On the relationship between silver concentration, surface roughness and photocatalytic activity of spin-coated TiO2 films.

This study explores the impact of silver doping on the physical and photocatalytic properties of spin-coated TiO2 films. TiO2 films were loaded with varying amounts of Ag (0.1, 0.5, 1, 1.5, 2, and 5 wt%) synthesized via sol-gel spin coating and employed for the photocatalytic oxidation of stearic acid. The effects of spin speed and the number of deposited layers on film thickness and roughness were also examined. Increasing the spin speed from 500 to 7000 rpm reduced the film thickness by a factor of approximately 4.4, while spin coating 1 to 10 layers at 3000 rpm increased the thickness by a factor of ca. 6. Ag doping enhanced photocatalytic activity, with the 1.5 wt% Ag/TiO2 film exhibiting the highest efficiency, leaving approximately 2% stearic acid on the surface after 40 minutes of reaction. However, higher concentrations of silver (greater than 2 wt%) decreased activity, with 33% of stearic acid remaining on the surface for the 5 wt% Ag/TiO2 film. The 1.5 wt% Ag/TiO2 film displayed reduced activity when its surface roughness exceeded ca. 3 µm.