One-dimensional (1-D) nanostructures including semiconducting single-walled carbon nanotube (SWNT) have been demonstrated as good candidates for ultra-sensitive chemical gas sensors because of the high surface-to-volume ratio of nanostructures and their unique electronic conductance. Unfunctionalized semiconducting SWNT based sensors have been demonstrated for detection of small molecules such as NH3 and NO2 under ambient conditions. However, the less than ideal sensitivity and lack of selectivity limit SWNTs in practical applications to detect many types of analytes such as volatile organic compounds (VOCs) and H2.
We have demonstrated a facile fabrication method to create gas sensors with higher sensitivity and selectivity by utilizing chemically and electrochemically functionalized SWNT networks.
SWNT with covalently attached poly-(m-aminobenzene sulfonic acid) (SWNT-PABs) and electrodeposited conducting polymer on SWNT (SWNT-CP) were investigated as sensing materials for real-time monitoring of ammonia, nitrogen dioxide, and VOCs. The results show superior sensitivity with low detection limit in part per billion concentration range, good reproducibility, and short response time (a few minutes) at room temperature compared to intrinsic SWNT based sensors. The effect of various deposition conditions (e.g. electrodeposition time, potential and dopant) and operating conditions (e.g. temperature and humidity) on the sensing performance were systematically investigated to obtain optimized sensors. Recent results including a discussion of the fundamental aspect of the sensing mechanisms and of the factors that affect sensing of various analytes will be presented at the conference.