MWCNT-conducting polymer composite based ammonia gas sensors: A new approach for complete recovery process

Highly sensitive ammonia gas sensors were fabricated using Multi-walled Carbon Nanotubes (MWCNTs) reinforced electrically conducting polymer composites following solution casting method. Two types of conducting polymers like poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) and polyaniline (PANI) were used and compared for their ammonia gas sensing properties at room temperature (RT). Both the sensors were found to exhibit excellent sensitivity and poor recovery for ammonia gas at room temperature, but as compared to PANI, PEDOT: PSS polymer composite was found to be more sensitive (with sensitivity of similar to 16%) with less response time (similar to 15 min). In addition, thermal behavior of both the composites was investigated in detail, where MWCNT-PEDOT:PSS composite showed significantly better thermal stability than MWCNT-PANI composite. Sensor recovery posed a great problem at room temperature and a new approach is proposed to get complete recovery, exclusively tested in polymer-CNT composite sensor, to lessen the heat dependence and improve the cycling behavior. A trial experiment is conducted in combination of heat and DC electric field to optimize the complete recovery of the MWCNT-PEDOT: PSS composite based sensor where the recovery time was reduced from 48 h to 20 min. It is believed that such stimulation process provides sufficient energy to desorb chemisorbed ammonia from CNT surface completely. (C) 2013 Elsevier B.V. All rights reserved.