A liquid crystal (LC)-based pH sensor for real-time monitoring of variations in localized pH values near the LC droplets was developed, and its applicability for the detection of acidic gases was explored. It was found that 4-cyano-4′-pentylbiphenyl (5CB), when doped with hexanoic acid (HA), shows a bright-fan-shaped (planar orientation of LCs) to dark-cross (homeotropic orientation of LCs) optical response to a minimal change of the pH value (from 6.5 to 6.6). The fast and intensive pH-driven optical response can be explained mainly with the orientational transitions of 5CB, induced by the protonation and deprotonation of HA at the interface of aqueous/LC droplet. Because of its high pH sensitivity, the LC-based sensor was further exploited for monitoring the local pH changes, which were originated from concentration changes of acidic gases. The results suggested that at an industrial scale/production environment, the sensor shows excellent performance for long-term monitoring and sensing of acidic gases. This type of LC-based sensor may find to fulfill its applicability potential in the trace measurement of acidic gases.

开发了一种基于液晶（LC）的pH传感器，用于实时监控LC液滴附近局部pH值的变化，并探索了其在检测酸性气体中的适用性。已发现，掺有己酸（HA）的4-氰基-4'-戊基联苯（5CB）对明亮的十字形（LC的垂直取向）表现出明亮的扇形（LC的平面取向）。 pH值的最小变化（从6.5到6.6）。快速和强烈的pH驱动的光学响应可以用5CB的取向转变来解释，该取向转变是由水/ LC液滴界面处HA的质子化和去质子化引起的。由于其对pH的高敏感性，基于LC的传感器被进一步用于监测局部pH的变化，这是由酸性气体的浓度变化引起的。结果表明，在工业规模/生产环境下，该传感器在长期监测和检测酸性气体方面显示出卓越的性能。这种基于LC的传感器可能会发现其在酸性气体的痕量测量中的适用性。