Photochemistry on surfaces. 4. Influence of support material on the photochemistry of an adsorbed dye

Abstract

The absorption and emission properties of rose bengal have been characterized on the surfaces of SiO₂, Al₂O₃, and TiO₂ particles. The intrinsic properties of these oxide supports play an important role in effecting and controlling the photochemistry of the adsorbed dye. On the Al₂O surface, a biphotonic photoionization process leads to the production of semioxidized dye. However, a charge injection from the excited dye into the conduction band dominates on the TiO₂ particles. Steady-state photolysis indicates a rapid photodegradation of the dye only on the surface of TiO₂. The diffuse reflectance laser flash photolysis experiments which elucidate the mechanism of photochemical processes on these oxide supports are described.