An Ion-In-Conjugation-Boosted Organic Semiconductor Gas Sensor Operating at High Temperature and Immune to Moisture

Organic electrical gas sensors have been developed for many decades because of their high sensitivity and selectivity. However, their industrialization is severely hindered by their intrinsic humidity susceptibility and poor recovery. Conventional organic sensory materials can only operate at room temperature owing to their weak intermolecular interactions. Herein, we demonstrate using a croconate polymer (poly-4,4'-biphenylcroconate) that the "ion-in-conjugation" concept enables organic gas sensors to operate at 100 °C and 70 % relative humidity with almost complete recovery. The fabricated sensor had a parts-per-billion (ppb) detection limit for NO₂ and showed the highest sensitivity (2526 ppm^-1 at 40 ppb) of all reported NO₂ chemiresistive sensors. Furthermore, charge transfer increased with temperature. Theoretical calculations and in situ FTIR spectra confirmed the ion-in-conjugation-inspired hydrogen bond as key for excellent sensitivity. A NO₂ alarm system was assembled to demonstrate the feasibility of this sensor.