Bulk synthesis of inorganic fullerene-like MS(2) (M=Mo, W) from the respective trioxides and the reaction mechanism

Recently, milligram quantities of MoS2 fullerene-like nanotubes and negative curvature polyhedra (generically called inorganic fullerene-like material, IF), were reproducibly obtained by a gas phase reaction from an oxide precursor (Feldman, Y.; Wasserman, E.; Srolovitz, D.J.; Tenne, R. Science 1995, 267, 222. Srolovitz, D. J.; Safran, S.A.; Homyonfer, M.; Tenne R. Phys. Rev. Lett. 1995, 74, 1778). The present work focuses on the mechanism of the synthesis of IF-MS(2) (M = W, Mo). The IF material is obtained from oxide particles smaller than ca. 0.2 mu m, while larger oxide particles result in 2H-MS(2) platelets. The key step in the reaction mechanism is the formation of a closed layer of MS(2), which isolates the nanoparticle from its surroundings and prevents its fusion into larger particles. Subsequently, the oxide core of the nanoparticle si progressively converted into a sulfide nanoparticle with an empty core (IF). Taking advantage of this process, we report here a routine for the fabrication of macroscopic quantities of a pure IF-WS2 phase with a very high yield. As anticipated, the size distribution of the IF material is determined by the size distribution of the oxide precursor. The present synthesis paves the way for a systematic study of these materials which are promising candidates for, e.g., solid lubrication.