FeO octahedral colloidal crystals.

We present a facile and controllable method for the large-scale fabrication of highly-ordered octahedral FeO colloidal 'single crystals' without the assistance of a substrate. Oleic acid is used to reduce the solubility of the nano-building blocks in colloidal solution and to induce a 'crystallization' process. Our colloidal crystals are of multimicron size and show typical crystallographic characteristics. They have a very robust structure and can serve as a novel ordered magnetic mesoporous material with a relatively narrow pore size distribution. The sample possesses an extremely high Verwey transition temperature ( T) of 100 K and a high saturation magnetization ( M) of 86 emu/g at 5 K based on its good crystallinity, as well as the interparticle dipolar interaction behavior arising from its unique structure. Electrochemical measurements have demonstrated the excellent capacity of the mesoporous colloidal crystals when used in lithium-ion batteries. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]