Experiments combined with first-principles calculations to compare the enhancement of Ag-doping and -functionalization on the sensing properties of two-dimensional SnS

Abstract

The potential of two-dimensional group-IV monochalcogenides MX (M = Ge, Sn; X = S, Se) as sensitive materials for gas sensors is being greatly explored. In this work, an exploration combined experimental and theoretical on pure SnS, Ag-doped and Ag-functionalized SnS for promising ethanol sensing performance is performed. A one-step solvothermal process was employed to synthesize pure SnS and Ag-doped SnS, and an environmentally friendly glucose induction method was used to prepare Ag-functionalized SnS. The sensing measurements towards 1–10 ppm ethanol exposure indicate that the doping and functionalization of Ag are both viable strategies in enhancing the sensing performance of SnS, and Ag-functionalization seems to be more effective. Compared with pure SnS, the sensing response of Ag-doped SnS to 10 ppm ethanol is revealed to increase by approximately 3.3 times, and that of Ag-functionalized SnS is about 4.4. It is also revealed that the sensors based on Ag-doped and Ag-functionalized SnS could show greatly improved selectivity. Further first-principles calculations on gas molecules adsorbed on the substrates was performed to demonstrate the enhanced sensing response and selectivity. It is clarified theoretically that the incorporation of Ag atoms could enhance the adsorption capability and charger transfer of the SnS surface to ethanol molecules, thus achieving obvious response enhancement and selectivity improvement. The present work demonstrates that Ag modification, including Ag-doping and Ag-functionalization, is highly effective for enhancing the response and selectivity of SnS towards ethanol vapor, and the modified sensors are promising for highly sensitive ethanol detection with low power consumption.