SiO2 encapsulated TiO2 nanotubes and nanofibers for self-cleaning polyurethane coatings

Abstract

Abstract TiO2 nanotubes and nanofibers are of great interest due to their defined dimensions, high specific surface areas, and enhanced photocatalytic activity. In the application of self-cleaning polymer coatings, the enhanced photocatalytic activity improves the self-cleaning ability but also facilitates photodegradation of the polymer matrix. In order to overcome the drawbacks of TiO2 nanotubes and nanofibers, a thin layer of SiO2 was coated onto the surface of TiO2 nanotubes and nanofibers in this work. The effect of the SiO2 shell on the photocatalytic activity of the TiO2 core was investigated by UV–vis spectroscopy, photodegradation of methylene blue solution, and measurement of photo-generated hydroxyl radicals. In general, the photocatalytic activity of the SiO2-coated TiO2 nanostructures decreased with an increasing amount of SiO2 coated onto the surface of TiO2 nanostructures. By incorporating SiO2-modified TiO2 nanostructures into the polyurethane (PU) matrix, it was found that the hydrophobicity and mechanical strength of the resulting composites was enhanced while the photocatalytic activity increased with increasing loading of the photocatalyst. This approach of coating TiO2 nanostructures with a thin layer of SiO2 provides a new route towards the development of long-lasting self-cleaning coatings using 1D TiO2.