The effect of basic pH on the elaboration of ZnFe2O4 nanoparticles by co-precipitation method: Structural, magnetic and hyperthermia characterization

•Structural and magnetic properties of zinc iron oxide nanoparticles.•The size of ZnFe2O4 nanoparticles increases from 19 to 33 nm with the increase of the PH of the solution.•The specific absorption heating rate is higher for larger and spherical particles. The present study reports on the synthesis and characterization of zinc iron oxide ZnFe2O4 magnetic nanoparticles (MNPs) using the co-precipitation method. Particular attention has been paid to study the influence of the pH in the range between 9 and 12 on both structural and magnetic properties of the MNPs. X-ray diffraction analysis shows the presence of a single phase of partially invers cubic spinel ferrites ZnFe2O4. Transmission Electron Microscopy (TEM) analysis shows the formation of highly crystalline MNPs and a change of shape from a polyhedral shape at pH 9 to a spherical-like shape for a pH 12. The MNPs mean-size increases from 19 to 33 nm with the increase of pH value. The ZnFe2O4 MNPs are superparamagnetic at room temperature displaying a magnetization of 12 emu/g at the maximum applied static magnetic field. The heating efficiency of spherical zinc ferrites MNPs was evaluated for hyperthermia application and displays a linear increment of the specific absorption rate (SAR) up to 125 (W/gFe) under an alternating magnetic field ranging from 5 to 65 kA/m and operating at a frequency of 355 kHz.