Ag–SiO2–TiO2 nanocomposite coatings with enhanced photoactivity for self-cleaning application on building materials

•Ag–TiO2–SiO2 photocatalysts are easily applied as sols to form coatings on stone.•N-octylamine acts as dispersant, catalyzer, pore coarsener and reducing agent.•Ag NPs (2–5 nm size) improve the photoactivity of TiO2–SiO2 nanocomposites.•The coatings show good adhesion and preserve stone esthetics.

The synthesis of improved photocatalysts capable of removing pollutants deposited on building surfaces is an important challenge for researchers nowadays. By using a simple and low-cost process we have synthesized mesoporous Ag–TiO2–SiO2 photocatalytic coatings that meet the requirements of outdoor application. These are new materials designed to give to the building material improved self-cleaning properties.We have varied the loading of TiO2 and Ag nanoparticles in order to investigate their effect on the photocatalytic activity of our nanocomposites. We find that the integration of higher Ag loadings in a TiO2–SiO2 network (10% w/w) significantly increase the photoactivity of the coating containing 1% (w/v) TiO2 due to the improved absorption of visible light and higher surface area of the photocatalyst. For higher TiO2 contents (4%) there is an increase in photoactivity for 1% (w/v) Ag loading. Higher amounts of Ag loadings (5% w/w) generate an undesired color change on stone or inhibit the sol–gel transition of the coatings (10% w/w).

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