A room temperature ammonia sensor based on MoTe₂ nanosheets modified with TiO₂ nanoparticles

Recently, as a member of transition metal dichalcogenides (TMDs), MoTe₂ and its heterojunctions have gradually become a research hotspot in gas sensing due to their unique properties. In this study, MoTe₂/TiO₂ heterojunctions were prepared using a simple hydrothermal method, and TiO₂ nanoparticles were uniformly anchored on the surface of flake MoTe₂. Compared with the single-phase MoTe₂, the MoTe₂/TiO₂ heterojunction based sensor demonstrates excellent ammonia detection capabilities at room temperature (22 ± 1℃). The sensor's response values to 1 ppm and 30 ppm ammonia are 28 % and 168 %, respectively, which are six times and three times greater than those of the single-component MoTe₂ material. The recovery time for the sensor detecting 30 ppm ammonia has been reduced from 430 s to 239 s. Furthermore, the sensor exhibits excellent selectivity, repeatability, time stability, and a lower detection limit (500 ppb). Analysis indicates that the enhancement in sensing performance is attributed to the formation of numerous nanoscale p-n heterojunctions between MoTe₂ and TiO₂ nanoparticles. Moreover, density functional theory (DFT) calculations have confirmed that the presence of heterojunctions enhances the electron transfer efficiency between ammonia and the sensing materials.