Electronic Modulation of MoS2 Nanosheets by N-Doping for Highly Sensitive NO2 Detection at Room Temperature

Transition metal dichalcogenide (TMD) materials hold great promise for gas sensors working at room temperature (RT). But the low response and slow dynamics derived from pristine TMDs remain a challenge toward their real applications. In this work, we report an efficient N-doping strategy to modulate the electronic structure of MoS2 nanosheets (N-MoS2) to achieve improved detection toward NO2. The effect of N-doping on the sensor properties, which has been rarely investigated, is elucidated by both experimental and computational studies. Due to N-doping, the Fermi level of N-MoS2 decreased from −5.29 to −5.33 eV and the band gap was reduced from 1.79 to 1.65 eV. The smaller band gap indicated the reduced resistance of N-MoS2 compared to that of original MoS2. As a result, the response of the MoS2 sensor to 10 ppm of NO2 was improved from 1.23 to 2.31 at RT. The sensor also has a limit of detection (LOD) of 62.5 ppb. To explain the effect of N-doping, density functional theory (DFT) calculations were conducted to figure out the important roles played by N-doping. This work demonstrates a pathway to modulate the chemical and electronic structures of TMD materials for advanced sensors.