The contact angles of the water droplets on TiO2 single crystal surfaces decreased and became superhydrophilic state by γ-ray irradiation. It was found that these behaviors were dependent on γ-ray irradiation atmosphere, i.e., in air and in N2 atmosphere (r. h.; 30%) as well as crystal faces of TiO2 single crystals, i.e., TiO2 (100) and (110) surfaces. It was also found from the results of UV–Vis and ESR measurements that γ-ray irradiation under N2 atmosphere led to the oxygen vacancies and associated Ti3+, regardless of the presence of gaseous water. Moreover, it was suggested that the organic molecules adsorbed on TiO2 single crystal surfaces decomposed by γ-ray irradiation.
TiO2 single Crystals hydrophilicity of TiO2 surfaces Contact angle v-irradiation water droplet