Asparagus racemosus leaf extract mediated bioconversion of nickel sulfate into nickel/nickel hydroxide nanoparticles: in vitro catalytic, antibacterial, and antioxidant activities

An eco-friendly approach was developed for the fabrication of nickel (Ni)/nickel hydroxide (Ni(OH)(2)) nanoparticles (NPs) from nickel sulfate as a precursor using phytochemically rich Asparagus racemosus Linn. leaf extract. The impacts of pH, temperature, leaf extract, nickel sulfate concentrations, and incubation period on NP particle size and stability were examined. The biosynthesis of Ni/Ni(OH)(2) NPs was investigated by a UV-visible spectrophotometer at a maximum wavelength of 363 nm. The X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform Infrared spectroscopy (FTIR), were utilized to illustrate the structure and morphology of Ni/Ni(OH)(2) NPs. The polyphenolic flavonoid phytochemical, i.e., quercetin-3-glucuronide of A. racemosus leaf extract, served as a stabilizing, capping, and reducing agent during the formation of Ni/Ni(OH)(2) NPs. These spherical NPs were highly stable, with size distributions in the range of 20-30 nm. They showed strong catalytic activities against methylene blue (MB) without as well as with exposure to direct sunlight, effective antibacterial (against Escherichia coli MTCC 1687, Staphylococcus aureus MTCC 902, as well as Pseudomonas aeruginosa MTCC 741), and excellent antioxidant activities (free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl). In conclusion, the biosynthesis of Ni/Ni(OH)(2) NPs using A. racemosus leaf extract is a cost-effective, easy, and safe approach with several uses as a photocatalyst, antibacterial, and antioxidant agent.