Ti₃C₂T_<i>x</i> MXene Liquid Crystal: Access to Create Background-Free and Easy-Made Alignment Medium.

Abstract

The formation of lyotropic liquid crystals (LCs) in two-dimensional (2D) colloidal dispersions enables the production of mesoscopic/macroscopic ordered materials from nanoscale building blocks. In contrast to graphene oxide (GO) LCs, the practical applications of MXene LCs are less exploited. This study bridges the gap by utilizing a simple and versatile fabrication method to prepare Ti₃C₂T_<i>x</i> MXene LC that can be applied as a background-free alignment medium for the residual dipolar coupling (RDC) measurement of organic molecules. Ti₃C₂T_<i>x</i> LC displays the size- and concentration-dependent alignment degree. Ti₃C₂T_<i>x</i> nanoflakes with an average size of around 600 nm can provide the quadrupolar ²H splitting of 71 Hz at a concentration of 50 mg/mL and show excellent fluidity at such a high concentration. Compared with other alignment media, Ti₃C₂T_<i>x</i> LC exhibits the features of no-background and narrow line broadening, which actualizes the acquirement of clean and high-quality NMR spectra for the accurate RDC extraction. Notably, the alignment of LCs is determined to be maintainable in the redispersed solution after freeze-drying, providing the great convenience for the preparation of alignment Ti₃C₂T_<i>x</i> media, long-term sample preservation, and quantitative evaluation of alignment degree. Meanwhile, the alignment LC media for RDC measurement can be established in other MXenes such as Ti₂CT_<i>x</i> and Ti₃CNT_<i>x</i>. Collectively, our findings demonstrate the potential of creating various alignment media from the fascinating MXene family.