National Institute Of Materials Physics - Romania

Publications

918 articles found

681. Physico-chemical Properties of Iron-oxide-dextrin Thin Films

Authors: Ciobanu, CS; Andronescu, E; Pall, L; Iconaru, SL; Gyorgy, E; Predoi, D

Published: DEC 2010, REVISTA DE CHIMIE, 61, 1211, DOI:

Iron oxide nanoparticles were synthesized in the presence of dextrin. The adsorption process of different dextrin molecules onto the surface of in water dispersed iron-oxide nanoparticles has been investigated to optimize the preparation of iron oxide magnetic fluids. An average iron oxide core size of 8 nm was found by transmission electron microscopy (TEM) for the samples. Scanning electron microscopy (SEM) micro-structural studies revealed a spherical shape of the particles. X-ray phase analysis revealed spinel structure of the iron oxide particles. The attachment of the dextrin on the particle surface was investigated by FTIR spectrometry. The dextrin coated iron oxide nanoparticles were used as targets in Pulsed Laser Deposition (PLD) experiments for thin films synthesis.

682. MAPLE preparation and characterization of benzil thin films

Authors: Socol, M; Socol, G; Rasoga, O; Stanculescu, F; Stanculescu, A; Mihailescu, I; Ionita, I; Preda, N; Enculescu, M; Antohe, S

Published: NOV 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1806, DOI:

In this study the Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique was used to prepare thin films from a low melting point (< 100 degrees C) organic compound (benzil). Optical properties of the films have been investigated by UV-VIS, FTIR and PL spectroscopy. Details about crystallinity were obtained by XRD measurements. FTIR spectra have confirmed the preservation of the chemical structure of the compound during the deposition process. SEM and AFM investigation have evidenced a topography of the MAPLE deposited films characterized by different grain size depending on the deposition conditions. Second harmonic generation measurements have revealed that the MAPLE deposited benzil films have preserved the optical nonliniar properties of the bulk crystalline benzil.

683. STRUCTURAL DETAILS OF THE Ag-As2S3 INTERFACE OBTAINED BY VACUUM THERMAL EVAPORATION FOLLOWED BY GREEN LASER IRRADIATION

Authors: Lorinczi, A; Velea, A; Matei, E; Simandan, ID; Popescu, M

Published: NOV 2010, CHALCOGENIDE LETTERS, 7, 612, DOI:

As2S3 on Ag heterostructures deposited onto microscope glass substrates have been prepared. The quality of the hetero-structures has been investigated by careful analysis of the scanning electron microscope pictures taken on the native cross-sections, produced after the vacuum deposition sequence and various green laser irradiation times. The As2S3 layer is not uniformly grown, but reveals a columnar-like structure and multi-scale aggregation.

684. Nano and micro-morphology modifications of Si (100) substrate induced by femtosecond laser pulse irradiations in air, water, CCl4 and C2Cl3F3

Authors: Ionel, L; Cristescu, CP; Jipa, F; Enculescu, M; Radoiu, M; Dabu, R; Zamfirescu, M; Ulmeanu, M

Published: NOV 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1924, DOI:

The aim of this study is to investigate the influence of the different media, e.g. air, water, CCl4 (carbon tetrachloride) and C2Cl3F3 (tricloro-trifluoro-ethane), when irradiating a Si (100) substrate, with a 200 femtosecond (fs) laser pulses of a Ti:sapphire laser operating at 775 nm. Various micro and nanomorphologies could be achieved by changing the media, the laser pulse energy and the number of pulses. It is shown that the resulting Si (100) surface presents a regulated morphology in air consisting of parallel ripples and the formation of regular arrays of submicrometer spikes on Si (100) in CCl4 and C2Cl2F3, respectively. Irradiation of a Si (100) substrate immersed in water creates a regularly structured surface but it doesn't facilitate the spikes formation. The potential use of the patterned Si substrates as model scaffolds for the systematic exploration of the role of 3D micro/nano morphology on cell adhesion and growth is envisaged.

685. Cobalt-doped ZnO prepared by electrochemistry: Chemistry, morphology, and magnetism

Authors: Matei, E; Enculescu, I; Vasilache, V; Teodorescu, CM

Published: NOV 2010, PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, 207, 2522, DOI: 10.1002/pssa.200925378

ZnO:Co thin films are prepared by electrochemical deposition at different overpotentials and investigated by scanning electron microscopy, optical spectroscopy, and cathodoluminescence, X-ray photoelectron spectroscopy and Kerr magnetometry (MOKE). An increase of structural disorder and crystallite reorientation are observed for cobalt-doped samples. MOKE magnetometry revealed room-temperature ferromagnetic behavior only for ZnO: Co deposited at -850 mV. These are the samples with the lower cobalt content and lowest structural perturbation of the ZnO matrix by cobalt. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

686. Biocompatibility Studies of Iron-oxide-dextrin Thin Films

Authors: Andronescu, E; Costache, M; Ciobanu, CS; Prodan, AM; Predoi, D

Published: OCT 2010, REVISTA DE CHIMIE, 61, 928, DOI:

Dextrin coated magnetic nanoparticles have been obtained by co-precipitation. As a second step biocompatible magnetic thin film has been synthesized from the iron oxide coated with dextrin powders by pulsed laser deposition technique. Biocompatibility tests consisting of osteoblast cells growth, viability and proliferation were monitored on the surface of the thin films. The cells morphology was characterized by scanning electron microscopy (SEM) after 48h.

687. Structural studies on serum albumins under green light irradiation

Authors: Comorosan, S; Polosan, S; Popescu, I; Ionescu, E; Mitrica, R; Cristache, L; State, AE

Published: OCT 2010, EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS, 39, 1491, DOI: 10.1007/s00249-010-0606-y

This paper presents two new experimental results: the protective effect of green light (GL) on ultraviolet (UV) denaturation of proteins, and the effect of GL on protein macromolecular structures. The protective effect of GL was revealed on two serum albumins, bovine (BSA) and human (HSA), and recorded by electrophoresis, absorption, and circular dichroism spectra. The effect of GL irradiation on protein structure was recorded by using fluorescence spectroscopy and electrophoresis. These new effects were modeled by quantum-chemistry computation using Gaussian 03W, leading to good fit between theoretical and experimental absorption and circular dichroism spectra. A mechanism for these phenomena is suggested, based on a double-photon absorption process. This nonlinear effect may lead to generation of long-lived Rydberg macromolecular systems, capable of long-range interactions. These newly suggested systems, with macroscopic quantum coherence behaviors, may block the UV denaturation processes.

688. Looking for new synthesis of hydroxyapatite doped with europium

Authors: Ciobanu, CS; Andronescu, E; Vasile, BS; Valsangiacom, CM; Ghita, RV; Predoi, D

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1519, DOI:

In this work, we synthesized the properties of bioactive nanocrystalline hydroxyapatite (HAp), Ca-10(PO4)(6)(OH)(2) ceramic powder and nanocrystalline HAp doped with europium (III). The europium doped hydroxyapatite with an atomic ratio Eu/(Eu +Ca) between 2% and 20% were synthesized. The structure, morphology and optical properties were characterized by Xray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The XRD results reveal that the obtained Eu: HAp shows the characteristic peaks of hydroxyapatite in a hexagonal lattice structure. The results indicated that Eu3+ has been successfully doped into the framework of HAp.

689. Dynamics of energy absorption versus crystallization in Bi4Ge3O12 (BGO) amorphous materials

Authors: Polosan, S

Published: OCT 2010, MATERIALS RESEARCH BULLETIN, 45, 1495, DOI: 10.1016/j.materresbull.2010.06.017

Theoretical and experimental determinations show that the intrinsic luminescence of BGO materials is strongly influenced by GeO4- tetrahedra around Bi3+ ions. Besides Bi3+ transitions, the excitonic spectra mask the BGO bandgap. Theoretical computations give the bandgap at 5.19 eV compared with the experimental one at 5.17 eV in BGO crystals and a significant decrease at 3.26 eV in the amorphous materials. This is due to the high disordering of the GeO4- tetrahedral which also reduces the refractive index of the amorphous materials. Formation of excitonic states and their overlap with the Bi3+ transitions suggests that the energy absorption takes place via the p-electrons of the O-2(-) ions and is then transferred to the Bi3+ p-electrons (excited states) close to the conduction band. Light emission appears after de-excitation to the ground state. (C) 2010 Elsevier Ltd. All rights reserved.

690. Synthesis of Eu-doped bismuth germanate nano-ceramic powder

Authors: Polosan, S; Matei, E; Logofatu, C

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1508, DOI:

Europium doped Bi(4)Ge(3)O(12) nanocrystals were successfully obtained by solid state reaction between precursor oxides at 800 degrees C. The XRD and XPS measurements shows an increasing of the lattice constant in the case of Eu:BGO nanocrystals, due to the electropositive character of Eu(III) ions compared with the host cations, which induces an ionic character for Eu-O bound and a more covalent one for the Ge-O bounds. The photoluminescence of Eu:BGO due to (5)D(0) -> (7)F(2) transition have a lower splitting compared with Eu:BGO monocrystals suggesting a lower crystal field in the sintered nanocrystals, due to a mixing between the crystalline and amorphous phases.