Enhancement of Luminescence in Anatase TiO₂ Photocatalysts by Ethanol under Hole-Scavenging Conditions

We studied the enhancement of the photoluminescence intensity of anatase TiO2 photocatalysts by adding ethanol vapor. Time-resolved measurements of luminescence and transient absorption indicated that the luminescence was due to excitons, and there was no luminescence associated with the recombination of trapped charges. We found that the ethanol-induced enhancement of the luminescence was dominated by an increase of the efficiency of generation of excitons. We concluded that this increased efficiency was due to the recombination of electrons that accumulated in particles due to hole-scavenging by ethanol with photogenerated holes before the holes were trapped at the surface of particles.