Gate-voltage controlled detection mode of dual-gate carbon-based FET gas sensor for trace-level trimethylamine...

Field effect transistor (FET) plays an important role in trace-level analyte detection due to the unique amplification ability. However, humidity interference cannot be neglected since the water-induced signal is also amplified when taking gas sensing test. How to effectively amplify the gas-induced signal and weaken the water-induced signal is a key problem to improve the humidity resistance of carbon-based FET sensor. Herein, an effective sensing mode is proposed for separating gas-induced signal from interference signal. To accommodate the detection mode, a carbon nanotubes (CNT)-based FET sensor with a dual-gate structure is rationally designed, where the target gas is identified via the sensing gate and the working state of the FET is adjusted by the electric field from the control gate, which facilitates the water dissociation to promote humidity resistance of the FET sensor. At room-temperature, the as-prepared FET sensor achieves excellent gas sensing performances toward 1-20 ppm of TMA under an optimal control gate voltage (-15 V). Taking the typical concentration threshold (10 ppm) for aquatic spoilage as an example, the responses of the FET sensor shows negligible drift (< 5 %) under 10-70 % relative humidity (RH), proving the reliability for freshness detection. This work provides a voltage-modulated gas detection mode via a dual-gate FET structure, offering a new approach to improve moisture resistance in FET-type gas sensors without requiring heating or light assistance.