Synthesis of polyhedral iron oxide nanocrystals bound by high-index facets

Abstract

High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts, special optical, electrical and magnetic devices. But the high surface energy of the high-index facets usually drives them to grow faster than the other facets and finally disappear during the crystal growth, which leads the synthesis of nanocrystals with high-indexed facets exposed to be a great challenge. Herein, we introduced two routes to control the synthesis of α-Fe2O3 polyhedrons with different sets of high-index facets, one using different metal ions (Ni2+, Cu2+ or Zn2+) as structure-directing agents and the other applying polymer surfactant sodium carboxymethyl cellulose (CMC) as additive. The growth process of high-index α-Fe2O3 polyhedrons was also discussed and possible growth mechanism was proposed.