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Air-stable p-type PFTPDOBT polymer with triphenodioxazine (TPDO) as the building block has been incorporated into a bottom-gate, bottom-contact organic thin-film transistor (OTFT) to detect putrescine (PUT) vapor in ambient conditions. Due to the doping effect, the PFTPDOBT devices showed increased mobility in air compared with in nitrogen. The highest mobility reached 0.03 cm2 V−1 s−1 after annealing at 250°C. The storage stability was evaluated based on the change in the mobility of PFTPDOBT sensors stored in air. Around 55% of the mobility remained after 1 month of air storage. Proper operational stability was obtained at an operating voltage of −100 V. Despite certain degradation, real-time detection of putrescine could be realized by IDS measurements through time under continuous bias. The detection limit of the PFTPDOBT sensor was found to be 9 ppm. Fast responses were shown with IDS and mobility decreases, which can be ascribed to a charge trapping effect induced by lone electron pairs in PUT molecules. Further improvements could be achieved to obtain better stability at low operational voltage by using dielectric materials with high dielectric constant, adding an encapsulation layer, or decreasing the capacitance per unit area. Such sensors with easy operation and low cost could be used for food safety inspection and marine environmental monitoring. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]