The Synthesis Of ZnO Multi-Shell Hollow Spheres And Gas Sensing Properties Research

ZnO is one kind of important functional materials in catalysis, cosmetic, pharmaceutical, solar and other fields. As one of the earliest use of semiconductor gas sensitive materials, it has been widely used because of its simple preparation, cheapness, non-toxic, and its advantages of good stability. In recent years, the various morphologies of ZnO materials have been prepared, such as nanowires, nanorods, nanoparticles, flower, tubular and so on. Different ZnO morphology shows different performance of gas sensitivity and selectivity. But the ultimate goal is to find such materials with good stability, good selectivity, low working temperature and high sensitivity in gas sensing.In this paper, the carbon microsphere (CMS) was used as sacrifice template. The ZnO multi-shell hollow structures were synthesized by the method of adsorption-calcining. The gas sensitive performance of the ZnO multi-shell hollow spheres was studied with anhydrous ethanol as the target gas. The result showed the triple-shell ZnO hollow spheres had the best gas sensitive performance. And then we prepared the triple-shell ZnO hollow microspheres with Sn element doping and Ag element loaded. And the gas sensitive properties of these materials were tested studied by testing C2H5OH and HCHO gas. The main research contents in this paper are as follows:Firstly, the carbon microspheres with different sizes were synthesized in hydrothermal system with sucrose and water. And the ZnO hollow microspheres were synthesized with the carbon microspheres as sacrifice templates. The carbon microsphere was characterized by infrared spectrum (IR), scanning electron microscope (SEM) and thermogravimetric analysis (TG). The representation results of Zete potential, IR and SEM demonstrated that the surface of carbon microspheres contains a lot of negatively charged, functional groups of-OH, and-COOH, and there are a large number of microporous. These characteristics are conducive to the adsorption of metal ions on carbon microspheres..Secbndly, the ZnO solid sphere(or zero-shell sphere), single-shell, double-shell, triple-shell hollow spheres were synthesized by the hydrothermal adsorption-calcination method and by adjusting the concentration of precursor, adsorption temperature, adsorption time, solvent composition, calcination speed, temperature program and so on. The ZnO hollow microspheres were characterized by SEM, transmission electron microscope (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDX), TG and specific surface characterization test (BET), a The gas sensitive performance of these materials was studied by testing C2H5OH gas. The results showed that the ZnO triple-shell hollow microspheres got the best gas sensitive property.Thirdly, the ZnO triple-shell hollow microsphere was selected because its best gas sensitive property. And then Sn element was doped through the method of co-adsorption and elemental silver was loaded by sodium borohydride reduction method for synthesizing SnO2-ZnON Ag/ZnO、SnO2-Ag/ZnO triple-shell hollow microspheres. And they were characterized by TEM, XRD, and EDX. Their gas sensitive properties were studied by testing ethanol. The results showed that SnO2-ZnO had a small improvement on the gas-sensing performance, but the gas sensitive performance of Ag/ZnO had significantly developement. In this chapter, the gas sensitive performances were tested by using other gases, such as acetone, methanol, formaldehyde, ammonia, chloroform, etc.