Photocatalytic properties of sol–gel titania film under fluorescent-light irradiation improved by silver negative-ion implantation

We have investigated on improvement of photocatalytic properties under fluorescent light of anatase-type titanium oxide film by using silver negative-ion implantation. The anatase films were prepared in a sol–gel method on a glass plate with a commercial sol material by spin-coating and baking at 500 °C for 30 min. Typical thickness of films was about 500 nm. Silver negative ions were implanted to these films at 30 keV with a dose in 1–5 × 1016 ions/cm2. For forming Ag nanoparticles and recovering ion-induced defects, the implanted samples were annealed at temperature in a range of 400–600 °C. All the samples showed a strong optical absorption at photon energy of about 2.2 eV after annealing at 300–500 °C. This means the existence of Ag nanoparticles in the films. In reduction test of methylene blue solution under fluorescent light, all samples showed improved photocatalytic properties. The best efficiency was obtained for the Ag-implanted sol–gel film with 1 × 1016 ions/cm2 after annealing at 400 °C, and it was higher by a factor of 1.6 than that of single rutile crystalline plate. The increase in the efficiency is considered to be due to existence of Ag nanoparticles in the film.