Highly Sensitive Room-Temperature Ammonia Sensors Based on Single-Wall Carbon Nanotubes Modified by PEDOT

An ammonia gas sensor material based on sulf- onic functionalized single-wall carbon nanotubes modified by poly(3,4-ethylenedioxythiophene), namely, PEDOT/SWCNT-SO ₃ H, was prepared via in situ polymerization. A thin active layer of PEDOT/SWCNT-SO ₃ H was deposited on a polyimide substrate with interdigital electrodes by air-brush spray coating. The morphology of the prepared material was studied by scanning electron microscopy, and the presence of PEDOT in the structure of SWCNT-SO ₃ H was examined with Raman spectroscopy. The obtained results showed that PEDOT was successfully bound to SWCNT-SO ₃ H and that this modification significantly improved the NH ₃ sensing performance of the sensor. The sensor exhibited a strong response to ammonia (102% at 50 ppm), minimal drift in the electrical resistance during cyclic exposure, and good spontaneous desorption, all at room temperature. In the range from 20 ppm to 100 ppm ammonia, the calibration curve is considered linear, with a sensitivity of a 0.7% resistance change per 1 ppm ammonia. Furthermore, the sensor shows the ability to detect ammonia at sub-ppm concentration, and the response is 4.4% at 300 ppb. With regard to the material structure, the sensing mechanisms of both materials, i.e., PEDOT/SWCNT-SO ₃ H and SWCNT-SO ₃ H, are discussed in the article.