Bio-approach ZnO/Ag nano-flowers: enhanced photocatalytic and photoexcited anti-microbial activities towards pathogenic bacteria

Abstract

Zinc oxide (ZnO) and silver (Ag) nanoparticles (NPs) are well proven as one of the most common anti-microbial agents used for many environmental applications. However, in the present study, Sargassum muticum (SM) -mediated nanoparticles (NPs) and its their nanocomposites (NCs) were proved to be photocatalytic and photoexcited anti-microbial agents. Drug-resistant superbugs (DRS) were isolated, cultured, and 16s rDNA identified as B. filamentosus; B. flexus; P. stutzeri; and A. baumannii. The anti-microbial and photoexcited anti-microbial studied by using various microbes such as pathogenic bacteria (PB),drug-resistant superbugs (DRS), and marine biofilm bacteria (MBB), respectively. The anti-microbial activity showed 80 μg/mL of flower-like SMZnO/Ag–NCs (S5) displayed a maximum growth inhibition of 21 mm against PB and a minimum of 11 mm against DRS. The photoexcited anti-microbial killing efficacy was observed in Gram-positive PB strains showed a maximum activity of 16.7 [ × 102] and a minimum in DRS 14.6 [ × 103] CFUs mL−1 and Gram-negative strains 9.4 [ × 102] and minimum in DRS 10.1 [ × 103] CFUs mL−1 display a reduced density within 20 min interval. The results indicate, that green NCs with UV-light phototherapy to generating reactive oxygen species (ROS) that cause bacterial cell death. In addition, the UV-light phototherapy combined with nano-flowers S5 attained an effective degradation of harmful toxic methylene blue (MB) dyes up to 98.6% upon 45 min of irradiation. Photostability/reusability of prepared nano-flowers S5 provided up to 6 consecutive cycles of usage towards MB decolorization for the aquatic environment as well as anti-microbial effects.