Layer-by-Layer Assembly of Highly Transparent SiO₂/TiO₂ Coatings with Antireflection and Self-Cleaning Properties

Highly transparent SiO₂/TiO₂ nanostructured coatings with antireflection (AR) and self-cleaning properties were prepared using a simple layer-by-layer deposition procedure. The external TiO₂ layer, which displayed photocatalytic and superhydrophilic properties, also provided the self-cleaning function. The internal SiO₂ layers, which have antireflection properties, can also shorten required self-cleaning time, significantly. Self-cleaning time could be controlled by SiO₂ layers at the bottom. The maximum transmittance of SiO₂/TiO₂ nanostructured coating to visible incident light reached 99%. The self-cleaning properties of the coatings were studied by the change of the water contact angle on octadecyltriethoxysilane-covered coatings under 1.0 mW cm^–2 ultraviolet light. Significant decrease in water contact angle that demonstrates the photodegradation ability of the coating was noted due to the internal porous SiO₂ nanostructured layers. Upon illumination by ultraviolet light, the coatings became superhydrophilic with water contact angles less than 3° thus greatly favouring the self-cleaning function of the films.