The influence of grain size on the magnetic properties of Fe3O4 nanocrystals synthesized by solvothermal method

Abstract

The peculiar magnetic properties of superparamagnetic iron oxide nanoparticles (SIONs) have spurred great interest in their potential application in enhancing medical images and drug delivery. Currently hindering the application of nanomagnetic particles in these fields is due to SIONs nonuniform size distribution, agglomeration, non-crystallinity, and low magnetic moment. In this paper, magnetic nanocrystals of different sizes and morphologies were prepared by the solvothermal method, which utilized an n-hexane-surfactant system with Fe(acac)3 and iron-powder precursors. The crystalline structure and particle size of grown SIONs are characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). HRTEM showed that the SIONs were approximately 5.6–6.8 nm in size with no agglomeration and a uniform distribution. Within the reaction time, HRTEM also confirmed that the shape and nanocrystals of SIONs had changed from an irregular crystal shape to triangles and quadrilaterals, and finally to hexagonal nanoparticles. According to the test results of the magnetic properties test and the literature, the material that has been synthesized is a superparamagnetic material. And the maximum saturation magnetization was 62.65 emu/g, which is reported among the largest magnetic properties of SIONs at a size of 6.8 nm.