Controllable Synthesis And Applications Ofα-Fe₂O₃Nanornaterial

Compared with bulk materials, nanomaterials have many advantages suchas surface effect, small size effect and quantum size effect which wouldmake it to be materials with special physical and chemical propertiesneeds. α-Fe₂O₃nanomaterials is the most stable n-type semiconductingoxide under natural environmental conditions, because of its low cost,environmentally friendly and strong corrosion resistance characteristics，alarge number of research about α-Fe₂O₃have been taken in the field ofsensing, catalysis, and pigment and so on. But Structure determines theproperties, especially in nano-materials, the interaction between theperformance and the size, structure, morphology of the material, and therequirements of the morphology of nanomaterials is particularly strict inmany places.Therefore, many works about size and morphology controllablesynthesis of α-Fe₂O₃nanomaterials have been reported in recent years.And, many synthesized methods have shown in these reports, which candivide into two parts: the first one is using ions, atoms or molecules asprecursors to prepare nanomaterials, including hydrothermal method,sol-gel method and so on; the second one is using block materials asprecursor to prepare nanoscaled materials through physical or chemicalrouts, such as mechano-shattering method and so on. In various synthesismethods, adjusting reaction temperature, reaction time, ratio of reactants,and concentration of reactants and adding to appropriate surfactants allcan control the size and morphology of products. Hydrothermal synthesisis a simple method which can prepare one-component, two-component orcomponents of compounds powder or crystal, and the nanocrystalline iscomplete with uniform particle size. Therefore, this method has beenwidely used. In this paper, we choose α-Fe₂O₃nanomaterials as research objects.Just by adjusting the experimental parameter, we get α-Fe₂O₃nanomaterials with different morphology, and study the application ofobtained3D α-Fe₂O₃flue-like nanomaterials in photocatalytic fields. Thedetail contents of this paper as follows:1. Ring-like materials have attracted intense research interestsbecause of their intriguing structural features and promising applications.In this work, we report an effective solvothermal method to preparesingle-crystalline α-Fe₂O₃nanorings with different morphologies withoutusing any templates. Hexagonal nanorings and circular nanorings havebeen obtained just by varying the pH of initial solution with HCl orNaOH. On the basis of a series of experiments and characterizations, thegrowth mechanism of these kinds of nanorings is explained by theinfluence of the pH values and different anionic ligands. Here thecooperative action of the VO₄^3- and SO₄^-2, involving adsorption andcoordination, is a crucial factor in bringing about the formation of theringlike structures.2. Uniform porous three-dimensional nanoarchitectures of α-Fe₂O₃with high yield have been synthesized by the route based on aNi²⁺/surfactant system. The obtained α-Fe₂O₃is flue-like porousmorphology with rough surface. What’s more, spatially ordered nodesand meshes are presented in these networks. By adjusting theexperimental parameters such as temperature, reaction time, proportion ofNi²⁺/PVP and types of cation, we can well control the morphology of thesamples. A possible formation mechanism is proposed to explain thegrowth of the flue-like nanostructures. The obtained flue-like porousα-Fe₂O₃has large specific surface area of88.82m²g^-1. They exhibitsignificantly enhanced visible-light-driven photocatalytic performance onthe degradation methylene blue, compared with α-Fe₂O₃nanoparticles.This work not only enriches the synthesis methods of porous architectures,but also facilitates the applications of α-Fe₂O₃in the fields of water treatment, sunlight utilization and so forth.