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 (ΔR_p/R_p0, ∼−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 ΔR_p/R_p0 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.