Preparation of large Co nanosheets with enhanced coercivity by a magnetic-field-assisted solvothermal approach free of surfactants, complexants or templates

We presented a magnetic-field-assisted solvothermal route to prepare hexagonal close-packed (hcp) large Co nanosheets free of any surfactants, complexants or templates. Scanning electron microscope (SEM) images showed that the typical size and thickness of the Co nanosheets were several microns and ca. 50 nm, respectively. Magnetic measurement indicated the coercivity of the sample reached 317.3 Oe, which was much higher than those of bulk Co metal and previously reported Co nanoplatelets. It was found that the solvents played a crucial role in determining the morphology and the crystal structures of the Co products, and the introduction of ethanol conduced to the formation of pure hcp phase Co microcrystal. The external magnetic field was also found to be indispensable for the formation of sheet-shaped morphology.