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Structure-directed Toward Inorganic Nanomaterials: Synthesis, Characterization and Structural-related Properties

Author: WuChangZheng
Tutor: XieYi
School: University of Science and Technology of China
Course: Inorganic Chemistry
Keywords: structure nanomaterials hierarchitectures theoretical analysis first-principle analysis lithium-ion battery structure-related properties
CLC: TB383.1
Type: PhD thesis
Year: 2007
Downloads: 877
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Abstract


The goal of this dissertation is to explore the controllable synthesis of functional inorganic nanostructures by the understanding of the structural characteristics of precursor reactants as well as the target products, providing the effective methodology to control both the phase and morphology of the final products. Based on these ideas, the general synthetic routes have been developed in the present dissertation. Moreover, by clearly understanding the morphology and crystal structural characteristics of the final product, the corresponding structure-dependent properties of the as-obtained functional inorganic nanomaterials, especially for the energy storage area, were also investigated in this dissertation. The details are summarized briefly as follows:1. By selecting proper reactant precursors to target-directed synthesis of functional inorganic nanomaterials, we successfully realized both the desired phase and morphology of the final product. (1) We present an effective synthetic protocol to produce high quality InN nanocrystals using indium iodide (InI3), one member of indium halides, as indium source at a low temperature of <250℃(far below the decomposition temperature of InN). Besides, we also report the first example for orientation-attachment process occurring between the metal nitride particles. (2) We have described a small carbon halides molecule (such as CCl4 and C2Cl6) route to growth of artistic nitrogen-doped carbon nanostructures with the artistic morphologies of nitrogen-doped carbon nanostructures such as particles, whiskers, square frameworks, lamellar layers, hollow spheres, smooth-shell vessels and the vessels with step edges, in which the nitrogen contents can be controlled by adjusting different reaction parameters (temperature, solvent, carbon source etc.). (3) Necklace-like carbon hollow nanospheres (NLCHNSs) have been successfully synthesized from the pentagon-including reactants, which provide a fine auxiliary example for the theory predictions that necklace-like hollow spheres are assumed to be composed by the regular occurrence of non-hexagonal rings at the atomic level. (4) We first constructed the finite cluster model of bamboo-like carbon nitride structure taking the C9N5H3 as an example. As desired, the C9N5H3 bamboo-like nanotubes were successfully prepared by the reaction of cyanuric chloride, ferrocene (Fe(C5H52), and sodium azide (NaN3) in a sealed solvent-free system. The as-prepared C9N5H3 bamboo-like nanotubes show a much higher irreversible and reversible capacity than that of the theoretical capacity of graphite (372 mAhg-1</sup>.2. We successfully developed the combination methodologies of the self-modeling properties of the final product’s crystal structure and the self-produced template route to grow and assemble the three-dimensional hierarchical nanostructures. (1) We developed a new simple chemical synthetic methodology to construct theγ-MnO2 three dimensional nanostructures. We believe that the formation ofγ-MnO2 nanowires is actually the outward embodiment of the nature of the initial crystal structure, while the newly born MnOX solid particles acted as the support for the construction ofγ-MnO2 3D nanostructures. Therefore, highly uniform urchin-likeγ-MnO2 nanostructures via the mild and the direct reaction between MnSO4 and KBrO3. (2) Due to the planar sheet nature of the building blocks in the new-phased VOOH, we used the in-situ produced N2 gas bubbles as the templates to construct VOOH hollow "dandelions". The whole way for hollow "dandelions" is simple and no post-treatment process in the hydrothermal process. The as-obtained VOOH hollow "dandelions" offer the first opportunity to investigate the Li+ charge and discharge electrochemical properties for V3+ oxides. The hollow-dandelion VOOH electrode represents important advantages in terms of low-temperature performance in lithium batteries. (3) We successfully prepared titanate 3D tubular hierarchitectures undergoing the self-produced template methodology coupled with precursor templating approach. The growth of titanate nanoflakes is actually the outward embodiment of the internal crystal structure, while the sacrificed templating effect of the intermediate precursor of TiOXCl2-2x(EN)y is well understood. The morphology-retaining chemical transformation from titanate to anatase titania occurs owing to the low lattice mismatch and structural similarity of titanate and anatase titania. Also, the anatase TiO2 product exhibits desirable photocatalytic activity over the Degussa P-25 TiO2 (Germany) and the rutile hollow spheres, showing good application potential.3. By clearly understanding the morphology and crystal structural characteristics of the final product, the corresponding structure-dependent properties of the as-obtained functional inorganic nanomaterials. (1) The hematite crystal structure is a rhombohedrally centered hexagonal structure of the corundum type with a closed-packed lattice, there are no tunnels or interlayer spacing for accommodating the inorganic ions any more. Therefore, it gives us the inspiration that the lithium intercalation performance and the gas sensors are expected to be improved by increasing the surface area or the porosity of hematite crystals. Note that this work not only provides the first example for the fabrication of hematite nanostructures sensors for detecting HCHO gas, but also gives us the information that the diameter size or porosity of nanorods can also influence the lithium intercalation performances. (2) New-phased hexagonal Cu2SnS3 with the uniform and well-dispersed nanoparticle morphology has been synthesized, representing the first hexagonal-system example in the Cu-Sn-E (S, Se) ternary chalcogenides. Both the theoretical calculation and experimental results give the unique metallic character of Cu2SnS3, which is significantly different from the traditional opinion that I-IV-VI ternary chalcogenides were regarded as small or middle band-gap semiconductors previously. Also, M(I)2SnS3 (M=Ag, Au, Rb, and Cs) serial compounds are a newly potential family ofconducting sulfides.

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