Allium cepa-based zinc oxide nanoparticles: characterization and biochemical potentials

In this research work, Allium cepa (AC)-bulb-based zinc oxide nanoparticles (ZnO-NPs) were prepared successfully through a green synthesis approach. Phytocompounds present in the AC bulb successfully reduced and stabilized zinc (II) (Zn²⁺) ions into ZnO-NPs. Syntheses of the liquid form (L-ZnO-NPs) and calcined form (C-ZnO-NPs) were carried out. The color change of the nanoparticle (NP) colloidal solution from transparent to yellow, the surface plasmon resonance peaks by ultraviolet–visible spectroscopic analyses at 350 and 370 nm and the infrared spectrum showing functional groups below 700 nm confirmed the synthesis of ZnO-NPs. The elemental composition of NPs revealed that the weight percentage of zinc was 66 and 61%, while that of oxygen was 24 and 26% in C-ZnO-NPs and L-ZnO-NPs respectively. The scanning electron microscopy and X-ray diffraction pattern confirmed the successful synthesis of rod-shaped, crystalline ZnO-NPs (30–35 nm) with a uniform distribution. The 2,2-diphenyl-1-picrylhydrazyl-assay-based antioxidant potentials of C-ZnO-NPs and L-ZnO-NPs were recorded as 72 and 65% inhibition, respectively, while the hydrogen peroxide (H₂O₂) radical-scavenging assays revealed 62 and 48% inhibition, respectively, at a 75 μl concentration. ZnO-NPs showed good antimicrobial, in vitro antidiabetic and antioxidant potential. Hence, AC-bulb-based ZnO-NPs synthesized through a green chemistry approach can be considered an innovative addition to the science of free radical scavenging, diabetes and microbial infection management.