Clay aerogels are relatively a new class of materials with number of merits suitable for many applications in various industrial sectors. With the current mandate to utilise environmentally friendly materials to produce functional materials, clay aerogels provide an attractive potential green solution to overcome thermal issues in construction. However for it to be effectively used as an insulation material, research work is required to address several critical issues and setbacks: the first of these is poor mechanical properties highlighted in the literature as its main weakness; the second is there extremely high hydrophilic and hygroscopic nature identified as the main research gap, which not only can cause a significant increase in thermal conductivity but also can disintegrate the aerogels. This thesis investigates and develops novel methodologies to overcome the associated setbacks through comprehensive characterisation and better understanding of mechanisms of formulation, architecture, behaviour and corresponding performance of clay aerogel constituents and composites: (I) The anisotropic structure of the aerogel was thoroughly investigated and its influence on properties was established; (II) By adjusting and tuning the mixing temperatures, the compressive modulus was enhanced by more than 7 folds; (III) Ultrasonic technologies were used to prepare organoclay- polyvinyl alcohol aerogel composites with 40% less moisture absorption in addition to lower thermal conductivity; (IV) Implementing organosilanes and isocyanates to prepare clay-PVA aerogels resulted in an effective method to reduce the moisture absorption by more than 40% with a 6 fold increase in compressive modulus; (VI) soluble water repellent was incorporated to prepare hydrophobic aerogel composites with contact angles of 140°; and (VII) Organosilanes and isocyanates are combined with a water repellent to generate highly functional clay aerogel composites. Overall this thesis paves the way for the industrialisation of functional clay-aerogel insulation materials for construction and other sectors.

Diblock copolymers like poly(styrene)-block-poly(2-vinylpyridine) pave the way for controllable self-assembled monolayers of nanoparticles. Using particular polymer weights and concentration, spherical micelles of PS-b-P2VP can be constructed with a non-polar PS corona and a polar P2VP core. Various precursor salts can be loaded into the core of the micelles due to interactions with the polar core which forms as the active site for nanoparticle growth. The PS corona protects the core from the atmosphere and non-polar solvents. The micelles can then act as nanobeakers for aqueous chemistry in two ways; spontaneous reactions between precursors result in nanoparticles or the trapping of precursor salts can be oxidized or reduced using polymer removal techniques like gas plasmas. In this way, reverse micelles are a facile method of growing metal, metal oxide or dielectric nanoparticles. Process parameters, such as concentration, molecular weights, nature of solvents and type of precursor salt, offer control over the periodicity and size of the monolayer of nanoparticles. Reverse micelle templating is a potentially useful nanofabrication method for tailor-made nanoparticles for use in electrical and optical devices which is not limited to form-factor of substrates. In this thesis, obstacles are identified that hinder the utility of PS-b-P2VP templated nanoparticles in device fabrication. The polymer is insulating which is detrimental to electrical applications. Additionally, the characterization of a monolayer of polymers, thus far, is limited to structural techniques such as SEM and AFM. This thesis sheds light on the mechanism of precursor loading in the micelle core, discusses the efficiency of different polymer removal techniques and uses vibrational spectroscopy for the characterization of monolayers of polymer, loaded polymer and nanoparticles. We have tested enhanced Raman methods using AFM probes to extend the resolution of normal Raman to view monolayers of empty polymers as well. Moreover, using FeCl3-loaded polymer micelles, the control offered by PS-b-P2VP templated growth on the crystal structure of nanoparticles is laid bare. The usefulness of the technique is further divulged by using ordered gamma-Fe2O3 nanoparticles in water-splitting photoanodes where they show an increased efficiency with the inclusion of nanoparticles and their periodicity. This is just an example of devices using reverse micelle templated nanoparticles, paving the way for future applications. The flexibility of this method is further revealed by constructing self-assembled Au/SnO2 nanojunctions within the PS-b-P2VP micelle cores. This was done by exploiting the spontaneous redox reaction between HAuCl4 and SnCl2 in an aqueous environment, and so can be replicated for other metals and metal oxides like Pt, Pd, Ag, TiO2 and ZnO2. The composite nanoparticles formed exhibit a tunable size and dispersion as typically seen with PS-b-P2VP micelles and so, can be used for various applications which require metal/metal oxide junctions. / Thesis / Doctor of Philosophy (PhD)

>Magister Scientiae - MSc / Due to the rapid depletion of fossil fuel reserves and the production of environmentally harmful by-products such as carbon dioxide, there is an urgent need for alternate sustainable clean energy. One of the leading candidates in this endeavour is hydrogen, which can be used as an energy carrier since it has a high energy density, zero emissions and is produced from non-depletable resources such as water. The major challenge hindering a hydrogen economy is the lack of safe and effective storage technologies for mobile applications. A prospective solution to this problem lies in the use of porous powdered materials, which adsorb the hydrogen gas. However, the integration of these powdered materials into a storage tank system, results in the pipelines being contaminated during filling cycles. This necessitates the shaping of the porous powdered materials. Among the many shaping techniques available, the electrospinning technique has been proposed as a promising technology since it is a versatile process that is easily scaled-up making it attractive for the applications of the study. Furthermore, the electrospinning process enables the synthesis of nano-sized fibres with attractive hydrogen sorption characteristics. In this regard, the current study employs the electrospinning technique to synthesise electrospun composite fibres for mobile hydrogen storage applications. After electrospinning three polymers, polyacrylonitrile (PAN) was selected as the most suitable polymer because it yielded bead-free electrospun fibres. However, the diameter of the PAN fibres was large/thick which prompted further optimisation of the electrospinning parameters. The optimised electrospinning conditions that yield unbeaded fibres within the desired diameter range (of 300-500 nm) were a PAN concentration of 10 wt%, a flow rate of 0.4 mL/h, a distance of 10 cm between the needle tip and collector plate, and an applied voltage of 8 kV. The study then progressed to the synthesis and characterisation of the pristine porous powdered materials which adsorb hydrogen gas. The porous powdered materials investigated were commercial zeolite 13X, its synthesised templated carbon derivative (ZTC) and Zr (UiO-66) and Cr (MIL-101) based metal-organic frameworks (MOFs). ZTC was synthesised via liquid impregnation coupled with chemical vapour deposition (CVD), and the MOFs were synthesised by the modulated solvothermal method. Analysis of the ZTCs morphology and phase crystallinity show that the carbon templated process using zeolites was successful, however, ZTC was amorphous compared to crystalline zeolite template. The BET surface area was assessed with the aid of nitrogen sorption isotherms for both zeolite 13X and ZTC, and values of 730 and 2717 m²/g, respectively were obtained. The hydrogen adsorption capacity for zeolite 13X was 1.6 wt% and increased to 2.4 wt% in the ZTC material at 77 K and 1 bar. The successful synthesis of well defined, crystalline MOFs was evident from X-ray diffraction and morphological analysis. The BET surface area and hydrogen adsorption for Zr MOF were 1186 m²/g and 1.5 wt%, respectively at 77 K and 1 bar. Cr MOF had a BET surface area of 2618 m²/g and hydrogen adsorption capacity of 1.9 wt% at 77 K and 1 bar. The main focus of the study was to synthesise electrospun composite fibres that can adsorb hydrogen gas and thus provide significant insight in this field of research. As such it examined composite fibres that incorporates porous powdered materials such as zeolite 13X, ZTCs, UiO-66 (Zr) MOF and MIL-101 (Cr) MOF and investigated their ability to adsorb hydrogen gas, which have not been reported previously. The synthesis of composite fibres was achieved by incorporating the porous powdered materials into the PAN resulting in a polymeric blend that was then electrospun. Morphological analysis illustrated that the porous powdered materials were successfully supported by or incorporated within the PAN fibres, forming composite fibres. The BET surface area of the 40 wt% zeolite-PAN and 12.5 wt% ZTC-PAN composite fibres were 440 and 1787 m²/g respectively. Zr MOF and Cr MOF composite fibres had a BET surface area of 815 and 1134 m²/g, respectively. The BET surface area had reduced by 40, 34, 31 and 57% for zeolite 13X, ZTC, Zr MOF and Cr MOF, respectively after these porous powdered materials were incorporated into PAN. The hydrogen adoption capacity for 40 wt% zeolite-PAN, 12.5 wt% ZTC-PAN, 20 wt% Zr MOFPAN and 20 wt% Cr MOF-PAN composite fibres was 0.8, 1.8, 0.9 and 1.1 wt%, respectively. This decrease was attributed to the limited amount of porous powdered materials that could be incorporated into the fibres since only 40 wt% of zeolite 13X, 12.5 wt% of ZTC and 20 wt% of the MOFs were loaded into their respective composite fibres. This was due to the fact that incorporation of greater amounts of porous powdered materials resulted in a viscous polymeric blend that was unable to be electrospun. It is evident from the study that electrospinning is a versatile process that is able to produce composite fibres with promising properties that can potentially advance the research in this field thus providing a practical solution to the problem of integrating loose powdered materials into an on-board hydrogen storage system. / CSIR Young Researchers Establishment Fund (YREF)

The development of new catalysts for organic synthesis is an important pursuit that enables the discovery of new and more efficient reactions and the identification of new reaction mechanisms. Cooperative catalytic systems and bimetallic catalysts represent unique approaches to catalyst development that achieve reactivity that cannot be obtained with a single catalyst or metal. These types of catalysts can activate substrates in unique ways, facilitate reactions under mild conditions, increase substrate scope, and provide access to completely new transformations. The first part of this work describes the development of a cooperative nickel-titanium-catalyzed amination of allylic alcohols. The cooperative effects of the two metals allow for mild reaction conditions that tolerate a larger substrate scope. A unique tandem cyclization amination is also shown that only takes place using both metals. Additionally, the benefits of using boron tethers are shown in the boron templated dimerization of allylic alcohols. This dimerization forms boron-protected 1,3-diols. Derivatization studies were performed that show the synthetic utility of this new transformation. The second portion of this work focuses on the development of a novel bimetallic rhodium complex and its use in organic synthesis. Using a 2-phosphinoimidazole ligand in the presence of carbon monoxide, a bimetallic Rh(II) complex is formed and purified in high yield. This complex shows versatile reactivity and performs reactions that are traditionally catalyzed by both Rh(I) and Rh(II) complexes. An X-ray crystal structure and DFT calculations confirm the bimetallic nature of this catalyst. Our catalyst shows a unique ability to perform reductive eliminations with weak nucleophiles where other rhodium catalysts perform -hydrogen elimination. The utility of this catalyst is shown in the intramolecular hydroamination of allenes to form small and medium sized nitrogen heterocycles. We also describe the development of a bimetallic trifluoroacetoxylation of allenes. This reaction only occurs with our bimetallic catalyst and over 30 examples are shown.

The ability to detect and quantify presence and concentration of unknown gasses is sought for applications ranging from environmental monitoring to medical analysis. Metal oxide based chemical sensing technology currently exists but the ability to provide a compositional gas breakdown reliably within a short time frame is not readily available. A very small sensor that can differentially identify the type and concentration of a gas is required. Novel methods of creating low cost and easily tuned one and two-dimensional gas sensing elements are explored. Tungsten trioxide has been thoroughly documented as an electrochromic coating, but highly sensitive WO3 elements with beam and nanowire structures have yet to be explored. Research of WO3 as a gas sensor encompasses three major components: A suitable sensing chamber with accurate analyte gas flow control and temperature control, a reliable method for WO3 deposition, and a high yield fabrication process. This thesis explores all three of these technologies. Chapter two starts with a summary of existing tungsten trioxide fabrication methods. An overview of WO3 processing follows. A comprehensive setup was designed and created to test the gas sensing response of a series of metal oxide based resistive elements through conductimetric analysis. Chapter three provides an in depth account of gas sensor test chamber design and testing. Critical test chamber aspects such as temperature control, precise gas flow control, highly efficient analyte gas switching and ease of use are presented. Chapter four outlines WO3 electrodeposition and the fabrication of beam structures for testing, while chapter five explores the templated electrodeposition of WO3 segments intercalated between gold nanowire segments. Finally, chapter six provides a summary of the research presented in this thesis as well as future directions and options available for further exploration of WO3 gas sensing elements. / Micro-Electro-Mechanical Systems (MEMS) and Nanosystems

Laboratory directed evolution have enabled the discovery of numerous functional natural and synthetic macromolecules with tailor-made functions. However, approaches that use enzymes to effect the crucial translation from an information carrier molecule such as DNA or RNA to synthetic polymers are limited to producing close analogs of nucleic acids, either due to a strict requirement to hybridize with a nucleic acid template or as a consequence of the limited substrate scope of polymerase enzymes. / Chemistry and Chemical Biology

Surfactant-templated, sol-gel based methodologies for the synthesis of tailored, nanostructured, hybrid inorganic–organic materials are incredibly powerful and versatile. Although growth in this field has been explosive in recent decades, a lot of room remains to contribute to the design and synthesis of new materials, as well as the development of advanced applications. In the work described herein, we firstly explored the synthesis of thick, mesoporous organosilica films and their application as functional coatings for solution-based, fibre-optic heavy metal sensors. Notably, sub-ppm level detection was observed for the detection of Pb(II) in mixed aqueous–organic media in short timeframes, and progress has been made toward synthesizing organotitania films that would allow for heavy metal sensing in purely aqueous solution. Furthermore, the utility of these types of surfactant-templated, organically-functionalized, mesostructured coatings has been preliminarily extended to other types of optical devices for heavy metal sensing. We have also explored the use of designer amphiphilic, alkyl oligosiloxane precursors for the tightly-controlled formation of thin, self-templated, hybrid nanostructured films. Moreover, films bearing uniaxial 2D hexagonal alignment over macroscopic length scales were obtained using polymer-treated substrates to control the interfacial interactions between the film precursors and the substrate surface. In addition, a relatively mild UV / ozone treatment was employed to remove the alkyl moieties from the films to yield porous materials without catastrophic loss of the as-synthesized, mesostructural order. Lastly, novel chiral, binaphthylene-based, periodic mesoporous organosilica (PMO) materials have been prepared. With the aim of demonstrating chiral recognition with such materials, porous, co-continuous capillary monoliths have been synthesized and applied as chiral stationary phases in nano-HPLC and CEC. Notably, enantioselective interactions between our materials and a chiral acetal-based analyte have been observed. Quantification of these enantioselective interactions in chiral PMOs by isothermal titration microcalorimetry is also being pursued. It has thus been demonstrated that a wide array of different functional materials may be accessed through template-based synthetic strategies. By varying parameters such the starting monomers, the sol composition, and the interfacial interactions between reacting species and a given substrate (to name a few), the resulting materials may be tailored to meet the demands of new and emerging technologies. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-05-24 19:50:17.478

No description available.

Carbon nanotubes are appealing materials for nanofabrication due to their unique properties and structures. However, for carbon nanotubes to be used in mass-fabricated devices, precise control of nanotube orientation and location on surfaces is critical. I have developed a technique to align single-walled carbon nanotubes (SWNTs) on surfaces from a droplet of nanotube suspension under gas flow. Fluid motion studies indicate that alignment is likely due to circulation of SWNTs in the droplet. My work provides a facile method for generating oriented nanotubes for nanodevice applications. I have also devised an approach for localizing SWNTs onto 1-pyrenemethylamine-decorated DNA on surfaces. I found that 63% of SWNTs on surfaces were anchored along DNA, and these nanotubes covered ~5% of the total DNA length. This technique was an initial demonstration of DNA-templated SWNT localization. In an improved method to localize SWNTs on DNA templates, dodecyltrimethylammonium bromide was utilized to suspend SWNTs in aqueous media and localize them on DNA electrostatically. SWNT positioning was controlled by the surface DNA arrangement, and the extent of deposition was influenced by the SWNT concentration and number of treatments. Under optimized conditions, 83% of the length of surface DNAs was covered with SWNTs, and 76% of the deposited SWNTs were on DNA. In some regions, nearly continuous SWNT assemblies were formed. This approach should be useful for the fabrication of nanotube nanowires in nanoelectronic circuits. Using my improved procedures, I have localized SWNTs on DNA templates across electrodes and measured the electrical properties of DNA-templated SWNT assemblies. When a DNA-templated SWNT was deposited on top of and bridging electrodes, the measured conductance was comparable to literature values. In contrast, SWNTs with end-on contacts to the sides of electrodes had conductances hundreds of times lower than literature values, probably due to gaps between the SWNT ends and the electrodes. This work provides a novel approach for localizing SWNTs across contacts in a controlled manner. These results may be useful in the fabrication of nanoelectronic devices such as transistors with SWNTs as active components. Moreover, this approach could be valuable in arranging SWNTs as electrical interconnects for nanoelectronics applications.

In the last 20 years there has been a number of synthetic and natural product based molecular replicators published in the literature. The majority of these systems have focused on the minimal model with only a few examples of cross-catalytic or reciprocal replication. Of the cross-catalytic systems investigated the majority focus around the use of natural products, oligonucleotides, peptides etc. This thesis will investigate the design, synthesis and kinetic analysis of both synthetic minimal and reciprocal replicating systems, and how these two forms of replication interact in a complex hypercyclic network. Chapter 1 introduces key concepts such as molecular recognition, intramolecularity/ enzyme kinetic, bisubstrate systems and the work conducted into replication systems to date. Chapter 2 describes the design, synthesis and kinetic analysis of a reciprocal replicating system, based on Diels-Alder and 1,3-dipolar cycloadditions, before going on to discuss what we have learned and how this system can be improved. Chapter 3 focuses on the design, synthesis and kinetic analysis of a replicating network (minimal and reciprocal replication), based on 1,3-dipolar cycloadditions. Initial individual systems are examined in isolation to determine their behavior and nature. After which the systems are combined to observe how each species interacts in a potential complex hypercyclic network. Chapter 4 investigates the redesign of the replicating network in Chapter 3 in order to overcome the problems identified from its kinetic analysis. Chapter 5 introduces the shift in direction away from kinetically controlled replicating networks towards systems in thermodynamic equilibrium.