different FSMA compositions show a rich spectrum of different behaviors. For one of the compositions (Ni52Fe20Co2Ga23Al3), the magnetoresistance (MR) showed a local minimum or, on the contrary, a local maxima of reduced amplitude on cooling, in the range of the MT, depending on the performed thermal treatments. In the same composition, by replacing one Al atom with a Co one, no local extremes are seen, the alloy having a concomitant magneto-structural transition. When the magnetic field was varied, the MR showed a nonmonotonic variation in the martensite phase for some compounds, possibly due to the dynamics of the martensite variants realignment. From the studied compositions, the highest MR found on the MT of -9% for 5 T is for Ni50Fe20Ga27Cu3.

1116. Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators

Authors: Krieger, JA; Chang, CZ; Husanu, MA; Sostina, D; Ernst, A; Otrokov, MM; Prokscha, T; Schmitt, T; Suter, A; Vergniory, MG; Chulkov, EV; Moodera, JS; Strocov, VN; Salman, Z

Published: NOV 2 2017, PHYSICAL REVIEW B, 96, DOI: 10.1103/PhysRevB.96.184402

We combine low energy muon spin rotation (LE-mu SR) and soft-x-ray angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and electronic properties of magnetically doped topological insulators, (Bi, Sb)(2)Te-3. We find that one achieves a full magnetic volume fraction in samples of (V/Cr)(x)(Bi, Sb)(2-x)Te-3 at doping levels x greater than or similar to 0.16. The observed magnetic transition is not sharp in temperature indicating a gradual magnetic ordering. We find that the evolution of magnetic ordering is consistent with formation of ferromagnetic islands which increase in number and/or volume with decreasing temperature. Resonant ARPES at the V L-3 edge reveals a nondispersing impurity band close to the Fermi level as well as V weight integrated into the host band structure. Calculations within the coherent potential approximation of the V contribution to the spectral function confirm that this impurity band is caused by V in substitutional sites. The implications of our results on the observation of the quantum anomalous Hall effect at mK temperatures are discussed.

1117. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

Authors: Xu, SY; Alidoust, N; Chang, GQ; Lu, H; Singh, B; Belopolski, I; Sanchez, DS; Zhang, X; Bian, G; Zheng, H; Husanu, MA; Bian, Y; Huang, SM; Hsu, CH; Chang, TR; Jeng, HT; Bansil, A; Neupert, T; Strocov, VN; Lin, H; Jia, SA; Hasan, MZ

Published: JUN 2017, SCIENCE ADVANCES, 3, DOI: 10.1126/sciadv.1603266

In quantum field theory, Weyl fermions are relativistic particles that travel at the speed of light and strictly obey the celebrated Lorentz symmetry. Their low-energy condensed matter analogs are Weyl semimetals, which are conductors whose electronic excitations mimic the Weyl fermion equation of motion. Although the traditional (type I) emergent Weyl fermions observed in TaAs still approximately respect Lorentz symmetry, recently, the so-called type II Weyl semimetal has been proposed, where the emergent Weyl quasiparticles break the Lorentz symmetry so strongly that they cannot be smoothly connected to Lorentz symmetric Weyl particles. Despite some evidence of nontrivial surface states, the direct observation of the type II bulk Weyl fermions remains elusive. We present the direct observation of the type II Weyl fermions in crystalline solid lanthanum aluminum germanide (LaAlGe) based on our photoemission data alone, without reliance on band structure calculations. Moreover, our systematic data agree with the theoretical calculations, providing further support on our experimental results.

1118. Cu-based composites as thermal barrier materials in DEMO divertor components

Authors: Galatanu, M; Enculescu, M; Ruiu, G; Popescu, B; Galatanu, A

Published: NOV 2017, FUSION ENGINEERING AND DESIGN, 124, 1134, DOI: 10.1016/j.fusengdes.2017.02.031

For DEMO fusion reactor an expected heat flux of about 10MW/m(2) should be extracted by the divertor which will have, most likely, an armour part made of W and a following heat sink part made of Cu, or ODS Cu alloy. Unfortunately, for these materials the optimum operating temperature windows do not overlap. Thermal barrier materials are interface materials included in such components, aiming to keep the temperatures of both armour and heat sink parts in the corresponding operating windows, and to mitigate the effects of their different thermomechanical properties. Here we propose a simple spark plasma sintering route to create Cu-based composites with a high content (10-40 vol%) of various dispersed materials (Al or Y oxides, C, SiC), allowing a fine tuning of the content and a large pool of predefined shapes and dimensions. The resulting specimens can be further joined to armour and heatsink components via a similar electrical field assisted technology. Micro-structural and thermal properties are investigated for these materials allowing to select the most suited materials in view of their thermal conductivity and thermal expansion coefficients. (C) 2017 The Authors. Published by Elsevier B.V.

1119. Synthesis, physicochemical characterization and cytotoxic properties of riboflavin loaded Myrj52-silver nanoparticles

Authors: Voicescu, M; Ionescu, S; Craciunescu, O; Tatia, R; Moldovan, L; Teodorescu, VS; Nistor, CL

Published: JUL 7 2017, NEW JOURNAL OF CHEMISTRY, 41, 5541, DOI: 10.1039/c7nj00571g

The synthesis and physicochemical characterization of riboflavin (RF) loaded Myrj52-silver nanoparticles (SNPs) were performed and their cytotoxic properties were evaluated. Transmission electron microscopy analysis showed the formation of colloidal spherical SNPs with an average size of similar to 12 nm. The structure, stability, dynamics and conformation of human serum albumin (HSA) binding RF on SNPs have been studied. The influence of RF on the secondary structure of HSA in the presence of SNPs showed a predominant alpha-helix structure (61.7%). No changes induced by RF binding to HSA were observed. The cytotoxicity of RF and RF-HSA loaded Myrj52-SNPs was evaluated in vitro using the Neutral Red assay and cell morphology observations in a culture of L929 fibroblast cells. The results have relevance with regard to the RF loaded Myrj52-SNP formulation for pharmaceuticals.

1120. Lipoic Acid Gold Nanoparticles Functionalized with Organic Compounds as Bioactive Materials

Authors: Turcu, I; Zarafu, I; Popa, M; Chifiriuc, MC; Bleotu, C; Culita, D; Ghica, C; Ionita, P

Published: FEB 2017, NANOMATERIALS, 7, DOI: 10.3390/nano7020043

Water soluble gold nanoparticles protected by lipoic acid were obtained and further functionalized by standard coupling reaction with 1-naphtylamine, 4-aminoantipyrine, and 4 0 -aminobenzo-15-crown-5 ether. Derivatives of lipoic acid with 1-naphtylamine, 4-aminoantipyrine, and 4 0 -aminobenzo-15-crown-5 ether were also obtained and characterized. All these were tested for their antimicrobial activity, as well as for their influence on mammalian cell viability and cellular cycle. In all cases a decreased antimicrobial activity of the obtained bioactive nanoparticles was observed as compared with the organic compounds, proving that a possible inactivation of the bioactive groups could occur during functionalization. However, both the gold nanoparticles as well as the functionalized bioactive nanosystems proved to be biocompatible at concentrations lower than 50 mu g/mL, as revealed by the cellular viability and cell cycle assay, demonstrating their potential for the development of novel antimicrobial agents.

1121. Structure, Magnetic Properties and Hyperfine Parameters of Nd-Substituted Ni-Fe-Ga Heusler Alloys

Authors: Sorescu, M; Tolea, F; Valeanu, M; Sofronie, M

Published: 2017, MRS ADVANCES, 2, 1346, DOI: 10.1557/adv.2017.70

Samples of Ni57-xNdxFe18Ga25 with x=2 and 4 were prepared in ribbon form by rapid quenching via melt spinning route. The samples were analyzed by X-ray diffraction (XRD), magnetic measurements and Mossbauer spectroscopy, both in the as-quenched form and after thermal annealing at 900 degrees C for 2 min and 400 degrees C for 2 hours. For x=2 the Nd atoms are completely dissolved in the Ni-Fe-Ga matrix, while for x=4 the additional occurrence of the secondary 2:17 phase could be resolved. These findings were supported by the analysis of hyperfine magnetic field distributions obtained from the non-linear least-squares fitting of the Mossbauer spectra.

1122. New ways to use the red mud waste as raw material for inorganic-organic hybrid hydrogels

Authors: Sandu, T; Sarbu, A; Zavoianu, R; Spatarelu, CP; Florea, M; Bradu, C; Mara, EL; Dragut, DV; Alexandrescu, E; Zaharia, A; Radu, AL

Published: DEC 10 2017, , DOI: 10.1016/j.minpro.2017.11.005

1123. Lead acetate film as precursor for two-step deposition of CH3NH3PbI3

Authors: Sima, M; Vasile, E; Sima, M

Published: MAY 2017, MATERIALS RESEARCH BULLETIN, 89, 96, DOI: 10.1016/j.materresbull.2017.01.031

This paper relates to a method for the preparation of lead acetate film and its use as precursor for twostep solution deposition of CH3NH3PbI3 perovskite film. For the preparation of perovskite film, lead acetate was used both in the form of trihydrate and dehydrated. The effects of lead acetate trihydrate dehydration on the structure of the resulted perovskite films were studied. The prepared perovskite films which consist of cuboid grains, show high surface coverage both on FTO and TiO2 substrates. XRD measurements have not revealed the presence of the PbI2 contaminant in perovskite film. Solvent vapor annealing method was employed to prepare perovskite film that contains lead iodide. Using impedance spectroscopy measurements, we further evaluated the influence of the prepared perovskite films on the performance of the photovoltaic devices. (C) 2017 Elsevier Ltd. All rights reserved.

1124. Self-assembled (Ni/Cu, Ti)-YSZ with potential applications for IT-SOFCs: Catalytic and electrochemical assessment

Authors: Somacescu, S; Navarrete, L; Florea, M; Calderon-Moreno, JM; Serra, JM

Published: JAN 5 2017, , DOI: 10.1016/j.jallcom.2016.08.193

1125. Intermediate selectivity in the oxidation of phenols using plasmonic Au/ZnO photocatalysts

Authors: Lin, F; Cojocaru, BE; Williams, LS; Cadigan, CA; Tian, CX; Grecu, MN; Xin, HL; Vyas, S; Parvulescu, VI; Richards, RM

Published: JUL 21 2017, NANOSCALE, 9, 9364, DOI: 10.1039/c7nr03868b

Tunable reaction selectivity on a single catalyst is a continual goal in chemical syntheses. Herein, we report an unexpected light-directed intermediate selectivity using well-known plasmonic photocatalysts. We observed distinct intermediate selectivity behaviors between using UV and visible light irradiations. Chemical computations and quenching experiments suggest that the radicals generated by the plasmonic excitation govern the light-directed selectivity. The broader impact of this work ranges from selective yield of desirable intermediates for subsequent syntheses without tedious separation procedures, to arousing interest in examining new opportunities for plasmonic photocatalysts.

1126. Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

Authors: Popescu-Pelin, G; Sima, F; Sima, LE; Mihailescu, CN; Luculescu, C; Iordache, I; Socol, M; Socol, G; Mihailescu, IN

Published: OCT 1 2017, APPLIED SURFACE SCIENCE, 418, 588, DOI: 10.1016/j.apsusc.2016.10.043

Pulsed Laser Deposition (PLD) and Matrix Assisted Pulsed Laser Evaporation (MAPLE) techniques were applied for growing hydroxyapatite (HA) thin films on titanium substrates. All experiments were conducted in a reaction chamber using a KrP* excimer laser source (lambda = 248 nm, TEWHM approximate to 25 ns). Half of the samples were post-deposition thermally treated at 500 degrees C in a flux of water vapours in order to restore crystallinity and improve adherence. Coating surface morphologies and topographies specific to the deposition method were evidenced by scanning electron, atomic force microscopy investigations and profilometry. They were shown to depend on deposition technique and also on the post-deposition treatment. Crystalline structure of the coatings evaluated by X-ray diffraction was improved after thermal treatment. Biocompatibility of coatings, cellular adhesion, proliferation and differentiation tests were conducted using human mesenchymal stem cells (MSCs). Results showed that annealed MAPLE deposited HA coatings were supporting MSCs proliferation, while annealed PLD obtained films were stimulating osteogenic differentiation. (C) 2016 Elsevier B.V. All rights reserved.

1127. CHARACTERIZATION OF CdS-DOPED GLASS FILMS OBTAINED BY PULSED LASER DEPOSITION

Authors: Iordanescu, CR; Elisa, M; Epurescu, G; Filipescu, M; Enculescu, M; Monteiro, RCC; Constantin, L

Published: 2017, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 47, 65, DOI:

In the present work we study the optical, struc-tural and morphological properties of CdS-doped glass films, deposited by Pulsed Laser Deposition (PLD) method. The glass target used for ablation was prepared by conventional melt-quenching technique and the semiconductor dopant, CdS powder, was embedded in the borosilicate melt glass host by continuous stirring. In order to improve the properties of the films, the laser wavelength was modified. Photoluminescence emission (PL) of CdSdoped glass films revealed a broad band located in the visible range. The structural analysis was carried out by micro-Raman spectroscopy, pointing out specific vibration modes for Si-O-Si bonds as well as for CdS dopant. The morphology and the chemical characterization of the films were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM).

1128. Antimicrobial polycaprolactone/polyethylene glycol embedded lysozyme coatings of Ti implants for osteoblast functional properties in tissue engineering

Authors: Visan, A; Cristescu, R; Stefan, N; Miroiu, M; Nita, C; Socol, M; Florica, C; Rasoga, O; Zgura, I; Sima, LE; Chiritoiu, M; Chifiriuc, MC; Holban, AM; Mihailescu, IN; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 243, DOI: 10.1016/j.apsusc.2016.11.129

In this study, coatings based on lysozyme embedded into a matrix of polyethylene glycol (PEG) and polycaprolactone (PCL) were fabricated by two different methods (Matrix Assisted Pulsed Laser Evaporation -MAPLE and Dip Coating) for obtaining antimicrobial coatings envisaged for long term medical applications. Coatings with different PEG: PCL compositions (3: 1; 1: 1; 1: 3) were synthesized in order to evaluate the antimicrobial activity of lysozyme embedded into the polymeric matrix. The main surface features, such as roughness and wettability, with impact on the microbial adhesion as well as on the eukaryote cell function were measured. The obtained composite coatings exhibited a significant antibacterial activity against Escherichia coli, Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus strains. As well, specific blended coatings showed appropriate viability, good spreading and normal cell morphology of SaOs2 human osteoblasts and mesenchymal stem cells (MSCs). These investigations highlight the suitability of biodegradable composites as implant coatings for decreasing the risk of bacterial contamination associated with prosthetic procedures. (C) 2016 Elsevier B.V. All rights reserved.

1129. Isotactic polypropylene-vapor grown carbon nanofibers composites: Electrical properties

Authors: Aldica, GV; Ciurea, ML; Chipara, DM; Lepadatu, AM; Lozano, K; Stavarache, I; Popa, S; Chipara, M

Published: OCT 10 2017, JOURNAL OF APPLIED POLYMER SCIENCE, 134, DOI: 10.1002/APP.45297

Nanocomposites have been obtained by dispersing various amounts of vapor grown carbon nanofibers within isotactic polypropylene. Thermal investigations done by differential scanning calorimetry and dynamic mechanical analysis revealed the effect of the vapor grown carbon nanofibers on the melting, crystallization, alpha, and beta relaxations. Direct current electrical features of these nanocomposites have been investigated and related to the thermal features of these nanocomposites. The effect of the loading with carbon nanofibers on the electrical properties of these nanocomposites is discussed within the percolation theory. The percolation threshold was estimated at about 5.5% wt carbon nanofibers. The temperature dependence of the direct current conductivity is analyzed in detail and it is concluded that the electronic hopping is the dominant transport mechanism. A transition from one-dimensional hopping towards a three-dimensional hopping was noticed as the concentration of carbon nanofibers was increased from 10% wt to 20% wt carbon nano-fiber. The possibility of a differential negative resistivity is suggested. (C) 2017 Wiley Periodicals, Inc.

1130. ONE SIDE POLYANILINE COATED FIBERS BASED ACTUATOR

Authors: Beregoi, M; Evanghelidis, A; Ganea, P; Iovu, H; Matei, E; Enculescu, I

Published: 2017, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 79, 130, DOI:

In this study, one side aligned PANI coated micro-fibers were fabricated in order to develop a novel actuator configuration. Thus, electrospun PMMA fibers were coated only on one side with a thin gold layer guiding in this way the deposition of PANI (only on the side with gold considering an adequate PANI deposition time). Further, the half-metalized fibers were employed as working microelectrodes for electrochemical deposition of PANI. The prepared PANI coated fibers present actuation properties when they are in contact with an electrolyte like 1 M H2SO4. By switching the potential between +1.4 and -0.2 V, the fiber strips move due to the swelling/shrinking and anisotropic deposition of PANI film.

1131. MAPLE prepared heterostructures with oligoazomethine: Fullerene derivative mixed layer for photovoltaic applications

Authors: Stanculescu, A; Rasoga, O; Socol, M; Vacareanu, L; Grigoras, M; Socol, G; Stanculescu, F; Breazu, C; Matei, E; Preda, N; Girtan, M

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 195, DOI: 10.1016/j.apsusc.2017.03.053

Mixed layers of azomethine oligomers containing 2,5-diamino-3,4-dicyanothiophene as central unit and triphenylamine (LV5) or carbazol (LV4) at both ends as donor and fullerene derivative, [6,6]-phenylC61 butyric acid butyl ester ([C60] PCB-C4) as acceptor, have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) on glass/ITO and Si substrates. The effect of weight ratio between donor and acceptor (1: 1; 1: 2) and solvent type (chloroform, dimethylsulphoxide) on the optical (UV-vis transmission/absorption, photoluminescence) and morphological properties of LV4 (LV5): [C60] PCB-C4 mixed layers has been evidenced. Dark and under illumination I-V characteristics of the heterostructures realized with these mixed layers sandwiched between ITO and Al electrodes have revealed a solar cell behavior for the heterostructures prepared with both LV4 and LV5 using chloroform as matrix solvent. The solar cell structure realized with oligomer LV5, glass/ITO/LV5: [C60] PCB-C4 (1: 1) has shown the best parameters. (C) 2017 Elsevier B.V. All rights reserved.

1132. Crystallization kinetics mechanism investigation of sol-gel-derived NaYF4:(Yb,Er) up-converting phosphors

Authors: Bartha, C; Secu, CE; Matei, E; Secu, M

Published: SEP 14 2017, CRYSTENGCOMM, 19, 5000, DOI: 10.1039/c7ce01265a

The crystallization mechanism of sol-gel-derived NaYF4:(Yb, Er) up-converting phosphors has been studied by differential scanning calorimetry analysis using both model-free and model fitting approaches. Structural and optical data have shown that the hexagonal NaYF4:(Yb, Er) phase crystallization process occurs at around 315 degrees C as a result of the thermal decomposition of the metal trifluoroacetates. As the annealing temperature increases, sphere-like microcrystals of about 1-2 mu m size (at 300 degrees C) break up into smaller ones (400-500 nm size) and finally collapse at higher temperatures (600 degrees C); the up-conversion luminescence signal intensity increases due to the crystallinity improvement and dehydration process. The crystallization process can be described as an autocatalytic-type reaction where the accompanying cubic NaYF4 phase played a catalytic role by reducing the energy barrier against the crystallization of the hexagonal NaYF4 phase, causing its fast self-accelerated crystallization. The energy resulting from the disintegration process of the initial NaYF4 microcrystals contributed to the growth and agglomeration processes and finally the collapse of the crystalline fragments with increasing temperature.

1133. Structural and Antimicrobial Evaluation of Silver Doped Hydroxyapatite- Polydimethylsiloxane Thin Layers

Authors: Iconaru, SL; Chifiriuc, MC; Groza, A

Published: 2017, JOURNAL OF NANOMATERIALS, 2017, DOI: 10.1155/2017/7492515

An Ag:HAp (x(Ag) = 0.5) powder was deposited by thermal evaporation technique as coating on a silicon substrate previously covered with a polydimethylsiloxane (PDMS) layer. The Ag: HAp-PDMS layers were characterized by Scanning ElectronMicroscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FT-IR). By infrared spectroscopy analysis, the phase composition of the Ag: HAp-PDMS layers was investigated. The antimicrobial activity of Ag: HAp-PDMS layers was tested against Escherichia coli, Staphylococcus aureus, and Candida albicans microbial strains. The microbial activity decreases significantly for the surveyed time intervals on Ag: HAp-PDMS layers.

1134. Light illumination effects on floating gate memory with Ge nanocrystals in HfO2

Authors: Palade, C; Slav, A; Lepadatu, AM; Lazanu, S; Ciurea, ML; Stoica, T

Published: 2017, 2017 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 40TH EDITION, 90, DOI:

The influence of light illumination on the programming of a capacitor floating gate memory based on Ge nanocrystals in HfO2 was studied. The capacitor was fabricated on a c-Si substrate by magnetron sputtering deposition of a layer sequence of HfO2/Ge-HfO2/HfO2 and post-growth rapid thermal annealing for nanocrystals formation at 600 degrees C. The illumination of the structure was performed through a semi-transparent Au contact (20% transparency). A maximum value of the light- induced change of 90% in C-V curve was obtained for 5 mW/cm(2) illumination during +5 V writing programming. The effect of the light exposure on the relative change of the C-V curve can be increased by reducing the writing time at 1 min.

1135. WETTABILITY BY WATER CONTACT ANGLE UPON THE SURFACE OF WOOL FABRICS COVERED WITH OXIDE NANOPARTICLES

Authors: Birzu, M; Frunza, L; Zgura, I; Cotorobai, VF; Ganea, CP; Preda, N; Enculescu, M

Published: JUL-SEP 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 931, DOI:

Wetting properties of wool textiles were studied either for the raw samples or for those functionalized via covering them at low temperature with nanoparticles of titanium dioxide or zinc oxide. Oxygen plasma pretreatment was performed before deposition. Characterization used optical examination, scanning electron microscopy, infrared spectroscopy, thermogravimetry, X-ray diffraction. Wetting properties were tested under static conditions by estimating the water contact angle. The sessile drop method was applied. The deposited matter represents 3 to 8 wt%, covering rather uniformly the fiber surface. Treated samples show mostly lower values of contact angle than the pristine ones. Cassie-Baxter model is discussed in relation to the equilibrium contact angle of the support.

1136. Magnetocapacitance in La0.7Sr0.3MnO3/Pb(Zr0.2Ti0.8)O-3/La0.7Sr0.3MnO3 multiferroic heterostructures

Authors: Hrib, LM; Pintilie, L; Alexe, M

Published: JUL 26 2017, SCIENTIFIC REPORTS, 7, DOI: 10.1038/s41598-017-06487-3

Measurements of the magnetocapacitance effect in epitaxial La0.7Sr0.3MnO3/Pb(Zr0.2Ti0.8)O-3/La0.7Sr0.3MnO3 heterostructures have been performed using a quasi-static method. Through capacitance-voltage measurements carried out under variable magnetic field it has been found that the magneto-capacitance depends on the orientation of the ferroelectric polarization. The value of magneto-capacitance can be as high as 1% in the voltage range near the ferroelectric coercive field. This has been attributed to a variation of the apparent built-in voltage of the PZT-LSMO Schottky barriers on applied magnetic field.

1137. Influence of single-walled carbon nanotubes enriched in semiconducting and metallic tubes on the electropolymerization of tetrabromo ortho-xylene: Insights on the synthesis mechanism of poly(ortho-phenylenevinylene)

Authors: Baibarac, M; Nila, A; Baltog, I; Lefrant, S; Mevellec, JY; Quillard, S; Humbert, B

Published: MAR 2017, EUROPEAN POLYMER JOURNAL, 88, 125, DOI: 10.1016/j.eurpolymj.2017.01.015

New composite materials based on single-walled carbon nanotubes effectively separated into semiconducting (S-SWNTs) and metallic tubes (M-SWNTs) and poly(ortho-phenylenevinylene) (POPV) were synthesized by the electrochemical polymerization of the alpha,alpha,alpha',alpha',-tetrabromo-o-xylene monomer onto the surface of Au supports covered with carbon nanotubes films. Using FTIR spectroscopy, an increase of the quinoid structure weight is highlighted when a charge transfer is induced to take place between the two constituents of the POPV/S-SWNT composite material. In addition, a down-shift of the Raman line belonging to POPV (from 530 cm-(1) to 515 cm(-1)), which was accoinpanied by an increase in relative peak intensity, is reported as a result of steric hindrance effects induced by the covalent bonding of POPV onto the S-SWNT surface. The non-covalent functionalization of M-SWNTs with POPV is demonstrated to occur by Raman scattering and FTIR spectroscopy. The photoluminescence (PL) spectrum of POPV exhibits two bands at 2.82 and 2.25 eV, which were assigned to the electronic emission transitions of macromolecular chains having 3 and 7-10 repeating units, respectively. We demonstrate that POPV photoluminescence quenching in the presence of M + S-SWNTs, M-SWNTs and S-SWNTs is achieved by tubes with chirality (14,7), (12,10) and (11,9), respectively. (C) 2017 Elsevier Ltd. All rights reserved.

1138. MEASUREMENT OF CHARGE CARRIER MOBILITY IN PEROVSKITE NANOWIRE FILMS BY PHOTO-CELIV METHOD

Authors: Aukstuolis, A; Girtan, M; Mousdis, GA; Mallet, R; Socol, M; Rasheed, M; Stanculescu, A

Published: JAN-MAR 2017, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 18, 41, DOI:

In this paper the holes' mobility for the configuration FTO/TiO2/CH3NH3PbI3/SpiroMeOTAD/Au was measured for the first time by the Photo-CELIV method. The TiO2 dense film was deposited by reactive sputtering at room temperature on FTO glass substrates. High crystalized perovskite films were deposited from solutions in one step by spin coating. Spiro-MeOTAD molecular glass was used as holes transporting layer. The highest holes' mobility from TiO2 thin film through the perovskite and Spiro MeOTAD film to the top gold electrode was of Order 8.5x10(-7) cm(2)/Vs.

1139. Oxygenophilic ionic liquids promote the oxygen reduction reaction in Pt-free carbon electrocatalysts

Authors: Qiao, M; Tang, C; Tanase, LC; Teodorescu, CM; Chen, CM; Zhang, Q; Titirici, MM

Published: SEP 1 2017, MATERIALS HORIZONS, 4, 899, DOI: 10.1039/c7mh00298j

We propose a novel idea to improve the surface properties of carbon-based Pt-free electrocatalysts in Polymer Electrolyte Membranes (PEMs) and Alkaline Fuel Cells (AFCs). Our concept is based on the addition of oxygenophilic and hydrophobic ionic liquids (ILs) to form a thin passivating layer at the triple point between the electrocatalyst-electrolyte-gas interface where the Oxygen Reduction Reaction (ORR) takes place.

1140. Polyaniline based microtubes as building-blocks for artificial muscle applications

Authors: Beregoi, M; Evanghelidis, A; Matei, E; Enculescu, I

Published: DEC 2017, SENSORS AND ACTUATORS B-CHEMICAL, 253, 583, DOI: 10.1016/j.snb.2017.06.128

Morphology is a key element in the functionality of low dimensional structures including here electroactive polymers, especially when applications such as muscle like actuators are sought. The reason is that morphology in the context of a high specific surface object strongly influences specific parameters such as ionic diffusion, conductivity and consequently the actuation capability of the system. In the present work a new architecture for microtube-based actuating elements is presented. Free-standing fibrillar microtubes with diameter in the range of micrometers and with a core-shell polyaniline/gold structure are fabricated through a scalable approach. Aligned electrospun poly(methyl methacrylate) fibers are coated with gold and are further employed as microstructured electrodes for the electrochemical deposition of polyaniline. Further the poly(methyl methacrylate) core was dissolved, leading to a tubular structure. The polyaniline/gold microtubes show complex, rapid and reversible movement patterns, with great stability and consistency over repeated actuation cycles. Thus, when the potential is swept between -0.2 and 1 V at different rates, the microtubes move, this movement being associated with the morphological and structural characteristics of the deposited polyaniline layer, a mechanism based on the expansion/contraction and conformational changes of the polymer chains due to the insertion/expulsion of ions. The response time of these electroactive microstructures during one cycle is in the range of seconds, a consequence of their low dimensionality and specific structure. Moreover the actuation takes place in different electrolytes including simulated gastric fluid, which enables a wide range of applications. (C) 2017 Elsevier B.V. All rights reserved.

1141. Aging phenomena and wettability control of plasma deposited carbon nanowall layers

Authors: Vizireanu, S; Ionita, MD; Ionita, ER; Stoica, SD; Teodorescu, CM; Husanu, MA; Apostol, NG; Baibarac, M; Panaitescu, D; Dinescu, G

Published: NOV 2017, PLASMA PROCESSES AND POLYMERS, 14, DOI: 10.1002/ppap.201700023

This paper reports on the aging of carbon nanowalls (CNW) and modification of their wettability by the storage time, growth conditions, and post-fabrication plasma treatments. The as-deposited CNW initially exhibit marked hydrophilic behavior (fresh CNW), but within a few days they become highly hydrophobic (aged CNW). Their final hydrophobicity is closely related to their topography which is controlled by the deposition parameters. In addition, subsequent fluorinated plasma treatments result in super-hydrophobic CNW layers, irrespective of the hydrophilic or hydrophobic character of the pre-treated samples. To explain this, we show that the CNW edges contain many defects initially, but such defects become passivated in time. As a result, the surfaces become highly hydrophobic after aging or fluorination, having inert stable terminations.

1142. PHOTOACTIVITY OF HEMATITE ELECTRODE PREPARED VIA ANODIC ELECTRODEPOSITION ON FTO AND FTO/TiO2 SUBSTRATES

Authors: Sima, M; Vasile, E; Sima, MA

Published: JUL-SEP 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 758, DOI:

The hematite films were prepared via anodic electrodeposition on FTO and FTO/mesoporous TiO2 substrates. The hematite photoanodes were characterized by X-ray diffraction and scanning electron microscopy. The performance of the prepared hematite photoanodes was assessed based on photocurrent-voltage curves and electrochemical impedance spectra. The modification of the hematite surface with nickel oxide nanoparticles improved the performance of the hematite photoanode while phosphorous doped hematite photoanode shows poor photoactivity. The onset of water oxidation photocurrent was cathodically shifted for hematite photoanodes prepared on FTO/TiO2 substrate.

1143. Thermal analysis on C6H10Ge2O7-doped MgB2

Authors: Aldica, G; Matei, C; Paun, A; Batalu, D; Ferbinteanu, M; Badica, P

Published: JAN 2017, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 127, 179, DOI: 10.1007/s10973-016-5877-9

Additives to MgB2 can improve the superconducting functional characteristics, such as critical current density (J (c)) and irreversibility field (H (irr)). Recently, we have shown that repagermanium (C6H10Ge2O7) is an effective additive, enhancing both J (c) and H (irr). To look into details of the processes taking place during the reactive sintering, a thermal analysis study (0.167 K s(-1), in Ar) is reported. We used differential scanning calorimetry between 298 and 863 K and simultaneous thermogravimetric-differential thermal analysis between 298 and 1233 K. Samples were mixtures of powders with composition 97 mol% MgB2 and 3 mol% C6H10Ge2O7. Up to 863 K, repagermanium decomposes by multiple steps and forms amorphous phases. A reaction with MgB2 is not observed. Above this temperature, partial decomposition of MgB2 occurs. Crystalline Ge and MgO are detected before formation of Mg2Ge and MgB4, when temperature approaches the melting point of Ge (1211 K). Carbon substitution for boron in the crystal lattice of MgB2 is observed for samples heated above 863 K. The amount of substitutional C does not significantly change with temperature.

1144. Tuning the liquid crystalline properties of palladium(II) metallomesogens: A study of rod-like to disc-like transition in cyclopalladated complexes with N-benzoyl thiourea derivatives

Authors: Micutz, M; Pasuk, I; Ilis, M

Published: OCT 2017, JOURNAL OF MOLECULAR LIQUIDS, 243, 156, DOI: 10.1016/j.molliq.2017.08.013

A new family of cyclometalated palladium(II) complexes with the non-symmetric dimeric liquid crystal Schiff base alpha-(4-cyanobipheny1-4'-yloxy)-omega-(4-n-decyloxyanilinebenzylidene-4'-oxy) hexane and alkoxysubstituted N-benzoyl thiourea (BTU) derivatives as auxiliary ligands was designed and prepared with the aim to study the influence of increasing the number of aliphatic chains on the molecular organization in the liquid crystal phase. The liquid crystalline behavior of these palladium(II) complexes was investigated by a combination of polarized optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction. A transition from the lamellar (complex 3a with two aliphatic chains on BTU ligand) to columnar organization (complexes 3b and 3c having three and four chains on BTU ligand, respectively) was evidenced for these palladium(II) complexes, which was correlated with the increase of the number of terminal chains at molecular periphery. (C) 2017 Elsevier B.V. All rights reserved.

1145. Synthesis and characterization of PLD glass phosphate films doped with CdS

Authors: Elisa, M; Iordanescu, CR; Vasiliu, IC; Feraru, ID; Epurescu, G; Filipescu, M; Plapcianu, C; Bartha, C; Trusca, R; Peretz, S

Published: MAR 2017, JOURNAL OF MATERIALS SCIENCE, 52, 2901, DOI: 10.1007/s10853-016-0583-3

In the present work, optical, structural and morphological properties of CdS-doped phosphate films obtained by pulsed laser deposition (PLD) method were investigated. In the deposition process, a target based on a mixture composed of Li2O-Al2O3-BaO-La2O3-ZnO-P2O5 glass and CdS powder as dopant was used. The phosphate glass target was obtained by non-conventional wet route of raw reagents processing followed by melt-quenching technique. The complex oxide composition of the glass as well as the final PLD target consisting in a mixture of glass and CdS powder followed by pressing and heat treatment represents the novelty of the work. CdS dopant particles were highlighted by X-ray diffraction analysis as well as by Raman spectroscopy. Thus, cubic CdS particles having less than 10 nm size corroborated with specific LO (longitudinal optical phonons) and 2LO CdS Raman peaks from 300 and 600 cm(-1), respectively, certified the presence of the dopant in the deposited films. Specific vibration modes for the vitreous phosphate matrix were revealed by fourier transform infrared spectroscopy, and spherulitic units characteristic to PLD technique were found by scanning electron microscopy and atomic force microscopy analyses. A relative large luminescence band located around 430 nm was provided by UV excitation, representative for CdS nanoparticles having about 9-10 nm size.

1146. MAPLE DEPOSITION OF PLGA MICROSPHERES FOR MEDICAL APPLICATIONS

Authors: Fufa, O; Socol, M; Preda, N; Grigorescu, S; Croitoru, S; Socol, G

Published: JAN-MAR 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 80, DOI:

The aim of our study was to synthesize and evaluate the physicochemical and biological properties of composite films based on poly(lactic-co-glycolic acid) copolymer and quercetin (PLGA/Q) microspheres. During our experiments, we firstly synthesized the PLGA/Q microspheres by using an oil-in-water emulsion-diffusion-evaporation method. Subsequently, the as-prepared composite material was subjected to the matrix assisted pulsed laser evaporation (MAPLE) technique, in order to obtain the PLGA/Q coatings. Relevant compositional and microstructural features of the synthesized samples were obtained by means of Fourier transform infrared spectroscopy (FTIR) and AFM (atomic force microscopy). The long-term biocompatibility of the synthesized films was in vitro evaluated by cellular viability and immunofluorescence assays.

1147. Transparent thin films of indium tin oxide: Morphology-optical investigations, inter dependence analyzes

Authors: Prepelita, P; Filipescu, M; Stavarache, I; Garoi, F; Craciun, D

Published: DEC 1 2017, APPLIED SURFACE SCIENCE, 424, 373, DOI: 10.1016/j.apsusc.2017.02.106

Using a fast and eco-friendly deposition method, ITO thin films with different thicknesses (0.5 mu m-0.7 mu m) were deposited on glass substrates by radio frequency magnetron sputtering technique. A comparative analysis of these oxide films was then carried out. AFM investigations showed that the deposited films were smooth, uniform and having a surface roughness smaller than 10 nm. X-ray diffraction investigations showed that all samples were polycrystalline and the grain sizes of the films, corresponding to (222) cubic reflection, were found to increase with the increasing film thickness. The optical properties, evaluated by UV-VIS-NIR (190-3000 nm) spectrophotometer, evidenced that the obtained thin films were highly transparent, with a transmission coefficient between 90 and 96%, depending on the film thickness. Various methods (Swanepoel and Drude) were employed to appreciate the optimal behaviour of transparent oxide films, in determining the dielectric optical parameters and refractive index dispersion for ITO films exhibiting interference patterns in the optical transmission spectra. The electrical conductivity also increased as the film thickness increased. (C) 2017 Elsevier B.V. All rights reserved.

1148. Magnetic properties of glass-ceramics obtained by crystallization of iron-rich borosilicate glasses

Authors: Sandu, V; Cimpoiasu, E; Kuncser, A; Nicolescu, MS

Published: SEP 2017, JOURNAL OF ADVANCED CERAMICS, 6, 261, DOI: 10.1007/s40145-017-0236-2

The specific dynamic magnetic response and magnetic relaxation phenomena in magnetite-based glass-ceramics by controlled crystallization of Fe-rich borosilicate glasses with 25 wt% Fe2O3, in the presence of two types of nucleating agents, Cr2O3 and P2O5, were investigated. The magnetic response is complex and shows contributions arising from two subsystems: a system with collective characteristics, superspin-glass like, and another one with single particle characteristics (superparamagnetic) with dipolar interaction. The nucleating agents have strong influence on the characteristic temperatures and anisotropy energy.

1149. Insight on thermal behaviour of new complexes of Ni(II), Cu(II) and Zn(II) with a bismacrocyclic ligand developed as biologically active species

Authors: Badea, M; Bucur, C; Chifiriuc, MC; Bleotu, C; Grecu, MN; Lazar, V; Marinescu, D; Olar, R

Published: JAN 2017, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 127, 497, DOI: 10.1007/s10973-016-5502-y

A multi-component reaction involving metal ion, amines and formaldehyde has been used for a series of decaaza bismacrocyclic complexes M2L(CH3COO)(4)center dot nH(2)O [(1) M: Ni, n = 2.5; (2) M:Cu, n = 1; (3) M:Zn, n = 10; L:1,3-bis(N,N-1,3,6,9,12-pentaazacyclotridecane)-benzene] preparation. Elemental analyses, ESI-MS, IR, UV-Vis-NIR, NMR and EPR spectra, magnetic susceptibility at room temperature, molar conductivities, as well as thermogravimetric analysis, provided data concerning complexes features. The macrocyclic ligand behaves as bischelate, resulting in either a square planar or an octahedral stereochemistry. The in vitro screening of the antimicrobial activity was performed against both reference and clinical isolates multi-drug-resistant strains. The overall antimicrobial potency of complexes was enhanced in comparison with the free ligand, against both planktonic and biofilm-embedded pathogenic strains. Complexes exhibit no cytotoxicity on the HCT 8 tumour cells. Thermogravimetric curves (TG, DTG and DTA) evidenced in air processes as water elimination, acetate into carbonate transformation as well as oxidative degradation of the bismacrocyclic ligand. The powder X-ray diffraction data indicate MO (M: Ni, Cu, Zn) as final product.

1150. Easy batch-scale production of cobalt ferrite nanopowders by two-step milling: Structural and magnetic characterization

Authors: Galizia, P; Cernea, M; Mihalache, V; Diamandescu, L; Maizza, G; Galassi, C

Published: SEP 15 2017, MATERIALS & DESIGN, 130, 335, DOI: 10.1016/j.matdes.2017.05.062

Cobalt ferrite (CF) powder was synthesized by solid state reaction method at two different calcination temperatures (1120 K and 1320 K) then milled in two steps, gradually reducing the milling media size. The first milling step results in CF nanoparticles with crystallite size of 33 nm showing fairly high coercivity (3.7 kOe), > 5 times higher than the non-milled material (0.7 kOe). The high coercivity was correlated to the crystallite size close to the single-domain limit, and to the strain increase up to 2.1%. This value of strain is the highest ever reported in literature for the CF and brings to the highest figure of merit for permanent magnets, (BH)(max)= 2.16 MGOe. After the second milling step the powder displays particle size of 9 nm, release of strain (epsilon = 1.2%), coercivity reduction that approaches 250 Oe and decrease of the deblocking temperature from 421 K to 317 K. The large tunability obtained by multi-step milling allows to use CF in different applications. In particular, the milled CF powder characterized by high microstrain is a good candidate for the realization of rare-earth-free permanent magnets (at least on the basis of the (BH)(max) product). For the first time, a correlation between the spin-canting angle and the degree of inversion, the crystallite size and the microstrain is presented and discussed. [GRAPHICS] .

1151. Pinning-Engineered YBa2Cu3Ox Thin Films

Authors: Mele, P; Crisan, A; Adam, MI

Published: 2017, VORTICES AND NANOSTRUCTURED SUPERCONDUCTORS, 261, 63, DOI: 10.1007/978-3-319-59355-5_2

1152. N-Doped graphene as a metal-free catalyst for glucose oxidation to succinic acid

Authors: Rizescu, C; Podolean, I; Albero, J; Parvulescu, VI; Coman, SM; Bucur, C; Puche, M; Garcia, H

Published: APR 21 2017, GREEN CHEMISTRY, 19, 2005, DOI: 10.1039/c7gc00473g

N-Containing graphenes obtained either by simultaneous amination and reduction of graphene oxide or by pyrolysis of chitosan under an inert atmosphere have been found to act as catalysts for the selective wet oxidation of glucose to succinic acid. Selectivity values over 60% at complete glucose conversion have been achieved by performing the reaction at 160 degrees C and 18 atm O-2 pressure for 20 h. This activity has been attributed to graphenic-type N atoms on graphene. The active N-containing graphene catalysts were used four times without observing a decrease in conversion and selectivity of the process. A mechanism having tartaric and fumaric acids as key intermediates is proposed.

1153. Influence of laser pulse frequency on the microstructure of aluminum nitride thin films synthesized by pulsed laser deposition

Authors: Antonova, K; Duta, L; Szekeres, A; Stan, GE; Mihailescu, IN; Anastasescu, M; Stroescu, H; Gartner, M

Published: FEB 1 2017, APPLIED SURFACE SCIENCE, 394, 204, DOI: 10.1016/j.apsusc.2016.10.114

Aluminum Nitride (AlN) thin films were synthesized on Si (100) wafers at 450 degrees C by pulsed laser deposition. A polycrystalline AlN target was multipulsed irradiated in a nitrogen ambient, at different laser pulse repetition rate. Grazing Incidence X-Ray Diffraction and Atomic Force Microscopy analyses evidenced nanocrystallites with a hexagonal lattice in the amorphous AlN matrix. The thickness and optical constants of the layers were determined by infrared spectroscopic ellipsometry. The optical properties were studied by Fourier Transform Infrared reflectance spectroscopy in polarised oblique incidence radiation. Berreman effect was observed around the longitudinal phonon modes of the crystalline AlN component. Angular dependence of the A(1)LO mode frequency was analysed and connected to the orientation of the particles' optical axis to the substrate surface normal. The role of the laser pulse frequency on the layers' properties is discussed on this basis. (C) 2016 Elsevier B.V. All rights reserved.

1154. Ultrasonic Measurements on Cyclodextrin/Hydroxyapatite Composites for Potential Water Depollution

Authors: Predoi, D; Predoi, MV; Iconaru, SL; El Kettani, MEC; Leduc, D; Prodan, AM

Published: JUN 2017, MATERIALS, 10, DOI: 10.3390/ma10060681

This paper presents structural, morphological and preliminary ultrasonic characterizations of the -Cyclodextrin/hydroxyapatite (CD-HAp) composites synthesized by an adapted co-precipitation method. The structural and morphological properties were evaluated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The specific surface area, pore size and pore volume were determined using the methods of Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH), respectively. The novelty of our study consists in preliminary ultrasonic measurements conducted on CD-HAp composite, uniformly dispersed in distilled water. The benefit of this non-destructive method was to facilitate and simplify the characterization techniques of nanoparticles. Our experiments proved that the efficiency of lead ion removal by CD-HAp composites depended on the initial concentration of lead. The maximum adsorption capacity of the solid phase, for Pb2+ indicated a higher rate of removal by the CD-HAp_2. These adsorption results bring valuable insight into the beneficial contribution of our compounds, for the removal of heavy metal ions from aqueous solutions. Furthermore, in the present study, was evaluated the toxic effect of lead ions adsorbed by hydroxyapatite from contaminated water on HeLa cells.

1155. Functional layered double hydroxides and their catalytic activity for 1,4-addition of n-octanol to 2-propenonitrile

Authors: Zavoianu, R; Pavel, OD; Cruceanu, A; Florea, M; Birjega, R

Published: SEP 15 2017, APPLIED CLAY SCIENCE, 146, 422, DOI: 10.1016/j.clay.2017.06.030

This contribution concerns the catalytic activity of functional layered double hydroxides (LDHs) for 1,4-addition of n-octanol to 2-propenonitrile aiming to investigate the influence of the organic interlayer anion nature on their physico-chemical and catalytic performances. Two series of functional LDHs, e.g. Mg2.5Al, and Zn2.5Al respectively, were synthesized by co-precipitation at pH 9.5 using a metal nitrates M2+ (NO3)(2)center dot 6H(2)O (M2+ = Mg, Zn), Al(NO3)(3)center dot 9H(2)O solution, an organic acid sodium salt (e.g. sodium dodecyl sulfate (NaDS), sodium laurate (NaL), or sodium stearate (NaS)) and NaOH solution for pH adjustment. XRD, DRIFTS and DR-UV-Vis-NIR characterizations indicated a better intercalation of DS in the interlayer region compared to L or S. The catalytic activity of these solids was related to both their organophilic character and basicity, Mg2.5Al-DS samples, which were more basic, showed a higher activity than Zn2.5Al-DS.

1156. Characterization of MAPLE deposited WO3 thin films for electrochromic applications

Authors: Boyadjiev, SI; Stefan, N; Szilagyi, IM; Mihailescu, N; Visan, A; Mihailescu, IN; Stan, GE; Besleaga, C; Iliev, MT; Gesheva, KA

Published: 2017, INERA WORKSHOP 2016: MEMBRANE AND LIQUID CRYSTAL NANOSTRUCTURES (MELINA 2016), 780, DOI: 10.1088/1742-6596/780/1/012013

Tungsten trioxide (WO3) is a widely studied material for electrochromic applications. The structure, morphology and optical properties of WO3 thin films, grown by matrix assisted pulsed laser evaporation (MAPLE) from monoclinic WO3 nano-sized particles, were investigated for their possible application as electrochromic layers. A KrF* excimer (lambda = 248 nm, .zeta(FWHM)=25 ns) laser source was used in all experiments. The MAPLE deposited WO3 thin films were studied by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXRD) and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry measurements were also performed, and the coloring and bleaching were observed. The morpho-structural investigations disclosed the synthesis of single-phase monoclinic WO3 films consisting of crystalline nano-grains embedded in an amorphous matrix. All thin films showed good electrochromic properties, thus validating application of the MAPLE deposition technique for the further development of electrochromic devices.

1157. Sustainable metal-free carbogels as oxygen reduction electrocatalysts

Authors: Preuss, K; Tanase, LC; Teodorescu, CM; Abrahams, I; Titirici, MM

Published: AUG 21 2017, JOURNAL OF MATERIALS CHEMISTRY A, 5, 16343, DOI: 10.1039/c7ta02001e

Tuneable nitrogen doped carbogels have been synthesised by a simple one-pot hydrothermal carbonisation, followed by pyrolysis at 1000 degrees C, using highly available and low cost precursors such as glucose and ovalbumin. Different physical activation ratios of nitrogen/oxygen were used to demonstrate a sustainable and easy method for changing surface area, pore size and elemental composition in order to investigate their effect on the oxygen reduction reaction when used as electrocatalysts. A ratio of nitrogen mixed with 2% of oxygen was found to be most beneficial for enhancing the catalytic activity by creating a high surface area of 874 m(2) g(-1) as well as a favourable ratio of pyridinic to graphitic nitrogen. The influence of sulphur doping and/or boron on the carbogel structure was investigated. Incorporation of sulphur does not interfere with the structure formation, but decreases the surface area and nitrogen content resulting in diminished ORR performance. However, boron doping with boric acid results in a different carbogel structure by acting as a catalyst, creating an altered morphology, surface area, pore properties and higher nitrogen content by fully utilising ovalbumin as a nitrogen source instead of as a structure directing/surface stabilising agent. Nitrogen content is found to determine the limiting current, while the oxygen content has a small influence on the onset potential. An assumed synergistic effect between nitrogen and boron generates higher electron transfer numbers and lower hydrogen peroxide yields in boron nitrogen co-doped carbogels than those observed in purely nitrogen doped systems.

1158. Defect-related light absorption, photoluminiscence and photocatalytic activity of SiO2 with tubular morphology

Authors: Anastasescu, C; Zaharescu, M; Angelescu, D; Munteanu, C; Bratan, V; Spataru, T; Negrila, C; Spataru, N; Balint, I

Published: JAN 2017, SOLAR ENERGY MATERIALS AND SOLAR CELLS, 159, 335, DOI: 10.1016/j.solmat.2016.09.032

The research describes the synthesis, optical, photocatalytic, electrochemical and photoelectrocatalytical properties of highly defected, low surface area, tubular SiO2. High surface density of light-absorbing defects is obtained by conducting the synthesis at low temperature (0 degrees C) and by optimizing the ratios between reactants. The calcined tubular SiO2 is characterized by intense and broad absorption band centered at approximate to 320 nm, spanning from deep UV to green. The formation of Si3+ surface defects by calcination is accompanied by a substantial intensification of light absorbing characteristics. The annealing leads also to appearance of intense photoluminescence bands centered at around 433 and 533 nm for excitation wavelengths 320-380 nm. The photocatalytic generation of H-2 and CO2 from water-methanol mixture under solar (AM 1.5) and visible (lambda > 390 nm) irradiation is performed to probe the capability of light-absorbing defects of SiO2 to work as active sites and to gather indirect information on nature of active sites. The electrochemical and photoelectrochemical activity of tubular SiO2 are highlighted by employing [Ru(bpy)(3)]Cl-2 complex as electron transfer witness. According to our results, highly defected nanotubular SiO2 exhibit uncommon optical, light harvesting, electronic and electrochemical properties with great potential for practical applications in numerous fields. (C) 2016 Elsevier B.V. All rights reserved.

1159. Relationship between ferromagnetism and, structure and morphology in un-doped ZnO and Fe-doped ZnO powders prepared by hydrothermal route

Authors: Mihalache, V; Cernea, M; Pasuk, I

Published: AUG 2017, CURRENT APPLIED PHYSICS, 17, 1135, DOI: 10.1016/j.cap.2017.03.020

The magnetic properties, in the 5 K-350 K temperature range, were investigated in relationship with the structure and morphology of Zn1-xFexO (x = 0, 0.01, 0.03) powders prepared by hydrothermal route. The magnetization measurements reveal that all powders are ferromagnetic at room temperature, with Curie temperature TT, higher than 350 K. The coercivity Hc takes values between 58 Oe and 107 Oe at 300 K and, between 217 Oe and 613 Oe at 5 K. The weak magnetization of the un-doped ZnO powder is temperature independent and was associated with the high surface to volume ratio of the powder particles (or the number of surface defects). The saturation magnetization M-s, was substantially enhanced (up to a factor of about 20 at 300 K and of about 200 at 5 K) at all temperatures as Fe concentration increased, in spite of reduction of the surface to volume ratio of the powder particles. The Hc vs. Tand FC/ZFC curves for the un-doped ZnO show typical ferromagnetic behavior, whereas for the Fe doped powders exhibit Ruderman-Kittel-Kasuya-Yosida (RKKY) - like and spin-glass-like behavior. The observed magnetic phenomena in Fe doped ZnO can be explained on the basis of "donor defects concentration magnetic cations concentration" phase diagram for dilute magnetic semiconductors. (C) 2017 Elsevier B.V. All rights reserved.

1160. Tuning the transmission phase by the dot size

Authors: Tolea, F; Tolea, M

Published: JAN 2017, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 85, 173, DOI: 10.1016/j.physe.2016.08.034

The phase shift of the electron's wave function after a tunneling event (i.e. the transmission phase) was at first measured for its fundamental or applicative relevance for quantum circuitry, but later the phase study self-motivated due to a number of unexpected results. One such result was the reduced increment of the phase on some resonances - with only fractions of pi - in the few-electrons "mesoscopic" regime. In this paper we address such a regime for a rectangular quantum dot and compute the total phase increase on the first four resonances by means of accurate configuration-interaction method and a generalized Friedel sum rule as proposed by Rontani (2006) [17]. Our findings confirm that the electronic correlations reduce the on-resonance phase growth which is also found to decrease quasi-linearly with the dot size, the decrease being more pronounced as the number of electrons on the dot is raised. Sudden jumps (of small amplitude) of the phase are found to accompany ground states spin transitions. (C) 2016 Elsevier B.V. All rights reserved.

1161. Interaction of New-Developed TiO2-Based Photocatalytic Nanoparticles with Pathogenic Microorganisms and Human Dermal and Pulmonary Fibroblasts

Authors: Nica, IC; Stan, MS; Popa, M; Chifiriuc, MC; Lazar, V; Pircalabioru, GG; Dumitrescu, I; Ignat, M; Feder, M; Tanase, LC; Mercioniu, I; Diamandescu, L; Dinischiotu, A

Published: FEB 2017, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, 18, DOI: 10.3390/ijms18020249

TiO2-based photocatalysts were obtained during previous years in order to limit pollution and to ease human daily living conditions due to their special properties. However, obtaining biocompatible photocatalysts is still a key problem, and the mechanism of their toxicity recently received increased attention. Two types of TiO2 nanoparticles co-doped with 1% of iron and nitrogen (TiO2-1% Fe-N) atoms were synthesized in hydrothermal conditions at pH of 8.5 (HT1) and 5.5 (HT2), and their antimicrobial activity and cytotoxic effects exerted on human pulmonary and dermal fibroblasts were assessed. These particles exhibited significant microbicidal and anti-biofilm activity, suggesting their potential application for microbial decontamination of different environments. In addition, our results demonstrated the biocompatibility of TiO2-1% Fe-N nanoparticles at low doses on lung and dermal cells, which may initiate oxidative stress through dose accumulation. Although no significant changes were observed between the two tested photocatalysts, the biological response was cell type specific and time- and dose-dependent; the lung cells proved to be more sensitive to nanoparticle exposure. Taken together, these experimental data provide useful information for future photocatalytic applications in the industrial, food, pharmaceutical, and medical fields.

1162. MORPHOLOGICAL AND OPTICAL PROPERTIES OF ELECTROSPUN SnO2 FIBERS

Authors: Busuioc, AD; Ciovica, I; Stoleriu, S; Enculescu, M; Evanghelidis, A; Visan, T

Published: OCT-DEC 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 1105, DOI:

The electrospinning technique was employed for the preparation of SnO2 fibers starting from a precursor solution consisting of a tin salt, polyvinylpyrrolidone as carrier polymer and N,N-dimethylformamide as dispersion medium. In order to achieve single-phase crystalline structures, the as-spun fibers were calcined at 500, 700 or 900 degrees C, with two different heating rates of 1 or 10 degrees C/min. The thermally treated samples were characterized in terms of structure, morphology and bandgap by employing X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and UV-Vis spectroscopy. A fine tuning of the bandgap width was attained through the selection of different values for the electrospinning and calcination parameters.

1163. Organic heterostructures deposited by MAPLE on AZO substrate

Authors: Socol, M; Preda, N; Stanculescu, A; Breazu, C; Florica, C; Stanculescu, F; Iftimie, S; Girtan, M; Popescu-Pelin, G; Socol, G

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 203, DOI: 10.1016/j.apsusc.2017.02.260

Organic heterostructures based on poly(3-hexylthiophene) (P3HT) and fullerene (C60) as blends or multilayer were deposited on Al:ZnO (AZO) by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. The AZO layers were obtained by Pulsed Laser Deposition (PLD) on glass substrate, the high quality of the films being reflected by the calculated figure of merit. The organic heterostructures were investigated from morphological, optical and electrical point of view by atomic force microscopy (AFM), UV-vis spectroscopy, photoluminescence (PL) and current-voltage (I-V) measurements, respectively. The increase of the C60 content in the blend heterostructure has as result a high roughness. Compared with the multilayer heterostructure, those based on blends present an improvement in the electrical properties. Under illumination, the highest current value was recorded for the heterostructure based on the blend with the higher C60 amount. The obtained results showed that MAPLE is a useful technique for the deposition of the organic heterostructures on AZO as transparent conductor electrode. (C) 2017 Elsevier B.V. All rights reserved.

1164. C-N cross-coupling on supported copper catalysts: The effect of the support, oxidation state, base and solvent (vol 341, pg 205, 2016)

Authors: Tirsoaga, A; Cojocaru, B; Teodorescu, C; Vasiliu, F; Grecu, MN; Ghica, D; Parvulescu, VI; Garcia, H

Published: JAN 2017, JOURNAL OF CATALYSIS, 345, 329, DOI: 10.1016/j.jcat.2016.11.016

1165. Thermal conductivity and diffusivity of Cu-Y alloys produced by different powder metallurgy routes

Authors: Carro, G; Munoz, A; Monge, MA; Savoini, B; Galatanu, A; Galatanu, M; Pareja, R

Published: NOV 2017, FUSION ENGINEERING AND DESIGN, 124, 1160, DOI: 10.1016/j.fusengdes.2017.01.017

Full density Cu-1%Y and Cu-0.8%Y alloys have been produced by different powder metallurgy routes and subsequent hot isostatic pressing. Some of the alloys have been subjected to equal channel angular pressing (ECAP) via B-c route up to 8 passes. ECAP deformation homogenizes and refines the microstructure up to attaining a sub-micron grain structure. Thermal properties have been characterized by the laser flash method in the temperature range 373-773 K. The ECAP process, irrespective of the production route, enhanced the thermal conductivity to values similar to those for CuCrZr (ITER grade). The linear thermal expansion coefficient was temperature independent for all materials. (C) 2017 Elsevier B.V. All rights reserved.

1166. Structural and optical properties of un-doped and doped Sr3Al2O6 obtained through the tartarate precursor method

Authors: Mindru, I; Gingasu, D; Patron, L; Marinescu, G; Culita, DC; Calderon-Moreno, JM; Preda, S; Secu, M

Published: DEC 15 2017, CERAMICS INTERNATIONAL, 43, 16675, DOI: 10.1016/j.ceramint.2017.09.057

Un-doped and doped strontium aluminates (Sr3Al2O6, Sr3Al2O6:Tb3+, Sr3Al2O6:Tb3+,Eu3+ and Sr3Al2O6:Tb3+,Eu3+/Eu2+) were synthesized through a soft chemical method - the tartarate precursor route. The tartarate precursors were characterized by infrared spectroscopy (IR) and thermal analysis. The strontium aluminates were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR). The XRD patterns confirmed the formation of single-phase cubic structure Sr3Al2O6 with average crystallite size of 18 nm. SEM micrographs showed porous polycrystalline powder microstructures and EDX analysis confirmed the incorporation of the dopant in the Sr3Al2O6 powders. The photoluminescence spectrum recorded on Sr3Al2O6: Tb3+,Eu3+ (obtained from tartarate precursor calcined in air) showed the typical f-f luminescences of the RE-ions. Subsequent calcination of this sample in reducing atmosphere is accompanied by new photoluminescence and thermoluminescence features associated to the Eu2+ ions.

1167. Effect of Cr2O3 on the magnetic properties of magnetite-based glass-ceramics obtained by controlled crystallization of Fe-containing aluminoborosilicate glass

Authors: Sandu, V; Greculeasa, S; Kuncser, A; Nicolescu, MS; Kuncser, V

Published: AUG 2017, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 37, 3099, DOI: 10.1016/j.jeurceramsoc.2017.03.055

The phase structure and magnetic properties of magnetite-based glass-ceramics obtained by crystallization of Fe-containing boroaluminosilicate glass melts are presented. The use of Cr2O3 as nucleating agent generated magnetite configurations showing a complex temperature dependence of the relaxation of the remanent magnetization. Specifically, the expected decrease in time of the remanent magnetization occurs only in a limited temperature range, whereas it increases at low and high temperatures (upward relaxation). We tentatively attribute these effects to the complex spin structure of the tiny magnetite nanoparticles, their complex size distribution and the interplay between the relaxation mechanisms in different temperature ranges. (C) 2017 Elsevier Ltd. All rights reserved.

1168. Optical properties of single-walled carbon nanotubes highly separated in semiconducting and metallic tubes functionalized with poly(vinylidene fluoride)

Authors: Matea, A; Baibarac, M; Baltog, I

Published: FEB 15 2017, JOURNAL OF MOLECULAR STRUCTURE, 1130, 45, DOI: 10.1016/j.molstruc.2016.10.017

In this paper, the interaction of poly(vinylidene fluoride) (PVDF) with single-walled carbon nanotubes (SWNTs) highly separated in metallic (M) and semiconducting (S) tubes is studied by resonant Raman scattering and FTIR spectroscopy. In this order, the PVDF/SWNTs membranes were prepared by the evaporation of dimethylformamide (DMF) from PVDF solutions containing i) the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) tubes (M + S-SWNTs), ii) SWNTs highly separated in metallic tubes (98%, M-SWNTs), and iii) SWNTs highly separated in semiconducting tubes (99%, S-SWNTs). An increase in the PVDF beta phase weight, highlighted by the increase in the absorbance of IR band at 843 cm(-1), is reported to take place in the presence of M + S-SWNTs and S-SWNTs. An increase of the PVDF gamma crystalline phase weight is reported for the PVDF/M + S-SWNTs, PVDF/M-SWNTs and PVDF/S-SWNTs membranes. Using Raman scattering, a donor-acceptor interaction is invoked to take place at the interface PVDF/M + S-SWNTs and PVDF/S-SWNTs. In the case of the membranes based on PVDF and M-SWNTs, the changes reported in Raman spectra of the two constituents are explained on the base induction-interaction forces between the permanent dipole of PVDF and induced dipole of M-SWNTs. (C) 2016 Elsevier B.V. All rights reserved.

1169. Down-/Up-Conversion Emission Enhancement by Li Addition: Improved Crystallization or Local Structure Distortion?

Authors: Avram, D; Cojocaru, B; Tiseanu, I; Florea, M; Tiseanu, C

Published: JUL 6 2017, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 14284, DOI: 10.1021/acs.jpcc.7b02897

Local symmetry distortion by Li addition is acknowledged as an effective strategy for enhancing the luminescence of lanthanide (Ln) doped into a wide range of lattice hosts. Despite extensive literature, direct evidence that supports Li-induced modification of the local crystal-field at the Ln sites is still missing. Herein, we show that the emission enhancement by Li addition in Ln,Li-Y2O3 is due to improved crystallization and not to local structure distortion. Our approach is based on the premise that any distortion/lowering of the local symmetry would reflect into the alteration of the emission shapes and shortening of the emission decays. To this aim, we have extensively investigated the evolution with Li addition and calcination temperature of down (optical and X-ray induced) and up-conversion (UPC) emission of Ln-Y2O3 measured across the visible to near-infrared range. First, a center to center (corresponding to Ln in the C-2 and S-6/C-3i sites of the cubic Y2O3 lattice) as well as global comparison of the emission properties of Li free and Li codoped Y2O3 are presented by use of Eu, Sm, Tb and Dy as local probes in the visible range. Next, the effect of Li on the up-conversion emission of Er-Y2O3 is analyzed in terms of UPC pathways, emission shape and intensity, decays and excitation spectra. It is concluded that Li addition does not change either the local structure around C-2 or S-6 Ln centers or the relative contribution of these. Moreover, it is found that the effects of Li doping on the emission properties of Ln-Y2O3 are like extending the calcination temperature of Li-free Ln-Y2O3 from 800 degrees C to similar to 1000-1100 degrees C. Additionally, a relatively intense 1500 to 980 nm UPC emission is evidenced for the first time for Er-Y2O3, while a relatively intense "emission around 1500 nm was measured under X-ray excitation. Taken together, our findings highlight the need for revisiting the traditional optimization strategy based on Li modification but also the promise of Er-Y2O3 nanoparticles for optical/X-ray applications in the near-infrared range.

1170. Anodic deposition of nanostructured hematite film using agarose gel as template. Application in water splitting

Authors: Sima, M; Vasile, E; Sima, A; Logofatu, C

Published: DEC 20 2017, ELECTROCHIMICA ACTA, 258, 1462, DOI: 10.1016/j.electacta.2017.12.013

The present study shows the results obtained in anodic electrodeposition of hematite precursor films in agarose gel template and photoelectrochemical characterization of the prepared hematite films. The peak current in cyclic voltammetry increases after each scan of the potential between -0.1 and 1.3 V for FTO electrode covered with a film of agarose gel in 0.1 M iron sulfate solution. The hematite samples with different thicknesses were prepared using template electrodeposition and annealing in air. The obtained nanostructured films were characterized by field emission scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The results show that a synergistic improvement of photocurrent density (1.14 mAcm(-2) at 1.23 V vs RHE) is induced by Sn-doping and slight surface modification of hematite with thin and discontinuous NiO film. The results indicate that thicker hematite films and hematite films strongly modified with NiO nanostructures show a reduced photoactivity. (C) 2017 Elsevier Ltd. All rights reserved.

1171. The spectrochemical behavior of composites based on poly (para-phenylenevinylene), reduced graphene oxide and pyrene

Authors: Ilie, M; Baibarac, M

Published: OCT 2017, OPTICAL MATERIALS, 72, 146, DOI: 10.1016/j.optmat.2017.06.002

A new composite material based on poly (para-phenylenevinylene) (PPV), pyrene (Py) and reduced graphene oxide (RGO) is synthesized using thermal conversion route. The properties of this material are investigated by Raman scattering, photoluminescence (PL), infrared (IR) and ultraviolet visible (UV-Vis) spectroscopy. Adding Py at PPV precursor solution (PPV PS) containing RGO, yields to important modifications in both vibrational and electronic properties of these composites. The presence of Py into PPV matrix determines a blue shift of PPV PL. According to Raman and IR studies, PPV is non-covalently functionalized with Py which interacts forward with RGO through pi-pi interactions causing an important modification into the polymer chains conjugation length. (C) 2017 Elsevier B.V. All rights reserved.

1172. Sensors based on mesoporous SnO2-CuWO4 with high selective sensitivity to H2S at low operating temperature

Authors: Stanoiu, A; Simion, CE; Calderon-Moreno, JM; Osiceanu, P; Florea, M; Teodorescu, VS; Somacescu, S

Published: JUN 5 2017, JOURNAL OF HAZARDOUS MATERIALS, 331, 160, DOI: 10.1016/j.jhazmat.2017.02.038

Development of new sensitive materials by different synthesis routes in order to emphasize the sensing properties for hazardous H2S detection is one of a nowadays challenge in the field of gas sensors. In this study we obtained mesoporous SnO2-CuWO4 with selective sensitivity to H2S by an inexpensive synthesis route with low environmental pollution level, using tripropylamine (TPA) as template and polyvinylpyrrolidone (PVP) as dispersant/stabilizer. In order to bring insights about the intrinsic properties, the powders were characterized by means of a variety of complementary techniques such as: X-Ray Diffraction, XRD; Transmission Electron Microscopy, TEM; High Resolution TEM, HRTEM; Raman Spectroscopy, RS; Porosity Analysis by N-2 adsorption/desorption, BET; Scanning Electron Microscopy, SEM and X-ray Photoelectron Spectroscopy, XPS. The sensors were fabricated by powders deposition via screen printing technique onto planar commercial Al2O3 substrates. The sensor signals towards H2S exposure at low operating temperature (100 degrees C) reaches values from 10(5) (for SnWCu600) to 10(6) (for SnWCu800) over the full range of concentrations (5-30 ppm). The recovery processes were induced by a short temperature trigger of 500 degrees C. The selective sensitivity was underlined with respect to the H2S, relative to other potential pollutants and relative humidity (10-70% RH). (C) 2017 Elsevier B.V. All rights reserved.

1173. Lignin Fragmentation onto Multifunctional Fe3O4@Nb2O5@Co@Re Catalysts: The Role of the Composition and Deposition Route of Rhenium

Authors: Opris, C; Cojocaru, B; Gheorghe, N; Tudorache, M; Coman, SM; Parvulescu, VI; Duraki, B; Krumeich, F; van Bokhoven, JA

Published: MAY 2017, ACS CATALYSIS, 7, 3267, DOI: 10.1021/acscatal.6b02915

Multifunctional Fe3O4@Nb2O5@Co@Re catalysts with metal loadings in the range of 2-7 wt % were prepared via a multistep process. Magnetic nanoparticles prepared by coprecipitation were covered with a niobia shell precipitated from an ammonium niobate oxalate complex in the presence of hexadecyltrimethylammonium bromide. The deposition of cobalt was performed using a deposition/precipitation procedure. Finally, rhenium has been deposited following three different routes: (i) impregnation, (ii) deposition and precipitation of rhenium chloride (ImC and PP, respectively), and (iii) impregnation with ammonium perrhenate (ImA). The characterization of these catalysts was achieved by X-ray diffraction, Raman, H-2 and NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy, and transmission electron microscopy showing the influence of the preparation procedure, reduction, and Re/Co cooperation on the degree of dispersion and reduction. ImC and ImA routes led to more reduced catalysts, and the decrease in cobalt content corresponded to more reduced rhenium. An inverse relation between the acidity and the degree of reduction has been found. The screening of these catalysts in the fragmentation of the lignin confirmed the role of the structural characteristics and solvent. ImC catalysts exhibited better catalytic activity, especially for low metal loadings [2%Co@3%Re, 85% yield of LF, 15.5% yield of LR in tetrahydrofuran (THF), and 14.5% yield of insoluble LR in THF]. Although the extent was smaller, the PP catalysts allowed a more advanced fragmentation of the lignin to fragments with molecular weights between 200 and 400 Da. The catalysts were totally recovered by application of a magnetic field and recycled six times without any loss of activity or selectivity.

1174. Photosensitive GeSi/TiO2 multilayers in VIS-NIR

Authors: Palade, C; Dascalescu, I; Slav, A; Lepadatu, AM; Lazanu, S; Stoica, T; Teodorescu, VS; Ciurea, ML; Comanescu, F; Muller, R; Dinescu, A; Enuica, A

Published: 2017, 2017 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 40TH EDITION, 70, DOI:

The electrical and photosensing properties correlated with structure and morphology of TiO2/(GeSi/TiO2)(2) multilayers are investigated. The multilayers are prepared by magnetron sputtering followed by rapid thermal annealing. Studies of Raman spectroscopy, transmission electron microscopy and X-ray diffraction are carried out. Measurements of dark current versus voltage and temperature are done. The photosensing properties are studied by measuring photocurrent spectra at different temperatures. We obtain multilayers with 10 - 15 nm Ge0.6Si0.4 nanocrystals (NCs) by annealing at 800 degrees C. We evidence the tunneling mechanism between neighbor NCs (T-1/2 law) in the dark current-temperature dependence. The photocurrent spectrum has a maximum with position shifting from 940 to 980 nm when the measurement temperature increases from 150 to 300 K, being due to the GeSi NCs.

1175. Physicochemical and antimicrobial properties of silver-doped hydroxyapatite collagen biocomposite

Authors: Predoi, D; Iconaru, SL; Albu, M; Petre, CC; Jiga, G

Published: JUN 2017, POLYMER ENGINEERING AND SCIENCE, 57, 545, DOI: 10.1002/pen.24553

Silver-doped hydroxyapatite (AgHAp) was prepared by co-precipitation method at room temperature. The obtained AgHAp was added in different amounts of collagen gel (AgHApC1 and AgHApC2). Afterward, the gel was lyophilized and the final AgHApC1 and AgHApC2 composite was achieved. The purity, crystallinity, and the phase composition of the AgHAp, AgHApC1, and AgHApC2 samples were evaluated by X-ray diffraction (XRD). The planes corresponding to the 2 values for hydroxyapatite were found in the three samples analyzed in agreement with the crystalline hydroxyapatite. In the Fourier transform infrared (FT-IR) spectra of AgHApC1 and AgHApC2 samples the peak characteristic to the presence of (2) phosphate mode at 472/cm was found. The peaks resulting from the (4) vibration of the P-O mode, (1) symmetric P-O stretching vibration and (3) P-O stretching vibration of PO43- were also evidenced in all the samples. The formation of agglomerated particles with uniform particle size was evidenced by scanning electron microscope (SEM). The uniform distribution of the constituent elements was evidenced by mapping analysis. Furthermore, the strong antibacterial activity of AgHAp, AgHApC1, and AgHApC2 samples against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial strains was shown. The inhibition zone increased drastically with the increase of silver concentration. POLYM. ENG. SCI., 57:537-545, 2017. (c) 2017 Society of Plastics Engineers

1176. Studies of vanadium and vanadium oxide based nanocomposite structures

Authors: Prilepov, V; Gashin, P; Popescu, M; Zalamai, V; Spoiala, D; Ketrush, P; Nasedchina, N

Published: MAY-JUN 2017, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 19, 405, DOI:

The results of the surface morphology studies as well as optical and electrical properties of nano -dimensional vanadium oxide composite structures deposited on various substrates- silica, glass substrates covered by conducting layer of SnO2, pure pyroceramics plates and the same covered by Al(2)O3, SiO2, Ta2O5 layers are presented. According to Raman spectroscopy results the thin film structure obtained on quartz corresponds to the a, -V2O5 orthorhombic phase. In contrast with this the Raman spectra of V2O5 films obtained on pyroceramics substrates, passivated by Al2O3, Ta2O5, SiO2 oxides, do not appear clearly marked narrow lines which indicate their amorphous character. The investigation of the optical properties of the fabricated layers in the spectral range of 200-1000 nm had revealed the presence of both allowed direct and indirect electron transitions. In the frequency range of 10(3)-10(7) Hz the real Z' and imaginary Z '' part of the total impedance of pyroceramics/Al2O3/Al/V2O5/AI structure were studied. The applied direct bias leads to a considerable Z', as well as Z '' decrease. The analysis of the obtained dependencies is carried out by using the method of equivalent circuits.

1177. Addition of Sb2O5 into MgB2 Superconductor Obtained by Spark Plasma Sintering

Authors: Badica, P; Burdusel, M; Popa, S; Hayasaka, Y; Ionescu, MA; Aldica, G

Published: AUG 2017, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 30, 2080, DOI: 10.1007/s10948-017-4016-6

High-density (92-98% of the theoretical density) MgB2 samples added with Sb2O5 ((MgB2)+ (Sb2O5) x, x = 0, 0.0025, 0.005, 0.015) were obtained by Spark Plasma Sintering. A higher amount of additive decreases density. In added samples, grains of secondary phases are located at MgB2 grain boundaries and they are of large size. Hence, Sb2O5 does not promote effective flux pinning, connectivity is lower, and this suppresses the critical current density and the irreversibility field. Pinning force-related parameters indicate that added samples are close to the point pinning region and they show a higher grain boundary pinning contribution when compared with pristine MgB2 sample and when temperature is lower. It is speculated that for fixed processing conditions and Sb-oxide phases, a lower stability of the additive, reflected by a lower melting temperature, may promote reactive processes to start earlier leading to coarsening of the grains belonging to secondary phases.

1178. Cyclometalated palladium(II) metallomesogens with Schiff bases and N-benzoyl thiourea derivatives as co-ligands

Authors: Ilis, M; Batalu, D; Pasuk, I; Circu, V

Published: MAY 2017, JOURNAL OF MOLECULAR LIQUIDS, 233, 51, DOI: 10.1016/j.molliq.2017.02.114

Two series of cyclometalated palladium(II) complexes based on Schiff bases and N-benzoylthiourea (BTU) ligands having four alkoxy groups at their periphery, with different number of carbon atoms, have been designed and prepared. The liquid crystalline behavior of these palladium(II) complexes was investigated by a combination of polarized optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis (TGA). The palladium(II) complexes are thermally stable on a broad temperature range up to 230 degrees C showing, depending on the alkoxy chain length, either monotropic or, for longest alkyl chain, enantiotropic smectic A and C phases. The luminescent properties of palladium(II) complexes were reported. These complexes show a yellow-orange solid-state emission at room temperature with two emission maxima at lambda(max) around 580 and 650 nm, respectively, with a shoulder around 710 nm, when the samples are irradiated in the 330-380 nm range. (C) 2017 Elsevier B.V. All rights reserved.

1179. Structure, transition temperature, and magnetoresistance of titanium-doped lanthanum barium manganite epilayers onto STO 001 substrates

Authors: Galca, AC; Oumezzine, M; Leca, A; Chirila, CF; Kuncser, V; Kuncser, A; Ghica, C; Pasuk, I; Oumezzine, M

Published: OCT 30 2017, APPLIED PHYSICS LETTERS, 111, DOI: 10.1063/1.4998011

We have developed a thin film structure with a maximum magnetoresistance effect (MRE) at room temperature, which is one of the operating requirements for many applications. It is shown that La0.67Ba0.33Ti0.02Mn0.98O3 epilayers obtained by pulsed laser deposition onto (001) SrTiO3 single crystal substrates exhibit the highest MRE, Delta R/R(H) approximate to 150% or Delta R/R(0) approximate to 60% under 5 T, at 300 K, a temperature near to the corresponding Curie temperature (T-C). Both doping with a tiny amount of titanium and induced stress due to lattice mismatch between the thin film and the substrate contribute to a decrease in T-C as compared to the pristine compound and therefore to the decrease in the temperature where the highest MRE is recorded. Published by AIP Publishing.

1180. POWDER-IN-TUBE TAPES OF MgB2 IN Fe-SHEATH PROCESSED BY EX-SITU SPARK PLASMA SINTERING

Authors: Burdusel, M; Ionescu, AM; Grigoroscuta, M; Batalu, D; Enculescu, M; Popa, S; Mihalache, V; Aldica, G; Badica, P

Published: 2017, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 79, 172, DOI:

Commercial MgB2 powder was loaded into a Fe-tube, by plastic deformation a tape of similar to 0.5 mm in thickness and 6.9 mm in width was obtained. Short pieces were processed by Spark Plasma Sintering (SPS) at 950, 1050 and 1150 degrees C for 3 min. The optimum sintering temperature is 1050 degrees C. From magnetic/electrical measurements, the onset critical temperature and the irreversibility field at 5 K were 38.7 / 38.9 K and 6.2 / 13.5 T, respectively. The pinning-force-related parameters indicate that the dominant flux pinning mechanism is of point pinning type. Contribution of grain boundary pinning is stronger at lower temperatures.

1181. Synthesis, Characterization, and Toxicity Evaluation of Dextran-Coated Iron Oxide Nanoparticles

Authors: Balas, M; Ciobanu, CS; Burtea, C; Stan, MS; Bezirtzoglou, E; Predoi, D; Dinischiotu, A

Published: FEB 2017, METALS, 7, DOI: 10.3390/met7020063

We report the synthesis of dextran-coated iron oxide magnetic nanoparticles (DIO-NPs) with spherical shape and uniform size distribution as well as their accumulation and toxic effects on Jurkat cells up to 72 h. The characterization of dextran-coated maghemite nanoparticles was done by X-ray diffraction and dynamic light scattering analyses, transmission electron microscopy imaging, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, magnetic hysteresis, and relaxometry measurements. The quantification of DIO-NPs intracellular uptake showed a progressive accumulation of iron as a function of time and dose accompanied by additional lysosome formation and an increasing darkening exhibited by a magnetic resonance imaging (MRI) scanner. The cytotoxicity assays revealed a decrease of cell viability and a loss of membrane integrity in a time-and dose-dependent manner. Exposure to DIO-NPs determined an increase in reactive oxygen species level up to 72 h. In the first two days of exposure, the level of reduced glutathione decreased and the amount of malondyaldehyde increased, but at the end of the experiment, their concentrations returned to control values. These nanoparticles could be used as contrast agents for MRI but several parameters concerning their interaction with the cells should be taken into consideration for a safe utilization.

1182. Potential application of Ni and Co stabilized zirconia as oxygen reduction reaction catalyst

Authors: Neatu, F; Trandafir, MM; Marcu, M; Preda, L; Calderon-Moreno, JM; Neatu, S; Somacescu, S; Florea, M

Published: APR 2017, CATALYSIS COMMUNICATIONS, 93, 42, DOI: 10.1016/j.catcom.2016.12.026

A new facile template method for the preparation of Ni, Co doped ZrO2 self-assembled electrocatalysts for oxygen reduction reaction was employed. The effect of the Ni and Co incorporation into ZrO2 lattice on the structural, texturaL surface chemistry and its activity on ORR was emphasized. As X-ray diffraction reveals, the pseudo-cubic lattice of the tetragonal ZrO2 polymorph (t-ZrO2) is stabilized when Ni and Co are co-doping ZrO2. The results indicate that the synergetic effects arisen from the intimate electronic interaction of the mixed oxides present in the lattice of the zirconia phase, i.e. Nil-xCoxO (or NiO and CoO) in NCZ enhance the electrocatalytic activity of the catalyst. (C) 2017 Elsevier B.V. All rights reserved.

1183. Production of Se-82 enriched Zinc Selenide (ZnSe) crystals for the study of neutrinoless double beta decay

Authors: Dafinei, I; Nagorny, S; Pirro, S; Cardani, L; Clemenza, M; Ferroni, F; Laubenstein, M; Nisi, S; Pattavina, L; Schaeffner, K; Di Vacri, ML; Boyarintsev, A; Breslavskii, I; Galkin, S; Lalayants, A; Rybalka, I; Zvereva, V; Enculescu, M

Published: OCT 1 2017, JOURNAL OF CRYSTAL GROWTH, 475, 170, DOI: 10.1016/j.jcrysgro.2017.06.013

High purity Zinc Selenide (ZnSe) crystals are produced starting from elemental Zn and Se to be used for the search of the neutrinoless double beta decay (0vDBD) of Se-82. In order to increase the number of emitting nuclides, enriched Se-82 is used. Dedicated production lines for the synthesis and conditioning of the (ZnSe)-Se-82 powder in order to make it suitable for crystal growth were assembled compliant with radiopurity constraints specific to rare event physics experiments. Besides routine check of impurities concentration, high sensitivity measurements are made for radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products used for ZnSe crystals production. Indications are given on the crystals perfection and how it is achieved. Since very expensive isotopically enriched material (Se-82) is used, a special attention is given for acquiring the maximum yield in the mass balance of all production stages. Production and certification protocols are presented and resulting ready-to-use (ZnSe)-Se-82 crystals are described. (C) 2017 Elsevier B. V. All rights reserved.

1184. Tb3+-doped alkaline-earth aluminates: Synthesis, characterization and optical properties

Authors: Mindru, I; Gingasu, D; Patron, L; Marinescu, G; Calderon-Moreno, JM; Diamandescu, L; Secu, M; Oprea, O

Published: JAN 2017, MATERIALS RESEARCH BULLETIN, 85, 248, DOI: 10.1016/j.materresbull.2016.09.024

Un-doped and Tb3+-doped calcium and strontium aluminates (CaAl2O4, CaAl2O4:Tb3+, SrAl2O4, SrAl2O4: Tb3+) were synthesized by a new soft chemical method the precursor route via the thermal decomposition of tartarate compounds. The complex precursors have been characterized by elemental chemical analysis, infrared spectroScopy (IR), luminescence spectroscopy and thermal analysis. X-ray diffraction (XRD), scanning electron microscopy (SEM), IR and Raman spectroscopy (RS) were used for the structural and morphological characterization of un-doped and doped alkaline-earth aluminate powders. Photoluminescence (PL) and Thermoluminescence (TL) properties of the aluminates were also investigated. The XRD patterns confirmed the formation of low-temperature structures: hexagonal structure for CaAl2O4 and monoclinic structure for SrAl2O4, with average crystallite size of 64 nm and 46 nm for CaAl2O4 and SrAl2O4, respectively. Microstructural analysis by SEM showed the homogeneous microstructure and fine particle size of the powder obtained by precursor method. (C) 2016 Elsevier Ltd. All rights reserved.

1185. UPCONVERSION AVALANCHE IN THE Yb3+/Ho3+ DOPED SiO2-LiYF4 NANO-GLASS CERAMIC

Authors: Secu, M

Published: OCT-DEC 2017, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 12, 1080, DOI:

The "avalanche" up-conversion properties of the glass-ceramics containing (Ho3+, Yb3+)doped LiYF4 nanocrystals have been studied by comparison to the corresponding nanocrystals and polycrystalline powder samples. Under 810 nm laser light pumping, all the samples showed "green" ((H-2(11/2), 4S(3/2)) -> I-4(15/2)) up-conversion luminescence. The pump power threshold for the avalanche mechanism is about 75mW for the nanocrystalline or polycrystalline powder samples indicating a weak influence of the nanosize related effects is but smaller of about 43mW for the nano-glass ceramic due to the high "local" Yb3+ concentrations.

1186. A comparative study of the structural, mechanical and tribological characteristics of TiSiC-Cr coatings prepared in CH4 and C2H2 reactive atmosphere by cathodic vacuum arc

Authors: Braic, M; Vladescu, A; Balaceanu, M; Luculescu, C; Padmanabhan, SC; Constantin, L; Morris, MA; Braic, V; Grigorescu, CEA; Ionescu, P; Dracea, MD; Logofatu, C

Published: APR 1 2017, APPLIED SURFACE SCIENCE, 400, 328, DOI: 10.1016/j.apsusc.2016.12.160

TiSiC-Cr coatings, with Cr and Si as additional elements, were deposited on Si, C 45 and 316 L steel substrates via cathodic arc evaporation. Two series of coatings with thicknesses in the range of 3.6-3.9 mu m were produced, using either CH4 or C2H2 as carbon containing gas. For each series, different coatings were prepared by varying the carbon rich gas flow rate between 90 and 130 sccm, while maintaining constant cathode currents (110 and 100A at TiSi and Cr cathodes, respectively), substrate bias (-200 V) and substrate temperature (similar to 320 degrees C). The coatings were analyzed for their mechanical characteristics (hardness, adhesion) and tribological performance (friction, wear), along with their elemental and phase composition, chemical bonds, crystalline structure and cross-sectional morphology. The coatings were found to be formed with nano-scale composite structures consisting of carbide crystallites (grain size of 3.1-8.2 nm) and amorphous hydrogenated carbon. The experimental results showed significant differences between the two coating series, where the films formed from C2H2 exhibited markedly superior characteristics in terms of microstructure, morphology, hardness, friction behaviour and wear resistance. For the coatings prepared using CH4, the measured values of crystallite size, hardness, friction coefficient and wear rate were in the ranges of 7.2-8.2 nm, 26-30 GPa, 0.3-0.4 and 2.1-4.8 x 10(-6) mm(3) N-1 m(-1), respectively, while for the coatings grown in C2H2, the values of these characteristics were found to be in the ranges of 3.1-3.7 nm, 41-45 GPa, 0.1-0.2 and 1.4-3.0 x 10(-6) mm(3) N-1 m(-1), respectively. Among the investigated coatings, the one produced using C2H2 at the highest flow rate (130 sccm) exhibited the highest hardness (45.1 GPa), the lowest friction coefficient (0.10) and the best wear resistance (wear rate of 1.4 x 10(-6) mm(3) N-1 m(-1)). (C) 2016 Elsevier B.V. All rights reserved.

1187. Hund and anti-Hund rules in circular molecules

Authors: Nita, M; Tolea, M; Marinescu, DC; Manolescu, A

Published: DEC 1 2017, PHYSICAL REVIEW B, 96, DOI: 10.1103/PhysRevB.96.235101

We study the validity of Hund's first rule for the spin multiplicity in circular molecules-made of real or artificial atoms such as quantum dots-by considering a perturbative approach in the Coulomb interaction in the extended Hubbard model with both on-site and long-range interactions. In this approximation, we show that an anti-Hund rule always defines the ground state in a molecule with 4N atoms at half-filling. In all other cases (i.e., number of atoms not a multiple of four, or a 4N molecule away from half-filling) both the singlet and the triplet outcomes are possible, as determined primarily by the total number of electrons in the system. In some instances, the Hund rule is always obeyed and the triplet ground state is realized mathematically for any values of the on-site and long-range interactions, while for other filling situations the singlet is also possible but only if the long-range interactions exceed a certain threshold, relatively to the on-site interaction.

1188. Electrochemical characterization of the Poly(2, 2 '-Bithiophene-co-Pyrene) Functionalized Single-Walled Carbon Nanotubes Films and Their Applications in Supercapacitors Field

Authors: Baibarac, M; Baltog, I; Daescu, M

Published: MAR 2017, INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE, 12, 2025, DOI: 10.20964/2017.03.60

The performance of the poly(2, 2'-bithiophene-co-pyrene) copolymer doped with bis(2-ethyl hexyl) sulfosuccinate sodium (AOT) anions [(PBTh-Py)(+)AOT(-)] and its composite with single-walled carbon nanotubes (SWNTs) [(PBTh-Py)(+)AOT(-)/SWNTs] as active materials for the electrodes of symmetrical supercapacitors is demonstrated in this work. Using cyclic voltammetry, the influence of the electrolyte concentration and the different cations on the oxidation and reduction processes at the electrolyte/electrode interface is reported. Using charge-discharge galvanostatic measurements in the case of the symmetrical-supercapacitors having as electrode active materials, the (PBTh-Py)(+)AOT(-) copolymer and the (PBTh-Py)(+)AOT(-)/SWNTs composite, values of the specific capacitance equal with 11.5 and 59 F g(-1), respectively, for current densities of 100 mA g(-1), were reported.

1189. Polypyrrole Actuator Based on Electrospun Microribbons

Authors: Beregoi, M; Evanghelidis, A; Diculescu, VC; Iovu, H; Enculescu, I

Published: NOV 1 2017, ACS APPLIED MATERIALS & INTERFACES, 9, 38075, DOI: 10.1021/acsami.7b13196

The development of soft actuators by using inexpensive raw materials and straightforward fabrication techniques, aiming at creating and developing muscle like micromanipulators, represents an important challenge nowadays. Providing such devices with biomimetic qualities, for example, sensing different external stimuli, adds even more complexity to the task. We developed electroactive polymer coated microribbons that undergo conformational changes in response to external physical and chemical parameters. These were prepared following three simple steps. During the first step nylon-6/6 microribbons were fabricated by electrospinning. In a second step the microribbons were one side coated with a metallic layer. Finally, a conducting layer of polypyrrole was added by means of electrochemical deposition. Strips of polypyrrole-coated aligned microribbon meshes were tested as actuators responding to current, pH, and temperature. The electrochemical activity of the microstructured actuators was investigated by recording cyclic voltammograms. Chronopontentiograms for specific current, pH, and temperature values were obtained in electrolytes with different compositions. It was shown that, upon variation of the external stimulus, the actuator undergoes conformational changes due to the reduction processes of the polypyrrole layer. The ability of the actuator to hold and release thin wires, and to collect polystyrene microspheres from the bottom of the electrochemical cell, was also investigated.

1190. From an Anomalous Peak Effect to a Second Magnetization Peak in Nb-rich Nb-Ti Alloys

Authors: Ionescu, AM; Ivan, I; Enculescu, M; Grigoroscuta, M; Miu, D; Valeanu, M; Badica, P; Miu, L

Published: APR 2017, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 30, 1108, DOI: 10.1007/s10948-016-3670-4

We investigated the evolution of the DC magnetic hysteresis curves of Nb0.89Ti0.11 alloys thermo-mechanically processed by intermediate heat treatments at 900 degrees C in vacuum and cold rolling (similar to 50% thickness reduction). Starting with a rectangular piece (similar to 0.4 mm thick) cut from the as-grown alloy, after the first thermo-mechanical treatment, the specimen exhibits over a wide temperature T interval a peak effect not far from the DC irreversibility line. With a supplemental thermo-mechanical treatment, the peak effect disappears and is substituted by a second magnetization peak ( where the characteristic fields are significantly lower) induced by pinning enhancement. The second magnetization peak was clearly seen at high temperatures only, due to the occurrence of thermo-magnetic instabilities in the low-T domain. In both cases, analysis of magnetic relaxation evidences a crossover towards plastic vortex creep accompanying the maximum in the effective critical current density. These results suggest a common nature of the observed effects, related to the disordering of the vortex system induced by pinning.

1191. Physical Mechanisms of Exchange Coupling Effects in Nanoparticulate Diluted Magnetic Oxides Obtained by Laser Pyrolysis

Authors: Kuncser, VE; Schinteie, GA; Kuncser, AC; Leca, A; Scarisoreanu, M; Morjan, I; Filoti, G

Published: APR 27 2017, JOURNAL OF PHYSICAL CHEMISTRY C, 121, 9069, DOI: 10.1021/acs.jpcc.7b01500

TiO2 nanoparticles, undoped and doped with Fe, have been prepared by laser pyrolysis and further investigated with respect to morphological, structural and magnetic aspects by transmission electron microscopy, diffractometry, Mossbauer spectroscopy, and magnetometry. The obtained nanoparticles, consisting of mainly anatase phase, agglomerate in clusters of tenths of units and present a large size distribution in the range from 5 to 40 nm. The anatase to rutile weight ratio (about 9) and the morphology of particles is similar in all analyzed samples (doped by up to 12 0,0 at. % Fe). Only Fe3+ ions in high spin-configuration were observed mainly at the, surface of TiO2 nanoparticles, either distributed or forming fine clusters of Fe oxide.;:Both a paramagnetic phase and a superparamagnetic one with blocking temperature lower than 50 K are superposed over a long-range ferromagnetic phase specific to diluted magnetic oxide systems. The influence of doping Fe ions on the magnetic behavior of each phase is discussed in detail. Evidences for interface exchange couplings (with unidirectional anisotropy in specific conditions) between the long-range ferromagnetic phase and the fine clusters (antiferromagnetic in nature), which become frozen below temperature of 50, K, are provided. The specificity of the processing route and the physical mechanisms responsible observed relevant magnetic features, which can be tailored for suitable applications, are discussed.

1192. Infrared dichroism studies and anisotropic photoluminescence properties of poly(para-phenylene vinylene) functionalized reduced graphene oxide

Authors: Baibarac, M; Ilie, M; Baltog, I; Lefrant, S; Humbert, B

Published: 2017, RSC ADVANCES, 7, 6942, DOI: 10.1039/c6ra26445j

Two methods were used for the synthesis of composites based on reduced graphene oxide (RGO) and poly(para-phenylene vinylene) (PPV) in un-doped and doped state, respectively, i.e. the annealing conversion (AC) of the PPV precursor solution (PS) at 300 degrees C and the electropolymerization (E) of alpha, alpha, alpha', alpha'-tetrabromo-p-xylene. In the case of the E method, a decrease in the distyrylbenzene (DSB) weight onto the RGO sheet surface in favor of PPV in doped state is demonstrated by the s and p polarized IR spectroscopy. The change of the orientation angle of the transition dipole moment vector for the IR bands at 835 and 964 cm(-1), in the case of the AC of the PPV PS, is a result of the p-p* interactions between the phenyl groups of PPV and the RGO sheets. The photoluminescence (PL) bands at 2.42 and 2.26 eV indicate the formation of PPV macromolecular chains (MCs) with lengths of 5 and 710 repeating units (RUs), respectively. The anisotropic PL studies performed on the composites RGO/PPV in un-doped and doped state, respectively, highlight an increase of the wrapping angle of RGO sheets with PPV MCs with lengths of 5 RUs, when graphene concentration increases.

1193. Oxide/metal/oxide electrodes for solar cell applications

Authors: Hrostea, L; Boclinca, M; Socol, M; Leontie, L; Stanculescu, A; Girtan, M

Published: APR 2017, SOLAR ENERGY, 146, 469, DOI: 10.1016/j.solener.2017.03.017

In this paper the influence of the heat treatment on the structural and optical properties of oxide single layer and multilayer transparent thin film structures of ITO/Au/ITO, AZO/Au/AZO, TiO2/Au/TiO2 and Bi2O3/Au/Bi2O3 type is studied. The single-layer oxides and respective multilayer structures have been deposited on glass substrates by successive DC magnetron sputtering using metallic targets ln:Sn, Zn:Al, Ti and Bi, in reactive (for the oxide films) or inert (for the metallic Au interlayer films) atmosphere. Good quality transparent conducting thin film structures have been obtained, with resistivity similar to 10(-4) Omega cm and transmittance similar to 75%. The wetting surface properties in function of time exposure at UV radiation (254 nm) have been also studied before and after heat treatment performed at 450 degrees C. (C) 2017 Elsevier Ltd. All rights reserved.

1194. Influence of TiO2 and Si on the exciton-phonon interaction in PbI2 and CdS semiconductors evidenced by Raman spectroscopy

Authors: Nila, A; Baltog, I; Dragoman, D; Baibarac, M; Mercioniu, I

Published: SEP 13 2017, JOURNAL OF PHYSICS-CONDENSED MATTER, 29, DOI: 10.1088/1361-648X/aa7cb3

The exciton-phonon interaction, considered as a stimulated Raman scattering process, is studied in different semiconductor mixtures: PbI2/TiO2, PbI2/Si and CdS/Si. Raman spectra recorded at excitation wavelengths of 514.5 and 488 nm for PbI2 and CdS, respectively, reveal a strong enhancement of the Raman lines peaked at 97 and 305 cm(-1), evaluated by the ratio I-TK/I-300 (K) between the relative intensities of the spectra recorded in the temperature range of 88-300 K. It is found that PbI2 and CdS exhibit a decrease in the Raman intensity modes with decreasing temperature, while in TiO2 and Si an increase in the Raman lines intensities peaked at 138 and 520 cm(-1) is observed. This behavior can be explained by an energy transfer process from PbI2 or CdS towards TiO2 and Si. This explanation is supported by the schematic potential energy levels diagram obtained from the density of states, which is calculated using the density functional theory. According to this energy levels diagram, the electrons are expected to migrate directly from the conduction band (CB) energetic levels of the PbI2 and CdS towards the CB levels of TiO2 and Si.

1195. Thermal behavior of new nickel(II) complexes with unsaturated carboxylates and heterocyclic N-donor ligands

Authors: Olar, R; Vlaicu, ID; Chifiriuc, MC; Bleotu, C; Stanica, N; Scaeteanu, GV; Silvestro, L; Dulea, C; Badea, M

Published: JAN 2017, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 127, 741, DOI: 10.1007/s10973-016-5445-3

Synthesis and characterization of four new Ni(II) complexes with mixed ligands have been reported in the present paper. As interest ligands, acrylate (acr) ion together with one N-donor heterocyclic ligand, namely benzimidazole (HBzIm), 2-methylbenzimidazole (2-MeBzIm), 5-methylbenzimidazole (5-MeBzIm) or 5,6-dimethylbenzimidazole (5,6-Me(2)BzIm), was chosen. The syntheses afforded the complexes formulated as [Ni(HBzIm)(2)(acr)(2)(H2O)]center dot 3H(2)O (1), [Ni(2-MeBzIm)(2)(acr)(2)(H2O)]center dot 1.5H(2)O (2), [Ni(5-MeBzIm)(2)(acr)(2)(H2O)] (3) and [Ni(5,6-Me(2)BzIm)(2)(acr)(2)] (4). Complexes (1) and (2) contain crystallization water molecules and coordinated water molecules, both their nature and presence being confirmed on the basis of IR spectra and thermal analysis. In contrast to above-mentioned complexes, (3) contains only coordinated water molecule, while (4) is an anhydrous compound. Based on electronic spectra and magnetic measurements, a distorted octahedral stereochemistry was proposed for all Ni(II) complexes. Acrylate ions act both as unidentate and chelate ligands in complexes (1)-(3), while in complex (4) act only as chelate ligands. All used N-donor ligands function as monodentate in all Ni(II) complexes. Biological properties of complexes (1)-(4) were evaluated against several Gram(+), Gram(-) bacterial strains and against fungus Candida albicans.

1196. Oral keratinocyte stem cells behavior on diamond like carbon films

Authors: Calenic, B; Greabu, M; Caruntu, C; Nicolescu, MI; Moraru, L; Surdu-Bob, CC; Badulescu, M; Anghel, A; Logofatu, C; Boda, D

Published: SEP-OCT 2016, ROMANIAN BIOTECHNOLOGICAL LETTERS, 21, 11922, DOI:

Diamond like carbon (DLC) is an amorphous carbon material suitable for use in a variety of in vivo biomedical applications, which may constitute a step forward in biotechnology of dental or orthopedic implants. Previous in vitro studies focusing on DLC films demonstrate that cellular behavior on DLC is cell type specific. The aim of the present study was to evaluate the interaction between DLC substrates and keratinocyte stem cells isolated from oral epithelia. Oral keratinocyte stem cells were isolated using a magnetic technique. Various DLC films were synthesized using Thermoionic Vacuum Arc plasma (TVA) by adjusting the distance between substrate and anode. We assessed important cell characteristics such as proliferation rate, colony forming efficiency of oral keratinocyte stem cells placed on various DLC films. Our results demonstrate that DLC substrates are biocompatible with the analyzed cell type, and do not affect cell size or colony forming efficiency, in specific conditions being able to stimulate their proliferative potential. The data demonstrates for the first time that oral keratinocyte stem cells are biocompatible with DLC films. Moreover the proliferative potential of cells may be enhanced by adjusting the deposition parameters of DLC films.

1197. PRELIMINARY STRUCTURAL ULTRASONIC CHARACTERIZATION OF HYDROXYAPATITE

Authors: Popa, CL; Antohe, S; Safciuc, F; El Kettani, MEC; Leduc, D; Antohe, F; Predoi, MV

Published: JUL-SEP 2016, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 11, 1006, DOI:

Synthetic hydroxyapatite (HAp) is one of the most commonly used material for a large variety of biomedical applications. This paper presents structural, morphological and preliminary ultrasonic characterizations of the HAp nanopowder synthesized by an adapted co-precipitation method. To this end, the structural and morphological properties were evaluated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Biological investigation were also performed in order to evidence the influence of HAp tablets on the development and growth of endothelial cells. The ultrasonic measurements obtained for the HAp dispersion allowed us to calculate the ultrasonic velocity and the attenuation. The study of ultrasonic waves propagation through dispersions could be used as future standard quality test, thus improving the quality of biomedical devices based on hydroxyapatite.

1198. Enamel Based Composite Layers Deposited on Titanium Substrate with Antifungal Activity

Authors: Iconaru, SL; Prodan, AM; Turculet, CS; Beuran, M; Ghita, RV; Costescu, A; Groza, A; Chifiriuc, MC; Chapon, P; Gaiaschi, S; Hristu, R; Stanciu, GA; Trusca, R; Ganciu, M; Raita, SM; Vineticu, N; Ciobanu, CS

Published: 2016, JOURNAL OF SPECTROSCOPY, 2016, DOI: 10.1155/2016/4361051

The goal of this paper was to investigate the antifungal activity of Enamel layers deposited on titanium substrate (Ti-Enamel) and Enamel layers deposited on titanium substrate previously coated with a vinyl polydimethylsiloxane layer (Ti-PDMS-Enamel). The physicochemical properties were also investigated. The Candida albicans biofilm development on the obtained layers was examined after 24 h, 48 h, and 72 h by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) after ethidium bromide staining. A significant inhibition of the fungal adherence and biofilm development was observed on Ti-Enamel layers. The antifungal results demonstrated that the use of new Ti-Enamel composite layers could represent a promising perspective for the prevention of fungal biofilms associated implant infections.

1199. LTCC-based Ceramic Microsystems with Integrated Fluidic Elements and Sensors

Authors: Belavic, D; Hodnik, M; Santo, M; Bolado, P; Ursic, H; Bradesko, A; Malic, B; Mercioniu, IF; Bencan, A; Makarovic, K; Ciobanu, RC; Schreiner, C

Published: 2016, PROCEEDINGS OF THE 2016 INTERNATIONAL CONFERENCE AND EXPOSITION ON ELECTRICAL AND POWER ENGINEERING (EPE 2016), 46, DOI: 10.1109/ICEPE.2016.7781299

In this contribution the design and fabrication of ceramic microsystems with integrated different microfluidic elements and sensors will be presented. Ceramic microsystems are based on unconventional application of low-temperature co-fired ceramic technology and materials. This unconventional application is related to three-dimensional ceramic structures, such as cantilevers, ledges, bridges, diaphragms, valleys, channels, holes and cavities, valves, mixers, diffusors, distributors, collectors, flow limiters, sensors, and actuators.

1200. Tailored electric and optical properties of Nd doped ZnO: from transparent conducting oxide to photon down-shifting thin films

Authors: Nistor, M; Mihut, L; Millon, E; Cachoncinlle, C; Hebert, C; Perriere, J

Published: 2016, RSC ADVANCES, 6, 41472, DOI: 10.1039/c6ra07669f

Nd-doped ZnO films with highly tunable properties were grown by pulsed electron beam deposition at 500 C on Si and c-cut single crystal substrates under oxygen gas. The effects of a slight change in the oxygen pressure (10(-2) to 2 x 10(-2) mbar) on the composition, structure and physical properties of the films were studied. Films grown at 10(-2) mbar present a low resistivity (5 x 10(-3) S-2 cm) and high transparency in visible range and do not show any near -infrared emission due to Nd3+ ions. On the contrary, films grown at 2 x 10(-2) mbar have high resistivity (>16 S-2 cm), high optical transparency and near infrared emission of the Nd3+ ions is observed under indirect excitation at 335 nm (i.e. absorption by the ZnO matrix and transfer to Nd3+ ions). These significant changes in physical properties, leading from transparent conducting oxide to photon down -shifting thin films, are related to growth mode in pulsed -electron beam deposition.

1201. Aggregates of Mn2+ Ions in Mesoporous Self-Assembled Cubic ZnS:Mn Quantum Dots: Composition, Localization, Structure, and Magnetic Properties

Authors: Nistor, SV; Stefan, M; Nistor, LC; Kuncser, V; Ghica, D; Vlaicu, ID

Published: JUL 7 2016, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 14466, DOI: 10.1021/acs.jpcc.6b04866

The source of collective magnetism in II-VI semiconductor quantum dots (QDs) doped with Mn2+ ions at high nominal impurity levels is still under debate. In the particular case of mesoporous, self-assembled cubic ZnS:Mn QDs, quantitative electron paramagnetic resonance (EPR) studies have shown that the Mn2+ ions incorporated in the core and on the surface of the QDs cannot be responsible for the observed collective magnetism because they remain in a diluted paramagnetic state up to the 50 000 ppm nominal concentration. Here we investigate the composition, localization, structure, and magnetic properties of the aggregates of Mn2+ ions incorporated in the mesoporous cZnS:Mn as a possible source of the observed collective magnetism. Samples of mesoporous cubic ZnS:Mn prepared by coprecipitation at several nominal impurity levels from 200 to 50 000 ppm are investigated by EPR, magnetometry, and analytical high resolution (scanning) transmission electron microscopy. The low temperature magnetic properties of the Mn2+ aggregates change from paramagnetic-like, for samples with nominal impurity levels up to 2000 ppm, to ones specific to larger clusters with distributed antiferromagnetic coupling at higher concentrations, behaving superparamagnetically above a certain temperature. There is also strong evidence that the Mn2+ aggregates responsible for the observed low temperature collective magnetism are incorporated as an amorphous phase of mainly Mn-Zn-O composition, localized in the interstices and pores of the mesoporous structure of the cubic ZnS:Mn QDs.

1202. Ultra-High Tunability of Ba(2/3)Sr(1/3) TiO3-Based Capacitors Under Low Electric Fields

Authors: Ghalem, A; Rammal, M; Huitema, L; Crunteanu, A; Madrangeas, V; Dutheil, P; Dumas-Bouchiat, F; Marchet, P; Champeaux, C; Trupina, L; Nedelcu, L; Banciu, MG

Published: JUL 2016, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, 26, 506, DOI: 10.1109/LMWC.2016.2576455

We report the high-frequency electrical characterization of Ba2/3Sr1/3 TiO3 (BST) thin films exhibiting a very high dielectric tunability with low losses at 2.45 GHz under very low applied electrical fields. BST layers were integrated in out-of-plane Metal-Insulator-Metal (MIM) devices with optimized Ir/MgO(100) bottom electrodes. The high frequency properties of BST films with thicknesses of 200 nm, 450 nm and 1450 nm were thoroughly investigated in the 100 MHz-10 GHz domain and exhibit extremely high capacitance tuning abilities of 82%, 81% and 70% respectively, under applied voltages as low as 10 V. MIM devices responses show the onset of acoustic resonances associated with the BST electrostrictive behavior under an electric field. By combining high tunability with low resistive losses under low applied voltages, these devices are opening promising avenues for their integration in high-performance tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used ISM (industrial, scientific and medical) frequency band.

1203. XPS Analysis of AuGeNi/Cleaved GaAs(110) Interface

Authors: Negrila, CC; Lazarescu, MF; Logofatu, C; Cotirlan, C; Ghita, RV; Frumosu, F; Trupina, L

Published: 2016, JOURNAL OF NANOMATERIALS, 2016, DOI: 10.1155/2016/7574526

The depth composition of the thin layer alloy, AuGeNi, devoted to acting as an ohmic contact on n-GaAs(110) has been investigated by in situ XPS combined with Argon ion sputtering techniques. The fresh cleaved surfaces, supposed to be free of oxygen, were usually deposited with a 200nm metallic layer in high vacuum conditions (better than 10(-7) torr), by thermal evaporation, and annealed at a 430-450 degrees Celsius temperature for 5 minutes. About 18 sessions of ion Ar surfaces etching and intermediate XPS measurements were performed in order to reveal the border of the metal/semiconductor interface. The atomic concentrations of the chemical elements have been approximated. Au4f, Ga3d, Ga2p, As3d, As2p, Ni2p(3/2), Ge3d, O1s, and C1s spectral lines were recorded. The Au, Ge, and Ni have a homogenous distribution while Ga and As tend to diffuse to the surface. Oxygen is present in the first layers of the surface while carbon completely disappears after the second etching step. The existence of an Au-Ga alloy was detected and XPS spectra show only metal Ni and Ge within the layer and at the interface. We tried to perform a study about the depth chemical composition profile analysis of AuGeNi layer on cleaved n-GaAs(110) by X-Ray Photoelectron Spectroscopy (XPS) technique.

1204. Non-isothermal crystallization kinetics growth of LiYF4(Yb,Er) nanoparticles

Authors: Bartha, C; Secu, CE; Secu, M

Published: DEC 2016, CERAMICS INTERNATIONAL, 42, 18736, DOI: 10.1016/j.ceramint.2016.09.012

The crystallization process of Yb3+/Er3+ codoped LiYF4 nanoparticles obtained by sol-gel method was studied using differential scanning calorimetry and X-ray diffraction. Thermal data obtained from differential scanning calorimetry measurements under non-isothermal conditions at different heating rates were examined using both model-free and model fitting approaches. It was shown that LiYF4 phase crystallization occurs at around 383 degrees C as a result of the thermal decomposition of trifluoracetates and is shifted to higher temperatures as the heating rate increases. Both Friedman and Ozawa-Flynn-Wall analyses have indicated that the activation energy and pre-exponential factor decrease slightly as the crystallization proceeds. According to the model-fitting approach (by using extended Prout-Tompkins nth-order, ath autocatalysis reaction), LiYF4 nanocrystalline phase is the result of an autocatalytic process where a second metastable phase YF3 acts as a catalyst that accelerates the crystallization process of the LiYF4 phase. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1205. Vapor transport growth of MoS2 nucleated on SiO2 patterns and graphene flakes

Authors: Stoica, T; Stoica, M; Duchamp, M; Tiedemann, A; Mantl, S; Grutzmacher, D; Buca, D; Kardynal, BE

Published: NOV 2016, NANO RESEARCH, 9, 3514, DOI: 10.1007/s12274-016-1227-2

Vapor transport growth of atomically thin MoS2 layers on patterned substrates is investigated, as it is a step towards the self-aligned growth and formation of heterojunctions, which could be useful in future applications. Enhanced formation of MoS2 flakes at the pattern edges is observed on both the substrates examined, namely, patterned thermal SiO2 on Si(100) and graphene flakes on SiO2. The diffusion driven growth leads to the formation of MoS2 monolayers (MLs) with sizes of tens of micrometers around the edges of SiO2 patterns. The growth mode and the optical quality of the MoS2 flakes can be controlled by varying the substrate temperature. Besides the lateral growth, 3R-type pyramids are obtained on prolonging the growth. Lateral MoS2-graphene heterostructures are obtained by using graphene flakes on SiO2 as a substrate.

1206. Thickness Influence on In Vitro Biocompatibility of Titanium Nitride Thin Films Synthesized by Pulsed Laser Deposition

Authors: Duta, L; Stan, GE; Popa, AC; Husanu, MA; Moga, S; Socol, M; Zgura, I; Miculescu, F; Urzica, I; Popescu, AC; Mihailescu, IN

Published: JAN 2016, MATERIALS, 9, DOI: 10.3390/ma9010038

We report a study on the biocompatibility vs. thickness in the case of titanium nitride (TiN) films synthesized on 410 medical grade stainless steel substrates by pulsed laser deposition. The films were grown in a nitrogen atmosphere, and their in vitro cytotoxicity was assessed according to ISO 10993-5 [1]. Extensive physical-chemical analyses have been carried out on the deposited structures with various thicknesses in order to explain the differences in biological behavior: profilometry, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction and surface energy measurements. XPS revealed the presence of titanium oxynitride beside TiN in amounts that vary with the film thickness. The cytocompatibility of films seems to be influenced by their TiN surface content. The thinner films seem to be more suitable for medical applications, due to the combined high values of bonding strength and superior cytocompatibility.

1207. INVESTIGATIONS ON THE PROPERTIES OF A TWO-DIMENSIONAL NANOPATTERNED METALLIC FILM

Authors: Breazu, C; Preda, N; Socol, M; Stanculescu, F; Matei, E; Stavarache, I; Iordache, G; Girtan, M; Rasoga, O; Stanculescu, A

Published: OCT-DEC 2016, Digest Journal of Nanomaterials and Biostructures, 11, 1229, DOI:

This paper presents some investigations of the effect of nanopatterning on the properties of aluminum layer deposited by sputtering. UV-Nanoimprint Lithography technique has been used for the realization of a 2D array of nanostructures (pillars) in aluminum film characterized by cylindrical shape and the following structural parameters: diameter between 400 nm and 490 nm, depth between 320 nm and 420 nm and periodicity of 1.1 mu m, which have been revealed by SEM and AFM measurements. The UV-Vis transmission, reflection and photoluminescence measurements have evidenced the effect of the nanopatterning on the optical properties of the A1 layer.

1208. Lignin fragmentation over magnetically recyclable composite Co@Nb2O5@Fe3O4 catalysts

Authors: Opris, C; Cojocaru, B; Gheorghe, N; Tudorache, M; Coman, SM; Parvulescu, VI; Duraki, B; Krumeich, F; van Bokhoven, JA

Published: JUL 2016, JOURNAL OF CATALYSIS, 339, 227, DOI: 10.1016/j.jcat.2016.04.002

Recoverable catalysts for lignin fragmentation were prepared as Xwt%Co@Nb2O5@Fe3O4 composites having magnetite as an inner core. A shell of niobia covering the magnetic nanoparticles (leading to intermediate Nb2O5@Fe3O4 composite) was deposed from a solution of ammonium niobate (V) oxalate complex by precipitation with NH3. Finally, the deposition of cobalt following the deposition-precipitation method generated the Xwt%Co3O4@Nb2O5@Fe3O4 composites that were reduced with hydrogen to Xwt %Co@Nb2O5@Fe3O4. Catalysts with loading of cobalt in the range X = 1-20 were prepared using this procedure. The different steps of the preparation were followed using various techniques such as surface area measurements, XRD, Raman and NH3-DRIFT spectroscopy, XPS, Mossbauer and TEM. On this basis it was concluded that the synthesized composites exhibit both Lewis and Bronsted acid sites associated with the niobia shell and contain finely dispersed cobalt nanoparticles. The fragmentation of lignin occurred on the constituent parts of this composite, i.e. Fe3O4, Nb2O5, Nb2O5@Fe3O4 but with lower performances. The addition of cobalt (Co@Nb2O5@Fe3O4 catalysts) led to a complete fragmentation of lignin where the dominant fragments were those containing C20-C28 molecules. This catalytic behavior is explained on the capability of niobia to catalyze the acidic hydrolysis of the beta-O-4' bounds and of Co to break the C-C bonds via hydrogenolysis. The optimization of the catalyst composition indicated a loading of 4 wt% as optimal. Working at 180 degrees C and 10 atm H-2 this catalyst allowed a conversion of 53% leading to a mixture containing over 96% in C20-C28 and C29-C37 fragments. The investigated catalysts were completely recyclable as it was showed in six successive cycles. No leaching of the elements included in the composition was determined by ICP-OES. (C) 2016 Elsevier Inc. All rights reserved.

1209. Correlation between strain and defects in Bi implanted Si

Authors: Palade, C; Lepadatu, AM; Slav, A; Ciurea, ML; Lazanu, S

Published: JUN 2016, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 93, 32, DOI: 10.1016/j.jpcs.2016.02.005

The strain in Si containing group-V impurities is a topical subject of study due to its potential applications in quantum computing. In this paper we study Bi-209 implanted Si concerning the correlation between the strain produced by stopped Bi ions and trapping characteristics of the defects resulted from implantation. The depths distributions of stopped ions and primary defects are simulated and the distributions of permanent defects are modelled for Si implanted with low fluence Bi-209 ions of 28 MeV kinetic energy. For comparison, these depths distributions were similarly calculated for I-127 ions with the same fluence and energy, implanted in Si. The results are compared with each other and correlated with the characteristics of traps in these systems, previously obtained. We demonstrate that the intensity of the strain field is the most important factor in changing of trap parameters, while the superposition between the region with strain and the region where defects are located is a second order effect. (C) 2016 Elsevier Ltd. All rights reserved.

1210. Interfacial mechanisms of novel laser-irradiated L1(0)-based nanocomposite magnets

Authors: Crisan, O; Crisan, AD; Enculescu, M

Published: APR 2016, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 122, DOI: 10.1007/s00339-016-9947-4

In melt-spun FePtB-based ribbons, the addition of Ag has been proven to decrease the temperature of phase transformation from the A1 fcc FePt phase to the hard magnetic tetragonal L1(0) phase. Alloys with 6 and 9 at.% Ag added to the initial FePtB have been synthesized by rapid solidification from the melt. The samples have been laser irradiated and submitted to nitriding procedure. This procedure has been proven beneficial for inducing complete transformation of A1 to L1(0) phase and a strong (001) texturing. Ag segregation combined to mechanisms of creation of vacancies and diffusion of N give rise to the formation of an intergranular disordered region and due to an improved interfacial coupling between FePt grains, enhanced coercivity and two-phase magnetic behavior is obtained.

1211. Non-volatile memory devices based on Ge nanocrystals

Authors: Vasilache, D; Cismaru, A; Dragoman, M; Stavarache, I; Palade, C; Lepadatu, AM; Ciurea, ML

Published: FEB 2016, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 213, 259, DOI: 10.1002/pssa.201532376

The article presents the fabrication and characterization of NV (non-volatile) memory devices based on SiO2/Ge/SiO2 trilayer structures on Si wafers. The trilayer structures were obtained by using the magnetron sputtering method for the deposition of gate SiO2 and intermediate Ge layers and the rapid thermal oxidation for the growth of tunnel SiO2 layer. Rapid thermal annealing was performed for obtaining Ge nanocrystals embedded in the SiO2 gate oxide, as charge-storage elements. Two NV cross bar memory structures based on two cell sizes of 300x300 and 100x100m(2) were manufactured. Capacity-voltage curves were measured on the memory devices, at different frequencies in the 1kHz-10MHz range at room temperature (RT) for evidencing the hysteresis loops and for showing that the devices keep memory in time at these frequencies. We have obtained capacity-voltage hysteresis curves with large memory window up to 2V. We demonstrate that the trilayer structure SiO2/Ge/SiO2/on Si with Ge NCs embedded in the SiO2 gate oxide is suitable for NV memory applications having a large number of cells.

1212. Photocatalytic, Antimicrobial and Biocompatibility Features of Cotton Knit Coated with Fe-N-Doped Titanium Dioxide Nanoparticles

Authors: Stan, MS; Nica, IC; Dinischiotu, A; Varzaru, E; Iordache, OG; Dumitrescu, I; Popa, M; Chifiriuc, MC; Pircalabioru, GG; Lazar, V; Bezirtzoglou, E; Feder, M; Diamandescu, L

Published: SEP 2016, MATERIALS, 9, DOI: 10.3390/ma9090789

Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO2-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 degrees C. The powders were characterized by X-ray diffraction (XRD), Mossbauer spectroscopy and X-ray photoelectron spectroscopy. The textiles coated with doped TiO2 were characterized by scanning electron microscopy and energy dispersive X-ray analyses, and their photocatalytic effect by trichromatic coordinates of the materials stained with methylene blue and coffee and exposed to UV, visible and solar light. The resulting doped TiO2 consists of a mixture of prevailing anatase phase and a small amount (similar to 15%-20%) of brookite, containing Fe3+ and nitrogen. By reusing dispersions of TiO2-1% Fe-N, high amounts of photocatalysts were deposited on the fabrics, and the photocatalytic activity was improved, especially under visible light. The treated fabrics exhibited specific antimicrobial features, which were dependent on their composition, microbial strain and incubation time. The in vitro biocompatibility evaluation on CCD-1070Sk dermal fibroblasts confirmed the absence of cytotoxicity after short-term exposure. These results highlight the potential of TiO2-1% Fe-N nanoparticles for further use in the development of innovative self-cleaning and antimicrobial photocatalytic cotton textiles. However, further studies are required in order to assess the long-term skin exposure effects and the possible particle release due to wearing.

1213. CoFe2O4 magnetic ceramic derived from gel and densified by spark plasma sintering

Authors: Cernea, M; Galizia, P; Ciuchi, I; Aldica, G; Mihalache, V; Diamandescu, L; Galassi, C

Published: JAN 25 2016, JOURNAL OF ALLOYS AND COMPOUNDS, 656, 862, DOI: 10.1016/j.jallcom.2015.09.271

Cobalt ferrite (CoFe2O4) has been successfully synthesized by sol-gel technique. Pellets were prepared by spark plasma sintering technique (SPS) from CoFe2O4 sol-gel derived powder. The rapid sintering of CoFe2O4 pellet by SPS at 950 degrees C, leads to a dense ceramic (97%(rho theoretic)) with average crystallite size of 71 nm. As revealed by X-ray diffraction and Mossbauer measurements, the obtained powder and SPS pellets are spinel ferrite with a cubic symmetry. Complex dielectric investigation performed on CoFe2O4 ceramic reveals multiple relaxation mechanisms while the magnetic measurements indicated a saturation magnetization value of similar to 83 A m(2)/kg at room temperature, which make them useful for applications in microwave domain. (C) 2015 Elsevier B.V. All rights reserved.

1214. Characterization of TiNi shape memory alloys obtained by spark plasma sintering process

Authors: Cirstea, CD; Tolea, F; Leonat, L; Lungu, M; Cucos, A; Cirstea, V; Tsakiris, V

Published: SEP-OCT 2016, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 18, 862, DOI:

This paper presents the research results on the thermal behavior of the 48.5% at Ti-Ni alloys, obtained by spark plasma sintering in vacuum under a pressure of 50 MPa, at temperatures of 850 degrees C and 900 degrees C and holding time of 5 minutes, and subsequently aged in argon for up to 30 minutes at 450 degrees C. Differential scanning calorimetry, dynamic mechanical and dilatometry analysis were used to characterize the transformation properties of the TiNi samples. All the results of differential scanning calorimetry and dynamic mechanical analysis confirmed the hypothesis that the stress-free thermally induced martensitic transformation exists in the investigated TiNi alloys. Annealing at lower temperatures (450 degrees C) in Ni-rich TiNi alloys led to precipitation process which facilitates the formation of the R-phase due to internal stress contributed by precipitates.

1215. Mechanism of the cathodic process coupled to the oxidation of iron monosulfide by dissolved oxygen

Authors: Duinea, MI; Costas, A; Baibarac, M; Chirita, P

Published: APR 1 2016, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 467, 59, DOI: 10.1016/j.jcis.2016.01.010

This study investigated the mechanism of iron monosulfide (FeS) oxidation by dissolved oxygen (O-2(aq)). Synthetic FeS was reacted with O-2(aq) for 6 days and at 25 degrees C. We have characterized the initial and reacted FeS surface using Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). It was found that during the aqueous oxidation of FeS new solid phases (disulfide, polysulfide, elemental sulfur, ferric oxyhydroxides and Fe3O4) develop on the mineral surface. The results of potentiodynamic polarization experiments show that after 2 days of FeS electrode immersion in oxygen bearing solution (OBS) at initial pH 5.1 and 25 degrees C the modulus of cathodic Tafel slopes dramatically decreases, from 393 mV/dec to 86 mV/dec. This decrease is ascribed to the change of the mechanism of electron transfer from cathodic sites to O-2 (mechanism of cathodic process). The oxidation current densities (j(ox)) indicate that mineral oxidative dissolution is not inhibited by pH increase up to 6.7. Another conclusion, which emerges from the analysis of j(ox), is that the dissolved Fe3+ does not intermediate the aqueous oxidation of FeS. The results of electrochemical impedance spectroscopy (EIS) show that after 2 days of contact between electrode and OBS the properties of FeS/water interface change. From the analysis of the EIS, FTIR spectroscopy, Raman spectroscopy and SEM/EDX data we can conclude that the change of FeS/water interface properties accompanies the formation of new solid phases on the mineral surface. The new characteristics of the surface layer and FeS/water interface do not cause the inhibition of mineral oxidation. (C) 2016 Elsevier Inc. All rights reserved.

1216. An adamantane-based COF: stability, adsorption capability, and behaviour as a catalyst and support for Pd and Au for the hydrogenation of nitrostyrene (vol 6, pg 8344, 2016)

Authors: Trandafir, MM; Pop, L; Hadade, ND; Florea, M; Neatu, F; Teodorescu, CM; Duraki, B; van Bokhoven, JA; Grosu, I; Parvulescu, VI; Garcia, H

Published: 2016, CATALYSIS SCIENCE & TECHNOLOGY, 6, 8573, DOI: 10.1039/c6cy90113a

1217. Ferritin surplus in mouse spleen 14 months after intravenous injection of iron oxide nanoparticles at clinical dose

Authors: Tamion, A; Hillenkamp, M; Hillion, A; Maraloiu, VA; Vlaicu, ID; Stefan, M; Ghica, D; Rositi, H; Chauveau, F; Blanchin, MG; Wiart, M; Dupuis, V

Published: AUG 2016, NANO RESEARCH, 9, 2410, DOI: 10.1007/s12274-016-1126-6

In this study, we followed the biodegradation of ultra-small superparamagnetic iron oxide nanoparticles injected intravenously at clinical doses in mice. An advanced fitting procedure for magnetic susceptibility curves and low-temperature hysteresis loops was used to fully characterize the magnetic size distribution as well as the magnetic anisotropy energy of the injected P904 nanoparticles (Guerbet Laboratory). Additional magnetometry measurements and transmission electronic microscopy observations were systematically performed to examine dehydrated samples from the spleen and liver of healthy C57B16 mice after nanoparticle injection, with sacrifice of the mice for up to 14 months. At 3 months after injection, the magnetic properties of the spleen and liver were dramatically different. While the liver showed no magnetic signals other than those also present in the reference species, the spleen showed an increased magnetic signal attributed to ferritin. This surplus of ferritin remained constant up to 14 months after injection.

1218. MULTI-WAVELENGTH LASER IRRADIATION OF Be-C-W COATINGS

Authors: Avotina, L; Marcu, A; Porosnicu, C; Lungu, M; Stancalie, A; Ilie, AG; Ganea, PC; Savastru, D; Kalnacs, J; Lungu, CP; Kizane, G; Antohe, S

Published: JAN-MAR 2016, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 11, 302, DOI:

BeCW (3:2:1) amorphous films were irradiated with three laser wavelengths of 300, 550 and 1350 nm having a comparable energy and respectively power density. Ablated volume and preferential ablation of lighter elements seemed independent of the photon's energy, but rather on their number. Carbon and Be clustering and crystal formation into the amorphous coating were more effective with more energetic photons. Graphite structures formation was recorded for fluencies below the ablation threshold. For longer laser wavelengths, carbon atoms tend to organize in ring structures and fullerene formation was recorded around the ablation zones. Be crystals formed in the ablation zone vicinity tend to be stretched toward the film surface and toward the ablation center suggesting more defects into the formed structures for these zones.

1219. Hydrogenation of Condensed Aromatic Compounds over Mesoporous Bifunctional Catalysts Following a Diels-Alder Adduct Pathway

Authors: Huyen, PT; Krivec, M; Kocevar, M; Bucur, IC; Rizescu, C; Parvulescu, VI

Published: MAR 18 2016, CHEMCATCHEM, 8, 1156, DOI: 10.1002/cctc.201501295

Pt(0.5wt%)-Al-SBA-15 and Pt(0.5wt%)-Al-MCM-41 bifunctional catalysts were prepared by wet impregnation and investigated in the hydrogenation of anthracene and the hydrogenolysis/hydrogenation of a series of synthesized Diels-Alder adducts with anthracene and anthracene derivatives. The mesoporous texture of the investigated catalysts allowed the hydrogenation of these substrates to a large extent. In direct correlation with the size of the Pt particles, Pt-Al-SBA-15 exhibited a higher activity. Both catalysts exhibited a strong Lewis acidity associated with the presence of the Al extra-framework species. The acidity of these catalysts afforded the esterification of the reaction byproduct, that is, succinic anhydride, with methanol or ethanol, and the hydrocracking/decyclization of one hydrogenated ring to lead to 1,2,3,4-tetrahydronaphthalene derivatives. A good correlation with the calculated values of the reaction Gibbs free energy has been evidenced.

1220. Structural and Biological Assessment of Zinc Doped Hydroxyapatite Nanoparticles

Authors: Popa, CL; Deniaud, A; Michaud-Soret, I; Guegan, R; Motelica-Heino, M; Predoi, D

Published: 2016, JOURNAL OF NANOMATERIALS, 2016, DOI: 10.1155/2016/1062878

The aim of the current research work was to study the physicochemical and biological properties of synthesized zinc doped hydroxyapatite (ZnHAp) nanoparticles with Zn concentrations x(Zn) = 0 (HAp), x(Zn) = 0.07 (7ZnHAp), and x(Zn) = 0.1 (10ZnHAp) for potential use in biological applications. The morphology, size, compositions, and incorporation of zinc into hydroxyapatite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Raman scattering, and X-Ray Photoelectron Spectroscopy (XPS). In addition, the cytotoxicity of ZnHAp nanoparticles was tested on both E. coli bacteria and human hepatocarcinoma cell line HepG2. The results showed that ZnHAp nanoparticles (HAp, 7ZnHAp, and 10ZnHAp) have slightly elongated morphologies with average diameters between 25 nm and 18 nm. On the other hand, a uniform and homogeneous distribution of the constituent elements (calcium, phosphorus, zinc, and oxygen) in the ZnHAp powder was noticed. Besides, FTIR and Raman analyses confirmed the proper hydroxyapatite structure of the synthesized ZnHAp nanoparticles with the signature of phosphate, carbonate, and hydroxyl groups. Moreover, it can be concluded that Zn doping at the tested concentrations is not inducing a specific prokaryote or eukaryote toxicity in HAp compounds.

1221. Exploring porous nanosilica-TEMPO as heterogeneous aerobic oxidation catalyst: the influence of supported gold clusters

Authors: Shakir, AJ; Florea, M; Culita, DC; Ionita, G; Ghica, C; Stavarache, C; Hanganu, A; Ionita, P

Published: FEB 2016, JOURNAL OF POROUS MATERIALS, 23, 254, DOI: 10.1007/s10934-015-0076-9

TEMPO stable free radical has been supported on porous silica nanoparticles in different ways and the resulted materials have been tested as heterogeneous oxidation catalyst of three benzylic alcohols using air as final oxidant and nitrosonium tetrafluoroborate as cocatalyst. Good to excellent yields were obtained. The catalytic system consists in fact in two coupled cycles, NO/NO2 and TEMPO+/TEMPO, able to convert under mild conditions (room temperature, air, metal and halogen free condition) alcohols into aldehydes or ketones. Under these conditions, supported TEMPO on silica nanoparticles containing gold clusters lowers the efficiency of the catalyst.

1222. New-developed TiO2-based photocatalytic nano particles exhibit biocompatibility on MRC-5 lung fibroblasts after short-term exposure

Authors: Dinischiotu, A; Nica, CI; Stan, MS; Dumitrescu, I; Diamandescu, L

Published: AUG 10 2016, JOURNAL OF BIOTECHNOLOGY, 231, S67, DOI: 10.1016/j.jbiotec.2016.05.246

1223. Optical properties of single-walled carbon nanotubes functionalized with copolymer poly(3,4-ethylenedioxythiophene-co-pyrene)

Authors: Baltog, I; Baibarac, M; Smaranda, I; Matea, A; Ilie, M; Mevellec, JY; Lefrant, S

Published: DEC 2016, OPTICAL MATERIALS, 62, 611, DOI: 10.1016/j.optmat.2016.11.005

Optical properties are reported for composites based on single-walled carbon nanotubes (SWNT5) and copolymer poly(3,4-ethylenedioxythiophene-co-pyrene) (PEDOT-Py) prepared by chemical polymerization of two monomers in the presence of carbon nanotubes. A charge transfer between SWNT5 and the PEDOT-Py copolymer was demonstrated by Raman scattering. The increase in the relative intensity of the Raman lines peaked at 440-577 cm(-1), which were assigned to the ethylenedioxy ring vibrational modes, indicated a significant hindrance steric in the case of the composites based on the PEDOT-Py copolymer and metallic SWNTs. The increase in the absorbance of IR band peaked at 984 cm(-1) occurred simultaneously with the disappearance of the IR band at 1639 cm(-1). This finding was a consequence of the formation of new covalent bonds between SWNTs and the thiophene and benzene rings of the repeating units of the PEDOT-Py copolymer. The photoluminescence (PL) quenching process of the PEDOT-Py copolymer was induced by semiconducting SWNTs. The PL quenching of PEDOT-Py copolymer in the presence of SWNT5 was. demonstrated based on the energy level diagrams of the two constituents of the PEDOT-Py/SWNTs composite material. (C) 2016 Elsevier B.V. All rights reserved.

1224. Combined ab initio and XPS Investigations of the Electronic Interactions of L-Cysteine Adsorbed on GaAs(100)

Authors: Juarez, MF; Toader, AM; Negrila, C; Santos, E; Lazarescu, V

Published: AUG 16 2016, CHEMISTRYSELECT, 1, 3634, DOI: 10.1002/slct.201600589

The adsorption of L-cysteine from ethanol solutions on GaAs(1 0 0) surfaces has been studied by XPS and density-functional theory (DFT). XPS data reveal that the formation of the adsorbate involves preferentially the As-sites for p-GaAs(1 0 0) and the Ga-sites for n-GaAs(1 0 0). The adsorbed species show different orientations of the functional groups to the surface for the different substrates. DFT calculations performed for both Ga-dimers and As-dimers terminated surfaces show that the adsorption is energetically favourable on both substrates. However, the adsorption energy is more negative on top of Ga-atoms. Here an important contribution for the stabilization of the adsorbate is the interaction of the functional groups with the surface. The parallel orientation found for the Ga-bound species by DFT calculations is in good agreement with the shift in the binding energy of the NH2/NH3+ species observed by XPS analysis.

1225. STRUCTURAL AND MAGNETIC PROPERTIES OF Sr2FeMoO6 OBTAINED AT LOW TEMPERATURES

Authors: Bartha, C; Plapcianu, C; Crisan, A; Enculescu, M; Leca, A

Published: JUL-SEP 2016, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 11, 780, DOI:

The double-perovskite Sr2FeMoO6 has been obtained by solid state method at low temperature (1060 degrees C) and a very short time of synthesis (up to 4h). Both, X-ray diffraction and scanning electron microscopy (SEM) confirmed the formation of Sr2FeMoO6 oxide with grain sizes around 160 mm, and a small amount of SrMoO4 as an impurity. Mossbauer spectroscopy revealed a mixed site population with Fe and Mo ions generating a structure type with population inversion. This structure has a critical influence on the magnetic properties, as confirmed by the magnetization and TC values, i.e 3.56 mu(B)/f.u and 415 K, respectively. The Sr2FeMoO6 behavior was interpreted in terms of ferrimagnetic couplings generated by the various distributions of local interactions between Fe and Mo neighbors while comparing the ideal structure should show antiferromagnetic coupling between the two sublattices.

1226. Investigations of Ar ion irradiation effects on nanocrystalline SiC thin films

Authors: Craciun, V; Craciun, D; Socol, G; Behdad, S; Boesl, B; Himcinschi, C; Makino, H; Socol, M; Simeone, D

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 345, DOI: 10.1016/j.apsusc.2015.12.130

The effects of 800 keV Ar ion irradiation on thin nanocrystalline SiC films grown on (100) Si substrates using the pulsed laser deposition (PLD) technique were investigated. On such PLD grown films, which were very dense, flat and smooth, X-ray reflectivity, glancing incidence X-ray diffraction and nanoindentation investigations were easily performed to evaluate changes induced by irradiation on the density, surface roughness, crystalline structure, and mechanical properties. Results indicated that the SiC films retained their crystalline nature, the cubic phase partially transforming into the hexagonal phase, which had a slightly higher lattice parameter then the as-deposited films. Simulations of X-ray reflectivity curves indicated a 3% decrease of the films density after irradiation. Nanoindentation results showed a significant decrease of the hardness and Young's modulus values with respect to those measured on as-deposited films. Raman and X-ray photoelectron spectroscopy investigations found an increase of the C-C bonds and a corresponding decrease of the Si-C bonds in the irradiated area, which could explain the degradation of mechanical properties. (C) 2015 Elsevier B.V. All rights reserved.

1227. Investigation of atmospheric corrosion by photon energy dependent luminescence and Raman spectroscopy in aged and freshly fractured g-,c-As2S3 with photosensitive realgar inclusions

Authors: Mitsa, V; Holomb, R; Marton, A; Veres, M; Toth, S; Himics, L; Lorinczi, A; Popescu, M

Published: DEC 1 2016, JOURNAL OF NON-CRYSTALLINE SOLIDS, 453, 27, DOI: 10.1016/j.jnoncrysol.2016.09.022

We have studied the light emission properties of aged glassy (g-) and crystalline (c-) As2S3 and freshly fractured glassy As2S3 with photosensitive realgar inclusions in the 1.5-4.5 eV spectral range and applying different excitation photon energies. Additionally, Raman scattering measurements were performed on g-As40S60 to investigate structural changes caused by corrosion of the glass in air. Major features in the luminescence spectra were observed at 1.65,1.87, 2.04, 226, 2.80 and 325 eV photon energies. The 1.65 eV band in photoluminescence spectra of g-As2S3 was identified to be related to the As side by comparison of the photoluminescence spectrum with literature data for As4S4 realgar crystal. A newly observed band at 1.87 eV was assigned to the As side in pararealgar occurring due to the light induced transformation from realgar to pararealgar phase. An oxidation process was found to take place during the aging and photo-aging accompanied with formation of As oxides, indicated by the emission bands at 2.04 and 226 eV. A rapid photo-oxidation process was observed in freshly fractured surfaces at room temperature which was connected with the light stimulated realgar-pararealgar transformation. (C) 2016 Elsevier B.V. All rights reserved.

1228. An adamantane-based COF: stability, adsorption capability, and behaviour as a catalyst and support for Pd and Au for the hydrogenation of nitrostyrene

Authors: Trandafir, MM; Pop, L; Hadade, ND; Florea, M; Neatu, F; Teodorescu, CM; Duraki, B; van Bokhoven, JA; Grosu, I; Parvulescu, VI; Garcia, H

Published: 2016, Catalysis Science & Technology, 6, 8354, DOI: 10.1039/c6cy01631f

A bimodal (micro/mesoporous) COF was synthesized by coupling tetrakis-1,3,5,7-(4'-iodophenyl) adamantane with 4,4'-diethynylbiphenyl following a Sonogashira protocol. The COF preparation strategy led, however, to the incomplete recovery of the palladium catalyst and ICP-OES analysis indicated that around 0.1 wt% palladium remained inside the pores. Noteworthily, the remnant palladium catalyst is still accessible and can be valorised in additional catalytic reactions like the hydrogenation of nitrostyrene. Further deposition of 0.5 wt% active metals (like palladium or gold) enhanced the catalytic activity and tuned the catalyst selectivity with respect to analogous metal catalysts prepared using active carbon as a support. The resulting COF-supported metal NPs are stable and recyclable catalysts. Under normal conditions, this COF is also able to adsorb large amounts of weak electrophilic gases like carbon dioxide.

1229. Fabrication of naturel pumice/hydroxyapatite composite for biomedical engineering

Authors: Komur, B; Lohse, T; Can, HM; Khalilova, G; Gecimli, ZN; Aydogdu, MO; Kalkandelen, C; Stan, GE; Sahin, YM; Sengil, AZ; Suleymanoglu, M; Kuruca, SE; Oktar, FN; Salman, S; Ekren, N; Ficai, A; Gunduz, O

Published: JUL 7 2016, BIOMEDICAL ENGINEERING ONLINE, 15, DOI: 10.1186/s12938-016-0203-0

Background: We evaluated the Bovine hydroxyapatite (BHA) structure. BHA powder was admixed with 5 and 10 wt% natural pumice (NP). Compression strength, Vickers micro hardness, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction studies were performed on the final NP-BHA composite products. The cells proliferation was investigated by MTT assay and SEM. Furthermore, the antimicrobial activity of NP-BHA samples was interrogated. Results: Variances in the sintering temperature (for 5 wt% NP composites) between 1000 and 1300 degrees C, reveal about 700 % increase in the microhardness (similar to 100 and 775 HV, respectively). Composites prepared at 1300 degrees C demonstrate the greatest compression strength with comparable result for 5 wt% NP content (87 MPa), which are significantly better than those for 10 wt% and those that do not include any NP (below 60 MPa, respectively). Conclusion: The results suggested the optimal parameters for the preparation of NP-BHA composites with increased mechanical properties and biocompatibility. Changes in micro-hardness and compression strength can be tailored by the tuning the NP concentration and sintering temperature. NP-BHA composites have demonstrated a remarkable potential for biomedical engineering applications such as bone graft and implant.

1230. Novel multiferroic (Pb-1 (-) Nd-3x/2(x))(Ti-0.98 (-) yFeyMn0.02)O-3 ceramics with coexisting ferroelectricity and ferromagnetism at ambient temperature

Authors: Craciun, F; Cernea, M; Fruth, V; Zaharescu, M; Atkinson, I; Stanica, N; Tanase, LC; Diamandescu, L; Iuga, A; Galassi, C

Published: NOV 15 2016, MATERIALS & DESIGN, 110, 704, DOI: 10.1016/j.matdes.2016.08.046

We report the evolution of structural, dielectric, ferroelectric and ferromagnetic properties in novel (Pb1 - 3x/2Ndx) (Ti0.98 - yFeyMn0.02)O-3 perovskite ceramics (x = 0.08, 0 < y < 0.05). We found room-temperature ferroelectric polarization and ferromagnetism for higher amount of iron ions(y >= 0.04). The paraelectric-ferroelectric phase transition occurred between 650 and 670 K for 0 <= y <= 0.05. Ferromagnetic hysteresis was measured at different temperatures on samples with y >= 0.04. Detailed structural analysis evidenced the variation of unit cell parameters with y increasing, confirming the substitution of the iron element in the lattice. Fe-57 Mtissbauer spectroscopy evidenced that iron ions occupy Ti positions in the perovskite lattice, with the oxidation state Fe3+ and two coordination types. X-ray photoelectron spectroscopy confirmed the presence of iron only as Fe3+ and, moreover, evidenced the presence of a substantial amount of Ti3+ ions in the structure. The presence of both Fe3+ (spin 5/2) in different coordinations as well as Ti3+ (spin 1/2) magnetic ions in B-site positions drives the occurrence of magnetic properties from low temperature to above room temperature, through superexchange Fe3+-O-Fe3+, Fe3+-O-Ti3+ and Ti3+-O-Ti3+ interactions. The finding of coexistent ferroelectric and ferromagnetic properties in these compounds ground the route to facile synthesis of multiferroics by simply doping a classical perovskite ferroelectric material like PbTiO3 with an adequate amount of transition magnetic ions. (C) 2016 Elsevier Ltd. All rights reserved.

1231. Joining Chemical Pressure and Epitaxial Strain to Yield Y-doped BiFeO3 Thin Films with High Dielectric Response

Authors: Scarisoreanu, ND; Craciun, F; Birjega, R; Ion, V; Teodorescu, VS; Ghica, C; Negrea, R; Dinescu, M

Published: MAY 9 2016, SCIENTIFIC REPORTS, 6, DOI: 10.1038/srep25535

BiFeO3 is one of the most promising multiferroic materials but undergoes two major drawbacks: low dielectric susceptibility and high dielectric loss. Here we report high in-plane dielectric permittivity (epsilon' similar to 2500) and low dielectric loss (tan delta < 0.01) obtained on Bi0.95Y0.05FeO3 films epitaxially grown on SrTiO3 (001) by pulsed laser deposition. High resolution transmission electron microscopy and geometric phase analysis evidenced nanostripe domains with alternating compressive/tensile strain and slight lattice rotations. Nanoscale mixed phase/domain ensembles are commonly found in different complex materials with giant dielectric/electromechanical (ferroelectric/relaxors) or magnetoresistance (manganites) response. Our work brings insight into the joined role of chemical pressure and epitaxial strain on the appearance of nanoscale stripe structure which creates conditions for easy reorientation and high dielectric response, and could be of more general relevance for the field of materials science where engineered materials with huge response to external stimuli are a highly priced target.

1232. Fabrication of antimicrobial silver-doped carbon structures by combinatorial pulsed laser deposition

Authors: Mihailescu, IN; Bociaga, D; Socol, G; Stan, GE; Chifiriuc, MC; Bleotu, C; Husanu, MA; Popescu-Pelin, G; Duta, L; Luculescu, CR; Negut, I; Hapenciuc, C; Besleaga, C; Zgura, I; Miculescu, F

Published: DEC 30 2016, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 515, 606, DOI: 10.1016/j.ijpharm.2016.10.041

We report on the selection by combinatorial pulsed laser deposition of Silver-doped Carbon structures with reliable physical-chemical characteristics and high efficiency against microbial biofilms. The investigation of the films was performed by scanning electron microscopy, high resolution atomic force microscopy, energy dispersive X-Ray Spectroscopy, X-ray diffraction, Raman spectroscopy, bonding strength "pull-out" tests, and surface energy measurements. In vitro biological assays were carried out using a large spectrum of bacterial and fungal strains, i.e., Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Enterococcus faecalis and Candida albicans. The biocompatibility of the films obtained was evaluated on MG63 mammalian cell cultures. The optimal combination with reasonable physical-chemical properties, efficient protection against microbial colonization and beneficial effects on human cells was found for Silver-doped Carbon films containing 2 to 7 at.% silver. These mixtures can be used to fabricate safe and efficient coatings of metallic implants, with the goal to decrease the risk of implant associated biofilm infections which are difficult to treat and often responsible for implant failure. (C) 2016 Elsevier B.V. All rights reserved.

1233. The Influence of the Dielectric Constant in Dielectric Resonator Antennas

Authors: Moni, MV; Tuta, L; Grecu, IV; Turcan, MG; Banciu, G

Published: 2016, 2016 INTERNATIONAL CONFERENCE ON COMMUNICATIONS (COMM 2016), 114, DOI:

This paper presents a comparison between dielectric resonator antennas with different dielectric constant parameter of the resonator. The antenna is fed with microstrip line. The dielectric resonators have cylindrical geometry. In HFSS software program, the simulations are up to compare the antennas' behavior as a function of different parameters, such as: center frequency, gain, frequency bandwidth etc.

1234. Effect of polyhedral oligomeric silsesquioxane nanoreinforcement on the properties of epoxy resin/monoglycidylether-terminated poly(dimethylsiloxane) nanocomposites

Authors: Florea, NM; Lungu. A; Balanuca, B; Badica, P; Craciun, L; Damian, CM; Enculescu, M; Ionescu, C; Tihan, G; Iovu, H

Published: AUG 2016, HIGH PERFORMANCE POLYMERS, 28, 734, DOI: 10.1177/0954008315595447

This article reports the synthesis and characterization of several types of organic-inorganic nanocomposites based on epoxy resin/monoglycidylether-terminated poly(dimethylsiloxane) reinforced with 2, 5, or 10 wt% polyhedral oligomeric silsesquioxanes (POSS) bearing one glycidyl (1GE-POSS) or eight glycidyl(8GE-POSS) groups. The morphological features of the studied samples were established through atomic force microscopy, contact angle measurements, X-ray photoelectron spectroscopy, and scanning electron microscopy/energy-dispersive X-ray spectroscopy, and it was demonstrated that 8GE-POSS is well dispersed within the polymer matrix, while 1GE-POSS exhibits a high tendency to form aggregates. Differential scanning calorimetry (DSC) and Fourier transform infrared resonance (FTIR) measurements are used to follow the curing behavior and to study the polymerization kinetics of epoxy groups. As evidenced by DSC and FTIR results, the inclusion of 8GE-POSS within the polymer matrix leads to a lower epoxy polymerization rate of the resulted nanocomposites than those reinforced with 1GE-POSS. The dynamic mechanical analysis results revealed that the thermomechanical properties are gradually improved with increasing of 8GE-POSS content due to the higher cross-linking density.

1235. Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification

Authors: Ungureanu, C; Dumitriu, C; Popescu, S; Enculescu, M; Tofan, V; Popescu, M; Pirvu, C

Published: FEB 2016, BIOELECTROCHEMISTRY, 107, 24, DOI: 10.1016/j.bioelechem.2015.09.001

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium,samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface. Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer. Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility. This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications. (C) 2015 Elsevier B.V. All rights reserved.

1236. Multiscale investigation of USPIO nanoparticles in atherosclerotic plaques and their catabolism and storage in vivo

Authors: Maraloiu, VA; Appaix, F; Broisat, A; Le Guellec, D; Teodorescu, VS; Ghezzi, C; van der Sanden, B; Blanchin, MG

Published: JAN 2016, NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE, 12, 200, DOI: 10.1016/j.nano.2015.08.005

The storage and catabolism of Ultrasmall SuperParamagnetic Iron Oxide (USPIO) nanoparticles were analyzed through a multiscale approach combining Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM) at different times after intravenous injection in an atherosclerotic ApoE(-/-) mouse model. The atherosclerotic plaque features and the USPIO heterogeneous biodistribution were revealed down from organ's scale to subcellular level. The biotransformation of the nanoparticle iron oxide (maghemite) core into ferritin, the non-toxic form of iron storage, was demonstrated for the first time ex vivo in atherosclerotic plaques as well as in spleen, the iron storage organ. These results rely on an innovative spatial and structural investigation of USPIO's catabolism in cellular phagolysosomes. This study showed that these nanoparticles were stored as non-toxic iron compounds: maghemite oxide or ferritin, which is promising for MRI detection of atherosclerotic plaques in clinics using these USPIOs. From the Clinical Editor: Advance in nanotechnology has brought new contrast agents for clinical imaging. In this article, the authors investigated the use and biotransformation of Ultrasmall Super-paramagnetic Iron Oxide (USPIO) nanoparticles for analysis of atherosclerotic plagues in Two Photon Laser Scanning Microscopy (TPLSM) and High-Resolution Transmission Electron Microscopy (HRTEM). The biophysical data generated from this study could enable the possible use of these nanoparticles for the benefits of clinical patients. (C) 2015 Elsevier Inc. All rights reserved.

1237. Physical Properties of Polycrystalline CuGeO3 Prepared by Field-assisted Sintering Technique

Authors: Ion, I; Sandu, V; Enculescu, M; Aldica, G; Ionescu, AM

Published: MAR 2016, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 29, 780, DOI: 10.1007/s10948-015-3343-8

The Peierls transition of polycrystalline CuGeO3 samples was investigated by thermal and magnetic investigations. We find that spin disorder induced by chain breaking and grain boundaries has similar effects to doping but without suppressing the spin-Peierls transition temperature or the spin-Peierls gap.

1238. High temperature superconducting materials based on Graphene / YBCO nanocomposite

Authors: Colie, M; Mihaiescu, D; Surdu, A; Trusca, R; Vasile, B; Istrati, D; Ficai, A; Plapcianu, C; Andronescu, E

Published: 2016, MATERIALS TODAY-PROCEEDINGS, 3, 2634, DOI: 10.1016/j.matpr.2016.06.006

New route synthesis of YBCO / graphene composite material is described in the present work. The oxide mixture and graphene were obtained separately and then mixed together by ball milling in the mass ratio graphene: YBCO = 1: 100. The oxide mixture was prepared by modified auto combustion reaction starting from stoichiometric amounts of yttrium acetate and barium and copper nitrates without any other organic compound addition. Graphene materials were prepared by reducing GO (i. e. oxidation of graphite powder by a modified Hummers method) with hidrazine sulphate. The final material resulted by applying the ballmilling method was investigated by XRD, SEM, Raman and HRTEM. (C) 2014 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the Conference Committee of 6th International Conference on Advanced Nano Materials.

1239. Intrinsic pyroelectric properties of thick, coarse grained Ba1-xSrxTiO3 ceramics

Authors: Ianculescu, A; Pintilie, I; Vasilescu, CA; Botea, M; Iuga, A; Melinescu, A; Dragan, N; Pintilie, L

Published: JUN 2016, CERAMICS INTERNATIONAL, 42, 10348, DOI: 10.1016/j.ceramint.2016.03.152

The intrinsic pyroelectric properties of thick, coarse grained Ba1-xSrxTiO3 (BST) ceramics were studied in relation with Sr content. The intrinsic values of the pyroelectric coefficient were determined directly from the frequency dependence of the measured pyroelectric signal by adapting the formalism developed for thin films deposited on thick substrates to thick and non-uniformly heated ceramics with uniform composition. Ceramic pellets, of about 1 mm thickness, with relative density of 89-95% were prepared using powder synthesized by the sol gel method. It was found that the intrinsic pyroelectric properties are enhanced by increasing the Sr content, while other features (e.g. tetragonality, grain size, polarization, transition temperature) decrease. The best intrinsic pyroelectric properties were obtained for 30% Sr content. The present results open the possibility to use large and thick BST ceramic pellets for manufacturing detectors useful for monitoring high power lasers. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1240. Ground state spin and excitation energies in half-filled Lieb lattices

Authors: Tolea, M; Nita, M

Published: OCT 3 2016, PHYSICAL REVIEW B, 94, DOI: 10.1103/PhysRevB.94.165103

We present detailed spectral calculations for small Lieb lattices having up to N = 4 number of cells, in the regime of half-filling, an instance of particular relevance for the nanomagnetism of discrete systems such as quantum dot arrays, due to the degenerate levels at midspectrum. While for the Hubbard interaction model-and even number of sites-the ground state spin is given by the Lieb theorem, the inclusion of long-range interaction-or odd number of sites-makes the spin state not known a priori, which justifies our approach. We calculate also the excitation energies, which are of experimental importance, and find significant variation induced by the interaction potential. One obtains insights on the mechanisms involved that impose as ground state the Lieb state with lower spin rather than the Hund one with maximum spin for the degenerate levels, showing this in the first and second orders of the interaction potential for the smaller lattices. The analytical results agree with the numerical ones, which are performed by exact diagonalization calculations or by a combined mean-field and configuration interaction method. While the Lieb state is always lower in energy than the Hund state, for strong long-range interaction, when possible, another minimal spin state is imposed as ground state.

1241. Watt-Level Output Power Operation From Diode-Laser Pumped Circular Buried Depressed-Cladding Waveguides Inscribed in Nd:YAG by Direct Femtosecond-Laser Writing

Authors: Salamu, G; Jipa, F; Zamfirescu, M; Pavel, N

Published: FEB 2016, IEEE PHOTONICS JOURNAL, 8, DOI: 10.1109/JPHOT.2015.2512263

Circular buried depressed-cladding waveguides have been inscribed in Nd:YAG ceramic media by direct writing with a femtosecond-laser beam. A classical step-by-step translation of the medium method, as well as a newly developed helical-moving technique, were employed to fabricate waveguides with 100-mu m diameter. Laser emission has been obtained under the pump with a fiber-coupled diode laser. Continuous-wave output power of 3.1 W at 1.06 mu m and 1.6 W at 1.3 mu m were achieved from a waveguide inscribed by helical movement in a 4.5-mm-long 1.1-at.% Nd:YAG; the overall optical-to-optical efficiency with respect to the absorbed pump power was 0.31 at 1.06 mu m and 0.17 at 1.3 mu m. Q-switch operation has been realized with Cr4+:YAG saturable absorber crystal. Using Cr4+:YAG with initial transmission of 0.90, an average output power of 680 2W has been measured from a waveguide that was written by the classical method in a 7.7-mm-long 1.1-at.% Nd:YAG ceramic. The laser pulse energy was 19.7 mu J, and the pulse peak power reached 7 kW.

1242. STRUCTURAL AND MORPHOLOGICAL EVOLUTIONS INDUCED BY THE ANNEALING OF CaF2 NANOCRYSTALLINE POWDERS BY USING Eu3+ ION PROBE LUMINESCENCE

Authors: Polosan, S; Secu, M; Enculescu, M

Published: APR-JUN 2016, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 11, 624, DOI:

Eu-doped CaF(2)nanocrystalline powders have been prepared by using co-precipitation technique. Structural and morphological modifications induced by annealing are followed by using Eu3+-ion probe. Theluminescence properties are changing gradually together with the morphology of doped CaF2 nanoparticles accompanied by anEu(3+)-> Eu2+ conversion. Cathodoluminescence measurements show uniform distribution of the europium dopant ions in the annealed samples accompanied by a strong increase of the integral photoluminescence signal. During annealing the cubic structure of CaF2 nanoparticles is altered going to the spherical morphology due to the Eu3+ ions incorporation. In the annealed samples Eu3+ ions are incorporated as Eu3+-O dimer centres with the coordination symmetry (C-2 nu); in the sintered samples there are two non-equivalent Eu3+ sites. The thermoluminescence peaks have been assigned to the recombination of the Eu3+ related traps in these sites.

1243. Unveiling the Mechanisms Leading to H-2 Production Promoted by Water Decomposition on Epitaxial Graphene at Room Temperature

Authors: Politano, A; Cattelan, M; Boukhvalov, DW; Campi, D; Cupolillo, A; Agnoli, S; Apostol, NG; Lacovig, P; Lizzit, S; Farias, D; Chiarello, G; Granozzi, G; Larcipretev, R

Published: APR 2016, ACS NANO, 10, 4549, DOI: 10.1021/acsnano.6b00554

By means of a combination of surface-science spectroscopies and theory, we investigate the mechanisms ruling the catalytic role of epitaxial graphene (Gr) grown on transition-metal substrates for the production of hydrogen from water. Water decomposition at the Gr/metal interface at room temperature provides a hydrogenated Gr sheet, which is buckled and decoupled from the metal substrate. We evaluate the performance of Gr/metal interface as a hydrogen storage medium, with a storage density in the Gr sheet comparable with state-of-the-art materials (1.42 wt %). Moreover, thermal programmed reaction experiments show that molecular hydrogen can be released upon heating the water-exposed Gr/metal interface above 400 K. The Gr hydro/dehydrogenation process might be exploited for an effective and eco-friendly device to produce (and store) hydrogen from water, i.e., starting from an almost unlimited source.

1244. Photoexpansion in amorphous As2S3: A new explanation

Authors: Lorinczi, A; Sava, F; Simandan, ID; Velea, A; Popescu, M

Published: SEP 1 2016, JOURNAL OF NON-CRYSTALLINE SOLIDS, 447, 125, DOI: 10.1016/j.jnoncrysol.2016.06.010

Thin amorphous As2S3 films show a giant photoexpansion of similar to 5% upon femtosecond laser illumination and this expansion remains after switching off the laser beam. To understand the structural modifications which occur during the photoexpansion process we assumed a molecular cluster structure of the amorphous As2S3. The focused femtosecond laser beam induces electrical charge redistribution on the sulfur atoms of each cluster, which increases the electrical repulsion between sulfur atoms, and thus induces an expansion of the clusters, by network reconfiguration, without breaking the bonds. An increase of the van der Waals distance between molecular clusters also takes place. (C) 2016 Elsevier B.V. All rights reserved.

1245. Up-conversion luminescence of BaCl2:Er3+ nanocrystals embedded in oxychloride nano-glass ceramic

Authors: Secu, M; Secu, CE

Published: JUN 2016, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 36, 1703, DOI: 10.1016/j.jeurceramsoc.2016.01.016

A novel glassy nanocomposite containing Er3+-doped BaCl2 nanocrystals of about tens of nm embedded in a silicate matrix has been prepared by using sol-gel route followed by controlled crystallization of the xerogel. Under 810 nm laser light pumping it shows green ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and red (F-4(9/2) -> I-4(15/2)) up-conversion luminescences ascribed by a two-photon processes. The luminescence signal recorded in the oxychloride nano-glass ceramic is only about 10% compared to the NaYF4:Er3+ (18%). In the nano glass ceramic there are effective non-radiative decay channels, most probably related to hydroxyl ions and surface defects acting as centers for the non-radiatively energy dissipation. (C) 2016 Elsevier Ltd. All rights reserved.

1246. Electrochromic properties of polyaniline-coated fiber webs for tissue engineering applications

Authors: Beregoi, M; Busuioc, C; Evanghelidis, A; Matei, E; Iordache, F; Radu, M; Dinischiotu, A; Enculescu, I

Published: AUG 30 2016, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 510, 473, DOI: 10.1016/j.ijpharm.2015.11.055

By combining the electrospinning method advantages (high surface-to-volume ratio, controlled morphology, varied composition and flexibility for the resulting structures) with the electrical activity of polyaniline, a new core-shell-type material with potential applications in the field of artificial muscles was synthesized. Thus, a poly(methylmethacrylate) solution was electrospun in optimized conditions to obtain randomly oriented polymer fiber webs. Further, a gold layer was sputtered on their surface in order to make them conductive and improve the mechanical properties. The metalized fiber webs were then covered with a PANI layer by in situ electrochemical polymerization starting from aniline and using sulphuric acid as oxidizing agent. By applying a small voltage on PANI-coated fiber webs in the presence of an electrolyte, the oxidation state of PANI changes, which is followed by the device color modification. The morphological, electrical and biological properties of the resulting multilayered material were also investigated. (C) 2015 Elsevier B.V. All rights reserved.

1247. Characterization of hydrogenated and deuterated silicon carbide films codeposited by magnetron sputtering

Authors: Pantelica, D; Ionescu, P; Petrascu, H; Dracea, MD; Statescu, M; Matei, E; Rasoga, O; Stancu, C; Marascu, V; Ion, V; Acsente, T; Dinescu, G

Published: MAR 15 2016, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 371, 326, DOI: 10.1016/j.nimb.2015.10.060

In this work we present the deposition of amorphous SiC thin films by radiofrequency dual magnetron sputtering. The dependence of the deposited films properties over the discharges electrical power and the effect of hydrogenous species (H-2 and/or D-2) addition to main discharge gas (Ar) were investigated. Accurate elemental analysis of the samples, including detection of hydrogen and deuterium, was performed by ion beam analysis (IBA) techniques: RBS (Rutherford Backscattering Spectrometry) and ERDA (Elastic Recoil Detection Analysis). SiCx thin films with thicknesses between 1700 and 4500 angstrom and C/Si ratio between 0.2/1 and 1.25/1 were obtained in different deposition conditions. The results prove that thin films of amorphous SiC with well controlled properties can be produced using radiofrequency dual magnetron sputtering. (C) 2015 Elsevier B.V. All rights reserved.

1248. BIOLOGICAL STUDIES ON DEXTRIN COATED IRON OXIDE NANOPARTICLES

Authors: Iconaru, SL; Turculet, C; Le Coustumer, P; Bleotu, C; Chifiriuc, MC; Lazar, V; Surugiu, A; Badea, M; Iordache, FM; Soare, M; Prodan, AM

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 1544, DOI:

In this study, dextrin coated iron oxide nanoparticles were obtained using an adapted chemical co-precipitation method. The size and morphology of the dextrin coated iron oxide nanoparticles (DIO-NPs) were analyzed by transmission electron microscopy (TEM). The scanning electron microscopy (SEM) analysis depicted information on the morphology of DIO-NPs. The elemental analysis was conducted by Energy-dispersive X-ray spectroscopy (EDAX). The iron oxide particles coated with dextrin have a spherical shape at nanometric scale with a narrow size distribution. The cytotoxicity assay was performed by quantification of HeLa cells viability, while the antimicrobial activities of the DIO-NPs were determined against ATCC reference and clinical microbial strains, i.e. Gram-positive bacteria (Staphylococcus aureus ATCC 6538) and yeast (Candida albicans 393). The obtained nanoparticles did not have cytotoxic effect on HeLa cells after a 24 h exposure to DIO-NPs and the morphology of the cells was not affected. A low toxic effect on HeLa cells was noticed after 48 h. The minimal inhibitory concentration of DIO-NPs was 1 mg/mL for both tested microbial strains.

1249. Structural, magnetic and magnetocaloric effects in epitaxial La0.67Ba0.33Ti0.02Mn0.98O3 ferromagnetic thin films grown on 001-oriented SrTiO3 substrates

Authors: Oumezzine, M; Galca, AC; Pasuk, I; Chirila, CF; Leca, A; Kuncser, V; Tanase, LC; Kuncser, A; Ghica, C; Oumezzine, M

Published: 2016, DALTON TRANSACTIONS, 45, 15040, DOI: 10.1039/c6dt01914e

Epitaxial La0.67Ba0.33Ti0.02Mn0.98O3 (denoted as LBTMO hereafter) thin films of approximately 95 nm thickness were deposited by a pulsed laser deposition technique onto SrTiO3 (STO) (001) substrates. High-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) investigations revealed that the films are epilayers with a four-fold symmetry around the [001] direction. Cross-sectional TEM and the presence of Pendellosung fringes in the XRD profiles demonstrate smooth interfaces. The STO substrate induces an in-plane compressive strain, which leads to a slight tetragonality of the film structure. The epilayers exhibit paramagnetic-to-ferromagnetic phase transitions at the Curie temperature T-C (286 K), close to room temperature. The magnetization easy axis lies in the film plane along the [100] direction of the (001) substrate. The magnetic entropy change (Delta S-M) associated with the second-order magnetic phase transition was determined via magnetization measurements in the temperature range between 210 and 350 K under different magnetic fields. The relative cooling power (RCP) of this film is about 220 J kg(-1), somewhat lower than that of bulk Gd (410 J kg(-1)) for a 50 kOe field change, making the LBTMO ferromagnetic thin films a promising candidate for micro/nanomagnetic refrigeration around room temperature. The proposed universal curve provides a simple method for extrapolating Delta S-M in a wide range of fields and temperatures, thus confirming the order of the magnetic transition in this system. The magnetic entropy (Delta S-M)(max) around T-C is proportional to (mu H-0/T-C)(2/3) in agreement with the mean-field theory, indicating the existence of long-range ferromagnetic interactions in epitaxial LBTMO thin films.

1250. Columnar bis(pyridinium) ionic liquid crystals derived from 4-hydroxypyridine: synthesis, mesomorphism and emission properties

Authors: Pana, A; Ilis, M; Staicu, T; Pasuk, I; Circu, V

Published: FEB 19 2016, LIQUID CRYSTALS, 43, 392, DOI: 10.1080/02678292.2015.1116630

A series of flexibly linked bis(pyridinium) salts with various counterions (Br-, PF6-, BF4- and OTf-) was designed and prepared starting from corresponding N-alkylated 4-pyridones precursors with mesogenic 3,4,5-tris(alkyloxy)benzyl moieties (alkyl=dodecyl or tetradecyl). These salts were investigated for their liquid crystalline properties by a combination of differential scanning calorimetry, polarising optical microscopy and temperature-dependent powder X-ray diffraction (XRD). Their thermal stability was checked by thermogravimetric analysis. All bis(pyridinium) salts, except the triflate salt with shorter terminal carbon chain, display an enantiotropic liquid crystalline behaviour with a hexagonal columnar (Col(h)) phase assigned on the basis of its characteristic texture and XRD studies. It was found that these luminescent bis(pyridinium) salts show weak emission in dichloromethane solutions at room temperature and a pronounced red-shifted emission in solid state. The emission properties of these bis(pyridinium) salts do not depend significantly on the nature of counterion employed.

1251. Dielectric and photoluminescence properties of Nd and Ga codoped-BaTiO3, prepared by sol-gel method

Authors: Cernea, M; Vasilescu, CA; Secu, M; Aldica, G; Surdu, A; Ganea, P

Published: NOV 2016, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 27, 11378, DOI: 10.1007/s10854-016-5262-2

Neodymium and gallium codoped barium titanate (Ba1-x-yNdxGayTiO3, x = 0.03, 0.05, 0.07, 0.1 and y = 0.03) were prepared by sol-gel method in order to investigate its dielectric and photoluminescence properties. The structure and morphology of Ba1-x-yNdxGayTiO3 powders calcined at 1100 A degrees C and sintered ceramics by spark plasma sintering (SPS) technique were analyzed using X-ray diffraction and scanning electron microscope, respectively. The photoluminescence and dielectric properties of Nd doped Ba0.97Ga0.03TiO3, (y = 0.03) as a function of Nd3+ concentration and sintering temperature were also investigated. The influence of Ga3+ and Nd3+ dopants on the crystalline phases, sintering process by SPS and macroscopic properties of Ba1-x-yNdxGayTiO3 ceramics was analyzed, as well as a weak hot emission from the 4F5/2 level. The sintered ceramics showed high dielectric constant and moderate dielectric losses. The highest value of the permittivity obtained for Ba1-x-yNdxGayTiO3 ceramics was E >(r) = 5890 at room temperature, 1 kHz and x = y = 0.03. This study shown that Nd3+ decreases the density of the pellets, increases the dielectric losses and decreases the dielectric constant of Ba0.97Ga0.03TiO3 ceramics. Therefore, the values of dielectric properties, at room temperature, of BaTiO3 doped with 3 at.% Ga and aecurrency sign7 at.% Nd are higher than those of undoped BaTiO3 ceramic.

1252. Polarized Raman spectra of phosphorene in edge and top view measuring configurations

Authors: Baibarac, M; Nila, A; Baltog, I

Published: 2016, RSC ADVANCES, 6, 58009, DOI: 10.1039/c6ra09682d

We demonstrate the anisotropic features of the A(1g), B-2g and A(2g) vibrational Raman modes of phosphorene by performing for the first time a comparison of two orthogonal polarized Raman scattering studies in edge and top view measuring configurations. Despite the orthogonality between the vibration modes of A(1g) and A(2g), they exhibit intense and very weak Raman intensities under light polarized along and transverse to the armchair edge, respectively, while the B-2g mode is virtually non-existent. The B-2g mode significantly appears only in the top view configuration. The studies performed under different intensities of excited light in the top view configuration are detailed for the sample rotated at 0 degrees, 40 degrees, 80 degrees and 130 degrees about the incident laser beam. The studies reveal a quadratic opposite behavior of the A(2g) and B-2g modes and an unusual angle dependence of the A(1g) vibrational mode. An unexpected behavior of the A(2g) Raman mode at higher intensities, which still persists for the A(1g) mode, is shown. The anomalous behavior of the A(1g) mode from the edge and top view and the A(2g) mode in the top view configuration is explained in terms of the layer stacking structures of phosphorene.

1253. Thermal analysis of repa-germanium (Ge-132)

Authors: Batalu, D; Paun, A; Ferbinteanu, M; Aldica, G; Vlaicu, AM; Teodorescu, VS; Badica, P

Published: NOV 20 2016, THERMOCHIMICA ACTA, 644, 27, DOI: 10.1016/j.tca.2016.10.005

Thermal behavior of repa-germanium (C6H10Ge2O7, Ge-132) during heating in air or in argon is investigated using DSC-TGA, XRD, SEM,TEM, and FT-IR measurements. Nine domains of thermal transformations were identified from room temperature to 1200 degrees C, in air or argon. The first reversible transformation is below 220 degrees C and it was assigned to an isomerization process, based on DSC, XRD and IR measurements. The next five transformation domains (220-910 degrees C) are decompositions accompanied by weight loss. The main product of thermal decomposition is Ge. The next transformation domain (910-970 degrees C) corresponds to melting of Ge, both in argon and air. In the air, this step is followed by oxidation of Ge (970-1100 degrees C) and, finally, by melting of GeO2. Amorphous phases formed between 220 and 720 degrees C. Observed processes are discussed based on crystal chemistry and bonds dynamics considerations. (C) 2016 Elsevier B.V. All rights reserved.

1254. Al2O3-cBN composites sintered by SPS and HPHT methods

Authors: Klimczyk, P; Cura, ME; Vlaicu, AM; Mercioniu, I; Wyzga, P; Jaworska, L; Hannula, SP

Published: JUN 2016, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 36, 1789, DOI: 10.1016/j.jeurceramsoc.2016.01.027

Spark Plasma Sintering (SPS) and High Pressure-High Temperature (HPHT) methods were chosen in order to study the behaviour of metastable cubic boron nitride (cBN) during sintering of Al2O3 + 30 vol.% cBN composites at low and high pressure. Relatively low sintering temperatures were used to avoid the undesired reverse transformation of cBN to hexagonal, graphite-like form. The microstructure, and phase composition as well as physical and mechanical properties of the resulting Al2O3-cBN composites were investigated. In the ball-on-disc tests, the coefficient of friction and the specific wear rate of the sintered samples were determined by rotating the sample against a stationary alumina ball. The best composites obtained by SPS (at 1300 degrees C/75 MPa) had slightly lower density, Young's modulus and hardness than those obtained by HPHT but their wear resistance was much better. Formation of hBN was suppressed up to 1300 degrees C during SPS consolidation at the pressure of 75 MPa. (C) 2016 Elsevier Ltd. All rights reserved.

1255. Exciton-phonon interaction in CdS of different morphological forms manifested as stimulated Raman scattering

Authors: Baibarac, M; Nila, A; Baltog, I

Published: JUN 1 2016, OPTICAL MATERIALS EXPRESS, 6, 1895, DOI: 10.1364/OME.6.001881

Raman studies performed on different morphologies of CdS samples indicate an exciton-phonon interaction (EPI) that manifests at low temperatures by different enhancements in intensity of the Raman spectra in the Stokes and anti-Stokes branches. This effect, interpreted as stimulated Raman effect, is conditioned on the appearance and strength by the degree of overlap of the excitation laser light with the excitonic photoluminescence band. EPI is greatest in samples characterized by high light diffusing power, which means a long path of light into the sample and a great overlapping of the two optical fields, i.e., the pump laser and excitonic light. (C) 2016 Optical Society of America

1256. Graphene addition to MgB2 superconductor obtained by ex-situ spark plasma sintering technique

Authors: Aldica, G; Burdusel, M; Popa, S; Hayasaka, Y; Badica, P

Published: MAY 2016, MATERIALS RESEARCH BULLETIN, 77, 211, DOI: 10.1016/j.materresbull.2016.01.041

Graphene nanopowder (G) with average thickness particle size of about 6-8 nm was added to MgB2 commercial powder. Starting composition was (MgB2)((1-x))(G)(x),x = 0.0125, 0.025, 0.05. Processing was performed by Spark Plasma Sintering (SPS) technique. All added samples have high density (above 95%). The critical temperature (T-c) and the lattice parameter a (c-axis lattice parameter is constant) show a small variation suggesting that carbon substitution for boron is low. TEM observations show the presence of un-reacted graphene plates supporting the T-c and structural results. It also indicates that G-addition does not modify the MgB2 microstructure. Despite this, there is an optimum doped sample (MgB2)(0.9875)(G)(0.0125) for which the critical current density at temperatures below 25 K is slightly higher at high magnetic fields than for the pristine sample. The addition of G is found as one of the least effective C-source additions enhancing J(c). We discuss results as being strongly related to variation of the residual stress. (C) 2016 Elsevier Ltd. All rights reserved.

1257. Effects of vanadium doping on sintering conditions and functional properties of Nb-Li co-doped PZT ceramics. Comments on Li location

Authors: Amarande, L; Miclea, C; Cioangher, M; Grecu, MN; Pasuk, I

Published: NOV 15 2016, JOURNAL OF ALLOYS AND COMPOUNDS, 685, 166, DOI: 10.1016/j.jallcom.2016.05.266

The effect of 1 and 2 mol % V addition on sintering conditions, structural and functional properties of NbeLi co-doped PZT ceramics, prepared by conventional ceramic method, was systematically studied, by different experimental techniques. The reported results show that the increasing amount of vanadium, as a substitute for niobium, decreases the optimal sintering temperature with 100-150 degrees C, but slightly reduces the piezoelectric, ferroelectric, and electromechanical properties of these ceramics. In addition, the presence of vanadium increases the lattice tetragonality and grain size, promoting a harder piezoelectric behaviour, mostly in the absence of niobium. EPR spectra exhibit well-defined hyperfine splitting characteristics for V4+ state, dispersed in the lattice as VO2+ ion. Additionally, complex paramagnetic defects (charged oxygen vacancies and associated defects) are evidenced for 2 mol % vanadium addition. The results were explained by assuming that vanadium promotes the B-site Li substitution, compensated by oxygen vacancies, while niobium facilitates the A-site Li substitution with lead vacancies formation and partial reduction of V5+ to V4+. Thus, indirect information about lithium location is provided. (C) 2016 Elsevier B.V. All rights reserved.

1258. POLYESTER FABRICS COVERED WITH AMORPHOUS TITANIUM DIOXIDE LAYERS: COMBINING WETTABILITY MEASUREMENTS AND PHOTOINDUCED HYDROPHILICITY TO ASSESS THEIR SURFACE PROPERTIES

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Cotorobai, VF; Ganea, CP

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 269, DOI:

Wettability properties of thin TiO2 amorphous layers obtained by sputtering or sol-gel onto polyester textile materials were investigated. Contact angle (CA) measurements by the sessile drop method were used to evaluate these properties. Comparison was performed with coated samples of related poly(lactic acid) material. The samples coated by sol gel have CAs a few degrees higher than those coated by sputtering. Wetting properties were conversely changed under alternate darkness/illumination conditions. Photoinduced hydrophilicity was observed even for these amorphous coating particles, being higher for sputtered samples than for sol gel ones.

1259. Oxidation of 5-hydroxymethyl furfural to 2,5-diformylfuran in aqueous media over heterogeneous manganese based catalysts

Authors: Neatu, F; Petrea, N; Petre, R; Somoghi, V; Florea, M; Parvulescu, VI

Published: DEC 1 2016, , DOI: 10.1016/j.cattod.2016.03.031

1260. Wicking behavior of fabrics described by simultaneous acquiring the images of the wet region and monitoring the liquid weight

Authors: Cotorobai, VF; Zgura, I; Birzu, M; Frunza, S; Frunza, L

Published: MAY 20 2016, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 497, 153, DOI: 10.1016/j.colsurfa.2016.02.040

An experimental study on the radial spreading of the liquid from a virtually infinite reservoir onto a horizontal fabric sample was performed using a simple setup which is presented in two variants: One variant (the simplest) collects the images of the wet spot during the radial outward wicking and the other variant collects the images simultaneously with the monitoring of the weight decrease of the liquid reservoir. We notice that recording with a webcam gives advantages in the subsequent data processing. Afterward, the resulting image series were processed with routines developed in LabVIEW to determine the area of the wet spot. The programs are better adapted to the inhomogeneous and anisotropic structure specific to textiles than the existent edge-finding algorithms. The time dependence of the wet area provides information about the wicking kinetics and further, by modeling the data, to the possible mechanism. The experiments were performed using solutions of red (rhodamin 6B) or blue (brilliant blue E133) dyes in linen and polyester samples differing besides the chemical structure in the roughness of their surfaces as well. The data allow an easy comparison between the textile behavior. Determination of the mass loss of the test liquid might be useful especially for the colored fabrics. The infinite reservoir case is compared with that of the finite reservoir. (C) 2016 Elsevier B.V. All rights reserved.

1261. Synthesis of Terephthalic Acid by p-Cymene Oxidation using Oxygen: Toward a More Sustainable Production of Bio-Polyethylene Terephthalate

Authors: Neatu, F; Culica, G; Florea, M; Parvulescu, VI; Cavani, F

Published: NOV 9 2016, , DOI: 10.1002/cssc.201600718

1262. Optical evidence for chemical interaction of the polyaniline/fullerene composites with N-methyl-2-pyrrolidinone

Authors: Baibarac, M; Baltog, I; Daescu, M; Lefrant, S; Chirita, P

Published: DEC 5 2016, JOURNAL OF MOLECULAR STRUCTURE, 1125, 349, DOI: 10.1016/j.molstruc.2016.07.001

Surface enhanced Raman scattering (SERS) spectroscopic studies reveal a particular chemical interaction of the polyaniline/fullerene (PANI/C-60) composite with N-methyl-2-pyrrolidinone (NMP). The chemical polymerization of aniline in the presence of sulfuric acid, potassium dichromate and fullerene has been used for the preparation of the PANI/C-60 composite. The polymerization reaction involves a doping of PANI with C-60 anion radicals. The interaction of the composite with NMP leads to a de-doping of PANI that involves a transformation of leucoemeraldine salt (LS) repeating units into leucoemeraldine base (LB). Additionally, a gradual increasing in the intensity of the Raman line at 1452 cm(-1) associated to the A(g)(2) pentagonal pinch mode of fullerene and a decrease in the intensity of the Raman lines of PANI are reported. This change arises from the formation of a charge-transfer complex C-60-NMP. The subsequent chemical treatment of PANI-LB with FeCl3 leads to the formation PANI-emeraldine salt. An inhibition of the transformation of PANI doped with C-60 anion radicals into a PANI-LB and the C-60-NMP charge transfer complex in the presence of CdS particles dispersed in NMP is demonstrated by SERS spectroscopy. (C) 2016 Elsevier B.V. All rights reserved.

1263. Time-gated down-/up-conversion emission of Ho-CeO2 and Ho, Yb-CeO2 nanoparticles

Authors: Avram, D; Porosnicu, I; Cojocaru, B; Florea, M; Tiseanu, C

Published: NOV 2016, , DOI: 10.1016/j.jlumin.2016.07.026

1264. Microwave dielectric properties of BNT-BT0.08 thin films prepared by sol-gel technique

Authors: Huitema, L; Cernea, M; Crunteanu, A; Trupina, L; Nedelcu, L; Banciu, MG; Ghalem, A; Rammal, M; Madrangeas, V; Passerieux, D; Dutheil, P; Dumas-Bouchiat, F; Marchet, P; Champeaux, C

Published: APR 14 2016, JOURNAL OF APPLIED PHYSICS, 119, DOI: 10.1063/1.4945822

We report for the first time the microwave characterization of 0.92(Bi0.5Na0.5)TiO(3-)0.08BaTiO(3) (BNT-BT0.08) ferroelectric thin films fabricated by the sol-gel method and integrated in both planar and out-of-plane tunable capacitors for agile high-frequency applications and particularly on the WiFi frequency band from 2.4 GHz to 2.49 GHz. The permittivity and loss tangent of the realized BNT-BT0.08 layers have been first measured by a resonant cavity method working at 12.5 GHz. Then, we integrated the ferroelectric material in planar inter-digitated capacitors (IDC) and in out-of-plane metal-insulator-metal (MIM) devices and investigated their specific properties (dielectric tunability and losses) on the whole 100 MHz-15 GHz frequency domain. The 3D finite-elements electromagnetic simulations of the IDC capacitances are fitting very well with their measured responses and confirm the dielectric properties determined with the cavity method. While IDCs are not exhibiting an optimal tunability, the MIM capacitor devices with optimized Ir/MgO(100) bottom electrodes demonstrate a high dielectric tunability, of 30% at 2.45 GHz under applied voltages as low as 10 V, and it is reaching 50% under 20V voltage bias at the same frequency. These high-frequency properties of the MIM devices integrating the BNT-BT0.08 films, combining a high tunability under low applied voltages indicate a wide integration potential for tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used industrial, scientific, and medical frequency band. (C) 2016 AIP Publishing LLC.

1265. Defect induced tunable near infrared emission of Er-CeO2 by heterovalent co-dopants

Authors: Florea, M; Avram, D; Cojocaru, B; Tiseanu, I; Parvulescu, V; Tiseanu, C

Published: JUL 21 2016, , DOI: 10.1039/c6cp02754g

1266. Graphene from Alginate Pyrolysis as a Metal-Free Catalyst for Hydrogenation of Nitro Compounds

Authors: Trandafir, MM; Florea, M; Neatu, F; Primo, A; Parvulescu, VI; Garcia, H

Published: JUL 7 2016, , DOI: 10.1002/cssc.201600197

1267. Advances in luminescence of lanthanide doped Y2O3: case of S-6 sites

Authors: Avram, D; Cojocaru, B; Florea, M; Tiseanu, C

Published: MAY 1 2016, , DOI: 10.1364/OME.6.001635

1268. Cross-coupling of p-xylene to 2,2 ',5,5 '-tetramethyl 1,1 '-biphenyl on supported vanadia catalysts

Authors: Mitran, G; Pavel, OD; Florea, M; Parvulescu, VI

Published: MAR 25 2016, , DOI: 10.1016/j.apcata.2016.01.010

1269. Hydrogen production from glycerol steam reforming over molybdena-alumina catalysts

Authors: Mitran, G; Pavel, OD; Florea, M; Mieritz, DG; Seo, DK

Published: MAR 5 2016, , DOI: 10.1016/j.catcom.2016.01.029

1270. Synthesis of ceria nanopowders by microwave-assisted hydrothermal method for dry reforming of methane

Authors: Matei-Rutkovska, F; Postole, G; Rotaru, CG; Florea, M; Parvulescu, VI; Gelin, P

Published: JAN 30 2016, , DOI: 10.1016/j.ijhydene.2015.12.097

1271. Effect of Mo/Ce ratio in Mo-Ce-Al catalysts on the hydrogen production by steam reforming of glycerol

Authors: Mitran, G; Pavel, OD; Mieritz, DG; Seo, DK; Florea, M

Published: 2016, , DOI: 10.1039/c6cy00999a

1272. Influence of metallic and semiconducting nanostructures on the optical properties of dye-doped polymer thin films

Authors: Enculescu, M; Matei, E

Published: SEP 1 2016, THIN SOLID FILMS, 614, 35, DOI: 10.1016/j.tsf.2015.12.021

Dye-doped polymer thin films were obtained by spin-coating of 8% polyvinylpyrrolidone (PVP) solutions (in ethanol). Ni or ZnO nanowires were incorporated in Rhodamine 6G doped polymer films (10(-4) M dye concentration). Optical and morphological properties of simple dye-doped polymer films and films containing metallic or semiconducting nanostructures were investigated. Optical microscopy and scanning electron microscopy were used to image the nanowires. The presence of Ni nanowires induces a small shift (2-3 nm) to longer wavelengths on the emission band of Rh 6G doped PVP film. The ZnO nanowires' presence was confirmed by X-ray diffraction measurements. An enhancement of the emission of the dye doped polymer is induced by the semiconducting structures. (C) 2015 Elsevier B.V. All rights reserved.

1273. Formation of pure-phase W2C nanoparticles through carbothermal reduction in the presence of Pd(0) nanoparticles

Authors: Mitran, RA; Radulescu, MC; Buhalteanu, L; Tanase, LC; Dumitrescu, DG; Matei, C

Published: OCT 15 2016, JOURNAL OF ALLOYS AND COMPOUNDS, 682, 685, DOI: 10.1016/j.jallcom.2016.05.022

The direct synthesis from elements of tungsten semicarbide, W2C, taking place in a narrow concentration range and at high temperatures, is unsuited for some applications requiring small particle sizes. We report an efficient synthesis method for obtaining pure phase W2C at low temperatures (< 1050 degrees C), through the carbothermal reduction of tungsten oxide species in the presence of metallic palladium nanoparticles obtained in situ. A 1:5 (at.) Pd:W ratio or higher yields pure phase W2C, while increasing the Pd content decreases the carburization temperature. The resulting composite materials contain Pd(0) and W2C particles well-dispersed on carbon, with sizes between 50 and 500 nm. The samples have been tested using cyclic voltammetry and chronoamperometry as potential anode materials for the electrooxidation of formic acid and show improved stability in comparison with commercial Pd and comparable current densities, up to 2 times higher than the commercial catalyst. (C) 2016 Elsevier B.V. All rights reserved.

1274. Bioactive glass thin films synthesized by advanced pulsed laser techniques

Authors: Mihailescu, N; Stan, GE; Ristoscu, C; Sopronyi, M; Mihailescu, IN

Published: 2016, INERA CONFERENCE: VAPOR PHASE TECHNOLOGIES FOR METAL OXIDE AND CARBON NANOSTRUCTURES, 764, DOI: 10.1088/1742-6596/764/1/012020

Bioactive materials play an increasingly important role in the biomaterials industry, and are extensively used in a range of applications, including biodegradable metallic implants. We report on Bioactive Glasses (BG) films deposition by pulsed laser techniques onto biodegradable substrates. The BG coatings were obtained using a KrF* excimer laser source (lambda= 248 nm, t(FWHM) <= 25 ns). Their thickness has been determined by Profilometry measurements, whilst their morphology has been analysed by Scanning Electron Microscopy (SEM). The obtained coatings fairly preserved the targets composition and structure, as revealed by Energy Dispersive X-Ray Spectroscopy, Grazing Incidence X-Ray Diffraction, and Fourier Transform Infra-Red Spectroscopy analyses.

1275. Combinatorial MAPLE deposition of antimicrobial orthopedic maps fabricated from chitosan and biomimetic apatite powders

Authors: Visan, A; Stan, GE; Ristoscu, C; Popescu-Pelin, G; Sopronyi, M; Besleaga, C; Luculescu, C; Chifiriuc, MC; Hussien, MD; Marsan, O; Kergourlay, E; Grossin, D; Brouillet, F; Mihailescu, IN

Published: SEP 10 2016, INTERNATIONAL JOURNAL OF PHARMACEUTICS, 511, 515, DOI: 10.1016/j.ijpharm.2016.07.015

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (lambda = 248 nm, tau(FWHM) = 25 ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosanrich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite. (C) 2016 Elsevier B.V. All rights reserved.

1276. Role of the dithiolate backbone on the passivation of p-GaAs(111)B surface

Authors: Preda, L; Anastasescu, M; Dobrescu, G; Negrila, C; Lazarescu, V

Published: JUN 15 2016, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 771, 63, DOI: 10.1016/j.jelechem.2016.03.046

Effects of the self-assembled layers of biphenyl 4,4'-dithiol (BPDT) and 1,8-octanedithiol (ODT) on the chemical and electronic properties of p-doped GaAs (111)-As terminated substrate, (p-GaAs(111)B), were investigated in order to evidence whether the hydrocarbon moiety plays a role in tailoring the semiconductor surface properties. The electrochemical properties of the BPDT and ODT coated p-GaAs(111)B substrates were studied by Electrochemical Impedance Spectroscopy (EIS). The structural and chemical changes caused by the dithiolate layers formed on p-GaAs(111)B substrates were monitored by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) investigations, respectively. The XPS data showed that BPDT and ODT bind to pGaAs(111)B via the thiol group. The ODT layer provides better protection against the further oxidation in air of p-GaAs(111)B substrate compared to the BPDT layer. The EIS investigations are in good agreement with XPS results, pointing to better insulating properties of the ODT layer compared to the BPDT layer in the electron transfer at the electrode/solution interface. The results evidenced that backbone plays an important role in tailoring the properties of p-GaAs(111)B substrate. (C) 2016 Elsevier B.V. All rights reserved.

1277. How morphology determines the charge storage properties of Ge nanocrystals in HfO2

Authors: Slav, A; Palade, C; Lepadatu, AM; Ciurea, ML; Teodorescu, VS; Lazanu, S; Maraloiu, AV; Logofatu, C; Braic, M; Kiss, A

Published: MAR 1 2016, SCRIPTA MATERIALIA, 113, 138, DOI: 10.1016/j.scriptamat.2015.10.028

The strong correlation between morphology and charge storage properties of HfO2/Ge/HfO2/Si trilayer structures was evidenced. The morphology of structures deposited by magnetron sputtering and electron beam evaporation was tailored by rapid thermal annealing and investigated by transmission electron microscopy, Raman and X-ray photoelectron spectroscopies. The best hysteresis loops (capacitance-voltage characteristics) were obtained for trilayers with high density Ge nanocrystals located in the position of as-deposited Ge layer. The decrease of Ge nanocrystals density narrows the memory window, by spreading Ge atoms into HfO2 matrix (sputtered trilayers), or by Ge atoms expulsion toward HfO2 nanocrystals surface (evaporated trilayers). (C) 2015 Elsevier Ltd. All rights reserved.

1278. Characteristics of Ce3+-doped barium titanate nanoshell tubes prepared by template-mediated colloidal chemistry

Authors: Ianculescu, AC; Vasilescu, CA; Trupina, L; Vasile, BS; Trusca, R; Cernea, M; Pintilie, L; Nicoara, A

Published: JUN 2016, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 36, 1642, DOI: 10.1016/j.jeurceramsoc.2016.01.045

5 mol% Ce3+-doped barium titanate nanoshell tubes were prepared via sol gel method using as template a polycarbonate membrane with channels of 200 nm diameter. FE-SEM analyses showed that continuous and uniform green tubes with length up to 15 mu m, an average outer diameter of 188.6 nm and wall thickness of 15.1 nm, were obtained. After calcination at 700 degrees C for 1 h, these amorphous 1D nanostructures were converted into polycrystalline tubes with an average outer diameter of 157.4 nm and a grain size of 43.4 nm, as high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) indicated. Thermo-Raman investigations pointed out diffuse phase transitions, inducing the preservation of a stable polar state at higher temperatures (up to 200 degrees C). Piezoresponse force microscopy (PFM) investigations on 5 mol% Ce3+-doped BaTiO3 nanoshell tubes revealed ferroelectric and piezoelectric behaviour which recommends these tubes for microelectronic devices. (C) 2016 Elsevier Ltd. All rights reserved.

1279. Structural and electrical properties of Nb doped TiO2 films prepared by the sol-gel layer-by-layer technique

Authors: Duta, M; Simeonov, S; Teodorescu, V; Predoana, L; Preda, S; Nicolescu, M; Marin, A; Spasov, D; Gartner, M; Zaharescu, M; Szekeres, A

Published: FEB 2016, MATERIALS RESEARCH BULLETIN, 74, 20, DOI: 10.1016/j.materresbull.2015.10.009

Thin films of 5 and 10-layered sol gel TiO2 were doped with 1.2 at.% Nb and their structural, optical and electrical properties were investigated. The films crystallized only in anatase phase, as evidenced by X-ray diffraction and selected area electron diffraction analyses. High resolution transmission electron microscopy revealed nanosized crystallites with amorphous boundaries. Current-voltage measurements on metal-TiO2 Si structures showed the formation of ri+ n heterojunction at the TiO2-Si interface with a rectification ratio of 10(4). The effective donor density varies between 10(16) and 10(17) cm(-3), depending on film thickness. The sheet energy densities under forward and reverse bias are in the order of 10(12) and 10(10) cm(-2) respectively. These values and the high specific resistivity (10(4) Omega cm) support the existence of compensating acceptor levels in these films. It was established that the conduction mechanism is based on space charge limited current via deep levels with different energy positions in the band gap. (C) 2015 Elsevier Ltd. All rights reserved.

1280. On the agent role of Mn2+ in redirecting the synthesis of Zn(OH)(2) towards nano-ZnO with variable morphology

Authors: Ghica, D; Vlaicu, ID; Stefan, M; Nistor, LC; Nistor, SV

Published: 2016, RSC ADVANCES, 6, 106741, DOI: 10.1039/c6ra23065b

One of the simplest routes to prepare polycrystalline Zn(OH)(2) is by coprecipitation, with zinc nitrate as a cation source. However, the addition of even minute amounts of manganese nitrate to the precursors used to prepare pure Zn(OH)(2) results in Mn2+ doped nanostructured ZnO. The comparison with other Mn2+ doped metal hydroxides prepared by the same coprecipitation method, involving metal nitrates precursors, shows that this behavior is unique, pertaining only to Zn(OH)(2). A systematic study of the samples prepared without and with variable amounts of Mn2+ ions, in the 1 to 5000 ppm nominal concentrations range showed that the re-routing of the reaction takes place even for the lowest nominal dopant concentration of 1 ppm. According to X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy investigations, both crystallite size and morphology of the resulting nanostructured ZnO samples varied with the Mn2+ nominal concentration. Moreover, quantitative electron paramagnetic resonance investigations showed that the incorporation rate of the Mn2+ ions at different sites in the nanostructured ZnO depended on the nominal Mn2+ concentration. The results are discussed in terms of the coordination properties of the Mn2+ and Zn2+ ions and the nature of the reaction precursors.

1281. Carbon Nanotubes-Hydroxyapatite Nanocomposites for an Improved Osteoblast Cell Response

Authors: Constanda, S; Stan, MS; Ciobanu, CS; Motelica-Heino, M; Guegan, R; Lafdi, K; Dinischiotu, A; Predoi, D

Published: 2016, JOURNAL OF NANOMATERIALS, 2016, DOI: 10.1155/2016/3941501

An alternative and simple coprecipitation method was developed to obtain carbon nanotube-hydroxyapatite (CNTs:HAp) based nanocomposites. The incorporation of CNTs (in a concentration of 5% and 10% of total weight of the nanocomposite) and their impact on both structural and biological properties were studied by using a set of standard complementary biological, microscopic, and spectroscopic techniques. The characteristic peaks of carbon structure in CNTs were not observed in the CNTs-HAp composites by X-ray diffraction analysis. Moreover, FTIR and Raman spectroscopies confirmed the presence of HAp as the main phase of the synthesized CNTs: HAp nanocomposites. The addition of CNTs considerably affected the nanocomposite morphology by increasing the average crystallite size from 18.7 nm (for raw HAp) to 28.6 nm (for CNTs:HAp-10), confirming their proper incorporation. The biocompatibility evaluation of CNTs:HAp-5 and CNTs:HAp-10 nanocomposites included the assessment of several parameters, such as cell viability, antioxidant response, and lipid peroxidation, on human G-292 osteoblast cell line. Our findings revealed good biocompatibility properties for CNTs: HAp nanocomposites prepared by the coprecipitation method supporting their potential uses in orthopedics and prosthetics.

1282. Pyramidal growth of ceria nanostructures by pulsed laser deposition

Authors: Barca, ES; Filipescu, M; Luculescu, C; Birjega, R; Ion, V; Dumitru, M; Nistor, LC; Stanciu, G; Abrudeanu, M; Munteanu, C; Dinescu, M

Published: FEB 15 2016, APPLIED SURFACE SCIENCE, 363, 251, DOI: 10.1016/j.apsusc.2015.12.064

We report in this paper on the deposition and characterization of CeO2 nanostructured thin films with hierarchical morphology. Micro -sized ceria powder (CeO2, 99.9% purity) was pressed to obtain a ceramic target. An ArF laser working at 193 nm irradiated the target in controlled oxygen gas flow at constant pressure (0.1 mbar). Silicon wafers used as substrates for thin films were heated at different temperatures, up to 773 K. The influence of substrate temperature on the structure and surface morphology of ceria thin films was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and scanning electron microscopy (SEM). The refractive indices and information about roughness and thickness were revealed by spectroellipsometry. Crystalline cubic ceria thin films exhibiting a hierarchical structure that combines columnar and dendritic growth were obtained at temperatures above 473 K. For the samples obtained at 773 K, columns ending in pyramidal formations with sharp edges and sizes of hundreds of nanometers were observed, indicating a high crystallinity of the layer. XRD analysis reveals a consistent increase of the X-ray coherence length/crystallite size along the [111] direction with increasing temperature. Using a semi -empirical formula, Raman crystallites sizes were calculated and it was found that size increases with the temperature increasing. The spectroellipsometry investigations evidenced the increasing of refractive index with the substrate temperature increase. High surface roughness and pyramidal structures were noticed from the atomic force microscopy images for layers deposited at substrate temperature above 473 K. (C) 2015 Elsevier B.V. All rights reserved.

1283. ELECTROCHEMICAL DEPOSITION OF ZINC TELLURIDE THIN FILMS FROM ETHALINE IONIC LIQUID

Authors: Catrangiu, AS; Beregoi, M; Cojocaru, A; Anicai, L; Cotarta, A; Visan, T

Published: MAY 2016, CHALCOGENIDE LETTERS, 13, 199, DOI:

The electrochemical deposition of ZnxTey thin films was studied in an ionic liquid consisted in choline chloride - ethylene glycol eutectic mixture (Ethaline). ZnCl2 and TeO2 precursors were dissolved in 5-24 millimolar concentrations and the temperature was maintained constant at 60 degrees C. Cyclic voltammograms on Pt from electrolytes with both Te4+ and Zn2+ ions displayed three cathodic processes as limiting currents or peaks: Te underpotential deposition, codeposition of ZnTe compound, and deposition of Zn-rich binary telluride. The corresponding anodic waves or peaks were also identified. The shape of Nyquist electrochemical impedance plots recorded on various applied polarization showed that the electrode first covers with a Te film, and then the more cathodic polarization produces a co-reduction of Te4+ with Zn2+ as ZnTe compound. The formation of Zn metal-rich ZnxTey film at excessive negative polarization is indicated by the lowest value of maximum phase angle in Bode plots. The Zn/Te ratio (apparent stoichiometry) in the films deposited on Cu substrate is controlled by carrying out constant potential electrolyses with different ionic ratios in Ethaline bath. Film morphology, elemental analysis, and crystalline structure were evidenced by SEM microscopy, EDX analysis and X-ray diffraction, respectively.

1284. Functionalization of carbon nanowalls by plasma jet in liquid treatment

Authors: Ionita, MD; Vizireanu, S; Stoica, SD; Ionita, M; Pandele, AM; Cucu, A; Stamatin, I; Nistor, LC; Dinescu, G

Published: FEB 9 2016, EUROPEAN PHYSICAL JOURNAL D, 70, DOI: 10.1140/epjd/e2016-60499-8

Submerged in liquid plasma treatment is a new approach for nanomaterials functionalization. This paper presents a surfactant free method for functionalization of graphene nano-platelets derived from carbon nanowalls through plasma jet treatment of their water suspensions. The untreated and under-liquid plasma treated suspensions were characterized in terms of their UV-Vis absorption, zeta-size, zeta-potential, pH, and conductivity. Investigation of dried material revealed that the graphene nano-sheets morphology and structure have been preserved, showing also new oxygen functional groups bonded to the carbon network after in liquid plasma treatment. The results demonstrate the efficiency of this technique in changing the properties of carbon nanowalls suspensions and also in getting functionalized multilayered graphene sheets.

1285. Preliminary Ultrasound Studies On Magnetic Fluids Based on Iron Oxide Nanoparticles

Authors: Popa, CL; Predoi, D; Soare, M; Petre, CC; Predoi, MV

Published: 2016, VIII INTERNATIONAL CONFERENCE ON TIMES OF POLYMERS AND COMPOSITES: FROM AEROSPACE TO NANOTECHNOLOGY, 1736, DOI: 10.1063/1.4949715

The study of various types of nanoparticles with different biomedical applications is of high interest in the last decades. For this purpose, among other techniques, ultrasounds have been used to characterize the aqueous solutions. A non-invasive method is preferable for the characterization of these materials, due to the fact that they are designed to be used for targeted delivery of a chemotherapeutic solution to the tumor site. The present research is focused on ultrasound characterization of solutions based on maghemite and 5-fluorouracil.

1286. Adhesion evaluation of different bioceramic coatings on Mg-Ca alloys for biomedical applications

Authors: Bita, AI; Stan, GE; Niculescu, M; Ciuca, I; Vasile, E; Antoniac, I

Published: 2016, JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY, 30, 1983, DOI: 10.1080/01694243.2016.1171569

The aim of this study was to evaluate the adhesion of different bioceramic coatings deposited by radio frequency magnetron sputtering on the biodegradable implant-type magnesium-calcium (MgCa) alloys. Hydroxyapatite (HA) and bioactive glass (BG) were chosen as coating materials, due to their remarkable biological potential. The morphology, composition, structure and adhesion of the deposited thin coatings was characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy and pull-out adherence measurements. A variation of the coating-to-substrate adhesion has been recorded and correlated with the physico-chemical results. The bonding strength values of the coatings were promising (being superior to the ISO13779-2:2008 fabrication standard for load-bearing biomedical coatings), and thus, encourage us to further proceed with the biological evaluation of the HA or BG coatings-MgCa substrate couples.

1287. Magnetite (Fe3O4) nanoparticles as adsorbents for As and Cu removal

Authors: Iconaru, SL; Guegan, R; Popa, CL; Motelica-Heino, M; Ciobanu, CS; Predoi, D

Published: DEC 2016, APPLIED CLAY SCIENCE, 134, 135, DOI: 10.1016/j.clay.2016.08.019

The aim of this study consisted to develop novel synthetic magnetite nanoparticles (nFe(3)O(4)) with preferential reactivity to trace elements (TE) for possible environmental applications as adsorbents. The synthetic magnetite materials obtained through the co-precipitation of both Fe3+ and Fe2+ ions (Fe2+ / Fe3+ = 0.5) were characterized by a set of complementary techniques: X-ray diffraction, transmission and scanning electron microscopy, Fourier transform infrared and Raman spectroscopy, and BET adsorption method. The resulting nFe(3)O(4) displayed a wide specific surface area (100 m(2) g(-1)) with particles reaching a size of about 10 nm, smaller than those of the well-crystallized commercial ones (cFe(3)O(4)) estimated at 80 nm while showing a BET surface area of 6.8 m(2) The adsorption properties of the synthetic nFe(3)O(4) magnetite nanoparticles were characterized and compared to the commercial analogous with the adsorption of both As and Cu. The equilibrium adsorption isotherms were properly fitted with Langmuir and Freundlich equation models and suggested that the developed iron oxides nanoparticles display a certain potential for removal and/or immobilization of TE from contaminated waters and/or soils, with an increase of 69.5% of the adsorbed amount compared to that of the commercial ones. (C) 2016 Elsevier B.V. All rights reserved.

1288. Electrical properties of templateless electrodeposited ZnO nanowires

Authors: Matei, E; Costas, A; Florica, C; Enculescu, M; Pintilie, I; Pintilie, L; Enculescu, I

Published: FEB 2016, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 42, 372, DOI: 10.1016/j.mssp.2015.11.007

Electrochemical deposition allows the preparation of ZnO nanostructures with precisely controlled morphology and properties, by finely tuning the process parameters. ZnO nanowires were deposited onto gold substrates by electrodeposition from a low concentration zinc nitrate bath Photolithography was employed for patterning interdigitated electrode systems onto silicon/silicon dioxide substrates and ZnO electrodeposition lead to wires connected to each other by bridging neighboring interdigits allowing electronic transport characterization. Optical measurements, i.e. reflection and photoluminescence spectroscopy, were performed and the results were correlated to electronic transport data. We found that we deal with a system for which one can apply a model of space charge limited currents with different traps energy distribution as a consequence of electrodeposition rate. Current versus temperature measurements show different behavior for lower and higher range of temperatures. Such nanowires, fabricated and contacted in a straightforward way, allow a wide area of applications ranging from conductometric bio- or chemo-sensors to optoelectronic devices. (C) 2015 Elsevier Ltd. All rights reserved.

1289. Magnetoelastic properties in polycrystalline ferromagnetic shape memory Heusler alloys

Authors: Sofronie, M; Tolea, F; Crisan, AD; Popescu, B; Valeanu, M

Published: 2016, 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21), 2, 1537, DOI: 10.1016/j.prostr.2016.06.194

The influence of the heat treatments on the martensitic transformation, magnetic properties and thermo- and magnetic induced strain on Ni50Fe20Ga27Cu3 ferromagnetic shape memory alloy prepared as ribbons by melt spinning technique are investigated. The degree of atomic order as effect of different thermal treatments produces important changes in the magneto-crystalline anisotropy of the martensite phase. The anomalies evidenced in the thermo-and magnetic-strain curves are discussed and correlated with the thermo-magnetic data. The transformation-induced strains with and without magnetic field have been measured, the results setting out the influence of the pre-martensitic transformation. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

1290. Studies of Aperture-Coupled Rectangular Dielectric Resonator Antenna Arrays

Authors: Turcan, MG; Moni, MV; Banciu, G

Published: 2016, 2016 INTERNATIONAL CONFERENCE ON COMMUNICATIONS (COMM 2016), 120, DOI:

In this paper, the design of aperture-couplet rectangular dielectric resonator antennas arrays is illustrated. The effect of slot feed on the dielectric resonator antenna (DRA) and the effect of the spacing between array elements is observed. This paperwork can be useful for WLAN applications with the operating frequency 5.8 GHz.

1291. Amorphous thin films in the gallium-chalcogen system

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Galca, AC; Matei, E; Socol, G; Gherendi, F; Savastru, D; Miclos, S

Published: JUN 2016, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 253, 1037, DOI: 10.1002/pssb.201552551

Thin amorphous films based on gallium-chalcogen (Ga-Ch), namely Ga2S3, Ga2Se3, Ga2Te3, and GaTe have been prepared by pulsed laser deposition (PLD). The films were characterized by X-ray diffraction, extended X-ray absorption fine structure (EXAFS), energy-dispersive X-ray spectroscopy (EDX), optical transmission spectroscopy, ellipsometry, and electrical measurements. Structural measurements showed that Ga is threefold coordinated, except the Te-based alloys were, it seems, only twofold coordinated, while the chalcogen is usually twofold coordinated. In all the compositions, layered and chain-like structures are assumed. The bandgaps range between 1.09 eV for Ga2Te3 and 2.21 eV for Ga2Se3. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1292. The relationship between magnetism and magneto-optical effects in rare earth doped aluminophosphate glasses

Authors: Valeanu, M; Sofronie, M; Galca, AC; Tolea, F; Elisa, M; Sava, B; Boroica, L; Kuncser, V

Published: FEB 25 2016, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 49, DOI: 10.1088/0022-3727/49/7/075001

Aluminophosphate glasses from the Li2O-BaO-Al2O3-P2O5 system with the addition of nonmagnetic and paramagnetic rare earth ions, were prepared using a wet nonconventional method to process the raw materials, followed by a melting-quenching procedure. The glasses obtained were characterized with respect to their magnetic and magneto-optical properties using superconducting quantum interference device magnetometry and spectroscopic ellipsometry. The assumption of a linear dependence of the Verdet constant on the magnetic susceptibility, with a proportionality constant dependent on the type of vitreous matrix and doping ion, is critically discussed. The diamagnetic and paramagnetic contributions to the Faraday rotation were separately analyzed and specific designs for optimal active and passive elements are proposed.

1293. Dielectric characterization of BaxSr1-xFe12O19 (x=0.05-0.35) ceramics

Authors: Cernea, M; Negrea, RF; Ciuchi, IV; Baldisserri, C; Trusca, R; Galassi, C

Published: JAN 2016, CERAMICS INTERNATIONAL, 42, 1056, DOI: 10.1016/j.ceramint.2015.09.029

BaxSr1-xFe12O19 (x=0.05, 0.15, 0.25, 0.35) ferrites were prepared by both the sol gel and conventional solid state reaction techniques. The structural characteristics and dielectric properties of these ferrites were investigated and compared. BaxSr1-xFe12O19 ceramics obtained by the sol gel method show homogeneous morphology and single crystalline phase while those prepared by solid state reaction route exhibit less homogeneous morphology, being accompanied by a secondary crystalline phase (BaFe2O4). The size of the grains varies in the range 200-300 nm for x=0.05-0.35 when the powders are prepared by sol gel method and, 600-700 nm for the powders prepared by solid state reaction. For the same value of x, the BaxSr1-xFe12O19 ferrites obtained via sol-gel display higher permittivity and lower dielectric losses compared to those prepared by solid state reaction route. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1294. Tellurium addition as a solution to improve compactness of ex-situ processed MgB2-SiC superconducting tapes

Authors: Sandu, V; Aldica, G; Popa, S; Enculescu, M; Badica, P

Published: JUN 2016, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 29, DOI: 10.1088/0953-2048/29/6/065012

Ex-situ spark plasma sintering (SPS) was used to obtain dense MgB2-based tapes in a Fe sheath with the starting composition (MgB2)(0.975) + (SiC)(0.025) + Te-0.01. Prior to the SPS procedure of tape formation, the samples were submitted to a series of cold working processes typical for the powder-in-tube technique. The tapes were compared with optimal doped bulk samples (having the same starting composition) and a pristine MgB2 tape. The morphology of the composite samples, the phase structure of both the core and the inner face of the metallic sheath shows the formation of a plethora of traces as a result of interaction between MgB2, additives, and the Fe sheath. Important critical parameters, like critical current density and the irreversibility field, show that there is a field and temperature range where the SiC and Te-added tapes display better critical parameters comparative to either pristine MgB2 tapes in the Fe sheath or SiC and Te doped MgB2 bulk samples.

1295. MAPLE preparation and characterization of mixed arylenevinylene based oligomers:C-60 layers

Authors: Stanculescu, A; Socol, G; Vacareanu, L; Socol, M; Rasoga, O; Breazu, C; Girtan, M; Stanculescu, F

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 289, DOI: 10.1016/j.apsusc.2015.11.250

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) of mixed layers based on two arylenevinylene oligomers, 1,4-bis [4-(N,N'-diphenylamino)phenylvinyl] benzene (L78) and 3,3'-bis(N-hexylcarbazole)vinylbenzene (L13) as donor and buckminsterfullerene (C-60) as acceptor, blended in three different weight ratios: 1:1, 1:2 and 1:3. The optical, morphological, structural and electrical properties of these mixed layers have been investigated emphasizing the effect of the layer composition and of the significant degree of disorder. I-V characteristics have revealed typically solar cell behaviour for the heterostructures prepared with mixed layers containing L78 (L13) and fullerene blended in a weight ratio of 1:2. The solar cell structure glass/ITO/L13:C-60/Al has shown the best parameters. (C) 2015 Elsevier B.V. All rights reserved.

1296. Innovative Self-Cleaning and Biocompatible Polyester Textiles Nano-Decorated with Fe-N-Doped Titanium Dioxide

Authors: Nica, IC; Stan, MS; Dinischiotu, A; Popa, M; Chifiriuc, MC; Lazar, V; Pircalabioru, GG; Bezirtzoglou, E; Iordache, OG; Varzaru, E; Dumitrescu, I; Feder, M; Vasiliu, F; Mercioniu, I; Diamandescu, L

Published: NOV 2016, NANOMATERIALS, 6, DOI: 10.3390/nano6110214

The development of innovative technologies to modify natural textiles holds an important impact for medical applications, including the prevention of contamination with microorganisms, particularly in the hospital environment. In our study, Fe and N co-doped TiO2 nanoparticles have been obtained via the hydrothermal route, at moderate temperature, followed by short thermal annealing at 400 degrees C. These particles were used to impregnate polyester (PES) materials which have been evaluated for their morphology, photocatalytic performance, antimicrobial activity against bacterial reference strains, and in vitro biocompatibility on human skin fibroblasts. Microscopic examination and quantitative assays have been used to evaluate the cellular morphology and viability, cell membrane integrity, and inflammatory response. All treated PES materials specifically inhibited the growth of Gram-negative bacilli strains after 15 min of contact, being particularly active against Pseudomonas aeruginosa. PES fabrics treated with photocatalysts did not affect cell membrane integrity nor induce inflammatory processes, proving good biocompatibility. These results demonstrate that the treatment of PES materials with TiO2-1% Fe-N particles could provide novel biocompatible fabrics with short term protection against microbial colonization, demonstrating their potential for the development of innovative textiles that could be used in biomedical applications for preventing patients' accidental contamination with microorganisms from the hospital environment.

1297. Structural Properties and Antifungal Activity against Candida albicans Biofilm of Different Composite Layers Based on Ag/Zn Doped Hydroxyapatite-Polydimethylsiloxanes

Authors: Groza, A; Ciobanu, CS; Popa, CL; Iconaru, SL; Chapon, P; Luculescu, C; Ganciu, M; Predoi, D

Published: APR 2016, POLYMERS, 8, DOI: 10.3390/polym8040131

Modern medicine is still struggling to find new and more effective methods for fighting off viruses, bacteria and fungi. Among the most dangerous and at times life-threatening fungi is Candida albicans. Our work is focused on surface and structural characterization of hydroxyapatite, silver doped hydroxyapatite and zinc doped hydroxyapatite deposited on a titanium substrate previously coated with polydimethylsiloxane (HAp-PDMS, Ag:HAp-PDMS, Zn:HAp-PDMS) by different techniques:Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES) and Fourier Transform Infrared Spectroscopy (FTIR). The morphological studies revealed that the use of the PDMS polymer as an interlayer improves the quality of the coatings. The structural characterizations of the thin films revealed the basic constituents of both apatitic and PDMS structure. In addition, the GD depth profiles indicated the formation of a composite material as well as the successful embedding of the HAp, Zn:HAp and Ag:HAp into the polymer. On the other hand, in vitro evaluation of the antifungal properties of Ag:HAp-PDMS and Zn:HAp-PDMS demonstrated the fungicidal effects of Ag:HAp-PDMS and the potential antifungal effect of Zn:HAp-PDMS composite layers against C. albicans biofilm. The results acquired in this research complete previous research on the potential use of new complex materials produced by nanotechnology in biomedicine.

1298. High atomic diffusivity during pulsed laser irradiation of TiON quasi-amorphous films

Authors: Teodorescu, VS; Maraloiu, AV; Negrea, RF; Ghica, D; Scarisoreanu, ND; Dinescu, M; Gartner, M; Blanchin, MG

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 251, DOI: 10.1016/j.apsusc.2015.11.188

Quasi-amorphous titanium oxynitride (TiON) films were obtained by annealing sol-gel anatase TiO2 films in NH3 atmosphere at 600 degrees C. These films were irradiated with 50 laser pulses using the fourth harmonic (266 nm) radiation of the Nd-YAG laser, with an average fluence of 20 mJ/cm(2). HRTEM observations of the pulsed laser irradiated films evidenced the rutile TiO2 nanocrystallites formation. The rutile structure was not present either in the TiON films before the laser irradiation, or in the initial sol-gel anatase TiO2 films. During the laser irradiation, the film structure remains in the solid state phase, as it results from the temperature estimation and microscopic observations. For the rutile nanocrystals formation, the atomic diffusion length of the oxygen and titanium atoms should be in the nanometric range during the laser pulse action, which implies a diffusivity close to the values observed in the liquid phase. We consider that the rutile phase formation is a proof of the fast atomic diffusion in the solid amorphous matrix, during the laser irradiation. (C) 2015 Published by Elsevier B.V.

1299. CdS quantum dots sensitized TiO2 nanotubes by matrix assisted pulsed laser evaporation method

Authors: Bjelajac, A; Petrovic, R; Socol, G; Mihailescu, IN; Enculescu, M; Grurriezescu, V; Pavlovic, V; Janackovic, D

Published: MAY 15 2016, CERAMICS INTERNATIONAL, 42, 9017, DOI: 10.1016/j.ceramint.2016.02.159

Within this study a matrix assisted pulsed laser evaporation technique was employed for deposition of CdS quantum dots onto TiO2 nanotubes. The number of laser pulses and laser fluence were varied to control the amount of CdS deposit. TiO2 nanotubes were obtained via anodization technique of sputtered Ti film on FTO glass. For CdS synthesis, dimethyl sulfoxide (DMSO) was used as a matrix of the target which absorbs radiation of KrF* laser (lambda=248 nm), then evaporates enabling the deposition of CdS quantum dots dispersed into DMSO. This study showed that the size of the CdS nanoparticles synthetized in DMSO can be controlled with microwave treatment that causes the release of S2- ions from DMSO for creation of CdS nuclei and/or their further growth. The optimization of CdS synthesis is achieved by varying the duration of the microwave treatment and the microwave power. The obtained TiO2 photo anodes with different amounts of CdS were assembled with PbS cathodes and the polysulfide electrolyte was injected between. The influence of amount of CdS deposit and the microwave treatment of CdS on photovoltaic performance of the fabricated solar cells were analyzed under AM1.5. The results showed that microwave treatment produced a Cd(S)-DMSO complex onto CdS nanoparticles which led to a higher current density of the solar cells obtained using microwave treated CdS target. Also, the increase of CdS content by increasing the number of laser pulses provided the enhance of I-V characteristics of the solar cells. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1300. Flexible heterostructures based on metal phthalocyanines thin films obtained by MAPLE

Authors: Socol, M; Preda, N; Rasoga, O; Breazu, C; Stavarache, I; Stanculescu, F; Socol, G; Gherendi, F; Grumezescu, V; Popescu-Pelin, G; Girtan, M; Stefan, N

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 410, DOI: 10.1016/j.apsusc.2015.10.166

Heterostructures based on zinc phthalocyanine (ZnPc), magnesium phthalocyanine (MgPc) and 5,10,15,20-tetra(4-pyrydil)21H,23H-porphine (TPyP) were deposited on ITO flexible substrates by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. Organic heterostructures containing (TPyP/ZnPc(MgPc)) stacked or (ZnPc(MgPc):TPyP) mixed layers were characterized by X-ray diffraction-XRD, photoluminescence-PL, UV-vis and FTIR spectroscopy. No chemical decomposition of the initial materials was observed. The investigated structures present a large spectral absorption in the visible range making them suitable for organic photovoltaics applications (OPV). Scanning electron microscopy-SEM and atomic force microscopy-AFM revealed morphologies typical for the films prepared by MAPLE. The current-voltage characteristics of the investigated structures, measured in dark and under light, present an improvement in the current value (similar to 3 order of magnitude larger) for the structure based on the mixed layer (Al/MgPc:TPyP/ITO) in comparison with the stacked layer (Al/MgPc//TPyP/ITO). A photogeneration process was evidenced in the case of structures Al/ZnPc:TPyP/ITO with mixed layers. (C) 2015 Elsevier B.V. All rights reserved.

1301. Non-volatile memory structures with Ge NCs-HfO2 intermediate layer

Authors: Palade, C; Slav, A; Lepadatu, AM; Maraloiu, AV; Lazanu, S; Logofatu, C; Teodorescu, VS; Ciurea, ML

Published: 2016, 2016 39TH INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 166, DOI:

The structure and charge storage properties of a trilayer structure with Ge nanocrystals embedded in HfO2 oxide were studied. The trilayer structure HfO2/Ge-HfO2/HfO2/p-Si was prepared by magnetron sputtering and subsequent rapid thermal annealing at 600 degrees C. The TEM investigations reveal the formation of Ge NCs embedded in crystalline HfO2 at the position of the Ge-HfO2 layer. The capacitors were made by Al evaporation on both front and backside of the trilayer structure. The C-V characteristics show a counterclockwise hysteresis with large memory window of 0.85 V which is given only by the contribution of the Ge NCs embedded in HfO2. The I-V characteristics show an asymmetric behavior, the currents are three times higher for the negative voltage than the positive one.

1302. Iodine Migration and Degradation of Perovskite Solar Cells Enhanced by Metallic Electrodes

Authors: Besleaga, C; Abramiuc, LE; Stancu, V; Tomulescu, AG; Sima, M; Trinca, L; Plugaru, N; Pintilie, L; Nemnes, GA; Iliescu, M; Svavarsson, HG; Manolescu, A; Pintilie, I

Published: DEC 15 2016, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 7, 5175, DOI: 10.1021/acs.jpclett.6b02375

We monitored the evolution in time of pinhole-free structures based on FTO/TiO2/CH3NH3PbI2.6Cl0.4 layers, with and without spiro-OMeTAD and counter electrodes (Ag, Mo/Ag, and Au), aged at 24 degrees C in a dark nitrogen atmosphere. In the absence of electrodes, no degradation occurs. While devices with Au show only a 10% drop in power conversion efficiency, remaining stable after a further overheating at 70 degrees C, >90% is lost when using Ag, with the process being slower for Mo/Ag. We demonstrate that iodine is dislocated by the electric field between the electrodes, and this is an intrinsic cause for electromigration of I- from the perovskite until it reaches the anode. The iodine exhaustion in the perovskite layer is produced when using Ag electrodes, and AgI is formed. We hypothesize that in the presence of Au the iodine migration is limited due to the buildup of I- negative space charge accumulated at the perovskite-OMeTAD interface.

1303. Distribution and interaction of Mn2+ ions incorporated in cubic ZnS quantum dots over a broad concentration range

Authors: Nistor, SV; Stefan, M; Nistor, LC; Ghica, D; Vlaicu, ID

Published: MAR 25 2016, JOURNAL OF ALLOYS AND COMPOUNDS, 662, 199, DOI: 10.1016/j.jallcom.2015.11.203

The distribution and interaction of isolated Mn2+ impurity ions incorporated in 2.9 nm average diameter cubic ZnS quantum dots (QDs), prepared by surfactant-assisted liquid-liquid synthesis with initial impurity concentrations in the 20-50,000 ppm range, has been investigated by electron paramagnetic resonance (EPR) spectroscopy. The well resolved spectra, observed in the whole investigated concentration range, reflect the localization of the Mn2+ ions in the core and on the surface of the cZnS: Mn QDs at isolated sites. According to the analysis of the dependences of the concentration of incorporated isolated Mn2+ ions vs. initial impurity concentration and of the core localized Mn2+ ions spectra line-width vs. actual concentration, the isolated Mn2+ ions remain in the whole concentrations range in a diluted paramagnetic state characterized by dipolar magnetic interactions. Pulse EPR measurements of the spinespin dipolar interaction for the incorporated Mn2+ ions confirm their diluted distribution, which excludes these ions as a possible source of collective magnetism properties. (C) 2015 Elsevier B.V. All rights reserved.

1304. CEMS MEASUREMENTS ON LOW Fe-57 DOPED ANATASE NANOPARTICLES

Authors: Bibicu, I; Constantinescu, S; Tarabasanu-Mihaila, D; Grecu, MN

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 1512, DOI:

We report the conversion electron Mossbauer spectroscopy (CEMS) used to analyze the iron valence states and magnetic ordering properties in Fe-57 low doped (0.1-1% at.) as prepared and anneale d anatase TiO2 nanoparticles. The spectra evidence the static and dynamic diversity of local defects around the Fe ions, localized mainly on the surface samples.

1305. Non-Hermitian approach of edge states and quantum transport in a magnetic field

Authors: Ostahie, B; Nita, M; Aldea, A

Published: NOV 21 2016, PHYSICAL REVIEW B, 94, DOI: 10.1103/PhysRevB.94.195431

We develop a manifest non-Hermitian approach of spectral and transport properties of two-dimensional mesoscopic systems in a strong magnetic field. The finite system to which several terminals are attached constitutes an open system that can be described by an effective Hamiltonian. The lifetime of the quantum states expressed by the energy imaginary part depends specifically on the lead-system coupling and makes the difference among three regimes: resonant, integer quantum Hall effect, and superradiant. The discussion is carried on in terms of edge state lifetime in different gaps, channel formation, role of hybridization, and transmission coefficients quantization. A toy model helps in understanding non-Hermitian aspects in open systems.

1306. Effect of thermal treatments in Ni-Fe-Ga with Co substitutions and Ni-Mn-Ga melt spun ribbons

Authors: Tolea, F; Sofronie, M; Crisan, AD; Popescu, B; Tolea, M; Valeanu, M

Published: 2016, 21ST EUROPEAN CONFERENCE ON FRACTURE, (ECF21), 2, 1480, DOI: 10.1016/j.prostr.2016.06.187

The effect of "in situ" thermal treatments (by DSC measurements) on the martensitic transformation in two representative Ni-Fe-Ga and Ni-Mn-Ga alloys has been studied and discussed by correlating the structural and magnetic properties. The alloys were prepared from high purity elements, by arc melting under argon protective atmosphere as bulk and also as melt-spun ribbons - an alternative preparation route that also allows to assess the influences of grains size and strain induced by this processing method. All samples presented reversible thermo-elastic transformations. The thermal treatments promote a reduction of the martensitic transformation temperatures in the Ni-Fe-Ga investigated samples, as opposed to the stoichiometric Ni2MnGa where the temperatures increase with increasing the annealing temperatures. Interestingly however, the off-stoichiometric Ni-Mn-Ga with increased Ni content recovers the behaviour with reduction of transformation temperatures by thermal treatments. The precipitation of the secondary FCC (gamma) phase is inherently found in Ni-Fe-Ga alloys with Ga <= 27% at, and also-although in lower amounts- in the off-stoichiometric Ni-Mn-Ga. The gamma phase is considered to contribute to the decrease of the MT temperatures (via valence electrons concentration depletion of the main matrix) and of the transformation heat as well as to the final structural degradation if the temperature of the thermal treatments is further increased. In addition, this phase, located mainly at the grain boundaries, is responsible for the improved ductility of Ni-Fe-Ga based alloys. Changes in the transformation heat due to thermal treatments are observed and discussed in both types of alloys, the maxima of the transformation heat being associated with the highest atomic order. Thermo-magnetic measurements show that Ni-Fe-Ga alloys have close magnetic and structural transitions temperatures, with promising applications for magnetic refrigeration. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

1307. INFRARED AND X-RAY PHOTOELECTRON SPECTROSCOPY IN SURFACE CHARACTERIZATION OF POLYDIMETHYLSILOXANE THIN FILMS GENERATED ON METALLIC SUBSTRATES IN MULTIPOINTS TO PLANE CORONA DISCHARGES

Authors: Groza, A; Surmeian, A; Diplasu, C; Negrila, C; Mihalcea, B; Ganciu, M

Published: 2016, ROMANIAN JOURNAL OF PHYSICS, 61, 656, DOI:

By coupling two spectral techniques, namely, X-ray photoelectron and specular reflection infrared spectroscopy at high reflection angles, we identified, in this paper,. the formation of SiO2 respectively SiOx (1 < x < 2) structures on the surface of polydimethylsiloxane thin films. These layers have been obtained as a result of placing a thin liquid film precursor on a germanium substrate under corona charge injection in multipoints to plane electrodes configuration in air at atmospheric pressure for 2 hours.

1308. Nematic ionic liquid crystals based on pyridinium salts derived from 4-hydroxypyridine

Authors: Pana, A; Pasuk, I; Micutz, M; Circu, V

Published: 2016, CRYSTENGCOMM, 18, 5069, DOI: 10.1039/c6ce00618c

A series of pyridinium salts with various counterions (Br-, NO3-, BF4-, PF6-, OTf- and SCN-) and different spacer chain lengths, which display a nematic phase, have been designed and prepared. They are derived from 4-hydroxypyridine and possess two mesogenic cyanobiphenyl groups attached to the pyridinium unit via a flexible long alkyl spacer (6, 9, 10). These salts exhibit solely a nematic phase with the thermal range influenced by the counterion employed and spacer length.

1309. BST thin film capacitors integrated within a frequency tunable antenna

Authors: Rammal, M; Huitema, L; Crunteanu, A; Passerieux, D; Cros, D; Monediere, T; Madrangeas, V; Dutheil, P; Champeaux, C; Dumas-Bouchiat, F; Marchet, P; Nedelcu, L; Trupina, L; Banciu, G; Cernea, M

Published: 2016, 2016 IEEE INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY (IWAT), 47, DOI:

Ferroelectric (FE) thin film varactors can be a convenient technology for tuning miniature antennas. In this paper we present the design of a compact, agile, wire patch antenna integrating barium strontium titanate (Ba(1-x)SrxTiO3, BST) thin film interdigitated capacitors (IDC). The IDCs values were measured at different temperatures and bias voltages ranging from 0 to 120 V showing a capacitance variation of more than 40% between 11-13 GHz and up to 28% in the 2-3 GHz frequency interval. Their integration within a compact antenna design allows tuning its operating frequency on the whole WiFi band, with efficiencies higher than 70%.

1310. Fast atomic diffusion in amorphous films induced by laser pulse annealing

Authors: Teodorescu, VS; Ghica, C; Maraloiu, AV; Kuncser, A; Lepadatu, AM; Stavarache, I; Ciurea, ML; Scarisoreanu, ND; Andrei, A; Dinescu, M

Published: 2016, 2016 39TH INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 158, DOI:

Fast atomic diffusion was evidenced in the surface layer of amorphous thin films of oxides and semiconductors irradiated with low fluence UV pulse laser. This process takes place in a surface layer with a thickness related to the laser radiation absorption depth in the target material and was revealed by the cross section transmission electron microscopy studies. These high values of diffusivity can be explained by supposing the glass transition transformation in the amorphous structure, triggered by the action of the laser pulse field. This effect can have application for controlling structural modifications at nanoscale of the thin films surface and also for inducing structural modification of interfaces between the film and substrate.

1311. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

Authors: Badica, P; Burdusel, M; Popa, S; Pasuk, I; Ivan, I; Borodianska, H; Vasylkiv, O; Kuncser, A; Ionescu, AM; Miu, L; Aldica, G

Published: OCT 2016, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 29, DOI: 10.1088/0953-2048/29/10/105020

High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N-2) atmosphere for different heating rates (10, 20 and 100 degrees C min(-1)) and compared with reference samples processed in vacuum and Ar. N-2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N-2 with a heating rate of 100 degrees C min(-1). At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

1312. Spark plasma sintered MgB2 co-added with c-BN and C-60

Authors: Ionescu, AM; Aldica, G; Popa, S; Enculescu, M; Sandu, V; Pasuk, I; Kuncser, A; Miu, L; Badica, P

Published: FEB 15 2016, MATERIALS CHEMISTRY AND PHYSICS, 170, 209, DOI: 10.1016/j.matchemphys.2015.12.040

High density (above 92%) superconducting bulks of MgB2 co-added with cubic BN (c-BN) and fullerenes (C-60) were obtained by the ex-situ spark plasma sintering (SPS). Compositions were (MgB2)((1-x))(C)(x)(c-BN)(0.01), x = 0.0125, 0.025, 0.05, 0.075. The co-added sample (MgB2)(0.975)(C)(0.025)(c-BN)(0.01) shows a marginally higher critical current density J(c) at intermediate magnetic fields and below 15 K than for optimum samples added with c-BN or C-60. For this sample, pinning is in the point pinning limit and the delta T-c mechanism is dominant. At high magnetic fields co-added samples are inferior to samples added with one additive, but are superior to pristine sample. Co-addition of c-BN and C-60 is not effective for vortex pinning when compared with individual addition. The result is discussed based on phase formation aspects, microstructural details and residual strain. It was found that in the presence of C-60, c-BN consumption with formation of MgNB9 is intensified with implications on different elements that influence pinning. (C) 2015 Elsevier B.V. All rights reserved.

1313. STRUCTURAL CHARACTERIZATION AND OPTICAL PROPERTIES OF HYDROXYAPATITE/COLLAGEN MATRIX

Authors: Popa, CL; Albu, M; Bartha, C; Costescu, A; Luculescu, C; Trusca, R; Antohe, S

Published: 2016, ROMANIAN REPORTS IN PHYSICS, 68, 1158, DOI:

This paper presents the synthesis and characterization of hydroxyapatite (HAp) and hydroxyapatite embedded in a collagen matrix (C-HAp6). The aim of this study was to investigate the influence of collagen on the structure and morphology of hydroxyapatite. According to the XRD patterns, the samples have the structure characteristic to hydroxyapatite. The FTIR and Raman spectra proved the successfully embedding of hydroxyapatite in the collagen matrix. Morphologically, the collagen increases the porosity of HAp. The collagen influences the structure and morphology of the hydroxyapatite causing a decrease of the mean particle size and/or a decrease of crystallinity while increasing the porosity.

1314. Influence of Single-Walled Carbon Nanotubes Enriched in Semiconducting and Metallic Tubes on the Vibrational and Photoluminescence Properties of Poly(para-phenylenevinylene)

Authors: Baibarac, M; Baltog, I; Ilie, M; Humbert, B; Lefrant, S; Negrila, C

Published: MAR 17 2016, JOURNAL OF PHYSICAL CHEMISTRY C, 120, 5705, DOI: 10.1021/acs.jpcc.5b11198

A new synthesis method based on the electrochemical reduction of alpha,alpha,alpha',alpha'-tetrabromo-p-xylene in the presence of single-walled carbon nanotubes (SWNTs) is used to obtain composites of carbon nanotubes (CNTs) functionalized with poly(para-phenyl-enevinylene) (PPV). To separate the effects of metallic and semiconducting CNTs on their interaction with PPV, the experiments are carried out with SWNTs enriched in semiconducting (S, 99%) and metallic (M, 98%) tubes. Significant changes in the relative intensity and shift of the radial breathing vibrational mode are reported in the Raman spectra of the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) entities and SWNTs enriched in M tubes (98%) that result from the electrofunctionalization with PPV. This different behavior originates in the noncovalent and covalent functionalization of SWNTs enriched in M and S SWNTs tubes with PPV, respectively. A gradual decrease in the absorption of the infrared (IR) bands of PPV situated in the spectral range of 750-1000 cm(-1) as a result of the increase of the polymer weight on the blank Au support is reported. The electrofunctionalization of the as-prepared SWNTs induces position changes of the PPV IR absorption bands. In the presence of S-enriched SWNTs, a significant increase in the absorbance of the two IR bands peaked at 1452 and 1471 cm(-1), which are assigned to the vibrational modes of the phenyl ring stretching and the quinoid structure of the PPV, respectively, is reported. This results from the covalent bonding of the PPV macromolecular chains onto the surface of the SWNTs enriched in S tubes. Our results also demonstrate that the photoluminescence quenching effect reported for the PPV/SWNTs composites is due to the metallic nanotubes.

1315. Growth of highly textured iridium thin films and their stability at high temperature in oxygen atmosphere

Authors: Trupina, L; Nedelcu, L; Negrila, C; Banciu, MG; Huitema, L; Crunteanu, A; Rammal, M; Ghalem, A

Published: SEP 2016, JOURNAL OF MATERIALS SCIENCE, 51, 8717, DOI: 10.1007/s10853-016-0131-1

The growth and thermal stability of textured iridium thin films used as bottom electrode in electronic devices based on ferroelectric materials were investigated. The thin films were grown using the dc magnetron sputtering technique. The Ir layers directly deposited on SiO2/Si substrates present a mixed (111) and (200) orientations, while the films grown on Ti seed layers exhibit a strong preferred (111) orientation favoured by good matching with the titanium lattice. The substrate temperature during the growth of iridium/titanium stack has a significant effect on the surface morphology of the iridium layer and its thermal stability. The as-grown surface of 20-nm-thick Ir films is smooth, having a root-mean-square (rms) roughness of 0.7 nm. After thermal annealing the Ir film shows an increased surface roughness due to the formation of agglomerations. The change in the surface morphology of the Ir layer is due to titanium diffusion and its oxidation. Thicker and better crystallised iridium thin films annealed in oxygen atmosphere at 700 A degrees C show a good thermal stability with only a slight modification of the surface morphology. Within the limits of experimental error, there is no change in the electrical resistivity before and after thermal annealing. The rms roughness has not varied significantly and the XPS investigation shows no traces of titanium oxide on iridium surface. Ir/Ti stack deposited under the optimum conditions could be successfully used as electrode in devices based on oxide thin films.

1316. Crystallization and luminescence properties of a new Eu3+-doped LaOCl nano-glass-ceramic

Authors: Secu, M; Secu, CE; Bartha, C

Published: JAN 2016, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 36, 207, DOI: 10.1016/j.jeurceramsoc.2015.09.001

Glassy nanocomposites containing Eu3+-doped LaOCl nanocrystals of about tens of nm size embedded in a silica matrix have been prepared by using sol-gel route followed by controlled crystallization of the xerogel. Crystallization behavior of LaOCl nanocristalline phase was discussed on the basis of thermal analysis, X-ray diffraction and photoluminescence measurements. LaOCl nanocrystalline phase precipitation is the result of lanthanum chloride hydrolytic and oxidative reactions. As the annealing temperature increases nanocrystallites size grows up to tens of nm; Eu3+-ions are gradually incorporated during the nanocrystals growth. Structural changes were studied using the Eu3+ as probe ion and the luminescence properties were analysed by using Judd-Ofelt theory. (C) 2015 Elsevier Ltd. All rights reserved.

1317. Characterization of a n+3C/n-4H SiC heterojunction diode

Authors: Minamisawa, RA; Mihaila, A; Farkas, I; Teodorescu, VS; Afanas'ev, VV; Hsu, CW; Janzen, E; Rahimo, M

Published: APR 4 2016, APPLIED PHYSICS LETTERS, 108, DOI: 10.1063/1.4945332

We report on the fabrication of n+3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to similar to 7 x 10(17) cm(-3) dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n+3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices. (C) 2016 AIP Publishing LLC.

1318. Structural, compositional, mechanical characterization and biological assessment of bovine-derived hydroxyapatite coatings reinforced with MgF2 or MgO for implants functionalization

Authors: Mihailescu, N; Stan, GE; Duta, L; Chifiriuc, MC; Bleotu, C; Sopronyi, M; Luculescu, C; Oktar, FN; Mihailescu, IN

Published: FEB 1 2016, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 59, 874, DOI: 10.1016/j.msec.2015.10.078

Hydroxyapatite (HA) is a consecrated biomaterial for bone reconstruction. In the form of thin films deposited by pulsed laser technologies, it can be used to cover metallic implants aiming to increase biocompatibility and osseointegration rate. HA of animal origin (bovine, BHA) reinforced with MgF2 (2 wt.%) or MgO (5 wt.%) were used for deposition of thin coatings with improved adherence, biocompatibility and antimicrobial activity. For pulsed laser deposition experiments, a KrF* (lambda = 248 nm, T-EWHM <= 25 ns) excimer laser source was used. The deposited structures were characterized from a physical-chemical point of view by X-Ray Diffraction, Fourier Transform Infra-Red Spectroscopy, Scanning Electron Microscopy in top- and cross-view modes, Energy Dispersive X-Ray Spectroscopy and Pull-out adherence tests. The microbiological assay using the HEp-2 cell line revealed that all target materials and deposited thin films are non-cytotoxic. We conducted tests on three strains isolated from patients with dental implants failure, i.e. Microccocus sp., Enterobacter sp. and Candida albi cans sp. The most significant anti-biofilm effect against Microcococcus sp. strain, at 72 h, was obtained in the presence of BHA:MgO thin films. For Enterobacter sp. strain a superior antimicrobial activity at 72 h was noticed, in respect with simple BHA or Ti control. The enhanced antimicrobial performances, correlated with good cytocompatibility and mechanical properties recommend these biomaterials as an alternative to synthetic HA for the fabrication of reliable implant coatings for dentistry and other applications. (C) 2015 Elsevier B.V. All rights reserved.

1319. Electrical transport properties and modelling of electrostrictive resonance phenomena in Ba2/3Sr1/3TiO3 thin films

Authors: Ghalem, A; Huitema, L; Crunteanu, A; Rammal, M; Trupina, L; Nedelcu, L; Banciu, MG; Dutheil, P; Constantinescu, C; Marchet, P; Dumas-Bouchiat, F; Champeaux, C

Published: NOV 14 2016, JOURNAL OF APPLIED PHYSICS, 120, DOI: 10.1063/1.4966942

We present the conduction mechanisms of Ba2/3Sr1/3TiO3 thin films integrated in metal-insulatormetal (MIM) capacitors and the modelling of the frequency-dependent electrostrictive resonances (in the 100 MHz-10 GHz domain) induced in the devices upon applying different voltage biases. Au/BST/Ir MIM structures on MgO substrates have been fabricated and, depending on their specific polarization, we highlighted different conduction mechanisms in the devices. Depending on the dc bias polarity, the conduction current across the material shows a space-charge-limited-current behavior under negative polarization, whereas under positive bias, the conduction obeys an electrode-limited Schottky-type law at the Au/BST interface. The application of an electric field on the device induces the onset of acoustic resonances related to electrostrictive phenomena in the ferroelectric material. We modeled these acoustic resonances over a wide frequency range, by using a modified Lakin model, which takes into account the dispersions of acoustic properties near the lower electrode/thin film interface. Published by AIP Publishing.

1320. Multi-stage pulsed laser deposition of aluminum nitride at different temperatures

Authors: Duta, L; Stan, GE; Stroescu, H; Gartner, M; Anastasescu, M; Fogarassy, Z; Mihailescu, N; Szekeres, A; Bakalova, S; Mihailescu, IN

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 150, DOI: 10.1016/j.apsusc.2015.10.093

We report on multi-stage pulsed laser deposition of aluminum nitride (AlN) on Si (100) wafers, at different temperatures. The first stage of deposition was carried out at 800 degrees C, the optimum temperature for AlN crystallization. In the second stage, the deposition was conducted at lower temperatures (room temperature, 350 degrees C or 450 degrees C), in ambient Nitrogen, at 0.1 Pa. The synthesized structures were analyzed by grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), atomic force microscopy and spectroscopic ellipsometry (SE). GIXRD measurements indicated that the two-stage deposited AlN samples exhibited a randomly oriented wurtzite structure with nanosized crystallites. The peaks were shifted to larger angles, indicative for smaller inter-planar distances. Remarkably, TEM images demonstrated that the high-temperature AlN "seed" layers (800 degrees C) promoted the growth of poly-crystalline AlN structures at lower deposition temperatures. When increasing the deposition temperature, the surface roughness of the samples exhibited values in the range of 0.4-2.3 nm. SE analyses showed structures which yield band gap values within the range of 4.0-5.7 eV. A correlation between the results of single and multi-stage AlN depositions was observed. (C) 2015 Elsevier B.V. All rights reserved.

1321. NANOTUBES OF Ba0.95Ce0.05Ti0.9875O3 PREPARED BY SOL-GEL CHEMISTRY

Authors: Cernea, M; Ianculescu, AC; Vasile, BS; Vasilescu, CA

Published: 2016, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 78, DOI:

Nanotubes of Ba0.95Ce0.05Ti0.9875O3 with an average diameter of 80 nm and wall thickness of similar to 8 nm were prepared from the precursor sol using as template a polycarbonate membrane with the pores diameter size of 100 nm. The Ce doped-BaTiO3 nanotubes calcined at 700 degrees C, 1h in air crystallized on the lattice of BaTiO3 cubic phase as indicated the high resolution transmission electron microscopy and selected area electron diffraction analyses. The nanotubes showed a polycrystalline structure with crystallites of 3-5 nm size. The results prove that we can prepare BaTiO3 doped with 5 at.% Ce nanotubes for future capacitor applications.

1322. ANTIMICROBIAL ACTIVITY OF EUROPIUM DOPED HYDROXYAPATITE POWDERS AFTER IMMERSION IN SBF SOLUTION

Authors: Andronescu, E; Surugiu, A; Badea, ML; Ciobanu, CS; Iosif, A

Published: 2016, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN SERIES B-CHEMISTRY AND MATERIALS SCIENCE, 78, DOI:

The europium doped hydroxypatite samples were obtained by an adapted coprecipitation method. After the synthesis, the samples were immersed in simulated body fluid (SBF) solution for 6 and 24 h respectively. After the immersion in the SBF solution, the morphology and antimicrobial activity of the powders were studied. Our antimicrobial studies revealed that all the samples exhibit antimicrobial activity against gram positive and gram negative strains.

1323. Europium Oxide-Hematite Magnetic Ceramic Nanoparticles

Authors: Sorescu, M; Diamandescu, L; DiGnazio, J; Xu, TH

Published: 2016, MRS ADVANCES, 1, DOI: 10.1557/adv.2015.16

Nanoparticle system with the composition xEu(2)O(3)-(1-x)alpha-Fe2O3 (x = 0.1 and 0.5) was successfully synthesized by mechanochemical activation of Eu2O3 and alpha-Fe2O3 mixtures for 0-12 hours of ball milling time. The study is of relevance to catalysis, biomedical, sensing and energy-related applications. Fe-57 and Eu-151 Mossbauer spectroscopy were used to investigate the phase evolution, solid solution formation and hyperfine parameters of xEu(2)O(3)-(1-x)alpha-Fe2O3 nanoparticle system under the mechanochemical activation process. The Fe-57 Mossbauer studies showed that the spectrum of the ball milled samples evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with europium oxide. This indicated the formation of the EuFeO3 perovskite for large x values and long milling times. The Eu-151 Mossbauer investigations showed that the isomer shift decreased with increasing milling time for all molar concentrations employed.

1324. Tuning Hydroxyapatite Particles' Characteristics for Solid Freeform Fabrication of Bone Scaffolds

Authors: Miculescu, F; Maidaniuc, A; Stan, GE; Miculescu, M; Voicu, SI; Cimpean, A; Mitran, V; Batalu, D

Published: 2016, ADVANCED COMPOSITE MATERIALS, 397, DOI:

Restoration of damaged bone tissue involves two traditional approaches: tissue grafting and alloplastic replacement. Recently, their limitations led to the development of tissue engineering, which uses degradable porous supports named "scaffolds". These porous structures (used both for tissue engineering and classic bone substitution applications) with customizable designs may be constructed by solid freeform fabrication (SFF) techniques. SFF uses various synthetic materials and may be adapted for creating ceramic-based scaffolds, which became popular due to increased demands for bone substitution materials. Among these materials, naturally derived ceramics are suitable candidates for bone replacement due to their resemblance with the mineral bone. Innovative optimization routes for preparing naturally derived ceramics with modulated properties implies the management of key parameters involved in heat treatment of animal hard tissues: temperature, heating environment, and cooling conditions. Both powders and bulk pieces are evaluated with complementary techniques that focus on compositional, morphological, and structural features. Finally, qualitative and quantitative biological assay in relevant cell culture of the compacted powders may assist extensive testing programs for further evaluation of different ceramic scaffolds. All these results contribute to effective assessment of ceramics tuning strategies and to subsequent modulation of their enhanced properties and long-term functionality.

1325. HfO2 with embedded Ge nanocrystals with memory effects

Authors: Palade, C; Slav, A; Lepadatu, AM; Maraloiu, AV; Teodorescu, VS; Ciurea, ML

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 48, DOI:

The charge storage properties of Ge nanocrystals-based MOS-like capacitors with tunnel and gate HfO2 are studied. HfO2/Ge/HfO2/Si trilayer structures were prepared by magnetron sputtering (in Ar) and subsequent rapid thermal annealing (650 degrees C). HfO2/Si structures were also prepared, some under similar conditions, while others were deposited in Ar:O-2. TEM investigations and C-V measurements were performed. TEM on annealed trilayers evidences the formation of ordered and precisely positioned array of Ge nanocrystals embedded in crystalline HfO2. The annealed Al/HfO2/Ge/HfO2/p-Si/Al capacitors present counterclockwise C-V hysteresis (0.8 V memory window) mainly given by Ge nanocrystals, with negligible contribution from crystallized-HfO2 traps.

1326. Electrical properties of single CdTe nanowires

Authors: Matei, E; Florica, C; Costas, A; Toimil-Molares, ME; Enculescu, I

Published: FEB 12 2015, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 6, 450, DOI: 10.3762/bjnano.6.45

Ion track, nanoporous membranes were employed as templates for the preparation of CdTe nanowires. For this purpose, electrochemical deposition from a bath containing Cd and Te ions was employed. This process leads to high aspect ratio CdTe nanowires, which were harvested and placed on a substrate with lithographically patterned, interdigitated electrodes. Focused ion beam-induced metallization was used to produce individual nanowires with electrical contacts and electrical measurements were performed on these individual nanowires. The influence of a bottom gate was investigated and it was found that surface passivation leads to improved transport properties.

1327. Surface-enhanced Raman scattering activity of niobium surface after irradiation with femtosecond laser pulses

Authors: Ivanov, VG; Vlakhov, ES; Stan, GE; Zamfirescu, M; Albu, C; Mihailescu, N; Negut, I; Luculescu, C; Socol, M; Ristoscu, C; Mihailescu, IN

Published: NOV 28 2015, JOURNAL OF APPLIED PHYSICS, 118, DOI: 10.1063/1.4936363

The chemical modification of the niobium (Nb) surface after irradiation with femtosecond laser pulses was investigated by scanning electron microscopy coupled with energy dispersive spectroscopy, atomic force microscopy, grazing incidence X-ray diffraction, and micro-Raman spectroscopy. The physical-chemical analyses indicated that the laser treatment results in oxidation of the Nb surface, as well as in the formation of Nb hydrides. Remarkably, after the samples' washing in ethanol, a strong Surface-Enhanced Raman Scattering (SERS) signal originating from the toluene residual traces was evidenced. Further, it was observed that the laser irradiated Nb surface is able to provide a SERS enhancement of similar to 1.3 x 10(3) times for rhodamine 6G solutions. Thus, for the first time it was shown that Nb/Nb oxide surfaces could exhibit SERS functionality, and so one can expect applications in biological/biochemical screening or for sensing of dangerous environmental substances. (C) 2015 AIP Publishing LLC.

1328. Revealing the Cu2+ ions localization at low symmetry Bi sites in photorefractive Bi12GeO20 crystals doped with Cu and V by high frequency EPR

Authors: Nistor, SV; Stefan, M; Goovaerts, E; Ramaz, F; Briat, B

Published: OCT 2015, JOURNAL OF MAGNETIC RESONANCE, 259, 94, DOI: 10.1016/j.jmr.2015.07.009

The sites of incorporation of Cu2+ impurity ions in Bi12GeO20 single crystals co-doped with copper and vanadium have been investigated by electron paramagnetic resonance (EPR). While the X-band EPR spectra consist of a simple broad (Delta B similar to 50 mT) line with anisotropic lineshape, the W-band EPR spectra exhibit well resolved, strongly anisotropic lines, due to transitions within the 3d(9)-D-2 ground manifold of the Cu2+ ions. The most intense group of lines, attributed to the dominant Cu2+(I) center, displays a characteristic four components hyperfine structure for magnetic field orientations close to a < 110 > direction. The g and A tensor main axes are very close to one of the 12 possible sets of orthogonal < 1-10 >, < 00-1 > and < 110 > crystal directions. Several less intense lines, with unresolved hyperfine structure and similar symmetry properties, mostly overlapped by the Cu2+(I) spectrum, were attributed to Cu-2 (+)(II) centers. The two paramagnetic centers are identified as substitutional Cu2+ ions at Bi3+ sites with low C-1 symmetry, very likely resulting from different configurations of neighboring charge compensating defects. (C) 2015 Elsevier Inc. All rights reserved.

1329. Sulfur treatment on n-GaSb (100) and surface antibacterial evaluation

Authors: Ghita, R; Iconaru, SL; Frumosu, F; Logofatu, C; Badea, ML; Holban, AM

Published: OCT 16 2015, TOXICOLOGY LETTERS, 238, S199, DOI: 10.1016/j.toxlet.2015.08.599

1330. Nanostructuring of GeTiO amorphous films by pulsed laser irradiation

Authors: Teodorescu, VS; Ghica, C; Maraloiu, AV; Vlaicu, M; Kuncser, A; Ciurea, ML; Stavarache, I; Lepadatu, AM; Scarisoreanu, ND; Andrei, A; Ion, V; Dinescu, M

Published: APR 7 2015, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 6, 900, DOI: 10.3762/bjnano.6.92

Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10-30 mJ/cm(2). The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm) of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 degrees C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm(2) and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the segregation of Ge atoms in the GeTiO matrix. The nanostructuring effects induced by the laser irradiation can be used in functionalizing the surface of the films.

1331. ELECTROSPRAYING OF ZnO MICROSTRUCTURES FOR ELECTRICAL CONTACTING

Authors: Costas, A; Florica, C; Evanghelidis, A; Enculescu, M; Preda, N; Enculescu, I

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1188, DOI:

ZnO complex microstructures were deposited onto interdigitated metallic electrodes by electrospraying. Simple methods, such as wet chemical precipitation and optical lithography, were used for the synthesis of flower-like and snowflake-like ZnO structures and for the preparation of interdigitated metallic electrodes, respectively. The electrosprayed ZnO particles preserve the structural, optical and morphological properties of the chemically synthesized ZnO powders. During the electrospraying process, the ZnO microstructures form bridges between the interdigitated metallic electrodes leading to electrical contacting. Changes in the electron transport through the ZnO microstructures are evidenced by their exposure to ammonia or their passivation with poly(methyl methacrylate). Merging such easy-scalable and low-cost techniques, devices based on electrosprayed complex ZnO structures can be designed.

1332. MAPLE fabrication of thin films based on kanamycin functionalized magnetite nanoparticles with anti-pathogenic properties

Authors: Grumezescu, V; Andronescu, E; Holban, AM; Mogoanta, L; Mogosanu, GD; Grumezescu, AM; Stanculescu, A; Socol, G; Iordache, F; Maniu, H; Chifiriuc, MC

Published: MAY 1 2015, APPLIED SURFACE SCIENCE, 336, 195, DOI: 10.1016/j.apsusc.2014.10.177

In this study we aimed to evaluate the biocompatibility and antimicrobial activity of kanamycin functionalized 5 nm-magnetite (Fe3O(4)@ KAN) nanoparticles thin films deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. A laser deposition regime was established in order to stoichiometrically transfer Fe3O4@ KAN thin films on silicone and glass substrates. Morphological and physico-chemical properties of powders and coatings were characterized by XRD, TEM, SEM, AFM and IR microscopy(IRM). Our nanostructured thin films have proved efficiency in the prevention of microbial adhesion and mature biofilms development as a result of antibiotic release in its active form. Furthermore, kanamycin functionalized nanostructures exhibit a good biocompatibility, both in vivo and in vitro, demonstrating their potential for implants application. This is the first study reporting the assessment of the in vivo biocompatibility of a magnetite-antimicrobial thin films produced by MAPLE technique. (C) 2014 Elsevier B.V. All rights reserved.

1333. Magnetic and transport properties of Ca1.5La0.5FeMo1-xWxO6 perovskites

Authors: Burzo, E; Balasz, I; Valeanu, M; Kozlenko, DP; Kichanov, SE; Rutkauskas, AV; Savenko, BN

Published: FEB 5 2015, JOURNAL OF ALLOYS AND COMPOUNDS, 621, 77, DOI: 10.1016/j.jallcom.2014.09.176

The Ca1.5La0.5FeMo1-xWxO6 double perovskites with x <= 0.3 crystallize in a monoclinic structure having space group P2(1)/n. The degree of crystallographic ordering is increased as the tungsten content is higher. As a result, there is an increase of both saturation magnetizations and Curie temperatures. The magnetic susceptibilities follow temperature dependences typical for a ferrimagnetic system. The valence states of iron and molybdenum ions as well their distributions in the lattice sites were determined. These data were correlated with magnetic and transport properties. (C) 2014 Elsevier B.V. All rights reserved.

1334. Spatially resolved nanostructural transformation in graphite under femtosecond laser irradiation

Authors: Marcu, A; Avotina, L; Porosnicu, C; Marin, A; Grigorescu, CEA; Ursescu, D; Lungu, M; Demitri, N; Lungu, CP

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 483, DOI: 10.1016/j.apsusc.2015.06.194

A polycrystalline graphite target was irradiated using infrared (800 nm) femtosecond (120 fs) laser pulses of different energies. Increase of sp(3) bonds percentage and possible diamond crystal formation were investigated 'in-depth' and on the irradiated surfaces. Synchrotron X-ray diffraction pattern have shown the presence of a diamond peak in one of the irradiated zones while X-ray photoelectron spectroscopy investigations have shown an increasing tendency of the sp(3) percent in the low power irradiated areas and similarly 'in the depth' of the higher power irradiated zones. Multiple wavelength Micro-Raman investigations have confirmed this trend along with an 'in-depth' (but not on the surface) increase of the crystallite size. Based on the wavelength dependent photon absorption into graphite, the observed effects are correlated with high density photon per atom and attributed to the melting and recrystallization processes taking place tens of nanometers below the target surface. (c) 2015 Elsevier B.V. All rights reserved.

1335. On the role of Fe ions on magnetic properties of doped TiO2 nanoparticles

Authors: Tolea, F; Grecu, MN; Kuncser, V; Constantinescu, SG; Ghica, D

Published: APR 6 2015, APPLIED PHYSICS LETTERS, 106, DOI: 10.1063/1.4917037

The role of iron doping on magnetic properties of hydrothermal anatase TiO2:Fe-57 (0-1 at. %) nanoparticles is investigated by combining superconducting quantum interference device magnetometry with Mossbauer and electron paramagnetic resonance techniques. The results on both as-prepared and thermally treated samples in reduced air atmosphere reveal complexity of magnetic interactions, in connection to certain iron ion electron configurations and defects (oxygen vacancies, F-center, and Ti3+ ions). The distribution of iron ions is predominantly at nanoparticle surface layers. Formation of weak ferromagnetic domains up to 380 K is mainly related to defects, supporting the bound magnetic polaron model. (C) 2015 AIP Publishing LLC.

1336. Distribution of plates' sizes tell the thermal history in a simulated martensitic-like phase transition

Authors: Tolea, F; Tolea, M; Sofronie, M; Valeanu, M

Published: JUL 2015, SOLID STATE COMMUNICATIONS, 213, 41, DOI: 10.1016/j.ssc.2015.04.016

A phenomenological 2D model, simulating the martensitic transformation, is built upon existing experimental observations that the size of the formed plates - in direct transformation - decreases as the temperature is lowered; then they transform back in reversed order. As such, if a reverse transformation is incomplete (arrested), the subsequent direct one will show anomalously a large number of big size plates - old plus newly formed - but consequentially a depletion of intermediate sizes, due to geometrical constraints, phenomenon that generates thermal memory. (C) 2015 Elsevier Ltd. All rights reserved.

1337. Heterogeneous Gold Catalyst: Synthesis, Characterization, and Application in 1,4-Addition of Boronic Acids to Enones

Authors: Moragues, A; Neatu, F; Parvulescu, VI; Marcos, MD; Amoros, P; Michelet, V

Published: SEP 2015, ACS CATALYSIS, 5, 5067, DOI: 10.1021/acscatal.5b01207

The new 1 wt % Au/TiO2-UVM-7 catalyst was prepared and fully characterized. This heterogeneous catalyst proved to be active, selective and recyclable for the unprecedented gold-catalyzed 1,4-addition of various functionalized arylboronic acids to 2-cyclohexen-1-one and other selected enones using toluene as a solvent. The gold-based catalyst was recycled two times and played an active role in this reaction, and the nature of the solvent determined a remarkable change in the products' selectivities.

1338. Growth and Characterization of Arc Evaporated TiSiC-Ni Coatings

Authors: Balaceanu, M; Parau, AC; Braic, M; Vladescu, A; Luculescu, CR; Logofatu, C; Braic, V

Published: JUN 2015, TRIBOLOGY LETTERS, 58, DOI: 10.1007/s11249-015-0521-6

TiSiC-Ni coatings, with Ni as alloying element, were prepared on Si, C 45, and 316 L steel substrates by cathodic arc technique in a reactive atmosphere of CH4. The coatings, with three different Ni contents (3.2, 6.8 and 16.2 at.%), were investigated in terms of microchemical and microstructural properties, mechanical characteristics and tribological performance using energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, hardness and adhesion measurements, and ball-on disc tribological testing. The coatings were found to consist of a mixture of different phases: face-centred cubic crystalline carbide, metallic Ni, and amorphous Si and C, with relative amounts depending on Ni concentration. All of the coatings exhibited dense and featureless morphologies. Ni addition to TiSiC coatings led to residual stress reduction (from -0.50 to -0.59 GPa) and improved adhesion strength (in the range 44-46 N). The TiSiC-Ni coatings with Ni contents below 7 at.% exhibited the best tribological properties under dry conditions (friction coefficients of similar to 0.32; wear rates from 3.16 to 3.66 x 10(-6) mm(3) N-1 m(-1)).

1339. Magnetic and Martensitic Transformations in the bulk and melt spun ribbons of Ni57-xNdxFe18Ga25 Ferromagnetic Shape Memory Alloys

Authors: Tolea, F; Crisan, AD; Sofronie, M; Tolea, M; Valeanu, M

Published: 2015, MATERIALS TODAY-PROCEEDINGS, 2, 878, DOI: 10.1016/j.matpr.2015.07.421

Influence of Nd substitution for Ni on the magnetic properties and the martensitic transformation (MT) characteristics are investigated on Ni57-xNdxFe18Ga25 (x=0 divided by 4) ferromagnetic shape memory alloys (FSMAs) in bulk and also in ribbons prepared by melt spinning method and subjected to different thermal treatments. Increasing the Nd content induces a decrease of both the Curie and the MT temperatures. (C) 2015 The Authors. Published by Elsevier Ltd.

1340. Pattern formation on silicon by laser-initiated liquid-assisted colloidal lithography

Authors: Ulmeanu, M; Petkov, P; Ursescu, D; Maraloiu, VA; Jipa, F; Brousseau, E; Ashfold, MNR

Published: NOV 13 2015, NANOTECHNOLOGY, 26, DOI: 10.1088/0957-4484/26/45/455303

We report sub-diffraction limited patterning of Si substrate surfaces by laser-initiated liquid-assisted colloidal lithography. The technique involves exposing a two-dimensional lattice of transparent colloidal particles spin coated on the substrate of interest (here Si) immersed in a liquid (e.g. methanol, acetone, carbon tetrachloride, toluene) to a single picosecond pulse of ultraviolet laser radiation. Surface patterns formed using colloidal particles with different radii in the range 195 nm <= R <= 1.5 mu m and liquids with differing indices of refraction (n(liquid)) are demonstrated, the detailed topographies of which are sensitively dependent upon whether the index of refraction of the colloidal particle (n(colloid)) is greater or smaller than n(liquid) (i.e. upon whether the incident light converges or diverges upon interaction with the particle). The spatial intensity modulation formed by diffraction of the single laser pulse by the colloidal particles is imprinted into the Si substrate.

1341. Tuning the properties of Ge and Si nanocrystals based structures by tailoring the preparation conditions Review

Authors: Ciurea, ML; Lepadatu, AM

Published: JAN-MAR 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 87, DOI:

Ge and Si nanocrystals (NCs), quantum dots (QDs), and amorphous nanoparticles (NPs) have a significant role in the developement of micro- and nanoelectronic devices due to capability to tune their electrical and photoconductive properties by tailoring the morphology and structure parameters. Ge and Si NCs/QDs/NPs are zero-dimensional (0D) systems and the SiO2 films containing them are percolative systems. In this review, the role of deposition and annealing conditions in the morphology and structure of Ge and Si NCs/QDs/NPs embedded in amorphous SiO2 matrix is discussed for a wide variety of films and multilayered structures. The electrical and photoconductive properties of nanostructures deposited by different techniques as magnetron sputtering, ion implantation, chemical vapour deposition, sol-gel and molecular beam epitaxy, and subsequently annealed in conventional furnace or by rapid thermal annealing under different conditions are analised. We demonstrate how the electrical and photoconductive properties of nanostructures can be tuned by varying the deposition and annealing parameters. The role of Si-rich oxide and defects in the formation of Ge and Si NCs is shown and the role of defects in improving electrical properties and enhancing the photoconductivity of films and multilayered structures is highlighted. We evidence the contribution of quantum confinement effect and show that the most probable transport mechanisms in these percolative systems are tunnelling and hopping.

1342. Influence of Thermal Treatment on the Antimicrobial Activity of Silver-Doped Biological Apatite

Authors: Popa, CL; Ciobanu, CS; Voicu, G; Vasile, E; Chifiriuc, MC; Iconaru, SL; Predoi, D

Published: DEC 29 2015, NANOSCALE RESEARCH LETTERS, 10, DOI: 10.1186/s11671-015-1211-x

In this paper, we report the structural and morphological properties of silver-doped hydroxyapatite (AgHAp) with a silver concentration x(Ag) = 0.5 before and after being thermal treated at 600 and 1000 degrees C. The results obtained by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy suggest that the structure of the samples changes gradually, from hydroxyapatite (AgHAp_40) to a predominant beta-TCP structure (AgHAp_1000), achieved when the thermal treatment temperature is 1000 degrees C. In the AgHAp_600 sample, the presence of two phases, HAp and beta-TCP, was highlighted. Also, scanning electron microscopy studies suggest that the shape and dimension of the nanoparticles begin to change when the temperature increases. The antimicrobial activity of the obtained compounds was evaluated against Klebsiella pneumoniae, Staphylococcus aureus, and Candida albicans strains.

1343. Submillimeter-wave properties of Zn2SiO4 ceramics

Authors: Nedelcu, L; Geambasu, CD; Banciu, MG; Iwamae, A; Furuya, T; Tani, M

Published: 2015, 2015 40TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ), DOI: 10.1109/IRMMW-THz.2015.7327946

Zinc silicate ceramics have been prepared by using conventional ceramic technology. Morphological, structural, and dielectric characterizations of the samples were performed using scanning electron microscopy, X-ray diffraction, and terahertz time-domain spectroscopy. The achieved absorption properties of zinc silicates make them very attractive solutions for submillimeter-wave applications.

1344. Thin films of amorphous Ga2S3 and rare-earth sulphides

Authors: Popescu, M; Lorinczi, A; Sava, F; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Socol, G; Jipa, F; Zamfirescu, M

Published: MAR 1 2015, MATERIALS LETTERS, 142, 231, DOI: 10.1016/j.matlet.2014.12.028

The aim of this research is to prepare amorphous thin films of undoped gallium sulphide and doped with rare-earth sulphides, of rare-earth sulphides and to investigate their physical properties. We have prepared thin amorphous films of Ga2S3, EuS, Er2S3, Gd2S3, and Ga2S3 doped with rare-earth sulphides (Ga2S3:EuS, Ga2S3:Er2S3, Ga2S3:Gd2S3) by Pulsed laser Deposition (PLD). The corresponding targets for preparation of amorphous thin films were obtained by Spark Plasma Sintering (SPS) from commercially available powders of binary sulphides. The structural results for the undoped and doped Ga2S3 thin films indicate a packing of disordered layers similar to that of amorphous As2S3. Femtosecond laser irradiation of the Ga2S3 thin films shows a photoexpansion effect at low laser power (85-100 mW) and an ablation effect at higher laser power (above 105 mW). The threshold between low power and high power pulses is situated at higher value for Ga2S3 (100 mW) in comparison with the case of As2S3 thin films (20 mW). (C) 2014 Elsevier B.V. All rights reserved.

1345. B4C in ex-situ spark plasma sintered MgB2

Authors: Burdusel, M; Aldica, G; Popa, S; Enculescu, M; Mihalache, V; Kuncser, A; Pasuk, I; Badica, P

Published: OCT 2015, CURRENT APPLIED PHYSICS, 15, 1270, DOI: 10.1016/j.cap.2015.07.017

Powder mixtures of MgB2 and B4C with composition ((MgB2) + (B4C) x, x = 0.005, 0.01, 0.03) were consolidated by Spark Plasma Sintering at 1150 degrees C for 3 min. The average particle size of B4C raw powder was relatively high of 4 mm. Despite this, it is shown that processing processes are fast and, as in the case of the in-situ routes, for our ex-situ method carbon substitutes for the boron in the crystal lattice of MgB2. Specifics of microstructure are discussed based on electron microscopy observations. Carbon substitution and microstructure contribute to enhancement of the critical current density J(c) at high magnetic fields and of the irreversibility field H-irr. Samples are shown to be in the point pinning limit with some tendency toward the grain boundary pinning depending on B4C doping amount and temperature. An optimum composition is found for x = 0.01: for this sample, at 20 K, a J(c) of 100 A/cm(2) is obtained at 5.35 T. This value is higher than for the pristine MgB2 sample and for an optimum ex-situ nano-SiC-doped sample obtained for the same SPS processing conditions. (C) 2015 Elsevier B.V. All rights reserved.

1346. Anti-Stokes Raman spectroscopy as a method to identify metallic and mixed metallic/semiconducting configurations of multi-walled carbon nanotubes

Authors: Baibarac, M; Matea, A; Ilie, M; Baltog, I; Magrez, A

Published: 2015, ANALYTICAL METHODS, 7, 6230, DOI: 10.1039/c5ay01281c

SERS studies were performed on films of two families of multi-wall carbon nanotubes (MWCNTs) under an excitation light of 514.5 nm and 647.1 nm. These included Aldrich-MWCNTs, which alternate semiconducting and metallic tubes and M-MWCNTs that contain only metallic tubes obtained by water assisted catalytic chemical vapour deposition (CCVD). The two families of MWCNTs reveal similar spectra in the Stokes branch, which feature an increasing Raman intensity when the glass substrate is replaced with an Au or Ag substrate, indicating a (surface enhanced Raman scattering) SERS mechanism. In the anti-Stokes branch, despite an enhancement of approximately 100 times compared to the predictions of the Boltzmann law, only Aldrich-MWCNTs exhibit a Raman spectrum with an intensity that increases as a result of the change in the glass substrate to Au or Ag, a fact that is revealed by the signature of the SERS process. The invariance of the Raman intensity in the anti-Stokes branch as a result of the change of the substrate is characteristic of M-MWCNTs and results from a Raman light scattering process that takes place only within the skin depth of the metallic structure.

1347. Doping Ultrasmall Cubic ZnS Nanocrystals with Mn2+ Ions over a Broad Nominal Concentration Range

Authors: Nistor, SV; Stefan, M; Nistor, LC; Ghica, D; Vlaicu, ID; Joita, AC

Published: OCT 15 2015, JOURNAL OF PHYSICAL CHEMISTRY C, 119, 23789, DOI: 10.1021/acs.jpcc.5b08113

Although impurity doping of nanocrystals is essential in controlling their physical properties for various applications, the doping mechanism of ultrasmall, colloidal II-VI semiconductor nanocrystals, corresponding to the initial stages of growth, is not yet understood. In this study the concentrations of Mn2+ ions in the core, on the surface, and as an agglomerated separate phase in 2.9 nm cubic ZnS nanocrystals, prepared by a surfactant-assisted liquid liquid synthesis within 20 to 20 000 ppm nominal impurity concentration range, have been determined by quantitative multifrequency electron paramagnetic resonance. The unexpected strong decrease in the core doping efficiency with the nominal concentration increase, in contrast to the small variation of the doping efficiency for the surface-bound Mn2+ ions, and the sizable core doping efficiency observed for 1.8 nm nanocrystals were explained with the extended lattice defect assisted mechanism of incorporation. According to this mechanism, which is not size or shape limited, being active from the initial growth stages, the incorporation of Mn2+ ions takes place at surface sites with high binding energy on dislocation steps formed by the emerging stacking defects. High resolution transmission electron microscopy confirms the presence of such stacking defects in a large proportion of the investigated cubic ZnS nanocrystals, ensuring the operation of the proposed doping mechanism.

1348. NIR to Vis - NIR up - conversion and X-ray excited emission of Er doped high Z BiOCl

Authors: Avram, D; Cojocaru, B; Florea, M; Teodorescu, V; Tiseanu, I; Tiseanu, C

Published: MAY 1 2015, OPTICAL MATERIALS EXPRESS, 5, 962, DOI: 10.1364/OME.5.000951

Herein, we investigate the emission properties of Er - BiOCl in the range of similar to 500 to 1700 nm under down - (488 and 973 nm) and NIR (telecom - wavelength at similar to 1500 nm) up - conversion excitation as well high energy X-ray excitation. The dependencies of red (similar to 670 nm) and NIR (similar to 800 nm) to green emission (similar to 543 nm) ratio with Er concentration, excitation mode and delay after laser pulse as well as the up - conversion excitation spectra and decays are analyzed in terms of competitive ground state absorption/excited state absorption and energy transfer up - conversion mechanisms. The CIE chromaticity diagram show single excitation (similar to 1500 nm), delay induced emission color change from yellowish green (delay of 0.001 ms) to reddish orange (delay of 1 ms). The X-ray induced emission of Er - BiOCl presents an atypical red to green emission ratio that exceeds that measured under optical down - conversion excitation by a factor of 13. The potential of Er - BiOCl for optical/X-ray imaging applications is discussed. (C)2015 Optical Society of America

1349. Consolidation of W-Ta composites: Hot isostatic pressing and spark and pulse plasma sintering

Authors: Dias, M; Guerreiro, F; Correia, JB; Galatanu, A; Rosinski, M; Monge, MA; Munoz, A; Alves, E; Carvalho, PA

Published: OCT 2015, FUSION ENGINEERING AND DESIGN, 98-99, 1955, DOI: 10.1016/j.fusengdes.2015.06.178

Composites consisting of tantalum fiber/powder dispersed in a nanostructured W matrix have been consolidated by spark and pulse plasma sintering as well as by hot isostatic pressing. The microstructural observations revealed that the tungsten-tantalum fiber composites consolidated by hot isostatic pressing and pulse plasma sintering presented a continuous layer of Ta2O5 phase at the W/Ta interfaces, while the samples consolidated by spark plasma sintering evidenced a Ta+Ta2O5 eutectic mixture due to the higher temperature of this consolidation process. Similar results have been obtained for the tungsten-tantalum powder composites. A (W, Ta) solid solution was detected around the prior nanostructured W particles in tungsten-tantalum powder composites consolidated by spark and pulse plasma sintering. Higher densifications were obtained for composites consolidated by hot isostatic pressing and pulse plasma sintering. (C) 2015 Elsevier B.V. All rights reserved.

1350. Photochemical processes developed in composite based on highly separated metallic and semiconducting SWCNTs functionalized with polydiphenylamine

Authors: Baibarac, M; Baltog, I; Smaranda, I; Magrez, A

Published: JAN 2015, CARBON, 81, 438, DOI: 10.1016/j.carbon.2014.09.075

The electrochemical polymerization of diphenylamine (DPA) onto electrodes of Pt coated with highly separated metallic (98%) or semiconducting (99%) single-walled carbon nanotubes (SWCNTs) in the presence of H3PW12O40 was performed by cyclic voltammetry in order to obtain composite materials based on polydiphenylamine (PDPA) doped with heteropolyanions of H3PW12O40 and carbon nanotubes. Our data demonstrate that the photoluminescence quenching effect of the PDPA doped with H3PW12O40 heteropolyanions in the presence of SWCNTs is due to the metallic component. Under UV irradiation of SWCNTs highly separated in metallic and semiconducting tubes functionalized with PDPA doped with heteropolyanions of H3PW12O40 new photochemical reactions are evidenced by photoluminescence studies. These reactions lead to a shortening of the macromolecular chain of PDPA. The photochemical process is more intense in the case semiconducting SWCNTs functionalized with PDPA doped with heteropolyanions in comparison to metallic SWCNTs functionalized with PDPA in doped state, it being a consequence of an additional chemical interaction between the DPA dimer doped with H3PW12O40 heteropolyanions and semiconducting SWCNTs. (C) 2014 Elsevier Ltd. All rights reserved.

1351. Study on structural recovery of graphite irradiated with swift heavy ions at high temperature

Authors: Pellemoine, F; Avilov, M; Bender, M; Ewing, RC; Fernandes, S; Lang, M; Li, WX; Mittig, W; Schein, M; Severin, D; Tomut, M; Trautmann, C; Zhang, FX

Published: DEC 15 2015, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 365, 524, DOI: 10.1016/j.nimb.2015.09.007

Thin graphite foils bombarded with an intense high-energy (8.6 MeV/u) gold beam reaching fluences up to 1 x 10(15) ions/cm(2) lead to swelling and electrical resistivity changes. As shown earlier, these effects are diminished with increasing irradiation temperature. The work reported here extends the investigation of beam induced changes of these samples by structural analysis using synchrotron X-ray diffraction and transmission electron microscope. A nearly complete recovery from swelling at irradiation temperatures above about 1500 degrees C is identified. (C) 2015 Elsevier B.V. All rights reserved.

1352. Field - dipole interactions in L-cysteine-thiolate self assembled at p- and n-GaAs(100) electrodes

Authors: Lazarescu, V; Toader, AM; Enache, M; Preda, L; Anastasescu, M; Dobrescu, G; Negrila, C; Lazarescu, MF

Published: SEP 10 2015, ELECTROCHIMICA ACTA, 176, 124, DOI: 10.1016/j.electacta.2015.06.121

L-cysteine-thiolate monolayers spontaneously self-assembled on p- and n-GaAs(100) electrodes have been investigated by electrochemical impedance spectroscopy in H2SO4 solutions. On p-doped samples a potential-induced reversible proton transfer occurs within the L-cysteine-thiolate layer during both forward and backward potential scans; in contrast, on n-doped samples it is observed only in the reverse scan. The XPS data and the fractal analysis of the AFM images point to the field - dipole interactions operating distinctively in the L-cysteine-thiolate layer formed at p-and n-doped semiconducting substrates as the origin of the observed difference. The interaction of this small but highly polar molecule with the electrostatic field driven by the diffuse distribution of the excess charge in the semiconductor subsurface region both in equilibrium and under polarization conditions turned out to play a key role in determining the optimal orientation of the two polar groups. The latter one seems to be a prerequisite for the potential-induced internal proton transfer. (C) 2015 Elsevier Ltd. All rights reserved.

1353. High-Field Pinning Potential in YBCO Films with Nanoengineered Pinning Centres

Authors: Collazos, JC; Guner, SB; Celik, ME; Oprea, A; Gencer, A; Crisan, A

Published: FEB 2015, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 28, 360, DOI: 10.1007/s10948-014-2671-4

Frequency-dependent AC susceptibility measurements have been used to estimate the critical current densities and pinning potential of two 1.1-mu m-thick YBCO films with nanoengineered pinning centres. The films were grown by pulsed laser deposition using a target with 4 % BaZrO3 nanoinclusions. Data were analysed in the framework of the Anderson-Kim model, collective pinning model, and a model due to Zeldov that implies a logarithmic dependence of pinning potential on the current density. It was found that the latter describes better our experimental data, and that the resulting pinning potential has reasonable high values in high magnetic field up to 9 T, indicating a high current-carrying capability in high magnetic fields.

1354. Fabrication and Raman scattering of a core-shell structure based on Mn doped ZnO and barium titanate

Authors: Sima, M; Baibarac, M; Vasile, E; Sima, M; Mihut, L

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1062, DOI: 10.1016/j.apsusc.2015.07.191

A combination of chemical and thermal annealing techniques was used to prepare an array of ZnO/Zn1-xMNxO/BaTiO3 nanorods. ZnO nanorod arrays were obtained by hydrothermal-electrochemical processes. The precursors for Zn1-xMnxO and BaTiO3, prepared by sol-gel technique were deposited by spin coating on the surface of ZnO nanorods. Each deposition stage was accompanied by thermal treatment stages. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and photoluminescence spectroscopy reveal the presence of a film of Zn1-xMnxO with wurtzite structure on the surface of ZnO nanorods. Transmission electron microscopy images demonstrate that a layer of BaTiO3 is deposited on the surface of each ZnO/Zn1-xMnxO core shell nanorod. BaTiO3 film onto the ZnO/Zn1-xMnxO core shell nanorods is also evidenced in Raman scattering by broadening of the Raman band situated in the spectral range 500-750 cm(-1). (C) 2015 Elsevier B.V. All rights reserved.

1355. Effect of optical coating in the thin-film system of chalcogenide glassy semiconductor-dielectric when recording the holographic optical information

Authors: Chirita, A; Prilepov, V; Popescu, M; Andries, I; Caraman, M; Jidcov, IU

Published: JUL-AUG 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 929, DOI:

In this paper we show that the possibility of obtaining the high values of efficiency of relief-phase holographic gratings formed in the photo-thermoplastic recording process holds not only due to the non-sinusoidal profile form, but also due to the effect of optical coating that appears in the two-layer system of photo-semiconductor deformed thermoplastic. Analyzed are the conditions, under which takes place the antireflection optical coating, reducing unwanted reflections from surfaces and thereby enhancing efficiency. It is shown that by careful choice of the thicknesses and refractive indices of the layers materials the efficiency of holographic gratings can be improved by 2-5 %.

1356. Synthesis, Structural and Electrical Properties of BNT-BTCe@SiO2 Core-Shell Heterostructure

Authors: Cernea, M; Vasile, BS; Ciuchi, IV; Iuga, A; Alexandrescu, E; Pintea, J; Galassi, C

Published: NOV 2015, SCIENCE OF ADVANCED MATERIALS, 7, 2305, DOI: 10.1166/sam.2015.2287

The influence of SiO2 layer in a core-shell BNT-BTCe@SiO2 heterostructure on the electrical properties of the BNT-BTCe core ceramic was investigated. The core-shell composite was prepared by coating BNT-BTCe powder with silica layer by a chemical process. BNT-BTCe grain-core was a solid solution of (Bi0.5Na0.5)TiO3 (BNT) and Ba0.95Ce0.05TiO3 (BTCe) with 92: 8 molar ratio. The thickness of the amorphous silica shell was about 128 nm and the size of the grain core was about 250 nm. The structure, microstructure, dielectric, ferroelectric and piezoelectric properties of BNT-BTCe@SiO2 core-shell powder and sintered ceramic were investigated and compared with those of the BNT-BTCe base material. We found that the values of permittivity (epsilon(r)) and dielectric losses of core-shell ceramic are lower and higher, respectively, than those of BNT-BTCe ceramic indicating that the SiO2 does not improve the dielectric properties of BNT-BTCe ceramic. For the BNT-BTCe@SiO2 composite, the silica layer leads to the increase of diffuseness degree of the phase transition and to a better ferroelectric relaxor. The sintered BNT-BTCe@SiO2 heterostructure shows higher remnant polarization P-r, higher coercive field E-c and higher piezoelectric constants (k(t), d(33), g(33), c(33)(E) and S-11(E)) than BNT-BTCe ceramic. The results of our study suggest that BNT-BTCe@SiO2 core-shell material could be interesting for applications in the ferroelectric and piezoelectric domains.

1357. The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

Authors: Aldica, G; Burdusel, M; Popa, S; Enculescu, M; Pasuk, I; Badica, P

Published: DEC 15 2015, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 519, 189, DOI: 10.1016/j.physc.2015.10.004

Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 degrees C/min were used. Samples have high density, above 95%. The onset critical temperature T-c, is about 38.8 K. There is an optimum heating rate of similar to 100 degrees C/min to maximize the critical current density J(c0), the irreversibility field H-irr, the product (J(c0) x mu H-0(irr)), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries. (C) 2015 Elsevier B.V. All rights reserved.

1358. Hearing shapes of few electrons quantum drums: A configuration-interaction study

Authors: Tolea, F; Tolea, M

Published: FEB 1 2015, PHYSICA B-CONDENSED MATTER, 458, 91, DOI: 10.1016/j.physb.2014.11.013

The - highly remarkable - existence of non-congruent yet vibrationally isospectral shapes has been first proved theoretically and then also tested experimentally - by using electromagnetic waves in cavities, vibrating smectic films or electrons in nanostructures. In this context, we address the question whether isospectrality holds if two or more electrons interact electrostatically, using the accurate configuration-interaction method, in a discrete representation of the Bilby and Hawk shapes. Isospectral pairs offer an unique possibility to test how identical sets of single-particle energies may combine differently in the few-electrons eigenmodes, due to different wave functions spatial distributions. Our results point towards the break down of isospectrality in the presence of interactions. Thus one should be able to "hear" the shapes of few electrons quantum drums. Interestingly however, for the analyzed two and three electrons cases, there exists an interaction strength (which can be tuned by changing the size of the shapes), for which the ground states energies of Bilby and Hawk coincide, but not the excited states as well Wigner localization is studied and shown to occur at about the same size for both Bilby and Hawk shapes. Next, an exercise is proposed to use the two-electrons charge density of the Bilby and Hawk ground states in the phase extraction scheme as proposed by Moon et al. (2008). Results show that out-of-phase regions appear if the linear size of the shapes exceeds the Bohr radius as occupation of higher Slater determinants becomes significant. (C) 2014 Elsevier B.V. All rights reserved.

1359. SYNTHESIS, CHARACTERIZATION AND CYTOTOXICITY EVALUATION ON ZINC DOPED HYDROXYAPATITE IN COLLAGEN MATRIX

Authors: Popa, CL; Bartha, CM; Albu, M; Guegan, R; Motelica-Heino, M; Chifiriuc, MC; Bleotu, C; Badea, ML; Antohe, S

Published: APR-JUN 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 691, DOI:

The goal of this study was to obtain at low temperature a functional nano-composite with characteristics similar to the natural bone by using a cost effective method. The structure and morphology of collagen coated zinc doped hydroxyapatite bio-composites (Zn:HAp-CBc) were examined by X-Ray diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD analysis revealed that the unique hexagonal Ca-10(PO4)(6)(OH)(2) in P-63m space group was observed in the obtained nanocomposites Zn: HAp-CBc. The cytotoxicity of the Zn: HAp-CBc was studied on HeLa cell lines. Cell cycle distribution after treatment was examined by flow cytometry analysis. Our preliminary in vitro studies revealed that the obtained composites based on Zn doped HAp embedded in collagen matrix have excellent biocompatibility and support their further characterization by in vivo approaches and development as a biomaterial used in bone regeneration.

1360. Structural and biological evaluation of lignin addition to simple and silver-doped hydroxyapatite thin films synthesized by matrix-assisted pulsed laser evaporation

Authors: Jankovic, A; Erakovic, S; Ristoscu, C; Mihailescu, N; Duta, L; Visan, A; Stan, GE; Popa, AC; Husanu, MA; Luculescu, CR; Srdic, VV; Janackovic, D; Miskovic-Stankovic, V; Bleotu, C; Chifiriuc, MC; Mihailescu, IN

Published: JAN 2015, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 26, DOI: 10.1007/s10856-014-5333-y

We report on thin film deposition by matrix-assisted pulsed laser evaporation of simple hydroxyapatite (HA) or silver (Ag) doped HA combined with the natural biopolymer organosolv lignin (Lig) (Ag:HA-Lig). Solid cryogenic target of aqueous dispersions of Ag:HA-Lig composite and its counterpart without silver (HA-Lig) were prepared for evaporation using a KrF* excimer laser source. The expulsed material was assembled onto TiO2/Ti substrata or silicon wafers and subjected to physical-chemical investigations. Smooth, uniform films adherent to substratum were observed. The chemical analyses confirmed the presence of the HA components, but also evidenced traces of Ag and Lig. Deposited HA was Ca deficient, which is indicative of a film with increased solubility. Recorded X-ray Diffraction patterns were characteristic for amorphous films. Lig presence in thin films was undoubtedly proved by both X-ray Photoelectron and Fourier Transform Infra-Red Spectroscopy analyses. The microbiological evaluation showed that the newly assembled surfaces exhibited an inhibitory activity both on the initial steps of biofilm forming, and on mature bacterial and fungal biofilm development. The intensity of the antibiofilm activity was positively influenced by the presence of the Lig and/or Ag, in the case of Staphylococcus aureus, Pseudomonas aeruginosa and Candida famata biofilms. The obtained surfaces exhibited a low cytotoxicity toward human mesenchymal stem cells, being therefore promising candidates for fabricating implantable biomaterials with increased biocompatibility and resistance to microbial colonization and further biofilm development.

1361. Effect of counterion on the mesomorphic behavior and optical properties of columnar pyridinium ionic liquid crystals derived from 4-hydroxypyridine

Authors: Pana, A; Badea, FL; Ilis, M; Staicu, T; Micutz, M; Pasuk, I; Circu, V

Published: MAR 5 2015, JOURNAL OF MOLECULAR STRUCTURE, 1083, 251, DOI: 10.1016/j.molstruc.2014.11.059

A series of 3,4,5-tridodecyloxybenzyl pyridinium salts derived from 4-hydroxypyridine has been designed and prepared. The liquid crystalline properties of these compounds were investigated by polarized optical microscopy, differential scanning calorimetry and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis. The N-3,4,5-tridodecyloxybenzyl-4-pyridone intermediate shows a monotropic columnar hexagonal mesophase ranging from 56 degrees C down to room temperature while the corresponding bromide dodecyl O-alkylated pyridinium salt shows one enantiotropic columnar mesophase and one additional monotropic columnar phase at lower temperatures. Replacing bromide ion (Br-) with other counterions (NO3-, BF4- and PF6-) resulted in mesophase suppression. These luminescent pyridinium salts show weak emission in dichloromethane solutions at room temperature and a pronounced red-shifted emission in solid state. Photoluminescent properties of the pyridinium salts do not depend significantly on the nature of counterion employed. (C) 2014 Elsevier B.V. All rights reserved.

1362. Study of formation of LiCoO2 using a modified Pechini aqueous sol-gel process

Authors: Predoana, L; Jitianu, A; Voicescu, M; Apostol, NG; Zaharescu, M

Published: MAY 2015, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 74, 418, DOI: 10.1007/s10971-014-3611-2

In the present study the formation of lithium cobaltite using a modified Pechini aqueous sol-gel process was investigated. The gelling processes in the lithium-cobalt-citric acid system in 1.1:1:1 molar ratio was performed at 80 A degrees C using aqueous solutions of 0.25 mol/dm(3) of Co(NO3)(2)center dot 6H(2)O with Li(NO3)center dot 6H(2)O or Co(CH3COO)(2)center dot 6H(2)O with Li(CH3COO)center dot 2H(2)O, respectively. The study of the mechanism of gelling of transition metal ion Co(II) in aqueous medium in the presence of lithium ions and citric acid as chelating agents was approached using mainly UV-Vis and FTIR spectroscopic methods. The UV-Vis spectroscopy indicated that the Co(II) ions are in a tetragonal distorted geometry characteristic to a D-4h group symmetry in the solutions in the early steps of the gels formation. After gelling at 80 A degrees C it was observed that the symmetry of the Co(II) ions becomes octahedral (O-h). From the FTIR spectra based on the frequency separation between the antisymmetric stretching nu(as)(COO-) and symmetric stretching nu(sym)(COO-) vibrations, it was identified that the carboxylic groups are bond as a bridging ligands. Using X-ray photoelectron spectroscopy it was identified that the cobalt is present in both final gels as Co(II) ions and the citrate ions are covalently bonded to the cobalt ions. The thermogravimetric/differential thermal analysis showed the thermal stability of the studied gels is higher in the low temperature range for the gels prepared using acetates. Based on the thermal analysis the Li-Co-CA gels were calcinated at 700 A degrees C for 6 h and for each gel a monophasic LiCoO2 was obtained.

1363. Preliminary histological studies on the influence of glycerol-iron-oxide nanoparticles

Authors: Popa, CL; Andronescu, E; Turculet, C; Beuran, M; Le Coustomer, P; Badea, ML; Surugiu, A; Prodan, AM

Published: SEP-OCT 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1576, DOI:

This paper reports structural and morphological studies as well as in vivo evaluation of glycerol-iron-oxide nanoparticles (GIO-NPs) in order to investigate their influence on different organic tissues. Transmission electron microscopy (TEM) studies confirm the structure characteristic to iron oxide nanoparticles and their ellipsoidal shape. The histopathological examinations indicated that the studied nanoparticles induce many morphological alterations to the liver, kidneys and spleen tissues 24h, 48h and 72h exposure.

1364. Antimicrobial activity of zinc doped hydroxyapaptite prepared by co-precipitation method

Authors: Popa, CL; Ciobanu, CS; Prodan, AM; Turculet, C; Badea, ML; Predoi, D

Published: OCT 16 2015, TOXICOLOGY LETTERS, 238, S198, DOI: 10.1016/j.toxlet.2015.08.596

1365. Arylation of alkynes over hydrotalcite docked Rh-m-TPPTC complex

Authors: Neatu, F; Ciobanu, M; Stoflea, LE; Frunza, L; Parvulescu, VI; Michelet, V

Published: JUN 1 2015, CATALYSIS TODAY, 247, 162, DOI: 10.1016/j.cattod.2014.07.004

Rh-m-TPPTC complex was successful immobilized onto a hydrotalcite Zn-Al to convert selectively in aqueous media both the symmetric and nonsymmetric alkynes into functionalized alkenes, with boronic acids. The complex preserved its activity after the ionic exchange, leading to excellent results (similar to 87%) for the symmetric alkynes and also for the non-symmetrical alkynes (up to 99%). (C) 2014 Elsevier B.V. All rights reserved.

1366. Analysis of bimodal thermally-induced denaturation of type I collagen extracted from calfskin

Authors: Staicu, T; Circu, V; Ionita, G; Ghica, C; Popa, VT; Micutz, M

Published: 2015, RSC ADVANCES, 5, 38406, DOI: 10.1039/c5ra02708j

The most widely occurring collagen in the extracellular matrix of the mammalian tissues - type I collagen has attracted huge interest from both theoretical and practical points of view. The results presented herein are mainly confined to a study of the thermal stability of type I collagen (CI) extracted from calfskin in acidic solutions (10(-2) M HCl). A two-step process associated with the heat-induced denaturation of CI was revealed by using ultra sensitive differential scanning calorimetry. The minor endothermic transition (peak temperatures of about 30.5-30.8 degrees C) has been assigned to the defibrillation of small supramolecular CI assemblies (occurring in solution) while the major endothermic transition (about 34.8-35.0 degrees C) has been ascribed to denaturation of CI, consisting of a complete unfolding of the native triple-helical conformation of the collagen molecule. The calorimetric data were supported by information obtained from capillary viscometry performed on the same solutions. The native state of CI (molecular integrity and triple-helical conformation) for all the systems studied in this paper was confirmed by transmission electron microscopy, ultraviolet circular dichroism and capillary viscometry. At the same time, based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis and an appropriate image processing of the corresponding electropherogram, a certain degree of intramolecular crosslinking of CI was detected, mainly between alpha 1 and alpha 2 chains of the collagen triple-helix. Such a feature seems to be caused by both the nature of the extraction procedure and the storage conditions.

1367. Microbial colonization of biopolymeric thin films containing natural compounds and antibiotics fabricated by MAPLE

Authors: Cristescu, R; Surdu, AV; Grumezescu, AM; Oprea, AE; Trusca, R; Vasile, O; Dorcioman, G; Visan, A; Socol, G; Mihailescu, IN; Mihaiescu, D; Enculescu, M; Chifiriuc, MC; Boehm, RD; Narayan, RJ; Chrisey, DB

Published: MAY 1 2015, APPLIED SURFACE SCIENCE, 336, 239, DOI: 10.1016/j.apsusc.2014.11.145

Although a great number of antibiotics are currently available, they are often rendered ineffective by the ability of microbial strains to develop genetic resistance and to grow in biofilms. Since many antimicrobial agents poorly penetrate biofilms, biofilm-associated infections often require high concentrations of antimicrobial agents for effective treatment. Among the various strategies that may be used to inhibit microbial biofilms, one strategy that has generated significant interest involves the use of bioactive surfaces that are resistant to microbial colonization. In this respect, we used matrix assisted pulsed laser evaporation (MAPLE) involving a pulsed KrF* excimer laser source (lambda = 248 nm, tau = 25 ns, nu = 10 Hz) to obtain thin composite biopolymeric films containing natural (flavonoid) or synthetic (antibiotic) compounds as bioactive substances. Chemical composition and film structures were investigated by Fourier transform infrared spectroscopy and X-ray diffraction. Films morphology was studied by scanning electron microscopy and transmission electron microscopy. The antimicrobial assay of the microbial biofilms formed on these films was assessed by the viable cell counts method. The flavonoid-containing thin films showed increased resistance to microbial colonization, highlighting their potential to be used for the design of anti-biofilm surfaces. (C) 2014 Elsevier B.V. All rights reserved.

1368. Spectro-microscopic photoemission evidence of charge uncompensated areas in Pb(Zr,Ti)O-3(001) layers

Authors: Popescu, DG; Husanu, MA; Trupina, L; Hrib, L; Pintilie, L; Barinov, A; Lizzit, S; Lacovig, P; Teodorescu, CM

Published: 2015, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 17, 520, DOI: 10.1039/c4cp04546g

Photoelectron spectroscopy studies of (001) oriented PbTi0.8Zr0.2O3 (PZT) single crystal layers with submicron resolution revealed areas with different Pb 5d binding energies, attributed to the different charge and polarization states of the film surface. Two novel effects are evidenced by using intense synchrotron radiation beam experiments: (i) the progressive increase of a low binding energy component for the Pb core levels (evidenced for both 5d and 4f, on two different measurement setups), which can be attributed to a partial decomposition of the PZT film at its surface and promoting the growth of metallic Pb during the photoemission process, with the eventuality of the progressive formation of areas with downwards ferroelectric polarization; (ii) for films annealed in oxygen under clean conditions (in an ultrahigh vacuum installation) a huge shift of the Pb 5d core levels (by 8-9 eV) towards higher binding energies is attributed to the formation of areas with depleted mobile charge carriers, whose surface density is insufficient to screen the depolarization field. This shift is attenuated progressively with time, as the sample is irradiated with high flux soft X-rays. The formation of these areas with strong internal electric field promotes these films as good candidates for photocatalysis and solar cells, since in the operation of these devices the ability to perform charge separation and to avoid electron-hole recombination is crucial.

1369. Optical Properties of Single-Walled Carbon Nanotubes Functionalized with Poly(2,2 '-bithiophene-co-pyrene) Copolymer

Authors: Smaranda, I; Baibarac, M; Ilie, M; Matea, A; Baltog, I; Lefrant, S

Published: 2015, CURRENT ORGANIC CHEMISTRY, 19, 661, DOI: 10.2174/1385272819666150311231454

The photoluminescent (PL) properties of composites based on single-walled carbon nanotubes (SWNTs) and poly(2,2'-bithiophene-co-pyrene) (PBTh-Py), prepared by in situ chemical polymerization of the two monomers in the presence of carbon nanotubes, are reported. We demonstrate that the functionalization of SWNTs with PBTh-Py copolymer is revealed through a gradual quenching process of PL with the increase of SWNT content (semiconducting component) in the composite mass. FTIR spectroscopy indicates the existence of several steric hindrance effects that originate in the covalent functionalization of SWNTs with PBTh-Py copolymer. The film deposition of PBTh-Py copolymer and PBTh-Py/SWNTs composite onto rough Au supports induces changes in the FTIR spectrum, which originate in an adsorption mechanism caused by the preferential orientation of molecules on the metallic support. Surface-enhanced Raman scattering (SERS) spectroscopy reveals the side-wall functionalization of SWNTs with PBTh-Py copolymer by changes in the shapes, peak position and relative intensities of different Raman lines.

1370. Ni-doped (CeO2-delta)-YSZ mesoarchitectured with nanocrystalline framework: the effect of thermal treatment on structure, surface chemistry and catalytic properties in the partial oxidation of methane (CPOM)

Authors: Somacescu, S; Florea, M; Osiceanu, P; Calderon-Moreno, JM; Ghica, C; Serra, JM

Published: NOV 3 2015, JOURNAL OF NANOPARTICLE RESEARCH, 17, DOI: 10.1007/s11051-015-3206-z

Ni-doped (CeO2-delta)-YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been synthesized by an original, facile and cheap approach based on Triton X100 nonionic surfactant as template and water as solvent at a strong basic pH value. Following the hydrothermal treatment under autogenous pressure (similar to 18 bars), Ni, Ce, Y, and Zr were well ordered as MA with nanocrystalline framework, assuring thermal stability. A comprehensive investigation of structure, texture, morphology, and surface chemistry was performed by means of a variety of complementary techniques (X-Ray Diffraction, XRD; Raman Spectroscopy, RS; Brunauer-Emmett-Teller, BET; Temperature-Programmed Reduction, TPR; Transmission Electron Microscopy, TEM and DF-STEM; X-ray Photoelectron Spectroscopy, XPS; Catalytic activity and selectivity). N-2 sorption measurements highlighted that the mesoporous structure is formed at 600 degrees C and remains stable at 800 degrees C. At 900 degrees C, the MA collapses, favoring the formation of macropores. The XRD and Raman Spectroscopy of all samples showed the presence of a pure, single phase with fluorite-type structure. At 900 degrees C, an increased tetragonal distortion of the cubic lattice was observed. The surface chemistry probed by XPS exhibits a mixture of oxidation states (Ce3+ + Ce4+) with high percentage of Ce3+ valence state similar to 35 % and (Ni3+ and Ni2+) oxidation states induced by the thermal treatment. These nanoparticles assembled into MA show high stability and selectivity over time in catalytic partial oxidation of methane (CPOM). These promising performances suggest an interesting prospect for introduction as anode within IT-SOFC assemblies.

1371. Inhibition of troilite (FeS) oxidative dissolution in air-saturated acidic solutions by O-ethyl-S-2-(2-hydroxy-3,5-diiodophenyl)-2-oxoethylxantogenate

Authors: Chirita, P; Constantin, CA; Badica, CE; Duinea, MI; Birsa, LM; Matei, E; Baltog, I

Published: MAY 1 2015, MATERIALS CHEMISTRY AND PHYSICS, 157, 107, DOI: 10.1016/j.matchemphys.2015.03.021

The inhibiting action of O-ethyl-S-2-(2-hydroxy-3,5-diiodophenyl)-2-oxoethylxantogenate (EHDO) on the oxidation of FeS in air-saturated solutions at pH 1.3 and 25 degrees C was studied using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The uninhibited and inhibited surfaces were characterized by scanning electron microscopy, energy dispersive X-ray analysis and Raman spectroscopy. It was found that EHDO acts as an anodic inhibitor. Also, it was found that the corrosion of Fe(0) is slower than the oxidative dissolution of uninhibited FeS but faster than the oxidative dissolution of inhibited FeS. This behavior makes EHDO a potential inhibitor of the corrosion of Fe(0) when covered by FeS. (C) 2015 Elsevier B.V. All rights reserved.

1372. Hydrothermal synthesis of nanostructured hybrids based on iron oxide and branched PEI polymers. Influence of high pressure on structure and morphology

Authors: Popescu, LM; Piticescu, RM; Petriceanu, M; Ottaviani, MF; Cangiotti, M; Vasile, E; Dirtu, MM; Wolff, M; Garcia, Y; Schinteie, G; Kuncser, V

Published: JUL 1 2015, MATERIALS CHEMISTRY AND PHYSICS, 161, 95, DOI: 10.1016/j.matchemphys.2015.05.018

Homogeneous hybrids in which iron oxide nanoparticles are entrapped within polymer structure are of interest for their potential applications in biomedical field, such as diagnostic, therapeutic and theranostic purposes. For this reason, hybrid nanomaterials based on branched polyethyleneimine (PEI) and iron oxide with different ratios were synthesized in a single step by hydrothermal procedure at high pressure and low temperature. Iron oxide is formed in the presence of branched PEI and the interaction between them takes place in the reaction medium. The influence of synthesis parameters on the hybrid formation, as well as chemical and structural properties was studied by means of FTIR, DSC-TG, HRTEM, electron paramagnetic resonance (EPR), magnetic measurements (SQUID) and Fe-57 Mossbauer analyses. It has been shown that synthesis parameters influence thermal stability and morphology of the hybrids. FeO(OH) crystallites of 2-5 nm are formed. Iron oxyhydroxide nanoparticles strongly entrapped in PEI structure are obtained. The low and distributed values of the specific spontaneous magnetisation in samples prepared under the same pressure conditions support the presence of very fine FeO(OH) nanoparticles, which formation and magnetic properties are depending on the mass ratio between iron oxide and PEI. (C) 2015 Elsevier B.V. All rights reserved.

1373. Organic-inorganic solar cell based on ZnO nanorod arrays

Authors: Sima, M; Vasile, E; Sima, M

Published: SEP-OCT 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1313, DOI:

In this study, we communicate an investigation on perovskite solar cell based on ZnO nanorod array and spiro OMeTAD film as electron and hole selective contacts. It was found that large thickness or small electrical conduction of the Li doped spiro OMeTAD layer and recombination processes at the interfaces contributed to the reduced efficiency of the solar cell.

1374. Encapsulation of iron atoms between framgments of graphene planes

Authors: Siklitskaya, AV; Ivanov-Omskii, VI; Chekulaev, MS; Yastrebov, SG; Smith, R; Slav, A; Morosanu, C; Kozyrev, SV

Published: OCT 2015, NANOSYSTEMS-PHYSICS CHEMISTRY MATHEMATICS, 6, DOI: 10.17586/2220-8054-2015-6-5-680-688

In this paper, we apply results of analysis of the Raman spectrum from an amorphous carbon film modified with iron (a - C : Fe) which leads to construction of clusters containing fragments of graphene and a layer of iron atoms. Such clusters may be candidates for the role of microwave radiation absorbers. For the Raman experiments we performed deposition of a thin film of a -C : Fe. Details of the film deposition process, together with the corresponding Raman experiments are presented in this paper. Comparison with a literature model was performed for the intensity ratio of the maxima for specific Raman bands, using the letter D to represent " disorder" and the letter G to represent "graphite". Comparison gives evidence for the existence of nanosize fragments of graphene embedded in an amorphous matrix of the a - C : Fe film. The diameter of the fragments is predicted to attain a value of about 1.2 nm. Moreover, in a comparison with experimental data for defective graphite, the position of the maximum of the D band for a- C : Fe appeared to be red shifted. This could support the proposition that damping of Raman-active oscillations occurs by an electron gas in fragments of graphene after introduction of iron, e. g. after intercalation. On the basis of these estimates, we modeled a symmetrical polycyclic aromatic hydrocarbon having a similar size and converted it into fragment of a graphene plane by removal of hydrogen atoms occupying the edge states. To preserve symmetry, we placed atoms of iron on top of the fragment, situating them exactly above the centers of hexagons at a certain distance and placed another fragment of graphene on the top of the iron atoms, symmetrically. For a distance of 2.52 angstrom between the centers of the hexagon and the iron atom, distortions of carbon-carbon valence bonds and angles were found to be minimal, as shown through optimization of the system's geometry using the Avogadro molecular editor. This result supports an hypothesis of graphene fragments during the growth of an amorphous carbon film modified by simultaneous addition of a dopant metal such as iron. This example may illustrate the stability of a two-dimensional electron gas confined between the fragments.

1375. Electric and pyroelectric properties of AIN thin films deposited by reactive magnetron sputtering on Si substrate

Authors: Stan, GE; Botea, M; Boni, GA; Pintilie, I; Pintilie, L

Published: OCT 30 2015, APPLIED SURFACE SCIENCE, 353, 1202, DOI: 10.1016/j.apsusc.2015.07.059

Electric and pyroelectric properties of AIN layers deposited on Si substrates with different resistivities were investigated. The dielectric constant was found to be around 12, while the conductance determined from dc current measurements was found to be in the 10(-9) to 10(-19) S range. The pyroelectric measurements were performed in voltage mode using two types of IR sources: a laser diode with 800 nm wavelength and a black body at 700 degrees C. A peculiar behavior was observed for the signal recorded when the laser diode was used as IR source. It was found that the Si substrate is introducing a signal component, due to the photogenerated carriers, which is adding to the pyroelectric signal generated by the AIN layer. This component is strongly dependent on the resistivity of the Si substrate. For strongly doped Si (Si++) the signal generated into the substrate represents only 10% of the recorded pyroelectric voltage. For electronic grade Si the signal generated into the substrate is about 100 times larger than the pyroelectric signal generated in the AIN layer. This effect can be used as an optical amplification of the pyroelectric signal. The frequency dependence observed for the pyroelectric signal recorded when the black body is used as IR source is typical for a pyroelectric detector. A value as large as 12.4 degrees C m(-2) K-1 was obtained for the pyroelectric coefficient using for estimation the constant signal at low modulation frequencies of the IR beam. However, the value of the pyroelectric coefficient is strongly affected by the electrical conductance of the AIN layer. As the conductance is frequency dependent it results that the value of the pyroelectric coefficient is frequency dependent, the value from above being valid only for very small frequencies of the temperature variation. It was also found that the electric and pyroelectric properties are dependent on the crystalline quality of the AIN layer. (C) 2015 Elsevier B.V. All rights reserved.

1376. STRAIN DRIVEN CHANGES OF DEFECT PARAMETERS IN HEAVY ION IMPLANTED Si

Authors: Palade, C; Lepadatu, AM; Slav, A; Ciurea, ML; Lazanu, S

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1381, DOI:

We analyse the influence of the strain field on the parameters of trapping centres. The system under study is high resistivity Si implanted with Bi6+ and I6+ ions respectively, of 28 MeV kinetic energy, 3(O) off <100> axis orientation and 5x10(11) ions/cm(2) fluence. The strain field is the consequence of size and mass difference of the irradiation ions in respect to the atoms of the lattice, and the defects are produced during the slowing-down of ions, as a result of the energy transfer from the ion to Si atoms. These results are of interest for the design and manufacturing of microelectronic devices incorporating strain, particularly for quantum computers with qubits based on the interaction of electronic and nuclear spins of group-V donors in Si.

1377. INVESTIGATIONS OF PULSED LASER DEPOSITED TiN THIN FILMS FOR TITANIUM IMPLANTS

Authors: Popescu-Pelin, G; Craciun, D; Socol, G; Cristea, D; Floroian, L; Badea, M; Socol, M; Craciun, V

Published: 2015, ROMANIAN REPORTS IN PHYSICS, 67, 1502, DOI:

TiN thin films were deposited at room temperature on polished Ti samples by PLD. GIXRD investigations showed that films were crystalline, with grain sizes around 25 run. Simulations of XRR curves indicated that the layers were dense and only slightly rougher than Ti substrates. Nanoindentation results showed that TiN films possessed a hardness of 26.8 GPa, much harder than Ti substrate, while scratch and wear tests found that films were adherent and exhibited a low friction coefficient of 0.16. Electrochemical tests performed in SBF indicated that the coated Ti samples exhibited significantly better behavior against corrosion than bare Ti samples.

1378. Effect of rare earth substitution in cobalt ferrite bulk materials

Authors: Bulai, G; Diamandescu, L; Dumitru, I; Gurlui, S; Feder, M; Caltun, OF

Published: SEP 15 2015, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 390, 131, DOI: 10.1016/j.jmmm.2015.04.089

The study was focused on the influence of small amounts of rare earth (RE=La, Ce, Sm, Gd, Dy, Ho, Er, Yb) addition on the microstructure, phase content and magnetic properties of cobalt ferrite bulk materials. The X-Ray diffraction measurements confirmed the formation of the spinel structure but also the presence of secondary phases of RE oxides or orthoferrite in small percentages (up to 3%). Density measurements obtained by Archimedes method revealed a similar to 1 g cm(-3) decrease for the RE doped cobalt ferrite samples compared with stoichiometric one. Both the Mossbauer and Fourier Transform Infrared Spectrocopy analysis results confirmed the formation of the spinet phase. The saturation magnetization and coercive field values of the doped samples obtained by Vibrating Sample Magnetometry were close to those of the pure cobalt ferrite. For magnetostrictive property studies the samples were analyzed using the strain gauge method. Higher maximum magnetostriction coefficients were found for the Ho, Ce, Sm and Yb doped cobalt ferrite bulk materials as related to the stoichiometric CoFe2O4 sample. Moreover, improved strain derivative was observed for these samples but at higher magnetic fields due to the low increase of the coercive field values for doped samples. (C) 2015 Elsevier B.V. All rights reserved.

1379. Structural and optical properties of fluorescent BaFBr-Eu2+@SiO2 core/shell phosphor heterostructure

Authors: Secu, M; Cernea, M; Secu, CE; Vasile, BS

Published: FEB 1 2015, MATERIALS CHEMISTRY AND PHYSICS, 151, 86, DOI: 10.1016/j.matchemphys.2014.11.038

Core-shell composites BaFBr:Eu2+@SiO2 were synthesized starting from BaFBr:Eu2+ nanophosphor powder prepared by precipitation method, followed by a silica gel coating process. Electron microscopy investigations have shown an average BaFBr:Eu2+ grains size of about 30 nm and 11 nm SiO2 shell thickness. The core-shell heterostructure exhibits Eu2+ luminescence at 385 nm that is improved during subsequent calcination at high temperatures up to 700 degrees C; the core-shell morphology (size and thickness) structure is preserved during the calcination. (C) 2014 Elsevier B.V. All rights reserved.

1380. Titanium dioxide layer deposited at low temperature upon polyester fabrics

Authors: Zgura, I; Frunza, S; Frunza, L; Enculescu, M; Florica, C; Ganea, CP; Negrila, CC; Diamandescu, L

Published: JUL-AUG 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1063, DOI:

TiO2 deposition by sputtering or sol-gel techniques was applied onto less thermal stable polyester textiles and onto a related poly(lactic acid) material. The temperature of deposition and of the further treatment was low enough as allowed by the support nature. Structural and spectroscopic characterization of the raw and coated samples has been performed. TiO2 coated particles are amorphous as indicated by X-ray diffraction and scanning electron microscopy. Sputtered layers consist in aggregates randomly distributed on the substrate while the sol gel layers show a uniform coverage of nanoparticles having a mosaic-like structure. The morphology of the sputtered layers depends on the deposition pressure as well. The loading degree estimated on the basis of the thermogravimetric data is rather low (ca. 2%), but the fabric properties are much influenced by the deposition. Photocatalytic activity also present on the coated surfaces was evaluated in the methylene blue degradation. TiO2 layer is quite adherent as checked by an ultra-sonication method.

1381. Anti-Stokes Raman spectroscopy as amethod to identify the metallic and semiconducting configurations of double-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Matea, A; Mihut, L; Lefrant, S

Published: JAN 2015, JOURNAL OF RAMAN SPECTROSCOPY, 46, 38, DOI: 10.1002/jrs.4597

Although Raman spectra reveal, as a signature of double-walled carbon nanotubes (DWCNTs), two radial breathing mode (RBM) lines associated with the inner and outer tubes, the specification of their nature as metallic or semiconducting remains a topic for debate. Investigating the spectral range of the RBM lines, we present a new procedure of the indexing of the semiconducting or metallic nature of the inner and outer shell that forms the DWCNT. The procedure exploits the difference between the intensities of recorded anti-Stokes Raman spectrum and the anti-Stokes spectrum calculated by applying the Boltzmann formulae to the recorded Stokes spectrum. The results indicate that the two spectra do not coincide with what should happen in a normal Raman process, namely, that there are RBM lines of the same intensity in both spectra, as well as RBM lines of higher intensity that are observed in the calculated spectrum. This discrepancy results from the surface-enhanced Raman scattering mechanism that operates differently on metallic or semiconducting nanotubes. In this context, the analysis of the RBM spectrum can reveal pairs of lines associated with the inner/outer shell structure of DWCNT, and when the intensities between the recorded and calculated spectra coincide, the nanotube is metallic; otherwise, the nanotube is semiconducting. Copyright (c) 2014 John Wiley & Sons, Ltd.

1382. Low Power Resistive Oxygen Sensor Based on Sonochemical SrTi0.6Fe0.4O2.8 (STFO40)

Authors: Stratulat, A; Serban, BC; de Luca, A; Avramescu, V; Cobianu, C; Brezeanu, M; Buiu, O; Diamandescu, L; Feder, M; Ali, SZ; Udrea, F

Published: JUL 2015, SENSORS, 15, 17506, DOI: 10.3390/s150717495

The current paper reports on a sonochemical synthesis method for manufacturing nanostructured (typical grain size of 50 nm) SrTi0.6Fe0.4O2.8 (Sono-STFO40) powder. This powder is characterized using X ray-diffraction (XRD), Mossbauer spectroscopy and Scanning Electron Microscopy (SEM), and results are compared with commercially available SrTi0.4Fe0.6O2.8 (STFO60) powder. In order to manufacture resistive oxygen sensors, both Sono-STFO40 and STFO60 are deposited, by dip-pen nanolithography (DPN) method, on an SOI (Silicon-on-Insulator) micro-hotplate, employing a tungsten heater embedded within a dielectric membrane. Oxygen detection tests are performed in both dry (RH = 0%) and humid (RH = 60%) nitrogen atmosphere, varying oxygen concentrations between 1% and 16% (v/v), at a constant heater temperature of 650 degrees C. The oxygen sensor, based on the Sono-STFO40 sensing layer, shows good sensitivity, low power consumption (80 mW), and short response time (25 s). These performance are comparable to those exhibited by state-of-the-art O-2 sensors based on STFO60, thus proving Sono-STFO40 to be a material suitable for oxygen detection in harsh environments.

1383. Chemically assembled light harvesting CuOx-TiO2 p-n heterostructures

Authors: Anastasescu, C; Spataru, N; Culita, D; Atkinson, I; Spataru, T; Bratan, V; Munteanu, C; Anastasescu, M; Negrila, C; Balint, I

Published: DEC 1 2015, CHEMICAL ENGINEERING JOURNAL, 281, 311, DOI: 10.1016/j.cej.2015.06.098

CuOx nanorods grown by calcination on a Cu plate and TiO2 successive layers were assembled by chemical means to obtain a broad band light captor. The synthesis of composite with complex architecture aimed at maximization of light absorption and at improvement of electron-holes separation of via the multiple n-p heterojunctions created at TiO2-CuOx boundaries, formed mostly by filling the pore network composite material with CuOx. Au nanoparticles were embedded into TiO2 matrix to enhance the light harvesting ability in visible domain via surface plasmon resonance (SPR) phenomenon and to help the photo-generated charge separation through the formation of Schottky barriers. Dual p-n semiconducting character of the composite was clearly evidenced by photoelectrochemical measurements. The composite material exhibited photoresponse even at wavelengths higher than 420 nm (in visible domain), both in cathodic and anodic regions. The enhanced light adsorption characteristics, the advancement in synthesis procedure of CuOx-Au_TiO2 composite material provide rationale for further development of novel light captor composites for photoenergy conversion. Other applications such electronics and gas sensors are envisaged. (C) 2015 Elsevier B.V. All rights reserved.

1384. Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

Authors: Ciobanu, CS; Groza, A; Iconaru, SL; Popa, CL; Chapon, P; Chifiriuc, MC; Hristu, R; Stanciu, GA; Negrila, CC; Ghita, RV; Ganciu, M; Predoi, D

Published: 2015, BIOMED RESEARCH INTERNATIONAL, 2015, DOI: 10.1155/2015/926513

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag: HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag: HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells.

1385. Scaling and passively Q-switch operation of a Nd:YAG laser pumped laterally through a YAG prism

Authors: Dascalu, T; Salamu, G; Sandu, O; Dinca, M; Pavel, N

Published: APR 2015, OPTICS AND LASER TECHNOLOGY, 67, 168, DOI: 10.1016/j.optlastec.2014.10.017

We report on scaling of a laser configuration in which a YAG prism is used to couple the pump beam from a fiber-coupled diode laser directly into a Nd:YAG medium. Several resonator geometries have been investigated. In free generation regime laser pulses at 1.06 mu m with energy of 22.1 mJ for the pump energy of 44.6 mJ were obtained from a 10.0 mm long, 1.0-at% Nd:YAG single crystal that had the high-reflectivity mirror coated directly on one of the laser crystal surface. The slope efficiency was 0.51. A similar uncoated Nd:YAG crystal placed in a plane-plane resonator delivered laser pulses with 17.8 mJ energy under the pump with 45.4 mJ energy, at 0.40 slope efficiency. Further, a passively Q-switched Nd:YAG/Cr4+:YAG composite ceramic laser pumped through a YAG prism has been built. Using a Cr4+:YAG saturable absorber of 0.85 initial transmission the device delivered laser pulses with 0.29 mJ energy and 11 ns duration. The output performances are compared to those obtained in a classical end-pumping scheme. (C) 2014 Elsevier Ltd. All rights reserved.

1386. Structural, thermal, Fe-57 and Eu-151 Mossbauer studies of Eu2O3-Fe2O3 ceramic nanostructures

Authors: Sorescu, M; Diamandescu, L; DiGnazio, J; Xu, TH

Published: JAN 2015, CERAMICS INTERNATIONAL, 41, 1588, DOI: 10.1016/j.ceramint.2014.09.094

xEu(2)O(3)-(1-x)alpha-Fe2O3 (x=0.1, 0.3, 0.5, and 0.7) nanoparticle system was successfully synthesized by mechanochemical activation of Eu2O3 and alpha-Fe2O3 mixtures for 0-12 h of ball milling time. The investigations aimed at exploring the formation of magnetic ceramic nanostructures, which are of crucial importance for catalysis and sensing applications. X-ray powder diffraction (XRD),as well as Fe-57 and Eu-151 Mossbauer spectroscopy and thermal analysis by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) was used to study the phase evolution of xEu(2)O(3)-(1-x)alpha-Fe2O3 nanoparticle system under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the particle size as a function of composition and milling times and indicated the formation of the EuFeO3 perovskite for large x values and long milling times. The Fe-57 Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with europium oxide. The Eu-151 Mossbauer investigations showed that the isomer shift decreased with increasing milling time for all molar concentrations employed. These results correlate well with the DSC/TGA analysis, which shows the consumption of hematite and the formation of EuFeO3 in the system under investigation. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1387. High Permittivity (1-x)Ba(Zr0.2Ti0.8)O-3 - x(Ba0.7Ca0.3)TiO3 (x=0.45) Epitaxial Thin Films with Nanoscale Phase Fluctuations

Authors: Scarisoreanu, ND; Craciun, F; Moldovan, A; Ion, V; Birjega, R; Ghica, C; Negrea, RF; Dinescu, M

Published: NOV 4 2015, ACS APPLIED MATERIALS & INTERFACES, 7, 23992, DOI: 10.1021/acsami.5b06745

Epitaxial (1 - x)Ba(Ti0.8Zr0.2)TiO3 - x(Ba0.7Ca0.3)TiO3, x = 0.45 (BCZT 45), thin films have been deposited on (001) SrTiO3 (STO) and (001/100) SrLaAlO4 (SLAO) substrates by pulsed laser deposition. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) confirmed the epitaxial growth of the films. A high structural quality has been evidenced for the BCZT/STO films. Geometric phase analysis (GPA) associated with the HRTEM enabled us to obtain microstrain analysis and the in-plane and out-of-plane lattice parameter variation on different areas. Tetragonality ratio fluctuations at nanoscale level which are relevant for the existence of nanodomains have been evidenced on the BCZT/STO films. The in-plane dielectric constant has been measured on interdigital electrodes deposited by lift-off technique on the top of the films. High values of dielectric permittivity (>3000) combined with low dielectric loss (<0.01) are obtained for BCZT 45 film deposited on STO substrate, showing nearly constant values between 1 kHz and 10 MHz. The high dielectric permittivity of BCZT thin films was attributed to their high structural quality and to the loss of rotation stability of the polarization associated with the presence of nanodomains. This results into a divergence of fluctuations of polarization direction and a peak of dielectric susceptibility. The enhanced switching of such nanodomain configuration was probed by piezoforce microscopy, by writing and reading domains during topography scanning.

1388. Physicochemical Characterization and In Vitro Cytotoxic Effect of 3-Hydroxyflavone in a Silver Nanoparticles Complex

Authors: Voicescu, M; Craciunescu, O; Moldovan, L; Anastasescu, M; Angelescu, DG; Teodorescu, VS

Published: SEP 2015, JOURNAL OF FLUORESCENCE, 25, 1223, DOI: 10.1007/s10895-015-1608-z

The aim of this work was to characterize the physico-chemical properties of 3-hydroxyflavone (3-HF) in a silver nanoparticles complex (SNPs) using UV-vis and Fluorescence spectroscopy, Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) analysis. One also evaluated its effect on the cell viability and morphology of L929 mouse fibroblast cells in vitro. The contribution of the carrier protein, Bovine Serum Albumin (BSA) to 3-HF properties has also been investigated. 3-HF in BSA/SNPs systems presented no cytotoxic effect in L929 mouse fibroblast cells at any of the tested concentrations. The results are discussed with relevance to the oxidative stress process.

1389. Correlation of optical reflectivity with numerical calculations for a two-dimensional photonic crystal designed in Ge

Authors: Husanu, MA; Popescu, DG; Ganea, CP; Anghel, I; Florica, C

Published: DEC 10 2015, EUROPEAN PHYSICAL JOURNAL D, 69, DOI: 10.1140/epjd/e2015-60478-7

A two dimensional photonic crystal (2DPhC) with triangular symmetry is investigated using optical reflectivity measurements and numerical calculations. The system has been obtained by direct laser writing, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer. A lattice of holes with well-defined symmetry has been designed. Analyzing the spectral signature of PBGs recorded experimentaly with finite difference time domain theoretical calculations one was able to prove the relation between the geometric parameters (hole format, lattice constant) of the system and its ability to trap and guide the radiation in specific energy range. It was shown that at low frequency and telecommunication ranges of transvelsal electric modes photonic band gap occur. This structure may have potential aplications in designing photonic devices with applications in energy storage and conversion as potential alternative to Si-based technology.

1390. Up-conversion luminescence of Er3+/Yb3+ co-doped LiYF4 nanocrystals in sol-gel derived oxyfluoride glass-ceramics

Authors: Secu, M; Secu, CE

Published: OCT 15 2015, JOURNAL OF NON-CRYSTALLINE SOLIDS, 426, 82, DOI: 10.1016/j.jnoncrysol.2015.07.010

Up-conversion properties of Yb3+/Er3+ co-doped LiYF4 nanocrystals embedded in a sol-gel derived oxyfluoride glass-ceramic have been studied by comparison to the corresponding polycrystalline sample. Under 980 rim laser light pumping, both Yb3+/Er3+ co-doped LiYF4 samples show green ((H-2(11/2,) S-4(3/2)) I-4(15/2)) and red (F-4(9/2) I-4(15/2)) up-conversion luminescences explained by a two-photon processes. The tendency for the saturation of the red up-conversion luminescence band observed in the glass ceramic was ascribed to a back energy transfer process Er3+-Yb3+ and cross-relaxation processes caused by the high Yb3+ and Er3+ ions Concentrations in the nanocrystals. (C) 2015 Elsevier B.V. All rights reserved.

1391. Mesostructured vanadia-alumina catalysts for the synthesis of vitamin K-3

Authors: Florea, M; Marin, RS; Palasanu, FM; Neatu, F; Parvulescu, VI

Published: OCT 1 2015, , DOI: 10.1016/j.cattod.2014.12.026

1392. Time delay and excitation mode induced tunable red/near-infrared to green emission ratio of Er doped BiOCl

Authors: Avram, D; Florea, M; Tiseanu, I; Tiseanu, C

Published: SEP 9 2015, , DOI: 10.1088/0022-3727/48/35/355501

1393. Deoxygenation of oleic acid: Influence of the synthesis route of Pd/mesoporous carbon nanocatalysts onto their activity and selectivity

Authors: Dragu, A; Kinayyigit, S; Garcia-Suarez, EJ; Florea, M; Stepan, E; Velea, S; Tanase, L; Colliere, V; Philippot, K; Granger, P; Parvulescu, VI

Published: SEP 5 2015, , DOI: 10.1016/j.apcata.2015.01.008

1394. Polarization induced self-doping in epitaxial Pb(Zr0.20Ti0.80)O-3 thin films

Authors: Pintilie, L; Ghica, C; Teodorescu, CM; Pintilie, I; Chirila, C; Pasuk, I; Trupina, L; Hrib, L; Boni, AG; Apostol, NG; Abramiuc, LE; Negrea, R; Stefan, M; Ghica, D

Published: OCT 8 2015, SCIENTIFIC REPORTS, 5, DOI: 10.1038/srep14974

The compensation of the depolarization field in ferroelectric layers requires the presence of a suitable amount of charges able to follow any variation of the ferroelectric polarization. These can be free carriers or charged defects located in the ferroelectric material or free carriers coming from the electrodes. Here we show that a self-doping phenomenon occurs in epitaxial, tetragonal ferroelectric films of Pb(Zr0.2Ti0.8)O-3, consisting in generation of point defects (vacancies) acting as donors/acceptors. These are introducing free carriers that partly compensate the depolarization field occurring in the film. It is found that the concentration of the free carriers introduced by selfdoping increases with decreasing the thickness of the ferroelectric layer, reaching values of the order of 10(26) m(-3) for 10 nm thick films. One the other hand, microscopic investigations show that, for thicknesses higher than 50 nm, the 2O/(Ti+Zr+Pb) atomic ratio increases with the thickness of the layers. These results suggest that the ratio between the oxygen and cation vacancies varies with the thickness of the layer in such a way that the net free carrier density is sufficient to efficiently compensate the depolarization field and to preserve the outward direction of the polarization.

1395. Toward a Unified Description of Luminescence-Local Structure Correlation in Ln Doped CeO2 Nanoparticles: Roles of Ln Ionic Radius, Ln Concentration, and Oxygen Vacancies

Authors: Avram, D; Sanchez-Dominguez, M; Cojocaru, B; Florea, M; Parvulescu, V; Tiseanu, C

Published: JUL 16 2015, , DOI: 10.1021/acs.jpcc.5b02240

1396. Effect of Mn addition on the thermal stability and magnetic properties of rapidly-quenched L1(0) FePt alloys

Authors: Crisan, O; Crisan, AD; Mercioniu, I; Pantelica, D; Pantelica, A; Vaucher, S; Nicula, R; Stir, M; Vasiliu, F

Published: OCT 2015, INTERMETALLICS, 65, 87, DOI: 10.1016/j.intermet.2015.06.008

Nano-composite magnets with L1(0) structure derived from binary FePt alloys and prepared as melt-spun ribbons are of current interest due to their higher operating temperature and the ability to be cast as a two-phase magnet with exchange spring magnetic properties, as both soft and hard magnetic phase may emerge from the same metastable precursor, i.e. the disordered cubic A1 phase. The present paper studies the effect of Mn addition on the thermal stability and phase structure, on the abundance of the hard magnetic phase and relative proportion of the soft ones, on the microstructure of the alloy as a function of temperature and on the overall magnetic properties. The interplay of the various magnetic sublattices in the ordering of the L1(0) phases as a consequence of introducing antiferromagnetically coupled Mn atoms in the alloy composition is discussed and interpreted in terms of microstructural changes induced by this addition as revealed by high resolution transmission electron microscopy and Xray diffraction. The temperature evolution of the phase composition and structural parameters is monitored using synchrotron radiation powder diffraction, while the compositional aspects are investigated using proton-induced X-ray emission and energy dispersive X-ray spectroscopy. Magnetic measurements reveal the magnetic parameters of interest (coercivity, remanence, Curie temperature, saturation magnetization), as well as the exchange-coupled two-phase nature of these magnets and provide information that hints at possible spin reorientation transitions in the Mn-containing planes of the L1(0) superlattice. (C) 2015 Elsevier Ltd. All rights reserved.

1397. Dry reforming of methane on ceria prepared by modified precipitation route

Authors: Rotaru, CG; Postole, G; Florea, M; Matei-Rutkovska, F; Parvulescu, VI; Gelin, P

Published: MAR 25 2015, , DOI: 10.1016/j.apcata.2015.01.024

1398. Pure and almost pure NIR emission of Tm and Tm,Yb-CeO2 under UV, X-ray and NIR up-conversion excitation: key roles of level selective antenna sensitization and charge-compensation

Authors: Avram, D; Cojocaru, B; Urda, A; Tiseanu, I; Florea, M; Tiseanu, C

Published: 2015, , DOI: 10.1039/c5cp03458b

1399. Advanced ceramics in the SnO2-ZnO binary system

Authors: Mihaiu, S; Toader, A; Atkinson, I; Mocioiu, OC; Hornoiu, C; Teodorescu, VS; Zaharescu, M

Published: APR 2015, CERAMICS INTERNATIONAL, 41, 4945, DOI: 10.1016/j.ceramint.2014.12.056

In the present work, we report a systematic study of the phase formation and sintering ability of different oxide compositions in the SnO2-ZnO binary system using solid state reactions. For some selected compositions mechanically activated powders were also investigated. Structural and morphological characterizations of the samples were performed by X-ray diffraction (XRD), FT-IR Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Only the formation of Zn2SnO4 binary compound was revealed in the experimental conditions. Based on the structural results the subsolidus equilibrium phase diagram was established. The sintering ability of the studied samples was also determined, establishing the compositions domains of obtaining dense or porous ceramics. The investigation by impedance spectroscopy in the 300-600 K temperature range shows that all studied samples exhibit n-type semiconductor behavior with low values of the activation energy (0.18-0.34 eV). (C) 2014 Elsevier Ltd and Teclma Group S.r.l. All rights reserved.

1400. OPTICAL AND PHOTOCATALYTIC PROPERTIES OF ELECTROSPUN ZnO FIBERS

Authors: Busuioc, C; Evanghelidis, A; Enculescu, M; Enculescu, I

Published: JUL-SEP 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 965, DOI:

ZnO nanofibers were obtained by electrospinning a solution of zinc acetate dihydrate and polyvinylpyrrolidone in N, N-dimethylformamide, followed by calcination at 500, 650 or 800 degrees C for 1 h. X-ray diffraction, selected area electron diffraction, scanning electron microscopy, transmission electron microscopy, reflectance spectroscopy and photoluminescence spectroscopy were used for the characterization of the resulting fibers. The thermally treated samples exhibit ZnO single phase with polycrystalline hexagonal structure. The morphological investigation revealed an accentuated contraction process during calcination, as well as the increase of the crystallite size and the appearance of a breaking tendency with the calcination temperature enhancement. Both UV and Visible emissions under excitation at 350 nm were showed by the optical studies, which also led to band gap values slightly lower than those reported for similar one-dimensional nanostructures. In order to assess the photocatalytic activity of ZnO fibers, the photodegradation of methylene blue in aqueous medium (10(-3) M) under UV irradiation (368 nm) was analyzed.

1401. Nanostructured Titanium Doped Iron Oxide Photoelectrodes for Water Splitting

Authors: Miclea, C; Amarande, L; Cioangher, MC; Miclea, CT; Mihailescu, M; Radu, C; Ivanov, A

Published: 2015, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 18, 105, DOI:

Water splitting by means of semiconducting photoelectrodes and solar light represents a promising alternative to conventional fossil fuel economy. In this process the photoactive electrode absorb sunlight directly thus initiating the photochemical reaction which create excess electrons in the conduction band of the semiconducting electrode. Titanium doped iron oxide seems to be a promising semiconducting material for photoelectrodes. Consequently, we investigated the effect of Ti doping on the structure, electrical and photoelectrochemical properties alpha-Fe2O3. The Ti doped alpha-Fe2O3 were prepared by a slightly modified mixed oxide route, consisting in a prolonged mixing of the raw materials in a high energy planetary ball mill until the particles decreased to the nanometric sizes. Optimum results were obtained for samples doped with 5 at. % titanium and sintered at 1200 degrees C. Photocurrents as high as 8.4 mA/cm(2), for illumination from a 300 W xenon lamp, were recorded for such samples. It is hoped that such photoelectrodes show promise for water splitting.

1402. Novel nanocornposites based on epoxy resin/epoxy-functionalized polydimethylsiloxane reinforced with POSS

Authors: Florea, NM; Lungu. A; Badica, P; Craciun, L; Enculescu, M; Ghita, DG; Ionescu, C; Zgirian, RG; Iovu, H

Published: JUN 15 2015, COMPOSITES PART B-ENGINEERING, 75, 234, DOI: 10.1016/j.compositesb.2015.01.043

The purpose of the present study is to develop novel nanocomposites based on diglycidylether of bisphenol A (DGEBA) combined with diglycidylether-terminated polydimethylsiloxane (DG-PDMS), reinforced with 10 wt.% (mono-/octa) epoxy POSS nanocages (MEP or OEP-POSS). DG-PDMS and POSS compounds were covalently incorporated into DGEBA resin via copolymerization of epoxy groups. The effect of both DG-PDMS and POSS nanoparticles on the curing reaction, glass transition temperature (T-g), thermal stability, hardness and morphology of DGEBA/DG-PDMS +/- POSS nanocomposites were studied by DSC, FTIR, DMA, TGA, SEM/EDX, AFM and contact angle measurements. SEM/EDX and AFM results prove that OEP-POSS is well dispersed within DGEBA/DG-PDMS polymer matrix, while MEP-POSS forms large POSS aggregates. The thermo-mechanical properties of POSS based nanocomposites are also in good correlation with morphology features. MEP-POSS based nanocomposite with heterogeneous dispersion of FOSS aggregates exhibits lower T-g value and thermal stability in comparison with OEP-POSS nanocomposite which exhibits a nanoscale dispersion of the PUSS cages. The obtained T-g of OEP-POSS based nanocomposite increases with 31 degrees C in comparison with the unreinforced matrix. Moreover, this nanocomposite shows the highest storage modulus (E') and hardness. (C) 2015 Elsevier Ltd. All rights reserved.

1403. SHAPE MEMORY PROPERTIES OF FeNiCoTi RIBBONS EVIDENCED BY MAGNETIC MEASUREMENTS

Authors: Tolea, F; Sofronie, M; Tolea, M; Kuncser, V; Valeanu, M

Published: APR-JUN 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 575, DOI:

The present work addresses the shape memory and (ferro) magnetic properties of Fe52Ni29-xCo15+xTi4 (with x=0, 3 and 6) alloys. The analysed samples were prepared as ribbons by the melt spinning method and subjected to thermal treatments. X-ray diffraction, DSC, thermomagnetic measurements and Mossbauer spectroscopy were used for a complete structural and magnetic characterization. Both the preparation route and the different Co addition induce specific effects which are discussed in detail. The sample with x=0 sustains an irreversible transformation, while a partial reversible transformation and a relatively increased Curie temperature were observed for sample with x=3. However, further increasing the Co content to x= 6 leads to a loss of the martensitic transformation.

1404. Electron Reconfiguration and Enhanced Phonon Activation in the Superconducting State of a FeSe0.3Te0.7 Single Crystal, as Evidenced by Mossbauer Spectroscopy

Authors: Greculeasa, S; Miu, L; Badica, P; Nie, J; Tolea, M; Kuncser, V

Published: JAN 15 2015, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 84, DOI: 10.7566/JPSJ.84.014701

The Mossbauer spectra of a FeSe0.3Te0.7 single crystal grown by the Bridgman method were analysed across the superconducting transition by considering the interplay between the structure and electron configuration of the transition metal. The magnetically determined superconducting critical temperature is T-C similar to 14 K. The Fe-57 Mossbauer spectra collected in the temperature range from 5 to 200K mainly have an asymmetric doublet pattern, which was conveniently fitted by the full Hamiltonian method. No effective magnetic moment ascribed to the superconducting phase was observed down to 5K. The unusual behaviour observed below similar to 17K for the chemical isomer shift and quadrupole splitting may be associated with an electron reconfiguration process intimately related to an unusual lattice distortion accompanying the superconducting transition. The decreasing trend of the total absorption spectral area and second-order Doppler shift during cooling the sample below the critical temperature, point to enhanced phonon activation in the superconducting state.

1405. Optical properties of Mn doped ZnO films and wires synthesized by thermal oxidation of ZnMn alloy

Authors: Sima, M; Mihut, L; Vasile, E; Sima, M; Logofatu, C

Published: SEP 1 2015, THIN SOLID FILMS, 590, 147, DOI: 10.1016/j.tsf.2015.07.072

Mn doped ZnO films and wires, having different manganese concentrations were synthesized by thermal oxidation of the corresponding ZnMn alloy films and wires electrodeposited on a gold substrate. Structural and optical properties were addressed with scanning electron microscopy, X-ray diffraction (XRD), Raman scattering and photoluminescence (PL). To estimate the manganese concentration in Mn doped ZnO films, X-ray photoelectron spectroscopy was used. XRD patterns indicate that the incorporation of Mn2+ ions into the Zn2+ site of ZnO lattice takes place. Quenching of the ZnO PL appears due to Mn2+ ions in the ZnO lattice. Moreover, a significant decrease in the green emission of ZnO is reported in the case of the Mn doped ZnO wire array with a Mn concentration of 1.45%. The wurtzite ZnO has a total of 12 phonon modes, namely, one longitudinal acoustic (LA), two transverse acoustic (TA), three longitudinal optical (LO), and six transverse optical branches. Compared to the undoped ZnO, a gradual up-shift of the Raman lines assigned to the 2LA and A(1) (LO) vibrational modes, from 482 and 567 cm(-1) to 532 and 580 cm(-1), respectively, takes place for the Mn doped ZnO films having a Mn concentration between 2 and 15%. Additionally, in the case of the Mn doped ZnO films with 7 and 15% Mn concentration, Raman spectra show the appearance and increase in the relative intensity of the ZnO Raman line assigned to the TA + LO vibrational mode in the 600-750 cm(-1) spectral range. For the Mn-doped ZnO wires, the presence of the Raman line peaking at 527 cm(-1) confirms the insertion of Mn2+ ions in ZnO lattice. (C) 2015 Elsevier B.V. All rights reserved.

1406. In-situ characterization of the optical and electronic properties in GeTe and GaSb thin films

Authors: Velea, A; Socol, G; Popescu, M; Galca, AC

Published: OCT 7 2015, JOURNAL OF APPLIED PHYSICS, 118, DOI: 10.1063/1.4932666

GeTe and GaSb thin films obtained by pulsed laser deposition were investigated by spectroscopic ellipsometry at controlled temperatures. The GeTe films were fully amorphous, while the GaSb films were partially crystalized in the as-deposited state. The Tauc-Lorentz model was employed to fit the experimental data. From the temperature study of the optical constants, it was observed the crystallization in the 150-160 degrees C range of GeTe amorphous films and between 230 and 240 degrees C of GaSb amorphous phase. A second transition in the resonance energy and the broadening parameter of the Lorentz oscillator was observed due to the crystallization of Sb after 250 degrees C. The temperatures of 85 degrees C and 130 degrees C are noticed as the start of the relaxation of the amorphous GeTe phase and as-deposited GaSb. The peaks of the imaginary part of the dielectric function red shifted after the phase change, while the variation with temperature of the crystalline phase follows the Varshni law. The electron-phonon coupling constants are 2.88 and 1.64 for c-GeTe and c-GaSb, respectively. An optical contrast up to 60% was obtained for GeTe films and a maximum value of 7.5% is revealed in the case GaSb, which is altered by the partial crystallinity of the as-deposited films. (C) 2015 AIP Publishing LLC.

1407. Highly Alloyed Steel Matrix for Tools Fabricated by Powder Metallurgy

Authors: Cojocaru, M; Velcea, F; Badica, P

Published: MAY 2015, SURFACE ENGINEERING AND APPLIED ELECTROCHEMISTRY, 51, DOI: 10.3103/S1068375515030059

Both Spark Plasma Sintering (SPS) and conventional sintering were applied to obtain bulks of ledeburitic highly alloyed steels for tools fabrication. Powder mixtures of the component elements, of com-pounds or of powders obtained through ball milling of the chips resulting from the processing of parts from steels of interest were used. When compared with traditional technologies (casting and plastic deformation), SPS and the use of milled chips resulted in the formation of microstructures with a high degree of distribution homogeneity and dimensional uniformity of the carbides. As is well known, the improvement of these param-eters leads to the maximization of the functional properties of tools.

1408. HETEROSTRUCTURES BASED ON SMALL MOLECULES ORGANIC COMPOUNDS

Authors: Socol, M; Rasoga, O; Breazu, C; Socol, G; Preda, N; Pasuk, I; Visan, D; Stavarache, I; Gherendi, F; Girtan, M; Sidwaba, U

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1392, DOI:

Heterostructures with layers from small molecules organic compounds were deposited on ITO/glass substrate by thermal vacuum evaporation (TVE) technique. Structural, optical and morphological investigations were carried out on the realised layers (zinc phthalocyanine-ZnPc, fullerene-C60 and 1,4,5,8-naphthalene-tetracarboxylic dianhydride-NTCDA). The films are polycrystalline keeping the morphological features characteristic to these materials. The prepared heterostructures reveal a large absorption domain in the visible domain. The current-voltage (I-V) characteristics of the investigated structures, recorded in dark, present an improvement in the current value (similar to one order of magnitude) for the standard structure (ITO/PEDOT: PSS/ZnPc/C60/NTCDA/Al) with a supplimentary layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). For the inverted structure (Al/NTCDA/C60/ZnPc/ITO) was also noticed an increased curent value in comparasion with that observed for the standard structure.

1409. Ruthenium oxide-hematite magnetic ceramic nanostructures

Authors: Stroh, C; Tolea, F; Valeanu, M; Diamandescu, L; Xu, TH; Sorescu, M

Published: DEC 2015, CERAMICS INTERNATIONAL, 41, 14375, DOI: 10.1016/j.ceramint.2015.07.070

xRuO(2)-(1-x)alpha-Fe2O3 (x=0.1, 0.3,0.5 and 0.7) nanoparticle systems were successfully synthesized by mechanochemical activation of RuO2 and alpha-Fe2O3 mixtures for 0-12 h of ball milling. Mossbauer spectroscopy, X-ray diffraction (XRD), magnetic measurements, simultaneous differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were employed to investigate the phase evolution of xRuO(2)- (1-x)alpha-Fe2O3 nanoparticle systems under the mechanochemical activation process. The Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for alpha-Fe2O3 (hematite) to four sextets and a doublet upon duration of the milling process with ruthenium oxide. Rietveld refinement of the XRD patterns yielded the values of lattice parameters as function of composition and milling times. The presence of Ru-substituted hematite and Fe-doped ruthenium oxide was evidenced and correlated with differences between ionic radii of Fe3+ and Ru4+. Magnetic measurements recorded at 5 and 300 K in applied magnetic fields of 50,000 and 100,000 Oe showed that the estimated saturation magnetization of the milled samples increased with ball milling time while preserving a multidomain magnetic structure. The Morin transformation was evidenced by zero-field cooling-field cooling (ZFC-FC) measurements in 200 Oe and 1 T, for samples milled for 0 and 8 h of mechanochemical activation. These results correlate well with the DSC-TGA measurements, which support the formation of mixedoxide solid solutions in the system under investigation. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1410. Thermoelectric doping effect in Ca3Co4-xNixO9 ceramics

Authors: Constantinescu, G; Rasekh, S; Torres, MA; Bosque, P; Madre, MA; Sotelo, A; Diez, JC

Published: JAN-FEB 2015, BOLETIN DE LA SOCIEDAD ESPANOLA DE CERAMICA Y VIDRIO, 54, 27, DOI: 10.1016/j.bsecv.2015.02.004

Ca3Co4-xNixO9 (x=0.01, 0.03, and 0.05) polycrystalline thermoelectric ceramics have been prepared by the classical solid state method. As a result of the Ni addition an increase in porosity has been detected. Moreover, the presence of Ni has been related with the increase of Ca2Co3O6 secondary phase and the appearance of a new NiO-CoO solid solution. However, for the 0.01-Ni doped samples an improvement in the thermoelectric performances has been measured. This effect has been related with a decrease in the resistivity values and an increase in the Seebeck coefficient. The raise in the power factor for the 0.01-Ni doped samples, compared with the undoped ones, is between 10 and 25% at 50 and 800 degrees C respectively. Moreover, the maximum power at 800 degrees C, around 0.25 mW/K-2.m, is significantly higher than the best results obtained in Ni doped samples reported previously in the literature. (C) 2015 Sociedad Espanola de Ceramica y Vidrio. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license

1411. MAPLE prepared heterostructures with arylene based polymer active layer for photovoltaic applications

Authors: Stanculescu, F; Rasoga, O; Catargiu, AM; Vacareanu, L; Socol, M; Breazu, C; Preda, N; Socol, G; Stanculescu, A

Published: MAY 1 2015, APPLIED SURFACE SCIENCE, 336, 248, DOI: 10.1016/j.apsusc.2014.11.146

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of heterostructures with single layer of arylene based polymer, poly[N-(2-ethylhexy1)2.7-carbazoly1 vinylene]/AMC16 and poly[N-(2-ethylhexy1)2.7-carbazolyl 1.4-phenylene ethynylene]/AMC22, and with layers of these polymers mixed with Buckminsterfullerene/C-60 in the weight ratio of 1:2 (AMC16: C60) and 1:3 (AMC22: C60). The deposited layers have been characterized by spectroscopic (UV-Vis-NIR, PL, FTIR) and microscopic (SEM, AFM) methods. The effect of the polymer particularities on the optical and electrical properties of the structures based on polymer and polymer: C-60 mixed layer has been analyzed. The study of the electrical properties has revealed typical solar cell behavior for the heterostructure prepared by MAPLE on glass/ITO/PEDOT-PSS with AMC16, AMC22 and AMC22: C-60 layer, confirming that this method is adequate for the preparation of polymeric and mixed active layers for solar cells applications. The highest photovoltaic effect was shown by the solar cell structure realized with single layer of AMC16 polymer: g1a55/ITO/PEDOT-PSSIA1VIC16/A1. (C) 2014 Elsevier B.V. All rights reserved.

1412. Impact of particle size and metal-support interaction on denitration behavior of well-defined Pt-Cu nanoparticles

Authors: Miyazaki, A; Matsuda, K; Papa, F; Scurtu, M; Negrila, C; Dobrescu, G; Balint, I

Published: 2015, CATALYSIS SCIENCE & TECHNOLOGY, 5, 503, DOI: 10.1039/c4cy00929k

Well-dispersed Pt-Cu nanoparticles with two average sizes were synthesized: small (approximate to 1.6 nm) and large (approximate to 4.8 nm), respectively. The effects of size and support on the catalytic behavior of the nanoparticles for denitration reaction were analyzed. Both the unsupported and alumina-supported nanoparticles of smaller average size (1.6 nm) were very active, completely converting NO3- and NO2- (an intermediate reaction product) to N-2 and NH4+. They were also more selective of N-2 compared to the larger particles. The effects of particle size and alumina support on the denitration rate constants were analyzed in detail. The kinetic investigation indicates that the catalytic behavior is strongly related to the size of Pt-Cu nanoparticles as well as to the metal-support interaction. Generally, the larger nanoparticles proved to be less active, but on the other hand, they are less influenced by the support than the smaller ones. The metal-support interaction for bimetallic nanoparticles with smaller average size proved to be a key factor both for nitrate and nitrite reduction. Consideration of the reaction mechanism is made in light of the experimental results.

1413. Intense heavy ion beam-induced temperature effects in carbon-based stripper foils

Authors: Kupka, K; Tomut, M; Simon, P; Hubert, C; Romanenko, A; Lommel, B; Trautmann, C

Published: SEP 2015, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY, 305, 882, DOI: 10.1007/s10967-015-4057-x

At the future FAIR facility, reliably working solid carbon stripper foils are desired for providing intermediate charge states to SIS18. With the expected high beam intensities, the foils experience enhanced degradation and limited lifetime due to severe radiation damage, stress waves, and thermal effects. This work presents systematic measurements of the temperature of different carbon-based stripper foils (amorphous, diamond-like, and carbon-nanotube based) exposed to 4.8 MeV/u U, Bi, and Au beams of different pulse intensities. Thermal and spectroscopic analyses were performed by means of infrared thermography and Fourier transform infrared spectroscopy. The resulting temperature depends on the foil thickness and strongly increases with increasing pulse intensity and repetition rate.

1414. Biomimetic nanocrystalline apatite coatings synthesized by Matrix Assisted Pulsed Laser Evaporation for medical applications (vol 181, pg 56, 2014)

Authors: Visan, A; Grossin, D; Stefan, N; Duta, L; Miroiu, FM; Stan, GE; Sopronyi, M; Luculescu, C; Freche, M; Marsan, O; Charvillat, C; Ciuca, S; Mihailescu, IN

Published: MAR 2015, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 193, 206, DOI: 10.1016/j.mseb.2014.10.011

1415. Nanostructured iridium oxide-hematite magnetic ceramic semiconductors

Authors: Limongelli, J; Tolea, F; Valeanu, M; Diamandescu, L; Xu, TH; Sorescu, M

Published: JAN 2015, CERAMICS INTERNATIONAL, 41, 343, DOI: 10.1016/j.ceramint.2014.08.076

xIrO(2)-(1-x)alpha-Fe2O3(x=0.1, 0.3 and 0.5) nanoparticle systems were successfully synthesized by mechanochemical activation of IrO2 and alpha-Fe2O3 mixtures for 0-12 h of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale, which is of crucial importance for catalysis, sensing and electrochemical applications. X-ray powder diffraction (XRD), Mossbauer spectroscopy, magnetic measurements and simultaneous differential scanning calorimetry (DSC) and thermal gravirnetric analysis (TGA) were used to study the phase evolution of xIrO(2)-(1-x)alpha-Fe2O3 nanoparticle systems under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the particle size and lattice parameters as function of composition and milling times and indicated the presence of Ir-substituted hematite and Fe-doped iridium oxide for large x values and long milling times. The Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with iridium oxide. Magnetic measurements recorded at 5 K in an applied magnetic field of 40,000 Oe showed that the saturation magnetization of the milled samples increased with ball milling time while preserving a multidomain magnetic structure. The unmilled sample at 5 K showed a spinflop type metarnagnetic transition around 30,000 Oe. The Morin transformation was evidenced by zero-field cooling field cooling (ZFC-FC) measurements in 200 Oe and 1 T and the transformation characteristic temperatures were shifted to lower values. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1416. Ge-Added MgB2 Superconductor Obtained by Ex Situ Spark Plasma Sintering

Authors: Batalu, D; Aldica, G; Burdusel, M; Popa, S; Enculescu, M; Pasuk, I; Miu, D; Badica, P

Published: FEB 2015, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 28, 534, DOI: 10.1007/s10948-014-2705-y

Spark plasma sintering (SPS) was applied for fabrication of dense (relative density > 97 %) bulk MgB2 samples added with Ge. Mixtures of MgB2 and Ge powders with starting compositions (MgB2) Ge (x) , x=0.005, 0.01, and 0.03 were used. Added samples show enhancement of the critical current density at high magnetic fields when compared to a pristine reference sample. The optimum composition is for x=0.005 and for this sample J (c)(20 K) =10(2)A/cm (2) is obtained at 5 T, while for the reference sample is obtained at 3.9 T. Ge does not substitute in the crystal lattice of MgB2 and T (c,onset) or T (c,midpoint) from magnetization measurements scatter within 0.15 or 0.3 K, respectively.

1417. Qualitative comparative analysis of MgB2 powder-in-tube wires: superconductivity and X-ray cone-bean microtomography

Authors: Badica, P; Tiseanu, I; Aldica, G; Craciunescu, T; Sandu, V; Jakob, G; Rindfleisch, M

Published: NOV-DEC 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 1649, DOI:

Commercial wires of MgB2 with different architectures and two different heat treatments were characterized with respect to their superconducting properties (T-c, J(c), H-irr, pinning force, macro flux jumps behaviour) through magnetic measurements and were visualized by 3D x-ray micro-tomography (XRT). For a particular architecture, heat treatment conditions of 625 degrees C/3 hrs or 700 degrees C/30 min produced relatively small differences, whereas the architecture of the wires showed a strong influence on superconducting characteristics. XRT checks the integrity of the wires easily detecting in a non-invasive way 3D macro defects and shows their hidden extended shape. XRT also allows a comparative geometry analysis between similar elements (e.g. filaments or filaments-matrix interfaces) from a particular wire or from wires with different architectures. Namely, XRT shows that the geometrical perfection (defined as the degree of departure of the geometry from the designed one) of the inner MgB2 filaments from the wires with 18 elements was lower than for the outermost ones from the same wires and was also lower than for the filaments from the wires with 7 elements. It is proposed that these results of geometrical perfection correlate with better overall superconducting quality of the wires with 7 filaments (except for the stronger presence of macro flux jumps in the wires with 7 filaments).

1418. Zinc oxide electroless deposition on electrospun PMMA fiber mats

Authors: Preda, N; Evanghelidis, A; Enculescu, M; Florica, C; Enculescu, I

Published: JAN 1 2015, MATERIALS LETTERS, 138, 242, DOI: 10.1016/j.matlet.2014.10.021

ZnO crystallites were grown by electroless deposition on poly(methyl methacrylate) (PMMA) fiber mats prepared by an electrospinning technique. The electroless deposition involves three steps: sensitization, activation and deposition, which were performed by subsequently dipping the PMMA fiber mats in the appropriate solutions. After the deposition the PMMA fibers are uniformly coated with ZnO prisms which show hexagonal wurtzite structure and optical signatures (band-gap value and emission bands) typical for this semiconductor. By combining electroless deposition and electrospinning, different semiconductor coated polymer fibers can be obtained for a wide range of applications. Both methods are appropriate for large scale production, being scalable, cheap, efficient and suitable for large-area covering techniques. (C) 2014 Elsevier B.V. All rights reserved.

1419. Ceramics and amorphous thin films based on gallium sulphide doped by rare-earth sulphides

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Badica, P; Burdusel, M; Galca, AC; Matei, E; Preda, N; Secu, M; Socol, G; Jipa, F; Zamfirescu, M; Balan, A

Published: APR 2015, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 30, DOI: 10.1088/0268-1242/30/4/044001

Bulk ceramics of Ga2S3 and rare-earth sulfides (EuS, Gd2S3, Er2S3) as well as combinations thereof have been prepared by spark plasma sintering (SPS). The disk-shaped ceramics were used as targets for pulsed laser deposition (PLD) experiments to obtain amorphous thin films. The properties of these new bulks and amorphous thin films have been investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), optical transmission spectroscopy, and atomic force microscopy (AFM). In order to test the photoexpansion effect in Gd2S3 and the possibility to create planar arrays of microlenses, the film was irradiated with femtosecond laser pulses at different powers. For low laser power pulses (up to 100mW power per pulse) a photoexpansion effect was observed, which leads to formation of hillocks with a height of 40-50 nm. EuS doped Gd2S3 thin film shows luminescence properties, which recommend them for optoelectronic applications.

1420. DEPOSITION OF TITANIUM DIOXIDE LAYERS UPON POLYESTER TEXTILE MATERIALS: CHECKING THE ADHERENCE BY ULTRA-SONICATION

Authors: Zgura, I; Frunza, S; Enculescu, M; Florica, C; Cotorobai, F

Published: 2015, ROMANIAN JOURNAL OF PHYSICS, 60, 494, DOI:

An important parameter of deposited thin films is their adhesion to the substrate materials, we focused on the adhesion of TiO2 layer by sol-gel or sputtering onto textile substrate as checked by an ultra-sonication method. The characterization-made prior and after the tests have shown a good adherence of the nanoparticles, despite the low deposition temperature.

1421. Additive-free 1,4-butanediol mediated synthesis: a suitable route to obtain nanostructured, mesoporous spherical zinc oxide materials with multifunctional properties

Authors: Visinescu, D; Scurtu, M; Negrea, R; Birjega, R; Culita, DC; Chifiriuc, MC; Draghici, C; Moreno, JC; Musuc, AM; Balint, I; Carp, O

Published: 2015, RSC ADVANCES, 5, 99989, DOI: 10.1039/c5ra20224h

A family of mesoporous, self-aggregated zinc oxide materials with spherical morphologies of high crystalline quality, is obtained through a facile, additive-free polyol procedure. The forced hydrolysis of zinc acetylacetonate in 1,4-butanediol (BD), in various reaction conditions, affords ZnO materials with versatile morphologies and optical properties. The reaction parameters (temperature, time and zinc source concentration) modulate the ZnO nanocrystallites size (from 8.1 to 13.2 nm), the spheres diameter (ranging from 50 up to 250 nm), the internal structure of the spherical aggregates (hollow or solid) and their specific surface area (from 31 to 92 m(2) g(-1)). Polycrystalline spheres with hollow cores are obtained at the lowest temperature (90 degrees C) and zinc cation concentration (0.1 M), while at higher reaction temperatures (140-180 degrees C), solid spherical aggregates are developed. A reaction mechanism for ZnO formation via zinc layered hydroxide (LDH-Zn) is proposed based on nuclear magnetic resonance (H-1 NMR and C-13 NMR) and powder X-ray diffraction (XRD) studies. The obtained ZnO materials have a functionalized surface, derived from the polyol and act as a nitrogen selective photocatalyst in the reduction reaction of NO3-. The organic residual attached on the ZnO surface plays a crucial role in the denitrification reaction, since the photo-cleaned sample showed negligible photocatalytic activity. The ZnO materials also exhibited microbicidal and anti-biofilm activity against reference and clinical strains, highlighting their potential for the development of novel antimicrobial formulations.

1422. Improvement of thermoelectric properties in Ca3Co4O9 ceramics by Ba doping

Authors: Constantinescu, G; Rasekh, S; Torres, MA; Madre, MA; Sotelo, A; Diez, JC

Published: JUN 2015, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 26, 3473, DOI: 10.1007/s10854-015-2856-z

Ca3-xBaxCo4O9 bulk polycrystalline thermoelectric ceramics with x = 0.00, 0.01, 0.03 and 0.05 have been prepared through a classical solid state method. Microstructural characterizations of sintered samples have shown that Ba has been incorporated into the Ca3Co4O9 and/or Ca3Co2O6 structures and that no Ba-based secondary phases have been produced. The apparent density values increase when the amount of barium is raised with respect to the undoped samples, reaching a maximum value of around 77 % of the Ca3Co4O9 theoretical density, for samples with the highest amount of barium. Electrical resistivity of doped samples decreases in the whole measured temperature range with respect to the undoped ones, while Seebeck coefficient remains practically unchanged. In conclusion, the improvement in resistivity leads to power factor values which are higher than the ones measured in undoped samples, fact which makes this bulk polycrystalline compound a promising candidate for high-temperature power generation applications in oxidative environments.

1423. Photoelectron spectroscopy and spectro-microscopy of Pb(Zr,Ti)O-3 (111) thin layers: Imaging ferroelectric domains with binding energy contrast

Authors: Husanu, MA; Popescu, DG; Tache, CA; Apostol, NG; Barinov, A; Lizzit, S; Lacovig, P; Teodorescu, CM

Published: OCT 15 2015, APPLIED SURFACE SCIENCE, 352, 81, DOI: 10.1016/j.apsusc.2015.01.153

The ability of photoelectron spectro-microscopy with sub-micrometer lateral resolution to identify ferroelectric domains by analysis of surface band bendings is demonstrated on lead zirco-titanate PZT(1 1 1) thin films grown by pulsed laser deposition. Conventional synchrotron radiation X-ray photoelectron spectroscopy allowed one to derive the surface composition of the sample and evidenced shifts toward higher binding energy when the sample is subject to intense soft X-ray beam. A basic model is developed which supposes that photogenerated carriers reduce the depolarization field, yielding a lower torque applied to the ferroelectric polarization. As a consequence, the out-of-plane component of the polarization increases. Domain migration during irradiation with soft X-ray is inferred from the relative amplitude of the components with different binding energy. When the flux density of soft X-ray is on the order of 1011 photons/(s mu m(2)), metal Pb clusters are formed at the surface on areas with the out-of-plane component of the polarization pointing outwards only. (C) 2015 Elsevier B.V. All rights reserved.

1424. Surface topography to reflectivity mapping in two-dimensional photonic crystals designed in germanium

Authors: Husanu, MA; Ganea, CP; Anghel, I; Florica, C; Rasoga, O; Popescu, DG

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1191, DOI: 10.1016/j.apsusc.2015.07.218

Light confinement in a two dimensional photonic crystal (2D PhC) with hexagonal symmetry is studied using infra-red reflectance spectromicroscopy and numerical calculations. The structure has been realized by laser ablation, using a pulsed laser (lambda = 775 nm), perforating an In-doped Ge wafer and creating a lattice of holes with well-defined symmetry. Correlating the spectral signature of the photonic gaps recorded experimentally with the results obtained in the finite difference time domain and finite difference frequency domain calculations, we established the relationship between the geometric parameters of the structure (lattice constants, shape of the hole) and its efficiency in trapping and guiding the radiation in a well-defined frequency range. Besides the gap in the low energy range of transversal electric modes, a second one is identified in the telecommunication range, originating in the localization of the leaky modes within the radiation continuum. The emerging picture is of a device with promising characteristics as an alternative to Si-based technology in photonic device fabrication with special emphasize in energy storage and conversion. (C) 2015 Elsevier B.V. All rights reserved.

1425. Direct low temperature hydrothermal synthesis of YFeO3 microcrystals

Authors: Racu, AV; Ursu, DH; Kuliukova, OV; Logofatu, C; Leca, A; Miclau, M

Published: FEB 1 2015, MATERIALS LETTERS, 140, 110, DOI: 10.1016/j.matlet.2014.10.129

In this work, we present a new, fast and high yield synthesis method for obtaining microcrystalline yttrium orthoferrite YFeO3, based on hydrothermal technique. The advantage of the method consists in the direct crystallization of the material without the necessity of the calcination. The quality of the so-obtained compound is checked by X-ray diffraction and XPS measurements. Unusual behavior of the zero field cooled (ZFC) - field cooled (FC) magnetization curves (ZFC > FC) was also observed in YFeO3 and a possible explanation could be related to the effect of the synthesis methods on the magnetic properties of yttrium orthoferrite. (C) 2014 Elsevier B.V. All rights reserved.

1426. Composite biodegradable biopolymer coatings of silk fibroin - Poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) for biomedical applications

Authors: Miroiu, FM; Stefan, N; Visan, AI; Nita, C; Luculescu, CR; Rasoga, O; Socol, M; Zgura, I; Cristescu, R; Craciun, D; Socol, G

Published: NOV 15 2015, APPLIED SURFACE SCIENCE, 355, 1131, DOI: 10.1016/j.apsusc.2015.07.120

Composite silk fibroin-poly(3-hydroxybutyric-acid-co-3-hydroxyvaleric-acid) (SF-PHBV) biodegradable coatings were grown by Matrix Assisted Pulsed Laser Evaporation on titanium substrates. Their physicochemical properties and particularly the degradation behavior in simulated body fluid at 37 degrees C were studied as first step of applicability in local controlled release for tissue regeneration applications. SF and PHBV, natural biopolymers with excellent biocompatibility, but different biodegradability and tensile strength properties, were combined in a composite to improve their properties as coatings for biomedical uses. FTIR analyses showed the stoichiometric transfer from targets to coatings by the presence in the spectra of the main absorption maxima characteristic of both polymers. XRD investigations confirmed the FTIR results showing differences in crystallization behavior with respect to the SF and PHBV content. Contact angle values obtained through wettability measurements indicated the MAPLE deposited coatings were highly hydrophilic; surfaces turning hydrophobic with the increase of the PHBV component. Degradation assays proved that higher PHBV contents resulted in enhanced resistance and a slower degradation rate of composite coatings in SBF. Distinct drug-release schemes could be obtained by adjusting the SF:PHBV ratio to controllably tuning the coatings degradation rate, from rapid-release formulas, where SF predominates, to prolonged sustained ones, for larger PHBV content. (C) 2015 Elsevier B.V. All rights reserved.

1427. Superior biofunctionality of dental implant fixtures uniformly coated with durable bioglass films by magnetron sputtering

Authors: Popa, AC; Stan, GE; Enculescu, M; Tanase, C; Tulyaganov, DU; Ferreira, JMF

Published: NOV 2015, JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, 51, 327, DOI: 10.1016/j.jmbbm.2015.07.028

Bioactive glasses are currently considered the suitable candidates to stir the quest for a new generation of osseous implants with superior biological/functional performance. In congruence with this vision, this contribution aims to introduce a reliable technological recipe for coating fairly complex 3D-shaped implants (e.g. dental screws) with uniform and mechanical resistant bioactive glass films by the radio-frequency magnetron sputtering method. The mechanical reliability of the bioactive glass films applied to real Ti dental implant fixtures has been evaluated by a procedure comprised of "cold" implantation in pig mandibular bone from a dead animal, followed by immediate tension-free extraction tests. The effects of the complex mechanical strains occurring during implantation were analysed by scanning electron microscopy coupled with electron dispersive spectroscopy. Extensive biocompatibility assays (MTS, immunofluorescence, Western blot) revealed that the bioactive glass films stimulated strong cellular adhesion and proliferation of human dental pulp stem cells, without promoting their differentiation. The ability of the implant coatings to conserve a healthy stem cell pool is promising to further endorse the fabrication of new osseointegration implant designs with extended lifetime. (C) 2015 Elsevier Ltd. All rights reserved.

1428. INDIRECT AMPLIFICATION OF THE PYROELECTRIC SIGNAL IN Pb(Zr,Ti)O-3 THIN FILMS BY THE PHOTO-GENERATION OF CARRIERS IN THE Si SUBSTRATES

Authors: Botea, M; Pintilie, L; Pintilie, I; Stancu, V

Published: APR-JUN 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 347, DOI:

An amplification of near three orders of magnitude was observed in Pb(Zr,Ti)O-3 (PZT) thin films deposited on Pt/Si substrates when the Si substrate is included as an impedance in series with the PZT capacitor. The effect is present only at wavelengths below 1100 nm, where the incident light can be absorbed in the Si substrate with generation of free carriers. These carriers in turns modulate the internal electric field inside the ferroelectric layer leading to a much larger variation of the polarization compared to the one generated only by the temperature variation. This fact leads to a considerable enhancement of the pyroelectric signal. The finding can be useful in designing pyroelectric detectors with enhanced characteristics for visible and near infrared region of the electromagnetic spectrum.

1429. Growth and characterization by STM of BiCo222 crystal objects: whiskers and bows

Authors: Burdusel, M; Miu, L; Zhao, PH; Yan, W; Han, YL; Nie, JC; Badica, P

Published: MAR-APR 2015, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 17, 430, DOI:

Lamellar crystal objects such as straight, curved or kinked whiskers, bows and objects with missing stripes were grown in a static air atmosphere from melt-quenched substrates with starting composition Bi1.5Sr1Ca1Co0.6Oy. The average EDS composition of the objects is Bi2Sr0.75Ca1.8Co1.94Oy and the crystal structure is of the phase usually denoted in the literature as Bi-2(Sr,Ca)(2)Co2Oy (BiCO222). Objects of other phases were not found. Curvature is in the (ab)-plane. By scanning tunneling spectroscopy (STS) a semiconducting energy gap was determined at 2.41 eV.

1430. Studies on Pr3+-Yb3+ codoped ZBLA as rare earth down convertor glasses for solar cells encapsulation

Authors: Merigeon, J; Maalej, O; Boulard, B; Stanculescu, A; Leontie, L; Mardare, D; Girtan, M

Published: OCT 2015, OPTICAL MATERIALS, 48, 246, DOI: 10.1016/j.optmat.2015.08.008

The non-absorption of photons with energies below the bandgap (E-g) and the thermalization of photons with energies higher than E-g are the dominant loss processes of single-junction solar cells. Rare earth doped glasses give the opportunity to convert the incident photons wavelength and hence to increase or decrease their energies. The conversion of photons energies by "up or down conversion" leads to the possibility to increase the efficiencies of all classes of single-junction solar cells. Depending on the nature of doping materials, two low energy photons can be converted into one high-energy photon (up-conversion), or one high energy photon, can be converted into two low energy photons (down-conversion). In this paper, Pr3+-Yb3+ down-conversion co-doped ZBLA glasses were tested as encapsulation materials for silicon solar cells. The J-V characterizations were done under solar simulator irradiation. The influence of Yb3+ concentration on the solar cells performances was investigated, showing that an optimum value between 0.5 and 2 mol% conducts to an increase of the device efficiency comparing to mono-doped ZBLA material. (C) 2015 Elsevier B.V. All rights reserved.

1431. EFFECT OF CHOLESTEROL ON THE DEPOSITION OF BETA-AMYLOID 1-40 AND 1-42 FILMS

Authors: Breazu, C; Stanculescu, A; Socol, M; Rasoga, O

Published: JAN-MAR 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 313, DOI:

We report the pressure vs area isotherms of Langmuir films of pure and doped with cholesterol (Ch) amyloid beta, A beta (1-40) and (1-42) at the air-water interface and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies of A beta (1-40) and (1-42) layers deposited from solution by drop cast and/or dipping and/or Langmuir-Blodgett on substrates of quartz and Si. The particularity of the substrate surface morphology determines the adhesion forces and plays an important role in the formation and stability of the multilayer films which are deposited on these substrates. The effect of cholesterol on the morphology of amyloids films and appearance of fibril structures is also analysed. AFM investigations have revealed the particularities of the aggregation process of the strongly hydrophobic A beta (1-42) on cholesterol films deposited by Langmuir-Blodgett on solid support of quartz and Si.

1432. Physicochemical Analysis of the Polydimethylsiloxane Interlayer Influence on a Hydroxyapatite Doped with Silver Coating

Authors: Popa, CL; Groza, A; Chapon, P; Ciobanu, CS; Ghita, RV; Trusca, R; Ganciu, M; Predoi, D

Published: 2015, JOURNAL OF NANOMATERIALS, 2015, DOI: 10.1155/2015/250617

We investigate by different complementary methods the processes occurring when a polydimethylsiloxane film is used as interlayer for a silver doped hydroxyapatite coating. The X-ray diffraction and Fourier Transform Infrared Spectroscopy measurements show that the hydroxyapatite doped with silver is in a crystalline form and some SiO44- ions formation takes place at the surface and in the bulk of the new hydroxyapatite doped with silver/polydimethylsiloxane composite layer. The possibility of SiO44- ions incorporation in the structure of silver doped hydroxyapatite by the mechanism of SiO44-/PO43- ions substitution is analysed. The new formed silver doped hydroxyapatite/polydimethylsiloxane composite layer is compact, homogeneous, with no cracks as it was shown by Scanning Electron Microscopy and Glow Discharge Optical Emission Spectrometry.

1433. TIME-FREQUENCY DOMAIN RADAR CROSS SECTION EVALUATION OF AN IAR 99 SCALED MODEL AIRCRAFT

Authors: Tusa, L; Nicolaescu, I; Moni, M; Banciu, MG

Published: 2015, PROCEEDINGS OF THE 2015 7TH INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTERS AND ARTIFICIAL INTELLIGENCE (ECAI), DOI:

Radar Cross Section (RCS) is a very important parameter of an aircraft. It is given by the overall signal reflected by the target when it is irradiated by electromagnetic waves in order to be detected and localized. The measurement of RCS for some aircrafts in real scenarios is a very complex and costly process because it needs a certain area for experiments, special equipment and a number of flights. Hence, in most cases the evaluation of RCS is made by measuring a scaled model aircraft in an anechoic chamber. This paper proposes a measurement scenario for IAR 99 and analysis the experimental data. This is the first evaluation of the IAR 99 radar cross section using measurements in time and frequency domain.

1434. A new class of thermotropic lanthanidomesogens: Eu(III) nitrate complexes with mesogenic 4-pyridone ligands

Authors: Pana, A; Chiriac, FL; Secu, M; Pasuk, I; Ferbinteanu, M; Micutz, M; Circu, V

Published: 2015, DALTON TRANSACTIONS, 44, 14199, DOI: 10.1039/c5dt01197c

A new class of thermotropic lanthanidomesogens has been designed and prepared. They are based on 4-pyridone ligands that possess mesogenic cyanobiphenyl groups attached to the 4-pyridone unit via a flexible long alkyl spacer and show a very high thermal stability (decomposition temperatures near 300 degrees C). Depending on the alkyl length spacer, these complexes exhibit a SmA phase with transition temperatures influenced by the number of mesogenic groups employed and the spacer length.

1435. Exciton-phonon interaction in PbI2 revealed by Raman and photoluminescence studies using excitation light overlapping the fundamental absorption edge

Authors: Baibarac, M; Smaranda, I; Scocioreanu, M; Mitran, RA; Enculescu, M; Galatanu, M; Baltog, I

Published: OCT 2015, MATERIALS RESEARCH BULLETIN, 70, 772, DOI: 10.1016/j.materresbull.2015.06.012

Enhancement at low temperatures of the Raman scattering excited by laser light situated near the edge of the fundamental absorption band is often encountered when studying nanoscale structures. Theory devoted to this phenomenon has established that it originates in an exciton-phonon interaction process, known as the Frohlich interaction, Such a phenomenon was observed in PbI2. The experimental data conclude that the enhancement of the Raman emission results from: (i) an optical excitation near edge of fundamental absorption band; (ii) it is conditioned by the existence of excitonic PL; (iii) its occurrence is different over stokes and anti-stokes Raman branches as result of the different overlapping of the Raman spectral range and the excitonic PL band profile; and (iv) it appears more intense in micrometric powders or in bulk crystalline material. These data are interpreted as stimulated Raman effect resulting from the mixing of the pump laser light and the excitonic light. (C) 2015 Elsevier Ltd. All rights reserved.

1436. Raman scattering and photoluminescence studies of ZnO nanowhiskers assembled as flowers in the presence of fullerene

Authors: Baibarac, M; Baltog, I; Matea, A; Lefrant, S

Published: JUN 1 2015, JOURNAL OF CRYSTAL GROWTH, 419, 164, DOI: 10.1016/j.jcrysgro.2015.03.028

In this work, the architecture of ZnO particles was found to be changed from nano-whiskers to flowers via the addition of fullerenes in the reaction mixture consisting of zinc chloride, sodium hydroxide and sodium dodecyl sulfate. The change in the morphological structure of ZnO particles is accompanied by a decrease in the photoluminescence (PL) intensity and the appearance of a new Raman line at 1594 cm(-1) that indicates the formation of the compound ZnC60. The growth of the ZnO flower-like particles occurs simultaneously with an aggregation process of C-60 in highly ordered structures, as evidenced in the Raman spectrum by a line at 2934 cm I. A mechanism for the growth of the ZnO flower-like particles is proposed in this work. (C) 2015 Elsevier B.V. All rights reserved.

1437. Fabrication of magnetite-based core-shell coated nanoparticles with antibacterial properties

Authors: Grumezescu, AM; Cristescu, R; Chifiriuc, MC; Dorcioman, G; Socol, G; Mihailescu, IN; Mihaiescu, DE; Ficai, A; Vasile, OR; Enculescu, M; Chrisey, DB

Published: MAR 2015, BIOFABRICATION, 7, DOI: 10.1088/1758-5090/7/1/015014

We report the fabrication of biofunctionalized magnetite core/sodium lauryl sulfate shell/antibiotic adsorption-shell nanoparticles assembled thin coatings by matrix assisted pulsed laser evaporation for antibacterial drug-targeted delivery. Magnetite nanoparticles have been synthesized and subsequently characterized by transmission electron microscopy and x-ray diffraction. The obtained thin coatings have been investigated by FTIR and scanning electron microscope, and tested by in vitro biological assays, for their influence on in vitro bacterial biofilm development and cytotoxicity on human epidermoid carcinoma (HEp2) cells.

1438. Quasi-static electric field-temperature diagrams in epitaxial relaxor ferroelectric films

Authors: Tyunina, M; Pintilie, I; Levoska, J; Pintilie, L

Published: JAN 2 2015, PHASE TRANSITIONS, 88, 81, DOI: 10.1080/01411594.2014.961151

Quasi-static polarization induced by dc electric field was studied in a broad range of temperatures in epitaxial films of relaxor ferroelectric PbMg1/3Nb2/3O3 and PbSc1/2Nb1/2O3. The electric field was applied and the response was measured along the out-of-plane crystal direction of the epitaxial perovskite-structure (001) oriented films. The films remained in the relaxor state in zero-field cooling. A new polar state can be induced by electric field at a critical temperature below 100 K. The critical field and the induced polarization increased on cooling and reached the bulk-like values at 20 K. The orientational anisotropy of thin-film dipolar systems is discussed as a possible reason for the observed stable relaxor state.

1439. Evaluation of Samarium Doped Hydroxyapatite, Ceramics for Medical Application: Antimicrobial Activity

Authors: Ciobanu, CS; Iconaru, SL; Popa, CL; Motelica-Heino, M; Predoi, D

Published: 2015, JOURNAL OF NANOMATERIALS, 2015, DOI: 10.1155/2015/849216

Samarium doped hydroxyapatite (Sm:HAp), Ca10-xSmx(PO4)(6)(OH)(2) (HAp), bionanoparticles with different x(Sm) have been successfully synthesized by coprecipitation method. Detailed characterization of samarium doped hydroxyapatite nanoparticles (Sm: HAp-NPs) was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). The biocompatibility of samarium doped hydroxyapatite was assessed by cell viability. The antibacterial activity of the Sm: HAp-NPs was tested against Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) andGram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus). A linear increase of antimicrobial activity of P. aeruginosa has been observed when concentrations of Sm: HAp-NPs in the samples with x(Sm) = 0.02 were higher than 0.125 mg/mL. For Sm: HAp-NPs with x(Sm) = 0.05 a significant increase of antibacterial activity on E. coli was observed in the range 0.5-1 mg/mL. For low concentrations of Sm: HAp-NPs (x(Sm) = 0.05) from 0.031 to 0.125 mg/mL a high antibacterial activity on Enterococcus faecalis has been noticed. A growth of the inhibitory effect on S. aureus was observed for all concentrations of Sm: HAp-NPs with x(Sm) = 0.02.

1440. Characteristics of 5 mol% Ce3+-doped barium titanate nanowires prepared by a combined route involving sol-gel chemistry and polycarbonate membrane-templated process

Authors: Vasilescu, CA; Trupina, L; Vasile, BS; Trusca, R; Cernea, M; Ianculescu, AC

Published: NOV 5 2015, JOURNAL OF NANOPARTICLE RESEARCH, 17, DOI: 10.1007/s11051-015-3241-9

Ba0.95Ce0.05Ti0.9875O3 nanowires were fabricated by sol-gel method using as template a polycarbonate membrane with channels of 100 nm diameter. FE-SEM analyses showed that continuous gel wires of length up to 17 mu m and an average diameter of 81 nm, were obtained. After calcination at 700 degrees C for 1 h, these green 1D nanostructures were converted into well-crystallised wires with an average diameter of 59.7 nm, as high-resolution transmission electron microscopy and selected area electron diffraction indicated. The piezoelectric activity of the Ba0.95Ce0.05Ti0.9875O3 nanowires was investigated using piezoresponse force microscopy (PFM) correlated with atomic force microscopy. The results of PFM measurements indicated that the wires exhibit a significant fraction of ferroelectric domains larger than the grains size and a good piezoelectric response.

1441. Influence of hole depletion and depolarizing field on the BaTiO3/La0.6Sr0.4MnO3 interface electronic structure revealed by photoelectron spectroscopy and first-principles calculations

Authors: Popescu, DG; Barrett, N; Chirila, C; Pasuk, I; Husanu, MA

Published: DEC 28 2015, PHYSICAL REVIEW B, 92, DOI: 10.1103/PhysRevB.92.235442

The effects of the bonding mechanism and band alignment in a ferroelectric (FE) BaTiO3/ferromagnetic La0.6Sr0.4MnO3 heterostructure are studied using x-ray photoelectron spectroscopy and first-principles calculations. The band lineup at the interface is determined by a combination of band bending and polarization-induced modification of core-hole screening. A Schottky barrier height for electrons of 1.22 +/- 0.17 eV is obtained in the case of downwards FE polarization of the top layer. The symmetry of the bonding states is emphasized by integrating the local density of states +/- 0.2 eV around the Fermi level, and strong dependence on the FE polarization is found: upwards, polarization stabilizes Ti t(2g) (xy) orbitals, while downwards, polarization favors Ti t(2g) (yz) symmetry. It is predicted that the abrupt (La, Sr)vertical bar TiO2 interface is magnetoelectrically active, leading to a A-type antiferromagnetic coupling of the first TiO2 interface layer with the underlying manganite layer through a superexchange mechanism.

1442. New antennas with dielectric resonators of axial symmetry

Authors: Geambasu, DC; Banciu, MG; Nedelcu, L; Ramer, R

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 142, DOI:

New type of dielectric resonator antennas (DRAs) with axial symmetry are proposed for frequencies around 5.8 GHz. Each element uses a high permittivity cylindrical resonator and a low permittivity resonator of a truncated cone shape. Two types of microstrip-fed DRAs were investigated. By coupling the resonance modes, the first type and the second type DRA exhibit fractional impedance bandwidth of 15.6% and 19.7%, respectively.

1443. Advances in Functionalized Materials Research

Authors: Predoi, D; Motelica-Heino, M; Le Coustumer, P

Published: 2015, JOURNAL OF NANOMATERIALS, 2015, DOI: 10.1155/2015/412690

1444. Optical properties and antimicrobial activity evaluation of europium/silver doped hydroxyapatite nanoparticles

Authors: Ciobanu, CS; Prodan, AM; Turculet, C; Iordache, F; Iconaru, SL; Popa, CL; Badea, ML; Predoi, D

Published: OCT 16 2015, TOXICOLOGY LETTERS, 238, S198, DOI: 10.1016/j.toxlet.2015.08.595

1445. 1D-polyaniline starting from self-assembled systems

Authors: Donescu, D; Ghiurea, M; Spataru, CI; StIng, G; Anghel, D; Baibarac, M; Baltog, I

Published: SEP 2015, COLLOID AND POLYMER SCIENCE, 293, 2524, DOI: 10.1007/s00396-015-3645-1

The radical polymerization of aniline hydrochloride (ANIHCl) in the presence of ammonium persulfate was studied. 1D-Polyaniline (PANI) with fibrillar morphologies was obtained in the presence of anionic surfactants. The changes of the PANI-template structures in aqueous solution were studied using static fluorescence measurements. The dispersed PANI nanoparticles were characterized using dynamic light scattering, scanning electron microscopy (SEM), and Raman and Fourier transform infrared spectroscopies. The thermal analysis and the electrical conductivity of the dried samples were also performed. The fluorescence measurements indicated that nanocrystals of ANIHCl form in water complexes with the anionic surfactants at smaller concentrations than the critical micellar concentration. The same method revealed that other organic complexes with sulfonate groups do not induce an increase of the hydrophobic region due to short hydrocarbon tails. The SEM micrographs and Raman spectra revealed that the PANI nanofibers are compact and different compared to the nanoparticles prepared without surfactants.

1446. Cylindrical Dielectric Resonator Antenna for Wireless Applications

Authors: Moni, MV; Banciu, G; Tuta, L

Published: 2015, 2015 23RD TELECOMMUNICATIONS FORUM TELFOR (TELFOR), 264, DOI:

The paper presents a CDRA (Cylindrical Dielectric Resonator Antenna) designed for wireless military and commercial applications. The antenna has been designed to radiate at 6.7 GHz, with a 160 MHz bandwidth at -10 dB. The antenna is made from a dielectric material with high quality factor. The dielectric resonator is Ba1-xPbxNd2Ti5O14 (BNT) and its relative permittivity has a value of 55.2. The feed technique used is direct coupling to micro strip-line.

1447. Electro-Optic Sampling of Terahertz Pulses Using BaTiO3 in Non-Collinear Cherenkov Phase-Matching Scheme

Authors: Ozawa, S; Hori, T; Azuma, S; Funkner, S; Niehues, G; Yamamoto, K; Furuya, T; Kitahara, H; Banciu, G; Nedelcu, L; Estacio, E; Bakunov, MI; Tani, M

Published: 2015, 2015 40TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ), DOI:

In this paper we report electro-optic (EO) sampling of THz pulses using ferroelectric crystal in the non-collinear Cherenkov phase-matching scheme, where an effective velocity matching is achieved in an EO crystal with a large refractive index in the THz frequency region. We demonstrate efficient THz EO sampling using LiNbO3 and BaTiO3 crystals in the Cherenkov-phase-matching scheme. It is shown that the efficiency of EO sampling with BaTiO3 is smaller than that with LiNbO3, even though the EO coefficient (r(33)) of BaTiO3 is three times higher than that of LiNbO3. The reason of the poor performance of BaTiO3 is attributed to the strong absorption in the THz frequency region.

1448. Hetero-epitaxial growth of TiC films on MgO(001) at 100 degrees C by DC reactive magnetron sputtering

Authors: Braic, M; Zoita, NC; Danila, M; Grigorescu, CEA; Logofatu, C

Published: AUG 31 2015, THIN SOLID FILMS, 589, 596, DOI: 10.1016/j.tsf.2015.06.021

Hetero-epitaxial TiC thin films were deposited at 100 degrees C on MgO(001) by DC reactive magnetron sputtering in a mixture of Ar and CH4. The 62 nm thick films were analyzed for elemental composition and chemical bonding by Auger electron spectroscopy, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. The crystallographic structure investigation by high resolution X-ray diffraction revealed that the films consist of two layers: an interface partially strained epilayer with high crystalline quality, and a relaxed layer, formed by columnar grains, maintaining the epitaxial relationship with the substrate. The films presented smooth surfaces (RMS roughness similar to 0.55 nm), with circular equi-sized grains/crystallites, as observed by atomic force microscopy. The Hall measurements in Van der Pauw geometry revealed relatively high resistivity value similar to 620 mu Omega cm, ascribed to electron scattering on interfaces, on grain boundaries and on different defects/dislocations. (C) 2015 Elsevier B.V. All rights reserved.

1449. New coordination polymers with chromato bridges: (1)(infinity)[Ni(phen)(H2O)(2)(mu-O2CrO2)] and (3)(infinity)[Mn(4,4 '-bipy)(H2O)(mu-O3CrO)]center dot H2O

Authors: Dumbrava, A; Olar, R; Badea, M; Maxim, C; Ghica, D; Andruh, M

Published: FEB 24 2015, INORGANICA CHIMICA ACTA, 426, 54, DOI: 10.1016/j.ica.2014.11.009

Two new coordination polymers have been assembled using the chromato ions as bridging ligands: (1)(infinity)[Ni(phen)(H2O)(2)(mu-O2CrO2)] 1, and (3)(infinity)[Mn(4,4'-bipy)(H2O)(mu-O3CrO)]center dot H2O 2. In crystal 1 the chromate ions act as bridges connecting two nickel ions through two oxygen atoms, resulting in infinite chains. 1,10-Phenanthroline acts as a blocking ligand. In compound 2, each chromato ion is connected to three manganese ions, resulting in layers which are parallel to the ab plane. The layers are constructed from {Mn3Cr3} meshes, each metal atom being shared between three other meshes. The structure is expanded into the third direction by connecting the inorganic layers through 4,4'-bipy spacers. The thermal decomposition of the two compounds has been investigated. (C) 2014 Elsevier B.V. All rights reserved.

1450. Synthesis, characterization and antimicrobial activity of copper(II) complexes with hydrazone derived from 3-hydroxy-5-(hydroxymethyl)-2-methylpyridine-4-carbaldehyde

Authors: Mezey, RS; Mathe, I; Shova, S; Grecu, MN; Rosu, T

Published: DEC 14 2015, POLYHEDRON, 102, 692, DOI: 10.1016/j.poly.2015.10.035

Pyridoxal isonicotinoyl hydrazone (HL) and its copper(II) complexes: [CuLCI(H2O)(2)] (I), [CuL(OAc)](H2O) (2), [CuL(OAcac)] (3), [CuL(NO3)](H2O) (4), [CuL2](H2O) (5) were synthesized and characterized. The ligand has been obtained by condensation of 3-hydroxy-5-(hydroxymethyl)-2-methylpyridine-4-carbaldehyde (pyridoxal) hydrochloride with isonicotinoyl hydrazide. The characterization of the formed compounds was done by H-1 NMR, C-13 NMR, UV-Vis, IR and EPR spectroscopy as well by thermal studies and elemental analysis. The crystal structure of HL has been determined by single crystal X-ray diffraction studies. The microbiological effect of the ligand and all five complexes against both Gram-positive and Gram-negative strains, Staphylococcus aureus ATTC 6538, Bacillus cereus ATCC 14579, Escherichia call W3110 and Pseudomonas aeruginosa ATCC 9027 was tested. (C) 2015 Elsevier Ltd. All rights reserved.

1451. NbF5-AIF(3) Catalysts: Design, Synthesis, and Application in Lactic Acid Synthesis from Cellulose

Authors: Coman, SM; Verziu, M; Tirsoaga, A; Jurca, B; Teodorescu, C; Kuncser, V; Parvulescu, VI; Scholz, G; Kemnitz, E

Published: MAY 2015, ACS CATALYSIS, 5, 3026, DOI: 10.1021/acscatal.5b00282

A series of niobium-modified aluminum hydroxide fluorides (denoted Nb@AIF(3)), prepared via a fluorolytic sol gel synthesis was investigated for the catalytic one-pot conversion of cellulose to lactic acid. The structure of the new acid catalysts is the result of the dispersion of niobium fluoride in an aluminum hydroxide fluoride matrix. The calcination of the catalysts at a relatively low temperature (350 degrees C) stabilized this structure. Catalytic performances in terms of lactic acid yields are directly correlated with the niobium content.

1452. Thermal stability, thermal expansion and grain-growth in exchange-coupled Fe-Pt-Ag-B bulk nanocomposite magnets

Authors: Nicula, R; Crisan, O; Crisan, AD; Mercioniu, I; Stir, M; Vasiliu, F

Published: FEB 15 2015, JOURNAL OF ALLOYS AND COMPOUNDS, 622, 870, DOI: 10.1016/j.jallcom.2014.10.181

Rare-earth free (RE-free) exchange coupling nanocomposite magnets are intensively studied nowadays due to their potential use in applications demanding stable high-temperature operation and corrosion resistance. In this respect, the FePt alloy system is one of the most actively addressed potential permanent magnet solutions. In FePt alloys, promising magnetic features arise from the co-existence of hard magnetic L1(0) FePt and soft magnetic L1(2) Fe3Pt phases emerged from the same metastable precursor. The present work deals with an in-situ temperature-resolved synchrotron radiation study of the thermal stability, thermal expansion and microstructure evolution in exchange-coupled FePtAgB alloys. The as-cast microstructural state as well as the optimized magnetic behavior are given as reference and correlated to the observed microstructural evolution with temperature. The melt-spun Fe48Pt28Ag6B18 alloy ribbons were examined in situ by synchrotron X-ray powder diffraction from ambient temperature up to 600 degrees C. The FePt-Fe3Pt exchange-coupled microstructure achieved by rapid solidification is not significantly altered during the high temperature exposure. The thermal expansion of the FePt L1(0) unit cell has been found to be strongly anisotropic, being essentially an in-plane expansion which may be seen as an anisotropic invar effect. For the FePt L1(0) phase, a significant deviation from linear thermal expansion is observed at the Curie temperature T-C = 477 degrees C. This non-linear behavior above T-C is tentatively linked to a diffusion/segregation mechanism of Ag. The promising hard magnetic properties as well as the direct formation of the L1(0) phase from the as-cast state are directly related to the presence of Ag in the intergranular regions. (C) 2014 Elsevier B.V. All rights reserved.

1453. Rapid determination of Faraday rotation in optical glasses by means of secondary Faraday modulator

Authors: Sofronie, M; Elisa, M; Sava, BA; Boroica, L; Valeanu, M; Kuncser, V

Published: MAY 2015, REVIEW OF SCIENTIFIC INSTRUMENTS, 86, DOI: 10.1063/1.4920920

A rapid high sensitive method for determining the Faraday rotation of optical glasses is proposed. Starting from an experimental setup based on a Faraday rod coupled to a lock-in amplifier in the detection chain, two methodologies were developed for providing reliable results on samples presenting low and large Faraday rotations. The proposed methodologies were critically discussed and compared, via results obtained in transmission geometry, on a new series of aluminophosphate glasses with or without rare-earth doping ions. An example on how the method can be used for a rapid examination of the optical homogeneity of the sample with respect to magneto-optical effects is also provided. (C) 2015 AIP Publishing LLC.

1454. Optical properties of bioactive europium doped hydroxyapatite (HAp:Eu3+)

Authors: Andronescu, E; Iordache, FM; Ciobanu, CS; Badea, ML; Costescu, A; Prodan, AM

Published: SEP-OCT 2015, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 9, 1159, DOI:

The aim of this study was to investigate the influence of Ca10-x Eu-x(PO4)(6)(OH)(2), ( x(Eu)=0; 0.05) before and after immersion in simulated body fluid (SBF) for 72 hours. The samples have been investigated by X-Ray Diffraction, FT-IR Spectroscopy, Raman Spectroscopy and Steady-State Photoluminescence. Moreover, it was studied the antibacterial activity of the powders against Staphylococcus aureus and Escherichia coli bacterial strains. Our studies revealed that after soaking in SBF solution, the average crystallite size of the samples increased. Moreover, it was noticed that the luminescence of the samples is strongly influenced by the immersion in SBF solution.

1455. Electro-optical properties of As-Se-S-dielectric structure for optical information recording in real time

Authors: Chirita, A; Prlepov, V; Popescu, M; Corsac, O; Chetrus, P; Nasedchina, N

Published: JUL-AUG 2015, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 9, 923, DOI:

The results of electro-optical properties studies of chalcogenide glassy semiconductors thin film structures based on Xat.%As2S3:(100-X)at.%As2Se3 system for holographic information recording on to photo-thermoplastic carriers in stationary and pulsed modes.

1456. The Role of Ambient Gas and Pressure on the Structuring of Hard Diamond-Like Carbon Films Synthesized by Pulsed Laser Deposition

Authors: Popescu, AC; Stan, GE; Duta, L; Nita, C; Popescu, C; Surdu, VA; Husanu, MA; Bita, B; Ghisleni, R; Himcinschi, C; Craciun, V

Published: JUN 2015, MATERIALS, 8, 3305, DOI: 10.3390/ma8063284

Hard carbon thin films were synthesized on Si (100) and quartz substrates by the Pulsed Laser Deposition (PLD) technique in vacuum or methane ambient to study their suitability for applications requiring high mechanical resistance. The deposited films' surface morphology was investigated by scanning electron microscopy, crystalline status by X-ray diffraction, packing and density by X-ray reflectivity, chemical bonding by Raman and X-ray photoelectron spectroscopy, adherence by pull-out measurements and mechanical properties by nanoindentation tests. Films synthesized in vacuum were a-C DLC type, while films synthesized in methane were categorized as a-C:H. The majority of PLD films consisted of two layers: one low density layer towards the surface and a higher density layer in contact with the substrate. The deposition gas pressure played a crucial role on films thickness, component layers thickness ratio, structure and mechanical properties. The films were smooth, amorphous and composed of a mixture of sp(3)-sp(2) carbon, with sp(3) content ranging between 50% and 90%. The thickness and density of the two constituent layers of a film directly determined its mechanical properties.

1457. Microstructure and properties of epitaxial Sr2FeMoO6 films containing SrMoO4 precipitates

Authors: Deniz, H; Preziosi, D; Alexe, M; Hesse, D; Eisenschmidt, C; Schmidt, G; Pintilie, L

Published: APR 2015, JOURNAL OF MATERIALS SCIENCE, 50, 3138, DOI: 10.1007/s10853-015-8874-7

Thin films of Sr2FeMoO6 (SFMO) were grown by pulsed laser deposition in non-optimized argon ambient pressures. The films were found to contain a high number of precipitates of foreign phases. The nature and microstructure of these phases were investigated in detail by high-resolution scanning transmission electron microscopy (STEM) and X-ray diffractometry (XRD). We found out that the dominant foreign phase embedded in the SFMO film matrix was SrMoO4 (SMO). Through STEM and XRD analysis, we determined that the SMO phase grows epitaxially with respect to the surrounding SFMO matrix and has a fairly good crystallinity. Although the SFMO films include many foreign precipitates, they still exhibit good conducting properties and moderate magnetization values. Tuning the growth of the SMO phase on top of SFMO films to obtain a natural tunnel barrier might pave the way for future applications of SFMO in spintronic devices.

1458. Synthesis and optical properties of TiO2-based magnetic nanocomposites

Authors: Scarisoreanu, M; Morjan, I; Fleaca, CT; Morjan, IP; Niculescu, AM; Dutu, E; Badoi, A; Birjega, R; Luculescu, C; Vasile, E; Danciu, V; Filoti, G

Published: MAY 1 2015, APPLIED SURFACE SCIENCE, 336, 342, DOI: 10.1016/j.apsusc.2014.12.125

Magnetic titania nanoparticles covered/embedded in SiO2 shell/matrix were simultaneously manufactured by the single-step laser pyrolysis. The present study is a continuation of our previous investigations on the TiO2/Fe and TiO2/HMDSO (hexamethyldisiloxane) derived-systems. The aim of this work is to study the synthesis by IR (Infrared) laser pyrolysis of magnetic TiO2 based nanocomposites which implies many concurrent processes induced in the gas phase by the laser radiation. The dependence between characteristic properties and the synthesis parameters was determined by many analytical and complementary methods: XRD (X-ray diffraction) structural analysis, UV-vis (ultraviolet-visible) and EDAX (energy-dispersive X-ray) spectroscopy, TEM and HRTEM (transmission electron microscopy at low and high resolution) analysis and magnetic measurements. The results of analysis indicate the presence of disordered silica, Fe, alpha-Fe2O3 and mixtures of anatase and rutile phases with mean crystallite dimensions (in the 14-34 nm range) with typical character of diluted magnetic oxide systems and a lower bandgap energy (E-g = 1.85 eV) as compared with TiO2 P25 Degussa sample. (C) 2014 Elsevier B.V. All rights reserved.

1459. Effect of thermal treatments on the structural and magnetic transitions in melt-spun Ni-Fe-Ga-(Co) ribbons

Authors: Tolea, F; Sofronie, M; Crisan, AD; Enculescu, M; Kuncser, V; Valeanu, M

Published: NOV 25 2015, JOURNAL OF ALLOYS AND COMPOUNDS, 650, 670, DOI: 10.1016/j.jallcom.2015.07.296

The effect of thermal treatments on the martensitic transformation in three representative Ni-Fe-Ga alloys with or without Co substitutions has been studied by calorimetry, X-ray diffractometry, scanning electron microscopy and magnetometry. The alloys were prepared as ribbons, by the melt spinning technique. The thermal treatments promote a reduction of the martensitic transformation temperature in all investigated samples, with the most pronounced decrease for the alloys with lower Ga content. Three different mechanisms induced by specific thermal treatments and responsible for the characteristic behaviour of the martensitic transformation, with respect to temperature and heat of transition, were observed and discussed in details. (C) 2015 Elsevier B.V. All rights reserved.

1460. Conformational changes and metastable states induced in proteins by green light

Authors: Comorosan, S; Popescu, I; Polosan, S; Pirvu, C; Ionescu, E; Paslaru, L; Apostol, M

Published: JAN 8 2015, EUROPEAN PHYSICAL JOURNAL B, 88, DOI: 10.1140/epjb/e2014-50717-8

In this paper we report conformational changes recorded on a protein molecule (alpha-amylase) under green light irradiation. In order to explain the experimental results we advanced the hypothesis that green light induces electric dipoles in the protein, which interact with each other, generating conformational modifications toward a more compact design, with different physical properties. The experiments were carried out with un-polarized light (lambda = 520 nm) from a light-emitting-diode (1000 lm, 20 W, 105 mW on the target). In view of the character of our hypothesis, and corroborated with all our experimental results, we suggest that this phenomenon may be more extended and general, specific for a larger class of proteins, occurring on the protein macromolecules under the green light. The effects of a-amylase protein irradiation were revealed by circular dichroism, fluorescence, Raman and FTIR-spectroscopies, zeta potential, cyclic voltammetry, electric impedance spectroscopy and atomic force microscopy. Tentatively, we term the novel conformations as P* (polarized) proteins.

1461. Luminescence properties of Eu3+-doped SiO2-LiYF4 glass-ceramic microrods

Authors: Secu, CE; Secu, M

Published: SEP 2015, OPTICAL MATERIALS, 47, 98, DOI: 10.1016/j.optmat.2015.07.009

Photoluminescence properties of the glass-ceramics microrods containing Eu3+-doped LiYF4 nanocrystals have been studied and characterized. Judd-Ofelt parameters and quantum efficiency has been computed from luminescence spectra and discussed by comparison to the glass ceramic bulk and pellet. The radiative decay rate A(rad) is higher in the glass ceramic rods (221 s(-1)) than in the glass ceramic bulk (130 s(-1)) but the quantum efficiency computed is very low (21%) compared to the glass-ceramic bulk (97%). There are effective non-radiative decay channels that might be related to an influence of the dimensional constraints imposed by the membrane pores during xerogel formation and subsequent glass ceramization. (C) 2015 Elsevier B.V. All rights reserved.

1462. Ignition of an automobile engine by high-peak power Nd:YAG/Cr4+:YAG laser-spark devices

Authors: Pavel, N; Dascalu, T; Salamu, G; Dinca, M; Boicea, N; Birtas, A

Published: DEC 28 2015, OPTICS EXPRESS, 23, 33037, DOI: 10.1364/OE.23.033028

Laser sparks that were built with high-peak power passively Q-switched Nd:YAG/Cr4+:YAG lasers have been used to operate a Renault automobile engine. The design of such a laser spark igniter is discussed. The Nd:YAG/Cr4+:YAG laser delivered pulses with energy of 4 mJ and 0.8-ns duration, corresponding to pulse peak power of 5 MW. The coefficients of variability of maximum pressure (COVPmax) and of indicated mean effective pressure (COVIMEP) and specific emissions like hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx) and carbon dioxide (CO2) were measured at various engine speeds and high loads. Improved engine stability in terms of COVPmax and COVPmax and decreased emissions of CO and HC were obtained for the engine that was run by laser sparks in comparison with classical ignition by electrical spark plugs. (C)2015 Optical Society of America

1463. Electrical manipulation of edge states in graphene and the effect on quantum Hall transport

Authors: Ostahie, B; Nita, M; Aldea, A

Published: APR 9 2015, PHYSICAL REVIEW B, 91, DOI: 10.1103/PhysRevB.91.155409

We investigate the properties of Dirac electrons in a finite graphene sample under a perpendicular magnetic field that emerge when an in-plane electric bias is also applied. The numerical analysis of the Hofstadter spectrum and of the edge-type wave functions evidence the presence of shortcut edge states that appear under the influence of the electric field. The states are characterized by a specific spatial distribution, which follows only partially the perimeter, and exhibit ridges that connect opposite sides of the graphene plaquette. Two kinds of such states have been found in different regions of the spectrum, and their particular spatial localization is shown along with the diamagnetic moments that reveal their chirality. By simulating a four-lead Hall device, we investigate the transport properties and observe unconventional plateaus of the integer quantum Hall effect that are associated with the presence of the shortcut edge states. We show the contributions of the novel states to the conductance matrix that determine the new transport properties. The shortcut edge states resulting from the splitting of the n = 0 Landau level represent a special case, giving rise to nontrivial transverse and longitudinal resistance.

1464. Magneto-Structural Properties and Magnetic Behavior of Fe-Pd Ribbons

Authors: Sofronie, MI; Tolea, F; Kuncser, V; Valeanu, MC; Filoti, G

Published: JAN 2015, IEEE TRANSACTIONS ON MAGNETICS, 51, DOI: 10.1109/TMAG.2014.2359226

Ribbons of Fe-Pd ferromagnetic shape memory alloys were prepared by rapid solidification via the melt-spinning technique. The effect of moderate and high temperature heat treatments on the martensitic transformation and the related changes of the magnetic behavior was analyzed by X-ray diffraction, differential scanning calorimetry and temperature, and field-dependent magnetometry. In addition, information about magnetic easy axis and magnetically field-induced strains (MFIS) were achieved from linear thermal expansion measurements performed under cooling at different applied fields. The observed low values of MFIS in the as-prepared ribbons are due, besides to the small size and random orientation of the grains, to the high atomic disorder inside the crystalline grains. The anisotropy field is enhanced by the reduced atomic disorder, as reflected by the increased MFIS values after thermal treatments.

1465. CHARACTERISATION OF TUNGSTEN NITRIDE LAYERS AND THEIR EROSION UNDER PLASMA EXPOSURE IN NANO-PSI

Authors: Alegre, D; Acsente, T; Martin-Rojo, AB; Oyarzabal, E; Tabares, FL; Dinescu, G; De Temmerman, G; Birjega, R; Logofatu, C; Kovac, J; Mozetic, M

Published: 2015, ROMANIAN REPORTS IN PHYSICS, 67, 546, DOI:

The properties of tungsten nitride thin films deposited by both reactive RF-magnetron sputtering from tungsten targets in Argon/N-2, and RF generated nitrogen ions bombardment of previously sequentially deposited tungsten layers have been investigated. Films exhibited smaller erosion than pure tungsten in Argon plasmas at NANO-PSI expanding thermal plasma device.

1466. Tailoring the electric and magnetic properties of submicron-sized metallic multilayered systems by TVA atomic inter-diffusion engineered processes

Authors: Miculescu, F; Jepu, I; Stan, GE; Miculescu, M; Voicu, SI; Cotrut, C; Pisu, TM; Ciuca, S

Published: DEC 15 2015, APPLIED SURFACE SCIENCE, 358, 626, DOI: 10.1016/j.apsusc.2015.08.247

Thermo-ionic Vacuum Arc evaporation method was selected for the synthesis of Fe/Cu/Ni/Cu multilayer structures on Si (1 0 0) substrates. The aim of the study was the preparation and characterization of structures featuring a giant magnetoresistance effect. This was accomplished by inducing the formation of nanosized ferromagnetic crystallites in multilayer nonmagnetic solutions via atomic inter-diffusion processes by the tuning of deposition parameters. Layer-by-layer and inter-diffused type structures were prepared and comparatively analyzed by scanning electron microscopy, X-ray microanalysis, atomic force microscopy, X-ray diffraction and high-resolution transmission electron microscopy coupled with selected area electron diffraction. We presented the influence of the microstructure on electric and magnetic properties of the submicron-sized multilayers. The dependence of the electric resistance and the magnetoresistance on the composition, structure, morphology and roughness of the layers was established. We obtained an electric resistance value of 1.22 Omega for the layer-by-layer type structure, and 0.46 Omega for the inter-diffusion designed structure. Using the atomic inter-diffusion we succeeded in achieving an improvement of the magnetoresistive effect, from 0.1% to 2.3%. (C) 2015 Elsevier B.V. All rights reserved.

1467. Magnetocaloric effect in Ni-Fe-Ga Heusler alloys with Co and Al substitutions

Authors: Tolea, F; Sofronie, M; Crisan, AD; Tolea, M; Valeanu, M

Published: 2015, ESOMAT 2015 - 10TH EUROPEAN SYMPOSIUM ON MARTENSITIC TRANSFORMATIONS, 33, DOI: 10.1051/matecconf/20153305008

The functionality of the ferromagnetic shape memory alloys is related to the martensitic and magnetic order-disorder transformations, both of which may be tailored by doping with other elements or by suitable thermal treatments, so that alloys with concomitant (or sequential but close) structural and magnetic phase transitions may be obtained. Concerning the magnetocaloric applications, it is assumed that the thin melt-spun ribbons assure a more efficient heat transfer. In the present work we investigate the influence of Co and Al substitutions on magnetocaloric effect characteristics of NiFeGa in bulk and also in ribbons prepared by melt spinning method and subjected to different thermal treatments. X-ray diffraction, differential scanning calorimetry, magnetocaloric and magnetoresistive characterizations have been performed. The results highlight the differences between the bulk and the ribbons (both as prepared and annealed) and the role of substitutions.

1468. Diode-laser pumping into the emitting level for efficient lasing of depressed cladding waveguides realized in Nd:YVO4 by the direct femtosecond-laser writing technique

Authors: Pavel, N; Salamu, G; Jipa, F; Zamfirescu, M

Published: SEP 22 2014, OPTICS EXPRESS, 22, 23065, DOI: 10.1364/OE.22.023057

Depressed cladding waveguides have been realized in Nd:YVO4 employing direct writing technique with a femtosecond-laser beam. It was shown that the output performances of such laser devices are improved by the reduction of the quantum defect between the pump wavelength and the laser wavelength. Thus, under the classical pump at 808 nm (i.e. into the F-4(5/2) level), a 100-mu m diameter circular waveguide inscribed in a 0.7-at.% Nd:YVO4 outputted 1.06-mu m laser pulses with 3.0-mJ energy, at 0.30 optical efficiency and slope efficiency of 0.32. The pump at 880 nm (i.e. directly into the F-4(3/2) emitting level) increased the pulse energy at 3.8 mJ and improved both optical efficiency and slope efficiency at 0.36 and 0.39, respectively. The same waveguide yielded continuous-wave 1.5-W output power at 1.06 mu m under the pump at 880 nm. Laser emission at 1.34 mu m was also improved using the pump into the F-4(3/2) emitting level of Nd:YVO4. (C)2014 Optical Society of America

1469. Compact antenna using ZST low-loss high dielectric constant material

Authors: Geambasu, DC; Leontin, T; Banciu, MG; Nedelcu, L; Nicolaescu, I

Published: 2014, 2014 22ND TELECOMMUNICATIONS FORUM TELFOR (TELFOR), 809, DOI:

Investigations on compact dielectric resonator antennas arc presented. Low-loss, high dielectric constant zirconium tin titanate (ZST) material was prepared by using solid state reaction method. The ZST resonators exhibit 36 dielectric relative permittivity, dielectric loss tangent 5x10(-4) and resonant frequency temperature coefficient between -4 to +4 ppm/degrees C. The developed resonators are very attractive for probe-fed resonator antenna for 2.66 GHz.

1470. OPTICAL CHARACTERISTICS OF SULPHUR-PASSIVATED n-GaAs (100) SURFACE

Authors: Ghita, RV; Grigorescu, CEA; Secu, M; Predoi, D; Frumosu, F; Cotirlan, C; Feraru, ID

Published: OCT-DEC 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 1478, DOI:

A genuine GaAs surface is covered with a relatively thick layer (similar to 10 nm) of native oxide pinning the surface Fermi level within the band gap of semiconductor. The method presented in this work is related to the sulphur passivation by treating n-GaAs(100) and (110) in sulphide solutions (e.g pure ammonium sulphide and sulphur monochloride) that combines both chemical electronic passivation by reducing the surface state density. The effects of passivation were put into evidence by Photoluminescence measurements where it was observed the variation of state density. The presence of sulphur dipoles at surface was presented in a diagram of Second Harmonic Generation analysis and the general aspect of sulphur compound was identified by SEM images. The presence of the covalent bond Ga-S and the variation of surface barrier as well as the effect of crystal orientation were put into evidence by micro-Raman Spectroscopy. At the surface of n-GaAs it is developed an adherent layer of sulphur compound as a resul of chemical interaction of sulphur ions with n-GaAs surface.

1471. EFFECTS OF PROCESS PARAMETERS ON GROWTH OF METAL PARTICLES BY ATMOSPHERIC PRESSURE PLASMA JET

Authors: Lazea-Stoyanova, A; Enculescu, M; Vizireanu, S; Marascu, V; Dinescu, G

Published: JUL-SEP 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 1247, DOI:

In this paper we report a procedure of growing metallic particles at atmospheric pressure by using a radiofrequency plasma jet, operated in inert gaseous atmosphere (argon). Iron metallic particles are manufactured, with sizes in the range of hundreds of nm up to a few microns, having as metal source the electrodes of the plasma jet discharge. The obtained particles are characterized with respect to their shape, size, morphology and size distribution. An emphasis is put on the relationship between the particle size distribution and process parameters, namely the substrate to nozzle distance and applied radiofrequency power.

1472. Studies on thermal, spectral, magnetic and biological properties of new Ni(II), Cu(II) and Zn(II) complexes with a bismacrocyclic ligand bearing an aromatic linker

Authors: Bucur, C; Badea, M; Chifiriuc, MC; Bleotu, C; Iorgulescu, EE; Badea, IA; Grecu, MN; Lazar, V; Patriciu, OI; Marinescu, D; Olar, R

Published: MAR 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 115, 2189, DOI: 10.1007/s10973-013-3460-1

Novel complexes of M2LCl4 center dot nH(2)O type (M:Ni, n = 4; M:Cu, n = 3 and M:Zn, n = 0; L: ligand resulted from 1,4-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde one-pot condensation) were synthesized and characterised by microanalytical, ESI-MS, IR, UV-Vis, H-1 NMR and EPR spectra, magnetic data at room temperature and molar conductivities as well. The electrochemical behaviour of complexes was investigated by cyclic voltammetry. Simultaneous TG/DTA measurements were performed in order to evidence the thermal behaviour of the obtained complexes. Processes such as water elimination, fragmentation and oxidative degradation of the organic ligand as well as chloride elimination occurred during thermal decomposition. The antimicrobial assays demonstrate that the compounds exhibited good antibacterial activity, especially against S. aureus and E. coli strains, the most active being the copper(II) complex, which also exhibited the most prominent anti-biofilm effect, suggesting its potential use for the development of new antimicrobial agents. The biological activity was correlated with log P (ow) values. All complexes disrupt the membrane integrity of HCT 8 tumour cells.

1473. Trapped magnetic field in a (NdFeB)-(MgB2) pair-type bulk magnet

Authors: Aldica, G; Burdusel, M; Badica, P

Published: OCT 15 2014, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 505, 23, DOI: 10.1016/j.physc.2014.07.001

Superconducting bulk discs, S, of 20 mm in diameter and 3.5 or 3.3 mm thickness of MgB2 (pristine or added with cubic BN, respectively) with density above 97% were prepared by Spark Plasma Sintering. Discs were combined in a pair-type sandwich-like arrangement with a permanent NdFeB axially magnetised magnet, PM (similar to 0.5 T). Measurement of the trapped field, B-tr, with temperature, time, and the reduction rate of the applied magnetic field was performed using a Hall sensor positioned at the centre between the superconductor and the permanent magnet. It is shown that the permanent magnet with certain polarity favors higher trapped field of the superconductor owing to suppression of flux jumps specific for high density MgB2 samples. The B-tr of the PM-S pair was 2.45 T (20 K) and 3.3 T (12 K). (C) 2014 Elsevier B.V. All rights reserved.

1474. Metallic Nanowires and Nanotubes Prepared by Template Replication

Authors: Matei, E; Enculescu, M; Preda, N; Florica, C; Costas, A; Busuioc, C; Molares, MET; Kuncser, V; Enculescu, I

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 165, DOI: 10.1007/978-3-662-44479-5_6

Low dimensional nanostructures represent a hot scientific field nowadays due mainly to the tremendous potential for applications. Low dimensions open the possibilities for both ultra-miniaturization and increase in functionality. Numerous procedures were developed for fabricating such nanostructures. Template replication represents a highly effective method in fabricating metallic nanowires and nanotubes. The approach is characterized by the excellent control in obtaining nano objects with the desired shape and dimensions. A large variety of templates are available ranging from viruses and proteins to nanoporous membranes fabricated by using swift heavy ion accelerators. In the following chapter the main steps involved in employing the method for fabricating metalic nanowires and nanotubes by replicating ion track nanoporous membranes were described. The steps include here membrane fabrication and replication and involve track etching and electrochemical metal deposition. The influence of the process parameters on the properties of the nanoobjects prepared by this approach was reviewed. It was found that simple experimental parameters can be chosen in such a way that the functionality of the nanowires or nanotubes can be finely tuned.

1475. Thermal behaviour and characterisation of new biologically active Cu(II) complexes with benzimidazole as main ligand

Authors: Badea, M; Vlaicu, ID; Olar, R; Constand, M; Bleotu, C; Chifiriuc, MC; Marutescu, L; Lazar, V; Grecu, MN; Marinescu, D

Published: NOV 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 118, 1133, DOI: 10.1007/s10973-014-3745-z

Four coordination compounds of copper(II) were synthesised and characterised in solid state by elemental analysis, infrared, electronic and EPR spectroscopy, as well as by thermal analysis (TG/DTA). The complexes were formulated on the basis of experimental data as: [Cu(BzIm)(2)(H2O)]center dot H2O (1), [Cu-2(Acr)(4)(HBzIm)(2)] (2), [Cu(Acr)(2)(HBzIm)(2)] (3) and [Cu(Acr)(2)(HBzIm)(2)(H2O)]center dot H2O (4). IR data are in accordance with the unidentate nature of benzimidazole, in complexes (2), (3) and (4), and bridge bidentate nature of benzimidazole, in complex (1), while acrylato acts as uni- or bridge/chelate ligand. The electronic spectra display the characteristic pattern of square planar, square pyramidal, or octahedral stereochemistry, also confirmed by EPR spectra. Thermal decomposition evidenced several well-defined steps as dehydration of complexes (1) and (4), benzimidazole molecule releases for all complexes and acrylate decomposition in carbonate for complexes (3) and (4). In all four cases, the final residue after thermal treatment in air flow is copper(II) oxide, formed during the decomposition steps for complexes (3) and (4), and, respectively, after the oxidation of the metallic copper for complexes (1) and (2). Antimicrobial activities of the complexes have been determined by in vitro assays, against various Gram-negative and Gram-positive bacterial and fungal strains. Copper(II) complexes were also evaluated for their cytotoxicity on eukaryotic cells.

1476. Abnormal anti-Stokes Raman scattering and surface-enhanced infrared absorption spectroscopy studies of carbon nanotubes electrochemically functionalized with poly(2,2 '-bithiophene-co-pyrene)

Authors: Baibarac, M; Baltog, I; Smaranda, I; Scocioreanu, M; Mevellec, JY; Lefrant, S

Published: AUG 1 2014, APPLIED SURFACE SCIENCE, 309, 21, DOI: 10.1016/j.apsusc.2014.04.114

A new composite material was synthesized via the electrochemical oxidation of 2,2'-bithiophene (BTh) and pyrene (Py) monomers dissolved in a solution of LiC1O(4) in CH3CN onto a working electrode of Au coated with a film of single-walled carbon nanotubes (SWNTs). The interaction of the poly(2,2'-bithiophene-co-pyrene) (PBTh-Py) with the SWNTs and the orientation of the copolymer on the working electrode were studied by anti-Stokes and Stokes Raman scattering and FTIR spectroscopy in the grazing-incidence angle reflection geometry. The Raman lines at 1464 and 1435 cm(-1), attributed to the symmetric stretching modes of the C=C bond in the quinoid and aromatic rings of the PBTh-Py copolymer, were observed when the working electrode is either a blank Au film or a Au support coated with a SWNT film. In the latter case, charge transfer occurs at the interface of the two constituents. This charge transfer leads to functionalization of the carbon nanotubes with the copolymer molecules. The presence of enhanced anti-Stokes Raman lines at -1461, -1435 and -1187 cm(-1) indicates a resonant optical excitation process of the PBTh-Py/SWNT composite. The FTIR spectra acquired under polarized light for the PBTh-Py copolymer electrosynthesized on a bare Au support reveal significant changes in the absorption bands situated in the spectral ranges of 1000-1150 and 1550-1650 cm(-1) that originate in the surface-enhanced IR absorption (SEIRA) processes. The functionalization of the SWNTs with the PBTh-Py copolymer is evidenced by the enhancement of the absorption of the FTIR bands at 793 and 846 cm(-1), which are assigned to the C S C deformation vibrational mode and the substituted benzene ring, respectively, due to the effects of steric hindrance that are induced for the copolymer molecules by the binding of carbon nanotubes. (C) 2014 Elsevier B.V. All rights reserved.

1477. Insulin loaded iron magnetic nanoparticle-graphene oxide composites: synthesis, characterization and application for in vivo delivery of insulin

Authors: Turcheniuk, K; Khanal, M; Motorina, A; Subramanian, P; Barras, A; Zaitsev, V; Kuncser, V; Leca, A; Martoriati, A; Cailliau, K; Bodart, JF; Boukherroub, R; Szunerits, S

Published: 2014, RSC ADVANCES, 4, 875, DOI: 10.1039/c3ra46307a

One of the focal subjects in insulin delivery is the development of insulin formulations that protect the native insulin from degradation under acidic pH in the stomach. In this work we show, for the first time, that a graphene oxide (GO) based matrix can ensure the stability of insulin at low pH. GO and GO modified with 2-nitrodopamine coated magnetic particle (GO-MPdop) matrices loaded with insulin were prepared and the pH triggered release of the insulin was studied. The loading of insulin on the GO nanomaterials proved to be extremely high at pH < 5.4 with a loading capacity of 100 +/- 3% on GO and 88 +/- 3% on GO-MPdop. The insulin-containing GO matrices were stable at acidic pH, while insulin was released when exposed to basic solutions (pH = 9.2). Using Xenopus laevis oocytes as a model we showed that the meiotic resumption rate of GO and GO-MPdop remained unaltered when pre-treated in acidic conditions, while pre-incubated insulin (without GO nanomaterials) has lost almost entirely its maturation effect. These results suggest that GO based nanomatrices are promising systems for the protection of insulin.

1478. Polysaccharide-assisted crystallization of ZnO micro/nanostructures

Authors: Preda, N; Enculescu, M; Enculescu, I

Published: JAN 15 2014, MATERIALS LETTERS, 115, 260, DOI: 10.1016/j.matlet.2013.10.081

ZnO micro/nanostructures with complex morphology were synthesized by a simple chemical reaction between zinc nitrate and hexamethylenetetramine in the presence of polysaccharides. X-ray diffraction analysis showed that all obtained samples are of wurtzite structure. The reflectance and room temperature photoluminescence spectra have been used to investigate the optical properties of the ZnO structures. The scanning electron microscopy images reveal that the ZnO morphology (star, double-jellyfish, double-raspberry and edelweiss-flower) can be easily changed by varying the polysaccharides: sodium alginate, gum arabic and chitosan. The polysaccharide-assisted crystallization method could provide a facile approach to synthesize other desired compounds with controllable morphology. (C) 2013 Elsevier B.V. All rights reserved.

1479. Field Effect Transistor with Electrodeposited ZnO Nanowire Channel

Authors: Florica, C; Matei, E; Costas, A; Molares, MET; Enculescu, I

Published: AUG 10 2014, ELECTROCHIMICA ACTA, 137, 297, DOI: 10.1016/j.electacta.2014.05.124

ZnO nanowires were prepared by electrochemical deposition in polycarbonate ion track templates. After the deposition process the polymer templates were dissolved in dichloromethane and the nanowires were harvested by ultrasonication in isopropyl. A droplet of nanowire suspension was placed on a Si/SiO2 substrate patterned with interdigitated electrodes. By means of electron beam lithography single nanowires were selected and provided with electrical contacts. We found that in order to obtain reliable electrical contacts and typical field effect characteristics the electrode deposition process needs to be adapted to the 3 D shape of the wires and that annealing and passivation treatments are necessary. (C) 2014 Elsevier Ltd. All rights reserved.

1480. Structural and magnetic properties of Li2O-Fe2O3 ceramic nanostructures

Authors: Sorescu, M; Bushunow, V; Diamandescu, L; Tolea, F; Valeanu, M; Xu, TH

Published: MAY 2014, CERAMICS INTERNATIONAL, 40, 5395, DOI: 10.1016/j.ceramint.2013.10.120

xLi(2)O-(1 x)alpha-Fe2O3 (x=0.1, 0.3, 0.5, and 0.7) nanoparticle systems were successfully synthesized by mechanochemical activation of Li2O and alpha-Fe2O3 mixtures for 0-12 h of ball milling time. The study aims at exploring the formation of magnetic oxide semiconductors at the nanoscale, which is of crucial importance for catalysis, sensing and electrochemical applications. X-ray powder diffraction (XRD), Mossbauer spectroscopy and magnetic measurements were used to study the phase evolution of xLi(2)O-(1 x)alpha-Fe2O3 nanoparticle systems under the mechanochemical activation process. Rietveld refinement of the XRD patterns yielded the values of the particle size as function of composition and milling times and indicated the presence of Li-substituted hematite and tetra lithium iron oxide LiFeO2, along with the formation of multiple phases for large x values and long milling times. The Mossbauer studies showed that the spectrum of the mechanochemically activated composites evolved from a sextet for hematite to sextets and a doublet upon duration of the milling process with lithium oxide. Magnetic measurements recorded at 5 K to room temperature (RT) in an applied magnetic field of 50,000 Oe showed that the magnetization of the milled samples is larger at low temperatures than at RT and increases with decreasing particle size. Zero field cooling measurements made possible the determination of the blocking temperatures of the specimens as function of ball milling time and evidenced the occurrence of superparamagnetism in the studied samples. This result correlates well with the observed presence of a quadrupole-split doublet in the Mossbauer spectra. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1481. Systematic investigation and in vitro biocompatibility studies on mesoporous europium doped hydroxyapatite

Authors: Popa, CL; Ciobanu, CS; Iconaru, SL; Stan, M; Dinischiotu, A; Negrila, CC; Motelica-Heino, M; Guegan, R; Predoi, D

Published: OCT 2014, CENTRAL EUROPEAN JOURNAL OF CHEMISTRY, 12, 1046, DOI: 10.2478/s11532-014-0554-y

This paper reports the systematic investigation of europium doped hydroxyapatite (Eu:HAp). A set of complementary techniques, namely Fourier Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller (BET) technique were used towards attaining a detailed understanding of Eu:HAp. The XPS analysis confirmed the substitution of Ca ions by Eu ions in the Eu:HAp samples. Secondly, Eu:HAp and pure HAp present type IV isotherms with a hysteresis loop at a relative pressure (P/P-0) between 0.4 and 1.0, indicating the presence of mesopores. Finally, the in vitro biological effects of Eu:HAp nanoparticles were evaluated by focusing on the F-actin filament pattern and heat shock proteins (Hsp) expression in HEK293 human kidney cell line. Fluorescence microscopy studies of the actin protein revealed no changes of the immunolabelling profile in the renal cells cultured in the presence of Eu:HAp nanoparticles. Hsp60, Hsp70 and Hsp90 expressions measured by Western blot analysis were not affected after 24 and 48 hours exposure. Taken together, these results confirmed the lack of toxicity and the biocompatibility of the Eu:HAp nanoparticles. Consequently, the possibility of using these nanoparticles for medical purposes without affecting the renal function can be envisaged.

1482. Effects of substrate and ambient gas on epitaxial growth indium oxide thin films

Authors: Nistor, M; Seiler, W; Hebert, C; Matei, E; Perriere, J

Published: JUL 15 2014, APPLIED SURFACE SCIENCE, 307, 460, DOI: 10.1016/j.apsusc.2014.04.056

Indium oxide thin films were grown by pulsed electron beam deposition method at 500 Con c-cut sapphire and (0 0 1) oriented LaAlO3 single crystal substrates in oxygen or argon gas. The effects of ambient gas and substrate symmetry on the growth of indium oxide thin films were studied. Stoichiometric In2O3 films are formed in oxygen, while oxygen deficient In2O2.5 films are grown in argon, with In metallic nanoclusters embedded in a In2O3 matrix (nanocomposite films). In both cases, epitaxial In2O3 films having the bixbyite phase were grown with various orientation relationships, depending upon the substrate symmetry and gas ambient (oxygen or argon). Domain matching epitaxy was used to describe the precise in-plane epitaxial film-substrate relationships. The differences in film texture were correlated to the differences in growth conditions, while the differences in the film properties were correlated to the film oxygen composition. (c) 2014 Elsevier B.V. All rights reserved.

1483. Forward current enhanced elimination of the radiation induced boron-oxygen complex in silicon n(+)-p diodes

Authors: Makarenko, LF; Lastovskii, SB; Yakushevich, HS; Moll, M; Pintilie, I

Published: NOV 2014, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 211, 2562, DOI: 10.1002/pssa.201431315

Using forward current injection with densities in the range 15-30A/cm(2) we can effectively eliminate the radiation-induced boron-oxygen complex, which is the main compensating center in irradiated Si solar cells. It was found that for a given forward current density the elimination rate is decreasing with increasing irradiation dose. Additionally, some evidences have been obtained on the negative-U properties of the radiation-induced boron-oxygen complex.

1484. Significant enhancement of the critical current density for cubic BN addition into ex situ spark plasma sintered MgB2

Authors: Badica, P; Aldica, G; Burdusel, M; Popa, S; Negrea, RF; Enculescu, M; Pasuk, I; Miu, L

Published: SEP 2014, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 27, DOI: 10.1088/0953-2048/27/9/095013

High density (above 93%) superconducting bulks of MgB2 with addition of hexagonal BN (h-BN) and cubic BN (c-BN) with compositions ((MgB2) + (BN)(x), x = 0.01, 0.03, 0.05) were obtained by ex situ spark plasma sintering. All the investigated samples have the critical temperature T-c = 38.8 K. The variation of the critical current density J(c) with the external magnetic field H for h-BN added sample is almost overlapping the J(c)(H) dependence for the pristine MgB2 sample. On the other hand, J(c) for the samples added with c-BN is larger at high magnetic fields, while the decrease of J(c) at low H is very small. At T = 20 K, a J(c) of 10(2) A cm(-2) is determined for the sample with x(c-BN) = 0.005 at H = 58 kOe, and for the sample with x(c-BN) = 0.01 at 54 kOe. Magnetic relaxation measurements indicate a significant flux pinning enhancement in MgB2 samples added with c-BN. It is proposed that the disorder at the interface caused by the convenient lattice matching relationship between the lateral plane of the MgB2 crystal prism and the face of the c-BN crystal cube is responsible for the observed vortex pinning increase.

1485. INFLUENCE OF 5,10,15,20-TETRAKIS(4-PYRIDYL)-21H,23H-PORPHYRIN ON THE CORROSION OF STEEL IN AQUEOUS SULFURIC ACID

Authors: Fagadar-Cosmaa, G; Taranu, BO; Birdeanu, M; Popescu, M; Fagadar-Cosma, E

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 557, DOI:

The inhibition ability of dissolved 5,10,15,20-tetrakis(4-pyridyl)-21H, 23H-porphine (TPyP) on the corrosion of carbon steelin H2SO4 5% was investigated by evaluating the mass loss from the volume of the evolved hydrogen and by direct weight measurements at different temperatures. Results indicated that the presence of TPyP was able to reduce the corrosion rate of steel with over 50% efficiency, depending on TPyP concentration and temperature. The surface state of steel was characterized by AFM before and after the steel sample was corroded in H2SO4 solution (5%), the smoothing and uniforming effect of porphyrin being obvious, especially at higher temperature.

1486. Thermally activated conversion of a silicate gel to an oxyfluoride glass ceramic: Optical study using Eu3+ probe ion

Authors: Secu, CE; Bartha, C; Polosan, S; Secu, M

Published: FEB 2014, JOURNAL OF LUMINESCENCE, 146, 543, DOI: 10.1016/j.jlumin.2013.10.013

Sol-gel route using metal alkoxides precursor and trifluoroacetic acid as in situ fluorination reagent has been used to prepare Eu3+ -doped silicate xerogel, followed by thermal annealing to obtain oxyfluoride glass ceramic containing Eu3+ -doped BaF2 nanocrystals. We have used Eu3+ as probe ion and we analyzed its characteristic features (photoluminescence, optical absorption and magnetic circular dichroism) to get information about the local environment around the ion during thermally activated evolution of the sol to xerogel and then glass ceramic. As the drying and annealing proceeds silica network is formed accompanied by precipitation of the nanofluoride crystalline phase; Eu3+ coordination changes gradually from a random and assymetric CF3COO- one (in the sol) to a symmetric one (in the BaF2 nanocrystals) given by the fluorine ions. Glass ceramization is based on a homogenous crystallization mechanism with BaF2 nucleation centres resulted from thermal decomposition of Ba-trifluoacetate at around 300 degrees C followed by subsequent growth into BaF2 nanocrystals above 600 degrees C; Eu3+-ions are incorporated during the nanocrystals growth. (C) 2013 Elsevier B.V. All rights reserved.

1487. FABRICATION, CHARACTERIZATION, TOXICITY AND BIOCOMPATIBILITY EVALUATION OF IRON OXIDE NANOPARTICLES

Authors: Popa, CL; Andronescu, E; Stoicea, M; Le Coustumer, P; Galaup, S; Beuran, M; Iordache, FM; Telcian, A; Bleotu, C; Prodan, AM

Published: JAN-MAR 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 25, DOI:

The iron oxide nanoparticles were synthetized by an adapted coprecpitation method. Stuctural and morphological characterization of the obtained iron oxide nanoparticles were investigated by X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Furthermore, in vitro and in vivo studies were investigated by cell viability assay and HeLa cells. For the analysis of iron oxide toxicity in vivo, several mice were treated with normal saline and iron oxide via intraperitoneal injection (IP). The XRD spectra showed the peaks associated to the spinel cubic lattice type with the lattice of 0.835 nm. By magnified TEM image, it could be observed that the samples have a uniform morphology with relatively spherical shape and nanometric size. Moreover, inverted fluorescence microscopy images of HeLa cells with normal phenotype and HeLa cells treated for 72 hourswith a suspension of gamma-Fe2O3 nanoparticles revealed the non-toxic character. The histophtological studies have demonstrated that at 72 hours after IP administration, the iron oxide nanoparticles are not accumulating in kidney and spleen, thus establishing their utility as drug delivery systems targeted to these organs.

1488. Synthesis and Raman scattering of multiferroic Fe-Pb(Zr0.2Ti0.8)O-3 core-shell wire arrays

Authors: Baibarac, M; Sima, M; Matei, E; Pasuk, I; Mihut, L

Published: JAN 2014, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 211, 205, DOI: 10.1002/pssa.201330062

A new method to fabricate an Fe-PZT core-shell wire arrays developed in three steps is reported in this paper. This involves the electrochemical growth of an iron wire array by template method, deposition by spin coating of the PZT precursor prepared by sol-gel technique on the iron wires surface and annealing treatment to obtain Fe-PZT core-shell structures. The structure of the Fe-PZT core-shell wire array was characterized by scanning electron microscopy (SEM) and Raman scattering. Raman lines situated at 372 and 575cm(-1) indicate the formation of the FeO particles on the Fe wires surface as a result of the use of an aqueous solution for electrochemical synthesis. An upshift of Raman lines of Fe decorated with FeO wires was observed after formation of Fe-PZT core-shell structure. The annealing treatment of this structure involves a partial transformation of the FeO into Fe2O3 particles both with structure rhombohedral and cubic that were evidenced by Raman lines peaked at 243 and 497cm(-1), respectively. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1489. Hydroxyapatite With Environmental Applications

Authors: Popa, CL; Ciobanu, CS; Petre, CC; Motelica-Heino, M; Iconaru, SL; Jiga, G; Predoi, D

Published: 2014, TIMES OF POLYMERS (TOP) AND COMPOSITES 2014, 1599, 321, DOI: 10.1063/1.4876842

The aim of this study was to synthetize new nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp) for lead removal in aqueous solutions. The morphological and compositional analysis of MTHAp was investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+ and at fixed pH of 5. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cation exchange reaction. Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb2+ ions from aqueous solution.

1490. Challenges of nanostructuring and functional properties for selected bulk materials obtained by reactive spark plasma sintering

Authors: Badica, P; Aldica, GV; Burdusel, M; Borodianska, H; Sakka, Y; Vasylkiv, O

Published: MAY 2014, JAPANESE JOURNAL OF APPLIED PHYSICS, 53, DOI: 10.7567/JJAP.53.05FB22

Sintered bulks require new approaches for the control and improvement of their functional characteristics. Nanostructuring, synergy effects at interfaces in a composite, and technology specific features are essential in this regard. In this work, for a better understanding of challenges, complex relationships between materials and technology and different practical concepts such as "transferability", "composite within a composite", and "multilevel design", and "multifunctionality", a comparative analysis is proposed for very different nano structured materials such as La0.9Sr0.1Ga0.8Mg0.2O3-x x solid electrolyte, hard B4C-based materials, and doped MgB2 superconductors. Samples were obtained by reactive spark plasma sintering (SPS). SPS is reconfirmed as a powerful processing technique that generates high-density unique bulk materials impossible to fabricate by other methods. However, it is shown that SPS is not universal and its suitability should be carefully considered depending on materials and targeted applications. (C) 2014 The Japan Society of Applied Physics

1491. Synthesis, physico-chemical characterization and thermal behavior of new complexes with N4O2 donor set

Authors: Olar, R; Scaeteanu, G; Vlaicu, ID; Marutescu, L; Badea, M

Published: NOV 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 118, 1202, DOI: 10.1007/s10973-014-3809-0

Three new coordinative compounds of the type [Co(en)(2)CO3]center dot 0.75H(2)O (1) and [M(en)(2)(H2O)(2)]CO3 ((2) M:Ni, (3) M:Cu; en: ethylenediamine) were synthesized and characterized. The IR and UV-Vis spectral data indicate that ethylenediamine acts as chelate, while carbonate ions act as bidentate chelate ligand for (1)/counter ion for (2) and (3) generating complexes with octahedral stereochemistry. The thermal behavior provided confirmation of the complexes composition, as well as the number and the nature of water molecules and the intervals of thermal stability. The biological assays revealed a good activity against Enterococcus faecium for copper complex.

1492. Strain-induced long range ferroelectric order and linear electro-optic effect in epitaxial relaxor thin films

Authors: Scarisoreanu, ND; Craciun, F; Birjega, R; Andrei, A; Ion, V; Negrea, RF; Ghica, C; Dinescu, M

Published: AUG 21 2014, JOURNAL OF APPLIED PHYSICS, 116, DOI: 10.1063/1.4893364

Relaxor ferroelectrics have neither long range ferroelectric order nor structural transformation down to the lowest temperatures, and display isotropic optical properties like quadratic electro-optic effect. However, if an anisotropy is forced through an external agent, like electric field or uniaxial strain, a ferroelectric and structural long range order can be induced in these materials. Here, we show that epitaxial strain in relaxor ferroelectric thin films can be employed to induce a linear electro-optic effect, opening the path to new strain-controlled electro-optic materials. Epitaxial thin films with Pb1-3x/2LaxZr0.2Ti0.8O3 (x = 0.22) composition grown by pulsed laser deposition on (001) SrRuO3/SrTiO3 single crystal heterostructures become tetragonal below the susceptibility peak, which occurs at a temperature 140K higher as compared to bulk. These films show piezoelectric properties and almost linear electro-optic behaviour. (C) 2014 AIP Publishing LLC.

1493. Influence of film thickness on the morphological and electrical properties of epitaxial TiC films deposited by reactive magnetron sputtering on MgO substrates

Authors: Zoita, NC; Braic, V; Danila, M; Vlaicu, AM; Logofatu, C; Grigorescu, CEA; Braic, M

Published: MAR 1 2014, JOURNAL OF CRYSTAL GROWTH, 389, 98, DOI: 10.1016/j.jcrysgro.2013.11.076

Epitaxial TiC films were deposited on MgO (001) by DC magnetron sputtering in a reactive atmosphere of Ar and CH4 at 800 degrees C. The films elemental composition and chemical bonding was investigated by Auger electron spectroscopy (AE5), X-ray photoelectron spectroscopy (XPS) and micro-Raman spectroscopy. The crystallographic structure, investigated by X-ray diffraction, exhibited an increased degree of (001) orientation with the film thickness, with a cube-on-cube epitaxial relationship with the substrate. The films morphology and electrical properties were determined by atomic force microscopy (AFM) and Hall measurements in Van der Pauw geometry. The influences of the film thickness (57-545 nm) on the morphological and electrical properties were investigated. The thinnest film presented the lowest resistivity, 160 [152, cm, showing an atomically flat surface, while higher values were obtained for the thicker films, explained by their different morphology dominated by low aspect ratio nanoislands/ nanocolumns. (C) 2013 Elsevier B.V. All rights reserved

1494. In-situ crystallization of GeTe\GaSb phase change memory stacked films

Authors: Velea, A; Borca, CN; Socol, G; Galca, AC; Grolimund, D; Popescu, M; van Bokhoven, JA

Published: DEC 21 2014, JOURNAL OF APPLIED PHYSICS, 116, DOI: 10.1063/1.4904741

Single and double layer phase change memory structures based on GeTe and GaSb thin films were deposited by pulsed laser deposition (PLD). Their crystallization behavior was studied using in-situ synchrotron techniques. Electrical resistance vs. temperature investigations, using the four points probe method, showed transition temperatures of 138 degrees C and 198 degrees C for GeTe and GaSb single films, respectively. It was found that after GeTe crystallization in the stacked films, Ga atoms from the GaSb layer diffused in the vacancies of the GeTe crystalline structure. Therefore, the crystallization temperature of the Sb-rich GaSb layer is decreased by more than 30 degrees C. Furthermore, at 210 degrees C, the antimony excess from GaSb films crystallizes as a secondary phase. At higher annealing temperatures, the crystalline Sb phase increased on the expense of GaSb crystalline phase which was reduced. Extended X-ray absorption fine structure (EXAFS) measurements at the Ga and Ge K-edges revealed changes in their local atomic environments as a function of the annealing temperature. Simulations unveil a tetrahedral configuration in the amorphous state and octahedral configuration in the crystalline state for Ge atoms, while Ga is four-fold coordinated in both as-deposited and annealed samples. (C) 2014 AIP Publishing LLC.

1495. Pulse annealing electron paramagnetic resonance with probing transition ions

Authors: Nistor, SV; Stefan, M; Ghica, D

Published: NOV 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 118, 1031, DOI: 10.1007/s10973-014-3743-1

The analysis of the sequence of electron paramagnetic resonance (EPR) spectra of trace amounts of substitutional probing paramagnetic ions incorporated in (nano)crystalline samples submitted to isothermal and isochronal pulse annealing treatments can offer a wealth of information on the thermally induced compositional and structural changes of the host material. The potential of this new thermal analysis method is illustrated here with results of such investigations on the thermal decomposition of crystalline zinc hydroxide (Zn(OH)(2)) and anhydrous zinc carbonate basic (Zn-5(CO3)(2)(OH)(6)) precursors containing trace amounts of substitutional Mn2+ probing ions into nanostructured zinc oxide-ZnO. The quantitative analysis of the sequence of isochronal pulse annealing EPR spectra could provide, besides the thermal decomposition curves of the two precursors, additional information about the structure of the resulting nanostructured ZnO, some of it hard to get by standard structural diffraction techniques. The analysis of both isochronal and isothermal pulse annealing EPR data was further used to investigate the crystallization mechanism of the initially formed nanostructured disordered ZnO and to quantitatively describe the further growth of the resulting ZnO nanocrystals with the increasing annealing temperature and duration.

1496. Origin of the stabilization of the metastable tetragonal high-pressure phase in SrCuO2 thin films grown on SrTiO3 substrates by pulsed laser deposition

Authors: Mihailescu, CN; Pasuk, I; Straticiuc, M; Nita, CR; Pantelica, D; Giapintzakis, J

Published: NOV 30 2014, APPLIED SURFACE SCIENCE, 320, 857, DOI: 10.1016/j.apsusc.2014.09.116

In this work we have systematically investigated the evolution of structure and stoichiometry in SrCuO2 films grown on TiO2-terminated SrTiO3 substrates as a function of the substrate temperature. Depending on the growth temperature SrCuO2/SrTiO3 films can exhibit either a pure tetragonal high-pressure phase, or a pure orthorhombic low-pressure phase, or a mixed phase. Our results indicate that at low substrate temperatures the non-equilibrium state of the growth process is responsible for the stabilization of the metastable tetragonal high-pressure structure in SrCuO2 thin films grown on ( 0 01) SrTiO3 substrates, whose lattice matches the metastable structure. In addition, at higher substrate temperatures thermodynamics become dominant over other factors and the SrCuO2 thin films are stabilized in the thermodynamically stable orthorhombic phase. (C) 2014 Elsevier B.V. All rights reserved.

1497. Electrochemical Grafting of Reduced Graphene Oxide with Polydiphenylamine Doped with Heteropolyanions and Its Optical Properties

Authors: Smaranda, I; Benito, AM; Maser, WK; Baltog, I; Baibarac, M

Published: NOV 6 2014, JOURNAL OF PHYSICAL CHEMISTRY C, 118, 25717, DOI: 10.1021/jp507324r

Electropolymerization of diphenylamine (DPA) onto a reduced graphene oxide (RGO) film was carried out to obtain a corresponding RGO/polydiphenylamie (PDPA) composite doped with phosphotungstic acid (H3PW12O40) heteropolyanions (PT). The synthesis was performed in the absence of light, since UVvis spectroscopy and photoluminescence (PL) studies on RGO/DPA blends irradiated by UV light revealed a partial transformation of the DPA monomer into oligomers of PDPA. Raman scattering demonstrates that the electropolymerization of DPA in the presence of H3PW12O40 (PTA) and RGO leads to the formation of PDPA covalently bonded to the RGO sheets (RGO/PDPA:PT). The presence of heteropolyanions in the PDPA matrix (PDPA:PT) is detected by FTIR spectroscopy. Comparing the PL excitation spectra of PDPA:PT and the RGO/PDPA:PT composite highlights an upshift of the band gap that is accompanied by a change in the composition of the PL spectrum in the spectral range of 2.253.54 eV. These changes originate in a charge transfer that takes place at the interface of nongrafted RGO and PDPA:PT. The gradual increase of the PL intensity of RGO covalently grafted with PDPA:PT reveals photochemical reactions under UV irradiation. These involve the CC stretching vibrational mode in the benzene ring of PDPA and indicate the transformation of an RGO/PDPA:PT composite containing HPW12O402 anions into an RGO/PDPA:PT composite stabilized by PW12O403 anions. These results not only provide important insights on the interactions between RGO, conjugated polymers, and stabilizing dopant ions but also impact on the synthesis conditions.

1498. Laser emission from diode-pumped Nd:YAG ceramic waveguide lasers realized by direct femtosecond-laser writing technique

Authors: Salamu, G; Jipa, F; Zamfirescu, M; Pavel, N

Published: MAR 10 2014, OPTICS EXPRESS, 22, 5182, DOI: 10.1364/OE.22.005177

We report on realization of buried waveguides in Nd: YAG ceramic media by direct femtosecond-laser writing technique and investigate the waveguides laser emission characteristics under the pump with fiber-coupled diode lasers. Laser pulses at 1.06 mu m with energy of 2.8 mJ for the pump with pulses of 13.1-mJ energy and continuous-wave output power of 0.49 W with overall optical efficiency of 0.13 were obtained from a 100-mu m diameter circular cladding waveguide realized in a 0.7-at.% Nd: YAG ceramic. A circular waveguide of 50-mu m diameter yielded laser pulses at 1.3 mu m with 1.2-mJ energy. (c) 2014 Optical Society of America

1499. Higher-Order Modes in High-Permittivity Cylindrical Dielectric Resonator Antenna Excited by an Off-Centered Rectangular Slot

Authors: Avadanei, OG; Banciu, MG; Nedelcu, L

Published: 2014, IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, 13, 1588, DOI: 10.1109/LAWP.2014.2344860

In this letter, we study the higher-order modes excited in a high-permittivity cylindrical dielectric resonator antenna (DRA), situated asymmetrically on top of a rectangular slot in the ground plane of a microstrip line. Besides the modes excited by a symmetric positioning of the DRA above the feeding slot, we identified five new modes: TEme(010), TEme(011), TEme(210), TEme(020), and TM212 respectively. The higher-order modes offer to the DRA antenna some interesting features: They have different radiation patterns for different operating modes; modes with close resonance frequency give wideband capabilities; and sometimes, when a mode has poor performance in one polarization, it is possible that another mode with close frequency can compensate it.

1500. Organic heterostructures based on arylenevinylene oligomers deposited by MAPLE

Authors: Socol, M; Preda, N; Vacareanu, L; Grigoras, M; Socol, G; Mihailescu, N; Stanculescu, F; Jelinek, M; Stanculescu, A; Stoicanescu, M

Published: MAY 30 2014, APPLIED SURFACE SCIENCE, 302, 222, DOI: 10.1016/j.apsusc.2013.12.091

Organic heterostructures were fabricated by matrix assisted pulsed laser evaporation (MAPLE) method using arylenevinylene oligomers based on triphenylamine (P78)/carbazole (P13) group and tris(8-hydroxyquinolinato)aluminum salt (Alq3). Optical properties of the organic multilayer structures were characterized by spectroscopic techniques: FTIR, UV-vis and photoluminescence (PL). A good transparency (over 60%) was remarked for the structures with two organic layers in the 550-800 nm range. Photoluminescence (PL) spectra proved that the emission characteristics of the materials have been preserved. I-V characteristics of (ITO/oligomer/Alq3/Al and ITO/Alq3/Al) heterostructures were symmetrically while rectifying properties of these heterostructures have not been observed. A comparison between the heterostructures made of layers with different thickness reveals that the higher current (8 x 10(-6) A at 1 V) was obtained for the ITO/P78/Alq3/Al heterostructure, which is characterized by a larger thickness of the double organic layer. AFM measurements revealed a similar topography while RMS values of the reported structures depend on the organic material. (C) 2013 Elsevier B.V. All rights reserved.

1501. Enhancement of smectic C mesophase stability by using branched alkyl chains in the auxiliary ligands of luminescent Pt(II) and Pd(II) complexes

Authors: Ilis, M; Micutz, M; Dumitrascu, F; Pasuk, I; Molard, Y; Roisnel, T; Circu, V

Published: FEB 17 2014, POLYHEDRON, 69, 39, DOI: 10.1016/j.poly.2013.11.015

A novel series of Pd(II) and Pt(II) complexes based on cyclometallated imine ligands and N-benzoylthiourea (BTU) derivatives as auxiliary ligands has been prepared and their liquid crystalline properties as well as photophysical properties have been investigated. The crystal structure of one cyclometallated Pt(II) complex with N-(p-F-phenyl)-N'-benzoylthiourea as a co-ligand has been solved. The liquid crystalline properties have been investigated by a combination of DSC, POM and variable temperature powder X-ray diffraction. These new metallomesogens display either a monotropic SmC phase or both SmA and SmC phases, depending on the number of alkoxy groups attached to the imine ligand, alkyl chain length or the use of branched alkoxy terminal groups. We found that the introduction of branched alkoxy terminal groups lead to lower transition temperatures and stabilization of the SmC phase in both the Pd(II) and Pt(II) complexes. While the Pd(II) complexes display no emission, the Pt(II) complexes show good emission properties in solution, in the solid state and as a PMMA film at room temperature, and their investigation is reported. (C) 2013 Elsevier Ltd. All rights reserved.

1502. Biocatalytic designs for the conversion of renewable glycerol into glycerol carbonate as a value-added product

Authors: Tudorache, M; Ghemes, G; Nae, A; Matei, E; Mercioniu, I; Kemnitz, E; Ritter, B; Coman, S; Parvulescu, VI

Published: DEC 2014, CENTRAL EUROPEAN JOURNAL OF CHEMISTRY, 12, 1270, DOI: 10.2478/s11532-014-0547-x

A comparative study of two different biocatalytic models, e.g. enzyme immobilized on magnetic particles (EIMP) and cross-linking enzyme aggregates onto magnetic particles (CLEMPA) was performed. The first model was designed as enzyme-immobilized on the magnetic particles surface (EIMP). The second model was constructed as a network structure with the enzyme aggregates and magnetic particles placed into the nodes and polyglutaraldehyde cross-linker as the network ledges. The design was called cross-linking enzyme aggregates onto magnetic particles (CLEMPA). The biocatalysts were prepared using lipase enzyme from Aspergillus niger for catalyzing the glycerol (Gly) conversion to glycerol carbonate (GlyC). The biocatalyst characteristics for both designs (EIMP and CLEMPA) were evaluated using scanning electron microscopy (SEM), laser light scattering (LLS) and UV-Vis techniques. The EIMP model was strongly influenced by the composition of the polymeric layer covering the particles surface, while the size of the magnetic particles affected mostly the CLEMPA design. Also, the biocatalytic capacity of the tested models was evaluated as maximum 52% Gly conversion with 90% GlyC selectivity for EIMP, and 73% Gly conversion with 77% GlyC selectivity for CLEMPA. Both biocatalytic models were successfully used to prepare GlyC from "crude" glycerol collected directly from the biodiesel process (e.g. 49% Gly conversion with 91% GlyC selectivity for EIMP and 70% Gly conversion with 80% GlyC selectivity for CLEMPA).

1503. Electrochemical Studies on the Growth Process of the Zinc Oxide Films from Nitrate Solutions

Authors: Dumitru, CS; Sima, M; Cojocaru, A

Published: JUL 2014, REVISTA DE CHIMIE, 65, 839, DOI:

The cathodic deposition of zinc oxide film on Pt from an aqueous solution containing 0.05 M Zn(NO3)(2) was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy. The film formation is an electroprecipitation process due to reduction of nitrate ion on the surface of working electrode in the presence of Zn2+ ions. A morphology of ZnO with hexagonal platelets was observed. The standard electromotive force of the cell reaction was calculated for both NO3/NO2 process and overall deposition process. Linear voltammograms and visual observations showed that polarizing the electrode at higher negative potentials than -1.1 V, the parallel reduction of zinc ion to zinc metal occurs together with reduction of nitrate ion to hydroxide ion; as a consequence, a partial amorphous state of ZnO film was recorded on SEM micrographs. Experimental impedance data and data calculated by fitting with an equivalent circuit showed that the ZnO formation involves an adsorption of complexed zinc ions on Pt electrode, before the charge transfer.

1504. Coulomb-assisted cavity feeding in nonresonant optical emission from a quantum dot

Authors: Florian, M; Gartner, P; Steinhoff, A; Gies, C; Jahnke, F

Published: APR 14 2014, PHYSICAL REVIEW B, 89, DOI: 10.1103/PhysRevB.89.161302

Recent experiments have demonstrated that for a quantum dot in an optical resonator, off-resonant cavity-mode emission can occur even for detunings of the order of 10 meV. We show that Coulomb-mediated Auger processes based on additional carriers in delocalized states can facilitate this far off-resonant emission. A theoretical approach is developed for the nonperturbative treatment of the Auger-assisted quantum-dot carrier recombination. Using this method we present numerical calculations of the far off-resonant cavity feeding rate and cavity mean photon number, confirming efficient coupling at higher densities of carriers in the delocalized states. In comparison to fast Auger-like intraband scattering processes, we find a reduced overall efficiency of Coulomb-mediated interband transitions due the required electron-hole correlations for the recombination processes.

1505. In vivo toxicity studies of superparamagnetic iron oxide nanoparticles in a silica matrix

Authors: Iconaru, SL; Prodan, AM; Ciobanu, CS; Motelica-Heino, M; Predoi, D

Published: SEP 2014, FEBS JOURNAL, 281, 748, DOI:

1506. Addition of Ho2O3 of different types to MgB2 in the ex-situ Spark Plasma Sintering: Simultaneous control of the critical current density at low and high magnetic fields

Authors: Aldica, G; Popa, S; Enculescu, M; Batalu, D; Miu, L; Ferbinteanu, M; Badica, P

Published: AUG 14 2014, MATERIALS CHEMISTRY AND PHYSICS, 146, 323, DOI: 10.1016/j.matchemphys.2014.03.030

Two different types of Ho2O3 powders (showing a much different morphology) were added to MgB2 in the ex-situ Spark Plasma Sintering (SPS). In the 5-25 K range, the first Ho2O3 powder type does not significantly suppress the critical current density J(c) at low magnetic fields and the second one enhances it at high fields, while their mixture simultaneously controls J(c) at both small and high magnetic fields so that the decrease is small at low fields and there is a notable enhancement at high fields when compared to pristine sample. The control of J(c)(H) is discussed versus specific characteristics of the raw powders, the resulting microstructure of the added SPS-ed samples and pinning details from magnetic relaxation measurements. (C) 2014 Elsevier B.V. All rights reserved.

1507. Photoluminescence quenching it disordered semiconductors from point of view of the barrier-cluster-heating model

Authors: Banik, I; Popescu, M

Published: NOV-DEC 2014, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 16, 1284, DOI:

The aim of this article is in the first place to familiarize the readers with barrier-cluster-heating model of the non-crystalline semiconductors, then briefly and digestedly present some results achieved by physical phenomena explanation in non-crystalline semiconductors within the frame of this model. The barrier-cluster-heating model of disordered semiconductor gives new view on photoluminescence in disordered semiconductors, too. This model enables to explain Stokes shift, Street's empirical law, fatigue effect, PLE-characteristic, electric field influence on photoluminescence, and some other physical phenomena in disordered semiconductors, including the photoinduced structural changes.

1508. Determination of the Electronic Energy Levels of Colloidal Nanocrystals using Field-Effect Transistors and Ab-Initio Calculations

Authors: Bisri, SZ; Degoli, E; Spallanzani, N; Krishnan, G; Kooi, BJ; Ghica, C; Yarema, M; Heiss, W; Pulci, O; Ossicini, S; Loi, MA

Published: AUG 27 2014, ADVANCED MATERIALS, 26, +, DOI: 10.1002/adma.201400660

Colloidal nanocrystals electronic energy levels are determined by strong size-dependent quantum confinement. Understanding the configuration of the energy levels of nanocrystal superlattices is vital in order to use them in heterostructures with other materials. A powerful method is reported to determine the energy levels of PbS nanocrystal assemblies by combining the utilization of electric-double-layer-gated transistors and advanced ab-initio theory.

1509. Nitrogen-doped and gold-loaded TiO2 photocatalysts synthesized by sequential reactive pulsed laser deposition

Authors: Duta, L; Popescu, C; Popescu, A; Motoc, M; Logofatu, C; Enesca, A; Duta, A; Gyorgy, E

Published: OCT 2014, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 117, 101, DOI: 10.1007/s00339-013-8220-3

Nitrogen-doped titanium oxide thin films covered by gold metal nanoparticles were grown on (001) SiO2 quartz substrates by pulsed laser deposition. A KrF* excimer laser source (lambda = 248 nm, tau (FWHM) a parts per thousand currency sign 25 ns, nu = 10 Hz) was used for the irradiation of TiO2 and gold metal targets. The experiments were performed in controlled reactive oxygen or nitrogen atmosphere. The layers were grown for photocatalytic applications. Evaluation of photocatalytic activity was performed by photodegradation of methyl orange under near-UV light irradiation. Our results show that nitrogen doping and addition of gold nanoparticles have complementary effects, photoactivity being significantly improved as compared to that of pure titanium oxide.

1510. Evidence of A-B site cooperation in the EuFeO3 perovskite from Eu-151 and Fe-57 Mossbauer spectroscopy, EXAFS, and toluene catalytic oxidation

Authors: Florea, M; Alifanti, M; Kuncser, V; Macovei, D; Apostol, N; Granger, P; Parvulescu, VI

Published: JUL 2014, JOURNAL OF CATALYSIS, 316, 140, DOI: 10.1016/j.jcat.2014.04.016

EuFeO3 perovskite was considered as a case study of the cooperative effects of the rare earth and transition metal elements in the total catalytic oxidation of aromatic hydrocarbons. For this purpose, a EuFeO3 perovskite was prepared using the citrate route. Extensive characterization was performed via ex situ and in situ methods. EXAFS revealed that oxygen vacancies are formed in the nearest neighborhood of Fe and next-nearest neighborhood of Eu. Combining Eu-151 and Fe-57 Mossbauer experiments also suggested local oxygen defects in the proximity of the Eu cations during the reaction, as well as cooperative electron delocalization effects between Eu and Fe. XPS has shown the +3 oxidation state of both Eu and Fe cations and the relatively strong ionicity of the Fe-O chemical bonds, as suggested by the weakened 2p(3/2) satellite in the Fe2p spectrum. A systematic change of this satellite with the A cation in AFeO(3) perovskites was also discussed. The thermal treatment of the catalyst at 623 K, in air or toluene, was accompanied by a partial reduction of Fe and a partial oxidation of Eu, respectively. The interaction between the two elements appeared to be influenced mainly by the temperature and only slightly by the sample environment during further treatments. Catalytic oxidation of toluene on this perovskite led only to the production of carbon dioxide and water with no side-product formation from partial oxidation reactions. All the characterization and catalytic results preferably agree with a Volkenstein mechanism. (C) 2014 Elsevier Inc. All rights reserved.

1511. Chalcogenide systems at the border of the glass-formation domain: A key for understanding the memory-switching phenomena

Authors: Popescu, M; Velea, A; Sava, F; Lorinczi, A

Published: JUL 2014, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 251, 1339, DOI: 10.1002/pssb.201350104

The compositions in the ternary chalcogenide systems from the demarcation region between the glass-formation domain (GFD) and the partially or fully crystalline formation domain seem to exhibit outstanding properties. We have shown in this paper that the compositions with the best memory-switching properties are situated at the border of the GFD in many systems. One can use this correlation to find new phase-change materials with better switching properties or to discover GFDs that were not observed yet. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1512. Biomimetic nanocrystalline apatite coatings synthesized by Matrix Assisted Pulsed Laser Evaporation for medical applications

Authors: Visan, A; Grossin, D; Stefan, N; Duta, L; Miroiu, FM; Stan, GE; Sopronyi, M; Luculescu, C; Freche, M; Marsan, O; Charvilat, C; Ciuca, S; Mihailescu, IN

Published: FEB 2014, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 181, 63, DOI: 10.1016/j.mseb.2013.11.007

We report the deposition by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique of biomimetic nanocrystalline apatite coatings on titanium substrates, with potential application in tissue engineering. The targets were prepared from metastable, nanometric, poorly crystalline apatite powders, analogous to mineral bone, synthesized through a biomimetic approach by double decomposition process. For the deposition of thin films, a KrF* excimer laser source was used (lambda = 248 nm, tau(FWHM) <= 25 ns). The analyses revealed the existence, in synthesized powders, of labile non-apatitic mineral ions, associated with the formation of a hydrated layer at the surface of the nanocrystals. The thin film analyses showed that the structural and chemical nature of the nanocrystalline apatite was prevalently preserved. The perpetuation of the non-apatitic environments was also observed. The study indicated that MAPLE is a suitable technique for the congruent transfer of a delicate material, such as the biomimetic hydrated nanohydroxyapatite. (C) 2013 Elsevier B.V. All rights reserved.

1513. New features in the anti-Stokes and Stokes Raman spectra of single-walled carbon nanotubes that are highly separated into their semiconducting and metallic nanotube components

Authors: Baibarac, M; Baltog, I; Mihut, L; Lefrant, S

Published: MAY 2014, JOURNAL OF RAMAN SPECTROSCOPY, 45, 331, DOI: 10.1002/jrs.4473

Surface-enhanced Raman scattering studies were performed using nonresonant (514.5 nm) and resonant (676.4 nm) optical excitations on single-walled carbon nanotubes thoroughly separated into semiconducting (pure 99%) and metallic (pure 98%) components. Regardless of the support (Au or Ag), the metallic nanotubes do not present an anomalous anti-Stokes Raman emission. Regardless of whether an on-resonant or off-resonant optical excitation is used, only the semiconducting nanotubes produce an abnormal anti-Stokes Raman emission that grows when increasing the excitation light intensity or temperature. The Raman studies under light polarized relative to the main nanotube axis demonstrate that only semiconducting nanotubes are sensitive toward changes in the polarization of the excitation light. Copyright (c) 2014 John Wiley & Sons, Ltd.

1514. The Influence of the Microstructure and Morphology of CeO2 Buffer Layer on the Properties of YBCO Films PLD Grown on Ni Tape

Authors: Mihalache, V; Stefan, N; Enculescu, I; Mihailescu, IN; Socol, M; Miroi, M

Published: NOV 2014, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 27, 2485, DOI: 10.1007/s10948-014-2679-9

YBa2Cu3O7-delta films were deposited on CeO2-buffered nickel substrates, with different buffer thickness. Full width at half maximum of rocking curve, Delta(omega), of CeO2 and yttrium barium copper oxide (YBCO), as well as the critical temperature, T-c, of YBCO were shown to be strongly dependent on buffer thickness. They behave similarly but not proportional to the buffer thickness increase. This and the fact that Delta(omega) vs. buffer thickness and T-c vs. buffer thickness for YBCO behave similar with RMS roughness vs. thickness of CeO2 indicates that the surface peculiarity of buffers is responsible for YBCO properties. More precisely, the surface of CeO2 films prepared by the chemical solution route based on propionic acid is prone to agglomerate (de-wet) and the degree of agglomeration depends in an intricate way on buffer thickness. We showed that nor RMS roughness neither (00l) texture degree can define alone the surface suitable for c-axis YBCO nucleation. The {111} faceted grains (even in the case of high (00l) texture) and other defects generated by agglomeration supply a low fraction of (00l) flat terminations of buffer that affect the nucleation of c-axis-oriented YBCO phase. Moreover, the thermal instability of the surface morphology of CeO2 buffers (further development of de-wetting process, {111} faceted grains, etc. during superconducting layer deposition) influence the quality of YBCO films.

1515. Transition in conduction mechanism in GeSi nanostructures

Authors: Palade, C; Lepadatu, AM; Stavarache, I; Teodorescu, VS; Ciurea, ML

Published: 2014, 2014 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 58, DOI:

GeSi-based nanostructures show unique properties which make them suitable for integrated circuit technology. The strong interest is to enhance their electronic properties in order to improve the device performance. In order to obtain fundamental knowledge on the electrical transport taking place in GeSi nanostructures we have investigated the effects of different microstructures on the electrical behavior of GeSi nanostructured films, by modifying the annealing conditions. We manufactured GeSi nanostructured films with equiatomic composition and different structures by co-sputtering followed by adequate annealing under different temperatures. For determining the electrical behavior we performed and modeled current-temperature I - T characteristics taking into account the films structures. We found that the electrical behavior changes with the film structure by evidencing a transition in conduction mechanism. In films that are almost crystallized, being formed of small GeSi nanocrystals separated by thin amorphous regions, the I - T dependence at low temperature is due to thermally activated tunneling of carriers between neighboring nanocrystals. In contrast, in the completely crystallized films with big GeSi nanocrystals and crystallized borders between them, the electrical behavior is a typical polycrystalline one. Our findings help to clarify the conduction mechanisms taking place in GeSi nanostructures and to provide a route to electronic devices with high performance based on these materials.

1516. Mechanisms of pulmonary toxicity developed at low and high doses of dextran-coated magnetite nanoparticles

Authors: Radu, M; Gheorghiu, A; Predoi, D; Hermenean, A; Ardelean, A; Dinischiotu, A

Published: SEP 10 2014, TOXICOLOGY LETTERS, 229, S78, DOI: 10.1016/j.toxlet.2014.06.301

1517. CLADDING WAVEGUIDES REALIZED IN Nd:YAG LASER MEDIA BY DIRECT WRITING WITH A FEMTOSECOND-LASER BEAM

Authors: Pavel, N; Salamu, G; Voicu, F; Jipa, F; Zamfirescu, M

Published: APR-JUN 2014, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 15, 158, DOI:

We report on realization of buried cladding waveguides in Nd:YAG single crystal and ceramic media by direct femtosecond (fs)-laser writing technique. A classical technique that moves the laser medium transversally to the fs-laser beam, as well as a new scheme in which the laser medium has a motion on a helical trajectory during the inscribing process was used. The waveguides laser emission performances at 1.06 and 1.3 mu m have been investigated under the pump at 807 nm with a fiber-coupled diode laser that was operated both in quasi-continuous wave (quasi-cw) and in cw regimes. Laser pulses with energy of 3.45 mJ at 1.06 mu m and of 1.05 mJ at 1.3 mu m (with overall optical-to-optical efficiency of 0.26 and 0.08, respectively) were obtained from a 50 mu m in diameter circular waveguide that was inscribed by the helical-moving techniques in a 5.0-mm long, 1.1-at.% Nd:YAG ceramic medium. Characteristics of the laser emission recorded in cw operation are discussed.

1518. Numerical Procedure for Optimizing Dye-Sensitized Solar Cells

Authors: Mitroi, MR; Fara, L; Ciurea, ML

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/378981

We propose a numerical procedure consisting of a simplified physical model and a numerical method with the aim of optimizing the performance parameters of dye-sensitized solar cells (DSSCs). We calculate the real rate of absorbed photons (in the dye spectral range) G(real)(x) by introducing a factor beta < 1 in order to simplify the light absorption and reflection on TCO electrode. We consider the electrical transport to be purely diffusive and the recombination process only to occur between electrons from the TiO2 conduction band and anions from the electrolyte. The used numerical method permits solving the system of differential equations resulting from the physical model. We apply the proposed numerical procedure on a classical DSSC based on Ruthenium dye in order to validate it. For this, we simulate the J-V characteristics and calculate the main parameters: short-circuit current density J(sc), open circuit voltage V-oc, fill factor FF, and power conversion efficiency eta. We analyze the influence of the nature of semiconductor (TiO2) and dye and also the influence of different technological parameters on the performance parameters of DSSCs. The obtained results show that the proposed numerical procedure is suitable for developing a numerical simulation platform for improving the DSSCs performance by choosing the optimal parameters.

1519. Annealing induced changes in the structure, optical and electrical properties of GeTiO2 nanostructured films

Authors: Stavarache, I; Lepadatu, AM; Teodorescu, VS; Galca, AC; Ciurea, ML

Published: AUG 1 2014, APPLIED SURFACE SCIENCE, 309, 174, DOI: 10.1016/j.apsusc.2014.04.212

The GeTiO2 amorphous films were deposited by magnetron sputtering and subsequently annealed at 400, 550, 600 and 700 degrees C for nanostructuring. The structure of annealed films was investigated by X-ray diffraction and transmission electron microscopy. The transmittance spectra of all annealed GeTiO2 films were measured and simulated by using Bruggeman effective medium approximation considering components of TiO2 anatase, crystalline Ge, GeO2 and voids determined from the structure investigations. The electrical behavior of 400, 600 and 700 degrees C annealed films was studied by measuring current-voltage characteristics. We found that by increasing the annealing temperature the films thickness decreases from 330 nm (as-deposited films) to 290 nm (700 degrees C annealed films). The 400 degrees C annealed films are amorphous, while all the others annealed at higher temperatures are crystallized (X-ray diffraction and transmission electron microscopy). In the 550 and 600 degrees C annealed films we found the (TiGe)O-2 rutile structure which is formed by starting from the GeO2 tetragonal structure with high Ti content. Additionally, these films contain TiO2 anatase structure and cubic Ge nanocrystals. At 700 degrees C annealing temperature, a surface layer of GeO2 tetragonal nanocrystals is formed by Ge diffusion and a part of Ge is lost. The experimental transmittance spectra indicate a broadening of the transparency range by increasing the annealing temperature, and the simulated ones also indicate this behavior with the decrease of Ge content, the experimental and simulated spectra being in good agreement. Also, the increase of annealing temperature produces an increase of electrical conductivity. (C) 2014 Elsevier B.V. All rights reserved.

1520. GeSiO Based Nanostructures: Electrical Behaviour Related to Morphology and Preparation Method

Authors: Ciurea, ML; Teodorescu, VS; Stavarache, I; Lepadatu, AM

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 73, DOI: 10.1007/978-3-662-44479-5_3

The structure of GeSiO films resulted from deposition and annealing conditions draws their electrical behaviour. GeSiO films prepared either by magnetron sputtering or sol-gel method and subsequently annealed are formed of Ge nanocrystals and/or amorphous Ge nanoparticles embedded in amorphous SiO2 matrix. Firstly, the size effect which is the main effect in these systems produces specific quantum confinement energy levels in the enlarged forbidden energy band gap in nanocrystals. Secondly, these films are percolative systems, so that the main conduction mechanisms which govern the electrical behaviour are the tunnelling and hopping between neighbouring Ge nanocrystals or amorphous nanoparticles. Accordingly, the charge transport is strongly determined by the structure and morphology of films.

1521. Intrinsic energy band alignment of functional oxides

Authors: Li, SY; Chen, F; Schafranek, R; Bayer, TJM; Rachut, K; Fuchs, A; Siol, S; Weidner, M; Hohmann, M; Pfeifer, V; Morasch, J; Ghinea, C; Arveux, E; Gunzler, R; Gassmann, J; Korber, C; Gassenbauer, Y; Sauberlich, F; Rao, GV; Payan, S; Maglione, M; Chirila, C; Pintilie, L; Jia, LC; Ellmer, K; Naderer, M; Reichmann, K; Bottger, U; Schmelzer, S; Frunza, RC; Ursic, H; Malic, B; Wu, WB; Erhart, P; Klein, A

Published: JUN 2014, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 8, 576, DOI: 10.1002/pssr.201409034

The energy band alignment at interfaces between different materials is a key factor, which determines the function of electronic devices. While the energy band alignment of conventional semiconductors is quite well understood, systematic experimental studies on oxides are still missing. This work presents an extensive study on the intrinsic energy band alignment of a wide range of functional oxides using photoelectron spectroscopy with in-situ sample preparation. The studied materials have particular technological importance in diverse fields as solar cells, piezotronics, multiferroics, photoelectrochemistry and oxide electronics. Particular efforts have been made to verify the validity of transitivity, in order to confirm the intrinsic nature of the obtained band alignment and to understand the underlying principles. Valence band offsets up to 1.6 eV are observed. The large variation of valence band maximum energy can be explained by the different orbital contributions to the density of states in the valence band. The framework provided by this work enables the general understanding and prediction of energy band alignment at oxide interfaces, and furthermore the tailoring of energy level matching for charge transfer in functional oxides. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1522. New multicomponent catalysts for the selective aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine

Authors: Opris, CM; Pavel, OD; Moragues, A; El Haskouri, J; Beltran, D; Amoros, P; Marcos, MD; Stoflea, LE; Parvulescu, VI

Published: 2014, CATALYSIS SCIENCE & TECHNOLOGY, 4, 4355, DOI: 10.1039/c4cy00795f

Aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine was carried out on new gold-based catalysts using as support bimodal UVM-7-like mesoporous silica containing Ni and Ce (or Sn) as oxide nanodomains partially embedded inside the mesoporous UVM-7 silica walls. These nanodomains acted as effective and stable inorganic anchors favoring the nucleation, growth and stability of supported gold particles. Following the atrane method ( a "one-pot" strategy able to harmonize the hydrolytic reactivity of different heteroelements through the use of complexes containing triethanolamine-derived ligands (atranes) as precursors) the stability of the oxide nanodomains during oxidation and thermal treatments was ensured. The catalysts were prepared using a two-step synthesis in which gold was incorporated through impregnation of previously synthesized bimodal porous silicas containing different heteroelements trapped by the silica mesostructure. The versatility of the preparative approach allowed the high surface area and accessibility of mesoporous silica and also an easy and homogeneous inclusion of heteroelements in one pot. Aerobic oxidative condensation of benzylamine on these catalysts occurred selectively only with the formation of N-benzylidenebenzylamine. While selectivity was total, the productivities (mol(product) g(cat)(-1) h(-1)) varied in a wide range as a function of catalyst composition (chemical composition and atomic ratios of the constitutive support elements). The catalytic behavior was merely controlled by the size of gold particles, but the support also exerts an influence. The best results were obtained on the mesoporous Au/Ce-60-Ni-10-UVM-7 catalyst having a 0.97( wt.%) gold content ( in the form of nanoparticles of ca. 4 nm) and preserving a relatively high surface area ( 566 m(2) g(-1)) and pore volume ( 0.91 cm(3) g(-1)). The comparison with the individual or bicomponent catalysts led to the conclusion of a cooperative interaction between the catalyst components. However, gold itself exhibits a higher activity than the promoters or co-catalysts (i.e. phases containing Ni and/or Ce).

1523. Formation and annealing of boron-oxygen defects in irradiated silicon and silicon-germanium n(+)-p structures

Authors: Makarenko, LF; Lastovskii, SB; Korshunov, FP; Moll, M; Pintilie, I; Abrosimov, NV

Published: 2014, INTERNATIONAL CONFERENCE ON DEFECTS IN SEMICONDUCTORS 2013, 1583, 126, DOI: 10.1063/1.4865618

New findings on the formation and annealing of interstitial boron-interstitial oxygen complex (BiOi) in p-type silicon are presented. Different types of n(+)-p structures irradiated with electrons and alpha-particles have been used for DLTS and MCTS studies. Electronic excitation essentially changes the formation rate of BiOi. It has been found that the increase of oxygen content slows the BiOi annealing rate down. The activation energy of the BiOi dissociation has been determined and it was found that germanium doping does not change the activation energy.

1524. Structural, down- and phase selective up-conversion emission properties of mixed valent Pr doped into oxides with tetravalent cations

Authors: Tiseanu, C; Parvulescu, V; Avram, D; Cojocaru, B; Apostol, N; Vela-Gonzalez, AV; Sanchez-Dominguez, M

Published: 2014, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 16, 5802, DOI: 10.1039/c3cp54899f

We report on structure-property relationships in Pr-doped CeO2 and ZrO2 using X-ray diffraction (XRD), Raman, UV to Vis Diffuse Reflectance (DR-UV/Vis), X-ray Photoelectron (XPS), and luminescence (PL) spectroscopies. Both 3+ and 4+ valence states of Pr are evidenced, irrespective of the host and calcination temperature, T (T = 500 and 1000 degrees C) with consequences on absorption, surface, vibrational and luminescence properties. Only zirconia represents a suitable host for Pr3+ luminescence. The distinct trivalent Pr centers and their excitation mechanism are identified in relation to the tetragonal and monoclinic phases of ZrO2. A near-infrared to visible up-conversion (UPC) emission of Pr3+ is observed upon excitation at 959 nm which occurs, most probably, via a two-photon excited state process. By using a multi-wavelength, time-gated excitation, the UPC process is established as phase selective, i.e. only Pr3+ located in the monoclinic sites of the mixed phase, monoclinic and tetragonal ZrO2 (T = 1000 degrees C) contribute to the UPC emission. We believe that, besides the local symmetry, a key role in phase selective UPC is played by the presence of Pr3+ low-lying 4f 5d levels. To the best of our knowledge, this is the first report of phase selective up-conversion emission in a lanthanide doped multi-phase host.

1525. Porous Methyltrimethoxysilane Coated Nanoscale-Hydroxyapatite for Removing Lead Ions from Aqueous Solutions

Authors: Ciobanu, CS; Iconaru, SL; Popa, CL; Costescu, A; Motelica-Heino, M; Predoi, D

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/361061

The aim of this study was to synthetize new porous nanoparticles based on methyltrimethoxysilane coated hydroxyapatite (MTHAp) for lead removal form aqueous solutions. The morphological and compositional analysis of MTHAp were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+ at a fixed pH value of 3 and 5 respectively. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into PbMTHAp_3 and PbMTHAp_5 via the adsorption of Pb2+ ions followed by a cation exchange reaction. The X-ray diffraction spectra of PbMTHAp_3 and PbMTHAp_5 revealed that the powders, after removal of the Pb2+ ions, were a mixture of Ca2.5Pb7.5(PO4)(6) (OH) 2, Pb2Ca4(PO4)(2)(SiO4), and Ca-10(PO4)(6)(OH)(2). Our results demonstrate that the porous hydroxyapatite nanoparticles can be used as an adsorbent for removing Pb2+ ions from aqueous solutions.

1526. Electrical properties related to the structure of GeSi nanostructured films

Authors: Ciurea, ML; Stavarache, I; Lepadatu, AM; Pasuk, I; Teodorescu, VS

Published: JUL 2014, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 251, 1346, DOI: 10.1002/pssb.201350112

GeSi nanostructured films were obtained by cosputtering from two Ge and Si targets and subsequent annealing in furnace in N-2 for 5 h at 700, 800 and 900 degrees C, with the aim to show the correlation between electrical properties and crystalline structure of the films. The as-deposited films are amorphous, have a Ge: Si composition of 55: 45 and 185 nm thickness. The film structure was investigated by XRD and TEM, and the electrical behaviour was studied by measuring current-voltage (I-V) and current-temperature (I-T) characteristics and by discussing them in correlation with the structure. Different electrical behaviours of GeSi films corresponding to different structures have been evidenced. The 700 degrees C annealed GeSi films are formed of nanocrystals (7-15 nm) separated by amorphous regions (1-2 nm). These films present a superlinear I-V characteristic typical of high field-assisted tunnelling through potential barriers (amorphous regions) between nanocrystals. The I-T characteristic at low temperature follows a T-1/2 law showing a thermally activated tunnelling of carriers between neighboring GeSi nanocrystals. The films annealed at 800 and 900 degrees C have a like behavior, they are completely crystallized and present linear I-V and Arrhenius I-T dependences reflecting the polycrystalline behaviour. [GRAPHICS] . (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1527. Laser Emission from Diode-Pumped Nd:YAG Cladding Waveguides Obtained by Direct Writing with a Femtosecond-Laser Beam

Authors: Salamu, G; Voicu, F; Jipa, F; Zamfirescu, M; Dascalu, T; Pavel, N

Published: 2014, LASER SOURCES AND APPLICATIONS II, 9135, DOI: 10.1117/12.2052250

Cladding waveguides have been realized in Nd:YAG by direct writing with a femtosecond-laser beam. A classical method that inscribes many tracks around the waveguide circumference with step-by-step translations of the laser medium, and a new technique in which the laser medium is moved on a helical trajectory and that delivers waveguides with well-defined walls were employed. Laser emission on the 1.06 mu m F-4(3/2)-> I-4(11/2) transition and at 1.3 mu m on the F-4(3/2)-> I-4(13/2) line was obtained under the pump with a fiber-coupled diode laser. Thus, laser pulses at 1.06 mu m with energy of 1.3 mJ for the pump at 807 nm with pulses of 12.5-mJ energy were recorded from a circular waveguide of 100-mu m diameter that was inscribed in a 5-mm long, 0.7-at.% Nd: YAG single crystal by the classical translation technique. A similar waveguide that was realized in a 5-mm long, 1.1-at.% Nd: YAG ceramic increased the 1.06-mu m laser pulse energy to 2.15 mJ for the pump pulses of 13.1-mJ energy. Furthermore, a circular waveguide of 100-mu m diameter that was inscribed in the Nd: YAG ceramic by the helical-movement method yielded pulses at 1.06 mu m with increased maximum energy of 3.2 mJ; the overall optical-to-optical efficiency was 0.24, and the laser operated with a slope efficiency of 0.29. The same device outputted laser pulses at 1.3 mu m with energy of 1.15 mJ.

1528. Self-organization and Size Effects in Amorphous Silicon

Authors: Popescu, M; Sava, F; Velea, A

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 45, DOI: 10.1007/978-3-662-44479-5_2

Self-organization and size effects in amorphous silicon have been investigated by modelling of the structure at nanoscale. The size effect related to the disorder in silicon is treated by the free energy balance in nanometric clusters using valence force field theory. The computed structural and energetical parameters of three continuous random network (CRN) models of amorphous silicon with 2,052, 156 and 155 atoms are compared with the experimental values. In order to show the importance of the interfaces between different a-Si clusters, two networks of 200 and 205 atoms were modelled separately and then linked using an amorphous and a crystalline interface. Also the voids in the a-Si clusters are investigated.

1529. Doping of MgB (2) Using Molecular Magnets as Precursors

Authors: Sandu, V; Badica, P; Aldica, G; Ferbinteanu, M; Hayasaka, Y

Published: AUG 2014, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 27, 1843, DOI: 10.1007/s10948-014-2538-8

We present the effect of single molecular magnet ([Fe(bpca) Dy-2(NO (3))(4)] a <...H (2) Oa <...4.5 CH (3) NO (2) and [Mn (2)(naften) (2)(CH 3COO)(CH 3OH)] a <...BPh (4)) thermolysis on the superconducting properties of polycrystalline MgB (2) samples when inserted and sintered by spark plasma sintering technique. As a result of pyrolysis, Fe- and Dy-magnetic compounds grow within the MgB (2) matrix and give a paramagnetic behavior in normal state, whereas the Mn-based compounds display negligible magnetic properties. We find that the magnetic critical current density of the as-obtained superconducting composites, as well as the pinning mechanism, is dependent on the magnetic background, with a noticeable advantage for the sample with magnetic compounds.

1530. BiFeO3 doped-BNT-BT0.08 piezoelectric and magnetic nanowires, derived from sol-gel precursor

Authors: Cernea, M; Trupina, L; Vasile, B; Bartha, C; Radu, R; Chirila, C; Teodorescu, A

Published: JAN 10 2014, JOURNAL OF NANOPARTICLE RESEARCH, 16, DOI: 10.1007/s11051-013-2231-z

Lead-free piezoelectric (Bi0.5Na0.5)(0.92)Ba0.08TiO3, doped with 5 mol %BiFeO3 (BNT-BT-BFO) nanowires was prepared from its corresponding precursor sol. A polycarbonate membrane with the thickness of 30 mu m and the pore diameter of 100 nm was used as template. Nanowires with average diameter of similar to 80 nm and different lengths of a few microns were prepared from BNT-BT-BFO precursor sol with similar to 0.03 M concentration. Ferroelectric and piezoelectric characterizations of BNT-BT-BFO nanowires were performed using AFM-PFM equipment. The HR-TEM micrograph of nanocrystals, SAED patterns, and XRD pattern indicated that BNT-BT-BFO nanowires crystallized on the lattice of rhombohedral (Na0.5Bi0.5TiO3) phase. The BNT-BT-BFO nanowires showed a significant piezoelectric response, suggesting a good piezoelectric behavior. The saturation magnetization of the nanowires, measured at room temperature and at 5 kOe magnetic field, was Ms = 0.061 emu/g. A saturated ferromagnetic hysteresis loop has been also obtained.

1531. Photoluminescence of Eu-doped LiYF4 thin films grown by pulsed laser deposition and matrix-assisted pulsed laser evaporation

Authors: Stokker-Cheregi, F; Matei, A; Dinescu, M; Secu, CE; Secu, M

Published: JAN 29 2014, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 47, DOI: 10.1088/0022-3727/47/4/045304

Matrix-assisted pulsed laser evaporation (MAPLE) has been investigated as an alternative to the pulsed laser deposition (PLD) technique for Eu3+-doped crystalline LiYF4 thin-films deposition. MAPLE assumes laser ablation of a frozen target made of the material of interest diluted in a solvent, rather than that of a bulk target, of either pressed powder or single crystal, used in the case of PLD. Our approach stems from the assumption that laser ablation of a frozen dilute target would result in thin films with improved morphology, as compared to PLD. Indeed, we find that roughness values of samples obtained by the MAPLE technique are four times lower than in the case of PLD. A lower transmittance was noticed for PLD obtained layers with respect to those grown by MAPLE due to strong scattering of light by the morphological defects. Photoluminescence spectra are showing characteristic Eu3+-ion luminescence bands at 578, 591, 612, 650 and 698 nm (D-5(0) -> F-7(J)); crystal field splitting of the bands indicates dopant ions incorporation in the host material during transfer by either PLD or MAPLE.

1532. BaFBr:Eu2+ nanophosphor-SiO2 hybrid entrapped in Anodise Alumina membrane pores array

Authors: Secu, CE; Matei, E; Secu, M; Damian, V

Published: SEP 2014, RADIATION MEASUREMENTS, 68, 41, DOI: 10.1016/j.radmeas.2014.07.001

Sol-gel template method has been used to prepare BaFBr:Eu2+ nanophosphor-SiO2 hybrid entrapped within the nanopores array (of about 200 nm size) of a comercial anodized alumina (AA) membrane. Structural and morphological measurements using electron microscopy (SEM) and X-ray diffraction (XRD) have shown the presence of the BaFBr:Eu2+ nanophosphor in the silica xerogel entrapped within the nanopores array; photoluminescence and X-ray excited luminescence measurements have shown Eu2+ luminescence at 395 nm accompanied by a broad band due to AA membrane. The method assures a relatively uniform spreading of the BaFBr nanophosphor into the AA membrane pores array without the nanoparticles agglomeration. Preliminary imaging tests have shown a spatial resolution in the micrometer range and even in the submicrometer range can be expected. As BaFBr:Eu2+ is a very efficient Xray phosphor the material might be used as X-ray micro-imaging detector. (C) 2014 Elsevier Ltd. All rights reserved.

1533. Indium-tin nanoscaled oxides synthesized under hydrothermal supercritical and postannealing pathway: Phase dynamics and characterization

Authors: Diamandescu, L; Tarabasanu-Mihaila, D; Feder, M; Enculescu, M; Teodorescu, VS; Constantinescu, S; Popescu, T; Bartha, C; Pap, Z

Published: FEB 14 2014, MATERIALS CHEMISTRY AND PHYSICS, 143, 1549, DOI: 10.1016/j.matchemphys.2013.11.064

With the aim of synthesizing the mixed nanoparticle system xIn(2)O(3)-(1-x)SnO2 over all molar concentration range 0 <= x <= 1, Delta x = 0.1, we performed hydrothermal supercritical experiments on indium-tin hydrogel resulted from InCl3-SnCl4 water solution. Nanophases isostructural with InOOH and SnO2 were obtained by hydrothermal reaction at 400 degrees C, in the molar concentration range of 0.1 <= x <= 0.7; at x = 0.8 and x = 0.9 only one phase, isostructural with InOOH, was observed. Samples calcined at 500 degrees C with x in the range of 0.2 <= x <= 0.7 contain a nanoscaled phase isostructural with rhombohedral In2O3 and a second one isostructural with tetrahedral SnO2. At x = 0.8 and x = 0.9 only one phase isostructural with rhombohedral In2O3 appears: rhombohedral ITO phase. The determined band gap energies could recommend the rhombohedral ITO structure for visible light photocatalytic applications. The phase dynamics together with the concentration range for existence of the solid solutions in the InOOH-SnO2 and In2O3-SnO2 composite semiconducting nanoparticle systems have been evidenced and discussed. (C) 2013 Elsevier B.V. All rights reserved.

1534. Cell Adhesion Response on Femtosecond Laser Initiated Liquid Assisted Silicon Surface

Authors: Ulmeanu, M; Sima, LE; Ursescu, D; Enculescu, M; Bazan, X; Quintana, I

Published: MAR 2014, CURRENT TOPICS IN MEDICINAL CHEMISTRY, 14, 629, DOI: 10.2174/1568026614666140118204946

Silicon substrates were irradiated at normal incidence with a femtosecond Ti:sapphire laser (Quatronix, 90 fs pulse duration, 1 kHz repetition rate, M-2 similar to 1.2, maximum energy peak 350 mJ) operating at a wavelength of 400 nm and focused via a microscope objective (Newport; UV Objective Model, 37x 0.11 N.A.). The laser scanning was assisted by liquids precursors media such as methanol and 1,1,2-trichlorotrifluoroethane. By altering the processing parameters, such as incident laser energy, scanning speed, and different irradiation media, various surface structures were produced on areas with 1 mm 2 dimensions. We analyzed the dependence of the surface morphology on laser pulse energy, scanning speed and irradiation media. Well ordered areas are developed without imposing any boundary conditions for the capillary waves that coarsens the ripple pattern. To assess biomaterial-driven cell adhesion response we investigated actin filaments organization and cell morphological changes following growth onto processed silicon substrates. Our study of bone cell progenitor interaction with laser nanoprocessed silicon lines has shown that cells anchor mainly to contact points along the nanostructured surface. Consequently, actin filaments are stretched towards the 15 mu m wide parallel lines increasing lateral cell spreading and changing the bipolar shape of mesenchymal stem cells.

1535. Simulation of the structure of GeAs4Te7 chalcogenide materials during memory switching

Authors: Popescu, M; Sava, F; Velea, A; Lorinczi, A; Simandan, ID

Published: JUL 2014, CANADIAN JOURNAL OF PHYSICS, 92, 680, DOI: 10.1139/cjp-2013-0561

The complex chalcogenides with excellent memory switching properties are mainly situated close to the border of glass formation domain. The simulation of the structural changes occurring during the memory switching process of a ternary chalcogenide composition has been carried out. The transition of a high resistivity GeAs4Te7 amorphous cluster with 120 atoms to a low resistivity crystalline cluster was analyzed. The coordination of atoms changes from that corresponding to 8-N coordination rule (two for tellurium, three for arsenic, and four for germanium) in the amorphous phase to six (the same for all atoms) in metastable crystalline phase. Because of spatial constraints exercised by the amorphous matrix, the amorphous cluster cannot expand. In these circumstances Te atoms seem to be over-coordinated (up to sixfold-coordinated). During the switching process, the atoms are moving on distances up to 4.0 angstrom. The average displacement is of 2.36 angstrom.

1536. DEPENDENCE ON THE DYE'S TYPE AND CONCENTRATION OF THE EMISSIVE PROPERTIES OF ELECTROSPUN DYE-DOPED BEADED NANOFIBERS

Authors: Enculescu, M; Evanghelidis, A; Busuioc, C; Florica, C; Costas, A; Oancea, M; Preda, N; Matei, E; Enculescu, I

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 816, DOI:

Luminescent polymer fibers were obtained by electrospinning solutions of 8% (in ethanol) polyvinylpyrrolidone (PVP) doped with three different dyes (coumarin 6, rhodamine 6G and sulforhodamine 101). Using the same parameters for the electrospinning process, nanofibers with diameters between 200 and 800 nm and different sizes and distributions of the beads were obtained as proven by scanning electron microscopy (SEM). We assessed the dependence of their emissive properties (intensity and wavelength) on the type of dye using photoluminescence (PL) spectra for the same concentration of the dopand dye (10(-3)M). Moreover, employing 4 different concentrations for coumarin 6 and rhodamine 6G (from 10(-3) to 10(-6) M) we evaluated the dependence with the concentration of the dye on the emissive properties of the electrospun dye-doped PVP nanofibers.

1537. Abnormal anti-Stokes Raman scattering and coherent backscattering as manifestation of Anderson localization of light in nonlinear mesoscopic materials

Authors: Smaranda, I; Mihut, L; Baibarac, M; Baltog, I; Lefrant, S

Published: SEP 2014, OPTICAL ENGINEERING, 53, DOI: 10.1117/1.OE.53.9.097109

We demonstrate that under continuous single-beam excitation, one can generate an abnormal antiStokes Raman emission (AASRE) whose properties are similar to a coherent anti-Stokes Raman scattering. The effect has been observed in mesoscopic materials, which possess intrinsically nonlinear properties [lithium niobate (LiNbO3), bismuth germanium oxide (Bi12GeO20; BGO), bismuth silicon oxide (Bi12GeO20; BSO)], which have a nonzero electric susceptibility of the third order, chi((3)) not equal 0. Corroborated Raman and coherent backscattering studies demonstrate that the occurrence of both effects is conditioned by the existence of a mesoscopic morphology of the sample, which is able to ensure efficient transport of the light inside the sample through a multiple light scattering mechanism. In this context, both AASRE and coherent backscattering effects are because of the Anderson localization of the light. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

1538. First principles calculations, neutron, and x-ray diffraction investigation of Y3Ni13B2, Y3Co13B2, and Y3Ni10Co3B2

Authors: Plugaru, N; Valeanu, M; Plugaru, R; Campo, J

Published: JAN 14 2014, JOURNAL OF APPLIED PHYSICS, 115, DOI: 10.1063/1.4862163

Fully relativistic calculations within the local spin density approximation and the generalized gradient approximation were performed to determine the local spin and orbital magnetic moments, as well as the magnetocrystalline anisotropy energy of Y3Ni13B2, Y3Co13B2, and Y3Ni10Co3B2 compounds. A weak in-plane magnetic anisotropy is determined for Y3Ni13B2, under the assumption of a crystallographic-like magnetic unit cell and collinear magnetic moments. The calculations predict considerable c-axis anisotropy for Y3Co13B2 and Y3Ni10Co3B2, but smaller than that of YCo5. The values of the magnetocrystalline anisotropy energy correlate well with both the magnitude of the orbital magnetic moment and the orbital magnetic moment anisotropy. The mixing between Co or Ni 3d states and B 2p states, observable at the bottom of the valence band of the 3d metal having a boron atom nearest neighbor, decreases the 3d spin and especially, the 3d orbital magnetic moments. Y3Ni13B2 and Y3Ni10Co3B2 were also investigated by powder neutron diffraction experiments, at temperatures between 1.8 and 249 K. The Co and Ni site averaged magnetic moments calculated in the mixed compound are in fair agreement with the values obtained by the refinement of the magnetic contribution to the diffraction pattern. (C) 2014 AIP Publishing LLC.

1539. Charge storage properties of HfO2/Ge-HfO2/SiO2 trilayer structures

Authors: Palade, C; Slav, A; Lepadatu, AM; Teodorescu, VS; Ciurea, ML

Published: 2014, 2014 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 62, DOI:

We report on the charge storage properties of trilayer structures consisting in sputtered gate HfO2/co-sputtered Ge-HfO2 layer/rapid thermal tunneling SiO2 oxide. Investigations of transmission electron microscopy and X-ray diffraction evidence the formation of HfO2 with mixed structure of monoclinic and tetragonal in the annealed structures. Capacitance-voltage (C-V) characteristics were measured on Al/HfO2/Ge-HfO2/SiO2/Si/Al metal-oxide-semiconductor capacitors based on as-deposited and annealed structures. Large C-V hysteresis is observed for the as-deposited structures and is controlled by traps present in oxide and interface. The annealing yields a C-V hysteresis with smaller memory window being due to injected charges in Ge nanocrystals.

1540. ZnS and ZnO Semiconductor Nanoparticles Doped with Mn2+ Ions. Size Effects Investigated by EPR Spectroscopy

Authors: Stefan, M; Nistor, SV; Ghica, D

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 27, DOI: 10.1007/978-3-662-44479-5_1

Electron paramagnetic resonance (EPR) spectroscopy has been extensively employed to investigate the presence, localization, distribution and interaction with the host crystalline lattice of the paramagnetic point defects (intrinsic defects and transition metal ions) in semiconductors. The retrieval of such information for nanostructured semiconductors is considerably more difficult, due to the high disorder level in such systems, reflected in broad, featureless EPR spectra. We show here how, with proper adjustments of the EPR experiments and accurate numerical analysis of the resulting spectra, it was possible to obtain more accurate information regarding the localization and structure of various Mn2+ centers in ZnS and ZnO semiconductor nanoparticles (NPs). This lead to the observation and investigation of size related effects such as the presence of the extended lattice defect assisted incorporation of impurities in small (similar to 3 nm) cubic ZnS NPs, the dominant size induced lattice disorder observed for ZnO NPs, independent of the synthesis procedures, or the three steps decomposition of the epsilon-Zn(OH)(2) disordered shell of ZnS NPs with formation of new oxy-hydrated zinc compounds. These effects can be used to synthesize semiconductor nanoparticles with controlled size distribution, doping level and functionalized surfaces for specific technological applications.

1541. Trapping centers in heavy ion irradiated silicon

Authors: Palade, C; Lazanu, S; Ciurea, ML

Published: 2014, 2014 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 128, DOI:

Low fluence heavy ions incident on high resistivity Si produce lattice defects which act as trapping centers, and produce also an important local field of strain. The strain field intensity increases with the increase of the difference in atomic size and mass between the ion and the Si atom host. We investigate the correlation between the change of trapping parameters and the strain field. The strain field produced by Bi ions in Si is two times more intense than in Si irradiated with I ions, and effects the Gaussian broadening of trapping levels and the temperature dependence of cross sections.

1542. Synthesis and characterisation of Ni(II), Cu(II), and Zn(II) complexes with an acyclic Mannich base functionalised with thioglycolate moiety

Authors: Dumbrava, A; Olar, R; Badea, M; Grecu, MN; Patrascu, F; Marutescu, L; Stanica, N

Published: MAR 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 115, 2455, DOI: 10.1007/s10973-013-3437-0

New complexes ML(CNS)center dot nH(2)O [M = Ni, n = 0.5; M = Cu, n = 4.5; M = Zn, n = 0.5, HL: 6-mercapto-(1,4,8,11-tetraazaundecanyl)-6-carboxylic acid)] have been synthesised, chemical analysed, and characterised by different spectroscopic techniques (IR, UV-Vis-NIR, H-1 NMR, EPR, ESI-MS), and magnetic measurements. Based on the IR spectra a dinuclear structure with the 1,3-CSN coordination was proposed for Ni(II) and Cu(II) complexes. The dinuclear structure of Cu(II) complex is also consistent with both magnetic behaviour and EPR spectrum. According to TG, DTG and DTA curves the thermal transformations are complex processes, including dehydration, Mannich base oxidative degradation and thiocyanate decomposition. The final product of decomposition is the most stable metallic oxide, as XRD data indicates. The new complexes were also screened for their microbicidal and antibiofilm properties.

1543. Epitaxial growth of Au on Ge(001) surface: Photoelectron spectroscopy measurements and first-principles calculations

Authors: Popescu, DG; Husanu, MA

Published: FEB 3 2014, THIN SOLID FILMS, 552, 249, DOI: 10.1016/j.tsf.2013.12.049

A single atomic Au layer is grown epitaxially on a Ge(001) surface featured by (2 x 1) reconstruction. The low energy electron diffraction pattern of the Au/Ge(001) surface indicates the formation of a square structure with the length of crystalline domains of similar to 3 nm. Ab-initio calculations show that Au growth stabilizes the Ge surface in symmetric dimers and angle-resolved photoelectron spectroscopy measurements reveal its metallic character. The modifications in the electronic properties of the Ge surface as a result of annealing are discussed and the consequences as reflected in X-ray photoelectron spectroscopy (XPS) measurements are underlined. The deformation density indicates the regions with covalent Au-Ge bonds. These bonds are identified from Au 4f and Ge 3d XPS data. (C) 2013 Elsevier B.V. All rights reserved.

1544. Superhydrophobic ZnO networks with high water adhesion

Authors: Florica, C; Preda, N; Enculescu, M; Zgura, I; Socol, M; Enculescu, I

Published: AUG 8 2014, NANOSCALE RESEARCH LETTERS, 9, DOI: 10.1186/1556-276X-9-385

ZnO structures were deposited using a simple chemical bath deposition technique onto interdigitated electrodes fabricated by a conventional photolithography method on SiO2/Si substrates. The X-ray diffraction studies show that the ZnO samples have a hexagonal wurtzite crystalline structure. The scanning electron microscopy observations prove that the substrates are uniformly covered by ZnO networks formed by monodisperse rods. The ZnO rod average diameter and length were tuned by controlling reactants' concentration and reaction time. Optical spectroscopy measurements demonstrate that all the samples display bandgap values and emission bands typical for ZnO. The electrical measurements reveal percolating networks which are highly sensitive when the samples are exposed to ammonia vapors, a variation in their resistance with the exposure time being evidenced. Other important characteristics are that the ZnO rod networks exhibit superhydrophobicity, with water contact angles exceeding 150 degrees and a high water droplet adhesion. Reproducible, easily scalable, and low-cost chemical bath deposition and photolithography techniques could provide a facile approach to fabricate such ZnO networks and devices based on them for a wide range of applications where multifunctionality, i.e., sensing and superhydrophobicity, properties are required.

1545. Recent progress in the synthesis of magnetic titania/iron-based, composite nanoparticles manufactured by laser pyrolysis

Authors: Fleaca, CT; Scarisoreanu, M; Morjan, I; Alexandrescu, R; Dumitrache, F; Luculescu, C; Morjan, IP; Birjega, R; Niculescu, AM; Filoti, G; Kuncser, V; Vasile, E; Danciu, V; Popa, M

Published: MAY 30 2014, APPLIED SURFACE SCIENCE, 302, 204, DOI: 10.1016/j.apsusc.2013.10.138

We report the continuous, single step synthesis of titania/iron-based magnetic nanocomposites in a single step using gas-phase laser pyrolysis technique by separately and simultaneously introducing the precursors (together with C2H4 sensitizer) in the reaction zone: Fe(CO)(5) on the central flow and, using air as carrier, TiCl4 on the annular coflow. The laser power and, for the last experiment, the injection geometry were modified in order to change the Fe/Ti ratio in the resulted nanopowders. Due to the specific geometry, the reaction zone (visible as a flame) have a reductive inner central zone surrounded by and oxidative environment, allowing the formation of the metallic-carbidic iron and/or iron-doped titania and iron oxide nanophases. The raw Fe-containing nanopowders have a ferromagnetic behavior, those synthesized at higher laser power and gas velocities show significant saturation magnetization M-s values (10-12 emu/g), whereas those obtained (with higher yield and carbon content) at lower laser power and gas velocities (using wider central nozzle cross-section) have a very weak magnetization (M-s similar to 0.05 emu/g) in spite of the higher ethylene carried Fe(CO)(5) flow. The powders were annealed in air at 400 degrees C show lower carbon content and, for those highly Fe-doped, the hematite phase formation. Preliminary tests using UV light confirm the photocatalytic action of the annealed nanopowders in salicylic acid degradation process in solution. (C) 2013 Elsevier B.V. All rights reserved.

1546. Influence of the Carbo-Chromization Process on the Microstructural, Hardness, and Corrosion Properties of 316L Sintered Stainless Steel

Authors: Iorga, S; Cojocaru, M; Chivu, A; Ciuca, S; Burdusel, M; Badica, P; Leuvrey, C; Schmerber, G; Ulhaq-Bouillet, C; Colis, S

Published: JUN 2014, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 45A, 3096, DOI: 10.1007/s11661-014-2247-8

We report on the changes on the microstructural, hardness, and corrosion properties induced by carbo-chromization of 316L stainless steel prepared by Spark Plasma Sintering technique. The thermo-chemical treatments have been performed using pack cementation. The carburizing and chromization were carried out between 1153 K (880 A degrees C)/4 h to 1253 K (980 A degrees C)/12 h and 1223 K (950 A degrees C)/6 h to 1273 K (1000 A degrees C)/12 h in a solid powder mixture of charcoal/BaCO3 and ferrochromium/alumina/NH4Cl, respectively. The obtained layers were investigated using X-ray and electron diffraction, optical and scanning electron microscopies, Vickers micro-hardness, and potentiodynamic measurements. The thickness of the carbo-chromized layer ranges between 300 and 500 mu m. Besides the host gamma-phase, the layers are mainly constituted of carbides (Fe7C3, Cr23C6, Cr7C3, and Fe3C) and traces of alpha'-martensite. The average hardness values decrease smoothly from 650 HV at the sample surface down to 200 HV at the center of the sample. The potentiodynamic tests revealed that the carbo-chromized samples have smaller corrosion resistance with respect to the untreated material. For strong chromization regimes, the corrosion rate is increased by a factor of four with respect to that of the untreated material, while the micro-hardness of the layer is three times larger. Such materials are suited to be used in environments where good corrosion resistance and wear properties are required.

1547. Lanthanide-lanthanide and lanthanide-defect interactions in co-doped ceria revealed by luminescence spectroscopy

Authors: Avram, D; Gheorghe, C; Rotaru, C; Cojocaru, B; Florea, M; Parvulescu, V; Tiseanu, C

Published: DEC 15 2014, , DOI: 10.1016/j.jallcom.2014.07.059

1548. Tough and dense boron carbide obtained by high-pressure (300 MPa) and low-temperature (1600 degrees C) spark plasma sintering

Authors: Badica, P; Grasso, S; Borodianska, H; Xie, SS; Li, PF; Tatarko, P; Reece, MJ; Sakka, Y; Vasylkiv, O

Published: APR 2014, JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 122, 275, DOI: 10.2109/jcersj2.122.271

Dense boron carbide (above 95%) was achieved through high pressure (300 MPa) and low temperature (1600 degrees C) Spark Plasma Sintering (SPS). This approach resulted in improvement of fracture toughness and of dynamic toughness when compared to corresponding toughness values of the sample sintered by conventional SPS (2100 degrees C, 50 MPa). Dynamic toughness was extracted from Split Hopkinson Pressure Bar measurements. Results are understood based on microstructure and on very different behaviour of the samples in respect to residual B2O3 and carbon available in the raw B4C powder. (C) 2014 The Ceramic Society of Japan. All rights reserved.

1549. Graphenes in the absence of metals as carbocatalysts for selective acetylene hydrogenation and alkene hydrogenation

Authors: Primo, A; Neatu, F; Florea, M; Parvulescu, V; Garcia, H

Published: OCT 2014, , DOI: 10.1038/ncomms6291

1550. Electric-field-induced transformations in epitaxial relaxor ferroelectric PbMg1/3Nb2/3O3 films

Authors: Tyunina, M; Pintilie, I; Iuga, A; Pintilie, L

Published: MAR 24 2014, PHYSICAL REVIEW B, 89, DOI: 10.1103/PhysRevB.89.094106

Electric-field-induced transformations are studied experimentally in cube-on-cube-type epitaxial film of relaxor ferroelectric (FE) PbMg1/3Nb2/3O3 grown on (001) MgO substrate. The dielectric response, polarization, and current are measured along the out-of-plane < 100 > direction of the film and analyzed as a function of temperature, frequency, and applied field. Compared to the < 100 > crystal, transformation of the low-temperature relaxor state to a new state in the (001) film takes place at considerably lower temperatures and larger fields. Based on the found bisigmoidal shape and the two scaling regimes of the current-voltage curves, the two corresponding electric-field-induced processes are suggested to be dipolar flips and flow of a phase boundary in the film. The field-induced state in the film is dynamic and unstable, and it differs from the field-induced FE state in the crystal. The robustness of the relaxor state to electric field in the film is discussed in relation to spatial anisotropy of the dipolar system in the (001) film.

1551. Comment on "High multi-photon visible upconversion emissions of Er3+ singly doped BiOCl microcrystals: A photon avalanche of Er3+ induced by 980 nm excitation" [Appl. Phys. Lett. 103, 231104 (2013)]

Authors: Tiseanu, C; Florea, M; Cojocaru, B

Published: JUN 9 2014, , DOI: 10.1063/1.4882167

1552. Thermal behavior of several stable hydrazyl free radicals and of their parent hydrazines

Authors: Marinescu, M; Zalaru, C; Florea, M; Ionita, P

Published: APR 2014, , DOI: 10.1007/s10973-013-3448-x

1553. Heavily impregnated ceria nanoparticles with europium oxide: spectroscopic evidences for homogenous solid solutions and intrinsic structure of Eu3+-oxygen environments

Authors: Avram, D; Rotaru, C; Cojocaru, B; Sanchez-Dominiguez, M; Florea, M; Tiseanu, C

Published: MAR 2014, , DOI: 10.1007/s10853-013-7904-6

1554. Antifungal activity of Ag:hydroxyapatite thin films synthesized by pulsed laser deposition on Ti and Ti modified by TiO2 nanotubes substrates

Authors: Erakovic, S; Jankovic, A; Ristoscu, C; Duta, L; Serban, N; Visan, A; Mihailescu, IN; Stan, GE; Socol, M; Iordache, O; Dumitrescu, I; Luculescu, CR; Janackovic, D; Miskovic-Stankovic, V

Published: FEB 28 2014, APPLIED SURFACE SCIENCE, 293, 45, DOI: 10.1016/j.apsusc.2013.12.029

Hydroxyapatite (HA) is a widely used biomaterial for implant thin films, largely recognized for its excellent capability to chemically bond to hard tissue inducing the osteogenesis without immune response from human tissues. Nowadays, intense research efforts are focused on development of antimicrobial HA doped thin films. In particular, HA doped with Ag (Ag:HA) is expected to inhibit the attachment of microbes and contamination of metallic implant surface. We herewith report on nano-sized HA and Ag:HA thin films synthesized by pulsed laser deposition on pure Ti and Ti modified with 100 nm diameter TiO2 nanotubes (fabricated by anodization of Ti plates) substrates. The HA-based thin films were characterized by SEM, AFM, EDS, FUR, and XRD. The cytotoxic activity was tested with HEp2 cells against controls. The antifungal efficiency of the deposited layers was tested against the Candida albicans and Aspergillus niger strains. The Ti substrates modified with TiO2 nanotubes covered with Ag:HA thin films showed the highest antifungal activity. (C) 2013 Elsevier B.V. All rights reserved.

1555. Laser synthesis of nanometric iron oxide films for thermo-sensing applications

Authors: Serban, N; Ristoscu, C; Socol, G; Stefan, N; Mihailescu, CN; Socol, M; Mulenko, SA; Petrov, YN; Gorbachuk, NT; Mihailescu, IN

Published: FEB 2014, MATERIALS RESEARCH BULLETIN, 50, 154, DOI: 10.1016/j.materresbull.2013.10.042

KrF* excimer laser pulses of 248 nm were used for the synthesis of nanometric iron oxide films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <1 0 0> Si and SiO2 substrates. The number of laser pulses was increased from 4000 to 6000, while ambient reactive oxygen pressure varied from 0.1 to 1.0 Pa. The film thickness depends on oxygen pressure, number of laser pulses and substrate nature. All films demonstrated semiconducting temperature behaviour with variable band gap (E-g) depending on oxygen pressure, substrate nature and temperature. Eg value was less than 1.0 eV for all deposited films. XRD analysis evidenced that films deposited on Si substrate have polycrystalline structure, while films deposited on SiO2 were amorphous. The higher oxygen pressure, the lower crystallinity of the deposited film was observed, resulting in change of thermo electromotive force coefficient (S) value. For larger substrate temperature, a better crystallization was observed in the deposited films, resulting in increased S coefficient value. The largest value of the S coefficient was about 8.7 mV/K in the range 290-295 K and it decreased to 1.0-1.6 mV/K when heating temperature changed from 240 to 330 K. The figure of merit of deposited structures was ZT = 3-6 in the range 240-330 K with a maximum of 12 at 300-304 K. We have shown that thermo-sensing characteristics of the films strongly depend on their electrical and structural properties. (C) 2013 Elsevier Ltd. All rights reserved.

1556. Frustration of ferroelectricity in epitaxial film of relaxor ferroelectric PbSc1/2Nb1/2O3

Authors: Tyunina, M; Pintilie, I; Iuga, A; Stratulat, MS; Pintilie, L

Published: AUG 13 2014, JOURNAL OF PHYSICS-CONDENSED MATTER, 26, DOI: 10.1088/0953-8984/26/32/325901

Relaxor-to-ferroelectric transformations induced by varying electric fields and temperatures are studied experimentally in acube-on-cubetype epitaxial PbSc1/2Nb1/2O3 film grown on La1/2Sr1/2CoO3/MgO(001). Dielectric response, quasi-static and dynamic polarization, and dynamic current-voltage characteristics evidence the absence of spontaneous relaxor-to-ferroelectric transition. The electricfield-induced transformation from a glass-like relaxor state to a new dynamic polar state is detected at low temperatures below 100 K only. The frustration of ferroelectricity is discussed in relation to orientational anisotropy of the dipolar system in the epitaxial (001) film.

1557. Correlation between Microstructure and Magnetic Properties on MnZn Ferrite with Bi2O3 Increasing Addition

Authors: Branzei, M; Cristea, I; Ciuca, I; Bibis, A; Feder, M

Published: 2014, ADVANCED MATERIALS AND STRUCTURES V, 216, 28, DOI: 10.4028/www.scientific.net/SSP.216.23

The aim of this paper is quantitative characterization of a MnZn ferrite with Bi2O3 increasing addition using the Image-Pro Plus software from Media Cybernetics. The sample matrix is a ferrite with the following chemical composition: Mn0.54Zn0.37Fe2.06O4. We applied the conventional ceramic technology in order to obtain the samples. Thus, the raw materials, i.e. alpha Fe2O3, Mn3O4, and ZnO, in a molar ratio 53:28:19 were mixed in suitable proportions in a steel ball-mill using demineralized water. The mixture was burn off at 800 degrees C for 1 hour, in air. The pre-sintered powder was milled in steel ball-mill with increasing addition of Bi2O3 (0.00, 0.01, 0.03, 0.05, 0.07, 0.10, 0.30, 0.50 wt %). For quick references, the sample without bismuth ions was denoted and the samples with increasing concentrations were numbered from "1", "7".

1558. High magnetic field enhancement of the critical current density by Ge, GeO2 and Ge2C6H10O7 additions to MgB2

Authors: Batalu, D; Aldica, G; Popa, S; Miu, L; Enculescu, M; Negrea, RF; Pasuk, I; Badica, P

Published: JUL 1 2014, SCRIPTA MATERIALIA, 82, 64, DOI: 10.1016/j.scriptamat.2014.03.024

Ge, GeO2 and Ge2C6H10O7 additions to MgB2 obtained by ex situ spark plasma sintering significantly enhance the critical current density J(c) in high magnetic fields. A J(c)(T = 20 K) of 102 A cm(-2) is obtained at 3.9 T in the pristine sample and at 5.8 T in the MgB2(Ge2C6H10O7)(0.0014) sample. The decrease in the critical temperature for added samples is less than 1 K and T-c(20 K, H = 0) shows a small decrease from 5.5 x 10(5) A cm(-2) in the pristine sample to 3.9 x 10(5) A cm(-2) in MgB2(Ge2C6H10O7)(0.0014) sample. Ge does not substitute into the MgB2 lattice. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

1559. Biological evaluation of 3-hydroxyflavone in a silver nanoparticles complex

Authors: Voicescu, M; Ionescu, S; Anastasescu, M; Craciunescu, O; Tatia, R; Moldovan, L; Angelescu, DG; Teodorescu, VS

Published: SEP 2014, FEBS JOURNAL, 281, 402, DOI:

1560. SYNTHESIS AND CHARACTERIZATION OF GLASS-CERAMIC SUPERCONDUCTORS IN (Pb, B)-DOPED Bi-Sr-Ca-Cu-O SYSTEM

Authors: Fruth, V; Tanase, G; Atkinson, I; Pandele Cusu, J; Aldica, G; Zaharescu, M

Published: JUN-JUL 2014, REVUE ROUMAINE DE CHIMIE, 59, 383, DOI:

Glass-ceramic superconductors in the Bi-Sr-Ca-Cu-O system were prepared by melt-quenching method in the presence of some additives (Pb, B). The studied glasses were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (DTA/TGA) and differential scanning calorimetry (DSC). On the crystallized ceramics obtained by the annealing the glasses, transport resistance and XRD measurements were also done. The glass transition temperatures (T-g) was found to range in the 380-430 degrees C domain, followed by a set of exothermal effects that could be assigned to the crystallization of the superconducting phases. The nucleation and growth of the crystals is influenced by both the nature of the oxides used as additives and by their ratio. So, the samples doped with low amount of B (x=0.1 and 0.2) present obvious transitions at about 110 K, highlighting the presence of the 2223 phase in highest amount and well interconnected.

1561. Non-isothermal free-models kinetic analysis on crystallization of europium-doped phosphate glasses

Authors: Sava, BA; Elisa, M; Bartha, C; Iordanescu, R; Feraru, I; Plapcianu, C; Patrascu, R

Published: SEP 2014, CERAMICS INTERNATIONAL, 40, 12395, DOI: 10.1016/j.ceramint.2014.04.089

A kinetic analysis under non-isothermal conditions has been performed on europium-doped phosphate glasses with molar composition 20.42 Li2O-10.25 Al2O3-58.49 P2O5-7.23 BaO-1.44 La2O3-2.16 Eu2O3 and particle size <30 mu m, >50 mu m. Differential scanning calorimetry measurements at four heating rates, from room temperature up to 900 degrees C using synthetic air have revealed that no significant mass change occurs during the heat treatment, as normally expected for glass samples. The step changes in heat flow signals are associated with the presence of three important effects: the first one, that occurs as a slope corresponds to the glass transition effect (T-g) is followed by two exothermic peaks, first of them more pronounced, associated with the first crystallization process (T-p1), while, the second one, lower in intensity corresponds to the second crystallization (T-p2) process. As expected, all peaks (T-g, T-p1 and T-p2) increase with the increasing of the heating rate. Both the activation energy of crystallization process and the crystallization mechanism were comparatively analyzed by two free-model estimations and using the formal theory of transformations for heterogeneous nucleation. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1562. Si/SiO2 quantum dots cause cytotoxicity in lung cells through redox homeostasis imbalance

Authors: Stan, MS; Memet, I; Sima, C; Popescu, T; Teodorescu, VS; Hermenean, A; Dinischiotu, A

Published: SEP 5 2014, CHEMICO-BIOLOGICAL INTERACTIONS, 220, 115, DOI: 10.1016/j.cbi.2014.06.020

Si/SiO2 quantum dots (QDs) are novel particles with unique physicochemical properties that promote them as potential candidates for biomedical applications. Although their interaction with human cells has been poorly investigated, oxidative stress appears to be the main factor involved in the cytotoxicity of these nanoparticles. In this study, we show for the first time the influence of Si/SiO2 QDs on cellular redox homeostasis and glutathione distribution in human lung fibroblasts. The nanoparticles morphology, composition and structure have been investigated using high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. MRC-5 cells (human lung fibroblasts) were incubated with various concentrations of Si/SiO2 QDs ranging between 25 and 200 mu g/mL for up to 72 h. The results of the MTT and sulforhodamine B assays showed that exposure to QDs led to a time-dependent decrease in cell viability and biomass. The increase in reactive oxygen species (ROS) and malondialdehyde (MDA) levels together with the lower glutathione content suggested that the cellular redox homeostasis was altered. Regarding GSH distribution, the first two days of treatment resulted in a localization of GSH mainly in the cytoplasm, while at longer incubation time the nuclear/cytoplasmic ratio indicated a nuclear localization. These modifications of cell redox state also affected the redox status of proteins, which was demonstrated by the accumulation of oxidized proteins and actin S-glutathionylation. In addition, the externalization of phosphatidylserine provided evidence that apoptosis might be responsible for cell death, but necrosis was also revealed. Our results suggest that Si/SiO2 quantum dots exerted cytotoxicity on MRC-5 cells by disturbing cellular homeostasis which had an effect upon protein redox status. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

1563. Stress Influenced Trapping Processes in Si Based Multi-Quantum Well Structures and Heavy Ions Implanted Si

Authors: Ciurea, ML; Lazanu, S

Published: 2014, INTERNATIONAL CONFERENCE OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2014 (ICCMSE 2014), 1618, 63, DOI: 10.1063/1.4897674

Multi-quantum well structures and Si wafers implanted with heavy iodine and bismuth ions are studied in order to evaluate the influence of stress on the parameters of trapping centers. The experimental method of thermostimullatedcurrents without applied bias is used, and the trapping centers are filled by illumination. By modeling the discharge curves, we found in multilayered structures the parameters of both 'normal' traps and 'stress-induced' ones, the last having a Gaussian-shaped temperature dependence of the cross section. The stress field due to the presence of stopped heavy ions implanted into Si was modeled by a permanent electric field. The increase of the strain from the neighborhood of I ions to the neighborhood of Bi ions produces the broadening of some energy levels and also a temperature dependence of the cross sections for all levels.

1564. Zinc Oxide and Polysaccharides: Promising Candidates for Functional Nanomaterials

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Florica, C; Evanghelidis, A; Matei, E; Enculescu, I

Published: 2014, SIZE EFFECTS IN NANOSTRUCTURES: BASICS AND APPLICATIONS, 205, 136, DOI: 10.1007/978-3-662-44479-5_5

Recently, ZnO and natural polysaccharides have received more and more attention as interesting components for designing complex functional nanomaterials, key elements being their high occurrence and low-cost. In this chapter are presented possibilities for tailoring the ZnO properties by using polysaccharides in the synthesis process as well as reports on the functionalization of cellulose-based natural fabrics with ZnO. In both cases, in the preparation step were used only simple and scalable wet chemical methods. The resulting materials with suitable characteristics, e.g. dependence of the ZnO nanostructures optical properties on their morphology or high-UV blocking and superhydrophobicity for ZnO-functionalized fabrics, can find applications in domains where such qualities are required.

1565. Electrochemical impedance spectroscopy investigations on the L-cysteine-thiolate self-assembled monolayers formed at p-GaAs(100) electrodes

Authors: Lazarescu, V; Enache, M; Anastasescu, M; Dobrescu, G; Negrila, C; Lazarescu, MF

Published: JUN 10 2014, ELECTROCHIMICA ACTA, 131, 51, DOI: 10.1016/j.electacta.2013.11.103

Electrochemical impedance spectroscopy investigations carried out in solutions with different pH brought evidence that the monolayers of L-cysteine-thiolate self-assembled on GaAs (hid) electrodes exert a complex molecular control over their electrochemical behavior. The analysis of the impedance spectra coupled with that of the XPS data and the AFM images taken before and after the EIS measurements reveled that both pH and applied potential brings significant changes at the electrified interface. The most important effect of pH is the conformational change of the L-cysteine-thiolate molecule observed at pH 11 that allows the interaction of the carboxyl group with the substrate atoms. A similar conformational change occurs at pH 5.5 but only under the applied potential control, being just a consequence of another major effect of the applied electric field. This is the H+ transfer inside the L-cysteine-thiolate film, an electric field driven process but pH dependent, which results in significant charge diminution both in the organic overlayer and in the semiconductor depletion region. (C) 2013 Elsevier Ltd. All rights reserved.

1566. Cu codoping control over magnetic precipitate formation in ZnCoO nanowires

Authors: Granville, S; Matei, E; Enculescu, I; Toimil-Molares, ME

Published: DEC 22 2014, APPLIED PHYSICS LETTERS, 105, DOI: 10.1063/1.4904987

Using electrodeposition, we have grown nanowires of ZnCoO with Cu codoping concentrations varying from 4-10 at. %, controlled only by the deposition potential. We demonstrate control over magnetic Co oxide nano-precipitate formation in the nanowires via the Cu concentration. The different magnetic behavior of the Co oxide nano-precipitates indicates the potential of ZnCoO for magnetic sensor applications. (C) 2014 AIP Publishing LLC.

1567. Nanomechanical characterization of bioglass films synthesized by magnetron sputtering

Authors: Popa, AC; Marques, VMF; Stan, GE; Husanu, MA; Galca, AC; Ghica, C; Tulyaganov, DU; Lemos, AF; Ferreira, JMF

Published: FEB 28 2014, THIN SOLID FILMS, 553, 172, DOI: 10.1016/j.tsf.2013.10.104

Bioactive glasses are osteoproductive-type inorganic materials possessing the highest indices of bioactivity in both bulk and thin film forms. The prerequisites for reliable implant-type coatings are both their biological and mechanical performances. Whilst the bioglass films' structural, chemical and biological properties have been studied extensively, information about their mechanical performance is scarce. Here, transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nanoindentation and pull-out measurements were employed to assess the morphological, chemical, structural and mechanical properties of the bioglass films deposited onto Ti substrates by radio-frequency magnetron sputtering (RF-MS). The biological safety of the thin bioglass films was evaluated preliminarily in vitro by investigating the adherence, proliferation and cytotoxicity of fibroblast cells cultivated on their surface. Our study emphasize the versatility of RF-MS, showing how bioglass films' features such as composition, structure, bonding strength, hardness, elastic modulus and biological response can be conveniently adapted by tuning the RF-MS working conditions, and therefore demonstrating the unexplored potential of this deposition technique for preparing quality biomimetic glass coatings. (C) 2013 Elsevier B. V. All rights reserved.

1568. Micropatterned ZnO rod arrays prepared by Au-catalyzed electroless deposition

Authors: Florica, C; Preda, N; Enculescu, M; Enculescu, I

Published: JUL 2014, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 8, 652, DOI: 10.1002/pssr.201409089

Micropatterned ZnO was synthesized by an electroless deposition process using Au stripes as catalytic surfaces. The Au-patterned electrodes were prepared on SiO2/Si wafers using photolithography. The site-selective deposition of patterned ZnO hexagonal rod arrays is confirmed by scanning electron microscopy. The ZnO micropatterned surface revealed a conversion of wettability from hydrophilic to super-hydrophobic depending on the deposition reaction parameters. The electrical measurements carried out at room temperature before and after exposure to ammonia vapors of the patterned ZnO arrays show a resistance variation with exposure time. Highly reproducible, easy scalable and low-cost, photolithography and electroless deposition techniques could provide a facile approach to fabricate functionalized micropatterns, for a wide range of applications. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1569. High-Order Modes in High Permittivity Cylindrical Dielectric Resonator Antenna Excited by a Wide Microstrip Line

Authors: Avadanei, OG; Banciu, MG; Nedelcu, L

Published: 2014, 2014 10TH INTERNATIONAL CONFERENCE ON COMMUNICATIONS (COMM), DOI:

The aim of the paper is to identify the modes that can be excited by a wide microstrip line, in a cylindrical DRA situated symmetrically above it, to study the radiating performances of these modes and to present their radiating patterns. We managed to identify thirteen high-order modes; among these modes, four of them: HEM112, TMme(311), TEme(112), and TEme(121) have high transmission performances.

1570. DRUG DELIVERY STUDY OF SINGLE-WALL CARBON NANOTUBES COVALENT FUNCTIONALIZED WITH CISPLATIN

Authors: Ciobotaru, CC; Damian, CM; Polosan, S; Prodana, M; Iovu, H

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 868, DOI:

Carbon nanotubes are widely studied components for drug delivery systems due to their high surface area and low chemical reactivity. The research presented in this paper deals with the synthesis of drug delivery systems based on single walled carbon nanotubes (SWCNTs) and the well-known cancer treatment drug Cisplatin. The new nanomaterials obtained through covalent bonding between carboxyl groups from the SWCNTs surface and amino groups from the Cisplatin structure were characterized from structural point of view. To evaluate the content of drug released the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was employed. The releasing profile shows a slow rate in the beginning followed by a spectacular increase after 180 minutes which means that this type of system could be used for prolonged release.

1571. Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core-shell heterostructure

Authors: Cernea, M; Vasile, BS; Boni, A; Iuga, A

Published: FEB 25 2014, JOURNAL OF ALLOYS AND COMPOUNDS, 587, 559, DOI: 10.1016/j.jallcom.2013.10.228

Perovskite complex ceramic oxides, BaTiO3 doped with 0.5 mol% Nb2O5 and then nanocoated with SiO2 (abbreviated as BT-Nb-0.005/SiO2) was successful prepared using conventional sol-gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb-0.005 core and BT-Nb-0.005/SiO2 core-shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core-shell composite with well-defined perovskite tetragonal phase of BaTiO3 was achieved. Furthermore, single crystalline BT-Nb-0.005/SiO2 core-nanoshell heterostructure with similar to 34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb-0.005 has suffered an alteration when the (BT-Nb-0.005)/SiO2 core-shell heterostructure was realized. One-dimensional BT-Nb-0.005/SiO2 core-shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb-0.005. The (BT-Nb-0.005)/SiO2 core-shell material could be interesting for application in the composite capacitors. (C) 2013 Elsevier B.V. All rights reserved.

1572. Luminescent liquid crystalline materials based on palladium(II) imine derivatives containing the 2-phenylpyridine core

Authors: Micutz, M; Ilis, M; Staicu, T; Dumitrascu, F; Pasuk, I; Molard, Y; Roisnel, T; Circu, V

Published: 2014, DALTON TRANSACTIONS, 43, 1161, DOI: 10.1039/c3dt52137k

In this work we report our studies concerning the synthesis and characterisation of a series of imine derivatives that incorporate the 2-phenylpyridine (2-ppy) core. These derivatives were used in the cyclo-metalating reactions of platinum(II) or palladium(II) in order to prepare several complexes with liquid crystalline properties. Depending on the starting materials used as well as the solvents employed, different metal complexes were obtained, some of them showing both liquid crystalline behaviour and luminescence properties at room temperature. It was found that, even if there are two competing coordination sites, the cyclometalation process takes place always at the 2-ppy core with (for Pt) or without (for Pd) the imine bond cleavage. We successfully showed that it is possible to prepare emissive room temperature liquid crystalline materials based on double cyclopalladated heteroleptic complexes by varying the volume fraction of the long flexible alkyl tails on the ancillary benzoylthiourea (BTU) ligands.

1573. Pulsed laser deposition of nanocrystalline SiC films

Authors: Socol, G; Galca, AC; Craciun, D; Hanna, M; Taylor, CR; Lambers, E; Craciun, V

Published: JUL 1 2014, APPLIED SURFACE SCIENCE, 306, 69, DOI: 10.1016/j.apsusc.2014.01.201

Thin SiC films were grown on (1 0 0) Si substrates at temperatures from 400 to 1000 degrees C under various CH4 pressures by the pulsed laser deposition (PLD) technique using a KrF excimer laser. After deposition, films were in situ annealed at their deposition temperature under 500 mbar of CH4 for 1.0-1.5h. X-ray reflectivity investigations showed that films exhibited mass densities similar to SiC single crystal samples, while symmetrical and grazing incidence X-ray diffraction investigations found that films deposited at 800 degrees C or higher substrate temperatures were nanocrystalline. Modeling of spectroscopic ellipsometry measurements indicated that the refractive index values were similar to those reported for bulk SiC, while X-ray photoelectron spectroscopy investigations found that films contained in bulk a relatively low oxygen concentration of around 1.0 at.%. Nanoindentation results showed that the deposited SiC films were very hard, with hardness values above 40 GPa for films deposited at temperatures higher than 800 degrees C. (C) 2014 Elsevier B.V. All rights reserved.

1574. Cladding waveguides realized in Nd:YAG ceramic by direct femtosecond-laser writing with a helical movement technique

Authors: Salamu, G; Jipa, F; Zamfirescu, M; Pavel, N

Published: APR 1 2014, OPTICAL MATERIALS EXPRESS, 4, 797, DOI: 10.1364/OME.4.000790

Circular cladding waveguides were realized in a 5.0-mm long, 1.1- at.% Nd:YAG ceramic by direct femtosecond-laser writing using a scheme in which the laser medium is moved on a helical trajectory along its axis and parallel to the writing direction. Laser emission was obtained under the pump with a fiber-coupled diode laser. A 100-mu m diameter waveguide delivered laser pulses at 1.06 mu m with 3.4-mJ energy for the pump with pulses of 13.1-mJ energy, at 0.30 slope efficiency; laser pulses at 1.3 mu m with 1.2-mJ energy were obtained from the same device. Comparison with a waveguide of the same dimension that was inscribed by the classical translation method of the laser medium is made. Efficient integrated lasers based on cladding waveguides that are pumped by fiber-coupled diode lasers could be realized by this writing method. (C) 2014 Optical Society of America

1575. Formation and Annealing of Metastable (Interstitial Oxygen)-(Interstitial Carbon) Complexes in n- and p-Type Silicon

Authors: Makarenko, LF; Korshunov, FP; Lastovskii, SB; Murin, LI; Moll, M; Pintilie, I

Published: NOV 2014, SEMICONDUCTORS, 48, 1462, DOI: 10.1134/S1063782614110141

It is shown experimentally that, in contrast to the stable configuration of (interstitial carbon)-(interstitial oxygen) complexes (CiOi), the corresponding metastable configuration (CiOi*) cannot be found in n-Si based structures by the method of capacitance spectroscopy. The rates of transformation CiOi* -> CiOi are practically the same for both n- and p-Si with a concentration of charge carriers of no higher than 10(13) cm(-3). It is established that the probabilities of the simultaneous formation of stable and metastable configurations of the complex under study in the case of the addition of an atom of interstitial carbon to an atom of interstitial oxygen is close to 50%. This is caused by the orientation dependence of the interaction potential of an atom of interstitial oxygen with an interstitial carbon atom, which diffuses to this oxygen atom.

1576. Laser prepared organic heterostructures based on star-shaped arylenevinylene compounds

Authors: Stanculescu, A; Socol, G; Grigoras, M; Ivan, T; Vacareanu, L; Socol, M; Rasoga, O; Breazu, C; Mihailescu, IN; Iordache, I; Preda, N; Stanculescu, F

Published: OCT 2014, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 117, 268, DOI: 10.1007/s00339-014-8521-1

This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) technique of organic bulk heterojunctions made from the mixture of a star-shaped arylenevinylene compound, 4,4',4aEuro(3)-tris[(4'-diphenylamino)styryl] triphenylamine as donor and fullerene derivative, [6, 6]-phenyl C61 butyric acid butyl ester, as acceptor, in the weight ratio 1:2. The mixed layer has been characterized by spectroscopic (UV-Vis, Fourier transform infrared) and microscopic (AFM) methods, and the effects of the deposition conditions (number of pulses) and of a buffer layer of poly(aniline-co-aniline propane sulfonic acid) or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) have been analyzed. The study of the electrical properties has revealed a typical solar cell behavior for the heterostructure glass/ITO/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/4,4',4aEuro(3)-tris[(4'-diphenylamino)styryl] triphenylamine: [6, 6]-phenyl C61 butyric acid butyl ester/Al, confirming that MAPLE could be an adequate method for the preparation of active layer based on bulk heterojunction for solar cells.

1577. The emergence of magnetic properties in (Pb0.845Sm0.08Fe0.035)(Ti0.98Mn0.02)O-3 and (Pb0.88Nd0.08)(Ti0.98Mn0.02)O-3 perovskite ceramics

Authors: Craciun, F; Dimitriu, E; Grigoras, M; Lupu, N; Vasile, BS; Cernea, M

Published: AUG 21 2014, JOURNAL OF APPLIED PHYSICS, 116, DOI: 10.1063/1.4893318

The emergence of magnetic properties and quadratic magnetoelectric coupling in a material with outstanding ferroelectric properties has been pursued. Thus, the multiferroicity driven by the substitution of rare earth R3+ ions (R = Sm, Nd) on the A-site of PbTiO3 perovskite ceramics has been investigated. In some samples, a transition element with large ionic radius, like Fe2+, has been also added on the A site. Polycrystalline ceramic samples with composition (Pb1-3x/2-yRxFey) (Ti0.98Mn0.02)O-3 (R = Sm; x = 0.08, y = 0.035) and (Pb1-3x/2Rx)(Ti0.98Mn0.02)O-3 (R = Nd, x = 0.08) have been prepared by conventional solid state ceramic processing, starting from reagent grade oxide powders. X-ray diffraction analysis confirmed the obtaining of a crystalline phase with tetragonal P4mm symmetry. Transmission electron microscopy and high resolution transmission electron microscopy investigations have been carried out in order to analyze the local structure. Temperature dependence of dielectric permittivity revealed a strong anomaly at the temperature T-c of the paraelectric-ferroelectric phase transition. Transition temperature values depend on the R ion type and are lower than in pure lead titanate by 80-100K. A broad anomaly of dielectric permittivity is found below 140-180K, where magnetization also increases due to the quadratic magnetoelectric coupling between ferroelectric and magnetic states. For the (Pb0.845Sm0.08Fe0.035)(Ti0.98Mn0.02)O-3 composition, the piezoelectric charge coefficient at room temperature was d(31) similar to-6.5 pC/N and the remanent magnetization Mr at room temperature was about 0.1 emu/g. (C) 2014 AIP Publishing LLC.

1578. Transmission phase lapses at zero energy in graphene quantum dots

Authors: Nita, M; Tolea, M; Ostahie, B

Published: SEP 2014, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 8, 793, DOI: 10.1002/pssr.201409228

We address theoretically the electronic transport through graphene quantum dots with the emphasis on the transmission phase. Analytical and numerical results are presented regarding the existence - or not - of a lapse of the transmittance phase (and, consequentially, a Fano zero in the transmittance) at the charge neutrality point. A simple universal criterium is found, the phase lapses being always present if the contact sites belong to the same sub-lattice. ((c) 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

1579. Investigation on the electrodeposition of Pt-(Bi,Sb)(2)Te-3 nanocomposite as film and wires

Authors: Sima, M; Vasile, E; Buda, M; Sima, M

Published: MAY 1 2014, ELECTROCHIMICA ACTA, 127, 214, DOI: 10.1016/j.electacta.2014.02.032

In this work we have investigated the electrochemical processes by which Pt nanoparticles were included in (Bi,Sb)(2)Te-3 films and submicrometer wires. Solutions containing ions of Bi3+, HTeO2+ and Sb3+ as well as Pt nanoparticles or [PtCl6](2-) ions were used for this study. For comparison, a solution with the same composition in Bi3+, HTeO2+ and Sb3+ ions was used to study the electrodeposition process of (Bi,Sb)(2)Te-3 films and submicrometer wires. Linear and cyclic voltammetry was employed in experiments to find the influences of addition to electrodeposition bath of Pt nanoparticles or [PtCl6](2-) ions on deposition process of (Bi,Sb)(2)Te-3 film. Pt-(Bi,Sb)(2)Te-3 nanocomposites has been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectrometry (EDX) to determine structural, morphological and compositional properties. Two mechanisms for Pt nanoparticles embedding in (Bi,Sb)(2)Te-3 films and wires have been proposed. (c) 2014 Elsevier Ltd. All rights reserved.

1580. Gold nano-island arrays on silicon as SERS active substrate for organic molecule detection

Authors: Ignat, T; Husanu, MA; Munoz, R; Kusko, M; Danila, M; Teodorescu, CM

Published: JAN 1 2014, THIN SOLID FILMS, 550, 360, DOI: 10.1016/j.tsf.2013.10.151

Gold islands forming highly controlled arrays have been fabricated by two potential step electrochemical deposition method using nanopatterned Si surface templates. In the present work, the Raman scattering studies realized using 11-mercaptoundecanoic probe molecule showed that such structures exhibit an enhanced Raman signal compared with nanostructured physical deposited thin gold film on flat silicon substrate and can be valued as surface-enhanced Raman scattering substrates. Besides the more appropriate management of nano-island arrays distribution, the high ratio of their Raman signals can be explain by the epitaxial-like growth mechanism of themetallic nano-islands, clearly showed by X-ray diffraction studies. Furthermore, the substrates enabled reproducibility and stability detection due to the chemically assembling of organothiol molecules, the X-ray photoelectron spectroscopy studies confirming formation of the thiolate species which corresponds to Au - S bonds, and also, the unwanted 'hot-spots' are missing, which make them suitable for high sensitivity biosensing applications. (C) 2013 Published by Elsevier B.V.

1581. Physical properties of AlxIn1-xN thin film alloys sputtered at low temperature

Authors: Besleaga, C; Galca, AC; Miclea, CF; Mercioniu, I; Enculescu, M; Stan, GE; Mateescu, AO; Dumitru, V; Costea, S

Published: OCT 21 2014, JOURNAL OF APPLIED PHYSICS, 116, DOI: 10.1063/1.4898565

In this paper, we report on the structural, optical, and electrical properties of a wide compositional range of AlxIn1-xN thin layers deposited on glass and polyethylene terephthalate substrates. AlxIn1-xN layers of controlled composition were obtained by a simple reactive magnetron co-sputtering protocol, using a single aluminium target with indium insets, by varying the Al/In target surface area ratio, and the composition of the deposition atmosphere. The relevant physical properties were investigated and discussed. It is shown that the texture of the thin films is dependent on the cation ratio, while the bowing parameters of lattice constants and band gap values are larger than those of epitaxial layers. (C) 2014 AIP Publishing LLC.

1582. Characterization of ferromagnetic double perovskite Sr2FeMoO6 prepared by various methods

Authors: Cernea, M; Vasiliu, F; Bartha, C; Plapcianu, C; Mercioniu, I

Published: SEP 2014, CERAMICS INTERNATIONAL, 40, 11609, DOI: 10.1016/j.ceramint.2014.03.142

Tetragonal Sr2FeMoO6 powders were prepared by the sol gel and solid-state reaction methods. The structure, microstructure and magnetic characteristics of the double perovskite Sr2FeMoO6 in the form of as-prepared powders and classical sintered ceramics were analyzed and compared. Moreover, the magnetic properties of Sr2FeMoO6 ceramics obtained by sol gel and solid state reaction methods and sintered by the classical method were compared with those of Sr2FeMoO6 ceramics obtained by the same two methods, but sintered by the spark plasma sintering technique. The morphology of the powders obtained from the gel precursor and oxides mixture was characterized by homogeneity, as well as the grains shape and size. The powder prepared by the sol gel method was finer (particle average size of 0.6 mu m) than those obtained from oxides mixture (particle average size of 0.9 mu m). Sintered ceramics with tetragonal Sr2FeMoO6 phase were prepared from the two mentioned powders by classical sintering at 1200 degrees C, 2 h in 5%H-2/Ar. The pellets obtained from the gel powder exhibited higher magnetic characteristics than those derived from the oxides mixture. The saturation magnetization and the total magnetic moment of the samples prepared by the sol-gel method were M-sat=41.18 emu/g and mu(exp)/f.u.=3.26, respectively, while for the samples derived from the oxides mixture were M-sat=40.77 emu/g and mu(exp)/f.u=3.10. Also, Sr2FeMoO6 pellets sintered by the conventional method showed higher saturation magnetization values than those sintered by spark plasma sintering technique. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1583. Spectroelectrochemical properties of the poly[(2,5-bisoctyloxy)-1,4-phenylenevinylene]/single-walled carbon nanotube composite

Authors: Baibarac, M; Baltog, I; Srnaranda, I; Ilie, M; Scocioreanu, M; Mevellec, JY; Lefrant, S

Published: SEP 2014, SYNTHETIC METALS, 195, 285, DOI: 10.1016/j.synthmet.2014.06.010

Using surface-enhanced Raman scattering (SERS) and photoluminescence (PL) studies, new data concerning the electrochemical oxidation both of poly[(2,5-bisoctyloxy)-1,4-phenylene-vinylene] (BO-PPV) and the BO-PPV/HIPCO single-walled carbon nanotubes (SWNTs) composite are presented in this paper. The SERS studies performed at the excitation wavelengths of 752 nm and 532 nm of the BO-PPV/SWNTs composite that ensure the resonant excitation of the semiconductor and metallic nanotubes, respectively, reveal that the mixing of the two constituents results, on the one hand, in an isolation of semiconducting nanotubes from the bundles containing both metallic and semiconducting tubes and, on the other hand, in a functionalization of metallic SWNTs with BO-PPV. The isolation of semiconducting SWNTs is demonstrated by the narrowing of the G band and the change of the ratio between the intensities of the Raman lines situated in the low-frequency range that are assigned to the radial breathing vibrational modes. An additional isolation of the semiconducting nanotubes from the SWNTs bundles is reported when an electro-oxidation of the BO-PPV/SWNTs composite was performed in the potential range of (0; +2) V vs. Ag/AgCl. According to the Fourier transformed infra-red (FTIR) spectra and the SERS studies performed at an excitation wavelength of 1064 nm, the chemical interaction of BO-PPV with HIPCO SWNTs reveals a charge transfer between the two constituents that leads to the formation of BO-PPV covalently functionalized SWNTs. The BO-PPV luminescence quenching effect induced by the presence of SWNTs that consists of a change in the relative intensities of the three PL bands of the polymer peaked at 1.73 eV, 1.9 eV and 2.07 eV is due to the metallic tubes. The appearance of a new emission band at 2.32 eV was regularly observed when electrochemical oxidation of the BO-PPV/SWNTs composite was performed in the potential range of (0; +2) V. The PL band at 2.32 eV corresponds to ClO4- ions, which compensates the positive charges of BO-PPV generated during the electrochemical doping process. (C) 2014 Elsevier B.V. All rights reserved.

1584. Laser prepared organic heterostuctures on glass/AZO substrates

Authors: Stanculescu, A; Socol, M; Rasoga, O; Mihailescu, IN; Socol, G; Preda, N; Breazu, C; Stanculescu, F

Published: MAY 30 2014, APPLIED SURFACE SCIENCE, 302, 176, DOI: 10.1016/j.apsusc.2014.01.181

This paper presents some studies about the bi-layer organic heterostructures realized with zinc phthalocyanine (ZnPc) as donor layer and 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA) as acceptor layer, on substrate of glass covered by Al doped ZnO (AZO) layer. These heterostructures have been prepared using laser techniques: pulsed laser deposition (PLD) in an atmosphere of oxygen for AZO films deposition and matrix assisted pulsed laser evaporation (MAPLE) for organic films deposition. The influence of the deposition conditions on the transmission of the organic films has been analysed. The effect of the oxygen plasma treatment, with duration of 5 min and 10 min, on the surface topography, structural and optical properties of AZO layers deposited by PLD and, as consequence, on the optical and electrical properties of the single layer (ZnPc) and bi-layer (ZnPc/NTCDA) organic heterostructure, deposited by MAPLE, was investigated. (C) 2014 Elsevier B.V. All rights reserved.

1585. Strain-induced modification of trap parameters due to the stopped ions in Bi-irradiated Si

Authors: Ciurea, ML; Lazanu, S; Slav, A; Palade, C

Published: NOV 2014, EPL, 108, DOI: 10.1209/0295-5075/108/36004

By implanting Bi in Si, a strong strain field due to the bigger atomic mass and size of stopped Bi ions than Si lattice ones is produced, together with irradiation defects. The controlled doping of Si with Bi leads to modern applications such as quantum information processing. Here we show that the parameters of trapping centres are modified under the strain field. In the literature there are no reports on this subject. We irradiated Si wafers with Bi6+ ions of 28MeV kinetic energy, 3 degrees off [100] axis orientation. The depth distributions of stopped ions and of primary defects were simulated. The traps produced by irradiation were investigated using the thermally stimulated currents method without bias. We recorded and modelled the discharge current curves. The strain field was modelled as a permanent and temperature-independent electric field. The traps of V-2, VO/CiCs, and CiOi and other two not assigned were evidenced. We have found that all trapping levels are broadened, and all capture cross-sections are temperature dependent which we attribute to the strong strain field produced by Bi. These results are important and must be taken into account in designing and manufacturing microelectronic devices incorporating strain, including the topical spin qubit ones. Copyright (C) EPLA, 2014

1586. Evaluation of the Segregation of Paramagnetic Impurities at Grain Boundaries in Nanostructured ZnO Films

Authors: Ghica, D; Stefan, M; Ghica, C; Stan, GE

Published: AUG 27 2014, ACS APPLIED MATERIALS & INTERFACES, 6, 14238, DOI: 10.1021/am5035329

Magnetic and electrical properties of the nanostructured ZnO films are affected by the nonrandom distribution of impurities in the film due to segregation at grain boundaries (GBs) or extended defects. However, mapping the nature and distribution of the impurities in the film is not trivial. Here we demonstrate a simple, statistically relevant, and nondestructive procedure of quantitative determination of the paramagnetic impurities segregated at the GBs in nanostructured semiconducting and insulating films. From correlated electron paramagnetic resonance and transmission electron microscopy investigations, we determined the localization of trace amounts of Mn2+ ions, present as native impurities in a ZnO film deposited by magnetron sputtering at room temperature. In the as-deposited ZnO film, the Mn2+ ions were all localized in nanosized pockets of highly disordered ZnO dispersed between nanocrystalline columns. After the samples had been annealed in air at >400 degrees C, the size of the intercrystalline region decreased and the diffusion in GBs was activated, resulting in the localization of a portion of the Mn2+ ions in the peripheral atomic layers of the ZnO columns neighboring the GBs. The proportion of Mn2+ ions still localized at the GBs after annealing at 600 degrees C was 37%. The proposed method for the assessment of the presence and nature of impurities and the quantitative evaluation of their distribution in semiconducting and insulating nanostructures is expected to find direct applications in nanotechnology, in the synthesis and quality assurance of thin films for spintronics and opto- and nanoelectronics.

1587. Enhancement of pyroelectric signal by continuous ultraviolet illumination of epitaxial Pb(Zr0.2Ti0.8)O-3 films

Authors: Pintilie, L; Botea, M; Iuga, A

Published: SEP 29 2014, APPLIED PHYSICS LETTERS, 105, DOI: 10.1063/1.4896855

The pyroelectric signal generated by an epitaxial Pb(Zr0.2Ti0.8)O-3 film can be enhanced by continuous illumination with ultraviolet (UV) light. The measured signal increases more than 2 times at low modulation frequencies of the incident infrared (IR) radiation (similar to 10 Hz) and at wavelengths where the short-circuit photocurrent presents the maximum value (similar to 280-300 nm). The tentative explanation is that the changes in polarization induced by the temperature variation under modulated IR illumination are generating a variable internal electric field, able to collect the photogenerated carriers produced under continuous UV illumination leading to an additional signal in phase with the pyroelectric one. This finding could be exploited for designing pyroelectric detectors with enhanced characteristics by combining both UV and IR responses. (C) 2014 AIP Publishing LLC.

1588. Polyester fabrics coated with SiOx nanoparticles by vacuum deposition at small angle. Structural characterization and wetting properties

Authors: Frunza, L; Zgura, I; Enculescu, M; Frunza, S; Ganea, CP; Rasoga, O; Cotorobai, F; Dorogan, A

Published: JAN-FEB 2014, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 16, 181, DOI:

Vacuum deposition at small angle was successfully applied in deposition of SiOx particles onto polyester textile materials; this deposition is here presented in comparison with that upon other materials made from poly(lactic acid), polyamide or hemp. Structural and spectroscopic characterization of deposited samples has been performed and compared with that of the raw materials. The deposited particles are amorphous. Contact angle measurement by the sessile drop method, was used to study the wettability behavior of the investigated composite systems. The hierarchical roughness structure generates hydrophylic properties onto polyester fabrics and the other functionalized samples after deposition. The deposition technique was proven to be highly reproducible, easy scalable and cheap, allowing a wide range of applications.

1589. UV SENSING EFFECT IN LANGMUIR-BLODGETT COMPLEX FILMS CONTAINING A NOVEL SYNTHESIZED Fe(III) PORPHYRIN

Authors: Baschir, L; Fagadar-Cosma, E; Creanga, I; Palade, A; Lascu, A; Birdeanu, M; Savastru, D; Savu, V; Antohe, S; Velea, A; Fagadar-Cosma, G; Popescu, M; Simandan, ID

Published: APR-JUN 2014, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 9, 857, DOI:

A novel structure of metalloporphyrin, namely: 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride, was successfully synthesized. UV sensitive structure based on barium stearate functionalized with the novel synthesized porphyrin and carbon nanotubes was obtained. A five monolayers structure was deposited from solution by Langmuir - Blodgett technique onto a ceramic substrate with interdigital platinum electrodes. The complex film shows sensitivity to UV radiation due to the fact that an electron is excited from a Fe d orbital into a porphyrin antibonding pi orbital and is moved onto the ligand that is attached, facilitating the charge separation, while the presence of SWCNT activates the transport of the charge carriers.

1590. Influence of 2,2 '-bipyridine on oxidative dissolution of iron monosulfide

Authors: Chirita, P; Badica, CE; Constantin, CA; Birsa, LM; Matei, E; Baibarac, M

Published: OCT-NOV 2014, SURFACE AND INTERFACE ANALYSIS, 46, 846, DOI: 10.1002/sia.5459

The 2,2'-bipyridine effects on iron monosulfide (FeS) oxidative dissolution rates have been examined by potentiodynamic polarization and electrochemical impedance spectroscopy. The adsorption of 2,2'-bipyridine to synthetic FeS was investigated by batch adsorption experiments, SEM, energy-dispersive X-ray analysis and Raman spectroscopy. The experiments were performed in air-saturated solutions at pH 5, 25 degrees C and an ionic strength of I = 0.004 M NaCl. Correlation between oxidative dissolution rates and 2,2'-bipyridine adsorption suggests that FeS oxidative dissolution is the result of two antagonistic processes: (i) the inhibiting adsorption of 2,2'-bipyridine on mineral surface and (ii) the promoting effect of 2,2'-bipyridine on the iron dissolution from FeS surface. Copyright (C) 2014 John Wiley & Sons, Ltd.

1591. Generation of Porous Alumina Layers in a Polydimethylsiloxane/Hydrogen Peroxide Medium on Aluminum Substrate in Corona Discharges

Authors: Groza, A; Surmeian, A; Diplasu, C; Luculescu, C; Negrila, C; Ganciu, M

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/578720

The porous alumina (Al2O3) layer obtained at the interface between polydimethylsiloxane/hydrogen peroxide medium and aluminum substrate under charged and neutral species injection produced in negative corona discharges in air at atmospheric pressure is analyzed by different methods in this paper. The scanning electron microscopy investigations showed the uniform distribution of the pores formed in the alumina layer and their columnar structures. Both energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) measurements indicate that during the anodization process of the aluminum in the polydimethylsiloxane/hydrogen peroxide medium in corona discharge the incorporation of silicon in the structure of the alumina layer is possible.

1592. In vitro toxicity evaluation of Ti4+-stabilized gamma-Bi2O3 sillenites

Authors: Popescu, T; Lupu, AR; Feder, M; Tarabasanu-Mihaila, D; Teodorescu, VS; Vlaicu, AM; Diamandescu, L

Published: DEC 2014, TOXICOLOGY IN VITRO, 28, 1530, DOI: 10.1016/j.tiv.2014.07.003

We report results regarding the in vitro toxicology of gamma-Bi2O3 represented by its isomorphous phase Bi12TiO20 (gamma-BTO). The gamma-BTO microparticles were synthesized by two methods: coprecipitation from a bismuth nitrate tetrabutyl titanate solution and solid state reaction of Bi2O3 and TiO2 oxides. The structural and morphological characteristics of the obtained materials were determined using X-ray diffraction (XRD), selected area electron diffraction (SAED), transmission (TEM) and scanning (SEM) electron microscopy. The elemental composition was investigated using energy dispersive spectrometry (EDS). The cytotoxicity and oxidative/nitrosative stress (intracellular reactive oxygen species (ROS) and nitric oxide (NO) release) induced by the studied microparticles in HepG2, SH-SY5Y and 3T3-L1 cell cultures were determined using the MIT, DCF-DA (2 ',7 '-dichlorfluorescein-diacetate) and Griess methods respectively. Depending on the cell type and gamma-BTO concentration, results showed only weak cytotoxic effects after 24 h of gamma-BTO exposure and cell proliferation effects for longer treatment times. Only reduced NO release increases (corresponding to high gamma-BTO concentrations) were detected in case of SH-SY5Y and 3T3-L1 cells. The intracellular ROS production (higher for HepG2 cells) appeared inversely proportional to the gamma-BTO concentration. The obtained results indicated a promising in vitro biocompatibility of gamma-BTO and encourage further studies regarding its potential for biomedical applications. (C) 2014 Elsevier Ltd. All rights reserved.

1593. Focusing geometry-induced size tailoring of silver nanoparticles obtained by laser ablation in water

Authors: Stasic, J; Joksic, G; Zivkovic, L; Mihailescu, IN; Ghica, C; Kuncser, A; Trtica, M

Published: OCT 2014, LASER PHYSICS, 24, DOI: 10.1088/1054-660X/24/10/106005

Silver nanoparticles were obtained by picosecond laser ablation in water at 1064 nm, using focusing geometry to design the particles' size. The position of the target surface with respect to the focal point strongly influences the NPs' size: above and in the focus it is up to 20 nm and below focus <= 150 nm. Generated particles have a spherical shape. The solutions were further employed on human cells and the tests showed a deteriorating effect on DNA.

1594. Tetraethyl Orthosilicate Coated Hydroxyapatite Powders for Lead Ions Removal from Aqueous Solutions

Authors: Ghita, RV; Iconaru, SL; Popa, CL; Costescu, A; Le Coustumer, P; Motelica-Heino, M; Ciobanu, CS

Published: 2014, JOURNAL OF NANOMATERIALS, 2014, DOI: 10.1155/2014/176426

The goal of this study was to synthetize and characterize a porous material based on tetraethyl orthosilicate (TEOS) coated hydroxyapatite (HApTh) after removal experiments of Pb2+ ions from aqueous solutions. In order to study the morphology and composition, the samples obtained after removal experiments of Pb2+ ions from aqueous solution with the initial Pb2+ ion concentrations of the aqueous solutions were 0.1g.L-1 (HApTh-50) and 0.9g.L-1 (HApTh-450) have been investigated by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). Removal experiments of Pb2+ ions were carried out in aqueous solutions with controlled concentration of Pb2+. After the removal experiment of Pb2+ ions from solutions, porous hydroxyapatite nanoparticles were transformed into HApTh-50 and HApTh-450 due to the adsorption of Pb2+ ions followed by a cation exchange reaction. The obtained results show that the porous HApTh nanopowders could be used for Pb2+ ions removal from aqueous solutions.

1595. Topological properties of the mesoscopic graphene plaquette: Quantum spin Hall effect due to spin imbalance

Authors: Ostahie, B; Nita, M; Aldea, A

Published: APR 15 2014, PHYSICAL REVIEW B, 89, DOI: 10.1103/PhysRevB.89.165412

We study the electronic properties of the confined honeycomb lattice in the presence of the intrinsic spin-orbit (ISO) interaction and perpendicular magnetic field, and report on uncommon aspects of the quantum spin Hall conductance corroborated by peculiar properties of the edge states. The ISO interaction induces two specific gaps in the Hofstadter spectrum, namely the "weak" topological gap defined by Beugeling et al. [Phys. Rev. B 86, 075118 (2012)], and spin-imbalanced gaps in the relativistic range of the energy spectrum. We analyze the evolution of the helical states with the magnetic field and with increasing Anderson disorder. The "edge" localization of the spin-dependent states and its dependence on the disorder strength is shown. The quantum transport, treated in the Landauer-Buttiker formalism, reveals interesting new plateaus of the quantum spin Hall effect (QSHE), and also of the integer quantum Hall effect (IQHE), in the energy ranges corresponding to the spin-imbalanced gaps. The properties of the spin-dependent transmittance matrix that determine the symmetries with respect to the spin, energy, and magnetic field of the longitudinal and transverse resistance are shown.

1596. Nonlinear features of surface-enhanced Raman scattering revealed under non-resonant and resonant optical excitation

Authors: Baibarac, M; Baltog, I; Mihut, L; Matea, A; Lefrant, S

Published: MAR 2014, JOURNAL OF OPTICS, 16, DOI: 10.1088/2040-8978/16/3/035003

By performing comparative Raman studies on nanometric thin films (9.5, 39, 88 and 185 nm) of copper phthalocyanine (CuPc) deposited on glass, Au and Ag supports, we demonstrate that the mechanism of the surface-enhanced Raman scattering (SERS) generated on Au and Ag substrates differs in the Stokes and anti-Stokes Raman branches depending on whether non-resonant (515.5 nm) or resonant (647.1 nm) optical excitation is applied. The evaluation of the SERS effect via the I-aS/I-S ratio reveals that this ratio is smaller or larger than that predicted by the Boltzmann law for non-resonant or resonant optical excitation, respectively. In the former case, the enhancement of the Stokes Raman emission is similar to a stimulated Raman process resulting from the plasmon coupling associated with the incident excitation light and spontaneous Stokes Raman emission. For the latter case, the amplification of the anti-Stokes Raman emission results from a wave-mixing process reminiscent of a single-beam CARS effect.

1597. Spontaneous collective coherence in driven dissipative cavity arrays

Authors: Ruiz-Rivas, J; del Valle, E; Gies, C; Gartner, P; Hartmann, MJ

Published: SEP 4 2014, PHYSICAL REVIEW A, 90, DOI: 10.1103/PhysRevA.90.033808

We study an array of dissipative tunnel-coupled cavities, each interacting with an incoherently pumped two-level emitter. For cavities in the lasing regime, we find correlations between the light fields of distant cavities, despite the dissipation and the incoherent nature of the pumping mechanism. These correlations decay faster than any power of the distance for arrays in any dimension but become increasingly long ranged with increasing photon tunneling between adjacent cavities. The interaction-dominated and the tunneling-dominated regimes show markedly different scaling of the correlation length which always remains finite due to the finite photon trapping time. We propose a series of observables to characterize the spontaneous buildup of collective coherence in the system.

1598. Substrate impact on optical and microstructural properties of TiO2-PEG sol-gel films

Authors: Anastasescu, M; Teodorescu, VS; Buiu, O; Osiceanu, P; Calderon-Moreno, JM; Predoana, L; Preda, S; Nicolescu, M; Marin, A; Serban, B; Mihaila, M; Stoica, M; Zaharescu, M; Gartner, M

Published: SEP 2014, CERAMICS INTERNATIONAL, 40, 11811, DOI: 10.1016/j.ceramint.2014.04.012

Nanosized TiO2 layers containing polyethylene glycol (PEG) with 20,000 molecular weight were prepared by sol gel method and deposited on three different substrates: microscope standard slides, Fluorine doped Tin Oxide (FTO) glass and Silicon, followed by thermal treatment at 450 degrees C. The effects of the substrate on the microstructural, morphological, chemical and optical properties of the films have been studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM), X-ray Photo-electron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE). The XRD showed that the film crystallization depends very much on the substrate used, thus the films deposited on glass are amorphous even after 1 h thermal treatment at 450 degrees C, while the films deposited on Silicon and FTO substrates are crystallized in anatase phase, in good agreement with the TEM analysis. The XPS analysis showed that a rather high carbon relative concentration in the TiO2 film (without PEG) exists; this suggests that an unavoidable carbon contamination occurs and is not related on the presence or absence of PEG. The thickness and surface roughness of the films are clearly dependent on the substrate type. The flat surfaces of glass and Si lead to the formation of thinner TiO2 films (around 30 nm thicknesses), while the FTO substrate surface leads to thicker film (thickness similar to 100 nm). The porosity of TiO2 films as found by SEM and TEM analyzes is dependent of substrate type; small pore sizes up to 20 nm are characteristic for the films deposited on glass, while larger pore sizes up to 200 nm are found for the films deposited on FTO substrate. Not least, the film transmissions in the visible region are also substrate dependent and the highest values (80%) were obtained for the films deposited on glass. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1599. Influence of morphology on the emissive properties of dye-doped PVP nanofibers produced by electrospinning

Authors: Enculescu, M; Evanghelidis, A; Enculescu, I

Published: DEC 2014, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 75, 1371, DOI: 10.1016/j.jpcs.2014.07.008

Dye-doped polymer micro- and nanofibers with tailored light emission properties have great potential for applications in optical, optoelectronic, or photonic devices. In this study, these types of structures were obtained by electrospinning rhodamine 6 G-doped polyvinylpyrrolidone (PVP) using a polymer solution of 10% (mass) concentration in ethanol. Polymer nanofibers with different morphologies (smooth and beaded) and diameters of about 500 nm were obtained using different electrospinning conditions with the same solutions. Fluorescence optical microscopy observations showed that the dye was distributed uniformly in the doped PVP nanofibers. Different shifts were observed when we compared the wavelength of the dye emission band peak of the smooth nanofibers (566 nm) and the wavelength of the dye emission band peak of the beaded fibers (561.5 nm) produced by electrospinning in different conditions with the wavelength of the emission band peak for transparent thin films produced by spin coating (558 nm) using the same polymer solution. This demonstrates that it is possible to tune the optical properties of electrospun dye-doped polymer nanofibers simply by modifying the morphology of the material, i.e., the parameters of the electrospinning process. (C) 2014 Elsevier Ltd. All rights reserved.

1600. Influence of co-dopants average valence on microstructural and electromechanical properties of lead titanate ceramics

Authors: Amarande, L; Miclea, C; Cioangher, M; Grecu, MN; Pasuk, I; Negrea, RF

Published: MAY 2014, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 34, 1200, DOI: 10.1016/j.jeurceramsoc.2013.12.002

Effects of Ni, Nb and Mn co-doping on microstructural, dielectric and electromechanical properties of lead titanate (PT) dense ceramics, obtained as a result of decreasing lattice anisotropy with increasing amount of co-dopants, were investigated. Different values of the average valence (AV) of Ni-Nb co-dopants were obtained by mutual valence compensation between these acceptor donor ions of various relative concentrations. Significantly higher amounts of Mn2+ (resulted by reduction of Mn4+ in presence of donor co-dopants) were found in materials with Ni-Nb AV >4+. These materials show higher coupling factors, correlated with higher mechanical quality factors, compared to the rest of materials. Hard-like piezoelectric behavior was manifested in materials with Ni-Nb AV <4+, whereas ceramics with Ni-Nb AV >4+, and without manganese, turned out to have a soft-like behavior. Electromechanical properties of PT ceramics are discussed in terms of average valence of Ni-Nb co-dopants and multivalence state of manganese. (C) 2013 Elsevier Ltd. All rights reserved.

1601. Liquid crystals based on silver carbene complexes derived from dimeric bis(imidazolium) bromide salts

Authors: Pana, A; Ilis, M; Micutz, M; Dumitrascu, F; Pasuk, I; Circu, V

Published: 2014, RSC ADVANCES, 4, 59497, DOI: 10.1039/c4ra11023d

A series of bis(imidazolium) salts with different mesogenic groups (cyanobiphenyl or cholesteryl) and their silver carbene complexes with Br- anion has been designed and prepared. The liquid crystalline behaviour of these ionic liquids and their corresponding silver-carbene complexes was investigated by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction while their thermal stability was studied by thermogravimetric analysis (TGA). The silver complexes are thermally stable on a broad temperature range with accessible transition temperatures close to ambient temperature. The compounds with cholesteryl groups show higher transition temperatures than the compounds possessing cyanobiphenyl mesogenic groups, but their thermal stability is limited by a slight decomposition before reaching the isotropic state. Interestingly, the bis(imidazolium) salt with two cyanobiphenyl groups at each side shows an enantiotropic nematic phase on a short range, being one of the few examples of ILC displaying nematic phase.

1602. LASER EMISSION IN DIODE-PUMPED Nd:YAG SINGLE-CRYSTAL WAVEGUIDES REALIZED BY DIRECT FEMTOSECOND-LASER WRITING TECHNIQUE

Authors: Salamu, G; Voicu, F; Pavel, N; Dascalu, T; Jipa, F; Zamfirescu, M

Published: 2013, ROMANIAN REPORTS IN PHYSICS, 65, 953, DOI:

Buried waveguides have been realized in a 0.7 at.% Nd:YAG single crystal using the direct-writing technique with a femtosecond laser. Efficient laser emission at 1.06 and 1.32 mu m is demonstrated and laser action at 0.94 mu m is obtained using the pump with fiber-coupled diode laser at 807 nm, the first demonstration of such devices.

1603. Photoluminescence decay time studies on ZnS in cubic and hexagonal phase and its mechanico-chemical interaction with polyaniline

Authors: Scocioreanu, M; Mihut, L; Baibarac, M; Baltog, I

Published: JUL 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1431, DOI: 10.1002/pssb.201248234

We report new photoluminescence (PL) data generated by pulsed optical excitation on the composites achieved by a mechanico-chemical reaction between ZnS in the cubic (c) and wurtzite (w) phases and polyaniline-emeraldine base (PANI-EB). Under continuous and pulsed optical excitation, powders of the (w)ZnS and (w)ZnS/PANI-EB composites display PL with different spectral compositions. Contrary to expectations, the (c)ZnS and the (c)ZnS/PANI-EB composite displayed weak PL and decay time in the range of nanoseconds. This results from the great involvement of the surface states in nanometric powders which creates efficient channels for the non-radiative recombination of the carriers. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1604. Te and SiC co-doped MgB2 obtained by an ex situ spark plasma sintering technique

Authors: Aldica, G; Popa, S; Enculescu, M; Badica, P

Published: MAR 2013, SCRIPTA MATERIALIA, 68, 431, DOI: 10.1016/j.scriptamat.2012.11.011

Ex situ spark plasma sintering was used to obtain dense MgB2 co-doped with SiC and Te. The composition (MgB2) + (SiC)(0.025) + Te-0.01 shows critical current densities J(c)(20 K, 5 T) of 3.5 x 10(2) A cm(-2) and J(c)(5 K, 9 T) of 2 x 10(3) A cm(-2). These values are higher than for pristine samples or those separately doped with Te or SiC. They are also comparable at high fields and temperatures with the best reported values for the co-doped MgB2 bulks produced by conventional in situ methods. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

1605. Magnetic defects in crystalline Zn(OH)(2) and nanocrystalline ZnO resulting from its thermal decomposition

Authors: Nistor, SV; Ghica, D; Stefan, M; Vlaicu, I; Barascu, JN; Bartha, C

Published: JAN 25 2013, JOURNAL OF ALLOYS AND COMPOUNDS, 548, 227, DOI: 10.1016/j.jallcom.2012.09.016

Trace amounts of substitutional Mn2+ ions and shallow donors magnetic centers were identified by electron paramagnetic resonance (EPR) in crystalline Zn(OH)(2) prepared by precipitation of a Zn-nitrate solution with NaOH. Strong changes in the Mn2+ ions spectrum, as well as a sharp increase in the concentration of the shallow donor centers were observed by EPR in the 110-140 degrees C temperature range, during pulse annealing experiments in air up to 240 degrees C. They reflect the decomposition of the crystalline Zn(OH)(2) host lattice into nanocrystalline ZnO, confirmed by X-ray diffraction and thermal analysis measurements. Accurate spin Hamiltonian parameters of the observed paramagnetic centers were determined by lineshape simulation and fitting of the EPR spectra, to be used as reference data in further studies of nanocrystalline systems involving Zn(OH)(2). (C) 2012 Elsevier B.V. All rights reserved.

1606. Magnetic Properties and Biological Activity Evaluation of Iron Oxide Nanoparticles

Authors: Prodan, AM; Iconaru, SL; Chifiriuc, CM; Bleotu, C; Ciobanu, CS; Motelica-Heino, M; Sizaret, S; Predoi, D

Published: 2013, JOURNAL OF NANOMATERIALS, 2013, DOI: 10.1155/2013/893970

The aim of this study was to provide information about the biological properties of iron oxide nanoparticles (IO-NPs) obtained in an aqueous suspension. The IO-NPs were characterized by transmission electron microscopy (TEM). Analysis of hysteresis loops data at room temperature for magnetic IO-NPs sample indicated that the IO-NPs were superparamagnetic at room temperature. The calculated saturation magnetization for magnetic iron oxide was M-s = 18.1 emu/g. The antimicrobial activity of the obtained PMC-NPs was tested against Gram-negative (Pseudomonas aeruginosa 1397, Escherichia coli ATCC 25922), Gram-positive (Enterococcus faecalis ATCC 29212, Bacillus subtilis IC 12488) bacterial as well as fungal (Candida krusei 963) strains. The obtained results suggested that the antimicrobial activity of IO-NPs is dependent on the metallic ions concentrations and on the microbial growth state, either planktonic or adherent. The obtained IO-NPs exhibited no cytotoxic effect on HeLa cells at the active antimicrobial concentrations.

1607. Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

Authors: Ciobanu, CS; Iconaru, SL; Chifiriuc, MC; Costescu, A; Le Coustumer, P; Predoi, D

Published: 2013, BIOMED RESEARCH INTERNATIONAL, 2013, DOI: 10.1155/2013/916218

The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications.. e aim of this study was the evaluation of Ca10-xAgx(PO4)(6)(OH)(2) nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100 degrees C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against ram-positive and ram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

1608. Self-assembled homojunction In2O3 transparent thin-film transistors

Authors: Gherendi, F; Nistor, M; Antohe, S; Ion, L; Enculescu, I; Mandache, NB

Published: AUG 2013, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 28, DOI: 10.1088/0268-1242/28/8/085002

Homojunction transparent thin-film In2O3 transistors were fabricated at room temperature. Self-assembled In2O3 source-channel-drain structures were grown by pulsed electron beam deposition using a shadow mask with a 300 mu m diameter wire as an obstacle placed at similar to 100 mu m distance from the substrate for growing the channel region behind it. The film resistivity varies from similar to 7 x 10(8) Omega cm in the channel region to similar to 10(-3) Omega cm in the source-drain regions. We explain this fact by the relative depletion of the indium incorporated in the channel region of the film due to the reduced flux of ablated species arriving on the substrate behind the obstacle, leading to a relative enrichment in oxygen compared to the source and drain regions. The gate insulator is a Y2O3 film grown by RF magnetron sputtering. The transistor operates in enhanced mode. The subthreshold swing is similar to 0.26 V/decade with an on/off current ratio of 1.5 x 10(7), and the saturation channel mobility is greater than 45 cm(2) V-1 s(-1).

1609. Phytosynthesis of gold nanoparticles using caesalpinia pulcherrima (peacock flower) flower extract and evaluation of their antimicrobial activities

Authors: Nagaraj, B; Divya, TK; Barasa, M; Krishnamurthy, NB; Dinesh, R; Negrila, CC; Predoi, D

Published: MAR-APR 2013, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 15, 304, DOI:

Caesalpinia pulcherrima (Linn) popularly known as Peacock flower in India belongs to family Caesalpiniace. In this work, we describe environment friendly technique for green synthesis of gold nanoparticles from AuCl4 solution using the Caesalpinia pulcherrima (Peacock flower) flower extract as reducing agent. The gold nanoparticles were characterized using UV-visible spectroscopy and transmission electron microscopy (TEM). The UV- visible spectra indicate a strong Plasmon resonance that is located at similar to 450 nm. The TEM analysis shows that products have spherical morphology with size ranging between 1.0-50 nm. The study also indicates that gold nanoparticles show good antimicrobial activities when compared to the standard antibiotics.

1610. PHOTOANODE FOR DYE-SENSITIZED SOLAR CELL BASED ON ELECTROPHORETICALLY DEPOSITED ZnO LAYER

Authors: Sima, M; Vasile, E; Sima, A

Published: APR-JUN 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 763, DOI:

Electrophoretic deposition (EPD) method is employed to obtain a thick ZnO layer on a ZnO nanorod array prepared in a hydrothermal-electrochemical process. ZnO nanorods have the role to improve the mechanical stability and adherence of ZnO layer deposited by electrophoretic technique. D149 dye is used as sensitizer for ZnO semiconductor. The thus prepared ZnO layer is used for the photoanode of dye-sensitized solar cell (DSC). Performance parameters were extracted from standard current-voltage characteristic (I-V) and charge transfer phenomena occurring at ZnO/dye/electrolyte was evaluated by electrochemical impedance spectroscopy (EIS).

1611. Influence of the TiO2 precursors on the thermal and structural stability of titanate-based nanotubes

Authors: Preda, S; Teodorescu, VS; Musuc, AM; Andronescu, C; Zaharescu, M

Published: FEB 2013, JOURNAL OF MATERIALS RESEARCH, 28, 303, DOI: 10.1557/jmr.2012.362

The influence of different TiO2 precursors (laboratory-prepared sol-gel powders, dried and thermally treated at 400 degrees C, and commercial powders such as anatase by Aldrich and P25 Aeroxide by Evonik) on the structure and morphology of the titanate nanotubes obtained by hydrothermal method was investigated by x-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. In all cases, titanate-based nanotubes were obtained, having similar structure and morphology. The effect of the thermal treatment on the structural stability was also studied by differential thermal analysis and thermogravimetry analysis (TG/DTA) and differetial scanning calorimetry (DSC) measurements up to 600 degrees C, to determine the transformation of titanate nanotubes into other phases. Complementarily, by XRD investigation, the phases that develop after the thermal treatment of the titanate nanotubes in 110-400 degrees C temperature range were identified. The TEM micrographs come to confirm the deterioration of morphology and transformation from nanotubes to particles. The thermal stability of the investigated nanotubes led to the conclusion that this property depends not only on the sodium content but also on the type of precursor. The highest thermal stability was noticed for the nanotubes synthesized starting with anatase (Aldrich) commercial powder.

1612. Structure and dielectric properties of low fluence excimer laser annealing of sol-gel HfO2 thin films deposited on Si wafer

Authors: Teodorescu, VS; Maraloiu, AV; Blanchin, MG; Yamada, T; Sandu, CS; Delaporte, P; Zaharescu, M

Published: 2013, 2013 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1-2, 80, DOI:

Sol-gel HfO2 thin films, prepared from etoxid precursor, were deposited onto silicon wafer substrates by dipcoating. Low fluence multipulse excimer laser processing was used for sol-gel film densification. The small duration of the laser pulse heating limits the quantity of oxygen atoms arriving from the surface at the HfO2/Si interface. Laser irradiations were performed using a XeCl (308 nm) excimer laser, with a homogeneous laser beam. The nanostructure evolution of the laser irradiated films, using different laser fluences between 30 and 120 mJ/cm(2) and different number of pulses, was studied by systematic cross section transmission electron microscope (XTEM) observations. Dielectric constant measurements were performed on the sol-gel HfO2 films samples after laser annealing. The optimum laser processing conditions were found to be a laser fluence of 80 mJ/cm(2) and 5000 to 10000 laser pulses. In these conditions, uniform densified HfO2 amorphous films with a dielectric constant of about 25 were obtained.

1613. ZnO films and nanorod/shell arrays electrodeposited on PET-ITO electrodes

Authors: Sima, M; Vasile, E; Sima, M

Published: APR 2013, MATERIALS RESEARCH BULLETIN, 48, 1586, DOI: 10.1016/j.materresbull.2012.12.045

In this work, ZnO films, nanorod and nanorod/shell arrays were synthesized on the surface of PET-ITO electrodes by electrochemical methods. ZnO films with high optical transmittance were prepared from a zinc nitrate solution using a pulsed current technique with a reduced pulse time (3 s). The X-ray diffraction pattern of ZnO film deposited on PET-ITO electrode showed that it has a polycrystalline structure with preferred orientations in the directions [0 0 2] and [1 03]. ZnO nanorods were synthesized on electrochemical seeded substrate in an aqueous solution containing zinc nitrate and hexamethylenetetramine. In order to increase the stability of PET-ITO electrode to electrochemical and chemical stresses during ZnO nanorods deposition the surface of the electrode was treated with a 17 wt% NH4F aqueous solution. Electrochemical stability of PET-ITO electrode was evaluated in a solution containing nitrate ions and hexamethylenetetramine. ZnO nanorod/shell arrays were fabricated using eosin Y as nanostructuring agent. Photoluminescence spectra of ZnO nanorod and ZnO nanorod/shell arrays prepared on the surface of PET-ITO electrode were discussed comparatively. By employing the 1.5 mu m-length ZnO nanorod/shell array covered with a Cu2O film a photovoltaic device was fabricated on the PET-ITO substrate. (C) 2012 Elsevier Ltd. All rights reserved.

1614. Structural, electric and magnetic properties of CoFe1.8RE0.2O4 (RE=Dy, Gd, La) bulk materials

Authors: Dascalu, G; Popescu, T; Feder, M; Caltun, OF

Published: MAY 2013, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 333, 74, DOI: 10.1016/j.jmmm.2012.12.048

We investigated the influence of rare earth (RE) additions on the structural, dielectric, magnetic and magnetostrictive properties of cobalt ferrite bulk materials. Three lanthanide ions with different ionic radii and magnetic properties were used as dopants: Dy, Gd, La. The structural properties of the sintered samples were investigated using X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The room temperature hysteresis loops were obtained using a vibrating sample magnetometer. The frequency dependence of dielectric permittivity and tangent loss was investigated in the 20 Hz-20 kHz range. The variation of the magnetoelectric response with applied dc magnetic field was analyzed. The insertion of rare earth elements influenced the structural characteristics of the samples (density, cell edge, porosity) and the magnetic and electric properties. An increase in coercive field and a decrease in saturation magnetization and magnetostriction coefficient were observed. These results can be partially explained by the weaker nature of the RE3+-Fe3+ interaction compared to Fe3+-Fe3+ interaction and to the antiferromagnetic alignment of the REFeO3 second phase observed in the diffraction patterns after sintering process. (C) 2012 Elsevier BY. All rights reserved.

1615. Combined influence of Coulomb interaction and polarons on the carrier dynamics in InGaAs quantum dots

Authors: Steinhoff, A; Kurtze, H; Gartner, P; Florian, M; Reuter, D; Wieck, AD; Bayer, M; Jahnke, F

Published: NOV 22 2013, PHYSICAL REVIEW B, 88, DOI: 10.1103/PhysRevB.88.205309

Experimental results for the carrier capture and relaxation dynamics in self-organized semiconductor quantum dots are analyzed using a microscopic theory. Time-resolved differential transmission changes of the quantum-dot transitions after ultrafast optical excitation of the barrier states are studied in a wide range of carrier temperatures and excitation densities. The measurements can be explained by quantum-dot polaron scattering and their excitation-dependent renormalization due to additional Coulomb scattering processes. Results of configuration-picture and single-particle-picture descriptions, both with nonperturbative transition rates, show good agreement with the experiments while Boltzmann scattering rates lead to a different excitation density and temperature dependence.

1616. Phonon-mediated off-resonant coupling effects in semiconductor quantum-dot lasers

Authors: Florian, M; Gartner, P; Gies, C; Jahnke, F

Published: MAR 18 2013, NEW JOURNAL OF PHYSICS, 15, DOI: 10.1088/1367-2630/15/3/035019

The impact of non-resonant background emitters in semiconductor quantum-dot microcavity lasers is addressed within theoretical investigations based on the solution of the von Neumann equation. Off-resonant coupling between emitter resonances and the cavity mode is enabled via phonons, which are included in the von Neumann dynamics by an effective Lindblad contribution. The results show enhanced coherent emission from non-resonantly coupled quantum dots, while the frequently used phenomenological cavity feeding mechanism only enhances the thermal component of the emission.

1617. Structural changes during toluene complete oxidation on supported EuFeO3 monitored by in situ Eu-151 and Fe-57 Mossbauer spectroscopy

Authors: Florea, M; Alifanti, M; Kuncser, V; Parvulescu, VI

Published: JUN 1 2013, CATALYSIS TODAY, 208, 59, DOI: 10.1016/j.cattod.2012.09.035

Pure EuFeO3 and ceria were prepared via a sol-gel citrate route and were calcined at 700 degrees C. Separately, a 20 wt% EuFeO3/CeO2 was prepared via incipient wetness impregnation of calcined ceria with citrate precursors and calcined in the same conditions. SBET, XRD, toluene chemisorption, toluene-TPD and in situ Eu-151 and Fe-57 Mossbauer investigations were performed. All characterization data indicate the formation of a well-dispersed EuFeO3 at the surface of CeO2. During the oxidation of toluene Eu-151 and Fe-57 Mossbauer spectroscopy suggested a cooperative effect of the cations. The catalysts were tested in total oxidation of toluene. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuFeO3. All structural changes during operation time were reversible. (C) 2012 Elsevier B.V. All rights reserved.

1618. Co environment and magnetic defects in anatase CoxTi1-O-x(2) nanopowders

Authors: Grecu, MN; Macovei, D; Ghica, D; Logofatu, C; Valsan, S; Apostol, NG; Lungu, GA; Negrea, RF; Piticescu, RR

Published: APR 22 2013, APPLIED PHYSICS LETTERS, 102, 161909, DOI: 10.1063/1.4802819

Cobalt environment and magnetic defects nature in hydrothermal synthesized anatase CoxTi1-xO2 nanopowders (0 <= x <= 0.1) are investigated by x-ray diffraction and a variety of spectroscopic techniques. One shows that cobalt is partially inserted in the anatase lattice, as Co2+ ions located on substitutional and interstitial sites. The fraction of the diluted Co is limited to 3 at.% for x >= 0.05, while the rest of the Co atoms gather into Co3O4 clusters. As found by electron paramagnetic resonance, the Co doping brings about hole-and electron-excess defects. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802819]

1619. Study on Europium-Doped Hydroxyapatite Nanoparticles by Fourier Transform Infrared Spectroscopy and Their Antimicrobial Properties

Authors: Iconaru, SL; Motelica-Heino, M; Predoi, D

Published: 2013, JOURNAL OF SPECTROSCOPY, 2013, DOI: 10.1155/2013/284285

Fourier transform infrared spectroscopy (FT-IR) analysis was conducted on europium-doped hydroxyapatite, Ca10-xEux (PO4)(6)(OH)(2) nanocrystalline powders (Eu:HAp) with 0 < x(Eu) < 0.2. Antimicrobial studies were also performed for the first time on Eu: HAp. The antimicrobial properties of Eu: HAp nanoparticles with 0 < x(Eu) <= 0.2 on Gram-negative (E. coli ATCC 25922, Pseudomonas aeruginosa 1397) andGram-positive (Staphylococcus aureus 0364, Enterococcus faecalis ATCC 29212) bacteria systems and a species of fungus (Candida albicans ATCC 10231) were reported. Our study demonstrates that the antimicrobial activity of Eu: HAp nanoparticles is dependent on the europium concentration.

1620. Structure, reactivity, electronic configuration and magnetism of samarium atomic layers deposited on Si(001) by molecular beam epitaxy

Authors: Gheorghe, NG; Lungu, GA; Husanu, MA; Costescu, RM; Macovei, D; Teodorescu, CM

Published: FEB 15 2013, APPLIED SURFACE SCIENCE, 267, DOI: 10.1016/j.apsusc.2012.08.016

The surface structure, interface reactivity, electron configuration and magnetic properties of Sm layers deposited on Si(0 0 1) at various temperatures are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and magneto-optical Kerr effect (MOKE). It is found that metal Sm is present on samples prepared at low temperature, with an interface layer containing SmSi2 and Sm4Si3. When samples are prepared at high temperature, much less metal Sm is found, with an increasing amount of SmSi2. Room temperature ferromagnetism is observed for all prepared layers, with a decrease of the saturation magnetization when samples are prepared at high temperature. It is found that ferromagnetism implies mostly a compound with approximate stoichiometry Sm4Si3. Also, the decrease in the intensity of the XAS 2p(3/2) -> 3d white lines with the corresponding increasing amount of SmSi2 may be explained by assuming a higher occupancy of Sm 5d orbitals (5d(2) configuration), most probably due to hybridation effects. (C) 2012 Elsevier B. V. All rights reserved.

1621. Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

Authors: Mazur, M; Barras, A; Kuncser, V; Galatanu, A; Zaitzev, V; Turcheniuk, KV; Woisel, P; Lyskawa, J; Laure, W; Siriwardena, A; Boukherroub, R; Szunerits, S

Published: 2013, NANOSCALE, 5, 2702, DOI: 10.1039/c3nr33506b

The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(I) catalyzed << click >> chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose.

1622. Influence of orbital contributions to the valence band alignment of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3

Authors: Li, SY; Morasch, J; Klein, A; Chirila, C; Pintilie, L; Jia, LC; Ellmer, K; Naderer, M; Reichmann, K; Groting, M; Albe, K

Published: JUL 17 2013, PHYSICAL REVIEW B, 88, DOI: 10.1103/PhysRevB.88.045428

The formation of an interface between Bi2O3, Fe2O3, BiFeO3, Bi0.5Na0.5TiO3, and the high work function metallic RuO2 is studied using photoelectron spectroscopy with in situ RuO2 deposition. Schottky barrier heights are derived and the valence band maximum energies of the studied materials are aligned with respect to each other as well as to other functional oxides like SrTiO3 and PbTiO3. The energy band alignment follows systematic trends compared to a large number of oxides, and can be understood in terms of the contribution of Fe 3d and Bi 6s/6p (lone pair) orbitals to electronic states near the valence band maximum. The results indicate that the valence band maxima are largely determined by the local environment of the cations, which allows to estimate valence band maximum energies of oxides with multiple cations from those of their parent binary compounds. The high valence band maximum of BiFeO3 is consistent with reported p-type conduction of acceptor doped material, while the high conduction band minimum makes n-type conduction unlikely.

1623. Direct Synthesis of Sorbitol and Glycerol from Cellulose over Ionic Ru/Magnetite Nanoparticles in the Absence of External Hydrogen

Authors: Negoi, A; Trotus, IT; Steiner, OM; Tudorache, M; Kuncser, V; Macovei, D; Parvulescu, VI; Coman, SM

Published: NOV 2013, CHEMSUSCHEM, 6, 2094, DOI: 10.1002/cssc.201300554

1624. MAPLE DEPOSITION OF PLGA MICRO- AND NANOPARTICLES EMBEDDED INTO POLYMERIC COATINGS

Authors: Socol, G; Preda, N; Socol, M; Sima, L; Luculescu, CR; Sima, F; Miroiu, M; Axente, E; Visan, A; Stefan, N; Cristescu, R; Dorcioman, G; Stanculescu, A; Radulescu, L; Mihailescu, IN

Published: APR-JUN 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 630, DOI:

We report the film deposition of Poly(D, L-lactide-co-glycolide) (PLGA) particle systems by matrix assisted pulsed laser evaporation (MAPLE) technique. PLGA+polyvinyl alcohol (PVA), PLGA+PVA+ bovine serum albumin (BSA) and PLGA+PVA+chitosan (CH) nanoparticles were prepared by an oil-in-water emulsion-diffusion-evaporation method. The average diameter of PLGA particles was between 180-250 nm. The coatings were obtained by laser evaporation of frozen targets prepared by mixing appropriate PLGA aqueous suspensions and dimethyl sulfoxide (DMSO) in three ratios. Depending on the DMSO content, we deposited PLGA particles embedded into polymeric layer mainly obtained due to the entirely or partially dissolving of nanoparticles into the initial solution. In vitro results showed that the distribution and morphology of osteoblast-like SaOs-2 cells on some PLGA particle coatings were similar with that of the positive control. The purpose of this study was to develop layers of PLGA particles for local controlled drug delivery.

1625. Influence of mechanical milling on the physical properties of SmCo5/Fe65Co35 type hard/soft magnetic nanocomposite

Authors: Dorolti, E; Trifu, AV; Isnard, O; Chicinas, I; Tolea, F; Valeanu, M; Pop, V

Published: MAY 25 2013, JOURNAL OF ALLOYS AND COMPOUNDS, 560, 194, DOI: 10.1016/j.jallcom.2013.01.140

The influence of milling type on the structural and magnetic behaviour of mechanically milled SmCo5/Fe65Co35 has been studied. By adjusting the mill speed parameters, (Omega/omega), three types of milling have been performed: shock mode process (SMP), friction mode process (FMP) and a combined shock followed by a friction mode process. It was found that in SMP conditions the remanent magnetization and composite coercivity increase with increasing milling time. The best exchange coupling, with a coercivity of 1.05 T, was obtained for samples milled for 8 h in SMP and annealed for 2 h at 550 degrees C. On the other hand, the low energy of FMP does not succeed in producing a microstructure adapted to favour the interphase exchange interactions between the soft and hard magnetic phases. A combined milling process does not change significantly the microstructure obtained previously after 8 h of SMP. This indicates that the microstructure of the composite is formed primarily during SMP while FMP, less energetic, does not drastically affect the crystallite size and crystallite shape of SMP samples. X-ray diffraction patterns were used to follow the evolution of the structure and microstructure. The diffusion of Fe and Co from Fe65Co35 to SmCo5 phase leads to the formation of Sm-2(Co,Fe)(17)/Fe-Co composite. The magnetic behaviour was checked from hysteresis curves and dM/dH vs. H plots. (C) 2013 Elsevier B.V. All rights reserved.

1626. Evolution of the Levels of Free Radicals Generated on Wheat Flour and Wheat Bran by Electron Beam

Authors: Brasoveanu, M; Craciun, G; Manaila, E; Ighigeanu, D; Nemtanu, MR; Grecu, MN

Published: SEP-OCT 2013, CEREAL CHEMISTRY, 90, 473, DOI: 10.1094/CCHEM-10-12-0131-R

This paper presents the experimental data regarding the levels of free radicals investigated by electron spin resonance (ESR) on wheat flour and wheat bran exposed to an electron beam. Samples were irradiated with an electron linear accelerator of 6 MeV and then stored at room temperature in air. ESR spectra of the samples indicated presence of free radicals induced by electron beam. Three types of free radicals have been detected in wheat flour, and signals typical for cellulose-like radicals have been noticed for wheat bran, their concentration increasing with the irradiation dose. The postirradiation storage of both sample types caused radical decay with a two-step pattern associated with fast decay of short-life radicals followed by slow reduction of long-life radicals. However, in the first step, the irradiated wheat bran exhibited more rapid decay of radicals than irradiated flour owing to their different complex matrixes, which led to paramagnetic structures of different origin after exposure to an electron beam. The ESR technique allows the detection of free radicals induced in wheat flour and bran by electron beam for a limited period after irradiation that could be shorter than the shelf life of the products.

1627. Magnetic configurations of Ni-Cu alloy nanowires obtained by the template method

Authors: Matei, E; Enculescu, I; Toimil-Molares, ME; Leca, A; Ghica, C; Kuncser, V

Published: AUG 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1863-3

High aspect ratio nanowires of Ni-Cu alloys have been synthesized by potentiostatic electrochemical deposition in etched ion-track membranes. The nickel-to-copper ratio in the nanowires was controlled via the deposition potential and electrochemical bath composition. We present a detailed study of nanowire properties including morphology, composition, and magnetic behavior. We report the magnetic configurations measured as function of the nanowire composition and discuss domain formation, anisotropy aspects, and local easy axis distributions.

1628. Single bath electrodeposition of samarium oxide/zinc oxide nanostructured films with intense, broad luminescence

Authors: Matei, E; Enculescu, M; Enculescu, I

Published: APR 15 2013, ELECTROCHIMICA ACTA, 95, 178, DOI: 10.1016/j.electacta.2013.02.044

Electrochemical deposition from a solution containing zinc and samarium ions, leads to a samarium oxide/zinc oxide sandwich-like structure with an intense, visible, broad luminescence peak centered at 550 nm. The successive deposition of the two materials is related to the bath composition and overpotential, taking place for values higher than a certain threshold. The zinc oxide film, first one to be deposited, presents typical hexagonal prism morphology while samaria coating films present a porous, nanowall like structure. The photoluminescence emission is at least 10 times more intense than in the case of typical electrodeposited ZnO films of similar thickness and does not appear in Sm2O3 films electrodeposited from solutions containing only Sm ions. Samples prepared in different conditions were characterized from the point of view of composition, structure, morphology and optical properties. The characteristics of the emission spectra of the films make them interesting for solid state lightning applications. (c) 2013 Elsevier Ltd. All rights reserved.

1629. Electronic transport in (La,Sr)MnO3-ferroelectric-(La,Sr)MnO3 epitaxial structures

Authors: Boni, AG; Pintilie, I; Pintilie, L; Preziosi, D; Deniz, H; Alexe, M

Published: JUN 14 2013, JOURNAL OF APPLIED PHYSICS, 113, DOI: 10.1063/1.4808335

The leakage current in all oxide epitaxial (La,Sr)MnO3-ferroelectric-(La,Sr)MnO3 structures, where the ferroelectric layer is either BaTiO3 or Pb(Zr0.2Ti0.8)O-3, was analyzed on a broad range of temperatures and for different thicknesses of the ferroelectric layer. It was found that, although the structures are nominally symmetric, the current-voltage (I-V) characteristics are asymmetric. The leakage current depends strongly on the thicknesses of the ferroelectric layer, on temperature and on the polarity of the applied voltage. Simple conduction mechanisms such as space charge limited currents or thermionic emission cannot explain in the same time the voltage, temperature, and thickness dependence of the experimentally measured leakage currents. A combination between interface limited charge injection and bulk controlled drift-diffusion (through hopping in the case of BTO and through band mobility in the case of PZT) is qualitatively explaining the experimental I-V characteristics. (C) 2013 AIP Publishing LLC.

1630. Nanotubes of piezoelectric BNT-BT0.08 obtained from sol-gel precursor

Authors: Cernea, M; Trupina, L; Vasile, BS; Trusca, R; Chirila, C

Published: JUL 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1787-y

Barium titanate-substituted bismuth titanate ((Bi0.5Na0.5)(0.92)Ba0.08TiO3, BNT-BT0.08) nanotubes were fabricated using sol-gel chemistry, spin casting, and a porous polycarbonate membrane template. The structure and morphology of the tubes have been investigated by scanning electron microscopy and transmission electron microscopy. The diameter and length of these tubes were about 650 nm and 20 mu m, respectively, and their wall thickness was about 50 nm. The tubes were polycrystalline with average grain size of similar to 40 nm. The BNT-BT0.08 nanotubes exhibited ferroelectric behavior as evidenced by saturated piezoresponse hysteresis loops and phase switching. BNT-BT0.08 piezoelectric nanotubes promise novel device architectures and enhanced electric properties.

1631. TECHNOLOGY OF CHALCOGENIDE GLASSY SEMICONDUCTOR LAYERS FABRICATION

Authors: Prilepov, V; Popescu, M; Chirita, A; Korshak, O; Ketrush, P; Nasedchina, N

Published: JUL 2013, CHALCOGENIDE LETTERS, 10, 257, DOI:

The results of the studies of thin layer structures based on chalcogenide glassy semiconductors (CGS) of As-Se-S system fabrication are presented in the given paper. The possibility of of As-Se-S system thin films obtaining with the given electro-physical parameters, was shown.

1632. EFFECT OF CNTS AND METAL-PHTHALOCYANINES ADDING ON THE PHOTO-ELECTRICAL BEHAVIOR OF THE PHOTOVOLTAIC STRUCTURES BASED ON POLYMERIC BLENDS

Authors: Baschir, L; Antohe, S; Radu, A; Constantineanu, R; Iftimie, S; Simandan, ID; Popescu, M

Published: OCT-DEC 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 1651, DOI:

Photovoltaic structures based on P3HT:PCBM(1:0.8) mixed with barium stearate (BS), carbon nanotubes (CNT) and different phtalocyanines (Coperphthalocyanine (CuPc), Zincphthalocyanine (ZnPc) and Magnesiumphthalocyanine (MgPc) were successfully prepared by spin-coating technique onto optical glass substrates covered with ITO and PEDOT:PSS. The goal of this study was to investigate the influence of barium stearate, carbon nanotubes and different small molecules of dyes mixed with the P3HT:PCBM "conventional" blend on the photovoltaic response of the "custom" obtained structures. The current-voltage characteristics were drawn in the dark and illumination and the external quantum efficiency was determined for each from the prepared samples.

1633. Optics of microlenses created by irradiation of As2S3 amorphous chalcogenide films with femtosecond laser pulses

Authors: Popescu, M; Velea, A; Miclos, S; Savastru, D

Published: APR 1 2013, PHILOSOPHICAL MAGAZINE LETTERS, 93, 220, DOI: 10.1080/09500839.2012.760058

Arrays of microlenses have been created on the surface of thin amorphous films of As2S3 by localized photoexpansion induced by femtosecond laser pulses. The profile of a typical microlens has been mathematically described. Ray-tracing analysis has been performed to determine the focal points in the red and near-infrared spectrum of electromagnetic radiation. These lie at distances of 1.21m at =650nm and 1.33m at =1.5m above the top of the microlens. It is suggested that the microlenses could be used in two-dimensional optoelectronic circuits or in fibre optics.

1634. Ultraviolet and visible up-conversion luminescence of Er3+/Yb3+ co-doped CaF2 nanocrystals in sol-gel derived glass-ceramics

Authors: Georgescu, S; Voiculescu, AM; Matei, C; Secu, CE; Negrea, RF; Secu, M

Published: NOV 2013, JOURNAL OF LUMINESCENCE, 143, 156, DOI: 10.1016/j.jlumin.2013.04.002

Glass-ceramics containing Er3+/Yb3+ codoped CaF2 nanocrystals have been prepared by using the controlled crystallization above 650 degrees C of the (Yb3+/Er3+) codoped CaF2-SiO2 xerogels. X-ray diffraction and scanning electron microscopy data have revealed the formation of CaF2 nanoctystals of about 16 nm size. For pumping at 973 nm, this glass-ceramics shows, besides green and red up-conversion luminescence, violet (at similar to 408 nm) and near-ultraviolet emission (at similar to 380 nm). The mechanisms responsible for the upconversion luminescence are presented and discussed. The fluorescence lifetimes of the metastable levels responsible for violet, green and red luminescence are measured and their quantum efficiencies are estimated. (C) 2013 Elsevier B.V. All rights reserved.

1635. Maghemite and poly-DL-alanine based core-shell multifunctional nanohybrids for environmental protection and biomedicine applications

Authors: Covaliu, CI; Paraschiv, G; Biris, SS; Jitaru, I; Vasile, E; Diamandescu, L; Velickovic, TC; Krstic, M; Ionita, V; Iovu, H; Matei, E

Published: NOV 15 2013, APPLIED SURFACE SCIENCE, 285, 95, DOI: 10.1016/j.apsusc.2013.08.059

This paper deals with the synthesis of two nanohybrid materials based on maghemite (gamma-Fe2O3) and poly-DL-alanine using a two-step procedure consisting of maghemite nanoparticles synthesis by microemulsion method and nanohybrids obtaining by coating of maghemite nanoparticles with poly-DL-alanine biopolymer in two different molar ratios (H1:5 and H1: 15). The maghemite and their corresponding nanohybrids were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoemission spectroscopy, Mossbauer spectroscopy, Transmission electron microscopy, High resolution transmission electron microscopy with selected area electron diffraction and Atomic absorption spectroscopy. The two nanohybrids under the investigation have the average particle sizes of 22 nm and 23 nm. The Fourier transform infrared spectroscopy spectra and X-ray photoemission spectroscopy data indicate the existence of some interactions between the maghemite nanoparticles and poly-DL-alanine shell. The saturation magnetization values for maghemite and the two nanohybrids determined by a Vibrating Sample Magnetometer correspond to a typical superparamagnetic behavior suitable for applying in biomedical field. Also, with respect of biomedical application the biological activity of maghemite and its corresponding nanohybrids was investigated on healthy human cells (PBMC) and cancerous cells (HeLa). Furthermore, in order to support the multifunctionality of the gamma-Fe2O3 sample and nanohybrids we also investigated their wastewater treatment properties by measuring the removal efficiency of heavy metal Cd (II) ions. (C) 2013 Elsevier B. V. All rights reserved.

1636. Eu3+ probe ion for rare-earth dopant site structure in sol-gel derived LiYF4 oxyfluoride glass-ceramic

Authors: Secu, CE; Negrea, RF; Secu, M

Published: OCT 2013, OPTICAL MATERIALS, 35, 2460, DOI: 10.1016/j.optmat.2013.06.053

Sol-gel route using metal alkoxides and trifluoroacetic acid as precursors has been used to prepare oxyfluoride glass-ceramic containing Eu3+-doped LiYF4 nanocrystals of about tens of nm size embedded in a silica matrix through controlled crystallization at higher temperatures of the xerogel. Photoluminescence spectra and decay curves recorded in the Eu3+-doped LiYF4 polycrystalline pellet and glass ceramic have been discussed using group-theoretical arguments. In the glass-ceramic Eu3+ ions are embedded dominantly inside the LiYF4 nanocrystals most probably as Eu-O center and/or dimer centers in low symmetry (C-2v) sites; oxygen ions were incorporated in their neighborhood during the glass ceramization. (C) 2013 Elsevier B.V. All rights reserved.

1637. Phenylboronic-Acid-Modified Nanoparticles: Potential Antiviral Therapeutics

Authors: Khanal, M; Vausselin, T; Barras, A; Bande, O; Turcheniuk, K; Benazza, M; Zaitsev, V; Teodorescu, CM; Boukherroub, R; Siriwardena, A; Dubuisson, J; Szunerits, S

Published: DEC 11 2013, ACS APPLIED MATERIALS & INTERFACES, 5, 12498, DOI: 10.1021/am403770q

Phenylboronic-acid-modified nanoparticles (NPs) are attracting considerable attention for biological and biomedical applications. We describe here a convenient and general protocol for attaching multiple copies of para-substituted phenylboronic acid moieties onto either iron-oxide-, silica-or diamond-derived NPs. The boronic acid fiinctionalized NPs are all fabricated by first modifying the surface of each particle type with 4-azidobenzoic ester functions. These azide-terminated nanostructures were then reacted with 4-[1-ozo-4-pentyn-1-yl) amino]phenylboronic acid units via a Cu(I) catalyzed Huisgen cycloaddition to furnish, conveniently, the corresponding boronic-acid modified NPs (or "borono-lectins") targeted in this work. The potential of these novel "borono-lectins" as antiviral inhibitors was investigated against the Hepatitis C virus (HCV) exploiting a bioassay that measures the potential of drugs to interfere with the ability of cell-culture-derived JFH1 virus particles to infect healthy hepatocytes. As far as we are aware, this is the first report that describes NP-derived viral entry inhibitors and thus serves as a "proof-of-concept" study. The novel viral entry activity demonstrated, and the fact that the described boronic-acid-functionalized NPs all display much reduced cellular toxicities compared with alternate NPs, sets the stage for their further investigation. The data supports that NP-derived borono-lectins should be pursued as a potential therapeutic strategy for blocking viral entry of HCV.

1638. Spectroelectrochemical properties of the single walled carbon nanotubes functionalized with polydiphenylamine doped with heteropolyanions

Authors: Smaranda, I; Baibarac, M; Baltog, I; Mevellec, JY; Lefrant, S

Published: JAN 2013, JOURNAL OF SOLID STATE CHEMISTRY, 197, 360, DOI: 10.1016/j.jssc.2012.08.015

A combined chemical-electrochemical method was used for covalent functionalization of single-walled carbon nanotube (SWNT) with polydiphenylamine (PDPA) doped with heteropolyanions of H3PMo12O40 center dot xH(2)O. The functionalization process induces in Raman spectra of SWNTs the following changes: (i) an increase in relative intensity of the D band, accompanied a gradual up-shift of the G band in the case of the semiconducting tubes and a decrease in the relative intensity of band peaked at 1540 cm(-1) is remarked in the case of the metallic tubes; (ii) in the anti-Stokes Raman spectrum an increase in the relative intensity of Raman line of metallic tubes peaked at -1560 cm(-1) is remarked when the cycles number increases. The additional down-shift of the FTIR bands belonging to H3PMo12O40 heteropolyanions (at 881, 943 and 1055 cm(-1)) and PDPA (at 688, 736 and 1016 cm(-1)) originates in hindrance steric effects induced the covalent functionalization of SWNTs with polymer molecules. Using Raman scattering and FTIR spectroscopy we demonstrate that chemical polymerization of diphenylamine in the presence of H3PMo12O40 center dot xH(2)O and SWNTs results in a composite of the type blend based on PDPA in un-doped state and SWNTs doped with H3PMo12O40 heteropolyanions. (C) 2012 Elsevier Inc. All rights reserved.

1639. EFFECT OF THERMAL ANNEALING ON THE STRUCTURAL AND OPTICAL PROPERTIES OF Ag/As2S3 MULTILAYERS

Authors: Sava, F; Lorinczi, A; Velea, A; Simandan, ID; Preda, N; Socol, G; Mihailescu, IN; Zamfira, CS; Cretu, NC; Popescu, M

Published: NOV 2013, CHALCOGENIDE LETTERS, 10, 471, DOI:

A complex structure of four double layers of Ag / As2S3 has been deposited by Pulsed Laser Deposition method on a glass substrate. The effects of thermal annealing on the structural and optical properties were investigated. An effect of layer mixing has been evidenced.

1640. Effect of Bismuth Irradiation on Crystalline Silicon

Authors: Palade, C; Slav, A; Ciurea, ML; Lazanu, S

Published: 2013, 2013 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1-2, 76, DOI:

N-type silicon single crystals with resistivity higher than 8000 Omega cm were irradiated with ions of Bi6+, of 28 MeV kinetic energy. At this energy, the ions are stopped into the wafer. Being much heavier and bigger than the host atoms, they produce major disturbances into the lattice. On the other hand, the produced collision cascade is the source of lattice defects which act as traps. We investigated them using the method of thermally stimulated currents without applied bias. The results are compared with those obtained from the analysis of silicon irradiated with I6+ ions.

1641. Structural and electrical properties of NBT-BT0.08 ceramic prepared by the pyrosol method

Authors: Ghitulica, C; Cernea, M; Vasile, BS; Andronescu, E; Vasile, OR; Dragoi, C; Trusca, R

Published: JUL 2013, CERAMICS INTERNATIONAL, 39, 5930, DOI: 10.1016/j.ceramint.2013.01.015

[(Bi0.5Na0.5)TiO3](0.92)-[BaTiO3](0.08) lead free piezoelectric materials were prepared by the pyrosol method. The as-obtained powder shows spherical grains of various sizes, composed of crystallites of about 10 nm. NBT-BT0.08 ceramic obtained at 700 degrees C show rhombohedral NBT as the main phase and traces of hexagonal Bi2O3 as secondary phase. The ceramics prepared from this powder and sintered at 1000 and 1100 degrees C are single phase with good dielectric and ferroelectric properties. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

1642. Efficient laser emission in diode-pumped Nd:YAG buried waveguides realized by direct femtosecond-laser writing

Authors: Pavel, N; Salamu, G; Voicu, F; Jipa, F; Zamfirescu, M; Dascalu, T

Published: SEP 2013, LASER PHYSICS LETTERS, 10, DOI: 10.1088/1612-2011/10/9/095802

Laser emission at 1.06 and 1.3 mu m under pumping with diode lasers was obtained from buried waveguides that were realized in a 0.7 at.% Nd:YAG single crystal by direct writing with a femtosecond laser. A depressed circular waveguide with a diameter of 110 mu m yielded laser pulses at 1.06 mu m with an energy of 1.4 mJ under the pump with pulses of 9.1 mJ energy at 807 nm; in continuous-wave operation, an output power of 0.54 W with optical to optical efficiency of 0.14 was achieved. Emission at 1.3 mu m is demonstrated for the first time from such waveguides, with an energy of 0.4 mJ per pulse. Results for laser emission in other depressed cladding types and two-line-type waveguides are discussed.

1643. Stability of carbon nanowalls against chemical attack with acid solutions

Authors: Vizireanu, S; Dinescu, G; Nistor, LC; Baibarac, M; Ruxanda, G; Stancu, M; Ciuparu, D

Published: JAN 2013, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 47, 65, DOI: 10.1016/j.physe.2012.09.027

In this paper we report on the stability of CNW layers, synthesized by a radiofrequency plasma jet, against the chemical attack with different acid solutions (sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid). We present the changes of the morphology and structure of the CNW caused by the post-growth chemical treatments. We demonstrate that self-sustaining and transferable CNW layers can be obtained, by chemically dissolving the substrates, while the initial characteristics of the material are well preserved. (C) 2012 Elsevier B.V. All rights reserved.

1644. Optical manipulation of complex molecular systems by high density green photons: experimental and theoretical evidence

Authors: Comorosan, S; Polosan, S; Popescu, I; Stamatin, I; Ionescu, E; Avramescu, S; Cune, LC; Apostol, M

Published: MAY 2013, EUROPEAN PHYSICAL JOURNAL B, 86, DOI: 10.1140/epjb/e2013-40049-8

The recent revolution in modern optical techniques revealed that light interaction with matter generates a force, known as optical force, which produces material properties known in physics as optical matter. The basic technique of the domain uses forces exerted by a strongly focused beam of light to trap small objects and subsequently to manipulate their local structures. The purpose of this paper is to develop an alternative approach, using irradiations with high-density-green-photons, which induce electric dipoles by polarization effects. The materials used for the experiments were long carbon chains which represent the framework of biological macromolecules. The physical techniques used to reveal the locally induced molecular arrangements were: dynamic viscosity, zeta potential, chemiluminescence, liquid chromatography; mass spectrometry, and Raman and infrared spectroscopy. The principal result of our experiments was the detection of different molecular arrangements within the mixture of alkane chains, generated by our optical manipulations. This induced "optical matter" displayed two material properties: antioxidant effects and large molecular aggregation effects. In order to bring the experimental results in relation with theory, we developed a physical model and the interacting force between polarizable bodies was computed. By numerical calculations stable structures for N = 6 and N = 8 particles were obtained.

1645. Effect of broadband light on Ag/As2S3 multilayers

Authors: Sava, F; Velea, A; Popescu, M; Lorinczi, A; Simandan, ID; Vlaicu, AM; Socol, G; Mihailescu, IN; Stefan, N

Published: OCT 1 2013, JOURNAL OF NON-CRYSTALLINE SOLIDS, 377, 161, DOI: 10.1016/j.jnoncrysol.2013.02.023

A sandwich structure of four double layers of Ag (5 nm)/As2S3 (82.7 nm) has been prepared by Pulsed Laser Deposition (PLD) method. The effect of broadband light on the multilayer structure has been investigated. The X-ray reflectivity (XRR) patterns after different irradiation times have been measured. Although the fully intermixing of Ag and As2S3 layers should be expected during irradiation with visible light, however even after 5 h of irradiation the intermixing is not completed. The characteristic features of XRR diagrams for long irradiation times have been interpreted by scattering of X-ray radiation on clusters of Ag or Ag-As2S3. (c) 2013 Elsevier B.V. All rights reserved.

1646. Thermal stability of new biologic active copper(II) complexes with 5,6-dimethylbenzimidazole

Authors: Vlaicu, ID; Constand, M; Olar, R; Marinescu, D; Grecu, MN; Lazar, V; Chifiriuc, MC; Badea, M

Published: SEP 2013, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 113, 1377, DOI: 10.1007/s10973-013-2948-z

Three new coordinative compounds that contain mixed ligands (5,6-dimethylbenzimidazole and acrylato anion) were synthesized and characterized. The features of complexes have been assigned from microanalytical, IR, UV-Vis and EPR spectra as well as thermal analysis. IR data are in accordance with unidentate nature of 5,6-dimethylbenzimidazole while the acrilato ion acts as uni- or bidentate ligand. The electronic spectra display the characteristic pattern of square pyramidal or octahedral stereochemistry, which were confirmed by the EPR spectra. Antibacterial and antifungal activities of the complexes have been determined in vitro, against various Gram-negative and Gram-positive bacteria and fungi. The tested complexes exhibited different spectra of antimicrobial activity and inhibited the microbial ability to colonize the inert surfaces, acting as potential anti-adherence and biofilm-controlling agents. Thermal decomposition evidenced several well-defined steps as dehydration (complex 2), 5,6-dimethylbenzimidazole molecule release (all complexes) and the acrylate decomposition in carbonate (complex 3). The final residue is in all cases copper (II) oxide.

1647. Morphological and structural characterization of SiC based composite nanostructures

Authors: Filipescu, M; Stokker-Cheregi, F; Colceag, D; Nedelcea, A; Birjega, R; Nistor, LC; Dinescu, M

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 100, DOI: 10.1016/j.apsusc.2013.03.166

This paper reports on producing SiC based nanostructures (SiC, W-SiC, CNS-SiC) by pulsed laser deposition (PLD) and radio-frequency plasma assisted PLD. Simple and composite targets (SiC, 3/4 SiC + 1/4 tungsten and 3/4 SiC + 1/4 graphite) were irradiated by a 266 nm pulsed laser beam having a pulse duration of 7 ns. The silicon substrates were kept either at room temperature or heated up to 600 degrees C. The depositions were performed in argon at various pressures, ranging from 0.05 mbar up to 2 mbar. The influence of deposition parameters on the structure, surface morphology and composition of different SiC based structures was studied by atomic force microscopy, scanning electron microscopy, secondary ion mass spectrometry, transmission electron microscopy and selected area electron diffraction. Fibers, tubes, nanoparticles and rolled sheets structures were obtained by varying laser fluence, substrate temperature, gas pressure and radio-frequency power. (C) 2013 Elsevier B. V. All rights reserved.

1648. Synthesis and properties of Ba(Zn1/3Ta2/3) O-3 for microwave and millimeter-wave applications (vol 516, pg 1558 , 2008)

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Alexandru, HV; Antohe, S; Andronescu, E; Jinga, S; Nita, P

Published: DEC 2 2013, THIN SOLID FILMS, 548, 663, DOI: 10.1016/j.tsf.2013.10.132

1649. Polymer Sphere Array Assisted ZnO Electroless Deposition

Authors: Preda, N; Enculescu, M; Enculescu, I

Published: JAN 1 2013, SOFT MATERIALS, 11, 464, DOI: 10.1080/1539445X.2012.693147

ZnO uniform films were deposited on polymer sphere arrays by an electroless technique. The low-dimensional ZnO particles were grown from an aqueous solution of zinc nitrate and dimethylamineborane. The X-ray diffraction studies demonstrate that the ZnO crystallites have a hexagonal wurtzite structure. The scanning electron microscopy images prove that ZnO hexagonal prisms are synthesized with a fairly uniform diameter of around 200 nm. From the contact angle measurements it was found that the electroless deposition on polymer sphere arrays of semiconductor hexagonal prisms leads to an improvement of ZnO hydrophobic properties.

1650. Nanosize induced effects in luminescent ZnS:Mn2+ quantum dots

Authors: Nistor, SV; Stefan, M; Ghica, D; Nistor, LC

Published: SEP 2013, RADIATION MEASUREMENTS, 56, 43, DOI: 10.1016/j.radmeas.2013.01.046

Nanocrystals (NCs) of II-VI semiconductors of few nanometers average size, called quantum dots (QDs), are now intensely investigated as radiation detectors. Besides the expected quantum confinement and influence of surface states, our electron paramagnetic resonance investigations of cZnS QDs doped with Mn2+ ions, correlated with structural data, underline that other properties should be also taken into consideration in developing the II VI semiconductor QDs as radiation detectors. Thus, the preferential localization of Mn2+ in the core of the cubic ZnS QDs at substitutional Zn2+ cation sites next to a stacking lattice defect is expected to lead, besides changes in the impurity energy levels, to specific aggregation properties. An outer shell of different composition can also influence the structural properties of the QDs core with effects on the optical properties as well. (C) 2013 Elsevier Ltd. All rights reserved.

1651. SOL-GEL HYBRID NANOCOMPOSITES WITH OXIDE NANOPARTICLES

Authors: Predoana, L; Gartner, M; Teodorescu, VS; Nicolescu, M; Anastasescu, M; Zaharescu, M

Published: FEB-MAR 2013, REVUE ROUMAINE DE CHIMIE, 58, 249, DOI:

In the present work the influence of the method of preparation on the characteristics of sol-gel hybrid nanocomposites with oxide nanoparticles was studied. The chosen system consists of a SiO2 matrix based on methyltriethoxysilane (MTEOS) and laboratory made TiO2:CeO2 (4:1) nanopowder. The doping of the matrix was realized either by dispersion of previously prepared binary nanopowder in the matrix solution or by in situ generation of the TiO2-CeO2 nanoparticles during the matrix hydrolysis-condensation processes. Films were deposited on silicon wafer and glass substrates by dip-coating method and were characterized as prepared and annealed at 120 degrees C. The optical and morphological properties were determined by spectroellipsometry (SE), scanning electron microscopy (SEM), atomic force microscopy (AFM), their structural characterization was realized by IR spectroscopy and the thermal behavior was determined by thermogravimetric and differential-thermal analysis (TG/DTA). All characterization methods have shown that by the two preparation routes materials with different characteristics were obtained.

1652. Periodic arrays of nanostructures in silicon and gallium arsenide by near-field enhanced laser irradiation in liquid precursors

Authors: Ulmeanu, M; Anghel, I; Filipescu, M; Luculescu, C; Enculescu, M; Zamfirescu, M

Published: FEB 5 2013, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 418, 51, DOI: 10.1016/j.colsurfa.2012.11.002

A simple approach to fabricate periodic arrays of ring bumps, disk and convex bumps or holes on silicon and gallium arsenide substrates is reported. In the process, a mono or double layer of 700 nm diameter silica colloidal particles were self-assembled on the substrates and a single pulse from a 200 fs laser at 387 nm wavelength was applied. The surfaces were irradiated at normal incidence by immersing the substrates in a glass container filled with acetone, carbon tetrachloride and 1,1,2-trichlor-trifluorethan liquid precursors. The influence of the medium on the near-field interactions for both substrates is investigated. (C) 2012 Elsevier B.V. All rights reserved.

1653. Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods

Authors: Cristescu, R; Popescu, C; Dorcioman, G; Miroiu, FM; Socol, G; Mihailescu, IN; Gittard, SD; Miller, PR; Narayan, RJ; Enculescu, M; Chrisey, DB

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 213, DOI: 10.1016/j.apsusc.2013.01.062

We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (lambda = 248 nm, tau = 25ns, nu = 10 Hz) was used to deposit composite thin films of poly(D,L-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA-gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer-drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces. (C) 2013 Elsevier B.V. All rights reserved.

1654. Wireless AlN sensor for condition based monitoring of industrial equipment

Authors: Ionescu, G; Ionescu, O; Popovici, S; Costea, S; Dumitru, V; Brezeanu, M; Stan, GE; Pasuk, I

Published: 2013, 2013 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1-2, 58, DOI:

This paper reports on the experimental realization and characterization of a wireless sensing system for machine-tool condition based monitoring. The system comprises a vibration sensor, an ARDUINO Leonardo development board and an RM 42 Blue tooth module. The sensing principle is based on a vibration sensor which includes a piezoelectric AlN layer deposited by sputtering on a flexible stainless steel foil. The functional testing of the sensor using a test stand for asynchronous engines equipped with frequency convertors is demonstrated.

1655. Microstructure-related magnetic properties in Co-implanted ZnO thin films

Authors: Nistor, LC; Ghica, C; Kuncser, V; Pantelica, D; Grob, JJ; Epurescu, G; Dinescu, M

Published: FEB 13 2013, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 46, DOI: 10.1088/0022-3727/46/6/065003

Highly textured ZnO thin films were implanted with Co ions at fluences of 1 x 10(16) and 1 x 10(17) ions cm(-2). Although their microstructure observed by analytical high-resolution electron microscopy was very different, SQUID magnetometer measurements showed qualitatively similar magnetic properties. In the low-fluence film, only small modifications, such as a slight amorphization, planar defects or very small (<1-1.5 nm) Co clusters, were hardly observable. Implantation at a higher fluence led to important changes in the film structure: heavy amorphization and metallic Co precipitates were identified by electron diffraction, energy dispersive x-ray spectroscopy (EDS), electron energy loss spectroscopy and scanning transmission electron microscopy spectrum imaging. EDS microanalysis additionally revealed the presence of similar to 2 at% Co atoms that were likely dissolved in the ZnO lattice at the atomic level. No Co oxides or other secondary oxide phases were detected. For both implanted samples, the dimensions of Co precipitates were below the superparamagnetic limit at room temperature. Thermo-magnetization curves and magnetic hysteresis loops measured in the temperature range from 5 to 300 K indicated two superimposed magnetic regimes, one predominant above 50 K and the other below 50 K. We analysed the possible mechanisms and quantitative contributions to explain the observed magnetic behaviour at low and room temperature.

1656. Single-walled carbon nanotubes functionalized with polydiphenylamine as active materials for applications in the supercapacitors field

Authors: Baibarac, M; Baltog, I; Frunza, S; Magrez, A; Schur, D; Zaginaichenko, SY

Published: FEB 2013, DIAMOND AND RELATED MATERIALS, 32, 82, DOI: 10.1016/j.diamond.2012.12.006

Composites based on polydiphenylamine (PDPA) doped with heteropolyanions of H3PW12O40 and single-walled carbon nanotubes (SWNTs) were prepared by electrochemical polymerization of diphenylamine (DPA) on carbon nanotube films deposited onto Pt electrodes. HRTEM studies reveal that the electrochemical polymerization leads to the filling the spaces between tubes which compose the bundles, creating a monolithic film on the Pt electrode. The resulting composites were tested as active materials in supercapacitors. Resonant Raman scattering studies showed that the electropolymerization of DPA in the presence of H3PW12O40 and SWNTs leads to the covalent functionalization of SWNTs with doped PDPA. The covalent functionalization of SWNTs with PDPA doped with H3PW12O40 heteropolyanions was revealed by FTIR spectroscopy, based on the changes in the vibrational features of PDPA and H3PW12O40. These changes included i) a down-shift of the PDPA IR bands, which was attributed to the C-H bending vibrational mode of benzene (B), C-aromatic-N, C-C stretching (B) + C-H bending (B) and C-C stretching vibrations of the B ring, from 1174, 1321, 1495 and 1603 cm(-1) to 1165, 1313, 1487 and 1599 cm-1, respectively; ii) a change in the peak positions of IR bands associated with the W = O and P-O-W vibration modes of H3PW12O40; and iii) a down-shift of the IR band situated in the spectral range 650-725 cm(-1), which was assigned to the inter-ring deformation vibration mode. The characterization of symmetric solid-state supercapacitors was performed for electrodes prepared from i) SWNTs functionalized with PDPA doped with H3PW12O40 heteropolyanions, ii) SWNTs electrochemically decorated with H3PW12O40 heteropolyanions, and iii). PDPA doped with H3PW12O40 heteropolyanions. Preliminary results indicate high discharge capacitance values of up to 157.2 mF/cm(2) for SWNTs functionalized with PDPA doped with H3PW12O40 heteropolyanions. The discharge capacitance of this material is superior to those recorded for SWNTs electrochemically decorated with H3PW12O40 heteropolyanions (similar to 18.2 mF/cm(2)) and PDPA doped with H3PW12O40 heteropolyanions (similar to 62.1 mF/cm(2)). (c) 2012 Elsevier B.V. All rights reserved.

1657. MORPHOLOGY-CONTROLLED SYNTHESIS OF ZnO STRUCTURES BY A SIMPLE WET CHEMICAL METHOD

Authors: Preda, N; Enculescu, M; Florica, C; Costas, A; Evanghelidis, A; Matei, E; Enculescu, I

Published: OCT-DEC 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 1600, DOI:

Zinc oxide particles were synthesized by a simple wet chemical method. Using zinc nitrate and various precipitating agents, like KOH, NaOH and (CH2)(6)N-4, particles with different morphologies were obtained. Also, the addition of a structure-directing agent, like gum arabic - a highly branched biopolymer, leads to a decrease in the ZnO particles size (for KOH and NaOH) and to a dramatical change of the ZnO particle shape in the case of (CH2)(6)N-4. The X-ray diffraction analysis showed that all obtained samples are of wurtzite structure. The reflectance and photoluminescence spectra have been used to investigate the optical properties of the ZnO structures. The morphologies observed by scanning electron microscopy reveal snowflake-like, flower-like, star-like and double-raspberry-like structures. A possible formation mechanism for ZnO micro/nanostructures with different morphologies was proposed. The biopolymer-assisted crystallization method could provide a facile approach to synthesize other desired compounds with controllable morphology.

1658. TRANSMISSION ELECTRON MICROSCOPY STUDY OF Ge NANOPARTICLES FORMED IN GeSiO FILMS BY ANNEALING IN HYDROGEN

Authors: Teodorescu, VS; Maraloiu, AV; Stavarache, I; Lepadatu, AM; Ciurea, ML

Published: OCT-DEC 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 1780, DOI:

This paper presents a detailed transmission electron microscopy (TEM) study of GeSiO films with Ge nanoparticles. The films with 2.5 mu m thickness were deposited by magnetron sputtering and subsequently annealed in H-2 at 2 atm and 500 degrees C for 2 h for nanostructuring. After H-2 annealing, the majority of the resulted Ge nanoparticles are amorphous, less than 5 nm in size, forming a uniform network in the film volume. Big Ge nanoparticles with sizes between 20 and 50 nm are also formed. Some of them are identified to be crystallized in the (Ge-III/ST12) tetragonal phase. The high resolution TEM observation induces the amorphysation of the Ge tetragonal phase, followed by the crystallization of the amorphous Ge phase in the cubic diamond structure (Ge-I), as an effect of electron irradiation. A secondary annealing performed in N-2 at 800 degrees C and 1 atm for 2 h induces formation of faceted cubic Ge nanoparticles distributed in the SiO2 matrix.

1659. MgB2 with Addition of Bi2O3 Obtained by Spark Plasma Sintering Technique

Authors: Burdusel, M; Aldica, G; Popa, S; Enculescu, M; Pasuk, I; Badica, P

Published: MAY 2013, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 26, 1556, DOI: 10.1007/s10948-012-2015-1

Bi2O3 and Bi-metal powders were mixed with MgB2 powder. Starting compositions were (MgB2)(Bi2O3) x, x = 0.0025, 0.005, 0.015, and (MgB2)(Bi)(y), y = 0.01. Mixtures were processed by Spark Plasma Sintering (SPS) technique. As obtained composite samples show high density, above 94 % of the theoretical density. Samples with Bi2O3 for x = 0.0025 and 0.005 show higher critical current densities, J(c), at high fields and at 20 K than for the pristine sample. Their irreversibility field, H-irr, is also higher. On the other hand, sample added with Bi-metal has lower J(c) and H-irr at any temperature than for the pristine sample.

1660. Ga and As competition for thiolate formation at p-GaAs(111) surfaces

Authors: Preda, L; Negrila, C; Lazarescu, MF; Enache, M; Anastasescu, M; Toader, AM; Ionescu, S; Lazarescu, V

Published: AUG 1 2013, ELECTROCHIMICA ACTA, 104, 11, DOI: 10.1016/j.electacta.2013.04.077

Self-assembled layers of 4,4'-thio-bis-benzene-thiolate spontaneously adsorbed on p-doped GaAs(1 1 1)A and GaAs(1 1 1)B electrodes were examined by EIS, XPS, and AFM investigations. XPS data provide evidence that (i) both As and Ga atoms are involved in the thiolate formation no matter which one is prevailing on the semiconducting surface and (ii) only one of the two thiol groups participates in the chemisorption bond. EIS and AFM results point to a more stable thiolate layer formed on the As-terminated surface than that formed on the Ga-terminated surface due to stronger self-assembling effects developed between the adsorbed species. (C) 2013 Elsevier Ltd. All rights reserved.

1661. InN Based Water Condensation Sensors on Glass and Flexible Plastic Substrates

Authors: Dumitru, V; Costea, S; Brezeanu, M; Stan, GE; Besleaga, C; Galca, AC; Ionescu, G; Ionescu, O

Published: DEC 2013, SENSORS, 13, 16949, DOI: 10.3390/s131216940

1662. Chalcogenide glasses in the frame of the barrier-cluster and local heating model

Authors: Banik, I; Popescu, M

Published: NOV-DEC 2013, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 15, 1184, DOI:

In physics of non crystalline materials there are many challenging problems. This article offers the explanation of the some phenomena in the disordered semiconductors, first of all in chalcogenide glasses on the fundamentyals of the barrier-cluster-heating model. This model assumes that an amorphous semiconductor consists of nanoregions (clusters), separated from each other by potential barriers. Barrier-cluster-heating model allows to explain many phenomena observed in chalcogenide glasses. In this article the mechanism of the appearance weak absorption tail (second exponential tails) of optical absorption in chalcogenide glasses is explained.

1663. Superhydrophobic properties of cotton fabrics functionalized with ZnO by electroless deposition

Authors: Preda, N; Enculescu, M; Zgura, I; Socol, M; Matei, E; Vasilache, V; Enculescu, I

Published: FEB 15 2013, MATERIALS CHEMISTRY AND PHYSICS, 138, 261, DOI: 10.1016/j.matchemphys.2012.11.054

Cotton fabrics were coated with arrays of ZnO hexagonal prisms using an electroless (catalytic/auto-catalytic) deposition process. A typical three step method, similar to those used for electroless deposition of metals on insulating substrates, consisting of pre-activation, activation and deposition steps was employed. The low-dimensional ZnO particles were grown from an aqueous solution containing zinc nitrate as source of zinc ions and dimethylamineborane as reducing agent. The as-obtained ZnO-coated cotton fabrics were characterized from the point of view of structure by X-ray diffraction (XRD) and morphology by scanning electron microscopy (SEM). The XRD studies demonstrate that the ZnO particles have a hexagonal wurtzite crystalline structure. The SEM observations prove that the cotton fibers are homogeneously covered by hexagonal prisms which have uniform base size of approximately 500 nm and height of 1 mu m. Optical spectroscopy measurements show that the functionalization with ZnO strongly decreases the transmittance in the UV vis region of the cotton fabrics. An important characteristic is that the ZnO-functionalized cotton fabrics exhibit superhydrophobicity, with water contact angles exceeding 150 degrees. The technique described is highly reproducible, easy scalable and cheap, allowing a wide range of applications. (C) 2012 Elsevier B.V. All rights reserved.

1664. Sequential Thermal Decomposition of the Shell of Cubic ZnS/Zn(OH)(2) Core-Shell Quantum Dots Observed With Mn2+ Probing Ions

Authors: Nistor, SV; Ghica, D; Stefan, M; Nistor, LC

Published: OCT 24 2013, JOURNAL OF PHYSICAL CHEMISTRY C, 117, 22028, DOI: 10.1021/jp4063093

Thermally induced changes in the structure and composition of the shell of tightly aggregated cubic ZnS/Zn(OH)(2) core shell quantum dots of 1.9 nm average core size were investigated by multifrequency electron paramagnetic resonance of Mn2+ probing ions. The observed three-steps temperature induced transformation of the Mn2+ surface centers in the 80-450 degrees C temperature range Zn(OH)(2) shell into ZnO, with the formation of the Zn2O(OH)(2) and Zn4O3(OH)(2) intermediate nanocompounds. The presence of a 0.3 to 1.9 nm thick surface layer of disordered nanomaterial separating the cubic ZnS cores and its shrinking to a few atomic layers by mass loss after annealing up to 350 degrees C was observed by high resolution transmission electron microscopy. Unlike the single step dehydration around 120 degrees C of the bulk epsilon-Zn(OH)(2), the complex decomposition of the epsilon-Zn(OH)(2) shell is attributed to its nanosized, disordered structure.

1665. COMPLEX LANGMUIR-BLODGETT FILMS BASED ON BARIUM STEARATE MULTILAYERS WITH CARBON NANOTUBES AND As2S3 NANOPARTICLES

Authors: Simandan, ID; Sava, F; Popescu, M; Lorinczi, A

Published: NOV 2013, CHALCOGENIDE LETTERS, 10, 484, DOI:

We have prepared complex multilayer films based on Barium stearate. The multilayer samples have been deposited by the Langmuir-Blodgett technique. The complex multilayers were also deposited on body sensor. The sample was then subjected to the illumination with UV light. We observed changes in the resistivity of the multilayer during the illumination

1666. Riboflavin enhanced fluorescence of highly reduced graphene oxide

Authors: Iliut, M; Gabudean, AM; Leordean, C; Simon, T; Teodorescu, CM; Astilean, S

Published: OCT 24 2013, CHEMICAL PHYSICS LETTERS, 586, 131, DOI: 10.1016/j.cplett.2013.09.032

The improvement of graphene derivates' fluorescence properties is a challenging topic and very few ways were reported up to now. In this Letter we propose an easy method to enhance the fluorescence of highly reduced graphene oxide (rGO) through non-covalent binding to a molecular fluorophore, namely the riboflavin (Rb). While the fluorescence of Rb is quenched, the Rb - decorated rGO exhibits strong blue fluorescence and significantly increased fluorescence lifetime, as compared to its pristine form. The data reported here represent a promising start towards tailoring the optical properties of rGOs, having utmost importance in optical applications. (C) 2013 Elsevier B.V. All rights reserved.

1667. Quantum Well Solar Cells: Physics, Materials and Technology

Authors: Ciurea, ML; Lepadatu, AM; Stavarache, I

Published: 2013, ADVANCED SOLAR CELL MATERIALS, TECHNOLOGY, MODELING, AND SIMULATION, 47, DOI: 10.4018/978-1-4666-1927-2.ch003

Quantum well solar cells with p-i-n structure are presented. The physical processes in multiple quantum well solar cells, the materials commonly used for photovoltaic applications, and technological aspects are analyzed. The quantum confinement effect produces resonant energy levels located in the valence and conduction bands of well layers. In addition, it produces energy quantum confinement levels located in the energy band gap of both well and barrier layers. The absorption on both resonant and quantum confinement levels leads to an extension of the internal quantum efficiency in near infrared domain. Several structures with different absorbers from 3-5 and 4 groups are described and discussed. Various technological and design solutions, such as multiple quantum well solar cells with graded band gap, with tandem configurations, with strain-balanced structure, and strain-balanced structure improved with nanoparticles deposited atop are analyzed. The cell parameters are discussed and related to the materials and technology.

1668. Lead incorporation mechanism in LiF crystals

Authors: D'Acapito, F; Pochet, P; Somma, F; Aloe, P; Montereali, RM; Vincenti, MA; Polosan, S

Published: FEB 25 2013, APPLIED PHYSICS LETTERS, 102, DOI: 10.1063/1.4793751

The doping process of LiF with Pb has been described by using structural ab initio modeling and experimental results. The values of formation energy of several complexes involving Pb ions show that the presence of charge-balancing vacancies ease the metal incorporation in the crystal. The metal successively captures the vacancies to form a final stable complex Pb-Li(center dot) + V-Li('). Experimental data from X-ray absorption spectroscopy confirm the presence of Pb in LiF crystals in this site revealing both Pb-F bonds and collinear Pb-F-Li atomic configurations. A maximum solubility of Pb in LiF of the order of 3 x 10(20)/cm(3) can be estimated from these calculations. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793751]

1669. Synergistic helium and deuterium blistering in tungsten-tantalum composites

Authors: Dias, M; Mateus, R; Catarino, N; Franco, N; Nunes, D; Correia, JB; Carvalho, PA; Hanada, K; Sarbu, C; Alves, E

Published: NOV 2013, JOURNAL OF NUCLEAR MATERIALS, 442, 74, DOI: 10.1016/j.jnucmat.2013.08.010

Tungsten-tantalum composites with 10 and 20 at.% Ta were prepared by ball milling W powder with Ta fibers and by consolidating the milled materials with spark plasma sintering. The composites were implanted at room temperature with He (30 key with a fluence 5 x 10(21) at/m(2)) and/or D+ (15 keV with a fluence 5 x 10(21) at/m(2)) ion beams. The materials were studied by scanning and high-resolution transmission electron microscopy, both coupled with energy dispersive X-ray spectroscopy, and by X-ray diffraction, Rutherford backscattering spectrometry and nuclear reaction analysis. The microstructure observations revealed that the milling operation resulted in severe fragmentation of the Ta fibers. Furthermore, during the consolidation process the Ta phase acted as oxygen getter and reduced the W oxide present in the original material. The surface of the tungsten-tantalum composites implanted with D+ remained essentially unaltered, while the materials implanted with He+ evidenced blisters on the Ta-rich regions. D retention in the composites increased with He pre-implantation. (C) 2013 Elsevier B.V. All rights reserved.

1670. Thermal, spectral, magnetic and antimicrobial behaviour of new Ni(II), Cu(II) and Zn(II) complexes with a hexaazamacrocyclic ligand

Authors: Patrascu, F; Badea, M; Grecu, MN; Stanica, N; Marutescu, L; Marinescu, D; Spinu, C; Tigae, C; Olar, R

Published: SEP 2013, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 113, 1429, DOI: 10.1007/s10973-012-2898-x

New species of type MLCl2 center dot nH(2)O (M:Ni, n = 6; M:Cu, n = 1.5 and M:Zn, n = 1; L: 1,8-bis(3'-ketopyridil)-1,3,6,8,10,13-hexaazacyclotetradecane, ligand resulted by 1,2-diaminoethane, nicotinamide and formaldehyde template condensation) were synthesised. The compounds were characterised by chemical analysis, ESI-MS, IR, NMR, UV-Vis-NIR and EPR spectroscopy as well as magnetic data at room temperature. The modifications in the IR and NMR spectra are in accordance with the condensation process. Electronic spectra indicate that Ni(II) adopts an octahedral stereochemistry while the surrounding of Cu(II) is square-pyramidal. The proposed stereochemistry was furthermore confirmed by magnetic moments and EPR spectrum at room temperature. The water is eliminated in one or two steps, respectively, while the oxidative degradation of the ligand and chloride decomposition occur in two steps. The final residues consist of the most stable metallic oxides as X-ray powder diffraction indicates. The newly synthesised compounds were evaluated for their antimicrobial effect against different bacterial and fungal strains.

1671. Spectroscopic analysis of the riboflavin-serum albumins interaction on silver nanoparticles

Authors: Voicescu, M; Angelescu, DG; Ionescu, S; Teodorescu, VS

Published: APR 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1555-z

Spectrophotometric behavior of riboflavin (RF) adsorbed on silver nanoparticles as well as its interaction with two serum albumins, BSA and HSA, respectively, has been evidenced. The time evolution of the plasmonic features of the complexes formed by RF/BSA/HSA and Ag(0) nanoparticles having an average diameter of 10.0 +/- 2.0 nm have been investigated by UV-Vis absorption spectroscopy. Using steady-state and time-resolved fluorescence spectroscopy, the structure, stability, and dynamics of the serum albumins have been studied. The efficiency of energy transfer process between RF and serum albumins on silver nanoparticles has been estimated. A reaction mechanism of RF with silver nanoparticles is also proposed and the results are discussed with relevance to the involvement of the silver nanoparticles to the redox process of RF and to the RF-serum albumins interaction into a silver nanoparticles complex.

1672. Toxicological aspects of PANC-1 cells exposure to iron oxide dextran-covered nanoparticles

Authors: Radu, M; Burtea, C; Predoi, D; Muller, R; Dinischiotu, A

Published: JUL 2013, FEBS JOURNAL, 280, 216, DOI:

1673. Possible mechanism of Ag photodiffusion in a-As2S3 thin films

Authors: Sava, F; Popescu, M; Lorinczi, A; Velea, A

Published: MAY 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1003, DOI: 10.1002/pssb.201248517

Monitoring the silver photodiffusion in thin amorphous As2S3 film is addressed with a new experimental setup. A possible photo-diffusion mechanism of silver into the a-As2S3 thin film under green laser diode light (=532nm) irradiation is proposed. The proposed mechanism is based on a gradual filling of the structural voids existing in the network of the thin chalcogenide layer. This mechanism is supported by XRD measurements, optical absorption, and modeling data.

1674. Weighting the influence of TiO2 anatase/brookite ratio in TiO2-Ag porous nanocomposites on visible photocatalytic performances

Authors: Iancu, V; Baia, M; Diamandescu, L; Pap, Z; Vlaicu, AM; Danciu, V; Baia, L

Published: AUG 15 2013, MATERIALS CHEMISTRY AND PHYSICS, 141, 239, DOI: 10.1016/j.matchemphys.2013.05.005

Nanocomposites based on TiO2 aerogel and Ag nanoparticles have been successfully obtained through different synthesis methods and their specific surface areas have been determined by N-2 sorption (BET method). The photocatalytic potential for salicylic acid degradation has been evaluated. It was found that under visible light irradiation, all synthesized nanocomposites exhibit higher photocatalytic activity than the commercially available Aeroxide P25. By correlating the structural parameters with the photocatalytic performances, it has been found that the Ag nanoparticles and brookite phase presence alongside the anatase play important roles on the visible photocatalysts behavior. For the Ag containing samples with mixed anatase brookite phases, it has been observed that the visible photocatalytic performance decreases with the increase in brookite crystalline phase content. On the other hand, the addition of Ag nanoparticles results, as expected, in a clear enhancement of the visible photocatalytic activity. (C) 2013 Elsevier B.V. All rights reserved.

1675. Growth and structural characterization of orthorhombic and tetragonal SrCuO2 thin films

Authors: Mihailescu, CN; Pasuk, I; Athanasopoulos, GI; Luculescu, C; Socol, M; Saint-Martin, R; Revcolevschi, A; Giapintzakis, J

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 135, DOI: 10.1016/j.apsusc.2012.12.029

Epitaxial SrCuO2 thin films were grown on (0 0 1) SrTiO3 substrates by pulsed laser deposition using a stoichiometric target. X-ray diffraction indicated that the SrCuO2 films undergo a structural phase transition as a function of the substrate temperature. Films deposited at temperatures below 600 degrees C exhibit a tetragonal phase with the c-axis oriented along the growth direction while films deposited at temperatures above 700 degrees C exhibit an orthorhombic phase with the b-axis oriented along the growth direction. Atomic force microscopy indicated that the as-grown film surfaces are rather smooth and the roughness increases with increasing substrate temperature. Energy dispersive X-ray spectroscopy in agreement with X-ray diffraction intensity ratio data revealed that all films are non-stoichiometric and contain Sr vacancies (Sr/Cu similar to 0.8). The influence of film-substrate lattice matching and substrate temperature on the structural phase transition is discussed. (C) 2012 Elsevier B.V. All rights reserved.

1676. Development of tungsten and tungsten alloys for DEMO divertor applications via MIM technology

Authors: Blagoeva, DT; Opschoor, J; van der Laan, JG; Sarbu, C; Pintsuk, G; Jong, M; Bakker, T; Ten Pierick, P; Nolles, H

Published: NOV 2013, JOURNAL OF NUCLEAR MATERIALS, 442, S203, DOI: 10.1016/j.jnucmat.2013.01.004

This paper is an overview of the very first results obtained on pure tungsten (W) and oxide dispersed strengthened (ODS) W alloys produced by the Metal Injection Molding (MIM) technique for fusion applications. An extensive mechanical and physical characterization was performed, together with microstructural material investigation. The reported work was accomplished within the framework of the European Fusion Development Agreement work program. The main objective was to develop suitable tungsten grades for structural and armor divertor applications in the future DEMO fusion reactor. (C) 2013 Elsevier B.V. All rights reserved.

1677. Magnetic properties of BaxSr1-xFe12O19 (x=0.05-0.35) ferrites prepared by different methods

Authors: Cernea, M; Sandu, SG; Galassi, C; Radu, R; Kuncser, V

Published: JUN 5 2013, JOURNAL OF ALLOYS AND COMPOUNDS, 561, 128, DOI: 10.1016/j.jallcom.2013.01.081

Hexagonal ferrites BaxSr1-xFe12O19 (x = 0.05, 0.15, 0.25, 0.35) were prepared by sol-gel and conventional solid state reaction techniques. Their magnetic properties, investigated by magnetometry and Mossbauer spectroscopy, were discussed in correlation to structural aspects. Whereas the hexaferrites obtained by sol-gel are almost single phase, the ones prepared by the conventional solid state reaction technique present a low amount of BaFe2O4 as secondary phase. All samples show a relative high coercive field and remanent magnetization, as specific features for permanent magnet behavior. The five Fe3+ sites of the specific elemental cell have been revealed and their relative occupancy has been derived from the Mossbauer spectra. The analyzed samples show a sensitivity of the magnetic properties (magnetic moment and anisotropy) with respect to the occupancy of the different Fe sites. (C) 2013 Elsevier B. V. All rights reserved.

1678. Preparation by sol-gel and solid state reaction methods and properties investigation of double perovskite Sr2FeMoO6

Authors: Cernea, M; Vasiliu, F; Plapcianu, C; Bartha, C; Mercioniu, I; Pasuk, I; Lowndes, R; Trusca, R; Aldica, GV; Pintilie, L

Published: NOV 2013, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33, 2490, DOI: 10.1016/j.jeurceramsoc.2013.03.026

Double perovskite Sr2FeMoO6 was prepared by two ways consisting in sol gel technique and solid-state reaction method. The resulting powders from gel and mixed oxides precursors showed microstructures consisting of very fine grains (0.5-0.8 mu m) and a crystalline perovskite structure. The structural and microstructural properties of the double perovskite Sr2FeMoO6 powders as-prepared and ceramics were compared. Tetragonal Sr2FeMoO6 pellets were prepared from the two powders by spark plasma sintering at: 1000, 1100 and 1200 degrees C and then annealing at 1200 degrees C, 2 h in 5%H-2/Ar. The pellets presented different magnetic characteristics. The saturation magnetization of the samples prepared by sol-gel is close to those prepared by conventional synthesis method. (C) 2013 Elsevier Ltd. All rights reserved.

1679. Postsynthetic Modification of a Metal-Organic Framework (MOF) Structure for Enantioselective Catalytic Epoxidation

Authors: Candu, N; Tudorache, M; Florea, M; Ilyes, E; Vasiliu, F; Mercioniu, I; Coman, SM; Haiduc, I; Andruh, M; Parvulescu, VI

Published: MAY 2013, CHEMPLUSCHEM, 78, 450, DOI: 10.1002/cplu.201300076

Postsynthetic modification of [Cu2(mand)2(hmt)] (mand=mandelic acid, hmt=hexamethylenetetramine) with a chiral, dimeric chromium(III)salen complex led to a robust structure. Characterization of this new material showed that it perfectly preserved the textural and structural properties of the parent metalorganic framework (MOF). Although epoxidation of trans-methyl cinnamate with hydrogen peroxide led to copper leaching of 23%, experiments performed with N-methylmorpholine-N-oxide indicated no leaching, even after 72h of exposure. The obtained chiral MOF is an effective catalyst for the enantioselective epoxidation of trans-methyl cinnamate and leads to (2R,3S)-phenylglycidate with a high enantiomeric excess at room temperature.

1680. BNT-BT0.08 wires derived from sol-gel precursor and their piezoelectric behavior

Authors: Cernea, M; Pintilie, L; Trupina, L; Vasile, BS; Chirila, C; Pasuk, I

Published: MAY 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1668-4

Lead-free piezoelectric (Bi0.5Na0.5)(0.92)Ba0.08TiO3, (abbreviated as BNT-BT0.08) wires were prepared using its corresponding precursor sol and, a polycarbonate template membrane. The polycarbonate membrane used has a thickness of 30 mu m and pore diameter of 300 nm. Uniform surface morphology of the wires with average diameter of 145 nm and a length of about 20 mu m was obtained when the concentration of the sol was 0.3 M. The ferroelectric and piezoelectric properties of an individual BNT-BT0.08 wire were investigated using the PFM technique. The hysteresis loops between the PFM phase and DC bias and, the characteristic butterfly loops of the PFM amplitude versus DC bias, indicated a ferroelectric and piezoelectric behavior of as-obtained BNT-BT0.08 wires.

1681. In-situ electric resistance measurements and annealing effects of graphite exposed to swift heavy ions

Authors: Fernandes, S; Pellemoine, F; Tomut, M; Avilov, M; Bender, M; Boulesteix, M; Krause, M; Mittig, W; Schein, M; Severin, D; Trautmann, C

Published: NOV 1 2013, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 314, 129, DOI: 10.1016/j.nimb.2013.04.060

To study the suitability of using graphite as material for high-power targets for rare isotope production at the future Facility for Rare Isotope Beams (FRIB) in the USA and at the Facility for Antiproton and Ion Research (FAIR) in Germany, thin foils of polycrystalline graphite were exposed to 8.6-MeV/u Au ions reaching a maximum fluence of 1 x 10(15) ions/cm(2). Foil irradiation temperatures of up to 1800 degrees C were obtained by ohmic heating. In-situ monitoring of the electrical resistance of the graphite foils during and after irradiation provided information on beam-induced radiation damage. The rate of electrical resistance increase as a function of fluence was found to decrease with increasing irradiation temperature, indicating a more efficient annealing of the irradiation-produced defects. This is corroborated by the observation that graphite foils irradiated at temperatures below about 800 degrees C showed cracks and pronounced deformations, which did not appear on the samples irradiated at higher temperatures. (C) 2013 Elsevier B.V. All rights reserved.

1682. Role of Hyperfine Coupling in Magnetic and Quadrupolar Ordering of Pr3Pd20Si6

Authors: Steinke, L; Mitsumoto, K; Miclea, CF; Weickert, F; Donni, A; Akatsu, M; Nemoto, Y; Goto, T; Kitazawa, H; Thalmeier, P; Brando, M

Published: AUG 14 2013, PHYSICAL REVIEW LETTERS, 111, DOI: 10.1103/PhysRevLett.111.077202

We study the ternary clathrate Pr3Pd20Si6 in specific heat and ac susceptibility measurements on a high-quality single crystal, distinguishing antiferromagnetic and antiferroquadrupolar ordering, as well as a hitherto unknown magnetic low-temperature transition. The specific heat shows the direct involvement of nuclear spin degrees of freedom in the antiferromagnetic ordering, which is well supported by our calculation of the hyperfine level scheme without adjustable parameters. Pr3Pd20Si6 is, therefore, one of the rare materials where the nuclear moments are involved in the formation of the magnetic ground state.

1683. Behavior of gold nanoparticles in a titania aerogel matrix: Photocatalytic activity assessment and structure investigations

Authors: Pap, Z; Radu, A; Hidi, IJ; Melinte, G; Diamandescu, L; Popescu, T; Baia, L; Danciu, V; Baia, M

Published: APR 2013, CHINESE JOURNAL OF CATALYSIS, 34, 740, DOI: 10.1016/S1872-2067(11)60500-7

TiO2-Au aerogels containing different amounts of gold nanoparticles of different sizes (5 and 16 nm) were successfully synthesized using a sol-gel procedure, and were tested for salicylic acid photo-degradation under UV irradiation. The structure and morphology of the obtained materials were investigated using X-ray diffraction, transmission electron microscopy, and N-2 adsorption-desorption measurements. UV-Vis spectroscopy was used to study the optical properties. The effects of the gold nanoparticles on the TiO2 crystallization process were twofold, as follows: (i) the number of crystallized zones was strongly related to the concentration of the gold nanoparticles, and (ii) the smaller gold particles increased the time taken for the crystallization of the samples. It was found that the noble metal-doped samples exhibited higher degradation rates compared with bare titania. It was found that the most active photocatalyst in each studied system was the sample with the highest concentration of gold nanoparticles. Additionally, the highest degradation rate value was obtained with the smallest Au nanoparticles (46.4 x 10(-3) mu mol/(L.s). (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier By. All rights reserved.

1684. EFFECT OF STRESS ON TRAPPING PHENOMENA IN SILICON: FROM SINGLE CRYSTAL TO NANOSTRUCTURES

Authors: Ciurea, ML

Published: 2013, ROMANIAN REPORTS IN PHYSICS, 65, 856, DOI:

In this article, we present and discuss how the stress influences the trapping phenomena in both the bulk Si and nanostructures based on Si. For this, we use single crystal Si irradiated with 28 MeV iodine ions of fluence (5 +/- 0.5) x 10(11) ions/cm(2) and 2D Si based nanostructures of (nc-Si/CaF2)(50) multilayers. The method of thermally stimulated discharge currents without bias was employed to investigate the trapping phenomena and the modeling of the discharge current curves was carried out. In the case of irradiated Si, we have modeled the discharge currents considering six trapping levels and a supplementary stress electric field independent of temperature superposed on the frozen-in electric field produced by the charged traps at low temperature. The stress electric field is due to the stopped iodine ions which are heavier than those of Si host. Six traps are evidenced and their parameters are calculated. In the (nc-Si/CaF2)(50) multilayer structures, we experimentally evidenced traps which produce in the discharge current maxima with two shapes. Three maxima have normal shape and the others five maxima are narrow and sharp looking like spikes. We modeled the discharge current curves taking for the concentration a power temperature dependence law, and for the cross section a Gaussian temperature dependence.

1685. Conduction mechanism versus annealing in SiO2 films with Ge nanoparticles

Authors: Palade, C; Lepadatu, AM; Stavarache, I; Teodorescu, VS; Ciurea, ML

Published: 2013, 2013 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1-2, 34, DOI:

This paper analyses and discusses the effect of Ge/Si atomic ratio and annealing temperature on the conduction mechanisms governing the electrical behavior of Ge-SiO2 films containing Ge nanoparticles embedded in amorphous SiO2 matrix. For this, the experimental conductance-temperature curves are modeled in correlation with the microstructure findings for two types of films. One type of films has a lower Ge/Si ratio of 0.73 and was obtained by magnetron sputtering followed by annealing in H-2, at 500 degrees C, while the second one has a higher ratio of 1.86 and was obtained also by sputtering, but was annealed in N-2, at 800 degrees C. Both types of films show an electrical behavior with a T-1/4 conductance dependence on temperature, typical for hopping mechanism.

1686. Structural and dielectric properties of Ba(X1/3Ta2/3)O-3 thin films grown by RF-PLD

Authors: Nedelcu, L; Scarisoreanu, ND; Chirila, C; Busuioc, C; Banciu, MG; Jinga, SI; Dinescu, M

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 161, DOI: 10.1016/j.apsusc.2012.10.124

Ba(X1/3Ta2/3)O-3 (X = Mg, Zn) thin films were grown on commercial Pt-coated Si substrates by radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD) method. Single phase Ba(Mg1/3Ta2/3)O-3 and Ba(Zn1/3Ta2/3)O-3 ceramic targets having an ordered hexagonal structure (with P (3) over bar m1 space group) were used for deposition. Structural, morphological and surface characterizations of the Ba(X1/3Ta2/3)O-3 (BXT) films were performed using X-ray diffraction, scanning electron microscopy and atomic force microscopy. X-ray diffraction studies evidenced a cubic (disordered) perovskite structure, with unit cell typical for Pm3m space group. Scanning electron microscopy investigations showed that BXT films have a columnar microstructure, which is oriented perpendicular to the substrate. The temperature dependence of the dielectric permittivity of the films was recorded at 100 kHz. Unlike targets, the BXT films exhibit positive values of the temperature coefficient of the dielectric permittivity. BaMg1/3Ta2/3O3 and BaZn1/3Ta2/3O3 thin films with dielectric constant of about 22.5 and 25, respectively have been obtained. (C) 2012 Elsevier B.V. All rights reserved.

1687. Structural and optical characterization of sol-gel derived Tm-doped BaTiO3 nanopowders and ceramics

Authors: Cernea, M; Secu, CE; Vasile, BS; Secu, M

Published: JAN 2013, CURRENT APPLIED PHYSICS, 13, 141, DOI: 10.1016/j.cap.2012.06.024

Nanocrystalline Tm3+(5%)-doped BaTiO3 (BT-Tm) has been synthesized by the sol-gel method. The morphology, structure, and optical properties of powders and ceramics were characterized. The average grain size of the gel precursor annealed at 700 and 900 degrees C was 20 nm and 30 nm, respectively. These powders were single phase and crystallized with a cubic structure while the BT-Tm sintered ceramics were crystallized with the tetragonal BaTiO3 structure. The photoluminescence spectra showed typical transitions of Tm3+ ions and a structure consistent with the Tm3+ ions incorporation in the BaTiO3 crystalline lattice. Thermoluminescence peaks recorded at 300 degrees C (for annealed samples) or at 230 degrees C for the ceramic sample were assigned to the recombination of the Tm2+-electron traps located mainly at the surface of the nano-crystals or inside the microcrystals, respectively. (C) 2012 Elsevier B.V. All rights reserved.

1688. Disorder in order: silicon versus graphene

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A

Published: MAY 2013, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 250, 1010, DOI: 10.1002/pssb.201248516

The topological transition from order to disorder in crystalline silicon was investigated by a computer simulation procedure. The gradually introduction of topological WootenWinerWeaire defect states makes the crystal change in a more and more disordered assembly of atoms. The characterization of deformation energy around a single defect state is analyzed. The topological transition from graphene structure to an amorphous carbon layer, by introduction of a high number of StoneWales defect-type states was evidenced. The comparison of the disordered structure in tetrahedrally bonded semiconductors (silicon) and a two-dimensional network based on graphene structure was made.

1689. Spectral and transport properties of the two-dimensional Lieb lattice

Authors: Nita, M; Ostahie, B; Aldea, A

Published: MAR 29 2013, PHYSICAL REVIEW B, 87, DOI: 10.1103/PhysRevB.87.125428

The specific topology of the line-centered square lattice (known also as the Lieb lattice) induces remarkable spectral properties such as the macroscopically degenerated zero-energy flat band, the Dirac cone in the low-energy spectrum, and the peculiar Hofstadter-type spectrum in a magnetic field. We study here the properties of the finite Lieb lattice with periodic and vanishing boundary conditions. We investigate the behavior of the flat band induced by disorder and external magnetic and electric fields. We show that in the confined Lieb plaquette threaded by a perpendicular magnetic flux there are edge states with nontrivial behavior. The specific class of twisted edge states, which have alternating chirality, are sensitive to disorder and do not support integer quantum Hall effect (IQHE), but contribute to the longitudinal resistance. The symmetry of the transmittance matrix in the energy range where these states are located is revealed. The diamagnetic moments of the bulk and edge states in the Dirac-Landau domain, and also of the flat states in crossed magnetic and electric fields are shown. DOI: 10.1103/PhysRevB.87.125428

1690. Giant pyroelectric coefficient determined from the frequency dependence of the pyroelectric signal generated by epitaxial Pb(Zr0.2Ti0.8)O-3 layers grown on single crystal SrTiO3 substrates

Authors: Botea, M; Iuga, A; Pintilie, L

Published: DEC 2 2013, APPLIED PHYSICS LETTERS, 103, DOI: 10.1063/1.4838035

Epitaxial Pb(Zr0.2Ti0.8)O-3 layers of good structural quality were grown on single crystal SrTiO3 substrates. The pyroelectric coefficient was estimated from the signal generated by the ferroelectric film working as a pyroelectric detector in the voltage mode, without pre-poling procedure. The obtained value is as high as 1.9 x 10(-3) C/m(2) K. The large value is attributed to the presence of 90 degrees ferroelectric domains and to the compressive misfit strain, leading to an enhanced ferroelectric polarization. (C) 2013 AIP Publishing LLC.

1691. Annealing temperature effect on structure and electrical properties of films formed of Ge nanoparticles in SiO2

Authors: Stavarache, I; Lepadatu, AM; Stoica, T; Ciurea, ML

Published: NOV 15 2013, APPLIED SURFACE SCIENCE, 285, 179, DOI: 10.1016/j.apsusc.2013.08.031

Ge-SiO2 films with high Ge/Si atomic ratio of about 1.86 were obtained by co-sputtering of Ge and SiO2 targets and subsequently annealed at different temperatures between 600 and 1000 C in a conventional furnace in order to show how the annealing process influences the film morphology concerning the Ge nanocrystal and/or amorphous nanoparticle formation and to study their electrical behaviour. Atomic force microscopy (AFM) imaging, Raman spectroscopy and electrical conductance measurements were performed in order to find out the annealing effect on the film surface morphology, as well as the Ge nanoparticle formation in correlation with the hopping conductivity of the films. AFM images show that the films annealed at 600 and 700 C present a granular surface with particle height of about 15 nm, while those annealed at higher temperatures have smoother surface. The Raman investigations evidence Ge nanocrystals (including small ones) coexisting with amorphous Ge in the films annealed at 600 C and show that almost all Ge is crystallized in the films annealed at 700 C. The annealing at 800 C disadvantages the Ge nanocrystal formation due to the strong Ge diffusion. This transition in Ge nanocrystals formation process by annealing temperature increase from 700 to 800 C revealed by AFM and Raman spectroscopy measurements corresponds to a change in the electrical transport mechanism. Thus, in the 700 C annealed films, the current depends on temperature according to a T-1/2 law which is typical for a tunnelling mechanism between neighbour Ge nanocrystals. In the 800C annealed films, the current-temperature characteristic has a T-114 dependence showing a hopping mechanism within an electronic band of localized states related to diffused Ge in SiO2. (C) 2013 Elsevier B.V. All rights reserved.

1692. A new green, ascorbic acid-assisted method for versatile synthesis of Au-graphene hybrids as efficient surface-enhanced Raman scattering platforms

Authors: Iliut, M; Leordean, C; Canpean, V; Teodorescu, CM; Astilean, S

Published: 2013, JOURNAL OF MATERIALS CHEMISTRY C, 1, 4104, DOI: 10.1039/c3tc30177j

A new green method for the synthesis of reduced graphene oxide-gold nanoparticle (rGO-AuNP) hybrids in aqueous solution that exploits the ability of ascorbic acid (AA) to operate as an effective dual agent for both graphene oxide (GO) and gold ion reduction is reported. Through careful investigation of the production of rGO-AuNP hybrids stabilized with polyvinylpyrrolidone (PVP), several versatile routes were devised with the aim of controlling the size, shape and distribution of AuNPs anchored onto the graphene sheets as well as the GO reduction. Particularly, when rGO is used as a platform for Au ion nucleation, a relative sparse distribution of AuNPs of size ranging from 20 nm to 50 nm is noticed. In contrast, when gold ions are added to the solution prior to any GO reduction, the density of large AuNPs is rather low relative to the uniformly packed small sized AuNPs (3-12 nm). The progress of GO reduction is explained by considering the contribution of the catalytic activity of AuNPs, besides the reducing activity of AA. Finally, a plausible mechanism for the nucleation and distribution of AuNPs onto the graphenic surface is assumed, highlighting the significance of oxygen moieties. The green method developed here is promising for the fabrication of gold-graphene nanocomposites with tunable surface "decoration", suitable for surface-enhanced Raman spectroscopy (SERS).

1693. Multi-layer haemocompatible diamond-like carbon coatings obtained by combined radio frequency plasma enhanced chemical vapor deposition and magnetron sputtering

Authors: Popa, AC; Stan, GE; Husanu, MA; Pasuk, I; Popescu, ID; Popescu, AC; Mihailescu, IN

Published: DEC 2013, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 24, 2707, DOI: 10.1007/s10856-013-5026-y

Radio-frequency Plasma Enhanced Chemical Vapour Deposition (in different methane dilutions) was used to synthesize adherent and haemocompatible diamond-like carbon (DLC) films on medical grade titanium substrates. The improvement of the adherence has been achieved by interposing a functional buffer layer with graded composition TixTiC1-x (x = 0-1) synthesized by magnetron co-sputtering. Bonding strength values of up to similar to 67 MPa have been measured by pull-out tests. Films with different sp(3)/sp(2) ratio have been obtained by changing the methane concentration in the deposition chamber. Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed for the physical-chemical characterization of the samples. The highest concentration of sp(3)-C (similar to 87 %), corresponding to a lower DLC surface energy (28.7 mJ/m(2) ), was deposited in a pure methane atmosphere. The biological response of the DLC films was assayed by a state-of-the-art biological analysis method (surface enhanced laser desorption/ionization-time of flight mass spectroscopy), in conjunction with other dedicated testing techniques: Western blot and partial thromboplastin time. The data support a cause-effect relationship between sp(3)-C content, surface energy and coagulation time, as well as between platelet-surface adherence properties and protein adsorption profiles.

1694. Silicon bump arrays by near-field enhanced femtosecond laser irradiation in fluorine liquid precursors

Authors: Ulmeanu, M; Anghel, I; Jipa, F; Filipescu, M; Enculescu, M; Zamfirescu, M

Published: AUG 1 2013, APPLIED SURFACE SCIENCE, 278, 304, DOI: 10.1016/j.apsusc.2013.01.050

A simple approach to fabricate periodic arrays of conical bumps on silicon (Si) substrate is reported. In the process, a single pulse from a 200 fs laser at 387 nm wavelength was applied on a self-assembled monolayer of 700 nm and 390 nm diameter silica spheres on a n-doped Si (1 0 0) wafer. The surface was irradiated at normal incidence by immersing the silicon substrates in a glass container filled with 1, 1, 2 trichlor-trifluorethan liquid precursors. After laser irradiation, at laser fluences in the range from 1 to 40 J/cm(2), a regular array of conical Si bumps was fabricated. The density of the Si bumps can be varied by varying the particle size diameter. The influence of the medium on the near-field interactions for both sizes silica particles layer is investigated. (C) 2013 Elsevier B.V. All rights reserved.

1695. Effect of tritiation on the superconducting properties of MgB2

Authors: Sandu, V; Aldica, G; Baibarac, M; Enachescu, M; Sandu, E; Chee, CY

Published: APR 2013, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 26, DOI: 10.1088/0953-2048/26/4/045014

We investigated the effect of tritium upload in the dense, polycrystalline MgB2 superconductor for 2 and 216 h. One basic property, the critical temperature T-c, slowly changes in time but is independent of the duration of tritium uptake. Immediately after tritiation, T-c shows a slight increase to 39.1 K but decreases to the critical temperature of the untritiated (pristine) sample, T-c = 38.8 K, after 370 days. The critical current density is strongly dependent on the tritium upload time, mainly at high magnetic fields. The underlying physics is discussed. This behaviour makes the use of MgB2 based conductors advantageous in tritium environments like fusion reactors.

1696. On the properties of aluminium doped zinc oxide thin films deposited on plastic substrates from ceramic targets

Authors: Girtan, M; Vlad, A; Mallet, R; Bodea, MA; Pedarnig, JD; Stanculescu, A; Mardare, D; Leontie, L; Antohe, S

Published: JUN 1 2013, APPLIED SURFACE SCIENCE, 274, 313, DOI: 10.1016/j.apsusc.2013.03.046

We report on the deposition of Al doped ZnO (AZO) thin films on unheated polyethylene terephthalate (PET) substrates by pulsed laser deposition technique using a UV excimer laser and Al2O3:ZnO ceramic targets (1.5 and 2 wt% Al2O3). The deposited AZO films have been investigated by atomic force microscopy, scanning electron microscopy, X-ray diffraction, and optical spectrophotometry. Films present excellent optical and electrical properties (transmission in the visible range T > 85%; resistivity at room temperature rho = 1.3 x 10(-3) Omega cm) as electrodes for plastic solar cells. A good correlation was found between deposition conditions (laser fluence) and structural, morphological, optical and electrical properties. (C) 2013 Elsevier B.V. All rights reserved.

1697. Direct sintering of SiC-W composites with enhanced thermal conductivity

Authors: Galatanu, M; Popescu, B; Enculescu, M; Tiseanu, I; Craciunescu, T; Galatanu, A

Published: OCT 2013, FUSION ENGINEERING AND DESIGN, 88, 2602, DOI: 10.1016/j.fusengdes.2013.05.036

Different types of SiC-W composites have been realized by spark plasma sintering in a single step process starting with beta SiC nanometric powder, W nanometric and micrometric sized powders, and W foils. SEM, EDX, XRD and X-ray tomography have been used to analyze the sample morphology while the thermal properties of the resulting materials have been investigated up to 1000 degrees C using a LFA thermal analyzer. The results show the possibility to produce dense W-SiC composites, with enhanced thermal conductivity using a relatively simple route. (C) 2013 Elsevier B.V. All rights reserved.

1698. Dense Ge nanocrystal layers embedded in oxide obtained by controlling the diffusion-crystallization process

Authors: Lepadatu, AM; Stoica, T; Stavarache, I; Teodorescu, VS; Buca, D; Ciurea, ML

Published: SEP 15 2013, JOURNAL OF NANOPARTICLE RESEARCH, 15, DOI: 10.1007/s11051-013-1981-y

Amorphous Ge/SiO2 multilayer structures deposited by magnetron sputtering have been annealed at different temperatures between 650 and 800 degrees C for obtaining Ge nanocrystals in oxide matrix. The properties of the annealed structures were investigated by transmission electron microscopy, Raman spectroscopy, and low temperature photoluminescence. The Ge crystallization is partially achieved at 650 degrees C and increases with annealing temperature. Insight of the Ge nanocrystal formation was acquired by comparing two annealing procedures, i.e., in a conventional tube furnace and by a rapid thermal annealing. By rapid thermal annealing in comparison to conventional furnace one, the Ge crystallization process is faster than Ge diffusion, resulting in the formation of more compact layers of Ge nanocrystals with 8-9.5-nm size as Raman spectroscopy reveals. These findings are important to improve the annealing efficiency in the nanocrystals formation for a precise control of their sizes and location in oxide matrix and for the possibility to create systems with interacting nanoparticles for charge or excitonic transfer. The infrared photoluminescence of Ge nanocrystals at low temperatures shows strong emission with two sharp peaks at about 1,000 meV.

1699. Iron Oxide Magnetic Nanoparticles: Characterization and Toxicity Evaluation by In Vitro and In Vivo Assays

Authors: Prodan, AM; Iconaru, SL; Ciobanu, CS; Chifiriuc, MC; Stoicea, M; Predoi, D

Published: 2013, JOURNAL OF NANOMATERIALS, 2013, DOI: 10.1155/2013/587021

The aim of this study was to evaluate the biological properties of iron oxide nanoparticles (IO-NPs) obtained in the aqueous suspension. The iron oxide nanoparticles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The biocompatibility of the iron oxide was demonstrated by the in vitro quantification of HeLa cells viability using propidium iodide (PI) and fluorescein diacetate (FdA) and the MTT colorimetric assay. The toxicity of small size iron oxide nanoparticles was also evaluated by means of histological examination on male Brown Norway rats after intraperitoneal injection. At the tested concentrations, the nanoparticles proved to be not cytotoxic on HeLa cells. The rat's behavior, as well as the histopathological aspect of liver, kidney, lung, and spleen tissues at 48 h after intraperitoneal injection did not present any modifications. The in vivo and in vitro assays suggested that the IO-NPs could be further used for developing new in vivo medical applications.

1700. Au-Ge bonding on a uniformly Au-covered Ge(001) surface

Authors: Popescu, DG; Husanu, MA

Published: APR 2013, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 7, 277, DOI: 10.1002/pssr.201307029

The structure and electronic properties of the system resulted by epitaxial growth of a single atomic Au layer on a heated Ge(001) surface featured by (2 x 1) reconstruction are studied. The deposition at similar to 750 K results in a well-ordered Au surface featured by ripples separated by four times the theoretical distance between two neighboring Au atoms. As revealed by valence-band photoemission studies, the Au/Ge(001) system has metallic character. Correlating X-ray photoelectron spectroscopy results with first-principles calculations we derive the implications on the covalent bonding of Au on the Ge dimer surface. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1701. Correlation of Lattice Disorder with Crystallite Size and the Growth Kinetics of Mn2+ Doped ZnO Nanocrystals Probed by Electron Paramagnetic Resonance

Authors: Stefan, M; Nistor, SV; Ghica, D

Published: MAR 2013, CRYSTAL GROWTH & DESIGN, 13, 1359, DOI: 10.1021/cg400037c

The correlation of the lattice disorder with the nanocrystal average size, in ZnO nanocrystals synthesized by several different methods, has been quantitatively monitored by line shape analysis of the multifrequency electron paramagnetic resonance (EPR) spectra of low concentrations of substitutional Mn2+ probing ions. The observed correlation between the line broadening parameter of the spectrum and the average ZnO nanocrystals size, independent of the synthesis procedure of the ZnO nanocrystals, demonstrates the dominance of the size related strain/disorder. On the basis of this result, a new method for determining the average ZnO nanocrystal size from the quantitative analysis of the EPR spectra of the Mn2+ probes was derived. The nanocrystallization of the disordered ZnO formed by the thermal decomposition of hydrozincite was monitored using this procedure. The observed ZnO nanocrystallite growth kinetics at lower temperatures was described by a structural relaxation mechanism consisting of the local ordering by rearrangements of the atoms in the interfaces/grain boundaries, with a growth activation energy of similar to 23 kJ/mol. When the nanostructured ZnO was more than 75% crystallized, another growth mechanism of the nanocrystals was found to occur, driven by the reduction of the total grain boundary energy.

1702. Precursor method-A nonconventional route for the synthesis of ZnCr2O4 spinel

Authors: Gingasu, D; Mindru, I; Patron, L; Culita, DC; Calderon-Moreno, JM; Diamandescu, L; Feder, M; Oprea, O

Published: SEP 2013, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 74, 1302, DOI: 10.1016/j.jpcs.2013.04.007

Zinc chromites (ZnCr2O4) have been synthesized via thermal decomposition of (NH4)(2)[ZnCr2(C4O6OH)(2)]center dot 9H(2)O and (NH4)(3)[ZnCr2(C6O7H11)(4)(OH)(7)]center dot H2O precursors. The complex precursors have been characterized by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-vis), thermal analysis and scanning electron microscopy (SEM). ZnCr2O4 samples have been investigated and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-vis) and photolumininescence (PL) spectroscopy and Brunauer-Emmett-Teller (BET) N-2 adsorption-desorption analyses. Nanoscaled (similar to 60 nm) single-phase zinc chromites were obtained by heating the precursors at 900 degrees C for 1 h. The influence of thermal treatment of tartarate precursor on structural, morphological and textural properties of ZnCr2O4 is discussed. (C) 2013 Elsevier Ltd. All rights reserved.

1703. Luminescent Eosin Y-SiO2 hybrid nano and microrods prepared by sol-gel template method

Authors: Secu, M; Secu, CE; Sima, M; Negrea, RF; Bartha, C; Dinescu, M; Damian, V

Published: NOV 2013, JOURNAL OF LUMINESCENCE, 143, 92, DOI: 10.1016/j.jlumin.2013.04.043

Sol-gel chemistry within the pores of a polycarbonate template membrane was used for the preparation of Eosin Y-SiO2 hybrid nano- and microrods, using tetraethylorthosilicate [TEOS, Si(OC2H5)(4)] as the precursor in the presence of trifluoroacetic acid (TFA) catalyst. The ethanolic solution of Eosin-Y was added to the silica sal to trap dye molecules inside the SiO2 gel network during the gelation. Structural and morphological characterization using scanning electron microscopy (SEM) and luminescence microscopy have shown the formation of rods with 200 nm and 1.2 mu m diameter and about 30 mu m length, exhibiting luminescence properties. Spectroscopic characterization has shown that the luminescence is due to Eosin-Y molecule in the xerogel porous network, surrounded by a solvation shell given mainly by the water. (C) 2013 Elsevier B.V. All rights reserved.

1704. Analysis of defect formation in semiconductor cryogenic bolometric detectors created by heavy dark matter

Authors: Lazanu, I; Ciurea, ML; Lazanu, S

Published: APR 2013, ASTROPARTICLE PHYSICS, 44, 14, DOI: 10.1016/j.astropartphys.2013.01.005

The cryogenic detectors in the form of bolometers are presently used for different applications, in particular for very rare or hypothetical events associated with new forms of matter, specifically related to searches for dark matter. In the detection of particles with a semiconductor as target and detector, usually two signals are measured: ionization and heat. The amplification of the thermal signal is obtained with the prescriptions from the Luke-Neganov effect. The energy deposited in the semiconductor lattice as stable defects in the form of Frenkel pairs at cryogenic temperatures, following the interaction of a dark matter particle, is evaluated and consequences for measured quantities are discussed. This contribution is included in the energy balance of the Luke effect. Applying the present model to germanium and silicon, we found that for the same incident weakly interacting massive particle the energy deposited in defects in germanium is about twice the value for silicon. (C) 2013 Elsevier B.V. All rights reserved.

1705. Functionalized magnetite silica thin films fabricated by MAPLE with antibiofilm properties

Authors: Mihaiescu, DE; Cristescu, R; Dorcioman, G; Popescu, CE; Nita, C; Socol, G; Mihailescu, IN; Grumezescu, AM; Gudovan, D; Enculescu, M; Negrea, RF; Ghica, C; Chifiriuc, C; Bleotu, C; Chrisey, DB

Published: MAR 2013, BIOFABRICATION, 5, DOI: 10.1088/1758-5082/5/1/015007

We report on the fabrication of magnetite/salicylic acid/silica shell/antibiotics (Fe3O4/SA/SiO2/ATB) thin films by matrix-assisted pulsed laser evaporation (MAPLE) to inert substrates. Fe3O4-based powder have been synthesized and investigated by XRD and TEM. All thin films were studied by FTIR, SEM and in vitro biological assays using Staphylococcus aureus and Pseudomonas aeruginosa reference strains, as well as eukaryotic HEp-2 cells. The influence of the obtained nanosystems on the microbial biofilm development as well as their biocompatibility has been assessed. For optimum deposition conditions, we obtained uniform adherent films with the composition identical with the raw materials. Fe3O4/SA/SiO2/ATB thin films had an inhibitory activity on the ability of microbial strains to initiate and develop mature biofilms, in a strain-and antibiotic-dependent manner. These magnetite silica thin films are promising candidates for the development of novel materials designed for the inhibition of medical biofilms formed by different pathogenic agents on common substrates, frequently implicated in the etiology of chronic and hard to treat infections.

1706. Investigation of thermal stability, spectral, magnetic, and antimicrobial behavior for new complexes of Ni(II), Cu(II), and Zn(II) with a bismacrocyclic ligand

Authors: Bucur, C; Korosec, RC; Badea, M; Calu, L; Chifiriuc, MC; Grecu, N; Stanica, N; Marinescu, D; Olar, R

Published: SEP 2013, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 113, 1295, DOI: 10.1007/s10973-012-2912-3

Novel complexes of type M2LCl4 center dot nH(2)O (M: Ni, n = 4; M: Cu, n = 2.5 and M: Zn, n = 1.5; L: ligand resulted from 1,3-phenylenediamine, 3,6-diazaoctane-1,8-diamine, and formaldehyde one-pot condensation) were synthesized and characterized. The ligand was also isolated and characterized. The complexes features have been assigned from microanalytical, electrospray ionization tandem mass spectrometry, IR, UV-vis, H-1 NMR, and EPR spectra as well as magnetic data at room temperature. Simultaneous thermogravimetric/dynamic scanning calorimetry/evolved gas analysis measurements were performed to evidence the nature of the gaseous products formed in each step. Processes as water elimination, fragmentation, and oxidative degradation of the organic ligand as well as chloride elimination were observed during the thermal decomposition. The final product of decomposition was metal(II) oxide except for copper complex where CuCl remained also in the oxide network. The complexes exhibited an improved antibacterial activity in comparison with the ligand concerning both planktonic as well as biofilm-embedded cells.

1707. Casimir effect demonstrated by Raman spectroscopy on trilayer graphene intercalated into stiff layered structures of surfactant

Authors: Baibarac, M; Baltog, I; Mihut, L; Pasuk, I; Lefrant, S

Published: JAN 2013, CARBON, 51, 142, DOI: 10.1016/j.carbon.2012.08.021

Polarized Raman scattering studies on stiff layered structure of surfactant intercalated with trilayer graphene were performed at different intensities and excitation wavelengths. The D and 2D Raman bands reach the highest and lowest intensity when the polarization of laser excitation light is oriented along and perpendicular on the edges. The 2D band discloses two lorentzian components, separated by similar to 40 cm(-1), which result from the action of interplanar forces, of Casimir nature. The value of similar to 40 cm(-1) is close to the energy value associated with E-2g interplanar layer shear mode evidenced so far only by neutron spectrometry. A new result regards the opposite variation of the intensities of D and 2D bands with the increase of the wavelength of the excitation light. This originates in the different origin of the D and 2D bands; the former is dependent on disorder including also the graphene edges while the latter, results from in a double resonant mechanism combined with a Casimir effect. One demonstrates that the magnitude of Casimir force, which activates interlayer vibration modes, depends on the carrier density on the graphene sheets which can be varied both by the intensity and the wavelength of the excitation laser light. (C) 2012 Elsevier Ltd. All rights reserved.

1708. Strong antibunching from electrically driven devices with long pulses: A regime for quantum-dot single-photon generation

Authors: Kessler, CA; Reischle, M; Hargart, F; Schulz, WM; Eichfelder, M; Rossbach, R; Jetter, M; Michler, P; Gartner, P; Florian, M; Gies, C; Jahnke, F

Published: SEP 19 2012, PHYSICAL REVIEW B, 86, DOI: 10.1103/PhysRevB.86.115326

We present excitation-pulse-width-and pump-power-dependent microelectroluminescence and photon statistics measurements on electrically driven single-photon devices based on InP/AlGaInP quantum dots (QDs). For an excitation regime far below QD saturation, the results show a characteristic decrease of the purity of the single-photon emission [g((2))(0) value] with increasing excitation pulse width. For stronger excitation pulses close to QD saturation, strong antibunching is maintained for a much larger pulse width. In this case the ground-state exciton emission, which is used for the single-photon source, is inhibited during the pump pulse due to the presence of higher excited states. This prevents multiple-ground-state emission and reexcitation during long pump pulses and delays the single-photon emission to the end of the pulse, as predicted by theory and confirmed experimentally.

1709. Dielectric and piezoelectric behaviors of NBT-BT0.05 processed by sol-gel method

Authors: Cernea, M; Vasile, BS; Capiani, C; Ioncea, A; Galassi, C

Published: JAN 2012, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 32, 139, DOI: 10.1016/j.jeurceramsoc.2011.07.038

(Na0.5Bi0.5)TiO3 doped with 5 mol% BaTiO3 (NBT-BT0.05) nanopowder was prepared by sol-gel method. Structural and microstructural investigations revealed a powder crystallized in the Na0.5Bi0.5TiO3 rhombohedral phase form. Ceramics processed from this powder show good dielectric (epsilon(r) = 3940 and tan delta = 0.016) and piezoelectric characteristics (d(33) = 77 pC/N, k(p) = 0.091, epsilon(T)(33) = 1080 and Q(m) = 197.5). The as-obtained NBT-BT0.05 ceramic appears effective for piezoelectric resonator and high power applications. (C) 2011 Elsevier Ltd. All rights reserved.

1710. The Influence of the Au Nanoparticles Dimension on the Photocatalytic Performances of TiO2-Au Porous Composites

Authors: Melinte, G; Baia, M; Georgescu, D; Baia, L; Iancu, V; Diamandescu, L; Popescu, T; Cotet, LC; Barbu-Tudoran, L; Danciu, V; Simon, S

Published: JAN 2012, ACTA PHYSICA POLONICA A, 121, 210, DOI: 10.12693/APhysPolA.121.208

The influence of Au nanoparticles dimension on the photocatalytic performances of the TiO2 aerogels-Au composites was evaluated. Structural and morphological peculiarities of the TiO2 aerogel, unloaded and loaded with 5 and 22 nm Au nanoparticles, were studied by transmission electron microscopy technique, X-ray diffraction and N-2-sorption measurements. UV-Vis diffuse reflectance measurements were performed to determine the band gap energies. The photocatalytic activity was evaluated by monitoring the salicylic acid photodegradation. It was found that the Au nanoparticles promote the anatase phase crystallization and produce the decrease of the specific surface area and band gap energy values. The porous composite with the smallest Au nanoparticles dimension exhibits the best photocatalytic performances.

1711. The influence of the chemical treatment on the ferromagnetic behavior of carbon nanotubes synthesized using ferromagnetic catalyst

Authors: Stancu, M; Ruxanda, G; Stanica, N; Dinescu, A; Nistor, L; Ciuparu, D

Published: JUL-AUG 2012, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 6, 726, DOI:

In this contribution we report results of our investigations on the ferromagnetic behavior of pristine and chemically treatedcarbon nanotubes, synthesized by AC arc discharge method using iron powder as catalyst. The magnetic properties of the carbon nanotubes samples before and after chemical treatment were measured at room temperature in a vibrating - sample magnetometer. We observed significant changes of the ferromagnetic behavior of carbon nanotubes after the purification and concluded that the magnetic properties of carbon nanotubes synthesized using ferromagnetic catalyst are governed by the ferromagnetic catalyst nanoparticles attached to their walls during synthesis.

1712. Luminescent micro- and nanofibers based on novel europium phthalate complex

Authors: Enculescu, M; Preda, N; Matei, E; Enculescu, I

Published: SEP 14 2012, MATERIALS CHEMISTRY AND PHYSICS, 136, 58, DOI: 10.1016/j.matchemphys.2012.06.018

We synthesized by wet chemical route a novel europium-potassium phthalate complex Eu3+K+[(COO)(2)(C6H4)](2). The compound is a white powder insoluble in water. X-ray diffraction evaluation shows that we obtained a new crystalline compound with no traces of the starting materials (potassium hydrogen phthalate and europium chloride). Scanning electron microscopy reveals that the powder consists of fiber-shaped structures with sizes larger than 250 nm in diameter. Energy dispersive X-ray analysis proves that the compound has a 1:1 europium-potassium ratio. Fourier transform infrared spectroscopy confirms the presence of the phthalate in the new compound. Photoluminescence and cathodoluminescence measurements show that the fiber-shaped structures are intensely luminescent with emission bands corresponding to the D-5(0) -> F-7(J) (J = 1-4) Eu (III) ion's transitions in the region between 580 nm and 700 nm, the most intense maximum being observed around 615 nm. Up-converted luminescence with a maximum at 315 nm was recorded. (c) 2012 Elsevier B.V. All rights reserved.

1713. Synthesis and characterization of bead-like particles based on chitosan and vinyl polymers

Authors: Preda, N; Enculescu, M

Published: SEP 2012, JOURNAL OF POLYMER RESEARCH, 19, DOI: 10.1007/s10965-012-9963-9

Styrene, methyl methacrylate and glycidyl methacrylate vinyl monomers were grafted onto chitosan by surfactant-free emulsion copolymerization using potassium persulfate as initiator. The grafted compounds were characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and zeta potential measurements. X-ray diffraction showed changes in the crystallinity pattern of chitosan after the copolymerization reaction. Evidence of grafting was confirmed by FTIR spectroscopy. From zeta potential measurements it is found that the surfaces of graft copolymers latex particles have positive charges resulting from the cationic chitosan molecules. The morphology evaluated by SEM, TEM and AFM proves that in the absence of chitosan, latexes of vinyl homopolymers contain quasi-monodispersed spheres with average diameter of about 400 nm or 250 nm while the graft copolymers latexes are formed by clustered irregular beads with average diameter around 100 nm.

1714. Structural, Optical, and Dielectric Properties of Bi1.5-xZn0.92-yNb1.5O6.92-delta Thin Films Grown by PLD on R-plane Sapphire and LaAlO3 Substrates

Authors: Le Febvrier, A; Galca, AC; Corredores, Y; Deputier, S; Bouquet, V; Demange, V; Castel, X; Sauleau, R; Lefort, R; Zhang, LY; Tanne, G; Pintilie, L; Guilloux-Viry, M

Published: OCT 2012, ACS APPLIED MATERIALS & INTERFACES, 4, 5233, DOI: 10.1021/am301152r

Bi1.5-xZn0.92-yNb1.5O6.92-delta thin films have the potential to be implemented in microwave devices. This work aims to establish the effect of the substrate and of the grain size on the optical and dielectric properties. Bi1.5-xZn0.92-yNb1.5O6.92-delta thin films were grown at 700 degrees C via pulsed-laser deposition on R-plane sapphire and (100)(pc) LaAlO3 substrates at various oxygen pressures (30, 50, and 70 Pa). The structure, morphology, dielectric and optical properties were investigated. Despite bismuth and zinc deficiencies, with respect to the Bi1.5Zn0.92Nb1.5O6.92 stoichiometry, the films show the expected cubic pyrochlore structure with a (100) epitaxial-like growth. Different morphologies and related optical and dielectric properties were achieved, depending on the substrate and the oxygen pressure. In contrast to thin films grown on (100)(pc) LaAlO3, the films deposited on R-plane sapphire are characterized by a graded refractive index along the layer thickness. The refractive index (n) at 630 nm and the relative permittivity (epsilon(t)) measured at 10 GHz increase with the grain size: on sapphire, n varies from 2.29 to 2.39 and epsilon(r) varies from 85 to 135, when the grain size increases from 37 nm to 77 nm. On the basis of this trend, visible ellipsometry can be used to probe the characteristics in the microwave range quickly, nondestructively, and at a low cost.

1715. NO2 sensing properties of Cr2O3 highlighted by work function investigations

Authors: Stanoiu, A; Simion, CE; Diamandescu, L; Tarabasanu-Mihaila, D; Feder, M

Published: NOV 1 2012, THIN SOLID FILMS, 522, 400, DOI: 10.1016/j.tsf.2012.09.003

Gas sensing peculiarities of chromiumoxide (Cr2O3) nanoparticles, obtained by hydrothermal reaction at moderate temperature and subsequent thermal annealing, were studied. The structure and morphology of the obtained Cr2O3 samples were investigated by X-ray diffraction and transmission electron microscopy techniques. Gas sensing measurements revealed their selective sensitivity to nitrogen dioxide (NO2) at 200 degrees C relative to carbon monoxide (CO), both in dry and humid air. Higher selectivity towards NO2 is attributed to the material surface reactivity even at low operating temperatures. This property was experimentally highlighted by work function changes, as a complementary investigation method to basic electrical resistance. Thus, it was observed that the surface reactivity of Cr2O3 (calcinated at 1000 degrees C) towards NO2 is higher compared to CO and less influenced by the relative humidity of the surrounding atmosphere. The present study reveals possible applications in the selective detection of NO2 based on Cr2O3. (C) 2012 Elsevier B.V. All rights reserved.

1716. Treatment of carrier scattering in quantum dots beyond the Boltzmann equation

Authors: Steinhoff, A; Gartner, P; Florian, M; Jahnke, F

Published: MAY 29 2012, PHYSICAL REVIEW B, 85, DOI: 10.1103/PhysRevB.85.205144

As quantum dots (QD) can confine a small number of carriers in localized states with discrete energies, it is questionable to neglect correlations between the carriers when describing their dynamics. We analyze the influence of carrier correlations in a single QD on Coulomb scattering processes, which are due to the contact with a quasicontinuum of wetting-layer (WL) states. Results obtained from a Boltzmann equation are compared with the fully correlated dynamics governed by a von Neumann-Lindblad equation. In a first step, we take into account correlations generated by the exact treatment of Pauli blocking due to the contributing QD carrier configurations. Subsequently, we include correlations generated by energy renormalizations due to Coulomb interaction between the QD carriers. It is shown that at low WL carrier densities, neither Pauli correlations nor Coulomb correlations can be safely neglected, if the dynamics of single-particle states in the QD are to be predicted qualitatively and quantitatively. In the high-density regime, both types of correlations play a lesser role and thus a description of carrier dynamics by a Boltzmann equation becomes reliable. Furthermore, the efficiency of WL-assisted scattering processes as well as scattering-induced dephasing rates depending on the WL carrier density are discussed.

1717. Modeling single quantum dots in microcavities

Authors: Gies, C; Florian, M; Jahnke, F; Gartner, P

Published: 2012, QUANTUM OPTICS WITH SEMICONDUCTOR NANOSTRUCTURES, 114, DOI:

This chapter presents a theoretical framework for the description of the light-matter interaction of a single semiconductor quantum dot in a microcavity. A particular focus is the semiconductor properties of the device, the contributions of various electronic configurations, and the embedded nature of the quantum dot due to its coupling to delocalized states. Stimulated emission from the excitonic ground state and from higher excited states is discussed together with the photon statistics and cavity emission spectra. The role of dephasing for transitions between different configurations is explained. We exploit a direct solution of the von Neumann equation for the statistical operator including the full light-matter interaction in terms of the Jaynes-Cummings interaction Hamiltonian, as well as the Coulomb interaction of the quantum-dot carriers. Various dissipative processes are systematically considered using Lindblad terms.

1718. TILT c AXIS CRYSTALLITE GROWTH OF ALUMINIUM NITRIDE FILMS BY REACTIVE RF-MAGNETRON SPUTTERING

Authors: Stan, GE; Pasuk, I; Trinca, LM; Galca, AC; Enculescu, M; Miculescu, F

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 50, DOI:

The article reports on the tilted growth of textured aluminium nitride thin films obtained by radio-frequency magnetron sputtering onto 50 mm diameter Si (111) wafers, in reactive atmosphere, in a planar sputtering system without tilting the substrate and with no additional sputtering geometry alterations. The films were investigated using, X-ray diffraction, spectroscopic ellipsometry and scanning electronic microscopy, done by local measurements on the wafer surface, at different distances from the centre. A progressive increase of the tilt angle when moving away from the sample centre has been found. The maximum tilt angle of the columnar AlN crystallites, obtained near the edges of the wafer, is about 7 degrees. The results showed also that tilting is associated with smaller thickness and larger dispersion of the c axis orientation. Synthesizing inclined c axis AlN films should allow the fabrication of surface acoustic wave devices based on shear waves for liquid sensor applications.

1719. A HIGH PERFORMANCE PIEZOCERAMIC MATERIAL FOR A VIBRATION TRANSDUCER FOR BALANCING OF ROTATING PARTS

Authors: Miclea, CT; Cioangher, M; Miclea, CF; Trupina, L; Miclea, C; Amarande, L; Spanulescu, S; Faibis, R

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 294, DOI:

A high performance piezoceramic material of PZT type, doped with 6 atomic % W, was prepared in order to be used as sensing element for a vibration transducer used to equilibrate the motor-fan group of auto vehicles. The piezoelectric parameters of material showed high values which recommended it for the vibration transducer. The transducer consists of a ring shaped active element sandwiched between two steel blocks. The transducer works in quasistatic regime, at frequencies much lower than the resonance frequency, being tightly screwed in the measurement system by a metallic cover attached at the back end.

1720. Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectors

Authors: Gherendi, M; Zoita, VL; Craciunescu, T; Johnson, MG; Pantea, A; Baltog, I; Edlington, T; Hellesen, C; Kiptily, V; Conroy, S; Murari, A; Popovichev, S

Published: OCT 2012, REVIEW OF SCIENTIFIC INSTRUMENTS, 83, DOI: 10.1063/1.4739410

The neutron field parameters (fluence and energy distribution) at a specific location outside the JET Torus Hall have been measured by means of super-heated fluid detectors (or "bubble detectors") in combination with an independent, time-of-flight, technique. The bubble detector assemblies were placed at the end of a vertical line of sight at about 16 m from the tokamak mid plane. Spatial distributions of the neutron fluence along the radial and toroidal directions have been obtained using two-dimensional arrays of bubble detectors. Using a set of three bubble detector spectrometers the neutron energy distribution was determined over a broad energy range, from about 10 keV to above 10 MeV, with an energy resolution of about 30% at 2.5 MeV. The very broad energy response allowed for the identification of energy features far from the main fusion component (around 2.45 MeV for deuterium discharges). [http://dx.doi.org/10.1063/1.4739410]

1721. Insight into non-linearly shaped superconducting whiskers via a synchrotron nanoprobe

Authors: Cagliero, S; Borfecchia, E; Mino, L; Calore, L; Bertolotti, F; Martinez-Criado, G; Operti, L; Agostino, A; Truccato, M; Badica, P; Lamberti, C

Published: DEC 2012, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 25, DOI: 10.1088/0953-2048/25/12/125002

We were successful in synthesizing non-linear YBa(2)Cu(3)Ox whiskers, i.e. half loops or kinked shapes, which are promising candidates for solid-state devices based on the intrinsic Josephson effect and with improved electrical connections. We report on a complete characterization of their structural properties via a synchrotron nanoprobe as well as laboratory single-crystal diffraction techniques. This investigation allowed us to fully disclose the growth mechanism, which leads to the formation of curved whiskers. The superconducting properties are evaluated in comparison with their straight counterpart, revealing a strong functional analogy and confirming their potential applicability in superconducting electronic devices.

1722. Investigation of X-ray induced radiation damage at the Si-SiO2 interface of silicon sensors for the European XFEL

Authors: Zhang, J; Fretwurst, E; Klanner, R; Pintilie, I; Schwandt, J; Turcato, M

Published: DEC 2012, JOURNAL OF INSTRUMENTATION, 7, DOI: 10.1088/1748-0221/7/12/C12012

Experiments at the European X-ray Free Electron Laser (XFEL) require silicon pixel sensors which can withstand X-ray doses up to 1 GGy. For the investigation of X-ray radiation damage up to these high doses, MOS capacitors and gate-controlled diodes built on high resistivity n-doped silicon with crystal orientations < 100 > and < 111 > produced by two vendors, CiS and Hamamatsu, have been irradiated with 12 keV X-rays at the DESY DORIS III synchrotron light source. Using capacitance/conductance-voltage, current-voltage and thermal dielectric relaxation current measurements, the surface densities of oxide charges and interface traps at the Si-SiO2 interface, and the surface-current densities have been determined as function of dose. Results indicate that the dose dependence of the surface density of oxide charges and the surface-current density depend on the crystal orientation and producer. In addition, the influence of the voltage applied to the gates of the MOS capacitor and the gate-controlled diode during X-ray irradiation on the surface density of oxide charges and the surface-current density has been investigated at doses of 100 kGy and 100MGy. It is found that both strongly depend on the gate voltage if the electric field in the oxide points from the surface of the SiO2 to the Si-SiO2 interface. Finally, annealing studies have been performed at 60 degrees C and 80 degrees C on MOS capacitors and gate-controlled diodes irradiated to 5MGy and the annealing kinetics of oxide charges and surface current determined.

1723. Hybrid dextran-iron oxide thin films deposited by laser techniques for biomedical applications

Authors: Predoi, D; Ciobanu, CS; Radu, M; Costache, M; Dinischiotu, A; Popescu, C; Axente, E; Mihailescu, IN; Gyorgy, E

Published: MAR 1 2012, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 32, 302, DOI: 10.1016/j.msec.2011.10.032

Iron oxide oxide nanoparticles were prepared by chemical co-precipitation method. The nanoparticles were mixed with dextran in distilled water. The obtained solutions were frozen in liquid nitrogen and used as targets during matrix assisted pulsed laser evaporation for the growth of hybrid, iron oxide nanoparticles-dextran thin films. Fourier Transform Infrared Spectroscopy and X-ray diffraction investigations revealed that the obtained films preserve the structure and composition of the initial, non-irradiated iron oxide-dextran composite material. The biocompatibility of the iron oxide-dextran thin films was demonstrated by 3-(4.5 dimethylthiazol-2yl)-2.5-diphenyltetrazolium bromide-based colorimetric assay, using human liver hepatocellular carcinoma cells. (C) 2011 Elsevier B.V. All rights reserved.

1724. Raman scattering and anti-Stokes luminescence in poly-paraphenylene vinylene/carbon nanotubes composites

Authors: Baibarac, M; Massuyeau, F; Wery, J; Baltog, I; Lefrant, S

Published: APR 15 2012, JOURNAL OF APPLIED PHYSICS, 111, DOI: 10.1063/1.4705403

In this paper, we present Raman scattering and luminescence of poly-paraphenylene vinylene/single-walled carbon nanotubes composites, focused on data recorded in the anti-Stokes branch. We demonstrate that, when the excitation energy is in the long wavelength tail of the fundamental absorption edge, an anti-Stokes signal is generated, whose origin is a photon absorption accompanied by a phonon process from lower to upper vibronic states. The efficiency of this anti-Stokes photo-luminescence is increased when composites films are deposited onto an Au rough surface acting as a surface enhanced Raman scattering substrate. This mechanism is explained by a coherent anti-Stokes Raman scattering-like process, as observed in other nano-structured materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4705403]

1725. Anti-Stokes Raman Scattering and Luminescence in Carbon Nanotube Nanostructures

Authors: Lefrant, S; Buisson, JP; Mevellec, JY; Massuyeau, F; Wery, J; Baibarac, M; Baltog, I

Published: 2012, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 554, 118, DOI: 10.1080/15421406.2012.633816

In this paper, we present recent results obtained on single-walled carbon nanotubes (SWNTs) and carbon nanotube/conjugated polymer composites by using resonant Raman scattering and Surface Enhanced Raman Scattering (SERS). Besides the characterization of these materials, we report on peculiar properties observed in the anti-Stokes Raman branch of the Raman spectra. They consist in an abnormal anti-Stokes Raman emission which is explained by a mechanism reminiscent of a Coherent anti-Stokes Raman Scattering (CARS) emission. It results from a wave mixing process between the incident laser light and Stokes Raman light, generated by the SERS mechanism. In a parallel way, we have investigated in details the resonance effects which also induce anomalies in the anti-Stokes/Stokes intensity ratios, as a function of several parameters including the observation temperature, the environmental conditions, the dilution in solvents, etc. Studies extended to composites based on carbon nanotubes and conjugated polymers reveal also interesting properties. In the case of poly(bithiophene) (PBTh), one observes a strong amplification of the 1450 cm(-1) Raman line in the anti-Stokes branch, generated by the plasmon excitation of metallic tubes. This phenomenon occurs in several other conjugated polymers such as PEDOT and PPV for modes located around 1500 cm(-1). The role of metallic SWNTs is discussed. Finally, an anti-Stokes luminescence excited in the low energy tail of the absorption band of PPV and PPV/SWNTs composites has even been observed for the first time, explained through a phonon-energy up-conversion mechanism.

1726. Dielectric properties of Ba(Zn1/3Ta2/3)O-3 thin films on Pt-coated Si substrates

Authors: Nedelcu, L; Mandache, NB; Toacsan, MI; Vlaicu, AM; Banciu, MG; Ioachim, A; Gherendi, F; Luculescu, CR; Nistor, M

Published: NOV 1 2012, THIN SOLID FILMS, 522, 116, DOI: 10.1016/j.tsf.2012.09.002

Ba(Zn1/3Ta2/3)O-3 (BZT) thin films were grown on Pt-coated Si substrates at 500 degrees C substrate temperatures by pulsed electron beam deposition method and post-annealed at 600 and 650 degrees C for 1 h. The X-ray diffraction patterns indicate that the as-grown films are partially crystallized but single-phase cubic perovskite structure was formed in annealed films. The temperature dependence of the dielectric constant of the BZT films was recorded in the -100 to + 100 degrees C range. The annealing treatment induces a decrease of the temperature coefficient of the dielectric permittivity with an order of magnitude, from 2000 to 100 ppm/degrees C. The influence of the annealing treatments on the temperature behavior of the BZT films was evidenced; a dielectric constant of about 21 at room temperature was obtained for the films annealed at 650 degrees C. (C) 2012 Elsevier B. V. All rights reserved.

1727. Large scale microstructuring on silicon surface in air and liquid by femtosecond laser pulses

Authors: Ulmeanu, M; Jipa, F; Radu, C; Enculescu, M; Zamfirescu, M

Published: SEP 15 2012, APPLIED SURFACE SCIENCE, 258, 9317, DOI: 10.1016/j.apsusc.2011.08.110

Large-scale microstructures were imprinted on the surface of silicon with dimensions of 1 mm x 1 mm by femtosecond laser line-by-line scanning irradiation. The scanning was made under air and under chlor/hydrogen based liquid layers. Scanning electron microscope investigations evidenced homogeneous surface microstructures, such as: ripples with sub-wavelengths dimensions, Si pillars and directional oriented bacilliform structures. The dependence of the surface morphology on laser energy, scanning speed and irradiation media was analyzed. In air, the microstructure changes from directional-arranged bacilliform structures to well-known ripple structures with a width of about 525 nm. When using the liquid media, we observe ripple structures with a width of about 370 nm and an overlapping of those that evolve in certain regions into Si pillars. The surfaces show interesting gradient topography behaviour which could be used as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth. By using chlor and hydrogen based liquids we were able to explore the microstructuring of the silicon by line-by-line irradiation process using the femtosecond laser. (C) 2011 Elsevier B. V. All rights reserved.

1728. Morphological, optical and electrical properties of samarium oxide thin films

Authors: Constantinescu, C; Ion, V; Galca, AC; Dinescu, M

Published: AUG 1 2012, THIN SOLID FILMS, 520, 6397, DOI: 10.1016/j.tsf.2012.06.049

We present here results on samarium oxide thin films, obtained by pulsed laser deposition and by radio frequency assisted pulsed laser deposition. Three different substrate types were used: silicon, platinum covered silicon and titanium covered silicon. The influence of the deposition parameters (oxygen pressure and laser fluence) on the structure and morphology of the thin films was studied. The substrate-thin film interface zone was investigated; the optical and electrical properties (the losses, dielectric constant and leakage currents) were also determined. (C) 2012 Elsevier B.V. All rights reserved.

1729. ELECTRODEPOSITION AND ANODIZING OF ZnMn ALLOY SUBMICRON WIRES

Authors: Sima, M; Sima, M

Published: JUL-SEP 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 882, DOI:

The study of the electrodeposition and anodic oxidation processes of ZnMn alloy submicron wires is reported; ZnMn wire arrays were electrodeposited using a pulse current technique and an aqueous solution containing 0.2 mol dm(-3) Zn(II)-EDTA + 0.2 mol dm(-3) MnSO4 + 0.6 mol dm(-3) sodium citrate. The obtained alloy was anodized at a current constant density, in a methoxyethanol solution containing sodium hydroxide and in an aqueous potassium zincate solution. Photoluminescence spectra and SEM images showed the presence of the oxide layer on the surface of the anodized ZnMn wires.

1730. Vaterite Synthesis via Gas-Liquid Route under Controlled pH Conditions

Authors: Udrea, I; Capat, C; Olaru, EA; Isopescu, R; Mihai, M; Mateescu, CD; Bradu, C

Published: JUN 20 2012, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 51, 8193, DOI: 10.1021/ie202221m

The purpose of this work was to obtain precipitated calcium carbonate (PCC) particles in polymorphic form of vaterite via gas-liquid route in controlled pH conditions. The effect of CO2 concentration (12.5-100%), feed gas (CO2-air) flow rate, pH, and conductivity of solution upon the PCC particles properties was studied. On the basis of the experimental data, the main factors leading to vaterite formation as major product were established. It was found that the buffer solution has a decisive role in determining polymorphic phase of PCC while CO2 concentration and feed gas flow rate have no significant influence. It was demonstrated that spherical vaterite particles of high purity can be produced under controlled reaction conditions. Also, some considerations on the mechanism of carbonation process were formulated.

1731. Stanford R. Ovshinsky Prize for Excellence in Amorphous Chalcogenides

Authors: Popescu, M

Published: OCT 2012, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 249, 1836, DOI: 10.1002/pssb.201200348

The short history of the Ovshinsky Prize conferred for Excellence in Amorphous Chalcogenides is presented.

1732. Epitaxial ferromagnetic samarium and samarium silicide synthesized on Si(001)

Authors: Costescu, RM; Gheorghe, NG; Husanu, MA; Lungu, GA; Macovei, D; Pintilie, I; Popescu, DG; Teodorescu, CM

Published: OCT 2012, JOURNAL OF MATERIALS SCIENCE, 47, DOI: 10.1007/s10853-012-6672-z

Samarium is deposited on Si(001) at various temperatures (room temperature to 400 A degrees C), and the surface structure, interface reactivity, electron configuration, and magnetic properties are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and magneto-optical Kerr effect (MOKE), respectively. It is found that metal Sm is present on samples prepared at room temperature with an interface layer containing mostly Sm2+ and a lower amount of Sm3+. When samples are prepared at high temperature, much less Sm-0 is found with an increasing amount of Sm2+. Freshly prepared Sm-0 and SmSi2 layers react strongly with oxygen from the residual gas, promoting formation of Sm2O3 at the expense of both metal Sm and SmSi2. Room temperature ferromagnetism is observed for all prepared layers with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly Sm3+ and Sm metal. In addition to these findings, this work proposes a new assignment of the Sm 3d chemically shifted components. Also, a noticeable variation of the XPS Sm 3d spin-orbit splitting is found as a function of the Sm ionization state.

1733. Thermal behaviour of some new complexes with decaaza bismacrocyclic ligand as potential antimicrobial species

Authors: Bucur, C; Badea, M; Larisa, C; Marinescu, D; Grecu, MN; Stanica, N; Chifiriuc, MC; Olar, R

Published: OCT 2012, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 110, 241, DOI: 10.1007/s10973-012-2199-4

Novel complexes of type M2L(CH3COO)(4)center dot nH(2)O (M:Ni, n = 4; M:Cu, n = 2 and M:Zn, n = 0; L: ligand resulted in 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR, UV-Vis, H-1 NMR, EPR as well as magnetic data at room temperature. Processes as water elimination as well as oxidative degradation of both organic components (bismacrocycle and acetate) were observed. The final product of decomposition was metal (II) oxide as powder X-ray diffraction indicates.

1734. BAND FERROMAGNETISM IN SYSTEMS WITH LINEAR DENSITY OF STATES

Authors: Lungu, GA; Apostol, NG; Morariu, M; Teodorescu, CM

Published: OCT-DEC 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, DOI:

The band (or Stoner) ferromagnetism in systems exhibiting a linear density of states, such as a graphene sheet, where the density of states g(e) is proportional to e, is investigated as function of temperature. The calculations are performed by neglecting spin-wave excitations and some arguments are presented for this approximation. It is found that the occurrence of ferromagnetism becomes easier at finite temperature than in the low temperature limit, especially for systems with low values of carrier density. An almost linear dependence of the magnetization on temperature is predicted; the temperature of vanishing magnetization is linear with the value of the equilibrium Fermi energy, irrespective of the value of the interaction (Hubbard) parameter. Also, for low values of the Hubbard energy an increase in the average value of the polarization with the temperature is predicted in the range of low temperatures. The most important application of such systems consists of control over the onset of magnetization by the charge density (the value of the Fermi energy).

1735. Persistent oscillatory currents in a 1D ring with Rashba and Dresselhaus spin-orbit interactions excited by a terahertz pulse

Authors: Nita, M; Marinescu, DC; Manolescu, A; Ostahie, B; Gudmundsson, V

Published: SEP 2012, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 46, 20, DOI: 10.1016/j.physe.2012.08.017

Persistent, oscillatory charge and spin currents are shown to be driven by a two-component terahertz laser pulse in a one-dimensional mesoscopic ring with Rashba and Dresselhaus spin-orbit interactions (SOI) linear in the electron momentum. The characteristic interference effects result from the opposite precession directions imposed on the electron spin by the two SOI couplings. The time dependence of the currents is obtained by solving numerically the equation of motion for the density operator, which is later employed in calculating statistical averages of quantum operators on few electron eigenstates. The parameterization of the problem is done in terms of the SOI coupling constants and of the phase difference between the two laser components. Our results indicate that the amplitude of the oscillations is controlled by the relative strength of the two SOI's, while their frequency is determined by the difference between the excitation energies of the electron states. Furthermore, the oscillations of the spin current acquire a beating pattern of higher frequency that we associate with the nutation of the electron spin between the quantization axes of the two SOI couplings. This phenomenon disappears at equal SOI strengths, whereby the opposite precessions occur with the same probability. (c) 2012 Elsevier B.V. All rights reserved.

1736. Synthesis and association of Ag(0) nanoparticles in aqueous Pluronic F127 triblock copolymer solutions

Authors: Angelescu, DG; Vasilescu, M; Anastasescu, M; Baratoiu, R; Donescu, D; Teodorescu, VS

Published: JAN 20 2012, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 394, 66, DOI: 10.1016/j.colsurfa.2011.11.025

Triblock copolymers poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) Pluronic F127 was employed as capping agent for the Ag(0) metallic nanoparticles synthesized by the chemical reduction of silver nitrate, AgNO3, with excess of sodium borohydride, NaBH4. The morphology and the kinetics of Ag(0) nanoparticles were studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), UV-vis absorption and fluorescence probe technique. Spherical polydisperse particles of 12 +/- 4 nm mean diameter at varying the Pluronic concentration in the range of 0.13-13 wt.% were reported. Apart from the stabilizing role, the triblock copolymer promoted the agglomeration of individual Ag(0) nanoparticles in small assemblies whose plasmon band features differed from those of the individual nanoparticles. The formation of Ag(0) nanoparticles-F127 complex took place after full reduction of the Ag ions and it was controlled by the F127 concentration. The nanoparticle morphology and the fluorescence probe technique suggested that the excess PI uronic drove indirectly the Ag(0) nanoparticles association. Free F127 polymeric micelles encountered above critical micellar concentration (cmc) promoted the partial desorption of the adsorbed triblock copolymer and subsequently weakened the stability of the individual nanoparticles. (C) 2011 Elsevier B.V. All rights reserved.

1737. Atomic structure and reactivity of ferromagnetic Fe deposited on Si(001)

Authors: Gheorghe, NG; Husanu, MA; Lungu, GA; Costescu, RM; Macovei, D; Teodorescu, CM

Published: FEB 2012, JOURNAL OF MATERIALS SCIENCE, 47, DOI: 10.1007/s10853-011-5963-0

This study presents a correlated study of structural, reactivity, and magnetic properties of ultrathin Fe layers grown on Si(001) by molecular beam epitaxy in ultrahigh vacuum. The interface reactivity is characterized by Auger electron spectroscopy. The surface structure is characterized by low electron energy diffraction with spot profile analysis. The magnetism of the synthesized layers is investigated by magneto-optical Kerr effect. At room temperature, metal Fe layers with poor long-range order are synthesized; these layers are ferromagnetic with an extremely low coercitive field (below 1 Oe). The reactivity with Si is low in this case, with formation of an interface layer of about 8 angstrom Fe equivalent thickness with about 7 at.% Si diffused. Samples synthesized at higher temperatures (500 degrees C) exhibit better long-range order, though the Fe reactivity with Si is higher and leads to the formation of an interface compound whose approximate stoichiometry is very close to Fe(3)Si. Once this compound is formed (for an equivalent Fe thickness of about 14 monolayers), disordered metal Fe islands are developing with subsequent Fe deposition, which contain also about 8 at.% Si diffused. These structures exhibit a much lower ferrimagnetism, with saturation magnetization about one order of magnitude lower than in the case of the room temperature synthesis. In this case of high temperature synthesis, two phases are observed, a ferrimagnetic one and a superparamagnetic one.

1738. ATOMIC STRUCTURE AND MAGNETISM OF PLD DEPOSITED Tio(2):Fe

Authors: Costescu, RM; Lungu, GA; Socol, G; Gheorghe, NG; Macovei, D; Negrila, CC; Logofatu, C; Husanu, MA; Popescu, DG; Tache, CA; Teodorescu, CM

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, DOI:

TiO2:Fe thin films prepared by pulsed laser deposition exhibit in some case light dependent saturation magnetization, as determined from Kerr magnetometry measurements performed in dark or by illuminating the sample. This phenomenon is studied in correlation with local atomic structure investigated by extended X-ray absorption fine structure, composition and chemical state analyzed by X-ray photoelectron spectroscopy and by X-ray absorption near-edge structure. It is found that light-controllable magnetism is a property of a mixture of Fe and oxidized Fe clusters embedded in the anatase TiO2 matrix.

1739. REACTIVITY, MAGNETISM AND LOCAL ATOMIC STRUCTURE IN FERROMAGNETIC FE LAYERS DEPOSITED ON SI(001)

Authors: Gheorghe, NG; Husanu, MA; Lungu, GA; Costescu, RM; Macovei, D; Popescu, DG; Teodorescu, CM

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, DOI:

This work presents recent studies concerning the synthesis of ultrathin ferromagnetic Fe layers on Si(001) and the correlated follow-up measurement of their structural properties, interface reactivity, and magnetism. This study is undertaken as function of the amount of Fe deposited and of substrate temperature. The interface reactivity is characterized by Auger electron spectroscopy. The surface structure is characterized by low electron energy diffraction (LEED). The local order of Fe atoms is investigated by X-ray absorption fine structure (XAFS) and the magnetism by magneto-optical Kerr effect (MOKE). A general trend established is that a higher deposition temperature stabilizes a better surface ordering, but also enhances Fe and Si interdiffusion and therefore decreases the magnetism. A surprising effect obtained by Fe deposition at room temperature is that, despite the rapid disappearance of the long range order with Fe deposition (no LEED pattern is observed for Fe coverage exceeding one monolayer), the material exhibits a significant uniaxial in-plane magnetic anisotropy. When the deposition is performed at high temperature (500 degrees C), a weak ferromagnetism is still observed, with saturation magnetization of about 10 % of the value obtained for room temperature deposition. The combined MOKE and EXAFS studies allowed inferring consistent values for the range of Fe thicknesses where the reaction takes place and the main properties of the distinct formed layers.

1740. CoNb2O6 Ceramic with Geometric Frustration

Authors: Sandu, V; Nicolescu, MS; Banciu, MG; Popa, S; Burdusel, M

Published: 2012, AUTOMATION EQUIPMENT AND SYSTEMS, PTS 1-4, 468-471, 545, DOI: 10.4028/www.scientific.net/AMR.468-471.542

We present the preparation, structure and physical properties of CoNb2O6 ceramics using spark plasma sintering technique. Magnetic data reveal the two antiferromagnetic transitions at 2.9 and 2 K. Microwave measurements gives epsilon(r) = 23.5 and a loss tangent of 29x10(-3).

1741. COMBINATORIAL PULSED LASER DEPOSITION OF AG-CONTAINING CALCIUM PHOSPHATE COATINGS

Authors: Socol, G; Socol, M; Sima, L; Petrescu, S; Enculescu, M; Sima, F; Miroiu, M; Popescu-Pelin, G; Stefan, N; Cristescu, R; Mihailescu, CN; Stanculescu, A; Sutan, C; Mihailescu, IN

Published: APR-JUN 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 576, DOI:

Embedding silver (Ag) into CaPs one could expect the enhancement of the antimicrobial performances of coatings for load bearing implants. The aim of this research was to evaluate whether the cellular morphology is influenced by the variation of Ag content, as well as by the solubility and morphological features of Ag-containing CaP coatings obtained by combinatorial pulsed laser deposition technique. In this view, we developed compositional libraries of either Ag and hydroxyapatite (HA) or Ag and beta-tricalcium phosphate (beta-TCP). The Ag content along the length of the combinatorial CaP coatings increased up to a maximum of similar to 1 at.%. SEM and AFM images evidenced the abundant presence of particulates typical for CaP coatings deposited by PLD. AFM histograms showed that the samples were rough with RMS values within 61-209 nm range. Ag content values up to 0.6 at. % into HA coatings were found nontoxic for mesenchymal stem cell (MSC) growth.

1742. Structure and electrical transport in films of Ge nanoparticles embedded in SiO2 matrix

Authors: Stavarache, I; Lepadatu, AM; Maraloiu, AV; Teodorescu, VS; Ciurea, ML

Published: JUL 2012, JOURNAL OF NANOPARTICLE RESEARCH, 14, DOI: 10.1007/s11051-012-0930-5

The films containing Ge nanoparticles embedded in SiO2 matrix were prepared by RF magnetron sputtering and subsequently by thermal annealing. Their structure was investigated by conventional transmission electron microscopy and high resolution transmission electron microscopy together with energy-dispersive X-ray spectroscopy. The electrical behavior of films was studied by measuring current-temperature and current-voltage characteristics. The structure investigation reveals two kinds of features: a low density of big Ge nanoparticles with sizes from 20 to 50 nm and a network of small amorphous Ge nanoregions/nanoparticles (5 nm size or less) with high density, both being embedded in amorphous SiO2 matrix. The electrical transport was shown to take place through the network of amorphous Ge nanoregions. At low temperature, the T-1/4 dependence of the current was evidenced, while at high temperature, the T-1 Arrhenius dependence was found. At both low and high temperatures, the conductivity is nearly constant. The behavior at low temperature was explained by the hopping mechanism on localized states located in a band near the Fermi energy, while at high temperature by the charge excitation to the extended states.

1743. Biomedical properties and preparation of iron oxide-dextran nanostructures by MAPLE technique

Authors: Ciobanu, CS; Iconaru, SL; Gyorgy, E; Radu, M; Costache, M; Dinischiotu, A; Le Coustumer, P; Lafdi, K; Predoi, D

Published: MAR 13 2012, CHEMISTRY CENTRAL JOURNAL, 6, DOI: 10.1186/1752-153X-6-17

Background: In this work the chemical structure of dextran-iron oxide thin films was reported. The films were obtained by MAPLE technique from composite targets containing 10 wt. % dextran with 1 and 5 wt.% iron oxide nanoparticles (IONPs). The IONPs were synthesized by co-precipitation method. A KrF* excimer laser source (lambda = 248 nm, tau(FWHM)congruent to 25 ns, nu = 10 Hz) was used for the growth of the hybrid, iron oxide NPs-dextran thin films. Results: Dextran coated iron oxide nanoparticles thin films were indexed into the spinel cubic lattice with a lattice parameter of 8.36 angstrom. The particle sized calculated was estimated at around 7.7 nm. The XPS shows that the binding energy of the Fe 2p(3/2) of two thin films of dextran coated iron oxide is consistent with Fe3+ oxides. The atomic percentage of the C, O and Fe are 66.71, 32.76 and 0.53 for the films deposited from composite targets containing 1 wt.% maghemite and 64.36, 33.92 and 1.72 respectively for the films deposited from composite targets containing 5 wt.% maghemite. In the case of cells cultivated on dextran coated 5% maghemite gamma-Fe2O3, the number of cells and the level of F-actin were lower compared to the other two types of thin films and control. Conclusions: The dextran-iron oxide continuous thin films obtained by MAPLE technique from composite targets containing 10 wt.% dextran as well as 1 and 5 wt.% iron oxide nanoparticles synthesized by co-precipitation method presented granular surface morphology. Our data proved a good viability of Hep G2 cells grown on dextran coated maghemite thin films. Also, no changes in cells morphology were noticed under phase contrast microscopy. The data strongly suggest the potential use of iron oxide-dextran nanocomposites as a potential marker for biomedical applications.

1744. Electrochemical Investigation of the Deposition/Dissolution of Selenium in Choline Chloride with Urea or Ethylene Glycol Ionic Liquids

Authors: Cojocaru, A; Sima, M

Published: FEB 2012, REVISTA DE CHIMIE, 63, 223, DOI:

The electrochemical behaviour of Se(IV) ion on Pt electrode in ionic liquids containing choline chloride - urea and choline chloride - ethylene glycol eutectics (1:2 mole ratio) was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in open air conditions. Cyclic voltammograms showed a cathodic peak of selenium massive deposition preceeded by one or more waves corresponding to UPD processes. It is followed by another cathodic peak of Se(II) anion formation. It was found a diffusion control of reduction process and, therefore, the value of the diffusion coefficient of Se(IV) ion in ChCl-urea ionic liquid at 60 degrees C was calculated. EIS spectra as Nyquist and Bode plots confirm the potential range for bulk selenium deposition and formation of thin selenium films.

1745. Cavity-assisted emission of polarization-entangled photons from biexcitons in quantum dots with fine-structure splitting

Authors: Schumacher, S; Forstner, J; Zrenner, A; Florian, M; Gies, C; Gartner, P; Jahnke, F

Published: FEB 27 2012, OPTICS EXPRESS, 20, 5342, DOI: 10.1364/OE.20.005335

We study the quantum properties and statistics of photons emitted by a quantum-dot biexciton inside a cavity. In the biexciton-exciton cascade, fine-structure splitting between exciton levels degrades polarization-entanglement for the emitted pair of photons. However, here we show that the polarization-entanglement can be preserved in such a system through simultaneous emission of two degenerate photons into cavity modes tuned to half the biexciton energy. Based on detailed theoretical calculations for realistic quantum-dot and cavity parameters, we quantify the degree of achievable entanglement. (C) 2012 Optical Society of America

1746. IODINE IRRADIATION INDUCED DEFECTS IN CRYSTALLINE SILICON

Authors: Slav, A; Lepadatu, AM; Palade, C; Stavarache, I; Iordache, G; Ciurea, ML; Lazanu, S; Mitroi, MR

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 276, DOI:

N-type P-doped silicon single crystals with resistivity higher than 8000 Omega cm were irradiated with I-127(6+) ions of 28 MeV kinetic energy. The penetration of the ions through the target and the processes of energy loss were simulated using the CTRIM Monte Carlo code, and point defect production was calculated in the frame of our diffusion-reaction model. Trapping phenomena were investigated using the method of thermally stimulated currents without applied bias. The modeling of the current-temperature curves takes into consideration both point defects and stress-type trapping centers, produced by the ions stopped into the crystal.

1747. High Hardness BaCb-(BxOy/BN) Composites with 3D Mesh-Like Fine Grain-Boundary Structure by Reactive Spark Plasma Sintering

Authors: Vasylkiv, O; Borodianska, H; Badica, P; Grasso, S; Sakka, Y; Tok, A; Su, LT; Bosman, M; Ma, J

Published: FEB 2012, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 12, 965, DOI: 10.1166/jnn.2012.5875

Boron carbide B4C powders were subject to reactive spark plasma sintering (also known as field assisted sintering, pulsed current sintering or plasma assisted sintering) under nitrogen atmosphere. For an optimum hexagonal BN (h-BN) content estimated from X-ray diffraction measurements at similar to 0.4 wt%, the as-prepared BaCb-(BxOy/BN) ceramic shows values of Berkovich and Vickers hardness of 56.7 +/- 3.1 GPa and 39.3 +/- 7.6 GPa, respectively. These values are higher than for the vacuum SPS processed B4C pristine sample and the h-BN -mechanically-added samples. XRD and electronic microscopy data suggest that in the samples produced by reactive SPS in N-2 atmosphere, and containing an estimated amount of 0.3-1.5% h-BN, the crystallite size of the boron carbide grains is decreasing with the increasing amount of N-2, while for the newly formed lamellar h-BN the crystallite size is almost constant (similar to 30-50 nm). BN is located at the grain boundaries between the boron carbide grains and it is wrapped and intercalated by a thin layer of boron oxide. BxOy/BN forms a fine and continuous 3D mesh-like structure that is a possible reason for good mechanical properties.

1748. Structural, optical, and electric properties of BNT-BT0.08 thin films processed by sol-gel technique

Authors: Cernea, M; Trupina, L; Dragoi, C; Galca, AC; Trinca, L

Published: OCT 2012, JOURNAL OF MATERIALS SCIENCE, 47, 6971, DOI: 10.1007/s10853-012-6646-1

Thin films with the composition [(Bi0.5Na0.5)TiO3](0.92)-[BaTiO3](0.08) (hereafter BNT-BT0.08) were deposited on Pt-Si by spin-coating from a stable sol precursor. The BNT-BT0.08 film, crystallized on the Bi0.5Na0.5TiO3 rhombohedral lattice, was obtained after annealing the film-gel at 700 A degrees C. The films have a smooth surface (Rms = 2.76 nm) and grains with ferroelectric domains. The film showed a bandgap of 3.25 eV and a refractive index of 2.20 at a wavelength of 630 nm. The dielectric characteristics of BNT-BT0.08 thin films were measured at room temperature and 10 kHz the dielectric constant (epsilon (r)) was 243 and the loss tangent (tan delta) was 0.38. The remnant polarization (P (r)) was 0.87 mu C/cm(2) and the coercive field (E (c)) was 220 kV/cm at 10 kHz and room temperature. The current density was approximately 2.7 x 10(-5) A/cm(2) at low electric fields (100 kV/cm). BNT-BT0.08 thin films shown piezoelectric properties (d (33eff) = 100 pm/V) comparable to those of PZT thin films.

1749. Pulsed laser deposition of transparent conductive oxide thin films on flexible substrates

Authors: Socol, G; Socol, M; Stefan, N; Axente, E; Popescu-Pelin, G; Craciun, D; Duta, L; Mihailescu, CN; Mihailescu, IN; Stanculescu, A; Visan, D; Sava, V; Galca, AC; Luculescu, CR; Craciun, V

Published: NOV 1 2012, APPLIED SURFACE SCIENCE, 260, 46, DOI: 10.1016/j.apsusc.2012.02.148

The influence of target-substrate distance during pulsed laser deposition of indium zinc oxide (IZO), indium tin oxide (ITO) and aluminium-doped zinc oxide (AZO) thin films grown on polyethylene terephthalate (PET) substrates was investigated. It was found that the properties of such flexible transparent conductive oxide (TCO)/PET electrodes critically depend on this parameter. The TCO films that were deposited at distances of 6 and 8 cm exhibited an optical transmittance higher than 90% in the visible range and electrical resistivities around 5 x 10(-4) Omega cm. In addition to these excellent electrical and optical characteristics the films grown at 8 cm distance were homogenous, smooth, adherent, and without cracks or any other extended defects, being suitable for opto-electronic device applications. (C) 2012 Elsevier B. V. All rights reserved.

1750. Superparamagnetic magnetite-divinylbenzene-maleic anhydride copolymer nanocomposites obtained by dispersion polymerization

Authors: Donescu, D; Raditoiu, V; Spataru, CI; Somoghi, R; Ghiurea, M; Radovici, C; Fierascu, RC; Schinteie, G; Leca, A; Kuncser, V

Published: OCT 2012, EUROPEAN POLYMER JOURNAL, 48, 1716, DOI: 10.1016/j.eurpolymj.2012.07.012

Magnetite alternating copolymers divinylbenzene-maleic anhydride (DVB-MA) composites were prepared by dispersion polymerization. Because magnetite is used as a complex with oleic acid (Fe(3)O(4)OLA), the final hybrids show good dispersion of inorganic nanofillers in the polymer matrix. The obtained composites were analyzed by infrared absorption spectrometry, diffuse reflectance in visible light, thermogravimetry, X-ray fluorescence, X-ray diffraction, dynamic light scattering, scanning electron microscopy and vibrating sample magnetometry. The obtained results indicate the successful preparation of magnetite nanoparticles with an average size of about 23 nm dispersed in micrometer size copolymer spherical particles, which relative content can be controlled via the processing parameters. A relationship between the relative content of magnetite nanoparticles and the size of the polymer particles, with direct influence on the diffuse reflectance in the visible domain, was observed. A superparamagnetic behavior was evidenced at room temperature with a blocking temperature lower than as expected from the bulk anisotropy constant and the average size of the magnetite nanoparticles. Both the unexpected low blocking temperature and the observed low specific magnetizations were explained by a defected and poor crystalline structure of the magnetite nanoparticles, giving rise to spin disorder and diminished crystalline anisotropy constant. (C) 2012 Elsevier Ltd. All rights reserved.

1751. Magnetic glass-ceramics

Authors: Sandu, V; Nicolescu, MS; Kuncser, V; Damian, R; Sandu, E

Published: JUN 2012, JOURNAL OF ADVANCED CERAMICS, 1, 143, DOI: 10.1007/s40145-012-0010-4

We present the magnetic properties of magnetic glass ceramics obtained by crystallization of Fe containing borosilicate glass. Two types of nucleators have been used: Cr2O3 and P2O5. The role of the nucleators proved to be crucial in the size and morphology of the crystallites developed within glassy matrix as well in the magnetic response. The former stimulates the growth of regular single crystals uniformly dispersed within the matrix whereas the latter leads to the formation of grains made of tiny (30 nm), nanocrystals. The magnetic response depends on the amount of Fe ions left dispersed within glassy matrix as paramagnetic ions. Although P2O5 leads to the best structural magnetite, almost 42% of Fe ions are left dispersed in the matrix without magnetic interaction. In the case of Cr2O3, the paramagnetic Fe is decreased to 12% but structural deficiency in the occupancy of the Fe sites of magnetite is revealed by Mossbauer spectroscopy.

1752. TRANSPORT MECHANISMS IN SiO2 FILMS WITH EMBEDDED GERMANIUM NANOPARTICLES

Authors: Palade, C; Lepadatu, AM; Stavarache, I; Maraloiu, AV; Teodorescu, VS; Ciurea, ML

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 94, DOI:

This paper reports on the conduction mechanisms in amorphous SiO2 films with embedded Ge nanoparticles. For this, measurements of current-temperature and current-voltage were employed and correlated with the microstructure results obtained from transmission electron microscopy (TEM). TEM images reveal that our films contain big Ge nanoparticles with low density and small Ge nanoparticles with high density, the last ones being the only responsible for the electrical transport. Two transport mechanisms were found at low and high temperature respectively, namely hopping on localized states in a band near Fermi level and charge excitation to the extended states at mobility edge.

1753. Preparation of nanostructured ZnO nanorods in a hydrothermal-electrochemical process

Authors: Sima, M; Vasile, E; Sima, M

Published: MAY 1 2012, THIN SOLID FILMS, 520, 4636, DOI: 10.1016/j.tsf.2011.10.116

An array of ZnO nanorods, each nanorod being covered with a shell of porous ZnO was prepared in two steps by hydrothermal-electrochemical processes. The growth of ZnO nanorods was achieved in a zinc nitrate and hexamethylenetetramine aqueous solution on fluorine-doped tin oxide film. The porous ZnO shell was grown from a similar solution in the presence of eosin Y as nanostructuring agent. A dye-sensitized solar cell was assembled using as photoanode an eosin Y sensitized ZnO nanorod/shell layer. (C) 2011 Elsevier B.V. All rights reserved.

1754. Monoesterase Activity of a Purple Acid Phosphatase Mimic with a Cyclam Platform

Authors: Comba, P; Gahan, LR; Hanson, GR; Mereacre, V; Noble, CJ; Powell, AK; Prisecaru, I; Schenk, G; Zajaczkowski-Fischer, M

Published: FEB 2012, CHEMISTRY-A EUROPEAN JOURNAL, 18, 1710, DOI: 10.1002/chem.201100229

The synthesis and characterization of a novel dinucleating ligand L (L=4,11-dimethyl-1,8-bis{2-[N-(di-2-pyridylmethyl)amino]ethyl}cyclam) and its mu-oxo-bridged diferric complex [(H2L){Fe-2(III)(O)}(Cl)(4)](2+) are reported. This diiron(III) complex is the first example of a truly functional purple acid phosphatase (PAP) mimic as it accelerates the hydrolysis of the activated phosphomonoester 2,4-dinitrophenyl phosphate (DNPP). The spectroscopic and kinetic data indicate that only substrates that are monodentately bound to one of the two ferric ions can be attacked by a suitable nucleophile. This is, most probably, a terminal iron(III)-bound hydroxide. DFT calculations support this assumption and also highlight the importance of secondary interactions, exerted by the protonated cyclam platform, for the positioning and activation of the iron(III)-bound substrate. Similar effects are postulated in the native enzyme but addressed in PAP mimics for the first time.

1755. Tartarate precursors to CoxZn1-xGa2O4 spinel oxides

Authors: Mindru, I; Gingasu, D; Marinescu, G; Patron, L; Diamandescu, L; Feder, M; Calderon-Moreno, JM; Stanica, N

Published: MAY 15 2012, MATERIALS CHEMISTRY AND PHYSICS, 134, 483, DOI: 10.1016/j.matchemphys.2012.03.019

The CoxZn1-xGa2O4 spinels (x=0.25, 0.5, 0.75, 1) were synthesized by a wet chemistry method-the precursor route via tartarate decomposition. The complex precursors have been characterized by IR. UV-Vis, magnetic measurements and luminescence spectroscopy. XRD, SEM, IR. UV-Vis and luminescence spectroscopy were used for the structural and morphological investigation of CoxZn1-xGa2O4 spinels; magnetic susceptibilities of the spinel were also measured. The X-ray diffraction patterns confirmed the formation of gallate spinet phase. CoxZn1-xGa2O4. (C) 2012 Elsevier B.V. All rights reserved.

1756. Catalytic hydroprocessing of lignin under thermal and ultrasound conditions

Authors: Finch, KBH; Richards, RM; Richel, A; Medvedovici, AV; Gheorghe, NG; Verziu, M; Coman, SM; Parvulescu, VI

Published: NOV 30 2012, CATALYSIS TODAY, 196, 10, DOI: 10.1016/j.cattod.2012.02.051

Lignin isolated from Miscanthus x giganteus using acidic (FAL) and basic (AL) conditions was thereafter subjected to catalytic depolymerization under thermal or ultrasonic activation. The characterization of lignin samples was achieved by thermogravimetric analysis and FTIR. Three different classes of catalysts containing nickel as the active species have been prepared in this respect: (i) nano-Ni(0) by reduction of NiCl2 with NaBH4 under ultrasonication, (ii) Fe3O4-(NiMgAlO)(x) and (NiAlO)(x) by calcination of Mg(Ni)-Al hydrotalcite incorporating Fe3O4, followed by reduction with hydrogen, and (iii) NiO(1 1 1) nanosheets by reduction of Ni(NO3)(2) with urea using benzyl alcohol as a structure directing agent. The catalysts were characterized by XRD and XPS techniques. Reduced mixed oxides displayed a moderate activity while a significant increase in conversion (up to 90%) was observed with nano-Ni(0) and NiO(1 1 1) nanosheets catalysts. The conversion and the mass distribution of the reaction products were strongly related to the procedure used for the extraction of lignin. In all the reactions AL samples had a greater extent of depolymerization. The performance from the tested catalysts under ultrasonic conditions was inferior to those tested under conventional heating conditions. The nature of the solvent was also found to be very important to this process, with the ionic liquid, 1-butyl-3-methylimidazolium acetate ([BMIM]OAc) demonstrating the best results in autoclave conditions and methanol under ultrasonic conditions. (C) 2012 Elsevier B. V. All rights reserved.

1757. Effects produced by iodine irradiation on high resistivity silicon

Authors: Lazanu, S; Slav, A; Lepadatu, AM; Stavarache, I; Palade, C; Iordache, G; Ciurea, ML

Published: DEC 10 2012, APPLIED PHYSICS LETTERS, 101, DOI: 10.1063/1.4772015

The effects of 5 x 10(11) cm(-2 6+)I(127) ions of 28 MeV kinetic energy on high resistivity (100) Si were studied. The profile of primary defects was simulated. The defects produced by irradiation which act as traps were investigated. Thermally stimulated current measurements without externally applied bias were used, and for this the traps were charged by illuminating samples with 1000, 800, and 400 nm wavelengths. The discharge currents were recorded and modeled, and therefore the parameters of the traps were determined. The presence of I ions, heavier than Si, stopped into the target was modeled as a temperature independent electric field. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772015]

1758. Possible mechanisms of switching in amorphous chalcogenides

Authors: Popescu, M; Velea, A

Published: OCT 2012, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 249, 1971, DOI: 10.1002/pssb.201200351

A new description of the switching phenomenon is given. The switching is regarded as due to the formation and breaking of the links between the dendrites of crystalline nuclei in bulk materials, as a consequence of the energy pumped by an electrical field. This mechanism explains the very short switching time (<20?ns), the possibility to get smart memories based on multisteps of resistivity and the high number of cycles supported by the cell (1016). A cellular automaton mechanism was created on the basis of this model for switching. Multistage memory in chalcogenide materials has also been explained by this mechanism.

1759. Influence of the substrate and nitrogen amount on the microstructural and optical properties of thin r.f.-sputtered ZnO films treated by rapid thermal annealing

Authors: Nicolescu, M; Anastasescu, M; Preda, S; Stroescu, H; Stoica, M; Teodorescu, VS; Aperathitis, E; Kampylafka, V; Modreanu, M; Zaharescu, M; Gartner, M

Published: NOV 15 2012, APPLIED SURFACE SCIENCE, 261, 823, DOI: 10.1016/j.apsusc.2012.08.104

N-doped ZnO (ZnO: N) thin films, intended to be used as one of the layers in solar cell applications were deposited by r.f. sputtering, using ZnN target (99.9% purity), on silicon and fused silica substrates. In the gas flow composition, Ar was kept constant (50%) and the O-2/N-2 ratio was varied as: 40%/10%, 25%/25% and 10%/40%. After deposition, rapid thermal annealing (RTA) at 400 and 550 degrees C for 1 min in N-2 ambient has been performed. The RTA impact on the optical and microstructural properties of ZnO: N thin films have been investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX), UV-vis-NIR spectroscopy, UV-vis-NIR spectroscopic ellipsometry (SE) and infrared ellipsometry (IR-SE). The as-deposited (ad) ZnO: N films are polycrystalline with preferentially oriented columnar crystals. After RTA we found ZnO: N films with improved crystallinity and fewer boundary defects. We report optical constants of ZnO: N from UV to IR spectral range as well as the infrared active phononic modes. (C) 2012 Elsevier B. V. All rights reserved.

1760. Sm3+-doped Sc2O3 polycrystalline ceramics: Spectroscopic investigation

Authors: Gheorghe, C; Lupei, A; Voicu, F; Enculescu, M

Published: SEP 15 2012, JOURNAL OF ALLOYS AND COMPOUNDS, 535, 82, DOI: 10.1016/j.jallcom.2012.04.083

Sm3+-doped Sc2O3 translucent polycrystalline ceramics were fabricated by solid-state reaction method in order to evaluate its potential for visible emission. The optical spectra in the UV-IR range of Sm3+ in these samples, at different temperatures (10-300 K), were performed. A series of data on Sm: Sc2O3 system not investigated previously were obtained from the analysis of the absorption and visible emission spectra as well as the emission kinetics: an extended energy level scheme, absorption cross sections for different bands, lifetimes, etc. Additional spectroscopic parameters were evaluated in the frame of the Judd-Ofelt (J-O) theory: J-O intensity parameters, oscillator strengths, radiative transitions probabilities, radiative lifetimes, branching ratios, and the cross sections (by Fuchtbauer-Ladenburg) of the main three visible emissions: (4)G(5/2) -> H-6(5/2) (yellow), (4)G(5/2) -> H-6(7/2) (orange) and (4)G(5/2) -> H-6(9/2) (red). (C) 2012 Elsevier B.V. All rights reserved.

1761. A Robust Metal-Organic Framework Constructed from Alkoxo-Bridged Binuclear Nodes and Hexamethylenetetramine Spacers: Crystal Structure and Sorption Studies

Authors: Ilyes, E; Florea, M; Madalan, AM; Haiduc, I; Parvulescu, VI; Andruh, M

Published: AUG 6 2012, , DOI: 10.1021/ic301139j

1762. Ferroelectric and dielectric multilayer heterostructures based on KTa0.65Nb0.35O3 and Bi1.5-xZn0.92-yNb1.5O6.92-1.5x-y grown by pulsed laser deposition and chemical solution deposition for high frequency tunable devices

Authors: Le Febvrier, A; Deputier, S; Bouquet, V; Demange, V; Ollivier, S; Galca, AC; Dragoi, C; Radu, R; Pintilie, L; Guilloux-Viry, M

Published: MAY 1 2012, THIN SOLID FILMS, 520, 4567, DOI: 10.1016/j.tsf.2011.10.142

Epitaxial growth of Bi1.5-xZn0.92-yNb1.5O6.92-1.5x-y (BZN) thin films was achieved on (100)(pc) LaAlO3 substrate by pulsed laser deposition (PLD) and by chemical solution deposition based on Pechini process. Effect of bismuth and zinc deficiency on the BZN thin films obtained by PLD was discussed, in relation with the starting target composition. Dielectric permittivity and bandgap values were determined from electrical and spectroscopic ellipsometry measurements performed on randomly oriented films grown on Pt/Si substrate. BZN thin films obtained by PLD exhibit, at 100 kHz, a dielectric constant of epsilon(r) = 203 and quite low dielectric losses of tan delta = 5 x 10(-2). Epitaxial ferroelectric - dielectric KTa0.65Nb0.35O3 (KTN) -Bi1.5-xZn0.92-yNb1.5O6.92-1.5x-y (KTN on BZN and BZN on KIN) bilayers were obtained by PLD on (100)(pc) LaAlO3 with the insertion of a suitable buffer layer of KNbO3 in the case of KTN on BZN. Such multilayer heterostructures with an epitaxial growth control of each layer are promising candidates for potential integration in microwave devices. (C) 2011 Elsevier B.V. All rights reserved.

1763. Magnetic Interfaces at the Nanoscale: From Fundamentals to Technological Applications

Authors: Angelakeris, M; Crisan, O; Martinez-Boubeta, C

Published: 2012, JOURNAL OF NANOMATERIALS, 2012, DOI: 10.1155/2012/619485

1764. NONLINEAR OPTICAL PROCESSES MANIFESTING AS ANDERSON LOCALIZATION OF LIGHT IN MESOSCOPIC MATERIALS

Authors: Baltog, I; Baibarac, M; Mihut, L; Smaranda, I; Lefrant, S

Published: APR-JUN 2012, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 13, 117, DOI:

Abnormal anti-Stokes Raman emission (AASRE) is defined by an anti-Stokes/Stokes intensity ratio much greater than expected on the basis of the equilibrium population of excited vibration states provided by the Boltzmann law. AASRE can be observed both in materials with intrinsic nonlinear optical properties as LiNbO3 or materials in which the nonlinear optical properties are induced by resonant optical excitation, as carbon nanotubes. Using a surface enhanced Raman scattering (SERS) device, consisting from single wall carbon nanotubes deposited on a rough Au or Ag support and LiNbO3 in form of powder, we demonstrate that under continuous single beam excitation they present AASRE whose properties are similar to a single beam pumped Coherent Anti-Stokes Raman Scattering. AASRE is usually accompanied by a coherent backscattering, it can be considered as Anderson localization of light that results from a wave-mixing mechanism of the incident laser light with a Stokes shifted Raman light produced by a spontaneous Raman light scattering process. The transport of the light inside of sample, giving rise to AASRE and coherent backscattering, is done by an elastic light scattering mechanism.

1765. Effect of Nucleators and Intermediates on the Magnetic Properties of Nanosized Magnetite Obtained by Glass Crystallization

Authors: Sandu, V; Nicolescu, MS; Kuncser, V; Popa, S; Pasuk, L; Sandu, E

Published: SEP 2012, JOURNAL OF COMPUTATIONAL AND THEORETICAL NANOSCIENCE, 9, 1545, DOI: 10.1166/jctn.2012.2241

We investigate the role of chromium and phosphorous oxides on the growth and magnetic properties of crystallized Fe-containing borosilicate glasses as well as their evolution under different thermal processing. The glasses have the ratio between SiO2 and Fe2O3 in the range 1.49 to 2.68 and Al2O3/MgO as intermediate/modifier oxides. X-ray diffraction and Mossbauer spectroscopy data revealed the presence of magnetite as the major crystalline phase in all as-prepared samples but additional amounts of hematite and of Fe-rich paramagnetic phases are also visible in some samples. The magnetic response is correlated with the disorder observed in the different sites (tetrahedral and octahedral) of the magnetite.

1766. Broadband near-infrared emission of chromium-doped sulfide glass-ceramics containing Ga2S3 nanocrystals

Authors: Ren, J; Li, B; Yang, G; Xu, WN; Zhang, ZH; Secu, M; Bercu, V; Zeng, HD; Chen, GR

Published: DEC 15 2012, OPTICS LETTERS, 37, 5045, DOI: 10.1364/OL.37.005043

Upon 808 nm excitation, an intense broadband near-infrared emission from Cr4+ has been observed in 80GeS(2)-20Ga(2)S(3) chalcogenide glass-ceramics (GCs) containing Ga2S3 nanocrystals. The emission band peaking at 1250 nm covers the O, E, S bands (1000-1500 nm). The formation of Ga2S3 nanocrystals (similar to 20 nm) increases the emission intensity of Cr4+ by more than three times. The quantum efficiency of the present GCs is as great as 36% at room temperature. (C) 2012 Optical Society of America

1767. Analysis of the phase lapse problem in closed interferometers

Authors: Tolea, M; Moldoveanu, V; Dinu, IV; Tanatar, B

Published: OCT 1 2012, PHYSICS LETTERS A, 376, 3234, DOI: 10.1016/j.physleta.2012.07.007

We investigate the connection between the asymmetry of the Fano resonances in a mesoscopic interferometer with an embedded quantum dot and the pi lapses in the phase of the "bare" dot transmittance. Consecutive Fano resonances with the same (opposite) sign of the Fano parameter imply the presence (absence) of a phase lapse with pi between the corresponding resonances of the dot. Our results suggest that the famous "phase lapse" problem, first reported by Schuster et al. [R. Schuster, E. Buks, M. Heiblum, D. Mahalu, V. Umansky, H. Shtrikman, Nature 385 (1997) 417], can therefore be experimentally addressed in closed interferometers. It is also proposed that the Fano effect can be used to extract the phase distributions of the eigenfunctions for a mesoscopic 20 shape, via the parity of the resonances. In the presence of electron-electron interaction, one can calculate the phases of the T-matrix elements. The numerical results lead to the same conclusions as for the non-interacting case. (C) 2012 Elsevier B.V. All rights reserved.

1768. MgB2 with addition of Sb2O3 obtained by spark plasma sintering technique

Authors: Burdusel, M; Aldica, G; Popa, S; Enculescu, M; Badica, P

Published: APR 2012, JOURNAL OF MATERIALS SCIENCE, 47, 3836, DOI: 10.1007/s10853-011-6238-5

Superconducting bulks of MgB2 with addition of Sb2O3 and Sb with different stoichiometric compositions ((MgB2) + (Sb2O3) (x) , x = 0.0025, 0.005, 0.015, and (MgB2) + (Sb)(y), y = 0.01) were obtained by the Spark Plasma Sintering (SPS) technique. All added samples have high density, above 95% and critical temperature, T (c), of 38.1-38.6 K. This result and XRD data suggest that Sb does not enter the lattice of MgB2. Impurity phases are Mg3Sb2, MgO, and MgB4. The optimum addition is Sb2O3 for x = 0.005. This sample shows the critical current density, J (c)(5 K, 0 T) = 4 x 10(5) A/cm(2) and J (c)(5 K, 7 T) = 6 x 10(2) A/cm(2), while the irreversibility field, H (irr) (5 K, 100 A/cm(2)) = 8.23 T. Indicated values of J (c) and H (irr) are higher than for the pristine sample. The mechanism of J (c) and H (irr) increase in the Sb2O3 added samples is complex and composed of opposite effects most probably involving morphology elements, the presence of nano metric MgB4 and the indirect influence of oxygen or oxygen and Sb. Crystallite size of MgB2 is decreasing when Sb-based additions are introduced and the effect is stronger for the Sb-metal addition. The sample with Sb-metal addition does not improve J (c) and H (irr) when compared with pristine sample.

1769. ELECTRICAL BEHAVIOUR RELATED TO STRUCTURE OF NANOSTRUCTURED GeSi FILMS ANNEALED AT 700 degrees C

Authors: Lepadatu, AM; Stavarache, I; Maraloiu, A; Palade, C; Teodorescu, VS; Ciurea, ML

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 112, DOI:

In this paper we continue the previous investigations on nanostructured GexSi1-x films. The films were deposited by magnetron sputtering and annealed in N-2 atmosphere at 700 degrees C. Their structure was investigated and correlated with the electrical behavior. For this, conventional and high-resolution transmission electron microscopy together with selected area electron diffraction was used. Electrical measurements of current-voltage and current-temperature curves were made. The majority of crystallites that forms the films have the composition Ge50Si50 and 15 - 30 nm size. The I - T characteristics have Arrhenius dependence, with two activation energies interpreted as transitions between quantum confinement levels.

1770. Spectroscopic ellipsometry investigations of Eu-doped oxy-fluoride glass and glass-ceramics

Authors: Galca, AC; Preda, N; Secu, CE; Luculescu, CR; Secu, M

Published: JUN 2012, OPTICAL MATERIALS, 34, 1496, DOI: 10.1016/j.optmat.2012.03.015

Oxyfluoride glass-ceramics in the system SiO2-Al2O3-CaF2-EuF3 containing Eu3+-doped CaF2 nanocrystals were produced by using controlled crystallization of melt-quenched glass. X-ray diffraction and scanning electron microscopy data have revealed the formation of CaF2 nanocrystals of about 50 nm size. The Eu3+-dopant ions act as the nucleating agent necessary to initiate the crystallization process. The refractive index is higher in the glass ceramics than in the initial glass and varies as the annealing time increases. Two competitive processes are responsible for this behavior, the crystallization of the CaF2 phase and the decrease of the glass ceramic mass density. (C) 2012 Elsevier B.V. All rights reserved.

1771. Synthesis and characterization of CdSe-doped Li2O-Al2O3-P2O5 glass

Authors: Vasiliu, IC; Elisa, M; Niciu, H; Iordanescu, R; Feraru, I; Ghervase, L

Published: 2012, 2012 12TH IEEE CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO), DOI:

The paper presents the synthesis and optical/structural characterization of 1% CdSe-doped Li2O-Al2O3-P2O5 glasses as promising materials for temperature sensors based on luminescence. The doped glasses were synthesized by a conventional dry route, embedding the dopant into the molten glass under continuous stirring. UV-Vis absorption revealed characteristic features for CdSe semiconductor with a cut-off correlated with the band gap of the dopant. Structural information was provided by FTIR and Raman spectroscopy. FTIR and Raman maxima are assigned to vibration modes characteristic for the phosphate vitreous network. Fluorescence spectroscopy by 365 nm excitation put in evidence the luminescent emission of the doped glass in the visible range. SEM images show CdSe particles which are responsible for the yellow color of the doped samples, being detected 12-24 nm quantum dots and the smaller particles are under the detection limit.

1772. Structural, dielectric, and piezoelectric properties of fine-grained NBT-BT0.11 ceramic derived from gel precursor

Authors: Cernea, M; Galassi, C; Vasile, BS; Capiani, C; Berbecaru, C; Pintilie, I; Pintilie, L

Published: AUG 2012, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 32, 2397, DOI: 10.1016/j.jeurceramsoc.2012.02.021

(Na1/2Bi1/2)TiO3 doped in situ with 11 inol% BaTiO3 (NBT-BT0.11) powders were synthesized by a sol-gel method, and the electrical properties of the resulting ceramics were investigated. The powders consisting of uniform and fine preliminary particles of about 50 nm were prepared by calcining the gel precursor at 700 degrees C. (Na1/2Bi1/2)(0.89)Ba0.11TiO3 ceramics, sintered at temperatures up to 1150 degrees C have a rhombohedral symmetry while the ceramic sintered at 1200 degrees C exhibits a tetragonal crystalline structure. The ceramics show high dielectric constant (epsilon(r) similar to 5456), dielectric loss of 0.02, depolarization temperature T-d similar to 110 degrees C and temperature corresponding to the maximum value of dielectric constant T-m similar to 262 degrees C. The dielectric constant (epsilon(33)) and the piezoelectric constant (d(33)) attain the maximum values of 924 and 13 pC/N, respectively, while the electromechanical coupling factor (k(p)) value is 0.035. The NBT-BT0.11 ceramics derived from sol-gel present high mechanical quality factor (Q(m) similar to 860). The dielectric and piezoelectric properties values of NBT-BT0.11 ceramics derived from sol-gel are smaller than those of samples produced by the conventional solid state reaction method, due to the grains size and oxygen vacancies that generate dipolar defects. (C) 2012 Elsevier Ltd. All rights reserved.

1773. Structural and piezoelectric characteristics of BNT-BT0.05 thin films processed by sol-gel technique

Authors: Cernea, M; Trupina, L; Dragoi, C; Vasile, BS; Trusca, R

Published: FEB 25 2012, JOURNAL OF ALLOYS AND COMPOUNDS, 515, 170, DOI: 10.1016/j.jallcom.2011.11.129

Polycrystalline ferroelectric lead-free (Bi0.5Na0.5)(0.95)Ba0.05TiO3 (BNT-NT0.05) thin films have been deposited on Pt/TiO2/SiO2/Si substrates by an optimized sol-gel/spin-coating process. The film thermal treated at 700 degrees C is dense and well crystallized in the rhombohedral perovskite phase. The film is composed of polyhedral shaped primary particles with an average size of approximately 35 nm, and has a smooth surface of 4.52 nm root mean square roughness (RMS). The nanoscale electrical properties of the film were investigated by piezoforce microscopy (PFM). The PFM data showed that most of the grains seem to be constituted of ferroelectric multiple domains. The maximum dielectric constant measured at zero bias voltage is about 210 and the leakage current density has a value of about 3 x 10(-5) A/cm(2) at an applied voltage about 8 V. These results indicate that, the BNT-NT0.05 thin film is a promising functional lead-free ferroelectric material. (C) 2011 Elsevier B. V. All rights reserved.

1774. PHYTOSYNTHESIS OF GOLD NANOPARTICLES USING CAESALPINIA PULCHERRIMA (PEACOCK FLOWER) FLOWER EXTRACT AND EVALUATION OF THEIR ANTIMICROBIAL ACTIVITIES

Authors: Nagaraj, B; Divya, TK; Barasa, M; Krishnamurthy, NB; Dinesh, R; Negrila, CC; Predoi, D

Published: JUL-SEP 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 905, DOI:

Caesalpinia pulcherrima (Linn) popularly known as Peacock flower in India belongs to family Caesalpiniace. In this work, we describe environment friendly technique for green synthesis of gold nanoparticles from AuCl4 solution using the Caesalpinia pulcherrima (Peacock flower) flower extract as reducing agent. The gold nanoparticles were characterized using UV-visible spectroscopy and transmission electron microscopy (TEM). The UV-visible spectra indicate a strong Plasmon resonance that is located at similar to 450 nm. The TEM analysis shows that products have spherical morphology with size ranging between 10-50 nm. The study also indicates that gold nanoparticles show good antimicrobial activities when compared to the standard antibiotics.

1775. Sol-gel template synthesis of luminescent glass-ceramic rods

Authors: Secu, M; Secu, CE; Sima, M

Published: APR 2012, JOURNAL OF NANOPARTICLE RESEARCH, 14, DOI: 10.1007/s11051-012-0772-1

We report an original way to prepare luminescent glass-ceramic microrods containing Eu3+ doped BaF2 nanocrystals by sol-gel chemistry within the pores of a polycarbonate template membrane. Structural characterization by scanning electron microscopy and X-ray diffraction has shown the formation of glass-ceramic microrods with 0.8-m diameter of and 10 mu m length in which BaF2 nanocrystals of about 30 nm size are embedded. Photoluminescence measurements have indicated the incorporation of Eu3+ ions inside the BaF2 nanocrystals in a broad range of sites with low coordination symmetry. The comparison made with the bulk glass-ceramic indicated an influence of the dimensional constraints imposed by the membrane pores during xerogel formation and subsequent glass ceramization.

1776. Matrix assisted pulsed laser evaporation of Mn-12(Propionate) thin films

Authors: Pervolaraki, M; Sima, F; Socol, G; Teodorescu, CM; Gheorghe, NG; Socol, M; Mihailescu, IN; Moushi, EE; Tasiopoulos, AJ; Athanasopoulos, GI; Viskadourakis, Z; Giapintzakis, J

Published: SEP 15 2012, APPLIED SURFACE SCIENCE, 258, 9474, DOI: 10.1016/j.apsusc.2011.10.136

Single molecule magnets are of great interest due to a multitude of potential applications for some of which thin films are required. Traditional physical vapor deposition techniques are not suitable for the deposition of these fragile materials with low decomposition temperatures. Matrix Assisted Pulsed Laser Evaporation technique has been employed for the growth of thin films of the single molecule magnet Mn-12(Propionate) on Si and glass substrates. In this paper we report on the appropriate growth conditions and also the morphology, chemical composition and magnetic behavior of the films. Continuous Mn-12(Propionate) films with properties similar to bulk materials have been obtained. (c) 2011 Elsevier B.V. All rights reserved.

1777. Controllable chirality-induced geometrical Hall effect in a frustrated highly correlated metal

Authors: Ueland, BG; Miclea, CF; Kato, Y; Ayala-Valenzuela, O; McDonald, RD; Okazaki, R; Tobash, PH; Torrez, MA; Ronning, F; Movshovich, R; Fisk, Z; Bauer, ED; Martin, I; Thompson, JD

Published: SEP 2012, NATURE COMMUNICATIONS, 3, DOI: 10.1038/ncomms2075

A current of electrons traversing a landscape of localized spins possessing non-coplanar magnetic order gains a geometrical (Berry) phase, which can lead to a Hall voltage independent of the spin-orbit coupling within the material-a geometrical Hall effect. Here we show that the highly correlated metal UCu5 possesses an unusually large controllable geometrical Hall effect at T < 1.2 K due to its frustration-induced magnetic order. The magnitude of the Hall response exceeds 20% of the nu = 1 quantum Hall effect per atomic layer, which translates into an effective magnetic field of several hundred Tesla acting on the electrons. The existence of such a large geometric Hall response in UCu5 opens a new field of enquiry into the importance of the role of frustration in highly correlated electron materials.

1778. Preparation and properties of nanocrystalline BNT- BTx piezoelectric ceramics by sol-gel and spark plasma sintering

Authors: Cernea, M; Poli, G; Aldica, GV; Berbecaru, C; Vasile, BS; Galassi, C

Published: JUL 2012, CURRENT APPLIED PHYSICS, 12, 1105, DOI: 10.1016/j.cap.2012.01.016

(Bi0.5Na0.5)TiO3 was doped in situ with 5, 8, and 11 mol% BaTiO3 (BNT-BTx; x = 0.05, 0.08 and 0.11) using a sol-gel technique. The resulting powders from gel precursors showed microstructures consisting of nano-sized grains and crystalline perovskite structure. Spark plasma sintering (SPS) technique was used to prepare high densified (98-99%rho(theor)) BNT-BTx ceramics from these nanopowders. The results confirm the spark plasma sintering method applied to nano-scale powders, obtained by sol-gel, as a viable route in producing nanostructured ceramics. The evolution of the structure and electrical properties of the ceramics with BaTiO3 concentration (x) was investigated. The permittivity of BNT-BT0.08 ceramic is higher (epsilon(r) = 2090, at 100 kHz) than that for x = 0.05 (epsilon(r) = 1350) and x = 0.11 (epsilon(r) = 1800). BNT-BT0.08 ceramic shows maximum values for the frequency constants (N-p, N-t), piezoelectric charge coefficient (d(31)) and piezoelectric voltage coefficient (g(31)), and minimum values for the electromechanical coupling factor (k(p)) and piezoelectric charge coefficient (d(33)). The electrical properties of these ceramics are influenced by grains size, oxygen deficiency and non-uniform internal stresses due to these oxygen deficiencies. BNT-BTx ceramics sintered by SPS seem to be good ceramic resonators with high mechanical quality factor (Q(m)). Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved.

1779. ZnO morphological, structural and optical properties control by electrodeposition potential sweep rate

Authors: Matei, E; Enculescu, M; Preda, N; Enculescu, I

Published: JUN 15 2012, MATERIALS CHEMISTRY AND PHYSICS, 134, 993, DOI: 10.1016/j.matchemphys.2012.03.101

ZnO films were electrodeposited from an aqueous nitrate bath on ITO/glass substrates. The process was performed not by the usual potentiostatic approach but by using potential ramps with different sweep rates. We tested these ramps in both directions i.e. either towards electronegative (direct) or electropositive (inverse) potential. As expected, the samples prepared in different deposition conditions show different morphology, different quality of crystalline structure and different optical properties. By employing inverse ramps we prepared films with high quality structural and optical properties. We assume that in these conditions the growth is followed by an etching process which preferentially removes the areas with high defect concentration and leads to the formation of hollow hexagonal prisms. (c) 2012 Elsevier B.V. All rights reserved.

1780. Phase extraction in disordered isospectral shapes

Authors: Tolea, M; Ostahie, B; Nita, M; Tolea, F; Aldea, A

Published: MAR 14 2012, PHYSICAL REVIEW E, 85, DOI: 10.1103/PhysRevE.85.036604

The phase of the electronic wave function is not directly measurable but, quite remarkably, it becomes accessible in pairs of isospectral shapes, as recently proposed in the experiment by Moon et al. [Science 319, 782 (2008)]. The method is based on a special property, called transplantation, which relates the eigenfunctions of the isospectral pairs, and allows us to extract the phase distributions, if the amplitude distributions are known. We numerically simulate such a phase extraction procedure in the presence of disorder, which is introduced both as Anderson disorder and as roughness at edges. With disorder, the transplantation can no longer lead to a perfect fit of the wave functions, however we show that a phase can still be extracted-defined as the phase that minimizes the misfit. Interestingly, this extracted phase coincides with (or differs negligibly from) the phase of the disorder-free system, up to a certain disorder amplitude, and a misfit of the wave functions as high as similar to 5%, proving a robustness of the phase extraction method against disorder. However, if the disorder is increased further, the extracted phase shows a puzzle structure, no longer correlated with the phase of the disorder-free system. A discrete model is used, which is the natural approach for disorder analysis. We provide a proof that discretization preserves isospectrality and the transplantation can be adapted to the discrete systems.

1781. Composites of MgB2 with Bi2O3, Bi, Sb2O3, or Sb Obtained by Ex-situ Spark Plasma Sintering

Authors: Badica, P; Aldica, G; Burdusel, M; Endo, K

Published: NOV 2012, JAPANESE JOURNAL OF APPLIED PHYSICS, 51, DOI: 10.1143/JJAP.51.11PG13

Mixtures of MgB2 and metal or oxide additions with starting compositions of (MgB2)(M2O3)(x), x = 0.0025, 0.005, 0.015, and (MgB2)(M)(y), y = 0.01, M = Bi, Sb, were processed by spark plasma sintering (SPS). As-obtained samples are composites with high density exceeding 94% of the theoretical values. Secondary phases indicate similar reactions for samples with Bi- or Sb-based additions. However, samples show very different superconducting characteristics depending on the addition type and amount. A direct correlation with the melting temperature of the addition could not be revealed, although some aspects will be discussed. From the critical current density (J(c)) and irreversibility field (H-irr) enhancement viewpoints, optimum additions are oxides for x = 0.0025; 0.005. Both oxides improve Jc at high fields, but Sb2O3 is effective up to 10 K, whereas Bi2O3 is effective up to 30 K. Metal additions decrease J(c) and H-irr when compared with a pristine MgB2 sample. (C) 2012 The Japan Society of Applied Physics

1782. Pulsed laser deposition of highly textured La5Ca9Cu24O41 films on SrLaAlO4 (100) and Gd3Ga5O12 (100) substrates

Authors: Pervolaraki, M; Pasuk, I; Stan, GE; Giapintzakis, J

Published: SEP 15 2012, APPLIED SURFACE SCIENCE, 258, 9479, DOI: 10.1016/j.apsusc.2012.02.145

The growth of La5Ca9Cu24O41 thin films on SrLaAlO4 (1 0 0) and Gd3Ga5O12 (1 0 0) substrates by pulsed laser deposition is reported in this paper. The influence of deposition process parameters, such as oxygen pressure, substrate temperature, and laser repetition rate, on the crystallinity, orientation and microstructure of the films has been investigated. X-ray diffraction and atomic force microscopy studies showed a clear dependence of the film crystallographic orientation and morphology (grain size) on the substrate temperature and the oxygen pressure used in the deposition process. (c) 2012 Elsevier B.V. All rights reserved.

1783. Mossbauer, TEM/SAED and XRD investigation on waste dumps of the Valea lui Stan gold mines

Authors: Constantinescu, SG; Udubasa, SS; Udubasa, G; Kuncser, V; Popescu-Pogrion, N; Mercioniu, I; Feder, M

Published: MAR 2012, HYPERFINE INTERACTIONS, 208, 84, DOI: 10.1007/s10751-011-0490-6

The complementary investigation techniques, Mossbauer spectroscopy, transmission electron microscopy with selected area electron diffraction (TEM/SAED), X-ray diffraction (XRD) have been used to investigate the fate of the Valea lui Stan, Romania, gold-ore nanoscale-minerals during the long time of residence in the waste dumps. The preliminary investigations showed such waste dumps to contain significant amount of metals which cannot be identified by conventional methods. An intense research activity started up in order to evaluate the possibilities to recycle Valea lui Stan waste dumps and to recover metals by chemical or phytoextraction procedures. The waste dumps naturally show different mineral constituents with clay minerals as major phases, observed by XRD-technique. Although the waste dumps materials have whitish-yellowish colours, MOSSBAUER technique evidences the presence of the finely dispersed iron bearing minerals. The authors are focusing to inspect and analyze Fe-compounds in the samples collected from Valea lui Stan's waste dumps in order to identify the magnetic phases by Mossbauer technique.

1784. Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions

Authors: Nita, M; Marinescu, DC; Ostahie, B; Manolescu, A; Gudmundsson, V

Published: 2012, ADVANCED MANY-BODY AND STATISTICAL METHODS IN MESOSCOPIC SYSTEMS, 338, DOI: 10.1088/1742-6596/338/1/012013

When subjected to a linearly polarized terahertz pulse, a mesoscopic ring endowed with spin-orbit interaction (SOT) of the Rashba-Dresselhaus type exhibits non-uniform azimuthal charge and spin distributions. Both types of SOT couplings are considered linear in the electron momentum. Our results are obtained within a formalism based on the equation of motion satisfied by the density operator which is solved numerically for different values of the angle 0, the angle determining the polarization direction of the laser pulse. Solutions thus obtained are later employed in determining the time-dependent charge and spin currents, whose values are calculated in the stationary limit. Both these currents exhibit an oscillatory behavior complicated in the case of the spin current by a beating pattern. We explain this occurrence on account of the two spin-orbit interactions which force the electron spin to oscillate between the two spin quantization axes corresponding to Rashba and Dresselhaus interactions. The oscillation frequencies are explained using the single particle spectrum.

1785. Synthesis and characterization of polysaccharide-maghemite composite nanoparticles and their antibacterial properties

Authors: Iconaru, SL; Prodan, AM; Motelica-Heino, M; Sizaret, S; Predoi, D

Published: OCT 22 2012, NANOSCALE RESEARCH LETTERS, 7, DOI: 10.1186/1556-276X-7-576

The aim of this study was to obtain saccharide (dextran and sucrose)-coated maghemite nanoparticles with antibacterial activity. The polysaccharide-coated maghemite nanoparticles were synthesized by an adapted coprecipitation method. X-ray diffraction (XRD) studies demonstrate that the obtained polysaccharide-coated maghemite nanoparticles can be indexed into the spinel cubic lattice with a lattice parameter of 8.35 angstrom. The refinement of XRD spectra indicated that no other phases except the maghemite are detectable. The characterization of the polysaccharide-coated maghemite nanoparticles by various techniques is described. The antibacterial activity of these polysaccharide-coated maghemite nanoparticles (NPs) was tested against Pseudomonas aeruginosa 1397, Enterococcus faecalis ATCC 29212, Candida krusei 963, and Escherichia coli ATCC 25922 and was found to be dependent on the polysaccharide type. The antibacterial activity of dextran-coated maghemite was significantly higher than that of sucrose-coated maghemite. The antibacterial studies showed the potential of dextran-coated iron oxide NPs to be used in a wide range of medical infections.

1786. Bi-2212 and Y123 highly curved single-crystal-like objects: whiskers, bows and ring-like structures

Authors: Badica, P; Agostino, A; Khan, MMR; Cagliero, S; Plapcianu, C; Pastero, L; Truccato, M; Hayasaka, Y; Jakob, G

Published: OCT 2012, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 25, DOI: 10.1088/0953-2048/25/10/105003

High-temperature superconducting objects of Bi2Sr2CaCu2O8 and YBa2Cu3O7 highly curved in the ab-plane, such as curved/ kinked whiskers, bows and ring-like structures, were obtained within a solid-liquid-solid (SLS) grass-like growth mechanism. As-grown objects are crystals with three-dimensional epitaxy similar to conventional single crystals: they can be viewed as crystal parts 'cut' from a conventional rectangular crystal. Between our curved objects and conventional crystals, whiskers or thin films there are some differences in the superconducting properties induced only by the shape factors and no new physics is observed. Some details of the growth mechanism are discussed, emphasizing curved-line formation.

1787. Improved antibunching by using high-excitation pulses from a single semiconductor quantum dot-a theoretical study

Authors: Florian, M; Gies, C; Gartner, P; Jahnke, F

Published: FEB 2012, JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS, 29, A35, DOI: 10.1364/JOSAB.29.000A31

We study the intensity dependence of single-photon emission from a single semiconductor quantum dot after pulsed excitation. A semiconductor model is introduced that accounts for various configurations resulting from the occupation of the localized single-particle states with carriers. A detailed account is given on how the photon correlation dynamics and the antibunching can be calculated. We predict a novel effect, where, for strong excitation, the formation of multiexciton configurations during the excitation pulse leads to an improved antibunching signature in g((2)). (C) 2012 Optical Society of America

1788. Spark-plasma-sintering temperature dependence of structural and piezoelectric properties of BNT-BT0.08 nanostructured ceramics

Authors: Cernea, M; Fochi, F; Aldica, GV; Vasile, BS; Trusca, R; Galassi, C

Published: APR 2012, JOURNAL OF MATERIALS SCIENCE, 47, 3673, DOI: 10.1007/s10853-011-6215-z

(Bi0.5Na0.5)TiO3 doped with 8 mol% BaTiO3 powder prepared by sol-gel was compacted and sintered by spark-plasma-sintering method. The influence of spark-plasma-sintering temperature on the densification and piezoelectric properties of these ceramics was studied. Starting from BNT-BT0.08 powder gel with a microstructure consisting of particles with average size of 50 nm, ceramics with grain size of 60-90 nm and density of about 98.9-99.6% of the theoretical density were obtained by spark-plasma-sintering at 800-900 A degrees C. Increasing the sintering temperature by SPS from 800 to 900 A degrees C lead to the increase of d (33), k (p), epsilon (33) (T) and, decrease of Q (m). Typical d (33) and k (p) values of BNT-BT0.08 ceramics sintered by spark-plasma-sintering at 900 A degrees C were 8 and 0.029, respectively.

1789. Effect of the morphology on the optical and electrical properties of polycarbonate film doped with aniline derivatives monomers

Authors: Stanculescu, F; Stanculescu, A; Girtan, M; Socol, M; Rasoga, O

Published: JAN 2012, SYNTHETIC METALS, 161, 2597, DOI: 10.1016/j.synthmet.2011.09.012

In this paper we present some comparative studies between the optical and electrical properties of the films prepared by vacuum evaporation from amidic monomeric compounds obtained from maleic anhydride and aniline derivative with different functional groups [CN; NO2], and the composite films prepared by spin-coating from a polycarbonate of bisphenol A matrix embedding clusters of these amidic monomers. We have emphasised the effect of the polymeric matrix on the properties of the synthesised monomers with the purpose to change the physical properties of the films (optical transmission, luminescence, electrical conduction, optical non-linear phenomena). The correlation between the morphology of the films and the optical and electrical properties has also been investigated. (C) 2011 Elsevier B.V. All rights reserved.

1790. Electronic effects at self-assembled 4,4 '-thio-bis-benzenethiolate protected Au nanoparticles on p-GaAs (100) electrodes

Authors: Enache, M; Preda, L; Negrila, C; Lazarescu, MF; Mercioniu, I; Santos, E; Anastasescu, M; Dobrescu, G; Lazarescu, V

Published: AUG 30 2012, ELECTROCHIMICA ACTA, 77, 16, DOI: 10.1016/j.electacta.2012.04.161

The effects of the self-assembled 4,4'-thio-bis-benzenethiolate protected gold nanoclusters onto a p-GaAs (1 0 0) electrode were examined by AFM, XPS, SHG and EIS investigations. The AFM and XPS results revealed a well-ordered overlayer exhibiting a bi-modal highly correlated fractal behavior which, however, cannot fully protect the semiconducting surface against the oxidation in air. The EIS data pointed out the influence exerted by the gold-monolayer protected clusters (Au-MPCs) over the charging/discharging processes observed at p-GaAs (1 0 0) electrode. Although the applied potential is varied linearly, the potential drop within the semiconductor space charge region as well as that across the Au-MPCs layer undergoes stepped changes supposed to result in the discrete charging of the Au-MPCs. These effects point to an electronic equilibrium between the Au-MPCs and the semiconducting substrate. Fermi level pinning and enhancement of the SHG response in the potential range where the surface/interface states in the semiconductor band gap become electrically active bring further proof in this respect. (c) 2012 Elsevier Ltd. All rights reserved.

1791. Laser processing issues of nanosized intermetallic Fe-Sn and metallic Sn particles

Authors: Alexandrescu, R; Morjan, I; Dumitrache, F; Birjega, R; Fleaca, C; Morjan, I; Scarisoreanu, M; Luculescu, CR; Dutu, E; Kuncser, V; Filoti, G; Vasile, E; Ciupina, V

Published: SEP 15 2012, APPLIED SURFACE SCIENCE, 258, 9426, DOI: 10.1016/j.apsusc.2012.01.159

Intermetallic Fe-Sn and nanocrystalline metallic Sn nanoparticles have been successfully synthesized from organic precursors using the laser pyrolysis technique with ethylene as sensitizer. Nano-structured Sn (single phase) was prepared by the pyrolysis of Sn(CH3)(4) (TMT) vapors. Controlled Fe/Sn atomic ratios, ranging from 0.69 to 1.64 were obtained for the prepared Fe-Sn nanopowders by the control of Fe(CO)(5) and TMT flows, respectively. XRD studies evidence three main phases: the tetragonal metallic Sn phase and the intermetallic FeSn2 phase and, to a much lesser extent, the cubic ternary carbide Fe3SnC. Complex core-shell structural characteristics were found by HRTEM analysis. More complete information about the Fe phase distributions in the new intermetallic Fe-Sn nanomaterial is provided by temperature dependent Fe-57 Mossbauer spectroscopy. (c) 2012 Elsevier B.V. All rights reserved.

1792. Superior Modes in High Permittivity Cylindrical Dielectric Resonator Antenna Excited by a Central Rectangular Slot

Authors: Avadanei, OG; Banciu, MG; Nicolaescu, I; Nedelcu, L

Published: NOV 2012, IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, 60, 5038, DOI: 10.1109/TAP.2012.2207692

High permittivity materials allow good miniaturization of microwave components, but the dielectric resonator antenna using these materials has the drawback of a reduced bandwidth. To overcome this disadvantage we wanted to obtain a relatively wideband high permittivity DRA using the superior modes. Using HFSS simulations, we identified some of the superior modes that appear in cylindrical DRAs situated on a conductor ground plane and excited by a symmetric rectangular slot made in the ground plane. We identified seven superior modes and, for all of them, the measured and theoretically calculated resonant frequencies did not differ by more than 6%. Knowing the possible excited modes in the antenna and the relations for their resonant frequencies, one can predict the operating frequencies of a cylindrical DRA excited by a central rectangular slot.

1793. Photoluminescence and Raman evidence for mechanico-chemical interaction of polyaniline-emeraldine base with ZnS in cubic and hexagonal phase

Authors: Scocioreanu, M; Baibarac, M; Baltog, I; Pasuk, I; Velula, T

Published: FEB 2012, JOURNAL OF SOLID STATE CHEMISTRY, 186, 223, DOI: 10.1016/j.jssc.2011.12.012

The mechanico-chemical interaction of a polyaniline-emeraldine base (PANI-EB) with ZnS in the cubic and wurtzite phases is studied by Raman spectroscopy and photoluminescence (PL). The results demonstrate that such an interaction leads to the formation of a PANI-salt and metallic Zn. Regardless of the structural form of the ZnS, the formation PANI-salt is indicated by a band in the Raman spectrum that shifts from 1162 to 1176 cm(-1) and the appearance of a new band at 1330 cm(-1) that indicates the protonated structure of a PANI-salt. The presence of the second product is determined by comparative PL studies performed on ZnS that has interacted mechanico-chemically with PANI-EB and metallic Zn powder. The variations of the PL spectra and their associated excitation spectra are explained as resulting from the charge collection processes that occur in the composite materials produced by the mechanico-chemical interaction between ZnS and PANI-EB or metallic Zn. (C) 2011 Elsevier Inc. All rights reserved.

1794. Electronic transmittance phase extracted from mesoscopic interferometers

Authors: Tolea, M; Moldoveanu, V; Dinu, IV; Tanatar, B

Published: OCT 13 2012, NANOSCALE RESEARCH LETTERS, 7, 7, DOI: 10.1186/1556-276X-7-568

The usual experimental set-up for measuring the wave function phase shift of electrons tunneling through a quantum dot (QD) embedded in a ring (i.e., the transmittance phase) is the so-called 'open' interferometer as first proposed by Schuster et al. in 1997, in which the electrons back-scattered at source and the drain contacts are absorbed by additional leads in order to exclude multiple interference. While in this case one can conveniently use a simple two-path interference formula to extract the QD transmittance phase, the open interferometer has also a number of draw-backs, such as a reduced signal and some uncertainty regarding the effects of the extra leads. Here we present a meaningful theoretical study of the QD transmittance phase in 'closed' interferometers (i.e., connected only to source and drain leads). By putting together data from existing literature and giving some new proofs, we show both analytically and by numerical simulations that the existence of phase lapses between consecutive resonances of the 'bare' QD is related to the signs of the corresponding Fano parameters - of the QD + ring system. More precisely, if the Fano parameters have the same sign, the transmittance phase of the QD exhibits a I lapse. Therefore, closed mesoscopic interferometers can be used to address the 'universal phase lapse' problem. Moreover, the data from already existing Fano interference experiments from Kobayashi et al. in 2003 can be used to infer the phase lapses.

1795. A facile hydrothermal route for the synthesis of alpha-FeOOH with controlled morphology

Authors: Raditoiu, V; Diamandescu, L; Corobea, MC; Raditoiu, A; Popescu-Pogrion, N; Nicolae, CA

Published: JUN 1 2012, JOURNAL OF CRYSTAL GROWTH, 348, 46, DOI: 10.1016/j.jcrysgro.2012.03.032

Nanoscaled alpha-FeOOH (goethite) with controlled morphology was synthesized via hydrothermal reaction at 145-155 degrees C from ferrous ions and an oxidant in the presence of a cationic surfactant. The formation of alpha-FeOOH was confirmed by X-ray diffraction (XRD), Mossbauer spectroscopy, FT-IR analysis and visible diffuse reflectance spectroscopy. The morphology of the product was analyzed by transmission electron microscopy (TEM). The particles obtained by the proposed method have a medium size of about 35 nm. The proposed growth mechanism takes into account two possible simultaneous pathways consisting of direct electrostatic interaction between FeOH groups and cetyltrimethylammonium bromide (CTAB) and adsorption of bicarbonate ions on the alpha-FeOOH surface followed by complexation of CTAB through ammonium head groups. (C) 2012 Elsevier B.V. All rights reserved.

1796. Ba(X1/3Ta2/3)O-3 COMPLEX PEROVSKITES FOR MICROWAVE AND MILLIMETER-WAVE APPLICATIONS

Authors: Nedelcu, L; Busuioc, C; Banciu, MG; Ramer, R

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 306, DOI:

Ba(X1/3Ta2/3)O-3 (X = Zn, Mg) perovskites were prepared by using the solid state reaction method. X-ray diffraction and scanning electron microscopy were employed for structural and morphological characterization of Ba(X1/3Ta2/3)O-3 samples. The dielectric constant of the resonators was 28 for Ba(Zn1/3Ta2/3)O-3 and 24 for Ba(Mg1/3Ta2/3)O-3. A strong influence of the cation ordering on the dielectric loss has been found. The achieved values of Q x f product, ranging from 100 to 200 THz, make Ba(X1/3Ta2/3)O-3 dielectric resonators attractive for microwave and millimetre-wave applications.

1797. Heterogeneous amination of bromobenzene over titania-supported gold catalysts

Authors: Ciobanu, M; Cojocaru, B; Teodorescu, C; Vasiliu, F; Coman, SM; Leitner, W; Parvulescu, VI

Published: DEC 2012, JOURNAL OF CATALYSIS, 296, 54, DOI: 10.1016/j.jcat.2012.09.002

Amination of bromobenzene with aniline was carried out on heterogeneous Au-TiO2 catalysts prepared using the deposition-precipitation method. The deposition of gold in loadings in the range 0.1-0.9 wt.% on titania occurred with the formation of gold particles with controlled size and oxidation state as demonstrated from TEM and XPS measurements. In addition, Raman and DR-UV-Vis investigation of these catalysts showed that the interaction of Au particles with the support stabilized the metallic state of gold. Catalytic results demonstrated that the conversion and selectivity depended on the gold-particle size and dispersion, while the mechanism of reaction was in direct relation with the reaction medium. Working in DMC, the solvent was playing the role of base. The advantage of working in DMC was avoiding the formation of KBr which is very difficult to be separated from the reaction products. HBr resulted as a by-product formed adducts with the coupling product, which was separated as crystals at room temperature by a simple filtration. However, in DMC, the reaction occurred with low selectivities. In dioxane, the presence of potassium ethoxide as base was mandatory. The reaction occurred with very high selectivities for moderate conversions. The conversion was limited by KBr released from the reaction. However, the use of the heterogeneous catalyst has the advantage of scavenger, since KBr becomes chemisorbed on the surface and could be simple removed by percolation and the catalyst can be reused. (C) 2012 Elsevier Inc. All rights reserved.

1798. CORTICAL BONE AS RESOURCE FOR PRODUCING BIOMIMETIC MATERIALS FOR CLINICAL USE

Authors: Miculescu, F; Stan, GE; Ciocan, LT; Miculescu, M; Berbecaru, A; Antoniac, I

Published: OCT-DEC 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 1677, DOI:

The search of new alternative materials for bone reconstruction is a major objective in biomaterials engineering and reconstructive medicine. In this study the compact bone derived materials are proposed, their structure and composition being modified by thermal treatments performed in 200-1200 degrees C range, using 200 degrees C temperature steps. The monitoring of the bone modifications under heat-treatment was carried out using thermal analysis (TGA-DSC), microstructural (SEM), compositional (EDS) and structural (FTIR, XRD) methods. Tailoring the bone material's morphological, chemical and structural properties by heat-treatments, expressed by the HA/beta-TCP compositional ratio, degree of crystallinity and porosity control, could lead to the obtaining of good quality bone substitute materials suitable for the bone regeneration of large osseous defects.

1799. ON TITANIUM OXIDE SPRAY DEPOSITED THIN FILMS FOR SOLAR CELLS APPLICATIONS

Authors: Vaiciulis, I; Girtan, M; Stanculescu, A; Leontie, L; Habelhames, F; Antohe, S

Published: OCT-DEC 2012, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 13, 342, DOI:

Titanium oxide is one of the most promising candidate for relatively low cost, simple manufacture and high-performance new generation solar cells and the recent achievements in dye-sensitized solar cells (DSSCs) efficiencies and life time confirm the fact that these new generation solar cells becomes one of the future solutions in energy conversion. In DSSCs the presence of a dense titanium oxide layer is necessary in order to avoid short circuits between electrodes. Then, the interest to have a second porous TiO2 layer is determined by the fact that compared to a flat surface, a dye-sensitized porous surface area increase the absorption and hence conduct to the increase of solar cells efficiencies. Generally these two layers are prepared by successive depositions using two different methods. In this paper we present a simple technique to prepare both layers during the same spraying process. Films morphology and structure of titanium oxide deposited on glass and ITO substrate was investigated by AFM, SEM and XRD respectively.

1800. Cylindrical resonator antenna manufactured with Barium Neodymium Titanate

Authors: Nicolaescu, I; Avadanei, OG; Nedelcu, L; Toacsan, MI; Banciu, MG; Andrei, I; Balmus, SB

Published: NOV-DEC 2012, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 14, 1010, DOI:

The rapid evolution of GPS, mobile and wireless communication systems in the last years is based, substantially, on ceramic based dielectrics with effect on miniaturization of components (antennas, filters, oscillators), cost and temperature stability. The development of high dielectric constant materials was critical for the dimensions reduction of the equipment but also for their performance improvements. These materials have high dielectric constant, epsilon(r), between 20 and 90; low losses in microwave and millimetre wave domain and a low variation of dielectric constant with the temperature. The paper describes a high dielectric constant material, Barium Neodymium Titanate - (Ba,Pb)Nd2Ti4O12 (BNT), and presents some results obtained by using this ceramic based material to manufacture a dielectric resonator antenna.

1801. Assessing toxicity of two types of magnetite nanoparticles in human hepatocarcinoma cells

Authors: Radu, M; Iconaru, SL; Predoi, D; Costache, M; Dinischiotu, A

Published: SEP 2012, FEBS JOURNAL, 279, 205, DOI:

1802. Synthesis of CdS nanostructures using template-assisted ammonia-free chemical bath deposition

Authors: Preda, N; Enculescu, M; Gherendi, F; Matei, E; Toimil-Molares, ME; Enculescu, I

Published: SEP 2012, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 73, 1089, DOI: 10.1016/j.jpcs.2012.05.003

CdS micro- and nano-structures (micro/nanotubes and nanostructured films) were obtained by ammonia-free chemical bath deposition using polymer templates (ion track-etched polycarbonate membranes and poly(styrene-hydroxyethyl methacrylate) nanosphere arrays). The semiconductor structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), optical absorption, photoluminescence and electrical measurements. The diameters of CdS tubes are between 300 nm and few microns and the lengths are up to tens of micrometers. The SEM images prove that the CdS films are nanostructured due to the deposition on the polymer nanosphere arrays. For both CdS structures (tubes and films) the XRD patterns show a hexagonal phase. The optical studies reveal a band gap value of about 2.5 - 2.6 eV and a red luminescence at similar to 1.77 eV. A higher increase of conductivity is observed for illuminating the CdS nanostructured film when compared to the simple semiconductor film. This is a consequence of the periodic patterning induced by the polymer nanosphere array. (C) 2012 Elsevier Ltd. All rights reserved.

1803. Optical and electrical properties of arylenevinylene compounds thin films prepared by vacuum evaporation

Authors: Rasoga, O; Vacareanu, L; Grigoras, M; Enculescu, M; Socol, M; Stanculescu, F; Ionita, I; Stanculescu, A

Published: JAN 2012, SYNTHETIC METALS, 161, 2617, DOI: 10.1016/j.synthmet.2011.10.001

This paper discusses the properties of two arylenevinylene oligomers thin films deposited by vacuum evaporation on different substrates. The morphology of the thin films was investigated by scanning electron microscopy and atomic force microscopy, and the optical properties by UV-Vis and fluorescence spectroscopy. The optical nonlinear phenomenon of two-photon absorption induced fluorescence has been evidenced in the thin films of these compounds. We have also investigated the electrical properties of semiconductor/insulator/semiconductor (ITO/oligomer/Si) heterostructures in correlation with the contact energetic barriers, morphological and structural properties of the layers. (C) 2011 Elsevier B.V. All rights reserved.

1804. Structure and Magnetic Properties of Nanosized Magnetite Obtained by Glass Recrystallization

Authors: Sandu, V; Nicolescu, MS; Kuncser, V; Popa, S; Pasuk, I; Ghica, C; Sandu, E

Published: JUN 2012, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 12, 5050, DOI: 10.1166/jnn.2012.4943

We present the preparation, structural and magnetic properties of nanosized magnetite obtained by the crystallization of a series of Fe-containing borosilicate glasses. Several compositions with the ratio Fe2O3/SiO2 spanning from 0.37 to 0.67 were investigated as a function of two nucleators Cr2O3 and P2O5, respectively, and modifiers and intermediates (Al2O3 and MgO). Mossbauer spectroscopy revealed the degree, the type and the location of disorder induced by a specific composition and nucleators. In addition to magnetite, it was also revealed the presence of large amounts of Fe-rich paramagnetic phases. The magnetic response is analysed in relation with the amount of Fe ions which remain dispersed in the glassy matrix as noninteracting (paramagnetic) ions. We discuss the role of the nucleators on the disorder in both tetrahedral and octahedral sites of the magnetite.

1805. Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles

Authors: Pana, O; Soran, ML; Leostean, C; Macavei, S; Gautron, E; Teodorescu, CM; Gheorghe, N; Chauvet, O

Published: FEB 15 2012, JOURNAL OF APPLIED PHYSICS, 111, DOI: 10.1063/1.3686662

Different hybrid structures were obtained by coating magnetic nanoparticles of perovskite type manganite at optimal doping (La0.67Sr0.33MnO3, LSMO) with different quantities of polypyrrole (PPy). The amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by high resolution transmission electron microscopy (HRTEM) and analyzed by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements in near edge structure (XANES) techniques. By analyzing the magnetic behavior of the samples one can observe that the surface modification of magnetic nanoparticles by PPy results in an increase in the saturation magnetization of the composites. The process is ascribed to paired electrons transferred from the delocalized p states of the PPy into the outer disordered layers of the manganite. The analysis of pre-edge peak of the Mn K-edge XANES spectra in the case of PPy coated LSMO nanoparticles indicates that the charge transfer between polymer and nanoparticles is (directed) going to missing or distorted oxygen positions, hence increasing the 3d electrons' mobility and orbital hybridization between the neighboring manganese ion. As a consequence, within the surface layers of LSMO nanoparticles, both energy bands disrupted the structure, and the double exchange process between Mn ions was reestablished determining the saturation magnetizations and pre-edge features increase, respectively. (C) 2012 American Institute of Physics. [doi:10.1063/1.3686662]

1806. Effect of Tritium Loading on the Superconducting Properties of Niobium and Tantalum

Authors: Sandu, V; Popa, S; Nicolescu, MS; Enachescu, M; Sandu, E

Published: AUG 2012, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 25, 1804, DOI: 10.1007/s10948-012-1551-z

Niobium and tantalum sheets were loaded with tritium and their superconducting properties were investigated. Superconductivity is rather robust in both materials though they belong to different types of superconductors. The critical temperature does not change in the case of Nb at low field but decreases slightly in the case of Ta. The tritium-loaded Nb shows a higher remanent magnetization which we attribute to the subsurface accumulation of defects, but the high field irreversible magnetization is smaller than for the bare sample. In the case of Ta, both the remanent magnetization and the irreversible magnetization are slightly reduced after tritiation.

1807. Mesoscopic Fano effect in a spin splitter with a side-coupled quantum dot

Authors: Moldoveanu, V; Tolea, M; Tanatar, B

Published: FEB 20 2012, PHYSICS LETTERS A, 376, 1083, DOI: 10.1016/j.physleta.2012.02.017

We investigate the interplay between the spin interference and the Fano effect in a three-lead mesoscopic ring with a side-coupled quantum dot (QD). A uniform Rashba spin-orbit coupling and a perpendicular magnetic field are tuned such that the ring operates as a spin splitter in the absence of the QD: one lead is used to inject unpolarized electrons and the remaining (output) leads collect almost polarized spin currents. By applying a gate potential to the quantum dot a pair of spin-split levels sweeps the bias window and leads to Fano interference. The steady-state spin and charge currents in the leads are calculated for a finite bias applied across the ring via the non-equilibrium Green's function formalism. When the QD levels participate to transport we find that the spin currents exhibit peaks and dips whereas the charge currents present Fano lineshapes. The location of the side-coupled quantum dot and the spin splitting of its levels also affect the interference and the output currents. The opposite response of output currents to the variation of the gate potential allows one to use this system as a single parameter current switch. We also analyze the dependence of the splitter efficiency on the spin splitting on the QD. (C) 2012 Elsevier B.V. All rights reserved.

1808. Magnetic pinning effects of epitaxial LaxSr1-xMnO3 nanostructured thin films on YBa2Cu3O7-delta layers

Authors: Petrisor, T; Gabor, MS; Tiusan, C; Galluzzi, V; Celentano, G; Popa, S; Boulle, A; Petrisor, T

Published: SEP 1 2012, JOURNAL OF APPLIED PHYSICS, 112, DOI: 10.1063/1.4748049

The present paper presents the effects of a nanostructured, ferromagnetic La1-xSrxMnO3(LSMO) thin film on the pinning characteristics of an epitaxial YBa2Cu3O7(YBCO) thin film deposited on top. Ordered arrays of LSMO grains were obtained upon growing the film on a terraced (001) SrTiO3 substrate. The analyses of magnetic measurements revealed the presence of a complex vortex pinning mechanism within the YBCO film. With respect to a reference single YBCO layer, an additional pinning potential was observed. Its temperature evolution suggests that a magnetic pinning mechanism is responsible for improved pinning characteristics in the high temperature and field region. Based on the morphology of the underlying LSMO buffer, a strong pinning force is expected to arise due to the anti-dot formations, where a high magnetization gradient exists. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748049]

1809. Enhancement of critical current density and irreversibility field by Te or TeO2 addition to MgB2 bulk processed by spark plasma sintering

Authors: Aldica, G; Popa, S; Enculescu, M; Badica, P

Published: APR 2012, SCRIPTA MATERIALIA, 66, 573, DOI: 10.1016/j.scriptamat.2012.01.006

Te metal or TeO2 were added to MgB2 ((MgB2) (A)(x), x = 0.005, 0.01, 0.03, A = addition). The mixtures were processed by spark plasma sintering. The critical current density J(c), of the samples containing the Te/TeO2 additions is enhanced at high fields and at temperatures up to 20K. The curve of J(c)(5 K, H) for the sample with optimum x(Te) = 0.01 shows no accelerated decrease up to 8 T (J(c)(5 K, 8 T) = 1.8 x 10(3) A cm(-2)). The irreversibility field of the samples containing the Te/TeO2 additions is also enhanced. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

1810. Abnormal Anti-Stokes Raman Emission and Infrared Dichroism Studies on Poly(p-phenylenevinylene)/Single-Walled Carbon Nanotube Composites

Authors: Baibarac, M; Baltog, I; Wery, J; Lefrant, S; Mevellec, JY

Published: DEC 6 2012, JOURNAL OF PHYSICAL CHEMISTRY C, 116, 25545, DOI: 10.1021/jp3070008

Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared spectroscopy (FTIR) in the grazing angle incident reflection geometry, new data concerning the abnormal anti-Stokes Raman emission (AASRE) and the molecular orientation of poly(p-phenylenevinylene) (PPV) deposited on metallic supports of Ag and Au are reported. The particular dependencies of the anti-Stokes Raman intensity on the Raman shift, the sample thickness, and the incident pump intensity are highlighted in this paper. In the spectral range of 800-1000 cm(-1), the FTIR spectra of PPV films deposited on Ag and Au supports show a dichroism similar to that reported for the free-standing PPV film. Significant differences are reported in the spectral range of 1400-1700 cm(-1) for the s- and p-polarized FTIR spectra of PPV films deposited on Au and Ag supports. The annealing treatment at 110 degrees C of the PPV precursor solution in the presence of single-walled carbon nanotubes (SWNTs) induces a noncovalent functionalization of carbon nanotubes with the polymer molecules, as evidenced by a decrease of the radial breathing mode intensity and a decrease in the strength of AASRE. The process of noncovalent functionalization of SWNTs with PPV induces a change of the orientation angle of the transition dipole moment vector for the absorption band at 835 cm(-1). This fact is explained on the basis of the pi-pi* interaction between the phenyl group of PPV and the sidewall of the nanotubes.

1811. Microwave Synthesis of Fullerene-Doped MgB2

Authors: Plapcianu, C; Agostino, A; Badica, P; Aldica, GV; Bonometti, E; Ieluzzi, G; Popa, S; Truccato, M; Cagliero, S; Sakka, Y; Vasylkiv, O; Vidu, R

Published: AUG 29 2012, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 51, 11010, DOI: 10.1021/ie3005429

Unconventional in situ synthesis of MgB2 undoped and doped with fullerene (C-60) was performed by using a single-mode microwave (MW) furnace. Structural properties suggested that C substitutes for B in the crystal lattice of MgB2, while the J(c) showed typical enhancement at high magnetic fields when C chemical doping occurred. This behavior was similar to published results for another field-activated unconventional method of processing, i.e., spark plasma sintering, and it was opposite to the conventional powder-in-tube method for which chemical substitution was not realized when using addition of C-60. Certain morphologically unique features such as the occurrence of needlelike grains were revealed in the MW samples. Our MW samples showed higher relative density (<= 83%) than previously reported data. Magnetic relaxation experiments suggested the presence of microscopic flux jumps in the MW samples, while macroscopic flux jumps were not observed.

1812. Electron magnetic resonance and Mossbauer studies on iron doped SnO2 nanoparticles

Authors: Grecu, MN; Constantinescu, SG; Ghica, D; Tarabasanu-Mihaila, D; Diamandescu, L

Published: MAR 2012, HYPERFINE INTERACTIONS, 205, 115, DOI: 10.1007/s10751-011-0447-9

Iron doped (0.25-7.5% molar) hydrothermal nano-SnO2 was characterized by electron magnetic resonance (EMR) and Mossbauer spectroscopies. Only a small fraction of transition metal ions are in magnetic ordered state, contrary to the similar crystallographic compound TiO2. Temperature dependences of spectra suggest that by increasing iron concentration, or annealing temperature, iron ions migrate to nanoparticles surfaces forming disordered iron oxides.

1813. Post-synthesis Carbon Nanowalls Transformation under Hydrogen, Oxygen, Nitrogen, Tetrafluoroethane and Sulfur Hexafluoride Plasma Treatments

Authors: Vizireanu, S; Ionita, MD; Dinescu, G; Enculescu, I; Baibarac, M; Baltog, I

Published: APR 2012, PLASMA PROCESSES AND POLYMERS, 9, 370, DOI: 10.1002/ppap.201100153

Carbon nanowalls (CNWs) functionalization allows the tailoring of some of their properties after they have been synthesized. Herewith we report on post-synthesis CNWs functionalization by plasma treatments. Radiofrequency plasmas generated in hydrogen, oxygen, nitrogen, tetrafluoroethane, and sulfur hexafluoride admixed to argon, were used. The changes of morphology, structure, chemical composition were determined by SEM, FTIR, Raman Spectroscopy, specifically for each gas mixture. The results point out to the surface erosion, the functional groups attachment, or to thin film coverage of CNWs material. Such processes strongly influence the material properties, as exemplified by the wettability: superhydrophilic or superhydrophobic surfaces are obtained starting from the same base CNWs material.

1814. Fano-Kondo oscillations of the conductance and thermopower in a mesoscopic transistor

Authors: Aldea, A; Tolea, M; Dinu, IV

Published: 2012, 14TH INTERNATIONAL CONFERENCE ON TRANSPORT IN INTERACTING DISORDERED SYSTEMS (TIDS-14), 376, DOI: 10.1088/1742-6596/376/1/012019

We study the conductance G and Seebeck coefficient S of a side-coupled double quantum dot system. The transport properties are the result of the competition between the Fano interference and Kondo correlations, being also controlled by the Coulomb blockade of the multilevel side-dot. The external parameters are the gate potential V-g applied on the side-dot and the temperature. When V-g is varied continuously the blockade is switched on and off periodically, resulting in oscillations of the transport coefficients. The profile of the oscillations and the temperature dependence are studied. An extended Anderson model and the Keldysh transport formalism are used.

1815. Zero bias anomalies in the Kondo regime of single and double quantum dots

Authors: Aldea, A; Tolea, M; Dinu, IV

Published: 2012, ADVANCED MANY-BODY AND STATISTICAL METHODS IN MESOSCOPIC SYSTEMS, 338, DOI: 10.1088/1742-6596/338/1/012001

The zero bias anomaly of the differential conductance of mesoscopic systems is a fingerprint of the electron-electron interaction. The common example is the peak of the differential conductance in Kondo mesoscopic systems. We show that in complex mesoscopic systems, in particular in the side-coupled double dot, the dip of the differential conductance at zero bias is also possible due to simultaneous effects of interference and correlations. The external parameters that control this effect are the temperature and the gate potential on the lateral dot. We argue that even in single dots, in a multiple lead configuration, the shift from suppression to enhancement of dI/dV with increasing bias is allowed if the bias applied on the leads is not symmetric. The differential conductance exhibits a peak-dip crossover, the effect being controlled by the strength of the asymmetry and the ratio of the dot-lead couplings. The scaling of the differential conductance for the double-dot system is also discussed. The results are obtained using an extended Anderson model, the Keldysh transport formalism and the equation of motion technique extended to the non-equilibrium.

1816. Biocatalytic microreactor incorporating HRP anchored on micro-/nano-lithographic patterns for flow oxidation of phenols

Authors: Tudorache, M; Mahalu, D; Teodorescu, C; Stan, R; Bala, C; Parvulescu, VI

Published: MAY 2011, JOURNAL OF MOLECULAR CATALYSIS B-ENZYMATIC, 69, 139, DOI: 10.1016/j.molcatb.2011.01.007

A highly durable and versatile micro scale biocatalytic reactor has been designed and investigated in the heterogeneous enzyme-catalytic oxidation of phenols. It consisted of optical or electron beam lithographic gold deposited layer with different thickness from nano- to micro-scale on a semiconductor surface. Horseradish peroxidase (H RP) enzyme was immobilized on the gold-surface using two different approaches (i.e., physical adsorption and self-assembled monolayer). Characterization of those HRP-gold surfaces was made using AFM (atomic force microscopy) coupled with ellipsometry measurements, SEM (scanning electron microscopy), STM (scanning tunneling microscopy) and spectrophotometric technique. The catalytic performances of the developed structures were investigated after their incorporation in microreactors using a recycling-flow system dedicated to phenols oxidation. In order to optimize the efficiency of the oxidation process it was checked the effect of the successively addition of the reagent, the influence of the reaction time, the stability and the reuse of the biocatalytic micro-system. Maximum phenol conversion was of 35.1%. In addition to phenol the system has also been investigated in oxidation of other phenolic compounds such as cathecol, hydroquinone, rezorcine, beta-naphtol, o/p-aminophenol and 4-metoxyphenol. (C) 2011 Elsevier B.V. All rights reserved.

1817. Magneto-optical investigations of rare earth doped sol-gel derived silicate xerogels

Authors: Secu, CE; Polosan, S; Secu, M

Published: AUG 2011, JOURNAL OF LUMINESCENCE, 131, 1752, DOI: 10.1016/j.jlumin.2011.04.031

Rare-earth doped xerogels (Eu3+, Sm3+, Ho3+, Pr3+) were prepared by using the sal-gel method and their magneto-optical and optical properties have been studied. The Magnetic Circular Dichroism (MCD) spectra are quite similar to those recorded in the RE-doped fluorozirconate glasses; the fine structures shown by the MCD spectra are better resolved compared to the optical absorption spectra. The MCD technique has been correlated with optical measurements in order to investigate the site symmetry in the particular case of Eu3+-doped xerogel and oxyfluoride glasses. In the xerogel, coordination symmetry around the Eu3+ ions is close to (D) under bar (3h) and is lower in the oxyfluoride glass. (C) 2011 Elsevier B.V. All rights reserved.

1818. Angle-resolved evanescent-wave cavity ring-down spectroscopy for thin film-solid interface characterization

Authors: Cotirlan, C; Logofatu, C; Rizea, A; Lazarescu, MF

Published: JUL 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 714, DOI:

A new method, that involves Evanescent-Wave Cavity Ring-Down Spectroscopy (EW-CRDS), is presented. This method is useful for the study of thin films on optical solid surfaces. The new design of experimental set-up incorporates a semicylindrical prism with a plane surface where the Total Internal Reflection (TIR) effect appears. The antireflex (AR) coated cylindrical surface of the prism induces the stability of resonant cavity. The evanescent wave generated at the plane surface of the prism probes the absorption by matter in the vicinity of the prism. A general discussion of design criteria is presented to quantify intrinsic losses, and then absorption spectra for Rhodamine chloride R590 from 555 to 560 nm are presented to demonstrate the sensitivity of the system. The layer of R590 on BK7 surfaces is deposited from a solution of R590 in ethanol (92% purity) with 51 mg/l concentration. After vaporization of the ethanol the dye layer on surfaces is supposed to be uniform. This implementation of TIR surface in a resonant cavity provides a powerful new spectroscopic tool especially to angle-resolved diagnostic for interfaces and thin-films. The loss spectrum can be obtained for an angular range from the TIR critical angle to a maximum angle when the resonance of system is lost.

1819. Accurate determination of the spin Hamiltonian parameters for Mn2+ ions in cubic ZnS nanocrystals by multifrequency EPR spectra analysis

Authors: Stefan, M; Nistor, SV; Barascu, JN

Published: JUN 2011, JOURNAL OF MAGNETIC RESONANCE, 210, 209, DOI: 10.1016/j.jmr.2011.03.004

Accurate determination of the spin Hamiltonian (SH) parameters, describing the electron paramagnetic resonance (EPR) spectra of paramagnetic impurity ions in wide band gap semiconductor nanocrystals, is essential for determining their localization and quantum properties. Here we present a procedure, based on publicly available software, for determining with higher accuracy the SH parameters of isolated Mn2+ impurity ions in small cubic ZnS nanocrystals. The procedure, which can be applied to other cubic II-VI semiconductor nanocrystals as well, is based on the analysis of both low and high frequency EPR spectra with line shape simulation and fitting computing programs, which include the hyperfine forbidden transitions and line broadening effects. The difficulties, limitations and errors which can affect the accuracy in determining some of the SH parameters are also discussed. (C) 2011 Elsevier Inc. All rights reserved.

1820. Substitutional and surface Mn2+ centers in cubic ZnS:Mn nanocrystals. A correlated EPR and photoluminescence study

Authors: Stefan, M; Nistor, SV; Ghica, D; Mateescu, CD; Nikl, M; Kucerkova, R

Published: JAN 20 2011, PHYSICAL REVIEW B, 83, DOI: 10.1103/PhysRevB.83.045301

The EPR, radioluminescence, and photoluminescence of cubic ZnS (cZnS) nanocrystals (NCs) with a narrow size distribution centered at 2 nm, doped with 0.1, 0.2, and 0.5 at.% Mn2+ ions were investigated. Besides the main lines from substitutional Mn2+ ions localized in the core of the NCs next to a stacking defect, the EPR spectra exhibited two broader hyperfine sextets, attributed to the so-called Mn(II)and Mn(III) surface centers, which could be separated by adequate thermal treatments. The contribution to the photoluminescence from the Mn2+ ions at various sites was further determined from the analysis of the steady-state and time-resolved photoluminescence data from cZnS: Mn NCs subjected to thermal treatments and from cZnS: Mn single crystals. Thus, the main emission consisting of two intense overlapping bands peaking at 596 and 630 nm was attributed to the T-4(1)-(6)A(1) transition of the substitutional Mn2+ ions in the core of the cZnS nanocrystals and to residual aggregated Mn2+ ions, respectively, the last ones being responsible for a broad EPR line observed in the X-band spectrum. The Mn(II) and Mn(III) centers, consisting of Mn2+ ions in the oxidized and hydrolyzed surface layer of the NCs, respectively, are only indirectly involved in the energy transfer to the substitutional Mn2+ centers, very likely through pairs interaction.

1821. Structural characterization and photoluminescence of nanocrystalline Ho-doped BaTiO3 derived from sol-gel method

Authors: Secu, M; Cernea, M; Secu, CE; Vasile, BS

Published: AUG 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 3128, DOI: 10.1007/s11051-011-0224-3

Nanocrystalline Ho-doped BaTiO3, with average nanocrystals size of 20 nm, have been prepared using a sol-gel combustion technique. The structural and morphological properties of the powders have been investigated by X-ray powder diffraction and high resolution transmission electron microscopy. Chemical states of the holmium on the Ba0.97Ho0.03TiO3 ceramic surface were analyzed using X-ray photoelectron spectroscopy. Furthermore, their photoluminescence properties were analyzed.

1822. Carbon layers cleaning from inside of narrow gaps by a RF glow discharge

Authors: Stancu, C; Teodorescu, M; Galca, AC; Dinescu, G

Published: JUL 25 2011, SURFACE & COATINGS TECHNOLOGY, 205, S438, DOI: 10.1016/j.surfcoat.2011.03.090

The paper focuses on the utilization of radiofrequency discharges at intermediate pressures for plasma removal of carbon residuals or layers from narrow gaps and channels. It is shown that by proper handling of the discharge power and pressure it is possible to control the development of plasma inside narrow gaps, in the proximity of surfaces to be cleaned. The discharge operation inside gaps having the width in the range 0.6-2 mm was demonstrated. The cleaning effectiveness is exemplified for castellated surfaces having rectangular gaps coated with hydrogenated amorphous carbon layers. Cleaning of large surfaces can be approached with a movable "plasma shower" type device. (C) 2011 Elsevier B.V. All rights reserved.

1823. Influence of Al doping agents nature on the physical properties of Al:ZnO films deposited by spin-coating technique

Authors: Ghomrani, FZ; Iftimie, S; Gabouze, N; Serier, A; Socol, M; Stanculescu, A; Sanchez, F; Antohe, S; Girtan, M

Published: MAR 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 251, DOI:

In this paper we present the morphological, structural, optical and electrical properties of aluminium doped zinc oxide films prepared by spin coating technique from a zinc acetate dihydrate and 2-methoxyethanol (0.5M) solution. AlCl3 and Al(NO3)(3) were used as doping agents in different concentrations (1at%, 4at% and 6at% in starting solution). After deposition, films were dried at 100 degrees C and then annealed at temperatures between 400 degrees C and 500 degrees C. The characterization of deposited layer was performed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and UV-Vis spectroscopy. The results show that the optical and electrical properties of the structures strongly depend on the deposition conditions of ZnO:Al. In addition, the resistivity can be easily varied depending on ZnO:Al annealing temperatures and Al concentration.

1824. Coulomb oscillations in the Fano-Kondo effect and zero-bias anomalies in a double-dot mesotransistor

Authors: Aldea, A; Tolea, M; Dinu, IV

Published: JUN 27 2011, PHYSICAL REVIEW B, 83, DOI: 10.1103/PhysRevB.83.245317

We investigate theoretically the transport properties of the side-coupled double quantum dots in connection with the experimental study of Sasaki et al. [Phys. Rev. Lett. 103, 266806 (2009)]. The setup consists of connecting the Kondo dot directly to the leads, while the side dot provides an interference path which affects the Kondo correlations. We analyze the oscillations of the source-drain current due to the periodical Coulomb blockade of the many-level side dot at the variation of the gate potential applied on it. The Fano profile of these oscillations may be controlled by the interdot coupling, level spacing of the side dot, and also by the temperature. The nonequilibrium conductance of the double-dot system exhibits zero-bias anomaly which, besides the usual enhancement, may show also a suppression (a diplike aspect) which occurs around the Fano zero. In the same region, the weak temperature dependence of the conductance indicates the suppression of the Kondo effect. Scaling properties of the nonequilibrium conductance in the Fano-Kondo regime are discussed. Since the Kondo temperature of the single-impurity Anderson model is no longer the proper scaling parameter, we look for an alternative specific to the double dot. The extended Anderson model, Keldysh formalism, and equation-of-motion technique are used.

1825. PRODUCTION AND CHARACTERIZATION OF CdTe WIRE ARRAYS FOR HYBRID INORGANIC/ORGANIC PHOTOVOLTAIC CELLS

Authors: Florica, C; Arghir, I; Ion, L; Enculescu, I; Antohe, VA; Radu, A; Radu, M; Chisulescu, G; Dina, N; Antohe, S

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 27, DOI:

A new approach for obtaining hybrid inorganic/organic photovoltaic structures, based on CdTe nanowires and organic dye films is reported. The wire arrays of CdTe (10(6) wires/cm(2)) were electrochemically grown using a template method. Ion track polycarbonate foils (30 micrometer thick) were used as templates and the growth conditions for obtaining good quality and stoichiometric CdTe nanowires were identified. After dissolving the polycarbonate template, a CdTe thin film (300 nm) has been deposited by thermal vacuum evaporation onto the wire array before the deposition of ZnPc film as organic absorber. Finally a ZnO thin film was deposited by Electron Pulsed Deposition on ZnPc, working as TCO top electrode. The structural, morphological, electrical and optical properties of each component layer are investigated. Typical parameters of the prepared photovoltaic structures are determined. The external quantum efficiency of the Au/wire array CdTe/CdTe(300 nm)/ZnPc/ZnO structures was significantly increased, with respect to that of Au/wire arrays CdTe/ZnPc/ZnO structures.

1826. Recent Progress in Synthesis, Vibrational Characterization and Applications Trend of Conjugated Polymers/Carbon Nanotubes Composites

Authors: Baibarac, M; Baltog, I; Lefrant, S

Published: APR 2011, CURRENT ORGANIC CHEMISTRY, 15, 1196, DOI: 10.2174/138527211795203022

This review deals with recent progress on the development of composite materials based on cojugated polymers (CPs) and carbon nanotubes (CNTs), both from fundamental and applied point of view. In the first part of the manuscript, we present the different types of composites, the new protocols used in their synthesis as well as their vibrational properties reported in the last five years. A brief review of the contribution of Raman light scattering and FTIR spectroscopy to establish the type of interaction between the two constituents is discussed for different cases, i.e. bi-layers of polymers and carbon nanotubes, CPs doped with CNTs and CNTs functionalized with CPs. Recently, anti-Stokes resonant Raman studies have appeared as fruithful tools in the evaluation of functionalization process of CNTs with CPs. The review provides also information on CPs/CNTs composite properties specific to applications in the field of energy storage, optical limiting and electron field emission devices, transistors, conducting textiles, sensors, rewritable devices, biomedical and food domains as well as how these materials have been optimized to generate exploitable properties.

1827. LUMINESCENCE OF EUROPIUM IN ARSENIC SULPHIDE MATRIX

Authors: Popescu, M; Lorinczi, A; Velea, A; Simandan, ID; Sava, F; Pavelescu, G; Niciu, GH; Niciu, DO; Mihailescu, IN; Socol, G; Stefan, N

Published: NOV 2011, CHALCOGENIDE LETTERS, 8, 702, DOI:

Thin films of arsenic sulphide have been obtained by Pulsed Laser Deposition from bulk As(2)S(3). A very thin layer of Eu(2)O(3) was deposited by PLD from a different target in the next deposition process. After a heat treatment at 180 degrees C for 45 minutes in inert atmosphere a structural transformation of the amorphous As(2)S(3) to realgar (As(2)S(2)) occurred and the film develops a strong luminescence effect.

1828. Study of flame development in 12% methane-air mixture ignited by laser

Authors: Salamu, G; Sandu, O; Voicu, F; Dejanu, M; Popa, D; Parlac, S; Ticos, C; Pavel, N; Dascalu, T

Published: NOV 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 1169, DOI:

A comparative study of ignition realized by a classical spark plug and by a Nd:YAG laser in 12% methane-air mixture was performed. Various parameters of the ignition, such as the peak pressure, the pressure building time, or the speed propagation of the flame front were recorded at various initial filling pressure of the combustion chamber, or function of the laser pulse energy. Advantages of ignition by laser in comparison with classical ignition by an electrical spark plug are discussed.

1829. Sensitizer localization and immune response in photodynamic therapy of B16 cells

Authors: Pop, SF; Ion, RM; Neagu, M; Constantin, C

Published: MAR 2011, LASER PHYSICS, 21, 581, DOI: 10.1134/S1054660X11050239

This paper proposes to extend the exploration of mouse melanoma B16 cells death by photodynamic therapy (PDT), under irradiation with different light sources and in the presence of 5,10,15,20-tetrap-sulphonato-phenyl-porphyrin (TSPP). The viability studies showed that B16 mouse melanoma is sensitive to photodynamic damage induced by TSPP 1 mM for either one, two, three or four hours. The control had TSPP added immediately prior to timelapse imaging (no incubation). They were then irradiated with red light He-Ne laser (lambda = 632.8 nm, energy 180 J/cm(2) for 20 min). Also, it has been used a laser diode GaInAs 25 mW/cm(2), lambda = 650 nm. The cells demonstrated clear morphological changes associated with apoptosis by mitochondrial pathway. There were changes in texture, as expected. Changes appeared to occur more quickly at lamp irradiation than at HeNe and GaInAs diode laser. Addition of TSPP just prior to exposure and observation, with no incubation, did not result in changes in cell morphology or cell death. Also, the proteins changes have been observed, because those with high molecular weights have been scissored under irradiation and this could be reason of the proteins concentrating in the area of low molecular weights, and the dissapearing of the proteic band of 75 kDa in the electrophoregramm. The immunized animals with B16-TSPP had the highest survival rate (40 days) by comparison with the control (death at 20 days) or with immunized animals with supernatants B16 (death at 25 days).

1830. Nonadiabatic generation of a pure spin current in a one-dimensional quantum ring with spin-orbit interaction

Authors: Nita, M; Marinescu, DC; Manolescu, A; Gudmundsson, V

Published: APR 18 2011, PHYSICAL REVIEW B, 83, DOI: 10.1103/PhysRevB.83.155427

We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a nonadiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal phase difference phi. The solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and they are used to calculate the time-dependent charge and spin currents. We find that there are critical values of phi at which the charge current disappears, while the spin current reaches a maximum or a minimum value.

1831. The effects of thermal treatment on the physical properties of Sr2FeMo1-xMxO6 perovskite with M = W, Ta and x <= 0.3

Authors: Burzo, E; Balasz, I; Valeanu, M; Pop, IG

Published: JAN 5 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 113, DOI: 10.1016/j.jallcom.2010.08.126

The Sr2FeMo1-xMxO6 double perovskites with M = W and Ta and x <= 0.3, were obtained by sintering at 1300 degrees C. during 4 and 8 h, respectively. The perovskites crystallize in a tetragonal structure having 14/mmm space group. The grains are more homogeneous when sintering time is increased. The samples sintered longer time show higher values of saturation magnetizations, resistivities and magnetoresistivities than the samples sintered during 4 h. The intergrain tunnelling magnetoresistance as well as the intragrain contributions, respectively were analysed as function of temperature and external field. The changes in the physical properties, when the sintering time is increased, have been correlated with the number of antisite defects as well as the nature of grain boundaries. (C) 2010 Elsevier B.V. All rights reserved.

1832. EFFECT OF TEMPERATURE ON THE MAGNETIC PROPERTIES OF CERAMIC MAGNETIC MATERIALS USED FOR TEMPERATURE TRANSDUCERS

Authors: Miclea, C; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; Plavitu, C; Spanulescu, I; Mihailescu, M

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 272, DOI:

Three ceramic magnetic compositions within the CuZnTi ferrite system, having the Curie temperatures centered around 60 degrees C, 80 degrees C and 100 degrees C, respectively were investigated in order to determine the time-temperature stability of their main magnetic properties. Rates of changes of 33, 66 and 100 ppm/h of the maximum slopes of permeability were found for the samples aged at 60 degrees C, 80 degrees C and 100 degrees C, respectively. The samples aged at temperatures higher than 200 degrees C show a rather sudden decrease of the maximum slope of permeability, but no shift of the Curie temperature and the working point, corresponding to the temperature where the slope has the maximum value. The results are discussed in terms of the migration processes of the cations, especially Cu2+, from metastable positions on which they were frozen during the rapid cooling of the samples from the sintering temperature, to the more stable ones, namely the octahedral sites into the spinel lattice.

1833. ELECTRICAL FIELD INDUCED PROPERTIES OF NEMATIC LIQUID CRYSTAL/COPOLYMER PARTICLES COMPOSITE

Authors: Manaila-Maximean, D; Rosu, C; Danila, O; Donescu, D; Ghiurea, M; Cotorobai, F

Published: 2011, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 73, 200, DOI:

Particles of the type divinylbenzene - maleic anhydride alternated copolymers have been synthesized. Their dimensions were determined by electron microscopy and are in the range 1-2 mu m. These particles were mixed by stirring and ultrasound with nematic liquid crystals ZLI 1221(Merck), in a concentration of 5% wt. (polymer/LC) and filled in conventional sandwich cells formed by ITO covered glass. Current-voltage characteristics and switching tunes have been studied.

1834. DIRECT OPTICAL ABSORPTION MEASUREMENTS IN GASEOUS MEDIA BY THE CAVITY RING-DOWN SPECTROSCOPY TECHNIQUE FOR THE DEVELOPMENT OF A LOSSMETER

Authors: Cotirlan-Simioniuc, C; Logofatu, C; Lazarescu, MF

Published: 2011, ROMANIAN REPORTS IN PHYSICS, 63, 1082, DOI:

1835. SENSOR OF NITROGEN DIOXIDE BASED ON SINGLE WALL CARBON NANOTUBES AND MANGANESE-PORPHYRIN

Authors: Popescu, M; Simandan, ID; Sava, F; Velea, A; Fagadar-Cosma, E

Published: JUL-SEP 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 1256, DOI:

New sensors based on single wall carbon nanotubes (SWCNTs) and porphyrins have been tested for sensitivity to NO(2) gas. SWCNTs embedded in barium stearate multilayers were deposited with the help of Langmuir-Blodgett technique. It was demonstrated a sensitive effect of the sensor for NO(2) gas. The coverage of the sensor with metalloporphyrin (Mn) leads to strong enhancing of the sensitive effect to NO(2), besides, the selectivity was preserved both around room temperature and at larger operating temperature (up to 200 degrees C). No sensitivity to CO and CH(4) was evidenced. The NO(2) sensitivity strongly increased at 100 degrees C but at high operation temperatures (150-200 degrees C) a different behaviour is observed, probably due to the structural change of porphyrin or porphyrin-SWCNT interaction. The reversibility of the sensor resistivity is reasonably good at the optimum operating temperature (100 degrees C).

1836. Optical properties of phase change memory Ge1Sb2Te4 glasses

Authors: Iovu, MS; Colomeico, EP; Benea, VG; Popescu, M; Lorinczi, A; Velea, A

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1486, DOI:

Phase change memory materials are promising for the next-generation of non-volatile flash memory that will serve in new mobile computing, entertainment and other handheld electronics. Among them are chalcogenide glasses Ge-Sb-Te (GST) which can exist in two separates structural states - amorphous and cristalline. Switching of the material from one to another state can be done by heating applying an electrical pulse or by exposure to intense laser beam. We report the changes of optical parameters of amorphous Ge1Sb2Te4 films under heat treatment and light exposure.

1837. Polydiphenylamine/carbon nanotube composites for applications in rechargeable lithium batteries

Authors: Baibarac, M; Baltog, I; Lefrant, S; Gomez-Romero, P

Published: FEB 15 2011, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 176, 120, DOI: 10.1016/j.mseb.2010.10.008

Polydiphenylamine/single walled carbon nanotube (PDPA/SWNT) composites were synthesized electrochemically aiming at their application as active electrode materials for rechargeable lithium batteries. The electrochemical polymerization of diphenylamine (DPA) on a SWNT film immersed in a 1 M HCl solution was studied by cyclic voltammetry. Comparing cyclic voltammograms recorded on a blank Pt electrode with those obtained for a SWNT film deposited on Pt electrode one observes in the latter case a decrease of the DPA reduction potential. To elucidate electrochemical polymerization mechanism, photoluminescence studies on DPA/SWNT and PDPA/SWNT systems were carried out. Additional information concerning the functionalization process of SWNT with PDPA was obtained by Raman and IR spectroscopy. Using the PDPA/SWNT composite as active material for the positive electrode of a rechargeable lithium cell (LiPF(6) electrolyte), the charge-discharge tests show a specific discharge capacity of ca. 245 mA h g(-1), much higher than the 35 mA h g(-1) for pure PDPA. (C) 2010 Elsevier B.V. All rights reserved.

1838. Investigations of Electrical and Electro-Optical Properties of Liquid Crystal/Copolymer-Clay Nanostructured Systems

Authors: Manaila Maximean, D; Rosu, C; Frunza, L; Ganea, P; Donescu, D; Ghiurea, M

Published: 2011, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 546, 155, DOI: 10.1080/15421406.2011.571946

We obtained a new system containing nematic liquid crystal doped with nanostructured copolymer-clay particles. The clay (Cloisite-type) was modified by copolymerization of maleic anhydride and divinyl benzene and the nanocomposite has intercalated structure. Current-voltage characteristics of the liquid crystal/copolymer-clay systems were analyzed and the electro-optical response at heating -cooling cycles for different applied electric fields is discussed. Dielectric spectroscopy measurements in the low frequency domain have shown different regimes of its temperature dependence as function of the sample nature and the applied voltage. Comparison is made with the bulk liquid crystal. Changes of the phase transition temperature are thus revealed.

1839. Improved Critical Current Densities in YBa2Cu3O7-delta Multilayer Films Interspaced with Palladium Nano-dots

Authors: Sarkar, A; Mikheenko, P; Dang, VS; Kechik, MMA; Abell, JS; Crisan, A

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 177, DOI: 10.1007/s10948-010-0914-6

Power applications of superconducting coated conductors in high magnetic fields require thick films with high critical current density J (c) and strong artificial pinning centers. Here, we report on the artificial pinning centers induced in YBCO quasi-multilayer films interspaced with palladium (Pd) nano-dots. Quasi-multilayered (QM) YBa2Cu3O7-delta (YBCO) films composed of YBCO layers interspaced with quasi-layers of palladium nano-dots were grown by pulsed laser deposition on SrTiO3(100) substrates. DC magnetization and frequency-dependent measurements showed high J (c) comparable with best YBCO films in thin quasi-multilayers and significant improvement of J (c) in thick quasi-multilayers. TEM study shows regions of planar defects, stacking faults, and pore formations suitable for immobilizing vortices. These defects significantly contribute to the pinning of magnetic flux and increase critical current in the films.

1840. Structural investigations of Ge nanoparticles embedded in an amorphous SiO2 matrix

Authors: Stavarache, I; Lepadatu, AM; Gheorghe, NG; Costescu, RM; Stan, GE; Marcov, D; Slav, A; Iordache, G; Stoica, TF; Iancu, V; Teodorescu, VS; Teodorescu, CM; Ciurea, ML

Published: JAN 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 232, DOI: 10.1007/s11051-010-0021-4

Transmission electron microscopy and X-ray photoelectron spectroscopy analyses are performed to investigate Ge nanoparticles embedded in an amorphous SiO2 matrix. GeSiO thin films are prepared by two methods, sol-gel and radio frequency magnetron sputtering. After the deposition, the sol-gel films are annealed in either N-2 (at 1 atm and 800 A degrees C) or H-2 (at 2 atm and 500 A degrees C), and the sputtered films in H-2 (at 2 atm and 500 A degrees C), to allow Ge segregation. Amorphous Ge-rich nanoparticles (3-7 nm size) are observed in sol-gel films. Crystalline Ge nanoparticles in the high pressure tetragonal phase (10-50 nm size) are identified in the sputtered films. The size of the nanoparticles increases with Ge concentration in the volume of the film. At the film surface, the Ge concentration is much larger that in the volume for both sol-gel and sputtered films. At the same time, at the film surface, only oxidized Ge is observed.

1841. Studies Concerning the Microhardness of Sintered Carbon Steels Obtained from Fe and Fe3C Nanopowders

Authors: Ciobanu, M; Nicolicescu, C; Bejan, S; Batin, G; Mercioniu, I

Published: 2011, RESEARCHES IN POWDER METALLURGY, 672, +, DOI: 10.4028/www.scientific.net/MSF.672.223

Replacing the graphite with carbides in the mixture with Fe powder may be an alternative technological process, by the fact that as carbides decompose when heated, the carbon is set free and diffuses into the Fe network ensuring chemical and structural homogeneity corresponding to sintered steels. Using cementite nanopowder mix with Fe powder is to ensure a better compaction by pressing, less time to decompose and C diffusion into the Fe network in a remarkably chemical homogeneity. The obtaining procedure for Fe3C consists in direct carburation of Fe powder in a special chamber.

1842. Eu3+-doped CaF2 nanocrystals in sol-gel derived glass-ceramics

Authors: Secu, M; Secu, CE; Ghica, C

Published: FEB 2011, OPTICAL MATERIALS, 33, 617, DOI: 10.1016/j.optmat.2010.11.016

Glass-ceramics containing Eu3+-doped CaF2 nanocrystals of about 16 nm size have been made using the controlled crystallization at higher temperatures of the Eu3+-doped CaF2-SiO2 xerogels. In the glass-ceramic material the Eu3+ ions are embedded in both silica network and in the non-centrosymmetric sites of the CaF2 nanocrystals structure. Lower phonon energy of CaF2 and the dehydratation processes reduce the probability of non-radiative de-excitations and as a result a luminescence enhancement and an increase of the PL lifetime is observed. Eu-doping modifies the traps distribution within the glass-ceramics and as a result an additional broad thermoluminescence peak at about 380 degrees C was observed. The peak was assigned to the recombination of the electrons thermal released from the Eu3+-related traps in the glass matrix and in the CaF2 nanocrystals. (C) 2010 Elsevier B.V. All rights reserved.

1843. Triple Band Resonant Antenna based on Composite Right-/Left-Handed Metamaterial Transmission Line

Authors: Ochetan, AB; Banciu, MG; Lojewski, G; Ramer, R

Published: 2011, ASIA-PACIFIC MICROWAVE CONFERENCE 2011, 645, DOI:

By taking advantage of the unique and unusual properties of the recent composite right-/left-handed metamaterial transmission line, we have designed a small-sized resonant antenna that can operate in three different frequency bands. The antenna is well matched to the outer network by the use of a compact matching circuit and the resulting radiation characteristics make it suitable for short-range wireless communication systems.

1844. Hybrid organic-inorganic materials based on poly(o-phenylenediamine) and polyoxometallate functionalized carbon nanotubes

Authors: Baibarac, M; Baltog, I; Smaranda, I; Scocioreanu, M; Lefrant, S

Published: JAN 31 2011, JOURNAL OF MOLECULAR STRUCTURE, 985, 218, DOI: 10.1016/j.molstruc.2010.10.044

The chemical polymerization of o-phenylenediamine (OPD) on single-walled carbon nanotubes (SWCNTs) in the presence of phosphomolybdic acid (H3PMo12O40 xH(2)O) has been studied by surface enhanced resonant Raman scattering (SERRS) spectroscopy. One demonstrates that an organic-inorganic hybrid composite of the type poly(o-phenylenediamine)/polyoxometallate-functionalized SWCNTs is produced by the chemical interaction between polyoxometallate-functionalized SWCNTs and poly(o-phenylenediamine) (POPD) doped with [H2PMo12O40](-) ions. According to TEM investigations, a result of the chemical interaction of SWCNT with H3PMo12O40 xH(2)O is the formation into the composite mass of tube fragments of shorter length, which behave like closed shell fullerenes since Raman fingerprint is given by lines situated at 240-275 and 1450-1472 cm(-1). The chemical polymerization of OPD on SWCNTs achieved in the absence of H3PMo12O40 xH(2)O leads to a covalent functionalization of the wall side of the tubes, which is revealed in Raman spectra, recorded at the excitation wavelength of 514 nm, by an enhancement of the lines associated with the tangential vibrational modes of SWCNTs. Using FTIR spectroscopy, significant hindrance steric effects are evidenced in the POPD/polyoxometallate-functionalized SWCNT composite. (c) 2010 Elsevier B.V. All rights reserved.

1845. Synthesis and characterization of indium oxide-hematite magnetic ceramic solid solution

Authors: Sorescu, M; Xu, TH; Diamandescu, L; Hileman, D

Published: JUL 2011, HYPERFINE INTERACTIONS, 199, 386, DOI: 10.1007/s10751-011-0267-y

Indium oxide-doped hematite xIn(2)O(3*) (1 - x) alpha-Fe2O3 (molar concentration x = 0.1-0.7) solid solutions were synthesized using mechanochemical activation by ball milling. XRD patterns yield the dependence of lattice parameters and grain size as function of milling time. After 12 h of milling, the completion of In3+ substitution of Fe3+ in hematite lattice occurs for x = 0.1. For x = 0.3, 0.5 and 0.7, the substitutions between In3+ and Fe3+ into hematite and respectively, In2O3 lattices occur simultaneously. The lattice parameters of alpha-Fe2O3 (a and c) and In2O3 (a) vary with milling time. For x = 0.1, Mossbauer spectra were fitted with one, two, or three sextets versus milling time, corresponding to gradual substitution of In3+ for Fe3+ in hematite lattice. For x = 0.3, Mossbauer spectra after milling were fitted with three sextets and two quadrupole-split doublets, representing In3+ substitution of Fe3+ in hematite lattice and Fe3+ substitution of In3+ in two different sites of In2O3 lattice. For x = 0.5 and 0.7, Mossbauer spectra fitting required two sextets and one quadrupole-split doublet, representing coexistence of In3+ substitution of Fe3+ in hematite lattice and Fe3+ substitution of In3+ in indium oxide lattice. The recoilless fraction studied versus milling time for each molar concentration exhibited low values, consistent with the occurrence of nanoparticles in the system. SEM/EDS measurements revealed that the mechanochemical activation by ball milling produced xIn(2)O(3*)(1 - x)alpha-Fe2O3 solid solution system with a wide range of particle size distribution, from nanometer to micrometer, but with a uniform distribution of Fe, In, and O elements.

1846. Composite right/left-handed metamaterial resonant antennas

Authors: Ochetan, AB; Banciu, MG; Lojewski, G

Published: SEP-OCT 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1347, DOI:

By taking advantage of the unique and unusual properties of the recent composite right/left-handed metamaterial transmission line, we have designed a shunt mode resonant antenna with a multi-band operation, and a series mode zero order resonant antenna, which is frequency independent. The antennas are well matched to the external network by using compact matching circuits. The resulting radiation characteristics make these antennas suitable for short-range wireless communications systems.

1847. Electronic and field emission properties of two-dimensional nanotori

Authors: Filip, MR; Filip, LD

Published: MAR 2011, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B, 29, DOI: 10.1116/1.3531935

The electronic properties of two-dimensional toroidal surfaces of nanometer size have been investigated by approximately solving the time-independent Schrodinger equation. The effects of the quantum confinement on the electron population of these structures were shown by studying the average electron density on the surface of the torus. The unique electron spread that resulted from such computations encouraged further study on the field emission properties of this two-dimensional manifold. The Wentzel-Kramers-Brillouin approximate approach was used for a preliminary study of the field emission properties of the nanotori for various geometrical parameters. (c) 2011 American Vacuum Society. [DOI: 10.1116/1.3531935]

1848. Preparation of graphene and its application in dye-sensitized solar cells

Authors: Sima, M; Enculescu, I; Sima, A

Published: MAR 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 418, DOI:

Graphene sheets were prepared using electrochemical and chemical steps followed graphite electrochemical oxidation, graphite chemical oxidation, ultrasound expholiation and chemical reduction of carbon material. Films of graphene were electrophoretically deposited from aqueous dispersion on FTO electrode. These films were tested as cathode for a dye-sensitized solar cell. The morphology of the prepared products was imaged by scanning electron microscopy; the intermediate compound, graphene oxide was characterized by IR spectroscopy.

1849. PREPARATION AND ELECTRICAL CHARACTERIZATION OF SiGe NANOSTRUCTURES

Authors: Stavarache, I; Lepadatu, AM; Pasuk, I; Teodorescu, VS; Ciurea, ML

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 52, DOI:

This paper presents the preparation and investigation of structure and electrical properties of nanostructures consisting of Si1-xGex nanocrystals. Nanostructures were prepared by RF magnetron sputtering, followed by thermal annealing. X-ray diffraction, TEM, high resolution TEM and SAED measurements were performed. Current-voltage and current-temperature characteristics were taken. Nanostructures have different electrical behavior. Current-voltage curves are linear, while current-temperature curves are dependent on the annealing temperature. In films annealed at 650 degrees C, electrical transport is controlled by quantum confinement effect and localized states (current-temperature characteristics), while in films annealed at 900 degrees C it is controlled by tunneling of thermally activated carriers between neighboring nanocrystals.

1850. Effect of aqueous comonomer solubility on the surfactant-free emulsion copolymerization of methyl methacrylate

Authors: Preda, N; Matei, E; Enculescu, M; Rusen, E; Mocanu, A; Marculescu, B; Enculescu, I

Published: JAN 2011, JOURNAL OF POLYMER RESEARCH, 18, 30, DOI: 10.1007/s10965-009-9387-3

Surfactant-free emulsion copolymerization was used to prepare methyl methacrylate-hydroxyethyl methacrylate (MMA-HEA) and methyl methacrylate-hydroxypropyl methacrylate (MMA-HPMA) latex particles. Also, glycidyl methacrylate (GMA) was grafted onto the surface of the preformed MMA-HPMA latex particles by seeded surfactant-free emulsion copolymerization. The copolymerization reactions were conducted at 75 A degrees C using a water-soluble initiator, potassium persulfate (KPS). The morphologies of copolymer latex particles were observed using Scanning electron microscopy (SEM). The influence of different reactions parameters (the MMA saturation concentration (Sr), the KPS concentration and the aqueous solubility of the comonomers (HEA or HPMA)) on the particles average diameter and particles size dispersity was investigated. The experimental results showed that the increase of initiator concentration induces in all investigated cases the increase of particles average diameter, while the presence of HEA or HPMA as comonomers in the copolymerization reaction of MMA (1,000% Sr) lead to a decrease of particles average diameter. At small KPS concentration the latex is monodisperse, the increase of the initiator concentration leading to the formation of polydisperse latex. In the case of grafting reaction of GMA onto the monodisperse preformed MMA-HEA latex particles, although the average diameter of the final particles doubles the latex remains quasi-monodisperse.

1851. Heteronuclear (Co-Ca, Co-Ba) 2,3-pyridinedicarboxylate complexes: synthesis, structure and physico-chemical properties

Authors: Lazarescu, A; Shova, S; Bartolome, J; Alonso, P; Arauzo, A; Balu, AM; Simonov, YA; Gdaniec, M; Turta, C; Filoti, G; Luque, R

Published: 2011, DALTON TRANSACTIONS, 40, 471, DOI: 10.1039/c0dt00858c

Three pyridine 2,3-dicarboxylate complexes have been synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffractometry. Their magnetic properties have also been studied by EPR and magnetisation measurements. The decomposition of such complexes in air leads to the generation of mixed metal oxides, as confirmed by powder X-ray diffraction.

1852. Eu3+ LUMINESCENCE IN As2S3 DOT NETWORK

Authors: Georgescu, S; Popescu, M; Sava, F; Velea, A; Pavelescu, G

Published: DEC 2011, CHALCOGENIDE LETTERS, 8, 738, DOI:

Thin films of As2S3 doped with Eu3+ were prepared by vacuum evaporation. It was measured the fluorescence spectra before and after a heat treatment at 180 degrees C for 45 minutes in inert atmosphere. After the heat treatment the transitions D-5(1) -> F-7(1), D-5(0) -> F-7(1) and D-5(0) -> F-7(2) were evidenced in the luminescence spectrum.

1853. One-dimensional composites based on single walled carbon nanotubes and poly(o-phenylenediamine)

Authors: Baibarac, M; Baltog, I; Scocioreanu, M; Ballesteros, B; Mevellec, JY; Lefrant, S

Published: NOV-DEC 2011, SYNTHETIC METALS, 161, 2354, DOI: 10.1016/j.synthmet.2011.09.001

The direct mixing of aqueous ferric chloride and o-phenylenediamine (OPD) solution at room temperature in the absence and presence of carbon nanotubes (CNTs) has been used to prepare poly(o-phenylenediamine) (POPD) micro-fibers and composites of the type CNTs/POPD having nanotubes incorporated in polymer fiber mass. Using surface enhanced infrared absorption (SEIRA) spectroscopy significant modifications in the low frequency range of the polymer spectrum are revealed when Au is used as metallic support. Similar variations are reported for the POPD samples prepared by the electropolymerization of OPD onto rough Au electrode. A covalent functionalization of CNTs with POPD and a doping process of POPD with radical anions of CNTs is proved by surface enhanced resonant Raman scattering and SEIRA spectroscopy. The X-ray diffraction (XRD) studies indicate a high crystallinity both for POPD and CNTs/POPD composites prepared by chemical or electrochemical methods. (C) 2011 Elsevier B.V. All rights reserved.

1854. Successful Cleaning and Study of Contamination of Si(001) in Ultrahigh Vacuum

Authors: Gheorghe, NG; Lungu, GA; Husanu, MA; Costescu, RM

Published: 2011, PHYSICS CONFERENCE (TIM-10), 1387, DOI: 10.1063/1.3647078

This paper presents the very first surface physics experiment performed in ultrahigh vacuum (UHV) in Romania, using a new molecular beam epitaxy (MBE) installation. Cleaning of a Si(001) wafer was achieved by using a very simple technique: sequences of annealing at 900-1000 degrees C in ultrahigh vacuum: low 10(-8) mbar, with a base pressure of 1.5 x 10(-10) mbar. The preparation procedure is quite reproducible and allows repeated cleaning of the Si(001) after contamination in ultrahigh vacuum. The Si(001) single crystal surface is characterized by low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED), and Auger electron spectroscopy (AES). The latter technique is utilized in order to investigate the sample contamination by the residual gas in the UHV chamber, as determined by a residual gas analyzer (RGA). Unambiguous assignment of oxidized and unoxidized silicon is provided; also, an important feature is that the LVV Auger peak at 90-92 eV cannot be solely attributed to clean Si (i.e. Si surrounded only by Si), but also to silicon atoms bounded with carbon. Even with a sum of partial pressures of oxygen and carbon containing molecules in the range of 5 x 10(-10) mbar, the sample is contaminated very quickly, having a (1/e) lifetime of about 76 minutes.

1855. Fe/Si(001) Ferromagnetic Layers: Reactivity, Local Atomic Structure and Magnetism

Authors: Lungu, GA; Costescu, RM; Anu, MAH; Gheorghe, NG

Published: 2011, PHYSICS CONFERENCE (TIM-10), 1387, DOI: 10.1063/1.3647075

Ultrathin ferromagnetic Fe layers on Si(001) have recently been synthesized using the molecular beam epitaxy (MBE) technique, and their structural and magnetic properties, as well as their interface reactivity have been investigated. The study was undertaken as function of the amount of Fe deposited and of substrate temperature. The interface reactivity was characterized by Auger electron spectroscopy (AES). The surface structure was characterized by low-energy electron diffraction (LEED). The magnetism was investigated by magneto-optical Kerr effect (MOKE). A higher deposition temperature stabilizes a better surface ordering, but it also enhances Fe and Si interdiffusion and it therefore decreases the magnetism. Despite the rapid disappearance of the long range order with Fe deposition at room temperature, the material exhibits a significant uniaxial in-plane magnetic anisotropy. For the Fe deposition performed at high temperature (500 degrees C), a weak ferromagnetism is still observed, with saturation magnetization of about 10 % of the value obtained previously. MOKE studies allowed inferring the main properties of the distinct formed layers.

1856. Surface versus volume effects in luminescent ceria nanocrystals synthesized by an oil-in-water microemulsion method

Authors: Tiseanu, C; Parvulescu, VI; Boutonnet, M; Cojocaru, B; Primus, PA; Teodorescu, CM; Solans, C; Dominguez, MS

Published: 2011, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 13, 17145, DOI: 10.1039/c1cp21135h

Pure and europium (Eu3+) doped cerium dioxide (CeO2) nanocrystals have been synthesized by a novel oil-in-water microemulsion reaction method under soft conditions. In-situ X-ray diffraction and RAMAN spectroscopy, high-resolution transmission electron microscopy, UV/Vis diffuse-reflectance and Fourier transform infrared spectroscopy as well as time-resolved photoluminescence spectroscopy were used to characterize the nanaocrystals. The as-synthesized powders are nanocrystalline and have a narrow size distribution centered on 3 nm and high surface area of similar to 250 m(2) g(-1). Only a small fraction of the europium ions substitutes for the bulk, cubic Ce4+ sites in the europium-doped ceria nanocrystals. Upon calcination up to 1000 degrees C, a remarkable high surface area of similar to 120 m(2) g (-1) is preserved whereas an enrichment of the surface Ce4+ relative to Ce3+ ions and relative strong europium emission with a lifetime of similar to 1.8 ms and FWHM as narrow as 10 cm(-1) are measured. Under excitation into the UV and visible spectral range, the europium doped ceria nanocrystals display a variable emission spanning the orange-red wavelengths. The tunable emission is explained by the heterogeneous distribution of the europium dopants within the ceria nanocrystals coupled with the progressive diffusion of the europium ions from the surface to the inner ceria sites and the selective participation of the ceria host to the emission sensitization. Effects of the bulk-doping and impregnation with europium on the ceria host structure and optical properties are also discussed.

1857. Maple prepared organic heterostructures for photovoltaic applications

Authors: Stanculescu, A; Socol, M; Socol, G; Mihailescu, IN; Girtan, M; Stanculescu, F

Published: SEP 2011, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 104, 928, DOI: 10.1007/s00339-011-6440-y

In this study, we present the deposition of ZnPc, Alq3, and PTCDA thin films using Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. We also report the realisation of multilayer structures, made by the successive application of MAPLE. The films have been characterized by spectroscopic (UV-VIS and Photoluminescence) and microscopic (SEM and AFM) methods, and the effect of different deposition conditions such as fluence, number of pulses, and target concentration on the properties has been analysed. This paper also presents some investigations on the electrical conduction in sandwich type structures ITO or Si/organic layer/Au or Cu and ITO/double organic layer/Cu, emphasising the dominant effect of the height of the energetic barriers at the inorganic/organic and organic/organic interfaces.

1858. 17 keV photon induced damage of Bi-2212 whiskers by synchrotron mu-beam exposure

Authors: Aldica, G; Cagliero, S; Agostino, A; Lamberti, C; Truccato, M

Published: MAR 2011, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 24, DOI: 10.1088/0953-2048/24/3/035009

Experimental data show that the normal state resistivity of superconducting Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi-2212) whiskers increases after a 6 h irradiation by a synchrotron mu-beam with 17 keV photons. We analyse this result on the basis of previously reported effects in Bi-2212 whiskers due to ageing or heating processes. A finite element model of the experimental setup clarifies that the heat load induced by the microbeam has to be excluded as a possible cause for the material changes. The knock on the interstitial, loosely bound, O species by secondary electrons is discussed as the most likely mechanism responsible for this effect.

1859. Nanocarbon embedded chalcogenides. Onion-like model

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Simandan, ID

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1453, DOI:

We modeled the equilibrium structure, at 0 K temperature, of some spherical As(2)S(3) molecules with only 12 rings of ten member (alternating As and S atoms) and 20 triangular faces: As(60)S(90) (like C(60)), As(140)S(210) (like C(140)), As(320)S(480) (like C(320)), grown on carbon fullerene and As(20)S(30) (like C(20)). We used a Monte-Carlo relaxation procedure in the frame of valence force fields theory. The onion-like configurations of the arsenic sulphide was demonstrated as possible. The deposited films of As(2)S(3) seen in the cross-section prove the presence of onion-like configurations even in pure As(2)S(3) material.

1860. Silver doped As2S3 chalcogenide films: A diffusion study

Authors: Lorinczi, A; Popescu, M; Sava, F; Velea, A; Simandan, ID

Published: 2011, PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 9, 8, 2620, DOI: 10.1002/pssc.201084096

Photo-diffusion of silver across an As2S3 thin film layer is studied, as continuing some earlier work about surface morphology modifications in double-layer structures of Ag and As2S3, and some qualitative preliminary results on lateral Ag diffusion in As2S3 thin films. An estimation of the Ag film's dissolution rate and the diffusion front's advancement rate in As,S3 is given based on crosssection measurements. In order to understand better the diffusion mechanism of Ag in As2S3, a structural model of the As2S3 matrix is used to estimate the amount of silver which might be hosted by an As2S3 layer in terms of molar ratio, and an interaction mechanism of the Ag with the chalcogenide matrix is proposed. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1861. Modelling of Calcium Carbonate Synthesis by Gas-Liquid Reaction Using CO2 from Flue Gases

Authors: Isopescu, R; Mihai, M; Capat, C; Olaru, A; Mateescu, C; Dumitrescu, O; Udrea, I

Published: 2011, PRES 2011: 14TH INTERNATIONAL CONFERENCE ON PROCESS INTEGRATION, MODELLING AND OPTIMISATION FOR ENERGY SAVING AND POLLUTION REDUCTION, PTS 1 AND 2, 25, +, DOI: 10.3303/CET1125119

Green house gases, carbon dioxide, ozone, nitrous oxide and chlorofluorocarbons, result inevitably from fossil fuels combustion. The capture of CO2 from flue gases is an effective way to prevent the threat of global warming. The usage of flue gases with low CO2 content in the synthesis of precipitated calcium carbonate, a valuable mineral compound, seems to be an interesting solution for CO2 permanent removal. The quality of the solid product obtained (pure polymorphic phase and narrow particle size distribution in micron and sub-micron domain), can increase the value of the process due to the various applications of calcium carbonate (as filler in paper industry, pharmaceuticals, plastic materials and rubber). The present paper analyzes the chemical absorption of CO2 from flue gases in a waste lime solution. The important advantage of this process over conventional technologies of CO2 removal is that it provides a mineral product with many industrial uses, the fine crystallized CaCO3. Based on experimental results a mathematical model including the chemical process and the precipitation of solid phase was developed. The CO2 absorption was modeled using the general model for mass transfer with chemical reaction. The crystallization steps were modeled in the frame of population balance equation. The kinetic parameters corresponding to the crystallization process including nucleation, particle growth and agglomeration were estimated by nonlinear regression using experimental particle size distribution data.

1862. Retrospective dosimetry assessment using the 380 degrees C thermoluminescence peak of tooth enamel

Authors: Secu, CE; Cherestes, M; Secu, M; Cherestes, C; Paraschiva, V; Barca, C

Published: OCT 2011, RADIATION MEASUREMENTS, 46, 1112, DOI: 10.1016/j.radmeas.2011.07.014

The thermoluminescence (TL) response to gamma-ray irradiation of tooth enamel is reported. The tooth enamel was separated from dentine by using mechanical and physico-chemical procedures followed by grinding (grain size 100 urn) and etching. Then was attributed to the recombination of CO(2)(-) radicals incorporated into or attached to the surface of hydroxyapatite crystals. The growth of the 380 degrees C peak with absorbed dose was examined with irradiated tooth enamel samples and reconstructed doses evaluated for tooth enamel samples from four human subjects. (C) 2011 Elsevier Ltd. All rights reserved.

1863. SUPPORTED Pt AND Pd CATALYSTS AS ADDITIVE FOR HYDROGEN ADSORPTION ENHANCEMENT IN MOFs

Authors: Ardelean, O; Blanita, G; Mihet, M; Coldea, I; Lupu, D; Palade, P

Published: JUN 2011, REVUE ROUMAINE DE CHIMIE, 56, +, DOI:

Hydrogen adsorption in Metal-Organic Frameworks is improved by using platinum and palladium on different carbon support: activated carbon or carbon nanofibres. Although, hydrogen adsorption is directly dependent of the specific surface area of the material, it is not the only factor contributing to the hydrogen adsorption, as presented in this work. Direct synthesis of metal-organic frameworks on supported Pt and Pd catalysts, reduces the surface area significantly, but the presence of the catalysts overcomes this drawback by improving hydrogen adsorption by a factor of 2.2, in case of platinum and by a factor of 1.4 in the case of palladium, compared to the metal-organic framework without catalysts.

1864. Electrochemical Growth of Eosin Y/Manganese Doped ZnO as Hybrid Films and Nanowires

Authors: Sima, M; Visan, T; Matei, E; Ungureanu, F; Enculescu, I; Sima, M

Published: 2011, ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS, 225, 339, DOI: 10.1524/zpch.2011.0042

The electrodeposition process of Eosin Y/ZnO:Mn as films and nanowires performed using a solution containing zinc and manganese nitrates + lactic acid mixture was studied by linear voltammetry. The films and wires grown by polarization at -1.1 V/SCE electrode potential were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Additionally, the Eosin Y presence was evidenced by optical measurements as absorption and photoluminescence spectroscopy. The manganese content in films depends on the nature of support electrode used. On the other hand, the presence of Eosin Y species in the deposition bath increased significantly the manganese concentration in the ZnO:Mn nanowires electrodeposited at -1.1 V/SCE.

1865. TRAPPING ASPECTS IN SILICON-BASED NANOSTRUCTURES

Authors: Ciurea, ML

Published: OCT-DEC 2011, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 12, 323, DOI:

Trapping aspects in two typical silicon-based nanostructures are investigated. Both 1D nanocrystalline porous silicon structures and 2D (nc-Si/CaF2)50 multilayered structures are considered. The curves of relaxation current versus temperature were obtained using the thermally stimulated currents method without external bias. Two types of maxima (rather broad maxima and spikes) were experimentally evidenced. The spikes are due to the stress-induced traps and their parameters are temperature dependent. To describe the trapping-detrapping-retrapping processes, a general model was proposed. The temperature dependence of stress-induced trap concentrations was described by a power law and the corresponding temperature dependence of cross-sections by a Gaussian law. The model was successfully applied on available experimental data.

1866. Sensitive detection of endocrine disrupters using ionic liquid - Single walled carbon nanotubes modified screen-printed based biosensors

Authors: Gurban, AM; Rotariu, L; Baibarac, M; Baltog, I; Bala, C

Published: SEP 30 2011, TALANTA, 85, 2013, DOI: 10.1016/j.talanta.2011.07.045

Simple and low cost biosensor based on screen-printed electrode for sensitive detection of some alkylphenols was developed, by entrapment of HRP in a nanocomposite gel based on single-walled carbon nanotubes (SWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid. Raman and FTIR spectroscopy, CV and EIS studies demonstrate the interaction between SWCNTs and ionic liquid. The nanocomposite gel, SWCNT-[BMIM][PF6] provides to the modified sensor a considerable enhanced electrocatalytic activity toward hydrogen peroxide reduction. The HRP based biosensor exhibits high sensitivity and good stability, allowing a detection of the alkylphenols at an applied potential of -0.2 V vs. Ag/AgCl, in linear range from 5.5 to 97.7 mu M 4 for 4-t-octylphenol and respectively, between 5.5 and 140 mu M for 4-n-nonylphenol, with a response time of about 5s. The detection limit was 1.1 mu M for 4-t-octylphenol, and respectively 0.4 mu M for 4-n-nonylphenol (S/N = 3). (C) 2011 Elsevier B.V. All rights reserved.

1867. Numerical analysis of J-V characteristics of a polymer solar cell

Authors: Mitroi, MR; Iancu, V; Fara, L; Ciurea, ML

Published: MAY 2011, PROGRESS IN PHOTOVOLTAICS, 19, 306, DOI: 10.1002/pip.1026

A numerical method to determine the cell parameters from the analysis of the J-V characteristics of a polymer solar cell is proposed. This method uses the equations given by the diode model, experimental data from the literature, and an adequate fitting procedure with seven fit parameters. Different aspects of the obtained results are discussed. Information concerning cell design optimization is also obtained. The method is of general application in the field of polymer solar cells, as well as to any kind of diode-like cell. Copyright (C) 2010 John Wiley & Sons, Ltd.

1868. Study of SiO2/Si Interface by Surface Techniques

Authors: Logofatu, C; Negrila, CC; Ghita, RV; Ungureanu, F; Cotirlan, C; Manea, CGAS; Lazarescu, MF

Published: 2011, CRYSTALLINE SILICON - PROPERTIES AND USES, 42, DOI:

1869. Silicon structuring by etching with liquid chlorine and fluorine precursors using femtosecond laser pulses

Authors: Radu, C; Simion, S; Zamfirescu, M; Ulmeanu, M; Enculescu, M; Radoiu, M

Published: AUG 1 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3619856

The aim of this study is to investigate the micrometer and submicrometer scale structuring of silicon by liquid chlorine and fluorine precursors with 200 fs laser pulses working at both fundamental (775 nm) and frequency doubled (387 nm) wavelengths. The silicon surface was irradiated at normal incidence by immersing the Si (111) substrates in a glass container filled with liquid chlorine (CCl(4)) and fluorine (C(2)Cl(3)F(3)) precursors. We report that silicon surfaces develop an array of spikes with single step irradiation processes at 775 nm and equally at 387 nm. When irradiating the Si surface with 400 pulses at 330 mJ/cm(2) laser fluence and a 775 nm wavelength, the average height of the formed Si spikes in the case of fluorine precursors is 4.2 mu m, with a full width at half maximum of 890 nm. At the same irradiation wavelength chlorine precursors develop Si spikes 4 mu m in height and with a full width at half maximum of 2.3 mu m with irradiation of 700 pulses at 560 mJ/cm(2) laser fluence. Well ordered areas of submicrometer spikes with an average height of about 500 nm and a width of 300 nm have been created by irradiation at 387 nm by chlorine precursors, whereas the fluorine precursors fabricate spikes with an average height of 700 nm and a width of about 200 nm. Atomic force microscopy and scanning electron microscopy of the surface show that the formation of the micrometer and sub-micrometer spikes involves a combination of capillary waves on the molten silicon surface and laser-induced etching of silicon, at both 775 nm and 387 nm wavelength irradiation. The energy-dispersive x-ray measurements indicate the presence of chlorine and fluorine precursors on the structured surface. The fluorine precursors create a more ordered area of Si spikes at both micrometer and sub-micrometer scales. The potential use of patterned Si substrates with gradient topography as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth is envisaged. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3619856]

1870. Intensity parameters of Tm3+ doped Sc2O3 transparent ceramic laser material

Authors: Gheorghe, C; Lupei, A; Lupei, V; Ikesue, A; Enculescu, M

Published: JAN 2011, OPTICAL MATERIALS, 33, 505, DOI: 10.1016/j.optmat.2010.10.032

This work is focused on spectral investigations of Tm3+ doped Sc2O3 transparent ceramic as potential material for diode-pumped solid-state laser emitting around 2 mu m. In the context of the Judd-Ofelt J-O) theory a series of spectroscopic parameters such as J-O intensity parameters, oscillator strengths, radiative transitions probabilities, and radiative lifetimes as well as branching ratios are evaluated. The gain cross-sections which lead to an estimation of the probable operating laser wavelength for the F-3(4) -> H-3(6) Tm3+ laser transition were also calculated. (C) 2010 Elsevier B.V. All rights reserved.

1871. Structural phase transformations in annealed cubic ZnS nanocrystals

Authors: Ghica, D; Nistor, SV; Nistor, LC; Stefan, M; Mateescu, CD

Published: SEP 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 4335, DOI: 10.1007/s11051-011-0379-y

The structural changes of cubic ZnS (cZnS) nanocrystals (NCs) doped with 0.2 at.% Mn2+ pulse annealed in vacuum and in air, up to 500 A degrees C, were investigated by multifrequency electron paramagnetic resonance (EPR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The samples, prepared by a surfactant (Tween20)-assisted liquid-liquid reaction at pH = 6, consist of NCs with a tight size distribution around 3 nm and high crystallinity self-assembled into a stable mesoporous structure. The EPR spectra of the as prepared samples contain only the characteristic lines of the substitutional Mn2+(I) centers. No spectra from Mn2+ ions localized in (hydro)oxidized regions of the NCs surface were observed. The absence of such a surface layer could explain the stability of the cubic (sphalerite) structure observed by XRD and TEM in the investigated cZnS:Mn NCs annealed in vacuum up to 500 A degrees C. The observation of the cubic-hexagonal transformation for the same NCs annealed in air supports the role of such layer in promoting this structural transformation. The narrowing of the EPR spectral lines above 200 A degrees C with the increase in the average size of the cZnS:Mn crystallites was observed. The effect was more pronounced for the sample annealed in air. EPR also revealed the formation of minute amounts of substitutional Mn2+-type centers in a hexagonal ZnO structure at T similar to 300 A degrees C, corresponding to the early stages of the thermally induced oxidation of the cZnS:Mn NCs.

1872. Influence of humidity on CO sensing with p-type CuO thick film gas sensors

Authors: Hubner, M; Simion, CE; Tomescu-Stanoiu, A; Pokhrel, S; Barsan, N; Weimar, U

Published: APR 20 2011, SENSORS AND ACTUATORS B-CHEMICAL, 153, 353, DOI: 10.1016/j.snb.2010.10.046

A model for the detection of CO in the presence of humidity is proposed for thick porous film gas sensors based on p-type CuO. The sensing mechanism is investigated by means of simultaneous DC electrical resistance and work function changes measurements combined with appropriate modeling of the conduction in the polycrystalline sensing film. The experiments were performed at 150 degrees C in dry and humid air backgrounds. The conclusion is that, very similarly to the case of undoped SnO2, the explanation of the cross-interference of water in the CO detection is the fact that both react with pre-adsorbed oxygen ions. (C) 2010 Elsevier B.V. All rights reserved.

1873. Mechanochemical synthesis and characterization of xIn(2)O(3)center dot(1-x)alpha-Fe2O3 nanostructure system

Authors: Sorescu, M; Xu, TH; Diamandescu, L

Published: APR 2011, JOURNAL OF MATERIALS SCIENCE, 46, 2358, DOI: 10.1007/s10853-010-5081-4

Indium oxide-doped hematite xIn(2)O(3)center dot(1 - x)alpha-Fe2O3 (x = 0.1-0.7) nanostructure system was synthesized using mechanochemical activation by ball milling and characterized by XRD, simultaneous DSC-TGA, and UV/Vis/NIR. The microstructure and thermal behavior of as obtained system were dependent on the starting In2O3 molar concentration x and ball milling time. XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time. After 12 h of ball milling, the completion of In3+ substitution of Fe3+ in hematite lattice occurs for x = 0.1, indicating that the solid solubility of In2O3 in hematite lattice is extended. For x = 0.3, 0.5, and 0.7, the substitutions between In3+ and Fe3+ into hematite and In2O3 lattice occur simultaneously. The lattice parameters a and c of hematite and lattice parameter a of indium oxide vary as a function of ball milling time. The changes of these parameters are due to ion substitutions between In3+ and Fe3+ and the decrease in the grain sizes. Ball milling has a strong effect on the thermal behavior and band gap energy of the as-obtained system. The hematite decomposition is enhanced due to the smaller hematite grain size. The crystallization of hematite and In2O3 was suppressed, with drops of enthalpy values due to the stronger solid-solid interactions after ball milling, which caused gradual In3+-Fe3+ substitution in hematite/In2O3 lattices. The band gap for hematite shifts to higher energy value, while that of indium oxide shifts to lower energy value after ball milling.

1874. Pulsed laser deposition of semiconducting crystalline double-doped barium titanate thin films on nickel substrates

Authors: Apostol, I; Stefan, N; Luculescu, CR; Birjega, R; Socol, M; Miroiu, M; Mihailescu, IN

Published: FEB 1 2011, APPLIED SURFACE SCIENCE, 257, 3576, DOI: 10.1016/j.apsusc.2010.11.078

We synthesized by pulsed laser deposition (Ba,Sr,Y)TiO3 and (Ba,Pb,Y)TiO3 thin films on mechanically polished nickel substrates. The synthesized thin films were analyzed for: crystalline structure by X-ray diffractometry, morphology and surface topography by atomic force microscopy, optical and scanning electron microscopy, and elemental composition by energy dispersive X-ray spectroscopy and electrical properties by electrical measurements. We have shown that film properties were determined by the dopants, target composition, and deposition parameters (oxygen pressure, substrate temperature and incident laser fluence). All films exhibited a semiconducting behavior, as proved by the decrease of electrical resistance with heating temperature. (C) 2010 Elsevier B. V. All rights reserved.

1875. Characterization of martensitic transformation in some Ni-Fe-Co-Ga ferromagnetic shape memory alloys

Authors: Tolea, F; Sofronie, M; Ghica, C; Valeanu, M

Published: MAY 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 566, DOI:

The martensitic transformation characteristics in two series of cobalt substituted Ni-Fe-Ga Ferromagnetic Shape Memory alloys have been studied by differential scanning calorimetry, X-ray diffraction, electrical resistivity and thermomagnetic measurements. Co substitution for Fe or Ni promotes an increase of the Curie temperatures but the changes of the martensitic transformation temperatures are in agreement with the valence electron concentration and unit cell volume variations. A large hysteresis observed between cooling and heating curves as feature of a first order phase transition was evidenced by r(T) and thermomagnetic measurements.

1876. Shape Memory NiTi Alloys Obtained by Powder Metallurgy Route

Authors: Lucaci, M; Valeanu, M; Orban, RL; Tsakiris, V; Cirstea, DC; Leonat, L

Published: 2011, RESEARCHES IN POWDER METALLURGY, 672, +, DOI: 10.4028/www.scientific.net/MSF.672.99

The effect of Fe, respective Cu, additions as substitute for Ni in NiTi shape memory alloys (SMAs) on the delaying of its phase transition and narrowing hysteresis are well known, NiTi-Fe and NiTi-Cu SMAs having applications especially to the actuators that require such properties. These SMAs are currently produced by conventional melting methods, which are energo-intensive and impose very severe processing conditions to avoid contamination. The results of researches presented in this paper prove the possibility of these SMAs obtaining by powder metallurgy via reactive sintering - more advantageous from both technical and economic point of view. A beneficial effect on both sintering and homogeneity of the obtained SMAs proved to have a controlled mechanical alloying applied to powder mixture before compacting and sintering.

1877. Band-gap correlations in Bi4Ge3O12 amorphous and glass-ceramic materials

Authors: Polosan, S; Galca, AC; Secu, M

Published: JAN 2011, SOLID STATE SCIENCES, 13, 53, DOI: 10.1016/j.solidstatesciences.2010.10.007

The Bi4Ge3O12 (BGO) glass materials were sintered from a mixture of oxides powders, rapidly heated and melted at 1323 K and poured on the graphite plates heated at different temperatures. Their optical properties are compared with BGO single crystals being strongly dependent by the experimental conditions, which influence the further stability of the samples. The dielectric functions of the samples reveal a clear difference between the two phases (amorphous and crystalline). The refractive index of the amorphous phase has lower values which indicate that the density of the material is diminishes. Also, a sign of disorder is seen in optical absorption (extinction coefficient). From the optical band gap determinations of those two phases, it is confirmed the disorder structure and red-shifts of the band gap value compared with crystalline phase. The absorption spectra are in good agreement with the ellipsometric measurements, regarding the transparency and the edge of the band gap. (C) 2010 Elsevier Masson SAS. All rights reserved.

1878. Silicon detectors for the sLHC

Authors: Affolder, A; Aleev, A; Allport, PP; Andricek, L; Artuso, M; Balbuena, JP; Barabash, L; Barber, T; Barcz, A; Bassignana, D; Bates, R; Battaglia, M; Beimforde, M; Bemardini, J; Betancourt, C; Bilei, GM; Bisello, D; Blue, A; Bohm, J; Bolla, G; Borgia, A; Borrello, L; Bortoletto, D; Boscardin, M; Bosma, MJ; Bowcock, TJV; Breindl, M; Broz, J; Bruzzi, M; Brzozowski, A; Buhmann, P; Buttar, C; Campabadal, F; Candelori, A; Casse, G; Charron, S; Chren, D; Cihangir, S; Cindro, V; Collins, P; Gil, EC; Costinoaia, CA; Creanza, D; Cristobal, C; Dalla Betta, GF; de Boer, W; De Palma, M; Demina, R; Dierlamm, A; Diez, S; Dobos, D; Doherty, F; Kittelmann, ID; Dolezal, Z; Dolgolenko, A; Dragoi, C; Driewer, A; Dutta, S; Eckstein, D; Eklund, L; Eremin, I; Eremin, V; Erfle, J; Fadeeva, N; Fahrer, M; Fiori, F; Fleta, C; Focardi, E; Forshaw, D; Fretwurst, E; Frey, M; Bates, AG; Gallrapp, C; Garcia, C; Gaubas, E; Genest, MH; Giolo, K; Glaser, M; Goessling, C; Golubev, A; Gorelov, I; Gregoire, G; Gregori, P; Grigoriev, E; Grillo, AA; Grinstein, S; Groza, A; Guskov, J; Hansen, TE; Harkonen, J; Hartjes, FG; Hartmann, F; Hoeferkamp, M; Horisberger, R; Houdayer, A; Hynds, D; Ilyashenko, I; Junkes, A; Kadys, A; Kaminski, P; Karpenko, A; Kaska, K; Kazuchits, N; Kazukauskas, V; Kharchuk, A; Khivrich, V; Kierstead, J; Klanner, R; Klingenberg, R; Kodys, P; Koffeman, E; Kohler, M; Kohout, Z; Korjenevski, S; Korolkov, I; Kozlowski, R; Kozubal, M; Kramberger, G; Kuhn, S; Kuleshov, S; Kuznetsov, A; Kwan, S; La Rosa, A; Lacasta, C; Lange, J; Lassila-Perini, K; Lastovetsky, V; Lazanu, I; Lazanu, S; Lebel, C; Lefeuvre, G; Lemaitre, V; Leroy, C; Li, Z; Lindstrom, G; Litovchenko, A; Litovchenko, P; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Macraighne, A; Maenpaa, T; Makarenko, LF; Mandic, I; Maneuski, D; Manna, N; Marco, R; Garcia, SII; Marunko, S; Masek, P; Mathieson, K; Matysek, M; Mekki, J; Messineo, A; Metcalfe, J; Mikestikova, M; Mikuz, M; Militaru, O; Minano, M; Miyamoto, J; Moll, M; Monokhov, E; Mori, R; Moser, HG; Muenstermann, D; Sanchez, FJM; Naletko, A; Nisius, R; Oshea, V; Pacifico, N; Pantano, D; Parkes, C; Parzefall, U; Passeri, D; Pawlowski, M; Pellegrini, G; Pernegger, H; Petasecca, M; Piemonte, C; Pignatel, GU; Pintilie, I; Pintilie, L; Piotrzkowski, K; Placekett, R; Pohlsen, T; Polivtsev, L; Popule, J; Pospisil, S; Preiss, J; Radicci, V; Radu, R; Raf, JM; Rando, R; Richter, R; Roeder, R; Roger, R; Rogozhkin, S; Rohe, T; Ronchin, S; Rott, C; Roy, A; Rummler, A; Ruzin, A; Sadrozinski, HFW; Sakalauskas, S; Samadashvili, N; Scaringella, M; Schumm, B; Seidel, S; Seiden, A; Shipsey, I; Sibille, J; Sicho, P; Slavicek, T; Solar, M; Soldevila-Serrano, U; Son, S; Sopko, V; Sopko, B; Spencer, N; Spiegel, L; Srivastava, A; Steinbrueck, G; Stewart, G; Stolze, D; Storasta, J; Surma, B; Svensson, BG; Tan, P; Tomasek, M; Toms, K; Tsiskaridze, S; Tsvetkov, A; Tuboltsev, Y; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Ullan, M; Vaitkus, JV; van Beuzekom, M; Verbitskaya, E; Alvarez, IV; Visser, J; Vossebeld, J; Vrba, V; Walz, M; Weigell, P; Wiik, L; Wilhelm, I; Wunstorf, R; Zaluzhny, A; Zavrtanik, M; Zelazko, J; Zen, M; Zhukov, V; Zontar, D; Zorzi, N

Published: DEC 1 2011, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 658, 16, DOI: 10.1016/j.nima.2011.04.045

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages. (C) 2011 Elsevier B.V. All rights reserved.

1879. Luminescent Dye-Doped KAP Nanorods Obtained by Template Assisted Crystallization

Authors: Enculescu, M; Neumann, R

Published: MAY 2011, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 11, 3948, DOI: 10.1166/jnn.2011.3832

Luminescent nanorods of potassium acid phthalate (KAP) doped with rhodamine 6G (Rh 6G) dye molecules were grown by template assisted crystallization. Pores with diameters ranging from tens of nanometers to few micrometers were obtained in polycarbonate foils after heavy-ion irradiation and subsequent chemical etching of the damage trails along the ion trajectories. Crystallization from solution was employed for filling of the pores with the dye-doped KAP rods. These nanostructures were characterized using scanning electron microscopy, optical absorption spectroscopy and photoluminescence detection. X-ray diffraction was used for structural analysis. The luminescence of the dye-doped rods undergoes a redshift when the diameter of the structures decreases. This shift is probably caused by increasing dye concentration in the rods with decreasing pore diameter. The luminescence originating from the Rh 6G presence is up-converted due to the second-harmonic generation in KAP.

1880. Substrate-target distance dependence of structural and optical properties in case of Pb(Zr,Ti)O-3 films obtained by pulsed laser deposition

Authors: Galca, AC; Stancu, V; Husanu, MA; Dragoi, C; Gheorghe, NG; Trupina, L; Enculescu, M; Vasile, E

Published: MAR 1 2011, APPLIED SURFACE SCIENCE, 257, 5943, DOI: 10.1016/j.apsusc.2011.01.056

The paper presents the influence of pulsed laser deposition (PLD) parameters on the structural and optical properties of PZT thin films grown on platinum substrate. X-ray diffraction (XRD), spectroscopic ellipsometry (SE) and X-ray photoelectron spectroscopy (XPS) are used to determine the thin film properties. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are employed to get additional information. By changing the distance between target and substrate, different crystalline orientations of PZT are obtained. The thin film thickness and its roughness, as well as the refractive index are also influenced by the chosen distance. (C) 2011 Elsevier B.V. All rights reserved.

1881. Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

Authors: Dragoi, C; Cernea, M; Trupina, L

Published: SEP 1 2011, APPLIED SURFACE SCIENCE, 257, 9605, DOI: 10.1016/j.apsusc.2011.06.075

The difficulties in synthesizing phase pure BaTiO3 doped-(Na0.5Bi0.5)TiO3 are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na0.5Bi0.5)TiO3-0.08BaTiO(3), (BNT-BT0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT0.08, thin films deposited by PLD on Pt/TiO2/SiO2/Si substrates are investigated in this paper. Perovskite structure of BNT-BT0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 degrees C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 mu C/cm(2) and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT0.08 thin film is ferroelectric at the nanoscale level and piezoelectric. (C) 2011 Elsevier B.V. All rights reserved.

1882. Stress-induced traps in multilayered structures

Authors: Ciurea, ML; Lazanu, S; Stavarache, I; Lepadatu, AM; Iancu, V; Mitroi, MR; Nigmatullin, RR; Baleanu, CM

Published: JAN 1 2011, JOURNAL OF APPLIED PHYSICS, 109, DOI: 10.1063/1.3525582

The trap parameters of defects in Si/CaF2 multilayered structures were determined from the analysis of optical charging spectroscopy measurements. Two kinds of maxima were observed. Some of them were rather broad, corresponding to "normal" traps, while the others, very sharp, were attributed to stress-induced traps. A procedure of optimal linear smoothing the noisy experimental data has been developed and applied. This procedure is based on finding the minimal value of the relative error with respect to the value of the smoothing window. In order to obtain a better accuracy for the description of the trapping-detrapping process, a Gaussian temperature dependence of the capture cross-sections characterizing the stress-induced traps was introduced. Both the normal and the stress-induced traps have been characterized, including some previously considered as only noise features. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3525582]

1883. Polymer-assisted crystallization of low-dimensional lead sulfide particles

Authors: Preda, N; Rusen, E; Enculescu, M; Matei, E; Marculescu, B; Enculescu, I

Published: AUG 2011, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 43, 1832, DOI: 10.1016/j.physe.2011.06.019

PbS micro- and nanoparticles were synthesized by a simple precipitation reaction of lead nitrate with thioacetamide in hydrosoluble polymer water solutions. The effects of four water soluble polymers: polyacrylamide (PAM), polyvinyl alcohol (PVA), polyethylene glycol (PEG) and poly-N-vinyl pyrrolidone (PVP) on the PbS crystallites morphology and structural properties were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that for the PbS particles obtained in the PVA. PEG and PVP, the (2 0 0) diffraction peak of the nanocrystals becomes dominant. The highest texture in the [2 0 0] direction was observed for the crystallites obtained in the presence of PVP. Polydisperse PbS particles with cubic morphology and size ranging from 100 nm to several microns are obtained in the case of PAM and PEG. Monodisperse cubic PbS crystallites with an average size of 200 nm are formed in the presence of PVA and PVP. (C) 2011 Elsevier B.V. All rights reserved.

1884. COMPLEX PHOTOCONDUCTORS CHALCOGEN-POLYMER

Authors: Simandan, ID; Velea, A; Popescu, M

Published: OCT 2011, CHALCOGENIDE LETTERS, 8, 614, DOI:

There was discovered a material with strong photoconduction effect. Langmuir-Blodgett film with barium stearate, and selenium carbazole has been prepared and tested for the change of conductivity (decrease) under the influence of UV-radiation. Change of resistance in a time scale of 0-400 seconds was evidenced. The UV radiation determines an increase of the electrical resistence and after switching off the illumination a slow decrease of the resistance occurs.

1885. Crystallization of Disordered Nanosized ZnO Formed by Thermal Decomposition of Nanocrystalline Hydrozincite

Authors: Nistor, SV; Nistor, LC; Stefan, M; Ghica, D; Aldica, G; Barascu, JN

Published: NOV 2011, CRYSTAL GROWTH & DESIGN, 11, 5038, DOI: 10.1021/cg2009286

The formation and crystallization of disordered nanosized ZnO resulting from the thermal decomposition of nanocrystalline hydrozincite [Zn-5(CO3)(2)(OH)(6)] has been Observed and investigated during pulse annealing experiments Up to 625 degrees C in air or vacuum by electron paramagnetic resonance of trace amounts of substitutional Mn2+ impurity ions, in correlation with X-ray diffraction and transmission electron microscopy measurements. The mesoporous structure of the disordered ZnO, which initially forms in air and vacuum at 225 and 175 degrees C, respectively, further transforms into nanocrystalline ZnO of increasing particle size and improved lattice quality at higher annealing temperatures. The crystallization process, which does not affect the concentration of the substitutional impurity ions, as well as the simultaneous presence of both disordered and crystalline phases, should be considered in further applications of the resulting nanosized ZnO.

1886. Thin films of arylenevinylene oligomers prepared by MAPLE for applications in non-linear optics

Authors: Stanculescu, A; Vacareanu, L; Grigoras, M; Socol, M; Socol, G; Stanculescu, F; Preda, N; Matei, E; Ionita, I; Girtan, M; Mihailescu, IN

Published: APR 1 2011, APPLIED SURFACE SCIENCE, 257, 5302, DOI: 10.1016/j.apsusc.2010.11.094

This paper discusses two arylenevinylene oligomers with optical nonlinear properties. Their trans molecular structure was confirmed by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. Second Harmonic Generation and two-photon fluorescence have been observed on Matrix Assisted Pulsed Laser Evaporation-deposited thin films. We have seen two local maxima in UV-Vis spectra and a red shift of the photoluminescence peak for carbazole-based oligomer, which can be correlated with a higher conformational flexibility and with strong polarization interactions in the solid state. Scanning Electron Microscopy and Atomic Force Microscopy images have revealed a grainy morphology of the film deposited on titanium and a higher roughness for carbazole-based oligomer. Second harmonic measurements have shown nearly equal values of the second-order nonlinear optical coefficient for the triphenylamine and carbazole-based oligomers for P-laser < 100 mW. z-Scan and x-scan representations of the carbazole-based oligomer film have shown strong two-photon fluorescence intensity inside the sample confirming a volume process, and a strong second harmonic at the surface of the sample determined by the surface morphology. (C) 2010 Elsevier B.V. All rights reserved.

1887. Microwave antennas based on Ba1-xPbxNd2Ti5O14

Authors: Ene-Dobre, M; Banciu, MG; Nedelcu, L; Stoica, G; Busuioc, C; Alexandru, HV

Published: SEP-OCT 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1304, DOI:

The Ba1-xPbxNd2Ti5O14 ceramic material (BNT) is very attractive for applications at frequencies around few GHz [1]. The temperature coefficient of the resonant frequency T-f decreases from + 70 ppm/degrees C to - 15 ppm/degrees C with the Pb content x increase up to 0.5. The samples with high Pb content exhibit a dielectric constant up to 86.6, but the product Q x f is several times lower than for such microwave ceramics as zirconium tin titanate [1-2]. When a product Q x f higher than 6000 is required in order to use the BNT materials at high frequencies, then the Pb content can result from the tradeoff between small temperature coefficient T-f and high quality factor Q. The features of the BNT dielectric resonators lead to the development of miniaturized dielectric resonator antenna (DRA) with improved characteristics. The DRAs of BNT ceramics presented in this paper exhibit an increased bandwidth due to an optimal height over diameter ratio. For an increased gain and shaping of the overall radiation pattern, an array of dielectric resonator antennas is proposed.

1888. Optical spectra of nitride quantum-dot systems: From tight-binding states to many-body effects

Authors: Seebeck, J; Lorke, M; Schulz, S; Schuh, K; Gartner, P; Jahnke, F

Published: AUG 2011, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 248, 1878, DOI: 10.1002/pssb.201147160

A microscopic theory for optical properties of self-assembled quantum-dot systems is presented. For nitride-based material systems, the single-particle states are determined from atomistic tight-binding (TB) calculations. This includes not only localized quantum-dot states but also delocalized wetting-layer states, since both contribute to the optical properties and are coupled via interaction processes. The TB wave functions are used to calculate matrix elements for optical dipole transitions as well as Coulomb and LO-phonon interaction of carriers. Absorption and gain spectra are investigated via a solution of the semiconductor Bloch equations including Coulomb interaction effects as well as dephasing due to carrier interaction with LO-phonons. Numerical results are presented for InN/GaN QD-WL systems and allow to investigate the excitation-density dependence of the optical spectra for this particular system. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1889. Combination of Ag Substrate Decoration with Introduction of BaZrO3 Nano-Inclusions for Enhancing Critical Current Density of YBa2Cu3O7 Films

Authors: Dang, VS; Mikheenko, P; Sarkar, A; Kechik, MMA; Abell, JS; Paturi, P; Huhtinen, H; Crisan, A

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 509, DOI: 10.1007/s10948-010-0981-8

The combination of two methods: Ag substrate decoration and introduction of BZO nano-inclusions has been used in a pulsed laser deposition (PLD) method to increase the critical density (J (c) ) of YBCO films. The films were deposited on single crystal SrTiO3 (STO) substrates decorated with various architecture of Ag nano-dots. We have studied the diameter and density of Ag nano-dots and their influence on J (c) of BZO-added YBCO films. We found that 15 laser pulses on the Ag target gives an optimum result in increasing J (c) in comparison with BZO-doped YBCO films of the same thickness in self-field and low applied magnetic fields. A higher number of laser pulses on the Ag target led to increasing critical current density in high applied magnetic fields only (above 2 T). We have studied films of the thickness from 0.4 mu m to 3.8 mu m and found that the highest J (c) at all applied fields investigated is achieved for a 1.2 mu m thick film. The transmission electron microscopy clearly shows BZO nano-rods that provide strong c-axis pinning centres in the films.

1890. Abnormal anti-Stokes Raman emission as single beam coherent anti-Stokes Raman scattering like process in LiNbO(3) and CdS powder

Authors: Baibarac, M; Baltog, I; Lefrant, S

Published: SEP 1 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3633936

Abnormal anti-Stokes Raman emission (AASRE) is defined by an anti-Stokes/Stokes intensity ratio much greater than expected on the basis of the equilibrium population of excited vibration states provided by the Boltzmann law. Using nonlinear optical materials such as LiNbO(3) and CdS in powder form, we demonstrate that under continuous single beam excitation it presents AASRE whose properties are similar to a single beam pumped Coherent Anti-Stokes Raman Scattering. We explain AASRE as resulting from a wave-mixing mechanism of the incident laser light with a Stokes shifted Raman light produced by a spontaneous Raman light scattering process, both strongly scattered inside the sample. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633936]

1891. Pure, smooth and dense W films obtained by an anodic arc plasma

Authors: Surdu-Bob, CC; Racolta, PM; Badulescu, M; Chiojdeanu, C; Arsene, N; Logofatu, C; Ionescu, C; Sporea, D; Gruia, I

Published: DEC 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 1340, DOI:

Tungsten films have a number of important applications. The techniques to produce quality films are very few and most of them use gases as precursors or as buffer. The Thermoionic Vacuum Arc (TVA) plasma is an original technique capable of producing pure, dense and very smooth Tungsten films of thicknesses from nanometers to tens of micrometers with no buffer gas or gas precursors. This paper presents characterisation of Tungsten films obtained by TVA in terms of composition and topography using XRF, XPS and AFM. The films studied are pure and contain a very thin surface oxide of WO(3). The influence of water vapors inherently present on the chamber walls to the film surface composition is also presented.

1892. Electrochemical functionalisation of SWNTs with poly(3,4-ethylenedioxythiophene) evidenced by anti-Stokes/Stokes Raman spectroscopy

Authors: Baltog, I; Baibarac, M; Lefrant, S; Mevellec, JY

Published: MAR 2011, JOURNAL OF RAMAN SPECTROSCOPY, 42, 312, DOI: 10.1002/jrs.2705

The capability of anti-Stokes/Stokes Raman spectroscopy to evaluate chemical interactions at the interface of a conducting polymer/carbon nanotubes is demonstrated. Electrochemical polymerisation of the monomer 3,4-ethylenedioxythiophene (EDOT) on a Au support covered with a single-walled carbon nanotube (SWNT) film immersed in a LiClO4/CH3CN solution was carried out. At the resonant optical excitation, which occurs when the energy of the exciting light coincides with the energy of an electronic transition, poly(3,4-ethylenedioxythiophene) (PEDOT) deposited electrochemically as a thin film of nanometric thickness on a rough Au support presents an abnormally intense anti-Stokes Raman spectrum. The additional increase in Raman intensity in the anti-Stokes branch observed when PEDOT is deposited on SWNTs is interpreted as resulting from the excitation of plasmons in the metallic nanotubes. A covalent functionalisation of SWNTs with PEDOT both in un-doped and doped states takes place when the electropolymerisation of EDOT, with stopping at +1.6 V versus Ag/Ag+, is performed on a SWNT film deposited on a Au plate. The presence of PEDOT covalently functionalised SWNTs is rationalised by (1) a downshift by a few wavenumbers of the polymer Raman line associated with the symmetric C-C stretching mode and (2) an upshift of the radial breathing modes of SWNTs, both variations revealing an interaction between SWNTs and the conjugated polymer. Raman studies performed at different excitation wavelengths indicate that the resonant optical excitation is the key condition to observe the abnormal anti-Stokes Raman effect. Copyright (C) 2010 John Wiley & Sons, Ltd.

1893. Optical spectroscopy of heavily Ho3+-doped BaY2F8 crystals

Authors: Tsuboi, T; Jang, KH; Polosan, S; Shimamura, K; Bettinelli, M; Seo, HJ

Published: APR 2011, JOURNAL OF LUMINESCENCE, 131, 700, DOI: 10.1016/j.jlumin.2010.11.020

The ultraviolet, visible, and near IR (0.8-2.4 mu m) luminescence spectra of BaY2F8 single crystals heavily doped with Ho3+ ions (10 and 30 mol%) have been investigated at room temperature and 12 K, together with the luminescence decay curves (up to 300 mu s) of the visible emission. Excitation in the visible region gives rise to very strong emission bands originating from the first I-5(7) level and located around 2070 nm. However the I-5(7) emission is not observed upon excitation at wavelengths shorter than 300 nm. The inter-ionic processes are found to shorten the decay times of the levels emitting in the visible region with respect to the corresponding radiative lifetimes. (C) 2010 Elsevier B.V. All rights reserved.

1894. Bovine Serum Albumin 3D Structure Determination by THz Spectroscopy and Molecular Modeling

Authors: Mernea, M; Leca, A; Dascalu, T; Mihailescu, D

Published: 2011, TERAHERTZ AND MID INFRARED RADIATION: GENERATION, DETECTION AND APPLICATIONS, +, DOI: 10.1007/978-94-007-0769-6_14

The low frequency collective movements of proteins associated with biologically relevant conformational transitions are situated in the terahertz (THz) spectral region. THz spectroscopy experiments have revealed that each molecular species has a unique absorption pattern in THz domain. We used time-domain THz spectroscopy (TDS) to study the conformation and flexibility of bovine serum albumin (BSA), a protein whose 3D structure is unknown. We performed THz spectroscopy experiments on lyophilized BSA. Theoretical spectra were obtained by normal modes analysis performed on BSA structures generated by homology modeling and molecular dynamics simulations. The agreement between experimental and theoretical data allowed us to validate the model of BSA and also to gain insight into BSA vibrations in THz domain.

1895. Martensitic transformation of Ti50Ni30Cu20 alloy prepared by powder metallurgy

Authors: Valeanu, M; Lucaci, M; Crisan, AD; Sofronie, M; Leonat, L; Kuncser, V

Published: MAR 31 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 4498, DOI: 10.1016/j.jallcom.2011.01.154

Phase transformation behavior of Ti50Ni30Cu20 shape memory alloys prepared by powder metallurgy is analyzed with respect to the duration of mechanical alloying. The processed blends were studied by differential scanning calorimetry and room temperature X-ray diffraction. The martensitic transformations evidenced by thermal scans are discussed in correlation with the relative phase content obtained from the refinement of the X-ray diffraction patterns. (c) 2011 Elsevier B.V. All rights reserved.

1896. In situ electrical conductivity and catalytic properties of copper ferrite synthesized by non-conventional methods

Authors: Munteanu, C; Caldararu, M; Gingasu, D; Feder, M; Diamandescu, L; Ionescu, NI

Published: DEC 2011, REACTION KINETICS MECHANISMS AND CATALYSIS, 104, 368, DOI: 10.1007/s11144-011-0357-5

The in situ electrical properties and the catalytic activity of copper ferrite obtained by co-precipitation and thermal decomposition of polynuclear coordination compounds were studied in the propane oxidation reaction. The sample prepared by complexation had a better catalytic activity. Based on the conductivity data and the relative phase distribution in fresh and used compounds, the results are discussed in terms of the redox-type mechanism.

1897. BNT ADVANCED CERAMICS FOR SLOT COUPLED DIELECTRIC RESONATOR ANTENNAS

Authors: Nicolaescu, I; Banciu, MG; Nedelcu, L; Avadanei, O; Radu, I

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 196, DOI:

Barium neodymium titanate (BNT) material was prepared and characterized. The very high dielectric constant, high Qxf product and controllable temperature coefficient recommend the BNT material for microwave applications. Slot coupled antennas with BNT resonators are investigated. The resonator shape effect on the antenna bandwidth is discussed.

1898. Benzylation of benzene with benzyl alcohol on zeolite catalysts

Authors: Candu, N; Florea, M; Coman, SM; Parvulescu, VI

Published: FEB 15 2011, , DOI: 10.1016/j.apcata.2010.11.044

1899. The integral magneto-refractive effect: A method of probing magneto-resistance

Authors: Vopsaroiu, M; Cain, MG; Kuncser, V

Published: SEP 1 2011, JOURNAL OF APPLIED PHYSICS, 110, DOI: 10.1063/1.3631778

We show that the optical infrared magneto-refractive effect can be used to probe magneto-resistance effects in absolute terms. A spin valve sample with synthetic anti-ferromagnet has been studied using non-contact infrared reflection spectroscopy measurements. Direct experimental comparison shows excellent agreement between electrical and optical measurements in both shape of the magneto-resistance curves and absolute values. This opens the possibility of developing fast and efficient tests of magneto-resistive samples and sensors using an in situ, non-contact, non-destructive optical approach, without the need to determine a calibration factor between the electrical and optical measurements. [doi:10.1063/1.3631778]

1900. 1-BUTANOL DEHYDRATION AND DEHYDROGENATION OVER VANADIUM ALUMINIUM OXYNITRIDE CATALYSTS

Authors: Florea, M; Delsarte, S; van Keulen, E; Grange, P

Published: FEB 2011, , DOI:

1901. Calculation of the quantum efficiency for the absorption on confinement levels in quantum dots

Authors: Iancu, V; Mitroi, MR; Lepadatu, AM; Stavarache, I; Ciurea, ML

Published: APR 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 1612, DOI: 10.1007/s11051-010-9913-6

The quantum efficiency of the absorption on quantum confinement levels is investigated. This is achieved by modeling the electron confinement in a spherical quantum dot (QD). The confinement levels are calculated using both infinite and finite rectangular quantum wells. The spectral internal quantum efficiency is evaluated within both the models, by computing Einstein's coefficients for the transitions between confinement levels. The size of QDs (1-3 nm radius) leads to negligible many body effects. The nature of the QD material and of the matrix embedding is taken into account in the finite rectangular quantum well approximation and introduces only a small correction. The temperature dependence of the efficiency is also taken into account. A numerical application is performed for a silicon QD of 2.5 nm radius, embedded in amorphous silica. It is proved that the absorption threshold shifts toward the far infrared limit and that the spectral internal quantum efficiency reaches 4-5% at the threshold.

1902. Spin dynamics in 57Fe-doped TiO2 anatase nanoparticles

Authors: Grecu, MN; Constantinescu, S; Tarabasanu-Mihaila, D; Ghica, D; Bibicu, I

Published: DEC 2011, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 248, 2931, DOI: 10.1002/pssb.201147124

In this paper we present electron paramagnetic resonance (EPR) and Mossbauer (transmission method, TMS and measurements in the scattering method, CEMS) experiments on Fe-57 (0.11at.%) doped nanocrystalline anatase-type TiO2, synthesized by a hydrothermal method. Different Fe3+ and Fe2+ ions positions, with various hyperfine interactions evidenced in Mossbauer spectra (MS), confirm a partial magnetic ordering at room temperature. The magnetic hyperfine fields in the TMS spectra, better resolved at lower temperatures, do not change essentially with temperature. The first CEMS measurements, carried out on iron-doped TiO2 nanoparticles, reveal a larger disorder in the surface particles layer. The temperature dependence of the double integral EPR spectral intensity, proportional with the sample susceptibility, shows an anomalous behaviour. It suggests the bound magnetic polaron (BMP) mechanism for the magnetic ordering.

1903. Introduction of the Ge nanostructures in a Si matrix via nanosphere lithography deposition

Authors: Ulmeanu, M; Ghica, C

Published: MAR 2011, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 5, 280, DOI:

Experimental studies on patterning hexagonal Ge nanostructures have been conducted on Si substrates through deposition of Ge with polystyrene spheres as a mask. The size distribution of the patterned Ge nanostructures is narrow with the full width at half maximum being less than 10% of the dot size. The two-dimensional patterned Ge nanostructures were further introduced in a Si matrix. Cross-section transmission electron microscopy reveals periodic dark stripes representing the deposited Ge dots in an a-Si matrix.

1904. From synthetic to natural nanoparticles: monitoring the biodegradation of SPIO (P904) into ferritin by electron microscopy

Authors: Lopez-Castro, JD; Maraloiu, AV; Delgado, JJ; Calvino, JJ; Blanchin, MG; Galvez, N; Dominguez-Vera, JM

Published: 2011, NANOSCALE, 3, 4599, DOI: 10.1039/c1nr10980d

A strong focus on Superparamagnetic Iron Oxide Nanoparticles (SPIOs) has been appreciated recently especially for their use in Magnetic Resonance Imaging (MRI). However, some questions are being raised over these particles due to their long-term toxicity related to the production of toxic free iron during their biodegradation. Here we show by Electron Microscopy how SPIOs (P904) (Guerbet, Paris) are degraded after they are taken up by macrophages, so that iron from the SPIO core is progressively incorporated into the iron-storing protein ferritin (a nontoxic form of iron).

1905. ZERO-ORDER RESONANT METAMATERIAL ANTENNA

Authors: Ochetan, AB; Banciu, MG; Lojewski, G

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 192, DOI:

In this paper we present a resonant antenna based on a composite right/left handed metamaterial structure. The antenna is designed to operate at the zero-order resonance. The antenna was fabricated and used in measuring the coverage of a UMTS cell.

1906. Stability Characterization of Quinazoline Derivative BG1188 by Optical Methods

Authors: Militaru, A; Smarandache, A; Mahamoud, A; Damian, V; Ganea, P; Alibert, S; Pages, JM; Pascu, ML

Published: 2011, ADVANCES IN LASEROLOGY - SELECTED PAPERS OF LASER FLORENCE 2010: THE 50TH BIRTHDAY OF LASER MEDICINE WORLD, 1364, 23, DOI: 10.1063/1.3626907

3-[2-(dimethylamino) ethyl]-6-nitroquinazolin-4(3H)-one, labeled BG1188, is a new synthesized compound, out of a series of quinazoline derivatives developed to fight the multidrug resistance of antibiotics acquired by bacteria. A characterization of the BG1188 powder was made using FTIR spectra in order to evidence the functional groups in the medicine's molecule. The ultraviolet-visible (UV-Vis) absorption spectra were used to study the stability of the BG1188 solutions in two solvents and at different temperatures. BG1188 concentration in ultrapure water was varied between 2x10(-3)M (stock solution) and 10(-6)M. The concentration recommended by higher activity on bacteria was 10(-3)M. For the same reason, this was the utilized concentration of BG1188 in dimethyl sulfoxide (DMSO). Time stability was characterized by comparing the time evolution of the UV-Vis absorption spectra of the BG1188 solutions in ultrapure deionized water or in DMSO. The spectra were recorded daily for about 4 months after the preparation for the BG1188 solutions in ultrapure water. Generally, samples are stable within the experimental errors at concentrations higher than 10(-5)M, but the stability time interval may vary from 119 days at 10(-4)M to 34 days at 10-5M. Time evolution of the absorption spectra at 10-3M in ultrapure water shows reproducibility within the measuring errors (+/- 1.045%) for time intervals up to 1032 hours (more than 40 days) after preparation. On the other hand, BG1188 solutions in DMSO may be considered unstable because the absorption spectra modify in terms of peak shapes and intensities, indicating that the samples exhibit modifications immediately after preparation. Regardless the solvent used, some aggregation phenomena took place and wire-like aggregates were observed in all the solutions with the naked eye. These aggregates were analyzed, tentatively, using optical microscopy and FTIR.

1907. Abnormal anti-Stokes Raman emission as a coherent anti-Stokes Raman scattering-like process in disordered media

Authors: Baltog, I; Baibarac, M; Smaranda, I; Lefrant, S

Published: MAY 14 2011, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, 44, DOI: 10.1088/0953-4075/44/9/095401

In this paper, we demonstrate that, by continuous single beam excitation, one can generate an abnormal anti-Stokes Raman emission (AASRE) whose properties are similar to a coherent anti-Stokes Raman scattering (CARS). The effect has been observed in materials which possess intrinsically nonlinear properties (LiNbO(3) and CdS), which have the electric susceptibility of third order different from zero, chi((3)) not equal 0, as well as in materials that become nonlinear under resonant optical excitation. In the latter case, we used poly-3,4-ethylendioxythiophene (PEDOT) in its undoped state deposited electrochemically on Au support. Raman studies corroborated with images of optical microscopy demonstrate that the production of AASRE is conditioned by the existence of a particular morphology of the sample able to ensure efficient transport of the light inside the sample through a multiple light scattering mechanism. In this context, it was found that LiNbO3 and CdS in powder form as well as the PEDOT films layered on a rough Au substrate are suitable morphological forms. We explain AASRE as resulting from a wave-mixing mechanism of the incident laser light omega(l) with a Stokes-shifted Raman light omega(S) produced by a spontaneous Raman light scattering process, both strongly scattered inside the sample. As a CARS process, AASRE is conditioned by the achievement of phase-matching requirements, which makes the difference between the wave vectors of mixing light close to zero, Delta k = /2k(l) - k(S) - k(CARS) /approximate to 0. In condensed media, the small dispersion of the refractive index makes Delta k approximate to 0 so that the formation of a favourable phase-matching geometry may be accomplished even at a crossing angle. of travelling scattered light omega(l) and omega(S). For tightly focused beams, the requirement of phase matching relaxes; it is no longer sensitive to the Raman shift, so that a wide intense anti-Stokes Raman spectrum is observed at an angle larger than the Stokes Raman spectrum.

1908. Characterization of Sucrose Thin Films for Biomedical Applications

Authors: Iconaru, SL; Ungureanu, F; Costescu, A; Costache, M; Dinischiotu, A; Predoi, D

Published: 2011, JOURNAL OF NANOMATERIALS, 2011, DOI: 10.1155/2011/291512

Sucrose is a natural osmolyte accumulated in the cells of organisms as they adapt to environmental stress. In vitro sucrose increases protein stability and forces partially unfolded structures to refold. Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by the thermal evaporation technique (P similar to 10(-5) torr). Characteristics of thin films were put into evidence by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and differential thermal analysis and thermal gravimetric analysis (TG/DTA). The experimental results confirm a uniform deposition of an adherent layer. In this paper we present a part of the characteristics of sucrose thin films deposited on glass in medium vacuum conditions, as a part of a culture medium for osteoblast cells. Osteoblast cells were used to determine proliferation, viability, and cytotoxicity interactions with sucrose powder and sucrose thin films. The osteoblast cells have been provided from the American Type Culture Collection (ATCC) Centre. The outcome of this study demonstrated the effectiveness of sucrose thin films as a possible nontoxic agent for biomedical applications.

1909. Piezoelectric BNT-BT0.11 thin films processed by sol-gel technique

Authors: Cernea, M; Galca, AC; Cioangher, MC; Dragoi, C; Ioncea, G

Published: SEP 2011, JOURNAL OF MATERIALS SCIENCE, 46, 5627, DOI: 10.1007/s10853-011-5512-x

0.89(Na0.5Bi0.5)TiO3-0.11BaTiO(3), (BNT-BT0.11) thin film was fabricated by sol-gel/spin coating process, on platinized silicon wafer. Perovskite structure with random orientation of crystallites has been obtained at 700 A degrees C. Piezoelectric activity of BNT-BT0.11 thin film was detected using piezoresponse force microscopy (PFM). Effective piezoelectric coefficient d (33eff) of such film, recorded at 5 V applied dc voltage, was similar to 29 pm/V, which is similar to other BNT-BT (x) thin films. The complex refractive index and dielectric function of BNT-BT0.11 thin films were also investigated. The high leakage current density significantly influences the dielectric, ferroelectric, and piezoelectric properties of the BNT-BT0.11 films.

1910. Effect of maleic anhydride-aniline derivative buffer layer on the properties of flexible substrate heterostructures: Indium tin oxide/nucleic acid base/metal

Authors: Stanculescu, A; Socol, M; Socol, G; Mihailescu, IN; Girtan, M; Preda, N; Albu, AM; Stanculescu, F

Published: DEC 1 2011, THIN SOLID FILMS, 520, 1258, DOI: 10.1016/j.tsf.2011.04.204

This paper presents some investigations on the properties of guanine (G) and cytosine (C) based heterostructures deposited on flexible substrates. The effects of two types of maleic anhydride-aniline derivatives (maleic anhydride-cyano aniline or maleic anhydride-2,4 dinitroaniline) buffer layer, deposited between indium tin oxide and (G) or (C) layer, on the optical and electrical properties of the heterostructures have been identified. The heterostructures containing a film of maleic anhydride-2,4 dinitroaniline have shown a good transparency and low photoluminescence invisible range. This buffer layer has determined an increase in the conductance only in the heterostructures based on (G) and (C) deposited on biaxially-oriented polyethylene terephthalate substrate. (C) 2011 Elsevier B. V. All rights reserved.

1911. Structural and thermoluminescence properties of undoped and Fe-doped-TiO2 nanopowders processed by sol-gel method

Authors: Cernea, M; Secu, M; Secu, CE; Baibarac, M; Vasile, BS

Published: JAN 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 85, DOI: 10.1007/s11051-010-0002-7

In this study, we report on the nanocrystalline powders of TiO2 and Fe-doped TiO2 (anatase and rutile phases) prepared by sol-gel method. The X-ray diffraction and Raman spectroscopy measurements indicated the presence of anatase or rutile phase in nanopowders. TEM micrographs showed 10 and 112 nm average particle sizes for anatase and rutile, respectively. Furthermore, their thermoluminescence properties were analyzed.

1912. TAILORING OF OPTICAL, COMPOSITIONAL AND ELECTRICAL PROPERTIES OF THE InxZn1-xO THIN FILMS OBTAINED BY COMBINATORIAL PULSED LASER DEPOSITION

Authors: Socol, G; Galca, AC; Luculescu, CR; Stanculescu, A; Socol, M; Stefan, N; Axente, E; Duta, L; Mihailescu, CM; Craciun, V; Craciun, D; Sava, V; Mihailescu, IN

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 115, DOI:

Indium Zinc Oxide compositional libraries were fabricated by combinatorial pulsed laser deposition technique on glass substrate at room temperature. Two pairs of targets with In atomic concentrations, In/(In+Zn), of 28 at.% and 56 at.% or 42 at.% and 70 at.% were employed. A high transparency was observed for all the coatings with transmittance values better than 95%. The maximum thicknesses of the samples, inferred by spectroscopic ellipsometry, were within the 174-310 nm range for the simple PLD films, whereas in case of combinatorial PLD coatings were 341 or 467 nm. Energy dispersive X-ray spectroscopy revealed that In content in the combinatorial films was in the 27-52 at. % range. From atomic force microscopy histograms we evidenced a decrease of the RMS roughness down to 1 nm with the increase of the In content. As a result of the compositional library studies two minimum values of the electrical resistivity were identified at 2.3x10(-3) Omega.cm and 8.6 x 10(-4) Omega.cm, which correspond to 28.8-29.5 at.% and 44-49 at% range of Indium content.

1913. NON-LINEAR BEHAVIOUR IN SILVER - ARSENIC SULFIDE SYSTEM

Authors: Popescu, M; Lorinczi, A; Gherendi, F; Nistor, M; Velea, A; Simandan, ID; Sava, F

Published: NOV-DEC 2011, JOURNAL OF OVONIC RESEARCH, 7, 133, DOI:

Non-linear phenomena have been observed in the Ag(paint)-As2S3 system. This behaviour is useful in rectifier devices and in dynamical switching devices based on chalcogenides.

1914. LUMINESCENCE OF ARSENIC SULPHIDE DOTS DOPED WITH EUROPIUM, PREPARED BY THERMAL EVAPORATION AND PULSED LASER DEPOSITION METHODS

Authors: Popescu, M; Velea, A; Simandan, ID; Sava, F; Lorinczi, A; Ghervase, L; Pavelescu, G; Mihailescu, IN; Socol, G; Georgescu, S

Published: DEC 2011, CHALCOGENIDE LETTERS, 8, 724, DOI:

Networks of dots made of As2S3 chalcogenide has been obtained by Vacuum Evaporation and Pulsed Laser Deposition from bulk glassy As2S3 by the adapted method of SCEV (screen evaporation method). A very thin layer of Eu2O3 was deposited from a different target in the final deposition process. After a heat treatment at 180 degrees C for 90 minutes in nitrogen atmosphere a structural transformation of the amorphous As2S3 to realgar (AsS) occurred in the PLD deposited dots and the network of dots develops a luminescence effect. (Received November 25, 2011; accepted December 2, 2011)

1915. Study of electrodeposition of (Bi,Sb)(2)Te-3 nanowires by voltammetric methods and electrochemical impedance spectroscopy

Authors: Sima, M; Vasile, E; Sima, M

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1602, DOI:

Nanostructured thermoelectric semiconductors are a promising material to convert waste heat to electricity for energy regeneration due to improvement of Seebeck coefficient and thermal conductivity reducing. Among various thermoelectric materials, bismuth telluride based alloys are the most used in the fabrication of TE devices. The processes associated with the electrodeposition of (Bi,Sb)(2)Te-3 nanowires and films are reported along with an analysis of the composition, morphology and structure of resulting materials. Electrochemical behavior was examined using cyclic and linear voltammetry and electrochemical impedance spectroscopy techniques.

1916. Synthesis and dielectric characterization of Ba0.6Sr0.4TiO3 ferroelectric ceramics

Authors: Nedelcu, L; Ioachim, A; Toacsan, M; Banciu, MG; Pasuk, I; Berbecaru, C; Alexandru, HV

Published: JUN 30 2011, THIN SOLID FILMS, 519, 5815, DOI: 10.1016/j.tsf.2010.12.191

Ferroelectric ceramics Ba0.6Sr0.4TiO3 (BST 40) were prepared, by solid-state reaction in the temperature range 1210-1450 degrees C. Maximum values of the ceramic densities were around 94% of their theoretical value. X-ray diffraction techniques (XRD) and scanning electron spectroscopy (SEM) were used to analyze the structure and the surface morphology of ceramics. Rounded, well defined or abnormal granular growth was observed in the SEM images, vs. sintering conditions and purity of the raw materials. In all samples, BST 40 ceramic is the major phase, but there are also present small amounts of secondary phases, as revealed in XRD diffraction patterns. Permittivity and dielectric loss measurements were performed in the temperature range - 150 to + 150 degrees C, and 150 Hz-5 MHz frequency values. Permittivity values rising from 1200 to 12,500, with increasing sintering temperatures, were recorded. Narrow and well defined transition peaks were noticed at higher sintering temperatures. Curie temperature was around 2 degrees C, for samples with the mentioned composition. Permittivity and losses vs. frequency show different behavior whether BST ceramics are in polar or non-polar state and with the distance toward phase transition. Microwave measurements performed at room temperature have shown lower values of permittivity, compared with similar data at low frequency, and dielectric losses lower than 1% at 0.7 GHz. The sintering conditions (temperatures, sintering time, etc.) and purity of the raw materials lead to important changes of transition temperatures in the polymorphic diagram, which we have built-for the other Ba1 - xSrxTiO(3) compositions (x = 0.25-0.90) sintered at 1260 degrees C for 2 h. (C) 2011 Elsevier B.V. All rights reserved.

1917. Magnetic Characterization of MgB2 Bulk Superconductor for Magnetic Field Mitigation Solutions

Authors: Gozzelino, L; Minetti, B; Gerbaldo, R; Ghigo, G; Laviano, F; Lopardo, G; Plapcianu, C; Agostino, A; Cagliero, S; Truccato, M; Zilberti, L; Mezzetti, E

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 312, DOI: 10.1007/s10948-010-0993-4

Magnetic shielding properties of MgB2 bulk samples synthesized by the SPS (Spark-Plasma-Sintering) technique were characterized in low applied magnetic fields at temperatures ranging from 20 to 37 K. The used growth technique allows one to produce this compound in different shapes and sizes required for shielding applications. In this framework, shielding magnetic-induction field profiles generated by MgB2-based shield components, shaped as planar thick disks, were measured by means of a suitable Hall probe in-plane array. The magnetic field distribution at different vertical distances above the sample was also obtained by a micrometric motion of the probe ensemble. Magnetic field profiles were then analyzed in the framework of the critical state model and the critical current density, J (c) , was evaluated. The J (c) magnitude indicates that the material under test is a good candidate for passive magnetic shield manufacturing up to temperatures close to the transition one.

1918. Local Structure at Mn2+ Ions in Vacuum Annealed Small Cubic ZnS Nanocrystals Self-Assembled Into a Mesoporous Structure

Authors: Nistor, SV; Ghica, D; Nistor, LC; Stefan, M; Mateescu, CD

Published: OCT 2011, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 11, 9303, DOI: 10.1166/jnn.2011.4306

A mesoporous structure of self-assembled nanocrystals of cubic ZnS doped with Mn2+ ions with a homogeneous distribution of pores of similar size was synthesized at room temperature by a surfactant-assisted liquid-liquid reaction. The component nanocrystals exhibit a high crystallinity and a tight size distribution centered at 2 nm, as well as the narrowest Electron Paramagnetic Resonance (EPA) spectra linewidth and the best resolution reported so-far, effects attributed to self-assembling. The observed EPA spectra consist of lines from the substitutional Mn2+(I) and surface Mn2+(II) and Mn2+(III) centers. Here we show that, in contrast with previous reports, our EPA spectra are highly sensitive to structural changes during pulse annealing in vacuum up to 500 degrees C. The changes are related to the transformation of the surface Mn2+ centers in new Mn2+ centers, attributed to an oxidation process in which the thermal decomposition of the Tween 20 additive, also observed by EPA, seems to be involved. We have also been able to observe, for the first time by EPR spectroscopy, the formation of the ZnO phase and the nanocrystals size increase, which occur during annealing up to 500 degrees C, structural changes confirmed by XRD and TEM observations on the samples previously investigated by EPR.

1919. Solid-state synthesis and spark plasma sintering of SrZrO3 ceramics

Authors: Popescu, B; Enache, S; Ghica, C; Valeanu, M

Published: JUN 2 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 6399, DOI: 10.1016/j.jallcom.2011.03.009

SrZrO3 powders are obtained by solid state reaction from SrCO3 and ZrO2 precursors, without involving intermediate calcination and grinding steps. The resulted powders are essentially within a single phase, with sub-micron average crystallite size. Pellets of these powders show a relatively poor sintering behavior, when fired up to 1600 degrees C. Alternatively, spark plasma sintering technique is used in order to obtain nearly 100% dense samples at the expense of excessive grain coarsening (i.e., up to 5 mu m in diameter). Crystalline structure, composition and morphology of the specimens obtained in this work are investigated by X-ray diffraction, scanning and transmission electron microscopy together with energy dispersive X-ray spectroscopy. (C) 2011 Elsevier B.V. All rights reserved.

1920. Microwave properties of Ba(Zn1/3Ta2/3)O-3 dielectric resonators

Authors: Nedelcu, L; Toacsan, MI; Banciu, MG; Ioachim, A

Published: JAN 12 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 481, DOI: 10.1016/j.jallcom.2010.09.069

Ba(Zn1/3Ta2/3)O-3 (BZT) dielectric resonators were prepared by solid-state reaction. The starting materials were BaCO3, ZnO, and Ta2O5 powders with high purity. The double calcined BZT pellets were sintered in air at temperatures of 1575, 1600, 1625, and 1650 degrees C for 4 h. The X-ray diffraction data allowed the study of the unit cell distortion degree and the presence of the secondary phases. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was observed with the increase of the sintering temperature. The dielectric constant of BZT resonators measured around 6 GHz was between 26 and 28. High values of Q x f product (120 THz) were obtained for BZT resonators sintered at 1650 degrees C/4 h. The temperature coefficient of the resonance frequency exhibits positive values less than 6 ppm/degrees C. The achieved dielectric parameters recommend BZT dielectric resonators for microwave and millimeter wave applications. (C) 2010 Elsevier B.V. All rights reserved.

1921. STUDY OF Ge NANOPARTICLES EMBEDDED IN AN AMORPHOUS SiO2 MATRIX WITH PHOTOCONDUCTIVE PROPERTIES

Authors: Lepadatu, AM; Stavarache, I; Stoica, TF; Ciurea, ML

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 73, DOI:

Electrical and photoconductive properties of films consisting of amorphous Ge nanoparticles uniformly distributed in amorphous SiO2 were studied. These films were prepared by sol-gel method and treated by rapid thermal annealing technique. Measurements of current-voltage and conductance-temperature characteristics, spectral and bias dependences of the photocurrent on samples with coplanar geometry of electrodes, were performed. The current-voltage characteristics have a weak rectifying behaviour. The variable range hopping transport mechanism, described by the Mott law, in amorphous materials, in the absence of dominant Coulomb interactions, was evidenced in the temperature dependence of the dark current. The samples exhibit very good photoconductive properties, explained by taking into account the Ge clusters and defects, produced by the rapid thermal annealing.

1922. PREPARATION INDUCED ELECTRICAL BEHAVIOUR OF GeSiO NANOSTRUCTURES

Authors: Stavarache, I; Lepadatu, AM; Ciurea, ML

Published: 2011, 2011 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS 2011), 34TH EDITION, VOLS 1 AND 2, 34, DOI:

GeSiO nanostructures obtained by using two different preparation methods, sol-gel and magnetron-sputtering were studied. They are formed from Ge nanoparticles dispersed in amorphous matrix, with different morphology depending on the preparation method. Electrical investigations (current-voltage and current-temperature measurements) were performed and experimental results were modelled. It was shown that preparation conditions induce the electrical behaviour of GeSiO films, so that the electrical transport in sputtered films is governed by a hopping mechanism, while in sol-gel ones it is dominated by the junction formed at the interface with Si substrate. Also, the temperature dependence of current shows different hopping mechanisms.

1923. Maleic Anhydride Copolymers with Ability to Bind Metal Ions. 1. Polydentate Amine Derivatives for Cr (III) Ions' Removal

Authors: Albu, AM; Mocioi, M; Mateescu, CD; Iosif, A

Published: AUG 15 2011, JOURNAL OF APPLIED POLYMER SCIENCE, 121, 1874, DOI: 10.1002/app.33668

New polymeric chelate structures derived from maleic anhydride-dicyclopentadiene copolymer (MA-DCPD) were synthesized by chemical modifications with triethylenetetramine ( TETA), from Riedel De HaSn AG Seelze, Hannover. Germany. Both amide and imide forms of these new polymers have been tested in the retention process of Cr (III) ions. Experimental results referring mainly to the retention capacity and retention efficiency, for different values of the working parameters: contact procedure, batch time, concentration of chelators, and pH, are presented. The polymer structures and their metal complexes were characterized by IR spectroscopy. IR spectra proved that the metal was coordinated by nitrogen from TETA. The thermal properties of modified polymers and polychelates were also examined. Based on these experimental results and literature data, we discuss a possible binding mechanism and suggest the polychelate structures. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:1867-1874, 2011

1924. New structural features of non-crystalline tetrahedrally bonded networks A modeling approach

Authors: Sava, F; Popescu, M

Published: JUL 1 2011, JOURNAL OF NON-CRYSTALLINE SOLIDS, 357, 2554, DOI: 10.1016/j.jnoncrysol.2011.02.056

A large model of amorphous silicon (2052 atoms) with 0.5% dangling bonds has been built and investigated. The refinement of the coordinates evidenced the presence of small domains with advanced ordering. These domains preclude the formation of crystallization nuclei and play an essential role in the redistribution of the defects in the material with homogenization of the free energy and stabilization against aging. An effect of amorphization of the ordered nuclei due to free energy redistribution is assessed. The glass relaxation of a-Si (a-Ge) occurring during heating below T(g) receives a natural explanation as a structural change from local quasi-ordering to homogeneous disordering. (C) 2011 Elsevier B.V. All rights reserved.

1925. (Ti,Cr,Nb)CN coatings deposited on nitrided high-speed steel by cathodic arc method

Authors: Braic, M; Braic, V; Balaceanu, M; Vladescu, A; Zoita, CN; Lungu, CP; Grigorescu, CEA; Grigore, E; Logoftu, C

Published: JUL 25 2011, SURFACE & COATINGS TECHNOLOGY, 205, S213, DOI: 10.1016/j.surfcoat.2011.03.030

The combined processes of plasma nitriding and cathodic arc deposition of (Ti,Cr,Nb)CN coatings were applied to HSS substrates. The nitrided layers, obtained in a mixture of H-2 (70%) and N-2 (30%) at two different temperatures (480 degrees C and 510 degrees C), were examined for the microhardness depth profiles. Characterization of the duplex coatings was performed by investigating elemental and phase composition, texture, hardness, friction and wear. XRD and XPS analyses revealed the formation of a mixture of a carbonitride fcc solid solution, in a dominant proportion, and metallic chromium. The film hardness was measured to be similar to 34 GPa. The duplex (Ti,Cr,Nb)CN coatings exhibited superior tribological behavior as compared to both nitrided layers and non-duplex coatings. (C) 2011 Elsevier B.V. All rights reserved.

1926. Nanoparticles size effects in thermoluminescence of oxyfluoride glass-ceramics containing Sm3+-doped CaF2 nanocrystals

Authors: Secu, M

Published: JUL 2011, JOURNAL OF NANOPARTICLE RESEARCH, 13, 2732, DOI: 10.1007/s11051-010-0181-2

Oxyfluoride glass-ceramic in the system SiO2-Al2O3-CaF2-SmF3 containing Sm3+-doped CaF2 nanocrystals in the range from 15 to 150 nm size were produced by using the controlled ceramization of the precursor glass. The incorporation of the Sm3+-dopant ion in the glass ceramic creates new electron-trapping centers and thermoluminescence (TL) method has been used in order to trace their evolution during glass ceramization. The 370 A degrees C TL peak observed in precursor glass has been assigned to the recombination of the electrons released from the Sm2+-traps in the amorphous glass network. In the glass-ceramic sample containing nanocrystals with about 15 nm size the new weak TL peaks at 270, 290, and 310 A degrees C were attributed to the recombination of the electrons released from the Sm2+-traps located mainly at the surface of the CaF2 nanocrystals. In the glass-ceramic sample containing nanocrystals with about 150 nm size, the new TL peaks at 232, 270, and 302 A degrees C size have been assigned to the recombination of the electrons released from the Sm2+-traps located inside the CaF2 nanocrystals.

1927. SIMULTANEOUSLY THERMIONIC VACUUM ARC DISCHARGES IN OBTAINING FERROMAGNETIC THIN FILMS

Authors: Jepu, I; Porosnicu, C; Mustata, I; Lungu, CP; Kunkser, V; Osiac, M; Iacobescu, G; Ionescu, V; Tudor, T

Published: 2011, ROMANIAN REPORTS IN PHYSICS, 63, 816, DOI:

High quality granular ferromagnetic thin films on glass and silicon wafer substrates were obtained using the original thermionic vacuum arc (TVA) method developed at National Institute for Laser, Plasma and Radiation Physics. We report obtaining of 77-200 nm thick Cu/Ni/Fe structures. An experimental set-up, with three simultaneously discharges, was made to obtain the desired thin film composition and thickness. The structural and morphological properties of the prepared nanostructured films were analyzed by AFM (Atomic Force Microscopy), XRD (X-ray Diffraction) and SEM (Scanning Electron Microscopy). Magneto-Optical Kerr Effect studies were made in order to infer the changes in polarization of an optical radiation due to the magnetic field influence. In order to obtain concluding electrical measurements results, cooper electrodes were deposited using the same method before and after the actual three material thin structures. In this way significant changes in the electrical resistance behavior were noticed and were correlated with TVA plasma parameters used for film preparation.

1928. Synergetic Pinning Centers in YBa2Cu3OX Films Through a Combination of Ag Nano-Dot Substrate Decoration, Ag/YBCO Quasi-Multilayers, and the Use of BaZrO3-Doped Target

Authors: Mikheenko, P; Dang, VS; Kechik, MMA; Sarkar, A; Paturi, P; Huhtinen, H; Abell, JS; Crisan, A

Published: JUN 2011, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 21, 3188, DOI: 10.1109/TASC.2010.2086041

We report on an original technique for nanoengineered pinning centers that combine three previously reported approaches: substrate decoration, quasi-multilayers and targets with secondary phase nanoinclusions. We have used a 4% BZO-doped YBCO target, and Ag nanodots, all grown by PLD. Such an approach gave interesting results in terms of pinning landscape, as proved by TEM studies. Angle-dependent measurements of critical current I-c showed that, for smaller fields, the absolute maximum in I-c occur for fields perpendicular to the a-b planes, while at larger fields the absolute maximum in I-c occurs for fields parallel to the a-b planes, in both cases with a clear second, local maxima. Measurements also showed a smooth change in the character of pinning with magnetic field, from the out-of-plane to in-plane-dominant pinning. For the out-of-plane magnetic field, the highest Ic-w (critical current per cm width) obtained so far, at 77.3 K, occurred in a 5.8 mu m Ag nanodots / BZO-doped YBCO trilayer: 782 A/cm-w in self-field, 167 A/cm-w in 1 T and 18 A/cm-w in 3 T.

1929. Dielectric and Ferroelectric Characterization of Ba0.95Tm0.05TiO3 Ceramics Derived from Sol to Gel

Authors: Cernea, M; Vasile, BS; Ganea, P; Radu, R; Mihalache, V; Husanu, A

Published: MAR 2011, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94, 741, DOI: 10.1111/j.1551-2916.2010.04179.x

Barium titanate (BaTiO3) has been doped in situ with 5 mol% thulium by a sol-gel method. The as-prepared gel powder consists of nanosized grains (20-30 nm) and crystallizes on the cubic BaTiO3 lattice, at 700 degrees C. Ba0.95Tm0.05TiO3 ceramics derived from this powder have tetragonal perovskite structure and contain a small amount of Tm2Ti2O7 pyrochlore phase. These ceramics exhibit dielectric constants of 4282-3240 and dielectric loss (tan delta) of 0.1077-0.0161 at Curie temperature T-c=132 degrees C and at 10 Hz-100 kHz, respectively. For a drive voltage of 400 V, the hysteresis loop recorded at the frequency of 100 Hz shows a remnant polarization (P-r) value of 76 mu C/cm2 and a coercive field (E-c) of 124 V and for 1 kHz a remnant polarization (P-r) value of 58 mu C/cm2 and a coercive field (E-c) of 116 V.

1930. ELECTRICAL PROPERTIES OF (Zn,Cu)O:Mn SUBMICRON WIRES

Authors: Ion, L; Antohe, S; Sima, A; Sima, M

Published: OCT-DEC 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 1700, DOI:

Arrays of multisegment Pd/(Zn,Cu)O:Mn/Pd submicron wires have been grown electrochemically into the pores of nuclear track polycarbonate membranes. Their transport properties were investigated, by measuring current-voltage (I-V) characteristics in a temperature range from 300 K down to 40 K. I-V characteristics of Pd/(Zn,Cu)O:Mn/Pd wires exhibited a symmetric, non-linear shape on applied bias voltage ranging from -20 V to +20V. The ohmic region corresponds to polarization voltage under 3.5V. Comparatively, I-V characteristics of Pd/ZnO/Pd array of wires with diameter about 500 nm are linear in the entire range of applied voltages (-20 V to +20V).

1931. Tailoring immobilization of immunoglobulin by excimer laser for biosensor applications

Authors: Sima, F; Axente, E; Ristoscu, C; Mihailescu, IN; Kononenko, TV; Nagovitsin, IA; Chudinova, G; Konov, VI; Socol, M; Enculescu, I; Sima, LE; Petrescu, SM

Published: FEB 2011, JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 96A, 394, DOI: 10.1002/jbm.a.32991

The sheltered transfer and immobilization of rabbit anti-human antiserum immunoglobulin G (IgG) by matrix-assisted pulsed laser evaporation (MAPLE) are reported. The iced targets submitted to laser irradiation consisted of 0.2-2 mg/mL IgG blended or not with lipid (L-a-phosphatidylcholine dipalmitoyl) dissolved in distilled water-based saline buffer. Thin IgG coatings were obtained at room temperature onto glass, fused silica, or silicon substrates. Ten thousand subsequent laser pulses of 0.33, 0.5, or 0.67 J/cm(2) fluence were applied for the synthesis of each sample. Morphology and composition of the thin films were studied by optical, scanning, and atomic force microscopy and Fourier transformed infrared spectrometry. Optical labeling methods such as spectrofluorimetry and fluorescence microscopy were selected to verify the biosensor transduction principle because of their high sensitivity for detecting low amounts of antigen (IgG). Protein immobilization to the substrate surface was demonstrated for all obtained structures after immersion in the donkey anti-rabbit secondary antibody solution. The IgG transfer and immobilization onto substrates were improved by addition of lipid to MAPLE solutions. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 384-394, 2011.

1932. Ba(Ti1-xSnx)O-3 (x=0.13) nanomaterials produced by low-temperature aqueous synthesis

Authors: Cernea, M; Trusca, R; Radu, R; Valsangiacom, C

Published: OCT 13 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 9937, DOI: 10.1016/j.jallcom.2011.07.101

BaTi0.87Sn0.13O3 (BTS13) nanopowder was prepared by low-temperature aqueous synthesis (LTAS) method. The evolution of the structure and microstructure of the precursor precipitate, heated at temperatures up to 1000 degrees C was studied by TGA, FT-IR, SEM and XRD techniques. The dried precipitate showed a microstructure consisting of nano-sized grains (similar to 40 nm) with great tendency to agglomeration. BaTi0.87Sn0.13O3 single phase was obtained at 800 degrees C. The ceramics prepared from as-obtained BTS13 powders (60-70 nm) show good dielectric and ferroelectric characteristics. The dielectric constant was about 4800 and the dielectric loss (tan delta) was 0.229 at 1 kHz and at the Curie temperature (31 degrees C). The remanent polarization (P-r) and the coercive field (E-C) of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were P-r = 13 mu C/cm(2) and E-C = 0.89 kV/cm. The ferroelectric parameters E-C and P-r decrease with increasing frequency in the domain 100 Hz to 10 kHz. (C) 2011 Elsevier B.V. All rights reserved.

1933. Synthesis of ZnO thin films by 40 ps @ 532 nm laser pulses

Authors: Ristoscu, C; Socol, M; Socol, G; Mihailescu, IN; Jafer, R; Al-Hadeethi, Y; Batani, D

Published: SEP 2011, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 104, 876, DOI: 10.1007/s00339-011-6429-6

The synthesis by pulsed laser deposition of ZnO thin films with a Nd:YAG laser system delivering pulses of 40 ps @ 532 nm is reported. The laser beam irradiated the target placed inside a vacuum chamber evacuated down to 1.33x10(-1) Pa. The incident laser fluence was of 28 J/cm(2) in a spot of 0.1 mm(2). The ablated material was collected onto double face polished (111) Si or quartz wafers placed parallel at a separation distance of 7 mm. The AFM, SEM, UV-Vis, FT-IR and absorption ellipsometry results indicated that we obtained pure ZnO films with a rather uniform surface, having an average roughness of 37 nm. We observed by SEM that particulates are present on ZnO film surface or embedded into bulk. Their density and dimension were intermediary between particulates observed on similar structures deposited with fs or ns laser pulses. We noticed that the density of the particulates is increasing while their average size is decreasing when passing from ns to ps and fs laser pulses. The average transmission in the UV-Vis spectral region was found to be higher than 85%.

1934. Electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride

Authors: Stavarache, I; Lepadatu, AM; Teodorescu, VS; Ciurea, ML; Iancu, V; Dragoman, M; Konstantinidis, G; Buiculescu, R

Published: 2011, NANOSCALE RESEARCH LETTERS, 6, DOI: 10.1186/1556-276X-6-88

The electrical behavior of multi-walled carbon nanotube network embedded in amorphous silicon nitride is studied by measuring the voltage and temperature dependences of the current. The microstructure of the network is investigated by cross-sectional transmission electron microscopy. The multi-walled carbon nanotube network has an uniform spatial extension in the silicon nitride matrix. The current-voltage and resistance-temperature characteristics are both linear, proving the metallic behavior of the network. The I-V curves present oscillations that are further analyzed by computing the conductance-voltage characteristics. The conductance presents minima and maxima that appear at the same voltage for both bias polarities, at both 20 and 298 K, and that are not periodic. These oscillations are interpreted as due to percolation processes. The voltage percolation thresholds are identified with the conductance minima.

1935. Chemically Modified (Nano)Silica as Sensitive Material for Arginine and Lysine

Authors: Tudose, M; Culita, D; Marinescu, G; Ghica, C; Ionita, P

Published: SEP 2011, JOURNAL OF INORGANIC AND ORGANOMETALLIC POLYMERS AND MATERIALS, 21, 497, DOI: 10.1007/s10904-011-9470-1

Silica has been derivatized with aminopropyl groups which subsequently have been chemically modified with N-methoxy-2,6-dinitroaniline derivatives to yield a solid which changes its color in the presence of arginine or lysine, from yellow to blue. Other amino-acids (such as glycine, valine, cysteine, cystine, alanine, phenylalanine, histidine) do not showed this behavior. The same procedure may be applied to silica nanoparticles. The new materials were characterized by UV-Vis, IR, and TEM.

1936. Non-linear and resonance effects in carbon nanotube structures

Authors: Lefrant, S; Buisson, JP; Mevellec, JY; Baibarac, M; Baltog, I

Published: JUL 2011, OPTICAL MATERIALS, 33, 1414, DOI: 10.1016/j.optmat.2011.03.014

In this paper, we report on Raman scattering and Surface Enhanced Raman Scattering (SERS) studies of single walled carbon nanotubes (SWNTs) and carbon nanotube/conjugated polymers composites. We demonstrate that under SERS conditions we induce an abnormal anti-Stokes Raman emission, that can be interpreted as being due to a "single-beam pumped" Coherent Anti-Stokes Raman Scattering (CARS) effect. We also investigate in detail the anti-Stokes/Stokes (aS/S) intensity ratios of the radial breathing modes (RBMs) of SWNTs as a function of several parameters. From calculations, we show that resonance phenomena mostly explain the aS/S intensity ratio anomalies, but only at low frequencies. In addition, we describe results obtained with polymers like poly(bithiophene) (PBTh) polymerized on carbon nanotube thin films which exhibit also an amplification of its high frequency Raman modes in the anti-Stokes branch, generated by the plasmon excitation of metallic tubes. This phenomenon occurs in several other materials such as composites based on SWNTs and conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) and polyparaphenylene-vinylene (PPV) for modes located around 1500 cm(-1). (C) 2011 Elsevier B.V. All rights reserved.

1937. Growth of highly oriented iridium oxide bottom electrode for Pb(Zr,Ti)O-3 thin films using titanium oxide seed layer

Authors: Trupina, L; Miclea, C; Amarande, L; Cioangher, M

Published: NOV 2011, JOURNAL OF MATERIALS SCIENCE, 46, 6834, DOI: 10.1007/s10853-011-5642-1

Due to its low resistivity and excellent thermal stability, IrO2 has attracted attention as an alternative for electrode material in ferroelectric integrated circuit applications. Oriented growth of IrO2 electrode film was investigated with the goal to control the texture of the PZT thin film. IrO2 films were prepared by DC reactive sputtering. PZT film was prepared by RF magnetron sputtering single target deposition method. The whole layer stack was grown onto amorphous thermal oxide of a silicon wafer. The results indicate that IrO2 thin film was preferentially (200) oriented when a TiO2 seeding layer was used. The orientation relationships along the whole PZT(111)/IrO2(200)/TiO2(200)/Ti structure was discussed.

1938. Hydrogen Generation from Photocatalytic Silver vertical bar Zinc Oxide Nanowires: Towards Multifunctional Multisegmented Nanowire Devices

Authors: Maijenburg, AW; Rodijk, EJB; Maas, MG; Enculescu, M; Blank, DHA; ten Elshof, JE

Published: OCT 4 2011, SMALL, 7, 2713, DOI: 10.1002/smll.201101198

1939. Unusual Behavior of a Novel Heterogeneous Chiral Dimer Cr(III)-Salen Complex in the Epoxidation/Epoxide Ring-Opening Reaction of trans-Methylcinnamate Ester

Authors: Protesescu, L; Tudorache, M; Neatu, S; Grecu, MN; Kemnitz, E; Filip, P; Parvulescu, VI; Coman, SM

Published: FEB 3 2011, JOURNAL OF PHYSICAL CHEMISTRY C, 115, 1122, DOI: 10.1021/jp106281z

A dimer chromium(III)-salen complex immobilized on modified silica is an effective catalyst for the epoxidation/epoxide ring-opening reaction of trans-methylcinnamate ester and gave significantly high ee in methyl (2R,3S)-2,3-dihydroxy-3-phenylpropionate. For the first time, it is shown that a donor ligand (e.g., Et3N) can be involved into the enantioselective mechanism of the product configuration. It is suggested that the additive is interacting with the reaction intermediate in a manner that prolongs its lifetime, thus affording a free rotation of the C-C single bond in this species and a selective collapse to the cis-epoxide product. In the presence of water, this epoxide led to methyl (2S,3R)-2,3-dihydroxy-3-phenylpropionate. Alternatively, the donor additives may give rise to a new chromium-based oxidant that effects epoxidation and its consecutive ring opening to diols via an unusual pathway.

1940. Bean-Livingston surface barriers for flux penetration in Bi2Sr2CaCu2O8+delta single crystals near the transition temperature

Authors: Mihalache, V; Dede, M; Oral, A; Miu, L

Published: OCT 2011, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 471, 565, DOI: 10.1016/j.physc.2011.04.015

The first field for magnetic flux penetration H in Bi2Sr2CaCu2O8+delta (Bi-2212) single crystals near the critical temperature T-c was investigated from the local magnetic hysteresis loops registered for different magnetic field H sweeping rates by using a scanning Hall probe microscope (SHPM) with similar to 1 mu m effective spatial resolution. Evidences for a significant role of the surface barrier were obtained: the asymmetric shape of the magnetization loops and an anomalous change in the slope of H-p(T) close to T-c. (C) 2011 Elsevier B.V. All rights reserved.

1941. Structural changes during the crystallization of the Bi4Ge3O12 glasses

Authors: Polosan, S; Nastase, F; Secu, M

Published: FEB 1 2011, JOURNAL OF NON-CRYSTALLINE SOLIDS, 357, 1113, DOI: 10.1016/j.jnoncrysol.2010.10.016

Bismuth-germanate glass ceramics with the composition 40% Bi2O3-60% GeO2 (in molar percents) were prepared through controlled crystallization of melt-quenched glass. The Raman and FTIR spectra recorded in the as-made glasses show broad bands at 240, 400, 780 cm(-1) and 400, 745 cm(-1) have been assigned Ge-O bonds which appear right after preparation. X-ray diffraction has shown that the as-made glasses are amorphous, but after annealing above the crystallization temperature at 558 degrees C, BGO nano-crystallites with a size of about 50 nm precipitate in the glass matrix. The Raman and FTIR spectra reveal sharp peaks associated to the "internal" and "external vibrations" of GeO4 tetrahedral groups inside the BGO nano-crystallites. In the glass ceramic sample the transparency region is shifted at longer wavelengths compared to as-made glass, due to the Rayleigh scattering on the BGO nano-crystallites. (C) 2010 Elsevier B.V. All rights reserved.

1942. Photoluminescence and Raman studies on tin dioxide powder and tin dioxide/single-walled carbon-nanotube composites

Authors: Gontia, II; Baibarac, M; Baltog, I

Published: JUN 2011, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 248, 1498, DOI: 10.1002/pssb.201046569

Photoluminescence (PL) and Raman spectroscopy were used to characterize the tin dioxide (SnO(2)) powder and the SnO(2)/single-walled carbon-nanotube (SWCNT) composites. The SnO(2) powder shows a strong PL broad band centered at 1.95 eV (635 nm) under excitation at 280 nm (4.43 eV) and four PL bands peaking at: 1.95 eV (635 nm), 2.67 eV (464 nm), 2.82 eV (439 nm), and 2.98 eV (416 nm) under excitation at 350 nm (3.54 eV). PL decay-time measurements of the SnO(2) powder indicates a PL lifetime of about 1.53 ns. In the SnO(2)/SWCNT composites, prepared mechanicochemically, a quenching of PL is observed as the concentration of SWCNT increases. The Raman spectra were recorded at two excitation wavelengths: 514.5 and 676.4 nm. At the excitation wavelength of 676.4 nm (1.83 eV), the Raman spectrum shows a narrowed asymmetric profile of the G band (similar to 1585 cm similar to 1), which indicates that in the SnO(2)/SWCNT composite there is an interaction between SnO(2) and metallic SWCNTs. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

1943. Optical and structural investigations on iron-containing phosphate glasses

Authors: Elisa, M; Iordanescu, R; Sava, BA; Aldica, G; Kuncser, V; Valsangiacom, C; Schinteie, G; Nastase, F; Nastase, C; Bercu, V; Volceanov, A; Peretz, S

Published: MAR 2011, JOURNAL OF MATERIALS SCIENCE, 46, 1570, DOI: 10.1007/s10853-010-4963-9

The article reports the preparation and complex characterization of iron-containing phosphate glasses considered to be ecological materials, as they contain nontoxic compounds related to environment. The oxide system Li2O-MgO-(CaO)-Al2O3-P2O5-(FeO/Fe2O3) was investigated in respect to its structural changes caused by MgO replacement with CaO and by the iron addition. UV-vis-NIR (ultraviolet-visible-near infrared) spectroscopy as well as thermo-gravimetric (TG) measurements, differential thermo-analysis (DTA), X-ray diffraction (XRD) analysis, electronic paramagnetic resonance (EPR), and Mossbauer (nuclear gamma resonance) spectroscopy have been used to investigate redox states and coordination symmetry of iron, together with vitreous network changes during the heat treatment up to 1000 degrees C. UV-vis-NIR transmission spectroscopy revealed no structural modifications when MgO was substituted by CaO, but noteworthy absorption bands attributed to Fe2+/Fe3+ species. TG analysis made in the 20-1000 degrees C range shows low weight loss accompanied by several thermal effects, as evidenced by DTA. XRD patterns for the glass samples heat treated at about 700 degrees C revealed the presence of different phosphate crystalline phases containing Mg, Al, and Fe ions. EPR spectroscopy revealed the presence of paramagnetic Fe3+ ions and the change of the first coordination symmetry, when the samples are heated below the vitreous transition temperature. Mossbauer spectroscopy has evidenced two paramagnetic species, Fe2+ and Fe3+, both in octahedral coordination symmetry and a clustering process supported by only Fe3+ ions.

1944. BIOCOMPATIBILITY STUDY OF EUROPIUM DOPED CRYSTALLINE HYDROXYAPATITE BIOCERAMICS

Authors: Ciobanu, CS; Massuyeau, F; Andronescu, E; Stan, MS; Dinischiotu, A; Predoi, D

Published: OCT-DEC 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 1647, DOI:

For the first time we presented the preliminary results of biocompatibility studies on bioceramic hydroxyapatite powders doped with europium Ca10-xEux(PO4)(6)(OH)(2), with 0.01 <= x(Eu) <= 0.2 prepared at low temperature by a simple coprecipitation approach. The X-ray diffraction (XRD) studies revealed the characteristic peaks of hydroxyapatite in each sample. No evidence for additional crystalline phases was found, proving the complete substitution of Eu in the HAp lattice in the whole range of concentrations. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The PL investigations shown the PL intensity changed considerably by varying the x(Eu). The value of x(Eu) in the hydroxyapatite formula has almost no effect on the wavelength of emission peaks. In order to test Hap_Eu biocompatibility, the effect of europium substituted hydroxyapatite nanocristalline powders with different x(Eu) on cell viability and proliferation of HEK293 cell line were evaluated. The in vitro investigation showed no significant decrease of viability of HEK293 cell line and low levels of intracellular lipid peroxidation in the Hap_Eu treated cells. In conclusion, the results suggest that Eu doped HAp has low toxicity and exhibit a good biocompatibility.

1945. Photoluminescence of poly (N vinylcarbazole)/carbon nanotubes composites

Authors: Gontia, II; Baibarac, M; Baltog, I

Published: MAY-JUN 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 582, DOI:

The photoluminescence (PL) of two types of poly (N-vinyl-carbazole)(PVK)/carbon nanotubes (CN) composites, prepared by chemical and electrochemical method, has been investigated. In comparison with the pure PVK, the chemically prepared PVK/NC sample shows a significant PL quenching and a shorter decay time. For the samples prepared electrochemically, PL increases in intensity, red shifts and gets longer decay time with the increase of voltammetric cycles number. In addition, the latter shows a change in emission from high-energy excimer to low-energy excimer after a treatment with NH(4)OH.

1946. Oxidative stress induced by two types of magnetite nanoparticules in HepG(2) cell line

Authors: Radu, M; Predoi, D; Costache, M; Dinischiotu, A

Published: AUG 28 2011, TOXICOLOGY LETTERS, 205, S288, DOI: 10.1016/j.toxlet.2011.05.973

1947. DEPENDENCE OF OPTICAL RESPONSE ON pH OF A WATER-SOLUBLE Zn(II)-METALLOPORPHYRIN

Authors: Fagadar-Cosma, E; Creanga, I; Maranescu, B; Palade, A; Lorinczi, A; Fagadar-Cosma, G; Popescu, M

Published: JAN-MAR 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 80, DOI:

Nowadays, porphyrin derivatives are extensively used as analytical reagents. This work put the basis for a rapid, simple and inexpensive method developed for pH determination. It was demonstrated the potential for a water soluble metalloporphyrin, 5,10,15,20-tetrakis(N-methyl-4-pyridyl) porphyrin-Zn(II) tetrachloride (Zn-TNMPyP) to be a potential optical pH sensor in the 5.5-10.5 domain. Monitoring of the variations in the absorption spectra of the Zn-TNMPyP, both regarding the Soret and the Q(0,1) band, generated by the exposure to different base concentrations allowed us to notice the linearity of the response at different pH values.

1948. Efficient dual functionality of highly porous nanocomposites based on TiO2 and noble metal particles

Authors: Baia, L; Diamandescu, L; Barbu-Tudoran, L; Peter, A; Melinte, G; Danciu, V; Baia, M

Published: FEB 10 2011, JOURNAL OF ALLOYS AND COMPOUNDS, 509, 2678, DOI: 10.1016/j.jallcom.2010.11.154

Porous nanocomposites based on TiO2 aerogels and Au and, respectively, Ag particles were synthesized and their dual functionality to decontaminate water, via photocatalysis, and to detect low concentrations of pollutants from water, via SERS technique, was evaluated using model pollutants. The apparent photodegradation rate constants of a standard pollutant molecule revealed a considerable improvement of the composites photocatalytic performances (even better than one order of magnitude) in comparison with the commercial product Degussa P25. The essential role of the contact between TiO2 and Au nanoparticles was demonstrated and the potential of all synthesized porous composites for photocatalytic experiments with visible light was pointed out. The lowest concentrations of contaminants adsorbed on the noble metal particles detectable by SEAS were found to depend on the composite and pollutant species type and were determined to be between 10(-3) and 5 x 10(-6) M, and 10(-8) and 10(-10) M for off and under resonant excitation, respectively. The morphological (BET, pore size distribution, TEM) and structural (Raman, XRD, diffuse reflectance) particularities of the obtained porous composites were also discussed. (C) 2010 Elsevier B.V. All rights reserved.

1949. Nano Techniques for Enhancing Critical Current in Superconducting YBCO Films

Authors: Mikheenko, P; Dang, VS; Kechik, MMA; Wang, Y; Sarkar, A; Tanner, JL; Abell, JS; Crisan, A

Published: JAN 2011, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 24, 1064, DOI: 10.1007/s10948-010-0861-2

A range of nano techniques is explored in order to increase the critical current in pulsed laser deposited (PLD) superconducting YBa2Cu3O (x) (YBCO) thin films. The structural measurements are linked with magnetic and transport measurements of the films. The effectiveness of PLD techniques is analyzed from the point of view of the dimensionality of nanostructures formed prior to and during the film growth. It is shown that a combination of two-dimensional substrate decoration with nanoparticles before the film deposition and one-dimensional growth of external phase nanorods during the deposition offers a high critical current in magnetic field both along the c-axis and in the ab-plane of YBCO.

1950. Composite, all-ceramics, high-peak power Nd:YAG/Cr4+:YAG monolithic micro-laser with multiple-beam output for engine ignition

Authors: Pavel, N; Tsunekane, M; Taira, T

Published: MAY 9 2011, OPTICS EXPRESS, 19, 9384, DOI: 10.1364/OE.19.009378

A passively Q-switched Nd:YAG/Cr4+:YAG micro-laser with three-beam output was realized. A single active laser source made of a composite, all-ceramics Nd: YAG/Cr4+:YAG monolithic cavity was pumped by three independent lines. At 5 Hz repetition rate, each line delivered laser pulses with similar to 2.4 mJ energy and 2.8-MW peak power. The M-2 factor of a laser beam was 3.7, and stable air breakdowns were realized. The increase of pump repetition rate up to 100 Hz improved the laser pulse energy by 6% and required similar to 6% increase of the pump pulse energy. Pulse timing of the laser-array beams can by adjusted by less than 5% tuning of an individual line pump energy, and therefore simultaneous multi-point ignition is possible. This kind of laser can be used for multi-point ignition of an automobile engine. (C) 2011 Optical Society of America

1951. Influence of defects on the switching speed of Ge2Sb2Te5

Authors: Velea, A; Popescu, M; Lorinczi, A; Sava, F; Simandan, ID; Mihai, C

Published: NOV-DEC 2011, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 13, 1596, DOI:

Chalcogenide phase change materials are one of the major contenders for the new non-volatile memory applications. Here is reported that the switching speed of Ge2Sb2Te5 is strongly dependent on the percent of defects in the material. Using cellular automata simulations it was shown that the size of the percolation cluster is minimum, thus the switching speed is maximum, for a percent of around 25% defects in the material. This is a property of the Ge2Sb2Te5 that can be useful for new phase change materials and devices design with better switching properties.

1952. Rare-earth doped sol-gel derived oxyfluoride glass-ceramics: Structural and optical characterization

Authors: Secu, CE; Secu, M; Ghica, C; Mihut, L

Published: SEP 2011, OPTICAL MATERIALS, 33, 1774, DOI: 10.1016/j.optmat.2011.06.004

Glass-ceramics containing RE3+-doped BaF2 nanocrystals (RE = Eu, Sm, Dy, Ho and Pr) with the size below 10 nm size have been made by using the controlled crystallization at higher temperatures of the RE3+-doped SiO2-BaF2 xerogels. Photoluminescence measurements have indicated the incorporation of the RE3+ ions in both silica network and in the BaF2 nanocrystals. Thermoluminescence measurements have shown a peak whose position depends on the nature of RE3+-dopant as it follows: 140 degrees C (for Ho3+, Dy3+), 340 degrees C (for Sm3+) and 370 degrees C (for Eu3+); in Eu3+-doped SiO2 glass the TL peak is shifted to 383 degrees C. The peaks in glass-ceramics were assigned to the recombination of the electrons thermal released from the RE3+-electron traps located in both glass-matrix and BaF2 nanocrystals. Within the series the trivalent lanthanide ions act as increasingly deeper electron trapping centres. (C) 2011 Elsevier B.V. All rights reserved.

1953. Sn-119- AND Fe-57- MOSSBAUER INVESTIGATION OF xSnO(2)-[(1-X)[alpha-Fe2O3] NANOPARTICLE SYSTEM. (I) MAGNETIC HYPERFINE FIELD DISTRIBUTION IN Sn-LOW DILUTE SYSTEM

Authors: Constantinescu, S; Diamandescu, L; Bibicu, I; Tarabasanu-Mihaila, D; Feder, M

Published: 2011, ROMANIAN JOURNAL OF PHYSICS, 56, 707, DOI:

A series of xSnO(2)-(1-x)alpha-Fe2O3 (x=0.0-1.0) was prepared by a hydrothermal route starting with an aqueous mixture of iron (III) chloride hexahydrate, FeCl3 center dot 6H(2)O, and tin (IV) chloride pentahydrate, SnCl4 center dot 5H(2)O. The as resulted nanoscaled powders have been investigated by X-ray diffraction (XRD) and Sn-119 Mossbauer spectroscopy in transmission geometry and conversion electron. Under x = 0.300, the spectra reveal the appearance of magnetic hyperfine induced structure. At x = 0.300, the spectrum shows a magnetic phase (M) with the percentage of about 17%. The appearance of hyperfine magnetic fields suggests the location of the nonmagnetic Sn4+ ions, surrounded by the Fe3+ ions, in the interstitial and substitutional sites of alpha-Fe2O3 phase. On the other hand, the dependence of the total spectrum areas, vs. molar concentration x, displays a jump around x similar to 0.45, suggesting a change of the characteristic Debye temperature in the Mossbauer factor. The reported spectra have been fitted and the obtained hyperfine parameters are discussed in terms of reduced dimensional effects, super-transferred hyperfine interactions (STHI) and magnetic hyperfine field distribution (MHFD).

1954. Temperature-dependent refractive index of potassium acid phthalate (KAP) in the visible and near-infrared

Authors: Moutzouris, K; Stavrakas, I; Triantis, D; Enculescu, M

Published: APR 2011, OPTICAL MATERIALS, 33, 816, DOI: 10.1016/j.optmat.2010.12.021

We report an investigation of the temperature-dependence of the refractive index of potassium acid phthalate (KAP) crystal. Refractive index measurements are based on a refractometer setup operating in a temperature range from 25 degrees C to 200 degrees C and using five different laser wavelengths in the visible and near-infrared. Temperature-dependent dispersion relations are proposed, with an average fitting quality that exceeds experimental accuracy, and compared to previous room-temperature Sellmeier equations. Consequently, the new relations are employed for the calculation of various linear and nonlinear optical properties of KAP. (C) 2011 Elsevier B.V. All rights reserved.

1955. PROPERTIES OF RARE EARTH Ga-La-S GLASSES OBTAINED BY RF INDUCTOR HEATING

Authors: Popescu, AA; Savastru, D; Miclos, S; Braic, V; Popescu, M; Manea, A; Kiss, A

Published: APR-JUN 2011, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 6, 348, DOI:

A new synthesis method for 70Ga(2)S(3)30La(2)S(3) (GLS) lanthanum based glass, which uses a RF-heating inductor, has been developed. The method gives the possibility to quench the melt without taking the crucible out of the reaction chamber. Glasses with good optical quality were obtained. The samples characterized by X-ray diffraction prove the amorphous state. The re-heating of GaLaS at temperatures of 620 degrees C leads to the appearance of large 30-80 mu m crystals, Ga3La1.66S7 structure being the main crystal form. High quality GLS thin films have been obtained by RF sputtering. The calculated refractive index was 2.48 for the thin films obtained by RF sputtering and 2.55 for bulk samples. Two kinds of the Urbach-density of state distribution are distinguished from optical transmission measurements corresponding to activation energies of 0.12 eV and 0.66 eV.

1956. Highly adherent bioactive glass thin films synthetized by magnetron sputtering at low temperature

Authors: Stan, GE; Pasuk, I; Husanu, MA; Enculescu, I; Pina, S; Lemos, AF; Tulyaganov, DU; El Mabrouk, K; Ferreira, JMF

Published: DEC 2011, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 22, 2710, DOI: 10.1007/s10856-011-4441-1

Thin (380-510 nm) films of a low silica content bioglass with MgO, B2O3, and CaF2 as additives were deposited at low-temperature (150A degrees C) by radio-frequency magnetron sputtering onto titanium substrates. The influence of sputtering conditions on morphology, structure, composition, bonding strength and in vitro bioactivity of sputtered bioglass films was investigated. Excellent pull-out adherence (similar to 73 MPa) was obtained when using a 0.3 Pa argon sputtering pressure (BG-a). The adherence declined (similar to 46 MPa) upon increasing the working pressure to 0.4 Pa (BG-b) or when using a reactive gas mixture (similar to 50 MPa). The SBF tests clearly demonstrated strong biomineralization features for all bioglass sputtered films. The biomineralization rate increased from BG-a to BG-b, and yet more for BG-c. A well-crystallized calcium hydrogen phosphate-like phase was observed after 3 and 15 days of immersion in SBF in all bioglass layers, which transformed monotonously into hydroxyapatite under prolonged SBF immersion. Alkali and alkali-earth salts (NaCl, KCl and CaCO3) were also found at the surface of samples soaked in SBF for 30 days. The study indicated that features such as composition, structure, adherence and bioactivity of bioglass films can be tailored simply by altering the magnetron sputtering working conditions, proving that this less explored technique is a promising alternative for preparing implant-type coatings.

1957. THE INFLUENCE OF SYNTHESIS PARAMETERS ON SIZE AND MORPHOLOGY OF POLY(STYRENE-HYDROXYETHYL METHACRYLATE) COLLOIDS

Authors: Preda, N; Enculescu, M; Matei, E; Enculescu, I

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1065, DOI:

Poly(styrene-hydroxyethyl methacrylate) [P(ST-HEMA)] latex particles were prepared by surfactant-free emulsion copolymerization. As water-soluble initiator was used potassium persulfate (KPS). The influence of different reactions parameters, such as the reaction temperature, the both monomers (ST and HEMA) concentrations and the KPS concentration on the particles average diameter and particles size dispersion was investigated. Generally monodisperse spherical particles are synthesized, but we also obtained stable large three-dimensional colloidal aggregates. These are formed by the agglomeration of monodispersed spheres in certain polymerization conditions. The P(ST-HEMA) monodispersed spheres with 350 nm average diameter were assembled into colloidal crystals using dip-coating technique. Colloidal crystals with different thickness were obtained by modifying two experimental factors, the colloidal concentration and the substrate lifting speed. The morphologies of copolymer latex particles and colloidal crystals were observed using scanning electron microscopy (SEM). The optical properties of colloidal crystals films were also investigated by transmission spectroscopy.

1958. Growth and optical characterization of Pb-, TI-doped LiF crystals

Authors: Somma, F; Montereali, RM; Vincenti, MA; Polosan, S; Secu, M

Published: AUG 2010, OPTICAL MATERIALS, 32, 1312, DOI: 10.1016/j.optmat.2010.04.038

Large and transparent LiF:Pb and LiF:TI crystals were successfully grown by using Kyropoulos method. They were characterized using spectroscopic measurements combined with differential thermal analysis and thermogravimetry (TG) analysis, in order to investigate the effect of dopants upon the optical properties of these crystals. The optical absorption peaks at 278 nm (for Pb) and 273 nm (for TI) have been assigned to the A-type transition of these ions. Photoluminescence spectra have shown bands at 350 nm (for TI) and 375 nm (for Pb), which have been associated to the dopant ions in different configurations in the lattice. (C) 2010 Elsevier B.V. All rights reserved.

1959. LASER INDUCED CRYSTALLIZATION IN SPUTTERED FeSiB THIN FILMS

Authors: Tolea, F; Stoica, M; Matei, E; Cristescu, CP

Published: 2010, UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS, 72, 256, DOI:

Thin films with nominal composition Fe(78)Si(9)B(13) generated by radio-frequency (rf) sputtering on Si substrates with (100) orientation were irradiated with an eyeliner laser with 130mJ/cm(2) fluence. Information on the induced structural changes were obtained by X-ray diffraction and scanning electron microscopy, while the magnetization curves were determined by the magneto-optical Kerr effect. The effects of the irradiation consist in the growing of crystallites,appearence of melted and ultra-fast frozen zones, surface oxidation and changes in the magnetic properties of the thin films.

1960. BINARY VANADIUM-CERIUM OXIDE NANOPOWDERS OBTAINED BY SOFT CHEMISTRY

Authors: Zaharescu, M; Todan, L; Predoana, L; Atkinson, I; Rusu, A; Andronescu, C; Teodorescu, V; Osiceanu, P

Published: NOV-DEC 2010, REVUE ROUMAINE DE CHIMIE, 55, +, DOI:

Vanadium-cerium oxide gels and films obtained by the sot-gel method have been widely studied, due to their catalytic, electrochemical, electronic and ionic properties, a result of their ability to form combinations in more than one valence state. V-Ce oxide powders were synthesized by wet chemical methods, in the presence and absence of polyols. The preparation of an aqueous dispersion of mixed vanadium oxide/CeO2 started from a solution of the corresponding metal oxide and metal salt, V2O5 and Ce(NH4)(NO3)(6), respectively. The powders were characterized by IR-spectroscopy, X-ray photoelectronic spectroscopy, X-ray diffraction, electronic microscopy (TEM, SAED, HRTEM). The influence of the ratio of the components (V/Ce) and of the polyol complexation agent on the structure and morphology of the obtained binary oxide powders was established.

1961. Investigations of the neodymium doped quartz glasses obtained by the hybrid sot-gel method

Authors: Niciu, H; Vasiliu, C; Manea, A; Radu, D; Secu, M; Onose, C; Ghervase, L; Niciu, D; Feraru, ID; Grigorescu, CEA

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1623, DOI:

Undoped and neodymium doped quartz glasses were obtained by the hybrid sol-gel method. The vitrification was performed in He atmosphere. The Nd(3+) characteristic absorption bands in the UV and VIS were put into evidence. Investigations in the NIR range revealed a small amount (86 ppm) of OH(-) in the vitreous matrix. FTIR and Raman spectra exhibit the SiO(2) glass characteristic vibrations and also the characteristic vibrations of Si-OH and Si-Cl bonds. The photoluminescence peaks at 640, 920 and 1080 nm belonging to the Nd(3+) doped quartz glass were evidenced.

1962. Field-assisted organization, substrate effects and magnetic behavior of Ag30Co70 core-shell nanoparticles

Authors: Crisan, AD; Angelakeris, M; Simeonidis, K; Tsiaoussis, I; Crisan, O

Published: NOV 2010, SOLID STATE SCIENCES, 12, 1911, DOI: 10.1016/j.solidstatesciences.2010.06.006

In core-shell systems with non-magnetic core and magnetic shell the electron transport and magnetic properties are expected to show enhanced behavior due to the particular morpho structural features of the conductive and magnetic regions This may lead to novel advanced GMR materials and spin valves This is the case of core-shell Ag-Co colloidal nanoscale particles that organize into regular arrays An insight on the structure and morphology of the newly synthesized Ag-Co nanoparticles deposited on different substrates will be presented The influence of the substrate on different morphologies and organization dynamics is discussed It is shown that the magnetic behavior of the Ag-Co nanoparticles is highly influenced by the corona-like morphology of Co shell chemical environment of the magnetic atoms and by the fact that they exhibit strongly reduced coordination due to the surface states (C) 2010 Elsevier Masson SAS All rights reserved

1963. TWO DIMENSIONAL PHOTONIC STRUCTURES BASED ON As-S CHALCOGENIDE GLASS

Authors: Popescu, M; Velea, A; Lorinczi, A; Zamfirescu, M; Jipa, F; Miclos, S; Popescu, A; Ciobanu, M; Savastru, D

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1105, DOI:

Two-dimensional photonic structure has been imprinted on the surface of arsenic sulphide glass using the pulses of a femtosecond laser. Due to the interaction of the laser beam with the glass, the laser traces were obtained as hillocks of around 150-200 nanometer in height, or holes of depth around 100-300 nm, without the need for a later etching stage as in the usual practice. The calculation of the band structure shows a photonic band gap between 0.9 and 1.0 c/a. By varying the energy of the laser pulse we have the possibility to choose between the two possibilities to produce a photonic structure made-up of hillocks or a photonic structure consisting of holes. The value of the threshold pulse power which controls the resulting surface morphology and the obtained photonic structure has found to be around 15 mW. The surface topography of the structures obtained has been investigated by atomic force microscopy (AFM).

1964. Synthesis and characterization of doped Ba(Mg1/3Ta2/3)O-3 ceramics

Authors: Jinga, C; Andronescu, E; Jinga, S; Ioachim, A; Nedelcu, L; Toacsan, MI

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 287, DOI:

Ba(Mg1/3Ta2/3)O-3 (BMT) ceramic is a dielectric material possessing an extremely high Qxf product value (up to 400 THz) at microwave frequencies. This makes it suitable for applications as a dielectric resonator for wireless communications. BMT samples, prepared by solid-state reaction and doped with Nb5+, V5+ or Ga3+, were employed for compositional, structural morphological characterization. In the present study, we report on the influence of dopants (type and quantity) and sintering temperature on the dielectric properties. It was found that the quality factor is maximum when Nb5+ is used as dopant.

1965. Backward Couplers Using Coupled Composite Right/Left-Handed Transmission Lines

Authors: Mocanu, IA; Militaru, N; Lojewski, G; Petrescu, T; Banciu, MG

Published: 2010, PROCEEDINGS OF THE 2010 8TH INTERNATIONAL CONFERENCE ON COMMUNICATIONS (COMM), 270, DOI:

A new asymmetric backward coupler is obtained by edge-coupling two types of composite right/left handed (CRLH) lines. This novel coupler is analyzed in a microwave range (1-10 GHz) and the magnitude of the scattering parameters reveals tight coupling effects (even 0 dB) in a dual frequency band and also very good directivity in the working band.

1966. Self-assembled artificial pinning centres in thick YBCO superconducting films

Authors: Mikheenko, P; Abell, JS; Sarkar, A; Dang, VS; Kechik, MMA; Tanner, JL; Paturi, P; Huhtinen, H; Babu, NH; Cardwell, DA; Crisan, A

Published: 2010, 9TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS 09), 234, DOI: 10.1088/1742-6596/234/2/022022

Strong, artificial pinning centres are required in superconducting films of large thickness for power applications in high magnetic fields. One of the methods for the introduction of pinning centres in such films is substrate decoration, i.e., growing nanoscale islands of certain materials on the substrate prior to the deposition of the superconducting film. Two other methods are building up a layered distribution of a second phase and homogeneous incorporation of second phase inclusions from a compositional target. In this paper, we compare the effectiveness of these methods in terms of the type of the self-assembly of nanoparticles. The comparison is made over a large set of YBa2Cu3O7 films of thickness up to 6.6 mu m deposited with Au, Ag, Pd, LaNiO3, PrBa2Cu3O7, YBCO, BaZrO3 and Gd2Ba4CuWOy nanoparticles. It is found that substrate-decoration self-assembly is able to provide higher critical current in low magnetic field than the incorporation of homogeneous second phase in the sample microstructure. By specific modification of substrate decoration we achieved the self-field critical current per centimetre of width of 896 A/cm at 77.3 K and 1620 A/cm at 65 K in a film of thickness of 4.8 mu m.

1967. MAPLE deposited thin monomer films of maleimidic derivatives for photonics

Authors: Stanculescu, A; Albu, AM; Socol, G; Stanculescu, F; Socol, M; Preda, N; Rasoga, O; Girtan, M; Iulian, I

Published: MAR 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 739, DOI:

This paper presents a study of some thin monomer films deposited by MAPLE. These monomers have been synthesised from maleic anhydride and aniline derivatives and are characterized by a molecular structure adequate for the generation of optical non-linear phenomena. UV-VIS, FTIR, Raman and Photoluminescence spectroscopy have been used to investigate the influence of the experimental conditions on the properties of the films. X-Ray Diffraction has evidenced a certain degree of disorder in the thin films, which is correlated with the randomly orientated molecules and AFM images have revealed different roughness for different monomer layers and different substrates. Second harmonic measurements have shown a strong signal emitted by the thin film prepared from the monomer with one [-NH-NH-] donor and two [-NO(2)] acceptor groups. This thin film is characterized by good transparency and low photoluminescence emission at excitation with the wavelength of the second harmonic (lambda-400 nm).

1968. SYNTHESIS AND LUMINESCENCE PROPERTIES OF Nd-DOPED CHALCOGENIDE GLASS (Ge5As2S13) (NdCl3) x (x=0.3%, 0.5%)

Authors: Georgescu, S; Voiculescu, AM; Salamu, S; Niciu, H; Niciu, D; Popescu, M; Lorinczi, A; Velea, A; Simandan, ID

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 624, DOI:

The synthesis of the chalcogenide glass (Ge5As2S13) doped by Nd3+ has been carried out. The bulk glass develops a small amount of Nd2O3 and As2O3 crystallites besides some amount of (NdCl3)*6H(2)O crystalline phase initially introduced during synthesis. The optical absorption spectra demonstrate the presence of the Nd3+ both in the amorphous phase and in crystalline combinations. The formation of Nd2O3 crystallites was explained by the reaction of water with neodymium chloride. The presence of As2O3 is due to the oxidation of As from the glass during preparation.

1969. Molecular mobility of nematic E7 confined to molecular sieves with a low filling degree

Authors: Bras, AR; Frunza, S; Guerreiro, L; Fonseca, IM; Corma, A; Frunza, L; Dionisio, M; Schonhals, A

Published: JUN 14 2010, JOURNAL OF CHEMICAL PHYSICS, 132, DOI: 10.1063/1.3432775

The nematic liquid crystalline mixture E7 was confined with similar filling degrees to molecular sieves with constant composition but different pore diameters (from 2.8 to 6.8 nm). Fourier transform infrared analysis proved that the E7 molecules interact via the cyanogroup with the pore walls of the molecular sieves. The molecular dynamics of the system was investigated by broadband dielectric spectroscopy (10(-2)-10(9) Hz) covering a wide temperature range of similar to 200 K from temperatures well above the isotropic-nematic transition down to the glass transition of bulk E7. A variety of relaxation processes is observed including two modes that are located close to the bulk behavior in its temperature dependence. For all confined samples, two relaxation processes, at frequencies lower than the processes observed for the bulk, were detected. At lower temperatures, their relaxation rates have different temperature dependencies whereas at higher temperatures, they seem to collapse into one chart. The temperature dependence of the slowest process (S-process) obeys the Vogel-Fulcher-Tammann law indicating a glassy dynamics of the E7 molecules anchored to the pore surface. The pore size dependence of both the Vogel temperature and fragility revealed a steplike transition around 4 nm pore size, which indicates a transition from a strong to a fragile behavior. The process with a relaxation rate in between the bulklike and the S-process (I-process) shows no dependence on the pore size. The agreement of the I-process with the behavior of a 5CB surface layer adsorbed on nonporous silica leads to the assignment of E7 molecules anchored at the outer surface of the microcrystals of the molecular sieves. (C) 2010 American Institute of Physics. [doi:10.1063/1.3432775]

1970. On the structural, morphological, optical and electrical properties of sol-gel deposited ZnO In films

Authors: Girtan, M; Socol, M; Pattier, B; Sylla, M; Stanculescu, A

Published: NOV 1 2010, THIN SOLID FILMS, 519, 577, DOI: 10.1016/j.tsf.2010.07.006

Indium-doped zinc oxide thin films deposition was performed by the sol-gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol Films were spin coated onto glass substrates After drying and after a heat treatment at 450 degrees C highly transparent (80%-90%) films were obtained The effect on the structural morphological optical and electrical thin films properties of the dopant concentration was investigated The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed (C) 2010 Elsevier B V All rights reserved

1971. Mossbauer investigation of hyperfine interactions in dilute Fe-SnO2 nanoparticles

Authors: Diamandescu, L; Constantinescu, S; Tarabasanu-Mihaila, D; Bibicu, I; Feder, M; Vlaicu, MA

Published: 2010, INTERNATIONAL CONFERENCE ON THE APPLICATIONS OF THE MOSSBAUER EFFECT (ICAME 2009), 217, DOI: 10.1088/1742-6596/217/1/012110

We present a Mossbauer (MS) analysis on the nanoparticle system xSnO(2)-(1-x)alpha-Fe2O3, (x is an element of [0.995 divided by 0.925]). The samples were prepared by a hydrothermal route and have been 50 % enriched in Fe-57. The MS spectra were recorded at room (RI) and liquid nitrogen temperature (LNT). Below x = 0.975 the MS consist in a paramagnetic pattern, while at x 0.975 magnetic hyperfine interactions were evidenced. The observed coexistence of paramagnetic and ordered magnetic phases is discussed by taking into account the role of oxygen vacancies (square), Sn-O and Sn-square distances together with the iron-oxygen configurations.

1972. Switching mechanism in amorphous chalcogenides

Authors: Popescu, M; Simandan, ID

Published: 2010, 16 ISCMP: PROGRESS IN SOLID STATE AND MOLECULAR ELECTRONICS, IONICS AND PHOTONICS, 253, DOI: 10.1088/1742-6596/253/1/012014

The electrical switching in solid compositions based on chalcogenide materials is discussed. Different mechanisms proposed for switching effect are reviewed. A new description of the switching phenomenon is done. The switching is regarded as due to formation and breaking of the links between the dendrites of crystalline nuclei in bulk materials, as a consequence of the energy pumped by an electrical field. This mechanism explains the very short switching time (<20ns), the possibility to get smart memories based on multisteps of resistivity and the high number of cycles supported by the cell (10(16)).

1973. A new ZnO photoanode for dye-sensitized solar cell

Authors: Sima, M; Secu, M; Sima, M; Vasile, E

Published: SEP 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1328, DOI:

The present work reports the preparation of nanostructured ZnO nanorods in a hydrothermal-electrochemical process and preliminary attempt to fabricate a dye-sensitized solar cell using this material as photoanode. Synthesis of ZnO nanorods in solutions with and without eosin Y dye, used as nanostructuring agent, was studied. ZnO nanorod arrays were characterized by photoluminescence spectroscopy, scanning electron microscopy and X-ray diffraction analysis. Fabricated dye-sensitized solar cell comprised a photoanode prepared with nanostructured ZnO nanorods and eosin Y dye, a platinum counter electrode and an electrolyte consisting of 0.5M KI + 0.03M I-2 in acetonitrile/ethylene carbonate (v/v=1/4). Performance parameters of dye-sensitized solar cell were extracted from standard current-voltage characteristic.

1974. Investigation of microstructural properties of nitrogen doped ZnO thin films formed by magnetron sputtering on silicon substrate

Authors: Nicolescu, M; Anastasescu, M; Preda, S; Calderon-Moreno, JM; Osiceanu, P; Gartner, M; Teodorescu, VS; Maraloiu, AV; Kampylafka, V; Aperathitis, E; Modreanu, M

Published: MAY 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 1051, DOI:

Zinc oxide (ZnO) is a semiconductor with a wurtzite-type structure, useful for a variety of optical, optoelectronic and piezoelectric applications. We report here on the post deposition treatment (Rapid Thermal Annealing at 400 and 550 degrees C) impact on the microstructural properties of N-doped ZnO (ZnO:N) thin films grown on silicon substrate by r.f. magnetron sputtering of ZnN target. The ZnO:N films have been characterized by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning (SEM) and Transmission (TEM) Electron Microscopy coupled with Energy Dispersive X-ray (EDX) and Selected Area Electron Diffraction (SAED) respectively and Fourier Transform Infrared (FTIR) Spectroscopy. XRD confirms that ZnO:N films are polycrystalline in the as deposited state. SEM, TEM and XRD measurements revealed a polycrystalline film with preferentially oriented columnar crystals. AFM studies reveal a drastic change of ZnO surface morphology upon RTA and the existence of areas with different roughness in the sample thermally treated at 400 degrees C. FTIR, XRD and TEM results shows that disorder associated mainly with grain boundary defects decreases as the annealing temperature increases.

1975. MAPLE preparation and characterization of benzil thin films

Authors: Socol, M; Socol, G; Rasoga, O; Stanculescu, F; Stanculescu, A; Mihailescu, I; Ionita, I; Preda, N; Enculescu, M; Antohe, S

Published: NOV 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1806, DOI:

In this study the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique was used to prepare thin films from a low melting point (< 100 degrees C) organic compound (benzil). Optical properties of the films have been investigated by UV-VIS, FTIR and PL spectroscopy. Details about crystallinity were obtained by XRD measurements. FTIR spectra have confirmed the preservation of the chemical structure of the compound during the deposition process. SEM and AFM investigation have evidenced a topography of the MAPLE deposited films characterized by different grain size depending on the deposition conditions. Second harmonic generation measurements have revealed that the MAPLE deposited benzil films have preserved the optical nonliniar properties of the bulk crystalline benzil.

1976. STRUCTURAL DETAILS OF THE Ag-As2S3 INTERFACE OBTAINED BY VACUUM THERMAL EVAPORATION FOLLOWED BY GREEN LASER IRRADIATION

Authors: Lorinczi, A; Velea, A; Matei, E; Simandan, ID; Popescu, M

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 612, DOI:

As2S3 on Ag heterostructures deposited onto microscope glass substrates have been prepared. The quality of the hetero-structures has been investigated by careful analysis of the scanning electron microscope pictures taken on the native cross-sections, produced after the vacuum deposition sequence and various green laser irradiation times. The As2S3 layer is not uniformly grown, but reveals a columnar-like structure and multi-scale aggregation.

1977. Dielectric Ba(Ti1-x Sn (x) )O-3 (x=0.13) ceramics, sintered by spark plasma and conventional methods

Authors: Aldica, G; Cernea, M; Ganea, P

Published: MAY 2010, JOURNAL OF MATERIALS SCIENCE, 45, 2610, DOI: 10.1007/s10853-010-4234-9

A two-step sintering approach composed of spark-plasma-sintering (SPS) technique at 1000 A degrees C for 1 min and under a uniaxial pressure of 63 MPa followed by conventional sintering at 1400 A degrees C for 3 h is proposed for synthesis of dense Ba(Ti0.87Sn0.13)O-3 ceramics. Starting powders had grain size of about 90 nm and were obtained by co-precipitation. The SPS pellets consist of submicron (300-500 nm) grains. X-ray diffraction analysis of as-prepared Ba(Ti0.87Sn0.13)O-3 ceramic shows the occurrence of cubic and tetragonal phase coexistence for the pellets obtained after SPS processing and the presence of only tetragonal phase in the samples after the second (conventional) sintering. Grain uniformity in the final product is high, with average size of similar to 2 mu m. The apparent densities of the sintered pellets at temperature of 1400 A degrees C were similar to 92% of the theoretical value of Ba(Ti0.87Sn0.13)O-3. The ceramics exhibit a high relative dielectric constant of 6,550 and a dielectric loss (tan delta) = 0.078 at Curie temperature of 63 A degrees C and 10 Hz.

1978. Magnetic Nanocomposites for Permanent Magnets

Authors: Tolea, F; Sofronie, M; Birsan, A; Schinteie, G; Kuncser, V; Valeanu, M

Published: 2010, TRENDS IN NANOPHYSICS: THEORY, EXPERIMENT AND TECHNOLOGY, 296, DOI: 10.1007/978-3-642-12070-1_12

The influence of different crystallization conditions on the microstructure and magnetic hardening of RE-Fe-B amorphous ribbons with different Fe concentrations and Pr and Nd as rare earth elements was analyzed. The microalloying effects of Zr and Ti substitution on the evolution of crystallization process and the magnetic hardening was also discussed. The final aim of this experimental study was to obtain performing exchange spring magnets with as much as lower content of the expensive RE material.

1979. COLUMN STUDY OF CADMIUM ADSORPTION ONTO POLYACRYLONITRILE/HYDROXYAPATITE COMPOSITE BEAD

Authors: Wang, X; Min, BG; Lyoo, WS; Chihaia, V; Gartner, M; Stoica, TF; Bae, JY; Suh, SH

Published: AUG 2010, REVUE ROUMAINE DE CHIMIE, 55, 447, DOI:

Macroporous polyacrylonitrile/hydroxyapatite (PAN/HAp) composite bead was studied for cadmium removal in a fixed-bed column. The morphology of PAN/HAp composite bead was measured. The adsorption performance of PAN/HAp composite bead in the column was examined by varying bed height and HAp amount in PAN bead. The maximum adsorption capacity and the exhaustion time were determined from the breakthrough curves. Experimental data was described using the Adams-Bohart model. Bed height did not exert large influence on the maximum adsorption capacity and the exhaustion time. The kinetic rate constant and the adsorption capacity of the bed were found to be affected by the total HAp amount.

1980. Luminescence of dye-doped KAP and KDP nanorods

Authors: Enculescu, M; Trautmann, C

Published: MAR-JUL 2010, RADIATION MEASUREMENTS, 45, 604, DOI: 10.1016/j.radmeas.2009.11.015

Rods of potassium acid phthalate (KAP) and potassium dihydrogen phosphate (KDP) doped with rhodamine 6G (Rh 6G) were grown using the template approach. Pores of hundreds of nanometers in diameter were obtained in polycarbonate (PC) foils after heavy ions irradiation and subsequent chemical etching. Crystallization from solution was used for filling the pores and the nanostructures were characterized using scanning electron microscopy and photoluminescence spectroscopy studies. SEM images of micro- and nano-rods (300 nm and 2.5 mu m diameter) indicate a crystalline growth tendency. When exciting the PC foils containing rods of 100 nm diameter emission bands appear at 581 nm for Rh 6G doped KAP and at 602 nm for Rh 6G doped KDP. A shift of the emission bands towards red was observed when the luminescent properties of the rods with diameters of 100 nm were compared with the luminescent properties of the bulk crystals and of the micrometrical sized rods. (C) 2009 Elsevier Ltd. All rights reserved.

1981. Films and crystalline powder of BiI3 intercalated with ammonia

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Pandele, J; Andronescu, C; Fruth, V

Published: JAN 2010, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 30, 479, DOI: 10.1016/j.jeurceramsoc.2009.05.046

Intercalation, i.e. the insertion of guest species in a crystalline layered structure, is an efficient route for generating new materials with novel properties. Thin films and crystalline powder of BiI3 layered semiconductor were intercalated by exposure to ammonia vapors at room temperature. The intercalated compound was studied by thermo-gravimetric analysis, differential scanning calorimetry, X-ray diffraction, UV-vis optical absorption, FTIR spectroscopy and Raman scattering. After exposure of BiI3 to ammonia the formation of a new phase, BiI3(NH3)(3.83), was evidenced by thermal analysis. The intercalation process leads to a blue shift of the BiI3 Optical absorption edge by 0.5 eV. The appearance of new Raman lines at 135 and 353 cm(-1) in the Raman spectrum of intercalated BiI3 is considered as an evidence of the chemical interaction between the ammonia molecules and BiI3 lattice. (C) 2009 Elsevier Ltd. All rights reserved.

1982. Investigations of the non-isothermal crystallization of CaF2 nanoparticles in Sm-doped oxy-fluoride glasses

Authors: Aldica, G; Secu, M

Published: JUL 15 2010, JOURNAL OF NON-CRYSTALLINE SOLIDS, 356, 1636, DOI: 10.1016/j.jnoncrysol.2010.06.017

Oxyfluoride glass samples in the system SiO2-Al2O3-CaF2-SmF3 were produced by using the melt-quenched technique and the kinetics of non-isothermal crystallization of CaF2 nano-crystals has been investigated. Differential thermal analysis (DTA) has shown an exothermic peak at about 700 degrees C which was assigned to the CaF2 nano-crystals precipitation within the glass matrix as was identified by X-ray diffraction (XRD) analysis of the annealed glass samples. It was shown the Ozawa model is most suitable for describing the behaviour of non-isothermal crystallization of CaF2 nano-crystals within the glass matrix. The mean value of the Avrami exponent was found 1.16 which indicates the diffusion-controlled growth process of nano-particles in the glass system with zero nucleation rate as the single operative mechanism; the activation energy of the crystallization is E-d = 379 +/- 25 kJ/mol (3.93 +/- 0.26 eV). The activation energy of the nano-crystals growth was computed within the same model and agrees very well with the activation energy of the crystallization. (C) 2010 Elsevier B.V. All rights reserved.

1983. EFFECTS OF PROTON IRRADIATION ON THE SPECTRAL PERFORMANCE OF PHOTOVOLTAIC CELLS BASED ON CdS/CdTe THIN FILMS

Authors: Ion, L; Enculescu, I; Iftimie, S; Ghenescu, V; Tazlaoanu, C; Besleaga, C; Mitran, TL; Antohe, VA; Gugiu, MM; Antohe, S

Published: AUG 2010, CHALCOGENIDE LETTERS, 7, 530, DOI:

Due to their physical and chemical properties (such as suitable band gaps, large absorption coefficients and good chemical stability) CdTe thin films are interesting for electronic and optoelectronic devices, including particularly photovoltaic cells for space technology. For that specific application, it is of prime importance to study in this type of materials the influence of ionizing radiations on their physical (structural, electrical and optical) properties. In this paper, the photovoltaic cells based on CdS/CdTe thin films, produced by thermal vacuum sublimation, were irradiated with 3 MeV protons at room temperature. The effects of irradiation were studied by investigating the changes in the electrical and optical properties of the cells. It was found that proton irradiation in the above mentioned conditions results mainly in the introduction of defects at the CdS/CdTe interface. A discussion about the possible origin of those defects is given.

1984. Application of spark plasma sintering to processing of dense Ba(Ti1-xSnx)O-3 (x=0.13) ceramic

Authors: Aldica, G; Cernea, M; Radu, R; Trusca, R

Published: AUG 27 2010, JOURNAL OF ALLOYS AND COMPOUNDS, 505, 277, DOI: 10.1016/j.jallcom.2010.06.044

Short time spark plasma sintering at 1200 degrees C for 10 min and under a uniaxial pressure of 95 MPa followed by annealing at 1100 degrees C for 5 h is proposed for synthesis of high density (99%) Ba(Ti0.87Sn0.13)O-3 ceramic. Starting powder of 450 nm was obtained by co-precipitation, while the average grain size in the sintered ceramic was of 580 nm. X-ray diffraction analysis of the as prepared Ba(Ti0.87Sn0.13)O-3 samples indicated the presence of single phase BaTi0.87Sn0.13O3 developed in the BaTiO3 cubic structure. Samples have high relative dielectric constant of 5680 and low dissipation factor (tan delta = 0.009) at Curie temperature of 57 degrees C and 1 kHz, good tunability and ferroelectric properties. Remarkable is that these results are from some points of view different than for the conventionally processed samples with similar stoichiometry. Some ideas in this regard are presented and this suggests that SPS can be useful for expanded possibilities in the control of the properties. (C) 2010 Elsevier B.V. All rights reserved.

1985. Semiconductor Hybrid Structure: Nanowires Embedded in a Matrix from the Same Material

Authors: Sima, M; Vasile, E; Sima, M; Matei, E

Published: 2010, SEMICONDUCTORS, METAL OXIDES, AND COMPOSITES: METALLIZATION AND ELECTRODEPOSITION OF THIN FILMS AND NANOSTRUCTURES, 25, 161, DOI: 10.1149/1.3318514

Hybrid systems obtained by incorporation of a nanostructurated material into a matrix from the same thermoelectric (TE) material are predicted to show an increased TE efficiency compared to classical bulk materials. The authors have synthesized Bi1.95Te2.7Se0.35 submicron wires by electrodeposition into a polycarbonate membrane; after polymer membrane dissolution, the wire array supported on a metallic film was electrochemically embedded in a Bi2Te2.65Se0.35 film in order to prepare a hybrid structure. Wires and hybrid structure were analyzed by scanning electron microscopy (SEM), energy X-ray spectrometry (EDX) and X-ray diffraction (XRD).

1986. Specificity of defects induced in silicon by RF-plasma hydrogenation

Authors: Ghica, C; Nistor, LC; Stefan, M; Ghica, D; Mironov, B; Vizireanu, S; Moldovan, A; Dinescu, M

Published: MAR 2010, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 98, 785, DOI: 10.1007/s00339-009-5527-1

Silicon wafers have been submitted to hydrogen RF-plasma treatment in various experimental conditions. Hydrogen RF-plasma treatment induced two kinds of effects on Si wafers, depending on the treatment conditions: surface corrugation and formation of structural defects below the free surface. Atomic force microscopy (AFM) investigations showed that the surface roughness significantly increased with the treatment duration, leading to the formation of pyramidal humps on the surface. The structural defects resulting after the plasma treatments were investigated by conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) techniques. The specificity of the induced extended defects due to hydrogen decoration was emphasized. Three types of extended defects were identified and characterized: planar defects in the {111} and {100} planes and nanometric voids. Point defects related to the hydrogenation process were investigated by electron paramagnetic resonance (EPR) in correlation with the electron microscopy results.

1987. Extreme vortex pinning in the noncentrosymmetric superconductor CePt3Si

Authors: Miclea, CF; Mota, AC; Nicklas, M; Cardoso, R; Steglich, F; Sigrist, M; Prokofiev, A; Bauer, E

Published: JAN 1 2010, PHYSICAL REVIEW B, 81, DOI: 10.1103/PhysRevB.81.014527

We report on the vortex dynamics of a single crystal of the noncentrosymmetric heavy-fermion superconductor CePt3Si. Decays of the remnant magnetization display a logarithmic time dependence with rates that follow the temperature dependence expected from the Kim-Anderson theory. The creep rates are lower than observed in any other centrosymmetric superconductor and are not caused by high critical currents. On the contrary, the critical current in CePt3Si is considerably lower than in other superconductors with strong vortex pinning indicating that an alternative impediment on the flux-line motion might be at work in this superconductor.

1988. X-ray excited luminescence and photoluminescence of Bi-4(GeO4)(3) glass-ceramics

Authors: Polosan, S; Secu, M

Published: MAR-JUL 2010, RADIATION MEASUREMENTS, 45, 411, DOI: 10.1016/j.radmeas.2010.01.040

Bi-4(GeO4)(3) glass materials have been characterized by X-ray excited luminescence, photoluminescence and cathodo-luminescence measurements. The materials were obtained by crystallization at different temperatures and their spectroscopic parameters were compared before and after crystallization. Thermoluminescence curves recorded after electron irradiation of BGO glass behave similarly to BGO crystals, showing several peaks between 408 K (135 degrees C) and 610 K (337 degrees C). The differences between the Bi-4(GeO4)(3) crystals and glass materials are believed to result from the random distribution of GeO4 tetrahedra around Bi3+ ions which influences the photoluminescence and TL parameters. The CL images of glass-ceramic samples obtained by partial crystallization at 600 degrees C show luminescent crystalline structures, which are probably responsible for the increase in scintillation efficiency. (C) 2010 Elsevier Ltd. All rights reserved.

1989. ADSORPTION COMPLEXES OF COLLAGENOUS POLYPEPTIDE-IONIC SURFACTANT IN AQUEOUS MEDIUM 2. THE INFLUENCE OF ADSORPTION COMPLEXES OF POLYPEPTIDE-IONIC SURFACTANT ON THERMAL STABILITY OF COLLAGEN TYPE I

Authors: Micutz, M; Staicu, T; Sulea, D; Leca, M; Ghica, C

Published: AUG 2010, REVUE ROUMAINE DE CHIMIE, 55, 510, DOI:

In the first part of this study it has shown that the interaction between collagenous polypeptides (collagen type I with native structure of triple helix and collagen hydrolyzates with no significant secondary structure) and ionic surfactants (sodium dodecyl sulfate and hexadecyl trimethylammonium bromide) involves the formation of micelle-like clusters of ionic surfactant adsorbed onto polypeptide backbone (polypeptide-surfactant complexes) at surfactant concentrations much lower than its cmc. The present investigation is focused on the influence of polypeptide-ionic surfactant complexation on thermal denaturation of the collagen type I extracted from calfskin and young horse tendons. On the basis of capillary viscometry, a good correlation between denaturation temperatures and activation energies of viscous flow for the dilute aqueous collagen-ionic surfactant solutions at pH 2.5 and 8.0 has been found. Beginning from that, it has established that the presence of ionic surfactant reduces thermal stability of the two collagens, with a more pronounced effect in the case of sodium dodecyl sulfate. Accordingly, it has been proposed a thermal denaturation mechanism of the collagen triple helix in the presence of ionic surfactants.

1990. Blue CoAl2O4 spinel via complexation method

Authors: Mindru, I; Marinescu, G; Gingasu, D; Patron, L; Ghica, C; Giurginca, M

Published: AUG 1 2010, MATERIALS CHEMISTRY AND PHYSICS, 122, 497, DOI: 10.1016/j.matchemphys.2010.03.032

Cobalt-aluminate spinel, CoAl2O4, has been synthesized by two synthesis variants of the complexation method: tartarate and gluconate routes. The complex precursors have been characterized by IR, UV-vis spectroscopy and thermal analysis. The cobalt-aluminate spinet has been investigated by XRD, IR, UV-vis and luminescence spectroscopy and TEM. The results indicated that in both cases the single-phase nanocrystalline CoAl2O4 spinet was formed. The average crystallite size from TEM images was in the range 50-60 nm. The emission spectra of CoAl2O4 in the visible region confirmed the presence of tetrahedral coordinated Co2+ ion. (C) 2010 Elsevier B.V. All rights reserved.

1991. Synthesis and structural characteristics of nitrogen doped TiO2 aerogels

Authors: Popa, M; Macovei, D; Indrea, E; Mercioniu, I; Popescu, IC; Danciu, V

Published: JUL 2010, MICROPOROUS AND MESOPOROUS MATERIALS, 132, 86, DOI: 10.1016/j.micromeso.2009.12.024

Nitrogen doped TiO2 aerogels were obtained by sol gel process followed by supercritical drying with liquid CO2. Urea and NH3 (25% aqueous solution) were used as nitrogen sources. The as-prepared aerogels were submitted to thermal treatments performed under different experimental conditions (temperature and heating time). Increasing the temperature from 450 degrees C to 550 degrees C a decrease about 32% and 15.4% of the particle size and surface OH groups' concentration, respectively and an increase about 21.4% of the incorporated nitrogen in TiO2 lattice were observed. The immersion of the TiO2 aerogels in NH3 solution induced a decreasing by 48.86% and by 80% of the S-BET and the aerogel porosity, respectively. The photocatalytic activity of the obtained N-doped TiO2 was found to depend mainly on the nitrogen incorporation in the TiO2 lattice. (C) 2009 Elsevier Inc. All rights reserved.

1992. Biocompatibility Studies of Iron-oxide-dextrin Thin Films

Authors: Andronescu, E; Costache, M; Ciobanu, CS; Prodan, AM; Predoi, D

Published: OCT 2010, REVISTA DE CHIMIE, 61, 928, DOI:

Dextrin coated magnetic nanoparticles have been obtained by co-precipitation. As a second step biocompatible magnetic thin film has been synthesized from the iron oxide coated with dextrin powders by pulsed laser deposition technique. Biocompatibility tests consisting of osteoblast cells growth, viability and proliferation were monitored on the surface of the thin films. The cells morphology was characterized by scanning electron microscopy (SEM) after 48h.

1993. Kinetics and optical properties of the silver nanoparticles in aqueous L64 block copolymer solutions

Authors: Angelescu, DG; Vasilescu, M; Somoghi, R; Donescu, D; Teodorescu, VS

Published: AUG 20 2010, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 366, 162, DOI: 10.1016/j.colsurfa.2010.06.001

Silver nanoparticles were prepared by the chemical reduction of silver nitrate, AgNO3, with excess of sodium borohydride, NaBH4, in dilute aqueous solutions containing triblock copolymers poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-poly(ethylene oxide) (PEO) Pluronic L64. The synthesis was completed in similar to 24h and produced highly stable particle dispersion. The growth of nanoparticles was assessed by combining Mie theory, UV-vis spectroscopy and dynamic light scattering, and the average particle size was determined from transmission electron microscopy. The silver nanoparticles were sterically stabilised as a result of the block copolymer adsorption onto the nanoparticle surface. Besides the stabilizing character, the copolymer affected the kinetics of particle growth, the size and optical properties of as-synthesized Ag nanoparticles. It was revealed that the particle formation took place in two distinct stages. The first step was dominated by Ag ion reduction and growth driven by accretion, while in the second stage coagulated clusters of nanoparticles were obtained obtained. The as-synthesized particles were polydisperse, the individual ones had a size of similar to 7.6 nm as given by transmission electron microscopy, and the hydrodynamic radius of clusters amounted to 60 nm. The silver nanoparticles exhibited broad and structured emission bands centered at 300 and 330 nm for excitation wavelengths in two different ranges, 220-240 nm and 260-290 nm, respectively. This process may be assigned to two emission components corresponding to two different excitation wavelength domains. (C) 2010 Elsevier B.V. All rights reserved.

1994. Study of the Kramers rare earth ions ground multiplet with a large orbital contribution by multifrequency EPR spectroscopy: Ce3+ in PbWO4 scintillator

Authors: Popescu, FF; Bercu, V; Barascu, JN; Martinelli, M; Massa, CA; Pardi, LA; Stefan, M; Nistor, SV; Nikl, M

Published: MAR 2010, OPTICAL MATERIALS, 32, 575, DOI: 10.1016/j.optmat.2009.11.015

A multifrequency Electron Paramagnetic Resonance (EPR) investigation of Ce3+ impurities in PbWO4 single-crystals at the conventional microwave frequency (CMF) (X-band: 9.43 GHz) and at the high frequencies/fields (HF) 95, 190 and 285 GHz was carried out. The resulting spectra are well described at all frequencies by an axial spin-Hamiltonian corresponding to an effective spin one-half system in a tetragonal site symmetry. The diagonal values of the effective g matrix of the lowest doublet of the ground multiplet, g(parallel to) and g_, are frequency dependent at high fields. For the magnetic field perpendicular to the tetragonal axis, the g_-parameter exhibits also a small azimuthal angular dependence, which is frequency dependent, corresponding to the tetragonal S-4 symmetry. These HF effects are associated with the mixing by the large Zeeman interaction of some of the upper-lying doublets of the ground multiplet into the lowest-lying doublet states. The CMF and multifrequency HF-EPR analysis gives a good description of the magnetic properties and allows an estimation of the crystal field splitting of the ground multiplet of Ce3+ ions with tetragonal symmetry S-4 in the PbWO4 scintillator. (c) 2009 Elsevier BM. All rights reserved.

1995. Optical properties of zinc oxide thin films doped with aluminum and lithium

Authors: Galca, AC; Secu, M; Vlad, A; Pedarnig, JD

Published: JUN 1 2010, THIN SOLID FILMS, 518, 4606, DOI: 10.1016/j.tsf.2009.12.041

Aluminum doped Zinc Oxide (AZO) and Lithium doped Zinc Oxide (LZO) thin films are obtained by Pulsed Laser Deposition (PLD) method. These films are characterized by using Spectroscopic Ellipsometry (SE), X-ray Diffraction (XRD) and Photoluminescence (PL). By modeling the ellipsometry spectra we get the dielectric functions, the optical band gap E(g), and the electrical properties. Our results show the influence of the processing parameters on the optical and structural properties of doped ZnO thin films. The post-annealing treatment applied to AZO thin films, changes strongly the optical properties, by lowering the resistivity and red-shifting the band gap. (C) 2009 Elsevier B.V. All rights reserved.

1996. Enhancing performances of a passively Q-switched Nd:YAG/Cr4+:YAG microlaser with a volume Bragg grating output coupler

Authors: Pavel, N; Tsunekane, M; Taira, T

Published: MAY 15 2010, OPTICS LETTERS, 35, 1619, DOI: 10.1364/OL.35.001617

A diode end-pumped Nd:YAG microlaser passively Q-switched by Cr4+:YAG with performances controlled by a volume Bragg grating (VBG) output coupler has been developed. Compared with operation at room temperature, the Q-switched laser pulse energy was increased, by a factor of 2 or more, by elevating the Nd:YAG temperature and locking the wavelength of emission with the VBG. Furthermore, the emission wavelength was tuned over 0.7 nm bandwidth by changing the VBG temperature while maintaining laser pulses of millijoule-level energy and short (less than 4 ns) duration. (C) 2010 Optical Society of America

1997. Direct Production of a Novel Iron-Based Nanocomposite from the Laser Pyrolysis of Fe(CO)(5)/MMA Mixtures: Structural and Sensing Properties

Authors: Alexandrescu, R; Morjan, I; Tomescu, A; Simion, CE; Scarisoreanu, M; Birjega, R; Fleaca, C; Gavrila, L; Soare, I; Dumitrache, F; Prodan, G

Published: 2010, JOURNAL OF NANOMATERIALS, 2010, DOI: 10.1155/2010/324532

Iron/iron oxide-based nanocomposites were prepared by IR laser sensitized pyrolysis of Fe(CO)(5) and methylmethacrylate (MMA) mixtures. The morphology of nanopowder analyzed by TEM indicated that mainly core-shell structures were obtained. X-ray diffraction techniques evidence the cores as formedmainly by iron/iron oxide crystalline phases. A partially degraded (carbonized) polymeric matrix is suggested for the coverage of the metallic particles. The nanocomposite structure at the variation of the laser density and of the MMA flow was studied. The new materials prepared as thick films were tested for their potential for acting as gas sensors. The temporal variation of the electrical resistance in presence of NO2, CO, and CO2, in dry and humid air was recorded. Preliminary results show that the samples obtained at higher laser power density exhibit rather high sensitivity towards NO2 detection and NO2 selectivity relatively to CO and CO2. An optimum working temperature of 200 degrees C was found.

1998. SEQUENTIAL DEPOSITION OF MULTISEGMENT NANOWIRES

Authors: Matei, E; Preda, N; Enculescu, M; Ansermet, JP; Molares, MET; Enculescu, I

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1076, DOI:

Electrochemical replication of nanoporous membranes represents a facile approach towards the fabrication of nanostructures with tailored properties. By the template method we prepared multisegment nanowires with tailored structure. The first step of the process was the fabrication of the nanoporous template by swift heavy ion irradiation and subsequent selective etching of the ion track. The next step was to fill the pores with the desired combination of materials. In this manner, by sequential electrodeposition steps of metal and semiconductor we prepared Ni - CdTe and Ni - ZnO - Ni nanowires.

1999. The effects of organic additives on induction time and characteristics of precipitated calcium carbonate

Authors: Isopescu, R; Mateescu, C; Mihai, M; Dabija, G

Published: NOV 2010, CHEMICAL ENGINEERING RESEARCH & DESIGN, 88, 1454, DOI: 10.1016/j.cherd.2009.10.002

The effects of an organic additive, polyoxyethylene sorbitan trioleate (Tween 85), on the induction time for the precipitation of calcium carbonate are experimentally and theoretically investigated. Calcium carbonate was precipitated from aqueous solutions of K2CO3 and Ca(NO)(3) at moderate supersaturations ranging between 5 and 16 with and without the organic additive. Experimentally it has been noticed that the induction period for CaCO3 precipitation increases at low supersaturation and is also influenced by temperature. An increase of the induction time was noticed when Tween 85 was added in the system. The "cluster coagulation model" proposed by Qian and Botsaris (1997), which combines nucleation models and coagulation theory, was used to explain the effects of operating parameters on the induction time in terms of interfacial energy and cluster sizes. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

2000. PREPARATION AND PROPERTIES OF BARIUM STEARATE MULTILAYERS WITH CARBON NANOTUBES, MANGANESE PORPHYRIN AND SILVER NITRATE

Authors: Simandan, ID; Popescu, M; Lorinczi, A; Velea, A; Fagadar-Cosma, E

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1033, DOI:

Barium stearate multilayer samples have been deposited by the Langmuir-Blodgett technique. Carbon nanotubes have been added in the deposition solution. The structural properties have been studied. The effect of the doped multilayers has been tested against the solution of ammonium nitrate in water. The effect of (5,10,15,20-tetraphenyl)-porphinato manganese (III) chloride, (MnTPP)Cl, on the multilayer sample has been tested. The change of resistivity of the multilayer samples modified by manganese porphyrin, as a function of the ultraviolet radiation has been discovered and investigated. The increase of the resistance during irradiation is a reversible process, although a slow one. This effect could give a basis for applications in UV sensors and switches. Finally, a photo-resistive effect (induced by UV light) has been discovered in Barium stearate layers doped by silver nitrate.

2001. Barium magnesium tantalate thin films deposited by RF-magnetron sputtering from a stoichiometric target

Authors: Braic, V; Kiss, A; Ioachim, A; Toacsan, M; Nedelcu, L; Braic, M

Published: DEC 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 2385, DOI:

Barium magnesium tantalate thin films are attractive materials for high-performance dielectric ceramics for microwave devices, exhibiting a high dielectric constant, a low loss and a near-zero temperature coefficient. We report on the successful deposition of polycrystalline barium magnesium tantalate thin films by RF magnetron sputtering method. The structural and morphological characterization data are presented.

2002. Origin of the fast magnetization relaxation at low temperatures in HTS with strong pinning

Authors: Miu, L; Ivan, I; Badica, P; Jakob, G; Miu, D; Mele, P; Matsumoto, K; Mukaida, M; Yoshida, Y; Horide, T; Ichinose, A; Horii, S

Published: NOV 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 1129, DOI: 10.1016/j.physc.2010.05.054

The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the low-T range is also evidenced. The collective (elastic) creep regime is generated by the T dependent macroscopic currents induced in the sample during standard magnetization measurements. (C) 2010 Elsevier B.V. All rights reserved.

2003. PRELIMINARY BIOCOMPATIBILITY STUDIES OF HYDROXYAPATITE COATED IRON OXIDE

Authors: Andronescu, E; Ciobanu, CS; Pall, L; Costache, M; Predoi, D

Published: 2010, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 40, 249, DOI:

Bioceramic composites were obtained by combining two biocompatible components (by example- in our studies - hydroxyapatite and iron oxide nanoparticles). The preparation method determines the particle size and shape, the size distribution, the surface chemistry of the iron oxide particles and consequently their magnetic properties. The samples were analysed by X-ray diffraction and IR spectroscopy. Their thermal behaviour was studied by thermogravimetric and thermodifferential analysis. These characterization techniques confirmed the presence of hydroxyapatite on the magnetite surface. Osteoblast cell cultures were used to determine cell proliferation, viability and cytotoxicity on interaction with the samples. The cultures displayed good in vitro behaviour.

2004. Mechanochemical and magnetomechanical synthesis of hematite nanoparticles

Authors: Sorescu, M; Diamandescu, L

Published: FEB 2010, HYPERFINE INTERACTIONS, 196, 358, DOI: 10.1007/s10751-010-0164-9

Samples of hematite were exposed to mechanochemical activation by high energy ball milling for 0-27 h. The milling-induced changes to the structural and magnetic properties of hematite were characterized by X-ray diffraction (XRD) and Mssbauer spectroscopy. The particle size was found to decrease from 80 to 16.5 nm after 8 h of ball milling time, followed by a small increase to 19.8 nm at the end of the milling period. An overall expansion of the crystalline lattice parameters a and c with the milling time was deduced. The magnetic hyperfine field decreased with the ball milling time, from 51.46 down to 50.68 T after 27 h of grinding. Magnetite and traces of iron were observed at the longest milling time employed. The recoilless fraction (f) was measured simultaneously using a dual Mssbauer absorber consisting of hematite and a stainless steel etalon. The f factor first decreased with the milling time due to occurrence of nanoparticles in the system, had a maximum at 12 h due to agglomerations of nanoparticles and exhibited a second maximum at 27 h, due to the appearance of magnetite in the system. More samples of hematite were subjected to magnetomechanical activation by magnetic ball milling for 52 and 134 h. A phase mixture of hematite and magnetite was observed.

2005. Surface Analysis of Protective Films Formed by Poly(vinyl) Alcohol on Titanium in Physiological Serum

Authors: Samide, A; Ciuciu, A; Logofatu, C; Preda, M

Published: JUN 2010, MATERIALE PLASTICE, 47, 177, DOI:

The implants surfaces investigated in the present study were modified with the films of poly (vinyl) alcohol (PVA) which were formed in physiological serum (0.9% NaCl). Surfaces evaluation included electrochemical measurements such as linear potentiometry (LP) and electrochemical impedance spectroscopy (EIS). These suggest that PVA acts by adsorption at site on the metal surface and formed a compact, adherent and uniform layer. The composition of layer was estimated using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/ EDX) and X-ray Photoelectron Spectroscopy (XPS) techniques, which confirm the adsorption of PVA on the surfaces, through -OH groups, with a specific affinity to the titanium sub-strate.

2006. NON-LINEAR RAMAN SCATTERING EFFECTS GENERATED BY THE SURFACE PLASMONS EXCITATION

Authors: Baltog, I; Baibarac, M; Mihut, L; Smaranda, I

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 593, DOI:

An inciting and much debated subject in the surface enhanced Raman (SERS) studies is an unusual anti-Stokes Raman spectrum distinguished by an abnormal intensity, increasing with the vibrational wavenumber and some discrepancies with regard to the Stokes spectrum. We demonstrate that the abnormal anti-Stokes Raman emission on single walled carbon nanotubes and poly(3,4-ethylenedioxy thiophene) synthtetized electrochemically appears as a consequence of two corroborating effects: resonance, which occurs when the energy of the excitation light is near or coincident with the energy of an electronically allowed transition, and the SERS effect achieved by the excitation of surface plasmons. An abnormal intense Raman emission in the Stokes branch, reminiscent to a stimulated Raman effect, which increases exponentially with the intensity of exciting light is reported for the first time in the case of SWNTs.

2007. In-plane gate transistors implanted with different channel geometries by focussed ion beam in positive mode pattern definition technique

Authors: Draghici, M; Diaconescu, D; Melnikov, A; Wieck, AD

Published: JAN 2010, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 207, 234, DOI: 10.1002/pssa.200925087

In-plane gate (IPG) transistors with various channel geometries have been fabricated by focus ion beam implantation technique in positive pattern definition mode on GaAs/Al(x)Ga(1-x)As heterostructures. Both n- and p-type channel transistors were obtained for either n- or p-doped heterostructures, by implantation of the channnel or the gate regions with the complementary dopant type to compensate the initial doping. The current-voltage charactristics showed that the channel can be fully controlled by a gate bias, i.e., it can be completely depleted or enhanced, but two gates are needed to control the channel. Different channel geometries were studied, the most efficient being the "Z-shaped" one. The n-type channel IPG transistors present source-drain currents of few hundreds of microamperes, which is two to three orders of magnitudes higher than that for the p-type channel ones. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2008. Pulsed thermoelectricity

Authors: Apostol, M; Nedelcu, M

Published: JUL 15 2010, JOURNAL OF APPLIED PHYSICS, 108, DOI: 10.1063/1.3456037

A special mechanism of thermoelectric transport is described, consisting of pulses of charge carriers which "fly" periodically through the external circuit from the hot end of the sample to the cold end, with a determined duration of the "on" and "off" times of the electric contacts, while maintaining continuously the thermal contacts. It is shown that such a "resonant" ideal thermogenerator may work cyclically, with the same efficiency quotient as the ideal efficiency quotient of the thermoelectric devices operated in the usual stationary transport regime but the electric flow and power are increased, as a consequence of the concentration of the charge carriers on pulses of small spatial extent. The process is reversible, in the sense that it can be operated either as a thermoelectric generator or as an electrothermal cooler. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3456037]

2009. Martensitic transformation and accompanying magnetic changes in Ni-Fe-Ga-Co alloys

Authors: Sofronie, M; Tolea, F; Kuncser, V; Valeanu, M

Published: JUN 1 2010, JOURNAL OF APPLIED PHYSICS, 107, DOI: 10.1063/1.3429231

Two series of cobalt substituted Ni-Fe-Ga ferromagnetic shape memory alloys with lower gallium content (< 27 at. %) were studied by differential scanning calorimetry, x-ray diffraction, and thermomagnetic measurements. Co substitution for Fe or Ni promotes an increase in the Curie temperatures and a variation in the martensitic transformation (MT) temperatures, in accord with the alloy valence electron concentration change. For alloys with MTs below room temperature, a field dependent thermomagnetic hysteresis was evidenced and discussed in connection with the effect of cobalt substitution, on the magnetic hardness of the martensite phase. A direct interpretation of the evolution of the thermomagnetic hysteresis versus the applied field was provided. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3429231]

2010. Surface topography and optical properties of nitrogen doped ZnO thin films formed by radio frequency magnetron sputtering on fused silica substrates

Authors: Nicolescu, M; Anastasescu, M; Preda, S; Calderon-Moreno, JM; Stroescu, H; Gartner, M; Teodorescu, VS; Maraloiu, AV; Kampylafka, V; Aperathitis, E; Modreanu, M

Published: JUN 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 1349, DOI:

We report here on the nitrogen doped ZnO (ZnO:N) thin films deposited by radio frequency (rf) magnetron sputtering using ZnN target (99.9% purity) on, unintentionally heated, fused silica substrates. After deposition Rapid Thermal Annealing (RTA) at 400 and 550 degrees C for 1min in N-2 ambient have been performed on the ZnO:N thin films. The RTA impact on the optical and microstructural properties of ZnO:N thin films have been investigated by X-ray diffraction, Atomic Force Microscopy, Scanning and Transmission Electron Microscopy coupled with Energy Dispersive X-ray analysis, UV-VIS-NIR spectrophotonnetry and UV-VIS-NIR-Far IR Spectroscopic Ellipsometry. XRD and AFM results revealed an improvement in the crystalline state of ZnO:N and a reduction in the films surface roughness following RTA. The EDX spectrum showed the presence of the nitrogen in small quantities in the ZnO structure (nitrogen/oxygen=1/8). The optical constants of ZnO:N from UV down to Far IR spectral range together with the infrared active modes for ZnO:N are also reported.

2011. N,N-dimethylbiguanide complexes displaying low cytotoxicity as potential large spectrum antimicrobial agents

Authors: Olar, R; Badea, M; Marinescu, D; Chifiriuc, MC; Bleotu, C; Grecu, MN; Iorgulescu, EE; Lazar, V

Published: JUL 2010, EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY, 45, 3034, DOI: 10.1016/j.ejmech.2010.03.033

The new complexes M(DMBG)(2)(ClO(4))(2) (M:Mn, Ni, Cu and Zn; DMBG: N,N-dimethylbiguanide) have been synthesized and characterized by IR, EPR, (1)H NMR, (13)C NMR as well as electronic spectroscopy data. Complex [Ni(DMBG)(2)](ClO(4))(2)center dot 2DMF (DMF: N,N-dimethylformamide) crystallizes in the monoclinic P2 (1)/c space group while [Cu(DMBG)(2)](ClO(4))(2) adopt monoclinic P21/c space group as X-ray single crystal data indicate. The redox behavior of complexes was investigated by cyclic voltammetry. The metal-free N, N-dimethylbiguanide and complexes exhibit specific anti-infective properties as demonstrated the low MIC values, a large antimicrobial spectrum and also inhibit the ability of Pseudomonas aeniginosa and Staphylococcus aureus strains to colonize the inert surfaces. The complexes exhibit also a low cytotoxicity levels on HeLa cells. (c) 2010 Elsevier Masson SAS. All rights reserved.

2012. Improved critical current densities in thick YBa2Cu3O7-delta multilayer films interspaced with non-superconducting YBa2Cu3Ox nanodots

Authors: Sarkar, A; Dang, VS; Mikheenko, P; Kechik, MMA; Abell, JS; Crisan, A

Published: NOV 1 2010, THIN SOLID FILMS, 519, 879, DOI: 10.1016/j.tsf.2010.08.102

We have fabricated and studied quasi-multilayered thick YBa2Cu3O7-delta (YBCO) films composed of several YBCO layers Interspaced with quasi-layers of non-superconducting YBa2Cu3Ox nanodots grown by Pulsed Laser Deposition on SrTiO3 (100) substrates Magnetization J(c)(B) at 773 K for these thick films showed significant improvement as compared to pure YBa2Cu3O7-delta films of same or even smaller thickness A high J(c)(B) in our quite thick films (1 mu m to 6 mu m) provides a very high total critical current per centimetre of the film width Ic-w Critical current as high as 830 A per cm width in self field and 77 3 K was achieved in 5 mu m thick quasi-multilayer film with non-superconducting YBa2Cu3Ox nanodots Frequency-dependent susceptibility measurements showed also an increase in the pinning potential The angular dependence of Ic-w at 86 5 K in 3 T shows a clear indication of anisotropic pinning centres aligned along the c-direction (C) 2010 Elsevier B V All rights reserved

2013. Study of magnetic nanovectors by Wet-STEM, a new ESEM mode in transmission

Authors: Maraloiu, VA; Hamoudeh, M; Fessi, H; Blanchin, MG

Published: DEC 15 2010, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 352, 392, DOI: 10.1016/j.jcis.2010.08.066

Many nanovectors used for therapy (drug targeting radiation therapy) or diagnostic such as Magnetic Resonance Imaging (MRI) have a composite structure consisting of an organic core or organic coverage encapsulating magnetic nanoparticles and they are commonly dispersed in liquid suspensions for intravenous injection Here is presented the application of a new Environmental Scanning Electron Microscopy (ESEM) mode in transmission so called Wet-STEM for transmission imaging of droplets of such suspensions This is illustrated by Wet-STEM images from PLLA/Re nanospheres (about 100-300 nm in diameter) loaded with magnetite nanoparticles (about 10 nm in diameter) and from iron oxide core (about 5 nm in size) MRI contrast agents both examples in aqueous suspensions It is shown that the Wet STEM mode allows both the collective behavior of such nanovectors in suspension to be characterized and the inner composite structure of individual vectors to be revealed Such experimental results are discussed by comparison with Monte Carlo computer simulations of the distribution of the electrons scattered through the samples in rather large solid angles (between 20 degrees and 47 degrees) corresponding to the detection conditions (C) 2010 Elsevier Inc All rights reserved

2014. Thermal analysis of two types of dextran-coated magnetite

Authors: Carp, O; Patron, L; Culita, DC; Budrugeac, P; Feder, M; Diamandescu, L

Published: JUL 2010, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 101, 187, DOI: 10.1007/s10973-009-0593-3

The thermal stability of two kinds of dextran-coated magnetite (dextran with molecular weight of 40,000 (Dex40) and 70,000 (Dex70)), obtained by dextran adsorption onto the magnetite surface is investigated in comparison with free dextran in air and argon atmosphere. The thermal behavior of the two free dextran types and corresponding coated magnetites is similar, but atmosphere dependent. The magnetite catalyzes the thermal decomposition of dextran, the adsorbed dextran displaying lower initial decomposition temperatures comparative with the free one in both working atmospheres. The dextran adsorbed onto the magnetite surface decomposes in air through a strong sharp exothermic process up to similar to 450 A degrees C while in argon atmosphere two endothermic stages are identified, one in the temperature range 160-450 A degrees C and the other at 530-800 A degrees C.

2015. IMPROVING THE CUBIC ZnS NANOCRYSTALS QUALITY BY SELF-ASSEMBLING INTO A MESOPOROUS STRUCTURE

Authors: Nistor, SV; Nistor, LC; Stefan, M; Ghica, D; Mateescu, CD; Birjega, R

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 328, DOI:

Nanocrystals of cubic ZnS (cZnS) doped with 02 % mol Mn2+, self-assembled into a mesoporous structure, have been prepared at room temperature by a surfactant-assisted liquid-liquid reaction The X-ray diffraction measurements confirm the formation of a sponge-like mesoporous structure built from ZnS nanocrystals with cubic (sphalerite) structure and pores of similar diameter of (1 8 +/- 0 2) nm. The Transmission Electron Microscopy (TEM) images show that the mesoporous structure consists of nanocrystals of cZnS with a tight size distribution centered around the average diameter value (21 +/- 0 3) nm The analysis of the observed Election Paramagnetic Resonance (EPR) spectrum demonstrates the presence of the Mn2+ activating ions at isolated sites in the mesoporous material, resulting in three types of paramagnetic centers called Mn2+(I), Mn2+(II) and Mn2+(III) The EPR spectrum of the Mn2+(I) center, attributed to substitutional Mn2+ ions at Zn2+ cation sites in the ZnS nanocrystals, exhibits the smallest linewidth values reported so far, reflecting an increased lattice ordering The high quality of the nanocrystals forming the mesoporous cZnS Mn, as reflected in a tight nanocrystallites size distribution and reduced crystallites lattice disorder, is attributed to the restraining effect of the self-assembling

2016. Mesoporous Tin-Triflate Based Catalysts for Transesterification of Sunflower Oil

Authors: Verziu, M; El Haskouri, J; Beltran, D; Amoros, P; Macovei, D; Gheorghe, NG; Teodorescu, CM; Coman, SM; Parvulescu, VI

Published: JUL 2010, TOPICS IN CATALYSIS, 53, 772, DOI: 10.1007/s11244-010-9468-x

Unimodal porous system (denoted as SnTf-MCM-41) and bimodal porosity (denoted as SnTf-UVM-7) were prepared in a two-step synthesis. The triflic acid was incorporated into previously synthesized Sn-containing porous silicas. Chemical analysis was carried out by electron probe microanalysis (EPMA), textural properties were determined by transmission electron microscopy (TEM) and from nitrogen adsorption-desorption isotherms (77 K), while structural characterization by X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) measurements. The structural characterization provided evidences on the direct interaction of triflate with incorporated tin species. The acidity of these catalysts was determined from the ammonia chemisorption measurements. The catalysts have been tested for transesterification of sunflower oil under both microwave and ultrasound activation. These experiments showed a direct reaction between the acidity of the catalysts and catalytic performances. No leaching of the triflate species or catalyst deactivation have been detected over several runs.

2017. Langmuir and Langmuir-Blodgett films based on stearic acid, barium stearate and carbon nanotubes

Authors: Simandan, ID; Sava, F; Velea, A; Lorinczi, A; Popescu, M

Published: AUG 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1181, DOI:

Langmuir films and Langmuir-Blodgett multilayers based on fatty acid (stearic acid, barium stearate) mixed with carbon nanotubes have been prepared and investigated by isothermal compression (for Langmuir films) and X-ray diffraction (for Langmuir-Blodgett multilayers). An irreversible modification has been observed in the case of Langmuir films doped by carbon nanotubes, due to reordering of the nanotubes in the film matrix.

2018. Integrated nanotechnology of pinning centers in YBa2Cu3Ox films

Authors: Mikheenko, P; Dang, VS; Tse, YY; Kechik, MMA; Paturi, P; Huhtinen, H; Wang, Y; Sarkar, A; Abell, JS; Crisan, A

Published: DEC 2010, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 23, DOI: 10.1088/0953-2048/23/12/125007

A controlled pinning change from the ab-plane dominant to the c-axis dominant has been achieved in a novel method of nanostructured YBa2Cu3Ox (YBCO) growth. The method is a synchronous self-assembly of BaZrO3 (BZO) and Ag-assisted YBCO nanothreads. The formation of entangled nanothreads increases the critical current density while keeping the critical temperature close to that in pure YBCO films. The nanothreads extend through the whole thickness of thick films, making the method suitable for increasing total critical current density per centimeter of width (Ic-w). Two growth mechanisms, the formation of BZO nanorods and YBCO nanocolumns, complement each other, form a coherent structure and produce samples with strong correlated pinning. In addition to the increase in Ic-w, correlated pinning leads to an increase in vortex melting temperature in a wide range of magnetic fields. The films grown by this method have high Ic-w both in low magnetic fields along the c axis and high magnetic fields in the ab plane of YBCO. Such a superconductor would be suitable for both cable and magnet applications.

2019. TEMPERATURE DEPENDENCE OF CAPTURE COEFFICIENTS IN TRAPPING PHENOMENA

Authors: Lepadatu, AM; Stavarache, I; Lazanu, S; Iancu, V; Mitroi, MR; Nigmatulin, RR; Ciurea, ML

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 374, DOI:

The temperature dependence of the capture coefficients in trapping phenomena is investigated. It is proved that, besides the dependence induced by the thermal velocity of the carriers, the stress-induced traps at the interfaces of the multi-layered structures present a supplementary temperature dependence. This dependence is found to be of Gaussian type and is in a good agreement with the experimental results.

2020. Novel Pd heterogeneous catalysts for cycloisomerisation of acetylenic carboxylic acids

Authors: Neatu, F; Protesescu, L; Florea, M; Parvulescu, VI; Teodorescu, CM; Apostol, N; Toullec, PY; Michelet, V

Published: DEC 2010, GREEN CHEMISTRY, 12, 2149, DOI: 10.1039/c0gc00258e

The Pd-TPPTS complex (TPPTS - trisodium salt of 3,3',3 ''-phosphanetriyl benzenesulfonic acid) and PdCl42- salt heterogenised onto Zn2AlNO3 layered double hydroxide (LDH) using an ion-exchange procedure, have been shown to be efficient green catalysts in the cycloisomerisation reaction of acetylenic carboxylic acids to the corresponding 5-membered heterocycles.

2021. Increased critical current density and pinning in thick Ag/YBa2Cu3O7-x multilayers

Authors: Dang, VS; Mikheenko, P; Sarkar, A; Kechik, MMA; Abell, JS; Crisan, A

Published: NOV 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 1241, DOI: 10.1016/j.physc.2010.05.083

We have investigated the superconducting properties of Ag/YBa2Cu3O7-x thick multilayers grown by Pulsed Laser Deposition, and found that the artificial pinning centres induced by Ag nanodots lead to a significant increase in critical current, especially in high applied magnetic fields. Transmission Electron Microscopy showed a columnar growth of YBa2Cu3O7-x, induced by Ag nanodots, while angle-dependent transport measurements revealed the existence of strong, both isotropic and c-axis correlated, artificial pinning centres. (C) 2010 Elsevier B.V. All rights reserved.

2022. Synthesis and characterization of xTiO(2 center dot)(1-x)alpha-Fe2O3 magnetic ceramic nanostructure system

Authors: Sorescu, M; Xu, TH; Diamandescu, L

Published: NOV 2010, MATERIALS CHARACTERIZATION, 61, 1118, DOI: 10.1016/j.matchar.2010.07.004

Rutile doped hematite xTiO(2) (1-x)alpha Fe2O3 (x=0 0-10) nanostructures were synthesized using mechanochemical activation by ball milling Their complex structural magnetic and thermal properties were characterized by X ray diffraction Mossbauer spectroscopy and simultaneous DSC-TGA XRD patterns yielded the dependence of lattice parameters and grain size as a function of ball milling time For the molar concentrations x=0 1 and 03 the Mossbauer spectra were fitted with one two three or four sextets corresponding to the degree of Ti ion substitution of Fe ions in hematite lattice After 12 h of ball milling the completion of Ti ion substitution of Fe ions in hematite lattice occurs for x=0 1 and 03 For x=0 5 and 07 Mossbauer spectra fitting required sextets and a quadrupole split doublet representing Fe ions substituting Ti ions in the rutile lattice The completion of Fe ion substitution of Ti ions in rutile lattice was not observed as indicated by XRD patterns and Mossbauer spectra for these two molar concentrations Simultaneous DSC-TGA measurements revealed that the mechanochemical activation by ball milling has a strong effect on the thermal behavior of this nanostructure system The enthalpy dropped dramatically after 2 h of milling time indicating the strong solid-solid interactions between TiO2 and a Fe2O3 after ball milling The change in weight loss of hematite was caused by the decrease of grain size and ion substitutions between Fe and Ti after mechanochemical activation (C) 2010 Elsevier Inc All rights reserved

2023. Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter

Authors: Draghici, M; Stamate, E

Published: APR 21 2010, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 43, DOI: 10.1088/0022-3727/43/15/155205

Highly electronegative plasmas were produced in Ar/SF6 gas mixtures in a dc discharge with multipolar magnetic confinement and transversal magnetic filter. Langmuir probe and mass spectrometry were used for plasma diagnostics. Plasma potential drift, the influence of small or large area biased electrodes on plasma parameters, the formation of the negative ion sheath and etching rates by positive and negative ions have been investigated for different experimental conditions. When the electron temperature was reduced below 1 eV the density ratio of negative ion to electron exceeded 100 even for very low amounts of SF6 gas. The plasma potential drift could be controlled by proper wall conditioning. A large electrode biased positively had no effect on plasma potential for density ratios of negative ions to electrons larger than 50. For similar electronegativities or higher a negative ion sheath could be formed by applying a positive bias of a few hundred volts.

2024. Analyzing the measured phase in the multichannel Aharonov-Bohm interferometer

Authors: Tolea, M; Nita, M; Aldea, A

Published: JUL 2010, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 42, 2236, DOI: 10.1016/j.physe.2010.04.022

We address the quantum dot phase measurement problem in an open Aharonov-Bohm interferometer, assuming multiple transport channels. In such a case, the quantum dot is characterized by more than one intrinsic phase for the electrons transmission. It is shown that the phase which would be extracted by the usual experimental method (i.e. by monitoring the shift of the Aharonov-Bohm oscillations, as in Schuster et al., Nature 385 (1997) 417) does not coincide with any of the dot intrinsic phases, but is a combination of them. The formula of the measured phase is given. The particular case of a quantum dot containing a S = 1/2 spin is discussed and variations of the measured phase with <pi are found, as a consequence of the multichannel transport. (C) 2010 Elsevier B.V. All rights reserved.

2025. Microstructure and ferroic properties of epitaxial [gamma-Fe2O3-BiFeO3]-Bi3.25La0.75Ti3O12 composite bilayers

Authors: Gautreau, O; Harnagea, C; Gunawan, L; Botton, GA; Pintilie, L; Singh, MP; Pignolet, A

Published: DEC 1 2010, JOURNAL OF APPLIED PHYSICS, 108, DOI: 10.1063/1.3514591

Epitaxial [gamma-Fe2O3-BiFeO3]/Bi3.25La0.75Ti3O12 and Bi3.25La0.75Ti3O12/[gamma-Fe2O3-BiFeO3] composite bilayers were grown on SrRuO3 coated (111) SrTiO3 substrates in order to investigate the influence of the morphology of the gamma-Fe2O3-BiFeO3 self assembled nanocomposite layer on the multiferroic properties of the bilayer. Both types of bilayers exhibit high resistivity and simultaneously ferroelectricity and ferrimagnetism at room temperature. When the gamma-Fe2O3-BiFeO3 composite layer is sandwiched between the Bi3.25La0.75Ti3O12 film and the substrate, the BiFeO3 component is not only subjected to epitaxial strain induced by the surface on top of which it grows but also to elastic interactions with the Bi3.25La0.75Ti3O12 capping layer. The latter indeed reduce the amount of gamma-Fe2O3 inclusions, affects the morphology of the grains in the gamma-Fe2O3-BiFeO3 layer, and increases the shape anisotropy of the gamma-Fe2O3 inclusions. Additionally, this modification in the microstructure of the gamma-Fe2O3-BiFeO3 layer induces an imprint in the ferroelectric hysteresis loop as well as a decrease in the saturation magnetization, and its magnetic easy axis direction changes from in-plane to out-of plane. (c) 2010 American Institute of Physics. [doi:10.1063/1.3514591]

2026. Left-handed structures for microwave applications

Authors: Mihai, IA; Banciu, MG; Ioachim, A; Militaru, N; Lojewski, G; Petrescu, T

Published: APR 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 908, DOI:

In this paper, dispersion/attenuation diagrams are investigated for purely left-handed (PLH) and for composite right/left handed (CRLH) transmission lines. The magnitude and phase of the S parameters of these structures are analyzed in a broadband (1-7 GHz) range. The investigations on microstrip CRLH lines demonstrate the presence of the left-handed range, the stop-band (only for the unbalanced lines) and the right-handed range. By edge-coupling two such CRLH lines, devices with new properties, different from conventional microstrip devices were obtained. Symmetric and asymmetric 0 dB backward couplers working in the stop-band of the CRLH line were achieved. Very short 3 dB couplers (with only 2 or 3 unit cells) were also investigated.

2027. Optical and structural studies on Ba(Mg1/3Ta2/3)O-3 thin films obtained by radiofrequency assisted pulsed plasma deposition

Authors: Scarisoreanu, ND; Galca, AC; Nedelcu, L; Ioachim, A; Toacsan, MI; Morintale, E; Stoica, SD; Dinescu, M

Published: SEP 1 2010, APPLIED SURFACE SCIENCE, 256, 6530, DOI: 10.1016/j.apsusc.2010.04.041

Single-phase Ba(Mg1/3Ta2/3)O-3 thin films were prepared by radiofrequency plasma beam assisted pulsed laser deposition (RF-PLD) starting from a bulk ceramic target synthesized by solid state reaction. Atomic force microscopy, X-ray diffraction and spectroscopic ellipsometry were used for morphological, structural and optical characterization of the BMT thin films. The X-ray diffraction spectra show that the films exhibit a polycrystalline cubic structure. From spectroscopic ellipsometry analysis, the refractive index varies with the thin films deposition parameters. By using the transmission spectra and assuming a direct band to band transition a band gap value of approximate to 4.72 eV has been obtained. (C) 2010 Elsevier B.V. All rights reserved.

2028. The influence of chemical composition on initial permeability frequency spectra of cobalt ferrites

Authors: Vilceanu, V; Feder, M; Boutiuc, L; Dumitru, I; Caltun, OF

Published: JUN 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 811, DOI:

In order to study the influence of the cations substitution on permeability of cobalt ferrites four series of samples with different chemical composition were prepared by conventional ceramic method. The calcined powders and sintered samples were characterized by X-ray diffraction and vibrating samples magnetometer. The microstructure of the samples was analyzed by surface electron microscopy. The initial permeability spectra at room temperature were plotted using the torus standard method. Chemical composition and the microstructure influence the magnetic properties and the initial permeability spectra of the cobalt ferrites samples. Small amount of manganese ions decreases the Curie temperature, increase the initial permeability and saturation magnetization and decreases the coercive magnetic field, thus improving the performances of cobalt ferrites for magnetostrictive sensors applications.

2029. Effect of the morphology on the optical and electrical properties of TPyP thin films deposited by vacuum evaporation

Authors: Socol, M; Rasoga, O; Stanculescu, F; Girtan, M; Stanculescu, A

Published: DEC 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 2038, DOI:

We have studied the effect of the morphology on the optical and electrical properties of the TPyP thin films deposited by vacuum evaporation on different substrates (Si with different characteristics, ITO, quartz and glass). The presence of some well-defined B and Q absorption bands has been evidenced. FTIR and photoluminescence measurements have been used to confirm the preservation of the chemical structure of the compound during the evaporation process. The contact Au/TPyP/Si(n) is rectifier, while a blocking behavior has been shown by Si(n)/TPyP/Si(n) and ITO/TPyP/Si(n) and an injector dominated behavior by Si(p)/TPyP/Si(p) and ITO/TPyP/Si(p) heterostructures. The best transmission was obtained on TPyP film deposited on ITO and the highest value of the current in heterostructures Si(n) electrode characterised by a large grain morphology and in consequence by a weak optical and charge carrier scattering at the grain boundaries.

2030. STRUCTURES EXHIBITING LEFT-HANDED PROPERTIES IN MICROWAVE RANGE

Authors: Banciu, MG; Ioachim, A; Militaru, N; Lojewski, G; Ramer, R

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 294, DOI:

New distributed multilayer microstrip structures are investigated in microwaves. The amplitude and phase responses are analyzed for different geometrical parameters, number of cells and dielectric constants of the dielectric layers. It is shown that the proposed structures exhibit left-handed properties in a frequency range near the resonance.

2031. Optical and morphologic properties of YVO4:Eu phosphor

Authors: Georgescu, S; Voiculescu, AM; Cotoi, E; Toma, O; Gheorghe, L; Achim, A; Matei, C; Enculescu, I; Matei, E; Osiac, M

Published: 2010, ROMOPTO 2009: NINTH CONFERENCE ON OPTICS: MICRO- TO NANOPHOTONICS II, 7469, DOI: 10.1117/12.866769

In this paper we present new results concerning the optical and morphologic properties of YVO4:Eu red nanophosphor prepared by a precipitation method and subsequently annealed in air at various temperatures. We monitored the morphologic changes induced by the thermal treatments using the optical spectroscopy (reflectance and luminescence spectra), XRD and electron microscopy. The annealing leads to an increase of the particle size and improvement of the order of the crystalline lattice of YVO4. The annealing at 800 degrees C produces the sample with the highest luminescence intensity.

2032. Redox behavior of hemin at p-GaAs(1 0 0) electrode

Authors: Toader, AM; Volanschi, E; Lazarescu, MF; Lazarescu, V

Published: DEC 30 2010, ELECTROCHIMICA ACTA, 56, 866, DOI: 10.1016/j.electacta.2010.09.083

Electrochemical behavior of hemin on p-GaAs(1 0 0) electrodes was examined by cyclic voltammetry (CV) and impedance spectroscopy (EIS) in phosphate buffer solutions (PBS) at pH 7.45. CV investigations in 0.6 mM hemin in PBS revealed a pair of reversible peaks at -0.44 and -0.32 V vs. SCE resulting in stable adsorbed species. EIS spectra analysis pointed out that these adsorbed species bring significant changes in the semiconductor surface state population and the potential drop distribution between the semiconductor space charge region and the Helmholtz layer. (C) 2010 Elsevier Ltd. All rights reserved.

2033. Nano and micro-morphology modifications of Si (100) substrate induced by femtosecond laser pulse irradiations in air, water, CCl4 and C2Cl3F3

Authors: Ionel, L; Cristescu, CP; Jipa, F; Enculescu, M; Radoiu, M; Dabu, R; Zamfirescu, M; Ulmeanu, M

Published: NOV 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1924, DOI:

The aim of this study is to investigate the influence of the different media, e.g. air, water, CCl4 (carbon tetrachloride) and C2Cl3F3 (tricloro-trifluoro-ethane), when irradiating a Si (100) substrate, with a 200 femtosecond (fs) laser pulses of a Ti:sapphire laser operating at 775 nm. Various micro and nanomorphologies could be achieved by changing the media, the laser pulse energy and the number of pulses. It is shown that the resulting Si (100) surface presents a regulated morphology in air consisting of parallel ripples and the formation of regular arrays of submicrometer spikes on Si (100) in CCl4 and C2Cl2F3, respectively. Irradiation of a Si (100) substrate immersed in water creates a regularly structured surface but it doesn't facilitate the spikes formation. The potential use of the patterned Si substrates as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth is envisaged.

2034. Porous Au-TiO2 aerogels nanoarchitectures for photodegradation processes

Authors: Peter, A; Baia, L; Baia, M; Indrea, E; Toderas, F; Danciu, V; Cosoveanu, V; Diamandescu, L

Published: MAY 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 1077, DOI:

Porous nanoarchitectures based on TiO2 aerogel and colloidal gold particles have been obtained by different synthesis routes: impregnation of TiO2 aerogel with Au colloid, impregnation of TiO2 gel with Au colloid and preparation of TiO2 gel in the presence of Au colloid. The as prepared composites have been thermal treated at 500 degrees C and their structural and morphological properties were investigated. The Raman spectra and XRD data demonstrated the anatase structure of the composite obtained by impregnation of TiO2 aerogel with Au colloid and the mixed anatase-brookite structure of those obtained by impregnation of TiO2 gel with Au colloid and by preparation of TiO2 gel in the presence of Au colloid, respectively. TEM analyses suggest that the Au particles on the TiO2 surface as individual particles, as well as clusters are present. The photocatalytic performances of the synthesized composites were tested in the salicylic acid photodecomposition process and it was found that they are strongly influenced by both anatase - brookite TiO2 structure and Au nanoparticles dispersion on the TiO2 surface.

2035. BEHAVIOR OF THE MAIN PROPETIES OF HARD AND SOFT TYPE PIEZOCERAMICS WITH TEMPERATURE FROM 2 TO 600 K

Authors: Miclea, C; Tanasoiu, T; Miclea, CF; Amarande, L; Cioangher, M; Trupina, L; Iuga, A; Spanulescu, I; Miclea, CT; David, C; Susu, M

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 304, DOI:

The application area of piezoceramic materials and devices based on such materials is continuously extended. The working conditions for such devices and structures may be sometimes very hard such as low and high temperatures, nuclear radiation, high pressure and so on. Such conditions may affect to some extent the transducer performances due to the changes of the basic properties of piezoceramic materials used as sensors. In this regard we have investigated the changes of the main piezoelectric properties of two typically hard and soft piezoceramics within a large temperature range from 2 to 600 K. All parameters measured showed a rather steady increase or decrease with increasing temperature. The results were discussed in terms of intrinsic and domain wall contribution to the dielectric and piezoelectric response of materials.

2036. Structure and Mossbauer measurements on SnSe2 bulk and thin films

Authors: Bibicu, I; Lorinczi, A; Velea, A; Sava, F; Popescu, M

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1571, DOI:

Thin films samples of SnSe2 deposited by PLD and PED have been prepared and studied by XRD and Mossbauer spectroscopy. The films are crystalline with a major phase of SnSe2 and minor phase of amorphous SnSe2. An oxidation process lead to the appearance of a thin layer of SnO2 on the surface of the PLD samples.

2037. Polymer-microporous host interactions probed by photoluminescence spectroscopy

Authors: Tiseanu, C; Parvulescu, VI; Cojocaru, B; Lorenz-Fonfria, VA; Kumke, M; Gessner, A; Enculescu, I

Published: 2010, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12, 3037, DOI: 10.1039/b922591a

Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.

2038. Modifications of the Catalytic Activity for Cyanoethylation Induced by the Memory Effect of Mg/Al-Type Modified Hydrotalcites

Authors: Pavel, OD; Birjega, R; Angelescu, E; Zavoianu, R; Florea, M; Mitran, G

Published: APR 2010, , DOI:

2039. Epoxidation of cyclohexene with O-2 and isobutyraldehyde catalysed by cobalt modified hydrotalcites

Authors: Angelescu, E; Ionescu, R; Pavel, OD; Zavoianu, R; Birjega, R; Luculescu, CR; Florea, M; Olar, R

Published: JAN 15 2010, , DOI: 10.1016/j.molcata.2009.09.009

2040. Properties and etching rates of negative ions in inductively coupled plasmas and dc discharges produced in Ar/SF6

Authors: Draghici, M; Stamate, E

Published: JUN 15 2010, JOURNAL OF APPLIED PHYSICS, 107, DOI: 10.1063/1.3452357

Negative ion production is investigated in a chamber with transversal magnetic filter operated in dc or inductively coupled plasma (ICP) modes in Ar/SF6 gas mixtures. Plasma parameters are evaluated by mass spectrometry and Langmuir probe for different discharge conditions. The density ratio of negative ion to electron exceeded 300 in dc mode while it was below 100 in the ICP mode. The possibility to apply a large positive bias to an electrode without affecting the plasma potential and the transition from a negative sheath to anodic glow are also investigated. The etching rates by positive and negative ions are evaluated on silicon substrate for different Ar/SF6 gas ratios. The etching rate by negative ions was with less than 5% smaller than that by positive ions. (C) 2010 American Institute of Physics. [doi:10.1063/1.3452357]

2041. Quantum Confinement in Nanometric Structures

Authors: Ciurea, ML; Iancu, V

Published: 2010, NEW TRENDS IN NANOTECHNOLOGY AND FRACTIONAL CALCULUS APPLICATIONS, +, DOI: 10.1007/978-90-481-3293-5_5

This paper discusses the quantum confinement effects in nanometric structures that form low dimensional systems. In such systems, each surface/interface acts like a potential barrier, i.e. the wall of a quantum well, generating new energy levels. These levels are computed in a model that uses the approximation of the infinite rectangular quantum wells. The model is adapted for 2D, 1D and 0D systems, respectively. Different applications are discussed. The differences between the model results and the experimental data are proved to be of the same order of magnitude as the differences between the levels computed within the frame of infinite and finite quantum well approximations.

2042. Multifrequency ESR Characterization of Paramagnetic Point Defects in Semiconducting Cubic BN Crystals

Authors: Nistor, SV; Stefan, M; Ghica, D; Goovaerts, E

Published: OCT 2010, APPLIED MAGNETIC RESONANCE, 39, 101, DOI: 10.1007/s00723-010-0136-x

Low-frequency (X-band) electron spin resonance (ESR) investigations on commercially available large-grained cubic boron nitride (cBN) superabrasive powders of various coloration, combined with high-frequency (W-band) ESR measurements on oriented submillimeter-size single crystallites selected from the same powder samples, resulted in a clear identification of several types of paramagnetic point defects. The resulting spin Hamiltonian parameters describing the ESR spectra observed in the 3-293 K temperature range and the photosensitivity of the paramagnetic defects observed in amber-colored cBN samples are reported. It is shown that the nature of the paramagnetic centers depends on the color of the investigated samples and that, in many cases, uncontrolled impurities seem to be involved in their structure.

2043. Characterization of lanthanum zirconate prepared by a nitrate-modified alkoxide synthesis route: From sol to crystalline powder

Authors: Ion, ED; Malic, B; Arcon, I; Gomilsek, JP; Kodre, A; Kosec, M

Published: JAN 2010, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 30, 575, DOI: 10.1016/j.jeurceramsoc.2009.04.009

We studied the synthesis of lanthanum zirconate from lanthanum nitrate and zirconium butoxide in the transition from liquid to amorphous and crystalline phase. Thermal behaviour of lanthanum nitrate dissolved in 2-methoxyethanol is different from that of the salt, which we ascribe to the potential coordination of the solvent to lanthanum atoms. IR analysis shows that lanthanum nitrate remains strongly associated in the solvent. The lanthanum environment in the lanthanum nitrate and lanthanum zirconate sols, determined by EXAFS, is similar to that of the lanthanum nitrate hydrate. The environment is completely changed in the dried lanthanum zirconate precursor powder and powder heated at 500 degrees C due to the decomposition of nitrates. Zirconium species form polynuclear oxo-alkoxide complexes during thermolysis and they are stable from room temperature to 500 degrees C. The powder heated up to 700 degrees C for 1 h is amorphous, while after heating at 800 degrees C for 1h pure pyrochlore phase crystallizes. No link between La and Zr species is established either in the sol or in the dried precursor powder or amorphous powder heated at 500 degrees C. The reaction between the metallic species proceeds as a solid-state reaction. The synthesis route ensures a very good mixing of the species at the nanometre level. (C) 2009 Elsevier Ltd. All rights reserved.

2044. Iron and chromium mixed-oxide nanocomposites

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D; Krupa, S; Feder, M

Published: FEB 2010, HYPERFINE INTERACTIONS, 196, 368, DOI: 10.1007/s10751-010-0165-8

Mixed oxides nanocomposites of the type xCr(2)O(3)-(1-x)alpha-Fe2O3 (x = 0.0-1.0) were synthesized using hydrothermal technique and characterized by X-ray diffraction (XRD) and Mossbauer spectroscopy. The same characterization methods were applied to a set of samples annealed at 600 degrees C for 2 h. High chromium content correlated with occurrence of amorphization effects and onset of superparamagnetism in the as-obtained samples. The structure and properties of the thermally annealed samples, however, are dominated by the equilibrium of two phases, Cr:Fe2O3 and Fe:Cr2O3. The final (x = 1.0) particle size of the nanocomposite is close to 19 nm.

2045. Removal of Reactive Black 5 azo dye from aqueous solutions by catalytic oxidation using CuO/Al2O3 and NiO/Al2O3

Authors: Bradu, C; Frunza, L; Mihalche, N; Avramescu, SM; Neata, M; Udrea, I

Published: JUN 7 2010, APPLIED CATALYSIS B-ENVIRONMENTAL, 96, 556, DOI: 10.1016/j.apcatb.2010.03.019

CuO/Al2O3 and NiO/Al2O3 catalysts prepared by incipient wetness impregnation were used for the oxidation of Reactive Black 5 (RB5) in aqueous solution. Removal of the dye was assessed by High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) measurements and the generation of the hydroxyl radicals in the process was evaluated by chemiluminescence measurements. To put in evidence the interaction RB5 - catalyst and the surface species formed onto catalysts during the oxidation, Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis was performed. A different behavior of the two catalytic systems was revealed by the comparative analysis of the data obtained from the adsorption and oxidation tests. Only CuO/Al2O3 was effective in the RB5 degradation, NiO/Al2O3 acted as a simple adsorbent. In the presence of CuO/Al2O3, at H2O2 concentration of 40 mM the azo dye was totally eliminated from both solution and catalyst surface after 4 h, with a mineralization degree higher than 90%. However, a strong inhibition of the catalytic oxidation of RB5 was observed in the presence of phosphate ions. In the conditions of hydrogen peroxide excess, the rate equation in the case of copper catalyst was simply expressed by a pseudo-first order equation and the model was found to fit well the data. The amount of copper leached from catalyst during the oxidation process was only 1.0-1.6% per cycle leading to the conclusion that the decrease of the dye mineralization with the number of cycles has to be explained mostly by the surface covering with the reaction products, at least to a certain extent. (C) 2010 Elsevier B.V. All rights reserved.

2046. Sol-gel synthesis and characterization of BaTiO3-doped (Bi0.5Na0.5)TiO3 piezoelectric ceramics

Authors: Cernea, M; Andronescu, E; Radu, R; FochiB, F; Galassi, C

Published: FEB 4 2010, JOURNAL OF ALLOYS AND COMPOUNDS, 490, 694, DOI: 10.1016/j.jallcom.2009.10.140

(Bi0.5Na0.5)TiO3 doped with 8 mol% BaTiO3 (BNT-BT0.08) powder was prepared by an acetate-alkoxide sol-gel method. The evolution of the structure and microstructure of the precursor gel, heated at various temperatures as well as, the piezoelectric and ferroelectric properties of BNT-BT0.08 ceramics were studied. Nanopowder of BNT-BT0.08 with average particles size of 30 nm and, crystallized on the perovskitic structure of (Bi0.5Na0.5)TiO3, were obtained from the precursor gel by heating at 600 degrees C, 3 h in air. The ceramics of composition 0.92(Bi0.5Na10.5)TiO3-0.08BaTiO(3), manufactured from the as-prepared nanostructured powder, present good dielectric properties (epsilon(r,max) = 4000-4500, tan delta = 0.02-0.03) and high mechanical quality factor (Q(m) similar to 500). (C) 2009 Elsevier B.V. All rights reserved.

2047. Linear and Non-Linear Optical Properties of Carbon Nanotubes

Authors: Lefrant, S; Buisson, JP; Mevellec, JY; Baibarac, M; Baltog, I

Published: 2010, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 522, 479, DOI: 10.1080/15421401003719910

Carbon nanotubes are attractive materials with numerous possibilities of applications in various domains. Nevertheless, pertinent characterization studies are required in order to insure reproducibility in preparation, handling and incorporation in devices. Several spectroscopic tools have been developed so far, such as transmission electron microscopy and near-field electrical microscopy. Optical techniques have also been improved with the use of Raman Scattering, Surface Enhanced Raman Scattering (SERS) and near-field optical spectroscopy (SNOM). These non-destructive techniques have been used for nanotubes after synthesis and exploited to follow the modifications of their spectroscopic features when they are functionalized or embedded in host matrices. In this paper, we show that, by using SERS conditions, a new effect is observed: a "single-beam pumped'' Coherent anti-Stokes Raman Scattering (CARS). We demonstrate that under a tight-focusing of the excitation light, this emission, resulting from a wave mixing process between the incident laser light (omega(l)) and Stokes Raman light (omega(s)), is generated by a Surface Enhanced Raman Scattering (SERS) mechanism. Since abnormal anti-Stokes/Stokes intensity ratios are also observed for carbon nanotubes in powders, we have investigated in details their behaviour as a function of several parameters which include the excitation wavelengths, the laser power, the sample support, as well as the presence of nanotubes in isolated or in bundled form. It appears that resonance phenomena explain the anti-Stokes/Stokes intensity ratios in the case of powders and that CARS is only observed when SERS conditions are used. In addition, we have investigated other materials in which anomalies are also observed. This is the case of poly(bithiophene) (PBTh) electrochemically polymerized on carbon nanotubes for which its main Raman line at 1450 cm(-1) is enhanced, this enhancement being presumably generated by the plasmon excitation of metallic tubes. In the case of PEDOT, the analysis of the anti-Stokes branch provides additional information on the functionalization of carbon nanotubes with this polymer.

2048. Boron nitride nano-structures produced by pulsed laser ablation in acetone

Authors: Nistor, LC; Epurescu, G; Dinescu, M; Dinescu, G

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012067

Different phases of boron nitride (BN) nano-structures are synthesized from an hBN ceramic target immersed in acetone, by ablation with a high power pulsed Nd: YAG laser. Transmission electron microscopy (TEM) and electron diffraction (ED) are used to identify the morphology and structure of the prepared colloidal suspensions. It is revealed that by varying solely a single experimental parameter, i.e. the laser pulse fluency, a large variety of BN nanostructures can be produced: nanotubes, very thin graphene-like foils, nano-curls and nanoparticles, all with the hexagonal graphite-like hBN structure, as well as high pressure BN phases: orthorhombic explosion E-BN nano-rods, or cubic diamond-like cBN nano-particles.

2049. PHYSICO-CHEMICAL PROPERTIES OF NANO-SIZED HEXAGONAL HYDROXYAPATITE POWDER SYNTHESIZED BY SOL-GEL

Authors: Costescu, A; Pasuk, I; Ungureanu, F; Dinischiotu, A; Costache, M; Huneau, F; Galaup, S; Le Coustumer, P; Predoi, D

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1000, DOI:

Calcium phosphate ceramic powders were synthesized via sol-gel method. The powders were sintered at 600 and 1000 degrees C and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM and TEM), elemental microanalysis (EDS), infrared spectroscopy (FTIR), and thermal analysis (TGA and DTA). The XRD analysis revealed a well crystallized hydroxyapatite (HAp) structure at all temperatures. At 1000 degrees C a small amount of CaO (about 1.2 %) was detected. The average crystallite size increased from 19 nm at 80 degrees C to about 125 nm at 1000 degrees C. FTIR spectra showed the presence of various PO43- and OH- groups present in the powders. In order to verify the biocompatibility of HAP powders with hFOB 1.19 osteoblasts cells, an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test was applied. It was noticed that the ceramics obtained at 1000 degrees C, increased the cell viability with 10%, 40% and 55% after 6, 12 respectively 24 h, whereas that obtained at 600 degrees C was less effective. Our results proved the high biocompatibility of calcium phosphate ceramic powders obtained by sol-gel and sintered at 1000 degrees C.

2050. Improved large mesoporous ordered molecular sieves-Stabilization and acid/base functionalization

Authors: Kosslick, H; Pitsch, I; Deutsch, J; Pohl, MM; Schulz, A; Vu, AT; Nguyen, DT; Frunza, L; Jaeger, C

Published: JUL 1 2010, CATALYSIS TODAY, 152, 60, DOI: 10.1016/j.cattod.2010.03.005

The preparation of nanoporous materials with enhanced stability using an improved synthesis route using reactive inorganic silica and alumina species is reported. This way improved mesoporous molecular sieves were obtained. The synthesized aluminum substituted mesoporous molecular materials (Al-MMS) contain very large pores of 50-200 angstrom size combined with an improved pore wall thickness. Increased wall thickness and Al substitution lead to an improved chemical stability against alkaline solution. The textural, structural and acid properties are investigated by physico-chemical methods. The catalytic performance acidic materials was tested in the benzoylation reaction; amino functionalized materials were studied in the base catalyzed Michael addition. (C) 2010 Elsevier B.V. All rights reserved.

2051. Structural and photoluminescence characterization of mesoporous silicon-phosphates

Authors: Tiseanu, C; Parvulescu, V; Parvulescu, V; Cotoi, E; Gessner, A; Kumke, M; Simon, S; Vasiliu, F

Published: SEP 5 2010, JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 215, 24, DOI: 10.1016/j.jphotochem.2010.07.015

Two different types of mesoporous silicon-phosphate supports using different surfactants (a mixture of (CH3)(3)C13H27NBr with an organophosphorus coupling molecule (HO-PO(i-C3H7)(2)) and with a co-surfactant ((C2H5)(3)(C6H5)PCl), respectively) were synthesized. Trivalent europium (Eu) ions were immobilized via ion-exchange on these supports. The resulting materials were characterized using nitrogen adsorption isotherms at -196 degrees C, thermogravimetric analysis, SEM, TEM, FT-IR, PXRD, CP/MAS. (HSi)-H-1-Si-29 and P-31 NMR, DR-UV-vis as well as steady-state and time-resolved photoluminescence spectroscopy. The results evidenced that the co-polymerization of silicon and phosphorous yielded a unique morphology in these materials. Following calcination at 450 and 900 degrees C europium-exchanged silicon-phosphates with great surface area (BET=600-705 m(2) g(-1)) and 3.4 nm sized mesopores were obtained. The differences among the optical properties of the non-calcined europium materials such as the emission lifetimes, local environment at the europium sites or the relative contribution of the upper excited levels to the total photoluminescence were assigned to the surfactants used in the synthesis. Calcination of the silicon-phosphates at higher temperatures than 450 degrees C did not induce major changes in the structural properties: in contrast, photoluminescence properties of europium were markedly improved in terms of intensity and average lifetime. (C) 2010 Elsevier B.V. All rights reserved.

2052. Artificial pinning in thick YBCO films: Pinning potential and c-axis correlation

Authors: Crisan, A; Mikheenko, P; Sarkar, A; Dang, VS; Kechik, MMA; Abell, JS; Paturi, P; Huhtinen, H

Published: OCT 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 843, DOI: 10.1016/j.physc.2010.02.033

We have introduced artificial pinning centres in thick (>1 mu m) YBCO films grown by Pulsed Laser Deposition using substrate decoration, quasi-multilayers, and target doping approaches. We have found that the frequency dependence of critical current density is consistent with a logarithmic dependence of pinning potential on current density. For most of materials used as nano-dots, artificially-induced pinning centres have a larger potential than natural ones. From angle-dependent in-field transport measurements and from Transmission Electron Microscopy we have found evidence of c-axis correlated pinning centres. (C) 2010 Elsevier B.V. All rights reserved.

2053. MOULDING PROCEDURE FOR THE PREPARATION OF INFRARED GLASSY MICROLENSES AND PRISMS BASED ON ARSENIC SULPHIDE CHALCOGENIDE GLASS

Authors: Niciu, H; Popescu, M; Velea, A; Lorinczi, A; Manea, A; Niciu, D; Lazarescu, M

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 629, DOI:

A new procedure for the production of infrared lenses and prisms based on As(2)S(3) chalcogeniude glass has been devised. Infrared components are obtained with the size in the range 100-1500 micrometers. The procedure allows for getting various curvature radii of the micrometer lenses, ranging from planno-convex to spherical ones.

2054. Mossbauer measurements on SnSe2

Authors: Bibicu, I; Lorinczi, A; Popescu, M

Published: 2010, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS, AND NANOTECHNOLOGIES V, 7821, DOI: 10.1117/12.881773

Tin chalcogenides SnX2 and SnX, where X = S, Se and Te present a particularly interest for their electronic properties and applications in gas sensors. The state of tin in these materials is important for understanding of the sensing effect and improvement of the sensor performances. Mossbauer spectroscopy is a widely used technique for the analysis of the local electronic structure or chemical bonding in solids. In this paper we applied Mossbauer technique for the investigation of bulk and thin films of SnSe2 chalcogenide. The films of SnSe2 chalcogenide were obtained by the methods: PLD ("Pulsed laser deposition") and PED ("Pulsed electron deposition"). Mossbauer measurements were performed by transmission (TMS), respectively conversion electron spectroscopy (CEMS). By CEMS spectroscopy surfaces, coatings and thin films containing Sn can be studied on substrates and to various depths up to 1000 nanometers.

2055. Nanostructured gold layers. II. Gold deposition onto polystyrene substrate

Authors: Zgura, I; Beica, T; Frunza, S; Rasoga, O; Galca, A; Frunza, L; Moldovan, A; Dinescu, M; Zaharia, C

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 359, DOI:

In the aim to improve the adherence of the nanostructured gold layers onto glass substrate, gold deposition has been first time performed onto a polystyrene (PS) layer. The PS layer of ca. 50nm was spin-coated onto glass plates from a toluene solution. Gold layers of 10-20nm were vacuum deposited at small incidence angle. We found that at variance from the plates with gold deposited directly on the glass, the plates with an intermediate PS layer do not peel under overnight treatment in ethanol solution. The layers were characterized by several methods. X-ray diffraction (XRD) measurements showed that gold peaks have the position corresponding to the face-centered cubic structure: However, the crystallites on the sample with PS layer seem to be a little bit smaller than those with gold deposited directly onto the glass. XR reflectometry measurements have given the thickness of the gold layer in good agreement with the value estimated from quartz monitor readings and with the ellipsometric data as well, Liquid crystal cells were obtained to observe the molecular alignment imposed by the nanostructured gold layer deposited onto PS film. A rather strong interaction of gold atoms with the substrate molecules can be considered on the basis of the XRD and ellipsometry measurements.

2056. INFLUENCE OF ULTRASOUNDS ON THE ARAGONITE SYNTHESIS

Authors: Chilibon, I; Mateescu, C; Isopescu, R; Mihai, M; Dumitrescu, O

Published: 2010, PROCEEDINGS OF THE 17TH INTERNATIONAL CONGRESS ON SOUND AND VIBRATION, DOI:

The precipitation of calcium carbonate by liquid-liquid reaction usually provides a mixture of polymorphs: rhombohedra calcite, orthorhombic aragonite with whiskers like particles and hexagonal vaterite with crystallites agglomerated as spheres. Calcite is the stable polymorph at ambient conditions. Recently the interest for aragonite, the high pressure polymorph is increasing because new fields, like biomaterials, are developing. We investigated the possibility of developing an aragonite type calcium carbonate with uniform particle size and submicron dimensions by precipitation in liquid-liquid reaction using double-jet precipitation method in the presence of ethanol, at the temperature of 50 degrees C, with a flow rate of the reagents of 10 ml/min. Two agitation modes were used: magnetic stirrer and an ultrasonic device. The ultrasonic field was applied either at the beginning of the reaction period or at the end of it. Intensity of the ultrasounds was also varied from 50 % to 100 %. All samples were examined by FTIR spectroscopy, scanning electron microscopy, and particle size analyzer. FTIR spectra proved that calcium carbonate synthesized in these conditions is almost pure aragonite. As example, the SEM image shows uniform product structure with fine rods with 2 divided by 3 mu m lengths and submicron diameters.

2057. Dielectric resonator antennas of ZST advanced cerramics

Authors: Ene-Dobre, M; Banciu, MG; Nedelcu, L; Ioachim, A; Alexandru, HV

Published: SEP 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 1929, DOI:

Investigations on dielectric on compact resonators antennas with enhanced characteristics are described in this paper. The dielectric resonators were of (Zr(0.8)Sn(0.2))TiO(4) ceramic material (ZST). It is shown that the doping with Mg reduces the sintering temperature and provides a high dielectric constant, low loss and high thermal stability in microwaves. The coupling with an extra resonator can offer a substantial bandwidth enhancement. Moreover, antenna array with four antenna elements provides a higher gain and a more directive radiation pattern.

2058. Structure and properties of silver doped SnSe2 and Ge2Sb2Te5 thin films prepared by pulsed laser deposition

Authors: Popescu, M; Velea, A; Sava, F; Lorinczi, A; Tomescu, A; Simion, C; Matei, E; Socol, G; Mihailescu, IN; Andonie, A; Stamatin, I

Published: MAR 2010, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 207, 520, DOI: 10.1002/pssa.200982900

Amorphous thin films of SnSe2 and Ge2Sb2Te5 doped by different amount of silver (0.1, 0.2, 0.5 and 1 Ag atoms per formula unit) have been prepared by pulsed laser deposition (PLD) starting from solid polycrystalline targets. The films were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The good gas sensing properties for CO, as well as the sensitivity for CH4 and NO of the Ag; doped SnSe2 films have been demonstrated in the composition SnSe2Ag0.2. The structural effect of silver introduced in Ge2Sb2Te5 matrix has been investigated. The freshly deposited thin films doped by various amount of Ag develop three phases: an amorphous one, and two crystalline phases consisting of a major fcc cubic phase of AgSbTe2 and a minor cubic phase of composition Ag2Te. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2059. Design of microwave bandpass filters with cross couplings, using electromagnetic field simulation and linear circuit optimization

Authors: Militaru, N; Lojewski, G; Banciu, MG

Published: APR 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 912, DOI:

In this paper a band-pass filter in microstrip technology, with cross couplings and with a pair of attenuation poles, is investigated. The equi-ripple in-band response and the location of the poles on the frequency axis can be precisely controlled through a new technique which combines accurate electromagnetic-field simulation and fast linear circuit optimization, allowing this way the design of band-pass filters with improved performances. To illustrate the procedure, a microstrip band-pass filter was designed, verified by em-field simulation, fabricated and tested. The response of the designed filter is in good agreement with the specification, confirming the possibilities of realizing microwave band-pass filters with rigorously controlled characteristics, with reduced design time and non-prohibitive computational effort.

2060. The influence of shape and potential barrier on confinement energy levels in quantum dots

Authors: Lepadatu, AM; Stavarache, I; Ciurea, ML; Iancu, V

Published: FEB 2010, JOURNAL OF APPLIED PHYSICS, 107, DOI: 10.1063/1.3284083

The influence of the shape of silicon quantum dots embedded in an amorphous silica matrix on the quantum confinement energy levels, as well as that of the Si/SiO2 potential barrier, are studied. The energy levels are computed using both the infinite and finite rectangular quantum well models for spherical quantum dots and the infinite rectangular quantum well for prolate spheroidal quantum dots. The results are compared with each other and also with the experimental activation energies obtained from the temperature dependence of the dark current. These activation energies are identified with the differences between the quantum confinement energies, subject to the selection rules. The finite rectangular quantum well model takes into account the experimental value of the finite potential barrier and the matrix-to-dot electron mass ratio. The energy levels are smaller than those for the infinite rectangular quantum well case; they decrease when the potential barrier decreases and the mass ratio increases. Different aspects of the models are discussed. All the errors are less than about 4%. The spheroidal shape lifts the degeneracy on the magnetic quantum number. The energy levels can decrease or increase with eccentricity as a consequence of the different quantum confinement effects along the major and minor axes. The supplementary information on the magnetic quantum number is beneficial for optical applications.

2061. Magnetoelectric properties of multiferroic cobalt ferrite and soft piezoelectric PZT particulate composites

Authors: Miclea, C; Tanasoiu, C; Amarande, L; Miclea, CF; Plavitu, C; Cioangher, M; Trupina, L; Miclea, CT; Tanasoiu, T; Susu, M; Voicu, I; Malczanek, V; Ivanov, A; David, C

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 276, DOI:

Multiferroic composite materials, consisting of piezoelectric and piezomagnetic phases, show electric polarization in the presence of a magnetic field and magnetization on applying an electric field, i.e. piezomagnetic phase causes polarization while piezoelectric phase causes changes in magnetization. The figure of merit of such multiferroic particulate composites is the magnetoelectric voltage coefficient representing the amount of polarization induced by a given magnetic field. In the present investigation we prepared and studied the properties of bulk particulate composites made from cobalt ferrite (COF) and a soft piezoelectric material (PZT). Composite samples, according to the formula xCOF center dot(1-x)PZT with 0 <= x <= 1 were prepared by mixing the COF and PZT powders, pressing them as discs and then sintered at 1200 degrees C for 3 hours. Structural, magnetic, piezoelectric and magnetoelectric characteristics of the sintered composites were determined as a function of the mass fraction of COF into PZT and magnetic field. The ME coefficient shows a maximum value of about 70 mV/cm.Oe for composites containing 40 % COF and 60 % PZT, in a DC magnetic field of 3 kOe at a frequency of 1 KHz of the ac magnetic field. Some of the dielectric and piezoelectric properties of the composite samples, as a function of the mass fraction x, were also determined.

2062. Optical and X-ray absorption spectroscopy in lead doped lithium fluoride crystals

Authors: Somma, F; Aloe, P; d'Acapito, F; Montereali, RM; Polosan, S; Secu, M; Vincenti, MA

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012035

LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb2+ ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L-III and L-I edges. XANES data reveal that Pb is present as Pb2+ whereas EXAFS data show that it is incorporated in the crystal and not forming PbF2 precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 degrees C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

2063. SiO2 nanospheres and tubes obtained by sol-gel method

Authors: Anastasescu, C; Anastasescu, M; Teodorescu, VS; Gartner, M; Zaharescu, M

Published: OCT 1 2010, JOURNAL OF NON-CRYSTALLINE SOLIDS, 356, 2640, DOI: 10.1016/j.jnoncrysol.2010.03.038

Multifunctional nanomaterials with one-dimensional structure have become very attractive because of their potential applications in biochemistry (bioseparation and biointeraction), drug delivery, catalysis, nanotechnology (optical sensors). In this work we report on the synthesis of SiO2 nanospheres and tubes, in a solution of tartaric acid (TTA), pure water and absolute ethanol, starting with tetraethyl orthosilicate (TEOS) via the addition of ammonium hydroxide. In order to characterize the obtained material, transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), thermogravimetric and thermodifferential analysis (DTA/TGA), FT-IR spectroscopy and spectroellipsometry (SE) were used. The tubes have an outer diameter of 0.1-0.2 mu m and length of some microns containing also spherical nanoparticles. The dimensions of the obtained nanotubes are tunable, their diameter and length depending on the synthesis conditions. In the presence of meso-tartaric acid no hollow tubes but nanospheres are obtained. The SiO2 tubes and nanospheres have similar structure but very different morphologies. The large surface area and the distinctive inner and outer surfaces represent a great advantage of the nanotubes over conventional nanoparticles, making these materials suitable for doping and differential functionalization. (C) 2010 Elsevier B.V. All rights reserved.

2064. Organic Photovoltaic Cells Based on ZnO Thin Film Electrodes

Authors: Ghica, C; Ion, L; Epurescu, G; Nistor, L; Antohe, S; Dinescu, M

Published: FEB 2010, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10, 1326, DOI: 10.1166/jnn.2010.1836

Due to its wide band-gap (ca. 3.4 eV), ZnO is a possible candidate material to be used as transparent electrode for a new class of photovoltaic (PV) cells. Also, an increased interest for the photovoltaic properties of several organic monomers and polymers (merocyanines, phthalocyanines and porphyrins) was noticed, because of their high optical absorption in the visible region of the spectrum allowing them to be used as potential inexpensive materials for solar cells. Preparation and properties of CuPc (copper phthalocyanine) based photovoltaic cells using ZnO thin films as transparent conductor electrodes are presented in this paper. ZnO layers are grown by pulsed laser deposition, while the organic layers are obtained by thermal evaporation. Structural characterization is performed by electron microscopy. Optical and transport properties of the mutilayered structures are obtained by electrical and spectro-photometric measurements. The influence of the ZnO-polymer interface on the external quantum efficiency (EQE) of the photovoltaic cell is clearly evidenced by our measurements.

2065. Lattice defect assisted incorporation of Mn2+ ions in cubic II-VI semiconductor quantum dots

Authors: Nistor, SV; Stefan, M; Nistor, LC; Ghica, D; Mateescu, CD; Barascu, JN

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012024

Electron paramagnetic resonance spectra from substitutional Mn2+ ions in quantum dots of cubic ZnS with tight size distribution centred at 2 nm were recorded in the 9.8 GHz and 34 GHz frequency bands. Their quantitative analysis with line shape simulation and fitting computer programs accounting for both forbidden transitions and line broadening effects demonstrate the presence of a local axial distortion attributed to a neighbouring extended planar stacking defect. The presence of such extended lattice defects, confirmed from a high resolution transmission electron microscopy study on presently investigated cubic ZnS quantum dots, seems to be essential in the incorporation and localization of Mn2+ activating ions in other cubic II-VI semiconductor quantum dots as well.

2066. Growth and Characterization of ZnO:Mn Submicron Wires via Electrodeposition from Nitrate-Lactic Acid Solution

Authors: Sima, M; Grecu, MN; Sima, M; Enculescu, I

Published: 2010, SEMICONDUCTORS, METAL OXIDES, AND COMPOSITES: METALLIZATION AND ELECTRODEPOSITION OF THIN FILMS AND NANOSTRUCTURES, 25, 171, DOI: 10.1149/1.3318515

Electrodeposition of manganese doped ZnO wires into polycarbonate membranes from an aqueous solution containing Zn(NO3)(2), Mn(NO3)(2) and lactic acid was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). The equivalent electrical circuits used for fitting experimental results were similar to those for characterization of metal/polymer coating systems. The precipitation of metal oxides in the pores of membrane used as template was observed at potentials between -0.9 and -1.15V/SCE. Morphology of the ZnO: Mn submicron wires arrays was observed by scanning electron microscopy and the Mn content of the obtained samples was measured by X-ray analysis. The submicron wires prepared at a potential of -1.1V/SCE have a composition expressed by the formula Zn0.97Mn0.03.

2067. QUANTITATIVE STRUCTURE - ACTIVITY RELATIONSHIP IN ANTIDIABETIC DRUGS BY USING TOPOLOGICAL DESCRIPTORS

Authors: Popescu, M; Velea, A; Mihai, C; Tivadar, S

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 633, DOI:

The quantitative structure - activity relationship in antidiabetic oral drugs has been analyzed on the basis of topological indices that allow to discriminate the structure of different molecules either small or large. The overall correlation structure - activity allows to find the best antidiabetic drugs and to predict the activity of new compound proposed as oral antidiabetic. The screened procedure based on topological indices prevents the expensive and long testing of a high number of compounds.

2068. Four-band printed antenna for personal communication systems

Authors: Cazanaru, D; Szilagyi, A; Banciu, MG

Published: FEB 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 204, DOI:

The paper describes a four-band, small-dimensions printed antenna intended to be integrated into modern wireless systems. The printed antenna has resonant slots, at slightly different frequencies. in order to provide a simultaneous response at four frequency bands in the operating spectral region. This type of antennas is proposed for the emerging multi-mode multi-band transceivers, which operate over a wide range of bands required by modern telecommunication systems. Measured data including return loss, antenna gain and radiation patterns are in good agreement with the simulated data.

2069. Incorporation and localization of substitutional Mn2+ ions in cubic ZnS quantum dots

Authors: Nistor, SV; Stefan, M; Nistor, LC; Goovaerts, E; Van Tendeloo, G

Published: JAN 15 2010, PHYSICAL REVIEW B, 81, DOI: 10.1103/PhysRevB.81.035336

Multifrequency electron paramagnetic resonance (EPR) and high resolution transmission electron microscopy (HRTEM) investigations were performed on small (2 nm) cubic ZnS nanocrystals (quantum dots-QDs) doped with 0.2% mol Mn2+, self-assembled into a mesoporous structure. The EPR data analysis shows that the substitutional Mn2+ ions are localized at Zn2+ sites subjected to a local axial lattice distortion, resulting in the observed zero-field-splitting parameter vertical bar D vertical bar = 41 x 10(-4) cm(-1). The local distortion is attributed to the presence in the second shell of ligands of a stacking fault or twin, which alters the normal stacking sequence of the cubic structure. The HRTEM results confirm the presence of such extended planar defects in a large percentage of the investigated QDs, which makes possible the proposed substitutional Mn2+ impurity ions localization model. Based on these results it is suggested that the high doping levels of Mn2+ ions observed in cubic ZnS and possible in other II-VI semiconductor QDs prepared at low temperatures can be explained by the assistance of the extended lattice defects in the impurities incorporation.

2070. Morphological and optical properties of doped potassium hydrogen phthalate crystals

Authors: Enculescu, M

Published: SEP 1 2010, PHYSICA B-CONDENSED MATTER, 405, 3727, DOI: 10.1016/j.physb.2010.05.074

Potassium hydrogen phthalate (KAP) crystals doped with rhodamine 6G (Rh 6G) and polyvinylpyrrolidone (PVP) were grown by solution evaporation technique. Nucleation occurred without the use of seeds and optically transparent crystals were obtained. The grown crystals were characterized by XRD measurements performed on crystals and their powders, optical transmission and photoluminescence measurements. The influence of the dopants on the structural, morphological and optical properties of the KAP crystals was analysed. Dopants do not change the structure of the single crystals while the addition of PVP changes the morphology of crystals from pseudo-hexagonal to rhomb. Three new XRD reflections are observed in all single-crystal and powder XRD spectra and are probably (0 3 0), (0 4 0) and (0 5 0) lines. The UV cut-off and transparency of the crystals are not changed by doping. Dye-doped KAP crystals exhibit a strong emission band centred at 550 nm excited with 480 nm wavelength. For the dye-doped crystals the up-conversion was investigated and its second harmonic origins are proved using photoluminescence measurements. (C) 2010 Elsevier B.V. All rights reserved.

2071. INFLUENCE OF PREPARATION METHOD ON STRUCTURAL PROPERTIES OF GeSiO NANOSYSTEMS

Authors: Stavarache, I; Lepadatu, AM; Teodorescu, V; Stoica, T; Pasuk, I; Stan, G; Iancu, V; Ciurea, ML

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 80, DOI: 10.1109/SMICND.2010.5650255

GeSiO nanosystems were obtained using two different preparation methods, sol-gel and magnetron-sputtering. Transmission electron microscopy measurements were performed to investigate the films structure. Amorphous and crystalline Ge dots embedded in amorphous silicon dioxide were observed. The Ge concentration in the GeSiO films was by Energy-dispersive X-ray spectroscopy.

2072. Passivation effects of 4,4'-thio-bis-benzenethiolate adsorbed layers on semiconducting electrodes

Authors: Lazarescu, V; Scurtu, R; Lazarescu, MF; Toader, AM; Volanschi, E

Published: NOV 30 2010, ELECTROCHIMICA ACTA, 55, 8301, DOI: 10.1016/j.electacta.2010.02.004

The effects of the self-assembled layers formed by adsorption of 4 4'-thio-bis-benzenethiol from ethanol solutions on p-S1(111) and p-GaAs(1 00) electrodes were examined by EIS AFM and XPS investigations All the experimental data led to the conclusion that the thio-bis-benzenethiolate film spontaneously formed on Si and GaAs surfaces brings about chemical passivation both in air and in solution as well as strong adsorbate-substrate interactions which affect the semiconductor surface state population and the field effects operating in the interfacial region Semiempirical PM3 molecular orbital calculations showed that electronic interaction of the thiolate film with the two semiconducting electrodes can be understood in terms of changes in the local density of the electronic states at the surface (C) 2010 Elsevier Ltd All rights reserved

2073. SYNTHESIS AND CHARACTERIZATION OF BIO-COMPATIBLE MAGHEMITE NANOPARTICLES

Authors: Predoi, D; Andronescu, E; Radu, M; Munteanu, MC; Dinischiotu, A

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 786, DOI:

The bio-compatible magnetic nanoparticles of maghemite were prepared by a chemical co-precipitation method and dextran was selected as the surfactant to suspend them. By transmission electron microscopy (TEM), the iron oxide nanoparticles appeared nearly spherical with an average diameter of about 8.0 +/- 1 nm. SAED pattern of iron oxide nanoparticles is indexed by a cubic gamma-Fe(2)O(3), the diffraction rings are attributed to the (220), (311), (400), (422), (511) and (440) planes, respectively. Regular fringes are clearly observed in the nanoparticle with a spacing of 0.24 nm, whigh is the (311) interplanar distance of the cubic maghemite. This is in perfect agreement with the X-Ray Diffraction (XRD) results, indicating that the nanoparticles are well crystallyzed in spite of their ultrafine sized. The attachment of the dextran on the particle surface was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. The biocompatibility of maghemite nanoparticles covered by dextran with HepG2 cells was checked by MTT test. Cell viability was > 98% when the iron concentration was 12.0 mu g iron/ml and 24.0 mu g iron/ml respectively. In conclusion, these nanoparticles presented a good biocompatibility with HepG2 cells, which was proportionally with the dilution level.

2074. Investigations of the Correlation Between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications

Authors: Stanculescu, A; Socol, M; Albu, AM; Rasoga, O; Stanculescu, F; Ionita, I; Enculescu, I

Published: 2010, ADVANCED MATERIALS FORUM V, PT 1 AND 2, 636-637, +, DOI: 10.4028/www.scientific.net/MSF.636-637.798

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

2075. Synthesis and properties of poly(methyl methacrylate-2-acrylamido-2methylpropane sulfonic acid)/PbS hybrid composite

Authors: Preda, N; Rusen, E; Musuc, A; Enculescu, M; Matei, E; Marculescu, B; Fruth, V; Enculescu, I

Published: AUG 2010, MATERIALS RESEARCH BULLETIN, 45, 1012, DOI: 10.1016/j.materresbull.2010.04.002

The synthesis of a new hybrid composite based on PUS nanoparticles and poly( methyl methacrylate-2acrylamido-2-methylpropane sulfonic acid) [P(MMA-AMPSA)] copolymer is reported. The chemical synthesis consists in two steps: (i) a surfactant-free emulsion copolymerization between methyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid and (ii) the generation of PbS particles in the presence of the P( MMA-AMPSA) latex, from the reaction between lead nitrate and thiourea. The composite was studied by scanning electron microscopy (SEM), X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis and differential scanning calorimetry. The microstructure observed using SEM proves that the PbS nanoparticles are well dispersed in the copolymer matrix. The X-ray diffraction measurements demonstrate that the PbS nanoparticles have a cubic rock salt structure. It was also found that the inorganic semiconductor nanoparticles improve the thermal stability of the copolymer matrix. (C) 2010 Elsevier Ltd. All rights reserved.

2076. CO sensing mechanism with WO3 based gas sensors

Authors: Hubner, M; Simion, CE; Haensch, A; Barsan, N; Weimar, U

Published: NOV 26 2010, SENSORS AND ACTUATORS B-CHEMICAL, 151, 106, DOI: 10.1016/j.snb.2010.09.040

The interaction between CO and WO3 based gas sensors was investigated in operando conditions by using resistance, catalytic conversion and DRIFTS measurements. The experimental results are showing that the sensing involves the reduction of the metal oxide, which is the opposite of the case of SnO2, the other extremely relevant material for semiconducting oxides based gas sensors. (C) 2010 Elsevier B.V. All rights reserved.

2077. Skin Layer Defects in Si by Optimized Treatment in Hydrogen RF Plasma

Authors: Ghica, C; Nistor, LC; Vizireanu, S; Dinescu, G; Moldovan, A; Dinescu, M

Published: DEC 20 2010, PLASMA PROCESSES AND POLYMERS, 7, 991, DOI: 10.1002/ppap.201000066

The first step of the smartcut (TM) process consists in inducing structural defects below the free surface of a silicon wafer, usually by implantation of light elements, such as hydrogen or helium. An alternative way to induce subsurface defects is by plasma treatment. In this work, we present a morphological and structural study on silicon wafers submitted to hydrogen plasma treatment, using two plasma-processing geometries. The parameters of the plasma treatment have been varied in order to limit the surface roughness and to confine the induced defects in a narrow region (50 nm) below the wafer surface. The morphological and structural investigations have been performed by AFM and TEM.

2078. Localization of Mn2+ Ions in Mesoporous ZnS

Authors: Nistor, SV; Stefan, M; Nistor, LC; Mateescu, CD; Birjega, R

Published: SEP 2010, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 10, 6205, DOI: 10.1166/jnn.2010.2599

Nanocrystalline cubic ZnS doped with 0.2% mol manganese, exhibiting a stable mesoporous structure, was synthesized at room temperature by a non toxic surfactant-assisted liquid liquid reaction. The X-ray diffraction measurements demonstrate the formation of a sponge-like mesoporous material built from cubic ZnS nanocrystals of 1.8 nm average sizes, with a tight distribution of pores of 1.8 nm mean diameter. The transmission electron microscopy images confirm the formation of the mesoporous structure with walls of 3.1 nm mean thickness built from cubic ZnS nanocrystallites of 2.1 nm average size. The resulting tight distribution of crystallites and pores yields a well resolved Electron Paramagnetic Resonance spectrum, with the narrowest reported component lines attributed to three types of isolated Mn2+ centers, called Mn2+ (I), Mn2+ (II) and Mn2+ (III). From the analysis of the spin Hamiltonian parameters it is shown that in the Mn2+ (I) centers the paramagnetic ion is situated at substitutional Zn sites in the ZnS nanocrystals, being also subjected to a small axial distortion. The relative concentration changes under thermal treatment experiments strongly suggest that in both Mn2+ (II) and Mn2+ (III) centers the Mn2+ ion is localized on the surface of the ZnS nanocrystallites, being bond to an oxygen ion in the first case and to an additional water molecule in the second case.

2079. Radiation induced defects in Tl+-doped LiF crystals

Authors: Polosan, S; Secu, M; Logofatu, C; Somma, F; Montereali, RM; Vincenti, MA

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012081

Tl+-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl+ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F-3(+) centres, in three steps, compared with the F-2 ones. The F-H recombination processes may induce the excitation-emission transitions of Tl+-ions.

2080. Transmission THz time domain system for biomolecules spectroscopy

Authors: Dinca, MP; Leca, A; Apostol, D; Mernea, M; Calborean, O; Mihailescu, D; Dascalu, T

Published: JAN 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 114, DOI:

A THz Time Domain Spectroscopy experimental set-up was built for studying the biomolecules absorption spectra in the THz range and obtaining information on their collective motions. Details on the set-up calibration and performances are presented, together with the used noise and artefacts reduction data processing techniques. Preliminary results on the absorbance spectrum of the solvated Bovine Serum Albumin (BSA) for different water concentration are given.

2081. Electrical investigations of holmium-doped BaTiO3 derived from sol-gel combustion

Authors: Cernea, M; Galassi, C; Vasile, BS; Ganea, P; Radu, R; Ghita, G

Published: JUN 2010, JOURNAL OF MATERIALS RESEARCH, 25, 1063, DOI: 10.1557/JMR.2010.0149

Holmium-doped BaTiO3 with composition Ba0.97Ho0.03TiO3 was prepared by sol-gel combustion method. A molar ratio of citrate/nitrate (CA/NO3- = 1.3) was used to prepare nanopowders of (Ba,Ho)TiO3. The structure and microstructure of (Ba,Ho)TiO3 powders and ceramics were investigated. The ceramics exhibit a dielectric constant of about 4400 and dielectric loss (tan delta = 0.267) at 10 Hz, and at the Curie temperature (T-c = 132 degrees C). The remanent polarization and the coercive field of Ba0.97Ho0.03TiO3 ceramics, at 1 kHz, were P-r = 6 mu C/cm(2) and E-C = 0.75 kV/cm. The dielectric and ferroelectric behavior of the holmium-doped BaTiO3 is influenced by the amphoteric character of Ho3+ ions.

2082. Soft type PZT material used to fabricate a high intensity air siren

Authors: Miclea, C; Iuga, A; Tanasoiu, C; Trupina, L; Cioangher, M; Miclea, CT; Malczanek, V; Susu, M; Voicu, I

Published: FEB 2010, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 12, 281, DOI:

A high quality soft type PZT material was designed and produced in order to be used as sensor for a high intensity air siren, Two thin disks from this material were assembled into a parallel bimorph type sensor with an intermediate metallic plate for the siren. This assembly behaves like an acoustic resonator in the high frequency audio range. This structure transforms the radial mode of vibration into a flexural one, with a much lower frequency. A mechanical impedance adapter was used in order to assure a good match between the oscillating ceramic and the surrounding air. A theoretical approach was outlined, which allows the evaluation of the resonance frequency for the working transducer. The theoretical and experimental data agree to a satisfactory degree up to the input errors assumed by the model. Acoustical and impedance measurements were made in order to appreciate the influence of the metallic plate on the frequency. The bimorph necessary for making the siren was designed as a parallel structure and the corresponding transducer was measured and evaluated. In order to increase the acoustic emission a frontal cardboard horn was added to the resonator.

2083. POLYMER-LIKE AND DIAMOND-LIKE CARBON COATINGS PREPARED BY RF-PECVD FOR BIOMEDICAL APPLICATIONS

Authors: Stan, GE; Marcov, DA; Popa, AC; Husanu, MA

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 718, DOI:

Hydrogenated amorphous carbon (a-C: H) films were grown by radio-frequency (1.78 MHz) plasma enhanced chemical vapour deposition technique onto medical grade Ti6Al4V substrates. By varying the deposition pressure (13.33 Pa and 53.33 Pa, respectively) and methane dilution (20% and 60%, respectively) several types of carbonic films were obtained, presenting different bonding structures, surface energies and morphological features reflected in their biological behaviour. FTIR, Raman, UV-Vis, XPS and AFM measurements were used for characterizing these structures. The surface energy was determined by contact angle measurements, and their thrombogenicity was tested by the activated partial thromboplastin time (aPTT) method. We have noticed that at the same values of methane in argon dilution but at different pressure values, the film structure was totally changed: soft polymer-like carbon (PLC) type at the higher pressure and hard diamond-like carbon (DLC) type at the lower pressure. Raman spectroscopy and XPS suggested that the highest sp(3) ratio (similar to 52%), was found for DLC films prepared in a 60% methane dilution in argon. It has been found that for both PLC and DLC structures the surface energy has a decreasing tendency with the methane concentration increase in the deposition atmosphere. Excellent aPTT results were obtained for the DLC-60 (18.6.+/- 0.3 min) and PLC-20 (17.4 +/- 0.5 min) structures, superior to those recorded for Ti6Al4V and PMMA commercial materials. These values recommend the prepared carbonic structures for medical applications: harder coatings (DLC) for metal prostheses (heart valves, acetabular cups etc.), while softer and flexible coatings (PLC) for the textile vessels or stents biofunctionalization.

2084. BIOGENIC PRODUCTION OF NANOPARTICLES

Authors: Popescu, M; Velea, A; Lorinczi, A

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1040, DOI:

Nanoparticles of interest in nanotechnology (design of nanodevices) and medicine (controlled-release of drugs) can be produced both by anorganic and organic synthesis. The biogenetic production is now of high interest due to simplicity of the procedures and their versatility. Several species of bacteria and plants are able to synthesize nanoparticles or to help in the process of their production. The paper gives an overview on the biogenetic production of nanomaterials.

2085. Prospects for new antimicrobials based on N,N-dimethylbiguanide complexes as effective agents on both planktonic and adhered microbial strains

Authors: Olar, R; Badea, M; Marinescu, D; Chifiriuc, CM; Bleotu, C; Grecu, MN; Iorgulescu, EE; Bucur, M; Lazar, V; Finaru, A

Published: JUL 2010, EUROPEAN JOURNAL OF MEDICINAL CHEMISTRY, 45, 2875, DOI: 10.1016/j.ejmech.2010.03.009

Metal-free N,N-dimethylbiguanidium acetate and novel complexes M(DMBG)(2)(CH(3)COO)(2)center dot nH(2)O (M: Mn (II), Ni(II), Cu(II) and Zn(II)) were screened for their antimicrobial properties against Gram-positive (Bacillus subtilis, Listeria monocytogenes, Staphylococcus aureus), Gram-negative (Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa) bacteria and fungal (Candida albicans) strains. The ability of compounds to inhibit the microbial adherence ability to the inert substratum as well as their cytotoxicity was also assessed. Our results are demonstrating that some of the tested compounds are exhibiting potent antimicrobial activity accompanied by low cytotoxicity on HeLa cells. The complexes were characterized using microanalytical, IR, EPR, (1)H NMR as well as UV-vis methods. The redox behaviour of complexes was investigated by cyclic voltammetry. The new derivative (HDMBG)(CH(3)COO) crystallizes in the monoclinic P2(1)/n space group as X-ray single-crystal data indicate. (C) 2010 Elsevier Masson SAS. All rights reserved.

2086. Study of multiphoton absorption processes in a perylenediimide derivative using thermal lensing technique

Authors: Taouri, A; Derbal, H; Mountasser, R; Girtan, M; Stanculescu, A; Sylla, M

Published: JAN 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 85, DOI:

Two multiphoton absorption processes were revealed in a perylenediimide derivative, at the wavelength of 1064 nm, by using the thermal lens technique. One of the observed multiphoton processes is two photon absorption (TPA) while the second is a four photons process. The value of the measured TPA coefficient is beta = 0.12 x 10(-19) cm W-1.

2087. Mossbauer measurements on SnSe(2)

Authors: Bibicu, I; Lorinczi, A; Popescu, M

Published: 2010, , DOI: 10.1117/12.881773

Tin chalcogenides SnX(2) and SnX, where X = S, Se and Te present a particularly interest for their electronic properties and applications in gas sensors. The state of tin in these materials is important for understanding of the sensing effect and improvement of the sensor performances. Mossbauer spectroscopy is a widely used technique for the analysis of the local electronic structure or chemical bonding in solids. In this paper we applied Mossbauer technique for the investigation of bulk and thin films of SnSe(2) chalcogenide. The films of SnSe2 chalcogenide were obtained by the methods: PLD ("Pulsed laser deposition") and PED ("Pulsed electron deposition"). Mossbauer measurements were performed by transmission (TMS), respectively conversion electron spectroscopy (CEMS). By CEMS spectroscopy surfaces, coatings and thin films containing Sn can be studied on substrates and to various depths up to 1000 nanometers.

2088. Optical properties of CdS electrodeposited nanowires

Authors: Matei, E; Preda, N; Enculescu, M; Sima, M; Sima, M; Enculescu, I

Published: OCT 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 1022, DOI:

Electrochemical deposition was performed in order to prepare CdS nanowires. The method employed for preparation of such high aspect ratio nanostructures was template replication. Ion track polycarbonate membranes were used as templates. The nanowires were studied by scanning electron microscopy (morphology characterization), energy dispersive X ray analysis (composition) and optical spectroscopy. Optical reflection spectroscopy was performed in order to determine the band gap value while photoluminescence spectroscopy was used for getting information regarding the point defects in the material.

2089. Carrier relaxation dynamics in self-assembled semiconductor quantum dots

Authors: Kurtze, H; Seebeck, J; Gartner, P; Yakovlev, DR; Reuter, D; Wieck, AD; Bayer, M; Jahnke, F

Published: DEC 2009, PHYSICAL REVIEW B, 80, DOI: 10.1103/PhysRevB.80.235319

Systematic time-resolved pump-probe studies with independent variation in pump and probe energies in combination with time-resolved photoluminescence measurements have been used to investigate the dynamics of carrier capture and carrier relaxation in self-assembled (In,Ga)As/GaAs semiconductor quantum dots. Even for weak excitation, where carrier-carrier scattering is less efficient, the lower-energy quantum-dot states are rapidly populated, whereas for increasing delay times between pump and probe pulses residual populations in the higher quantum-dot states are found. A quantum-kinetic description of the carrier interaction with LO phonons is used for a treatment beyond perturbation theory to include polaron effects and to account also for the non-Markovian dynamics. On this level, the theory for the carrier-phonon interaction confirms fast initial carrier relaxation that becomes incomplete for longer times and results in a nonthermal carrier population in the considered low-temperature regime.

2090. Characterization of Superconducting Wires By Cone-Beam Micro-Tomography

Authors: Tiseanu, I; Craciunescu, T; Badica, P; Aldica, GV; Rindfleisch, M

Published: 2009, 2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), VOLS 1-9, +, DOI:

Commercial wires of Nb3Sn and NIgB2 were inspected through X-ray cone-beam micro-tomography (mu CT). Details of the architecture of the wires of different topologies were visualized. In the case of MgB2 wires this allowed to compare the geometrical perfection of the component elements between the wires with 18 and 7 superconducting sub-elements heat treated for different conditions. Defects such as 3D voids and interruption of the diffusion barriers were also visualized. High resolution 3D-mu CT observations of the Nb3Sn wire architecture allowed also direct and non-invasive determination of the twist-pitch parameter. 3D tomography shows important advantages over 2D traditional microscopy methods.

2091. Photonic molecular effects associated to the sputtering process in a glow discharge optical emission spectrometer

Authors: Surmeian, A; Groza, A; Diplasu, C; Ganciu, M; Teodorescu, CM; Tempez, A; Chapon, P

Published: JAN 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 43, DOI:

Spectral emission of a Xenon discharge in the presence of NaCl powder is strongly modified and dominated by the XeCl excimer band at 308 nm. Materials introduced in gas electrical discharges interact with the reactive species produced in the plasma: electrons, ions and metastable atoms. In this paper, the influence of ions and metastable atoms of a capacitive RF Xenon discharge plasma (20W, 30MHz) 5 Torr on the structure of a NaCl powder introduced in the discharge has been investigated.

2092. INVESTIGATION OF ELECTRICAL PROPERTIES OF CARBON NANOTUBES

Authors: Ciurea, ML; Stavarache, I; Lepadatu, AM; Iancu, V; Dragoman, M; Konstantinidis, G; Buiculescu, R

Published: 2009, CAS: 2009 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI: 10.1109/SMICND.2009.5336593

This paper presents the investigation of electrical properties of carbon nanotubes (CNT). A sandwich configuration, quartz substrate/Cr/Al/CNT (partially immersed in SiN)/Cr/Al was investigated. The CNT are mainly oriented parallel with the electrodes. Current - voltage characteristics were taken at 20 K and room temperature and a current - temperature characteristic was taken at constant voltage (20 mV). The I - V characteristics are almost linear, while the G - V characteristics present some peaks and dips, interpreted as voltage percolation thresholds. The I - T and R - T characteristics are also linear (except at low temperatures). The investigated structures have a high electrical polarizability.

2093. Optical fiber coupling to a laser diode through chalcogenide microlenses

Authors: Velea, A; Rusu, M; Popescu, M

Published: OCT 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1383, DOI:

Microspherical lenses (50 divided by 800 mu m in diameter) based on glassy As(2)S(3), have been produced by a special flame melting technique. The microlenses have been used for focusing the red - infrared laser light at the end of an optical fiber. Microlens arrays have been produced and applied in coupling optical fibers to a light remitting diode (LED), in order to increase the intensity. A double ball lens coupling scheme has been designed and manufactured.

2094. Microstrip Bandpass Filters with a Maximum Number of Attenuation Poles

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2009, 2009 32ND INTERNATIONAL SPRING SEMINAR ON ELECTRONICS TECHNOLOGY, +, DOI:

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of attenuation poles equal to the order of the filter, is investigated. The location of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adjacent channels. A microstrip bandpass filter with the novel configuration was designed, verified by em-field simulation, fabricated and tested. The response of the designed filter are in good agreement with the specification, confirming the possibilities of realizing microwave band-pass filters of a relatively low order with moderate losses and with improved selectivity performances.

2095. Structure and properties of (Cu Ca Bi) doped KNN lead-free piezoceramics

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Trupina, L; Cioangher, M; Miclea, CT; Malczanek, V; Susu, M; Voicu, I; Ivanov, A

Published: SEP 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 946, DOI:

Lead free ceramics in the system (1-x)KNN x(Bi2O3,CaO,CuO) with 0.0 <= x <= 0.1 were synthesized by the usual solid state reaction and their structural and piezoelectric properties were investigated Dense samples with densities of about 4 68 g/cm(3) were prepared by sintering at an optimum temperature of 1150 degrees C for 6 h Only perovskite phase was detected by X-ray investigation in all samples A typical MPB where orthorombic-tetragonal phases coexist was detected for a doping level of 0.06 where the piezoelectric parameters showed maximum values Planar coupling factor, as much as 0.46, piezoelectric charge constant of 270 pC/N and mechanical quality factor Q(m) of 75 were recorded for the samples situated within the MPB.

2096. Direct synthesis of Y doped BaTiO3 powder by sol-precipitation method

Authors: Cernea, M

Published: AUG 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1195, DOI:

Ultra fine and homogeneous BaTiO3 doped with 0.5 at% yttrium powder was prepared by sol-precipitation method using barium acetate, titanium (IV) diisopropoxide bis-acetylacetonate and yttrium (III) butoxide as starting precursors. The effect of pH value on the precipitate formation from the sot is pointed out in this paper. The grain size of the precipitate was about 100-200 nm. The structural evolution of the precursor precipitate as function of temperature was investigated. Ba0.995Y0.005TiO3 single phase was obtained at 1300 degrees C. The ceramics manufactured from the as-prepared powder presented good dielectric characteristics (dielectric constant = 2152 and dielectric loss (tan delta) = 4.54% at the Curie temperature of 125 degrees C). These ceramics are expected to be useful in dielectric applications.

2097. Synthesis and characterization of Mn2+ doped ZnS nanocrystals self-assembled in a tight mesoporous structure

Authors: Nistor, SV; Nistor, LC; Stefan, M; Mateescu, CD; Birjega, R; Solovieva, N; Nikl, M

Published: JUL-AUG 2009, SUPERLATTICES AND MICROSTRUCTURES, 46, 311, DOI: 10.1016/j.spmi.2008.10.001

We report the synthesis, by a surfactant-assisted liquid-liquid reaction, of nanocrystalline ZnS doped with 0.2 mol% Mn2+ ions self-assembled in a mesoporous structure. The XRD measurements demonstrate the formation of a sponge-like mesoporous material with a tight distribution of pores of 1.8 nm mean diameter built from cubic ZnS nanocrystals of 1.8 nm average size. TEM investigation confirms the formation of the mesoporous structure with walls of 3.1 nm mean thickness built from nanocrystallites of cubic ZnS. The ordering effect of self-assembling, which is reflected in the tight size distribution of crystallites and pores, might be also responsible for the well resolved EPR spectra, attributed to the presence of three types of isolated Mn2+ paramagnetic centers. (C) 2008 Elsevier Ltd. All rights reserved.

2098. Electrochemically deposited thermoelectric Bi(2)(Se,Te)(3) nanowires

Authors: Sima, M; Vasile, E; Sima, M

Published: JUN 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 542, DOI:

The processes associated with the electrodeposition of thermoelectric Bi(2)(Se,Te)(3) nanowires are reported along with an analysis of the composition, morphology and structure of resulting material. Electrochemical behavior was examined using cyclic and linear voltarnmetry techniques. Energy dispersive X-ray spectrometry (EDX) indicates that the composition of self-standing Bi(2)(Se, Te)(3) wires can be controlled by the electrodeposition method. The composition of Bi(2)(Se,Te)(3) Wires prepared at a potential of -0.01V vs SCE is close to Bi(2)Te(27)Se(0.3). The structure and morphology of Bi(2)(Se,Te)(3) nanowires were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

2099. MAPLE prepared polymeric thin films for non-linear optic applications

Authors: Socol, G; Mihailescu, IN; Albu, AM; Antohe, S; Stanculescu, F; Stanculescu, A; Mihut, L; Preda, N; Socol, M; Rasoga, O

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5614, DOI: 10.1016/j.apsusc.2008.07.206

This paper presents a study of some functionalised copolymers thin films prepared on silicon and quartz substrates by matrix assisted pulsed laser evaporation ( MAPLE) method. Two polymeric structures have been synthesised by the copolymerisation of maleic anhydride and methyl methacrylate, respectively, maleic anhydride and vinyl benzyl chloride and their subsequent functionalisation with 2,4-dinitroaniline. UV-Vis, FTIR, Raman and photoluminescence spectroscopy have been used to investigate the influence on the properties of the films of different substrate temperature ( 150 degrees C and 250 degrees C), background N-2 pressure (5-30 Pa) and polymer concentration in target (2% and 3%). We have evidenced that this deposition process does not damage the chemical structure of the polymers. SEM investigations revealed the droplets type morphology of the polymeric films with thickness between 41 nm and 105 nm calculated from ellipsometric measurements. (C) 2008 Elsevier B. V. All rights reserved.

2100. Direct laser writing of two-dimensional photonic structures in amorphous As2S3 thin films

Authors: Popescu, A; Miclos, S; Savastru, D; Savastru, R; Ciobanu, M; Popescu, M; Lorinczi, A; Sava, F; Velea, A; Jipa, F; Zamfirescu, M

Published: NOV 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1880, DOI:

A method for building photonic structures in As2S3 amorphous chalcogenide films has been developed. 2-D photonic configurations characterized by a regular assembly of rods (triangular lattice) or gratings with traces of micrometer period have been obtained. A femto-second laser has been used in photonic crystal registration. The simulation performed on these photonic configuration shows that the obtained chalcogenide structures could be efficient for operation in the infrared range around several micrometers wavelength.

2101. Photoluminescence and Raman spectroscopy studies on polyaniline/PbI2 composite

Authors: Baibarac, M; Baltog, I; Lefrant, S

Published: APR 2009, JOURNAL OF SOLID STATE CHEMISTRY, 182, 835, DOI: 10.1016/j.jssc.2009.01.007

Functionalization of PbI2 with conjugated polymers (polyaniline-emeraldine base (PANI-EB) or polyaniline-emeraldine salt (PANI-ES)) is demonstrated by Raman and luminescence studies. PbI2/PANI hybrid material was prepared by electrochemical polymerization of aniline onto the PbI2 modified Pt electrode and mechanico-chemical reaction between the two constituents. PANI interacting with the PbI2 gives rise to new Raman bands at 80,144 and 170 cm(-1). First line reveals the formation of "stacking faults" that disrupt the I-Pb-I layers stacking along the c axis by the insertion of polymer molecules. The bands at 144 and 170 cm(-1) are attributed to the vibrational mode associated with Pb-NHR ''(2) (R '' = C6H4) bond. The functionalization of PbI2 with PANI-EB brings forth the PANI-ES form. Depending on the semiconducting (PANI-EB) or conducting (PANI-ES) properties of the polymer in the PbI2/PANI intercalated material, a partial or total collection of the charges generated under band to band irradiation is revealed by photoluminescence studies. (C) 2009 Elsevier Inc. All rights reserved.

2102. Carbon nanotubes from ethanol on Fe-Co/MgO catalysts and related interface phenomena

Authors: Lupu, D; Biris, AR; Baltog, I; Baibarac, M; Kuncser, V; Schinteie, G; Valeanu, M; Lefrant, S; Biris, AS; Misan, I; Filoti, G

Published: MAR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 347, DOI:

Mossbauer spectroscopy studies of Fe-Co/MgO catalysts proved that a high dispersion degree of Fe may be achieved for catalysts containing Fe/Co in a ratio close to 1. During materials processing. the presence of hydrogen at high temperatures, even for short time, induced an increased particle size of the catalytic Fe. The evaluation of various iron species from their areas in the Mossbauer spectra revealed the dependence of the nanotube amount on (FeCo alloy + Fe2+) content in the catalyst, in good agreement with literature mechanisms. The Raman spectra show that carbon nanotubes synthesized from ethanol in argon flow on 4.5%Fe:4.5%Co/MgO are richer in low diameter (0.7-1.0nm) tubes than those obtained at low ethanol pressure, in agreement with the effects of hydrogen reported in literature. The close similarity with the Raman spectra of Aldrich double-walled carbon nanotubes and from literature, recommends the syntheses in argon flow as better conditions for double-walled carbon nanotube growth.

2103. Ba(Zn1/3Ta2/3)O-3 Ceramics for Microwave and Millimeter-wave Applications

Authors: Alexandru, HV; Ioachim, A; Toacsan, MI; Nedelcu, L; Banciu, MG; Berbecaru, C; Voicu, G; Jinga, S; Andronescu, E

Published: 2009, INTERDISCIPLINARY TRANSPORT PHENOMENA: FLUID, THERMAL, BIOLOGICAL, MATERIALS, AND SPACE SCIENCES, 1161, 553, DOI: 10.1111/j.1749-6632.2008.04077.x

The Ba(Zn1/3Ta2/3)O-3 (BZT) ceramic samples were prepared by solid-state reaction and sintered in the range 1550-1650 degrees C for 2 h. Several methods-X-ray diffraction (XRD) and scanning electron microscopy (SEM)-were used for structural and morphological characterization. The unit cell distortion and the presence of the secondary phase content were studied by XRD. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was noticed with the increase of the sintering temperature. SEM investigations revealed polyhedral well-faceted grains and large grain size distribution. The dielectric properties in the microwave range were measured at room temperature and at 1 kHz on a large temperature interval (+/- 150 degrees C). The dielectric parameters were correlated with morphological and structural properties. Ceramic samples were annealed at 1410 degrees C for 30 h to improve the microwave properties. The dielectric constant of BZT samples measured at 6 GHz and at 1 kHz was between 27 and 28 on the whole temperature range, that is, typical values for BZT material. The temperature coefficient of the resonance frequency at 6 GHz exhibits positive values less than 6 ppm/degrees C.

2104. Raman spectroscopic evidence for interfacial interactions in poly(bithiophene)/single-walled carbon nanotube composites

Authors: Baibarac, M; Baltog, I; Lefrant, S

Published: APR 2009, CARBON, 47, 1398, DOI: 10.1016/j.carbon.2009.01.031

Electrochemical polymerization of 2,2'-bithiophene (BTh) on single-walled carbon nanotube (SWCNT) films has been studied by Raman scattering and infrared absorption spectroscopy. Covalent functionalization of SWCNTs with poly(bithiophene) (PBTh) in its un-doped and doped states is demonstrated. The occurrence of a charge transfer process at the interface of PBTh and SWCNTs, is shown by: (i) an up-shift of the Raman lines associated with the radial breathing modes of SWCNTs that reveals both a doping process and an additional twisting together as a rope with the conducting polymer as binding agent; (ii) a new Raman band in the range 1430-1450 cm(-1) indicating the functionalization of SWCNTs with PBTh in doped and un-doped states; (iii) strong absorption bands situated in the interval 600-800 cm(-1) resulting from steric hindrance produced by the nanotube binding to the polymeric chain. Treatment of the PBTh/SWCNT composite with aqueous NH4OH Solution forms un-doped PBTh covalently functionalized SWCNTs. At the resonant excitation of the metallic tubes, an additionally enhanced Raman process is generated by plasmon excitation in the metallic nanotubes. It is evidenced by a particular behavior in the Stokes and anti-Stokes branch of the PBTh Raman line at 1450 cm(-1). (C) 2009 Elsevier Ltd. All rights reserved.

2105. Radiofrequency plasma beam deposition of various forms of carbon based thin films and their characterization

Authors: Vizireanu, S; Stoica, SD; Mitu, B; Husanu, MA; Galca, A; Nistor, L; Dinescu, G

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5381, DOI: 10.1016/j.apsusc.2008.08.042

The characteristics of carbonic materials obtained by downstream deposition in a low pressure argon plasma beam injected with acetylene are reported. The influence of substrate temperature, presence of Ni catalyst and hydrogen in gas composition on the material properties is described. By increasing the substrate temperature, an enhanced order in the material is revealed by Raman spectroscopy, while FTIR measurements show a decreasing of the hydrogen content and the disappearing of sp(1) hybridized carbon in the deposit. The SEM and Raman investigation show a clear tendency of crystalline phases formation when hydrogen is assisting the deposition. (C) 2008 Elsevier B. V. All rights reserved.

2106. Origin of the X-ray magnetic circular dichroism at the L-edges of the rare-earths in RxR ' Al-1-x(2) systems

Authors: Chaboy, J; Laguna-Marco, MA; Piquer, C; Boada, R; Plugaru, N; Maruyama, H; Kawamura, N

Published: MAY 2009, JOURNAL OF SYNCHROTRON RADIATION, 16, 412, DOI: 10.1107/S0909049509009807

An X-ray magnetic circular dichroism (XMCD) study performed at the rare-earth L-2,L-3-edges in the RxR'Al-1-x(2) compounds is presented. It is shown that both R and R' atoms contribute to the XMCD recorded at the L-edges of the selected rare-earth, either R or R'. The amplitude of the XMCD signal is not directly correlated to the magnetization or to the value of the individual (R, R') magnetic moments, but it is related to the molecular field acting on the rare-earth tuned in the photoabsorption process. This result closes a longstanding study of the origin of the XMCD at the L-edge of the rare-earths in multi-component systems, allowing a full understanding of the exact nature of these signals.

2107. Intercalation of Layered Metal Iodides with Pyridine Evidenced by Raman Spectroscopy

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I

Published: JUL 2009, ACTA PHYSICA POLONICA A, 116, 83, DOI: 10.12693/APhysPolA.116.81

PbI2, BiI3, CdI2 and AgI crystalline samples intercalated with pyridine have been studied by Raman spectroscopy. Comparing the Raman spectra of pristine metal iodides with those of intercalated samples we have shown the coexistence, in the host crystalline lattice, of two adsorbed forms: a physisorbed one, featured by weak forces of van der Waals type and a chemisorbed one, involving stronger forces related to an electrostatic interaction. The physisorbed form is consistent with the molecules inserted into the interlayer spaces while the chemisorbed form is represented by the molecules forming coordination complexes with the crystalline lattice cations. The crucial role in the formation of such complexes is played by the lone pair of nitrogen atom belonging to the molecules.

2108. ADSORPTION COMPLEXES OF COLLAGENOUS POLYPEPTIDE-IONIC SURFACTANT IN AQUEOUS MEDIUM 1. THE FORMATION OF MICELLAR STRUCTURE OF IONIC SURFACTANT ADSORBED ONTO COLLAGENOUS POLYPEPTIDE CHAIN

Authors: Micutz, M; Staicu, T; Leca, M; Ghica, C

Published: NOV-DEC 2009, REVUE ROUMAINE DE CHIMIE, 54, +, DOI:

The paper reports on the main findings issued from studying the formation of adsorbed micelle-like clusters of ionic surfactant (sodium dodecyl sulfate and hexadecyl trimethylammonium bromide) onto molecule of collagenous polypeptide (collagen hydrolyzates and calfskin collagen type 1). Capillary viscometry, UV-circular dichroism, transmission electron microscopy and surfactant titration method were used to characterize the macromolecular component of the studied systems. To highlight the critical aggregation concentration (cac) and the critical saturation concentration (T-2) in the investigated polypeptide-surfactant systems, the steady-state fluorescence of pyrene (1(1)/1(3) rule) and the surface tension measurements (the droplet volume method) were availed. The study revealed a significant decrease of the effective micelle concentration of surfactant (cue) in the presence of polypeptide irrespective of pH and a critical concentration T-2 depending on the system composition and pH.

2109. Crystalline-amorphous and amorphous-amorphous transitions in phase-change materials

Authors: Popescu, M; Sava, F; Velea, A; Lorinczi, A

Published: OCT 1 2009, JOURNAL OF NON-CRYSTALLINE SOLIDS, 355, 1823, DOI: 10.1016/j.jnoncrysol.2009.04.053

The transition from the crystalline state to amorphous state and back has been studied in the particular case of the GeSb2Te4 phase-change material by a computer simulation procedure. Modelling at the nanoscale indicates specific structural characteristics, especially the multiplicity of the amorphous phase as opposite to the uniqueness of the crystalline phase. in the particular case of the Si(12)Ge(10)AS(30)Te(48) switching glass two types of ordering have been pointed out and characterized. (C) 2009 Elsevier B.V. All rights reserved.

2110. Point and extended defects in irradiated silicon and consequences for detectors

Authors: Lazanu, S; Ciurea, ML; Lazanu, I

Published: 2009, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, NO 8, 6, +, DOI: 10.1002/pssc.200881434

The interactions by which ions lose their energy in silicon are investigated at the microscopic level. this theoretical study put in evidence that the ionization could also represent a source of structural defects, and, contrary to the processes initiated by elementary particles, could generate extended primary defects, as, e.g. four-fold coordinated defects, due to the simultaneous breaking of bond for more neighbouring atoms in the lattice in a single interaction, in the ionisation core. The average energy transferred per atom is calculated, and also the energy spent by ionisation. The time dependence of the temperature in the ionisation core is derived in some simplifying assumptions. These contributions not considered yet in the studies of degradation of silicon detectors in radiation fields and could account for the discrepancies observed between models and measurements at microscopic versus device level for hadrons and ions. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2111. Nitridation and crystallization of titanium oxynitride by thermal treatment of TiO2-anatase films in NH3

Authors: Trapalis, C; Calderon-Moreno, JM; Todorova, N; Teodorescu, VS; Stoica, M; Nicolescu, M; Anastasescu, M; Gartner, M; Zaharescu, M

Published: NOV 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1814, DOI:

Nitrogen is often used for doping TiO2 films to improve their photocatalytic properties in visible light. Multilayer TiO2 anatase films were deposited by sol-gel method on quartz substrate and thermally treated in O-2 and NH3 flow in 500-800 degrees C range. The effect of the annealing treatment (temperature and atmosphere) on the structural properties of TiO2 films was studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Nitridation causes the amorphization of the anatase tetragonal phase at 600 degrees C. The film re-crystallization into the cubic oxynitride phase is observed at 800 degrees C. EDX results confirms that the incorporation of nitrogen into the amorphous films takes place before thermally activated growth of the oxynitride phase and demonstrates that the relative O:N composition in the crystalline phase is dependent on the temperature of the thermal treatment.

2112. Kondo peaks and dips in the differential conductance of a multi-lead quantum dot: Dependence on bias conditions

Authors: Tolea, M; Dinu, IV; Aldea, A

Published: JAN 2009, PHYSICAL REVIEW B, 79, DOI: 10.1103/PhysRevB.79.033306

We study the differential conductance in the Kondo regime of a quantum dot coupled to multiple leads. When the bias is applied symmetrically on two of the leads (V and -V, as usual in experiments) while the others are grounded, the conductance through the biased leads always shows the expected enhancement at zero bias. However, under asymmetrically applied bias (V and lambda V, with lambda>0), a suppression-dip-appears in the differential conductance if the asymmetry coefficient lambda is beyond a given threshold lambda(0)=3 root 1+r determined by the ratio r of the dot-lead couplings. This is a recipe to determine experimentally this ratio which is important for the quantum-dot devices. This finding is a direct result of the Keldysh transport formalism. For the illustration we use a many-lead Anderson Hamiltonian, the Green's functions being calculated in the Lacroix approximation, which is generalized to the case of nonequilibrium.

2113. Submicron wires with nanosized grain structure

Authors: Sima, M; Ion, L; Antohe, S; Vasile, E

Published: DEC 2009, SUPERLATTICES AND MICROSTRUCTURES, 46, 839, DOI: 10.1016/j.spmi.2009.09.010

Recent results have shown that size-effects in nanostructured materials may enable much more efficient thermoelectric devices. In this paper, the electrochemical preparation of Bi(1.95)Te(2.7)Se(0.35) and Bi(2.15)Te(2.55)Se(0.3) submicron wires arrays with nanosized grain structure is reported. X-ray diffraction (XRD) analysis has indicated the presence of nanosized crystallites in the structure of the wires; high resolution transmission electron microscopy (HRTEM) investigations have confirmed the formation of crystallites with geometrical dimensions of 5-14 nm and random orientations in the structure of these wires. These wires were further analyzed by field emission scanning electron microscopy (FESEM). The measurement of the transport properties showed that a highly degenerate semiconductor with a large thermopower (-125 mu V K(-1) at 300 K) and a low resistivity was obtained. (C) 2009 Elsevier Ltd. All rights reserved.

2114. ZnO particles of wurtzite structure as a component in ZnO/carbon nanotube composite

Authors: Baibarac, M; Baltog, I; Velula, T; Pasuk, I; Lefrant, S; Gautier, N

Published: NOV 4 2009, JOURNAL OF PHYSICS-CONDENSED MATTER, 21, DOI: 10.1088/0953-8984/21/44/445801

Composites based on carbon nanotubes and ZnO particles with needle shapes were prepared for applications in energy storage. Depending on the temperature (85 or 25 degrees C) at which the reaction between NaOH and ZnCl(2) was carried out, particles with two different morphologies: needle-shaped (NS) and double-pyramid-shaped (DPS), respectively, are obtained. Scanning electron microscopy, photoluminescence, UV-Vis absorption spectroscopy, x-ray diffraction and Raman light scattering studies reveal that the NS and DPS particles belong to ZnO with wurtzite (WZ) structure and epsilon-Zn(OH)(2) as precursors of ZnO, respectively. Using the ZnO/carbon nanotube composite as a negative electrode and an electrolytic solution containing LiPF(6), the charge-discharge characteristics of rechargeable lithium ions cells were determined. Additional information concerning the electrochemical reactions at the interface of the two electrodes was obtained by cyclic voltammetry.

2115. Optical and EPR investigations of the thermal treatment effects on YVO4 nanocrystals

Authors: Georgescu, S; Cotoi, E; Voiculescu, AM; Toma, O; Grecu, MN; Borca, E; Hodorogea, S

Published: DEC 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 1387, DOI:

YVO4 nanocrystals doped with Eu (5 at.%) or Gd (1 at.%) were synthesized by precipitation method and annealed at various temperatures between 60 degrees C and 900 degrees C. The average size (coherence domain) of the YVO4 and nanocrystals, estimated from X-ray diffraction measurements, varies from similar to 7 nm to similar to 60 nm, function of the annealing temperature. The morphological transformations produced by thermal treatments in YVO4 nanocrystals were monitored using optical spectroscopy with Eu3+ as probe and EPR spectroscopy, the paramagnetic probe being Gd3+.

2116. EPR AND X-RAY DIFFRACTION INVESTIGATION OF SOME GREEK MARBLES AND LIMESTONES

Authors: Duliu, OG; Grecu, MN; Cristea, C

Published: 2009, ROMANIAN REPORTS IN PHYSICS, 61, 499, DOI:

12 different marble and limestone samples collected from well-known Greek quarries have been investigated by X-ray diffraction and electron paramagnetic resonance (EPR). Xray diffraction spectra permitted to determine both major (calcite and dolomite) and minor (quartz or magnesite) mineralogical components. EPR has been used to investigate the same samples unirradiated and after 10 kGy gamma-ray irradiation. The unirradiated samples display typical EPR spectra of Mn2+ in calcite and dolomite as well as a superposition of these while some samples displayed EPR free radicals signals of centers (low field signal) and centers (high field signal). From X-ray diffraction and EPR spectra it was possible to extract numerical values of several numerical parameters such as dolomite to calcite ratio, EPR intensity parameter, and low field to high field EPR signals intensity ratio. These values as well as the correlation coefficients between the digital functions that described the low field Mn2+ ions EPR line have been used as entry data for cluster analysis to quantify the resemblance and differences between analyzed samples.

2117. Alignment of the CMS silicon strip tracker during standalone commissioning

Authors: Adam, W; Bergauer, T; Dragicevic, M; (...) Lungu, GA; (...) Tsang, KV (CMS Tracker Collaboration)

Published: JUL 2009, JOURNAL OF INSTRUMENTATION, 4, T07001, DOI: 10.1088/1748-0221/4/07/T07001

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 degrees C to -15 degrees C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) mu m RMS in the outer (inner) part of the barrel.

2118. Performance studies of the CMS Strip Tracker before installation

Authors: Adam, W; Bergauer, T; Dragicevic, M; (...) Lungu, GA; (...) Tsang, KV (CMS Tracker Collaboration)

Published: JUN 2009, JOURNAL OF INSTRUMENTATION, 4, P06009, DOI: 10.1088/1748-0221/4/06/P06009

In March 2007 the assembly of the Silicon Strip Tracker was completed at the Tracker Integration Facility at CERN. Nearly 15% of the detector was instrumented using cables, fiber optics, power supplies, and electronics intended for the operation at the LHC. A local chiller was used to circulate the coolant for low temperature operation. In order to understand the efficiency and alignment of the strip tracker modules, a cosmic ray trigger was implemented. From March through July 4.5 million triggers were recorded. This period, referred to as the Sector Test, provided practical experience with the operation of the Tracker, especially safety, data acquisition, power, and cooling systems. This paper describes the performance of the strip system during the Sector Test, which consisted of five distinct periods defined by the coolant temperature. Significant emphasis is placed on comparisons between the data and results from Monte Carlo studies.

2119. Stand-alone cosmic muon reconstruction before installation of the CMS silicon strip tracker

Authors: Adam, W; Bergauer, T; Dragicevic, M; (...) Lungu, GA; (...) Tsang, KV (CMS Tracker Collaboration)

Published: MAY 2009, JOURNAL OF INSTRUMENTATION, 4, P05004, DOI: 10.1088/1748-0221/4/05/P05004

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15% of the final silicon strip detector, and over 4.7 million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

2120. Silver/amorphous As2S3 heterostructure

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Leonovici, M; Zamfira, S

Published: NOV 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1594, DOI:

The heterostructure Ag/As2S3 was deposited on glass substrate in two configurations: Ag/As2S3/glass and As2S3/Ag/glass. The effect of light emitted by a halogen lamp has been investigated by optical microscopy and X-ray diffraction. Particular morphological and structural aspects were revealed. Lateral diffusion rate of Ag has been determined.

2121. Fabrication of submicrometer periodic structures using interference lithography and two-layer chalcogenide photoresist

Authors: Indutnyi, IZ; Popescu, M; Lorinczi, A; Sava, F; Min'ko, VI; Shepeliavyi, PE; Dan'ko, VA

Published: DEC 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 1971, DOI:

Technological process of interference lithography using two-layer chalcogenide photoresist were investigated. Top As(40)S(30)Se(30) layer is photoresist with a high selectivity and can be used for recording of interference pattern and formation of first lithographic mask. Second, more thick As(4)Ge(30)S(66) layer, almost is not sensitive to light, but dissolves in weak (0.05%) water solution of KOH. That, optimizing the etchant solutions for both layers, exposure and time of etching it is possible to carry out the technological process of formation of the lithographic mask with high modulation and with the groove form close to rectangular. This technology has been used for the fabrication of one- and two-dimensional periodic structures. Using two layer As(40)S(30)Se(30)-As(4)Ge(30)S(66) photoresist, we have fabricated the diffraction gratings and two-dimensional periodic structures with elements of submicron size. Relief parameters and diffractions properties of the obtained structures and their dependence on etching time are studied.

2122. Preparation and Characterization of Polar Aniline Functionalized Copolymers Thin Films for Optical Non-Linear Applications

Authors: Stanculescu, A; Rasoga, O; Preda, N; Socol, M; Stanculescu, F; Ionita, I; Albu, AM; Socol, G

Published: 2009, FERROELECTRICS, 389, 173, DOI: 10.1080/00150190902993291

This paper presents a study of two monomeric structures containing functional groups with different electronegativities [NH/NH-NH and NO2] and two different polymeric structures prepared by the copolymerisation of maleic anhydride and methylmethacrylate/maleic anhydride and vinyl benzyl chloride, and subsequent functionalization with 2,4 dinitroaniline. Thin films have been prepared by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and UV-VIS, FTIR, Raman and Photoluminescence Spectroscopy have been used to comparatively investigate the properties of the synthesised compounds. We have evidenced the second harmonic emission (SHG), process sustained by the asymmetry of the chemical structure, which is correlated with the crystallization in non-centrosymmeric structures.

2123. CATALYTIC AND ELECTRICAL PROPERTIES OF IRON OXIDE IN DEEP PROPANE OXIDATION

Authors: Munteanu, C; Ionescu, NI; Feder, M; Diamandescu, L; Caldararu, M

Published: NOV-DEC 2009, REVUE ROUMAINE DE CHIMIE, 54, +, DOI:

The catalytic activity of hematite (alpha-Fe(2)o(3)) was studied in deep propane oxidation. Propane conversion to CO(2) was more than 90% at 400 degrees C in excess of oxygen. The AC electrical conductivity measurements performed in situ showed that at low temperature the surface conductivity is influenced by the presence of moisture in the feed which is adsorbed on the surface. Based on the conductivity data obtained in absence of oxygen coupled with information provided by Mossbauer spectroscopy, the results are discussed in terms of the redox-type mechanism.

2124. Sol-gel doped TiO2 nanomaterials: a comparative study

Authors: Raileanu, M; Crisan, M; Dragan, N; Crisan, D; Galtayries, A; Braileanu, A; Ianculescu, A; Teodorescu, VS; Nitoi, I; Anastasescu, M

Published: SEP 2009, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 51, 329, DOI: 10.1007/s10971-009-2017-z

Among the great number of sol-gel prepared nanomaterials, TiO2 has attracted significant interest due to its high photocatalytic activity, excellent functionality, thermal stability and non-toxicity. The photocatalytic degradation of pollutants using un-doped and doped TiO2 nanopowders or thin films is very attractive for applications in environmental protection, as a possible solution for water purification. The present work describes a comparative structural and chemical study of un-doped TiO2 and the corresponding S- and Ag-doped materials. The photocatalytic activity was established by testing the degradation of organic chloride compounds from aqueous solutions. Sol-gel Ag-doped TiO2 coatings, prepared by co-gelation and sol-gel Ag-doped TiO2 coatings obtained from nanopowders were also compared. Their structural evolution and crystallization behaviour (lattice parameters, crystallite sizes, internal strains) with thermal treatment were followed by thermal analysis, X-ray diffraction, transmission electron microscopy, atomic force microscopy and specific surface areas measurements. X-ray photoelectron spectroscopy analyses were performed to characterize the surface composition and S or Ag speciation, which was used to interpret the catalytic data.

2125. Effect of Nickel-Niobium Co-Doping on Structural, Electromechanical, and Dielectric Properties of Lead Titanate Ceramics

Authors: Amarande, L; Miclea, C; Tanasoiu, T; Iuga, A; Cioangher, MC; Trupina, L; Grecu, MN; Pasuk, I

Published: SEP 2009, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, 56, 1798, DOI: 10.1109/TUFFC.2009.1251

Lead titanate (PT) ceramics co-doped with 8 to 13 mol% Ni-Nb, by substituting titanium ions, were prepared by conventional ceramic method and the influence of Ni-Nb doping level on their mopho-structural, electromechanical and dielectric properties was investigated. Dense tetragonal PT ceramics were obtained for 8 to 12 mol% Ni-Nb co-doping. Lattice anisotropy decreased from 1.053 to 1.046 with increasing doping level. Large thickness coupling factors of 0.4 were obtained for 8, 11, and 12 mol% Ni-Nb. Large electromechanical anisotropy of 10 was obtained for 8 mol% Ni-Nb. It was found that Ni-Nb co-doping has both softening and hardening effects as a function of donor or acceptor behavior of different amounts of Ni-Nb. For 13 mol% Ni-Nb, segregation of a small amount of a secondary phase occurs, lattice constants and tetragonality significantly decrease and the resulting ceramic becomes very hard.

2126. Total oxidation of toluene on ferrite-type catalysts

Authors: Florea, M; Alifanti, M; Parvulescu, VI; Mihaila-Tarabasanu, D; Diamandescu, L; Feder, M; Negrila, C; Frunza, L

Published: MAR 30 2009, CATALYSIS TODAY, 141, 366, DOI: 10.1016/j.cattod.2008.05.005

Ferrite catalysts were prepared following two routes, i.e. the hydrothermal one and the calcination of an oxide mixture. In the first route sodium hydroxide, ferrous sulfate and the sulfate of the substituting ion (Mn, Ni) were used. The ferrites obtained using this route was NixFe3-xO4 (x = 0.5) and MnxFe3-xO4 (x similar to 0.65). Following the second route were prepared three samples: NiFe2O4, Ni0.5Zn0.5Fe2O4 and MnFe2O4. Two of them contain the corresponding ferrites while the latter is a presintered oxide mixture (Fe2O3-Mn2O3). All the samples were fully characterized using chemical analysis, X-ray fluorescence spectroscopy and EDX, nitrogen adsorption-desorption isotherms at -196 degrees C, X-ray diffraction (XRD), FTIR, scanning electron microscopy and XPS. The catalytic activity evaluation was made using a mixture of 1700 ppm vol. of toluene and air flowing at 100 ml min(-1) raising the temperature up to 600 degrees C in steps of 25 degrees C. Among these systems the sample representing the presintered Fe2O3-Mn2O3 mixture showed the highest activity. (C) 2008 Elsevier B.V. All rights reserved.

2127. Thin films of Cu(II)-o,o '-dihydroxy azobenzene nanoparticle-embedded polyacrylic acid (PAA) for nonlinear optical applications developed by matrix assisted pulsed laser evaporation (MAPLE)

Authors: Constantinescu, C; Emandi, A; Vasiliu, C; Negrila, C; Logofatu, C; Cotarlan, C; Lazarescu, M

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5485, DOI: 10.1016/j.apsusc.2008.10.012

Thin films based on two different metal-organic systems are developed by MAPLE and their nonlinear optical applications are explored. A complex of o,o'-dihydroxy azobenzene with Cu(2+) cation is found to organize as a non-central symmetric crystallite. A simple protocol is developed for the in situ fabrication of highly monodisperse copper-complex nanoparticles in a polymer film matrix of polyacrylic acid. The thin films were deposited on quartz substrates by MAPLE ( matrix assisted pulsed laser evaporation) using a Nd:YAG laser working at 355 nm. Atomic force microscopy (AFM), Fourier transform infrared ( FTIR), X-ray photoelectron spectroscopy (XPS), and optical second harmonic generation (SHG) were performed on the samples. The optical limiting capability of the nanoparticle-embedded polymer film is investigated. (C) 2008 Elsevier B. V. All rights reserved.

2128. Influence of long-range dipolar interactions on the phase stability and hysteresis shapes of ferroelectric and antiferroelectric multilayers

Authors: Misirlioglu, IB; Pintilie, L; Alexe, M; Hesse, D

Published: OCT 2009, JOURNAL OF MATERIALS SCIENCE, 44, 5363, DOI: 10.1007/s10853-009-3451-6

Phase transition and field driven hysteresis evolution of a two-dimensional Ising grid consisting of ferroelectric-antiferroelectric multilayers that take into account the long range dipolar interactions were simulated by a Monte-Carlo method. Simulations were carried out for a 1 + 1 bilayer and a 5 + 5 superlattice. Phase stabilities of components comprising the structures with an electrostatic-like coupling term were also studied. An electrostatic-like coupling, in the absence of an applied field, can drive the ferroelectric layers toward 180A degrees domains with very flat domain interfaces mainly due to the competition between this term and the dipole-dipole interaction. The antiferroelectric layers do not undergo an antiferroelectric-to-ferroelectric transition under the influence of an electrostatic-like coupling between layers as the ferroelectric layer splits into periodic domains at the expense of the domain wall energy. The long-range interactions become significant near the interfaces. For high periodicity structures with several interfaces, the interlayer long-range interactions substantially impact the configuration of the ferroelectric layers while the antiferroelectric layers remain quite stable unless these layers are near the Neel temperature. In systems investigated with several interfaces, the hysteresis loops do not exhibit a clear presence of antiferroelectricity that could be expected in the presence of anti-parallel dipoles, i.e., the switching takes place abruptly. Some recent experimental observations in ferroelectric-antiferroelectric multilayers are discussed where we conclude that the different electrical properties of bilayers and superlattices are not only due to strain effects alone but also due to long-range interactions. The latter manifests itself particularly in superlattices where layers are periodically exposed to each other at the interfaces.

2129. Optical advanced spectroscopic techniques for the study of nano-structured materials: Applications to carbon nanotubes

Authors: Lefrant, S; Baltog, I; Baibarac, M

Published: NOV 2009, SYNTHETIC METALS, 159, 2176, DOI: 10.1016/j.synthmet.2009.08.029

In this paper, we present the anti-Stokes Raman scattering as a technique allowing investigations of materials at a nanoscale level. When the energy of the excitation light coincides with the energy of an electronic transition, a strong anti-Stokes Raman spectrum with respect to the prediction of the Maxwell-Boltzman (MB) law is regularly observed. Under a tight-focusing of the excitation light, the anti-Stokes Raman emission is reminiscent of Coherent anti-Stokes Raman Scattering (CARS). It has been detected on carbon nanotubes (CNTs), prototypes of nanometric materials, as well as on other compounds such as copper phthalocyanine (CuPc), poly(bithiophene) (PBTh), poly(3,4-ethylene dioxythiophene) (PEDOT), polyparaphenylene vinylene (PPV) layered as thin films on a metallic support in which are generated surface plasmons. We demonstrate that nanostructures by themselves can be of importance by generating non-linear phenomena that can be exploited for studying such materials and in particular carbon nanotubes. (C) 2009 Elsevier B.V. All rights reserved.

2130. Critical current density and pinning potential in YBa2Cu3O7-delta thick films ablated from a BaZrO3-doped nanocrystalline target

Authors: Crisan, A; Kechik, MMA; Mikheenko, P; Dang, VS; Sarkar, A; Abell, JS; Paturi, P; Huhtinen, H

Published: APR 2009, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 22, DOI: 10.1088/0953-2048/22/4/045014

We report on the pulsed laser deposition and characterization of thick (1.27 mu m) films ablated from a nanocrystalline YBa2Cu3O7-delta (YBCO) target doped with 4 wt% BaZrO3 (BZO), nYBCO/BZO. DC magnetization measurements have shown a four-to five-fold increase in the critical current density J(c) and a three- to four-fold increase in the maximum pinning force in comparison with 1 mu m thick films grown from a commercial microcrystalline YBCO target, at both 77.3 and 65 K. We have found that the frequency-dependent critical current densities J(c)(f(0)/f) estimated from susceptibility measurements are linear in a double-logarithmic plot ( where f is the frequency of the AC field and f(0) is a macroscopic attempt frequency of about 10(6) Hz), consistent with a logarithmic dependence of the pinning potential on the current density, and are again several times higher in nYBCO/BZO thick films. From the slopes of the J(c)(f(0)/f) dependences we have also estimated the values of pinning potentials in fields between 3 and 5 T.

2131. Modelling of dissolution kinetics of thin amorphous chalcogenide films

Authors: Popescu, M; Sava, F; Lorinczi, A; Velea, A; Vlcek, M; Jain, H

Published: 2009, PHILOSOPHICAL MAGAZINE LETTERS, 89, 376, DOI: 10.1080/09500830902960117

A theoretical relationship for the dissolution kinetics of thin chalcogenide films is proposed. The influence of light irradiation on the film dissolution is taken into account. The theoretical curves are in good agreement with the experimental dissolution results obtained for As2S3 thin amorphous films.

2132. ABSORPTION AND LUMINESCENCE PROPERTIES OF C-70 AGGREGATES IN SOLVENT MIXTURES

Authors: Husanu, AM; Baltog, I; Baibarac, M; Preda, N; Mihut, L; Velula, T; Bucur, C

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 538, DOI:

We report the formation of stable C-70 aggregate forms in o-dichlorobenzene/N-methyl-2-pyrrolidinone (DCB/NMP) and o-dichlorobenzene/acetonitrile (DCB/ACN) mixtures and their characterization by UV-VIS absorption spectroscopy and photoluminescence. As NMP acts on C-70 both as a solvent and reactant due to the unpaired electrons of the amidic nitrogen atom, molecular complexes (C-70/NMP) that aggregate slowly are formed by the binding of the NMP molecule to the fullerene cage. This interaction is seen in the UV-VIS absorption spectra of C-70 in DCB/NMP solvent mixtures by a gradual modification of the absorption spectra when increasing the NMP concentration. On the other hand, DCB and ACN combined form it typical solvent/non-solvent mixture favoring an intense aggregation of fullerenes. This yields to the C-70 clusters formations, having different size, similar to a precipitation process. Their characteristic is an abrupt variation in the absorbance appearing when the ACN is used in a greater extent. This different behavior of C-70 aggregation in DCB/NMP and DCB/ACN mixtures is also seen in their luminescence spectra recorded at different excitation wavelengths. While the PL spectra of C-70 solvated in DCB/NMP solution keeps almost the same modified shape irrespective the NMP concentration, the luminescence spectra Of C-70 in DCB/ACN mixture partially regains the powder C-70 PL signature as the ACN concentration is increased.

2133. Dielectric Properties of Paraelectric Ba1-xSrxTiO3 Ceramics

Authors: Nedelcu, L; Toacsan, MI; Banciu, MG; Ioachim, A

Published: 2009, FERROELECTRICS, 391, 41, DOI: 10.1080/00150190903001086

Ba1-xSrxTiO3 solid solutions with x = 0.4, 0.5, 0.6 and 0.75 were prepared by solid state reaction at 1260 degrees C. The complex dielectric constant dispersion was investigated in the frequency range 1Hz divided by 10 MHz for temperatures between -100 degrees C and 100 degrees C. Microwave measurements, performed at room temperature, show amonotonically decrease of the permittivity from about 3000 to 300 with the increase of the strontium content. Moreover, the variation of the dielectric loss from 0.8% to less than 0.2% with the increase with x was observed. The results indicate that the paraelectric Ba1-xSrxTiO3 materials are suitable for microwave applications.

2134. THE INTERCALATION OF PbI2 WITH 2,2 '-BIPYRIDINE EVIDENCED BY PHOTOLUMINESCENCE. FT-IR AND RAMAN SPECTROSCOPY

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Husanu, M; Bucur, C; Velula, T

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 675, DOI:

Hybrid material based on PbI2 intercalated with 2,2'-bypiridine (BIPY) was investigated by correlated studies of photoluminescence. infrared absorption and Raman spectroscopy. The PbI2(BIPY) intercalated compound has been synthesized by the chemical reaction of K1 and Pb(NO3)(2) in aqueous BIPY solution The optical studies reveal different properties for the hybrid material in comparison with those of pure PbI2 and BIPY. In the photoluminescence spectrum of the intercalated compound. recorded at liquid nitrogen temperature a new intense hand emission with maximum at 2 07 eV is observed. The excitation spectrum reveals it broad hand featured by several maxima at 2.77, 3.34 and 3 70 eV. New absorption bands at about 1589, 1489, 1435, 1312, 1009 cm(-1) are observed in the IR spectrum of PbI2(BIPY). The Raman spectrum of intercalated compound discloses new lines at 67, 83, 127 cm(-1) and the shift of two Raman lines from 994 cm(-1) to 1010 cm(-1) and from 1045 cm(-1) to 1060 cm(-1). A charge transfer process, leading to the formation of lead-BIPY coordination complexes. is considered its responsible for the strong host-guest interaction revealed by almost all experimental data

2135. THE SIMULATION IN THE REAL CONDITIONS OF ANTIBACTERIAL ACTIVITY OF TiO2 (Fe) FILMS WITH OPTIMIZED MORPHOLOGY

Authors: Gartner, M; Anastasescu, C; Zaharescu, M; Enache, M; Dumitru, L; Stoica, T; Stoica, TF; Trapalis, C

Published: 2009, NANOSTRUCTURED MATERIALS AND NANOTECHNOLOGY II, 29, +, DOI:

The aim of this study was to provide and characterize nanostructured TiO2 films for application in the depollution of the contaminated water against Escherichia coli (E. coli). The nanometric size of particles and the porosity of the films have been correlated with the technological parameters of the deposition process. For this aim three-layer TiO2 films were deposited by sol-gel and dip-coating method on SiO2/glass substrate. Iron (1 and 7%) and polyethylene glycol (PEG(600)) (0.014-0.110 M) were added to the coating solutions to study their effect on the porosity of the samples and respectively on the amorphous to anatase phase transition, as well as on the antibacterial activity. The samples were characterized using different complementary methods such as X-ray Diffraction (XRD), Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM), dynamics (growth and adherence) of E. coli development versus nanofilm composition (where the amount of bacterial inoculums used was closer to those Found in wasted waters). The obtained films have shown low toughness (values bellow 0.74 nm) and the particle size in nanometric range. The direct optical band gap values increases with the Fe content tip to 2.64 eV (470 nm), leading to an active photocatalyst tinder visible light (in our case under natural illumination condition). The inhibitory effect towards the E. Coli is Correlated with PEG and Fe concentration and was found to he the strongest for the sample containing 0.069 M PEG.

2136. Evolution of the surface morphology with temperature, in oxidant atmosphere, of Ba (Ti1-xSnx)O-3 (x=0.13) thin films

Authors: Cernea, M; Trupina, L; Plapcianu, C; Trusca, R; Galassi, C

Published: SEP 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 950, DOI:

Thin films of Ba(Ti1-xSnx)O-3 with x = 0.13 have been deposited by rf-magnetron sputtering and their growth morphology and structure vs annealing temperature, in oxygen atmosphere, have been investigated The films deposited on silicon-platinum substrates, at room temperature, in Ar atmosphere were amorphous The as-obtained films had a mean surface roughness (RMS) around 6.529 nm and a grain size of about 150 nm By annealing the film up to 1150 degrees C in oxygen, the grains size increases up to 1-1.5 mu m in diameter Films containing BaTi0.87Sn0.13 as crystalline phase with the cubic structure of BaTiO3 and, bundle-like morphology were obtained by heating the film at 1250 degrees C for 3h in oxygen The as-obtained film showed the preferential (110) and (100) orientations

2137. Surface Enhanced Raman Scattering Studies on Poly(3,4-ethylene dioxythiophene)/Single-Walled Carbon Nanotubes Composites and Their Application to Rechargeable Lithium Batteries

Authors: Baltog, I; Baibarac, M; Lefrant, S; Gomez-Romero, P

Published: OCT 2009, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 9, 6209, DOI: 10.1166/jnn.2009.1548

In this paper, surface enhanced Raman scattering (SERS) studies on the chemical polymerization of 3,4-ethylene dioxythiophene (EDOT) in the presence of single-walled carbon nanotubes (SWNTs) are reported. Both a non-covalent and covalent functionalization of SWNTs with poly(3,4-ethylene dioxythiophene) (PEDOT) is invoked as a result of the following variations induced in the SERS spectra of PEDOT and SWNTs: (i) the appearance of a Raman line at 140 cm(-1) indicating the formation of a new covalent bond between PEDOT and SWNTs; (ii) an increase in the intensity of the Raman line at 705 cm(-1), associated with the deformation vibration mode of C-S-C bond, the result of a steric hindrance effect induced by the bonding of PEDOT on SWNTs; and (iii) the enhancement of the Raman band with maximum at 1540 cm(-1) (G(-) component) in SWNTs when the PEDOT weight in the PEDOT/SWNTs composite increases. Using the PEDOT/SWNTs composite as a positive electrode and an electrolytic solution containing LiPF6, the charge-discharge characteristics of the rechargeable lithium cells are determined. High specific discharge capacity are reported for the PEDOT/SWNTs composite (ca. 218 mAh g(-1)) in comparison with PEDOT doped with FeCl4- ions (ca. 25 mAh g(-1)).

2138. STRUCTURAL AND OPTICAL PROPERTIES OF SOL-GEL DERIVED HYDROXYAPATITE FILMS IN DIFFERENT STAGES OF CRYSTALLIZATION AND DENSIFICATION PROCESSES

Authors: Tionica, S; Gartner, M; Ianculescu, A; Anastasescu, M; Slav, A; Pasuk, I; Stoica, T; Zaharescu, M

Published: 2009, NANOSTRUCTURED MATERIALS AND NANOTECHNOLOGY II, 29, +, DOI:

Hydroxyapatite (HAp) films, widely used as a biocompatible material for hard tissues repairing. are studied in this paper for a better control and understanding of the crystallization and densification of sol-gel deposited layers. Calcium nitrate and triethyl phosphite diluted in alcohols were used as calcium and phosphorus precursors. HAp coatings were obtained by spinning method, followed by drying and annealing in the range 130-750 degrees C. Specific temperatures of the chemical reactions of HAp formation have been revealed by thermogravimetric analysis (TG-DTA). Structural. chemical and optical characterizations of the films were performed by Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX) facilities, X-ray diffraction (XRD). Fourier Transform Infrared Spectroscopy (FTIR) and Spectral Ellipsometry (SE). The film crystallinity increases with file annealing temperature above 550 degrees C. XRD lines of HAp crystallographic planes become narrow at 750 degrees. and correspond to a single crystallographic phase. The Film morphology depends not only on annealing history but also on the synthesis parameters. Thus. layers with large grains of well sinterized HAp nano-crystals can be obtained. Using EDX measurements, the Ca/P ratio was found close to the stoichiometric value in the well sinterized HAp grain regions and slightly increased 1.82 for boundary regions between grains. The density of pores usually observed in sol-gel derived films was estimated for different samples using modeling of SE data.

2139. Optical Advanced Spectroscopic Techniques for the Study of Nano-Structured Materials Such as Carbon Nanotubes

Authors: Lefrant, S; Baltog, I; Baibarac, M

Published: AUG 2009, JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS, 4, 206, DOI: 10.1166/jno.2009.1022

Optical techniques allowing observations and spectroscopic investigations of materials at a nanoscale have been recently developed and applied to carbon nanotubes. They are briefly presented, including Scanning near-field optical microscopy, together with the Surface Enhanced or Tip Enhanced Raman Scattering. Even if new physical properties are difficult to extract from observed data, we show that nanostructures can generate non linear phenomena that can be exploited for studying nano-materials and in particular carbon nanotubes. By measuring the anti-Stokes/Stokes ratios of the Raman bands which present strong anomalies with respect to the prediction of the Maxwell-Boltzman law, one can distinguish between semi-conducting and metallic tubes on one hand and between isolated and bundled nanotubes on the other hand.

2140. Charge carrier transport phenomena in some organic heterojunctions

Authors: Rasoga, OL; Socol, M; Stanculescu, F

Published: APR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 514, DOI:

This paper presents investigations on the electrical transport phenomena in sandwich type inorganic/single (double) organic layer/inorganic such as silicon; ITO/TPyP, Alq3, alpha-NPD; ZnPc; perylene" PTCDA/silicon and inorganic (metal)/organic/metal such as silicon (A/)/ZnPc; alpha-NPD; TPyP/copper, Al, structures, prepared by vacuum evaporation. For most of these heterostructures the IN characteristics in the static regime have a near ohmic behaviour only at low voltages (<1 V) that changes in a power dependence with a coefficient n=2 or n=3 at higher voltages because of the space charge or trapped charge phenomena. For the same applied voltage, the n type Si electrode injects more charge carriers in TpyP than in Alq3. For higher voltages (>10V) an increased number of charge carriers are injected from n type Si in Alq3 compared to TpyP. The injection properties of the interface ITO, Cu, Al electrode/organic layer have also been investigated. The best injection has been obtained through ITO/ZnPc interface. For a grid configuration of the Al electrodes the transport phenomena are determined by the resistivity of the structure.

2141. Novel Microwave Planar Bandpass Filter Structures With Strongly Asymmetric Characteristics

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2009, 2009 MEDITERRANEAN MICROWAVE SYMPOSIUM, +, DOI:

In this paper the problem of designing simple low-cost planar microwave bandpass filters with strongly asymmetric characteristics, filters that can very efficiently attenuate one of the two adjacent channels, is investigated. In case of a fourth-order filter, the usual quadruplet structure leads to two transmission zeros located one on each side of the passband, but higher attenuation can be obtained for one of the two adjacent channels by designing filters with two transmission zeros in the same (upper or lower) stopband. The new topology investigated in this paper offers the possibility of designing such quadruplets with two transmission zeroes situated both on the same side of the passband, in prescribed and controlled positions. Filters with this novel structure can provide very high attenuation not only at a single frequency, but in a larger adjacent frequency band.

2142. STRUCTURAL MODELLING OF NANO-CARBONS AND NANO-CHALCOGENIDES

Authors: Sava, F; Popescu, M

Published: JAN-APR 2009, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 10, 25, DOI:

The structure of nano-carbon objects (ball-like, nanotubes, defected graphenes) has been modeled by a Monte-Carlo computer procedure. The structure of nano-chalcogenides objects based on two-dimensional network of arsenic sulphide has been modeled. The results were compared to the experimental data whenever possible. The structural modelling was proved as a powerful method for predicting new nano-structural elements in various low-dimensional materials.

2143. Interface States in 4H-and 6H-SiC MOS Capacitors: a Comparative Study between Conductance Spectroscopy and Thermal Dielectric Relaxation Current Technique

Authors: Lovlie, LS; Pintilie, I; Kumar, SCP; Grossner, U; Svensson, BG; Beljakowa, S; Reshanov, SA; Krieger, M; Pensl, G

Published: 2009, SILICON CARBIDE AND RELATED MATERIALS 2008, 615-617, 500, DOI: 10.4028/www.scientific.net/MSF.615-617.497

The purpose of this work is to compare the density of shallow interface states (D-it) at the interface of SiO2/SiC MOS capacitors as deducted by the conductance spectroscopy (CS) and thermally dielectric relaxation current (TDRC) techniques. Both capacitors of 4H- and 6H-SiC (n-type) arc investigated, and both ordinary dry oxidation and,in improved industrial procedure have been employed. The two techniques are found to give rather good agreement for interface states located >= 0.3 eV below the conduction band edge (E-c) while for more shallow states vastly different distributions of D-it are obtained. Different reasons for these contradictory results are discussed, such as strong temperature and energy dependence of the capture cross section of the shallow interface States.

2144. Coprecipitated Cobalt Ferrite for Sensors

Authors: Boutiuc, LM; Dumitru, I; Caltun, OF; Feder, M; Vilceanu, V

Published: JUN 2009, SENSOR LETTERS, 7, 246, DOI: 10.1166/sl.2009.1067

In order to determine the influence of the sintering temperature on the performances of the magnetostrictive materials based sensor for stress, three series of cobalt ferrite (CoFe2O4) samples were prepared by coprecipitation method. These samples were sintered at 1050 degrees C, 1100 degrees C, 1150 degrees C. The spinel structure and the presence of the residual phases were investigated by X-ray diffractometry, scanning electron microscopy and vibrating sample magnetometry. Magnetostrictive properties of the samples were measured by strain gauge technique, in a direction which is parallel to the direction of the applied field. This study was focused on the influence of sintering temperature on magnetic properties and on magnetostriction coefficients. The study reveals that the increase of the sintering temperature increased the magnetostriction coefficients but decreased the strain derivative. Cobalt ferrite obtained by this method can be good candidates for sensors.

2145. Matrix-assisted photo-amorphization effect in As40S30Se30 films with silver

Authors: Popescu, M; Petkov, K; Sava, F; Taseeva, J; Lorinczi, A; Velea, A

Published: DEC 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 2003, DOI:

Matrix assisted photo-amorphization effect has been observed in thin chalcogenide films of composition As40S30Se30 deposited by thermal evaporation on silicon wafer substrate covered by silver. The initial films contain Ag2S and Ag4SeS crystallites embedded in an amorphous matrix. Illumination by a cold light halogen lamp induces the disappearance of the crystalline fraction and leads to significant changes in the diffraction pattern of the amorphous films.

2146. Improvement of Pinning Force and Critical Current Density in Thick YBa (2) Cu (3) O (7-delta) Films Grown on SrTiO (3) Substrates Decorated with LaNiO (3) Nanodots

Authors: Crisan, A; Sarkar, A; Mikheenko, P; Dang, VS; Kechik, MMA; Abell, JS

Published: OCT 2009, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 22, 636, DOI: 10.1007/s10948-009-0452-2

We have investigated by DC magnetization measurements and frequency-dependent AC susceptibility the critical current density (J (c)), pinning force (F (p)) and pinning potential in thick (1.3-1.6 mu m) YBa2Cu3O7-delta (YBCO) films grown by Pulsed Laser Deposition on SrTiO3 substrates decorated with LaNiO3 nanodots deposited by a few (5-15) laser pulses, in comparison with those of a 1 mu m thick YBCO reference sample. Experiments show that the highest improvement of superconducting properties was achieved for films grown on substrates decorated with 10 laser pulses on the LaNiO3 target, which have, at 77.3 K, a J (c) of 40-125% higher than in pure YBCO in fields between 1 and 2 T, and F (p) increased by 40%. These results could be important for further improvement of current-carrying capability of coated conductors for in-field power applications.

2147. Quantum well effect in bulk PbI2 crystals revealed by the anisotropy of photoluminescence and Raman spectra

Authors: Baltog, I; Baibarac, M; Lefrant, S

Published: JAN 14 2009, JOURNAL OF PHYSICS-CONDENSED MATTER, 21, DOI: 10.1088/0953-8984/21/2/025507

On subjecting a bulk 2H-PbI2 crystal to vacuum annealing at 500 K followed by a sudden cooling at liquid nitrogen temperature stacking faults are generated that separate distinct layers of nanometric thickness in which different numbers of I-Pb-I atomic layers are bundled together. Such structures, containing two, three, four, five etc I-Pb-I atomic layers, behave as quantum wells of different widths. The signature of such a transformation is given by a shift towards higher energies of the fundamental absorption edge, which is experimentally revealed by specific anisotropies in the photoluminescence and Raman spectra. The quantum confining effect is made visible by specific variations of a wide extra-excitonic band (G) at 2.06 eV that originates in the radiative recombination of carriers (electrons and holes), trapped on the surface defects. The excitation spectrum of the G band, with p polarized exciting light, reveals a fine structure comprised of narrow bands at 2.75, 2.64, 2.59 and 2.56 eV, which are associated with the PbI2 quantum wells formed from two, three, four and five I-Pb-I atomic layers of 0.7 nm thickness. Regardless of the polarization state of the laser exciting light of 514.5 nm (2.41 eV), which is close to the band gap energy of PbI2 (2.52 eV), the Raman scattering on bulk as-grown PbI2 crystals has the character of a resonant process. For p polarized exciting light, the Raman scattering process on vacuum annealed PbI2 becomes non-resonant. This originates from the quantum well structures generated inside the crystal, whose band gap energies are higher than the energy of the exciting light.

2148. Characteristics of Vacuum Deposited Sucrose Thin Films

Authors: Ungureanu, F; Predoi, D; Ghita, RV; Vatasescu-Balcan, RA; Costache, M

Published: 2009, INTERFACE CONTROLLED ORGANIC THIN FILMS, 129, 71, DOI: 10.1007/978-3-540-95930-4_11

Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p similar to 10-5 torr). The surface morphology was putted into evidence by FT-IR and SEM analysis. The experimental results confirm a uniform deposition of an adherent sucrose layer. The biological tests (e.g., cell morphology and cell viability evaluated by measuring mitochondrial dehydrogenise activity with MTT assay) confirm the properties of sucrose thin films as bioactive material. The human fetal osteoblast system grown on thin sucrose film was used for the determination of cell proliferation, cell viability and cell morphology studies.

2149. Influence of dye concentration on optical properties of rhodamine 6G doped KAP crystals

Authors: Enculescu, M; Matei, E; Preda, N; Enculescu, I

Published: NOV 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 1212, DOI:

Crystals of potassium acid phthalate (KAP) doped with rhodamine 6G (Rh 6G) were grown by slow evaporation method from aqueous solutions. Crystals of good optical quality suitable for optical applications were obtained. Different concentrations of rhodamine 6G (10(-5) M, 2x10(-5) M, 5x10(-5) M and 10(-4) M in the growth solutions) were used in order to tune the optical properties of the crystals. Depending of the dye concentration, the absorption spectra of the dye-doped crystals show several bands in the range between 360 nm and 526 nm. The photoluminescence of the KAP crystals induced by the dye-doping reveals two emission bands peaking at 540 nm and 560 nm.

2150. Microwave Investigations on Some Microstrip Left-Handed Structures

Authors: Banciu, MG; Mihai, IA; Militaru, N; Lojewski, G; Petrescu, T

Published: 2009, TELSIKS 2009, VOLS 1 AND 2, +, DOI:

Microstrip structures with left-handed properties are investigated in frequency domain. A method of extracting material effective parameters from the two-port scattering parameters is developed and applied to the proposed left-handed structures.

2151. Photoluminescence and thermoluminescence of ZnO nano-needle arrays and films

Authors: Secu, CE; Sima, M

Published: APR 2009, OPTICAL MATERIALS, 31, 880, DOI: 10.1016/j.optmat.2008.10.025

ZnO nano-needle arrays and films have been prepared by anodic etching of ZnO foil at constant current in potassium zincate solution and sodium hydroxide alcoholic solution, respectively. Photoluminescence (PL) spectra recorded on ZnO nano-needles have shown a broad band at 585 nm due to the native oxygen defects incorporated during the synthesis processes; in a ZnO film-type sample this band is replaced by another one at 432 nm. Thermoluminescence (TL) glow curves recorded on ZnO nano-needle arrays have shown a broad peak at about 360 degrees C similar to that observed in ZnO polycrystalline powder. A very strong TL peak at about 325 degrees C superimposed on a broad one has been observed in a ZnO film-type sample. TL recorded on ZnO nano-needles has tentatively been attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centres; the TL mechanism is supported by a recovery effect of the PL and TL after storage in air. (C) 2008 Elsevier B.V. All rights reserved.

2152. Pulsed-laser deposition of smooth thin films of Er, Pr and Nd doped glasses

Authors: Epurescu, G; Vlad, A; Bodea, MA; Vasiliu, C; Dumitrescu, O; Niciu, H; Elisa, M; Siraj, K; Pedarnig, JD; Bauerle, D; Filipescu, M; Nedelcea, A; Galca, AC; Grigorescu, CEA; Dinescu, M

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5298, DOI: 10.1016/j.apsusc.2008.10.038

Thin films of complex oxides have been obtained by pulsed-laser deposition (PLD) from glass targets belonging to the system Li2O-Al2O3-P2O5-(RE)(2)O-3, with RE = Nd, Pr, Er. The films were deposited on quartz, silicon and ITO/glass substrates using a F-2 laser (lambda = 157 nm, iota approximate to 20 ns) for ablation in vacuum. The structural, morphological and optical properties of the oxide films were investigated through IR and UV-VIS spectroscopy, Atomic Force Microscopy (AFM), Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy (SEM-EDX) and Spectroscopic Ellipsometry. The laser wavelength was found to be the key parameter to obtain thin films with very smooth surface. In this way new possibilities are opened to grow multilayer structures for photonic applications. (C) 2008 Elsevier B. V. All rights reserved.

2153. Calcium Carbonate Synthesis in Ultrasonic Field

Authors: Mihai, M; Turtoi, D; Isopescu, R; Mateescu, C; Chilibon, I

Published: JUN 2009, REVISTA DE CHIMIE, 60, 631, DOI:

Precipitated calcium carbonate as vaterite and small amounts of calcite, with submicron sizes was obtained by a two stages reaction, In the first stage, the limestone was transformed with carbon dioxide in calcium bicarbonate in the absence and the presence of an ultrasonic applied field (35kHz and 0.52 W/cm(2)). The ultrasonic intensity and specific power, the device immersion depth in column suspension and the cavitation was observed to accelerate the dissolving rate of calcium carbonate. In the second stage, the solution of calcium bicarbonate was aerated to obtain calcium carbonate. The experiment was conducted in the absence and the presence of an ultrasonic applied field. The precipitation rate and the calcium carbonate particles size distribution were found to be influenced by the ultrasonic field. The morphology of the crystals formed was unaffected by the ultrasonic field.

2154. Chromium doping of epitaxial PbZr0.2Ti0.8O3 thin films

Authors: Feigl, L; Pippel, E; Pintilie, L; Alexe, M; Hesse, D

Published: JUN 15 2009, JOURNAL OF APPLIED PHYSICS, 105, DOI: 10.1063/1.3141733

Epitaxial ferroelectric PbZr0.2Ti0.8O3 thin films were grown by pulsed laser deposition. PbZr0.2Ti0.8O3 was doped with Cr acting as acceptor ion. Microstructural characterization was performed by (high resolution) transmission electron microscopy. The voltage dependence of polarization, dielectric constant, and leakage current were measured with respect to the Cr content. To derive the electronic properties, PZT was considered as a wide-gap semiconductor which allows treating the metal-PZT interface as a Schottky contact. The Cr was found to facilitate the elastic relaxation of the film. Furthermore, the leakage current was increased through a reduction of the Schottky barrier. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3141733]

2155. VIBRATIONAL PROPERTIES OF POLYANILINE FUNCTIONALIZED PbI2

Authors: Baltog, I; Baibarac, M; Mihut, L; Preda, N; Velula, T; Bucur, C; Husanu, M

Published: 2009, ROMANIAN JOURNAL OF PHYSICS, 54, 688, DOI:

Functionalization of PbI2 with polyaniline-emeraldine base (PANI-EB) or polyaniline-emeraldine salt (PANI-ES) is demonstrated by Raman spectroscopy. Two functionalization methods were used: electrochemical polymerization of aniline onto the PbI2 modified Pt electrode and the mechanico-chemical reaction between PANI and PbI2. The functionalization induces changes in the Raman spectrum of PbI2 that consist in the appearance of new Raman lines with the peaks at 80, 144 and 170 cm(-1) The first line is the signature of the "stacking faults" that disrupt the stacking sequence of layers I-Pb-I atomic layers along the c crystalline axis by the intercalation of polymer molecules The bands at 144 and 170 cm(-1) are attributed to a vibrational mode associated to the Pb-NHR"(2) (R" = C6H4) bond.

2156. Growth and optical characteristics of coumarin 6 doped potassium hydrogen phthalate (KAP) crystals

Authors: Enculescu, M

Published: DEC 2009, OPTICAL MATERIALS, 32, 285, DOI: 10.1016/j.optmat.2009.08.002

Single-crystals of potassium hydrogen phthalate (KAP) doped with coumarin 6 (C6) were grown by solution evaporation technique. Powder X-ray diffraction. optical transmission and luminescence measurements were performed. The structure and morphology of the KAP crystals are not changed with the incorporation of the dye. Transparency of the dye-doped crystals is suited for non-linear optical (NLO) applications and UV cut-off is not changed when compared with the pure KAP crystals. The dye-doped crystals present an absorption band at 350 nm while the growth solution exhibits a peak at 400 nm. The doped crystals have a strong emission band at 450 nm that is excited at 350 nm and the second harmonic generating (SHG) properties are demonstrated using luminescence measurements. (C) 2009 Elsevier B.V. All rights reserved.

2157. Potential-Induced Conformational Changes in an alpha-CN-terthiophene Thiolate Film on GaAs(110)

Authors: Lazarescu, V; Scurtu, R; Lazarescu, MF; Toader, AM; Volanschi, E; Santos, E; Jones, H; Gotz, G; Bauerle, P

Published: JUN 2 2009, LANGMUIR, 25, 6531, DOI: 10.1021/la900043k

Second harmonic generation (SHG) investigations on alpha-CN-terthiophene-thiolate-covered GaAs(110) electrodes in 1 N H2SO4 solution revealed significant changes in the rotational anisotropy of the SH response. The enhancement of the 1- and the 3-fold contributions around -250 mV suggests changes in the symmetry properties of the delocalized electron system due to an alteration of the adsorption geometry induced by the applied potentials. The analysis of the EIS data showed that in the potential region where the SH signal exhibits the more important changes the Mott-Schottky plot undergoes a pronounced shift to more negative potentials as a result of the charging of the surface states grouped about 1.06 eV below the conduction band edge. Semiempirical MO calculations suggest that the most energetically favorable interaction implies electron transfer from the semiconductor conduction band to the lowest unoccupied molecular orbital of the organic molecule with epsilon(LUMO) = -1.707 eV. Such a chemisorption bond bringing the organic molecule to a quasi-planar position is well supported by the major changes in the XPS spectra of the electrochemically biased samples with respect to the as-prepared ones. Two distinct N Is species instead of one and a shift of 1.6 eV to higher BE of the terthiophene S 2s core level are strong evidence for a potential-induced change in the adsorption geometry. Taking into account that the acceptor-like surface state group located close to the semiconductor valence edge (E-C,E-S = -1.06 eV) may correspond to the LUMO level (shifted downward by the adsorption process), we assume that the organic molecule, initially adsorbed by the thiolate end, undergoes a conformational change from a tilted to an almost flat position when the applied potential brings the semiconductor Fermi level into its neighborhood. This assumption is in a very good agreement with the potential-induced variation in the thiol thickness estimated from the thiol capacitance.

2158. Structural investigations of sol-gel derived silicate gels using Eu3+ ion-probe luminescence

Authors: Secu, CE; Predoi, D; Secu, M; Cernea, M; Aldica, G

Published: SEP 2009, OPTICAL MATERIALS, 31, 1748, DOI: 10.1016/j.optmat.2009.05.009

Undoped and Eu3+-doped CaF2-SiO2 gels were prepared by the sol-gel method and their optical properties have been studied. The UV-VIS-NIR absorption and photoluminescence spectra have shown the bands typical for the Eu3+ ions transitions. When the Eu-doped gel is annealed at temperatures up to 800 degrees C (i.e. above the CaF2 crystallisation peak at similar to 460 degrees C) the photoluminescence spectra intensity increase, the 590 nm (D-5(0) -> F-7(1)) and 620 nm (D-5(0) -> F-7(2)) luminescence bands become comparable and a structuring of the 620 nm band is observed. The phonon sidebands peaks associated with the F-5(0) -> D-7(2) transition of the Eu3+ ion were observed at around 1000 and 620 cm(-1) and have been assigned to the Si-O and Ca-O bonds, respectively. A phonon sideband signal in the range of 3007400 cm(-1) was attributed to Ca-F bonds in the precipitated CaF2 phase. From the optical absorption, photoluminescence and phonon sidebands spectra we have concluded that in the gels annealed at 800 degrees C, the Eu3+ ions are incorporated into the silica network and in the precipitated CaF2 phase. (c) 2009 Elsevier B.V. All rights reserved.

2159. Atomic force microscopy study of TiO2 sol-gel films thermally treated under NH3 atmosphere

Authors: Trapalis, C; Todorova, N; Anastasescu, M; Anastasescu, C; Stoica, M; Gartner, M; Zaharescu, M; Stoica, T

Published: OCT 1 2009, THIN SOLID FILMS, 517, 6247, DOI: 10.1016/j.tsf.2009.02.070

Multilayered TiO2 films were obtained by sol-gel and dipping deposition on quartz substrate followed by thermal treatment under NH3 atmosphere. In an attempt to understand the close relationship between microstructural characteristics and the synthesis parameters, a systematic research of the structure and the morphology of NH3 modified TiO2 sol-gel films by XRD and Atomic Force Microscopy is reported. The surface morphology has been evaluated in terms of grains size, fractal dimension and surface roughness. For each surface, it was found a self-similar behavior (with mean fractal dimension in the range of 2.67-3.00) related to an optimum morphology favorable to maintain a nano-size distribution of the grains. The root mean square (RMS) roughness of the samples was found to be in the range of 0.72-6.02 nm. (C) 2009 Elsevier B.V. All rights reserved.

2160. In-depth investigation of EPR spectra of Mn2+ ions in ZnS single crystals with pure cubic structure

Authors: Nistor, SV; Stefan, M

Published: APR 8 2009, JOURNAL OF PHYSICS-CONDENSED MATTER, 21, DOI: 10.1088/0953-8984/21/14/145408

The X (9.8 GHz)-band electron paramagnetic resonance (EPR) properties of substitutional Mn2+ ions in high quality cubic ZnS single crystals grown from PbCl2 flux have been thoroughly investigated. Accurate spin Hamiltonian (SH) parameters: g = 2.002 25 +/- 0.000 06; a = (7.987 +/- 0.008) x 10(-4) cm(-1) and A = -(63.88 +/- 0.02) x 10(-4) cm(-1) were obtained by simulation and fitting to the experimentally allowed transitions recorded for the magnetic field aligned within +/- 0.25 degrees along the main crystal axes. The normally forbidden hyperfine M = + 1/2 <->-1/2, Delta m = +/- 1 transitions were also observed. Their position was found to be in agreement, within the experimental accuracy of Delta H = +/- 0.01 mT, with calculations using the same SH parameters. The angular variation of the ratios of the intensities of the central forbidden to the allowed transitions could be accounted for only by including an additional constant contribution. The observed line broadening of the M = +/- 1/2 <->+/- 3/2 and +/- 3/2 <->+/- 5/2 fine structure transitions and their line width variation in a (110) plane have been quantitatively described by considering a random distribution of lattice strains at the Mn2+ impurity ions. The influence of the forbidden transitions and line broadening on the EPR spectra line shape of the Mn2+ ions in cubic ZnS crystalline powders is also examined.

2161. Local environment of vanadium in V/Al/O-mixed oxide catalyst for propane ammoxidation: Characterization by in situ valence-to-core X-ray emission spectroscopy and X-ray absorption spectroscopy

Authors: Safonova, OV; Florea, M; Bilde, J; Delichere, P; Millet, JMM

Published: NOV 15 2009, , DOI: 10.1016/j.jcat.2009.09.014

2162. Transesterification of vegetable oils on basic large mesoporous alumina supported alkaline fluorides-Evidences of the nature of the active site and catalytic performances

Authors: Verziu, M; Florea, M; Simon, S; Simon, V; Filip, P; Parvulescu, VI; Hardacre, C

Published: APR 1 2009, , DOI: 10.1016/j.jcat.2009.01.012

2163. Synthesis and sensing properties of mixed oxide magnetic nanoparticles

Authors: Sorescu, M; Diamandescu, L; Tomescu, A; Krupa, S

Published: MAR 22 2009, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 237, DOI:

2164. XPS analysis of n-GaP(111) native and etched surfaces

Authors: Cotirlan, C; Logofatu, C; Negrila, CC; Ghita, RV; Manea, AS; Lazarescu, MF

Published: APR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 390, DOI:

The obtaining of a good ohmic contacts on the semiconductor material surfaces is strongly depending on the ability of the cleaning procedures to remove the native oxides and also, in the case of the compounds, to keep the surface stoichiometry. In this work, the XPS technique has been used in order to compare the efficiency of both, chemical etching and the Ar+ ion sputtering methods as to be suitable cleaning procedures in the case of n-GaP semiconductor compound surfaces preparation for the optoelectronic devices obtaining. The results have revealed some differences in the final surface composition/stoichiometry. The atomic ratio P/Ga within the outer layer of the single crystalline sample (similar to 100 angstrom) has been evaluated. The presence of residual of surface oxides was recorded after performing the chemical cleaning.

2165. Raman and FTIR spectroscopy as valuable tools for the characterization of polymer and carbon nanotube based composites

Authors: Lefrant, S; Baibarac, M; Baltog, I

Published: 2009, JOURNAL OF MATERIALS CHEMISTRY, 19, 5704, DOI: 10.1039/b821136a

The combination of the unique properties of carbon nanotubes (CNTs) with conjugated polymers makes their combined composite materials interesting as multifunctional systems with great potential. Supercapacitors, lithium rechargeable batteries, sensors, photovoltaic cells and photodiodes, optical limiting devices, solar cells, high-resolution printable conductors, electromagnetic absorbers and advanced transistors are among the most promising applications. Knowledge of the molecular structure of such compounds is essential for a better use, and for that reason vibrational spectroscopies are fruitful techniques. Therefore, this feature article presents recent progress in the characterization of composites based on conjugated polymers and carbon nanotubes. The contribution of Raman scattering and FTIR spectroscopy to establish the type of interaction between the two constituents will be discussed for different cases, i.e. bi-layers of polymers and carbon nanotubes, doped conjugated polymers with carbon nanotubes and covalently functionalized carbon nanotubes with conjugated polymers. In addition, surface enhanced Raman scattering (SERS) has also proven to be a suitable technique for characterization by providing signal enhancements, allowing for instance the detection of reactions at interfaces or the exploitation of properties associated with nanostructures. As an example, an extra increase of the Raman signal of a polymer deposited on a carbon nanotube thin film demonstrates the generation of surface plasmons in metallic tubes.

2166. Surface states- and field-effects at p- and n-doped GaAs(111)A/solution interface

Authors: Scurtu, R; Ionescu, NI; Lazarescu, M; Lazarescu, V

Published: 2009, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11, 1770, DOI: 10.1039/b817045b

We have investigated the behaviour of n- and p-doped GaAs(111) A electrodes in sulfuric acid solution by electrochemical impedance spectroscopy (EIS) and second harmonic generation (SHG) measurements. The potential dependence of the SHG response was found to be closely related to the changes in the surface state population, as revealed by analysis of the impedance data. The nature of the majority of carriers turned out to be a key factor in shaping the surface state- and field-effect on the second harmonic generation process.

2167. Amorphous research in Romania: Past, present and latest results

Authors: Popescu, M; Croitoru, N

Published: AUG 2009, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 246, 1793, DOI: 10.1002/pssb.200982006

In the early days of amorphous research, Romania was deeply involved in the development of the field of amorphous semiconductors within a close collaboration with Boris Kolomiets. The first researches in this field are discussed and further rapid developments up to the present are shown. The latest results in the field of amorphous semiconductor:, with special emphasis on chalcogenide glasses are presented. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2168. Optical and structural investigations on rare earth-doped thin films of phosphate glasses prepared by pulsed laser deposition

Authors: Vasiliu, C; Epurescu, G; Niciu, H; Dumitrescu, O; Negrila, C; Elisa, M; Filipescu, M; Dinescu, M; Grigorescu, CEA

Published: JAN 2009, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 20, 289, DOI: 10.1007/s10854-008-9583-7

Thin films of phosphate glasses were prepared by pulsed laser deposition in oxygen atmosphere on ITO-coated glass and silicon substrates respectively, using a Nd:YAG laser (266 nm). The targets were Li(2)O-Al(2)O(3)-P(2)O(5) bulk glasses doped with Pr and Nd. Infrared transmission-, energy dispersive X-ray- and X-ray photoemission spectroscopy investigations carried out on targets as well as on the deposited films proved a satisfactory compositions transfer on both substrates. Scanning electron microscopy and atomic force microscopy show continuous films with glassy spheres. Processes where substrates were positioned perpendicularly to targets produced discontinuous drops free films.

2169. Magnetic Temperature Transducers Made from Copper Based Soft Ferrite

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Spanulescu, I; Cioangher, M; Miclea, CT

Published: 2009, SMART MATERIALS & MICRO/NANOSYSTEMS, 54, 69, DOI:

Soft ferrites in the CuZnTi system, having the chemical composition Cu1-x-yZnxTiyFe2O4 with 0.5 <= x <= 0.7 and 0.00 <= y <= 0.05 were investigated as a function of composition, sintering temperature and cooling speed, in order to obtain materials with different Curie temperatures, between 30 and 180 degrees C and very high change rate of permeability with temperature around their Curie points. Such materials are well suited to use as high sensitive magnetic temperature sensors and transducers for temperature control. Zn and Ti additions to copper ferrite change the Curie temperature in a controllable manner, thus being possible to produce ferrite material with a fine control of the Curie point at any desired temperature. Most important was the behavior of magnetic permeability with temperature around the Curie point, where it may change with about 60 %/degrees C by a proper choice of the cooling speed of samples from the sintering temperature to room temperature. This makes such materials extremely attractive as magnetic temperature sensors of high sensitivity. Two applications Of Such materials as temperature sensors, namely an ultrathermostat and an on-off switch type relay were designed. Their functionality and performances are presented and discussed.

2170. Crystallization and spectroscopic properties of Eu-doped CaF2 nanocrystals in transparent oxyfluoride glass-ceramics

Authors: Secu, M; Secu, CE; Polosan, S; Aldica, G; Ghica, C

Published: OCT 1 2009, JOURNAL OF NON-CRYSTALLINE SOLIDS, 355, 1872, DOI: 10.1016/j.jnoncrysol.2009.04.062

Transparent oxyfluoride glass-ceramic in the system SiO2-Al2O3-CaF2-EuF2 containing Eu-doped CaF2 nanocrystals were produced by using the controlled crystallization of melt-quenched glass. X-ray diffraction and transmission electron microscopy data have revealed the formation of the CaF2 nanocrystals of about 65 nm size. Photoluminescence spectra have shown an increase of the splitting of the luminescences associated to the Eu3+ ion along with annealing time which is consistent with the Eu3+ environment evolving from a glassy to a crystalline state. (C) 2009 Elsevier B.V. All rights reserved.

2171. Peak-dip crossover of the differential conductance in mesoscopic systems with quantum impurities

Authors: Aldea, A; Tolea, M; Dinu, IV

Published: 2009, 25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 2, 150, DOI: 10.1088/1742-6596/150/2/022001

We investigate the differential conductance dI/dV for the interacting T-shape model, using an approach based on the Keldysh formalism and the Lacroix solution for the equation of motion. A peak-dip crossover has been noticed by changing the hybridization between the two dots. For the same model, the combined interaction and interference processes give rise to the Fano-Kondo effect with an interesting crossing point of the isoterms below the Kondo temperature A tentative explanation of these effects is given in terms of the many-body spectral properties of the system.

2172. Vibrational properties of the electrochemically synthesized polyindole/single-walled carbon nanotubes composite

Authors: Baibarac, M; Baltog, I; Scocioreanu, M; Lefrant, S; Mevellec, JY

Published: DEC 2009, SYNTHETIC METALS, 159, 2555, DOI: 10.1016/j.synthmet.2009.09.010

Electrochemical polymerization of indole in a LiClO4/CH3CN solution on a single-walled carbon nanotubes (SWNTs) film was studied by cyclic voltammetry, Raman scattering and FTIR spectroscopy. Comparing the cyclic voltammograms recorded on a blank Pt electrode with those obtained when carbon nanotubes films were previously deposited onto the Pt electrode, a down-shift of the indole reduction peak potential in the latter case was observed. Raman spectroscopy studies indicate that the electrochemical deposition of polyindole (PIN) onto the SWNT film results in a breaking of SWNT bundles into individual tubes. A covalent functionalization of SWNTs with PIN in the doped state is demonstrated by FTIR spectroscopy, when an increase in the intensity of the absorption band at 1045 cm(-1) is observed. Besides, Raman and FTIR studies performed on samples electrochemically prepared and thereafter post-chemically reacted with an NH4OH solution, indicate both a roping process of individual tubes with PIN as a binding agent and a strong steric hindrance effect. (C) 2009 Elsevier B.V. All rights reserved.

2173. Composites containing confined n-octyl-cyanobiphenyl: Monomer and dimer species in the surface layer by in situ FTIR spectroscopy

Authors: Frunza, L; Frunza, S; Poterasu, M; Beica, T; Kosslick, H; Stoenescu, D

Published: MAR 2009, SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY, 72, 253, DOI: 10.1016/j.saa.2008.09.001

Confinement of 4-n-octyl-4'-cyanobiphenyl (8CB) to nanoporous molecular sieves with hexagonal structure of cylindrical pores (4.6 nm diameter) is studied. Thermogravimetric investigations have indicated that the pores are completely filled. Several surface species inside the pores and onto the external surface of the grains were demonstrated by differential thermal analysis and by in situ infrared spectroscopy. Arguments are given that bulk-like monomer and dimer species along with hydrogen bonded ones might coexist in the so-called surface layer, but their population varies drastically as function of the temperature. In addition, chemical changes of the confined liquid crystal are quite possible inside these nanopores, at temperatures lower than for the bulk. (c) 2008 Published by Elsevier B.V.

2174. COMMUTON - A NEW CONCEPT IN SWITCHING MATERIALS

Authors: Popescu, M; Velea, A; Lorinczi, A; Sava, F

Published: MAR-APR 2009, JOURNAL OF OVONIC RESEARCH, 5, 34, DOI:

A switching unit can be defined as the smallest unit that preserves the property of switching in memory materials. Atomic switching unit is discussed, molecular switching units are described and supramolecular units in phase change materials are evidenced and discussed. The "commuton", as basic switching unit, could give more insight into the particular properties of the switching phenomena in various solid materials.

2175. Orientation-dependent potential barriers in case of epitaxial Pt-BiFeO3-SrRuO3 capacitors

Authors: Pintilie, L; Dragoi, C; Chu, YH; Martin, LW; Ramesh, R; Alexe, M

Published: JUN 8 2009, APPLIED PHYSICS LETTERS, 94, DOI: 10.1063/1.3152784

The leakage current in epitaxial BiFeO3 capacitors with bottom SrRuO3 and top Pt electrodes, grown by pulsed laser deposition on SrTiO3 (100), SrTiO3 (110), and SrTiO3 (111) substrates, is investigated by current-voltage (I-V) measurements in the 100-300 K temperature range. It is found that the leakage current is interface-limited and strongly dependent on the orientation of the substrate. The potential barriers at the electrode interfaces are estimated to about 0.6, 0.77, and 0.93 eV for the (100), (110), and (111) orientations, respectively.

2176. Electropolymerization of N-Ethylcarbazole on Single Walled Carbon Nanotubes-Cyclic Voltammetry, Raman and FTIR Studies

Authors: Baibarac, M; Baltog, I; Mihut, L; Mevellec, JY; Lefrant, S

Published: OCT 2009, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 9, 6203, DOI: 10.1166/jnn.2009.1547

The electrochemical polymerization of N-ethyl carbazole (EK) on carbon nanotubes (CNs) films immersed in a LiClO4/acetonitrile solution was studied by cyclic voltammetry. Cyclic voltammo-grams recorded on a blank Pt electrode were compared with those obtained when CNs films were deposited on a Pt plate. In the latter case, the oxidation maximum is not clearly observed. Using the Raman scattering studies, oligomers of poly(N-ethyl carbazole) (PEK) on CNs are shown to be formed. A covalent functionalization of CNs with the PEK oligomers is demonstrated by FTIR spectroscopy studies. The formation of new C-C covalent bonds between CNs and the benzene ring of PEK induces steric hindrance effects that are shown in FTIR spectra by the increase in the intensity of the absorption band at 1072 cm(-1) attributed to the vibration of C-H in plane deformation of aromatic ring. The influence of the monomer and the supporting electrolyte concentration as well as the sweep rate on the polymerization conditions in the case of the composites based on the PEK oligomers and CNs were also investigated.

2177. Nanostructured Ferrite Formation in Borosilicate Glass

Authors: Sandu, V; Popa, S; Pasuk, I; Enculescu, I; Nicolescu, MS; Radicescu, S

Published: 2009, MULTI-FUNCTIONAL MATERIALS AND STRUCTURES II, PTS 1 AND 2, 79-82, +, DOI: 10.4028/www.scientific.net/AMR.79-82.445

We present the preparation, structural, and magnetic properties of a series of Fe-containing borosilicate glasses as a function of the ratio SiO2/Fe2O3 which is ranging from 1.49 to 2.68. The role of nucleators (Cr2O3 and P2O5) was also investigated. X-Ray diffraction has revealed the formation of magnetite as the major or unique crystalline phase. As SEM micrographs have revealed, the addition of P2O5 give rise to a finer structure as compared with Cr2O3. In addition, the same oxide decreases the temperature of structural transition with almost 100 degrees C. The magnetization data reveal a two step transition at low temperatures: a high temperature transition at T-v = 128 K, which we attribute to the Verwey transition, and a low temperature transition at T-s = 48 K which, most likely, is the result of change in the dynamic of the domain motion.

2178. Semiconductor detectors for high radiation fields: microscopic processes in materials and the control of device parameters

Authors: Lazanu, S; Ciurea, ML; Lazanu, I

Published: DEC 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 2154, DOI:

The knowledge of the effects of radiation in semiconductor devices, in particular in detectors, represents an important and active field of research. The influence of isovalent impurities, carbon and germanium, on the radiation damage of silicon for detectors is investigated in the frame of a quantitative phenomenological model for defect kinetics, developed previously by the authors. The concentrations of defects induced by irradiation in materials with different doping levels are calculated, as well as the leakage current and effective carrier concentrations in p-n junction detectors made from these materials. The beneficial effect of Ge on the radiation damage of silicon is deduced.

2179. PHASE CHANGE MATERIALS: CHEMICAL BONDING AND STRUCTURAL PROPERTIES

Authors: Velea, A; Popescu, M

Published: SEP-DEC 2009, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 10, 236, DOI:

The phase change materials are the most important materials in the class of chalcogenides (combination of chalcogens (S, Se and Te) with metalloids or metals). The outstanding property of these materials is the switching from a high electrical resistivity state to low electrical resistivity state and back under a moderate voltage. The thin film materials are used in computer memories, CD and DVD devices with performing speed and storage capacity. We have studied several thin solid films made of Ge-Sb-Te in order to assess the switching quality of different compositions. In order to systemize the whole class of chalcogenide phase change materials we have investigated the correlation between different crystallo-chemical parameters and the ionicity of the elements. Binary and ternary compounds are distributed into several distinct groups. The most favorable phase change materials are situated in a specific range of mean ionicity and mean glass formation ability. The results give the possibility to design new compositions with better switching properties.

2180. Vortex avalanches in the noncentrosymmetric superconductor Li2Pt3B

Authors: Miclea, CF; Mota, AC; Sigrist, M; Steglich, F; Sayles, TA; Taylor, BJ; McElroy, CA; Maple, MB

Published: OCT 2009, PHYSICAL REVIEW B, 80, DOI: 10.1103/PhysRevB.80.132502

We investigated the vortex dynamics in the noncentrosymmetric superconductor Li2Pt3B in the temperature range 0.1-2.8 K. Two different logarithmic creep regimes in the decay of the remanent magnetization from the Bean critical state have been observed. In the first regime, the creep rate is extraordinarily small, indicating the existence of an unconventional very effective pinning mechanism. At a certain time, a vortex avalanche occurs that increases the logarithmic creep rate by a factor of about 5 to 10 depending on the temperature. This may indicate that certain barriers against flux motion are present and they can be opened under increased pressure exerted by the vortices.

2181. Current dependent angular magnetoresistance in strongly Pr-doped Y Ba2Cu3O7-delta single crystal

Authors: Sandu, V; Gyawali, P; Katuwal, T; Almasan, CC; Taylor, BJ; Maple, MB

Published: 2009, 25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5: SUPERCONDUCTIVITY, 150, DOI: 10.1088/1742-6596/150/5/052222

We report a strong dependence of the angular magneto resistance (AMR) on the current density in Y0.47Pr0.53Ba2Cu3O7-delta single crystal above the critical temperature T-c = 13 K for any applied field up to 14 T. We estimated the current dependence from the angular dependence of the top resistance R-top, as measured on the face where the current is applied, and the bottom resistance R-bot as measured on the opposite face. At any temperature, both below and above T-c, R-top decreases as the field becomes parallel to the current and ab-plane with an angle dependence that suggests an important contribution arising from the vortex flow. R-bot evolves from a monotonic to nonmonotonic angle dependence with three minima and two maxima in the angle range 0 - 180 degrees as the temperature increases. For less Pr-doped samples, Y0.58Pr0.42Ba2Cu3O7-delta (T-c = 39 K) and Y0.68Pr0.32Ba2Cu3O7-delta (T-c = 55 K), where the interplane resistivity is much lower, both R-top and R-bot follow the same monotonic angle dependence in all temperature and field range.

2182. Pinning Centers Induced in YBCO Films by Nano-Dots in Substrate Decoration and Quasi-Superlattice Approaches

Authors: Mikheenko, P; Sarkar, A; Dang, VS; Tanner, JL; Kechik, MMA; Abell, JS; Crisan, A

Published: JUN 2009, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 19, 3494, DOI: 10.1109/TASC.2009.2018307

For power applications of superconducting films, the critical current density (J(c)) and the thickness of the film (d) should be as high as possible. Since J(c) decreases with both thickness and magnetic field, artificial pinning centers in addition to natural ones are required to keep J(c) high. The earliest cost-effective method used for introducing artificial pinning centers was the so-called substrate decoration, i.e., growing nanoscale islands (nano-dots) of certain materials on the substrate prior to the deposition of the superconducting thin film. Later on other two approaches proved to be successful: building up a layered distribution of a second phase using a multilayer deposition (quasi-superlattices) and distributing a secondary phase in the film from a compositionally changed target. Several materials have been used for the creation of artificial pinning centers. Here we report on the artificial pinning centers induced in YBCO thick films by substrate decoration and quasi-superlattice approaches using nano-dots of Ag, Au, Pd or non-superconducting YBCO. The cross-sectional AFM images show evidence of c-axis correlated columnar defects. These defects significantly contribute to the pinning of magnetic flux and increase critical current in the films.

2183. FROM NUCLEAR MATTER TO STRANGE QUARK MATTER - SOME CHARACTERISTICS OF THE INTERACTIONS IN ORDINARY MATTER

Authors: Lazanu, I; Chera, M; Iordanescu, R; Nita, C; Lazanu, S

Published: 2009, ROMANIAN REPORTS IN PHYSICS, 61, 221, DOI:

The existence of Strange Quark Matter as a new stable or metastable form of existence of matter has been postulated by various authors quite a few years ago. Because until now a theory to predict the existence and the properties of these strangelets does not exist, it is absolutely necessary to investigate the peculiarities of their interactions with matter versus ordinary nuclear matter interactions. In the present contribution, some peculiarities of the ionization and nuclear energy loss of strangelets with matter are investigated in comparison with ordinary ions, as a useful tool for their search. The rescattering mechanism could produce sub-threshold reactions and thus it is suggested as a possibility to discriminate between ordinary isotopes and very heavy (candidates for) strangelets with the same charge number.

2184. NEW TOPOLOGIES FOR PLANAR MICROWAVE BAND-PASS FILTERS WITH STRONGLY ASYMMETRIC CHARACTERISTICS

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2009, CAS: 2009 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI:

In this paper the problem of designing simple low-cost planar microwave band-pass filters with strongly asymmetric characteristics, filters that can very efficiently attenuate an adjacent channel, is investigated. For a fourth-order filter, the usual quadruplet structure leads to two transmission zeros, located one on each side of the passband For one of the two adjacent channels, a higher attenuation can be obtained by designing filters with two transmission zeros with prescribed positions in the same stopband (upper or lower). The new topology investigated in this paper offers the possibility of designing such quadruplets with two transmission zeroes situated both on the same side of the passband, in prescribed and controlled positions. Filters with this novel structure can provide very high attenuation not only at a single frequency, but in a larger adjacent frequency band.

2185. Radiation induced defects in Pb2+-doped LiF crystals

Authors: Somma, F; Montereali, RM; Vincenti, MA; Polosan, S; Secu, M

Published: 2009, 2008 INTERNATIONAL CONFERENCE ON LUMINESCENCE AND OPTICAL SPECTROSCOPY OF CONDENSED MATTER, 2, 221, DOI: 10.1016/j.phpro.2009.07.013

The influence of Pb2+ doping on the optical properties of LiF crystals before and after irradiation with X-ray was studied by using optical absorption and photoluminescence measurements. After irradiation it was observed an increase of the absorption due to primary and aggregate electronic defects together with a higher photoluminescence signals associated with the F-2 and F-3(+) colour centres in doped samples compared with the undoped ones.

2186. A new model for the structure of chalcogenide glasses: The closed cluster model

Authors: Popescu, M; Sava, F; Lorinczi, A

Published: OCT 1 2009, JOURNAL OF NON-CRYSTALLINE SOLIDS, 355, 1819, DOI: 10.1016/j.jnoncrysol.2009.05.066

A new model is proposed for the structure of low atomic coordination chalcogenide glasses. The closed clusters model is based on the various types of clusters, packed by van der Waals forces in a molecular-type packing. Arguments are given to support the new model, taken as example the typical chalcogenide glass As2S3. (C) 2009 Elsevier B.V. All rights reserved.

2187. Microwave Bandpass Filters with Multiple Couplings, Designed Using Electromagnetic Simulations and Linear Circuit Optimization

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2009, ISSCS 2009: INTERNATIONAL SYMPOSIUM ON SIGNALS, CIRCUITS AND SYSTEMS, VOLS 1 AND 2, PROCEEDINGS,, +, DOI:

In this paper a bandpass planar filter, with cross-couplings and with a pair of attenuation poles, is investigated. The equi-ripple in-band response and the location of the poles on the frequency axis can be precisely controlled by using a new technique which combines accurate electromagnetic field simulations and fast linear circuit optimization, allowing the design of bandpass filters with improved performances. To illustrate the procedure, a microstrip bandpass filter was designed, verified by em-field simulation, fabricated and tested. The response of the designed filter is in good agreement with the specification, confirming the possibilities of realizing microwave bandpass filters with rigorously controlled characteristics, with reduced design time and non-prohibitive computational effort.

2188. Study of the ground multiplet of Kramers rare earth ions in solid matrices by multifrequency electron paramagnetic resonance spectroscopy: Nd3+ in PbWO4 single-crystals

Authors: Popescu, FF; Bercu, V; Barascu, JN; Martinelli, M; Massa, CA; Pardi, LA; Stefan, M; Nistor, SV; Nikl, M; Bohacek, P

Published: JUL 21 2009, JOURNAL OF CHEMICAL PHYSICS, 131, DOI: 10.1063/1.3180697

A multifrequency electron paramagnetic resonance (EPR) investigation of Nd3+ impurities in PbWO4 single-crystals at the conventional microwave frequency (MF) 9.43 GHz, and at the 95, 190, and 285 GHz high frequencies was carried out. The resulting spectra are well described at all frequencies by an axial spin-Hamiltonian corresponding to an effective electron spin of one-half and to a tetragonal symmetry. For the magnetic field along the tetragonal axis, the g(-)factor and the hyperfine constant A of the lowest doublet of the ground multiplet decreases with frequency increase. For the magnetic field perpendicular to the tetragonal axis, the g(perpendicular to)-factor exhibits a small azimuthal angular dependence that increases with increasing the frequency due to the S-4 site symmetry. The azimuthal angular dependence allows to clearly distinguish between different local axial symmetries. These properties are interpreted as high field/frequency (HF) effects associated with the mixing by the large Zeeman interaction of some of the upper-lying doublets of the ground multiplet into the lowest-lying doublet states. We show that from the combined analysis of the multifrequency MF- and HF-EPR spectra and of the optical data, an accurate description of the ground multiplet of the Kramers rare earth ions in solid matrices can be derived.

2189. TiO2-CeO2 Nanometric Powders Prepared by Sol-Gel Method

Authors: Zaharescu, M; Wittmar, A; Teodorescu, V; Andronescu, C; Wittmar, M; Veith, M

Published: 2009, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 635, +, DOI: 10.1002/zaac.200900186

Nanometric powders in the TiO2-CeO2 System were synthesized using sol-gel methods aiming at corrosion inhibitor preparation. The precursors employed were Ti(OiPr)(4) as TiO2 source and Ce(NO3)(3)center dot 6H(2)O or Ce(CH3CO2)(3)center dot xH(2)O as CeO2 source. Several parameters were varied, like the cerium precursor (cerium nitrate or cerium acetate) and the TiO2:CeO2 molar ratios. For both cerium sources binary powders with TiO2:CeO2 = 4:1 or 1:1 molar ratios were prepared. The obtained materials were dried 12 h in an oven at 100 degrees C and then thermally treated for 1 h at 400 degrees C with a heating rate of 1 degrees C.min(-1) in order to eliminate the water and organic residues. In all cases, nanometric - predominantly amorphous - powders have been obtained which crystallized after the I h thermal treatment at 400 degrees C. The only exception was recorded for the TiO2:CeO2 = 4:1 composition prepared from the Ce(NO3)(3)-6H(2)O precursor which remained amorphous after the thermal treatment. Even though the primary particle sizes were similar to 4-5 nm, the material is constituted from aggregates larger than 50 nm. The desired presence of cerium in two valence states, necessary in active corrosion protection, was achieved and it was put into evidence by XPS and DTA/TGA for the TiO2:CeO2 = 4:1 binary compositions. Future studies have to be performed in order to reduce the agglomeration of the material.

2190. Films and crystalline powder of PbI2 intercalated with ammonia and pyridine

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Ramer, R; Pandele, J; Andronescu, C; Fruth, V

Published: JAN 2009, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 20, 470, DOI: 10.1007/s10854-008-9681-6

Thin films and crystalline powder of PbI2 intercalated with ammonia or pyridine have been studied by optical absorption, Raman scattering, photoluminescence, FTIR spectroscopy and thermo-gravimetric analysis. Ammonia intercalated PbI2 shows an increased optical band gap, of about 0.6 eV, with an intense broad emission band peaking at about 2.3 eV as signature in the photoluminescence spectrum. The intercalation of PbI2 with ammonia is noticed in the Raman spectrum by the appearance of new lines situated in low frequency range. The D-3d coordination geometry of Pb2+ in the PbI2 crystal is reduced by compression to orthorhombic one, the distribution of the electronic states in valence band is also changed. Thus, the top of the valence band undergo a deformation inducing a weakness of the interaction between the lead and iodine ions within a layer. Also the PbI2 intercalated with pyridine is featured by optical and vibration properties different that of pure crystalline powder. Finally, the intercalation of PbI2 with different molecules changes the basic semiconducting properties of the crystal. Thermal analyses and infrared absorption spectra have been used to study the desorption of guests species from PbI2 in order to evaluate the stability range and morphological changes with temperature.

2191. Synthesis, structural characterization, and photocatalytic properties of iron-doped TiO2 aerogels

Authors: Popa, M; Diamandescu, L; Vasiliu, F; Teodorescu, CM; Cosoveanu, V; Baia, M; Feder, M; Baia, L; Danciu, V

Published: JAN 2009, JOURNAL OF MATERIALS SCIENCE, 44, 364, DOI: 10.1007/s10853-008-3147-3

Fe(III)-doped TiO2 aerogels are prepared by acid catalyzed sol-gel method followed by supercritical drying, and then heat treatment. Raman spectra together with X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns of the iron-doped TiO2 aerogel samples revealed the existence of both anatase and brookite crystalline phases. It was found that the brookite phase formation is favored by the increase of the iron content in the dried samples. XRD measurements show that the lattice constant c of anatase phase decreases with the dopant addition, while the value of a remains essentially unchanged. The microstructure of the investigated samples is relatively compact with small mesopores as revealed from transmission electron microscopy (TEM). The most enhanced photocatalytic activity was exhibited by the TiO2 aerogel sample with 1.8 at.% Fe(III) whose apparent rate constant of the salicylic acid photodegradation was found to be of almost six times higher than that of Degussa P25.

2192. Preparation and characterization of nitrogen-doped TiO2 nanoparticles by the laser pyrolysis of N2O-containing gas mixtures

Authors: Alexandrescu, R; Scarisoreanu, M; Morjan, I; Birjega, R; Fleaca, C; Luculescu, C; Soare, I; Cretu, O; Negrila, CC; Lazarescu, N; Ciupina, V

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5377, DOI: 10.1016/j.apsusc.2008.08.046

Nitrogen-doped TiO2 nanoparticles have been prepared by the IR laser pyrolysis technique. A sensitized mixture of TiCl4 (vapors) and N2O was used as titanium and nitrogen precursors, respectively. The structural properties of the resultant N-doped nanoparticles such as the phase formation and the average particle size and distributions were investigated by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The phase composition varied from almost pure anatase to mixtures of rutile and anatase. A decrease of the mean particle diameters from about 18 nm in case of the almost pure anatase sample to about 13 nm in case of the anatase-rutile mixture is observed. XPS analysis suggests and interstitial character of the doping process. (C) 2008 Elsevier B. V. All rights reserved.

2193. Synthesis of narrow diameter distribution carbon nanotubes on ZnO supported catalysts

Authors: Lupu, D; Biris, AR; Watanabe, F; Li, ZR; Dervishi, E; Saini, V; Xu, Y; Biris, AS; Baibarac, M; Baltog, I

Published: MAY 12 2009, CHEMICAL PHYSICS LETTERS, 473, 304, DOI: 10.1016/j.cplett.2009.03.069

Multiwall carbon nanotubes, as indicated by electron microscopy and spectroscopy, were grown over a novel Co(5 wt.%)/ZnO catalyst by using a cold wall radio-frequency catalytic chemical vapor deposition method. The nanotubes were found to have a rather narrow diameter distribution, which can be explained by the formation over the ZnO support particles of uniform Co clusters, as shown by high resolution transmission electron microscopy studies. The growth of carbon nanotubes over such a support could represent a fast and reliable method to develop in one step 3D ZnO-CNTs heterogeneous composites of any size or shape, for use in advanced applications. (c) 2009 Elsevier B.V. All rights reserved.

2194. Effects of dopants and oxygen non-stoichiometry on thermodynamic and magnetic properties of micro- and nanostructured perovskite type manganites

Authors: Tanasescu, S; Grecu, MN; Urse, M; Teodorescu, F; Giurgiu, LM; Chiriac, H; Totir, ND

Published: JUL 2009, ADVANCES IN APPLIED CERAMICS, 108, 279, DOI: 10.1179/174367609X414044

The aim of the paper is to evidence the effect of the composition and oxygen stoichiometry on the thermodynamic, spin dynamics and magnetic properties of some micro- and nanostructured substituted manganites La(1-x)A(x)Mn(1-y)B(y)O(3-delta)(A=Ca; B=Co, Fe; x=0.33; y=0, 0.02 and 0.04). The partial molar thermodynamic properties of oxygen dissolution in the perovskite phase as well the equilibrium partial pressures of oxygen have been obtained using solid electrolyte electrochemical cells [ electromotive force measurement (EMF)] method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with EMF measurements. Using electron paramagnetic resonance spectroscopy, the spin dynamics has been investigated. Particular attention was devoted to the discussion concerning the influence of doping on polaron activation energy E-a and exchange coupling integral J between Mn spins. The results were correlated with the variation of both saturation magnetisation M-s and Curie temperature T-c. The data were discussed in relation to significant changes in the overall concentration of defects. New features related to the modifications in properties connected with the nanocrystalline state were evidenced.

2195. Fast and Simple Specimen Preparation for TEM Studies of Oxide Films Deposited on Silicon Wafers

Authors: Teodorescu, VS; Blanchin, MG

Published: FEB 2009, MICROSCOPY AND MICROANALYSIS, 15, 19, DOI: 10.1017/S1431927609090011

We present a fast and simple method to prepare specimen,, for transmission electron microscopy Studies of oxide thin films deposited oil silicon Substrates. The method consists of scratching the film surface using I pointed diamond tip, in a special manner. Small and thin fragments are then detached front the film and its substrate. Depending oil the scratching direction, the fragments call be used for plan-view or cross-section imaging. High-resolution images call be also obtained from thin edges of the film fragments. The method is demonstrated in the Case Of HfO2 sol-gel films deposited on [100] Si wafer substrates.

2196. Chalcogenide photonic structures

Authors: Popescu, M; Savastru, D; Popescu, A; Miclos, S; Lorinczi, A; Sava, F; Velea, A; Baschir, L; Ciobanu, M; Matei, E; Socol, G; Mihailescu, IN; Niciu, H

Published: SEP 2009, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 3, 859, DOI:

Chalcogenide glasses can be tailored for getting special configurations with photonic crystal properties A review on the advances in chalcogenide glass photonics is given Several methods to prepare two-dimensional photonic As-S glass and three-dimensional packing have been developed, and the photonic structures have been characterized Numerical simulations have also been performed The chalcogenide photonic structures fabricated by micro-technological procedures are described and tuned to work in the far infrared region of the electromagnetic spectrum

2197. Artificial pinning centres in YBa2Cu3O7-delta thin films by Gd2Ba4CuWOy nanophase inclusions

Authors: Kechik, MMA; Mikheenko, P; Sarkar, A; Dang, VS; Babu, NH; Cardwell, DA; Abell, JS; Crisan, A

Published: MAR 2009, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 22, DOI: 10.1088/0953-2048/22/3/034020

Artificial pinning centres produced by Gd2Ba4CuWOy (2411W) nanophase inclusions in YBa2Cu3Oy (YBCO) thin films grown by pulsed laser deposition (PLD) using a YBCO target containing 1 mol% 2411W have been investigated. For comparison, YBCO thin films have been grown under the same conditions using a pure (commercial) YBCO target. The resulting films were characterized by AC susceptibility (superconducting transition) and SQUID magnetometry (critical current density, J(c)), and by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) spectroscopy and atomic force microscopy (AFM) (structure, morphology and chemical composition). J(c) of the film grown from the composite target is practically the same as that measured for the reference sample at 5 K over the whole range of applied field up to 4.5 T. For temperatures higher than 50 K, however, the presence of the nano-inclusions leads to increased J(c). The relative enhancement in J(c) increases with further increase in temperature. J(c) of the film containing nanophase inclusions is between two and three times higher than that of the reference sample at 77.3 K and 1.5 T. This can be explained by considering the dimensions of nanophase inclusions compared with the temperature-dependent coherence length. Susceptibility measurements reveal that, apart from a large and sharp transition at about 91 K, there is a secondary, smaller and broader transition between 88 and 84 K in the YBCO film containing nanophase inclusions. This can be explained by substitutions of compatible atoms between YBCO and the 2411W phase (Gd with Y), which might also create additional pinning centres of delta T-c-type.

2198. Study of the ground multiplet of Kramers rare earth ions in solid matrices by multifrequency electron paramagnetic resonance spectroscopy: Nd3+ in PbWO4 single-crystals (vol 131, 034505, 2009)

Authors: Popescu, FF; Bercu, V; Barascu, JN; Martinelli, M; Massa, CA; Pardi, LA; Stefan, M; Nistor, SV; Nikl, M; Bohacek, P

Published: DEC 28 2009, JOURNAL OF CHEMICAL PHYSICS, 131, DOI: 10.1063/1.3280223

2199. On morphological, structural and electrical properties of vacuum deposited pentacene thin films

Authors: Girtan, M; Dabos-Seignon, S; Stanculescu, A

Published: MAY 22 2009, VACUUM, 83, 1163, DOI: 10.1016/j.vacuum.2009.03.001

Films of different thickness (50,100,150 and 200 nm) were deposited by thermal evaporation in vacuum on two types of substrates glass and ITO. The deposition was performed under a pressure of 10(-6) mB with a rate of 0.25 nm/s. Films surface investigations showed morphological and structural changes in function of films thickness and the nature of the substrate. Films optical transmission was analysed in the 280-1600 nm spectral range and the electrical measurements were done in low vacuum (10(-1):10(-2) mB) and in dark. (c) 2009 Elsevier Ltd. All rights reserved.

2200. Optical properties of pulsed-laser deposited ZnO thin films

Authors: Bazavan, R; Ion, L; Socol, G; Enculescu, I; Bazavan, D; Tazlaoanu, C; Lorinczi, A; Mihailescu, IN; Popescu, M; Antohe, S

Published: APR 2009, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 11, 428, DOI:

ZnO thin films were deposited by pulsed laser deposition (PLD) technique on optical glass substrate. Structural analysis by X-ray diffraction revealed a wurtzite phase ZnO, highly textured, with (002) planes perpendicular to the growth direction. They were optically characterized by absorption and transmission spectrometry. The wavelength dependence of the refractive index was extracted from transmission data by using a numerical fitting procedure.

2201. Synthesis and sensing properties of zirconium-doped hematite nanoparticles

Authors: Sorescu, M; Diamandescu, L; Tomescu, A; Krupa, S

Published: AUG 1 2009, PHYSICA B-CONDENSED MATTER, 404, 2165, DOI: 10.1016/j.physb.2009.04.006

Zirconium-doped hematite particles of the type xZrO(2)-(1-x)alpha-Fe(2)O(3) (x = 0.1, 0.5) were synthesized using mechanochemical activation and characterized by X-ray diffraction (XRD) and Mossbauer spectroscopy. For x = 0.1 all zirconia was dissolved in the hematite lattice after 12 h of ball milling and a particle size of 9 nm was obtained. We obtained the recoilless fraction as function of the ball milling time for each value of the molar concentration x. The appearance of nanoparticles in the system was demonstrated based on these plots. We further correlated the structural properties of the zirconium-doped hematite system with the sensing properties of the best candidate in the series. These were measured as function of temperature, gas concentration (carbon monoxide and methane) and variable humidity of air. The material system was found to be sensitive over the entire range of CO concentrations and the linearity of the sensor signal was not affected by the relative humidity of air, qualities which make it the ideal system for gas sensing. (C) 2009 Elsevier B.V. All rights reserved.

2202. Structural investigations of ITO-ZnO films grown by the combinatorial pulsed laser deposition technique

Authors: Craciun, D; Socol, G; Stefan, N; Miroiu, M; Mihailescu, IN; Galca, AC; Craciun, V

Published: MAR 1 2009, APPLIED SURFACE SCIENCE, 255, 5291, DOI: 10.1016/j.apsusc.2008.07.120

Mixtures of transparent and conductive oxides such as ITO-ZnO have been grown by a combinatorial pulsed laser deposition technique from two targets that were located 15 mm apart. The films were deposited on (1 0 0) Si and quartz substrates that were heated at temperatures from 300 to 500 degrees C. Measurements of the In to Zn ratios along the transversal axis of the substrates, which passes through the maximum thickness points corresponding to each target position were performed using energy dispersive X-ray spectroscopy and spectroscopic ellipsometry. From simulations of the X-ray reflectivity spectra, collected with a 2 mm mask on different locations along the transversal axis of the samples, the density and thickness of the deposited films were calculated and then the In to Zn ratios. The crystalline structure and electrical properties of the deposited films were also investigated along the same axis. Changes in the ratio of In/Zn along this axis resulted in changes of the film lattice constant and texture. (C) 2008 Elsevier B. V. All rights reserved.

2203. Transport properties of electrodeposited ZnO nanowires

Authors: Tazlaoanu, C; Ion, L; Enculescu, I; Sima, M; Enculescu, M; Matei, E; Neumann, R; Bazavan, R; Bazavan, D; Antohe, S

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2507, DOI: 10.1016/j.physe.2007.07.013

ZnO nanowires were electrodeposited by using a template approach. Ion track polycarbonate foils (30 mu m thick) were used as templates. Current-voltage (I-V) characteristics were recorded in the temperature range 40-300 K. I-V characteristics show a symmetric, non-linear shape, at temperatures greater than 240 K and voltages greater than 15 V. At lower temperatures, linear characteristics were recorded for the voltage range used. The temperature dependence of the electrical resistance is activated, with activation energy of 0.42 eV at temperatures greater than 240 K. (C) 2007 Elsevier B.V. All rights reserved.

2204. Exchange bias and spin valve systems with Fe-Mn antiferromagnetic pinning layers, obtained by the thermo-ionic vacuum arc method

Authors: Kuncser, V; Valeanu, M; Schinteie, G; Filoti, G; Mustata, I; Lungu, CP; Anghel, A; Chiriac, H; Vladoiu, R; Bartolome, J

Published: JUL 2008, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 320, E230, DOI: 10.1016/j.jmmm.2008.02.054

Exchange bias and spin valve systems with Fe-Mn antiferromagnetic layers of different Fe concentrations were obtained by the thermo-ionic vacuum arc method. The adherence of the multilayer system to the Si substrate depends on the Fe-Mn composition. The overall roughness depends on the growing order of the antiferromagnetic/ferromagnetic layers. Very low blocking temperatures for exchange bias were observed for the considered compositions of the Fe-Mn layer. The coercive forces of both the pinned and the free layers of spin valve structures can be considerably modified along a large set of samples simultaneously prepared. (C) 2008 Elsevier B.V. All rights reserved.

2205. Photoluminescence properties of composites based on zinc oxyde and single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Husanu, M; Velula, T; Bucur, C; Mihut, L; Preda, N

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 293, DOI:

Photoluminescence (PL) properties of the composites based on zinc oxide (ZnO) and single-walled carbon nanotubes (SWNTs) prepared by hydrothermal synthesis are studied in this paper. The emission and excitation spectra of nanometric ZnO powder are dramatically influenced by the adsorption of different molecules coming from the environment. Therefore, a special attention is given to reveal the influences of adsorption/de-sorption process on photoluminescence properties of zinc oxide nanoparticles. A quenching effect of the intrinsic PL is observed regularly when the ZnO is synthesized in the presence of SWNTs, i.e. when a ZnO/SWNTs composite is formed. A distinct feature of the ZnO/SWNTs composite, is an emission band with a maximum at 405-450 nm.

2206. Characteristics of arc plasma deposited TiAlZrCN coatings

Authors: Balaceanu, M; Braic, V; Kiss, A; Zoita, CN; Vladescu, A; Braic, M; Tudor, I; Popescu, A; Ripeanu, R; Logofatu, C; Negrila, CC

Published: MAY 15 2008, SURFACE & COATINGS TECHNOLOGY, 202, 3987, DOI: 10.1016/j.surfcoat.2008.02.005

TiAlZrCN superhard coatings, in which Ti and Al were additions to ZrCN base compound, were prepared by the cathodic arc method. The films were deposited on Si, plain carbon steel and high-speed steel substrates in a mixture of N-2 and CH4 gases. Elemental and phase composition, chemical bondings, texture, surface roughness, hardness, adhesion, tribological characteristics and erosive-corrosive resistance were investigates as a function of gas composition and total gas flow rate, using XPS, GDOES and XRD techniques, surface profilometry, microhardness and scratch adhesion measurements, tribological and erosive tests. It was shown that the properties and performance of the coatings were strongly dependent on the CH4/(CH4+N-2) flow rate and also on the total gas flow. The tribological and anti-erosive characteristics of the TiAlZrCN coatings were found to be superior to those of reference films (ZrN, ZrC, ZrCN, and TiAlCN). Maximum hardness values (42-45 GPa) were obtained for the films prepared at CH4/(CH4+N2) ratios ranging from 0.2 to 0.4. (c) 2008 Elsevier B.V. All rights reserved.

2207. Amorphous chalcogenide materials with smart memory

Authors: Popescu, M

Published: 2008, SMART MATERIALS FOR ENERGY, COMMUNICATIONS AND SECURITY, 29, DOI: 10.1007/978-1-4020-8796-7_3

Intelligent machines using multi-level memory chips are at the ends of our fingers. The first prototypes of smart memories are under construction. The science behind the devices is growing up very rapidly. New materials with multi-level storage are discovered and tested. The applications of the smart memories are extensive and in the same time rewarding for the welfare of the human kind.

2208. Rapidly solidified ferromagnetic shape memory alloys

Authors: Craciunescu, CM; Ercuta, A; Mitelea, I; Valeanu, M; Teodorescu, VS; Lupu, N; Chiriac, H

Published: MAY 2008, EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 158, 165, DOI: 10.1140/epjst/e2008-00670-6

Ferromagnetic shape memory alloys have been manufactured by various techniques involving rapid solidification. Bulk alloys have been obtained by extracting the melted alloy in especially designed copper molds; glass coated wires have been obtained by drawing the melt from glass recipients followed by water cooling and ribbons have been fabricated by melt-spinning. Microstructural observations show particular solidification aspects of fractured areas, while ferromagnetic behavior has been detected in glass coated wires obtained by rapid solidification. The martensitic microstructure was observed on Co-Ni-Ga rapid solidified bulk alloys and Fe-Pd ribbons. The memory effect was detected using a Vibran system that allows the detection of the phase transition for the ribbons and by visual observation for other specimens. The conclusions of the observations are related to the comparison between the ferromagnetic behaviors of shape memory alloys solidified using different techniques.

2209. Interference lithography using chalcogenide inorganic photoresist

Authors: Indutnyy, IZ; Popescu, M; Lorinczi, A; Sava, F; Min'ko, VI; Shepeliavyi, PE

Published: DEC 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3192, DOI:

There was investigated the application of inorganic photo-resist based on three-component chalcogenide films for fabrication of submicrometer periodic relief on silicon wafers using interference lithography. For this purpose. technological process of resistive two-layer chalcogenide-Cr mask formation on a silicon surface was developed, and silicon anisotropic etching was optimized, too. This technology has been used for the fabrication of diffraction gratings and two-dimensional periodic structures on Si (100) surface. The obtained relief patterns were used to form photonic structures by oblique deposition of silicon monoxide in vacuum.

2210. AlN SAW structures for GHz applications

Authors: Muller, A; Konstantinidis, G; Neculoiu, D; Dinescu, A; Morosanu, C; Stavrinidis, A; Dragoman, M; Vasilache, D; Buiculescu, C; Petrini, I; Anton, C

Published: 2008, APMC: 2008 ASIA PACIFIC MICROWAVE CONFERENCE (APMC 2008), VOLS 1-5, +, DOI:

2211. Calcium phosphate ceramics for biomedical applications

Authors: Predoi, D; Vatasescu-Balcan, RA; Pasuk, I; Trusca, R; Costache, M

Published: AUG 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2155, DOI:

Calcium phosphate compounds have been studied for biomedical applications due to chemical and structural similarity to the mineral phase of bone and tooth. The composition, physico-chemical properties, crystal size and morphology of synthetic apatite are extremely sensitive to preparative conditions and sometimes it resulted into non-stoichiometric calcium deficient hydroxyapatite (HAp) powders. The present paper describes the synthesis of calcium phosphate ceramics powders via a sol-gel method, The powders were sintered at 600 and 800 degrees C. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDXS) were used for characterization and evaluation of the phase composition, morphology and particle size of samples, The functional group of the coatings were analyzed using Fourier transform infrared (FTIR). The XRD analysis revealed a well crystallized HA structure at both temperatures. At 800 degrees C a small amount of CaO (about 0.4%) was detected. The mean crystallite size, determined from the breadth of the diffraction lines, increases from 30 nm at 600 degrees C to about 110 nm at 800 degrees C. FTIR spectra showed the presence of various PO43- and OH- groups present in the powders. Osteoblast cells were used to determine cell proliferation, viability and citotoxicity after interaction with the prepared bioceramics, by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole) assay. We note that the viability of HAp-600 starts to decrease after 12h, while the viability of HAp-800 decreases after 6h.

2212. Antiferroelectric-like behavior in polycrystalline Pb(Zr0.2Ti0.8)O-3-BiFeO3 multilayers prepared by sol-gel method

Authors: Pintilie, L; Stancu, V; Dragoi, C; Vlaicu, M

Published: NOV 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3149, DOI:

Pb(Zr0.2Ti0.8)O-3-BiFeO3 (PZT-BFO) multilayer structures were realized by sol-gel on Pt/Si substrate and their electrical properties were investigated using top Pt, Au and Cu electrodes. All multilayers start and end with PZT films. The polarization-voltage and current-voltage hysteresis loops resemble to those encountered in case of antiferroelectric (AFE) films, although component materials are both ferroelectric (FE). The AFE-like behavior is more clearly visible in the case of three-layer structures of PZT-BFO-PZT type, and it is not dependent of the metal used as top electrode. After fatigue cycling the polarization hysteresis apparently changes from characteristic AFE double-loop to FE single loop, although the four switching current peaks characteristic for an AFE behavior are still present in the current hysteresis. These results suggest the presence of an AFE interfacial coupling between the PZT and BFO layers.

2213. Magnetite nanoparticles obtained from the system Fe(III)/Fe(II) - glycine

Authors: Gingasu, D; Mindru, I; Patron, L; Diamandescu, L; Feder, M

Published: MAR 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 503, DOI:

Magnetite nanoparticles were synthesized from Fe3+/Fe2+ salts in the presence of glycine (2:1:8-2:1:3 ratio metal ions/glycine) using NH4OH 25% as precipitating agent. The parameters which influence the synthesis are discussed. The magnetite powders were characterized by XRD, IR spectra, magnetic measurements and Mossbauer spectra. The average diameter of crystallites is in the range 10 - 13 nm. The magnetization value is similar to 43 emu/g.

2214. Potassium hydrogen phthalate (KAP) micro- and nano-rods prepared by a template approach

Authors: Enculescu, M

Published: JUN 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1504, DOI:

Micro and nanorods of potassium acid phthalate (KAP) with diameters ranging from a hundred nanometers to tens of microns were obtained by solution growth in polycarbonate (PC) ion track templates. The ion track templates were produced by swift heavy ion irradiation of PC foils (e.g. U with 11.4 MeV/nucleon specific energy) and subsequently etching. After the growth the host templates were partially dissolved in dichlormethane and imagined by scanning electron microscopy. The template approach allows the fabrication of arrays of uniform nanostructures with a controlled morphology.

2215. Thermoluminescence of ZnF2 : Mn

Authors: Jipa, S; Zaharescu, T; Kappel, W; Secu, M; Secu, CE; Lungulescu, M; Mantsch, A

Published: MAR 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 557, DOI:

The thermoluminescence of undoped and Mn-doped ZnF2 Was investigated at the dopant concentration of 1.5 % mole Mn after gamma - ray irradiation at room temperature. The glow curve from undoped ZnF2 presents two peaks centered at 86 degrees C and 273 degrees C, while the ZnF2:Mn presents two peaks located at higher temperatures (325 degrees C and 365 degrees C), whose height ratio is modified with dose. The dose responses and fading process were also examined. The radiative thermostimulated recombination was found to be of the second kinetic order based on the geometric factor calculation. The trap parameters were obtained as activation energy and frequency factor.

2216. Rough Bioglass films prepared by magnetron sputtering

Authors: Slav, A; Ianculescu, A; Morosanu, C; Saranti, A; Koutselas, I; Agathopoulos, S; Karakassides, MA

Published: 2008, BIOCERAMICS, VOL 20, PTS 1 AND 2, 361-363, +, DOI: 10.4028/www.scientific.net/KEM.361-363.245

Bioglass films were prepared by reactive magnetron sputtering from a 45S5 target and than annealed in air tip to 550 T in order to relax the mechanical stresses. The mixtures (0, 7 and 15%) of oxygen and argon were used in order to modify the films stoichiometry. Morphological and compositional studies were performed by SEM coupled with an EDAX system. FTIR and micro Raman measurements were performed in order to investigate the molecular vibrations of the BG structure. A modified composition respect to the target one Was found for all the films, with lower silicon dioxide concentrations. The films displayed rough surfaces with spherical particles of 10-20 mu m diameter embedded in the surfaces. The Raman results evidenced important carbonate lines besides the silica-phosphate bands.

2217. A PZT Based Material for Bimorph Type Transducers and a New Optical Method to Evaluate the Bimorph Performance

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Spanulescu, I; Plavitu, CN; Cioangher, M; Trupina, L; Miclea, CT; Susu, M

Published: 2008, ADVANCED MATERIALS FORUM IV, 587-588, +, DOI: 10.4028/www.scientific.net/MSF.587-588.253

The displacement devices using piezoceramic sensors play an important role in many fields. Soft type piezoelectric materials used for such sensors arc more appealing because of their lower coercive field, relatively low modulus of elasticity, high electromechanical coupling factors and piezoelectric strain coefficients. We designed a PZT type material doped with niobium and nickel to increase the strain coefficient and still retaining a high coupling coefficient. The chemical formula was Pb0.9Ba0.08Nb0.03Ni0.06Zr0.46Ti0.40O3. The main piezoelectric parameters were: d(33)=680 pm/V. d(31)=-235 pm/V, k(p)=0.64 and k(31)=0.42. A unimorph transducer was made from a thin sheet of such a piezoceramic material, tightly bonded on a thin optically polished glass plate and mounted as a cantilever. The performance of this transducer was evaluated by means of a new optical method which makes use of the Moire deflectometry and provides high precision. The method is rather simply and consists mainly in the following: the Moire fringes rotate when the bimorph bends under the influence of the electric field and by measuring the rotating angle of the fringes one can easily determine the bimorph curvature and the free end displacement.

2218. X-ray micro-tomography as a tool for quantitative characterization of advanced materials manufacturing processes

Authors: Tiseanu, I; Craciunescu, T; Aldica, GV; Lovea, M

Published: 2008, MULTI-FUNCTIONAL MATERIALS AND STRUCTURES, PTS 1 AND 2, 47-50, +, DOI: 10.4028/www.scientific.net/AMR.47-50.698

The potential of X-ray micro-tomography in characterizing the relevant material issues as identified during manufacturing processes was investigated. For this purpose, the 3D X-ray micro-tomography (X mu RT) analysis was applied to the characterization of structural integrity of Nb3Sn superconducting wires of differing topology and the evolution of the density distribution of ceramic samples manufactured by Field Assisted Sintering Techniques (FAST). The latter technique was used to consolidate the ceramic, metal (Ni) and composite powders (MgB2). The usual scanning electron microscope (SEM) technique was enhanced by the high resolution X mu RT in order to describe the volumetric density distribution before sintering and at different moments of the thermal cycle. Two types of samples sintered Ni and high density MgB2 superconductors with typical volume of 0.8 divided by 1.5-10-9 m(3) were sampled at space resolution around 5 mu m. For the sintered Ni, the 3D reconstructed volumes revealed the grain connectivity, necks formation and particle rearrangement in the densification process. The X mu RT analysis was essential in explaining the differences in superconducting properties of MgB2 samples in terms of different volumetric structures. For the Nb3Sn multifilamentary wire which is at basis of many practical superconductors, the 3D tomography enabled the determination of the number of inter-filament contacts as well as the twist-pitch parameter. Advantages of our method versus the invasive etching techniques for the determination of the twist-pitch parameter were outlined.

2219. Particular signature of isolated and bundled carbon nanotubes in their Raman spectra

Authors: Husanu, M; Baibarac, M; Baltog, I

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 699, DOI:

The efficiency of different surfactants (anionic, cationic, neutral) as chemical agents favoring in the unbinding of nanotube bundles in isolated entities is investigated by Raman and UV-VIS-NIR spectroscopy. ne neutral surfactants Tween 20 - polyoxyethylene sorbitan monolaurate (T-20-PSM) and Tween 80 - polyoxyethylene (80) sorbitan monooleate (T-80-PSM) have been found the most efficient. The isolated single walled carbon nanotubes (SWNTs) nanotubes are apprised at lambda(exc) = 1064 nm by two simultaneous modifications of the Raman spectra: i) narrowing of the band associated to the transversal vibration modes, i.e., G band (similar to 1592 cm(-1)); ii) change of shape of the complex band associated to the radial vibration modes (RBM) consequent on the decrease of the intensity of the components associated with the bundled nanotubes. The individualization of nanotubes is evidenced also in the UV-VIS-NIR absorption spectra by the appearance of a fine structure in the wide absorption band (similar to 1400-1750 nm) that is associated with the transitions E-S(11) of semiconducting SWNTs. The fine structure grows gradually with the separation degree in isolated nanotubes entities.

2220. Single-beam pumped coherent anti-Stokes Raman scattering on carbon nanotubes thin films excited through surface plasmons

Authors: Baltog, I; Baibarac, M; Lefrant, S

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2385, DOI: 10.1016/j.physe.2007.07.022

In this paper, we propose an interpretation for an abnormal anti-Stokes Raman emission observed on nanometric thin films of different materials and in particular carbon nanotubes. We demonstrate that under a tight-focusing of the excitation light, a coherent anti-stokes Raman scattering (CARS) emission is produced, resulting from a wave mixing process between the incident laser light (omega(1)) and Stokes Raman light (omega(s)) generated by a surface enhanced Raman scattering (SERS) mechanism. Although the Stokes/anti-Stokes intensity ratio has been explained differently, we present here the results which corroborate the CARS emission. They can be summarized as follows: (i) a square relationship between the CARS signal intensity and the film thickness; (ii) a square relationship between the CARS signal intensity and the exciting laser intensity; (iii) a dependence of the CARS intensity on the numerical aperture (NA) of the microscope objective used for the detection of the anti-Stokes emission. Such effects are not specific to carbon nanotubes and have been observed with other materials accommodated in similar conditions on rough metallic surfaces acting as SERS supports. (c) 2007 Elsevier B.V. All rights reserved.

2221. Mossbauer spectroscopy study on the corrosion inhibition of carbon steel in hydrochloric acid solution

Authors: Samide, AP; Bibicu, I; Agiu, M; Preda, M

Published: JAN 31 2008, MATERIALS LETTERS, 62, 322, DOI: 10.1016/j.matlet.2007.05.025

The effect of ammonium polymolybdate (APM) on the corrosion of carbon steel in a solution of 1 M HCl was studied by weight loss and Mossbauer spectrometry. Inhibition efficiencies (P) have been obtained from weight measurement. The inhibition efficiencies increased with increase APM concentration. Mossbauer spectrometry shows that a superficial compound is formed on the electrode surface as a result of corrosion. (c) 2007 Elsevier B.V. All rights reserved.

2222. Morphology of Si nanocrystallites embedded in SiO2 matrix

Authors: Teodorescu, VS; Ciurea, ML; Iancu, V; Blanchin, MG

Published: NOV 2008, JOURNAL OF MATERIALS RESEARCH, 23, 2995, DOI: 10.1557/JMR.2008.0358

The nanostructure of Si-x(SiO2)(1-x) films deposited on quartz substrate, where x varies from 0 to 1, was determined by high-resolution transmission electron microscopy in the sample regions with x approximate to 0.1, 0.2. 0.5. and 0.75. In the Si-0.5(SiO2)(0.5) region, the formation of a Si nanocrystallite network was established. At high concentrations of Si nanocrystallites, nanotwins and stacking faults occurred in the crystallites. Large Si crystallites appeared at x >= 0.5 in the quartz Substrate under the interface, while the film presented nanopores over the interface. The mechanisms for the formation of the nanocrystallites were discussed and correlated with the film properties.

2223. Photonic crystals based on amorphous chalcogenides

Authors: Popescu, M; Nezzane, D

Published: JAN 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 28, DOI:

Amorphous chalcogenide structures are proposed for designing meta-materials as e.g. photonic crystals with stop gaps in the far infrared and microwave range. Micrometer diameter lenslets made of As2S3 glass are used to this purpose. Special heat treatment is proposed to get a shrinkage of the structure built from stacks of lenslets, and creating a modulated woodpile configuration based on the photo-fluidity effect in arsenic sulphide chalcogenides. The simple procedure allows the tuning of the lattice parameter in order to reach the desired optical or microwave properties of the photonic crystal with stop band gaps.

2224. Non-covalent functionalization of carbon nanotubes: Experimental evidence for isolated and bundled tubes

Authors: Husanu, M; Baibarac, M; Baltog, I

Published: OCT 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 41, 69, DOI: 10.1016/j.physe.2008.06.001

Single-walled carbon nanotubes (SWNTs) may be used in technological applications as individual entities instead of bundled tubes. The Raman signature of these two forms is still a controversial subject. The profile, peak position and relative intensity of the Raman band associated with the tangential vibration modes (G band similar to 1600cm(-1)) and radial vibration modes (RBM similar to 100-200cm(-1)) are the main parameters which can reveal the dispersion state of nanotubes. Resonant Raman scattering and absorption spectroscopy on SWNTs furnish complementary information concerning the efficiency of the nanotube dispersion in individual entities. (C) 2008 Elsevier B.V. All rights reserved.

2225. Optical cooling of single-walled carbon nanotubes as revealed by their anti-Stokes Raman spectra

Authors: Baltog, I; Baibarac, M; Lefrant, S

Published: JUL 9 2008, JOURNAL OF PHYSICS-CONDENSED MATTER, 20, DOI: 10.1088/0953-8984/20/27/275215

Semiconducting single-walled carbon nanotubes resonantly excited by the interband E-22(S) electronic transitions (at 1064 nm) display for the two components of the radial Raman band-one associated with the isolated tubes and the other associated with the bundled tubes-an anti-Stokes/Stokes Raman intensity ratio (I-aS/I-S) which deviates oppositely from the predictions of the Maxwell-Boltzmann formula. A cooling and heating vibration process, evidenced by an enhancement and diminishment of (I-aS/I-S), appears in the isolated and bundled nanotubes, respectively. Here we confirm a cooling process, observed only for semiconducting nanotubes, which emerges from the relaxation of the E-22(S) excited state by the electronic relaxation from E-22(S) to E-11(S) that precedes the spontaneous luminescence emission at E-11(S). Metallic nanotubes do not exhibit luminescence and no cooling effect is observed. Both semiconducting and metallic nanotubes show for the bundled component of the radial Raman band an enhancement of (I-aS/I-S) such as is frequently observed in a coherent anti-Stokes Raman scattering process.

2226. Polypyrrole - porous silicon nanocomposites

Authors: Popa, C; Turcu, R; Craciunescu, I; Nan, A; Ciurea, ML; Stavarache, I; Iancu, V

Published: SEP 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2324, DOI:

In this work we report the synthesis and characterization of the polypyrrole - porous silicon nanocomposites. Our main goal is to control the growth of conducting polypyrrole into the alveolar pores of porous silicon, in order to get a functionalized nanocomposite with the required properties for application as electrode in microfluidic devices. Porous silicon was electrochemically etched from (100) p-type silicon wafers. Different silicon resistivities (from 1.8 to 11 Omega cm) and preparation conditions (different electrolyte concentrations and current densities) were used. The electrodeposition of polypyrrole into porous silicon was carried out galvanostatically, at a constant current density 2.5 mA/cm(2) from a solution containing acetonitrile, the monomer, pyrrole and p-toluensulfonic acid as electrolyte. The polymerization time was varied in order to investigate the growing process of polypyrrole into the pores. The morphology and of the as-prepared nanocomposites was investigated by SEM. The existence of PPY into porous silicon is evidenced by the EDX spectra of the nanocomposite. The electrical characterization evidences the relative contributions of the polypyrrole and the substrate resistivity, respectively.

2227. Capacitance-voltage characteristics of heterostructures with high leakage currents

Authors: Goldenblum, A; Stancu, V; Buda, M; Iordache, G; Pintilie, I; Negrila, C; Botila, T

Published: MAR 1 2008, JOURNAL OF APPLIED PHYSICS, 103, DOI: 10.1063/1.2844210

Leakage currents determine bumps in the capacitance-voltage characteristics of metal-oxide-semiconductor-type heterostructures with capacitance values larger than the insulator capacitance. A nearly parallel shift with frequency is also observed. These aspects are connected with the presence of a high density of interface states. We illustrate these effects for the case of nano-PbS/SiO2/Si heterostructures. The phenomena were simulated and we propose a method to quickly estimate the interface state density level of a heterostructure when leakage channels are present. (C) 2008 American Institute of Physics.

2228. Vortex imaging with varying temperature revealed by SHPM on Bi(2)Sr(2)CaCu(2)O8+y

Authors: Mihalache, V; Dede, M; Oral, A; Sandu, V

Published: APR 1 2008, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 468, 836, DOI: 10.1016/j.physc.2007.11.059

Scanning Hall probe microscopy with an effective spatial resolution of similar to 1 mu m has been used to investigate the vortex structures in superconducting Bi2Sr2CaCu2O8+delta single crystals in the temperature range 77.3-81.3 K and zero applied field (in the presence of the earth field). The vortex images were obtained in real time mode as the temperature increased slowly for 3.36 h. At 77.3 K, the vortices were arranged in a chain structure. With the increase of the temperature, two jumps in the vortex array occur at 77.3 K, immediately when the temperature starts to rise, and at 79.2 K with a good stability between jumps. The second jump is accompanied by the jump in the average magnetic induction when bundles of 4-5 additional vortices enter the scanning area and the vortex array get disordered. These directly visualized transitions in the vortex lattice are consistent with a vortex creep over the surface barriers at high temperatures. A short movie is presented. (c) 2008 Elsevier B.V. All rights reserved.

2229. Characterization of high performance PbS photodetectors

Authors: Buda, M; Iordache, G; Stantcu, V; Botila, T

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 310, DOI:

Dark noise plays an important role in electronic devices, especially in detectors. Performance of infrared detectors is reflected by parameters such as detectivity and specific detectivity, strongly related to the noise spectral density. This work summarizes the results on characterization of high-performance PbS photo detectors, using a certification pending method developed by the laboratory, in agreement to the standard ISO/CEI 17025:2005. The method is validated for a resistor of known resistance, by comparing the Johnson thermal noise using two different methods: first, the fast Fourier transform measured with a Stanford Research Systems SR785 Spectrum Analyzer and second using a Stanford SR830 lock-in amplifier which measures the rms noise for a certain frequency. We studied the influence of physical dimensions on the performance of thin film polycrystalline PbS photoresistors in the planar geometry. Measurements were performed to compare the dark noise of PbS photoresistors with that in high quality metal thin film resistors. The laboratory setup used for the measurements is appropriate to accurately determine typical parameters of infrared detectors such as spectral responsivity, blackbody responsivity, specific detectivity, and noise spectral density.

2230. Influence of polyvinylpyrolidone as an additive in electrochemical preparation of ZnO nanowires and nanostructured thin films

Authors: Enculescu, I; Matei, E; Sima, M; Enculescu, M; Sima, M; Ghica, C

Published: MAR-APR 2008, SURFACE AND INTERFACE ANALYSIS, 40, 560, DOI: 10.1002/sia.2749

Preparation of ZnO in different nano-morphological forms became a hot topic during the last few years. This tendency was motivated by the wide field of potential applications ranging from optics to electronics and spintronics. In the present work, we deal with the preparation of ZnO nanowires and nanostructured thin films using electrochemical deposition. ZnO nanowires were grown using the template approach, namely by replicating the nanopores of polycarbonate ion track membranes. The method yields uniform arrays of nanowires with the morphology controlled by the shape and size of the templates pores. Adding polyvinylpyrolidone as an additive in the growth bath became a necessity due to the fact that polycarbonate ion track membranes are usually hydrophobic and thus filling of the nanopores with the growth electrolyte is rather difficult. In order to better understand the influence of the additive on the electrochemical deposition of such nanostructures, similar experiments were performed for the deposition of ZnO thin films. Scanning electron microscopy, X-ray diffraction and optical spectroscopy measurements were performed for characterization of the deposited structures. Copyright (c) 2008 John Wiley & Sons, Ltd.

2231. Time drift compensation of the electronic balance during the measurement of liquid crystal density

Authors: Poterasu, M

Published: FEB 2008, MEASUREMENT SCIENCE AND TECHNOLOGY, 19, DOI: 10.1088/0957-0233/19/2/025102

A novel method for compensating the noise of the electronic balance used in lengthy experiments, such as studying the temperature dependence of liquid crystal density, is presented. It is shown, by numerical simulation of density measurement that the method can reduce both drift and random noise errors. This is accomplished using a stepwise temperature ramp and using arctangent type functions as basis vectors for modeling the signal variations whose coefficients are determined by numerical regression at every temperature step. Drift is derived from the overall deviation from the modeled signal and noise is reduced by the averaging effect of the numerical regression. The simulations show that in the considered case the proposed drift compensation method can give more accurate results than traditional methods. From the point of view of signal processing, the method resembles a numerical lock-in amplifier method, but as opposed to that, it uses a non-cyclic stepwise signal modulation.

2232. Comparison between PZT thin films deposited on stainless steel and on platinum/silicon substrate

Authors: Stancu, V; Sava, F; Lisca, M; Pintilie, L; Popescu, M

Published: 2008, INTERFACIAL NANOSTRUCTURES IN CERAMICS: A MULTISCALE APPROACH, 94, DOI: 10.1088/1742-6596/94/1/012012

Pb(Zr1-xTix)O-3 (PZT) thin films were prepared by sol-gel method on stainless steel (SS) and on platinum-coated silicon substrate (Pt/Si). The structure revealed by X-ray diffraction shows strong crystallographic orientation: (110) and (100), respectively. The crystallite size shows significant differences: d((00l))((SS))= 27.1 nm, d((h00))((Pt)) = 88 nm. The tetragonal splitting is (Delta c/c)((ss))=3.55 % and (Delta c/c)((pt))=3.32 %. The ferroelectric hysteresis loop in the static mode is characterized by remanentpolarization of 25 mu C/cm(2) and coercive field of 45 kV/cm for SS substrate, while for Pt/Si substrate the values are 10 mu C/cm(2) and 39 kV/cm, respectively. The leakage current is about 3 orders of magnitude lower in the PZT film deposited on SS. The better properties of the PZT deposited on SS are explained by the presence of large single crystal-like crystallites, which make the film closer to epitaxial ones. The results show the potential of growing epitaxial films on low-price substrates such as stainless-steel.

2233. Effect of additives on nickel nanowires electrochemical deposition

Authors: Matei, E; Enculescu, I; Enculescu, M; Neumann, R

Published: MAR 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 511, DOI:

The paper presents the effect of additives on nickel nanowires preparation by employing a template approach. The nanostructures were obtained by electrochemical deposition in ion track nanoporous membranes. The main goal was to find a wetting agent which increases the pores filling efficiency. Due to the fact that the polycarbonate nanoporous membranes used as templates are strongly hydrophobic problems appear when filling the nanopores with the aqueous electrochemical baths. We found that polyvinylpyrrolidone (PVP) added in the bath improves membrane wetting, thus increasing the deposition efficiency up to 80%. Electrochemical polarization and chronoamperometry were employed for identifying and studying the processes which take place in the case of cathodic deposition of nickel nanowires. Scanning electron microscopy was employed for nanostructure morphology characterization.

2234. Structural and photocatalytic properties of iron- and europium-doped TiO2 nanoparticles obtained under hydrothermal conditions

Authors: Diamandescu, L; Vasiliu, F; Tarabasanu-Mihaila, D; Feder, M; Vlaicu, AM; Teodorescu, CM; Macovei, D; Enculescu, I; Parvulescu, V; Vasile, E

Published: NOV 15 2008, MATERIALS CHEMISTRY AND PHYSICS, 112, 153, DOI: 10.1016/j.matchemphys.2008.05.023

Iron- and europium-doped (<= 1 at.%)TiO2 nanoparticles powders have been synthesized by a hydrothermal route at 200 degrees C, starting with TiCl4, FeCl3 center dot 6H(2)O and EuCl3 center dot 6H(2)O. The structure, morphology and optical peculiarities were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), extended X-ray absorption fine structure (EXAFS), Mossbauer spectroscopy and UV-vis measurements. The photocatalytic performance was analysed in the photodegradation reaction of phenol. Rietveld refinements of XRD patterns reveal that the as-prepared samples consist in iron- and europium-doped TiO2 in the tetragonal anatase structural shape, with particle size as low as 15 nm. By means of Mossbauer spectroscopy on both Fe-57 and Eu-151 isotopes as well as by EXAFS analyses, the presence of Fe3+ and/or Eu3+ ions in the nanosized powders has been evidenced. It was found that iron and europium ions can substitute for titanium in the anatase structure. From the UV-vis reflection spectra, by using the transformed Kubelka-Munk functions, the band gap energy (E-g) of the hydrothermal samples has been determined in comparison with that of Degussa P-25 photocatalyst. A decrease of E-g from 2.9eV found for Degussa photocatalyst to 2.8 eV for the titania doped with 1 at.% Fe has been evidenced, indicating a valuable absorption shift (similar to 20 nm) towards visible light region. However, the best photocatalytic activity in the photodegradation reaction of phenol was evidenced for the hydrothermal sample, TiO2: 1 at.% Fe, 0.5 at.% Eu, in both UV and visible light regions. The photocatalytic activities of iron-doped and iron-europium-codoped samples are high and practically the same only in visible light. The photocatalytic properties in Correlation with the structural and optical peculiarities of the hydrothermal samples are discussed. (C) 2008 Elsevier B.V. All rights reserved.

2235. SBN thin films growth by RF plasma beam assisted pulsed laser deposition

Authors: Scarisoreanu, ND; Dinescu, G; Birjega, R; Dinescu, M; Pantelica, D; Velisa, G; Scintee, N; Galca, AC

Published: NOV 2008, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 93, 800, DOI: 10.1007/s00339-008-4753-2

SBN thin films were grown on MgO and Silicon substrates by PLD and RF-PLD (radiofrequency assisted PLD) starting from single crystal Sr0.6Ba0.4Nb2O6 and ceramic Sr0.5Ba0.5Nb2O6 stoichiometric targets. Morphological and structural analyses were performed on the SBN layers by AFM and XRD and optical properties were measured by spectroellipsometry. The films composition was determined by Rutherford Backscattering Spectrometry. The best set of experimental conditions for obtaining crystalline, c-axis preferential texture and with dominant 31 degrees in-plane orientation relative to the MgO (100) axis is identified.

2236. Analytical expression for the quantum dot contribution to the quasistatic capacitance for conduction band characterization

Authors: Buda, M; Iordache, G; Mokkapati, S; Fu, L; Jolley, G; Tan, HH; Jagadish, C; Buda, M

Published: JUL 15 2008, JOURNAL OF APPLIED PHYSICS, 104, DOI: 10.1063/1.2959681

This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipole), is also derived from fitting of the C- V experimental data. (c) 2008 American Institute of Physics.

2237. Electron and hole trapping in irradiated PbBr2 : Tl single crystals

Authors: Stefan, M; Nistor, SV; Darabont, A; Neamtu, C; Goovaerts, E

Published: JUN 2008, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 266, 2761, DOI: 10.1016/j.nimb.2008.03.179

Several hole trapped centres, namely Tl2+, self-trapped hole and A-type centres, were observed by ESR in PbBr2:Tl single crystals after X-ray irradiation at 77 K. The corresponding spectra are visible up to 200 K for all three defect centres. The STH centres are observed at higher temperatures than in the undoped PbBr2 single crystals, probably due to the stabilising effect of the Tl+ impurities. The ESR parameters of the Tl2+ centre point to stronger covalency effects in PbBr2 than in the isostructural PbCl2 crystals. All hole trapped centres started decaying around 160 K, probably due to recombination with nonparamagnetic electron trapped centres. Besides a small concentration of self-trapped electron centres, no other electron trapped centres were observed. (c) 2008 Elsevier B.V. All rights reserved.

2238. Electrical transport in crystalline perylene derivatives films for electronic devices

Authors: Stanculescu, A; Stanculescu, F; Socol, M; Grigorescu, O

Published: DEC 2008, SOLID STATE SCIENCES, 10, 1767, DOI: 10.1016/j.solidstatesciences.2008.03.023

This paper presents investigations on the electrical transport phenomena in perylene and PTCDA emphasising the particularities of the charge carrier injection at the contacts with inorganic semiconductors (Si) and metals (Cu, Al) and the effect of the supplementary organic layer (ZnPc, alpha-NPD) on the electrical conduction. The I-V characteristics for different delay and integration times, at forward and reverse bias, have evidenced a dominant ohmic behaviour of these SIS and MIS structures at low voltage (<0.1 V) and limitations of the current induced by the space charge and trap charge at voltages >1 V. An intermediate organic layer (ZnPc) with higher ionisation potential than PTCDA and lower electron affinity than perylene improves the charge carrier injection and the conduction properties of the Si/PTCDA/Si and forward biased Cu/perylene/Si heterostructures. No increase in the hole injection was obtained in Si(p)/perylene/Si(p) heterostructure introducing an a-NPD layer. (C) 2008 Elsevier Masson SAS. All rights reserved.

2239. Capacitance spectroscopy study of InGaAs/GaAs quantum dot structures

Authors: Buda, M; Iordache, G; Mokkapati, S; Tan, HH; Jagadish, C; Stancu, V; Botila, T

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 326, DOI:

Self assembled InGaAs/GaAs quantum dots (QD) have a great potential for high performance optoelectronic devices such as low threshold laser diodes, infrared detectors, modulators, memories. In order to characterize the behavior of the QD system, we use two p(+)-n structures grown epitaxially on GaAs under similar conditions. The first structure acts as reference while in the second structure a single QD self-assembled layer is introduced in the middle of the n-GaAs matrix layer. The structure is designed such that for OV applied bias the QD layer lies outside the depleted region. When the reverse bias is increased, the charge from the QD system is removed and the depletion layer moves further into the GaAs matrix material. The electronic structure of the QD is investigated using two methods: photoluminescence, in order to characterize the transition energies between electron and hole levels in the QD system and capacitance spectroscopy in order to study the electron levels in the conduction band only. In addition, admittance spectroscopy spectra are measured in order to characterize the carrier transport mechanism. There is no evident step in the capacitance versus frequency behavior at room temperature in the range 1 Hz-1 MHz, indicating a large carrier cross section caption and/or a low activation energy for the carrier transport between the dot system and the wetting layer and GaAs barriers. The plateau in the C-V behavior, due to charging or discharging of the QD system is modeled using the solution of a Poisson equation and the resulting energy of the electron states within the conduction band and QD size distribution are correlated with results from photoluminescence studies, which involve transitions between energy levels both from the conduction and valence bands.

2240. The effects of thermal treatments on microwave dielectric properties of Ba(Zn1/3Ta2/3.)O-3 ceramics

Authors: Ioachim, A; Nedelcu, L; Andronescu, E; Jinga, S; Toacsan, MI; Banciu, MG; Lorinczi, A; Popescu, M

Published: JAN 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 212, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1550 divided by 1650 degrees C for 2 h. XRD, SEM and EDX were employed for compositional, structural and morphological characterization. An additional annealing at 410 degrees C for 10 hours was performed in order to improve the dielectric parameters. The dielectric constant and quality factor of BZT dielectric resonators measured by using Hakki-Coleman method around 6 GHz was between 25 and 29. The temperature coefficient of the resonance frequency exhibits positive values less than 6 ppm/degrees C. The best parameters of BZT dielectric resonators were achieved for the samples sintered at 1650 degrees C with additional thermal treatment (square(r) = 29, Q x f = 100 THz).

2241. Investigation of nanocrystalline Pbs/n-Si heterostructures for optoelectronic applications

Authors: Buda, M; Stancu, V; Iordache, G; Pintilie, L; Pintilie, I; Buda, M; Botila, T

Published: FEB 15 2008, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 147, 288, DOI: 10.1016/j.mseb.2007.09.070

The nano-crystalline PbS/n-Si heterostructure was studied using photocurrent spectra, I-V and C-V characteristics and admittance spectroscopy. The frequency dependent junction capacitance and conductance measurements show the presence of two contributions: first, a defect related mechanism which we attribute to a deep trap level with a large cross-section in nano-crystals with smaller sizes around 5 nm at the interface with Si and a second mechanism with an activation energy of about 250 meV, attributed to carrier transport in relatively large PbS grains of about 15 nm in size. (c) 2007 Elsevier B.V. All fights reserved.

2242. Optical spectroscopy and thermoluminescence of electrolytically colored KCl:Tl+ crystals

Authors: Polosan, S; Enculescu, M; Secu, M; Apostol, E

Published: NOV 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3011, DOI:

The paper presents the spectroscopic properties of electrolytic colored KCl:Tl and KCI:Tl+Ca crystals and the assignments of the new defects which are formed during electron injection process. The new formed defects Tl-0 and Tl-0+Ca2+ with the metal in the anionic sites, presents very high photoluminescence properties in the near infrared region. Together with those centers, the F-centers, their aggregates and the holes centers are formed during electrolytic coloring process. Their properties were studied by optical absorption (OA), photoluminescence (PL) and thermoluminescence (TL) measurements and compared with those obtained by ionizing irradiation in uncolored KCl:Tl crystals. The results suggest a more efficient Tl+-> Tl-0 process in the case of Ca2+ codoped samples due to the prolonged time of electrons injection, low temperature and high electric field.

2243. Hyperfine interactions and dynamics characteristics of Sn-119 in xSnO(2)-(1-x)alpha-Fe2O3 nanoparticle system

Authors: Constantinescu, S; Diamandescu, L; Bibicu, I; Tarabasanu-Mihaila, D; Feder, M

Published: JUN 2008, HYPERFINE INTERACTIONS, 184, 89, DOI: 10.1007/s10751-008-9770-1

The hyperfine interactions and dynamics aspects in nanoparticles system of the xSnO(2)-(1-x)alpha-Fe2O3 (x = 0.0-1.0) have been investigated by Sn-119-Mossbauer and XRD techniques. The change revealed by the XRD (XRDSs) and Mossbauer spectra (MSs) vs. x was discussed in terms of the phase and lattice-dynamics changes. The evidences of the triple hyperfine magnetic fields' distributions (MHFDs) and their dependencies x (< 0.175) are discussed taking into account the super-transferred hyperfine interactions (STHI), the local disorder Sn4+/Fe3+ around the tin isotope probe and the reduced dimension effect.

2244. Concentration dependence of luminescence properties in praseodymium and praseodymium/ytterbium-doped lutetium double phosphates

Authors: Legendziewicz, J; Guzik, M; Cybinska, J; Stefan, A; Lupei, V

Published: JUL 2008, OPTICAL MATERIALS, 30, 1671, DOI: 10.1016/j.optmat.2007.11.004

In this paper we present a comparative optical study of praseodymium and praseodymium/ytterbium-doped lutetium double phosphates in the wide spectral range (VUV-IR) and for various concentrations of the activators. The absorption and emission spectra of Na3Lu(PO4)(2):Pr3+ and Na3Lu(PO4)(2):Pr3+, Yb3+ were measured at room and low temperatures. It was shown that spectroscopic properties of investigated systems strongly depend on the concentration ratio of the Pr3+ and Yb3+ ions. (c) 2007 Published by Elsevier B.V.

2245. Investigation of metal-oxide semiconductor field-effect transistor-like Si/SiO2/(nano)crystalline PbS heterostructures

Authors: Stancu, V; Buda, M; Pintilie, L; Pintilie, I; Botila, T; Iordache, G

Published: APR 30 2008, THIN SOLID FILMS, 516, 4306, DOI: 10.1016/j.tsf.2007.11.116

The influence of the gate voltage on photoconductivity in P-Si/SiO2/(nano)crystalline PbS, Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET)-like structures is investigated. The effect on the photo-signal in the wavelength range 500-1180 nm is opposite compared to the effect in the wavelength range 1600-2500 nm: a negative gate voltage increases the signal in the short wavelength range and decreases it for the long wavelength range. The opposite is valid for a positive gate bias. An on-off ratio better than 85 times is obtained for the spectral range 500-1180 nm, corresponding to the absorption in p-Si and better than 3.5 times for the spectral range 1600-2500 nm corresponding to the absorption in the (nano)crystal line PbS region, respectively. (c) 2007 Elsevier B.V. All rights reserved.

2246. Silver quantum dots deposited on YAG coated silicon wafer

Authors: Popescu, M; Sava, F; Lorincz, A; Daroczi, L; Kokenyesi, S; Mihailescu, IN; Socol, G

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 787, DOI:

Silver nano-dots have been deposited by a special procedure on the surface of a YAG coated silicon wafer. Sizes of 40-100 nm and a self-organized distribution according to the pattern of the pattern of defects (dislocations, terraces, etc.) on the wafer's surface were revealed. The procedure is simple and can be applied for the controlled deposition of small silver clusters to be used both in medicine and in nano-electronic devices.

2247. InN Thin Films Deposition by rf Magnetron Sputtering

Authors: Braic, MT; Zoita, CN; Braic, VT; Toacsan, MI; Ioachim, AT

Published: 2008, 2008 33RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES, VOLS 1 AND 2, +, DOI:

InN thin films were grown by reactive magnetron sputtering in a UHV system, using Ar and N-2 as working gases. Electrical and optical investigations of the films were correlated with their structural and morphological characteristics in order to obtain good quality films for THz applications.

2248. Sol-gel synthesis and characterization of fine-grained ceramics in the alumina-titania system

Authors: Otterstein, E; Karapetyan, G; Nicula, R; Stir, M; Schick, C; Burkel, E

Published: FEB 5 2008, THERMOCHIMICA ACTA, 468, 14, DOI: 10.1016/j.tca.2007.11.023

Fine-grained ceramics of the Al2O3-TiO2 system were synthesised by reactive sintering of sol-gel precursors (Al- and Ti-alkoxides). The thermal behaviour of the as-prepared xerogels was examined by thermal analysis and X-ray powder diffraction. Preliminary results concerning powder consolidation into bulk ceramic parts using spark plasma sintering (SPS) are discussed. (c) 2007 Elsevier B.V. All rights reserved.

2249. SAW AND FBAR RESONATORS FOR GHZ APPLICATIONS BASED ON MICROMACHINING AND NANOPROCESSING OF WIDE BANDGAP SEMICONDUCTORS

Authors: Muller, A; Konstantinidis, G; Neculoiu, D; Dragoman, M; Dinescu, A; Stavrinidis, A; Vasilache, D; Morosanu, C

Published: 2008, 2008 IEEE 25TH CONVENTION OF ELECTRICAL AND ELECTRONICS ENGINEERS IN ISRAEL, VOLS 1 AND 2, +, DOI:

The 4G mobile communication systems are expected to work within the 3-6 GHz range. The development, in the last years, of wide band gap (WGB) semiconductor technologies has opened the perspective of manufacturing SAW (surface acoustic wave) and FBAR (film bulk acoustic resonator) devices for application in the GHz frequency range. SAW type structures with a resonance frequency of about 2.8 GHz and 3.2 GHz have been successfully developed on a thin AlN layer sputtered on high resistivity silicon. Nanolithography was used to manufacture the interdigitated transducer. FBAR resonators have been manufactured using micromachining techniques of GaN/Si and AlN/Si wafers. FBAR structures based on self sustainable AlN and GaN membranes with a thickness lower then 0.5 mu m have been obtained. Resonance frequencies of about 4.8 GHz have been obtained for GaN based FBAR structures and about 10GHz for AlN based FBAR structures.

2250. Single-beam pumped coherent anti-Stokes Raman scattering on carbon nanotubes

Authors: Lefrant, S; Buisson, JP; Mevellec, JY; Baltog, I; Baibarac, M

Published: OCT 2008, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 245, 2224, DOI: 10.1002/pssb.200879567

Giant optical fields locally generated in nanoscale metal structures through the local excitation of surface plasmons underlie a variety of nonlinear optical processes. Using silver and gold rough metallic films, reproducible enhancements of the Raman signal on various materials including carbon nano-tubes have been demonstrated. In addition, an abnormal anti-Stokes Raman emission, reminiscent of Coherent anti-Stokes Raman Scattering (CARS), is accurately observed on nano-metric thin films. We demonstrate that under a tight focusing of the excitation light, a CARS-type emission, resulting from a wave mixing process between the incident laser light and Stokes Raman light generated by a SERS mechanism, is produced. The results which corroborate the CARS emission are the following: a square relation between the CARS signal intensity and the film thickness; a square relationship between the CARS signal intensity and the exciting laser intensity; a dependence of the CARS intensity on the numerical aperture (NA) of the microscope objective used for the detection of the anti-Stokes signal; a polarization ratio in the anti-Stokes side always greater in comparison with that measured for an usual Stokes Raman signal. We demonstrate also that this mechanism may contribute to a clear identification of the state of the observed nanotubes, i.e. in isolated or bundled forms, even when tubes are in powders. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2251. PbSe nanowires grown by the template method

Authors: Sima, M; Enculescu, I; Sima, M

Published: 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 70, DOI:

PbSe nanowires were prepared using the template method. Polycarbonate ion track membranes with pore sizes ranging between 50 nm and 1.5 mu m were used as templates. The deposition of PbSe in the pores of the template was performed electrochemically. The influence of the deposition potential and membrane porosity on the morphology and composition of the prepared nanowires was studied. The composition of the wires has been determined by EDX measurements for different potentials. Scanning electron microscopy revealed the morphology of the deposited nanowires. X ray diffraction has been used for structural measurements.

2252. Transport through quantum dots with magnetic impurities

Authors: Tolea, M; Aldea, A; Bulka, BR

Published: JUL 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1758, DOI:

We analyze the electronic transport through a quantum dot that contains a magnetic impurity. The coherent transport of electrons is governed by the quantum confinement inside the dot, but is also influenced by the exchange interaction with the impurity. The interplay between the two gives raise to the singlet-triplet splitting of the energy levels available for the tunneling electron. In this paper, we focus on the charge fluctuations and, more precisely, the height of the conductance peaks. We show that the conductance peaks corresponding to the triplet levels are three times higher than those corresponding to singlet levels, if electronic correlations are neglected (for non-interacting dots, when an exact solution can be obtained). Next, we consider the Coulomb repulsion and the many-body correlations. In this case, the singlet/triplet peak height ratio has a complex behavior. Usually the highest peak corresponds to the state that is lowest in energy (ground state), regardless if it is singlet or triplet. In the end, we get an insight on the Kondo regime for such a system, and show the formation of three Kondo peaks. We use the equation of motion method with appropriate decoupling.

2253. Irradiation defects in superhard cubic boron nitride single crystals

Authors: Nistor, SV; Ghica, D; Stefan, M; Nistor, LC; Goovaerts, E; Taniguchi, T

Published: JUN 2008, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 266, 2787, DOI: 10.1016/j.nimb.2008.03.117

Single crystallites of superhard, semiconducting, n-type, amber colored and p-type, blue colored, Be-doped cubic boron nitride have been irradiated either with UV (350 nm) light or with an intense beam of accelerated (1 MeV) electrons. The examination of the irradiated samples at low temperatures by high frequency W (95 GHz)-band electron spin resonance reveals several new, radiation-induced, isotropic paramagnetic centers. The UV irradiation of both types of crystals yields centers involving very likely protons. In the amber c-BN crystals the irradiation with I MeV electrons results in the formation of vacancy associated paramagnetic defects and quasi-free electrons in colloidal particles. (C) 2008 Elsevier B.V. All rights reserved.

2254. ELECTRIC, FERROELECTRIC AND PHOTOELECTRIC PROPERTIES OF Pb(Zr,Ti)O-3-Nb:SrTiO3 JUNCTIONS

Authors: Pintilie, L; Pintilie, I; Vrejoiu, I; Alexe, M

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703406

The electric, ferroelectric and photoelectric properties of Pb(Zr,Ti)O-3-Nb:SrTiO3 (PZT-STON) junctions were investigated on a broad range of temperatures. It was found that the hysteresis loop is strongly asymmetric, due to the asymmetry in the leakage current. The capacitance-voltage characteristic has a butterfly shape although it is also asymmetric because of the different nucleation and compensation conditions at the two interfaces. The junction shows a strong photovoltaic effect in the 200500 run wavelength range as short-circuit currents Of the order of nA for an illuminated surface of 0.018 mm(2). This makes the PZT-STON junctions attractive for UV optoelectronic applications.

2255. Thermal behaviour study of some sol-gel TiO2 based materials

Authors: Crisan, M; Braileanu, A; Crisan, D; Raileanu, M; Dragan, N; Mardare, D; Teodorescu, V; Ianculescu, A; Birjega, R; Dumitru, M

Published: APR 2008, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 92, 13, DOI: 10.1007/s10973-007-8720-5

Among the great number of sol-gel materials prepared, TiO2 holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light. This work has studied some un-doped and Pd-doped sol-gel TiO2 nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous TiO2 matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between the synthesis conditions and the properties of titania narrosized materials, such as thermal stability, phase composition, crystallinity, morphology and size of particles, and the influence of dopant was investigated. The influence of Pd on TiO2 crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology. The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.

2256. Direct measurement of depth-dependent Fe spin structure during magnetization reversal in Fe/MnF2 exchange-coupled bilayers

Authors: Macedo, WAA; Sahoo, B; Eisenmenger, J; Martins, MD; Keune, W; Kuncser, V; Rohlsberger, R; Leupold, O; Ruffer, R; Nogues, J; Liu, K; Schlage, K; Schuller, IK

Published: DEC 2008, PHYSICAL REVIEW B, 78, DOI: 10.1103/PhysRevB.78.224401

We measured directly the depth-dependent Fe spin rotation upon magnetization reversal in exchange-coupled Fe/MnF2 bilayers using nuclear resonant scattering of synchrotron radiation from an Fe-57-probe layer buried at different depths within the Fe film. Our results show that the exchange-biased ferromagnetic layer develops a noncollinear spin structure along the film normal direction, reminiscent of a partial domain wall parallel to the Fe/MnF2 interface. This is contrary to most theoretical models of exchange bias which assume a collinear spin structure in the ferromagnetic layer.

2257. Structure and dielectric properties of HfO2 films prepared by a sol-gel route

Authors: Blanchin, MG; Canut, B; Lambert, Y; Teodorescu, VS; Barau, A; Zaharescu, M

Published: AUG 2008, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 47, 172, DOI: 10.1007/s10971-008-1758-4

Mono- and multilayer HfO2 sol-gel thin films have been deposited on silicon wafers by dip-coating technique using a solution based on hafnium ethoxide as precursor. The densification/crystallization process was achieved by classical annealing between 400 and 600 degrees C for 0.5 h (after drying at 100 degrees C). Systematic TEM studies were performed to observe the evolution of the thin film structure depending on the annealing temperature. The overall density of the films was determined from RBS spectrometry correlated with cross section (XTEM) thickness measurements. After annealing at 450 degrees C the films are amorphous with a nanoporous structure showing also some incipient crystallization. After annealing at 550 degrees C the films are totally crystallized. The HfO2 grains grow in colonies having the same crystalline orientation with respect to the film plane, including faceted nanopores. During annealing a nanometric SiO2 layer is formed at the interface with the silicon substrate; the thickness of this layer increases with the annealing temperature. Capacitive measurements allowed determining the value of the dielectric constant as 25 for four layer films, i.e. very close to the value for the bulk material.

2258. Substituted cobalt ferrites for sensors applications

Authors: Caltun, O; Dumitru, I; Feder, M; Lupu, N; Chiriac, H

Published: OCT 2008, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 320, E873, DOI: 10.1016/j.jmmm.2008.04.067

The aim of this work was to study the influence of the sintering temperature and of the substitution level on the Curie temperature and on the magnetostriction coefficients for four series of cobalt ferrites sintered by conventional ceramic method. The microstructure of the samples was characterized using X-ray diffractometry and scanning surface electron microscopy. Vibrating sample magnetometry and strain gauge measurements were used to characterize the magnetic and magnetostriction properties. The study proves that a small amount of manganese substitution for iron decrease drastically the Curie temperature but in the same time decrease the specific magnetization and magnetostriction coefficient. Despite this drawback, the manganese substituted cobalt ferrites present the largest strain derivative. The maximum of the magnetostriction coefficient is also influenced by the stoichiometry of the cobalt ferrites. The magnetostriction coefficient of cobalt ferrite can be enhanced by substitution of small fraction of iron or cobalt by silicon or manganese, this implying the modification of the strain derivative as well as magnetostriction at lower magnetic fields. The maximum magnetostriction can be tuned by substitution levels and sintering parameters. (C) 2008 Elsevier B.V. All rights reserved.

2259. Preparation and Properties of Cobalt Doped ZnO Nanowires

Authors: Enculescu, I; Matei, E; Sima, M; Neumann, R; Granville, S; Ansermet, JP

Published: NOV 2008, IEEE TRANSACTIONS ON MAGNETICS, 44, 2680, DOI: 10.1109/TMAG.2008.2003242

The template method was used for preparing Zn1-xCoxO nanowires with x ranging from 0.01 to 0.05. Thus, electrochemical deposition was employed for filling up the pores of polycarbonate ion track nanoporous membranes with the desired material. The method allows a good control over the morphology and composition of the deposited nanowires, as evidenced by scanning electron microscopy (SEM) and energy dispersive X ray analysis (EDX). Measurements of the magnetic properties showed a paramagnetic behavior of the nanowire arrays for the whole set of temperatures and Co concentrations.

2260. Vibrational and photoluminescence properties of composites based on zinc oxide and single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Lefrant, S; Mevellec, JY; Husanu, M

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2564, DOI: 10.1016/j.physe.2007.09.034

Composites based on zinc oxide (ZnO) nanoparticles and single-walled carbon nanotubes (SWNTs) were investigated by photoluminescence (PL) and Raman scattering. The room temperature PL spectrum of ZnO at the excitation wavelength of 335 nm displays a narrow excitonic band, peaking at 368 nm (3.36eV), and a wide one, disclosing two components with maxima at about 444 nm (2.79eV) and 560 nm (2.21eV) which are associated to the local oxygen vacancies and oxygen excess, respectively. Regardless the preparation method of the ZnO/SWNTs compound (electrochemical, mechanicochemical and hydrothermal synthesis), PL spectra reveal an increased quenching tendency with the concentration of nanotubes in the composite mass. As distinct feature in the PL spectra of ZnO/SWNTs composites are two bands, one at 450 nm (2.75 nm) and another one attributed to the formation of a donor-acceptor complex at 680 nm (1.82eV). The role of the dispersion of carbon nanotubes in the ZnO/SWNTs composite is observed by Raman scattering with the excitation wavelength of 676 nm. (C) 2007 Elsevier B.V. All rights reserved.

2261. Optica and structural properties of polythiophene-like films deposited by plasma polymerization

Authors: Galca, AC; Satulu, V; Ionita, MD; Bercu, M; Barna, E; Dumitru, M; Mitu, B; Dinescu, G

Published: AUG 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2037, DOI:

Polymer-like organic thin films obtained by plasma techniques are of wide interest for various applications. Polythiophene-like thin films were deposited by plasma polymerization in a parallel plate radiofrequency reactor starting from thiophene vapors. The optical properties of the films were obtained from spectroscopic ellipsometry, in the 250-1250 nm range. The calculated band gap is in agreement with a polythiophene-like material consisting of cross-linking of oligomers. The presence of functional groups and film stability against oxidation is analyzed by FTIR spectrometry. The monitoring of functional groups incorporation during the film deposition was done by analyzing the integral intensities of specific absorption bands and led to the conclusion that homogeneous films are obtained whatever the process duration.

2262. Scanning electron microscopy and resistive transition of in-situ grown YBCO films by pulsed laser deposition

Authors: Branescu, M; Ward, I; Huh, J; Matsushita, Y; Zeltzer, G

Published: 2008, INTERFACIAL NANOSTRUCTURES IN CERAMICS: A MULTISCALE APPROACH, 94, DOI: 10.1088/1742-6596/94/1/012007

In this paper we summarize the deposition parameters, the crystalline structure and the critical temperature of the in-situ grown YBa2Cu3O7-delta(YBCO) films obtained by pulsed laser deposition (PLD) using our kinetic cool-down regime, described in previous papers. We analyze the resistive transition curves and the corresponding scanning electron microscopy (SEM) pictures of the best in-situ grown YBCO films, in order to better characterize the films and refine the deposition process. SEM pictures reveal the typical surface morphology of both in-situ grown and post-deposition, oxygen atmosphere annealed YBCO films. A significant smoother surface of the in-situ grown films is obtained.

2263. Optical spectroscopy of Yb2+ ions in YbF3-doped CaF2 crystals

Authors: Nicoara, I; Lighezan, L; Enculescu, M; Enculescu, I

Published: APR 2008, JOURNAL OF CRYSTAL GROWTH, 310, 2032, DOI: 10.1016/j.jcrysgro.2007.11.183

Transparent colorless Ca1-xYbxF2+x (X = 0-0007-0.016) crystals were grown using the vertical Bridgman technique. In order to obtain efficient Yb3+-Yb2+ conversion in the as-grown crystals, a special procedure has been developed. Room temperature optical absorption spectra reveal the characteristic UV absorption bands of the Yb2+ ions in the as-grown crystals, with intensities more than 10 times higher than those reported by other authors using various conversion procedures. The influence of YbF3 content and of codoping with Pb2+ ions on the absorption and emission spectra has been studied. Room temperature emission bands in the near UV (not reported before) and in the visible spectral domain have been observed. The emission intensity depends on the dopant concentration. A comparison of our results with those obtained by other authors is also given. (c) 2007 Elsevier B.V. All rights reserved.

2264. Electrical properties of electrodeposited CdS nanowires

Authors: Ghenescu, M; Ion, L; Enculescu, I; Tazlaoanu, C; Antohe, VA; Sima, M; Enculescu, M; Matei, E; Neumann, R; Ghenescu, O; Covlea, V; Antohe, S

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2488, DOI: 10.1016/j.physe.2007.09.188

A template method was used to obtain cadmium sulfide (CdS) nanowires. Polymer ion tracks foils (30 mu m tick) were used as templates, after etching with solutions containing NaOH and methanol. CdS nanowires were electrochemically grown in the resulting pores. The nanowires were contacted by sputtering a gold layer on top of the membrane, and the electrical properties were recorded in the temperature range 40-300K. An activated electrical resistance was observed, with activation energy of 0.27eV at temperatures larger than 180 K. I-V characteristics show a symmetric, non-linear shape, in the voltage range used in this experiment. (C) 2007 Elsevier B.V. All rights reserved.

2265. Phase-change electrical memory elements and devices

Authors: Popescu, M; Lorinczi, A; Sava, F; Velea, A; Matei, E; Socol, G; Mihailescu, IN

Published: OCT 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2621, DOI:

Electrical memory elements based on Ge-Sb-Te pure and doped by Sn-Se have been obtained by pulsed laser deposition on special substrates covered by gold as well as on common glass. A set of electrical memory elements in a 4x4 matrix structure on the glass substrate has been produced. Devices with 3 and 10 memory elements have been constructed and tested for their memory properties. The special features of the voltage-current characteristics have been revealed.

2266. Coherent and incoherent transport through T-shaped double quantum dots

Authors: Moldoveanu, V; Tolea, M; Tanatar, B

Published: MAR 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 1104, DOI: 10.1016/j.physe.2007.08.012

We investigate the measurement induced dephasing of the Fano effect in the electronic transport through a double quantum dot mesoscopic interferometer coupled to a charge detector. The current and the differential conductance are computed within the Keldysh formalism, taking into account of the inelastic processes due to the dot-detector interaction. We show that the visibility of the Fano lineshape is reduced by applying a finite bias on the charge detector. (C) 2007 Elsevier B.V. All rights reserved.

2267. The influence of the top-contact metal on the ferroelectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)O-3 thin films

Authors: Pintilie, L; Vrejoiu, I; Hesse, D; Alexe, M

Published: DEC 1 2008, JOURNAL OF APPLIED PHYSICS, 104, DOI: 10.1063/1.3021293

Electrical properties, i.e., dielectric hysteresis and leakage current, of epitaxial Pb(Zr0.2Ti0.8)O-3 films with bottom SrRuO3 electrode and different metals as top contact were investigated. The leakage current is largely insensitive to the work function of the top metal but increases with decreasing electronegativity as well as with decreasing number of electrons on the d-shell of the top metal. The best rectifying properties are obtained for metals with complete d-shell (Cu, Au, Ag, Pd), while the metals with few electrons on the d-shell (Ta, Cr) form Ohmic-like contacts. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3021293]

2268. Capacitance tuning in antiferroelectric-ferroelectric PbZrO(3)-Pb(Zr(0.8)Ti(0.2))O(3) epitaxial multilayers

Authors: Pintilie, L; Boldyreva, K; Alexe, M; Hesse, D

Published: JAN 14 2008, NEW JOURNAL OF PHYSICS, 10, DOI: 10.1088/1367-2630/10/1/013003

The capacitance of PbZrO(3)-Pb(Zr(0.8)TiO(0.2))O(3) epitaxial multilayers is significantly enhanced as the number of interfaces increases at the same total thickness of the structure. A possible explanation for this enhancement can be the increase of the dielectric susceptibility due to the presence of some interfacial polarization related, for instance, to trapped charges at the multilayer interfaces. The presented results suggest that capacitance tuning is achievable in antiferroelectric-ferroelectric epitaxial multilayers.

2269. MICROWAVE FILTERS WITH MULTIPLE CROSS-COUPLINGS AND MAXIMUM NUMBER OF CONTROLLED ATTENUATION POLES

Authors: Lojewski, G; Militaru, N; Banciu, MG

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703373

In this paper a novel configuration of microwave planar filters, with multiple cross-couplings and with a number of poles of attenuation NZ equal to the order N of the filter, is investigated The position of the poles on the frequency axis can be controlled, allowing the design of band-pass filters with improved selectivity with respect to the adjacent channels. The new configurations were designed and verified by em-field simulation. The responses of the designed filters are in good agreement with the specification, confirming the possibilities of designing microwave band-pass filters of a relatively low order with moderate losses and with improved performances.

2270. Obtaining of phtalocyaninic dyes using solvothermal methods

Authors: Boscornea, C; Grigoriu, N; Tarabasanu-Mihaila, D; Robu, M

Published: APR 2008, REVISTA DE CHIMIE, 59, 375, DOI:

Metallo- phtalocyanines were obtained in good yields by the solvothermal method, a new and original synthesis method, optimized in real laboratory conditions. The structures were characterized by elemental analysis, UV-VIS and IR spectroscopy. Some of the compounds (iron phthalocyanine) were assigned by Mossbauer spectroscopy.

2271. Study of iron oxide nanoparticles coated with dextrin obtained by coprecipitation

Authors: Vatasescu-Balcan, RA; Predoi, D; Ungureanu, F; Costache, M

Published: MAR 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 696, DOI:

In this paper we present the preparation and biological tests of iron oxide nanoparticles coated with dextrin. Iron oxide was also prepared by co-precipitation. The samples were characterized by transmission electron microscopy (TEM) and 14 scanning electron microscopy (SEM). Biocompatibility test of the iron oxide nanoparticles coated with dextrin substrate has been done using primary osteoblast cell line. After osteoblast culture achievement, the cells were treated with trypsin 0.05% and splitted in 35/35 mm Petri dish. The influence in vitro was assessed using primary osteoblast cell line and various techniques to observe cell-particles interactions. The results of these analyses are presented in this work.

2272. INVESTIGATION ON MICROWAVE SIGNAL PROPAGATION THROUGH SOME LEFT-HANDED STRUCTURES

Authors: Banciu, MG; Ioachim, A; Militaru, N; Lojewski, G

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703340

Some aspects of microwave propagation through left-handed materials are investigated in this paper. The strong distortion of a Gaussian TEM pulse through a material with negative refraction index is studied in the time domain. Moreover, a method of extracting the constitutive parameters of a material by using the scattering parameters of a sample two-port is developed This method is then applied to some left-handed microstrip structures.

2273. Experimental modelling of the radionuclides diffusion process in uranifer tailing dump

Authors: Bragea, M; Perju, D; Jinescu, G; Toro, L; Cristache, C

Published: JAN 2008, REVISTA DE CHIMIE, 59, 78, DOI:

Generally, the uranifer tailings dump are not protected. During the time appear chemical and physical modifications which favour spreading of the radioactive contaminant into the environment, because of the waters provided from precipitations with pH variation (acid rainfall, snow), solar radiance, variation of temperature and humidity, interaction of different minerals from the waste rock with infiltration water during the flow, leading to precipitations phenomenon, ionic exchange, adsorption and re-dissolving [2]. As a rule, the speed of radionuclides diffusion from radioactive tailings dump depends on each of these factors and is very specific to the hydro and geochemistry of the nearest rocks [7]. Because of that, the scientific research is very difficult and will obliges us to study through the simplified physical systems but maintaining the important parameters which are influencing the diffusion process of the contaminant in the environment. The main objective of this paper is to characterize hydro and geochemistry properties controlling the migration of radionuclides extracted from tailings dump into the environment, including the processes of sorption and adsorption and neglecting other physical processes as precipitation, ion exchange or some other geochemical interactions within the system. For this purpose we made studies on Ra-226 and U-nal extraction from uranifer tailings dump analyzed in pure water in dynamic system, studies about the influence of clay presence on speed of diffusion process in sorption and adsorption phenomenon. Finally we made a prediction for long term about variation of concentrations of Ra-226 and U-nal based on experimental data using some software programs from literature [8].

2274. Correlation between the method of preparation and the properties of the sol-gel HfO2 thin films

Authors: Zaharescu, M; Teodorescu, VS; Gartner, M; Blanchin, MG; Barau, A; Anastasescu, M

Published: JAN 15 2008, JOURNAL OF NON-CRYSTALLINE SOLIDS, 354, 415, DOI: 10.1016/j.jnoncrysol.2007.07.097

This work describes the preparation of HfO2. thin films by the sol-gel method, starting with different precursors such as hafnium ethoxide, hafnium 2,4-pentadionate and hafnium chloride. From the solution prepared as mentioned above, thin films on silicon wafer substrates have been realized by 'dip-coating' with a pulling out speed of 5 cm min(-1). The films densification was achieved by thermal treatment for 10 min at 100 degrees C and 30 min at 450 degrees C or 600 degrees C, with a heating rate of 1 degrees C min(-1). The structural and optical properties of the films are determined employing spectroellipsometric (SE) measurements in the visible range (0.4-0.7 mu m), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The main objective of this paper was to establish a correlation between the method of preparation (precursor, annealing temperature) and the properties of the obtained films. The samples prepared from pentadionate and ethoxide precursors are homogenous and uniform in thickness. The samples prepared starting from chloride precursor are thicker and proved to be less uniform in thickness. Higher non-uniformity develops in multi-deposition films or in crystallized films. A nano-porosity is present in the quasi-amorphous films as well in the crystallized one. For the samples deposited on silicon wafer, the thermal treatment induced the formation of a SiO2 layer at the coating-substrate interface. (C) 2007 Elsevier B.V. All rights reserved.

2275. High temperature thermoluminescence of Mn2+-doped MgF2 phosphor for personal dosimetry

Authors: Secu, M; Secu, CE; Jipa, S; Zaharescu, T; Cutrubinis, M

Published: FEB-JUN 2008, RADIATION MEASUREMENTS, 43, 386, DOI: 10.1016/j.radmeas.2007.11.047

Thermoluminescence (TL) curve recorded after gamma-irradiation at room temperature of Mn2+-doped MgF2 phosphor shows TL peaks at 91, 147, 200, 235 and 295 degrees C. The 147 degrees C peak was tentatively attributed to the F centres recombination with hole centres trapped in the neighbourhood of the Mn2+ impurity. This peak shows a good stability (low fading) and has been used to characterise the TL phosphor dosimetric properties. TL dose dependence has shown a good linearity in the range from 0.2 to 10 mGy, which makes it suitable for personal and medical dosimetry. The TL curves recorded after gamma rays or particles irradiation are similar, which suggests the possibility to use the phosphor also for particle detection. (C) 2007 Elsevier Ltd. All rights reserved.

2276. Nanostructured PZT type thin films prepared by thermonic vacuum arc method

Authors: Rasleanu, D; Ionescu, V; Prodan, G; Ciupina, V; Lungu, CP; Surdu-Bob, C; Osiac, M; Pompilian, O; Badulescu, M; Lungu. AM; Ticos, C; Zaroschi, V; Trupina, L; Miclea, C

Published: NOV 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3047, DOI:

PZT type films were prepared using the thermionic vacuum arc (TVA) method; a crucible filled PZT type powder (PbO/ZrO/TiO) was heated by a thermo-electron beam emitted by the circular cathode of the TVA gun. Applying high voltage potential (3000 +/- 200V) on the anode from a regulated HEINZINGER high voltage power supply the thermo-electrons were accelerated toward the anode crucible, evaporating the anode materials and initiating a plasma discharge. The morphology and the structure of the prepared films analyzed by transmission electron microscopy, (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy, showed nanostructured, smooth thin films with specific PZT stoichiometry.

2277. Doping dependence of vortex regimes in Y1-xPrxBa2CU3O7-delta single crystals

Authors: Gyawali, P; Sandu, V; Almasan, CC; Taylor, BJ; Maple, MB

Published: MAY 2008, PHYSICAL REVIEW B, 77, DOI: 10.1103/PhysRevB.77.174504

Magnetic relaxation measurements on a series of Y1-xPrxBa2CU3O7-delta (x=0.13, 0.34, and 0.47) single crystals were performed over a large field and temperature range in order to investigate the characteristics of the vortex matter across the second magnetization peak (SMP). The magnitude of the SMP varies nonmonotonically with Pr concentration, i.e., the irreversible magnetization normalized by its value at the onset field H-on displays a maximum for the x=0.34 single crystal. The two characteristic fields, H,,, and H,,, follow different temperature T dependences: H-on proportional to T-nu on and H-sp proportional to [1-(T/T-c)(2)](nu sp). The extracted values of the apparent activation energy U* and the creep exponent mu display a maximum at a field H-on < H* < H-sp. Their field dependences point toward the coexistence of both elastic and plastic creep for H > H-on. The degree of participation of each creep mechanism is determined by the charge carrier density, which controls both the elastic properties of the vortex matter and the pinning potential.

2278. Vibrational and photoluminescence properties of the polystyrene functionalized single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Lefrant, S; Mevellec, JY; Bucur, C

Published: JUL-OCT 2008, DIAMOND AND RELATED MATERIALS, 17, 1388, DOI: 10.1016/j.diamond.2008.01.061

Using surface enhanced Raman scattering (SERS) and FTIR spectroscopy, a covalent functionalization of single wall carbon nanotubes (SWNTs) with polystyrene (PST) is demonstrated. For this, two types PST/SWNTs composites were used: one resulting from the radical polymerization reaction of styrene achieved at 90 degrees C in the presence of benzene and benzoyl peroxide, latter being the initiator and another obtained by mixing the two constituents. These compounds reveal different SERS and photoluminescence spectra. The main experimental facts supporting the covalent functionalization of SWNTs with PST are provided by FTIR spectroscopy. In this frame significant is the increase of the intensities of absorption bands at 1270 and 1721 cm(-1), which are associated with the tangential C-H bending+C-O stretching and C=O stretching vibration modes, respectively. The presence of these absorption bands in the FTIR spectra of the PST/C-60 composites proves the formation of a compound with a similar molecular structure. in the case of polystyrene functionalized SWNTs, the appearance of a new FTIR band at ca. 1635 cm(-1) attributed to the C-C in cyclic hydrocarbons ring di-substituted vibration mode indicates the formation of an additional reaction product. (C) 2008 Elsevier B.V. All rights reserved.

2279. A Study of the Changes Produced by Sintering on the Shape and Densification of Green Compacted Samples

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Amarande, L; Plavitu, C; Cioangher, M; Trupina, L; Miclea, CT; David, C

Published: 2008, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 11, 107, DOI:

In order to determine the effect of sample shape, compacting pressure and green density gradients on the final shape and density of sintered bodies a study was made on a PZT type powder, pressed within a large range of shapes from long cylinders up to thin discs and at pressures ranging between 40 and 180 MPa. Important shape distorsion were found for both long cylinders and thin discs but surprisingly the final density was not essentially changed even if the green compacted density showed important changes with in the samples. Differences in the shrink age of diameter and thickness brought about by sintering for samples with different shapes were found.

2280. Investigation on the nitrogen doping of multilayered, porous TiO2 thin films

Authors: Gartner, M; Osiceanu, P; Anastasescu, M; Stoica, T; Stoica, TF; Trapalis, C; Glannakopoulou, T; Todorova, N; Lagoyannis, A

Published: SEP 30 2008, THIN SOLID FILMS, 516, 8189, DOI: 10.1016/j.tsf.2008.04.027

N-doping is often used to improve the photocatalytic properties of TiO2, films in order to achieve visible light response. In this work, we study the effect of annealing treatment (temperature and atmosphere) on the structural and optical properties of undoped and N-doped TiO2, films by means of X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and UV-VIS optical transmission spectroscopy. Porous five-layer TiO2, films were deposited by sol-gel method on quartz substrate and thermally treated in oxygen or NH3 flow at 500 and 600 degrees C. Significant doping effect was achieved after annealing at 600 degrees C in NH3 and a shift in optical bandgap value down to visible range (2.69 eV) was observed. (C) 2008 Elsevier B.V. All rights reserved.

2281. Photocatalytic and structural properties of mixed titania and zirconia aerogels

Authors: Danciu, V; Baia, L; Cosoveanu, V; Baia, M; Vasiliu, F; Diamandescu, L; Teodorescu, CM; Feder, M; Popp, J

Published: 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 80, DOI:

A series of TiO2-ZrO2 aerogels with different ZrO2 contents (3-10 %) were prepared by an acid catalyzed sol-gel method followed by low-temperature supercritical drying and heat treatment. The structure and morphology of mixed aerogels were studied by means of Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), xenon sorption and elemental analysis. XRD spectra refinements show that the calcined TiO2-ZrO2 aerogels consist mainly in anatase phase accompanied by a small fraction of tetragonal ZrO2. The Raman spectra proof that the network of the calcined mixed aerogels mainly preserves an anatase structure similar to that of the calcined TiO2 aerogel. The TEM images reveal that the anatase particles present round shapes with a highly homogeneous size (about 3-8 nm). Areas containing chains of amorphous tetragonal zirconia were also identified by the TEM investigations. The addition of zirconia to titania significantly increased the surface area and stabilized the anatase phase of titania. The best catalytic efficiency for the salicylic acid photodecomposition was obtained for the aerogel with 9.39% zirconia that exhibited an apparent rate constant of about three times higher than that of the pure titania aerogel.

2282. Luminescence and EPR study of ZnO : Mn : Cu nanowire array

Authors: Sima, M; Enculescu, I; Grecu, MN; Secu, M; Sima, M; Matei, E; Vasile, V

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2498, DOI: 10.1016/j.physe.2007.08.075

We report on photoluminescence studies on manganese and copper-doped ZnO nanowire array prepared by template method. The ZnO:Mn:Cu semiconductor grown using the electrochemical technique was characterized by electron paramagnetic resonance (EPR) and optical reflection measurements. Morphology and the structure were observed by SEM and X-ray diffraction. The photoluminescence of this system was correlated with manganese and copper concentration in the ZnO matrix. (C) 2007 Elsevier B.V. All rights reserved.

2283. The impact of the "memory effect" on the catalytic activity of Mg/Al; Mg,Zn/Al; Mg/Al,Ga hydrotalcite-like compounds used as catalysts for cycloxene epoxidation

Authors: Angelescu, E; Pavel, OD; Birjega, R; Florea, M; Zavoianu, R

Published: JUN 15 2008, , DOI: 10.1016/j.apcata.2007.12.022

2284. The modification induced by UV radiation in spherical microlenses made of glassy arsenic sulphide

Authors: Rusu, M; Velea, A; Popescu, M

Published: DEC 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3171, DOI:

Spherical arsenic chalcogenide glass microlenses have been attached to optical fibers. The assembly was subjected to UV-radiation for different time intervals in different conditions of temperature. As a consequence, the focusing of the beam changes due to the modification of the refractive index, and of the structure, induced by photo-melting followed by crystallization. In the same time for high irradiation times the habitus of the lens changes into a prismatic one due probably to photomelting of the glass accompanied by a crystallization process.

2285. WO(x)-CeO(2) and WO(x)-Nb(2)O(5) catalysts deactivation during hexane isomerization

Authors: Mamede, AS; Payen, E; Granger, P; Florea, M; Parvulescu, VI

Published: MAY 2008, , DOI: 10.1002/aic.11468

2286. Mo-V-M-O (M = Ni, Cu, Zn, Sb, Ta) MIXED METAL OXIDES PREPARED BY SOLID-SOLID REACTIONS FOR OXIDATIVE DEHYDROGENATION OF ISOBUTANE

Authors: Mitran, G; Marcu, IC; Florea, M; Sandulescu, I

Published: MAY 2008, , DOI:

2287. PLD and RF-PLD synthesis of Ba0.6Sr0.4TiO3 ferroelectric thin films for electrically controlled devices

Authors: Nedelcu, L; Ioachim, A; Toacsan, MI; Banciu, MG; Pasuk, I; Buda, M; Scarisoreanu, N; Ion, V; Dinescu, M

Published: NOV 2008, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 93, 679, DOI: 10.1007/s00339-008-4694-9

Ba0.6Sr0.4TiO3 (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition (PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with size of spherical grains up to 150 nm. The capacitance-voltage (C-V) characteristics of the BST films were performed by applying a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been measured at room temperature.

2288. Study of osteoblast interaction with iron oxide nanoparticles coated with dextrin in cell culture

Authors: Vatasescu-Balcan, RA; Predoi, D; Costache, M

Published: JUN 2008, FEBS JOURNAL, 275, 374, DOI:

2289. MODELING OF TRAP DISCHARGING PROCESSES IN MULTIPLE QUANTUM WELL STRUCTURES

Authors: Ciurea, ML; Iancu, V; Stavarache, I; Lepadatu, AM; Rusnac, E

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703332

The paper presents the modeling of trap discharging processes in Multiple Quantum Well nanostructures. The coupling between trapping and detrapping phenomena, due to the CaF2 buffer layers is discussed. The relative role of tunneling and displacement currents is also analyzed. The model allows the determination of trap parameters that are not directly measurable. The results are in good agreement with the experimental data.

2290. Copper(II) complexes with N,N-dimethylbiguanide - Thermal, spectroscopic and biological characterization

Authors: Olar, R; Badea, M; Grecu, MN; Marinescu, D; Lazar, P; Balotescu, C

Published: APR 2008, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 92, 243, DOI: 10.1007/s10973-007-8767-3

The N,N-dimethylbiguanide (HDMBG) complexes [Cu-2(HDMBG)(2)Cl-4] (1) and respectively [Cu(HDMBG)(2)]Cl-2 center dot 2H(2)O (2) exhibit in vitro antimicrobial activity. The complexes were characterised by IR, electronic as well as EPR spectra. The IR spectra of complexes show the pattern of N,N-dimethylbiguanide coordinated as chelate. The electronic and EPR data are in agreement with a square pyramidal stereochemistry for (1) and a square planar one for (2). The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative strains (Escherichia coli, Klebsiella spp. and Enterobacter sp.) isolated from the hospital environment. The thermal analysis has evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. The thermal behaviour in nitrogen is complex according to TG and DTA curves including melting., dehydration as well as compounds decomposition.

2291. Shape memory and associated properties in Fe-Mn-Si-based ribbons produced by melt-spinning

Authors: Valeanu, M; Filoti, G; Kuncser, V; Tolea, F; Popescu, B; Galatanu, A; Schinteie, G; Jianu, AD; Mitelea, I; Schinle, D; Craciunescu, CM

Published: JUL 2008, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 320, E167, DOI: 10.1016/j.jmmm.2008.02.105

Four Fe-Mn-Si alloys, Fe(62)Mn(32)Si(6), Fe(62)Mn(20)Si(5)Cr(8)Ni(5), Fe(62)Mn(16)Si(5)Cr(12)Ni(5) and Fe(65)Mn(9)Si(7)Cr(10)Ni(9), were obtained by the melt-spinning method. The samples were structurally, magnetic and shape memory effect (SME) investigated, both ''as quenched'' and thermally treated. The Mn-rich compositions show different phase, magnetic behavior and SME in comparison with Mn-poor compositions. The thermal treatments generate transformation between the two existing majority phases (alpha and gamma), related magnetization and SME behavior. The features are derived from the corroboration of structural, magnetic interaction and magnitude of SME data. (c) 2008 Elsevier B.V. All rights reserved.

2292. Nickel nanotubes prepared by electroless deposition in ion track templates

Authors: Enculescu, I; Sima, M; Enculescu, M; Matei, E; Molares, MET; Cornelius, T

Published: MAR 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 136, DOI:

Nickel nano- and micro- tubes were prepared by electroless deposition in ion track template membranes. By choosing the appropriate etching conditions membranes with cylindrical or conical pores were obtained allowing the preparation of cylindrical or conical tubules. The activation of the membranes was a two step process. The bath used for deposition was an acidic one. Typically for acidic bath deposition, by energy dispersive X ray analysis, a phosphorous content of up to 10 % was found in the deposit.

2293. Self-sustained output power pulsations in InGaAs quantum dot ridge-waveguide lasers

Authors: Mokkapati, S; Tan, HH; Jagadish, C; Buda, M

Published: JAN 14 2008, APPLIED PHYSICS LETTERS, 92, DOI: 10.1063/1.2830998

Self-sustained pulsations in the output power of metal-organic chemical vapor deposition grown ridge-waveguide lasers with InGaAs quantum dot active region are reported. The characteristics of the output power pulsations (range, frequency, and modulation depth) are presented. The origin of the pulsations is explained in terms of the properties of the quantum dot active region.

2294. The influence of chemical composition on magnetic properties and magnetostriction coefficient of cobalt ferrites

Authors: Caltun, O; Dumitru, I; Feder, M; Diamandescu, L; Bibicu, I; Vasiliu, F; Lupu, N; Vilceanu, V

Published: JUL 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1778, DOI:

Four series of cobalt ferrites were prepared by conventional ceramic method. Calcined powders were analyzed by X-ray diffraction and Mossbauer spectroscopy to characterize the crystal structure. Green bodies were sinterized at temperatures between 1250 degrees-1300 degrees C, in air, for 5 hours. Chemical composition of samples and sintering parameters have a strong influence on the magnetic and magnetostrictive properties of the sintering bodies.

2295. Spectroscopic ellipsometry study of amorphous SrxBa1-xNb2O6 thin films obtained by pulsed laser deposition

Authors: Ion, V; Galca, AC; Scarisoreanu, ND; Filipescu, M; Dinescu, M

Published: 2008, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 5, 5, +, DOI: 10.1002/pssc.200777818

Optical properties of amorphous Strontium Barium Niobate (a-SBN) thin film are investigated using spectroscopic ellipsometry. Since the SBN can be applied to optoelectronic devices, the dispersion of refractive index is desirable. The films are obtained by Pulsed Laser Deposition (PLD) onto MgO and Si substrates by targeting a SBN:60 monocrystal: The dielectric function of a-SBN is approximated using a single Tauc-Lorentz oscillator model. Thicknesses of the films and of their rough layer are in agreement with SEM and AFM results. The dispersion of the refractive index is presented in the 1 - 5 eV range.

2296. Fractal antennas for wireless communications

Authors: Nicolaescu, I; Goga, G; Banciu, MG; Ioachim, A

Published: 2008, 2008 IEEE INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS AND NOVEL METAMATERIALS, CONFERENCE PROCEEDINGS, +, DOI:

Design, simulation fabrication and measurement of fractal antennas for wireless communications are presented in this paper Two types of geometries, Le. Sierpinski gasket and Koch curve, were investigated The proposed antennas are compact, can operate for multiple frequency bands and exhibit small mutual coupling.

2297. A simple and efficient route to active and dispersed silica supported palladium nanoparticles

Authors: Barau, A; Budarin, V; Caragheorgheopol, A; Luque, R; Macquarrie, DJ; Prelle, A; Teodorescu, VS; Zaharescu, M

Published: AUG 2008, CATALYSIS LETTERS, 124, 214, DOI: 10.1007/s10562-008-9465-x

Various mesoporous silica supported Pd materials were prepared by different methodologies in order to control and optimize the metal nanoparticle sizes for catalytic applications. The catalytic activities (conversion, mol% and selectivity to methyl-cinnamate) of the supported palladium catalysts were investigated in the Heck reaction under microwave irradiation using various haloarenes. Pd materials prepared by co-precipitation exhibited a very poor activity in the Heck reaction compared to that of Pd impregnated samples. Impregnated materials prepared without the use of a specific reducing agent had comparable activities to those of APTS-NaBH4 reduced Pd materials, validating the simplicity of the methodology. High selectivities to methylcinnamate were obtained for all materials.

2298. Materials processing with radiofrequency plasmas at low and atmospheric pressure

Authors: Dinescu, G; Mitu, B; Vizireanu, S; Ionita, ER; Luciu, I; Ionita, MD; Stancu, C; Stancu, CE; Acsente, T; Nistor, L; Kravets, L

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 690, DOI:

The paper presents a few examples relevant for the application of radiofrequency plasmas for processing of materials and surfaces. The examples have been chosen in order to match the trends in plasma processing science, namely processing at atmospheric pressure, growth of nanostructured materials and design of filtration systems responsive to external stimuli.

2299. Alternating barium stearate and copper stearate LB thin films

Authors: Popescu, M; Lorinczi, A; Velea, A; Sava, F

Published: DEC 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3415, DOI:

Alternating layers based on copper and barium stearate have been prepared. The interlayer distance for both type of stearates have been determined by X-ray diffraction. It was found that the interlayer distance for an alternating assembly depends on the actual type of the stearate layer. Thus we demonstrated the possibility to control the inter-layer distance by choosing an appropriate sequency of layers. It is suggested that such layers may serve as high precision thickness standard at the angstrom level.

2300. Raman and photoluminescence studies on intercalated lead iodide with pyridine and iodine

Authors: Preda, N; Mihut, L; Baibarac, M; Husanu, M; Bucur, C; Baltog, I

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 322, DOI:

Intercalated PbI2 compounds were prepared by exposing crystalline films and crystalline powders of lead iodide to pyridine or iodine vapor at room temperature. Correlated studies of optical absorption, Raman scattering and low temperature photoluminescence (PL) reveal different properties in comparison with those of pure crystalline PbI2 powder. Depending of the nature of intercalated molecules (organic or inorganic) the basic semiconducting properties of PbI2 are dramatically modified. The main signature of iodine intercalated PbI2 consists in a luminescence band peaking at 2.24 eV appearing at 77 K under 350 nm excitation light. In the case of pyridine intercalated PbI2 a new intense band at about 3.3 eV in the absorption spectrum is observed. The the PL spectra of pyridine intercalated PbI2 at 77 K change substantially when the excitation wavelength. The Raman spectra confirm the presence of pyridine between the PbI2 layers.

2301. Structure and sensing properties of 0.1SnO(2)-0-9 alpha-Fe2O3 system

Authors: Sorescu, M; Diamandescu, L; Tomescu, A; Tarabasanu-Mihaila, D; Teodorescu, V

Published: JAN 15 2008, MATERIALS CHEMISTRY AND PHYSICS, 107, 131, DOI: 10.1016/j.matchemphys.2007.06.062

The mixed oxide system 0.1SnO(2)-0-9 alpha-Fe2O3 (Sn1) was synthesized using the hydrothermal method and characterized using X-ray diffraction (XRD), Mossbauer spectroscopy and transmission electron microscopy (TEM). Sensing properties in both CH4 and CO were recorded as a function of temperature, humidity and concentration. The results were compared with those obtained for SnO2 (Sn10). It has been observed that Sn1 displays superior stability and sensitivity for methane as compared to Sn10. For both Sn1 and Sn10, the sensitivity to methane and carbon monoxide is influenced by temperature. In contradistinction to Sn10, Sn1 presents a reduced sensitivity to water vapors. A model based on the simultaneous evaluation of the electrical resistance and workfunction was elaborated to describe the selectivity of Sn1. (c) 2007 Elsevier B.V. All rights reserved.

2302. DESIGN AND CHARACTERIZATION OF STYRENE-BASED PROTON EXCHANGE MEMBRANES

Authors: Ebrasu, D; Petreanu, I; Patularu, L; Stefanescu, I; Valeanu, M

Published: 2008, FUNCTIONALIZED NANOSCALE MATERIALS, DEVICES AND SYSTEMS, +, DOI: 10.1007/978-1-4020-8903-9_36

This paper deals with preparation of PEM, based on commercial block copolymer of the styrene-butadiene. The copolymer was structurally changed by sulfonation followed by cross linking, in order to design a Proton Exchange Membrane for Fuel Cells. The membranes were structural tested by FTIR Spectroscopy and Scanning Electron Microscopy. Ionic Exchange Capacity (IEC) and thermal behavior by Differential Scanning Calorimetry (DSC) were measured too.

2303. Electrical characterization of thiols self-assembled layers on GaP (111) structures

Authors: Ghita, RV; Lazarescu, V; Logofatu, C; Negrila, CC; Lazarescu, MF

Published: OCT 2008, MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING, 11, 397, DOI: 10.1016/j.mssp.2008.11.012

The experimental studies on III-V semiconductor compounds surface passivation phenomena are mainly dedicated to solve some technological problems as those regarding the ways to keep the chemical stability of native oxides on surfaces. Self-assembled monolayers (SAMs) provide a simple way to produce relatively ordered structures at a molecular scale, which seems to be capable to protect the clean surface against the evolution of oxidation process. In this respect, thin films of SAMs of aliphatic thiol (dodencanthiol-CH3(CH2)(11)SH) and aromatic thiol (4, 4' tiobisbenzenthiol-S (C6H4SH)(2) have been deposited on the surface of Gap (111) samples. The electrical properties measurements of some structures based on GaP compound was performed. There were recorded current-voltage (I-V) characteristics for complex structures AuGeNi/R-SH/GaP and AuGeNi/Ar-SH/GaP in darkness and also exposed to a Xe lamp. In dark and in "reverse bias" way, the I-V characteristics present the feature of a Zenner diode for GaP/Ar-SH and a gradual increase of current for GaP/R-SH. In dark and "in forward bias" way, the current increases as for a normal diode for both GaP/Ar-SH and GaP/R-SH structures. The complex structures (e.g.: In/AuGeNi/R-SH/GaP/R-SH/AuGeNi/In) are less sensitive to light. The SEM analysis performed on a GaP/R-SH surface shows a continuous packed up layer while GaP/Ar-SH looks like an inhomogeneous deposition of layers with different thickness regions. The diodes' ideality factors determined from I-V characteristics are unusually high (n >> 2) as a possible result of inhomogeneous Schottky contacts or due to ageing effects, in the field of degradation. (C) 2009 Elsevier Ltd. All rights reserved.

2304. A HIGH PERFORMANCE PZT TYPE MATERIAL USED AS SENSOR FOR AN AUDIO HIGH FREQUENCY PIEZOELECTRIC SIREN

Authors: Miclea, C; Tanasoiu, C; Iuga, A; Spanulescu, I; Miclea, CF; Plavitu, C; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; Tanasoiu, T

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703364

A high quality PZT type material was designed and produced in order to be used as sensor for a high internsity siren. Two disks from this materials were assembled into a parallel bimorph type transducer with an intermediate metallic plate. This assembly behaves like an acoustic resonator in the high frequency audio range. The fundamental of the flexural mode for a free resonator is taken into account Its frequency dependence on the geometry of the system and on its material properties is computed using the results for a circular plate with clamped edges and an observation on the equivalence between the movement of a particular part of a resonator in a stationary state and the movement of that pari separated from the resonator but with the same border conditions. Acoustical and impedance measurements were made in order to appreciate the influence of the metallic plate on the frequency. In order to increase the acoustic emission a frontal cardboard horn was added to the resonator.

2305. Hydroxyapatite films obtained by sol-gel and sputtering

Authors: Stoica, TF; Morosanu, C; Slav, A; Stoica, T; Osiceanu, P; Anastasescu, C; Gartner, M; Zaharescu, A

Published: SEP 30 2008, THIN SOLID FILMS, 516, 8116, DOI: 10.1016/j.tsf.2008.04.071

Hydroxyapatite (HA) biocoatings were obtained using two different deposition methods: sol-gel and sputtering. A direct comparison of films obtained using different techniques is necessary because of possible formation of multi-phases and components in HA films. HA films were investigated using spectroscopic ellipsometry (SE) as a powerful method to evaluate composition and structural properties of the films. For both types of films, sputtering and sol-gel, a weak dispersion of the refractive index within the wavelength range 0.4-0.7 pm was found. This corresponds to a high energy bandgap and a high optical transparency in the UV-VIS range. The internal porosity varying in a wide range in the sol-gel films was evaluated using a modeling of SE data. Additionally to SE Studies, structural, chemical and optical characterizations of the Films were performed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Two absorption bands observed in the wavelength ranges 550-600 cm(-1) and 1000-1200 cm(-1) can be attributed to the major absorption modes associated with HA in agreement with published data. Prom XPS analysis, the atom ratio Ca/P was found for sol-gel films close to the stoichiometric value 1.67. For sputtering films, a higher Ca/P ratio of about 2.1 was estimated. However, similar FTIR spectra have been recorded for both sputtering and sol-gel films. XRD Studies show also similar crystallization conditions by annealing at temperatures higher than 500 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

2306. Charge fluctuations in quantum point contact

Authors: Bulka, BR; Dinu, IV; Tolea, M

Published: MAY 2008, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 40, 2617, DOI: 10.1016/j.physe.2007.08.001

We present studies of the role of charge fluctuations in transport through a quantum point contact (QPC). Our model of QPC is based on assumption of a specific electronic energy structure with a resonant level below the electronic sub-band. We show that charge fluctuations lead to a dynamical Coulomb blockade effect, which is responsible for reduction of the conductance to the value 2/3 x (2e(2)/h). The evolution of conductance with a magnetic field and as a function of source-drain voltage is presented as well. The conductance plateau at 2/3 x (2e(2)/h) evolves continuously with an increase of the voltage to a 0.8 or 0.4 plateau, depending on the relative position of the resonant state with respect to the Fermi energy at zero bias. Our simple model shows many similarities with experimental characteristics. (C) 2007 Elsevier B.V. All rights reserved.

2307. Simulation of nanoparticle formation by condensation from the gaseous phase

Authors: Nicolae, I; Popescu, M

Published: SEP 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2473, DOI:

The paper reports the computer simulation of nanoparticle formation based on classical homogenous condensation theory with the purpose of understanding nanoparticle formation and the dependence of their size distribution on process parameters. The simulation has been performed for the case of silicon. The process of condensation with the formation of clusters due to the high cooling speed (similar to 10(4)-10(5) K/s) is considered.

2308. Ferroelectric/Antiferroelectric Pb(Zr0.8Ti0.2)O3/PbZrO3 Epitaxial Multilayers: Growth and Thickness-Dependent Properties

Authors: Boldyreva, K; Pintilie, L; Lotnyk, A; Misirlioglu, IB; Alexe, M; Hesse, D

Published: 2008, FERROELECTRICS, 370, 146, DOI: 10.1080/00150190802384492

Epitaxial ferroelectric/antiferroelectric PbZr0.8Ti0.2O3/PbZrO3 multilayers were grown on SrTiO3(100) substrates, covered with a SrRuO3 (100) bottom electrode and a thin tetragonal PbZr0.2Ti0.8O3 buffer layer, using pulsed laser deposition. Polarization-field, switching current-voltage and capacitance-voltage curves show a mixed antiferroelectric-ferroelectric behavior of the multilayers with an individual layer thickness above 10 nm, but below 10 nm the multilayers show only ferroelectric behavior. Obviously the PbZrO3 layers thinner than 10 nm underwent a transition into the ferroelectric state. An X-ray diffraction -2 scan showed a corresponding orthorhombic-to-rhombohedral transition of the PbZrO3 layers. The observations are discussed in terms of a strain effect.

2309. Functional ZnO thin films obtained by radiofrequency beam assisted pulsed laser deposition

Authors: Epurescu, G; Scarisoreanu, ND; Matei, DG; Dinescu, G; Ghica, C; Nistor, LC; Dinescu, M

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, +, DOI:

Piezoelectric and p type semiconductor ZnO thin films were deposited by radiofrequency beam assisted pulsed laser deposition. Optical, electrical and structural properties were found to depend on both deposition parameters and radiofrequency beam characteristics.

2310. Raman and FTIR studies on electro-reduction of single-walled carbon nanotube films in the presence of Li salts

Authors: Baltog, I; Baibarac, M; Lefrant, S; Mevellec, JY

Published: JUL-OCT 2008, DIAMOND AND RELATED MATERIALS, 17, 1564, DOI: 10.1016/j.diamond.2008.01.041

Electrochemical reduction of single-walled carbon nanotube (SWNT) films in the presence of Li salts dissolved ill acetonitrile (AN), as an anhydrous medium, was investigated by Raman scattering, FTIR spectroscopy and TEM studies. Differences between the in-situ and ex-situ Raman spectra recorded on the SWNT films immersed in the Li salt/AN solution consist in the fort-nation of two reaction products with different stability in air. One corresponds to SWNTs doped with Li+ ions, a compound that is instable in air. The other, stable in air, exhibits in the Raman spectrum recorded at excitation wavelengths of 676 and 1064 nm an enhanced D band, a disappearance of the Breit-Wigner-Fano component and a significant decrease in the radial breaching mode intensity. Besides, in FTIR spectra, one observes: i) a down-shift of the absorption bands from 1456 and 1540 cm(-1) to 1440 and 15 10 cm(-1), respectively accompanied by an increase of their intensities and ii) an up-shift of the IR band from 1170 to 1192 cm(-1). The influence of the applied reduction potential and cycle voltammograms number on the vibrational features of the second product is shown, too. A recovery of the initial vibrational features of SWNTs is achieved by a subsequent treatment with an aqueous HCl 1M solution. (C) 2008 Elsevier B.V. All rights reserved.

2311. Microstructural and magnetic characterization of CuNb/Nb3Sn wires with different architectures

Authors: Sandim, MJR; Cangani, MP; Sandim, HRZ; Ghivelder, L; Awaji, S; Badica, P; Watanabe, K

Published: JUN 2008, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 18, 1025, DOI: 10.1109/TASC.2008.920575

In this work we focus on the microstructural and magnetic characterization of CuNb/Nb3Sn wires with different architectures (design and reinforcement). The microstructural characterization was performed using scanning electron microscopy. AC magnetic susceptibility was measured with field applied both parallel and perpendicular to the wire axis. The heat treatment performed to form the A-15 superconducting phase leads to partial spheroidization followed by coarsening of the Nb filaments in the reinforcement material. The differences concerning the microstructure of the reinforcement material among the investigated wires were reflected in the broadening of the superconducting transition of Nb, more evident for a field applied parallel to the wire axis. From the magnetic data the wires were also compared in terms of the superconducting volume fraction.

2312. Photochemistry aspects of the laser pyrolysis addressing the preparation of oxide semiconductor photocatalysts

Authors: Alexandrescu, R; Morjan, I; Dumitrache, F; Scarisoreanu, M; Soare, I; Fleaca, C; Birjega, R; Popovici, E; Gavrila, L; Prodan, G; Ciupina, V; Filoti, G; Kuncser, V; Vekas, L

Published: 2008, INTERNATIONAL JOURNAL OF PHOTOENERGY, 2008, DOI: 10.1155/2008/604181

The laser pyrolysis is a powerful and a versatile tool for the gas-phase synthesis of nanoparticles. In this paper, some fundamental and applicative characteristics of this technique are outlined and recent results obtained in the preparation of gamma iron oxide (gamma-Fe2O3) and titania (TiO2) semiconductor nanostructures are illustrated. Nanosized iron oxide particles (4 to 9 nm diameter values) have been directly synthesized by the laser-induced pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer)/ethylene (as sensitizer). Temperature-dependent Mossbauer spectroscopy shows that mainly maghemite is present in the sample obtained at higher laser power. The use of selected Fe2O3 samples for the preparation of water-dispersed magnetic nanofluids is also discussed. TiO2 nanoparticles comprising a mixture of anatase and rutile phases were synthesized via the laser pyrolysis of TiCl4- (vapors) based gas-phase mixtures. High precursor concentration of the oxidizer was found to favor the prevalent anatase phase (about 90%) in the titania nanopowders. Copyright (C) 2008 R. Alexandrescu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

2313. Hybrid metal (gold)-inorganic (silica) nanoparticles: Synthesis, characterization, and spin-labeling

Authors: Ionita, P; Ghica, C; Caproiu, MT; Ionita, G

Published: SEP 2008, JOURNAL OF INORGANIC AND ORGANOMETALLIC POLYMERS AND MATERIALS, 18, 419, DOI: 10.1007/s10904-008-9210-3

Water-soluble gold nanoparticles, capped with captopril, have been synthesized and characterized. Their average size is 2.3 nm, with a spherical shape. These gold nanoparticles can be easily labeled with stable free radicals (4-amino-tempo) by a coupling reaction performed in the presence of 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ). Both synthesized and spin-labeled gold nanoparticles can be incorporated into much bigger (100 nm) silica nanoparticles using the Stober method, thus forming hybrid metal (gold)-inorganic (silica) nanoparticles. These hybrid silica nanoparticles (containing or not spin-labeled gold nanoparticles) can be easily spin-labeled with another stable free radical (4-isocyanato-tempo), leading to the formation of a double spin-labeled material. In this way, some stable free radicals are attached on the gold surface while others are attached on the silica surface. Three types of EPR spectra were recorded and discussed for the hybrid gold-silica nanoparticles: (1) where the spin labels are attached to the embedded gold nanoparticles, (2) where the spin labels are attached to the silica nanoparticles, and (3) in the case of the double spin labeled material where both gold and silica nanoparticles are spin-labeled. Influence of different solvents on the EPR spectra is also discussed.

2314. Angle-resolved XPS structural investigation of GaAs surfaces

Authors: Negrila, CC; Logofatu, C; Ghita, RV; Cotirlan, C; Ungureanu, F; Manea, AS; Lazarescu, MF

Published: APR 2008, JOURNAL OF CRYSTAL GROWTH, 310, 1582, DOI: 10.1016/j.jcrysgro.2007.11.001

Angle-resolved X-ray photoelectron spectroscopy (ARXPS) analysis has been performed on GaAs (10 0) surfaces in different conditions as naturally oxidized, Ar+ ion sputtering (E = 1-5 keV) and chemical etching in H2SO4/H2O2/H2O(3: 1: 1). The most sensitive angle to the surface compositional changes was the take-off angle (TOA): 25 degrees. Native oxide phases on GaAs consist of a mixture of Ga2O3, As2O3 and As2O5. Ar+ ion sputtering procedure modifies the surface composition, in the altered layer where the concentration ratio C-Ga/C-As tends to 1.5-1.6. Wet chemical etching removes the oxide layer and the As-rich region from the surface. In the experiment combining chemical etching with Ar+ ion sputtering for cleaning purpose, the native oxides are removed from the surface and C-Ga/C-As tends to stoichiometry. The experiment on native oxide reconstruction after storage in high-vacuum conditions (P similar to 10(-8) Torr) provides evidence of the high reactivity of GaAs (10 0) surfaces. We have observed the presence of an As oxide (BE = 43 eV) within a concentration range of 2-3%. (C) 2007 Elsevier B.V. All rights reserved.

2315. Pyramidal morphology of InN thin films deposited by reactive RF-magnetron sputtering

Authors: Zoita, NC; Besleaga, C; Braic, L; Mitran, T; Vlaicu, M

Published: DEC 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 797, DOI:

Indium nitride is an attractive semiconductor material for optoelectronic applications, high-speed electronics and solar cells. We report deposition of polycrystalline InN thin films with pyramidal morphology on different substrates by reactive RF magnetron sputtering method. The morphological characterization if the films are presented in corroboration with the deposition parameters and the observed crystallographic structure.

2316. The synthesis of doped manganese cobalt ferrites by auto combustion technique

Authors: Palamaru, MN; Iordan, AR; Aruxandei, CD; Gorodea, IA; Perianu, EA; Dumitru, I; Feder, M; Caltun, OF

Published: JUL 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1856, DOI:

CoMnxFe2-xO4 with x = 0; 0.10; 0.25; 0.40; 0.60 and 2.0 were prepared by low temperature combustion method. The samples were investigated using X-ray diffraction analysis at room temperature. All the synthesized samples exhibited XRD patterns specific for cubic spinel phase with a space group Fd3m. Infrared spectroscopic analysis, using KBr pellets in the range 400 - 4000 cm(-1) was carried out using a FTIR 600Plus Fourier transform infrared spectrometer. The magnetic properties of samples have been characterized at room temperature using a vibrating sample magnetometer, the magnetic properties measurements demonstrate an increase of the saturation magnetization with the increase of Mn content.

2317. High-Q BZT ceramics for microwave applications

Authors: Ioachim, A; Toacsan, MI; Nedelcu, L; Mihut, L

Published: 2008, PROCEEDINGS OF THE 6TH WSEAS INTERNATIONAL CONFERENCE ON APPLIED ELECTROMAGNETICS, WIRELESS AND OPTI, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) ceramics were prepared by solid-state reaction and sintered in air at temperatures in the range 1550-1650 degrees C, for 2 hours. In order to improve the microwave and millimeter wave properties, annealing treatment at 1400 degrees C for 10 hours was applied. The long-range order with a 2:1 ratio of Ta and Zn ions on the octahedral positions of the perovskite structure and the vibrational modes were investigated by using XRD and Raman spectroscopy as function of sintering temperature. Presence of small amount of secondary phase, Ba8ZnTa6O24, affects Q factor even in the dense, highly ordered samples. The dielectric parameters were measured in the microwave range by Hakki-Coleman method and were correlated with structural and optical properties. Sintering temperature higher than 1600 degrees C are required for BZT ceramics in order to obtain low microwave loss (Q x f similar to 100 THz).

2318. Resonant Raman scattering and absorption spectroscopy studies on individual carbon nanotubes in surfactant solutions

Authors: Husanu, M; Baibarac, M; Preda, N; Baltog, I

Published: JUL 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 1726, DOI:

Carbon Nanotubes are exotic low-dimensional systems, and due to their remarkable properties, are promising components for technological applications. The electronic and vibrational signatures raising from their existence as individual entities or associated in bundles, is still a controversed subject. A careful analysis of the G (similar to 1600 cm(-1)) and RBM (100-200 cm(-1)) band features as: profile, peak position and intensity in the Raman spectra may be a valuable indication about their dispersion state. The UV-VIS-NIR absorption spectrum comes to support this assumption. Observing the absorption spectra associated to resonant excitation of semiconducting and metallic nanotubes, may reveal complementary informations concerning the individualization procedure efficiency.

2319. Defects in silicon: From bulk crystals to nanostructures

Authors: Ciurea, ML; Iancu, V; Lazanu, S; Lepadatu, AM; Rusnac, E; Stavarache, I

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, 748, DOI:

Defects in silicon are studied as function of the dimensionality of the investigated structures. Defects produced by strong irradiation in bulk crystals, like vacancies or interstitial defects, induce other defects, so that the irradiated devices are irreversibly damaged. Defects in nanostructures are shown to be produced mainly by surface/interface states and strains, and are therefore specific to the investigated structure. The modeling of the experimental methods allows the determination of defect parameters that are not directly measurable. The carriers capture on quantum confinement levels in OD systems has a similar behavior with the trapping phenomena.

2320. A penetration depth study on the non-centrosymmetric superconductors Li-2(Pd1-xPtx)(3)B

Authors: Yuan, HQ; Salamon, MB; Badica, P; Togano, K

Published: APR 1 2008, PHYSICA B-CONDENSED MATTER, 403, 1139, DOI: 10.1016/j.physb.2007.10.343

We study the superconducting order parameter in the non-centrosymmetric compounds Li-2(Pd1-xPtx)(3)B (x = 0, 0.3, 0.7 and 1) by measuring magnetic penetration depth lambda(T). The low temperature lambda(T) shows a linear temperature dependence for x >= 0.3, but follows exponential-like behavior for lower Pt contents. These findings suggest that a spin-triplet state might gradually develop with increasing x due to the broken inversion symmetry. Published by Elsevier B.V.

2321. Sensitivity to Reducing Gases of Polymer-Iron Nanocomposite Materials

Authors: Tomescu, A; Simion, CE; Alexandrescu, R; Morjan, I; Scarisoreanu, M

Published: 2008, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 11, 95, DOI:

Electrical properties of new Polymer-Iron nanocomposite materials obtained by laser pyrolysis were investigated, in order to find applications for the detection of reducing gases. The aim of this paper was to prove the necessity of complex experimental investigation in order to point out the contribution of different types of adsorption. Usually resistance measurement cannot fully describe the surface interactions. The electronaffinity changes are of real interest for in-field conditions which always involve humidity of surrounding gas atmosphere. On the other hand, the nanocomposite materials can be a solution for specific gas-sensing properties.

2322. Precipitation of super-fine calcium carbonate by controlled double jet method: solid phase characterization and estimation of kinetic parameters

Authors: Mateescu, CD; Isopescu, R; Branzoi, F; Mihai, M; Chilibon, I

Published: OCT 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2674, DOI:

Super - fine calcium carbonate was prepared by double jet precipitation method. The values of the estimated kinetics parameters show that nucleation is the dominant mechanism in all experimental runs.

2323. Doped sol-gel TiO2 films for biological applications

Authors: Gartner, M; Trapalis, C; Todorova, N; Giannakopoulou, T; Dobrescu, G; Anastasescu, M; Osiceanu, P; Ghita, A; Enache, M; Dumitru, L; Stoica, T; Zaharescu, M; Bae, JY; Suh, SH

Published: MAY 20 2008, BULLETIN OF THE KOREAN CHEMICAL SOCIETY, 29, 1042, DOI:

Mono and multilayer TiO2(Fe, PEG(600)) films were deposited by the dip-coating on SiO2/glass substrate using sol-gel method. In an attempt to improve the antibacterial properties of doped TiO2 films, the influence of the iron oxides and polyethilenglycol (PEG(600)) on the morphological, optical, surface chemical composition and biological properties of nanostructured layers was studied. Complementary measurements were performed including Spectroscopic Ellipsometry (SE), Scanning Electron Microscopy (SEM) coupled with the fractal analysis, X-Ray Photoelectron Spectroscopy (XPS) and antibacterial tests. It was found that different concentrations of Fe and PEG(600) added to coating solution strongly influence the porosity and morphology at nanometric scale related to fractal behaviour and the elemental and chemical states of the surfaces as well. The thermal treatment under oxidative atmosphere leads to films densification and oxides phase stabilization. The antibacterial activity of coatings against Escherichia Coli bacteria was examined by specific antibacterial tests.

2324. Processes involved in the high-temperature thermoluminescence of a Mn2+-doped MgF2 phosphor

Authors: Secu, M; Jipa, S; Secul, CE; Zaharescu, T; Georgescu, R; Cutrubinis, M

Published: JAN 2008, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 245, 162, DOI: 10.1002/pssb.200743108

The thermoluminescence (TL) glow curve recorded after gamma-irradiation at room temperature of Mn-2-doped MgF2 phosphor shows two intense TL peaks at 364 K and 420 K accompanied by several weaker peaks up to 600 K. The TL spectra have shown Mn2+ luminescence at 560 nm. The 364 K TL peak disappears after one day of storage, and so is probably related to the recombination of carriers from some shallow traps. Based on thermal bleaching and optical bleaching (in the 260 nm F-centre absorption band) experiments, the 420 K TL peak was ascribed to the thermally activated recombination between an F-centre and a hole centre trapped in the neighbourhood of the Mn2+ impurity which results in Mn2+ luminescence.

2325. Iron oxide colloids and their heterogenization by silica sol-gel entrapment: Catalytic and magnetic properties

Authors: Neatu, F; Kraynov, A; D'Souza, L; Parvulescu, VI; Kranjc, K; Kocevar, M; Kuncser, V; Richards, R

Published: AUG 31 2008, APPLIED CATALYSIS A-GENERAL, 346, 35, DOI: 10.1016/j.apcata.2008.04.024

Fe3O4 colloids modified by the chiral ligand cinchonidine were prepared with the goal of obtaining a magnetic and catalytic nano-material and were subsequently embedded in silica to form a heterogeneous catalyst. The systems were characterized by TEM and XRD measurements, while the Mossbauer technique was applied for measuring the magnetic properties of the Fe3O4 colloids. The hyperfine magnetic field distribution was consistent with one type of Fe oxide, namely, the magnetite (Fe304). These colloids, both as 'quasi-homogenous catalysts' (or soluble heterogeneous catalysts) and embedded in silica (heterogeneous catalysts) were employed in the selective hydrogenolysis of complex bicyclo[2.2.2]oct-7-enes (bicyclo[2.2.2]oct-2-enes when unsubstituted). (C) 2008 Published by Elsevier B.V.

2326. MICROWAVE COMPACT FILTERS USING MULTILAYER STRUCTURES

Authors: Militaru, N; Lojewski, G; Banciu, MG

Published: OCT-DEC 2008, REVUE ROUMAINE DES SCIENCES TECHNIQUES-SERIE ELECTROTECHNIQUE ET ENERGETIQUE, 53, 472, DOI:

This paper is dedicated mainly to the study of couplings between planar resonators in multilayer structures with modified (defected) ground plane. Couplings between two miniaturized resonators are investigated, by full electromagnetic field simulation. Based on the results of this study, several models of planar microwave bandpass filters, with a single or with two apertures, are designed, verified by simulation, fabricated and measured. Compared to the classical filters, these novel structures show a good compactness and can offer some technological advantages.

2327. Ceramic materials Ba(1-x)SrxTiO3 for electronics - Synthesis and characterization

Authors: Berbecaru, C; Alexandru, HV; Porosnicu, C; Velea, A; Ioachim, A; Nedelcu, L; Tonsan, M

Published: SEP 30 2008, THIN SOLID FILMS, 516, 8214, DOI: 10.1016/j.tsf.2008.04.031

Ceramics (Ba1-xSrx)TiO3, (BST) with x=0.25; 0.35; 0.40; 0.50; 0.60; 0.75; 0.90 were prepared by sintering method from BaCO3, SrCO3 and TiO2 of high purity (99.98%). The solid-state reaction was employed to obtain pure and doped BST ceramic samples. In order to improve the sintering process the following additives were added: 1.0 wt.% MgO and 1 wt.% MnO2. The sintering treatment was performed in die temperature range 1200 to 1260 degrees C, for 2 h. Archimedean method was used for ceramic density measurements, which was found to depend linearly on strontium content: rho(x)=5.4(2)-0.8(8).x, (g/cm(3)). SEM, EDX and XRD methods were used for sample characterization. Morphology, pores and grain size distribution of both pure and doped ceramics were investigated by SEM analysis. A bimodal grain distribution could be observed in pure BST for x <= 0.25, whereas a uniform one was noticed for doped samples of x = 0.25. Well faceted grains of similar to 5 pm size, Could be seen for x=0.75 samples. Pores size has grown with the increase of Sr content. X-ray diffraction patterns have shown a dominant perovskite structure and some other minor phases. Dielectric permittivity and loss were investigated at 1kHz, in the temperature range - 150 to + 150 degrees C, at a pace of similar to 2 degrees C /min. Sharp transitions, with higher peaks values of permittivity were noticed with the increase of the sintering temperature. A shift Of the Curie points to lower values was noticed with the increase of Sr content, according to the equation: Tc = 127.4-331.x. Measured at room temperature, in the frequency range of similar to 1 GHz, permittivity was found to increase and losses to decrease with the sintering temperature. For x <= 0.35 permittivity of the samples, being in the ferroelectric phase could not be measured in microwave domain at room temperature. Our results point to important application of these BST compositions for microwave devices. (C) 2008 Elsevier B.V. All rights reserved.

2328. Measurement-induced decoherence in electronic interferometry at nanoscale

Authors: Moldoveanu, V; Tanatar, B; Tolea, M

Published: SEP 29 2008, PHYSICS LETTERS A, 372, 6196, DOI: 10.1016/j.physleta.2008.07.079

We introduce a theoretical formalism describing a wide class of 'Which Path' experiments in mesoscopic/nanoscopic transport. The physical system involves a mesoscopic interferometer (e.g. an Aharonov-Bohm ring with embedded dots or a side-coupled quantum dot) which is electrostatically coupled to a nearby quantum point constriction. Due to the charge sensing effect the latter acts as a charge detector. Therefore the interference pattern can be monitored indirectly by looking at the current characteristics of the detector as shown in the experimental work of Buks et al. [E. Buks, R. Schuster, M. Heiblum, D. Mahalu, V. Umansky, Nature (London) 391 (1998) 871]. We use the non-equilibrium Green-Keldysh formalism and a second order perturbative treatment of the Coulomb interaction in order to compute the relevant transport properties. it is shown that in the presence of the Coulomb interaction the current through the detector exhibits oscillations as a function of the magnetic field applied on a single-dot AB interferometer. We also discuss the dependence of the visibility of the Aharonov-Bohm oscillations on the gate potential applied to the dot. (C) 2008 Elsevier B.V. All rights reserved.

2329. Coexistence of ferroelectricity and antiferroelectricity in epitaxial PbZrO3 films with different orientations

Authors: Pintilie, L; Boldyreva, K; Alexe, M; Hesse, D

Published: JAN 15 2008, JOURNAL OF APPLIED PHYSICS, 103, DOI: 10.1063/1.2831023

The temperature dependence of the ferroelectric hysteresis and capacitance in PbZrO3 epitaxial films with (120)(O) and (001)(O) orientations was investigated in the 4.2-400 K temperature range. It was found that the films with (120)(O) orientation show a mixture of ferroelectric and antiferroelectric phases on the entire temperature range up to room temperature, with the ferroelectric phase more stable at low temperatures. Above room temperature the (120)(O) oriented films seem to behave only as an antiferroelectric material. By contrast, films with (001)(O) orientation show only ferroelectric behavior up to a temperature of about 60 K when the single hysteresis loop splits into a double loop characteristic for antiferroelectrics. Above this temperature the (001)(O) oriented films show only antiferroelectric behavior up to 400 K. The temperature dependence of capacitance and loss tangent clearly shows a maximum at around 16 K in the case of the (001)(O) oriented film. This might be associated with a low temperature ferroelectric-antiferroelectric phase transition. However, this transition is not visible in the (120)(O) oriented films. (C) 2008 American Institute of Physics.

2330. Correlation of Structural and MW-MMW Dielectric Properties with Vibrational Modes in BaX1/3Ta2/3O3 Complex Perovskites

Authors: Toacsan, MI; Ioachim, A; Nedelcu, L; Banciu, MG; Mihut, L; Szilagyi, A

Published: 2008, 2008 33RD INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES, VOLS 1 AND 2, +, DOI:

Ceramic based Ba(Zn1/3Ta2/3)O-3 materials were prepared by solid-state reaction. Studies on microwave dielectric parameters in correlation with structural and Raman investigations were performed. Sintering temperatures higher than 1600 degrees C are required in order to obtain dielectric properties suitable for millimeter wave applications.

2331. Polaron activation energy as evidenced by EMR in colossal magnetoresistive nanowires

Authors: Popa, A; Toloman, D; Grecu, MN; Mihailescu, G; Darabont, A; Pop, CVL; Raita, O; Fardis, M; Idziak, S; Hoffmann, SK; Giurgiu, LM

Published: JUL 2008, APPLIED MAGNETIC RESONANCE, 34, 26, DOI: 10.1007/s00723-008-0097-5

In the present work an X-band electron magnetic resonance (EMR) investigation in the paramagnetic regime of colossal magnetoresistive manganite La2/3Ca1/3 MnO3 (LCMO) nanowires was carried out. The temperature dependence of the EMR line width has been analyzed in terms of the small polaron hopping scenario. From this analysis, the polaron activation energy E-a in LCMO nanowires was evaluated. A discussion is given concerning the factors which could explain the smaller value of E-a as compared with the corresponding ones for LCMO nanoparticles.

2332. Carbon nanowalls growth by radiofrequency plasma-beam-enhanced chemical vapor deposition

Authors: Vizireanu, S; Nistor, L; Haupt, M; Katzenmaier, V; Oehr, C; Dinescu, G

Published: APR 4 2008, PLASMA PROCESSES AND POLYMERS, 5, 268, DOI: 10.1002/ppap.200700120

We report the remote growth of carbon nanowalls in a plasma beam sustained by an expanding argon radiofrequency discharge and injected with a small amount of acetylene in the presence of hydrogen as active gas. The growth process was investigated by varying the mass flow rates, ratio and nature of gases (argon, ammonia/hydrogen, and acetylene), the substrate temperature, and the radiofrequency power. Scanning and transmission electron microscopy, Raman spectroscopy, and electron diffraction methods were used for the investigation of the deposited material. We found that although materials with various morphologies can be generally obtained, nanostructured carbon material with a 2D morphology is obtained with a specific range of parameter values.

2333. Magnetic characterization of some nanometric iron oxides

Authors: Grecu, VV; Constantinescu, S; Grecu, MN; Olar, R; Badea, M; Turcu, R

Published: APR 2008, HYPERFINE INTERACTIONS, 183, 214, DOI: 10.1007/s10751-008-9753-2

Nanosized magnetite particles embedded in polypyrrole matrix have been studied by Mossbauer and electron magnetic resonance spectroscopy. Comparison with as grown magnetite is made. Hyperfine fields distribution is determined and line shape of resonance curves are discussed in terms of composite structure, sizes and treatments.

2334. EIS studies of electrodeposition process of manganese and copper doped ZnO wires

Authors: Sima, M; Enculescu, I; Sima, M; Vasile, E; Visan, T

Published: MAR-APR 2008, SURFACE AND INTERFACE ANALYSIS, 40, 565, DOI: 10.1002/sia.2721

Electrodeposition of manganese- and copper-doped ZnO wires into polycarbonate membranes, from an aqueous solution containing 0.05 mol dm(-3) Zn(NO3)(2)+ 0.01 mol dm(-3) Mn(NO3)(2)+ 0.0005 mol dm(-3) Cu(NO3)(2)+ 0.0075 mol dm(-3) lactic acid, pH = 4.7 was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). The equivalent electrical circuits for fitting experimental results were similar to those for characterization of metal/polymer coating systems. impedance data and voltarnmetric curves showed that an increase of local pH due to reduction process of nitrate ions induces the co-precipitations of metal ions in the proximity of electrode as oxides. Copyright (c) 2008 John Wiley & Sons, Ltd.

2335. Comparative Study on the Microstructural and Magnetic Properties of Cobalt Ferrites Synthesized by Ceramic and Oxidation Wet Methods

Authors: Feder, M; Diamandescu, L; Bibicu, I; Caltun, OF; Dumitru, I; Boutiuc, L; Chiriac, H; Lupu, N; Vilceanu, V; Vilceanu, M

Published: NOV 2008, IEEE TRANSACTIONS ON MAGNETICS, 44, 2939, DOI: 10.1109/TMAG.2008.2002200

CoFe2O4 and CoMn0.2Fe1.8O4 ferrites were synthesized using standard solid state phase ceramic method and coprecipitation and oxidation method. X-ray diffraction, Mossbauer spectroscopy, and surface electron microscopy were used to characterize the samples' microstructures. Vibrating sample measurement and strain gauge technique were used to characterize the magnetic and magnetostrictive properties of both powders and sintered samples, respectively. The specific magnetization increased from 55 emu/g for stoichiometric ferrite samples obtained by conventional method to 179 emu/g for coprecipitated ferite powders respectively. In the manganese substituted cobalt ferrite case the specific magnetization increased only twice, from 77 emu/g to 168 emu/g. The maximum magnetostrictive coefficient of coprecipitated samples of 145 ppm is smaller compared to that of solid state phase ceramic samples of 195 ppm. The most important benefit in the case of the coprecipitated and oxidized samples is the four fold increase of the maximum strain derivative compared to solid state phase ceramic samples.

2336. A SOLID STATE NANO-GENERATOR: CONCEPT, DESIGN AND THEORETICAL ESTIMATIONS

Authors: Vopsaroiu, M; Cain, MG; Kuncser, V; Blackburn, J

Published: 2008, FUNCTIONALIZED NANOSCALE MATERIALS, DEVICES AND SYSTEMS, +, DOI: 10.1007/978-1-4020-8903-9_44

Nano-technology is a very attractive area of research and innovation because it allows the current trends in miniaturization to continue. The transition from micro scale to nano scale devices has already taken place in many applications such as electronics, magnetic recording and nano-biophysics. However, as we scale down the size of the structures and devices, it becomes obvious that the classical behavior will break down at the nano-scale and an interesting superposition of classical and quantum effects will emerge. Therefore, the validity of classical physics is questioned and many aspects of physics are now being revisited from the point of view of nano-technologies. In line with the new developments in miniaturization and nano-technologies, we propose in this letter a simple mechanism that applies the Faraday effect at the nano-scale in order to create a possible solid-state energy nano-generator device. The proposed nano-generator functionality is based oil what we shall call the Super-Paramagnetic Electromotive Force (SPEF) effect. This has the potential to produce a very small voltage on short time scales by converting directly thermal energy at room temperature to electromotive energy Without the need for external work or mechanical motion.

2337. Ab INITIO STUDY OF NEUTRAL OXYGEN VACANCIES IN RUTILE TiO2

Authors: Plugaru, R; Artigas, M; Plugaru, N

Published: 2008, CAS: 2008 INTERNATIONAL SEMICONDUCTOR CONFERENCE, PROCEEDINGS, +, DOI: 10.1109/SMICND.2008.4703393

We present results of ab initio. supercell calculations performed in the DFT-L(S)DA framework on rutile TiO2 phase with neutral oxygen vacancies (OVs), in the low defect concentration range (<= 6.25 at. %). The different OVs distributions in the supercell allow us to determine the localization and structure of the vacancy-induced states, the effect of vacancy concentration on the occupation numbers, as well as vacancy energetics. The present studs, benefits of the high accuracy in the total energy and band structure calculations of the full potential method utilized

2338. Structural evolution from the sol to the PbZrO3 precursor powders prepared by an alkoxide-based sol-gel route

Authors: Ion, ED; Malic, B; Arcon, I; Kodre, A; Kosec, M

Published: FEB 2008, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 45, 218, DOI: 10.1007/s10971-007-1655-2

PbZrO3 powders have been prepared by an alkoxide-based sol-gel route, starting from lead acetate, zirconium n-butoxide, and n-butanol as a solvent, and hydrolysed with different amounts of water in neutral and alkaline medium. The local environment of Zr and Pb atoms was pursued from the sol to the dried (150 degrees C) and heated (400 degrees C) powders, by extended x-ray absorption fine structure (EXAFS). The analysis of the sol revealed links between Pb and Zr, and even more links between Zr and Zr. The metal neighbourhoods in the dried powders are not influenced by the hydrolysis conditions. Pb-Zr correlations are gradually lost from the sol to the dried and heated powders, while the loss of Zr-Zr correlations is considerably lower.

2339. Depth profiling Raman spectroscopy of a thin YBa(2)Cu(3)O(7-delta) film

Authors: Branescu, M; Naudin, C; Gartner, M; Nemes, G

Published: SEP 30 2008, THIN SOLID FILMS, 516, 8194, DOI: 10.1016/j.tsf.2008.04.074

High spectral (1.5 cm(-1)) and spatial (similar to 1000 nm lateral and vertical) resolution Raman spectra taken at room temperature in the depth of a thin (350 nm) YBCO film with good superconducting properties are presented and discussed. The differences between Raman spectra corresponding to different depths in the film are interpreted as depth-dependant changes in the film's structure, degree of oxygenation, and superconducting properties. These changes are in agreement to what we expect from a film obtained by pulsed laser deposition technique. The resonance of the most significant Raman shift (500 cm(-1)), monitoring the oxygen content of YBCO films, for 488 nm excitation light, was used to overcome the relatively small penetration depth of visible light in YBCO (similar to 200 nm). We found the range of parameters for the depth profiling Raman system such as to obtain the maximum signal intensity and a reasonable number of distinctive Raman spectra corresponding to different depths of the YBCO film. (C) 2008 Elsevier B.V. All rights reserved.

2340. Synthesis and properties of Ba(Zn1/3Ta2/3)O-3 for microwave and millimeter wave applications

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Alexandru, HV; Antohe, S; Andronescu, E; Jinga, S; Nita, P

Published: FEB 15 2008, THIN SOLID FILMS, 516, 1562, DOI: 10.1016/j.tsf.2007.03.151

High dielectric materials have gained an important position in microwave electronics by reducing the size and cost of components for a wide range of applications from mobile telephony to spatial communications. Ba(Zn1/3Ta2/3)O-3 (BZT) is an A(B'B '')O-3 type perovskite material, showing ultra high values of the quality factor Q. Ceramic-based BZT dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1400 divided by 1600 degrees C for 4 h. Compositional, structural and morphological characterization were performed by using XRD, SEM and EDX analysis. The dielectric properties were measured in the microwave range (6 divided by 7 GHz). An additional annealing at 1400 degrees C for 10 h has improved some dielectric parameters. For samples sintered at temperatures higher than 1500 degrees C, the permittivity values were obtained in the interval 30 divided by 35 and almost do not change the value after the annealing. The Q x f product substantially increases up to about 135,000 GHz, exhibiting a low temperature coefficient of the resonant frequency (tau(f)) in microwaves. The best parameters were obtained for the samples sintered at 1600 degrees C with additional annealing. The achieved high values of the Q x f product recommend these materials for microwave and millimeter wave applications. (C) 2007 Elsevier B.V. All rights reserved.

2341. Radiation characteristics of a novel compact microstrip patch resonator

Authors: Militaru, N; Banciu, MG; Nedelcu, L; Lojewski, G

Published: 2008, ECCSC 08: 4TH EUROPEAN CONFERENCE ON CIRCUITS AND SYSTEMS FOR COMMUNICATIONS, +, DOI: 10.1109/ECCSC.2008.4611680

In this paper a new type of dual-mode compact resonator for mobile communication systems, in the 900 MHz frequency band, is investigated. This compact planar resonator, developed on a 0.635 mm substrate with a 10.8 dielectric constant, has a square shape with an edge of 20.5 mm. For this dual resonator, several methods of modes coupling were considered. The radiation characteristics of this new resonator were investigated.

2342. Combinatorial pulsed laser deposition of thin films

Authors: Craciun, V; Craciun, D; Mihailescu, IN; Socol, G; Stefan, N; Miroiu, M; Galca, AC; Bourne, G

Published: 2008, HIGH-POWER LASER ABLATION VII, PTS 1-2, 7005, DOI: 10.1117/12.782589

Pulsed Laser Deposition (PLD) is an ideal technique to be used for combinatorial approaches. By simply changing the deposition targets one can obtain alternating layers with different periodicities both vertically and laterally, along the substrate surface. By changing the laser impact area location and the number of pulses on each target used for ablation, one can grow films with a continuous variation of the chemical composition, which will be a function of the location on the substrate. To illustrate the advantages and versatility of this Combinatorial PLD (C-PLD) technique, several examples of films used in applications where more than one property should be tailored or optimized are presented. Investigations of thermo-chemical stability, chemical bonding and crystalline structure of thin films of mixtures of HfO2 and Al2O3 that are used as high-k dielectric layers in advanced C-MOS transistors is the first example, followed by a study of structural, mechanical, optical and electrical properties of mixtures of indium tin oxide and doped or pure zinc oxide that are used as transparent and conductive layers. The third example is from the deposition of multilayers of ZrC and ZrN with variable thicknesses to obtain hard coatings.

2343. FexOy nanoparticles embedded in sol-gel vitreous silica. The effect of the catalyst nature

Authors: Raileanu, M; Crisan, M; Braileanu, A; Dragan, N; Zaharescu, M; Stan, C; Predoi, D; Kuncser, V; Marinescu, VE; Hodorogea, SM

Published: JAN 15 2008, JOURNAL OF NON-CRYSTALLINE SOLIDS, 354, 631, DOI: 10.1016/j.jnoncrysol.2007.07.070

This work reports on recently investigated structural and magnetic properties of three FexOy-SiO2 nanocomposites prepared by the alkoxide route of the sol-gel method. Depending on the presence or absence of catalyst and on its nature (acidic or basic), important differences among the samples have been observed from the point of view of their structure and properties. (c) 2007 Elsevier B.V. All rights reserved.

2344. Influence of bilayer period on the characteristics of nanornetre-scale ZrN/TiAIN multilayers

Authors: Vladescu, A; Kiss, A; Popescu, A; Braic, M; Balaceanu, M; Braic, V; Tudor, I; Logofatu, C; Negrila, CC; Rapeanu, R

Published: FEB 2008, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 8, 721, DOI: 10.1166/jnn.2008.D218

in the last decade, considerable research effort was directed to the deposition of multilayer films with layer thicknesses in the nanometer range (superlattice coatings), in order to increase the performance of various cutting tools and machine parts. The goal of the present work was to investigate the main microstructural, mechanical and wear resistance characteristics of a superlattice coating, consisting of alternate multilayer ZrN/TiAIN films, with various bilayer periods (5 divided by 20 nm). The coatings were deposited by the cathodic arc method on Si, plain carbon steel and high speed steel substrates to be used as wear resistance surfaces. The multilayer structures were prepared by using shutters placed in front of each cathode (Zr and Ti + Al). The characteristics of multilayer structures (elemental and phase composition, texture, Vickers microhardness, thickness, adhesion, and wear resistance) were determined by using various techniques (AES, XPS, XRD, microhardness measurements, scratch, and tribological tests). A comparison with the properties of ZrN and TiAIN single-layer coatings was carried out.

2345. Magnetic properties of Sr2FeMo1-xMxO6 perovskites with M=W or Ta

Authors: Balasz, I; Burzo, E; Valeanu, M

Published: 2007, SIX INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION, 899, 763, DOI:

The Sr2FeMo1-xMxO6 perovskites with M = W or Ta and x <= 0.3 were studied by x-ray and electron microscopy. The magnetic and magnetoresistive properties were correlated with their microstructures. The effect of sintering time on their physical properties was analysed.

2346. Structure-property relationships in the xZnO-(1-x) alpha-Fe2O3 nanoparticle system

Authors: Sorescu, M; Diamandescu, L; Wood, J

Published: 2007, ZINC OXIDE AND RELATED MATERIALS, 957, +, DOI:

The xZnO-(1-x)alpha-Fe2O3 nanoparticles system has been obtained by mechanochemical activation for x=0.1. 0.3 and 0.5 and for ball milling times ranging from 2 to 24 hours. Structural and morphological characteristics of the zinc-doped hematite system were investigated by X-ray diffraction (XRD) and Mossbauer spectroscopy. As ZnO is not soluble in hematite in the bulk form, the present study clearly demonstrates that the solubility limits of an immiscible system can be extended beyond the limits in the solid state by mechanochemical activation. Moreover, this synthesis route allowed us to reach nanometric particle dimensions, which would make the materials very important for gas sensing applications.

2347. Antennas with prefractal geometry for wireless communications

Authors: Goga, G; Hongu, A; Nicolaescu, I; Banciu, MG; Ioachim, A

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI: 10.1109/SMICND.2007.4519704

Design, simulation fabrication and measurement of prefractal antennas for wireless communications are presented in this paper Two types of geometries, i.e. Sierpinski gasket and Koch curve, were investigated. The proposed antennas are compact, can operate for multiple frequency bands and exhibit small mutual coupling.

2348. Temperature dependence of the main piezoelectric parameters of a Nb-Li doped PZT ceramic

Authors: Miclea, C; Tanasoiu, C; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; David, C

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

A study was made on the temperature behavior of the main piezoelectric parameters, namely the electromechanical coupling factor k(p), the mechanical quality factor Q, the dielectric permittivity (real and imaginary part), the loss tangent t(g) and the piezoelectric charge constants 6133 and d(31) of a soft type piezoelectric material. It was evidenced that temperatures under 150 degrees C do not influence these parameters, which means that every transducer made from this type of material may be successfully used up to this temperature. Between 150 degrees C and 250 degrees C, the piezoelectric properties undergo more or less important changes, mainly due to the depoling effect. After that, at temperatures over 250 degrees C, they degrade very rapidly, tending to zero.

2349. Sintering behavior of hard-soft PZT-Type composite ceramics

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Spanulescu, I; Trupina, L; Cioangher, M; Miclea, CT

Published: 2007, FERROELECTRICS, 351, 186, DOI: 10.1080/00150190701354265

Functionally graded materials represent a new class of composite type materials characterized by a continuous variation of properties through the thickness direction. Due to this they found numerous applications in aerospace, automobile, biomedical or nuclear industries. Bilayered structures made from typically hard and typically soft PZT type materials as well as plain hard and soft and intimately mixed hard and soft samples were prepared by green pressed powdersfollowed by sintering at different temperatures between 1000 and 1300 degrees C. The dielectric and piezoelectric properties of sintered compacts were determined in relation with the nature of the interdiffusion layer involved. Electron microscopy as well as X-Ray diffractometry was used to get an insight into the interfacial diffusion process. The composition and the width of the interdiffusion layer depend on temperature. The mechanism of the interdiffusion layer and materials properties were discussed in terms of the ionic diffusion coefficients and activation energies of the species which take place into the diffusion process.

2350. Iron oxide in a silica matrix prepared by the sol-gel method

Authors: Predoi, D; Crisan, O; Jitianu, A; Valsangiacom, MC; Raileanu, M; Crisan, M; Zaharescu, M

Published: JUN 4 2007, THIN SOLID FILMS, 515, 6323, DOI: 10.1016/j.tsf.2006.11.148

FexOy-SiO2 nanocomposites were prepared by sol-gel method by using two SiO2 sources and Fe(SO4)(2)center dot 7H(2)O as raw materials. The amorphous gels were thermally treated up to 1000 degrees C. The initial gel and the thermally treated samples were characterized by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) and infrared spectroscopy. The presence of hematite was confirmed by the obtained Mossbauer spectra which showed the characteristic sextet. The total amount and the size distributions of the hematite nanoparticles can be controlled via the initial precursors and subsequent by annealing conditions. (C) 2006 Elsevier B.V. All rights reserved.

2351. Optical characterization of the phosphate glasses containing pair transition ions

Authors: Elisa, M; Grigorescu, C; Vasiliu, I; Bulinski, M; Kuncser, V; Predoi, D; Filoti, G; Meghea, A; Iftimie, N; Giurginca, M; Onose, C

Published: MAR 2007, OPTICAL AND QUANTUM ELECTRONICS, 39, 531, DOI: 10.1007/s11082-007-9097-1

The paper deals with optical and electronic properties of the aluminophosphate glasses containing Fe-Mn and Fe-Cr ion pairs in different concentration. The influence of the mixed alkali ions over the electronic properties has been investigated. The optical behavior (optical transmission) of the glass samples has been studied by UV-VIS spectroscopy and the refractive index dependency on wavelength has been discussed. The transmission spectra show features specific for the doping transition ions (TM), revealing different oxidation states of iron (Fe2+/Fe3+), manganese (Mn2+/Mn3+) and chromium (Cr3+/Cr6+) in the vitreous network. Mossbauer spectroscopy offers information regarding the TM oxidation states, redox processes and the iron coordination symmetry in the vitreous network. In the case of Fe-Mn doped glasses, the percentage of Fe2+ is about 40% and a doubled iron content leads to an increasing of Fe2+ percentage up to 53%. The replacing of lithium ions by natrium ions (mixed alkali effect) provides an increasing of the Fe2+ percentage up to 56%. The occurrence of the tetrahedral or octahedral symmetry of Fe(2+)supercript stop ions bonded by O2- ions depends on the transition ion nature and Li+/Na+ ratio. Infrared absorption spectra of the pair transition ions-doped aluminophosphate glasses reveal optical phonons specific for the phosphate glass matrix.

2352. Transitions of barium strontium titanate ferroelectric ceramics for different strontium content

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, A; Antohe, S; Berbecaru, C; Georgescu, L; Stoica, G; Alexandru, HV

Published: JUN 4 2007, THIN SOLID FILMS, 515, 6293, DOI: 10.1016/j.tsf.2006.11.097

Ceramic based barium strontium titanate (BST) solid solutions with the formula Ba1-xSrxTiO3 are very important candidates for a wide range device applications. Several doped (Mn and Mg) and undoped samples were prepared by standard solid-state reaction. Special emphasis was put on compositions with x=0.35 and 0.60, with high potential for applications. The samples were sintered at temperatures in the 1200 divided by 1260 degrees C range. Structural X-ray diffraction analysis preformed confirms the perovskite structure. The dielectric parameters were investigated in a wide temperature range between - 150 and 150 degrees C. The temperature was cyclically changed in both directions, up and down, at a rate of less than 2 degrees C/ min. Both permittivity and dielectric loss were measured at low frequencies, 1 kHz. The peak values of the permittivity are increasing from 2000 to 4000 with the sintering temperature increase. Moreover the dielectric parameters were measured at room temperature in microwave domain (1 divided by 2 GHz). The Curie temperature of BST samples with x=0.35 and x=0.6 is in agreement with the Curie point dependence on Sr content, as we have previously reported. (C) 2007 Published by Elsevier B.V.

2353. Study of non catalytic oxidehydrogenation of isobutane in an integral reactor

Authors: Grecu, MN; Burducea, G; Grecu, V; Moldovan, R; Beica, T; Zgura, I

Published: MAR 2007, REVUE ROUMAINE DE CHIMIE, 52, 281, DOI:

X-band ESR spectra of the calamitic and discotic lyotropic nematic phases in sodium dodecyl sulphate (SDS)/decanol/water system, doped with paramagnetic nitroxide free radicals are analyzed in this paper. The studied temperature range was chosen to include phase transitions of the lyotropic systems. The variation of the surfactant hydrocarbon chains ordering versus temperature is determined by the hyperfine splitting tensor (,4) and the spectroscopic splitting tensor ((g) under bar) anisotropies. The temperature dependence of the molecular order parameters for both lyotropic systems and the corresponding angular fluctuations are presented and discussed.

2354. Barium strontium titanate-based perovskite materials for microwave applications

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Vasiliu, F; Alexandru, HV; Berbecaru, C; Stoica, G

Published: 2007, PROGRESS IN SOLID STATE CHEMISTRY, 35, 520, DOI: 10.1016/j.progsolidstchem.2007.01.017

Ba1-xSrxTiO3 solid solutions were prepared by solid-state reaction from raw materials. Four compositions with x = 0.25, 0.50, 0.75 and 0.90 have been investigated. The perovskite type and polycrystalline structure of the BST samples were revealed by X-ray diffraction data. The morphology, grain size distribution, porous structure and elemental composition of the sintered ceramics were analyzed by using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) microanalysis. The temperature dependence of permittivity and of dielectric loss tangent at low frequency (1 kHz) showed decrease of Curie temperature with increase of Sr content. Microwave measurements (1 GHz) showed substantial decrease of the dielectric constant from about 1600 to 200 and also of the losses from 12% to less than 2% with the Sr concentration increase from x = 0.25 to x = 0.90. Moreover, the addition of MgO and MnO2 1 wt.% each, improved sintering process and lowered the microwave losses up to 0.2%. (c) 2007 Elsevier Ltd. All rights reserved.

2355. Properties of TiO2 thin films deposited by RF magnetron sputtering

Authors: Sima, C; Waldhauser, W; Lackner, J; Kahn, M; Nicolae, I; Viespe, C; Grigoriu, C; Manea, A

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1449, DOI:

TiO2 thin films deposited by RF magnetron sputtering have been investigated. The films were deposited on glass, ITO/glass and silicon at room temperature. The deposition was carried out in different experimental conditions, starting from a pure Ti target. We studied the influence of the experimental deposition parameters (power sputtering, Ar and O-2 flow rate) on the film properties' The deposition typical conditions were 300-500 W, 10-45 sccm Ar, 3.3-30 sccm O-2, at a pressure around 2.7x10(-3) mbar. The film structure, morphology, deposition rate, and optical transmission were investigated. Rutile phase was obtained. The titania films deposited with a rate 4-16 nm/minute had 50-1500 nm thickness. Two kinds of TiO2 films have been obtained depending on the experimental conditions'. nanocrystalline films with roughness of 3-10 nm and another one with droplets 2-8 mu m. The optical transmission in the visible range was between 70 and 95%.

2356. Thermoluminescence and optically stimulated luminescence of gamma-irradiated mineral zircon

Authors: Secu, M; Vainshtein, D; Turkin, A; den Hartog, HW

Published: 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 3, 4, +, DOI: 10.1002/pssc.200673738

Thermoluminescence (TL) manifested by gamma-irradiated mineral zircon has shown a strong TL peak at about 165 degrees C which is due to recombination of electrons and Dy3+ related shallow hole traps. After they have been removed by a short preheat we have observed two TL peaks at 300-320 degrees C and approximate to 420 degrees C, which are mainly due to recombination of electrons and Tb3+ related hole traps centres yielding its characteristic luminescence. The experimental results indicate that optically stimulated luminescence (OSL) is due to luminescent emission of Tb3+ ions and [SiO4](4-) groups. The deep traps related to the 420 degrees C TL peak contribute to the Tb3+ related OSL. The deep traps related to the 300-320 degrees C TL peak contribute to OSL associated with the luminescent emission of [SiO4](4-) groups. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhem.

2357. Structural and optical properties of the SiO2-P2O5 films obtained by sol-gel method

Authors: Vasiliu, I; Gartner, M; Anastasescu, M; Todan, L; Predoana, L; Elisa, M; Negrila, C; Ungureanu, F; Logofatu, C; Moldovan, A; Birjega, R; Zaharescu, M

Published: JUN 4 2007, THIN SOLID FILMS, 515, 6605, DOI: 10.1016/j.tsf.2006.11.106

A comparative study of the sol-gel films prepared in the SiO2-P2O5 system starting with triethylphosphate, triethylphosphite and phosphoric acid as P precursors was performed. The work addresses basic aspects of physics, chemistry, and engineering of oxide films for applications in microelectronics, sensing, nano-photonics, and optoelectronics by establishing the influence of different precursors on the composition, structure and optical properties of the obtained films. The influence of the type of substrate (glass and indium tin oxide coated glass) and of the thermal treatment (200 and 500 degrees C on their structure and properties was studied. By spectroscopic ellipsometry, X-Ray photoemission spectroscopy and atomic force microscopy measurements the high vaporization of the phosphorous during the densification of the films by thermal treatment was noticed when P-alkoxides were used. The phosphoric acid that forms chemical bond with silica network during the sol-gel process leads to better incorporation of P in the silica network as compared to the P-alkoxides. (C) 2006 Elsevier B.V. All rights reserved.

2358. Dielectric properties of fine grains barium titanate ceramics prepared by mechanochemical synthesis

Authors: Miclea, C; Tanasoiu, C; Spanulescu, I; Miclea, CF; Gheorghiu, A; Amarande, L; Cioangher, M

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

Barium titanate was prepared by the advanced procedure of mechanochemical synthesis from barium and titanium oxides after 50 hours of milling. The X-ray examination of the milled powders showed the phase evolution during synthesis and the perovskite phase was initiated after 5 hours and was completed after 50 hours. Sintered samples from these nanopowders show different dielectric properties for fine and coarse grained ceramics. Samples with an average grain size of 2 mu m showed the highest dielectric constant of 5800 at room temperature. A sharp maximum of the dielectric constant with values of about 16000 was recorded at the Curie temperature.

2359. Preliminary study on detection of irradiated foodstuffs from the Romanian market

Authors: Cutrubinis, M; Chirita, D; Savu, D; Secu, CE; Mihai, R; Secu, M; Ponta, C

Published: AUG-SEP 2007, RADIATION PHYSICS AND CHEMISTRY, 76, 1454, DOI: 10.1016/j.radphyschem.2007.02.049

In order to fulfil the European task for market survey in food irradiation the first Romanian laboratory for detection of irradiated foodstuffs was established at IRASM Irradiation Centre. In this preliminary study, a wide range of Romanian food samples (spices, vegetables and meat) gamma irradiated at IRASM have been studied using different detection methods: (1) DNA comet assay, (2) thermoluminescence (TL) and (3) electron spin resonance (ESR) for foodstuffs containing bone or cellulose. The results suggest that there is no general available detection method and there is no perfect detection method. In conclusion, in order to carry out a correct identification of radiation treatment of a food sample it is recommended to use at least two standardised detection methods. (c) 2007 Elsevier Ltd. All rights reserved.

2360. Sequence of phases in the hydrothermal synthesis of zinc-doped magnetite system

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D; Teodorescu, V

Published: DEC 15 2007, MATERIALS CHEMISTRY AND PHYSICS, 106, 278, DOI: 10.1016/j.matchemphys.2007.06.001

Hydrothermal techniques have been used to synthesize samples of ZnxFe3-O-x(4) (x = 0.0-1.0) starting with ZnSO4 center dot 7H(2)O/FeSO4 center dot 7H(2)O aqueous solution. The sequence of phases, structural and magnetic properties were followed by X-ray diffraction (XRD), Mossbauer spectroscopy and transmission electron microscopy (TEM). Refinement of the XRD spectra yielded the dependence of the lattice parameters of zinc-doped magnetite and zinc ferrite phase as function of the Zn molar concentration x. As well, the particle diameter was derived and represented as a function of Zn content x. As a function of Zn concentration, the phase content of hydrothermally synthesized samples was found to consist of zinc-doped magnetite, goethite and zinc ferrite. Consistent with the XRD results, Mossbauer spectroscopy data indicate the presence of magnetite and goethite at x <= 0.2, magnetite and zinc ferrite at x <= 0.9 and pure zinc ferrite only at high zinc concentrations. The presence of different magnetite phases was confirmed by TEM and particles with a size of 50 nm were identified. Our results show that zinc ferrite is formed at high zinc concentration by the hydrothermal method and an acicular component of goethite-magnetite is obtained at low zinc content. (C) 2007 Elsevier B.V. All rights reserved.

2361. Structure, properties and gas sensing effect of SnSe2 films prepared by pulsed laser deposition method

Authors: Popescu, M; Sava, F; Lorinczi, A; Socol, G; Mihailescu, IN; Tomescu, A; Simion, C

Published: JUN 15 2007, JOURNAL OF NON-CRYSTALLINE SOLIDS, 353, 1869, DOI: 10.1016/j.jnoncrysol.2007.02.055

Amorphous SnSe, films were prepared by pulsed laser deposition (PLD) from solid polycrystalline targets. The atomic scale structure has been revealed by X-ray diffraction. Hardness and electrical properties were measured. Strong gas sensing properties have been evidenced for the first time in heat treated films. (c) 2007 Elsevier B.V. All rights reserved.

2362. Magnesium doped (Zr-0.8, Sn-0.2)TiO4 ceramics for microwave devices

Authors: Nedelcu, L; Ioachim, A; Toacsan, MI; Banciu, MG; Dutu, CA; Lifei, F; Vasiliu, F; Stoica, G

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1729, DOI:

Magnesium doped (Zr0.8Sn0.2)TiO4 material has been prepared by solid state reaction and characterized. The samples were sintered in the temperature range of 1270 divided by 1315 degrees C for 2 hours. The effect of sintering temperature on structural and dielectric properties was investigated. The 0.2 wt.% MgO addition improves the sintering process and well sintered samples with a high value of bulk density were achieved. The material exhibits a dielectric constant epsilon(r) similar to 36.6 and high values of the Qxf product, greater than 61000 at microwave frequencies. The dielectric properties make the magnesium doped (Zr0.8Sn0.2)TiO4 material very attractive for such microwave applications as dielectric resonators, filters, dielectric antennas, substrates for hybrid microwave integrated circuits, etc.

2363. New polymeric structures designed for the removal of Cu(II) ions from aqueous solutions

Authors: Mocioi, M; Albu, AM; Mateescu, C; Voicu, G; Rusen, E; Marculescu, B; Mutihac, L

Published: FEB 5 2007, JOURNAL OF APPLIED POLYMER SCIENCE, 103, 1405, DOI: 10.1002/app.24655

New polymeric structures obtained by chemical transformations of maleic anhydride/dicyclopentadiene copolymer with triethylenetetraamine, p-aminobenzoic acid, and p-aminophenylacetic acid were used for the removal Cu(II) ions from aqueous solutions. The experimental values prove the importance of the chelator nature and of the macromolecular chain geometry for the retention efficiency. The retention efficiency (eta(r)), the retention capacity (Q(e)), and the distribution coefficient of the metal ion into the polymer matrix (K-d) are realized by evaluation of residual Cu(II) ions in the effluent waters, by atomic adsorption. Also are discussed the influence of pH, the thermal stability of the polymer, and their polymer-metal complex, as well as the particular aspects regarding the contact procedure and the batch time. Based on the polymers and polymer-metal complexes characterization a potential retention mechanism is proposed. All polymer supports as well theirs metal-complexes are characterized by ATD and FTIR measurements. (c) 2006 Wiley Periodicals, Inc.

2364. Some contributions to the understanding of the puzzle of physical processes of degradation in irradiated silicon

Authors: Lazanu, S; Lazanu, I; Ciurea, ML

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI:

In the present paper, we intend to bring some clarifications related to the role played by primary defects in long term degradation, to the dependence of degradation on the orientation of the wafer, as well as on the spatial distribution of the degradation produced by low energy particle irradiation.

2365. On the anomalous microwave power dependency of both non-resonant and CU2+ resonant microwave absorption in a YBa2CU3O7-delta type superconductor

Authors: Velter-Stefanescu, M; Duhu, OG

Published: 2007, SIX INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION, 899, 668, DOI:

A ceramic high temperature superconductor [HTS] of Y-Ba-Cu-O type has been investigated at 77 K by using a standard X-band Electron Paramagnetic Resonance (EPR) configuration. At very low microwave power (< 1 mW) the non-resonant or zero field signal (ZFS) was in phase with DPPH signal, pleading for an unambiguous absorption process, but it commutes to a typical superconductor signal (i.e. opposite to DPPH signal phase) with increasing the microwave power. At the same time, CU2+ signal appreciably changes its shape with increasing microwave power. These anomalous behaviors could be in part explained by a conventional SQUID response at microwave frequency by taking into account that the sample itself could be described by a collection of both Josephson and proximity junctions.

2366. Couplings control in a compact microstrip dual-mode resonator

Authors: Banciu, MG; Ioachim, A; Ramer, R; Militaru, N; Lojewski, G

Published: SEP 2007, MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, 49, 2295, DOI: 10.1002/mop.22722

A compact microstrip dual-mode resonator with slots in the ground plane is presented in this paper. Several methods for coupling between the dual modes are investigated. One of the methods involves using slots in the ground plane in order to enhance the external coupling and to introduce the necessary perturbation to the initially symmetrical structure. The proposed device requires a surface area about 6 tunes smaller than the area needed for a conventional patch dual-mode resonator. (C) 2007 Wiley Periodicals, Inc.

2367. Obtaining of Ni base intermetallic alloys by solidification control

Authors: Lucaci, M; Orban, RL; Lazarescu, M; Gavriliu, S; Lungu, M; Patroi, D

Published: 2007, MATERIALS AND TECHNOLOGIES, 23, +, DOI: 10.4028/www.scientific.net/AMR.23.283

Directional solidification techniques have been applied to produce Ni based intermetallic alloys with preferentially oriented columnar crystals extended along the complete length and parallel to the solidification direction. Enhanced ductility is expected from such alloys. In this paper we present the research results concerning the application of this technique to some complex Ni3Al-Fe-B alloys obtained from compacted mixtures of elemental powders. The corresponding master alloys have been obtained in a vacuum induction furnace by the known Exo-Melt process [1]. The directional solidification of these alloys was subsequently performed on cylindrical samples, at two solidification rates, 30 and 15 mm/h. The influence of the rate and composition used on the dimensional variations, densities, microstructure, constituent phases and lattice parameters, as well as on the surface chemical composition have been documented and are presented in the paper.

2368. The colloidal route of the sol-gel process - an alternative to produce Fe3O4-SiO2 nanocomposites

Authors: Raileanu, M; Crisan, M; Ballo, A; Cosma, C; Petre, J; Stan, C; Predoi, D; Valsangiacom, CM; Tolea, F; Secu, C

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1402, DOI:

The iron oxide-based nanomaterials have a great importance because of their impact on a wide number of industries. They have many properties and applications in domains as: environmental protection, biomedical, catalysis, information displays and electronics. In order to avoid the tendency of nanoparticles to aggregate, they are often included in sol-gel derived silica matrices, thus being also ensured a homogeneous dispersion of the ultra-fine metal oxide particles in the host matrix. The reasons of the attempt are both an economic and a non-pollutant one, tacking into account the fact that it is well known that aqueous silica sol is cheaper and less toxic than TEOS. The Fe3O4 was introduced in the reaction mixture as aqueous suspension. A final iron content related to SiO2 of 3% wt. was chosen for the prepared nanocomposite. Thermal analysis, IR spectroscopy, XRD and TEM methods have been used for the structural characterisation,. Some experiments of water depollution (from As) have been proceeded using the prepared Fe3O4-SiO2 nanocomposite.

2369. Effect of the sintering temperature on the Ba(Zn1/3Ta2/3)O-3 dielectric properties

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Feder, M; Plapcianu, C; Lifei, F; Nita, P

Published: 2007, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 27, 1122, DOI: 10.1016/j.jeurceramsoc.2006.05.023

Preparation of dielectric materials with optimal properties for wireless applications requires special thermal treatments due to the difficult control of the cationic ordering. The BZT samples prepared by solid-state reaction were sintered at temperatures in the range 1400-1600 degrees C for 4 h. For compositional, structural and morphological characterization, XRD, SEM and EDX were employed. The order-disorder transition of the BZT material was analyzed. With the increase of the sintering temperature, a long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was observed. The dielectric parameters were measured in the microwave range and were correlated with morphological and structural properties. In order to improve the microwave properties, annealing treatment at 1400 degrees C for 10 h was performed. Sintering temperatures greater than 1550 degrees C are required for undoped BZT compositions, in order to obtain low microwave loss (Qf > 100,000). (c) 2006 Elsevier Ltd. All rights reserved.

2370. A. comparative study of micro crystalline and nanocrystalline lead sulfide based PbS/SiO2/Si heterostructures

Authors: Stancu, V; Pentia, E; Goldenblum, A; Buda, M; Iordache, G; Botila, T

Published: 2007, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 10, 66, DOI:

The PbS micro-crystalline and nano-crystalline films were obtained using the Chemical Bath Deposition method. We investigated comparatively the structural, electrical and photoconductive properties of these films deposited on glass. PbS/SiO2/Si heterostructures made with nanocrystalline PbS layers present interesting peculiarities. Their C-V curves show hysterezis. In a field effect arrangement it is possible to control the photoconductive short and long wavelength ratio response. The heterostructure properties were explained by taking into account the interface charged traps.

2371. Irreversible magnetization above critical temperature in superconducting Y0.47Pr0.53Ba2Cu3O7-delta

Authors: Sandu, V; Gyawali, P; Katuwal, T; Amasan, CC; Taylor, BJ; Maple, MB

Published: 2007, SIX INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION, 899, +, DOI:

Using magnetization measurements, we report the existence of an irreversibility in the magnetization in Y0.47Pr0.53Ba2Cu3O7-delta single crystals above the critical temperature (T-c = 13 K) that is visible up to 200 K. Magnetization vs temperature displays irreversibility up to an applied field of 500 Oe. We noticed a weak irreversibility at high temperatures and a stronger one at low temperatures. In the weak irreversibility regime, both zero-field- and field-cooled magnetization follow similar Curie-Weiss (C-W) dependences, with slightly different parameters. The C-W parameters, decrease fast with increasing field. The C-W temperature is negative, suggesting that the average interaction between spins is antiferromagnetic. All these data suggest that the paramagnetic state is in fact a free spin liquid containing floating antiferromagnetic clusters as well as superconducting phase fluctuations.

2372. FSDP-related correlations in chalcogenide glasses

Authors: Kavetskyy, T; Shpotyuk, O; Popescu, M; Lorinczi, A; Sava, F

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3081, DOI:

A first sharp diffraction peak (FSDP) is the most sensitive characteristic to medium range order in non-crystalline solids with speculative origin up to now. The compositional trends in the FSDP position and full width at half maximum are tested on the example of pseudo-binary Sb2S3-As2S3 and Sb2S3-GeS2 systems of chalcogenide glasses. The FSDP-related correlations are found for the investigated materials and considered in terms of packing factor of amorphous layers and experimental density of glass.

2373. High temperature thermolumineseence of BaFCl : EU2+ X-ray storage phosphor

Authors: Secu, CE; Secu, M; Predoi, D

Published: 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 3, 4, +, DOI: 10.1002/pssc.200673736

Thermoluminescence (TL) of Eu2+-doped BaFCl polycrystalline powders X- ray irradiated at room temperature show several TL peaks at 364 K, 408 K, 470 K, 524 K and 646 K. Thermally activated recombination processes responsible for TL have been studied using complementary techniques as TL and its bleaching, diffuse reflectance, X-ray excited luminescence (XL) and photostimulated luminescence (PSL). Experimental results indicate that F(Cr) centres are the dominant electron trap centres, the Eu2+-trapped hole aggregate centres playing the role of recombination centres. The 470 K and 646 K TSL glow peaks are assigned to the recombination inside the triple aggregates (Eu2+ - hole centre - F(Cl-) centre). The remaining 408 K and 524 K TL peaks are tentatively assigned to recombination between F centres and double aggregates (Eu2+ - hole centre). (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2374. Formation of icosahedral phase in an Al93Fe3Cr2Ti2 bulk alloy

Authors: Kim, KB; Xu, W; Tomut, M; Stoica, M; Calin, M; Yi, S; Lee, WH; Eckert, J

Published: JUN 14 2007, JOURNAL OF ALLOYS AND COMPOUNDS, 436, L4, DOI: 10.1016/j.jallcom.2006.06.106

The microstructural investigation of a suction-cast Al93Fe3Cr2Ti2 bulk alloy reveals that an icosahedral phase forms together with monoclinic Al-13(Fe,Cr)(4) and tetragonal Al3Ti in an alpha-Al matrix. The icosahedral phase is often surrounded by Al3Ti particles indicating that the formation of the icosahedral phase strongly competes with the Al3Ti phase. Chemical analysis reveals that Ti has a strong influence to stabilize the Al3Ti phase. In contrast, both Cr and Fe are effective to stabilize the icosahedral phase. (C) 2006 Elsevier B.V. All rights reserved.

2375. Transport through a multiply connected interacting mesoscopic system using the Keldysh formalism

Authors: Dinu, IV; Tolea, M; Aldea, A

Published: SEP 2007, PHYSICAL REVIEW B, 76, DOI: 10.1103/PhysRevB.76.113302

We apply the Keldysh formalism in order to derive a current formula easy to use for a system with many sites, one of which is interacting. The main technical challenge is to deal with the lesser Green's function. It turns out that, in the case of the left-right symmetry, the knowledge of the lesser Green's function is not necessary and an exact current formula can be expressed in terms of retarded Green's functions only. The application is done for a triangular interferometer which gives a good account of the Fano-Kondo effect. It is found that the interference effects, in the context of Kondo correlations, give rise to a point in the parameter space where the conductance is temperature independent. We include a comparison with the results from Ng's ansatz [Phys. Rev. Lett. 70, 3635 (1993)], which are less accurate, but can be used also in the absence of the above mentioned symmetry.

2376. Thermal treatments effects on microwave dielectric properties of Ba(Zn1/3Ta2/3)O-3 ceramics

Authors: Ioachim, A; Toacsan, MI; Nedelcu, L; Banciu, MG; Dutu, CA; Andronescu, E; Jinga, S

Published: 2007, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 10, 268, DOI:

Ba(Zn1/3Ta2/3)O-3 dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1 400 divided by 1 600 degrees C for 4 h. Morphostructural characterization was performed by using SEM and XRD. The dielectric properties were measured in the microwave range (6 divided by 7 GHz). An additional annealing at 1 400 degrees C for 10 hours was performed in order to improve the dielectric parameters. The best parameters were achieved for the samples sintered at 1 600 degrees C with additional thermal treatment.

2377. Pulsed laser deposition of co-based Tailored-Heusler alloys

Authors: Grigoreseu, CEA; Valerio, E; Monnereau, O; Tortet, L; Argeme, L; Pavelescu, G; Manea, SA; Ducu, C; Malinovski, A; Trodahl, HJ; Bittar, A; Strickland, N; Notonier, R; Branford, WR; Autric, M

Published: JUL 31 2007, APPLIED SURFACE SCIENCE, 253, 8106, DOI: 10.1016/j.apsusc.2007.02.133

Thin films of nonstoichiometric Heusler alloys Co2MnSbxSn1-x (x = 0.2; 0.4; 0.6; 0.8) have been grown by pulsed laser deposition (double-target/double beam configuration) on Si (10 0) substrates using a KrF excimer laser (lambda = 248 nm, tau = 20 ns). The substrate temperature was held at 300 K in all experiments to prevent interface interdiffusion of the species. A comparison between the compositions of films and corresponding targets has been done through energy dispersive X-ray spectroscopy (EDS) analysis showing a very satisfactory match. Scanning electron microscopy (SEM) imaging served to investigate the morphology of the films in order to determine the size and density of droplets which may influence the optical data. Optical conductivity derived from reflectivity measurements shows absorption onsets close to 1eV, which corresponds to the onset of valence-to-conduction transitions in the minority spin bands theoretically predicted. The values of the saturation magnetisation measured at 300 K on the quaternary alloys are very close to those of ternary ones for which either half-metallic properties or high spin polarisation were theoretically predicted. (c) 2007 Elsevier B.V. All rights reserved.

2378. Effects of chemical structure on the electrical properties of some polymers with imidic structure

Authors: Cosutchi, AI; Hulubei, C; Buda, M; Botila, T; Ioan, S

Published: JUN 26 2007, E-POLYMERS, DOI:

The electrical properties of two types of imidic polymers, i.e. copolymaleimides containing azobenzene groups and epiclon-based polyimides with their corresponding poly( amic acid)s, have been investigated. The dielectric constant and electrical conductance were experimentally measured over the 1-100 KHz frequency range. Also, the dielectric constants for all samples were determined from the experimentally and theoretically evaluated refractive indices at optical frequencies, when Maxwell's relationship can be applied. From the current-voltage characteristic I( U), electrical resistance can be determined, providing information on the relationship between the nature of the material and its electric properties. The obtained values show that epiclon-based polyimides and copolymaleimides present higher electrical resistivity than the poly( amic acid) s. The dissipation factor was evaluated, revealing low energy loss under the form of heat in the studied dielectrics. These results show that these polymeric materials are good insulators, which recommends them for microelectronic applications.

2379. Structural and magnetic properties of FexOy nanoparticles dispersed in silica matrix

Authors: Predoi, D; Clerac, R; Raileanu, M; Crisan, M; Zaharescu, M

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1498, DOI:

Some FexOy-SiO2 composites were prepared by the colloidal and alkoxidic route of the sol-gel method. The dried gels were thermally treated and the samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared absorption (IR) spectroscopy, magnetic susceptibility measurements and Mossbauer spectroscopy. Nanoparticles of gamma and /or alpha iron oxide phase of different size were obtained in the silica matrix depending on the gelation conditions and on the thermal treatment. It was observed that the particle sizes and the thermal stability of the iron oxide phases strongly depend on the preparation method. At temperatures above 400 degrees C, the gamma-phase begins to transform to the alpha-phase.

2380. Spectral response of Au-Ti Schottky barrier on semi-insulating GaAs

Authors: Ghita, RV; Logofatu, C; Negrila, C; Cotirlan, C; Ghita, P; Manea, AS; Lazarescu, MF

Published: APR 2007, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 204, 1029, DOI: 10.1002/pssa.200674107

For the fabrication of the rectifying contact, respectively the Schottky diode structure on semi-insulating GaAs (100) oriented, Cr-doped, with a resistivity of rho similar to 10(6) - 10(7) Omega cm we have used Au-Ti contact. The Ti contact was deposited on a plasma etched GaAs surface in high vacuum (10(-8) torr), Au was deposited in medium vacuum (10(-6) torr) and the Au-Ti/GaAs interface was formed by a rapid thermal annealing procedure at T = 320 - 360 degrees C in low vacuum (10(-1) torr). The representative I-V characteristics in dark and under illumination at different power levels are presented. It is worth to mention that we estimate a barrier height of Phi(B) similar to 0.84 V (in the frame of thermionic emission model). The spectral response at two operating points and at different temperatures is presented. The signal has a maximum in the Delta lambda range (850-950) nm, which corresponds to the generation of photo-carriers due to a band-to-band direct transition. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2381. The atomic scale modelling of nanomaterials

Authors: Popescu, M

Published: MAY-JUN 2007, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 68, 694, DOI: 10.1016/j.jpcs.2007.02.050

Atomic scale modelling of various nano-clusters has been pet-formed. Amorphous/crystalline transition has been modelled in phase change memory materials. The modelling gives the possibility to select the physically realistic configurations, to be prepared and applied in nano-devices. (c) 2007 Elsevier Ltd. All rights reserved.

2382. Fractal characteristics of metal clusters self-assembled in alkali halide matrices

Authors: Enculescu, M; Enculescu, I

Published: 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 3, 4, +, DOI: 10.1002/pssc.200673716

Metal nanoclusters of Ag and An were obtained in alkali halide crystals (NaCl, KBr and KCl). The fractal character of the structures is proved by the fractal dimensions calculated using a home made computer program. The self aggregation of the metallic structures is governed in both cases (Ag and Au) by the DLA mechanism. This is proved by the values of the fractal dimension calculated using two methods, sandbox and box-counting, which are between 1.7 and 1.8 for Ag and for Au between 1.7 and 1.9. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2383. Atomic structure of As25Si40Te35 glass

Authors: Kaban, I; Gruner, S; Jovari, P; Kehr, M; Hoyer, W; Delaplane, RG; Popescu, M

Published: AUG 22 2007, JOURNAL OF PHYSICS-CONDENSED MATTER, 19, DOI: 10.1088/0953-8984/19/33/335210

Glassy As25Si40Te35 has been studied by x-ray and neutron diffraction as well as x-ray absorption spectroscopy ( EXAFS) at As and Te K-edges. Simultaneous modelling of the four independent measurements by means of the reverse Monte Carlo ( RMC) simulation technique allowed the separation of partial pair distribution functions and estimation of the corresponding coordination numbers. It is shown that the atomic structure of As25Si40Te35 glass can be presented as a three-dimensional network of twofold coordinated Te, threefold coordinated As and fourfold coordinated Si atoms.

2384. Annealing effects on properties of Ba(Zn1/3Ta2/3)O-3 dielectric materials

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Andronescu, E; Jinga, S

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

Ba(Zn1/3Ta2/3)O-3 dielectric materials were prepared by, solid state reaction. The samples were sintered at temperatures in the range 1400 divided by. 1600 degrees C for 4 h. Morphostructural characterization was performed by using SE l and XRD. The dielectric properties were measured in the microwave range (6 divided by 7 GHz). An additional annealing at 1400 degrees C for 10 hours was performed in order to improve the dielectric parameters. The best parameters were achieved for the samples sintered at 1600 degrees C with additional thermal treatment.

2385. Planar microwave bandpass filters with defected ground resonators

Authors: Militaru, N; Lojewski, G; Banciu, MG

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

In this paper a study of some planar microwave band pass filters composed of defected ground resonators is presented. Different kinds of couplings between two defected ground resonators are investigated: electric coupling, magnetic-coupling different mixed couplings. The values of the coupling and two coefficients are extracted from the simulation results, obtained by using a full-wave EM-field simulation software. On the basis of this study, some second-order coupled planar microwave bandpass Chebyshev of Chebyshev filters are designed. The simulated performances of these novel filter structures are very close to the filler requirements, validating this way the design method and its results.

2386. Preparation of Ba2Ti9O20 from oxalates

Authors: Cernea, M

Published: JUL 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2261, DOI:

A barium titanate precursor with barium: titanium ratio of 2: 9 was prepared by coprecipitation of mixed barium and titanium chlorides with ammonium oxalate aqueous solution at pH 7-7.5. Single-phase of Ba2Ti9O20 crystallised in the triclinic system and dense ceramic are obtained by sintering at 1375 degrees C for 4-8.5 h. The grain size of the sintered ceramics is 3 to 5 mu m. Dielectric properties of the sintered ceramics in the microwave frequency region were measured using the TE0(11) mode. Good microwave characteristics for Ba2Ti9O20 Were found. At 5 GHz, the dielectric constant and the dielectric loss (tg sigma) were 36 respectively, 0.6x10(-3). The quality factor due to dielectric loss at 5 GHz was similar to 1700.

2387. Novel microwave bandpass filters using defected-ground structures

Authors: Mititaru, N; Banciu, MG; Lojewski, G

Published: APR 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1064, DOI:

In this paper a study of some microwave microstrip bandpass filters (BPF) using defected ground structures (DGS) is presented. This technique allows designs of tight couplings without the necessity of using very narrow coupling gaps. Based on the results of the study, four-pole cross-coupled planar microwave bandpass filters with a single and with two ground slots are designed, fabricated and measured. The performances of these novel structures indicate some technological advantages, compared to classical microstrip filters, without defected ground.

2388. Superconductivity in the complex metallic alloy beta-Al3Mg2

Authors: Bauer, E; Kaldarar, H; Lackner, R; Michor, H; Steiner, W; Scheidt, EW; Galatanu, A; Marabelli, F; Wazumi, T; Kumagai, K; Feuerbacher, M

Published: JUL 2007, PHYSICAL REVIEW B, 76, DOI: 10.1103/PhysRevB.76.014528

Transport and thermodynamic properties were studied for the complex metallic compound beta-Al3Mg2, composed of 925 atoms per unit cell. beta-Al3Mg2 exhibits bulk superconductivity below T-c=0.87 K. An exponential temperature dependence of the specific heat well below T-c indicates BCS-like behavior with a nodeless gap of width Delta(BCS)(0)approximate to 1.5 K. The coherence length is derived as xi(0)=4.85x10(-8) m and the Ginzburg Landau parameter kappa(GL)approximate to 13, characterizing beta-Al3Mg2 as a type II superconductor. Superconductivity in beta-Al3Mg2 occurs in the absence of inversion symmetry of the crystal. Surprisingly, in spite of the rather complex crystal structure of beta-Al3Mg2, physical properties turn out to be quite simple.

2389. Thermal analysis of some polynuclear coordination compounds

Authors: Patron, L; Budrugeac, P; Balu, A; Carp, O; Diamandescu, L; Feder, M

Published: APR 2007, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 88, 277, DOI: 10.1007/s10973-006-8080-6

The thermal behaviour of five polynuclear coordination compounds containing tartaric anion as ligand, namely (NH(4))(3)[LnFe(C(4)O(6)H(4))(3)(OH)(3)] (Ln=La and Eu), (NH(4))(2)[PrFe(C(4)O(6)H(4))(3)(OH)(2)] and (NH(4))[LnFe(C(4)O(6)H(4))(3)(OH)]center dot 3H(2)O (Ln=Nd and Gd) was investigated. The reaction progress was studied by TG/DTA and FTIR measurements. Oxalates and oxocarbonates were identified as intermediates. In the case of Ln=La, Nd, Pr, Eu and Gd, pure LnFeO(3) was obtained as final decomposition product. The thermal decomposition of Eu-Fe compound, leads to a mixture of mixed (ortho-ferrite (EuFeO(3)) and garnet (Eu(3)Fe(5)O(12))) and simple oxides (Eu(2)O(3) and alpha-Fe(2)O(3)).

2390. Synthesis of iron-doped anatase-TiO2 powders by a particulate sol-gel route

Authors: Cernea, M; Valsangiacom, C; Trusca, R; Vasiliu, F

Published: AUG 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2652, DOI:

TiO2 anatase doped with 0.5 at%Fe powders were prepared by sol-gel technique. Titanium (IV) butoxide and iron (III) acetylacetonate were used as starting precursors, n-butanol as solvent, acetylacetone is added as a chelating agent and acetic acid to decrease the kinetics of the hydrolysis and condensation of Ti(O-Bu-n)(4). The evolution of the network bonds and the structural characterization of the gel were studied by thermogravimetric analysis (TG), differential thermal analysis (DTA), differential thermogravimetric analysis (DTG), Fourier transform infrared spectroscopy(FTIR) scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques, respectively. A gelprecusor nanopowder with the mean grain size of about 15-20 nm was obtained. In order to prepare a Fe-cloped TiO2 material with the structure of the anatase, a thermal treatment at 450 degrees C, 3 h in air, was fund enough.

2391. Ge dots embedded in silicon dioxide using sol-gel deposition

Authors: Stoica, TF; Gartner, M; Teodorescu, VS; Stoica, T

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3274, DOI:

A versatile method, that of sol-gel deposition was used to produce Si1-xGexO2 films on Si substrates. Samples after annealing at different temperatures are investigated by different techniques including high-resolution transmission electron microscopy and spectral ellipsometry. It was revealed that, by annealing at high temperatures, Ge accumulates in small clusters (5-10nm) inside of the oxide layer. By ellipsometric investigations, valuable data about the temperature evolution of the composition and optical constants were obtained.

2392. Influence of the recrystallization processes on the structure and magnetic properties of the Nd2Fe14B/alpha-Fe nanocomposites

Authors: Kappel, W; Codescu, MM; Valeanu, M; Stancu, N; Pintea, J; Lifei, F; Jianu, A; Patroi, D; Patroi, E

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1828, DOI:

Exchange-coupled Nd2Fe14B/alpha-Fe nanocomposite magnets receives considerable research interest, because these are regarded as promising candidate materials for permanent magnets, with an adequate performance while keeping the content of relatively expensive Nd low. The advantage of these new magnetic materials are the lower rare earth content (and consequently, cheaper magnets with better corrosion resistance). The Nd2Fe14B/alpha-Fe nanocomposites were obtained by recrystallisation treatment from an amorphous phase prepared by melt-spinning. For Fe contents, between 83 and 85 at. %, we have obtained the hardening of the alpha-Fe phase by exchange interactions between the hard Nd2Fe14B phase and the soft alpha-Fe phase. The evolution of the structure and main magnetic characteristics after different annealing conditions was studied. For all isotropic permanent magnets obtained from the prepared nanocomposites was measured a remanence ratio higher than 0.5, which confirm the existence of the mentioned exchange interactions.

2393. Preparation of metallic nanowires with magnetic properties using the template method

Authors: Enculescu, I; Sima, M; Enculescu, M; Ghica, C; Enache, M; Neumann, R

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1470, DOI:

Metallic nanowires with magnetic properties were prepared by electrochemical deposition in nanoporous ion track membranes. Thus, we prepared Co-Cu alloy and Co/Cu multilayered nanowires. The technique allows the preparation of uniform arrays of parallel nanowires with desired properties. The process of electrochemical deposition of metals in nanoporous membranes was studied by means of cyclic voltammetry and impedance spectroscopy. The influences of deposition conditions such as bath composition, temperature and deposition potential on the morphological, structural and compositional properties of the nanowires were systematically studied.

2394. Some aspects regarding the complex alloying of the Ni3Al intermetallic compound with substitutional and interstitial elements

Authors: Lucaci, M; Orban, RL; Patroi, D; Hodorogea, S; Bibicu, I; Lungu, M

Published: 2007, MATERIALS AND TECHNOLOGIES, 23, +, DOI: 10.4028/www.scientific.net/AMR.23.67

Research results focussed on the combined influence of iron and boron, in proportions of 0.5 and up to 10 wt.% respectively, in complex alloyed Ni3Al synthesised by Self Propagating High Temperature Synthesis (SHS) in the thermo-explosion mode at two ignition temperatures, 950 and 1150 degrees C, are presented. By XRD and Mossbauer spectroscopy it was established that for 950 degrees C ignition temperature, the evolved heat is not high enough for the added Fe to be fully incorporated into the synthesised Ni3Al phase, a temperature of 1150 degrees C being required. For this temperature, the density of the synthesised alloys, their capacity to be cold deformed by re-pressing, hardness and bending strength variations as a function of B and Fe contents, proved their cumulative effects of the ductility and mechanical properties of complex alloyed Ni3Al enhancing.

2395. Abnormal anti-Stokes Raman spectra of single walled carbon nanotubes raised from coherent anti-Stokes Raman scattering and optical cooling processes

Authors: Baltog, I; Baibarac, M; Mihut, L; Lefrant, S

Published: MAR 2007, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 2, 198, DOI:

For the single-walled carbon nanotubes, the higher values of anti-Stokes/Stokes Raman intensity ratio (I(as)/I(s)) then the predictions of the Maxwell-Bolzmann formula indicates a CARS emission resulting from a wave mixing process between the incident laser light (omega(l)) and Stokes Raman light (omega(s)) generated by a SERS mechanism. The weaker value of (I(as)/Is) observed at resonant excitation of semiconducting nanotubes in the E(22)(S) van Hove state, relates a quantum cooling process occurred during the relaxation of the E22S excited state in two steps-by phonon emission from E(22)(S) to E(11)(S) followed by a spontaneous luminescence emission at E(11)(S).

2396. Ferroelectric ceramics based on the BaO-SrO-TiO2 ternary system for microwave applications

Authors: Ioachim, A; Ramer, R; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Vasiliu, F; Alexandru, HV; Berbecaru, C; Stoica, G; Nita, P

Published: 2007, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 27, 1180, DOI: 10.1016/j.jeurceramsoc.2006.05.086

Ba1-xSrxTiO3 solid solutions with x = 0.25, 0.5, 0.75 and 0.9 were prepared by solid-state reaction from powder oxides with high purity. In order to improve the granular growth 1 wt.% MgO and 1 wt.% MnO2 was added to the calcined powders. Samples were sintered for 2 h at 1230 and 1260 degrees C. Structural parameters, grain sizes, bulk densities and microwave dielectric parameters were determined. A monotonic decrease of the Curie temperature with the increase of strontium content was determined by low-frequency dielectric measurements. Microwave measurements around 1 GHz showed substantial decrease of the permittivity with the x increase from about 1080 to 200. Also, the variation of losses from 11 % to less than 0.2% was observed. The results indicate the BST ceramic as dielectric material, which can be utilized in paraelectric state for microwave devices. (c) 2006 Elsevier Ltd. All rights reserved.

2397. Thickness-driven antiferroelectric-to-ferroelectric phase transition of thin PbZrO3 layers in epitaxial PbZrO3/PbZr0.8Ti0.2O3 multilayers (vol 91, art no 122915, 2007)

Authors: Boldyreva, K; Pintilie, L; Lotnyk, A; Misirlioglu, IB; Alexe, M; Hesse, D

Published: NOV 12 2007, APPLIED PHYSICS LETTERS, 91, DOI: 10.1063/1.2811708

2398. Asymmetric localization in disordered Landau bands

Authors: Nita, M; Aldea, A; Zittartz, J

Published: JUN 6 2007, JOURNAL OF PHYSICS-CONDENSED MATTER, 19, DOI: 10.1088/0953-8984/19/22/226217

We show that, due to band mixing, the eigenstate localization within the disordered Landau bands gets an asymmetric structure: the degree of localization increases in the lower part of the band and decreases in the upper one. The calculation is performed for a two-dimensional lattice with the Anderson disorder potential and we prove that this effect is related to the upper shift of the extended states within the band and is enhanced by the disorder strength. The asymmetric localization and the energy shift disappear when the interband coupling is switched off.

2399. A study on the inhibition of carbon steel corrosion in an 1M HC1 solution by using ammonium polymolibdate (APM)

Authors: Patru, A; Bibicu, I; Floroiu, M; Preda, M; Tutunaru, B

Published: JUN 2007, REVUE ROUMAINE DE CHIMIE, 52, 576, DOI:

The effect of ammonium polymolybdate (APM) on the corrosion of carbon steel in a solution of 1M HC1 was studied by weight loss, electrochemical measurement and Mossbauer Spectrometry. Inhibition efficiencies (P) were obtained from weight measurement and galvanostatic polarization. The inhibition efficiencies increased with concentration, but decreased with temperature. Free energies of activation (E-a for the inhibition processes were estimated from rate constant data obtained at different temperatures and different concentration of APM. Mossbauer spectrometry shows that a superficial compound is formed on the electrode surface as a result of corrosion.

2400. Effect of the metallic contact on the electrical properties of organic semiconductor film

Authors: Stanculescu, F; Stanculescu, A; Socol, M

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1357, DOI:

Sandwich type (MIS) heterostructures based on layers of organic semiconductors as meta-dinitrobenzene (m-DNB) and perylene or perylene derivative 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) have been prepared using alternative methods (rapid thermal directional solidification or two-steps, vacuum evaporation and deposition process) on different substrates (single crystal silicon wafer and textolite covered with copper film). Subsequently indium, gallium, aluminium of high purity (5N) and silver have been used for the preparations of the metallic contacts. This paper presents some investigations of the contact between different organic semiconductors and several metals: meta-dinitrobenzene/Cu, perylene/In, peryiene/Al, perylene/Ga, perylene/Ag, PTCDA/AI, PTCDA/Ga, and PTCDA/Ag. The comparative study of the electrical conduction properties of these organic semi conductor/metal contacts has emphasised significant differences depending on the metal type, metal/organic semiconductor interface properties and quality of the contact, which is determined by the preparation method (pressing, melting, vacuum evaporation, painting) and selected contact cinfiguration. The experimental data obtained using the 2 points contact geometry have evidenced linear or power IN dependences of the investigated metallic contacts emphasising the importance of the space-charge phenomenon and defects on the charge carriers' transport in these structures.

2401. Ferroelectric polarization-leakage current relation in high quality epitaxial Pb(Zr, Ti)O-3 films

Authors: Pintilie, L; Vrejoiu, I; Hesse, D; LeRhun, G; Alexe, M

Published: MAR 2007, PHYSICAL REVIEW B, 75, DOI: 10.1103/PhysRevB.75.104103

Leakage current measurements were performed on epitaxial, single-crystal quality Pb(Zr,Ti)O-3 films with thicknesses in the 50-300 nm range. It was found that the voltage behavior of the leakage current has a minor dependence on thickness, which rules out the space-charge limited currents as main leakage source. Temperature-dependent measurements were performed to obtain more information on the transport mechanism through the metal-ferroelectric-metal (MFM) structure. The results are analyzed in the frame of interface-controlled Schottky emission. A surprisingly low value of only 0.12-0.13 eV was obtained for the potential barrier, which is much smaller than the reported value of 0.87 eV [I. Stolichnov , Appl. Phys. Lett. 75, 1790 (1999)]. The result is explained by the effect of the ferroelectric polarization on the potential barrier height. The low value of the effective Richardson constant, of the order of 10(-7)-10(-6) A/cm(2) K-2, suggests that the pure thermionic emission is not the adequate conduction mechanism for epitaxial MFM structures. The true mechanism might be interface-controlled injection, followed by a low mobility drift through the film volume.

2402. Influence of geometrical properties on light emission of ZnO nanowires

Authors: Enculescu, I; Sima, M; Enculescu, M; Enache, M; Vasile, V; Neumann, R

Published: SEP 2007, OPTICAL MATERIALS, 30, 75, DOI: 10.1016/j.optmat.2007.01.002

The present paper deals with the preparation and study of optical properties of ZnO nanowires. Nanoporous ion track polycarbonate foils were used as templates for ZnO nanowires growth by electrochemical deposition. The growth was performed using an aqueous electrochemical bath at a temperature of 70 degrees C. SEM and TEM were employed to study the morphological properties of the nanowires. Electron diffraction was employed for structural characterization. Reflection and photoluminescence spectroscopy were used for optical characterization. A comparison between the properties of electrodeposited thin films and nanowires of ZnO was made from the point of view of photoluminescence properties. (c) 2007 Elsevier B.V. All rights reserved.

2403. Thickness oscillation effect in photoexpansion and photocontraction of amorphous selenium

Authors: Popescu, M; Sava, F; Shimakawa, K; Ikeda, Y; Babin, V

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3562, DOI:

Thickness oscillations under light irradiation or by switching-off the light have been revealed in amorphous selenium films. The explanation was given in the frame of a theory that takes into account the balance between the expansion of the inter-chain distance due to electrical charging and better ordering of chains due to freedom of chains to accommodate into the structure as a result of the diminishing or increasing of the spatial hindrance.

2404. Characterization of Ba0.5Sr0.5TiO3 thin films for tuneable devices

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Sava, F; Popescu, M; Scarisoreanu, N; Dinescu, M

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

Barium strontium titanate (BST) bulk ceramic c was used as target for PLD thin film deposition. In order to avoid stoichiometry modification during the deposition, a more reactive oxidant ambient in the chamber was produced by, using a radiofrequency discharge 13.56 MHz, 150 W. Thin films of stoichiometric BST was deposited on alumina substrate with the thickness between 400 and 500 nm heated at 650 degrees C. An aditional anealing was made at 800 degrees C for 6 hours. XRD and SEM were used,for sample characterization, Capacity measurements tit 100 kHz were performed versus temperature.

2405. Why the energy levels observed in electrical transport, phototransport and photoluminescence are different?

Authors: Ciurea, ML; Iancu, V

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI: 10.1109/SMICND.2007.4519643

The paper presents an analysis of the electrical transport, phototransport and photoluminescence measurements performed on silicon-based nanocrystalline systems. The experimental results are discussed within the frame of a quantum confinement model. It is proved that the differences between the energy levels identified in the measurements are related to the quantum selection rules specific to each process. It is also proved that, at nanometric scale, the nature of the atoms composing the nanocrystal represents a first order correction, while the size represents a zero order factor.

2406. Thickness dependence of crystallization process for hydroxyapatite thin films

Authors: Mercioniu, I; Ciuca, S; Pasuk, I; Slav, A; Morosanu, C; Bercu, M

Published: AUG 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2538, DOI:

Hydroxyapatite (HAP) thin films (0.2 pm, 0.3 pm and 1.2 mu m thickness) were grown by RF magnetron sputtering in argon atmosphere onto silicon substrates at high deposition rates (0.6 mu m/h). Crystalline HAP films were obtained using a low temperature (100 degrees C) followed by post-deposition annealing at 300 degrees C, 450 degrees C, 500 degrees C and 550 degrees C in environmental air for 1 hour. An important influence of the films thickness upon the crystallization degree was noticed at intermediate annealing temperatures, as obtained from XRD measurements. For low and high temperatures similar values were obtained with a better crystallization degree for the thinner films. FTIR absorption led to the same conclusion considering the shape of stretching and bending PO4 lines. This suggests that the crystallization process has a diffusion component besides usual thermal activation process.

2407. Micro and nanorods of alkali halides grown in polymer templates

Authors: Enculescu, M; Enculescu, I; Sima, M; Neumann, R; Trautmann, C

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1563, DOI:

Porous membranes containing cylindrical pores with diameters ranging from a few tens of nanometers to a few tens of micrometers were prepared by using the ion track technique. Swift heavy ions (e.g. Au with 11.4 MeV/nucleon specific energy) were used for creating the ion tracks in polycarbonate foils. Etching was performed using an aqueous solution of NaOH containing methanol. The growth of the alkali-halides micro- and nanorods was performed by evaporation from a saturated solution. The rods were imaged using scanning electron microscopy. The method opens up the possibility of growing nanostructures with applications as nanolaser media or nanoscintillators.

2408. Memory effects in Si/SiO2/nano-crystalline PbS reterostructures

Authors: Buda, M; Stancu, V; Pentia, E; Botila, T

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

The mechanism of charge storage in p Si/SiO2 /nano-crystalline PbS heterostructures is investigated using capacitance - voltage (C-V) and conductance-voltage (G-V) measurements at different frequencies. The nano-crystalline thin PbS films were obtained using the Chemical Bath Deposition method with a shorter reaction time and without doping element in the reducing bath. The C-V curves show hysterezis indicating charge storage with a maximum charge density of 3x10(11) cm(-2) for the highest measurement frequency of 100 kHz. The charge storage capacity is enhanced in the rase of using a nano-crystalline PbS thin film instead of a standard macro-crystalline film.

2409. Controlled dephasing in single-dot Aharonov-Bohm interferometers

Authors: Moldoveanu, V; Tolea, M; Tanatar, B

Published: JAN 2007, PHYSICAL REVIEW B, 75, DOI: 10.1103/PhysRevB.75.045309

We study the Fano effect and the visibility of the Aharonov-Bohm oscillations for a mesoscopic interferometer with an embedded quantum dot in the presence of a nearby second dot. When the electron-electron interaction between the two dots is considered the nearby dot acts as a charge detector. We compute the currents through the interferometer and detector within the Keldysh formalism and the self-energy of the nonequilibrium Green's functions is found up to the second order in the interaction strength. The current formula contains a correction to the Landauer-Buttiker formula. Its contribution to transport and dephasing is discussed. As the bias applied on the detector is increased, the amplitude of both the Fano resonance and Aharonov-Bohm oscillations are considerably reduced due to controlled dephasing. This result is explained by analyzing the behavior of the imaginary part of the interaction self-energy as a function of energy and bias. We emphasize as well the role of the ring-dot coupling. Our theoretical results are consistent with the experimental observation of Buks [Nature 391, 871 (1998)].

2410. Theoretical study of electronic transport through a small quantum dot with a magnetic impurity

Authors: Tolea, M; Bulka, BR

Published: MAR 2007, PHYSICAL REVIEW B, 75, DOI: 10.1103/PhysRevB.75.125301

We model a small quantum dot with a magnetic impurity by the Anderson Hamiltonian with a supplementary exchange interaction term. The transport calculations are performed by means of the Green functions within the equation of motion scheme, in which two decoupling procedures are proposed, for high and low temperatures, respectively. The paper focuses on the charge fluctuations for such a system, an aspect not addressed before, as well as on the Kondo resonance. We show a specific role of the excited state, which can be observed in transport and in spin-spin correlations. Our studies show a many-body feature of the phase shift of transmitted electrons, which is manifested in a specific dip. In the Kondo regime, our calculations complement existing theoretical results. The system shows three Kondo peaks in the density of states: one at the Fermi energy and two side peaks, at a distance corresponding to the singlet-triplet level spacing. The existence of the central peak is conditioned by a degenerate state (the triplet) below the Fermi energy.

2411. X-ray optics - a tool for X-ray diagnostic and therapy

Authors: Bradaczek, M; Popescu, M

Published: JUL 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1948, DOI:

X-ray optics is a relatively new instrument for the configuration X-ray beams. Presently this method is mainly used for diffraction and material tests. Although there are problems for medical use because of the larger wavelength (lower energy), for some applications it might be suitable.

2412. Short-circuit photocurrent in epitaxial lead zirconate-titanate thin films

Authors: Pintilie, L; Vrejoiu, I; Rhun, GL; Alexe, M

Published: MAR 15 2007, JOURNAL OF APPLIED PHYSICS, 101, DOI: 10.1063/1.2560217

Photovoltaic properties of the metal-ferroelectric-metal structures, having SrRuO3 metal oxide electrodes and Pb(Zr,Ti)O-3 (PZT) as ferroelectric layer, are investigated by the short-circuit photocurrent (SC-PHC) in the 200-800 nm wavelength domain. The band-gap dependence on the Zr content was determined from the spectral distribution of the SC-PHC signal. It was found that the band-gap value increases linearly with the Zr content, from about 3.9 eV to about 4.4 eV. It is shown that the sign and the magnitude of the signal depend on the internal bias and on the spontaneous polarization direction and value. The photocurrent describes a hysteresis loop similar to that of the ferroelectric polarization and can be used as a nondestructive readout of the nonvolatile memories based on PZT films. The existence of a significant SC-PHC signal at wavelengths corresponding to subgap energies is attributed to the presence of charged, deep levels in the forbidden band. It is also shown that the epitaxial PZT films have the potential for solid-state UV detectors, with current responsivity as high as 1 mA/W. The results are not entirely consistent with a bulk photovoltaic effect and are discussed in the frame of a Schottky barrier model for the metal-ferroelectric interface. (c) 2007 American Institute of Physics.

2413. Quantum confinement model for phototransport processes in nanocrystalline porous silicon

Authors: Ciurea, ML; Stavarache, I; Iancu, V

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

The paper presents a quantum confinement model which describes the phototransport processes in nanocrystalline porous silicon. The model supposes that the nanocrystallites surface/interface acts as the walls of an infinite rectangular quantum well, introducing discrete confinement energy levels. This model is proved able to also describe the photoluminescence and the temperature dependence of the dark current in the same samples. Its results are in agreement with the Microstructure investigations.

2414. Evidence for microwave-induced recrystallization in NiZn ferrites

Authors: Sorescu, M; Diamandescu, L; Ramesh, PD; Roy, R; Daly, A; Bruno, Z

Published: FEB 15 2007, MATERIALS CHEMISTRY AND PHYSICS, 101, 414, DOI: 10.1016/j.matchemphys.2006.07.006

A series of ferrites was prepared using the microwave method, starting with hematite as precursor in the Ni1-xZnxFe2O4 (x =0-1) system. After synthesis, the NiZn ferrite samples were irradiated with a microwave field for 90 s. X-ray diffraction (XRD) measurements were performed to yield the lattice constant as function of the amount x of Zn substitution, before and after irradiation. The lattice parameter was found to increase much slower with increasing x for the microwave irradiated specimens. Mossbauer spectroscopy was performed at room temperature and spectra were analyzed using the binomial distribution. For x = 0.4, 0.5 and 0.6 the resonance lines are much sharper for the irradiated samples and indicate that a microwave-induced recrystallization of the NiZn ferrites occurs in the composition range specified. (c) 2006 Elsevier B.V. All rights reserved.

2415. Hydroxyapatite-iron oxide bioceramic prepared using nano-size powders

Authors: Predoi, D; Barsan, M; Andronescu, E; Vatasescu-Balcan, RA; Costache, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3613, DOI:

The hydroxyapatite (HAp) is an important material for orthopedics and dentistry applications. In the present study a simple method was tried for added the iron oxide nanoparticles into HAp so as to establish and induce a biocompatibility. In the research the mechanism of the coated of iron oxide with HAp would also be described by the analysis of X-ray diffractometer, scanning electron microscope and Fourier transformation infrared. Osteoblast cells were permanent monitored to detect any possible influence due to samples that might alter the cell growth, viability and proliferation.

2416. Effect of temperature on the main piezoelectric parameters of a soft PZT ceramic

Authors: Miclea, C; Tanasoiu, C; Amarande, L; Miclea, CF; Plavitu, C; Cioangher, M; Trupina, L; Miclea, CT; David, C

Published: 2007, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 10, 250, DOI:

The temperature behavior of the main piezoelectric parameters, such as the electromechanical coupling factor k(p), the mechanical quality factor Qm, the dielectric permittivity epsilon (real and imaginary part), the loss tangent tan delta, the piezoelectric charge constants d(33) and d(31) and the voltage constants 933 and 931 of a soft type piezoelectric material was investigated. The results showed that temperatures under 150 degrees C do not influence these parameters, which indicate that every transducer made from this type of material may be successfully used up to this temperature. Between 150 degrees C and 250 degrees C, the piezoelectric properties undergo more or less important changes, mainly due to the depoling effect and above that, at temperatures over 250 degrees C, they degrade very rapidly, tending to zero.

2417. Interfacial titanium oxide between hydroxyapatite and TiAlFe substrate

Authors: Nelea, V; Morosanu, C; Bercu, M; Mihailescu, IN

Published: DEC 2007, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 18, 2354, DOI: 10.1007/s10856-007-3135-1

The interface between nano-crystalline hydroxyapatite (HA) thin films and a titanium alloy (Ti5Al2.5Fe) has been studied by means of Fourier transform infrared spectrophotometry and X-ray diffraction at grazing incidence. The HA thin films were deposited by radio-frequency magnetron sputtering in low pressure dry argon on substrates kept at low temperature or heated at 550 degrees C. The effect of film treatment by sputtering and annealing in humid air, as a simple, effective way of restoring the crystallinity and stoichiometry of the HA bulk, was studied in correlation with the development of a titanium oxide layer at the film-substrate interface. An interfacial TiO2 film grew at the interface during annealing in moist air, while a TiO2 layer diffused into the HA films when directly sputtered at 550 degrees C. The formation of an interfacial titanium oxide layer was inhibited by the insertion of a crystalline TiN buffer interlayer between the substrate and the HA film. Separately, the mechanical characteristics of the different HA films were monitored by nanoindentation to find out how they had been affected.

2418. Microwave dielectric properties of BaTi4O9-Nd2O3, BaTi4O9-Sm2O3 and BaTi4O9-WO3 ceramics

Authors: Cernea, M

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3794, DOI:

Barium tetratitanate (BaTiO9) powder, synthesized by coprecipitation method, was used to prepare BaTi4O9-Nd2O3, BaTi4O9-Sm2O3 and BaTi4O9-WO3 ceramics with microwave dielectric properties. The structure and microwave dielectric properties were studied. BaNd2Ti5O14 and BaSm2Ti4O12 single-phase ceramics were obtained from BaTi4O9:Nd2O3=1:1 and BaTi4O9:Sm2O3=1:1, respectively. A multiple phases ceramic containing mainly BaWO4 and small amounts of Ba2Ti9O20 and BaTi4O9 was obtained from BaTi4O9:WO3=1:1. BaTi4O9-Nd2O3, BaTi4O9-Sm2O3 and BaTi4O9-WO3, ceramics sintered at 1375 degrees C for 8.5 h in air, shown good microwave dielectric properties.

2419. Electrical characteristics of nano-PbS/SiO2/Si heterostructures obtained by chemical bath method

Authors: Goldenblum, A; Stancu, V; Buda, M; Iordache, G; Botila, T; Negrila, C

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3802, DOI:

The PbS/SiO2/Si structures show a clockwise hysteresis of capacitance-voltage (C-V) characteristics. The loop width increases with temperature and sweep time. The conductance-voltage (G-V) characteristics also present a hysteresis effect with two bumps. Both characteristics show a strong shift with frequency. We show that these effects are determined by the positive mobile ions injected in the oxide region during the chemical bath deposition of PbS and by the high concentration Of Si/SiO2 interface states. The corresponding C-V and G-V characteristics are simulated and the main peculiarities of the experimental results are well reproduced by the modeled curves.

2420. Structural transition and intermediate (Boolchand) phase in amorphous thin films of the AS(2)S(3)-GeS2 system

Authors: Petkov, K; Popescu, M; Lorinczi, A; Sava, F; Zamfira, S; Leonovici, M

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3092, DOI:

The structure of the chalcogenide glass films of composition As2S3-GeS2 has been investigated bu X-ray diffraction. The relation between the quasi-distance as evidenced from the first sharp diffraction peak, and the composition ration has been estabilished. The Boolchand (intermediate) phase was found ro be characterized by large structuro-compositional fluctuations.

2421. Deposition and properties of CdTe nanowires prepared by template replication

Authors: Enculescu, I; Sima, M; Enculescu, M; Enache, M; Ion, L; Antohe, S; Neumann, R

Published: MAY 2007, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 244, 1611, DOI: 10.1002/pssb.200675109

We used the template method to prepare CdTe wires with diameters ranging from 80 nm to 1 mu m. As templates we used polycarbonate and polyethilene tereplitalate ion track membranes and as the method of filling the pores of such membranes we employed electrochemical deposition. The conditions (i.e. bath composition and deposition potential) necessary to obtain the stoichiometric composition of the semiconductor were found. Scanning and transmission electron microscopy were employed for morphological characterization of the nano and microwires. Energy dispersive X-ray analysis was employed for determining the Cd/Te ratio. Selected area electron diffraction was employed for structural measurements. Reflection spectroscopy measurements were performed on nanowire arrays for determining the band gap of the deposited nanostructures. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2422. A PZT type piezoceramic material with high planar coupling factor used for a miniature bimorph ventilator

Authors: Miclea, C; Iuga, A; Tanasoiu, C; Amarande, L; Cioangher, M; Miclea, CT

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1515, DOI:

New PZT type ceramic materials, doped with Ni, were prepared by the usual solid state reaction. The best composition proved to be the one containing 6% atomic Ni and having the following chemical formula: Pb0.95Bi0.03Nb0.02Zr0.51 Ti0.43Ni0.06O3. Rectangular samples of this powder were pressed and sintered at 1200 OC for 4 hours and then it was cut in thin slices used to construct an efficient bimorph type ventilator to be used in miniaturized devices for cooling. Miniature ventilators made of PZT ceramics are preferred due to their smallness, high electromechanical efficiency and lack of rotating parts and last but not least of contiguous electrical contacts. We made such a device by using two thin ceramic PZT plates of the material with the best piezoelectric properties, assembled in a flexural oscillator through a proper bimorph association. The emerging doublet behaves itself very much like a bimetal system and possesses a good developed flexural mode. Attaching a metallic elastic plate to the bimorph produces a highly efficient miniature ventilator. A theoretical quantitative study of this flexural bimorph system with elastic plate attached was proposed.

2423. Accelerate ageing of PZT-type ceramics

Authors: Toacsan, MI; Ioachim, A; Nedelcu, L; Alexandru, HV

Published: 2007, PROGRESS IN SOLID STATE CHEMISTRY, 35, 537, DOI: 10.1016/j.progsolidstchem.2007.01.018

Accelerate ageing of lead zirconate-titanate ferroceramics (PZT) by fast neutron irradiation is investigated. The ferroelectric behavior of Pb1-wMw(Zr,Ti)O-3, where w < 0.5 wt%, M = Li, Nb, Cr, Bi, Mn, Sb, La for Zr/Ti ratio = 51.5/48.5, prepared by solid state reaction, is strongly affected by fast neutron irradiation at Phi(i) = (10(13) divided by 10(18)) n/cm(2) integrated fluxes. Structural investigations (XRD and SEM) reveal modifications of the microstructure, porosity and elementary cell parameters. High irradiation levels induce tetragonal-cubic at the same time with a ferro-paraelectric transition. The micrographs show the evolution of 90 degrees and 180 degrees walls as well as herringbone structure typical for tetragonal distortions with irradiation level. A relation between macroscopic characteristics (piezoelectric and dielectric) and microscopic properties (crystallographic parameters, porous structure and grain morphology) as function of irradiation doses can be established using a model based on microstructural parameters. These results offer opportunities to understand the fundamentals of radiation effects upon piezoelectric ceramics. (c) 2007 Elsevier Ltd. All rights reserved.

2424. Properties of TiO2 thin films prepared by different techniques

Authors: Ungureanu, F; Medianu, R; Ghita, RV; Negrila, CC; Ghita, P; Manea, AS; Lazarescu, MF

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1461, DOI:

TiO2 thin films prepared by sol-gel method and by RF magnetron sputtering deposited on p-Si(111), n-GaAs(100), and glass have been investigated by XRD, XPS and AFM techniques. The characteristics of the film: colour, adherence and composition are presented in the case of thermal treatments (500 degrees C and 800 degrees C) for sol-gel deposited films as well as for RF sputtering. The TiO2 plasma deposited film is uniform, homogeneous and stoichiometric.

2425. Theoretical and experimental study of dielectric and optical properties of some epiclon based polyimides

Authors: Cosutchi, AI; Hulubei, C; Buda, M; Botila, T; Ioan, S

Published: JUL 2007, REVUE ROUMAINE DE CHIMIE, 52, 670, DOI:

The dielectric and optical properties of a series of aromatic polyimides synthesized by solution polycondensation of equimolar amounts of 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexeiiyl-1,2-dicarboxylic acid anhydride (epiclon) and diamines, in N-methylpyrrolidinone as solvent, under inert atmosphere were investigated. The effect of diamine type, which contains phenilenic units in the vicinity of methylenic groups or ether linkages, on the refractive index and dielectric constant was examined from theoretical and experimental data. Minimizing polarizability by modification of number of polarizable groups per unit volume in polyimide backbone determines lower values for dielectric constant. Thus, optical dielectric constants obtained from the refractive indices are low and are less influenced by the Ar groups. Higher values of the dielectric constant corresponding to the dipolar polarization are observed by decreasing frequency from 100 KHz to 1 KHz due to the increase of the polarization of induced dipoles, depending on the chemical structures.

2426. Mesoscopic Fano effect in an Aharonov-Bohm interferometer Coulomb-coupled to a nearby quantum dot

Authors: Tolea, M; Moldoveanu, V; Tanatar, B

Published: 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 2, 4, +, DOI: 10.1002/pssc.200673304

Motivated by the pionieering experiments of Buks et al. [Nature 391, 871 (1998)] we investigate the visibility of the Fano effect in a single-dot Aharonov-Bohm interferometer which is Coulomb-coupled to a nearby quantum dot. The latter acts as a 'Which Path Detector' and is coupled to two leads on which a finite bias is applied. Using the non-equilibrium Keldysh-Green function formalism we compute the currents through the detector and the interferometer. We take into account the first two contributions to the interaction self energy and emphasize the correction to the Landauer formula which appears beyond the single-particle approximation. Particular attention is given to the coherence properties of the interferometer in the presence of the electron-electron interaction between the embedded dot and the detector. We show that when the detector is subjected to a finite bias the amplitude of Aharonov-Bohm oscillations of the current through the interferometer decreases. The Fano line is in turn rather stable under interaction. Our results generalize an earlier work of Silva and Levit [Phys. Rev. B 63, 201309 (2001)] and complement the existing description of the controlled dephasing. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2427. Broadband planar filters with enhanced couplings using defected ground structures

Authors: Militaru, N; Banciu, MG; Lojewski, G

Published: 2007, 2006 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, +, DOI:

In this paper a study of some microwave microstrip bandpass filters (BPF) using defected ground structures (DGS) is presented. This technique allows designs of tight couplings without the necessity of using very narrow coupling gaps. Based on the results of the study, four-pole cross-coupled planar microwave bandpass filters were designed, with a single of. with two ground slots. Compared to similar microstrip filters without defected ground, the simulated performances of these novel structures indicate some technological advantages.

2428. Aperture couplings in multilayer filtering structures

Authors: Militaru, N; Lojewski, G; Banciu, MG

Published: 2007, ISSCS 2007: INTERNATIONAL SYMPOSIUM ON SIGNALS, CIRCUITS AND SYSTEMS, VOLS 1 AND 2, +, DOI:

In multilayer structures apertures in metallic sheets can be used as coupling elements between resonators located on different layers, allowing very compact filter designs. In this paper, some novel types of planar microwave bandpass filters, using aperture couplings, in structures with three metallic layers, are considered. Couplings between two miniaturized resonators are investigated, by full electromagnetic field simulation. Based on the results of this study, several models of planar microwave bandpass filters, with a single or with two apertures, are designed, verified by simulation, fabricated and measured. Compared to the classical filters, these novel structures show a good compactness and can offer some technological advantages.

2429. ZnO : Mn : Cu nanowires prepared by template method

Authors: Sima, M; Enculescu, I; Sima, M; Enache, M; Vasile, E; Ansermet, JP

Published: MAY 2007, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 244, 1527, DOI: 10.1002/pssb.200675126

Manganese and copper doped ZnO films and nanowire arrays were prepared by cathodic electrodeposition from aqueous solution. The electrochemical process was examined by linear voltammetry and the morphology and the composition of obtained semiconductor were observed by SEM and EDX measurements. Optical absorption spectra indicated the presence of copper in ZnO: Mn: Cu nanowire arrays as Cu2+ ions. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2430. Gas-sensing by Polymer-Iron nanocomposite materials

Authors: Tomescu, A; Simion, CE; Alexandrescu, R; Morjan, I; Scarisoreanu, M

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI:

Electrical properties of new Polymer-Iron nanocomposite materials obtained by laser pyrolysis were investigated, in order to find applications for the detection of reducing gases. The aim of this paper was to prove the necessity of complex experimental investigation in order to point out the contribution of different types of adsorption. Usually resistance measurement cannot fully describe the surface interactions. The electron affinity changes are of real interest for in-field conditions which always involve humidity of surrounding gas-atmosphere. On the other hand, the nanocomposite materials can be a solution for specific gas-sensing properties.

2431. Characterization of PbZrO3 prepared using an alkoxide-based sol-gel synthesis route with different hydrolysis conditions

Authors: Ion, ED; Malic, B; Kosec, M

Published: 2007, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 27, 4352, DOI: 10.1016/j.jeurceramsoc.2007.02.158

PbZrO3 precursor powders were prepared from lead acetate and zirconium n-butoxide in n-butanol and hydrolysed with R-w (molar ratio of water/lead acetate) = 2 and 15 at different pH values. Upon heating the organic groups were removed in two steps for the precursor prepared at R-w = 2, and in one step at R-w = 15. The perovskite phase crystallizes at approximately 700 degrees C, irrespective of the hydrolysis conditions. (c) 2007 Elsevier Ltd. All rights reserved.

2432. Multiple wavelength InGaAs quantum dot lasers using ion implantation induced intermixing

Authors: Mokkapati, S; Du, S; Buda, M; Fu, L; Tan, HH; Jagadish, C

Published: NOV 2007, NANOSCALE RESEARCH LETTERS, 2, 553, DOI: 10.1007/s11671-007-9097-x

We demonstrate multiple wavelength InGaAs quantum dot lasers using ion implantation induced intermixing. Proton implantation, followed by annealing is used to create differential interdiffusion in the active region of the devices. The characteristics (lasing-spectra, threshold currents and slope efficiencies) of the multi-wavelength devices are compared to those of as-grown devices and the differences are explained in terms of altered energy level spacing in the annealed quantum dots.

2433. Structure of PZT thin films deposited on stainless steel and on platinum/silicon substrate

Authors: Stancu, V; Sava, F; Lisca, M; Pintilie, L; Popescu, M

Published: SEP 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2969, DOI:

2434. Mean-field theory for Bose-Hubbard model under a magnetic field

Authors: Oktel, MO; Nita, M; Tanatar, B

Published: JAN 2007, PHYSICAL REVIEW B, 75, DOI: 10.1103/PhysRevB.75.045133

We consider the superfluid-insulator transition for cold bosons under an effective magnetic field. We investigate how the applied magnetic field affects the Mott transition within mean-field theory and find that the critical hopping strength (t/U)(c) increases with the applied field. The increase in the critical hopping follows the bandwidth of the Hofstadter butterfly at the given value of the magnetic field. We also calculate the magnetization and superfluid density within mean-field theory.

2435. Current perpendicular to plane single-nanowire GMR sensor

Authors: Enculescu, I; Toimil-Molares, ME; Zet, C; Daub, M; Westerberg, L; Neumann, R; Spohr, R

Published: JAN 2007, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 86, 47, DOI: 10.1007/s00339-006-3738-2

By electrochemical deposition in a single nanopore membrane we fabricate Cu/Co layered single nanowires, that exhibit up to 10% magnetoresistance at room temperature. Single nanopore membranes are prepared by irradiating polycarbonate membranes with exactly one swift heavy ion, and by subsequent chemical etching of the single ion track. Both dc and pulsed electrodeposition of single wires consisting of Cu-Co alloy and Cu/Co multilayers respectively, are performed from a bath containing the two metal ions. By sputtering a gold electrode on the upper membrane surface, the single nanowire embedded in the flexible polymer foil is reliably contacted. While alloy wires exhibit anisotropic magnetoresistance (AMR), multilayer wires display current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) behavior. This demonstrates that both the fabrication and contacting methods are very suitable for the investigation of transport properties, without the necessity of lithographic processes and without manipulation of the nanowires. In addition, the method opens up many new possibilities for single nanowire-based sensors.

2436. Microwave properties of Ba1-xPbxNd2Ti5O14 dielectric resonators

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, CA; Stoica, G

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1575, DOI:

The Ba1-xPbxNd2Ti5O14 (BNT: Pb) ceramics are appropriate for microwave devices due to their high dielectric constant and low loss in the microwave domain. Samples with x Pb content in the range 0 + 0.5 were prepared by solid-state reaction and sintered at temperatures T-s = 1230 + 1260 degrees C. XRD and SEM analysis indicate very good crystalline structure and polyhedral well formed grains. Controlled temperature coefficient of resonant frequency alpha is essential for dielectric resonators. The temperature coefficient of the resonant frequency alpha takes values from - 15 ppm/degrees C to + 70 ppm/degrees C. Highdensity values and adequate microwave parameters were obtained for x = 0.5 Pb content. The BNT: Pb ceramics sintered at 1250 degrees C and 1260 degrees C for 2 hours are suitable for dielectric resonators for frequencies up to 5 GHz. epsilon r = 76 + 87 and Q x f similar to 5000 GHz).

2437. Lanthanum zirconate nanoparticles and ceramics produced using a nitrate-modified alkoxide synthesis route

Authors: Ion, ED; Malic, B; Kosec, M

Published: DEC 2007, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 44, 209, DOI: 10.1007/s10971-007-1625-8

Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based precursor derived from dehydrated lanthanum nitrate, zirconium n-butoxide and 2-methoxyethanol. Upon heating, the decomposition of the organic groups was promoted by the nitrate groups, yielding a porous powder that crystallized into a pyrochlore phase at 800 degrees C. The powder that was heat treated at 900 degrees C for 1 h was composed of friable agglomerates of approximately 60-nm-sized nanoparticles. The ceramics obtained from the powder heat treated at 900 degrees C and milled for 30 min reached a relative density of 97.9 % after sintering at 1,400 degrees C for 10 h, which is at least 100 degrees C lower than the typically reported temperatures for this material.

2438. Wide band gap semiconductor SAW type devices for GHz applications, manufactured using nano-lithographic techniques

Authors: Muller, A; Dinescu, A; Konstantinidis, G; Vasilache, D; Dragoman, M; Morosanu, C; Sajin, G; Neculoiu, A

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI: 10.1109/SMICND.2007.4519695

This paper presents experiments to develop SAW structures with operating frequencies in the GHz range. The experiments were developed on AlN and GaN thin films with nano-metric lines for the IDT. The nanolithography was performed at IMT with the new purchased VEGA 5136 LM SEM from TESCAN and ELPHY Plus EBL from Raith GmbH. There were obtained some very good quality inerdigitated Ti/Au structures (with 30 digits and 29 interdigits 300nm wide, 220nm high and and 200 mu m long). Lift-off techniques to remove the undesired metal were used On wafer microwave measurements of the SAW structure (performed at IMT on the new purchased Anritsu vector analyzer equipped with Suss Microtec probes), have demonstrated its functionality. It was evidenced a pronounced resonance at about 2.8GHz.

2439. Influence of the phosphorous precursors on the structure and properties of the SiO2-P(2)O(5)sol-gel films

Authors: Vasiliu, C; Grigorescu, C; Pavelescu, G; Predoana, L; Todan, L; Gartner, M; Anastasescu, M; Negrila, C; Logofatu, C; Moldovan, A; Zaharescu, M

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1410, DOI:

Thin films in the SiO2-P2O5 system are intensely studied due to their applications in microelectronics, sensing, nanophotonics, optoelectronics and as ionic conductors. Sol-gel is the most used method for preparation of such films. Previous studies established the very low reactivity of the phosphorous alkoxides and the high tendency of the phosphorous oxide to volatilise at thermal treatment. In order to identify the most appropriate precursor for obtaining layers with desired composition and properties a systematic study of the sol-gel film preparation using different phosphorous precursors was carried out. The films were deposited on ITO/SiO2 coated glass substrates at room temperature. To check the influence of the type of precursors on the layers thermal stability and properties a post deposition annealing was performed at temperatures of 150 and 200 degrees C. The film characterization was carried out using various techniques as Spectroscopic Ellipsometry (SE), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR).

2440. Mossbauer spectral study of NdFe1-xGaxO3 perovskites

Authors: Rubin, J; Piquer, C; Filoti, G; Parra-Borderias, M; Bartolome, F; Bartolome, J

Published: SEP 2007, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 316, E687, DOI: 10.1016/j.jmmm.2007.03.062

The Fe-57 Mossbauer spectra of NdFe1 (-x) GaxO3 ( x = 0, 0.1, 0.2, 0.25, 0.5 and 0.7) have been measured at room temperature (RT). For x < 0.5 the spectra have been fitted with magnetic sextets with their areas following a binomial distribution of Fe surroundings with Ga neighbours. The spectra for x = 0.5 and 0.7 show paramagnetic doublets, which account for the percolation effect induced by the non-magnetic Ga substitution for Fe, which has been estimated to be x = 0.43 at RT. The analysis of the hyperfine field values as a function of the Ga concentration shows the effect of the variations of the antiferromagnetic sublattice magnetization. Moreover, the dependence of this field with the number of susbstituted neighbours suggests an increase of the average Fe-O-Fe exchange interaction as a consequence of the lattice contraction when Ga susbtitutes for Fe. (c) 2007 Elsevier B.V. All rights reserved.

2441. Effects of porosity on ferroelectric properties of Pb(Zr0.2Ti0.8)O-3 flims

Authors: Stancu, V; Lisca, M; Boerasu, I; Pintilie, L; Kosec, M

Published: JUN 4 2007, THIN SOLID FILMS, 515, 6561, DOI: 10.1016/j.tsf.2006.11.165

The sol-gel deposition method has been successfully applied to obtain Pb(Zr0.2Ti0.8)03 thin films on platinized silicon wafers. Addition of different amounts (7-15 wt.%) of organic macromolecular polyvinylpyrrolidone in the precursor solution prior to spin coating proves to be an excellent method for obtaining porous films. The crystal structure of as deposited films was analyzed by X-ray diffraction. The porous films show perovskite phase after annealing at 650 degrees C. The surface morphology has been studied by Atomic Force Microscopy and Scanning Electron Microscopy. The surface profile indicates a roughness of the film of 5 nm and no microcracks on the surface. The ferroelectric behavior was proved for each film, by hysteresis loops and by the "butterfly" shape of the capacitance-voltage characteristics. The remnant polarization and the coercive field decrease while the amount of added PVP increases. (C) 2006 Elsevier B.V. All rights reserved.

2442. TiO2-based nanopowders obtained from different Ti-alkoxides

Authors: Crisan, M; Braileanu, A; Raileanu, M; Crisan, D; Teodorescu, VS; Birjega, R; Marinescu, VE; Madarasz, J; Pokol, G

Published: APR 2007, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 88, 176, DOI: 10.1007/s10973-006-8125-x

Pure TiO2 and S-doped TiO2 sol-gel nanopowders were prepared by controlled hydrolysis-condensation of titanium alkoxides. The influence of different Ti-alkoxides (tetraethyl-, tetraisopropyl- and tetrabutyl-orthotitanate) used in obtaining TiO2 porous materials in similar conditions (water/alkoxide ratio, solvent/alkoxide ratio, pH and temperature of reaction) has been investigated. The relationship between the synthesis conditions and the properties of titania nanosized powders, such as thermal stability, phase composition, crystallinity, morphology and size of particles, BET surface area and the influence of dopant was investigated. The nature of the alkyl group strongly influences the main characteristics of the obtained oxide powders, fact which is pointed out by thermal analysis, X-ray diffraction, TEM and BET surface area measurements.

2443. Ba(Ti1-xSnx)O-3 (x=0.13) dielectric ceramics prepared by coprecipitation

Authors: Cernea, M; Manea, A; Piazza, D; Galassi, C; Vasile, E

Published: JUN 2007, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 90, 1732, DOI: 10.1111/j.1551-2916.2007.01648.x

Fine-grain BaTi0.87Sn0.13O3 (BTS13) powder was synthesized from an oxalate precursor and used to prepare sintered ferroelectric BTS13 ceramics. The evolution of the morphology and structure of a BTS13 precipitate precursor as a function of temperature was analyzed. We compare the sintering behavior as well as the dielectric properties of the BTS13 ceramics obtained using uniaxial and cold isostatic pressing.

2444. Poly(N-vinyl carbazole) and carbon nanotubes based composites and their application to rechargeable lithium batteries

Authors: Baibarac, M; Lira-Cantu, M; Sol, JO; Baltog, I; Casan-Pastor, N; Gomez-Romero, P

Published: SEP 2007, COMPOSITES SCIENCE AND TECHNOLOGY, 67, 2563, DOI: 10.1016/j.compscitech.2006.12.008

In order to prepare poly(N-vinyl carbazole) (PVK) and carbon nanotube (CNs) based composites, electrochemical polymerization of N-vinyl carbazole (NVK) was studied by cyclic voltammetry (CV) in LiClO4/acetonitrile solutions. Cyclic voltammograms recorded on a blank Pt electrode and those obtained when single or multi-walled carbon nanotubes (SWNTs or MWNTs) films were previously deposited onto the Pt electrode show a down-shift of the VK reduction peak potential in the latter case. The influence of monomer concentration and supporting electrolyte on the polymerization conditions and electrochemical properties of these composite materials were also investigated. Morphologic aspects as well as the photoluminescence properties of the PVK/CNs composite were also investigated. A covalent functionalization of carbon nanotubes with PVK is suggested on the basis of infrared (IR) spectroscopic studies. Using the PVK/CN composite as a positive electrode and an electrolytic solution containing LiPF6, a higher specific discharge capacity of the rechargeable lithium cells, similar to 45 and 115 mA h g(-1), are reported for PVK functionalized SWNTs and MWNTs, respectively. (c) 2007 Elsevier Ltd. All rights reserved.

2445. Plasma-assisted catalysis total oxidation of trichloroethylene over gold nano-particles embedded in SBA-15 catalysts

Authors: Magureanu, M; Mandache, NB; Hu, JC; Richards, R; Florea, M; Parvulescu, VI

Published: NOV 15 2007, , DOI: 10.1016/j.apcatb.2007.05.030

2446. BST thin films obtained by PLD for applications in electronics

Authors: Scarisoreanu, N; Filipescu, M; Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Dutu, A; Buda, M; Alexandru, HV; Dinescu, M

Published: JUL 31 2007, APPLIED SURFACE SCIENCE, 253, 8257, DOI: 10.1016/j.apsusc.2007.02.111

Barium strontium titanate (BST) bulk ceramic with composition Ba0.5Sr0.5TiO3 was produced by solid-state reaction and was used as target for PLD thin film deposition. A Nd-YAG laser, working at 5-10 Hz and different wavelengths has been used. Thin films of stoichiometric BST were deposited on alumina substrate with the thickness between 400 and 500 nm. An aditional annealing was carried out at 800 degrees C for 6 h. XRD and SEM were used for sample characterization. Capacity measurements were performed versus temperature at 100 kHz in a large temperature range. A diffuse ferroelectric-paraelectric phase transition with T-C = -72 degrees C for the BST thin film was determined. A 5% tunability was measured in the transition region. (c) 2007 Elsevier B.V. All rights reserved.

2447. Acylation of different amino derivatives with fatty acids on UL-MFI-type catalysts

Authors: Musteata, M; Musteata, V; Dinu, A; Florea, M; Hoang, VT; Trong-On, D; Kaliaguine, S; Parvulescu, VI

Published: NOV 2007, , DOI: 10.1351/pac200779112059

2448. Varieties of nanostructured carbon grown by expanding radiofrequency plasma beam

Authors: Vizireanu, S; Mitu, B; Dinescu, G; Nistor, L; Ghica, C; Maraloiu, A; Stancu, M; Ruxandra, G

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1652, DOI:

Results regarding the growth of carbon nanostructures by using a low-pressure expanding radiofrequency plasma jet are reported. The growth was performed in an argon plasma injected with acetylene precursor, in the presence of ammonia or hydrogen, on a substrate covered with nickel or cobalt catalysts. Various forms of nanostructured carbon material were obtained, depending on the catalyst size, ammonia or hydrogen / acetylene ratio and substrate temperature. The results exemplified in the paper describe nickel nanoparticles coated in highly ordered graphite shells, granular carbon, two dimensional carbon nanoflakes, nanowires and nanorods.

2449. Metal-triflate ionic liquid systems immobilized onto mesoporous MS41 materials as new and efficient catalysts for N-acylation

Authors: Coman, SM; Florea, M; Parvulescu, VI; David, V; Medvedovici, A; De Vos, D; Jacobs, PA; Poncelet, G; Grange, P

Published: JUL 25 2007, , DOI: 10.1016/j.jcat.2007.04.022

2450. Resistive sensor for water salinity

Authors: Popescu, M; Lorinczi, A; Sava, F; Savu, V; Savastru, D

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3956, DOI:

A simple electrical resistance sensor for monitoring of the coastal marine waters has been developed. The good sensitivity and reproducibility of the measurements make this sensor attractive for using in the research of the mixing of sweet (river) waters with the marine water, as well as the variation in the depth of the sea of the water salinity. Another advantage of the sensor is the possibility to monitor the water salinity by simply tracing the electrical resistance when the sensor is drawn at the surface or vertically in the sea and ocean waters.

2451. Ceria-based oxides as supports for LaCoO3 perovskite; catalysts for total oxidation of VOC

Authors: Alifanti, M; Florea, M; Parvulescu, VI

Published: JAN 31 2007, , DOI: 10.1016/j.apcatb.2005.10.037

2452. Correlated electrons and transport in a quantum point contact and in a double-quantum-dot system

Authors: Bulka, BR; Kostyrko, T; Tolea, M; Dinu, IV

Published: JUN 27 2007, JOURNAL OF PHYSICS-CONDENSED MATTER, 19, DOI: 10.1088/0953-8984/19/25/255211

A problem of electronic correlations is considered for two specific mesoscopic systems: the quantum point contact (QPC) and the double quantum dot (2QD) system. The systems are described using a generalized Anderson Hamiltonian. We show that charge fluctuations are relevant for electronic transport. In the QPC a local accumulation of charge and the dynamical Coulomb blockade effect lead to the 0.7 structure in the conductance characteristics. The evolution of the conductance with a magnetic field and in non-equilibrium situations is presented as well. The double quantum dot is studied in the approach, in which correlations within the 2QD are treated exactly, whereas the coupling of the 2QD to the leads is considered in the approximation valid at temperatures above the Kondo temperature. We analyse the evolution of the gate voltage dependence of the spin correlation functions and the conductance with the change of the interdot hopping. For the hopping parameter greater than a threshold value of the on-dot repulsion the physics of the device is dominated by the ground state eigenstates of the 2QD and antiferromagnetic correlations in the case of the doubly occupied 2QD. With a decrease of the interdot hopping repulsion below the threshold we observe a significant reduction of the antiferromagnetic coupling between the dots together with an enhanced occupation of the triplet states.

2453. Trapping phenomena in silicon-based nanocrystalline semiconductors

Authors: Ciurea, ML; Iancu, V; Mitroi, MR

Published: OCT 2007, SOLID-STATE ELECTRONICS, 51, 1337, DOI: 10.1016/j.sse.2007.07.002

In this paper, the trapping phenomena in silicon-based nanocrystalline semiconductors are studied. We propose a general and complete model for optical charging spectroscopy measurements, which takes into account the trapping-detrapping-retrapping processes and all the types of discharge currents that can occur in a nanocrystalline system. The model was applied to the measurements performed on multi-quantum well structures, (nc-Si/CaF2)(50), as well as on nanocrystalline porous silicon. This way, the trap parameters that are not directly measurable were determined. (C) 2007 Elsevier Ltd. All rights reserved.

2454. Dielectric properties of BZT ceramics for microwave applications

Authors: Ioachim, A; Toacsan, MI; Nedelcu, L; Banciu, MG; Dutu, CA; Andronescu, E; Jinga, S; Nita, P; Alexandru, HV

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1838, DOI:

High permittivity dielectric materials (epsilon(r) > 20) are used in mobile communications due to low dielectric loss in microwaves and millimeter waves, specific temperature dependence of the dielectric properties and high dielectric permittivity, which allows device miniaturization. Preparation of Ba(Zn1/3Ta2/3)O-3 ceramic materials (BZT) with optimal properties for applications requires special thermal treatments due to the difficult control of the cationic ordering. The samples were prepared by using solid-state reaction, doped with Eu2O3, ZrO2, Nb2O5, or Al2O3-Y2O3 and sintered at the following temperatures: 1400, 1500, 1550 degrees C for 2 or 3 hours. In order to improve the microwave properties, annealing treatments at 1410 degrees C for 10h or 30h were performed on ceramic samples. XRD was used for compositional and structural characterization. The XRD data allowed the study of the transition from the pseudo-cubic cell to the hexagonal cell. The dielectric properties were measured in the microwave range and were correlated with additives and structural properties. Sintering temperatures greater than 1500 degrees C are required for doped BZT compositions, in order to obtain high dielectric constant (epsilon(r) similar to 28) and high quality factor (Q = 10000 at 10 GHz).

2455. (Te/SnSe2)(3) multilayers deposited by pulsed laser deposition. Structure and gas sensing properties

Authors: Lorinczi, A; Sava, F; Tomescu, A; Simion, C; Socol, G; Mihailescu, IN; Popescu, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3492, DOI:

Multilayers made of alternative layers of composition SnSe2 and tellurium (three pairs) have been prepared by pulsed laser deposition (PLD). The complex films have been investigated by X-ray diffraction. After a special annealing in oxygen fluence at various temperatures, up to 620 degrees C, the films were investigated both by X-ray diffraction and for gas sensing. Gas sensing properties were tested for water vapours, carbon monoxide (CO) and methane (CH4). After annealing at high temperature, the structure of the multilayer samples show oxide phases like TeO2, SnO2 and a mixed oxide ternary phase SnTe3O8. The annealed multilayers show good sensing properties to water vapours and CO gas.

2456. Field-activated sintering of skutterudites

Authors: Kodash, VY; Groza, JR; Aldica, G; Toprak, MS; Li, S; Mamoun, M

Published: SEP 2007, SCRIPTA MATERIALIA, 57, 511, DOI: 10.1016/j.scriptamat.2007.05.032

Skutterudite (Co0.92Ni0.08)(4) Sb11.88Te0.12 powder has been consolidated under an applied electrical field using a field-assisted sintering technique (FAST). The low FAST sintering temperature and relatively high heating rate considerably reduce grain growth during sintering. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

2457. The study of the passive film formed on the surface of 316L stainless steel in artificial physiological media

Authors: Tutunaru, B; Patru, A; Bibicu, I; Preda, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3404, DOI:

This work is aimed at providing a better understanding of the biocompatibility of 316L stainless steel in the human body, where various biomolecules are able to bind metal ions and convey them from the surface of orthopaedic implant to various parts of the body. The passivation behavior of orthopaedic 316L implant was studied by associating the electrochemical methods (Differential Pulse Voltammetry and Cyclic Voltammetry) with the surface M(Mossbauer spectroscopy as a function of type of physiological media; glucydic, proteic and lipidic. Was studied the electrochemical behaviour of steel in three artificial media: Aminosteryl, Intralipid and Kabiven in the concentrations corresponding to the administration dosages. The results were discussed in the context of the formation of passive film which stability strongly depends on the corrosive activity of the physiological media in the order: Aminosteryl < Kabiven < Intralipid.

2458. Phototransport and photoluminescence in nanocrystalline porous silicon

Authors: Iancu, V; Ciurea, ML; Stavarache, I; Teodorescu, VS

Published: AUG 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2643, DOI:

The paper presents the phototransport and photoluminescence investigations on nanocrystalline porous silicon. Spectral dependence curves of the phototransport and photoluminescence were taken at room temperature. A typical phototransport curve presents several maxima and shoulders, while the photoluminescence curves present only one maximum. The temperature dependence of the phototransport was measured in the 85 - 250 K range for different wavelengths. All these curves present only one activation energy on the whole temperature interval. The experimental results are interpreted taking into account a quantum confinement model. Previous microstructure investigations proved that the studied nanocrystalline porous silicon is formed by a nanowire network. Then, the electron Hamiltonian can be split into the sum of a 1D longitudinal Bloch part and a 2D transversal part, the nanowire wall acting like a potential well. Thus, a number of discrete energy levels will appear into the band gap. Both phototransport and photoluminescence maxima are due to the transitions between these levels, corresponding to a mean nanowire diameter of 3.2 nm, in good agreement with the previous microstructure and electrical transport investigations. On the contrary, the temperature dependence of the phototransport is determined by the surface states located on the internal surface and/or the interface between nanocrystallites.

2459. SiOx-P2O5 films: promising components in photonic structure

Authors: Vasiliu, I; Gartner, M; Anastasescu, M; Todan, L; Predoana, L; Elisa, M; Grigorescu, C; Negrila, C; Logofatu, C; Enculescu, M; Moldovan, A; Pavelescu, G; Zaharescu, M

Published: MAR 2007, OPTICAL AND QUANTUM ELECTRONICS, 39, 521, DOI: 10.1007/s11082-007-9096-2

We intend to prepare periodic multilayered structures for photonic applications. With this goal we have performed a study of some characteristics of SiO (x) -P2O5 films deposited by the sol-gel method on glass and ITO (InSnO (x) )-coated glass. The as prepared films were annealed to different temperatures (150 and 200 degrees C). The chemical composition of the samples was determined by X-ray Photoelectron Spectroscopy (XPS). The XPS results revealed the presence of P in the as-deposited films. The structural an optical properties were examined by Fourier Transform Infrared Spectroscopy (FTIR), Spectroellipsometry (SE) and UV Transmission Spectroscopy. IR spectra of the deposited films attest the interaction of an amorphous SiO2 with the H3PO4 used as a P-precursor. Refractive indices for individual SiO (x) -P2O5 determined from SE measurements show a densification of the layer structure with the increasing temperature in the thermal treatment. The UV transmission spectra revealed a lower transmission for the sol-gel SiO (x) -P2O5 films as compared to ITO/glass substrate. AFM images proved the densification of the films with annealing in agreement with the ellipsometric results.

2460. Hybrid approach to the synthesis of FePt/Fe3B nanocomposite magnets

Authors: Crisan, O; Angelakeris, M; Kehagias, T; Filoti, G

Published: SEP 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2737, DOI:

Exchange coupling between alternatively dispersed hard and soft magnetic phases, gives rise to exchange spring magnets with enhanced energy product (BH)(max) that are believed to represent a novel class of permanent magnets with improved properties. The synthesis of a hybrid nanocomposite system made of soft magnetic Fe3B melt spun ribbon and hard magnetic Fe-Pt thin film, obtained by e-beam co-deposition in ultrahigh vacuum onto the ribbons, is reported. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction are used for structural characterization of these hybrid samples. Magnetic measurements provide observation of a drastic decrease of the saturation magnetization, compatible with the exchange coupling between hard and soft magnetic phases in the melt spun/thin film samples.

2461. Synthesis and characterization of the xZnO-(1-x)alpha-Fe2O3 nanoparticles system

Authors: Sorescu, M; Diamandescu, L; Wood, J

Published: MAR 2007, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 68, 430, DOI: 10.1016/j.jpcs.2006.12.007

The xZnO-(1-x)alpha-Fe2O3 nanoparticles system has been obtained by mechanochemical activation for x = 0.1, 0.3 and 0.5 and for ball milling times ranging from 2 to 24 h. Structural and morphological characteristics of the zinc-doped hematite system were investigated by X-ray diffraction (XRD) and Mossbauer spectroscopy. The Rietveld structure of the XRD spectra yielded the dependence of the particle size and lattice constant on the amount x of Zn substitutions and as function of the ball milling time. The x = 0.1 XRD spectra are consistent with line broadening as Zn substitutes Fe in the hematite structure and the appearance of the zinc ferrite phase at milling times longer than 4 h. Similar results were obtained for x = 0.3, while for x = 0.5 the zinc ferrite phase occurred at 2 h and entirely dominated the spectrum at 24 h milling time. The Mossbauer spectra corresponding to x = 0.1 exhibit line broadening as the ball milling time increases, in agreement with the model of local atomic environment. Because of this reason, the Mossbauer spectrum for 12 h of milling had to be fitted with two sextets. For x = 0.3 and 12 milling hours, the Mossbauer spectrum reveals the occurrence of a quadrupole-split doublet, with the hyperfine parameters characteristic to zinc ferrite, ZnFe2O4. This doublet clearly dominates the Mossbauer spectrum for x = 0.5 and 24 h of milling, demonstrating that the entire system of nanoparticles consists finally of zinc ferrite. As ZnO is not soluble in hematite in the bulk form, the present study clearly demonstrates that the solubility limits of an immiscible system can be extended beyond the limits in the solid state by mechanochemical activation. Moreover, this synthesis route allowed us to reach nanometric particle dimensions, which would make the materials very important for gas sensing applications. (c) 2006 Elsevier Ltd. All rights reserved.

2462. Characterization of fine grain Ba0.995Y0.005TiO3 ceramics obtained from gel-precursor nanopowder

Authors: Cernea, M; Monnereau, O; Llewellyn, P; Vasile, E

Published: MAR 2007, JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 7, 1020, DOI: 10.1166/jnn.2007.209

Using an acetate-alkoxide sol-gel route in which the precursors are barium acetate, yttriurn isopropoxide and titanium diisopropoxide bis-acetylacetonate, we prepared a ferroelectric material with the formula: Ba1-xYxTiO3, x = 0.005. SEM analysis showed a polymeric microstructure of the gel due to the chelated titanium alkoxide precursor used as starting materials. The evolution of the structure and microstructure of the precursor gel heated at temperatures up to 1000 degrees C was studied by various techniques. The powder obtained by heating the gel at 1100 degrees C presented a homogeneous structure consisting of submicronic particles (similar to 200 mm). XRD and SAED analyses revealed that Ba0.995Y0.005TiO3 nanocrystals of about 5-10 rim appeared at 600 degrees C, together with BaCO3. The presence of barium carbonate was identified also by IR spectroscopy and thermal analyses. The ceramics obtained from the as-prepared powder presented good dielectric properties (capacitance = 840 pF/dielectric constant = 3860 and dielectric loss (tan delta) 0.078 at Curie temperatures of 120-121 degrees C).

2463. Electrostatic electron piston pump with in-plane gate transistors

Authors: Draghici, M; Salloch, D; Melnikov, A; Wieck, AD

Published: AUG 2007, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 244, 3014, DOI: 10.1002/pssb.200675613

We have demonstrated an electron pump with in-plane gate (IPG) transistors fabricated by focused ion beam (FIB) implantation on GaAs-A1(x)Ga(1-x)As modulation-doped heterostructure with a two-dimensional electron gas (2DEG). The maskless fabrication process does not require any alignment between the circuit elements including the sources, the drains and the gates of the IPG transistors. Although, the device is operating at low frequencies (tens of kHz), it is capable to produce a current more than one order of magnitude higher than other electron pumps based on Coulomb blockade and single electron tunneling effects. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2464. Qualitative characterization of YBa2Cu3O7-delta films using low spectral resolution Raman spectroscopy

Authors: Branescu, M; Morjan, I; Dumitrache, F; Sandu, I

Published: 2007, ADVANCED LASER TECHNOLOGIES 2006, 6606, DOI: 10.1117/12.729507

We describe our low spectral resolution Raman system that allows us to directly appreciate the quality of YBa2Cu3O7-delta (YBCO) films, obtained by pulsed laser deposition on LaAlO3 substrate. We identify the basic features of YBCO films' spectral fingerprints, validated by high spectral resolution analysis, described in previous reports. This fast and non-destructive valuable analytical tool functions at a convenient time and environment after deposition.

2465. Hydrogenation effects in R2Fe14Si2 (R = Y, Nd, Dy and Er) offstoichiometric compounds

Authors: Sorescu, M; Diamandescu, L; Pourarian, F

Published: MAR 2007, INTERMETALLICS, 15, 381, DOI: 10.1016/j.intermet.2006.08.009

Samples of R2Fe14Si2 (R = Y, Nd, Dy and Er) solid solutions were prepared by arc melting and exposed to hydrogenation. Characterization of hydrogenation effects was done using X-ray diffraction (XRD) and Mossbauer spectroscopy. Rietveld refining of the XRD spectra showed that both lattice parameters a and c increased after hydrogenation, with the exception of Er2Fe14Si2, for which they decreased slightly. The values of the magnetic hyperfine fields corresponding to the four inequivalent lattice sites were found to increase after hydrogenation in all offstoichiometric compounds investigated. Changes in the relative site occupancies were observed. Our study is the first to evidence hydrogenation effects on the hyperfine magnetic fields in intermetallics. (c) 2006 Elsevier Ltd. All rights reserved.

2466. Raman and SERS studies of single-walled carbon nanotubes and Nanotubes/Conjugated polymers composites

Authors: Lefrant, S; Buisson, JP; Mevellec, JY; Baibarac, M; Baltog, I

Published: 2007, FUNDAMENTAL AND APPLIED SPECTROSCOPY, 935, +, DOI:

In this paper, we recall the main characteristics of Raman spectra of single-walled carbon nanotubes. We illustrate our studies by results obtained on HiPCO samples on one hand, and "arc electric" samples on the other hand by using two different excitation wavelengths. We focus on the peculiarity of observing separately semi-conducting and metallic tubes. We emphasize also the role played by the radial breathing modes whose frequency depends on the tube diameter and on the need to take into account the interactions between tubes when they are in bundles in order to determine accurately the tube diameter distribution. Finally we demonstrate briefly the evidence of using the SERB (surface enhanced Raman scattering) spectroscopy to study reactions at interfaces or between components in nanotubes/conjugated polymers composites.

2467. DC conductivity in GeSb2Te4 and (GeSb2Te4)(90)(SnSe2)(10) phase change materials

Authors: Popescu, M; Kubliha, M; Kaluzny, J; Velea, A; Lorinczi, A

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3953, DOI:

The dc electrical conductivity of the bulk amorphous GeSb2Te4 material has been investigated. Pure and samples doped by 10 at. % SnSe2 have been measured. The conductivity in the samples has been compared with that of SnSe2 bulk sample. The activation energy of the doped sample is 0.165 eV. During heating the conductivity of doped material increases, reaches a maximum and then decreases. The comparison with the pure SnSe2 samples allows to explain this behavior by the release above 148 degrees C of a small amount of selenium not bonded in the network.

2468. Time-resolved luminescence spectroscopy of Eu2+ in BaFCl : Eu2+ X-ray storage phosphor

Authors: Secu, M; Secu, CE; Vasile, V; Predoi, D; Gazdaru, DM

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1802, DOI:

Photoluminescence (PL) spectra recorded at room temperature (RT) in polycrystalline BaFCI:Eu2+ X-ray storage phosphor have shown the europium associated luminescences, a broad luminescence band at 385nm (3.22eV) with a 3.3 +/- 0.1 mu s PL lifetime accompanied by a luminescence line at about 368nm (3.37eV). The energy difference Delta EB-L =226cm(-1) between the two excited levels from which the europium associated band and line luminescences took place was computed. An additional broad luminescence band at about 425nm (2.92eV) with 0.7 +/- 0.1 mu s PL lifetime has been attributed to the europium luminescence perturbed by an impurity. Time resolved spectroscopy measurements have shown that no other impurity luminescences (like oxygen-vacancy centres) can be observed at RT except the europium associated ones.

2469. Performance of as-reacted and multiple bent ('pre-bent') practical Nb3Sn bronze route wires with different architectures

Authors: Badica, P; Awaji, S; Nishijima, G; Oguro, H; Sandim, MJR; Cangani, MP; Ghivelder, L; Katagiri, K; Watanbe, K

Published: MAR 2007, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 20, 280, DOI: 10.1088/0953-2048/20/3/028

Six practical composite wires of Nb3Sn (Furukawa Electric Co, Ltd) with different architectures ( design and reinforcement) were compared from the normal state resistance R, critical temperatures T-c(onset), T-c(offset) and Delta T-c, upper critical field B-c2 ( at 4.2 K) and critical current density J(c) points of view. Wires were as follows: three of near-the-edge reinforcement design with Nb reinforcement of 0, 21, 50 vol% in the CuNb region, and two of central reinforcement design with Nb of 21 and 50 vol%. One wire with near the edge 50% vol Nb reinforcement had a different reinforcement/superconductor ratio. As-reacted wires show very different patterns of R, T-c(onset), T-c(offset), Delta T-c, B-c2 and J(c). For the superconducting parameters this is probably due to different 3D thermal residual strains. Data suggest that the architecture of the as-reacted wire can control residual strain values and distribution. During multiple bending of the wires at room temperature ( named pre-bending), introduction of the reinforcement improves relaxation of the 3D residual strain and especially of the lateral components. As a consequence, B-c2 and J(c) versus pre-bending strain, epsilon(pb), are enhanced to values closer to those of the Nb3Sn in the stress-free state. Relative enhancement of these critical parameters for the reinforced wires is higher than for the reinforcement-free wire. Evolution during pre-bending and maximum attained absolute values of the superconducting parameters can be grouped roughly as a function of near-the-edge or central reinforcement design. Variation of the superconducting parameters suggests that the pre-bent state may depend on the as-reacted one ( which is a function of wire architecture and processing history); when J(c) was low as in the case of as-reacted wires with central reinforcement, during pre-bending, despite a relatively high J(c) enhancement, this parameter attained lower absolute maximum values than for the other wires. Depending on the wire, when pre-bending strain epsilon(pb) = 0.8 - 1%, the enhancement of non-Cu J(c) at 4.2 K in the pre-bent wire is by up to 43.5% at 15 T compared to the as-reacted case. The maximum absolute value of J(c) is obtained for the near-the-edge reinforcement pre-bent wires with 21 and 50% vol Nb. B-c2 of these wires was lower than for the other reinforced wires and higher than for the reinforcement-free wire. Pre-bent wires with near-the-edge reinforcement are identified as new and promising candidates for fabrication of react-and-wind coils with improved performance.

2470. Photosensitization of ZnO nanostructured thin films with organic dyes

Authors: Tazlaoanu, C; Ion, L; Socol, G; Socol, M; Mihailescu, IN; Stanculescu, F; Enculescu, I; Ionescu, F; Magherusan, L; Antohe, S

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1346, DOI:

We report in this contribution on the photosensitization effect of ZnO nanostructured thin films with copper-phthalocyanine (CuPc). ZnO films were prepared by pulsed laser deposition (PLD), on optical glass substrates, covered with 300 nm thick ITO films. The structure and morphology of ZnO films were optimized for photovoltaic-cell applications by controlling the growing conditions. ZnO films (wurtzite type) were (001) preferentially oriented in the growth direction. Organic dyes were vacuum sublimated on ZnO films, and subsequently a 300 nm thick copper film was vacuum sublimated on top of the structure, acting as an ohmic contact. Action spectra of ITO/ZnO/CuPc/Cu photovoltaic structures were recorded and a well defined response was observed in the range of absorption bands of organic dyes. The dark IN characteristics were also recorded, and electrical characterizations of the photovoltaic structures are given. The measured fourth quadrant IN characteristics under integral illumination (photoelement regime), allowed us to extract the typical photovoltaic cells parameters.

2471. Morphology of CaCO3 precipitated in ultrasonic field

Authors: Mateescu, CD; Mocioi, M; Sarbu, C; Branzoi, F; Chilibon, I

Published: 2007, SIX INTERNATIONAL CONFERENCE OF THE BALKAN PHYSICAL UNION, 899, 626, DOI:

Synthesis of CaCO3 was performed in ultrasonic field in order to improve its properties. The evolution of the precipitation reaction in ultrasonic field provided a solid phase with aragonite morphology slightly impurified with vaterite. Particles dimensions were diminished, the solid phase presenting an important fraction of nanometer size particles.

2472. Sintering distorsion produced by differences in green density and sample shape of PZT compacted powders

Authors: Miclea, C; Tanasoiu, C; Spanulescu, I; Miclea, CF; Gheorghiu, A; Amarande, L; Cioangher, M; Trupina, L; Miclea, CT; David, C

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, +, DOI:

A study was made to determine the effect of sample shape, compacting pressure and green density gradients on the final shape and density of sintered bodies. Experiments were carried out on a PZT type powder, pressed with a large range of shapes from long cylinders up to thin discs, at pressures ranging between 40 and 180 MPa. Important shape distorsion were found for both long cylinders and thin discs but surprisingly the final density was not essentially changed even if the green compacted density showed important changes within the samples. Differences in shrinkage of diameter and thickness brought about by sintering for samples with different shapes were found.

2473. Raman and photoluminescence studies on low-dimensional PbI2 particles embedded in polymer matrix

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1361, DOI:

Pbl(2) crystallite incorporated in optically transparent polyacrylamide and poly (vinyl alcohol) matrix have been studied by Raman scattering, photoluminescence (PL) at low temperature and Scanning Electron Microscopy (SEM). The small particles of Pbl(2) embedded in different host matrix were prepared by: i) cooling to the room temperature a boiling saturated aqueous Pbl(2) solution containing polyacrylamide or poly (vinyl alcohol) and ii) by chemical reaction of KI and Pb(NO3)2 in aqueous polyacrylamide solution. In all cases, were identified hexagonal platelets of Pbl(2) and rods like particles. The rods are featured by a similar Raman spectrum and a specific green emission (cca 550 nm). Modification of the Raman and PL spectra results from a compressing effect produced by the penetration between the Pbl(2) layers of different molecular species. By compression the hybridized electronic level situated at the top of valence band, formed by the contribution.of the 6s and 5p states of Pb2+ and l ions, undergo a deformation that induces a weakness of the interaction between the lead ion and iodine electron within a layer so that the photoluminescence of intercalated Pbl(2) acquires the characteristics of Pb2+ emission when it is dissolved in an alkali halide crystal.

2474. Hydrothermal synthesis and structural characterisation of xTiO(2)-(1-x)alpha-Fe2O3 mixed oxide nanoparticles

Authors: Diamandescu, L; Feder, M; Tarabasanu-Mihaila, D; Vasiliu, F

Published: JUN 15 2007, APPLIED CATALYSIS A-GENERAL, 325, 275, DOI: 10.1016/j.apcata.2007.02.039

xTiO(2)-(1- x)alpha-Fe2O3 (x = 0.0-1.0) mixed oxide nanoparticle, system ha, been synthesized by a hydothermal route, X-ray diffraction, Mossbauer spectroscopy and electron microscopy have been used to study the structure, morphology and substitution in the nanosized samples. Experimental evidence for the solubility limits of Ti4+, in alpha-Fe2O3 lattice and of Fe3+ in TiO2 structure is given. (c) 2007 Elsevier B.V. All rights reserved.

2475. Structural and dielectric investigations of donor-acceptor substituted PZT ceramics

Authors: Dimitriu, E; Iuga, A; Ramer, R; Sandu, I; Cernea, M

Published: 2007, FERROELECTRICS, 353, 582, DOI: 10.1080/00150190701368091

Scanning electron microscopy (SEM) and energy dispersive X-ray measurements reveal inhomogeneities in the distribution of elements in W-, Li- doped PZT materials with the composition PbZr0.51 Ti0.49-2.5x W1.5xLixO3 (x = 0.03 and 0.05). Increasing the tungsten concentration leads to an increase of inhomegenities number in the PZT matrix. The high sintering temperature and Li+ concentration contribute to the vitreous aspect Of the materials. X-ray diffraction patterns revealed the Presence of both rhombohedral and tetragonal phases in the two materials. Considering the materials as composites with a 0-3 connectivity pattern, a mathematical approach is proposed. This was used to calculate the contribution of the agglomerations to the experimental dielectric constant.

2476. Thickness-driven antiferroelectric-to-ferroelectric phase transition of thin PbZrO3 layers in epitaxial PbZrO3/Pb(Zr0.8Ti0.2)O-3 multilayers

Authors: Boldyreva, K; Pintilie, L; Lotnyk, A; Misirlioglu, IB; Alexe, M; Hesse, D

Published: SEP 17 2007, APPLIED PHYSICS LETTERS, 91, DOI: 10.1063/1.2789401

Epitaxial antiferroelectric/ferroelectric PbZrO3/PbZr0.8Ti0.2O3 multilayers were grown on SrRuO3-electroded SrTiO3(100) substrates by pulsed laser deposition. Polarization-field and switching current-voltage curves show a mixed antiferroelectric-ferroelectric behavior of the multilayers with an individual layer thickness above 10 nm, whereas below 10 nm the multilayers show only ferroelectric behavior. Clearly the PbZrO3 layers thinner than 10 nm experienced a transition into the ferroelectric state. X-ray diffraction reciprocal space mapping showed a corresponding orthorhombic-to-rhombohedral transition of the PbZrO3 layers. The observations are discussed in terms of the influence of strain.

2477. Dielectric and morphological studies of BST ferroelectric ceramics

Authors: Ioachim, A; Vasiliu, F; Toacsan, MI; Nedelcu, L; Banciu, MG; Alexandru, HV; Stoica, G

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1581, DOI:

Barium strontium titanate with molar formula Ba0.75Sr0.25 TiO3 (BST) was prepared from raw materials by solid-state reaction. Samples were sintered at 1230 degrees C and 1260 degrees C for 2 h. In order to improve the sintering process, 1 wt. % MgO and 1 wt. % MnO2 were used as sintering additives. The sinterability, structural, morphological and dielectric properties of pure and doped BST samples were investigated. Perovskite structure of polycrystalline BST ceramics was determined by Xray diffraction. SEM investigations revealed a grain and pore size distribution, which is shifted to higher values by a slight increase of the sintering temperature from 1230 degrees C to 1260 degrees C. In the presence of additives, a better sintering and grain refining could be observed, whereas their lack induce a strong effect of exaggerated grain growth, by forming of large faceted grains. The presence of Mn ions in the doped BST ceramics was revealed by the EDX analysis. On the other hand, Mg ions are not evidenced. Temperature dependence of dielectric constant measured at 1 kHz shows a diffuse ferroelectric-paraelectric transition, which can be attributed to the large size dispersion of grains. The increase of sintering temperature leads to a shift of the Curie temperature to higher values.

2478. Characterisation of magnetic iron oxide in hydroxyapatite

Authors: Birsan, M; Predoi, D; Birsan, C; Secu, CE; Andronescu, F

Published: JUN 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1832, DOI:

In order to be used for medical applications, a material must exhibit many specific characteristics, of which the most fundamental is related to biocompatibility. Lately, the iron oxide nanoparticles are preferred for biomedical applications because they present a superparamagnetic behaviour at room temperature. The preparation method and conditions of iron oxide nanoparticles represents some of the most important challenges that will determine the particle size and shape, the size distribution, the surface chemistry of the particles and consequently their magnetic properties. The samples were characterized by X-ray diffractions (XRD), transmission electron microscopy (TEM) and infrared spectroscopy.

2479. Localized energy levels generated in Magnetic Czochralski silicon by proton irradiation and their influence on the sign of space charge density

Authors: Scaringella, M; Menichelli, D; Bruzzi, M; Macchiolo, A; Piemonte, C; Zorzi, N; Candelori, A; Eremin, V; Verbitskaya, E; Pintilie, I

Published: JAN 11 2007, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 570, 329, DOI: 10.1016/j.nima.2006.09.033

The microscopic damage produced in diodes made of n-type Magnetic Czochralski (MCz) silicon by 24 GeV and 26 MeV protons, up to the fluence of 1.3 x 10(15) cm(-2) 1 MeV equivalent neutrons, has been investigated and results are compared to the damage produced in devices made of standard Floating Zone (STFZ) silicon. It is found by means of Thermally Stimulated Currents (TSC) that the production of a radiation induced charged defect is enhanced in MCz, and might be in part responsible for the differences observed in the two materials at room temperature. The influence of defects on the sign of the space charge density has been studied by current transients at constant temperature i(T, t) and by Transient Current Technique (TCT). Type inversion is not revealed up to the highest investigated fluence. Full depletion voltage V-dep measurements versus fluence exhibits a minimum close to 2 x 10(14) cm(-2) 1 MeV equivalent neutrons; at the same fluence, V-dep measured as a function of annealing time changes its initial slope from positive to negative. It is shown by numerical simulations that these features can be accounted by the formation of a double junction, even in absence of type inversion. (c) 2006 Elsevier B.V. All rights reserved.

2480. Semiconductor nanowires obtained by template method

Authors: Sima, M; Enculescu, I; Sima, M; Vasile, E

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1554, DOI:

One-dimensional structures having uniform diameters were prepared by electrochemical deposition using polycarbonate membranes as templates. Lead chalcogenides and ZnO tubes and rods growth processes were presented comparatively. The tendency of PbTe and PbSe semiconductors to grow as tubes both in membrane micro and nanopores was explained based on the absorption of lead ions on the pore wall.

2481. Organic thin film transistors with HfO2 high-k gate dielectric grown by anodic oxidation or deposited by sol-gel

Authors: Tardy, J; Erouej, M; Deman, AL; Gagnalre, A; Teodorescu, V; Blanchin, MG; Canut, B; Barau, A; Zaharescu, M

Published: FEB-MAR 2007, MICROELECTRONICS RELIABILITY, 47, 377, DOI: 10.1016/j.microrel.2006.01.012

We report here on pentacene based organic field effect transistors (OFETs) with a high-k HfO2 gate oxide. HfO2 layers were prepared by two different methods: anodic oxidation and sol-gel. A comparison of the two processes on the electrical properties of OFETs is given. Ultra thin nanoporous (20 nm) sol-gel deposited oxide films were obtained following an annealing at 450 degrees C. They lead to high mobility and stable devices (mu = 0.12 cm(2)/V S). On the other hand, devices with anodic HfO2 revealed a little bit more leaky and show some hysteresis. Anodization, however, presents the advantage of being a fully room temperature process, compatible with plastic substrates. Stability and response to a bias stress are also reported. (c) 2006 Elsevier Ltd. All rights reserved.

2482. Crystallization of PLD deposited ITO thin films by thermal treating in various gaseous environments

Authors: Viespe, C; Grigoriu, C; Popescua, M; Sava, F; Lorinczi, A; Velea, A; Zamfira, S

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3566, DOI:

ITO films of composition (In2O3)(0.9) - (SnO2)(0.1) have been prepared by pulsed laser deposition (PLD).The films were found to be amorphous. The structure and evolution of the films during annealing in air, oxygen atmosphere and reducing atmosphere (CO2) have been investigated by X-ray diffraction. The films annealed in ambient atmosphere start to crystallize under 250 degrees C annealing temperature. The films treated in oxygen atmosphere crystallize at higher temperature (similar to 300 degrees C).

2483. Growth of ZrSnTiO thin films by pulsed-laser deposition

Authors: Nistor, M; Ioachim, A; Gallas, B; Defourneau, D; Perriere, J; Seiler, W

Published: MAR 7 2007, JOURNAL OF PHYSICS-CONDENSED MATTER, 19, DOI: 10.1088/0953-8984/19/9/096006

The formation of ZrSnTiO thin films by pulsed-laser deposition has been studied. By the complementary use of Rutherford backscattering spectrometry, x-ray diffraction and scanning electron microscopy, the composition, crystalline structure and surface morphology of the films were investigated. The optimum conditions for the growth of dense, stoichiometric and crystalline films were determined, i.e. substrate temperature of 700 degrees C and oxygen pressure in the 10(-3)-0.1 mbar range. Such ZrSnTiO films present the classical orthorhombic structure for growth on Si substrates, while the use of MgO single crystal substrates leads to the formation of epitaxial ZrSnTiO films with a tetragonal structure. This previously unobserved ZrSnTiO crystalline phase obtained in thin film form is the result of an epitaxy stabilization effect, and presents improved optical properties as shown by the results of spectroscopic ellipsometry measurements. Moreover, the films grown at 700 degrees C under low oxygen pressure (< 10(-5) mbar) were composed of a Sn rich surface layer superimposed on an understoichiometric zirconium titanate oxide film near the substrate. This last layer, which crystallizes in a cubic structure and has never been reported in bulk material, could be related to the presence of oxygen vacancies in the films grown in these conditions.

2484. Microstructure and properties of barium titanate ceramics prepared by mechanochemical synthesis

Authors: Miclea, C; Tanasoiu, C; Spanulescu, I; Miclea, CF; Gheorghiu, A; Amarande, L; Cioangher, M; Miclea, CT

Published: 2007, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 10, 345, DOI:

The new advanced procedure of mechanochemical synthesis was used to prepare barium titanate from barium and titanium oxides. The X-ray examination of the powders milled for different times showed the phase evolution during synthesis. The perovskite phase was initiated after 5 hours of milling and was completed after 50 hours. Sintered samples from these nanopowders show different dielectric properties depending on their morphostructure. Thus for samples with an average grain size of 2 mu m we obtained the highest dielectric constant of 5 800 at room temperature. A sharp maximum of the dielectric constant with values of about 16 000 was recorded at the Curie temperature.

2485. Defected ground dual-mode resonators and filters

Authors: Banciu, MG; Militaru, N; Lojewski, G

Published: 2007, 2007 IEEE 18TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, VOLS 1-9, +, DOI:

A microstrip defected ground structure dual mode filter is presented. Several methods for coupling between the dual modes are investigated. Defected ground structure is used to enhance the external coupling and to introduce the necessary perturbation to the initially symmetrical structure. The proposed device is compact, requiring a surface area of about 6 times smaller than the area needed for a conventional patch dual mode resonator.

2486. Structural studies on some doped CdS thin films deposited by thermal evaporation

Authors: Iacomi, F; Purica, M; Budianu, E; Prepelita, P; Macovei, D

Published: MAY 31 2007, THIN SOLID FILMS, 515, 6084, DOI: 10.1016/j.tsf.2006.12.091

The influence of the Mn, Se and Sb impurities on the structure and morphology of US thin films grown on p(+) Si wafers was studied. The starting powders were mixed in the same molar ratios (0.3%) and deposited in the same conditions by vacuum thermal evaporation. X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and reflectance studies made on thermal treated thin films (573 K, 2 h in air) evidenced that thin films have a hexagonal oriented structure, and that dopants enter into the US lattice merely by substitution. The dopant nature influences the thin film thickness and chemical composition. The doped US thin films have roughness in nanometer region and a reflectivity lower than 40%. Silicon substrate acts as a template and favors the retention of Mn and scatters the Sb dopants. The CdS:Se thin film is thicker than CdS:Mn and CdS:Sb ones and is a mixture of doped and undoped nanocrystals. (C) 2007 Elsevier B.V All rights reserved.

2487. Powder neutron diffraction of Nd3Co13-xNixB2 compounds

Authors: Plugaru, N; Rubin, J; Bartolome, J; Campo, J; Cuello, GJ; Tovar, M; Prokhnenko, O

Published: SEP 2007, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 316, E441, DOI: 10.1016/j.jmmm.2007.02.173

We report results of a powder neutron diffraction study on the crystal structure and local magnetic moments in Nd3Co13-x NixB2 compounds with Nd3Ni13B2- type structure. The largest 3d magnetic moment resides at the 4 h sites. Nd magnetic moment is reduced with respect to the free ion value. Preferential Ni substitution for Co is also found at the 4h site. The refined magnetization direction is consistent with the T-x phase diagram derived from magnetization data. (c) 2007 Elsevier B. V. All rights reserved.

2488. AFM and complementary XRD measurements of in situ grown YBCO films obtained by pulsed laser deposition

Authors: Branescu, M; Vailionis, A; Huh, J; Moldovan, A; Socol, G

Published: JUL 31 2007, APPLIED SURFACE SCIENCE, 253, 8183, DOI: 10.1016/j.apsusc.2007.02.160

We report an optimized kinetic regime to grow in situ YBa2Cu3O7-delta (YBCO) films on LaAlO3 substrates, by pulsed laser deposition (PLD), which is technically more advantageous than the usual one. Atomic force microscope (AFM) pictures show that the in situ grown YBCO films have much smoother surfaces than the post-deposition annealed YBCO films. The influence of the substrate's surface quality and that of the pulsed laser fluence used in the deposition process on the surface quality and on the critical temperature (T-C) of the in situ YBCO films are described. For measurements we utilized the atomic force microscopy and X-ray diffraction (XRD) techniques. (c) 2007 Elsevier B.V. All rights reserved.

2489. First measurement of the nonlinear coefficient for Gd1-xLuxCa4O(BO3)(3) and Gd1-xScxCa4O(BO3)(3) crystals

Authors: Andersen, MT; Mortensen, JL; Germershausen, S; Tidemand-Lichtenberg, P; Buchhave, P; Gheorghe, L; Lupei, V; Loiseau, P; Aka, G

Published: APR 16 2007, OPTICS EXPRESS, 15, 4901, DOI: 10.1364/OE.15.004893

The effective nonlinear coefficient and temperature acceptance bandwidth of three Lu and Sc co-doped GdCa4O(BO3) 3 type nonlinear crystals were measured. NCPM for SHG in to the blue-UV spectral region can be obtained by controlling the co-dopant concentration. Measurements were based on intra-cavity SHG of a CW Ti: Sapphire laser, and the effective nonlinear coefficients were found to be in the range of 0.5 to 0.6 pm/V for the three crystals used. The FWHM temperature acceptance bandwidth was measured to be more than 35 degrees C using a 6 mm long Gd0.871Lu0.129Ca4O(BO3)(3) crystal. A maximum of 115 mW at 407.3 nm in a single direction was measured using a 6.5 mm long Gd0.96Sc0.04Ca4O(BO3)(3) crystal. (c) 2007 Optical Society of America.

2490. Characteristics of hydroxyapatite thin films

Authors: Predoi, D; Ghita, RV; Ungureanu, F; Negrila, CC; Vatasescu-Balcan, RA; Costache, M

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3831, DOI:

Thin films of hydroxyapatite (HAp) (Ca-10(PO4)(6)(OH)(2)) were vacuum deposited on different substrates (quartz and silver) in connection with biomedical applications. Characteristics of thin films were putted into evidence by (SEM) and (XPS) analysis. The FT-IR spectroscopy was performed on hydroxyapatite powder and thin films deposited on quartz. The deposition of HAp thin films presents good surface quality as a smooth and an adherent layer. The biological tests confirm the characteristics of these thin films as bioactive materials. The hydroxyapatite thin films supports have a micro cell configuration that allows them to be used for obtaining medical biocompatible supports.

2491. Structure, morphology and magnetic properties of Fe-Au core-shell nanoparticles

Authors: Pana, O; Teodorescu, CM; Chauvet, O; Payen, C; Macovei, D; Turcu, R; Soran, ML; Aldea, N; Barbu, L

Published: SEP 15 2007, SURFACE SCIENCE, 601, 4357, DOI: 10.1016/j.susc.2007.06.024

The aim of the present work is the investigation of the core-shell Fe@Au nanoparticles obtained by the inverse micelles method. Also hybrid structures between Fe@Au nanoparticles and the well-known conducting polymer polypyrrole (PPY) were obtained and investigated. The properties of the composites were investigated by TEM, HRTEM, X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS) and magnetization measurements. The TEM, HRTEM measurements show that two categories of core-shell nanoparticles with mean diameters of 5 nm and 25 nm, respectively, are formed. The XPS investigations of the core-shell Fe@Au nanoparticles indicate that besides Fe-0 inside the cores, small amounts of Fen,111, located onto the gold surface were also formed during the samples preparation. The magnetization of the investigated nanocomposites measured versus increasing and decreasing magnetic field shows no hysteresis loop, this behavior being consistent with a superparamagnetic behavior. The behavior of the SQUID magnetization vs. temperature under field cooled (FC) and zero field cooled (ZFC) at 0.1 T magnetic field for Fe@Au nanoparticles confirmed the existence of superparamagnetism. The superparamagnetic model was used to fit the experimental magnetization vs. applied magnetic field as it was measured by SQUID up to 5 T. (C) 2007 Elsevier B.V. All rights reserved.

2492. Investigation by electrochemical impedance spectroscopy of electrodeposition of zinc-oxide microwires using nitrate bv template method

Authors: Sima, M; Manea, AC; Sima, M; Visan, T

Published: AUG 2007, REVISTA DE CHIMIE, 58, 746, DOI:

Comparative experiments regarding electrodeposition of zinc oxide either as films on Pt and Au substrates or as microwires grown in microporous polycarbonate membranes were carried out using nitrate aqueous solutions as electrolyte. Linear sweep voltammetry and electrochemical impedance spectroscopy together with SEM and XRD techniques were used for investigation. The equivalent electrical circuits for fitting experimental results were similar to those for characterisation of metal/polymer coating systems.

2493. Crystallization processes in Fe-Pt-Nb-B melt spun ribbons

Authors: Crisan, AD; Crisan, O; Randrianantoandro, N; Valeanu, M; Morariu, M; Burkel, E

Published: SEP 2007, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS, 27, 1285, DOI: 10.1016/j.msec.2006.08.031

Intermetallic Fe-Pt-Nb-B alloys with 3 different compositions have been synthesized by rapid solidification technique and their phase structure was characterized by means of X-ray diffraction and Mossbauer spectrometry. It is shown that Fe68Pt21Nb2B9 and Fe65Pt25Nb2B8 as-east samples consist mainly of A1 soft magnetic f.c.c. Fe-Pt phase, while the Fe68Pt13Nb2B17 as-cast sample exhibits topological short-range order, typical for amorphous ribbons. Crystallization processes in the amorphous sample and phase evolution with the temperature have been studied using differential scanning calorimetry (DSC). The occurrence of exothermic peaks is related to structural transformations in the alloys and the crystallization process is shown to be highly dependent upon the heating rate in the DSC process. (C) 2006 Elsevier B.V. All rights reserved.

2494. Dielectric properties of (Ba,Sr)TiO3 thin films for applications in electronics

Authors: Ioachim, A; Toacsan, MI; Nedelcu, L; Banciu, MG; Dutu, CA; Buda, M; Sava, F; Popescu, M; Scarisoreanu, N; Dinescu, M

Published: 2007, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 10, 354, DOI:

Barium strontium titanate (BST) bulk ceramic was used as target for PLD thin film deposition. In order to avoid stoichiometry modification during the deposition, a more reactive oxidant ambient in the chamber was produced by rising a radiofrequency discharge 13.56 MHz, 150 W. Thin films of stoichiometric BST was deposited on alumina substrate with the thickness between 400 and 500 nm heated at 650 degrees C. An aditional anealing was made at 800 degrees C for 6 hours. XRD and SEM were used for sample characterization. Capacity measurements at 100 kHz were performed versus temperature.

2495. The ferroectric-electric characterization of PZT-PbS composites

Authors: Stancu, V; Buda, M; Pintilie, L; Popescu, M; Sava, F

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1520, DOI:

A new method for the preparation of PbS/PZT composite materials is proposed. The PZT matrix has been obtained using the sol-gel method on Pt-coated Si substrates. The PbS (nano) crystals were subsequently obtained by dipping the porous PZT matrix in Pb(NO3)(2) and Na2S solutions at room temperature. The XRD spectra show the presence of the tetragonal phase of PZT. The microstructure of the film was analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The size of the PbS (nano)-particles at the sample's surface is about 25 nm, estimated from the AFM analysis. The roughness of the sample's surface is about 5 nm. The porosity of the composite, estimated from the SEM analysis in cross-section is smaller than for the reference PZT porous matrix. The equivalent dielectric constant of the composite increases by a factor of 4-5 in comparison with the porous PZT reference and does not depend on the thickness of the surface PbS (nano)-crystalline layer. The saturated polarization (Ps) value for the PZT-PbS composite is smaller than that corresponding to the bulk PZT but higher than for the reference porous PZT. We attribute these effects to the partial filling of the pores in the PZT matrix with PbS.

2496. Spectroscopic evidence for the bulk polymerization of N-vinyl carbazole in the presence of single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Lefrant, S; Gomez-Romero, P

Published: AUG 24 2007, POLYMER, 48, 5288, DOI: 10.1016/j.polymer.2007.07.008

The bulk polymerization reaction of N-vinylcarbazole (VK) at 70 degrees C in the presence of single-walled carbon nanotubes (SWNTs) leads to a new composite, whose optical properties were studied by photoluminescence (PL), surface enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopies. A dramatic reduction of the poly(N-vinylcarbazole) (PVK) PL efficiency and a change in the vibrational structure of the PL spectrum of this polymer were observed by adding SWNTs to the synthesis mixture. Steric hindrance effects were evidenced both in SERS spectra of the VK when it interacts mechanico-chemically with SWNTs and in FTIR spectra of the un-doped PVK/SWNTs' composites. Cyclic voltammetry was used to demonstrate the doping process of PVK in PVK/SWNTs' composite. (c) 2007 Elsevier Ltd. All rights reserved.

2497. Effect of lead content on the structure and piezoelectric properties of hard type lead titanate-zirconate ceramics

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Amarande, L; Gheorghiu, A; Spanulescu, I; Plavitu, C; Miclea, CT; Cioangher, MC; Trupina, L; Iuga, A

Published: 2007, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 27, 4059, DOI: 10.1016/J.jeurceramsoc.2007.02.094

In the present investigation we studied the effect of lead content on a hard type ceramics starting from lack to excess PbO. Specimens of Pb-x(Mn0.017Sb0.033Zr0.48Ti0.47)O-3 with 0.96 <= x <= 1.06 were prepared by conventional oxide mixing technique and sintered at temperatures between 1280 and 1350 degrees C. In samples with lower Ph concentration the pyrochlore phase appeared, while in those with higher Pb an excess of PbO phase was detected. These phases proved detrimental for the properties of sintered ceramics. The highest values of piezoelectric properties were observed only for samples with an excess lead of about 2% sintered at 1340 degrees C, indicating that it represents the optimum amount of PbO. For such samples, the density p was 7.77 g/cm (3). the remnant polarization P, was 37 mu C/cm(3) the planar coupling coefficient k(P) was 0.57 and the charge constant d(33) was 340 C-P/N. (c) 2007 Elsevier Ltd. All rights reserved.

2498. Electronic shell structure and carrier dynamics of high aspect ratio InP single quantum dots

Authors: Beirne, GJ; Reischle, M; Rossbach, R; Schulz, WM; Jetter, M; Seebeck, J; Gartner, P; Gies, C; Jahnke, F; Michler, P

Published: MAY 2007, PHYSICAL REVIEW B, 75, DOI: 10.1103/PhysRevB.75.195302

Systematic excitation-power-density dependent and time-resolved single-dot photoluminescence studies have been performed on type-I InP/Ga0.51In0.49P quantum dots. These dots are rather flat and therefore exhibit larger than normal single-dot ground-state transition energies ranging from 1.791 to 1.873 eV. As a result of their low height, the dots have a very high aspect ratio (ratio of width to height) of approximately 27:1. In general, even at high excitation power densities, the dots with ground-state transition energies above 1.82 eV exhibit only s-shell emission, while the larger dots exhibiting ground-state emission below 1.82 eV tend to exhibit emission from several (in some cases up to eight) shells. Calculations indicate that this change is due to the smaller dots having only one confined election level while the larger dots have two or more. Time-resolved investigations indicate the presence of fast carrier relaxation and recombination processes for both dot types, however, only the larger dots display clear interlevel relaxation effects as expected. The temporal behavior has been qualitatively simulated using a rate equation model. Also, in a more detailed analysis, the fast carrier relaxation is described on the basis of a quantum kinetic treatment of the carrier-phonon interaction. Finally, the dots display a clear single-photon emission signature in photon statistics measurements.

2499. Tin nanoclusters obtained in potassium chloride by thermal annealing

Authors: Apostol, E; Enculescu, M; Polosan, S; Vasile, E; Topa, V

Published: 2007, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4, NO 3, 4, +, DOI: 10.1002/pssc.200673734

Tin nanoclusters were obtained in potassium chloride crystals following the electrolytic coloration of KCl:Sn2+ and KCl:Sn2++Ca2+ crystals and thermal annealing at various temperatures and times. Electrolytic coloration of KCl:Sn2+ crystals produces electronic centers inside of samples, presumably negative metal ions of tin. Optical absorption measurements were performed on as grown sample, colored and thermal annealed samples. The behavior of the samples with Sn colloids was compared with theoretical predictions according to Mie's theory. Tin nanoclusters in KCl exhibit an absorption band with a peak at 215 nm. The structure of the nanoclusters was studied by optical absorption and transmission electron microscopy means. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2500. Comparative characterization of PbS macro- and nano-crystalline photoresistive detectors

Authors: Iordache, G; Buda, M; Stancu, V; Botila, T

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 202, DOI: 10.1109/SMICND.2007.4519680

A comparative study of photodetector performance for nano- and micro-crystalline PbS thin layers is presented Both types of PbS films were obtained using the Chemical Bath Deposition method. To prepare nano-crystalline thin films we used a short reaction time with no doping Bi added At low levels of irradiance (0.1 mW/cm(2)) and room temperature (RT), the macro-crystalline PbS outperforms its nano-crystalline counterpart, by a factor of 6 for the value of Delta R/R-dark. However the nano-crystalline photodetectors show significantly lower optical quenching for large values of irradiance (approximate to 500 mW/cm(2)) at RT and better Delta R/R-dark performance at lower temperature, with an optimum temperature Of 150 K. The low frequency noise behavior is a superposition of 1/f flicker noise at low frequency and generation-recombination and thermal noise at higher frequency. The proportionaliiy factor between the 1/f noise and the DC dark current for the series resistor is 1.5 times larger for the nano-crystalline photodetector at room temperature.

2501. Light absorption process in CdSxSe1-x doped alumino-phosphate glass

Authors: Stanculescu, A; Stanculescu, F; Elisa, M

Published: APR 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 835, DOI:

We present a study of the effect of the crystallites composition and size on the optical properties of vitreous aluminophosphate matrix doped with CdSxSe1-x crystallites. The influences of the glass matrix composition and, heat treatment temperature and duration on the stoichiometry of the crystalline phase have been investigated by optical methods. We have studied the effect of the sodium oxide contained in the matrix, annealing temperature variation from 425 degrees C to 475 degrees C and duration variation from 2 h to 6 h on the light absorption process, evaluating an optical band gap energy between E-g=1.74 eV and E-g=2.29 eV associated with changes in the composition of the crystallites. The blue shift of the absorption edge observed in samples containing Na2O annealed at 425 degrees C for 4 h or at 450 degrees C for 2 h was attributed to a variation in the crystallites' composition because their size is not favourable to the quantum confinement. We have also investigated the effect of individual CdS and CdSe clusters on the absorption properties of the aluminophosphate glass and on the process of zinc incorporation in the crystalline phase. We have made some assumptions concerning the effect of the aluminophosphate glass matrix on the direct band to band light absorption mechanism characterising the II-IV bulk semiconductor.

2502. Dielectric resonators for microwave and millimeter wave applications

Authors: Nedelcu, L; Toacsan, MI; Banciu, MG; Ioachim, A

Published: 2007, CAS 2007 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 278, DOI: 10.1109/SMICND.2007.4519700

Three types of materials for dielectric resonators are presented in this paper. The Pb-BNT materials show the highest dielectric constant (similar to 85). A very small controllable temperature coefficient if in the range (-2 divided by +4) ppm/degrees C can be achieved by using dielectric resonators Mg-(Zr0.8Sn0.2)TiO4. On the other hand, the resonators made of Ba(Zn1/3Ta2/3)O-3 exhibit the highest values for the Qxf product, ranging from 50000 to 130000 GHz, which make them attractive for millimetre wave applications.

2503. Glassiness and superconductivity in strongly Pr-doped YBa2Cu3O7-delta single crystals

Authors: Sandu, V; Gyawali, P; Katuwal, T; Almasan, CC; Taylor, BJ; Maple, MB

Published: MAY 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 1280, DOI:

We present magnetization data on superconducting strongly Pr-doped YBa2Cu3O7-6 showing the existence of irreversibility at temperatures much higher than superconducting critical temperature and Neel temperatures for both planar Cu and Pr systems. A model in terms of cluster glass is proposed.

2504. Depth Raman spectra and laser-induced structural and oxygenation changes in thick YBa2Cu3O7-delta films

Authors: Branescu, M; Naudin, C

Published: MAR 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 663, DOI:

We describe an experiment of inducing structural and oxygenation changes in small volumes of a thick YBa2Cu3O7-delta (YBCO) film by subjecting the film to a focused Ar laser beam used as the pump source for a depth profiling Raman scattering system. The laser-induced changes were evidenced by high spectral and spatial resolution Raman spectra taken at different depths of the film, before and after the films' exposure. The irradiation and the measurement were done at room temperature in a regular air environment.

2505. Stoichiometric arsenic sulphoselenides as testing probes for positron trapping in chalcogenide glasses

Authors: Hyla, M; Filipecki, J; Shpryuk, O; Popescuc, M; Balitska, V

Published: OCT 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3181, DOI:

Positron annihilation lifetime (PAL) measurements are performed for stoichiometric glassy arsenic sulphide g-AS(2)S(3) and selenide g-AS(2)Se(3) in order to probe the corresponding model of positron trapping. An ORTEC spectrometer with Na-22 source placed between two sandwiched glass samples was used in our experiments, the obtained spectra being treated with LT computer program. Two identical samples of g-A(2)S(3) and g-AS(2)Se(3) of about similar to 1.5 mm in thickness prepared from high-purity elemental constituents by conventional melt-quenching route and additionally annealed near glass transition to avoid the inner stressed regions were tested. It is shown that two-state positron trapping model is valid for both glasses, the process of positron trapping being saturated in extended free-volume defects like to atomic vacancies and their agglomerates. Despite difference in the character of nanovoid radius distribution estimated theoretically for g-AS(2)S(3) and g-AS(2)Se(3), they have very close average free volumes resulting in the observed similarity of PAL data. But, in contrast to g-AS(2)Se(3), which has at least three sets of nanovoids centered near similar to 1.5 angstrom, similar to 2.3 angstrom and similar to 2.9 angstrom, only two sets of nanovoids centered near similar to 1.3 angstrom and at similar to 2.8 angstrom are proper to g-AS(2)S(3) giving only one variant of fitting.

2506. Structural (ME, XRD, NGR, ESR) investigations on some sulphides from costesti, valea lui stan and jidostita gold ores (Southern Carpathians, Romania)

Authors: Udubasa, SS; Constantinescu, S; Grecu, MN; Popescu-Pogrion, N; Udubasa, G; Popescu, GC; Tolea, F; Popescu, IV

Published: 2007, ROMANIAN JOURNAL OF PHYSICS, 52, 104, DOI:

An extensive investigation of the gold ores in the South Carpathians (Costesti, Valea lui Stan si Jidostita) has performed, using different chemical and physics experimental techniques. The used structural techniques have been the electron microscopy, X-ray diffraction, Mossbauer effect and electron spin resonance. The investigation of the representative samples by the structural techniques relieved new minerals in the gold ores, the presence of the "coral like" aggregates of nanometric gold solid bubbles.

2507. Percolation phenomena in Si-SiO2 nanocomposite films

Authors: Stavarache, I; Ciurea, ML

Published: AUG 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 2647, DOI:

Current-voltage characteristics of samples containing silicon nanodots embedded in an amorphous silicon dioxide matrix were investigated. A percolation mechanism was evidenced by the dependence on the concentration of the initial differential conductance and by the appearance of several thresholds in the I-V characteristics.

2508. The influence of the substrate nature on the iron repartition in the titania matrix

Authors: Iacomi, F; Mardare, D; Grecu, MN; Macovei, D; Vida-Simiti, I

Published: JUL 1 2007, SURFACE SCIENCE, 601, 2695, DOI: 10.1016/j.susc.2006.12.024

Fe-doped titania films were deposited by RF sputtering onto different substrates (glass and ITO/glass) in the same deposition run. The rutile nanocrystalline structure of Fe-doped thin films deposited on glass substrates and anatase nanocrystalline structure of Fe-doped thin films deposited on ITO/glass substrates were evidenced by XRD. SEM investigations showed a smooth surface with a dense nanostructure. XPS study evidenced an almost stoichiometric composition with different iron contents. EPR and XPS studies evidenced that iron entered into TiO2 lattice by substitution, as isolated and dimer species. In Fe-doped thin films deposited on ITO/glass substrates the iron content is ten times higher than in Fe-doped thin films deposited on glass substrates and that a part of them entered as Fe2+. (C) 2007 Elsevier B.V. All rights reserved.

2509. Electrosynthesis of the poly(N-vinyl carbazole)/carbon nanotubes composite for applications in the supercapacitors field

Authors: Baibarac, M; Gomez-Romero, P; Lira-Cantu, M; Casan-Pastor, N; Mestres, N; Lefrant, S

Published: OCT 2006, EUROPEAN POLYMER JOURNAL, 42, 2312, DOI: 10.1016/j.eurpolymj.2006.05.019

Electrochemical polymerization of N-vinyl carbazole (VK) on carbon nanotube (CN) films was studied by cyclic voltammetry in LiClO4/acetonitrile solutions. Cyclic voltammograms recorded on a blank Pt electrode were compared with those obtained when single or multi-walled CN films were deposited on the Pt electrode; in the latter case, a down-shift of the VK reduction peak potential was observed. Functionalization of CNs with poly(N-vinyl carbazole) (PVK) was invoked by Raman scattering and UV-VIS-NIR spectroscopic studies. The influence of sweep rate on the electrochemical properties of the PVK/CN nanocomposite and the performance of supercapacitors constructed using PVK-functionalized single-walled carbon nanotube electrodes were also evaluated. (c) 2006 Elsevier Ltd. All rights reserved.

2510. Synthesis, structure and properties of heterotrinuclear carboxylate complexes [Fe2M(Ca, Sr, Ba)O(CCl3COO)(6)(THF)n]

Authors: Prodius, D; Turta, C; Mereacre, V; Shova, S; Gdaniec, M; Simonov, Y; Lipkowski, J; Kuncser, V; Filoti, G; Caneschi, A

Published: JUL 10 2006, POLYHEDRON, 25, 2182, DOI: 10.1016/j.poly.2006.01.019

Three novel mu(3)-oxo trinuclear carboxylates [Fe2CaO(CCl3COO),(THF)(4)] center dot THF (1), [Fe2SrO(CCl3COO)(6)(THF)(6)] center dot 0.5H(2)O center dot 0.5THF (2) and [Fe2BaO(CCl3COO)(6)(THF)(6)] center dot 0.5H(2)O center dot 0.5THF (3) have been synthesised and subsequently characterised by X-ray structure analysis, thermal gravimetry (TG), infra red (IR) spectroscopy and magnetic measurements. Compounds I and 3 are molecular complexes with s- and d-metals displayed in the apexes of isosceles triangles with a triply bridging oxygen atom at its centre. The Ca center dot center dot center dot Fe and Ba center dot center dot center dot Fe separations have the values 3.750(1) and 4.177(1) angstrom, respectively. In comparison with these. Fe center dot center dot center dot Fe separations, 3.229(2) angstrom in 1 and 3.201(1) angstrom in 3, appear much shorter. The molecular complexes obey C-2 symmetry with the twofold axis passing through s metal and mu(3)-oxo atom. The coordination numbers are 6, 7 and 9 for iron. calcium and barium correspondingly. Magnetic studies reveal the presence of an antiferromagnetic exchange in the isosceles triangular skeletons of the trinuclear species. Using the spin Hamiltonian H = -2J(12)[S1S2], the fitting parameters g(Fe) = 2.00. J(Fe-Fe) = -58.90 cm(-1) for 1 and -60.40 cm(-1) for 3; g(Fe) = 2.14, J(Fe-Fe) = -75.40 cm(-1) for 2 have been estimated. (c) 2006 Elsevier Ltd. All rights reserved.

2511. Calcium carbonate precipitation in ultrasonic field

Authors: Mateescu, CD; Mocioi, M; Sarbu, C; Isopescu, R; Chilibon, I; Branzoi, F

Published: 2006, BIWIC 2006, +, DOI:

An unconventional synthesis method, implying ultrasonic field, was tested in order to improve the properties of CaCo3 precipitated via liquid-liquid route. Working parameters for calcium carbonate precipitation in the absence of ultrasonic field so that the solid material displays aragonite morphology were established. The evolution of the precipitation reaction in ultrasonic field provided a solid phase with aragonite morphology slightly, impurified with vaterite. Grain size distribution was signficantly improved. The solid phase presents an important fraction of nanometer size particles.

2512. Synthesis and electron spin resonance of La2/3Ca1/3MnO3 nanowires

Authors: Toloman, D; Mihailescu, G; Darabont, A; Pop, CVL; Olenic, L; Popa, A; Raita, O; Jivanescu, M; Grecu, MN; Giurgiu, LM; Idziak, S; Hoffmann, SK

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 469, DOI:

La2/3Ca1/3MnO3 (LCMO) nanowires were prepared using a sol-gel process and an anodically oxidized aluminum template. Scanning electron microscopy (SEM) shows that the nanowires are almost parallel and their diameter is around 40 nm. The temperature dependence of the electron spin resonance (ESR) linewidth is similar to that observed for the case of nanostructured LCMO. From this dependence, the determined magnetic transition temperature, T-C, of the LCMO nanowires, is of the order of 120-130 K.

2513. S-wave spin-triplet order in superconductors without inversion symmetry: Li2Pd3B and Li2Pt3B

Authors: Yuan, HQ; Agterberg, DF; Hayashi, N; Badica, P; Vandervelde, D; Togano, K; Sigrist, M; Salamon, MB

Published: JUL 7 2006, PHYSICAL REVIEW LETTERS, 97, DOI: 10.1103/PhysRevLett.97.017006

We investigate the order parameter of noncentrosymmetric superconductors Li2Pd3B and Li2Pt3B via the behavior of the penetration depth lambda(T). The low-temperature penetration depth shows BCS-like behavior in Li2Pd3B, while in Li2Pt3B it follows a linear temperature dependence. We propose that broken inversion symmetry and the accompanying antisymmetric spin-orbit coupling, which admix spin-singlet and spin-triplet pairing, are responsible for this behavior. The triplet contribution is weak in Li2Pd3B, leading to a wholly open but anisotropic gap. The significantly larger spin-orbit coupling in Li2Pt3B allows the spin-triplet component to be larger in Li2Pt3B, producing line nodes in the energy gap as evidenced by the linear temperature dependence of lambda(T). The experimental data are in quantitative agreement with theory.

2514. Growth and characterization of high density stoichiometric SiO2 dot arrays on Si through an anodic porous alumina template

Authors: Kokonou, M; Nassiopoulou, AG; Giannakopoulos, KP; Travlos, A; Stoica, T; Kennou, S

Published: MAY 14 2006, NANOTECHNOLOGY, 17, 2151, DOI: 10.1088/0957-4484/17/9/011

In this work, we present the fabrication and full characterization of stoichiometric SiO2 nanoisland arrays ( dots) on silicon, grown through an anodic porous alumina template. Atomic force and transmission electron microscopy (AFM, TEM) were used to characterize the morphology, size, size distribution and density of the dots as a function of the anodization time used. It was found that dot density is lower for very short anodization times, and it stabilizes after a certain time. The dot height increases rapidly after nucleation, reaching values of 8 - 10 nm. With prolonged oxidation the dots continue to nucleate to fill the available area on the silicon surface underneath the porous alumina, while the well developed dots grow in height and width, reaching saturation values at 14 and 55 nm respectively. X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy ( EELS) were used to investigate the stoichiometry and surface coverage of the dots.

2515. Chalcogenides - Past, present, future

Authors: Popescu, M

Published: JUN 15 2006, JOURNAL OF NON-CRYSTALLINE SOLIDS, 352, 891, DOI: 10.1016/j.jnoncrysol.2005.11.126

A review of the evolution of the amorphous chalcogenide field of research from early times up to the present state of the art is presented. On the basis of recent achievements a bright future for these materials is predicted. (c) 2006 Elsevier B.V. All rights reserved.

2516. EPR and TEM characterization of electrolurninescent Alq(3)

Authors: Grecu, MN; Ghica, C; Mirea, A; Grecu, VV; Schwoerer, M

Published: 2006, ADVANCED MATERIALS FORUM III, PTS 1 AND 2, 514-516, 137, DOI: 10.4028/www.scientific.net/MSF.514-516.133

EPR and TEM investigations on sublimated solid Alq(3), [tris(8-hydroxyquinoline)aluminum(Ill)] are reported. Different paramagnetic centers in microcrystalline Alq3 fractions as synthesized and annealed are observed. Their nature, thermal treatment dependence, as well as correlation with the crystal structure are analyzed. The existence of randomly oriented triplets and quartets in annealed Alq3 fractions is evidenced from the temperature dependence of X- and Q-band EPR spectra. The spin Hamiltonian parameters are given and proposals for the model structures are made.

2517. FexOy-SiO2 nanocomposites studied by Mossbauer spectroscopy

Authors: Predoi, D; Kuncser, V; Zaharescu, M; Jitianu, A; Crisan, M; Keune, W; Sahoo, B; Filoti, G; Raileanu, M

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 522, DOI:

FexOy-SiO2 nanocomposites were obtained via the sol-gel method, by using three different precursors for the silica matrix. The morphology and the iron phase composition is strongly influenced by the precursors. The presence of magnetically ordered goethite and fayalite is evidenced by low temperature Mossbauer spectroscopy. Subsequent annealing treatments performed on the initial samples have induced the formation of hematite nanoparticles in the silica matrix, mainly on the account of the goethite decomposition. The total amount and the size distribution of the hematite nanoparticles can be controlled via the initial precursors and the subsequent annealing conditions. The simultaneous analysis of the iron phase composition and of the local magnetic interactions in the analysed samples is performed.

2518. Growth of ZnO micro and nanowires using the template method

Authors: Sima, M; Enculescu, I; Vasile, E

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 828, DOI:

The electrochemical deposition in ion track nanoporous membranes was employed for ZnO micro and nanowires preparation. A ZnNO3 bath was employed for the deposition, performed at -800 mV (vs. SCE) and at temperatures around 90 degrees C. Scanning and transmission electron microscopy were used to characterize the wires from a morphological point of view. Electron and X-ray diffraction were employed for the characterization of materials from the point of view of structure. The technique allowed the fabrication of nanowire arrays with good morphological and structural quality.

2519. Radiological impact of C-14

Authors: Bucur, C; Olteanu, M; Olteanu, C; Pavelescu, M

Published: APR 2006, REVISTA DE CHIMIE, 57, 367, DOI:

Near surface disposal is considered a suitable option for the disposal of short-lived low and intermediate level waste (LILW) containing radionuclides which decay to insignificant radiation levels within a few decades or centuries. LILW containing limited concentrations of long-lived radionuclides may also be disposed of in near surface facilities. The main radionuclides in short lived LILW are Cs-137 and Sr-90 and therefore, a period of 300 years for the post-closure institutional controls would correspond to about ten half-lives of these radionuclides. The longer-lived radionuclides, such as C-14, I-129, Tc-99 will continue to be released even after that period due to the engineering barriers degradation. The paper presents the post closure radiological impact of LIL waste disposal due to the C-14, one of the long life radionuclides presented in the LILW generated at Cernavoda Nuclear Power Plant.

2520. Synthesis of Nb doped lead zirconate titanate by chemical methods

Authors: Costa, AL; Montanari, G; Galassi, C; Cernea, M; Bezzi, F; Albonetti, S

Published: JUN 2006, ADVANCED ENGINEERING MATERIALS, 8, 576, DOI: 10.1002/adem.200500235

2521. Electron microscopy of gamma-irradiated polyethylene

Authors: Bercia, R; Tirnovan, M; Bercia, C; Popescu-Pogrion, N

Published: APR 2006, SURFACE AND INTERFACE ANALYSIS, 38, 556, DOI: 10.1002/sia.2275

In this paper, we have studied the structure and the phase transformations in thin films (obtained by evaporation from gamma-irradiated polyethylene bulks - ageing polymer) before and after laser irradiation. We made a comparison between the following samples: A - thin films obtained from gamma-irradiated polyethylene bulk and not subjected to laser irradiation; B - thin films obtained from gamma-irradiated polyethylene bulk and subjected to laser irradiation. We have revealed many modifications in the dielectric and structural properties of the thin films, depending on the dose, dose rate and the time of laser irradiation (in the case of samples B). The thickness of all deposited films was 90 nm. The samples (non-irradiated or irradiated) were analysed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), in combination with selected area electron diffraction (SAED). We have also presented the structure of non-aged and non-irradiated thin polyethylene films (control polyethylene film), in which we observed a particularly puzzling phase between an incipient spherulitic phase and a fine structure of the spherulitic phase (specifically for thin PE films structure). After gamma- and laser irradiations, we observed a strong modification of the structure. The spherulitic phase was transformed. We observed large, amorphous, transparent crystals containing many defects, carbon precipitates, the beginning of crystallisation revealed by electron diffraction, treeing and breakdown figures (usually after laser irradiation). Copyright (C) 2006 John Wiley & Sons, Ltd.

2522. Electronic transport in Si-SiO2 nanocomposite films

Authors: Ciurea, ML; Teodorescu, VS; Iancu, V; Balberg, I

Published: MAY 20 2006, CHEMICAL PHYSICS LETTERS, 423, 228, DOI: 10.1016/j.cplett.2006.03.070

We report experimental investigations and modeling of the electronic transport in Si-SiO2 nanocomposite films. The current-voltage characteristics measured at room temperature are interpreted as due to high field-assisted tunneling. The activation energies from the current-temperature curves,are given by the energy separations between quantum confinement electronic states, determined from a quantum well model. Consequently, the calculated mean diameter of a nanodot (5.2 nm) is in good agreement with the microstructure data (5 nm). Also, the potential barrier between nanocrystalline Si and amorphous SiO2, previously obtained for nanocrystalline oxidized porous Si (2.2 eV), is confirmed. (c) 2006 Elsevier B.V. All rights reserved.

2523. Core-shell effects in granular perovskite manganites

Authors: Pana, O; Giurgiu, LM; Darabont, A; Iancu, V; Ciurea, M; Grecu, MN; Bot, A

Published: JAN-MAR 2006, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 67, 627, DOI: 10.1016/j.jpcs.2005.10.148

Unusual conductivity behavior, is observed in the semiconducting phase of granular manganites. It is characterized by, at a certain temperature, of a switching process between two activation energies. A core-shell model is developed to explain the presence of the conductivity of the two activation energies. The model suggests that inside the disordered thin outer layer the energy bands are split into isolated energy levels. Additional correlations between paramagnetic behavior and the existence of the two activation energies within the core-shell model are furnished by the ESR spectroscopic technique. (c) 2006 Published by Elsevier Ltd.

2524. Numerical taxonomy: Mn2+ EPR line shape as a criterion in provenance studies

Authors: Duliu, OG; Velter-Stefanescu, M

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1561, DOI:

The Mn2+ EPR spectra of 12 marbles and limestones (calcitic, dolomitic and calci-dolomitic) collected from different Greek quarries have been analysed by means of cluster analyses numerical taxonomy. By means of Mn2+ EPR line shape this technique allowed classifying all samples in concordance with their mineralogical structure. Accordingly, we have found that while Euclidean and power distances showed to be more adequate in differentiating samples belonging to the same petrologic group, the Perason's correlation coefficient is most suitable to discriminate samples having different mineralogical composition.

2525. Spectroscopic and X-ray diffraction study of high T-c epitaxial YBCO thin films obtained by pulsed laser deposition

Authors: Branescu, M; Vailionis, A; Gartner, M; Anastasescu, M

Published: OCT 31 2006, APPLIED SURFACE SCIENCE, 253, 404, DOI: 10.1016/j.apsusc.2006.06.022

We report spectroscopic characterization of epitaxial YBCO thin films grown on LaAlO3 by pulsed laser deposition. Raman spectroscopy and spectroscopic ellipsometry were used for film characterization and the results were correlated with X-ray diffraction measurements. The mentioned techniques allowed us to analyze crystallographic, micro-structural, and morphological properties of YBCO thin films. We also demonstrated that relatively low resolution Raman spectroscopy and spectroscopic ellipsometry are reliable techniques for a rapid and non-destructive characterization of epitaxial YBCO thin films. (c) 2006 Elsevier B.V All rights reserved.

2526. Electrical properties of nanocrystalline silicon

Authors: Ciurea, ML

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 19, DOI:

The transport properties of nanocrystalline silicon films are presented. The studies were performed on fresh and stabilized nanocrystalline porous silicon (nc-PS) and on Si/SiO2 nanocomposite films. Current-voltage characteristics and the temperature dependence of the dark current were measured on both systems. From the current-voltage characteristics of the oxidized nc-PS, the Si-SiO2 potential barrier was determined (2.2 eV). The Si/SiO2 measurements proved that the main conduction mechanism for the nanodot systems is the field-assisted tunneling under Coulomb blockade. The quantum confinement was evidenced by the activation energies observed in the current-temperature characteristics and it was modeled by means of an infinite quantum well. The trapping-detrapping processes were studied by using the Optical Charging Spectroscopy (OCS) method: the traps are filled by illumination with a suitable wavelength at low temperature and the detrapping is produced by heating at a constant rate. The experimental investigations evidenced six trapping levels in nc-PS, four located at the surface/interface and two deep ones located in the bulk. The deepest level was observed only in oxidized samples. The modeling of the OCS trapping-detrapping processes allows for the determination of the characteristic parameters that cannot be directly obtained from the measurements.

2527. Fractal analysis of the atomic force microscopy images of sulfide-covered GaAs(00) surfaces

Authors: Lazarescu, V; Dobrescu, G; Lazarescu, MF; Logofatu, C; Savu, B; Stanciu, GA

Published: MAR-APR 2006, SCANNING, 28, 86, DOI:

2528. Ion beam and complementary SEM and XRD characterization of YBa2Cu3O7-x films obtained by pulsed laser deposition

Authors: Branescu, M; Thome, L; Pantelica, D; Ward, I; Vailionis, A; Ionescu, P

Published: AUG 2006, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 249, 914, DOI: 10.1016/j.nimb.2006.03.162

We report two ion beam analysis techniques, elastic recoil detection analysis (ERDA) and Rutherford backscattering (RBS), to characterize YBa2CU3O7-x (YBCO) films, obtained in situ by pulsed laser deposition (PLD). Initially, ERDA measurements were performed on a thin film to evaluate the PLD rate. RBS measurements correlated with complementary scanning electron microscopy and X-ray diffraction measurements were performed afterwards on a good quality thick YBCO film to determine its stoichiometry, thickness, crystalline structure and surface morphology. (c) 2006 Elsevier B.V. All rights reserved.

2529. Loss of phosphorous in silica-phosphate sol-gel films

Authors: Anastasescu, M; Gartner, M; Ghita, A; Predoana, L; Todan, L; Zaharescu, M; Vasiliu, C; Grigorescu, C; Negrila, C

Published: DEC 2006, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 40, 333, DOI: 10.1007/s10971-006-8775-y

Phosphosilicate films with 90%SiO2-10%P2O5 molar composition, derived from tetraethoxysilane as SiO2 precursor and triethylphosphate, triethylphosphite or phosphoric acid as P2O5 precursors were prepared using the sol-gel method. The films were deposited on glass and ITO coated glass supports. The influence of the type of P2O5 precursor, type of substrate and of the thermal treatment (200, 300 and 500 degrees C) on their structure and properties was studied. By spectroellipsometric and XPS measurements the high vaporization of the phosphorous during the densification of the films by thermal treatment was noticed when alkoxide were used, underlying that the mentioned precursors are not recommended for thin phosphosilicate films preparation. The phosphoric acid that forms chemical bond with silica network during the sol-gel process lead to better incorporation of P in the silica network as compared to the P-alkoxides.

2530. Angstrom-science, angstrom-technology, angstrom-devices: A new challenge

Authors: Popescu, M

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 768, DOI:

Beyond nano-science is angstrom-science, beyond nano-technology is angstrom-technology, beyond nano-devices are angstrom-devices. Beyond these new emerging fields in materials physics is to ride on electron, but this is almost pure phantasy.

2531. Effect of lead content and B-site substitutions on dielectric and piezoelectric properties of PZT ceramics

Authors: Dimitriu, E; Craciun, F; Cernea, M; Ramer, R

Published: 2006, ADVANCED MATERIALS FORUM III, PTS 1 AND 2, 514-516, 192, DOI: 10.4028/www.scientific.net/MSF.514-516.188

The behaviour of the dielectric and piezoelectric properties of doped PZT ceramics, with variable lead content, has been investigated from -50 degrees C to room temperature. The PZT materials were prepared by the oxide technique and samples were sintered as pellets, at various temperatures. Niobium and lithium ions have been substituted for Ti4+, Zr4+ in the PZT matrix, and a small amount of Bi2O3 was added to cause A-position vacancies. The lead content in the four materials prepared varies in a narrow range, from 0.97 to 1.029 lead atoms, while the concentration of all other components are maintained constant. The microstructure of samples, evaluated by SEM technique and XRD analysis evidenced the presence of the tetragonal phase characteristic for the PZT 52/48. The dielectric and piezoelectric constants measured on poled samples depends on the sintering temperature, defects and domain walls, lead content.

2532. Crystallite size effect in PbS thin films grown on glass substrates by chemical bath deposition

Authors: Popa, A; Lisca, M; Stancu, V; Buda, M; Pentia, E; Botila, T

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 45, DOI:

Nanocrystalline PbS thin films were grown on glass substrates using Chemical Bath Deposition (CBD) method. The presence of nanocrystals was revealed by optical absorption and photocurrent measurements. We have compared the absorption threshold between large size and nanocrystalline PbS. Our study was performed in order to demonstrate that the size of the PbS thin films crystallites affects the photoelectric properties of the material. Using the Scanning Electron Microscopy (SEM) we have determined that the grains inside large size PbS crystallites are 300 nm. From the optical absorption measurements we have determined that the size of PbS nanocrystals is between 5-50 nm. The photoconduction measurements show that large size PbS has a maximum in infrared situated at 2.4 mu m, and in PbS nanocrystalline thin film this maximum is shifted toward smaller wavelengths towards visible and near infrared.

2533. The SANS facility at the Pitesti 14MW TRIGA reactor

Authors: Ionita, I; Grabcev, B; Todireanu, S; Constantin, F; Shvetsov, V; Anghel, E; Popescu, G; Mincu, M; Datcu, A

Published: 2006, CRYSTALLOGRAPHY REPORTS, 51, S31, DOI: 10.1134/S1063774506070066

The SANS facility existing at the Pitesti 14MW TRIGA reactor is presented. The main characteristics and the preliminary evaluation of the installation performances are given. A monochromatic neutron beam with 1.5 angstrom <= lambda <= 5 angstrom is produced by a mechanical velocity selector with helical slots. A fruitful partnership was established between INR Pitesti (Romania) and JINR Dubna (Russia). The first step in this cooperation consists in the manufacturing in Dubna of a battery of gas-filled positional detectors devoted to the SANS instrument.

2534. Unstressed carbon-metal films deposited by thermionic vacuum arc method

Authors: Lungu, CP; Mustata, I; Musa, G; Lungu. AM; Brinza, O; Moldovan, C; Rotaru, C; Iosub, R; Sava, F; Popescu, M; Vladoiu, R; Ciupina, V; Prodan, G; Apetroaei, N

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 77, DOI:

A novel method based on thermo-ionic vacuum arc plasma was developed to grow metal-carbon zero stress films for MEMS applications. The method chosen to prepare metal-carbon films uses an electron beam emitted by an externally heated cathode accelerated by a high anodic voltage. Applying a high voltage (1-6 kV) between cathode and anode bright plasma was ignited in carbon atoms. In order to minimize the internal stress and to get films with increased adherence, interlayer and graded interlayer with Fe, Cr, Al and Ni was deposited. The prepared films were characterized by XPS, XRD, AFM and ellipsometry.

2535. Epitaxial silicon detectors for particle tracking - Radiation tolerance at extreme hadron fluences

Authors: Lindstrom, G; Dolenc, I; Fretwurst, E; Honniger, F; Kramberger, G; Moll, M; Nossarzewska, E; Pintilie, I; Roder, R

Published: NOV 30 2006, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 568, 71, DOI: 10.1016/j.nima.2006.05.203

Diodes processed on n-type epitaxial silicon with a thickness of 25, 50 and 75 mu m had been irradiated with reactor neutrons and high-energy protons (24 GeV/c) up to integrated fluences of Phi(eq) = 10(16) cm(-2). Systematic experiments on radiation-induced damage effects revealed the following results: in contrast to standard and oxygen-enriched float zone (FZ) silicon devices no space charge sign inversion was observed after irradiation. It is shown that the radiation-generated concentration of deep acceptors, dominating the behavior of n-type FZ diodes, is compensated by creation of shallow donors. Thus a positive space charge is maintained throughout the irradiation up to the highest fluence and even during prolonged elevated-temperature annealing cycles. Defect analysis studies using thermally stimulated current measurements attribute the effect to a damage-induced shallow donor at E-C-0.23 eV. It is argued that, as in the case of thermal donors, oxygen dimers, out diffusing from the Cz substrate during the diode processing, are responsible precursers. Results from extensive annealing experiments at elevated temperatures are verified by comparison with prolonged room-temperature annealing. These results showed that in contrast to FZ detectors, which always have to be cooled, room-temperature storage during beam off periods of future elementary particle physics experiments would even be beneficial for n-type epi-silicon detectors. A dedicated experiment at CERN-PS had successfully proven this expectation. It was verified, that in such a scenario the depletion voltage for the epi-detector could always be kept at a moderate level throughout the full S-LHC operation (foreseen upgrade of the large hadron collider). Practically no difference with respect to FZ-silicon devices was found in the damage-induced bulk generation current. The charge trapping measured with Sr-90 electrons (mip's) is also almost identical to what was expected. A charge collection efficiency of 60% (2500 e) in 50 mu m n-type epi-diodes after 24 GeV/c proton irradiation with Phi(eq) = 6.2 x 10(15) cm(-2) was reported recently, independent of the operating temperature down to -20 degrees C. (c) 2006 Elsevier B.V. All rights reserved.

2536. Investigation of chemical and grain boundary effects in highly ordered Sr2FeMoO6: XPS and Mossbauer studies

Authors: Raekers, M; Kuepper, K; Hesse, H; Balasz, I; Deac, IG; Constantinescu, S; Burzo, E; Valeanu, M; Neumann, M

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 460, DOI:

We have studied the oxidation states of Fe and Mo and the presence of grain boundaries in the magneto resistive (MR) compounds Sr2FeMoO6 by means of x-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy and electrical resistivity measurements. XPS of the Mo 3d and Fe 3s core levels is indicating a mixed valence state involving around 30% Fe3+ - Mo5+ and 70% Fe2+ - Mo6+ states. Mossbauer studies confirm the presence of a valence fluctuation state and an essential amount of grain boundaries in the present Sr2FeMoO6 crystals. Resistivities and magnetoresistance studies evidenced strong grain boundary effects.

2537. Mesoscopic Fano effect in Aharonov-Bohm rings with an embedded double dot

Authors: Tanatar, B; Moldoveanu, V; Tolea, M; Aldea, A

Published: 2006, LOW TEMPERATURE PHYSICS, PTS A AND B, 850, +, DOI:

We investigate theoretically in a tight-binding model the transport properties of the Aharonov-Bohm interferometer (ABI) with one dot embedded in each of its arms. For weak interdot coupling the model Hamiltonian describes the system considered in the experiments of Holleitner et al. [Phys. Rev. Lett. 87, 256802 (2001)]. The electronic transmittance of the interferometer is computed within the Landauer-Buttiker formalism while the coexistence of resonant and coherent transport is explicitly emphasized by using the Feschbach formula. The latter produces effective Hamiltonians whose spectral properties describe the tunneling processes through each dot. We reproduce numerically the stability charging diagrams reported in the experiments of Holleitner et al. When the magnetic flux is fixed and one dot is set to resonance the interferometer transmittance shows Fano, lineshapes as a function of the gate voltage applied to the other dot. Our model includes the effect of the magnetic field on the dot levels and explains the change of the asymmetric tail as the magnetic flux is varied. The transmittance assigned to the Fano, dips located in the almost crossing point of the charging diagrams shows Aharonov-Bohm oscillations.

2538. XPS study of Ti/oxidized GaAs interface

Authors: Grita, RV; Logofatu, C; Negrila, C; Manea, AS; Cernea, M; Ciupina, V; Lazarescu, MF

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 36, DOI:

X-Ray Photoelectron Spectroscopy (XPS) analysis was performed on Ti/oxidized GaAs. This interface is prepared by chemical etching in a mixture of reagents, followed by a vacuum deposition of a nanometer Ti layer. The surface sensitivity of XPS (typically 40-100 angstrom), makes the technique ideal for the measurements of oxidation states and oxide layer thickness on III-V compounds. The study of Ti/oxidized GaAs put into evidence a lack of stoichiometry at the semiconductor surface due to the presence of a volatile element (As). At the interface Ti/Oxide/n-GaAs common oxides are present: Ga2O3, As2O3 and As2O5, together with titanium oxide. The XPS spectra recorded on the sample surface sputtered with 5 keV Ar+ ions (in two steps: t = 15 min, t = 45 min) were analyzed using SDP subroutines program facilities. The As signal at the interface after t = 15 min plasma etching is related to GaAs, As2O3 and over 40% from a GaAs oxidation complex or due to intermetallic oxide of Ti. After the last plasma etching at the surface of GaAs the stoichiometry was demonstrated: the signal of As and Ga arises commonly from GaAs. It was remarked a broader titanium line profile, which arises from titanium oxide and from different intermediate states at the interface.

2539. Epitaxial-quality PZT: insulator or semiconductor?

Authors: Pintilie, L; Lisca, M; Alexe, M

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 12, DOI:

The lead zirconate-titanate (PZT) epitaxial thin films are analyzed as being p-type, wide-gap semiconductors with standard Schottky contacts. The results of the hysteresis, capacitance-voltage (C-V), and current-voltage (I-V) measurements are explained in the frame of the classical model for metal-semiconductor Schottky contacts, in which the effect of the ferroelectric polarization on band-bending was considered. The presence of the deep traps was also considered and their effect on the measured quantities was discussed. The free carrier concentration was estimated to about 3 x 10(18) cm(-3), with a remnant polarization of 40 mu C/cm(2), and with an effective density of the fixed charges in the depletion region of about 1.8 x 10(19) cm(-3).

2540. Fano interference in mesoscopic rings with quantum dots

Authors: Moldoveanu, V; Aldea, A; Tolea, M

Published: 2006, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 2, 3, +, DOI: 10.1002/pssc.200562736

We propose a general formalism for describing the coexistence of coherent and resonant transport in hybrid mesoscopic structures. The approach is based on Landauer- Buttiker formula for the electronic transmittance and on an old formula of Feshbach. The latter gives the complete Green function of coupled subsystems in terms of effective Green functions of the disconnected parts and provides informations about the individual contributions of each subsystem to transport. Motivated by the experiments of Kobayashi et al.(Phys. Rev. Lett. 88, 256806 (2002)) and Holleitner et al. (Phys. Rev. Lett. 87, 256802 (2001)) we apply the formalism to study transport in Aharonov-Bohm interferometers (ABI) containing one or two coupled two-dimensional quantum dots (QD). In the single dot case, we reproduce and explain the magnetic field control of the Fano interference and investigate the interaction effects in a self-consistent approach. In the double dot case, we obtain the charging diagrams and establish precise criteria for the observation of mesoscopic Fano effect and AB oscillations. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2541. Electron paramagnetic resonance properties of Gd3+ ions in PbWO4 scintillator crystals

Authors: Nistor, SV; Stefan, M; Goovaerts, E; Nikl, M; Bohacek, P

Published: JAN 18 2006, JOURNAL OF PHYSICS-CONDENSED MATTER, 18, 728, DOI: 10.1088/0953-8984/18/2/025

The properties of the electron paramagnetic resonance spectra of Gd3+ ions in PbWO4 single crystals have been investigated in the X-band microwave frequency region, in the 1.5 to 290 K temperature range. The observed S-4 symmetry of the local crystal field at the Gd3+ impurity ions strongly suggests that the Gd3+ ions substitute for the Pb2+ lattice cations, with charge compensation at a distance. The spin Hamiltonian parameters are comparable with those of the Gd3+ ions in other isomorphous tungstates. The temperature variation of the fine structure parameters B-2(0) and B-4(0) points to an energy transfer between the impurity ions and the host lattice, which takes place mainly through a local vibrational mode of frequency omega = 3.1 x 1013 rad s(-1).

2542. Fe3O4-SiO2 nanocomposites obtained via alkoxide and colloidal route

Authors: Jitianu, A; Raileanu, M; Crisan, M; Predoi, D; Jitianu, M; Stanciu, L; Zaharescu, M

Published: DEC 2006, JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 40, 323, DOI: 10.1007/s10971-006-9321-7

The magnetic nanocomposite materials represent an important class of nanomaterials extensively studied nowadays due to their varied applications from medical diagnostic to storage information. The iron oxides in silica matrix systems are highly investigated. The sol-gel method is a suitable way of preparation of Fe3O4-SiO2 nanocomposite materials, since this method allowed the preparation of nanocomposite materials with narrow size distribution of magnetite in silica matrix. In the present work, nanocomposite materials in the Fe3O4-SiO2 system were prepared by sol-gel method via alkoxide and aqueous route. As SiO2 sources, tetraethoxysilan (TEOS) for the alkoxide route, as well as silica sol Ludox (30%) for the aqueous route, were used. This study shows the influence of the type of silica matrix on the structure, size, and distribution of the Fe3O4 nanoparticles in the Fe3O4-SiO2 systems. The gels were annealed at 550 degrees C in order to consolidate the matrices. The structural characterization of the obtained materials via the two preparation routes was performed by DTA/TGA analysis, X-ray diffraction, IR and Mossbauer spectroscopy, Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED).

2543. Effect of dopant on the physical properties of polymer films for microphotonics

Authors: Obreja, P; Cristea, D; Budianu, E; Rebigan, R; Kuncser, V; Bulinski, M; Filoti, G

Published: 2006, PROGRESS IN SOLID STATE CHEMISTRY, 34, 109, DOI: 10.1016/j.progsolidstchem.2005.11.051

This paper presents experimental results concerning the influence of the additives on the physical properties of polymer films. Metal oxides/inorganic salts were used as additives in vinyl-polymers solutions. The physical properties of the metal doped polymer films can be significantly modified by the composition of the doping elements and the curing conditions of the polymer. Morphologic, electronic, magnetic and optic properties of the doped polymers were analysed by AFM. SEM. Mossbauer spectroscopy and optical measurements. The film composition and the deposition processes were optimized to allow a better control of the optical parameters (refractive index. transmission). to reduce the processing temperatures and to improve the chemical sensitivity of the films for sensor applications. These compounds can be easily spin coated onto a variety of directly patterned semiconductor substrates. (C) 2005 Elsevier Ltd. All rights reserved.

2544. Magnetic interactions in NdFeB bulk permanent magnets with additions

Authors: Chiriac, H; Lupu, N; Chiriac, C; Valeanu, M; Kuncser, V

Published: OCT 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1769, DOI:

NdFeB-based bulk nanocomposite permanent magnets (with Dy and Co partially substituting Nd and Fe, respectively) with additions of Early Transition Metals (ETM = Mo, Ti, Zr, Cu, Nb, V, W), in form of rods with diameters ranging from 0.5 to 0.8 mm, have been prepared by devitrification annealing of amorphous and partly-amorphous precursors produced by injection die casting. A fully amorphous structure was obtained for rods with the diameter as large as 0.6 mm. The as-cast rod samples are magnetically soft and the magnetic hardness develops as the samples are devitrified to the optimum nanostructure. The best-achieved hard magnetic properties have been obtained for the optimum devitrified (15 min at 630 degrees C) Nd(3)Dy(1)F(3)e(66)Co(10)B(20) samples of 0.6 mm in diameter: H-i(c) = 296 kA/m, mu M-0(r) = 0.86 T, Mr/M-max = 0.65 and (BH)(max), = 74 kJ/m. The Mossbauer spectra indicate the coexistence of 4 magnetic phases: 2:14:1, alpha-Fe, Fe3B and a short-range ordered intermetallic Fe-B-type phase.

2545. Mechanism of homeotropic alignment of a doped liquid crystal

Authors: Beica, T; Moldovan, R; Zgura, I; Frunza, S; Poterasu, M

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1515, DOI:

In the paper, the physico-chemical orientation mechanism on solid surfaces for a liquid crystal (NP5 from Merck) doped for homeotropic alignment, is tested. For that, the dispersion and polar parts of surface tension of the liquid crystal are determined. Using substrates with and without adsorbed surfactant, the dispersion and polar parts of the surface tension of the substrates were also measured. Comparison of liquid and solid surface tensions, involved in the physico-chemical mechanism, failed to explain the difference of the molecular alignment for the two substrates. In the presence of the surfactant adsorbed on the surface, the steric model probably gives the explanation for the homeotropic alignment.

2546. Optical properties of 3,4,9,10-perylenetetracarboxylic dianhydride and 8-hydroxyquinoline aluminum salt films prepared by vacuum deposition

Authors: Stanculescu, A; Stanculescu, F; Tugulea, L; Socol, M

Published: 2006, ADVANCED MATERIALS FORUM III, PTS 1 AND 2, 514-516, 960, DOI: 10.4028/www.scientific.net/MSF.514-516.956

The main purpose of this paper is to investigate the optical properties of PTCDA and Alq3 films, prepared by two steps, vacuum evaporation and deposition processes on platelets of glass, quartz, and indium-tin-oxide (ITO) coated glass. We have emphasised the bands structure of the absorption spectra with peaks situated at 358 nm, 374 nm, 475 nm and 552 nm in PTCDA, respectively 232 nm, 261 nm and 380 nm in Alq3 that confirms the dominant presence of Alq3 meridianal molecular isomer. For PTCDA films deposited on glass coated with ITO, the structure of the weak double peak at low wavelength is partially modified, but the positions of the two important absorption peaks situated at 2.25 eV and 2.61 eV are unchanged. The two different luminescence emission peaks obtained in Alq3 for different excitation wavelengths (gimel=360 nm and gimel=520 nm) suggest the existence of the facial isomer beside the meridianal one. We have evidenced a significant Stocks shift in the spectra (Delta E-PTCDA=0.40 eV; Delta E-Alq3=0.9 eV) and a large Frank-Condon shift (0.40-2.3 eV), suggesting important effect associated respectively with the solid state structure and important conformational differences between the ground and excited state.

2547. Radiation tolerance of epitaxial silicon detectors at very large proton fluences

Authors: Lindstrom, G; Fretwurst, E; Honniger, F; Kramberger, G; Moller-Iven, M; Pintilie, I; Schramm, A

Published: JAN 15 2006, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 556, 458, DOI: 10.1016/j.nima.2005.10.103

Detectors processed on epitaxial silicon are a promising solution for the extreme radiation levels in the innermost tracking layers at future particle physics experiments as in the upgraded (S-LHC). In order to systematically investigate their radiation tolerance.. sets of 25 and 50-mu m-thick diodes had been irradiated with 24GeV/c protons up to fluences Of Phi(eq) = 10(16) cm(-2). The full depletion voltage was measured during full isothermal annealing cycles at both 60 and 80 degrees C. A voltage of only 290 V was measured for the 50 mu m diodes after Phi(eq) = 1016cm(-2). In contrast to likewise thin float zone (FZ) diodes, the depletion voltage in epi-devices decreases with annealing during foreseen operational and storage periods. Low-temperature storage during beam-off periods as inevitable for FZ devices could be avoided. The reverse annealing components reveal an overall similar functional time dependence as observed in FZ diodes. However, the most important stable component is drastically different. In contrast to the well-known negative space charge build up observed in FZ diodes, the behavior in epi-diodes can only be explained by an additional formation of positive space charge. The immense improvement of the radiation tolerance of epi-detectors is thus attributed to a compensation effect between acceptor generation and donor creation unique for the epi-material. Charge collection efficiency drops only to about 80% after Phi(eq) = 6 x 10(15)cm(-2) proving that epi-detectors are indeed adequate candidates for the tracking area at extremely large radiation levels. (c) 2005 Elsevier B.V. All rights reserved.

2548. Spectroscopic studies on nanocomposites obtained by functionalization of carbon nanotubes with conducting polymers

Authors: Lefrant, S; Baibarac, M; Baltog, I

Published: 2006, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 447, 403, DOI: 10.1080/15421400500385332

Vibrational properties of composites based on single-walled carbon nanotubes (SWNTs) and conducting polymers of the type polyaniline (PANI) and poly (3,4-ethylene dioxythiophene) (PEDOT) are reported. For PANI-functionalized SWNTs, the intensity increase of the Raman band at 178 cm(-1) , associated with radial breathing modes of SWNTs bundles, indicates an additional roping of nanotubes due to the presence of the polymer. The interaction of this composite with NH4OH solution involves an internal redox reaction between PANI and SWNTs. Thus, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. The functionalization of SWNT side walls with PEDOT is invoked as well.

2549. Quantum dots and nanowires grown by metal-organic chemical vapor deposition for optoelectronic device applications

Authors: Tan, HH; Sears, K; Mokkapati, S; Fu, L; Kim, Y; McGowan, P; Buda, M; Jagadish, C

Published: NOV-DEC 2006, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 12, 1254, DOI: 10.1109/JSTQE.2006.882663

This paper discusses the growth of In(Ga)As quantum dots (QDs) and nanowires by metal-organic chemical vapor deposition and their application to optoelectronic devices. The performance characteristics of QD lasers and QD photodetectors as well as the selective area growth of QDs for integrated devices are reported.

2550. Self-organization in amorphous semiconductors and chalcogenide glasses

Authors: Popescu, M

Published: DEC 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 2168, DOI:

It is shown that self-organization in non-crystalline networks of amorphous semiconductors, as well as in non-crystalline chalcogenide materials is rather a rule than an exception. The fundamental principles are stated on the basis of few examples. The most extended order in glasses is given by the uniform distribution of large stochastic clusters.

2551. Nanostructural configurations in As2S3 glass

Authors: Popescu, M; Sava, F; Lorinczi, A; Anghel, A

Published: APR 2006, PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B, 47, 157, DOI:

Various closed nanocluster configurations based on the stoichiometric arsenic-chalcogen composition have been built and relaxed by a computer Monte Carlo procedure. They can be used in the construction of the glass network. A model with random packing of various large, closed nano-clusters has been devised and fairly good agreement with experimental data for As2S3 has been obtained.

2552. Model of the interband nonlinear absorption in amorphous chalcogenides: Quasi-linear analytical solutions

Authors: Babin, V; Popescu, M; Ciobanu, M; Nicolae, ND; Talianu, C; Ciuciu, G

Published: APR 2006, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 17, 314, DOI: 10.1007/s10854-006-6949-6

It is proposed a quasi-linear algorithm for the solving the kinetic equations system, which describes the excitation and relaxation processes in the electronic and phononic subsystems of amorphous chalcogenides. The nonlinear interaction between an optical field and an amorphous chalcogenide medium is analyzed. The nonlinear interaction between an excitation incident optical field and the non-crystalline chalcogenide materials, evidences the specific nonlinear phenomena in amorphous semiconductors, which have no correspondent in the case of crystalline semiconductors. The model is limited to phenomena occurring in chalcogenide semiconductors, simultaneously with the optical field propagation, by neglecting the excitation phenomena.

2553. Polarization fatigue and frequency-dependent recovery in Pb(Zr,Ti)O-3 epitaxial thin films with SrRuO3 electrodes

Authors: Pintilie, L; Vrejoiu, I; Hesse, D; Alexe, M

Published: MAR 6 2006, APPLIED PHYSICS LETTERS, 88, DOI: 10.1063/1.2186074

Fatigue is investigated in epitaxial Pb(Zr,Ti)O-3 films grown on SrRuO3/SrTiO3 substrates with Pt or SrRuO3 (SRO) top electrodes. It was experimentally determined that fatigue occurs irrespective of whether the top electrode is Pt or SRO. The fatigue behavior is strongly dependent on the frequency. A polarization recovery was observed for both types of top electrodes, but the recovery is almost complete for a SRO top electrode and only about 40% from the initial polarization value for Pt top electrodes. The results are tentatively explained by the frequency response of the deep traps and by migration of oxygen vacancies.

2554. Quantum kinetic theory of phonon-assisted carrier transitions in nitride based quantum-dot systems

Authors: Seebeck, J; Nielsen, TR; Lorke, M; Gartner, P; Jahnke, F

Published: 2006, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 6, 3, 2033, DOI: 10.1002/pssc.200565227

A microscopic theory for the interaction of carriers with LO phonons is used to study ultrafast capture and relaxation dynamics in semiconductor quantum dots. Energy renormalization due to carrier-phonon interaction leads to quantum-dot polarons which are included in quantum-kinetic equations to describe scattering processes. Our results show efficient capture and relaxation processes. For an InGaN quantum-dot system the influence of the strong built-in electrostatic field on the carrier dynamics is investigated. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2555. Mossbauer study of the hyperfine interactions and spin dynamics in alpha-iron(II) phthalocyanine

Authors: Filoti, G; Kuz'min, MD; Bartolome, J

Published: OCT 2006, PHYSICAL REVIEW B, 74, DOI: 10.1103/PhysRevB.74.134420

The Fe-57 Mossbauer spectroscopy on alpha-iron(II) phthalocyanine (FePc) as a function of temperature (1.3 < T < 295 K) and applied field (0 < B < 10 T) has been used to study the peculiar magnetic properties of this ferromagnetic quasilinear chain type compound. One sextet with an internal hyperfine field B-int=66.2 T was observed at 1.3 K, a very large value for a bivalent iron with S=1 pointing to the existence of large positive orbital and dipolar contributions in the investigated FePc. Under an applied field, the experimental spectra exhibited two nonequivalent Fe positions, due to spin canting, with the values for the hyperfine fields of the split sextets increasing with increasing field, an indication that unlike most cases, B-int in alpha-FePc is positive, i.e., parallel to the magnetic moment of iron. Therefore, the origin of the large hyperfine field is the orbital moment rather than the Fermi's contact interaction. This fact is ascribed to the orbital degeneracy of the ground state of Fe(II) in the present configuration, where an unpaired hole occupies the orbital doublet (d(xz), d(yz)). This feature supports and explains the magnetization and susceptibility data as well as the anomalously high hyperfine field observed at Fe-57 nucleus. The relaxational behavior in the ac susceptibility and Mossbauer spectra found in the region 5-20 K was ascribed to solitonlike motion of domain walls within the magnetic chains, with a single-kink activation energy of 72 K.

2556. The 'in-plane' angular spin distribution in layered systems as obtained by Fe-57 Mossbauer spectroscopy (vol 196, pg 135, 2002)

Authors: Kuncser, V; Keune, W; Vopsaroiu, M; Bissell, PR

Published: APR 2006, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 245, 542, DOI: 10.1016/j.nimb.2006.01.022

2557. Criteria for the occurrence of negative resonant magnetoresistance in magnetic tunnel junctions

Authors: Tolea, M; Aldea, A; Tolea, F

Published: SEP 2006, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 243, R86, DOI: 10.1002/pssb.200642347

The dependence of the driven-current through a tunnel junction on the relative orientation of the magnetization in the electrodes deviates from the Julliere formula when the current is resonant through impurity levels. For asymmetric coupling of the impurities to the electrodes, the magnetoresistance can even be negative on the resonance. Such inversion in sign is due to the fact that not only the density of states in the electrodes is important (for both orientations of spins), but also the density of states at the impurity position, which has a specific behavior. We find the exact conditions under which the negative magnetoresistance occurs, as function of both polarization and coupling asymmetry. The resonant magnetoresistance may have single or double-dip aspect, depending on the mentioned parameters.

2558. Self-organization and anisotropy in amorphous chalcogenides

Authors: Popescu, M; Sava, F; Lorinczi, A

Published: JUN 15 2006, JOURNAL OF NON-CRYSTALLINE SOLIDS, 352, 1509, DOI: 10.1016/j.jnoncrysol.2005.11.140

The intermediate, self-organized phase, in the As-Se system has been modeled on the basis of clusters with one or more selenium-selenium bridges. The X-ray diffraction patterns of the glass models at the limits of the 'floppy phase-stressed rigid phase' window have been calculated. The structural and optical anisotropy in a matrix of clusters containing Se-Se bonds is supposed to be a consequence of breaking and re-linking the broken clusters in the direction of the polarized light beam that acts upon the chalcogenide material. (c) 2006 Elsevier B.V. All rights reserved.

2559. Band-pass filters with (Zr-0.8, Sn-0.2)TiO4 dielectric resonators

Authors: Ioachim, A; Banciu, MG; Nedelcu, L; Dutu, CA

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 943, DOI:

Band-pass filters with dielectric resonators of (Zr-0.8, Sn-0.2)TiO4 ceramic materials (ZST) were developed for X-band applications. The ZST materials exhibit a dielectric constant of about 36.8 and low loss in microwave range. A Qxf product higher than 50,000 was achieved for the ZST samples with 0.2 % wt NiO sintering addition. The external coupling was performed using microstrip lines on a substrate of 9.22 dielectric constant and 0.635 mill height. Filters with a minimum insertion loss between 0.46 dB and 1.74 dB, the bandwidth between 40 MHz and 170 MHz and with the central frequency around 10 GHz were manufactured.

2560. Interference in a system of coupled quantum wires: Theoretical study of electronic transport

Authors: Bulka, BR; Tolea, M; Dinu, IV

Published: NOV 2006, PHYSICAL REVIEW B, 74, DOI: 10.1103/PhysRevB.74.205301

Theoretical studies of the coherent electronic transport in a system of coupled quantum wires show that switching on the conducting channel in one wire can be manifested in the other coupled wires. Interference processes and electronic correlations are taken into account in our studies on the same footing. The conductance changes depend on the interference conditions of a transmitted wave with that one reflected from the wires that indirectly influence the transport. We show that electronic correlations lead to a dynamical Coulomb blockade effect, which changes the conductance response quantitatively but its shape is still kept the same. Our results are discussed in correspondence with an experiment recently performed by Morimoto [Appl. Phys. Lett. 82, 3952 (2003)] on a system of coupled quantum wires.

2561. Couplings control in the defected ground star-geometry dual-mode filter

Authors: Banciu, MG; Shen, S; Ramer, R; Militaru, N; Lojewski, G

Published: 2006, 2006 EUROPEAN MICROWAVE CONFERENCE, VOLS 1-4, +, DOI:

Investigations on coupling coefficients in a stargeometry filter with defected ground are presented in this paper. The device is compact, requiring a surface area of more than 6 times smaller than the area needed for a conventional patch dual mode resonator.

2562. Effect of nitridation on the electronic environment of vanadium in VAlO(N) powder catalysts, used for the ammoxidation of propane

Authors: Silversmit, G; Poelman, H; De Gryse, R; Bras, W; Nikitenko, S; Florea, M; Grange, P; Delsarte, S

Published: DEC 15 2006, , DOI: 10.1016/j.cattod.2006.07.013

2563. Optical properties of polycarbonate organic matrix/cadmium sulphide clusters composite material

Authors: Stanculescu, A; Stanculescu, F; Socol, M

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1061, DOI:

This paper presents the investigation of the optical properties of bisphenol A polycarbonate organic matrix/CdS clusters composite material in correlation with the method for the films' preparation using as precursors cadmium acetate (Cd(CH3COO)(2)), respectively ammonium thiocyanate (NH4CNS), and as general solvent for all the components, is dimethyformamide. The effect of the heat treatment temperature (90 degrees C or 150 degrees C) on the position and shape of the fundamental absorption edge was investigated for given substrate, drying conditions and duration (1.5 h or 0.5 h) of the heat treatment. A large blue shift of the absorption edge was evidenced in films prepared in vertical configuration and thermally treated at 90 degrees C for 1.5 h, which can be associated with a small dimension of the CdS crystallites and in consequence with quantum confinement effects. Using the effective mass theory we have deduced a crystallite dimension in the range 8.8-15 nm. We also have studied the interaction of the light with this composite material evaluating an optical band gap between 2.92 and 3.69 eV (depending on the preparation and annealing conditions) and an absorption mechanism in CdS clusters closer to an indirect transition and deviated from the normal direct absorption process in bulk CdS semiconductor.

2564. Hydrogen storage in Mg-Ni-Fe compounds prepared by melt spinning and ball milling

Authors: Palade, P; Sartori, S; Maddalena, A; Principi, G; Lo Russo, S; Lazarescu, M; Schinteie, G; Kuncser, V; Filoti, G

Published: MAY 18 2006, JOURNAL OF ALLOYS AND COMPOUNDS, 415, 176, DOI: 10.1016/j.jallcom.2005.08.017

Magnesium-rich Mg-Ni-Fe intermetallic compounds have been prepared by two different routes: (a) short time ball milling of ribbons obtained by melt spinning; (b) long time ball milling of a mixture of MgH2, Ni and Fe powders. The first type of samples displays an hydrogen desorption kinetics better than the second one. Pressure composition isotherm measurements exhibit for both type of samples two plateaux, the lower and wider corresponding to the MgH2 phase and the upper and shorter corresponding to the Mg2NiH4 phase. The presence of the two types of hydrides is confirmed by X-ray diffraction analysis. Mossbauer spectroscopy shows that in melt spun and subsequently milled samples iron is mainly in a disordered structure and segregates after hydrogenation, while in directly milled powders remains mainly unalloyed. After multiple hydrogen absorption/desorption cycles the main part of iron is in metallic state in samples of both types, those of first type preserving better hydrogen desorption kinetics. (c) 2005 Elsevier B.V. All rights reserved.

2565. Understanding the role of nitridation in butan-1-ol and butan-2-ol dehydration mechanisms over oxynitrides

Authors: Delsarte, S; Florea, M; Mauge, F; Grange, P

Published: AUG 1 2006, , DOI: 10.1016/j.cattod.2006.01.033

2566. High surface area Mo-V-Te-Nb-O catalysts: Preparation, characterization and catalytic behaviour in ammoxidation of propane

Authors: Florea, M; Mamede, AS; Eloy, P; Parvulescu, VI; Gaigneaux, EM

Published: MAR 15 2006, , DOI: 10.1016/j.cattod.2005.11.080

2567. Mechanico-chemical interaction of SWNTs with different host matrices evidenced by SERS spectroscopy

Authors: Lefrant, S; Baibarac, M; Mihut, L; Baltog, I

Published: NOV 2006, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 243, 3439, DOI: 10.1002/pssb.200669184

Surface enhanced Raman scattering (SERS) performed with 676.4 and 1064 nm excitations were used to investigate single-walled carbon nanotubes (SWNTs) thin films prepared from platelets obtained by nonhydrostatic compression at 0.58 GPa. SWNTs were compressed alone or dispersed into chemical reactive and non-reactive host matrices. SERS spectra indicate that by compression, SWNTs break into fragments of different sizes, which in turn can react or not with the host matrix. In inorganic hosts (KI, Ag) donor-acceptor complexes are formed. The appearance of short fragments of SWNTs with a closed-shell fullerenes behaviour is revealed in SERS spectra. This typical signature appears in the Raman spectrum as a line at ca. 1460 cm(-1) associated with a pentagonal pinch mode. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2568. Effect of LaCoO3 perovskite deposition on ceria-based supports on total oxidation of VOC

Authors: Alifanti, M; Florea, M; Cortes-Corberan, V; Endruschat, U; Delmon, B; Parvulescu, VI

Published: MAR 15 2006, , DOI: 10.1016/j.cattod.2005.11.017

2569. Electrical properties of as-grown molecular beam epitaxy high-k gate dielectrics deposited on silicon

Authors: Goldenblum, A; Pintilie, I; Buda, M; Popa, A; Lisca, M; Botila, T; Teodorescu, V; Dimoulas, A; Vellianitis, G

Published: MAR 15 2006, JOURNAL OF APPLIED PHYSICS, 99, DOI: 10.1063/1.2180428

The carrier transport mechanisms in as-grown LaAlO3 and La2Hf2O7 high-k insulator layers deposited on n- and p-Si were deduced from temperature dependent C-V and I-V characteristics correlated with photoelectric measurements. Large, parallel shifts in the high frequency C-V curves are explained by the presence of a large density of interface states and an approximate analytical formula relating the density of states to the C-V shift is deduced. The space charge limited current is explained by the existence of impurity channels situated energetically near the conduction or valence band of silicon.

2570. Preparation of Mo-V-Te-Nb mixed oxides using the template route

Authors: Florea, M; Gaigneaux, EM; Parvulescu, VI

Published: 2006, , DOI: 10.1016/S0167-2991(06)80979-1

2571. Effect of Auger recombination on the performance of p-doped quantum dot lasers

Authors: Mokkapati, S; Buda, M; Tan, HH; Jagadish, C

Published: APR 17 2006, APPLIED PHYSICS LETTERS, 88, DOI: 10.1063/1.2193433

Experimental results on spontaneous emission rates from InGaAs quantum dot lasers that can be explained theoretically by considering the influence of nonradiative mixed state recombinations in the quantum dot-wetting layer system are presented. Our model qualitatively explains the experimental results such as an increase in the threshold current density, temperature stability, and a narrower gain spectrum due to doping the quantum dot active region with the acceptors. Our model also predicts that moderate acceptor concentrations can improve the laser performance at higher carrier injection densities; but high acceptor concentrations deteriorate the laser performance due to the nonradiative Auger recombination that counteracts the benefits of increased spontaneous emission rates.

2572. Substitutional effects in RFe3 intermetallics (R = Dy, Sm, Y)

Authors: Sorescu, M; Diamandescu, L; Valeanu, M

Published: MAR 2006, INTERMETALLICS, 14, 335, DOI: 10.1016/j.intermet.2005.06.010

Samples of RFe3 (R = Dy, Sm, Y) were doped with Si, Al and Ti and studied by Mossbauer spectroscopy and X-ray diffraction. Most Mossbauer spectra were analyzed with three sextets, corresponding to the 6c, 3b and 18 h inequivalent lattice sites for iron. A quadrupole split doublet was also present in some spectra, which became dominant for the case of A] substitution. The collapse of the hyperfine magnetic structure is a magnetic effect due to substitutions: the X-ray diffraction patterns yielded a particle size of about 100 nm, thus precluding the occurrence of superparamagnetism in these systems. (c) 2005 Elsevier Ltd. All rights reserved.

2573. Mossbauer spectral study of RFe11.3W0.7 compounds (R = Dy, Ho, Er, and Lu)

Authors: Lazar, DP; Plugaru, N; Kuncser, V; Valeanu, M; Filoti, G; Bartolome, J; Rubin, J

Published: JUL 2006, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 302, 67, DOI: 10.1016/j.jmmm.2005.08.030

The series of compounds RFe11.3W0.7, where R = Dy, Ho, Er, and Lu, has been measured by Mossbauer spectroscopy between 15 and 295 K. A model which takes into account the Wigner-Seitz cell local environment of each iron site, the distribution of tungsten atoms on the 8i site, and the temperature-dependent magnetic structures of the compounds has been used to analyse the spectra. The assignment and the temperature dependencies of the hyperfine fields and the isomer shifts are in complete agreement with the Wigner-Seitz; cell analysis of the three iron sites in RFe11.3W0.7 compounds. The plausible orientations of the iron magnetic moments in the canted magnetic phase of ErFe11.3W0.7 compound have been established by a thorough Mossbauer spectral analysis. The Mossbauer spectra of DyFe11.3W0.7 clearly show the influence of the two spin re-orientations occurring in this compound and indicate the directions of the iron magnetic moments in both canted and planar magnetic arrangements. (c) 2005 Elsevier B.V. All rights reserved.

2574. A penetration depth study on Li2Pd3B and Li2Pt3B

Authors: Yuan, HQ; Vandervelde, D; Salamon, MB; Badica, P; Togano, K

Published: 2006, LOW TEMPERATURE PHYSICS, PTS A AND B, 850, +, DOI:

In this paper we present a penetration depth study on the newly discovered superconductors Li2Pd3B and Li2Pt3B. Surprisingly, the low-temperature penetration depth lambda(T) demonstrates distinct behavior in these two isostructural compounds. In Li2Pd3B, lambda(T) follows an exponential decay and can be nicely fitted by a two-gap BCS superconducting model with a small gap Delta(1)=3.2K and a large gap Delta(2)=11.5K. However, linear temperature dependence of lambda(T) is observed in Li2Pt3B below 03T(c), giving evidence of line nodes in the energy gap.

2575. Fabrication and characterisation of GaAs Gunn diode chips for applications at 77 GHz in automotive industry

Authors: Forster, A; Stock, J; Montanari, S; Lepsa, MI; Luth, H

Published: APR 2006, SENSORS, 6, 360, DOI:

GaAs-based Gunn diodes with graded AlGaAs hot electron injector heterostructures have been developed under the special needs in automotive applications. The fabrication of the Gunn diode chips was based on total substrate removal and processing of integrated Au heat sinks. Especially, the thermal and RF behavior of the diodes have been analyzed by DC, impedance and S-parameter measurements. The electrical investigations have revealed the functionality of the hot electron injector. An optimized layer structure could fulfill the requirements in adaptive cruise control (ACC) systems at 77 GHz with typical output power between 50 and 90 mW.

2576. Quantum confinement modeling of electrical and optical processes in nanocrystalline silicon

Authors: Ciurea, ML; Iancu, V; Stavarache, I

Published: DEC 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 2160, DOI:

The paper presents a quantum confinement model for the electrical transport, the phototransport and the photoluminescence phenomena in nanocrystalline silicon. The infinite rectangular quantum well was proved to be the best choice for the investigated systems - nanocrystalline porous silicon and silicon nanodots embedded in an amorphous silicon dioxide matrix. Previous microstructure investigations have shown that the nanocrystalline porous silicon is formed by a nanowire network, so that the electron Hamiltonian is the sum of a one-dimensional Bloch-like Hamiltonian and a two-dimensional infinite rectangular quantum well. In the case of the silicon nanodots, the quantum well is three-dimensional. In both cases, the quantum well introduces quantum confinement levels in the band gap, the investigated phenomena being related with transitions between these levels.

2577. Giant magnetoresistive coatings using thermionic vacuum are technology

Authors: Anghel, A; Luncu, CP; Mustata, I; Zaroschi, V; Lungu. AM; Barbu, I; Badulescu, M; Pompilian, O; Schinteie, G; Predoi, D; Kunkser, V; Filoti, G; Apetroaei, N

Published: 2006, CZECHOSLOVAK JOURNAL OF PHYSICS, 56, B23, DOI: 10.1007/s10582-006-0173-8

Giant magnetoresistive (GMR) coatings on silicon, glass and Kapton were prepared by simultaneous thermionic vacuum are (TVA) discharges in high vacuum conditions. The magnetic metal or alloy (Fe, Co, Ni, Permalloy) together with the noble non magnetic metal were deposited on substrates having different positions relative to the discharges. Local magnetic interactions and Fe-phase composition were obtained by Mossbauer spectroscopy whereas the magnetoresistance effects were measured by a dc method using a four-point configuration with perpendicular to plane magnetic fields up to 0.8 T. The surface morphology of the coatings was characterized by atomic force microscopy (AFM) in contact mode.

2578. In situ structural changes during toluene complete oxidation on supported EuCoO3 monitored with Eu-151 Mossbauer spectroscopy

Authors: Alifanti, M; Florea, M; Filotti, G; Kuncser, V; Cortes-Corberan, V; Parvulescu, VI

Published: SEP 30 2006, CATALYSIS TODAY, 117, 336, DOI: 10.1016/j.cattod.2006.05.036

Ceria-zirconia supported (10 and 20 wt.% EuCoO3) versus bulk EuCoO3 perovskite were prepared via citrate decomposition at 700 degrees C and tested for toluene complete oxidation. S-BET, XRD, XPS, H-2-TPD and in situ Eu-151 Mossbauer investigations were performed. Electron delocalization processes around the Eu cations are induced by the reaction, as proved via the evolution of the Mossbauer parameters. All characterization data indicate the formation of a well-dispersed EuCoO3 at the surface of Ce0.9Zr0.1O2 for the 10 wt.% loading and larger crystallite formation for 20 wt.% loading. In terms of intrinsic activity for toluene combustion, supported catalysts were more active than bulk EuCoO3. All structural changes during operation time are reversible. (C) 2006 Elsevier B.V. All rights reserved.

2579. Thermodynamic properties and spin dynamics of some micro and nanostructured magnetoresistive lanthanum manganites

Authors: Tanasescu, S; Marinescu, C; Maxim, F; Raita, O; Grecu, MN; Giurgiu, L

Published: 2006, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 26, 3010, DOI: 10.1016/j.jeurceramsoc.2006.02.020

The spin dynamics and thermodynamic properties of micro- and nanostructured lanthanum manganites La0.67Ca0.33Mn1-xMeO3 (Me = Al; x = 0-0.05) have been studied in order to evidence new features related to the effect of different compositional variables on the thermodynamic and magnetic behaviour. By electron paramagnetic resonance (EPR) spectroscopy, the influence of the grain size and the Mn substitution effects on the spin dynamics were investigated. A solid state electrochemical method was used to obtain the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen. The influence of the oxygen stoichiometry change on the thermodynamic properties has been investigated. The results were correlated with the average Mn valence values as determined by redox titration. In this paper an alternative method is proposed to estimate the contribution made by oxygen vacancies in balancing the local charge in CMR manganites. (c) 2006 Elsevier Ltd. All rights reserved.

2580. Scaling of conductivity through the critical temperature in Y0.54Pr0.46Ba2Cu3O7

Authors: Sandu, V; Katuwal, T; Taylor, BJ; Maple, MB; Almasan, CC

Published: 2006, LOW TEMPERATURE PHYSICS, PTS A AND B, 850, +, DOI:

In-plane conductivity sigma(ab) curves of Y0.54Pr0.46Ba2Cu3O7 single crystals, measured at constant temperature T in magnetic fields H tilted with an angle theta relative to the c-axis, were found to map onto a single curve in a sigma(ab) vs Hcos theta plot. This scaling occurs both below and above the critical temperature T-c, maintaining the same convexity, and is consistent with the dissipation caused by the motion of two-dimensional (2D) vortices. This indicates the presence of 2D vortices above T-c. A second scaling sigma(ab)(Hcos theta) takes place at higher T-c with an opposite convexity. This scaling is consistent with the dissipation of quasiparticies. There is a T range between these two regimes where no scaling is found. We attribute the absence of scaling in this intermediate regime to a 2D to 3D crossover in the vortex matter.

2581. Amorphous SnSe2 films

Authors: Sava, F; Lorinczi, A; Popescu, M; Socol, G; Axente, E; Mihailescu, IN; Nistor, M

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1371, DOI:

Amorphous SnSe2 films were prepared by pulsed laser deposition (PLD) and pulsed electron deposition (PED) from solid polycrystalline targets. The atomic scale structure has been revealed by X-ray diffraction. Hardness properties and electrical properties were measured. The peculiarities of the structures of the films prepared by PLD and PED methods were investigated discussed.

2582. Fractal structures of gold obtained by diffusion limited aggregation in alkali halide crystals

Authors: Enculescu, M; Enculescu, I; Topa, V

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1233, DOI:

Nanostructures of gold embedded in potassium chloride matrices were obtained after the doped crystals growth, by electrolytical colouring, and by thermal treatment. When the TEM images of the nanostructures were analyzed using fractal geometry it means was proved that the self assembling of the metallic structures is governed by the diffusion limited aggregation (DLA) mechanism. The values of the fractal dimension, which were in all cases between 1.7 and 1.9, calculated using two methods, sandbox and box-counting, proved the DLA mechanism.

2583. Influence of carrier-carrier and carrier-phonon correlations on optical absorption and gain in quantum-dot systems

Authors: Lorke, M; Nielsen, TR; Seebeck, J; Gartner, P; Jahnke, F

Published: FEB 2006, PHYSICAL REVIEW B, 73, DOI: 10.1103/PhysRevB.73.085324

A microscopic theory is used to study the optical properties of semiconductor quantum dots. The dephasing of a coherent excitation and line shifts of the interband transitions due to carrier-carrier Coulomb interaction and carrier-phonon interaction are determined from a quantum kinetic treatment of correlation processes. We investigate the density dependence of both mechanisms and clarify the importance of various dephasing channels involving the localized and delocalized states of the system.

2584. Microscopic theory of carrier-carrier scattering in nitride based quantum-dot systems

Authors: Nielsen, TR; Seebeck, J; Lorke, M; Gartner, P; Jahnke, F

Published: 2006, PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 6, 3, 2042, DOI: 10.1002/pssc.200565124

A microscopic theory is applied to study carrier-carrier Coulomb scattering in nitride-based quantum dots. Kinetic equations for the carrier population are used to define capture and relaxation rates. For the states involved in the scattering processes, the combined influence of the quantum-confined Stark effect and many-body renormalizations is taken into account. It is shown that the charge separation due to the built-in field is accompanied with strong Hartree energy shifts, which can increase the scattering efficiency. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2585. A distinctive signature in the Raman and photoluminescence spectra of intercalated PbI2

Authors: Preda, N; Mihut, L; Baibarac, M; Baltog, I; Lefrant, S

Published: OCT 4 2006, JOURNAL OF PHYSICS-CONDENSED MATTER, 18, 8912, DOI: 10.1088/0953-8984/18/39/020

Through correlated studies using scanning electron microscopy (SEM), Raman spectroscopy and low-temperature photoluminescence (PL) we have demonstrated that the intercalated PbI2 with ammonia, poly (vinyl alcohol) and polyacrylamide are characterized by a distinctive signature in the Raman and photoluminescence spectra. After intercalation, the Raman spectrum of PbI2 reveals an orthorhombic structure, identical with that observed on the micrometric scale, of KPbI3 rod-like particles resulting from the reaction between Pb(NO3)(2) and KI, carried out in liquid media such as ethanol and acetonitrile. The rods and the intercalated PbI2 are characterized by a new and strong emission band at 2.23 eV (about 550 nm) that appears at 77 K under an excitation wavelength of about 340 nm. Modification of the Raman and PL spectra results from a compressing effect produced by the penetration between the PbI2 layers of different molecular species. The compression acting primarily on the iodine layers has the result of lowering the contribution of the 5p states of I- ions to the constitution of the electronic level situated at the top of valence band of PbI2, so that the photoluminescence of intercalated PbI2 acquires the characteristics of Pb2+ emission when it is dissolved in an alkali halide crystal.

2586. Electrochemically functionalized carbon nanotubes and their application to rechargeable lithium batteries

Authors: Baibarac, M; Lira-Cantu, M; Oro-Sole, J; Casan-Pastor, N; Gomez-Romero, P

Published: AUG 2006, SMALL, 2, 1082, DOI: 10.1002/smll.200600148

Electrochemical polymerization of N-vinyl carbazole (VC) on carbon nanotube (CNT) films was studied by cyclic voltammetry (CV) in LiClO4/acetonitrile solutions. Comparing the cyclic voltammograms recorded on a blank Pt electrode with those obtained when single- or multi-walled carbon nanotube (SWNT or MWNT) films were previously deposited onto the Pt electrode, a downshift of the VC reduction peak potential is observed in the latter case. The influences of monomer concentration, type of solvent, and supporting electrolyte on the polymerization conditions and electrochemical properties of these composite materials are also investigated. The morphological aspects of poly(N-vinyl carbazole) (PVC)-functionalized CNTs are revealed by transmission electron microscopy (TEM) studies. A covalent functionalization of carbon nanotubes with PVC is invoked as a result of attenuated total reflection infrared (ATR-IR) spectroscopic studies. Using PVC-functionalized CNTs as a positive electrode and an electrolytic solution containing LiPF6, the charge-discharge characteristics of the rechargeable lithium cells are determined. High specific discharge capacity (approximate to 45 and 115 mA h g(-1)) is reported for PVC-functionalized single- and multi-walled carbon nanotubes, respectively.

2587. In situ grown epitaxial YBa2Cu3O7-x thin films by pulsed laser deposition under reduced oxygen pressure during cool-down time

Authors: Branescu, M; Vailionis, A; Ward, I; Huh, J; Socol, G

Published: APR 30 2006, APPLIED SURFACE SCIENCE, 252, 4577, DOI: 10.1016/j.apsusc.2005.07.137

We report novel pulsed laser deposition conditions that were used to obtain superconducting epitaxial YBCO thin films, grown in situ using an oxygen pressure lower than the usual one during the cool-down time. We studied the influence of the PLD conditions as substrate temperature, oxygen pressure, laser fluence, and number of laser pulses on the crystallographic and morphological features, and on the superconducting properties of the films. Good superconducting properties were obtained without a high temperature post-deposition annealing process. A maximum critical temperature of 88.6 K was obtained. (c) 2005 Elsevier B.V. All rights reserved.

2588. Structure effects on the magnetism of AgCo nanoparticles

Authors: Crisan, O; Angelakeris, M; Simeonidis, K; Kehagias, T; Komninou, P; Giersig, M; Flevaris, NK

Published: NOV 2006, ACTA MATERIALIA, 54, 5260, DOI: 10.1016/j.actamat.2006.06.053

Fabrication by colloidal chemistry and an extended structural and magnetic investigation are reported for AgCo bimetallic colloidal nanoparticles using X-ray diffraction, transmission electron microscopy and superconducting quantum interference device magnetometry. The AgCo nanoparticles exhibit a core-shell structure, with a face-centred cubic Ag core and a hexagonal close-packed Co (either complete or partial) shell. A bimodal size distribution of superparamagnetic (SPNI) nanoparticles together with a small fraction of nanoparticles ferrornagnetic at room temperature has been determined and their influence on magnetic properties is discussed. The arrays of self-assembled nanoparticles exhibit a lack of saturation of magnetisation and typical SPM behaviour. The annealing of the arrays greatly enhances the ferromagnetic character of the samples. Finally, the observed magnetic behaviour of the AgCo nanoparticles is correlated with surface spin disorder induced by the particular structural features of the sample, high fraction of magnetic atoms in surface states and finite-size effects. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

2589. Tunnelling magnetoresistance of a T-shaped Fano dot

Authors: Tolea, M; Bulka, BR

Published: JAN 2006, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 243, 254, DOI: 10.1002/pssb.200562462

We show the role of the Fano interference on the magnetoresistance properties of a T-shaped double-dot placed between ferromagnetic electrodes. In the linear voltage regime, the magnetoresistance is a non-monotonic function of the gate voltage. We find high values of the magnetoresistance at the Fano dip and far from it. For resonant transmission, the magnetoresistance is lower and it can be negative for asymmetric couplings. Particularities of the system in nonequilibrium transport are also analysed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2590. Optical and electronic properties of (Fe+Sb): PVA for real time holography

Authors: Kuncser, V; Bulinski, M; Krautwald, S; Franke, H; Wagner, FE; Cristea, D; Palade, P; Plapcianu, C; Filoti, G

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1229, DOI:

The electron transfer processes induced by the ultraviolet exposure of the Fe and Sb doped polyvinyl alcohol (PVA) thin films were studied in comparison with those appeared in the correspondent mono (Fe or Sb) doped ones. Samples with different thickness and subjected to different exposures were analysed by optical absorption as well as by Fe-57 and Sb-121 Mossbauer spectroscopy. The influence of each element from the pair on the electronic mechanism activated by the ultraviolet exposure was investigated. Accordingly, the (Fe+Sb) doped PVA presents improved electronic characteristics, in respect to the specific behaviour of single metal doped polymer recording media for real time holography.

2591. Development of compact cross-coupled filters for mobile communications

Authors: Banciu, MG

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 216, DOI:

Investigations on compact devices developed for the second (2G) and the third (3G) mobile communications systems are presented in this paper. Four-pole and six-pole filters were designed by cross-coupling new compact planar resonators. The coupling constants were investigated as functions of coupling gaps. Several models of the pass-band filters were manufactured and characterized. They exhibit steeper responses due to the cross-couplings, which introduce transmission zeros on each side of the pass-band. Moreover, due to their shapes, the resonators exhibit a first,high order response at more than twice the fundamental frequency, therefore the filters show an enlarged rejection band. The measured filter responses are in a good agreement with the simulated responses. The developed filters are compact, cost-effective and suitable to be designed on high dielectric constant ceramic substrates, or for high temperature superconducting (HTS) circuits.

2592. Structure of bulk glassy As2Se3 and As2S3

Authors: Georgescu, G; Sava, F; Rares-Medianu, M

Published: OCT 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1805, DOI:

The structure of bulk glassy As2Se3 has been investigated by X-ray diffraction. The structure was compared with that of bulk glass As2S3 measured in the same conditions. Similarities and differences have been pointed out.

2593. Manganese doped sol-gel materials with catalytic properties

Authors: Crisan, M; Raileanu, M; Preda, S; Zaharescu, M; Valean, AM; Popovici, EJ; Teodorescu, VS; Matejec, V; Mrazek, J

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 819, DOI:

In the present study manganese doped alumina and silica gels and thin films deposited on different substrates (refractory metals, silicon wafers) were obtained by the alkoxide and aqueous routes of the sol-gel method. The characterization of the films was realized by X-ray diffraction (XRD), and spectroellipsometry (SE) methods. The un-supported gels (obtained by the gelation of the solutions used for the film deposition) were characterized by DTA/TG analysis, IR spectroscopy, transmission electron-microscopy and electron diffraction (TEM and SAED) and BET method (adsorption of krypton at temperature of liquid nitrogen) for surface area and pores volume determination. The sol-gel materials were tested as catalysts for the ozone decomposition.

2594. Characterization of BaTi4O9 ceramics by Raman spectroscopy and XPS after ion etching

Authors: Catalin, N; Cernea, M

Published: OCT 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1883, DOI:

Barium tetratitanate (BaTi4O9) ceramic prepared by coprecipitation method was analyzed by Raman spectroscopy and by X-ray photoelectron spectroscopy (XPS). The orthorhombic crystalline structure of BaTi4O9 ceramic sintered at 1300 degrees C for 2h in air was identified on the Raman spectrum. The sample was etched in argon plasma and then analysed by XPS. The etching process did not influence significantly the XPS spectra of barium and titan suggesting a good compositional homogeneity of the BaTi4O9 ceramic prepared by oxalate method.

2595. Investigations of the nonhomogeneities in organic molecular crystalline materials using Kubelka-Munk theory

Authors: Socol, M; Stanculescu, A

Published: FEB 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 190, DOI:

This paper presents a study of the nonhomogeneities in doped meta-dinitrobenzene (m-DNB) crystalline films. These growth defects lying in the film plane with dimensions smaller than the films thickness are correlated with the effect of the dopant on the crystallization regime in the dendritic growth conditions. To evaluate the dimension of the growth nonhomogeneities we have used a model based on the Kubelka-Munk theory, emphasising the general constraints imposed to the sample and the experimental set-up, and developing a more complex model through a step-by-step relaxation of these constraints, that ensures a better approximation for our experimental configuration. We have deduced higher scattering coefficients in m-DNB doped with 1,3 dihydroxybenzene (resorcinol) than in m-DNB doped with 8-hydroxyquinoline (oxine) films prepared by a rapid thermal solidification process. We also have emphasised that for the films of m-DNB doped with oxine the size of the scattering centers is larger than the wavelength of the radiation and in films of m-DNB doped with resorcinol the radiation scattering corresponds to a multiple scattering process leading to the superposition of different scattering mechanisms on centers with different dimensions.

2596. High-k Mg-doped ZST for microwave applications

Authors: Ioachim, A; Banciu, MG; Toacsen, MI; Nedelcu, L; Ghetu, D; Alexandru, HV; Berbecaru, C; Dutu, A; Stoica, G

Published: OCT 31 2006, APPLIED SURFACE SCIENCE, 253, 338, DOI: 10.1016/j.apsusc.2006.06.006

The (Zr0.8Sn0.2)TiO4 material (ZST), has been prepared by solid state reaction and characterized. The samples were sintered in the temperature range of 1260-1320 degrees C for 2 h. The effects of sintering parameters like sintering temperature (T-s) and MgO addition (0.2 wt.%) on structural and dielectric properties were investigated. Bulk density increases from 4900 to 5050 kg/m(3) with the increase of sintering temperature. The effect of MgO addition is to lower the sintering temperature in order to obtain well sintered samples with high value of bulk density. The material exhibits a dielectric constant epsilon(r) similar to 37 and high values of the Q x f product, greater than 45,000, at microwave frequencies. The dielectric properties make the ZST material very attractive for microwave applications such as dielectric resonators, filters, dielectric antennas, substrates for hybrid microwave integrated circuits, etc. (c) 2006 Elsevier B.V. All rights reserved.

2597. Dopant influence on BST ferroelectric solid solutions family

Authors: Ioachim, A; Alexandru, HV; Berbecaru, C; Antohe, S; Stanculescu, F; Banciu, MG; Toacsen, MI; Nedelcu, L; Ghetu, D; Dutu, A; Stoica, G

Published: JUL 2006, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS, 26, 1161, DOI: 10.1016/j.msec.2005.09.045

Solid solutions of the Ba1-xSrxTiO3 (BST) type are very attractive for applications in information technology, but also in microwaves for such electrically controlled devices as phase shifters, tunable filters, steerable antennas, varactors, etc. A family of solid solutions with x = 25, 50, 75, 90% was prepared by standard powder technology-solid state reaction and sintered at 1230 degrees C and 1260 degrees C. Dielectric permittivity and loss at low (1 kHz) and high frequency (1 divided by 2 GHz) were measured on a large temperature range - 200 degrees C divided by + 200 degrees C. The influence of Sr content and of I wt.% MgO and I wt.% MnO2 doping on the complex dielectric constant was studied. The dielectric permittivity at high frequencies and room temperature considerably decreases with the increase of Sr content. Similarly, low frequency measurements showed a severe and almost linear decrease of the Curie Point with the increase of Sr fraction. At low Sr content, the measured ceramic densities slowly decrease with Sr fraction and represent about 92% of the X-ray density rho(g/cm(3)) approximate to 5.99-0.99x. At x=90% Sr concentration, very low-density ceramics were obtained with both sintering temperatures. (c) 2005 Elsevier B.V All rights reserved.

2598. Shallow energy levels induced by gamma rays in standard and oxygenated floating zone silicon

Authors: Menichelli, D; Scaringella, M; Miglio, S; Bruzzi, M; Pintilie, I; Fretwurst, E

Published: SEP 2006, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 84, 453, DOI: 10.1007/s00339-006-3640-y

Shallow defect levels in floating zone (FZ) and diffusion oxygenated FZ (DOFZ) silicon, before and after irradiation with a Co-60 gamma-source up to 300 Mrad, have been studied by thermally stimulated currents (TSC) and deep level transient spectroscopy (DLTS) in the temperature range 4.2-110 K. Besides vacancy oxygen (VO) and interstitial-substitutional carbon (CiCs) emissions, several TSC peaks have been observed. A trap with an activation energy of 11 meV has been observed at 6 K only in irradiated DOFZ. Two hole traps at 80 meV and 95 meV have been observed both in irradiated FZ and DOFZ, while a trap at 100 meV, related to an interstitial-oxygen (IO2) complex, has been revealed only in irradiated DOFZ. A TSC peak close to 24 K has been resolved into two components, whose concentrations are independent of irradiation fluence: a trap at 55 meV and a level which remains charged after emission at 80 meV. Our measurements confirm the formation, only in DOFZ, of a radiation induced donor at 230 meV. It appears to be responsible for the improved radiation hardness of oxygenated Si together with the suppression of deep acceptors, since no shallower radiation-induced donors have been detected in DOFZ samples.

2599. Doped aromatic derivatives wide-gap crystalline semiconductor structured layers for electronic application

Authors: Stanculescu, A; Stanculescu, F; Alexandru, H; Socol, M

Published: JAN 20 2006, THIN SOLID FILMS, 495, 393, DOI: 10.1016/j.tsf.2005.08.243

We present some investigations on the electrical conductivity of two benzene substituted derivatives (m-DNB, benzil) emphasizing the correlation between the molecular structure, purity, structural defects and the particularities of the conduction mechanisms. The influence of inorganic/organic doping on the I-V plots of silicon/wide-gap organic semiconductor/silicon heterostructures has been analysed. The most significant increase in the conductance has been obtained for organic crystalline films of benzil doped with 3 wt.% m-DNB and m-DNB films doped with I wt.% oxine or 10 wt.% resorcinol. The influence of the silicon wafer's properties as resistivity, conduction type and surface processing on the carrier transport properties in these structures has been studied. We have remarked an increase in the conductance of the organic films of m-DNB doped with oxine or resorcinol in heterostructures realized with chemically polished, "n" type single crystal silicon wafers, compared to lapped ones. A special type of conduction mechanism given by a Poole-Frenkel dependence was evidenced in resorcinol doped m-DNB in the low voltages range. (c) 2005 Elsevier B.V. All rights reserved.

2600. Sol-gel synthesis and characterization of Ce doped-BaTiO3

Authors: Cernea, M; Monnereau, O; Llewellyn, P; Tortet, L; Galassi, C

Published: 2006, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 26, 3246, DOI: 10.1016/j.jeurceramsoc.2005.09.039

Barium titanate (BaTiO3) have been doped "in situ" with 5.5 mol% cerium by a sol-gel method using barium acetate, titanium (IV) isopropoxide, and cerium (III) acetylacetonate as starting materials. The dried gel showed a microstructure consisting of nano-sized grains (similar to 140 nm) with great tendency to agglomeration. Several thermal analysis techniques were used to study the decomposition process of the gel. The presence of hydroxyls up to 720 degrees C suggests a strong bonding Ti-OH that is responsible for the existence of aggregates even at high temperatures. The as-prepared gel powder was found to be amorphous, and then decomposes through oxides and barium carbonate around 500 degrees C and crystallizes on the perovskite structure of tetragonal BaTiO3 at 1100 degrees C for 3h in air. A small influence of the frequency on the dielectric properties of the Ba0.945Ce0.055TiO3 ceramics was observed in 100Hz to 1 MHz domain. At the Curie temperature point (22 degrees C) the dielectric constant was 10130 at 100 Hz while the dielectric loss (tan delta) was 0.018. (c) 2005-Elsevier Ltd. All rights reserved.

2601. Paracrystallinity or randomness: a challenge for noncrystalline structure

Authors: Popescu, M; Leonovici, M

Published: OCT 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1837, DOI:

The structure of low coordinated disordered materials can be understood in the frame of basically different theories: the formation of a continuous random network with all the valence bonds satisfied, the formation of small clusters (amorphites) having all the bond at the margins satisfied (closed clusters) or open clusters with many dangling bonds that are partially compensated due to the formation of valence alternation pairs, and last but not least the formation of so-called nanoparacrystalline structures, i.e. deformed nano-crystalline structures. We show that an intermediate model based on a mixture of closed and open clusters as well as layer like configurations can explain the structure and properties of the binary arsenic chalcogenide glasses.

2602. Stable radiation-induced donor generation and its influence on the radiation tolerance of silicon diodes

Authors: Pintilie, I; Buda, M; Fretwurst, E; Lindstrom, G; Stahl, J

Published: JAN 1 2006, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 556, 208, DOI: 10.1016/j.nima.2005.10.013

Four different kinds of silicon materials (standard float zone-FZ, oxygen enriched FZ-DOFZ, Czoehralski-Cz and thin epitaxial layers grown on Cz substrates-Epi/Cz) have been investigated in this work. They have been irradiated with (CO)-C-60-gamma- radiation and 24 GeV/c protons. The differences in the changes observed in the effective doping concentration (N-eff) after proton irradiation of Cz and Epi silicon can be explained by the balance between the formation of two types of defects-a deep acceptor (the I center, referred to as It, in this paper in order to avoid any confusion with interstitials) and a shallow donor (the bistable donor (BD) complex). While the formation of the I-P center depends on the concentration of interstitial oxygen, the BD is generated in materials with high concentration of oxygen dimers. Following the generation of the IO2i defect-detected after low irradiation fluences only in Epi and Cz material-the average dimer concentration in 50 put Epi/Cz was estimated to be of only 2.7 times lower than in Cz diodes. A value of similar to 2.7 x 10(-12) cm(2) for the electron capture cross-section of the Thermal Double Donors (TDDs), present in the Cz material, was also measured for the first time. The positive space charge introduced by ionization of the BD centers in Epi diodes was directly determined from TSC experiments for two irradiation fluences. The determined values show a linear fluence dependence for the formation of BD centers. By taking into account the BD and the I-p center generation as well as the donor removal, the change of the effective doping concentration N-eff at 20 degrees C in Epi/Cz and Cz diodes after an annealing time of 120 min at 60 degrees C can be explained up to a negative space charge introduction rate of similar to 2.2 x 10(-2) cm(-1) thought to be determined by negatively charged clusters. Long-time annealing experiments at 80 degrees C have shown that the generation of BDs represents a stable damage. (c) 2005 Elsevier B.V. All rights reserved.

2603. Positron annihilation lifetime spectroscopy as experimental probe of free volume concepts in network glasses

Authors: Shpotyuk, O; Kovalskiy, A; Filipecki, J; Kavetskyy, T; Popescu, M

Published: APR 2006, PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B, 47, 135, DOI:

Positron annihilation lifetime spectroscopy (PALS) is tested for use as an alternative experimental probe of free volume concepts in network chalcogenide glasses. PALS measurements are carried out within binary As-Se and ternary GeAs(Sb)-S systems on the examples of g-As2Se3 and samples from stoichiometric As(Sb)(2)S-3-GeS2 and nonstoichiometric As(Sb)(2)S-3-Ge2S3 cross sections. The effect of high energy gamma-irradiation on PALS parameters is studied for ternary glass compositions. The role of induced defect related positron traps in annihilation processes is illustrated. The correlations between nanovoid sizes obtained from PALS, Monte Carlo simulation and first sharp diffraction peak (FSDP) measurements in the framework of Elliott's model are established on the example of g-As2Se3, in order to study the nanovoid topology in the real glass structure. It is shown that nanovoids with average radius of 2.9 angstrom, being effective traps for positrons with 0.37 ns defect related lifetime, are also detected within nanovoid distribution data obtained from Monte Carlo simulation. Suggesting that this group of nanovoids is responsible for the void based origin of FSDP, the analytical relationship between FSDP position and nanovoid diameter is proposed for layer like As2X3-type structures.

2604. Thickness effect in Pb(Zr0.2Ti0.8)O-3 ferroelectric thin films grown by pulsed laser deposition

Authors: Lisca, M; Pintilie, L; Alexe, M; Teodorescu, CM

Published: APR 30 2006, APPLIED SURFACE SCIENCE, 252, 4552, DOI: 10.1016/j.apsusc.2005.07.149

Epitaxial Pb(Zr,Ti)O-3 (PZT) thin films with thicknesses in the range of 50-200 nin and with 0.2 Zr/(Zr + Ti) ratio, were grown by pulsed laser deposition (PLD). The substrates used for PLD deposition are single crystalline 0.5% Nb-doped (1 0 0)SrTiO3 (STON). SrRuO3 (SRO) thin films were deposited as bottom and top electrodes in order to have minimum structural misfit, to insure on one side high quality growth, and on the other side to minimize the influence of the ext,ended structural defects. Structural and electrical characterization was performed. The epitaxial PZT films are c-axis oriented and have an average roughness of 0.4 nm. The ferroelectric behavior was proved in all investigated films by the presence of the hysteresis loops and by the butterfly shape of the capacitance-voltage (C-V) characteristics. The ferroelectricity was present even in the samples with relative high leakage currents, down to a thickness of 50 nm. These results are essential when small thickness is needed for miniaturization of ferroelectric devices using PZT. (c) 2005 Elsevier B.V. All rights reserved.

2605. Single-ion and molecular contributions to the zero-field splitting in an iron(III)-oxo dimer studied by single crystal W-band EPR

Authors: ter Heerdt, P; Stefan, M; Goovaerts, E; Caneschi, A; Cornia, A

Published: MAR 2006, JOURNAL OF MAGNETIC RESONANCE, 179, 37, DOI: 10.1016/j.jmr.2005.10.016

Detailed knowledge of the type and strength of pair interactions between high-spin metal ions is paramount to the understanding and design of molecular magnetic materials. In this work, the anisotropic magnetic interactions in a beta-diketonate-alkoxide iron(III) dimer compound, [Fe-2(OCH3)(2)(dbM)(4), Hdbm = diberizoyhriethane] (Fe-2) have been investigated by single crystal electron paramagnetic resonance (EPR) in the W-band (at 95 GHz). The diamagnetic Substitution method. was employed using the isomorphous gallium(III)-based compound doped with iron(III) to produce Ga-Fe dimers(GaFe). The single-ion zero-field splitting(ZFS) tensor could be separately determined in GaFe with the iron ion in a local environment quasi-identical to the one in Fe2. Its principal directions are found to point in arbitrary directions, uncorrelated with the Fe-O bonds. The Fe2 EPR spectra consist of transitions within the lowest multiplet states S = 1, 2, 3, which were analyzed using the full Spill Hamiltonian description of all exchange coupled pair of s = 5/2 spins. The anisotropic spin-spin interaction tensor of Fe2 possesses a principal axis close to the Fe-Fe direction and was shown to arise both from through-space (dipolar) and through-bond (anisotropic exchange) contributions. The latter involves ail rhombic component J(E) = (J(X) - J(Y))/2 approximate to 0.093 cm(-1) of magnitude comparable. to the dipolar interaction, and even to the rhombic part of the single-ion ZFS (E = 0.097 cm(-1)). Our results show that the anisotropic exchange, usually neglected for S-type ions, is significant for the anisotropic interactions in exchange-coupled iron(III) clusters, including the Fe-4 and Fe-8 families of single-molecule magnets and the anti Ferrornagnetic iron wheels. (c) 2005 Elsevier Inc. All rights reserved.

2606. New polypyrrole-multiwall carbon nanotubes hybrid materials

Authors: Turcu, R; Darabont, AL; Nan, A; Aldea, N; Macovei, D; Bica, D; Vekas, L; Pana, O; Soran, ML; Koos, AA; Biro, LP

Published: APR 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 647, DOI:

We report the synthesis and characterization of new hybrid materials based on conducting polypyrrole (PPY) and multi wall carbon nanotubes (MWCNTs). MWCNTs were prepared by spray-pyrolysis of liquid hydrocarbon-ferrocene solution in an Ar atmosphere. The composites (PPY-CNT) were obtained by in-situ chemical oxidative polymerization of pyrrole in aqueous solution containing MWCNTs. The addition of a water based Fe3O4 nanofluid to the polymerization solution results in the formation of a new hybrid nanostructure of MWCNTs coated with PPY containing magnetic nanoparticles. The properties of PPY composites were investigated by TEM, SEM, FTIR spectroscopy and X-ray diffraction (XRD) measurements. MWCNTs covered with PPY have a rough surface, containing some globular forms typical for the polymer. Significant differences between IR spectra for PPY and PPY-CNT nanocomposites appear for the bands ascribed to pyrrole ring vibrations, suggesting that an interaction between the polymer and CNT occurs and this could change the polymer conformation. XRD analysis shows that the crystalline structure of MWCNTs doesn't change significantly by the association with conducting PPY.

2607. Light absorption in meta-dinitrobenzene and benzyl crystalline films

Authors: Stanculescu, F; Stanculescu, A; Socol, M

Published: JUN 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1056, DOI:

This paper presents the optical absorption properties in crystalline meta-clinitrobenzene (m-DNB) and benzil. The optical band gap as an intrinsic property of these crystalline compounds has been studied using UV-VIS Spectroscopy on thin film. Analysing absorption near the fundamental absorption edge we have deduced the wide band gap semiconductor behaviour of these aromatic derivatives. Processing the experimental transmission data using a function obtained by the superposition of a linear function and a power function we have evaluated the band gap energy in m-DNB, E-g=2.90 eV and emphasised the same two edges patterns of the light absorption spectrum in benzil deposited on glass as for benzil deposited on quartz, with energetic thresholds slowly moved through lower energies, E-g1=2.79 eV and E-g2=3.49 eV. We have also remarked no significant change in the absorption spectrum in benzil induced by the dopant (organic and inorganic).

2608. Laser ablated Fe100-xPdx and Fe100-xMnx thin films (x=20 and 50)

Authors: Sorescu, M; Diamandescu, L; Grabias, A

Published: JUN 2006, INTERMETALLICS, 14, 783, DOI: 10.1016/j.intermet.2005.11.010

Thin films (50 nm) of Fe100-xPdx and Fe100-xMnx (x=20 and 50) were deposited by laser ablation on a Si wafer and studied by X-ray diffraction (XRD) and conversion electron Mossbauer spectroscopy (CEMS). In all cases, the XRD patterns of the target surface before and after ablation show a congruent transfer of ablated material. For the Fe80Pd20 thin, film, XRD spectra show the formation of FePd, iron, Pd oxide and traces of hematite in the ablated film. Complementary information obtained by CEMS indicates the presence of an upper 50-nm thick surface layer of hematite in the deposited film. Fe50Pd50 phase was observed by CEMS and a Pd oxide component was identified by XRD, along with traces of hematite. In the case of Fe80Mn20, the CEMS spectrum is consistent with the Occurrence of the anti ferromagnetic FeMn phase and the XRD pattern also shows the presence of Fe in the structure. For the system Fe50Mn50, we obtain by CEMS an antiferromagnetic phase of FeMn and by XRD we trace the presence of nanohematite and in-depth iron. For x=20 in both iron-rich systems investigated, we observe the segregation of iron with subsequent conversion to hematite. The study shows that the stoichiometry of the compounds plays a decisive role in determining their structural and magnetic properties. (c) 2006 Elsevier Ltd. All rights reserved.

2609. High temperature mixed state c-axis dissipation in low carrier density Y0.54Pr0.46Ba2Cu3O7-delta

Authors: Katuwal, T; Sandu, V; Almasan, CC; Taylor, BJ; Maple, MB

Published: APR 2006, PHYSICAL REVIEW B, 73, DOI: 10.1103/PhysRevB.73.144510

The nature of the out-of-plane dissipation was investigated in underdoped Y0.54Pr0.46Ba2Cu3O7-delta single crystals at temperatures close to the critical temperature. For this goal, temperature- and angle-dependent out-of-plane resistivity measurements were carried out both below and above the critical temperature. We found that the Ambegaokar-Halperin relationship [V. Ambegaokar and B. I. Halperin, Phys. Rev. Lett. 22, 1364 (1969)] depicts very well the angular magnetoresistivity in the investigated range of field and temperature. The main finding is that the in-plane phase fluctuations decouple the layers above the critical temperature and the charge transport is governed only by the quasiparticles. We also have calculated the interlayer Josephson critical current density, which was found to be much smaller than the one predicted by the theory of layered superconductors. This discrepancy could be a result of the d-wave symmetry of the order parameter and/or of the non-BCS temperature dependence of the c-axis penetration length.

2610. Synthesis of La and Nb doped PZT powder by the gel-combustion method

Authors: Cernea, M; Montanari, G; Galassi, C; Costa, AL

Published: MAR 28 2006, NANOTECHNOLOGY, 17, 1735, DOI: 10.1088/0957-4484/17/6/031

Lanthanum and niobium doped PZT with composition (Pb0.93La0.07)[(Zr0.60Ti0.40)](0.9825)Nb0.0175O3 (PZTLN) was prepared by the gel-combustion method. A precursor sol was obtained from lead nitrate, zirconyl nitrate, lanthanum oxide, peroxo-citrato-niobium and a peroxo-citrate complex of titanium isopropoxide as starting precursors. Various molar ratios of citrate/nitrate (CA/NO3- = 1.3, 0.36 and 0.09) were used to prepare very fine powders of PZTLN. The gels resulting from these sols were transformed into powders by an auto-combustion process at,< 400 degrees C. The powders consisted of rhombohedral PZT (PbZr0.60Ti0.40O3), pyrochlore (Pb2Ti2O6) and lead carbonate ((Pb2OCO3)-C-.) phases. The pure rhombohedral phase is found in PZTLN pellets sintered at 1100 degrees C for all citrate/nitrate ratios. Titanium and niobium precursors were modified with peroxo radicals. During the gel-combustion reaction, the temperature of the gel increases, leading to lead evaporation. The loss of lead as well as the particle size increases as the CA/NO3- ratio decreases. The smallest grained powder (about 50 nm) was obtained with the ratio CA/NO3- equal to 0.09.

2611. Signature of the magnetic transitions in Y0.2Pr0.8Ba2Cu3O7.delta in high field angular magnetoresistivity

Authors: Sandu, V; Zhang, C; Almasan, CC; Taylor, BJ; Maple, MB

Published: 2006, YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS, 51, +, DOI: 10.1088/1742-6596/51/1/052

In-plane (ab) and out-of-plane (c-axis) magnetoresistivity display different symmetry crossovers and/or transitions in 14 T magnetic field applied parallel to the CuO2 planes. The in-plane magnetoresistivity crosses over from four-fold symmetry below 6 K to two-fold symmetry at higher temperatures, which becomes dominant at temperatures higher than 40 K. The out-of-plane magnetoresistivity changes at 17 K from four fold symmetry to ordinary sin2 theta at higher temperatures. The behaviour of the c-axis magnetoresistivity can be ascribed to the antiferromagnetic ordering of the Pr spins whereas the symmetry change of the in-plane magnetoresistivity at 6 K might be attributed to commensurate to incommensurate crossovers of the spin subsystems. The antiferromagnetic order of the Cu(2) sublattice seems to have only a week effect on the magnetoresistivity.

2612. Structural and microstructural properties of porous PZT films

Authors: Stancu, V; Boerasu, I; Lisca, M; Pintilie, L; Popescu, M; Sava, F

Published: AUG 2006, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 8, 1497, DOI:

PbZr1-XTiXO3 (PZT) film was prepared by addition of polymer polyvinylpirrolidone (PVP) in the PZT precursor and hydrolysis of the PZT precursor sol. Porous thin films were prepared by spin coating on Pt-coated Si substrate. The structure of the films was investigated by X-ray diffraction (XRD). (100)-oriented PZT 20180 film was obtained by hydrolysis of sol. PVP addition leads to the (110)-orientation of the film. The surface microstructure of the films was characterised with Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The surface profile indicates a films roughness of 5 nm. No micro-cracks were observed on film surface. The average remnant polarization and the coercive field were obtained from the hysteresis loop measurements. The ferroelectric behavior has been evidenced by the presence of the butterfly shape of the capacitance-voltage characteristics. Experimental results show that the dielectric constant of the PZT porous film is lower than that of the dense film.

2613. Ohmic contacts for GaAs based nanocolumns

Authors: Wensorra, J; Lepsa, MI; Indlekofer, KM; Forster, A; Jaschinsky, P; Voigtlander, B; Pirug, G; Luth, H

Published: NOV 2006, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 203, 3564, DOI: 10.1002/pssa.200622484

Nonalloyed ohmic contacts with lateral dimensions in the sub-100 nm range have been processed and characterized. The contacts are suitable for the fabrication of GaAs/AlGaAs nanocolumns designed in a 'top down' approach. They are realized on n-type GaAs using a thin low-temperature grown GaAs cap layer and Ti/Au metallization. For the lateral patterning of the nanoscaled ohmic contacts, electron-beam lithography based on Hydrogen Silsesquioxan (HSQ) negative resist is used, followed by sputtering and plasma etching of the metals. The I-V characteristics show ohmic contact behavior and demonstrate the scaling of the proposed contacts down to 50 nm lateral dimension. The specific contact resistance is situated in the range of 1-2 x 10(-5) Omega cm(2). (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2614. Effect of UV radiation on the semi-interpenetrating polymer networks based on polyurethane and epoxy maleate of bisphenol A

Authors: Rosu, L; Cascaval, CN; Ciobanu, C; Rosu, D; Ion, ED; Morosanu, C; Enachescu, M

Published: JAN 15 2005, JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 169, 185, DOI: 10.1016/j.jphotochem.2004.06.008

The behavior of two semi-interpenetrating polymer networks (S-IPNs) based on polyurethane (PU) and epoxy maleate of bisphenol A (EMBA) under exposure to UV radiation for long period of times (up to 200 h) was investigated. The networks obtained by the specific mixture under certain thermal treatment included in their structures crosslinked EMBA and linear PU. Advanced photooxidative degradation took place for long time of UV irradiation (over 160 h, especially), with almost a total destruction of the raw structures. The important modification of both the surface and of the morphology of the tested samples with the time of irradiation was also analyzed. Simultaneously, as compared to results obtained for short time of UV radiations (up to 10 h), where the mechanical properties of the tested samples improved, long time of UV radiations led to deterioration of many of the mechanical properties. (C) 2004 Elsevier B.V. All rights reserved.

2615. Nickel-doped (Zr-0.8, Sn-0.2)TiO4 for microwave and millimeter-wave applications

Authors: Ioachim, A; Banciu, MG; Toacsan, MI; Nedelcu, L; Ghetu, D; Alexandru, HV; Stoica, G; Annino, G; Cassettari, M; Martinelli, M

Published: APR 25 2005, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 118, 209, DOI: 10.1016/j.mseb.2004.12.071

(Zr-0.8, Sn-0.2)TiO4 ternary compounds (ZST) have been prepared by conventional solid-state reaction from raw materials. The effects of such sintering parameters as sintering temperature, sintering time, and NiO addition on structural and dielectric properties were investigated. The material exhibits a dielectric constant epsilon(r), similar to 36.0 and high values of the product Qf of the intrinsic quality factor Q and the frequency f from 32,170 to 50,000 at microwave frequencies. The dielectric loss tan delta values of ZST ceramics are decreased by low-level doping of NiO, while the temperature coefficient of the resonance frequency tau(f) takes values in the range -2 to +4ppm/degrees C. Investigations on whispering gallery modes revealed low dielectric loss in millimetre-wave domain. An intrinsic quality factor of 480 was measured at 115.6GHz. Dielectric resonators and substrates of ZST material were manufactured. The dielectric properties make the ZST material very attractive to microwave and millimeter-wave applications, such as dielectric resonators, filters, planar antennas, hybrid microwave integrated circuits, etc. (c) 2005 Elsevier B.V. All rights reserved.

2616. Optical photoinduced phenomena and holographic recording in amorphous As-Se thin films

Authors: Iovu, MS; Ciorba, VG; Colomeico, EP; Iovu, MA; Nastase, AM; Prisacari, A; Popescu, M; Shpotyuk, OI

Published: OCT 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2339, DOI:

The effect of light-induced photodarkening in amorphous As100-xSex (x=40 divided by 98) thin films for different thickness and film composition was investigated. It was established a strong dependence of the red shift of the absorption edge and refractive index under light irradiation on the film composition and thermal treatment. It was established that the more sensitive films to photodarkening and holographic recording correspond to non-stoichiometric compositions of As55Se45 and As60Se40 glasses. The experimental results are interpreted in terms of structural optical polymerization process, which includes the transformation of As4Se4 and Se-2 structural units in homogenius AsSe3/2 network.

2617. Studies of ohmic contact and Schottky barriers on Au-Ge/GaAs and Au-Ti/GaAs

Authors: Ghita, RV; Logofatu, C; Negrila, C; Manea, AS; Cernea, M; Lazarescu, MF

Published: DEC 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 3037, DOI:

Gallium Arsenide (GaAs) has increasingly become an important compound-semiconductor material suited for high speed digital circuits, microwaves and detectors for high energy physics. For the fabrication of ohmic contacts on GaAs (semi-insulating- SI) wafers with characteristics as: Cr doped, (100) oriented, and p similar to 10(6)similar to 10(7) Omega cm, has been used alloyed contact Au-Ge. The ohmic film was deposited in a high vacuum chamber (10(-8) Torr), on a plasma etched surface of GaAs, followed by a rapid thermal annealing (RTA) at 450 degrees C in low vacuum. For the fabrication of the rectifying contact-respectively the Schottky diode structure, we have used the same GaAs substrates. The wafers were degreased in a standard cleaning procedure, followed by a chemical etching. The Au-Ti contact has been deposited by thermal evaporation in vacuum (10(-6) torr) followed by a RFA procedure at 300-320 degrees C. The carrier transport mechanisms through M/S interface are strongly influenced by the doping concentration in the semiconductor and temperature. There are presented the experimental I-V characteristics for selected samples in dark and illumination conditions. Schottky barriers height on Au-Ti/GaAs was 0.7325 V in accord with mean values on n and p type GaAs (0.5-0.8 V). The aim of this work is to fabricate a competitive X-ray detector.

2618. Heavy ion induced damage in NaCl and KCl crystals

Authors: Enculescu, M; Schwartz, K; Trautmann, C; Toulemonde, M

Published: APR 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 229, 405, DOI: 10.1016/j.nimb.2004.12.131

NaCl and KCI single crystals were irradiated with swift heavy ions (An, Ph, Bi and U) of energy between 560 and 2640 MeV. The damage induced by the ions was studied using optical absorption spectroscopy, chemical etching and small-angle X-ray scattering. The damage in the tracks is dominated by the creation of simple color centers (F and V-3 centers). Their concentration increases as a function of fluence, saturating when single tracks overlap. The F-center containingly track zone extends up to several tens of nanometers. In addition to this large track halo, there exists also a much smaller region (1-2 nm) close to the ion trajectory in which defect aggregates are formed. Indications for this track core are given by the preferential chemical etchability of ion tracks and also by the anisotropic pattern produced by small-angle X-ray scattering. This halo-core track structure is very similar as in LiF, however given by the higher mobility of the primary hole centers in NaCl and KCl, recombination with electrons is facilitated resulting in a lower efficiency for defect creation. (c) 2005 Elsevier B.V. All rights reserved.

2619. Green coffee decontamination by electron beam irradiation

Authors: Nemtanu, MR; Brasoveanu, M; Grecu, MN; Minea, R

Published: OCT 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 240, 86, DOI: 10.1016/j.nimb.2005.06.092

Microbiological load of green coffee is a real problem considering that it is extremely sensitive to contamination. Irradiation is a decontamination method for a lot of foodstuffs, being a feasible, very effective and environment friendly one. Beans and ground green coffee were irradiated with electron beams up to 40 kGy. Microbial load, rheological behavior, electron paramagnetic resonance (EPR) and visible spectroscopy were carried out. The results show that electron beam irradiation of green coffee could decontaminate it without severe changes in its properties. (c) 2005 Elsevier B.V. All rights reserved.

2620. The influence of Cu on the morphological and chemical properties of nanostructured TiO2 films

Authors: Gartner, M; Ghita, A; Anastasescu, M; Osiceanu, P; Dobrescu, G; Zaharescu, M; Macovei, D; Modreanu, M; Trapalis, C; Kordas, G

Published: FEB 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 405, DOI:

TiO2 multilayer films were deposited by the sol-gel method on glass and SiO2/glass substrates. 10% of Cu was added to the coating solution, to study its effect on the amorphous to anatase phase transition, with a view to improving the photocatalytic activity. Densification of the films was obtained by thermal treatment at 500 degrees C for 1 hour in oxidative and reductive conditions. In order to check the correlation between the influence of copper, substrate and annealing temperatures on the structural, morphological and optical properties, the samples were characterized by FTIR, XPS, SEM and fractal analysis. Transformation of CuO from as-prepared samples into Cu2O and metallic Cu, depending on the treatment conditions, was shown. The composition and stoichiometry of the oxide films in the first atomic layers were quantitatively determined as chemical state relative concentrations.

2621. Recoilless fraction of tin-doped hematite nanoparticles obtained by hydrothermal synthesis

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D

Published: JAN 2005, MATERIALS LETTERS, 59, 25, DOI: 10.1016/j.matlet.2004.09.009

Tin-doped hematite nanoparticles (1-x)alpha-Fe2O3-xSnO(2) were synthesized using the hydrothermal method. The samples were characterized using Mossbauer spectroscopy as a function of the substitution level x. The recoilless fraction was determined using the dual absorber method introduced by us [M. Sorescu, Mater. Lett. 54 (2002) 256]. It has been observed that the recoilless fraction of the hematite samples first decreases with increasing the amount x of tin substitution, then increases as iron enters the SnO2 lattice and, finally, it slightly decreases again as the particle size of the nanoparticles decreases. (C) 2004 Elsevier B.V. All rights reserved.

2622. Disordered chalcogenide optoelectronic materials: Phenomena and applications

Authors: Popescu, M

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2210, DOI:

The glassy, amorphous and disordered chalcogenide materials, important for optoelectronic applications, are discussed. The main optical and optoelectronic phenomena, specific to these materials are shown, and the applications based on these phenomena are evidenced.

2623. X-ray absorption near edge structure of As2Se3 and As4Se4 thin amorphous films

Authors: Popescu, M; Sava, F; Aldea, N; Xie, YN; Hu, TD; Tao, L; Leonovici, M

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1806, DOI:

X-ray absorption spectroscopy has been used to get information on the structure of chalcogenide glasses. The data analysis was focused on the near edge X-ray absorption spectrum. The experimental As and Se K-edge absorption spectra of thin films of As2Se3 and As4Se4 have been measured in Beijing synchrotron at the beam line, using a double crystal monochromator with Si (111) crystals. The near-edge absorption curves were resolved in two components: the strong white line at the energy threshold and the first oscillatory part following the white line at approximately 7-8 eV above the K-edge, which undergoes changes in shape and position as a function of the modifications in the atomic structure induced by the change of composition. The XANES characteristic for the two types of films allows to conclude that the local disorder around As and Se is different. The non-stoichiometric composition, As4Se4, exhibits more disorder than the stoichiometric one.

2624. Temperature dependence of the electron paramagnetic resonance spectra of Mn2+, impurity ions in PbWO4 single crystals

Authors: Stefan, M; Nistor, SV; Goovaerts, E; Nikl, M; Bohacek, P

Published: FEB 2 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, 728, DOI: 10.1088/0953-8984/17/4/014

The temperature variation of the fine and hyperfine parameters of Mn2+ in single crystals of PbWO4 in the low temperature range reveals the presence of a resonant mode of frequency omega = 8.8 x 10(12) rad s(-1). Moreover, above 60 K, where the temperature induced broadening becomes dominant, a T-2 variation of the relaxation time was inferred from the analysis of the temperature dependence of the Mn2+ linewidth. This variation is attributed to a Raman relaxation process due to the coupling with the same local resonant mode.

2625. Metal-ferroelectric-metal structures with Schottky contacts. II. Analysis of the experimental current-voltage and capacitance-voltage characteristics of Pb(Zr,Ti)O-3 thin films - art. no. 123104

Authors: Pintilie, L; Boerasu, I; Gomes, MJM; Zhao, T; Ramesh, R; Alexe, M

Published: DEC 15 2005, JOURNAL OF APPLIED PHYSICS, 98, DOI: 10.1063/1.2148623

A modified model of metal-semiconductor contacts is applied to analyze the capacitance-voltage and current-voltage characteristics of metal-ferroelectric-metal structures. The ferroelectric polarization is considered as a sheet of surface charge situated at a fixed distance from the interface. The presumable high concentration of structural defects acting as active electric traps is taken into account by introducing a deep acceptorlike level. The model is applied on a set of metal-Pb(Zr,Ti)O-3-metal samples with different Zr/Ti ratios, deposited by different methods, and having different thicknesses, electrode materials, and electrode areas. Values around 10(18) cm(-3) were estimated for the hole concentration from capacitance-voltage measurements. The space-charge density near the electrode, estimated from current-voltage measurements, is in the 10(20)-10(21) cm(-3) range. The total thickness of the interface layer ranges from 3 to 35 nm, depending on the Zr/Ti ratio, on the shape of the hysteresis loop, and on the electrode material. The simulated I-V characteristics is fitted to the experimental one using the potential barrier and Richardson's constant as parameters. The potential barrier is determined to be in the 1.09-1.37 eV range and Richardson's constant is 520 A cm(-2) K-2. (c) 2005 American Institute of Physics.

2626. Functionalization of single-walled carbon nanotubes with conducting polymers evidenced by Raman and FTIR spectroscopy

Authors: Lefrant, S; Baibarac, M; Baltog, I; Mevellec, JY; Godon, C; Chauvet, O

Published: MAR-JUL 2005, DIAMOND AND RELATED MATERIALS, 14, 872, DOI: 10.1016/j.diamond.2004.11.035

Using Raman scattering and Fourier transform infrared (FTIR) spectroscopy, we show that the vibrational properties of single-walled carbon nanotubes (SWNTs) functionalized with conducting polymers (CPs), such as polyaniline (PANI) and poly (3, 4-ethylenedioxythiophene) (PEDOT), are different depending on the synthesis method. In the case of SWNTs electrochemically functionalized with PANT, the increase in intensity of the Raman band at 178 cm(-1), associated with radial breathing modes of bundled SWNTs, indicates that an additional roping of nanotubes with PANT takes place. Besides, the functionalization of SWNTs with PANT induces strong steric hindrance effects observed in FTIR spectra by the enhancement of bands at ca. 740-750 and 772 cm(-1) associated to the deformation vibrations of the benzoid and quinoid ring, respectively. Raman spectra recorded after the electropolymerization of 3, 4-ethylenedioxythiophene (EDOT) on the SWNTs film reveal that a side-wall functionalization takes place. (c) 2005 Elsevier B.V. All rights reserved.

2627. Absorption and photoluminescence properties of Cds : Mn2+: Cu+ nanostructures

Authors: Sima, M; Enculescu, I; Ghiordanescu, V; Mihut, L

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1955, DOI:

A layer of doped CdS nanocrystals was deposited on the surfaces of nanopores of polyethyleneterephtalate (PET) membranes. Optical absorption measurements were used to determine the bandgaps of the nanocrystals; CdS:Mn2+ and CdS:Mn2+:Cu+ show a blue and red shift, respectively, relative to the band gap of nanostructurated CdS. Photoluminescence spectra of the doped and undoped CdS samples exhibit wide bands covering the visible spectrum range.

2628. Surface chemistry of plasma deposited ZrC hard coatings

Authors: Balaceanu, M; Braic, M; Braic, V; Vladescu, A; Negrila, CC

Published: OCT 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2560, DOI:

X-ray Photoelectron Spectroscopy (XPS) was used to investigate the chemical state of ZrC coatings deposited by cathodic arc method. A chemistry model of the ZrC films has been proposed. It was pointed out that on the films surface a highly oxidized passive layer, containing also carbon and oxygen as contaminants, was formed. The film bulk was composed by a mixture of ZrC (the dominant phase), ZrO2 and free carbon.

2629. Properties of ZnO thin films prepared by radio-frequency plasma beam assisted laser ablation

Authors: Scarisoreanu, N; Matei, DG; Dinescu, G; Epurescu, G; Ghica, C; Nistor, LC; Dinescu, M

Published: JUL 15 2005, APPLIED SURFACE SCIENCE, 247, 525, DOI: 10.1016/j.apsusc.2005.01.140

Zinc oxide thin films were obtained by laser ablation of a Zn target in oxygen reactive atmosphere, the oxygen being supplied either by a standard gas inlet valve or from a radio-frequency (rf) oxygen plasma. Pt-coated silicon and MgO were used as substrates. The influence of the deposition parameters as laser wavelength (266, 355, 1064 nm), laser fluence (1.5-20 J/cm(2)) and oxygen pressure (1-60 Pa) was studied. The influence of the rf plasma beam addition on the morphological proprieties of zinc oxide films was particularly investigated, simultaneously with several configurations of the direction of the ablation plasma, the rf plasma beam and the substrate. The obtained films, with thicknesses in the range of 50 nm to 1 mu m have been characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), transmission electron microscopy (TEM). (c) 2005 Elsevier B.V. All rights reserved.

2630. Ferroelectric solid solutions (Ba,Sr)TiO3 for microwave applications

Authors: Alexandru, HV; Berbecaru, C; Stanculescu, F; Ioachim, A; Banciu, MG; Toacsen, MI; Nedelcu, L; Ghetu, D; Stoica, G

Published: APR 25 2005, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 118, 96, DOI: 10.1016/j.mseb.2004.12.070

There is an increasing demand of high permittivity ferroelectric materials in microwave devices. Particularly, the Ba1-xSrxTiO3 system (BST), presents a major interest for electrically controlled devices, such as tunable filters, steerable antennas, phase shifters, varactors, etc. [F. De Flaviis, N.G. Alexopoulos, O.M. Stafsudd, IEEE Trans. Microw. Theory Tech., MTT-45 (6) (1997) 963-969]. Solid solutions with X=25, 50, 75, 90% were prepared by standard ceramic technology (solid state reaction) and sintered at 1230 and 1260 degrees C. The temperature dependence of permittivity and of losses at low frequency (1 kHz) has shown interesting results [A. loachim, M.I. Toacsen, M.G. Banciu, L. Nedelcu, D. Ghetu, H.V. Alexandru, C. Berbecaru, G. Stoica, Proceedings on the XVII International Conference on Electromagnetic Fields and Materials, Warszawa, May 2004, pp. 78-82]. The unit cell volume depends linearly on the Sr content ohm (angstrom(3)) = 61.1 + 3.6X (estimated from Ref. [D. Roy, S. D. Krupandihi, Appl. Phys. Lett. 62 (1993) 1056-1058]). The measured densities of our samples p (g/cm(3)); approximate to 5.50 - 1.00X, represent about 92% of the X-ray estimated density p (g/cm(3)) approximate to 5.99 - 0.99X. Microwave measurements around 1 GHz show substantial decrease of the permittivity from about 1600 to 200 and also of the losses from 0.8% to less than 0.15% with the Sr concentration increase, X = 50-90%. It is concluded that sintering temperature has to be increased for samples of high Sr concentration. Moreover, the addition of MgO and MnO2, 1 wt.% each, improve sintering conditions and decreases the microwave losses. Experimental data show an approximate linear decrease of the Curie point, versus X strontium concentration, according to the formula: T-C (degrees C) approximate to 120-360X. Room temperature permittivity and dielectric loss have been measured in microwaves range using the Hakki-Coleman method. (c) 2005 Elsevier B.V All rights reserved.

2631. SERS, FT-IR and photoluminescence studies on single-walled carbon nanotubes/conducting polymers composites

Authors: Lefrant, S; Baibarac, M; Baltog, I; Godon, C; Mevellec, JY; Wery, J; Faulques, E; Mihut, L; Aarab, H; Chauvet, O

Published: DEC 15 2005, SYNTHETIC METALS, 155, 669, DOI: 10.1016/j.synthmet.2005.08.026

Surface-enhanced Raman scattering (SERS), Fourier transform infrared (FT-IR) and photoluminescence (PL) spectroscopies were used to investigate composites based on single-walled carbon nanotubes (SWNTs) and different conducting polymers like polyaniline (PANI), polyparaphenylene vinylene (PPV) and poly 3-hexylthiophene (3-PHT). In the case of SWNTs/PANI, different composites are obtained by adding dispersed SWNTs powder to the polymer solutions and by chemical polymerization of aniline in presence of SWNTs. The difference originates in the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs in fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FT-IR spectra of the composites PANI/SWNTs and PANI/C-60, chemically synthesized. Electrochemical polymerization of aniline in an HCl solution on a SWNT film leads to a covalent functionalization of SWNTs with PANI. In this case, Raman scattering data suggest an additional nanombes roping with PANI as a binding agent. A post treatment with the NH4OH solution of polymer-functionalized SWNTs involves an internal redox reaction between PANI and carbon nanotubes. As a result, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. In the case of PPV and 3-PHT, the effect of the concentration of SWNTs on the photoluminescence properties will be described and compared, as probes of interaction. (C) 2005 Elsevier B.V. All rights reserved.

2632. Magnetic properties of nanostructured materials - Monte Carlo simulation and experimental approach for nanocrystalline alloys and core-shell nanoparticles

Authors: Crisan, O; Greneche, JM; Labaye, Y; Berger, L; Crisan, AD; Angelakeris, M; LeBreton, JM; Flevaris, NK

Published: 2005, PROPERTIES AND APPLICATIONS OF NANOCRYSTALLINE ALLOYS FROM AMORPHOUS PRECURSORS, 184, 266, DOI:

The magnetic properties of FINEMET-type nanocrystalline alloys and isolated ferromagnetic AgCo nanoparticles are investigated both experimentally and numerically. Theoretical models of spins that simulate ideal nanocrystalline alloys and isolated nanoparticles are considered while their magnetic properties are derived from Monte Carlo simulation of low-temperature spin ordering. Interesting features such as magnetic polarization of the matrix due to penetrating fields arising from nanograins and the role played by the crystalline fraction in the overall L magnetic behaviour, in the case of nanocrystalline alloys are investigated. For isolated nanoparticles it is shown that the competition between surface and bulk anisotropy gives rise to surface spin disorder that, together with finite-size effects, is responsible for the experimentally observed lack of saturation of the magnetization in high applied fields. These simulation results are confirmed by experimental data obtained on FINEMET nanocrystalline alloys and isolated ferromagnetic AgCo colloidal nanoparticles.

2633. Effect of hydrogenation on defect reactions in silicon particle detectors

Authors: Makarenko, LF; Korshunov, FP; Lastovski, SB; Kazuchits, NM; Rusetsky, MS; Fretwurst, E; Lindstrom, G; Moll, M; Pintilie, I; Zamiatin, NI

Published: 2005, GETTERING AND DEFECT ENGINEERING IN SEMICONDUCTOR TECHNOLOGY XI, 108-109, 222, DOI: 10.4028/www.scientific.net/SSP.108-109.217

The influence of preliminary treatment in hydrogen plasma on elimination of radiation defects and formation of thermal donors has been studied in detector structures made of standard and oxygenated float zone silicon has been studied. A new type of thermal donors has been found in as-treated diodes. These thermal donors are unstable and can be eliminated by heat-treatment at 200-250 degrees C. After irradiation with 3.5 MeV electrons the detectors had been annealed at temperatures of 50-350 degrees C. It has been found that preliminary hydrogenation at 300 degrees C leads to disappearance of main vacancy-type radiation defects at lower annealing temperatures, The annealing of hydrogenated and irradiated crystals is accompanied by hydrogen redistribution and formation of hydrogen-related donors. Preliminary irradiation influences on both these processes.

2634. Micro-structure and magnetic properties of Fe-Cu nanocomposites for anisotropic permanent magnets

Authors: Kuncser, V; Valeanu, M; Lifei, F; Predoi, D; Jianu, A; Kappel, W; Codescu, M; Patroi, E; Pasuk, I; Bulinski, M; Filoti, G

Published: MAY 31 2005, JOURNAL OF ALLOYS AND COMPOUNDS, 395, 6, DOI: 10.1016/j.jallcom.2004.11.059

Melt spun ribbons of FexCu100-x were obtained by different procedures, in order to maximize the dispersion of the Fe atoms in the Cu matrix. Subsequent thermal and mechanical treatments were used for a controlled crystallization process of the soft magnetic phase. A detailed analysis of structural aspects and crystallization dynamics and their relation with the magnetic behavior of the Fe-Cu ribbons has been obtained via Mossbauer spectroscopy, X-ray diffraction (XRD) and magnetic measurements. In order to obtain composite permanent magnets with shape anisotropy, the optimal conditions and the suitable processing were established. &COPY; 2004 Elsevier B.V. All rights reserved.

2635. Effect of laser process parameters on the surface abosorbtivity

Authors: Demian, G; Taca, M; Gutu, I; Demian, M

Published: 2005, CROSS-DISCIPLINARY APPLIED RESEARCH IN MATERIALS SCIENCE AND TECHNOLOGY, 480, 211, DOI: 10.4028/www.scientific.net/MSF.480-481.207

Hardening laser surface offers new possibilities for the enhancement of the mechanical resistance of superficial layers. Essential for the laser treatment processes is the efficiency at which the incident laser power is coupled into the work piece. The aim of the work was to study the effect of some factors such as spot shape, beam angle of incidence and surface coating on the steel surface absorptivity. Samples made of carbon steel were laser processed using a CW CO2 - 1,2 kW laser unit. Different process parameters (beam power, spot dimension and traverse speed), were used. The microstructure of laser hardened layers which have been investigated by optical microscopy. The mechanical characterization of the layers has been done by hardness measurements. Correlation has been established between the structure of the laser-processed layers and the process parameters.

2636. Study of the corrosion inhibition of carbon-steel in dilute ammoniacal media using N-ciclohexil-benzothiazole-sulphenamida

Authors: Samide, A; Bibicu, I; Rogalski, MS; Preda, M

Published: MAY 2005, CORROSION SCIENCE, 47, 1127, DOI: 10.1016/j.corsci.2004.06.018

The inhibiting effect of N-ciclohexil-benzothiazole-sulphenamida (NCBSA) on the corrosion of carbon-steel in diluted ammonia solution at room temperature has been studied by Mossbauer spectroscopy, electrochemical measurements, weight loss and surface microscopic analysis. A decrease in the corrosion spot concentration with the increase of the NCBSA concentration indicates a good adsorbability of NCBSA on the metal surface. Mossbauer spectrometry shows the formation of a layer at the surface of the corroded sample, which is interpreted in terms of the formation of complexes between NCBSA and the metal cations present in the carbon-steel structure. (c) 2004 Elsevier Ltd. All rights reserved.

2637. Pulsed laser deposition of thin films of various full Heusler alloys CO2MnX (X = Si, Ga, Ge, Sn, SbSn) at moderate temperature

Authors: Valerio, E; Grigorescu, C; Manea, SA; Guinneton, F; Branford, WR; Autric, M

Published: JUL 15 2005, APPLIED SURFACE SCIENCE, 247, 156, DOI: 10.1016/j.apsusc.2005.01.079

This work presents pulsed laser deposition of cobalt-based Hensler thin films Co2MnX (X = Si, Ga, Ge, Sn, SbSn) on different substrates (Si, GaAs, InAs). The deposition processes developed in vacuum (about 10(-5) Pa) to avoid oxidation of the films and targets. The temperature of the substrates during the depositions was kept below 500 K to minimise interface interdiffusion. From X-ray diffraction, we found that the films are crystalline and slightly oriented. The stoichiometric composition of the films was further checked by EDS, while the size and density of droplets were determined by SEM. The magnetic properties of the films are consistent with those of the bulk material used as target. (c) 2005 Elsevier B.V. All rights reserved.

2638. Electrochemical and vibrational properties of single-walled carbon nanotubes in hydrochloric acid solutions

Authors: Lefrant, S; Baibarac, M; Baltog, I; Velula, T; Mevellec, JY; Chauvet, O

Published: MAR-JUL 2005, DIAMOND AND RELATED MATERIALS, 14, 880, DOI: 10.1016/j.diamond.2004.12.016

Raman spectroscopy and cyclic voltammetry (CV) are used for the investigation of the oxidation-reduction processes of single-wall carbon nanotubes (SWNTs) films in an HCl 0.5 M solution. In the potential ranges (+100; +800) and (0; +1500) mV vs. saturated calomel electrode (SCE), the oxidation-reduction reactions of SWNT films, in both aqueous and semi-aqueous HCl 0.5 M solutions, are reversible and irreversible, respectively. At potentials higher than +1000 mV vs. SCE, SWNTs break in fragments of different sizes. A post-treatment with an alkaline solution results in a partial restoration of the SWNTs. The functionalization of SWNTs with polydipherylamine (PDPA) is presented as an application of the reversible oxidation-reduction reactions of nanotubes in an HCl 0.5 M solution. In order to differentiate between a deposition of successive layers of the polymer and a functionalization process, a spectroelectrochemical study of the deposition of polypyrrole (PPY) on SWNT films was carried out, too. (c) 2004 Elsevier B.V. All rights reserved.

2639. Structural and magnetic properties of NiZn and Zn ferrite thin films obtained by laser ablation deposition

Authors: Sorescu, M; Diamandescu, L; Swaminathan, R; McHenry, ME; Feder, M

Published: MAY 15 2005, JOURNAL OF APPLIED PHYSICS, 97, DOI: 10.1063/1.1854416

sLaser ablation deposition has been used to synthesize nanoscale ferrite structures. Our investigations were performed on NiZn and Zn ferrite films deposited on silicon(100) substrates. Films produced by laser ablation at room temperature were annealed at 550 degrees C for 1 h. Other films were deposited directly at a 550 degrees C substrate temperature without subsequent annealing. Complementary x-ray diffraction and superconducting quantum interference device magnetometry measurements helped identify the optimum laser ablation deposition conditions for obtaining the desired nanoferrite structures. From the hysteresis loops at 300 and 10 K we. identified the paramagnetic or ferromagnetic behavior of the films. The zero field cooled-field cooled (ZFC-FC) magnetization, M(T), curves yielded the value of the blocking temperature in both NiZn and Zn ferrite systems. (c) 2005 American Institute of Physics.

2640. Elimination and formation of electrically active defects in hydrogenated silicon particle detectors irradiated with electrons

Authors: Makarenko, LF; Korshunov, FP; Lastovski, SB; Kazuchits, NM; Rusetsky, MS; Fretwurst, E; Lindstrom, G; Moll, M; Pintilie, I; Zamiatin, NI

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 81, DOI: 10.1016/j.nima.2005.06.010

The influence of preliminary treatment in hydrogen plasma on elimination of radiation defects and formation of thermal donors has been studied in detector structures made of standard float zone silicon. The detectors were irradiated with 3.5MeV electrons and annealed at temperatures of 50-350 degrees C. It has been found that preliminary hydrogenation at 300 degrees C leads to disappearance of divacancies and vacancy-oxygen complexes at lower annealing temperatures. The annealing of hydrogenated and irradiated crystals is accompanied by hydrogen redistribution and formation of hydrogen-related donors. (c) 2005 Elsevier B.V. All rights reserved.

2641. Influence of the grain size on polaron transport in nanostructured La2/3Ca1/3MnO3 evidenced by EPR

Authors: Raita, O; Grecu, MN; Filip, X; Toloman, D; Giurgiu, LM; Idziak, S; Hoffmann, SK

Published: JUL 2005, ACTA PHYSICA POLONICA A, 108, 118, DOI: 10.12693/APhysPolA.108.113

We report an electron paramagnetic resonance investigation of the grain size effects on the polaron transport in the paramagnetic regime of nanosized La2/3Ca1/3MnO3 manganites. The temperature dependences of the EPR integral intensity were analyzed in terms of spin-spin exchange interaction and small polaron hopping scenarios. The polaron activation energy decreases with the reduction of the grain size. A discussion is given concerning the factors which could explain the observed change.

2642. A neural network approach to the design of the high frequency devices

Authors: Banciu, MG; Ioachim, A

Published: 2005, CAS 2005: INTERNATIONAL SEMICONDUCTOR CONFERENCE, 1-2, 118, DOI:

Designing the high-frequenqy devices by using artificial neural network's (ANN) emphasize the ANN propensity for storing knowledge, for generalizing patterns in data and for offering computational efficiency. Two neural models are discussed in this paper. The model of a band-pass forward-coupled filter uses the ARMA coefficients, which describe the FDTD signal at the output port of the filter in time-domain. On the contrary, the second model, which was developed for a tunable planar resonator, uses directly the device response in frequency-domain.

2643. Coherent anti-Stokes Raman scattering on single-walled carbon nanotubes and copper phthalocyanine thin films excited through surface plasmons

Authors: Baltog, I; Baibarac, M; Lefrant, S

Published: NOV 2005, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS, 7, 639, DOI: 10.1088/1464-4258/7/11/003

Experimental data indicating an anti-Stokes Raman emission, reminiscent of coherent anti-Stokes Raman scattering (CARS), that originates in a wave-mixing process between the incident laser light (omega(1)) and Stokes Raman light (omega(s)) generated by a surface enhanced Raman scattering (SERS) mechanism are reported. The variation of anti-Stokes SERS spectra of single-walled carbon nanotubes (SWNTs) and copper phthalocyanine (CuPc) as a function of the film thickness, laser excitation intensity and numerical aperture of the microscopic objective used for collecting the scattered light are presented as experimental arguments.

2644. Fullerene and nanotubes based on arsenic networks. A modelling study

Authors: Zamfira, S; Popescu, M; Sava, F

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2034, DOI:

Arsenic is the main component of many chalcogenide glasses. Due to its triple co-ordination arsenic has the tendency to form two-dimensional networks in both crystalline and amorphous state. Besides the layered form of arsenic it exists molecular arsenic. Small molecules are characteristic to this form of arsenic. Large arsenic clusters have been not identified up to now in amorphous films. A modelling study was carried out in order to demonstrate the possibility to find or to prepare fullerene-like configurations based on arsenic as well as nanotubes (or nanowires) of various diameters.

2645. Sol-gel synthesis and characterization of BaTiO3 powder

Authors: Cernea, M

Published: DEC 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 3022, DOI:

Barium acetylacetonate and titanium (IV) isopropoxide, dissolved in adequate solvents, were used to produce stoichiometric BaTiO3. The purity of the gel powder was > 99.98%, The particle size range was 80 nm for the dried gel powder and 1-1.5 mu m for the powder calcined at 950 degrees C. X-ray analyses indicates that the material calcined at 950 degrees C in air or, at 825 degrees C under vacuum, exhibits a tetragonal, poorly crystallized, BaTiO3 structure. The powder pressed and sintered at 1275 degrees C show high dielectric constants, i.e. 1300 at 25 degrees C and, 3020 at the Curie temperature (104 degrees C). The melting point for BaTiO3 prepared by sol-gel technique is 1290 degrees C.

2646. Microstructural characterization of polycrystalline Alq(3) grown by sublimation

Authors: Ghica, C; Grecu, MN; Gmeiner, J; Grecu, VV

Published: DEC 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 3003, DOI:

A microstructural investigation on polycrystalline electroluminescent Alq(3) obtained by train sublimation method is reported in the paper. The morphology and crystalline structure of the obtained Alq3 phases have been analyzed by transmission electron microscopy performed on samples collected from 3 different regions along the sublimation tube.

2647. (Zr, Sn)TiO4 thin films for application in electronics

Authors: Nistor, M; Gherendi, F; Magureanu, M; Mandache, NB; Ioachim, A; Banciu, MG; Nedelcu, L; Popescu, M; Sava, F; Alexandru, HV

Published: JUL 15 2005, APPLIED SURFACE SCIENCE, 247, 174, DOI: 10.1016/j.apsusc.2005.01.124

Thin films of zirconium tin titanate, (Zr0.8Sn0.2)TiO4 (ZST) were deposited using a pulsed electron beam source based on a channel-spark discharge for target ablation. An advanced degree of crystallization was obtained for the films deposited on alumina substrate post-annealed at 1000 degrees C. The crystalline lattice constants of the films are very close to those of the target material, which confirms the same stoichiometry in ZST films and in the bulk. (c) 2005 Elsevier B.V. All rights reserved.

2648. Morphology and shape evolution of the copper monosulfide nanocrystallites with the reaction time

Authors: Simonescu, CM; Teodorescu, VS; Brezeanu, M; Melinescu, A

Published: JUN 2005, REVISTA DE CHIMIE, 56, 614, DOI:

Copper monosulfide nanocrystallites have been obtained by reaction between copper acetate and sodium thiosulphate (1:4) at 90 +/- 5 degrees C. The powder was studied by X ray diffraction, IR spectrometry and TEM - transmission electron microscopy and electron diffraction. The copper monosulfide crystallites have been obtained in spherical or discoidal "nodules" which are bonded in much bigger aggregates. The dimensions of the copper monosulfide crystallites are small (10 to 15 nm) near the nucleation center (indicated by an arrow) and bigger at the edges of the spherical nodule (60 to 80 nm). The evolution of the morphology and the shape of the crystallite aggregate with the reaction time allows to propose a nucleation and a crystal growth mechanism for this system.

2649. High frequency investigation of graded gap injectors for GaAs Gunn diodes

Authors: Montanari, S; Forster, A; Lepsa, MI; Luth, H

Published: FEB 2005, SOLID-STATE ELECTRONICS, 49, 250, DOI: 10.1016/j.sse.2004.08.014

In this work, we present a detailed high frequency characterization of conventional and optimized Gunn-diodes containing a graded gap injector. It is shown that the Al-concentration in the hot electron injector influences the occupation of the Gamma- and L-valleys and hence the electron drift velocity in the active Gunn layer. Quantitative values for the occupation of the L-valley can be extracted from the S-parameter measurements. (C) 2004 Elsevier Ltd. All rights reserved.

2650. Molecular organic crystalline matrix for hybrid organic-inorganic (nano) composite materials

Authors: Stanculescu, A; Tugulea, L; Alexandru, HV; Stanculescu, F; Socol, M

Published: FEB 15 2005, JOURNAL OF CRYSTAL GROWTH, 275, E1786, DOI: 10.1016/j.jcrysgro.2004.11.210

Metal-doped benzil crystals have been grown by thermal gradient solidification in a vertical transparent growth configuration to investigate the effect of metallic guest on the ordered organic host. We have identified the conditions for growing homogeneous, optically good crystals of benzil doped with sodium and silver, limiting the effect of supercooling, low thermal conductivity and anisotropy of the growth speed (temperature gradient at the liquid-solid interface: 10-25 degrees C, moving speed of the growth interface 2.0 mm/h). The nature and concentration of the dopant are parameters affecting, through the growth process, the crystalline perfection and the optical properties of the organic matrix. Bulk optical characterisation, by spectrophotometrical methods, has offered details on some intrinsic properties of the system metal particles/benzil crystalline matrix. Analytical processing of the experimental data emphasised that benzil is a wide optical band gap organic semiconductor E-g = 2: 65 eV: We also have investigated the effect of sodium and silver on the properties of benzil crystal as potential transparent semiconductor matrix for (nano) composite metal/molecular organic material. With the increase of sodium concentration from c = 1 to 6 wt%, a small narrowing of the band gap has been remarked. The same behaviour has been found for benzil doped with silver (c = 2wt%) compared to pure benzil. (C) 2004 Elsevier B.V. All rights reserved.

2651. Ba1-xSrxTiO3 ceramics for tunable microwave devices

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Ghetu, D; Dutu, AC; Vasiliu, F; Alexandru, HV; Berbecaru, C; Stoica, G; Nita, P

Published: 2005, CAS 2005: INTERNATIONAL SEMICONDUCTOR CONFERENCE, 1-2, 280, DOI:

The paper describes the investigations of Ba1-xSrxTiO3 ceramic materials prepared by solid-state reaction techniques. The addition of MgO and MnO2 improves sintering process and decreases the dielectric loss. The materials exhibit a dielectric constant epsilon(r) similar to 1000 and low loss tan delta similar to 10(-3) at microwave frequencies.

2652. Fe-Cu granular thin films with giant magnetoresistance by thermionic vacuum arc method: Preparation and structural characterization

Authors: Kuncser, V; Mustata, I; Lungu, CP; Lungu. AM; Zaroschi, V; Keune, W; Sahoo, B; Stromberg, F; Walterfang, M; Ion, L; Filoti, G

Published: OCT 1 2005, SURFACE & COATINGS TECHNOLOGY, 200, 983, DOI: 10.1016/j.surfcoat.2005.01.031

Simultaneous discharges of Fe and Cu metal sources by thermoionic vacuum arc (TVA) were used as a new procedure for preparation of granular Fe-Cu thin films with sensibly enhanced room temperature giant magnetoresistive effects. The possibilities to produce thin films with a wide range of structural and magneto-transport characteristics are emphasized. The structural aspects of granular Fe-Cu thin films deposited onto Kapton are investigated via X-ray diffractometry, atomic force microscopy and Mossbauer spectroscopy. The magneto-transport properties are strongly related to composition, structure and magnetic interactions inside the films. (c) 2005 Elsevier B.V. All rights reserved.

2653. Interface trap density in amorphous La2Hf2O7/SiO2 high-kappa gate stacks on Si

Authors: Mereu, B; Dimoulas, A; Vellianitis, G; Apostolopoulos, G; Scholz, R; Alexe, M

Published: FEB 2005, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 80, 257, DOI: 10.1007/s00339-004-2910-9

The present paper investigates the interface trap density of a new high-kappa gate dielectric stack, La2Hf2O7/SiO2 on Silicon. Amorphous La2Hf2O7 thin films are deposited by metal evaporation in the presence of atomic oxygen beams on an ultra-thin SiO2 layer (1.5 nm) grown by rapid thermal oxidation on a p-type Si substrate. A combination of electrical (C-V) and cross sectional TEM measurements indicates a value of the dielectric constant kappa of about 19 +/- 2.2. The interface states density (D-it) was measured using the conductance method for different La2Hf2O7 thicknesses ranging from 3 nm to 14 nm. Dit ranges from 3.4 x 10(10) eV(-1) cm(-2) to 4.8 x 10(12) eV(-1) cm(-2) and shows a quasi-linear dependence on the La2Hf2O7 layer thickness. The interface state density increase with film thickness could have different explanations, such as oxygen de-passivation and/or defect generation at the Si-SiO2 interface, formation of a new Si-SiO2 interface by Si oxidation or alternatively, the SiO2 interfacial layer reduction by oxygen vacancies.

2654. Surface enhanced Raman scattering and photoluminescence studies on single-walled carbon nanotubes submitted to non-hydrostatic compression

Authors: Baibarac, M; Baltog, I; Mihut, L; Preda, N; Velula, T; Godon, C; Mevellec, JY; Wery, J; Lefrant, S

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2181, DOI:

Single-walled carbon nanotubes (SWNTs) under a moderate non-hydrostatic pressure, of 0.58 GPa, undergo a non-reversible transformation. Due to the plastic deformations, structural defects and carbon nanotube fragments of different size are produced. Short fragments of spherical or ellipsoidal form, behaving as closed-shell fullerenes are observed both by Raman spectroscopy and photoluminescence (PL). The main vibrational indicative of the fragments of shorter length is the band at similar to 1458 cm(-1) that is regularly observed in the Raman spectra of fullerene. Similar to fullerenes self assemblies, the interaction between the nanotube fragments is noticed in the Raman spectrum by the band at similar to 94 cm(-1) that reveals an inter-particle vibration mode. When the nanotubes are dispersed into host matrix, as aromatic hydrocarbons (AHs) with isolated or condensed phenyl rings, supplementary mechanico-chemical reactions take place. For AHs with isolated phenyl rings, like biphenyl or p-terphenyl, a chemical functionalization of SWNT fragments is demonstrated by the appearance of a new Raman band at 1160 cm(-1). In PL spectra, the interaction of SWNTs with AHs, is noticed by a detailed vibronic structure appearing in the high energy side of the emission spectrum, that increase with the weight of SWNTs in the AHs/SWNTs mixtures.

2655. Recent advancements in the development of radiation hard semiconductor detectors for S-LHC

Authors: Fretwurst, E; Adey, J; Al-Ajili, A; Alfieri, G; Allport, PP; Artuso, M; Assouak, S; Avset, BS; Barabashi, L; Barcz, A; Bates, R; Biagi, SF; Bilei, GM; Bisello, D; Blue, A; Blumenau, A; Boisvert, V; Bolla, G; Bondarenko, G; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, TJV; Brodbeck, TJ; Broz, J; Bruzzi, M; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Charron, S; Chilingarov, A; Chren, D; Cindro, V; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, L; Dalla Betta, GF; Dawson, I; de Boer, W; De Palma, M; Demina, R; Dervan, P; Dittongo, S; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Ferbel, T; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Garcia, C; Garcia-Navarro, JE; Gaubas, E; Genest, MH; Gill, KA; Giolo, K; Glaser, M; Goessling, C; Golovine, V; Sevilla, SG; Gorelov, I; Goss, J; Bates, AG; Gregoire, G; Gregori, P; Grigoriev, E; Grillo, AA; Groza, A; Guskov, J; Haddad, L; Harkonen, J; Hauler, F; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R; Horn, M; Houdayer, A; Hourahine, B; Hughes, G; Ilyashenko, I; Irmscher, K; Ivanov, A; Jarasiunas, K; Johansen, KMH; Jones, BK; Jones, R; Joram, C; Jungermann, L; Kalinina, E; Kaminski, P; Karpenko, A; Karpov, A; Kazlauskiene, V; Kazukauskas, V; Khivrich, V; Khomenkov, V; Kierstead, J; Klaiber-Lodewigs, J; Klingenberg, R; Kodys, P; Kohout, Z; Korjenevski, S; Koski, M; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lassila-Perini, K; Lastovetsky, V; Latino, G; Lazanu, I; Lazanu, S; Lebedev, A; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindstrom, G; Linhart, V; Litovchenko, P; Litovchenko, A; Giudice, AL; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Makarenko, LF; Mandic, I; Manfredotti, C; Manna, N; Garcia, SM; Marunko, S; Mathieson, K; Melone, J; Menichelli, D; Messineo, A; Metcalfe, J; Miglio, S; Mikuz, M; Miyamoto, J; Moll, M; Monakhov, E; Moscatelli, F; Naoumov, D; Nossarzewska-Orlowska, E; Nysten, J; Olivero, P; Oshea, V; Palviainen, T; Paolini, C; Parkes, C; Pesseri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, M; Plemonte, C; Pignatel, GU; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, A; Popule, J; Pospisil, S; Pozza, A; Radicci, V; Rafi, JM; Rando, R; Roeder, R; Rohe, T; Ronchin, S; Rott, C; Roy, A; Ruzin, A; Sadrozinski, HFW; Sakalauskas, S; Scaringella, M; Schiavulli, L; Schnetzer, S; Schumm, B; Sciortino, S; Scorzoni, A; Segneri, G; Seidel, S; Seiden, A; Sellberg, G; Sellin, P; Sentenac, D; Shipsey, I; Sicho, P; Sloan, T; Solar, M; Son, S; Sopko, B; Sopko, V; Spencer, N; Stahl, J; Stolze, D; Stone, R; Storasta, J; Strokan, N; Sudzius, M; Surma, B; Suvorov, A; Svensson, BG; Tipton, P; Tomasek, M; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullan, M; Vaitkus, JV; Velthuis, J; Verbitskaya, E; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Yiuri, Y; Zabierowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 19, DOI: 10.1016/j.nima.2005.05.039

The proposed luminosity upgrade of the Large Hadron Collider (S-LHC) at CERN will demand the innermost layers of the vertex detectors to sustain fluences of about 10(16) hadrons/cm(2). Due to the high multiplicity of tracks, the required spatial resolution and the extremely harsh radiation field new detector concepts and semiconductor materials have to be explored for a possible solution of this challenge. The CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has started in 2002 an R&D program for the development of detector technologies that will fulfill the requirements of the S-LHC. Different strategies are followed by RD50 to improve the radiation tolerance. These include the development of defect engineered silicon like Czochralski, epitaxial and oxygen-enriched silicon and of other semiconductor materials like SiC and GaN as well as extensive studies of the microscopic defects responsible for the degradation of irradiated sensors. Further, with 3D, Semi-3D and thin devices new detector concepts have been evaluated. These and other recent advancements of the RD50 collaboration are presented and discussed. (c) 2005 Elsevier B.V. All rights reserved.

2656. Microwave dielectric properties of doped Ba0.5Sr0.5TiO3 ceramics correlated with sintering temperature

Authors: Ioachim, A; Banciu, MG; Nedelcu, L

Published: DEC 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 3027, DOI:

Ba0.5Sr0.5TiO3 ferroelectric ceramics (BST) were prepared by solid-state reaction. The effect of sintering temperature T, on microwave dielectric properties was studied. Also, the influence of 1 wt % MgO and 1 wt % MnO2 doping on the dielectric parameters was investigated. The morphological aspects of samples were studied by scanning electron microscopy (SEM). The microwave measurements at room temperature revealed dielectric constant around 1.000 and loss smaller than 1 % at 1.1 GHz. Also, the dielectric parameters at low frequency were determined. The results indicate that the BST dielectric ceramics are suitable for manufacturing electric field controlled components such as tunable resonators, phase shifters, steerable antennas etc.

2657. Radiation-hard semiconductor detectors for SuperLHC

Authors: Bruzzi, M; Adey, J; Al-Ajili, A; Alexandrov, P; Alfieri, G; Allport, PP; Andreazza, A; Artuso, M; Assouak, S; Avset, BS; Barabash, L; Baranova, E; Barcz, A; Basile, A; Bates, R; Belova, N; Biagi, SF; Bilei, GM; Bisello, D; Blue, A; Blumenau, B; Boisvert, V; Bolla, G; Bondarenko, G; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, TJV; Brodbeck, TJ; Broz, J; Brukhanov, A; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Chilingarov, A; Chren, D; Cindro, V; Citterio, M; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, W; Cvetkov, V; Dalla Betta, GF; Davies, G; Dawson, I; de Boer, W; De Palma, M; Demina, R; Dervan, P; Dierlamm, A; Dittongo, S; Dobrzanski, L; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Ferbel, T; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Franchenko, S; Fretwurst, E; Gamaz, F; Garcia, C; Garcia-Navarro, JE; Gaubas, E; Genest, MH; Gill, KA; Giolo, K; Glaser, M; Goessling, C; Golovine, V; Sevilla, SG; Gorelov, I; Goss, J; Gouldwell, A; Gregoire, G; Gregori, P; Grigoriev, E; Grigson, C; Grillo, A; Groza, A; Guskov, J; Haddad, L; Harkonen, J; Harding, R; Hauler, F; Hayama, S; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R; Horn, M; Houdayer, A; Hourahine, B; Hruban, A; Hughes, G; Ilyashenko, I; Irmscher, K; Ivanov, A; Jarasiunas, K; Jin, T; Jones, BK; Jones, R; Joram, C; Jungermann, L; Kalinina, E; Kaminski, P; Karpenko, A; Karpov, A; Kazlauskiene, V; Kazukauskas, V; Khivrich, V; Khomenkov, V; Kierstead, J; Klaiber-Lodewigs, J; Kleverman, M; Klingenberg, R; Kodys, P; Kohout, Z; Korjenevski, S; Kowalik, A; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lari, T; Lassila-Perini, K; Lastovetsky, V; Latino, G; Latushkin, S; Lazanu, S; Lazanu, I; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindstrom, G; Lindstrom, L; Linhart, V; Litovchenko, A; Litovchenko, P; Litvinov, V; Lo Giudice, A; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Mainwood, A; Makarenko, LF; Mandic, I; Manfredotti, C; Garcia, SM; Marunko, S; Mathieson, K; Mozzanti, A; Melone, J; Menichelli, D; Meroni, C; Messineo, A; Miglio, S; Mikuz, M; Miyamoto, J; Moll, M; Monakhov, E; Moscatelli, F; Murin, L; Nava, F; Naoumov, D; Nossarzewska-Orlowska, E; Nummela, S; Nysten, J; Olivero, P; Oshea, V; Palviainen, T; Paolini, C; Parkes, C; Passeri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, M; Piatkowski, B; Piemonte, C; Pignatel, GU; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, AI; Popule, J; Pospisil, S; Pucker, G; Radicci, V; Rafi, JM; Ragusa, F; Rahman, M; Rando, R; Roeder, R; Rohe, T; Ronchin, S; Rott, C; Roy, P; Roy, A; Ruzin, A; Ryazanov, A; Sadrozinski, HFW; Sakalauskas, S; Scaringella, M; Schiavulli, L; Schnetzer, S; Schumm, B; Sciortino, S; Scorzoni, A; Segneri, G; Seidel, S; Seiden, A; Sellberg, G; Sellin, P; Sentenac, D; Shipsey, I; Sicho, P; Sloan, T; Solar, M; Son, S; Sopko, B; Spencer, N; Stahl, J; Stavitski, I; Stolze, D; Stone, R; Storasta, J; Strokan, N; Strupinski, W; Sudzius, M; Surma, B; Suuronen, J; Suvorov, A; Svensson, BG; Tipton, P; Tomasek, M; Troncon, C; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullan, M; Vaitkus, JV; Vanni, P; Velthuis, J; Verzellesi, G; Verbitskaya, E; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Zablerowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N

Published: APR 1 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 541, 201, DOI: 10.1016/j.nima.2005.01.056

An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work. 2005 Published by Elsevier B.V.

2658. Microchemical and mechanical characteristics of arc plasma deposited TiAlN and TiN/TiAlN coatings

Authors: Braic, M; Braic, V; Balaceanu, M; Pavelescu, G; Vladescu, A; Tudor, I; Popescu, A; Borsos, Z; Logofatu, C; Negrila, CC

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 676, DOI:

Single layer TiAlN and alternate TiN/TiAlN multilayered hard coatings were deposited on Si, plain carbon steel and high-speed steel substrates by the cathodic are technique. Chemical composition, phase composition, texture, Vickers microhardness, adhesion, bilayer period, sliding friction coefficient and wear resistance were investigated by XPS, EDX and XRD analyses, microhardness measurements, scratch and tribological tests.

2659. Quantum confinement in nanocrystalline silicon

Authors: Ciurea, ML

Published: OCT 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2346, DOI:

Quantum confinement effects in different kinds of nanocrystalline silicon systems are experimentally and theoretically investigated. Porous silicon structured as a nanowire network and silicon nanodots embedded in amorphous silicon dioxide are studied. The main quantum confinement effect in both cases is represented by the appearance of new energy levels in the silicon band gap. The corresponding energies can be experimentally determined from the current - temperature characteristics, which show an Arrhenius-like behavior. The curves present several activation energies between liquid nitrogen temperature and room temperature. The energy levels can be evaluated from a quantum well model. The fundamental level is located at the top of the valence band. The change of the activation energy is then related with the filling of the levels. The ratios of the consecutive activation energies in the current - temperature characteristics prove that the excitation undergoes the angular momentum conservation law imposed by the applied electric field. The estimation of the mean size of the nanocrystals from the values of the activation energies is in good agreement with the microstructure investigations performed on the samples. The confinement levels are also in good agreement with the photoluminescence measurements..

2660. Development of radiation tolerant semiconductor detectors for the Super-LHC

Authors: Moll, M; Adey, J; Al-Ajili, A; Alfieri, G; Allport, PP; Artuso, M; Assouak, S; Avset, BS; Barabash, L; Barcz, A; Bates, R; Biagi, SF; Bilei, GM; Bisello, D; Blue, A; Blumenau, A; Boisvert, V; Bolla, G; Bondarenko, G; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, TJV; Brodbeck, TJ; Broz, J; Bruzzi, M; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Charron, S; Chilingarov, A; Chren, D; Cindro, V; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, W; Dalla Betta, GF; Dawson, I; de Boer, W; De Palma, M; Demina, R; Dervan, P; Dittongo, S; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Fretwurst, E; Garcia, C; Garcia-Navarro, JE; Gaubas, E; Genest, MH; Gill, KA; Giolo, K; Glaser, M; Goessling, C; Golovine, V; Sevilla, SG; Gorelov, I; Goss, J; Bates, AG; Gregoire, G; Gregori, P; Grigoriev, E; Grillo, AA; Groza, A; Guskov, J; Haddad, L; Harkonen, J; Hauler, F; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R; Horn, M; Houdayer, A; Hourahine, B; Hughes, G; Ilyashenko, I; Irmscher, K; Ivanov, A; Jarasiunas, K; Johansen, KMH; Jones, BK; Jones, R; Joram, C; Jungermann, L; Kalinina, E; Kaminski, P; Karpenko, A; Karpov, A; Kazlauskiene, V; Kazukauskas, V; Khivrich, V; Khomenkov, V; Kierstead, J; Klaiber-Lodewigs, J; Klingenberga, R; Kodys, P; Kohout, Z; Korjenevski, S; Koski, M; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lassila-Perini, K; Lastovetsky, V; Latino, G; Lazanu, S; Lazanu, I; Lebedev, A; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindstrom, G; Linhart, V; Litovchenko, A; Litovchenko, P; Lo Giudice, A; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Makarenko, LF; Mandic, I; Manfredotti, C; Manna, N; Marti i Garcia, S; Marunko, S; Mathieson, K; Melone, J; Menichelli, D; Messineo, A; Metcalfe, J; Miglio, S; Mikuz, M; Miyamoto, J; Monakhov, E; Moscatelli, F; Naoumov, D; Nossarzewska-Orlowska, E; Nysten, J; Olivera, P; OShea, V; Palvialnen, T; Paolini, C; Parkes, C; Passeri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, K; Piemonte, C; Pignatel, GU; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, A; Popule, J; Pospisil, S; Pozza, A; Radicci, V; Rafi, JM; Rando, R; Roeder, R; Rohe, T; Ronchin, S; Rott, C; Roy, A; Ruzin, A; Sadrozinski, HFW; Sakalauskas, S; Scaringella, M; Schiavulli, L; Schnetzer, S; Schumm, B; Sciortino, S; Scorzoni, A; Segneri, G; Seidel, S; Seiden, A; Sellberg, G; Sellin, P; Sentenac, D; Shipsey, I; Sicho, P; Sloan, T; Solar, M; Son, S; Sopko, B; Sopko, V; Spencer, N; Stahl, J; Stolze, D; Stone, R; Storasta, J; Strokan, N; Sudzius, M; Surma, B; Suvorov, A; Svensson, BG; Tipton, P; Tomasek, M; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullan, M; Vaitkus, JV; Velthuis, J; Verbitskaya, E; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Yiuri, Y; Zabierowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N

Published: JUL 1 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 546, 107, DOI: 10.1016/j.nima.2005.03.044

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 10(35) cm(-2) s(-1) Will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi-3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented. (c) 2005 Elsevier B.V. All rights reserved.

2661. X-band filter manufactured with ZST dielectric resonators

Authors: Ioachim, A; Banciu, MG; Toacsin, MI; Nedeleu, L; Dutu, CA; Radu, I; Nicolaescu, I

Published: 2005, CAS 2005: INTERNATIONAL SEMICONDUCTOR CONFERENCE, 1-2, 102, DOI:

Band-pass filters with dielectric resonators of (Zr-0.8, Sn-0.2,)TiO4 ceramic materials (ZST) were developed for X-band applications. The ZST materials exhibit a dielectric constant of about 36.8 and low loss in microwave range. A Qxf product higher than 50,000 was achieved for the ZST samples with 0.2% wt NiO sintering addition. The external coupling was performed Using microstrip lines on a substrate of 9.22 dielectric constant and 0.635 mm height. Filters with minimum insertion loss between 0.46 dB and 1.74 dB, the bandwidth between 40 MHz and 170 MHz and with the central frequency around 10 GHz were manufactured.

2662. On the relaxation mechanisms of some radiation induced free radicals in polymers

Authors: Velter-Stefanescu, M; Duliu, OG; Preda, N

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 989, DOI:

Electronic spin-lattice relaxation measurements performed in X and Q bands on electrons irradiated polyethylene, polycarbonate and polymethylmethacrylate have shown that at liquid helium temperatures and higher, up to 12K, the spin-lattice relaxation time of radiation induced free radicals does not depend on the magnetic. field but varies inverse proportionally with the square of absolute temperature and free radicals concentration. These peculiarities have been well explained by admitting that below 77 K there is a considerable amount of stable free radicals coupled in pairs that mediate the spin-lattice relaxation process of single radicals. Consequently, we have proposed an analytical equation that, within this hypothesis, quantitatively describes all these particularities.

2663. CNT-based cathode material for DMFC

Authors: Rohland, B; Pietrzak, M; Moller, S; Bunescu, MC; Wienecke, M; Barfels, T; Bunescu, MC

Published: 2005, FULLERENES NANOTUBES AND CARBON NANOSTRUCTURES, 13, 522, DOI: 10.1081/FST-200039478

New cathode material for Direct Methanol Fuel Cells (DMFC) based on multi-wall carbon nanotubes (MWCNT), aiming to improving the power density of the cell was analysed. Commercially available MWCNTs were oxidized in a mixture of HNO3 and H2SO4. Pt catalyst was electroless deposited using a chloroplatinic acid solution, based on H-2 (PtCl6) center dot 6H(2)O. The morphology of the deposits was analysed by TEM and SEM. Uniformly distributed nano particles of Pt with diameters of approximately 5 nm along the MWCNTs surface, agglomerates of thick Pt deposits, as well as complete uncoated nanotubes were observed. An optimisation of the size and distribution of the Pt particles could be obtained by varying the process parameters (dispersion time and solution concentration). The MWCNTs + Pt were used to produced a paste, which was screen-printed on Nation foil. The membrane electrode assembly (MEA) was tested at 40 degrees C with air and 3% methanol in water. The performances were improved as compared with the standard DMFC electrodes.

2664. Coherent anti-Stokes Raman scattering on single-walled carbon nanotube thin films excited through surface plasmons

Authors: Baltog, I; Baibarac, M; Lefrant, S

Published: DEC 2005, PHYSICAL REVIEW B, 72, DOI: 10.1103/PhysRevB.72.245402

We report experimental data that indicate an anti-Stokes Raman emission, reminiscent of coherent anti-Stokes raman scattering. It originates from a wave mixing process between the incident laser light (omega(l)) and Stokes Raman light (omega(s)) generated by a surface enhanced Raman scattering (SERS) mechanism. The variation of anti-Stokes SERS spectra of single-walled carbon nanotubes, copper phthalocyanine, and poly(bithiophene) as a function of the film thickness, the laser excitation intensity, and the numerical aperture of the microscopic objective used for collecting the scattered light demonstrate the described phenomenon.

2665. Cornpact cross-coupled filters for UMTS applications

Authors: Banciu, MG; Lojewski, G; Ioachim, A; Militaru, N

Published: 2005, ISSCS 2005: International Symposium on Signals, Circuits and Systems, Vols 1 and 2, Proceedings, 728, DOI:

Very compact planar resonators were developed for the 1950 MHz frequency band. Resonators are of the stepped-impedance (SIR) type and they are folded, in order to occupy a very small surface area. On a 6.635 mm height commercial substrate with a 10.8 dielectric constant, a resonator can be fitted into a square with an edge size of 5.8 m. Small-size filters were designed by cross-coupling the compact resonators. The four-pole filters have an improved response due to the cross-couplings, which introduces transmission zeros on each side of the pass-band. The filters were manufactured and characterized. The measurement data are in good agreement with the electromagnetic field simulations. The developed filters are small-size and cost-effective and their technology is simple,. without any via holes, air-bridges or lumped elements.

2666. Polarization reversal and capacitance-voltage characteristic of epitaxial Pb(Zr,Ti)O-3 layers

Authors: Pintilie, L; Lisca, M; Alexe, M

Published: MAY 9 2005, APPLIED PHYSICS LETTERS, 86, DOI: 10.1063/1.1926403

Capacitance-voltage (C-V) measurements were performed on epitaxial layers of PbsZr(0.2)Ti(0.8)dO(3) (PZT) with top and bottom SrRuO3 (SRO) electrodes. It is shown that the sharp capacitance peak/discontinuity which is present in the C-V characteristics at different frequencies is directly associated with the polarization reversal. The ferroelectric film is assumed as a large band-gap semiconductor with Schottky contacts at the metal-ferroelectric interfaces. The capacitance discontinuity at the reversal scoercived voltage is associated with a discontinuity in the built-in potential at the PZT/ SRO interfaces. The C-V characteristics for voltage ranges outside the coercive values can be used to extract the free carrier concentrations as in the case of Schottky metal-semiconductor contacts. The carrier concentration was found to be (2-4) x 10(18) cm(-3), independent of measuring frequency and temperature up to 1 MHz and 170 degrees C, respectively, suggesting completely ionized shallow impurities. (c) 2005 American Institute of Physics.

2667. Fano regime of one-dot Aharonov-Bohm interferometers

Authors: Moldoveanu, V; Tolea, M; Gudmundsson, V; Manolescu, A

Published: AUG 2005, PHYSICAL REVIEW B, 72, DOI: 10.1103/PhysRevB.72.085338

We use the Landauer-Buttiker formalism to study the mesoscopic Fano effect in Aharonov-Bohm rings with an embedded two-dimensional noninteracting dot. The magnetic field dependence of the dot levels leads to a global shift of the Fano lines which becomes important for small ring/dot area ratios. As the magnetic field is varied the Fano dips move periodically from one side of the peak to the other, as reported by Kobayashi [Phys. Rev. Lett. 88, 256806 (2002)]. We show that this effect appears due to a specific magnetic control of the difference between the phase of the single nonresonant path via the free arm of the ring and the global phase of all trajectories involving resonant tunnelings through the dot.

2668. Interstitial void structure in Cu-Sn liquid alloy as revealed from reverse Monte Carlo modelling

Authors: Hoyer, W; Kleinhempel, R; Lorinczi, A; Pohlers, A; Popescu, M; Sava, F

Published: FEB 9 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, S36, DOI: 10.1088/0953-8984/17/5/004

A model for the structure of copper-tin liquid alloy has been developed using the standard reverse Monte Carlo method. The interstitial void structure (size distribution) was analysed. The effects of various kinds of voids (small size and large size) on the interference function and radial distribution function were investigated. Predictions related to the formation of some ternary alloys by filling the interstices of the basic alloy were advanced.

2669. Unconventional method of obtaining nanocrystallites from copper sulfides

Authors: Simonescu, CM; Teodorescu, VE; Patron, L; Giurginca, M; Capatina, C

Published: AUG 2005, REVISTA DE CHIMIE, 56, 812, DOI:

In this article the obtaining and characterization of a mixture of copper sulfide (CuS, Cu9S, CuS2) is presented. The characterization was made by IR Spectroscopy, X-ray Powder Diffraction (XRD) and Transmission Electron Microscopy (TEM). The sulfide mixture represents an aggregate of small particles with an average diameter of 20-30 nm and particles with the diameter of about 500 nm. The smaller particles have the cuboidal morphology and correspond to CuS2; the bigger ones have the hexagonal morphology and correspond to CuS, and Cu9S8.

2670. High-K ZST material for microwave and millimeter wave applications

Authors: Ioachim, A; Ramer, R; Toacsan, MI; Banciu, MG; Nedelcu, L; Ghetu, D; Stoica, G; Annino, G; Cassetari, M; Martinelli, M

Published: 2005, Smart Materials III, 5648, 376, DOI: 10.1117/12.582428

Wireless communications systems require new materials with special properties in specific frequency bands. The investigations on ZST type ceramics, (Zr0.8Sn0.2)TiO4, presented in this paper, recommend this materials for applications in microwaves and millimeter waves. The ZST materials were prepared using a standard solid-state reaction technology. The samples morphology, phase-composition and microstructure investigations were performed by using the scanning electron microscopy (SEM), and energy-disperse X-ray spectrometry (EDX). The crystalline phases were identified by X-ray diffractometry (XRD). The electromagnetic properties were investigated on ZST resonators by using a Computer Aided Measurement (CAM) in microwaves, combining a HP 8757C network analyzer and a HP 8350B sweep oscillator. The dielectric characteristics at millimeter waves were analyzed by investigation of the Whispering Gallery Modes on ZST disks. The low level NiO doping provides ZST materials with temperature coefficient tau(f) in the range (-2 divided by +4) ppm/degrees C and decreases the dielectric loss. Materials with high values of the Q f product up to 50,000 and a dielectric constant about 36 at microwave frequencies were obtained. ZST dielectric resonators and substrates for hybrid integrated circuits with dimensions 1" x 1" and thickness in the range 0.6 divided by 1 mm were manufactured.

2671. Experiments on pulsed laser deposition and characterization of epitaxially in-situ grown YBa2Cu3O7-x thin films

Authors: Branescu, M; Teodorescu, VS; Socol, G; Balasz, I; Ducu, C; Jaklovszky, J

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 972, DOI:

Experimental results concerning the pulsed laser deposition parameters of in-situ epitaxially grown high crystalline quality YBa2Cu3O7-x thin films are reported. The structural and morphological properties of the deposited films analyzed by transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and Raman spectroscopy are also presented. The YBa2Cu3O7-x thin films, predominantly c-axis oriented had required the smallest oxygen pressure during the cool-down time reported to date.

2672. Ni nanowires electrodeposited in single ion track templates

Authors: Daub, M; Enculescu, I; Neumann, R; Spohr, R

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 870, DOI:

30-mu m thick polycarbonate foils were irradiated with single swift heavy ions (,e.g. Au 11.4 MeV/nucleon). After etching with solutions containing NaOH and methanol, templates containing single conical pores were obtained. The size and the shape of the nanopores depend on etching conditions such as time of etching, concentration and temperature of the etching solution. By electrochemical deposition of nickel, nanowires were grown in the single pores. The nanowires were contacted by sputtering a gold layer on top of the membrane. The magnetic measurements indicated that the nanowires possess around 1% anisotropic magnetoresistance. The current-voltage characteristic of a Ni nanowire shows a linear behavior for current densities smaller than 10(8) A/cm(2). The maximum current density that a single Ni wire can withstand was found to be 3x 10(8) A/cm(2).

2673. Mechanico-chemical interaction of single-walled carbon nanotubes with different host matrices evidenced by SERS spectroscopy

Authors: Baibarac, M; Baltog, I; Lefrant, S; Godon, C; Mevellec, JY

Published: APR 23 2005, CHEMICAL PHYSICS LETTERS, 406, 227, DOI: 10.1016/j.cplett.2005.02.113

Surface enhanced Raman scattering with 676.4 and 1064 nm excitations was used to investigate single-walled carbon nanotubes (SWNTs) compressed non-hydro statically at 0.58 GPa, alone or dispersed into chemical reactive and non-reactive host matrices. By compression, SWNTs break in fragments of different size. Between SWNTs fragments and the host matrix various mechanico-chemical reactions take place. In matrices such KI and Ag, donor-acceptor complexes are formed. In aromatic hydrocarbons like biphenyl or p-terphenyl, an ionic and covalent functionalization of SWNTs fragments is demonstrated by new bands at 1160 and 1458 cm(-1), the latter being associated to an A(g)(2) pentagonal pinch mode. (c) 2005 Elsevier B.V. All rights reserved.

2674. Surface-enhanced Raman scattering studies on C-60 fullerene self-assemblies

Authors: Baibarac, M; Mihut, L; Preda, N; Baltog, I; Mevellec, JY; Lefrant, S

Published: 2005, CARBON, 43, 9, DOI: 10.1016/j.carbon.2004.08.020

Surface-enhanced Raman scattering (SERS) was used to investigate C-60 self-assembling in solvents like pyrrolidine (Py) and Nmethyl-2-pyrrolidinone (NMP) as well as in binary mixtures of o-dichlorobenzene (DCB)/acetonitrile (ACN) and DCB/NMP. For a correct evaluation of the modifications of Raman spectra induced by the C-60 aggregation, we have also presented the variations due to the measuring method, i.e., the signal dependence of the metallic support type and the surface roughness. The interaction between C-60 and the Au substrate, appearing as a chemical component in SERS generation, is mainly evidenced by a band at similar to342cm(-1). In the aggregated phase, the intermolecular interactions lead to a reduction in the parent I-h C-60 symmetry as observed by a modified phonon spectrum. As a general feature, the spectral range below 800cm(-1) is the most diagnostic for the aggregate assignment, the main indicative being the disappearance of the Raman bands associated to the radial vibration modes. SERS measurements have revealed two stages in the self-assembling of C-60 in NMP. In the beginning, charge-transfer molecular complexes that associate slowly in stable aggregates are formed by the binding of an NMP molecule to the C-60 cage. These complexes are noticed in the SERS spectrum by the replacement of the original H-g(l) band at similar to269cm(-1) with two others at similar to255 and similar to246cm(-1). In the aggregated phase, when using NMP and P as a solvent, the Raman spectrum reveals new bands that appear around 94 and 110-118cm(-1), which are associated with the interball interactions. In a DCB/ACN solvent mixture, the self-assembling process is driven by weak van der Waals type forces and resembles a precipitation, yielding C60 clusters of different size. (C) 2004 Published by Elsevier Ltd.

2675. Microspheres, planoconvex microlenses and optical fibres based on glassy As2S3

Authors: Popescu, M; Sava, F; Lorinczi, A; Savastru, D; Miclos, S; Savastru, R

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1106, DOI:

Microspheres and planoconvex lenses (50 divided by 400 mu m in diameter) based on glassy As2S3, an important infrared material, have been produced by a special flame melting technique. Glassy fibres of 45 mu m in diameter, with the length of 10-20 cm have been drawn from melt. The morphological properties of these optical elements have been investigated.

2676. Growth and characterization of a-axis textured ZnO thin films

Authors: Nistor, LC; Ghica, C; Matei, D; Dinescu, G; Dinescu, M; Van Tendeloo, G

Published: APR 15 2005, JOURNAL OF CRYSTAL GROWTH, 277, 31, DOI: 10.1016/j.jcrysgro.2004.12.162

Smooth a-axis oriented ZnO thin films are grown on (001) MgO substrates by pulsed laser deposition assisted by a very directional radio frequency oxygen plasma. The structure of the film is examined by X-ray diffraction, electron diffraction and high resolution electron microscopy. The film grows with vertical columns and is highly textured. Two preferential orientation relations between the ZnO film and the MgO substrate are observed: (10010)(ZnO) vertical bar vertical bar (002)(MgO); [0002](ZnO)vertical bar vertical bar[2 0 0](MgO) and (1010)(ZnO) vertical bar (002)(ZnO) vertical bar vertical bar [200](MgO) [1210](MgO). The film/substrate interface is flat and strained because of the rather large lattice mismatch between the (1010) plane of ZnO and the (002) plane of MgO. (c) 2005 Elsevier B.V. All rights reserved.

2677. Radiation-induced donor generation in epitaxial and Cz diodes

Authors: Pintilie, I; Buda, M; Fretwurst, E; Honniger, F; Lindstrom, G; Stahl, J

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 60, DOI: 10.1016/j.nima.2005.06.006

Thin epitaxial layers grown on Cz substrates (Epi) and high resistivity Cz diodes have been irradiated with fluences of 2 x 10(14) cm(-2) 24 GeV protons. It is shown that the differences in the changes observed in the effective doping concentration (N-eff) after irradiation of Epi silicon can be explained by the balance between the formation of two type of defects-a deep acceptor (the I center) and a shallow donor (the BD complex). The BD concentration in Epi material is evaluated to be similar to 1.3 x 10(12) cm(-3). (c) 2005 Elsevier B.V. All rights reserved.

2678. A(II)B(VI) photoresistances by sintering-sublimation technics

Authors: Nazarenco, I; Jaklovszky, J; Ghiordanescu, V; Sava, BA; Albeanu, I; Dumitrescu, M; Ulieru, D

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2118, DOI:

The sintering-sublimation technics was conceived for increasing the reliability of the photoconductive devices, by decreasing the concentration of mobiles donors, which are utilised for photoconductive material sensibilisation. The technics combines three different technics: the vapor phase deposition; the vacuum vaporising; the ceramic sinterisation. This special technics gives stoichiometric layers. The technics avoids dissociation (the flash sublimation technic), sublimates the compounds from two different sources, on heated support, or sublimates the compound, with Cd excess. It was investigated, by mass spectrometry and optical absorption studies, the presence, in gaseous state, of the A(II)B(VI) molecules. The condensation on the substrate of the vapors is difficult because the Cd, Zn and Hg elements have difficulties in the condensation process. The Frenkel model, of the condensation, can be successfully used for describing the process. This model uses the observations concerning the difficulty of the condensation on supports of those elements, at higher temperatures than 90 - 195 K. It is supposed that the support surface is a potential surface, with holes and potential walls, whose dimensions can not overcome the interatomic distances, for polished surfaces.

2679. Characterization of oxygen dimer-enriched silicon detectors

Authors: Boisvert, V; Lindstrom, JL; Moll, M; Murin, LI; Pintilie, I

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 55, DOI: 10.1016/j.nima.2005.06.005

Various types of silicon material and silicon p(+)n diodes have been treated to increase the concentration of the oxygen dimer (02) defect. This was done by exposing the bulk material and the diodes to 6 MeV electrons at a temperature of about 350 degrees C. FTIR spectroscopy has been performed on the processed material confirming the formation of oxygen dimer defects in Czochralski silicon pieces. We also show results from TSC characterization on processed diodes. Finally, we investigated the influence of the dimer enrichment process on the depletion voltage of silicon diodes and performed 24 GeV/c proton irradiations to study the evolution of the macroscopic diode characteristics as a function of fluence. (c) 2005 Elsevier B.V. All rights reserved.

2680. Supported perovskites for total oxidation of toluene

Authors: Alifanti, M; Florea, M; Somacescu, S; Parvulescu, VI

Published: SEP 1 2005, , DOI: 10.1016/j.apcatb.2005.02.018

2681. Vanadium aluminium oxynitride catalysts for propane ammoxidation reaction - Effect of the V/Al ratio on the structure and catalytic behviour

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY 26 2005, , DOI: 10.1016/j.apcata.2005.02.032

2682. Evidence for the participation of lattice nitrogen from vanadium aluminum oxynitrides in propane ammoxidation

Authors: Olea, M; Florea, M; Sack, I; Silvy, RP; Gaigneaux, EM; Marin, GB; Grange, P

Published: MAY 15 2005, , DOI: 10.1016/j.jcat.2005.02.020

2683. Supported Co-based perovskites as catalysts for total oxidation of methane

Authors: Alifanti, M; Blangenois, N; Florea, M; Delmon, B

Published: MAR 8 2005, , DOI: 10.1016/j.apcata.2004.11.005

2684. Structural phase transition induced in Fe50Rh50 alloys by high pressure

Authors: Kuncser, V; Nicula, R; Ponkratz, U; Jianu, A; Stir, M; Burkel, E; Filoti, G

Published: JAN 11 2005, JOURNAL OF ALLOYS AND COMPOUNDS, 386, 11, DOI: 10.1016/j.jallcom.2004.04.139

The equiatomic composition of the FeRh alloy was studied by in situ high pressure energy dispersive X-ray experiments. Pressures as high as 19 GPa were generated using a diamond anvil cell. An incomplete bcc --> fcc phase transition was evidenced, both bcc and fcc phases coexisting above 10.0 GPa. The transition is accompanied by a decrease of the lattice parameter of the remaining bcc phase by approx. 1.5%. A substantial low lattice parameter was observed for the newly formed fee phase, reflecting a rather compressed structure. (C) 2004 Elsevier B.V. All rights reserved.

2685. Atomic scale structure of Ge30As4S66

Authors: Sava, F; Anghel, A; Kaban, I; Hoyer, W; Popescu, M

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1975, DOI:

The structure of a glassy sample of Ge30As4S66 has been measured by means of synchrotron radiation. X - ray diffraction data were processed and the atomo-electronic radial function (AERDF) was calculated. The high resolution AERDF curve allowed for an accurate determination of the first order distances between the atoms and the coordination numbers. A model of spatial structure, based on the concept of raft configuration was tested. An other model of the structure based on the continuous random network concept (CRN) was tried. The general conclusion drawn from this study supports the idea that raft and disordered configurations interlinked so that the dangling bonds in the structure be minimized, is the best model for such type of glass.

2686. Comparison of the luminescence properties of the x-ray storage phosphors BaCl2 : Ce3+ and BaBr2 : Ce

Authors: Selling, J; Corradi, G; Secu, M; Schweizer, S

Published: DEC 21 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, 8078, DOI: 10.1088/0953-8984/17/50/024

The single-crystalline x-ray storage phosphor BaCl2:Ce3+ has been investigated by photo- and x-ray luminescence, and also by observing the afterglow and the photostimulated luminescence (PSL). A single active Ce3+ site has been observed with a characteristic emission doublet at 349 and 373 nm at room temperature. The PSL stimulation spectrum shows a clear resemblance to F-type absorption spectra in undoped BaCl2, indicating that the PSL-active electron centres are F-type centres. The results are compared with previous photoluminescence, PSL and new x-ray luminescence data on BaBr2:Ce3+. The integral PSL efficiency in the chloride is found to be somewhat smaller than in the bromide, which is still large enough for storage phosphor applications, while the efficiency in the bromide may be even larger or comparable to that of the commercial x-ray storage phosphor BaFBr2:Eu2+.

2687. Paramagnetic defect centres in crystalline Alq(3)

Authors: Grecu, MN; Mirea, A; Ghica, C; Colle, M; Schwoerer, M

Published: OCT 5 2005, JOURNAL OF PHYSICS-CONDENSED MATTER, 17, 6283, DOI: 10.1088/0953-8984/17/39/012

X- and Q-band electron paramagnetic resonance (EPR) investigation of different crystalline Alq(3) (tris(8-hydroxyquinoline)aluminium (III)) fractions formed by a train sublimation method are reported. Several paramagnetic defect centres corresponding to 1/2, 1, and 3/2 spin are observed at room temperature. Their intensity is dependent on the temperature, nature of the crystalline phase, and preparation conditions. Spectra simulation and analysis based on the spin Hamiltonian appropriate to a high spin system (S >=, 1) suggest the existence of randomly oriented triplets and quartets in annealed Alq(3) fractions. The crystalline Alq(3) phases responsible for the EPR powder spectra have been identified by transmission electron microscopy measurements performed on these sample fractions.

2688. Photostimulable defects in nano-crystallites in fluorozirconate glasses

Authors: Schweizer, S; Spaeth, JM; Secu, M; Edgar, A; Williams, GVM

Published: JAN 2005, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 202, 249, DOI: 10.1002/pssa.200460220

The photostimulated luminescence (PSL) from Eu-doped fluorobromo- and fluorochlorozirconate glass-ceramics is reviewed. The PSL is attributed to the characteristic emission of Eu2+ present in BaX2 (X = Br, Cl) crystallites which form in the glass upon thermal processing. Both the photoluminescence intensity and the PSL efficiency increase with the size of the crystallites in a way that is consistent with a PSL-inert surface layer surrounding the crystallites. The increasing crystallite sizes also result in decreased optical transparency at the stimulation wavelength due to scattering. (C) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2689. Properties of high-porosity sol-gel derived indium-tin oxide films

Authors: Stoica, TF; Gartner, M; Stoica, T; Losurdo, M; Teodorescu, VS; Blanchin, MG; Zaharescu, M

Published: OCT 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2358, DOI:

Indium-tin oxide (ITO) sol-gel films have been obtained with the void concentration up to 50%. The films are nanostructured with nanocrystals of In2O3:Sn and nanovoids. The information obtained from derivative thermo-gravimetry was used to design the annealing program for ITO film formation with a high void concentration. Multilayer films were obtained by successive deposition. The thickness of one layer was about 9 nm. By successive depositions, the void density of the film is reduced. Quantitative analysis of the void density has been performed by spectroscopic ellipsometry. The conductivity of the films can be varied in a large range by annealing in vacuum or in air, at temperature higher than 200 degrees C.

2690. Resonant and coherent transport through Aharonov-Bohm interferometers with coupled quantum dots

Authors: Moldoveanu, V; Tolea, M; Aldea, A; Tanatar, B

Published: MAR 2005, PHYSICAL REVIEW B, 71, DOI: 10.1103/PhysRevB.71.125338

A detailed description of the tunneling processes, within Aharonov-Bohm (AB) rings containing two-dimensional quantum dots is presented. We show that the electronic propagation through the interferometer is controlled by the spectral properties of the embedded dots and by their coupling with the ring. The transmittance of the interferometer is computed by the Landauer-Buttiker formula. Numerical results are presented for an AB interferometer containing two coupled dots. The charging diagrams for a double-dot interferometer and the Aharonov-Bohm oscillations are obtained, in agreement with the recent experimental results of Holleitner et al. [Phys. Rev. Lett. 87, 256802 (2001)] We identify conditions in which the system shows Fano line shapes. The direction of the asymetric tail depends on the capacitive coupling and on the magnetic field. We discuss our results in connection with the experiments of Kobayashi et al. [Phys. Rev. Lett. 88, 256806 (2002)] in the case of a single dot.

2691. Magnetically modulated microwave absorption investigation of Bi1.8Pb0.4Sr1.8Ba0.2Ca2Cu3Ox/(LiF)(y) superconducting system

Authors: Velter-Stefanescu, M; Duliu, OG; Mihalache, V

Published: JUN 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1561, DOI:

The effect of LiF content on the 2223 phase of the high temperature superconducting system Bi1.8Pb0.4Sr1.8Ba0.2Ca2Cu3Ox/(LiF)(y) (y = 0.02 to 0.15) was investigated by means of magnetically modulated microwave absorption (MAMMA). The experimental results confirmed a two fold increase of the superconducting phase content together with a slight rise (around 2 %) of the critical temperature for y=0.07. At the same time, for y between 0.05 and 0.12 the -Delta T-c(mw)/Delta B ratio was practically constant and equal to (18.5 +/- 1.5) KT-1, a typical value for 2223 superconducting phase.

2692. Magnetic and Mossbauer spectral studies of R3Fe29-x,MOx compounds (R = Y, Nd, Sm, Gd, Tb, and Dy)

Authors: Lazar, DP; Valeanu, M; Galatanu, A; Leonovici, MR; Dafinei, A; Ion, L

Published: APR 19 2005, JOURNAL OF ALLOYS AND COMPOUNDS, 392, 39, DOI: 10.1016/j.jallcom.2004.09.012

The investigation of the structure, magnetic and Mossbauer properties for the series of R-3(Fe,MO)(29) compounds has been performed, where R = Y, Nd, Sm, Gd, Tb, and Dy. The crystallographic structure of the ternary phase compounds has been investigated by Rietveld refinement of the X-ray diffraction patterns obtained at room temperature. The quality of the single-phase compounds was also checked by thermomagnetic measurements, from room temperature to above the Curie temperatures. From the magnetic isotherms for the free powder samples, measured at 4.2 K, the saturation magnetizations and the iron average magnetic moments have been derived. Fe-57 Mossbauer spectra of the R3 (Fe,MO)29 compounds have been measured at 15 K. The analysis of spectra, in a model which takes into account both the Fe atom nearest neighbor numbers and the Fe-Fe nearest neighbor bond lengths, indicates that the transferred contribution to the hyperfine field at the iron sites, due to rare earth moments, can be correlated with the rare earth effective spin. (c) 2004 Elsevier B.V. All rights reserved.

2693. Mossbauer effect study of correlation between structure and exchange-bias effect in ferromagnetic Fe/antiferromagnetic FeSn2 bilayers

Authors: Kuncser, VE; Stromberg, F; Acet, M; Keune, W

Published: MAR 15 2005, JOURNAL OF APPLIED PHYSICS, 97, DOI: 10.1063/1.1858879

Antiferromagnetic (AF) FeSn2(001) epitaxial and polycrystalline layers were grown in ultrahigh vacuum under various conditions on clean InSb(001) substrates and covered by polycrystalline ferromagnetic Fe layers, forming a new system with exchange bias. Isotopically enriched Fe-57- and (FeSn2)-Fe-57-tracer layers were placed on either side of the Fe/FeSn2 interface for a microscopic investigation of the spin structure and atomic interdiffusion phenomena in near-interfacial regions by Fe-57 conversion electron Mossbauer spectroscopy (CEMS) at room temperature and T=10 K. Several spectral components, assigned to pure bcc Fe, Sn-containing bcc Fe, AF-ordered FeSn2, and paramagnetic FeSn2 were resolved in the CEM spectra. Evidence is provided for interdiffusion across the interface. The temperature dependence of the exchange-bias field H-E was measured by magnetometry. The CEMS data provide evidence for a correlation between H-E at low T and chemical disorder (defects) in the FeSn2 films via the intensity of the paramagnetic line. These results support the assumption that exchange bias is related to the presence of AF domains formed via magnetic defects in the antiferromagnet. The T dependence of H-E suggests interfacial exchange-coupling energies higher than the AF wall energy. (C) 2005 American Institute of Physics.

2694. Lead-based ferroelectric compounds: Insulators or semiconductors?

Authors: Pintilie, L; Lisca, M; Alexe, M

Published: 2005, INTEGRATED FERROELECTRICS, 73, 48, DOI: 10.1080/10584580500413434

Lead zirconate-titanate (PZT) epitaxial thin films are considered wide-gap p-type semiconductors with standard Schottky contacts. Capacitance-voltage, current-voltage, as well as the dielectric hysteresis are analyzed using a model based on the conventional metal-semiconductor Schottky contact in which the effect of the ferroelectric polarization on band-bending was considered. In addition, presence of the deep traps and its effect on the measured quantities were considered and discussed. For a single-crystal like PZT films with a remnant polarization of 40 mu C/cm(2) the free carrier concentration is estimated to about 3 x 10(18) cm(-3), whereas the effective density of the fixed charges in the depletion region is of about 1.8 x 10(19) cm(-3) .

2695. Surface-enhanced Raman scattering, photoluminescence and viscosity studies on C-60 aggregates in N-metryl-2-pyrrolidinone

Authors: Baltog, I; Mihut, L; Baibarac, M; Preda, N; Velula, T; Lefrant, S

Published: AUG 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 2172, DOI:

Correlated studies of Surface Enhanced Raman Scattering (SERS) spectroscopy, photoluminescence (PL) and viscosity on aggregation of C-60 fullerene in N-methyl-2-pyrrolidinone (NMP) solutions were performed. The aggregation is a result of storing of the solutions at the room temperature for different periods of time. The modified phonon spectrum in the aggregate phase is a consequence of the intermolecular interactions that lead to a large reduction in parent I-h C-60 symmetry. The Raman range below 800 cm(-1) is the most diagnostic for aggregate assignment. Substitution of the original of H, (1) band from similar to 269 cm(-1) with a new one at similar to 255 cm(-1) relates the formation of (C-60, NMP) complexes. In the second stage of aggregation, this band shifts at similar to 246 cm(-1) and a new band, associate to the interball interaction, is formed at similar to 94 cm(-1). PL emission of the C-60 solutes in NMP presents two components, one in red (1.92-2.00 eV) and another in green (2.18-2.3 eV), which originate in two successive processes. Their weights depend on C-60 concentration and on storage time. In the beginning are formed quickly molecular complexes (C-60, NMP) by charge transfer, which on associate slowly in stable aggregates. A dependence of specific viscosity on C-60 solution concentration is observed too.

2696. Surface-enhanced Raman scattering studies on chemically transformed carbon nanotube thin films

Authors: Lefrant, S; Baltog, I; Baibarac, M

Published: JUN-JUL 2005, JOURNAL OF RAMAN SPECTROSCOPY, 36, 698, DOI: 10.1002/jrs.1351

We review our experimental data obtained by Raman spectroscopy on single-walled carbon nanotubes (SWNTs) using surface-enhanced Raman scattering (SERS). We focused on the study of the dependence of the SERS spectra of SWNTs on both the rough metallic substrate type and the film thickness. In particular, we show that degradation of the nanotubes, mainly metallic, occurs for very thin films with the formation of graphitic, fullerene-like or amorphous carbon particles. We show also that SWNTs reacting with H2SO4 form a salt of the hydrogensulfate type similar to that resulting from graphite-H2SO4 interaction. SWNTs exhibit a complicated spectroelectrochemical behavior in aqueous and non-aqueous H2SO4 solutions that depends also on the sweep potential range. We demonstrate that the oxidation-reduction processes have a quasi-reversible or irreversible character. Finally, SERS studies on compressed SWNTs in different host matrices, inorganic and organic, reveal nanotube breaking and that tube fragments may react or not with the host matrix used. Copyright (c) 2005 John Wiley & Sons, Ltd.

2697. Swift heavy ion irradiation effects on doped alkali halides

Authors: Enculescu, M

Published: DEC 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 3056, DOI:

The effects produced by heavy ion irradiation in KBr:Ag and KCl:Ag crystals are investigated using optical spectroscopy. For KCl, the results are compared with the effects obtained in the pure crystals. After irradiation with heavy ions up to 11.2 MeV/u specific energy, the absorption bands suffer a series of changes, related to the structure of defects and also to their dimensions. In the high Ag concentrated samples, the Ag+ ions are changing their valence to Ag- while in the samples containing Ag nanoclusters the irradiation induces changes in the nanocluster size.

2698. Net current generation in a 1D quantum ring at zero magnetic field

Authors: Gylfadottir, SS; Nita, M; Gudmundsson, V; Manolescu, A

Published: MAR 2005, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 27, 283, DOI: 10.1016/j.physe.2004.12.002

We study a non-adiabatic excitation of an electron system in a 1D quantum ring radiated by a short terahertz pulse. The response of two models, a continuous and a discrete, is explored. By introducing a spatial asymmetry in the external perturbation, a net current can be generated in the ring at a zero magnetic field. Effect of impurities and ratchets are investigated in combination with symmetric and asymmetric external excitation. (c) 2005 Elsevier B.V. All rights reserved.

2699. Field effects and surface states in second harmonic generation at n-GaAs(h k l) electrodes

Authors: Lazarescu, V; Scurtu, R; Lazarescu, MF; Santos, E; Jones, H; Schmickler, W

Published: SEP 5 2005, ELECTROCHIMICA ACTA, 50, 4836, DOI: 10.1016/j.electacta.2005.02.069

Second harmonic generation from n-doped GaAs(111)-A, GaAs(111)-B and GaAs(110) electrodes in sulfuric acid solution has been compared at an incident wavelength of 1064 nm over a potential range, where Faradaic process are excluded. In the p-in/p-out polarization configuration, the rotational anisotropy of the SH response reflects the symmetry of the crystal surface. The isotropic part of the response depends significantly on the applied electric field in the space-charge region, suggesting that the dominant part of the SH response is generated in the near-surface depletion region. The effects of the applied potential on the isotropic amplitude of the SH-signal show, however, that the high density of the surface/interface states at the Fermi level, revealed in impedance spectroscopy, may play an important role as well. (C) 2005 Elsevier Ltd. All rights reserved.

2700. Quantum confinement in the photoluminescence of nanocrystalline porous silicon

Authors: Stavarache, I; Ciurea, ML; Iancu, V

Published: 2005, CAS 2005: INTERNATIONAL SEMICONDUCTOR CONFERENCE, 1-2, 58, DOI:

The paper presents the photoluminescence of nanocrystalline porous silicon. Two maxima were observed for rather fresh samples, one located at the infrared edge of the visible range and the other one in red. After ageing, the first maximum vanishes, suggesting its relation with the surface states, while the red one undergoes a significant blue shift. A simple quantum confinement model allows to correlate the photon energy of the red maximum with a transition between two confinement levels and to interpret the blue shift in terms of size reduction by oxidation. These results are in good agreement with previous microstructure measurements.

2701. Correlated photon-pair emission from a charged single quantum dot - art. no. 235308

Authors: Ulrich, SM; Benyoucef, M; Michler, P; Baer, N; Gartner, P; Jahnke, F; Schwab, M; Kurtze, H; Bayer, M; Fafard, S; Wasilewski, Z; Forchel, A

Published: JUN 2005, PHYSICAL REVIEW B, 71, DOI: 10.1103/PhysRevB.71.235328

The optical creation and recombination of charged biexciton and trion complexes in an (In,Ga)As/GaAs quantum dot is investigated by microphotoluminescence spectroscopy. Under the condition of quasiresonant pulsed excitation into the p shell we find nearly background-free photoluminescence from single quantum dots where multiple-photon (> 1) emission is fully suppressed. This reflects almost perfect triggered single-photon emission. Photon cross-correlation measurements demonstrate the temporally correlated decay of charged biexciton and trion states. Our calculations provide strong evidence for radiative decay from the excited trion state, thus indicating a long-lived p-electron spin configuration.

2702. Local interactions and electronic phenomena in substituted LaFeO3 perovskites

Authors: Russo, U; Nodari, L; Faticanti, M; Kuncser, V; Filoti, G

Published: JAN 14 2005, SOLID STATE IONICS, 176, 102, DOI: 10.1016/j.ssi.2004.06.001

Effects of electronic charge disproportionation were observed by Fe-57 Mossbauer spectroscopy at low temperatures in substituted LaFeO3 perovskites as (La1-xCax)FeO3 and La(Fe1-xMgx)O-3 (xless than or equal to0.5). The presence of both Fe3+ and Fe5+ species was evidenced in both series of compounds. Direct evidence for disproportionation was supported by correlating the Mossbauer results with the chemical determination of tetravalent iron at RT. The evolution of hyperfine parameters vs. substitution degree was comparatively analysed for Fe3+ and Fe5+ ions in relation to their electronic microscopic origin. Electron delocalisation processes are discussed in terms of ion distribution and valence state. (C) 2004 Elsevier B.V. All rights reserved.

2703. Preparation and properties of langasite and YAG amorphous films

Authors: Popescu, M; Sava, F; Lorinczi, A; Stegarescu, M; Georgescu, S; Mihailescu, IN; Socol, G; Stanoi, D; Daroczi, L; Kokenyesi, A; Leonovici, M; Wagner, D

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 966, DOI:

Amorphous thin films of langasite and YAG have been prepared from crystals targets by pulsed laser deposition, at room temperature, in vacuum, on silicon wafers. Bulges of micrometer size are formed on the film surface. Larger size bulges (10-50 micrometers in diameter) are characteristic to the annealed langasite films. Annealing at high temperatures leads to the crystallization of the films. The annealed langasite films (850 degrees C) are polycrystalline and partially oriented with the plane (001) parallel to the surface of the silicon wafer. The bulges break easily in the heat treated films. Their empty structure was remarked on the electron microscope images. The YAG films annealed at 1100 degrees C shows a crystalline YAG phase depleted in Y and traces of Y2O3. An interesting feature is the presence of silver particles spread along the macrodefects (fracture lines) of the film.

2704. Thermal behavior of substituted FeCo-based metallic glasses

Authors: Sorescu, M; Um, CY; McHenry, ME; Diamandescu, L

Published: APR 1 2005, JOURNAL OF NON-CRYSTALLINE SOLIDS, 351, 667, DOI: 10.1016/j.jnoncrysol.2005.01.062

Three compositions of metallic glasses, Fe58Co24Nb3Ta1Mo1B13, Fe61.5Co20.5Nb3Ta1Mo1B13 and Fe66Co18Si1B15 were prepared by rapid quenching from the melt and subsequently annealed for 1 hour at 450, 650 and 750 degrees C. The samples were analyzed by X-ray diffraction (XRD) and Mossbauer spectroscopy. All Mossbauer spectra were fitted with a six-line pattern corresponding to the crystalline alpha-(FeCo) phase and a hyperfine magnetic field distribution representing the amorphous component. The Moss-bauer spectra of annealed Fe66CO18B15 revealed the presence of a secondary crystalline phase, namely (FeCO)(3)(BSi). Moreover, the last Mossbauer spectrum in the set was fitted with an additional sextet, corresponding to the appearance of hematite in the system. It is inferred that the addition of Nb, Ta and Mo considerably delays the onset of bulk crystallization and iron oxidation in these systems. The XRD patterns are in qualitative agreement with the Mossbauer results and are consistent with a surface layer of hematite nanoparticles in the system. The activation energy of 4.34 eV for oxidation was estimated from the Mossbauer results. (c) 2005 Published by Elsevier B.V..

2705. Optical and electronic properties of the aluminophosphate glasses doped with 3d-transition metal ions

Authors: Elisa, M; Grigorescu, CEA; Vasiliu, C; Bulinski, M; Kuncser, V; Predoi, D; Filoti, G; Meghea, A; Iftimie, N; Giurginca, M

Published: OCT 2005, REVIEWS ON ADVANCED MATERIALS SCIENCE, 10, 374, DOI:

Aluminophosphate glasses doped with Fe, Mn, and Cr have been obtained by a wet non-conventional method. Structural information was provided by IR absorption spectra in the range 2000-500 cm(-1). The optical behaviour (transmission and refractive index) of the samples has been studied by UV-VIS-NIR spectroscopy. The Fe valence state and the local coordination were also analysed via Fe-57 Mossbauer spectroscopy, whose data revealed the redox equilibrium in the Fe-doped glasses according to the redox potentials of the transition ions.

2706. Coulomb scattering in nitride-based self-assembled quantum dot systems

Authors: Nielsen, TR; Gartner, P; Lorke, M; Seebeck, J; Jahnke, F

Published: DEC 2005, PHYSICAL REVIEW B, 72, DOI: 10.1103/PhysRevB.72.235311

We study the carrier capture and relaxation due to Coulomb scattering in group-III nitride quantum dots on the basis of population kinetics. For the states involved in the scattering processes the combined influence of the quantum-confined Stark effect and many-body renormalizations is taken into account. The charge separation induced by the built-in field has important consequences on the capture and relaxation rates. It is shown that its main effect comes through the renormalization of the energies of the states involved in the collisions and leads to an increase in the scattering efficency.

2707. Raman spectra of AsxSe100-x glasses doped with metals

Authors: Iovu, MS; Kamitsos, EI; Varsamis, CPE; Boolchand, P; Popescu, M

Published: JUN 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 1221, DOI:

Chalcogenide glasses in the system AsxSe100=x, as well as As40Se60 and As50Se50 glasses doped with metals (Bi, Ge, Cd, Ag, Sn, Mn, Dy and Sm) were investigated by Raman spectroscopy. The Raman spectra of AsxSe100-x with 0 <= x <= 10 suggest that the majority building units are Se chains and See closed rings. At higher As contents, new structural units are formed from As and Se atoms. The Raman profiles for x > 50 are characterized by the presence of strong narrow bands indicating the high ordering in the structure of these glassy materials. The doped samples with small amounts of metals, 0.1 - 1.0 at.%, do not show appreciable changes in their short-range order structure, with the exception of the 0.5 at.% Dy-doped sample. For the sample As50Se50+7.5 at.% Sn, there is direct evidence for the formation of new Sn-based structural units, such as Sn(Se-1/2)(4) tetrahedra.

2708. Metal-ferroelectric-metal heterostructures with Schottky contacts. I. Influence of the ferroelectric properties

Authors: Pintilie, L; Alexe, M

Published: DEC 15 2005, JOURNAL OF APPLIED PHYSICS, 98, DOI: 10.1063/1.2148622

A model for metal-ferroelectric-metal heterostructures with Schottky contacts is proposed. The model adapts the general theories of metal-semiconductor rectifying contacts for the particular case of metal-ferroelectric contact by introducing the ferroelectric polarization as a sheet of surface charge located at a finite distance from the electrode interface, a deep trapping level of high concentration, and the static and dynamic values of the dielectric constant. Consequences of the proposed model on relevant quantities of the Schottky contact such as builtin voltage, charge density, and depletion width, as well as on the interpretation of the current-voltage and capacitance-voltage characteristics are discussed in detail. (c) 2005 American Institute of Physics.

2709. Nondestructive evaluation of misfit dislocation densities in ZnSe/GaAs heterostructures by x-ray diffuse scattering

Authors: Alexe, G; Heinke, H; Haase, L; Hommel, D; Schreiber, J; Albrecht, M; Strunk, HR

Published: MAY 15 2005, JOURNAL OF APPLIED PHYSICS, 97, DOI: 10.1063/1.1896438

Estimating the low densities of misfit dislocations in epitaxial layers in the early stages of relaxation is difficult, requiring a very sensitive method. The characteristic patterns of diffuse x-ray scattering are therefore utilized to quantify the linear density of misfit dislocations. This is demonstrated for ZnSe/GaAs(001) heterostructures with ZnSe layer thickness slightly above the critical thickness. The densities that resulted from calculated patterns of x-ray scattering perpendicular to the diffraction vector are found to be in good agreement with the results of cathodoluminescence and transmission electron microscopy. Moreover, the diffuse x-ray scattering is used to quantitatively study the thermally induced increase in the linear densities of misfit dislocations. Samples are annealed at various temperatures for increasing periods successively and are analyzed between the annealing steps by high-resolution x-ray diffraction. The density of dislocations is found to saturate for longer annealing periods. The saturation value and the rate of increase of the dislocation density depend both on the annealing temperature and on the crystallographic direction. (c) 2005 American Institute of Physics.

2710. Photoluminescence of manganese- and copper-doped CdS nanowires

Authors: Ghiordanescu, V; Sima, M; Enculescu, I; Grecu, MN; Mihut, L; Secu, M; Neumann, R

Published: FEB 2005, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 202, 454, DOI: 10.1002/pssa.200406927

Arrays of US: Mn2+ : Cu+ micro- and nanowires grown in polycarbonate ion-track templates exhibit photoluminescence in the spectral domain ranging from 500 to 800 mn at room temperature. A comparison with similar US and CdS:Mn2+ wire arrays is presented. The individual contributions to the emission spectra of Cu+ and Mn2+ ions in the US matrix are explained using their energy level schemes. Also SEM, EDX and EPR data are given or these wires. (c) 2005 WILEY-VCH Verlag GmbH A Co. KGaA, Weinheim.

2711. Spin magnetoconductance in the mesoscopic spin-interferometer

Authors: Aldea, A; Tolea, M; Zittartz, J

Published: JUL 2005, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 28, 202, DOI: 10.1016/j.physe.2005.03.013

We investigate the properties of the electron spin-transmission through an Aharonov-Bohm interferometer with an embedded two-dimensional (2D) multilevel quantum dot containing magnetic impurities. A suitable formalism is developed. The amplitude and the phase of the flip- and non-flip-transmittances are calculated numerically as function of the magnetic field. The effects induced by the exchange interaction and those arising from the 2D character of the dot are shown. (c) 2005 Elsevier B.V. All rights reserved.

2712. Electron beam irradiation for biological decontamination of Spirulina platensis

Authors: Brasoveanu, M; Nemtanu, M; Minea, R; Grecu, MN; Mazilu, E; Radulescu, N

Published: OCT 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 240, 90, DOI: 10.1016/j.nimb.2005.06.093

The Cyanobacterium Spirulina is commercialized for its use in health foods and for therapeutic purposes due to its valuable constituents particularly proteins and vitamins. The aim of the paper is to study the Spirulina platensis behaviour when it is electron beam irradiated for biological decontamination. Microbial load, antioxidant activity, enzymatic inhibition, electron spin resonance (ESR) and UV-Vis spectra were measured for doses up to 80 kGy. The results were correlated with doses in order to find where decontamination is efficient, keeping the Spirulina qualities. (c) 2005 Elsevier B.V. All rights reserved.

2713. Heusler bulk materials as targets for pulsed laser deposition: growth and characterisation

Authors: Manea, AS; Monnereau, O; Notonier, R; Guinneton, F; Logofatu, C; Tortet, L; Garnier, A; Mitrea, M; Negrila, C; Branford, W; Grigorescu, CEA

Published: FEB 15 2005, JOURNAL OF CRYSTAL GROWTH, 275, E1792, DOI: 10.1016/j.jcrysgro.2004.11.213

This work concerns the preparation and characterisation of homogeneous bulk Co2Mn (Si, Ge, Ga, Sn Sb0.8Sn0.2) to be used as targets for pulsed laser deposition of magnetic contacts for spintronic devices. The samples have been prepared by direct synthesis from elemental powders followed by vertical gradient freeze. Characterisation of their structural properties and compositional homogeneity was performed by X-ray diffraction and energy-dispersive X-ray spectroscopy combined with scanning electron microscopy. The results show one-phase for the Heusler alloys. The Curie temperatures of the samples have been measured by both thermogravimetric analysis and differential scanning calorimetry and are in a good agreement with the previously published values. The saturation magnetisation values are close to the values for single crystals. (C) 2004 Elsevier B.V. All rights reserved.

2714. YBa2Cu3O7-delta : Li superconductor system investigated by direct microwave absorption method

Authors: Velter-Stefanescu, M; Duliu, OG; Sandu, V

Published: APR 2005, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 7, 977, DOI:

The influence of thermal neutrons irradiation at different fluencies on the superconductivity properties of Li (2 at. %) doped YBa2Cu3O7-delta system has been investigated by direct microwave absorption method. We have noticed changes of the superconducting properties of the 123 phase that depend on the neutron fluency. By increasing fluency, initially, the phase structure supports a disordering, then a re-ordering accompanied by a significant increase of the average critical temperature T-c to 85.7 K and finally we observed a degradation of the 123 the phase accompanied by a diminishing of T-c. The intragranular dephasing magnetic field B-d, i.e. the direct microwave absorption (DMA) parameter associated with the magnetic field dependence of the critical current density exhibited an opposite tendency, initially decreasing and then increasing at a value close to those of unirradiated samples. We also noticed only on the irradiated samples the presence of a flatness of the DMA curves around 0.5 T, consistent with the expression of a peak effect.

2715. Effect of neutron irradiation on some piezoelectric properties of PZT type ceramics

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Spanulescu, I; Cioangher, M

Published: SEP 2005, JOURNAL DE PHYSIQUE IV, 128, 120, DOI: 10.1051/jp4:2005128018

Soft and hard type piezoceramic sintered samples were subjected to neutron irradiation in fluxes up to, 10(18) n/cm(2) and the changes of the basic properties brought about by irradiation were investigated. The results showed that intermediate irradiation levels of up to 10(15) n/cm(2) do not change significantly the properties, but higher levels changed them. Thus the electromechanical coupling factor, the dielectric permittivity and losses decreased while the mechanical quality factor increases with increasing neutron flux for both types of materials. Changes of the lattice constants a and c were also observed. The main defects produced by neutron irradiation are oxygen vacancies but they are not entirely responsible for the modification of the materials properties. Some other factors such as domain pinning and lattice deformation can contribute to the properties degradation.

2716. Space-charge-limited current involving carrier injection into impurity bands of high-k insulators

Authors: Goldenblum, A; Pintilie, I; Buda, M; Popa, A; Botila, T; Dimoulas, A; Vellianitis, G

Published: MAY 16 2005, APPLIED PHYSICS LETTERS, 86, DOI: 10.1063/1.1935045

Photoelectrical measurements have shown that the current flow through La2Hf2O7 and LaAlO3 high-k insulator layers deposited on silicon takes place via impurity channels. A space charge limited current is evidenced, for different insulator thicknesses and temperatures, by the square law dependence of current versus voltage. The analysis demonstrates that this space charge limited (SCL) current in thin insulator films can be explained only by the presence of impurity channels situated near the Fermi level of the injecting contact. Many other aspects related to the SCL current behavior were found. (c) 2005 American Institute of Physics.

2717. Evidence for vortices in the pseudogap region of Y1-xPrxBa2Cu3O7 from angular magnetoresistivity measurements

Authors: Sandu, V; Cimpoiasu, E; Katuwal, T; Li, S; Maple, MB; Almasan, CC

Published: OCT 22 2004, PHYSICAL REVIEW LETTERS, 93, DOI: 10.1103/PhysRevLett.93.177005

In-plane angular magnetoresistivity Deltarho(ab)(anis) measurements were made on Y1-xPrxBa2Cu3O7-delta single crystals in the pseudogap region. For xgreater than or equal to0.2 single crystals, Deltarho(ab)(anis)(theta) displays a deviation from the typical quasiparticle contribution (proportional tosin(2)theta) for temperatures smaller than a certain value T-phi in the pseudogap region. This deviation is consistent with a flux-flow type contribution to angular magnetoresistivity, indicating the presence of vortexlike excitations above the zero-field critical temperature in the pseudogap region.

2718. Influence of TiC deposition by cvd on Hartmetal type steel substrate

Authors: Stegarescu, M; Hoyer, W

Published: JUN 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 495, DOI:

The structure and properties (crystallographic phases, hardness) of Hartmetal-type steel we re investigated. The modification of the Hartmetal surface as a consequence of a special treatment with the purpose to improve the hardness by deposition of TiC films by chemical vapour deposition (CVD) was carefully analysed.

2719. Manganese and copper doped CdS nanowire arrays preparation

Authors: Sima, M; Enculescu, I; Ioncea, A; Visan, T; Trautmann, C

Published: DEC 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 1198, DOI:

Manganese and copper doped CdS nanowires were obtained by the template technique in a two step process. In the first step metallic alloy CdMnCu nano and microwires were electrodeposited in ion track membranes with pore diameters in the range 150 nm-2 mum. In the following step the resulted nanowires were anodized in a sodium sulphide alkaline solution. Electron microscopy results show participation of the whole metallic wire in the anodization process; manganese and copper doped CdS wires are obtained The composition of micro and nanowires was determined by energy dispersive X-ray analysis.

2720. Chemical growth of calcium phosphate layers on magnetron sputtered HA films

Authors: Verestiuc, L; Morosanu, C; Bercu, M; Pasuk, I; Mihailescu, IN

Published: MAR 15 2004, JOURNAL OF CRYSTAL GROWTH, 264, 491, DOI: 10.1016/j.jcrysgro.2004.01.015

Chemical growth of calcium phosphate films on top of apatite structures is an essential step for promoting implants integration in human bones. We used for chemical growth silicon wafers either covered with crystalline and amorphous hydroxyapatite films or uncoated. To promote growing, the structures have been immersed in simulated body fluids for 21 days at 37degreesC. The growth stages were monitored by atomic spectroscopy of Ca and P ions in solution. The calcium phosphate deposits were investigated by X-ray diffraction, optical and atomic force microscopy and FTIR spectroscopy. The grown structures onto sputtered hydroxyapatite were amorphous and smooth. The depositions performed directly on silicon substrates are mild. (C) 2004 Elsevier B.V. All rights reserved.

2721. BNT ceramics synthesis and characterization

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Alexandru, H; Berbecaru, C; Ghetu, D; Stoica, G

Published: JUN 15 2004, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 109, 187, DOI: 10.1016/j.mseb.2003.10.116

Investigations on barium neodymium titanate (BNT) prepared by solid state reaction techniques are presented in this paper. The samples were sintered at temperatures, T-s, in a range 1200-1300degreesC. High density values and adequate microwave parameters were obtained by adding 0.5 mol PbO substitutional for BaO. A decrease of the Curie temperature with the increase of the Nd2O3 concentration was confirmed. For the sample with 28 wt.% Nd2O3, 0.5 mol PbO pyroelectric data indicate Curie temperature around 75 K, therefore, at room temperatures, the materials are in paraelectric phase. BNT ceramics with high Nd2O3 concentration (28 wt.%), sintered at 1250degreesC for 2 h appear to be suitable for dielectric resonators for frequencies up to 3 GHz (epsilon(r)=80-90 and Q = 2000). (C) 2003 Elsevier B.V. All rights reserved.

2722. Hydroxyapatite thin films grown by pulsed laser deposition and radio-frequency magnetron sputtering: comparative study

Authors: Nelea, V; Morosanu, C; Iliescu, M; Mihailescu, IN

Published: APR 30 2004, APPLIED SURFACE SCIENCE, 228, 356, DOI: 10.1016/j.apsusc.2004.01.029

Hydroxyapatite (HA) thin films for applications in the biomedical field were grown by pulsed laser deposition (PLD) and radio-frequency magnetron sputtering (RF-MS) techniques. The depositions were performed from pure hydroxyapatite targets on Ti-5Al-2.5Fe (TiAlFe) alloys substrates. In order to prevent the HA film penetration by Ti atoms or ions diffused from the Ti-based alloy during and after deposition, the substrates were pre-coated with a thin buffer layer of TiN. In both cases, TiN was introduced by reactive PLD from TiN targets in low-pressure N-2. The PLD films were grown in vacuum onto room temperature substrates. The RF-MS films were deposited in low-pressure argon on substrates heated at 550 degreesC. The initially amorphous PLD thin films were annealed at 550 degreesC for 1 h in ambient air in order to restore the initial crystalline structure of HA target. The thickness of the PLD and RF-MS films were similar to1 mum and similar to350 nm, respectively. All films were structurally studied by scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray spectrometry (EDS) and white light confocal microscopy (WLCM). The mechanical properties of the films were tested by Berkovich nano-indentation. Both PLD and RF-MS films mostly contain HA phase and exhibit good mechanical characteristics. Peaks of CaO were noticed as secondary phase in the GIXRD patterns only for RF-MS films. By its turn, the sputtered films were smoother as compared to the ones deposited by PLD (50 nm versus 250 nm average roughness). The R-F-MS films were harder, more mechanically resistant and have a higher Young modulus. (C) 2004 Elsevier B.V. All rights reserved.

2723. Amorphous thin films based on paraffin doped chalcogenides, prepared by pulsed laser deposition

Authors: Popescu, M; Sava, F; Lorinczi, A; Mihailescu, IN; Socol, G; Axente, E; Kaban, I; Hoyer, W

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 167, DOI:

A chalcogenide material of composition Se42S58, doped by 10 wt.% paraffins has been prepared as thin films by pulsed laser deposition. The structural properties of the films have been investigated by X-ray diffraction. Sample stabilization was carried out by annealing at temperatures around 100degreesC.

2724. Soft chemical synthesis and characterisation of some substituted ferrites

Authors: Olar, R; Badea, M; Diamandescu, L; Cristurean, E; Marinescu, D; Mihaila-Tarabasanu, D; Stanica, N; Brezeanu, M

Published: JAN 28 2004, JOURNAL OF ALLOYS AND COMPOUNDS, 363, 262, DOI: 10.1016/S0925-8388(03)00452-3

Substituted ferrites with the chemical composition MxFe1-xFe2O4-nH(2)O (M: Mn(II), x: 0.35, n: 0.4; M: Ni(II), x: 0.38, n: 1; M: Zn(II), x: 0.45, n: 0.35) have been prepared by a soft chemical method using as starting materials magnetite and suitable acetates. These compounds have been characterised by elemental chemical analysis, thermal analysis, IR spectroscopy, X-ray diffraction on powder, transmission electron microscopy studies as well as Mossbauer spectroscopy and magnetic measurements at room temperature. The X-ray diffraction study indicates that the substituted ferrites adopt a cubic structure and the size of particles determined from the diffraction peak is fairly close to that indicated for agglomerates by transmission electron microscopy. The magnetic methods agree to the substitution of Fe(II) in the octahedral positions preserving the inversed spinel structure. (C) 2003 Elsevier B.V. All rights reserved.

2725. Spectroellipsometric study of the sol-gel nanocrystalline ITO multilayer films

Authors: Stoica, TF; Gartner, M; Losurdo, M; Teodorescu, V; Blanchin, M; Stoica, T; Zaharescu, M

Published: MAY 1 2004, THIN SOLID FILMS, 455, 512, DOI: 10.1016/j.tsf.2003.11.251

Tin-doped indium oxide (ITO) thin films have been deposited by sol-gel process using 'sols' of indium and tin isopropoxides. The thickness of one deposited ITO layer is approximately 50 nm. The desired thickness was obtained by 1-5 successive depositions. The XTEM cross-sectional view of an ITO sample with five depositions showed a clear delimitation of the layers with an alternating structure dense/porous ITO layers. The void fraction in porous regions varies between 20 and 25%. Cubic bixbyite In2O3 nanocrystals with size of 10-20 nm and no phases separation of tin oxide were observed. The optical properties of the films have been investigated by optical transmission and spectroscopic ellipsometry. Reliable optical constants and porosity are obtained only with the model of internal structure based on XTEM results. (C) 2003 Elsevier B.V. All rights reserved.

2726. Methods for preparation of BaTiO3 thin films

Authors: Cernea, M

Published: DEC 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 1356, DOI:

Chemical, physical and electrochemical general methods used for deposition of various materials were tested for preparation of BaTiO3 films. Researchers are focusing on the influence of processing parameters on the stoichiometry and the properties of BaTiO3 films for each deposition method. Dielectric properties of BaTiO3 thin films prepared by different methods shown various values suggesting that the optimal parameters for deposition of BaTiO3 be not well known. Great efforts are concentrated on the economical aspect of the deposition process. In the case of BaTiO3 films, it is important to prepare crystallized films at low temperatures. The methods for deposition of BaTiO3 look into and develop continuous due to increase of the domain to use of BaTiO3 films.

2727. Synthesis of spinelic oxides using polynuclear malates coordination compounds. Nickel ferrite

Authors: Mindru, I; Patron, L; Carp, O; Marinescu, G; Pascu, M; Pascu, G; Diamandescu, L

Published: MAR-APR 2004, REVUE ROUMAINE DE CHIMIE, 49, 245, DOI:

Nickel ferrite was obtained by the thermal decomposition of three malates coordination compounds: [Fe2Ni(C4H4O5)(2.5)(OH)(2)]NO3.5H(2)O, [Fe2Ni(C4H8N2O3)(4)](NO3)(8).24H(2)O and (NH4)[Fe2Ni(C4H4O5)(3)(OH)(3)].3H(2)O. The solid state transformations were investigated by means of TG/DTA analysis, IR, X-ray diffraction, Mossbauer, magnetic and BET investigations. The solid state mechanisms, as well as the characteristics of the final products are strongly influenced by the nature of the precursors, especially by their homogeneity at atomic scale and composition.

2728. alpha-Fe2O3-In2O3 mixed oxide nanoparticles synthesized under hydrothermal supercritical conditions

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D

Published: OCT 2004, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 65, 1725, DOI: 10.1016/j.jpcs.2004.05.002

alpha-Fe2O3-In2O3 mixed oxide nanoparticles system has been synthesized by hydrothermal supercritical and postannealing route, starting with (1-x)Fe(NO3)(3)(.)9H(2)O(.)xIn(NO3)(3)(.)5H(2)O aqueous solution (x = 0-1). X-ray diffraction and Mossbauer spectroscopy have been used to study the phase structure and substitutions in the nanosized samples. The concentration regions for the existence of the solid solutions in the alpha-Fe2O3-In2O3 nanoparticle system together with the solubility limits of In3+ ions in the hematite lattice and of Fe3+ ions in the cubic In2O3 structure have been evidenced. In general, the substitution level is considerably lower than the nominal concentration x. A justification of the processes leading to the formation of iron and indium phases in the investigated supercritical hydrothermal system has been given. (C) 2004 Elsevier Ltd. All rights reserved.

2729. Impedance spectroscopy studies on doped polyanilines

Authors: Hui, D; Alexandrescu, R; Chipara, M; Morjan, I; Aldica, G; Chipara, MD; Lau, KT

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 824, DOI:

Impedance spectroscopy studies on polyaniline doped by various amounts of HCl are reported. The measurements were performed at room temperature, over a wide range of frequencies [1000 Hz to 45 MHz]. The experimental data shows that the resistance dominates the AC behavior of polyaniline confirming that the charge transport occurs through an one-dimensional hopping process.

2730. Facet oxidation and degradation of AlGaAs/GaAs pulsed laser diodes

Authors: Ghita, RV; Lazarescu, MF; Manea, AS; Logofatu, C; Vasile, E; Ciupina, V

Published: 2004, ROMOPTO 2003: SEVENTH CONFERENCE ON OPTICS, 5581, 273, DOI: 10.1117/12.582822

Oxide films grow in atmosphere as a result of oxidation reaction and mass transport of the element through the oxide film. In most III-V compounds (as GaAs) semiconductor oxides of III-element and V-element are formed individually. The AlGaAs/GaAs laser diodes were exposed to facet oxidation at mirror surfaces in normal environmental conditions for a storage process. It was observed a decrease of optical output power in the early stage of experiment together with a constancy of the ratio P/P(0) for the long time term (month). We suggest the development at the mirror laser facet of a natural oxide film as Ga2O3 and GaAsO.. We present a SEM (Scanning Electron Microscopy) image of a natural oxide film grown in atmosphere at the surface of AlGaAs as laser facet, as well as a picture of a facet oxidation of a laser device. The EDS (Electron Dispersion Spectrum) of a natural oxide put into evidence the O (Kalpha) signal. Dielectric coating using Al2O3 and a-Si layers protected a part of laser devices, and at the mirror surface a reflectivity of 70% in the emission range of the laser (890nm) was measured. The emitted power for dielectric coated devices was constant, so the rapid degradation process was slowed down.

2731. Local magnetic interactions in Fe/RE2Fe14B nanocomposite systems

Authors: Kuncser, V; Valeanu, M; Lifei, F; Jianu, A; Kappel, W; Filoti, G

Published: 2004, SECOND SEEHEIM CONFERENCE ON MAGNETISM, PROCEEDINGS, 3506, DOI: 10.1002/pssc.200405491

The Fe spin configurations in both the soft- and hard- magnetic phases of nanocomposite Fe/RE2Fe14B exchange-spring ribbons have been analysed by Mossbauer spectroscopy. New criteria for evaluating the inter-phase exchange-coupling strength are proposed. The coupling strength is discussed in relation to the annealing conditions and the relative content of the soft magnetic phase.

2732. Electron spin resonance and DC electrical investigations on chlorine doped polyanilines

Authors: Chipara, M; Aldica, G; Hui, D; Dimonie, M; Lau, KT; Georgescu, L; Munteanu, I; Marascoiu, H

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 305, DOI:

Electron spin resonance and DC electrical investigations on the effect of chlorine doping on emeraldine base polyaniline are reported. From the experimental data it is concluded that the chlorine doping of polyanilines increases the conductivity and that the charge transport is well described by an one dimensional variable range hopping, up to a doping level of 15% Cl/N. The characteristic temperature rises as the doping level is increased. Electron spin resonance investigations revealed the contribution of polarons to the charge transport. The absence of high spin bipolarons was proved by electron spin resonance data within the experimental errors. At high doping levels, the mesoscopic nature of charge transport in polyanilines is confirmed by the Dysonian shape of the resonance lines.

2733. Photo-induced transformations in glass

Authors: Popescu, M

Published: 2004, SEMICONDUCTING CHALCOGENIDE GLASS I: GLASS FORMATION, STRUCTURE, AND STIMULATED TRANSFORMATIONS IN CHALCOGENIDE GLASSES, 78, 213, DOI: 10.1016/S0080-8784(04)80047-4

2734. Fluorescence of substituted aromatic derivatives crystalline materials for optical non-linear applications

Authors: Stanculescu, A; Tugulea, L; Stanculescu, F; Socol, M

Published: 2004, ROMOPTO 2003: SEVENTH CONFERENCE ON OPTICS, 5581, 607, DOI: 10.1117/12.583028

Our fluorescence study gave information on the presence of chemical defects and irregularities in crystal structure, offering a good tool for quality evaluation of organic crystalline materials. We have analysed the correlation between the bulk or thin film samples' quality determined by experimental parameters (thermal gradient, moving speed of the growth interface, crucible configuration, slow or fast solidification rates) and the fluorescence characteristics for pure meta-dinitrobenzene and meta-dinitrobenzene doped with 8 hydroxyquinoline or 1,3 dihydroxybenzene. The comparative study of the position and shape of the fluorescence emissions for pure and controlled doped materials nave us information on the chemical defects.

2735. Pyroelectric current spectroscopy: example of application on Nb doped Pb(Zr0.92Ti0.08)O-3 ceramics for infrared detection

Authors: Pintilie, L; Pereira, M; Gomes, MJM; Boerasu, I

Published: SEP 21 2004, SENSORS AND ACTUATORS A-PHYSICAL, 115, 190, DOI: 10.1016/j.sna.2004.01.020

Pyroelectric current spectroscopy (PCS) was used to investigate the homogeneity of the Nb doped lead zirconate-titanate Pb(Zr-0.92 Ti-0.08)O-3, (PZT) ceramics intended to be used in the infrared (IR) pyroelectric detectors manufacturing. The non-homogeneous composition in the ceramic volume is reflected by the occurrence of several peaks in the PCS spectra, suggesting the presence of PZT phases with different Zr/Ti ratio, thus having different transition temperatures. The non-homogeneity was confirmed by compositional analysis performed using an Energy Dispersive X-ray Spectrometer (EDAX) attached to a Scanning Electron Microscope (SEM). PCS can be a useful tool in optimizing the calcination and sintering parameters (temperature and time) during ceramic preparation. (C) 2004 Elsevier B.V. All rights reserved.

2736. Anomalous current transients related to defect discharge in irradiated silicon diodes

Authors: Menichelli, D; Scaringella, M; Bruzzi, M; Pintilie, I; Fretwurst, E

Published: NOV 2004, PHYSICAL REVIEW B, 70, DOI: 10.1103/PhysRevB.70.195209

Nonmonotonic current transients at constant temperature, following a pulsed charge injection, have been observed in silicon diodes heavily irradiated with gamma rays. The features of the transients have been studied at different temperatures and using various reverse biases. The particular shape of the measured transients is interpreted, with the help of numeric simulations, in terms of a strong time dependency of the space charge density due to the discharge of radiation induced deep traps. In particular, a nonmonotonic transient is generated if the discharge of a dominant trap determines the change of the space charge sign (type inversion). In this case the active volume of the sample, from which the current is collected, is increased during the discharge and causes the sample to become fully depleted for a short time. During this time interval the active volume reaches its maximum value and a peak is produced in the transient shape. The measurement of this peak provides a sensitive way to detect type inversion in semiconductor devices and to determine the responsible energy levels. The correlation of nonmonotonic transients with thermally stimulated current spectra and the distortion produced in deep level transient spectroscopy spectra are discussed in detail.

2737. Nano-sized barium zirconate powders obtained by the sol-gel method

Authors: Dediu, OG; Crisan, M; Aldica, G; Zaharescu, M

Published: OCT 2004, REVUE ROUMAINE DE CHIMIE, 49, 817, DOI:

Nanoparticles of barium zirconate were obtained by the sol-gel method starting from different barium sources and zirconium n-butoxide in butanol. The intermediate wet gels were obtained by hydrolysis of the precursors with water excess, at room temperature. The dried gels were characterized by DTA and IR techniques and were thermally treated in air to obtain crystalline products. XRD and TEM methods proved the formation of barium zirconate nanopowders. According to XRD and TEM data, better results were obtained when starting with barium nitrate than with barium acetate precursors.

2738. Preparation and characterization of Ce-doped BaTiO3 thin films by pulsed laser deposition

Authors: Cernea, M; Ianculescu, A; Monnereau, O; Argeme, L; Bley, V; Bastide, B; Logofatu, C

Published: APR 15 2004, JOURNAL OF MATERIALS SCIENCE, 39, 2759, DOI: 10.1023/B:JMSC.0000021450.39778.81

Thin films of BaTiO3 doped with 5.5 mol% CeO2 have been deposited on Pt/Si substrate by pulsed laser deposition. These films crystallize on the tetragonal BaTiO3 structure without any preferential orientation. Ce-doped BaTiO3 films deposited by PLD at 675degreesC in 30 Pa ambient oxygen exhibits a smooth surface: mean surface roughness (Rms) of 48 nm, mean size of grain of similar to40 Angstrom, average size of aggregates of similar to 315 nm. Thin films as prepared presented good dielectric characteristics: dielectric constant and dielectrics loss ( tan delta) at a frequency of 1 KHz were 220 and 0.2, respectively. The temperature dependence of dielectric constant exhibited a diffuse ferroelectric to paraelectric phase transition at about 0 - 10degreesC. The ferroelectric nature of Ce-doped BaTiO3 film was confirmed by the hysteresis of the C-V curves. (C) 2004 Kluwer Academic Publishers.

2739. Mossbauer study of manganese-doped magnetite below the Verwey transition

Authors: Sorescu, M; Diamandescu, L; Brand, RA; Tarabasanu-Mihaila, D

Published: FEB 2004, MATERIALS LETTERS, 58, 888, DOI: 10.1016/j.matlet.2003.07.028

Samples of FC3-xMnxO4 (x=0-0.6) were studied below the Verwey transition (T=122, 77, and 4.2 K) by Fe-57 Mossbauer spectroscopy. Considering that Mn2+ substitutes for Fe2+ on octahedral sites, we inferred the existence of five subspectra at all temperatures, one for Fe3+ ions on tetrahedral sites, two for Fe3+ ions on octahedral sites, and two for Fe2+ ions on octahedral sites. The hyperfine magnetic fields of one Fe3+ sublattice and two Fe2+ sublattices decrease slightly with increasing the amount x of Mn substitutions. The results are consistent with the existence of localized octahedral Fe3+ and Fe2+ spin states below the Verwey temperature. (C) 2003 Elsevier B.V. All rights reserved.

2740. Structural and electrical properties of sol-gel deposited Pb(Zr0.92Ti0.08)O-3 thin films doped with Nb

Authors: Pintilie, L; Boerasu, I; Pereira, M; Gomes, WJM

Published: JUN 15 2004, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 109, 177, DOI: 10.1016/j.mseb.2003.10.043

Pb(Zr, Ti)O-3 (PZT) thin films with Zr/Ti ratio of 92/8 and doped with up to 4 at.% Nb were deposited by sol-gel on Pt coated Si substrates. The scope was to investigate the influence of Nb additive on the structural, optical and electrical properties of Zr-rich PZT phase. it was found that a residual pyrochlore phase stabilizes with increasing the Nb content. The remnant polarization, the coercive field, and the dielectric losses increase with increasing Nb content. The presence of the pyroelectric effect was also evidenced on as-deposited layers. The films have potential for light detection in the infrared region of the electromagnetic spectrum (pyroelectric effect). (C) 2003 Elsevier B.V. All rights reserved.

2741. Packing models of yttrium doped alpha-Al2O3: Study of porosity

Authors: Popescu-Pogrion, N; Bercia, R; Tirnovan, M

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 1075, DOI:

Dopant yttrium at 150 p.p.m. level (Y to Al atomic ratio) in ultra -high purity polycrystalline alumina has been found to be, together with the coefficient of porosity, the reason of grain growth : with abnormal grain growth (AGG) or with uniform grains. The powder, green bodies and sintering samples were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and packing models. In this paper we studied by mathematical modeling the correlation between structure of powder and green bodies in correlation with the porosity in sintering compacts. A formula, which describes the packing of the spherical-cylindrical homogeneous particles, has been obtained. The porosity of the low Y doped alpha-Al2O3 was investigated.

2742. Structural and magnetic properties of iron species/SiO2 nanocomposites obtained by sol-gel methods

Authors: Predoi, D; Kuncser, V; Zaharescu, M; Keune, W; Sahoo, B; Valeanu, M; Crisan, M; Raileanu, M; Jitianu, A; Filoti, G

Published: 2004, SECOND SEEHEIM CONFERENCE ON MAGNETISM, PROCEEDINGS, 3510, DOI:

The phase composition, local structure and magnetic interactions were investigated in FexOx-SiO2 nanocomposites obtained by modern sol-gel methods. The very sensitive method of Mossbauer spectroscopy has evidenced the strong influence of the silica matrix precursor on the iron phase composition in the initial composites as well as on the size distribution of the hematite nanoparticles obtained by suitable thermal annealing treatments.

2743. Magnetic interactions and spin structure in composite Fe/Nd2Fe14B systems

Authors: Kuncser, V; Valeanu, M; Lifei, F; Predoi, D; Palade, P; Schinteie, G; Crisan, O; Filoti, G

Published: MAY 2004, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, 799, DOI: 10.1016/j.jmmm.2003.12.1279

Local magnetic interactions and spin configurations in alpha-Fe/Nd2Fe14B composite exchange-spring magnets have been investigated by Mossbauer spectroscopy and the magnetic behaviour was analysed by magnetometry. A new method for the evaluation of the coupling strength between soft and hard magnetic phases is proposed. (C) 2003 Elsevier B.V. All rights reserved.

2744. Covalent functionalization of single-walled carbon nanotubes by aniline electrochemical polymerization

Authors: Baibarac, M; Baltog, I; Godon, C; Lefrant, S; Chauvet, O

Published: 2004, CARBON, 42, 3152, DOI: 10.1016/j.carbon.2004.07.030

Electrochemical polymerization of aniline in an HCl solution on a single-walled carbon nanotubes (SWNTs) film has been studied by Raman and FTIR spectroscopy. It is shown that this method leads to a covalent functionalization of SWNTs with polyaniline (PANI). A careful study in Raman scattering shows that the increase in the intensity of the band at 178cm(-1) associated with radial breathing modes of SWNTs bundles suggests an additional nanotubes roping with PANI as a binding agent. A post chemical treatment with the NH4OH solution of polymer-functionalized SWNTs involves an internal redox reaction between PANI and carbon nanotubes. As a result, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. (C) 2004 Elsevier Ltd. All rights reserved.

2745. New aspects in laser ablation process of the YBCO thin films

Authors: Branescu, M; Socol, G; Pantelica, D; Negoita, F; Lifei, F; Jaklovszky, J; Moldovan, A; Grigorescu, S

Published: 2004, ROMOPTO 2003: SEVENTH CONFERENCE ON OPTICS, 5581, 478, DOI: 10.1117/12.582974

In this paper, we report some experimental results concerning new aspects in laser ablation process of the YBCO thin film. Both structural and superconducting properties of the studied films were analyzed by transmission electron microscopy, selected area electron diffraction, elastic recoil detection analysis, Raman spectra, atomic force microscopy images and the ac magnetic susceptibility. We have obtained the epitaxial films with relative large area of c-axis grown film and high critical temperature, without any post ablation annealing process.

2746. Hydrothermal synthesis and structural characterization of (1-x)alpha-Fe2O3-xSnO(2) nanoparticles

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D; Teodorescu, VS; Howard, BH

Published: MAY 2004, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 65, 1029, DOI: 10.1016/j.jpcs.2003.10.062

Structural and morphological characteristics of (1 - x)alpha-Fe2O3-xSnO(2) (x = 0.0- 1.0) nanoparticles obtained under hydrothermal conditions have been investigated by X-ray diffraction (XRD), transmission Mossbauer spectroscopy, scanning and transmission electron microscopy as well as energy dispersive X-ray analysis. On the basis of the Rietveld structure refinements of the XRD spectra at low tin concentrations, it was found that Sn4+ ions partially substitute for Fe3+ at the octahedral sites and also occupy the interstitial octahedral sites which are vacant in alpha-Fe2O3 corundum structure. A phase separation of alpha-Fe2O3 and SnO2 was observed for x greater than or equal to 0.4 : the alpha-Fe2O3 Structure containing tin decreases simultaneously with the increase of the SnO2 phase containing substitutional iron ions. The mean particle dimension decreases from 70 to 6 DID, as the molar fraction x increases up to x = 1.0. The estimated solubility limits in the nanoparticle system (1 - x)alpha-Fe2O3-xSnO(2) synthesized under hydrothermal conditions are: x less than or equal to 0.2 for Sn4+ in alpha-Fe2O3 and x greater than or equal to 0.7 for Fe3+ in SnO2. (C) 2003 Elsevier Ltd. All rights reserved.

2747. High-T-c phase obtained in the Pb/Sb doped Bi-Sr-Ca-Cu-O system

Authors: Fruth, V; Popa, M; Ianculescu, A; Stir, M; Preda, S; Aldica, G

Published: 2004, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 24, 1830, DOI: 10.1016/S0955-2219(03)00449-7

Partial replacement of Bi by Pb and Sb produces materials of high-T-c pure phase, with antimony playing an important role in accelerating the formation of the phase with the higher superconductive transition in the Bi-Sr-Ca-Cu-O system. The influence of the antimony precursors on the superconducting phases mechanism formation was examined. Using a solid state reaction route, two nominal compositions Bi(1.6)Pb(0.3)Sb(0.1)Sr(2)Ca(2)Cu(3)Oy and Bi(1.6)Pb(0.4)Sb(0.1)Sr(2)Ca(2)Cu(4)Oy were investigated. The sources of antimony were Sb2O3 alphaSb(2)O(4) and a prepared mixture Bi1.9Sb0.1Ox. The mechanism formation of the phases upon annealing was investigated using X-ray diffraction and simultaneous thermal analysis. Electrical properties of the obtained materials were evaluated. The presence of the antimony ions determined a higher reactivity of the system as well as the promotion of the superconducting high-T-c phase enhancement. (C) 2003 Elsevier Ltd. All rights reserved.

2748. EPR characterization of Mn2+ impurity ions in PbWO4 single crystals

Authors: Nistor, SV; Stefan, M; Goovaerts, E; Nikl, M; Bohacek, P

Published: AUG-DEC 2004, RADIATION MEASUREMENTS, 38, 658, DOI: 10.1016/j.radmeas.2003.12.024

The electron paramagnetic resonance (EPR) properties of the Mn2+ ions in PbWO4 single crystals grown by the Czochralski method have been investigated in the X-band microwave frequency, at T = 20 K. The angular dependence of the EPR line positions obtained by rotating the magnetic field in the main crystallographic planes shows that the local symmetry at the Mn2+ impurity ions is tetragonal, strongly suggesting that the Mn2+ ions substitute for the Pb2+ lattice cations, without charge compensation. The resulting spin Hamiltonian parameters compare well with the corresponding values for the Mn2+ ions in other isomorphous tungstates. The observed strong angular variation of the EPR linewidth has been quantitatively described considering a random distribution of lattice strains. (C) 2003 Elsevier Ltd. All rights reserved.

2749. SERS spectroscopy studies on the electrochemical oxidation of single-walled carbon nanotubes in sulfuric acid solutions

Authors: Lefrant, S; Baibarac, M; Baltog, I; Mevellec, JY; Mihut, L; Chauvet, O

Published: JUL 22 2004, SYNTHETIC METALS, 144, 142, DOI: 10.1016/j.synthmet.2004.02.010

Surface-enhanced Raman scattering (SERS) and cyclic voltammetry (CV) were used to investigate oxidation-reduction processes of single-wall carbon nanotube (SWNT) films deposited on Au supports in 0.5 M H2SO4 solutions. In the potential range (0; +1000) and (0; +1500)mV versus saturated calomel electrode (SCE), the oxidation-reduction reactions of SWNT films are quasi-reversible and irreversible, respectively. Anodic polarization of SWNT films until +1000 mV versus SCE produced compounds similar to the bisulfate intercalated graphite. Regardless of excitation wavelength, i.e. 1064 or 676.4 nm, variation in the Raman spectra exhibited a decrease in the intensity of the bands associated with the radial breathing mode (RBM) situated in the 120-240 cm(-1) spectral range. Also an increase in the intensity of the D band is accompanied an up-shift of this band. A gradual decrease of the Breit-Wigner-Fano component was observed at lambda(exc) = 676.4 mn. Partial restoration of the Raman spectra was achieved by a subsequent alkaline solution treatment. Potentials higher than +1000 mV versus SCE resulted in SWNTs breakage and fragments of different length were formed such as closed-shell fullerene. This was observed in the SERS spectrum by: (i) the disappearance of the RBM band, (ii) the increased D-band shifted to ca. 1330 cm(-1) and (iii) the appearance of a new band at 1494 cm(-1), frequently observed also in the Raman spectrum of fullerenes on the type C-70, C-84, C-119, as well as in its derivative compounds (e.g. C60O, clathrates, etc.). Appearance and increase in the intensity of the Raman band at 1494 cm(-1) as result of an anodic polarization of the SWNT film in solution of H2SO4 0.5 M in 1-butanol is a further evidence of the nanotubes breakage. (C) 2004 Elsevier B.V. All rights reserved.

2750. Disorder effects on the properties of two-dimensional finite systems in perpendicular magnetic field: the tight binding approach

Authors: Aldea, A; Nita, M; Dinu, V; Tolea, M

Published: JUL 2004, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 241, 2096, DOI: 10.1002/pssb.200404781

We review some aspects concerning the disorder effects on the spectral properties of 2D electronic systems with relevance for the transport and orbital magnetism in perpendicular magnetic field. The lattice model and random Anderson disorder are used. The discussion is carried out separately for periodic and hard wall boundary conditions. The degree of localization is evidenced by the calculation of the inverse participation number of the eigenstates of the Hamiltonian and a striking asymmetry of the localization effect of states in the Landau band is reported. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2751. Pulsed laser deposition of biocompatible polymers: a comparative study in case of pullulan

Authors: Cristescu, R; Stamatin, I; Mihaiescu, DE; Ghica, C; Albulescu, M; Mihailescu, IN; Chrisey, DB

Published: APR 1 2004, THIN SOLID FILMS, 453, 268, DOI: 10.1016/j.tsf.2003.11.145

We report some results of a comparison between thin films of pullulan biopolymer obtained by pulsed laser deposition (PLD) and matrix-assisted pulsed laser evaporation (MAPLE). In experiments we used a KrF* laser source generating pulses of 248 nm and 20 ns pulse duration. We demonstrate by Fourier transformed infrared spectroscopy (FTIR) that MAPLE is more appropriate than conventional PLD for transfer with high structural fidelity of biopolymers from target to substrate. In case of MAPLE, besides FTIR spectra, atomic force microscopy micrographs and scanning electron microscopy images prove that the film composition and structure strongly depend on the solvent used for the targets preparation: distilled water, ethylene glycol, ethanol, tert-butanol and dimethyl sulfoxide. Our best results for pullulan deposition were obtained using dimethyl sulfoxide as a solvent. This is the first report of successful MAPLE deposition of this material as thin films. (C) 2003 Elsevier B.V. All rights reserved.

2752. New planar compact dual mode filters for mobile communications

Authors: Banciu, MG; Lojewski, G; Ioachim, A; Nedelcu, L; Militaru, N; Shen, A; Ramer, R

Published: 2004, 2004 International Semiconductor Conference, Vols 1and 2, Proceedings, 140, DOI:

A new type of dual mode filter is proposed for mobile communications systems in 900 MHz frequency bandwidth such as GSM or GPRS. The planar filters were developed on a 0.635 mm substrate with a 10.8 dielectric constant. Several methods of modes coupling were investigated. Each dual mode resonator has a square-shape with the edge 20.5 mm and contributes with two poles to the filter response.

2753. Effects of cobalt substitutions in spring magnets

Authors: Sorescu, M; Diamandescu, L; Valeanu, M; Jianu, A

Published: DEC 15 2004, JOURNAL OF MATERIALS SCIENCE, 39, 7389, DOI: 10.1023/B:JMSC.0000048757.56163.40

2754. Conduction mechanisms in silicon-based nanocomposites

Authors: Iancu, V; Draghici, M; Jdira, L; Ciurea, ML

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 56, DOI:

Electrical conduction mechanisms in Si-SiO2 nanocomposite films were experimentally investigated and theoretically modelled. The films with silicon volume concentration varying from 0% to 100% were deposited on rectangular quartz substrates. They were prepared by co-sputtering CVD from two targets, one of silicon and one of silicon dioxide. Their middle part is formed by Si nanodots embedded in SiO2. 50 parallel aluminium electrodes were deposited, forming 49 coplanar samples, centred around x = 45% Si concentration. The microstructure investigations proved that the silicon nanodots have diameters between 4 nm (x = 23%) and 36 nm (x = 81%). The current-voltage characteristics were measured at room temperature, in the -25 divided by +25 V interval. The obtained curves are symmetric and superlinear. As the current - voltage characteristic is determined by the maximum resistance met by the carriers in their path, the experimental curve is modelled by the field-assisted tunnelling under Coulomb blockade. The used parameters are correlated with previous results obtained on nanocrystalline porous silicon. The correlation coefficient between the theoretical formula and the experimental data is greater than 99.95%.

2755. EPR probing of low temperature structural phases of Rb2ZnCl4 crystals with Tl-0 and Tl2+ centers

Authors: Stefan, M; Nistor, SV; Goovaerts, E; Schoemaker, D

Published: MAR 2004, PHYSICAL REVIEW B, 69, DOI: 10.1103/PhysRevB.69.104107

Thallium related paramagnetic centers of Tl2+ (6s(1)) and Tl-0 (6p(1)) type were produced by low temperature x-ray irradiation in ferroelectric Rb2ZnCl4:Tl single crystals. Extensive EPR investigations have been performed in order to elucidate their intrinsic properties and sensitivity as paramagnetic probes for structural phase transitions studies. Compared to the s-type Tl2+ centers, already used in many such studies, it was found that the p-type Tl-0 centers are much more sensitive to the small variations in the local crystal field associated with these transformations. Their EPR spectra provided information about the unit cell tripling in the P2(1)cn phase, as well as the symmetry lowering and lattice dynamics in the C1c1 phase. The temperature induced, continuous changes observed in the EPR spectra of both Tl-0 and Tl2+ centers were explained by the influence of the soft modes responsible for the 74-K structural phase transition.

2756. Modelling of large molecular clusters in the non-crystalline As2S3

Authors: Popescu, M; Sava, F; Lorinczi, A

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 890, DOI:

Modelling of several large molecular clusters possible to be formed in non-crystalline arsenic chalcogenides (As2S3, As2Se3 or mixed compositions) during cooling down of the melts has been performed. The structure of minimum free energy was calculated in the frame of valence force field theory using a Monte-Carlo-Metropolis method. The structural characteristics of the clusters were computed after energy relaxation. There was demonstrated that specific cluster configurations of the type nano-hat, nano-pie and nanotube are crystallo-chemically compatible with the non-crystalline structure of the arsenic chalcogenides.

2757. Electric and ferroelectric properties of Pb(Zr0.2Ti0.8)O-3 thin films deposited by pulsed laser deposition on single crystalline substrates

Authors: Pintilie, L; Lisca, M; Alexe, M

Published: 2004, 2004 International Semiconductor Conference, Vols 1and 2, Proceedings, 418, DOI:

Epitaxial Pb(Zr0.2Ti0.8)O-3 (PZT) thin films were grown on single crystalline Nb-doped SrTiO3 (STON) substrates by Pulsed Laser Deposition (PLD). The top electrode was SrRuO3. The investigated electric and ferroelectric properties have revealed a strong asymmetry of the two PZT-electrode interfaces. A qualitative explanation based on the possible existence of a n(+) - p junction at the STON-PZT interface is suggested.

2758. The electrodeposition of semiconductor nanowires with thermoelectric properties using "template" method

Authors: Sima, M; Enculescu, I; Visan, T

Published: OCT 2004, REVISTA DE CHIMIE, 55, 746, DOI:

A binary telluride (CdTe) as well as a ternary telluride (PbSeTe) were electrodeposited in the pores of a track-etched polycarbonate membrane, resulting nanowires and nanotubes. Either acid or alkaline solutions were used for preparing CdTe compound, whereas the ternary PbSe1-xTex compound was deposited from an acid solution, only. The investigation of electrode mechanisms was performed by cyclic voltammetry. The nanostructures were visualized using scanning electron microscopy (SEM).

2759. X-ray diffraction and microscopy investigations of structural inhomogeneities in NiMnSb crystallised from the melt

Authors: Monnereau, O; Guinneton, F; Tortet, L; Garnier, A; Notonier, R; Cernea, M; Manea, SA; Grigorescu, C

Published: NOV 2004, JOURNAL DE PHYSIQUE IV, 118, 350, DOI: 10.1051/jp4:2004118040

Our present work investigates the structural properties of bulk NiMnSb prepared by growth from the melt, using various thermal regimes. We studied the compositional behaviour of the polycrystalline material obtained from stoichiometric 1: 1:1 and respectively off-stoichiometric melts. The latter samples were grown with Mn excess up to 10% and respectively Ni deficiency between 2 and 10%. The X-ray diffraction and the Scanning electron microscopy complement each other in the characterisation of the phases occurring in the samples. The synthesis of NiMnSb starting from an initially stoichiometric mixture associated with a thermal treatment presenting plateaus gives the best results. Also, it seems that the presence of an excess of Mn is not sufficient to prevent the occurrence of the NiSb stray phase.

2760. Poly (vinyl-alcohol) films for microphotonics

Authors: Obreja, P; Cristea, D; Budianu, E; Gavrila, R; Kusko, M; Kuncser, V

Published: 2004, 16TH INTERNATIONAL CONFERENCE ON MICROELECTRONICS, PROCEEDINGS, 679, DOI:

The paper presents experimental results concerning the influence of additives from a solution of the PVA on the optical properties of the polymer. The refractive index of the poly (vinyl-alcohol) was modified through the addition of inorganic materials and showed values between 1.5 and 2 (depending on the compositions and the curing conditions of the polymer. The transmittance indicated values above 80%. The additives we used were metal oxides/inorganic salts. The composition and the deposition processes were optimized to allow a better control of the optical parameters (refractive index, transmittance), to reduce the processing temperatures and to improve photosensitivity. PVA with these new light-sensitive compositions can be easily spin coated onto variety of semiconductor substrate and directly patterned. A process was developed for channel waveguides fabrication.

2761. The first specimen of tetranuclear (Fe-III, Ln(III)) clusters assembled by carboxylate ligands: synthesis, structure, Mossbauer spectra, and magnetic properties of [Fe3EuO2(CCl3COO)(8)H2O(THF)(3)]center dot THF

Authors: Turta, C; Prodius, D; Mereacre, V; Shova, S; Gdaniec, M; Simonov, YA; Kuncser, V; Filoti, G; Caneschi, A; Sorace, L

Published: APR 2004, INORGANIC CHEMISTRY COMMUNICATIONS, 7, 579, DOI: 10.1016/j.inoche.2004.02.025

The reaction of the neutral cluster [Fe2BaO(CCl3COO)(6)(THF)(6)] with Eu(NO3)(3) . 6H(2)O in methanol affords novel tetra-nuclear Fe-Eu complex [Fe3EuO2(CCl3COO)(8)H2O(THF)(3)] . THF (1), which displays interesting Mossbauer spectra and magnetic behaviour. (C) 2004 Elsevier B.V. All rights reserved.

2762. Size-strain line-broadening analysis of the ceria round-robin sample

Authors: Balzar, D; Audebrand, N; Daymond, MR; Fitch, A; Hewat, A; Langford, JI; Le Bail, A; Louer, D; Masson, O; McCowan, CN; Popa, NC; Stephens, PW; Toby, BH

Published: DEC 2004, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 37, 924, DOI: 10.1107/S0021889804022551

The results of both a line-broadening study on a ceria sample and a size - strain round robin on diffraction line-broadening methods, which was sponsored by the Commission on Powder Diffraction of the International Union of Crystallography, are presented. The sample was prepared by heating hydrated ceria at 923 K for 45 h. Another ceria sample was prepared to correct for the effects of instrumental broadening by annealing commercially obtained ceria at 1573 K for 3 h and slowly cooling it in the furnace. The diffraction measurements were carried out with two laboratory and two synchrotron X-ray sources, two constant-wavelength neutron and a time-of-flight (TOF) neutron source. Diffraction measurements were analyzed by three methods: the model assuming a lognormal size distribution of spherical crystallites, Warren-Averbach analysis and Rietveld refinement. The last two methods detected a relatively small strain in the sample, as opposed to the first method. Assuming a strain-free sample, the results from all three methods agree well. The average real crystallite size, on the assumption of a spherical crystallite shape, is 191 (5) Angstrom. The scatter of results given by different instruments is relatively small, although significantly larger than the estimated standard uncertainties. The Rietveld refinement results for this ceria sample indicate that the diffraction peaks can be successfully approximated with a pseudo-Voigt function. In a common approximation used in Rietveld refinement programs, this implies that the size-broadened profile cannot be approximated by a Lorentzian but by a full Voigt or pseudo-Voigt function. In the second part of this paper, the results of the round robin on the size - strain line-broadening analysis methods are presented, which was conducted through the participation of 18 groups from 12 countries. Participants have reported results obtained by analyzing data that were collected on the two ceria samples at seven instruments. The analysis of results received in terms of coherently diffracting, both volume-weighted and area-weighted apparent domain size are reported. Although there is a reasonable agreement, the reported results on the volume-weighted domain size show significantly higher scatter than those on the area-weighted domain size. This is most likely due to a significant number of results reporting a high value of strain. Most of those results were obtained by Rietveld refinement in which the Gaussian size parameter was not refined, thus erroneously assigning size-related broadening to other effects. A comparison of results with the average of the three-way comparative analysis from the first part shows a good agreement.

2763. Effect of dopant on the intrinsic properties of some multifunctional aromatic compounds films for target applications

Authors: Stanculescu, A; Antohe, S; Alexandru, HV; Tugulea, L; Stanculescu, F; Socol, M

Published: DEC 7 2004, SYNTHETIC METALS, 147, 220, DOI: 10.1016/j.synthmet.2004.07.010

UV-VIS transmission and fluorescence spectroscopy have been used to study some intrinsic properties of crystalline films of pure metadinitrobenzene (m-DNB) and, pure and doped benzil. We have evaluated the band gap energy, E-g = 2.92 eV, emphasising the near classical semiconductor behaviour of m-DNB. The two bands split of the (n, pi*) level is assumed to be the origin the two edges absorption in benzil films with the energetic thresholds at E-g1 = 2.84 eV and E-g2 = 3.55 eV. The red shift of the emission peak in m-DNB films has been correlated with the process of self-absorption of the emitted radiation in the thicker film. The effect of the impurities on the shape and position of the emission peaks in benzil has been investigated and we have observed no significant shift of the absorption peak situated at 3.25 eV. We also have identified a three steps process for the relaxation of the excited crystalline lattice of benzil involving the geometrical change of the (S-1) excited state, the intersystem crossing and the radiative decay by phosphorescence with a peak at 2.30 eV. The small blue shift of this emission peak in benzil highly doped with sodium has been attributed to the modification of the molecular geometry of benzil as a result of the change in the trans-planar molecular configuration induced by the chemical reaction between the atoms of alkali metal and the carbonyl groups. (C) 2004 Elsevier B.V All rights reserved.

2764. X-ray diffraction on cyanide-hardened iron plates

Authors: Popescu, M; Hoyer, W; Stegarescu, M; Cornet, A; Broll, N

Published: NOV 2004, JOURNAL DE PHYSIQUE IV, 118, 353, DOI: 10.1051/jp4:2004118041

2765. Correlation of structure and magnetism of AgCo nanoparticle arrays

Authors: Crisan, O; Angelakeris, M; Nogues, M; Kehagias, T; Komninou, P; Sobal, N; Giersig, M; Flevaris, NK

Published: MAY 2004, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, E1254, DOI: 10.1016/j.jmmm.2003.12.304

The bimetallic AgCo nanoparticles synthesized by colloidal chemistry and deposited onto Si(100) substrate are investigated. Size-selective mechanisms of colloidal crystallization during the self-organization are evidenced. The magnetic behavior is studied and correlated with the nanoparticles structure and morphology. (C) 2003 Elsevier B.V. All rights reserved.

2766. Carbon material deposition by remote RF plasma beam

Authors: Mitu, B; Vizireanu, S; Petcu, C; Dinescu, G; Dinescu, M; Birjega, R; Teodorescu, VS

Published: MAR 1 2004, SURFACE & COATINGS TECHNOLOGY, 180, 243, DOI: 10.1016/j.surfcoat.2003.10.147

Hydrogenated and nitrogenated carbon films were obtained by PECVD with carbon species supplied by acetylene gas injected into an argon or argon/nitrogen remote plasma generated by an expanding radiofrequency discharge. The properties of carbon material like the nature of bonds, morphology, surface topography, crystallinity are presented. The reaction pathways linking the precursors with the depositing species, as revealed by emission spectroscopy, are discussed. (C) 2003 Elsevier B.V. All rights reserved.

2767. Possible nano-tube configurations in arsenic chalcogenides

Authors: Lorinczi, A; Popescu, M; Sava, F

Published: JUN 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 492, DOI:

Modeling of nano-tube clusters based on As,S(Se)(3) has been performed. The structural data were calculated on a single nano-tube model of As2S3. For the first time electron microscope images of nanometer size objects in As2Se3 and AS(5.5)Se(4.5) glass have been observed and discussed.

2768. Naturally generated beams by quasi-optical phenomena

Authors: Branescu, M

Published: 2004, FREE AND GUIDED OPTICAL BEAMS, 235, DOI: 10.1142/9789812702531_0024

The paper describes the specific quasi-optical phenomena involved in the generation of the celestial and biological radiation. It examines the generation of the free space and guided biological beams in the presence of the ambient celestial primordial isotropic background. Josephson and Kerr mechanisms provide an explanation of the concept of bio-coherence as a novel possibility of electromagnetic communication.

2769. A study of the corrosion inhibition of carbon-steel in dilluted ammonia media using 2-mercapto-benzothiazol (MBT)

Authors: Samide, A; Bibicu, I; Rogalski, M; Preda, M

Published: 2004, ACTA CHIMICA SLOVENICA, 51, 136, DOI:

The inhibiting effect of MBT has been studied regarding the corrosion of carbon-steel in diluted ammonia solution at room temperature. The effects of the inhibitor have been demonstrated using weight loss and electrochemical measurements. The increase of the inhibitor concentration leads to a decrease in the corrosion rate and in the corrosion current. The microscopic analysis of the surface of the electrode shows a decrease of the corrosion spots with the increase of the MBT concentration. This indicates a good adsorbability of MBT on the metal surface. Mossbauer spectrometry shows the formation of a superficial film on the surface of the corroded sample in the presence of MBT. This film provides a good corrosion protection for the sample.

2770. Modeling of the amorphous diamond-like carbon

Authors: Popescu, M; Sava, F; Bradaczek, H

Published: NOV 2004, JOURNAL DE PHYSIQUE IV, 118, 96, DOI: 10.1051/jp4:2004118011

The atomic ordering of the amorphous diamond-like carbon at the scale larger than short-range order is directly related to the characteristics of the array of interstitial voids. The large interstitial voids are responsible for the first diffraction peak, while the smaller ones (second and third order size of the voids) are responsible especially for the intensity and position of the second peaks in the interference function (structure factor).

2771. The closed cluster model and the charged coordination defects in chalcogenide glasses

Authors: Popescu, M

Published: DEC 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 1152, DOI:

A closed cluster model for the binary arsenic-chalcogen glasses seems to be attractive for the explanation of the structural and electronic properties of non-crystalline chalcogenides. In the same time the direct consequence of the model is the absence of the defects of coordination. The full implication is discussed.

2772. Magnetic interactions and spin configuration in FeRh and Fe/FeRh systems

Authors: Kuncser, V; Keune, W; Sahoo, B; Duman, E; Acet, M; Radu, F; Valeanu, M; Crisan, O; Filoti, G

Published: MAY 2004, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, 350, DOI: 10.1016/j.jmmm.2003.11.199

The magnetic interactions and the Fe spin structure have been studied in Fe(6 nm)/FeRh systems by magnetometry, magneto-optic Kerr effect and conversion electron Mossbauer spectroscopy. A spin-flop coupling mechanism, with the interfacial spins of the ferromagnetic phase perpendicular to the spins of the antiferromagnetic phase was experimentally proved. (C) 2004 Elsevier B.V. All rights reserved.

2773. Doped TGS crystals for IR detection and sensors

Authors: Alexandru, HV; Berbecaru, C; Stanculescu, F; Pintilie, L; Matei, I; Lisca, M

Published: AUG 16 2004, SENSORS AND ACTUATORS A-PHYSICAL, 113, 392, DOI: 10.1016/j.sna.2004.03.046

Triglycine sulfate crystals (TGS) doped With L- and D-alanine, respectively, where grown in paraelectric phase at 52 degreesC. They show stable parameters versus pure TGS crystals, lower permittivities and losses, i.e. higher pyroelectric figure of merit. L- and D-alanine-doped crystals show a mirror asymmetry of the growth habit along the ferroelectric axis. Hysteresis loop of pure and doped samples were automatically recorded. Internal bias field of about I kV/cm, induced by the two dopants, stabilizes the polarization components P+ and P- in opposite directions. Spontaneous polarization of doped crystals shows two unequal P+/P- components, having a peculiar dependence on the ac applied electric field. Dopage simulation of pure TGS samples, using several bias fields, shows even more complicated pattern. Pyroelectric coefficients were evaluated from pyroelectric current measurements. A remarkable asymmetry of the pyroelectric coefficient peak values for the enantiomorphous-doped crystals was noticed, crossing up and down the Curie point. This fact suggests a non-equivalent L/D-alanine dopant substitution of the glycine group GI in the host lattice. It has been shown that the pyroelectric coefficient can be increased at room temperature, under an optimized dc electric field applied on the pyroelectric wafer. Doped crystals are suitable for IR detector and for more stable gas sensors applications in pollution monitoring. (C) 2004 Elsevier B.V. All rights reserved.

2774. Structural and magnetic properties of polypyrrole nanocomposites

Authors: Turcu, R; Peter, I; Pana, O; Giurgiu, L; Aldea, N; Barz, B; Grecu, MN; Coldea, A

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 417, 727, DOI: 10.1080/15421400490478939

We report the synthesis and characterization of conducting polymer nanocomposites based on polypyrrole (PPY) and Fe2O3 magnetic particles. The global structure of PPY nanocomposites was obtained by X-ray Diffraction (XRD) method using a new approximation based on Generalized Fermi Function. The local structural parameters of Fe sites in Fe2O3 nanocrystallites embedded in PPY were determined by X-ray Absorption Spectroscopy (EXAFS). The lack of hysteresis loop for the magnetization curves of the composite PPY-Fe2O3 indicates a superparamagnetic behavior which is typical for nanosized magnetic particles.

2775. Microstructure of Si/Sio(2) nanocomposite films

Authors: Teodorescu, VS; Ciurea, ML; Iancu, V; Blanchin, MG

Published: 2004, 2004 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1AND 2, PROCEEDINGS, 62, DOI: 10.1109/SMICND.2004.1402802

The paper presents the inicrostructure of the Si/SiO2 nanocomposite films prepared by co-sputtering from Si and SiO2 targets. High resolution transmission electron microscopy and electron diffraction were used to reveal and compare the structures with different silicon/oxygen (SiOx, 0 < x < 2) coinposition. Si nanocrystallites have been evidenced clearly in the SiO1.6 areas. Percolation limits between the Si crystallites was observed in the x=1 areas. The morphology of the Si nanocrystallites and the amorphous SiO2 zones were compared in regions with different composition.

2776. Structure and electrical properties of electron irradiated CdSe thin films

Authors: Ion, L; Antohe, S; Popescu, M; Scarlat, F; Sava, F; Ionescu, F

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 119, DOI:

Structural and electrical properties of polycrystalline CdSe thin films irradiated with high-energy electrons are analyzed. The samples were prepared by vacuum deposition onto optical glass substrate. Their structure and the temperature dependence of the electrical resistance were determined, both before and after irradiation with 6 MeV electrons and fluencies up to 10(16) electronS/cm(2). There were no measurable changes in the crystalline structure of the films after irradiation. Electrical properties are controlled by a defect level of donor type, possibly a selenium vacancy, with two charge states having ionization energies of about 0.40 eV, respectively 0.22 eV. Irradiation increases significantly the concentration of those defects.

2777. Optical and electronic properties of polyvinyl alcohol doped with pairs of mixed valence metal ions

Authors: Bulinski, M; Kuncser, V; Plapcianu, C; Krautwald, S; Franke, H; Rotaru, P; Filoti, G

Published: SEP 7 2004, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 37, 2441, DOI: 10.1088/0022-3727/37/17/015

The electronic mechanisms induced by the UV exposure of thin films of polyvinyl alcohol doped with pairs of mixed valence metal ions were studied in relation to their optical behaviour by Mossbauer spectroscopy and optical absorption. The results obtained definitely point to the role of each element from the pair in the electronic mechanism involved, with influence on the optical properties regarding applications in real-time holography and integrated optics.

2778. Nematic-isotropic interfacial tension anisotropy of a calamitic lyotropic liquid crystal

Authors: Beica, T; Moldovan, R; Tintaru, M; Puica, MR; Enache, I; Frunza, S

Published: MAR 2004, LIQUID CRYSTALS, 31, 332, DOI: 10.1080/02678290410001648642

In a planar oriented sample of a calamitic nematic lyotropic system ( mixture of sodium lauryl sulphate/water/decanol), isotropic pretransitional domains appear at the nematic to isotropic transition. The domains are oblong in shape with the long axis along the orientational direction. We show experimental evidence that this oblong shape is determined by the nematic-isotropic interfacial tension anisotropy. Two uniparametric models of simple angular dependences for the interfacial tension are tested. Using the differential system obtained from the Young-Laplace condition at the nematic-isotropic interface, the domain shape can be numerically calculated for each value of the interfacial tension anisotropy. By processing the values of the transmitted light through both an isolated isotropic domain and its surrounding nematic zone, we obtain the anisotropy of the interfacial tension as the main fitting parameter. An estimation of the ratio of the extreme values for the interfacial tension is given.

2779. Epoxidation of cyclohexene on silicalite embedded BiOx clusters

Authors: Parvulescu, VI; Florea, M; Gelbard, G; Centeno, MA; Macovei, D; Lemay, G; Kaliaguine, S

Published: 2004, RECENT ADVANCES IN THE SCIENCE AND TECHNOLOGY OF ZEOLITES AND RELATED MATERIALS, PTS A - C, 154, 2654, DOI:

Silicalite embedded BiOx Clusters were prepared both with and without Na using sodium silicate and tetraethylorthosilicate as silicium precursors. Catalysts with 3 and 5 wt% Bi were obtained. The MFl structure was established from XRD, TEM, and N-2 adsorption measurements. No deterioration of the silicalite framework by bismuth was observed. Bi exists as BiOx clusters as evidenced from XPS and EXAFS characterization. These clusters are localized inside the silicalite channels. Py-FTIR measurements indicated that 5wt% Bi led to the formation of strong Lewis acid sites. Epoxidation of cyclohexene was found to depend oil both Bi and Na content. On 3%Bi-ZSM-5 it occurred with rather good conversion and selectivity to epoxide. No visible leaching was evidenced. The catalysts were reused for several runs.

2780. Flux lenses in the crossing lattices regime of layered superconductors

Authors: Cole, D; Crisan, A; Bending, SJ; Tamegai, T; van der Beek, K; Konczykowski, M

Published: MAY 1 2004, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 404, 102, DOI: 10.1016/j.physc.2003.09.108

We report here measurements of flux lensing behaviour which have been performed on Bi2Sr2CaCu2O8+delta single crystals placed on top of linear Hall probe arrays. In the crossing lattices regime we observe significant flux focussing as the in-plane field is swept up with a small constant density of pancake vortices. We also observe a sharp discontinous lock-in feature in local magnetic induction when the net field is close to the a-b plane. (C) 2004 Elsevier B.V. All rights reserved.

2781. C-60 aggregates in pyrrolidine and N-methyl-2-pyrrolidinone evidenced by surface-enhanced Raman scaterring spectra

Authors: Baibarac, M; Preda, N; Mihut, L; Velula, T; Baltog, I; Mevellec, JY; Lefrant, S

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 417, 587, DOI: 10.1080/15421400490478434

At room temperature, soluted C-60 in pyrrolidine and N-methyl-2-pyrrolidinone associates slowly in stable aggregates. The process originates in the charge transfer from the solvent molecules as electron donors towards fullerene. In the aggregate phase the intermolecular interactions lead to a large reduction in parent I-h C-60 symmetry such that a modified phonon spectrum is observed. Using the surface-enhanced Raman scattering we demonstrate that the Raman range below 800 cm(-1) is most diagnostic for aggregate assignment. In particular, the strong decrease of the radial breathing mode and appearance of new bands at 110 and 93 cm(-1) due to the interball interactions must be noticed.

2782. Sers spectra of polyaniline/carbon nanotubes and polyaniline/fullerene composites

Authors: Baibarac, M; Baltog, I; Lefrant, S; Mevellec, JY; Chauvet, O

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 415, 155, DOI: 10.1080/15421400490481269

SERS and FTIR spectra of M and S composites, provided by adding of single-walled carbon nanotubes (SWNTs) to the polyaniline (PANI) solution and chemical polymerization of aniline, respectively are different. The difference originates in the irreversible transformation of SWNTs in the polymerization medium. This explains the similarity of SERS and FTIR spectra of PANI/SWNTs and PANI/C-60 composites, chemically synthesized. For M composites, strong hindrance effects are evidenced by band at 773-755 cm(-1) associated to the vibration of deformation of the benzene and quinoid ring. The charge transfer is illustrated for all compounds by absorption band at 1144 cm(-1).

2783. Influence of deep levels on space charge density at different temperatures in gamma-irradiated silicon

Authors: Menichelli, D; Scaringella, M; Miglio, S; Bruzzi, M; Li, Z; Fretwurst, E; Pintilie, I

Published: SEP 1 2004, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 530, 145, DOI: 10.1016/j.nima.2004.05.062

In this work, it is shown that the analysis of thermally stimulated currents (TSC) and current transients (CT) at constant temperature can be a suitable tool to study the influence of deep levels on space charge density N(T) in irradiated silicon diodes. In particular, the occurrence of space charge sign inversion (SCSI) can be related to signal discontinuities in TSC and CT measurements. This approach has been adopted in this work to study devices made of standard Float Zone (FZ) and Diffusion Oxygenated Float Zone silicon, irradiated by gamma-rays up to a dose of 300 Mrad. Our study shows that all the samples are inverted at 50 K after a low-temperature excitation. Several space charge sign inversions, from positive to negative and vice versa, have been observed between cryogenic and room temperature, and have been related to carriers emission from dominating deep traps. Only standard FZ silicon remains inverted at room temperature after a dose of 300 Mrad. (C) 2004 Elsevier B.V. All rights reserved.

2784. Deposition of hydroxyapatite thin films by Nd : YAG laser ablation: a microstructural study

Authors: Nistor, LC; Ghica, C; Teodorescu, VS; Nistor, SV; Dinescu, M; Matei, D; Frangis, N; Vouroutzis, N; Liutas, C

Published: NOV 2 2004, MATERIALS RESEARCH BULLETIN, 39, 2101, DOI: 10.1016/j.materresbull.2004.07.006

Hydroxyapatite (HA) thin films has been successfully deposited by Nd:YAG laser ablation lambda = 532 nm. The morphology and microstructure of the deposited layers was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Polycrystalline HA films were directly obtained with the substrate at 300 degreesC and without introducing water vapors in the deposition chamber. Electron paramagnetic resonance (EPR) measurements show that the oxygen stoichiometry in the HA films is also maintained. Depositions performed at lambda = 335 nm laser wavelength and 300 degreesC substrate temperature resulted in polycrystalline layers of mixed composition of HA and tricalciumphosphate (TCP). (C) 2004 Elsevier Ltd. All rights reserved.

2785. Spin magnetization of a strongly correlated electron gas confined in a two-dimensional finite lattice

Authors: Nita, M; Dinu, V; Aldea, A; Tanatar, B

Published: FEB 2004, PHYSICAL REVIEW B, 69, DOI: 10.1103/PhysRevB.69.073106

The influence of disorder and interaction effects on the ground state polarization of the two-dimensional correlated electron gas is studied by numerical investigations of the unrestricted Hartree-Fock approach. With the model of Anderson disorder a continuous increase of the spin magnetization until the fully polarized regime is obtained. The ferromagnetic ground state is found to be favorable when the electron number is lowered and the interaction and disorder parameters are suitably chosen.

2786. Steel corrosion in diluted ammoniac solutions studied by Mossbauer spectrometry

Authors: Bibicu, I; Samide, A; Preda, M

Published: AUG 2004, MATERIALS LETTERS, 58, 2653, DOI: 10.1016/j.matlet.2004.03.043

The corrosion product films that were formed on industrial, low-carbon concentration Fe-C steel after immersion in diluted ammoniac solutions were investigated by 57 Fe Mossbauer spectroscopy. The amorphous Fe3+ oxyhydroxide was the major constituent of the corrosion layers. Layer thickness increased as NH3 concentration changed from 10(-1) to 10(-4) N. All GEMS spectra indicated a magnetic anisotropy on the surface of the samples. (C) 2004 Elsevier B.V. All rights reserved.

2787. Modelling of the complex carbon structure: Fullerene-nanotubule

Authors: Lorinczi, A; Popescu, M; Sava, F; Anghel, A

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 352, DOI:

The complex structure fullerene(C-60)-nanotubule has been built from special plastic units and relaxed by a computer Monte-Carlo - Metropolis procedure. The purpose was to show that interconnection fullerene-nanotubule is possible from the energetical point of view. The results open the way towards the assessing the possibility to create nano-conductors and connections between different parts of nano-devices, using nano-carbon configurations filled by metal atoms.

2788. Influence of the co-precipitation pH on the physico-chemical and catalytic properties of vanadium aluminum oxide catalyst

Authors: Blangenois, N; Florea, M; Grange, P; Silvy, RP; Chenakin, SP; Bastin, JM; Kruse, N; Barbero, BP; Cadus, L

Published: JUN 10 2004, , DOI: 10.1016/j.apcata.2003.12.008

2789. Growth and properties of Pb(Zr0.92Ti0.08)O-3 thin films

Authors: Boerasu, I; Pintilie, L; Gomes, MJM; Pereira, M

Published: 2004, INTEGRATED FERROELECTRICS, 62, 87, DOI: 10.1080/10584580490460556

Lead zirconate-titanate (PZT) thin films with Zr/Ti ratio of 92/8 were deposited by sol-gel on Pt(111)-coated Si(100) and single crystal MgO(100) substrates. The films crystallize differently on the two type of substrates: in case of the films deposited on Pt the perovskite structure is established only after oxygen annealing, while for the films deposited on MgO annealing in air is enough. The films are polycrystalline with some preferred orientation that is substrate dependent. Average values of 2.1 muC/cm(2) and 78 kV/cm were obtained for remnant polarization and coercive field, respectively. The I-V characteristic at low to medium voltages is dominated by field enhanced Schottky emission, with Ln(J)similar to(V + V-bi)(1/4) dependence of the current density. A value of about 3.85 eV was estimated for the band-gap from optical measurements.

2790. Vanadium aluminium oxynitride catalyst for propane ammoxidation

Authors: Florea, M; Silvy, RP; Grange, P

Published: MAY-JUN 2004, , DOI:

2791. Influence of the nitrogen content on butan-1-ol and butan-2-ol dehydration properties of nitrided phosphates

Authors: Delsarte, S; Florea, M; Grange, P

Published: MAY-JUN 2004, , DOI:

2792. Influence of the preparation conditions on the physico-chemical and catalytic properties of a vanadium-aluminum oxynitride propane ammoxidation catalyst

Authors: Silvy, RP; Blangenois, N; Florea, M; Grange, P; Cadus, L; Barbero, B

Published: MAY-JUN 2004, , DOI:

2793. Dynamics of the surface layer in cyanobiphenyl-aerosil nanocomposites with a high silica density

Authors: Frunza, S; Frunza, L; Tintaru, M; Enache, I; Beica, T; Schonhals, A

Published: JUL 2004, LIQUID CRYSTALS, 31, 922, DOI: 10.1080/02678290410001675147

Composites were prepared from an aerosil and 4-n-alkyl-4'cyanobiphenyls with five to eight carbon atoms in the alkyl chain. Their high silica density of similar to7 g aerosil in 1 cm(3) of liquid crystal (LC) allows the observation of the behaviour of a thin cyanobiphenyl layer (having nearly a monolayer structure) on the silica particles. The systems are investigated by dielectric spectroscopy (10(-2)-10(9) Hz) in a large temperature range (220-370 K). All the composites show a (main) relaxation process at frequencies much lower than the processes observed for the bulk LC that was assigned to the dynamics of the molecules in the surface layer. The temperature dependence of its characteristic frequencies obeys the Vogel-Fulcher-Tammann law, which is found to be typical for glass-forming liquids. The quasi two-dimensional character of the glass transition in the surface layer is discussed for the first time. At the nematic-to-isotropic transition temperature of the bulk, the composites show a continuous decrease of the characteristic frequencies as a function of the alkyl chain length, while the bulk LCs show the well known odd-even behaviour. The magnitude and temperature dependence of the slow relaxation process in the composites (molecules on an outer surface) agree with those of the same molecules confined to the nanopores of molecular sieves (internal surface).

2794. Magnetic nanostructures obtained by colloidal crystallization onto patterned substrates

Authors: Crisan, O; Angelakeris, M; Vouroutzis, N; Crisan, AD; Pavlidou, E; Kostic, I; Sobal, N; Giersig, M; Flevaris, NK

Published: MAY 2004, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, E1287, DOI: 10.1016/j.jmmm.2003.12.184

Colloidal solutions of magnetic nanoparticles are regularly dispersed onto patterned substrates in order to form novel magnetic nanostructures. The morphology of these nanostructures is investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM) and their structure is correlated with magnetic properties. It is shown that, depending on the nature of the substrate, different nanoparticle growth modes are identified during the colloidal crystallization. (C) 2003 Elsevier B.V. All rights reserved.

2795. FexCu1-x alloys for permanent magnets

Authors: Kappel, W; Codescu, MM; Pasuk, I; Patroi, E; Kuncser, V; Valeanu, M; Predoi, D; Filoti, G

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 978, DOI:

New magnetic composite materials, ribbon samples, with nominal compositions FexCu1-x (x=0.2; 0.5; 0.8) were obtained by the melt spinning technique. Various information was provided via X-ray diffraction, Mossbauer and magnetic measurements. The structural aspects: phase composition, size and texture effects, have been corroborated with magnetic properties. Finally, the possibility to choose the adequate composition and the suitable processing in order to obtain desired anisotropic magnetic materials were presented.

2796. Natural quasi-optical sources of high coherent radiation

Authors: Branescu, M

Published: 2004, ROMOPTO 2003: SEVENTH CONFERENCE ON OPTICS, 5581, 286, DOI: 10.1117/12.582838

The paper describes the specific quasi-optical phenomena involved in the generation of the high coherent celestial and biological radiation. It examines the generation mechanism of the high coherent radiation in the living systems in the presence of the ambient celestial primordial isotropic background. Josephson and Kerr mechanisms provide an explanation of the concept of bio-coherence as a novel possibility of electromagnetic communication.

2797. Dielectric ceramics based on the ZrO2-SnO2-TiO2 ternary system for microwave and milimeter wave applications

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Ghetu, D; Stoica, G; Annino, G; Cassetari, M; Martinelli, M

Published: 2004, 2004 International Semiconductor Conference, Vols 1and 2, Proceedings, 426, DOI:

The paper describes the investigations of (Zr0.8Sn0.2)TiO4 compounds prepared by solid-state reaction techniques. The effect of La2O3, ZnO and NiO addition on microwave dielectric properties was investigated. The samples were sintered at temperatures T-s = 1280 divided by 1400 degrees C The inaterials exhibit a dielectric constant epsilon(r) similar to 36 and high values of the Q f productfroin 30,000 to 55,000 at microwave frequencies. The measured temperature coefficient of the resonance frequency tau(f) takes values in the range (-2 divided by+4) ppm/degrees C.

2798. EPR investigation of nanosized La0.67Ca0.33MnO3-delta manganites

Authors: Giurgiu, LM; Grecu, MN; Darabont, A; Raita, O; Filip, X; Pana, O; Toloman, D

Published: 2004, APPLIED MAGNETIC RESONANCE, 27, 150, DOI: 10.1007/BF03166309

We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of nanosized La0.67Ca0.33MnO3-delta manganites. The temperature dependences of the EPR line width and integral intensity have been analyzed in terms of the bottlenecked spin relaxation and small polaron hopping scenarios. The exchange coupling integral between Mn3+ and Mn4+ ions and the polaron activation energy decrease with the reduction of grain size. A discussion is given concerning the factors which could explain the observed changes.

2799. Second harmonic generation at the GaAs(111)-B|solution interface

Authors: Lazarescu, V; Lazarescu, MF; Jones, H; Schmickler, W

Published: JUN 15 2004, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 567, 261, DOI: 10.1016/j.jelechem.2003.12.035

Second harmonic generation from the interface between GaAs(111)-B and an aqueous electrolyte has been investigated at a long wavelength (1064 nm) and at two shorter ones (865 and 815 nm). The signal showed the symmetry of the crystal; the isotropic amplitude was found to vary substantially with the electrode potential, indicating that a major part of the signal is generated near the interface. The potential dependence was stronger at shorter wavelengths. Impedance spectroscopy revealed the existence of surface states, which may affect the magnitude of the signal. (C) 2004 Elsevier B.V. All rights reserved.

2800. Photoluminescence studies on [C60] fullerene solutions in N-methyl-2-pyrrolidinone and pyrrolidine

Authors: Mihut, L; Preda, N; Baibarac, M; Baltog, I; Lefrant, S; Wery, J

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 415, 21, DOI: 10.1080/15421400490478209

Photoluminescence (PL) spectra of C-60 solutions in N-methyl-2-pyrrolidinone (NMP) show a drastic increase of the PL intensity if the solutions are stored longer periods of time. Two distinct spectral components, one in the red (1.92-2.00 eV) and another in the green (2.18-2.3 eV) were identified in the whole PL emission. Their weights depend on C-60 concentration and on storage time. The two emissions come from two successive processes running with different kinetics. Charge transfer, leading to (C-60, NMP) loose molecular complexes and a slow aggregation process of these entities seems to originate the red and green emission, respectively. Similar PL properties are found when pyrrolidine (P) is used as solvent.

2801. Properties of Pb(Zr-0.Ti-92(0).(08))O-3 thin films deposited by sol-gel

Authors: Pintilie, L; Boerasu, I; Gomes, M; Pereira, M

Published: JUN 30 2004, THIN SOLID FILMS, 458, 120, DOI: 10.1016/j.tsf.2003.12.057

Lead zirconate-titanate (PZT) thin films with Zr/Ti ratio of 92/8 were deposited by sol-gel on Pt coated silicon and single crystal MgO(100) substrates. In case of the films deposited on Pt the perovskite structure is established only after oxygen annealing, while for the films deposited on MgO annealing in air is enough. The films are polycrystalline with preferred orientation that is substrate dependent ((110) on Pt and (100)/(200) on MgO). Average values of 2.10 muC/cm(2) and 78 kV/cm were obtained for remnant polarization and coercive field, respectively. The I-V characteristic at low-to-intermediate electric fields is controlled by thermionic emission, but the Schottky representation is Ln(current)-(voltage)(1/4), implying that the film behaves like a semiconductor and not like an insulator. From transmission-reflectance measurements a value of 3.85 +/- 0.05 eV was estimated for the band gap, while the refraction index in the transparency region was found to be 2.6. A pyroelectric signal was detected on as grown films, making them attractive for infrared detection. (C) 2003 Elsevier B.V. All rights reserved.

2802. Second harmonic generation and impedance spectroscopy at n-GaAs(100) electrodes

Authors: Lazarescu, V; Lazarescu, MF; Santos, E; Schmickler, W

Published: SEP 30 2004, ELECTROCHIMICA ACTA, 49, 4238, DOI: 10.1016/j.electacta.2004.04.017

Second harmonic generation from n-GaAs(100) electrodes in sulfuric acid solution has been investigated at an incident wavelength of 1064 nm over a potential range where Faradaic processes are excluded. In the p-in/p-out polarization configuration, the rotational anisotropy in the nonlinear response was found to depend both on the doping level and the applied potential. The effects of the applied potential on the isotropic amplitude of the SHG signal turned out to be closely related to the population of surface states as revealed by impedance spectroscopy, indicating that these states could play a significant role in second harmonic generation. (C) 2004 Elsevier Ltd. All rights reserved.

2803. Optical recording in sulfur-selenium layers

Authors: Popescu, M; Sava, F; Lorinczi, A; Savastru, R; Savastru, D; Radvan, R; Mihailescu, IN

Published: SEP 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 886, DOI:

Selenium-sulphur layers prepared by warm pressing or deposited by pulsed laser deposition (PLD) on silicon wafers were subjected to laser pulses in order to test the possibility of recording the optical information in these glassy materials. There was demonstrated that the contrast of reflectivity between the irradiated places and the amorphous matrix could be used for storage of information at a reasonable density.

2804. Enhancement of critical current density in YBa2Cu3O7-delta thin films grown using PLD on YSZ (001) surface modified with Ag nano-dots

Authors: Ionescu, M; Li, AH; Zhao, Y; Liu, HK; Crisan, A

Published: JUL 7 2004, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 37, 1828, DOI: 10.1088/0022-3727/37/13/014

Y123 thin films were grown by pulsed laser deposition (PLD) on YSZ (001) substrate. Prior to the film deposition, a discontinuous layer of Ag was deposited on the substrate, also using PLD, in the form of separate islands. Atomic force microscopy (AFM) investigation of the Ag layer showed that its morphology consisted of self-assembled islands of nanometre size, randomly distributed on the surface of the substrate, called nano-dots. The Y123 superconducting films grown on such a surface were characterized using AFM, x-ray diffraction, secondary electron microscopy, ac susceptibility and dc magnetization. The results show that there is no significant difference in surface morphology, crystallographic orientation, phase composition or superconducting transition temperature between the Y123 films grown on YSZ (001) with an Ag nano-dots layer and a control Y123 film grown on a virgin YSZ (001) surface. On the other hand, at 77 K, the magnetic critical current density (J(c)(m)) was three times higher for the Y123 film grown on YSZ with the modified (001) surface than for the film grown on YSZ with a virgin (001) surface. At 5 K the enhancement of J(c)(m) was approximately seven times, at both low and high fields. This suggests an increase in pinning, caused presumably by point defects formed in the Y123 film above the Ag islands.

2805. Nanocrystalline rhombohedral In2O3 synthesized by hydrothermal and postannealing pathways

Authors: Sorescu, M; Diamandescu, L; Tarabasanu-Mihaila, D; Teodorescu, VS

Published: JAN 15 2004, JOURNAL OF MATERIALS SCIENCE, 39, 677, DOI: 10.1023/B:JMSC.0000011529.01603.fc

2806. Measurements of optical anisotropy of a calamitic lyotropic liquid crystal

Authors: Beica, T; Moldovan, R; Tintaru, M; Enache, I; Frunza, S

Published: FEB 2004, CRYSTAL RESEARCH AND TECHNOLOGY, 39, 156, DOI: 10.1002/crat.200310163

Optical bireffingence measurements for a calamitic lyotropic liquid crystal containing sodium lauryl sulphate/decanol/water are presented. A value of the order of 10(-3) was obtained, much smaller than that of thermotropic liquid crystals. The order parameter temperature dependence is evaluated using an extrapolating method and taking into accounts the influence of the micelle shape. (C) 2004 WILEY-VCR Verlag GmbH & Co. KGaA, Weinheim.

2807. Oxides ferroelectric (Ba, Sr)TiO3 for microwave devices

Authors: Alexandru, HV; Berbecaru, C; Ioachim, A; Toacsen, MI; Banciu, MG; Nedelcu, L; Ghetu, D

Published: JUN 15 2004, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 109, 159, DOI: 10.1016/j.mseb.2003.10.034

Barium-strontium titanate (BST), ternary ceramic compounds with the molar formula (Ba1-xSrx)TiO3, were prepared by solid-state reaction from raw materials. Three compositions with x = 0.25, 0.50 and 0.75, have been checked. Samples with two type of thermal treatment at 1230 and 1260degreesC have been manufactured and analyzed. Perovskite type, polycrystalline structure of the BST ceramics was revealed by the X-ray diffraction data at room temperature. Strontium ion (Sr2+) enters substitutionally on the Ba2+ site. A small decrease in the unit cell volume with the Sr content increase was observed. Dielectric measurements have been performed at low and high frequencies. The temperature dependence of low frequency permittivity shows large interval of ferroelectric transition, which appears to be merely due to dispersion of crystallites dimensions. The increasing concentration of Sr ion leads to a shift of the Curie point below room temperature. Experimental data show a linear decrease of the Curie point T-C (degreesC); approximate to 120-360x, versus x Strontium fraction. Room temperature permittivity and dielectric loss have been measured in microwaves by using the Hakki-Coleman method. BST samples prepared using water as a milling medium exhibit lower porosity and lower dielectric loss in microwaves than samples prepared using acetone as a milling medium. Dielectric loss Of 10(-3) at 1 GHz shows that this ceramic material is quite suitable for high frequency device applications. (C) 2003 Elsevier B.V. All rights reserved.

2808. Electrochemical deposition of PBSe1-xTex nanorod arrays using ion track etched membranes as template

Authors: Sima, M; Enculescu, I; Visan, T; Spohr, R; Trautmann, C

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 418, 755, DOI: 10.1080/15421400490478885

Lead chalcogenides (PbS, PbSe, PbTe) are narrow band gap semiconductors which have been studied in the field of IR detection and thermoelectric devices. The template method is a general approach for synthesizing nanomaterials within the pores of membranes. The membranes employed contain cylindrical pores with monodisperse diameters, and corresponding cylindrical nanostructures are obtained. The aim of the present study was to prepare PbSe1-xTex nanorod arrays using electrodeposition. The process was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The resulted PbSe1-xTex nanostructures were characterized using scanning electron microscopy (SEM) as well as energy dispersive X-ray analysis (EDAX).

2809. On the optical properties of micro- and nanometric size PbI2 particles

Authors: Baibarac, M; Preda, N; Mihut, L; Baltog, I; Lefrant, S; Mevellec, JY

Published: APR 7 2004, JOURNAL OF PHYSICS-CONDENSED MATTER, 16, 2356, DOI: 10.1088/0953-8984/16/13/014

Scanning electron microscopy, Raman scattering, UV-VIS absorption spectroscopy and low temperature photoluminescence (PL) were used to examine small particles produced by the chemical reaction between Pb(NO3)(2) and KI in different liquid media: water, methanol, ethanol and acetonitrile. By stoichiometric changes in the synthesis reaction, platelets of PbI2 and rods probably of KPbI3 are produced. Regardless of shape and size, these particles exhibit almost the same PL, which consists of two intense bands centred around the 2.5 (E band) and 2.0 eV (G band), in turn similar to that of a crystalline slide or a micrometric powder, both prepared from a PbI2 single-crystal grown from the melt. Crystalline PbI2 platelets exhibit an E band with two components, at 2.49 (E-F band) and 2.47 eV (E-T band), originating in the recombination of the free and trapped excitons produced by inter-band irradiation. A close relation between the enhancement of the E-T and G band reveals that they are linked to the surface defects. For the rod-like particles, the PL spectrum is somewhat similar to that of a Pb2+ ion introduced into an alkaline halide lattice, which as for any ns(2) ion displays two emission bands, A(T) and A(X), whose correspondents are E and G bands.

2810. Raman studies of carbon nanotubes and polymer nanotube composites

Authors: Lefrant, S; Buisson, JP; Schreiber, J; Chauvet, O; Baibarac, M; Baltog, I

Published: 2004, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 415, 132, DOI: 10.1080/15421400490482844

In this paper, we present Raman studies of different carbon nanotubes systems like single-walled nanotubes (SWNTs), multi-walled nanotubes (MWNTs) or composites prepared with different conjugated or non-conjugated polymers. We have focused our studies on the interactions that can take place in these systems and in general modify the characteristics of individual tubes. By introducing Van der Waals interactions between tubes, we are able to interpret experimental Raman spectra. In the case of SWNTs, we have put in evidence the so-called "bundle'' effect that consists of an upshift of the frequency of the RBM of 10 to 16 cm(-1), depending on the size of the bundles. In MWNTs, one can calculate the low frequency Raman modes observed experimentally. We found that they originate from the radial breathing modes of isolated tubes with an upshift that depends on the number of shells constituting the tube and we were then able to calculate the intensity of such modes. Finally, in polymer/nanotubes composites, we demonstrate that interactions take place between the two constituents in two different cases: PPV/SWNTs and PANI/SWNTs. The role of the method of preparation of composites is particularly put in evidence.

2811. Time-resolved photoluminescence analysis of distribution and migration of terbium ions in zeolites X

Authors: Tiseanu, C; Frunza, L; Kumke, M

Published: OCT 30 2004, PHYSICA B-CONDENSED MATTER, 352, 365, DOI: 10.1016/j.physb.2004.08.015

The photoluminescence (PL) dynamics of terbium-exchanged zeolites X was investigated upon laser excitation at 355 nm. The results evidenced the presence of at least two terbium main environments with PL lifetimes varying between 391-411 and 753-770 mus. The two-site nature of terbium distribution in zeolites X permitted a quantitative analysis of the migration process of terbium ions inside the pores and cavities upon dehydration in air at 200 degreesC. Besides the increase of the PL lifetimes with about 30% and 80% compared to those of the hydrated zeolite, a fraction of almost 30% of terbium ions was estimated to migrate from the supercages to the neighboring sodalites or hexagonal prisms. Our results evidenced for the first time the capability of time-resolved luminescence spectroscopy in quantitatively tracking for the intrazeolitic migration of lanthanides. (C) 2004 Elsevier B.V. All rights reserved.

2812. Electrodeposition of CdTe nanorods in ion track membranes

Authors: Sima, M; Enculescu, I; Trautmann, C; Neumann, R

Published: MAR 2004, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 6, 125, DOI:

CdTe nanowires were electrodeposited in ion track membranes with pore diameters in the range 100-2000 nm. Acidic and basic baths were tested for obtaining materials with good stoichiometry. The cyclic voltammograms were compared for the case of deposition on a carbon rotating disc and on the porous membrane substrates, the differences being attributed to the additional resistance induced by the pores. For larger pores a tendency of growing hollow structures was observed.

2813. Effects of Zr and Ti substitutions on the crystallization processes of Fe3B/Nd2Fe14B nanocomposite magnetic system

Authors: Jianu, A; Valeanu, M; Lazar, DP; Lifei, F; Bunescu, C; Pop, V

Published: MAY 2004, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, 1494, DOI: 10.1016/j.jmmm.2003.12.1005

The influence of Zr and Ti substitutions on the formation of a nanocomposite magnet was studied by high-temperature X-ray diffraction and magnetic measurements. It has been shown that Ti and especially Zr additions favorably change the crystallization temperatures and the sequence of phase transformations which leads to an exchange coupled magnet, even in a composition range that promotes the precipitation of the detrimental Nd2Fe23B3 phase. (C) 2003 Elsevier B.V. All rights reserved.

2814. Surface study of the corrosion of carbon steel in solutions of ammonium salts using Mossbauer spectrometry

Authors: Samide, A; Bibicu, I; Rogalski, MS; Preda, M

Published: 2004, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY, 261, 596, DOI: 10.1023/B:JRNC.0000037100.27713.bf

The effect of the NO3- anion on the corrosion of carbon steel in a solution of 0.1M NH4Cl (pH 5.5) was studied by galvanostatic polarization and Mossbauer spectrometry. The anion has an inhibiting effect by decreasing the expansion rate of generalized corrosion of carbon steel in a solution of 0.1M NH4Cl-Mossbauer spectroscopy shows that a superficial compound is formed on the electrode surface as a result of corrosion, presenting no magnetic ordering. Its parameters show the initial stage of corrosion. We assume that at this stage the main corrosion product is a mixture of ferrihydrite Fe(III) and FeOOH (alpha and/or gamma).

2815. ESR characterization of point defects in amber colored c-BN super abrasive powders

Authors: Nistor, SV; Ghica, D; Stefan, M; Bouwen, A; Goovaerts, E

Published: SEP 2004, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 201, 2590, DOI: 10.1002/pssa.200405194

Cubic boron nitride (c-BN) crystalline superabrasive powder (Borazon** CBN 400), consisting of 200-300 microns sized amber colored crystallites prepared by HP/HT synthesis, has been examined from 2.1 K to 293 K by X-band ESR spectroscopy. The observed spectrum consists of a component line A1, visible in the whole temperature range, and two component lines A2 and A3, visible at high and low temperatures, respectively. The A1 and A3 lines originate from transitions inside S = 1/2 ground states of distinct paramagnetic species and A2 from transitions inside an excited state of another paramagnetic center. The intensity of the A1 and A3 lines changes differently during in situ low temperature illumination in the UV-VIS range. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

2816. Influence of crystal growth technology on the tolerance to radiation of silicon for detectors at future accelerators

Authors: Lazanu, S; Lazanu, I; Ciurea, ML

Published: 2004, 2004 International Semiconductor Conference, Vols 1and 2, Proceedings, 422, DOI:

Silicon detectors represent an important option for the Large Hadron Collider and for its upgrades in luminosity and energy, especially for the tracking system. The main limitation in their utilisation comes from the degradation in the hostile radiation environment where they, will work for long time, without the possibility to be changed. The main goal of this paper is to study, the role of growth technology on stable defect concentrations produced by long-time continuous irradiation in the radiation field estimated for LHC and SLHC.

2817. Structural, electrical, and photoelectrical properties of CdxPb1-xS thin films prepared by chemical bath deposition

Authors: Pentia, E; Draghici, V; Sarau, G; Mereu, B; Pintilie, L; Sava, F; Popescu, M

Published: 2004, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 151, G733, DOI: 10.1149/1.1800673

CdxPb1-xS (0 less than or equal to x less than or equal to 1) thin films were prepared on glass substrates using the chemical bath deposition method. The structural, electrical, and photoelectrical properties of the films were investigated, and all were dependent on the x value. For x > 0.5 (high Cd content), the films show a poor crystallinity and weak photoconductivity. For x < 0.5 (high Pb content), the films exhibit a good crystallinity, with an average size of the crystallites of 100 nm, and good photoconductivity. The threshold voltage of photoconductivity is shifted to lower wavelengths with increasing Cd content. The experimental results point toward possible ternary deposition on some composition ranges (near pure PbS or CdS); whereas, for the rest, the deposited film is rather a mixture of phases [not CdxPb1-xS but (CdS)(x)(PbS)(1-x)]. (C) 2004 The Electrochemical Society.

2818. Monte Carlo simulation study of magnetic behaviour of core-shell bimetallic nanoparticles

Authors: Crisan, O; Tornau, EE; Petrauskas, V; Angelakeris, M

Published: 2004, SECOND SEEHEIM CONFERENCE ON MAGNETISM, PROCEEDINGS, 3763, DOI: 10.1002/pssc.200405549

The magnetic properties of core-shell-type nanoparticles with non-magnetic core and ferromagnetic shell are modeled using Monte Carlo simulation. The influence of the surface spin disorder on the magnetization and Curie temperature of magnetic states is studied. Due to competition between exchange coupling and surface anisotropy, rotation of the magnetization axis is observed, as the surface anisotropy of the ferromagnetic shell is increased. It is shown that the exchange coupling at the core-shell interface can influence the shape of the temperature dependence of total magnetization. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

2819. Orbital magnetization of single and double quantum dots in a tight-binding model

Authors: Aldea, A; Moldoveanu, V; Nita, M; Manolescu, A; Gudmundsson, V; Tanatar, B

Published: JAN 15 2003, PHYSICAL REVIEW B, 67, DOI: 10.1103/PhysRevB.67.035324

We calculate the orbital magnetization of single and double quantum dots coupled both by Coulomb interaction and by electron tunneling. The electronic states of the quantum dots are calculated in a tight-binding model, and the magnetization is discussed in relation to the energy spectrum and to the edge and bulk states. We identify effects of chirality of the electronic orbits and of the anticrossing of the energy levels when the magnetic field is varied. We also consider the effects of detuning the energy spectra of the quantum dots by an external gate potential. We compare our results with the recent experiments of Oosterkamp [Phys. Rev. Lett. 80, 4951 (1998)].

2820. Structure and properties of As25Te35Si40 glass

Authors: Lorinczi, A; Sava, F; Iovu, M; Leonovici, M; Halm, T; Popescu, M; Hoyer, W

Published: NOV 2003, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 240, 36, DOI: 10.1002/pssb.200301850

The glassy composition As25Te35Si40 was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Raman spectroscopy, and infrared absorption (IR) measurements. X-ray diffraction patterns at room temperature and at temperatures around T-g were recorded and the radial distribution functions have been calculated. A continuous random network model for the ideal homogeneous glass structure has been proposed.

2821. Electron-doped superconductivity induced by oxygen vacancies in as-grown Sr0.6Ca0.4CuO2-delta infinite-layer films

Authors: Nie, JC; Badica, P; Hirai, M; Sundaresan, A; Crisan, A; Kito, H; Terada, N; Kodama, Y; Iyo, A; Tanaka, Y; Ihara, H

Published: JAN 2003, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 16, L3, DOI: 10.1088/0953-2048/16/1/101

Thin films of the infinite-layer compound Sr0.6Ca0.4CuO2-delta have been prepared by off-axis rf magnetron sputtering on SrTiO3 (001). For an opt mum level of oxygen vacancy superconductivity was observed (T-c onset = 42 K and T-c(rho=0) = 11 K). Structural and transport data suggesting n-type superconductivity are presented and discussed. Infinite-layer thin films of Sr0.5Ca0.4CuO2-delta, without trivalent cation doping and showing n-type superconductivity, are reported for the first time.

2822. Magnetic properties of gamma-Fe2O3 nanoparticles

Authors: Predoi, D; Kuncser, V; Nogues, M; Tronc, E; Jolive, JP; Filoti, G; Schinteie, G

Published: MAR 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 216, DOI:

The gamma-Fe2O3 nanoparticles with different surface states are investigated by X-ray Diffraction, Electron Microscopy, Differential Thermal Analysis and magnetic: measurements in low applied field. The influence of the adsorbed species (H2O and sulphate complexes) on the inter-particle magnetic interactions is analysed in relation to both the magnetic states of the surface and the inter-particle distance.

2823. Spin dynamics investigated by EPR in the paramagnetic regime of La2/3Ca1/3Mn1/3MexO3 (Me = Al, In) manganites

Authors: Giurgiu, LV; Grecu, MN; Filip, X; Raita, O; Darabont, A; Gavre, D; Blasco, J

Published: 2003, APPLIED MAGNETIC RESONANCE, 24, 360, DOI: 10.1007/BF03166936

We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of the colossal magnetoresistive manganites La2/3Ca1/3Mn1-xMexO3 (Me = Al, In; x less than or equal to 0.05). The temperature dependences of the EPR linewidth and integral intensity have been analyzed in terms of the bottleneck spin relaxation and small-polaron hopping models. The exchange coupling integral between Mn3+ and Mn4+ ions and the polaron activation energy decrease with increasing doping level. A discussion is given concerning the factors which could explain the observed changes.

2824. Nitric oxide binding properties of neuroglobin - A characterization by EPR and flash photolysis

Authors: Van Doorslaer, S; Dewilde, S; Kiger, L; Nistor, SV; Goovaerts, E; Marden, MC; Moens, L

Published: FEB 14 2003, JOURNAL OF BIOLOGICAL CHEMISTRY, 278, 4925, DOI: 10.1074/jbc.M210617200

Neuroglobin is a recently discovered member of the globin superfamily. Combined electron paramagnetic resonance and optical measurements show that, in Escherichia coli cell cultures with low O-2 concentration overexpressing wild-type mouse recombinant neuroglobin, the heme protein is mainly in a hexacoordinated deoxy ferrous form (F8His-Fe2+-E7His), whereby for a small fraction of the protein the endogenous protein ligand is replaced by NO. Analogous studies for mutated neuroglobin (mutation of E7-His to Leu, Val, or Gin) reveal the predominant presence of the nitrosyl ferrous form. After sonication of the cells wild-type neuroglobin oxidizes rapidly to the hexacoordinated ferric form, whereas NO ligation initially protects the mutants from oxidation. Flash photolysis studies of wild-type neuroglobin and its E7 mutants show high recombination rates (k(on)) and low dissociation rates (k(off)) for NO, indicating a high intrinsic affinity for this ligand similar to that of other hemoglobins. Since the rate-limiting step in ligand combination with the deoxy-hexacoordinated wild-type form involves the dissociation of the protein ligand, NO binding is slower than for the related mutants. Structural and kinetic characteristics of neuroglobin and its mutants are analyzed. NO production in rapidly growing E. coli cell cultures is discussed.

2825. Intra- and inter-grain critical current density in (Cu,C): 1234 superconductors

Authors: Crisan, A; Badica, P; Hirai, M; Kito, H; Iyo, A; Tanaka, Y

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 422, DOI: 10.1016/S0921-4534(02)02550-9

From DC magnetization studies in fields up to 14 T and temperatures between 20 and 100 K, we estimated the intra-and inter-grain critical current density J(c) of (Cu,C): 1234 high-T-c superconductors, in the frame of critical state models. The inter-grain J(c) was determined by comparing the magnetization loops of as-grown sample and of the ground sample. Finally, short comments on J(c) resulted from AC susceptibility measurements and of the impressive increase of intra-grain J(c) due to heavy-ion and neutron irradiation are presented. (C) 2003 Elsevier Science B.V. All rights reserved.

2826. Copper nanowires electrodeposited in etched single-ion track templates

Authors: Enculescu, I; Siwy, Z; Dobrev, D; Trautmann, C; Toimil-Molares, ME; Neumann, R; Hjort, K; Westerberg, L; Spohr, R

Published: NOV 2003, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 77, 755, DOI: 10.1007/s00339-003-2216-3

The replication of single-ion track templates opens up the possibility of accessing electrical properties of nanowires without using lithographic techniques. Polycarbonate foils of 30-mum thickness were irradiated with single swift heavy ions (e.g. An 11.4 or Xe 8.3 MeV/nucleon). By controlled one-sided etching of the damage trail caused by the ion, templates containing a single conical pore were prepared. The narrow pore openings had diameters down to 25 nm and opening angles up to 2degrees. By electrochemical deposition of copper, single conical wires were obtained. The electric current recorded during electrodeposition reflects the geometry of the pore. The wires were provided with electrical contacts. Current-voltage measurements confirmed that their resistance was ohmic. The wires could withstand a maximum current density above 10(8) A/cm(2).

2827. Densification of In2O3: Sn multilayered films elaborated by the dip-coating sol-gel route

Authors: Daoudi, K; Canut, B; Blanchin, MG; Sandu, CS; Teodorescu, VS; Roger, JA

Published: NOV 24 2003, THIN SOLID FILMS, 445, 25, DOI: 10.1016/S0040-6090(03)01061-7

Indium Tin Oxide (ITO) thin films have been deposited by the Sol-Gel Dip-Coating technique, the starting solutions being prepared from chlorides. These multilayered films were crystallized by means of a classical heat treatment at temperatures ranging from 500 to 600 degreesC. Five stacked layers are necessary to obtain a global electrical resistivity value of 2.9 x 10(-3) Omega cm, for 500 degreesC annealed film. The paper focuses on the study of the structure of such multilayered deposits, and on the densification process, using transmission electron microscopy, Rutherford Back-scattering Spectrometry and electrical resistivity measurements. This analysis reveals structural inhomogeneities and different crystallite growth processes as a function of annealing temperature and number of deposited layers. (C) 2003 Elsevier B.V. All rights reserved.

2828. A Mossbauer study of manganese-doped magnetite

Authors: Sorescu, M; Tarabasanu-Mihaila, D; Diamandescu, L

Published: MAR 2003, MATERIALS LETTERS, 57, 1869, DOI: 10.1016/S0167-577X(02)01092-3

A series of Fe3 - xMxO4 samples with x = 0-0.6. was prepared using the hydrothermal method. The system was characterized using transmission Mossbauer spectroscopy. The dependence of the site hyperfine magnetic. fields and populations on the content x of Mn substitution was derived from the spectra. The results are consistent with Mn2+ ions substituting for Fe2+ ions in the octahedral B sublattice. In particular, the site-specific substitution of Mn ions for the B2 sites was evidenced. (C) 2002 Elsevier Science B.V. All rights reserved.

2829. Surface particularities in pulsed laser ablation/deposition of the ferromagnetic alloy NiMnSb

Authors: Grigorescu, CEA; Manea, SA; Mitrea, M; Monnereau, O; Notonier, R; Tortet, L; Keschawarz, R; Giapintzakis, J; Klini, A; Zorba, V; Androulakis, J; Fotakis, C

Published: MAY 15 2003, APPLIED SURFACE SCIENCE, 212, 84, DOI: 10.1016/S0169-4332(03)00404-5

In this work we investigate the surface morphology and stoichiometry of the ablated targets employed with pulsed laser deposition (PLD) of thin films of the ferromagnetic half-Heusler alloy NiMnSb. The NiMnSb targets were: a pressed and sintered pellet and, respectively, polycrystalline discs grown by RF melting. The films were deposited using a KrF excimer laser (lambda = 248 nm, tau = 30 ns, 600 mJ/pulse maximum) delivering pulses at a repetition rate of 10 Hz. SEM observations show different morphologies of the ablated surfaces in the two cases, which are further correlated with EDX analyses to explore surface segregation phenomena. The corresponding films are also considered. Apparently, the crystalline targets keep better the initial stoichiometry than the pressed ones, which in principle would indicate higher film stoichiometry and hence enhanced quality. (C) 2003 Elsevier Science B.V. All rights reserved.

2830. Study of interactions in carbon nanotubes systems by using Raman and SERS spectroscopy

Authors: Lefrant, S; Buisson, JP; Schreiber, J; Chauvet, O; Baibarac, M; Baltog, I

Published: OCT 9 2003, SYNTHETIC METALS, 139, 785, DOI: 10.1016/S0379-6779(03)00264-9

We present results obtained on carbon nanotube systems by means of Raman scattering and surface enhanced Raman scattering (SERS). Such systems consist of single-walled nanotubes (SWNTs), multi-walled nanotubes (MWNTs), or polymer/nanotubes composites. In particular, we have focused our studies on the interactions taking place in these compounds which lead to an upshift of the radial breathing mode (RBM) in the case of SWNTs, either when they are arranged in bundles or embedded in polymers. Similar calculations has allowed us to interpret the low frequency Raman modes observed in purified MWNTs. We show that they come from the RBM of individual tubes. From intensity calculations performed to simulate Raman spectra, we demonstrate the importance of two experimental parameters, namely the diameter of internal tubes and the number of shells which constitute the MWNTs, such parameters being extracted experimentally from high resolution transmission electron microscopy images. (C) 2003 Elsevier Science B.V. All rights reserved.

2831. Compact microstrip resonators for 900 MHz frequency band

Authors: Banciu, MG; Ramer, R; Ioachim, A

Published: MAY 2003, IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, 13, 177, DOI: 10.1109/LMWC.2003.811673

A technique to reduce the size of planar resonators is investigated using a transmission line model and it finite-difference time-domain (FDTD) method. New miniaturized square microstrip resonators are proposed for 900 MHz band. T he resonators offer low impedance sections leading to a better handling of power. The feasibility of compact filters using the proposed resonators is demonstrated. The input/output coupling lines of a two-pole. filter have been positioned in a way that produces a filter response with transmission zeros on the both sides of the pass-band. Sharper skirts and higher out-of-band rejection are obtained for four-pole filters with cross-coupled resonators.

2832. TlBa(2)Ca(2)Cu(3)O(y) superconducting films on MgO with different morphologies

Authors: Badica, P; Sundaresan, A; Crisan, A; Nie, JC; Hirai, M; Fujiwara, S; Kito, H; Ihara, H

Published: JAN 1 2003, , DOI: 10.1016/S0921-4534(02)01836-1

TlBa(2)Ca(2)Cu(3)O(y) (Tl-1223) superconducting films were prepared under identical conditions, on MgO substrates with different morphologies resulting from heat treatments at temperatures between 600 and 1350 degreesC. The superconducting films have almost the same morphology, in-plane alignment and composition, but different critical current densities J(c). Critical current density J(c) determined at 77.3 K differs for films with various annealed MgO substrates, by a factor of 5 in zero field and 10 in 1 T. The behavior of J(c) is discussed in relation with the flatness of the MgO surface, and with pinning effects induced by the Ca-segregates. For the present work, the best films were obtained for the un-annealed (as-received) substrates and for substrates treated at 1350 degreesC. In these samples, the substrate's flatness and morphology with regular steps are essential for high quality of the superconducting films. In the films grown on MgO annealed between 800 and 1200 degreesC and showing rough surface and Ca-segregates, J(c) was lower. However, J(c) was increasing with heat treatment temperature of the substrate, possibly due to the Ca-segregates inducing or acting as pinning centers. The effects of Ca-segregates are of interest for maximization of the quality of the high-temperature superconducting films. In the literature, up to now, these effects have not been considered and therefore Ca-segregates removal has been recommended. (C) 2002 Elsevier Science B.V. All rights reserved.

2833. A study of the SnO2 and CuSb2O6 based solid solutions: Electrical and magnetic properties

Authors: Scarlat, O; Payne, AC; Mihaiu, S; Aldica, G; Zaharescu, M

Published: DEC 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1002, DOI:

Two types of solid solutions (i.e, Sn1-xCux/3Sb2x/3O2 and Cu1-xSb2(1-x)Sn3xO6 mixed crystals), have been experimentally evidenced over a large concentration range, in the SnO2 - CuSb2O6 binary system, For these two types of solid solutions, the measured values of the unit cell parameters obey Vegard's rule. The electric and magnetic properties of the Sn0.50Cu0.167Sb0.33O2 and Cu0.923Sb1.836Sn0.231O6 mixed crystals, with compositions placed at the maximum solid solubility limit, on either side, were evaluated over 77 to 1123 K and 2 to sample exhibited semiconducting behaviour, with 300 K, respectively. Sn0.50Cu0.167Sb0.33O2 sample exhibited semiconducting behaviour, with activation energy E-d (eV) and Seebeck coefficient (muV/grd) values close to the values reported for metals, while the Cu0.923Sb1.836Sn0.231O6 sample can be treated as insulators. Short - range magnetic ordering has been evidenced at about 60 K for the CuSb2O6 binary compound and Cu0.923Sb1.836Sn0.231O6 mixed crystal, wiib calculated magnetic moments in good agreement with literature data. In contrast, the Sn0.50Cu0.167Sb0.33O2 mixed crystal presented only a paramagnetic behaviour.

2834. The study on the inhibition of steel-carbon corrosion with ethylenethioureea (ETU) in ammonium chloride using Mossbauer spectrometry

Authors: Samide, A; Bibicu, I; Rogalski, M; Preda, M

Published: NOV 2003, REVISTA DE CHIMIE, 54, 931, DOI:

The inhibiting effect of ETU has been studied regarding the corrosion of carbon-steel in NH4Cl 0.1 M solution at 25degreesC and 50degreesC. The effects of the inhibitor have been demonstrated using weight loss and electrochemical measurements as well as Mossbauer spectrometry. The efficiency of ETU increases with the raise of the concentration, but lowers with the temperature. An activation energy was determined using the Arrhenius equation. The experimental data characterize a Langmuir type adsorption isotherm and the results were correlated to the adsorption of the inhibitor Mossbauer spectrometry shows the formation of a superficial film on the surface of the corroded sample in the presence of ETU. This film provides a good corrosion protection for the sample.

2835. BNT ceramics in paraelectric phase: Dielectric properties

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Plapcianu, C; Alexandru, H; Berbecaru, C; Stoica, G

Published: 2003, 2003 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 318, DOI: 10.1109/SMICND.2003.1252443

The paper describes the investigations of Nd doped Barium titanate (BNT) ferroelectric ceramic materials prepared by solid state reaction techniques. The decrease of the Curie temperature with the increase of the Nd2O3 concentration from 0 to 28 wt % was observed. High density values of BNT ceramics were obtained by adding 0.5 mol % PbO substitutional for BaO. The samples were sintered at temperatures T-s=1200divided by12600degreesC. At room temperature, the materials are in paraclectric phase, suitable for high frequency applications.

2836. Effects of in doping investigated by ESR in colossal magnetoresistive manganite La2/3Ca1/3MnO3

Authors: Raita, O; Grecu, MN; Filip, X; Darabont, A; Gavre, D; Blasco, J; Giurgiu, LV

Published: MAR 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 292, DOI:

The effects of the substitution for Mn with In in the colossal magnetoresistive manganites La2/3Ca1/3Mn1-xInxO3 (x less than or equal to 0.05) have been investigated by ESR. The temperature and x dependence of the resonance linewidth have been investigated and discussed in terms of the spin-spin (exchange) interaction scenario. In the paramagnetic regime, the exchange coupling integral, J, between Mn3+ and Mn4+ spins shows a decrease with increasing x. It could arise from the weakening of the double - exchange interaction upon doping, which reduces the exchange field at the Mn sites, The high temperature limit of the ESR linewidth does not depend on the doping level.

2837. Structure and properties of As25Te35Si40 glass

Authors: Popescu, M; Lorinczi, A; Sava, F; Stegarescu, M; Iovu, M; Leonovici, M; Halm, T; Hoyer, W

Published: OCT 1 2003, JOURNAL OF NON-CRYSTALLINE SOLIDS, 326, 393, DOI: 10.1016/S0022-3093(03)00444-7

The glassy composition As25Te35Si40 was investigated by microhardness, differential scanning calorimetry, X-ray diffraction, electrical conductivity and Raman spectroscopy measurements. A continuous random network model of the glass structure has been developed. (C) 2003 Elsevier B.V. All rights reserved.

2838. Chemical interaction of chalcogenide vitreous semiconductors with absorbed impurities induced by gamma-irradiation

Authors: Shpotyuk, O; Kovalskiy, A; Kavetskyy, T; Golovchak, R; Popescu, M

Published: 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1185, DOI:

The chemical interaction of chalcogenide vitreous semiconductors (ChVS) with absorbed impurities induced by high-energetic (E>1 MeV) gamma-irradiation has been investigated at the example of vitreous v-As2S3. Radiation-induced processes of oxidation, hydrogenization, hydratation, carbonization and hydrocarbonization have been observed in this material after prolonged gamma-irradiation and studied using IR spectroscopy (4000-400 cm(-1)), laser mass-spectroscopy methods and electron microprobe analysis.

2839. ZST type material for dielectric resonators and substrates for hybrid integrated circuits

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Stoica, G; Annino, G; Cassettari, M; Martinelli, M; Ramer, R

Published: 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1398, DOI:

(Zr0.8Sn0.2)TiO4 ceramic (ZST) has been prepared and characterized. The effects of sintering parameters such as sintering temperature, sintering time and NiO addition on structural and dielectric properties were investigated. The material has a dielectric constant epsilon(r) similar to 36.0 and high values of the Q . f product from 32,170 to 50,000 at microwave frequencies. The tan delta values are decreased by low level doping, of NiO, while the temperature coefficient of the resonance frequency tau(f) takes values in the range (-2divided by+4) ppm/degreesC. Investigations on whispering gallery modes revealed low dielectric losses in millimeter wave domain. An intrinsic quality factor of 480 was measured at 136.3 GHz. Dielectric resonators and substrates of ZST material were manufactured. The dielectric properties make the ZST material very attractive to microwave and millimeter wave applications such as filters, hybrid microwave integrated circuits, etc.

2840. Modeling of optical charging spectroscopy investigation of trapping phenomena in nanocrystalline porous silicon

Authors: Iancu, V; Ciurea, ML; Draghici, M

Published: JUL 1 2003, JOURNAL OF APPLIED PHYSICS, 94, 223, DOI: 10.1063/1.1576301

A model for trapping phenomena in nanocrystalline silicon investigated by the optical charging spectroscopy method is proposed. The model takes into account all the possible contributions to the discharge current. The results previously obtained on fresh and passivated porous silicon samples are interpreted within the framework of the model, which provides a good fit to the experimental data. The role played by the different kinds of trapping centers (donors and acceptors, surface and bulk) and the different trap parameters is analyzed. (C) 2003 American Institute of Physics.

2841. Effect of substitutions on the hyperfine magnetic field in Nd-based intermetallics

Authors: Sorescu, M; Valeanu, M; Diamandescu, L

Published: AUG 2003, INTERMETALLICS, 11, 754, DOI: 10.1016/S0966-9795(03)00076-1

The present work is focused on several 2:17 intermetallic compounds, namely Nd2Fe15Si2, Nd2Fe15Al2, Nd2Fe15SiAl and Nd2Fe15SiMn as well as several 1:12 intermetallic compounds, such as NdFe10Si2, NdFe10Al2, NdFe10SiAl and NdFe10MnAl. The substitutional effect on their magnetic properties is studied by Mossbauer spectroscopy using hyperfine magnetic field distributions. The single-phase structure of both classes of intermetallics was supported by X-ray diffraction (XRD) measurements. (C) 2003 Elsevier Ltd. All rights reserved.

2842. Electron-doped superconductivity in Sr1-xCaxCuO2-delta infinite-layer thin films

Authors: Nie, JC; Badica, P; Hirai, M; Kodama, Y; Crisan, A; Sundaresan, A; Tanaka, Y; Ihara, H

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 442, DOI: 10.1016/S0921-4534(02)02568-6

Thin films of infinite-layer compound Sr1-xCaxCuO2-delta have been prepared by rf magnetron sputtering. For an optimum level of oxygen vacancy superconductivities were observed (T-c (onset) = 42 and 50 K, T-c(rho=0) = 11 and 20 K). Structural and transport data suggest that the doping mechanism is electron-type. The superconducting transitions were also confirmed by ac susceptibility. Further increase of doping showed to destroy superconductivity. (C) 2003 Elsevier Science B.V. All rights reserved.

2843. ESR studies on laser beam irradiated polyethyleneterephtalate

Authors: Chipara, M; Romero, JR; Chipara, MD; Georgescu, L; Constantinescu, L; Secu, C; Morosanu, C

Published: SEP 2003, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 211, 121, DOI: 10.1016/S0168-583X(03)01179-0

Electron spin resonance investigations on polyethyleneterephtalate irradiated with a YAG-Nd laser are reported. The dependence of electron spin resonance spectra on the incident laser beam intensity (power) is studied. It is noticed that the concentration of free radicals has a sigmoidal dependence on the crystal current, presenting saturation at high incident powers. The nature of free radicals induced by laser irradiation is discussed. (C) 2003 Elsevier B.V. All rights reserved.

2844. EPR study of the low temperature ferroelectic phase transition in Cu2+ doped Rb2ZnCl4 single crystals

Authors: Stefan, M; Nistor, SV; Schoemaker, D; Ursu, L

Published: SEP 2003, SOLID STATE COMMUNICATIONS, 127, 698, DOI: 10.1016/S0038-1098(03)00649-5

Temperature dependent EPR measurements on copper doped Rb2ZnCl4 single crystals allowed us to evidence and study the P2(1)cn <----> ClcI structural phase transition that takes place in this compound at 74.6 K. From the two types Of Cu2+ centers localized at different anionic sites, called Cu2+(I) and Cu2+(II), which are formed in this compound, only the Cu2+(II) centers exhibit observable changes in their EPR spectra, attributable to the symmetry lowering. The observed changes have been related to the soft-mode responsible for the structural phase transition. (C) 2003 Elsevier Ltd. All rights reserved.

2845. Field effect assisted thermally stimulated currents in CdS thin films deposited on SiO2/Si substrates

Authors: Lisca, M; Pentia, E; Saran, G; Pintilie, L; Pintilie, I; Botila, T

Published: DEC 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 852, DOI:

Field effect assisted Thermally Stimulated Currents (TSC) measurements were used to differentiate between electron and hole traps in CdS thin films deposited on SiO2/Si substrate. The electrode configuration was designed as for a pseudo-MOS structure, with drain and source contacts on the CdS film surface and using the Si substrate as gate electrode. Electron or hole traps will be favored to fill-up depending on the polarity of the gate voltage applied during illumination at low temperatures. Collection of the thermally released electrons or holes in the drain circuit will depend also on the polarity of the gate voltage applied during heating at constant rate. Comparing the results with those obtained in case of US films deposited on glass, it is possible to differentiate between SiO2/CdS interface traps and bulk CdS ones.

2846. Densification and crystallization of SnO2 : Sb sol-gel films using excimer laser annealing

Authors: Sandu, CS; Teodorescu, VS; Ghica, C; Canut, B; Blanchin, MG; Roger, JA; Brioude, A; Bret, T; Hoffmann, P; Garapon, C

Published: MAR 15 2003, APPLIED SURFACE SCIENCE, 208, 387, DOI: 10.1016/S0169-4332(02)01412-5

We have successfully applied laser annealing to sol-gel deposited SnO2:Sb thin films in order to achieve their crystallization. The as-deposited films are quasi-amorphous and electrically non-conductive. After laser annealing they crystallize and become conductive. This paper presents a comparative study of the laser annealed films and shows the influence of the irradiation parameters on the crystallization process and the electrical behavior of the films. Our results are quite promising in view of applying this kind of treatment to films deposited on thermally sensitive substrates (e.g. polymers). (C) 2002 Elsevier Science B.V. All rights reserved.

2847. New results in pulsed laser deposition of poly-methyl-methacrylate thin films

Authors: Cristescu, R; Socol, G; Mihailescu, IN; Popescu, M; Sava, F; Ion, E; Morosanu, CO; Stamatin, I

Published: MAR 15 2003, APPLIED SURFACE SCIENCE, 208, 650, DOI: 10.1016/S0169-4332(02)01415-0

Thin organic films based on poly-methyl-methacrylate (PMMA) polymer have been obtained by pulsed laser deposition (PLD) on silicon substrates. The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectroscopy (RS). We observed that the film composition and structure depend on the laser fluence and on the temperature of the substrate during deposition. (C) 2002 Elsevier Science B.V. All rights reserved.

2848. TlBa2Ca2Cu3Oy superconducting films on MgO with different morphologies

Authors: Badica, P; Sundaresan, A; Crisan, A; Nie, JC; Hirai, M; Fujiwara, S; Kito, H; Ihara, H

Published: JAN 1 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 383, 490, DOI: 10.1016/S0921-4534(02)01836-1

TlBa2Ca2Cu3Oy (Tl-1223) superconducting films were prepared under identical conditions, on MgO substrates with different morphologies resulting from heat treatments at temperatures between 600 and 1350 degreesC. The superconducting films have almost the same morphology, in-plane alignment and composition, but different critical current densities J(c). Critical current density J(c) determined at 77.3 K differs for films with various annealed MgO substrates, by a factor of 5 in zero field and 10 in 1 T. The behavior of J(c) is discussed in relation with the flatness of the MgO surface, and with pinning effects induced by the Ca-segregates. For the present work, the best films were obtained for the un-annealed (as-received) substrates and for substrates treated at 1350 degreesC. In these samples, the substrate's flatness and morphology with regular steps are essential for high quality of the superconducting films. In the films grown on MgO annealed between 800 and 1200 degreesC and showing rough surface and Ca-segregates, J(c) was lower. However, J(c) was increasing with heat treatment temperature of the substrate, possibly due to the Ca-segregates inducing or acting as pinning centers. The effects of Ca-segregates are of interest for maximization of the quality of the high-temperature superconducting films. In the literature, up to now, these effects have not been considered and therefore Ca-segregates removal has been recommended. (C) 2002 Elsevier Science B.V. All rights reserved.

2849. ESR studies on collagen irradiated with protons

Authors: Chipara, M; Romero, JR; Ignat, M; Constantinescu, B; Secu, C

Published: APR 2003, POLYMER DEGRADATION AND STABILITY, 80, 49, DOI: 10.1016/S0141-3910(02)00381-6

Electron spin resonance investigations on collagen irradiated with protons are reported. The resonance spectra were assigned to a convolution of lines due to similar toCH(2)-CH2. residues and peroxy radicals. Raising the temperature of the sample (in air), the concentration of similar toCH(2)-CH2. residues decreases while, the concentration of peroxy radicals increases due to the denaturation induced enhancement of the oxidation process. An increase in the apparent intensity of the recorded spectrum has been observed around 100 degreesC and ascribed to the release of adsorbed water molecules. (C) 2003 Elsevier Science Ltd. All rights reserved.

2850. Competition between ferroelectric and semiconductor properties in Pb(Zr0.65Ti0.35)O-3 thin films deposited by sol-gel

Authors: Boerasu, I; Pintilie, L; Pereira, M; Vasilevskiy, MI; Gomes, MJM

Published: APR 15 2003, JOURNAL OF APPLIED PHYSICS, 93, 4783, DOI: 10.1063/1.1562009

Asymmetric metal-ferroelectric-metal (MFM) structures were manufactured by sol-gel deposition of a lead zirconate-titanate (PZT with Zr/Ti ratio 65/35) film on Pt-coated Si, with a Au top electrode. The average remnant polarization of 9 muC/cm2 and the coercive field of 39 kV/cm were obtained from the hysteresis loop measurements. A detailed analysis of the polarization-electric field (P-E), capacitance-voltage (C-V), and current-voltage (I-V) measurement results allowed us to estimate the near-electrode space-charge region thickness (roughly half of the film thickness at zero voltage), net doping concentration (around 10(18) cm(-3)), built-in potential (in the 0.4-0.8 V range, depending on the injecting electrode), and dynamic dielectric constant (5.2). The current logarithm-voltage dependence for the field-enhanced Schottky emission obeys a "1/4" law. The spectral distribution of the short circuit current measured under continuous light illumination in the 290-800 nm range exhibits a cutoff wavelength at 370 nm and a maximum sensitivity at about 340 nm. The estimated band-gap energy of the PZT material is 3.35 eV. The MFM structure is discussed in terms of two back-to-back Schottky diodes with a ferroelectric material in between. It is concluded that the semiconductor properties of the films are not negligible and, in certain conditions, are dominating over the ferroelectric ones. (C) 2003 American Institute of Physics.

2851. Bar-configuration in hall measurements with GaAs

Authors: Ghita, RV; Logofatu, C; Negrila, C; Lazarescu, MF; Manea, AS; Ciupina, V

Published: MAR 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 363, DOI:

The electrical and transport properties of GaAs crystals such as resistivity (rho), mobility (mu) and carrier concentration (n) depend on the purity and defects of a particular crystal. These parameters are normally obtained by performing a simple Hall effect analysis in a bar configuration. The technical procedure is connected with the design of appropriate contacts for Hall bar configuration. In order to ensure good ohmic contacts oil GaAs, thin metal layers of Au-Ge-Ni have been deposited in high vacuum followed by heat treatment in low vacuum. Hall effect measurement is important for checking the quality of the GaAs wafers. We analyzed various GaAs wafers with (100) and (110), orientation obtained by LEC and HB methods. The resistivity of the wafers varied from low resistivity, n-type doped crystals (n = 10(18) cm(-3)), to high resistivity crystals (n = 10(14) cm(-3)). This paper presents the data of Hall characterization of wafers cut from GaAs crystals grown by different methods (LEC, HB).

2852. Easy axis distribution in modern nanoparticle storage media: A new methodological approach

Authors: Kuncser, V; Keune, W; Vopsaroiu, M; Bissell, PR; Sahoo, B; Filoti, G

Published: MAR 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 226, DOI:

Easy axis distribution in metal particle magnetic tapes for linear digital data storage were studied by Mossbauer spectroscopy and magnetometry, for comparison. Qualitative and quantitative agreement between the distribution parameters deduced at room temperature via the two different techniques was found. The proposed methodology based on the interpretation of the Mossbauer data has the advantage that it can be applied at different temperatures and for very thin films. Moreover, angular spin distribution. at low temperatures were obtained by Mossbauer spectroscopy and discussed with respect to the room temperature results. There was evidenced that the room temperature easy axis angular distribution contains both static orientation and dynamical components.

2853. X-ray photoelectron spectroscopy study on n-type GaAs

Authors: Ghita, RV; Negrila, C; Manea, AS; Logofatu, C; Cernea, M; Lazarescu, MF

Published: DEC 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 863, DOI:

A surface characterization has been performed on n-type GaAs (Si: GaAs) samples by using X-ray photoelectron spectroscopy (XPS) technique in order to get information on the degree of surface contamination during the device processing steps. The GaAs samples were etched by "in situ" ion sputtering (Ar plasma) before and after carrying out the measurements. According to XPS measurements the native oxide layer on as-received surface contains As2O3, AS(2)O(5) and Ga2O3. Large amounts of C and O are also present at surface before plasma cleaning of surface: C-C bonds, chemisorbed oxygen atoms. The XPS spectra recorded on the surface sample sputtered with 5 keV Ar+ ions were analyzed using SDP subroutines program facilities. After the first sputtering step it was observed different shifts of the principal peaks of GaAs bonding and compounds together with a modification of the relative peak intensities. The C1s and O1s peak size decreased but remained still significant. The following sputtering steps lead to a drastically decrease of C and 0 peaks down to the noise level.

2854. BPSCCO superconductor with addition of Ag2O synthesized under electrical field

Authors: Aldica, G; Groza, JR; Badica, P; Bunescu, MC

Published: DEC 2003, JOURNAL OF SUPERCONDUCTIVITY, 16, 1005, DOI: 10.1023/A:1026295408106

Ag2O-doped (1.2% wt.) nitrate freeze-dried powders (Bi : Pb : Sr : Ca : Cu = 1.7 : 0.3 : 2 : 2.5 : 3.5) were processed under an external electrical field and 17.5 MPa pressure at 800 degreesC, for 4 min in vacuum. Final heat treatments (HT) were applied at 835 - 850 degreesC for 70 h. in air (Bi, Pb)(2)Sr2CaCu2Ox (2212-phase) was formed by electrical field processing in just 4 min. Electrical field application enhanced (Bi, Pb)(2)Sr2Ca2Cu3Oy (2223-phase) formation during final HT. Ag2O additions to field sintered BSCCO ceramics increased the amount of 2223-phase and the zero resistance critical temperature (T-e(R=0)) by similar to 4 k.

2855. Compact filters with cross-coupled resonators

Authors: Banciu, MG; Lojewski, G; Ioachim, A

Published: 2003, 2003 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 116, DOI: 10.1109/SMICND.2003.1251357

Designs of new compact filters using cross-coupled resonators are presented. The square shape resonators require only 40% of the area of folded open loop half-wavelength resonators. The filters were designed for the 900 MHz band of the mobile communications systems (GSM, GPRS, etc.). The cross coupling provides a better filter skirt for a higher selectivity. The effect of the resonator finite quality factors was confirmed for the cross-coupled filters.

2856. Microstructure and mechanical properties of hydroxyapatite thin films grown by RF magnetron sputtering

Authors: Nelea, V; Morosanu, C; Iliescu, M; Mihailescu, IN

Published: AUG 22 2003, SURFACE & COATINGS TECHNOLOGY, 173, 322, DOI: 10.1016/S0257-8972(03)00729-1

Hydroxyapatite (HA) thin films for applications in bone prosthesis fabrication were obtained by the radio-frequency magnetron sputtering technique. The depositions were performed from pure HA targets on Si and Ti-5AI-2.5Fe alloy substrates. In some experiments a buffer layer of TiN was introduced by pulsed laser deposition before HA coating. The films were deposited in low-pressure argon or Ar-O-2 mixtures at substrate temperatures ranging from 70 to 550 degreesC. We observed that the films grown at temperatures below 300 degreesC were prevalently amorphous and contain a small amount of crystalline material. The initial crystalline structure of the target is reconstructed after 1 h films annealing at 550 degreesC in ambient air. Both the films directly deposited at 550 degreesC and the ones obtained at room temperature and after that annealed at this temperature-mostly contain the HA phase and exhibit good mechanical characteristics. Weaker peaks of CaO secondary phase are visible in the X-ray diffraction patterns of the films directly grown at 550 degreesC. Traces of TiO2 were detected at the interface with the metallic substrate in case of structures grown without the TiN interlayer. All films were smooth, with an average surface roughness of 50 nm. The films grown on TiN interlayer are harder, have higher elasticity modulus values and an increased mechanical resistance at the indenter penetration. (C) 2003 Elsevier Science B.V. All rights reserved.

2857. Preparation of Tl-2212 and -1223 superconductor thin films and their microwave properties

Authors: Sundaresan, A; Asada, H; Crisan, A; Nie, JC; Kito, H; Iyo, A; Tanaka, Y; Kusunoki, M; Ohshima, S

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 474, DOI: 10.1016/S0921-4534(02)02585-6

Tl2Ba2CaCu2Oy (Tl-2212) and Tl(Ba,Sr)(2)Ca2Cu3Oy (Tl-1223) superconductor thin films have been prepared on CeO2 buffered sapphire substrate by an ex situ process namely, amorphous phase epitaxy (APE) method. In the case of Tl-1223, an amorphous layer of TlSr2CaCu2Oy (TlSr-1212) was deposited on top Of CeO2 layer to avoid chemical reaction between Tl-1223, containing Ba, and CeO2 layers. All films are epitaxial with smooth surface and excellent crystallinity. Superconducting transition temperatures (T-c) of Tl-2212 and 1223 are around 95 and 104 K, respectively. Critical current density (J(c)) at 77 K measured on 5 x 5 mm. films by inductive technique is as high as 2 MA/cm(2). Surface resistance R-s of Tl-2212 films measured by a dielectric resonator technique at 38 GHz is comparable to the best YBCO films. (C) 2003 Elsevier Science B.V. All rights reserved.

2858. Coupled confinement effect on the photoluminescence and electrical transport in porous silicon

Authors: Ciurea, ML; Draghici, M; Iancu, V; Reshotko, M; Balberg, I

Published: MAY 2003, JOURNAL OF LUMINESCENCE, 102, 497, DOI: 10.1016/S2313(02)00589-6

In this paper we report correlations between the structure, the photoluminescence and the transport properties of luminescent porous silicon. These correlations combined with the observed temperature dependence of tunneling characteristics yield quite a wholesome (pea-pod-like) model for this system. (C) 2002 Elsevier Science B.V. All rights reserved.

2859. Microscopic modelling of defects production and their annealing after irradiation in silicon for HEP particle detectors

Authors: Lazanu, S; Lazanu, I; Bruzzi, M

Published: NOV 21 2003, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 514, 17, DOI: 10.1016/j.nima.2003.08.078

In this contribution, the production of defects in radiation fields and their evolution toward equilibrium in silicon for detector uses has been modelled. In the quantitative model developed, the generation rate of primary defects is calculated starting from the projectile-silicon interaction and from recoil energy redistribution in the lattice. Vacancy-interstitial annihilation, interstitial migration to sinks, divacancy and vacancy-impurity complex (VP, VO, V2O, CiOi and CiCs) formation are considered. The results of the model support the experimental available data. The correlation between the initial material parameters, temperature, irradiation and annealing history is established. The model predictions could be a useful clue in obtaining harder materials for detectors at the new generation of accelerators or for space missions. (C) 2003 Elsevier B.V. All rights reserved.

2860. Flux-creep annealing in Bi2CaCu2O8+delta and La2-xSrxCuO4 single crystals at low temperatures

Authors: Miu, L; Tamegai, T; Tokunaga, M

Published: NOV 21 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 399, 80, DOI: 10.1016/S0921-4534(03)01300-5

We performed flux-creep annealing experiments on disordered (overdoped) Bi2Sr2CaCu2O8+delta and La2-xSrxCuO4 single crystals in remnant magnetic field at T = 10 K, where, as generally accepted, the vortex creep process is thermally activated, and at T = 2 and 1.8 K, in the putative quantum creep regime. A simple data analysis shows that the variation of the creep barrier U with the current density J remains qualitatively the same, regardless of T. In the case of La2-xSrxCuO4 single crystals in remnant field U(J) diverges in the low-J limit, and flux-creep annealing considerably reduces the normalized relaxation rate S at low T. We emphasize that the relatively large "residual" S values appearing below a certain crossover temperature in "standard" magnetization relaxation experiments are mainly due to the usually fixed relaxation time window in the conditions of a strong U(J) nonlinearity. (C) 2003 Published by Elsevier B.V.

2861. Polyaniline and carbon nanotubes based composites containing whole units and fragments of nanotubes

Authors: Baibarac, M; Baltog, I; Lefrant, S; Mevellec, JY; Chauvet, O

Published: OCT 21 2003, CHEMISTRY OF MATERIALS, 15, 4156, DOI: 10.1021/cm021287x

Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared (FTIR) spectroscopy, we show that composites based on polyaniline (PANI) and single-walled carbon nanotubes (SWNTs) are different when they are prepared by two different methods: (1) by adding dispersed SWNTs to the polymer solutions and (2) by chemical polymerization of aniline in the presence of SWNTs. The difference originates from the irreversible chemical transformation of SWNTs in the polymerization medium. The synthesis medium used for the preparation of PANI transforms SWNTs into fragments of shorter length like closed-shell fullerenes. This explains the similarity of SERS and FTIR spectra of the composites PANI/SWNTs and PANI/C-60 chemically prepared. All compounds exhibit an absorption band at 1144 cm(-1) in their FTIR spectra, increasing with the carbon nanoparticules content, as a signature of a charge transfer between the constituents. Besides, the FTIR spectrum of the compounds obtained by adding SWNTs to the polymer solution display an intense absorption band with two components at 773 and 755 cm(-1), which are associated with the vibration of deformation of the benzene and the quinoid ring, respectively. This indicates a strong hindrance effect produced by the binding on the polymer chain of voluminous carbon particles as nanotubes and large fragments of nanotubes.

2862. Influence of the reaction conditions on the activity properties of vanadium-aluminium oxynitride propane ammoxidation catalyst

Authors: Florea, M; Silvy, RP; Grange, P

Published: DEC 8 2003, , DOI: 10.1016/S0926-860X(03)00591-X

2863. Propane ammoxidation catalyst based on vanadium-aluminum oxynitride

Authors: Silvy, RP; Florea, M; Blangenois, N; Grange, P

Published: AUG 2003, , DOI: 10.1002/aic.690490830

2864. Eu-doped PT-type ceramics. I. Preparation and structural investigation

Authors: Dimitriu, E; Ion, ED; Constantinescu, S; Bunescu, M; Ramer, R

Published: 2003, FERROELECTRICS, 294, 92, DOI: 10.1080/00150190390238658

Two series of PT-type materials doped with Eu+3 with the formula PbxEuyTi0.98Mn0.02O3 (x=0.98, 1.00 and y=0.00, 0.02, 0.04, 0.08, 0.12) were prepared by conventional ceramic technique. The compounds with compensated and uncompensated valences were sintered between 1150 and 1220degreesC. The two types of compounds and the content of the donor ion, Eu+3 , influence the mechanical and dielectric properties of sintered samples. The spectra and data obtained on Eu-151 Mossbauer measurements are discussed.

2865. New class of catalysts for the propane ammoxidation process based on vanadium aluminum oxynitrides

Authors: Florea, M; Prady-Silvy, R; Grange, P

Published: APR 2003, , DOI: 10.1023/A:1022857211248

2866. Preparation and structural investigation of epitaxially grown antiferromagnetic FeSn2(001) thin films on InSb(001)

Authors: Kuncser, V; Doi, M; Sahoo, B; Stromberg, F; Keune, W

Published: SEP 1 2003, JOURNAL OF APPLIED PHYSICS, 94, 3581, DOI: 10.1063/1.1595144

Antiferromagnetic FeSn2(001) thin films with different thicknesses and relatively low Neel temperatures were grown on InSb(001)(4x2) surfaces by molecular-beam epitaxy. The Neel temperature could be increased to above room temperature by subsequent thermal annealing. In situ structural characterization was performed by high- and low-energy electron diffraction. The degree of the structural (001) texture as a function of the preparation and annealing conditions was investigated by x-ray diffractometry. The local magnetic properties and the spin structure were studied using Fe-57 conversion electron Mossbauer spectroscopy (CEMS) at different temperatures. The epitaxial FeSn2(001) thin films exhibit in-plane Fe spin orientation and appear to be suitable antiferromagnets for studying the interfacial spin structure in exchange-biased bilayers by CEMS. (C) 2003 American Institute of Physics.

2867. Self-organization in non-crystalline solids

Authors: Popescu, M

Published: 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1068, DOI:

It is shown that self-organization can be revealed in non-crystalline materials. Experimental and modelling studies are discussed. The importance of the Boolchand intermediary phase for the chalcogenide network glasses with self-organization is pointed out. The basical principles of self-organization are the key for the production of nano-materials with new properties.

2868. Growth and properties of Pb(ZrxTi1-x)O-3 step graded-structures

Authors: Boerasu, I; Pintilie, L; Pereira, M; Gomes, MJM; Vilarinho, PM

Published: SEP 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 775, DOI:

Pb(Zr-x Ti1-x)O-3 (x = 55, 65, 92), PZT step graded-structure have been deposited by sol-gel technique on Pt-coated Si. Up-graded and down-graded structures has been obtained by changing the Zr/Ti ratio in steps a long to the film thickness. Up means that the ratio was increased from the bottom to the top while down means it was decreased. The properties of these films were investigated and compared with those of conventional films with homogeneous composition. It was found that the properties of up and down graded structures are completely different. Up-graded films have better ferroelectric properties than the downgraded ones. Pyroelectric signal could be detected also on as-grown up-graded films, in accordance with the structural results that show a strong (100) orientation in this case, The coercive field of the up-graded film is lower than the values obtained in case of homogeneous films with the same Zr/Ti ratios like those used in the graded structures.

2869. Self-organization in simulated arsenic chalcogenide networks

Authors: Popescu, M

Published: OCT 1 2003, JOURNAL OF NON-CRYSTALLINE SOLIDS, 326, 388, DOI: 10.1016/S0022-3093(03)00443-5

Polymerization-depolymerization processes induced by bandgap light irradiation with alternating high and low intensity light control the nano-scale extension of disordered layer-like clusters in arsenic rich chalcogenides. These processes resulting in a fractal morphology of the clusters were simulated in the frame of a Monte-Carlo-Metropolis method. The fractal model for photo-darkening and photo-bleaching phenomena in arsenic chalcogenides is discussed. (C) 2003 Elsevier B.V. All rights reserved.

2870. Morphology, structure and optical properties of sol-gel ITO thin films

Authors: Stoica, TF; Teodorescu, VS; Blanchin, MG; Stoica, TA; Gartner, M; Losurdo, M; Zaharescu, M

Published: AUG 15 2003, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 101, 226, DOI: 10.1016/S0921-5107(02)00667-0

The alkoxidic route and the spinning deposition were used to prepare monolayer sol-gel indium tin oxide (ITO) films. The morphology and crystalline structure were investigated by cross-section transmission electron microscopy (XTEM) and atomic force microscopy (AFM). The ITO sol-gel mono-layer contains three regions of different porosities. The basic crystalline structure is that of the In2O3 lattice. The optical properties have been studied by optical transmission and spectroscopic ellipsometry. (C) 2003 Elsevier Science B.V. All rights reserved.

2871. Anisotropies in ferromagnetic nanoparticles: simulation and experimental approach

Authors: Crisan, O; Angelakeris, M; Flevaris, NK; Sobal, N; Giersig, M

Published: SEP 15 2003, SENSORS AND ACTUATORS A-PHYSICAL, 106, 133, DOI: 10.1016/S0924-4247(03)00150-X

Magnetic behavior of the isolated ferromagnetic bimetallic nanoparticles is investigated in relation with the competition between exchange interaction and surface and bulk anisotropies. Experimental results on AgCo bimetallic nanoparticles are presented and correlated with Monte Carlo simulation of low temperature spin ordering. The nature of spin disorder at the surface, responsible for the reduction of the overall saturation magnetization is briefly discussed. (C) 2003 Elsevier B.V. All rights reserved.

2872. LiF addition to (Cu,C) Ba2Ca3Cu4Oy superconductor

Authors: Badica, P; Crisan, A; Hirai, M; Iyo, A; Kito, H; Aldica, G; Tanaka, Y

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 396, DOI: 10.1016/S0921-4534(02)02535-2

Samples of (Cu0.6C0.4)Ba2Ca3Cu4Oy ((Cu,C)-1234) with addition of 0.1 mol LiF have been synthesized by high pressure technique. It was found that LiF promotes' the formation of superconducting phases with n higher than 4 of the (Cu,C)Ba2Can-1CunOy series. In order to obtain single-phase samples, for the same synthesis conditions, the oxygen content in the starting mixture (supplied by AgO) should be increased from 0.45 to 0.73 mol AgO, when using LiF. Samples with LiF have shown a certain morphology suggesting an enhanced 2D and suppressed 3D type of growth assisted by a liquid phase. T-c decreased from 116.5 to 113 K for the sample with LiF, but at the same time the transition width also decreased and J(c) has shown a fish-tail effect. (C) 2003 Elsevier Science B.V. All rights reserved.

2873. Au-induced perpendicular magnetization in Fe films grown on Si(001)

Authors: Zavaliche, F; Wulfhekel, W; Przybylski, M; Bodea, S; Grabowski, J; Kirschner, J

Published: APR 7 2003, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 36, 784, DOI: 10.1088/0022-3727/36/7/302

We report on Fe films grown on Au-buffered Si(001) showing perpendicular magnetization at ambient temperatures. The in-plane magnetization in ultra-thin Fe films grown at 150 K reorients irreversibly out-of-plane as a result of annealing close to room temperature. A Au cap layer which is expected to segregate to the top of the Fe film may be responsible for this behaviour. This hypothesis is based on the observation of an in-plane to out-of-plane reorientation of magnetization upon the growth of an ultra-thin Au cap layer on a slightly thicker Fe film. The origin of such a strong out-of-plane anisotropy of Fe induced by Au is discussed.

2874. Preparation of Tl-2212 and Tl-1223 superconductor thin films and their microwave surface resistance

Authors: Sundaresan, A; Asada, H; Crisan, A; Nie, JC; Kito, H; Iyo, A; Tanaka, Y; Kusunoki, M; Ohshima, S

Published: JUN 2003, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, 13, 2916, DOI: 10.1109/TASC.2003.812045

Epitaxial Tl2Ba2CaCu2Oy and Tl(Ba,Sr)(2)Ca-2 Cu3Oy thin films have been prepared on CeO2 buffered sapphire substrate by an ex situ process with high reproducibility. Microstructure analysis of the surface of the TI-2212 films showed well connected and smaller sized grains of 1 mum or less. In the case of TI-1223 film, plate-like crystals with pits and pin holes could be observed. The superconducting critical temperatures of both films are around 96 K. Critical current density measured by ac susceptibility technique is as high as 1 MA/cm(2) at 77 K. The microwave surface resistance of these films was measured over a wide range of temperatures by a HTS-sapphire-HTS resonator method at 38 GHz on films with area 10 mm x 10 mm. The temperature dependence of surface resistance of TI-2212 film follows very closely to that of the best YBCO films on MgO substrate, whereas the TI-1223 exhibits slightly higher values resulting from an inferior surface morphology.

2875. Optical and electronic properties of metal doped polymers for integrated optics

Authors: Bulinski, M; Kuncser, V; Cristea, D; Plapcianu, C; Krautwald, S; Franke, H; Wagner, FE; Filoti, G

Published: MAR 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 335, DOI:

The electronic mechanism responsible for the optical behavior of the mixed Fe and Sn doped polymers were studied in comparison with the correspondent single doped (Fe or Sn) ones. Optical absorption as well as Fe-57 and Sn-119 Mossbauer measurements were performed on different UV exposed films. The new data provided the role of each element from the pair on the involved electronic mechanism induced by irradiation.

2876. Frequency agile BST materials for microwave applications

Authors: Ioachim, A; Toacsan, MI; Banciu, MG; Nedelcu, L; Plapcianu, C; Alexandru, H; Berbecaru, C; Ghetu, D; Stoica, G; Ramer, R

Published: 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 1393, DOI:

(Ba1-xSrx)TiO3 solid solution (BST), with different molar compositions (x = 0.25, 0.5, 0.75, 0.9) Were prepared by conventional solid-state reaction from raw materials. Structural parameters, crystallite sizes and bulk densities were determined. Perovskite type polycrystalline structure of the BST ceramics was revealed by X-ray diffraction (XRD) data. The dependence of permittivity and losses at low frequency (1 kHz) was analyzed. The microwave investigations at room temperature revealed dielectric constant around 1000 and loss smaller than 1% at 1.1 GHz. The results indicate that some BST dielectric ceramics are suitable in paraelectric phase for microwave devices. The dielectric constant can be adjusted by using a DC-bias field and such materials are appropriate for manufacturing electric field controlled components such as resonators, phase shifters etc.

2877. Annealing effect of the irreversibility fields in (Cu,C)Ba2Can-1CunOy (n=3 and 4)

Authors: Hirai, M; Iyo, A; Kito, H; Crisan, A; Tokiwa, K; Watanabe, T; Arai, J; Tanaka, Y

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 428, DOI: 10.1016/S0921-4534(02)02552-2

Annealing effect of the irreversibility fields (H-irr) in (Cu,C)Ba2Ca2Cu3Oy ((Cu,C)-1223) and (Cu,C)Ba2Ca3Cu4Oy ((Cu,C)-1234) have been investigated. The samples prepared under high pressure were post-annealed in nitrogen gas in the temperature range of 400-500degreesC. H-irr of (Cu,C)-1234 was improved after annealing at 450degreesC while T-c remained almost constant. This suggests that carrier density of five-coordinated CuO2 planes or conductivity of charge reservoir layers is changed by annealing while keeping that of four-coordinated CuO2 planes almost constant. Both samples show H-irr similar or equal to 4 T at 90 K by the post-annealing, which is quite attractive for practical application. (C) 2003 Elsevier Science B.V. All rights reserved.

2878. Heavy-ion irradiation dependence of the superconducting properties of (Cu,C)Ba2Ca3Cu4O10.5-delta

Authors: Kito, H; Iyo, A; Crisan, AI; Hirai, M; Tokumoto, M; Okayasu, S; Sasase, M; Ihara, H; Tanaka, Y

Published: MAY 2003, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 388, 712, DOI: 10.1016/S0921-4534(02)02488-7

To enhance or improve critical currents density (J(c)) and irreversibility field (H-irr) of (Cu,C)Ba2Ca3Cu4O10.5-delta ((Cu,C)-1234), pinning centers were introduced by heavy-ion irradiation. The polycrystalline samples were irradiated with An(15+) ions (240 MeV energy) at various fluence of 1 x 10(11), 2.5 x 10(11) and 5 x 10(11) ions/cm(2). J(c) and H-irr were determined for the irradiated samples as well as unirradiated samples. J(c) (77 K, 1 T) increase from 3.9 x 10(4) A/cm(2) to 4.1 x 10(6) A/cm(2) for at fluence of 1 x 10(11) ions/cm(2) of heavy-ion irradiated sample and decreases with further increase of fluence. These results indicate the possibility of further enhancement of Jc and of achieving a very high H-irr of (Cu,C)-1234 below a fluence of 1 x 10(11) ions/cm(2). (C) 2003 Elsevier Science B.V. All rights reserved.

2879. Magnetism and anisotropy in core-shell nanoparticles

Authors: Crisan, O; Angelakeris, M; Flevaris, NK; Filoti, G

Published: DEC 2003, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 5, 962, DOI:

The subject of magnetic anisotropy in nanostructured materials is of considerable interest from both experimental and theoretical points of view. Systems that consist of either isolated or interacting nanoparticles are shown to exhibit different magnetic properties of the nanoparticle surface than those of the bulk. This altering of magnetic behavior is mainly related to surface spins structure cot-related with finite size effects, providing that the nanoparticles are sufficiently small so that the surface-to-volume atomic ratio would be high enough. This work reports on both the simulation and experimental approach on the magnetic behavior of ferromagnetic nanoparticles. We investigate the competition between surface and bulk magnetocrystalline anisotropy in small magnetic particles. The experimentally obtained magnetic data for ferromagnetic core-shell-type AgCo nanoparticles are interpreted consistently with the results of Monte Carlo simulation of the magnetic behavior of single domain nanoparticles.

2880. Spectroscopic study of As2S3 glasses doped with Dy, Sm and Mn

Authors: Iovu, MS; Shutov, SD; Andriesh, AM; Kamitsos, EI; Varsamis, CPE; Furniss, D; Seddon, AB; Popescu, M

Published: OCT 1 2003, JOURNAL OF NON-CRYSTALLINE SOLIDS, 326, 310, DOI: 10.1016/S0022-3093(03)00418-6

The effect of rare earth (Dy and Sm) and transition metal (Mn) luminescent impurities on the optical properties of As2S3 glasses is studied in a wide spectral region. The Raman, IR, band-to-band and edge absorption spectroscopy are employed to obtain information about the incorporation of impurity ions in the host glass structure and the corresponding changes in intrinsic optical characteristics. The effect of metal impurity on both extended and localized electronic states is revealed. (C) 2003 Elsevier B.V. All rights reserved.

2881. Complex semiconducting ceramic

Authors: Leonovici, M; Steflea, M; Popescu, MA

Published: MAY 2003, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 23, 886, DOI: 10.1016/S0955-2219(02)00228-5

Complex semiconducting ceramic compositions were prepared. Structure, crystallite morphology, hardness and electrical conduction were investigated. After annealing at 150 degreesC a distinct crystalline phase was obtained and the ceramic became compact, hard, of higher resistivity, while preserving the basic semiconducting properties (C) 2002 Elsevier Science Ltd. All rights reserved.

2882. Hybridization effects in some UTSi (2 : 1 : 3;1 : 1 : 1;2 : 3 : 1) compounds

Authors: Lupsa, I; Valeanu, M

Published: OCT 20 2003, MODERN PHYSICS LETTERS B, 17, 1282, DOI: 10.1142/S0217984903006311

The presence of magnetic moments in uranium atoms in some of U2TSi3, UTSi and U2T3Si (T is a 3d, 4d or 5d transition element) compounds is discussed in terms of the hybridization of s, p, d and f atomic orbitals. The hybridization strength in these ternary series of isostructural compounds was calculated using the semiquantitative band structure approach of Straub and Harrison. The prediction criterion for the presence of magnetic ordering, comparing the band width with a critical energy, seems to hold. The dominant influence of fd hybridization effects in the change of magnetic properties inside an isostructural group is in evidence.

2883. Simple model of polarization offset of graded ferroelectric structures

Authors: Pintilie, L; Boerasu, I; Gomes, MJM

Published: JUN 15 2003, JOURNAL OF APPLIED PHYSICS, 93, 9967, DOI: 10.1063/1.1577401

The abnormal polarization offset observed in case of graded ferroelectric structures is explained assuming the presence of a nonreversible part of polarization due to the imposed polarization gradient. It is shown that an upper limit for the offset should exist, fixed by the remnant polarization of the component materials considered as independent layers. This is valid for the structures in which polarization increases or decreases in steps from one layer to the other, but should also be valid for the structures with continuous gradient. However, large values of the charge offset could be achieved in the last case. The electric field dependence of the polarization offset is predicted, together with the possibility of obtaining large nonconventional pyroelectric coefficients. The simulation developed in the case of a bilayer ferroelectric structure and using data from the lead-lanthanum-zirconate-titanate system describes well the observed features of the graded ferroelectric structures. (C) 2003 American Institute of Physics.

2884. Fabrication of novel magnetic nanostructures by colloidal bimetallic nanocrystals and multilayers

Authors: Angelakeris, M; Crisan, O; Papaioannou, E; Vouroutzis, N; Tsiaoussis, I; Pavlidou, E; Crisan, AD; Kostic, I; Sobal, N; Giersig, M; Flevaris, NK

Published: DEC 15 2003, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS, 23, 878, DOI: 10.1016/j.msec.2003.09.147

Recent developments of lithographic techniques as well as improved chemical synthesis methods allow researchers to engineer novel nanostructured materials consisting of arrays of self-organized nanocrystals and multilayers grown as patterns on different substrates. In our case, the magnetic nanostructures consist either of multilayers directly deposited on pre-patterned substrates to form regular arrays of stripes and grooves or colloidal solutions of self-organized bimetallic Ag/Co nanoparticles on patterned and nonpatterned substrates. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed in order to study the surface morphology of the 2D patterning arrays and the 3D nanostructures. The development of periodic arrays of magnetic patterns of micrometer size is strongly dependent on technological parameters such as: film, thickness, distances, size and shape of the patterns. Moreover, it is shown that the substrate morphology significantly affects the colloidal crystallization of magnetic nanoparticles and leads to different growth modes. This will ultimately affect the overall magnetic behavior of the nanostructures. Consequently, the combination of self-assembly and patterning allows for the controlled fabrication of the novel magnetic nanostructures at a macroscopic level and the study of fundamental aspects in magnetism such as quantum tunneling magnetization and magneto-transport properties along well-defined nanosized patterns. (C) 2003 Elsevier B.V. All rights reserved.

2885. Polynuclear coordination compounds as precursors for CuFe2O4

Authors: Marinescu, G; Patron, L; Carp, O; Diamandescu, L; Stanica, N; Meghea, A; Brezeanu, M; Grenier, JC; Etourneau, J

Published: 2002, JOURNAL OF MATERIALS CHEMISTRY, 12, 3462, DOI: 10.1039/b206604c

The possibility of obtaining copper ferrite through the thermal decomposition of the two polynuclear coordination compounds: (NH4)(8) [Fe2Cu(C2O4)(8)](I) and [Fe2Cu(C2O4)(2) (OH)(4)].4H(2)O (II) was considered. The polynuclear compounds were characterized by various physical chemical techniques, e. g., IR, UV-VIS, EPR, Mossbauer spectra, thermal analysis and magnetic measurements. The final products obtained after thermal decomposition of the complex compounds were analysed by X-ray diffraction. A mixture of tetragonal CuFe2O4, alpha-Fe2O3 and CuO is generated from the thermolysis of compound I, while a clean tetragonal CuFe2O4 with saturation magnetization of 26.89 emu g(-1) is obtained from compound II.

2886. SERS studies on single-walled carbon nanotubes submitted to chemical transformation with sulfuric acid

Authors: Lefrant, S; Baltog, I; Baibarac, M; Mevellec, JY; Chauvet, O

Published: 2002, CARBON, 40, 2211, DOI: 10.1016/S0008-6223(02)00089-1

Surface-enhanced Raman scattering (SERS) at 676.44 nm and 1064 nm excitation wavelengths was used to investigate chemical transformation of single-walled carbon nanotubes (SWNTs) deposited on a gold support. Sulfuric acid was used as the chemical reagent. Special attention was paid to the changes in the Raman bands associated to radial and tangential vibration modes. Partial restoration of the Raman spectra by a Subsequent alkaline treatment indicates a transformation with a certain degree of reversibility. The recovery reaction achieved with a 0.5 M KOH solution showed that the variations of tangential and radial band groups are not correlated. The intensity changes of the radial bands is a principal indicator for the chemical transformation of the SWNTs. Particular attention was paid to radial bands at 164 and 176 cm(-1), observed with 1064 nm and 676.44 nm excitation wavelength, respectively, and their 14 cm(-1) up-shifted replicas i.e. the bands at 178 and 190 cm(-1). A different behavior of these bands in the anti-Stokes side was observed. (C) 2002 Elsevier Science Ltd. All rights reserved.

2887. Growth of TlBa2Ca2Cu3Oy superconducting thin film on CeO2 buffered sapphire substrate

Authors: Sundaresan, A; Nie, JC; Hirai, M; Crisan, A; Fujiwara, S; Asada, H; Badica, P; Ishiura, Y; Kito, H; Ihara, H

Published: OCT 1 2002, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 378, 1286, DOI: 10.1016/S0921-4534(02)01692-1

We report the growth of TlBa2Ca2Cu3Oy superconducting thin film on CeO2 buffered r-cut sapphire substrate by amorphous phase epitaxy method, wherein an amorphous phase of a composition, TlBa2Ca3Cu4Oy was deposited by rf magnetron sputtering and subsequently crystallized by annealing at high temperatures in a closed system. There exists an optimum thickness of about 200 Angstrom of CeO2 buffer layer that gives a smooth buffer layer surface. At the temperature around 840 degreesC we get only Tl-2212 phase and for a longer annealing time it results in Tl-1212 phase. At higher temperatures Ba reacts with Ce to form BaCeO3. To avoid this reaction process we introduced another amorphous buffer layer, TlSr2CaCu2Oy onto CeO2 layer. By this method we could prepare a good quality TI-1223 thin film which showed a T-c of 104 K and a J(c) = 0.3 MA/cm(2) at 77 K and 0.1 T field. (C) 2002 Elsevier Science B.V. All rights reserved.

2888. The effect of rare-earth impurity on the photodarkening relaxation in as-evaporated amorphous As2Se3 : Pr and As2Se3 : Dy films

Authors: Iovu, MS; Shutov, SD; Boolchand, P; Colomeico, EP; Ciorba, VG; Iovu, SM; Popescu, M

Published: DEC 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 861, DOI:

The effect of foreign impurity atoms (Dy and Pr) in as-evaporated amorphous As2Se3 thin films on the photodarkening relaxation was investigated. The photodarkening amplitude depends on the kind and concentration of rare-earth dopant, as well as on the thickness of the sample. The observed variation of photodarkening amplitude with the sample thickness is due on the amount of absorbed photons generating the photodarkening effect. The photodarkening kinetics is described by a stretched exponential function with the dispersion parameter alpha less than or equal to 0.5, which indicates high dispersion of the relaxation process in untreated as-deposited chalcogenide films.

2889. A Mossbauer study of the Verwey transition in cobalt-doped magnetite

Authors: Sorescu, M; Grabias, A; Brand, RA; Voss, J; Tarabasanu-Mihaila, D; Diamandescu, L

Published: MAY 2002, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 246, 403, DOI: 10.1016/S0304-8853(02)00112-9

The low-temperature behavior of the Co-doped magnetite is studied. The Fe3-xCoxO4 powders (x = 0.01 - 1) have been prepared by the hydrothermal method. In order to investigate the cobalt influence on the structure of magnetite, transmission Mossbauer spectroscopy measurements were performed at temperatures close and below the Verwey transition temperature characteristic for pure magnetite (122 and 77 K, respectively). All spectra were fitted with five components and related to nonequivalent Fe2+ and Fe3+ sites. The hyperfine parameters of these sites as well as their relative fractions in the powder samples were determined. (C) 2002 Elsevier Science B.V. All rights reserved.

2890. AC susceptibility and higher harmonics studies of heavy-ion irradiated CuBa2Ca3Cu4Oy bulk superconductor with highest irreversibility field above liquid-nitrogen temperature

Authors: Crisan, A; Iyo, A; Kito, H; Tanaka, Y; Hirai, M; Sasase, M; Okayasu, S; Ihara, H

Published: OCT 1 2002, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 378, 117, DOI: 10.1016/S0921-4534(02)01393-X

A 50 mum thick slice of (Cu,C)Ba2Ca3Cu4Oy (CU:1234) bulk superconductor grown by high-pressure synthesis technique was irradiated with high-energy (240 MeV) Au15+ ions (10(11) cm(-2)). Complimentary DC magnetization measurements up to 5 T showed an increase in critical current density by two orders of magnitude. AC susceptibility studies were performed in DC magnetic fields up to 14 T and at various temperatures, using various AC field amplitudes (up to 15 Oe) and frequencies (up to 10 kHz). Critical current densities at various temperatures and fields were estimated from critical state model. Using the third harmonic response of the sample we were able to separate different contributions to the dissipation: inter-grain regions, grains without columnar defects (heavy-ions penetration depth is about one quarter of sample's thickness), and grains with columnar defects. In irradiated grains, we could observe a peak-effect in the field dependence of critical current density at high DC fields and temperatures between 85 and 105 K, suggesting the possibility of the highest irreversibility field at liquid nitrogen temperature. (C) 2002 Elsevier Science B.V. All rights reserved.

2891. Magnetism and phase structure of crystallized Sm-Fe-B melt spun ribbons

Authors: Crisan, O; Le Breton, JM; Nogues, M; Machizaud, F; Filoti, G

Published: DEC 2 2002, JOURNAL OF PHYSICS-CONDENSED MATTER, 14, 12609, DOI: 10.1088/0953-8984/14/47/331

The crystallization of amorphous SmxFe80-xB20 melt spun ribbons is studied over an extended range of composition (0 < x < 8). Differential scanning calorimetry scans reveal different endo- and exothermic effects depending upon the composition. X-ray diffraction and Mossbauer studies for samples annealed at temperatures close to the onset of the first exothermic effect prove that, during the primary crystallization of the amorphous ribbons, both alpha-Fe and Fe3B phases appear-with Sm ions randomly accommodating the Fe sites in the tetragonal Fe3B lattice-while the subsequent exothermic reactions correspond to the decomposition of the metastable Fe3B phase into alpha-Fe and Fe2B and to the formation of the ternary Sm1.1Fe4B4 phase. Fully crystallized ribbons with Sm contents lower than about 7 at.% show the co-existence between alpha-Fe and Fe2B soft magnetic phases and the Sm2Fe14B magnetic one. The enhancement of magnetic properties with increasing relative proportion of magnetic phase is discussed and correlated with exchange coupling and spin wave stiffness data obtained from the magnetic measurements.

2892. High temperature magnetic behaviour of iron-based nanocrystalline alloys

Authors: Randrianantoandro, N; Labaye, I; Berger, L; Crisan, O; Grafoute, M; Calvayrac, F; Greneche, JM

Published: JUN 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 198, DOI:

After a presentation of structural aspects of iron-based nanocrystalline alloys, the magnetic behaviours of those two-phase magnetic structures are conceptually discussed at high temperatures as a function of the crystalline volumetric fraction, on the basis of the magnetic correlation length compared to the distances between crystalline grains. In addition, some results predicted by an approach based on Monte-Carlo simulation are then briefly presented: they show a qualitative agreement with experimental results.

2893. Reactive-field-assisted-sintering of freeze-dried powders in the BSCCO system

Authors: Badica, P; Aldica, G; Groza, JR; Bunescu, MC; Mandache, S

Published: JAN 2002, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 15, 42, DOI: 10.1088/0953-2048/15/1/307

The reactive-field-assisted-sintering technique (RFAST) has been applied to freeze-dried decomposed precursor powders with a starting cation composition of Bi:Pb:Sr:Ca:Cu = 1.7:0.3:2.0:2.5:3.5. A short time (< 15 min) RFAST treatment at 800-900degreesC did not lead to the formation of Bi2Sr2Ca2Cu3O10+x, (2223-phase). But RFAST was favourable to Bi2Sr2CaCu2O8+y, (2212-phase) formation particularly in samples with a low content of the 2212-phase in the precursor powder. Heat treatment (HT) after RFAST showed that the 2223 phase could form more rapidly than in freeze-dried pressed and sintered pellets produced by the traditional technique. The resultant ceramics after 70 h of annealing contain 75% 2223-phase and have T-c(R=0) = 100.7 K, T-c = 109.5 K and DeltaT(c) = 22.4 K.

2894. Electrosynthesis and properties of some substituted polyanilines in phosphate buffer

Authors: Sima, M; Buda, M; Vasile, E; Visan, T

Published: JAN-FEB 2002, REVUE ROUMAINE DE CHIMIE, 47, 193, DOI:

The electropolymerizations of 2-aminohippuric acid methyl ester and 2-aminobenzoic acid methyl ester monomers in phosphate buffer (pH = 6.5) were studied. The formation of thin films at the platinum electrode surface is observed as main product and the electrosynthesis process of the two substituted polyanilines shows the voltammetric characteristics of the polyaniline film electrosynthesis. The necessary charge to deposit 0.05 mum poly(2-aminohippuric acid methyl ester) or poly(2-aminobenzoic acid methyl ester) films is about 60 mC/cm(2). The polymer films were investigated by electrochemical impedance spectroscopy. On the basis of the obtained results we propose the equivalent circuit for these polymer films.

2895. Quasi-optical dynamical surface resistance characterization of HTS laser ablated films

Authors: Branescu, M; Jaklovszky, J; Ristoscu, C; Mihailescu, IN

Published: 2002, ALT'01 INTERNATIONAL CONFERENCE ON ADVANCED LASER TECHNOLOGIES, 4762, 246, DOI: 10.1117/12.478643

The paper presents a syntheses of the last data concerning the optimal parameters of the deposition process to obtain the best dynamic quality HTS thin films in connection with the most precise dynamic measurement method known to date. The paper makes a comparison between the performances achieved by the classical dynamical surface resistance nondestructive measurement techniques of the HTS laser ablated thin films and the quasi-optical high performances one.

2896. Microstrip filters using new compact resonators

Authors: Banciu, MG; Ramer, R; Ioachim, A

Published: FEB 28 2002, ELECTRONICS LETTERS, 38, 229, DOI: 10.1049/el:20020174

Compact two-pole and four-pole passband filters in 900 MHz frequency band using novel square microstrip resonators are presented. The measured filters' responses demonstrate the feasibility of selective filters using these new resonators.

2897. Relaxation of photodarkening in amorphous As-Se films doped with metals

Authors: Iovu, MS; Shutov, SD; Popescu, M

Published: APR 1 2002, JOURNAL OF NON-CRYSTALLINE SOLIDS, 299, 928, DOI: 10.1016/S0022-3093(01)00992-9

Photodarkening relaxation under light exposure of a-As2Se3 amorphous films doped with 0.5 at.% of metals Sn, Mn, Sm or Dy and a-AsSe films doped up to 10.0 at.% Sn was studied to determine its dependence on the type and concentration of impurities and thermal treatments. Both factors reduce photodarkening with the degree of reduction dependent on the type of impurity. The relaxation process may be described by a stretched exponential with the dispersion parameter 0.4 less than or equal to alpha < 0.9 and the time constant increasing with Impurity concentration or thermal annealing. The results are discussed in the context of the recently formulated 'slip-motion' model of photodarkening in chalecgenide glasses. (C) 2002 Elsevier Science B.V. All rights reserved.

2898. Synthesis and structure of trinuclear iron acetate [Fe3O(CH3COO)(6)(H2O)(3)][AuCl4]center dot 6H(2)O

Authors: Turte, KI; Shova, SG; Meriacre, VM; Gdaniec, M; Simonov, YA; Lipkowski, J; Bartolome, J; Wagner, F; Filoti, G

Published: JAN-FEB 2002, JOURNAL OF STRUCTURAL CHEMISTRY, 43, 117, DOI: 10.1023/A:1016082018299

Iron acetate of composition [Fe3O(H3COO)(6)(H2O3)][AuCl4].6H(2)O (1) was synthesized and investigated by X-ray diffraction analysis and Mossbauer spectroscopy. The [Fe3O(CH3COO)(6)(H2O)(3)](+) complex cation has a structure typical for mu(3)-O bridged trinuclear ferric compounds with iron atoms lying at the vertices of a regular triangle with an oxygen atom at the center. The iron atoms are each coordinated by 4 oxygen atoms of the four bridging carboxylic groups, the mu(3)-O bridging atom, and the coordinated water molecule in the trans-position to the tatter. In the trinuclear cation, the Fe(Ill) ions are coupled by antiferromagnetic exchange interactions with the exchange parameter J = -29.0 cm(-1) (HDVV model for D-3h symmetry). The specific role of the solvate water molecules in structure formation is discussed.

2899. A model for structures growth by sodium electrodiffusion in quartz crystals

Authors: Enculescu, I; Iliescu, B; Enculescu, M; Covalcica, I

Published: 2002, CRYSTAL RESEARCH AND TECHNOLOGY, 37, 874, DOI: 10.1002/1521-4079(200208)37:8<868::AID-CRAT868>3.0.CO;2-J

Dendritic structures were grown inside the quartz crystal by electrodiffusion of sodium ions from a NaCl layer at the anode. The electric field was applied along the optical axis Z and the structures were grown in the xy plane. An experimental arrangement using a pointed cathode and a graphite plate anode was employed. X ray diffraction analysis shows that the structures' chemical composition is a mixture of sodium silicates. To explain the structures' growth a model is proposed. The model is a bidimensional one. The transport of the particles along the Z axis structural channels by the electric field was taken into account by introducing a probability of generating the particles in the growth plane as a function of the distance to the cathode. The computer generated results and the experimental ones were compared and a good correlation was found.

2900. Some experimental results on electrical Ni/Cr contacts on thermoconductive materials

Authors: Morosanu, C; Nedelcu, M

Published: 2002, XXI INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS ICT '02, 570, DOI: 10.1109/ICT.2002.1190382

Some Cr, Ni films have been deposited by RF (1.78 MHz) magnetron sputtering onto thermoelectric materials substrates at low temperatures (<100 degreesC). We have found good adherence values (>100 kgf/cm(2)) onto n and p type substrates. Peltier devices prepared from these wafers and tested using the standard procedure (Melcor Corp.) demonstrated good values of various electrical parameters, similar with those obtained using classical contacts. This research proved the possibility of producing good quality Peltier devices using Ni/Cr electrical contacts obtained by a large scale and versatile deposition method.

2901. Modification of surface-enhanced Raman scattering spectra of single-walled carbon nanotubes as a function of nanotube film thickness

Authors: Lefrant, S; Baltog, I; Baibarac, M; Schreiber, J; Chauvet, O

Published: JUN 15 2002, PHYSICAL REVIEW B, 65, DOI: 10.1103/PhysRevB.65.235401

In this paper we report modifications of the surface enhanced Raman scattering (SERS) spectra with film thickness of carbon single-walled nanotubes (SWNTs). The decrease of film thickness reveals an increased degree of disorder, which is interpreted in terms of degradation of the single-walled nanotubes and the formation of particles similar to highly oriented pyrolytic graphite (HOPG), C-60 and amorphous carbon. The degradation of the nanotubes, dependent on the metal substrate type and its morphology, is explained on the basis of interactions between the nanotubes and the metal substrate. The D band, which is an indicator of the degree of disorder, increases its intensity when the film thickness is decreased. SERS spectra recorded at different excitation wavelengths reveal that metallic nanotubes are primarily affected. A mutual correlation was found between the variations in the relative intensity of the D band and the Breit-Wigner-Fano component due to metallic tubes displayed by Raman bands situated in the 1500-1600 cm(-1) range. A direct interaction between C-60 and nanotubes is revealed by comparative SERS spectra on SWNTs and (SWNTs+C-60) films. At lambda(exc)=676.4 nm the narrowing in the lower energy side of the broad band associated to tangential vibration modes indicates that the metallic tubes are involved in the formation of a [(SWNT)C-+(60)-] complex type.

2902. SIZE-STRAIN ROUND ROBIN: FIRST RESULTS AND THE COMPARATIVE ANALYSIS OF THE MEASUREMENTS

Authors: Balzar, D; Audebrand, N; Daymond, MR; Fitch, A; Hewat, A; Langford, JI; Le Bail, A; Louer, D; Masson, O; Popa, NC; Stephens, PW; Toby, B

Published: 2002, ACTA CRYSTALLOGRAPHICA A-FOUNDATION AND ADVANCES, 58, C24, DOI: 10.1107/S010876730208604X

2903. Structural and piezoelectric properties of rare earth doped PbTiO3 ceramics

Authors: Dimitriu, E; Boerasu, I; Pereira, M; Gomes, MJM; Tanasoiu, C

Published: 2002, FERROELECTRICS, 273, 2650, DOI:

Structural and piezoelectric properties of PbTiO3 (PT) ceramics materials doped with different rare earth elements were investigated. The basic chemical formula was Pb(0.88)Ln(0.08)Ti(0.98)Mn(0.02)O(3), where Ln stands for rare earth element (Ce, Pr, Gd, Nd). The powders were prepared by conventional ceramic method. All samples showed a tetragonal perovskite structure at room temperature. After sintering, bulk materials with high density were achieved for all compositions. Followed by XRD, the cell evolution and the structural anisotropy depend on the lanthanide ionic radius. The crystallite size was estimated from XRD measurements. Piezoelectric measurements (d(33) and k(p)) were performed using resonance - antiresonance frequencies. Ce-doped PT showed the highest d(33) coefficient (similar to39pC/N), while for the other doped materials d(33) was only of the order 30 pC/N.

2904. Thin films of langasite (La3Ga5SiO14) prepared by pulsed laser deposition

Authors: Popescu, M; Sava, F; Georgescu, S; Gheorghe, L; Mihailescu, IN; Cristescu, R; Socol, G; Bradaczek, H

Published: SEP 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 818, DOI:

Thin films of langasite (La3Ga5SiO14) have been prepared from langasite crystal targets by pulsed laser deposition. The films deposited at room temperature on silicon wafers are amorphous. After annealing at 700 degreesC, in normal atmosphere, the films crystallize as polycrystalline langasite oriented with the plane (001) parallel to the surface of the silicon substrate.

2905. Calcium phosphate thin film processing by pulsed laser deposition and in situ assisted ultraviolet pulsed laser deposition

Authors: Nelea, V; Pelletier, H; Iliescu, M; Werckmann, J; Craciun, V; Mihailescu, IN; Ristoscu, C; Ghica, C

Published: DEC 2002, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 13, 1173, DOI: 10.1023/A:1021150207350

Calcium orthophosphates (CaP) and hydroxyapatite (HA) were intensively studied in order to design and develop a new generation of bioactive and osteoconductive bone prostheses. The main drawback now in the CaP and HA thin films processing persists in their poor mechanical characteristics, namely hardness, tensile and cohesive strength, and adherence to the metallic substrate. We report here a critical comparison between the microstructure and mechanical properties of HA and CaP thin films grown by two methods. The films were grown by KrF* pulsed laser deposition (PLD) or KrF* pulsed laser deposition assisted by in situ ultraviolet radiation emitted by a low pressure Hg lamp (UV-assisted PLD). The PLD films were deposited at room temperature, in vacuum on Ti-5Al-2.5Fe alloy substrate previously coated with a TiN buffer layer. After deposition the films were annealed in ambient air at 500-600 C. The UV-assisted PLD films were grown in (10(-2)-10(-1) Pa) oxygen directly on Ti-5Al-2.5Fe substrates heated at 500-600 degreesC. The films grown by classical PLD are crystalline and stoichiometric. The films grown by UV-assisted PLD were crystalline and exhibit the best mechanical characteristics with values of hardness and Young modulus of 6-7 and 150-170 GPa, respectively, which are unusually high for the calcium phosphate ceramics. To the difference of PLD films, in the case of UV-assisted PLD, the GIXRD spectra show the decomposition of HA in Ca2P2O7, Ca2P2O9 and CaO. The UV lamp radiation enhanced the gas reactivity and atoms mobility during processing, increasing the tensile strength of the film, while the HA structure was destroyed. (C) 2002 Kluwer Academic Publishers.

2906. Cum-1Bam(Sr,Ca)(n)Cun+1O2m+2n+1 superlattice thin film by layer-by-layer growth techniques

Authors: Nie, JC; Sundaresan, A; Hirai, M; Ishiura, Y; Badica, P; Crisan, A; Ihara, H

Published: OCT 1 2002, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 378, 1282, DOI: 10.1016/S0921-4534(02)01690-8

Thin films of Cum-1Bam(Sr,Ca)(n)Cun+1O2m+2n+1, i.e., [BaCuO2](m)/[(Sr,Ca)CuO2](n) superlattices have been grown by layer-by-layer growth method with rf magnetron sputtering on NdGaO3(1 1 0) substrate. Two targets with the compositions BaCuO2 and (Sr,Ca)CuO2, which form the charge reservoir and superconducting layers, respectively, were used. [BaCuO2](m)/[(Sr,Ca)CuO2](n) superlattice was grown at 460-520 degreesC in a gas mixture of Ar and N2O by alternatively depositing the charge reservoir layer and superconducting layer. The superlattice modulation is close to that of high pressure synthesized bulk materials. By means of the layer-by-layer growth method, a system of Cu-based artificial lattice structures is formed. Electrical transport properties of these superlattices were also investigated. (C) 2002 Elsevier Science B.V. All rights reserved.

2907. Stud of Ag-- and Ag-0-type centers in X- and gamma-ray irradiated NaCl : Ag+, KCl : Ag+ and NaCl : Ag+ + Ca2+ crystals

Authors: Topa, V; Tsuboi, T; Dragusin, M

Published: MAY 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 191, 300, DOI: 10.1016/S0168-583X(02)00579-7

Creation of Ag and Ag-0 centers by irradiation with ionizing radiations has been investigated using NaCl and KCl crystals containing various concentrations of Ag+ ions and using Ca2+-codoped NaCl:Ag+ and KCI:Ag+ crystals. From the absorption spectra, it is observed that Ag- center perturbed by Ca2+ ion is also created besides the Ag- and Ag-0 centers. It is confirmed that Ag- and Ag-0 centers increase with increasing the concentration of doped Ag- ions. It is suggested that there are two kinds of Ag(c)(0)v(a) centers (i.e. Ag-0 accompanied by vacancy at the nearest neighbor) with different site symmetries depending on the location of vacancy. (C) 2002 Published by Elsevier Science B.V.

2908. X-ray diffraction analysis of the vitreous alloy Ag-As2S3

Authors: Popescu, M; Sava, F; Cornet, A; Broll, N

Published: JUL 2002, JOURNAL DE PHYSIQUE IV, 12, 49, DOI: 10.1051/jp4:20020211

The structure of several silver alloyed arsenic chalocgenide has been determined by X-ray diffraction. For low silver doping the disordered layer structure, characteristic to the glassy As2S3; is retained as demonstrated by the well developed first sharp diffraction peak in the X-ray diffraction pattern. For high amount of silver introduced in the As2S3; matrix, the disoredered layer configurations disappear, as shown by the diminishing and even disappearance of the first sharp diffraction peak in the X-ray patterns. A three-dimensional structure based on Ag2S-type configuration is formed.

2909. Third-harmonic susceptibility for studying dissipation in heavy ion irradiated (Cu,C)Ba2Ca3Cu4O12-y high-temperature superconductors

Authors: Crisan, A; Badica, P; Hirai, M; Kito, H; Iyo, A; Tanaka, Y

Published: AUG 2002, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 15, 1243, DOI: 10.1088/0953-2048/15/8/313

A slice of the (Cu,C)Ba2Ca3Cu4O12-y bulk superconductor grown by high-pressure synthesis was polished down to a thickness of 50 mum, and then irradiated with high-energy (240 MeV) Au15+, ions (10 11 cm(-2)). Since the length of the ion tracks was estimated to be 12.2 mum, our sample consists of two different types of grain, with and without columnar defects, having very different critical current densities. Using the third-harmonic response of the sample, we were able to separate the small dissipation in the irradiated grains from the much larger dissipation in the non-irradiated grains, in a certain experimental range of temperature, field and current density. The critical current density was estimated from critical state models. For temperatures in the range of 85-105 K, we observed a peak effect at high dc magnetic fields, suggesting the possibility of a record irreversibility field at 77.3 K.

2910. Magnetic properties of RFe11.3W0.7 (R=Dy, Ho, Er, and Lu): On the R-Fe exchange interaction in the R(Fe,T)(12) class of compounds

Authors: Plugaru, N; Rubin, J; Bartolome, J; Piquer, C; Artigas, M

Published: APR 1 2002, PHYSICAL REVIEW B, 65, DOI: 10.1103/PhysRevB.65.134419

Results of x-ray powder diffraction and magnetic measurements performed on RFe11.3W0.7 compounds, where R=Dy, Ho, Er, and Lu, are presented. The Curie temperature, saturation magnetization, and spin reorientation transitions are discussed in relation to several RFe12-xTx systems, where T=Ta, Nb, Mo, Ti, and the x-substituent concentration is within a narrow range x=0.5-1.0. In these systems, the dependence of the Curie temperature versus the unit cell volume, for a given R partner, suggests combined size and electronic effects produced by the T atom. The strengths of the rare-earth-iron and iron-iron exchange interactions are evaluated in the mean-field framework, and analyzed with reference to RFe12-xTx compounds, with T=Ta, Re, Nb, Mo, Ti, Cr, and V. Based on (i) the phenomenological mean-field model accounting for the sublattice of conduction band electrons, (ii) Brooks' reinterpretation of Campbell's formulation of the intersublattice exchange, and (iii) Wigner-Seitz cell analysis, we explore the role played by the conduction band electrons, particularly the nd-type electrons (n=3, 4, 5), on the intersublattice exchange coupling in the iron-rich RFe12-xTx class of compounds. It is proposed that the variation in the conduction-electron density, by varying the T element type and concentration, leads to a modification of the 5d band occupancy number and consequently, of the R-Fe intersublattice exchange coupling.

2911. Non-equilibrium electronic processes in nanocrystalline silicon

Authors: Ciurea, ML; Iancu, V; Draghici, M; Jdira, L

Published: 2002, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS, AND NANOTECHNOLOGIES, 5227, 273, DOI:

Nanocrystalline silicon is studied with a view to obtaining a new photonic material. Non-equilibrium electronic processes in such materials play a significant role. We have studied trapping phenomena in nanocrystalline porous silicon and nanocrystalline silicon-based Multi-Quantum Wells structures by means of Optical Charging Spectroscopy method, which is a very good and sensitive method. We have also analyzed the modeling of the processes that occur during our measurements. This modeling allows us to separate the relative contribution of the different types of discharge currents that can appear: ohmic conduction currents of either equilibrium or non-equilibrium carriers, displacement currents, diffusion currents and tunneling currents through insulating layers (in Multi-Quantum Wells structures). It also allows us to increase the accuracy of the determination of the experimental trap parameters and to determine parameters that are not directly measurable. The model can be applied to other nanocrystalline semiconductors and can be easily generalized for other high resistivity materials.

2912. Superconducting properties of the heavy-ions and neutron irradiated (Cu,C)Ba2Can-1CunO2n+4-delta (n-3, 4 and 5)

Authors: Kito, H; Iyo, A; Hirai, M; Crisan, A; Tokumoto, M; Okayasu, S; Sasase, M; Ihara, H

Published: OCT 1 2002, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 378, 332, DOI: 10.1016/S0921-4534(02)01437-5

For further enhancement of critical currents density J(c) and irreversibility field H-irr of (Cu1-xCx) Ba2Can-1CunO2n+4-delta ((Cu,C)-(n - 1)n, n = 3, 4 and 5) family, pinning centers were introduced by ion and neutron irradiation in these compounds. The polycrystalline samples were irradiated with 3.6 x 10(17) neutrons/cm(2) or with Au15+ ions (240 MeV energy) at a fluence of 1 x 10(11) ions/cm(2). J(c) and H-irr were determined for the irradiated samples as well as unirradiated samples. The intragrain J(c) was evaluated from M-H curves using Bean's critical state model. In (Cu,C-12(n - 1) n, J(c) (77 K, 1 T) shows a remarkable increase from 3.9 x 10(4) to 9.1 x 10(5) A/cm(2) for neutron irradiated (Cu,C- 1234 and from 3.9 x 10(4) to 4.1 x 10(6) A/cm(2) for heavy-ion irradiated (Cu,C)-1234. These results indicate the possibility of further enhancement of J(c) and of achieving a very high H-irr of (Cu,C)-1234 in (Cu,C)-12(n - 1)n family. (C) 2002 Elsevier Science B.V. All rights reserved.

2913. Structure, properties and modelling of As25Te35Si40 glass

Authors: Popescu, MA; Lorinczi, AA; Sava, FA; Iovu, MB; Leonovici, MC; Stegarescu, MA; Halm, TD; Hoyer, WD

Published: 2002, XIIITH INTERNATIONAL SYMPOSIUM ON NON-OXIDE GLASSES AND NEW OPTICAL GLASSES PTS 1 AND 2, 84, DOI:

Glassy composition As25Te35Si40 was investigated by microhardness, differential scanning calorimetry, X-ray diffraction, electrical conductivity and Raman spectroscopy measurements. A continuous random network model of the glass structure has been developed.

2914. Magnetic and electronic properties of DyNi5-xAlx compounds

Authors: Burzo, E; Chiuzbaian, SG; Neumann, M; Valeanu, M; Chioncel, L; Creanga, I

Published: DEC 15 2002, JOURNAL OF APPLIED PHYSICS, 92, 7368, DOI: 10.1063/1.1521257

The DyNi5-xAlx compounds crystallize in CaCu5-type structure for an aluminum content xless than or equal to1.5 and in HoNi2.6Ga2.4 type for xgreater than or equal to2. The saturation moments per formula unit extrapolated at 0 K, in composition range x<2 are similar to9.2 mu(B) in agreement with x-ray photoelectron spectroscopy studies which show negligible crystal field effects. For xgreater than or equal to2 a mictomagnetic type contribution to magnetic ordering develops which becomes dominant only for the DyNi2Al3 compound. Band structure calculations on DyNi5-xAlx show that the Dy 5d band is polarized parallel to the 4f moment. For DyNi5 the nickel moments at 2c and 3g sites are antiparallel oriented to that of Dy. The nickel contributions to magnetization decrease when increasing aluminum content and are near nil for xgreater than or equal to2. Above the Curie points the reciprocal susceptibilities follow linear dependencies. The effective nickel moments decrease from 2.11 mu(B)/atom (x=0) to 0.87 mu(B)/atom (x=2.5). The magnetic behavior of nickel is analyzed in models which take into account the electron correlation effects in d bands. (C) 2002 American Institute of Physics.

2915. Thermally stimulated current method applied to highly irradiated silicon diodes

Authors: Pintilie, I; Tivarus, C; Pintilie, L; Moll, M; Fretwurst, E; Lindstroem, G

Published: JAN 11 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 476, 657, DOI: 10.1016/S0168-9002(01)01654-0

We propose an improved method for the analysis of Thermally Stimulated Currents (TSC) measured on highly irradiated silicon diodes. The proposed TSC formula for the evaluation of a set of TSC spectra obtained with different reverse biases leads not only to the concentration of electron and hole traps visible in the spectra but also gives an estimation for the concentration of defects which not give rise to a peak in the 30-220 K TSC temperature range (very shallow or very deep levels). The method is applied to a diode irradiated with a neutron fluence of phi(n) = 1.82 x 10(13) n/cm(2). (C) 2002 Published by Elsevier Science B.V.

2916. Properties of titanium based hard coatings deposited by the cathodic arc method I. Microchemical and microstructural characteristics

Authors: Balaceanu, M; Braic, M; Macovei, D; Genet, MJ; Manea, A; Pantelica, D; Braic, V; Negoita, F

Published: MAR 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 114, DOI:

TiN, TiC and Ti(C,N) hard coatings were deposited on Si substrates by a cathodic are system. Various investigation techniques (ERDA, XPS, and XRD) were used to analyze the microchemical and microstructural characteristics of the films (surface chemistry, chemical composition, texture) prepared under different deposition conditions.

2917. Bi2-xSbxTe3 thick thermoelectric films obtained by electrodeposition from hydrochloric acid solutions

Authors: Nedelcu, M; Sima, M; Manea, AS; Lazarescu, MF; Ghita, RV; Craciunoiu, F; Visan, T

Published: MAR 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 106, DOI:

A method to produce composition modulated Bi2-xSbxTe3 alloys by electrodeposition has been developed. The electrolyte, which consists in a HCl 6M (pH = 0) aqueous solution, allows for the co-deposition of bismuth, antimony and tellurium to be accomplished at room temperature on glassy carbon, platinum or nickel electrode. The composition of the films, their crystal structures and morphology were studied as function of electrochemical parameters and bath composition. It is shown that the electrodeposits are monophasic and exhibit a polycrystalline state. The electrical resistivity was of the order of 7-10 mOmegacm, whereas the electrodeposition rate value was 30-50 mum/h for the films with good thermoelectric properties.

2918. Preparation of BaTi4O9 from oxalates

Authors: Cernea, M; Chirtop, E; Neacsu, D; Pasuk, I; Iordanescu, S

Published: FEB 2002, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 85, 503, DOI:

A barium titanate precursor with a barium:titanium ratio of 1:4 was prepared by controlled coprecipitation of mixed barium and titanium species with an ammonium oxalate aqueous solution at pH 7. The results of thermal analysis and IR measurement show that the obtained precursor is a mixture of BaC2O4.0.5H(2)O and TiO(OH)(2).1.5H(2)O in a molar ratio of 1:4. Crystallized BaTi4O9 was obtained by the thermal decomposition of a precipitate precursor at 1300degreesC for 2 h in air. The dimensions of the powder calcined at 1000degreesC are between 100 and 300 nm. The grain dimensions of the sintered sample for 2 h at 1300degreesC are of the order of 10 to 30 mum. Dielectric properties of disk-shaped sintered specimens in the microwave frequency region were measured using the TE011 mode. Excellent microwave characteristics for BaTi4O9-epsilon = 38 +/- 0.5, Q = 3800-4000 at 6-7 GHz and tau(f) = 11 +/- 0.7 ppm/degreesC-were found.

2919. Self-organization in simulated arsenic chalcogenide networks

Authors: Popescu, M

Published: 2002, XIIITH INTERNATIONAL SYMPOSIUM ON NON-OXIDE GLASSES AND NEW OPTICAL GLASSES PTS 1 AND 2, 430, DOI:

Polymerization-depolymerization processes induced by irradiation with alternate high and low intensity light control the nano-scale extension of disordered layer-like units in arsenic chalcogenides. These processes were simulated in the frame of a Monte-Carlo-Metropolis method. A model for photodarkening and photobleaching phenomena in layered chalcogenides was proposed.

2920. The "in-plane" angular spin distribution in layered systems as obtained by Fe-57 Mossbauer spectroscopy

Authors: Kuncser, V; Keune, W; Vopsaroiu, M; Bissell, PR

Published: NOV 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 196, 147, DOI: 10.1016/S0168-583X(02)01274-0

A practical approach for in-plane angular spin distributions in layered systems, as obtained by Mossbauer spectroscopy, is discussed. The line intensity ratio R-23 of a Mossbauer pattern is expressed versus particular distribution parameters in unidirectional, step-shaped and ellipse-type models. The distribution parameters are deduced from experimental spectra taken by rotating the sample in its own plane. Three-dimensional spin distributions with small out-of-plane components can be analysed using the same method. The procedure is exemplified on four samples containing metallic nano-particles. The in-plane angular magnetic moment distributions derived with this method are compared with the results from bulk vector vibrating sample magnetometry in order to prove the accuracy of the described technique. (C) 2002 Elsevier Science B.V. All rights reserved.

2921. Phonons in colloidal crystals

Authors: Penciu, RS; Kafesaki, M; Fytas, G; Economou, EN; Steffen, W; Hollingsworth, A; Russel, WB

Published: JUN 2002, EUROPHYSICS LETTERS, 58, 704, DOI: 10.1209/epl/i2002-00322-3

The dispersion curves of the phonons propagating in polycrystalline suspensions of hard-sphere colloids are measured by Brillouin scattering and calculated by band structure techniques. Acoustic-like and optical-like experimental phonon dispersion relations are attributed to the interplay of the solvent matrix mode with the single-sphere vibration eigen-modes in these lattice structures.

2922. Raman and SERS studies of carbon nanotubes

Authors: Lefrant, S; Baibarac, M; Baltog, I; Buisson, JP; Chauvet, O

Published: 2002, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 374, 334, DOI: 10.1080/10587250210472

Since the discovery of carbon nanotubes, Raman Scattering Spectroscopy and transmission Electron Microscopy have been proved to be powerful for a detailed investigation of their properties. In TEM, a direct observation can be made, whereas Raman Scattering is used extensively to probe the different samples via their vibrational properties. In this paper, we report on recent results obtained in both single-walled carbon nanotubes (SWNTs), multiwalled-carbon nanotubes (MWNTs) and PMMA/nanotubes composites. In addition, in the case of SWNTs, we present studies carried out in Raman scattering when SERS (Surface Enhanced Raman Scattering) conditions are used. In particular, we put in evidence an increased state of disorder at the interface nanotubes/metallic support when the nanotube film thickness is decreased. Strong degradations can be observed primarily on metallic tubes with a concomitant formation of C-60-like molecules. In the case of MWNTs, calculations of interactions between concentric tubes lead to the occurrence of low frequency vibrational modes, in good agreement with experiments.

2923. Temperature dependence of the density of calamitic and discotic nematic lyotropic liquid crystals containing sodium lauryl sulphate/decanol/water

Authors: Beica, T; Moldovan, R; Puica, MR; Frunza, S

Published: OCT 2002, LIQUID CRYSTALS, 29, 1278, DOI: 10.1080/713935619

Experimental results for the temperature dependence of density at normal pressure for two compositions of sodium lauryl sulphate/decanol/water solutions, exhibiting either a calamitic or a discotic lyotropic nematic phase at room temperature, are presented. Within the limits of experimental precision (+/-1 x 10(-5) g cm(-3)), the systems show no jump in density at the nematic to isotropic phase transition. Over the studied temperature range, the mean thermal expansion coefficients were also evaluated.

2924. Magnetic properties of alpha-iron(II) phthalocyanine

Authors: Evangelisti, M; Bartolome, J; de Jongh, LJ; Filoti, G

Published: OCT 1 2002, PHYSICAL REVIEW B, 66, DOI: 10.1103/PhysRevB.66.144410

We report on the magnetic properties of the supramolecular compound iron(II) phthalocyanine in its alpha form. dc- and ac-susceptometry measurements and Mossbauer experiments show that the iron atoms are strongly magnetically coupled into ferromagnetic Ising chains with very weak antiferromagnetic interchain coupling. The transition to three-dimensional (3D) magnetic ordering below 10 K is hindered by the presence of impurities or other defects, by which the domain-wall arrangements along individual chains become gradually blocked/frozen, leading to a disordered 3D distribution of ferromagnetic chain segments. Below 5 K, field-cooled and zero-field-cooled magnetization measurements show strong irreversible behavior, attributed to pinning of the domain walls by the randomly distributed defects in combination with the interchain coupling. High-field magnetization experiments reveal a canted arrangement of the moments in adjacent ferromagnetic chains.

2925. TlSr2CaCu2Oy template for the growth of superconducting Tl(Ba, Sr)(2)Ca2Cu3Oy thin films on CeO2 buffered sapphire

Authors: Sundaresan, A; Crisan, A; Nie, JC; Hirai, M; Asada, H; Kito, H; Tanaka, Y; Ihara, H

Published: JUN 2002, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 15, 963, DOI: 10.1088/0953-2048/15/6/322

Thin films of Tl(Ba, Sr)(2)Ca2Cu3Oy superconductor have been grown on CeO2 buffered r-cut sapphire substrate with the use of a template TlSr2CaCu2Oy by the amorphous phase epitaxy method. By using this template containing Sr, we have overcome the problem of chemical reactions between Ba and Cc present in the superconducting and buffer layers, respectively, at the normal processing temperatures of 840-890 degreesC. Films grown by this method have an excellent c-axis orientation as well as in-plane alignment with the TlSr2CaCu2Oy template, which in turn is aligned with the CeO2 layers. These films have superconducting critical temperature values up to 104 K and critical current density values as high as 1 MA cm(-2) at 77.3 K and 0 T.

2926. Chemical deposited Pd on GaAs

Authors: Ghita, RV; Nedelcu, M; Lazarescu, MF

Published: 2002, CRYSTAL RESEARCH AND TECHNOLOGY, 37, 328, DOI: 10.1002/1521-4079(200204)37:4<323::AID-CRAT323>3.3.CO;2-8

The chemical deposition of palladium on n and p-GaAs from an aqueous solution of PdCl2, in strong acid medium can be an alternative technique for contacts on GaAs. This paper presents the variations of palladium films thickness (measured by an interferometric method) as a function of solution concentration, reaction time and substrate conductivity. There are presented data concerning the adhesion of palladium films (measured by a mechanical method) related to the film thickness. From a comparative study concerning the adhesion of evaporated films such as: Au/n-GaAs, Ag/n-GaAs, AnGe/n-GaAs and Pd/n-GaAs, it results the conclusion that the adhesion of palladium films are of the same order of magnitude as the metallic films evaporated without an annealing procedure.

2927. Fractal patterns formed by thermal treatment in alkali halide crystals

Authors: Enculescu, M; Enculescu, I; Topa, V; Vasile, E

Published: NOV-DEC 2002, PHYSICA B-CONDENSED MATTER, 324, 392, DOI: 10.1016/S0921-4526(02)01451-5

We have succeeded in growing nanocrystals of Ag structured like fractals in several solid matrices (NaG, KBr and KCl). These are shown to be diffusion-limited aggregates when fractal dimensions were evaluated. Depending upon the crystal in which the fractal structures were obtained, the fractal dimensions of the Ag nanoclusters were found to be between 1.73 and 1.81. (C) 2002 Elsevier Science B.V. All rights reserved.

2928. Silver nanoclusters in potassium halides obtained from Ag--ions by electron detachment

Authors: Enculescu, M; Topa, V; Vasile, E

Published: MAY 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 191, 436, DOI: 10.1016/S0168-583X(02)00587-6

We studied by means of optical absorption and transmission electron microscopy the formation of Ag nanoclusters from Ag--ions in three different potassium halides (KCl, KI and KBr). By stepwise UV illumination at a suitable temperature, the electrons of Ag--ions were detached and the controlled formation and growth of Ag nanoclusters from Ago-atoms take place. At the same time, the detached electrons are captured by K+-ions, proved by the appearance of K-colloid bands. The kinetics of the conversion Ag- + hv + U --> Ag nanoclusters was followed by monitoring the Ag--ions and Ag nanoclusters absorption. The temperatures of illumination are different, depending on the matrix in which Ag nanoclusters are formed (220 degreesC for KCl, 160 degreesC for KBr and 140 degreesC for KI). By optical absorption and TEM we proved that the nanoclusters of Ag obtained by our method are separated, spherical and ovoidal, with average diameters between 7.5 and 50 nm. (C) 2002 Elsevier Science B.V. All rights reserved.

2929. Tl-0 and Tl2+ centers as paramagnetic probes for the 74K phase transition in Rb2ZnCl4

Authors: Stefan, M; Nistor, SV; Schoemaker, D

Published: 2002, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 157, 697, DOI: 10.1080/10420150215809

Tl-0 (6 p(1)) irradiation centers are proposed as new paramagnetic probes for structural phase transition investigations. The P2(1)cn --> C1 c1 phase transition in Rb-2 ZnCl4 single crystals is monitored using the Tl-0 and the well-known Tl2+ (6 s(1)) paramagnetic probes. The anomalous temperature dependence exhibited by the EPR spectra of both types of centers in the C1 c1 phase was analyzed considering a soft mode contribution.

2930. Theoretical calculations of the primary defects induced by pions and protons in SiC

Authors: Lazanu, S; Lazanu, I; Borchi, E; Bruzzi, M

Published: JUN 11 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 485, 773, DOI: 10.1016/S0168-9002(01)02147-7

In the present work, the bulk degradation of SiC in hadron (pion and proton) fields, in the energy range between 100 MeV and 10 GeV. is characterised theoretically by means of the concentration of primary defects per unit fluence. The results are compared to the similar ones corresponding to diamond, silicon and GaAs. (C) 2001 Elsevier Science B.V. All rights reserved.

2931. Structural features and mechanism of reversible photoinduced transformations in amorphous chalcogenides

Authors: Popescu, M; Hoyer, W

Published: DEC 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 873, DOI:

The structural configurations that govern the behavior of the amorphous chalcogenides under excitation are the nano-scale, disordered, layer-like clusters. The competition between breaking, formation and switching of bonds at the cluster boundaries, accompanied by precipitation-dissolution phenomena, gives rise to fractal morphology of these clusters and to the reversible scalar photo-structural effects. The photoinduced anisotropy phenomena are explained in the frame of a model with stimulation of chiral elements induced by polarized light in the disordered layers of the clusters.

2932. Investigation of semi-insulating oxygen-doped GaAs

Authors: Lazarescu, MF; Pantelica, D; Manea, AS; Ghita, RV; Negoita, F

Published: MAY 2002, JOURNAL OF CRYSTAL GROWTH, 240, 406, DOI: 10.1016/S0022-0248(02)00948-X

We found Oxygen-doped GaAs crystals to be suitable materials for CO2 laser optical component preparation, with application at 10.6 mum. An optical transmission of 55% in the IR spectrum range, between 2 and 15 mum has been reached for such a GaAs type material. The GaAs crystals that we have analysed were grown by two procedures: Horizontal Bridgman (HB) and Liquid Encapsulated Czochralski (LEC). The FIB method has been used for obtaining pure (undoped) crystals, while the oxygen-doped GaAs ingots were grown by LEC technique. The two types of samples processed in the same manner as regards mechanical polishing and chemical etching, which were investigated by Hall measurements, optical transmission spectrometry and elastic recoil detection analysis (ERDA) technique. The GaAs:O (LEC) has near semi-insulating properties as can be observed from the results of the electrical resistivity and Hall effect measurements. The ERDA spectrum shows an intense signal of oxygen in the bulk of GaAs:O (LEC) crystals, while the oxygen signal is not present in the ERDA spectrum of the undoped GaAs (HB). We consider that these results could recommend the ERDA technique as a possible qualitative and quantitative analysis in an ion-beam accelerator for oxygen content in oxygen-doped GaAs crystals. The analysis is not sensitive to the native oxide, as could be seen by measuring GaAs (HB) undoped crystals. (C) 2002 Elsevier Science B.V. All rights reserved.

2933. Nanocapsules of biodegradable polymers: preparation and characterization by direct high resolution electron microscopy

Authors: Guinebretiere, S; Briancon, S; Fessi, H; Teodorescu, VS; Blanchin, MG

Published: SEP 1 2002, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS, 21, 142, DOI: 10.1016/S0928-4931(02)00073-5

In the field of pharmaceutical applications relying on encapsulation of drug by polymer coating, capsules based on biodegradable polymers with mean size of about 500 nm have been obtained by a patented emulsion-diffusion method. The morphology, size and structure of the nanocapsules (NC) control their pharmaceutical properties, especially release of the drug. Here is reported a decisive contribution of transmission electron microscopy (TEM) in revealing the controlled form and size of the NC: mean size values measured by TEM do agree with data obtained by laser granulometry. Moreover, the TEM magnification allows an estimation of the membrane thickness. (C) 2002 Elsevier Science B.V. All rights reserved.

2934. C-60-polymer nanocomposites: evidence for interface interaction

Authors: Giusca, C; Baibarac, M; Lefrant, S; Chauvet, O; Baltog, I; Devenyi, A; Manaila, R

Published: 2002, CARBON, 40, 1574, DOI: 10.1016/S0008-6223(02)00024-6

Polyaniline-fullerene (PA-C-60) composites have been studied by Surface Enhanced Raman scattering (SERS) spectroscopy and X-ray diffraction. They were obtained by mixing solutions of polyaniline-emeraldine base (PA-EB) and C-60, as well as by chemical synthesis from aniline, sulfuric acid and potassium dichromate, with addition of C-60. The Raman bands peaking at 1330-1370 cm(-1). associated with a protonated structure Were used as indicative for changes of the PA-EB phonon spectrum resulting from C-60 doping. The two types of compounds show different SERS spectra, also dependent on the metallic support used (An or Ag). Variation of the SERS spectra with the type of metallic support is related to a chemical interface interaction between composite and metal. In mixture samples, a doped polymeric chain (with ionically attached C-60(-)) was evidenced by an increased fraction of quinoid rings. The SERS spectra of the chemically synthesized PA-C-60 reveals the existence of two polymeric structures: a doped PA (doped with C-60(-) ions) and an undoped one, the latter with a structure of 'pendant chain' type. Structural (XRD) data reveal the presence of C-60 nano-zones, with a lattice parameter increase of 0.3-0.6%, attributed to slight oxidation. Detailed analysis of the fcc(111) line asymmetry suggests, in mixture samples, a boundary zone with an 'expanded' lattice. induced by ionic interface effects. (C) 2002 Elsevier Science Ltd. All rights reserved.

2935. Quantum macroscopic coherent phenomena in biocommunication

Authors: Branescu, M

Published: 2002, ALT'01 INTERNATIONAL CONFERENCE ON ADVANCED LASER TECHNOLOGIES, 4762, 391, DOI: 10.1117/12.478664

The proposal of coherent electromagnetic processes as the engine for biological dynamics and biocommunications suggest that the quantum macroscopic coherent phenomena as Bose condensation and laser threshold could be present in living cells. A possible correlation between environmental primordial cosmic background radiation and Josephson experimental evidence is discussed.

2936. Superconducting properties from AC susceptibility and harmonic generation in CuBa2Ca3Cu4Oy bulk superconductors

Authors: Crisan, A; Iyo, A; Tanaka, Y; Hirai, M; Tokumoto, M; Ihara, H

Published: MAY 15 2001, PHYSICA C, 353, 240, DOI: 10.1016/S0921-4534(00)01744-5

We measured for the first time the fundamental and higher harmonic components of AC susceptibility of CuBa2Ca3Cu4Oy superconductor produced by the high-pressure technique, in various experimental conditions (temperature, DC magnetic field, AC held amplitude and frequency). The results are discussed qualitatively in the frame of the critical state and other models in the literature. By using a very simple frequency-dependent critical state model, we estimated the parameters of practical interest, critical current density and pinning potential at various DC fields and temperatures and the irreversibility field. We also extrapolated our estimations to both practical temperature of 77 K and longer time scale as of DC magnetization and transport measurements. The results appeared to be quite self-consistent. (C) 2001 Published by Elsevier Science B.V.

2937. Effect of metal addition on the properties of As2Se3 glass

Authors: Leonovici, M; Steflea, M; Iovu, M; Popescu, M

Published: APR 2001, PHILOSOPHICAL MAGAZINE B-PHYSICS OF CONDENSED MATTER STATISTICAL MECHANICS ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES, 81, 364, DOI: 10.1080/13642810108226408

The effects of the incorporation of small amounts of Sn, Mn and Sm (0.5 at.%) on the structure and transport properties of glassy As2Se3 have been investigated. The metals influence both the disordered network structure of the glass matrix and the transport properties in accordance with the chemical properties of the doping elements. On metal addition, the electrical conductivity increases while the photoconductivity decreases. For Sm-modified glass, the position of the characteristic photoconduction band shifts toward higher photon energy. For Sn, the band shift is almost negligible and, for the addition of Mn, a photoresponse was not detected.

2938. Thermally stimulated current method applied on diodes with high concentration of deep trapping levels

Authors: Pintilie, I; Pintilie, L; Moll, M; Fretwurst, E; Lindstroem, G

Published: JAN 22 2001, APPLIED PHYSICS LETTERS, 78, 552, DOI: 10.1063/1.1335852

We propose an improved method of thermally stimulated currents (TSC) spectra analysis in the case of diodes having a concentration of traps higher than that of doping impurities. Beside the calculation of trap concentrations from TSC peaks analysis, the method allows us to evaluate the density and the type of the very deep trapping level which, due to the contribution of leakage current, can not be detected in a real TSC experiment. The proposed method is applied to a p(+)-n Silicon diode irradiated with 1.82x10(13)neutrons/cm(2). (C) 2001 American Institute of Physics.

2939. Subthreshold carrier-LO phonon dynamics in semiconductors with intermediate polaron coupling: A purely quantum kinetic relaxation channel

Authors: Betz, M; Goger, G; Laubereau, A; Gartner, P; Banyai, L; Haug, H; Ortner, K; Becker, CR; Leitenstorfer, A

Published: MAY 14 2001, PHYSICAL REVIEW LETTERS, 86, 4687, DOI: 10.1103/PhysRevLett.86.4684

Femtosecond transmission spectra of highly polar CdTe are compared to more covalent GaAs contrasting semiclassical kinetics with two-time quantum kinetics based on the Dyson equation. Nonequilibrium heavy holes in CdTe show ultrafast energy redistribution via the Frohlich mechanism even if photoexcited below the LO phonon energy. This subthreshold relaxation is a genuine quantum kinetic effect. It gains importance if the polaron self-energy is comparable to the phonon energy. Conservation of the free-particle energies is not required under these conditions.

2940. Modelling of the structure and structural transformations in amorphous chalcogenides

Authors: Popescu, M

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 286, DOI:

Computer relaxed structural models of arsenic based chalcogenide glasses allowed to demonstrate that the atomic configurations in these materials are anisotropic with a strong tendency to extend as disordered layers. In the frame of these models the photostructural transformations and photoinduced anisotropy find a straightforward explanation.

2941. Enhanced magnetization at integer quantum Hall states

Authors: Meinel, I; Grundler, D; Heitmann, D; Manolescu, A; Gudmundsson, V; Wegscheider, W; Bichler, M

Published: SEP 15 2001, PHYSICAL REVIEW B, 64, DOI: 10.1103/PhysRevB.64.121306

We report on enhancements in the magnetization of two-dimensional electron systems in the quantum Hall regime. The observed discontinuities in the magnetization exceed the predictions for interacting electrons calculated in the Hartree-Fock approximation where only the exchange enhancement of the energy gaps is taken into account. We attribute the further enhancement to many-body correlation effects, i.e., filling factor dependent screening within the screened Hartree-Fock approximation. With this, the discontinuities in the magnetization no longer reflect the discontinuities of the chemical potential, but its behavior in the vicinity of integer filling factors.

2942. Non-Heisenberg magnetic behavior of a triangular bridged heterometallic Fe-2(III)Co(II) complex: Evidence of strong orbital contributions

Authors: Tsukerblat, BS; Palii, AV; Mirovitskii, VY; Ostrovsky, SM; Turta, K; Jovmir, T; Shova, S; Bartolome, J; Evangelisti, M; Filoti, G

Published: NOV 22 2001, JOURNAL OF CHEMICAL PHYSICS, 115, 9535, DOI: 10.1063/1.1413988

We report the synthesis, magnetization and ac susceptibility of the triangular mu (3)-oxo-bridged heterometallic complex [Fe2CoO(CH3COO)(6)(3-Cl-Py)(3)], in powder form. The model Hamiltonian is elaborated involving isotropic exchange interactions Fe(III)-Fe(III) and Co(II)-Fe(III) dealing with the real spins of high-spin Co(II) and Fe(III) ions, and also spin-orbit coupling and low-symmetry crystal field (C-2v) acting within the T-4(1g) ground manifold of Co(II) ion. The outlined general model takes into account strong anisotropic orbital contribution to the magnetic characteristics of the whole system arising from Co(II) ion with unquenched orbital angular momentum. The treatment of the Hamiltonian is performed with the use of the irreducible tensor operator technique. The influence of the exchange and spin-orbital interactions on the magnetic properties of Fe-2(III)Co(II) clusters is revealed. The result of calculations in the framework of the isotropic model (neglecting low-symmetry crystal field) are in a good agreement with the experimentally observed magnetization versus magnetic field, as well as with the unusual temperature behavior of the magnetic susceptibility of the powder samples (1.8-250 K). The states of the system are enumerated by the quantum number of the total angular momentum J, these hybrid states are combined from the sets of full and intermediate spins of Fe2Co triangle and orbital angular momentum of Co(II), (with fictious L=1). The best fit to the experimental data is achieved for the exchange parameters J(Fe-Fe)=-87.5 cm(-1), J(Fe-Co)=-17 cm(-1) and orbital reduction factor for Co(II) ion kappa =0.93. The ground state and the first excited one are found to possess total angular momentum J=1/2, Effective g-factors for the ground- and first-excited states calculated using the hybrid spin-orbital functions prove to be 4.3 and 0.75, that are distinctly different from the pure spin value 2 peculiar for the Heisenberg model. The comparison of the magnetic measurements with the theory clearly demonstrates the insufficiency of a simple Heisenberg spin-coupling model as evidenced by the discovered strong orbital magnetic contribution. (C) 2001 American Institute of Physics.

2943. Surface tension of some liquid crystals in the cyanobiphenyl series

Authors: Tintaru, M; Moldovan, R; Belca, T; Frunza, S

Published: MAY 2001, LIQUID CRYSTALS, 28, 797, DOI: 10.1080/02678290010025459

The temperature dependence of the surface tension was measured by the pendant drop method for four compounds from the homologous series of alkylcyanobiphenyls (nCB), in the nematic liquid crystal and isotropic phases, For SCB (oclylcyanobiphenyl) the temperature dependence was also measured in the smectic range. Not very close to the Isotropic transition temperature, and with the exception of 8CB, the surface tension decreases with increase in temperature in the nematic range. A downward jump at the transition temperature was observed for all liquid crystals studied. The shape of the drop in the smectic A phase of 8CB gives indications of stratification in a system of terraces.

2944. The stability of cadmium chalcogenide pigments in the process of laser cleaning of painted surfaces

Authors: Radvan, R; Popovici, N; Savastru, R; Ghica, C; Sava, F; Popescu, M

Published: DEC 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 902, DOI:

Pigments based on cadmium selenide sulphides and cadmium sulfides were analysed as regarding their structure and stability against the laser irradiation, a new technique for cleaning the painted surfaces in artwork restoration, The pulsed Nd:YAG laser radiation determines the effusion of some sulphur from the red pigment Cd(S,Se) and significant decrease of the average size of the crystallites. The color turns to dark red. For yellow pigment (CdS) no change of crystallite size was detected after laser irradiation.

2945. A magnetic study of magnetoresistive Cu-(SmCo5)-Fe heterogranular alloys

Authors: Crisan, O; Le Breton, JM; Jianu, A; Maignan, A; Nogues, M; Teillet, J; Filoti, G

Published: AUG 2001, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 234, 99, DOI: 10.1016/S0304-8853(01)00279-7

The magnetic interactions between the nanograins in heterogeneous granular Cu-(SmCo5)-Fe ribbons were evaluated with a classical mean field model to obtain the exchange coupling as well as the magnetic moment per nanoparticle. The samples were subjected to various thermal treatments and a significant magnetoresistive effect was obtained when the optimal annealing conditions had been achieved. (C) 2001 Elsevier Science B.V. All rights reserved.

2946. Optical properties of polyaniline/CdS nanocrystals composite film

Authors: Ghiordanescu, V; Sima, M; Nedelcu, M; Giubelan, M

Published: MAR 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 93, DOI:

The optical spectra of CdS nanocrystals embedded in polyaniline matrix have been studied. The presence of surface states is revealed both in absorption and emission spectra. The polymer matrix determines a shift of the absorption edge of CdS nanocrystals, towards higher energies.

2947. Preparation and characterization of Ce-doped BaTiO3 thin films by r.f. sputtering

Authors: Cernea, M; Matei, I; Iuga, A; Logofatu, C

Published: OCT 2001, JOURNAL OF MATERIALS SCIENCE, 36, 5030, DOI: 10.1023/A:1011858319581

Ce-doped BaTiO3 thin films prepared on silicon-platinium by r.f. sputtering has been investigated. BaTiO3 doped with 5.5 mol%CeO2 thin film was deposited at 550 degreesC substrate temperature in an Ar atmosfere. The crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy with EDAX. Analysis by X-ray diffraction patterns show that the crystalline film with a cubic structure of BaTiO3, was obtained. The surface morphology (roughness, the grain size and the droplet size) of the thin film surface was examined by atomic force microscopy (AFM). The grain size is about 160 nm, the droplet size is about 0.675 mum and the roughness is 36.88 nm. EDAX analysis established a composition of the film to be identical with that of the target (BaTiO3 doped with 5.5 mol%CeO2). The broad peak in the capacitance versus temperature curve at the Curie point indicate that the r.f. sputtered Ce-doped BaTiO3 film is ferroelectric. The values of the capacitance of the thin film at 1 KHz were found to be 86 pF and the loss dielectric was tan delta = 0.0875. The film exibits a dielectric anomaly peak at 23 degreesC showing ferroelectric to paraelectric phase transition. (C) 2001 Kluwer Academic Publishers.

2948. Mass-loading effect on parameters of quartz and langasite resonators: Recent results

Authors: Mateescu, I; Johnson, G; Manea, A; Hatzakis, M; Tsoi, E; Tsoukalas, D

Published: JAN-FEB 2001, ANNALES DE CHIMIE-SCIENCE DES MATERIAUX, 26, 171, DOI: 10.1016/S0151-9107(01)90031-5

This paper presents some of the more relevant results concerning the mass-loading influence on quartz resonators and monolithic filter characteristics, and recent experimental results about the mass-loading effect on electrical parameters of langasite resonators. Based on the Ballato's transmission-line analogs of the trapped-energy resonators vibrating in thickness-shear mode, the mass-loading effect on resonator characteristics was studied. The effective mass-loading, motional inductance and quality factor of quartz and langasite resonators, as a function of harmonic order for various electrode parameters, were computed. In the frame of the Tiersten's analysis of monolithic structure, the theoretical calculations of the coupling coefficient of two-pole quartz and langasite monolithic filters as a function of mass-loading were performed. The analysis of these results shows that the mass-loading influence on characteristics of langasite resonators and monolithic filters is lower than on those of the quartz devices.

2949. La2O3-doped BaTiO3 thin films obtained by pulsed laser deposition

Authors: Cernea, M; Mihailescu, IN; Martin, C; Ristoscu, C; Iliescu, M

Published: DEC 2001, JOURNAL OF MODERN OPTICS, 48, 2189, DOI: 10.1080/09500340108235509

La2O3-doped barium titanate (BaTiO3) thin films have been obtained by pulsed laser deposition. The structure and quality of deposited films were characterized by X-ray diffraction and scanning electron microscopy. A smooth surface was obtained when the films were deposited in 30 Pa ambient oxygen. The composition (elements and oxides) of the thin films were close to those of the target. The layer obtained by pulsed laser deposition from a target of BaTiO3 doped with 0.5 at.% La exhibits good dielectric characteristics: capacitance 88 pF, Curie temperature 59 degreesC and dielectrics loss, tan delta, 0.084.

2950. Concentration dependence in the Landau-de Gennes theory for nematic lyotropic liquid crystals

Authors: Moldovan, R; Puica, MR

Published: JUL 23 2001, PHYSICS LETTERS A, 286, 209, DOI: 10.1016/S0375-9601(01)00410-8

The Letter presents an attempt to include the concentration dependence in the Landau-de Gennes theory for the nematic to isotropic phase transition for nematic lyotropic liquid crystals by introducing a critical concentration for the lyotropic solutions. This allows to describe phase transitions of micellar solutions as depending on temperature and concentration. An estimation of phenomenological coefficients of the CsPFO/water system is made, and we obtained the trends of the order parameter curves in function of temperature and concentration in good agreement with experimental results from literature. (C) 2001 Elsevier Science B.V. All rights reserved.

2951. Anisotropic scattering and quantum magnetoresistivities of a periodically modulated two-dimensional electron gas

Authors: Manolescu, A; Gerhardts, RR; Suhrke, M; Rossler, U

Published: MAR 15 2001, PHYSICAL REVIEW B, 63, DOI: 10.1103/PhysRevB.63.115322

We calculate the longitudinal conductivities of a two-dimensional noninteracting electron gas in a uniform magnetic field and a lateral electric or magnetic periodic modulation in one spatial direction, in the quantum regime. We consider the effects of the electron-impurity scattering anisotropy through the vertex corrections on the Kubo formula, which are calculated with the Bethe-Salpeter equation, in the self-consistent Born approximation. We find that due to the scattering anisotropy the band conductivity increases,:and the scattering conductivities decrease and become anisotropic. Our results are in qualitative agreement with recent experiments.

2952. Visible light emission from Cd1-xMnxS nanocrystals

Authors: Ghiordanescu, V; Sima, M; Grecu, MN; Mihut, L

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 524, DOI:

The luminescence spectra of some Cd1-xMnxS nanocrystals have been measured at room and liquid nitrogen temperature. The Mn2+ ions give rise to a broad emission band centered at about 580 nm, between the emission bands of CdS host.

2953. Coulomb effects on the transport properties of quantum dots in a strong magnetic field

Authors: Moldoveanu, V; Aldea, A; Manolescu, A; Nita, M

Published: JAN 15 2001, PHYSICAL REVIEW B, 63, DOI: 10.1103/PhysRevB.63.045301

We investigate the transport properties of quantum dots placed in a strong magnetic field using a quantum-mechanical approach based on the two-dimensional tight-binding Hamiltonian with direct Coulomb interaction and the Landauer-Buttiker formalism. The electronic transmittance and the Hall resistance show Coulomb oscillations and also prove multiple addition processes. We identify this feature as the "bunching" of electrons observed in recent experiments and give an elementary explanation in terms of spectral characteristics of the dot. The spatial distribution of the added electrons may distinguish between the edge and bulk states and it has specific features for bunched electrons. The dependence of the charging energy on the number of electrons is discussed for a strong magnetic field. The crossover from the tunneling to quantum Hall regime is analyzed in terms of dot-lead coupling.

2954. PbSe1-xTex thick thermoelectric films obtained by electrochemical deposition from aqueous solutions

Authors: Nedelcu, M; Sima, M; Visan, T; Pascu, T

Published: 2001, TWENTIETH INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS, 330, DOI: 10.1109/ICT.2001.979898

This work describes the study of PbSe1-xTex film electrodeposition on glassy carbon and ITO electrodes in acid solutions (0.1 M HNO3), using cyclic voltammetry and rotating-disk techniques. Electrochemical impedance spectroscopy study of PbSe1-xTex film in 0.1M HNO3 were also presented.

2955. Evaluation of performance capabilities of emitters and detectors based on a common MQW structure

Authors: Cengher, D; Aperathitis, E; Androulidaki, M; Deligeorgis, G; Kayambaki, M; Hatzopoulos, Z; Tzanetakis, P; Georgakilas, A

Published: MAR 22 2001, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 80, 244, DOI: 10.1016/S0921-5107(00)00614-0

Photodetectors (PDs) based on three separate confinement-multiple quantum well (SCH-MQW) structures (with 2, 4 and 8 QWs) and sis graded-index (GRIN) SCH-MQW structures were studied for two types of devices: guided wave and non-guided wave devices. Non-guided wave devices were processed and the capacitance and the responsivity, in the wavelength range of 750-990 nm, were determined for various bias voltages. Guided wave PDs were simulated using the transfer matrix method for optical mode calculation and the minimum length of the detectors was calculated for absorbing 99% of the incident light. The junction capacitance of the guided wave PDs was calculated from the measured capacitance of non-guided wave devices and the minimum size of the devices, values of 215, 101, and 52 fF were obtained for 2, 4 and 8 QW SCH-MQW structures. Laser diodes were also fabricated from the three different SCH-MQW structures. Threshold current densities (J(th)) of 737. 755 and 1210 A cm(-2) were measured for 2, 4 and 8 QWs, respectively. Further improvement was achieved using GRINSCH-MQW structures and LDs with 4 QWs exhibited 33% decrease in J(th) and 22% increase in slope efficiency. (C) 2001 Elsevier Science B.V. All rights reserved.

2956. Aspects in HTS laser ablation thin film technology and characterization

Authors: Branescu, M; Gyorgy, E; Ristoscu, C; Mihailescu, IN; Jaklovsky, J; Mihalache, V

Published: 2001, 11TH INTERNATIONAL SCHOOL ON QUANTUM ELECTRONICS: LASER PHYSICS AND APPLICATIONS, 4397, 313, DOI: 10.1117/12.425154

Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposition with an excimer KrF* (lambda =248 nm, tau (FWHM)greater than or equal to 20 ns) laser source from a stoichiometric target. In the present paper we report details of the technology of pulsed laser deposition of high-temperature superconductor thin films, substrates' requirements and high-temperature superconductor thin film characterisation. The study of some parameters' intercorelations for optimisation of the technology of the pulsed laser deposition of high-temperature superconductor thin films is also analysed Moreover, the contacting technology and techniques of characterisation are described.

2957. Developments for radiation hard silicon detectors by defect engineering - results by the CERN RD48 (ROSE) Collaboration

Authors: Lindstrom, G; Ahmed, M; Albergo, S; Allport, P; Anderson, D; Andricek, L; Angarano, MM; Augelli, V; Bacchetta, N; Bartalini, P; Bates, R; Biggeri, U; Bilei, GM; Bisello, D; Boemi, D; Borchi, E; Botila, T; Brodbeck, TJ; Bruzzi, M; Budzynski, T; Burger, P; Campabadal, F; Casse, G; Catacchini, E; Chilingarov, A; Ciampolini, P; Cindro, V; Costa, MJ; Creanza, D; Clauws, P; Da Via, C; Davies, G; De Boer, W; Dell'Orso, R; De Palma, M; Dezillie, B; Eremin, V; Evrard, O; Fallica, G; Fanourakis, G; Feick, H; Focardi, E; Fonseca, L; Fretwurst, E; Fuster, J; Gabathuler, K; Glaser, M; Grabiec, P; Grigoriev, E; Hall, G; Hanlon, M; Hauler, F; Heising, S; Holmes-Siedle, A; Horisberger, R; Hughes, G; Huhtinen, M; Ilyashenko, I; Ivanov, A; Jones, BK; Jungermann, L; Kaminsky, A; Kohout, Z; Kramberger, G; Kuhnke, M; Kwan, S; Lemeilleur, F; Leroy, C; Letheren, M; Li, Z; Ligonzo, T; Linhart, V; Litovchenko, P; Loukas, D; Lozano, M; Luczynski, Z; Lutz, G; MacEvoy, B; Manolopoulos, S; Markou, A; Martinez, C; Messineo, A; Mikuz, M; Moll, M; Nossarzewska, E; Ottaviani, G; Oshea, V; Parrini, G; Passeri, D; Petre, D; Pickford, A; Pintilie, I; Pintilie, L; Pospisil, S; Potenza, R; Radicci, V; Raine, C; Rafi, JM; Ratoff, PN; Richter, RH; Riedler, P; Roe, S; Roy, P; Ruzin, A; Ryazanov, AI; Santocchia, A; Schiavulli, L; Sicho, P; Siotis, I; Sloan, T; Slysz, W; Smith, K; Solanky, M; Sopko, B; Stolze, K; Avset, BS; Svensson, B; Tivarus, C; Tonelli, G; Tricomi, A; Tzamarias, S; Valvo, G; Vasilescu, A; Vayaki, A; Verbitskaya, E; Verdini, P; Vrba, V; Watts, S; Weber, ER; Wegrzecki, M; Wegrzecka, I; Weilhammer, P; Wheadon, R; Wilburn, C; Wilhelm, I; Wunstorf, R; Wustenfeld, J; Wyss, J; Zankel, K; Zabierowski, P; Zontar, D

Published: JUN 1 2001, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 465, 69, DOI: 10.1016/S0168-9002(01)00347-3

This report summarises the final results obtained by the RD48 collaboration. The emphasis is on the more practical aspects directly relevant for LHC applications. The report is based on the comprehensive survey given in the 1999 status report (RD48 3rd Status Report, CERN/LHCC 2000-009, December 1999), a recent conference report (Lindstrom et al, (RD48), and some latest experimental results. Additional data have been reported in the last ROSE workshop (5th ROSE workshop, CERN, CERN/LEB 2000-005), A compilation of all RD48 internal reports and a full publication list can be found on the RD48 homepage (http://cern.ch/RD48/). The success of the oxygen enrichment of FZ-silicon as a highly powerful defect engineering technique and its optimisation with various commercial manufacturers are reported. The focus is on the changes of the effective doping concentration (depletion voltage). The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified: projections to operational scenarios for main LHC experiments demonstrate vital benefits. Progress in the microscopic understanding of damage effects as well as the application of defect kinetics models and device modelling for the prediction of the macroscopic behaviour was also been achieved but will not be covered in detail. (C) 2001 Elsevier Science B.V. All rights reserved.

2958. Radiation hard silicon detectors - developments by the RD48 (ROSE) collaboration

Authors: Lindstrom, G; Ahmed, M; Albergo, S; Allport, P; Anderson, D; Andricek, L; Angarano, MM; Augelli, V; Bacchetta, N; Bartalini, P; Bates, R; Biggeri, U; Bilei, GM; Bisello, D; Boemi, D; Borchi, E; Botila, T; Brodbeck, TJ; Bruzzi, M; Budzynski, T; Burger, P; Campabadal, F; Casse, G; Catacchini, E; Chilingarov, A; Ciampolini, P; Cindro, V; Costa, MJ; Creanza, D; Clauws, P; Da Via, C; Davies, G; De Boer, W; Dell'Orso, R; De Palma, M; Dezillie, B; Eremin, V; Evrard, O; Fallica, G; Fanourakis, G; Feick, H; Focardi, E; Fonseca, L; Fretwurst, E; Fuster, J; Gabathuler, K; Glaser, M; Grabiec, P; Grigoriev, E; Hall, G; Hanlon, M; Hauler, F; Heising, S; Holmes-Siedle, A; Horisberger, R; Hughes, G; Huhtinen, M; Ilyashenko, I; Ivanov, A; Jones, BK; Jungermann, L; Kaminsky, A; Kohout, Z; Kramberger, G; Kuhnke, M; Kwan, S; Lemeilleur, F; Leroy, C; Letheren, M; Li, Z; Ligonzo, T; Linhart, V; Litovchenko, P; Loukas, D; Lozano, M; Luczynski, Z; Lutz, G; MacEvoy, B; Manolopoulos, S; Markou, A; Martinez, C; Messineo, A; Mikuz, M; Moll, M; Nossarzewska, E; Ottaviani, G; Oshea, V; Parrini, G; Passeri, D; Petre, D; Pickford, A; Pintilie, I; Pintilie, L; Pospisil, S; Potenza, R; Raine, C; Rafi, JM; Ratoff, PN; Richter, RH; Riedler, P; Roe, S; Roy, P; Ruzin, A; Ryazanov, AI; Santocchia, A; Schiavulli, L; Sicho, P; Siotis, I; Sloan, T; Slysz, W; Smith, K; Solanky, M; Sopko, B; Stolze, K; Avset, BS; Svensson, B; Tivarus, C; Tonelli, G; Tricomi, A; Tzamarias, S; Valvo, G; Vasilescu, A; Vayaki, A; Verbitskaya, E; Verdini, P; Vrba, V; Watts, S; Weber, ER; Wegrzecki, M; Wegrzecka, I; Weilhammer, P; Wheadon, R; Wilburn, C; Wilhelm, I; Wunstorf, R; Wustenfeld, J; Wyss, J; Zankel, K; Zabierowski, P; Zontar, D

Published: JUL 1 2001, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 466, 326, DOI: 10.1016/S0168-9002(01)00560-5

The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors. capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2 x 10(17) O/cm(3) in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5 x 10(14)cm(-2) (1 MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the "Hamburg model": its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed. including differences due to charged and neutral hadron irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.

2959. Nondiverging vortex pinning barriers at low current densities across the putative elastic vortex-glass-vortex-liquid transition in YBa2Cu3O7-delta films

Authors: Miu, L; Basset, M; Jakob, G; Rodriguez, H; Adrian, H

Published: DEC 1 2001, PHYSICAL REVIEW B, 64, DOI: 10.1103/PhysRevB.64.220502

A detailed analysis of the electric field-current density (E - J) characteristics of YBa2Cu3O7-delta films across the putative thermally induced elastic vortex-glass-vortex-liquid transition predicted by the E(J) curve scaling reveals that the expected increase of the collective pinning barriers with decreasing J is cut off in the low-J region, signaling a dissipation process which involves the plastic deformation of the vortex system. The temperature and magnetic field dependence of the pinning barriers at low J does not change across the scaling-predicted glass transition line. For the investigated magnetic field range (0.5-7 T), over a relatively large temperature interval, in YBa2Cu3O7-delta films there appears a continuous crossover in a pinned plastic vortex assembly, rather than a thermally induced elastic vortex-glass-vortex-liquid transition.

2960. Trapping levels in (nc-Si/CaF2)(n) multi-quantum wells

Authors: Ioannou-Sougleridis, V; Nassiopoulou, AG; Ciurea, ML; Bassani, F; d'Avitaya, FA

Published: AUG 20 2001, MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS, 15, 47, DOI: 10.1016/S0928-4931(01)00215-6

Trapping levels which govern the vertical transport in (nc-Si/CaF2)(n) multi-quantum wells were investigated using two different techniques: (a) the temperature dependence of the dark current and (b) the thermally stimulated depolarization current technique (TSDC). Measurements by the first technique showed that the conduction mechanism was thermally activated above 200 K with activation energies of 0.35-0.7 eV, These activation energies were found to increase with increasing electric field. TSDC measurements showed also the existence of at least one broad peak above 200 K with estimated activation energies in the range of 0.4-0.45 eV. Analysis of the peak by the fractional heating method showed a continuous distribution of defect states from 0.3 to 0.83 eV. (C) 2001 Elsevier Science B.V. All rights reserved.

2961. Fourth-order zero-field splitting parameters of [Mn(cyclam)Br-2]Br determined by single-crystal W-band EPR

Authors: Mossin, S; Stefan, M; ter Heerdt, P; Bouwen, A; Goovaerts, E; Weihe, H

Published: 2001, APPLIED MAGNETIC RESONANCE, 21, 596, DOI: 10.1007/BF03162431

Single-crystal W-band (95 GHz) electron paramagnetic resonance (EPR) studies have been performed at 20 K and at room temperature on a tetragonal Mn(III) compound with potential application as a building block for high-spin clusters. The observed EPR spectra correspond to an anisotropic high-spin S = 2 ground state and have been attributed to equivalent centers related by fourfold symmetry. Accurate values for the spin Hamiltonian parameters were obtained from the analysis of the data at both temperatures. At 20 K the contribution of fourth-order zero-field splitting terms was shown to be significant, with parameter values B-4(0) = 0.0009(3) cm(-1), B2 = 0.0006(2) cm(-1) and 4 4 B-4(4) = 0.0017(3) cm(-1), to be considered together with the second-order parameters D = -1.1677(7) cm(-1) and E = -0.0135(6) cm(-1).

2962. Influence of gamma irradiation on the thermal stability of blends of PP with previously treated sisal fiber

Authors: Albano, C; Reyes, J; Ichazo, M; Gonzalez, J; Chipara, MI

Published: 2001, POLYMER DEGRADATION AND STABILITY, 73, 236, DOI: 10.1016/S0141-3910(01)00036-2

In this work, the thermal degradation of PP blends with previously treated sisal fiber (10mm), and gamma irradiated in air at different doses (10, 25, 50, 60, 70 kGy), is studied. The treatment to which sisal fibers were previously submitted were: (a) the addition of a coupling agent (Silane A-172), 1% by weight, (b) a chemical treatment at different times (1/2 and 1 h) with NaOH, and (c) the addition of a functionalized polypropylene known as Polybond 3150 and 3200, 5% by weight. After the treatment, mixtures of PP with 20% of sisal fibers were prepared. Their thermograms were analyzed using different integral methods in order to evaluate the activation energy. For the blend of PP with sisal fibers, previously treated for 1 h with NaOH, the largest value amounted to 60 kJ/mol (approximately) for irradiation doses under 40 kGy. At higher irradiation doses a decay on the activation energy was observed. When the fibers were treated with NaOH for 30 min, the activation energy decreased from 55 kJ/mol to values under 45 kJ/mol, when subjected to high irradiation doses (> 50 kGy). This can be explained by the fact that, when sisal fibers are treated with NaOH solutions over a longer time, impurities and lignin are better removed resulting in a higher surface roughness; as a consequence a higher polymer to fiber interaction is possible, which, in turn, makes the blend more stable at low irradiation doses. Instead, when the sisal fibers were treated with silane, the activation energy for thermal degradation decreased at higher irradiation doses until an inversion of the tendency was observed for the 50 kGy dose; this may imply that this irradiation induces the production of PP-filler bridges. With composites containing compatibilizers, a similar behavior as with silane was observed but with the inversion on the tendency at 70 kGy. From these results, it can be concluded that a l-h treatment with NaOH produces a higher thermal stability than the others. Moreover, this treatment has the best profit/cost ratio, which makes it commercially profitable when compared with others. The mathematical analysis shows that the blend of PP with NaOH-treated sisal fiber at the two treatment times (1 h and 1/2 h), showed competing degradation and single decomposition processes for the irradiation intervals between 0-50 kGy and 50-70 kGy, respectively. Regarding the blends of PP with silane-treated sisal fiber or Polybond addition showed bimolecular decomposition behavior for both irradiation intervals. (C) 2001 Elsevier Science Ltd. All rights reserved.

2963. UV irradiation effects in pure and tin-doped amorphous AsSe films

Authors: Popescu, M; Iovu, M; Hoyer, W; Shpotyuk, O; Sava, F; Lorinczi, A

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 306, DOI:

Pure and tin-doped AsSe amorphous films were investigated. The changes in the MRO induced by Sn were analysed be accurate profiling the first sharp diffraction peak (FSDP) in the X-ray diffraction diagram. A shift of FSDP as a function of tin concentration was observed. The structural changes induced by ultraviolet rays (lambda = 336 nm) for various time intervals of irradiation were revealed by small angle X-ray diffraction. It was revealed the formation of a special layer at the surface of the films. whose thickness increases during UV irradiation.

2964. Point defects in cubic boron nitride crystals

Authors: Nistor, SV; Stefan, M; Goovaerts, E; Bouwen, A; Schoemaker, D; Dinca, G

Published: MAR-JUL 2001, DIAMOND AND RELATED MATERIALS, 10, 1411, DOI: 10.1016/S0925-9635(00)00396-4

The results of a low-temperature study by high frequency (94 GHz) EPR on brown-to-dark colored single crystals selected from cBN crystalline powders prepared by the HPHT technique with boron excess, are presented. Previous investigations by low frequency (9.4 GHz) EPR spectroscopy on such dark polycrystalline c-BN powders resulted in the identification of two paramagnetic species D1 and D2 associated with the brown-to-dark coloration, the spectrum of the latter one being observed only above 100 K. The present research identifies the D1 species, studied by EPR at low temperatures, as consisting mainly from anisotropic paramagnetic centers with electron spin S = 1/2, local symmetry axis along one of the crystal [111] axes and principal g values g(parallel to) = 2.0032 +/- 0.0009 and g(perpendicular to) = 2.0094 +/- 0.0005 at T = 10 K. (C) 2001 Elsevier Science B.V. All rights reserved.

2965. A study on the radical species formed during the polycrystalline solid state radiolysis of the potassium and barium bichromates

Authors: Constantinescu, M; Constantinescu, O; Contineanu, M

Published: SEP 2001, REVISTA DE CHIMIE, 52, 484, DOI:

An EPR study, of the paramagnetic centers formed by irradiation of polycrystalline K2Cr2O7 and BaCr2O7 was made, In the EPR spectra of the gamma irradiated powder samples, at room temperature, the presence of three types of paramagnetic centers iv as observed. According to their EPR parameters and thermal behaviour. these centers were attributed to the Cr(O)over dot(4)(3-), Cr-2(O)over dot(7)(3-) and Cr(O)over dot(3)(-) radicals respectively,. An adequate mechanism radiolysis has been established.

2966. Bi2-xSbxTe3 thick thermoelectric films obtained by electrodeposition from hydrochloric acid solutions.

Authors: Nedelcu, M; Sima, M; Visan, T; Pascu, T; Franga, I; Craciunoiu, F

Published: 2001, TWENTIETH INTERNATIONAL CONFERENCE ON THERMOELECTRICS, PROCEEDINGS, 326, DOI: 10.1109/ICT.2001.979897

A method to produce composition modulated Bi2-xSbxTe3 alloys by electrodeposition has been developed. The electrolyte, which consists in a HCl 6M (pH = 0) aqueous solution, allows the codeposition of bismuth, antimony and tellurium to be accomplished at room temperature on glassy carbon, platinum or nickel electrode. The composition of the films. their crystal structures and morphology were studied as function of electrochemical parameters and bath composition. It is shown that the electrodeposits are monophasic and exhibit a polycrystalline state. The electrical resistivity was of the order of 7-10 mOmegacm, whereas the electrodeposition rate value was 30-50 mum/h for the films with good thermoelectric properties.

2967. Atomic 6p-Tl-0 centers in ferroelectric Rb2ZnCl4 crystals

Authors: Stefan, M; Nistor, SV; Schoemaker, D

Published: 2001, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 155, 377, DOI: 10.1080/10420150108214140

Several Tl-0 (6s(2)6p(1))-type paramagnetic centers, produced by low temperature X-ray irradiation, were observed and studied by electron spin resonance (ESR) in the orthorhombic ferroelectric phase of thallium doped Rb2ZnCl4 crystals. The centers were formed by electron trapping at Tl+ ions localized substitutionally at Rb+ sites. The number and properties of the observed centers account for the tripling of the unit cell in the ferroelectric phase.

2968. Internal structure of the nanosized sol-gel ITO thin films

Authors: Stoica, TF; Teodorescu, VS; Blanchin, MG; Stoica, TA; Gartner, M; Zaharescu, M

Published: 2001, 2001 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOL 1 & 2, PROCEEDINGS, 66, DOI:

The alkoxide route and the spinning deposition were used to prepare sol gel ITO films. The morphology and crystalline structure were investigated by Cross-section Transmission Electron Microscopy and Atomic Force Microscopy. The inside of the ITO layer has three regions of different porosity and the basic crystalline structure is that of the In2O3 lattice. Three types of surface morphological structures were found from AFM images.

2969. Multifrequency ESR studies of paramagnetic point defects in cubic boron nitride crystals

Authors: Nistor, SV; Stefan, M; Schoemaker, D; Goovaerts, E; Dinca, G

Published: 2001, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 156, 194, DOI: 10.1080/10420150108216892

Dark-brown crystalline powders and selected single crystals of cubic boron nitride grown by the HP-HT method, with boron excess, have been studied in a broad temperature range by electron spin resonance (ESR) in the X and W microwave frequency bands, respectively. The X-band spectra consist of two superimposed lorentzian components attributed to two types of related paramagnetic defects called D1 and D2, respectively. According to the W-band data, the D I centre exhibits local axial < 111 > symmetry and ground spin state S = 1/2, with g(parallel to) = 2,0033 and g(perpendicular to) = 2.0094 at T = 10 K. The broad D2 line, observed only in the X-band, at g = 2.0084, at higher temperatures, seems to result from transitions inside the excited levels of another boron related defect.

2970. PbSe1-xTex thick thermoelectric films obtained by electrochemical deposition from aqueous solutions

Authors: Nedelcu, M; Sima, M; Stoica, T; Manea, AS; Lazarescu, MF; Visan, T

Published: DEC 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 914, DOI:

It is presented a study of PbSe1-xTex thick films electrodeposition on glassy carbon and ITO electrodes in acid solutions (0.1M HNO3), using cyclic voltammetry and rotating-disk techniques. Electrochemical impedance spectroscopy study of PbSe1-xTex film in 0.1M HNO3 is reported.

2971. Spectroscopic studies of bulk As2S3 glasses and amorphous films doped with Dy, Sm and Mn

Authors: Iovu, MS; Shutov, SD; Andriesh, AM; Kamitsos, EI; Varsamis, CPE; Furniss, D; Seddon, AB; Popescu, M

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 454, DOI:

The effect of rare earth (Dy and Sm) and transition metal (Mn) luminescent impurities on the optical properties of As2S3 glass is studied in a wide spectral region. The Raman, infrared, band-to-band and edge absorption spectroscopies are employed to obtain information about the incorporation of impurity ions in the host glass structure and the corresponding changes in intrinsic optical characteristics. The effects of light-soaking and thermal treatment on the doped As2S3 glasses were examined as well. In the fundamental absorption region a reflectivity maximum at 2.98 eV shows blue (Dy, Sm) or red (Mn) shift depending on the electronegativity of the impurity, in accordance with the corresponding variations of the glass structure. Near the edge absorption the impurity affects strongly the slope and the magnitude of the weak absorption tail. In the wide range of transparency the addition of impurity suppresses several absorption bands indicating the interaction of dopants with the host glass contaminations. Some variations of the characteristic Raman spectra under light exposure acid thermal ageing of doped glasses were registered. The observed effects of metal dopants on the As2S3 glass are discussed in connection with the expected behaviour of the impurities in the glass.

2972. Microparacrystalline model for medium-range order in non-crystalline chalcogenides

Authors: Popescu, M; Bradaczek, H

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 254, DOI:

The medium range order in disordered chalcogenides has been explained by the existence of reminiscent crystal-like configurations with distorted arrangement of the atoms. Using the paracrystalline theory, two parameters have been defined for the characterization of the MRO in glass: paracrystallite thickness and paracrystallite distortion.

2973. SERS studies on disordered carbon nanotube thin films

Authors: Baibarac, M; Benoit, JM; Lefrant, S; Baltog, I; Schreiber, J; Bernier, P; Chauvet, O

Published: MAR 15 2001, SYNTHETIC METALS, 121, 1200, DOI: 10.1016/S0379-6779(00)00735-9

The SERS technique has been proved to be successful to study Single-Walled Carbon Nanotubes (SWNT's), with the observation of peculiar features. In this study, we present more specifically the Raman features which are strongly dependent on the morphology of the nanotube thin films, their thickness, the interfacial effects between films and support, the effect of solvent used to disperse the nanotubes onto the metallic surface.

2974. Luminescence of oxidized porous silicon: Surface-induced emissions from disordered silica micro- to nanotextures

Authors: Fritsch, E; Mihut, L; Baibarac, M; Baltog, I; Ostrooumov, M; Lefrant, S; Wery, J

Published: NOV 1 2001, JOURNAL OF APPLIED PHYSICS, 90, 4782, DOI: 10.1063/1.1410887

The luminescence spectra of fully oxidized porous silicon show two broad bands and one vibronic structure between 2 and 3.3 eV, all excited at 340 or 275 nm (3.65 and 4.51 eV). Two of these structures have not been described previously. Interestingly, these emissions are found in other forms of amorphous or disordered silica with high specific surfaces: frosted silica glass, silica gel, even various natural opals. These emissions disappear when the surface is passivated. They are, therefore, attributed to surface-related defects. The vibronic structure involves a nearly free SiO4 tetrahedron. Another vibronic structure found only in some opals is attributed to the uranyl group. (C) 2001 American Institute of Physics.

2975. Thermo and photoluminescence of silicate laser glass doped with neodymium

Authors: Grigoras, B; Cerchez, M; Ionescu, L; Secu, M; Matei, L; Trutia, A

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 562, DOI:

The luminescence and thermoluminescence have been measured in vitreous materials doped with Nd3+. The luminescence spectra show a maximum at 400 nm and a shoulder at about 440 nm. The measured global thermoluminescence shows a broad band with a maximum at 270 degreesC, which suggest a continuous distribution of electron traps induced by ionizing radiation. Thermoluminescence measured through two optical filters which transmit at about 400 nm and 440 nm wavelength shows a structured behavior with two glow peaks at 270 degreesC and 330 degreesC. This apparently contradictory behavior has been explained by the existence in this material of a continuous distribution of tr ap levels and a discrete distribution of recombination levels. The 270 degreesC and 330 degreesC glow peaks have been interpreted as being due to recombination of the electrons released from electron traps with O2-. and Nd3+ hole centers. Due to the high stability of the defects induced by the radiation observed from thermoluminescence measurements, this material could be used as a new radiation detector.

2976. Transmission electron microscopy study of silicon nitride amorphous films obtained by reactive pulsed laser deposition

Authors: Teodorescu, VS; Nistor, LC; Popescu, M; Mihailescu, IN; Gyorgy, E; Van Landuyt, J; Perrone, A

Published: OCT 1 2001, THIN SOLID FILMS, 397, 16, DOI: 10.1016/S0040-6090(01)01408-0

In situ decomposition of silicon nitride films was observed by high-resolution electron microscopy. The films, which were produced by reactive pulsed laser deposition from Si wafer targets at 50-100 Pa ammonia pressure, had a prevalent content of hydrogen-doped, amorphous, non-stoichiometric silicon nitride. A layered morphology of the film, consisting of a density variation in the amorphous structure, developed under electron beam irradiation. This morphology became evident only in cross-sectional observation and was related to the stress-relaxation effect, based on a rearrangement of the bonds, We presume that the stress field anisotropy in the amorphous structure must be related to the presence of some bond texture in the as-grown, amorphous film. (C) 2001 Elsevier Science B.V. All rights reserved.

2977. Laser pulse effects in Se-S glassy thick films

Authors: Savastru, D; Savastru, R; Ion, L; Popescu, M

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 310, DOI:

Amorphous thick films in the system Se-S have been prepared by splat-cooling Local irradiation of the films with laser pulses of various intensities and wavelengths were carried out. The effects induced by laser pulses with special emphasis to the eutectic composition Se42S58 were investigated by optical microscopy and before and after annealing of the films. For low density of power incident on the film, a local photo-darkening effect is observed. For mean power density the photo-darkened region increases. For high power density a considerable destructive effect appears, which determine the appearance of clusters of bubbles after annealing the film at the softening temperature.

2978. Investigations of pyroelectric properties of pure and alanine doped TGS crystals

Authors: Costache, M; Matei, I; Pintilie, L; Alexandru, HV; Berbecaru, C

Published: MAR 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 81, DOI:

Pyroelectric measurements were performed on pure and on L or D alanine doped TCS. Crystals were grown in paraelectric phase (similar to 52 degreesC) from solutions by slow evaporation of the solvent. Pyroelectric current was measured by, crossing the Curie point, both on heating and cooling. Spontaneous polarization P-S(T) was also recorded using the charge integration method. The pyroelectric current of pure TGS samples along with the spontaneous polarization were detected only on heating, using a poling procedure similar to those applied to ceramic ferroelectrics. The remarkable asymmetry of measured pyroelectric coefficient of D and I. alanine doped samples suggests a non-equivalent substitution of glycine in the host lattice.

2979. Ru-MCM-41 catalysts for diastereoselective hydrogenation

Authors: Florea, M; Sevinci, M; Parvulescu, VI; Lemay, G; Kaliaguine, S

Published: JUN 2001, , DOI: 10.1016/S1387-1811(01)00224-4

2980. Influence of the deposition configuration on the composition, structure and morphology of La0.6Y0.07Ca0.33Mn3-delta thin films obtained by pulsed laser deposition

Authors: Ghica, C; Valeanu, M; Nistor, LC; Teodorescu, V; Sandu, C; Ristoscu, C; Mihailescu, IN; Werckmann, J; Deville, JP

Published: DEC 2001, INTERNATIONAL JOURNAL OF INORGANIC MATERIALS, 3, 1256, DOI: 10.1016/S1466-6049(01)00153-2

We present a structural and morphological study on La0.6Y0.07Ca0.33MnO3-delta (LYCMO) thin films deposited by laser ablation onto MgO-buffered silicon wafers using two deposition configurations named on-axis and off-axis. All thin films have been deposited at high temperatures in an oxygen atmosphere. A comparative study between the on-axis and off-axis samples is performed by transmission electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy. The films are polycrystalline and show a columnar morphology. The off-axis sample shows a better crystalline texture, although slight compositional variations have been found. (C) 2001 Elsevier Science Ltd. All rights reserved.

2981. C-60-polymer nanocomposites: Evidence for interface interaction

Authors: Giusca, C; Alexe, G; Baibarac, M; Baltog, I; Manaila, R; Devenyi, A

Published: 2001, EPDIC 7: EUROPEAN POWDER DIFFRACTION, PTS 1 AND 2, 378-3, 388, DOI: 10.4028/www.scientific.net/MSF.378-381.383

Structure of polyaniline (PAN)-C-60 nanocomposites was investigated by X-ray diffraction. Raman Spectroscopy was also used in order to find evidence for the C-60 - polymer interface interaction.

2982. Single-crystal high-frequency electron paramagnetic resonance investigation of a tetranuclear iron(III) single-molecule magnet

Authors: Bouwen, A; Caneschi, A; Gatteschi, D; Goovaerts, E; Schoemaker, D; Sorace, L; Stefan, M

Published: APR 5 2001, JOURNAL OF PHYSICAL CHEMISTRY B, 105, 2663, DOI: 10.1021/jp003441d

A high-frequency (95 GHz) electron paramagnetic resonance (EPR) study is reported on single crystals of the planar tetranuclear complex Fe-4(OCH3)(6)(dpm)(6) (where Hdpm = dipivaloylmethane), which has been previously shown to present typical single-molecule magnet behavior. The spectra, all originating from the S = 5 ground state, possess quasi-axial symmetry along the normal to the plane defined by the four Fe(m) ions. The measured spectra are shown to belong to three different structural variations of the compound, resulting from disorder in the ligands around two of the Fe(III) ions. Accurate values could be obtained for the second- and fourth-order crystal field parameters related to the parallel EPR spectra, while the other parameters could be determined only for the dominant species. The separation between individual lines is decreasing and vanishing with increasing temperature. This effect is attributed to the contribution of fast relaxing excited states, whose population is varying with temperature.

2983. Symmetry and hyperfine magnetic fields in Nd-based intermetallics

Authors: Sorescu, M; Grabias, A; Valeanu, M

Published: JAN 2001, INTERMETALLICS, 9, 71, DOI: 10.1016/S0966-9795(00)00099-6

Intermetallics of the type NdCo9-xFexSi2Cy (x = 3; 5; 6; 7 and y = 0; 1) and Nd2Co15-xFexSi2Cy (x = 7; 9; 12 and y = 0; 1) were prepared by are melting in order to study the competing effects of Fe and Co substitutions on the magnetic hyperfine fields as well as the effects of interstitial carbon additions on the symmetry and local magnetic properties in these systems. The investigations were performed by X-ray diffraction, Mossbauer spectroscopy and hysteresis loop measurements. Both site and average hyperfine magnetic field values were analyzed in order to discriminate between the Fe and Co contributions to the local atomic environments in these systems. While a higher Fe content as well as a higher Co content can both lead to an increase in the site magnetic fields, it was found that the model based on hyperfine field distributions provides a better description of the trends observed in hyperfine magnetic fields in these compounds. (C) 2001 Elsevier Science Ltd. All rights reserved.

2984. Traps in (nc-Si/CaF2)(50) nanostructures

Authors: Draghici, M; Jdira, L; Iancu, V; Ioannou-Sougleridis, V; Nassiopoulou, A; Ciurea, ML

Published: 2001, CAS: 2002 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, PROCEEDINGS, 122, DOI:

Traps in Multi-Quantum Wells (nc-Si/CaF2)(50) nanostructures using Optical Charging Spectroscopy method were investigated. Three maxima and a final abrupt increase were found in the discharge current versus temperature characteristics. The relative contributions of the tunneling and displacement currents through the insulating calcium fluoride were analyzed.

2985. Non steady-state thermoelectric conduction

Authors: Apostol, M; Nedelcu, M

Published: MAR 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 132, DOI:

It is shown that the figure of merit of a thermoelectric couple can be appreciably improved by using a pulsed current transferred from the thermoelectric circuit. In the frame of this theory un unusual drop of temperature in a thermoelectric circuit is possible. An ultrafast process of thermoelectric conduction is described, whose increased performance is realized by minimizing the effects of thermal dissipation.

2986. Design and fabrication preamble of a microstrip HTS antenna

Authors: Ramer, R; Banciu, MG; Dimitriu, E; Pham, MS; Vu, TB

Published: MAY-AUG 2001, INDUSTRIAL CERAMICS, 21, 113, DOI:

High temperature superconducting (HTS) thin films were used to design and manufacture microstrip antennas. The high temperature superconducting thin dims of YBa2Cu3O7+delta type were deposed on lanthanum aluminate LaAlO3 substrates by using the RF magnetron sputtering technique. The transition temperature T-c and current density J(c) values proved the high quality of our films. Antenna structure consisted of three low losses dielectric layers. The radiating disk and ground plane with feeding aperture were deposed on one layer and the microstrip feeding line on another layer. The third dielectric layer separates the feeding slot from the feeding line. The measured resonant frequencies and antenna patterns validate the design technique.

2987. SEM, EDS and WAXD microstructural characterization of a new enamel used as a protective and thermal barrier

Authors: Pencea, I; Manoliu, V; Vasiliu, F; Britchi, M; Olteanu, M

Published: 2001, INTERNATIONAL JOURNAL OF MATERIALS & PRODUCT TECHNOLOGY, 16, 668, DOI: 10.1504/IJMPT.2001.001287

A new enamel has been developed to be used as a protective and thermal barrier coating of aircraft engine components subjected to thermal shocks and corrosion. This enamel is based upon the oxide system SiO2-BaO CaO-Cr2O3 and can stand about 1100 degreesC without losing its adherence and main protective characteristics. The microstructural element concentration and crystalline phases have been studied using scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and wide angle X-ray diffraction (WAXD) in order to offer a better understanding of the enamel characteristics.

2988. Magneto-thermoelectric alloys obtained by electrodeposition

Authors: Nedelcu, M; Sima, M; Aldica, G; Apostol, E

Published: 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 720, DOI:

When a magnetic field is applied on a narrow gap semiconductor with high hole mobility, a substantial rise in the figure of merit can be observed due to Ethinghausen effect. The most important proof of this effect was achieved by using Bi-Sb alloys. The present paper is devoted to performance of the electrochemical synthesis of Bi-Sb alloys from acid aqueous solutions and to the investigations of physico-chemical. properties of these alloys. Thick films of Bi-Sb alloy were electrodeposited from both chloride and perchlorate solutions. The electro-deposited films obtained from perclorate solutions are thicker, more compact and more uniform. The Bi/Sb ratio in the solution bulk was found to be approximately the same to the Bi/Sb ratio in the electrodeposited alloy. The Hall effect was measured by a home-made apparatus. The range of the magnetic field (B) determined by a standard induction coil was 0.05-1 T. Carrier concentration, n is 10(18) cm(-3) and increases slow in the choosen magnetic range.

2989. Site and distributed hyperfine magnetic fields in synthetic magnetite

Authors: Sorescu, M; Tarabasanu, D; Diamandescu, L

Published: SEP 2000, INTERNATIONAL JOURNAL OF INORGANIC MATERIALS, 2, 374, DOI: 10.1016/S1466-6049(00)00039-8

We synthesized Fe3-xCoxO4 (x=0-0.6) using the hydrothermal method at 300 degrees C in order to demonstrate substitution effects on the hyperfine magnetic fields and populations of the tetrahedral (A) and octahedral (B) sites of magnetite. Our Mossbauer spectroscopy results were first analyzed using the site model, which provided direct evidence for the presence of the Co substitution in the (B) sublattice. This was accompanied by a systematic increase of the hyperfine magnetic field at (B) sites. The mechanism we propose relies on the substitution of Fe2+ by Co2+ in the (B) sublattice and is supported by the observed dependence of the populations of the (A) and (B) sites on the content x of cobalt substitution. Finally, the Mossbauer spectroscopy results were also analyzed using the hyperfine magnetic field distribution model for direct comparison. For the first time, it was demonstrated that the held values provided by the site model fall within the standard deviation obtained from the distribution model. (C) 2000 Elsevier Science Ltd. All rights reserved.

2990. Nitrogen and hydrogen in thick diamond films grown by microwave plasma enhanced chemical vapor deposition at variable H-2 flow rates

Authors: Nistor, SV; Stefan, M; Ralchenko, V; Khomich, AV; Schoemaker, D

Published: JUN 15 2000, JOURNAL OF APPLIED PHYSICS, 87, 8746, DOI: 10.1063/1.373604

The presence and concentration of nitrogen and hydrogen impurities in thick diamond films grown by microwave plasma chemical vapor deposition at various H-2 gas flow rates, keeping a constant [CH4]:[H-2]=2.5% concentration ratio, have been determined by electron spin resonance and optical absorption spectroscopy. The relative concentration of both impurities, present as paramagnetic atomic species with different relaxation properties, has been found by ESR measurements to decrease exponentially with the increase in the H-2 gas flow rate. Moreover, the resulting values were proportional to the content of substitutional nitrogen and CHx groups obtained from infrared and ultraviolet-visible optical absorption measurements, respectively. The decrease in the concentration of both impurities with an increase in the quality of the studied diamond films, early observed from high resolution electron microscopy studies on the same samples, strongly suggests that the incorporation of both impurities, as paramagnetic atomic species, is directly related to the concentration of the extended lattice defects. (C) 2000 American Institute of Physics. [S0021- 8979(00)08611-4].

2991. Investigation of trapping levels in standard, nitrogenated and oxygenated Si p-n junctions by thermally stimulated currents

Authors: Pintilie, I; Petre, D; Pintilie, L; Tivarus, C; Petris, M; Botila, T

Published: JAN 11 2000, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 439, 309, DOI: 10.1016/S0168-9002(99)00845-1

The trapping levels induced in p-n Si junctions by irradiation with 24 GeV proton were investigated using Thermally Stimulated Currents (TSC) methods in the 90-300 K temperature range. Several trapping levels, with activation energies between 0.27 and 0.57 eV, were put into evidence. The spatial distribution of the traps was investigated using different wavelengths for the light used to fill the traps. The results lead to the conclusion that the deepest trapping levels are not uniformly distributed in the volume of the sample. For the most important trapping level the average introduction rate was estimated to 0.9-1.2 cm(-1). The activation energy and the capture cross-section of this trapping level seems to depend on the impurity element introduced in Si. (C) 2000 Elsevier Science B.V. All rights reserved.

2992. Structural investigation of a La0.6Y0.07Ca0.33MnO3 thin film by high resolution transmission electron microscopy

Authors: Ghica, C; Nistor, LC; Teodorescu, VS; Valeanu, M; Ristoscu, C; Mihailescu, IN; Deville, JP; Werckmann, J

Published: MAR 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 72, DOI:

The morphology and structure of a La0.6Y0.07Ca0.33MnO3 thin film is studied by transmission electron microscopy. The film was grown by pulsed laser deposition (PLD) on an MgO-buffered silicon <100> wafer. The as-deposited films are polycrystalline and show a columnar morphology. We present a detailed high-resolution transmission electron microscopy structural study concerning a possible monoclinic distortion of the orthorhombic LYCMO crystal cell. (Received February 22, 2000; accepted March 10, 2000).

2993. Characterization of carbon nitride films deposited by hollow cathode discharge process

Authors: Balaceanu, M; Grigore, E; Truica-Marasescu, F; Pantelica, D; Negoita, F; Pavelescu, G; Ionescu, F

Published: MAR 2000, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 161, 1006, DOI: 10.1016/S0168-583X(99)00957-X

Elastic recoil detection analysis (ERDA) has been applied to determine the composition of carbon nitride and hydrogenated carbon nitride films prepared by hollow cathode discharge process. The films were deposited on Si (111) substrates. The films were also characterized by Fourier transform infrared spectroscopy (FTIR). The influence of the main deposition parameters (substrate bias voltage, nitrogen injection mode) on the film properties was investigated. (C) 1000 Elsevier Science B.V. All rights reserved.

2994. Synthesis and characterization of carbon nitride thin films obtained by laser induced chemical vapour deposition

Authors: Crunteanu, A; Charbonnier, M; Romand, M; Vasiliu, F; Pantelica, D; Negoita, F; Alexandrescu, R

Published: MAR 2000, SURFACE & COATINGS TECHNOLOGY, 125, 307, DOI: 10.1016/S0257-8972(99)00577-0

Carbon nitride thin films (CNx) were produced by UV laser (ArF, lambda=193 nm) induced chemical vapour deposition from C2H2/NH3 mixtures, on Si and TiN/Si substrates. The surface and bulk composition of the deposited layers were investigated by X-ray photoelectron spectrometry (XPS) and elastic recoil detection analysis (ERDA), respectively. Nitrogen was found to be singly and doubly bonded to carbon, as revealed by FTIR spectrometry. Specific morphology of the films was evidenced by transmission electron microscopy (TEM), while selected area electron diffraction (SAED) confirms the presence of nano-crystallites in the layers. The calculated d-lattice spacings fit rather well with theoretical and experimental data for alpha- and beta-C3N4. (C) 2000 Elsevier Science S.A. All rights reserved.

2995. Optical characterization of dielectric borophosphosilicate glass

Authors: Gartner, M; Modreanu, M; Bosch, S; Stoica, T

Published: APR-MAY 2000, MICROELECTRONICS RELIABILITY, 40, 620, DOI: 10.1016/S0026-2714(99)00291-7

Atmospheric pressure chemical vapour deposition films of borophosphosilicate glass with different contents of phosphorus and boron can be successfully used as masks for etching of silicon in KOH solution. The optical properties of these films were pointed out by spectroellipsometric measurements, using different theoretical models (such as Cauchy and Wemple-DiDomenico models). (C) 2000 Elsevier Science Ltd. All rights reserved.

2996. Mn-site doping effects in the giant magnetoresistive perovskite La2/3Ca1/3MnO3: An EPR investigation

Authors: Giurgiu, LV; Grecu, MN; Filip, X; Darabont, A; Indrea, E; Deac, IG; Filip, C; Ordean, R; Popescu, GD; Surducan, E; Blasco, J; Papavassiliou, G

Published: DEC 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 378, DOI:

The effects of aluminium doping on Mn site in the magnetoresistive La-2/3 Ca-1/3 Mn1-x, AlxO3 (x less than or equal to 0.05) powders have been investigated by EPR. The temperature and x dependence of the resonance linewidth has been investigated and discussed in terms of exchange narrowing and spin-lattice relaxation. In the paramagnetic regime, the exchange coupling integral, J, between Mn3+ and Mn4+ ions shows a decrease with increasing x. it could arises from weakening of the double-exchange interaction by aluminium doping which reduces the exchange field at the Mn sites.

2997. Sr-ferrite thin films grown on sapphire by pulsed laser deposition

Authors: Koleva, ME; Zotova, S; Atanasov, PA; Tomov, RI; Ristoscu, C; Nelea, V; Chiritescu, C; Gyorgy, E; Ghica, C; Mihailescu, IN

Published: DEC 15 2000, APPLIED SURFACE SCIENCE, 168, 113, DOI: 10.1016/S0169-4332(00)00612-7

High-quality epitaxial strontium-hexaferrite (SrFe12O19) thin films were grown by pulsed laser deposition (PLD) on c-cut sapphire using KrF* excimer laser at a fluency of 2 J/cm(2) and substrate temperature of 800 degreesC in 100 mTorr oxygen environment. The X-ray diffraction (XRD) and morphology analyzes showed films with excellent crystalline structure and Aat surface. The thickness was found to influence considerably the surface morphology and magnetic properties of the as-deposited films. The highest orientation and the best morphology with smooth surface and fine grain structure was obtained for the him having a thickness of 750 nm. The highest coercive force of 1453 Oe was measured for this film in perpendicular to the plane direction. (C) 2000 Elsevier Science B.V. All rights reserved.

2998. Air bubbles in water: A strongly multiple scattering medium for acoustic waves

Authors: Kafesaki, M; Penciu, RS; Economou, EN

Published: JUN 26 2000, PHYSICAL REVIEW LETTERS, 84, 6053, DOI: 10.1103/PhysRevLett.84.6050

Using a newly developed multiple scattering scheme, we calculate band structure and transmission properties for acoustic waves propagating in bubbly water. We prove that the multiple scattering effects are responsible for the creation of wide gaps in the transmission even in the presence of strong positional and size disorder.

2999. Preparation and properties of Ce-doped BaTiO3 thin films by r. f. sputtering

Authors: Cernea, M; Iliescu, M; Matei, I; Iuga, A; Logofatu, C

Published: 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 692, DOI:

Ce-doped BaTiO3 thin films prepared on silicon-platinium by r.f. sputtering has been investigated. BaTiO3 doped with 5.5 mol.%CeO2 thin film was deposited at 550 degreesC substrate temperature in Ar atmosfere. The crystal structure and shape were examined by X-ray diffraction and scanning electron microscopy with EDAX. Analysis by X-ray diffraction patterns show that the crystalline film with a cubic structure of BaTiO3, was obtained. The surface morphology (roughness, the grain size and the droplet size) of the thin film surface was examined by atomic force microscopy (AFM). The grain size is about 160 nm, the droplet size is about 0.675 mum and the roughness is 36.88 nm. EDAX analyse established a composition of the film identicaly with that of target (BaTiO3 doped with 5.5 mol.%CeO2). The broad peak in the capacitance versus temperature curve at Curie point indicate that the r.f. sputtered Ce-doped BaTiO3 film is ferroelectric. The values of the capacitance of the thin film at 1 KWz were found to be 86 pF and the loss dielectric was tan delta =0.0875. The film have presented dielectric anomaly peak at 23 degreesC showing ferroelectric to paraelectric phase transition.

3000. Paracrystallinity

Authors: Bradaczek, H; Hildebrandt, G; Popescu, M

Published: 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 656, DOI:

There was a wide range of structures which are neither monocrystalline nor amorphous. Setting up a general model for such structures is very difficult because lattice distortions have different reasons and configurations. Therefore only approximations can be simulated. One of the most useful approximation is the model of paracrystals mainly developed by R. Hosemann. His idea was to postulate the distance to the neighbour atom or particle by a certain statistics. Starting with the linear "paracrystal" it is very easy to generate a statistical distribution of atoms or panicles. But even for two dimensional paracrystals the problem arises that the diagonal statistics does not obey the general idea of the paracrystal. Several attempts have been made to model the two or three dimensional paracrystal but only the present authors potential field model offers the possibility to simulate those structures. The basic idea is very simple. To each of the atoms (or particles) positive center Gaussian functions are attributed together with a certain number of negative Gaussian traps; there interaction leads to the position of the neighbour atoms. Using the Monte Carte method each of the neighbours can occupy a statistically generated position. So the three dimensional paracrystal can be generated. Several possibilities of additional parameters enable to adapt the model to the wanted conditions.

3001. Doping and metallic-support effect evidenced on SERS spectra of polyaniline thin films

Authors: Baibarac, M; Mihut, L; Louarn, G; Lefrant, S; Baltog, I

Published: OCT 1 2000, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, 38, 2609, DOI: 10.1002/1099-0488(20001001)38:19<2599::AID-POLB120>3.0.CO;2-Y

Surface-enhanced Raman scattering (SERS) is a process with origins, electromagnetic and chemical. The electromagnetic enhancement consists of the excitation of surface plasmons in the metallic support of the thin film. With only the electromagnetic enhancement mechanism, the surface spectra should not differ from volume Raman spectra. However, between SERS and volume Raman spectra, there are differences resulting from the chemical reactions taking place at the polymer/metal interface, intermediated by solvent molecules, that finally depend on the types of polymers and metallic supports. Polyaniline (PAN) is an excellent material to emphasize the chemical component of SERS. This is due to its particular structure with a repeating unit that contains two entities at different weights-a reduced state and an oxidized state-that, in turn, react differently with a metallic substrate. SERS spectra depend on the oxidizing properties of the metal surface, which involves an intermediate compound of the types Ag2O and Au2O3 when N-methyl-2-pyrrolidinone is used as the solvent. This article presents new results concerning the surface chemical effects that produce variations of the PAN SERS spectra. The SERS spectra of the PAN emeraldine base (PAN-EB) layered on Au support are characterized by a semiquinoid structure that we believe is induced on the intermediate compound Au2O3. In the presence of H2SO4, the SERS spectra change gradually as the degree of acid protonation doping increases. The SERS spectra of the fully protonated PAN-EB are identical to those obtained on PAN emeraldine salt (PAN-ES) synthesized by cyclic voltammetry in an acid medium and are invariable with the type of metallic support. The SERS spectra show that the emeraldine salt can be partially or totally deprotonated with water or NH4OH. The deprotonation is complete for the Ag support and partial for the Au support. The SERS spectra of the fully protonated PAN-EB are characterized by a double band with maxima at about 1330 and 1370 cm(-1). Although the generation process of positive charge on the macromolecular chain of PAN-EB doped in the presence of (C4H9)(4)NBF4 is similar to that due to protonic acid doping, involving cation addition (C4H9+ or H+ ions, respectively) in SERS spectra, the complex band situated at about 1330-1370 cm(-1) no longer appears. The doping of PAN-EB with FeCl3 produces two polymer cm forms: a salt type characterized by a protonated structure similar to that found for PAN-ES and a base type similar to the leucoemeraldine form. (C) 2000 John Wiley & Sons, Inc.

3002. Optical and morphological propel-ties of laser photo-deposited hydrogenated CNx thin films

Authors: Crunteanu, A; Charbonnier, M; Romand, M; Mugnier, J; Sandu, C

Published: DEC 15 2000, APPLIED SURFACE SCIENCE, 168, 51, DOI: 10.1016/S0169-4332(00)00581-X

The optical and morphological properties of hydrogenated carbon nitride thin films obtained by ArF excimer laser photodeposition (lambda = 193 nm) from different ammonia/acetylene mixtures were investigated. The optical properties of the films depend on the nitrogen content. The band gap deduced from measurements of the optical absorption coefficient in the UV-VIS spectrum is found to be superior to 2.3 eV. Film thicknesses and refraction indexes were investigated by m-lines spectroscopy The refraction index varies from 1.66 to 1.72. The microstructure of the deposited films as revealed by scanning and transmission electron microscopy is discussed as a function of the deposition parameters. 2000 Elsevier Science B.V. All rights reserved.

3003. Electron-hole recombination in PbCl2 : T1 crystals

Authors: Nistor, SV; Stefan, M; Goovaerts, E; Schoemaker, D

Published: MAY 2000, JOURNAL OF LUMINESCENCE, 87-9, 551, DOI: 10.1016/S0022-2313(99)00287-2

A correlated ESR and optical emission study on samples doped with different concentrations of Tl+ impurity ions shows the involvement of paramagnetic Pb-2(3+) self-trapped electron centers (STEL) and trapped hole A centers in the electron-hole recombination responsible for the 2.6 eV blue-green luminescence. (C) 2000 Elsevier Science B.V. All rights reserved.

3004. Modeling of a photostimulable complex induced by X-ray irradiation of BaFCl : Eu X-ray storage phosphor

Authors: Secu, M; Matei, L; Serban, T; Apostol, E; Silion, C

Published: MAR 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 63, DOI:

Photostimulated luminescence (PSL) and diffuse reflectance measurements on X-ray irradiated BaFCl:Eu2+ microcrystalline powders were performed. We have investigated the nature of radiation induced defects involved in the photostimulation effect and its recombination mechanism. The experimental data sustain that X-ray irradiation gives rise to (F(Cl-) - O-F(-) - EU2+) photostimulable complexes and we have proposed several geometrical configurations of these complexes. (Received January 27, 2000; accepted February 16, 2000).

3005. Formation of polycrystalline and microcrystalline composite thin films by codeposition and surface chemical reaction

Authors: Barna, PB; Adamik, M; Labar, J; Kover, L; Toth, J; Devenyi, A; Manaila, R

Published: MAR 2000, SURFACE & COATINGS TECHNOLOGY, 125, 150, DOI: 10.1016/S0257-8972(99)00595-2

The formation mechanisms of nanocrystalline composite structures are discussed, and results on co-deposited material system of C-60-Au, C-60-Cu as well as Al-SiOx are presented. Three type of structures are distinguished in the composite films, depending on the concentration of the additive. The decisive structure-forming phenomena are the kinetic segregation of the minority species and the chemical reaction of the deposited components. (C) 2000 Published by Elsevier Science S.A. All rights reserved.

3006. The effect of metal dopants on photodarkening kinetics in amorphous AsSe and As2Se3 thin films

Authors: Iovu, MS; Shutov, SD; Rebeja, SZ; Colomeyco, EP; Popescu, M

Published: OCT 2000, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 181, 537, DOI: 10.1002/1521-396X(200010)181:2<529::AID-PSSA529>3.0.CO;2-D

Photodarkening relaxation under light exposure of a-As2Se3 amorphous films doped with 0.5 at.% of metals Sn, Mn, Sm or Dy and a-AsSe films doped with Sn up to 10.0 at.% Sn was studied in dependence on the impurity and thermal treating. Both factors reduce photodarkening and the degree of reduction depends on the type of impurity. The relaxation process may be described by a stretched exponential with the dispersion parameter 0.4 less than or equal to alpha 1 and time constant increasing with embedding of impurity or thermal annealing. The results are discussed in the frame of the recently forwarded "slip-motion" model of photodarkening in chalcogenide glasses.

3007. Optical absorption of Ag- centres in KCl: line shape calculation

Authors: Zota, S; Enculescu, M

Published: FEB 2000, PHYSICA B, 275, 343, DOI: 10.1016/S0921-4526(99)00762-0

The line shapes of the absorption spectra of KCl: Ag- are calculated at several temperatures in the range 80-300 K and are compared with the experimental results. The complete 12 x 12 Hamiltonian matrix of the system, which includes the linear electron-lattice interaction, was diagonalized directly and the integration has been performed by the Gaussian quadrature method. The results explain most of the characteristic features experimentally observed. (C) 2000 Elsevier Science B.V. All rights reserved.

3008. EPR observation of first point defects in cubic boron nitride crystalline powders

Authors: Nistor, SV; Stefan, M; Schoemaker, D; Dinca, G

Published: 2000, SOLID STATE COMMUNICATIONS, 115, 44, DOI: 10.1016/S0038-1098(00)00135-6

An X-band electron paramagnetic resonance (EPR) study of nominally pure, diamond-like cubic boron nitride (c-BN) crystalline powders, has led to the first identification of a spectrum attributed to two related paramagnetic species. The composite EPR spectrum can be observed only in dark brown colored powders known to contain excess of boron. It consists of two superimposed lorentzian components, called D1 and D2, centered at g1 = 2.0063 and g2 = 2.0084, with peak-to-peak linewidths of 3.3 and 17.9 mT, respectively. The temperature dependence of the integrated intensities, their linewidths and intensity ratio D2/D1 allows one to conclude that the narrow line D1 originates from EPR transitions inside a S = 1/2 ground doublet and the broad line D2 from transitions inside the excited levels of another center. Evidence suggests that both centers are boron related paramagnetic species. (C) 2000 Elsevier Science Ltd. All rights reserved.

3009. Size distribution and optical properties of self-assembled Ge on Si

Authors: Vescan, L; Goryll, M; Stoica, T; Gartner, P; Grimm, K; Chretien, O; Mateeva, E; Dieker, C; Hollander, B

Published: OCT 2000, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 71, 432, DOI: 10.1007/s003390000555

The distribution of Ge islands is analysed in order to understand their optical behaviour. The Ce islands described in this paper were deposited by low-pressure chemical vapour deposition at relatively high temperature (700 degrees C), therefore the diffusion length of adatoms is high (similar to 100 mu m) and thus, not the limiting factor for nucleation. By changing the deposition time and the coverage, square-based pyramids, domes and relaxed domes are nucleated. Mainly domes emit light, the emission being in the wavelength range 1.38-1.55 mu m. When pyramids or relaxed domes are present, the photoluminescence broadens and decreases in intensity. The electroluminescence of vertically correlated islands increases with the number of layers, i.e. with the number of islands. The nucleation of islands on patterned (001) Si is changed when the deposition is performed on Si mesas with high index facets. The size distribution becomes narrower when the mesa size is decreased. An intermixing of up Bo 40% Si in the 2D layer was determined from photoluminescence data. PIN diodes fabricated on patterned wafers show an area-dependent electroluminecence related to a different microstructure of islands on large and small mesas. Finally, the lateral ordering on {hkl} facets is discussed.

3010. Crystal and molecular structure of complex compound [Fe3O(CH3COO)(6)(H2O)(3)](2)[ZnCl4]center dot 2H(2)O

Authors: Shova, SG; Cadelnic, IG; Gdaniec, M; Simonov, YA; Jovmir, TC; Filoti, G; Bulhac, II; Turta, CI

Published: MAY-JUN 2000, CRYSTALLOGRAPHY REPORTS, 45, 421, DOI:

The X-ray crystal structure of trinuclear iron acetate [Fe3O(CH3COO)(6)(H2O)(3)](2)[ZnCl4]. 2H(2)O was determined. The crystal has a ionic structure. It is monoclinic, a = 25.363(7), b = 14.533(4), c = 15.692(4) Angstrom, beta = 103.11(2)degrees, space group C2/c, and R = 0.0685. The structure of the cationic complex [Fe3O(CH3COO)(6)(H2O)(3)](+) is typical of trinuclear iron(III) compounds containing a mu(3)-O bridge: the iron atoms are situated at the vertices of an almost equilateral triangle with the O atom at the center. Each Fe atom is coordinated by four O atoms of bridging carboxy groups, the mu(3)-bridging O atom, and the water molecule in the trans position to the latter O atom. Mossbauer spectroscopy evidence indicates the high-spin state (S = 5/2) of the iron(III) ions. (C) 2000 MAIK "Nauka/Interperiodica".

3011. The Mossbauer and magnetic resonances investigations of structural phase transitions in K2ZnCl4 crystals

Authors: Constantinescu, S; Grecu, MN

Published: JAN 2000, EUROPEAN PHYSICAL JOURNAL B, 13, 233, DOI: 10.1007/s100510050027

The experimental data carried out by Mossbauer and magnetic resonances investigations of the structural phase transitions in K2ZnCl4 crystals are discussed by a simple electrostatic model, calculating, the lattice contributions to the local electric potential V(r), electric field intensity E(r) a,nd electric field gradient tensor, V-alpha beta(r) and taking into account both the fractional electric point charges and rigid lattice approximations. The validity of the model is proved by a good fit of the computing results and experimental data of quadrupole splitting parameters at K Bites obtained by K-39-NMR methods in high temperature incommensurate phase (similar to Pnam symmetry). The experimental results obtained by Mossbauer and EPR methods in commensurate phase (Pna2(1) symmetry) of iron and copper doped K2ZnCl4 crystals are explained by relaxing the rigid lattice approximation. The insertion of probe ions appear to be done on not-exactly-Zn2+ site.

3012. Electrical properties of nanocrystalline porous silicon

Authors: Ciurea, ML; Iancu, V

Published: 2000, 2000 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, CAS 2000 PROCEEDINGS, 64, DOI: 10.1109/SMICND.2000.890188

Conduction properties as well as trapping phenomena in nanocrystalline porous silicon films are investigated in relation to their microstructure. Theoretical models to describe the phenomena are proposed. The main results presented in this paper are: the two-scale porosity of our porous silicon films, the decisive role of the quantum confinement to the conduction phenomena and the prominent part played by the oxidation on the surface effects.

3013. Symmetry and hyperfine fields in R2Fe17-xVxCy (R=Y, Gd; x=1, 1.5, 2 and y=0,1) intermetallics

Authors: Sorescu, M; Valeanu, M

Published: MAY 1 2000, JOURNAL OF APPLIED PHYSICS, 87, 6727, DOI: 10.1063/1.372821

Magnetic compounds of the type R2Fe17-xVx (R=Y, Gd and x=1, 1.5, 2) were synthesized by arc melting (with or without interstitial carbon) and studied by x-ray diffraction (XRD), Mossbauer spectroscopy, and hysteresis loop measurements. Compounds with the structure Y2Fe17-xVx (x=1, 1.5, 2) were found to be hexagonal, whereas the intermetallics containing carbon introduced by melting and those of the type Gd2Fe17-xVx (x=1, 1.5, 2) were found to be rhombohedral. For each symmetry, the lattice parameters a/c were obtained from the XRD spectra and a considerable expansion of the unit cell volume was observed in the Y2Fe17-xVxC (x=1, 1.5, 2) systems as effect of carbon additions. Room-temperature transmission Mossbauer spectra were analyzed considering the various inequivalent iron sites and yielded the average hyperfine magnetic field. This field was studied as a function of vanadium content x for all classes of compounds under investigation. The maximum hyperfine field values were obtained for the carbides. The hysteresis loops recorded at 4.2 K in an applied field of 1.5 T provided complementary information on the saturation magnetization as a function of vanadium substitution for each group of intermetallics involved. (C) 2000 American Institute of Physics. [S0021-8979(00)24408-3].

3014. Characterization of ITO thin films prepared by spinning deposition starting from a sol-gel process

Authors: Stoica, TF; Stoica, TA; Zaharescu, M; Popescu, M; Sava, F; Popescu-Pogrion, N; Frunza, L

Published: 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 688, DOI:

ITO thin films were deposited by spin coating method starting from indium and tin propoxide in the frame of a sol-gel process. Films with the thickness corresponding to 68 nm for one layer deposition were produced and characterized by X-ray diffraction, transmission electron microscopy and infrared reflection spectroscopy. Low conductivity polycrystalline films exhibiting cubical structure (bixbyite-type) and good adherence were obtained.

3015. Rapid synthesis of polycrystalline CuGa1-xInxTe2 compounds

Authors: Gaburici, D; Lazarescu, MF; Manea, A; Sandu, V

Published: 2000, CRYSTAL RESEARCH AND TECHNOLOGY, 35, 270, DOI: 10.1002/1521-4079(200003)35:3<265::AID-CRAT265>3.0.CO;2-9

A series of CuGa1-xInxTe2 bulk quatemary compounds (x=0.17, 0.33, 0.50, 0.67, 0.83) has been synthesized from the corresponding stoichiometric melts by a rapid cooling procedure. The same procedure was used to obtain the ternary bulk compounds CuGaTe2 and CuInTe2 with the aim to compare, according the Vegard law, the match between molar fraction of the indium (x) and the lattice parameters for the aforementioned quatemary compounds. The nature of the crystalline phases, the local structure homogeneity and stoichiometry of these compounds have been investigated by x-ray diffraction (XRD) and scanning electron microscopy (SERI) techniques. The analysis revealed the presence of the chalcopyritic structure for all the samples.

3016. Trapping levels in nanocrystalline porous silicon

Authors: Ciurea, ML; Draghici, M; Lazanu, S; Iancu, V; Nassiopoulou, A; Ioannou, V; Tsakiri, V

Published: MAY 22 2000, APPLIED PHYSICS LETTERS, 76, 3069, DOI: 10.1063/1.126581

Trapping levels in fresh (one month) and naturally aged (one year) nanocrystalline porous silicon have been investigated using the optical charging spectroscopy method. Four significant maxima and/or shoulders were observed for fresh samples and five for aged ones. They have been attributed to five and six trapping levels, respectively. The trapping centers corresponding to the most shallow four levels are situated at or nearby the internal surface of the porous silicon films. (C) 2000 American Institute of Physics. [S0003-6951(00)01621-1].

3017. Fish-tail effect and its evolution under neutron irradiation in Li-doped YBa2Cu3O7-x

Authors: Sandu, V; Oussena, M; de Groot, PAJ

Published: AUG 2000, JOURNAL OF SUPERCONDUCTIVITY, 13, 528, DOI: 10.1023/A:1007860431003

The evolution of the critical current density of Li-doped YBa2Cu3O7-x polycrystalline samples submitted to neutron irradiation is investigated as function of magnetic field (0 less than or equal to B less than or equal to 6 T) temperature (5 less than or equal to T less than or equal to 85 K) and neutron fluence (0 less than or equal to Phi less than or equal to 9.98 x 10(17) cm(-2)). At fluences lower than 10(17) cm(-2), a second peak in j(s) vs. B dependence is present (fish-tail effect). Its magnitude decreases with increasing the fluence. Above 10(17) cm(-2), the second peak of current density completely disappears; instead, the logarithmic susceptibility shows a second peak at a certain field B-infi. A dependence of B-infi on fluence is proposed.

3018. Thermal annealing effects in pure and copper doped Na2O.4B(2)O(3) glass

Authors: Popescu, MA; Leonovici, MR; Ioanid, A; Iova, F

Published: OCT 2000, PHYSICS AND CHEMISTRY OF GLASSES, 41, 316, DOI:

Sodium borate (Na2O.4B(2)O(3)) and copper doped glasses were investigated with respect to the effects of thermal annealing below the softening temperature. X-ray diffraction, optical spectroscopy and electron spin resonance methods were used. Annealing of the glass network results in a partial healing of the structural defects and a redistribution of the borate structural units, so that copper atoms situated in tetrahedral coordination in as-quenched samples adopt a distorted octahedral configuration after annealing.

3019. X-ray diffraction analysis of thermal relaxation and exchanges induced by ultraviolet rays in thin amorphous films of Ge-As-Se chalcogenides

Authors: Popescu, M

Published: SEP 2000, JOURNAL DE PHYSIQUE IV, 10, 20, DOI: 10.1051/jp4:20001002

Thermal relaxation and the relaxation induced by UV radiation in thin amorphous films of composition Ge(x)As(40.x)Se(60) (0 less than or equal to x less than or equal to 40) have been investigated by diffraction de rayons X. The structural results allowed to suggest the models for the atomic scale transformations.

3020. Influence of the sintering time and pressing force of the pellets on the morphology of the superconducting phases in BSCCO system

Authors: Bunescu, MC; Aldica, G; Vasiliu, F; Nita, P; Vasile, E

Published: AUG 2000, JOURNAL OF MATERIALS SCIENCE, 35, 4205, DOI: 10.1023/A:1004879514314

The influence of the sintering time and pressing force on the pellets on the occurrence and morphology of the superconducting phases in BSCCO system were studied. Scanning electron microscopy, X-ray microanalysis and X-ray diffraction were used to identify the phases and their morphologies. The 2223 crystals had a plate-like morphology and 2212, a polyhedral-like one. The optimum parameters in order to obtain a majority of 2223 phase were identified: i.e. a longer sintering time and medium pressing force. (C) 2000 Kluwer Academic Publishers.

3021. Effect of metal additives on photodarkening kinetics in amorphous As2Se3 films

Authors: Iovu, M; Shutov, S; Rebeja, S; Colomeyco, E; Popescu, M

Published: MAR 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 58, DOI:

Photodarkening relaxation under light exposure of a-As2Se3 amorphous films doped with 0.5 at.% tin, manganese, samarium and dysposium, separately introduced, was studied in dependence on the impurity type and thermal annealing. Both factors reduce photodarkening and the degree of reduction depends on the type of impurity. The relaxation process may be described by a stretched exponential with the dispersive parameter 0.5<alpha<l and time constant increasing by thermal annealing. The results are discussed in the frame of recently proposed "slip-motion" model of photodarkening in chalcogenide glasses. (Received February 11, 2000; accepted February 29, 2000).

3022. Oxidation-induced modifications of trap parameters in nanocrystalline porous silicon

Authors: Draghici, M; Miu, M; Iancu, V; Nassiopoulou, A; Kleps, I; Angelescu, A; Ciurea, ML

Published: NOV 2000, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 182, 243, DOI: 10.1002/1521-396X(200011)182:1<239::AID-PSSA239>3.0.CO;2-K

The changes produced by anodic and natural oxidation upon the trap parameters in nanocrystalline porous silicon were compared. To put them in evidence, we used optical charging spectroscopy The same trapping It levels (with the same activation energies) were observed after both oxidation processes. In comparison with flesh samples, a new trapping level (the deepest one) appears and the concentrations of the surface traps strongly diminish.

3023. Synthesis of PLSnZT ceramics with large displacement constants via a sol-gel colloidal process

Authors: Piticescu, RM; Meghea, A; Popescu, M

Published: 2000, INTERNATIONAL JOURNAL OF MATERIALS & PRODUCT TECHNOLOGY, 15, 269, DOI:

The PLSnZT powders were obtained from soluble peroxide precursors of Ti(IV) and Zr(IV) by precipitation with lead nitrate, lanthanum nitrate and tin chloride solutions. The precipitation of Pb(II), Ti(IV) and Zr(IV) from solution in pseudobinar systems was studied as a function of pH and temperature. The structural evolution of powders was studied using XRD. The powders were pressed, sintered, coated with silver paste and poled in silicon oil at high voltage. The density, contraction, electrical permitivity epsilon(33) and displacement constants d(31) were determined as a function of composition and thermal treatment temperature. The same values were measured for the material with the same composition obtained in the classical ceramic route by solid state reaction. The density (8.1 g/cm(-3)), relative electrical permitivity (500) and d(31) (16 x 10(-12) m.V-1) obtained by the sol-gel colloidal route at a sintering temperature of 1100 degrees C were 30-40% higher comparing with the same constants in the classical route at a sintering temperature of 1250-1300 degrees C.

3024. Preparation and optical properties of BaFCl : Eu2+ X-ray storage phosphor

Authors: Secu, M; Matei, L; Serban, T; Apostol, E; Aldica, G; Silion, C

Published: NOV 2000, OPTICAL MATERIALS, 15, 122, DOI: 10.1016/S0925-3467(00)00022-7

A new method for the preparation of BaFCl:Eu2+ has been developed. A coprecipitation chemical reaction between BaCl2 and NaF acidified aqueous solution has been used. Doping with Eu2+ was carried out by adding EuF3 during preparation time. A thermal treatment in vacuum similar to those used in the sintering process of supraconductive ceramics was used in order to accomplish the chemical reaction and to improve the homogeneity of europium ion distribution. Finally, a fine powder consisting of microcrystalline, 4-5 mu m grains was obtained. The product has been checked by X-ray diffractometry and characterised by optical methods. Photoluminescence (PL) measurements attest the europium impurification and oxygen contamination during preparation, which has a great importance for the photostimulability properties of the compound. Photostimulated luminescence (PSL) of the X-irradiated samples shows good performance as X-ray storage phosphor. (C) 2000 Elsevier Science B.V. All rights reserved.

3025. C-Ni amorphous multilayers studied by atomic force microscopy

Authors: Ulmeanu, M; Serghei, A; Mihailescu, IN; Budau, P; Enachescu, M

Published: SEP 22 2000, APPLIED SURFACE SCIENCE, 165, 115, DOI: 10.1016/S0169-4332(00)00362-7

Amorphous C-Ni superlattice films designed as normal-incidence reflector for 5 nm have been grown on quartz substrate by magnetron sputter deposition. A new digital signal processor-based atomic force microscope (AFM) system has been involved in investigating the surface topography of the final surface of the multilayer structure as well as the substrate. In the first step, roughness measurements involving AFM-tips with different radius curvature indicate the C-Ni multilayer surface profile as being in the nanometer and sub-nanometer range, representing a high quality ended surface of the reflectors. In the second step, a study of the roughness distribution using power spectral density functions (PSD) calculated from AFM measurements was performed. The analysis of the amplitudes of the PSD spectra for the multilayer and the substrate surface provided the evidence of the optimized deposition parameters. The shape of the PSD curves for multilayer and substrate reveals fractal profiles with the same distribution of the roughness for both of them, attesting the influence of the substrate on the quality of the reflectors. (C) 2000 Elsevier Science B.V. All rights reserved.

3026. SERS spectra of mono and bisphthalocyanine complexes deposited on Ag and Au supports

Authors: Faulques, E; Baibarac, M; Galmiche, L; L'Her, M; Pondaven, A; Baltog, I

Published: 2000, SPECTROSCOPY LETTERS, 33, 631, DOI: 10.1080/00387010009350144

In this letter, we present a study of surface-enhanced Raman spectra of thin layers of phthalocyanine (Pc) complexes deposited on Ag and Au rough surfaces. The materials of this work are MgPc (monophthalocyanine) and the asymmetrical lutetium bisphthalocyanine (tBu)(4)PcLuPcCl8 (Pc'LuPc ") under three oxidation states. Enhancement of specific bands is observed depending on the surface and the oxidation state. SERS signatures of neutral, oxidised and reduced Pc'LuPc " are identified.

3027. Structural and magnetic investigation of nonstoichiometric YFe10V2 and its interstitial carbide prepared by arc-melting

Authors: Plugaru, N; Lazar, DP; Galatanu, A; Morariu, M; Wiesinger, G; Kottar, A; Vasile, E

Published: MAR 14 2000, JOURNAL OF ALLOYS AND COMPOUNDS, 299, 54, DOI: 10.1016/S0925-8388(99)00791-4

A far-from-equilibrium preparation route and using a particular combination of starting materials led us to obtain nonstoichiometric Y(Fe,V)(12) and its interstitial carbide. Structural analysis and EDAX results reveal the formation of the main 1:12 phase with the ThMn12-type structure, with 13-15% vacancies at the 3d metal sites. Insertion of interstitial carbon increases the T-C and magnetization of the 1:12 phase, whereas the unit cell volume remains unchanged. The effects of vacancies and interstitial carbon on the Mossbauer hyperfine fields and isomer shifts are discussed with reference to the calculated quantities. (C) 2000 Elsevier Science S.A. All rights reserved.

3028. Icosahedral Al-Mn phases grown in diffusion-limited conditions

Authors: Popescu, R; Barna, PB; Constantin, M; Devenyi, A; Manaila, R

Published: FEB 1 2000, THIN SOLID FILMS, 360, 51, DOI: 10.1016/S0040-6090(99)01085-8

Sequential deposition of Mn on a polycrystalline Al layer at 523-573 K was found to result in an anomalous icosahedral (i) Al-Mn phase, characterized by alterations of intensity- and linewidth ratios. The anomalies suggest a non-equilibrium atom distribution, related to the limited diffusion of Al through the already-formed layer of i-AlMn. The activation energy of Al diffusion was inferred from X-ray diffraction (XRD) data taken for different deposition temperatures. (C) 2000 Elsevier Science S.A. All rights reserved.

3029. Experimental investigation of the nonlinear optical response in Fe : PVA

Authors: Bulinski, M; Iova, I; Belea, A; Kuncser, V; Filoti, G

Published: JAN 2000, JOURNAL OF MATERIALS SCIENCE LETTERS, 19, 28, DOI: 10.1023/A:1006739412409

3030. Nature and properties of the radical species formed during the radiolysis of some oxianions

Authors: Contineanu, M; Constantinescu, O

Published: NOV 2000, REVISTA DE CHIMIE, 51, 836, DOI:

The paper presents the study of paramagnetic centres formed by gamma -rays irradiation of polycristalline (NHa)(2)SeO4 and (HH4)(2)SeO3 at 77 K and at room temperature. From the e.s.r. spectra and from the behaviour on heating NH3+ radical as well as radicals from selenium: SeO4-, SeO3-, SeO2- were put into evidence. The spin density values on oxygen and selenium orbitals were calculated. A mechanism of formation of these species is suggested.

3031. Direct evidence of spontaneous quantum dot formation in a thick InGaN epilayer

Authors: Nistor, L; Bender, H; Vantomme, A; Wu, MF; Van Landuyt, J; O'Donnell, KP; Martin, R; Jacobs, K; Moerman, I

Published: JUL 24 2000, APPLIED PHYSICS LETTERS, 77, 509, DOI: 10.1063/1.127026

We report a direct observation of quantum dots formed spontaneously in a thick InGaN epilayer by high resolution transmission electron microscopy. Investigation of a (280 nm thick) In0.22Ga0.78N single layer, emitting in the blue/green spectral region, reveals quantum dots with estimated sizes in the range of 1.5-3 nm. Such sizes are in very good agreement with calculations based on the luminescence spectra of this specimen. (C) 2000 American Institute of Physics. [S0003-6951(00)00930-X].

3032. Growth and characterization of low-temperature grown GaN with high Fe doping

Authors: Akinaga, H; Nemeth, S; De Boeck, J; Nistor, L; Bender, H; Borghs, G; Ofuchi, H; Oshima, M

Published: DEC 25 2000, APPLIED PHYSICS LETTERS, 77, 4379, DOI: 10.1063/1.1335547

We succeeded in growing highly Fe-doped GaN films by solid-source molecular beam epitaxy using an electron-cyclotron-resonance microwave nitrogen plasma. The substrate temperature was in the range of 380-520 degreesC. The samples were analyzed by x-ray diffraction and transmission electron microscopy, and showed hexagonal (wurtzite) or cubic (zincblende) structure or a mixture of both phases. The Fe concentration was on the order of 10(19) cm(-3) and extended x-ray absorption fine structure data show that the Fe is substituting the Ga in GaN. The magnetization measurements as a function of temperature reveal ferromagnetic properties below 100 K for the sample grown at the lowest temperature. (C) 2000 American Institute of Physics. [S0003- 6951(01)00601-5].

3033. Studies concerning secondary synthesis processes in [Bi(Pb)](2)[Sr(Ba)](2)Ca(2)Cu(3)Oy freeze dried superconducting ceramic

Authors: Badica, P; Aldica, G; Bunescu, MC; Nemyrovsky, AV

Published: APR 2000, JOURNAL OF MATERIALS SCIENCE LETTERS, 19, 563, DOI: 10.1023/A:1006765825483

3034. Structural comparison between La0.60Y0.07Ca0.33MnO3-delta bulk and pulsed laser deposited thin films

Authors: Teodorescu, VS; Nistor, LC; Valeanu, M; Ghica, C; Sandu, C; Mihailescu, IN; Ristoscu, C; Deville, JP; Werckmann, J

Published: MAR 2000, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 211, 60, DOI: 10.1016/S0304-8853(99)00713-1

This work is a comparative study of the structural and magneto-transport properties of La0.60Y0.07Ca0.33MnO3-delta (LYCMO) as bulk and thin film. The bulk samples were prepared by solid-state reaction between the corresponding metallic oxides mixed in stoichiometric ratios. The thin film was deposited by pulsed laser deposition on an MgO single crystal using an excimer laser. We show that the structure and stoichiometry of the bulk target are perfectly reproduced in the thin film. We measured the magnetoresistive effect on both the LYCMO pellet and the thin film by using the four-probe technique. The maximum of the MR effect is 680% on the polycrystalline thin film in a 2T magnetic field. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

3035. Size distribution and electroluminescence of self-assembled Ge dots

Authors: Vescan, L; Stoica, T; Chretien, O; Goryll, M; Mateeva, E; Muck, A

Published: MAY 15 2000, JOURNAL OF APPLIED PHYSICS, 87, 7282, DOI: 10.1063/1.372980

In this article we study the electroluminescence of p-i-n diode structures with Ge dots consisting of coherent three-dimensional small (pyramids) and larger (dome) islands. The Ge dots are formed through strain-induced islanding. The diode structures, including one layer with Ge dots, were deposited on Si mesas with variable areas in order to study the influence of limited area deposition on self-assembling. It was observed that the reduction of deposited area improves island uniformity. The combined analysis of island distribution and electroluminescence spectra has lead to the conclusion that domes in small diodes have a smaller Si content or are less relaxed than domes in larger diodes. The diodes are found to emit up to room temperature near the optical communication wavelength of 1.3 microns. (C) 2000 American Institute of Physics. [S0021-8979(00)04610-7].

3036. Microparacrystalline model for medium range order in covalent glasses

Authors: Bradaczek, H; Popescu, M

Published: JUN 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 158, DOI:

The medium-range order in covalent glasses was analyzed in the frame of the paracrystalline theory. This theory, earlier applied to lamellar and fibrous structures, finds in the chalcogenide glasses an interesting working case.

3037. The inhibition of the corrosion of Armco iron in HCl solutions in the presence of surfactants of the type of N-alkyl quaternary ammonium salts

Authors: Branzoi, V; Branzoi, F; Baibarac, M

Published: AUG 15 2000, MATERIALS CHEMISTRY AND PHYSICS, 65, 297, DOI: 10.1016/S0254-0584(00)00260-1

The polarization behaviour of Armco iron in aqueous solutions of HCl with and without inhibitors has been studied by the potentiostatic method. At lower overvoltage values, the dissolution process is controlled by activation, while at higher overvoltage values, the dissolution process is controlled by diffusion. The inhibition of this metal corrosion in the aqueous solutions of HCl has been studied using four surfactants. Under the critical micelle concentration (CMC), the inhibition of these four surfactants is negligible. At a concentration higher than the CMC, the inhibiting action of tetradecyl trimethyl ammonium iodide (TTAI), tetradecyl trimethyl ammonium bromide (TTAB), hexadecyl trimethyl ammonium bromide (HTAB) and dodecyl trimethyl ammonium bromide (DTAB) increases rapidly. The process of inhibition was attributed to the formation of adsorbed film on the metal surface, that protects the metal against corrosive agents. Protection efficiency improved when the inhibitor concentration and the length of the alkyl chain were increased. The four quaternary ammonium salts tested were adsorbed on the Armco iron surface according to a Langmuir isotherm. (C) 2000 Elsevier Science S.A. All rights reserved.

3038. Collapse of the magnetic hyperfine structure of barium hexaferrite by mechanochemical activation

Authors: Sorescu, M; Grabias, A; Diamandescu, L; Tarabasanu, D

Published: MAR 2000, JOURNAL OF MATERIALS SYNTHESIS AND PROCESSING, 8, 72, DOI: 10.1023/A:1026565802246

The collapse of the magnetic hyperfine structure of barium hexaferrite as an effect of mechanochemical activation was investigated. The various inequivalent sites and phases present in the milled material were studied by transmission Mossbauer spectroscopy. Barium hexaferrite nanoparticles were obtained after only 2 h of milling time and were found to coexist with iron oxide particles for longer times of exposure to mechanochemical activation. The milled samples were then subjected to thermal annealing, in order to test the reversibility of the collapse of the hyperfine structure. The thermal annealing performed (700 degreesC, 1 h) was partly successful in restoring the magnetic hyperfine structure of milled hexaferrite. Complementary information was obtained using transmission electron microscopy (TEM) and electron diffraction (ED).

3039. Ferroelectric properties of Pb1-3y/2Lay(Zr0.4Ti0.6)O-3 structures with La concentration gradients

Authors: Boerasu, I; Pintilie, L; Kosec, M

Published: OCT 2 2000, APPLIED PHYSICS LETTERS, 77, 2233, DOI: 10.1063/1.1313814

Graded ferroelectric (GF) structures were obtained by successive deposition of Pb1-3y/2Lay(Zr0.4Ti0.6)O-3 films with different La contents on Pt/TiO2Si substrates. The method used for deposition was sol gel. The final structure consists of four layers, starting from the Pt electrode to the top gold electrode: (1) no La; (2) 4% La; (3) 8% La; and (4) 12% La. Ferroelectric properties of the GF structure were investigated, and an anomalous shift of the hysteresis loop along the polarization axis was found. The sense of this shift depends on the initial direction of the ferroelectric polarization. The presence of hysteresis displacement "up" or "down" can be explained if the presence of a built-in charge in the GF structure is admitted. The built-in potential produced by this charge is computed using a simple theoretical model. (C) 2000 American Institute of Physics. [S0003-6951(00)01040-8].

3040. Magnetization and level statistics at the quantum Hall liquid-insulator transition in the lattice model

Authors: Nita, M; Aldea, A; Zittartz, J

Published: DEC 15 2000, PHYSICAL REVIEW B, 62, 15370, DOI: 10.1103/PhysRevB.62.15367

Statistics of level spacing and magnetization are studied for the phase diagram of the integer quantum Hall effect in a two-dimensional finite lattice model with Anderson disorder.

3041. Some annealing effects in proton irradiated silicon detectors

Authors: Pintilie, I; Petris, M; Tivarus, C; Moll, M; Fretwurst, E; Lindstroem, G

Published: 2000, 2000 INTERNATIONAL SEMICONDUCTOR CONFERENCE, VOLS 1 AND 2, CAS 2000 PROCEEDINGS, 262, DOI:

Annealing studies of a proton irradiated Si test diode (1MeV- neutron equivalent fluence is phi (eq) = 1.82x10(13) cm(-2)) were performed. The macroscopic characterization shows that during the annealing experiment the type inversion effect happened. The changes in the microscopic features during the annealing treatment were investigated using Thermally Stimulated Current method.

3042. Radiation damage on p-type silicon detectors

Authors: Pirollo, S; Biggeri, U; Borchi, E; Bruzzi, M; Catacchini, E; Lazanu, S; Li, Z; Sciortino, S

Published: APR 21 1999, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 426, 130, DOI: 10.1016/S0168-9002(98)01480-6

Two sets of p-type silicon thigh resistivity bulk and low resistivity epitaxial) samples and one set of n(+)-p junctions have been irradiated with fast neutrons up to 8 x 10(13) cm(-2). I-V and C-V characteristics as well as Thermally Stimulated Currents (TSC) and Hall Effect (HE) analyses have been performed on the irradiated samples and diodes in view to determine the radiation-induced damage and the change in the electrical properties. A change in the effective carrier concentration and in the leakage current after irradiation similar to the one found for p(+)-n detectors has been observed in p-type diodes. An increase with the fluence of the resistivity and Hall coefficient was measured at room temperature both for the low and high resistivity sets. This evidence has been explained in terms of a two-level model taking into account a linear increase in concentration with the fluence of the main radiation-induced defects observed with TSC, probably related to divacancy and carbon-oxygen complex. (C) 1999 Elsevier Science B.V. All rights reserved.

3043. Design for a focusing high-resolution neutron crystal diffractometer

Authors: Ionita, I; Stoica, AD; Popovici, M; Popa, NC

Published: JUL 21 1999, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 431, 520, DOI: 10.1016/S0168-9002(99)00280-6

A new concept of high-resolution focusing configuration begins to be accepted as an alternative solution to the existing conventional configurations. Among the earliest work performed in this direction is that performed at the Institute for Nuclear Research, Pitesti. These results are presented below. The experimentally determined resolution properties for two focusing configurations obtained at TRIGA reactor Pitesti and at VVRS reactor Bucharest are given in order to be compared with those obtained for the conventional ones. The principles to get focusing in crystal neutron diffractometry are presented. The main characteristics for a focusing instrument are given. (C) 1999 Elsevier Science B.V. All rights reserved.

3044. Jahn-Teller configurations in natural spinels

Authors: Kuncser, V; Russo, U; Graziani, R; Della Giusta, A; Palade, P; Bulinski, M; Filoti, G

Published: DEC 1999, PHYSICS AND CHEMISTRY OF MINERALS, 27, 102, DOI: 10.1007/s002690050245

The local configurations and related hyperfine interactions of the tetrahedrally coordinated Fe2+ in two natural spinels were investigated. A special fitting procedure of the Mossbauer spectra is proposed in order to cover the involved mechanisms over the whole temperature range. The behavior of the quadrupole splitting vs temperature was successfully explained in terms of the split of the electronic 3d ground state doublet under a non-cooperative Jahn-Teller effect also providing estimates of the splitting energy for each configuration.

3045. On the lead determination in alkali halides by spectroscopic method

Authors: Dan, C; Topa, V; Lazarescu, MF

Published: 1999, CRYSTAL RESEARCH AND TECHNOLOGY, 34, 895, DOI: 10.1002/(SICI)1521-4079(199908)34:7<891::AID-CRAT891>3.3.CO;2-B

The octahedral complex [PbX6](4,) (X=Cl, Br) in natrium/potassium chloride or bromide monocrystals as well as in the concentrated solutions of these alkali halides, impurified by lead, shows a characteristic absorption in the region 250-300 nm. Using the height of this absorption band, a quantitative method for determination of lead in the range 8'10(14) - 3.2'10(16) atoms/cm(3) of halide monocrystals or 0.5 20 mg/ml of solutions respectively, was elaborated. Standard graphs of the peak extinction of [PbX6](4) in natrium/potassium chloride and bromide as function of the lead concentration have been obtained.

3046. ESR of paramagnetic atom defects in CVD-grown diamond

Authors: Nistor, SV; Stefan, M; Ralchenko, V; Goovaerts, E; Schoemaker, D

Published: 1999, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 149, 307, DOI: 10.1080/10420159908230172

ESR measurements in the 9 and 94 GHz microwave frequency bands were performed on thick free-standing polycrystalline diamond films grown by microwave plasma enhanced CVD from CH4/H-2 mixtures under variable deposition conditions. An exponential decrease in the concentration of the N-0 centres with increase in the H-2 flow rate was found. Neither H1 nor H2 centres could be detected.

3047. Trap characterization for Bi4Ti3O12 thin films by thermally stimulated currents

Authors: Pintilie, L; Pintilie, I; Petre, D; Botila, T; Alexe, M

Published: JUL 1999, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 69, 109, DOI: 10.1007/s003390050980

Thermally stimulated current (TSC) measurements performed in the 100 K-400 K temperature range on Bi4Ti3O12 (BiT) thin films annealed at 550 degrees C and 700 degrees C had revealed two trapping levels having activation energies of 0.55 eV and 0.6 eV. The total trap concentration was estimated at 10(15) cm(-3) for the samples annealed at 550 degrees C and 3 x 10(15) cm(-3) for a 700 degrees C annealing and the trap capture cross-section was estimated about 10(-18) cm(2). From the temperature dependence of the dark current in the temperature range 20 degrees C-120 degrees C the conduction mechanism activation energy was found to be about 0.956-0.978 eV. The electrical conductivity depends not only on the sample annealing temperature but also whether the measurement is performed in vacuum or air. The results on the dark conductivity are discussed considering the influence of oxygen atoms and oxygen vacancies.

3048. Electric field properties at cationic sites in normal, incommensurate and commensurate K2ZnCl4 crystals

Authors: Grecu, MN; Constantinescu, S

Published: 1999, APPLIED MAGNETIC RESONANCE, 16, 382, DOI: 10.1007/BF03161925

The local electric properties at K and Zn sites in the normal, incommensurate and commensurate phases of K2ZnCl4, as derived from a numerical computation of the lattice contributions to the electric potential V(r), electric field intensity E(r) and electric field gradient tensor V-alpha beta(r) are reported. The numerical data obtained at each cationic position were correlated with the experimental K-39 NMR, Cu2+ and Mn2+ EPR and Fe-57 Mossbauer results in pure and doped K2ZnCl4. A proportionality between crystal field and zero-field splitting was taken into account for Mn2+, whereas for K+, Cu2+ and Fe3+ ions the electric field gradient is directly related to the crystal field parameter. By this comparison, on computations done in the ionic fractional charge and relaxed lattice approximations, the insertion of probe-species of iron, copper and manganese ions on off-center Zn sites is proposed. The K-39 electric field gradient tensor calculations in the incommensurate phase fit well with the NMR data reported recently.

3049. ESR of trapped-electron Fe+ centres in chlorinated SrCl2 crystals

Authors: Nistor, SV; Stefan, M; Bouwen, A; Schoemaker, D

Published: 1999, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 149, 207, DOI: 10.1080/10420159908230156

Two Fe+ centres have been identified by ESR after X-ray irradiation at 80 K of chlorinated SrCl2 : Fe2+ crystals. Both centres, with tetragonal symmetry, consist of an Fe+ ion with a neighbouring charged defect along the [001] symmetry axis. The substitutional Fe+ ion of the Fe+(I) centre is strongly off-centre displaced in the Fe+(II) centres, in the middle of a square of four nearest neighbour chlorine ligands.

3050. Defects in non-crystalline materials

Authors: Popescu, M; Bradaczek, H

Published: MAR 1999, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 1, 16, DOI:

3051. XTEM study of Al doped TiO2 anatase epitaxial films deposited on MgO by pulsed laser deposition

Authors: Teodorescu, VS; Blanchin, MG; Garapon, C; Champeaux, C

Published: NOV 1999, JOURNAL OF MATERIALS SCIENCE, 34, 5476, DOI: 10.1023/A:1004796008417

Al doped TiO2 anatase films epitaxially grown by Pulsed Laser Deposition (PLD) on MgO single crystal substrates have been studied by cross-section transmission electron microscopy. The main structural features of such films are the columnar morphology of the anatase grains and the formation of a spinel buffer layer at the TiO2/MgO interface. The spinel layer is Al rich and displays a steep gradient in Mg composition. Correlation between the microstructure and the optical properties of the films is presented also. (C) 1999 Kluwer Academic Publishers.

3052. Orientational transitions in nematic liquid crystals on substrates with controlled topography

Authors: Moldovan, R; Beica, T; Frunza, S; Tintaru, M

Published: 1999, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 329, 661, DOI:

Orientational transitions induced by temperature variation, in cells with nematic liquid crystal having limiting substrates with controlled topography, are presented. The variable topography was obtained by SiOx deposition in vacuum at an incidence angle around 85 degrees, or by depositions of polyvinyl alcohol (PVA) with different thicknesses, on glasses with the same SiOx deposition. The experimental results are explained by a phenomenological model based on the Landau-de Gennes free energy expansion, taking into account the anisotropy of the substrate.

3053. Transmission electron microscopy study of thin films and surface implanted wafers of LiNbO3

Authors: Teodorescu, VS; Ghica, C; Blanchin, MG; Moretti, P

Published: JUN 1999, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 1, 48, DOI:

Thin films prepared by pulsed laser deposition and single crystal implanted LiNbO3 wafers used in optoelectronic technology were studied by transmission electron microscopy. The use of high electron beam density for high resolution imaging induced a decomposition effect in the implanted LiNbO3 lattice. It is shown that the most probable decomposition leads to the formation of NbO2 nuclei by a topotactic solid state reaction along the pseudo-cubic directions of the lithium niobate matrix. It is also shown that powdered LiNbO3 specimens or samples obtained by preparation of cross section of LiNbO3 thin films are more stable in the electron beam, compared with the samples obtained from implanted LiNbO3 wafers.

3054. Spectroscopical study of amorphous AsSe : Sn films

Authors: Iovu, MS; Syrbu, NN; Shutov, SD; Vasiliev, IA; Rebeja, S; Colomeico, E; Popescu, M; Sava, F

Published: OCT 16 1999, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 175, 622, DOI: 10.1002/(SICI)1521-396X(199910)175:2<615::AID-PSSA615>3.0.CO;2-N

The effect of tin impurities on optical spectra of thermally deposited AsSe films doped with Sn (1 to 10 at%) was studied in a wide energy interval from 0.8 to 6.2 eV by combination of reflection, absorption, photoresponse and photocapacitance spectroscopies. Most changes have been detected at the fundamental absorption edge over which a correlation between the band tail width and optical gap is demonstrated for various tin concentrations. The tin induced absorption band associated with a localized energy level at about 1.6 eV in the gap was revealed. Distinct variations in the reflectivity spectra of the fundamental absorption region suggest a tin assistance in the formation of the valence band states of the material.

3055. Interfacial chemical effect evidenced on SERS spectra of polyaniline thin films deposited on rough metallic supports

Authors: Baibarac, M; Mihut, L; Louarn, G; Mevellec, JY; Wery, J; Lefrant, S; Baltog, I

Published: DEC 1999, JOURNAL OF RAMAN SPECTROSCOPY, 30, 1113, DOI: 10.1002/(SICI)1097-4555(199912)30:12<1105::AID-JRS507>3.0.CO;2-3

Surface-enhanced Raman scattering (SERS) has proved to be an effective technique for studying the structural properties of conducting polymer thin films. The enhancement process has a twofold origin, electromagnetic and chemical, The electromagnetic enhancement, which is the dominant mechanism in SERS generation, consists in the excitation of localized and delocalized surface plasmons (SPs) in the metallic support of the thin film, The Raman emission of the adsorbed molecules on the metal surface (the most efficient being Ag, Au and Cu) is due to the intense evanescent electromagnetic field located at the interface between the metal and the surrounding medium. The second enhancing mechanism for SERS is of chemical origin, involving the formation of new chemical bonds between the molecules and the metal surface, with the polarizability thus becoming considerably higher than that of the free molecules. This mechanism is as a rule accompanied by a metal-molecule or molecule-metal charge transfer, which partly accounts for the success of the SERS studies on conducting polymers. Unfortunately, these studies have revealed that the chemical effects at the polymer-metal interface varied substantially depending on the various types of polymer and metallic support. In this context, polyaniline containing two different entities (a reduced and an oxidized state) in its repeating units exhibits specific alterations in its SERS spectra depending on the type of metallic support. This paper presents new results concerning the structure of emeraldine-base and emeraldine-salt polyaniline thin films deposited on rough Ag and Au supports. The effect on the SERS spectra of the polymer-metal and polymer-ambient interface chemical reactions is also described. The presence of an interface compound depending on the oxidizing properties of the metallic support has a strong influence on the SERS spectra, no matter how the PAN films were deposited on the support (whether by solvent evaporation or by an electrochemical process, i.e. cyclic voltammetry). When an emeraldine base is doped with HSO4- ions, it turns into an emeraldine salt, which exhibits a disordered state in its macromolecular chain, leading to a modified profile of the similar to 1162 cm(-1) Raman line which is associated with the C-H bond of the quinoid ring. The Lorentzian profile is altered by the addition of a Gaussian profile component. For a rough Ag support, the SERS spectra show that the transformation of emeraldine base films into emeraldine salt films is a reversible process, Copyright (C) 1999 John Wiley & Sons, Ltd.

3056. Silver nanocrystals obtained by the ionization of Ag--ions in KCl

Authors: Vasile, E; Datcu, M; Polosan, S; Apostol, E; Topa, V

Published: MAR 1999, JOURNAL OF CRYSTAL GROWTH, 198, 810, DOI: 10.1016/S0022-0248(98)01112-9

This paper discusses the formation of "corals" arranged silver nanocrystals in a KCl matrix starting from Ag- ions ( similar to 10(17) ions/cm(3)) by subsequent thermal annealing at temperatures between 400-700 degrees C and 250 degrees C. In the last case only, by illumination with total radiation of a 100W Xe-lamp, spherical separated silver clusters were obtained. The stepwise annealing processes were followed by the recording of the optical absorption spectra at 20 degrees C. The sizes of silver clusters were determined through transmission electron microscopy. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

3057. Influence of He, Ne and Kr addition in reactive Ar/N-2 dc magnetron plasma on TiN deposition

Authors: Braic, M; Zoita, CN; Braic, V; Kiss, A; Popescu, M; Musa, G

Published: MAY 1999, VACUUM, 53, 45, DOI: 10.1016/S0042-207X(98)00419-9

A reactive DC magnetron discharge produced in a TIN deposition system was investigated using optical emission spectroscopy. The influence of He, Ne and Kr addition into an Ar + N-2 working atmosphere was investigated. Addition of small percentages of He or Ne in the working atmosphere of Ar + N-2, caused a decrease of the N-2(+) (B)/N-2(C) ratio, whle with Kr addition the ratio increased. The known decrease of the relative intensity of Ti lines for N-2 addition was also observed for He addition, while it increases when Ne and Kr are added. XRD analysis of TiN thin films revealed that He addition determines the same effect as N-2. This behavior is explained by N and N+ density increase for He addition. (C) 1999 Elsevier Science Ltd. All rights reserved.

3058. Low-loss low-confinement GaAs-AlGaAs DQW laser diode with optical trap layer for high-power operation

Authors: Buda, M; van der Vleuten, WC; Iordache, G; Acket, GA; van de Roer, TG; van Es, CM; van Roy, BH; Smalbrugge, E

Published: FEB 1999, IEEE PHOTONICS TECHNOLOGY LETTERS, 11, 163, DOI: 10.1109/68.740690

A low-confinement asymmetric GaAs-AlGaAs double-quantum-well molecular-beam-epitaxy grown laser diode structure with optical trap layer is characterized. The value of the internal absorption coefficient is as low as 1.4 cm(-1), while keeping the series resistance at values comparable with symmetrical quantum-well gradient index structures in the same material system. Uncoated devices show COD values of 35 mW/mu m. If coated, this should scale to about 90 mW/mu m, The threshold current density is about 1000 A/cm(2) for 2-mm-long devices and a considerable part of it is probably due to recombination in the optical trap layer. Fundamental mode operation is limited to 120-180 mW for 6.5-mu m-wide ridge waveguide uncoated devices and to 200-300 mW for 13.5-mu m-wide ones, because of thermal waveguiding effects, These values are measured under pulsed conditions, 10 mu s/l ms.

3059. An XPS and XRD study of physical and chemical homogeneity of Pb(Zr,Ti)O-3 thin films obtained by pulsed laser deposition

Authors: Verardi, P; Craciun, F; Mirenghi, L; Dinescu, M; Sandu, V

Published: JAN 1999, APPLIED SURFACE SCIENCE, 138, 556, DOI: 10.1016/S0169-4332(98)00577-7

Pb(Zr,Ti)O-3 (PZT) oriented films deposited by laser ablation on Bu(lll)/Si(lll) have been tested by different techniques for their physico-chemical homogeneity. The samples have been divided in different zones, in order to verify the existence of chemical and structural differences between different regions. Few techniques like X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been employed for characterization. XRD analyses showed differences regarding the crystallographic content and the degree of orientation between zones subjected to the plasma arriving at different angles of incidence on the sample surface. In the same zones XPS studies have been performed by a VG ESCALAB 210 Spectrometer, using a non-monochromatic AlKalpha X-ray source (300 W) in the five channel hemispherical analyzer. Wide scans in the binding energy scale 0-1200 eV, at 50 eV analyzer pass energy, were collected both from the as received surface and after sputter cleaning in order to put into evidence all the constituents of the film. Narrow scans of Ti 2p, Zr 3d, Pb 4f and O 1s is were also acquired at 20 eV and 0.1 eV/channel pass energy and 100 ms of dwell time in order to give a better insight into the chemical bonds form and a semiquantitative analyze of the present chemical species. The piezoelectric properties of different zones were also measured, (C) 1999 Published by Elsevier Science B.V. All rights reserved.

3060. Fe-57 Mossbauer study of Pr-m(Fe, MO)(n) compounds with m : n=2 : 17 and 1 : 12

Authors: Morariu, M; Lazar, DP; Galatanu, A; Plugaru, N; Kuncser, V; Filoti, G; Hilscher, G; Kottar, A

Published: MAR 30 1999, JOURNAL OF ALLOYS AND COMPOUNDS, 285, 47, DOI: 10.1016/S0925-8388(98)01055-X

The effects of Mo substitution in Pr2Fe17-xMox and PrFe12-xMox compounds were investigated by X-ray diffraction, magnetic measurements and Mossbauer spectroscopy. Different fitting procedures, using magnetic sextets at low temperature, magnetic sextets and quadrupole doublets at room temperature and paramagnetic doublets well above the Curie points, had to be considered in order to analyze the Mossbauer spectra. The Mossbauer data obtained on the Mo-containing compounds stand for distributions of the hyperfine fields due to the random distributions of Mo over the 6c sites in the 2:17 and 8i sites in the 1:12 compounds. The variations in the isomer shifts and hyperfine fields with composition are discussed in relationship to the local environment details at the different iron sites. Site-specific information on the electronic effects due to Fe(Sd)-Mo(4d) states hybridization are derived. (C) 1999 Elsevier Science S.A. All rights reserved.

3061. Characterization of perchlorate or sulphate doped polyaniline films by electrochemical impedance spectroscopy

Authors: Visan, T; Sima, M; Buda, M; Marin, G

Published: MAY 1999, REVUE ROUMAINE DE CHIMIE, 44, 517, DOI:

Cyclic voltammetry and impedance spectroscopy were used for study of polyaniline in acid solutions. Impedance spectra were presented both as Bode diagrams and Nyquist representations. The capacitive charging behaviour and anion (ClO4-, HSO4-) insertion/elimination reaction of the polymer film were discussed on the basis of a simplified Randles circuit model. The examined scanning electron micrographs have also shown that the nature of dopant anion changes the film morphology.

3062. Effective elastic moduli of a composite containing rigid spheres at nondilute concentrations: A multiple scattering approach

Authors: Mondescu, RP; Muthukumar, M

Published: JAN 8 1999, JOURNAL OF CHEMICAL PHYSICS, 110, 1137, DOI: 10.1063/1.478186

Based on the multiple scattering technique [K. F. Freed and M. Muthukumar, J. Chem. Phys. 69, 2657 (1978); 68, 2088 (1978); M. Muthukumar and K. H. Freed, J. Chem. Phys. 70, 5875 (1979)] previously applied to the study of suspensions of spheres and polymers, we propose an approach to the computation of the effective elastic properties of a composite material containing rigid, mono-sized, randomly dispersed, spherical particles. Our method incorporates the many-body, long-range elastic interactions among inclusions. The effective medium equations are constructed and numerically solved self-consistently. We have calculated the effective shear mu' and Young E' moduli, as well as the effective Poisson ratio sigma', as functions of the particle volume fraction Phi and of the Poisson ratio a of the continuous phase. Comparisons with two sets of experimental data-glass beads in a polymer matrix and tungsten carbide particles in a cobalt matrix (Wc/Co)-and to a previous theoretical solution, are also presented. Our model can predict the effective Poisson ratio of the Wc/Co system for Phi less than or equal to 1 and for the glass/polymer system for Phi less than or equal to 0.5. In particular, the present work describes accurately composites with a high volume fraction of inclusions, where a percolation transition occurs. Very good agreement with the experimental data are obtained for E' and mu' when Phi less than or equal to 0.4, for both systems. (C) 1999 American Institute of Physics. [S0021-9606(98)50148-1].

3063. ESR of paramagnetic Tl2+-type centres in Rb2ZnCl4 crystals

Authors: Stefan, M; Nistor, SV; Schoemaker, D

Published: 1999, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 150, 368, DOI: 10.1080/10420159908226258

Tl2+(6s(1))-type of paramagnetic centres, produced by low temperature X-ray irradiation, were observed in the low temperature ferroelectric phases of Rb2ZnCl4 : TICl crystals. The difference between the spin-Hamiltonian parameters of the main centre, determined in the two phases, is attributed to the symmetry lowering at phase transition.

3064. Structure, IR and Mossbauer spectra, and magnetic properties of [Fe2CoO(CH3COO)(6)(3-Cl-Py)(3)]center dot 1/4 3-Cl-Py center dot 1/4(CH3)(2)CO center dot 1/2H(2)O

Authors: Jovmir, TC; Turta, CI; Shova, SG; Simonov, YA; Gdaniec, M; Bulgac, II; Cadelnic, IG; Filoti, G

Published: NOV-DEC 1999, JOURNAL OF STRUCTURAL CHEMISTRY, 40, 913, DOI: 10.1007/BF02700699

The structure of the heteronuclear iron acetate [Fe2CoO(CH3COO)(6)(3-Cl-Py)(3)]. 1/4 . 3-Cl-PyX1/4(CH3)(2)CO . 1/2H(2)O was determined by X-ray structure analysis. The crystal has a molecular structure and is monoclinic with lattice parameters a = 21.034(4), b = 8.398(2), c = 23.360 Angstrom, beta = 98.28(3)degrees, R = 0.0656, space group P2(1)/c. The trinuclear complex [Fe2CoO(CH3COO)(6)(H2O)(3)] has a structure typical for iron(III) mu(3)-O compounds with iron atoms lying at the vertices of the equilateral triangle centered by an oxygen atom. The metal atoms are each coordinated to four oxygen atoms of the four bridging carboxy groups, the bridging oxygen atom (mu(3)-O), and the coordinated 3-chloropyridine molecule which is trans relative to the latter atom. According to Mossbauer spectroscopy data, the iron(III) ions are in the high-spin state. The value of (mu(ef))(mole)/mu(3) at room temperature and its temperature dependence suggest that the resulting magnetic exchange interaction between the paramagnetic centers of the cluster is antiferromagnetic.

3065. FT-IR investigation of organic discharge in polluted water II. Monitoring of cyclohexylamine and morpholine

Authors: Jelev, A; Ciobanu, MF; Frunza, L

Published: 1999, CHEMICAL PAPERS-CHEMICKE ZVESTI, 53, 101, DOI:

Aliquots of waste water from power stations were analyzed by a FT-IR spectroscopic procedure and showed both qualitatively and quantitatively the presence of cyclohexylamine and morpholine. The detection limit and the sensitivity of the method were investigated and the validity of the Lambert-Beer law was checked. To maintain the selectivity of the method the pH must be maintained around 6.

3066. Multilayer structures deposited by laser ablation

Authors: Dinescu, M; Stanciu, C; Ghica, D; Dinu, R; Sandu, V; Nastase, N; Balucani, M; Bondarenko, V; Frachina, L; Lamedica, G; Ferrari, A

Published: APR 20 1999, SENSORS AND ACTUATORS A-PHYSICAL, 74, 30, DOI: 10.1016/S0924-4247(98)00331-8

TiN/Si structures were deposited on Si wafers by pulsed laser deposition technique. The highly conductive TiN films were grown on heated (100) Si substrates by laser ablation of a high purity Ti target in nitrogen reactive atmosphere. Subsequently, the Si layer was deposited by laser ablation of a Si target in vacuum (down to 10(-6) mbar) or in low pressure inert gas. The nitrogen gas pressure and the substrate temperature were found to strongly influence the TiN film structure and orientation. The degree of crystallinity of the Si layer grown on the TiN film was found to depend on Si/TiN collector temperature. Values below 550 degrees C (the threshold of TiN oxidation activation) were used in the experiments. Techniques as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), High Resolution Transmission Electron Microscopy (HRTEM), Scanning Force Microscopy (SFM) have been used to characterize the deposited structures. The TiN/Si structure rectifying properties were tested. The obtained Si/TiN/Si structure could be suitable for the building of Permeable Base Transistor (PBT, vertical MESFET) devices. (C) 1999 Elsevier Science S.A. All rights reserved.

3067. Hall effect analysis in irradiated silicon samples with different resistivities

Authors: Borchi, E; Bruzzi, M; Dezillie, B; Lazanu, S; Li, Z; Pirollo, S

Published: AUG 1999, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 46, 838, DOI: 10.1109/23.790687

The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 Omega-cm up to 30 K Omega-cm, grown, using different techniques, as Float-Zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolves toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects. A deep acceptor and a deep donor,probably related to the divacancy and to the CiOi complex, are placed in the upper and lower half of the forbidden gap, respectively. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of approximate to 10(14) n/cm(2).

3068. Photoconductive properties of Bi4Ti3O12/Si heterostructures with different thickness of the Bi4Ti3O12 film

Authors: Pintilie, L; Pintilie, I; Alexe, M

Published: 1999, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 19, 1476, DOI: 10.1016/S0955-2219(98)00455-5

Ferroelectric Bi4Ti3O12 (BiT) thin films of different thicknesses were deposited on p-type Si substrates using the Chemical Solution Deposition (CSD) method. The films were crystallized by the conventional thermal annealing for 30 min at temperatures in the 500-700 degrees C range. It was found that the shape of the photoconductive signal spectral distribution is dependent on the film thickness. For thin films (150 nm) four peaks were observed (400, 500, 860 and 1075 nm) and the photoconductive signal occurs only if the Si substrate is negatively biased. For thicker films (500 nm) only two peaks were observed (370 and 1075 nm) and the photoconductive signal occurs no matter the polarity of the applied voltage. (C) 1999 Elsevier Science Limited. All rights reserved.

3069. Growth of metal structures in quartz crystals by electrodiffusion

Authors: Iliescu, B; Enculescu, I; Vasiliu, F; Secu, M

Published: MAR 1999, JOURNAL OF CRYSTAL GROWTH, 198, 510, DOI: 10.1016/S0022-0248(98)01039-2

Metal structures in quartz crystals were obtained by electrodiffusion in air with different metal sources at the anode. The dynamics and the properties of these structures, for different conditions of temperature, applied electric field and anode material were studied. Current-voltage characteristics, Arrhenius plot, optical microscopy, electronic microscopy and thermoluminescence glow curve were employed. (C) 1999 Elsevier Science B.V. All rights reserved.

3070. Colloidal sol-gel ITO films on tube grown silicon

Authors: Stoica, TF; Stoica, TA; Vanca, V; Lakatos, E; Zaharescu, M

Published: JUL 6 1999, THIN SOLID FILMS, 348, 278, DOI: 10.1016/S0040-6090(99)00136-4

Electrical and optical properties of colloidal PTO sol-gel films on glass substrates have been investigated. The optical gap of 3.14 eV and room temperature conductivity of 4 Ohm(-1) cm(-1) were obtained on ITO layers of about 500 Angstrom thickness. Heterostructures of ITO/n-Si have been obtained by colloidal sol-gel deposition of ITO. In this deposition method, the oxidation of silicon during the heterostructure formation can be avoided. The silicon substrates were cut out of silicon tubes. Electrical and photoelectric properties of these structures have been studied in comparison with those of p-n tube-Si junctions obtained by thermal boron diffusion. On ITO/n-Si heterojunctions, the spectral quantum efficiency has a maximum value of about two times higher and a blue shift of the maximum position from 0.75 to 0.6 mu m, than those for p-n junctions. A theoretical investigation of the I-V curves for ITO/n-Si heterojunctions under various illumination levels has been performed and contribution of the tunneling and series resistance phenomena were evaluated. (C) 1999 Elsevier Science S.A. All rights reserved.

3071. Studies by SERS spectroscopy of the structural properties of conducting polymers and carbon nanotubes

Authors: Lefrant, S; Baltog, I; de la Chapelle, ML; Baibarac, M; Louarn, G; Journet, C; Bernier, P

Published: MAY 1999, SYNTHETIC METALS, 101, 187, DOI: 10.1016/S0379-6779(98)00307-5

After being dispersed in liquid solvents (Ethanol, CHCl3), conducting polymers and singlewalled nanotubes have been deposited on ruguous substrats (Au, Ag, Cu). With FT Raman technique (laser excitation : 1064 nm), we have obtained SERS signal of both conductiong polymers and singlewalled nanotubes. The Raman signals change with substrat and/or solvent, which could be correlated with the size of clusters formed at the surface and then to the deposition mechanism. The main advantage of the >SERS technique will be emphasized in terms of enhancement as a powerful technique to study nanoparticles.

3072. Microstructural aspects related to carriers transport properties of nanocrystalline porous silicon films

Authors: Ciurea, ML; Teodorescu, VS; Nistor, LC; Blanchin, MG

Published: SEP 1999, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, 146, 3521, DOI: 10.1149/1.1392507

A microstructural investigation of porous silicon films, related with a study of carriers transport. is presented. Scanning electron microscopy and conventional transmission electron microscopy with selected area electron diffraction were performed. The films show a double scale porosity: the macroporosity forms an alveolar structure at a micrometric scale and the nanoporosity forms a silicon nanowires network in the alveolar walls and at their surface. Current-voltage characteristics in the -5 to +5 V range and the temperature dependence of dark current in the 150-330 K interval at low voltage were measured. The transport properties are explained by means of a simplified quantum confinement model. Two symmetries of the nanowires, cylindrical and square, are investigated and the differences between them are shown to be insignificant. (C) 1999 The Electrochemical Society. S0013-4651(98)12-109-2. All rights reserved.

3073. Growth of pure and doped Rb2ZnCl4 and K2ZnCl4 single crystals by Czochralski technique

Authors: Stefan, M; Nistor, SV; Mateescu, DC; Abakumov, AM

Published: APR 1999, JOURNAL OF CRYSTAL GROWTH, 200, 154, DOI: 10.1016/S0022-0248(98)01247-0

High-quality single crystals of Rb2ZnCl4 and K2ZnCl4, pure or doped with Cu, Mn, Cd, Tl, Sn, Pb and In cations, were grown by Czochralski technique in argon atmosphere, using an experimental setup that allows direct visual access to the whole growth zone. Slowly cooled crystals exhibit excellent cleavage properties. Fastly cooled crystals do cleave poorly. As shown by X-ray diffraction studies, such K2ZnCl4 samples exhibit inclusions of the high-temperature Pmcn phase with lattice parameters a = 7.263(2) Angstrom, b = 12.562(2) Angstrom and c = 8.960(4) Angstrom in the P2(1) cn room temperature stable phase. ESR and optical spectroscopy studies revealed the localization and valence state of the cation dopants. (C) 1999 Elsevier Science B.V. All rights reserved.

3074. Irradiation damage in LiNbO3 crystals studied by transmission electron microscopy

Authors: Teodorescu, VS; Blanchin, MG

Published: 1999, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 150, 184, DOI: 10.1080/10420159908226227

Transmission electron microscopy of Er implanted LiNbO3 crystals reveals a structural modification due to the electron bi am irradiation, which consists of the decomposition of LiNbO3 in niobium oxide nanometric size domains. The corresponding electron diffraction patterns do fit at best with the NbO2 simple tetragonal phase. The orientation of the oxide nuclei is along the pseudo-cubic directions of the lithium niobate.

3075. Structure and properties of As2S3 and As2Se3 glasses modified with Dy, Sm and Mn

Authors: Iovu, M; Shutov, S; Popescu, M; Furniss, D; Kukkonen, L; Seddon, AB

Published: JUN 1999, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 1, 24, DOI:

The effect of low amounts of dysprosium, samarium and manganese (0.1 - 0.5 at.%) on the properties of the chalcogenide glassy semiconductors As2S3 and As2Se3 is investigated The metals have significant influence on the structural, optical, electrical and photoelectric characteristics. The fundamental absorption edge shifts towards longer wavelengths with doping. The largest shift was observed for As2S3 glasses doped with Dy and Mn. The conductivity is significantly increased by addition of Mn and Dy. All the dopants hamper the photoconductivity with the exception of 0.5 at. % Dy in As2Se3 which generates a broad secondary band in the photoconductivity spectrum near 1.05 eV, ascribed to small amounts of crystalline phase. Close correlation was revealed between the medium range order in the network, the metal electronegativity and the activation energy of conductivity.

3076. Pulsed laser deposition of multilayer TiN/Pb(ZrxTi1-x)O-3 for piezoelectric microdevices

Authors: Verardi, P; Dinescu, M; Craciun, F; Dinu, R; Sandu, V; Tapfer, L; Cappello, A

Published: APR 20 1999, SENSORS AND ACTUATORS A-PHYSICAL, 74, 44, DOI: 10.1016/S0924-4247(98)00342-2

Multilayer Pb(ZrTi)O-3 (PZT)/TiN/Si structures were grown by two subsequent laser ablation processes in reactive atmosphere. First, a fee-oriented TiN film was deposited by laser ablation of a Ti target in high-purity nitrogen reactive gas. Subsequently, a crystalline, piezoelectric PZT film was grown by reactive ablation of a PZT target in oxygen atmosphere. Both deposition processes were conducted at quite low Si(100) substrate temperature: 350 degrees C for TiN and 370 degrees C for PZT, in the same experimental setup (Nd-YAG laser, lambda = 1060 nm, energy/pulse 0.3 J, t(FWHM) = 10 ns). TiN film properties were analyzed by XRD and electric measurements. After the deposition of the PZT layer, the obtained structure was first characterized by XRD, SEM and SIMS techniques. Testing measurements performed after the deposition by thermal evaporation of an Al layer as top electrode on the PZT/TiN/Si structure confirm that they can be used as sensor transducer element. The TiN (as high conductive nitride) layer replaces the former Au layer used as bottom electrode. In this way, the Au diffusion inside the Si substrate, as well as in the deposited layer, is avoided, as could be observed from a comparative study of the SIMS spectra recorded for PZT/TiN/Si and PZT/Au/Si configurations. (C) 1999 Elsevier Science S.A. All rights reserved.

3077. Physico-chemical properties and X-ray study of trinuclear carboxylate [Fe3O(CH3COO)(6)(H2O)(3)](2)[PtCl6]center dot 8H(2)O

Authors: Turta, C; Shova, S; Meriacre, V; Cadelnic, I; Gdaniec, M; Simonov, YA; Filoti, G

Published: APR 1999, POLISH JOURNAL OF CHEMISTRY, 73, 618, DOI:

Trinuclear carboxylate compound [Fe3O(CH3COO)(6)(H2O)(3)](2)[PtCl6].8H(2)O has been studied by Mossbauer spectroscopy, magnetochemistry, thermal analysis and X-ray crystallography. Crystal data: monoclinic, space group P2(1)/n a = 10.505(2), b = 14.278(3), c = 19.885(4) Angstrom, beta = 96.00(3)degrees and Z = 2. The final R-value is 0.027 for 4606 reflections with I greater than or equal to 2 sigma(I). The crystal consists of the complex [Fe3O(CH3COO)(6)(H2O)(3)](+) cations, centrosymmetric [PtCl6](2-) anions and water molecules. The [Fe3O(CH3COO)(6)(H2O)(3)](+) cation has the typical structure of a trinuclear iron(III) compound with mu(3)-O bridge. All crystal components are connected via a system of hydrogen bonds into a 3D network. Mossbauer spectrum displays at room temperature a single quadrupole doublet with an isomer shift of 0.70 mm/s and quadrupole splitting of 0.48 mm/s, consistent with high-spin Fe(III). mu(eff) per Fe atom (3.25 mu(B) at 293 K and 2.23 mu(B) at 120 K), indicate the antiferromagnetic coupling between the paramagnetic iron ions with J = -31 cm(-1).

3078. Recoilless Rayleigh scattering on Rb2ZnCl4 around the normal-incommensurate phase transition point

Authors: Enescu, SE; Bibicu, I; Grecu, MN; Kluger, A

Published: 1999, SOLID STATE COMMUNICATIONS, 111, 303, DOI: 10.1016/S0038-1098(99)00218-5

The normal-incommensurate phase transition in Rb2ZnCl4 was studied by Rayleigh scattering of Mossbauer radiation. The discontinuity in resonance effect (epsilon) proves a stepwise variation of the inelastic component of the scattered radiation. The result is discussed in connection with the photon-phonon interaction. (C) 1999 Elsevier Science Ltd. All rights reserved.

3079. Low metal loading Ru-MCM-41 stereocontrolled hydrogenation of prostaglandin intermediates

Authors: Coman, S; Florea, M; Cocu, F; Parvulescu, VI; Jacobs, PA; Danumah, C; Kaliaguine, S

Published: NOV 7 1999, , DOI: 10.1039/a907119i

3080. Electron spin resonance in gamma-Fe2O3 nanoparticles dispersed in a polymer matrix

Authors: Prodan, D; Grecu, VV; Grecu, MN; Tronc, E; Jolivet, JP

Published: SEP 1999, MEASUREMENT SCIENCE AND TECHNOLOGY, 10, L43, DOI: 10.1088/0957-0233/10/9/101

gamma-Fe2O3 nanoparticles dispersed in a polymer matrix have been characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The electron paramagnetic resonance (EPR) in 64 Angstrom particles of gamma-Fe2O3 dispersed in a polymer matrix has been investigated in the range 136-286 K.

3081. Nanostructure and phase distributions in (Cu0.80Fe0.20)(100-x)B-x melt spun ribbons studied by Mossbauer spectroscopy

Authors: Kuncser, V; Rosenberg, M; Yavari, AR; Filoti, G

Published: JUL 20 1999, JOURNAL OF ALLOYS AND COMPOUNDS, 289, 276, DOI: 10.1016/S0925-8388(99)00163-2

The analysis of the Mossbauer spectra of (Cu0.8Fe0.2)(100-x))B-x the melt spun ribbons taken at several temperatures between 4.2 K and room temperature allowed us to identify the occurring Fe-containing phases: alpha-Fe, gamma-Fe and <(Cu)under bar>Fe solid solutions. The presence of B inhibits the phase transformation from fee to bcc Fe. For x = 0 and 1, the amount of Fe in the <(Cu)under bar>Fe solid solution is close to 3 at.% solubility limit, while for x=3 besides crystalline Fe3B, a supersaturated phase of 9.7 at.% Fe in the <(Cu)under bar>Fe solid solution was found, showing a strong deviation from the binary equilibrium phase diagram. (C) 1999 Elsevier Science S.A. All rights reserved.

3082. Structural characterization of CxByNz (x = 0.1 to x = 0.2) layers obtained by laser-driven synthesis

Authors: Morjan, I; Conde, O; Oliveira, M; Vasiliu, F

Published: FEB 26 1999, THIN SOLID FILMS, 340, 105, DOI: 10.1016/S0040-6090(98)01354-6

CxByNz layers have been prepared by laser-assisted chemical vapour deposition (CVD) in a gas atmosphere containing C2H4, B2H6 and NH3 where the starting composition ratio could vary in a large range. The characterization of these C-B-N materials was made by XRD, EPMA, XPS, optical and scanning electron microscopy. The chemical composition of C-B-N layers tended to a composition C1B6N3 on the line BN-'B3C'. The turbostratic structure of C-B-N layers could be influenced and modified as a function of composition. XPS investigations confirmed the single-phase nature and the existence of bonding between all the elements. Some planar structures, containing especially CB2N groups, were suggested for the 'unit cell' of these C-B-N solid solutions, in agreement with EPMA and XPS analysis. (C) 1999 Elsevier Science S.A. All rights reserved.

3083. Off-center displacement of Fe+ ions in irradiated SrCl2 : Fe crystals grown in chlorine

Authors: Nistor, SV; Stefan, M; Schoemaker, D

Published: AUG 1999, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 214, 236, DOI: 10.1002/(SICI)1521-3951(199908)214:2<229::AID-PSSB229>3.0.CO;2-H

Chlorinated SrCl2:Fe2+ crystals exhibit, after X-ray irradiation, two trapped-electron Fe+(I) and Fe+(II) centers both with axial [001] symmetry, but different EPR spectrum parameters and production properties. The analysis of the experimental data strongly suggests a substitutional eight-fold coordination of the Fe+ ion in the Fe+(I) center and a strong [001] off-center displacement to a fourfold coordinated site in the Fe+(II) center resulting in S = 3/2 and S = 1/2 ground states, respectively.

3084. Nanoelectronics needs new materials

Authors: Alexe, M

Published: JAN 1999, PHYSICS WORLD, 12, 22, DOI:

3085. Structural characterization of FeCrP-type mesoscopic system

Authors: Mihalca, I; Morariu, M; Lita, M; Bibicu, I; Ercuta, A; Luca, D

Published: JUL 1999, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 201, 57, DOI: 10.1016/S0304-8853(99)00169-9

The paper describes the structural properties of some Fe80-xCrxP20 (1 less than or equal to x less than or equal to 7) mesoscopic (similar to 1 mu m) particles produced by mechanical alloying. The influence of the atomic concentration of Cr and that of the milling time are examined. The hyperfine held distribution obtained from the room temperature Mossbauer spectra of the as-milled samples exhibits three well separated peaks, associated with different chemical short range order, and depending on the atomic concentration of Cr atoms. (C) 1999 Elsevier Science B.V. All rights reserved.

3086. The crucial role of particle morphology in the magnetic properties of haematite

Authors: Sorescu, M; Brand, RA; Mihaila-Tarabasanu, D; Diamandescu, L

Published: APR 15 1999, JOURNAL OF APPLIED PHYSICS, 85, 5548, DOI: 10.1063/1.369890

Haematite particles of four different morphologies (polyhedral, platelike, needlelike and disk shaped) were synthesized by the hydrothermal method. The morphology and average particle diameter (1.4, 7.4, 0.2, and 0.12 mm, respectively) were determined by transmission electron microscopy combined with electron diffraction. The haematite samples were studied by transmission Mossbauer spectroscopy in the temperature range 4.2-300 K. In all cases, a weak ferromagnetic (WF) phase was present above the Morin temperature of 230 K and found to coexist with an antiferromagnetic (AF) phase below this temperature. However, the populations of the two phases at 230 K were demonstrated to depend on the morphology of the particles. Moreover, the WF and AF phases exhibit a different dependence of the magnetic texture on temperature and particle morphology. (C) 1999 American Institute of Physics. [S0021-8979(99)66908-0].

3087. Structural and magnetic characterization of R2Fe17-xVx (R = Y, Gd and x=1, 1.5, 2) compounds and their carbides

Authors: Sorescu, M; Valeanu, M

Published: NOV-DEC 1999, INTERNATIONAL JOURNAL OF INORGANIC MATERIALS, 1, 309, DOI: 10.1016/S1466-6049(99)00044-6

Magnetic compounds of the type R2Fe17-xVx (R=Y, Gd and x = 1, 1.5, 2) were synthesized by are melting (with or without interstitial carbon) and studied by X-ray diffraction (XRD), Mossbauer spectroscopy and hysteresis loop measurements. Compounds with the structure Y2Fe17-xVx (x = 1, 1.5, 2) are hexagonal, whereas the intermetallics containing carbon introduced by melting and those of the type Gd2Fe17-xVx (x = 1, 1.5, 2) are rhombohedral. For each symmetry, the lattice parameters a/c were obtained from the XRD spectra and a considerable expansion of the unit cell volume was observed in the Y2Fe17-xVxC (x = 1, 1.5, 2) systems. Room temperature transmission Mossbauer spectra were analyzed using two methods: fit with several sextets, corresponding to the various inequivalent iron sites and fit with a hyperfine magnetic field distribution, to yield the average hyperfine magnetic field. The average hyperfine magnetic field was studied as a function of vanadium content x for all classes of compounds under investigation. The maximum hyperfine field values were obtained for the carbides. The hysteresis loops recorded at 4.2 K in an applied field of 1.5 T provided complementary information on the saturation magnetization as a function of vanadium substitution for each group of intermetallics involved. (C) 1999 Elsevier Science Ltd. All rights reserved.

3088. Statistics of an ideal polymer in a multistable potential: Exact solutions and instanton approximation

Authors: Mondescu, RP; Muthukumar, M

Published: JUN 22 1999, JOURNAL OF CHEMICAL PHYSICS, 110, 12249, DOI: 10.1063/1.479162

We have considered the stationary state of a one-dimensional Gaussian polymer chain of length Nl (N is number of segments, l is the Kuhn length) subjected to a one-parameter class of exactly solvable, symmetric, repulsive potentials with multiple (two or three) minima. We have calculated analytically and numerically the exact Green's function G(R\R-';L) and the mean-square end-to-end distance [(R-R-')(2)], respectively, of the polymer chain. The instanton approximation is translated in polymer physics language and used to analyze the conformation of the polymer chain in its ground state, by evaluating the average number of folds that connect the potential minima. All quantities are functions of the barrier height and of the separation between wells. Our results show that for a given length N, the polymer expands with increasing barrier width until a maximum value of [(R-R-')(2)] is reached. Afterwards, the polymer apparently collapses in one of the wells. This behavior defines a critical length N* and may offer the possibility of applications in separation and pattern recognition processes. (C) 1999 American Institute of Physics. [S0021-9606(99)50122-0].

3089. Synthesis and characterization of CN thin films by IR laser deposition in a flow reactor

Authors: Crunteanu, A; Alexandrescu, R; Cojocaru, S; Charbonnier, M; Romand, M; Vasiliu, F

Published: SEP 1999, JOURNAL DE PHYSIQUE IV, 9, 424, DOI: 10.1051/jp4:1999852

Carbon nitride (CNx) this films were produced by CO2 laser (lambda=10.6 mu m) irradiation of mixtures containing C2H2/N2O/NH3, in a flow reactor, on Si substrates. The experimental parameters (partial concentrations of the reactants, gas flows. total pressure) were chosen in order to maximize the nitrogen incorporation in films. Chemical composition and bonding structure of the deposited films were investigated by; X-ray photoelectron spectroscopy (XPS). Thus, it was found that nitrogen is chemically bonded to C in sp(2) or sp(3) configurations, the NIC ratio (considering only the N atoms bonded to carbon) being similar to 20%. Scanning electron microscopy (SEM) shows a specific growth morphology, while the transmission electron diffraction (TED) and X-ray diffraction (XRD) analysis revealed that the CN, films were crystalline, with diffraction lines that marches rather well with those of the predicted beta-C3N4 form.

3090. Growth of carbon nickel multilayer for X-ray-UV optics by RF reactive magnetron sputtering

Authors: Georgescu, G; Nelea, V; Ulmeanu, M; Ghica, C; Nastase, N

Published: JUL 1999, APPLIED SURFACE SCIENCE, 148, 146, DOI: 10.1016/S0169-4332(99)00219-6

Amorphous C/Ni superlattice films designed as normal-incidence reflector for 5 nm have been grown on float-glass substrates by magnetron sputter deposition in Ar discharge. A comprehensive set of characterization techniques has been applied: grazing X-ray reflection (0.154 nm), atomic force microscopy and transmission electron microscopy in order to determine the quality of the structure. By comparing the results, it could be concluded that RF-magnetron sputtering technique is a good choice for growing such layered synthetic microstructures. (C) 1999 Elsevier Science B.V. All rights reserved.

3091. Superconductor-ferroelectric heterostructures

Authors: Constantin, C; Ramer, R; Matei, I; Trupina, L; Stegarescu, M

Published: 1999, FERROELECTRICS, 225, 1092, DOI:

Superconductor-ferroelectric heterostructures were prepared by deposition of ferroelectric doped-PZT type material on the top of the superconductor YBCO thin films. Both, ferroelectric and superconductor thin films were obtained by off-axis RF magnetron sputtering method with a single target. On these heterostructures, measurements were made in order to evidence the influence of contact between the two materials on the electrical and thermal parameters. X-ray diffraction patterns of superconductor thin film show a good crystallization c-axis oriented perpendicular to the substrate plane, and a perovskite structure without traces of pyrochlore at 550 degrees C the ferroelectric thin film deposited by RF magnetron sputtering (off axis method). Important variations of the critical temperature of superconductor films have been obtained, due to the increased dielectric permittivity (epsilon).

3092. Photoconductivity of SrBi2Ta2O9 thin films

Authors: Pintilie, L; Alexe, M

Published: 1999, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 19, 1488, DOI: 10.1016/S0955-2219(98)00460-9

Photoconductive properties of SrBi2Ta2O9 thin films in the 250-400 nm wavelength range were investigated. The films were deposited on Pt/SiO2/Si substrates using the Chemical Solution Deposition and were crystallized by conventional thermal annealing at 850 degrees C. One sensitivity maximum was observed in the spectral distribution of the photoconductive signal and was attributed to band-to-band generation in the film. The wavelength corresponding to this maximum was found to be dependent on the applied voltage, on the delay time, defined as the time between the application of light on the film and the reading of the generated photocurrent, and on the wavelengths sweeping direction tug or down). The gap value was estimated to be around 3.94-4 eV. (C) 1999 Elsevier Science Limited. All rights reserved.

3093. Structural and magnetic properties of magnetoresistive Cu-Co-Fe ribbons

Authors: Crisan, O; Le Breton, JM; Jianu, A; Maignan, A; Nogues, M; Teillet, J; Filoti, G

Published: MAY 1999, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 196, 469, DOI: 10.1016/S0304-8853(98)00822-1

Melt-spun Cu80Co10Fe10 ribbons are shown to exhibit a nanogranular structure with magnetic alpha-Fe(Co) grains segregated from the Cu-rich matrix after appropriate annealing. The Cu matrix purification as well as the magnetic properties of the alpha-Fe(Co) grains existing in a range of sizes are studied using X-ray diffraction, Mossbauer spectrometry and magnetic measurements. There is an optimum annealing for obtaining a high magnetoresistive effect. (C) 1999 Elsevier Science B.V. All rights reserved.

3094. Structural properties of some conducting polymers and carbon nanotubes investigated by SERS spectroscopy

Authors: Lefrant, S; Baltog, I; de la Chapelle, ML; Baibarac, M; Louarn, G; Journet, C; Bernier, P

Published: MAR 26 1999, SYNTHETIC METALS, 100, 27, DOI: 10.1016/S0379-6779(98)00175-1

In this paper, we present Surface Enhanced Raman Scattering (SERS) experiments performed successfully on some conducting polymers and carbon nanotubes deposited in thin films on rough metallic surfaces. The enhancement mechanism in SERS has a twofold origin: electromagnetic and chemical. The electromagnetic enhancement is, however, the dominant mechanism and consists in the excitation of localized and delocalized surface plasmons (SP). The second enhancing mechanism for SERS, not yet convincingly supported by experimental data, is of chemical origin. This mechanism is due to the increase of the polarizability of the molecules on the metal surface under the action of the incident radiation, leading to the formation of new chemical bonds between the molecules and the metal surface. Unfortunately, the experimental data available to argue the presence of a chemical process are scarce and scattered. In this paper, we try to present some details regarding this aspect. In order to do so, we studied poly 3-hexylthiophene (3-PHT) and polyaniline (PAN) as a function of the type of the rough metallic support (Ag, Au or Cu), the oxidization state and thickness of the polymer layer. We studied also carbon single walled nanotubes. Our experiments reveal the existence of a chemical surface effect. The results obtained for 3-PHT show that SERS spectra depend on the oxidizing properties of the metal surface and on the nature of the solvent. This dependence is explained by the existence of some interfacial reactions that lead to the formation of interface compounds. The SERS measurements reported here reveal an increase of the intensities of the Raman lines, accompanied by a modification of the corresponding intensity ratios, when the degree of doping is increased. We observe for the first time by SERS spectroscopy that doping of 3-PHT with FeCl3 leads to the appearance of a state of disorder in the structure of the macromolecular chain, as a result of steric hindrance effects. The type of the rough metallic support can modify SERS spectra and such an effect is clearly shown for the polyaniline case. No such dependence on metallic support type is observed on the SERS spectra of carbon nanotubes. (C) 1999 Published by Elsevier Science S.A. All rights reserved.

3095. Surface order parameter and polar anchoring energy in nematic liquid crystals

Authors: Moldovan, R; Tintaru, M; Beica, T; Frunza, S

Published: 1999, CRYSTAL RESEARCH AND TECHNOLOGY, 34, 1321, DOI: 10.1002/(SICI)1521-4079(199912)34:10<1315::AID-CRAT1315>3.0.CO;2-V

The trends of temperature dependence of the surface order parameter and of the anchoring strength coefficient are theoretically evaluated in the Landau-de Gennes phenomenological theory for nematic liquid crystals. The cases of planar, homeotropic and tilted alignment at a planar limiting surface are considered. It is shown that the cases with surface order parameter greater than the bulk one or smaller than this can occur in function of the phenomenological coefficients in the surface free energy expression. The anchoring strength coefficient, W, diminishes when temperature approaches the nematic-isotropic point, after passing through a maximum in most of cases. The possibility of a nonzero anchoring strength at temperatures above the transition temperature is revealed. The obtained trends of W(T) describe well a large variety of experimental results from literature.

3096. Application of contrast variation method in SANS experiments with ferrofluids

Authors: Grabcev, B; Balasoiu, M; Tirziu, A; Kuklin, AI; Bica, D

Published: JUL 1999, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 201, 143, DOI: 10.1016/S0304-8853(99)00095-5

The contrast variation method, applied in a neutron small angle scattering experiment, was used to simultaneously obtain information about molecular and magnetic structure of ferrofluids. Limitations caused by size polydispersity of particles were considered. (C) 1999 Elsevier Science B.V. All rights reserved.

3097. On the crystal-to-mesophase phase transition in copper(II) salts of even-chain fatty acids

Authors: Fausto, R; Duarte, MLTS; Moita, MFR; Frunza, L; Beica, T; Frunza, S

Published: 1998, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 53, 139, DOI: 10.1023/A:1010111519530

The phase transition from the solid state to the liquid crystal state was investigated for the copper(II) salts of the fatty acids with 10, 12, 14, 16 or 18 carbon atoms in the chain, by measuring the temperature dependence of the conductance and capacitance of a cell containing the material under investigation. The temperatures deduced from these dependences agree reasonably with those found by DSC measurements and with those to be found in the literature. Differences in dielectric behaviour between the samples are qualitatively discussed.

3098. GaN thin films deposition by laser ablation of liquid Ga target in nitrogen reactive atmosphere

Authors: Dinescu, M; Verardi, P; Boulmer-Leborgne, C; Gerardi, C; Mirenghi, L; Sandu, V

Published: MAY 1998, APPLIED SURFACE SCIENCE, 127, 563, DOI: 10.1016/S0169-4332(97)00705-8

GaN thin films were deposited by laser ablation of liquid Ga target in nitrogen reactive atmosphere. An Nd-YAG laser (lambda = 1.06 mu m, tau(FWHM) = 10 ns) of 0.35 J energy/pulse was used as laser source. The nitrogen pressure was varied in the range of 10(-2) to 10(-1) mbar. As substrates, we used (0001) sapphire plates and (100) Si wafers, coated or uncoated with ZnO as buffer layers, and heated below 300 degrees C. Different analysis techniques evidenced the characteristics of the deposited films. SIMS profiles corresponding to N and Ga in-depth distribution carried out the presence of layers of the order of 130-150 nm, with uniform distribution of Ga and N inside the layer. XPS studies evidenced the Ga-N bonding. The Nls signal contains as main peak the one centered at 397.3 eV and corresponding to Ga-N bond. From the distance between the photoelectron Ga 3d peak and the Auger Ga LMM peak, the calculated Auger parameter of 1083.9 eV corresponds to the one reported in literature for GaN compound (1084.05 eV). Both techniques evidenced an oxygen contamination below 5%. XRD recorded spectra show the presence of a peak assigned to (002) GaN crystalline orientation. Optical absorption spectroscopy studies in the UV-visible range evidenced a high transparency (over 80% transmission) for the deposited films. The energy band gap obtained from the absorption spectra was found to be larger than 3.6 eV. (C) 1998 Elsevier Science B.V.

3099. Iron-oxide-based nanoparticles produced by pulsed infrared laser pyrolysis of Fe(CO)(5)

Authors: Alexandrescu, R; Morjan, I; Crunteanu, A; Cojocaru, S; Petcu, S; Teodorescu, V; Huisken, F; Kohn, B; Ehbrecht, M

Published: SEP 1 1998, MATERIALS CHEMISTRY AND PHYSICS, 55, 121, DOI: 10.1016/S0254-0584(98)00145-X

The synthesis of nanosized (1-100 nm) particles is an active research field in chemical processing technologies. The process may be of particular relevance in the case of the widely used iron-based materials. In this paper, we report on the preparation and characterization of ultrafine powders produced by pulsed infrared laser pyrolysis of iron pentacarbonyl, Fe(CO)(5), in sensitized mixtures. The synthesis is performed in a flow reactor, at rather high pressure (400 mbar) and high laser fluence (similar to 5 J cm(-2)). The average diameter of the particles is 30 nm. Different characterization methods of the fine powder aged in atmosphere indicate the presence of a substantial oxidic portion, identified as the beta-Fe2O3 . H2O form. Some experimental observations suggest the possibility of iron-oxides formation during synthesis in the flow reactor. The relevant mechanisms for this reaction route are discussed. (C) 1998 Elsevier Science S.A. All rights reserved.

3100. The influence of lithium halides on the superconducting properties of YB2Cu3O7-x

Authors: Sandu, V; Jaklovszky, J; Cimpoiasu, E; Bunescu, MC

Published: DEC 1998, JOURNAL OF SUPERCONDUCTIVITY, 11, 661, DOI: 10.1023/A:1022664300837

The effects of addition to YBa2Cu3O7-x Of lithium halides (YBa2Cu3O7-x (LIF)(gamma) and YBa2Cu3O7-x (LiCl)(gamma)) on the structural, electric, magnetic, and transport properties are analyzed. Both structural and superconducting properties depend weakly on the lithium content up to gamma=0.10. The critical temperature keeps on a value well above 91 K for a small amount of lithium halide (reaching 93.48 K for gamma=0.02 in YBa2Cu3O7-x (LiF)(gamma) and 91.30 K in YBa2Cu3O7-x (LiCl)(gamma)), but for higher concentration of Li it rapidly decreases (81.68 K for gamma=0.20). The same behavior is exhibited in the lower intragranular critical field. The intragranular critical current density depends on the magnetic field as a power law: j(c)proportional to B-alpha, with a lithium-concentration-dependent a. The voltage-current characteristics follow a law typical for granular superconductors, V proportional to(I-I-c(B, T))(n(B,T)). The dependence of the intergranular critical current, I-c, and of the exponent, n, on temperature, magnetic field, and concentration is analyzed.

3101. Azimuthal anchoring of nematic on undulated substrate: Elasticity versus memory

Authors: Barberi, R; Dozov, I; Giocondo, M; Iovane, M; Martinot-Lagarde, P; Stoenescu, D; Tonchev, S; Tsonev, LV

Published: NOV 1998, EUROPEAN PHYSICAL JOURNAL B, 6, 91, DOI: 10.1007/s100510050529

We measure the azimuthal anchoring energy of the nematic 5CB on sinusoidal holographic unidimensional and bidimensional gratings. We find that the anchoring strength is almost the same for all of the gratings and up to one order of magnitude stronger than expected by the topographic mechanism proposed by Berreman. We observe strong memory effects which dominate both the elastic anchoring and the easy axis gliding. We show that these memory effects limit from below the anchoring energy and are the main obstacle in the realization of substrates with weak anchoring conditions.

3102. Magnetic properties and cation distribution in iron containing pyrochlores

Authors: Filoti, G; Rosenberg, M; Kuncser, V; Seling, B; Fries, T; Spies, A; Kemmler-Sack, S

Published: MAR 27 1998, JOURNAL OF ALLOYS AND COMPOUNDS, 268, 21, DOI: 10.1016/S0925-8388(97)00621-X

Iron-containing pyrochlores, having ions with various valencies on the B-sites, were investigated by magnetic measurements and Mossbauer spectroscopy. The influence of the ionic radius and of the valence state of the different cations accommodated on A or B sites on the super-exchange interactions and local distortions was emphasized. Three local configurations of iron were given as evidence in agreement with a model based on a random distribution of ions over the B-sites. (C) 1998 Elsevier Science S.A.

3103. Influence of Gd addition on the magnetic properties of Fe-Cu-Nb-Si-B ribbons

Authors: Crisan, O; Le Breton, JM; Nogues, M; Machizaud, F; Jianu, A; Teillet, J; Filoti, G

Published: JUN 1998, JOURNAL DE PHYSIQUE IV, 8, 118, DOI: 10.1051/jp4:1998227

The magnetic properties of the amorphous and nanocrystallized Fe-Cu-Nb-Si-B and Fe-Gd-Cu-Nb-Si-B ribbons are studied using temperature dependence of the specific magnetization. A two-phase ferromagnetic behaviour is obtained for the magnetization curves. Gd addition tends to stabilize the interfacial (grain boundary) phase by forming a metastable Gd-Fe-B phase, leading to the coexistence of two phases up to thermal treatments as high as 993K.

3104. Mirror electron microscopy investigations of thin polyethylene films subjected to high voltage

Authors: Godehardt, R; Heydenreich, J; Popescu-Pogrion, N; Tirnovan, M

Published: APR 1 1998, THIN SOLID FILMS, 317, 236, DOI: 10.1016/S0040-6090(97)00522-1

The practical importance of these studies comes from the fact that, the local degradation of dielectric layers due to the treeing discharge leads to the increment of energy losses and finally to the electric breakdown of the films. The thickness of the deposition layers was 1000 Angstrom. For the application of high voltage, we used the needle-plane system. The Mirror Electron Microscopy (MEM) investigations in polyethylene films without the application of high voltage have shown electrical inhomogeneities. After the application of high voltage (4 to 12 kV), thin polyethylene films have no electrical inhomogeneities because the sites corresponding to local conduction filaments are the starting points for pre-breakdown phenomenon. (C) 1998 Elsevier Science S.A.

3105. The molecular structure of some urea and thiourea derivatives

Authors: Bally, I; Simion, C; Mazus, MD; Deleanu, C; Popa, N; Bally, D

Published: APR 20 1998, JOURNAL OF MOLECULAR STRUCTURE, 446, 68, DOI: 10.1016/S0022-2860(97)00400-6

The molecular structures for N-phenyl-N'-acetylurea, N-phenyl-N'-capronylthiourea, and N - phenyl - N' - benzoyl thiourea have been characterized by X-ray diffraction and NMR spectroscopy. The relative positions of atoms in the parent molecular fragment, common to all three analyzed compounds, are discussed. (C) 1998 Elsevier Science B.V.

3106. On polyaniline - Polyvinylchloride blends

Authors: Chipara, MI; Munteanu, I; Notingher, P; Chipara, MD; Romero, JR; Negreanu, B; Panaitescu, D

Published: 1998, PROCEEDINGS OF THE 1998 IEEE INTERNATIONAL CONFERENCE ON CONDUCTION AND BREAKDOWN IN SOLID DIELECTRICS - ICSD '98, 374, DOI: 10.1109/ICSD.1998.709303

3107. Elastic stress relaxation in TiN and ZrN hard coatings

Authors: Manaila, R; Biro, D; Barna, PB; Popescu, R; Fratiloiu, D; Adamik, M; Devenyi, A

Published: 1998, COST 516 TRIBOLOGY SYMPOSIUM, 180, 324, DOI:

3108. Detailed structure of a Pb-doped Bi2Sr2CuO6 superconductor

Authors: Ito, Y; Vlaicu, AM; Mukoyama, T; Sato, S; Yoshikado, S; Julien, C; Chong, I; Ikeda, Y; Takano, M; Sherman, EY

Published: AUG 1 1998, PHYSICAL REVIEW B, 58, 2858, DOI: 10.1103/PhysRevB.58.2851

The crystal structure of (Bi1.82Pb0.18) (ST1.84Pb0.16) CuO6 was determined from single-crystal intensity data measured on a four-circle diffractometer. The structure is orthorhombic, space group Cccm (No. 66); the lattice parameters: a=5.392(3) Angstrom, b=24.603(5) Angstrom, c=5.300(3) Angstrom, V=703.2 (5) Angstrom(3) (the space group can be denoted as Amaa by a cyclic transformation of the cell constants). The R value was 0.048 for 418 unique reflections with I>3.00 sigma(I). One of the O atoms bonded to Bi ions is disordered at two sites with a half occupancy and B-eq=3.6(6) Angstrom(2); although the thermal parameter is not so large as that reported by Torardi et al. [Phys. Rev. B 38, 225 (1988)], the disorder suggests that the crystal has a lower symmetry. The valence state of the Cu ion in the present compound was evaluated to be trivalent based on the Cu-O distances [Asbrink and Norrby, Acta Crystallogr. B 26, 8 (1970)] and the valence of Bi was estimated in comparison with that in other compounds. The O(3) sublattice dynamics in these types of superconductors is discussed based on the structural investigations.

3109. Electrical behaviour of fresh and stored porous silicon films

Authors: Ciurea, ML; Baltog, I; Lazar, M; Iancu, V; Lazanu, S; Pentia, E

Published: JUL 18 1998, THIN SOLID FILMS, 325, 277, DOI: 10.1016/S0040-6090(98)00429-5

We have measured I-V and C-V characteristics, the temperature dependence of dark currents, and thermally stimulated depolarisation currents on fresh and stored samples of photoluminescent porous silicon, By storage in ambient, the low rectifying I-V curves become strong rectifying, and C-V curves become MIS-like. I-T characteristics for fresh samples have only one activation energy, in the 0.49-0.55 eV range. After storage, a slightly modified value, of about 0.50-0.60 eV is observed at low temperatures only. At about 280 K, the activation energy suddenly changes to 1.20-1.80 eV. Also, both the number and the positions of maxima in thermally stimulated depolarisation currents change by storage. The annealing at about 50 degrees C induces small reversible changes in I-T characteristics and strong irreversible ones in thermally stimulated depolarisation currents, both for fresh and stored samples. A simplified quantum confinement model is proposed to explain the main aspects of the electrical behaviour of porous silicon films. The surface and/or interface contributions are observed especially in thermally stimulated depolarisation currents. The changes induced by storage are attributed to the oxidation process of the internal surface of porous silicon films. (C) 1998 Elsevier Science S.A. All rights reserved.

3110. The role of radiation damage structure and fine scale precipitation in the pinning improvement of thermal neutron irradiated lithium fluoride-doped YBa2Cu3O7-x

Authors: Vasiliu, F; Sandu, V; Nita, P; Popa, S; Cimpoiasu, E; Bunescu, MC

Published: JUL 20 1998, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 303, 219, DOI: 10.1016/S0921-4534(98)00254-8

The improvement of intragranular critical current density, j(c), and flux pinning obtained by thermal neutron irradiation (fluences between 10(16) - 10(18) neutrons/cm(2)) in YBa2Cu3O7,(-x) doped with 8 mol% lithium fluoride (LiF) (YBCO-LIF) is explained by the occurrence of various irradiation defects (point defect clusters, dislocation loops, stacking faults) observed by transmission electron microscopy (TEM), A twin fading process is also revealed accompanied by a lowering of the orthorhombicity index. At higher irradiation fluences (similar to 5 x 10(17) 10(18) neutrons/cm(2)), a new mechanism related to the dispersion of fine Cu2O precipitates in the superconducting YBCO-LiF matrix could explain the enhancement of up to eight times obtained for j(c) values. A good agreement between the dependence of the measured j(c) values on the applied magnetic field and the calculated curves, j(c) = f(B), derived from a theoretical model, previously proposed for the pinning contribution of fine particles dispersed in YBCO matrix, is obtained. The role of thermal neutron irradiation for the flux pinning improvement by introducing of strong pinning centers (irradiation defects and Cu2O microdispersoids) is also discussed. (C) 1998 Elsevier Science B.V. All rights reserved.

3111. Mossbauer and magnetic study of substituted magnetites

Authors: Sorescu, M; Mihaila-Tarabasanu, D; Diamandescu, L

Published: APR 20 1998, APPLIED PHYSICS LETTERS, 72, 2049, DOI: 10.1063/1.121260

Co, Ni, Mn, Cr, and Cu substituted magnetites were prepared by the hydrothermal method at 300 degrees C, with concentrations ranging from 8.2% to 12.5%. Transmission electron microscopy determined the average particle diameter (Phi) to be in the hundred of nm range and the morphological modifications induced by the various substitutions employed, Hysteresis loop measurements were performed to determine the coercive field H-c, and saturation magnetic moment m(s). While H-c decreased with increasing (Phi), the particle shape was found to play an important role in explaining the dependence of m(s) on (Phi). Transmission Mossbauer spectroscopy was used to determine the site preference of the substitutions and their effect on the hyperfine magnetic fields. The room-temperature Mossbauer spectra were analyzed assuming a random distribution of substitutents using the binomial distribution from the ionic crystal point of view. Superparamagnetic particles were observed at room temperature in the case of Cu and Cr substituted magnetites. (C) 1998 American Institute of Physics.

3112. Microwave spectroscopy in YBCO superconductors: Influence of neutron irradiation on the 123 phase

Authors: Velter-Stefanescu, M; Totovana, A; Sandu, V

Published: JUN 1998, JOURNAL OF SUPERCONDUCTIVITY, 11, 330, DOI: 10.1023/A:1022619128787

The high-T-c superconducting system YBa2Cu3Odelta:Li (123) was investigated by microwave absorption. The effect of neutron irradiation on the 123 phase as well as the dependence of the resulting modification both on the neutron fluence and on the doping behavior with Li are discussed. The results show a significant improvement of the superconducting characteristics: critical temperature, phase homogeneity, and critical current densities for a certain neutron fluence. We have found that the optinum neutron fluence for irradiation is 4.98 x 10(21) m(-2).

3113. Reactivity of the Bi, Sr, Ca, Cu oxalate powders used in BSCCO preparation

Authors: Popa, M; Totovana, A; Popescu, L; Dragan, N; Zaharescu, M

Published: 1998, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 18, 1271, DOI: 10.1016/S0955-2219(98)00052-1

The solution chemistry of oxalate coprecipitation of Bi, Si, Ca, Cu has frequently! been used in the synthesis of Bi-based ceramic systems, although there are different opinions referring to some major aspects, such as coprecipitation pH and precipitating agent. In the present work we established the precipitation conditions of Bi, Sr, Ca, Cu individual oxalates and of the quaternary! mixture. The initial and thermally treated oxalate powders were characterized bq! XRD, IR, BET methods and TEM observation. The decomposition conditions were established based on a DTA/TG study. The powders resulted from the decomposition of Bi and Cu oxalates contain the corresponding oxides and the Ca and Sr oxalates decomposition lead to the carbonates obtaining. In each case a high reactivity and a very small powder particle size were observed. A very good powder homogeneity has also been noticed in the final mixture of oxalates. Compared to superconducting ceramic materials realized by a classic route, the reactive oxalate powders allow the decrease of both thermal treatment periods and temperature, emphasizing a high microstructure homogeneity of the ceramic body. (C) 1998 Elsevier Science Limited. All rights reserved.

3114. Amorphous Se/CdSe and SiOx/CdSe multilayers

Authors: Popescu, M; Sava, F; Lorinczi, A; Vateva, E; Nesheva, D; Tchaushev, G; Mihailescu, IN; Koch, PJ; Obst, S; Bradaczek, H

Published: 1998, FIFTH CONFERENCE ON OPTICS (ROMOPTO '97), PTS 1 AND 2, 3405, 964, DOI: 10.1117/12.312698

Amorphous multilayers based on Se and CdSe alternated sublayers were succesfully prepared by thermal vacuum evaporation and laser ablation with the periodicity of 22 nm. The multilayer structure is stable up to similar to 70 degrees C. In the samples prepared by laser ablation a large contraction of the multilayer stacking occurs by annealing. Amorphous SiOx/CdSe multilayers with the periodicity of similar to 15 nm were successfully prepared by thermal vacuum evaporation. The structure is stable up to 400 degrees C annealing temperature. Pulse excimer laser irradiation of the SiOx based multilayer produces an expansion of the interlayer distance with similar to 0.33%.

3115. X-ray diffraction analysis of porous silicon

Authors: Popescu, M; Sava, F; Lorinczi, A; Mihailescu, IN; Cojocaru, I; Mihailova, G

Published: OCT 1998, JOURNAL DE PHYSIQUE IV, 8, 37, DOI: 10.1051/jp4:1998505

The modification of the ideal lattice parameter in porous silicon has been determined by X-ray diffraction. A contraction effect has been detected in several samples. There was shown that the position of the photoluminescence band is related to the modification of the lattice parameter. The quantum theory of confinement in wires was used for the interpretation of the experimental data.

3116. Characterization of carbon nitride thin films deposited by a combined RF and DC plasma beam

Authors: Dinescu, G; Aldea, E; Musa, G; van de Sanden, MCM; de Graaf, A; Ghica, C; Gartner, M; Andrei, A

Published: JUL 18 1998, THIN SOLID FILMS, 325, 129, DOI: 10.1016/S0040-6090(98)00509-4

Thin carbon nitride films have been deposited on silicon(100) substrates downstream of a nitrogen plasma beam generated in a combined RF (13.56 MHz, 40-50 W) and DC (voltage +/-200 V, power 1-10 W) discharge between a graphite electrode and a graphite nozzle. By combining the RF and DC sources the capability of rf field to create extended plasmas is used together with the enhanced sputtering and biasing effect of the DC source. The plasma characteristics (electron temperature, presence of molecular species) have been studied by optical emission spectroscopy. Deposition rates of 2.5-3 nm/s are obtained at the centre of the plasma beam and at a few centimetres distance from the nozzle. The films have been investigated by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, scanning and transmission electron microscopy, and microhardness measurements. The films have an overall N:C ratio of 0.28 but the distribution of different nitrogen bonds depends upon the DC bias conditions. In the spectral range 0.3-0.7 mu m the refractive index increases slightly from 1.5 to 2.2. The films are amorphous, with morphology consisting of a columnar structure. The columns have a diameter of about 20 nm. A hardness of 24 GPa has been measured. (C) 1998 Elsevier Science S.A. All rights reserved.

3117. Selective epitaxial growth of strained SiGe/Si for optoelectronic devices

Authors: Vescan, L; Stoica, T; Goryll, M; Grimm, K

Published: FEB 27 1998, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 51, 169, DOI: 10.1016/S0921-5107(97)00253-5

Two aspects of the selective epitaxial growth of Si and Si(1-x)Ge(x) will be discussed. First the facet formation as dependent on the oxide wall orientation and the lateral size of oxide openings. Besides the often cited {111}, {113} and {110} planes additional planes were observed, the {119} and the {0 1 12} planes. Second, the reduction of misfit dislocation density by reducing the area of the pads allows strained Si(1-x)Ge(x) layers to grow much thicker than the critical thickness. As an application for the latter the electroluminescence of forward biased PIN diodes with strained Si(0.80)Ge(0.20)/Si(001) will be discussed as being dependent on the thickness of the SiGe layer. It was found that in thicker strained samples the band edge electroluminescence persists up to room temperature. Quantitative modelling of the electroluminescence could explain the temperature and SiGe thickness dependence of the electroluminescence. (C) 1998 Elsevier Science S.A. All rights reserved.

3118. Synthesis and magnetic properties of haematite with different particle morphologies

Authors: Sorescu, M; Brand, RA; Mihaila-Tarabasanu, D; Diamandescu, L

Published: OCT 23 1998, JOURNAL OF ALLOYS AND COMPOUNDS, 280, 278, DOI: 10.1016/S0925-8388(98)00719-1

Haematite particles of four different morphologies (polyhedral, platelike, needlelike and diskshape) were synthesized by the hydrothermal method. The morphology and average particle diameter (1.4; 7.4; 0.2 and 0.12 mu m, respectively) were determined by transmission electron microscopy (TEM) combined with electron diffraction. The haematite samples were studied by transmission Mossbauer spectroscopy in the temperature range 4.2-300 K. In all cases, a weak ferromagnetic phase (WF) was present above the Morin temperature of 230 K and found to coexist with an antiferromagnetic phase (Ali) below this temperature. However, the populations of the two phases at 230 K were demonstrated to depend on the morphology of the particles. Moreover, the WF and AF phases exhibit a different dependence of the magnetic texture on temperature and particle morphology. (C) 1998 Elsevier Science S.A. All rights reserved.

3119. Formation of F-2(-) color centers in LiF monocrystals by electron irradiation and their applications

Authors: Jurba, M; Baltateanu, N; Spanulescu, I; Spanulescu, SI; Gheorghiu, A

Published: JUN 1998, EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS, 2, 256, DOI: 10.1051/epjap:1998190

Formation conditions, optical nonlinear properties and applications of F2- color centers in LiF monocrystals are investigated. The efficiency of F-2(-) centers generation depending of irradiation conditions and content of OH- impurities of the LiF monocrystal are also presented. Thermal stability of the centers generated by electron irradiation was studied. It was measured the variation of absorption factor of the LiF: F-2(-) crystal in the -40 degrees C to 60 degrees C temperature range. The LiF: F-2(-) crystals obtained by an efficient method of irradiation with electrons generated by a linear accelerator were employed in Q-switching a Nd:YAG laser cavity with output energies of 18 mJ and fluctuations less than 5% in the -40 degrees C to 60 degrees C temperature range.

3120. Electrical and optical characterization of PbTiO3/Si heterostructures for applications in optoelectronics

Authors: Dragoi, V; Pintilie, L; Pintilie, I; Petre, D; Boerasu, I; Alexe, M

Published: 1998, FIFTH CONFERENCE ON OPTICS (ROMOPTO '97), PTS 1 AND 2, 3405, 851, DOI: 10.1117/12.312674

The ferroelectric/semiconductor heterostructures were fabricated by sol-gel deposition of lead titanate (PT) thin films on a single-crystalline p-type Si wafers. The ETT films were crystallyzed by a conventional thermal annealing for 30 min at temperatures ranging from 575 degrees C to 675 degrees C. Current-voltage and capacitance-voltage characteristics show a hysteresis which can be due to the spontaneous polarization of PbTiO3. The current-voltage characteristics exhibit a diode behaviour while the capacitance-voltage exhibits a large memory window, up to 3.5 V, for the films annealed at 600-650 degrees C. At the illumination with modulated light, a.c. photovoltage was detected on a broad range of wavelengths (0.35+4 mu m) for all samples. The spectral distribution of the photoelectric signal in the UV-Vis-IR domain shows two local maxima. A model is proposed to explain the observed experimental results.

3121. Photo-induced softening and hardening in Ge-As-S amorphous films

Authors: Popescu, M; Sava, F; Lorinczi, A; Skordeva, E; Koch, PJ; Bradaczek, H

Published: 1998, JOURNAL OF NON-CRYSTALLINE SOLIDS, 227, 722, DOI: 10.1016/S0022-3093(98)00236-1

Hardness, X-ray diffraction and transmission as well as infrared reflection measurements on virgin and ultraviolet (UV)-irradiated amorphous films of the GexAs40-xS60 system have been performed. The UV light induces film softening for x < 19 and film hardening for x > 19. The structure remains amorphous but the distance characteristic of medium range order decreases for x < 19 and increases for x > 19. Photo-contraction of the films (up to similar to 12%) has been revealed from IR spectra and X-ray transmission experiments. A main effect of UV light is the release of sulphur. (C) 1998 Elsevier Science B.V. All rights reserved.

3122. Quantum confinement model for electric transport phenomena in fresh and stored photoluminescent porous silicon films

Authors: Iancu, V; Ciurea, ML

Published: OCT 1998, SOLID-STATE ELECTRONICS, 42, 1896, DOI: 10.1016/S0038-1101(98)00160-9

A quantum confinement model is proposed to explain the electrical transport properties in fresh and stored porous silicon (PS) films. In the present paper, the model is verified for the temperature dependence of the dark current. The studied samples are Formed mainly by a network of nanowires, suggesting the separation of the electron Hamiltonian into a longitudinal and a transversal part. The last one can be well described by a two-dimensional (2D) cylindrical infinite quantum well? whose levels determine the dark current activation energies. The storage oxidation induces modifications both in the number and the values of the activation energies, which are in excellent agreement with our model. (C) 1998 Elsevier Science Ltd. All rights reserved.

3123. Electron and hole trapping in PbCl2 and PbCl2 : Tl crystals

Authors: Nistor, SV; Goovaerts, E; Stefan, M; Schoemaker, D

Published: MAY 1998, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 141, 541, DOI: 10.1016/S0168-583X(98)00051-2

Formation of primary paramagnetic point defects under low temperature X-ray irradiation have been studied by ESR and optical absorption in pure and thallium doped PbCl2 single crystals. Besides Pb-2(3+) self-trapped electron (STEL) centers the PbCl2 : Tl crystals exhibit trapped-electron (PbTl)(+)-type centers. Based on production properties of paramagnetic centers it is suggested that besides forming Tl-2 divided by centers the holes are self trapped at pairs of neighbouring Cl- anions resulting in V-k type centers with various orientation and length of the Cl-Cl axis. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

3124. Brownian motion and polymer statistics on certain curved manifolds

Authors: Mondescu, RP; Muthukumar, M

Published: APR 1998, PHYSICAL REVIEW E, 57, 4419, DOI: 10.1103/PhysRevE.57.4411

In this paper we have considered a Gaussian polymer chain of length L as an intrinsic object enclosed on a surface embedded in the Euclidean space. When the surfaces are the sphere SD-1 in D dimensions and the cylinder, the cone and the curved torus in R-3. We have calculated analytically and numerically (using the diffusion equation and the path-integral approach) the probability distribution function G(R\R';L) of the end-to-end vector R-R' and the mean-square end-to-end distance ((R-R')(2)) of the polymer chain. Our findings are that the curvature of the surfaces induces a geometrical localization area; at short scales (L-->0) the polymer is locally flat and the mean-square end-to-end distance is just the Gaussian value Ll (l = Kuhn length), independent of the metric properties of the surface; at large scales (L-->infinity), ((R-R')(2)) tends to a constant value in the sphere case, and it is linear in L for the cylinder and reaches different constant values las a function of the geometry of the surface) for the curved torus. In the case of the cone, contraction of the chain is induced at all length scales by the presence of the vertex, as a function of the opening angle 2 alpha and the end position R' of the chain. Explicit crossover formulas are derived for G(R\R';L) and ((R-R')(2)).

3125. Theoretical model for carriers transport in nanocrystalline porous silicon films

Authors: Ciurea, ML; Iancu, V; Pavelescu, G; Baltog, I

Published: 1998, CAS'98 PROCEEDINGS - 1998 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 21ST EDITION, VOLS 1 AND 2, 112, DOI:

A quantum confinement model is proposed to explain the carriers transport in a nanowire network of porous silicon. The electron Hamiltonian is written as the sum of the longitudinal and the transversal contributions. The last one corresponds to a two-dimensional infinite cylindrical quantum well, whose energy levels determine the activation energies observed in the temperature dependence of the dark current. The model is in excellent agreement with the experimental data.

3126. Change of the optical properties of porous silicon by post anodization treatments

Authors: Pavelescu, G; Ciurea, ML; Mihut, L; Galeata, G; Lengyel, E; Baltog, I; Roger, JP

Published: 1998, CAS'98 PROCEEDINGS - 1998 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 21ST EDITION, VOLS 1 AND 2, 458, DOI:

Optical properties of as prepared porous silicon (PS) were compared with those of thermally treated and chemically cleaned samples. The change of the photoluminescence (PL) spectra correlated with ellipsometric. reflectance and Raman measurements leads us to conclude that the adsorbed species in the PS nanocrystalline structure play an important role in the origin of the PI emission, at least for as - anodized samples.

3127. Photoelectric effects in chemical solution deposited Bi4Ti3O12 thin films

Authors: Pintilie, L; Alexe, M; Pignolet, A; Hesse, D

Published: DEC 1998, JOURNAL DE PHYSIQUE IV, 8, 104, DOI: 10.1051/jp4:1998916

Bismuth titanate ferroelectric thin films were deposited on platinum coated silicon using chemical solution deposition. Photoconductive and photovoltaic effects were observed both in continuous and modulated light. With the increasing of the annealing temperature the maximum of the photoconductive signal spectral distribution is moving toward longer wavelengths, from 340 nm to 370 nm. The existence of the photovoltaic effect could be due to some potential barriers existing at the grain boundaries and me enlargement of its spectral distribution toward longer wavelengths could be due to the presence of some traps at the grain boundaries.

3128. X-ray-absorption features from multielectron excitations above Xe L edges

Authors: Ito, Y; Vlaicu, AM; Tochio, T; Mukoyama, T; Takahashi, M; Emura, S; Azuma, Y

Published: FEB 1998, PHYSICAL REVIEW A, 57, 878, DOI: 10.1103/PhysRevA.57.873

The x-ray-absorption cross section above the L edges in xenon gas has been measured using synchrotron radiation. Multielectron excitation effects are investigated over a few hundred eV region from the Xe L-I, L-II, and L-III edges and the contributions from the effects of shake-up and shake-off to the photoabsorption spectrum are elucidated. Several multielectron excitation features were detected and analyzed by the theoretical energy of the shake-up process. Previous observations of the [2(s,p)5(s,p)] and [2(s,p)4d] transitions have been confirmed. [2(s,p)4p] transitions are clearly identified in the present study. It is very difficult to detect the [2s3s] multielectron transition with the sensitivity of similar to 2.0 x 10(-4) at the L edge jump. The [2s3d] edge was distinguished using the first derivative of the absorption curve. A new transition is found between [2(s,p)4p] and [2(s,p)4d] transitions and identified as a three-electron transition [2(s,p)4d5p]. Moreover, the difference in the behavior of the multielectron excitation as a function of x-ray energy among the L-I and L-II, or L-III edges is confirmed and investigated. [S1050-2947(98)01802-2].

3129. Silicon linear image sensors for photometry

Authors: Cimpoca, V; Cengher, D; Crisan, C; Olariu, N; Oros, C; Cimpoca, M

Published: 1998, CAS'98 PROCEEDINGS - 1998 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 21ST EDITION, VOLS 1 AND 2, 70, DOI:

The paper describes a new linear image sensor for photometry by applying bipolar technology (Standard Buried Collector-SEC) to the manufacture of self-scanning linear photodiode arrays. On a monolithic chip we have designed 128 to 1024 linear photodiodes, demultiplexing system and signals processing system. A dynamic simulation and a real-time measurement have been implemented, that allow to take into account every operational phase of detection. The dialogue between the various functions is established by message's transmission, using common data areas stored on disks or in central memory of PC compatible computer.

3130. Interaction of alpha particle beams with metallic glasses

Authors: Sorescu, M; Barb, D

Published: SEP 18 1998, ACTA MATERIALIA, 46, 5531, DOI: 10.1016/S1359-6454(98)00179-7

Samples of Fe40Ni38Mo4B18, Fe78B13Si9 and Fe66Co18B15Si1 metallic glasses, selected with respect to the different values of their magnetostriction constants, were irradiated with alpha particle beams (W = 2.8 MeV) using radiation doses of 10(16) and 10(17)/cm(2). The fundamental effects underlying the interaction of alpha particle beams with amorphous magnets were studied by transmission and conversion electron Mossbauer spectroscopy (CEMS), hysteresis loops and a.c. susceptibility measurements, and scanning electron microscopy (SEM). The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. Differences between bulk and surface behaviors of the magnetic texture and constituent phases were evidenced. Radiation-driven changes in the saturation magnetic moment, coercive held, real and imaginary components of the a.c. response were observed for all samples studied and found to depend on the radiation dose employed. The surface morphology of the radiation-induced crystalline precipitates was shown to vary as a function of composition, such that both spherical and dendritical modes of growth were observed. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in these systems. (C) 1998 Acta Metallurgica inc. Published by Elsevier Science Ltd. All rights reserved.

3131. Anodization of n and p-GaAs in ethylene glycol-water-tartaric acid mixture

Authors: Buda, M; Cengher, D; Diaconescu, D; Buda, M

Published: JUL 1998, JOURNAL OF APPLIED ELECTROCHEMISTRY, 28, 749, DOI: 10.1023/A:1003254429884

This paper describes the pulsed constant current anodization of n(+) and p(+)-GaAs in ethylene glycol-water-tartaric acid (AGW) mixture, up to 17 mA cm(-2). A 0.26 mu m thick film is obtained for a final voltage of 135V at 4.3 mA cm(-2) pulsed current density. Cyclic voltammetry showed that the initial growth of a monolayer anodic pride can be described by a charge transfer with uncompensated cell resistance model. The relationship between peak current, peak voltage and scan rate has been verified for this process, based on the above model.

3132. Quantum analog of channeled electron trajectories in periodic magnetic and electric fields

Authors: Manolescu, A; Zwerschke, SDM; Nita, M; Gossmann, UJ; Gerhardts, RR

Published: DEC 1998, PHYSICA B-CONDENSED MATTER, 256, 379, DOI: 10.1016/S0921-4526(98)00564-X

We calculate the quantum states corresponding to the drifting and channeled classical orbits in a two-dimensional electron gas (2DEG) with strong magnetic and electric modulations along one spatial direction, x. The channeled states carry high, concentrated currents along the y-axis, and are confined in an effective potential well. The quantum and the classical states are compared. (C) 1998 Elsevier Science B.V. All rights reserved.

3133. Theoretical calculation of diamond damage by pi(+)/pi(-) mesons in the Delta(33) resonance energy range

Authors: Lazanu, I; Lazanu, S; Borchi, E; Bruzzi, M

Published: APR 1 1998, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 406, 266, DOI:

The non-ionising energy loss and the concentration of primary radiation defects induced by charged pions, in the energy range 50-500 MeV, in bulk diamond have been calculated in order to characterise its radiation resistance. The mechanisms by which the pion imparts energy to the diamond lattice have been analysed and their contribution has been evaluated starting from the nuclear data on pion-carbon interaction. The energy partition of the primary recoil nuclei between ionisation and displacements has been calculated in the frame of the Lindhard theory. It has been found that diamond, from the point of view of concentration of primary defects, is approximately one order of magnitude harder than silicon in pion fields, in the energy range of the Delta(33) resonance, and about two orders of magnitude harder than GaAs in the same energy region. (C) 1998 Elsevier Science B.V. All rights reserved.

3134. A Mossbauer spectroscopy and magnetic study of FeRh

Authors: Rosenberg, M; Kuncser, V; Crisan, O; Hernando, A; Navarro, E; Filoti, G

Published: JAN 1998, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 177, 136, DOI: 10.1016/S0304-8853(97)00662-8

A Mossbauer and magnetic study of FeRh has been undertaken in order to understand better the remarkable properties of both melt-spun BCC and ball-milled FCC-phases of the anti-invar FeRh alloy. (C) 1998 Elsevier Science B.V. All rights reserved.

3135. Synthesis and properties of Ni-Zn ferrite thin films

Authors: Neamtu, J; Nogues, M; Gavrila, H; Barb, D

Published: JUN 1998, JOURNAL DE PHYSIQUE IV, 8, 260, DOI: 10.1051/jp4:1998261

We have investigated the magnetic and structural properties of polycrystalline Ni-Zn ferrite thin films with thicknesses of about 1000 Angstrom. The films were prepared by R F sputtering deposition in 1.5x10(-3) mbar argon atmosphere, using targets with nominal composition Ni0.7Zn0.3Fe2O4. The effects of substrate temperature and post deposition heat treatment of thin films were examined. The X-ray spectra of Fe-Ni-Zn oxides deposits reveal the formation of spinel phase of Ni-Zn ferrite. that is characteristic for these materials. only for temperatures higher than 500 degrees C. TEM and ED indicate that the initially amorphous thin films. deposited at 100 degrees C, become polycrystalline by heat treatment. The grain size of the crystallites is 800 Angstrom to 1000 Angstrom for Ni-Zn ferrite thin films annealed at 900 degrees C. V.S.M. measurements show coercive fields of 12 kA/m for thin films annealed at 900 degrees C. which are larger than those found for Ni-Zn ferrite targets. This value of coercive field is related to the shape anisotropy originated by the film microstructure and with the increase in the number of low angle grain boundaries, which act as pinning sites for domain walls. Saturation magnetization values of 220-250mT for Ni-Zn ferrite thin films are higher than half of bulk values.

3136. Modeling of photostructural effects in chalcogenide glasses

Authors: Popescu, M; Lorinczi, A; Sava, F

Published: OCT 1998, JOURNAL DE PHYSIQUE IV, 8, 14, DOI: 10.1051/jp4:1998502

The reversible photostructural effects observed in the amorphous thin films and in chalcogenide glasses based on arsenic have been explained with the help of computer relaxed models. Two photostructural mechanisms have been established: the incorporation of the chalcogenide molecular fraction into the disordered layers and the change of the relative positions of the atoms in the layers without destroying the bonding network. In the frame of this atomic scale mechanisms it is possible to explain the reversible photodarkening and the photoanisotropy observed in the chalcogenide thin Alms and bulk glasses.

3137. Cobalt-manganese oxide thin films thermistors obtained by MOD

Authors: Dragoi, V; Alexe, M

Published: 1998, CAS'98 PROCEEDINGS - 1998 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 21ST EDITION, VOLS 1 AND 2, 300, DOI:

Co1.4Mn1.6O4 (CMO) thin films were deposited onto silicon by Metalorganic Decomposition (MOD) method. Structure, composition and morphology were investigated by Electron Dispersive X-Ray Spectroscopy (EDX) and X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Electrical measurements showed possible applications as negative temperature coefficient (NTC) thermistors.

3138. XTEM study of Al doped TiO2 anatase epitaxial films deposited on MgO by pulse laser deposition

Authors: Teodorescu, VS; Blanchin, MG; Champeaux, C; Garapon, C

Published: 1998, ELECTRON MICROSCOPY 1998, VOL 2: MATERIALS SCIENCE 1, 658, DOI:

3139. Electroluminescence of strained SiGe/Si selectively grown above the critical thickness for plastic relaxation

Authors: Stoica, T; Vescan, L; Goryll, M

Published: MAR 15 1998, JOURNAL OF APPLIED PHYSICS, 83, 3373, DOI: 10.1063/1.367104

Electroluminescence of strained Si0.80Ge0.20Si(001) pin diodes has been investigated experimentally and by quantitative modeling. The key aspect of this investigation was that by selective epitaxial growth the experimental critical thickness for plastic relaxation (80 nm at T-epi=700 degrees C and large areas) could be increased in finite pads. SiGe layers with thickness of 60, 72 or 370 nm have been grown within the intrinsic i region of pin structures. Samples free of misfit dislocations revealed electroluminescence with the SiGe no-phonon peak and its transversal optical-phonon replica corresponding to interband transitions. It was found that by increasing the thickness of the SiGe layer the drop in the electroluminescence with increasing temperature could be shifted to higher temperature, so that for the 370 nm thick SiGe sample the emission was observed to persist still at 300 K. Modeling based on drift-diffusion and carrier recombination equations was used to simulate the current-voltage characteristics of the pin diodes and their band gap electroluminescence. It was found that the modeling results can account for the temperature and thickness dependence of the electroluminescence. Hole and electron Shockley-Read-Hall recombination times could be evaluated. (C) 1998 American Institute of Physics.

3140. SERS spectra of poly(3-hexylthiophene) in oxidized and unoxidized states

Authors: Baibarac, M; Lapkowski, M; Pron, A; Lefrant, S; Baltog, I

Published: SEP 1998, JOURNAL OF RAMAN SPECTROSCOPY, 29, 832, DOI: 10.1002/(SICI)1097-4555(199809)29:9<825::AID-JRS309>3.3.CO;2-U

Surface enhanced Raman scattering (SERS) is being increasingly used for the study of the structural properties of conducting polymer thin films. It is generally accepted that the enhancement process has an electromagnetic origin, arising from the excitation of surface plasmons in the metal support on which the polymer film is deposited. However, the electromagnetic enhancement is also accompanied by a chemical process, for which available experimental data are scarce. The chemical process originates from the increase in the polarizability of the molecules at the metal surface under the action of the incident radiation, which leads to the formation of new chemical bonds with the atoms of the metal support. The present work was devoted to the study of the SERS spectra of poly(3-hexylthiophene) deposited on rough Ag and Au supports by evaporating the solvent from a solution of known concentration. The experiments revealed the existence of a chemical surface effect. The results obtained show that the SERS spectra depend on the oxidizing properties of the metal surface and on the nature of the solvent. This dependence is explained by the existence of some interfacial reactions that lead to the formation of interface compounds of the type MeX (Me = Ag or Au, X = Cl or O). The SERS measurements reported here reveal an increase in the intensities of the Raman lines, accompanied by a modification of the corresponding intensity ratios, when the degree of doping is increased. It was observed for the first time by SERS spectroscopy that the doping of 3-PHT with FeCl3 leads to the appearance of a state of disorder in the structure of the macromolecular chain, as a result of steric hindrance effects. (C) 1998 John Whey & Sons, Ltd.

3141. The diffraction efficiency in Fe : PVA explained by Mossbauer spectroscopy

Authors: Kuncser, V; Filoti, G; Podgorsek, R; Biebricher, M; Franke, H

Published: SEP 21 1998, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 31, 2318, DOI: 10.1088/0022-3727/31/18/017

The UV exposure of Fe:PVA thin films induces modifications of both the refractive index and the absorption coefficient. M-line spectroscopy showed the variation of the refractive index while Mossbauer measurements present the Fe2+/Fe3+ ratio versus the exposure energy. The diffraction efficiency experimental data were satisfactorily explained in correlation with the Fe2+/Fe3+ ratio.

3142. EPR study of low temperature phase transitions in Mn2+ doped K2ZnCl4

Authors: Grecu, MN; Cevc, P; Blinc, R

Published: JAN 1998, SOLID STATE COMMUNICATIONS, 105, 15, DOI: 10.1016/S0038-1098(97)10041-2

The EPR spectra of Mn2+ doped K2ZnCl4 show an anomalously large broadening of the Zn site Mn2+ lines between 152.5 K and 145 K, i.e. just above the transition to the low temperature commensurate phase of A1a1 symmetry. The line broadening is related to a distribution of rotations of the ZnCl4 tetrahedra and supports the existence of a second incommensurate phase in this temperature range as reported by Gesi. (C) 1997 Published by Elsevier Science Ltd.

3143. QHE, magnetoresistance and disordered transport on 2D mesoscopic plaquettes

Authors: Aldea, A; Gartner, P; Nita, M

Published: JAN 1998, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 205, 356, DOI: 10.1002/(SICI)1521-3951(199801)205:1<351::AID-PSSB351>3.3.CO;2-Z

The transport properties of a rectangular mesoscopic plaquette in the presence of a perpendicular magnetic field are studied in a tight-binding model with randomly distributed traps. The longitudinal and Hall resistances are calculated in the four-probe Landauer-Buttiker formalism which accounts automatically both for the quantum coherence and the trapping-induced localization. The localized character of eigenvectors and the specific aspect of the density of states at a given magnetic flux are correlated with the behaviour of the mentioned resistances as function of the Fermi energy. The Hall insulator and quantum Hall regimes are evidenced. The magnetic field dependence of the configurational averages of the longitudinal and Hal; resistance is studied in a purely quantum-mechanical approach. Both, negative and positive magnetoresistances are found.

3144. On the photoluminescence decay in porous silicon films

Authors: Baltog, I; Ciurea, ML; Pavelescu, G; Mihut, L; Baibarac, M

Published: 1998, FIFTH CONFERENCE ON OPTICS (ROMOPTO '97), PTS 1 AND 2, 3405, 626, DOI: 10.1117/12.312818

The photoluminescence (PL) decay measurements were performed on porous silicon films. It was observed that the two components of FL, one of them fast (ns) and the other slow (mu s or ms sometimes) have different contributions to PL signal, depending on the wavelength of the excitation light. The slow component of PL was in details investigated. Time decay cures for different excitation (337.1 nm, 470 nm and 550nm) and emission (550, 650, 700, 800 and 860 nm) wavelengths and also for different excitation intensities were taken. All decay curves were fitted with a stretched exponential. The slow component of PL was proposed to be attributed to the radiative recombination on surfaces.

3145. Electrochemical performance and chemical properties of oxidic cathode materials for 4 V rechargeable Li-ion batteries

Authors: Ott, A; Endres, P; Klein, V; Fuchs, B; Jager, A; Mayer, HA; Kemmler-Sack, S; Praas, HW; Brandt, K; Filoti, G; Kunczer, V; Rosenberg, M

Published: MAR 30 1998, JOURNAL OF POWER SOURCES, 72, 8, DOI: 10.1016/S0378-7753(97)02772-9

The systems Li1-xMn2-xO4-delta acid Li1-xNi1+xO2 were studied as oxidic cathode materials for 4 V rechargeable Li-ion cells. From a comparison of the results it follows that the spinel system can be subdivided into three regions: in region I (0 less than or equal to x < 0.05) the electrochemical performance is unsatisfying due to a large volume reduction of about 7.5%, inducing stress, multiphase materials and capacity fading. Region II (0.05 less than or similar to x less than or similar to 0.2) contains the best cathode material with a composition near x = 0.1. The spinel framework is stable against Li extraction. In region III (0.2 less than or equal to x less than or equal to 1/3) the capacity is too low for an application in the 4 V region. In the system Li1-xNi1+xO2 the highest capacity is observed for LiNiO2 with x = 0. Experimental difficulties during material synthesis were overcome by suppression of the decomposition of LiNiO2 into Li1-xNi1+xO2, Li2O and O-2. (C) 1998 Elsevier Science S.A. All rights reserved.

3146. Mn(II) recovery from aqueous systems by flotation

Authors: Stoica, L; Dinculescu, M; Plapcianu, CG

Published: OCT 1998, WATER RESEARCH, 32, 3030, DOI: 10.1016/S0043-1354(98)00065-7

Various aqueous systems produced by different technologies can contain Mn(II) in the concentration range of 50 divided by 1000 mg x l(-1), which represents a pollution source but also can be used for the separation-recovery of useful compounds. The present paper presents the results of the researches concerning Mn(II) recovery from "model" and real aqueous systems by the precipitate flotation method, dissolved air flotation (DAF) variant, with izoalkylcarboxillic acid as collector. The following influencing factors were studied: pH, collector concentration, metallic ion concentration, necessary gas flow and foam processing with Mn(II) recovery as oxide. The separation mechanism by the collector-Mn(II) interaction at optimal conditions is also studied. Therefore, a correlation of chemical analysis results with electronic and vibrational spectra and thermal analysis is made. The results of the experimental data plead for the recovery separation of Mn(II) from aqueous systems and its recovery as oxide after thermal decomposition of the species contained in the foam. (C) 1998 Elsevier Science Ltd. All rights reserved.

3147. Elastic model for twisted nematic textures in OOBA layers

Authors: Frunza, S; Frunza, L; Petrov, M; Barbero, G

Published: FEB 1998, LIQUID CRYSTALS, 24, 218, DOI: 10.1080/026782998207389

An elastic model for the twisted nematic texture observed in nematic cells containing octyloxybenzoic acid is proposed. According to the model the twisted textures are due to the presence of cybotactic groups which are responsible for the chirality of the liquid crystal. We show that by assuming for the density of cybotactic groups a critical temperature behaviour close to a special temperature, the experimental data can be well interpreted by our mechanical model.

3148. The inhibition of the corrosion of Armco iron in hydrochloric acid solutions by organic surfactants

Authors: Branzoi, V; Branzoi, F; Baibarac, M; Popa, MV

Published: JUN 1998, REVUE ROUMAINE DE CHIMIE, 43, 513, DOI:

The polarization behaviour of Armco iron in solutions of HCl with and without inhibitors has been studied by potentiostatic method. At lower overvoltage values the dissolution process is controlled by activation, while at higher overvoltage values the dissolution process is controlled by diffusion. The inhibition of this metal corrosion in the aqueous solutions of HCl has been studied using three surfactants. Under the critical micelle concentration the inhibition of those three surfactants is negligible. At a concentration higher than critical micelle concentration, the inhibiting action of surfactants increases rapidly. The process of inhibition was attributed to the formation of the adsorbed film on the metal surface, that protects the metal against the corrosive agents.

3149. Syntheses and structural study of trinuclear iron acetates [Fe3O(CH3COO)(6)(H2O)(3)]Cl center dot 6H(2)O and [Fe3O(CH3COO)(6)(H2O)(3)][FeCl4]center dot 2CH(3)COOH

Authors: Shova, SG; Cadelnic, IG; Gdaniec, M; Simonov, YA; Jovmir, TC; Meriacre, VM; Filoti, G; Turta, CI

Published: SEP-OCT 1998, JOURNAL OF STRUCTURAL CHEMISTRY, 39, 761, DOI: 10.1007/BF02903548

The structure of two trinuclear iron acetates [Fe3O(CH3COO)(6)(H2O)(3)]Cl . 6H(2)O (I) and [Fe3O(CH3COO)(6)(H2O)(3)][FeCl4]. 2CH(3)COOH (II) was determined by X-ray diffraction analysis. Crystals I and II are ionic and belong to the orthorhombic system with parameters a = 13.704(3), b = 23.332(5), c = 9.167(2) Angstrom, R = 0.0355, space group P2(1)2(1)2 for I and a = 10.145(4), b = 15.323(6), c 22.999(8) Angstrom, R = 0.0752, space group Pbc2(1) for II. The complex cation [Fe3O(CH3COO)(6)(H2O)(3)](+) has a mu(3)-O-bridged structure typical for trinuclear iron(III) compounds. As shown by Mossbauer spectroscopy, the iron(III) ions are in the high-spin state. In trinuclear cations, antiferromagnetic exchange interaction takes place between the Fe(III) ions with the exchange parameter J = -26.69 cm(-1) for N (Heisenberg-Dirac-Van Vleck model for D-3h symmetry).

3150. The gallophosphate molecular sieve cloverite as a host for liquid crystals

Authors: Zubowa, HL; Kosslick, H; Carius, HE; Frunza, S; Frunza, L; Landmesser, H; Richter, M; Schreier, E; Steinike, U; Fricke, R

Published: MAY 1998, MICROPOROUS AND MESOPOROUS MATERIALS, 21, 474, DOI: 10.1016/S1387-1811(98)00065-1

The gallophosphate cloverite has been investigated because of its applicability to act as a host for larger molecules. 4-n-pentyl-4'-cyanobiphenyl (5CB) and 4-n-octyl-4'-cyanobiphenyl (8CB) liquid crystals were used as guest molecules. The results show that the adsorption of liquid crystals from the gas phase proceeds without destruction of the cloverite structure. The typical phase properties of the liquid crystals remain unchanged after adsorption on cloverite: however, they appear with lower intensity in the DSC curve. A new smectic phase seems to be formed inside the cloverite pore system. FTIR measurements show the interaction of 5CB with the Lewis and Bronsted acid sites of cloverite. Desorption of liquid crystals out of the pore system proceeds slowly under liberation of the POH groups of the lattice. In summary, the results show that the gallophosphate cloverite is a suitable host for large molecules. (C) 1998 Elsevier Science B.V. All rights reserved.

3151. Crystallization of a-Si : H films by rapid thermal annealing

Authors: Szekeres, A; Gartner, M; Vasiliu, F; Marinov, M; Beshkov, G

Published: 1998, JOURNAL OF NON-CRYSTALLINE SOLIDS, 227, 957, DOI: 10.1016/S0022-3093(98)00263-4

The effect of rapid thermal annealing on the structural properties of hydrogenated amorphous silicon (a-Si:H) as a function of annealing time and temperature is studied by spectroscopic ellipsometry in the spectral region of 300-1200 nm, X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED) methods. After annealing at 850 and 1050 degrees C, the a-Si:H films are predominantly amorphous and consist of two sublayers which contain a mixture of amorphous and crystalline silicon and voids, the volume fractions of which are temperature-dependent. Annealing of these a-Si:H samples at 1250 degrees C results in a completely crystallized and void-free structure. (C) 1998 Elsevier Science B.V. All rights reserved.

3152. Pulsed-laser and alpha particle irradiation effects in Fe-based glassy ferromagnets

Authors: Toacsan, MI; Barb, D; Sorescu, M; Constantinescu, B; Jeloaica, L

Published: 1998, FIFTH CONFERENCE ON OPTICS (ROMOPTO '97), PTS 1 AND 2, 3405, 317, DOI: 10.1117/12.312772

A comparatively study of pulsed - laser and alpha particle irradiation effects in metallic glasses has been performed in order to understand the relationship between magnetic behaviour and select variations in the structural characteristics of alloy phases. Samples of Fe78B13Si9 and Fe66CO18B15Si metallic glasses were irradiated with a pulsed excimer laser (lambda=308nm, tau=10ns) and alpha particle beams (W = 2.8 MeV) using radiation doses of 10(16) and 10(17)cm(-2). Irradiation - driven changes in the magnetic anisotropy and phase equilibrium of alloy samples were studied by Mossbauer Spectroscopy and scanning electron microscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformations or revitrification depend on the specific irradiation and sample composition.

3153. Study by transmission electron microscopy and electron diffraction of thin polyethylene films

Authors: Popescu-Pogrion, N; Tirnovan, M

Published: APR 1 1998, THIN SOLID FILMS, 317, 234, DOI: 10.1016/S0040-6090(97)00521-X

Polyethylene thin films of different thickness have been obtained by evaporation method, We have produced the treeing discharge by electron beam irradiation. The films have been examined by transmission electron microscopy (TEM) and electron diffraction (ED), before and after irradiation. It is observed that: (1) the polyethylene thin films have a structure of the fine spherulites before irradiation; (2) structural damages (channels, treeing figures and zones in which the material was melted and resolidified) accompanying the space charge produced in thin polyethylene films. (C) 1998 Elsevier Science S.A.

3154. Electrical properties of sandwich structures with aluminum nitride layers

Authors: Tanase, M; Morosanu, C; Dumitru, V; Tugulea, L; Tomozeiu, N

Published: 1998, CAS'98 PROCEEDINGS - 1998 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 21ST EDITION, VOLS 1 AND 2, 224, DOI:

Electrical properties of adherent, low stressed aluminum nitride films prepared by magnetron sputtering have been studied. Arrhenius plots in the 100 degrees-170 degrees C range of temperature and transient current curves with different bias steps (af room temperature and 150 degrees C) have been performed. The conduction activation energy has been found and ifs dependence on subsequent annealings has been studied. A phenomenological conduction model at the ITO-AIN interface based on the shape of the transient curves has been elaborated The conditions of behaviour of AlN as a highly insulating layer (sputtering conditions, thicknesses, anealing temperatures) have been established.

3155. Hyperfine fields and Fe magnetic moments in Fe-Rh alloys: a Mossbauer spectroscopy study

Authors: Filoti, G; Kuncsea, V; Navarro, E; Hernando, A; Rosenberg, M

Published: AUG 21 1998, JOURNAL OF ALLOYS AND COMPOUNDS, 278, 68, DOI: 10.1016/S0925-8388(98)00591-X

The Mossbauer spectra of the melt-spun and subsequently intensively ball-milled Fe65Rh35, Fe50Rh50 and Fe26Rh74 alloys with fee structure are characterized at 4.2 K by broad hyperfine field distributions. The magnetic critical temperatures are 60(5) for the first one and, respectively, 85(5) K for the second and the latter composition, in good agreement with recent magnetic susceptibility studies. The distributions arise as result of the chemical disorder, local strains and atomic displacements, owing to the drastic ball-milling process. The values of the Fe magnetic moments at the peaks of the hyperfine field distributions reached 1.1, 1.6 and 1.9 mu(B) with decreasing iron concentration in semi-quantitative agreement with earlier experimental and recent theoretical evaluations of Fe moments in gamma-Fe and fee Fe50Rh50. Above 400 K an irreversible transformation to the bcc structure occurs for the two Fe-rich alloys with three types of Fe sites in the Fe richest alloy and two different Fe sites in the partially disordered Fe50Rh50. Our analysis allowed us to describe the nn atomic arrangements around these sites. (C) 1998 Elsevier Science S.A. All rights reserved.

3156. Three-dimensional memory effect in fluorescent photosensitive glass activated by europium and cerium

Authors: Pavel, E; Mihailescu, IN; Hening, A; Vlad, VI; Tugulea, L; Diamandescu, L; Bibicu, I; Chipara, M

Published: AUG 15 1998, OPTICS LETTERS, 23, 1306, DOI: 10.1364/OL.23.001304

The persistent extinction of fluorescence emission of Eu(3+) in glasses activated with europium and cerium is reported for the first time to the authors' knowledge. The glass samples containing EU(3+) and Ce(3+) were initially colorless and transparent and exhibited intense emission peaks at 592 ana 612 nm assigned to the (5)D0-(7)F(1,2) transitions of EU3+. Th, complete extinction of the Eu(3+)-ion emission was obtained as an effect of multipulse excimer-UV-laser (lambda = 248 nm, tau(FWHM) greater than or equal to 20 ns) irradiation of the glass samples. Fluorescence microscopy, Mossbauer spectrometry, and electron spin resonance were applied for investigation of the modifications induced by the laser treatment. As a decisive proof of the extinction of fluorescence me succeeded in recording three-dimensional fluorescent photographic patterns within the activated samples. (C) 1998 Optical Society of America.

3157. Nanocrystalline gold in Au-doped thin C-60 films

Authors: Devenyi, A; Manaila, R; Belu-Marian, A; Macovei, D; Manciu, M; Popescu, EM; Tanase, M; Fratiloiu, D; Mihai, ND; Barna, PB; Labar, J; Safran, G; Kovacs, A; Braun, T

Published: DEC 14 1998, THIN SOLID FILMS, 335, 265, DOI: 10.1016/S0040-6090(98)00871-2

Thin Au-C-60 films with global composition AuxC100-x (x between 0.35 and 4.50 at.%) were prepared by vacuum co-deposition and investigated by X-I ay diffraction, EDS, XTEM and electrical transport. Evidence indicated the formation of distorted nanocrystalline Au, presumably stabilized by interface electron transfer into C-60 LUMO. Electrical results are interpreted in the frame of the dominant current model, with a continuous density of localized states induced by Au in the C60 gap. There is also evidence for variable range hopping at low temperatures. (C) 1998 Elsevier Science S.A. All rights reserved.

3158. Bi4Ti3O12 ferroelectric thin film ultraviolet detectors

Authors: Pintilie, L; Alexe, M; Pignolet, A; Hesse, D

Published: JUL 20 1998, APPLIED PHYSICS LETTERS, 73, 344, DOI: 10.1063/1.121828

Bi4Ti3O12 (BiT) ferroelectric thin films were used as photoconductive or photovoltaic ultraviolet detectors. The maximum of the spectral distribution lies around 370 or 390 nm, depending on whether the incident light is continuous or modulated. The maximum current responsivity obtained for the films annealed at 700 degrees C is about 0.01 A/W. The specific detectivity is 5.5 x 10(8) cm W-1 Hz(1/2) at a modulation frequency of 20 Hz. The frequency characteristics of the photovoltaic signal measured in modulated light suggests a 1/f frequency dependence of this signal. (C) 1998 American Institute of Physics.

3159. Non-ionising energy deposition of pions in GaAs and Si for radiation damage studies

Authors: Lazanu, S; Lazanu, I; Biggeri, U; Borchi, E; Bruzzi, M

Published: FEB 1998, NUCLEAR PHYSICS B, 414, DOI: 10.1016/S0920-5632(97)00595-1

The dependence of the displacement damage induced by pions in GaAs has been evaluated, in the energy range 50 -1000 MeV, using the Lindhard theory and parametrised values of the pion-nucleus interaction. The curves corresponding to the NIEL produced by protons, neutrons, and pions in Si and in GaAs intersect, in the limit of calculation errors, in the region 50 - 80 MeV, at a NIEL of 2 - 5.5 MeV cm(2)/g. The energy dependence of the NIEL of pions in Si and GaAs is discussed in correlation with the simulated pion spectra at new hadron colliders.

3160. SERS spectra of polyaniline thin films deposited on rough Ag, Au and Cu. Polymer film thickness and roughness parameter dependence of SERS spectra

Authors: Baibarac, M; Cochet, M; Lapkowski, M; Mihut, L; Lefrant, S; Baltog, I

Published: JUL 15 1998, SYNTHETIC METALS, 96, 70, DOI: 10.1016/S0379-6779(98)00065-4

Surface-enhanced Raman scattering (SERS) has lately proved to be an effective technique which has led to its increasing application for studying the structural properties of conducting polymer thin films. It is generally accepted that the enhancement process has an electromagnetic origin arising from the excitation of surface plasmons (SPs) in the metal support on which the polymer film is deposited. However, the electromagnetic enhancement is also accompanied by a chemical process, on which only scarce experimental data are available at present. The chemical process originates in an increased polarizability of the molecules at the metal surface under the action of an incident radiation, as a result of which new chemical bonds are formed with the atoms of the metal support. This paper is devoted to the study of the SERS spectra under 1064 nm excitation for two forms of polyaniline, one of the emeraldine base type and the other of the emeraldine salt type. Our purpose has been to identify the chemical effects at the polymer/metal interface that are involved in specific modifications of the SERS spectra. The following results concerning SERS spectrum variation with metal support type (AE, Au and Cu) have been obtained. An oxidation of emeraldine base taking place at the polymer/metal interface has been revealed. In the case of emeraldine salt, an oxidized form of polyaniline, the SERS spectra remain unchanged regardless of the changes in the metal support, which proves the stability of this form. A new result has been obtained as SERS spectroscopy revealed an electron delocalization process taking place in the emeraldine salt molecule as a result of an electron transfer from metal to the polymer molecule occurring on the level of quinoid rings. The concept of a rough Raman-active surface has been clarified by using a parameter Wa, similar to the grating groove depth/grating periodicity ratio which occurs when a diffraction grating is used as optic coupler. (C) 1998 Elsevier Science S.A. All rights reserved.

3161. Effect of aluminium on phase stability in the Gd3Co11(B,Al)(4) system

Authors: Galatanu, A; Kottar, A; Artigas, M; Plugaru, N; Lazar, DP

Published: NOV 14 1997, JOURNAL OF ALLOYS AND COMPOUNDS, 262, 362, DOI: 10.1016/S0925-8388(97)00408-8

In the Gd3Co11B4-xAlx alloys the ternary 3:11:4 phase with Ce3Co11B4 structure is formed with an Al content x approximate to 0.5 substituting for boron. The fraction of this phase decreases as the boron content decreases in the samples. The Al, Co and Gd in excess form Gd(Co,Al)(5) with CaCu5-type structure, and the fraction of this phase increases with increasing x. X-ray diffraction results show that these phases are not at equilibrium. A strong preference of aluminium for the 3g site in the CaCu5-type structure is determined by Rietveld refinement of the X-ray diffraction pattern of the end-series compound (x = 4). (C) 1997 Elsevier Science S.A.

3162. Optical and Mossbauer study of the real time holographic organometallic material Fe:PVA

Authors: Kuncser, V; Avramescu, A; Filoti, G; Rotaru, P; Podgorsek, R; Biebricher, M; Franke, H

Published: JUL 5 1997, JOURNAL OF ALLOYS AND COMPOUNDS, 256, 275, DOI: 10.1016/S0925-8388(96)03111-8

The Fe:PVA thin films were studied by optical and Mossbauer spectroscopy. Both the absorption and Mossbauer spectra are dependent on the PVA dilution and ferric chloride concentration. A strong correlation between the optical and Mossbauer results was found, indicating the major role of the iron electronic local levels in the optical phenomena. A relation between the various absorption probabilities and also indirect information about the Debye temperatures were obtained. (C) 1997 Elsevier Science S.A.

3163. The effect of LiOH addition to the superconducting properties of YBa2Cu3O7-x

Authors: Sandu, V; Jaklovszky, J; Cimpoiasu, E; Bunescu, MC

Published: JUN 1997, JOURNAL OF SUPERCONDUCTIVITY, 10, 239, DOI: 10.1007/BF02770557

The effect of LiOH addition to YBa2Cu3O7-x is presented. The crystal structure remains orthorhombic, but the orthorhombic splitting decreases from 0.0171 at 2 at. % Li to 0.0158 at 50 at. % Li. The critical temperature exhibits a decrease from 91-.18 to 83.79 K in the same range of lithium concentrations. From the magnetization curves were obtained the lower critical fields and the intragranular critical current density. The latter exhibits a negative power law, j(c) proportional to B-alpha, with alpha approximate to 1/2. V-I characteristics are typical for grained superconducting materials: V proportional to(I-I-c)(n(B,T)). The transport critical current dependence on temperature and magnetic field is also presented.

3164. Current-voltage characteristics of long Bi2Sr2Ca2Cu3O10/Ag multifilamentary tapes at different bending strains

Authors: AlMosawi, MK; Crisan, A; Beduz, C; Phillips, D; Haldar, P

Published: SEP 15 1997, PHYSICA C, 289, 69, DOI: 10.1016/S0921-4534(97)01587-6

The current-voltage (I-V) characteristics of long Bi2Sr2Ca2Cu3O10/Ag (Bi:2223) multifilamentary tapes with different bending strains were measured in a large range of dissipation (10(-12)-10(-3) V/cm). The experimental data were successfully interpreted in terms of current-induced unbinding of the thermally-created vortex-antivortex pairs by taking into account the size limitation of vortex fluctuations. It was found that the shape of the I-V curves can be explained by the contributions to the dissipation of superconducting intergrain contacts having different qualities (i.e. different critical currents) and by the appearance of micro-cracks during the bending process. (C) 1997 Elsevier Science B.V.

3165. ESR investigations on ion beam irradiated polymers

Authors: Chipara, MI

Published: AUG 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 131, 90, DOI: 10.1016/S0168-583X(97)00382-0

Electron spin resonance investigations on ion beam irradiated polymers are reviewed from a critical point of view. The nature of free radicals produced by heavy ion bombardment is discussed in detail, in connection with the main hypotheses (thermal spikes and secondary electrons). ESR investigations on cellulose nitrate irradiated with accelerated oxygen ions are reported. From the temperature dependence of resonance line parameters, the presence of exchange interaction is noticed and the generation of free radicals at 200 degrees C is studied. (C) 1997 Elsevier Science B.V.

3166. The Au-substituted Al-Cu-Fe icosahedral phase: Evidence for bond hybridization

Authors: Popescu, R; Macovei, D; Manciu, M; Zavaliche, F; Fratiloiu, D; Jianu, A; Devenyi, A; Manaila, R; Xie, Y; Hu, T; Orton, BR; Cernik, RJ; Tang, CC

Published: SEP 8 1997, JOURNAL OF PHYSICS-CONDENSED MATTER, 9, 7540, DOI: 10.1088/0953-8984/9/36/003

Au-substituted Al-Cu-Fe icosahedral phases, Al62Cu25.5-xAuxFe12.5 (x less than or equal to 7) were prepared by melt spinning. EDS data showed that Cu as well as Al atoms are effectively substituted for with Au. The hypercubic lattice parameter of as-quenched samples slowly increases with x, while phonon-and phason-type disorders are not affected by Au substitution. Experimental structure factors for 'sum' lines were used to derive an average radius of the atomic hypersurfaces. Comparison of experimental versus calculated ratios of structure factors for different models yielded information about the Au distribution over the icosahedral sites. It was inferred that a fraction of the gold shapes its Al surrounding in a AuAl2-type configuration. Evidence was found for d-sp hybridization of Au-Al bonds, on the basis of the 'white-line' area at the Au L-3 absorption edge.

3167. Non-ionising energy loss of pions in thin silicon samples

Authors: Lazanu, I; Lazanu, S; Biggeri, U; Borchi, E; Bruzzi, M

Published: APR 1 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 388, 374, DOI: 10.1016/S0168-9002(96)01251-X

The dependence of the displacement damage induced by pions in silicon has been calculated as a function of their kinetic energy, between 50 and 1000 MeV, using data on pion-silicon interaction. The region of the delta resonance has been carefully considered. because it corresponds to a sharp maximum in the spectra of simulated pion production in the central cavity of LHC. Results are reported on previous calculations and on experimental damage data measured in silicon detectors irradiated with pions.

3168. Interfacial dielectric losses in Co-doped Ni-Zn ferrites

Authors: Nicoara, G; Steflea, M; Toacsan, M

Published: MAR 1997, JOURNAL DE PHYSIQUE IV, 7, 228, DOI: 10.1051/jp4:1997186

The temperature and frequency dependence of tg delta and epsilon' for Ni0.8Zn0.2CoxFe2-x ferrites was studied in the 10(2)-10(6) Hz frequency range and 20-200 degrees C temperature range. The experimental curves exhibit aspects very dependent of composition. To verify that interfacial losses, expected to appear in this type of system are compatible with the experimental results a calculation of the dielectric permittivity and dielectric loss using the Koops' model was made. A good correlation between calculated and experimental curves was found.

3169. The glass transition phenomenon in macromolecular systems

Authors: Chipara, MI

Published: JUN 1997, PHYSICA B, 234, 265, DOI: 10.1016/S0921-4526(96)00950-7

An extended Williams-Landel-Ferry equation is derived within the free volume approximation. This equation relates the jump frequency of an arbitrary molecule (around the glass transition temperature) to the segmental jump frequency at the glass transition temperature. The connection with the usual WLF equation is discussed.

3170. Temperature induced surface transitions in liquid crystal planar-tilted hybrid cells

Authors: Moldovan, R; Frunza, S; Beica, T; Tintaru, M; Ghiordanescu, V

Published: 1997, CRYSTAL RESEARCH AND TECHNOLOGY, 32, 675, DOI: 10.1002/crat.2170320510

Temperature induced surface transitions in liquid crystal hybrid cells with asymmetrical anchoring, planar to one surface and tilted to the other, are experimentally studied. The results are theoretically explained by an elastic theory and the resulting values for the effective splay-bend elastic constant for a given liquid crystal, as well as the parameters characterising the anchoring on the boundary surface with tilted anchoring are compared with data from previous experiments, with good agreement.

3171. Specific plateaus of the quantum Hall effect induced by an applied bias

Authors: Aldea, A; Gartner, P; Manolescu, A; Nita, M

Published: MAY 15 1997, PHYSICAL REVIEW B, 55, 13392, DOI: 10.1103/PhysRevB.55.R13389

The spectrum and the eigenstates of a finite two-dimensional tight-binding electronic system, with Dirichlet boundary conditions, in a magnetic field and with an external linear potential are studied. The eigenstates show an equipotential character, and may cross the plaquette in the direction perpendicular to the electric field. When leads are added to the plaquette, the channels carrying the current may be shortcut by equipotentials, resulting in additional plateaus situated between the usual integer-quantum-Hall-effect plateaus. This ideals confirmed by a numerical calculation within the four-terminal Landauer-Buttiker approach.

3172. Intermediate-range order in silica gels

Authors: Manaila, R; Popescu, R; Vasilescu, A; Zaharescu, M

Published: JUN 16 1997, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 161, 328, DOI: 10.1002/1521-396X(199706)161:2<317::AID-PSSA317>3.0.CO;2-X

Fresh silica gels prepared by the sol-gel route with acid catalysis display typical alterations of the X-ray diffraction (XRD) pattern, in comparison with vitreous (v) silica. A positive shift of the first peak at k(1) is noticed, which also shows excess broadening. The changes can be accounted for by the alteration of the intermediate-range order (IRO) in gels; in comparison with v-SiO2 Thermal annealing causes a gradual decrease in the shift and broadening of the first peak, suggesting that the evolution of the vitrification can be followed on the basis of XRD data. Two types of IRO alteration were modelled, which account quantitatively for the experimental observations using a phe nomenological disorder parameter b. The evolution of the b values with annealing temperature reveals well-defined stages in the vitrification process.

3173. Influence of small addition of Ti4+ ions on the properties of high permeability ferrite

Authors: Neamtu, J; Toacsen, MI; Barb, D

Published: MAR 1997, JOURNAL DE PHYSIQUE IV, 7, 80, DOI: 10.1051/jp4:1997120

Mn-Zn ferrites substituted with Ti4+ ions are now becoming commercially important. The substitution with titanium ions in Mn-Zn ferrite is recommended for ferrites with low losses and low temperature factor of initial permeability, T-k/mu(i) because of the shift of the secondary maximum of permeability, SMP, towards lower temperatures [1] and the increase of the d.c.resistivity [3,4,5]. The present paper reports the results obtained by substitution of a small amount of titamium ions to high permeability ferrite Mn0.51Zn0.43Fe0.062+Fe2O4, by adequate reduction of Zn2+ content. The magnetic and electric properties improve: d.c. electrical resistivity increases while the loss factor tg delta/mu(i) and disaccommodation decrease. By addition of 0.35% by weight TiO2 the initial permeability, at 20 degrees C, improves.. We remark the flattening of mu(i)(T) curves with the increase of content of Ti4+ ions and the diminution of the peak at the Curie point, facts that can be associated with two points of anisotropy compensation instead of one, the second minimum of K-1 being in the neighborhood of T-c. Structural and magnetic properties of high permeability ferrite with substitution of titanium ions confirm thar Ti(4+)ions make pairs with Fe2+ ions.[4,6].

3174. Radiation damage effects on X- and gamma-ray N+PP+ silicon detectors

Authors: Cimpoca, V; Petris, M; Ruscu, R; Moraru, R; Breten, M; Cimpoca, M

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 518, DOI:

The paper describes some results concerning technology and behaviour of X-and gamma-ray N+PP+ silicon defectors used in physics research, industrial and medical radiography and non-destructive testing. Devices manufactured under this technology proved to be stable alter an exposure in high intensity the dose range of 10 krad-5 Mrad. Nuclear radiation resistance was studied by irradiation with Co-60 gamma source (1.17, 1.33 MeV) at dose rates of 59 krad/hour and 570 krad/hour.

3175. Influence of some n-type InSb properties on the main parameters of infrared photoconductive detectors

Authors: Grigorescu, CEA; Manea, SA; Lazarescu, MF; Botila, T; Munteanu, I; Necsoiu, T

Published: FEB 1997, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 44, 273, DOI: 10.1016/S0921-5107(96)01789-8

Infrared photoconductive detectors were prepared from three undoped n-type InSb single crystals with different electron concentration and mobility values. The single crystals were grown by the Czochralski method. The spectral responsivity and spectral detectivity of the detectors were determined as functions of the power dissipation density of the device. A remarkable improvement in performance was observed for the purest specimen in comparison with earlier reported data. (C) 1997 Elsevier Science S.A.

3176. Evidence from DR spectra and TPR on the oxidic forms occurring in NiO-Al2O3 systems

Authors: Craiu, M; Marchidan, F; Manaila, R; Stanica, N

Published: APR 1997, REVUE ROUMAINE DE CHIMIE, 42, 287, DOI:

The UV/Vis diffuse reflectance (DR) spectra of NiO-Al2O3 systems obtained by mechanical mixing of oxides followed by calcination between 350 and 1400 degrees C are used for a detailed discussion and the reactualisation of an earlier band assignment. From temperature-programmed reduction (TPR) curves, a percent distribution of the total nickel content among various oxidic species, identified by hydrogen consumption peaks, was estimated. An attempt was made to estimate the fraction of octahedral Ni2+ ions in the spinel forms from the same TPR data. The results were correlated with XRD data and magnetisation measurements on the reduced samples.

3177. Physics of optimal resonant tunneling

Authors: Racec, PN; Stoica, T; Popescu, C; Lepsa, M; vandeRoer, TG

Published: AUG 15 1997, PHYSICAL REVIEW B, 56, 3597, DOI: 10.1103/PhysRevB.56.3595

The optimal resonant tunneling, or the complete tunneling transparence of a biased double-barrier resonant-tunneling (DBRT) structure, is discussed. It is shown that its physics does not rest on the departure from the constant potential within the barriers and well, due to the applied electric field, but on the effective symmetry of the rectangular-barrier profile, which approximates the real potential profile for the corresponding applied bias.

3178. Structure and hardness modifications induced by UV light in Ge-As-S amorphous chalcogenide films

Authors: Popescu, M; Skordeva, E; Arsova, D; Vateva, E; Sava, F; Lorinczi, A

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 470, DOI:

X-ray diffraction and transmission experiments as well as hardness measurements on virgin and ultra violet (UV)-irradiated amorphous films in the system GexAs40-xS60 have been performed. The W-light determines the plm softening for x<19 and film hardening for x>19. The structure remains amorphous but the distance characteristic to medium range order (MRO) shows variations as a function of composition and irradiation time. The main effect of the UV light is the release of a significant amount of sulphur.

3179. Medium range order in chalcogenide glasses

Authors: Popescu, M

Published: 1997, PHYSICS AND APPLICATIONS OF NON-CRYSTALLINE SEMICONDUCTORS IN OPTOELECTRONICS, 36, 232, DOI:

3180. Ni-Zn ferrite nanoparticles prepared by ball milling

Authors: Nicoara, G; Fratiloiu, D; Nogues, M; Dormann, JL; Vasiliu, F

Published: 1997, SYNTHESIS AND PROPERTIES OF MECHANICALLY ALLOYED AND NANOCRYSTALLINE MATERIALS, PTS 1 AND 2 - ISMANAM-96, 235-2, 150, DOI: 10.4028/www.scientific.net/MSF.235-238.145

Samples consisting of Ni0.8Zn0.2Fe2O4 nanoparticles, both interconnected or dispersed in a matrix, were prepared by high energy ball milling, starting from bulk material previously synthesised by the conventional ceramic method at 1250 degrees C under O-2 flux. Samples with different grain size were performed. The as-milled samples were characterised by chemical analysis, X-ray diffraction and transmission electron microscopy (TEM). The nondispersed samples consist of grains with a mean size of 100 nm and a large size distribution. The dispersed powder in silica shows individual particles almost spherical with size ranging from 8 up to 50 nm. A good agreement was obtained between X-ray and TEM results. Because the as-milled powder showed after 200 hours of milling a high impurity degree, due to the stainless steel vial and balls, an original method was used to separate the phases. Magnetic measurements and Mossbauer spectra were performed.

3181. Radiation-specific free radicals in biological systems: detection and applications

Authors: Grecu, VV; Duliu, OG; Pascanu, S; Oproiu, C; Georgescu, R; Chipara, MI

Published: DEC 1997, PHYSICA MEDICA, 13, 273, DOI:

In the biological effect of ionizing radiation, a very important process is the production of free radicals and their reactions with one another and with other biomolecules. Electron Spin Resonance (ESR) spectroscopy is an appropriate method to detect the free radicals produced by irradiation and also to estimate their concentration. The samples were irradiated at a linear electron accelerator, The ESR measurements were performed using X-band spectrometers. The resonance spectra of irradiated complex biological materials are presented and discussed. Interesting applications of the ESR method in the field of radiation treatment of biological material are outlined.

3182. Impurity-V-K centres' associations in KI crystals containing lighter halogens

Authors: Matei, L; Serban, T; Secu, M; Beica, T

Published: JUN 1997, JOURNAL OF LUMINESCENCE, 72-4, 692, DOI: 10.1016/S0022-2313(97)00039-2

An attempt has been made to put in evidence the modified V-K centres in low temperature UV irradiated Kl:Cl crystals. The interpretation of the results seems to favour a new type of V-K centre localised near an impurity halogen instead of a heteronuclear V-K centre.

3183. Site occupation and Fe-57 Mossbauer spectra of RE6Fe14-xMx with RE=Nd, Pr and M=Ga, Al

Authors: Kuncser, V; Rosenberg, M; Buschow, KHJ; Filoti, G

Published: JUN 20 1997, JOURNAL OF ALLOYS AND COMPOUNDS, 255, 66, DOI: 10.1016/S0925-8388(96)02851-4

A Mossbauer spectroscopy study of the intermetallics RE6Fe14-xMx where RE=Nd or Pr, M=Ga or Al and x=1 or 2 was undertaken. A comparative analysis of the Mossbauer spectra showed that the second Al or Ga atom substitutes preferentially for the Fe atoms located at the 161 sites. The reduction of the hyperfine fields in Nd6Fe12M2, as compared with Nd6Fe13M, mainly at the 16k, 161, and 161(2) and the corresponding decrease of the average Fe moment gives rise to a total magnetic moment of 41 mu(B) per formula unit in excellent agreement with previous saturation magnetisation measurements.

3184. Model predictions for the radiation damage in semiconductors

Authors: Lazanu, S; Lazanu, I; Biggeri, U; Borchi, E; Bruzzi, M

Published: 1997, INTERNATIONAL CONFERENCE ON NUCLEAR DATA FOR SCIENCE AND TECHNOLOGY, VOL 59, PT 1 AND 2, 59, 1530, DOI:

3185. Diffractive investigation of the domain structure in amorphous semiconductors

Authors: Popescu, MA

Published: 1997, INTERNATIONAL CONFERENCE ON CORRELATION OPTICS, 3317, 293, DOI: 10.1117/12.295695

The non-crystalline semiconductors (amorphous tetrahedrally bonded Si, Ge, amorphous and vitreous chalcogenides) exhibit a domain structure. These domains (which we call amorphites) have very small size (1-3 nm) and are separated by abrupt interfaces with highly distorted covalent bonds. The diffraction effects produced by short-wavelength electromagnetic radiation (X-rays) in various simulated networks have been investigated.

3186. Accurate equivalent-network modelling of GaAs/AlAs based resonant tunnelling diodes with thin barrier layers

Authors: Kwaspen, JJM; Lepsa, MI; van de Roer, TG; van der Vleuten, W

Published: SEP 11 1997, ELECTRONICS LETTERS, 33, 1658, DOI: 10.1049/el:19971107

The small-signal intrinsic impedance of GaAs/AlAs based resonant tunnelling diodes with thin barriers has been measured at room temperature over the full 0-2V bias-voltage and 0.05-40.05GHz frequency ranges, on stable, non-oscillating devices. The classical Esaki and the quantum-inductance equivalent circuits were used to model the impedance for CAD purposes. Information about the quasibound-state lifetime against bias-voltage was extracted.

3187. Magnetic field sensor with linear response

Authors: Logofatu, M; Munteanu, I; Logofatu, B; Lazarescu, MF

Published: APR 1997, SENSORS AND ACTUATORS A-PHYSICAL, 59, 152, DOI: 10.1016/S0924-4247(97)80165-3

In this work, an InAs classical Hall effect based magnetic field sensor with linear response up to 1.00 T at room temperature is reported. InAs used is homogeneous polycrystalline n-type material. A supplementary simulation circuit and a suitable soft are used to insure a linear dependence of the Hall voltage on the magnetic induction. A 'butterfly' form for the sensor is used to increase the magnitude of the Hall signal. The influence of the magnetoresistive effect and irradiation with thermal neutrons on the response of the sensor is also investigated. (C) 1997 Elsevier Science S.A.

3188. A model of the metallic surface-emitting second harmonic generator

Authors: Popa, A; Lazarescu, MF; Dabu, R; Stratan, A

Published: SEP 1997, IEEE JOURNAL OF QUANTUM ELECTRONICS, 33, 1480, DOI: 10.1109/3.622625

We present an accurate calculation of the intensity of the second harmonic radiation generated by the reflection of the incident radiation from a metal surface, This radiation is due to two currents, The first current results from the rapid variation of the normal component of the oscillating electric field in the vicinity of the surface and depends on both conduction and bound electrons, The second one results from the action of the Lorentz force on conduction electrons, We show that if the adiabatic and the Thomas-Fermi assumptions are considered, then an accurate calculation of these currents is possible and leads to a simple relation of the intensity of the second harmonic radiation.

3189. Large area pulsed laser deposition of aurivillius-type layered perovskite thin films

Authors: Pignolet, A; Welke, S; Curran, C; Alexe, M; Senz, S; Hesse, D

Published: 1997, FERROELECTRICS, 202, 298, DOI: 10.1080/00150199708213487

Thin films of Aurivillius-type layered perovskites of Bi4Ti3O12 and SrBi2Ta2O9 have been epitaxially deposited by PLD on SrTiO3 single crystal substrates. Bi4Ti3O12 has been deposited as well on a CeO2/YSZ/Si(100) buffer layer, and on Pt-coated oxidized silicon for electrical measurements. Using a new technique for large area PLD, Bi4Ti3O12 has also been deposited on a whole (100)-oriented 3 '' Si wafer. The obtained films have a homogeneous thickness over the whole wafer corresponding to an area of about 45 cm(2). The composition, structure, and electrical properties of the films are presented.

3190. Influence of the melt growth configuration on the structural properties of langasite crystals

Authors: Manea, AS; Lazarescu, MF; Mateescu, I; Pop, G; Ghita, C

Published: DEC 1997, ANNALES DE CHIMIE-SCIENCE DES MATERIAUX, 22, 738, DOI:

An alternative technique for the synthesis and crystal growth of langasite (La3Ga5SiO14) is presented. In order to keep constant the compound stoichiometry during these processes, we have used the raw material charge (mixed oxides) in a pressed pellet shape and also we have built a thermal screening system surrounded by separately controlled RF coils. In this way, a suitable solid/liquid interface shape has been obtained.

3191. Amorphous rf-sputtered Si100-xNix thin films with O<=x<=15 at.%: Structural, optical and electrical properties

Authors: BeluMarian, A; Serbanescu, MD; Manaila, R; Stoica, T; Dragomir, A; Zavaliche, F; Tanase, M; Devenyi, A

Published: JUN 1 1997, THIN SOLID FILMS, 301, 202, DOI: 10.1016/S0040-6090(97)00007-2

The temperature dependence of the conductivity (between 15 and 300 K) and optical transmission spectra (between 0.8-3.5 mu m) have been measured on r.f.-sputtered Si100-xNix with 0 less than or equal to x less than or equal to 15. The films were characterized by Rutherford backscattering spectroscopy and X-ray diffraction. Changes in the optical sub-bandgap structure, with corresponding changes in the conduction mechanism take place by varying the Ni content. The films are amorphous, showing a main broad diffraction peak. Its position deviates, for this concentrationrange, from 2(kF) (k(F) = Fermi radius), the alloy losing the Hume-Rothery character present for 50 less than or equal to x less than or equal to 60.

3192. The influence of the structure on the electrical and magnetic properties of Bi2Sr2CaCu2O8+delta single crystals

Authors: Aldica, G; Crisan, A; VelterStefanescu, M; Mandache, S; Bunescu, MC

Published: MAR 1 1997, JOURNAL OF MATERIALS SCIENCE, 32, 1199, DOI: 10.1023/A:1018579817471

The correlation between the structure, chemical composition, electrical and magnetic properties of Bi2Sr2CaCu2O8+delta single crystals is presented. As revealed by SEM measurements, the small samples (approximately 1 mm x 1 mm x 0.2 mm) are stacks of thin plates (1-2 mu m). Microcompositional measurements (energy dispersive spectroscopy) show the Bi2Sr2CaCu2O8+delta (2212)-phase and a small quantity of residual phases enriched in bismuth and strontium and calcium-deficient. Magnetically modulated microwave absorption measurements (MAMMA) lead to a value for the anisotropy of the upper critical field of about 7, which is more than twice the reported value for YBa2Cu3O7-delta single crystals (also determined from MAMMA responses). The plot of the resistance versus temperature suggests that only the first 10-20 plates from the surface of the sample have a contribution to the sample conductivity. The imaginary part, chi'', of the magnetic susceptibility of our samples shows three peaks.

3193. Effect of doping with Nb2O5 on the magnetic and structural properties of Mn-Zn ferrite

Authors: Neamtu, J; Barb, D; Toacsen, MI; Morariu, M; Vasiliu, F

Published: MAR 1997, JOURNAL DE PHYSIQUE IV, 7, 74, DOI: 10.1051/jp4:1997117

The present paper reports the magnetic and structural properties of manganese -zinc ferrites obtained by the addition of small amount of Nb2O5 (0.03-0.1%g). For power applications of Mn-Zn ferrite it is necessary to have the Secundary Maximum of Permeability (SMP) and correspondingly low losses, in the domain of positive temperature, 50-100 degrees C. The magnetic properties: initial permeability, power losses, temperature factor of permeability and T-c improve by the addition of 0.03-0.07%g Nb2O5 to the Mn-Zn ferrite.Magnetic and structural results: XRD, SEM2+EDX analysis, suggest that Nb5+ ions partially dissolve in the ferrite lattice, substituting Fe3+ octahedral and loosely bounding Fe2+ ions.

3194. Radiation effects on polyoctenamer

Authors: Chipara, MI; Georgescu, L; Oproiu, C; Chipara, MD; Niculescu, A; Galatanu, N; Reyes, JR; Secu, CE

Published: AUG 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 131, 191, DOI: 10.1016/S0168-583X(97)00339-X

The effect of electron beams on polyoctenamer is investigated by viscosimetry, swelling and electron spin resonance spectroscopy. From these experimental investigations it has been deduced that the main degradation process in polyoctenamer is its crosslinking during electron beam irradiation in air, at room temperature. (C) 1997 Elsevier Science B.V.

3195. Structural properties of conducting and semiconducting polymers

Authors: Galatanu, A; Chipara, MI; Chipara, MD; Toacsen, M

Published: JUN 1997, PHYSICA B, 234, 244, DOI: 10.1016/S0921-4526(96)00925-8

Electron spin resonance investigations on polyethylene-polyaniline blends are reported. The temperature dependence of resonance line parameters, in the temperature range 270-400 K is investigated in detail.

3196. X- and gamma-ray N+PP+ silicon detectors with high radiation resistance

Authors: Cimpoca, V; Petris, M; Ruscu, R; Breten, M; Moraru, R

Published: 1997, HARD X-RAY AND GAMMA-RAY DETECTOR PHYSICS, OPTICS, AND APPLICATIONS, 3115, 271, DOI: 10.1117/12.277693

The paper describes some results concerning technology and behaviour of X-and gamma-ray N+PP+ silicon detectors used in physics research, industrial and medical radiography and non-destructive testing. These detectors work at the room-temperature and can be used individually to detect X-and soft gamma-rays, or coupled with scintillators for higher incoming energies. Electrical characteristics of these photodiodes, their modification after exposure to radiation and results of spectroscopic X-and gamma-ray measurements are discussed Devices manufactured under this technology proved to be stable after an exposure in high intensity gamma field with the dose range of 10 krad-5 Mrad: Nuclear radiation resistance was studied by irradiation with Co-60 gamma source (1.17, 1.33 MeV) at dose rates of 59 krad/hour and 570 krad/hour. Results indicate that proposed structures enable the development of reliable silicon detectors to be used in a high gamma-radiation environments encountered in a lot of applications.

3197. Preparation and structure of lanthanum stearate films

Authors: Popescu, M; Gutberlet, T; Kastowsky, M; Koch, PJ; Bradaczek, H

Published: JUL 30 1997, THIN SOLID FILMS, 304, 326, DOI: 10.1016/S0040-6090(97)00073-4

Lanthanum stearate films were prepared by the conventional Langmuir-Blodgett method and by a dragging procedure. Multilayers have been obtained and studied by X-ray diffraction. The electron density distribution normal to the bilayer plane has been calculated. (C) 1997 Elsevier Science S.A.

3198. SEM studies on BSCCO superconducting ceramic produced by spray frozen, freeze drying technique

Authors: Bunescu, MC; Aldica, G; Badica, P; Vasiliu, F; Nita, P; Mandache, S

Published: AUG 1 1997, PHYSICA C, 281, 197, DOI: 10.1016/S0921-4534(97)00633-3

Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) have been used to evidence the occurrence, morphology and microcomposition of the superconducting phases (Bi,Pb)(2)Sr2Ca2Cu3O10+delta (2223) and (Bi,Pb)(2)Sr2CaCu2O8+delta (2212), and of other non-superconducting phases, in the sintered pellets obtained from nitrate solution by spray frozen, freeze drying technique. For decomposition of the nitrate powder four different heat treatments were used. Superconducting and structure properties of the pellets have been tested by AC susceptibility measurements (610 Hz, 0.5 Oe) and X-ray diffraction analysis, respectively. A correlation between the SEM and EDS observations and the superconducting properties has been established. (C) 1997 Elsevier Science B.V.

3199. Thermal stability of amorphous Se/CdSe multilayers

Authors: Popescu, M; Sava, F; Lorinczi, A; Vateva, E; Nesheva, D; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H

Published: AUG 1997, SOLID STATE COMMUNICATIONS, 103, 434, DOI: 10.1016/S0038-1098(97)00207-X

The thermal stability of amorphous Se/CdSe multilayers has been investigated by X-ray diffraction. The multilayer structure is stable up to similar to 60 degrees C. After annealing at higher temperatures hexagonal selenium and hexagonal CdSe phases with nanometric crystallite size were revealed. (C) 1997 Elsevier Science Ltd.

3200. Modal behaviour of weak index guided stripes in low confinement laser diodes

Authors: Buda, M; Diaconescu, D; Iordache, G; Cengher, D

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 496, DOI:

This paper presents the optical field behaviour of relatively large stripes, long laser diodes. The devices were designed to operate in the fundamental lateral mode. The stripe width, of order of 16 mu m, involves a very low refractive index step at the ridge edges and the operation of the diode in weak index guided regime. This index profile and subsequently, the optical field distribution is very easily disturbed by carrier injection or by temperature The paper aims to characterise the influence of direct current intensity on lateral far field.

3201. A Mossbauer study of Y3Co11-xFexB4 compounds

Authors: Sorescu, M; Brand, RA; Plugaru, N; Barb, D

Published: FEB 1997, MATERIALS LETTERS, 30, 238, DOI: 10.1016/S0167-577X(96)00202-9

Pseudo-ternary magnetic compounds Y3Co11-xFexB4 (x = 2, 4, 5 and 6) were studied by Fe-57 Mossbauer spectroscopy at 293 and 4.2 K. The effect of Fe substitution on the hyperfine parameters and site preference is reported.

3202. Studies of C-60 thin films using surface photovoltage spectroscopy

Authors: Mishori, B; Shapira, Y; BeluMarian, A; Manciu, M; Devenyi, A

Published: JAN 3 1997, CHEMICAL PHYSICS LETTERS, 264, 167, DOI: 10.1016/S0009-2614(96)01292-4

The electronic structure of polycrystalline C-60 thin films has been investigated using surface photovoltage spectroscopy (SPS) and conductivity measurements. The films show n-type semiconductivity with an activation energy of approximate to 0.8 eV as found from the temperature dependence of the conductivity at high temperatures. The electronic structure emerging from our SPS results comprises a 1.6 eV photoconduction gap, a mobility gap of about 2.25 eV and two gap states, a donor and an acceptor, at 0.35 and 0.8 eV, respectively, below the photoconduction edge. The proposed model positions the Fermi level between these two localised levels. Thus, the high-temperature conductivity is due to electrons excited across the photoconduction gap.

3203. Model predictions for the NIEL of high energy pions in Si and GaAs

Authors: Lazanu, S; Lazanu, I; Biggeri, U; Borchi, E; Bruzzi, M

Published: JUL 11 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 394, 234, DOI: 10.1016/S0168-9002(97)00669-4

The concept of NIEL (Non Ionising Energy Loss) is usually considered to correlate the effects of the displacement damage produced in the material bulk by different particles in different energy ranges. An evaluation of the NIEL is especially important for those semiconductors which are planned to be used in the extreme radiation environment of the new generation of colliders as LHC. In the present work, a calculation of the pion NIEL in silicon and GaAs, in the energy region up to 50 GeV is reported and discussed. The energy dependence of the NIEL is found to follow the resonant structures of the pion-nuclei interactions, where the strongest effect is due to the Delta(33) resonance. Above 1 GeV a slight monotonic decreasing behaviour of the NIEL has been found, both for Si and GaAs.

3204. Localization and charge conversion of copper in Rb2ZnCl4:Cu crystals: An ESR and optical absorption study

Authors: Stefan, M; Nistor, SV; Grecu, NM; Schoemaker, D

Published: AUG 1997, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 202, 1011, DOI: 10.1002/1521-3951(199708)202:2<999::AID-PSSB999>3.0.CO;2-5

Electron spin resonance and optical studies reveal the presence of both Cu2+ and Cu+ centers in Rb2ZnCl4:Cu single crystals grown from melt and their conversion by X- or gamma-irradiation. Two types of paramagnetic Cu2+ centers with different concentrations and production properties have been identified. The more abundant Cu2+(I) center consists of a Cu2+ ion substituting for Zn2+ at the center of a ZnC42- tetrahedron. The less abundant Cu2+(II) center seems to be situated at a Rb site. Production experiments strongly suggest that during the crystal growth copper enters the Rb2ZnCl4 lattice as Cu2+, mainly at Zn2+ sites, part of it being afterwards converted to Cu+ precursor centers. The presence of a neighboring-charge compensating anion vacancy and its departure during the radiolytic Cu+(I) --> Cu2+(I) conversion seems to play an essential role in the stabilization of the Cu+(I) and Cu2+(I) centers, respectively.

3205. Local effects of interstitial versus substitutional atoms in Y(2)Fe(17-x)M(x)A(y) compounds, with M=Al or Si and A=C or N

Authors: Plugaru, N; Morariu, M; Galatanu, A; Lazar, DP; Barb, D

Published: DEC 15 1997, JOURNAL OF APPLIED PHYSICS, 82, 6202, DOI: 10.1063/1.366504

Interstitial Y(2)Fe(17-x)M(x)C(y) compounds, with M=A1 or Si and x less than or equal to 2, y less than or equal to 1, were investigated by (57)Fe Mossbauer spectroscopy at room temperature. In the analysis of the spectra, the preferential occupation by Al or Si of the Fe (12k) sites in the hexagonal R(2)Fe(17) phase was taken into account. The hyperfine parameters variations are discussed on the grounds of local crystallographic details at the inequivalent iron sites, altered by the composition modifications. The low values of the isomer shifts and quadrupole interactions suggest small electronic charge redistribution in Y(2)Fe(17-x)M(x)A(y) as compared to Y(2)Fe(17). However, the isomer shift variations upon Wigner-Seitz cell volume changes evidence for screening and electron transfer effects. In order to provide a more consistent picture of the local effects of interstitial versus substitutional atoms in R(2)(Fe,M)(17)A(y) compounds, the discussion of the present results is extended to (57)Fe Mossbauer data obtained on the parent compounds and their nitrides. (C) 1997 American Institute of Physics.

3206. Electrical properties of porous silicon stabilised by storage in ambient

Authors: Ciurea, ML; Lazar, M; Lazanu, S; Pentia, E; Dragoi, V

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 180, DOI:

The electrical transport of stabilised porous silicon layers was investigated. The samples were stored in ambient for 1,5-2 years, A MIS-like C-V characteristic, a strong rectifying I-V curve and I-T dependence with two activation energies were obtained, Thermally stimulated depolarization currents have an activation energy of 0.81-0.87 eV. The electrical properties are discussed in the frame of a quantum confinement model, keeping into account the surface component.

3207. Thermally stimulated currents in PbTiO3 thin films

Authors: Pintilie, L; Alexe, M; Pintilie, I; Boierasu, I

Published: 1997, FERROELECTRICS, 201, 223, DOI: 10.1080/00150199708228371

Using the Thermally Stimulated Current (TSC) method, the activation energy of trapping levels in sol-gel deposited lead titanate films was determined. Four levels were found in films annealed at 550 degrees C and 600 degrees C. Their activation energies are: E-1 = 0.23 eV, E-2 = 0.30 eV, E-3 = 0.34 eV and E-4 = 0.40 eV. For the films annealed at 650 degrees C only one level (E-2) was observed. It was found that the TSC magnitude decreases if the same sample is subjected to several cycles of cooling and heating between 100 K and 373 K in vacuum. This suggests a ''healing'' of the traps, probably due to the desorption of some gaseous species from the surface of the ferroelectric thin film.

3208. On an anomalous kinetic in irradiated polymers around the glass transition temperature

Authors: Chipara, MI

Published: AUG 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 131, 187, DOI: 10.1016/S0168-583X(97)00340-6

Anomalies occurring in irradiated polymers within the glass transition range, as reported by various authors are critically reviewed. A theoretical description for such processes, is developed within the free volume approximation. The discrepancies between the temperature at which such anomalies are noticed and the glass transition temperature have been ascribed to the fact that the volume of radiation-induced radicals is not equal with the segmental one. The agreement between experiment and theory is good. (C) 1997 Elsevier Science B.V.

3209. CV and Hall effect analysis on neutron irradiated silicon detectors

Authors: Biggeri, U; Borchi, E; Bruzzi, M; Lazanu, S; Li, Z

Published: APR 1 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 388, 334, DOI: 10.1016/S0168-9002(97)00006-5

Four contact bulk samples and p(+)n junction diodes produced from high resistivity n-type silicon wafers of the same ingot have been irradiated with 1 MeV-neutron fluences between 10(12) and 3 x 10(13) cm(-2). The effective impurity concentration N-eff has been calculated from CV measurements in irradiated diodes, and bulk resistivity has been measured with the Van der Pauw method on four contact samples. The experimental resistivity and N-eff dependence on the irradiation fluence, self-annealing time and storage temperature have been modeled considering the exponential shallow donor decay and the creation of acceptor traps in the irradiated silicon. A numerical fit to the experimental data, based on the solution of the neutrality and Poisson equations, has been carried out considering an equivalent deep acceptor defect created during and after irradiation in the silicon lattice. The energy level and the introduction rate of this defect, evaluated as best-fit parameters in the numerical procedure, are E-t = 0.60-0.65 eV above the valence band edge and b similar to 0.06 cm(-1).

3210. Hall effect measurements on proton-irradiated ROSE samples

Authors: Biggeri, U; Borchi, E; Bruzzi, M; Pirollo, S; Sciortino, S; Lazanu, S; Li, Z

Published: NOV 21 1997, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 400, 123, DOI: 10.1016/S0168-9002(97)00930-3

Bulk samples obtained from two wafers of a silicon monocrystal material produced by float-zone refinement have been analysed using the four-point probe method. One of the two wafers comes from an oxygenated ingot; two sets of pure and oxygenated samples have been irradiated with 24 GeV/c protons in the fluence range from 10(13) to 1.74 x 10(14) p/cm(2). Van der Pauw resistivity and Hall coefficient have been measured before and after irradiation as a function of the temperature. A thermal treatment (30 min at 100 degrees C) has been performed to accelerate the reverse annealing effect in the irradiated silicon. The irradiated samples show the same exponential dependence of the resistivity and of the Hall coefficient on the temperature corresponding to the presence of radiation-induced deep energy levels around 0.6-0.7 eV in the silicon gap. The free carrier concentrations (n, p) have been evaluated in the investigated fluence range. The inversion of the conductivity type from n to p occurred, respectively, at 7 x 10(13) and at 4 x 10(13) p/cm(2) before and after the annealing treatment for both the two sets. Only slight differences have been detected between the pure and the oxygenated samples.

3211. Variable rate spin freezing and long range antiferromagnetic order in Bi2FeRhO6

Authors: Filoti, G; Kuncser, V; Rosenberg, M; Schinzer, C; KemmlerSack, S

Published: JUL 5 1997, JOURNAL OF ALLOYS AND COMPOUNDS, 256, 91, DOI: 10.1016/S0925-8388(96)03110-6

A magnetic susceptibility and Mossbauer spectroscopy study of the perovskite Bi2FeRhO6 was undertaken. A freezing start temperature around 270 K was evidenced by both methods. Unlike homogeneous magnetic systems the freezing occurs by involving continuously more and more Fe spins with decreasing temperature over the whole interval down to 4.2 K. At low temperature some evidence for long range antiferromagnetic interactions was found. The Mossbauer data allowed a satisfactory description of the peculiar temperature dependence of the magnetic susceptibility as a superposition of a slain glass antiferromagnetic component and a paramagnetic one. The gradual spin freezing and the absence of percolation derived from the strong influence of the short range interactions, their strengths reflecting the random distribution of the Fe and Rh ions over the B sites of the ABO(3) perovskite. (C) 1997 Elsevier Science S.A.

3212. ESR investigations on the thermal degradation of polyepichlorohydrin

Authors: Chipara, MI; Corciovei, M; Sarbu, T; Romero, JR; Chipara, MD; Taran, F

Published: 1997, POLYMER DEGRADATION AND STABILITY, 57, 217, DOI: 10.1016/S0141-3910(97)00002-5

Electron spin resonance investigations on the thermal degradation in air of stabilized and crude polyepichlorohydrins are reported. The temperature dependence of resonance line parameters, in the temperature range 250-500 degrees C, has been investigated. The activation energy has been estimated for the total free-radical generation processes. lit situ experiments on crude and stabilized polyepichlorohydrins are reported. For the sample stabilized with amines the appearance of nitroxide-like free radicals has been noticed. (C) 1997 Elsevier Science Limited.

3213. FTIR investigation of organic discharge in polluted water .1. Renex monitoring study

Authors: Jelev, A; Ciobanu, MF; Frunza, L

Published: 1997, SPECTROSCOPY LETTERS, 30, 1154, DOI: 10.1080/00387019708006713

Aliquots of waste water from power stations were analyzed by a special procedure in order to put in evidence the presence of renex, a nonionic detergent. The investigations were performed spectroscopically by FTIR technique. Qualitative and quantitative features of the procedure were established as specific peaks, detection limit and method sensibility. The validity of Lambert-Beer law was checked. Taking into account the selectivity of the method it results the necessity of separating renex from nitrogenous bases in the analyzed water.

3214. Microhardness and elastic properties of bulk glasses and thin films of the GexSb40-xS60 family

Authors: Pamukchieva, V; Savova, E; Popescu, M

Published: OCT 1997, PHYSICS AND CHEMISTRY OF GLASSES, 38, 262, DOI:

The microhardness (H) of bulk glasses and thin films of the GexSb40-xS60 family has been measured. The volume of the micro-voids (Vh), their formation energy (Eh) and the modulus of elasticity (E) have been calculated. It is assumed that the bulk glasses and thin films have different elasticity levels due to the deformation of specific chemical bonds.

3215. Investigation of the light induced refractive index changes in Fe:PVA

Authors: Kuncser, V; Filoti, G; Avramescu, A; Podgorsek, R; Biebricher, M; Franke, H

Published: JUL 25 1997, JOURNAL OF ALLOYS AND COMPOUNDS, 257, 292, DOI: 10.1016/S0925-8388(97)00021-2

The light induced modifications in thin films of Fe:PVA were studied by optical and Mossbauer spectroscopy. Under the UV exposure both the refractive index and the absorption coefficient are changing. The real part of the refractive index is measured using m-line Spectroscopy. As a function of UV exposure, the optical absorption as well as the Mossbauer spectra were measured. A correlation between the optical and the measured Fe2+/Fe3+ ratio is discussed. (C) 1997 Elsevier Science S.A.

3216. Lattice misfit and elastic strain distribution in heteroepitaxial InP/InGaAs structure

Authors: Stoica, AD; Popa, N; Stoica, M; Sachelarie, D; Sachelarie, M; Rusu, E

Published: 1997, CAS '97 PROCEEDINGS - 1997 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 20TH EDITION, VOLS 1 AND 2, 482, DOI:

We obtained a multilayer heteroepitaxial structure of In-0.53 Ga-0.47 As-type deposed on (100) oriented We selected deliberately different thickness and doping concentrations df each layer for their potential applications in very high frequency bipolar transistors. A sequence of six epilayers were realized by vapour phase epitaxy. The characterization of crystallographic and semiconducting properties in correlation with technological processes is performed by TSC-method and by double crystal InP substrate. We propose a kinematics model of X-ray diffraction in heteroepitaxial multilayer structures of InP/InGaAs. It is based on a discontinuous lattice misfit and elastic strain distribution. The model fits well the rocking curves obtained for both (004) and (224) reflecting planes. The values of the lattice misfit and the elastic strains in the plane of lamellae were calculated.

3217. Analysis of 6-nm AlGaAs SQW low-confinement laser structures for very high-power operation

Authors: Buda, M; vandeRoer, TG; Kaufmann, LMF; Iordache, G; Cengher, D; Diaconescu, D; PetrescuPrahova, IB; Haverkort, JEM; vanderVleuten, W; Wolter, JH

Published: APR 1997, IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 3, 179, DOI: 10.1109/2944.605652

This paper reports experimental results on single quantum-well separate confinement heterostructures (SQW SCH) with low-confinement factor, designed for very high-power operation, The maximum power output for AR/HR coated 3-mm-long devices, measured in very short pulsed conditions (100 ns/1 kHz), from 10-mu m-wide stripes was as high as 6.4 W before catastrophical optical degradation, If scaled to continuous-wave (CW) conditions, this value would be 800-1100 mW, which would mean a factor of 2-2.7 times more than reported for the best devices with normal design for threshold minimization, The absorption coefficient for the symmetrical structure is as low as 1.1 cm(-1), in spite of the low trapping efficiency of carriers in the quantum well (QW), The maximum differential efficiency is 40% (both faces, uncoated devices) for symmetrical structure and 33% for the asymmetrical one (all measurements in pulsed conditions), Threshold current densities were 800 A/cm(2) for 5-mm-long devices in the symmetrical case and 2200 A/cm(2) in the asymmetrical one, The effects of inefficient carrier trapping in the QW on the threshold current densities and differential efficiency are discussed.

3218. On the uniform composition of InxGa1-xSb (x=0.20) bulk crystals for special optoelectronic devices

Authors: Manea, SA; Munteanu, II; Grigorescu, CEA; Logofatu, MF; Lazarescu, MF

Published: MAY 1996, OPTICAL ENGINEERING, 35, 1359, DOI: 10.1117/1.600633

Polycrystalline p-type InxGa1-xSb (x=0.20) for optoelectronic devices has been obtained by rapid direct synthesis from high-purity (99.9999%) In, Ga, and Sb. The uniformity of the composition has been checked by neutron activation analysis and also by x-ray diffractometry (Vegard-law approximation). From Hall-effect measurements an acceptor concentration of 3.2x10(17) cm(-3) and a mobility of 628 cm(2)A/ s for holes, at liquid nitrogen temperature, have been determined, and from absorption measurements, a quite diffuse edge for the optical absorption coefficient resulted. This paper describes the method of rapid direct synthesis of the ternary compound and the techniques used for the characterization of this material for special optoelectronic applications. (C) 1996 Society of Photo-Optical Instrumentation Engineers.

3219. STOICHIOMETRY EFFECTS ON THE Nd3+ CENTRES IN LiNbO3:Nd3+

Authors: Loro, H; Hernandez, J; Camarillo, E; Murrieta, H; Voda, M; Jaque, F; Sole, JG

Published: 1996, FERROELECTRICS, 185, 36, DOI: 10.1080/00150199608210473

LiNbO3 crystals with three different stoicliiometries(0,88; 0,945 and 1) in the melt were grown and dcped with the same concentration of Nd3+ (0.33%). The Nd3+ centres were systematically investigated by laser spectroscopy for these three crystals. The same Nd3+ centres were obtained for all stoichiometries but its relative distribution depends on the [Li]/[Nb] ratio.

3220. Preparation and structure of ordered films of iron carboxylate complexes

Authors: Popescu, M; Turta, C; Meriacre, V; Zubareva, V; Gutberlet, T; Bradaczek, H

Published: MAR 1996, THIN SOLID FILMS, 274, 146, DOI: 10.1016/0040-6090(95)07080-X

Several iron complexes containing a tri-iron-oxo-cation linked to short chain fatty acids have been used in the preparation of films by self-assembling from solution on glass slides via two procedures: direct evaporation and dragging out. The ordered lamellar structure thus obtained has been investigated by X-ray diffraction. A relation between the lamellar spacing and the disorder in the film has been obtained from the X-ray diffraction data.

3221. Electrical and structural properties of anodized porous silicon

Authors: Ciurea, ML; Pentia, E; Lazar, M; BeluMarian, A; Zavaliche, F; Manaila, R

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 236, DOI:

3222. Optical and microstructural properties of TiO2(Ni2+) thin films

Authors: Parlog, C; Gartner, M; Osiceanu, P; Teodorescu, V; Moise, F; Ianculescu, A

Published: 1996, CERAMICS INTERNATIONAL, 22, 99, DOI: 10.1016/0272-8842(95)00062-3

Coloured TiO2(Ni2+) thin coatings doped with transitional metals (Ni) were deposited on different substrates (silicon wafers, glass, aluminum) by the sol-gel dip coating process. Complementary techniques (XPS, SE, TEM, XRD, Absorption Spectroscopy) were used to characterize the surface stoichiometry and optical properties, as well as the structure and texture of the thermally treated gels. The presence of fully oxidized film in the outer layers, crystallization in heat treatment to anatase and rutile, formation of porous and coloured films due to the influence of the dopant and the reaction with the substrate, as well as a decrease by three orders of magnitude of the resistivity of Ni-doped films, are reported.

3223. Thermal stability of Se/CdSe multilayers

Authors: Popescu, M; Sava, F; Lorinczi, A; Koch, PJ; Gutberlet, T; Uebach, W; Bradaczek, H; Vateva, E; Nesheva, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 304, DOI:

3224. Amorphous phase in electrochemically oxidized porous silicon

Authors: Popescu, MA; Chumash, VN; Cojocaru, I; Jain, VK; Gupta, A

Published: JUN 1996, PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES, 73, 1731, DOI: 10.1080/01418619608243009

An amorphous phase has been demonstrated in porous silicon prepared by anodization of silicon wafers. The radial distribution function has been calculated on the basis of the X-ray diffraction pattern recorded from a typical sample. There was revealed an amorphous phase of composition SiO1.6.

3225. Morin-like spin reorientation in BiPb-2201 ferrates with iron in octahedral oxygen coordination

Authors: Rosenberg, M; Sinnemann, T; Filoti, G; KemmlerSack, S

Published: APR 15 1996, JOURNAL OF APPLIED PHYSICS, 79, 5259, DOI: 10.1063/1.361917

From a Mossbauer spectroscopy study of-the BiPbSrCaFe6+z ferrate, prepared under different conditions, strong evidence for a variety of Morin-like spin-reorientation processes similar to the ones occuring in hematite was found. The phase evolution, their energetical and dynamical Mossbauer parameters as well as the spin-rotational process are described in detail and finally correlated with a proposed mechanism. (C) 1996 American Institute of Physics.

3226. A phenomenological model for the macroscopic characteristics of irradiated silicon

Authors: Borchi, E; Bruzzi, M; Biggeri, U; Lazanu, S

Published: SEP 1996, NUOVO CIMENTO DELLA SOCIETA ITALIANA DI FISICA A-NUCLEI PARTICLES AND FIELDS, 109, 1341, DOI: 10.1007/BF02773519

The dependence of the carrier concentrations, of the resistivity and of the Hall coefficient of irradiated silicon on the neutron fluence has been investigated, starting from the supposition that the main phenomena induced by irradiation in the semiconductor bulk are shallow-donor removal and deep-centres creation. The free parameters of the model are the initial doping of the starting material, the permitted energy level values of the radiation-induced centres in the semiconductor band gap and their introduction rates. The influence of each parameter on the calculated dependences is studied in detail, for three cases: one deep acceptor-like centre, two deep accepters and one deep acceptor plus one deep donor-like centre. Each of the three cases is discussed in correspondence with different experimental results.

3227. Photovoltaic effect in PbS/PbTiO3/Si heterostructures

Authors: Pintilie, L; Alexe, M; Pintilie, I; Botila, T

Published: SEP 9 1996, APPLIED PHYSICS LETTERS, 69, 1573, DOI: 10.1063/1.117033

PbS/PbTiO3/Si heterostructures were prepared by successive depositions of a PbTiO3 thin film using the sol-gel method and of a PbS thin film using the coprecipitation method on a bulk silicon wafer. The current-voltage characteristic of the heterostructure is of a diode type. The heterostructure is sensitive over a broad range of wavelengths, from 0.35 to 3 mu m, when illuminated with continuous light or with modulated Light. Three sensitivity peaks are observed, at 2.7, 0.95, and 0.38 mu m. The measured signals are attributed to a photovoltaic effect which appears in the studied heterostructure.

3228. On the determination of birefringence of liquid crystals by the interference method

Authors: Moldovan, R; Tintaru, M; Frunza, S; Beica, T; Polosan, S

Published: 1996, CRYSTAL RESEARCH AND TECHNOLOGY, 31, 955, DOI: 10.1002/crat.2170310724

A new method of processing the experimental data in the interference method for the determination of birefringence of liquid crystals which allows obtaining results in good agreement with those from prism or wedge methods, is presented.

3229. Spin probe investigation of molecular motions in polyepichlorohydrin .1.

Authors: Chipara, MI; Barb, D; Notingher, PV; Georgescu, L; Sarbu, T

Published: FEB 1996, POLYMER, 37, 712, DOI: 10.1016/0032-3861(96)83160-0

Spin probe investigations on the molecular motions in the glass transition range are reported. Within the free volume approximation, a Fox-Flory dependence of the narrowing temperature on the molecular masses is derived. The experimental results support this theoretical prediction. The glass transition temperature is estimated from the spin probe data, within various approaches, and compared to the results obtained by differential scanning calorimetry.

3230. Polymer degradation within the glass transition range

Authors: Chipara, MI; Chipara, MD; Romero, JR

Published: 1996, IEEE 1996 ANNUAL REPORT - CONFERENCE ON ELECTRICAL INSULATION AND DIELECTRIC PHENOMENA, VOLS I & II, 820, DOI:

Polymer degradation around the glass transition temperature exhibits frequently an anomalous behaviour. Starting from the hypothesis that such anomalies are related to the glass transition phenomenon, the most relevant data reported in the literature are reviewed and a theoretical description, based on the free volume approximation is suggested. The degradation process is split in three steps. It is proved that the dominant contributions come from the defect's diffusion step and from the proper chemical stage, which may be supposed to be statistically independent. It is explain, using an extended WLF equation why these anomalies are not located exactly at the glass transition temperature. The agreement between theory and experimental data reported elsewhere is good.

3231. Coulomb interaction effects on the magnetoconductivity of laterally modulated two-dimensional electron systems

Authors: Manolescu, A; Gerhardts, RR; Tornow, M; Weiss, D; vonKlitzing, K; Weimann, G

Published: 1996, SURFACE SCIENCE, 361, 516, DOI: 10.1016/0039-6028(96)00458-X

For a 2D electron system in a 1D periodic potential modulation, a complicated structure of Shubnikov-de Haas peaks has been measured and qualitatively explained by a transport calculation including interaction effects in the Hartree-Fock approximation.

3232. Corrosion behavior of some amorphous aluminium mixed-metal transition-metal alloys (Al-Mm-MT)

Authors: Ciolac, S; Calin, M; Roman, R; Jianu, A

Published: JAN 1996, REVISTA DE CHIMIE, 47, 66, DOI:

The results of the potentiostatic polarization studies taken on some Al-Mm-MT metallic glasses in reducing acid media are presented. The rest potentials development and the electrochemical parameters evaluated from the anodic and cathodic curves were correlated with the alloys composition, and related to those of the alloying components in crystalline state. Our results indicate that: alloying with rare earths does not affect interface processes; the transition metals interfere with the hydrogen reduction kinetics determining its acceleration by increasing Ni content in the alloy composition; substitution of Ni by Fe contributes to corrosion rate reduction, to passive state extension and stabilization, so that Al-Mm-Fe alloy behaves better than Al-Mm-(Fe, Ni) and Al-Mm-Ni alloys.

3233. Photoelectric properties of PbTiO3/Si heterostructures

Authors: Alexe, M; Pintilie, L; Pintilie, I; Pignolet, A; Senz, S; Hesse, D

Published: 1996, FERROELECTRIC THIN FILMS V, 433, 430, DOI: 10.1557/PROC-433-425

Photoelectric properties of PbTiO3/Si heterostructures were investigated over a broad range of wavelengths. The spectral distribution of the a.c. open-circuit voltage was measured for wavelengths ranging from 0.35 mu m to 4 mu m. Two local peaks are observed at 0.38 mu m and 0.9 mu m which can be attributed to band-to-band excitations in PbTiO3 and Si respectively. The shape of the a.c. signal depends both on the light intensity and on the wavelength. When the heterojunction is reverse-biased, a d.c. photocurrent was observed which has a similar spectral distribution as the a.c. open-circuit voltage.

3234. Visible photoluminescence in porous silicon prepared in different conditions - Temperature dependence and decay

Authors: Ciurea, ML; Pentia, E; Manea, A; BeluMarian, A; Baltog, I

Published: JUN 1996, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 195, 645, DOI: 10.1002/pssb.2221950230

Measurements of the visible photoluminescence and the decay of the photoluminescence, performed at different temperatures on porous silicon films, prepared by the anodization process under different conditions on (100) p-type silicon wafers are reported. A separation of the broad visible band of the photoluminescence in two subbands with maxima situated at 1.54 and 1.72 eV at room temperature related to the preparation conditions is obtained. This separation is still present at low temperatures but is very weak. The PL decay process is well described by a bimolecular recombination. The decay time alpha(-1) is in the order of microseconds at room temperature and nanoseconds at liquid nitrogen temperature.

3235. The influence of the argon pressure and substrate temperature on the structure of rf-sputtered CrNi(65:35), CrNi(50:50) and CrNi(20:8O) thin films

Authors: Birjega, MI; Alexe, M

Published: APR 1 1996, THIN SOLID FILMS, 275, 154, DOI: 10.1016/0040-6090(95)07030-3

The effect of deposition parameters such as substrate temperature and argon pressure on the structure of continuous CrNi(65:35), CrNi(50:50) and CrNi(20:50) thin films r.f. sputtered onto air-cleaved and electrically coloured alkali halide substrates are investigated by transmission electron diffraction. The observed phases are: nanocrystalline phases belonging to the equilibrium solid state solutions [gamma-Ni(fcc) and alpha-Cr(bcc)] and CrO (NaCl-type) oxide; single icosahedral amorphous phase; amorphous separated phases, the icosahedral amorphous phase corresponding to CrNi and the other to CrO (NaCl-type) oxide; an icosahedral amorphous phase with alpha-Cr (bcc) solid solution nanocrystals; nanocrystalline phases belonging to gamma-Ni(fcc) solid solution and the CrO (NaCl-type) oxide; nanocrystalline phases belonging to [gamma-NiC(fcc) and alpha-Cr(bcc)] solid solutions and the CrO (NaCl-type) oxide; microcrystalline phases belonging to [gamma-Ni(fcc) and alpha-Cr(bcc)] solid solutions and CrO (NaCl-type) oxide. Thermodynamic and kinetic arguments are put forward in order to explain the complex dependences in the growth of various phases and their relation to the equilibrium phase diagram of the bulk Cr-Ni system.

3236. The effect of Pt and Pd surface doping on the response of nanocrystalline tin dioxide gas sensors to CO

Authors: SchweizerBerberich, M; Zheng, JG; Weimar, U; Gopel, W; Barsan, N; Pentia, E; Tomescu, A

Published: FEB 1996, SENSORS AND ACTUATORS B-CHEMICAL, 31, 75, DOI: 10.1016/0925-4005(96)80018-9

SnO2 sensors were prepared by precipitating Sn(OH)(4) from an aqueous solution of SnCl4 or by evaporating SnO2 in the UHV. Subsequent X-ray and TEM measurements show grain sizes in the nanometer range after annealing at different temperatures or annealing times. The effect of Pt and Pd doping upon the response to CO is studied. Parameters, which we focused on, are sensor signal dependent on the operating temperature and dependent on the gas concentration. The results for ceramic sensors are compared with those for thin film sensors.

3237. Bond hybridization in Au alloys: Extracting structural information from the x-ray-absorption white line

Authors: Manaila, R; Orton, BR; Macovei, D; Manciu, M; AdilSmith, I

Published: APR 1 1996, PHYSICAL REVIEW B, 53, 8167, DOI: 10.1103/PhysRevB.53.8164

Au L(3) x-ray-absorption near-edge spectra were measured with synchrotron radiation on a series of Au-X compounds, with X=Ga, In, Ge, and Sn. The white-line feature of the spectra, as a rough measure of charge transfer upon compound formation, was related to the local composition around the Au atoms. This enabled us to estimate the local An environment, in cases where its knowledge is missing.

3238. Dielectric and DSC investigations of 4-n-substituted benzoic and cyclohexane carboxylic acids .1. Textural changes in homologous 4-n-alkoxybenzoic acids

Authors: Frunza, L; Frunza, S; Petrov, M; Sparavigna, A; Torgova, SI

Published: 1996, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION C-MOLECULAR MATERIALS, 6, 223, DOI:

We present the results of dielectric- and differential scanning calorimetry investigations on several homologous of 4-n- alkoxybenzoic acids: in particular the 4-n-heptyl-, -octyl-, -nonyloxybenzoic acids are studied. Our measurements confirm the existence in the nematic phase of a textural transition, which on cooling changes a well ordered state, f.i. a twisted state, to a highly distorted one, characterized by the appearance of a multidomain structure. Such a transition turns out to be reversible, with a small hysteresis. The transition exhibits a clear evidence for the 4-n-octyl- and the 4-n-nonyloxybenzoic acids. On the contrary, the presence of this transition in the 4-n-heptyloxybenzoic acid is suggested by a small peak only in the curve of the dielectric permittivity. The effect of the simultaneous presence in the nematic phase of open and closed dimers and of cybotactic clusters can explain the observed dielectric behavior.

3239. Spectroellipsometric studies on TiNx films

Authors: Pavelescu, G; Braic, M; Braic, V; Melinte, L; Melinte, D

Published: MAY 1996, OPTICAL ENGINEERING, 35, 1342, DOI: 10.1117/1.600625

TIN, films are deposited on glass in a modified de planar three-magnetron geometry. The ellipsometric and reflectance measurements reveal the influence of the substrate bias and of the Ar:N-2 partial pressure ratio on the stoichiometry and optical properties of the films. The stoichiometric structure is obtained for only certain bias voltage and Ar:N, ratio values. The value of the plasma energy omega(p) confirmed the film stoichiometry, as determined from x-ray diffractometry. (C) 1996 Society of Photo-Optical instrumentation Engineers.

3240. Self annealing effect on neutron irradiated silicon detectors by hall effect analysis

Authors: Biggeri, U; Borchi, E; Bruzzi, M; Lazanu, S; Li, Z

Published: JUN 1996, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, 43, 1604, DOI: 10.1109/23.507154

High resistivity n-type silicon samples have been irradiated with similar to 1MeV neutrons at fluences between 10(12) and 10(14) n/cm(-2). The radiation induced changes in Hall coefficient and resistivity have been analysed by Hall Effect measurement during a storage time of approximately seven months at room temperature. The Hall coefficient measured for the most irradiated samples, exposed to fluences higher than 4x10(13) cm(-2), has switched from negative to positive values approximately 200 days after the irradiation. This experimental evidence explains the reverse annealing effect observed in neutron irradiated silicon detectors as being related to the creation of a deep acceptor level which causes the change in conductivity from n to p-type of the irradiated silicon bulk during self annealing. The behaviour of irradiated devices has been analyzed with a model taking into account donor removal and acceptor creation. Results are in agreement with others obtained with different experimental techniques.

3241. Structural parameters of multilayers as deduced from X-ray specular reflectivity: Effect of statistical thickness fluctuations

Authors: Manciu, M; Kordos, P; Hartdegen, H; Manaila, R

Published: DEC 1 1996, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 29, 637, DOI: 10.1107/S0021889896006358

An analysis is given of the way in which thickness fluctuations in a multilayer can affect the grazing incidence X-ray reflectivity pattern. It is shown that peak shifts, broadening and height variations can result. They alter in a predictable way the parameter values derived from a fit with an ideal lattice. A principle for designed Bragg reflectors is also proposed.

3242. X-ray photoelectron spectroscopy of solid films of tungsten and titanium carbonitride produced by reactive laser ablation

Authors: Chitica, N; Lita, A; Marin, G; Mihailescu, IN; Popescu, M; Grivas, C; Hatziapostolou, A

Published: JUL 1996, JOURNAL DE PHYSIQUE IV, 6, 465, DOI: 10.1051/jp4:1996442

Thin films of tungsten and titanium carbonitrides have been prepared by reactive laser ablation of tungsten and titanium targets in a methane (propane) atmosphere with small amounts of nitrogen, at low pressure. The films have been investigated by X-ray diffraction. It was shown that the films are mainly composed of tungsten carbides and titanium nitrides. The microhardness of the samples reaches 2600 GPa for tungsten based films and 2200 GPa for titanium based films.

3243. X-rays and structure of amorphous materials

Authors: Popescu, M

Published: JUL 1996, JOURNAL DE PHYSIQUE IV, 6, 40, DOI: 10.1051/jp4:1996404

The three types of order in the non-crystalline solids are described: the short range order, the intermediate range order or medium-range order and the super-order. After pointing out how the diffraction patterns express the various types of ordering in the amorphous network, we discussed the structural models developed for some amorphous materials: tetrahedral semiconductors, diamond like-carbons and the triple coordinated pnictides (e.g. arsenic). We showed the performances of the computer-assisted modelling studies.

3244. Symmetric SQW structure with low confinement factor for high power laser diodes

Authors: Buda, M; Iordache, G; Vlaicu, M; Cengher, D; Diaconescu, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 210, DOI:

3245. Temperature induced surface transitions in liquid crystal tilted homogeneous cells

Authors: Moldovan, R; Frunza, S; Beica, T; Tintaru, M

Published: MAR 1996, LIQUID CRYSTALS, 20, 335, DOI: 10.1080/02678299608032042

Temperature induced surface transitions in liquid crystal tilted homogeneous cells are experimentally studied. The results are theoretically explained by an elastic theory of surface transitions and the resulting values for the effective splay-bend elastic constant (k) over bar(13) for each liquid crystal material are compared with the results from experience with other types of surface anchoring.

3246. THE MEDIUM-RANGE STRUCTURE OF AMORPHOUS HYDROGENATED SILICON

Authors: POPESCU, MA

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 144, DOI: 10.1016/0022-3093(95)00342-8

A new model for the medium-range order in amorphous hydrogenated silicon is proposed that qualitatively explains a variety of experimental data. The model consists of a packing of continuous random network domains separated by distorted interfaces accumulating dangling and hydrogenated bands and hydrogen clusters.

3247. INTERFACE TRAPPING STATES IN MISIM STRUCTURES, WITH ZNS-MN

Authors: PETRE, D; PINTILIE, I; CIUREA, ML; BOTILA, T

Published: MAY 1 1995, THIN SOLID FILMS, 260, 57, DOI: 10.1016/0040-6090(94)06467-9

Optical charging spectroscopy and thermally stimulated depolarization measurements were performed on metal-insulator-semiconductor-insulator-metal structures with a ZnS:Mn active layer. Two groups of trapping centres situated at every insulator-semiconductor interface were in evidence. Their depths were found to be centred at 0.55 eV and 0.875 eV respectively in the forbidden gap of a ZnS:Mn film. A partial thermal healing of these interface states was observed.

3248. THE KINETICS OF THE LASER-INDUCED STRUCTURAL-CHANGES IN AS2S3 AMORPHOUS FILMS

Authors: BERTOLOTTI, M; MICHELOTTI, F; CHUMASH, V; CHERBARI, P; POPESCU, M; ZAMFIRA, S

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 660, DOI: 10.1016/0022-3093(95)00429-7

The intensity dependent complex character of the photodarkening of virgin As2S3 samples exposed to continuous wave (CW) and pulsed laser radiation has been measured. Excitation in the CW and pulsed (picosecond) regime for the same irradiation doses leads to significant differences in the photodarkening curves. It is shown that the kinetics of the photodarkening can be decomposed into several processes related to structural transformations in As2S3: defect elimination and stabilization, polymerization of the structural entities, decomposition followed by arsenic clustering and arsenic oxidation.

3249. Dielectric relaxation investigations of new synthetized organo-metallic liquid crystal

Authors: Beica, T; AlexeIonescu, AL; Ionescu, AT; Miraldi, E; Pucci, D; Rajteri, M

Published: 1995, MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 270, 100, DOI: 10.1080/10587259508031019

An impedance spectroscopy experimental characterization of a new synthetized Palladium complex organo-metallic liquid crystal is reported. It has been found that although organo-metallic complexes modify some of the physical properties of the liquid crystals, namely transition temperatures, values of the relaxation times and conductivity, they still have, in the nematic phase, the general behaviour of the usual liquid crystals. In particular the low frequency conductivity is very small, so one can conclude that the considered organo-metallic liquid crystal behaves like a good insulator. The temperature dependence of the static parallel and perpendicular components of the dielectric tensor are reported.

3250. STRUCTURAL PARAMETERS OF MULTILAYERS FROM X-RAY REFLECTIVITY - AN EASY-TO-HANDLE APPROACH

Authors: MANCIU, M; DUDAS, L; SURGERS, C; MANAILA, R

Published: APR 1 1995, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 28, 167, DOI: 10.1107/S0021889894010071

An analytical approximation was derived for the calculation of the grazing-incidence X-ray reflectivity pattern in a defect-free multilayer. The approximation is valid in the low-reflectivity theta ranges. For k = (4 pi sin theta)/lambda > 0.28 Angstrom(-1) (theta > 2 degrees with Cu K alpha radiation), the formula deviates by at most 1% from the rigorous matricial approach in the case of most metallic multilayers. The main advantage of the approximation is that it allows the identification of features in the reflectance pattern, from which desired structural parameters (average layer thicknesses, external and internal roughness) can be estimated easily. This approach yields average structural parameters, best approximating those of a real multilayer but ignoring possible defects.

3251. THE MAGNETIC-PROPERTIES OF TRINUCLEAR FE(III) SUBSTITUTED CARBOXYLATE CLUSTERS

Authors: TURTA, KI; SOLONENCO, AO; BULGAK, II; JOVMIR, FK; ROSENBERG, M; STELMASZYK, P; FILOTI, G

Published: MAR 1995, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY-ARTICLES, 190, 355, DOI: 10.1007/BF02040011

The new Fe(III) complexes with isosceles or equilateral configurations showed atypical magnetic behaviour with a magnetic susceptibility which does not obey the Curie-Weiss law. The experimental data were fitted by using the Heisenberg-Dirac-van Vleck model with a spin Hamiltonian containing different exchange parameters in the case of isosceles configuration. A more elaborate Hamiltonian, taking into account the perturbation arising from a biquadratic exchange interaction was used in the case of equilateral configurations.

3252. EFFECT OF INTERGROWTH DEFECTS ON THE X-RAY-DIFFRACTION PATTERN

Authors: MANAILA, R; MALIS, O; MANCIU, M; DEVENYI, A

Published: JAN 16 1995, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 147, 43, DOI: 10.1002/pssa.2211470104

The presence of intergrowth with a different spacing inside a layered phase causes significant alterations in the X-ray diffraction pattern, concerning both line positions and widths. An analysis of these changes, based on a Hendricks-Teller-type formalism yields estimates about the defect nature, concentration and short-range order. The procedure was exemplified by simulation of XRD patterns for Bi-based oxidic superconductors, in which intergrowths of related phases are often present inside the matrix phase.

3253. A NOTE ON OFF-CENTER DIFFUSION

Authors: DESPA, F; APOSTOL, M

Published: APR 1995, SOLID STATE COMMUNICATIONS, 94, 155, DOI: 10.1016/0038-1098(94)00855-8

Within a one-dimensional model of off-centre diffusion it is shown that the diffusion coefficient depends on the number of off-centre sites and on their orientation relative to the host lattice.

3254. EPR spectra of Cr3+ ions in LiNbO3:ZnO and LiNbO3:CaO

Authors: Bravo, D; Martin, A; Voda, M; Lopez, FJ

Published: 1995, RADIATION EFFECTS AND DEFECTS IN SOLIDS, 134, 264, DOI: 10.1080/10420159508227227

The electron paramagnetic resonance spectra of Cr3+ in LiNbO3 co-doped with ZnO or CaO (approximate to 6%) have been studied. Both impurities give rise to the same effect as that observed in MgO-doped samples: a strong diminution of the anisotropic (axial) spectrum reported for LiNbO3:Cr and the appearance of an intense and isotropic line. The origin of this line in the co-doped samples is discussed.

3255. AZIMUTHAL CORRELATION-FUNCTIONS AND THE ENERGY OF VANISHING FLOW IN NUCLEUS-NUCLEUS COLLISIONS

Authors: BUTA, A; ANGELIQUE, JC; AUGER, G; BIZARD, G; BROU, R; CABOT, C; CASSAGNOU, Y; CREMA, E; CUSSOL, D; ELMASRI, Y; EUDES, P; GONIN, M; HAGEL, K; HE, ZY; KERAMBRUN, A; LEBRUN, C; LEGRAIN, R; PATRY, JP; PEGHAIRE, A; PETER, J; POPESCU, R; REGIMBART, R; ROSATO, E; SAINTLAURENT, F; STECKMEYER, JC; TAMAIN, B; VIENT, E; WADA, R

Published: FEB 20 1995, NUCLEAR PHYSICS A, 584, 412, DOI: 10.1016/0375-9474(94)00520-W

A method is proposed for estimating the energy of vanishing flow (also called balance energy, E(bal)) without reconstructing the reaction plane. This method is based on the shapes of experimental particle-particle azimuthal correlation functions. It is used for determining E(bal) for three systems: Ar + Al, Zn + Ti, Zn + Ni. The results are compared with estimations using flow-parameter analysis and with theoretical expectations.

3256. POLARIZED ABSORPTION OF ND3+ IN LINBO3 - EFFECT OF MGO CODOPING

Authors: LORO, H; VODA, M; JAQUE, F; SOLE, JG; SANTIUSTE, JEM

Published: JUN 1 1995, JOURNAL OF APPLIED PHYSICS, 77, 5935, DOI: 10.1063/1.359174

3257. CONDUCTIVITY OF RF-SPUTTERED NI-100-X-SI-X THIN-FILMS WITH 33-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-77 AT.PERCENT

Authors: BELUMARIAN, A; SERBANESCU, MD; MANAILA, R; IVANOV, E; MALIS, O; DEVENYI, A

Published: APR 1 1995, THIN SOLID FILMS, 259, 112, DOI: 10.1016/0040-6090(94)06408-3

The temperature dependence of the electrical resistance of r.f.-sputtered Ni-Si thin films with variable Si content in the range 33-77 at.% (as determined by Rutherford backscattering spectroscopy) was measured between - 190 degrees C and the annealing temperature T-t (T-tmax=300 degrees C). The as-deposited films were investigated by X-ray diffraction and transmission electron microscopy, and were found to exhibit an amorphous structure (different from that of amorphous Si), except those films with a composition favourable for silicide formation. The temperature dependence of the conductivity of these films is interpreted in the framework of the weak localization model and electron-electron interactions. Annealing at 300 degrees C brings about a transformation from an amorphous structure into a microcrystalline structure comprising different silicides, whose electrical resistance displays a classical metallic temperature dependence, except for the sample with x = 77 at.%, which remains amorphous, although its conductivity increases with temperature.

3258. QUASI-REVERSIBLE TRANSFORMATIONS IN THE ((BI,PB)O)(2)SR2-XCAXBIN-1FENO3N+1+Z (X=0 AND X=1) SYSTEM AND THEIR INFLUENCE ON THE IRON DISTRIBUTION AND MAGNETIC-PROPERTIES OF THE ARISING PHASES

Authors: FILOTI, G; ROSENBERG, M; SPANU, V; KEMMLERSACK, S; STEUDTNER, C

Published: AUG 1 1995, JOURNAL OF ALLOYS AND COMPOUNDS, 226, 99, DOI: 10.1016/0925-8388(95)01602-3

A phase analysis of the components resulting from a complex program of reactions for the preparation of ((Bi, Pb)O)(2)-Sr2-xCaxBin-1 FenO3n+1+z with x = 0, x = 0 and n = 1, n = 2, using Fe-57 Mossbauer spectroscopy, was performed. Whereas for the phases with n=1 only relatively slight differences in the values of the Neel temperature between 207 and 250 K were found, the phases with n = 2 presented stronger differences, the magnetic ordering temperatures ranging for different conditions of reactions between 205 and 512 K. The two-phase sample with n=2 ordered magnetically below 60 K. An increase in the duration and/or temperature of reaction resulted in compounds with a high degree of inhomogeneity in the vicinity of the Fe sites leading to a distribution of Fe spin freezing temperatures. All the phases studied with n=1 exhibited a Morin spin reorientation transition, with the spins parallel to the c-axis at low temperatures and perpendicular to it above 100-150 K. In all the samples studied about 4%-11% Fe in the form of high spin Fe4+ was present, the corresponding Mossbauer sextet vanishing at higher temperatures because of faster electron hopping.

3259. CHEMICAL TRENDS OF ICOSAHEDRAL ORDER IN AL-CU-TM QUASI-CRYSTALS

Authors: POPESCU, R; JIANU, A; MANCIU, M; NICULA, R; MANAILA, R

Published: APR 15 1995, JOURNAL OF ALLOYS AND COMPOUNDS, 221, 247, DOI: 10.1016/0925-8388(94)01440-X

Icosahedral alloys with the composition Al(62)Cu(25.5)TM(12.5) (TM=V, Cr, Mn, Fe, Co, Ni) were prepared by melt spinning. Prevailing icosahedral phases were found for TM=Cr, Mn and Fe. Phonon and random phason disorder were evaluated by an analysis of X-ray diffraction linewidths. A marked chemical trend was noted for phonon-type disorder, which increases in the sequence Fe<Mn<Cr. The parameter of the hypercubic lattice for the Mn-based icosahedral phase allows information to be derived on the metallic valence of Mn and its local coordination via the effective atomic radius.

3260. SINTERING TIME AND PROPERTIES OF YBA2CU3O-SIMILAR-TO-7 SUPERCONDUCTING CERAMICS

Authors: ALDICA, G; POPESCU, M; POPA, S; BUNESCU, MC; BADICA, P

Published: JUN 1995, JOURNAL OF SUPERCONDUCTIVITY, 8, 372, DOI: 10.1007/BF00728173

The effect of annealing duration in oxygen flow on the superconducting characteristics of YBa2Cu3Osimilar to 7 bulk ceramics was investigated by structural, electrical, magnetic, and electronic microscopy investigations. The long-time annealing is deleterious for the superconductivity in YBa2Cu3Osimilar to 7 ceramics. The optimum time interval for annealing is from 20 to 70 h at 950 degrees C, and within this range the maximum value of T-c is obtained.

3261. FE-57 MOSSBAUER STUDY OF GD(2)FE(14-X)M(X)C COMPOUNDS WITH M=NI, SI, CU, V

Authors: MORARIU, M; ROGALSKI, M; VALEANU, M; PLUGARU, N; BURZO, E

Published: FEB 1995, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 140, 1002, DOI: 10.1016/0304-8853(94)01499-X

Gd(2)Fe(14-x)M(x)C compounds, with M = Ni, Si, Cu or V and x less than or equal to 1.5 were investigated by Fe-57 Mossbauer spectroscopy. A preferential substitution of iron sites by the M elements is evidenced. The hyperfine parameters are discussed in correlation with the data obtained by magnetic measurements.

3262. EFFECTS OF ANNEALING ON THE CONDUCTIVITY OF C-60 THIN-FILMS

Authors: BELUMARIAN, A; MANAILA, R; STOICA, T; DRAGOMIR, A; MANCIU, M; DEVENYI, A; BRAUN, T

Published: 1995, FULLERENE SCIENCE AND TECHNOLOGY, 3, 509, DOI: 10.1080/153638X9508543803

Films of C-60, at different stages of annealing of T-c = 200 degrees and 300 degrees C have been electrical characterized over the temperature domain from -130 degrees C to T-c. X-ray diffraction revealed a random polycrystalline fee structure with stacking defects of an intrinsic nature, due to deposition conditions. The value of room-temperature conductivity was found to be in the range (6.3-1.0)*10(-10) (Omega cm)(-1). In the stable annealed state the conductivity showed an activated temperature dependence above 423 K and a non-activated dependence below 330-280 K. The activation energies E(2) 0.8 eV (film thickness 0.70 mu m) and E(2) = 1.0 eV (film thickness 2.40 mu m) were in good agreement with the energy gap values (1.63 eV and 2.08 eV) which were deduced from the al;sorption spectral dependence. Annealing decreased the non-activated contribution to conduction, extending the intrinsic conduction temperature range.

3263. A comparative study of zinc-polyaniline electrochemical cells having sulfate and chloride electrolytes

Authors: Sima, M; Visan, T; Buda, M

Published: AUG 1995, JOURNAL OF POWER SOURCES, 56, 136, DOI: 10.1016/0378-7753(95)80024-B

Polyaniline (PANI) films were investigated at 20 degrees C as the positive electrodes for Zn/PANI secondary cells containing either 1 M ZnCl2, 0.5 M NH4Cl or 1 M ZnSO4, 0.18 M (NH4)(2)SO4 electrolytes, respectively, at pH=4.5, Cyclic voltammograms showed similar behaviour for the thin PANI films as those in highly acid media. From the discharge curves specific capacities were calculated of 127-130 Ah kg(-1) for the Zn/PANI, Cl- cell and 82-107 Ah kg(-1) for the Zn/PANI, SO42- cell. Charging limit values of 1.48 V for the Zn/PANI, Cl- cell and 1.52 V for the Zn/PANI SO42- cell were obtained in order to prevent the electrochemical inactivation of the polymer. After 20 to 30 cycles the capacity of both cells decreases rapidly and then levels off. The self-discharge process is important only in the first approximately 80 h, after which the open-circuit voltage remains constant. Zn/PANI, Cl- cell showed better electrical characteristics for use as a secondary system.

3264. INFLUENCE OF INITIAL CONDITIONS ON THE OPTICAL AND ELECTRICAL CHARACTERIZATION OF SILLENITE-TYPE CRYSTALS

Authors: HAMRI, A; SECU, M; TOPA, V; BRIAT, B

Published: JAN 1995, OPTICAL MATERIALS, 4, 201, DOI: 10.1016/0925-3467(94)00101-4

We compare a set of results concerning our measurement of the optical absorption (OA), photoconductivity (PC), thermally stimulated currents (TSC) and thermally stimulated luminescence (TSL) on the same crystal. We also investigate the effects of various preillumination treatments at room or liquid nitrogen temperature. We conclude that illumination with infrared light (rather than solely red) plays an important role which has been underestimated in the past.

3265. EXCIMER-LASER PROCESSING OF AMORPHOUS AND NANOCRYSTALLINE FE73.5CU1NB3SI22.5-XBX (X=6 AND 9)

Authors: SORESCU, M; KNOBBE, ET; BARB, D

Published: JAN 1995, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 56, 87, DOI: 10.1016/0022-3697(94)00139-1

The effects of pulsed excimer laser irradiation (lambda = 308 nm, tau = 10 ns) on the magnetic and structural properties of amorphous and nanocrystalline Fe73.5Cu1Nb3Si22.5-xBx (x = 6 and 9) were investigated by transmission Mossbauer spectroscopy, scanning electron microscopy and energy-dispersive X-ray analysis. In the amorphous specimens, two types of compositionally-dependent kinetics have been deduced for the laser-induced changes to the easy magnetization axis: controlled magnetic anisotropy (x = 9) and random distribution of magnetic moment directions (x = 6). Micrometer-size crystalline precipitates of alpha-Fe have been observed in the Fe73.5Cu1Nb3Si16.5B6 sample irradiated at the highest repetition rate. Pulsed excimer laser treatment of nanocrystalline Fe73.5Cu1Nb3Si13.5B9 has been found to enhance the fraction of crystalline Fe-Si alloy (18 at. %) with DO3 structure, and to determine a random distribution of magnetic moment directions in the remaining amorphous grain boundary phase. Excimer laser processing is suggested as a powerful tool for controlling the magnetic anisotropy and phase equilibrium in amorphous and nanocrystalline materials

3266. THERMAL-ANALYSIS OF THE PYROELECTRIC BIMORPH AS RADIATION DETECTOR

Authors: ALEXE, M; PINTILIE, L

Published: OCT 1995, INFRARED PHYSICS & TECHNOLOGY, 36, 954, DOI: 10.1016/1350-4495(95)00027-V

Thermal analysis of a pyroelectric bimorph structure, performed for a sinusoidally modulate heat flow, reveals the possibility to obtain a larger signal than in the case of a homogenous pyroelectric structure. The ratio between the signal generated from a bimorph structure and the signal generated from a homogenous structure, in the same conditions, depends on the material properties and on the modulation frequency. This ratio, computed for a particular bimorph, is up to four at 1000 Hz.

3267. Neutron powder diffraction and magnetic properties of Pb-0212

Authors: Seling, B; Schinzer, C; Ehmann, A; KemmlerSack, S; Filoti, G; Rosenberg, M; Linhart, J; Reimers, W

Published: DEC 1995, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 152, 497, DOI: 10.1002/pssa.2211520217

Several cuprates of type Pb-0212 are prepared. The crystal structure is refined from neutron powder diffraction and X-ray diffraction data as tetragonal (space group 14/mmm). interestingly, Pb is simultaneously present in two atomic positions with CN 8 and 9 and considered as Pb4+ and Pb2+ Superconductivity with T-c between 30 and 75 K is observed in the system Pb0.5La1.5-xSr1+xCu2Oy. However, in as-prepared powdered materials the superconducting volume fraction remains low due to the formation of grain boundaries acting as weak links, whereas a significant improvement is obtained in bulk materials by use of flux. Mossbauer and susceptibility measurements of Fe substituted materials indicate the development of a spin glass like behaviour at low temperatures.

3268. HIGH POWER OPERATION OF LOW CONFINEMENT LASER DIODE STRUCTURE

Authors: PETRESCUPRAHOVA, IB; BUDA, M; IORDACHE, G; KAROUTA, F; SMALBRUGGE, E; VANDEROER, TG; KAUFMANN, LMF; WOLTER, JH; VANDERVLEUTEN, WG

Published: 1995, FOURTH CONFERENCE IN OPTICS, ROMOPTO '94, 2461, 9, DOI: 10.1117/12.203458

3269. ND3+ CENTERS INDUCED BY ZNO OR MGO CODOPING LINBO3

Authors: CAMARILLO, E; HERNANDEZ, J; GARCIASOLE, J; CALDINO, U; SANTIUSTE, JEM; LORO, H; VODA, M; JAQUE, F; MURRIETA, H

Published: DEC 4 1995, JOURNAL OF PHYSICS-CONDENSED MATTER, 7, 9641, DOI: 10.1088/0953-8984/7/49/025

Laser spectroscopy has been applied to systematically investigate the effect of MgO or ZnO codoping on the Nd3+ centres formed in LiNbO3. Both codopant oxides produce the same effect, so two new Nd3+ centres appear in both LiNbO3(MgO):Nd and LiNbO3(ZnO):Nd crystals. These new centres correspond to a small percentage (less than 1%) of Nd3+ ions, which are displaced from Li+ sites to a new lattice site. The possible sites for these Nd3+ centres are discussed.

3270. A preliminary study on the preparation and physical properties of some high T-c superconductors (Y,Tm)-Ba-Cu oxides

Authors: Osiceanu, P; Aldica, G; Popescu, M; Patron, L; Plostinaru, S; Spacu, P

Published: JUL-AUG 1995, REVUE ROUMAINE DE CHIMIE, 40, 849, DOI:

High T-c bulk superconductors Y(Tm)Ba2Cu3O7-x and YSryBa2-yCu3O7-x were pre pared following new synthesis routes by the method of thermal decomposition of polynuclear coordination complexes. The best superconducting samples were obtained using oxalic and malic acids as ligands. The effect of substituting of Pa by Sr nas a decrease of T-c with increasing the Sr:Ba ratio. Electrical resistance, magnetic susceptibility and structural measurements have been performed on the superconducting samples.

3271. TI NITRIDE PHASES IN THIN-FILMS DEPOSITED BY DC MAGNETRON SPUTTERING

Authors: MANAILA, R; BIRO, D; BARNA, PB; ADAMIK, M; ZAVALICHE, F; CRACIUN, S; DEVENYI, A

Published: OCT 1995, APPLIED SURFACE SCIENCE, 91, 302, DOI: 10.1016/0169-4332(95)00134-4

Ti nitride films were deposited by DC magnetron sputtering on HSS and Si substrates. X-ray diffraction showed the formation of single-phase delta-TiN. (111) texture was found in most films, as well as stacking disorder on (111) planes, both correlated with deposition parameters, including the degree of plasma ionization. Evidence was found for plastic deformation relaxing film stress, The structure data are correlated with film microstructure and microhardness.

3272. EFFECT OF INTERGROWTH DEFECTS ON THE X-RAY-DIFFRACTION PATTERN .2. A CASE-STUDY OF BI-BASED SUPERCONDUCTORS

Authors: MALIS, O; MANCIU, M; MANAILA, R; DEVENYI, A

Published: FEB 1995, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 147, 333, DOI: 10.1002/pssa.2211470204

In Part I a general equation was derived for the intensity diffracted by a matrix phase containing intergrowths. It was applied to the case of Bi2Sr2Can-1CunOy phases (n = 2, 3) with stacking defects (''wrong'' number n of Cu-O planes in a half-cell). A least-squares program based on this equation yields the nature, concentration, and short-range order of the defect intergrowths. The program uses the peak shifts which are induced by the presence of defects. The analysis is exemplified on several BSCCO samples, whose defect state informs about the formation steps of the superconducting phases.

3273. NEUTRON POWDER DIFFRACTION AND MAGNETIC-PROPERTIES OF BI-0212

Authors: SELING, B; SCHINZER, C; EHMANN, A; KEMMLERSACK, S; FILOTI, G; ROSENBERG, M; LINHART, J; REIMERS, W

Published: SEP 15 1995, PHYSICA C, 251, 246, DOI: 10.1016/0921-4534(95)00418-1

A series of cuprates of type Bi-0212 has been prepared. The crystal structure was refined from neutron powder diffraction data at room temperature and 10 K as tetragonal (space group I4/mmm). Mossbauer and susceptibility measurements of the Fe substituted material indicate the development of a spin glass-like behavior at low temperatures. Superconductivity with T-c around 30 K is observed in the system Bi0.5La1.5-xYxSrCu2Oy. An increase of the hole-carrier concentration is obtained by suitable incorporation of Bi, Pb, La and Sr on the nine coordinated 4e positions with an improvement of T-c to 75 K.

3274. INTERMEDIATE-RANGE ORDER IN BASE-CATALYZED SOL-GEL SILICA

Authors: POPESCU, R; ZAHARESCU, M; VASILESCU, A; CATANA, G; MANAILA, R

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 139, DOI: 10.1016/0022-3093(95)00341-X

The intermediate-range order (IRO) in silica gels is investigated by X-ray diffraction and infrared absorption. The IRO degradation in fresh gels with respect to v-SiO2 and its recovery upon annealing are quantitatively characterized.

3275. NI SILICIDES FORMATION AND PROPERTIES IN RF-SPUTTERED NI-100-X-SI-X THIN-FILMS

Authors: BELUMARIAN, A; SERBANESCU, MD; MANAILA, R; DEVENYI, A

Published: OCT 1995, APPLIED SURFACE SCIENCE, 91, 67, DOI: 10.1016/0169-4332(95)00095-X

The temperature dependence of the electrical resistance R(T) for RF sputtered Ni-100-x-Si-x thin films (33 less than or equal to x less than or equal to 56 at%, as determined by Rutherford backscattering spectroscopy) was measured between -190 degrees C and the annealing temperature T, (T-a max = 300 degrees C). Structure investigations by X-ray diffraction revealed the preferential formation of silicide phases in as-deposited films as dependent on composition: gamma-Ni5Si2 (for x = 33), delta-Ni2Si (37 less than or equal to x less than or equal to 40) and zeta-NiSi2 (for x = 56). For intermediary compositions, amorphous alloys are formed. Annealing at 200 and 300 degrees C induces crystallization of the amorphous films into the gamma-Ni5Si2 phase (with zeta-NiSi2 admixture). The preferential formation of silicide phases is discussed taking into account the phenomenological rule of ''effective formation heat''. The temperature dependence of electrical resistance for as-deposited and annealed gamma and delta polycrystalline silicide thin films exhibits a classic metallic behaviour (different from that of polycrystalline Ni thin films). The very different R(T) behaviour of as-deposited and annealed polycrystalline zeta-phase is interpreted taking into account the weak localization contribution.

3276. TEMPERATURE-DEPENDENCE OF SURFACE-TENSION OF LIQUID-CRYSTALS AT THE PHASE-TRANSITION

Authors: MOLDOVAN, R; TINTARU, M; BEICA, T; FRUNZA, S; STOENESCU, DN

Published: FEB 20 1995, MODERN PHYSICS LETTERS B, 9, 242, DOI: 10.1142/S0217984995000231

The surface tension is calculated as the excess of the free energy per unit area, due to the presence of a surface layer, using Landau-de Gennes expansions, in the hypothesis of a first order transition in the bulk and taking into account the dependence of the surface free energy from the surface tilt angle. The surface order parameter is calculated and surface-ordered phase above the phase transition temperature has been found. A variety of calculated surface tension versus temperature curves with a jump at the phase transition, with positive or negative slope, well describing the experimental data from literature, have been attained.

3277. EFFECT OF NITROGENATION ON THE MAGNETIC-PROPERTIES OF R2FE17-XSIX COMPOUNDS, WITH R=Y OR GD

Authors: VALEANU, M; PLUGARU, N

Published: FEB 1994, MATERIALS LETTERS, 18, 335, DOI: 10.1016/0167-577X(94)90018-3

The competitive effects of iron substitution by silicon and of the interstitial nitrogen atoms on the structural and magnetic properties of R2Fe17-xSix compounds, with R=Y or Gd, are analysed. The values of Curie temperatures and of mean iron moments are correlated to the exchange interactions (between iron atoms) in the parent and nitrogenated compounds. The magnetic behaviour of iron is analysed on the basis of the mean field model and it is shown to present mainly a localized character in the interstitial compounds.

3278. DESIGN OF A 1 W, SINGLE FILAMENT LASER-DIODE

Authors: PETRESCUPRAHOVA, IB; BUDA, M; VANDEROER, TG

Published: SEP 1994, IEICE TRANSACTIONS ON ELECTRONICS, E77C, 1478, DOI:

A design of a high power laser structure is presented which is based on an increase of the cavity length as well as a maximization of the stripe width. This requires a low value for the modal attenuation coefficient and a low optical confinement factor. A model is presented from which the modal gain, the confinement factor, the active region thickness, the stripe width, the length and the reflection coefficients can be calculated. A variant for all design parameters needed to reach 1 W emission in the fundamental lateral mode is given. These values are used to design the epitaxial structure.

3279. STEREOSELECTIVITY OF CYCLOOLEFIN POLYMERIZATION WITH WCL6-BASED CATALYTIC-SYSTEMS

Authors: DIMONIE, M; COCA, S; TEODORESCU, M; POPESCU, L; CHIPARA, M; DRAGUTAN, V

Published: MAY 24 1994, JOURNAL OF MOLECULAR CATALYSIS, 90, 124, DOI: 10.1016/0304-5102(93)E0311-4

The stereochemistry of ring-opening metathesis polymerization of several cycloolefins (cyclopentene, cyclooctene, 1,5-cyclooctadiene, cyclododecene) in the presence of WCl6-based catalysts (WCl6/iBu3Al/epichlorohydrin, WCl6/iBu3Al/Chloranil, WCl6/phenylacetylene, WCl6/Ph4Sn, WCl6/allyl4Si, WCl6/iBu2AlOAliBu2) has been carefully examined. The product stereoselectivity and polymer microstructure were greatly dependent on the nature of the catalytic system and reaction conditions; the nature of the cycloolefin also influenced the steric course of the reaction. An important stereochemical consequence was that the cis and trans content of the polyalkenamer greatly depended on the oxidation state of the W-atom, catalyst activity and reaction temperature. The relationship between the microstructure of several polyalkenamers (polypentenamer, polyoctenamer, polydodecenamer) obtained with the above catalytic systems and cycloolefin reactivity or catalyst nature is fully illustrated. The role of the ligand as well as of the cocatalyst and activator is also shown. The particular stereochemical behaviour of cycloolefins in the presence of the studied WCl6-based catalytic systems is discussed in terms of the metallacarbene-metallacyclobutane mechanism. The steric effects induced by the coordinating cycloolefin and the existing ligands at the transition metal are also considered.

3280. ESR INVESTIGATIONS ON ION-BEAM IRRADIATED POLYCARBONATE

Authors: CHIPARA, MI; GRECU, VV; NOTINGHER, PV; ROMERO, JR; CHIPARA, MD

Published: JUN 1994, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 88, 422, DOI: 10.1016/0168-583X(94)95393-7

Electron spin resonance (ESR) investigations with a polycarbonate solid state nuclear detector, irradiated with oxygen ions, are reported. The nature of the paramagnetic defects induced by irradiation is discussed. The temperature dependence of resonance line parameters is studied. From the experimental data, obtained by ESR, spectroscopy, the activation energy for defect recombination, the average isotropic exchange integral between paramagnetic defects as well as the average distance between defects, are estimated. Correlations with latent tracks structure are discussed.

3281. TRAPPING LEVELS IN BI12SIO20 CRYSTALS

Authors: PETRE, D; PINTILIE, I; BOTILA, T; CIUREA, ML

Published: AUG 15 1994, JOURNAL OF APPLIED PHYSICS, 76, 2219, DOI: 10.1063/1.357637

Localized levels play a major role in the electro-optic properties of Bi12SiO2O (BSO) crystals. The activation energy of trapping levels was studied by different laboratories using various methods (e.g., thermally stimulated currents and photoinduced current transient spectroscopy). A more sensitive investigation of traps in undoped BSO single crystals has been performed by optical charging spectroscopy. The presence of traps in the energy range 0.2-1.1 eV was found, and the results are in good agreement with previous studies. On the other hand, this method led us to suggest that the trapping levels observed can be both electron traps and hole traps. For deep trapping levels at higher temperatures, a strong temperature dependence of the cross section was observed.

3282. LAALO3 THIN-FILMS DEPOSITED ON SILICON AND SAPPHIRE AS BUFFER LAYERS FOR YBA2CU3O7-X

Authors: SANDU, V; JAKLOVSZKY, J; MIU, D; DRAGULINESCU, D; GRIGORIU, C; BUNESCU, MC

Published: AUG 15 1994, JOURNAL OF MATERIALS SCIENCE LETTERS, 13, 1225, DOI: 10.1007/BF00241019

3283. EXISTENCE OF ENANTIOMERIC PHASE-SEPARATION IN A 3-DIMENSIONAL LATTICE-GAS MODEL

Authors: HUCKABY, DA; PITIS, R; SHINMI, M

Published: JUN 1994, JOURNAL OF STATISTICAL PHYSICS, 75, 995, DOI: 10.1007/BF02186754

A three-dimensional lattice gas model for enantiomeric phase separation is introduced. The enantiomeric molecules (d and 1) are the two nonsuperimposable mirror images having the molecular structure C(AB)2, where C is a tetrahedrally bonded carbon atom with one bond to each end of two AB groups. The lattice gas model consists of a body-centered cubic lattice, each site of which can be either vacant or occupied by a molecule oriented so that the A and B groups point toward neighboring lattice sites. Pairs of molecules interact with short-range, orientationally-dependent interactions. For a domain of interaction parameters, the Pirogov-Sinai extension of the Peierls argument is used to prove that d-rich and l-rich phases exist in the model at sufficiently low temperature. For another domain of interaction parameters, at sufficiently high chemical potential there is an infinite number of ground states, each containing a racemic mixture of d and l molecules.

3284. RESISTIVITY AND MAGNETORESISTANCE-ELASTORESISTANCE OF POLYCRYSTALLINE NI-SI THIN-FILMS

Authors: BELUMARIAN, A; SERBANESCU, MD; MANAILA, R; TEODORESCU, V; IVANOV, I

Published: FEB 1 1994, THIN SOLID FILMS, 238, 317, DOI: 10.1016/0040-6090(94)90072-8

The temperature dependence of the resistivity and magnetoresistance-elastoresistance of r.f.-sputtered Ni-Si thin films with variable silicon content (0-24 at.%) (determined by Rutherford backscattering spectroscopy) annealed to 300 degrees C was measured. The films, investigated by X-ray diffraction and transmission electron microscopy, exhibit a polycrystalline structure of the Ni f.c.c. type with a disorder degree which increases with the silicon content and a metallic-type conduction mechanism. The ferromagnetic properties of Ni are still preserved in the Ni-Si thin films up to 8.8 at.% silicon content.

3285. CURVED CRYSTAL OPTICS AND THE RESOLUTION FORMALISM - PROGRAMS AND OPTIMIZATION PROCEDURES

Authors: POPOVICI, M; YELON, WB; BERLINER, R; STOICA, AD; IONITA, I; LAW, R

Published: JAN 8 1994, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 338, 110, DOI: 10.1016/0168-9002(94)90168-6

The problem of computing the neutron optics of curved-crystal spectrometers is reviewed. The conditions of focusing in scattering and the limitations to achievable resolutions are discussed. Experience with programs for resolution-intensity optimization is presented. Computational examples are given of high resolution configurations with bent crystals and open beams, showing significant intensity gain over conventional techniques. Quasi-elastic scattering measurements at energy transfer resolutions below 10 mu eV are shown to be feasible at high luminosity. Curved monochromators for high resolution neutron powder diffraction, combining the beam focusing onto sample with focusing in scattering, are also discussed.

3286. STUDY OF THE PINNING POTENTIAL IN BI2SR2CACU2O8+DELTA HTSC BY DC MAGNETIZATION MEASUREMENTS IN THE SUBCRITICAL DYNAMIC FLUX-CREEP REGIME

Authors: PELIGRAD, DN; KAESS, U; NEBENDAHL, B; KESSLER, C; DULCIC, A; MEHRING, M

Published: DEC 1994, PHYSICA C, 235, 2041, DOI: 10.1016/0921-4534(94)92241-1

Due to fast relaxation of magnetization and high critical current densities it is difficult in HTSC to reach the critical state experimentally. In order to obtain complete information about it from subcritical state measurements an extrapolation scheme based on the sweep rate dependence of the hysteresis widths has been developed.

3287. HIGHLY HOMOGENEOUS POLYCRYSTALLINE HGTE SYNTHESIS UNDER PRESSURE

Authors: LAZARESCU, MF; MANEA, AS

Published: 1994, CRYSTAL RESEARCH AND TECHNOLOGY, 29, 43, DOI: 10.1002/crat.2170290112

A high pressure technique for the direct synthesis of polycrystalline HgTe in quartz ampoules is presented. An excess of mercury as well as a quasi-static regime of the inert gas pressure al melt temperatures up to 750 degrees C have been used. X-ray diffraction and SEM confirmed the structural homogeneity of the synthesized material.

3288. HYPERFINE FIELDS AND MAGNETIC-ANISOTROPY IN FE100-XGDX THIN-FILMS AND FE80-XGDXB20 (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-24) THIN-FILMS AND RIBBONS

Authors: KUNCSER, V; FILOTI, G; SERBANESCU, MD; JIANU, A; CRISTEA, L; DORMANN, JL; NOGUES, M; MAKNANI, J

Published: 1994, HYPERFINE INTERACTIONS, 94, 2326, DOI: 10.1007/BF02063782

Mossbauer measurements performed on Fe100-xGdx thin films and on Fe80-xGdxB20 both as thin films and ribbons show a dependence of the spins orientation and [H-hyp] versus temperature, Gd content and preparation conditions. Increasing the Gd content, the initial low anisotropy disappears and [H-hyp] decreases. A sharp increase of the anisotopy with temperature in ribbons with low Gd concentration is evidenced.

3289. RELATION OF STARTING PRECURSORS TO THE RESULTING HIGH-T-C PHASES IN THE PB AND SB DOPED BI-SR-CA-CU-O SYSTEM

Authors: CONSTANTINESCU, F; HOLIASTOU, M; NIARCHOS, D; NICOLAIDES, GK; VASILIU, F; BUNESCU, C; ALDICA, G

Published: FEB 1994, JOURNAL OF MATERIALS RESEARCH, 9, 296, DOI: 10.1557/JMR.1994.0292

The introduction of more reactive precursors for Pb and Sr (oxalates), as well as Ca (citrate) and the use of a Bi nitrate decomposition route, has increased the percentage of the high-T-c (2223) phase in the Bi-Sr-Ca-Cu-O (BSCCO) system. Partial substitution of Bi(Pb) with Sb gives an almost single (2223) phase sample. In addition, a single (2212) phase sample is obtained when high purity Bi2O3 is used as a precursor, whereas Bi acetate leads to semiconducting behavior. The morphology of the samples is studied with a scanning electron microscope (SEM), the stoichiometry with energy-dispersive x-ray analysis (EDAX), and the structure with x-ray diffraction (XRD), while the superconducting properties are investigated by de-resistivity, ac-susceptibility, and SQUID magnetometry techniques.

3290. ESR INVESTIGATIONS OF POLYPENTENAMERS DEGRADATION

Authors: DIMONIE, M; COCA, S; CHIPARA, MI; ROMERO, JR; POPESCU, L

Published: 1994, INTERNATIONAL JOURNAL OF POLYMERIC MATERIALS, 24, 279, DOI: 10.1080/00914039408028570

Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall generation of free radicals and the associated constant rate, are estimated.

3291. STACKING DEFECTS IN C-60 FILMS

Authors: MANCIU, M; MANAILA, R; DEVENYI, A

Published: 1994, FULLERENE SCIENCE AND TECHNOLOGY, 2, 289, DOI: 10.1080/15363839408009551

The structure of pollycrystalline C60 films prepared by sublimation from 99.9% pure C60 powder and from graphite soot was investigated by X-ray diffraction. A complex fcc (111) line was found in the former samples. Comparison of experimental and simulated (111) profiles allowed to assess quantitatively the degree of stacking disorder introduced during the growth of the film. Probabilities could be derived for continuation of already started fcc and hcp sequences, thereby characterizing the statistical microstructure of the C60 films. Also, the relative magnitudes of inter- and intra-layer disorder can be estimated. The films deposited from graphite soot show a high structural disorder.

3292. LINIO2 - QUANTUM LIQUID OF CONCENTRATED SPIN-GLASS

Authors: ROSENBERG, M; STELMASZYK, P; KLEIN, V; KEMMLERSACK, S; FILOTI, G

Published: MAY 15 1994, JOURNAL OF APPLIED PHYSICS, 75, 6815, DOI: 10.1063/1.356816

From the magnetic and Mossbauer spectroscopy study of LiNi1-xFexO2 With x = 0, 0.01, 0.05, and 0.10 evidence for strong ferromagnetic correlations and spin freezing at low temperatures was found, reminding many characteristic features of spin glass behavior in variance with models describing the ground state of LiNiO2 as a quantum liquid.

3293. ESR INVESTIGATION OF ION-BEAM IRRADIATED POLYETHYLENE

Authors: CHIPARA, MI; IFRIM, A; GRECU, VV; TOACSAN, MI; POPESCUPOGRION, N; IONESCU, A; CHIPARA, MD; ROMERO, JR

Published: 1994, POLYMER DEGRADATION AND STABILITY, 43, 169, DOI: 10.1016/0141-3910(94)90065-5

Electron spin resonance (ESR) investigations of polyethylene, irradiated with accelerated sulphur ions, are reported- The temperature dependence of resonance line parameters in the range 20-260-degrees-C, has been studied. Additional ESR data on polyethylene irradiated with neutrons as well as on polyethylene thermally degraded in air are presented. The nature of the free radicals induced by irradiation is discussed.

3294. IMPURITY SITES OF LINBO3ER3+ CODOPED WITH MGO OR ZNO

Authors: NUNEZ, L; DUCHOWICZ, R; VODA, M; CUSSO, F

Published: APR 1994, JOURNAL DE PHYSIQUE IV, 4, 446, DOI: 10.1051/jp4:19944106

The optical properties of Er3+ doped LiNbO3, LiNbO3(MgO) and LiNbO3(ZnO) have been studied. Polarized absorption and laser excited luminescence spectra at liquid-He temperature show different structure dependent on the co-dopants (MgO, ZnO). The relationship between the optical characteristics and the impurity sites location is discussed.

3295. EXPERIMENTAL-DETERMINATION OF THE EFFECTIVE SPLAY-BEND ELASTIC-CONSTANT

Authors: BARBERI, R; BARBERO, G; GIOCONDO, M; MOLDOVAN, R

Published: SEP 1994, PHYSICAL REVIEW E, 50, 2099, DOI: 10.1103/PhysRevE.50.2093

The temperature-induced surface alignment transitions in nematic liquid crystals are analyzed. It is shown that it is possible to interpret the experimental data by means of an elastic model in which the effective splay-bend surfacelike elastic constant is taken into account. This effective elastic constant is defined as the sum of the usual splay-bend and spontaneous splay elastic constant. In this framework the experimental data seem to indicate that the easy axis characterizing the nematic-substrate interaction is independent of the liquid crystal. It depends only on the evaporation geometry (we use flat glass plates vacuum coated by SiO) and on the surfactant dissolved in the liquid crystal. The value of the effective splay-bend elastic constant is obtained for three different liquid crystals in the nematic phase.

3296. AN X-RAY STUDY OF GENERALIZED CANTOR SUPERLATTICES

Authors: JARRENDAHL, K; BIRCH, J; DULEA, M; ARWIN, H; SUNDGREN, JE

Published: JUN 15 1994, THIN SOLID FILMS, 246, 125, DOI: 10.1016/0040-6090(94)90740-4

Amorphous Ge/Si and crystalline Mo/V superlattices have been grown by dual-target d.c. magnetron sputtering with modulations according to finite approximants of various generalized Cantor sequences. The samples were investigated with both conventional powder X-ray diffractometry and high-resolution X-ray diffractometry as well as transmission electron microscopy. The experimental X-ray results were compared with derived analytical expressions for the locations and scalings of the diffraction peaks. Results from the X-ray measurements and the analytical expressions were also compared with numerical reflectivity simulations. The analytical and numerical calculations show good agreement with the experimental results.

3297. THE INFLUENCE OF THE MELT COOLING RATE ON THE PROPERTIES OF YIG SINGLE-CRYSTAL GROWN BY THE FLUX METHOD FROM SINTERED POLYCRYSTALLINE MATERIAL

Authors: LAZARESCU, MF; MANEA, AS; ELENA, E

Published: 1994, CRYSTAL RESEARCH AND TECHNOLOGY, 29, 894, DOI: 10.1002/crat.2170290621

A method for the single crystal growth of Yttrium Iron Garnet (YIG) in a PbO/PbF2/B2O3 flux mixture with a melt cooling rate of 1-2.5 degrees C/h is described. In order to keep constant the crystal stoichiometry as well as its specific structural and magnetic properties at such high rates of the cooling process, a previously sintered polycrystalline garnet has been used as raw material. The YIG single crystal quality was checked-up by metallographic analysis, X-ray diffraction, SEM, and magnetic susceptibility measurements.

3298. EVIDENCE FOR SPIN FREEZING AND FERROMAGNETIC SHORT-RANGE CORRELATIONS IN FE-57-DOPED LINIO2

Authors: FILOTI, G; ROSENBERG, M; STELMASZYK, P; ZHOU, R; KEMMLERSACK, S; KLEIN, V

Published: 1994, HYPERFINE INTERACTIONS, 88, 95, DOI: 10.1007/BF02068706

Evidence for a frozen spin ground state and a mixed magnetic ordered and paramagnetic state at intermediate temperatures was found in Fe-57-doped LiNiO2, using Mossbauer spectroscopy. The magnetic measurements, in agreement with Mossbauer data, suggest short-range ferromagnetic correlations at low temperatures and the occurrence of a paramagnetic phase below the spin freezing temperature.

3299. METAMAGNETISM AND SPIN ARRANGEMENT IN ND6FE13SN

Authors: ROSENBERG, M; ZHOU, RJ; VELICESCU, M; SCHREY, P; FILOTI, G

Published: MAY 15 1994, JOURNAL OF APPLIED PHYSICS, 75, 6588, DOI: 10.1063/1.356903

A magnetic and Mossbauer spectroscopy study of nonoriented and magnetically oriented samples of Nd6Fe13Sn was performed. At 4.2 K a metamagnetic transition takes place in a field of 7.1 T. Strong evidence for antiferromagnetic spin arrangements in the iron magnetic sublattice and antiferromagnetism of the Nd moments with only a small contribution to the net magnetization in fields up to 14 T was found.

3300. ON SOME TRANSITION-METAL COMPLEXES HAVING ORIENTATIONAL PROPERTIES

Authors: FRUNZA, S; FITI, M; FRUNZA, L; STOENESCU, DN; MOLDOVAN, R; BEICA, T

Published: FEB 1994, LIQUID CRYSTALS, 16, 285, DOI: 10.1080/02678299408029152

The orientation properties of some complexes of chromium (III) or cobalt (II) with oxygen-containing ligands are presented. The orientation obtained is mostly homeotropic. The possibility of anchoring by coordination of liquid crystal (LC) molecules to the transition metal ion within the alignment layer is discussed on the basis of spectroscopic arguments.

3301. STRUCTURAL AND ELECTROCHEMICAL EFFECTS INDUCED IN METALLIC GLASSES BY MECHANICAL DEFORMATION

Authors: POPESCU, MA

Published: MAR 1994, JOURNAL OF NON-CRYSTALLINE SOLIDS, 169, 159, DOI: 10.1016/0022-3093(94)90235-6

Plastic deformation of glassy ribbons of Fe80B20 leads to the partial destruction of the short-range compositional order of the material. The electrochemical potential measured between two electrodes made from glass ribbons of composition Fe40Ni40B20 shows a non-linear dependence of potential on the uniaxial deformation of one electrode. These effects explain the reduction of corrosion resistance of the glassy metallic alloys subjected to deformation.

3302. HIGH-FIELD MOSSBAUER STUDY OF THE RANDOMLY CANTED LI-FE-TI SYSTEM

Authors: SEQQAT, M; DORMANN, JL; NOGUES, M; JOVE, J; NICOARA, G

Published: 1994, HYPERFINE INTERACTIONS, 94, 2021, DOI: 10.1007/BF02063733

In-field Mossbauer studies have been performed on the Li-0.5(1+t)(l+r)Fe2.5-1.5tTitO4 system with 1.10 less than or equal to t less than or equal to 1.40. The disordered magnetic properties depend strongly on the chemical disorder and local order induced by thermal treatments. The results are in agreement with low- and high-field magnetization measurements. Locally canted states are observed, with the degree of magnetic disorder depending on the composition and (or) the local chemical disorder.

3303. MAGNETIC-PROPERTIES OF GD2FE14-XMX COMPOUNDS WITH M=NI, SI, CU OR V M

Authors: BURZO, E; LAFOREST, J; PLUGARU, N; VALEANU, M; STANCIU, L

Published: MAR 1994, IEEE TRANSACTIONS ON MAGNETICS, 30, 627, DOI: 10.1109/20.312356

The Gd2Fe14-xMxC compounds form solid solutions in the composition ranges x less-than-or-equal-to 1.0 for M = Cu or V and x less-than-or-equal-to 1.5 for M = Si or Ni The Curie temperatures increase when Fe is replaced by Ni, Cu and Si and decrease when this is substituted by V. The above behaviour is correlated with site occupancy of substitutional elements in P4(2)/mnmm-type lattice. The decrease of magnetizations, at 4.2 K as result of substitutions, is greater than that expected from simple dilution behaviour. The magnetic data are analysed in correlation with those obtained in corresponding borides.

3304. COMPLEX CARBIDES IN SYNTHETIC DIAMOND CRYSTALS PRODUCED AT SIMILAR-TO 5.5 GPA

Authors: PAVEL, E; BALUTA, G; BARB, D; LAZAR, DP; MORARIU, M; POPESCU, M; SORESCU, M

Published: MAR 15 1993, JOURNAL OF MATERIALS SCIENCE, 28, 1647, DOI: 10.1007/BF00363361

Characterization of (Fe1-xNix)3C and (Fe1-xCOx)3C identified in metallic inclusions in synthetic diamond crystals grown in Fe-Ni-C and Fe-Co-C systems at a pressure of approximately 5.5 GPa and a temperature of approximately 1800 K was carried out using X-ray microprobe analysis, X-ray diffraction, hardness data, Mossbauer and magnetic measurements. The result suggests that in (Fe1-xCox)3C, metallic atoms have an electronic structure similar to that of Co.

3305. ND3+ MULTISITES IN THE DISORDERED CA3GA2GE3O12 LASER CRYSTAL

Authors: CALDINO, U; VODA, M; JAQUE, F; SOLE, JG; KAMINSKII, AA

Published: OCT 1 1993, CHEMICAL PHYSICS LETTERS, 213, 88, DOI: 10.1016/0009-2614(93)85422-K

Laser excited site-selective spectroscopy of Nd3+ ions in Ca3Ga2Ge3O12 garnet crystals has been investigated in the F-4(3/2)-->I-4(11/2) and F-4(3/2)-->I-4(9/2) regions. Six non-equivalent sites were observed for the Nd3+ in this material. The energy levels of some relevant multiplets were obtained for each Nd3+ site. The evolution of the non-equivalent Nd3+ CryStal field sites in Ca3Ga2Ge3O12 as a function of dopant concentration has been investigated in the range up to 8 at%. The nature of the Nd3+ sites in terms of the possible charge compensating defects is discussed. The formation of Nd3+-Nd3+ pairs is suggested.

3306. FE-57 HYPERFINE FIELDS AND MAGNETIC-ANISOTROPY OF SM2FE17NX INTERSTITIALS WITH INTERMEDIATE NITROGEN CONCENTRATIONS

Authors: ROSENBERG, M; ZHOU, RJ; KATTER, M; SCHULTZ, L; FILOTI, G

Published: MAY 15 1993, JOURNAL OF APPLIED PHYSICS, 73, 6037, DOI: 10.1063/1.353461

From the compositional dependence of the hyperfine fields at the iron sites of Sm2Fe17Nx alloys with 0 less-than-or-equal-to x less-than-or-equal-to 2.94, evidence for cone anisotropy for x=0.4 and uniaxial anisotropy at least for x greater-than-or-equal-to 0.81 has been found. The analysis of the volume dependence of the hyperfine fields allowed us to separate contributions arising from the anisotropy of the orbital component of the iron moment and from the change of the spin moments owing to magnetovolume and bonding effects. The temperature dependence of the average hyperfine field and of the hyperfine fields at the four different nonequivalent Fe sites suggests weak itinerant ferromagnetism for Sm2Fe17N2.94.

3307. ORIENTATIONAL PROPERTIES OF PVA COATED SIO FILMS

Authors: FRUNZA, S; MOLDOVAN, R; BEICA, T; STOENESCU, D; TINTARU, M

Published: 1993, LIQUID CRYSTALS, 14, 296, DOI: 10.1080/02678299308027643

A new method for producing tilt angle in liquid crystal cells is proposed. The method requires a SiO vacuum deposition layer which is subsequently covered with a polyvinyl alcohol (PVA) layer, obtained by dipping in a solution. It was possible to obtain tilt angles between 7 and 30-degrees by changing the concentration of PVA in the solution.

3308. PROMOTION OF HIGH-TC PHASE IN B-DOPED (BI,PB)2SR2CA2CU3OY SUPERCONDUCTORS PREPARED BY THE MELT-QUENCHING METHOD

Authors: FRUTH, V; ZAHARESCU, M; ALDICA, G

Published: MAR-JUN 1993, APPLIED SUPERCONDUCTIVITY, 1, 707, DOI: 10.1016/0964-1807(93)90280-F

We prepared superconducting Bi1.6Pb0.4-xBxSr2Ca2CU3Oy (x=0, 0.1, 0.2, 0.3 and 0.4) ceramics by the melt-quenching method and examined the effect of B addition on the formation of the high-Tc phase.The temperatures and sequence of formation of the superconducting phases within this composition were determined using simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA), X- ray powder diffraction (XRD). It was found that the bulk ceramics with x=0.1 and 0.2 exhibited superconductivity with a critical temperature range of 95-100 K. The lowering of the partial melting temperature caused by the coexistence of Pb and B elements is effective for the formation mechanism of the high-Tc phase.

3309. SPECTROSCOPY OF MN-2+ IONS IN CDCL2

Authors: GHIORDANESCU, V; VODA, M; PEDRINI, C

Published: APR 16 1993, CHEMICAL PHYSICS LETTERS, 205, 414, DOI: 10.1016/0009-2614(93)87143-Q

An investigation of ultraviolet absorption and excitation spectra of Cd1-xMnCl2 Crystals is reported. At lower temperatures, T < 77 K, it is shown that a number of lines are associated with the manganese ions. No assignments are given for room temperature excitation spectra because the Mn2+ states are in the fundamental absorption edge.

3310. STABILITY OF SOME STRUCTURES IN A CHOLESTERIC LIQUID-CRYSTAL LAYER FOR TILTED ANCHORING

Authors: BEICA, T; FRUNZA, S; MOLDOVAN, R; GIURGEA, M; TINTARU, M

Published: JAN 1993, LIQUID CRYSTALS, 13, 138, DOI: 10.1080/02678299308029059

An analysis of the permitted structures for a cholesteric liquid crystal based on the continuum theory as a function of the anchoring conditions and the thickness of the liquid crystal layer is presented. A new type of bistability is found. The stability domains of various structure types are given.

3311. SIO2-SM2O3 VITREOUS FILMS VIA THE SOL-GEL METHOD

Authors: ZAHARESCU, M; PIRLOG, C; GARTNER, M; MOISE, F; TEODORESCU, V

Published: AUG 15 1993, JOURNAL OF MATERIALS SCIENCE, 28, 4441, DOI: 10.1007/BF01154953

SiO2-Sm2O3 vitreous films 120 nm thick were obtained via the sol-gel method. Infrared, energy-dispersive analysis of X-rays, spectroscopic ellipsometry and absorption spectroscopy showed a total inclusion of samarium in the silica matrix, which remains amorphous up to 1000-degrees-C. The inclusion of the samarium ion increases the porosity. The optical properties of films were investigated by spectro-ellipsometry, and the parameters obtained were compared with those obtained by other techniques.

3312. TIME-RESOLVED NEUTRON-DIFFRACTION STUDY OF THE SUPERCONDUCTING PHASE-FORMATION PROCESS IN THE BI(PB)-SR-CA-CU-O SYSTEM

Authors: ALDICA, G; MIRONOVA, GM; POPA, NC; STOICA, AD; STOICA, MG

Published: AUG 1993, JOURNAL OF SUPERCONDUCTIVITY, 6, 278, DOI: 10.1007/BF00626269

The results of real-time neutron diffraction measurements during the superconducting phase formation process in the Bi(Pb)-Sr Ca-Cu-O system are reported. A Sr-Ca-Cu-O type precursor, with the same stoichiometry as the 2223 phase, was used as starting material, and the temperature range favorable to the formation of the 2223 phase was investigated. The diffraction patterns were processed by a multiphase Rietveld refinement. The formation and decomposition of the 2201 and 2212 phases were directly observed. Experimental evidence on the existence of a partially melted phase in the range 855-860-degrees-C, involved in the formation of the 2223 phase, is discussed.

3313. IR SPECTROSCOPIC MEASUREMENTS OF CRYSTALLINITY AND PHASE PURITY OF ZSM-5 SAMPLES

Authors: FRUNZA, L; DINCA, V; VAGAON, M; CRISAN, D; FLORESCU, I; MANOIU, D; CRISAN, M; RAGAN, N

Published: MAR 1993, REVUE ROUMAINE DE CHIMIE, 38, 246, DOI:

The use of IR spectroscopic method to choose the best batches of ZSM-5 zeolites. is discussed. The crystallinity and the particle size were estimated from IR spectra and by XRD and electron microscopy measurements.

3314. MAGNETIC-PROPERTIES OF FE100-XGDX THIN-FILMS AND FE80-XGDXB20 THIN-FILMS AND RIBBONS (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-20)

Authors: FILOTI, G; KUNCSER, V; SERBANESCU, MD; JIANU, A; CRISTEA, L; NOGUES, M; DORMANN, JL; MAKNANI, J

Published: NOV 1993, IEEE TRANSACTIONS ON MAGNETICS, 29, 3125, DOI: 10.1109/20.280879

Magnetic and Mossbauer experiments were performed on Fe100-xGdx thin films and on Fe80-xGdxB20 both in thin films and ribbons for x less-than-or-equal-to 20. The ferrimagnetic order is perturbed by the presence of B and Fe-interactions are.different. For small Gd content, the low anisotropy is in the film plane, while for greater Gd the anisotropy goes out of the plane giving typical features of hysteresis loops and strong decrease of Mossbauer hyperfine fields.

3315. UNUSUAL SCALING OF THE SPECTRUM IN A DETERMINISTIC APERIODIC TIGHT-BINDING MODEL

Authors: DULEA, M; JOHANSSON, M; RIKLUND, R

Published: APR 1 1993, PHYSICAL REVIEW B, 47, 8551, DOI: 10.1103/PhysRevB.47.8547

Local and global scaling properties of the integrated density of states of the tight-binding Rudin-Shapiro model are numerically derived by investigating the dependence of the bandwidths of its periodic approximants on the size of the unit cells. Scaling relations intermediate between the power and exponential laws are found for various values of the energy and amplitude of the on-site potential V. An analysis of the global properties of the spectrum performed in the case when V is equal to the hopping integral t points out its multifractal structure. Multifractal arguments together with earlier results concerning the nature of the wave functions indicate a pure point spectrum for V greater t, while for smaller values of the amplitude V the spectrum reveals a mixed character.

3316. HISTORY DEPENDENT STRUCTURAL-PROPERTIES OF ALUMINA-SUPPORTED NICKEL-OXIDE

Authors: CRAIU, M; MARCHIDAN, R; IVANA, E; BUTUCELEA, A; NISTOR, L

Published: SEP 1993, REACTION KINETICS AND CATALYSIS LETTERS, 50, 32, DOI: 10.1007/BF02062185

The formation of nickel oxide from Ni-Al takovite-like compounds has been investigated. Information about the stoichiometry of the NiO phase obtained by Diffuse Reflectance (DR) spectroscopy is discussed in connection with TPR and solubility data.

3317. MODEL PHASES FOR SELECTIVE OXIDATION AND AMMOXIDATION .3. METASTABLE ION DISTRIBUTIONS IN SCHEELITE-TYPE BI-FE-MO OXIDES

Authors: MANAILA, R; CALDARARU, M; CALDARARU, H; FILOTI, G

Published: 1992, ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS, 178, 252, DOI:

Structural models are proposed for cation distribution on substitutional and interstitial sites in the scheelite-like Bi-Fe-Mo-oxides. Experimental data derived from X-ray diffraction and Mossbauer spectrometry yield an unitary image, in which the actual distribution depends on the composition and the calcination temperature.

3318. PREPARATION OF PURE AND DOPED CDF2 SINGLE-CRYSTALS

Authors: VODA, M; NISTOR, SV; GHIORDANESCU, V

Published: MAY 1992, JOURNAL OF CRYSTAL GROWTH, 119, 344, DOI: 10.1016/0022-0248(92)90689-G

This paper describes the growth of CdF2 single crystals using the Bridgman method. Unwanted vapour reactions are avoided by using an argon atmosphere and glassy carbon crucibles. The installation for the growth of CdF2 single crystals is described in detail. Optical absorption of CdF2 crystals is shown for wavelengths of 200 to 800 nm. Transmission spectrum in the 2.5-10-mu-m range shows a low level of impurities which do not affect the optical qualities.

3319. SPECTROSCOPY, FLUORESCENCE MECHANISMS AND ENERGY TRANSFERS IN CADMIUM CHLORIDE DOUBLY DOPED WITH COPPER AND MANGANESE

Authors: VODA, M; GHIORDANESCU, V; PEDRINI, C

Published: AUG 24 1992, JOURNAL OF PHYSICS-CONDENSED MATTER, 4, 7152, DOI: 10.1088/0953-8984/4/34/014

We have observed and identified the optical excitation and emission spectra of Mn2+ ions in the doubly doped CdCl2:Mn:CU system between 77 and 300 K. A comparison is made with the singly doped CdCl2 system. The temperature dependence of the absorption strength is explained by vibrational electronic interaction, and the quantum efficiency is close to unity for low-Mn2+-concentration crystals. In CdCl2 the 1E(g) state of Cu+ lies in the conduction band. By excitation in the main absorption band, 1A1g --> 1E(g), of Cu+ in CdCl2:Mn:Cu crystals an energy transfer to Mn2+ ions takes place through intermediate metastable states (excimer-like species) which form in the lattice near the Cu+ centres. Because these states thermally ionize, the energy transfer rate decreases when the temperature increases and above 100 K the photoionization of Cu+ centres becomes dominant.

3320. CONTRIBUTION TO THE STUDY OF FORMATION MECHANISM OF THE COMPOUNDS IN THE BI2O3-(SR,CA)O-CUO SYSTEM

Authors: ZAHARESCU, M; BRAILEANU, A; MANAILA, R; FRUTH, V; TANASE, G

Published: APR 1992, MATERIALS RESEARCH BULLETIN, 27, 498, DOI: 10.1016/0025-5408(92)90027-W

The formation mechanism of definite compounds, under non-isothermal conditions, in binary and pseudobinary systems of the type Bi2O3-MO and CuO-MO, where M = Sr, Ca and Sr + Ca and in the pseudoternary system Bi2O3-(Sr,Ca)O-CuO has been studied. It has been established that the components of systems containing Bi2O3 and CaO exhibit much higher reactivity than those of the systems containing SrO and CuO. In the pseudoternary system superconducting phases are formed at low temperature with preferential participation of calcium. with increasing temperature incorporation of Sr and Cu in a preformed network takes place.

3321. LOCALIZATION OF ELECTRONS AND ELECTROMAGNETIC-WAVES IN A DETERMINISTIC APERIODIC SYSTEM

Authors: DULEA, M; JOHANSSON, M; RIKLUND, R

Published: JAN 1 1992, PHYSICAL REVIEW B, 45, 114, DOI: 10.1103/PhysRevB.45.105

Electron localization and optical transmission in one-dimensional systems with two components distributed according to the Rudin-Shapiro sequence are investigated. The nature of the eigenstates in the diagonal tight-binding model is studied by making use of nonlinear recurrence relations satisfied by the associated transfer matrices and their traces. It is shown that the wave functions display a wide range of features going from weak to exponential localization. Numerical computations lead to the conjecture that the localization property is generic. Nevertheless, a countable dense set of critical values of the on-site potential amplitude is found for which a class of extended states exists. Accordingly, the numerical investigation of the time evolution of the electronic wave packets displays a subdiffusive behavior when the potential amplitude becomes critical. Finally, a study of the optical properties of the Rudin-Shapiro dielectric multilayer shows strong similarities with the behavior of the disordered multilayers regarding the development of gaps in the transmission spectra.

3322. MODEL PHASES FOR SELECTIVE OXIDATION AND AMMOXIDATION .2. TERNARY IRON-BISMUTH-MOLYBDENUM OXIDE PHASES

Authors: CALDARARU, H; FILOTI, G; MANAILA, R; CALDARARU, M; IONESCU, NI; SELENINA, M; SCHNABEL, KH

Published: 1992, ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-INTERNATIONAL JOURNAL OF RESEARCH IN PHYSICAL CHEMISTRY & CHEMICAL PHYSICS, 177, 92, DOI:

The location of the Fe3+ ions in the iron-containing scheelite structures of Bi3FeMO2O12 and Bi2Fe2Mo2O12 samples (which have been prepared under various temperature treatments) has been investigated by X-ray diffraction. Mossbauer and electron spin resonance (ESR) spectroscopies. The alteration of the crystalline structure and of the Fe3+ ion location have been followed after static reduction in propylene and reoxidation. The catalytic activity of the samples in the reaction of propylene oxidation to acrolein has been measured. The structural data have indicated for the Bi3FeMo2O12 samples tetragonal or monoclinic scheelite-type structure for the low (450-degrees-C) and high (560-degrees-C) temperature preparations, respectively, with the Fe3+ ions located in tetrahedral (4a) sites; this position is not affected by the reduction. A quantitative analysis of the structural data on Bi2Fe2Mo2O12 preparations led to the important conclusion that such a compositional phase exists only as a metastable, low-temperature one; at higher temperatures. Fe3+ ions in excess of Bi3FeMo2O12 composition are segregated on octahedral interstitial, ferric molybdate and/or alpha-Fe2O3 sites. Thus, this conclusion sheds light on the debated question of these phases as well defined compounds. Correlations between structure and catalytic activity data are discussed, taking into account the actual structures found in this study.

3323. SELECTIVE HYDROGENATION OF STYRENE UPON PD-SM/GAMMA-AL2O3 CATALYSTS .1. PREPARATION AND CHARACTERIZATION OF THE CATALYSTS

Authors: PARVULESCU, V; BIRJEGA, M; PARVULESCU, V; MACOVEI, D; ANDREI, A; ANGELESCU, E; NICOLESCU, IV

Published: MAR 1992, REVUE ROUMAINE DE CHIMIE, 37, 344, DOI:

In the paper the properties of some Pd-Sm/gamma Al2O3 catalysts with different contents of palladium obtained by the successive method of impregnation have been studied. The metallographic microscopy determinations showed that by impregnating samarium upon a Pd/gamma Al2O3 supported catalyst a penetrating front, mostly different from the one of samarium, has resulted depending on the existent concentration of palladium upon the support and also a different migration front of the platinic metal. From the electronic microscopy determinations, electronic diffraction and EXAF3, the state in which the samarium is found after impregnation and after the drying and reduction, respectively, was established. Based on these determinations a mechanism of samarium impregnation was suggested.

3324. TRACE-MAP INVARIANT AND ZERO-ENERGY STATES OF THE TIGHT-BINDING RUDIN-SHAPIRO MODEL

Authors: DULEA, M; JOHANSSON, M; RIKLUND, R

Published: AUG 1 1992, PHYSICAL REVIEW B, 46, 3304, DOI: 10.1103/PhysRevB.46.3296

The localization of electrons in a one-dimensional tight-binding model with diagonal aperiodicity given by the Rudin-Shapiro sequence is studied in the frame of the transfer-matrix formalism. It is proved that the trace map of the model possesses a polynomial invariant. It is also proved that an infinite sequence of values of the on-site potential exists such that for each of these the energy E = 0 lies in the spectrum of the periodic approximants corresponding to the even generations of the chain. Accurate numerical computations show that the states associated to the center of the spectrum are weaker than exponentially localized even for rather small amplitudes of the on-site potential. Scaling laws that govern the spatial decay and self-similarity of these states are derived for various values of the potential strength. It is also shown that the decrease of the potential amplitude qualitatively changes the self-similarity of the wave functions on increasing length scales.

3325. HOPPING CONDUCTIVITY OF THE FIBONACCI-CHAIN QUASI-CRYSTAL - COMMENT

Authors: DULEA, M; ALDEA, A

Published: OCT 1 1992, PHYSICAL REVIEW B, 46, 8643, DOI: 10.1103/PhysRevB.46.8642

This Comment refers to a recent publication on the ac hopping conduction of the Fibonacci chain [Phys. Rev. B 43, 1183 (1991)]. The renormalization procedure proposed by its authors gives a correct formula for the conductivity [Eq. (15)]. Nevertheless, their conclusion regarding the vanishing of the dc conductivity disagrees with the low-frequency asymptotics previously derived by us for the same model, and also disagrees with the general result given by the resistance-network analogy of the Miller-Abrahams rate equations. Their result assumes the factorization of the frequency in Eq. (15), which we prove is not true. We show also that their numerical curves, which apparently support their conclusion, are strongly influenced by errors in the low-frequency range.

3326. PREPARATION AND PROPERTIES OF HIGH TCGDBA2CU3O-SIMILAR-TO-7 SUPERCONDUCTING CERAMICS OBTAINED FROM GADOLINIUM NITRATE

Authors: ALDICA, G; POPA, S; MANDACHE, S; POPESCU, M; JAKLOVSZKY, J; CRUCEANU, E

Published: MAR 1992, REVUE ROUMAINE DE CHIMIE, 37, 312, DOI:

Structural, electrical and magnetic data are reported on superconducting polycrystalline GdBa2Cu3Oapproximately7 materials obtained from Gd(NO3)3 .6 H2O, CuO and BaCO3 powders by a solid state reaction. The samples are single phase with orthorhombic distorted perovskite structure and with a critical temperature of approximately 90 K.

3327. LINE SHIFTS IN CRYSTAL POWDER DIFFRACTOMETERS

Authors: POPOVICI, M; STOICA, AD

Published: JUN 1 1992, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 25, 335, DOI: 10.1107/S0021889891011433

The linear relations of the neutron and X-ray optics in crystal powder diffractometers are extended with second-order terms. An expression for the angular deviation from the Bragg-peak position is derived which reduces to that of Wilson [Mathematical Theory of X-ray Powder Diffractometers (1963). Amsterdam: Philips Technical Library] for the case of characteristic X-rays in parafocusing geometry. A technique of computing second-order aberration effects is described. Line-shift formulae are given for conventional and curved-crystal diffractometers.

3328. PERIODIC STRUCTURES IN A TWISTED NEMATIC LIQUID-CRYSTAL CELL UNDER DC EXCITATION

Authors: FRUNZA, S; MOLDOVAN, R; BEICA, T; GIURGEA, M; STOENESCU, DN

Published: NOV 1 1992, EUROPHYSICS LETTERS, 20, 411, DOI: 10.1209/0295-5075/20/5/005

Some new results concerning the appearance of a periodic structure in a pi/2-twist cell filled with MBBA under d.c. excitation are reported. This structure consists of rectilinear domains whose orientation varies with the applied voltage around the normal to the molecular orientation in the middle of the cell and this variation covers a large range of angles even for fixed polarity of the excitation. When the polarity is changed, the sense of the domain orientation is also changed.

3329. NANOCRYSTALS GROWN IN AMORPHOUS CR AND CRNI THIN-FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; CONSTANTIN, CA

Published: 1991, ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS, 20, 371, DOI: 10.1007/BF01544013

The structure of vacuum annealed amorphous sputtered Cr and CrNi (55:45) thin films has been studied by transmission electron microscopy (TEM) and electron diffraction (TED). The thin films with thicknesses ranging from 150 to 600 angstrom were annealed while still on their alkali halide substrates under high vacuum at temperatures ranging from 200 to 370-degrees-C. The TEM and TED data permitted to establish the annealing conditions (temperature, duration), which lead to the nucleation and growth of nanosized crystals in the Cr and CrNi icosahedral glasses.

3330. PEAK EFFECT IN THE MAGNETIC-FIELD DEPENDENCE OF THE TRANSPORT CRITICAL-CURRENT DENSITY IN HIGH-TC SUPERCONDUCTING CERAMICS

Authors: MIU, L; ALDICA, G; HOROBIOWSKI, M; WLOSEWICZ, D

Published: DEC 1991, JOURNAL OF SUPERCONDUCTIVITY, 4, 427, DOI: 10.1007/BF00635859

The maximum observed in the magnetic field dependence of the transport critical-current density of high-T(c) superconducting ceramics was analyzed. Transport critical current and magnetization measurements performed on Bi(Pb)-Sr-Ca-Cu-O bulk sintered samples allowed us to conclude that such a maximum may result from the influence of demagnetization effects at low applied field values and an increase of the intergrannular pinning at higher fields.

3331. ASSESSING STACKING-FAULTS IN BI-SR-CA-CU-O PHASES BY X-RAY-DIFFRACTION

Authors: MANAILA, R; MIU, L; ZAHARESCU, M

Published: AUG 1 1991, JOURNAL OF MATERIALS SCIENCE, 26, 4141, DOI:

A Hendricks-Teller analysis of the X-ray diffraction line shifts in Bi-Sr-Ca-Cu-O phases allows an estimate of the stacking fault probabilities (missing or extra Cu-O layers). The probability values suggest some conclusions about the mutual relationships of the 2201, 2212 and 2223 phases and the kinetics of their formation.

3332. NON-ARCHIMEDEAN MODEL FOR THE RELAXATION PROCESS OF THE PHOTOINDUCED DARKENING IN AMORPHOUS-CHALCOGENIDE FILMS

Authors: POPESCU, M; ANDRIESH, A; CHUMASH, V; ENACHI, N; COJOCARU, I; GROZESCU, A

Published: DEC 1991, JOURNAL OF NON-CRYSTALLINE SOLIDS, 137, 976, DOI: 10.1016/S0022-3093(05)80283-2

The relaxation of the darkening induced by nanosecond laser pulses in amorphous chalcogenide thin films (AsSe and As2Se3) was modelled on the basis of a non-archimedean (ultrametric) approach. While for AsSe only a single time scale of evolution was evidenced (tentatively related to the simple, molecular structure of the glass) in As2Se3 three time scales were evidenced and discussed in the frame of a complex hierarchical structure of the glass with layer fragments, clusters of layers (amorphites) and, possibly, bigger domains.

3333. MEDIUM RANGE ORDER IN HIGH SURFACE-AREA AMORPHOUS SILICAS

Authors: MANAILA, R; ZAHARESCU, M

Published: APR 1990, JOURNAL OF MATERIALS SCIENCE, 25, 2099, DOI: 10.1007/BF01045771

3334. IR STUDY OF METAL-SUPPORT INTERACTIONS IN NI AL2O3 CATALYSTS FOR CO HYDROGENATION

Authors: FRUNZA, L; UDREA, M; UDREA, I; CAPAT, C; CRISAN, D; NICOLESCU, IV

Published: FEB 1990, REVUE ROUMAINE DE CHIMIE, 35, 227, DOI:

3335. MORPHOLOGY OF V2O5 PRECIPITATES

Authors: NISTOR, L; SERBAN, S; TEODORESCU, V; VELTERSTEANESCU, M; MANAILA, R; IOVITA, V

Published: APR 1990, REVISTA DE CHIMIE, 41, 385, DOI:

3336. MODEL PHASES FOR SELECTIVE OXIDATION AND AMMOXIDATION CATALYSTS .1. FERRIC MOLYBDATE

Authors: FILOTI, G; MANAILA, R; CALDARARU, H; CALDARARU, M; IONESCU, NI; SELENINA, M; SCHNABEL, KH

Published: 1990, ZEITSCHRIFT FUR PHYSIKALISCHE CHEMIE-LEIPZIG, 271, 319, DOI:

3337. UTILIZATION OF NMR-SPECTROSCOPY FOR THE DETERMINATION OF POLYACRYLAMIDE SOLUTIONS CONCENTRATION

Authors: CONTINEANU, M; CONSTANTINESCU, O

Published: SEP 1990, REVISTA DE CHIMIE, 41, 730, DOI:

A method of the determination of the concentration of the Medasol type hydrolized and non-hydrolized polyacrylamide in aqueous solution by higy resolution MNR is presented. The method may be applied to dilute solutions under the conditions presented in this paper.

3338. TRANSMISSION OF LIGHT THROUGH DETERMINISTIC APERIODIC NON-FIBONACCIAN MULTILAYERS

Authors: DULEA, M; SEVERIN, M; RIKLUND, R

Published: AUG 15 1990, PHYSICAL REVIEW B, 42, 3689, DOI: 10.1103/PhysRevB.42.3680

3339. CRYSTALLINE PHASES IN SUPERCONDUCTING BI-SR-CA-CU2-O-X CERAMIC

Authors: POPESCU, M; ALDICA, G; SARBU, C; PAUSESCU, P; CRUCEANU, E; VASILIU, F; APOSTOL, M

Published: DEC 16 1990, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 122, 643, DOI: 10.1002/pssa.2211220225

The crystalline phases in the superconducting ceramic Bi:Sr:Ca:Cu2:O(x) exhibiting either low superconducting transition (almost-equal-to 80 K) or both, low and high superconducting transitions (almost-equal-to 110 K) are identified by X-ray and electron diffraction. Two types of modulated structures are observed and their relation to T(c) is discussed within the frame of the oxygen-displacive mode theory.

3340. LOCAL MAGNETIC-INTERACTIONS AND SHORT-RANGE ORDER IN AMORPHOUS GDXFE1-X FILMS

Authors: MANAILA, R; FILOTI, G; FLORESCU, V; SERBANESCU, MD; DRINCIU, C

Published: MAY 1990, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 86, 288, DOI: 10.1016/0304-8853(90)90133-B

3341. MAGNETIC-PROPERTIES AND STRUCTURE OF RARE-EARTH TRANSITION-METAL THIN-FILMS IMPLANTED WITH AR+ IONS

Authors: FLORESCU, V; SERBANESCU, MD; MANAILA, R; GRANT, WA

Published: NOV 1990, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 92, 142, DOI: 10.1016/0304-8853(90)90690-R

3342. TECTONIC IMPLICATIONS OF PALEOMAGNETIC RESEARCH INTO UPPER CRETACEOUS MAGMATIC ROCKS IN THE APUSENI MOUNTAINS, ROMANIA

Authors: PATRASCU, S; BLEAHU, M; PANAIOTU, C

Published: AUG 20 1990, TECTONOPHYSICS, 180, 322, DOI: 10.1016/0040-1951(90)90316-Z

3343. DEGRADATION AND STABILIZATION OF EPICHLOROHYDRIN ELASTOMERS

Authors: CORCIOVEI, M; TARAN, F; SARBU, T; IVAN, G; DANILA, E; GIURGINCA, M; CHIPARA, M

Published: 1990, INTERNATIONAL JOURNAL OF POLYMERIC MATERIALS, 13, 146, DOI: 10.1080/00914039008039468

3344. MOSSBAUER INVESTIGATION OF FE-CU-K CATALYSTS FOR HYDROCARBON SYNTHESIS

Authors: FILOTI, G; SPANU, V; UDREA, I; UDREA, M; CAPAT, C; NICOLESCU, IV

Published: FEB 1990, REVUE ROUMAINE DE CHIMIE, 35, 219, DOI:

3345. THE ROLE OF THE INSULATING LAYERS IN THE HIGH-TEMPERATURE SUPERCONDUCTORS - THE CALCULATION OF TC

Authors: CRISAN, M; VACARU, D

Published: 1990, ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER, 78, 218, DOI: 10.1007/BF01307838

3346. STRUCTURAL EFFECT INDUCED BY ULTRASONICS IN EGG LECITHIN MEMBRANES DOPED BY PROCAINE

Authors: POPESCU, MA; IONESCU, MS; MORARIU, VV; FRANGOPOL, PT

Published: OCT-DEC 1989, REVUE ROUMAINE DE BIOCHIMIE, 26, 344, DOI:

3347. CRITICAL-TEMPERATURE OF LOW-DIMENSIONAL HIGH-TC SUPERCONDUCTORS

Authors: CRISAN, M; VACARU, D

Published: 1989, ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER, 76, 166, DOI: 10.1007/BF01312679

3348. PHASE-COMPOSITION AND STRUCTURE IN FE-MG-O CATALYSTS FOR OXYDEHYDROGENATION OF N-BUTENES TO BUTADIENE

Authors: NICOLESCU, IV; NEDELCU, G; MANAILA, R; IVASCU, M; AVRAMESCU, F; SPANU, V; FILOTI, G

Published: APR 1989, REVUE ROUMAINE DE CHIMIE, 34, 1054, DOI:

3349. HEMOGLOBIN LIGAND KINETICS IN THE MICROSECOND TIME RANGE AS A FUNCTION OF PH

Authors: SERBANESCU, RM; FRUNZA, L; MUSA, M; GANCIU, M

Published: 1989, STUDIA BIOPHYSICA, 131, 175, DOI:

3350. PERIODIC AND QUASIPERIODIC WAVEFUNCTIONS IN A CLASS OF ONE-DIMENSIONAL QUASICRYSTALS - AN ANALYTICAL TREATMENT

Authors: SEVERIN, M; DULEA, M; RIKLUND, R

Published: NOV 13 1989, JOURNAL OF PHYSICS-CONDENSED MATTER, 1, 8858, DOI: 10.1088/0953-8984/1/45/010

3351. DETERMINATION OF CORRESPONDENCE BETWEEN ETHANOL CONCENTRATION IN AQUEOUS SYSTEMS AND IN VAPORS BY SNO2 SENSORS

Authors: IONESCU, R; VANCU, A; BIRSAN, N; MOTRONEA, M

Published: MAR 1989, REVISTA DE CHIMIE, 40, 258, DOI:

3352. ELECTRICAL AND MAGNETIC-PROPERTIES OF HIGH-TC SUPERCONDUCTORS (Y, TM)-BA-CU OXIDES

Authors: OSICEANU, P; PATRON, L; PLOSTINARU, S; CONTESCU, A; CRISTEA, L; VASS, M; ALDICA, G; MANDACHE, S; PAUSESCU, P; PETRASCU, M

Published: JUL 1989, REVUE ROUMAINE DE CHIMIE, 34, 1544, DOI:

3353. ON THE GEOTHERMAL REGIME OF THE MOESIAN PLATFORM AND GETIC DEPRESSION

Authors: ANDREESCU, M; BURST, D; DEMETRESCU, C; ENE, M; POLONIC, G

Published: AUG 1 1989, TECTONOPHYSICS, 164, 286, DOI: 10.1016/0040-1951(89)90021-8

3354. INTERFERENCE FILTER FOR 2.5-5-MU-M WAVELENGTH RANGE

Authors: NAZARENCO, I; POPESCU, M; MEDIANU, R; CAMPEANU, R

Published: MAY 1989, INFRARED PHYSICS, 29, 292, DOI: 10.1016/0020-0891(89)90065-1

3355. ESR STUDIES ON ALCL3 BASED CATALYTIC-SYSTEMS

Authors: CEAUSESCU, E; CORCIOVEI, M; DIMONIE, M; BARB, D; CHIPARA, M; SARBU, T

Published: MAY 1989, REVUE ROUMAINE DE CHIMIE, 34, 1130, DOI:

3356. FEATURES OF THERMAL-DEGRADATION OF ALIPHATIC POLYSULFIDE RUBBERS

Authors: CHAUSHESKU, E; KORSHAK, VV; PAVLOVA, SSA; GRIBKOVA, PN; BALYKOVA, TN; PETROVSKII, PV; KORCHEVEI, M; TARAN, F; KIPARE, M

Published: OCT 1989, VYSOKOMOLEKULYARNYE SOEDINENIYA SERIYA A, 31, 2196, DOI:

3357. MECHANISM OF GAS-DETECTION IN POLYCRYSTALLINE THICK-FILM SNO2 SENSORS

Authors: BARSAN, N; GRIGOROVICI, R; IONESCU, R; MOTRONEA, M; VANCU, A

Published: APR 1 1989, THIN SOLID FILMS, 171, 63, DOI: 10.1016/0040-6090(89)90033-3

3358. ON THE RELATIONS BETWEEN THE DELTA-CR AND ALPHA-CR PHASES

Authors: BIRJEGA, MI; POPESCUPOGRION, N

Published: APR 1 1989, THIN SOLID FILMS, 171, 41, DOI: 10.1016/0040-6090(89)90031-X

3359. ON THE NEUTRON REFLECTIVITY OF BENT PERFECT CRYSTALS

Authors: STOICA, AD; POPOVICI, M

Published: OCT 1 1989, JOURNAL OF APPLIED CRYSTALLOGRAPHY, 22, 454, DOI: 10.1107/S0021889889005637

3360. GEILIKMAN-KRESIN FORMULA FOR 2D HIGH-TC SUPERCONDUCTORS

Authors: CRISAN, M

Published: 1989, ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER, 74, 153, DOI: 10.1007/BF01307380

3361. ESR STUDIES ON MELINEX IRRADIATED WITH OXYGEN IONS

Authors: BARB, D; CHIPARA, MI; VELTERSTEFANESCU, M; APPEL, PY; ROGALSKI, M; PERELYGIN, V

Published: 1989, NUCLEAR TRACKS AND RADIATION MEASUREMENTS, 16, 67, DOI:

3362. STRUCTURE AND SUPERCONDUCTIVITY OF BI-(PB)-CA-SR-CU-O CERAMICS PROCESSED BY ARC MELTING

Authors: ALDICA, G; POPESCU, M; CRUCEANU, E; MIU, L; JAKLOVSZKY, J; MANDACHE, S

Published: DEC 1989, JOURNAL OF SUPERCONDUCTIVITY, 2, 511, DOI: 10.1007/BF00627563

3363. RELAXATION FROM TRANSIENT AND STATIONARY STATES IN THE DEFORMED ALIGNED PHASE (DAP) EFFECT IN QUASI-HOMEOTROPIC LIQUID-CRYSTAL LAYERS

Authors: FRUNZA, S; BEICA, T; MOLDOVAN, R; GIURGEA, M; COTOROBAI, F

Published: FEB 1988, LIQUID CRYSTALS, 3, 297, DOI: 10.1080/02678298808086375

3364. HIGH-TEMPERATURE SUPERCONDUCTIVITY IN COPPER-OXIDE CERAMICS BASED ON YTTRIUM CONCENTRATE

Authors: CRUCEANU, E; ALDICA, G; POPESCU, M; POPA, S

Published: 1988, REVUE ROUMAINE DE PHYSIQUE, 33, 490, DOI:

3365. INDUCTION MODEL FOR THE SECULAR VARIATION OF THE GEOMAGNETIC-FIELD IN EUROPE

Authors: DEMETRESCU, C; ANDREESCU, M; NESTIANU, T

Published: APR 1988, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 50, 271, DOI: 10.1016/0031-9201(88)90107-0

3366. MORPHOLOGY OF LEAD ZIRCONATE-TITANATE SINTERING PRECURSORS

Authors: ZBEREA, I; CONSTANTINESCU, F; ROBU, M

Published: 1988, REVUE ROUMAINE DE PHYSIQUE, 33, &, DOI:

3367. POSITIVE MAGNETORESISTANCE IN THE AMORPHOUS GDCO3 FILMS - COULOMB INTERACTION EFFECT

Authors: MAJ, W; SERBANESCU, MD

Published: DEC 1988, JOURNAL DE PHYSIQUE, 49, 1356, DOI: 10.1051/jphyscol:19888620

3368. THE FAR FIELD OF THE TRANSVERSE-MODE RADIATION IN LASER STRUCTURES WITH SEPARATE LIMITATION

Authors: PETRESCUPRAHOVA, IB; LAZANU, S; LEPSA, M; MIHAILOVICI, P

Published: NOV 1988, KVANTOVAYA ELEKTRONIKA, 15, 2217, DOI:

3369. INFLUENCE OF THE PREPARATION CONDITIONS ON THE DIAMAGNETIC RESPONSE OF HIGH-TCYBA2CU3OX SUPERCONDUCTOR

Authors: MIU, L; POPA, S; POPESCU, M; PAVEL, E

Published: 1988, ZEITSCHRIFT FUR PHYSIK B-CONDENSED MATTER, 70, 424, DOI: 10.1007/BF01312114

3370. X-RAY-DIFFRACTION INVESTIGATION OF THE STRUCTURAL MODIFICATIONS INDUCED BY NEOMYCIN-B IN EGG LECITHIN MULTILAYERS

Authors: POPESCU, MA; IONESCU, MS; FRANGOPOL, PT

Published: OCT-DEC 1988, REVUE ROUMAINE DE BIOCHIMIE, 25, 318, DOI:

3371. LONG-TIME ASYMPTOTICS IN THE ONE-DIMENSIONAL TRAPPING PROBLEM WITH LARGE BIAS

Authors: ALDEA, A; DULEA, M; GARTNER, P

Published: AUG 1988, JOURNAL OF STATISTICAL PHYSICS, 52, 1068, DOI: 10.1007/BF01019739

3372. X-RAY-DIFFRACTION INVESTIGATION OF THE STRUCTURAL MODIFICATIONS INDUCED BY PROCAINE AND LIDOCAINE IN EGG LECITHIN MEMBRANES

Authors: POPESCU, MA; IONESCU, MS; FRANGOPOL, PT

Published: JUL-SEP 1988, REVUE ROUMAINE DE BIOCHIMIE, 25, 253, DOI:

3373. HOPPING CONDUCTION ON APERIODIC CHAINS

Authors: ALDEA, A; DULEA, M

Published: APR 18 1988, PHYSICAL REVIEW LETTERS, 60, 1675, DOI: 10.1103/PhysRevLett.60.1672

3374. EFFECTS OF ION-IMPLANTATION ON MAGNETIC AND STRUCTURAL-PROPERTIES OF AMORPHOUS GD-CO THIN-FILMS

Authors: FLORESCU, V; ALTAMIMI, Z; SERBANESCU, MD; MANAILA, R; GRANT, WA

Published: MAR 1988, IEEE TRANSACTIONS ON MAGNETICS, 24, 1737, DOI: 10.1109/20.11586

3375. ON THE ELECTRONIC-STRUCTURE OF BIS(ISOTHIOCYANATO)TETRAKIS(4-BENZOYL-PYRIDINE)IRON(II)

Authors: ANDRUH, M; FILOTI, G; BREZEANU, M

Published: JUL 1988, REVUE ROUMAINE DE CHIMIE, 33, 676, DOI:

3376. ANALYSIS OF THE RELATION BETWEEN STRUCTURE AND THE SUPERCONDUCTING TRANSITION IN YBA2CU3O-7

Authors: POPESCU, M; MIU, L; CRUCEANU, E

Published: MAY 1988, PHILOSOPHICAL MAGAZINE LETTERS, 57, 276, DOI: 10.1080/09500838808203778

3377. SYNTHESIS OF NICKEL FERRITE FROM POLYNUCLEAR COORDINATION-COMPOUNDS .3. STRUCTURAL DATA OF NIFE2O4 OBTAINED BY THE WET FERRITIZATION METHOD

Authors: ILIE, I; BREZEANU, M; PATRON, L; SEGAL, E; FILOTI, G

Published: SEP-OCT 1988, REVUE ROUMAINE DE CHIMIE, 33, 891, DOI:

3378. SYNTHESIS OF NICKEL FERRITE FROM POLYNUCLEAR COORDINATION-COMPOUNDS

Authors: ILIE, I; PATRON, L; BREZEANU, M; SEGAL, E; FILOTI, G

Published: AUG 1987, JOURNAL OF MATERIALS SCIENCE LETTERS, 6, 934, DOI: 10.1007/BF01729872

3379. STRUCTURAL MODELING OF THE AMORPHOUS-AMORPHOUS INTERFACE

Authors: POPESCU, M

Published: FEB 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 90, 334, DOI: 10.1016/S0022-3093(87)80438-6

3380. ON THE ANDERSON LOCALIZATION AND UNIVERSAL DEGRADATION OF THE CRITICAL-TEMPERATURE IN SUPERCONDUCTORS

Authors: CRISAN, M

Published: SEP 21 1987, PHYSICS LETTERS A, 124, 197, DOI: 10.1016/0375-9601(87)90251-9

3381. GD AMORPHOUS-SILICON OBTAINED FROM TRICHLORSILANE

Authors: POPESCU, C; STOICA, T; DRAGOMIR, A; NENCIU, A; NICOLAE, M; IVAN, P; IONESCU, S

Published: DEC 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 97-8, 1434, DOI: 10.1016/0022-3093(87)90343-7

3382. THE GAUGE-THEORY AND THE TOPOLOGICAL DISORDER

Authors: COHEN, V; POPESCU, M

Published: FEB 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 90, 68, DOI: 10.1016/S0022-3093(87)80385-X

3383. ATOMIC-SCALE STRUCTURE OF AMORPHOUS AND LIQUID SULFUR

Authors: POPESCU, M

Published: DEC 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 97-8, 190, DOI: 10.1016/0022-3093(87)90044-5

3384. COMPUTER-ASSISTED MODELING OF PHOTOSTRUCTURAL TRANSFORMATIONS IN AMORPHOUS AS3SE2

Authors: POPESCU, M

Published: FEB 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 90, 536, DOI: 10.1016/S0022-3093(87)80480-5

3385. SYNTHESIS OF NICKEL FERRITE FROM POLYNUCLEAR COORDINATION-COMPOUNDS .1. STUDY OF THE DRY FERRITIZATION PROCESS

Authors: ILIE, I; BREZEANU, M; PATRON, L; SEGAL, E; FILOTI, G

Published: NOV-DEC 1987, REVUE ROUMAINE DE CHIMIE, 32, 1115, DOI:

3386. PHOTOLUMINESCENCE OF THE HOPPING DISORDERED-SYSTEMS WITH ELECTRICAL BIAS

Authors: DULEA, M; ALDEA, A

Published: FEB 1987, JOURNAL OF NON-CRYSTALLINE SOLIDS, 90, 464, DOI: 10.1016/S0022-3093(87)80464-7

3387. PREPARATION AND PROPERTIES OF HIGH-TEMPERATURE SUPERCONDUCTORS IN Y-BA-CU-O SYSTEM

Authors: MIU, L; POPA, S; POPESCU, M; CRUCEANU, E

Published: 1987, REVUE ROUMAINE DE PHYSIQUE, 32, 1013, DOI:

3388. STRUCTURE AND PROPERTIES OF THE ZNO.NFE2O3 CATALYSTS SYSTEM IN THE OXYDEHYDROGENATION REACTION(I)

Authors: NICOLESCU, IV; MANAILA, R; CHAAR, MA; FILOTI, G

Published: JAN 1986, REVUE ROUMAINE DE CHIMIE, 31, 104, DOI:

3389. POLYMORPHISM OF THE BINARY MIXTURE OF SITOSTERYL CHLORIDE AND CHOLESTERYL LAURATE

Authors: PLOSCEANU, C; SOCACIU, M; CUCULESCU, I; DRAGOMIR, A; SAVIN, O

Published: 1986, CRYSTAL RESEARCH AND TECHNOLOGY, 21, K145, DOI: 10.1002/crat.2170210831

3390. AC CONDUCTIVITY OF A DISORDERED CHAIN - REAL-SPACE RENORMALIZATION-GROUP APPROACH

Authors: ALDEA, A; DULEA, M

Published: JUL 30 1986, JOURNAL OF PHYSICS C-SOLID STATE PHYSICS, 19, 4062, DOI: 10.1088/0022-3719/19/21/010

3391. LOCAL ORDER IN HIGH SURFACE-AREA AMORPHOUS SILICA

Authors: MANAILA, R; ZAHARESCU, M

Published: DEC 16 1986, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 98, 382, DOI: 10.1002/pssa.2210980207

3392. STRUCTURAL STUDIES ON SOME IRON 8-OXI-QUINOLINATES USING MOSSBAUER-SPECTROSCOPY

Authors: BARB, D; MORARIU, M; COZAR, O; ZNAMIROVSCHI, V; SEMENIUC, R

Published: AUG 5 1986, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY-LETTERS, 106, 26, DOI: 10.1007/BF02164987

3393. PREPARATION OF BARIUM HEXAFERRITE BY A HYDROTHERMAL METHOD - STRUCTURE AND MAGNETIC-PROPERTIES

Authors: BARB, D; DIAMANDESCU, L; RUSI, A; TARABASANUMIHAILA, D; MORARIU, M; TEODORESCU, V

Published: APR 1986, JOURNAL OF MATERIALS SCIENCE, 21, 1122, DOI: 10.1007/BF00553240

3394. STUDY OF SUPPORTED PALLADIUM CATALYSTS VARIOUSLY HEAT-TREATED IN HYDROGEN USING MICROACTIVITY TESTING, TRANSMISSION ELECTRON-MICROSCOPY, X-RAY-ANALYSIS AND THE EXTENDED X-RAY ABSORPTION FINE-STRUCTURE TECHNIQUE

Authors: LEONTE, O; BIRJEGA, M; MACOVEI, D; PAUSESCU, P; POPESCUPOGRION, N; GEORGESCU, M

Published: JUL-AUG 1986, SURFACE & COATINGS TECHNOLOGY, 28, 357, DOI: 10.1016/0257-8972(86)90091-5

3395. LARGE-SCALE MODELING OF AMORPHOUS-GERMANIUM

Authors: POPESCU, M

Published: 1985, JOURNAL OF NON-CRYSTALLINE SOLIDS, 75, 482, DOI: 10.1016/0022-3093(85)90260-1

3396. COMPOSITE BOSON-FERMION MODELS WITH SUPERFLUID TRANSITIONS - 2-FERMION AND 4-FERMION CORRELATIONS

Authors: APOSTOL, M

Published: 1985, REVUE ROUMAINE DE PHYSIQUE, 30, 830, DOI:

3397. MODELING OF THE STRUCTURE OF AMORPHOUS ICE

Authors: POPESCU, M

Published: 1985, JOURNAL OF NON-CRYSTALLINE SOLIDS, 75, 488, DOI: 10.1016/0022-3093(85)90261-3

3398. ELECTRON-SPIN-RESONANCE INVESTIGATION OF THE INTERACTION BETWEEN WCL6-BASED CATALYSTS AND CYCLO-OLEFINS

Authors: CEAUSESCU, E; CORNILESCU, A; NICOLESCU, E; POPESCU, M; COCA, S; BELLOIU, C; OPRESCU, C; DIMONIE, M; HUBCA, G; DRAGUTAN, V; CHIPARA, M

Published: 1985, JOURNAL OF MOLECULAR CATALYSIS, 28, 357, DOI: 10.1016/0304-5102(85)87040-1

3399. SYNTHESIS OF BEADED POLYVINYL-ALCOHOL BY SUSPENSION METHANOLYSIS OF POLYVINYL ACETATE - DERIVATIZATION AND SOME APPLICATIONS

Authors: DIMONIE, M; SCHELL, HD; HUBCA, G; MATEESCU, MA; OPRESCU, CG; TODIREANU, S; MAIOR, O; LANGURI, J; IOSIF, M

Published: 1985, JOURNAL OF MACROMOLECULAR SCIENCE-CHEMISTRY, A22, 754, DOI: 10.1080/00222338508056633

3400. NEW ASPECTS OF THE RING-OPENING POLYMERIZATION OF CYCLOOLEFINS

Authors: CEAUSESCU, E; DIMONIE, M; CORNILESCU, A; CHIPARA, M; GHEORGHIU, M; DRAGUTAN, V

Published: 1985, JOURNAL OF MACROMOLECULAR SCIENCE-CHEMISTRY, A22, 876, DOI: 10.1080/00222338508056640

3401. OVSHINSKY MIXED HALOGEN EFFECT - EVIDENCE AND TENTATIVE EXPLANATION

Authors: POPESCU, M

Published: 1985, JOURNAL OF NON-CRYSTALLINE SOLIDS, 75, 194, DOI: 10.1016/0022-3093(85)90221-2

3402. CONTROL OF MOLECULAR-ORIENTATION IN TWIST NEMATIC, LIQUID-CRYSTAL CELLS

Authors: BEICA, T; FRUNZA, S; GIURGEA, M; MOLDOVAN, R

Published: 1985, CRYSTAL RESEARCH AND TECHNOLOGY, 20, 878, DOI: 10.1002/crat.2170200637

3403. NEW ASPECTS OF THE MECHANISM OF THE RING-OPENING POLYMERIZATION OF CYCLO-OLEFINS

Authors: CEAUSESCU, E; CORNILESCU, A; NICOLESCU, E; POPESCU, M; COCA, S; BELLOIU, C; DIMONIE, M; GHERORGHUI, M; DRAGUTAN, V; CHIPARA, M

Published: 1985, JOURNAL OF MOLECULAR CATALYSIS, 28, 349, DOI: 10.1016/0304-5102(85)87039-5

3404. EVIDENCE OF MANY CHARACTERISTIC TEMPERATURES IN LITIZN FERRITES WITH TITANIUM CONTENT

Authors: NICOARA, G; GUILLOT, M

Published: SEP 1985, JOURNAL DE PHYSIQUE, 46, 440, DOI: 10.1051/jphyscol:1985684

3405. TRANSMISSION ELECTRON-MICROSCOPY AND ELECTRON-DIFFRACTION STUDY OF GAMMA-CR2O3 AND ALPHA-CR2O3 FINE PARTICLES

Authors: BIRJEGA, MI; ZBEREA, I; POPESCUPOGRION, N

Published: 1985, REVUE ROUMAINE DE PHYSIQUE, 30, &, DOI:

3406. CHARACTERISTICS OF THE SECULAR VARIATION OF THE GEOMAGNETIC-FIELD BETWEEN 1964-1981 IN ROMANIA

Authors: DEMETRESCU, C; ANDREESCU, M; ENE, M; NESTIANU, T

Published: 1985, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 37, 51, DOI: 10.1016/0031-9201(85)90062-7

3407. STABILITY AND DEGRADATION OF THIN SILVER FILMS VACUUM EVAPORATED ONTO ALKALI-HALIDE SUBSTRATES

Authors: BIRJEGA, MI; BIRJEGA, RM; POPESCUPOGRION, N

Published: SEP 28 1985, THIN SOLID FILMS, 131, 302, DOI: 10.1016/0040-6090(85)90150-6

3408. STUDY OF LIGHT-SCATTERING IN DIETHYLENE GLYCOL-BENZENE AND DIETHYLENE GLYCOL-TOLUENE SYSTEMS

Authors: GIURGEA, M; SANDULESCU, D; VOLATIE, P

Published: 1985, REVUE ROUMAINE DE PHYSIQUE, 30, 778, DOI:

3409. THE EFFECTS OF IRON ON ULTRAVIOLET PROTECTION AND COLOR CHARACTERISTICS OF EMERALD GREEN GLASSES

Authors: GHIORDANESCU, V; CERCHEZ, MV

Published: 1985, GLASS TECHNOLOGY, 26, 62, DOI:

3410. PHYSICAL-PROPERTIES OF THE CATALYST USED FOR THE PARTIAL OXIDATION OF ANTHRACENE TO ANTHRAQUINONE .1. MOSSBAUER STUDY

Authors: SPINZI, A; BURZO, E; ROGALSKI, M

Published: 1985, REACTION KINETICS AND CATALYSIS LETTERS, 28, 187, DOI: 10.1007/BF02116776

3411. ON THE INDUCING OF A SPIRAL INTEGRATED MAGNETIC HEAD

Authors: CIUREANU, P; KORONY, G; CIOBANU, M

Published: 1984, REVUE ROUMAINE DE PHYSIQUE, 29, 232, DOI:

3412. ELECTRICAL-RESISTANCE OF THIN NICR FILMS IN THE FREQUENCY-RANGE 10-110 MHZ

Authors: POPESCUPOGRION, N; BIRJEGA, MI

Published: 1984, REVUE ROUMAINE DE PHYSIQUE, 29, &, DOI:

3413. PARTICULARITIES IN THE APPEARANCE OF THE CRXOY PHASE IN NICR THIN-FILMS

Authors: BIRJEGA, MI; CONSTANTIN, CA; FLORESCU, IT; POPESCUPOGRION, N; SARBU, C

Published: 1984, REVUE ROUMAINE DE PHYSIQUE, 29, &, DOI:

3414. MAGNETIC DOMAIN-STRUCTURE AND THERMOMAGNETIC WRITING ON AMORPHOUS GD-CO THIN-FILMS

Authors: SERBANESCU, MD; FLORESCU, V; MATEICIUC, V; POPA, A

Published: 1984, REVUE ROUMAINE DE PHYSIQUE, 29, 388, DOI:

3415. SOME PECULIAR PROPERTIES OF CROSS-LINKED POLYVINYL-ALCOHOL (CL-PVA) RELATED TO THE RETICULATION DEGREE

Authors: MATEESCU, MA; SCHELL, HD; DIMONIE, M; TODIREANU, S; MAIOR, O

Published: 1984, POLYMER BULLETIN, 11, 427, DOI: 10.1007/BF00265481

3416. DEFECT FORMATION IN AMORPHOUS STRUCTURES AS REVEALED BY COMPUTER-SIMULATION

Authors: POPESCU, M

Published: 1984, THIN SOLID FILMS, 121, 347, DOI: 10.1016/0040-6090(84)90059-2

3417. ON THE PHASE-TRANSITION OF KH2PO4 AT T-ALMOST-EQUAL-TO-110-DEGREES-C

Authors: IOANID, A; POPESCU, M; VLAHOVICI, N; BUNGET, I

Published: 1984, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 82, K128, DOI: 10.1002/pssa.2210820235

3418. ON THE NATURE OF ACTIVE-CENTERS AND THEIR INTERACTIONS

Authors: CHIPARA, MI; GEORGESCU, L

Published: 1983, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH, 209, 405, DOI: 10.1016/0167-5087(83)90830-X

3419. COMPUTER MODELING OF THE ATOMIC SCALE STRUCTURE OF AN AMORPHOUS GE-FE ALLOY WITH LOW FE CONTENT

Authors: POPESCU, MA

Published: 1983, JOURNAL OF NON-CRYSTALLINE SOLIDS, 56, 278, DOI: 10.1016/0022-3093(83)90480-5

3420. ELECTRON-SPIN-RESONANCE STUDIES ON PET IRRADIATED WITH HIGH-ENERGY IONS

Authors: CHIPARA, MI; BUNGET, I; GEORGESCU, R; GEORGESCU, E; VILCOV, I

Published: 1983, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH, 209, 400, DOI: 10.1016/0167-5087(83)90829-3

3421. SOLID-SOLUTIONS BASED ON V2O5 .3. PHYSICAL-PROPERTIES

Authors: BURZO, E; STANESCU, L; TEODORESCU, V; CHIPARA, M

Published: 1983, REVISTA DE CHIMIE, 34, 621, DOI:

3422. PERIPHERAL AND CENTRAL NUCLEUS-NUCLEUS COLLISIONS AT 4.2 GEV/C PER NUCLEON

Authors: AGAKISHIEV, HN; ABDINOV, OB; MEKHDIEV, RR; SULEIMANOV, MK; AHABABIAN, N; BAATAR, T; BALDIN, AM; BARTKE, J; BOGDANOWICZ, J; CHEPLAKOV, AP; GASPARIAN, AP; GRISHIN, VG; IVANOVSKAYA, IA; KANAREK, T; KLADNITSKAYA, EN; KONDOR, E; KOPYLOVA, DK; KOWALSKI, M; KVATADZE, RA; LYUBIMOV, VB; NIKITINA, VF; SOLOVIEV, MI; TONEEV, VD; CHASNIKOV, IY; IZBASAROV, MI; VINITSKY, AK; BACKOVIC, S; DAMIANOVIC, V; DRNDAREVIC, S; KRMPOTIC, D; KRPIC, D; SIMIC, L; BALEA, E; BALEA, O; BOLDEA, V; HACMAN, S; PONTA, T; GUDIMA, KK; KELOGLU, YP; ANOSHIN, AI; EROFEEVA, IN; DIDENKO, LA; LYUTOV, SI; MELNIKOVA, NN; MURZIN, VS; POPOVA, VM; SARYCHEVA, LI; SHCHEGLOVA, LM; SMIRNOVA, LN; SOLOMIN, AN; TONEEVA, GP; KORBEL, Z; TRKA, Z; TRKOVA, Y; ISMATOVA, FA; MUMINOV, MM; SUVONOV, I; ANGELOV, N; GREKOVA, LD; KERACHEV, P; SEMERDZHIEV, H; TEMNIKOV, PP; AZIMOV, SA; EDGOROV, SO; INOGAMOV, SV; YULDASHEV, AA; YULDASHEV, BS; AMAGLOBELI, NS; GRIGALASHVILI, NS; DASAEVA, MA; METREVELI, ZV; TEVZADZE, YV; TOPURIDZE, MV; TUVDENDORZH, D; SHARKHU, G; ARMUTLIJSKY, D; KOCHNEV, N; PROKOPIEVA, S; BIALKOWSKA, H; ARAKELIAN, SG; GULKANIAN, GR; KIRAKOSIAN, ZA; KORCHAGIN, SA; RAVINOVICH, IM; VARTANIAN, VA

Published: 1983, ZEITSCHRIFT FUR PHYSIK C-PARTICLES AND FIELDS, 16, 317, DOI: 10.1007/BF01577098

3423. HYDROGEN ABSORPTION IN MG-NI-FE ALLOYS

Authors: LUPU, D; BIRIS, A; INDREA, E; ALDEA, N; BUCUR, RV; MORARIU, M

Published: 1983, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 8, 799, DOI: 10.1016/0360-3199(83)90210-0

3424. PHOTO-ELECTROCHEMICAL BEHAVIOR OF SINTERED ALPHA-FE2O3 ELECTRODES

Authors: FAUR, M; FAUR, M; MICLEA, C

Published: 1983, REVUE ROUMAINE DE PHYSIQUE, 28, 737, DOI:

3425. METHANE SYNTHESIS FROM CO/H2O MIXTURE ON SUPPORTED NICKEL-CATALYSTS .3. FORMATION OF SURFACE CARBON AND ITS ROLE IN THE REACTION-MECHANISM

Authors: UDREA, I; UDREA, M; FRUNZA, L

Published: 1982, REACTION KINETICS AND CATALYSIS LETTERS, 21, 268, DOI: 10.1007/BF02070622

3426. EPITAXIAL-GROWTH OF THIN GOLD-FILMS ONTO PURE AND DOPED NACL AND KCL SUBSTRATES

Authors: BIRJEGA, MI; POPESCUPOGRION, N; TOPA, V

Published: 1982, THIN SOLID FILMS, 94, 73, DOI: 10.1016/0040-6090(82)90031-1

3427. MOSSBAUER STUDIES ON MOCI (ROMANIA) METEORITE

Authors: BARB, D; MORARIU, M; DIAMANDESCU, L; ZNAMIROVSCHI, V; CIURCHEA, D; MOTIU, A

Published: 1982, ANNALES DE GEOPHYSIQUE, 38, 879, DOI:

3428. METHANE SYNTHESIS FROM CO/H2O MIXTURE ON SUPPORTED NICKEL-CATALYSTS .2. SURFACE SPECIES IN CO-H-2 AND CO-D2O INTERACTION BY IR SPECTROSCOPY

Authors: UDREA, I; UDREA, M; FRUNZA, L

Published: 1982, REACTION KINETICS AND CATALYSIS LETTERS, 21, 264, DOI: 10.1007/BF02070621

3429. CRYSTALLIZATION OF AMORPHOUS SPUTTERED 55-PERCENT-CR-45-PERCENT-NI THIN-FILMS

Authors: BIRJEGA, MI; CONSTANTIN, CA; FLORESCU, IT; SARBU, C

Published: 1982, THIN SOLID FILMS, 92, 321, DOI: 10.1016/0040-6090(82)90154-7

3430. METHANE SYNTHESIS FROM CO/H2O MIXTURE ON SUPPORTED NICKEL-CATALYSTS .1. INFLUENCE OF THE SUPPORT ON THE CATALYTIC PROPERTIES

Authors: UDREA, I; UDREA, M; FRUNZA, L

Published: 1982, REACTION KINETICS AND CATALYSIS LETTERS, 21, 259, DOI: 10.1007/BF02070620

3431. LATTICE DAMAGE AT RECOIL TIN IMPURITY IN METALLIC CADMIUM

Authors: IONESCUBUJOR, M; IORDACHESCU, A; IVANOV, EA; PLOSTINARU, D; PASCOVICI, G

Published: 1981, HYPERFINE INTERACTIONS, 11, 175, DOI: 10.1007/BF01026474

3432. STRUCTURAL MODELING OF THE ANNEALING EFFECT IN AMORPHOUS-SEMICONDUCTORS AND METALLIC GLASSES

Authors: POPESCU, M

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 997, DOI:

3433. SPIN EXCHANGE INTERACTION OPTICAL-SPECTRA OF THE CO++ ION IN CDCL2 AND CDBR2 SINGLE-CRYSTALS

Authors: TRUTIA, A; IOVA, F; VODA, M

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 1027, DOI:

3434. CHARACTERISTICS OF DOMAINS APPEARING IN NEMATIC LIQUID-CRYSTALS BELOW THE THRESHOLD VOLTAGE OF CHEVRONS

Authors: NASTA, L; LUPU, A; GIURGEA, M

Published: 1981, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 71, 76, DOI: 10.1080/00268948108072718

3435. NEUTRON-DIFFRACTION ON LIQUID GALLIUM

Authors: PADUREANU, I; RAPEANU, S; ROTARESCU, G; CRACIUN, C; ION, M; BASCOVEANU, I

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 595, DOI:

3436. PHOTOCONDUCTIVITY AND PHOTO-VOLTAIC EFFECTS IN SPUTTERED CDTE THIN-FILMS

Authors: CIUREA, ML; BOTILA, T

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 973, DOI:

3437. TRANSMISSION MOSSBAUER POLARIZER

Authors: BARB, D; ROGALSKI, M; BIBICU, T

Published: 1981, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH, 188, 471, DOI: 10.1016/0029-554X(81)90531-0

3438. STRUCTURAL MODELING OF THE LIQUID-STATE OF TETRAHEDRALLY BONDED SEMICONDUCTORS

Authors: POPESCU, M

Published: 1981, JOURNAL DE PHYSIQUE, 42, 1046, DOI: 10.1051/jphyscol:19814228

3439. THE EFFECT OF FAST-NEUTRONS UPON THE ELECTRICAL-CONDUCTIVITY OF ZNS-CRYSTALS

Authors: TOACSAN, MI; NAZAROV, VM; COJOCARU, LN

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 182, DOI:

3440. ORDERING PROCESSES IN THE LITHIUM FERRITE WITH SUBSTITUTIONS

Authors: MOISIN, AM; FEDER, M; MITEA, D

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 73, DOI:

3441. MICROMECHANISMS OF CRYSTALLIZATION IN AMORPHOUS CRNI THIN-FILMS

Authors: BIRJEGA, MI; CONSTANTIN, CA; FLORESCU, IT; SARBU, C

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, &, DOI:

3442. LASER-ABSORPTION IN A SPARK INDUCED BY HIGH-POWER TEA-CO2 RADIATION ON A METALLIC TARGET IN VACUUM

Authors: MOLDOVAN, M; BARBULESCU, D; DINESCU, M; APOSTOL, I; DRAGANESCU, V; MIHAILESCU, IN; MORJAN, I

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 1079, DOI:

3443. ON ELECTROCONVECTIVE DOMAINS IN NEMATIC LIQUID-CRYSTALS

Authors: NASTA, L; GIURGEA, M

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 1006, DOI:

3444. NITRIDING EFFECT OF NITROGEN-HYDROGEN LOW-POWER PLASMATRON

Authors: ELOSAIRY, MAM; MUSA, G; IOVA, I; LUNGU, CP

Published: 1981, REVUE ROUMAINE DE PHYSIQUE, 26, 374, DOI:

3445. LATENT AND ETCHED TRACK FORMATION IN POLYMERIC DETECTORS - A THERMODYNAMIC APPROACH

Authors: CHIPARA, M; GEORGESCU, L; CHIPARA, M

Published: 1981, NUCLEAR TRACKS AND RADIATION MEASUREMENTS, 5, 342, DOI: 10.1016/0191-278X(81)90244-4

3446. CROSS-SECTIONS AND SCATTERING LAW FOR ZIRCONIUM AND ZIRCONIUM ALLOYS IN THERMAL-ENERGY RANGE

Authors: RAPEANU, S; PADUREANU, I; ROTARESCU, G; CRACIUN, C; ION, M; BASCOVEANU, I

Published: 1980, REVUE ROUMAINE DE PHYSIQUE, 25, 1055, DOI:

3447. LIGHT-INDUCED-CHANGES IN ELECTRICAL-PROPERTIES OF AS3SE2 THIN-FILMS

Authors: BOTILA, T; ALDEA, ML

Published: 1980, JOURNAL OF NON-CRYSTALLINE SOLIDS, 35-6, 1083, DOI: 10.1016/0022-3093(80)90343-9

3448. FURTHER INVESTIGATIONS CONCERNING ELECTRON-SPIN RESONANCE AND ELECTRICAL-PROPERTIES OF PB(CH3COO)2.3H2O-MN2+ SINGLE-CRYSTALS

Authors: TEODORESCU, M; ALECU, ID

Published: 1980, JOURNAL OF PHYSICAL CHEMISTRY, 84, 932, DOI: 10.1021/j100445a029

3449. SOLID ELECTROLYTE TIMING CELL AND COULOMETER

Authors: IGNAT, F; TRUTIA, A; VODA, M

Published: 1980, REVUE ROUMAINE DE PHYSIQUE, 25, 184, DOI:

3450. CONDITIONS LEADING TO THE EPITAXIAL-GROWTH OF VACUUM EVAPORATED AG THIN-FILMS ONTO DOPED ALKALI-HALIDE SUBSTRATE

Authors: BIRJEGA, MI; FLORESCU, IT; SARBU, C; TOPA, V

Published: 1980, REVUE ROUMAINE DE PHYSIQUE, 25, 696, DOI:

3451. TRAPS IN POLYCRYSTALLINE CDTE THIN-FILMS

Authors: CIUREA, ML; BOTILA, T

Published: 1980, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 61, 491, DOI: 10.1002/pssa.2210610220

3452. HOLE STRUCTURE OF COMPUTER-MODELS OF NON-CRYSTALLINE MATERIALS

Authors: POPESCU, MA

Published: 1980, JOURNAL OF NON-CRYSTALLINE SOLIDS, 35-6, 554, DOI: 10.1016/0022-3093(80)90652-3

3453. PERMEABILITY OF ALUMINO-SILICATE COATINGS ON VITROCERAMIC NUCLEAR-FUEL ELEMENTS

Authors: CRIVAT, D; GORAN, M

Published: 1980, JOURNAL OF NUCLEAR MATERIALS, 95, 227, DOI: 10.1016/0022-3115(80)90098-7

3454. CRYSTALLINE-STRUCTURE AND PROPYLENE OXIDATION IN COMPLEX BISMUTH-MOLYBDENUM OXIDE CATALYSTS

Authors: MANAILA, R; IONESCU, NI; CALDARARU, M

Published: 1980, ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 466, 231, DOI: 10.1002/zaac.19804660128

3455. CHARACTERIZATION OF CUBIC ZNS CRYSTALS GROWN FROM FLUX

Authors: NISTOR, LC; NISTOR, SV; TOACSAN, MI

Published: 1980, JOURNAL OF CRYSTAL GROWTH, 50, 561, DOI: 10.1016/0022-0248(80)90109-8

3456. PLASMA-TARGET COUPLING IN THE CASE OF TEA-CO2 LASER-PRODUCED BREAKDOWN IN FRONT OF A SOLID TARGET

Authors: URSU, I; APOSTOL, I; DINESCU, M; MIHAILESCU, IN; MOLDOVAN, M; PROKHOROV, AM; AGEEV, VP; KONOV, VI; SILENOK, AV; CHAPLIEV, MI

Published: 1980, OPTICS COMMUNICATIONS, 35, 99, DOI: 10.1016/0030-4018(80)90367-3

3457. PARTICULARITIES IN THE GROWTH-BEHAVIOR OF VACUUM EVAPORATED CO THIN-FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; SARBU, C; TOPA, V

Published: 1980, REVUE ROUMAINE DE PHYSIQUE, 25, &, DOI:

3458. EXTENDED MODULATION OF THE X-RAY RAMAN EDGE - NEW METHOD FOR THE STRUCTURAL INVESTIGATION OF LOW ATOMIC-NUMBER NON-CRYSTALLINE MATERIALS

Authors: POPESCU, MA

Published: 1980, JOURNAL OF NON-CRYSTALLINE SOLIDS, 35-6, 566, DOI: 10.1016/0022-3093(80)90654-7

3459. INFRARED INVESTIGATION OF PYRIDINE ADSORPTION AND INTERACTION WITH A NI-CO-CR-AL2O3 CATALYST

Authors: FRUNZA, L; UDREA, M; UDREA, I; NICOLESCU, IV

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, 1005, DOI:

3460. COALESCENCE BEHAVIOR OF GOLD PARTICLES VACUUM EVAPORATED ONTO DOPED ALKALI-HALIDE SUBSTRATES

Authors: BIRJEGA, MI; POPESCUPOGRION, N; TEODORESCU, V; TOPA, V

Published: 1979, THIN SOLID FILMS, 57, 269, DOI: 10.1016/0040-6090(79)90161-5

3461. LIQUID-CRYSTAL DISPLAYS (LCD) .1. REALIZATION OF A DISPLAY BASED ON DYNAMIC LIGHT-SCATTERING

Authors: BEICA, T; FRUNZA, S; GIURGEA, M; MATEI, L; SERBAN, T; VODA, M

Published: 1979, STUDII SI CERCETARI DE FIZICA, 31, 913, DOI:

3462. ATOMIC-STRUCTURE AND THE EXTENDED MODULATION OF THE X-RAY RAMAN-SCATTERING EDGE

Authors: POPESCU, M

Published: 1979, PHYSICS LETTERS A, 73, 262, DOI: 10.1016/0375-9601(79)90726-6

3463. BACKSCATTERED PHOTON ANGULAR-DISTRIBUTION FOR OBLIQUE-INCIDENCE

Authors: ONCESCU, MC

Published: 1979, STUDII SI CERCETARI DE FIZICA, 31, 1060, DOI:

3464. SPECTROPHOTOMETRIC AND SPECTROFLUORIMETRIC INVESTIGATION OF AGGREGATION OF SOME ANTHRAQUINONE DERIVATIVES

Authors: ZAHARIA, CN; HORER, OL; TARABASANUMIHAILA, C; GIURGEA, M

Published: 1979, TALANTA, 26, 66, DOI: 10.1016/0039-9140(79)80159-9

3465. NUCLEAR-QUADRUPOLE INTERACTION IN INDIUM METAL

Authors: THOMPSON, MD; DAS, TP; CIOBANU, G

Published: 1979, BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, 24, 429, DOI:

3466. PARTICULARITIES IN THE GROWTH-BEHAVIOR OF VACUUM-EVAPORATED CHROMIUM THIN-FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; SARBU, C; TOPA, V

Published: 1979, THIN SOLID FILMS, 58, 221, DOI: 10.1016/0040-6090(79)90240-2

3467. LIQUID-CRYSTAL DISPLAYS (LCD) .2. REALIZATION OF DISPLAYS BASED ON THE SCHADT-HELFRICH EFFECT

Authors: BEICA, T; FRUNZA, S; GIURGEA, M; MATEI, L; SERBAN, T; VODA, M

Published: 1979, STUDII SI CERCETARI DE FIZICA, 31, 1026, DOI:

3468. POLYCRYSTALLINE INAS OBTAINING AND SOME SEMICONDUCTING PROPERTIES

Authors: CONSTANTINESCU, C; LAZARESCU, MF; GEORGESCU, M; DUMITRIU, MT

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, 706, DOI:

3469. LONG-RANGE ORDER (LRO) IN THIN NICR (70-30) FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; SARBU, C

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, &, DOI:

3470. SOME PECULIARITIES IN THE ORIENTED GROWTH OF THE VACUUM EVAPORATED AG THIN-FILMS ONTO DOPED ALKALI-HALIDE SUBSTRATES

Authors: BIRJEGA, MI; POPESCUPOGRION, N; SARBU, C; TOPA, V

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, &, DOI:

3471. SOME NONEQUILIBRIUM PHENOMENA IN SPUTTERED CDTE THIN-FILMS

Authors: VALENTOVIC, D; CERVENAK, J; LUBY, S; ALDEA, ML; BOTILA, T

Published: 1979, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 56, 347, DOI: 10.1002/pssa.2210560138

3472. PHYSICAL-PROPERTIES OF POLYCRYSTALLINE CADMIUM-SULFIDE OBTAINED BY CERAMIC TECHNOLOGY

Authors: BUNGET, I; LEONOVICI, MR; MIHAI, V; POPESCU, M; ALEXANDRU, H; STEFLEA, M; OANID, A

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, 66, DOI:

3473. STRUCTURAL TRANSFORMATIONS INDUCED DURING THE ANNEALING OF THIN NI-CR FILMS

Authors: BIRJEGA, MI; POPESCUPOGRION, N; SARBU, C; TEODORESCU, IA

Published: 1979, THIN SOLID FILMS, 57, 341, DOI: 10.1016/0040-6090(79)90175-5

3474. NUCLEATION AND GROWTH OF VACUUM EVAPORATED AU DEPOSITS ONTO KI SUBSTRATES

Authors: BIRJEGA, MI; TOPA, V; TEODORESCU, V

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, &, DOI:

3475. MICROSTRUCTURAL CHANGES IN GAMMA-IRRADIATED POLYPROPILENE DURING THE TRANSITION FROM THE GLASSY STATE TO THE HIGH ELASTIC STATE

Authors: CHIPARA, M; BAICAN, R

Published: 1979, STUDII SI CERCETARI DE FIZICA, 31, 1020, DOI:

3476. MODELS FOR PREEQUILIBRIUM DECAY

Authors: AVRIGEANU, M

Published: 1979, STUDII SI CERCETARI DE FIZICA, 31, 1098, DOI:

3477. CATION DISTRIBUTION IN COBALT FERRITE-ALUMINATES

Authors: POPESCU, M; GHIZDEANU, C

Published: 1979, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 52, K172, DOI: 10.1002/pssa.2210520259

3478. ACIDITY BY INFRARED-SPECTROSCOPY OF SOME TOPOCHEMICAL ALUMINAS

Authors: NICOLESCU, IV; UDREA, M; NICOLESCU, A; FRUNZA, L

Published: 1979, REVUE ROUMAINE DE PHYSIQUE, 24, 678, DOI:

3479. THEORY OF NUCLEAR-QUADRUPOLE INTERACTION IN CADMIUM USING A 1ST-PRINCIPLE PSEUDOPOTENTIAL

Authors: THOMPSON, MD; DAS, TP; CIOBANU, G

Published: 1979, BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, 24, 428, DOI:

3480. CHARACTERISTICS OF A BI-DIMENSIONAL STRUCTURE IN TWIST CELLS WITH NEMATIC LIQUID-CRYSTALS

Authors: NASTA, L; LUPU, A; BEICA, T; SERBAN, T; MATEI, L; GIURGEA, M

Published: 1979, MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 53, 146, DOI: 10.1080/00268947908083991

3481. ESR STUDY OF ACTIVE CENTERS RECOMBINATION KINETICS IN GAMMA-IRRADIATED POLYPROPYLENE (PP)

Authors: BAICAN, R; CHIPARA, M

Published: 1978, STUDII SI CERCETARI DE FIZICA, 30, 667, DOI:

3482. ESTIMATION OF UNKNOWN NUCLEAR MASSES BY MEANS OF GENERALIZED MASS RELATIONSHIPS .1. GENERALIZED MASS RELATIONSHIPS PRIOR TO GARVEY-KELSON TYPE RELATIONSHIPS

Authors: POPA, MS

Published: 1978, STUDII SI CERCETARI DE FIZICA, 30, 108, DOI:

3483. STUDY OF GROWTH OF VACUUM CONDENSED AU PARTICLES ONTO (100) SURFACES OF KBR KCI AND NACL SUBSTRATES WITH COLLOIDAL CENTERS

Authors: BIRJEGA, MI; TOPA, V; TEODORESCU, V

Published: 1978, STUDII SI CERCETARI DE FIZICA, 30, 196, DOI:

3484. NEW COLOR-CENTERS IN KCL - (TL++CA2+) AND KCL - (TL++SR2+) CRYSTALS

Authors: IOAN, A; TOPA, V; GIURGEA, M

Published: 1978, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 89, 520, DOI: 10.1002/pssb.2220890221

3485. CHARACTERISTICS OF A HIGH-VOLTAGE PENNING DISCHARGE IN A MAGNETIC-MIRROR FIELD

Authors: POPOVICI, C; BALACEANU, M; MATEESCU, I

Published: 1977, REVUE ROUMAINE DE PHYSIQUE, 22, 482, DOI:

3486. PLASMA SOURCE OF NEUTRAL PARTICLES AT HEAVY-ION COLLECTIVE DUBNA JINR ACCELERATOR

Authors: GHEORGHE, V; MIHAILOV, MI; NOVIKOV, VG; SARANTSEV, VP; SHESTAKOV, BA

Published: 1977, REVUE ROUMAINE DE PHYSIQUE, 22, 331, DOI:

3487. GROWTH OF KCI SINGLE-CRYSTALS FOR HIGH-POWER CO2-LASER OPTICS

Authors: GHIORDANESCU, V; NISTOR, LC; NISTOR, SV; TEODORESCU, V; VODA, M

Published: 1977, REVUE ROUMAINE DE PHYSIQUE, 22, 666, DOI:

3488. EVALUATION OF SOLIDANGLE AND SELF-ABSORPTION FACTORS BY MONTE-CARLO METHOD

Authors: BERCEANU, I; PETRASCU, M; SIMION, V

Published: 1977, STUDII SI CERCETARI DE FIZICA, 29, 1106, DOI:

3489. CONCENTRATION OF IMPURITY ION CLUSTERS IN A 2-DIMENSIONAL HOST LATTICE

Authors: TRUTIA, A; IOVA, F; VODA, M

Published: 1977, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 84, 824, DOI: 10.1002/pssb.2220840249

3490. STRUCTURAL MODEL OF GLASSY CDGEAS2

Authors: POPESCU, M; MANAILA, R; GRIGOROVICI, R

Published: 1977, JOURNAL OF NON-CRYSTALLINE SOLIDS, 23, 241, DOI: 10.1016/0022-3093(77)90007-2

3491. CONSIDERATIONS ON FIELD PROBLEM STRUCTURE

Authors: PAVELESCU, M

Published: 1977, STUDII SI CERCETARI DE FIZICA, 29, 733, DOI:

3492. SWITCH EFFECT IN A XENON FILLED THERMIONIC TRIODE

Authors: NASTASE, L; CRISTESCU, M; MUSA, G

Published: 1977, REVUE ROUMAINE DE PHYSIQUE, 22, 97, DOI:

3493. MULTIPHOTON IONIZATION OF RUBIDIUM

Authors: COLLINS, CB; CURRY, SM; JOHNSON, BW; MIRZA, MY; CHELLEHMALZADEH, MA; ANDERSON, JA; POPESCU, D; POPESCU, I

Published: 1976, PHYSICAL REVIEW A, 14, 1671, DOI: 10.1103/PhysRevA.14.1662

3494. NEW TYPE OF DOMAIN-STRUCTURE IN NEMATIC LIQUID-CRYSTALS

Authors: PETRESCU, P; GIURGEA, M

Published: 1976, PHYSICS LETTERS A, 59, 42, DOI: 10.1016/0375-9601(76)90346-7

3495. STRUCTURE AND PHYSICAL-PROPERTIES OF GLASSY AS2S3GEX SYSTEM

Authors: ANDREICHIN, R; NIKIFOROVA, M; SKORDEVA, E; YURUKOVA, L; GRIGOROVICI, R; MANAILA, R; POPESCU, M; VANCU, A

Published: 1976, JOURNAL OF NON-CRYSTALLINE SOLIDS, 20, 122, DOI: 10.1016/0022-3093(76)90110-1

3496. STUDIES ON CHARGE-TRANSFER SPECTRUM OF CO++ IN KCL

Authors: TRUTIA, A; VODA, M

Published: 1976, JOURNAL OF CHEMICAL PHYSICS, 64, 2720, DOI: 10.1063/1.432594

3497. STRUCTURE OF GOLD THIN-FILMS EVAPORATED ONTO ALKALI-HALIDE SUBSTRATES WITH COLLOIDAL CENTERS

Authors: BIRJEGA, MI; TOPA, V; TEODORESCU, V

Published: 1976, THIN SOLID FILMS, 32, 211, DOI: 10.1016/0040-6090(76)90292-3

3498. LOCALIZED LEVELS IN ENERGY-GAP OF PBI2 CRYSTALS EVIDENCED BY TSC METHOD

Authors: CONSTANTINESCU, M; GHITA, C; GHITA, L; BALTOG, I

Published: 1976, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 38, K178, DOI: 10.1002/pssa.2210380260

3499. CONFINEMENT OF PLASMA IN MAGNETIC MIRRORS

Authors: BALACEANU, M; BRANDUS, L; POPOVICI, C

Published: 1976, REVUE ROUMAINE DE PHYSIQUE, 21, 151, DOI:

3500. RELAXED RANDOM NETWORK MODEL OF GEAS2TE7 GLASS

Authors: POPESCU, M

Published: 1976, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 35, 360, DOI: 10.1002/pssa.2210350138

3501. (ALPHA,P) REACTION ON ODD CU AND GA ISOTOPES

Authors: BUCURESCU, D; DRAGULESCU, E; IVASCU, M; AVRIGEANU, M; SEMENESCU, G

Published: 1976, REVUE ROUMAINE DE PHYSIQUE, 21, 104, DOI:

3502. PLASMA GUN AS PULSED ATOMS SOURCE

Authors: GHEORGHE, V; MIHAILOV, MI; NOVIKOV, VG; SARANTSEV, VP; SHESTAKOV, BA

Published: 1976, REVUE ROUMAINE DE PHYSIQUE, 21, 212, DOI:

3503. STATE OF DISPERSION OF PB2+ IN HIGHLY DOPED KCI CRYSTALS

Authors: MARCULESCU, L; POPESCU, M; BALTOG, I; GHITA, C

Published: 1976, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 77, 706, DOI: 10.1002/pssb.2220770234

3504. FINE-STRUCTURE MEASUREMENTS OF 2-PHOTON TRANSITIONS IN ATOMIC CESIUM WITH A TUNABLE DYE LASER

Authors: CURRY, SM; COLLINS, CB; MIRZA, MY; POPESCU, D; POPESCU, I

Published: 1976, OPTICS COMMUNICATIONS, 16, 255, DOI: 10.1016/0030-4018(76)90229-7

3505. DEPENDENCE OF WILLIAMS DOMAINS WIDTH ON THRESHOLD VOLTAGE

Authors: GIURGEA, M; SERBAN, T; MATEI, L; BEICA, T; NASTA, L; LUPU, A

Published: 1976, PHYSICS LETTERS A, 57, 338, DOI: 10.1016/0375-9601(76)90600-9

3506. MULTIPHOTON EXCITATION OF ATOMIC RUBIDIUM WITH A TUNABLE DYE LASER

Authors: COLLINS, CB; CURRY, SM; JOHNSON, BW; MIRZA, MY; POPESCU, D; POPESCU, I

Published: 1975, BULLETIN OF THE AMERICAN PHYSICAL SOCIETY, 20, 246, DOI:

3507. LOCALIZED LEVELS IN PBI2 BAND-GAP INDUCED BY THERMAL TREATMENT AND IRRADIATION

Authors: BALTOG, I; CONSTANTINESCU, M; GHITA, C; GHITA, L

Published: 1975, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 27, K41, DOI: 10.1002/pssa.2210270148

3508. STABLE, REPRODUCIBLE, MICROSECOND-DURATION LIGHT-SOURCE

Authors: ZAHARESCU, M; ZOITA, A; ZOITA, V

Published: 1975, REVUE ROUMAINE DE PHYSIQUE, 20, &, DOI:

3509. OPTICAL-SPECTRUM OF CDCL2-MN SINGLE-CRYSTALS

Authors: TRUTIA, A; GHIORDANESCU, V; VODA, M

Published: 1975, PHYSICA STATUS SOLIDI B-BASIC RESEARCH, 70, K22, DOI:

3510. PLASMA SHEATH PROPAGATION IN A COAXIAL ACCELERATOR

Authors: IONESCUBUJOR, T; IORDANESCU, S; MANDACHE, N; ZAHARESCU, M; ZOITA, A; ZOITA, V

Published: 1975, REVUE ROUMAINE DE PHYSIQUE, 20, 58, DOI:

3511. OCCURRENCE OF ENHANCED TC IN RE-GA SYSTEM

Authors: NICULESCU, D; BRADEA, I; POPA, M; IVANCIU, O; CRUCEANU, E

Published: 1975, PHYSICS LETTERS A, 55, 234, DOI: 10.1016/0375-9601(75)90724-0

3512. LANDAU DIAMAGNETISM

Authors: ANGELESCU, N; NENCIU, G; BUNDARU, M

Published: 1975, COMMUNICATIONS IN MATHEMATICAL PHYSICS, 42, 28, DOI: 10.1007/BF01609430

3513. SYNTHESIS AND ELECTRICAL BEHAVIOR OF GA2MG5 TYPE STRUCTURE COMPOUNDS

Authors: POPA, M; BRADEA, I; IVANCIU, O; NICULESCU, D; CRUCEANU, E

Published: 1975, MATERIALS RESEARCH BULLETIN, 10, 1353, DOI: 10.1016/0025-5408(75)90096-3

3514. PERTURBATION OF GIBBS SEMIGROUPS

Authors: ANGELESCU, N; NENCIU, G; BUNDARU, M

Published: 1975, COMMUNICATIONS IN MATHEMATICAL PHYSICS, 42, 30, DOI: 10.1007/BF01609431

3515. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: OCT 2021 , TOPICS IN CATALYSIS, DOI: 10.1007/s11244-021-01513-1

3516. Pulsed Laser Deposition Films Based on CdSe-Doped Zinc Aluminophosphate Glass

Authors: Elisa, M; Iordache, SM; Iordache, AM; Rusu, MI; Socol, G; Filipescu, M; Bartha, C; Enculescu, M

Published: , , DOI: 10.1007/s11837-020-04150-3

3517. Insight on Ni(II) and Cu(II) complexes of biguanide derivatives developed as effective antimicrobial and antitumour agents

Authors: Badea, M; Grecu, MN; Chifiriuc, MC; Bleotu, C; Popa, M; Iorgulescu, EE; Avram, S; Uivarosi, V; Munteanu, AC; Ghica, D; Olar, R

Published: , APPLIED ORGANOMETALLIC CHEMISTRY, e6155, DOI: 10.1002/aoc.6155

3518. Structural and Optical Investigations of Ce3+/Mn2+-Doped LaPO4 Phosphors

Authors: Aitmellal, O; Oufni, L; Messous, MY; Neatu, F; Florea, M; Neatu, S; Rostas, AM; Secu, M

Published: , JOURNAL OF ELECTRONIC MATERIALS, DOI: 10.1007/s11664-020-08678-7

3519. Ecological formulation for improving resveratrol stability and release in aqueous environment

Authors: Todan, L; Voicescu, M; Culita, DC; Pandele-Cusu, J; Albu, C; Kuncser, AC

Published: , CHEMICAL PAPERS, DOI: 10.1007/s11696-020-01409-6

3520. Nanocrystalline rhenium-doped TiO2: an efficient catalyst in the one-pot conversion of carbohydrates into levulinic acid. The synergistic effect between Bronsted and Lewis acid sites

Authors: Avramescu, S; Ene, CD; Ciobanu, M; Schnee, J; Devred, F; Bucur, C; Vasile, E; Colaciello, L; Richards, R; Gaigneaux, EM; Verziu, MN

Published: , CATALYSIS SCIENCE & TECHNOLOGY, DOI: 10.1039/d1cy01450a

3521.

Authors: Neatu, S; Neatu, F; Diculescu, VC; Trandafir, MM; Petr

Published: , , DOI:

3522. Insight on spectral, thermal and biological behaviour of some Cu(II) complexes with saturated pentaazamacrocyclic ligands bearing amino acid residues

Authors: Patrascu, E; Badea, M; Korosin, NC; Korosec, RC; Ruta, LL; Farcasanu, IC; Grecu, MN; Guillaumet, G; Olar, R

Published: , , DOI: 10.1007/s10973-020-09259-w

3523. STUDIES ABOUT STRUCTURAL AND THERMAL INVESTIGATIONS ON Ti50Ni30Cu20 ALLOYS OBTAINED BY DIFFERENT TECHNOLOGICAL PROCESSES

Authors: Cirstea, CD; Lucaci, M; Valeanu, M; Sofronie, M; Bujoreanu, LG; Lungu, MV; Tsakiris, V; Cucos, A; Talpeanu, D; Enescu, E

Published: , ROMANIAN JOURNAL OF PHYSICS, 2021, DOI: 601

3524. Physico-chemical properties of two anhydrous azathioprine forms and their interaction with typical pharmaceutical excipients: highlighting new findings in drug formulation development

Authors: Barbatu, A; Lungan, MA; Toulbe, N; Smaranda, I; Daescu, M; Baibarac, M; Manta, CM

Published: , DRUG DEVELOPMENT AND INDUSTRIAL PHARMACY, DOI:

3525. Textile Materials Treatment With Mixture of TiO2:N and SiO(2)Nanoparticles for Improvement of Their Self-Cleaning Properties

Authors: Mateescu, AO; Mateescu, G; Burducea, I; Mereuta, P; Chirila, L; Popescu, A; Stroe, M; Nila, A; Baibarac, M

Published: SEP 2020 , JOURNAL OF NATURAL FIBERS, DOI: 10.1080/15440478.2020.1818349

3526. Impact of Iridium Oxide Electrodes on the Ferroelectric Phase of Thin Hf0.5Zr0.5O2 Films

Authors: Mittmann, T; Szyjka, T; Alex, H; Istrate, MC; Lomenzo, PD; Baumgarten, L; Muller, M; Jones, JL; Pintilie, L; Mikolajick, T; Schroeder, U

Published: , PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 2100012, DOI: 10.1002/pssr.202100012

3527. Copper(II) species with 1-(o-tolyl)biguanide: Structural characterization, ROS scavenging, antibacterial activity, biocompatibility and in silico studies

Authors: Maxim, C; Badea, M; Rostas, AM; Chifiriuc, MC; Pircalabioru, GG; Avram, S; Olar, R

Published: , APPLIED ORGANOMETALLIC CHEMISTRY, DOI: e6471

3528. A green way for pyruvic acid synthesis from biomass-derived L-malic acid on tetrahedral versus octahedral cobalt sites/hematite

Authors: Mitran, G; Urda, A; Pavel, OD; Neatu, S; Florea, M; Neatu, F

Published: , BIOMASS CONVERSION AND BIOREFINERY, DOI:

3529. NANOMAGNETIC IRON OXIDE SOLUTION FOR FERTILIZATION ON WHEAT PLANTS

Authors: Cimpeanu, C; Badea, ML; Ciobanu, CS; Savulescu, E; Badulescu, L; Petcu, E; Mustatea, P; Raita, SM; Barbuceanu, F; Furnaris, F; Predoi, G

Published: , ROMANIAN AGRICULTURAL RESEARCH, 2021, 67, DOI:

3530. Synthesis and Characterization of Graphite Oxide Derived TiO2-Carbon Composites as Potential Electrocatalyst Supports

Authors: Ayyubov, I; Borbath, I; Paszti, Z; Sebestyen, Z; Mihaly, J; Szabo, T; Illes, E; Domjan, A; Florea, M; Radu, D; Kuncser, A; Tompos, A; Talas, E

Published: , TOPICS IN CATALYSIS, DOI:

3531. Applications of MAX phases and MXenes as catalysts

Authors: Chirica, IM; Mirea, AG; Neatu, S; Florea, M; Barsoum, MW; Neatu, F

Published: , JOURNAL OF MATERIALS CHEMISTRY A, DOI: 10.1039/d1ta04097a

3532. Sonogashira Synthesis of New Porous Aromatic Framework- Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling

Authors: Cata, L; Terenti, N; Cociug, C; Hadade, ND; Grosu, I; Bucur, C; Cojocaru, B; Parvulescu, VI; Mazur, M; Cejka, J

Published: , ACS APPLIED MATERIALS & INTERFACES, DOI:

Palladium nanoparticles entrapped in porous aromatic frameworks (PAFs) or covalent organic frameworks may promote heterogeneous catalytic reactions. However, preparing such materials as active nanocatalysts usually requires additional steps for palladium entrapment and reduction. This paper reports as a new approach, a simple procedure leading to the self-entrapment of Pd nanoparticles within the PAF structure. Thus, the selected Sonogashira synthesis affords PAF-entrapped Pd nanoparticles that can catalyze the C-C Suzuki-Miyaura cross-coupling reactions. Following this new concept, PAFs were synthesized via Sonogashira cross-coupling of the tetraiodurated derivative of tetraphenyladamantane or spiro-9,9 '-bifluorene with 1,6-diethynylpyrene, then characterized them using powder X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, X-ray photoelectron spectroscopy, high-resolution scanning transmission electron microscopy, and textural properties (i.e., adsorption-desorption isotherms). The PAF-entrapped Pd nanocatalysts showed high catalytic activity in Suzuki-Miyaura coupling reactions (demonstrated by preserving the turnover frequency values) and stability (demonstrated by palladium leaching and recycling experiments). This new approach presents a new class of PAFs with unique structural, topological, and compositional complexities as entrapped metal nanocatalysts or for other diverse applications.

3533. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: DEC 2021 , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, DOI: 10.1002/pssa.202100521

3534. Effects of the Severe Plastic Deformation on the Magnetic Properties of Zr13Co87 Ribbons

Authors: Popescu, B; Palade, P; Sofronie, M; Kuncser, A; Gurau, C; Gurau, G; Tolea, F

Published: , METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, DOI: 10.1007/s11661-021-06507-y

3535. MICROSTRUCTURE, MAGNETIC AND MAGNETOSTRICTIVE BEHAVIOUR IN RAPIDLY QUENCHED OFF-STOICHIOMETRIC Ni-Mn-Ga FERROMAGNETIC SHAPE MEMORY ALLOYS

Authors: Sofronie, M; Tolea, F; Enculescu, M; Pasuk, I; Popescu, B

Published: , ROMANIAN REPORTS IN PHYSICS, 2022, DOI: 503

3536. Argon pressure dependent optoelectronic characteristics of amorphous tin oxide thin films obtained by non-reactive RF sputtering process

Authors: Ziani, N; Galca, AC; Belkaid, MS; Stavarache, I

Published: , JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, DOI: 10.1007/s10854-021-05861-2

3537. Pyrolysis and combustion of polystyrene composites based on graphene oxide functionalized with 3-(methacryloyloxy)-propyltrimethoxysilane

Authors: Anghel, I; Lisa, G; Sofran, IE; Mitroi-Symeonidis, FC; Rusu, MM; Baia, M; Baia, L; Magyari, K; Danciu, V; Cotet, LC; Stroe, M; Baibarac, M

Published: , JOURNAL OF POLYMER ENGINEERING, 2021, 626, DOI:

3538. Antiproliferative and antibacterial properties of biocompatible copper(II) complexes bearing chelating N,N-heterocycle ligands and potential mechanisms of action

Authors: Olar, R; Badea, M; Bacalum, M; Raileanu, M; Ruta, LL; Farcasanu, IC; Rostas, AM; Vlaicu, ID; Popa, M; Chifiriuc, MC

Published: , BIOMETALS, DOI: 10.1007/s10534-021-00334-9

3539. Martensitic Transformation and Magnetic Properties of Ni57Fe18Ga25 Shape Memory Alloy Subjected to Severe Plastic Deformation

Authors: Popescu, B; Gurau, C; Gurau, G; Tolea, M; Sofronie, M; Tolea, F

Published: , TRANSACTIONS OF THE INDIAN INSTITUTE OF METALS, DOI: 10.1007/s12666-021-02293-8

3540. A nanoscale continuous transition from the monoclinic to ferroelectric orthorhombic phase inside HfO2 nanocrystals stabilized by HfO2 capping and self-controlled Ge doping

Authors: Palade, C; Lepadatu, AM; Slav, A; Cojocaru, O; Iuga, A; Maraloiu, VA; Moldovan, A; Dinescu, M; Teodorescu, VS; Stoica, T; Ciurea, ML

Published: , JOURNAL OF MATERIALS CHEMISTRY C, DOI: 10.1039/d1tc02921e

3541. An antibody-based amperometric biosensor for 20S proteasome activity and inhibitor screening dagger

Authors: Barsan, MM; Diculescu, VC

Published: , ANALYST, DOI: 10.1039/d0an02426k

3542. Organic Heterostructures with Indium-Free Transparent Conductor Electrode for Optoelectronic Applications

Authors: Petre, G; Stanculescu, A; Girtan, M; Socol, M; Breazu, C; Vacareanu, L; Preda, N; Rasoga, O; Stanculescu, F; Doroshkevich, AS

Published: , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, DOI: 2100521

3543. BIOPHYSICAL ASPECTS OF BIO-NANOSILVER GENERATED FROM URTICA DIOICA LEAVES AND VITIS VINIFERA FRUITS' EXTRACTS

Authors: Barbinta-Patrascu, ME; Nichita, C; Badea, N; Ungureanu, C; Bacalum, M; Zgura, I; Iosif, L; Antohe, S

Published: , ROMANIAN REPORTS IN PHYSICS, 2021, DOI: 601

3544. Chalcogenide Science in Romania

Authors: Lorinczi, A; Badica, P; Botila, T; Ciurea, M; Velea, A; Popescu, A; Socol, G; Antohe, S; Nedelcu, N; Sobetkii, A

Published: , , DOI: 10.1002/pssb.202000284

3545. Effect of starting materials and sintering temperature on microstructure and optical properties of Y2O3:Yb(3+)5 at% transparent ceramics

Authors: Yavetskiy, RP; Balabanov, AE; Parkhomenko, SV; Kryzhanovska, OS; Doroshenko, AG; Mateychenko, PV; Tolmachev, AV; Li, J; Jiang, N; Gheorghe, L; Enculescu, M

Published: , , DOI: 10.1007/s40145-020-0416-3

3546. Textile Materials Treatment With Mixture of TiO2:N and SiO(2)Nanoparticles for Improvement of Their Self-Cleaning Properties

Authors: Mateescu, AO; Mateescu, G; Burducea, I; Mereuta, P; Chirila, L; Popescu, A; Stroe, M; Nila, A; Baibarac, M

Published: , JOURNAL OF NATURAL FIBERS, DOI: 10.1080/15440478.2020.1818349

3547. Structural properties and near-infrared light from Ce3+/Nd3+-co-doped LaPO4 nanophosphors for solar cell applications

Authors: AitMellal, O; Oufni, L; Messous, MY; Tahri, M; Neatu, S; Florea, M; Neatu, F; Secu, M

Published: , JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, DOI:

Dr. Mihaela Stegarescu

Scientific Researcher

Publications

1. Thermal Stability and Irradiation Resistance of (CrFeTiTa)70W30 and VFeTiTaW High Entropy Alloys

2. Structural Analysis of Colloidal Titania-Based Ribbons and Their Self-Assembly upon Drying

3. Catalytic behaviour of CuOx and VOx on Ti3SiC2 support for direct oxidation of methane

4. Bilayered metallic cathodes consisting of pure Mg and Zn:Al thin films optimized by Laser-induced Thermionic Vacuum Arc (LTVA) technology

5. Comparative study of the Cu-TiO2 nanostructures obtained by sol-gel and microwave assisted sol-gel methods

6. Beneficial role of silicotungstic acid presence on the WO3-modified boron-doped diamond substrate on the electrocatalytic activity for methanol anodic oxidation of supported platinum

7. Ultra-Sensitive, Self-powered, CMOS-Compatible Near-Infrared Photodetectors for Wide-Ranging Applications

8. Synthesis of dynamic N-acylhydrazone-based macrocycles

9. Influence of Electron Beam Irradiation and RPMI Immersion on the Development of Magnesium-Doped Hydroxyapatite/Chitosan Composite Bioactive Layers for Biomedical Applications

10. Non-destructive ultrasonic inspections of small-scale mock-ups provided with advanced tungsten armours for DEMO divertor target

11. Composite Films Based on Poly(3-hexylthiophene):Perylene Diimide Derivative:Copper Sulfide Nanoparticles Deposited by Matrix Assisted Pulsed Laser Evaporation on Flexible Substrates for Photovoltaic Applications

12. Cobalt oxyhydroxide co-catalyst loaded onto Al:SrTiO3 surface to boost photocatalytic performance

13. Development of Chrome-Doped Hydroxyapatite in a PVA Matrix Enriched with Amoxicillin for Biomedical Applications

14. Phase evolution in low Fe concentration V1 _xFexO2compounds: Phase diagram and annealing effects

15. Ensemble Machine Learning for the Prediction and Understanding of the Refractive Index in Chalcogenide Glasses

16. Modeling of potential field data for detecting structural and tectonic framework of Esh El Mellaha area, Red Sea, Egypt

17. Annealing temperature, a key factor in shaping Ag-decorated TiO2 aerogels as efficient visible-light photocatalysts

18. Electrochemical assay for the quantification of anticancer drugs and their inhibition mechanism

19. Electrochemical bienzymatic biosensor for pyruvate kinase activity evaluation and inhibitor screening

20. Chrome Doped Hydroxyapatite Enriched with Amoxicillin Layers for Biomedical Applications

21. Phosphorothioated oligonucleotides on gold-coated electrospun polymeric fibers for electrochemical genosensors

22. Influence of flexible substrate nature covered with ITO on the characteristics of organic heterostructures fabricated by laser deposition techniques

23. Exploring the fabrication, properties, and morphology of fluorine substituted hydroxyapatite coatings

24. Monophasic Titanate-Based Photocatalyst with Heteroatom Mixed Iso-Aliovalency Enabling Water Oxidation

25. Martensitic transformation dynamics and mechanical properties investigation in spark plasma sintered Ni-Mn-Ga shape memory alloys

26. Comprehensive Physicochemical and Biological Analysis of Hydroxyapatite/Dextran Powders before and after Immersion in Kokubo Solution

27. Enhancement of luminescence of ZnS:Ag treated in low power radio frequency argon plasma and excited with an electron beam at 13 keV

28. New Nanobioceramics Based on Hydroxyapatite for Biomedical Applications: Stability and Properties

29. Effect of molecular adsorption on the conductivity of selectively grown, interconnected 2D-MoS2 atomically thin flake structures

30. Composites Based on Poly(ortho-toluidine) and WS2 Sheets for Applications in the Supercapacitor Field

31. Exploring the Synthesis of Cu2(Zn,Cd)SnS4 at High Temperatures as a Route for High-Efficiency Solar Cells

32. Large-scale synthesis of monolayer WS2 by low-temperature sulfurization of oxidized magnetron sputtered monolayer W precursors in a microreactor

33. Synthesis, characterization, and photocatalytic efficiency of Mg-doped ZnO nanoparticles for basic Fuchsin dye degradation: Experimental and theoretical insights

34. Influence of Cr on the quaternary FeTaTiW medium entropy alloy

35. Ultrasound-assisted synthesis of (3-cyclodextrin/hydroxyapatite composites as a green and safe additive for enhancing leather properties

36. Phase Transitions in Dimer/Layered Sb-Based Hybrid Halide Perovskites: An In-Depth Analysis of Structural and Spectroscopic Properties

37. Ru/Beta Zeolite Catalysts for Levulinic Acid Hydrogenation: The Importance of Catalyst Synthesis Methodology

38. Recent highlights from INDRA and FAZIA

39. 2025 roadmap on 3D nanomagnetism

40. Induced antibacterial activity of printable composite materials: Influence of the conjoined modulation of ampicillin/hydroxyapatite/graphene nanoplatelets ratios

41. Optical, structural and electrical proprieties of composites based on MoS2, WS2 and poly(ortho-toluidine)

42. Electrochemical detection of superoxide anion in living systems: Recent trends and clinical implications

43. Electrical properties of epitaxial PZT-LSMO magnetoelectric heterostructures: the effect of the interface with the electrodes

44. Experimental study on thermal evolution from precursor gel to crystallized MgO for biomedical applications

45. α-MoO3 Micro- and Nanoparticles as Catalysts for Biofuel Production

46. Aluminum doped zinc oxide nanoplatelets based sensor with enhanced hydrogen sulfide detection

47. Development of new scaffolds for bone substitution by electrospinning and laser ablation

48. Boosting poly(ε-caprolactone) with oleic acid: a green catalyst-driven approach for high-performance antioxidant and antibacterial biodegradable polymers

49. Supercapacitor devices based on multiphase MgTiO3 perovskites doped with Mn2+ ions

50. Fast charging and high-efficiency sputter-deposited silicon thin film anodes for Li-ion batteries

51. Two decades of continuous progresses and breakthroughs in the field of bioactive ceramics and glasses driven by CICECO-hub scientists (vol 40, pg 104, 2024)

52. Physicochemical and Preliminary Biological Properties of Thin Films Based on Fluoride-Doped Hydroxyapatite in a Dextran Matrix for Biomedical Applications

53. A general algorithm for determining the conductivity zeros in large molecular nanostructures: applications to rectangular graphene sheets

54. Induced Effects of Nano-Patterned Substrates on the Electrical and Photo-Electrical Properties of PTB7-Th:ICBA (1:1, wt.%) Bulk-Heterojunction Solar Cells

55. High-Entropy Ti, Zr, Hf, Ta Multiphase Diboride with Deformation Resistance up to 2000 °C

56. Electron transporting bilayers for perovskite solar cells: Spray coating deposition of c-TiO2/m-SnO2-quantum dots

57. Enhanced photocatalytic performance of V2O5 NRs/RGO nanocomposites for Rhodamine-B decolorization under solar irradiation: Experimental and theoretical study

58. Strain engineering of epitaxial perovskite-type LaFeO3/ BiFeO3 heterostructures for photoelectrochemical water splitting

59. Reduced graphene oxide- based multilayer transparent conductive electrodes

60. Tailoring Structural Distortions and Ionic Defects as Alternative Strategy to Modulate Reactive Oxygen Species and Photocatalytic Activity in SnO2 Nanoparticles

61. Detection and Selective Sorption of Copper Ions by a COF-Modified Melamine Sponge

62. Experimental and theoretical perspective on band gap modulation in Sr modified BaTiO3 capacitors 2+

63. Microwave surface resistance in MgB2: Effect of Te and cubic-BN addition on flux flow and pinning

64. APPLICATION OF SPECTRAL GAMMA-RAY LOGS TO DETERMINE THE LITHOFACIES AND DEPOSITIONAL ENVIRONMENT OF THE LAM MEMBER, HABBAN OILFIELD, SAB'ATAYN BASIN (Yemen)

65. Thermally Interpenetrated Co-Ni Mixed Oxide as Efficient Oxygen Evolution Electrodes

66. Influence of in-situ hydrogenation on photoelectrical properties of amorphous and nanocrystalline GeSn deposited by magnetron sputtering

67. Influence of Shale on Petrophysical Properties and Reservoir Quality: Insights from the Matulla Formation, Saqqara Field, Gulf of Suez, Egypt

68. Cells proliferation on surfaces functionalized with amyloid beta peptide fibrils

69. Synthesis and photocatalytic activity of WO3 nanocomposites incorporating GO and MWCNTs for enhanced Rhodamine-B degradation

70. Charge Transfer-Driven Conversion of Molecular Oxygen to Doublet State on Vanadium Diselenide (VSe2) Surface at Room Temperature

71. Distortion of charge carrier trapping centers during incipient phase transformations in TiO2 can enhance its photocatalytic performance

72. Ce-doped ZnO photoanode with enhanced photoelectrochemical performance

73. Growth of pyramidal nanostructures in CeO2-x thin films: Characterization and morphology modeling

74. Composites of Titanium-Molybdenum Mixed Oxides and Non-Traditional Carbon Materials: Innovative Supports for Platinum Electrocatalysts for Polymer Electrolyte Membrane Fuel Cells

75. The Effect of Loading W&V:TiO2 Nanoparticles with Noble Metals for CH4 Detection

76. Tri-layered Si/Co3O4/ZnO heterojunction for high-performance visible photodetection

77. Enhancing Short-Wave Infrared Photosensitivity of SiGe Nanocrystals-Based Films through Embedding Matrix-Induced Passivation, Stress, and Nanocrystallization

49. Supercapacitor devices based on multiphase MgTiO3 perovskites doped with Mn²⁺ ions

62. Experimental and theoretical perspective on band gap modulation in Sr modified BaTiO3 capacitors ²⁺