Doped TiO2 for preventing biodeterioration of cultural heritage building materials

The aim of this study is the comparison between different biocide based on TiO2 photo activity to protect and to maintenance stone surfaces reducing the biodeterioration processes. Photocatalysts TiO2 and doped TiO2 (with different metal ions: Ag, Fe, Sr) were prepared by prepared by sol–gel and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence and optical absorbance measurements. The antibacterial activity studies of TiO2 and doped TiO2 were evaluated by photocatalytic reaction against Gram-positive and Gram-negative bacterial strains under sunlight irradiation. To assess compatibility with stone substrates, the TiO2 and M-TiO2 were dispersed in a binder (at different powder/binder ratios and color tests were carried out. It has been found that Ag/AgFe/Ag Sr doped TiO2 have the higher disinfection efficiency than that of pure TiO2 due to the effect of silver species, but only the Ag-TiO2 provide a colorimetric variation extremely low and fully compatible with Architectural Heritage guidelines.