An ultra-sensitively ammonia-responsive gas sensor based on Ag@sulfur nanosheets

Nanomaterials-based gas sensors are conducive to online, real-time monitoring and large-scale production due to their simplicity, low energy consumption and miniaturization. Conventional nanomaterial-based (metal oxide semiconductor or two-dimensional nanomaterials) gas sensors are less sensitive (ppm-ppb level). So, it is significantly meaningful to develop new gas-sensing materials. Herein, Ag@sulfur nanosheets (S-NSs) nanocomposite-based sensor is explored for ultrasensitive detection of NH3 in dry air at room temperature at parts per trillion (ppt) level. Introducing Ag nanoparticles (NPs) on S-NSs, improved electrical conductivity and created more effective adsorption sites, leading to a high response rate of 1.92 for 3 ppt NH3. The developed Ag@ S-NSs sensor showed a linear response to NH3 in the range of 3-70 ppt with correlation coefficient of 0.996. Moreover, the developed Ag@S-NSs sensor showed fast response and recovery time (28/7 s) to NH3. The probable sensing mechanism is supposed that the polarization-induction of NH3 changed of electronic energy level of Ag@S-NSs, and the changed energy is at approximately the same energy level of the Ag@S-NSs itself. Thus, a response signal caused by NH3 with low concentration can also be felt by Ag@S-NSs sensing materials itself.