Thermal annealing induced evolution of morphological, structural, optical and photocatalytic properties of Ag-TiO2 nanocomposite thin films

Plasmonic nanocomposite coatings are important for applications ranging from solar photovoltaics to environmental remediation. Plasmonic Ag-TiO2 nanocomposites were fabricated by atom beam sputtering. Morphological and microstructural variations in Ag-TiO2 nanocomposite thin film upon thermal annealing were investigated. FESEM studies revealed nanoparticles which grew in size and also aggregated forming nanostructures with shape anisotropy on surface upon annealing. The nanocomposite nature of the film with Ag and TiO2 nanocrystals was confirmed by X-ray diffraction. UV-Vis DRS spectra showed significant improvement in absorbance due to the plasmonic properties of aggregated Ag nanostructures formed and improvement in the crystallinity of the film upon annealing. Ag-TiO2 nanocomposite coatings were used for solar light induced photocatalytic degradation of methylene blue in water. The Ag-TiO2 coating annealed at 600 degrees C was found to be the most efficient photocatalyst degrading 2.5 mu M MB in water in only 20 min, which is exciting for practical applications. The tentative mechanism underlying the observed enhancement in the photocatalytic efficiency of Ag-TiO2 coating upon annealing is proposed.