Versatile Cutting Method for Producing Fluorescent Ultrasmall MXene Sheets.

As a recently created inorganic nanosheet material, MXene has received growing attention and has become a hotspot of intensive research. The efficient morphology control of this class of material could bring enormous possibilities for creating marvelous properties and functions; however, this type of research is very scarce. In this work, we demonstrate a general and mild approach for creating ultrasmall MXenes by simultaneous intralayer cutting and interlayer delamination. Taking the most commonly studied Ti3C2 as an illustrative example, the resulting product possessed monolayer thickness with a lateral dimension of 2-8 nm and exhibited bright and tunable fluorescence. Further, the method could also be employed to synthesize ultrasmall sheets of other MXene phases, for example, Nb2C or Ti2C. Importantly, although the strong covalent M-C bond was to some extent broken, all of the characterizations suggested that the chemical structure was composed of well-maintained host layers without observation of any serious damages, demonstrating the superior reaction efficiencies and safeties of our methods. This work may provide a facile and general approach to modulate various nanoscale materials and could further stimulate the vast applications of MXene materials in many optical-related fields.