Dye-Sensitized Commercial TiO₂ for the Construction of Robust Nanocoatings with the Enhanced Transmittance and Visible-Light-Activated Photocatalytic Self-Cleaning Properties

TiO2-based nanocoatings exhibit great promise in practical applications owing to their superior photocatalytic property. However, because of the wide band gap of TiO2, its photocatalytic capacity is only limited in the ultraviolet range. Herein, we designed and constructed robust SiO2@TiO2 composite nanocoatings with improved transmittance and visible-light-activated photocatalytic self-cleaning properties. Sulfonated cobalt(II) phthalocyanine (CoPcTs) was used as an organic dye to sensitize commercial TiO2 nanoparticles (Degussa P25) to form CoPcTs-P25 for visible-light photocatalysis. CoPcTs-P25 and small-sized solid silica nanoparticles (SSNs) were utilized as two building blocks, and acid-catalyzed silica sol (ACSS) was used as a binder to fabricate the nanocoatings via a simple dip-coating method without requiring any post-processing. By tuning the mass ratios of SSNs to CoPcTs-P25, the nanocoating with the optimized property showed the highest transmittance of ca. 97.0% at the wavelength of 566 nm, higher photocatalytic activity of degrading the organic pollutants than N–TiO2-based nanocoatings, high mechanical firmness of 3H level in pencil hardness test and 4A level in tape adhesion test, and good weather resistance. In short, the dye-sensitized commercial P25 TiO2 nanoparticles should be a promising building block for low-cost and easy preparation of robust nanocoatings with enhanced transmittance and visible-light-activated photocatalytic self-cleaning properties.