Growth Mechanism of MoS₂ Fullerene-like Nanoparticles by Gas-Phase Synthesis

Inorganic fullerene-like (hollow onionlike) nanoparticles (IF) and nanotubes have attracted considerable interest in recent years, due to their unusual crystallographic morphology and their interesting physical properties. IF-MoS 2 and nanotubes were first synthesized by a gas-phase reaction from MoO 3 powder. This process consists of three steps: (1) evaporation of the MoO 3 powder as molecular clusters; (2) condensation of the oxide clusters to give MoO 3 - x nanosize particles; (3) sulfidization of the suboxide nanoparticles to generate IF nanoparticles. The evaporation of MoO 3 (step 1) and the IF particle formation from the oxide nanoparticles (step 3) have been investigated already, while the mechanism for the suboxide nanoparticles formation (step 2) has not been studied before and is reported here. According to the present model, a partial reduction of the trioxide molecular clusters (3−5 molecules) leads to the formation of MoO 3 - x nanoparticles (5−300-nm particles size) the precursor for IF - MoS 2 . A mathematical model, which takes into account the diffusion of the reactants into the reaction zone, the chemical reactions, and the boundary conditions obtained from the experiments, is established and solved. Based on the comprehensive understanding of the IF-MoS 2 growth mechanism from MoO 3 powder and the solution of the diffusion equations, a gas-phase reactor, which allowed reproducible preparation of a pure IF-MoS 2 powder (50 mg per batch) with controllable sizes, is demonstrated.