Zhao You, Yu Qinghua, Cheng Wei-Wei, Li Jia-Qian, Zhang Ai-Qing, Lei Xinxiang, Yang Yingkui, Qin Si-Yong
Laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, South-Central University for Nationalities, Wuhan 430074, P. R. China.
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Textiles, Donghua University, Shanghai 201620, P. R. China.
ACS Nano. 2022 Apr 26;16(4):5454-5462. doi: 10.1021/acsnano.1c09512. Epub 2022 Mar 21.
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 TiCT MXene LC that can be applied as a background-free alignment medium for the residual dipolar coupling (RDC) measurement of organic molecules. TiCT LC displays the size- and concentration-dependent alignment degree. TiCT nanoflakes with an average size of around 600 nm can provide the quadrupolar H 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, TiCT 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 TiCT 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 TiCT and TiCNT. Collectively, our findings demonstrate the potential of creating various alignment media from the fascinating MXene family.
二维（2D）胶体分散体中溶致液晶（LC）的形成使得能够从纳米级构建块生产介观/宏观有序材料。与氧化石墨烯（GO）LC相比，MXene LC的实际应用较少被开发。本研究通过利用一种简单通用的制备方法来制备TiCT MXene LC，弥合了这一差距，该LC可作为用于有机分子剩余偶极耦合（RDC）测量的无背景取向介质。TiCT LC表现出尺寸和浓度依赖性的取向度。平均尺寸约为600 nm的TiCT纳米片在浓度为50 mg/mL时可提供71 Hz的四极H分裂，并且在如此高的浓度下表现出优异的流动性。与其他取向介质相比，TiCT LC具有无背景和线宽变窄的特点，这实现了获取用于准确提取RDC的清晰高质量NMR光谱。值得注意的是，LC的取向在冷冻干燥后的再分散溶液中被确定为可维持的，这为制备取向TiCT介质、长期样品保存和取向度的定量评估提供了极大的便利。同时，可在其他MXenes（如TiCT和TiCNT）中建立用于RDC测量的取向LC介质。总的来说，我们的研究结果证明了从迷人的MXene家族中创建各种取向介质的潜力。
