Direct detection of OH radicals diffused to the gas phase from the UV-irradiated photocatalytic TiO2 surfaces by means of laser-induced fluorescence spectroscopy

The important roles of OH radicals for remote oxidation using TiO2 photocatalysts were evidenced by the in situ detection of OH radicals in the gas phase using the laser-induced fluorescence (LIF) technique. The appearance of OD-LIF intensities after the exposure of D2O vapors over TiO2 powders and the decrease of the time-resolved signals of OH-LIF intensities with increasing calcined temperatures of TiO2 powders suggested that the exchangeable water at the TiO2 surface is the origin of the diffused OH radicals.