Highly dispersed gold nanoparticles assembled in mesoporous titania films of cubic configuration

Highly dispersed Au nanoparticles (NPs) of average size of 9–12 nm were successfully assembled in mesopores of titania thin films, through H2-reduction of AuCl4-. The well organized mesoporous nanostructure was characterized by using small-angle X-ray scattering, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, secondary ion mass spectroscopy and UV–vis spectrophotometry. Au NPs embedded in the mesoporous nanostructure exhibited enhanced thermal stability, up to 450 °C, which is attributed to the spatial confinement effect of the mesopores with cubic configuration. An obvious surface plasmon resonance was observed at 570 nm in the UV–vis absorption spectra of Au NPs embedded in the mesoporous thin films. The red shift and broadening of plasmon band observed for Au NPs are accounted for by the interaction between Au NPs and mesoporous titania framework. The mesoporous TiO2/Au nanocomposite films show optically allowed direct transition of titania, where the incorporation of Au NPs evidently reduces the bandgap of titania.