Use of self-assembled monolayers, metal ions and smectic liquid crystals to detect organophosphonates
- 作者：Yang ; Kun-Lin ; Cadwell ; Katie ; Abbott ; Nicholas L.
- 关键词：Self-assembled monolayer ; Organophosphonate ; Liquid crystals ; 8CB ; Copper complex
- 刊名：Sensors and Actuators B ; Chemical
- 出版年：2005
- 期刊代码：161_09254005
- 类别：et
- 出版时间：January 3, 2005
- 卷：104
- 期：1
- 页码：50-56
- 文件大小：234 K
摘要
Smectic liquid crystals form stable, micrometer-thick films when deposited onto the surfaces of solids. In this paper, we report that orientational transitions of thin films of the smectic liquid crystal (LC), 4′-octyl-4-biphenyl-carbonitrile (8CB) supported on surfaces presenting copper ions can be exploited to detect the presence of organophosphonate compounds at parts-per-billion (ppb) levels in gas phases. The orientational transition of the 8CB is driven by the competitive binding of the nitrile groups of 8CB and dimethyl methyl phosphonate (DMMP) for the surface-immobilized copper ions. Because the orientational transition of the LC can be observed by using a polarizing film and the naked eye, this detection scheme does not require complex instrumentation to transduce the signal. The film of LC responds to 10ppbv of DMMP and the initial response time is approximately 20s. The system is also demonstrated to exhibit molecular specificity. The LC does not respond to gaseous streams containing 1%of the saturated vapor concentrations of ethanol (770ppm), hexane (1990ppm) and acetone (3020ppm) and 75%relative humidity of water.