Nanosized titanium dioxide (TiO2) is synthesized by laser-induced pyrolysis using titanium isopropoxide as a liquid precursor. The specific surface area of as-produced nanopowders measured by the Brunauer–Emmett–Teller method (BET) varies from 84 to 110 m2 g−1. X-ray diffraction (XRD) and Raman scattering showed that the TiO2 nanocrystals had an anatase structure. The grain size of the nanoparticles was estimated from scanning electron microscopy, XRD and BET measurements. The reflection spectra of nanocrystalline TiO2 pressed pellets has been measured in the region between 80 and 1500 cm−1 by Fourier transform infrared spectroscopy. To interpret the experimental results, a model based on a generalized Bruggeman effective medium approximation of a dielectric function has been proposed. It is based on the polycrystalline character of TiO2 nanoparticles including island-structure and porosity of the nanopowders, along with the anatase single crystal dielectric functions. Thus, by comparing the results of calculated and experimental infrared (IR) spectra, the values of microscopic parameters of nanocrystalline powders can be deduced.

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Properties of CdS thin films were investigated applying atomic force microscopy (AFM) and Raman spectroscopy. CdS thin films were prepared by using thermal evaporation technique under base pressure 2 x 10-5 torr. The quality of these films was investigated by AFM spectroscopy. We apply Raman scattering to investigate optical properties of CdS thin films, and reveal existence of surface optical phonon (SOP) mode at 297 cm-1. Effective permittivity of mixture were modeled by Maxwell - Garnet approximation. [Projekat Ministarstva nauke Republike Srbije, br. 45003]

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Titanium dioxide (TiO2) nanopowders were prepared by laser-induced pyrolysis. Raman scattering showed that prepared TiO2 nanocrystals have anatase TiO2 structure. Specific surface area of the powders varies from 84 to 110 m2/g, while the grain size of nanoparticles is between 30 and 70 nm, depending on preparation conditions. We measured photoluminescence (PL) spectra of TiO2 nanocrystals. Under laser irradiation with photon energy between 2.41 and 2.71 eV the TiO2 nanocrystals displayed strong visible light emission, even at excitation power as low as 0.05 W/cm2. The line shape and position of this broad luminescence band vary with excitation energy. As PL spectra of anatase TiO2 can be attributed to three kinds of physical origins (self-trapped excitons, surface states and oxygen vacancies) in this paper we try to resolve which of them are dominant for different TiO2 nanopowders of different grain size.