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

Recently, Tungsten disulfide (WS2) nanosheets are widely used for room-temperature NH3 sensing. However, the lower sensitivity and the microstructural instability severely limit its potential application. Here, few-or mono-layer WS2 nanosheets decorated with different amounts of TiO2 quantum dots (QDs) were successfully prepared for room-temperature NH3 sensing. The gas sensing studies revealed that the nanohybrids exhibited significantly enhanced sensitivity to NH3 at room temperature. The response of nanohybrids with the optimal molar ratio to 250 ppm NH3 is nearly 17 times higher than that of the pristine WS2. Especially, the TiO2 QDs decorated WS2 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 WS2 and the TiO2 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. (C) 2017 Elsevier B.V. All rights reserved.