Synthesis and characterization of iron/iron oxide core/shell nanocubes

A simple method for the preparation of iron/iron oxide nanoparticles with core/shell cubic morphology is presented. The synthesis of the nanocubes was carried out through decomposition of a preformed iron oleate complex at high temperature. Although this procedure has been shown previously to produce monodisperse magnetite sphercs,[1] the use of squalene as a solvent and the presence of sodium oleate was found to induce cube formation. A detailed high-resolution transmission electron microscopy (HRTEM) analysis of the nanocubes was performed for structural characterization. The core/shell structure, an iron core surrounded by magnetite (Fe3O4) shell, was confirmed by fast Fourier transform (FFT) filtering analysis. The results obtained by HRTEM analysis are in agreement with X-ray Photoelectron Spectroscopy (XPS) and magnetic analysis. The Fe nanocubes are superparamagnetic at room temperature with a saturation magnetization M-S = 101 A M-2 kg(-1) and magnetic anisotropy density K-eff = 1.6 x 10(5) J m-3 at low temperatures.