One Batch Exfoliation and Assembly of Two-Dimensional Transition Metal Dichalcogenide Nanosheets Using Electrophoretic Deposition

Abstract

Two-dimensional (2-D) transition metal dichalcogenides (TMDs) are a family of nanostructures possessing exciting physical properties relevant toward applications often requiring fabrication of macroscopic films and networks. Here, we demonstrate electrophoretic deposition (EPD) for assembly of a broad range of 2-D TMDs, including molybdenum disulfide (MoS 2 ), molybdenum diselenide (MoSe 2 ), and tungsten disulfide (WS 2 ), into uniform coatings that can be universally applied on both planar and porous three-dimensional foam electrodes. This assembly process can be directly coupled with solvent exfoliation to yield one-batch processing capable of transforming bulk TMD powders into functional films and coatings of 2-D TMD nanostructures. EPD from common exfoliating solvents 1-methyl-2-pyrollidone (NMP) and acetonitrile (ACN) indicates assembly kinetics governed by the inherent solution properties of the solvents, with poorer exfoliation in ACN compared to NMP, but more rapid deposition kinetics in ACN compared to NMP. In-situ absorbance monitoring indicates the capability to completely deposit all dispersed mass of highly purified 2-D TMDs onto a solid substrate. Overall, our work demonstrates EPD as a versatile and efficient route to assemble 2-D TMD nanostructures directly from exfoliated dispersions into planar and 3-D substrates for use in diverse applications.The heightened interest in two-dimensional (2-D) materials in recent years has led to tremendous interest in the novel electronic, optical, chemical, and electrochemical properties of these materials that can strongly differ from that observed in bulk materials. 1-3 Specifically, the transition metal dichalcogenides (TMDs) have received widespread attention due to the versatile chemical and electronic properties that arise from the available compositions, structures, and dimensionalities. 4-6 Unlike 2-D carbon sheets, TMDs represent a group of elements exhibiting a variable bandgap dependent on the number of layers in the sample, the elemental composition, and the presence of doping atoms which make them ideal for electronic and electrochemical devices. 7 TMDs are represented by the general formula MX 2 , and are composed of both a transition metal element (M) and a chalcogen species (X). Materials with this general formula characteristically possess a unique layered structure in which covalently bonded planes of M and X atoms are held together through weak van der Waals interaction. This unique atomic architecture enables facile exfoliation of the material to ultra-thin structures as small as one layer thick when starting with bulk materials. 8 Despite this straightforward route for liquid processing, current methods to produce high quality TMD materials for applications pivot around high cost, energy intensive, and low-yield techniques such as chemical vapor deposition or mechanical cleavage. 9 These routes are not suited for producing vast quantities of material, and this is a significant challenge for many applications, such as in electrochemical (e....

Engineering the Edges of MoS2 (WS2) Crystals for Direct Exfoliation into Monolayers in Polar Micromolecular Solvents

“…Monolayer MoS 2 and WS 2 nanosheets dispersed in water are less stable, with 75% concentration retention for MoS 2 and 72% concentration retention for WS 2 . The stability can also be reflected by performing ζ-potential tests, because nanomaterial solution stability is closely related to electrical double layers on the nanomaterial surface . In general, dispersed nanomaterials are stable with ζ-potential values of less than −30 mV. , Each dispersion was tested three times, and the average value is reported (Figure S16).…”

Formation and Photodynamic Behavior of Transition Metal Dichalcogenide Nanosheet–Fullerene Inorganic/Organic Nanohybrids on Semiconducting Electrodes

“…Therefore, we applied the electrophoretic deposition method to prepare the single‐component TMD and the TMD–C 60 composite films. Upon subjecting the aggregate dispersion to a high dc voltage (200 V for 120 s with 6 mm distance between the electrodes), the aggregates of (C 60 ) m , (TMD) m , and (TMD+C 60 ) m , which are negatively charged in the mixed solvent, were driven towards the positively charged, nanostructured SnO 2 electrodes on fluorine‐doped tin oxide (FTO) to yield the corresponding films, FTO/SnO 2 /(C 60 ) m , FTO/SnO 2 /(TMD) m , and FTO/SnO 2 /(TMD+C 60 ) m , respectively . With increasing time of deposition, the FTO/SnO 2 electrode turned brown for (C 60 ) m and dark brown for (TMD) m and (TMD+C 60 ) m with simultaneous bleaching of the aggregate solution.…”

Electrophoretic deposition of graphene-related materials: A review of the fundamentals

“…One of the particular attractions is that it can be applied to create a wide range of different morphologies adjusted to the contrasting needs of different applications. Many of the same concepts will be applicable to the rapidly growing research field associated with other 2d layered materials, including transition metal dichalcogenides [170], layered double hydroxides [171], and layered nitrides [172], either in isolation, or hybridised with GRMs [84].…”