Optics and Photonics Society of Iran

Titanium dioxide (TiO₂) nanostructures were synthesized by sol–gel method. For investigation on optical properties, crystalline structure and morphology of the nanopowders, UV-visible spectroscopy, X-ray diffraction method and scanning electron microscopy were carried out. Different parameters for preparation of the gel such as the concentration of raw material and annealing temperature were more effective on the characteristics of the nanopowders. Optical adsorption spectra showed that adsorption edge increased by increasing annealing temperature that was indicates decreasing of energy band gap and so increasing particle size. SEM micrographs presented that the size of TiO₂ nanostructures in the temperature range of 300 to 500 °C were in the range of 10 to 23nm that was inferred by increasing annealing temperature, the mean size of nabopowders was increased. In other hand, XRD results indicated that by increasing annealing temperature, rutile phase was enhanced in the spectrum as in 300^◦ C, both anatase and rutile phases were seen, and at 400^◦C, anatase phase was reduced and rutile phase was increased, and finally at 500^◦C, anatase phase was obviously changed to rutile phase. Moreover, annealing temperature can improve the crystallinity of TiO₂ nanopowders.