Synthesis and characterization of zinc substituted magnetite nanoparticles and their application to magneto-motive ultrasound imaging

•Zn-substituted magnetite nanoparticles were synthesized via a simple coprecipitation method.•Significant enhancement in saturation magnetization was achieved.•All samples were examined for magneto-motive ultrasound imaging (MMUS).•The sample with enhanced saturation magnetization optimized the MMUS signal. Biomedical application of magnetic nanoparticles is a rapidly growing research field. For medical diagnostic purposes, these nanoparticles are mostly used as imaging contrast agents. Magneto-motive ultrasound (MMUS) is an example of imaging techniques where superparamagnetic nanoparticles are used as contrast agent. Since it is a relatively new technique, much research is yet in progress to optimize the magnetic properties of these contrast agents. In this study, Zn-substituted magnetic (nominal composition ZnxFe1−xFe2O4, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles with aim of enhancing the saturation magnetization were successfully synthesized by the coprecipitation method. The effect of zinc on morphology, structure and magnetic properties of the prepared nanoparticles was studied and their potential for MMUS imaging was investigated. X-Ray diffraction results showed that all samples had spinel structure and incorporating zinc in magnetite structure led to an increase in its lattice parameter, on the other hand TEM images revealed that particle size was decreased with zinc concentration. EDX analysis of the samples confirmed the incorporation of zinc in magnetite structure with a relatively good agreement with nominal values. Low, room and high temperature magnetic properties of the samples were investigated using vibrating sample magnetometer (VSM). Room temperature M-H curves along with zero-field-cooling measurements showed all samples were superparamagnetic and saturation magnetization at x = 0.1 zinc concentration increased drastically. All prepared samples were examined as contrast agents in MMUS imaging and the results confirmed the direct role of magnetization in enhancement of MMUS signals.