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Organic - organic self-assembly synthesis of novel carbon nanostructures and its morphology control and characterization of

Author: ZuoZuo
Tutor: ZhaoDongYuan
School: Fudan University
Course: Inorganic Chemistry
Keywords: carbon nanostructures polymer nanostructures mesoporous carbons self-assembly solution phase synthesis morphology control aerosol-assisted assembly solvothermal reaction thermal stability
CLC: TB383.1
Type: PhD thesis
Year: 2007
Downloads: 920
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Abstract

Nanostructured materials have attracted extensive attention of researchers due to their great potential applications. Carbon nanostructures, such as fullerenes, carbon nanotubes and carbon onions, are materials of increasing interest due to their excellent electronic properties as well as their good physical and chemical properties. Conventionally, the solid phase interaction, such as chemical vapor deposition, arc-discharge, laser ablation and plasma radiation, is extensively used in the synthesis of carbon nanostructures because it allows relatively high energy assisted conditions. These synthesis methods have limitations in terms of large-scale and economical production because of their harsh synthetic conditions and low production yields. However, carbon nanostructures have seldom been reported by solution methods which is well suited for studying growth mechanisms of colloidal nanocrystals, especially for nucleation. Therefore, solution method could promisingly be applied in the synthesis of carbon nanostructures which may solve the present synthetic challenges and contribute to the further understanding of the growth mechanisms of carbon nanostructures.The scientific issues of this thesis are based on the concept of synthesis and organic-organic self-assembly of carbon nanostructures in a confined environment. First, we have developed new synthesis strategies of polymer/carbon nanostructures with alternative composites by choosing several kinds of carbon precursors. Secondly, the morphology control and thermal stability of novel mesostructured polymer/carbon materials were studied by using couples of modern analytic techniques. The content of this thesis includes synthesis and characteration of nanostructured and nanoporous carbons, reaction mechanism research, and exploration of the applicable properties.In Chapter 2, a surfactant-templated polymerization method was engaged in fabricating PFA nanostrutures under a solvothermal condition. Single crystalline PFA nanostructures with wire-like morphology were successfully synthesized for the first time under an organic-organic assisted assembly. Both the size and shape of PFA nanostructures can be controlled by the species of organic templates and the reaction time. Furthermore, the organic-organic assembly under the solvothermal process is compatible in fabricating 1-D polymeric nanostructures with different components. In Chapter 3, we demonstrate a low-temperature solution-phase synthesis of graphitic nanostructures by using furfural alcohol and mesophase pitches as carbon precursors through a hot injection method. The kinetics of the nucleation and growth has been sucessfully controlled during the carbon nanostructure evolutions. As a result, three kinds of graphite nanostructures could be obtained by varying the reaction time （5～30 min） or the concentration of H₂SO₄ (0.038～0.061 mol L^-1) in the oleic acid solution. The hot injection synthesis offers a broad synthetic strategy which could be applied into various aromatic molecular polymerization systems in synthesizing high-quality graphite nanostructures. Those materials will surely provide more interesting properties for advanced researches. The assemblies of the aromatic molecules in the solution may be useful for studying the mechanisms of the graphite structural organizations in nanoscale.In Chapter 4, one-step EISA method was engaged in the synthesis of spherical mesoporous polymers via an aerosol-assisted process in which amphiphilic triblock copolymers （PEO-PPO-PEO） were used as templates and a soluble low-molecular weight resol were used as carbon precursors. The block copolymer plays a very important role in directing the organic-organic assemblies. The pore structure of the particles with no visible defects could be simply controlled by adjusting concentrations of surfactants in the reactions or by choosing block copolymers with different EO-block lengths. This approach provides an efficient and productive route to synthesize mesoporous polymer/carbon particles with controllable particle size and pore structures.In Chapter 5, the thermal stabilities of ordered mesoporous carbon FDU-15 are demonstrated by using CO₂, O₂ or water vapor as the activating gases. The effects of activation temperature and treatment time on the thermal behaviors of FDU-15 are systematically investigated for a better understanding of the pore structure and carbon pore wall textures under these conditions. The activation process can simply increase the specific surface area and pore volume of the mesoporous carbons, and open the mesopore channels randomly. It is found that FDU-15 after carbonization at 900℃is thermally stable under CO₂ at 750℃, O₂ at 350℃and water vapor at 800℃for at least 3 h. CO₂ gas is a mild atmosphere to produce great mesopore volumes, while water vapor activation renders a continuous increase of micropore volumes and O₂ gas can rapidly destroy the carbon mesostructures. The residues from activation procedure can provide ordered mesoporous structures with high surface area and adjustable micro- and mesoporosity which are highly desirable for potential applications such as selective heterogeneous catalysis and adsorption.By using the concept of organic-organic self-assembly, three kinds of carbon nanostructures have been successfully developed under solution reactions: 1. 1D crystalline polymer nanostructures with controllable sizes; 2. graphitic carbon nanostructures with different morphologies; 3. mesoporous carbon spheres. Through these serial synthesis investigations, we hope to go deep into the understanding of the principles for the organic-organic assembly, and furthermore, rationally design and preparation of novel materials with better functionality.

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