Capacitive Chemical Sensors Based on Two-Dimensional WSe₂

We demonstrated capacitive-type chemical sensors (chemicapacitor sensors) based on two-dimensional (2D) tungsten diselenide (WSe2). The integration of 2D materials with high surface-to-volume ratios and a capacitor resulted in excellent chemical sensing with high selectivity, high sensitivity, and fast response. WSe2-based 2D chemicapacitors were fabricated by combining exfoliated WSe2 flakes with parallel-plate capacitors. The sensing ability of WSe2-based 2D chemicapacitors towards NO2 molecules was characterized by monitoring the changes in capacitance (ΔC/C0, ∼65%) and parallel resistance (ΔRp/Rp0, ∼-90%) due to the adsorption of NO2 molecules (200 ppm). Transient sensing characteristics with fast response and recovery were achieved with adequate reproducibility. Interestingly, ΔC/C0 and ΔRp/Rp0 exhibited different behaviors, which can be a useful value for distinguishing between different target gas molecules. Our novel approach provides a convenient and effective method for producing 2D chemicapacitor sensors at low cost and with low power consumption.