The effect of different protonic acid doping on the sensitivity of polyaniline to ammonia gas

In this study, a room temperature operable and selective ammonia (NH 3 ) gas sensor based on polyaniline (PANI) nanocomposite was successfully developed on the interdigital electrode through a chemical oxidative polymerization process. This work reports the first instance of PANI being doped with amino acid (Serine) as a protonic acid, while PANI was also doped with nitric acid (HNO 3 ) and tartaric acid (Tartaric-acid) for the control experiment. The composition of materials, surface morphology, and structural elucidation of PANI@Serine were systematically analyzed using X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and X-ray diffraction, respectively. The gas sensing performances of the PANI@Serine sensor were thoroughly studied and compared with PANI@HNO 3 and PANI@Tartaric-acid. The PANI@Serine sensor exhibited excellent gas sensing capabilities towards NH 3 at 25 ± 2 °C, with a response of 6.12 towards 16 ppm of NH 3 . This response was 4.29 times higher than PANI@Tartaric-acid and 5.81 times higher than PANI@HNO 3 sensor. Furthermore, the PANI@Serine sensor demonstrated a low detection limit of 10 ppm NH 3 , favorable recovery characteristics and stability, selectivity, and response. The density functional theory (DFT) of the three doped PANI was extensively calculated, and the adsorption behavior of NH 3 was analyzed. The results revealed that PANI@Serine exhibited a double adsorption effect on NH 3 gas molecules, with significantly higher adsorption performance compared to PANI@HNO 3 and PANI@Tartaric-acid.