Photocatalytic activity of nickel oxide nanoparticles synthesized via green route using Nigella sativa seed extract
摘要
Catalytic applications of nanoparticles (NPs) for the removal of toxic dyes from wastewater has motived researchers to synthesize different metal NPs employing different methods under different conditions. In current study, nickel oxide NPs (NiO NPs) have been successfully synthesized via green method using Nigella sativa (black seeds) extract as reducing and stabilizing agent. A comparative study has been conducted between the two samples i.e. uncalcined (S1) and calcined (S2) NiO NPs. Synthesized NiO NPs were characterized by different analytical techniques UV–Vis, FTIR, zeta potential, particle size analyzer, photoluminescence, XRD and SEM. Results (280 to 350 nm with a minor shift) of UV–Vis spectroscopy and FTIR analysis (Ni–O band at 650 cm−1) confirmed synthesis of the NPs in both the samples. Intensity peaks in FTIR spectrum of S2 sample are stronger that indicate enhanced crystallinity. The crystallite size of NiO NPs was 6.55 nm calculated using XRD spectrum data and SEM images reveled rod like structure of NiO NPs with uniform distribution of particles. The optical energy band-gap was found to be about 5.21 eV for S1 sample while S2 sample exhibited reduced band-gap of 3.56 eV. The photocatalytic potential of NiO NPs was investigated under sunlight through the decolorization reaction of methylene blue (MB) and congo red (CR) dye. The synthesized calcined NiO NPs exhibited an excellent catalytic degradation of MB and CR dye (72% and 62% respectively) in lesser time as compared to uncalcined NPs. Current study recommends post synthesis treatments such as calcination of the NPs to achieve their maximum efficiency towards pollutant degradation.