Defect-engineered Ag/ZnO and Ag₂O/ZnO nanomaterials prepared with nanoparticles synthesized by a sustainable sol–gel method and their biological responses

ZnO/Ag and ZnO/Ag₂O nanocomposites were produced using ZnO nanoparticles synthesized via a starch-mediated sol–gel method. XRD and Rietveld refinement confirmed the wurtzite-like structure of spherical 16-nm ZnO nanocrystals. These nanocrystals were further decorated with cubic nearly spherical ~ 7-nm Ag and irregular ~ 6-nm Ag₂O nanocrystals, resulting in nanocomposites with distinct structural characteristics. The morphological analysis confirmed the distinct shapes and sizes of Ag, Ag₂O, and ZnO nanoparticles. The nanocomposites exhibited a tuned optical bandgap and structural defects like \({V}_{Zn}\) $V_{\mathit{Zn}}$ , V_O, and \({V}_{O}^{+}\) $V_O^{+}$ . In vitro biological tests revealed that the Ag₂O/ZnO nanocomposite displayed significantly enhanced antidiabetic, antimicrobial, and antioxidant activities. These enhanced biological properties were attributed in part to the unique morphology of Ag₂O nanoparticles and the defective nature of ZnO/Ag₂O nanocomposite. These results demonstrate that the green-synthesized ZnO nanoparticles decorated with Ag₂O emerge as a promising material for biomedical applications.