Photoluminescence in anatase titanium dioxide nanocrystals

Titanium dioxide (TiO2) nanocrystals were prepared by a hydrolysis process of tetrabutyl titanate. X-ray diffraction and Raman scattering showed that the as-prepared TiO2 nanocrystals have anatase structure of TiO2, and that the monophase anatase nanocrystals can be achieved through a series of anne aling treatments below 650 degrees C. We measured photoluminescence (PL) sp ectra of the TiO2 nanocrystals. Under 2.41-2.71 eV laser irradiation, the T iO2 nanocrystals displayed strong visible light emission with maxima of 2.1 5-2.29 eV even at excitation power as low as 0.06 W/cm(2) To identify the P L mechanism in the TiO2 nanocrystals, the dependences of the PL intensity o n excitation power and irradiation time were investigated. The experimental results indicated that the radiative recombination is mediated by localize d levels related to surface defects residing in TiO2 nanocrystallites.