Dual-Phase Carbon Nanotube Chemiresistor Array Utilizing Hygroscopic Aqueous Films for SelectiveDetection of Toxic Compounds

Abstract

Hydrolyzable toxic compounds, such as organophosphates, pose a significant threat to human health and the environment. Although many gas sensors have been developed to detect these hydrolyzable toxic compounds, sensors that utilize hydrolysis as a detection mechanism have not been developed due tothe rapid evaporation of water in an open-air environment. In this work, we present an approach for the detection of hydrolyzable toxic compounds using a carbon nanotube (CNT)-based chemiresistor coated withan aqueous solution of hygroscopic salts. The hygroscopic salt, including LiCl, LiBr, and H PO , remains as aliquid film indefinitely, owing to their extremely low deliquescence relative humidity (DRH). Upon exposure tohydrolyzable toxic compounds, such dimethly methylphosphonate (DMMP) and Triethyl phosphate (TEP), theresistance of sensors showed a large change, which was much greater than that of dry CNT chemiresistorswithout the aqueous film. Raman spectra were used for identification to determine the amount and direction ofthe resistance change based on the presence and type of hygroscopic salt solution. The sensors also exhibitedhigh sensitivity and selectivity toward hydrolyzable compounds, indicating their potential use in thediscrimination of a wide range water-dissolvable and/or hydrolyzable chemical compounds. Our approachsuggests a promising solution for the detection of hydrolyzable toxic compounds in an open-air environment