Polyol Synthesis of Magnetite Nanocrystals in a Thermostable Ionic Liquid

Abstract

We report on the development of a facile, one-pot synthesis of single-crystalline magnetite (Fe3O4) nanoparticles (NPs) based on the thermal decomposition of the nontoxic iron precursor iron(III)acetylacetonate within the ionic liquid trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([P6,6,6,14][Tf2N]) using 1,2-hexadecanediol as a polyol reducing agent in an “iono-polyol” process. In this expedient approach, the [P6,6,6,14][Tf2N] acts both as a low-volatility, thermostable solvent and as the colloid-stabilizing agent, eliminating the requirement for additional surface-capping agents. Performing the synthesis at 300 or 350 °C yielded quasi-spherical, monodispersed Fe3O4 NPs with a mean size of 14 nm. Evidence from thermogravimetry, X-ray fluorescence, and infrared analysis is consistent with nanocrystal coverage by a partial bilayer of [P6,6,6,14][Tf2N], accounting for the excellent dispersibility of the Fe3O4 NPs in solvents such as hexane, toluene, and methylene chloride. Time-dependent t...