Green Synthesis, Characterization, and Biological Evaluation of CuO–ZnO Nanoparticles Using <i>Cyphostemma Setosum</i> Leaf Extract

Abstract The present study details the successful green synthesis, thorough characterization, and extensive biological assessment of CuO–ZnO nanoparticles (NPs) by using aqueous leaf extract of Cyphostemma setosum . UV–vis., spectroscopy identified a distinct absorption peak at 240 nm, indicative of direct band gap transitions, with the optical band gap estimated to be 3.32 eV. FT‐IR spectral analysis confirmed the presence of significant functional groups, including hydroxyl (3380 cm⁻¹) and nitrile (2102 cm⁻¹), which suggest effective capping and stabilization of the synthesized NPs. XRD patterns validated the formation of well‐crystallized CuO–ZnO phases, a finding further corroborated by SEM and TEM images that revealed a spherical morphology with particle sizes ranging from 20 to 50 nm. The selected area electron diffraction (SAED) pattern indicated a high degree of crystallinity. Antifungal activity of the CuO–ZnO NPs demonstrated significant efficacy, with inhibition zones progressively increasing over time. Antibacterial assays indicated that the synthesized NPs exhibited enhanced activity against both Gram‐negative and Gram‐positive bacteria, with C. freundii and A. brasilense showing inhibition zones of 22 and 21 mm, respectively. DNA binding studies revealed strong interactions of synthesized CuO—ZnO NPs with DNA, as the binding constant ( K b ) of 1.8 × 10⁵ M⁻¹.