State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian, 116023, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian, 116023, China.
Solid State Nucl Magn Reson. 2021 Apr;112:101711. doi: 10.1016/j.ssnmr.2020.101711. Epub 2021 Jan 11.
With the recent advances in NMR hardware and probe design technology, magic-angle spinning (MAS) rates over 100 kHz are accessible now, even on commercial solid NMR probes. Under such fast MAS conditions, excellent spectral resolution has been achieved by efficient suppression of anisotropic interactions, which also opens an avenue to the proton-detected NMR experiments in solids. Numerous methods have been developed to take full advantage of fast MAS during the last decades. Among them, dipolar recoupling techniques under fast MAS play vital roles in the determination of the molecular structure and dynamics, and are also key elements in multi-dimensional correlation NMR experiments. Herein, we review the dipolar recoupling techniques, especially those developed in the past two decades for fast-to-ultrafast MAS conditions. A major focus for our discussion is the ratio of RF field strength (in frequency) to MAS frequency, ν/ν, in different pulse sequences, which determines whether these dipolar recoupling techniques are suitable for NMR experiments under fast MAS conditions. Systematic comparisons are made among both heteronuclear and homonuclear dipolar recoupling schemes. In addition, the schemes developed specially for proton-detection NMR experiments under ultrafast MAS conditions are highlighted as well.
随着 NMR 硬件和探头设计技术的最新进展，现在即使在商业固态 NMR 探头中，也可以实现超过 100 kHz 的魔角旋转 (MAS) 速度。在如此快速的 MAS 条件下，通过有效抑制各向异性相互作用实现了优异的光谱分辨率，这也为固态中的质子检测 NMR 实验开辟了道路。在过去的几十年中，已经开发了许多方法来充分利用快速 MAS。其中，在快速 MAS 下的偶极子重聚技术在确定分子结构和动力学方面发挥着重要作用，也是多维相关 NMR 实验的关键要素。本文综述了偶极子重聚技术，特别是过去二十年中针对快速到超快速 MAS 条件开发的技术。我们讨论的重点主要是不同脉冲序列中射频场强度（频率）与 MAS 频率之比 ν/ν，它决定了这些偶极子重聚技术是否适用于快速 MAS 条件下的 NMR 实验。对异核和同核偶极子重聚方案进行了系统比较。此外，还突出了专门为超快速 MAS 条件下的质子检测 NMR 实验开发的方案。
