Hole oxidation on TiO₂ films in aqueous solutions studied by using OTS SAMs as a probe

An approach was developed to investigate hole oxidation on TiO₂ films in aqueous solutions by using octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs) as a probe, in which the adsorption and surface diffusion of the reactants were exculded. Under UV irradiation, the water contact angle of the OTS SAMs on TiO₂ films in water decreased obviously. In the presence of hole scavengers, the decrease of water contact angle for the OTS SAMs on TiO₂ films with UV irradiation was inhibited apparently, while the effect of ·OH radical scavengers and fluoride on the decrease of water contact angle was very small. It indicated that direct hole oxidation played a major role in photocatalytic removal of alkyl chains on TiO₂ films in aqueous solutions.