Chemiresistive sensor arrays based on noncovalently functionalized multi-walled carbon nanotubes for ozone detection

Carbon nanotubes are considered as one of the leading candidate materials for the high-performance, internet of thing (IoT)-based gas sensor operating at room temperature. Multi-walled carbon nanotubes (MWCNTs) as a sensing platform were noncovalently functionalized by six kinds of functional modifiers to discriminatively detect ozone (O-3). Compared with the MWCNTs, the responses of functionalized MWCNTs to 5 ppm of O-3 were improved by about 68.8-258.3% and the highest response reached 34.4%. The maximum response of functionalized MWCNTs to 100% relative humidity was just 5.6%, displaying the excellent endurance to humidity. After two months, the decrease in the response value of the most sensitive sensor to O-3 was no more than 15%, showing the good long-term stability. Furthermore, the sensor array was optimized according to principal component analysis and achieved the discriminative detection of six analytes in 30 s at room temperature. For the most sensitive sensor of the sensor array, the theoretical limit of detection for O-3 is determined to be 24.2 ppb. Importantly, it could be coupled with the image recognition and cloud computing for a rapid diagnostic detection of gaseous pollutants under the background of the rapid development of IoT.