MoSe2-based room temperature gas sensor with a sub-parts-per-billion limit for ammonia and N,N-dimethylformamide†

A limit of detection of toxic gases at the level of ppb is critical for industrial safety. Here, we designed a room temperature MoSe₂-based sensor for dual detection of ammonia (NH₃) and N,N-dimethylformamide (DMF). The MoSe₂/TiO₂ composite exhibits a rapid and highly selective response to both NH₃ and DMF compared to other industrial analytes. The MoSe₂/TiO₂ heterostructures exhibit a band gap of 0.31 eV, highlighting their electronic structure, adsorption energy, and fundamental gas sensing mechanism. NH₃ and DMF demonstrated robust spontaneous adsorption on the below-MoSe₂ surface, exhibiting the lowest adsorption energy (−0.12 eV) and (−0.09 eV) of NH₃ and DMF, respectively. Bader charge analysis revealed charge transfer from the gas molecule to the heterostructure surface, enhancing its conductivity and gas detection sensitivity. The adsorption of NH₃ on the MoSe₂ site is exothermic whereas on the TiO₂ side it is endothermic, indicating the potential of MoSe₂/TiO₂ composites for efficient room-temperature gas sensing. The sensor achieved an 85% higher response to NH₃ and an 80% higher response to DMF, with density functional theory (DFT) simulations confirming a high negative adsorption energy. Detection limits were calculated at 4.91 ppb for NH₃ and 7.82 ppb for DMF under 40% relative humidity, with robust sensitivity across varying humidity levels. Response times were reasonably stable, with NH₃ detection at 150 s and recovery in 37–110 s, while DMF was detected in 150–160 s and recovered in 45–74 s. This study highlights the potential of the MoSe₂/TiO₂ composite in real-time, room-temperature monitoring of both NH₃ and DMF, making it a valuable tool for industrial safety and environmental monitoring without the need for external recovery mechanisms.