Environment friendly synthesis of nickel ferrite nanoparticles using Brassica oleracea var. capitate (green cabbage) as a fuel and their structural and magnetic characterizations

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Environment friendly green synthesis, alternate to the chemical approach has been discussed in the current study. Extract of readily available plant, Brassica oleracea var. capitate was used as a natural fuel (reducing and capping agent) to synthesize nickel ferrite (NiFe2O4) nanoparticles by using sol-gel auto combustion method. The samples were calcined at 300 °C and 500 °C. X-Ray diffraction (XRD) analysis was used to confirm the crystalline structure of the synthesized NiFe2O4 nanoparticles. Scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), UV–Visible diffused reflectance spectroscopy (UV–vis DRS), and vibrating sample magnetometer (VSM) analysis were used to interpret the morphological, elemental, optical and magnetic properties of the synthesized nanoparticles. The single phase crystalline nature was revealed by XRD analysis, with average crystallite sizes of 18.16 nm and 24.57 nm. The surface morphology showed the spherical shape with average particle size 26.62 nm and 37.54 nm. Phase purity of the samples were identified using EDX analysis. FTIR was also used to verify the formation of pure phase ferrites. The optical band gap was determined using UV–vis DRS spectra, which was found to decrease from 2.68 eV to 2.64 eV as the calcination temperature was raised. The ferromagnetic property of the samples was clearly demonstrated by VSM studies. The value of saturation magnetization was found to increases from 30.49 emu/g to 35.20 emu/g as the calcination temperature was raised. The increasing trend in coercivity with increasing particle size indicated the single domain ferromagnetic nature of nanoparticles. Additionally a comparison study of all available NiFe2O4 synthesized via green routes was carried out. Better magnetic properties and higher band gap was observed than previously reported NiFe2O4 nanoparticles synthesized by green routes.