Enhanced photocatalytic activity of mesoporous SiO2/TiO2 sol–gel coatings doped with Ag nanoparticles

Abstract

In the present study, as-prepared silver nanoparticles have been incorporated into SiO2 and TiO2 sols. The characterisation of the silver nanoparticles was performed through transmission electron microscopy, grazing X-ray diffraction, and UV?visible spectroscopy, before and after mixing with the different sols. Multilayer coatings doped with silver nanoparticles were also prepared by combining different compositions and analysed by TEM and GXRD. The photocatalytic activity was studied through the degradation of methyl orange in aqueous solution under UV light exposure. High photocatalytic efficiency was observed for all the multilayer coatings. The highest efficiency was obtained for the Ag?SiO2/TiO2 mesoporous system that reached a degradation percentage of methyl orange up to 94 % after 2.5 h of irradiation, near the complete elimination of the pollutant. The mechanism that explains the high photocatalytic efficiency of this multilayer coating is associated with the high porosity of the mesoporous coatings and with the increase in the local electric field, associated with the effect of plasmon resonance surface produced for the presence of metallic silver nanoparticles in the SiO2 film.