Tracking the morphology and phase transformations of anodic iron oxide nanotubes using X-ray spectroscopy

X-ray spectroscopic techniques have been employed to investigate highly ordered iron oxide nanotubes (NTs) prepared by iron anodization in a fluorine-containing electrolyte followed with annealing at elevated temperatures. NTs undergo morphology and phase evolutions from amorphous NTs to single crystalline nanoplates, then nanoflakes, and finally to a polycrystalline film. X-ray diffraction and X-ray absorption near edge structure have been used for the investigation. We show that fluorine incorporation can be used as an effective morphology tailoring tool for the engineering of efficient iron oxide nanostructures.