Caratteristiche fotocatalitiche e antibatteriche di nanomateriali

A currently very active area in nanotechnology concerns the development of treatments based on photocatalytic titanium dioxide. This compound gives antibacterial, self-cleaning and de-pollution properties to materials on which it is applied. The titania treatments applied on marble or other stones may offer an innovative help for preventive conservation of cultural assets, minimizing the cleaning operations and so decreasing the maintenance costs. In this work, products containing TiO2 as anatase were studied, which is the photocatalytic active form for accelerating the decomposition and oxidation reactions of organic and inorganic air pollutants; thanks to this mechanism, the deposition of dark substances can be reduced. Moreover its antibacterial properties can be useful in order to limit the biological attack on stone. Nano titania suspensions in water were evaluated both in vitro, in order to verify their antibacterial activity, and after deposition on a marble sample exposed outdoor for eight months, for testing their resistance to microbiological attacks. The same compounds were applied to other marble samples and their photocatalytic activity was tested by NOx de-pollution measurements in a photoreactor, and by the methylene blue discoloration test. Results obtained in terms of photocatalytic and antibacterial efficacy were satisfactory. Titania also gives high hydrophilicity to surfaces. For this reason other solutions, where nanoparticles are associated with hydrophobic compounds, were studied. These formulations were applied on marble, travertine and Lecce stone specimens, and exposed outdoor in an urban area for eight months. On the treated surfaces the morphological distribution of the products, the photocatalytic efficiency of titania and the contact angle before and after their outdoor exposition were evaluated. Before the aging test, every formulation gave good photocatalytic efficiency, and the formulations containing a water repellent gave hydrophobic properties to the surfaces. After ageing the concentration of titania on the surface and consequently its photocatalytic properties were decreased. In comparison to the other products, the TiO2 nanosuspension (PARNASOS series) preserves the better ability in the degradation of organic compounds.