α-Fe₂O₃ nanocrystals: Controllable SSA-assisted hydrothermal synthesis, growth mechanism, and magnetic properties

α-Fe₂O₃ nanocrystals with different morphologies were successfully synthesized by a facile 5-sulfosalicylic acid dihydrate (SSA)-assisted hydrothermal process, in the absence of any template or surfactant in the system. The chelating ligand SSA, pH values of Fe-SSA complex solution, and alkaline reagents play important roles in the morphological control of the α-Fe₂O₃ nanostructures. Magnetic hysteresis measurements reveal that the size of the nanostructures has a remarkable effect on the magnetic properties at room temperature. A possible formation mechanism for controllable synthesis of these α-Fe ₂O₃ nanocrystals was proposed. In addition, the successful synthesis of honeycomb-like hierarchical Ni(OH)₂ structures and Co₃O₄ microspheres in our experiments gave further evidence for the wide applicability of the SSA-assisted hydrothermal synthesis process. The results suggest that this process may be a convenient and effective approach to controllable synthesis of a variety metal oxides and hydrates nanostructures.