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A real GaAs surface is covered with a relatively thick layer (~nm) of native oxide responsi- ble for the surface Fermi level pinning within the band gap of the semiconductor. The method presented in this work is the sulphur passivation by treating the semiconductor in sulphide solutions that combines both chemical and electronic passivation by reducing the surface state density (e.g., pure ammonium sulphide and sulphur monochloride). The passivated surface was examined by SEM, EDS and XPS techniques, that put into evidence the existence of an adherent layer of sulphur compound as a result of chemical interaction of sulphur ions with n-GaAs surface.

The main purpose of this study was to evaluate the inhibitory effect of glycerol- iron oxide thin films on Methicillin-Resistant Staphylococcus aureus (MRSA). Our results suggest that glycerol-iron oxide thin films could be used in the future for various biomedical and pharmaceutical applications. The glycerol-iron oxide thin films have been deposited by spin coating method on a silicon (111) substrate. The structural properties have been studied by X-ray diffraction (XRD) and scanning electron spectroscopy (SEM). The XRD investigations of the prepared thin films demonstrate that the crystal structure of glycerol-iron oxide nanoparticles was not changed after spin coating deposition. On the other hand, the SEM micrographs suggest that the size of the glycerol-iron oxide microspheres increased with the increase of glycerol exhibiting narrow size distributions. The qualitative depth profile of glycerol-iron oxide thin films was identified by glow discharge optical emission spectroscopy (GDOES). The GDOES spectra revealed the presence of the main elements: Fe, O, C, H, and Si. The antimicrobial activity of glycerol-iron oxide thin films was evaluated by measuring the zone of inhibition. After 18 hours of incubation at 37°C, the diameters of the zones of complete inhibition have been measured obtaining values around 25 mm. [ABSTRACT FROM AUTHOR]

The bio-compatible magnetic nanoparticles of maghemite were prepared by a chemical coprecipitation 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 γ-Fe2O3, 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 μg iron /ml and 24.0 μg iron /ml respectively. In conclusion, these nanoparticles presented a good biocompatibility with HepG2 cells, which was proportionally with the dilution level. [ABSTRACT FROM AUTHOR]

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∼ 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. [ABSTRACT FROM AUTHOR]

Abstract: Undoped and Eu3+-doped CaF2–SiO2 gels were prepared by the sol–gel method and their optical properties have been studied. The UV–VIS–NIR absorption and photoluminescence spectra have shown the bands typical for the Eu3+ ions transitions. When the Eu-doped gel is annealed at temperatures up to 800°C (i.e. above the CaF2 crystallisation peak at ∼460°C) the photoluminescence spectra intensity increase, the 590nm and 620nm luminescence bands become comparable and a structuring of the 620nm band is observed. The phonon sidebands peaks associated with the transition of the Eu3+ ion were observed at around 1000 and 620cm−1 and have been assigned to the Si–O and Ca–O bonds, respectively. A phonon sideband signal in the range of 300–400cm−1 was attributed to Ca–F bonds in the precipitated CaF2 phase. From the optical absorption, photoluminescence and phonon sidebands spectra we have concluded that in the gels annealed at 800°C, the Eu3+ ions are incorporated into the silica network and in the precipitated CaF2 phase. [Copyright &y& Elsevier]