Synthesis of iron oxide nanorods and nanocubes in an imidazolium ionic liquid

This paper reports the synthesis of iron oxide nanostructures with well-defined shapes, including rod, cube, and sphere, in 1-butyl-3-methylimidazolium bis(triflylmethyl-sulfonyl) imide ([BMIM][Tf₂N]) ionic liquid (IL). Surfactants including oleic acid and oleylamine, which are commonly used as surface capping agents for size and shape control in molecular solvents, can be employed for making morphologically well-defined nanostructures in this IL. Iron pentacarbonyl thermally decomposes at elevated temperatures in [BMIM][Tf₂N] ionic liquid and subsequently form nanoparticles. Nanorods, nanocubes, and spherical particles were synthesized depending mainly on the reaction temperatures and surfactants. X-ray diffraction and transmission electron microscopy data indicated these nanostructures were largely cubic iron oxide, maghemite. Our results show that imidazolium-based ionic liquids can be used as solvent for achieving very high level control over the size and shape of nanostructures. The approach developed in this work can potentially be used as a viable method for making various other uniform nanostructures in ionic liquids.