Preparation of Highly Functional TiO 2 ‐Based Thin‐Film Photocatalysts by Ion Engineering Techniques, Photocatalysis, and Photo‐Induced Superhydrophilicity

Abstract

Highly transparent TiO 2 and TiO 2 -based binary oxide thin films were prepared using an ionized cluster beam (ICB) deposition method. The transparent TiO 2 thin films showed high photocatalytic performance due to their low scattering of incident light as compared to TiO 2 powders. As well, the thin films showed high surface wettability under UV light irradiation, depending on the surface morphology, surface area, and crystal phase. Then, we discussed the mechanism of the photoinduced surface wettability changes using near-infrared spectroscopy and clarified that the hydrogen bond networks between H 2 O molecules on the TiO 2 surface lessen during UV light irradiation. Furthermore, the TiO 2 –SiO 2 binary oxide thin films contained unique tetrahedral TiO 4 species incorporated within the SiO 2 matrices but did not show efficient photoresponse in the surface wettability. In contrast, the TiO 2 –B 2 O 3 thin films contained the TiO 2 nanoclusters within the B 2 O 3 matrices and showed high surface wettability under UV light irradiation. Crystalline TiO 2 thin films with an anatase structure were prepared on polycarbonate substrates at 100 °C using an radio-frequency-magnetron sputtering deposition method. The TiO 2 thin films showed high transparency and mechanical stability against scratching and bending. The TiO 2 thin films on polycarbonates exhibited photoinduced surface wettability under UV light irradiation of 0.05−1 mW cm −2 .