A valve-assisted snapshot approach to understand the hydrothermal synthesis of α-Fe2O3nanorods

Abstract

A novel valve-assisted pressure autoclave is described, facilitating ‘snapshot’ investigations of hydrothermal synthesis (HS) product suspensions rapidly quenched in liquid nitrogen. The approach gives near in situ descriptions of the HS reaction products, as characterised using transmission electron microscopy, and provides fundamental insight into the mechanisms of crystal growth. An investigation into the development of α-Fe₂O₃ nanorods from aqueous FeCl₃ solution clarifies the role of intermediate β-FeOOH nanorod and α-Fe₂O₃ nanoparticle phases during α-Fe₂O₃ nanorod growth. It is shown that intermediate β-FeOOH precipitation and dissolution occurs alongside the anisotropic growth of α-Fe₂O₃ nanorods through the coalescence of primary α-Fe₂O₃ nanoparticles. It is considered that this valve-assisted technique will be widely applicable to the study of many other HS systems.