Structural Change of TiO₂(110) Surface Involved in the Photoinduced Wettability Transition

Abstract

A hydrophobic TiO₂ surface can be converted to a hydrophilic one by UV light irradiation. This phenomenon was discovered more than 20 years ago and has been used in a variety of coating applications. However, the mechanism is not well understood. In particular, it is still not clear whether and how the surface structure is involved. We studied the possible structural change of the rutile-TiO₂(110) surface by using X-ray crystal truncation rod (CTR) scattering. We demonstrated the occurrence of a surface structural change during the photoirradiation by using the high-speed CTR scattering profile measurement in a wavelength dispersive mode. We determined the structure of the hydrophobic (non-irradiated) and hydrophilic (photoirradiated) surfaces based on static CTR data, and proposed a possible mechanism of the water wettability transition.