Ultrafast NH₃ gas sensor based on phthalocyanine-optimized non-covalent hybrid of carbon nanotubes with pyrrole

The development of innovative methods for optimizing carbon nanotube-based gas sensors for rapid and sensitive detection of ammonia remains challenging. Here, MCNT@PPy/TfmpoPcCo hybrid with a uniform 3-D network were prepared by tightly combining tetra-β-trifluoromethylphenoxyphthalocyanine cobalt (TfmpoPcCo) on the surface of MCNT@PPy through π-π interactions and used to construct NH₃ sensor, while the MCNT@PPy were obtained by in-situ polymerization of PPy onto the side wall of MCNT. TfmpoPcCo not only adsorbs on the MCNT@PPy side wall due to its structure advantages, but also acts as a sensor accelerator. MCNT@PPy/TfmpoPcCo sensor show higher NH₃ sensing performance than the MCNT, PPy and TfmpoPcCo under same operating conditions, especially in ultrafast response/recovery time (11.7 s/91.8 s to 50 ppm NH₃) with low limit-of-detection of 11 ppb at room temperature (20 °C) and excellent gas selectivity. In addition, the MCNT@PPy/TfmpoPcCo sensor preserve superior gas response (26.2% to 50 ppm NH₃) as well as outstanding stability over 60 days and humidity resistance. The excellent NH₃ sensing properties are attributed to the excellent gas selectivity of TfmpoPcCo, the unique redox characteristics of PPy to ammonia (NH₃), and the good electron transport ability and stability of MCNT. The synergistic optimization strategy of ternary materials is of great significance towards the exploration and construction of ideal materials for gas sensor in the future.