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Proceedings Paper

Using liquid crystals as optical gas sensors to detect thiol vapors
Author(s): Huan Xu; Kun-Lin Yang
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Paper Abstract

We show that the optical texture of a layer of liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) supported on a thiol-sensitive layer can be applied to detect 1-octanethiol and other vaporous thiols with high specificity. As demonstrated in our ellipsometry and XPS results, a thiol-sensitive layer comprising a layer of (PEI) and copper ions is capable of oxidizing thiols to disulfides and immobilizing them on the surface. Because of the hydrophobic hydrocarbon chain of 1- octanethiol, the immobilization of 1-octanethiol lowers the surface energy. Thus, after a thin layer of 5CB is supported on the surface, the lower surface energy causes 5CB to adopt different orientations in regions where copper ions were deposited. Because 5CB is a birefrigent material, different orientations of 5CB also result in distinct optical textures, which are visible to the naked eye under a pair of polarizers.

Paper Details

Date Published: 18 May 2009
PDF: 7 pages
Proc. SPIE 7356, Optical Sensors 2009, 735611 (18 May 2009); doi: 10.1117/12.819892
Show Author Affiliations
Huan Xu, National Univ. of Singapore (Singapore)
Kun-Lin Yang, National Univ. of Singapore (Singapore)

Published in SPIE Proceedings Vol. 7356:
Optical Sensors 2009
Francesco Baldini; Jiri Homola; Robert A. Lieberman, Editor(s)

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