University of Southern California, USA
Posters & Accepted Abstracts: Res. Rev. J Mat. Sci
Binary nickel sulfides exist in a variety of phases and stoichiometries, including NiS2, Ni3S4, α-NiS, β-NiS, Ni9S8, Ni7S6 and Ni3S2. Distinct phases of the binary nickel sulfide system have potential to be used as bifunctional catalysts for water splitting, cathode materials for lithium-ion batteries, absorber layers for solar cells, hydrodesulfurization catalysts, or supercapacitors. However, the complicated nature of the Ni–S phase diagram makes the solution synthesis of phase-pure colloidal nanocrystals challenging. In this presentation, the phase- and morphology-controlled solution synthesis of colloidal nickel sulfide nanocrystals is demonstrated. Nanocrystals of Ni3S4, α-NiS, β-NiS, Ni9S8 and Ni3S2 can be independently prepared by tuning key synthetic parameters of S:Ni precursor ratio, capping ligand, reaction time and temperature. S:Ni ratio and temperature influences the phase of nanocrystals, a phase transformation from cubic Ni3S4 to hexagonal α-NiS and then rhombohedral β-NiS with increasing S:Ni ratios and temperature is observed. 1-dodecanethiol is shown as an important phase and shape-directing agent. In the presence of 1-dodecanethiol, Ni9S8 nanocrystals with quasi-spherical morphology or Ni3S2 nanoparticles with a multi-pod like morphology can be obtained by using various disubstituted thioureas are sulfur precursors.