Synthesis and magnetic properties of NiS1 + x nanocrystallines

Hexagonal α-NiS nanocrystals and Ni3S4 nanoplates have been prepared by a colloidal chemical process in oleylamine. X-Ray diffraction (XRD), transmission electron microscope (TEM), field-emission scanning electron microscope (FESEM), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the products. The self-assembly hollow spheres by α-NiS nanocrystals are observed. XPS study indicates that the products' surface contains excess sulfur which would enhance the density of active sites on the catalyst surface for hydrogenolysis process. Magnetization measurement indicates that the α-NiS and Ni3S4 are no longer antiferromagnetic; both of them show paramagnetism due to the size effect.