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.