CO gas sensing of ZnO nanostructures synthesized by an assisted microwave wet chemical route

A simple wet chemical process assisted by microwave has been investigated for the synthesis of ZnO nanostructures for sensing applications. Characterization results have shown that microwave irradiation is able to quickly convert the reaction product zinc hydroxide into single phase crystalline ZnO. Different ZnO nanostructures (spherical-, flower- and star-like) have been prepared by adapting the experimental conditions. These ZnO nanostructures have been tested for CO gas monitoring by depositing them as thick films on an interdigitated alumina substrate and evaluating the surface resistance of the deposited layer as a function of operating temperature and CO concentrations. The gas sensitivity tests have demonstrated that the ZnO nanostructures, especially flower-like morphology, exhibit high sensitivity to CO proving their applicability in gas sensors. The role of the nanostructure on the sensing properties of ZnO is also discussed.