Conducting plasma polymerized polypyrrole thin films as carbon dioxide gas sensors

This paper describes the production of conducting polypyrrole (PPy) thin films by plasma-enhanced chemical vapor deposition (PECVD) and its posterior use for sensing applications of carbon dioxide (CO ₂). Since PECVD yields the non-conducting form of PPy, a doping process consisting of exposure to iodine vapor is required to obtain electrically conducting samples. Differences in the chemical state and topography between the doped and undoped systems are studied and characterized to demonstrate the doping effect on the polymer. Furthermore, changes in conductivity after exposure to CO ₂ gas are measured to evaluate the use of these thin films as chemical sensors. The results suggest that plasma polymerized films show a good sensitivity and reproducibility in the analyte detection. This work reports for first time the potential use of plasma polymerized polypyrrole thin films for sensor applications, based on the changes of electrical conductivity when exposed to carbon dioxide. AFM images corresponding to the surface topography of PPy thin films before (1) and after 60min of iodine doping (2) are presented to show the chemical and physical changes involved in the doping process.