Formulation of geopolymer coating spray and its antifungal activity

This study aimed to develop an antifungal coating using a geopolymer in combination with zinc oxide nano- particles (ZnONPs). The coating spray was formulated by adjusting the Si/Al ratio, while maintaining a constant Na/Al ratio. This study assessed the performance of coatings on cement mortar and evaluated their resistance to biodeterioration using Cladosporium under UV and dark conditions. At the optimal Si/Al ratio, an adhesion strength of 0.90 MPa was obtained. However, the adhesion strength abruptly decreased when ZnONPs were introduced to the spray formulation and decreased slightly further with an increase in ZnONP content. Beyond the initial period, mycelial growth on the geopolymer coating without ZnONPs gradually reduced and eventually disappeared after 28 days, which was attributed to the high-pH environment. However, the geopolymer coating incorporating ZnONPs exhibited enhanced antifungal activity compared to that of the ZnONP-free coating. Under UV light, the geopolymer coating with ZnONPs resulted in less mycelial growth than under dark conditions.