Photocatalytic dye degradation and photoexcited anti-microbial activities of green zinc oxide nanoparticles synthesized<i>via Sargassum muticum</i>extracts

Abstract

Drug-resistant superbugs (DRS) were isolated from hospital sewage waste and confirmed by a 16S rDNA molecular technique as <i>B. filamentosus</i>, <i>B. flexus</i>, <i>P. stutzeri</i>, and <i>A. baumannii</i>. Green nanotechnologies provide a new promising alternative pathway that was found to be much safer, eco-friendly, and has economic benefits over physical/chemical methods. <i>Sargassum muticum</i> (SM) mediated zinc oxide nanoparticles (ZnO-NPs) were proved to be photocatalytic and anti-microbial agents. Anti-microbial action was demonstrated by a maximal growth inhibition activity of 18 mm against <i>A. baumannii</i> and a minimal of 12 mm against <i>B. flexus</i> at 80 μg mL^-1 concentrations. The anti-microbial mechanism of SMZnO-NPs employed a biphasic phenomenon persuaded by an osmotic shock that can attack the DRS bacterial cells directly and lead to death. In addition, photocatalytic activity was investigated by SMZnO-NPs for the degradation of methylene blue (MB) dye under different light conditions. Natural sunlight irradiation shows effective enhancement with the highest efficiencies of 96% being achieved within 60 min compared to UV-light and visible-light. The reusability of SMZnO-NPs provides up to 6 consecutive cycles towards MB decolorization for environmental water cleansing.