Highly sensitive organic thin-film transistors based sensor for putrescine detection

Organic thin-film transistor (OTFT) sensors based on a diketopyrrolopyrrole–thiophene polymer (PDQT) were fabricated to detect putrescine (PUT) vapors in air. Electrical properties and film characteristics of the sensors were examined with IV characterization, AFM and XRD. Upon PUT exposure, PDQT sensors showed fast responses and quick recovery. Two groups of sensors with different active layer thickness were compared for stability and sensitivity. Although with less stability under ambient conditions, sensors with thinner layers showed high sensitivity toward PUT with detection limit of 3 ppb. The group with thicker layers exhibited ideal long-term stability through 8 weeks of air storage along with proper reusability and reproducibility. The PDQT sensors showed a selectivity toward ammonia and biogenic amines. A preliminary test with food samples was carried out where PDQT sensors gave promising responses toward food-emitted vapors. Such sensors might be used in real-time freshness monitoring with further modification to lower the operational voltage and improve the stability.