Composition-dependent ammonia response of polyaniline–graphene composite films

Ammonia is a widely encountered chemical in industrial, environmental, and biomedical contexts, and its interactions with conducting polymer-based materials remain of interest. In this work, flexible polyaniline–graphene (PANI-Gr) composite films were prepared using chemically synthesized polyaniline and graphene, with graphene content systematically varied from PANI-rich to graphene-rich compositions. Morphological, structural, and property studies (FESEM, XRD, FTIR, and electrical resistance) revealed a variation of the system from a continuous polymer matrix to a network dominated by graphene flakes. Baseline electrical resistance variations pointed to a change in transport properties, with polaron hopping contributing to junction resistance modulation as graphene concentration increased. This change was reflected in the chemiresistive response of the sample to ammonia vapor, with the response varying from 6 (pristine PANI) to 22 (70% graphene). The response behavior is discussed in relation to morphological features, interface junction resistance, and the evolving contribution of polymer- and graphene-dominated transport mechanisms. This was further validated using an Arduino-based measurement unit, which exhibited a high signal-to-noise ratio (>240) and a low resistance resolution (∼0.4%). Overall, this study highlights how composite architecture and graphene loading influence electrical transport and ammonia response in flexible PANI–graphene films, providing insight into composition-dependent chemiresistive behavior in conducting polymer composites.