The dye-sensitized nanocrystalline TiO2 colloidal suspension in aqueous systems has been applied for H-2 evolution in the photocatalytic water splitting under visible irradiation. We have reported that the conversion efficiency is strongly influenced by the combination of dye-sensitizers and co-existing species in the suspension system. We herein analyze the fluorescence quenching of the dye-sensitized TiO2 nanoparticles in the suspensions and photoelectrochemical properties of dye-sensitized nanoporous TiO2 films. The combination of dye-sensitizers and co-existing species dominates the charge recombination resulting in significant differences in the efficiencies of the proton reduction into H-2. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.