National Institute Of Materials Physics - Romania

Publications

860 articles found

651. Optical and morphologic properties of YVO4:Eu phosphor

Authors: Georgescu, S; Voiculescu, AM; Cotoi, E; Toma, O; Gheorghe, L; Achim, A; Matei, C; Enculescu, I; Matei, E; Osiac, M

Published: 2010, ROMOPTO 2009: NINTH CONFERENCE ON OPTICS: MICRO- TO NANOPHOTONICS II, 7469, DOI: 10.1117/12.866769

In this paper we present new results concerning the optical and morphologic properties of YVO4:Eu red nanophosphor prepared by a precipitation method and subsequently annealed in air at various temperatures. We monitored the morphologic changes induced by the thermal treatments using the optical spectroscopy (reflectance and luminescence spectra), XRD and electron microscopy. The annealing leads to an increase of the particle size and improvement of the order of the crystalline lattice of YVO4. The annealing at 800 degrees C produces the sample with the highest luminescence intensity.

652. Polymer-microporous host interactions probed by photoluminescence spectroscopy

Authors: Tiseanu, C; Parvulescu, VI; Cojocaru, B; Lorenz-Fonfria, VA; Kumke, M; Gessner, A; Enculescu, I

Published: 2010, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 12, 3037, DOI: 10.1039/b922591a

Zeolites NaY and ZSM-5 were used as hosts for styrene polymerization after ion-exchange with europium ions. The parent and hybrid, polystyrene coated Eu-NaY (Eu-NaY/PS) and Eu-ZSM-5 (Eu-ZSM-5/PS) zeolites were investigated by using thermal analysis, SEM, PXRD, FT-IR, DR-UV/Vis, steady state and time-resolved photoluminescence spectroscopy. FT-IR spectra evidenced for the interaction between the zeolitic hosts and polystyrene while the PXRD spectra supported for the presence of the polymer inside the channels/pores of Eu-NaY/PS and Eu-ZSM-5/PS materials. The optical properties of Eu-NaY/PS and Eu-ZSM-5/PS were significantly changed relative to those of the parent zeolites, giving further evidence for the presence of polymer inside zeolites. An interesting case is presented by NaY zeolite: following styrene polymerization, the polymer interacted selectively with one of the two main species co-existing inside zeolite while for ZSM-5 a similar effect was not observed.

653. PHYSICO-CHEMICAL PROPERTIES OF NANO-SIZED HEXAGONAL HYDROXYAPATITE POWDER SYNTHESIZED BY SOL-GEL

Authors: Costescu, A; Pasuk, I; Ungureanu, F; Dinischiotu, A; Costache, M; Huneau, F; Galaup, S; Le Coustumer, P; Predoi, D

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1000, DOI:

Calcium phosphate ceramic powders were synthesized via sol-gel method. The powders were sintered at 600 and 1000 degrees C and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM and TEM), elemental microanalysis (EDS), infrared spectroscopy (FTIR), and thermal analysis (TGA and DTA). The XRD analysis revealed a well crystallized hydroxyapatite (HAp) structure at all temperatures. At 1000 degrees C a small amount of CaO (about 1.2 %) was detected. The average crystallite size increased from 19 nm at 80 degrees C to about 125 nm at 1000 degrees C. FTIR spectra showed the presence of various PO43- and OH- groups present in the powders. In order to verify the biocompatibility of HAP powders with hFOB 1.19 osteoblasts cells, an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test was applied. It was noticed that the ceramics obtained at 1000 degrees C, increased the cell viability with 10%, 40% and 55% after 6, 12 respectively 24 h, whereas that obtained at 600 degrees C was less effective. Our results proved the high biocompatibility of calcium phosphate ceramic powders obtained by sol-gel and sintered at 1000 degrees C.

654. Optical and X-ray absorption spectroscopy in lead doped lithium fluoride crystals

Authors: Somma, F; Aloe, P; d'Acapito, F; Montereali, RM; Polosan, S; Secu, M; Vincenti, MA

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012035

LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb2+ ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L-III and L-I edges. XANES data reveal that Pb is present as Pb2+ whereas EXAFS data show that it is incorporated in the crystal and not forming PbF2 precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 degrees C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

655. Growth and Characterization of ZnO:Mn Submicron Wires via Electrodeposition from Nitrate-Lactic Acid Solution

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

Published: 2010, SEMICONDUCTORS, METAL OXIDES, AND COMPOSITES: METALLIZATION AND ELECTRODEPOSITION OF THIN FILMS AND NANOSTRUCTURES, 25, 171, DOI: 10.1149/1.3318515

Electrodeposition of manganese doped ZnO wires into polycarbonate membranes from an aqueous solution containing Zn(NO3)(2), Mn(NO3)(2) and lactic acid was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). The equivalent electrical circuits used for fitting experimental results were similar to those for characterization of metal/polymer coating systems. The precipitation of metal oxides in the pores of membrane used as template was observed at potentials between -0.9 and -1.15V/SCE. Morphology of the ZnO: Mn submicron wires arrays was observed by scanning electron microscopy and the Mn content of the obtained samples was measured by X-ray analysis. The submicron wires prepared at a potential of -1.1V/SCE have a composition expressed by the formula Zn0.97Mn0.03.

656. SYNTHESIS AND CHARACTERIZATION OF BIO-COMPATIBLE MAGHEMITE NANOPARTICLES

Authors: Predoi, D; Andronescu, E; Radu, M; Munteanu, MC; Dinischiotu, A

Published: JUL-SEP 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 786, DOI:

The bio-compatible magnetic nanoparticles of maghemite were prepared by a chemical co-precipitation method and dextran was selected as the surfactant to suspend them. By transmission electron microscopy (TEM), the iron oxide nanoparticles appeared nearly spherical with an average diameter of about 8.0 +/- 1 nm. SAED pattern of iron oxide nanoparticles is indexed by a cubic gamma-Fe(2)O(3), the diffraction rings are attributed to the (220), (311), (400), (422), (511) and (440) planes, respectively. Regular fringes are clearly observed in the nanoparticle with a spacing of 0.24 nm, whigh is the (311) interplanar distance of the cubic maghemite. This is in perfect agreement with the X-Ray Diffraction (XRD) results, indicating that the nanoparticles are well crystallyzed in spite of their ultrafine sized. The attachment of the dextran on the particle surface was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. The biocompatibility of maghemite nanoparticles covered by dextran with HepG2 cells was checked by MTT test. Cell viability was > 98% when the iron concentration was 12.0 mu g iron/ml and 24.0 mu g iron/ml respectively. In conclusion, these nanoparticles presented a good biocompatibility with HepG2 cells, which was proportionally with the dilution level.

657. Investigations of the Correlation Between the Preparation Method and the Properties of Anilinic Derivative Functionalised Polymer Thin Films for Non-Linear Optical Applications

Authors: Stanculescu, A; Socol, M; Albu, AM; Rasoga, O; Stanculescu, F; Ionita, I; Enculescu, I

Published: 2010, ADVANCED MATERIALS FORUM V, PT 1 AND 2, 636-637, +, DOI: 10.4028/www.scientific.net/MSF.636-637.798

This paper presents a study of two copolymers, maleic anhydride and methylmethacrilate/maleic anhydride and vinyl benzyl chloride, functionalised with polar chromophoric groups such as 2,4 dinitroaniline. Thin films have been prepared by vacuum evaporation and spin coating methods on silicon and glass substrates. UV-VIS, FTIR, XRD and Photoluminescence Spectroscopy have been used to comparatively investigate the effect of the preparation method on the properties of the thin films obtained with functionalized copolymer. SEM has evidenced differences in the morphologies of the layers suggesting a degradation of the polymeric chain during the evaporation process to fragments that conserve unchanged the chromophoric group. This explains the presence of two types of non-linear phenomena, the second harmonic emission and two-photon luminescence emissions for both vacuum evaporated and spin coated films.

658. Radiation induced defects in Tl+-doped LiF crystals

Authors: Polosan, S; Secu, M; Logofatu, C; Somma, F; Montereali, RM; Vincenti, MA

Published: 2010, 11TH EUROPHYSICAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS (EURODIM 2010), 15, DOI: 10.1088/1757-899X/15/1/012081

Tl+-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl+ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F-3(+) centres, in three steps, compared with the F-2 ones. The F-H recombination processes may induce the excitation-emission transitions of Tl+-ions.

659. PHYSICO-CHEMICAL STUDIES OF SUCROSE THIN FILMS

Authors: Predoi, D

Published: APR-JUN 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 377, DOI:

Sucrose is a natural osmolyte accumulated in cells of organisms as they adapt to environmental stress. In vitro sucrose increases protein stability and forces partially unfolded structures to refold. Thin films of sucrose (C12H22O11) were deposited on thin cut glass substrates by thermal evaporation technique (p similar to 10(-5) torr). Characteristics of thin films were putted into evidence by Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM) and differential thermal analysis and thermal gravimetric analysis (TG/DTA). The experimental results confirm a uniform deposition of an adherent layer.

660. Growth and optical characteristics of coumarin 6 doped potassium hydrogen phthalate (KAP) crystals

Authors: Enculescu, M

Published: DEC 2009, OPTICAL MATERIALS, 32, 285, DOI: 10.1016/j.optmat.2009.08.002

Single-crystals of potassium hydrogen phthalate (KAP) doped with coumarin 6 (C6) were grown by solution evaporation technique. Powder X-ray diffraction. optical transmission and luminescence measurements were performed. The structure and morphology of the KAP crystals are not changed with the incorporation of the dye. Transparency of the dye-doped crystals is suited for non-linear optical (NLO) applications and UV cut-off is not changed when compared with the pure KAP crystals. The dye-doped crystals present an absorption band at 350 nm while the growth solution exhibits a peak at 400 nm. The doped crystals have a strong emission band at 450 nm that is excited at 350 nm and the second harmonic generating (SHG) properties are demonstrated using luminescence measurements. (C) 2009 Elsevier B.V. All rights reserved.