Green Synthesis of ZnO/Fe ₃ O ₄ /Ag Ternary Nanocomposite for Enhanced 4‐Nitrophenol Catalytic Reduction and Antibacterial Activity

ABSTRACT The present study investigates a green synthesis technique for metal oxide nanocomposites, zinc oxide (ZnO), iron oxide (Fe 3 O 4 ), ZnO/Fe 3 O 4 (ZF), and ZnO/Fe 3 O 4 /Ag (ZFA), which were successfully synthesized using Solanum violaceum fruit extract. The structure, morphology, and stability of the synthesized nanomaterials were characterized using X‐ray diffraction (XRD), field emission scanning electron microscope (FE‐SEM), energy dispersive X‐ray spectroscopy (EDS), Fourier transform infra‐red spectroscopy (FT‐IR), vibrating sample magnetometer (VSM) and UV–vis spectroscopy. XRD measurement confirmed the phase purity. From the FE‐SEM image, the particles are spherical in shape with an average particle size of 15 nm. Band gap energies, calculated using Tauc's plot revealed a decrease in the band gap of nanocomposites with the addition of Fe 3 O 4 and Ag. ZFA exhibit superparamagnetic behavior, achieving 98% catalytic reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) in 9 min. The catalytic reduction based on the Langmuir–Hinshelwood principle was investigated. The nanocomposite shows significant antibacterial activity against both Gram‐positive bacterium, Staphylococcus aureus , and Gram‐negative bacterium, Salmonella typhi . The green‐synthesized nanocomposite is magnetically separable, and can be used up to five consecutive cycles. The excellent catalytic and antibacterial properties of eco‐friendly ternary ZFA make it a potential nanocatalyst for sustainable wastewater treatment and environmental remediation.