National Institute Of Materials Physics - Romania

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5781 articles found

2871. SiO2 nanospheres and tubes obtained by sol-gel method

Authors: Anastasescu, C; Anastasescu, M; Teodorescu, VS; Gartner, M; Zaharescu, M

Published: OCT 1 2010, JOURNAL OF NON-CRYSTALLINE SOLIDS, 356, 2640, DOI: 10.1016/j.jnoncrysol.2010.03.038

Multifunctional nanomaterials with one-dimensional structure have become very attractive because of their potential applications in biochemistry (bioseparation and biointeraction), drug delivery, catalysis, nanotechnology (optical sensors). In this work we report on the synthesis of SiO2 nanospheres and tubes, in a solution of tartaric acid (TTA), pure water and absolute ethanol, starting with tetraethyl orthosilicate (TEOS) via the addition of ammonium hydroxide. In order to characterize the obtained material, transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), thermogravimetric and thermodifferential analysis (DTA/TGA), FT-IR spectroscopy and spectroellipsometry (SE) were used. The tubes have an outer diameter of 0.1-0.2 mu m and length of some microns containing also spherical nanoparticles. The dimensions of the obtained nanotubes are tunable, their diameter and length depending on the synthesis conditions. In the presence of meso-tartaric acid no hollow tubes but nanospheres are obtained. The SiO2 tubes and nanospheres have similar structure but very different morphologies. The large surface area and the distinctive inner and outer surfaces represent a great advantage of the nanotubes over conventional nanoparticles, making these materials suitable for doping and differential functionalization. (C) 2010 Elsevier B.V. All rights reserved.

2872. Investigations of the neodymium doped quartz glasses obtained by the hybrid sot-gel method

Authors: Niciu, H; Vasiliu, C; Manea, A; Radu, D; Secu, M; Onose, C; Ghervase, L; Niciu, D; Feraru, ID; Grigorescu, CEA

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1623, DOI:

Undoped and neodymium doped quartz glasses were obtained by the hybrid sol-gel method. The vitrification was performed in He atmosphere. The Nd(3+) characteristic absorption bands in the UV and VIS were put into evidence. Investigations in the NIR range revealed a small amount (86 ppm) of OH(-) in the vitreous matrix. FTIR and Raman spectra exhibit the SiO(2) glass characteristic vibrations and also the characteristic vibrations of Si-OH and Si-Cl bonds. The photoluminescence peaks at 640, 920 and 1080 nm belonging to the Nd(3+) doped quartz glass were evidenced.

2873. 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.

2874. 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.

2875. 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.

2876. Vibrational and molecular dynamics of a nanoconfined liquid crystal

Authors: Schonhals, A; Frunza, S; Frunza, L; Unruh, T; Frick, B; Zorn, R

Published: OCT 2010, EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS, 189, 255, DOI: 10.1140/epjst/e2010-01329-5

The effect of a nanometer confinement on the vibrational and molecular dynamics of a liquid crystals E7 was studied by dielectric spectroscopy (DS) and neutron scattering (NS). E7 undergoes a glass transition phenomenon besides the nematic to isotropic phase transition. As confining host a molecular sieve of the MCM-41 type is used having cylindrical pores with a radius of 1.25 nm. The results obtained by both methods are compared in detail.

2877. Biomineralization capability of adherent bio-glass films prepared by magnetron sputtering (vol 21, pg 1047, 2010)

Authors: Stan, GE; Pina, S; Tulyaganov, DU; Ferreira, JMF; Pasuk, I; Morosanu, CO

Published: OCT 2010, JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 21, 2899, DOI: 10.1007/s10856-010-4040-6

2878. 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.

2879. Non-centro-symmetric superconductors Li2Pd3B and Li-2(Pd0.8Pt0.2)(3)B: amplitude and phase fluctuation analysis of the experimental magnetization data

Authors: Badica, P; Salem-Sugui, S; Alvarenga, AD; Jakob, G

Published: OCT 2010, SUPERCONDUCTOR SCIENCE & TECHNOLOGY, 23, DOI: 10.1088/0953-2048/23/10/105018

We report on magnetization data obtained as a function of temperature and magnetic field in Li-2(Pd0.8Pt0.2)(3)B and Li2Pd3B non-centro-symmetric superconductors. Reversible magnetization curves were plotted as M-1/2 versus T. This allows study of the asymptotic behavior of the averaged order parameter amplitude (gap) near the superconducting transition. Results of the analysis show, as expected, a mean field superconducting transition for Li2Pd3B. By contrast, a large deviation from the mean field behavior is revealed for Li-2(Pd0.8Pt0.2)(3)B. This is interpreted as due to the strength of the non-s-wave spin-triplet pairing in this Pt-containing compound which produces nodes in the order parameter and, consequently, phase fluctuations. The diamagnetic signal above T-c(H) in Li2Pd3B is well explained by superconducting Gaussian fluctuations and agrees with the observed mean field transition. For Li-2(Pd0.8Pt0.2)(3)B the diamagnetic signal above T-c(H) is much higher than the expected Gaussian values and appears to be well explained by three-dimensional critical fluctuations of the lowest-Landau-level type, which somehow agrees with the scenario of a phase mediated transition.

2880. Structure and Mossbauer measurements on SnSe2 bulk and thin films

Authors: Bibicu, I; Lorinczi, A; Velea, A; Sava, F; Popescu, M

Published: OCT 2010, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 4, 1571, DOI:

Thin films samples of SnSe2 deposited by PLD and PED have been prepared and studied by XRD and Mossbauer spectroscopy. The films are crystalline with a major phase of SnSe2 and minor phase of amorphous SnSe2. An oxidation process lead to the appearance of a thin layer of SnO2 on the surface of the PLD samples.