Croton macrostachyus Bark Extract-Assisted Sustainable Synthesis of CuO Nanomaterials for 4-Nitrophenol Catalytic Reduction and Antibacterial Applications

Environmental pollution and sustainability issues require environmentally friendly solutions. In this study, we synthesized copper oxide nanoparticles (CuO NPs) using a sol––gel method with Croton macrostachyus bark extract for application in environmental remediation and as an antimicrobial agent. The uncalcined CuO NPs (200 mg/mL) demonstrated strong antimicrobial activity, with inhibition zones of 22 ± 1.3 mm against Staphylococcus aureus and 11 ± 0.7 mm against Escherichia coli. Moreover, the nanoparticles efficiently catalyzed the reduction of 4-nitrophenol, achieving 98.79% degradation within 8 min (Kapp = 0.507 min−1). These findings show that CuO NPs synthesized from the extract of Croton macrostachyus provide a sustainable and efficient approach for addressing both environmental pollution and antibacterial resistance.