NH3 and H2S real-time detection in the humid air by two-layer Langmuir-Schaefer OFETs

Development of highly-sensitive low-power low cost sensors for toxic gas detection is a challenging task for today. Here we present a novel simple and fast approach for fabrication of reusable gas sensors for NH3 and H2S real-time detection based on Langmuir-Schaefer (LS) monolayer organic field-effect transistors with an active layer modified by an additional metal-containing porphyrin receptor layer. The devices prepared worked at room temperature and were found to be highly sensitive to the presence of ammonia and hydrogen sulfide at concentrations lower than 1 ppm. They demonstrated the improvement of both limit of detection (down to ca. 60-70 ppb) and sensitivity in the air with relative humidity up to 60 % as compared to the LS monolayer devices without a receptor layer. Incorporation of the receptor layer on top of the LS semiconducting monolayer does not influence on its electrical performance, response and recovery times, while provides the device sensitivity enhancement as well as allows tuning the sensor selectivity. Impressive combination of the sensor high sensitivity and reproducibility with fast response and full recovery after finishing the analyte exposure enables utilizing the fabricated two-layer OFETs as chemo-sensors in real gas analyzing systems.