Nanostructured polyaniline-based composites for ppb range ammonia sensing

Thin (1–40 μm) films of nanostructured polyaniline (PANI)-based composites are suggested for ppb range ammonia sensing. Three types of the composites have been studied: two core–shell systems with a poly(butyl acrylate) (PBuA) or poly(vinylidene fluoride) (PVDF) core and a PANI shell, and a composite based on PANI nanofibers embedded in a polyurethane (PU) matrix. Nanofibers and core–shell nanoparticles had a diameter around 100–200 nm. The gas sensing ability of the nanostructured films was compared to ammonia concentrations from 20 ppb to 10 ppm through the change of the sensors resistance. All the composites showed high performances in terms of response time, reversibility and detection limit. Specifically, the last parameter was below 100 ppb for films formed of the core–shell nanoparticles and below 20 ppb for the nanofiber based composites. However, while the response times were similar for all of the samples, the films made of the contacting core–shell nanoparticles had a higher sensitivity than PANI nanofibers embedded in the PU film matrix. The obtained results showed that nanostructured PANI-based composites of different morphologies can be used as ultra-sensitive and low cost ammonia gas sensors.