Green Synthesis of ZnO-CuO nanocomposite using Annona reticulata leaf extract for antibacterial, seed germination, and protein interaction studies

In this study, the ZnO-CuO (ZC, ZC-5, and ZC-10) nanocomposites synthesized using Annona reticulata leaf extract as a reducing and stabilising agent. The structural, functional and optical properties were analyzed using different analytical techniques such as XRD,, FE-SEM, HR-TEM, XPS, FT-IR, TGA, UV-Vis DRS, and photoluminescence spectra. XRD confirmed the crystallinity of the nanocomposites, while the HR-TEM and SAED patterns confirmed the morphology and diffraction patterns for ZnO-CuO nanocomposite. FT-IR confirmed the presence of Zn-O, Cu-O vibrational bands and XPS confirmed formation of the nanocomposite, showing the peaks for Zn 2p and Cu 2p respectively. UV Vis-DRS confirmed the tunable optical properties and a reduced band gap. Further, steady state fluorescence spectra of bovine serum albumin (BSA) with ZC-10 nanocomposite showed static quenching with a binding constant of (K sv =24.85, K b =1.87 × 10²) and approximately two binding sites ( n = 1.8). The nanocomposites showed concentration-dependent antibacterial activity, against Gram-positive Staphylococcus aureus and Gram-negative bacteria P. aureginosa . Seed germination assays using on Abelmoschus esculentus seeds showed germination percentage of 69.44% at 0.1 mg/mL. These findings illustrate the green synthesized ZnO-CuO nanocomposite suitable for different applications in antibacterial, seed germination and biomolecular interaction.