α-Fe2O3 hierarchically hollow microspheres self-assembled with nanosheets: surfactant-free solvothermal synthesis, magnetic and photocatalytic properties

Abstract

A surfactant-free solvothermal combined with precursor thermal transformation method has been developed for the preparation of α-Fe₂O₃ hierarchically hollow microspheres assembled with nanosheets. First, a solvothermal treatment is employed to prepare the precursor consisting of hierarchically hollow microspheres assembled with nanosheets using Fe(NO₃)₃ as the only inorganic reactant without any other additive in mixed solvents of dimethylformamide and ethylene glycol, and α-Fe₂O₃ hierarchically hollow microspheres assembled with nanosheets are subsequently obtained by thermal treatment of the precursor powder in air at 450 °C for 2 h. The morphology of the precursor can be well preserved during thermal transformation from the precursor to α-Fe₂O₃ hierarchically hollow microspheres. The samples are characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen absorption-desorption isotherm, and thermogravimetric (TG) analysis. The effect of the solvent on the morphology of precursors as well as the formation process of the hierarchically hollow microspheres are investigated. The magnetic properties and photocatalytic activity of α-Fe₂O₃ hierarchically hollow microspheres assembled with nanosheets are discussed.