Enhancing gas-sensing property and sensing mechanism at molecule level of the hollow microspheres assembled with ZnO nanoflakes exposing {001} facets

The hollow microspheres assembled with ZnO nanoflakes exposing {001} facets have been successfully synthesized by annealing ZnS nanospheres at 550 degrees C for 2 h. Response of the hollow microspheres assembled from ZnO nanoflakes for ethanol, acetone, or triethylamine is significantly higher than hollow microspheres assembled from ZnO nanorod with dominant {100} facets. The exposed Zn-terminated (001) face is considered to be an active surface for gas sensing. Threefold coordinated Zn (Zn-3c) atom with a dangling bond on the Zn-terminated (001) surface serves as a gas-sensing active atom, and thus a gas-sensing mechanism at atomic and molecular level is proposed. The concept of unsaturated Zn-3c atoms as a gas-sensing active atoms will be useful for designing of high-performance sensing materials.