National Institute Of Materials Physics - Romania

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847 articles found

461. Silver Azide Nanoparticles Embedded into Silica as Energetic Nano-materials

Authors: Ghica, C; Damian, R; Culita, D; Turcu, I; Ionita, P

Published: 2015, MATERIALS SCIENCE-MEDZIAGOTYRA, 21, 332, DOI: 10.5755/j01.ms.21.3.6926

Silver azide is a primary high explosive that can be initiated by different means. In this work, silver azide nanoparticles were obtained, embedded into silica, and further derivatized with biotin. TEM, DLS, and IR measurements were used to characterize the hybrid energetic nanoparticles. The hybrid nanoparticles are made from an explosive core (silver azide) and a shell (silica), to which has been attached through an organic linker a biological target vectot (biotin). These hybrid nanoparticles can be used as models to study smart energetic nano-materials

462. HETEROSTRUCTURES BASED ON SMALL MOLECULES ORGANIC COMPOUNDS

Authors: Socol, M; Rasoga, O; Breazu, C; Socol, G; Preda, N; Pasuk, I; Visan, D; Stavarache, I; Gherendi, F; Girtan, M; Sidwaba, U

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1392, DOI:

Heterostructures with layers from small molecules organic compounds were deposited on ITO/glass substrate by thermal vacuum evaporation (TVE) technique. Structural, optical and morphological investigations were carried out on the realised layers (zinc phthalocyanine-ZnPc, fullerene-C60 and 1,4,5,8-naphthalene-tetracarboxylic dianhydride-NTCDA). The films are polycrystalline keeping the morphological features characteristic to these materials. The prepared heterostructures reveal a large absorption domain in the visible domain. The current-voltage (I-V) characteristics of the investigated structures, recorded in dark, present an improvement in the current value (similar to one order of magnitude) for the standard structure (ITO/PEDOT: PSS/ZnPc/C60/NTCDA/Al) with a supplimentary layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). For the inverted structure (Al/NTCDA/C60/ZnPc/ITO) was also noticed an increased curent value in comparasion with that observed for the standard structure.

463. Additive-free 1,4-butanediol mediated synthesis: a suitable route to obtain nanostructured, mesoporous spherical zinc oxide materials with multifunctional properties

Authors: Visinescu, D; Scurtu, M; Negrea, R; Birjega, R; Culita, DC; Chifiriuc, MC; Draghici, C; Moreno, JC; Musuc, AM; Balint, I; Carp, O

Published: 2015, RSC ADVANCES, 5, 99989, DOI: 10.1039/c5ra20224h

A family of mesoporous, self-aggregated zinc oxide materials with spherical morphologies of high crystalline quality, is obtained through a facile, additive-free polyol procedure. The forced hydrolysis of zinc acetylacetonate in 1,4-butanediol (BD), in various reaction conditions, affords ZnO materials with versatile morphologies and optical properties. The reaction parameters (temperature, time and zinc source concentration) modulate the ZnO nanocrystallites size (from 8.1 to 13.2 nm), the spheres diameter (ranging from 50 up to 250 nm), the internal structure of the spherical aggregates (hollow or solid) and their specific surface area (from 31 to 92 m(2) g(-1)). Polycrystalline spheres with hollow cores are obtained at the lowest temperature (90 degrees C) and zinc cation concentration (0.1 M), while at higher reaction temperatures (140-180 degrees C), solid spherical aggregates are developed. A reaction mechanism for ZnO formation via zinc layered hydroxide (LDH-Zn) is proposed based on nuclear magnetic resonance (H-1 NMR and C-13 NMR) and powder X-ray diffraction (XRD) studies. The obtained ZnO materials have a functionalized surface, derived from the polyol and act as a nitrogen selective photocatalyst in the reduction reaction of NO3-. The organic residual attached on the ZnO surface plays a crucial role in the denitrification reaction, since the photo-cleaned sample showed negligible photocatalytic activity. The ZnO materials also exhibited microbicidal and anti-biofilm activity against reference and clinical strains, highlighting their potential for the development of novel antimicrobial formulations.

464. Influence of strain field on nanoscale electronic processes in silicon-based semiconductors

Authors: Lepadatu, AM; Palade, C; Slav, A; Lazanu, S

Published: 2015, 2015 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), 44, DOI:

The effects of strain field are studied in Si wafers implanted with heavy iodine and bismuth ions and in multi-quantum well structures. The experimental method of thermally stimulated currents without applied bias is used, and the trapping centres parameters are determined by modelling the discharge curves. In both cases, the strain field produces temperature-dependent parameters of trapping levels. So, due to the high strain field in the neighbourhood of implanted ions, energy levels broaden and cross sections become temperature dependent. In multilayer structures, for the trapping centres corresponding to strain-induced defects both concentrations and capture cross sections are temperature dependent.

465. ELECTRICAL CONDUCTIVITY STUDIES OF SCANDIA DOPED CERIA CERAMIC COMPOSITES

Authors: Ionascu, AM; Raikova, G; Mladenova, E; Mercioniu, I

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1280, DOI:

In this paper electrical conductivity analysis of a new material, designed to be used as a solid electrolyte for intermediate temperature fuel cells (IT-SOFC) was performed. The material is based on a composite of scandia doped ceria (SDC) and yttria doped alumina (YA) which ensures higher mechanical stability. The initial powders were obtained by sol-gel method. The samples were prepared by cold pressing and sintering at 1500 degrees C. Materials with variation of the composition (SDC/YA = 95/5; 90/10, 85/15 mass %) were studied. The conductivity was determined by Electrochemical Impedance Spectroscopy. According of the electrochemical analysis the composites with 5 and 10 mass % YA exhibit better conductivity. The results are in correlation with morphological investigation, realized by SEM.

466. Supported Pd-Cu Nanoparticles for Water Phase Reduction of Nitrates. Influence of the Support and of the pH Conditions

Authors: Papa, F; Balint, I; Negrila, C; Olaru, EA; Zgura, I; Bradu, C

Published: DEC 10 2014, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 53, 19103, DOI: 10.1021/ie503070f

PdCu nanoparticles were synthesized by the alkaline polyol method and further supported on alumina or titania. The nanoparticles show a crystalline Pd core and a shell rich in amorphous copper as was put in evidence by complex characterization methods (X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and CO chemisorption). The performances of as-prepared catalysts in the water phase reduction of nitrate were assessed in comparison with catalysts obtained by impregnation. Supported nanoparticle catalysts show a high activity in the reduction of nitrates, better than the impregnated catalysts. The importance of the support choice was discussed. The catalyst based on PdCu nanoparticles supported on titania (PCT-np) is the most active, selective, and stable among those investigated. Also, the influence of pH conditions on the PCT-np catalyst performances was emphasized.

467. Biocatalytic designs for the conversion of renewable glycerol into glycerol carbonate as a value-added product

Authors: Tudorache, M; Ghemes, G; Nae, A; Matei, E; Mercioniu, I; Kemnitz, E; Ritter, B; Coman, S; Parvulescu, VI

Published: DEC 2014, CENTRAL EUROPEAN JOURNAL OF CHEMISTRY, 12, 1270, DOI: 10.2478/s11532-014-0547-x

A comparative study of two different biocatalytic models, e.g. enzyme immobilized on magnetic particles (EIMP) and cross-linking enzyme aggregates onto magnetic particles (CLEMPA) was performed. The first model was designed as enzyme-immobilized on the magnetic particles surface (EIMP). The second model was constructed as a network structure with the enzyme aggregates and magnetic particles placed into the nodes and polyglutaraldehyde cross-linker as the network ledges. The design was called cross-linking enzyme aggregates onto magnetic particles (CLEMPA). The biocatalysts were prepared using lipase enzyme from Aspergillus niger for catalyzing the glycerol (Gly) conversion to glycerol carbonate (GlyC). The biocatalyst characteristics for both designs (EIMP and CLEMPA) were evaluated using scanning electron microscopy (SEM), laser light scattering (LLS) and UV-Vis techniques. The EIMP model was strongly influenced by the composition of the polymeric layer covering the particles surface, while the size of the magnetic particles affected mostly the CLEMPA design. Also, the biocatalytic capacity of the tested models was evaluated as maximum 52% Gly conversion with 90% GlyC selectivity for EIMP, and 73% Gly conversion with 77% GlyC selectivity for CLEMPA. Both biocatalytic models were successfully used to prepare GlyC from "crude" glycerol collected directly from the biodiesel process (e.g. 49% Gly conversion with 91% GlyC selectivity for EIMP and 70% Gly conversion with 80% GlyC selectivity for CLEMPA).

468. In vitro toxicity evaluation of Ti4+-stabilized gamma-Bi2O3 sillenites

Authors: Popescu, T; Lupu, AR; Feder, M; Tarabasanu-Mihaila, D; Teodorescu, VS; Vlaicu, AM; Diamandescu, L

Published: DEC 2014, TOXICOLOGY IN VITRO, 28, 1530, DOI: 10.1016/j.tiv.2014.07.003

We report results regarding the in vitro toxicology of gamma-Bi2O3 represented by its isomorphous phase Bi12TiO20 (gamma-BTO). The gamma-BTO microparticles were synthesized by two methods: coprecipitation from a bismuth nitrate tetrabutyl titanate solution and solid state reaction of Bi2O3 and TiO2 oxides. The structural and morphological characteristics of the obtained materials were determined using X-ray diffraction (XRD), selected area electron diffraction (SAED), transmission (TEM) and scanning (SEM) electron microscopy. The elemental composition was investigated using energy dispersive spectrometry (EDS). The cytotoxicity and oxidative/nitrosative stress (intracellular reactive oxygen species (ROS) and nitric oxide (NO) release) induced by the studied microparticles in HepG2, SH-SY5Y and 3T3-L1 cell cultures were determined using the MIT, DCF-DA (2 ',7 '-dichlorfluorescein-diacetate) and Griess methods respectively. Depending on the cell type and gamma-BTO concentration, results showed only weak cytotoxic effects after 24 h of gamma-BTO exposure and cell proliferation effects for longer treatment times. Only reduced NO release increases (corresponding to high gamma-BTO concentrations) were detected in case of SH-SY5Y and 3T3-L1 cells. The intracellular ROS production (higher for HepG2 cells) appeared inversely proportional to the gamma-BTO concentration. The obtained results indicated a promising in vitro biocompatibility of gamma-BTO and encourage further studies regarding its potential for biomedical applications. (C) 2014 Elsevier Ltd. All rights reserved.

469. Pulse annealing electron paramagnetic resonance with probing transition ions

Authors: Nistor, SV; Stefan, M; Ghica, D

Published: NOV 2014, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 118, 1031, DOI: 10.1007/s10973-014-3743-1

The analysis of the sequence of electron paramagnetic resonance (EPR) spectra of trace amounts of substitutional probing paramagnetic ions incorporated in (nano)crystalline samples submitted to isothermal and isochronal pulse annealing treatments can offer a wealth of information on the thermally induced compositional and structural changes of the host material. The potential of this new thermal analysis method is illustrated here with results of such investigations on the thermal decomposition of crystalline zinc hydroxide (Zn(OH)(2)) and anhydrous zinc carbonate basic (Zn-5(CO3)(2)(OH)(6)) precursors containing trace amounts of substitutional Mn2+ probing ions into nanostructured zinc oxide-ZnO. The quantitative analysis of the sequence of isochronal pulse annealing EPR spectra could provide, besides the thermal decomposition curves of the two precursors, additional information about the structure of the resulting nanostructured ZnO, some of it hard to get by standard structural diffraction techniques. The analysis of both isochronal and isothermal pulse annealing EPR data was further used to investigate the crystallization mechanism of the initially formed nanostructured disordered ZnO and to quantitatively describe the further growth of the resulting ZnO nanocrystals with the increasing annealing temperature and duration.

470. Strain-induced modification of trap parameters due to the stopped ions in Bi-irradiated Si

Authors: Ciurea, ML; Lazanu, S; Slav, A; Palade, C

Published: NOV 2014, EPL, 108, DOI: 10.1209/0295-5075/108/36004

By implanting Bi in Si, a strong strain field due to the bigger atomic mass and size of stopped Bi ions than Si lattice ones is produced, together with irradiation defects. The controlled doping of Si with Bi leads to modern applications such as quantum information processing. Here we show that the parameters of trapping centres are modified under the strain field. In the literature there are no reports on this subject. We irradiated Si wafers with Bi6+ ions of 28MeV kinetic energy, 3 degrees off [100] axis orientation. The depth distributions of stopped ions and of primary defects were simulated. The traps produced by irradiation were investigated using the thermally stimulated currents method without bias. We recorded and modelled the discharge current curves. The strain field was modelled as a permanent and temperature-independent electric field. The traps of V-2, VO/CiCs, and CiOi and other two not assigned were evidenced. We have found that all trapping levels are broadened, and all capture cross-sections are temperature dependent which we attribute to the strong strain field produced by Bi. These results are important and must be taken into account in designing and manufacturing microelectronic devices incorporating strain, including the topical spin qubit ones. Copyright (C) EPLA, 2014