Self-cleaning and de-polluting stone surfaces: TiO2 nanoparticles for limestone

To evaluate the self-cleaning and de-polluting properties of a transparent titania coating, in this investigationa titanium dioxide based suspension was deposited by spray coating on travertine, a porous limestonelargely used as building material. To assess compatibility with stone substrates, microstructureanalysis, color and gloss measurements, static contact angle analysis and two different water absorptiontests were carried out. Self-cleaning and de-polluting activities were assessed by the use of rhodamine Bdecoloration and NOx degradation tests. The results showed good compatibility with stone surfaces andevident efficiency, allowing the use of titania coatings for real outdoor applications.