Ethylene diamine-assisted synthesis of iron oxide nanoparticles in high-boiling polyolys.

The decomposition of iron(III) acetylacetonate in high-boiling polyols such as diethylene glycole is an efficient way to produce water-soluble iron oxide nanoparticles (IONPs) with small sizes. We present an extension of this method by introducing ethylene diamine (EDA) or diethylene triamine (DTA) as a structure-directing agent and adding polyvinylpyrrolidone (PVP) as a stabilizing agent. The synthesis was studied with respect to effects of the chain length of the polyol used as solvent, the chain length of the structure-directing agent, the presence of PVP, the heating rate, and the nature of the precursor. By varying these parameters, we were able to show, that probably an interplay of the structure-directing agent and the polyol plays an important role for the stabilization and growth of the different facets of the IONP crystal. The chain length of the polyol used as solvent alters the influence of EDA or DTA as stabilizer of {111} facets, leading to IONPs with spherical, tetrahedral, or nanoplate morphology and mean diameters ranging from 4 nm up to 25 nm. PVP in the reaction medium narrows down particle size and shape distributions and promotes the formation of very stable, water-based colloidal solutions. The saturation magnetization of the particles was determined by a superconducting quantum interference device (SQUID) and their ability to act as a T2-contrast agent was tested by magnetic resonance imaging (MRI).