Magnetic Properties of Nano(iron Oxide)-Decorated Graphene Oxide

Graphene oxide (GO) decorated with magnetic iron oxide nanoparticles is of great interest due to its potential applications in nanomedicine, electromagnetic insulation, and electro-catalysis. Herein, we studied the effect of the preparation conditions by hydrothermal synthesis on the phase composition of graphene oxide decorated with iron oxide nanoparticles. GO samples using two different amounts of a 2Fe3+/Fe2+ solution were prepared under a pH = 11, whereas hydrazine treatment was done to half the batch. Electron microscopy images show that Fe-oxide nanoparticles with an average size of 5-10 nm appeared decorating graphene platelets. Graphene oxide decorated rolls form in hydrazine-treated samples. Infrared spectra suggest a mixture of iron oxide phases with increased goethite upon hydrazine treatment. X-ray diffraction and X-ray Absorption Near Edge Structure spectroscopy (XANES) in the Fe K-edge determined the relative amount of the resulting iron oxide phases. Mixtures of magnetite, maghemite, hematite, and goethite were observed depending on the sample preparation conditions. The effect of phase composition on the magnetic properties was also studied. The saturation magnetization varied from 3.5 to ca. 50 Am2/kg at 300 K; it is proportional to the magnetite/maghemite content and reduces as the amount of goethite increases. The coercive field in the samples increases up to 1.6-2.4 mT at 300 K. The saturation magnetization has a slower decay with temperature when compared to a reference sample of magnetite nanoparticles, which suggests a magnetoelectric coupling due to the nanoparticle distribution onto the conductive graphene sheet.