Preparation of a sandwich colloid involving TiO2 and AgI (hexagonal) particles in alkaline aqueous solution is described. Time-resolved optical absorption experiments are reported that involve pulsed laser excitation at 355 Mn (TiO2 bandgap) and at 410 MI (AgI bandgap). Charge carrier dynamics was probed directly by transient absorption measurements in the near-infrared and by reaction with methyl viologen (MV(2+)). Reduction of MV(2+) was observed to occur over a period of 100-200 mu s. MV(+) so produced reduced AgI to silver. By contrast, MV(2+) reduction upon bandgap excitation of neat alkaline TiO2 colloid was complete within 1 mu s. These observations signal a prolonged electron-hole separation in the case of the AgI/TiO2 sol and indicate the formation of sandwich particles.