Abstract: The magnetite nanoparticles were synthesized by thermal decomposition of iron(Ⅲ) acetylacetonate(Fe(acac)3) in methoxy polyethylene glycol(MPEG), which was used as solvent, reducing agent, and modifying agent in this reaction. The morphologies and phase compositions of the nanoparticles were determined by transmission electron microscopy and X-ray diffraction, respectively. The modification of the nanoparticles was characterized using Fourier transform infrared spectroscopy. Magnetic properties were measured using superconducting quantum interference device(SQUID). The zeta potential of the nanoparticles was determined. The results indicate that the magnetite nanoparticles obtained in this way have a much uniform size and monodispersion. The diameter is about (10.1±1.6) nm. The nanoparticles show superparamagnetic behavior at 300 K with saturation magnetization of 45 A·m2/kg. The FTIR spectroscopic results prove the existence of —COO- covalently attached to the surface of the magnetite nanoparticles, and the zeta potential results show that the nanoparticles have negative surface about -25 mV. Compared with the magnetite nanoparticles synthesized in triethylene glycol(TREG), the nanoparticles synthesized in MPEG show a longer dispersion time in deionized water(for more than 60 days), due to the steric and electrostatic interactions between the nanoparticles.

Key words: iron oxide nanoparticles, superparamagnetism, methoxy polyethylene glycol, stability