Influence of ZnO on structural magneto-optical dielectric and antibacterial properties of NiFe2O4 (ZnO-NiFe2O4) nanocomposites prepared by sol–gel method

The present work investigates the structural, optical, magneto-dielectric and antibacterial characteristics of ZnO-NiFe₂O₄ nanocomposites (NCs). Spinel NiFe₂O₄ and ZnO powders were synthesized individually by the sol–gel method. Then by using the ultrasonification technique, a series of (1-x)NiFe₂O₄+xZnO (x = 0.0, 0.15, 0.30, and 0.45) NCs were prepared. Powder XRD pattern confirms the existence of both spinel NiFe₂O₄ and ZnO peaks in the nanocomposites. The observation reveals that as the amount of ZnO in the nanocomposite, there is an increase in the lattice constant from 8.372 Å to 8.383 Å. The addition of ZnO in the nanocomposites broadens the light-absorbing range and raises the band gap (eV) energy from 1.7 eV to 2.5 eV. The dielectric constant measured at 1 kHz decreased from 496 to 403 as the ZnO content in the nanocomposite increased. However, the dielectric constant for NF_0.4/ZnO_0.6 NCs measured at 1 kHz increased from 403 to 583 for an applied magnetic field of 7000 Oe. Spinel NiFe₂O₄ with ZnO content shows lesser saturation magnetization (M_s) and coercivity compared to pure NiFe₂O₄. The magneto-capacitance (MC%) as a function of the magnetic field for all composition shows a positive response. NF_0.55/ZnO_0.45 (40 µg/ml) NCs showed better antimicrobial activity as compared to NiFe₂O₄ (40 µg/ml). This study may extend the scope of this composite as an electrode material in supercapacitors.