Microwave probing of electronic processes in small particle suspensions

Abstract

The electronic properties of small particles of semiconducting materials have attracted considerable attention because they can mediate the photolytic decomposition of water^1–6; a property which may prove useful in solar energy storage devices. Information about the initial electron–hole state formed on photolysis and the subsequent conduction and electron transfer processes occurring at the particle–solvent interface has previously been gained indirectly through steady-state and flash-photolysis studies of colloidal solutions that also contain well known electron donor and/or acceptor molecules. A more direct, ‘electrical’ method of probing such systems might be expected to lead to a more detailed understanding of the primary photoionization event and the ensuing bulk and surface electronic processes. We demonstrate here the feasibility of such direct probing of microscopic particles of semiconductor materials (TiO₂, CdS and Se) suspended in a nonpolar liquid medium.