Dual-Gate Modulation in a Quantum Dots/MoS₂ Thin-Film Transistor Gas Sensor

Mastering the surface chemistry of quantum dots (QDs) has enabled a remarkable gas-sensing response as well as impressive air stability. To overcome the intrinsic receptor-transducer mismatch of QDs, PbS QDs used as sensitive NO₂ receptors are spin-coated on top of a few-layer MoS₂ and incorporated into a thin-film transistor (TFT) gas sensor. This architecture enables the separation of the electron transduction function from the chemical reception function. A comparison study through size engineering of QDs combined with TFT device modeling suggests a unique dual-gate modulation related to the capacitance coupling effect of QDs. The favorable increase in sensor output current by 3 orders of magnitude is ascribed to the high mobility of the few-layer MoS₂. The optimal sensor exhibits a sensitive (LOD ∼ 0.6 ppb), selective, and recoverable response at room temperature. Because of the dual-gate modulation, the sensor performance is further optimized by varying the gate voltage (a two-fold increase in response to 1 ppm of NO₂).