Monitoring the two-dimensional concentration profile of toluene vapors by using polymer-stabilized nematic liquid crystals in microchannels

Abstract

Many volatile organic compounds (VOCs) are hazardous to human health and their concentrations need to be monitored over a large area. However, most chemical sensors can only be used for point detection. In this paper, we report a method to obtain a two-dimensional (2D) concentration profile of toluene vapor by using polymer-stabilized liquid crystals (PSLCs). After the PSLC sample is exposed to toluene vapor ranging from 9300 to 2800 ppm, the PSLC changes its interference color according to different local toluene concentrations. By using the interference color, we can obtain a 2D concentration profile of toluene inside the PSLC and study the diffusion of toluene inside the PSLC in great detail. We also determine the diffusion coefficient of dissolved toluene inside the PSLC to be 1.01 × 10⁻⁶ cm² s⁻¹.