Flexible self-powered high-performance ammonia sensor based on Au-decorated MoSe2 nanoflowers driven by single layer MoS2-flake piezoelectric nanogenerator

Smart sensing devices with high reliability and self-powered features are critical in future generation wearable applications. In this paper, we reported for the first time a room temperature Au-MoSe2 composite ammonia (NH3) sensor driven by a novel flexible piezoelectric nanogenerator (PENG) based on two-dimensional (2D) semiconductor MoS2 flake. Moreover, we also demonstrated the MoS2-based PENG device attached to the human body for harvesting diverse body motion energy, demonstrating its strong potential for applications in wearable devices. A series of characterizations of 2D piezoelectric semiconductor MoS2 and Au-MoSe2 sensing materials were carried out. The Au-MoSe2 composite-based ammonia sensor with MoS2 PENG showed a higher response (Va/Vg = 29 @ 100 ppm NH3) toward NH3 than that of MoSe2 counterpart (Va/Vg = 25 @ 100 ppm NH3). And it has superior selectivity and outstanding long-term stability. Moreover, the sensor also has a fast response/recovery time (18 s/16 s) towards 20 ppm NH3. Finally, the enhanced sensing mechanism of Au-MoSe2 composite toward NH3 was discussed by using first-principle calculations based on density functional theory.