Poly(aniline)-based ammonia sensors: Understanding the role of polyurethane on structural/morphological properties and sensing performances

Highly sensitive ammonia (NH3) sensors based on acidic-doped polyaniline (PAni) and polyurethane (PU) are proposed using the facile drop-cast technique. The mass ratios between the polymers were varied in order to elucidate the influence of PU on the film structure and sensing performances of PAni. The supramolecular arrangement changes according to the polymer proportions without impacting the doping of PAni, phenomenon observed in the morphological and optical measurements. The results of the devices showed that the presence of PU can significantly enhance the sensitivity of the sensors without interfering with the main sensing features of PAni, and the proportion variation affects directly the characteristics and performances of the device. We also verified that the PU/PAni sensors present good repeatability and ability to promptly respond to random ammonia concentration variation. Moreover, PU mitigated the influence of humidity on the sensors, which tends to lower their response toward ammonia, and also decreased the drift of the devices which increases their lifespan within a device operating range. The PU/PAni films offer a potential option for applications requiring low-concentration detection of NH3, such as indoor air quality and medical diagnosis.