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.