Effect of Ag nanoparticle size on the plasmonic photocatalytic properties of TiO₂ thin films

Photocatalytic TiO₂ films combined with Ag nanoparticles (NPs) embedded-SiO₂ films were fabricated by means of a RF magnetron sputtering and subsequent rapid thermal annealing (RTA). X-ray diffraction results show that the TiO₂ films have anatase phase when annealed at [email protected]. The Ag NPs were formed by deposition and subsequent annealing at 600°C. Scanning electron microscopy (SEM) results show that the density of the NPs decreases with increasing Ag film thickness. For example, the average NP diameter varies from ~19.3 to ~55.9nm as the film thickness increases from 2 to 12nm. Transmittance measurements show that as the Ag NP size decreases, the plasmonic peaks shift towards the shorter-wavelength region and become narrower. It is further shown that under UV-illumination (352nm), all the TiO₂ films with the Ag NPs show higher methylene blue decomposition rates compared to the TiO₂ only films and the TiO₂ films with Ag NP (a 7nm-thick Ag film) show the best decomposition rate among the samples possibly due to the combined effects of optimized localized field amplification and radiative efficiency.