Templated growth of polyaniline for enhanced gas sensing response in flexible sensors: experiments and simulations

Abstract

Gas sensors using polyaniline structures fabricated from non-templated structures (homogeneous solution growth) and templated structures (heterogeneous growth using a functionalized substrate) have shown different sensing performances in the literature, and the sensing mechanism explaining variation of their sensing performance is not well understood. This is the motivation of the present work. In this study, camphor sulphonic acid doped polyaniline structures, synthesized utilizing both non-templated and templated growth approach, fabricated on polyethylene terephthalate substrates were used for gas sensing. The detailed characterizations of the sensing films were done by FE-SEM, FTIR, UV–vis spectroscopy and then the films were utilized for the sensing of NH3, CO2 and NO2 gases in N2 medium. Vertical arrangement of the facile polyaniline structures in templated grown films was useful for gas sensing application. Gas sensing responses were studied and found to improve in comparison to that of non-templated structures. For both templated and non-templated grown films, a response trend was observed as NO2 > NH3 > CO2. Computational studies were performed and showed that templated grown structures formed cages due to entanglement of the functional groups, which were not seen with non-templated grown structures. Cages serve as the strong van der Waals dominated binding sites for the analytes due to the presence of the surrounding aromatic rings. In addition, with binding energy calculations, the sensing interactions for different analytes were observed to be higher for the templated grown films, compared to that of the non-templated grown ones. Also based on energy considerations, the barrier of interactions for the different analytes was studied for the templated grown films and the reason for the trend of preferential response to different analytes was explained through energy barrier consideration. Results from both simulations studies and experimental observations showed a similar response trend towards gas sensing.