Portable liquid crystal droplet array in the capillary for rapid and sensitive detection of organophosphate nerve agents

Abstract

In this study, we report formation of the liquid crystal (LC) droplet array in the capillary and demonstrate its application in rapid, sensitive, and label-free detection of the dimethyl methylphosphonate (DMMP) vapor for the first time. When Cu(ClO4)2-doped LC droplets encounter DMMP, the optical response of the LC changes from the dark appearance to the bright appearance in 90 s. It is caused by the stronger coordination interaction of Cu(ClO4)2 with the phosphoryl group of DMMP than the nitrile group of 4-cyano-4′-pentylbiphenyl (5CB). The limit of detection reaches as low as 2.0 ppb. Interestingly, the optical response of the LC droplets changes from the bright appearance to the dark appearance in 10 min after putting the LC sensors in fresh air. Noteworthy, the LC droplets also show excellent performance even after used for 12 times and still work very well after the storage at room temperature for 2 weeks. Overall, this portable, low-cost, and reusable LC sensing platform has remarkable sensitivity, high selectivity, excellent reversibility, and very good stability, which makes it very promising in the detection of the organophosphate nerve agents.