Meso-tetrakis (4-sulphonatophenyl)porphyrin (TSPP) and its complex with TiO 2 were studied by absorption, fluorescence, and steady-state and time-resolved photothermal spectroscopy. A TiO 2 -TSPP complex was obtained by covalent bonding of anionic porphyrin with the nanostructural form of TiO 2 . The TiO 2 colloidal carriers modifying the thermal energy distribution and considerably influencing the photophysical processes were found to lead to changes in the population of the porphyrin singlet and triplet states, resulting in singlet oxygen generation and/or electron transfer.