Method of detection of volatile organic compounds using liquid crystals that form a blue phase; and device for stabilization and thickness control of liquid crystal films
Methods and compositions for detecting a targeted analyte, such as volatile organic compound (VOCs), are disclosed. Specifically, a cholesteric liquid crystal composition comprising a nematic liquid crystal and a chiral dopant transitions to a liquid crystal blue phase or undergoes other optical changes when in contact with a sample containing the analyte. The phase transition can be readily detected with the naked eye. The disclosed methods and compositions may be used in, for example, dosimeters for detecting analyte (e.g., VOC) exposure. Methods and compositions for producing arrays of liquid crystal thin films are also disclosed. The surface between the microwells in a microwell array is coated with a liquid-crystal-phobic material, such as a fluorinated polymer or a fluorinated silane, creating isolated microwell domains that are preferentially wetted by liquid crystal. Liquid crystal can be added to the microwell domains by simple techniques such as spin coating.
1. A blue phase-forming liquid crystal composition for detecting a target analyte in a sample, comprising a nematic liquid crystal, a chiral dopant, and a non-volatile organic compound that increases the sensitivity of response of the blue phase-forming liquid crystal composition to the target analyte, wherein the weight % of chiral dopant in the composition is from 20% to 60%.
2. The composition of claim 1 , wherein the chiral dopant is selected from the group consisting of S-811 ((S)-Octan-2-yl 4-((4-(hexyloxy)benzoyl)oxy)benzoate), R-811 ((R)-Octan-2-yl 4-((4-(hexyloxy)benzoyl)oxy)benzoate),
CB 15 ((S)-4-(2-methylbutyl)-4-cyanobiphenyl), S-1011, R-1011, S-2011, and R-2011.
3. The composition of claim 1 , wherein the non-volatile organic compound is:
(a) a polymer or a polycyclic aromatic compound; or
(b) selected from the group consisting of pyrene, phenanthrene, polystyrene, benzoic acid, biphenyl, a halogenated biphenyl, and benzopyrene.
4. An array-based device for detecting and/or quantifying a target analyte in a sample, comprising a plurality of blue phase-forming liquid crystal compositions of claim 1 .