Amino acids doped PANI sensitive materials for ammonia gas sensors operated at room temperature

Due to the limitations of sensing materials and their poor sensing characteristics, the application of NH3 sensors at room temperature still poses numerous challenges. Currently, the research on polyaniline (PANI) primarily focuses on investigating the impact of nano oxides, graphene, and other doping modifications. In this study, we systematically examine the NH3 sensitivity of PANI doped with amino acids such as alanine, glycine, methionine, proline, and others, acting as protonic acids. A planar room temperature NH3 sensor was prepared using a protective gas spraying method. The nanostructure, phase composition, microstructure, and element distribution of the sensing materials were analyzed through characterization methods such as FTIR, Raman, XRD, and FSEM-EDS. The results indicate that PANI@Alanine demonstrates high gas response value, selectivity, repeatability, and a low detection limit as a room temperature NH3 sensor. In terms of mechanism, the adsorption process of PANI@M (PANI@Alanine, PANI@Glycine, PANI@Methionine, PANI@Proline) materials in the adsorption of NH3 or H2O or NH3 + H2O was calculated using first principle density functional theory (DFT). The study reveals a synergistic effect and competitive adsorption relationship between NH3 and H2O in the adsorption process on PANI@M materials. This research serves as a valuable reference for investigating the gas sensitivity of protonic acid doped PANI and enhances our understanding of its sensing mechanism.