One-pot green synthesis of Fe₃O₄@ZnO core-shell nanocomposites with multifunctional properties

This study introduces an economical, one-step, and eco-friendly method for synthesizing Fe₃O₄@ZnO magnetic core-shell nanocomposites (Fe₃O₄@ZnO MNCs) using an aqueous leaf extract of Cordia myxa (C. myxa). The effects of zinc salt concentration and calcination temperature were investigated, and the products were characterized using XRD, FE-SEM, TEM, BET, FT-IR, TGA, and VSM techniques. The optimized nanocomposite was spherical, with an average size of 23.01 nm, exhibited superparamagnetic behavior, had a point of zero charge at pH 7.3, and a specific surface area of 18.2 m² g⁻¹. It showed moderate antioxidant activity and antibacterial effects against Gram-positive (Listeria, Micrococcus) and Gram-negative (Salmonella) bacteria. The adsorption performance for Congo red (CR) dye was evaluated and optimized via Central Composite Design (CCD) in Response Surface Methodology (RSM). Under optimal conditions (adsorbent dosage 11.6 mg L⁻¹, pH 6.0, contact time 74 min), nearly 100% dye removal was achieved, highlighting the nanocomposite's strong potential for pollutant removal and environmental remediation.