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Solution-phase Preparation, Characterization and Properties of Ternary Oxide Micro/nanomaterials

Author: ZhangLei
Tutor: ChenXueTai
School: Nanjing University
Course: Inorganic Chemistry
Keywords: Hierarchical structure microwave solvothermal magnetic property photocatalysis
CLC: TB383.1
Type: PhD thesis
Year: 2011
Downloads: 138
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Abstract

Over the past decade, the design and synthesis of ternary oxides micro/nanostructures with well-defined size and morphology have attracted extensive attention due to their unique properties and potential applications. Recently, the solution-phase construction and patterning of inorganic materials with complex multi-dimensional and hierarchical structures is an important development in the science of organized matter. Materials with such structures exhibit distinguishable electric, magnetic, optical, thermodynamic and mechanical properties, which become the fundamental for design and investigation novel nanodevices, thus exciting considerable research interest of chemistry, physics, and biology etcetera. The objective of this Dissertation is to explore new avenue for the solution-phase fabrication of hierarchical nanostructures and the investigation into their applications. Some simple and effective synthetic approaches have been developed for assembling highly ordered functional structures. The main results are summarized below:1. Nanosheet-assembled Fe2(MoO4)3 microstructures were successfully prepared via a facile microwave-assisted hydrothermal approach, employing Fe(NO3)3-9H2O and (NH4)6Mo7O4·4H2O as starting materials, dilute nitric acid as pH adjuster. The phases and morphologies of the products were characterized by powder X-ray diffraction, energy dispersive spectrometry, transmission electron microscopy, and scanning electron microscopy. Several factors, including the amount of nitric acid, reaction time, temperature and iron source, played crucial roles in the formation of the Fe2(MoO4)3 multilayer stacked structures. Moreover, the photocatalytic properties of the as-prepared Fe2(MoO4)3 samples were also investigated.2. Nanoparticles-assembled FeMoO4 hierarchical hollow spheres were successfully prepared via a facile microwave-assisted solution-phase approach, employing Fe(NO3)3·9H2O and (NH4)6Mo7O4·4H2O as starting materials, water and glycerol as solvent. The phases and morphologies of the products were characterized by powder X-ray diffraction, energy dispersive spectrometry, transmission electron microscopy and scanning electron microscopy. Experimental results indicated that the gas bubbles produced in the process played as soft templates for the formation of hollow structures. Long reaction time was in favor of the self-assembly of the nanoparticles. The appropriate volume of glycerol could increase the viscosity of reaction medium, which effectively tuned the reactivity and diffusion rate of the reagents and kept the bubble "alive".3. Well-aligned Zn2GeO4 nanorod bundles were successfully prepared via a facile microwave-assisted hydrothermal approach, employing Zn(Ac)2·2H2O, GeO2 and ethylenediamine as starting materials, water and PEG-400 as solvent. The phase and morphology of the product was characterized by powder X-ray diffraction, energy dispersive spectrometry, high resolution transmission electron microscopy, and scanning electron microscopy. Experiments indicated that high reaction temperature and long reaction time were in favor of the formation Zn2GeO4 nanorod bundles with pure phase. The appropriate volume of PEG-400 could increase the viscosity of reaction medium, which effectively tuned the reactivity and diffusion rate of the reagents and avoided the agglomeration of the product. The suitable amount of En was found to be essential for the formation of such hierarchical microstructures of Zn2GeO4 nanobundles due to strong base, coordination and well-known structure-directing effect. Moreover, the Zn2GeO4 sample exhibited excellent photocatalytic property for the degradation of MO and RhB. 4. Erythrocyte-like Cd2Ge2O6 superstructures have been successfully prepared via a facile and rapid microwave-assisted solution-phase route, employing Cd(Ac)2’2H2O and GeO2 as starting materials, hydrazine monohydrate as pH adjuster. The phase and morphology of the product were characterized by powder X-ray diffraction, X-ray photoelectron spectrum, energy dispersive spectrometry, high resolution transmission electron microscopy and scanning electron microscopy. Experiments indicated that high reaction temperature and long reaction time facilitated the formation of pure phase Cd2Ge2O6 product. The suitable volume of hydrazine monohydrate was found to be essential for the formation of such Cd2Ge2O6 superstructures due to its well-known linking and base effect. UV-vis diffuse reflectance spectrum of Cd2Ge2O6 sample showed that the absorption edge of Cd2Ge2O6 sample was 318 nm, corresponding to a band gap of～3.91 eV.5. Two kinds of BiOBr nanosheets-assembled microspheres were successfully prepared via a facile, rapid and reliable microwave-assisted solvothermal route, employing Bi(NO3)3·5H2O and cetyltrimethylammonium bromide as starting reagents in the absence or presence of oleic acid. The phase and morphology of the products were characterized by powder X-ray diffraction, energy dispersive spectrometry, high resolution transmission electron microscopy and scanning electron microscopy. Interestingly, both samples exhibited not only strong adsorption abilities, but also excellent photocatalytic activities for methyl orange, rhodamine B and phenol.6. Nanoparticles-assembled BiFeO3 microrods were successfully prepared via a facile solvothermal route, employing Bi(NO3)3·5H2O and Fe(NO3)3·9H2O as starting materials, NaOH as pH adjuster, PVP as surfactant. The phase and morphology of the products were characterized by powder X-ray diffraction, energy dispersive spectrometry, inductively coupled plasma atomic emission spectroscopy, FT-IR spectrscopy and scanning electron microscopy. Experiments indicated that the appropriate amount of NaOH, high reaction temperature and long reaction time facilitated the formation of pure phase BiFeO3 product. The linking effect originated from the interactions between polymer molecules could direct the self-assembly of building blocks into one dimensional nanoparticles-assembled BiFeO3 microrods. Magnetic properties showed that the BiFeO3 nanoparticles and microrods exhibited a weak ferromagnetic order at room temperature and the rod-like product possessed larger coercive force than the nanoparticles.

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