Synergistic Phytogenic Synthesis of Copper Nanoparticles Using <i>Camellia sinensis</i> and <i>Ocimum sanctum</i>: Structural, Potent Antibacterial, and Mechanistic Insights

This pioneering study reports the robust green synthesis of copper nanoparticles (CuNPs) through a highly synergistic approach employing aqueous extracts of Camellia sinensis (green tea) and Ocimum sanctum (tulsi). This innovative dual-extract method fundamentally enhances reduction kinetics and significantly boosts nanoparticle stability. The synthesized CuNPs underwent rigorous characterization using UV-Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and zeta potential analysis. These analyses conclusively confirmed the formation of uniformly spherical, highly crystalline nanoparticles ranging from 20–50 nm, exhibiting an exceptionally stable negative zeta potential of –29.5 mV. The underlying phytochemical reduction and capping mechanisms are elucidated in detail, highlighting the critical role of catechins (from C. sinensis) and eugenol (from O. sanctum) through well-defined tautomeric shifts. Furthermore, comprehensive antibacterial assays demonstrated superior and potent activity of these synergistic CuNPs against both Escherichia coli and Staphylococcus aureus, unequivocally showcasing their remarkable biomedical potential. This green, eminently eco-friendly, and highly scalable approach represents a significant advancement for sustainable nanoparticle synthesis, perfectly aligning with the principles of cutting-edge sustainable nanotechnology.