Spectroscopic characterization of the surface of iron oxide nanocrystals

The surface of highly monodisperse magnetic iron oxide (gamma-Fe2O3) nanocrystals was thoroughly investigated by FTIR, NMR, and mass spectroscopy. The nanocrystals were prepared by a thermal decomposition method now widely used for the preparation of magnetic metal and metal oxide nanocrystals. This method takes advantage of oleic acid as a means to passivate the surface and render the particles stable with respect to aggregation or grain growth and keeps them highly dispersed in a variety of organic media. The nature of this surface in terms of ligand structure and the role of oleic acid during the synthesis remained somewhat undetermined until this report. We provide spectroscopic evidence of an oleic acid ligand structural change during gamma-Fe2O3 nanocrystal synthesis.