Behavior of single-walled carbon nanotube-based gas sensors at various temperatures of treatment and operation

Abstract

The behavior of single-walled carbon nanotube (SWNT)-based gas sensors at various conditions of operation was reported. The sensors were fabricated from SWNT powder by the screen-printing method, followed by an annealing pretreatment in open-air for 2h at various temperatures to enhance the sensor characteristics. It was found that, the annealing at a suitable temperature not only removed the residual solvent and amorphous impurities from the SWNTs, but also opened the nanotube-caps, resulting in enhancement the sensor sensitivity. Subsequently, the sensor annealed at 200°C was employed for detection ammonia (NH3) in 500sccm nitrogen (N2) flowing. After 10min exposing to 5ppm NH3 at room temperature, the resistance of the sensor increased up to 8% in comparison with its initial value. The sensitivity increased as the NH3 concentration increased but was diminished when NH3 concentration reached to 40ppm. The sensor recovery was amended either by increasing the carrier gas flux or by heating in desorption time. By choosing a suitable regime of operation, in which the carrier gas flux, the heating duration and temperature were appropriately controlled, the characteristics of the SWNT-based sensor such as recovery and reproducibility were significantly improved.