Solar light active silver/iron oxide/zinc oxide heterostructure for photodegradation of ciprofloxacin, transformation products and antibacterial activity.

This paper reports on the multitasking potential of a silver/iron oxide/zinc oxide (Ag/Fe2O3/ZnO) heterostructure, which was used for the photocatalytic decomposition of ciprofloxacin (CPX) and bacterial disinfection. The Ag/Fe2O3/ZnO heterostructure was successfully prepared using a facile precipitation method, and characterization results showed interesting structural, morphological, compositional and luminescent properties. The morphological results of the prepared heterostructure confirmed the deposition of Ag nanoparticles onto the surface of ZnO nanoplates and Fe2O3 nanorods. Treatment studies showed that the Ag/Fe2O3/ZnO heterostructure had superior solar light driven photocatalytic activity towards CPX degradation (76.4%) compared to bare Fe2O3 nanorods (43.2%) and ZnO nanoplates (63.1%), Ag/Fe2O3 (28.2%) and Ag/ZnO (64.5%) under optimized conditions (initial CPX concentration: 10 mg/L; pH 4; catalyst loading: 0.3 g/L). Reactive species study confirmed the roles of e-, h+, OH and O2- in the photocatalytic degradation process. This photocatalytic behaviour of the Ag/Fe2O3/ZnO heterostructure could be attributed to the improved full solar spectrum harvesting capacity, separation of charge carriers and migration of e-/h+ across the heterostructure interface. In addition, the Ag/Fe2O3/ZnO heterostructure also showed good antibacterial activity against Escherichia coli (E. coli) under both dark and visible light conditions. This might be due to generation of reactive oxygen species during the reaction. To the best of our knowledge, this is the first study till date on the utilization of Ag/Fe2O3/ZnO heterostructure for the photocatalytic degradation of CPX and E. coli bacteria disinfection. Therefore, this work offers an attractive path to design ZnO-based ternary heterostructures for solar-driven applications in wastewater remediation.