Direct observation of liquid crystals using cryo-TEM : specimen preparation and low-dose imaging

Gao, Min (Electron microscopist) ; Kim, Young-Ki; Zhang, Cuiyu; Borshch, Volodymyr; Zhou, Shuang; Park, Heung-Shik; Jákli, A. (Antal); Lavrentovich, Oleg D.; Tamba, Maria-Gabriela; Kohlmeier, Alexandra, 1978-; Mehl, Georg H.; Weissflog, Wolfgang; Studer, Daniel Franz; Zuber, Benoît; Gnägi, Helmut; Lin, Fang (Chemist)

Department of Chemistry; Department of Chemistry; Department of Chemistry
Freeze fracture; High-pressure freezing; CEMOVIS; Thermotropic; Lyotropic
2014

Journal article


Rights
©2016 University of Hull
Abstract

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. © 2014 Wiley Periodicals, Inc.

Publisher
The University of Hull
Peer reviewed
Yes
Language
English
Extent
2 MB
Identifier
hull:12823

Journal

Journal title
Microscopy research and technique
Publication date
2014
Publisher
Wiley
DOI
10.1002/jemt.22397
ISSN (Print)
1059-910X
ISSN (Electronic)
1097-0029
Volume
77
Issue
10
Start page
754
End page
772
Notes

Author's accepted manuscript of article: Gao, M., Kim, Y.-K., Zhang, C., Borshch, V., Zhou, S., Park, H.-S., Jákli, A., Lavrentovich, O. D., Tamba, M.-G., Kohlmeier, A., Mehl, G. H., Weissflog, W., Studer, D., Zuber, B., Gnägi, H. and Lin, F. (2014), Direct observation of liquid crystals using cryo-TEM: Specimen preparation and low-dose imaging. Microsc. Res. Tech., 77: 754–772.

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