Synthesis and identification of structural, optical, electrical, and magnetic properties of novel ZnFe₂O₄/NiO nanocomposites

Novel nanocomposites (NCs) of (100-x) ZnFe₂O₄/x NiO (x = 0, 10, 20, 30, 40, 50, and 100 wt. %) NCs have been successfully synthesized by the two-step co-precipitation method. The XRD analysis showed the formation of both phases without any impurities. The FTIR spectroscopy provided characteristic vibrations of Zn–O, Fe–O, and Ni–O, which also confirmed the coexistence of both phases and the high purity of the samples. The TEM images revealed the rounded-cubes morphology of the nanocomposites with an average particle size ranging between 17 and 27 nm. The UV–vis spectroscopy showed that the absorbance edge of the synthesized NCs was slightly red-shifted with increasing NiO content. This indicates the narrowing of the optical bandgap due to the incorporation of sub-bandgap energy levels, triggered by the interface and surface defects. Furthermore, among all the nanocomposites, the nanocomposite with x = 30 wt. % NiO exhibited the lowest PL emission intensity and possibly, the highest photocatalytic activity. The DC electrical conductivity was greatly enhanced with the addition of NiO to ZnFe₂O₄ NPs for x ≥ 30 wt. %. This increase may be due to the excessive charge accumulation on the various interfaces existing in the ZnFe₂O₄/NiO nanocomposites with increasing NiO content. Finally, the magnetic measurements displayed that ZnFe₂O₄/NiO NCs have superparamagnetic behavior with soft ferromagnetic of ferrites. The saturation magnetization (Ms) increased with increasing NiO content, which is useful for better magnetic recoverable photocatalyst. In addition, the δM–H plot showed stronger exchange coupling interaction between the magnetic phases in ZnFe₂O₄/NiO NCs. (paper)