Solution synthesis of triangular and hexagonal nickel nanosheets with the aid of tungsten hexacarbonyl

The preparation of magnetic metal nanocrystals with strong shape-anisotropy has attracted great research interest in recent years due to their unique applications in fields such as magnetic materials and catalysis. This paper explores a non-aqueous one-pot route to synthesizing triangular and hexagonal Ni nanosheets with an average edge length that can be reduced to 15 nm. In the synthesis, a widely used Ni precursor, nickel(II)acetylacetonate, is reduced by oleylamine in the presence of tungsten hexacarbonyl. An important aspect of such a synthetic strategy is that the nucleation temperature of the Ni nanocrystals can be as low as 150 degrees C. In the meantime, a shape-anisotropic nanostructure can be achieved. By increasing the reaction temperature and aging time, nanosheets with larger sizes are obtained. A possible formation mechanism is proposed for the as-prepared Ni nanosheets. Magnetic measurements show that all the prepared Ni nanosheets exhibit ferromagnetic characteristics at room temperature and larger magnetic anisotropy compared to spherical nanoparticles is evident.