Room temperature ammonia gas sensor based on different acid-doped polyaniline-polyvinyl alcohol blends

Abstract

In the present work, we reported the performance of the gas sensor based on polyaniline-polyvinyl alcohol (PANI-PVA) thin-film to develop a usable sensor. The PANI-PVA were doped with camphorsulphonic acid (CSA), naphtalenesulfonic acid (NSA), dodecyl benzene sulfonic acid (DBSA) and p-toluene sulfonic acid (PTSA). CSA doped PANI nanocomposite sensors were fabricated on glass substrates by dripping and their gas sensing characteristics for ammonia (NH₃) were investigated at room temperature. PANI was prepared by the dispersion polymerization method. An appropriate amount of PANI and acid were mixed in a mortar and pestle. The mixture was dissolved in 100 mL of water, stirring at room temperature for 3 hours. The blend solution was then used to cast films on glass slides. PANI-PVA blend films are characterized for surface as well as structural morphology SEM and XRD. The morphological analysis shows nanoparticle formation of different shapes depending upon the dopant types. The XRD pictures show some shorts of crystallinity in the blend films. The FTIR spectra show chemical crosslinking between the polymers. The thermal study reveals three steps of degradation of the polymer blends. The electrical properties studies are conducted by in-plane I-V characteristics, and four probe conductivity. We used our blend as an ammonia gas sensor. Among all four sensors the blend film doped with DBSA had good sensitivity and reversibility. This might be because of its enhanced surface morphology that facilitates good adsorption and desorption of ammonia gas on the surface and high conductivity. In this study, ammonia gas sensors based on PANI-PVA composite films were prepared by a solution casting method. The composite films have been characterized by XRD, FTIR and SEM measurements. The SEM images have shown that PANI-PVA film has a different morphology based on the types of doping acids. The film presents significant resistivity upon exposure to ammonia gas at room temperature. It was found that these sensors are sensitive, stable, fast in response and easy to regenerate at room temperature. The advantages of this composite sensor compared to the pure PANI sensor are its fast regeneration associated with improved mechanical properties and chemical stability.