Photochemistry on Semiconductor Surfaces. Visible Light Induced Oxidation of C₆₀ on TiO₂ Nanoparticles

The photochemical behavior of C60 adsorbed on TiO2 particles has been investigated using diffuse reflectance laser flash photolysis. At submonolayer coverages, irreversible oxidation of C60 is observed on titanium dioxide particles. A photochemical transient with a difference absorption maxima at ∼390 nm and at wavelengths greater than 700 is observed following the 532 nm laser pulse excitation of the C60-coated TiO2 particles. This transient is not sensitive to the presence of oxygen. The bleaching in the 600 nm region confirms the depletion of C60 during the surface photochemical oxidation of C60. Formation of both triplet excited state and the oxidation product are observed at higher coverages. This suggests that direct interaction with the oxide surface is crucial for observing the photochemical oxidation of C60. A biphotonic electron ejection from excited C60 is followed by the formation of fullerene epoxide on the TiO2 surface. The diffuse reflectance laser flash photolysis experiments which highlight the surface photochemistry process of C60 are presented.

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