Design, Synthesis And Gas Sensing Investigation Of Functional Nanomaterials

With the developments in the science of nanomaterials and nanotechnology, the scientific research communities over the world are more likely to focus on how to use nanotechnology to improve human life than on how to synthesize various nanostructured materials. Moreover, the design and development of novel and efficient synthetic strategies for nanomaterials are playing an important role in the development of modern nanoscience. The development of economic, simple, efficient, green, environmental-and user-friendly synthesis approaches is also the crucial center in the research field of nanomaterials. Nowadays, nanomaterials have shown great promise for the application of chemical gas sensors. This dissertation focuses on the tailor of structures and compositions of nanomaterials, as well as their application in advanced gas sensors. We have comprehensively investigated the sensor performances of zero- and one-dimensional and hierarchically porous nanostructures. Combing the unique morphology of metal oxide base materials and the catalytic activity of noble metal nanoparticles could provide us with a new direction for exploring novel sensor materials. The main research contents in this thesis are summarized as follows:1. SnO₂ nanoparticles with a small size have been prepared by using a simple hydrolysis method of ethoxide. The gas sensing properties of the prepared SnO₂ nanoparticles were studied according to the"size effect"discussed in chapter one.2. Porous SnO₂, ZnO and CeO₂ hollow spheres were prepared by hydrothermal method using carbon spheres as the template. The porous shells and large inner voids make the hollow materials highly promising gas sensors. The gas sensor performances of these hollow spheres and solid commercial powders were investigated and compared to elucidate the promoting effect of the unique structures on the gas sensor properties.3. Pt/WO3 nanopowder and Au/SnO₂ hollow spheres were obtained using a conventional ammonia hydrolysis-precipitation method and examined as sensor materials. The size control of Au nanoparticles is hard to achieve using the conventional ammonia hydrolysis-precipitation method, hence, we have designed a one-pot strategy using lysine as both the capping and the linking reagents. There is no need for the pre-functionalization of the support materials. The formation of small sized noble metals and attachment onto the support were finished simultaneously. This one-pot method is more advantageous due to its simplicity, generality and low toxity and can be used to synthesize various noble metal-loaded nanomaterials.4. A simple and none-template precursor-calcination method was developed based on the combination of hydrothermal method and post annealing treatment. 3D hierarchally porous ZnO architectures were obtained using facile method and demonstrated superior sensor performances to ZnO nanopowder, due to its large surface-to-volume ratio. Mesoporous SnO nanomaterials were prepared for the first time using a hydrothermal method without the need of post-calcination. Furthermore, the mesoporous SnO nanomaterials showed good cycling performance for Li-ion battery.5. Inorganic-inorganicα-Fe₂O₃@ZnO hybrid nanospindles, inorganic-organic SnO₂@PPy composite hollow spheres and multicomponent reduced graphene oxide/SnO₂/Au nanomaterials were synthesized using a two-step hydrothermal, chemical in-situ polymerization and facile one-pot method, respectively. Theα-Fe₂O₃@ZnO hybrid nanospindles and SnO₂@PPy composite hollow spheres demonstrated great promise for application in gas sensors, providing a new direction toward exploring advanced sensor materials. The successful synthesis of ternary reduced graphene oxide/SnO₂/Au nanomaterials gave a direct example using the facile one-pot solution-based procedure for the construction of multicomponent nanomaterials.