LAUSR

Uniform triclinic and monoclinic tungsten oxide (WO3) nanosheets were synthesized by facile hydrothermal process and thermal annealing at 250 and 450 °C, respectively. Acetone-sensing properties of the as-synthesized WO3 nanosheets were investigated with the aim of disease diagnose and environment detection. Triclinic WO3 nanosheets exhibited superior acetone selective and sensing performances (response ~ 2.04 to 1 ppm of acetone at 230 °C) to that of monoclinic WO3 nanosheets (response ~ 1.37 to 1 ppm of acetone and negligible selectivity). The mechanisms of acetone selective and sensing properties of triclinic WO3 were discussed in detail. Photoluminescence results and surface structure study revealed that the triclinic WO3 nanosheets exhibited higher defect level and more unsaturated coordinated O atoms than monoclinic WO3 nanosheets on their surfaces. These defects and O atoms can act as chemical adsorption sites where acetone molecules could be adsorbed and react directly. Meanwhile, triclinic WO3 exhibit lower symmetry and larger extent of polarization in comparison with monoclinic WO3. The induced large dipole moment contributes to strong interaction at these chemisorption sites between triclinic WO3 nanosheets and acetone molecules with a larger dipole moment than the other tested gases.