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

• Published in: Materials & design Vol. 114; pp. 364 - 372
• Main Authors: Zarzuela, Rafael, Carbú, María, Gil, M.L. Almoraima, Cantoral, Jesús M., Mosquera, María J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-01-2017
• Subjects: Bacteria; Biocide; Biocides; Biofouling; Building stone; Buildings; Consolidant; Copper oxide; Microorganisms; Nanocomposites; Silica nanocomposite; Silicon dioxide; Sol gel process; Stone; Consolidant; Building stone; Copper oxide; Biocide; Biofouling; Silica nanocomposite
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2016.11.009

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 the highest concentration of CuONPs, in the studied range (0.00–0.35% w/v), was not the most effective because it causes a NPs precipitation, decreasing the biocidal effect, and the resulting material is heterogeneous and fragile. An intermediate proportion of CuONPs provides a suitable consolidant and biocide performance.
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•The synthetized SiO2/CuONPs nanocomposite acts as a multifunctional (biocide and consolidant) coating for building stone.•The coatings inhibited the growth of bacteria (E. coli) and yeast (S. cerevisiae) up to an 85% and 77%, respectively.•The CuONPs, immobilized in the silica matrix, release Cu2+ ions, which play an important role in the biocide effect.•The addition of CuONPs promotes the formation of SiO2 nuclei, reducing the gel time and decreasing SiO2 particle size.•A high proportion of CuONPs (≥0.35%) causes agglomeration and, subsequently, decreases the performance.