Plant-mediated fabrication of plasmonic-magnetic Ag-Fe ₃ O ₄ nanocomposites for broad-spectrum photocatalytic wastewater treatment

This study presents a sustainable, green synthesis of silver-coated magnetite nanocomposites (Ag-Fe3O4) using Brachychiton populneus leaf extract, aiming to develop an efficient and reusable photocatalyst for wastewater treatment. The nanocomposites combine the visible-light plasmonic activity of silver nanoparticles (AgNPs) with the magnetic recovery capability of Fe3O4, resulting in a multifunctional hybrid material. Comprehensive characterization using XRD, SEM, EDX, FTIR, UV–Vis spectroscopy, BET surface area analysis, and VSM confirmed successful formation of Ag-Fe3O4 with a mesoporous structure, uniform particle distribution, reduced bandgap (1.95 eV), and strong magnetic properties. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) and Congo red (CR) under visible light. The composite demonstrated superior photocatalytic efficiency, achieving 97% and 92% degradation of MB and CR (20 ppm), respectively, within 30 min, significantly outperforming individual AgNPs and Fe3O4. Kinetic studies confirmed pseudo-first-order reaction behavior. The enhanced activity was attributed to the synergistic effect of Ag and Fe3O4, which improved light absorption, interfacial charge separation, and reactive oxygen species (ROS) generation. This work highlights the potential of green-synthesized Ag-Fe3O4 as a highly efficient, magnetically recoverable, and environmentally friendly photocatalyst for wastewater remediation applications.