Liquid crystal based optical sensor for detection of vaporous butylamine in air

A liquid crystal (LC)-based optical sensor has been developed to detect vaporous butylamine in air. This LC sensor doped with lauric aldehyde (LA) shows fast and distinct bright-to-dark optical response to butylamine vapor. For example, when the LA doping concentration is 0.1 wt%, the LC shows a rapid bright-to-dark optical response within 2 min after it is exposed to 10 ppmv of butylamine. This optical response is attributed to an orientational transition of LC triggered by a reaction between LA and butylamine. This LC sensor also exhibits reversibility after the sensor is exposed to open air. In addition to primary amines (such as butylamine and octylamine), this LC-based sensor responds to secondary amines (such as diisopropylamine), but the detection limit is 200 ppmv, which is much higher than butylamine.