Singlet oxygen formation in photocatalytic TiO2 aqueous suspension

Abstract

The formation of reactive singlet oxygen molecule (¹O₂), the a¹Δ_g state of excited O₂, in the photocatalytic TiO₂ aqueous suspension system was shown to be evident by detecting the near-infrared phosphorescence at 1270 nm by means of a gated photon counting method. The lifetimes of O₂(¹Δ_g) in three different media (water, ethanol, 1∶1 water–ethanol mixture) were elucidated and compared with those reported in corresponding homogeneous media. Based on the comparison of the lifetime with those of the other reactive species such as OH radicals and trapped holes, the contribution of ¹O₂ to the actual photocatalytic procedure was discussed.