Mixed Zn–Ni spinel ferrites: Structure, magnetic hyperthermia and photocatalytic properties

Abstract

Synthesis of high quality, narrow size distributed superparamagnetic nanoparticles with high saturation magnetization is imperative for biomedical and environmental remediation applications. This study reports the synthesis of narrow size distributed, small diameter, high-quality Zn1-xNixFe2O4 (x = 0.1, 0.3 and 0.5) nanoparticles with increased saturation mass magnetization for localized superparamagnetic hyperthermia and photocatalysis applications. Narrow size distributed samples with around 10 nm average diameter were synthesized, in the presence of surfactant, by solvothermal reflux method. All the samples show good colloidal stability through electrostatic stabilization with zeta potentials around - 60 mV. The heating capacity or specific heat generation rate (SHR) of synthesized superparamagnetic nanoparticles was determined through the calorimetric method. The x = 0.1, 0.3 and 0.5 samples show SHR = 372, 399 and 410 W g−1 of nanoparticles, respectively, under 35.28 kA/m and 316 kHz field parameters. These SHR values are higher than that of samples synthesized by other methods. Similarly, saturation mass magnetization value increases with Ni2+ concentration in the sample. The enhancement was attributed to preferential octahedral ligand sites occupation by Ni2+ ions in spinel lattice due to high crystal field stabilization energy. Photocatalytic activity of all nanoparticles was studied by methylene blue (MB) dye degradation under visible light. The data shows that degradation efficiency increases with Ni2+ concentration in the sample. All samples were characterized through X-ray powder diffraction (XRPD) profile, transmission electron microscopy (TEM), Fourier transformed infrared spectra (FT-IR), zeta potential distribution curve, thermogravimetric analysis (TGA) curve, vibrating sample magnetometer (VSM), transient temperature curves, and UV–visible–NIR photo-absorption spectra.