Acetone sensor based on WO3 nanocrystallines with oxygen defects for low concentration detection

In this work, the monoclinic and hexagonal phase of WO3 nanocrystallines are prepared by a facile one-pot microwave assisted hydrothermal method. The obtained WO3 are fabricated as gas sensors to detect acetone vapor. The microstructure and sensing performances of different WO3 phases are studied comparatively. The results show that the precursor pH value affects precipitation of H2WO4 and subsequently decomposition of H2WO4 to WO3. Hydrochloric acid plays very important role both in adjusting pH and modulating WO3 morphology. The monoclinic WO3 with oxygen vacancy exhibits outstanding high sensitivity and fast response to a wide concentration range of acetone (0.25 ppm–100 ppm). The response value reaches 3.8–250 ppb, and 31–100 ppm respectively, at optimal working temperature of 320 °C. The detection limit is estimated as low as 7.5 ppb. The excellent sensing performance of the monoclinic WO3 is attributed to the lattice oxygen defects which facilitate acetone adsorption on the material surface. Furthermore, the strong dipole moment interactions between monoclinic WO3 and acetone molecules help enhancing the selectivity.