Photocatalytic performances of mesoporous TiO₂ films doped with gold clusters

We report on the single-pot fabrication of ordered mesoporous crystallized titania films doped with gold. Au is incorporated in TiO₂ films by adding to the coating solution precursors such as AuCl₃ or monodisperse Au₁₁³⁺ nanoclusters, and Au nanoparticles are formed by calcination. A systematic study is performed to correlate structure, Au doping and photocatalytic activity of such films. Two-dimensional small angle X-ray scattering (2D-SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM) and porosimetry-ellipsometry show that the films retain their mesoporous order even for doping levels as high as 1% Au:Ti atomic ratio. Wide angle X-ray scattering (WAXS), and cyclovoltammetry (CV) show that Au₁₁³⁺ nanoclusters promote the formation of the TiO ₂ (B) phase in competition with the anatase phase. AuCl₃ stabilizes instead only the anatase phase. The highest photocatalytic activity is exhibited by films where Au₁₁³⁺ is employed as a precursor, which we attribute to the combination of the mixed anatase/TiO ₂ (B) phase, of Au nanoparticle doping and of a well-ordered mesoporous TiO₂ matrix.