Structural characterization of PEDOT and PANI conductive polymers

Abstract

Detecting toxic gases released in homes, in industrial settings, and under environmental conditions is of great importance. In this context, gas sensors have recently become one of the most significant technological advancements in our daily lives. Applications of gas sensors include the detection of toxic and explosive gases for the purposes of protecting human health, reducing environmental pollution, and monitoring air quality. Today, there are various techniques used for gas detection. Based on their operating principles, these include catalytic gas sensors, acoustic gas sensors, optical gas sensors, and semiconductor metal oxide gas sensors. Metal oxide gas sensors stand out in gas measurement systems due to their advantages, such as low cost, ease of production, compact size, and simple measurement electronics. However, in addition to these advantages, they also have some disadvantages, such as high operating temperatures and low mechanical strength. When comparing metal oxide gas sensors that operate at high temperatures with conductive polymer gas sensors, conductive polymer-based gas sensors offer many advanced features. Conductive polymer-based gas sensors exhibit high sensitivity and fast response times at room temperature and are used as selective sensing materials. These sensors are relatively simple to manufacture and are mechanically robust. For these reasons, the use of conductive polymer-based gas sensors is significant. As part of this thesis, gas sensors to be produced using conductive polymers—as an alternative to the metal oxide materials commonly used in gas sensor applications in the literature—were investigated. In this thesis, studies were conducted on the conductive polymers polyaline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), and PANI/PEDOT (binary) structures. The structural, surface, and sensor properties of gas sensor samples produced using these materials were examined comparatively. As part of this thesis, PEDOT nanoparticles were synthesized using the oxidative emulsion polymerization technique, resulting in particles approximately 75 nm in size. The organic phase consists of chloroform and EDOT; the aqueous phase consists of PSS-co-MA and deionized water. The polydispersity index of the particles is < 0.5. The obtained PEDOT nanoparticles were mixed into a PANI solution prepared in PVA at different ratios (%PEDOT:PANI; 50:50, 30:70, and 70:30). The blended films were compared with 100% PEDOT and 100% PANI films. The best properties in terms of structural and morphological compatibility were obtained from the 50:50 PEDOT:PANI blend. The gas detection performance of each sample produced as part of this thesis was examined. As expected, pure PEDOT films exhibited the fastest response and recovery kinetics. The highest percentage change in voltage in response to ammonia gas, at 41%, was achieved with the 50:50 PEDOT:PANI composite film. The results obtained in this thesis demonstrate that PEDOT:PANI composite films are suitable for use as gas sensors in advanced technologies.