Photocatalytic activities of WO3@TiO2 nanoparticles coated on a limestone surface

We present an experimental study on the photocatalytic activity of WO3@TiO2 nanoparticles (40–50 nm) coated on a limestone surface. WO3 was synthesized via a hydrothermal process with added TiO2 P25 nanoparticles and characterized using SEM, TEM, EDS, XRD, and UV–vis diffusive reflective spectroscopy. The aqueous colloidal solutions were deposited on limestone surfaces. The photocatalytic efficiency of the thin films to degrade airborne inorganic and organic pollutants or the antimicrobial ability to prevent soiling and microorganism proliferation was assessed by monitoring the color changes of stained methylene blue dye molecules. Our results show that these nanoparticle catalysts can be used in building envelope coating for environmental purification. The best performance is achieved for a WO3 to TiO2 weight ratio of 2%, with a performance improvement of about 12% under 13 h Xe light illumination.