Green synthesis and characterization of CuO nanoparticles using Acacia auriculiformis and Bauhinia variegata leaf extract for antibacterial applications

Green synthesis of metal oxide nanoparticles (NPs) has become a viable solution to the traditional chemical processes to overcome toxicity, extreme cost, and environmental hazards. In this study, copper oxide (CuO) NPs were synthesized using aqueous leaf extracts of Acacia auriculiformis (S1) and Bauhinia variegata (S2) as natural reducing and stabilizing agents, with copper(II) sulfate pentahydrate (CuSO₄·5H₂O) as precursor under identical reaction conditions. UV-Vis spectroscopy, FTIR, XRD and TEM were used in order to characterize the synthesized NPs. UV–Vis absorption peaks confirmed the formation of CuO NPs, FTIR analysis revealed phytochemical functional groups responsible for capping and stabilization. XRD patterns suggested a monoclinic crystalline structure and TEM analysis showed average diameter of around ∼20 nm (S1) and ∼36 nm (S2). Antimicrobial assessment against Escherichia coli and Staphylococcus aureus has shown an inhibition zone of 28–30 mm (S1) and 23–28 mm (S2) respectively, indicating superior bioactivity of A. auriculiformis -derived NPs. The novelty of this work lies in the comparative analysis of two phytochemically different plant extracts under controlled synthesis conditions has revealed that the phytochemical richness has a direct correlation with the particle size, and antimicrobial activity. The present work presents a low cost, scalable, and greener method of synthesizing functional CuO nanomaterials with a strong potential in biomedical and antibacterial applications.