Investigation On The Preparation And Gas Sensing Properties Of ZnO/SnO₂ Nanocomposites

The research and development of new gas sensitive materials with high performance is of great significance to improve the performance of oxide semiconductor gas sensor. In this thesis, on the basis of reviewing the research progress of metal oxide semiconductor gas sensing materials in detail, different morphological ZnO/SnO2 nanocomposites were successfully synthesized by a combining method of SnO sacrifice template method and hydrothermal/solvothermal synthesis, and the gas sensing properties of the as-prepared materials have also been investigated. The following parts show the main results and conclusions of our research.1. SnO hierarchical microstructures with different morphologies including sphere-like microstructures, flower-like hierarchical structures and porous structures assembled with nanosheets, were successfully synthesized via solvothermal route. The self-assembled mechanism of sphere-like and flower-like SnO hierarchical microstructures has been discussed. And the role of CTAB in the forming process of flower-like hierarchical structures has also been investigated. The influence of the introduction of PEG 400 on the features and size of nanosheets assembled SnO porous structures has been compared.2. Choosing the prefabricated flower-like hierarchical structures SnO as sacrifice templates, flower-like hierarchical ZnO/Sn O2 composites assembled with ZnO NPs and SnO2 nanosheets were successfully synthesized by heat treatment technique. Through the research, it can be found that besides of the ZnO/SnO2 heterojunctions, the dispersion and quantity of ZnO NPs also has an important influence on the gas sensing properties of the composite. When the ZnO content is 10 wt.%, the formed ZnO NPs on SnO2 sheet-like petals are well dispersed. The gas sensing performance to ethanol of this material based gas sensor is evidently superior to other composites with different components.3. Needle-like ZnO nanorods as base material were firstly synthesized via a hydrothermal method. Subsequently, ZnO/SnO2 core-shell nanorodes were successfully prepared through uniformly decorating a Sn O2 shell with the thickness of 20-25 nm on the surface of as-prepared ZnO nanorods by a facile solvothermal method. The response of the gas sensor based on as-prepared ZnO/SnO2 core-shell NRs to 100 ppm ethanol is as high as 29.5 at 340 oC, and the response and recovery times are found to be about 18 s and 11 s, respectively.