Understanding the Growth Mechanism of α-Fe2O3 Nanoparticles through a Controlled Shape Transformation

The growth mechanism of α-Fe2O3 nanoparticles in solution has been elucidated from a comprehensive analysis on the shape and morphology of obtained particles. It is found that the hydrothermal synthesis of α-Fe2O3 nanoparticles from ferric chloride precursor follows two stages: the initial nucleation of α-Fe2O3 nuclei and the subsequent ripening of nuclei into various shapes. The initial nucleation involves the formation of polynuclears from hydrolysis of Fe3+ salt precursors, followed by the growth of β-FeOOH nanowires with an akaganeite structure, and then into two-line ferrihydrite nanoparticles through a dissolution–recrystallization process. In the subsequent ripening process, we suggest that the formation of large α-Fe2O3 particles follows the dissolution of two-line ferrihydrite and then precipitation and oriented aggregation of α-Fe2O3 nuclei rather than the oriented aggregation of ferrihydrite nanoparticles followed by phase transformation. The oriented attachment of {104} facets between α-Fe2O3 ...