Development of functionalized single-walled carbon nanotube gas sensors

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 properties. Intrinsic semiconducting SWNTs based sensors have been used to detect small molecules including ammonia and nitrogen dioxide under ambient conditions. However, the less than ideal sensitivity and lack of selectivity limit SWNTs based sensors in practical applications to detect multiple analytes.; In this dissertation, I demonstrated a facile fabrication method to create nanosensors and nanosensor arrays with higher sensitivity and selectivity by utilizing functionalized SWNT networks.; SWNTs with covalently functionalized poly-(m-aminobenzene sulfonic acid) (SWNT-PABS) and electrodeposited conducting polymer (i.e. polyaniline) on SWNT were used as novel sensing materials for real-time monitoring of ammonia, nitrogen dioxide, and water vapor. The results show improved sensitivity and selectivity with low detection limit in part per billion concentration range, good reproducibility, and short response time at room temperature compared to intrinsic SWNT based sensors. The humidity independent ammonia sensors were also fabricated by electrodepositing polyaniline (PANI) with camphor-sulfonic acid (CSA) onto SWNT. 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.; In addition, six nanosensor arrays were fabricated by functionalized SWNTs with five different sensing materials including PANI, PEI, Pd, Au, and SnO2. The response of the sensor array to ammonia, nitrogen dioxide, hydrogen, and hydrogen sulfide carries the "fingerprints" of each targeted gas. The response of sensor array is more redundant and fault tolerant than an individual sensor. A low cost inkjet printing technique was developed to fabricate flexible SWNTs sensors and SWNT-PABS sensors, which showed the good response to ammonia and nitrogen dioxide.; My results show that electrochemically functionalized SWNTs is a new route to create high density sensor array with promising sensing performance in cost effective matter.