Preparation of monodisperse magnetite nanoparticles under mild conditions

In this paper, we reported a method to prepare monodisperse magnetite nanoparticles at mild temperature using cheap and non-toxic precursors. It overcomes the shortages of chemical co-precipitation method and thermal decomposition method and combines the advantages of facile, cheap, large-scale, monodisperse, nanosize, and low synthesis temperature and low toxic. In this method, FeCl3 · 6H2O, FeCl2 · 4H2O and sodium oleate were mixed in toluene/ethanol/water mixture solvent and refluxed at 74 °C to prepare magnetite nanoparticles directly. The nanoparticles were characterized by transmission electron microscopy, dynamic light scattering, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer and thermogravimetric analysis. The magnetic properties of nanoparticles were measured by superconducting quantum interference device. The results showed that the nanoparticles are well-monodisperse with about 4–5 nm of average diameter. The nanoparticles were proved to be superparamagnetic with saturated magnetization 23.6 emu/g and blocking temperature 24.4 K. A possible formation mechanism of monodisperse magnetite nanoparticles was presented at the same time.