EFFECTS OF SURFACE LIGANDS ON THE FORMATION OF SPHERICAL HOLLOW NICKEL PHOSPHIDE NANOPARTICLES AND THEIR SELF-ASSEMBLIES

Abstract

Nickel phosphide nanoparticles have been well known for their electrical, catalytic, and corrosion-resistant properties. In the synthesis of hollow nickel phosphide nanoparticles, the role of surface ligands was very important in forming hollow structures. Thus, in this article, we systematically investigated the effects of different ligands on the formation of spherical hollow nickel phosphide nanoparticles. Specifically, our results showed that when primary amines with long alkyl chains were used, spherical hollow nickel phosphide nanoparticles were obtained. On the other hand, when amines with bulky head groups, bulky alkyl chains, or ligands with different head groups were used, spherical hollow nickel phosphide nanoparticles did not form. Furthermore, moderate use of tri-n-octylphosphine (TOP), another surface ligand and P precursor, was also a contributing factor to the hollow nickel phosphide formation. Interestingly, we discovered that limited use of TOP induced self-assembling of spherical hollow nickel phosphide nanoparticles into micro-sized assemblies. The assemblies were spherical, compact and uniform, which further showing the use of surface ligands as a tool to engineer novel material structures from the nano-/micro-scales. We are currently directing our efforts toward more understanding of the self-assembling mechanism at the sub-nano scale as well as proposing possible application for our nanoparticles and their assemblies.