Development of MWCNTs/alumina composite-based sensor for trace level ammonia gas sensing

Abstract

Multi-walled carbon nanotube (MWCNT)/alumina (Al2O3) composite thin film-based low cost, rigid and highly efficient sensors were developed for trace level ammonia (NH3) gas sensing applications. Composite films were prepared by dispersing MWCNTs in varying concentration in alumina solution following the sol-gel process. The sensor response as a function MWCNT concentrations were measured and compared. The notable characteristics of these sensors are fast response time (10 minutes), and excellent reproducibility with detection level up to 6 ppm. Although poor NH3 desorption causes a high recovery time, fast and complete recovery was acquired using appropriate thermal treatment protocol. The sensitivity was found to be proportional to NH3 concentrations in the range 6–25 ppm and then gradually saturated at higher concentrations. However, a decrease in the sensor response was observed with increase in concentrations of MWCNTs.