Single- to Triple-Wall WS2 Nanotubes Obtained by High-Power Plasma Ablation of WS2 Multiwall Nanotubes

Abstract

Abstract:The synthesis of inorganic nanotubes (INT) from layered compounds of a small size (<10 nm in diameter) and number of layers (<4) is not a trivial task. Calculations based on density functional tight-binding theory (DFTB) predict that under highly exergonic conditions, the reaction could be driven into a "window" of (meta-) stability, where 1-3-layer nanotubes will be formed. Indeed, in this study, single-to triple-wall WS 2 nanotubes with a diameter of 3-7 nm and a length of 20-100 nm were produced by high-power plasma irradiation of multiwall WS 2 nanotubes. As target materials, plane crystals (2H), quasi spherical nanoparticles (IF) and multiwall, 20-30 layers, WS 2 nanotubes were assessed. Surprisingly, only INT-WS 2 treated by plasma resulted in very small, and of a few layers, "daughter" nanotubules. The daughter nanotubes occur mostly attached to the outer surface of the predecessor, i.e., the multiwall "mother" nanotubes. OPEN ACCESSInorganics 2014, 2 178They appear having either a common growth axis with the multiwall nanotube or tilted by approximately 30° or 60° with respect to its axis. This suggests that the daughter nanotubes are generated by exfoliation along specific crystallographic directions. A growth mechanism for the daughter nanotubes is proposed. High resolution transmission and scanning electron microscopy (HRTEM/HRSEM) analyses revealed the distinctive nanoscale structures and helped elucidating their growth mechanism.

Thin WS2 nanotubes from W18O49 nanowires

“…It should be noted that the interlayer separation of this nanotube is different at the two sides with one side being 0.64 nm and the other 0.76 nm, suggesting that this nanotube has two nonconcentric shells. The interlayer separation of bulk 2H-WS 2 crystals is 0.62 nm and the interlayer separation multi-walled WS 2 nanotubes varied between 0.63 and 0.65 nm [25]. Since the outer diameter is 1.4 nm larger than the inner diameter, the closer contact of one side would lead to a larger separation of the other side.…”

“…Several experimental methods have been explored to synthesize WS 2 nanotubes, including gas-solid reactions CONTACT Lu-Chang Qin lcqin@unc.edu Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA [3,[13][14][15][16][17][18][19][20], chemical transport [21,22], irradiation activation [23][24][25], sulphurization of tungsten film [26], and the solution route [27]. Most of the synthetic methods are based on high-temperature gas-solid reactions, where hydrogen and hydrogen sulfide or sulfur and metal oxide precursors were used as the reactants [20].…”

“…Whitby et al [29] reported use of multi-walled carbon nanotubes as templates for synthesis of single-walled WS 2 nanotubes. As for template-free methods, it was concluded that the generation of such thin nanotubes requires highly exergonic conditions to drive the reactions into windows of stability far enough from equilibrium, such as using laser ablation [25]. However, it was also suggested that these thin nanotubes were not obtainable by the conventional thermally driven process (<1000°C), which is not sufficiently exergonic.…”

Charge Transfer Variability in Misfit Layer Compounds: Comparison of SnS‐SnS2 and LaS‐TaS2

“…Inorganic 2D materials show a special distinction compared to graphene: most of them are semiconducting, such as e.g. MoS 2 , WS 2 , SnS, and SnS 2 . This is a crucial advantage in applied nanosciences, because the non‐zero band gap – in the case of e. g. MoS 2 and WS 2 – can be used for building electrical devices like nano‐transistors on the atomic and molecular scale .…”

Surface Defects as a Tool to Solubilize and Functionalize WS2 Nanotubes

“…Reductive sulfidization of WO x nanoparticles has proven to be the most efficient method for the synthesis of WS 2 nanoparticles, either as IFs or as NTs. [29][30][31][32] In addition, templateassisted self-assembly, [33] electron-beam irradiation, [34] arc discharge, [35][36][37] and laser ablation [38] have been employed. Herein, we show that the structure of the metal oxide precursors has a considerable effect on the defect density of WS 2 nanoparticles obtained by reductive sulfidization.…”