Controlled Synthesis of Uniform Cobalt Phosphide Hyperbranched Nanocrystals Using Tri-n-octylphosphine Oxide as a Phosphorus Source

A new method to produce hyperbranched Co2P nanocrystals that are uniform in size, shape, and symmetry was developed. In this reaction tri-n-octylphosphine oxide (TOPO) was used as both a solvent and a phosphorus source. The reaction exhibits a novel monomer-saturation-dependent tunability between Co metal nanoparticle (NP) and Co2P NP products. The morphology of Co2P can be controlled from sheallike structures to hexagonal symmetric structures by varying the concentration of the surfactant. This unique product differs significantly from other reported hyperbranched nanocrystals in that the highly anisotropic shapes can be stabilized as the majority shape (>84%). This is the first known use of TOPO as a reagent as well as a coordinating background solvent in NP synthesis.