Detection of gas-phase analytes using liquid crystals

Abstract

Provided herein is technology relating to detecting gaseous analytes and particularly, but not exclusively, to devices and methods related to detecting gaseous analytes by monitoring changes in liquid crystals upon exposure to the gaseous analytes.

We claim: 
     
         1 . A method for detecting an analyte in a gaseous phase, the method comprising:
 1) providing a liquid crystal assay device comprising a liquid crystal composition and a surface in a channel;   2) exposing the liquid crystal assay device to a sample suspected of comprising an analyte;   3) contacting the surface with a liquid crystal; and   4) interrogating the liquid crystal assay device to detect the analyte,   wherein a change in a property of the liquid crystal composition in the liquid crystal assay device caused by an interaction of the analyte with the liquid crystal assay device is indicative of the presence of the analyte.   
     
     
         2 . The method of  claim 1  wherein the surface comprises a functional group and an interaction of the analyte with the functional group causes the change in the property of the liquid crystal composition. 
     
     
         3 . The method of  claim 1  wherein the functional group is specific for the analyte. 
     
     
         4 . The method of  claim 1  wherein the surface comprises a substrate of glass, silicon, or gold. 
     
     
         5 . The method of  claim 1  wherein the functional group is 4-aminothiophenol. 
     
     
         6 . The method of  claim 1  wherein the surface is functionalized with a lead salt, a zinc salt, a manganese salt, a chromium salt, an indium salt, a gallium salt, or a mixture thereof. 
     
     
         7 . The method of  claim 1  wherein the liquid crystal is MBBA, MLC-2080, MLC-2081, E7, or a mixture thereof. 
     
     
         8 . The method of  claim 1  wherein the analyte is H 2 S, HCHO, or NO 2 . 
     
     
         9 . The method of  claim 1  wherein the interrogation comprises measuring a change in a property selected from the group consisting of optical anisotropy, magnetic anisotropy, dielectric anisotropy, and phase transition temperature. 
     
     
         10 . The method of  claim 1  wherein exposing the liquid crystal assay device to a sample suspected of comprising an analyte causes a phase transition in the liquid crystal composition from a first phase selected from the group consisting of an isotropic phase, a nematic phase, or a smectic phase to a second phase selected from the group consisting of an isotropic phase, a nematic phase, and a smectic phase. 
     
     
         11 . The method of  claim 1  wherein the liquid crystal composition undergoes an orientational transition in the presence of the analyte. 
     
     
         12 . The method of  claim 1  further comprising quantifying an analyte concentration by measuring the brightness of a reacted area. 
     
     
         13 . The method of  claim 1  further comprising quantifying an analyte concentration by measuring a length of a reacted channel. 
     
     
         14 . The method of  claim 1  further comprising quantifying an analyte concentration by measuring a distance of a birefringent channel from a site of exposure of the liquid crystal assay device to the sample suspected of comprising the analyte. 
     
     
         15 . The method of  claim 1  wherein the interrogation comprises measuring a reflection or a transmission of polarized light. 
     
     
         16 . The method of  claim 14  wherein the distance is 1 to 200 mm. 
     
     
         17 . The method of  claim 1 , wherein said change in a property of the liquid crystal composition is detectable in real-time. 
     
     
         18 . The method of  claim 1 , wherein said the presence of said analyte is detected in real-time. 
     
     
         19 . The method of  claim 1  further comprising exposing the liquid crystal assay device to the analyte prior to exposing the liquid crystal assay device to a sample suspected of comprising an analyte. 
     
     
         20 . A method for monitoring a subject's exposure to a toxic gas, the method comprising:
 1) providing to the subject a dosimeter badge comprising a liquid crystal assay device;   2) measuring a change in a property of a liquid crystal composition in the liquid crystal assay device caused by an interaction of the toxic gas with the liquid crystal composition; and   3) reporting an exposure to the toxic gas.   
     
     
         21 . The method of  claim 20 , wherein said reporting is in real-time. 
     
     
         22 . The method of  claim 20  wherein the liquid crystal assay device comprises:
 a) a first surface contacting a composition comprising a liquid crystal; 
 b) a second surface; and 
 c) a headspace between the composition comprising the liquid crystal and the second surface. 
 
     
     
         23 . The method of  claim 20  wherein the liquid crystal assay device comprises a surface in a channel and the method further comprises contacting the surface with a liquid crystal.