Surfactant effects on the microstructures of Fe3O4 nanoparticles synthesized by microemulsion method

A water-in-oil microemulsion route has been devised to synthesize nanosized magnetite (Fe3O4) particles using different kinds of surfactant as the surfactant phase, n-heptane as the oil phase, and n-hexanol as the co-surfactant phase, respectively. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and 57Fe Mössbauer technique were employed to investigate the characteristic of the nanoparticles. The Fe3O4 powder derived from various microemulsions possessed an average spherical particle size of 13–15 nm based on TEM observation. The 57Fe Mössbauer spectroscopy results reveal that surfactant structure plays an important role in regulating the microstructure of Fe3O4 nanoparticles. The relationships among the crystal lattice defect (vacancy parameter), magnetite stoichiometry and the surfactant structure have been discussed in terms of headgroup charge, hydrophobic chain length, headgroup size. The temperature effects on the particle size and defect are performed and the most remarkable factor of surfactant structures on the lattice defect and magnetite stoichiometry against the temperature variation is also discussed. Moreover, the influence of lattice defect and magnetite stoichiometry on the magnetic property has also been explored.