Abstract:

MoS₂ nanoparticles of size <5 nm have been synthesized via the reaction of Mo(CO)₆ with elemental sulfur in trioctylphosphine oxide and 1-octadecene at temperatures from 270 to 330 °C. The MoS₂ nanoparticles are discrete and dispersible in a variety of nonpolar organic solvents, including toluene, chloroform, and pyridine. The size of the particles can be effectively tuned by varying the temperature, yielding nearly monodisperse samples (<10% standard deviation) as evidenced by transmission electron microscopy (TEM). Additionally, larger (20–50 nm) onion- and tube-shaped MoS₂ nanoparticles can be obtained by decreasing the amount of the coordinating solvent (trioctylphosphine oxide) relative to 1-octadecene. As-prepared samples are poorly crystalline, showing only weak contrast in the TEM and an absence of the first-order (00l) reflection in powder X-ray diffraction that is indicative of regular MoS₂ stacking. Samples heated in situ in the TEM are observed to develop contrast and lattice fringes as the temperature is raised to 550 °C. Ex-situ heated samples show the appearance of the first order (00l) reflection at temperatures >870 °C.