Photochemical generation of singlet oxygen on non-transition-metal oxide surfaces

Abstract

Irradiation of the non-transition-metal oxide powders silica gel, aluminium oxide and magnesium oxide in the presence of oxygen results in the formation of singlet oxygen (¹O₂). Two specific chemical traps were used to detect ¹O₂: 1,2-dimethylcyclohexene and geminally deuterated [²H₆]-2,3-dimethylbut-2-ene. Both compounds gave product distributions characteristic of singlet-oxygen reactions when irradiated on the metal oxide surfaces. These results support previous suggestions that singlet oxygen is formed through an energy-transfer process involving oxygen and excitons on the metal oxide surface. Under the same reaction conditions TiO₂ showed no production of ¹O₂.