National Institute Of Materials Physics - Romania

The dispersion and the polar independent contributions to the surface free energy in the case of fused quartz plates were evaluated by contact angle measurements against a series of liquids like water, glycerol, ethylene glycol, dimethyl sulfoxide and a nematic mixture NP5 of azoxybenzene type compounds. The smooth fused quartz plates were thermally pretreated at 240 degrees C and 1000 degrees C to decrease the number of surface hydroxyl groups; their surface was characterized by X-ray photoelectron spectroscopy. The contact angle data were further processed applying either the approach of Owens-Wendt with geometric mean or the Wu's approach of harmonic mean of nonpolar and polar interactions. The liquids were chosen thus to fulfill Della Volpe and Siboni's criterion namely that these have the condition number of system matrix low enough. The values obtained for the components of surface free energy were discussed in comparison with the results obtained in literature for crystalline quartz or for other silica forms as bulk or films. The study has shown a decrease of the polar component of the surface tension by increase of the pretreatment temperature.

We report on the synthesis of advanced nanostructured hydroxyapatite (HA) thin films onto 3D titanium (Ti) mesh substrates by Pulsed Laser Deposition method. Morphological and structural investigations as well as pull-out tests proved the stoichiometric transfer of crystalline HA films along with their good adherence. In vivo tests were performed on 12 patients (six with simple Ti mesh, six with Ti mesh biofunctionalized with HA). The tomodensitometry analysis of the cranial control scans evidenced the process of osseogenesis. For four patients with implanted HA/Ti mesh structures, the modification of the value obtained on Hounsfield scale was observed at the level of implant, proving the progress of osseointegration. We conclude that the structures exhibit excellent bonding strength and functionality, and are suitable for neurosurgical applications.

This study aims to present the manufacture of polymer photonic crystals (PCs) and the study of the influence of PbS quantum dots on their optical properties. Monodisperse latexes resulting from the polymerization of styrene and acrylic acid were obtained by a soap-free emulsion copolymerization process and their optical response was modified using PbS high refractive index nanoparticles. A stop-band modulation was achieved by controlling the nanoparticles concentration that resulted in the altering of the self-assembly process. Thus, at low PbS concentrations, a blue-shift of the band-gap was registered, whereas at high concentrations, a red-shift was measured. The hybrid materials were investigated by DLS, SEM, HRTEM, UV-VIS and XRD analyses.

The presence and structure of paramagnetic point defects in C-13 and O-17 implanted ultrapure Si single-crystal material, two impurities which seem to play a major role in the detectors performance degradation and radiation resistance enhancement, respectively, are reported before and after irradiation with 6 MeV electrons. The investigation, performed by Q-band electron spin resonance spectroscopy in the 300 - 10 K temperature range, included also reference ultrapure and O-16 doped single-crystal Si-platelets. It resulted in the observation of points defects associated with lattice defects as dangling bonds and impurities.

Single crystal ZnO nanowires grown by pulsed laser deposition (PLD) and vapour-liquid-solid (VLS) technique respectively, were in-situ and ex-situ covered with additional ZnO shell layers. Luminescence investigation revealed significant luminescence spectra shift from UV to blue emission band of the obtained structures while changing the deposited shell layer film thickness. But with no monotone variation with the deposited film thicknesses. While the luminescence changes are generally considered as being determined by the ratio between core emission lines intensity and shell 'defects' lines intensity, the strongest changes in the photoluminescence spectra were obtained in our experiments for the nanometer order shell layer thicknesses. The comparison between luminescence results and luminescence studies on 50 nm ZnO nanoparticles clusterization, together with HRTEM investigations of the ZnO shell layer suggest that the nanoparticle-nanowire interface, respectively the coupling between the ZnO single crystal core and ZnO nanostructured shell layer, might play a significant role in the luminescence spectra changes.

A new green method for the synthesis of reduced graphene oxide-gold nanoparticle (rGO-AuNP) hybrids in aqueous solution that exploits the ability of ascorbic acid (AA) to operate as an effective dual agent for both graphene oxide (GO) and gold ion reduction is reported. Through careful investigation of the production of rGO-AuNP hybrids stabilized with polyvinylpyrrolidone (PVP), several versatile routes were devised with the aim of controlling the size, shape and distribution of AuNPs anchored onto the graphene sheets as well as the GO reduction. Particularly, when rGO is used as a platform for Au ion nucleation, a relative sparse distribution of AuNPs of size ranging from 20 nm to 50 nm is noticed. In contrast, when gold ions are added to the solution prior to any GO reduction, the density of large AuNPs is rather low relative to the uniformly packed small sized AuNPs (3-12 nm). The progress of GO reduction is explained by considering the contribution of the catalytic activity of AuNPs, besides the reducing activity of AA. Finally, a plausible mechanism for the nucleation and distribution of AuNPs onto the graphenic surface is assumed, highlighting the significance of oxygen moieties. The green method developed here is promising for the fabrication of gold-graphene nanocomposites with tunable surface "decoration", suitable for surface-enhanced Raman spectroscopy (SERS).

The aim of this study was to evaluate the biological properties of iron oxide nanoparticles (IO-NPs) obtained in the aqueous suspension. The iron oxide nanoparticles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The biocompatibility of the iron oxide was demonstrated by the in vitro quantification of HeLa cells viability using propidium iodide (PI) and fluorescein diacetate (FdA) and the MTT colorimetric assay. The toxicity of small size iron oxide nanoparticles was also evaluated by means of histological examination on male Brown Norway rats after intraperitoneal injection. At the tested concentrations, the nanoparticles proved to be not cytotoxic on HeLa cells. The rat's behavior, as well as the histopathological aspect of liver, kidney, lung, and spleen tissues at 48 h after intraperitoneal injection did not present any modifications. The in vivo and in vitro assays suggested that the IO-NPs could be further used for developing new in vivo medical applications.

Upon 808 nm excitation, an intense broadband near-infrared emission from Cr4+ has been observed in 80GeS(2)-20Ga(2)S(3) chalcogenide glass-ceramics (GCs) containing Ga2S3 nanocrystals. The emission band peaking at 1250 nm covers the O, E, S bands (1000-1500 nm). The formation of Ga2S3 nanocrystals (similar to 20 nm) increases the emission intensity of Cr4+ by more than three times. The quantum efficiency of the present GCs is as great as 36% at room temperature. (C) 2012 Optical Society of America

ZnO-x%Eu2O3 (x=5 wt.%) binary oxide with straight strips morphology was successfully synthesized by hydrothermal route, using cetyltrimethylammonium bromide (CTAB) as template ZnSO4. Eu(NO3)(3)center dot 5H(2)O as inorganic precursors and ammonium hydroxide solution 28% NH3 for adjusting the pH to 11 value. The morphology, structure, photoluminescence and surface chemistry were investigated. The results highlighted that ZnO-Eu2O3 binary oxide shows straight strip morphology and crystalline framework indexed to wurtzite ZnO while Eu2O3 was detected as secondary phase. Surface chemistry revealed the presence of Eu3+. High sensor signal to 3 ppm NO2 together with its low sensitivity towards CO recommend this material as a good candidate in selective detection of NO2. (C) 2012 Elsevier B.V. All rights reserved.

The effects of 5 x 10(11) cm(-2 6+)I(127) ions of 28 MeV kinetic energy on high resistivity (100) Si were studied. The profile of primary defects was simulated. The defects produced by irradiation which act as traps were investigated. Thermally stimulated current measurements without externally applied bias were used, and for this the traps were charged by illuminating samples with 1000, 800, and 400 nm wavelengths. The discharge currents were recorded and modeled, and therefore the parameters of the traps were determined. The presence of I ions, heavier than Si, stopped into the target was modeled as a temperature independent electric field. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772015]