Morphology -: controlled synthesis of α-FeOOH and its derivatives

alpha-FeOOH nanocrystals were synthesized in high yield via a facile and template-free hydrothermal method at low temperature. The morphology and composition of the samples were controlled by slowly releasing the SO42- ions from ammonium persulfate. The rod-like, bundle-like, and urchin-like alpha-FeOOH nanocrystals could be acquired respectively through a direct hydrothermal route with different quantities of SO42- ions. The rod-like a-FeOOH nanocrystals obtained have a diameter of 5-25 nm and a length of 100-200 nm. When the molar ratio of iron to SO42- was 1:1, the product was pure a-FeOOH phase. However, as the molar ratio was decreased from 1:1 to 1:4, pure FeSO4OH center dot 2H(2)O phase was obtained. When the molar ratio was between 1: 4 and 1: 1, the prepared product was composed of two phases (alpha-FeOOH and FeSO4OH center dot 2H(2)O). After hydrothermally aging the as-synthesized alpha-FeOOH nanorods at 180 degrees C for 1 d, alpha-Fe2O3 nanorods were obtained. However, the edge of the alpha-Fe2O3 nanorods was sword- like and different from the blunt edge of alpha-FeOOH nanorods due to a recrystallization mechanism.