Abstract

Layered treatments of natural stones based on dispersions of experimental nano-TiO2 and commercial TEOS, showing photocatalytic and self-cleaning properties have been set-up and tested. To enhance nano-TiO2 efficacy, a surface pre-treatment with tetraethyl orthosilicate has been proposed to avoid the penetration of NPs into the crystalline porous substrates and to improve their adhesion to the stone. Two treatment applications - wet-on-wet and wet-on-dry -have been compared, showing different results. A strong interaction Si-O-Ti has proved to be the key factor for the successful treatment, leaving the bandgap and relevant properties of nano-TiO2 unaltered. The layered treatments have been tested on a porous calcarenite (Noto stone) and a very compact marble (Carrara marble). The combined SiO2-nano-TiO2 treatments can find application in suitable cases where a surface consolidation is needed, ensuring a depolluting and self-cleaning durable activity