Optical detection of organic vapors using cholesteric liquid crystals

The two organic vapors are acetone and toluene, which are identified using the colorimetry of cholesteric liquid crystals. The helical structure of cholesteric liquid crystal is diffused by organic vapor molecules, and the reflection spectrum of the cholesteric liquid crystal is red-shifted. The reflection spectra of the cholesteric liquid crystal reveal that the rates of variation of reflected color with the absorption of acetone and toluene vapors are different markedly because of the diversity of molecular polarities in the different molecular polarities of acetone and toluene vapors. A higher molecular polarity of the vapor causes a greater shift in the reflected color of cholesteric liquid crystal.