Interaction of fatty acid chain length with NiFe2O4 nanoparticles

This work deals with the preparation of nickel ferrite (NiFe2O4) nanoparticles utilizing the co-precipitation technique and coating them with three different fatty acids viz. oleic acid, capric acid and myristic acid. Different synthesis parameters such as concentration ratio of precursor: fatty acids, reaction time and reaction temperature were considered to study their effect on the structural as well as magnetic properties of the synthesized nanoparticle. Bare nanoparticles and fatty acid coated nanoparticle thus prepared was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), vibrating sample magnetometer (VSM), transmission electron microscopes (TEM) and energy dispersive X-ray (EDX) analysis. The FTIR results suggested the intensity of the peaks decreased with an increase in length of fatty acid chain. TEM analysis revealed the spherical shape of the nanoparticles which was well dispersed after coating. The broad diffraction peaks during the XRD analysis corresponded to the Bragg reflections from (220), (222), (400), (511) and (333) planes and confirmed the formation of pure NiFe2O4 phase with cubic spinel structure. From SEM analysis it was observed that the size of the nanoparticles increased with fatty acid coating. Magnetic characterization was carried out at room temperature and M (H) loops were obtained with coercivity (Hc) = 97.2 Oe and magnetic saturation (Ms) = 53.5 emu/g with the hysteresis loop confirming the prepared samples to be ferromagnetic in nature. The dispersion stability of both uncoated and coated nanoparticles was also studied. The uncoated nanoparticles remained dispersed for 4 h, whereas the myristic acid coated nanoparticles showed highest dispersion stability till 144 h.