Morphology-dependent gas-sensing properties of ZnO nanostructures for chlorophenol.

The crystal-plane effect of ZnO nanostructures on the toxic 2-chlorophenol gas-sensing properties was examined. Three kinds of single-crystalline ZnO nanostructures including nanoawls, nanorods, and nanodisks were synthesized by using different capping agents via simple hydrothermal routes. Different crystal surfaces were expected for these ZnO nanostructures. The sensing tests results showed that ZnO nanodisks exhibited the greatest sensitivity for the detection of toxic 2-chlorophenol. The results revealed that the sensitivity of these ZnO samples was heavily dependent on their exposed surfaces. The polar (0001) planes were most reactive and could be considered as the critical factor for the gas-sensing performance. In addition, calculations using density functional theory were employed to simulate the gas-sensing reaction involving surface reconstruction and charge transfer both of which result in the change of electronic conductance of ZnO.