National Institute Of Materials Physics - Romania

Publications

5714 articles found

2301. Study on Europium-Doped Hydroxyapatite Nanoparticles by Fourier Transform Infrared Spectroscopy and Their Antimicrobial Properties

Authors: Iconaru, SL; Motelica-Heino, M; Predoi, D

Published: 2013, JOURNAL OF SPECTROSCOPY, 2013, DOI: 10.1155/2013/284285

Fourier transform infrared spectroscopy (FT-IR) analysis was conducted on europium-doped hydroxyapatite, Ca10-xEux (PO4)(6)(OH)(2) nanocrystalline powders (Eu:HAp) with 0 < x(Eu) < 0.2. Antimicrobial studies were also performed for the first time on Eu: HAp. The antimicrobial properties of Eu: HAp nanoparticles with 0 < x(Eu) <= 0.2 on Gram-negative (E. coli ATCC 25922, Pseudomonas aeruginosa 1397) andGram-positive (Staphylococcus aureus 0364, Enterococcus faecalis ATCC 29212) bacteria systems and a species of fungus (Candida albicans ATCC 10231) were reported. Our study demonstrates that the antimicrobial activity of Eu: HAp nanoparticles is dependent on the europium concentration.

2302. Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

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

Published: 2013, NANOSCALE, 5, 2702, DOI: 10.1039/c3nr33506b

The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(I) catalyzed << click >> chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose.

2303. FERROMAGNETISM AND REACTIVITY OF FE DEPOSITED ON GaAs(001) BY MAGNETRON SPUTTERING

Authors: Vasilache, V; Lungu, GA; Logofatu, C; Medianu, RV; Teodorescu, CM

Published: JAN-MAR 2013, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 8, DOI:

Iron layers are grown on GaAs(001) single crystal wavers by magnetron sputtering and characterized by magneto-optical Kerr effect (MOKE) and X-ray photoelectron spectroscopy (XPS). It is found that all deposited layers, starting with 2 nm thickness, are ferromagnetic at room temperature with a relatively high coercitive field (500 to 750 Oe). The average Fe magnetic moment is larger for the thinnest Fe film deposited, of about 0.52 Bohr magnetons per Fe atom. The average Fe magnetic moment decreases to 0.26 Bohr magnetons, then to 0.17 Bohr magnetons for 4 and 8 nm, resepctively. XPS evidenced that the outermost Fe layers are oxidized; however, the thinnest Fe film presented the lower oxidation state. We may connect this reaction with Fe-As bonds, resulting in a nonferromagnetic interface compound. Indeed, XPS depth profiling of the 8 nm sample evidenced the formation of a very thin (about 1.4 nm) Fe metal layer immediately at the interface with GaAs. In this layer, Fe may reach an atomic magnetic moment as high as 1 Bohr magneton.

2304. 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.

2305. 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.

2306. 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.

2307. 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.

2308. 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.

2309. 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.

2310. 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.