Template synthesis and mesostructural characterization of ordered mesoporous silica, titania and carbon materials have been systematically investigated in this study. In order to obtain a better understanding of the template-precursor relationship, there are two templates adopted in this research. One is the ¡§liquid crystal template (LCT)¡¨, composed of surfactants via self-assembly pathway; the other is the ¡§ordered silica spheres template¡¨, composed of monodispersed SiO2 spheres (~40 nm) via gravity sedimentation. This work was carried out in four related directions: (1) Synthesis and functionalization of ordered mesoporous silicate (MCM-41 and MCM-48) via cationic surfactant template; (2) Using anionic surfactant template-assisted via urea treatment to control the morphology of the TiO2; (3) Synthesis of ordered mesoporous anatase TiO2 via cationic surfactant template; (4) Synthesis of ordered mesoporous carbon from mesophase pitch solution via silica spheres template. Mesoporous silica materials MCM-41 and MCM-48 have been synthesized and identified. The MCM-41 has a hexagonal phase (p6m) with surface area of 1006.90 m2/g and pore size of 37.65 Å, The MCM-48 has cubic phase ( ) with surface area of 1093.34 m2/g and pore size of 29.20 Å. The calcined MCM-41was rehydrated by heating in water and functionalized with 3-amino propyltrimethoxysilane; this functionalized mesoporous silica is targeted as a template of metal oxides, such as TiO2. appears the same tendency of parent MCM-41 in the N2 sorption isotherm measurements. Nanocrystalline TiO2 rods and hollow-tubes with an engraved pattern on the surface have been prepared by the anionic template-assisted sol-gel synthesis via urea treatment and under hydrothermal condition. X-ray diffractometry (XRD) results indicate that these nanocrystallines consist predominantly of anatase TiO2, with minor amounts of rutile and brookite. The crystallographic facetting found from SEM and TEM further reveals the polymorphic nature of the nanocrystalline TiO2 thus prepared. A ¡§reverse micelle¡¨ formation mechanism taking into account the hydrothermal temperature, the pH effect of the sol-gel system, the isoelectric point, the formation of micelles, and the electrostatic interaction between the anionic surfactant and the growing TiO2 particulates is proposed to illustrate the competition between the physical micelle assembly of the ionic surfactants and the chemical hydrolysis and condensation reactions of the Ti precursors. Ordered mesoporous TiO2 materials with an anatase framework have been synthesized by using a cationic surfactant template and soluble peroxytitanates as Ti precursor through an S+I− self-assembly pathway. The low-angle X-ray diffraction (XRD) pattern of the as-prepared mesoporous TiO2 materials indicates a hexagonal mesostructure. XRD and TEM results and N2 sorption isotherms measurements indicate the calcined mesoporous TiO2 possesses an anatase crystalline framework having a maximum pore size of 6.9 nm and a maximum BET specific surface area of 284 m2/g. This ordered mesoporous TiO2 also demonstrates a high photocatalytic activity for degradation of methylene blue under ultraviolet irradiation. Under a lower carbonization temperature and with a mesophase pitch solution as the carbon precursor, ordered mesoporous carbon thick films with 35-nm pore size have been synthesized using SiO2 spheres as the template. The pore size of the mesoporous carbon thus fabricated was the smallest one ever reported using silica templates. SEM and TEM patterns show a discernible morphology of an ordered cubic close-packing of the mesopores interconnected via holes of 6 nm in diameter. From this study, the template synthesis has been proven to be an effective method to fabricate mesoporous silica, polymorphic titania, ordered mesoporous TiO2, and ordered mesoporous carbon materials. Further utilization of this template synthesis is expected to offer a variety of porous networks with a wide range of pore sizes, well-defined morphologies on controllable length scales, and various chemical functionalities to match the needs of different applications.

Ordered mesoporous materials have attracted much attention recently for use in a wide range of applications. The oxidising materials, ceria (CeO₂) and CGO (Ce₀.₉Gd₀.₁O[subscript(2-δ)]) have both been synthesised with ordered mesopores, but a method for the simple fabrication of these materials in high yields with crystalline pore walls has not yet been reported in the literature. This thesis details the development of the vacuum impregnation method for the synthesis of ordered mesoporous materials with emphasis on ceria and CGO. Using the vacuum impregnation method both materials were successfully prepared. The materials exhibited the porous single crystal morphology in high yields, with unusual crystallographic features. Nitrogen physisorption, transmission electron microscopy (TEM), TEM tomography and temperature programmed studies were employed. Temperature programmed studies showed the materials to be catalytically active at lower temperatures than traditionally-prepared ceria. Photovoltaic studies showed that the materials exhibited efficient exciton quenching. The observation of nanowire extrusion during the synthetic procedure assisted in the postulation of a mechanism for product formation in the vacuum impregnation method. The vacuum impregnation method was subsequently shown to be applicable to the synthesis of other materials, with encouraging results presented for ordered mesoporous carbon and Zr₀.₈₄Y₀.₁₆O[subscript(2-δ)]. The syntheses of ordered mesoporous La₀.₈₅Sr₀.₁₅GaO[subscript(3-δ)] and La₀.₇₆Sr₀.₁₉CoO[subscript(3-δ)] were unsuccessful.

The design of nanoparticles in mesoporous supports is explored through synthetic strategies of electrophoretic deposition and electroless deposition with application towards energy storage. Electrophoretic deposition of nanoparticles into a mesoporous thin film is examined using charged nanocrystals in a low-permittivity solvent. To provide a basis for the deposition, the mechanism of particle charging in a low-permittivity solvent was studied. Dispersions of carbon black particles in toluene with an anionic surfactant were characterized using differential-phase optical coherence tomography with close electrode spacing to measure the electrophoretic mobility. The particle charge in concentrated dispersions was found to decrease as a function of increasing surfactant concentration. Partitioning of cations between the surfactant-laden particle surface and micelle cores in the double-layer was found to govern the dynamics of particle charging. Subsequently, charged Au nanocrystals were deposited by electrophoresis within perpendicular mesochannels of a TiO2 support. High loadings of 21 wt% Au with good dispersion were achieved within the mesoporous TiO2 support using electrophoretic deposition, which would otherwise be inhibited by the weak nanocrystal-support interaction. According to a modified Fokker-Planck equation, the mean penetration depth of a single nanocrystal inside of the perpendicular pores was found to be dependent on the electric field strength, electrophoretic mobility, pore diameter, nanocrystal size, and local deposition rate constant. Nanocomposites for electrochemical capacitors were designed via electroless deposition of redox-active MnO2 in a high surface area mesoporous carbon support. Disordered mesoporous carbon supports with a pore size of ~8 nm were used both in amorphous (AMC) and graphitic (GMC) form, with a ~1000-fold larger conductivity for GMC. High loadings of 30 wt% MnO2 were achieved in the AMC in the form of ~1 nm thick domains, which were highly dispersed throughout the support. Oxidation of the GMC was necessary to facilitate wetting and deposition of the MnO2 precursor in order to achieve high loadings of 35 wt% MnO2 with ~1 nm thickness. High gravimetric MnO2 pseudocapacitances of >500 F/gMnO2 were achieved at low loadings and low scan rate of 2 mV/s for both carbon supports. However, at high scan rates ≥100 mV/s, the MnO2 pseudocapacitance is twofold larger for MnO2/GMC, relative to MnO2/AMC. Sodium ion diffusion throughout both MnO2/AMC and MnO2/GMC was shown to be facile. For the GMC versus AMC support, the higher MnO2 pseudocapacitance is attributed to the higher electronic conductivity, which facilitates electron transport to the MnO2 domains. / text

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M.Sc. (Chemistry) / According to the International Union of Applied Chemistry (IUPAC) mesoporous silica materials are a class of materials which contain pore size with diameters ranging from 2 to 50 nm. Due to their attractive features such as large surface area along with tunable pore size, accessible silano groups and easy functionalization make them with special properties to be employed as stationary phases for different chromatographic applications such as clean up, preconcentration, purification and separation of analytical samples. Organic–inorganic mesoporous hybrid materials are a new class of materials obtained when an inorganic material, such as mesoporous silicas are surface modified using an organic material via silylation. The main advantage of these hybrid materials is that they are formed by combining dissimilar properties of inorganic and organic materials into one material. Whereas the inorganic materials provide rigidity and thermal stability, the organic components provide flexibility, dielectric, ductility, and processability. Therefore the advantages of these hybrid materials lead them to be used over a wide range of applications. The main objective of this study was to synthesize organic-inorganic hybrid mesoporous silica materials for use as stationary phases for solid phase extraction and high performance liquid chromatography columns. The materials were prepared under basic conditions using silica gel and tetraethyl orthosilicate used as a source of silica and modified by either surface polymerization or grafting methods using octadecyltrimethoxysilane followed endcapping with hexamethyldisilazane. The materials were characterized before and after surface modification using different analytical methods. Scanning electron microscopy (SEM) pictures showed that the morphology of the materials remained unchanged after surface modification.

Student Number : 0107507J - PhD thesis - School of Chemistry - Faculty of Science / Periodic mesoporous organosilica (PMO) materials (consisting of ethane groups in the framework) and bifunctional periodic mesoporous organosilica materials (consisting of ethane groups in the framework and either glycidoxypropyl groups or aminopropyl groups in the channels) were synthesized by the sol-gel method under basic conditions. Ethanesilica materials were synthesized by condensation of 1,2-bistrimethoxysilylethane (BTME) and by co-condensation of BTME with tetraethylorthosilicate (TEOS). Bifunctional periodic mesoporous organosilica materials were synthesized by the co-condensation of BTME with either 3- glycidoxypropyltriethoxysilane (GPTS) or 3-aminopropyltriethoxysilane (APTS). Cetyltrimethylammonium bromide was used as the structure-directing template. Cobalt ion incorporated ethanesilica and modified ethanesilica materials were synthesized in situ by adding cobalt nitrate to the reaction mixture. Cobalt was also supported on ethanesilica materials and APTS-modified materials by using the incipient wetness impregnation method. Raman spectroscopy and diffuse reflectance infrared spectroscopy (DRIFTS) results confirmed the formation of organosilica materials and showed that the surfactant was removed by solvent extraction. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the ethane portion of the materials (originating from the bridging ethane group in BTME) only decomposed at temperatures > 400 oC. These techniques also showed that the surfactant is removed by solvent extraction. Cobalt ion incorporation was confirmed by Raman spectroscopy and UV-vis diffuse reflectance spectroscopy. Powder powder X-ray diffraction (XRD) and nitrogen adsorption data indicated that the mesophase and textural properties of the materials are dependent on the reaction conditions (i.e. ageing duration, ageing temperature, amount of silica precursor(s), amount of water and amount of base (NH4OH)). The periodicity of the materials was indicated by the presence of low angle diffraction peaks in powder X-ray diffraction patterns. Cubic and hexagonal mesophases were identified using powder X-ray diffraction. When solvent extraction is prolonged, the BET surface area and the pore volume increase, while the average pore diameter decreases. Materials with more dominant XRD structural features and larger d values, higher surface areas, lower pore volumes and average pore diameters are obtained when low ageing temperatures are used. For samples prepared from a mixture of BTME and TEOS at a given temperature, the surface area was found to increase with increasing amount of TEOS added. This trend was observed for materials with and without cobalt. Type IV isotherms, typical of mesoporous materials, were obtained for ethanesilica and modified ethanesilica materials prepared without cobalt. For cobalt incorporated periodic mesoporous ethanesilica materials, the XRD lattice parameter (d100) increased whereas surface area and pore volume decreased with increasing cobalt loading. Nitrogen gas adsorption on samples with varying ratios of BTME:GPTS or BTME:APTS revealed that increasing the amount of GPTS or APTS affects pore size, surface area and pore volume as well as shapes of the isotherms and hysteresis loops. The hysteresis loops of the Type IV isotherms obtained for GPTS-modified ethane silica materials (without cobalt) change from Type H3 to Type H4. There is a tendency for pore sizes to change from mesopore to micropore when the amount of GPTS is increased. Isotherms of cobalt incorporated GPTS-modified ethane silica materials changed from Type IV to Type I. The surface area, pore volume and pore diameter decreased with increasing loading of GPTS or APTS as well as after cobalt incorporation.

The development of mesoporous titania (meso-TiO2) films is a considerable research goal in the field of mesoporous material development due to their proven applicability in solar cells and phtocatalysts. In this work, the meso-TiO2 films were fabricated through different methods and these home-made titania structures were applied in DSSCs and photocatalysts. Meso-TiO2 powders were first prepared from ethanol/water or ethanol solvent. The meso-TiO2 made from the ethanol/water solvent did not have an ordered mesostructure, but that made from ethanol solvent had 2D-hexagonal mesostructure. Films were prepared by adding ordered meso-TiO2 particles into paste formulations of P25 nanoparticles with weight proportion ranging from 0 to 100%. These were used to form films by doctor blading, and the influence of paste composition on film structure, morphology, porosity, optical properties and cell performance were investigated. Secondly, ordered meso-TiO2 films were fabricated by dip coating from aqueous or ethanol solvent. Both films had cubic mesostructures, but the film coated from aqueous solvent was not uniform. The film formed from ethanol solvent was doped with sulphur. The effects of doping on the mesostructure, morphology, structure, optical properties and photocatalytic activity were studied. The thickness of films was increased by repeated coating. The number of layers had an influence on the mesostructure, morphology, optical properties and cell performance when these films were applied in DSSCs Finally, a novel method was adopted to prepared meso-TiO2 films. Molecular titania precursors or titania colloidal seeds were used as the titania source. Both of them can be used to prepare free-standing hybrid films at air-water interface by a self-assembly method, however the one synthesised from the molecular titania precursor did not contain very much titania and became a powder after calcination. In contrast, after calcination, the films formed from the colloidal titania solution remained intact, and were composed of mixtures of TiO2 nanoparticles and nanowires with mesopores arising from interparticle porosity. These films were applied in DSSCs. This interfacial method was also successfully extended to prepare free-standing ZnO films from a molecular precursor. After calcination, the free-standing ZnO films were found to be composed of rough spheres formed by flocculation of smaller nanoparticles.

Mesoporous aggregates of nanocrystalline zeolites with MFI and BEA frameworks have been synthesized using a one-pot and single structure directing agent method. The effect of different reaction conditions, such as temperature, time, pH and water content, on the particle size, surface area and mesopore volume has been studied. Nanocrystalline and mesoporous ZSM-5, β and Y zeolites were modified with different transition metals and the resulting single- and double metal containing catalyst materials were characterized. Nanocrystalline Silicalite-1 zeolite samples with varying particle size were functionalized with different organosilane groups and the cytotoxic activity of the zeolite nanocrystals was studied as a function of particle size, concentration, organic functional group type, as well as the type of cell line. Framework stability of nanocrystalline NaY zeolite was tested under different pH conditions. The synthesized zeolites used in this work were characterized using a variety of physicochemical methods, including powder X-ray diffraction, Solid State NMR, nitrogen sorption, electron microscopy, Inductively Coupled Plasma - Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.

Silica is one of the most abundant elements on the planet, has flexible bonding properties and generally excellent stability. Because of these properties, silica has been a vital component in technologies ranging from ancient glassware to modern supercomputers. Silica is able to form a wide range of materials both alone and as a component of larger material frameworks. Porous silica based nanomaterials are rapidly growing in importance because of their many applications in a wide variety of fields. This thesis focuses on the synthesis of silica based porous nanomaterials: nanocrystalline zeolites, mesoporous silica nanoparticles, and iron oxide core/shell nanocomposites. The synthetic conditions of these materials were varied in order to maximize efficiency, minimize environmental impact, and produce high quality material with far reaching potential applications. The materials were characterized by physicochemical techniques including Transmission Electron Microscopy, Dynamic Light Scattering, Powder X-Ray Diffraction, Solid State NMR, and Nitrogen Adsorption Isotherms. The materials were evaluated and conditions were controlled to produce high yields of quality nanomaterials and hypothesize methods for further synthetic control. The products will be used in studies involving nanoparticle toxicity, environmental remediation, and drug delivery.