Composition dependent variation in structural, morphological, optical and magnetic properties of biogenic CuO/NiO mixed oxides nanoparticles

A series of CuO/NiO nanoparticles with different Cu and Ni precursor concentrations represented as N12 (1:2), N22 (1:1) and N21 (2:1) (Cu+2:Ni+2) were produced by modified green solution combustion route using Moringa oleifera leaves extract as an organic fuel. The prepared CuO/NiO nanoparticles were analytically characterized using UV-Vis diffuse reflectance spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and vibrating sample magnetometry. Morphological studies showed uniform and nearly monodisperse nanoparticles having average grain size of 34 nm for N22 nanoparticles while the N12 and N21 compositions showed uniform nanoparticles with the grain size of 12 nm and 22 nm respectively. The existence of CuO and NiO phases in nanoparticles was verified by XPS analysis. N12, N22 and N21 had band gaps in the range of 2.19-2.49 eV and specific surface area in the range of 4.92-11.2 m2/g. The susceptibility vs. temperature plots for mixed oxides nanoparticles showed distinct magnetic behaviour for different ratio. The coercivity and saturation magnetization reached a maximum value for N22 (130 Oe and 0.133 emu/g). These biogenic nanoparticles could be a strong choice for biological applications due to their soft magnetic behaviour and biocompatibility.