Nanocrystalline TiO2 by sol-gel: Characterisation and photocatalytic activity on Modica and Comiso stones

A self-cleaning photocatalytic coating based on TiO2 nanoparticles has been applied to Modica and Comiso calcarenites. TiO2 sol was applied directly to the surface or after a SiO2 intermediate layer. Photocatalytic activity of the coatings (TiO2 and SiO2/TiO2) was assessed under UV irradiation through methyl orange dye degradation tests. Good photodegradation activity and satisfactory compatibility between the sol and the surface of the investigated limestones is obtained.