Mxene-Directed Dual Amphiphilicity at Liquid, Solid, and Gas Interfaces.

MXenes represent a category of two-dimensional functional nanomaterials with remarkable structural and chemical properties, which have been manipulated into different architectures for versatile applications. These manipulation processes generally take place at the interfaces between liquid, solid, and gas; and therefore, the investigation of the interfacial property of MXenes is the key. Here we show that MXenes exhibit amphiphilic behaviours at interfaces. Different from common amphiphiles, MXenes have the dual function of both colloidal and molecular activities owing to their two abrupt structural length scales: their large lateral sheet size allows for behaving like colloidal amphiphiles for creating emulsions, while their small sheet thickness allows for serving as molecular amphiphiles for dispersing solid substances. Further, such dual colloidal-molecular amphiphility has driven MXenes to accumulate at the interfaces of water and nitrogen gas, and the assembly into thin film electrodes for electrochemical energy storage. All these findings open up enormous opportunities for processing various MXenes-related functional materials and devices.