Simple and low-temperature polyaniline-based flexible ammonia sensor: a step towards laboratory synthesis to economical device design

Flexible and highly sensitive polyaniline-based (PAni) ammonia (NH₃) gas sensors were developed through in-situ chemical oxidative polymerization of aniline on a polyethylene terephthalate substrate at three different temperatures, viz. 35 °C, 0 °C and -5 °C. In the initial stage, they were characterized with respect to their structural, morphological, and compositional analysis studies and in the second stage, the selectivity towards oxidizing (nitrogen dioxide, NO₂) and reducing (NH₃, ethanol, methanol and hydrogen sulphide, H₂S) gases was tested. The sensor fabricated at 0 °C showed an optimum response of 26% to 100 ppm NH₃ gas, which was superior to those obtained for the sensors developed at 35 °C (19%) and -5 °C (23%). The as-developed low-temperature flexible gas sensor demonstrated fast response (19 s) as well as recovery time (36 s) periods, 99% reproducibility and good stability, revealing commercial application potential for example in industry where high temperature operation is prohibited. Impedance spectroscopy was used to investigate the plausible interaction mechanism of the NH₃ gas molecules with the flexible PAni. The operation of the NH₃ gas sensor device, fabricated on a laboratory scale, was tested and explored as a demo-video clip.