Luminescence properties of an anatase TiO2 photocatalyst under conditions of trap site excitation

Trap states located below the conduction band edge are potentially key factors that control the photocatalytic activities of TiO2. Here, we used a time-resolved photoluminescence approach to characterize these trap states in an anatase TiO2. Direct excitation of trap sites was performed by laser excitation. When the excitation energy was below the band gap energy, the luminescence decay profile contained a more prominent fast decay component compared with that when the excitation energy was above the band gap energy. We attribute this finding to site-selective excitation of regions of deformed structure near the surface of the TiO2 particle.