Detection of gas-phase analytes using liquid crystals
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.
1. A method for detecting an analyte in a gaseous phase, the method comprising:
1) providing a liquid crystal assay device comprising:
a) a first surface contacting a composition comprising a liquid crystal so that the liquid crystal forms a liquid crystal film on the first surface;
b) a second surface;
c) a headspace between the liquid crystal film on the first surface and the second surface;
2) exposing the liquid crystal assay device to a sample suspected of comprising an analyte; and
3) detecting the presence of 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 first 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 2 wherein the functional group is specific for the analyte.
4. The method of claim 2 wherein the functional group is 4-aminothiophenol.
5. The method of claim 1 wherein the headspace is 5 to 50 microns.
6. The method of claim 1 , wherein said headspace is variable.
7. The method of claim 1 , wherein said first and second surfaces form a compartment having first and second open ends, wherein the headspace at said first end is from 1 to 20 microns above the liquid crystal film and the headspace at the second end is from 21 to 100 microns above the liquid crystal film.
8. The method of claim 1 wherein the first surface further comprises micro-pillars.
9. The method of claim 1 wherein the second surface is functionalized with (Tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane.
10. The method of claim 1 wherein the first 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.
11. The method of claim 1 wherein the analyte is H 2 S, HCHO, or NO 2 .
12. The method of claim 1 wherein the detecting comprises measuring a change in a property of the liquid crystal composition selected from the group consisting of optical appearance, optical absorbance, optical anisotropy, magnetic anisotropy, dielectric anisotropy, and phase transition temperature.
13. 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.
14. The method of claim 1 wherein the liquid crystal composition undergoes an orientational transition in the presence of the analyte.
15. The method of claim 1 further comprising quantifying an analyte concentration by measuring brightness of a reacted area of the liquid crystal device.
16. The method of claim 1 further comprising quantifying an analyte concentration by measuring a size of a reacted area of the liquid crystal device.
17. The method of claim 1 further comprising quantifying an analyte concentration by measuring a distance of a birefringent front from a site of exposure of the liquid crystal assay device to the sample suspected of comprising the analyte.
18. The method of claim 1 wherein the detecting comprises measuring a reflection or a transmission of polarized light from the liquid crystal assay device.
19. The method of claim 1 further comprising exposing the liquid crystal assay device to a sub-responsive amount of the analyte before exposing the liquid crystal assay device to a sample suspected of comprising the analyte.