A study was carried out on formulations of organic-inorganic hybrids and their subsequent use as matrices for unidirectional carbon fibre-reinforced composites. The hybrids consist of low molecular weight polyimide precursors and silica which is generated in-situ via the sol-gel route. A special feature of these systems is the use of organofunctional trialkoxysilanes as coupling agents for the two phases and for controlling the resultant morphology. Enhancements are obtained in physicochemical, thermal and mechanical properties of hybrids through morphological modifications achieved in the parent polyimide and silicate materials. Small variations to the composition of the precursors display a substantial effect both on the kinetics of the associated reactions and the final properties of hybrids, often as a result of a change in miscibility of the organic and the inorganic components of the system. The processability of the matrix was evaluated with respect to the fabrication of composites, which in this case is strongly influenced by the gelation behaviour of both the organic pre-polymer and also the inorganic sol-gel component. The kinetics of gelation reactions were examined by dynamic viscometry and by practical tests based on visual observation of the cessation of flow. Differential scanning calorimetry, infrared spectroscopy, thermogravimetric analysis and electron microscopy formed part of the evaluation of the matrix materials. Composites were produced by application of the matrix solution from a variety of formulations on pre-tensioned fibres, followed by vacuum drying and curing under pressure at high temperatures. The properties of these composites were determined by such methods as dynamic mechanical thermal analysis, flexural testing and thermomechanical analysis. From the results obtained in this study, it is concluded that the inclusion of silicate phase in a polyimide matrix in the form of fine co-continuous networks improves the thermal and mechanical properties of the base material, although these are dependent on the overall silicate content and the amount of the coupling agent. High loadings of the coupling agent can cause degradation by chain scission and a reduction of the crosslinking density of the organic pre-polymer.

No description available.

Porous inorganic materials that can be used in applications such as catalysis and separations have been intensely studied due to their potential stability, ease of recovery and high surface areas. Organic-inorganic hybrid materials meet these criteria by exploiting the physical robustness of porous inorganic materials and the chemical functionality of organic materials. While amorphous oxides are widely used industrially as inorganic supports, disordered pore structures make them difficult to characterize. Ordered-mesoporous-silica (OMS), such as SBA-15, that have ordered pores structures simplify characterization and are useful models for studying hybrid materials. Dendrimers, once appropriately functionalized, have high densities of uniformly distributed functional groups. In this thesis, melamine-based dendrimer/SBA-15 hybrids were synthesized and characterized using a wide range of analytical techniques. This thesis shows that the porosity can be independently altered by varying 1) the dendrimer generation, 2) the linker molecule, and 3) the surface amine loading. Cu(II) sequestration results demonstrate that the peripheral functional groups of the dendrimer are readily accessible for binding. This thesis also describes preliminary work toward preparing an enantioselective catalyst using L-proline supported on OMS. This work includes the synthesis and testing of three dendrimer-like proline derivatives. Future work in this area is outlined and will include synthesizing catalysts based on the dendrimer hybrid system previously described. Solution dendrimer syntheses will also be performed to create solution-based catalysts.

Porous inorganic materials that can be used in applications such as catalysis and separations have been intensely studied due to their potential stability, ease of recovery and high surface areas. Organic-inorganic hybrid materials meet these criteria by exploiting the physical robustness of porous inorganic materials and the chemical functionality of organic materials. While amorphous oxides are widely used industrially as inorganic supports, disordered pore structures make them difficult to characterize. Ordered-mesoporous-silica (OMS), such as SBA-15, that have ordered pores structures simplify characterization and are useful models for studying hybrid materials. Dendrimers, once appropriately functionalized, have high densities of uniformly distributed functional groups. In this thesis, melamine-based dendrimer/SBA-15 hybrids were synthesized and characterized using a wide range of analytical techniques. This thesis shows that the porosity can be independently altered by varying 1) the dendrimer generation, 2) the linker molecule, and 3) the surface amine loading. Cu(II) sequestration results demonstrate that the peripheral functional groups of the dendrimer are readily accessible for binding. This thesis also describes preliminary work toward preparing an enantioselective catalyst using L-proline supported on OMS. This work includes the synthesis and testing of three dendrimer-like proline derivatives. Future work in this area is outlined and will include synthesizing catalysts based on the dendrimer hybrid system previously described. Solution dendrimer syntheses will also be performed to create solution-based catalysts.

Kyle Heller, for the Master of Science degree in Mechanical Engineering, presented on October 2020, at Southern Illinois University Carbondale.MAJOR PROFESSOR: Dr. Kanchan Mondal Using powder X-ray diffraction, a material can have its crystalline structure identified. Powder X-ray diffraction alone is not enough if a material is unknown. Usually the exact chemical formula of the material is known, or a secondary analytical method is used to extract additional data in order to analyze the crystalline structure using Bragg’s law and the interplanar relationships. Secondary analytical methods are not as easy or inexpensive though. Generic values could be placed into the more basic structure types to obtain a rough idea of potential crystal types including space groups for the material based on its diffraction peaks. However, with a material that has an unknown spacing between its atoms (d-spacing) this is harder to implement. Thus, the use of a secondary software was employed to further analyze the possibilities. In this thesis, the software used for data extraction and refining were Expo 2014 and CrystalMaker X paired with CrystalDiffract and the final visualization was achieved using Endeavor. Two different titanium based organic inorganic halide perovskites (Dye 3 and Dye 4) prepared at different temperatures were evaluated to identify the crystallographic structure using only x-ray data available. The crystal parameters were calculated, and potential unit cells were visualized. Both the materials were found to be 4 (ABX3) type perovskites. The organic component for Dye 3 was methyl ammonium ion and that of Dye 4 was formamidinium ion. These perovskites have shown potential for use as sensitizers in visible light photovoltaic cells. It was concluded that Dye 4 was orthorhombic with a space grouping of C m c a (space group 64). The associated values were a = b =7.94 Å and c =11.55 Å. Dye 3 was also found to be orthorhombic with space grouping of P c c n (space group 56) being a better fit than C m c a. The associated values were a=b=16 Å and c=11 Å.

This thesis concerns the synthesis of N^N- and N^C-chelate four coordinate organoboron compounds and the investigation of their photophysical and photochemical properties. The preparation of a novel BODIPY derivative possessing unusual dual emissive property has been accomplished. The origin of the dual emission was determined through a detailed investigation. The use of the new BODIPY compound as a highly effective surface ligand for achieving highly uniform and monodispersed PbS nanoparticles has been demonstrated. Electronic communication between BODIPY ligands at the nanoparticle surface and the PbS core has also been established. The incorporation of BODIPY-bearing PbS nanoparticles into a simple photovoltaic device was shown to enhance the device’s performance. The preparation of two new BODIPY molecules decorated with either BMes2(vinyl) units or N^C-chelate boryl units has been achieved. Substitution at the meso or the 2,6-positions of the BODIPY core resulted in a significant shift of the emission energy with respect to that of the parent compound. In contrast, replacement of the fluorine substituents with BMes2-vinyl or B(ppy)Mes2-alkynyl groups did not affect the emission wavelength. Both molecules exhibited excellent photophysical properties in solution and the solid state. The BMes2(vinyl) unit greatly enhances BODIPY fluorescence efficiency in a PMMA matrix. Meanwhile, the photoreactivity of the N^C-chelate boryl unit is switched off completely by the BODIPY ligand via intramolecular energy transfer. A new class of N^C-chelate organoboron compounds have been synthesized. This class of compounds has been found to display unprecedented photo-reactivity, namely, photo-elimination reactions, which enabled the synthesis of new B-N substituted phenanthrene compounds in high conversion yields. The new B-N substituted phenanthrene compounds exhibited excellent absorptive and emissive properties with potential applications in optoelectronic devices. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-04-22 15:53:14.091

Polyoxometalates (POMs), which are inorganic metal oxide cluster anions with discrete structures, have been extensively studied in recent years due to their large variety of applications such as medicine, biology, catalysis, material sciences and chemical analysis. Ruthenium polypyridyl complexes have been extensively studied for their applications as photosensitizers in solar energy conversion and photoelectronic materials. Recently, ruthenium heterocyclic ligand complex-based building blocks have been used for the synthesis of hybrid organic-inorganic solids through the self-assembly. We are interested in the synthesis of ruthenium polypyridyl complexes and polyoxometalate anions through different ways such as coordination bonds, hydrogen bonds and ionic bonds to form hybrid organic-inorganic solids. Here, we report four novel hybrid organicinorganic compounds, [Ru(2,2¡¦-bpy)3]2[SiW12O40] (1), [Ru(2,2¡¦- bpy)2(CH3CN)2]2[SiW12O40] (2), [Ru(2,2¡¦-bpy)3][W6O19] (3), and [Ru(2,2¡¦- bpy)3]2[Mo8O26]„ª5H2O (4) ), (2,2¡¦-bpy = 2,2¡¦-bipyridine). Compounds 1, 3, and 4 were synthesized under hydrothermal reaction methods and compound 2 was synthesized by room temperature solution method. These solids were characterized by elemental analysis, UV-vis spectroscopy, fluorescence spectroscopy, thermogravimetric analysis, IR spectroscopy, powder X-ray diffraction, and Single crystal X-ray diffraction. X-ray xii crystallographic study showed that the crystal structures of compounds 1, 2, 3 and 4 were constructed by Coulombic forces and supramolecular interactions. These molecular compounds were further connected and formed 3D structure through Cƒ{H„ª„ª„ªOPOM and other weak interactions. Spectroscopic studies demonstrated that electronic communication occurred between POMs and the sensitizers.

No description available.

ZnO nanowire arrays (NWAs) and Al-doped ZnO (AZO) cathodes were applied in hybrid organic / inorganic solar cells for lower-cost solar energy. Parameters for the electrodeposition of ZnO NWAs and the fabrication of NWA-free baseline devices were systematically optimized using ITO as the cathodes. High efficiencies of up to 5.4% were achieved. Incorporation of the ZnO NWAs into the baseline devices significantly reduced their efficiencies due to possible shorting in the active layer. Devices fabricated using AZO cathodes were characterized. The AZO-based devices achieved efficiencies of up to ~4.8%, showing promising results for the application of AZO as an ITO alternative. Formation of numerous large nanoplatelets was observed during the electrodeposition of ZnO NWAs on AZO cathodes. The NWAs grown on AZO cathodes were also non-uniform. Future studies were proposed to address the issues with incorporation of ZnO NWAs in hybrid solar cells and their combination with AZO cathodes.

ZnO nanowire arrays (NWAs) and Al-doped ZnO (AZO) cathodes were applied in hybrid organic / inorganic solar cells for lower-cost solar energy. Parameters for the electrodeposition of ZnO NWAs and the fabrication of NWA-free baseline devices were systematically optimized using ITO as the cathodes. High efficiencies of up to 5.4% were achieved. Incorporation of the ZnO NWAs into the baseline devices significantly reduced their efficiencies due to possible shorting in the active layer. Devices fabricated using AZO cathodes were characterized. The AZO-based devices achieved efficiencies of up to ~4.8%, showing promising results for the application of AZO as an ITO alternative. Formation of numerous large nanoplatelets was observed during the electrodeposition of ZnO NWAs on AZO cathodes. The NWAs grown on AZO cathodes were also non-uniform. Future studies were proposed to address the issues with incorporation of ZnO NWAs in hybrid solar cells and their combination with AZO cathodes.