Study On Synthesis And Gas Sensing Properties Of ZnO Composite Nanomaterials

The living environment of human is inseparable with the environment gas.Atmospheric pollution gas mainly includes the sulfur,carbon,nitrogen compounds,hydrocarbons and halogen compounds.With the development of science and technology,people stay indoors about 80% of the time in one day.Therefore,indoor air quality directly affects the human body health.TVOC?total volatile organic compounds?is a kind of gas which has serious influence on indoor air quality.It has carcinogenicity and irritation to the person's skin and mucous membrane,which can be gas under the ambient conditions and mixed with other gases to become a potential human health ‘killer'.However,for the most widely used metal oxide semiconductor gas sensor,the widespread lack is poor selectivity and sensitivity.Pure ZnO gas sensors always have low sensitivity,poor selectivity and stability.For MOS gas sensor,the micro size,composition and structure of gas sensitive material play the key role of sensitive performance?response,response/recovery time,stability?.On one hand,hollow/core-shell structure leads to a less agglomeration and porous surface,which is in favor of gas diffusion and increasing of reaction rate.On the other hand,because of the strong interface interaction and large specific surface area,nanocomposites show synergistic effect with higher response.Therefore,this thesis combines these two advantages to synthesize two ZnO composite materials with hollow/core-shell structure,which are used for gas sensing test in the next.The detail is in the following:?1?Firstly,the carbon ball is synthesized from glucose as a sacrificial template through hydrothermal,and then hollow Zn Fe₂O₄-ZnO composite spheres were prepared.The as-synthesized material was fabricated to a sensor using to testing acetone gas.XRD and EDS-mapping results show that EDS-mapping analysis clearly revealed that ZnO and Zn Fe₂O₄ were nested with each other forming a composite sphere rather than sosoloid,isolating ZnO and Zn Fe₂O₄ hollow spheres.Testing results show that hollow Zn Fe₂O₄-ZnO composite spheres have higher response than Zn Fe₂O₄-ZnO composite nanoparticles at the same working temperature.What's more,hollow Zn Fe₂O₄-ZnO composite spheres show fast response not only towards acetone but also to methylbenzene,trimethylamine and ammonia.?2?Firstly,the carbon ball is synthesized from glucose as a sacrificial template through hydrothermal,and then hollow SnO₂ spheres were prepared as core.ZnO shell was coated using surfactant to obtain unique core-hollow-shell structure.The results show that gas sensing properties of core-shell SnO₂@ZnO spheres were better than hollow SnO₂ spheres and ZnO nanoparticles.Synergistic effect of SnO₂ and ZnO and unique hollow structure of core-shell SnO₂@ZnO spheres were the important factor,which insure the micro condition.This paper offers two hollow composite materials with porous surface.Gas sensitive results proved that controlling microstructure and composition of the material is an effective way to improve its sensitive performance.The morphology of thesis enriches the relationship between material microscopic scales,composition and macro sensitive properties,which provided more possibilities for the development of new composite materials with hollow/core-shell structure in the field of gas sensor.