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Microorganisms naturally colonize rock-based materials in outdoor environments, thereby contributing to their degradation. Fungi, especially in tropical environments with abundant water and favorable temperatures, play a significant role in biodegradation. However, many aspects of the microorganism-stone interaction, including fungal colonization dynamics and the impact of treatment applications, remain unclear. This study conducted a four-year in-situ evaluation of fungal community dynamics on limestone surfaces in the Temple of the Warriors at the Chichén Itzá archaeological site in Mexico, focusing on cleaning and treatment using nanoparticles (NPs). These NPs included zinc oxide (ZnO) and CaZn 2 (OH) 6 ·2H 2 O (CZ)-based NPs synthesized via sol-gel (CZ-SG) and mechanochemical methods (CZ-MC), as well as CZ/Ca(OH) 2 -based products (CZ:Ca-SG). The microbial colonization cover was assessed using colorimetric measurements, and the surface was sampled for fungal community isolation and identification. The results demonstrated significant impacts of cleaning and nanomaterial applications on cultivable fungal communities (melanized filamentous, hyaline, and microcolonial fungi), altering composition, dynamics, and stone surface coloration. In particular, ZnO NPs caused 50 % decline in fungal species and individuals, whereas CZ:Ca-SG NPs displaced most species, indicating effective inhibition of the cultivable fungal community. Microcolonial fungi (MCF), known for their tolerance to withstand harsh environmental conditions, were the only fungal group found in the CZ:Ca-SG treatment. In contrast, CZ-SG and CZ-MC increased the abundance of melanized species, resulting in darkening and reduced color intensity. This study highlights the importance of microcolonial fungi that are tolerant to cleaning and coating procedures in the preservation of stone cultural heritage. These findings enhance our understanding of fungal colonization dynamics following treatment and provide valuable insights into the challenges associated with preserving stone materials in tropical environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Recent research has increasingly focused on synthesizing nanoparticles (NPs) through various methods to determine how these processes influence their characteristics, and consequently, their biological activity. Calcium zinc hydroxide dihydrate (CaZn2(OH)6·2H2O) nanoparticles, designates as CZ, were obtained via sol–gel (CZ-SG), hydrothermal (CZ-HT), and microwave (CZ-MW) methods, and their properties were characterized using XRD, SEM, TEM, and BET analyses. The different synthesis revealed distinct CZ nanoparticle attributes, including variations in crystallite sizes (72 nm for CZ-SG, 65 nm for CZ-HT and CZ-MW) and morphologies (fibrous for CZ-HT and spherical agglomerates for CZ-SG and CZ-MW). Surface area analysis showed low values across all synthesis methods, with CZ-HT exhibiting the best surface area (8.154 m2/g). The investigation also explored how these synthesis routes influence antifungal efficacy against fourteen fungal strains associated with the biodeterioration of limestone cultural heritage structures. Our results highlight the notable antifungal activity of CZ-NPs, particularly those synthesized via the CZ-HT method, which demonstrated the most effective antifungal action as evidenced by the lowest minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). This effectiveness is attributed to the unique fibrous morphology, which proves to be highly inhibitory to fungal cell proliferation. These findings not only advance our understanding of CZ NPs-mediated antifungal mechanisms but also open a new effort for the development of effective preservation strategies for cultural heritage conservation. [ABSTRACT FROM AUTHOR]

Fungal growth on construction materials in tropical climates can degrade aesthetics and manifestations on modern and historical sick buildings, affecting the health of their inhabitants. This study synthesized ZnO nanoparticles with enhanced antifungal properties using a precipitation method. Different concentrations (25%, 50%, and 100%) of Eichhornia crassipes aqueous extract were used with Zn(NO3)2·6H2O as the precursor to evaluate their spectroscopic, morphological, textural, and antifungal properties. X-ray diffraction confirmed the hexagonal wurtzite phase of ZnO with crystallite sizes up to 20 nm. Fourier-transform infrared spectroscopy identified absorption bands at 426, 503, and 567 cm−1 for ZnO-100, ZnO-50, and ZnO-25, respectively. Nitrogen physisorption indicated a type II isotherm with macropores and a fractal dimension coefficient near 2 across all concentrations. Polydispersity index analysis showed that ZnO-50 had a higher PDI, indicating a broader size distribution, while ZnO-25 and ZnO-100 exhibited lower PDI values, reflecting uniform and monodisperse particle sizes. FESEM observations revealed semi-spherical ZnO morphologies prone to agglomeration, particularly in ZnO-25. Antifungal tests highlighted ZnO-25 as the most effective, especially against Phoma sp. with an MFC/MIC ratio of 78 µg/mL. Poisoned plate assays demonstrated over 50% inhibition at 312 µg/mL for all tested fungi, outperforming commercial antifungals. The results indicate that ZnO NPs synthesized using E. crassipes extract effectively inhibit fungal growth on construction materials. This procedure offers a practical approach to improving the durability of building aesthetics and may contribute to reducing the health risks associated with exposure to fungal compounds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Deterioration by microbial activity is common in the built cultural heritage, where phototrophic microorganisms are primary colonizers that form complex communities associated with heterotrophic microorganisms. Therefore, this article analyses the antiphototrophic effect of ZnO and CaZn2(OH)6·2H2O (CZ) nanoparticles (NPs) on three limestone lithotype coupons (Xcambo, red limestone and shellstone). The nanomaterials were obtained via sol–gel (SG), hydrothermal (HT) and mechanochemical (MS) routes and characterized using powder X‐ray diffraction and scanning electron microscopy. Two concentrations of NPs (5000 and 10 000 μg mL−1) were applied to the coupons; afterwards, phototrophic microorganisms isolated from Chichén‐Itzá, Yucatan were inoculated. The percentage of protection was calculated with ImageJ software, and chromatic parameters were measured to identify visible changes in the stones. RESULTS: The results show differences in the protective effect and color variations depending on the nanomaterials and phototrophic microorganisms applied in the limestone coupons. CZ and ZnO protect more than 72% on the surface of shellstone and Xcambo except for ZnO‐SG in shellstone. The growth of Gloeocapsa sp. in red limestone with ZnO‐SG and CZ‐SG was equal to or greater than that of the control without NPs. In general, the NPs protect the limestone surface against phototrophic microorganisms up to 10% more than commercial algaecide. The coupons treated with ZnO‐HT and CZ‐HT have greater protection against biofilm formation than other coatings. CONCLUSIONS: In general, the coatings show a higher antiphototrophic protection than the controls, mainly the CZ‐HT coatings, with better results at lower concentration. Therefore, these nanomaterials could be used to inhibit the formation of biofilms on built cultural heritage. © 2022 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]