Water Dispersible, Positively and Negatively Charged MoS₂ Nanosheets: Surface Chemistry and the Role of Surfactant Binding

Abstract

Stable aqueous dispersions of atomically thin layered MoS2 nanosheets have been obtained by sonication in the presence of ionic surfactants. The dispersions are stabilized by electrostatic repulsion between the sheets, and we show that the sign of the charge on the MoS2 nanosheets, either positive or negative, can be can be controlled by the choice of the surfactant. Using techniques from solution NMR, we show that the surfactant chains are weakly bound to the MoS2 sheets and undergo rapid exchange with free surfactant chains present in the dispersion. In situ nuclear Overhauser effect spectroscopic measurements provide direct evidence that the surfactant chains lie flat, arranged randomly on the basal plane of the MoS2 nanosheets with their charged headgroup exposed. These results provide a chemical perspective for understanding the stability of these inorganic nanosheets in aqueous dispersions and the origin of the charge on the sheets.

Prussian Blue@MoS2Layer Composites as Highly Efficient Cathodes for Sodium‐ and Potassium‐Ion Batteries

“…The quality of the exfoliated material was evaluated by powder X‐ray diffraction (PXRD), UV–vis, Raman spectroscopy, transmission electron microscopy (TEM), and atomic force microscopy (AFM) (Figures S1–S3, S5, S6, S8, and S9; Table S1, Supporting Information). As expected, and confirmed by zeta potential (ZP), n ‐BuLi exfoliated MoS 2 flakes are partially reduced (zeta potentials around −45 mV) and form stable dispersions due to interlayer electrostatic repulsions …”

Comparison of MoS2, WS2, and Graphene Oxide for DNA Adsorption and Sensing

“…As such, the charge 14 on the surfactant headgroups is less important. 48 This is in direct competition with the adsorbed DNA since the same force was involved. On the other hand, GO adsorption is based on other forces and is thus less affected.…”

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

“…Since the surface of MoS 2 is hydrophobic, it is challenging to exfoliate and disperse it in water without using surfactants or surface modification. Among the several approaches for MoS 2 exfoliation, the simplest and most straightforward involves liquid-phase exfoliation of bulk MoS 2 powders by ultrasonication in either appropriate solvent [25], ionic surfactants [26] or polyelectrolyte [4]. Therefore, to exfoliate and dispersed the MoS 2 in water, we have used PAA to functionalize the MoS 2 surface using sonication-assisted liquid phase exfoliation (see the experimental section and Scheme 1).…”