Single-Walled and Multi-Walled Carbon Nanotube Sensors for Volatile Organic Compound (VOC) Detection

Recent advancements and progressions in carbon nanotubes and other carbon-based materials have demonstrated their capabilities and potential for gas sensor applications. Carbon nanotubes are renowned for their high surface area, excellent electrical conductivity, and large aspect ratio, which make them ideal candidates for sensitive and selective gas sensors. This study investigates the application and fabrication of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) as chemiresistors with a focus on sensitivity to volatile organic compounds (VOCs) such as acetone, ethanol, and isopropanol. To evaluate the sensor’s performance, sensors were fabricated by drop-casting CNT ink onto an electrode, left to dry, then placed in an enclosed chamber and exposed to select VOCs at various ppm levels. By using a potentiostat and running a galvanostatic test, a constant current is applied onto the sensor while concurrently exposing VOCs into the chamber via a gas-flow setup. Observing the change in voltage allows for the change in resistance to be measured, determining how well the sensor responds, with changes of up to kilo-Ohms range being noted, indicating the high sensitivity that SWCNT and MWCNT sensors have shown towards VOC detection. After a series of tests using the fabricated MWCNT sensor, results have shown a resistance change of 187 Ohms from 4.66 kohms to 4.85 kohms within 30 seconds, with 80% of the change happening in 10 seconds. Similarly, the results from SWCNT tests have shown a resistance change of 1.670 kohms from 26.2 kohms to 27.9 kohms within 500 seconds. There are strengths associated with each type of sensor tested, with MWCNT presenting a quicker response and SWCNT presenting a larger change in resistance. These results suggest the capability of CNT sensors to be applied in applications such as VOC or gas-leak monitoring in both residential and commercial settings. The gathered data shows great promise towards the use of CNT sensors with complex VOC detection in widespread applications as well as the development of a low-cost, low-power sensor with high sensitivity.