Room-temperature selective and ultra-sensitive NO₂ detection using a TiO₂/PEDOT p–n nanocomposite sensor

Detecting nitrogen dioxide (NO 2 ) at low concentrations and under ambient conditions remains a significant challenge in environmental sensing. In this work, we report a highly responsive TiO 2 /PEDOT nanocomposite sensor engineered through a facile in situ polymerization approach. The composite integrates the high surface reactivity of n-type TiO 2 nanoparticles that provide superior conductivity and ambient operability of p-type PEDOT, forming a synergistic p–n heterojunction that enables efficient charge separation and signal amplification at room temperature, without the need for thermal activation or extrinsic dopants, thereby distinguishing this system from previously reported TiO₂–polymer composites. Comprehensive material characterization confirmed successful nanocomposite formation and favorable structural properties. The sensor demonstrated a high response of 119.9% at 400 ppm when exposed to NO 2 gas, with recovery and response times of 137 s and 117 s, respectively, all at room temperature. Furthermore, the device showed excellent repeatability, reproducibility across sensor batches, and operational stability over 30 days. These results show that the TiO 2 /PEDOT nanocomposite, which combines sensitivity, selectivity, and practicality, is a potential option for NO 2 sensing systems.