A simple synthetic route to MoS₂ and WS₂ nanoparticles and thin films

We produced both MoS₂ and WS₂ nanoparticles by thermally decomposing M(CO)₆ (M = Mo, W) in excess of H₂S by using a hot filament. Both highly pure crystalline MoS₂ and WS₂ nanoparticles were efficiently produced over the filament temperature range from 300 to 800 °C. Particle diameter ranged from 2.0 to 5.0 nm and from 3.0 to 6.0 nm for MoS₂ and WS₂ nanoparticles, respectively. Fullerene-like particles such as nanotubes, onions, and empty and nested hollows were not produced. Both MoS₂ and WS₂ nanoparticles have a hexagonal close packed structure. Cell constants are determined to be a = 3.09 and c = 12.61 Å and a = 3.09 and c = 12.47 Å for MoS₂ and WS₂ nanoparticles, respectively, which are all consistent with the corresponding bulk values. Thin films of MoS₂ and WS₂ were also prepared by chemical vapor deposition of MoS₂ and WS₂ on stainless steel disks at 600-650 °C and low friction coefficients were obtained at an ambient atmosphere for both MoS₂ and WS₂ thin films, implying that they can serve as good solid lubricants.