National Institute Of Materials Physics - Romania

Publications

860 articles found

521. Anti-biofilm activity of maghemite nanoparticles coated with dextran

Authors: Ciobanu, CS; Iconaru, SL; Predoi, D

Published: JUL 2013, FEBS JOURNAL, 280, 359, DOI:

522. Antimicrobial activity of silver doped hydroxyapaptite thin films

Authors: Ciobanu, CS; Iconaru, SL; Chapon, P; Predoi, D

Published: JUL 2013, FEBS JOURNAL, 280, 360, DOI:

523. Toxicological aspects of PANC-1 cells exposure to iron oxide dextran-covered nanoparticles

Authors: Radu, M; Burtea, C; Predoi, D; Muller, R; Dinischiotu, A

Published: JUL 2013, FEBS JOURNAL, 280, 216, DOI:

524. Optical manipulation of complex molecular systems by high density green photons: experimental and theoretical evidence

Authors: Comorosan, S; Polosan, S; Popescu, I; Stamatin, I; Ionescu, E; Avramescu, S; Cune, LC; Apostol, M

Published: MAY 2013, EUROPEAN PHYSICAL JOURNAL B, 86, DOI: 10.1140/epjb/e2013-40049-8

The recent revolution in modern optical techniques revealed that light interaction with matter generates a force, known as optical force, which produces material properties known in physics as optical matter. The basic technique of the domain uses forces exerted by a strongly focused beam of light to trap small objects and subsequently to manipulate their local structures. The purpose of this paper is to develop an alternative approach, using irradiations with high-density-green-photons, which induce electric dipoles by polarization effects. The materials used for the experiments were long carbon chains which represent the framework of biological macromolecules. The physical techniques used to reveal the locally induced molecular arrangements were: dynamic viscosity, zeta potential, chemiluminescence, liquid chromatography; mass spectrometry, and Raman and infrared spectroscopy. The principal result of our experiments was the detection of different molecular arrangements within the mixture of alkane chains, generated by our optical manipulations. This induced "optical matter" displayed two material properties: antioxidant effects and large molecular aggregation effects. In order to bring the experimental results in relation with theory, we developed a physical model and the interacting force between polarizable bodies was computed. By numerical calculations stable structures for N = 6 and N = 8 particles were obtained.

525. MgB2 with Addition of Bi2O3 Obtained by Spark Plasma Sintering Technique

Authors: Burdusel, M; Aldica, G; Popa, S; Enculescu, M; Pasuk, I; Badica, P

Published: MAY 2013, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 26, 1556, DOI: 10.1007/s10948-012-2015-1

Bi2O3 and Bi-metal powders were mixed with MgB2 powder. Starting compositions were (MgB2)(Bi2O3) x, x = 0.0025, 0.005, 0.015, and (MgB2)(Bi)(y), y = 0.01. Mixtures were processed by Spark Plasma Sintering (SPS) technique. As obtained composite samples show high density, above 94 % of the theoretical density. Samples with Bi2O3 for x = 0.0025 and 0.005 show higher critical current densities, J(c), at high fields and at 20 K than for the pristine sample. Their irreversibility field, H-irr, is also higher. On the other hand, sample added with Bi-metal has lower J(c) and H-irr at any temperature than for the pristine sample.

526. Single bath electrodeposition of samarium oxide/zinc oxide nanostructured films with intense, broad luminescence

Authors: Matei, E; Enculescu, M; Enculescu, I

Published: APR 15 2013, ELECTROCHIMICA ACTA, 95, 178, DOI: 10.1016/j.electacta.2013.02.044

Electrochemical deposition from a solution containing zinc and samarium ions, leads to a samarium oxide/zinc oxide sandwich-like structure with an intense, visible, broad luminescence peak centered at 550 nm. The successive deposition of the two materials is related to the bath composition and overpotential, taking place for values higher than a certain threshold. The zinc oxide film, first one to be deposited, presents typical hexagonal prism morphology while samaria coating films present a porous, nanowall like structure. The photoluminescence emission is at least 10 times more intense than in the case of typical electrodeposited ZnO films of similar thickness and does not appear in Sm2O3 films electrodeposited from solutions containing only Sm ions. Samples prepared in different conditions were characterized from the point of view of composition, structure, morphology and optical properties. The characteristics of the emission spectra of the films make them interesting for solid state lightning applications. (c) 2013 Elsevier Ltd. All rights reserved.

527. Structural properties of silver doped hydroxyapatite and their biocompatibility

Authors: Ciobanu, CS; Iconaru, SL; Pasuk, I; Vasile, BS; Lupu, AR; Hermenean, A; Dinischiotu, A; Predoi, D

Published: APR 1 2013, MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 33, 1402, DOI: 10.1016/j.msec.2012.12.042

The aim of this study was to obtain a novel hydroxyapatite-based material with high biocompatibility. The structural properties of the samples were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The X-ray diffraction studies revealed the characteristic peaks of hydroxyapatite in each sample. Other phases or impurities were not observed. The scanning electron microscopy observations suggest that the doping components have no influence on the surface morphology of the samples, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O) and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) and X-ray Photoelectron Spectroscopy analyses. Nanocrystalline silver doped HAp stimulated viability and potentiated the activation of murine macrophages. (C) 2012 Elsevier B.V. All rights reserved.

528. Structural Characterization and Magnetic Properties of Iron Oxides Biological Polymers

Authors: Iconaru, SL; Ciobanu, CS; Le Coustumer, P; Predoi, D

Published: APR 2013, JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, 26, 855, DOI: 10.1007/s10948-012-1855-z

Iron oxide nanoparticles (IONs) coated with different biological (dextran, sucrose) polymers have been synthesized by the coprecipitation method. Biological polymers coated iron oxide nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). Zero field cooled and field cooled magnetizations measurements are also reported. We present a preliminary study of the influence of biological polymer on the interaction effects in powders. The temperature, T (max), of the maximum, increased from 25 K (dextran) to 52 K (sucrose). These values are due to the decrease of interparticle interactions, mainly as a result of the interparticle distance increase.

529. Spectral and transport properties of the two-dimensional Lieb lattice

Authors: Nita, M; Ostahie, B; Aldea, A

Published: MAR 29 2013, PHYSICAL REVIEW B, 87, DOI: 10.1103/PhysRevB.87.125428

The specific topology of the line-centered square lattice (known also as the Lieb lattice) induces remarkable spectral properties such as the macroscopically degenerated zero-energy flat band, the Dirac cone in the low-energy spectrum, and the peculiar Hofstadter-type spectrum in a magnetic field. We study here the properties of the finite Lieb lattice with periodic and vanishing boundary conditions. We investigate the behavior of the flat band induced by disorder and external magnetic and electric fields. We show that in the confined Lieb plaquette threaded by a perpendicular magnetic flux there are edge states with nontrivial behavior. The specific class of twisted edge states, which have alternating chirality, are sensitive to disorder and do not support integer quantum Hall effect (IQHE), but contribute to the longitudinal resistance. The symmetry of the transmittance matrix in the energy range where these states are located is revealed. The diamagnetic moments of the bulk and edge states in the Dirac-Landau domain, and also of the flat states in crossed magnetic and electric fields are shown. DOI: 10.1103/PhysRevB.87.125428

530. Te and SiC co-doped MgB2 obtained by an ex situ spark plasma sintering technique

Authors: Aldica, G; Popa, S; Enculescu, M; Badica, P

Published: MAR 2013, SCRIPTA MATERIALIA, 68, 431, DOI: 10.1016/j.scriptamat.2012.11.011

Ex situ spark plasma sintering was used to obtain dense MgB2 co-doped with SiC and Te. The composition (MgB2) + (SiC)(0.025) + Te-0.01 shows critical current densities J(c)(20 K, 5 T) of 3.5 x 10(2) A cm(-2) and J(c)(5 K, 9 T) of 2 x 10(3) A cm(-2). These values are higher than for pristine samples or those separately doped with Te or SiC. They are also comparable at high fields and temperatures with the best reported values for the co-doped MgB2 bulks produced by conventional in situ methods. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.