Fabrication And Characterization Of ZnO/TiO₂ And SnO₂/TiO₂ Heteroarchitectures

Hierarchical meso- and nanostructures of functional materials such as metal oxides have attracted considerable interests due to their unique properties and potential applications in advanced devices and systems. The performance of materials depends not only on their chemical composition, phase, size and morphology, but their assemblies as well. The controlled growths and structural characterizations of materials are of considerable significant.At present, the research on the construction of heterostructures is mainly concentrated on chemical vapor deposition and thermal evaporation. Nevertheless, complicated experimental procedures and critical conditions, e.g. high temperature or high pressure, were usually required to obtain these fantastic hierarchical materials. Compared with other approaches, hydrothermal method is regarded as an attractive candidate for synthesis of homogeneous architectures due to the advantages of environmentally-friendly, simplicity, easy-controllability and low cost. In this thesis, an effective two-step route was reported to synthesize hierarchical structures by combination of electrospinning and hydrothermal method. The main contents of the research were listed as below:1. ZnO/TiO₂ hierarchical material with tunable structures were synthesized by combination of electrospinning and hydrothermal method, the influence of preparation conditions on the epitaxial ZnO structures have been investigated. With precursor concentration ranging from 0.015mol/L～0.045mol/L , ZnO/TiO₂ hierarchical structures can be obtained with high dendity ZnO nanorods growth on the TiO₂ electrospinning fibers. By adding trisodium citrate to the hydrothermal system, a layer of uniform ZnO nanoplates grown on TiO₂ fibers were generated and the formation mechanism of the secondary growth ZnO structures have been investigated.2. SnO₂/TiO₂ hierarchical structures were successfully synthesized by changing the hydrothermal growth conditions. The influence of preparation conditions on the epitaxial SnO₂ structures has been investigated. The result shows that, with concentration ratio of 20:1(NaOH to SnCl4), SnO₂/TiO₂ hierarchical structures with a layer of uniform SnO₂ nanorods grown on the suface of TiO₂ fibers can be obtained. The possible formation mechanism of the secondary growth of SnO₂ nanorods is also proposed.3. The wettability of as-prepared TiO₂ fibers, ZnO/TiO₂ and SnO₂/TiO₂ hierarchical structures were investigated in detail. The initial water contact angel was super-hydrophilic with a cntact angle of 0°. The TiO₂ fibers and ZnO/TiO₂ hetrojunctions could keep super-hydrophilicty even stored in the dark fou several months. However, the surface of SnO₂/TiO₂ heterostructures displayes hydrophilic, super-hydrophobic. The result shows that the formation of the dual switchable surface wettablity of SnO₂/TiO₂ was due to the unique surface structure of the films induced by the epitaxial growth of SnO₂ nanorods.