Rapid synthesis and optical properties of hematite (α-Fe ₂O₃) nanostructures using a simple thermal decomposition method

Hematite nanostructures were prepared by a simple technique using the thermal decomposition of iron (III) nitrate 9-hydrate at different temperatures under air atmosphere. Observations using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that the morphology of the nanostructures changed as the temperature was varied while their size increased with increasing preparation time. Samples prepared at 300, 400, and 500 °C were made of particles with a quantum dots (QDs) size. X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) confirmed that the as-synthesized powders are pure α-Fe₂O₃. The optical energy gap of the samples varied from 3.2 eV to 2.7 eV as the preparation temperature increased from 300 °C to 600 °C. Crown