Synthesis Of Several Functional Materials With Hollow And Core-shell Morphologies By Colloidal Carbonaceous Spheres Template Method

As several well-known functional material, LaCCO3OH, ZnFe2O4, titanium dioxide and ceria have been widely applied in such fields as catalysts, gas sensors, and optics owing to their unique properties. However, during the practical application procedures, several problems were exposed due to the limits caused by their own structures, such as the wide band gap of TiO2 and nonselectivity of CeO2. In this dissertation, colloidal carbonaceous spheres template method was introduced in order to improve the sensitive and photocatalytic properties from two aspects-element decoration and structural modification.Firstly, C@LaCO3OH core-shell microspheres have been synthesized by a hydrothermal method using colloidal carbonaceous spheres (CCSs) as template and its by-products as reactant without any other precipitating agent added in the reaction system. The FT-IR and XRD results indicated the successful formation of the well-crystallized LaCO3OH shell with hexagonal crystal structure on the CCSs' surface. The morphology and qualitative elemental chemical analysis were characterized by SEM, TEM, and EDS. The effects of co-solvent on the crystallinity of the LaCO3OH shell were also studied. In addition, the UV-visible spectrum was also employed to investigate the optical property of the products. Further, a possible formation mechanism of the core-shell structure was proposed.Secondly, sensitivity of gas sensor materials is relies on two aspects:(1) structures and properties of material itself, (2) specific surface area. In this chapter, ZnFe2-xRexO4 (Re=Eu, Sm) hollow microspheres were synthesized successfully by in situ carbon microspheres template in order to improve the gas-sensitivity from the morphology modifications and element doping. Through gas-sensitive performance test, the best working voltage and the maximum sensitivity of doped ferrite in ethanol and acetone atmosphere were determined.C/Ag:CeO2 and C/Ag:TiO2 hollow microspheres were prepared by a simple tri-functional one-pot colloidal carbonaceous spheres template method. The characterizations for the physicochemical properties of the prepared samples were carried out by XRD, TEM, EDS, and XPS. Both the XRD and XPS results indicate the metal nature of silver within the products, which can improve the selective and catalytic activity of the CeO2-based catalyst. The existence of embedded amorphous carbon was identified by TEM, EDS, and XPS. The degradation of rhodamine B under natural light irradiation was employed to evaluate the photocatalytic activity of the prepared samples. The Ag composition was realized through the reducibility of glucose in the one-pot hydrothermal procedure and the embedded carbon was achieved in the removal process of carbon cores via a rapid combustion process. The obtained materials with metal element decoration, nonmetal element decoration and structural modification will be potentially applied in the catalytic and diluted magnetic semiconductors fields.