Green synthesis of Cu, Fe, and Cu/Fe nanomaterials using Khaya senegalensis and investigation of their photocatalytic reduction of 4-nitrophenol and antibacterial properties

The persistent environmental and health threats posed by nitroaromatic pollutants particularly 4-nitrophenol (4-NP), and the rise of multidrug-resistant bacterial pathogens demand sustainable, efficient, and eco-friendly remediation strategies. To address these challenges, this study aimed to develop monometallic (CuO and Fe₂O₃) and bimetallic (CuO/Fe₂O₃) nanoparticles via a green, one-pot synthesis using Khaya senegalensis leaf extract, leveraging its rich phytochemical content (notably flavonoids and tannins) as natural reducing and capping agents. The synthesized nanoparticles were characterized using UV–Vis spectroscopy, XRD, FTIR, and HAADF STEM, confirming the formation of spherical, monodispersed particles (20–50 nm) with distinct surface plasmon resonance peaks at 224 nm (CuO), 290 nm (Fe₂O₃), and a redshifted peak at 295 nm (CuO/Fe₂O₃). The XRD analysis revealed the crystallite sizes of CuO, Fe2O3 and CuO/Fe₂O₃ NPs to be 26, 22 and 28 nm, respectively. Bimetallic CuO/Fe₂O₃ nanocomposite demonstrated exceptional photocatalytic efficiency, achieving complete reduction of 4-NP to 4-aminophenol in just 2 minutes, over 50% faster than monometallic counterparts. Furthermore, it exhibited potent antibacterial activity, with minimum inhibitory concentrations (MIC) of 8 µg/mL against Escherichia coli and Bacillus subtilis, and 40 µg/mL against Pseudomonas aeruginosa, alongside minimum bactericidal concentrations (MBC) of 16 µg/mL and 80 µg/mL, respectively. These results underscore the multifunctional potential of K. senegalensis-derived CuO/Fe₂O₃ nanocomposites as green, high-performance agents for simultaneous environmental detoxification and antimicrobial applications. We recommend their further development for scalable water treatment and as alternatives to conventional antibiotics, particularly against resilient Gram-negative pathogens.