Photoinduced changes of adsorbed water on a TiO2 photocatalytic film as studied by 1H NMR spectroscopy

The enhancement of the signal intensity of water molecularly adsorbed on TiO2 films could be observed on UV irradiation by H-1 NMR spectroscopy, which has been difficult to elucidate so far with alternative spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS). It was also confirmed that the enhanced NMR signals resulted from the photoinduced hydrophilic conversion of the film surface decreased back to the original state with the recovery to the less hydrophilic state of the TiO2 film surface when the film was kept in the dark.