This dissertation addresses the synthesis of oriented mesoporous ceramic films by evaporation induced self-assembly of surfactants and ceramic precursors in films dip coated from ethanol-rich sols. First, the kinetics of silica polycondensation in surfactant templated sol-gel films is studied both before and after deposition using infrared spectroscopy. These observations reveal an induction time (with minimal condensation rate) before curing begins in certain surfactant-templated silica films, which can be utilized to perform post-synthesis modification. This induction time is maximized at high humidity, and by long nonionic surfactant headgroups (rather than, for instance, a trimethylammonium headgroup). The second part of the dissertation addresses lattice Monte Carlo (MC) simulation of the effects of confinement on the 2D hexagonally close packed (HCP) phase formed by 60 vol% surfactant in a polar solvent. The effects of size and type of confining geometry (slit, cylindrical and spherical cavities) and of surface chemistry are simulated. The HCP mesophase orients orthogonal to chemically neutral surfaces which attract both head and tail of the surfactant equally. Novel mesophase geometries are simulated including radially oriented micelles, concentric helices, and concentric porous shells. Utilizing fundamental insights from the kinetics and MC studies, the third part of the dissertation describes the synthesis of silica films with orthogonally tilted HCP mesophase on chemically neutral surfaces. Crosslinking a random copolymer of polyethylene oxide (PEO)-polyproplyene oxide (PPO) on glass slides results in chemically neutral surfaces for the PEO-PPO-PEO triblock copolymer template (P123) used here. The orthogonal orientation of the HCP channels is confirmed using advanced x-ray scattering techniques and electron microscopy. The final part of the dissertation discusses applications of ceramic films with orthogonally tilted (ortho-) HCP mesophase. Silica membranes with ortho-HCP pores are prepared on porous alumina supports, and show permeability of ethanol orders of magnitude greater than films with parallel-oriented HCP channels. Size-selective filtration of gold nanoparticles confirms the absence of any nanoscale cracks in the membranes. For a second application, we prepare titania films with ortho-HCP mesopores. Careful crystallization of the films followed by spinning on an organic hole conducting polymer (P3HT) leads to active bulk heterojunction solar cells.

The field of mesoporous materials has been expanding rapidly in recent years, and has come to include a wide variety of different types of materials from organic to inorganic, as well as hybrid materials that encompass both worlds. The following account explores one type of mesoporous materials, specifically those consisting of silica with an attached organic group that have come to be known as periodic mesoporous organosilicas (PMOs). Much of the work here involves incorporating new types of organic groups into a mesoporous framework for the purpose of adding a useful functionality, either chemical or physical, to the material. Firstly it is shown that a borazine moiety can be successfully incorporated into a mesoporous material with a very high loading. It was further shown that once incorporated into the material many of the borazine moieties are available for further chemical reactions with acids and transition metals. Next, a new class of materials termed hybrid periodic mesoporous organosilicas (HPMOs) was developed that was able to circumvent many of the problems associated with PMO self-assembly. Now, using very simple techniques, virtually any type of silsesquioxane can be incorporated into a PMO, and the organic group can be specifically at the surface of the pores, thereby maximizing its accessibility. And finally, a PMO is made that incorporates buckyballs, and it is shown that, given the right synthetic conditions, the buckyballs are homogeneously distributed throughout the material.

Thesis (Ph. D.)--Michigan State University. Dept. of Chemistry, 2006. / Title from PDF t.p. (viewed on Apr. 16, 2009) Includes bibliographical references. Also issued in print.

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 462-468).

Thesis (Ph.D.) - University of St Andrews, March 2008. / Restricted until 14th March 2009.

Philosophiae Doctor - PhD / Carbon dioxide emissions have become a major concern as they are one of the contributing factors to the “green-house” effect. Recently, much effort has been put into separating carbon dioxide (CO2) from flue gases linked to the combustion processes at fixed point sources. The development of solid sorbents for adsorption based on CO2 capture has attracted much attention. Ordered Mesoporous Silica (OMS) materials have recently attracted much attention as solid adsorbents for capturing CO2. OMS have been investigated for this purpose owing to their high pore volume, large surface area and ease of functionalizationIn this work we report on the synthesis of OMS viz. MCM-41 and SBA-15 along with amorphous silica as adsorbents for CO2 capture. MCM-41 was prepared with surfactants having different alkyl chain lengths (C14TABr, C16TABr and C18TABr) where TABr is trimethylammonium bromide. SBA-15 was prepared using a Triblock copolymer as a structure directing agent for the organization of polymerizing silica species. Commercial amorphous silica gel was used for comparative purposes. Initial characterization OMS with powder X-Ray diffraction (XRD) and small angle diffraction (SAXS) yielded diffraction patterns which may be associated with well-ordered structures of hexagonal mesoporous material. Ease of preparation for MCM-41 materials allowed for convenient scale- up, obtaining highly ordered mesoporous silica MCM-41 at room temperature. SBA-15 was also found to be scaled up with considerable ease through increasing the volume of the autoclave during hydrothermal treatment. Structural, morphological and textural properties of the adsorbents were characterized by N2 physisorption measurements, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). TEM confirmed the hexagonal structure; SEM showed that C14MCM-41 had spheroidal particle morphology whereas SBA-15 displayed rod-like structures. High surface areas of up to 1302, 1186, 1211 and 1024 m2/g for C14MCM-41, C16MCM-41, C18MCM-41 and SBA-15, respectively were obtained. The pore size of MCM-41 materials was increased from 2.6 nm for C14MCM-41 to 4.4 nm in diameter for C18MCM-41 using surfactants with different alkyl chain lengths. CO2 adsorption characteristics of OMS were studied using CO2-temperature programmed desorption (TPD). The results showed that C14MCM-41, C16MCM- 41, C18MCM-41 and SBA-15 desorbed 0.19, 0.16, 0.11 and 0.26 mmol/g respectively. The synthesized OMS were then further modified by grafting various amine moieties on their surfaces in order to increase their CO2 adsorptive capabilities. 3-(Aminopropyl)triethoxysilane (APS), N-[3-(trimethoxysilyl)propyl]ethylene- diamine (TPED), 3-chloropropyl)-trimethoxysilane (CPS), ethyl 2-bromopropanoate, tris(2-aminoethyl)amine (TREN) and guanidine. Several characterization techniques such as XRD, SAXS, HRTEM, HRSEM, TGA, Fourier Transform Infra-Red (FT-IR) spectroscopy, CO2 isotherms and CO2-TPD were used to analyze amine grafted solid sorbents for CO2 capture. The results revealed that the structural integrity of the amine modified sorbents was not compromised during the grafting process. The structural properties of the supports, such as surface area and pore size, nature of amine and the number of amine groups, affected the loading and CO2 adsorption capacity of chemically grafted sorbents. APS grafted amorphous silica gel adsorbed 0.67 mmol/g CO2, which proved to be the highest compared to C18MCM-41 and SBA-15 grafted with APS and TPED. C18MCM-41, SBA-15 and amorphous silica gel were also grafted with TREN and adsorbed 0.42, 0.51 and 0.27 mmol/g of CO2, respectively. A systematic study of guanidine grafted on C14MCM-41, C16MCM-41 and C18MCM-41 was investigated, for the first time, to the best of our knowledge. Structural properties like variation in pore size, proved to enhance the adsorption capacity of the adsorbent, coupled with the guanidine molecules grafted on MCM-41 materials. C18MCM-41-guanidine showed the highest CO2 uptake of the guanidine grafted MCM-41 materials, adsorbing 0.30 mmol/g. A novel synthetic route to TPED-TREN grafted C18MCM-41 and SBA-15, using ethyl 2-bromopropanoate as a linker, was investigated as a potential adsorbent for CO2 capture, for the first time. C18MCM-41-TPED-TREN and SBA-15-TPED-TREN CO2 adsorption capacity were found to be 0.14 and 0.14 mmol/g, respectively.

In this study, two kinds of mesoporous materials were prepared. The first was a silica mesostructure grown within a porous aluminium oxide membrane columnar material (hybrid-AOM). This was prepared using a sol-gel technique with Pluronic P123 triblock copolymer as the structure-directing agent and tetraethyl orthosilicate as the inorganic source. The hybrid-AOM had a similar pore size distribution to that of as-prepared SBA-15 but showed an amorphous character, as demonstrated by nitrogen adsorption and SAXRD. The second type of material was a continuous mesoporous silica thin film, prepared by the dip-coating technique using Pluronic F127 triblock copolymer as the structure-directing agent and the same silica source as hybrid-AOM. The film, which was self-assembled on substrates such as indium tin oxide (ITO), glass and gold, exhibited long-range ordered mesostructures after several treatments and aging. Grazing incidence small-angle X-ray scattering method (GISAXS) showed that the thin film contracted in a direction perpendicular to the substrate after drying and surfactant removal.Removal of the surfactant template from both materials in order to create porous silica was achieved by calcination, ethanol extraction and peroxide-Fe treatments. Calcination was found to be the best method to remove surfactant from both mesostructures (hybrid-AOM and thin film). However, this was found to cause cracking and crumpling of the hybrid-AOM with the evaporated gold being easily peeled off after calcination. Ethanol extraction was thus applied where calcination was not suitable. The surfactant removal was confirmed using an infrared spectroscopy and the structure was confirmed after extraction using 1D X-ray diffraction (XRD). The surface morphology, porosity and crystallinity of the mesostructures prepared were characterized by nitrogen adsorption, scanning electron microscopy and small angle XRD. To form modified electrodes, the hybrid-AOM template was coated by evaporation with pure gold on one side, whilst the mesostructured thin film was grown on either gold or ITO. The permeability of the void space for both hybrid and thin film samples was calculated from the cyclic voltammetry response of a neutral probe (FcMeOH). Cationic ([Ru(bpy)3]2+) and anionic (I-) electroactive species were used to observe the electrochemical response under different pH regimes. FcMeOH was also used to study the effect of KCl concentration on the silica surface charge. Gold and platinum were electrochemically deposited using mesoporous silica as a template.

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In this dissertation, mesoporous silica thin films with tunable features at the nanoscale were fabricated using the triblock copolymer template pathway, with the aim of specifically harvesting the low molecular weight peptides and proteins from human serum, which has been regarded as a potential source of diagnostic biomarkers for the early detection of disease. The superior properties of mesoporous silica have been demonstrated in applications which include chemical sensing, filtration, catalysis, drug-delivery and selective biomolecular uptake. These properties depend on the architectural, physical and chemical properties of the materials, which in turn are determined by the processing parameters in evaporation-induced self-assembly (EISA). Using the different polymer templates and polymer concentration in the precursor solution, various pore size distributions, pore structures and surface hydrophilicities were obtained and applied for nanotexture-selective recovery of low mass proteins. With the assistance of mass spectrometry and statistic analysis, we demonstrated the correlation between the nanophase characteristics of the mesoporous silica thin film and the specificity and efficacy of low mass proteome harvesting. In addition, to overcome the limitations of the pre-functionalization method in polymer selection, plasma ashing was used for the first time for the treatment of the mesoporous silica surface prior to chemical modification. Opposite surface charges due to the different functional groups used, resulted in a distinctive selectivity of the low molecular weight proteins from the serum sample. The mesoporous silica chips operate with extraordinary rapidity, high reproducibility, no sample pre-processing, and substantial independence from sample acquisition and storage temperature.In conclusion our study demonstrates that the ability to tune the physicochemical properties of mesoporous silica surfaces has the potential to promote the use of this material as a tool for the selective separation and concentration of the low molecular weight proteome from complex biological fluids. / text