The Modified Liquid-Liquid Interface: The Effect of an Interfacial Layer of MoS2 on Ion Transfer

Abstract

MoS2 nanosheets have been assembled at the water|1,2-dichlorobenzene (DCB) interface into uniform films, and the ion-transfer properties investigated by voltammetry at the interface between immiscible electrolyte solutions. Remarkably, interfacial MoS2 films were found to enhance the simple and facilitated transfer of cationic species while restricting the transport of anionic species. The enhancement is attributed to a localised increase in the cationic concentration at the interface due to the adsorption onto the negatively charged surface of the exfoliated MoS2 nanosheets. Size-selectivity for the cationic species was also recognized as a feature of such films. Characterisation of the interfacial film's structure revealed the inclusion of multiple emulsified droplets stabilised by MoS2, where the droplet number and size depend on the concentration of the MoS2 dispersion. Besides increasing the interfacial corrugation and area, the emulsified droplets are believed to influence the mass transport mechanism across the interface. Cyclic voltammetric measurements of saturated films suggested a capillary-like structure of these films. While the capillaries/nanochannels allow them to have a degree of size-selectivity that depends on the thickness/density of the film, they also affect the diffusion zones towards and away from the interface. Consequently, steady-state conditions of mass transport similar to those found in solid-state supported micro-ITIES are observed in these nanofilms.