Optical acetone vapor sensors based on chiral nematic liquid crystals and reactive chiral dopants

Accurate monitoring of exposure to organic vapors, such as acetone, is an important part of maintaining a safe working environment and adhering to long- and short-term exposure limits. Here, a novel acetone vapor detection system is described based on the use of a reactive chiral dopant in a nematic liquid crystal thin film, which can accurately monitor the total exposure over a given time frame through changes in the reflection band of the film. It is found that films exposed to 1000 parts per million by volume (ppmv) of acetone vapor for 2 h exhibit a shift in reflection band of 12 nm, with smaller shifts observed at lower concentrations of acetone. Such sensors have potential applications in industrial hygiene. A novel sensor based on a chiral nematic liquid crystal doped with a reactive dopant is fabricated and investigated. It is found that the sensor acts as a real-time integrator, responding to the total acetone dose by changing the wavelength of the reflection maximum of the chiral nematic liquid crystal. The sensitivity and cross-sensitivity of the sensor are investigated.