The utilization of time-resolved dielectric loss to probe the role of the surface in heterogeneous photochemistry

The measurement of time-resolved (or transient) dielectric loss in semiconductors using an e.p.r. spectrometer interfaced to a flash-photolysis system is discussed. In particular, it is demonstrated that aqueous dispersions of pigments can readily be studied using this technique. In this way, the system can be monitored in the presence of donors and acceptors where dynamic interfacial redox reactions are occurring. A flow system was utilized to avoid setting problems as well as providing the potential for the acquisition of first-flash kinetic data. Finally, surface modified pigments are contrasted to their corresponding starting materials.