Direct Observation of Liquid Crystals Using Cryo-TEM: Specimen Preparation and Low-Dose Imaging
Direct Observation of Liquid Crystals Using Cryo-TEM: Specimen Preparation and Low-Dose Imaging
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DOI：
10.1002/jemt.22397
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发表时间：
2014-10-01
影响因子：
2.5
通讯作者：
Lin, Fang
中科院分区：
文献类型：
--
作者：
Gao, Min;Kim, Young-Ki;Lin, Fang
由于样品制备的复杂性和严重的辐射损伤，液晶(LCS)是直接透射电子显微镜(TEM)研究中一类具有挑战性的材料。在本文中，我们总结了一系列的样品制备方法，包括薄膜和冷冻切片方法，作为一套全面的工具包，使高分辨率的直接低温电子显微镜观察大范围的液晶。我们还利用低温电子显微镜和复制品冷冻断裂电子显微镜对热致和溶致液晶进行了对比分析。在回顾以往工作的基础上，介绍了一些新的概念，如悬浮热致液晶薄膜、溶致液晶的高压冷冻和冷冻切片，以及直接和间接复制透射电子显微镜技术的互补应用。在液晶研究中的几个重要问题上，包括为向列型弯芯热致液晶中纳米尺度近晶微区的存在提供直接证据，对扭曲-弯曲向列相的全面理解，以及探索溶致色调液晶中柱状聚集体的堆积等，亚纳米分辨低温电子显微镜的意义被证明。直接的电子显微镜观察为各种电子显微镜技术开辟了道路，表明电子显微镜(复制、冷冻和原位技术)总体上可能是解决LC研究中缺乏有效的分子水平的结构探针的一个有前途的部分。Microsc.技术资源。2014年，77：754-772。(C)2014年威利期刊公司。
Liquid crystals (LCs) represent a challenging group of materials for direct transmission electron microscopy (TEM) studies due to the complications in specimen preparation and the severe radiation damage. In this paper, we summarize a series of specimen preparation methods, including thin film and cryo-sectioning approaches, as a comprehensive toolset enabling high-resolution direct cryo-TEM observation of a broad range of LCs. We also present comparative analysis using cryo-TEM and replica freeze-fracture TEM on both thermotropic and lyotropic LCs. In addition to the revisits of previous practices, some new concepts are introduced, e.g., suspended thermotropic LC thin films, combined high-pressure freezing and cryo-sectioning of lyotropic LCs, and the complementary applications of direct TEM and indirect replica TEM techniques. The significance of subnanometer resolution cryo-TEM observation is demonstrated in a few important issues in LC studies, including providing direct evidences for the existence of nanoscale smectic domains in nematic bent-core thermotropic LCs, comprehensive understanding of the twist-bend nematic phase, and probing the packing of columnar aggregates in lyotropic chromonic LCs. Direct TEM observation opens ways to a variety of TEM techniques, suggesting that TEM (replica, cryo, and in situ techniques), in general, may be a promising part of the solution to the lack of effective structural probe at the molecular scale in LC studies. Microsc. Res. Tech. 77:754-772, 2014. (c) 2014 Wiley Periodicals, Inc.