NIMP| Viorica Florescu, Author at NIMP

Publications

1. Experimental Band Structure of Pb(Zr,Ti)O-3: 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: JAN 2023, ADVANCED SCIENCE, 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.

2. Multifunctional Magnetic Nanocomposites: Innovative Processing and Applications

Authors: Kuncser, V

Published: JAN 2023, NANOMATERIALS, 13, 206, DOI: 10.3390/nano13010206

Multifunctional magnetic nanocomposites are among those heterogeneous nanosized systems where at least one phase component is magnetic and can act as an intermediate of either the actuation or the response of the overall system. The main advantage of heterogeneous nanosystems is the possibility of combining and inter-influencing the electronic properties of constituent interfaced nanophases. Consequently, unique physico-chemical properties of the hybrid materials of interest in various applications can be obtained. This Special Issue of Nanomaterials highlights the most advanced processing and characterization tools of some multifunctional magnetic nanocomposites and heterogeneous systems of interest in various applications, from biomedicine to sensoristics and energy-saving materials.

3. 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.

4. Partial Replacement of Dimethylformamide with Less Toxic Solvents in the Fabrication Process of Mixed-Halide Perovskite Films

Authors: Stancu, V; Tomulescu, AG; Leonat, LN; Balescu, LM; Galca, AC; Toma, V; Besleaga, C; Derbali, S; Pintilie, I

Published: FEB 2023, COATINGS, 13, 378, DOI: 10.3390/coatings13020378

The technology of perovskite solar cells (PSC) is getting close to breaching the consumer market. Yet, one of the current challenges is to reduce the toxicity during their fabrication by reducing the use of the toxic solvents involved in the perovskite fabrication process. A good solubilization of lead halides used in hybrid perovskite preparation is required, and it is only possible with polar solvents. A mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is the most popular solvent combination for a perovskite precursor solution. DMF is necessary to ensure a good dissolution of lead iodide, but it is also the most toxic solvent. In this paper, we study the replacement of the dimethylformamide with presumably less toxic alternatives, such as N-methyl-2-Pyrrolidone (NMP) and ethyl acetate (EA), for the preparation of the K(0.1)FA(0.7)MA(0.2)PbI(2.8)Cl(0.2) (KFAMA) hybrid perovskite. The perovskite thin films were investigated by various characterization techniques: X-ray diffraction, atomic force microscopy, scanning electron microscopy, and UV-vis spectroscopy, while the photovoltaic parameters were determined by measuring the IV curves of the corresponding solar cells. The present study shows that by keeping the same deposition parameters as when only DMF solvent is used, the partial solvent substitution with NMP and EA gives promising results for reducing the toxicity of the fabrication process of KFAMA-based PSCs. Thus, with no specific optimization of the deposition process, and for the maximum possible partial substitution of DMF with NMP and EA solvents, the loss in the power conversion efficiency (PCE) value is only 35% and 18%, respectively, associated with the more structural defects promoted by NMP and EA.

5. Resistive-like Behavior of Ferroelectric p-n Bilayer Structures Based on Epitaxial Pb(Zr0.2Ti0.8)O-3 Thin Films

Authors: Boni, AG; Chirila, C; Trupina, L; Radu, C; Filip, LD; Moldoveanu, V; Pintilie, I; Pintilie, L

Published: JAN 2023, ACS APPLIED ELECTRONIC MATERIALS, DOI: 10.1021/acsaelm.2c01497

The p-n junctions are the building blocks of nowadays electronic devices. The n- or p-type conductivity is obtained in classic semiconductors, like Si, by doping with atoms acting as donors or acceptors, respectively. Doping was used in ferroelectrics to influence the transition temperature, magnitude of some physical properties, but not necessarily conduction type. Therefore, comprehensive studies to obtain true ferroelectric p-n junctions by controlled doping are missing. Recently, it has been shown that Pb(Zr0.2Ti0.8)O-3 films doped with & AP;1% atomic Nb (n-type doping) or Fe (p-type doping) have different orientations of polarization in the as-grown state. Knowing that polarization orientation depends on doping type, the next step is to build ferroelectric p-n homojunctions and to study their properties in relation to ferroelectric polarization. p-n and n-p structures were grown for this purpose by successive deposition of Nb-doped and Fe-doped Pb(Zr,Ti)O-3 layers with different thicknesses. We find that these p-n homojunctions are ferroelectric, but the magnitude of the polarization and coercive field, as well as the dominant polarization orientation in the as-grown state, depend on the conduction type of the first grown layer. The I-V characteristics are quasi-linear, although the interfaces with the electrodes behaves as Schottky contacts. The resistance extracted from the I-V characteristics displays an exponential dependence on temperature, with an activation energy in the range of 0.14-0.17 eV. These results are explained assuming that the total current in the junction is the total of electron and hole injections at the electrode interfaces. It is shown that for relatively low doping concentrations, the current density contains a dominant term with a linear voltage dependence and an exponential temperature dependence, as observed experimentally, and a secondary (correction) term that is dependent on the free carrier density and can induce non-linear voltage dependence when this density is significant.

6. 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.

7. 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.

8. Partial replacement of Pb2+ in MAPbI(2.6)Cl(0.4) 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.

9. Experimental Band Structure of Pb(Zr,Ti)O-3: 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

10. 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.

11. 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.

12. Ferroelectricity Induced by Oxygen Vacancies in Rhombohedral ZrO2 Thin Films

Authors: Lenzi, V; Silva, JPB; Smid, B; Matolin, V; Istrate, CM; Ghica, C; MacManus-Driscoll, JL; Marques, L

Published: MAR 2023, ENERGY & ENVIRONMENTAL MATERIALS, DOI: 10.1002/eem2.12500

Rhombohedral phase HfxZr1-xO2 (HZO, x from 0 to 1) films are promising for achieving robust ferroelectric polarization without the need for an initial wake-up pre-cycling, as is normally the case for the more commonly studied orthorhombic phase. However, a large spontaneous polarization observed in rhombohedral films is not fully understood, and there are also large discrepancies between experimental and theoretical predictions. In this work, in rhombohedral ZrO2 thin films, we show that oxygen vacancies are not only a key factor for stabilizing the phase, but they are also a source of ferroelectric polarization in the films. This is shown experimentally through the investigation of the structural properties, chemical composition and the ferroelectric properties of the films before and after an annealing at moderate temperature (400 degrees C) in an oxygen environment to reduce the V-O concentration compared. The experimental work is supported by density functional theory (DFT) calculations which show that the rhombohedral phase is the most stable one in highly oxygen defective ZrO2 films. The DFT calculations also show that V-O contribute to the ferroelectric polarization. Our findings reveal the importance of V-O for stabilizing rhombohedral ZrO2 thin films with superior ferroelectric properties.

13. Surface species of nematic mixture E7 in hard confinement: spectroscopic investigations cannot distinguish among the E7 components interacting with the support surface

Authors: Frunza, L; Zgura, I; Ganea, CP; Loiko, VA; Manaila-Maximean, D

Published: MAR 2023, LIQUID CRYSTALS, DOI: 10.1080/02678292.2023.2182379

Properties of surface species of the nematic mixture E7 in contact with inorganic oxides (especially those containing more or less aluminium ions) are in detail investigated by infrared spectroscopy and thermogravimetry. The absorption infrared peaks were decomposed into Gaussian components, the procedure allowing an easier comparison with the behaviour of related composites. We worked at enough small concentrations of the E7 relatively to support this ratio permitting the (partial) elimination of the species belonging to the bulk. Species put here in evidence are species that are hydrogen bonded to the surface of OH groups, molecules randomly oriented on the surface, some species bonded by involvement of pi electrons of the CN group to the aluminium ions, thus implying a strong interaction to the support. Supramolecular assemblies of E7 molecules are thus followed up.

14. 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: JAN 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.

15. 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.

16. 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: MAR 2023, ADVANCED SCIENCE, 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.

17. Magnetite-Based Nanostructured Coatings Functionalized with Nigella sativa and Dicloxacillin for Improved Wound Dressings

Authors: Dorcioman, G; Hudita, A; Galateanu, B; Craciun, D; Mercioniu, I; Oprea, OC; Negut, I; Grumezescu, V; Grumezescu, AM; Ditu, LM; Holban, AM

Published: JAN 2023, ANTIBIOTICS-BASEL, 12, 59, DOI: 10.3390/antibiotics12010059

In this study, we report the performance improvement of wound dressings by covering them with magnetite-based nanostructured coatings. The magnetite nanoparticles (Fe3O4 NPs) were functionalized with Nigella sativa (N. sativa) powder/essential oil and dicloxacillin and were synthesized as coatings by matrix assisted pulsed laser evaporation (MAPLE). The expected effects of this combination of materials are: (i) to reduce microbial contamination, and (ii) to promote rapid wound healing. The crystalline nature of core/shell Fe3O4 NPs and coatings was determined by X-ray diffraction (XRD). Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA) have been coupled to investigate the stability and thermal degradation of core/shell nanoparticle components. The coatings' morphology was examined by scanning electron microscopy (SEM). The distribution of chemical elements and functional groups in the resulting coatings was evidenced by Fourier transform infrared (FTIR) spectrometry. In order to simulate the interaction between wound dressings and epithelial tissues and to evaluate the drug release in time, the samples were immersed in simulated body fluid (SBF) and investigated after different durations of time. The antimicrobial effect was evaluated in planktonic (free-floating) and attached (biofilms) bacteria models. The biocompatibility and regenerative properties of the nanostructured coatings were evaluated in vitro, at cellular, biochemical, and the molecular level. The obtained results show that magnetite-based nanostructured coatings functionalized with N. sativa and dicloxacillin are biocompatible and show an enhanced antimicrobial effect against Gram positive and Gram negative opportunistic bacteria.

18. Grain size-driven effect on the functional properties in Ba0.6Sr0.4TiO3 ceramics consolidated by spark plasma sintering

Authors: Patru, RE; Stanciu, CA; Soare, EM; Surdu, VA; Trusca, RD; Nicoara, AI; Vasile, BS; Boni, G; Amarande, L; Horchidan, N; Curecheriu, LP; Mitoseriu, L; Pintilie, L; Pintilie, I; Ianculescu, AC

Published: JUL 2023, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 43, DOI: 10.1016/j.jeurceramsoc.2023.02.013

Dense fine-grained Ba0.6Sr0.4TiO3 ceramics with submicronic grains sizes (GS) have been prepared using nanopowders synthesized via sol-gel route and consolidated by Spark Plasma Sintering (SPS). By changing SPS parameters, the GS was reduced from 214 nm to 74 nm. Diffuse ferroelectric-paraelectric phase transitions and low values of dielectric permittivity (<1000) at the Curie temperature (T-C similar to 280 K) were revealed by Impedance Spectroscopy in all sintered ceramics. The GS reduction from submicron to nanoscale range reflects in a gradually diminishment of dielectric constant, tunability, polarisation and storage energy properties. Raman spectroscopy investigations pointed out the presence of polar nanoclusters above the T-C. The short-range polar order is affected by the GS decrease, but becomes more thermally stable. The observed properties of Ba0.6Sr0.4TiO3 nanostructured ceramics are interpreted by considering the interplay between the GS reduction, the role of low-permittivity grain boundaries and the diffuse character of the ferroelectric-to-paraelectric transformation.

19. 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; Circu, 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.

20. 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: FEB 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.

21. 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.

22. '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.

23. Influence of erbium doping on the structural, magnetic and optical properties of hematite (?-Fe(2)O( )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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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.

30. 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.

31. Unified approach to cyclotron and plasmon resonances in a periodic two-dimensional GaAs electron gas hosting the Hofstadter butterfly

Authors: Gudmundsson, V; Mughnetsyan, V; Abdullah, NR; Tang, CS; Moldoveanu, V; Manolescu, A

Published: APR 7 2022, PHYSICAL REVIEW B, 105, 155302, DOI: 10.1103/PhysRevB.105.155302

We present theoretical calculations for the cyclotron resonance and various magnetoplasmon modes of a Coulomb interacting two-dimensional GaAs electron gas (2DEG) modulated as a lateral superlattice of quantum dots subjected to an external perpendicular constant magnetic field. We use a real-time excitation approach based on the Liouville???von Neumann equation for the density operator, that can go beyond linear response delivering information of all longitudinal and transverse collective modes of interest to the same order. We perform an extensive analysis of the coexisting collective modes due to the lateral confinement and the magnetic field for a different number of electrons in each dot. In the limit of vanishing dot modulation of the 2DEG we find signs of the structure of the Hofstadter butterfly in the excitation spectra.

32. Ferrofluids and bio-ferrofluids: looking back and stepping forward

Authors: Socoliuc, V; Avdeev, MV; Kuncser, V; Turcu, R; Tombacz, E; Vekas, 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.

33. 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.

34. 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.

35. Impact of band-bending on the k-resolved electronic structure of Si-doped GaN

Authors: Lev, LL; Maiboroda, IO; Grichuk, ES; Chumakov, NK; Schroter, 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.

36. 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.

37. 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; Diez, N; Ferrero, GA; Sevilla, M; Szilagyi, 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; Gregoire, A; Perisse, C; Zhao, XY; Vodovotz, Y; Earley, B; Finnveden, G; Bjorklund, 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.

38. 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; Circu, V

Published: JAN 1 2022, POLYHEDRON, 211, 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.

39. 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, I

Published: MAR 2022, JOURNAL OF SOLID STATE CHEMISTRY, 307, 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%).

40. Catalytic transformation of the marine polysaccharide ulvan into rare sugars, tartaric and succinic acids

Authors: Podolean, I; Coman, SM; Bucur, C; Teodorescu, C; Kikionis, S; Ioannou, E; Roussis, V; Primo, A; Garcia, H; Parvulescu, VI

Published: JAN 1 2022, CATALYSIS TODAY, 383, 357, DOI: 10.1016/j.cattod.2020.06.086

The green macroalga Ulva rigida represents a promising feedstock for biorefinary due to its fast growth and cosmopolitan distribution. The main component of the cell walls of U. rigida is a sulfated glucuronorhamnan polysaccharide known as ulvan. Herein it was found that due to the high (hydrogen)sulfate group content of ulvan, hydrothermal autohydrolysis at 130 degrees C renders a high percentage of rhamnose (78-79 % recovery from the initial content in the raw material), a rare sugar of high added value. In addition, acid catalysis by a triflate-based graphene oxide under oxygen-free conditions at 180 degrees C affords moderate amounts of tartaric acid (24-26 %). The same triflate-based graphene oxide catalyst under oxygen pressure yields remarkably high percentages of succinic acid (65 %). The catalyst preserves its activity for at least five consecutive reuses.

41. 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.

42. 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.

43.
Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose & nbsp;

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, 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( 60)Co 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.

44. Electrochemical characterization of shikonin and in-situ evaluation of interaction with DNA

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

Published: SEP 15 2022, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 921, 116663, DOI: 10.1016/j.jelechem.2022.116663

Shikonin, a natural compound with pharmaceutical properties, has attracted interest due to its anti-oxidant properties, potential anti-cancer activity and activity over several biological pathways, such as dsDNA transcription/replication of cancer cells and inhibition of pyruvate kinase M2. The electrochemical behavior of shikonin in aqueous media was investigated at glassy carbon electrodes by cyclic and differential pulse voltammetry. The reduction involves the quinone moiety and formation of a semiquinone intermediate. In the absence of dissolved oxygen, the reduction is reversible while in normal atmosphere leads to formation of superoxide cation. The oxidation occurs at the dihydroxy moiety and reversibility was only observed in acid electrolytes. A redox mechanism was proposed. The interaction between shikonin and dsDNA was evaluated in incubated solutions and in situ with the dsDNA-electrochemical biosensor. The mechanism of interaction is time-dependent and follows an initial binding step at the grooves of the double strand leading to conformational modifications recognized through the variation of guanine and adenine oxidation peaks. The in-situ electrochemical production of the semiquinone intermediate leads to a preferential interaction with guanine residues, promoting their oxidation and consequently occurrence 8-oxo-guanine. An interaction mechanism was proposed.

45. Controlling polarization direction in epitaxial Pb(Zr0.2Ti0.8)O-3 films through Nb (n-type) and Fe (p-type) doping

Authors: Chirila, CF; Stancu, V; Boni, GA; Pasuk, I; Trupina, L; Filip, LD; Radu, C; Pintilie, I; Pintilie, L

Published: JAN 14 2022, SCIENTIFIC REPORTS, 12, 755, DOI: 10.1038/s41598-022-04802-1

Fe (acceptor) and Nb (donor) doped epitaxial Pb(Zr0.2Ti0.8)O-3 (PZT) films were grown on single crystal SrTiO3 substrates and their electric properties were compared to those of un-doped PZT layers deposited in similar conditions. All the films were grown from targets produced from high purity precursor oxides and the doping was in the limit of 1% atomic in both cases. The remnant polarization, the coercive field and the potential barriers at electrode interfaces are different, with lowest values for Fe doping and highest values for Nb doping, with un-doped PZT in between. The dielectric constant is larger in the doped films, while the effective density of charge carriers is of the same order of magnitude. An interesting result was obtained from piezoelectric force microscopy (PFM) investigations. It was found that the as-grown Nb-doped PZT has polarization orientated upward, while the Fe-doped PZT has polarization oriented mostly downward. This difference is explained by the change in the conduction type, thus in the sign of the carriers involved in the compensation of the depolarization field during the growth. In the Nb-doped film the majority carriers are electrons, which tend to accumulate to the growing surface, leaving positively charged ions at the interface with the bottom SrRuO3 electrode, thus favouring an upward orientation of polarization. For Fe-doped film the dominant carriers are holes, thus the sign of charges is opposite at the growing surface and the bottom electrode interface, favouring downward orientation of polarization. These findings open the way to obtain p-n ferroelectric homojunctions and suggest that PFM can be used to identify the type of conduction in PZT upon the dominant direction of polarization in the as-grown films.

46. 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.

47. Effect of the supersaturation with nitrogen on the structure refinement and magnetic properties of mechanically alloyed and heated Fe14Cr ferritic alloys

Authors: Mihalache, V; Pasuk, I; Mercioniu, I

Published: SEP-OCT 2022, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 20, DOI: 10.1016/j.jmrt.2022.07.190

Nano-nitride reinforcement of Fe-Cr alloys are under intense investigations, e.g., along with oxide-strengthened, nitride-strengthened reduced activation steels with superior high temperature mechanical properties are developed as materials for nuclear energy applications. Fe14Cr alloy powders were produced by mechanical milling for up to 170 h under a nitrogen atmosphere followed by heating under an Ar5%H-2 atmosphere to 600 degrees C-1120 degrees C. The samples were investigated by means of X-ray diffraction, DTA/TG and magnetic measurements. CrN, detected after milling for 58 h, reached 39 wt % (5.3 wt.% total N) at 170 h milling. The ferrite supersaturated with nitrogen shows a strong decrease in grain size and saturation magnetization, an increase in lattice constant, microstrain and coercivity, H-c. Upon heating, the metastable ultrafine alpha-ferrite and CrN in the as-milled samples undergo transformations and recrystallization into ferrite grains free of super-saturation, whose microstructure follows a continuous relaxation. The supersaturation with nitrogen was retained upon heating in the relatively stable ferrite crystalized at the milling stage. This microstructure undergoes a discontinuous relaxation in the 800 degrees C-1120 degrees C region: a pronounced decrease of grain size (down to similar to 25 nm), an increase of lattice constant, microstrain and H-c. These improvements were associated with features of discontinuous precipitation reaction of coherent nitride precipitates (involving a new alpha ''-phase with expanded lattice), in connection with the heating in the austenite phase field. Such microstructure refinement or (nitride) strengthening of Fe14Cr alloys can be achieved on powders milled for much less time as compared to previously reported (oxide dispersion) strengthening of Fe14Cr-W-Ti ferritic steels. (C) 2022 The Authors. Published by Elsevier B.V.

48. 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: JUL 2022, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 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.

49. Half-metallic properties of Zr2CrAl ferrimagnetic full-Heusler compound, investigated in tetragonal, orthorhombic and rhombohedral crystal structures

Authors: Birsan, A; Kuncser, V

Published: APR 15 2022, JOURNAL OF ALLOYS AND COMPOUNDS, 900, 163491, DOI: 10.1016/j.jallcom.2021.163491

The research efforts focused on the implementation of Heusler materials into spintronic heterostructures triggered the investigations on the half-metallic and magnetic properties on Zr2CrAl ferrimagnetic com-pound.The theoretical investigations based on Density Functional Theory were performed on the tetragonal,orthorhombic and rhombohedral distortions of the typical inverse-Heusler cubic crystalline structure, previously reported. The compound exhibits half-metallic characteristics for all deformations considered. The slight variations in volume of the unit cell do not destroy the high spin polarization state.The band gap from minority spin channel slightly decreases in orthorhombic and rhombohedral deformations.The total magnetic moment calculated per formula unit is integer (equal to 1(mu B)/f.u.) and follows the Slater-Pauling rule for all cases investigated. The antiferromagnetic coupling between the Zr and Cratoms was preserved. The functionality of ferrimagnetic full-Heusler alloys to be used as overlayers in the production of epitaxially deposited heterostructures on substrates with crystalline structures other than cubic was proven. (C) 2021 Elsevier B.V. All rights reserved.

50. Effective Hamiltonians in the quantum Rabi problem

Authors: Gartner, P; Moldoveanu, V

Published: FEB 4 2022, PHYSICAL REVIEW A, 105, 023704, DOI: 10.1103/PhysRevA.105.023704

We revisit the theoretical description of the ultrastrong light-matter interaction in terms of exactly solvable effective Hamiltonians. A perturbative approach based on polaronic and spin-dependent squeezing transforma-tions provides an effective Hamiltonian for the quantum Rabi model up to the second order in the expansion parameter. The model consistently includes both rotating and counter-rotating terms, going therefore beyond the rotating-wave approximation. Analytical and numerical results show that the proposed Hamiltonian performs better than the Bloch-Siegert model when calculating operator averages (e.g., the mean photon number and number of excitations). This improvement is due to a refined calculation of the dressed states within the present model. Regarding the frequency shift induced by the qubit-photon interaction, we find a different sign from the Bloch-Siegert value. This influences the structure of the eigenstates in a nontrivial way and ensures the correct calculation of the number of excitations associated with a given dressed state. As a consistency check, we show that the exactly solvable independent boson model is reproduced as a special limit case of the perturbative Hamiltonian.

51. 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.

52. 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%.

53. Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films

Authors: Locovei, C; Radu, C; Kuncser, A; Iacob, N; Schinteie, G; Stanciu, A; Iftimie, S; Kuncser, V

Published: APR 2022, NANOMATERIALS, 12, 1176, DOI: 10.3390/nano12071176

AuxFe1-x nanophase thin films of different compositions and thicknesses were prepared by co-deposition magnetron sputtering. Complex morpho-structural and magnetic investigations of the films were performed by X-ray Diffraction, cross-section Transmission Electron Microscopy, Selected Area Electron Diffraction, Magneto Optical Kerr Effect, Superconducting Quantum Interference Device magnetometry and Conversion Electron Mossbauer Spectroscopy. It was proven that depending on the preparation conditions, different configurations of defect alpha-Fe magnetic clusters, i.e., randomly distributed or auto-assembled in lamellar or filiform configurations, can be formed in the Au matrix. A close relationship between the Fe clustering process and the type of the crystalline structure of the Au matrix was underlined, with the stabilization of a hexagonal phase at a composition close to 70 at. % of Au and at optimal thickness. Due to different types of inter-cluster magnetic interactions and spin anisotropies, different types of magnetic order from 2D Ising type to 3D Heisenberg type, as well as superparamagnetic behavior of non-interacting Fe clusters of similar average size, were evidenced.

54. 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)).

55. 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.

56. The Synergistic Effect of the Laser Beam on the Thermionic Vacuum Arc Method for Titanium-Doped Chromium Thin Film Deposition

Authors: Vladoiu, R; Mandes, A; Dinca, V; Ciupina, V; Matei, E; Polosan, S

Published: APR 2022, COATINGS, 12, 470, DOI: 10.3390/coatings12040470

Laser-Induced Thermionic Vacuum Arc (LTVA) provides a better way to produce uniform metallic thin films than the classical Thermionic Vacuum Arc (TVA) method. In Ti-doped chromium thin films produced using LTVA, the amorphous chromium is superimposed with small bcc chromium nanoparticles. These amorphous/crystalline structures with small crystallites induce lower roughness and electrical resistivity, reducing electron-phonon scattering and increasing charge transport across LTVA thin films. A significant shift in resistivity for the LTVA samples is observed due to electron scattering on the phonon-crystalline structures in the TVA samples which exhibit larger crystallites. Meanwhile, the wettability measurements reveal a higher contact angle, resulting in a lower surface free energy and consecutively lower dissociation energy for the LTVA-produced thin films than the TVA samples.

57. 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.

58. 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.

59. Full Length Article Towards high degree of c-axis orientation in MgB2 bulks

Authors: Grigoroscuta, MA; Aldica, GV; Burdusel, M; Sandu, V; Kuncser, A; Pasuk, I; 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

60. Chitosan-Hyaluronan Nanoparticles for Vinblastine Sulfate Delivery: Characterization and Internalization Studies on K-562 Cells

Authors: Cannava, C; De Gaetano, F; Stancanelli, R; Venuti, V; Paladini, G; Caridi, F; Ghica, C; Crupi, V; Majolino, D; Ferlazzo, G; Tommasini, S; Ventura, CA

Published: MAY 2022, PHARMACEUTICS, 14, 942, DOI: 10.3390/pharmaceutics14050942

In the present study, we developed chitosan/hyaluronan nanoparticles (CS/HY NPs) for tumor targeting with vinblastine sulfate (VBL), that can be directed to the CD44 transmembrane receptor, over-expressed in cancer cells. NPs were prepared by coating with HY-preformed chitosan/tripolyphosphate (CS/TPP) NPs, or by polyelectrolyte complexation of CS with HY. NPs with a mean hydrodynamic radius (R-H) of 110 nm, 12% polydispersity index and negative zeta potential values were obtained by a direct complexation process. Transmission Electron Microscopy (TEM) images showed spherical NPs with a non-homogeneous matrix, probably due to a random localization of CS and HY interacting chains. The intermolecular interactions occurring between CS and HY upon NPs formation were experimentally evidenced by micro-Raman (mu-Raman) spectroscopy, through the analysis of the spectral changes of characteristic vibrational bands of HY during NP formation, in order to reveal the involvement of specific chemical groups in the process. Optimized NP formulation efficiently encapsulated VBL, producing a drug sustained release for 20 h. In vitro studies demonstrated a fast internalization of labeled CS/HY NPs (within 6 h) on K-562 human myeloid leukemia cells. Pre-saturation of CD44 by free HY produced a slowing-down of NP uptake over 24 h, demonstrating the need of CD44 for the internalization of HY-based NPs.

61. Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

Authors: Stanciu, AE; Schinteie, G; Kuncser, AC; Locovei, C; Trupina, L; Iacob, N; Leca, A; Borca, B; Kuncser, V

Published: SEP 2022, COATINGS, 12, 1366, DOI: 10.3390/coatings12091366

The manipulation of magnetic anisotropy represents the fundamental prerequisite for the application of magnetic materials. Here we present the vectorial magnetic properties of nanostructured systems and thin films of Fe and FeCo prepared on linearly trenched Mo templates with thermally controlled periodicity. The magnetic properties of the nanosystems are engineered by tuning the shape, size, thickness, and composition parameters of the thin films. Thus, we control coercivity, magnetization, orientation of the easy axis of magnetization, and the long-range magnetic order of the system in the function of the temperature. We distinguish magnetic components that emerge from the complex morpho-structural features of the undulating Fe or FeCo nanostructured films on trenched Mo templates: (i) assembly of magnetic nanowires and (ii) assembly of magnetic islands/clusters. Uniaxial anisotropy at room temperature was proven, characterized, and explained in the case of all systems. Our work contributes to the understanding of magnetic properties necessary for possible further applications of linear systems and undulated thin films.

62. SOME ASPECTS REGARDING PRECIPITATES IN THE NiTi SHAPE MEMORY MATERIALS

Authors: Cirstea, CD; Tolea, F; Patroi, D; Cirstea, V; Tsakiris, V

Published: 2022, ROMANIAN JOURNAL OF PHYSICS, 67, 903, DOI:

NiTi cylindrical materials were obtained by spark plasma sintering at 850??C or 900??C from high purity Ni and Ti powders. These mixtures were previously processed by mechanical alloying for 8 and 15 hours. In order to increase the alloy homogeneity, the NiTi materials were subjected to post aging treatment in protective atmosphere at constant temperature 400??C and cooling in water with ice. All samples were characterized by optical microscopy, differential calorimetry (DSC), X-ray measurements (XRD) and micro/nanoindentation measurements. The results demonstrate that the NiTi materials obtained by this preparation route have good mechanical properties and can serve as a quantitative reference for the microstructure design of shape memory materials for various applications, such as the biomedical ones.

63. 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.

64. Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose

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.

65. 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.

66. 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.

67. 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; Circu, 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.

68. Magnetic Core-Shell Iron Oxides-Based Nanophotocatalysts and Nanoadsorbents for Multifunctional Thin Films

Authors: Musat, V; Stanica, N; Anghel, EM; Atkinson, I; Culita, DC; Polosan, S; Crintea, L; Ceoromila, AC; Buruiana, CT; Carp, O

Published: MAY 2022, MEMBRANES, 12, 466, DOI: 10.3390/membranes12050466

In recent years, iron oxides-based nanostructured composite materials are of particular interest for the preparation of multifunctional thin films and membranes to be used in sustainable magnetic field adsorption and photocatalysis processes, intelligent coatings, and packing or bio-medical applications. In this paper, superparamagnetic iron oxide (core)-silica (shell) nanoparticles suitable for thin films and membrane functionalization were obtained by co-precipitation and ultrasonic-assisted sol-gel methods. The comparative/combined effect of the magnetic core co-precipitation temperature (80 and 95 degrees C) and ZnO-doping of the silica shell on the photocatalytic and nano-sorption properties of the resulted composite nanoparticles were investigated by ultraviolet-visible (UV-VIS) spectroscopy monitoring the discoloration of methylene blue (MB) solution under ultraviolet (UV) irradiation and darkness, respectively. The morphology, structure, textural, and magnetic parameters of the investigated powders were evidenced by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) measurements, and saturation magnetization (vibrating sample magnetometry, VSM). The intraparticle diffusion model controlled the MB adsorption. The pseudo- and second-order kinetics described the MB photodegradation. When using SiO2-shell functionalized nanoparticles, the adsorption and photodegradation constant rates are three-four times higher than for using starting core iron oxide nanoparticles. The obtained magnetic nanoparticles (MNPs) were tested for films deposition.

69. Nanometric-Thick Metal-Free h-Boron Nitride/Graphene Films as Base Catalyst for the Synthesis of Benzoxazoles

Authors: Rendon-Patino, A; Primo, A; Cojocaru, B; Ion, SG; Popescu, DG; Parvulescu, V; Garcia, H

Published: JUN 22 2022, CHEMCATCHEM, 14, e202200356, DOI: 10.1002/cctc.202200356

Catalysts are frequently used as pelletized powdered materials, but rarely as thin films. The present work reports the use of 2D h-boron nitride on few layers defective graphene (h-BN/fl-G) films of about 10 nm thickness as base catalyst for the synthesis of benzoxazoles by coupling a 2-amino-phenol with p-substituted benzaldehydes. The synthesis of benzoxazole derivatives has aroused much interest in the last decades due to their application as potent anticancer agents against MCF-7 and MDA-MB-231 breast cancer cells. The results demonstrate that these nanometer-thick films exhibit three orders of magnitude higher activity than K2CO3 taken as benchmark base catalyst. The activity and selectivity of h-BN/fl-G films depend on the nature of substituents on benzaldehyde, the solvent and reaction temperature.

70. Doped microporous graphitic carbons as metal-free catalysts for the selective hydrogenation of alkynes to alkenes

Authors: Primo, A; Rendon-Patino, A; Bucur, C; Jurca, A; Cojocaru, B; Parvulescu, VI; Garcia, H

Published: JAN 2022, JOURNAL OF CATALYSIS, 405, DOI: 10.1016/j.jcat.2021.11.034

Microporous graphitic carbons obtained by pyrolysis of a-cyclodextrin have been conveniently doped with N and P elements by performing the thermal graphitization adding urea or phosphoric acid as source of these elements. Electron microscopy shows that doping does not influence the structure and dimensions of the micropores, while XPS reveals the distribution of these dopant elements in two main families corresponding to pyridinic and pryrrolic N atoms and to triphenylphosphine and triphenylphosphine oxide for P doping. Thermo-programmed desorption of H2, CO2 and NH3 indicates that the presence of dopant element is responsible for chemisorption of these gases and introduces basic and acid sites. These desorption measurements agree with the catalytic performance of the series of carbons for the chemo and stereo selective hydrogenation of internal aliphatic and aromatic alkynes to cis configured alkenes. N/P doped microporous carbons were found to be stable under the reaction conditions, according to the constant TOF values and XRD and XPS characterization of the materials after their use as catalysts. In addition microporosity appears to play a positive effect by comparing the activity of microporous carbons with the performance of analogous N/P-doped graphenes. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

71. 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: 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.

72. 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; Circu, 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.

73. 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.

74. 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: FEB 2022, ACS APPLIED MATERIALS & INTERFACES, 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 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.

75. 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.

76. Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O-2, N-2, 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.

77. 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.

78. 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.

79. 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.

80. 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.

81. 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, 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%.

82. 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, 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.

83. 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, 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.

84. Synthesis of titanium nitride via hybrid nanocomposites based on mesoporous TiO2/acrylonitrile

Authors: Locovei, C; Chiriac, AL; Miron, A; Iftimie, S; Antohe, VA; Sarbu, A; Dumitru, A

Published: MAR 3 2021, SCIENTIFIC REPORTS, 11, DOI: 10.1038/s41598-021-84484-3

In the present study, the synthesis of titanium nitride (TiN) by carbothermal reduction nitridation (CRN) reaction using nanocomposites made of mesoporous TiO2/acrylonitrile with different content of inorganic phase were explored. The choice of hybrid nanocomposite as precursor for the synthesis of TiN was made due to the possibility of having an intimate interface between the organic and inorganic phases in the mixture that can favours CRN reaction. Subsequently, the hybrid composites have been subjected to four-step thermal treatments at 290 degrees C, 550 degrees C, 1000 degrees C and 1400 degrees C under nitrogen atmosphere. The XRD results after thermal treatment at 1000 degrees C under nitrogen flow show the coexistence of two crystalline phases of TiO2, i.e. anatase and rutile, as well as TiN phase, together with the detection of amorphous carbon that proved the initiation of CRN reaction. Furthermore, the observations based on XRD patterns of samples thermally treated at 1400 degrees C in nitrogen atmosphere were in agreement with SEM analysis, that shows the formation of TiN by CRN reaction via hybrid nanocomposites mesoporous TiO2/acrylonitrile.

85. Hybrid Nanostructures Obtained by Transport and Condensation of Tungsten Oxide Vapours onto CNW Templates

Authors: Carpen, LG; Acsente, T; Satulu, V; Matei, E; Vizireanu, S; Bita, BI; Dinescu, G

Published: APR 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11040835

We present hybrid nanomaterial architectures, consisting of carbon nanowalls (CNW) templates decorated with tungsten oxide nanoparticles, synthesized using a mechanism based on tungsten oxide sublimation, vapor transport, followed by vapor condensation, in the absence or presence of plasma. The key steps in the decoration mechanism are the sublimation of tungsten oxides, when are exposed in vacuum at high temperature (800 degrees C), and their redeposition on colder surfaces (400-600 degrees C). The morphology and chemical composition of the hybrid architectures, as obtained from Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy, are discussed with respect to substrate nature and the physical conditions of synthesis. We pointed out that the decoration process is strongly dependent on the temperature of the CNW templates and plasma presence. Thus, the decoration process performed with plasma was effective for a wider range of template temperatures, in contrast with the decoration process performed without plasma. The results are useful for applications using the sensing and photochemical properties of tungsten oxides, and have also relevance for fusion technology, tungsten walls erosion and material redeposition being widely observed in fusion machines.

86. An antibody-based amperometric biosensor for 20S proteasome activity and inhibitor screening dagger

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.

87. 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, 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.

88. All-Oxide p-n Junction Thermoelectric Generator Based on SnOx and ZnO Thin Films

Authors: Vieira, EMF; Silva, JPB; Veltruska, K; Istrate, CM; Lenzi, V; Trifiletti, V; Lorenzi, B; Matolin, V; Ghica, C; Marques, L; Fenwick, O; Goncalves, LM

Published: JUL 28 2021, ACS APPLIED MATERIALS & INTERFACES, 13, 35196, DOI: 10.1021/acsami.1c09748

Achieving thermoelectric devices with high performance based on low-cost and nontoxic materials is extremely challenging. Moreover, as we move toward an Internet-of-Things society, a miniaturized local power source such as a thermoelectric generator (TEG) is desired to power increasing numbers of wireless sensors. Therefore, in this work, an all-oxide p-n junction TEG composed of low-cost, abundant, and nontoxic materials, such as n-type ZnO and p-type SnOx thin films, deposited on borosilicate glass substrate is proposed. A type II heterojunction between SnOx and ZnO films was predicted by density functional theory (DFT) calculations and confirmed experimentally by X-ray photoelectron spectroscopy (XPS). Moreover, scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy (EDS) show a sharp interface between the SnOx and ZnO layers, confirming the high quality of the p-n junction even after annealing at 523 K. ZnO and SnOx thin films exhibit Seebeck coefficients (alpha) of similar to 121 and similar to 258 mu V/K, respectively, at 298 K, resulting in power factors (PF) of 180 mu W/m K-2 (for ZnO) and 37 mu W/m K-2 (for SnOx). Moreover, the thermal conductivities of ZnO and SnOx films are 8.7 and 1.24 W/m K, respectively, at 298 K, with no significant changes until 575 K. The four pairs all-oxide TEG generated a maximum power output (P-out) of 1.8 nW (approximate to 126 mu W/cm(2)) at a temperature difference of 160 K. The output voltage (V-out) and output current (I-ou(t)) at the maximum power output of the TEG are 124 mV and 0.0146 mu A, respectively. This work paves the way for achieving a high-performance TEG device based on oxide thin films.

89. 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, 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.

90. Design of highly transparent conductive optical coatings optimized for oblique angle light incidence

Authors: Nedelcu, N; Chiroiu, V; Munteanu, L; Girip, I; Rugina, C; Lorinczi, A; Matei, E; Sobetkii, A

Published: AUG 2021, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 127, DOI: 10.1007/s00339-021-04726-z

In this paper, three deposition techniques are combined to create a window material with high average transmission at oblique angles of incidence. Spectrophotometry and ellipsometry measurements, respectively, yield the optical constants n and k. In contrast with other analyses on the subject, a high average transmission, higher than 91% in the 450-900 nm spectral range, is obtained at incident angles of 20-25 degrees. The refractive index and extinction coefficient are determined by the Swanepoel method. The iterative optimization performed using the OpenFilters software leads to an antireflection (AR) multilayer with low reflection and high transmission. The surface quality of the films was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed compact, continuous, and smooth films.

91. Temperature and thickness dependent magnetostatic properties of [Fe/Py]/FeMn/Py multilayers

Authors: Polishchuk, DM; Nakonechna, OI; Lytvynenko, YM; Kuncser, V; Savina, YO; Pashchenko, VO; Kravets, AF; Tovstolytkin, AI; Korenivski, V

Published: JUN 2021, LOW TEMPERATURE PHYSICS, 47, 487, DOI: 10.1063/10.0004971

The magnetic properties of thin-film multilayers [Fe/Py]/FeMn/Py are investigated as a function of temperature and thickness of the antiferromagnetic FeMn spacer using SQUID magnetometry. The observed behavior differs substantially for the structures with 6 nm and 15 nm FeMn spacers. While the 15 nm FeMn structure exhibits exchange pinning of both ferromagnetic layers in the entire measurement temperature interval from 5 to 300 K, the 6 nm FeMn structure becomes exchange de-pinned in the vicinity of room temperature. The depinned state is characterized by a single hysteresis loop centered at zero field and having enhanced magnetic coercivity. The observed properties are explained in terms of finite-size effects and possible ferromagnetic interlayer coupling through the thin antiferromagnetic spacer.

92. 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, 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.

93. 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, 626, 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.

94. 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, 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.</p>

95. 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, 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.

96. 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, 1323, DOI: 10.1016/j.jmrt.2021.06.001

97. Niobia-based magnetic nanocomposites: Design and application in direct glucose dehydration to HMF

Authors: Tirsoaga, A; Kuncser, V; Parvulescu, VI; Coman, SM

Published: APR 15 2021, CATALYSIS TODAY, 366, 56, DOI: 10.1016/j.cattod.2020.09.033

Niobia-based magnetic nanocomposites were prepared by covering magnetite nanoparticle cores (Fe3O4, MNP) with either Nb2O5 or Nb2O5-SiO2 shells using a two-step procedure. In the first step magnetite nanoparticles were prepared by the coprecipitation method. The second step involved their coverage with either Nb2O5 shells, through a precipitation method, or with Nb2O5-SiO2 shells, through a sol-gel protocol followed by precipitation in the presence of the CTAB surfactant. The obtained materials were exhaustively characterised by X-ray diffraction, Mossbauer spectroscopy, magnetic measurements, ICP-OES, DRIFT and Raman spectroscopy, and CO2 - and NH3-TPD measurements, and investigated for glucose dehydration to HMF. The catalytic performances were directly correlated to the nature of the supported niobia phases, which, in turn, has been dictated by the niobia content and the preparation route. The high selectivity to HMF was correlated with to the large pseudohexagonal niobium oxide (TT-Nb2O5) phase while the catalytic activity was directly correlated to the small nanoparticles size. A proper combination of these features led to an optimum catalytic system for the selective production of HMF through glucose dehydration. A third important feature making the developed catalyst promising is its magnetic property, ensured by the magnetite nanoparticles core. This allowed its easy separation from the reaction products.

98. Thermal Gating of Magnon Exchange in Magnetic Multilayers with Antiferromagnetic Spacers

Authors: Polishchuk, DM; Tykhonenko-Polishchuk, YO; Lytvynenko, YM; Rostas, AM; Gomonay, OV; Korenivski, V

Published: JUN 4 2021, PHYSICAL REVIEW LETTERS, 126, DOI: 10.1103/PhysRevLett.126.227203

We observe a strong thermally controlled magnon-mediated interlayer coupling of two ferromagnetic layers via an antiferromagnetic spacer in spin-valve type trilayers. The effect manifests itself as a coherent switching as well as collective resonant precession of the two ferromagnets, which can be controlled by varying temperature and the spacer thickness. We explain the observed behavior as due to a strong hybridization of the ferro- and antiferromagnetic magnon modes in the trilayer at temperatures just below the Neel temperature of the antiferromagnetic spacer.

99. 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, 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.

100. 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, 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.

101. 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: Bertela, 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, 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.

102. Accidental Impurities in Epitaxial Pb(Zr0.2Ti0.8)O-3 Thin Films Grown by Pulsed Laser Deposition and Their Impact on the Macroscopic Electric Properties

Authors: Boni, GA; Chirila, CF; Stancu, V; Amarande, L; Pasuk, I; Trupina, L; Istrate, CM; Radu, C; Tomulescu, A; Neatu, S; Pintilie, I; Pintilie, L

Published: MAY 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11051177

Structural and electrical properties of epitaxial Pb(Zr0.2Ti0.8)O-3 films grown by pulsed laser deposition from targets with different purities are investigated in this study. One target was produced in-house by using high purity precursor oxides (at least 99.99%), and the other target was a commercial product (99.9% purity). It was found that the out-of-plane lattice constant is about 0.15% larger and the a domains amount is lower for the film grown from the commercial target. The polarization value is slightly lower, the dielectric constant is larger, and the height of the potential barrier at the electrode interfaces is larger for the film deposited from the pure target. The differences are attributed to the accidental impurities, with a larger amount in the commercial target as revealed by composition analysis using inductive coupling plasma-mass spectrometry. The heterovalent impurities can act as donors or acceptors, modifying the electronic characteristics. Thus, mastering impurities is a prerequisite for obtaining reliable and reproducible properties and advancing towards all ferroelectric devices.

103. 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, 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.

104. Semiconductor/relaxor 0-3 type composites: A novel strategy for energy storage capacitors

Authors: Jayakrishnan, AR; Silva, JPB; Kamakshi, K; Annapureddy, V; Mercioniu, IF; Sekhar, KC

Published: MAR 2021, JOURNAL OF SCIENCE-ADVANCED MATERIALS AND DEVICES, 6, 26, DOI: 10.1016/j.jsamd.2020.09.012

We report a novel strategy to enhance the dielectric breakdown strength and the energy storage performance of lead-free relaxor ferroelectric ceramics through the fabrication of semiconductor/relaxor 0-3 type composites based on 0.6Ba(Zr0.2Ti0.8)O-3-0.4(Ba0.7Ca0.3)TiO3 [BZCT] and ZnO. X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) measurements confirm the formation of semiconductor/relaxor 0-3 type composites, in which ZnO particles are randomly distributed at the grain boundaries of BZCT. Further, the XRD analysis suggests a structural phase change from a tetragonal to a pseudocubic phase as the ZnO content increases from 0 to 5 wt. % in BZCT/ZnO composites. The pseudocubic phase favors the relaxor behavior of the composites as is evident from dielectric studies. The polarization-electric field (P-E) loops reveal the ferroelectric nature of the BZCT/ZnO composites. The energy storage properties of BZCT/ZnO composite ceramics as a function of different wt. % of ZnO are found to be optimum at 1 wt. % with a recoverable energy density of 2.61 J/cm(3) and an efficiency of 74.2%, at an electric field of 282 kV/cm. Besides, an enhancement of 166% in the electric breakdown and 220% in the recoverable energy density was achieved compared to the BZCT ceramics due to the improved density and the large value of Delta P = P-m - P-r (25.55 mu C/cm(2)). Therefore, this work evidences that the formation of the semiconductor/relaxor 0-3 type composites can be an effective way to significantly improve the energy storage performance of lead-free relaxor ferroelectric ceramics. (C) 2020 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.

105. 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, 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.

106. Comparison between lead free BaTio(3)/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, 755, 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.

107. Spin-vibron coupling effects in single-molecule magnets grafted to a nanoelectromechanical system

Authors: Moldoveanu, V; Dragomir, R

Published: AUG 23 2021, PHYSICAL REVIEW B, 104, DOI: 10.1103/PhysRevB.104.075441

We present a theoretical analysis of the interplay between the spin-vibron and electron-vibron interactions in a hybrid system made of a single-molecule magnet and a suspended conductor. The latter is coupled to particle reservoirs and supports quantized vibrational modes which, once activated, interact with the localized magnetic moment S of the nanomagnet. The dynamics of the molecular spin, the average vibron number, and the transient currents are calculated from the reduced density operator of the hybrid system. We focus on the effect of the vibron-assisted transitions from the lowest energy spin doublet S-z = +/- S to higher energy excited states. The numerical simulations performed for the simplest case S = 2 prove that the vibron-assisted spin transitions and dynamics can be described in terms of a three-level Lambda model borrowed from quantum optics. In particular we predict the existence of Rabi oscillations of the transient currents as fingerprints of the spin-vibron coupling. The role of symmetric or asymmetric bias configurations in setting different mixtures of molecular spin states in the steady-state regime is also emphasized.

108. 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, 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.

109. 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, 2184, 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.

110. An antibody-based amperometric biosensor for 20S proteasome activity and inhibitor screening

Authors: Barsan, MM; Diculescu, VC

Published: MAY 21 2021, ANALYST, 146, 3224, DOI: 10.1039/d0an02426k

111. 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, 2103, 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.

112. Band-Order Anomaly at the gamma-Al2O3/SrTiO3 Interface Drives the Electron-Mobility Boost

Authors: Chikina, A; Christensen, DV; Borisov, V; Husanu, MA; Chen, YZ; Wang, XQ; Schmitt, T; Radovic, M; Nagaosa, N; Mishchenko, AS; Valenti, R; Pryds, N; Strocov, VN

Published: MAR 23 2021, ACS NANO, 15, 4356, 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.

113. Beyond Nitrogen in the Oxygen Reduction Reaction on Nitrogen-Doped Carbons: A NEXAFS Investigation

Authors: Tanasa, E; Maxim, FI; Erniyazov, T; Iacob, MT; Skala, T; Tanase, LC; Ianasi, C; Moisescu, C; Miron, C; Ardelean, I; Antohe, VA; Fagadar-Cosma, E; Stamatin, SN

Published: MAY 2021, NANOMATERIALS, 11, 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.

114. 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, 176, 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.

115. 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, 33389, 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.

116. 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, 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.

117. Zn-Fe-oxide nanostructures of different iron concentrations for multifunctional applications: properties and precursor influence

Authors: Mihalache, V; Negrila, C; Mercioniu, I; Iacob, N; Kuncser, V

Published: AUG 14 2021, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 23, 16127, DOI: 10.1039/d1cp01002f

Zn-Fe-O nanoparticle systems (Z3F, Z20F and Z60F) were produced by changing the Zn:Fe ratio (0.97 : 0.03, 0.8 : 0.2 and 0.4 : 0.6 in at%, respectively) in Zn(ii)-Fe(iii)-carboxylate precursors. According to X-ray diffraction, Z60F is nearly single-phase ZnFe2O4 (5.9 nm crystallite size), Z20F is a ZnO/ZnFe2O4 nanocomposite consisting of 48.8% ZnFe2O4 (4.7 nm crystallite size), and Z3F is apparently pure ZnO (9.5 nm). We found evidence for a ZnFe2O4 spinel of high inversion degree (80-100%) and with superparamagnetic (SPM) behaviour at room temperature in all three samples by a remarkable correlation between HRTEM, FTIR, XPS, Mossbauer and magnetization analyses. Iron modifies the decomposition process of the precursor and enhances its viscosity, which appears to favour the separation of Zn- and Fe-rich phases. As a consequence, two-phase systems of individual nanocrystals/nanoparticles (ZnO and ZnFe2O4) are formed. The large anisotropy constant, 10(6)-10(7) erg cm(-3), of the ZnFe2O4 nanoparticles and the concentration dependence of their magnetic energy barrier are explained in terms of interparticle interactions interlinked with finite size effects and high inversion degree; these factors also control the other parameters of importance for applications, including the blocking temperature (13-111 K), saturation magnetization (1.08-17.7 emu g(-1) at 300 K, 4.6-44.8 emu g(-1) at 5 K) and coercivity (85.4-491 Oe at 5 K). Magnetic dynamic results, particularly modelled by the Neel-Brown and Vogel-Fulcher laws, yield fitting parameters which validate the presence of concentration-dependent dipole-like interactions between ZnFe2O4 nanoparticles. A fraction of iron was found in the Fe2+ state, presumably substituting for Zn2+ in zinc oxide; however, the samples behave like ZnFe2O4 SPM nanoclusters/nanoparticles dispersed in a nonmagnetic ZnO particle assembly, rather than Zn(Fe)O dilute magnetic semiconductors. The relevance of the properties of the investigated material for specific applications is highlighted throughout the manuscript.

118. 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, 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.

119. 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, 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.

120. 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, 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%.

121. Gold coated electrospun polymeric fibres as new electrode platform for glucose oxidase immobilization

Authors: Aldea, A; Leote, RJB; Matei, E; Evanghelidis, A; Enculescu, I; Diculescu, VC

Published: JUN 2021, MICROCHEMICAL JOURNAL, 165, 106108, DOI: 10.1016/j.microc.2021.106108

Fibres of poly(methyl methacrylate) were obtained by electrospinning, subjected to coating with a gold layer and then attached on a thin polyethylene terephthalate substrate in order to obtain flexible electrodes for biosensing applications. The morphology of these electrodes, investigated by scanning electron microscopy showed multilayers of random oriented fibres of approx. 400 nm diameter. The electrochemical characterization of these flexible electrodes was performed by cyclic voltammetry and electrochemical impedance spectroscopy in acid and neutral media, in the absence and in the presence of redox probes, proving their superior performance (e.g. 5fold current density value) when compared to planar gold electrodes obtained on silicon wafers. The electrodes obtained from conductive electrospun polymeric fibres nets were tested by cyclic voltammetry and amperometry for the detection of hydrogen peroxide with a sensitivity of 0.84 mA cm-2 mM-1 and a detection limit of 20.40 ?M. The immobilization of the model enzyme glucose oxidase at the surface of the gold-coated electrospun polymeric fibres electrode was investigated and the obtained biosensor was applied for glucose determination in aqueous solutions by fixed potential amperometry with a sensitivity of 3.10 ?A cm-2 mM-1, a detection limit of 0.33 mM, and reduced interferences. Also, the practical applicability of the biosensor was tested for the detection of glucose in artificial sweat and serum samples.

122. 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, 12366, 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.

123. 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, VI; Garcia, H

Published: JUN 15 2021, APPLIED CATALYSIS B-ENVIRONMENTAL, 287, 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.

124. 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, 229, 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.

125. 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, 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.

126. 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, 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.

127. 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; Szilagyi, IM; Pokol, G; Zaharescu, M

Published: MAR 2021, REVUE ROUMAINE DE CHIMIE, 66, 229, 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.

128. 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, 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.

129. 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, 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.

130. Multilevel Memristive GeTe Devices

Authors: Velea, A; Dumitru, V; Sava, F; Galca, AC; Mihai, C

Published: MAR 2021, PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS, 15, DOI: 10.1002/pssr.202000475

Phase-change memories have reached an advanced degree of maturity, although, to be able to meet the increasing storage demand, multilevel capability is needed. A GeTe memristor is obtained in an amorphous state and it is subjected to a specific thermal treatment which initiates the transition toward the crystalline state. It is found that this crystalline state initialization process is highly beneficial for subsequently obtaining a large number of intermediate resistive states between the high and low resistive states. Multiple resistance levels are achieved by operating the devices in both DC sweeps and rectangular pulse modes in the low-voltage subthreshold regime. The conduction is modeled using a space charge limited conduction model, showing three distinct conduction regions in the high resistive state which merge toward a single conduction region as the low resistive state is approached. The obtained memristors can be used as multilevel nonvolatile memories or as synapses in neuromorphic computing.

131. 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, 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.

132. 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, 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.

133. 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, 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.

134. 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; Circu, V

Published: APR 2021, MOLECULES, 26, 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)).

135. 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, 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.

136. Self-induction and magnetic effects in electron transport through a photon cavity

Authors: Gudmundsson, V; Abdullah, NR; Tang, CS; Manolescu, A; Moldoveanu, V

Published: MAR 2021, PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, 127, DOI: 10.1016/j.physe.2020.114544

We explore higher order dynamical effects in the transport through a two-dimensional nanoscale electron system embedded in a three-dimensional far-infrared photon cavity. The nanoscale system is considered to be a short quantum wire with a single circular quantum dot defined in a GaAs heterostructure. The whole system, the external leads and the central system are placed in a constant perpendicular magnetic field. The Coulomb interaction of the electrons, the paraand diamagnetic electron-photon interactions are all treated by a numerically exact diagonalization using step-wise truncations of the appropriate many-body Fock spaces. We focus on the difference in transport properties between a description within an electric dipole approximation and a description including all higher order terms in a single photon mode model. We find small effects mostly caused by an electrical quadrupole and a magnetic dipole terms that depend strongly on the polarization of the cavity field with respect to the transport direction and the photon energy. When the polarization is aligned along the transport direction we find indications of a weak self-induction that we analyze and compare to the classical counterpart, and the self-energy contribution of high-order interaction terms to the states the electrons cascade through on their way through the system. Like expected the electron-photon interaction is well described in the dipole approximation when it is augmented by the lowest order diamagnetic part for a nanoscale system in a cavity in an external magnetic field.

137. 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, 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.

138. 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, 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.

139. Magneto-optical properties of borophosphate glasses co-doped with Tb3+ and Dy(3+)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, 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.

140. 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, 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.

141. 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, 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.

142. Influence of Thickness on the Magnetic and Magnetotransport Properties of Epitaxial La0.7Sr0.3MnO3 Films Deposited on STO (001)

Authors: Greculeasa, SG; Stanciu, AE; Leca, A; Kuncser, A; Hrib, L; Chirila, C; Pasuk, I; Kuncser, V

Published: DEC 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11123389

Epitaxial La0.7Sr0.3MnO3 films with different thicknesses (9-90 nm) were deposited on SrTiO3 (0 0 1) substrates by pulsed laser deposition. The films have been investigated with respect to morpho-structural, magnetic, and magneto-transport properties, which have been proven to be thickness dependent. Magnetic contributions with different switching mechanisms were evidenced, depending on the perovskite film thickness. The Curie temperature increases with the film thickness. In addition, colossal magnetoresistance effects of up to 29% above room temperature were evidenced and discussed in respect to the magnetic behavior and film thickness.

143. Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Authors: Alfe, M; Gargiulo, V; Amati, M; Maraloiu, VA; Maddalena, P; Lettieri, S

Published: JUL 2021, CATALYSTS, 11, 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.

144. 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, 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.

145. 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, 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.

146. Thickness-Dependent Photoelectrochemical Water Splitting Properties of Self-Assembled Nanostructured LaFeO3 Perovskite Thin Films

Authors: Andrei, F; Ion, V; Birjega, R; Dinescu, M; Enea, N; Pantelica, D; Mihai, MD; Maraloiu, VA; Teodorescu, VS; Marcu, IC; Scarisoreanu, ND

Published: JUN 2021, NANOMATERIALS, 11, 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.

147. Homogeneous versus Inhomogeneous Polarization Switching in PZT Thin Films: Impact of the Structural Quality and Correlation to the Negative Capacitance Effect

Authors: Pintilie, L; Boni, GA; Chirila, CF; Stancu, V; Trupina, L; Istrate, CM; Radu, C; Pintilie, I

Published: AUG 2021, NANOMATERIALS, 11, DOI: 10.3390/nano11082124

Polarization switching in ferroelectric films is exploited in many applications, such as non-volatile memories and negative capacitance field affect transistors. This can be inhomogeneous or homogeneous, depending on if ferroelectric domains are forming or not during the switching process. The relation between the polarization switching, the structural quality of the films and the negative capacitance was not studied in depth. Here, Pb(Zr0.2Ti0.8)O-3 (PZT) layers were deposited by pulse laser deposition (PLD) and sol-gel (SG) on single crystal SrTiO3 (STO) and Si substrates, respectively. The structural quality was analyzed by X-ray diffraction and transmission electron microscopy, while the electric properties were investigated by performing hysteresis, dynamic dielectric measurements, and piezo-electric force microscopy analysis. It was found that the PZT layers grown by PLD on SRO/STO substrates are epitaxial while the layers deposited by SG on Pt/Si are polycrystalline. The polarization value decreases as the structure changes from epitaxial to polycrystalline, as well as the magnitude of the leakage current and of the differential negative capacitance, while the switching changes from homogeneous to inhomogeneous. The results are explained by the compensation rate of the depolarization field during the switching process, which is much faster in epitaxial films than in polycrystalline ones.

148. 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, 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.

149. TiO2 nanoparticles coated with bio-inspired ligands for the safer-by-design development of photocatalytic paints

Authors: Laisney, J; Rosset, A; Bartolomei, V; Predoi, D; Truffier-Boutry, D; Artous, S; Berge, V; Brochard, G; Michaud-Soret, I

Published: JAN 1 2021, ENVIRONMENTAL SCIENCE-NANO, 8, 310, DOI: 10.1039/d0en00947d

Addition of titanium dioxide nanoparticles (TiO2 NPs) in photocatalytic paints represents a promising alternative aiming to mineralize gaseous pollutants, such as volatile organic compounds (VOCs). However, the risks of release of nanoparticles to human health and the environmental impact have to be taken carefully into account for their development. To take into account these risks, we develop a new method of TiO2 NP synthesis. Here, we report the electrostatic stabilization in aqueous medium with pyrophosphate buffers of different pH ranges followed by coating with bio-inspired molecules (lysine, deferoxamine, dopamine) and polymers (polyacrylic acid, polyethylene glycol, polydopamine) of 4-5 nm spherical photocatalytic TiO2 NPs for the development of safer-by-design photocatalytic paint. Characterization of the so-formed TiO2 nanocomposites by dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) showed the good grafting of the ligands on the TiO2 surface and an enhanced stability in water compared to the pristine TiO2 NPs. The photocatalytic activity of the TiO2 nanocomposites was investigated by following the degradation of methylene blue (MB) under irradiation. The results showed a modulation of the photocatalytic activity (decrease or increase of the MB degradation rate) as a function of the nature/binding strength of the bio-inspired coating on the oxide surface. Finally, the most promising nanocomposites were incorporated in paints on which preliminary chalking assays were performed after storage for one year in the dark or in interior daylight.

150. High-Performance Functionalized Magnetic Nanoparticles with Tailored Sizes and Shapes for Localized Hyperthermia Applications

Authors: Craciunescu, I; Palade, P; Iacob, N; Ispas, GM; Stanciu, AE; Kuncser, V; Turcu, RP

Published: MAY 27 2021, JOURNAL OF PHYSICAL CHEMISTRY C, 125, 11146, DOI: 10.1021/acs.jpcc.1c01053

Magnetite (Fe3O4) and ferrite (MFe2O4, M = Mn, Zn) hydrophobic magnetic nanoparticles with various shapes and sizes were synthesized by high-temperature reaction of organic precursor solutions. Spherical, cubic, hexagonal, and octahedral shapes and sizes ranging from 10 to 100 nm were obtained. It has been proven that the reported high capability of tailoring the shape and the size of the surface-coated nanoparticles allows controlling a variety of properties that are relevant to many potential applications. Structurally well-formed hydrophobic magnetic nanoparticles with high saturation magnetization values are reported. The hydrophobic oleic acid shell was successfully transformed by a simple and environmentally friendly oxidative scission method into azelaic acid. The morphostructural characteristics, size distributions, chemical composition, and magnetic properties of the resulting hydrophilic nanoparticles were investigated by electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Mossbauer spectroscopy, superconducting quantum interference device, and vibrating sample magnetometry. Magnetic hyperthermia measurements have been performed in a specially designed sample holder placed in an inductor with copper windings assuring alternating magnetic fields of safely biological amplitude-frequency products. The optimal shape with a specific size range for nanoparticles dispersed in various carriers providing the best heating efficiency is reported.

151. 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, 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)).

152. Combining Fluorinated Polymers with Ag Nanoparticles as a Route to Enhance Optical Properties of Composite Materials

Authors: Satulu, V; Mitu, B; Ion, V; Marascu, V; Matei, E; Stancu, C; Dinescu, G

Published: AUG 2020, POLYMERS, 12, DOI: 10.3390/polym12081640

Polymer-based nanocomposites have recently received considerable attention due to their unique properties, which makes them feasible for applications in optics, sensors, energy, life sciences, etc. The present work focuses on the synthesis of nanocomposites consisting of a polytetrafluorethylene-like matrix in which metallic nano-silver are embedded, by using multiple magnetron plasmas. By successively exposing the substrate to separate RF magnetrons using as combination of target materials polytetrafluorethylene (PTFE) and silver, individual control of each deposition process is insured, allowing obtaining of structures in which silver nanoparticles are entrapped in-between two PTFE layers with given thicknesses. The topographical and morphological characteristics investigated by means of Scanning Electron Microscopy and Atomic Force Microscopy techniques evidenced the very presence of Ag nanoparticles with typical dimension 7 nm. The chemical composition at various depositing steps was evaluated through X-ray Photoelectron Spectroscopy. We show that the presence of the top PTFE layer prevents silver oxidation, while its thickness allows the tailoring of optical properties, as evidenced by spectroellipsometry. The appearance of chemical bonds between silver atoms and PTFE atoms at interfaces is observed, pointing out that despite of pure physical deposition processes, a chemical interaction between the polymeric matrix and metal is promoted by plasma.

153. Tuning structural and magnetic properties of Fe oxide nanoparticles by specific hydrogenation treatments

Authors: Greculeasa, SG; Palade, P; Schinteie, G; Leca, A; Dumitrache, F; Lungu, I; Prodan, G; Kuncser, A; Kuncser, V

Published: OCT 14 2020, SCIENTIFIC REPORTS, 10, DOI: 10.1038/s41598-020-74188-5

Structural and magnetic properties of Fe oxide nanoparticles prepared by laser pyrolysis and annealed in high pressure hydrogen atmosphere were investigated. The annealing treatments were performed at 200 degrees C (sample A200C) and 300 degrees C (sample A300C). The as prepared sample, A, consists of nanoparticles with similar to 4 nm mean particle size and contains C (similar to 11 at.%), Fe and O. The Fe/O ratio is between gamma-Fe2O3 and Fe3O4 stoichiometric ratios. A change in the oxidation state, crystallinity and particle size is evidenced for the nanoparticles in sample A200C. The Fe oxide nanoparticles are completely reduced in sample A300C to alpha-Fe single phase. The blocking temperature increases from 106 K in A to 110 K in A200C and above room temperature in A300C, where strong inter-particle interactions are evidenced. Magnetic parameters, of interest for applications, have been considerably varied by the specific hydrogenation treatments, in direct connection to the induced specific changes of particle size, crystallinity and phase composition. For the A and A200C samples, a field cooling dependent unidirectional anisotropy was observed especially at low temperatures, supporting the presence of nanoparticles with core-shell-like structures. Surprisingly high M-S values, almost 50% higher than for bulk metallic Fe, were evidenced in sample A300C.

154. 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, 786, 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.

155. 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, 56171, 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.

156. UAV identification system based on memristor physical unclonable functions

Authors: Ionescu, O; Besleaga, C; Dumitru, V; Pricop, E

Published: 2020, PROCEEDINGS OF THE 2020 12TH INTERNATIONAL CONFERENCE ON ELECTRONICS, COMPUTERS AND ARTIFICIAL INTELLIGENCE (ECAI-2020), DOI:

The latest decades presented a large development of various size and types of Unmanned Aerial Vehicles (UAVs). Nowadays, there are over 200 million UAVs used in various applications and there it is a large effort to adopt national and international regulation for using them. There it is a real need for the development of a reliable system for UAVs identity verification that can be implemented and used at global level. To this moment the software-based methods such as MAC address, IDs memorized on devices are prone to a large number of cyber-security vulnerabilities and attacks. This paper presents an innovative hardware-based identification solution which could be adapted to UAVs in a non-intrusive manner. The proposed solution is based on physical unclonable functions (PUF), which are implemented by using memristors. The proposed solution is very low cost and high performance. By using memristors, it is possible to generate a very large number of unclonable IDs, using only a few electrical components. This solution could be incorporated in any UAVs systems without major modifications and not affecting their flight parameters.

157. Transport, AC susceptibility, DC magnetization, and magnetic relaxation studies of YBa2Cu3O7 films with synergetic pinning centers grown by PLD

Authors: Crisan, A; Ivan, I; Miu, L; Becherscu, N; Dang, VS

Published: JUL 20 2020, MODERN PHYSICS LETTERS B, 34, DOI: 10.1142/S0217984920400606

We have grown, by Pulsed Laser Deposition (PLD), a large number of YBa2Cu3O7 films with artificial pinning centers, with various impurities, various architectures and thickness, and various techniques of nano-scale pinning engineering: substrate decoration, BaZrO3 (BZO) nano-inclusions, and (quasi) multilayer architecture. Here we will present the results regarding vortex matter, dynamics, and pinning, in some of our best samples. Magnetic relaxation studies with magnetic field perpendicular to the film show that in both cases the splayed defects and/or nanoscale inclusions help reduce the dissipation in certain field-temperature range, by inhibiting the detrimental double vortex-kink formation. The response of the vortex system to AC excitation is rather complex but extremely useful for the characterization of the vortex dynamics. We have measured AC susceptibility in various DC fields, with various AC fields and frequencies and found that the effective vortex activation energy U-eff has a logarithmic dependence on the AC-field-induced current density J. Synergetic pinning centers assured a low anisotropy of the critical current for various field orientations, a property desired in coil/solenoid applications.

158. 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, 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.

159. Structural and functional properties of BaTiO3 porous ceramics produced by using pollen as sacrificial template

Authors: Lukacs, VA; Stanculescu, R; Curecheriu, L; Ciomaga, CE; Horchidan, N; Cioclea, C; Mitoseriu, L

Published: JAN 2020, CERAMICS INTERNATIONAL, 46, 530, DOI: 10.1016/j.ceramint.2019.08.292

The present paper reports the dependence of structural and functional properties on the porosity level with values down to 50% in BaTiO3 ceramics. Micro-porosity (pore size below 15 pm) with (0-3) connectivity has been produced by using dried pollen particles as sacrificial template. The properties of such porous ceramics are mostly affected by porosity, but also by possible small doping with foreign ions resulted from the template and by small variations of Ba/Ti stoichiometry at the ceramic-pore interfaces, as observed by a shift of the Curie temperature towards lower values when porosity level increases. The dielectric relaxation evidenced a few processes characterised by different activation energies which seem to be not affected by porosity, i.e. they might be assigned to the ceramic part and not to the ceramic-pore interfaces. When increasing porosity, a regular tilting of P(E) loops and increasing of coercivity and reducing polarization were observed, as result of reduction of active ferroelectric component and to the field inhomogeneity in such ceramics.

160. Lead-Free BNT-BT0.08/CoFe2O4 Core-Shell Nanostructures with Potential Multifunctional Applications

Authors: Cernea, M; Radu, R; Amorin, H; Greculeasa, SG; Vasile, BS; Surdu, VA; Ganea, P; Trusca, R; Hattab, M; Galassi, C

Published: APR 2020, NANOMATERIALS, 10, 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.

161. The Influence of Synthesis Parameters on Structural and Magnetic Properties of Iron Oxide Nanomaterials

Authors: Cursaru, LM; Piticescu, RM; Dragut, DV; Tudor, IA; Kuncser, V; Iacob, N; Stoiciu, F

Published: JAN 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10010085

Magnetic iron oxides have been used in biomedical applications, such as contrast agents for magnetic resonance imaging, carriers for controlled drug delivery and immunoassays, or magnetic hyperthermia for the past 40 years. Our aim is to investigate the effect of pressure and temperature on the structural, thermal, and magnetic properties of iron oxides prepared by hydrothermal synthesis at temperatures of 100-200 degrees C and pressures of 20-1000 bar. It has been found that pressure influences the type of iron oxide crystalline phase. Thus, the results obtained by Mossbauer characterization are in excellent agreement with X-ray diffraction and optical microscopy characterization, showing that, for lower pressure values (<100 bar), hematite is formed, while, at pressures >100 bar, the major crystalline phase is goethite. In addition, thermal analysis results are consistent with particle size analysis by X-ray diffraction, confirming the crystallization of the synthesized iron oxides. One order of magnitude higher magnetization has been obtained for sample synthesized at 1000 bar. The same sample provides after annealing treatment, the highest amount of good quality magnetite leading to a magnetization at saturation of 30 emu/g and a coercive field of 1000 Oe at 10 K and 450 Oe at 300 K, convenient for various applications.

162. Unexpected magneto-functionalities of amorphous Fe-Gd thin films crossing the magnetization compensation point

Authors: Stanciu, AE; Schinteie, G; Kuncser, A; Iacob, N; Trupina, L; Ionita, I; Crisan, O; Kuncser, V

Published: MAR 15 2020, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 498, DOI: 10.1016/j.jmmm.2019.166173

A complex investigation of the morpho-structural, magnetic, magneto-optical and magneto-transport properties of amorphous Fe-Gd thin films crossing the magnetization compensation point is reported and the unexpected observed magneto-functionalities are discussed. A tendency of magnetic domain formation with increasing the Fe content over the compensation concentration is observed. The switch from a reversed Magneto-optical Kerr Effect loop to a direct loop when increasing the Fe content over the compensation point is explained via the specific contribution to the rotation of the polarization vector from each magnetic sublattice, belonging to Fe and Gd, respectively. Local atomic configurations and magnetic interactions ascertained the amorphous character and revealed an out-ofplane orientation of the magnetic moment of Fe above the compensation point. The thermomagnetic curves prove a concentration dependent behavior, explained by weakly coupled magnetization relaxation processes of the two magnetic sub-lattices. On the other hand, the magnetic hysteresis loops gave evidence of two exchange coupled magnetic phases with different coercive fields. According to structural and Fe-57 Mossbauer Spectroscopy results, the two phases correspond to definite nanosized volumes of two different average concentrations (one of them closer to the compensation point) which are randomly distributed in the film. The unexpected single step-like behavior of the magneto-resistivity curves was explained by dissimilar switching of the spins in these two magnetic phases distributed in nano-sized volumes.

163. 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, 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.

164. Quantum turnstile regime of nanoelectromechanical systems

Authors: Dragomir, R; Moldoveanu, V; Stanciu, S; Tanatar, B

Published: APR 7 2020, PHYSICAL REVIEW B, 101, DOI: 10.1103/PhysRevB.101.165409

The effects of a turnstile operation on the current-induced vibron dynamics in nanoelectromechanical systems (NEMS) are analyzed in the framework of the generalized master equation. In our simulations each turnstile cycle allows the pumping of up to two interacting electrons across a biased mesoscopic subsystem which is electrostatically coupled to the vibrational mode of a nanoresonator. The time-dependent mean vibron number is very sensitive to the turnstile driving, rapidly increasing/decreasing along the charging/discharging sequences. This sequence of heating and cooling cycles experienced by the nanoresonator is due to specific vibron-assisted sequential tunneling processes along a turnstile period. At the end of each charging/discharging cycle the nanoresonator is described by a linear combination of vibron-dressed states s(v). associated to an electronic configuration nu. If the turnstile operation leads to complete electronic depletion the nanoresonator returns to its equilibrium position, i.e., its displacement vanishes. It turns out that a suitable bias applied on the NEMS leads to a slow but complete cooling at the end of the turnstile cycle. Our calculations show that the quantum turnstile regime switches the dynamics of the NEMS between vibron-dressed subspaces with different electronic occupation numbers. We predict that the turnstile control of the electron-vibron interaction induces measurable changes on the input and output transient currents.

165. Estimation of the pyroelectric coefficient for ceramic Pb(Zr,Ti)O-3 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, 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.

166. Synthesis and characterization of magnetic oxide nanoparticles and corresponding thin films for wastewaters treatment

Authors: Crintea, L; Musat, V; Polosan, S; Cantaragiu, A; Basliu, V; Dediu, A; Dinica, R

Published: JUL 2020, OVIDIUS UNIVERSITY ANNALS OF CHEMISTRY, 31, 131, DOI: 10.2478/auoc-2020-0021

Industrial wastewater can be properly treated using nanotechnologies and nanomaterials. This paper presents the synthesis and characterization of three series of magnetic nanoparticles (MNPs) and corresponding thin films, used for the degradation of organic compounds and removal of heavy metals from industrial wastewater. The samples were obtained by co-precipitation from a ferric (Fe3+) and ferrous (Fe2+) ions solution in a molar ratio of 2:1, at temperatures between 80-95 degrees C. The characterization of the samples was performed by scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods. The magnetic nanoparticles were deposited on glass substrates by the centrifugal coating technique and the optical and magneto-optical activity was investigated by UV- Vis spectroscopy and magnetic circular dichroism technique (MCD). The effect of the investigated samples on the decomposition under UV irradiation of organic dyes was monitored by UV-Vis spectroscopy. Our preliminary results have shown that the magnetite and maghemite MNPs can be effective in UV degradation of methylene blue (MB) dye.

167. Optimization of magnetic fluid hyperthermia with respect to nanoparticle shape-related parameters: case of magnetite ellipsoidal nanoparticles

Authors: Iacob, N; Kuncser, A; Comanescu, C; Palade, P; Kuncser, V

Published: MAY 22 2020, JOURNAL OF NANOPARTICLE RESEARCH, 22, DOI: 10.1007/s11051-020-04842-6

Issues related to the optimization of heat transfer mechanisms dominated by superparamagnetic relaxation are considered in the case of AC (alternating current) magnetic field hyperthermia procedures. The key role in the conversion of electromagnetic energy to the thermal one via the superparamagnetic relaxation mechanism is played by the magnetic anisotropy of nanoparticles, easily to be controlled via the shape anisotropy component. The optimization process has been discussed in the case of magnetite (Fe3O4) ellipsoidal nanoparticles with dominant shape anisotropy dispersed in different media. Nanoparticles of different sizes and aspect ratios have been considered in correlation with those specific parameters of the actuating AC magnetic field which respect an established biological safely criterion. It has been proven that the dissipated power can be maximized for a given set of biological compatible RF (radiofrequency) field parameters (frequency and field amplitude at the sample space) only for specific pairs of particle sizes and aspect ratios. For instance, it has been shown that ellipsoidal magnetite nanoparticles with 10 nm equatorial size and aspect ratio of 2 are optimal for a maximum transferred power under radiofrequency excitations of 250 kHz and field amplitude of 20 kA/m, if high viscosity dispersion media are used. The methodology for deriving the optimal shape (geometrical) parameters of a specific type of nanoparticles in conditions of using available radiofrequency excitations, or vice versa, for deriving the optimal radiofrequency working parameters in the case of ferrofluids with specific nanoparticles (type and geometry) is described and discussed in detail.

168. Electron paramagnetic resonance and microstructural insights into the thermal behavior of simonkolleite nanoplatelets

Authors: Rostas, AM; Kuncser, AC; Ghica, D; Palici, A; Maraloiu, VA; Vlaicu, ID

Published: MAY 7 2020, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 22, 9512, DOI: 10.1039/d0cp00641f

The aim of this paper is the study of the thermal behavior of the simonkolleite Zn-5(OH)(8)Cl-2 center dot H2O (ZHC) by electron paramagnetic resonance (EPR) spectroscopy, in particular. It is well known that during heating ZHC undergoes a complex transformation which involves several overlapping stages. However, with reference to the data reported on this subject, it can be concluded that there is still an ongoing debate regarding the intermediate stages of this process. The data presented in this study support a simple decomposition process of the ZHC prepared using the precipitation method. The EPR data correlated to the data obtained by other experimental techniques, such as XRD, TEM, SEM and EDX, indicate that during the thermal treatment the ZHC suffers a partial decomposition to ZnO with no intermediate products. After annealing at 500 degrees C for 1 h, a recombination process of ZHC is observed. Moreover, the kinetics associated to these decomposition steps were determined and the evolution of the paramagnetic centers was also followed and studied. This study offers new information related to the thermal behavior of ZHC, especially regarding the EPR data which is reported for the first time on this subject and material.

169. 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, 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.

170. 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, 3939, 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.

171. 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:

172. Perovskite ferroelectric thin film as an efficient interface to enhance the photovoltaic characteristics of Si/SnO(x)heterojunctions

Authors: Silva, JPB; Vieira, EMF; Silva, JMB; Gwozdz, K; Figueiras, FG; Veltruska, K; Matolin, 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, 11326, 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.

173. 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, 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.

174. 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, 10326, 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.

175. 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, 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.

176. 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, 33886, 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.

177. 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, 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.

178. ZnO nanostructures grown on ITO coated glass substrate by hybrid microwave-assisted hydrothermal method

Authors: Filip, A; Musat, V; Tigau, N; Polosan, S; Pimentel, A; Ferreira, S; Gomes, D; Calmeiro, T; Martins, R; Fortunato, E

Published: APR 2020, OPTIK, 208, DOI: 10.1016/j.ijleo.2020.164372

Over the last decades, zinc oxide nanostructures (NSs) have been studied due to outstanding chemical and physical properties, able to serve a plethora of applications. The growth of NSs on different substrates coated with ITO film allow their direct implementation in various micro-/nano-devices. The microwave-assisted hydrothermal method is a new hybrid approach used for synthesis of oxide NSs due to unique advantages in energy efficiency/high reaction rate and possibility of obtaining different morphologies with size and shape-controlled, which are relevant for some applications. In this paper, we present a simple one step synthesis of ZnO 1D and 2D NSs with homogeneous distribution and orientation perpendicular to substrates covered with ITO film, using a microwave-assisted hydrothermal method. The effect of seed layer treatment on the structure, morphology and optical properties of the obtained NSs have been investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV/VIS/NIR and photoluminescence spectroscopy. The obtained ZnO NSs with 1D and 2D morphologies show high visible transmittance between 80-90 % and band gap energy values between 3.27 and 3.22 eV. The I-V curves and photoluminescence spectra indicate good ohmic contacts on both sides (ITO and Au-top electrodes) and highlight the effect of the thermal treatment of seed layer on the photoluminescence emission and electrical conductivity of the obtained NSs.

179. 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, 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.

180. Controlling Single Molecule Conductance by a Locally Induced Chemical Reaction on Individual Thiophene Units

Authors: Michnowicz, T; Borca, B; Petuya, R; Schendel, V; Pristl, M; Pentegov, I; Kraft, U; Klauk, H; Wahl, P; Mutombo, P; Jelinek, P; Arnau, A; Schlickum, U; Kern, K

Published: APR 6 2020, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 59, 6212, 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.

181. Unidirectional Magnetic Anisotropy in Dense Vertically-Standing Arrays of Passivated Nickel Nanotubes

Authors: Locovei, C; Filipoiu, N; Kuncser, A; Stanciu, AE; Antohe, S; Florica, CF; Costas, A; Enculescu, I; Piraux, L; Kuncser, V; Antohe, VA

Published: DEC 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10122444

We report the facile and low-cost preparation as well as detailed characterization of dense arrays of passivated ferromagnetic nickel (Ni) nanotubes (NTs) vertically-supported onto solid Au-coated Si substrates. The proposed fabrication method relies on electrochemical synthesis within the nanopores of a supported anodic aluminum oxide (AAO) template and allows for fine tuning of the NTs ferromagnetic walls just by changing the cathodic reduction potential during the nanostructures' electrochemical growth. Subsequently, the experimental platform allowed further passivation of the Ni NTs with the formation of ultra-thin antiferromagnetic layers of nickel oxide (NiO). Using adequately adapted magnetic measurements, we afterwards demonstrated that the thickness of the NT walls and of the thin antiferromagneticNiO layer, strongly influences the magnetic behavior of the dense array of exchange-coupled Ni/NiO NTs. The specific magnetic properties of these hybrid ferromagnetic/antiferromagnetic nanosystems were then correlated with the morpho-structural and geometrical parameters of the NTs, as well as ultimately strengthened by additionally-implemented micromagnetic simulations. The effect of the unidirectional anisotropy strongly amplified by the cylindrical geometry of the ferromagnetic/antiferromagnetic interfaces has been investigated with the magnetic field applied both parallel and perpendicular to the NTs axis.

182. 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, 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.

183. 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, 687, 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.

184. 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, 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.

185. 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, 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.

186. 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, 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.

187. 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, 3990, 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.

188. Ionophore- Nafion (TM) modified gold-coated electrospun polymeric fibers electrodes for determination of electrolytes

Authors: Aldea, A; Matei, E; Leote, RJB; Rau, I; Enculescu, I; Diculescu, VC

Published: DEC 10 2020, ELECTROCHIMICA ACTA, 363, 137239, DOI: 10.1016/j.electacta.2020.137239

The present work describes the electrochemical properties of ionophores immobilized at the surface of electrodes obtained from electrospun polymeric fibers, in order to develop sensors for the analysis of electrolytes. Poly(methyl methacrylate) submicrometer fibers were prepared by electrospinning, coated with a gold layer by magnetron sputtering and then transferred on polyethylene terephthalate (PET) in order to obtained flexible electrodes. The ionophores were immobilized at the surface of these electrodes by drop-casting a ionophore-Nafion mixed solution. The sensor surface was investigated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy in order to understand the morphology and distribution of a model Ca2+ ionophore over the electrode surface. Also, Fourier-transformed infrared spectroscopy was performed and demonstrated that the model Ca2+ ionophore can be immobilized in the nafion matrix maintaining its conformation, while cyclic voltammetry and electrochemical impedance spectroscopy demonstrated that the Ca2+ ionophore allows the diffusion of target ions through this this type of membrane. In order to prove the concept of ionophore-based sensors for the analysis of some electrolytes, Ca2+, NH4+, Cl- and H+ ionophore immobilized in a nafion matrix at the surface of these flexible electrodes were tested and the determination of the target ions performed by potentiometry in different media including artificial sweat. Finally, sensitivities, limits of detection, selectivity coefficients were determined. (C) 2020 Elsevier Ltd. All rights reserved.

189. 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, 18420, 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.

190. Dielectric investigations on carbon nanotubes doped polymer dispersed liquid crystal films

Authors: Ganea, CP; Manaila-Maximean, D; Circu, V

Published: OCT 8 2020, EUROPEAN PHYSICAL JOURNAL PLUS, 135, DOI: 10.1140/epjp/s13360-020-00795-w

We obtained carbon nanotubes (CNTs) doped polymer dispersed liquid crystal (PDLC) films using the nematic E7 and polymethyl methacrylate, a composite that combines the benefic characteristic of the liquid crystals (LC) and carbon nanoparticles. The clearing temperatures recorded by differential scanning calorimetry for the PDLC blends were found to be lower than the value recorded for pure E7 LC mixture with no significant impact of the CNTs' concentration. Broadband dielectric spectroscopy (DS) measurements were performed in the (10(-1) / 107) Hz frequency range, in the temperature domain (280-350) K. From the DS study, a two order magnitude variation of the conductivity over the entire temperature range was observed. The presence of CNTs results in an increase of electrical conductivity, with increasing concentration. Because the loss tangent spectra have complex shapes, they were fitted using the generalized Havriliak-Negami functions, and the characteristic relaxation times were extracted. The dependency of the characteristic relaxation time on temperature was modeled using the Vogel-Fulcher-Tammann function, and it showed a temperature variation according to the Arrhenius law. The increase of the CNT concentration increases the activation energy of the molecular electric dipoles of the LC. The interface LC-polymer interactions influence the nematic to isotropic phase transition of the LC.

191. Mechano-chemical versus co-precipitation for the preparation of Y-modified LDHs for cyclohexene oxidation and Claisen-Schmidt condensations

Authors: Pavel, OD; Stamate, AE; Zavoianu, R; Bucur, IC; Birjega, R; Angelescu, E; Parvulescu, VI

Published: SEP 5 2020, APPLIED CATALYSIS A-GENERAL, 605, DOI: 10.1016/j.apcata.2020.117797

Y-modified LDHs with atomic Mg2+/(Al3+ + Y3+) of 3 and Al3+/Y3+ ratios of 0.5, 1 and 1.5 were prepared following two preparation methods, i.e. the co-precipitation and mechano-chemical one. The substitution of Al by Y in the brucite-type layer was less effective for the samples prepared by co-precipitation compared to those prepared via mechano-chemical route. In spite the fact yttrium has a larger ionic radius (0.9 angstrom) the structural characterizations of these solids confirmed that the layered structure incorporates part of it in the octahedral positions. Further, the reconstruction of the layered structure after an exposure to water for 1 h was more effective for the solid prepared by co-precipitation. The yttrium modified LDHs showed better catalytic activities for cyclohexene oxidation to the corresponding epoxide than the un-modified LDH sample. Then, mixed oxides derived from yttrium-LDH showed very high conversions and selectivities for the synthesis of chalcone.

192. 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, 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.

193. 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, 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.

194. Structural Changes in Palladium Nanofilms during Thermal Oxidation

Authors: Samoylov, AM; Ivkov, SA; Pelipenko, DI; Sharov, MK; Tsyganova, VO; Agapov, BL; Tutov, EA; Badica, P

Published: OCT 2020, INORGANIC MATERIALS, 56, 1026, 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.

195. Electrochemical Immunosensing Platform for the Determination of the 20S Proteasome Using an Aminophenylboronic/Poly-indole-6-carboxylic Acid-Modified Electrode

Authors: Martinez-Rojas, F; Diculescu, VC; Armijo, F

Published: AUG 17 2020, ACS APPLIED BIO MATERIALS, 3, 4948, DOI: 10.1021/acsabm.0c00478

The first electrochemical immunosensor for the determination of the 20S proteasome (P20S) was developed, entailing the immobilization of an antibody on an aminophenylboronic/poly-indole-6-carboxylic acid-modified electrode. The proposed electrochemical bioplatform is a simple and feasible analytical tool applicable for the determination of P20S in human plasma, considering its high clinical and biological relevance. Cyclic voltammetry, electrochemical impedance spectroscopy, and square wave voltammetry (SWV) were used to determine the optimal step-by-step process to obtain the electrochemical immunosensor. The interaction of P20S with the recognition layer of the immobilized antibody on the nanostructured surface took place by incubating the electrode in a P20S solution at 20 degrees C for 2 h. Using SWV as an electro-analytical technique, this immunosensor can quantify P20S. The current was linear with the P20S concentration within two dynamic concentration ranges from 20.0 to 80.0 and 80.0 to 200.0 ng.mL(-1) (r(2) = 0.992 and 0.98, respectively) with a limit of detection and quantification of 6 and 18 ng.mL(-1), respectively. Moreover, the immunosensor showed considerable repeatability and reproducibility, when the determination was done in human serum, which confirms that it is a promising alternative for direct detection of P20S in biological fluids with minimal interference.

196. Charge transfer reaction mechanisms of epoxyketone and boronated peptides at glassy carbon and boron doped diamond electrodes

Authors: de Jesus, CSH; Enache, TA; Diculescu, VC

Published: DEC 1 2020, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 878, DOI: 10.1016/j.jelechem.2020.114733

The ubiquitin-proteasome system regulates the level of proteins within cells through controlled proteolysis. In some diseases, the system function is dysregulated turning the ubiquitin-proteasome complex into a target for drug development. The redox behavior of proteasome inhibitors, epoxyketone and boronated peptides carfilzomib, oprozomib and delanzomib was investigated by voltammetric methods using glassy carbon and boron doped diamond electrodes. It was showed that the oxidation of epoxyketone peptides carfilzomib and oprozomib occurred in one step at glassy carbon electrode surface while at boron doped diamond two consecutive charge transfer reactions due to different adsorption orientation at the electrode surface were observed. The moieties of these peptides, involved in the oxidation process, were morpholine for carfilzomib and thiazole for oprozomib. For the boronated peptide delanzomib, two irreversible and independent redox processes, oxidation at +0.80 V and reduction at -1.40 V were identified in neutral media at both electrodes. The oxidation reaction occurred at the amino group close to the pyridine moiety of delanzomib with the transfer of one electron and one proton whereas the reduction process takes place at pyridine ring in a two-electrons two-protons mechanism. Redox mechanisms were proposed and the implications on the proteasome inhibition discussed.

197. Hierarchical composites of B4C-TiB2 eutectic particles reinforced with Ti

Authors: Solodkyi, I; Bogomol, I; Bolbut, V; Loboda, P; Kuncser, A; Vasylkiv, O; Badica, P

Published: DEC 15 2020, CERAMICS INTERNATIONAL, 46, 28144, DOI: 10.1016/j.ceramint.2020.07.312

Eutectic particles of B4C-TiB2 were reinforced with Ti by spark plasma sintering (SPS) or infiltration. The SPSed samples with 20, 30 and 40 wt. % Ti consisted of ceramic phases, and had a bicontinuous macrostructure formed by the Ti-rich region and the eutectic particles region, while the infiltrated sample was a complex composite comprised of a 3D Ti-rich continuous network, composite in nature, that contained Ti-metal and in which are embedded isolated ceramic (eutectic) particles. The SPSed samples are brittle with the maximum bending strength of 300 MPa for the 30 wt. % Ti, higher than for a reference sample produced by SPS from directionally solidified eutectic particles. A higher amount of added Ti results in a higher displacement in the bending test suggesting a higher fracture toughness. Simultaneous strengthening and toughening of the composite was realized. The infiltrated sample was ductile, while its bending strength (220 MPa) was comparable to the values measured for the brittle as-introduced reference sample and the sample with 20 wt. % Ti, both produced by SPS. In the SPSed and infiltrated samples at the interface between the Ti-rich region and B4C-TiB2 eutectic particles, a local 'pull-out' intergranular fracturing mechanism mainly involving Ti-B 1D-grains was observed. This local micromechanism together with a 'pull out' macromechanism of the eutectic grains from the Ti-rich component are considered important for the bridging/anchoring behavior responsible for the strengthening and toughening processes in our novel hierarchical composites.

198. HfO2-Al2O3 Dielectric Layer for a Performing Metal-Ferroelectric-Insulator-Semiconductor Structure with a Ferroelectric 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3 Thin Film

Authors: Silva, JPB; Sekhar, KC; Veltruska, K; Matolin, V; Negrea, RF; Ghica, C; Oliveira, MJS; Moreira, JA; Pereira, M; Gomes, MJM

Published: SEP 22 2020, ACS APPLIED ELECTRONIC MATERIALS, 2, 2787, 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.

199. 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, 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.

200. 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, 12325, 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.

201. 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, 140, 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.

202. Electrospun conductive gold covered polycaprolactone fibers as electrochemical sensors for O-2 monitoring in cell culture media

Authors: Serban, A; Evanghelidis, A; Onea, M; Diculescu, V; Enculescu, I; Barsan, MM

Published: FEB 2020, ELECTROCHEMISTRY COMMUNICATIONS, 111, 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.

203. 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, 5908, 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.

204. Mesoporous Cobalt Ferrite Nanosystems Obtained by Surfactant-Assisted Hydrothermal Method: Tuning Morpho-structural and Magnetic Properties via pH-Variation

Authors: Palade, P; Comanescu, C; Kuncser, A; Berger, D; Matei, C; Iacob, N; Kuncser, V

Published: MAR 2020, NANOMATERIALS, 10, DOI: 10.3390/nano10030476

A facile and cheap surfactant-assisted hydrothermal method was used to prepare mesoporous cobalt ferrite nanosystems with BET surface area up to 151 m(2)/g. These mesostructures with high BET surface areas and pore sizes are made from assemblies of nanoparticles (NPs) with average sizes between 7.8 and 9.6 nm depending on the initial pH conditions. The pH proved to be the key factor for controlling not only NP size, but also the phase purity and the porosity properties of the mesostructures. At pH values lower than 7, a parasite hematite phase begins to form. The sample obtained at pH = 7.3 has magnetization at saturation M-s = 38 emu/g at 300 K (54.3 emu/g at 10 K) and BET surface area S-BET = 151 m(2)/g, whereas the one obtained at pH = 8.3 has M-s = 68 emu/g at 300 K (83.6 emu/g at 10 K) and S-BET = 101 m(2)/g. The magnetic coercive field values at 10 K are high at up to 12,780 Oe, with a maximum coercive field reached for the sample obtained at pH = 8.3. Decreased magnetic performances are obtained at pH values higher than 9. The iron occupancies of the tetrahedral and octahedral sites belonging to the cobalt ferrite spinel structure were extracted through decomposition of the Mossbauer patterns in spectral components. The magnetic anisotropy constants of the investigated NPs were estimated from the temperature dependence of the hyperfine magnetic field. Taking into consideration the high values of BET surface area and the magnetic anisotropy constants as well as the significant magnetizations for saturation at ambient temperature, and the fact that all parameters can be adjusted through the initial pH conditions, these materials are very promising as recyclable anti-polluting agents, magnetically separable catalysts, and targeted drug delivery vehicles.

205. 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, 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.

206. Polarized emission and dielectric studies of novel lanthanidomesogens based on 4-pyridone ligands

Authors: Ilinca, T; Manaila-Maximean, D; Ganea, PC; Pasuk, I; Circu, V

Published: 2020, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS AND NANOTECHNOLOGIES X, 11718, DOI: 10.1117/12.2572109

Novel lanthanidomesogens based on lanthanide nitrates carrying three 4-pyridone ligands having two alkoxy chains at the periphery were synthesized and their structure was assigned based on IR spectroscopy and elemental analysis. Their thermal stability was evaluated by TG analysis confirming that the decomposition starts at very high temperatures around 300 degrees C. The liquid crystalline properties were investigated by using a combination of techniques: polarized optical microscopy (POM) and differential scanning calorimetry (DSC) and, for selected compounds, by variable-temperature powder X-ray diffraction. The new liquid crystal display a hexagonal columnar phase (Col(h)) between 63 degrees C and 242 degrees C, depending on the length of the alkyl chain Dielectric spectroscopy on a wide frequency range was used to evaluate the dipolar relaxation processes. The emission properties of a mixture of E7 doped with a selected europium complex filled in a planar cell were investigated on changing the applied voltage, ranging from 0V up to 15V.

207. Reticulated Mesoporous TiO2 Scaffold, Fabricated by Spray Coating, for Large-Area Perovskite Solar Cells

Authors: Tomulescu, AG; Stancu, V; Besleaga, C; Enculescu, M; Nemnes, GA; Florea, M; Dumitru, V; Pintilie, L; Pintilie, I; Leonat, L

Published: JAN 2020, ENERGY TECHNOLOGY, 8, DOI: 10.1002/ente.201900922

Development of reproducible, low-cost fabrication technologies that are readily adaptable to large-scale production, is one of the main challenges in the field of perovskite solar cells (PSCs). So far, for all the other layers in a solar cell, large-area deposition methods have been adapted, except for mesoporous fabrication. Herein, the fabrication of mesoporous TiO2 scaffolds using a large-area deposition technique, such as spray coating, is shown. Moreover, this technique induces the formation of a very specific reticulated structure with well-delimited, oval-shaped cavities. The cavities have irregular dimensions, with diameters in the range of 3-7 mu m, approximate to 350 nm height, resulting in an overall increase in roughness of one order of magnitude, compared with the spin-coated mesoporous scaffold. Using this rough structured mesoporous TiO2 in PSCs not only does not affect the efficiency of solar cells but actually improves it from an average of 10% to 12% in comparison with the devices containing a spin-coated mesoporous scaffold.

208. Morphological and structural investigation of the poly(Vinyl chloride) / graphene oxide composites

Authors: Stingescu, L., Cadar, C., Cotet, L.C., Baia, L., Saszet, K., Magyari, K., Mihis, A.G., Fort, C.I., Stroe, M., Matei, E., Nila, A., Anghel, I., Baia, M., Baibarac, M., Danciu, V.

Published: 2020, , 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 µm to 227 µm. Using Raman scattering, we report that as increasing the GO concentration in the PVC mass, the ratio between the relative intensities of the Raman glines 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 sp2 to sp3. 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° to 26° 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. © 2020, Universitatea Babes-Bolyai, Catedra de Filosofie Sistematica. All rights reserved.

209. 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, 25053, 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.

210. 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, 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.

211. Polymer Dispersed Liquid Crystals doped with nanoparticles: electric and electro-optical properties

Authors: Manaila-Maximean, D; Ganea, P; Loiko, VA; Konkolovich, AV; Circu, V; Danila, O; Barar, A

Published: 2020, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS AND NANOTECHNOLOGIES X, 11718, DOI: 10.1117/12.2572104

Polymer Dispersed Liquid Crystal (PDLC) films are composite materials consisting of LC droplets embedded in polymers. In order to decrease the switching voltage of these devices, we prepared PDLC films doped with single wall carbon nanotubes (SWCNTs). The mesomorphic properties of the films were investigated by polarizing optical microscopy (POM). The electrical characteristics have been investigated using a Broadband Dielectric Spectrometer in a frequency domain (0.01-10(7)) Hz and a temperature range (280-350) K. Some key aspects of an optical model for the analysis of the coherent transmittance of PDLC - NP films are presented.

212. 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; Munoz-Garcia, AB; Maddalena, P

Published: FEB 13 2020, JOURNAL OF PHYSICAL CHEMISTRY C, 124, 3576, 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.

213. Analog IGZO Memristor With Extended Capabilities

Authors: Dumitru, V; Besleaga, C; Ionescu, ON

Published: 2020, IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY, 8, 700, DOI: 10.1109/JEDS.2020.3006000

In this paper an IGZO memristor with multiple states and analog tuning extended capability is reported. The device has a planar structure and is fabricated by magnetron sputtering on glass substrate. The device resistance could be gradually increased and decreased within the range of one order of magnitude. Larger resistance changes are also possible but they are mostly irreversible. The obtained memristor looks promising to be used as electronic synapse in hardware implemented artificial neural networks or for applications in analog computing and cryptography.

214. Effect of proton fluence on the superconducting properties of MgB2. irradiated with protons of high energy

Authors: Sandu, V; Ionescu, AM; Ivan, I; Craciun, L; Aldica, G

Published: NOV 15 2020, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 578, DOI: 10.1016/j.physc.2020.1353734

Effects of proton irradiation on the superconducting properties of sintered MgB2 samples were investigated as a function of proton fluence at fixed energy. All experimental data suggest that critical current densities, irreversibility field and creep activation energy are enhanced because of the complex disorder, which mainly affects the grain boundaries, brought on the crystalline structure by the energetic protons.

215. 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, 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).

216. 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, 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.

217. Wafer-scale graphene-ferroelectric HfO2/Ge-HfO2/HfO(2)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, 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.

218. 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, DOI: 10.1016/j.jallcom.2020.155546

219. (Ba,Sr)TiO3 solid solutions sintered from sol-gel derived powders: An insight into the composition and temperature dependent dielectric behavior

Authors: Patru, RE; Ganea, CP; Stanciu, CA; Surdu, VA; Trusca, R; Ianculescu, AC; Pintilie, I; Pintilie, L

Published: MAR 2020, CERAMICS INTERNATIONAL, 46, 4190, DOI: 10.1016/j.ceramint.2019.10.136

Single-phase Ba1-xSrxTiO3 (BST) perovskite ceramics with 0.3 <= x <= 0.4 were prepared from powders synthesized via sol-gel route. The compositions have the ferroelectric-paraelectric phase transition close to room temperature. At 20 degrees C the BST ceramics are ferroelectric for 0.3 <= x <= 0.35 and paraelectric for x = 0.375 and x = 0.40. The study follows the relation between the structural changes produced when increasing the Sr content and the dielectric properties at low intensity electric fields. It is found that the grain size and tetragonality decreases as the Sr content increases. Analyses of complex permittivity and impedance spectroscopy reveal the temperature and frequency dependencies of the dielectric properties. The phase transitions seem to be of first order for all compositions, with a thermal hysteresis that decreases with increasing the Sr content, fact attributed to the corresponding increase of the grain boundaries weight allowing a more efficient stress relaxation in the structure during the change of the symmetry from cubic to tetragonal. The diffusiveness degree during the phase transition is increasing with Sr content, suggesting some relaxor-type contribution attributed to smaller grain size. The ac conductivity follows the universal Jonscher law, with an ac component having the power parameter s independent of Sr content, and a dc component that it is thermally activated with an activation energy of about 0.7-0.77 eV attributed to oxygen vacancies acting as donor-like defects. The fit of impedance spectra at different temperatures and frequencies is obtained by using an equivalent circuit accounting the grains, grain boundaries, electrode interfaces and the local contributions produced by reorientation of defect dipoles or defect clusters. All the component circuits have significant variations around phase transitions. These are discussed in relation to structural changes occurring during transition and considering the changes in the distribution of various charges when polarization vanishes.

220. 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, 238, 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.

221. 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, 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.

222. 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, 258, 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.

223. Effect of titanium oxide nanoparticles on the dielectric properties and ionic conductivity of a new smectic bis-imidazolium salt with dodecyl sulfate anion and cyanobiphenyl mesogenic groups

Authors: Ganea, CP; Circu, V; Manaila-Maximean, D

Published: NOV 1 2020, JOURNAL OF MOLECULAR LIQUIDS, 317, DOI: 10.1016/j.molliq.2020.113939

A new bis-imidazolium salt with two cyanobiphenyl groups and dodecyl sulfate counterion (BIC) was prepared by the metathesis reaction of the bromide salt with sodium dodecyl sulfate. The ILC shows at room-temperature a stable smectic A phase, confirmed by differential scanning calorimetry, polarized optical microscopy, and powder X-ray diffraction investigations. The ILC was doped with TiO2 nanoparticles, having a high specific area, in concentrations of 0.1%, 0.2%, 1% and 2%. Broadband Dielectric Spectroscopy spectra have been registered in the (10-1-107) Hz frequency range, and (250-330) K temperature domain. The study shows that at constant frequency, the conductivity increases with the temperature and dopant concentration. The characteristic times of the observed relaxation processes showed a temperature variation according to the Vogel-Fulcher-Tammann law. Higher values of characteristic times were calculated at the increase of the thickness of the sample. On the other hand, the increase of the concentration of TiO2 nanoparticles leads to a decrease of the characteristic relaxation times. In order to detectwhether the obtained high permittivity increase is due to the Maxwell-Wagner or Electrode Polarization (EP) type phenomena, studies were made on samples of the same concentration, but different thicknesses, and EP was assigned as the main cause of this dielectric constant variation. (C) 2020 Elsevier B.V. All rights reserved.

224. Magnetic Fe@Y Composites as Efficient Recoverable Catalysts for the Valorization of the Recalcitrant Marine Sulfated Polysaccharide Ulvan

Authors: Prech, J; Ioannou, E; Roussis, V; Kuncser, V; Podolean, I; Coman, SM; Valtchev, V; Parvulescu, VI

Published: JAN 13 2020, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 8, 328, DOI: 10.1021/acssuschemeng.9b05406

Magnetic Fe@Y composites (carbon-coated magnetic iron nanoparticles incorporated in zeolite Y) with 5-8 wt % Fe were synthesized and characterized. Overall acidity of the samples ranged between 2.0 and 2.47 mmol/g and is mostly attributed to Lewis acid sites. The obtained materials were proven to catalyze the hydrolysis of the marine sulfated polysaccharide ulvan with high conversion rates. The distribution of the reaction products depended on the reaction conditions and the concentration of ulvan. The catalytic property catalytic performance correlations clearly showed that the acid zeolite Y is the active phase for the hydrolysis of ulvan, while the iron nanoparticles enable the catalyst separation in a magnetic field. Under oxygen pressure, the selectivity was completely changed to favor succinic acid production. All Fe@Y composites were recycled 10 times with no change in their catalytic performance after recovery via a simple magnetic separation and washing with water.

225. 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.

226. 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.

227. Complex exchange coupling mechanisms in SRO/BFO/Fe heterostructures

Authors: Greculeasa, SG; Schinteie, G; Hrib, LM; Stancu, V; Pasuk, I; Kuncser, A; Kuncser, V

Published: JAN 30 2019, JOURNAL OF ALLOYS AND COMPOUNDS, 773, 345, DOI: 10.1016/j.jallcom.2018.09.208

Temperature dependent interfacial coupling mechanisms in SRO/BFO/Fe layered structures were investigated. The BFO/Fe heterostructures were prepared by PLD and sputtering, respectively, on the STO(0 0 1) substrate with a 20 nm SRO buffer layer. An annealing treatment in external magnetic field was further applied. Complex characterizations with X-ray diffraction, atomic force microscopy, Transmission Electron Microscopy, Mossbauer spectroscopy, magneto-optic Kerr effect and SQUID magnetometry were performed. Before annealing, the films show good crystallization and epitaxy of the SRO and BFO layers with smooth interfaces. Two coupling mechanisms of the ferromagnetic layers (top Fe and bottom SRO, respectively) to the epitaxial BFO film with mainly antiferromagnetic structure were evidenced in the as deposited samples at low temperatures. Negative exchange bias fields of up to 67(10) Oe and 37(5) Oe at low temperatures were observed for the two ferromagnetic components, respectively, depending on the thickness of the Fe layer. The field annealing treatments induce a specific morphology and magnetic spin structure at both interfaces of the BFO spacer layer, giving rise to a long range magnetostatic coupling between the two ferromagnetic films, in addition to the interfacial couplings. Moreover, the experimentally evidenced Fe clusters penetrating the BFO/Fe interface toward the BFO layer give support for this interaction. As an additional consequence, a considerable enhancement of both uniaxial and unidirectional anisotropies as well as an increased blocking temperature of exchange bias were obtained. The involved exchange coupling mechanisms were discussed in detail. (C) 2018 Elsevier B.V. All rights reserved.

228. 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.

229. Phase Control in Hafnia: New Synthesis Approach and Convergence of Average and Local Structure Properties

Authors: Cojocaru, B; Avram, D; Negrea, R; Ghica, C; Kessler, VG; Seisenbaeva, GA; Parvulescu, VI; Tiseanu, C

Published: MAY 2019, ACS OMEGA, 4, 8891, DOI: 10.1021/acsomega.9b00580

Technologically relevant tetragonal/cubic phases of HfO2 can be stabilized at room temperature by doping with trivalent rare earths using various approaches denoted generically as bulk coprecipitation. Using in situ/ex situ X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy, and in situ/ex situ site-selective, time-gated luminescence spectroscopy, we show that wet impregnation of hafnia nanoparticles with 10% Eu oxide followed by mild calcination in air at 500 degrees C produces an efficient stabilization of the cubic phase, comparable to that obtained by bulk precipitation. The physical reasons behind the apparently conflictual data concerning the actual crystallographic phase and the local symmetry around the Eu stabilizer and how these can be mediated by luminescence analysis are also discussed. Apparently, the cubic crystal structure symmetry determined by XRD results in a pseudocubic/tetragonal local structure around Eu determined by luminescence. Considering the recent findings on wet impregnated CeO2 and ZrO2, it is concluded that CeO2, ZrO2, and HfO2 represent a unique case of a family of oxides that is extremely tolerant to heavy doping by wet impregnation. In this way, the same batch of preformed nanoparticles can be doped with different lanthanide concentrations or with various lanthanides at a fixed concentration, allowing a systematic and reliable investigation of the effect of doping, lanthanide type, and lanthanide concentration on the various functionalities of these technologically relevant oxides.

230. Electrochemical Sensor for Carbonyl Groups in Oxidized Proteins

Authors: Enache, TA; Matei, E; Diculescu, VC

Published: FEB 5 2019, ANALYTICAL CHEMISTRY, 91, 1927, DOI: 10.1021/acs.analchem.8b03969

The interaction of proteins with free radicals leads, among other types of damages, to the production of stable carbonyl groups, which can be used as a quantification of oxidative stress at proteins level. The aim of this study was the development of an electrochemical sensor for the detection of carbonyl groups in proteins oxidized by reactive oxygen species. Its working principle is based on the redox properties of dinitrophenylhydrazine (DNPH). BSA was used as a model protein and its oxidation achieved through Fenton reactions. Using differential pulse voltammetry at glassy carbon electrode, the electrochemical behavior of DNPH and of the native and oxidized BSA was investigated in solution. It has been shown that the hydrazine moiety of the DNPH is the electroactive center and is responsible for carbonyl complexation. Special attention was paid to the immobilization of the DNPH in order to retain its redox properties, and this was achieved on a mixed 4-styrenesulfonic acid-nafion matrix. The sensor's surface characterization and the detection of carbonyl groups in oxidized protein were performed by voltammetry, Fourier-transformed infrared spectroscopy and scanning electron microscopy while the voltammetric results were confirmed by surface plasmon resonance measurements. It has been shown that upon interaction with carbonyl groups of the oxidized protein, the oxidation peak of the hydrazine moiety of DNPH decreases as a function of incubation time and protein concentration. The sensor sensitivity was 0.015 nmol carbonyl per mg of oxidized protein and detection limits of 50 mu g oxidized BSA and 0.75 pmol carbonyls.

231. 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.

232. 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.

233. 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.

234. Bi1-xEuxFeO3 Powders: Synthesis, Characterization, Magnetic and Photoluminescence Properties

Authors: Surdu, VA; Trusca, RD; Vasile, BS; Oprea, OC; Tanasa, E; Diamandescu, L; Andronescu, E; Ianculescu, AC

Published: OCT 2019, NANOMATERIALS, 9, DOI: 10.3390/nano9101465

Europium substituted bismuth ferrite powders were synthesized by the sol-gel technique. The precursor xerogel was characterized by thermal analysis. Bi1-xEuxFeO3 (x = 0-0.20) powders obtained after thermal treatment of the xerogel at 600 degrees C for 30 min were investigated by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, and Mossbauer spectroscopy. Magnetic behavior at room temperature was tested using vibrating sample magnetometry. The comparative results showed that europium has a beneficial effect on the stabilization of the perovskite structure and induced a weak ferromagnetism. The particle size decreases after the introduction of Eu3+ from 167 nm for x = 0 to 51 nm for x = 0.20. Photoluminescence spectroscopy showed the enhancement of the characteristic emission peaks intensity with the increase of Eu3+ concentration.

235. 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.

236. 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.

237. 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.

238. CO2 methanation catalyzed by oriented MoS2 nanoplatelets supported on few layers graphene

Authors: Primo, A; He, JB; Jurca, B; Cojocaru, B; Bucur, C; Parvulescu, VI; Garcia, H

Published: MAY 15 2019, APPLIED CATALYSIS B-ENVIRONMENTAL, 245, 359, DOI: 10.1016/j.apcatb.2018.12.034

Powders of molybdenum disulfide platelets strongly grafted on graphene have been prepared by pyrolysis of ammonium alginate containing adsorbed various proportions of (NH4)(2)MoS4. After pyrolysis, formation of MoS2 supported on graphene was determined by XRD and electron microscopy and spectroscopic techniques. MoS2/G exhibits catalytic activity for the methanation of CO2, the performance being optimal at intermediate loadings. The catalytic activity of sharply contrasts with that of bulk MoS2 that promotes the reverse water gas shift, affording CO as the main product. Characterization of the spent MoS2/G catalyst shows the partial conversion of external MoS2 into MoO3. Comparison of the catalytic activity of MoS2/G with that of MoO3/G shows that the latter is less efficient, but more selective for CO2 methanation.

239. N-Doped Defective Graphene from Biomass as Catalyst for CO2 Hydrogenation to Methane

Authors: Jurca, B; Bucur, C; Primo, A; Concepcion, P; Parvulescu, VI; Garcia, H

Published: FEB 6 2019, CHEMCATCHEM, 11, 990, DOI: 10.1002/cctc.201801984

N-doped, defective graphene obtained by pyrolysis of chitosan at 900 degrees C under Ar exhibits catalytic activity for the Sabatier hydrogenation of CO2 to CH4 at temperatures about 500 degrees C with estimated turnover frequencies and activation energy values of 73.17s(-1) and 24.3 kcal x mol(-1), respectively. It has been found that this enhanced catalytic activity compared to other related doped defective graphenes derives from the presence of pyridinic N atoms that adsorbs CO2 forming carbamate-type adsorbates.

240. 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.

241. 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.

242. 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.

243. 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.

244. Effect of the process control agent in the ball-milled powders and SPS-consolidation temperature on the grain refinement, density and Vickers hardness of Fe14Cr ODS ferritic alloys

Authors: Mihalache, V; Mercioniu, I; Velea, A; Palade, P

Published: APR 1 2019, POWDER TECHNOLOGY, 347, 113, DOI: 10.1016/j.powtec.2019.02.006

Fe-14Cr-0.4Ti-0.25Y(2)O(3) ferritic steels were produced by varying the amount of residual process control agent, PCA (ethanol), in the ball-milled powders and changing the spark-plasma-sintering, SPS, temperature. Near the-oretical density (99.3%), high Vickers hardness (501-920 HV, measured by applying a load of 100 g for 5 s) and fine grain size (26-36 nm), very stable against heating, can be achieved on ODS ferritic steels, consolidated from powders with a low amount of PCA and processing temperature in the range of 1000 degrees C-1100 degrees C. Additional grain refinement occurs near alpha -> gamma transition which is generated by the reaction of the traces of PCA with the ferritic matrix upon heating. High local temperatures and the evolved thermally activated processes, at the contact points between particles/at the particle surfaces during SPS-consolidation, were demonstrated to be the main factors responsible for improved densities and hardness. The role of PCA in the sintering, thermal and microstructure particularities and its impact on the quality of the final steel was thoroughly analysed throughout the work. (C) 2019 Elsevier B.V. All rights reserved.

245. 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.

246. Fabrication and characterization of Ru-doped LiCuFe2O4 nanoparticles and their capacitive and resistive humidity sensor applications

Authors: Manikandan, V; Tudorache, F; Petrila, J; Mane, RS; Kuncser, V; Vasile, B; Morgan, D; Vigneselvan, S; Mirzaei, A

Published: MAR 15 2019, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 474, 569, DOI: 10.1016/j.jmmm.2018.11.072

Polycrystalline ruthenium-doped lithium-copper-ferrite (Ru - LiCuFe2O4)nanoparticles (NPs) are synthesized using a simple and cost-effective chemical co-precipitation method and annealed at different temperatures for increasing the crystallinity. The transmission and scanning electron microscopy images have confirmed the presence of soft agglomerations and cuboids for the samples annealed at 1100 degrees C. X-ray photoelectron results along with Raman spectra have collectively demonstrated the presence of Ru in the structure of Ru - LiCuFe2O4 NPs. The dielectric properties of as-synthesized Ru - LiCuFe2O4 NPs are investigated using LCR meter where the smaller NPs demonstrates a higher dielectric constant. Also, the results of magnetic measurements of annealed Ru - LiCuFe2O4 NPs have corroborated a soft magnetic nature due to the pinning sites that endow lower coercivity, remanence and saturation magnetization than that of the pristine one. The variation of permittivity and electrical resistivity with respect to frequency under humidity conditions suggested that this material has a potential to use as capacitive and resistive humidity sensor. The results of this study open the doors for utilization of metal-doped magnetic ferrites for humidity sensing applications.

247. 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.

248. 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.

249. 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.

250. 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.

251. 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.

252. A Dyson Equation for Non-Equilibrium Green's Functions in the Partition-Free Setting

Authors: Cornean, HD; Moldoveanu, V; Pillet, CA

Published: JUL 2019, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 256, DOI: 10.1002/pssb.201800447

Here a small interacting sample, coupled to several non-interacting leads is considered. Initially, the system is at thermal equilibrium. At some instant t(0) the system is set into the so-called partition-free transport scenario by turning on a bias on the leads. Using the theory of Volterra operators we rigorously formulate a Dyson equation for the retarded Green's function and we establish a closed formula for the associated proper interaction self-energy.

253. 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.

254. Rapid thermal annealing for high-quality ITO thin films deposited by radio-frequency magnetron sputtering

Authors: Prepelita, P; Stavarache, I; Craciun, D; Garoi, F; Negrila, C; Sbarcea, BG; Craciun, V

Published: JUL 25 2019, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 10, 1522, DOI: 10.3762/bjnano.10.149

In this work, rapid thermal annealing (RTA) was applied to indium tin oxide (ITO) films in ambient atmosphere, resulting in significant improvements of the quality of the ITO films that are commonly used as conductive transparent electrodes for photovoltaic structures. Starting from a single sintered target (purity 99.95%), ITO thin films of predefined thickness (230 nm, 300 nm and 370 nm) were deposited at room temperature by radio-frequency magnetron sputtering (rfMS). After deposition, the films were subjected to a RTA process at 575 degrees C (heating rate 20 degrees C/s), maintained at this temperature for 10 minutes, then cooled down to room temperature at a rate of 20 degrees C/s. The film structure was modified by changing the deposition thickness or the RTA process. X-ray diffraction investigations revealed a cubic nanocrystalline structure for the as-deposited ITO films. After RTA, polycrystalline compounds with a textured (222) plane were observed. X-ray photon spectroscopy was used to confirm the beneficial effect of the RTA treatment on the ITO chemical composition. Using a Tauc plot, values of the optical band gap ranging from 3.17 to 3.67 eV were estimated. These values depend on the heat treatment and the thickness of the sample. Highly conductive indium tin oxide thin films (rho = 7.4 x 10(-5) Omega cm) were obtained after RTA treatment in an open atmosphere. Such films could be used to manufacture transparent contact electrodes for solar cells.

255. 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.

256. Voltammetric and mass spectrometry investigation of methionine oxidation

Authors: Diculescu, VC; Enache, TA

Published: FEB 1 2019, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 834, 129, DOI: 10.1016/j.jelechem.2018.12.058

The electro-oxidation mechanism of free methionine and bound within different peptide sequences was investigated by voltammetry, at glassy carbon electrode, and mass spectrometry. It is proposed that the electro-oxidation of free methionine occurs in two steps, each involving the transfer of one electron and turns pH-independent from mild acid to mild alkaline electrolytes. The first oxidation reaction leads to the formation of a cation radical stabilized either through the amino group resulting in the dehydromethionine intermediate, or by interaction with a neutral methionine molecule leading to production of a dimer cationic radical. The dehydromethionine hydrolysis gave methionine sulfoxide as final oxidation product, whereas a future oxidation of methionine dimer cation radical, i.e. the second electro-oxidation step, results in a methionine dimer dication. Moreover, at high acid media, the protonated amino group influence the electro-oxidation process to take place via proton transfer mechanism. The presence of methionine sulfoxide and of the dimer cationic radical as oxidation products of methionine was confirmed by mass spectroscopy.

257. PHOTO-ELECTRICAL PROPERTIES OF THIN FILMS WITH GE NANOPARTICLES EMBEDDED IN TIO2 MATRIX

Authors: Stavarache, I; Maraloiu, VA

Published: 2019, ROMANIAN REPORTS IN PHYSICS, 71, DOI:

We present photo-electrical properties of thin films formed of Ge nanoparticles in TiO2 correlated with structure and morphology. The films co-deposited on Si using magnetron sputtering were annealed in conventional oven at 550 degrees C. We performed structure investigations by X-ray diffraction, transmission electron microscopy and measured current-voltage characteristics in dark and under illumination at different temperatures. We show that the films are formed of cubic Ge nanoparticles in nanostructured anatase TiO2 matrix. Also, (TiGe)O-2 with rutile structure was observed. The films have high photosensitivity under white light as the ratio between photo- and dark currents (-1 V) is of similar to 10(2).

258. 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.

259. 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.

260. Generalized Master Equation Approach to Time-Dependent Many-Body Transport

Authors: Moldoveanu, V; Manolescu, A; Gudmundsson, V

Published: AUG 2019, ENTROPY, 21, DOI: 10.3390/e21080731

We recall theoretical studies on transient transport through interacting mesoscopic systems. It is shown that a generalized master equation (GME) written and solved in terms of many-body states provides the suitable formal framework to capture both the effects of the Coulomb interaction and electron-photon coupling due to a surrounding single-mode cavity. We outline the derivation of this equation within the Nakajima-Zwanzig formalism and point out technical problems related to its numerical implementation for more realistic systems which can neither be described by non-interacting two-level models nor by a steady-state Markov-Lindblad equation. We first solve the GME for a lattice model and discuss the dynamics of many-body states in a two-dimensional nanowire, the dynamical onset of the current-current correlations in electrostatically coupled parallel quantum dots and transient thermoelectric properties. Secondly, we rely on a continuous model to get the Rabi oscillations of the photocurrent through a double-dot etched in a nanowire and embedded in a quantum cavity. A many-body Markovian version of the GME for cavity-coupled systems is also presented.

261. 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.

262. Cavity-Photon-Induced High-Order Transitions between Ground States of Quantum Dots

Authors: Gudmundsson, V; Abdullah, NR; Tang, CS; Manolescu, A; Moldoveanu, V

Published: NOV 2019, ANNALEN DER PHYSIK, 531, DOI: 10.1002/andp.201900306

It is shown that quantum electromagnetic transitions to high orders are essential to describe the time-dependent path of a nanoscale electron system in a Coulomb blockade regime when coupled to external leads and placed in a 3D rectangular photon cavity. The electronic system consists of two quantum dots embedded asymmetrically in a short quantum wire. The two lowest in energy spin degenerate electron states are mostly localized in each dot with only a tiny probability in the other dot. In the presence of the leads, a slow high-order transition between the ground states of the two quantum dots is identified. The Fourier power spectrum for photon-photon correlations in the steady state shows a Fano type of resonance for the frequency of the slow transition. Full account is taken of the geometry of the multilevel electronic system, and the electron-electron Coulomb interactions together with the para- and diamagnetic electron-photon interactions are treated with step-wise exact numerical diagonalization and truncation of appropriate many-body Fock spaces. The matrix elements for all interactions are computed analytically or numerically exactly.

263. Physical properties of indium zinc oxide and aluminium zinc oxide thin films deposited by radio-frequency magnetron sputtering

Authors: Vasile, N; Iftimie, S; Acsente, T; Locovei, C; Calugar, AI; Radu, A; Ion, L; Antohe, VA; Manica, D; Toma, O; Dinescu, G; Antohe, S

Published: DEC 2019, MATERIALS RESEARCH EXPRESS, 6, DOI: 10.1088/2053-1591/ab688d

Indium-doped zinc oxide (IZO) and aluminium-doped zinc oxide (AZO) thin films were grown by radio-frequency (RF) magnetron sputtering onto optical glass substrates and their structural, morphological, and optical properties were discussed in terms of varying the sputtering power as 40 W, 60 W, 80 W, and 100 W. No heating substrate or any post-thermal treatment was performed. The structural features were analyzed by grazing incidence X-ray diffraction and revealed the amorphous phase for IZO samples, while the AZO thin films inherited the Wurtzite structure of zinc oxide. The morphological properties were investigated by atomic force microscopy (AFM), in tapping mode and scanning electronmicroscopy (SEM). The AFM images showed relatively uniform and smooth surfaces for all prepared structures. The optical transmission spectra proved the excellent theoretical values of transparency for metallic oxides in the visible region of the electromagnetic spectrum, i.e. similar to 60% for IZO and similar to 70% for AZO. The obtained results showed that even without any thermal treatment the structural, morphological, and optical properties of IZO and AZO thin films prepared by RF magnetron sputtering are similar with those for samples subjected to medium or high temperatures.

264. 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.

265. Energy-enhanced deposition of copper thin films by bipolar high power impulse magnetron sputtering

Authors: Velicu, IL; Ianos, GT; Porosnicu, C; Mihaila, I; Burducea, I; Velea, A; Cristea, D; Munteanu, D; Tiron, V

Published: FEB 15 2019, SURFACE & COATINGS TECHNOLOGY, 359, 107, DOI: 10.1016/j.surfcoat.2018.12.079

Bipolar Pulse High Power Impulse Magnetron Sputtering (BP-HiPIMS) was investigated and used in this work to control the ion bombardment process of growing thin films and to improve their structure and properties. Energy-resolving mass spectroscopy was used to investigate the effect of reverse target voltage on the ion energies and fluxes during BP-HiPIMS of a high-purity copper target, in argon gas. It was found that the reverse target voltage provides a wide range of ion energies and fluxes incident to the growing film, which, in turn, produce a wide variety of effects during the deposition process, improving the adhesion strength and influencing both surface and bulk properties. Fast ICCD imaging was used to investigate both HiPIMS and BP-HiPIMS plasma dynamics. The temporal and spatial distributions of plasma potential measurements were performed in order to explain the mechanisms for accelerating the ions. The topological, structural and mechanical properties of the deposited coatings were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), thermal desorption spectroscopy (TDS), scanning electron microscopy (SEM), nanoindentation and scratch tests. The obtained results indicate an energy-enhanced deposition process during BP-HiPIMS, the deposited films being characterized by smooth surfaces, dense microstructure, small inert gas inclusions, high elastic strain to failure, scratch resistance and good adhesion to the substrate. These improvements in the films' structure and properties may be attributed to the intense and energetic ion bombardment taking place during the deposition process. During BP-HiPIMS operation, there is no net increase in the deposition rate as compared to the monopolar regime due to the re-sputtering process.

266. 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.

267. 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.

268. Formation peculiarities and optical properties of highly-doped (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics

Authors: Kryzhanovska, OS; Baumer, VN; Parkhomenko, SV; Doroshenko, AG; Yavetskiy, RP; Balabanov, AE; Tolmachev, AV; Skorik, SN; Li, J; Kuncser, A

Published: SEP 2019, CERAMICS INTERNATIONAL, 45, 16007, DOI: 10.1016/j.ceramint.2019.05.111

Formation peculiarities of highly-doped (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics have been studied by X-ray diffraction and electron microscopy methods. The phase composition evolution of 1.81Y(2)O(3).0.18La(2)O(3)0.01Yb(2)O(3) powder mixtures annealed at the temperatures of 1100, 1200, 1300, and 1400 degrees C has been studied by XRD. It has been shown that Yb2O3 phase dissolves in Y2O3 matrix in the calcination temperature range of 1300-1400 degrees C. Complete dissolution of La2O3 in Y2O3 matrix occurs at temperatures above 1400 degrees C. La3+ ions enter in Y2O3 and Yb2O3 crystal structures simultaneously in the 1200-1300 degrees C range, which leads to a remarkable increase in the volume of the corresponding crystal lattices. The possible reasons for suppressing the crystalline growth of Y2O3 and Yb2O3 cubic phases have been discussed. Finally, (Y(0.86)La(0.09)Vb(0.05))(2)O-3 transparent ceramics have been obtained by solid-state vacuum sintering at 1650-1750 degrees C. Ceramics synthesized at a temperature of 1750 degrees C have been characterized by an in-line optical transmittance of 60% and a homogeneous distribution of constituent components within the volume and along the grain boundaries.

269. 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.

270. 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.

271. 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.

272. Enhancement in magnetic and dielectric properties of the ruthenium-doped copper ferrite(Ru - CuFe2O4) nanoparticles

Authors: Manikandan, V; Kuncser, V; Vasile, B; Kavita, S; Vigneselvan, S; Mane, RS

Published: APR 15 2019, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 476, 23, DOI: 10.1016/j.jmmm.2018.12.050

Ruthenium-doped copper ferrite(Ru - CuFe2O4) nanoparticles (NPs) have been synthesized using a simple and cost-effective wet chemical co-precipitation deposition method. The crystallographic scanning electron microscopy images confirm cubic crystal structure and agglomerated-type surface appearance. The crystallite sizes are 6-24 nm in the range. Dielectric measurement analysis estimates the dielectric constant and loss of Ru - CuFe2O4 NPs. In this connection, dielectric constant and loss are reduced virtue of air annealing for various temperatures. Also, the dielectric loss confirms the relaxation peak. From magnetic measurement results, the coercivity decreases whereas saturation and remanence magnetization are increased. These features have approved the soft magnetic nature in the Ru - CuFe2O4 NPs.

273. Nitrogen-doped graphene as metal free basic catalyst for coupling reactions

Authors: Candu, N; Man, I; Simion, A; Cojocaru, B; Coman, SM; Bucur, C; Primo, A; Garcia, H; Parvulescu, VI

Published: AUG 2019, JOURNAL OF CATALYSIS, 376, 247, DOI: 10.1016/j.jcat.2019.07.011

N-doped defective graphene [(N)G] obtained by pyrolysis at 900 degrees C of chitosan contains about 3.7% of residual N atoms, distributed as pyridinic, pyrrolic and graphitic N atoms. It has been found that (N)G acts as basic catalyst promoting two classical C-C bond forming nucleophilic additions in organic chemistry, such as the Michael and the Henry additions. Computational calculations at DFT level of models corresponding to the various N atoms leads to the conclusion that N atoms are more stable at the periphery of the graphene sheets and that H adsorption on these sites is a suitable descriptor to correlate with the catalytic activity of the various sites. According to these calculations the most active sites are pyridinic N atoms at zig-zag edges of the sheets. In addition, N as dopant changes the reactivity of the neigh. bour C atoms. Water was found a suitable solvent to achieve high conversions in both reactions. In this solvent the initial distribution of N atoms is affected due to the easy protonation of the N-py to N-pyH sites. As an effect, C edge sites adjacent at N-PyH with an appropriate reactivity towards the alpha-C-H bond breaking are formed. The present results show the general activity of N-doped graphene as base catalysts and illustrate the potential of carbocatalysis to promote reactions of general interest in organic synthesis. (C) 2019 Elsevier Inc. All rights reserved.

274. 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.

275. Coexisting spin and Rabi oscillations at intermediate time regimes in electron transport through a photon cavity

Authors: Gudmundsson, V; Gestsson, H; Abdullah, NR; Tang, CS; Manolescu, A; Moldoveanu, V

Published: MAR 1 2019, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 10, 616, DOI: 10.3762/bjnano.10.61

In this work, we theoretically model the time-dependent transport through an asymmetric double quantum dot etched in a two-dimensional wire embedded in a far-infrared (FIR) photon cavity. For the transient and the intermediate time regimes, the current and the average photon number are calculated by solving a Markovian master equation in the dressed-states picture, with the Coulomb interaction also taken into account. We predict that in the presence of a transverse magnetic field the interdot Rabi oscillations appearing in the intermediate and transient regime coexist with slower non-equilibrium fluctuations in the occupation of states for opposite spin orientation. The interdot Rabi oscillation induces charge oscillations across the system and a phase difference between the transient source and drain currents. We point out a difference between the steady-state correlation functions in the Coulomb blocking and the photon-assisted transport regimes.

276. 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.

277. Ferroelectric Field Effect Transistors Based on PZT and IGZO

Authors: Besleaga, C; Radu, R; Balescu, LM; Stancu, V; Costas, A; Dumitru, V; Stan, G; Pintilie, L

Published: 2019, IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY, 7, 275, DOI: 10.1109/JEDS.2019.2895367

Ferroelectric field effect transistors (FeFETs) based on lead zirconate titanate (PZT) ferroelectric material and amorphous-indium-gallium-zinc oxide (a-IGZO) were developed and characterized. The PZT material was processed by a sol-gel method and then used as ferroelectric gate. The a-IGZO thin films, having the role of channel semiconductor, were deposited by radio-frequency magnetron sputtering, at a temperature of similar to 50 degrees C. Characteristics of a typical field effect transistor with SiO2 gate insulator, grown on highly doped silicon, and of the PZT-based FeFET were compared. It was proven that the FeFETs had promising performances in terms of I-on/I-off ratio (i.e., 10(6)) and IDS retention behavior.

278. Structural Change in Ni-Fe-Ga Magnetic Shape Memory Alloys after Severe Plastic Deformation

Authors: Gurau, G; Gurau, C; Tolea, F; Sampath, V

Published: JUN 2 2019, MATERIALS, 12, DOI: 10.3390/ma12121939

Severe plastic deformation (SPD) is widely considered to be the most efficient process in obtaining ultrafine-grained bulk materials. The aim of this study is to examine the effects of the SPD process on Ni-Fe-Ga ferromagnetic shape memory alloys (FSMA). High-speed high-pressure torsion (HSHPT) was applied in the as-cast state. The exerted key parameters of deformation are described. Microstructural changes, including morphology that were the result of processing, were investigated by optical and scanning electron microscopy. Energy-dispersive X-ray spectroscopy was used to study the two-phase microstructure of the alloys. The influence of deformation on microstructural features, such as martensitic plates, intragranular gamma phase precipitates, and grain boundaries' dependence of the extent of deformation is disclosed by transmission electron microscopy. Moreover, the work brings to light the influence of deformation on the characteristics of martensitic transformation (MT). Vickers hardness measurements were carried out on disks obtained by SPD so as to correlate the hardness with the microstructure. The method represents a feasible alternative to obtain ultrafine-grained bulk Ni-Fe-Ga alloys.

279. STRUCTURAL EVOLUTION OF THE NiTi/NiFeGa SMART HYBRID MATERIAL DURING SEVERE PLASTIC DEFORMATION

Authors: Gurau, C; Gurau, G; Tolea, F; Sampath, V

Published: JUL-SEP 2019, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 14, 546, DOI:

High speed high pressure torsion (HSHPT) a patented new approach is proposed to fabricate nanocomposites. The goal of this work is to investigate the NiTi/NiFeGa bilayer hybrid material with nano- and submicrocrystalline structure under the influence of HSHPT. Apart from the grain refinement, the effectiveness of the joint are revealed scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties of the composite layers in bulk and after severe plastic deformation are investigated. Bi-layered composite disks consisting of NiTi shape memory alloy and NiFeGa - Heusler type alloy, exhibit thermoelastic structural martensitic transformation. Submicrocrystalline structure is formed in the both layers of the hybrid material. It is also ascertained significant hardening of each layer of the hybrid as a result of HSHPT. The results highlight market differences between the bulk and the hybrid and the role of severe plastic deformation on martensitic transformation.

280. Effects of high temperature and ultraviolet radiation on polymer composites

Authors: Ching, YC; Gunathilake, TMSU; Ching, KY; Chuah, CH; Sandu, V; Singh, R; Liou, NS

Published: 2019, DURABILITY AND LIFE PREDICTION IN BIOCOMPOSITES, FIBRE-REINFORCED COMPOSITES AND HYBRID COMPOSITES, 426, DOI: 10.1016/B978-0-08-102290-0.00018-0

281. 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.

282. 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.

283. 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.

284. 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.

285. 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.

286. 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.

287. Physical properties of Cu and Dy co-doped ZnO thin films prepared by radio frequency magnetron sputtering for hybrid organic/inorganic electronic devices

Authors: Locovei, C; Coman, D; Radu, A; Ion, L; Antohe, VA; Vasile, N; Dumitru, A; Iftimie, S; Antohe, S

Published: SEP 1 2019, THIN SOLID FILMS, 685, 384, DOI: 10.1016/j.tsf.2019.06.027

Copper (Cu) and dysprosium (Dy) co-doped zinc oxide (ZnO) thin films were fabricated by radio frequency magnetron sputtering (RF-magnetron sputtering) using a homemade target having the atomic percentage of Cu and Dy of 1%, onto optical glass substrates and quartz substrates. The structural, morphological, optical, and electrical properties of fabricated ZnO:(Cu, Dy) structures were analyzed and discussed. It was found that all samples have hexagonal Wurtzite structure. Optical transmission measurements indicate values larger than 75% in the 400-2500 nm ranges. The current-voltage characteristics of hybrid heterojunctions based on ZnO:(Cu, Dy) and poly(3-hexylthiophene-2.5-diyl) (P3HT) or copper (II) phthalocyanine (CuPc) thin films were acquired in the dark, in ambient atmosphere, and they exhibit the typical diode behavior, almost free of electrical hysteresis.

288. 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.

289. Synthesis and thermal, emission and dielectric properties of liquid crystalline Eu(III), Sm(III) and Tb(III) complexes based on mesogenic 4-pyridone ligands functionalized with cyanobiphenyl groups

Authors: Chiriac, LF; Ganea, PC; Manaila-Maximean, D; Pasuk, I; Circu, V

Published: SEP 15 2019, JOURNAL OF MOLECULAR LIQUIDS, 290, DOI: 10.1016/j.molliq.2019.111184

New thermotropic lanthanidomesogens based on Eu(III), Sm(III) and Tb(III) with N-alkylated 4-pyridones mesogenic ligands, having two cyanobiphenyl groups attached via long alkoxy spacers, with 6, 9 and 10 carbons atoms in 3,5-positions of a benzyl unit, have been designed and investigated. The liquid crystal behavior was assessed by differential scanning calorimetry, the mesophases being assigned by polarized light microscopy based on their characteristic textures and confirmed by variable temperature X-ray powder diffraction analysis. The three N-alkylated 4-pyridones nematic ligands reacted with lanthanide nitrates to yield new lanthanidomesogens with a stable and reproducible smectic A phase up to 125 degrees C. The emission spectra of the complexes have shown the characteristic emission of the lanthanide trivalent ions, over the entire temperature range of SmA phase up to isotropic state. The dielectric spectroscopy measurements performed in the temperature range of existence of the liquid crystal phase, both in the low frequency (LF) domain 0.01-10 MHz and in the high frequency (HF) range, 1 MHz-3 GHz, revealed three dipolar relaxation processes. The characteristic times have been obtained by fitting the spectra of the dielectric loss with a two component Havriliak-Negami function. The activation constant/energy was determined from the Vogel-Fiilcher-Tammann law. (C) 2019 Elsevier B.V. All rights reserved.

290. 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.

291. 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.

292. 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.

293. 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.

294. 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.

295. On the relaxation time of interacting superparamagnetic nanoparticles and implications for magnetic fluid hyperthermia

Authors: Kuncser, A; Iacob, N; Kuncser, VE

Published: JUN 24 2019, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 10, 1289, DOI: 10.3762/bjnano.10.127

A critical discussion on the presently available models for the relaxation time of magnetic nanoparticles approaching the superparamagnetic regime in the presence of interparticle dipolar interactions is considered. The direct implications of such interactions for magnetic fluid hyperthermia therapy through susceptibility loss mechanisms give rise to an indirect method for their study via specific absorption rate measurements performed on ferrofluids of different volume fractions. The theoretical support for the specific evolution of the relaxation time constant and the anisotropy energy barrier versus the interparticle interactions in a perturbation approach of the simple Neel expression for the relaxation time is provided via static and time-dependent micromagnetic simulations.

296. 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.

297. Backaction effects in cavity-coupled quantum conductors

Authors: Moldoveanu, V; Dinu, IV; Manolescu, A; Gudmundsson, V

Published: SEP 12 2019, PHYSICAL REVIEW B, 100, DOI: 10.1103/PhysRevB.100.125416

We study the electronic transport through a pair of distant nanosystems (S-a and S-b) embedded in a single-mode cavity. Each system is connected to source and drain particle reservoirs and the electron-photon coupling is described by the Tavis-Cummings model. The generalized master equation approach provides the reduced density operator of the double system in the dressed-states basis. It is shown that the photon-mediated coupling between the two subsystems leaves a signature on their transient and steady-state currents. In particular, a suitable bias applied on subsystem S-b induces a photon-assisted current in the other subsystem S-a which is otherwise in the Coulomb blockade. We also predict that a transient current passing through one subsystem triggers a charge transfer between the optically active levels of the second subsystem even if the latter is not connected to the leads. As a result of backaction, the transient current through the open system develops Rabi oscillations (ROs) whose period depends on the initial state of the closed system.

298. 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.

299. Negative ion-induced deuterium retention in mixed W-Al layers co-deposited in dual-HiPIMS

Authors: Dinca, P; Tiron, V; Velicu, IL; Porosnicu, C; Butoi, B; Velea, A; Grigore, E; Costin, C; Lungu, CP

Published: APR 15 2019, SURFACE & COATINGS TECHNOLOGY, 363, 281, DOI: 10.1016/j.surfcoat.2019.02.019

Co-sputtering of tungsten-aluminum fusion relevant materials in a dual-High Power Impulse Magnetron Sputtering discharge, operated in different Ar-D-2 gas mixtures, was investigated in gas phase by means of energy-resolving mass spectrometry. Experimental results indicate that the total ion flux and its composition are strongly dependent on sputtering gas composition and the average power applied to the targets. During single HiPIMS operation with W target, the D- ions are the most abundant species. The measured D- ion flux shows an increase with the rising of D-2 content in Ar-D-2 gas mixture and a linear increase with the power applied to the W target. In contrast, during dual-HiPIMS operation, a decrease of D- ion flux was observed when the input power applied to the Al target was increased. The origin of different deuterium ion species and retention mechanisms are discussed. The surface morphology, microstructure and chemical composition of the W-Al coatings obtained in Ar-D-2, were investigated by means of, Atomic Force Microscopy, X-ray diffraction and Glow Discharge Optical Emission Spectroscopy. GDOES depth profiles show the presence of a large amount of deuterium (up to 21 at.%) in the mixed W-Al layers and indicate that the D retention in the mixed W-Al layers is mainly related to the W in-depth concentration and less dependent on the Al one. The intense and energetic bombardment of the growing film with D- ions seems to be responsible for the large amount of D retained in the W-Al layers.

300. 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.

301. 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.

302. Synthesis and characterization of biocompatible polymer-ceramic film structures as favorable interface in guided bone regeneration

Authors: Dascalu, CA; Maidaniuc, A; Pandele, AM; Voicu, SI; Machedon-Pisu, T; Stan, GE; Cimpean, A; Mitran, V; Antoniac, IV; Miculescu, F

Published: NOV 15 2019, APPLIED SURFACE SCIENCE, 494, 352, DOI: 10.1016/j.apsusc.2019.07.098

The bone regeneration field targeted lately the development of new products based on precursors of natural origin. This study aimed to obtain the optimal design of polymer-ceramic composites for guided bone regeneration application from cellulose acetate (CA) and hydroxyapatite (HA) by varying three relevant parameters: the amount of HA powder added to the CA matrix (in the 20-40 wt% range), the HA particles size (max. 20 mu m vs. max. 40 mu m) and the homogenization time required for HA powder dispersion in the CA matrix (1 min vs. 4 min). For polymer-ceramic film structures preparation, the phase inversion by immersion in water method was used. This involved the deposition of composite solution (i.e. CA with 20-40 wt% HA) on a glass support, followed by sizing it at a thickness of 0.2 mm. The obtained film structures were investigated in terms of morphocompositional and structural properties. The surface features evaluation was achieved by surface wettability, roughness, water permeation, protein retention and in vitro evaluation of MC3T3-E1 morphology and viability. Further, ceramic particle distribution throughout samples volume was provided by computed tomography methods. These investigations targeted the validation of the prepared composite film structures as viable solutions for guided bone regeneration.

303. Interaction and Size Effects in Open Nano-Electromechanical Systems

Authors: Tanatar, B; Moldoveanu, V; Dragomir, R; Stanciu, S

Published: JUN 2019, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 256, DOI: 10.1002/pssb.201800443

The time-dependent transport of a 2D quantum wire (QW) connected to source/drain leads and electrostatically coupled to a singly-clamped InAs cantilever is investigated. The latter is placed above the nanowire and acts as a nanoresonator (NR) in the quantum regime. The vibron dynamics and the transport properties of this nano-electromechanical system (NEMS) are described within a generalized master equation approach which is exact with respect to the electron-vibron coupling. A detailed description of the electron-vibron coupling by taking into account its dependence on the wavefunctions of the quantum nanowire is introduced. It is shown that the tunneling processes in the QW trigger periodic oscillations of the average vibron number even in the absence of a bias. The time-dependent filling of the vibronic states changes as the nanoresonator is swept along the quantum wire.

304. 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.

305. Vortex dynamics driven by AC magnetic field in YBCO thin films with complex pinning structures

Authors: Ivan, I; Ionescu, AM; Sandu, V; Crisan, A; Miu, L

Published: OCT 2018, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 31, DOI: 10.1088/1361-6668/aadbfd

We investigated the AC magnetic response of a YBa2Cu3O7 film with embedded BaZrO3 nanorods and Y2O3 nanoparticles at a static magnetic field H-dc lower than the matching field H-Phi. We proposed a practical formula for the determination of the induced current J during AC susceptibility measurements, which allows us to directly obtain the pinning potential U-c from the characteristics of electric field E versus J. We show that the dynamic critical current J(d) induced at the depinning frequency f(d) can be experimentally obtained by measuring m'(T) and m ''(T) at different frequencies and amplitudes. It was found that the value of f(d) obtained by extrapolation of J to J(d) in the PHz domain is much higher than the frequency reported for ordinary YBa2Cu3O7 thin films as determined by microwave impedance measurements. AC susceptibility, vortex dynamics, pinning energy, depinning frequency, dynamic critical current, microwave impedance measurements

306. 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.

307. 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.

308. 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.

309. 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.

310. 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.

311. Theoretical investigation of the structural, optical and magnetic properties of Mn doped and (Mn, Cr) co-doped CdS in its cubic structure

Authors: Aimouch, DE; Meskine, S; Birsan, A; Kuncser, V; Zaoui, A; Boukortt, A

Published: JUL 1 2018, MATERIALS CHEMISTRY AND PHYSICS, 213, 258, DOI: 10.1016/j.matchemphys.2018.03.089

The electronic, magnetic and optical properties of doped CdS:Mn and co-doped CdS:Mn, Cr cubic structures were studied via Density Functional Theory and subsequently compared with the properties of undoped CdS. The doped compound presents semiconducting character similar to the undoped CdS, while the co-doped compound exhibits half metallic properties with a high spin polarization at the Fermi energy. The magnetic moments as well as the trend of magnetic exchange parameters of CdS:Mn and CdS:Mn,Cr, have been analyzed, in addition to the dielectric functions, by starting from calculated density of states for spin polarized configurations. The calculated absorption coefficients lead to direct information on the spectral energy distribution in the range of optoelectronic applications. The optical band gaps of doped and co-doped compounds are higher as compared to the undoped CdS, making the first compounds more interesting for possible technological applications for high density magneto-optical recording. (C) 2018 Elsevier B.V. All rights reserved.

312. Voltammetric and atomic force microscopy characterization of chymotrypsin, trypsin and caspase activities of proteasome

Authors: de Jesus, CSH; Paquim, AMC; Diculescu, VC

Published: MAY 15 2018, CATALYSIS TODAY, 306, 293, DOI: 10.1016/j.cattod.2017.01.012

Proteasome is a multicatalytic enzyme complex responsible for proteolysis of damaged proteins and an important target for drug discovery in the pharmaceutical industry. Development of fast and economic strategies for detection of proteasome activity and inhibition is a topic of intensive research. The activity of the 20S proteasome was investigated by voltammetry and atomic force microscopy. The hydrolysis of peptide bonds was studied in incubated solutions of proteasome with oligopeptide sequences specific to each chymotrypsin, trypsin and caspase activity of proteasome, before and after inhibition with epoxomicin. The time-dependence of the proteolysis and the effect of substrate and inhibitor concentrations on the rate of enzymatic reaction were investigated. Different interaction mechanisms were characterized and enzyme kinetic parameters determined. The adsorption patterns of reaction mixture components were characterized by atomic force microscopy in order to understand the processes when saturation of enzyme catalytic centres occurs for high substrate concentrations. (C) 2017 Elsevier B.V. All rights reserved.

313. Spherical cobalt/cobalt oxide - Carbon composite anodes for enhanced lithium-ion storage

Authors: Patrinoiu, G; Etacheri, V; Somacescu, S; Teodorescu, VS; Birjega, R; Culita, DC; Hong, CN; Calderon-Moreno, JM; Pol, VG; Carp, O

Published: FEB 20 2018, ELECTROCHIMICA ACTA, 264, 202, DOI: 10.1016/j.electacta.2018.01.098

Herein we report a simple and scalable route to synthesize porous cobalt/cobalt oxide - carbon sphere composites as anode material for rechargeable lithium-ion batteries. It involves the impregnation of starch-derived hydrochar spheres with a cobalt salt, followed by a heat treatment (700 degrees C) under inert atmosphere. The obtained high surface area (similar to 670 m(2) g(-1)), submicron spheres (similar to 300 nm diameter) with high-degree of microporosity (81%) consist of an amorphous carbon matrix with embedded Co/CoO nanoparticles (similar to 6 nm sized), having a total cobalt content of 6.2 wt%. The hybrid sphere anodes demonstrated superior specific capacity, rate performance and cycling stability. Discharge capacities of 520 and 310 mA h g(-1) are observed at charge-discharge rates of 0.1 and 1C respectively. No significant capacity fading is identified on prolonged cycling at various current densities. The electrode also demonstrated excellent structural stability during extended charge-discharge processes. (c) 2018 Elsevier Ltd. All rights reserved.

314. 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.

315. 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.

316. 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.

317. Dielectric properties of a bisimidazolium salt with dodecyl sulfate anion doped with carbon nanotubes

Authors: Manaila Maximean, D; Circu, V; Ganea, CP

Published: JAN 16 2018, BEILSTEIN JOURNAL OF NANOTECHNOLOGY, 9, 174, DOI: 10.3762/bjnano.9.19

A new bisimidazolium salt with dodecyl sulfate as counterion has been designed and prepared. This salt shows a SmA phase that is stable at room temperature. The new ionic liquid crystal (ILC) was characterized by H-1 NMR, C-13 NMR and IR spectroscopy. Its liquid crystalline properties were analyzed by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) studies. The dielectric spectra of the ILC doped with different concentrations of carbon nanotubes (CNT) were recorded over a wide frequency and temperature range of 10(-1) to 10(7) Hz and 293-338 K, respectively. The values of the activation energy were found in the range of 0.46-0.61 eV; the characteristic time was obtained by fitting the spectra of the dielectric loss with the Havriliak-Negami functions. As a result of doping the ILC with CNT, the electric conductivity increases significantly. Ionic conductivity is dominant and it was indirectly observed through the electrode polarization (EP) effect. The very high dielectric permittivity values and the decrease of the electric conductivity at low frequencies confirm the presence of EP.

318. 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.

319. Structural and optical properties of optimized amorphous GeTe films for memory applications

Authors: Galca, AC; Sava, F; Simandan, ID; Bucur, C; Dumitru, V; Porosnicu, C; Mihai, C; Velea, A

Published: NOV 1 2018, JOURNAL OF NON-CRYSTALLINE SOLIDS, 499, 7, DOI: 10.1016/j.jnoncrysol.2018.07.007

Chalcogenide amorphous materials, such as GeTe, are known to exhibit deposition dependent optical and structural properties. The formation of a single and homogeneous amorphous GeTe (a-GeTe) phase is questionable since the deposited films can be mixtures of monoelemental nanoclusters. In this work, we employed two deposition techniques, pulsed laser deposition from a polycrystalline GeTe target and co-sputtering from two distinct Ge and Te targets, respectively, to obtain a-GeTe films. To improve the homogeneity of the amorphous phase obtained by magnetron sputtering, the substrate temperature was varied from room temperature up to 180 degrees C. The samples were investigated by X-ray diffraction, X-ray reflectometry, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. It was found that the film mass density, optical bandgap, refractive index and absolute reflectivity become progressively larger with increasing substrate temperature, due to the minimization of voids fraction and the number of dangling bonds in the amorphous structure. Moreover, X-ray photoelectron spectroscopy results prove the formation of Ge-Te bonds and therefore of the GeTe alloy at the optimal substrate temperature of 180 degrees C. This study reveals the importance of optimizing the deposition conditions for obtaining a specific amorphous phase, which enables the atomic rearrangements responsible for fast phase-change needed in memory applications.

320. Many-body effects in transport through a quantum-dot cavity system

Authors: Dinu, IV; Moldoveanu, V; Gartner, P

Published: MAY 25 2018, PHYSICAL REVIEW B, 97, DOI: 10.1103/PhysRevB.97.195442

We theoretically describe electric transport through an optically active quantum dot embedded in a single-mode cavity, and coupled to source-drain particle reservoirs. The populations of various many-body configurations (e.g., excitons, trions, biexciton) and the photon-number occupancies are calculated from a master equation which is derived in the basis of dressed states. These take into account both the Coulomb and the light-matter interaction. The former is essential in the description of the transport, while for the latter we identify situations in which it can be neglected in the expression of tunneling rates. The fermionic nature of the particle reservoirs plays an important role in the argument. The master equation is numerically solved for the s-shell many-body configurations of disk-shaped quantum dots. If the cavity is tuned to the biexciton-exciton transition, the most efficient optical processes take place in a three-level A system. The alternative exciton-ground-state route is inhibited as nonresonant due to the biexciton binding energy. The steady-state current is analyzed as a function of the photon frequency and the coupling to the leads. An unexpected feature appears in its dependence on the cavity loss rate, which turns out to be nonmonotonic.

321. 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.

322. 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.

323. 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.

324. From Glucose Direct to Succinic Acid: an Optimized Recyclable Bi-functional Ru@MNP-MWCNT Catalyst

Authors: Podolean, I; Cojocaru, B; Garcia, H; Teodorescu, C; Parvulescu, VI; Coman, SM

Published: NOV 2018, TOPICS IN CATALYSIS, 61, 1876, DOI: 10.1007/s11244-018-1012-4

Ru@MNP-MWCNT catalysts were obtained via functionalization of nanostructured carbon-based carriers (ie, MWCNT) with base molecules (ie, 2-aminophenol and ethylenediamine) followed by the complexation with RuCl3. These structures demonstrated a highly efficient behavior for the selective wet oxidation of levulinic acid and glucose to succinic acid. However, to ensure an easy recovery and high recyclability the MWCNTs nanotubes were modified by incorporation of super-paramagnetic Fe3O4 nanoparticles into porous structure. Besides the catalytic performances the resulted composites showed a good mechanical resistance.

325. 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).

326. 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.

327. H2S sensing mechanism of SnO2-CuWO4 operated under pulsed temperature modulation

Authors: Simion, CE; Somacescu, S; Teodorescu, VS; Osiceanu, P; Stanoiu, A

Published: APR 15 2018, SENSORS AND ACTUATORS B-CHEMICAL, 259, 268, DOI: 10.1016/j.snb.2017.12.027

This paper reports the sensing mechanism of SnO2-CuWO4 mixed oxides towards H2S detection revealed through Pulsed Temperature Mode (PTM). After thick film deposition onto commercial substrates, the final annealing temperature enhances the material reliability through the changes occurred during the experimental conditions. PTM approach represents a tradeoff in terms of sensing mechanism versus sensing performance, in order to get insights about the fundamental aspects. The measurements have been done under dynamic gas flow conditions, in the presence of 50% relative humidity (RH). The gas sensors based on SnO2-CuWO4 exhibit sensor signals higher than 100 to 10 ppm H2S, low cross-sensitivity to common gaseous interfering agents (CO, CH4, NH3, SO2), average selective sensitivity of 8.64 towards the main interfering NO2 gas, moderate response (4 min)/recovery (5 min) transients and power consumption. In order to emphasize the role of moisture towards H2S detection mechanism, the photoacoustic spectroscopic insights were correlated with Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy results. Such approach has shown promising aspects towards further operational sensitive devices. (c) 2017 Elsevier B.V. All rights reserved.

328. 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.

329. 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.

330. 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

331. 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.

332. Full Tetragonal Phase Stabilization in ZrO2 Nanoparticles Using Wet Impregnation: Interplay of Host Structure, Dopant Concentration and Sensitivity of Characterization Technique

Authors: Colbea, C; Avram, D; Cojocaru, B; Negrea, R; Ghica, C; Kessler, VG; Seisenbaeva, GA; Parvulescu, V; Tiseanu, C

Published: DEC 2018, NANOMATERIALS, 8, DOI: 10.3390/nano8120988

Here, we show that wet impregnation of ZrO2 nanoparticles with 10% and 20% Eu oxide followed by thermal anneal in air above 500 degrees C produces full stabilization of the tetragonal phase of ZrO2 without evidencing any phase separation. The bare ZrO2 nanoparticles were obtained using three synthetic methods: oil in water microemulsion, rapid hydrothermal, and citrate complexation methods. The homogeneity of the solid solutions was assessed using X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, and advanced luminescence spectroscopy. Our findings show that wet impregnation, which is a recognized method for obtaining surface doped oxides, can be successfully used for obtaining doped oxides in the bulk with good homogeneity at the atomic scale. The limits of characterization technique in detecting minor phases and the roles of dopant concentration and host structure in formation of phase stabilized solid solutions are also analyzed and discussed.

333. 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.

334. 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.

335. 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.

336. CoFe2-xCrxO4 ferrites: synthesis, characterization and their catalytic activity

Authors: Mindru, I; Gingasu, D; Diamandescu, L; Patron, L; Marinescu, G; Culita, DC; Calderon-Moreno, JM; Preda, S; Oprea, O; Parvulescu, V

Published: DEC 2018, CHEMICAL PAPERS, 72, 3213, DOI: 10.1007/s11696-018-0553-0

Chromium substituted cobalt ferrites CoFe2-xCrxO4 (x=0; 1; 1.5) were synthesized through a soft chemistry methodthe gluconate precursor route. The gluconate precursors were characterized by infrared spectroscopy (IR), ultraviolet-visible spectroscopy and thermal analysis. The spinel oxide powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Mossbauer spectroscopy and Brunauer-Emmett-Teller N-2 adsorption-desorption analyses. XRD indicated the formation of the spinel-type phase with good crystallinity. The mean crystalline domains size decreased from 23.8 to 17.8nm with the increase in the chromium content. SEM revealed faceted particles for which the particle sizes varied significantly with the chromium content. The chromium substituted cobalt ferrites were found to have high catalytic performance.

337. Ambiguous Role of Growth-Induced Defects on the Semiconductor-to-Metal Characteristics in Epitaxial VO2/TiO2 Thin Films

Authors: Mihailescu, CN; Symeou, E; Svoukis, E; Negrea, RF; Ghica, C; Teodorescu, V; Tanase, LC; Negrila, C; Giapintzakis, J

Published: APR 25 2018, ACS APPLIED MATERIALS & INTERFACES, 10, 14144, DOI: 10.1021/acsami.8b01436

Controlling the semiconductor-to-metal transition temperature in epitaxial VO2 thin films remains an unresolved question both at the fundamental as well as the application level. Within the scope of this work, the effects of growth temperature on the structure, chemical composition, interface coherency and electrical characteristics of rutile VO2 epitaxial thin films grown on TiO2 substrates are investigated. It is hereby deduced that the transition temperature is lower than the bulk value of 340 K. However, it is found to approach this value as a function of increased growth temperature even though it is accompanied by a contraction along the V4+-V4+ bond direction, the crystallographic c-axis lattice parameter. Additionally, it is demonstrated that films grown at low substrate temperatures exhibit a relaxed state and a strongly reduced transition temperature. It is suggested that, besides thermal and epitaxial strain, growth-induced defects may strongly affect the electronic phase transition. The results of this work reveal the difficulty in extracting the intrinsic material response to strain, when the exact contribution of all strain sources cannot be effectively determined. The findings also bear implications on the limitations in obtaining the recently predicted novel semi-Dirac point phase in VO2/TiO2 multilayer structures.

338. Synthesis and characterization of dextran-coated iron oxide nanoparticles

Authors: Predescu, AM; Matei, E; Berbecaru, AC; Pantilimon, C; Dragan, C; Vidu, R; Predescu, C; Kuncser, V

Published: MAR 2018, ROYAL SOCIETY OPEN SCIENCE, 5, DOI: 10.1098/rsos.171525

Synthesis and characterization of iron oxide nanoparticles coated with a large molar weight dextran for environmental applications are reported. The first experiments involved the synthesis of iron oxide nanoparticles which were coated with dextran at different concentrations. The synthesis was performed by a co-precipitation technique, while the coating of iron oxide nanoparticles was carried out in solution. The obtained nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry, Fourier transform infrared spectroscopy and superconducting quantum interference device magnetometry. The results demonstrated a successful coating of iron oxide nanoparticles with large molar weight dextran, of which agglomeration tendency depended on the amount of dextran in the coating solution. SEM and TEM observations have shown that the iron oxide nanoparticles are of about 7 nm in size.

339. 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.

340. CHARACTERIZATION OF SURFACE AND INTERFACE OF Fe-C STEEL UNDER ELECTROLYTIC GALVANIZATION

Authors: Bibicu, I; Bulea, C; Diamandescu, L; Rus, V; Popescu, T; Mercioniu, I

Published: JUL-SEP 2018, PROCEEDINGS OF THE ROMANIAN ACADEMY SERIES A-MATHEMATICS PHYSICS TECHNICAL SCIENCES INFORMATION SCIENCE, 19, 430, DOI:

Low carbon Fe-C steel surface has been studied before and after electrolytic galvanization. The corrosion products formed under atmospheric conditions on the Fe-C steel were identified and characterised by X-ray diffraction (XRD), transmission Mossbauer spectroscopy, conversion electron Mossbauer spectroscopy (CEMS), and conversion X-ray Mossbauer spectroscopy (CXMS). In decreasing order of abundance the found corrosion phases were magnetite, hematite, and goethite. After the surface preparation, an electrolytic galvanization process was applied. A magnetic anisotropy was evidenced after preparation, in the superficial layer of around 250 nm thickness. Scanning electron microscopy (SEM) analyses evidenced the formation of a uniform thin Zn film of 8 mu m at the surface of steel. No other Fe-Zn phases were identified at the steel-Zn interface.

341. 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.

342. 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.

343. 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:

344. 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.

345. Irreversibility in Rolled Tantalum

Authors: Sandu, V; Cimpoiasu, E

Published: JUL 2018, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 31, 2054, DOI: 10.1007/s10948-017-4433-6

We investigated the magnetic and thermodynamic properties of rolled tantalum in superconducting state. The magnetization shows a crossover from type I to type II superconductivity as the magnetic field increases beyond the thermodynamic critical field. In both regimes, the sample shows a substantial irreversibility of the magnetization which we attribute to the pinning of the entities that characterize the intermediate and mixed states. Magnetic relaxation data taken in the intermediate state shows an important contribution of the quantum tunnelling below 3.7 K.

346. 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.

347. 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.

348. 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.

349. AlN/Si based SAW resonators for very high sensitivity temperature sensors

Authors: Nicoloiu, A; Muller, A; Zdru, I; Vasilache, D; Stan, GE; Nastase, C; Dumitru, V; Dinescu, A

Published: 2018, 2018 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS), DOI:

In the current work we present AlN/Si based Surface Acoustic Wave (SAW) devices exploited as high sensitivity temperature sensors. The experimental results show that the resonance frequency varies between 3.2 and 5.5 GHz, depending on the finger/Interdigit spacing width and metal thickness. The temperature measurements were performed between -250 degrees C and +150 degrees C in a cryostat. The sensitivities were investigated between 24-150 degrees C and the values were compared to the results obtained for similar GaN/Si based SAW structures.

350. 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.

351. 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.

352. 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.

353. 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.

354. 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:

355. A Mathematical Account of the NEGF Formalism

Authors: Cornean, HD; Moldoveanu, V; Pillet, CA

Published: FEB 2018, ANNALES HENRI POINCARE, 19, 442, DOI: 10.1007/s00023-017-0638-2

The main goal of this paper is to put on solid mathematical grounds the so-called non-equilibrium Green's function transport formalism for open systems. In particular, we derive the Jauho-Meir-Wingreen formula for the time-dependent current through an interacting sample coupled to non-interacting leads. Our proof is non-perturbative and uses neither complex-time Keldysh contours nor Langreth rules of 'analytic continuation.' We also discuss other technical identities (Langreth, Keldysh) involving various many-body Green's functions. Finally, we study the Dyson equation for the advanced/retarded interacting Green's function and we rigorously construct its (irreducible) self-energy, using the theory of Volterra operators.

356. Local configurations and atomic intermixing in as-quenched and annealed Fe1-xCrx and Fe1-xMox ribbons

Authors: Stanciu, AE; Greculeasa, SG; Bartha, C; Schinteie, G; Palade, P; Kuncser, A; Leca, A; Filoti, G; Birsan, A; Crisan, O; Kuncser, V

Published: 2018, PHILOSOPHICAL MAGAZINE, 98, 1067, DOI: 10.1080/14786435.2018.1425556

Local atomic configuration, phase composition and atomic intermixing in Fe-rich Fe1-xCrx and Fe1-xMox ribbons (x = 0.05, 0.10, 0.15), of potential interest for high-temperature applications and nuclear devices, are investigated in this study in relation to specific processing and annealing routes. The Fe-based thin ribbons have been prepared by induction melting, followed by melt spinning and further annealed in He at temperatures up to 1250 degrees C. The complex structural, compositional and atomic configuration characterisation has been performed by means of X-ray diffraction (XRD), transmission Mossbauer spectroscopy and differential scanning calorimetry (TG-DSC). The XRD analysis indicates the formation of the desired solid solutions with body-centred cubic (bcc) structure in the as-quenched state. The Mossbauer spectroscopy results have been analysed in terms of the two-shell model. The distribution of Cr/Mo atoms in the first two coordination spheres is not homogeneous, especially after annealing, as supported by the short-range order parameters. In addition, high-temperature annealing treatments give rise to oxidation of Fe (to haematite, maghemite and magnetite) at the surface of the ribbons. Fe1-xCrx alloys are structurally more stable than the Mo counterpart under annealing at 700 degrees C. Annealing at 1250 degrees C in He enhances drastically the Cr clustering around Fe nuclei.

357. 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.

358. Polymer Dispersed Liquid Crystals films doped with carbon nanotubes - preparation methods

Authors: Manaila-Maximean, D; Circu, V; Ganea, P; Barar, A; Danila, O; Staicu, T; Loiko, VA; Konkolovich, AV; Miskevich, AA

Published: 2018, ADVANCED TOPICS IN OPTOELECTRONICS, MICROELECTRONICS, AND NANOTECHNOLOGIES IX, 10977, DOI: 10.1117/12.2326186

Polymer Dispersed Liquid Crystals (PDLC) are composite materials consisting of small liquid crystal (LC) droplets surrounded by a polymer matrix. Due to their relatively easy preparation and processing, the PDLC devices found many applications such as displays, architectural windows, energy control devices, projection displays, spatial light modulators, polarizers. Carbon nanotubes (CNT) have excellent mobility and are suitable as doping nanoparticles in order to improve the electrically-controlled orientation of LC. This paper presents the methods of preparation of PDLC doped with CNT. Experimental results are presented for the films obtained by solvent induced polymerization method, using polymethyl methacrylate and a nematic LC, E7. The obtained films are characterized by polarized optical microscopy, differential scanning calorimetry and electro-optical transmission.

359. 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.

360. H2S selective sensitivity of Cu doped BaSrTiO3 under operando conditions and the associated sensing mechanism

Authors: Stanoiu, A; Piticescu, RM; Simion, CE; Rusti-Ciobota, CF; Florea, OG; Teodorescu, VS; Osiceanu, P; Sobetkii, A; Badilita, V

Published: JUL 1 2018, SENSORS AND ACTUATORS B-CHEMICAL, 264, 336, DOI: 10.1016/j.snb.2018.03.013

Nanostructured Cu mol. 5% doped perovskite material Ba0.75Sr0.25TiO3 was synthesized under hydrothermal conditions and further on deposited via RF sputtering technique onto commercial Al2O3 substrates provided with Au interdigital electrodes and Pt heater. The obtained thin films have been analyzed by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), X-ray photoelectron spectroscopy (XPS), Differential Scanning Calorimetry-Thermogravimetry (DSC-TG) and electrical investigations. The H2S (5-90 ppm) gas-surface interaction at moderate operating temperature (T-op = 250 degrees C) associated with the interplay between the pre-adsorbed oxygen species and surface dipolar hydroxyl groups, has been highlighted by simultaneous work function and electrical resistance measurements. By correlation with the XPS spectra, the dominant role of surface hydroxylation was revealed and the subsequent gas sensing mechanism under operando conditions has been addressed. (C) 2018 Elsevier B.V. All rights reserved.

361. 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.

362. 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.

363. 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.

364. 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.

365. 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.

366. 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.

367. 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).

368. 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.

369. 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.

370. Thermal analysis, microstructure and impurity phases evolution in Fe14Cr ferritic steel powders ball-milled in air and under an argon atmosphere

Authors: Mihalache, V; Mercioniu, I; Aldica, G; Pasuk, I

Published: OCT 2018, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 134, 474, DOI: 10.1007/s10973-018-7274-z

Refined structure of the ferritic phase induced by mechanical milling (under reducing atmosphere) and its thermal stability are required in various applications of nanostructured ferritic alloys. The impurification with nitrogen and oxygen uptaken from the air is very probable during ball-milling, especially at the long-time high-energy milling conditions. As a rule, these interstitial impurities in as-milled powders are in quantities under the sensibility limit of conventional measurement techniques, such as XRD and SEM/ EDS. To evidence the tendency for microstructure modification by impurities introduced during milling, the Fe-14Cr-3W-0.4Ti-0.25Y(2)O(3) (Fe14Cr) ferritic steel powders (re)loaded in air and milled up to 170 h with interruption of the milling process, and heated up to 1373 K were investigated by thermal analysis in correlation with X-ray diffraction and scanning electron microscopy. XRD failed to detect the impurities in powders milled up to 38 h in air although a consistent mass loss related to the degassing of N-2 was registered in thermogravimetric, TG, curves. (Fe,Cr)(4)N, fcc-c, (Fe, Cr)(2)O-3 impurity phases in powders milled over 38 h in air and (Fe,Cr)(2)O-4 formed upon heating were readily detected by XRD. The analysis of these results allowed to better understand the impurification process and to generalise it for any as-milled Fe-Cr-based alloy powder processed in any milling conditions irrespective of the milling atmosphere, duration and thus, of amounts of contaminants. The quality of three powders milled for 170 h in three different conditions was compared: in air, under an argon atmosphere with interruptions of the milling process and under an argon atmosphere without interruption of the milling process. The contamination of powder milled for 170 h under an argon atmosphere without interruption of the milling process is insignificant (corresponding to less than 0.5 mass% mass loss in TG) as compared to powders obtained in the other two milling conditions. New approaches for minimising the contamination from air are suggested.

371. Flux Channeling in YBa2Cu3O7 Superlattices

Authors: Mollatt, HJS; Dang, VS; Qureishy, T; Mikheenko, P; Crisan, A

Published: 2018, PROCEEDINGS OF THE 2018 IEEE 8TH INTERNATIONAL CONFERENCE NANOMATERIALS: APPLICATION & PROPERTIES (NAP-2018), DOI:

We report unusual effect of channeled magnetic flux motion in YBa2Cu3O7-delta/PrBa2Cu3O7-delta superlattices grown by pulsed laser deposition. Magneto-optical imaging reveals that flux moves along a set of parallel and perpendicular lines, while optical microscopy does not show any features on the surface that may be linked to this effect. In contrast, scanning electron microscopy registers sub-micron fractures in the superlattices corresponding to these flux lines, but the magnetic flux channels are much wider than the width of these fractures. To further clarify the origin of flux channels, electrical transport measurements on the superlattices have been performed. Their current-voltage characteristics reveal the presence of distinctive branches related to the flux motion along the selective channels, following which magnetic flux crosses sample in a shortest and least resistive way. The application of very large current overheated the superlattice along these channels, evaporating superconducting material and exposing, wider than in the superconductor, fractures in the substrate. It is concluded that motion of flux in the channels is controlled not only by the presence of nano-fractures in YBa2Cu3O7-delta/PrBa2Cu3O7_delta, but also by stress developed in the superconducting material due to the fracturing of the substrate.

372. 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.

373. High hexitols selectivity in cellulose hydrolytic hydrogenation over platinum (Pt) vs. ruthenium (Ru) catalysts supported on micro/mesoporous carbon

Authors: Lazaridis, PA; Karakoulia, SA; Teodorescu, C; Apostol, N; Macovei, D; Panteli, A; Delimitis, A; Coman, SM; Parvulescu, VI; Triantafyllidis, KS

Published: OCT 5 2017, APPLIED CATALYSIS B-ENVIRONMENTAL, 214, 14, DOI: 10.1016/j.apcatb.2017.05.031

The "one-pot" hydrolyltic hydrogenation of cellulose towards C2-C6 sugar alcohols has been recognized as one of the most promising biomass valorization routes for the production of high added-value chemicals. In this work, we studied the performance of Ru and Pt catalysts supported on micro/mesoporous activated carbon, in the hydrolytic hydrogenation of microcrystalline and ball-milled cellulose, in neat water, at 180 C and at relatively low hydrogen pressure of 2 MPa. The impact of metal loading (1-5 wt.%), metal reduction method (H2 at 350 C or NaBH4) and acidification (sulfonation) of the AC support on cellulose conversion and selectivity to the various products were systematically addressed. It was shown that Pt is significantly more selective towards hexitols (sorbitol and mannitol) compared to Ru, in glucose rich reaction media, such as those offered by the easily hydrolyzed ball-milled cellulose. For example, the 5wt%PtIAC-SO3H catalyst afforded hexitols yield of 69.5 wt.% (at 96.1% conversion) compared to 10.9 wt.% (at 95.2% wt.% conversion) obtained by the corresponding Ru catalyst, the latter being also selective towards glycerol and propane-1,2-diol (propylene glycol). A relatively moderate metal loading, such as in 3 wt.%Ru/AC-SO3H, was more favorable for hexitols production (44.5 wt.% yield, at 94.8 wt.% conversion) with Ru catalysts. These results were also verified by glucose hydrogenation experiments that were conducted at the same experimental conditions. Both Pt and Ru exhibited relatively high glucose hydrogenation activity towards hexitols, versus retro-aldol reactions that lead directly to smaller C2-C4 compounds, while the difference in the final product yields between the two metals was attributed to the higher hexitols hydrogenolysis (C C cleavage) reactivity of Ru. HRTEM data showed the formation of metallic crystalline Pt and Ru nanoparticles (<= 4 nm, depending on loading) as well as of amorphous oxygen-rich M(O)(x)(delta+) phases, which were also confirmed by the XPS data. The presence of these phases which may be a source of acidity, as well as the bacisity of the parent AC used in this study, were mainly responsible for inducing isomerization, retro-aldol and dehydration reactions leading eventually to increased glycerol and propylene glycol selectivity, as was observed for both low-metal catalysts, i.e. 1 wt.% Pt or Ru/AC. (C) 2017 Elsevier B.V. All rights reserved.

374. 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.

375. 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.

376. Synergetic pinning centres in BaZrO3-doped YBa2Cu3O7-x films induced by SrTiO3 nanolayers

Authors: Crisan, A; Dang, VS; Mikheenko, P; Ionescu, AM; Ivan, I; Miu, L

Published: APR 2017, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 30, DOI: 10.1088/1361-6668/aa5edf

We report on the enhancement of critical current density (J(c)) and the unusual behaviour of its dependence on field orientation in YBa2Cu3O7-x (YBCO) nanostructured films by a combination of substrate decoration with Ag nano-dots, of the incorporation of BaZrO3 (BZO) nano-particles and nano-rods, and of multilayer architecture (a thin SrTiO3 layer separating two 1.5 mu m-thick YBCO layers). SrTiO3 insulating layers were 15, 30 or 45 nm thick. The highest improvement of J(c) in applied magnetic fields along the c-axis and smaller than 1 T occurs in the bi-layer with 30 nm-thick STO, but the influence of STO thickness is small. Our thick nanostructured films show significant improvement of J(c) in the magnetic field along the ab-plane direction. The presence of BZO nano-rods, ab-plane defects and nano particles of BZO and Y2O3 was observed in transmission electron microscopy (TEM) images of the film. The peculiarities of artificial pinning centres revealed in the TEM images of the nanostructured films are used to explain an unusual split of the peak in the J(c) dependence on the magnetic field along the ab-plane of YBCO. Effective pinning potentials in high magnetic fields have rather high values for such thick films.

377. 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.

378. 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.

379. Nano-engineered pinning centres in YBCO superconducting films

Authors: Crisan, A; Dang, VS; Mikheenko, P

Published: FEB 15 2017, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 533, 132, DOI: 10.1016/j.physc.2016.06.011

For practical applications of superconducting materials in applied magnetic fields, artificial pinning centres in addition to natural ones are required to oppose the Lorentz force. These pinning centres are actually various types of defects in the superconductor matrix. The pinning centres can be categorised on their dimension (volume, surface or point) and on their character (normal cores or AK cores). Different samples have been produced by Pulsed Laser Deposition, with various thicknesses, temperatures and nanostructured additions to the superconducting matrix. They have been characterized by SQUID Magnetic Properties Measurement System and Physical Properties Measurement System, as well as by Transmission Electron Microscopy (TEM). Correlations between pinning architecture, TEM images, and critical currents at various fields and field orientations will be shown for a large number of YBa2Cu3Ox films with various types and architectures of artificial pinning centres. (C) 2016 Elsevier B.V. All rights reserved.

380. 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.

381. 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.

382. 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.

383. 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.

384. 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.

385. 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).

386. 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.

387. Significant change of local atomic configurations at surface of reduced activation Eurofer steels induced by hydrogenation treatments

Authors: Greculeasa, SG; Palade, P; Schinteie, G; Kuncser, A; Stanciu, A; Lungu, GA; Porosnicu, C; Lungu, CP; Kuncser, V

Published: APR 30 2017, APPLIED SURFACE SCIENCE, 402, DOI: 10.1016/j.apsusc.2017.01.056

Reduced-activation steels such as Eurofer alloys are candidates for supporting plasma facing components into kamak-like nuclear fusion reactors. In order to investigate the impact of hydrogen/deuterium insertion in their crystalline lattice, annealing treatments in hydrogen atmosphere have been applied on Eurofer slabs. The resulting samples have been analyzed with respect to local structure and atomic configuration both before and after successive annealing treatments, by X-ray diffractometry (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and conversion electron Mossbauer spectroscopy (CEMS). The corroborated data point out for a bcc type structure of the non-hydrogenated alloy, with an average alloy composition approaching Fe0.9Cr0.1 along a depth of about 100 nm. EDS elemental maps do not indicate surface inhomogeneities in concentration whereas the Mossbauer spectra prove significant deviations from a homogeneous alloying. The hydrogenation increases the expulsion of the Cr atoms toward the surface layer and decreases their oxidation, with considerable influence on the surface properties of the steel. The hydrogenation treatment is therefore proposed as a potential alternative for a convenient engineering of the surface of different Fe-Cr based alloys.(C) 2017 Elsevier B.V. All rights reserved.

388. 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.

389. 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.

390. 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.

391. 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.

392. 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.

393. Photo-sensitive Ge nanocrystal based films controlled by substrate deposition temperature

Authors: Stavarache, I; Maraloiu, VA; Negrila, C; Prepelita, P; Gruia, I; Iordache, G

Published: OCT 2017, SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 32, DOI: 10.1088/1361-6641/aa8154

Lowering the temperature of crystallization by deposition of thin films on a heated substrate represents the easiest way to find new means to develop and improve new working devices based on nanocrystals embedded in thin films. The improvements are strongly related with the increasing of operation speed, substantially decreasing the energy consumption and reducing unit fabrication costs of the respective semiconductor devices. This approach avoids major problems, such as those related to diffusion or difficulties in controlling nanocrystallites size, which appear during thermal treatments at high temperatures after deposition. This article reports on a significant progress given by structuring Ge nanocrystals (Ge-NCs) embedded in silicon dioxide (SiO2) thin films by heating the substrate at 400 degrees C during co-deposition of Ge and SiO2 by magnetron sputtering. As a proof-of-concept, a Si/Ge-NCs:SiO2 photo-sensitive structure was fabricated thereof and characterized. The structure shows superior performance on broad operation bandwidth from visible to near-infrared, as strong rectification properties in dark, significant current rise in the inversion mode when illuminated, high responsivity, high photo-detectivity of 10(14) Jones, quick response and significant conversion efficiency with peak value reaching 850% at -1 V and about 1000 nm. This simple preparation approach brings an important contribution to the effort of structuring Ge nanocrystallites in SiO2 thin films at a lower temperature for the purpose of using these materials for devices in optoelectronics, solar cells and electronics on flexible substrates.

394. Unpinning of heavy hole spin in magnetic quantum dots

Authors: Dinu, IV; Moldoveanu, V; Dragomir, R; Tanatar, B

Published: MAY 2017, PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 254, DOI: 10.1002/pssb.201600800

Using the k<bold>p theory and configuration interaction method</bold>, we analyze the effect of heavy hole-light hole (HH-LH) mixing in CdTe quantum dots (QDs) with a single manganese (Mn) ion. We find that the hole-Mn exchange switches the coupling between two excitons whose Luttinger spinors have both HH and LH components. If the magnetic dopant is off-centered and the QD is subjected to a single pulse the system periodically bounces between bright and dark mostly HH excitons with opposite HH spins. A pump-and-probe setup allows to estimate the efficiency of this HH spin unpinning from the biexciton response. The biexciton absorption spectrum is also discussed.

395. Exact and approximate analytical solutions of Weiss equation of ferromagnetism and their experimental relevance

Authors: Barsan, V; Kuncser, V

Published: 2017, PHILOSOPHICAL MAGAZINE LETTERS, 97, 371, DOI: 10.1080/09500839.2017.1366081

The recent progress in the theory of generalised Lambert functions makes possible to solve exactly the Weiss equation of ferromagnetism. However, this solution is quite inconvenient for practical purposes. Precise approximate analytical solutions are obtained, giving the temperature dependence of the spontaneous magnetization, and also the dependence of the magnetization on both temperature and external magnetic field. The experimental relevance of these results, mainly for the determination of the Curie temperature, is discussed.

396. A general perspective on the magnetization reversal in cylindrical soft magnetic nanowires with dominant shape anisotropy

Authors: Kuncser, A; Antohe, S; Kuncser, V

Published: FEB 1 2017, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 423, 38, DOI: 10.1016/j.jmmm.2016.09.066

Peculiarities of the magnetization reversal process in cylindrical Ni-Cu soft magnetic nanowires with dominant shape anisotropy are analyzed via both static and time dependent micromagnetic simulations. A reversible process involving acoherent-like spin rotation is always observed for magnetic fields applied perpendicularly to the easy axis whereas nucleation of domain walls is introduced for fields applied along the easy axis. Simple criteria for making distinction between a Stoner-Wohlfarth type rotation and a nucleation mechanism in systems with uniaxial magnetic anisotropy are discussed. Superposed reversal mechanisms can be in action for magnetic fields applied at arbitrary angles with respect to the easy axis within the condition of an enough strong axial component required by the nucleation. The dynamics of the domain wall, involving two different stages (nucleation and propagation), is discussed with respect to initial computing conditions and orientations of the magnetic field. A nucleation time of about 3 ns and corkscrew domain walls propagating with a constant velocity of about 150 m/s are obtained in case of Ni-Cu alloy (Ni rich side) NWs with diameters of 40 nm and high aspect ratio.

397. 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.

398. 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.

399. 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.

400. Tuning magneto-transport properties of Fe-Au granular thin films by cluster organization

Authors: Stanciu, AE; Kuncser, A; Schinteie, G; Palade, P; Leca, A; Greculeasa, SG; Catrina, A; Kuncser, V

Published: JUL 12 2017, JOURNAL OF PHYSICS D-APPLIED PHYSICS, 50, DOI: 10.1088/1361-6463/aa7405

A comparative study of morpho-structural, magnetic and magneto-transport properties of two Fe-Au granular films with different concentrations of Fe nanoclusters of almost similar size is reported. Different organizations of the Fe clusters, i.e. in lamellar-like or random-like configuration, were obtained by varying the amount of Fe in the Fe-Au films. The specific magnetic behaviour was investigated with respect to local structure and morpho-structural aspects by combining magneto-optic Kerr effect and superconducting quantum interference device magnetometry, Fe-57 conversion electron Mossbauer spectroscopy and a wide range of electron microscopy techniques. A strong in-plane magnetic texture with uniaxial anisotropy was observed in the case of the lamellar-like organization of the clusters (specific to the Fe-Au film with higher Fe concentration) whereas a superparamagnetic behaviour was evidenced in the case of random distribution of the clusters (specific to the Fe-Au film with lower Fe concentration), despite the similar average size of the clusters in the two samples. Specific magnetoresistance effects were investigated with respect to both the involved magnetic configurations and magnetic interactions of the Fe clusters.

401. Chalcogenide thin films deposited by rfMS technique using a single quaternary target

Authors: Prepelita, P; Stavarache, I; Negrila, C; Garoi, F; Craciun, V

Published: DEC 1 2017, APPLIED SURFACE SCIENCE, 424, 427, DOI: 10.1016/j.apsusc.2016.11.071

Thin films of chalcogenide, Cu(In, Ga) Se-2 have been obtained using a single quaternary target by radio frequency magnetron sputtering method, with thickness in the range 750 nm to 1200 nm. X-ray photoelectron spectroscopy investigations showed, that the composition of Cu(In, Ga) Se-2 thin films was very similar to that of the used target CuIn0.75Ga0.25Se2. Identification of the chemical composition of Cu(In, Ga) Se-2 thin films by XPS performed in high vacuum, emphasized that the samples exhibit surface features suitable to be integrated into the structure of solar cells. Atomic Force Microscopy and Scanning Electron Microscopy investigations showed that surface morphology was influenced by the increase in thickness of the Cu(In, Ga) Se-2 layer. From X-Ray Diffraction investigations it was found that all films were polycrystalline, having a tetragonal lattice with a preferential orientation along the (112) direction. The optical reflectance as a function of wavelength was measured for the studied samples. The increase in thickness of the Cu(In, Ga) Se-2 absorber determined a decrease of its optical bandgap value from 1.53 eV to 1.44 eV. The results presented in this paper showed an excellent alternative of obtaining Cu(In, Ga) Se-2 compound thin films from a single target. (C) 2016 Elsevier B.V. All rights reserved.

402. 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.

403. 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.

404. 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.

405. Tunable dielectric properties in polyacrylonitrile/multiwall carbon nanotube composites

Authors: Palade, S; Pantazi, A; Vulpe, S; Berbecaru, C; Tucureanu, V; Oprea, O; Negrea, RF; Dragoman, D

Published: AUG 2017, POLYMER COMPOSITES, 38, 1748, DOI: 10.1002/pc.23744

Composites containing polyacrylonitrile (PAN) and different mass contents of multiwall carbon nanotubes (MWCNTs) were prepared and structurally investigated. X-ray Diffraction of pristine PAN reveals the presence of crystalline and amorphous phases which change their ratio under thermal annealing and addition of MWCNT. For as prepared samples, thermal analysis reveals two glass transition temperatures, which support the hypothesis that unoriented PAN is a two-phase material. Infrared spectrum of as prepared PAN suggests that the polymer is not stabilized. Dielectric investigations of PAN/MWCNT composites show that permittivity has a strong increase as the MWCNT mass content increases, while the dielectric losses are comparable in all samples. These results suggest that PAN/MWCNT composites could find important applications in electronics. POLYM. COMPOS., 38:1741-1748, 2017. (c) 2015 Society of Plastics Engineers

406. 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.

407. 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.

408. Progress in Hydroxyapatite-Starch Based Sustainable Biomaterials for Biomedical Bone Substitution Applications

Authors: Miculescu, F; Maidaniuc, A; Voicu, SI; Thakur, VK; Stan, GE; Ciocan, LT

Published: OCT 2017, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 5, 8512, DOI: 10.1021/acssuschemeng.7b02314

Hydroxyapatite is a calcium phosphate intensively proposed as a bone substitution material because of its resemblance to the constituents of minerals present in natural bone. Since hydroxyapatite's properties are mainly adequate for nonload bearing applications, different solutions are being tested for improving these properties and upgrading them near the target values of natural bone. On the other hand, starch (a natural and biodegradable polymer) and its blends with other polymers have been proposed as constituents in hydroxyapatite mixtures due to the adhesive, gelling, and swelling abilities of starch particles, useful in preparing well dispersed suspensions and consolidated ceramic bodies. This article presents the perspectives of incorporating starch and starch blends in hydroxyapatite materials. Based on the role of starch within the materials, the review covers its use as (i) a polymeric matrix in hydroxyapatite composites used as adhesives, bone cements, bone waxes, drug-delivery devices or scaffolds and (ii) a sacrificial binder for fabrication of porous hydroxyapatite scaffolds. The suitability of these materials for bone reconstruction has becomes a reachable aim considering the recent advancements in ceramic fabrication and the current possibilities of controlling the processing parameters.

409. 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.

410. 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.

411. Properties of perovskite ferroelectrics deposited on F doped SnO2 electrodes and the prospect of their integration into perovskite solar cells

Authors: Pintilie, I; Stancu, V; Tomulescu, A; Radu, R; Stan, CB; Trinca, L; Pintilie, L

Published: DEC 5 2017, MATERIALS & DESIGN, 135, 121, DOI: 10.1016/j.matdes.2017.09.013

The integration of ferroelectrics in perovskite solar cells is proposed as possible way to enhance charge collection efficiency. First results on solar cellmanufactured with PbTiO3 (PTO) instead of TiO2 have shown negligible values for the power conversion efficiency (PCE). This is explained by the high serial resistance of sol-gel deposited PTO on F:SnO2 electrodes (FTO). Although PTO layer has remnant polarization of 22 mu C/cm(2), the high potential barrier (0.25 +/- 0.05 eV) at the FTO/PTO interface and lowcarriermobility (10(-8) cm(2) V-1 s(-1)) compared to TiO2 leads to high serial resistance. Better results were obtained with thinner PTO layers grown by pulsed laser deposition, with PCE values up to 0.6%. Further enhancement was obtained by replacing PTO with BaTiO3 (BTO), with PCE value reaching about 0.8% after poling the cell with +3 V. The most important finding was that the magnitude of the short circuit current increases with the amplitude of the poling voltage while the value of the open-circuit voltage remains about the same, around 0.9 V. This is explained through more efficient collection of the charges generated under illumination in the absorber layer due to the polarization that is present in the ferroelectric film. (C) 2017 Elsevier Ltd. All rights reserved.

412. Bis-imidazolium salts with alkyl sulfates as counterions: synthesis and liquid crystalline properties

Authors: Ilinca, TA; Pasuk, I; Circu, V

Published: OCT 7 2017, NEW JOURNAL OF CHEMISTRY, 41, 11124, DOI: 10.1039/c7nj02561k

A series of flexibly linked bis-imidazolium salts with alkyl sulfate anions having different chain lengths (10, 12, 14) was designed and prepared starting from 1,1'-(alpha,omega-alkanediyl)-bisimidazole and alkyl bromides (14 or 16 carbon atoms) followed by metathesis with the corresponding sodium salts. These compounds were investigated because of their liquid crystalline properties using a combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and temperature dependent powder X-ray diffraction (XRD). All nine bis-imidazolium compounds with alkyl sulfate anions show liquid crystalline properties which were influenced by flexible spacer length, alkyl tail length and, finally, the length of alkyl chains attached to sulfate groups. Broader mesophase ranges were found for compounds with a shorter spacer (six carbon atoms), about 70 degrees C. For compounds with a spacer of ten carbon atoms, higher mesophase ranges and clearing temperatures were found for longer alkyl tails (sixteen carbon atoms). Increasing the length of alkyl chains attached to sulfate anions resulted in higher clearing temperatures for compounds with the longer spacer. The variation in the carbon atom number of the alkyl sulfate anion for bis-imidazolium compounds with the shorter spacer has almost no impact on their SmA phase stability.

413. 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.

414. 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.

415. 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] .

416. Applications of DNA-Electrochemical Biosensors in Cancer Research

Authors: Chiorcea-Paquim, AM; Oliveira, SCB; Diculescu, VC; Oliveira-Brett, AM

Published: 2017, PAST, PRESENT AND FUTURE CHALLENGES OF BIOSENSORS AND BIOANALYTICAL TOOLS IN ANALYTICAL CHEMISTRY: A TRIBUTE TO PROFESSOR MARCO MASCINI, 77, 336, DOI: 10.1016/bs.coac.2017.06.003

417. 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.

418. Review on peculiar issues of field emission in vacuum nanoelectronic devices

Authors: Filip, V; Filip, LD; Wong, H

Published: DEC 2017, SOLID-STATE ELECTRONICS, 138, 15, DOI: 10.1016/j.sse.2017.09.010

Some of the modern aspects of field emission based electron sources have been collated in a short and comprehensive review. The usually overlooked peculiar aspects in this research field have been particularly emphasized in order to increase the interest in further fundamental studies and technological applications. The vast material was roughly split in two main branches which occasionally overlap: the electron emission devices based on chemically homogeneous nanostructured surfaces and the more complex nanocomposite emitting surfaces.

419. Characterization of PLD grown WO3 thin films for gas sensing

Authors: Boyadjiev, SI; Georgieva, V; Stefan, N; Stan, GE; Mihailescu, N; Visan, A; Mihailescu, IN; Besleaga, C; Szilagyi, IM

Published: SEP 30 2017, APPLIED SURFACE SCIENCE, 417, 223, DOI: 10.1016/j.apsusc.2017.03.212

Tungsten trioxide (WO3) thin films were grown by pulsed laser deposition (PLD) with the aim to be applied in gas sensors. The films were studied by atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and profilometry. To study the gas sensing behavior of these WO3 films, they were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was applied to analyze their gas sensitivity. Synthesis of tetragonal-WO3 films starting from a target with predominantly monoclinic WO3 phase was observed. The films deposited at 300 degrees C presented a surface topology favorable for the sorption properties, consisting of a film matrix with protruding craters/cavities. QCM prototype sensors with such films were tested for NO2 sensing. The PLD grown WO3 thin films show good sensitivity and fast reaction at room temperature, even in as-deposited state. With the presented technology, the manufacturing of QCM gas sensors is simple, fast and cost-effective, and it is also suitable for energy-effective portable equipment for on-line monitoring of environmental changes. (C) 2017 Elsevier B.V. All rights reserved.

420. 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.

421. 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.

422. Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure

Authors: Besleaga, C; Dumitru, V; Trinca, LM; Popa, AC; Negrila, CC; Kolodziejczyk, L; Luculescu, CR; Ionescu, GC; Ripeanu, RG; Vladescu, A; Stan, GE

Published: NOV 2017, NANOMATERIALS, 7, DOI: 10.3390/nano7110394

Aluminum Nitride (AlN) has been long time being regarded as highly interesting material for developing sensing applications (including biosensors and implantable sensors). AlN, due to its appealing electronic properties, is envisaged lately to serve as a multi-functional biosensing platform. Although generally exploited for its intrinsic piezoelectricity, its surface morphology and mechanical performance (elastic modulus, hardness, wear, scratch and tensile resistance to delamination, adherence to the substrate), corrosion resistance and cytocompatibility are also essential features for high performance sustainable biosensor devices. However, information about AlN suitability for such applications is rather scarce or at best scattered and incomplete. Here, we aim to deliver a comprehensive evaluation of the morpho-structural, compositional, mechanical, electrochemical and biological properties of reactive radio-frequency magnetron sputtered AlN nanostructured thin films with various degrees of c-axis texturing, deposited at a low temperature (similar to 50 degrees C) on Si (100) substrates. The inter-conditionality elicited between the base pressure level attained in the reactor chamber and crystalline quality of AlN films is highlighted. The potential suitability of nanostructured AlN (in form of thin films) for the realization of various type of sensors (with emphasis on bio-sensors) is thoroughly probed, thus unveiling its advantages and limitations, as well as suggesting paths to safely exploit the remarkable prospects of this type of materials.

423. 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.

424. 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

425. 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.

426. 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.

427. 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.

428. 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.

429. 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.

430. TEMPERATURE INFLUENCE ON THE CAPACITANCE-VOLTAGE HYSTERESIS OF TRANSPARENT a-IGZO/PZT/FTO MFS-HETEROSTRUCTURE

Authors: Trinca, LM; Besleaga, C; Stancu, V; Radu, R; Iuga, A; Boni, AG; Galca, AC; Pintilie, L

Published: 2017, ROMANIAN REPORTS IN PHYSICS, 69, DOI:

Capacitance-voltage (C-V) hysteresis of metal-ferroelectric-semiconductor (MFS) structure based on a-In2GaZnO5.5 and Pb0.2Zr0.8TiO3 layers are recorded in the 350-470 K range. The structure is grown on FTO/glass to obtain a transparent MFS. The memory functionality of the heterostructure is proved through C-V and P-V characteristics. The memory window is dependent on the temperature, the largest value of 2.5 V being obtained at 470 K, where the contribution of the ferroelectric-semiconductor interface defect states is minimized. The direction of C-V hysteresis is clockwise at 350 K, and it turns counterclockwise at higher temperatures where the ferroelectric polarization has the main contribution.

431. 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.

432. 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.

433. 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.

434. 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.

435. 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.

436. 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.

437. 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.

438. Oriented Au nanoplatelets on graphene promote Suzuki-Miyaura coupling with higher efficiency and different reactivity pattern than supported palladium

Authors: Candu, N; Dhakshinamoorthy, A; Apostol, N; Teodorescu, C; Corma, A; Garcia, H; Parvulescu, VI

Published: AUG 2017, JOURNAL OF CATALYSIS, 352, 66, DOI: 10.1016/j.jcat.2017.04.034

Facet 111 oriented Au nanoplatelets (20-40 nm wide, 3-4 nm height) grafted on graphene ((Au) over bar /fl-G) are about three orders of magnitude more efficient than Pd nanoparticles supported on graphene to promote Suzuki-Miyaura coupling. In contrast to Pd catalysis, it is shown here that the product yields in Suzuki-Miyaura coupling catalyzed by Au nanoparticles follow the order chlorobenzene > bromobenzene > iodobenzene. Kinetic studies show that this reactivity order is the result of the poisoning effect of halides for Au that is much higher for I- than Br- and much higher than for Cl-, due to adsorption. This strong iodide adsorption leading to Au catalyst deactivation was predicted by DFT calculations of Au clusters. (Au) over bar /fl-G are about one order of magnitude more efficient than small Au nanoparticles (4-6 nm) obtained by the polyol method supported on graphene. Our results can have impact in organic synthesis, showing the advantage of (Au) over bar /fl-G as catalyst for Suzuki-Miyaura couplings. (C) 2017 Elsevier Inc. All rights reserved.

439. Local Ordering at the Interface of the TiO2-WO3 Bi-Layers

Authors: Macovei, D; Dascaleanu, V; Teodorescu, CM; Luca, D

Published: 2016, NANOSTRUCTURES AND THIN FILMS FOR MULTIFUNCTIONAL APPLICATIONS: TECHNOLOGY, PROPERTIES AND DEVICES, 331, DOI: 10.1007/978-3-319-30198-3_10

Reducing the recombination rate of photo-generated electron-hole pairs in the surface of pristine TiO2 materials can be done, among others, via local spatial charge separation in the photocatalytically active surface region. A local electric field acting for this purpose can be ensured, for instance, in hetero-junction regions formed at the interface between a TiO2 film and a WO3 ultra-thin layer. The option for the WO3-TiO2 semiconductor pair is related to the suitable fit of their band structures. To model the interface, a more in-depth knowledge of local atomic environment is required. Here, we discuss the local atomic ordering and the related effects in the interface region of TiO2/WO3 and WO3/TiO2 structures grown on Si (100) substrates. Materials characterization was done by using XRD, XPS and XAS techniques. We demonstrate that tungsten atoms enter as W6+ or W4+ cations into the rutile-type TiO2 lattice, by substituting the Ti4+ cations. While W6+-Ti4+ substitution leaves the surrounding rutile matrix unchanged, the W4+-Ti4+ substitution induces a local rutile-to-anatase transition. The current results are relevant in designing new applications structures with enhanced photocatalytic performances.

440. Methanol oxidation at carbon paste electrodes modified with (Pt-Ru)/carbon aerogels nanocomposites

Authors: Fort, CI; Cotet, LC; Vasiliu, F; Marginean, P; Danciu, V; Popescu, IC

Published: APR 1 2016, MATERIALS CHEMISTRY AND PHYSICS, 172, 188, DOI: 10.1016/j.matchemphys.2016.01.061

Mesoporous carbon aerogels (CAs) impregnated with (Pt-Ru) nanoparticles were prepared, incorporated into carbon paste electrodes (CPEs) and investigated as electrocatalysts for CH3OH electro-oxidation. The sol gel method, followed by supercritical drying with liquid CO2 and thermal pyrolysis in an inert atmosphere, was used to obtain high mesoporous CAs. (Pt-Ru)/CAs nanocomposites with various (Pt-Ru) loading were prepared by using Ru(AcAc)(3) and H2PtCl6 as metal precursors and the impregnation method. The morpho-structural peculiarities of the so prepared (Pt-Ru)/CAs electrocatalysts were examined by using elemental analysis, N2 adsorption -desorption isotherms, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and selected area electron diffraction (SAED). Cyclic voltammetry measurements, carried out at (Pt-Ru)/CA-CPEs incorporating nanocomposites with various Pt-Ru loading and different specific surface areas, showed that CA with the highest specific surface area (843 m(2)/g) and impregnated with 6% (w/w) (Pt Ru) nanoparticles exhibit the best CH3OH electro-oxidation efficiency. The Michaelis Menten formalism was used to describe the dependence of the oxidation peak current on the CH3OH concentration, allowing the estimation of the modified electrodes sensitivities. Thus, for (Pt-Ru, 10%)/CA(535)-CPE was observed the highest sensitivity (12.5 +/- 0.8 mA/M) and, at the same time, the highest maximum current density ever reported (153.1 mA/cm(2) for 2 M CH3OH and an applied potential of 600 mV vs. SHE). (C) 2016 Elsevier B.V. All rights reserved.

441. 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.

442. 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.

443. Laser-induced forward transfer of carbon nanowalls for soft electrodes fabrication

Authors: Constantinescu, C; Vizireanu, S; Ion, V; Aldica, G; Stoica, SD; Lazea-Stoyanova, A; Alloncle, AP; Delaporte, P; Dinescu, G

Published: JUN 30 2016, APPLIED SURFACE SCIENCE, 374, 55, DOI: 10.1016/j.apsusc.2015.09.089

Carbon nanowalls (CNW) are two-dimensional interconnected graphitic nanostructures that have a few mu m in length and height, reaching typical thicknesses of a few tens of nm. We present results on such layers synthesized in a low pressure argon plasma jet, injected with acetylene and hydrogen, on transparent substrates (quartz) heated at 600 degrees C, without catalyst. Thermogravimetric analysis reveals that the CNW are stable up to 420 degrees C in air, and Raman spectroscopy investigations highlight their graphene-like structure. Finally, using a pulsed Nd:YAG laser device (355 nm, 50 ps), we show that 2D-arrays of CNW (pixels and lines) can be printed by laser-induced forward transfer (LIFT), preserving their architecture and structure. Electrical measurements on 1 mu m thick CNW demonstrate typical values in the range of 357.5-358.4 Omega for the samples grown on Au/Cr electrodes, and in the range of 450.1-474.7 Omega for the LIFT printed lines (under positive, negative, and neutral polarization; 1 kHz-5 MHz frequency range; 500 mV and 1 V, respectively). Their morphology is highlighted by means of optical and electronic microscopy. Such structures have potential applications as soft conductive lines, in sensor development and/or embedding purposes. (C) 2015 Elsevier B.V. All rights reserved.

444. Submicrometer Hollow Bioglass Cones Deposited by Radio Frequency Magnetron Sputtering: Formation Mechanism, Properties, and Prospective Biomedical Applications

Authors: Popa, AC; Stan, GE; Besleaga, C; Ion, L; Maraloiu, VA; Tulyaganov, DU; Ferreira, JMF

Published: FEB 24 2016, ACS APPLIED MATERIALS & INTERFACES, 8, 4367, DOI: 10.1021/acsami.6b00606

This work reports on the unprecedented magnetron sputtering deposition of submicrometric hollow cones of bioactive glass at low temperature in the absence of any template or catalyst. The influence of sputtering conditions on the formation and development of bioglass cones was studied. It was shown that larger populations of well-developed cones could be achieved by increasing the argon sputtering pressure. A mechanism describing the growth of bioglass hollow cones is presented, offering the links for process control and reproducibility of the cone features. The composition, structure, and morphology of the as-synthesized hollow cones were investigated by energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), grazing incidence geometry X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM)-selected area electron diffraction (SAED). The in vitro biological performance, assessed by degradation tests (ISO 10993-14) and cytocompatibility assays (ISO 10993-5) in endothelial cell cultures, was excellent. This allied with resorbability and the unique morphological features make the submicrometer hollow cones interesting candidate material devices for focal transitory permeabilization of the blood brain barrier in the treatment of carcinoma and neurodegenerative disorders.

445. 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.

446. 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.

447. 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.

448. 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.

449. 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

450. 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.

451. Be/W and W/Be bilayers deposited on Si substrates with hydrogenated Fe-Cr and Fe-Cr-Al interlayers for plasma facing components

Authors: Greculeasa, SG; Palade, P; Schinteie, G; Lungu, GA; Porosnicu, C; Jepu, I; Lungu, CP; Kuncser, V

Published: DEC 2016, JOURNAL OF NUCLEAR MATERIALS, 481, DOI: 10.1016/j.jnucmat.2016.09.010

Be/W and W/Be bilayers, of interest in regard to the specific behavior of plasma facing components (PFCs) were deposited on Si substrates by thermionic vacuum arc, with Fe, Fe-Cr and Fe-Cr-Al interlayers. The interlayers, with compositions approaching the one of the reduced activation steels used in supporting PFCs, were subsequently annealed in hydrogen atmosphere. The multilayers were characterized with respect to morphologic, structural, diffusional and atomic intermixing aspects via XRD, XRR, X-ray photoemission spectroscopy and Mossbauer spectroscopy. All as-prepared samples present partially amorphous structures. A main alpha-Fe phase is observed, as well as (superparamagnetic) secondary Fe oxides, metallic Fe with Si, Cr, W and Be neighbors, Be-rich Fe-Be and Fe-Si phases. High amounts of tungsten and tungsten oxides were also evidenced in the Fe layer. The strong atomic intermixing of W and Be layers was indirectly supported by the unusual densities of Wand Be layers and Fe-57 Mossbauer spectroscopy results. (C) 2016 Elsevier B.V. All rights reserved.

452. 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.

453. 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.

454. 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.

455. 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.

456. 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.

457. 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.

458. 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.

459. 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.

460. 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.

461. AMMONIA SENSING WITH 5 MOL% LANTHANUM DOPED BARIUM STRONTIUM TITANATE UNDER HUMID AIR BACKGROUND

Authors: Simion, CE; Stanoiu, A; Teodorescu, VS; Rusti, CF; Piticescu, RM; Vasile, E; Vasile, E; Tudor, IA

Published: FEB 2016, REVUE ROUMAINE DE CHIMIE, 61, +, DOI:

Nanostructured Ba0.7Sr0.3TiO3 (BST) with 5 molar % of Lanthanum (La) have been synthesized using a high pressure hydrothermal chemical route. The structural and morphological investigations were performed. Termogravimetry/differential scanning calorimetry and Raman investigations have been also employed to analyse the as-prepared material. The gas sensing investigations have indicated the ability of La doped BST to detect ammonia, when operated at room temperature in humid background. The obtained results were discussed with respect to the possible gas-sill-face interaction mechanism. In addition, the said material showed low cross-sensitivity to other possible interfering gases: methane, carbon monoxide, nitrogen dioxide, sulphur dioxide and hydrogen sulphide.

462. 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.

463. 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.

464. 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.

465. 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.

466. 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.

467. 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.

468. Ultra-Thin Epitaxial Tungsten Carbide Schottky Contacts in 4H-SiC

Authors: Knoll, L; Teodorescu, V; Minamisawa, RA

Published: OCT 2016, IEEE ELECTRON DEVICE LETTERS, 37, 1320, DOI: 10.1109/LED.2016.2604488

We demonstrate the fabrication and characterization of epitaxial W2C Schottky contacts into 4H-SiC via sputtering deposition of ultra-thin W followed by thermal annealing. The alloying reaction occurs below 600 degrees C, yielding a stable layer up to 1200 degrees C. The epitaxial layer is hexagonal, unexpectedly forming W2C phase even at the lowest annealing temperature, which is predicted to occur at 1500 degrees C in bulk systems. Schottky contacts based on epitaxial W2C films exhibit smoother interface morphology, higher thermal stability, lower turn-ON voltage and about similar to 50% reduction in Schottky-contact resistance compared with thick Ti Schottky contacts.

469. Effect of P2O5 on the Structural and Magnetic Properties of Magnetite-Based Glass-Ceramics

Authors: Sandu, V; Greculeasa, S; Kuncser, A; Kuncser, V

Viorica Florescu

Publications

1. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

2. Multifunctional Magnetic Nanocomposites: Innovative Processing and Applications

3. In situ Electrochemical Evaluation of the Interaction of dsDNA with the Proteasome Inhibitor Anticancer Drug Bortezomib

4. Partial Replacement of Dimethylformamide with Less Toxic Solvents in the Fabrication Process of Mixed-Halide Perovskite Films

5. Resistive-like Behavior of Ferroelectric p-n Bilayer Structures Based on Epitaxial Pb(Zr0.2Ti0.8)O-3 Thin Films

6. Growth and characterization of Cu-Ni-Sn-S films electrodeposited at different applied potentials

7. Carbon Inks-Based Screen-Printed Electrodes for Qualitative Analysis of Amino Acids

8. Partial replacement of Pb2+ in MAPbI(2.6)Cl(0.4) perovskite films and their photovoltaic performance

9. Experimental Band Structure of Pb(Zr,Ti)O-3: Mechanism of Ferroelectric Stabilization

10. Burdock-Derived Composites Based on Biogenic Gold, Silver Chloride and Zinc Oxide Particles as Green Multifunctional Platforms for Biomedical Applications and Environmental Protection

11. Synthetic peptide array on gold for the electrochemical assessment of the 20S proteasome activity and effect of inhibitory compounds

12. Ferroelectricity Induced by Oxygen Vacancies in Rhombohedral ZrO2 Thin Films

13. Surface species of nematic mixture E7 in hard confinement: spectroscopic investigations cannot distinguish among the E7 components interacting with the support surface

14. Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO3)-PVDF Sub-Percolative Hybrid Composites

15. Synthesis and Anti-Melanoma Activity of L-Cysteine-Coated Iron Oxide Nanoparticles Loaded with Doxorubicin

16. Ferroelectric Orthorhombic ZrO2 Thin Films Achieved Through Nanosecond Laser Annealing

17. Magnetite-Based Nanostructured Coatings Functionalized with Nigella sativa and Dicloxacillin for Improved Wound Dressings

18. Grain size-driven effect on the functional properties in Ba0.6Sr0.4TiO3 ceramics consolidated by spark plasma sintering

19. 3D Porous Collagen Matrices-A Reservoir for In Vitro Simultaneous Release of Tannic Acid and Chlorhexidine

20. Chiral and Catalytic Effects of Site-Specific Molecular Adsorption

21. Microscopic mechanism of ferroelectric properties in barium hexaferrites

22. 'Put variety in White': Multi-analytical investigation of the white pigments inlaid on Early Chalcolithic pottery from Southern Romania

23. Influence of erbium doping on the structural, magnetic and optical properties of hematite (?-Fe(2)O( )3) nanorods

24. Dielectric, piezoelectric and magnetic behavior of CoFe2O4/BNT-BT0.08 monolayer thin films composites

25. Ferroelectricity modulates polaronic coupling at multiferroic interfaces

26. Epoxy Coatings Containing Modified Graphene for Electromagnetic Shielding

27. BaTiO3 nanocubes-Gelatin composites for piezoelectric harvesting: Modeling and experimental study

28. Antimicrobial Properties of TiO2 Microparticles Coated with Ca- and Cu-Based Composite Layers

29. Synthesis and characterization of some C-Ti based multilayer and composite nanostructures

30. Effect of the Cadmium Telluride Deposition Method on the Covering Degree of Electrodes Based on Copper Nanowire Arrays

31. Unified approach to cyclotron and plasmon resonances in a periodic two-dimensional GaAs electron gas hosting the Hofstadter butterfly

32. Ferrofluids and bio-ferrofluids: looking back and stepping forward

33. Multifunctional Zn-Doped ITO Sol-Gel Films Deposited on Different Substrates: Application as CO2-Sensing Material

34. C-doped TiO2 nanotubes with pulsed laser deposited Bi2O3 films for photovoltaic application

35. Impact of band-bending on the k-resolved electronic structure of Si-doped GaN

36. Electric Energy Storage Effect in Hydrated ZrO2-Nanostructured System

37. The sustainable materials roadmap

38. Luminescent heteroleptic copper(I) complexes with phosphine and N-benzoyl thiourea ligands: Synthesis, structure and emission properties

39. The effect of noble metal addition on the properties of oxide semiconductors nanoparticles

40. Catalytic transformation of the marine polysaccharide ulvan into rare sugars, tartaric and succinic acids

41. Monodispersed nanoplatelets of samarium oxides for biosensing applications in biological fluids

42. Metallized electrospun polymeric fibers for electrochemical sensors and actuators

43.Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose & nbsp;

44. Electrochemical characterization of shikonin and in-situ evaluation of interaction with DNA

45. Controlling polarization direction in epitaxial Pb(Zr0.2Ti0.8)O-3 films through Nb (n-type) and Fe (p-type) doping

46. Memory Properties of Zr-Doped ZrO2 MOS-like Capacitor

47. Effect of the supersaturation with nitrogen on the structure refinement and magnetic properties of mechanically alloyed and heated Fe14Cr ferritic alloys

48. MgB2 with Addition of Cubic BN and Ge2C6H10O7 Obtained by Spark Plasma Sintering Technique

49. Half-metallic properties of Zr2CrAl ferrimagnetic full-Heusler compound, investigated in tetragonal, orthorhombic and rhombohedral crystal structures

50. Effective Hamiltonians in the quantum Rabi problem

51. Bulk and surface characteristics of co-electrodeposited Cu2FeSnS4 thin films sulfurized at different annealing temperatures

52. Effect of chlorine and bromine on the perovskite crystal growth in mesoscopic heterojunction photovoltaic device

53. Relationship between the Formation of Magnetic Clusters and Hexagonal Phase of Gold Matrix in AuxFe1-x Nanophase Thin Films

54. Structural and transport properties of Cu2CoSnS4 films prepared by spray pyrolysis

55. New superdielectric materials: (1-x) SrFe12O19 - x BNT-BT nanocomposites

56. The Synergistic Effect of the Laser Beam on the Thermionic Vacuum Arc Method for Titanium-Doped Chromium Thin Film Deposition

57. Enhanced magnetocaloric properties of La0.8K0.2-xPbxMnO3 nanoparticles by optimizing Pb doping concentrations

58. Unidirectional Magnetic Anisotropy in Molybdenum Dioxide-Hematite Mixed-Oxide Nanostructures

59. Full Length Article Towards high degree of c-axis orientation in MgB2 bulks

60. Chitosan-Hyaluronan Nanoparticles for Vinblastine Sulfate Delivery: Characterization and Internalization Studies on K-562 Cells

61. Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

62. SOME ASPECTS REGARDING PRECIPITATES IN THE NiTi SHAPE MEMORY MATERIALS

63. Effect of annealing on the structural, optical and electrical properties of (F, Zn) double doped SnO2 nanoparticles obtained by the laser pyrolysis method

64. Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose

65. Quantification of cell oxygenation in 2D constructs of metallized electrospun polycaprolactone fibers encapsulating human valvular interstitial cells

66. SiGeSn Quantum Dots in HfO2 for Floating Gate Memory Capacitors

67. 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

68. Magnetic Core-Shell Iron Oxides-Based Nanophotocatalysts and Nanoadsorbents for Multifunctional Thin Films

69. Nanometric-Thick Metal-Free h-Boron Nitride/Graphene Films as Base Catalyst for the Synthesis of Benzoxazoles

70. Doped microporous graphitic carbons as metal-free catalysts for the selective hydrogenation of alkynes to alkenes

71. Sonogashira Synthesis of New Porous Aromatic Framework-Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling

72. 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

73. Graphene/Ferroelectric (Ge-Doped HfO2) Adaptable Transistors Acting as Reconfigurable Logic Gates

74. Sonogashira Synthesis of New Porous Aromatic Framework- Entrapped Palladium Nanoparticles as Heterogeneous Catalysts for Suzuki-Miyaura Cross-Coupling

75. Enhanced photoelectrochemical activity of WO3-decorated native titania films by mild laser treatment

76. Thin Film Fabrication by Pulsed Laser Deposition from TiO2 Targets in O-2, N-2, He, or Ar for Dye-Sensitized Solar Cells

77. Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO3 Nanofillers

78. Soft Chemistry Synthesis and Characterization of CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) Ferrite

43.
Ageing studies of Multi-Strip Multi-Gap Resistive Plate Counters based on low resistivity glass electrodes in high irradiation dose & nbsp;