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.