Synthesis, Photocatalytic, and Antifungal Properties of MgO, ZnO and Zn/Mg Oxide Nanoparticles for the Protection of Calcareous Stone Heritage

Abstract

More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg1–x Zn x O, x = 0.096) NPs obtained by sol–gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg1–x Zn x O NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg1–x Zn x O NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg1–x Zn x O NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly efficient antifungal protection for calcareous stone heritage.

Comparative Study on the Fungicidal Activity of Metallic MgO Nanoparticles and Macroscale MgO Against Soilborne Fungal Phytopathogens

“…In particular, Huang et al, further demonstrated that peptide linkages in the bacterial cell wall are physically damaged by the generation of superoxide ions on the surface of nMgO (Huang et al, 2005). Conceivably, nMgO have enormous potential as antibacterial agents, effectively suppressing agricultural bacterial and fungal diseases caused by Ralstonia solanacearum, a medical and foodborne pathogen (Jin and He, 2011;Parizi et al, 2014;Imada et al, 2016;Sierra-Fernandez et al, 2017;Cai et al, 2018a). Nonetheless, investigations on the effects of nMgO on fungal pathogens and on elaborate antimycotic mechanisms have scarcely been reported before (Jin and He, 2011).…”

Synthesis of CuS and ZnO/Zn(OH)2 nanoparticles and their evaluation for in vitro antibacterial and antifungal activities

“…Green chemistry utilizes nontoxic chemicals and environmentally friendly solvents for synthesizing NPs, which clearly shows a different path in eliminating wastes before it is generated. Nowadays, inorganic metal NPs such as MgO and ZnO, Ag, Au, Cu, Cu 2 O and Cu/Cu 2 O are increasingly used as antimicrobials owing to their stability and long shelf life compared with the organic antimicrobial agents. The exploration of nanostructures offers new possibilities in biological context, and owing to the fact that the surface area of particles increases by decreasing particle size, biological activity enhances per given mass in comparison with larger particles …”

Antimicrobial engineered nanoparticles in the built cultural heritage context and their ecotoxicological impact on animals and plants: a brief review

“…However, there is another type of nanoparticles that are produced by man, known as engineered nanoparticles (ENPs), which are manufactured using different materials such as metal oxides, metals, carbon, polymers and lipids [1]. The potential of nanoparticles (NPs) for conservation of built structures has been established for the consolidation of decayed materials, production of de-polluting surfaces, self-cleaning, surface enhancement or as a biocide to reduce biodeterioration [2][3][4][5]. Titanium dioxide (anatase) has been employed for many years [6,7] and in some respects has become the gold standard for self-cleaning surfaces.…”