Microstructures and Visible Photoluminescence of TiO2 Nanocrystals

Nanocrystalline titanium dioxide (TiO2) of anatase structure was prepared by a hydrolysis process of tetrabutyl titanate. The microstructures were examined by X-ray diffraction and Raman spectroscopy. The TiO2 nanocrystals with particle sizes from 6.8 to 27.9 nm were obtained through an annealing treatment of the as-prepared nanocrystals at various temperatures. Photoluminescence (PL) properties of TiO2 nanocrystals were investigated at various annealing temperatures (particle sizes), exciting powers, and exciting photon energies, respectively. The strongest visible emission was observed in the nanocrystals annealed at 300 °C, with a particle size of 7.9 nm. The experimental results manifested that the visible PL arises from a radiative recombination of electrons via intrinsic surface states of TiO2 nanoparticles.