Enhanced photocatalytic and antibacterial activity of ZnO/Ag nanostructure synthesized by Tamarindus indica pulp extract

In this paper, we report a one-step, sunlight-irradiated synthesis of ZnO nanostructures (NSs) covered with Ag nanoparticles (NPs) using Tamarindus indica pulp extract (TPE) and their applications to photocatalytic and antibacterial activity. TPE contains phytochemicals that act as reducing and stabilizing agents for the distribution of uniform Ag NPs of approximately 5 nm on the surface of ZnO NSs. The photocatalysis of the synthesized bare ZnO and ZnO/Ag (0.5 wt%) NSs was evaluated under UVA light and dye degradation results for methylene blue (MB) are 68% for ZnO and 94% for ZnO/Ag after 120 min. For methylene orange (MO), bare ZnO and ZnO/Ag NSs were degraded 40% and 81%, respectively, after 150 min. Moreover, the photocatalyst also showed good recycling stability even after five cycles. In addition to dye degradation, the ZnO/Ag NSs were able to show antibacterial activity against E. coli, P. aeruginosa, S. aureus, and B. subtilis at a concentration of 2 mg/ml. They showed higher activity against Gram-positive than gram-negative bacteria, which showed the influence of Ag metal on the enhanced photocatalytic and antibacterial activity of ZnO NSs. Our findings suggested that ZnO/Ag NSs can be synthesized by a facile and ecofriendly method using TPE and showed superior performance for UVA photocatalysis and antibacterial activity compared to bare ZnO.