Infrared study of laser synthesized anatase TiO2 nanopowders

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