Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation

Abstract

Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS 2 ) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS 2 samples exhibit strong photoluminescence without further chemical treatment.

Production of monolayer-rich gold-decorated 2H–WS2 nanosheets by defect engineering

“…3i) shows that the ML-enriched nanosheets of l-WS 2 are significantly larger ( oL4 = 140 nm) than in other reported procedures, where they are typically o 70 nm. 17,18 Furthermore, this emphasizes that the WS 2 lateral size in the final, ML-enriched purified l-WS 2 -Au dispersion (140 nm) is similar to the initial l-WS 2 dispersion (115 nm) prior to the reaction. A plot of nanosheet length vs. thickness (Fig.…”

“…Size selection can be achieved by centrifugation, but MLs are small and the procedures are extremely time consuming. [17][18][19] Secondly, chemical functionalisation to further tailor the materials' properties on demand is currently in its infancy. [20][21][22] With few exceptions, 23,24 the covalent chemistry is currently limited to CE-1T-TMDs, which are of less interest in optoelectronic applications due to its lack of visible optical absorption or emission.…”

Water-Assisted Synthesis of Molybdenum Disulfide Film with Single Organic Liquid Precursor

“…4(e). The hexagonal dots are assigned to the (10–10) and (11–20) planes of MoS 2 , according to a previous report 47 . The high-resolution TEM image in Fig.…”

Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

“…6,37 That nanosheets can be stably dispersed in liquids greatly facilitates further processing. For example nanosheets can be size-selected by controlled centrifugation 23,[37][38][39][40][41] or chemically modified via functionalization protocols. [42][43][44] In addition, the dispersions can easily be formed into thin films or mixed with other materials to form composites.…”