Rutile thin film responsive to visible light and with high UV light sensitivity

A transparent rutile thin film 100 nm thick was fabricated on a quartz glass substrate; it was responsive to visible light and had a higher sensitivity to UV light than an anatase thin film formed by sol–gel method under identical conditions. The crystal structure was determined by observations using X-ray diffraction, Raman spectra, and a transmission electron microscope. The oxygen/titanium ratio of the rutile thin films was 1.78 according to the XPS peaks. The photoreactivity and photoinduced hydrophilicity of the rutile thin films was examined by measuring the pseudo first-order rate for the decoloration of methylene blue in an aqueous solution and the water contact angle, respectively. The high photoreactivity and photosensitivity of the O-deficient rutile thin film, whose optical band edge and refractive index were 3.10 eV and 2.2, respectively, were due to electron traps and assisted by O-defects within the rutile particles.