A novel single wall carbon nanotubes-based sensor doped with lithium for ammonia gas detection

To deposit SWCNTs (single wall carbon nanotubes) on substrates and evaluate their gas sensing properties, a pair of interdigitated electrodes was made by sputtering Au on Si/SiO2. SWCNTs were first doped with lithium by heating with LiNO3 and HNO3 for 12 h. Then SWCNTs-lithium doped was well-dispersed in dimethylformamide (DMF). By using electrophoresis and applying a DC voltage, the SWCNTs were forced to deposit between the two electrodes. The deposited SWCNT on the electrodes were heat treated at 350 degrees C for 5 h. with Ar to eliminate the DMF adsorbed layer. The electrical response of this sensor has been measured by exposing the films to NH3 (500 ppm) at different operating temperatures between 25 degrees C to 280 degrees C. The response to NH3 has been found to be a maximum at around 150 degrees C and a high sensitivity of 34% was achieved.