The Synthesis And Characteristics Of Hierarchical SnO₂/α-Fe₂O₃Nanorings And Nanotubes

The performance of nanomaterials depends not only on their chemical composition, morphology, size and crystalline phase, but also on their assemblies. Therefore, the controlled growth of nanostructures with special architectures is of importance for their applications. Among various nanostructures, hierarchical nano-heterostructures have attracted intensive attention in past few years because of their unique properties and potential applications.In this thesis, novel hierarchical SnO2/a-Fe2O3nano-heterostructures were prepared usingα-Fe203nanoring and nanotubes as both seeds and templates. The method that we developed is simple and effective. We have studies the physical properties of hierarchical SnO2/a-Fe2O3nanoring and nanotube heterostructures and the performance of photocatalysis with respect to a-Fe2O3hollow nanostructures. The main achievements of this study are as follows:(1) A series of a-Fe2O3nanotubes and nanorings with different morphology and size have been successfully synthesized by simple anion-assisted hydrothermal method. The influences of the reaction conditions on the morphology and size of the products have been studied. The formation mechanism of a-Fe2O3nanotubes and nanorings was also investigated. The results indicate that nanoring with outer diameter of160nm and70nm and nanotube with outer diameter of90-110nm, lengths of250-400nm are successfully obtained from this method..(2) Hierarchical SnO2/a-Fe2O3nano-heterostructures were synthesized by hydrothermal method. The formation mechanism of the secondary growth of SnO2nanorods arrays on precursors is also proposed. TEM and HRTEM studies suggested that (101) snO2/(110) a-Fe2O3 interfacial orientation relationship is formed between the SnO2and a-Fe2O3. UV-Vis diffuse reflectance spectracharacterization indicates that the SnO2/a-Fe2O3heterostructures exhibits excellent UV-Visible absorption and large specific surface area. The compositions of SnO2and Fe2O3have been confirmed by X-ray photoelectronic spectra (XPS). The hierarchical SnO2/α-Fe2O3nanorings and nanotubes have also been phase transferred into magnetic SnO2/α-Fe3O4under H2flow at360℃. The prilimary studies on crystalline structure and magnetic properties of the SnO2/y-Fe2O3indicate that the morphology can be retained after纳米材料一般是借助某种作用力让两种晶格匹配的材料互相接触,使它们之间形成明显(3) The organic methylene blue(MB) trihydrate aqueous solution was taken as tl simulation pollutants to investigate the photocatalytic activity of SnO2/a-Fe2O nano-heterostructures. The results show that the SnO2/a-Fe2O3nano-heterostructures exhib much better photocatalytic activity as comparison to the pure a-Fe2O3nanostructures und both UV and visible light. This is ascribed to the formation of heterostructure at the interfa(?) that could improve the electron-hole separation efficiency.