National Institute Of Materials Physics - Romania

Publications

860 articles found

471. Analysis of bimodal thermally-induced denaturation of type I collagen extracted from calfskin

Authors: Staicu, T; Circu, V; Ionita, G; Ghica, C; Popa, VT; Micutz, M

Published: 2015, RSC ADVANCES, 5, 38406, DOI: 10.1039/c5ra02708j

The most widely occurring collagen in the extracellular matrix of the mammalian tissues - type I collagen has attracted huge interest from both theoretical and practical points of view. The results presented herein are mainly confined to a study of the thermal stability of type I collagen (CI) extracted from calfskin in acidic solutions (10(-2) M HCl). A two-step process associated with the heat-induced denaturation of CI was revealed by using ultra sensitive differential scanning calorimetry. The minor endothermic transition (peak temperatures of about 30.5-30.8 degrees C) has been assigned to the defibrillation of small supramolecular CI assemblies (occurring in solution) while the major endothermic transition (about 34.8-35.0 degrees C) has been ascribed to denaturation of CI, consisting of a complete unfolding of the native triple-helical conformation of the collagen molecule. The calorimetric data were supported by information obtained from capillary viscometry performed on the same solutions. The native state of CI (molecular integrity and triple-helical conformation) for all the systems studied in this paper was confirmed by transmission electron microscopy, ultraviolet circular dichroism and capillary viscometry. At the same time, based on the sodium dodecyl sulphate-polyacrylamide gel electrophoresis and an appropriate image processing of the corresponding electropherogram, a certain degree of intramolecular crosslinking of CI was detected, mainly between alpha 1 and alpha 2 chains of the collagen triple-helix. Such a feature seems to be caused by both the nature of the extraction procedure and the storage conditions.

472. STRAIN DRIVEN CHANGES OF DEFECT PARAMETERS IN HEAVY ION IMPLANTED Si

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

Published: OCT-DEC 2015, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 10, 1381, DOI:

We analyse the influence of the strain field on the parameters of trapping centres. The system under study is high resistivity Si implanted with Bi6+ and I6+ ions respectively, of 28 MeV kinetic energy, 3(O) off <100> axis orientation and 5x10(11) ions/cm(2) fluence. The strain field is the consequence of size and mass difference of the irradiation ions in respect to the atoms of the lattice, and the defects are produced during the slowing-down of ions, as a result of the energy transfer from the ion to Si atoms. These results are of interest for the design and manufacturing of microelectronic devices incorporating strain, particularly for quantum computers with qubits based on the interaction of electronic and nuclear spins of group-V donors in Si.

473. Nanostructured Titanium Doped Iron Oxide Photoelectrodes for Water Splitting

Authors: Miclea, C; Amarande, L; Cioangher, MC; Miclea, CT; Mihailescu, M; Radu, C; Ivanov, A

Published: 2015, ROMANIAN JOURNAL OF INFORMATION SCIENCE AND TECHNOLOGY, 18, 105, DOI:

Water splitting by means of semiconducting photoelectrodes and solar light represents a promising alternative to conventional fossil fuel economy. In this process the photoactive electrode absorb sunlight directly thus initiating the photochemical reaction which create excess electrons in the conduction band of the semiconducting electrode. Titanium doped iron oxide seems to be a promising semiconducting material for photoelectrodes. Consequently, we investigated the effect of Ti doping on the structure, electrical and photoelectrochemical properties alpha-Fe2O3. The Ti doped alpha-Fe2O3 were prepared by a slightly modified mixed oxide route, consisting in a prolonged mixing of the raw materials in a high energy planetary ball mill until the particles decreased to the nanometric sizes. Optimum results were obtained for samples doped with 5 at. % titanium and sintered at 1200 degrees C. Photocurrents as high as 8.4 mA/cm(2), for illumination from a 300 W xenon lamp, were recorded for such samples. It is hoped that such photoelectrodes show promise for water splitting.

474. 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

475. 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.

476. 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.

477. 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.

478. 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.

479. 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.

480. 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).