Effect of phosphate on the morphology of hydrothermally synthesised β-FeOOH and α-Fe2O3 nanoparticles

Abstract

β-FeOOH and α-Fe2O3 nanoparticles have been grown from an FeCl3 solution precursor in the presence of an ammonium dihydrogen phosphate surfactant through the process of hydrothermal synthesis. β-FeOOH production varied from small, rounded nanoparticles (∼ 45 nm) to larger nanorods (∼ 120 nm in length) depending on the stage of synthesis at which the surfactant was added. Larger α-Fe 2O3 nanorods (∼ 70 nm wide and ∼ 450 nm in length) were synthesised from a β-FeOOH suspension at 200°C upon phosphate addition prior to initial β-FeOOH precipitation. The anisotropic growth of α-Fe2O3 was associated with the preferential adsorption of PO43- anions onto α-Fe 2O3 crystal planes parallel to the c-axis. Phosphate addition to the suspension subsequent to the initial β-FeOOH precipitation inhibited the phase transformation to α-Fe2O3 at 200°C and assisted with increasing the β-FeOOH particle size. © 2010 IOP Publishing Ltd.