The antifungal efficacy of nano-metals supported TiO₂ and ozone on the resistant Aspergillus niger spore

Recently, antimicrobial efficacy of nano-metals has been extensively investigated. However, most of the related studies focused on the bactericidal effectiveness. Molds, especially their spores, are more resistant than bacteria, and can build a high concentration in houses due to dampness. Therefore, a comprehensive evaluation of the antifungal effectiveness of nano-metals is necessary.In this study, the nano-metals (Ag, Cu and Ni) supported catalysts were successfully prepared by the incipient wetness impregnation method, while the titanium dioxide (Degussa (Evonik) P25) nanoparticle was served as the support. The antifungal experiments of Aspergillus niger spores were conducted on two surfaces (quartz and putty) in the darkness with and without ozone exposure, respectively. The critical Ag concentration to inhibit the germination and growth of A. niger spores of 5wt% nano Ag catalyst was 65mg/mL, lower than several cases in previous studies. The inactivation rate constants (k) of A. niger spores on nano-metals supported catalysts in the presence of ozone (k=0.475-0.966h^-1) were much higher than those in the absence of ozone (k=0.001-0.268h^-1). However, on the surface of TiO₂ particles, no antifungal effect was observed until 6-h exposure to ozone. Consequently, ozone has a synergetic effect on nano-metals antifungal efficacy.