Tuning reactivity of Bi₂MoO₆ nanosheets sensors toward NH₃ via Ag doping and nanoparticle modification

Noble metal-doping and modification are proved effective in improving the gas-response performance of semiconductor sensors. In this study, we developed a promising Bi₂MoO₆ (BMO)-based gas sensor capable of sensing ppb-level NH₃ at room temperature via introducing silver (Ag). The BMO samples with different Ag doping and modification ratios were successfully formed via one-step solvothermal and glucose reduction techniques, respectively, which could be confirmed by the results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) techniques. Compared to bare BMO, the gas-sensing properties of both Ag-doped and Ag surface-modified BMO samples were improved to various extents, respectively. In particular, the 5% Ag-modified BMO sensor with the highest response (G_g/G_a = 37.6 to 200 ppb NH₃), long-term stability, and low threshold concentration (50 ppb) at 20% RH. Based on the spillover effect and metal-semiconductor junctions of Ag nanoparticles, the enhanced sensing response towards NH₃ can be thoroughly illustrated. Combined with the first-principles calculations, the adsorption energy, density of states, and charge transfer of Ag-modified BMO were further performed to demonstrate the high sensing response and ultra-low detection limit.