(261h) Electrochemically and Chemically Functionalized Single-Walled Carbon Nanotube Network for Gas Sensing

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.