Rapid synthesis and optical properties of hematite (α-Fe2O3) nanostructures using a simple thermal decomposition method

► A novel method for the synthesis of hematite nanopowder is reported. ► The morphology of α-Fe2O3 changed with altering the preparation temperature. ► The coral like nano α-Fe2O3 prepared at 500 and 600°C showed novel optical behavior. ► The coral like nano α-Fe2O3 could be used to enhance efficiency of the solar cells. 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 3.2eV to 2.7eV as the preparation temperature increased from 300°C to 600°C.