CuO/SiO2 nanocomposites: A multifunctional coating for application on building stone

Abstract

The decay of building materials is generally caused by the combination of chemical, physical and biological agents. Therefore, the development of products that combine multiple protection mechanisms is desirable. We have developed, via a sol-gel route, CuO/SiO2 nanocomposites with application as a multifunctional protective treatment for building stones. In this work, we demonstrate that CuONPs act as a catalyst of the sol-gel process and promote the formation of nucleation centers, affecting the final structure of the nanocomposites. We also conclude that the nanocomposites increase mechanical resistance and decrease microbial growth of two reference laboratory microorganisms (bacteria and yeast) on a typical building limestone. Moreover, the release of Cu2+ ions is the most likely mechanism for the biocidal effect. Finally, we find that a 0.15% concentration of CuONPs is the optimal value for both consolidant and biocidal action. A higher proportion of CuONPs causes a precipitation of NPs, decreasing the biocidal effect and the resulting material is heterogeneous and fragile.