Controllable Synthesis of Single-Crystalline Fe₃O₄ Polyhedra Possessing the Active Basal Facets

In the present paper, we report on the controllable preparation of single-crystalline Fe 3 O 4 microrhombic dodecahedra possessing the active basal facets in high yield through a facile hydrothermal route. The growth mechanism of the microcrystals is discussed. From a crystallographic point of view, the shapes of the crystals are determined by the ratio of the growth rate along <100> to <111> directions. The pH values of the precursor solution strongly affected the morphologies of the products. When pH value was adjusted to 8–10, well-defined Fe 3 O 4 truncated microrhombic dodecahedra exposing the active basal surfaces ({110}) with narrow size-distribution (<10%) were obtained. The sizes of the Fe 3 O 4 truncated microrhombic dodecahedra are dependent upon the reaction time. The magnetic properties of the products are sensitive to the crystal size. The synthesized well-defined Fe 3 O 4 microcrystals with active basal facets may have important applications in many fields.