Ammonia sensing properties of PPy nanostructures (urchins/flowers) towards low-cost and flexible gas sensors at room temperature

High-performance room-temperature gas sensors have tremendous potential in real-world applications like air quality control, food safety, and health monitoring. In this work, we report an eco-friendly and one-step route for the chemical synthesis of hierarchical polypyrrole (PPy) nanotubes assembled urchins and flower-like nanostructures via a template-assisted method and examine their morphology-dependent gas sensing characteristics. The ammonia sensor was mounted on low-cost and highly flexible polyvinylidene fluoride (PVDF) membrane substrate for the fabrication of flexible sensor. The polypyrrole urchins and flower-like nanostructures exhibited high surface area of 194.9 m²/g and 101.05 m²/g along with highly porous structure confirmed by BET and SEM characterization. The nanotubes assembled urchin-like structure of PPy exhibited great response, repeatability, and long-term durability to NH₃ gas in the range of 1–200 ppm owing to their high porosity, excellent flexibility, and large surface area. In addition, the PPy urchins based sensor exhibited low response time (23 s) and very high response of 34.7% towards 100 ppm concentration of ammonia gas at room temperature. From the flexibility point of view, proposed flexible sensor showed high mechanical robustness under extreme bending conditions, i.e. 90⁰ bending angle and 400 bending cycles by showing no considerable change in response even after these extreme bending conditions. The proposed flexible gas sensor remarkable performance to detect ammonia at room temperature indicates its tremendous potential for wearable electronics applications.