New surface-directed vapour transport methods for the controlled growth of nickel sulfide nanomaterials

Highly symmetrical, isotropic nickel disulfide (NiS₂) nanocubes have been synthesised via a Physical Vapour Transport (PVT) method in which sulfur vapour generated insitu is reacted with nickel-coated silica substrates. Systematic studies demonstrate the effect of the reactant ratio, substrate, metal layer thickness, and reaction temperature on the synthesis and growth process. The evolution of structure and composition has been followed by diffraction and electron microscopy techniques, and the size of the NiS ₂ cubes can be varied from below 200nm to 1-2μm across. Magnetic properties of the disulfide nanomaterials have been determined using SQUID magnetometry. Initial experiments also demonstrate that related Chemical Vapour Transport (CVT) techniques can be exploited to produce alternative compositions in the Ni-S system with varying morphologies that can be controlled via chemical and physical reaction parameters.