Single-molecule precursor-based approaches to cobalt sulphide nanostructures

Cobalt complexes of 1,1,5,5-tetramethyl-2,4-dithiobiuret, [Co{N(SCNMe2)(2)}(3)] (1), and 1,1,5,5-tetraisopropyl-2-thiobiuret, [Co{N((SOCNPr2)-Pr-i)(2)}(2)] (2), have been synthesized and characterized. Both complexes were used as single-molecule precursors for the preparation of cobalt sulphide nanoparticles by thermolysis in hexadecylamine, octadecylamine or oleylamine. The powder X-ray diffraction pattern of as-prepared nanoparticles showed the hexagonal phase of Co1-xS from complex 1 and mixtures of cubic and hexagonal Co4S3 from complex 2. Transmission electron microscopy images of material prepared from complex 1 showed spherical and trigonally shaped particles in the size range of 1015 nm; whereas spheres, rods, trigonal prisms and pentagonally and hexagonally faceted crystallites were observed from complex 2. This observation is the first of the Co4S3 phase in a nanodispersed form.