ABSTRACT
Some information on the primary processes of photocatalysis has been obtained by laser flash photolysis studies using colloidal semiconductor solutions and suspensions. Early flash photolysis studies suffered, however, from the inherent problem that a large number of electron/hole pairs were generated in each semicon-ductor particle (usually titanium dioxide) per laser pulse [4]. Due to the considerable progress in synthetic methods to produce nanosized semiconductor clusters with extremely small and well-defined diameters, several research groups were able to employ experimental conditions which ensured that on the average less than one electron/hole pair was formed per semiconductor cluster during each light pulse [5-7]. Consequently Serpone et al [5] and Bowman et al [6] have recently published very interesting work using picosecond or even sub-picosecond time resolution to study the primary events following band gap excitation of titanium dioxide colloids. Bahnemann and co-workers [7] have discussed details of the interfacial electron transfer between semiconductor particles and solutes in the surrounding electrolyte.
