Detection of O3 and NH3 using hybrid tin dioxide/carbon nanotubes sensors: Influence of materials and processing on sensor's sensitivity

A tin oxide (SnO2)/arc-discharge single walled carbon nanotubes (SWNTs) hybrid material based sensor was developed for the detection of NH3 and O3 at room temperature. The gas sensitive composite thin films were prepared using sol gel and dip coating techniques, and characterized by transmission electron microscopy, atomic force microscopy and Raman spectroscopy. Overall, the hybrid material based sensor is found to have an enhanced sensitivity as compared to pure SnO2 or pure SWNTs based sensors. An optimum annealing temperature of the composite of 300 °C was determined. The detection limit at room temperature was evaluated at 1 ppm and lower than 20 ppb for NH3 and O3, respectively. Moreover, the hybrid sensor exhibited a fast response (few minutes), a good sensitivity and a full recovery at room temperature. The sensor efficiency has also been demonstrated to strongly depend on the SWNT source used for sensor fabrication (4 different commercial sources have been tested). These results open the way towards further optimized hybrid sensors.