Preparation of Hyperbranched Structures of α-Fe2O3

Figure 1. XRD pattern of snowflake-like α-Fe2O3 synthesized at [FeCl3] = 0.05 M and [KCN] = 2.00 M under hydrothermal conditions for 16 h at 140 C. Hierarchical structures of metal oxides comprised of nanoparticles, nanorods, and nanobelts as building blocks have attracted great interest due to their novel structures, properties, and applications. However, the preparation of high-quality crystals with hyperbranched structures is a challenging issue. The majority of these structures are formed by hierarchical self-assembly mechanisms, and the snowflake-like morphology is a typical example of a hyperbranched structure. Considerable effort has been devoted to the synthesis of metal oxides and metal sulfides with snowflake-like morphologies. α-Fe2O3 is an n-type semiconductor with a band gap of 2.1eV, and is used today in catalysis, sensors, magnetic recording media, rechargeable lithium batteries, and as a pigment. Various techniques have been used to synthesize α-Fe2O3 with rod, wire, spindle, flower, and dendritic morphologies. However, relatively little is known of fabricating α-Fe2O3 with a snowflake-like morphology, and all successful attempts to date have involved the hydrothermal decomposition of K3[Fe(CN)6], which makes it difficult to examine the evolution of hyperbranched structures due to the difficulty of controlling the decomposition rate of K3[Fe(CN)6]. Here we report a simple method for producing hyperbranched structures of αFe2O3 based on a hydrothermal reaction in aqueous solutions containing KCN and FeCl3.