Using ZnO nanoparticles in fungal inhibition and self-protection of exposed marble columns in historic sites

Abstract

The marble columns at many historic sites represent one of the most important and fundamental architectural elements in a building. They are almost always subject to serious damage, whether in the base, middle, or crowns of columns by fungal infection. In most cases, the microbial deterioration affects the physical and mechanical properties of historic marble columns, which have in turn been affected by other damaging factors (e.g., weathering from the elements or mechanical damage), leading to their partial or total collapse. In this current study, researchers are turning to new technologies in order to find the ideal solution to inhibit fungal growth, and, in turn achieve the total protection of exposed historic marble columns. The photocatalytic inorganic nanoparticles of ZnO have been employed for the purpose of long-term protection of exposed marble columns by inhibiting microbial-fungal attack and forming a protective surface layer. ZnO nanoparticles were dispersed in laboratory synthesized acrylic polymer to create a combined biocidal and consolidating coating to be applied on historic marble columns substrate. The synthesized nanocomposite coating was characterized and applied to marble samples collected from various archeological sites in Egypt. The protecting effect of synthesized nanocoating against fungal attack by Aspergillus niger and Penicillium sp., in addition to RH/Temperature, UVaging, and mechanical deterioration, was studied. The consolidating action of the obtained mixtures was evaluated through microscopic examination and capillary water absorption. Further, colorimetric measurements have been performed to evaluate the optical appearance of the columns. ZnO nanocomposites displayed better performance when compared to the pure synthesized acrylic polymer. The coated ZnO nanoparticles enhanced the durability of stone surface to resist the fungal attack when subjected to inoculums containing Aspergillus niger and Penicillium sp. and improved the resistance to UVaging, relative humidity, and thermal effect compared to the samples coated with the acrylic polymer without ZnO nanoparticles. Self-protection properties were confirmed without any obvious color changes on marble surfaces.

Nanostructured Coatings for Stone Protection: An Overview

“…Crystalline titanium dioxide is the most used photocatalyst, but also other metal oxide nanoparticles were used, such as ZnO, ZnTiO 3, and CuO (Ruffolo et al, 2010;Zarzuela et al, 2018;Aldosari et al, 2019) with similar results in terms of selfcleaning and biocidal efficacy. Other experiments have been carried out by doping TiO 2 with elements such as silver, copper, gold and nitrogen (Ruffolo et al, 2013;La Russa et al, 2014;Banerjee et al, 2015;Bergamonti et al, 2017).…”

Nanoparticles as Anti-Microbial, Anti-Inflammatory, and Remineralizing Agents in Oral Care Cosmetics: A Review of the Current Situation

“…ZnO NPs fight against bacteria [142,145,146], viruses [147], and fungi [148]. The anti-microbial activity of ZnO NPs (Table 1) depends on synthesis techniques, physico-chemical characteristics, evaluation tools, and techniques used to generate three-dimensional structures [149,150].…”

Aspergillus niger Environmental Isolates and Their Specific Diversity Through Metabolite Profiling

“…Aspergillus niger is a cosmopolitan representative of microscopic filamentous fungi. Although the main source of this strain is soil, it frequently occurs in various other sources, such as historical and archaeological objects ( Abdel-Kareem, 2010 ; Pangallo et al, 2012 ; Aldosari et al, 2019 ; Geweely et al, 2019 ) or indoor environments ( Egbuta et al, 2017 ; Omar et al, 2018 ). The ability of Aspergillus niger to produce substances of various types, such as low molecular weight organic acids (e.g., gluconic, citric, itaconic, oxalic, malic, acetic, lactic, and others), enzymes (e.g., amylase, aryl-phosphatase, β-glucosidase, cellulase, lipase, and others) as well as other products of metabolism, has great use not only in the food, medicine, pharmaceutical, and chemical industries but also in mineral biotechnology ( Steiger et al, 2013 ; Akhtar et al, 2014 ; Utobo and Tewari, 2014 ; Adeleke et al, 2017 ; Odoni et al, 2017 ).…”