Fabrication of phytochemical enriched ZnO grafted on few-layered graphene sheets and evaluation of biological and catalytic activity for degradation of medical effluents

Abstract

The consumption of contaminated water by humans and animals has resulted in the proliferation of various diseases and environmental pollution. In particular, pharmaceutical effluents are notable as one of the main contaminants in water bodies. Here, zinc oxide nanoparticles (ZnO NPs) were synthesized using Strychnos potatorumseed extract and acted as a reducing and capping agent. Furthermore, the nanocomposite effectively integrated ZnO with reduced graphene oxide (rGO) through reflux. ZnO NPs exhibited a hexagonal wurtzite structure with a crystallite size of 18.3 nm and spherical morphology. The few layers of rGO sheets were wrapped with ZnO NPs, as observed in FESEM images. The surface area was estimated at 28.93 and 103.77 m²/g for ZnO and ZnO-rGO, respectively. Correspondingly, the optical properties of materials correlated with energy gaps of 3.41 and 2.93 eV. The XPS analysis confirms the presence of ZnO-rGO by identifying the distinctive binding energy peaks. The ZnO-rGO nanocomposite exhibited enhanced antibacterial activity, with zones of inhibition measuring 26 mm for S. aureus and 25 mm for E. coli, compared to ZnO NPs. Further, the prepared nanomaterials were used as catalysts to degrade Amlodipine and Metformin drug pollutants under sunlight exposure. ZnO-rGO nanocomposite showed the maximum degradation efficiency of 92.68 % and 95.78 % for Amlodipine and Metformin, respectively. Overall, rGO-wrapped ZnO nanocomposite is versatile for degrading pharmaceutical pollutants and combating bacterial infections.

Keywords: Amlodipine; Metformin; Photocatalytic degradation; Strychnos potatorumseed; ZnO NPs; ZnO-rGO nanocomposite.