In Situ Evaluation of New Silica Nanosystems as Long-Lasting Methods to Prevent Stone Monument Biodeterioration

Abstract

Microbial colonization can lead to various biodeterioration phenomena in outdoor stone monuments. To prevent these issues and mitigate the negative effects of chemical control, recent research has focused on encapsulating biocides in nanostructures. We tested the antifouling efficiency of the new multifunctional coating through in situ experiments performed on the Aurelian Walls in Rome. We selected two different biocides (2-mercaptobenzothiazole and zosteric sodium salt) and loaded them into two different silica nanocontainers (nanocapsules and mesoporous particles), which were dispersed in TEOS coatings. These coatings were applied to four common lithotypes (marble, travertine, mortar, and brick). Subsequently, we accelerated the colonization by inoculating microorganisms onto half of the samples, subjecting all samples to aging cycles. We conducted colorimetric, infrared spectroscopy, and other microscopic analyses to assess their durability and antimicrobial action. Our 3-year survey indicates that the coatings demonstrated antifoulant efficiency across all samples, with higher effectiveness observed on brick and mortar compared to travertine and marble. Among the nanostructures, nanocapsules exhibited greater efficiency than mesoporous particles, and regarding the biocides, the commercial one outperformed the natural one. These findings highlighted the potential of such systems in preserving cultural heritage; however, further research and product development is imperative for practical implementation.

In Vitro Viability Tests of New Ecofriendly Nanosystems Incorporating Essential Oils for Long-Lasting Conservation of Stone Artworks

“…The research provides valuable insights into the potential of silica nanocapsules for preserving cultural heritage artifacts. These good results can be the starting point to test their application on the stone surface incorporated in the gel, microemulsion or coating [56,64,73]. However, as proven by previous studies [61,62,65], the synthesis and the nanoencapsulation step strictly depends on addressing the observed limitations, such as the fluctuating efficacy trends, which demand more extensive investigations.…”

“…More recently, we also evaluated their effectiveness for a long-lasting efficacy, through in situ tests, located in favorable conditions of humidity and solar radiations [64]. The experimentations gave interesting results, and then, continuing the previous research, this ongoing study focuses on testing new stone coatings formulated with promising green biocides compatible with silica nanocapsules for a controlled release.…”