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

Abstract

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-MoS2 and nanotubes were first synthesized by a gas-phase reaction from MoO3 powder. This process consists of three steps: (1) evaporation of the MoO3 powder as molecular clusters; (2) condensation of the oxide clusters to give MoO3 - x nanosize particles; (3) sulfidization of the suboxide nanoparticles to generate IF nanoparticles. The evaporation of MoO3 (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 MoO3 - x nanoparticles (5−300-nm particles size)the precursor for IF-MoS2. 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-MoS2 growth mechanism from MoO3 powder and the solution of the diffusion equations, a gas-phase reactor, which allowed reproducible preparation of a pure IF-MoS2 powder (50 mg per batch) with controllable sizes, is demonstrated.

Synthesis of WS2 and MoS2 fullerene-like nanoparticles from solid precursors

“…Furthermore, the F i g u r e 6 s h o w s r e p r e s e n t a t i v e I F -M o S 2 nanoparticles generated in photothermal ablation experiments (IF-MoS 2 was not detected in any of the furnace experiments), albeit at low yields (<1%). The observed particles are small (~30 70 nm in linear dimension) due to the formation mechanism of IFMoS 2 being somewhat different from that of IF-WS 2 [35]. The reaction mechanism for the synthesis of IF-MoS 2 is more complex than that of the tungsten analogue [35].…”

“…The observed particles are small (~30 70 nm in linear dimension) due to the formation mechanism of IFMoS 2 being somewhat different from that of IF-WS 2 [35]. The reaction mechanism for the synthesis of IF-MoS 2 is more complex than that of the tungsten analogue [35]. The size of the nanoparticles is determined by the rate of MoO 3 evaporation and its reduction by the hot hydrogen gas, which can be controlled by a proper temperature gradient.…”

“…The WO 3 precursor powder consisted mostly of nanoparticles below 200 nm in size. The MoO 3 precursor powder particles were as large as a few microns, but because MoO 3 powder evaporates at temperatures above ~650 °C [35], the particle size is irrelevant for the synthesis of IF-MoS 2 . Rather, the size of the product nanoparticles is determined by the rate of oxide reduction within the reactor.…”

Fabrication of Porous MoS2 with Controllable Morphology and Specific Surface Area for Hydrodeoxygenation

“…6,7 High-temperature sublimation has been used to prepare MoS 2 nanotubes or fullerene-like MoS 2 , but this approach su®ers from the disadvantages of high energy consumption and small-scale production. 8,9 Hydrothermal or solvothermal methods employing di®erent temperatures, solvents, and raw materials can be used to prepare MoS 2 with di®erent morphologies, such as nanowires, nanospheres, 10 nanorods, 11 nanosheets, 12 etc. These methods o®er control over the morphology, crystal types, and speci¯c surface area, but lead to a wide pore-size distribution.…”

Closed-cage clusters in the gaseous and condensed phases derived from sonochemically synthesized MoS2 nanoflakes

“…The formation of inorganic fullerenes [3] from layered compounds like metal dichalcogenides MX 2 (M ϭ Mo, W; X ϭ S, Se) and their application in the field of tribology [4] generated further interest. There are several synthetic approaches such as gas-phase deposition [5,6], laser ablation [7,8], electron irradiation [9], and high-temperature chemical routes [10,11] for the synthesis of clusters. Nano forms of these materials have their own advantages over the corresponding bulk materials.…”