Impact of plasma polymerized Iodine-Doped thiophene films for enhanced sensing response towards industrial VOCs

Volatile organic compounds (VOCs) are majorly used in the manufacturing industry and are hazardous to the sustainability of the environment. Polymeric sensors, rather than more traditional metal oxide sensors, are currently taking the lead attention in the greater part of VOC sensing investigations. In polymeric sensors, plasma polymerized thiophene (PPTh) films are being investigated because of their unique properties, wasteless fabrication, and feasibility for commercial mass manufacturing. In the present study, we fabricated PPTh films powered by a 13.6 MHz RF generator with a vacuum level of 10-3 Torr in a home-built plasma system. The gas sensor investigation of PPTh and iodine-doped PPTh samples with various VOCs, such as ethanol, methanol, acetone, benzene, toluene, and dichloromethane, was carried out systematically. The iodine-doped PPTh 10-20 films (48 hr) showed the highest sensitivity for ethanol (-180) and methanol (-120) as compared to PPTh for ethanol (-110) at 1000 ppm gas concentration. A sensitivity degradation study over 60 days revealed the long-term stability of the films in the air. The polar hopping mechanism and decreased charge transport centers after reaction with the hydroxyl group are responsible for resulted sensitivity of iodine-doped PPTh films towards alcohols.