Fabrication of Liquid Crystal Droplet Patterns for Monitoring Aldehyde Vapors

Abstract

A sensing method based on the pattern of liquid crystal droplets was developed for detecting and monitoring low levels of organic aldehyde vapors. Exposure of the LC droplet pattern covered with glycine solution to aldehyde vapors induced an optical signal transition from a bright fan shape to a dark cross appearance, as observed by polarized light microscopy. Aldehyde and glycine react at the air/solution interface to form a Schiff-base compound, which controls the orientation of the LCs and induces a change in the optical signals of the LC droplet pattern. The results show that the glycine/LC droplet pattern system is particularly sensitive and selective to aldehydes. In the actual environment, the sensor is exposed to the aldehyde and the signal transition is completed within a few minutes (2-7 min). The LC-based method has the advantages of simple construction, easy operation, convenient data reading, and shows excellent prospects for real-time detection of aldehyde vapors.

Keywords: Schiff bases; aldehyde vapor; droplet; liquid crystals; sensors.