Effect of NH ₃ gas on the electrical properties of single-walled carbon nanotube bundles

This study deals with the fabrication of sensors from single-walled carbon nanotubes (SWNTs) of 1.2 nm in diameters by a screen-printing method. These sensors have been exposed to ammonia (NH ₃) gas at room temperature with nitrogen as the carrier gas. It was found that the electrical properties of SWNTs alter with temperature or the adsorption of ammonia gas. The SWNT is very sensitive to NH ₃ gas. It can detect NH ₃ in as low as concentration of 5 ppm. The sensitivity increases with increasing concentration. A saturation state is established at a concentration of ∼40 ppm, and the sensitivity of the sensor continues to increase in conjunction with an increase in concentration levels. Both the heating and increasing flux rates of carrier gas are used to improve gas desorption. The adsorption mechanism of gaseous molecules on SWNT bundle is discussed.