Synthesis and shape evolution of α-Fe2O3 nanophase through two-step oriented aggregation in solvothermal system

The synthesis and shape evolution of α-Fe2O3 nanoparticles through oriented aggregation in solvothermal system were investigated. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) revealed that the three-dimensional (3D) flower-like α-Fe2O3 nanophase was formed by two-step crystallographically oriented aggregations, and then evolved to polyhedral nanoparticles by conventional Ostwald ripening. The organic solvent N, N-dimethylformamide (DMF) played an important role not only in chemical reaction, but also in oriented aggregation-based self-assembly.