Preparation Of α-Fe₂O₃ Nanostructures Using Imidozalium-type Ionic Liquids-moduated Solution Phase Methods

α-Fe2O3, as a kind of semiconductor materials, is the most stable phase of iron oxide under ambient conditions. In view of its low band gap, α-Fe203 can adsorb visible light substantially. It has been widely investigated for potential applications in energy storage, environmental, electronics, optics etc due to its unique physicochemical properties, such as environmentally friendliness, good optical stability, abundant, and so forth. The characteristics of nanoparticles are closely related totheir dispersion, size and shape, so shape control is a primarily direction in α-Fe2O3 nanoparticles research. Ionic liquids (ILs), which are liquid salts at room temperature, are organic solvents composed of lager cations and smaller anions. Ionic liquids are used as green solvent for high expectations since its discovery and provide a new opportunity for nanoparticles preparation. But compared with the traditional methods, nanoparticle preparationusing ionic liquid systems still need further investigation. ILs was simply used as common surfactant in the previous works. And the effect type between the ionic liquids and the goal products has still not been achieved. In this thesis, valuable explorations have been carried out on preparation of α-Fe2O3 nanomaterials with the assistance of simple imidozalium-type ionic liquids under hydrothermal conditions. We also investigated the formation mechanism of α-Fe2O3 nanomaterials in different shapes. The lithium storage performance and photocatalytic activity of these nannnoparticles were also investigated. This thesis is divided into three sections, which are summarized as following:Part Ⅰ exhibited a brief introduction of the research background. The concept of nanomaterials was briefly reviewed, and the structural characterization and properties of α-Fe2O3 were introduced. And then, the progress of α-Fe2O3 nanoparticles which containing their morphologies and preparations was also reviewed. Simultaneously, the properties of ionic liquids and use in the preparation of nanoparticles were summarized. Finally, we introduced the application of a-Fe2O3nanomaterials in fields of lithium storage and photodegration.Part Ⅱ, we investigated the preparation of a-Fe2O3nanostructures in long-chain imidozalium-type ionicliquids mixed systems which is based on the polyol process. A facile and mild one-step approach for the fabrication of hierarchical urchin-like α-Fe2O3 nanostructures in aqueous solutions of sodium dodecyl sulfonate (SDS), 1-dodecyl-3-methylimidazolium bromide (C12mimBr) and ethylene glycol (EG) under hydro-thermal conditions was first described. The addition of EG and utilizing Fe2+ ionsas the source of iron were our "protection" reactions to guarantee the equilibrium between hydrolysis and oxidation of Fe3+. And the mixed SDS/C12mimBr micelles are regarded as structure directing agents. The results of SAED and XRD exhibited the obtained a-Fe2O3are well crystallized hexagonal structure. The roles of the molar ratio of anionic/cationic surfactants, EG, and reaction time were investigated in detail. On the basis of the experimental results, a possible growth process for the hierarchical nanostructures has been proposed, which mainly contains three stages including the oxidation of the Fe2+, the formation of FeOOH, FeOOH dehydration to form α-Fe2O3 and the diffusion and orientedattachment crystal growth of the particles. When evaluated aspotential anode materials for lithium-ion batteries, thehierarchical urchin-like α-Fe2O3exhibited a high first-cycle discharge capacity of 1696.4 mA⊙h⊙g-1 and excellent cycling performance. When used in the photocatalytic experiment, the urchin-like a-Fe2O3 only took 40 min to finish the degradation. We could probably attribute this superior performance of the obtained urchins to the unique structures.Part III, a functionalized ionic liquids, [Bmim][PhCOO], was synthesized, and then, we use it to prepare well-dispersed a-Fe2O3 nanostructures with controlled dimensionality and shape. The dendrites (3D) can be tailored to hexagonal plates (2D) and rods (1D) only by changing the molar ratio of [Bmim][PhCOO] to K3[Fe(CN)6]. We acknowledged the growth direction of different shaped a-Fe2O3 nanostructures from the results of SEM, HRTEM and SAED. [Bmim][PhCOO] is found to play a key role in the evolution of α-Fe2O3 with different shapes:the nucleation rate is influenced by the hydrolysis of [PhCOO]- anions, and the [Bmim]+cations can favorably stabilize the {1010} facets due to the hydrogen bond-co-π-π. stacking interaction. Furthermore, the visible light induced photodegradation of RhB reveals that α-Fe2O3 rodsexhibit higher photocatalytic activity compared to dendrites and plates. Interestingly, with the process proceeding, the photoactivity of these samples increases successively.