Adsorbed thallium(I) ions as a probe of surface charge in UV-irradiated titania/aqueous solution interfaces

Thallium(I) is shown to be a sensitive probe of titania particle/aqueous so lution interfaces in the dark and under ultraviolet (UV) illumination. We s how that experimental conditions can be chosen such that photocatalytic red uction or oxidation of this probe is avoided. Thus, any changes in the meas ured solution levels of this probe can be simply attributed to correspondin g variations in its adsorption tendency on the TiO2 particle surface. Data are presented on how this interfacial probe tracks modulations in the oxide surface charge induced either by variations in solution pH or by UV irradi ation.