Effect of γ-ray irradiation on the wettability of TiO2 single crystals

The contact angles of the water droplets on TiO2 single crystal surfaces decreased and became superhydrophilic state by gamma-ray irradiation. It was found that these behaviors were dependent on gamma-ray irradiation atmosphere, i.e., in air and in N-2 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 gamma-ray irradiation under N-2 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 gamma-ray irradiation.