2D WS2 nanosheets with TiO2 quantum dots decoration for high-performance ammonia gas sensing at room temperature

Recently, Tungsten disulfide (WS 2 ) nanosheets are widely used for room-temperature NH 3 sensing. However, the lower sensitivity and the microstructural instability severely limit its potential application. Here, few- or mono-layer WS 2 nanosheets decorated with different amounts of TiO 2 quantum dots (QDs) were successfully prepared for room-temperature NH 3 sensing. The gas sensing studies revealed that the nanohybrids exhibited significantly enhanced sensitivity to NH 3 at room temperature. The response of nanohybrids with the optimal molar ratio to 250   ppm NH 3 is nearly 17 times higher than that of the pristine WS 2 . Especially, the TiO 2 QDs decorated WS 2 nanohybrids showed almost no decline in sensitivity after several testing cycles, indicating the long-term stability of the nanohybrids-based sensing materials. The sensing mechanism based on the largely enhanced sensitivity and the long-term stability of nanohybrids also discussed in detail. It was believed that the largely enhanced sensitivity was attributed to the effective electron transfer between the WS 2 and the TiO 2 QDs through S O Ti bonding, which was confirmed by XPS analysis. We hope that this work could help us to further understand the QDs sensitization mechanism and could provide a guideline to explore more transition metal dichalcogenides-based gas sensors with even higher sensing performances.