Biosynthesis of ZnO/Ag nanocomposites heterostructure for efficient photocatalytic degradation of antibiotics and synthetic dyes

Abstract This study addresses the pressing issue of environmental pollution caused by antibiotics and synthetic dyes in aquatic ecosystems, presenting a novel approach for their efficient photocatalytic degradation. Zinc oxide (ZnO)-based nanoscale photocatalysts, including ZnO nanoparticles (NPs) and ZnO/Ag nanocomposite heterostructure (NCH), were synthesized through an innovative and eco-friendly method utilizing an extract derived from discarded lemon peels as a biogenic reducing agent. The synthesized materials were extensively characterized through UV spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results confirmed the different morphologies of ZnO NPs and ZnO/Ag NCH, with average sizes of 20 nm and 42 nm, respectively. Notably, the ZnO NPs and ZnO/Ag NCH exhibited optical bandgap energies of 3.2 eV and 2.85 eV, respectively, signifying their potential as efficient photocatalysts. Under natural sunlight irradiation, these materials demonstrated exceptional photocatalytic activity, achieving a remarkable 98.8 % degradation rate for metronidazole and 90 % for ciprofloxacin in just 12 min. Furthermore, the ZnO NPs effectively removed 84 % of Toluidine Blue and 77 % of Congo red after 120 min, while ZnO/Ag NCH enhanced degradation rates to approximately 90.5 % for Toluidine Blue and 86 % for Congo Red. This research highlights the significant physicochemical properties and novel synthesis methods employed, positioning these sustainable nanomaterials as promising solutions for mitigating environmental pollution effectively.