Laboratory for Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Am Chem Soc. 2010 Mar 10;132(9):2961-7. doi: 10.1021/ja907826z.
A new approach to optical monitors for gases is introduced using cholesteric liquid crystals doped with reactive chiral compounds. The approach is based on cholesteric pitch length changes caused by a change in helical twisting power (HTP) of the chiral dopants upon reaction with the analyte. The concept is demonstrated for monitoring carbon dioxide via reversible carbamate formation and for oxygen using the irreversible oxidation of a chiral dithiol to a disulfide. Monitoring of CO(2) was achieved by doping a commercial cholesteric liquid crystalline mixture (E7) with 1.6% mol of the 1:1 complex of an optically pure diamine with a TADDOL derivative. Upon exposure to carbon dioxide, the reflection band of a thin film of the mixture shifted from 637 to 495 nm as a consequence of dissociation of the complex after carbamate formation of the diamine. An O(2) monitor was obtained by doping E7 with a chiral binaphthyl dithiol derivative and a nonresponsive codopant. The reflection band of the oxygen monitor film changed from 542 to 600 nm, due to the conformational change accompanying oxidation of the dithiol to disulfide. These monitoring mechanisms hold promise for application in smart packaging, where carbon dioxide and oxygen are of special interest because of their roles in food preservation.
提出了一种使用掺杂了反应性手性化合物的胆甾相液晶的气体光学监测新方法。该方法基于手性掺杂剂与分析物反应时螺旋扭转力（HTP）的变化引起的胆甾相螺距长度的变化。该概念通过可逆氨基甲酸酯形成来监测二氧化碳，以及通过手性二硫醇不可逆氧化为二硫化物来监测氧气进行了演示。通过用光学纯二胺与 TADDOL 衍生物的 1:1 配合物掺杂商业胆甾相液晶混合物（E7），实现了对 CO2 的监测。暴露于二氧化碳后，混合物的薄膜的反射带从 637nm 移动到 495nm，这是由于二胺的氨基甲酸酯形成后配合物的离解。通过用手性联萘二硫醇衍生物和非响应性共掺杂剂掺杂 E7，获得了氧气监测器。由于二硫醇氧化为二硫化物伴随的构象变化，氧气监测器薄膜的反射带从 542nm 变为 600nm。这些监测机制有望在智能包装中应用，因为二氧化碳和氧气在食品保鲜中因其作用而受到特别关注。
