Effects of surface functionalization with alkylalkoxysilanes on the structure, visible light photoactivity and biocidal performance of Ag-TiO2 nanoparticles

Surface-modified Ag/TiO2 photocatalysts with enhanced activity under visible light and biocidal properties have been produced through a two-stage method involving the functionalization of TiO2 nanoparticles(NPs) with –SH or –NH terminated alkoxysilanes and deposition of AgNPs. The functionalization process increased the yield of the Ag deposition and promoted a more homogeneous distribution of the Ag over the TiO2 surface. The highest stability, homogeneity and visible range absorption was achieved by –NH functionalization. However, the modification with –SH groups alters the size of the AgNPs and decreases the effectiveness due to formation of Ag2S. The increased absorption in the visible spectrum accelerated the organic dye degradation under solar light, although aggregation processes affected their effectiveness under UV-A. The incorporation of AgNPs allowed for the elimination of phototrophic microorganisms under white light at very low Ag concentrations whereas TiO2 and –SH functionalized Ag/TiO2 showed no biocidal activity.This work has been supported by the Spanish Government/FEDER-EU (MAT2013-42934-R and MAT2017-84228-R), and the Government of Andalusia (FEDER-UCA18-106613 and Group TEP-243). R. Zarzuela would also like to thank the Spanish Government for his pre-doctoral grant (FPU14/02054). Ministerio de Ciencia e Innovación Grant numbers: MAT2013-42934-R, MAT2017-84228-R Junta de Andalucía Grant numbers: FEDER-UCA18-106613, TEP-243