PHOTOCHEMISTRY ON SEMICONDUCTOR SURFACES - VISIBLE-LIGHT INDUCED OXIDATION OF C-60 ON TIO2 NANOPARTICLES

The photochemical behavior of C-60 adsorbed on TiO2 particles has been investigated using diffuse reflectance laser flash photolysis. At sub monolayer coverages, irreversible oxidation of C-60 is observed on tit anium dioxide particles. A photochemical transient with a difference a bsorption maxima at similar to 390 nm and at wavelengths greater than 700 is observed following the 532 nm laser pulse excitation of the C-6 0-coated TiO2 particles. This transient is not sensitive to the presen ce of oxygen. The bleaching in the 600 nm region confirms the depletio n of C-60 during the surface photochemical oxidation of C-60. Formatio n of both triplet excited state and the oxidation product are observed at higher coverages. This suggests that direct interaction with the o xide surface is crucial for observing the photochemical oxidation of C -60. A biphotonic electron ejection from excited C-60 is followed by t he formation of fullerene epoxide on the TiO2 surface. The diffuse ref lectance laser flash photolysis experiments which highlight the surfac e photochemistry process of C-60 are presented.