Mesostructured Fe Oxide Synthesized by Ligand-Assisted Templating with a Chelating Triol Surfactant

Abstract

The synthesis and properties of sulfate- and phosphate-free mesostructured iron oxide prepared using a chelating triol surfactant are reported. Materials synthesized using metal−surfactant ratios of 1:1, 2:1, 3:1, and 4:1 all showed a broad single reflection in the XRD at low angle corresponding to a wormhole mesostructure, as well as small higher angle peaks consistent with the presence of a small amount of maghemite and hemitite. TEM images confirmed the wormhole structure of the mesophase, while also revealing rodlike crystals corresponding to one or both of the two known phases of iron oxide observed in the XRD. Attempts to remove the surfactant by washing or chemical treatment were unsuccessful. Calcination led to a complete collapse of the structure and crystallization of the mesophase into maghemite. Magnetic studies provided evidence for the formation of superparamagnetic iron oxide particles within the walls of the mesostructure in addition to a small magnetic contribution arising from the presence of larger maghemite crystallites, while the calcined materials behaved more like a soft ferromagnet.