Fundamental reactions in TiO₂ nanocrystallite aqueous solutions studied by pulse radiolysis

Reactions of the hydrated electron, H atoms, 2-propanol, and methanol radicals with the TiO₂ nano-particles have been studied either directly or by competition kinetics. The radicals were produced by radiolysis of 2-propanol, t-butanol, or methanol aqueous solutions in acid pH's. The reactions involve electron injection to the conduction band. As expected, the t-butanol radical is inert towards TiO₂ under our conditions, while the other reducing radicals react with TiO₂. The reactivity decreases in the order: e_aq^-H>CH₃COHCH₃>CH ₂OH. Two TiO₂ nanocrystallite sizes, with average diameters of 1.0 and 4.7nm were compared. For equal concentrations (in terms of TiO₂ molecules), the rate of electron injection shows relatively little dependency on particle size. The rates of interfacial electron transfer and transfer coefficient are also reported.