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Synthesis and Properties of Nano-metal Oxide by Polyol Process

Author: WangJianWei
Tutor: ChenKeZheng
School: Qingdao University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: magnetite polyol process superparamagnetic zinc oxide crystal structure diluted magnetic semiconductors ZnFe2O4
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 121
Quote: 1
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Abstract


As is well known, many metal oxides are functional materials with excellent physical and chemical properties, and widely applied in many fields including optics, catalysts, microelectronic devices, energy storage and conversion. Chemical preparation of novel nanostructures and the investigation of their general formation processes may be a solution to the precise control of their sizes, structures and morphology. It is of great significance to tailor the property of materials in a controllable way by altering their structure, morphology, or composition. In this paper,systematic explorations have been carried out on new synthetic strategies of metal oxides based on the nonaqueous method. The main points can be summarized as follows:Magnetite nanoparticles have been successfully synthesized in liquid polyols at elevated temperature. Polyol solvent plays a crucial role in determining the morphology and colloidal stability of the resulting particles. The structure and morphology of the nanoparticles were studied using XRD, TEM and FTIR. The magnetic properties of the samples were measured using magnetic properties measurement system （MPMS） of Quantum Design. The results show that as-prepared magnetite nanoparticles are monodisperse, highly crystalline and superparamagnetic at room temperature. The nanoparticles can be easily dispersed in aqueous media and other polar solvents due to coated by a layer of hydrophilic polyol ligands in situ.A facile polyol process was established to prepare zinc oxide monodispersed nanoparticles with controlled shapes and sizes. The different morphologic zinc oxide nanoparticles were obtained by varying reaction condition. The uniform spherical particles were obtained in the presence of whisking. The uniform nanorod-like multi- crystal particles were obtained without whisking. The single-crystal uniform nanorod-like particles were obtained by adding the amount of water in the presence of whisking. So the water played a crucial role in determining the morphology and structure of the synthesized particles. Increasing the amount of water enlarged the aspect ratio of the rod-shaped particles. ZnO nanoparticles were in situ transformed to single-crystal structure by the addition of water. Furthermore, we investigated the growth process of nanorod-shaped ZnO by varying the reaction temperature. Finally, The optical properties of different morphologic zinc oxide nanoparticles have been also investigated.A facile polyol process was established to prepare superparamagnetic Fe-doped ZnO nanoparticles in liquid polyol using Fe（acac）3 and Zn（acac）2 as precursors and triethylene glycol as solvent. Scanning electron microscopy （SEM） images showed that as-prepared nanoparticles are uniform in size and morphology. X-ray diffraction （XRD） analysis revealed that the nanoparticles are of wurtzite structure without impure phase. The successful doping of Fe element into ZnO host was evident by XRD lines shifting and energy dispersive X-ray spectroscopy （EDS） results. Magnetization measurements demonstrated that the Fe-doped ZnO nanoparticles were superparamagnetic at room temperature.ZnFe2O4 nanoparticles were prepared by polyol process based on thermal decomposition of Fe（acac）3 and Zn（acac）2 in triethylene glycol （TEG）.The ZnFe2O4 nanoparticles were studied by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and Quantum Design MPMS SQUID. The results show that the sample has a relatively narrow size distribution with an average particle size of 6nm. The ZnFe2O4 nanoparticles can be easily dispersed in aqueous media. The as-synthesized zinc ferrite nanocrystals are superparamagnetic at room temperature.

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