Ultrathin WO3 nanosheets modified by g-C3N4 for highly efficient acetone vapor detection

In this work, ultrathin WO3 nanosheets were prepared by self-assembly approach and their phase and morphology were regulated by changing the heat treatment temperature. Then, g-C3N4 modified WO3 nanosheets sensitive material was fabricated via a facile liquid ultrasonic mixing method. The microstructure, morphology, chemical composition, oxidation state and surface area of WO3 nanosheets and g-C3N4/WO3 nanocomposite were comparatively studied by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscope (TEM), X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett-Teller (BET). Sensing performances of WO3 nanosheets and g-C3N4/WO3 composite with different g-C3N4 loading amount were investigated with acetone as a target gas. Compared to WO3 nanosheets, the g-C3N4/WO3 gas sensor exhibits good response, excellent selectivity, transient response and trace detection ability to acetone vapor. Effects of g-C3N4 content on gas sensitivity were also investigated. The response (R-a /R-g) of the gas sensor based on 1 wt% g-C3N4/WO3 was 35 toward 100 ppm acetone at 340 degrees C, which was about 300% higher than the response value of pure WO3 sensor. The sensor also showed a fast response/recovery speed (9 s/3.8 s) and a wide linear detection range (from 0.5 ppm to 500 ppm). These unique sensing properties were attributed to the synergistic effects including the contribution of WO3 ultrathin nanosheets, suitable crystal phase and porous surface, and the sensitization of g-C3N4, which increases the specific surface area and regulates the electrical properties. This work will contribute to the development of new acetone sensors and expand the application of g-C3N4 composite materials.