Synthesis, growth mechanism and characterization of single crystalline alpha-Fe2O3 spherical nanoparticles

In the present report, we proposed a simple and efficient method for synthesizing single crystalline alpha-Fe2O3 spherical nanoparticles array into hexagonal dipyramid (HGDP) hierarchical structures using urea as a surface-active agent to control the growth and nucleation of the iron species. Growth mechanisms for the formation of HGDP hierarchical structures have been also proposed. Single crystalline feature, structural morphology and size of the nanoparticles were investigated by X-ray diffraction (XRD), Scanning and Transmission electron microscopy (SEM). The spectroscopic techniques such as; FT-IR, UV-VIS absorption and Raman spectroscopy were used to investigate optical response of the synthesized nanoparticles. Optical energy band gap was calculated to be 2.57 eV and 2.21 eV corresponding to direct and indirect transitions, respectively. The magnetic properties of the single crystalline nanoparticle were also investigated by Vibrating sample magnetometer (VSM) and found that they are weak ferromagnetic in nature. The values of saturation magnetization, remanent magnetization and coercivity were found to be 0.5925 emu/g and 0.1642 emu/g and approximately 1650 Oe, respectively.