National Institute Of Materials Physics - Romania

Publications

5781 articles found

2371. LOW TEMPERATURE TEM INVESTIGATION OF ELECTRON BEAM INDUCED DECOMPOSITION OF NANOCRYSTALLINE HYDROZINCITE INTO ZnO

Authors: Nistor, LC; Nistor, SV; Ghica, D

Published: 2013, ROMANIAN REPORTS IN PHYSICS, 65, 192, DOI:

The fast decomposition of hydrozincite [Zn-5(CO3)(2)(OH)(6)] into ZnO observed in the transmission electron microscope could be slowed down and investigated in situ by operating the microscope at very low electron beam current densities and cooling the specimen down to -160 degrees C. Thus, it was possible to observe and pursue the distinct structural steps of the disruption of the hydrozincite lattice due to the energetic emission of H2O and CO2 gases. The initially formed disordered ZnO phase was found to further crystalize resulting in a mesoporous structure of small ZnO nanocrystals.

2372. MAPLE DEPOSITION OF PLGA MICRO- AND NANOPARTICLES EMBEDDED INTO POLYMERIC COATINGS

Authors: Socol, G; Preda, N; Socol, M; Sima, L; Luculescu, CR; Sima, F; Miroiu, M; Axente, E; Visan, A; Stefan, N; Cristescu, R; Dorcioman, G; Stanculescu, A; Radulescu, L; Mihailescu, IN

Published: APR-JUN 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 630, DOI:

We report the film deposition of Poly(D, L-lactide-co-glycolide) (PLGA) particle systems by matrix assisted pulsed laser evaporation (MAPLE) technique. PLGA+polyvinyl alcohol (PVA), PLGA+PVA+ bovine serum albumin (BSA) and PLGA+PVA+chitosan (CH) nanoparticles were prepared by an oil-in-water emulsion-diffusion-evaporation method. The average diameter of PLGA particles was between 180-250 nm. The coatings were obtained by laser evaporation of frozen targets prepared by mixing appropriate PLGA aqueous suspensions and dimethyl sulfoxide (DMSO) in three ratios. Depending on the DMSO content, we deposited PLGA particles embedded into polymeric layer mainly obtained due to the entirely or partially dissolving of nanoparticles into the initial solution. In vitro results showed that the distribution and morphology of osteoblast-like SaOs-2 cells on some PLGA particle coatings were similar with that of the positive control. The purpose of this study was to develop layers of PLGA particles for local controlled drug delivery.

2373. Evolution of the Levels of Free Radicals Generated on Wheat Flour and Wheat Bran by Electron Beam

Authors: Brasoveanu, M; Craciun, G; Manaila, E; Ighigeanu, D; Nemtanu, MR; Grecu, MN

Published: SEP-OCT 2013, CEREAL CHEMISTRY, 90, 473, DOI: 10.1094/CCHEM-10-12-0131-R

This paper presents the experimental data regarding the levels of free radicals investigated by electron spin resonance (ESR) on wheat flour and wheat bran exposed to an electron beam. Samples were irradiated with an electron linear accelerator of 6 MeV and then stored at room temperature in air. ESR spectra of the samples indicated presence of free radicals induced by electron beam. Three types of free radicals have been detected in wheat flour, and signals typical for cellulose-like radicals have been noticed for wheat bran, their concentration increasing with the irradiation dose. The postirradiation storage of both sample types caused radical decay with a two-step pattern associated with fast decay of short-life radicals followed by slow reduction of long-life radicals. However, in the first step, the irradiated wheat bran exhibited more rapid decay of radicals than irradiated flour owing to their different complex matrixes, which led to paramagnetic structures of different origin after exposure to an electron beam. The ESR technique allows the detection of free radicals induced in wheat flour and bran by electron beam for a limited period after irradiation that could be shorter than the shelf life of the products.

2374. Ru-based magnetic nanoparticles (MNP) for succinic acid synthesis from levulinic acid

Authors: Podolean, L; Kuncser, V; Gheorghe, N; Macovei, D; Parvulescu, VI; Coman, SM

Published: 2013, GREEN CHEMISTRY, 15, 3082, DOI: 10.1039/c3gc41120f

Ru(III)/functionalized silica-coated magnetic nanoparticles (Ru(III)-MNP) were proven to be a highly active, selective and easily recoverable catalyst for the oxidation of levulinic acid to succinic acid under green conditions.

2375. Physico-chemical and antibacterial studies on silver doped nano-hydroxyapatite

Authors: Ciobanu, CS; Andronescu, E; Prodan, AM; Pall, L; Costescu, A; Le Coustumer, P; Huneau, F; Marutescu, L; Ene, NI; Trusca, R; Barna, ES; Iconaru, SL

Published: JUL-AUG 2013, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 15, 922, DOI:

In this paper we show that preparation of Ag doped hydroxyapatite by an adapted co-precipitation method at 100 C has several advantages over other techniques. Specifically, it can generate highly crystalline nanopowder Ag:HAp which could be used for implantable medical devices. The XRD of HAp (x(Ag) = 0) and Ag:HAp (x(Ag) = 0.05, and x(Ag) = 0.4) also demonstrates that powders obtained by co-precipitation at 100 C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The SEM results suggested that Ag+ doping had little influence on the morphology and dimension of the samples. It can be seen that all the samples consist of elipsoidal particles. The antibactericidal activity of Ag:HAp-NPs with x(Ag) = 0, x(Ag) = 0.05, and x(Ag) = 0.4 on Bacilus and E.coli ESBL 1576 were presented. The Ag:HAp-NPs with x(Ag) = 0.05, and x(Ag) = 0.4 inhibited the biofilm development both by the gram-positive (Staphylococcus aureus 0364) and the gram-negative (Providencia stuartii 1116) strains. On the other hand, our studies have shown that Ag:HAp with x(Ag) = 0 had no antibacterial activity against gram-positive and gram-negative bacteria.

2376. EFFECT OF CNTS AND METAL-PHTHALOCYANINES ADDING ON THE PHOTO-ELECTRICAL BEHAVIOR OF THE PHOTOVOLTAIC STRUCTURES BASED ON POLYMERIC BLENDS

Authors: Baschir, L; Antohe, S; Radu, A; Constantineanu, R; Iftimie, S; Simandan, ID; Popescu, M

Published: OCT-DEC 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 1651, DOI:

Photovoltaic structures based on P3HT:PCBM(1:0.8) mixed with barium stearate (BS), carbon nanotubes (CNT) and different phtalocyanines (Coperphthalocyanine (CuPc), Zincphthalocyanine (ZnPc) and Magnesiumphthalocyanine (MgPc) were successfully prepared by spin-coating technique onto optical glass substrates covered with ITO and PEDOT:PSS. The goal of this study was to investigate the influence of barium stearate, carbon nanotubes and different small molecules of dyes mixed with the P3HT:PCBM "conventional" blend on the photovoltaic response of the "custom" obtained structures. The current-voltage characteristics were drawn in the dark and illumination and the external quantum efficiency was determined for each from the prepared samples.

2377. Effect of Bismuth Irradiation on Crystalline Silicon

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

Published: 2013, 2013 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1-2, 76, DOI:

N-type silicon single crystals with resistivity higher than 8000 Omega cm were irradiated with ions of Bi6+, of 28 MeV kinetic energy. At this energy, the ions are stopped into the wafer. Being much heavier and bigger than the host atoms, they produce major disturbances into the lattice. On the other hand, the produced collision cascade is the source of lattice defects which act as traps. We investigated them using the method of thermally stimulated currents without applied bias. The results are compared with those obtained from the analysis of silicon irradiated with I6+ ions.

2378. THE INFLUENCE OF HOST BONE SUBSTRATE IN TITANIUM MESH CRANIOPLASTY

Authors: Chiriac, A; Stan, GE; Iliescu, B; Poeata, I

Published: APR-JUN 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, 735, DOI:

Reconstructive surgery of bone defects in the calvarium makes use of a multitude of biological and artificial materials. Due to the increased number of such medical casuistry in the recent years, a special attention was dedicated to the biocompatibility and osteointegrative properties of various types of biomaterials. Titanium emerged to be a promising cranioplasty material due to its excellent mechanical properties and biocompatibility. However, the way the host calvarial bone reacts to the titanium implant has not been fully understood. Here, we evaluate the influence of cranial bone substrate on the osteoconduction and osseointegration of titanium mesh implants. The pattern of bone tissue reaction in the areas of contact with metallic implant is analyzed by means of bone density measurements on the computer tomography images. Twenty-eight patients underwent cranioplasty with titanium mesh implants for bone cranial defects due to different aetiology. With the aid of visual analogue scales, the patients' status (osteointegration degree, comfort and cosmetics) was evaluated after 3 - 14 months since surgery (implantation).

2379. Fabrication, Characterization, and Antimicrobial Activity, Evaluation of Low Silver Concentrations in Silver-Doped Hydroxyapatite Nanoparticles

Authors: Costescu, A; Ciobanu, CS; Iconaru, SL; Ghita, RV; Chifiriuc, CM; Marutescu, LG; Predoi, D

Published: 2013, JOURNAL OF NANOMATERIALS, 2013, DOI: 10.1155/2013/194854

The aim of this study was the evaluation of (Ca10-x Ag-x)(PO4)(6) (OH)(2) nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years as a major public health problem worldwide. In this paper, we report a comparison of the antimicrobial activity of low concentrations silver-doped hydroxyapatite nanoparticles. Thesilver-doped nanocrystalline hydroxyapatite powder was synthesized at 100 degrees C indeionised water. The as-prepared Ag: Hap nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, and FT-Raman spectroscopy. X-ray diffraction (XRD) studies demonstrate that powders obtained by coprecipitation at 100 degrees C exhibit the apatite characteristics with good crystal structure, without any new phase or impurities found. FT-IR and FT-Raman spectroscopy revealed the presence of the various vibrational modes corresponding to phosphates and hydroxyl groups and the absence of any band characteristic to silver. The specific microbiological assays demonstrated that Ag: HAp-NPs exhibited antimicrobial features, but interacted differently with the Gram-positive, Gram-negative bacterial and fungal tested strains.

2380. SOL-GEL HYBRID NANOCOMPOSITES WITH OXIDE NANOPARTICLES

Authors: Predoana, L; Gartner, M; Teodorescu, VS; Nicolescu, M; Anastasescu, M; Zaharescu, M

Published: FEB-MAR 2013, REVUE ROUMAINE DE CHIMIE, 58, 249, DOI:

In the present work the influence of the method of preparation on the characteristics of sol-gel hybrid nanocomposites with oxide nanoparticles was studied. The chosen system consists of a SiO2 matrix based on methyltriethoxysilane (MTEOS) and laboratory made TiO2:CeO2 (4:1) nanopowder. The doping of the matrix was realized either by dispersion of previously prepared binary nanopowder in the matrix solution or by in situ generation of the TiO2-CeO2 nanoparticles during the matrix hydrolysis-condensation processes. Films were deposited on silicon wafer and glass substrates by dip-coating method and were characterized as prepared and annealed at 120 degrees C. The optical and morphological properties were determined by spectroellipsometry (SE), scanning electron microscopy (SEM), atomic force microscopy (AFM), their structural characterization was realized by IR spectroscopy and the thermal behavior was determined by thermogravimetric and differential-thermal analysis (TG/DTA). All characterization methods have shown that by the two preparation routes materials with different characteristics were obtained.