Allium cepa-assisted biogenic silica dioxide nanoparticles: their production, structural characterization, and antioxidant activity

The silica dioxide nanoparticles that were produced using the plant extract via green synthesis proved to be more effective with more beneficial properties. In this study, the silica dioxide nanoparticles were fabricated with the aqueous extract of Allium cepa bulb via a green chemistry approach. The novelty of the present research was to utilize the bulb extract as a capping and reducing agent. The synthesized nanoparticles were characterized using X-ray crystallography (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) analysis. Also, the antioxidant activity of A. cepa-mediated silica nanoparticles was analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The results obtained from the characterizations have determined that the produced particles are spherical with no agglomeration, are well-dispersed and amorphous with an average size of 18 ± 2 nm, have good thermal stability, and contain possible functional groups (Si-O). The elemental composition of silica dioxide nanoparticles was investigated by EDX analysis and it confirms the existence of Si and O. TGA analysis determines the weight loss of 37.9% in as-biosynthesized silica dioxide nanoparticles. DPPH analysis revealed that the Allium cepa bulb-mediated silica dioxide nanoparticles show better antioxidant activity. The IC₅₀ value of silica dioxide nanoparticles was calculated as 256.35 μg/mL. This study shows that the A. cepa-mediated synthesis of silica nanoparticles could have potential applications in biomedical applications.