Study On Novel Methods For Synthesis Of Nanoparticles And Mesoporous Metal Oxide Materials

"Nanostructured Materials", also called "Nanomaterials", are materials with one or more dimensions in the 1-100 nm range, including nanosized materials and nanoporous materials. These materials, notable for their extremely small feature size, have special physic-chemical properties and have the potential for wide-ranging applications, such as catalysis, adsorption, separation, sensor, drug delivery and photoelectricity. In this work, magnetite nanoparticles, meso-macroporous TiO2, and ordered mesoporous metal oxides (including Fe2O3, Cr2O3,In2O3, CeO2,Co3O4, NiO, ITO and Mn3O4) have been synthesized in novel ways. The sizes, morphology,phase and properties of these materials have been controlled and adjusted using feasible methods. Especially, the actual mechanism, which affects the synthesis, has been studied in detail. The main contents of this dissertation are following:Novel and facileβ-cyclodextrin-assisted (β-CD-assisted) or sucrose-assisted methods have been employed to prepare superparamagnetic Fe3O4 nanoparticles from a’single iron precursor of FeCl3. Various characterization involving X-raydiffraction (XRD), standard and high-resolution transmission electron microscopy (TEM and HRTEM), electron diffraction (ED), and Raman spectroscopy has integrally testified the formation of pure magnetite nanoparticles with homogeneous morphology. The size of nanoparticles can be adjusted by varying the concentration ofβ-CD or sucrose. The success is ascribed to in situ formation of reducing agent originating from the self-decomposition of P-CD or sucrose under the reaction conditions, which partly reduces Fe3+ ions into Fe2+ ions for final formation of Fe3O4. Another function ofβ-CD or sucrose is also discussed:that they also act as the coating agent to prevent particle growth and agglomeration, which allows the formation of nanoscale and superparamagnetic magnetite with different particle sizes. The saturation magnetization of the as-obtained magnetite is measured and is strongly related to the particle size.Cell-assemblies with different cell shapes have been used as macrotemplates in the bioinspired synthesis of hierarchical meso-macroporous titania with tunable macroporous morphology. The porous materials exhibit relatively homogeneous and uniform macropores with spheroidal, baculiform, and wormlike porous shapes, respectively. The photocatalytic performance of the meso-macroporous titania has also been evaluated by degrading methylene blue (MB) under UV irradiation, which indicates that an optimal catalyst should combine large pores (enabling high substance flow rates) with smaller pores (ensuring high substrate-substance contact) in a connected network.During the synthesis of mesoprous metal oxides using nanocasting method from metal nitrate precursors, a simple and general "thermal treatment" strategy to control the morphology of mesoporous periodicity and crystallinity in a large range has been found. The mechanism behind the phenomenon is discussed in detail and explained clearly as "migration mechanism". The preparation of mesoporous hematite will be first demonstrated as an example, followed by all the other metal oxide examples (including Cr2O3, In2O3, CeO2, Co3O4, NiO and Mn3O4). The morphology and crystallinity can be controlled from ordered mesoporous particles in micrometer dimension with high crystallinity to nanoparticles with low crystallinity in succession. The thermal treatment temperature for Fe2O3 can be decreased from 600℃to only 150℃.Ordered mesoporous indium tin oxide (ITO) materials have been synthesized using nanocasting method with post-doping strategy. The mesoporous morphology and crystallinity can be controlled easily using "migration mechanism" from ordered mesoporous particles in micrometer dimension with high crystallinity to nanoparticles with low crystallinity in succession. The structure, morphology, transparent and conducting properties of the ITO materials have been discussed in detail with different tin contents, thermal treatment atmosphere and temperatures.