Surface modification of TiO2 (rutile) by metal negative ion implantation for improving catalytic properties

In order to improve photocatalytic property of rutile TiO2, metal negative ions were implanted to rutile substrates, and their optical absorption and photocatalytic efficiencies were investigated. Cu and Ag negative ions were implanted at 50 and 65 keV, respectively, with a dose in a range of 3×1016–1×1017 ions/cm2. In optical absorption properties after annealed, Cu- and Ag-implanted rutiles showed a clear optical absorption with a peak near photon energy of 1.9 and 2.0 eV, respectively. This means that implanted metal atoms gathered to form metal nanoparticles of Cu or Ag in the surface layer. We tested decolorization of Methylene Blue solution by implanted rutiles under irradiation of a fluorescent light. Both Cu- and Ag-implanted rutiles after annealed at 400 °C showed better photocatalytic efficiencies by approximately 1.8 times than that of unimplanted rutile, although as-implanted samples had worse properties. This improved photocatalytic performance is contributed to the existence of metal nanoparticles in the surface layer as well as recovery of implantation damages in surface layer by heat treatment.