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Brookite Formation in TiO2[BOND]Ag Nanocomposites and Visible-Light-Induced Templated Growth of Ag Nanostructures in TiO2



TiO2[BOND]Ag-nanocomposites exhibit various desirable properties that make them suitable for a variety of applications, for example in photocatalysis and as bactericidal coatings. In this work, a new method for processing TiO2[BOND]Ag nanocomposites is presented. The nanocomposite films are fabricated from one precursor solution with high silver loading of up to 50%. The resulting films exhibit a microstructure consisting of TiO2[BOND]AgxO nanocomposites with a largely XRD-amorphous TiO2 matrix containing brookite nanocrystals. This specific microstructure absorbs in the visible range so that photoreduction of Ag ions can be accomplished by using visible light. The thin films can be patterned using simple shadow masks. The illuminated areas show a high density of self-organized nanoparticles (SNPs) and nanorods (SNRs), which are templated by the TiO2 porous network. The particle size can be tuned by varying the irradiation time. Most of the SNPs and SNRs form faceted crystals, which are mostly a combination of {111} and {110}. The application of these films as substrates for surface-enhanced Raman scattering is shown. Enhancement factors as high as 4.6 × 106 could be obtained using rhodamine 6G dye molecules. More applications should involve photocatalytic water purification using visible light.