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Calcium hydroxide samples, obtained as a precipitate from the mixing of solutions of sodium hydroxide with a variety of calcium salts in the optional presence of ethanol and a silylating agent, have been characterised by the techniques of nitrogen adsorption, water vapour adsorption , thermogravimetric analysis, Fourier-transform infra-red spectroscopy, ultra-violet spectroscopy and electron microscopy. The morphology of the samples varied from octahedral crystals to hexagonal prisms to sheets. The individual morphology depends on the conditions of precipitation, the nature and concentration of the calcium salt(s) and the nature of the precipitation medium. It has been shown that a large excess of sodium hydroxide results in octahedral forms, calcium salt(s) in approximate equimolar amount or in large excess to the sodium hydroxide results in hexagonal forms, and sheets are formed in the presence of ethanolic precipitation medium. A poisoning mechanism has been suggested in terms of the morphological properties of the samples. It has been found that the sheet forms of calcium hydroxide can be stabilised by reaction with a silylating agent, resulting in greater thermal stability and chemical stability of the surface. Silylation was found not to occur by direct contact between the precipitated calcium hydroxide samples and silylating agents. Silylation only occurred when precipitation was carried out in the presence of a solution of the silylating agent in absolute ethanol. The silylation of the surface of calcium hydroxide has been found to stabilise the material. Reaction of this with 3-aminopropyltriethoxysilane formed an intermediate which subsequently reacted with p-nitrobenzoyl chloride to form an inorganic - organic composite. The technique of thermogravimetric analysis has been employed to measure the thermal stability of the samples. It has been found that the samples exhibit major weight losses at around 688K for the non-silylated samples and around 918K for the silylated samples. The BETnitrogen and the BET-H20 surface areas of the samples range typically from --1 to 43 m2g-1 , and from 9 to 798 m2g-1 respectively. On the basis of this evidence, taken together with the isotherm shapes it has been shown that: the samples are non-porous; non-silylated calcium hydroxide samples are more hydrophobic than the silylated samples, but upon heat-treatment in air below the decomposition temperature the silylated samples became more hydrophobic, whereas the non-silylated samples became more hydrophilic; samples heated in air at above the decomposition temperature exhibit a dramatic increase in hydrophilicity, the H 20-BET surface areas becoming —800 m2g-1 for non silylated samples, compared to 368 - 600 m 2g-1 for silylated samples, indicative of chemisorption following decomposition of the calcium hydroxide to form calcium oxide.

Porous media and transport within them play technically important roles in many of our industries. However, classical mean field engineering descriptions used to model the complex interactions between the porous medium and the fluids and colloids within it are not completely satisfactory. The design capability of the engineering community would be greatly enhanced if these models could be more clearly linked to the mesoscopic details of the fluid/suspension/porous solid systems. This would allow cheaper, yet quicker, and more innovative design and optimization of systems involving fluid/suspension flow in porous media. Modern techniques for the explicit mesoscopic modelling of porous media, and fluid and colloid transport within them, have developed to a point where their combination in a single simulation tool can be contemplated. However, at present, no such tool exists. The aim of this study was to design and test a comprehensive simulation tool that could accurately model the transport phenomena of any given fluid and colloidal system within any given porous medium at a mesoscopic level. Lattice gas automata (LGA) modelling techniques for fluid and colloid transport, and the Joshi/Quiblier/Adler (JQA) statistical method for reconstructing porous media, were uniquely combined to achieve this. The results of simulations were compared to measurements obtained using an experimental apparatus. The objectives of the study were to: 1) determine a priori the permeability of porous media, and; 2) simulate deposition phenomena observed experimentally. The study showed that permeabilities predicted using the simulation tool were lower than those determined experimentally. Several causes for this were identified, all of which can be addressed in the short-term. Simulated changes in fluid velocity and particle concentration were found to alter the rate and pattern of deposition in a manner consistent with experimental results. Furthermore, the tool provided a rich description of fundamental physical phenomena at the pore scale level. These preliminary findings indicate that the combination of these models provide the basis for further development leading to a mesoscopic modelling tool capable of predicting fluid and colloid transport in porous media.

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Colloids are promising building blocks in material synthesis because of their controllability of size and surface properties. The synthesis of chemically and/or geometrically anisotropic colloidal particles has received attentions with the expectation of building blocks for complex structures. However, the synthesis of anisotropic colloidal particles is by far more difficult than the synthesis of spherical colloidal particles. Lack of monodispersity and productivity of many anisotropic particles often limits their applications as a building block for complex structures. Thus, it is highly desirable to develop methods which can produce a large amount of monodisperse non-spherical particles with controllable asymmetric surface properties. This dissertation details the work for developing such a method. The major result of this dissertation is a synthetic method to produce monodisperse non-spherical colloids with anisotropic surface property in a large quantity. The anisotropic colloid, which we call it as Dimer particle, has two fused lobes like a dumbbell and each lobe’s size can be independently controlled. We present a novel method to synthesize sub-micron size Dimer particles. This method can produce a large amount of submicron-sized Dimer particles with good monodispersity and well-controlled shape. Submicron-sized Dimer particles have been highly desired since they can be used as a building block for self assembly using Brownian motion, colloidal surfactant for Pickering emulsion, and photonic materials. To fully take advantage of the anisotropy of the particles, we develop a facile method to tailor the surface property of each lobe independently by asymmetrically coating the particles with gold nanoparticles. This method doesn’t need the arrangement of particles onto any type of interfaces. Asymmetric coating of gold nanoparticles can be carried out simply by mixing Dimer particles with gold nanoparticles. The formation mechanism of the submicron-sized Dimer particles is explained with evidences. Finally, we illustrate that Dimer particles show rich phase behavior under electric fields and explain the behavior by considering various interactions involved in the system. Our investigation shows that electric field can effectively control the orientation and assembled structure of Dimer particles. In conclusion, these asymmetrically functionalized Dimer particles are promising building blocks to generate suprastructures that will be useful in photonic, electronic and diagnostic applications. / Engineering and Applied Sciences

Deoxyribonucleic acid (DNA) aptamers are oligonucleotides with high specificity and affinity for non-nucleotide targets ranging from molecular species to cellular proteins. Their high affinity, rapid synthesis, and the ease with which they can be chemically modified to include convenient chemical groups (e.g. amine group on 5’ end) make them excellent adaptable ligands for use in colloidal drug delivery vehicles for both uptake and release of therapeutic agents. This work uses pre-identified aptamers for vascular endothelial growth factor (VEGF) to investigate the design of one such vehicle for controlled uptake and release of target therapeutics and analyzes the ability of particle-immobilized aptamers to bind both nucleotide and non-nucleotide targets. Aptamer sequences are immobilized on colloidal microspheres and binding activity of both the primary DNA and protein targets are directly monitored using flow cytometry. Additionally, the dual nature of aptamer-target binding is further investigated by evaluating the effects of simultaneous and serial incubation of the primary targets. Finally, the ability to recover the functionality of the aptamer is evaluated after displacement of the primary DNA target through DNA mediated interactions. It has been shown that the nature of aptamer-target interactions are complex in nature, requiring optimization for each species incorporated into a delivery vehicle; however, partial recovery of aptamer functionality was achieved after hybridization with the primary DNA target.

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