National Institute Of Materials Physics - Romania

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873 articles found

731. Photoluminescence properties of composites based on zinc oxyde and single-walled carbon nanotubes

Authors: Baibarac, M; Baltog, I; Husanu, M; Velula, T; Bucur, C; Mihut, L; Preda, N

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 293, DOI:

Photoluminescence (PL) properties of the composites based on zinc oxide (ZnO) and single-walled carbon nanotubes (SWNTs) prepared by hydrothermal synthesis are studied in this paper. The emission and excitation spectra of nanometric ZnO powder are dramatically influenced by the adsorption of different molecules coming from the environment. Therefore, a special attention is given to reveal the influences of adsorption/de-sorption process on photoluminescence properties of zinc oxide nanoparticles. A quenching effect of the intrinsic PL is observed regularly when the ZnO is synthesized in the presence of SWNTs, i.e. when a ZnO/SWNTs composite is formed. A distinct feature of the ZnO/SWNTs composite, is an emission band with a maximum at 405-450 nm.

732. Raman and photoluminescence studies on intercalated lead iodide with pyridine and iodine

Authors: Preda, N; Mihut, L; Baibarac, M; Husanu, M; Bucur, C; Baltog, I

Published: FEB 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 322, DOI:

Intercalated PbI2 compounds were prepared by exposing crystalline films and crystalline powders of lead iodide to pyridine or iodine vapor at room temperature. Correlated studies of optical absorption, Raman scattering and low temperature photoluminescence (PL) reveal different properties in comparison with those of pure crystalline PbI2 powder. Depending of the nature of intercalated molecules (organic or inorganic) the basic semiconducting properties of PbI2 are dramatically modified. The main signature of iodine intercalated PbI2 consists in a luminescence band peaking at 2.24 eV appearing at 77 K under 350 nm excitation light. In the case of pyridine intercalated PbI2 a new intense band at about 3.3 eV in the absorption spectrum is observed. The the PL spectra of pyridine intercalated PbI2 at 77 K change substantially when the excitation wavelength. The Raman spectra confirm the presence of pyridine between the PbI2 layers.

733. FexOy nanoparticles embedded in sol-gel vitreous silica. The effect of the catalyst nature

Authors: Raileanu, M; Crisan, M; Braileanu, A; Dragan, N; Zaharescu, M; Stan, C; Predoi, D; Kuncser, V; Marinescu, VE; Hodorogea, SM

Published: JAN 15 2008, JOURNAL OF NON-CRYSTALLINE SOLIDS, 354, 631, DOI: 10.1016/j.jnoncrysol.2007.07.070

This work reports on recently investigated structural and magnetic properties of three FexOy-SiO2 nanocomposites prepared by the alkoxide route of the sol-gel method. Depending on the presence or absence of catalyst and on its nature (acidic or basic), important differences among the samples have been observed from the point of view of their structure and properties. (c) 2007 Elsevier B.V. All rights reserved.

734. Osteoblast interaction with iron oxide nanoparticles coated with dextrin in cell culture

Authors: Predoi, D; Vatasescu-Balcan, RA

Published: JAN 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 157, DOI:

The iron oxide nanoparticles and iron oxide nanoparticles coated with dextrin have been synthesized using aqueous solution of ferric and ferrous ions and mixtures of dextrin with sodium salt. The size of the iron-oxide nanoparticles are controlled by the concentration of sodium salt in the medium. An average size of iron oxide and iron oxide coated with dextrin was found by transmission electron microscopie (TEM). The iron oxide nanoparticles are nearly spherical with an average diameter of about 8.0 +/- 1 nm. The iron oxide nanoparticles coated with dextrin appear to cluster-like aggregates. The average diameter of these nanoparticles is about 6 1 nm. The attachment of the dextrin on the particle surface was confirmed by FTIR spectroscopy and scanning electron microscopy (SEM). Osteoblasts used to determine the cell proliferation, viability and citotoxicity interaction with iron oxide nanoparticles coated with dextrin has been obtained from the upper part of the patient's femur.

735. Influence of polyvinylpyrolidone as an additive in electrochemical preparation of ZnO nanowires and nanostructured thin films

Authors: Enculescu, I; Matei, E; Sima, M; Enculescu, M; Sima, M; Ghica, C

Published: MAR-APR 2008, SURFACE AND INTERFACE ANALYSIS, 40, 560, DOI: 10.1002/sia.2749

Preparation of ZnO in different nano-morphological forms became a hot topic during the last few years. This tendency was motivated by the wide field of potential applications ranging from optics to electronics and spintronics. In the present work, we deal with the preparation of ZnO nanowires and nanostructured thin films using electrochemical deposition. ZnO nanowires were grown using the template approach, namely by replicating the nanopores of polycarbonate ion track membranes. The method yields uniform arrays of nanowires with the morphology controlled by the shape and size of the templates pores. Adding polyvinylpyrolidone as an additive in the growth bath became a necessity due to the fact that polycarbonate ion track membranes are usually hydrophobic and thus filling of the nanopores with the growth electrolyte is rather difficult. In order to better understand the influence of the additive on the electrochemical deposition of such nanostructures, similar experiments were performed for the deposition of ZnO thin films. Scanning electron microscopy, X-ray diffraction and optical spectroscopy measurements were performed for characterization of the deposited structures. Copyright (c) 2008 John Wiley & Sons, Ltd.

736. PbSe nanowires grown by the template method

Authors: Sima, M; Enculescu, I; Sima, M

Published: 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 70, DOI:

PbSe nanowires were prepared using the template method. Polycarbonate ion track membranes with pore sizes ranging between 50 nm and 1.5 mu m were used as templates. The deposition of PbSe in the pores of the template was performed electrochemically. The influence of the deposition potential and membrane porosity on the morphology and composition of the prepared nanowires was studied. The composition of the wires has been determined by EDX measurements for different potentials. Scanning electron microscopy revealed the morphology of the deposited nanowires. X ray diffraction has been used for structural measurements.

737. The synthesis and characterization of poly vinyl chloride chemically modified with C-60

Authors: Rusen, E; Marculescu, B; Butac, L; Preda, N; Mihut, L

Published: MAY-JUN 2008, FULLERENES NANOTUBES AND CARBON NANOSTRUCTURES, 16, 185, DOI: 10.1080/15363830802042563

The fullerenated poly vinyl chloride was synthesized by the addition reaction of azido-substituted poly vinyl chloride with C-60. Structural characterization carried out using Raman and FTIR spectroscopy confirm the presence Of C-60 chemically bound in the new compound. Also, the photoluminescence properties of fullerenated poly vinyl chloride are considerably changed from those Of C-60.

738. EIS studies of electrodeposition process of manganese and copper doped ZnO wires

Authors: Sima, M; Enculescu, I; Sima, M; Vasile, E; Visan, T

Published: MAR-APR 2008, SURFACE AND INTERFACE ANALYSIS, 40, 565, DOI: 10.1002/sia.2721

Electrodeposition of manganese- and copper-doped ZnO wires into polycarbonate membranes, from an aqueous solution containing 0.05 mol dm(-3) Zn(NO3)(2)+ 0.01 mol dm(-3) Mn(NO3)(2)+ 0.0005 mol dm(-3) Cu(NO3)(2)+ 0.0075 mol dm(-3) lactic acid, pH = 4.7 was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). The equivalent electrical circuits for fitting experimental results were similar to those for characterization of metal/polymer coating systems. impedance data and voltarnmetric curves showed that an increase of local pH due to reduction process of nitrate ions induces the co-precipitations of metal ions in the proximity of electrode as oxides. Copyright (c) 2008 John Wiley & Sons, Ltd.

739. Characteristics of hydroxyapatite thin films

Authors: Predoi, D; Ghita, RV; Ungureanu, F; Negrila, CC; Vatasescu-Balcan, RA; Costache, M

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3831, DOI:

Thin films of hydroxyapatite (HAp) (Ca-10(PO4)(6)(OH)(2)) were vacuum deposited on different substrates (quartz and silver) in connection with biomedical applications. Characteristics of thin films were putted into evidence by (SEM) and (XPS) analysis. The FT-IR spectroscopy was performed on hydroxyapatite powder and thin films deposited on quartz. The deposition of HAp thin films presents good surface quality as a smooth and an adherent layer. The biological tests confirm the characteristics of these thin films as bioactive materials. The hydroxyapatite thin films supports have a micro cell configuration that allows them to be used for obtaining medical biocompatible supports.

740. Hydroxyapatite-iron oxide bioceramic prepared using nano-size powders

Authors: Predoi, D; Barsan, M; Andronescu, E; Vatasescu-Balcan, RA; Costache, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3613, DOI:

The hydroxyapatite (HAp) is an important material for orthopedics and dentistry applications. In the present study a simple method was tried for added the iron oxide nanoparticles into HAp so as to establish and induce a biocompatibility. In the research the mechanism of the coated of iron oxide with HAp would also be described by the analysis of X-ray diffractometer, scanning electron microscope and Fourier transformation infrared. Osteoblast cells were permanent monitored to detect any possible influence due to samples that might alter the cell growth, viability and proliferation.