Samples of zeolite Y containing 2,4,6-tripherylpyrylium or tris(bipyridyl)ruthenium(II) have been prepared and their photophysical and photochemical properties compared to those of the same samples containing encapsulated nanoscopic TiO2 clusters as relays. The emission of encapsulated Ru(bpy)(3)(2+) and TP+ photolumophores undergoes static quenching in the presence of codoped TiO2 clusters. This is the expected behavior for systems, where photosensitizer and relay lack diffusional mobility. Time-resolved diffuse reflectance laser flash photolysis shows the transient generation of TP. pyranyl radical and Ru(bpy)(3)(3+), upon irradiation of TP+ and Ru(bpy)(3)(2+) in the presence of TiO2, respectively. This provides firm support for the occurrence of photoinduced electron transfer between excited TP+ as acceptor and TiO2 clusters as donors and from Ru(bpy)(3)(2+) to the conduction band of TiO2. Using the photoinactivation of horseradish peroxidase as a test reaction in aqueous medium, a synergism has been found with respect to the activity of Ru(bpy)(3)(2+) or TP+ photocatalysts when incorporated inside the supercages of zeolite Y in the presence of TiO2 nanoclusters.