Preparation Of ZnO-based Heterogeneous Nanostructures And Research On Their Humidity Sensing Performances

Humidity sensors are playing an increasingly important role in such fields as our daily life,medical and health,agricultural and industrial manufacturing,and food storage and transportation.The metal oxides such as ZnO and SnO₂have a wide range of application prospects in the field of humidity sensors,attracting the attention of a large number of researchers,due to their good humidity sensing properties.In order to further improve the humidity sensing performances of metal oxides such as ZnO and SnO₂to increase their utilization in practical,various methods and measures have been proposed.Thereinto,compounding them with another material with humidity sensing properties is regarded as one of the most common and effective methods.In this paper,the ZnO-NiO heterogeneous nanorods and ZnO-SnO₂heterogeneous films were successfully synthesized by the chemical solution method,based on the ZnO nanorods prepared through the hydrothermal method.What's more,their humidity sensing performances and mechanism have been researched and analyzed.For the two heterostructures of ZnO-NiO and ZnO-SnO₂,we first characterized them by the technologies of XRD,XPS,SEM and so on.The characterization results not only proved the successful preparation of ZnO-NiO and ZnO-SnO₂heterostructures,but also revealed the process of the transformation of these two heterostructures from ZnO nanorods,respectively.The humidity sensing performances test showed that the performances of ZnO-NiO heterogeneous nanorods and ZnO-SnO₂heterogeneous films both have been significantly improved compared with ZnO nanorods.And it is specifically represented by the much higher responses(the responses of such two kinds of heterostructures can reach 819.19 and 4 orders of magnitude,respectively),greatly improved adsorption and desorption speed,and better linearity in linear and logarithmic coordinates,respectively.Through the analysis of EIS impedance spectroscopy,the changes in the humidity sensing process of the two ZnO-based heterostructures with the increase of humidity were studied.The humidity sensing process of ZnO-NiO heterogeneous nanorods gradually changed from the state with only the electron transfer effect,to the state with only the proton conduction effect,as the humidity gradually increases.For the ZnO-SnO₂heterogeneous films,their humidity sensing process changed from the state with only the electron transfer effect at low humidity,to the state with the coexistence of the electron transfer effect and the proton conduction effect at high humidity.The reasons for the improved humidity sensing performances of the two heterostructures,can be concluded that the rougher surfaces of the two heterostructures provide more adsorption sites so as to promote the proton conduction effect.Meanwhile,the electron depletion layer formed in the heterojunction promotes the electron transfer effect.The both promotions of the proton conduction effect and the electron transfer effect are the main reasons for improving the humidity sensing performances of the two heterostructures.In this dissertation,the experimental results prove that the synthesis of heterostructure is an effective method to improve the humidity sensing performances of metal oxides.In addition,the mechanism has been analyzed and discussed.