Characterization, Biological Activities and Environmental Application of the Manilkara zapota Wrapped CaO-CuO Nanocomposite

Abstract

Plant-based metal oxide nanoparticles have gained considerable interest in recent years due to their important biological applications. The present study aimed to synthesize, characterize, and test the environmental applications of a Manilkara zapota leaf-wrapped CaO–CuO nanocomposite. A phytochemical-rich extract was used as a reducing or stabilizing agent during synthesis; therefore, the synthesis route was entirely eco-friendly. The fabrication and structural properties were confirmed using UV-Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Atomic force microscopy (AFM). XRD analysis confirmed the crystalline structure, and TEM revealed that the nanocomposite was nearly spherical, with an average size of 22.41 nm. Optical studies showed a direct band gap energy of 3.32 eV, providing evidence of the semiconductor behavior of the nanocomposite. The antioxidant and anti-inflammatory activities reached their maximum values at 250 µg/mL and 50 µg/mL, respectively, indicating progressive free radical scavenging and anti-inflammatory potential. The inhibition zone diameter was determined to be 13.51, 14.25, 14.31, and 16.8 mm for Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus, respectively. P. aeruginosa exhibited maximum antimicrobial and antibiofilm activity at a nanocomposite concentration of 100 µg/mL. Furthermore, the photocatalytic activity of the nanocomposite was investigated, achieving 81.14% Congo red dye decolorization under 80 min of sunlight irradiation. The reaction was followed by the first-order kinetic model with a constant rate of 0.0219 min^− 1. This study demonstrates that the green-synthesized CaO–CuO nanocomposite holds significant promise as a sustainable, multi-target material for biomedical and environmental remediation applications.