Sensing methamphetamine with chemiresistive sensors based on polythiophene-blended single-walled carbon nanotubes

A highly sensitive and selective carbon nanotube-based vapor sensor was developed toward the detection of methamphetamine vapor, one of the most widespread, harmful and addictive illegal drugs in the world. Poly[3-(6-carboxyhexyl)thiophene-2,5-diyl)] (P3CT) was chosen to non-covalently functionalize carbon nanotubes, which can facilitate the suspension of carbon nanotubes in the solvents as well as introduce a carboxylic acid functional group. The carboxylic acid group in the polymer acts as a binder of organic amines via acid-base interaction. The P3CT-functionalized carbon nanotube sensors show sensitivity to n-methylphenethylamine (NMPEA), a detection simulant of methamphetamine, as low as 4 ppb. The sensors were able to distinguish NMPEA from two other amine compounds, various volatile chemical compounds (VOCs), and water vapor by observing the recoverability of the sensor's signal after exposure. The sensor showed higher sensitivity to amine vapors even when the vapor concentrations of amines were several orders of magnitude lower than those of the VOCs. Our research gives a simple but effective method for detecting trace amounts of methamphetamine in ambient air. Meanwhile, the sensor developed in this study can be used as one component in a next generation portable, intelligent, and low-cost chemical sensor array system for more complex real-life applications.