A Sensitive Acetone Sensor Based on WS2/WO3 Nanosheets with p-n Heterojunctions

Gas sensors based on heterojunctions have attracted extensive attention because of their high sensitivities over monolithic metal oxide. However, it is difficult to obtain homogeneous and stable heterojunctions by traditional synthesis methods. Herein, we proposed an in situ oxidation technique to fabricate WS2/WO3 nanosheets with p-n heterojunctions in a convenient and controllable manner. Through this method, the ratio of WS2/WO3 can be effectively regulated by adjusting the oxidant concentration and oxidation time. The obtained WS2/WO3 nanosheets were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), etc. Then, a gas sensor based on WS2/WO3-4 heterojunctions was constructed to detect acetone in a wide range of 20–500 ppm. It was also found that the WS2/WO3-4-based sensor exhibited excellent repeatability, selectivity, and long-term stability for acetone determination. The sensitivity of the sensor toward 100 ppm acetone was 3.5, which was much higher than that of pure WO3. The results indicated that construction of heterojunctions could be therefore considered as a favorable method for improving the sensitivity of the prepared gas sensor. Moreover, this work provides a simple and flexible avenue to synthesize heterojunctions with high structural homogeneity for applications in various fields.