Cds nanoparticles, prepared in a reverse micellar system, were immobilized directly onto alkanedithiol-modified Zn-doped silica particles, which were themselves prepared via hydrolysis of tetraethylorthosilicate in the presence of Zn(NO3)(2) followed by contact with dithiol molecules. The resulting CdS-Zn-SiO2 composite was then used as a photocatalyst for the generation of H-2 from 2-propanol aqueous solution. Under UV irradiation (lambda > 300 nm), a high photocatalytic activity was observed for the CdS-Zn-SiO2 composite material. This is effected by electron transfer from the photoexcited ZnS (dithiol-bonded Zn on SiO2) to CdS nanoparticles. The photocatalytic activity is increased with a decrease in the number of methylene groups in the dithiol molecules, according to the rank order 1,10-decanedithiol < 1,6-hexanedithiol < 1,2ethanedithiol.