Time-resolved infrared absorption spectroscopy of photogenerated electrons in platinized TiO2 particles

Kinetics of photogenerated electrons in platinized TiO2 (P-25) particles were observed by time-resolved infrared (IR) absorption spectroscopy with AC-coupled detection of cw probe light. The sample irradiated by UV pulse (355 nm and 10 ns) gave transient absorption which monotonously increased in intensity with decreasing wavenumber from 3000 to 900 cm−1. Photogenerated electrons trapped in shallow mid-gap states were proposed to originate the transient absorption. The decay kinetics of the trapped electrons were fitted to a multi-exponential formula with six lifetimes ranging from 1×10−7 to 3×10−1 s.