Two-Dimensional Nanosheets and Layered Hybrids of MoS₂ and WS₂ through Exfoliation of Ammoniated MS₂ (M = Mo,W)

Abstract

Ammoniated MS 2 (M = Mo,W) have been synthesized by reacting Li x MS 2 with a saturated solution of ammonium chloride. While, largely neutral NH 3 is present in the interlayer of ammoniated MoS 2 , equal amounts of NH 3 and NH 4 + ions are present in the tungsten analog. The ammoniated MS 2 exfoliate readily in a variety of polar solvents with exfoliation being best in water. Ammoniated WS 2 forms a more stable colloidal dispersion compared to the Mo analog because the ammonium ions do not deintercalate easily from the layers even on exfoliation. The dispersions are comprised of large nanosheets of MS 2 with lateral dimensions in the order of micrometers. The layers could be restacked from the colloidal dispersions by evaporating the solvent. While the colloidal dispersions of ammoniated MoS 2 yield NH 3 -free MoS 2 on restacking, the dispersions of ammoniated WS 2 yield WS 2 intercalated with NH 4 + ions. Co-stacking of MoS 2 and WS 2 nanosheets from a mixture of both the colloidal dispersions results in MoS 2 −WS 2 hybrids in which the MoS 2 and WS 2 nanosheets are randomly stacked. Photoluminescence measurements of MS 2 nanosheets and MoS 2 −WS 2 hybrids indicate phase stability and existence of direct bandgap.

Interlayer Nanoarchitectonics of Two‐Dimensional Transition‐Metal Dichalcogenides Nanosheets for Energy Storage and Conversion Applications

“…However, the ammoniated MoS 2 presents a single endothermic peak centered at 80 °C corresponding to NH 3 . [65] The intercalated species contains both [66,67] The reaction is as follows:…”

“…[70] Co-stacking of exfoliated MoS 2 and WS 2 monolayer dispersions results in formation of MoS 2 −WS 2 hybrid with an interlayer spacing of 0.65 nm. [65] Conducting polyethylene oxide (PEO) intercalated MoS 2 (PEOMoS 2 ) with expanded interlayer spacing by the exfoliation/restacking route has been investigated. [71][72][73][74] In a typical process (Figure 4A) Figure 4B).…”

“…The reported interlayer spacings in Reproduced with permission. [65] Copyright 2014, American Chemical Society.…”

Ionic strength induced electrodeposition of two-dimensional layered MoS 2 nanosheets

“…Dispersion of bulk MoS 2 in solvents, particularly in water, and its exfoliation into few layers nanosheet is a critical step towards exploring its application [2,4,5,7]. Since the surface of MoS 2 is hydrophobic, it is challenging to exfoliate and disperse it in water without using surfactants or surface modification.…”

“…The bulk MoS 2 consists of S Mo S sheets stacked by weak van der Waals interactions, which provide their unique mechanical, chemical and physical properties [5]. It has been shown that the MoS 2 obtained from the delamination of layers through mechanical cleavage or liquid exfoliation, exhibited outstanding performance in various applications as compared with bulk MoS 2 [2,[6][7][8]. Therefore, deposition of a few layers of MoS 2 is highly desirable and could be particularly useful for various applications including hydrodesulfurization [9] and hydrogen evolution catalysis [3].…”