Controlled Synthesis Of Zinc Oxide Composite Gas-sensitive Materials And Their Gas Sensing Properties

In recent years, with the development of industrialization of our coutury, a large discharge of industrial waste gas, car exhaust and other harmful gases has seriously threaten human life and health. Zic oxide which is N-type metal oxide semiconductor has excellent physical and chemical properties and thermal stability. It is one of the widely used sensitive materials. However, with the constant improvement of gas detection requirements, The response, selectivity and operating temperature of traditional zinc oxide have not been meet the requirements of practical application. Therefor, taking into account production costs and service life of the premise, we designed zinc oxide-based composite gas-sensing materials which have simple process and excellent gas sensing performance. And we also further studied the formation and gas sensing performance of all composite products, as follows:We have synthetized the self-assembly of mesoporous ZnO/Co3O4 microspheres product using a facile PVP assisted solvothermal method. We chose PVP as a flexible template, zinc acetate as zinc source, cobalt acetate as cobalt source, glycol as solvent. The particle size of the product is 0.5～1.5μm,which is made up of a large number of oxide particles with an average size of 40 nm. We have studied the mechanism of ZnO/Co3O4 mesoporous microsphere, which can be described as the formation of PVP flexible templates,self-assembled nanoparticles, Ostwald riping and calcination. Specially, the formation of PVP soft template played a key role in the whole process. Gas sensing tests show that mesoporous ZnO/Co3O4 microspheres sensor had improved sensing performance compared with pure ZnO sensor because of the presence of p-n heterojunction between ZnO and Co3O4.We have successfully synthetized nest-shaped ZnO/CuO product using a PVP assisted hydrothermal method. The size of the product is 2～3μm, m which is made up of a large number of porous nanosheets with thickness of about 50 nm. In addition, there are lots of voids among nanosheets, which greatly improved the surface area. The formation of nest-shaped ZnO/CuO product can be described as nucleation, growth, Ostwald ripening, crystal growth process and calcination. The surfactant type and the amount of alkaline source played crucial role in the formation of nest-shaped ZnO/CuO product. Gas sensing tests show that compared to the pure ZnO sensor, nest-shaped ZnO/CuO gas sensor showed a lower operating temperature and higher response to ethanol.We have successfully prepared ZnO/α-Fe2O3 microspheres product by a simple solvothermal method. The size of the microspheres is about 100 nm which assembled by a large number of nanoparticles. Its formation process can be described as ZnO and α-Fe2O3 crstal nucleation, growth and calcination process. Gas sensing test results show that,ZnO/α-Fe2O3 microspheres gas sensor had excellent gas sensing performance to ethanol. It has simple preparation process, which is more suitable for the detection of ethanol gas-sensitive material compared with pure zinc oxide.