Flexible and Printed Chemiresistive Ammonia Gas Sensors Based on Carbon Nanotube and Conjugated Polymers: A Comparison of Response and Recovery Performance

Carbon nanotube (CNT)-based chemiresistive gas sensors are known to not fully recover to the baseline after gas exposure. This is why often heat is applied to thermally activate sensor and improve the gas desorption process occurring at the surface. In this letter, we combine single-walled CNTs (SWCNTs) with conjugated polymers (CPs), i.e., Poly(3-hexylthiophene)(P3HT), to realize chemiresistive gas sensors with improved recovery. Five configurations were fabricated with diverse positions of the sensing material layers with respect to the interdigitated electrodes (IDEs), namely: SWCNTs/IDEs and P3HT/IDEs as controls for the CNTs and P3HT singular materials: SWCNTs/P3HT/IDEs, SWCNTs/IDEs/P3HT, and P3HT/SWCNTs/IDEs as combined sensing materials layers configurations. The results show that in particular, the P3HT/SWCNTs/IDEs sensors exhibit better performance with respect to the other configurations when exposed to 5, 25, and 50 ppm NH
$_{3}$
. Improvements in terms of response time (103 s faster at 5 ppm), sensor response (+26.83% at 50 ppm), and improved recovery to the baseline (+25.69% and +11.34% at 5 and 50 ppm, respectively) were obtained when evaluated against SWCNTs/IDEs sensors. These findings suggest that addition of CPs (i.e., P3HT) may be a promising approach to enhance the performance and stability of SWCNTs-based chemiresistive gas sensors, providing a new direction for future research in this field. Future research to investigate the effect of others CPs on the CNTs based chemiresistive gas sensors will be needed to realize more efficient and reliable ammonia gas sensors.