This graphical abstract highlights the Eco-Friendly Synthesis of ZnO and Ag-Doped ZnO Nanoparticles Using Onion Peel Extract, which is a sustainable approach to synthesizing nanomaterials. The green synthesis route helped utilize the waste generated from onions to synthesize ZnO and Ag-doped ZnO nanoparticles and this green synthesis route promotes sustainability.

Abstract

Zinc oxide nanoparticles (ZnO NPs) and silver (Ag)-doped zinc oxide nanoparticles (Ag-ZnO NPs) have been synthesized by the environment-friendly green synthesis method using onion (Allium cepa L.) peel. The XRD spectra show that the ZnO NPs have a hexagonal wurtzite structure, while the Ag-doped ZnO NPs have a face-centered cubic structure. The average crystallite size of ZnO NPs was found to be reduced due to the doping of Ag. The FTIR spectra of ZnO NPs and Ag-ZnO NPs show that the functional group is within the range of 1500–4000 cm⁻¹. The SEM spectrograph reveals that the ZnO NPs have spherical-shaped morphology, and the Ag-doped ZnO NPs exhibit smaller and irregularly shaped morphology. EDX analysis confirms the presence of zinc and oxygen, indicating ZnO Nps, whereas the detection of silver along with zinc and oxygen confirms Ag-ZnO NPs. The absorbance graph shows that Ag-ZnO NPs contain two peaks at 222 and 365 nm, respectively. Therefore, the addition of Ag to ZnO as a dopant dropped the energy band gap of ZnO NPs from 3.37 to 2.28 eV.