Humidity-enhanced NH3 sensor based on carbon quantum dots-modified SnS

Recently, SnS is been extensively investigated in the field of gas sensors due to its unique wrinkled honeycomb structure and high specific surface. However, the weak response to NH3 at room temperature and especially poor moisture resistance limit the application of SnS in high humidity environments. To overcome these challenges, carbon quantum dots (CQDs) with hydroxyl and carboxyl groups on the surface were employed to modify SnS in this work, and the nanocomposite of SnS/CQDs was prepared by hydrothermal and stirring methods, respectively. It is revealed that the hydrothermally prepared nanocomposite SnS/CQDs shows much higher density of CQDs attached to the SnS nanosheets compared to the stirred samples. Resultantly, the hydrothermally prepared SnS/CQDs sensor can sense NH3 in ppb level and has a 4.78-fold higher response to 10 ppm NH3 than pure SnS, which are attributed to the heterogeneous structure of SnS/CQDs. Notably, its response value to 2.5 ppm NH3 at 97 % RH (3.67) is 1.44 times higher than that at 25 % RH, showing a unique humidity-enhanced effect. It was further explained by combining first-principles calculations and humidity-boosted NH3 adsorption-ionization model. This study provides a feasible way to explore the application potential of SnS-based nanocomposites in high humidity environments.