Synthesis of Magnetic Nanocrystals by Thermal Decomposition in Glycol Media: Effect of Process Variables and Mechanistic Study

The nucleation and growth of water dispersible iron-oxide nanoparticles synthesized by high temperature decomposition of iron(III) acetylacetonate in the presence of different solvents has been studied. A battery of techniques was used to characterize the products obtained under different conditions and to elucidate the synthesis mechanism. Results show that the synthesis of iron-oxide nanoparticles in triethylene glycol (TEG) proceeds through a multistep process whose first stage is likely to be the formation of an intermediate TEG-iron-complex that evolves into a low-crystallinity iron-oxide-organic precursor during aging at 180 °C. Raising the temperature above 240 °C caused the thermal decomposition of the precursor and the sudden nucleation of small iron-oxide nanocrystals. Keeping the reactant mixture at 280 °C led to the growth of iron-oxide nanocrystals, as did increasing the time at reflux temperature, the amount of initial iron precursor or the use high boiling point solvents. The particle size ...