Synthesis And Properties Of Transition Metal Oxide Hybrid Nanostructures

The hybrid nanostructure is an important research area in nanomaterials due to their unique properties. Because the nanomaterials display a wide variety of unusual behavior comparing to their bulk counterparts, there are a lot of important applications for them. The material with single component usually cannot meet the requirement of mulfunctionalities, and a direct route is to integrate different functional materials. Recently there are tremendous achievements in the field of synthesizing hybrid nanostructure. But effective combination of different components in the hybrid structures is still a challenge due to the random nucleation of a second phase or the random mixing of different components.Iron oxides have attracted considerable attention because of their low processing cost and high resistance to corrosion and wide variety of potential uses. Hematite (α-Fe₂O₃) is the most stable iron oxide, with n-type semiconducting properties under ambient conditions, has been used in catalysts, pigments, gas sensors, and lithium-ion batteries. Magnetite is widely used as catalysis, magnetic fluids, biotechnology/biomedicine, data storage, and environmental remediation for its unique electric and magnetic properties. TiO₂ has many promising applications in areas ranging from photovoltaics and photocatalysis to photo-electrochromics and sensors. With the development of the technology in synthesis one-dimensional nanostructure, one-dimensional TiO₂ nanostructure has attracted more attention. TiO₂, a most representative photocatalysts, is a green material which is expected to resolve the problem of energy shortage and environmental pollution. However, pure TiO₂ is low in quantum efficiency and narrow in spectral responding region. These disadvantages place a restriction on its applications. Accordingly, one of the problems in photocatalysis field is to modify TiO₂ and prepare more reactive photocatalysts. Also, it is difficult to recycle TiO₂ powder in nanoscale. We prepare the one-dimensional hybrid nanostructure of TiO₂ by solvothermal method, which could enhence the photocatalytic property and overcome the disadvantage of recycling of TiO₂ powder.We prepared magnetite and hematite under solvothermal conditions by changing different alcohols while Fe(NO₃)₃·9H₂O is used as single iron source and without any additives. We find that the polyols play an important role in the selective synthesis of magnetite and hematite nanoparticles. As polyols with neighboring hydroxyl groups is used, Fe₃O₄ nanoparticles are formed. While the polyols have hydroxyl groups neighboring more than two carbons on the carbon chains,α-Fe₂O₃ nanoparticles are preferred. On the basis of this result, we preparedα-Fe₂O₃ nanoparticles/TiO₂ nanowires and Fe₃O₄ nanoparticles/TiO₂ nanowires hybrid structures via hydrothermal (solvothermal) method. The magnetic properties of the samples are studied. The formation of hybrid structures has significant influence on the magnetic properties. The Morin transition temperature ofα-Fe₂O₃ nanoparticles/TiO₂ nanowires hybrid structure is 190 K. Whereas there is no observable Morin transition for the corresponding isolatedα-Fe₂O₃ nanoparticles with similar average particles size of ca. 20 nm. The blocking temperature of Fe₃O₄ nanoparticles/TiO₂ nanowires hybrid structures also decresed compared with that of the pure Fe₃O₄ with similar average particles size. We also extend our study to fabricate Ag nanoparticles/titanate nanowires and Ag nanoparticles/TiO₂ nanowires hybrid structures while N,N-Dimethylform amide is used as solvent. But we failed in preparing Cu2O nanoparticles/TiO₂ nanowires hybrid structures.