Dissertations / Theses on the topic 'Mesoporous silica'

Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Jacob. Karl; Committee Member: Griffin. Anselm; Committee Member: Tannenbaum. Rina; Committee Member: Thio. Yonathan S; Committee Member: Yao. Donggang. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Mesoporous silica particles are of significant interest for biomedical applications due to their good general biocompatibility compared to other nanoparticle matrices such as quantum dots, high specific surface areas up to 1000 m2/g, and extreme synthetic tunability in terms of particle size, pore size and topology, core material, and surface functionalization. For one application, drug delivery, mesoporous silica nanoparticles (MSNs) of two pore structures, MCM-41 – parallel, hexagonally ordered pores approximately 3 nm in diameter – and wormhole (WO) – interconnected, disordered pores also approximately 3 nm in diameter – were synthesized with particle diameters under 100 nm. Additionally, a magnetic Fe3O4 nanoparticle core was incorporated into Fe3O4-core WO-MS-shell particles. The particles were loaded with doxorubicin, a chemotherapeutic, and the drug release into phosphate buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The data were fit to three models: Korsmeyer-Peppas, first order exponential release, and Weibull. The Korsmeyer-Peppas model provided useful information concerning the kinetics and mechanism of drug release from each MSN type. A small but statistically significant difference in the release kinetics was found due to the different pore topologies. A much larger kinetic effect was observed due to the inclusion of an iron oxide core. Applying a static magnetic field to the Fe3O4-core WO-MS shell particles did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials. In vitro cell studies were conducted to determine the cytotoxicity of the bare and doxorubicin-loaded materials against three cancerous cell lines – A549 human lung carcinoma cells, HEC50CO human endometrial cancer cells, and CT26 mouse colon cancer cells. The MCM-41 and WO MSNs generally displayed similar toxicities within each cell line, and the Fe3O4-core WO-MS shell particles were less toxic. Doxorubicin-loaded particles generally displayed greater toxicity than bare MSNs, but the A549 cells were very resistant to all concentrations of MSNs tested. For another biomedical application, tissue phantom development, mesoporous silica particles with approximately 10 μm diameters and C18 surface functionalization were evaluated for their use as a substrate for optical tissue phantoms. Tissue phantoms are synthetic imitations of biological material, and C18-modified silica provides a substrate that is simple to load with optically active biological molecules. The molecules are then hydrophobically trapped to maintain a clear optical boundary between the biological loading within the particle and an aqueous suspension gel. Several preparation techniques were evaluated for the dispersal of hydrophobic particles in aqueous media, and qualitative analysis indicated that surfactant coating of the outer surface could fully disperse the hydrophobic particle while maintaining the clear optical boundary. A novel analysis was developed to provide a single numerical indicator of clustering for a quantitative assessment of particle dispersal in tissue phantoms.

Metalle werden oft während ihrer Anwendung korrosiven Bedingungen ausgesetzt, was ihre Alterungsbeständigkeit reduziert. Deswegen werden korrosionsanfällige Metalle, wie Aluminiumlegierungen mit Schutzbeschichtungen versehen, um den Korrosionsprozess aktiv oder passiv zu verhindern. Die klassischen Schutzbeschichtungen funktionieren als physikalische Barriere zwischen Metall und korrosiver Umgebung und bieten einen passiven Korrosionsschutz nur, wenn sie unbeschädigt sind. Im Gegensatz dazu kann die Korrosion auch im Fall einer Beschädigung mittels aktiver Schutzbeschichtungen gehemmt werden. Chromathaltige Beschichtungen bieten heutzutage den besten aktiven Korrosionsschutz für Aluminiumlegierungen. Aufgrund ihrer Giftigkeit wurden diese weltweit verboten und müssen durch neue umweltfreundliche Schutzbeschichtungen ersetzt werden. Ein potentieller Ersatz sind Schutzbeschichtungen mit integrierten Nano- und Mikrobehältern, die mit ungiftigem Inhibitor gefüllt sind. In dieser Arbeit werden die Entwicklung und Optimierung solcher aktiver Schutzbeschichtungen für die industriell wichtige Aluminiumlegierung AA2024-T3 dargestellt Mesoporöse Silika-Behälter wurden mit dem ungiftigen Inhibitor (2-Mercaptobenzothiazol) beladen und dann in die Matrix anorganischer (SiOx/ZrOx) oder organischer (wasserbasiert) Schichten dispergiert. Zwei Sorten von Silika-Behältern mit unterschiedlichen Größen (d ≈ 80 and 700 nm) wurden verwendet. Diese haben eine große spezifische Oberfläche (≈ 1000 m² g-1), eine enge Porengrößenverteilung mit mittlerer Porenweite ≈ 3 nm und ein großes Porenvolumen (≈ 1 mL g-1). Dank dieser Eigenschaften können große Inhibitormengen im Behälterinneren adsorbiert und gehalten werden. Die Inhibitormoleküle werden bei korrosionsbedingter Erhöhung des pH-Wertes gelöst und freigegeben. Die Konzentration, Position und Größe der integrierten Behälter wurden variiert um die besten Bedingungen für einen optimalen Korrosionsschutz zu bestimmen. Es wurde festgestellt, dass eine gute Korrosionsschutzleistung durch einen Kompromiss zwischen ausreichender Inhibitormenge und guten Barriereeigenschaften hervorgerufen wird. Diese Studie erweitert das Wissen über die wichtigsten Faktoren, die den Korrosionsschutz beeinflussen. Somit wurde die Entwicklung effizienter, aktiver Schutzbeschichtungen ermöglicht, die auf mit Inhibitor beladenen Behältern basieren.
Metals are often used in environments that are conducive to corrosion, which leads to a reduction in their mechanical properties and durability. Coatings are applied to corrosion-prone metals such as aluminum alloys to inhibit the destructive surface process of corrosion in a passive or active way. Standard anticorrosive coatings function as a physical barrier between the material and the corrosive environment and provide passive protection only when intact. In contrast, active protection prevents or slows down corrosion even when the main barrier is damaged. The most effective industrially used active corrosion inhibition for aluminum alloys is provided by chromate conversion coatings. However, their toxicity and worldwide restriction provoke an urgent need for finding environmentally friendly corrosion preventing systems. A promising approach to replace the toxic chromate coatings is to embed particles containing nontoxic inhibitor in a passive coating matrix. This work presents the development and optimization of effective anticorrosive coatings for the industrially important aluminum alloy, AA2024-T3 using this approach. The protective coatings were prepared by dispersing mesoporous silica containers, loaded with the nontoxic corrosion inhibitor 2-mercaptobenzothiazole, in a passive sol-gel (SiOx/ZrOx) or organic water-based layer. Two types of porous silica containers with different sizes (d ≈ 80 and 700 nm, respectively) were investigated. The studied robust containers exhibit high surface area (≈ 1000 m² g-1), narrow pore size distribution (dpore ≈ 3 nm) and large pore volume (≈ 1 mL g-1) as determined by N2 sorption measurements. These properties favored the subsequent adsorption and storage of a relatively large amount of inhibitor as well as its release in response to pH changes induced by the corrosion process. The concentration, position and size of the embedded containers were varied to ascertain the optimum conditions for overall anticorrosion performance. Attaining high anticorrosion efficiency was found to require a compromise between delivering an optimal amount of corrosion inhibitor and preserving the coating barrier properties. This study broadens the knowledge about the main factors influencing the coating anticorrosion efficiency and assists the development of optimum active anticorrosive coatings doped with inhibitor loaded containers.

Catalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material’s morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter. In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH4F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method. It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH4F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH4F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants. The separated particles can be attached to substrates, either during the particle synthesis or by post grafting prior to calcination. The film formation during the one-pot-synthesis was studied and a formation mechanism including nucleation of elongated micelles on the substrate was suggested. During the post grafting film synthesis, the medium in which the particles are dispersed, as well as functionalization of both particle and substrate are crucial for the post grafting process. The pores are easily accessible independent of the method, even though they are aligned parallel to the substrate when the one-pot-method is used, while post grafting gives a perpendicular pore orientation. In summary, this work aims to give an understanding for the formation of the synthesized material, and how to tune the material properties by alterations in parameter space. Successful syntheses of four different particle morphologies and two new types of films were performed, and the pore size could easily be tuned by various methods.

The main theme of this dissertation is the fabrication and analysis of modified mesoporous silica membranes for separation applications. Synthesis methods for mesoporous silica membranes have been developed to enhance the transport performance and quality of the membranes, such as permeability, pore volume, and surface area. Then, synthesized membranes were modified with different organic groups to tailor selectivity in separations. The collected studies of modified mesoporous silica membranes showed that appropriate functionalization on newly synthesized novel membranes leads to promising structural and permeation properties. First, a seeded growth method was developed for synthesis of MCM-48 membranes on alumina supports, thereby extending the seeded growth technique used for zeolite membranes to mesoporous silica membrane synthesis. The surface properties of the MCM-48 membranes were then modified by silylation with hexamethyldisilazane (HMDS). In comparison to MCM-48 membranes previously synthesized by the in situ growth technique, much less silica infiltration into the alumina support was observed. The pore structure of the MCM-48 membranes demonstrated that a large accessible pore volume was available for molecular permeation and pore modification to tailor selectivity. The gas permeation properties of the calcined and silylated MCM-48 membranes were consistent with a Knudsen-like mechanism, albeit with a substantial influence of gas-solid interactions in the mesopores. The silylated MCM-48 membranes were evaluated for pervaporative separation of ethanol (EtOH), methyl ethyl ketone (MEK), and ethyl acetate (EA) from their dilute aqueous solutions. The synthesized membranes exhibited high pervaporative separation factors and organic fluxes. The selective separation of organic/water mixtures with MCM-48 membranes were attributed to both the organophilic nature of the surface and the effective pore size of the silylated mesopores. Next, the synthesis and organic/water separation properties of mesoporous silica membranes supported on low-cost and scalable polymeric (polyamide-imide) hollow fibers and modified by trimethylsilylation with HMDS was studied. Thin, defect-free membranes that exhibited high gas permeances consistent with Knudsen-like diffusion through the mesopores were prepared. Silylation of these membranes did not affect the integrity of the mesoporous silica structure and the underlying polymeric hollow fiber, but led to capping of the surface silanol groups in the mesopores with trimethylsilyl groups. The silylated mesoporous membranes were evaluated for pervaporative separation of EtOH, MEK, EA, iso-butanol, and n-butanol from their dilute aqueous solutions. The membranes showed higher separation factors than those of flat membranes, along with high organic fluxes. The large increase in hydrophobicity of the membranes upon silylation allowed upgrading of the feed mixtures to permeate streams with considerably higher organic content. The selective separation of organic/water mixtures with the fiber-supported mesoporous silica membranes was attributed to both the organophilic nature of the surface (yielding good adsorption selectivity) and the effective pore size of the silylated mesopores (giving good fluxes). Comparison with other types of organic/water separation membranes revealed that the present silylated membrane platform shows good promise for use in organic/water separation applications due to its high flux, scalable and low-cost fabrication methodology, and good separation factors that can be further enhanced by tailoring the mesopore modification chemistry. Further, the gas transport properties of aziridine-functionalized mesoporous silica membranes on polymeric hollow fibers have also investigated. The mesoporous membranes were amine-functionalized with aziridine and their transport properties were studied to understand the effects of surface functionalization on gas separations. This new hybrid aminosilica membrane showed interesting and counter-intuitive N₂ selective permeation properties in dry CO₂/N₂ separations. Detailed characterization of the membrane structure and its permeation behavior showed that such behavior was due to the strong adsorption of CO₂, leading to reduced gas flux because of CO₂-induced amine crosslinking in the mesopores. This hyper-branched aminosilica membrane showed CO₂ selective properties when applied to humid gas permeation. Water molecules in the humid gas affected the adsorption of CO₂ molecules by causing a lower degree of crosslinking, allowing facilitated transport of CO₂.

A literature review of medical implant applications of mesoporous silica films was written, highlighting the advantages and limitations of different film synthesis methods. Both films synthesized through the EISA sol-gel method and particulate films, including those synthesized through the direct growth method, were reviewed and discussed. All films were found to have their strengths and weaknesses, however, the films synthesized through the direct growth method was found to be the most promising type for coating implants. In addition to the literature review, copper-doped mesoporous silica films were synthesized on titanium grade 2 substrates. SEM shows that particles grown on all the films and EDX elemental analysis confirms the presence of copper in the material. Nitrogen physisorption measurements show that particles with incorporated copper have a higher specific surface area, and pore volume compared to un-doped particles. No copper content could be confirmed through FTIR. The particles grown on titanium substrates were more rod-like compared to the ones grown on the silicon substrates as control.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
In recent years, mesoporous silica has attracted considerable scientifical and industrial interest. This material possess physical and chemical properties, which makes it to be used in a variety of applications. These properties include thermal stability, mechanical strength and low solubility, which makes it an ideal matrix support for catalysts. The heterogeneous catalysis has the advantage of separating catalyst from the reaction medium, which justifies the interest in heterogeneous catalysts. Coordination compounds are widely used in homogeneous catalytic processes, based on this there is a growing interest in producing catalytic systems onto heterogeneous silica matrices making very interesting materials. In this work, ruthenium complexes, [RuIICl2(dppb)(PPh3)] and [RuIIICl3(dppb)(OH2)] were synthesized and immobilized onto mesoporous silica matrices modified with aminopropyl and bipyridine groups forming the systems known as Si-apts-bipy-RuIICl2dppb and Si-apts-[bipy-RuIIICl2dppb]Cl-. These systems were characterized by spectroscopic techniques (FTIR, NMR and electronic absorption), electrochemical (cyclic and square wave voltammetry), thermogravimetry (TG), isotherms of adsorption / desorption of N2 and elemental analysis (CHN). The N2 adsorption isotherms using BJH (Barret, Joyner and Halenda) method for matrices shows the synthesized material has characteristics of micro and mesoporous with predominantly mesopore size. Si-apts-bipy-RuIICl2dppb system was the only one that showed catalytic activity in the reaction of hydrogenation of acetophenone with a yield of 53%. The development of catalysts in solid matrices is an area of great interest, which has justified this work.
A sÃlica mesoporosa à um material bastante versÃtil, com porosidade fÃcil de ser moldada tanto em forma quanto em tamanho, alÃm de possuir propriedades fÃsicas e quÃmicas que lhe possibilitam diversas aplicaÃÃes. Dessas propriedades destacamos a sua estabilidade tÃrmica, sua resistÃncia mecÃnica e sua pouca solubilidade as quais a tornam um suporte ideal para catalisadores. Nesse sentido, o uso de compostos de coordenaÃÃo ancorados em matrizes sÃlidas torna-se um interessante sistema a ser estudado, tendo em vista as propriedades, jà bem conhecidas, de alguns complexos metÃlicos de atuarem em catÃlise homogÃnea. De acordo com dados na literatura hà um contÃnuo interesse na sÃntese e caracterizaÃÃo de materiais mesoestruturados aplicados a heterogeinizaÃÃo de catalisadores, como por exemplo, o uso de compostos de coordenaÃÃo. Neste trabalho os complexos de rutÃnio, [RuIICl2(dppb)(PPh3)] e [RuIIICl3(dppb)(OH2)] foram sintetizados e imobilizados em matrizes de sÃlica mesoporosa modificada com grupos aminopropil e bipiridinÃcos, formando os sistemas denominados como Si-apts-bipy-RuIICl2dppb e Si-apts-[bipy-RuIIICl2dppb]Cl. Estes sistemas foram caracterizados por tÃcnicas espectroscÃpicas (FTIR, UV-Vis e RMN de 13C, 29Si e 31P), eletroquÃmicas (voltametria CÃclica e Voltametria de onda quadrada), termogravimÃtricas (TG), isotermas de adsorÃÃo/desorÃÃo de N2 e anÃlise elementar (CHN). As isotermas de N2 para adsorÃÃo pelo mÃtodo BJH (Barret, Joyner e Halenda) para as matrizes indicam que o material sintetizado neste trabalho apresenta caraterÃsticas micro e mesoporosas com predominÃncia de mesoporos. Dos materiais sintetizados apenas o sistema Si-apts-bipy-RuIICl2dppb apresentou atividade catalÃtica na reaÃÃo de hidrogenaÃÃo da acetofenona com um rendimento de 53%. O desenvolvimento de catalisadores em matrizes sÃlidas à uma Ãrea ampla e de grande interesse o que justifica o desenvolvimento deste trabalho.

The work described in this thesis is concerned with the development of ordered mesoporous silicas by direct templating from lyotropic liquid crystal phases of the surfactants Pluronic PI23, Pluronic F127, CTAB and Brij 78. The factors affecting the regularity, morphology, pore diameter and wall thickness of the templated mesoporous silicas were examined by exploring the reaction composition space and plotting the structural properties on TMOS/surfactant/water ternary diagrams. The silicas were studied using the complementary techniques of small angle X-ray diffraction, transmission electron microscopy and N? adsorption isotherms. Mesoporous silicas with hexagonal (H,) pore morphologies templated from the Hi phase of CTAB were prepared from fumed silica/CTAB/water/NaOH mixtures under hydrothermal conditions. The mesostructure showed very good long-range order and very narrow pore size distributions, with -3.4 mn diameter pores and -1.4 mn thick walls. In addition, mesoporous silicas were prepared using a sol-gel route from TMOS/surfactant/0.5 M HCl(aq) mixtures at 45°C. The central regions of the ternary diagrams of these mixtures were explored. Using Pluronic PI23, mesoporous silicas with hexagonal (Hi) pore morphologies were formed with pore diameters in the range of 5 - 10 nm. With Brij 78 and Pluronic F127, mesoporous silicas with 3d cubic pore morphologies were formed with pore diameters in the range of 2.9 - 4.5 mn and 4 - 1 0 nm for Brij 78 and Pluronic F127 respectively. The mesoporous silicas produced via the sol-gel route had the most ordered structures with a TMOS:water molar ratio in the range of 1:5 to 1:7, leaving little water present after hydrolysis. For ordered silicas, the sum of the pore diameter and wall thickness is roughly constant, where the pore diameter decreases with increasing TMOS content and decreasing surfactant content there is commensurate increase in wall thickness. Finally, 1,3,5 trimethyl benzene was used to swell the hydrophobic core of Pluronic PI 23 and F127 micelles, allowing the templating of mesoporous silica with pore diameters up to 14 nm.

We discus methods for fabrication of silica and composite nanoparticles, which can be used in various biomedical applications. The most promising types of such nanostructures are hollow silica nanosheres, sil-ica coated plasmon-resonant nanoparticles (gold nanorods and gold-silver nanocages) and nanorattles. Mesoporous silica shell can be doped by desirable targeting molecules. Here we present the results of for-mation of nanocomposites composed of gold nanorods and double-layer silica shell. The secondary mesopo-rous silica shell is doped with a photosensitizer (hematoporphyrine in our case). We demonstate some of promising theranostics applications of these nanocomposites for bioimaging and in vivo therapy of tumors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35481

The adsorption of cytochrome c onto mesoporous silica (MCM-41) was investigated in this study. MCM-41 was synthesized and characterized by different methods. The pore size of MCM-41 was calculated from each method and all were in agreement with each other. Result from SAXS method showed a well ordered 2D hexagonal structure of MCM- 41. To investigate the effect of pH on adsorption process, different buffers were used with various pH in the range from 3.8 to 10.7. It was observed that the maximum adsorption occurs at pH near the isoelectric point of cytochrome c. The surface charges of cytochrome c and MCM-41 play an essential role for the process of adsorption. Desorption of cytochrome c from MCM-41 was investigated as well. Pure water and buffers with pH 7.1 and 10.7 were used to study the desorption. The result shows that desorption of cytochrome c from MCM-41 takes place at a pH above its isoelectric point.

Materials chemistry represents a very broad, but extremely applicable field of study to everyday life. Since many of the useful applications of these ‘sponge-like’ porous materials are dependent on the amount of surface area, the development and use of highly-porous materials with tremendous surface areas significantly enhances the effectiveness of these materials. Examples of such traditional applications include adsorption, separation, and catalytic applications. The study of porous materials has brought the ability to accurately synthesize and modify these materials to meet specific application requirements. The field of porous materials has been traditionally dominated by many “natural” or traditionally inspired materials such as zeolites and porous carbon materials. Although very effective, these materials have very small pore-windows that prevent their application in all but very small molecule applications. This limitation drove the development of large pore-window materials in the 1990s, known as mesoporous materials. Mesoporous materials are defined by IUPAC as possessing pore-openings between 20 and 500 Å. This much broader size-range spurred the use of mesoporous materials into other applications, including large-molecule heterogeneous catalysis and biomedical applications. Chapter one of this dissertation presents an introduction to the field of mesoporous materials, with both silica based and carbon based materials covered. Chapter two and three cover the development of a new mesoporous/microporous silica material. The purpose of this material was to combines the advantages of both types of materials, namely the large pore-opening of mesoporous materials with the stability of a traditional microporous material. The combined material, named MMM-2, is doped with titanium heteroatoms for use in catalytic reactions. The chapter presents a thorough study of the synthesis and characterization of MMM-2 along with its application as a more effective catalysis in the oxidation of cyclohexene. Chapters four and five further extend the work on the MMM-2 materials by incorporating aluminum into the silica framework to form a solid acid-catalyst. Again, thorough treatment is given to the synthesis and characterization of this material. Al- MMM-2 is shown to possess unique structural properties relative to the pure mesoporous and microporous materials that it is related to. Moreover, Al-MMM-2 is shown to be more effective in acid-catalysis reactions as well as possessing improved structural stability upon the reuse of the material in successive reaction cycles. Chapters six and seven cover the use of the mesoporous material, APMS in the adsorption and delivery of DNA. APMS, which is spherically shaped, is shown to be an effective adsorbant of DNA into its internal pores with adsorption determined to be dependent on several factors such as the ionic environment, pore size, and surface characteristics. Finally, chapter eight covers the templated synthesis and characterization of a new, spherically shaped, porous carbon material. This material, based upon APMS, provides tremendous increase in surface area and pore volume relative to its silica parent. The large increase in the physical properties provides enhanced adsorption of DNA.

The synthesis of mesoporous silica thin films using surfactant templating typically leads to an inaccessible pore orientation, making these films not suitable for membrane applications. Recent advances in thin film synthesis provide for the alignment of hexagonal pores in a direction orthogonal to the surface when templated on chemically neutral surfaces. In this work, orthogonal thin film silica membranes are synthesized on alumina supports using block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) as the template. The orthogonal pore structure is achieved by sandwiching membranes between two chemically neutral surfaces, resulting in 90 nm thick films. Solvent flux of ethanol through the membrane demonstrates pore accessibility and suggests a silica pore size of approximately 10 nm. The permeability of ions and fluorescently tagged solutes (ranging from 4,000 to 70,000 Da) is used to demonstrate the membrane’s size selectivity characteristics. A size cut off occurs at 69,000 Da for the model protein BSA. By functionalizing the silica surface with a long chained alkyl group using n-decyltriethoxysilane (D-TEOS), the transport properties of the membranes can be altered. Contact angle measurements and FTIR results show the surface to be very hydrophobic after functionalization. Solvent flux of ethanol through the silica thin film membrane is similar before and after functionalization, but water flux decreases. Thin film silica membranes show much promise for applications in catalysis, bio-sensing, and affinity separations.

A range of mesoporous materials based on SBA-15 have been prepared and characterised. The materials were templated by neutral block copolymer P123, and typically have a hexagonal (p6mm) pore structure, with high surface areas and narrow pore size distributions. The removal of the surfactant template by calcination and solvent extraction has been investigated. The aqueous stability of this material, and the hydrolysis of the surface was studied. Organic functional groups were incorporated into the silica surface by co-condensation, or by post synthesis grafting. A range of functional groups were incorporated, including amine, carboxy, allyl and thiol groups. The pore size of the materials was controlled by the addition of trimethoxybenzene during synthesis, which significantly increased the pore size and uptake capacity of the materials. The adsorption of CALB by SBA-15 was investigated, with support materials extracted by calcination or solvent extraction. Rapid uptake at high loading was observed, with a maximum loading of 450 mg g-1 measured. The leaching of the enzyme from the support was investigated, and found to be high with unfunctionalised supports. The leaching from functionalised supports incorporating sulfur groups was significantly reduced. The activity of the immobilised CALB was measured by tributyrin hydrolysis in aqueous media, and by enantioselective transesterification of (R)-1-phenylethanol in organic media. The effect of surface functionalisation for reusability and thermal stability in aqueous systems was investigated. Preliminary studies of supported CALB for dynamic kinetic resolution were carried out, with an investigation of acidic zeolites and a mesoporous supported catalyst for 1-phenylethanol racemisation. The encapsulation of immobilised CALB was investigated, and the activity and reusability of these systems studied.

In nature, chaperonins stabilise enzymes and protect them from high temperature and unfavourable solution conditions. We are inspired by some of chaperonins’ fundamental properties when investigating materials for enzyme immobilisation. In this project, mesoporous silica SBA-15 is used as a synthetic chaperonin analogue because of its controlled mesopore diameter and its negatively charged surface. Mesoporous silica SBA-15 have been synthesised by an acidic sol-gel method. The morphologies and textural parameters of the SBA-15 have been characterised using electron microscopy, gas physisorption, and small-angle Xray scattering. The synthesised SBA-15 samples are used to immobilise several model proteins: myoglobin, lysozyme, trypsin, and pepsin. At equilibrium, protein immobilisation can be described by the Langmuir model of physical adsorption. The maximum amount of protein that can be adsorbed onto SBA-15 increases with increasing pore diameter. The kinetics of adsorption of the protein myoglobin is found to be affected by the pore size of the SBA-15, with the protein diffusing faster through a larger pore. Immobilising enzymes to SBA-15 is shown to increase their biocatalytic activity under some solution conditions. For myoglobin and lysozyme, the protective effects were strongest in solutions where the enzyme is strongly electrostatically attracted to the silica surface. Immobilised myoglobin is also found to be protected from digestion by the protease pepsin. For trypsin, the relationship between electrostatic attraction and improved activity was inconclusive. SBA-15 pore size was shown to affect the activity of the smallest enzyme, lysozyme. In summary, this thesis recommends the following prioritisations for enzyme immobilisation: strong electrostatic attraction between enzyme and material, followed by pore size just exceeding the diameter of the enzyme. By determining the relative importance of these parameters, this thesis increases the fundamental understanding of enzyme immobilisation by physical adsorption onto porous materials.

This contribution describes design, preparation and physico-chemical characterization of a new photo-stable hybrid antenna based on mesoporous SBA-15 silica. Concepts of host-guest chemistry are applied in such a way that one or more photoactive guest molecules are incorporated into the silica channels and on the outer surface, acting as energy harvesting and transferring units. The presented composite system be-haves as efficient Förster resonance energy transfer (FRET) pair and shows high photoluminescence and stability towards photodegradation, representing an important step forward in the search for new efficient materials with opto-electronic applications. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35498

The aim of this project was to develop new route to silica and silica based materials through utilizing green techniques and demonstrate its following applications. Due to the properties of supercritical fluids including high diffusivity, low dynamic viscosity and low surface tension, supercritical fluid (SCF) is becoming a potential alternative solvent class in materials chemistry. The physical properties of SCF could be tuned to more liquid- or more gas- like thus providing an enhanced selectivity of the solubility performance of SCF. Several conditions such as reaction time, pressure and temperature were have been taken into consideration for the synthesis of a spherical mesoporous silica using supercritical carbon dioxide as solvent. Bio-oil has successfully been utilized to prepare carbon-silica composites (CSCs) from mesoporous silicas. These CSCs comprise a thin film of carbon dispersed over the silica matrix and exhibit porosity similar to parent silica with BET surface areas ranging from 39 to 636 m2/g and pore volumes ranging from 0.03 to 0.31 cm3/g. The surface properties of resulting materials can be simply tuned by the variation of preparation temperatures leading to a continuum of functionalities ranging from polar hydroxyl rich surfaces to carbonaceous aromatic surfaces. The as-synthesised CSC was subsequently used as solid support for the deposition of palladium nanoparticles to catalyse the Heck reaction. This CSC catalyst exhibited a high catalytic activity and excellent reusability for the Heck reaction using either conventional solvent NMP or propylene carbonate. It should be noted that a side product - methyl 3,3-diphenylacrylate was generated during the reaction using CSC catalyst in propylene carbonate with the yield of up to 15.5%. The CSCs were also used to prepare carbonaceous materials by silica etching process. After silica removal, a mesoporous carbonaceous material with the morphology ranging from rod-like to tubular-like could be synthesised.

En la present tesi doctoral, s'ha desenvolupat un sistema d'alliberament de fàrmacs sensible a pH basat en nanopartícules mesoporoses de sílice (MSN). Els porus de la nanopartícula estan radialment obstruïts mitjançant la funcionalització de cadenes de PEG, substituïdes amb un fàrmac en un dels seus extrems. L'objectiu d'aquesta nova metodologia és la de preservar la càrrega interna d'aquestes MSN. En primer lloc, s'ha estudiat el concepte d'obstrucció radial per avaluar la utilitat pràctica d'aquest mètode. Per aquesta raó, diferents tipus de cadenes de PEG amb càrrega, a saber, amines quaternàries i PEG neutrals, s'han funcionalitzat sobre la MSN per estudiar la seva capacitat d'obstrucció. Com a prova de concepte, s'ha estudiat l'alliberament de safranina en medi fisiològic (pH 7.4). Els resultats obtinguts han demostrat que les cadenes de PEG que contenen una càrrega positiva obstrueixen millor els porus que les cadenes de PEG neutres de la mateixa longitud. Utilitzant aquesta aproximació, s'ha dissenyat un sistema d'alliberament de fàrmacs per a la vehiculització de camptotecina (CPT) i topotecan (TPT). En primer lloc, un dels anteriors fàrmacs s’ha adsorbit dins dels porus de la MSN. Posteriorment, els porus s’han segellat mitjançant una cadena de PEG que conté doxorrubicina (DOX) en un dels seus extrems (DOX-PEG). L'estabilitat d'aquest sistema en condicions fisiològiques prova l'eficàcia de l'obstrucció radial. D'altra banda, en condicions àcides, es produeix un alliberament descontrolat dels fàrmacs. Així mateix, els experiments de citotoxicitat in vitro han demostrat que el sistema pot alliberar CPT i DOX en les cèl·lules cancerígenes HeLa, aconseguint un major efecte sinèrgic que la combinació de TPT i DOX. També s'ha sintetitzat un profàrmac de la CPT amb l'objectiu d'augmentar la seva càrrega en una MSN i millorar així el seu efecte sinèrgic amb la DOX. Per dur-ho a terme, s’ha unit una cadena de PEG escindible a la CPT. Emprant aquesta estratègia s'ha aconseguit carregar un 30% més de CPT a l'interior de les MSN. El sistema mostra una gran estabilitat en condicions fisiològiques, ja que s’observa un alliberament negligible dels fàrmacs. A més, s'ha avaluat la citotoxicitat de sistema en dues línies cel·lulars diferents: HeLa i HepG2. Els resultats obtinguts demostren que el nou profàrmac sintetitzat amb combinació amb la DOX té un major efecte sinèrgic en les cèl·lules HepG2. D'altra banda, la selectivitat de les MSN cap a les cèl·lules HepG2 s'ha millorat mitjançant la funcionalització sobre el grup DOX-PEG amb el lligant àcid glicirretinic (GA). Per fer-ho, s'ha emprat la mateixa aproximació radial establerta pels altres sistemes. Els estudis d'internalització cel·lular han demostrat que aquest nou sistema és capaç de discriminar entre cèl·lules HeLa i HepG2, acumulant-se preferentment en aquestes últimes. Finalment, s'ha avaluat un sistema d'administració triple de medicaments amb l'objectiu de superar l'efecte de resistència dels tumors a múltiples fàrmacs. Aquesta acció es pot emprendre mitjançant la combinació d’agents quimioterapèutics, DOX i CPT, amb un agent fototerapèutic (ftalocianina). Referent a això, s'ha sintetitzat un nou conjugat de la CPT amb una ftalocianina. Aquest conjugat s'ha carregat dins dels porus de la MSN i posteriorment s'han segellat amb el grup DOX-PEG. Els experiments d'internalització cel·lular han demostrat l'endocitosi d'aquest sistema en les cèl·lules HeLa i el posterior alliberament dels fàrmacs. Així mateix, s'ha avaluat in vitro l'efecte sinèrgic entre la DOX i la CPT.
En la presente tesis doctoral, se ha desarrollado un sistema de liberación de fármacos sensible a pH basado en nanopartículas mesoporosas de sílice (MSN). Los poros de la nanopartícula están radialmente obstruidos mediante la funcionalización de cadenas de PEG, sustituidas con un fármaco en uno de sus extremos. El objetivo de esta nueva metodología es la de preservar la carga interna de estas MSN. En primer lugar, se ha estudiado el concepto de obstrucción radial para evaluar la utilidad práctica de este método. Por esta razón, diferentes tipos de cadenas de PEG con carga, a saber, aminas cuaternarias y PEG neutrales, se han funcionalizado sobre la MSN para estudiar su capacidad de obstrucción. Como prueba de concepto, se ha estudiado la liberación de safranina en medio fisiológico (pH 7.4). Los resultados obtenidos han demostrado que las cadenas de PEG que contienen una carga positiva obstruyen mejor los poros que las cadenas de PEG neutrales de la misma longitud. Utilizando esta aproximación, se ha diseñado un sistema de liberación de fármacos para la vehiculización de camptotecina (CPT) y topotecán (TPT). En primer lugar, uno de los anteriores fármacos se ha adsorbido dentro de los poros de la MSN. Posteriormente, los poros se han sellado mediante una cadena de PEG que contiene doxorrubicina (DOX) en uno de sus extremos (DOX-PEG). La estabilidad de dicho sistema en condiciones fisiológicas prueba la eficacia de la obstrucción radial. Por otro lado, en condiciones ácidas, se produce una liberación descontrolada de los fármacos. Asimismo, los experimentos de citotoxicidad in vitro han demostrado que el sistema puede liberar CPT y DOX en las células cancerígenas HeLa, logrando un mayor efecto sinérgico que la combinación de TPT y DOX. También se ha sintetizado un profármaco de la CPT con el objetivo de aumentar su carga en una MSN y mejorar así su efecto sinérgico con la DOX. Para llevarlo a cabo, se ha unido una cadena escindible de PEG a la CPT. Empleando esta estrategia se ha conseguido cargar un 30% más de CPT en el interior de las MSN. El sistema muestra una gran estabilidad en condiciones fisiológicas, ya que se observa una liberación negligible de los fármacos. Además, se ha evaluado la citotoxicidad del sistema en dos líneas celulares diferentes: HeLa y HepG2. Los resultados obtenidos demuestran que el nuevo profármaco sintetizado en combinación con DOX, resulta en un mayor efecto sinérgico en las células HepG2. Por otro lado, la selectividad de las MSN hacia las células HepG2 se ha mejorado mediante la introducción del ligando ácido glicirretínico (GA) sobre el grupo DOX-PEG. Para llevarlo a cabo, se ha empleado la misma aproximación radial establecida para los otros sistemas. Los estudios de internalización celular han demostrado que este nuevo sistema es capaz de discriminar entre las células HeLa y HepG2, acumulándose preferentemente en estas últimas. Finalmente, se ha evaluado un sistema de administración triple de medicamentos con el objetivo de superar el efecto de resistencia de los tumores a múltiples fármacos. Esta acción se puede emprender mediante la combinación de medicamentos quimioterapéuticos, DOX y CPT, con un agente fototerapéutico (ftalocianina). Por esta razón, se ha sintetizado un nuevo conjugado de la CPT con una ftalocianina. Dicho conjugado se ha cargado dentro de los poros de la MSN y posteriormente se han sellado con el grupo DOX-PEG. Los experimentos de internalización celular han demostrado la endocitosis de este sistema en las células HeLa y la posterior liberación de los fármacos. Asimismo, se ha evaluado in vitro el efecto sinérgico entre la DOX y la CPT.
In this PhD dissertation, a pH-responsive multiple drug delivery system (DDS) based on mesoporous silica nanoparticles (MSN) with a radial-capping of its pores has been developed. This is a new concept that relies on the functionalization of the particle surface with PEG chains substituted with a drug at its end to preserve the inner cargo of the MSN. First, the concept of radial-capping has been studied to assess the practical usefulness of such capping method. Thus, different types of charged PEGs, namely quaternary amines and neutral PEGs, have been introduced upon an MSN in order to study its capping ability. As a proof of concept, the dye safranin was loaded into the nanoparticles pores, which were subsequently capped with PEGs chains. Then, the release of safranin was assessed under physiological conditions (pH 7.4). The results obtained demonstrated that PEG chains possessing positive charge provides a more efficient capping than the neutral PEGs of the same length. Using this approach, a drug delivery system (DDS) based on the radial capping for the delivery of camptothecin (CPT) and topotecan (TPT) has been studied. CPT or TPT has been loaded within the pores of an MSN, and subsequently sealed with a PEG chain decorated with doxorubicin (DOX) at its end (DOX-PEG moiety). The system is stable under physiological conditions (pH 7.4) which confirms the effectiveness of the radial capping. On the other hand, under acidic pH, a burst release of drugs takes place. Furthermore, the in vitro cytotoxicity test has demonstrated that this DDS can effectively deliver CPT and DOX to HeLa cells achieving a better synergistic effect than the combination of TPT and DOX. With the aim to improve the loading of CPT to enhance the synergistic effect with the latter system (DOX-PEG moiety), a prodrug of CPT has been synthesised. To do so, a cleavable reductive short PEG chain has been bonded to CPT. An increase of loading of 30% has been achieved in comparison with the unmodified drug. The stability of the radial-capping methodology has been tested as mentioned above. Under physiological conditions, the release of drugs is negligible. The cytotoxicity activity of the system has been tested in two different cell lines: HeLa and HepG2 cells. The results showed a better synergistic effect of this new synthesised system towards HepG2 cells. In order to further improve the selectivity of the system towards HepG2 cells, the MSN were decorated with glycyrrhetinic acid (GA) ligand over the DOX-PEG moiety. Uptake studies have shown that this new system preferably accumulates in HepG2 cells in comparison to HeLa cells. Finally, a tri-deliver system of drugs has been developed with the aim to try to overcome the multiple drug-resistant (MDR) effect by the combination of chemotherapeutic drugs (DOX and CPT) with a phototherapeutic agent (phthalocyanine). In this regard, a new CPT conjugate with a phthalocyanine has been synthesised and loaded within the pores of an MSN. Then, the system has been sealed with the DOX-PEG moiety. The uptake studies have demonstrated the proper endocytosis of the system inside HeLa cells and the subsequent delivery of the three drugs in the cytoplasm and nucleus. Furthermore, the synergistic effect of DOX and CPT has been assessed in vitro.

The field of mesoporous silica has been studied for about 20 years but it is still an area attracting a lot of attention. The use of novel templating molecules and several issues related to the synthesis and fine structural details are still poorly understood. These aspects are of special relevance to the theme of this thesis, which includes novel work on three fronts; the synthesis, characterization and applications of mesoporous materials. The work described in this thesis aims to contribute to the mesoporous field by developing novel methods of mesoporous silica synthesis without relying on surfactant micelles as the templating agent but focusing instead on the stacking arrangement of aromatic molecules such as folic acid. The novel route presented here leads to 2D hexagonal structures with p6mm symmetry possessing high mesoporosity and large surface areas. The versatility of this route at various synthesis temperatures and using hydrothermal treatments has also been investigated. A novel strategy is also proposed for the synthesis of mesocaged materials with Pm3n symmetry structures. The mechanism relies on the penetration of the neutral propylamino moiety of a co-structure directing agent into the hydrophobic core of the surfactant micelles. Beside these novel pathways, the effect of hydrothermal treatment (HT) at 100 oC on the 3D cubic Ia3d structure (AMS-6) over a long period of time was also examined, and the results show a phase transformation from a 3D cubic Ia3d to a 2D hexagonal p6mm structure and a return to the 3D cubic Ia3d structure at a later stage in the synthesis. This unexpected result is discussed. In this work, the detailed structural characterization of mesoporous materials using electron microscopy techniques is an important task. In particular, to extend previous knowledge, the fine structural details of mesocaged materials possessing Pm3n symmetry prepared with various amphiphilic surfactants under acidic and alkaline conditions has been investigated using electron crystallography and sorption studies. The results show subtle fine structural differences with materials prepared under alkaline conditions exhibiting the largest mesocage sizes. The cage and window sizes are primarily determined by the charge density of the surfactant and the thickness of the hydration layer surrounding the surfactant micelles. The relationship between the mesoporous structure and its function has been investigated by evaluating the rate of release of amphiphilic molecules, used as model molecules, from the internal pore structures of mesoporous materials with different pore geometries. In a similar study, the rate of proton diffusion from a liquid surrounding the mesoporous nanoparticles into the pore system of AMS-n was also assessed. The results show that the diffusion coefficients for the proton absorption process are higher than those for the release of the surfactant template molecules, with more complex 3D mesocaged particles showing the highest diffusion coefficients in both cases. Finally, the quantity of CO2 adsorption was measured by modifying the internal surfaces of mesocaged material with n-propylamino groups. Results show that the cage-connecting window sizes limit the surface coverage of n-propylamino groups by pore blocking and affect the volume of CO2 adsorption. In addition, at the molecular level, CO2 adsorption shows physisorption or chemisorption depending on the localized distribution of n-propylamino groups, as studied by in-situ infrared spectroscopy.

Mesoporous silica with a hexagonally ordered pore structure (SBA-15) has been synthesized. Through variations in the synthesis conditions several morphologies, such as fibers, sheets and separate rods, have been realized. Furthermore, additions of heptane and NH4F make it possible to synthesize SBA-15 with pores as large as 18 nm in the sheet morphology. Mechanisms for the formation of different morphologies have been suggested. In the case of fibers and sheets, the amount of heptane present during the synthesis determines the final morphology. For low concentrations, the heptane enters the micelles and increases the pore size while the particles (crystallites) attaches to each other end to end. When the heptane concentration increases, the heptane droplets increase in size, and above a critical droplet size the crystallites attach with one short end towards the droplet, forming the sheet morphology. The crystallites can also be separated. This is the case of the rod morphology. The separation is performed by shortening the stirring time and increasing the HCl concentration. The increased amount of HCl increases the hydration rate of the silica precursor, which can be used to control the thickness and length of the rods. Furthermore, the reaction time has been decreased from 20 h for all morphologies to less than 4 hours. The materials have been characterized with nitrogen sorption, electron microscopy and x-ray diffraction. Also, thermogravimetric analysis and fourier transformed infrared spectroscopy have been used for studying the removal of surfactants.

Using true liquid crystal templating (TLCT), a one-pot method for preparing mesoporous silicas containing metal nanoparticles is available. The method leads to well-defined systems with possible applications is selective catalysis. Using this approach, a range of metal-doped variants of hexagonal silicas (general MCM-41 family) are prepared and show surface areas >1000 m2 g–1 and pore diameters of ca 30 Å. Specifically, palladium doped-MCM-41-like silicas are prepared and are shown to be active in the selective oxidation of crotyl alcohol and the activity of the system has been investigated as a function of both metal loading and the pore length – the latter affecting mass transport and therefore rate of conversion. Templating on Pluronic P123 leads to doped SBA-15-like materials, but in contrast to the findings with low-concentration templating as commonly reported, TLCT leads to materials with surface areas of about 400 m2 g–1, which is accounted for by the absence of micropores. Catalytic results from these SBA-15 materials will also be presented.

The human body and many living organisms are comprised of very complex biological system with distinct metabolism. In order to understand life activities, we need to monitor the individual chemical interactions happening in vivo. Bioimaging with naked organic dye molecules always suffers from drawbacks such as photobleaching and biocompatibility issues. Silica matrix protects the fluorophores from external environment and provides hydrophilic shell, which improves the photostability and biocompatibility of dye molecules. A nanocarrier, which is highly compatible with the target metabolic system, may be beneficial for therapeutic and diagnostic applications in living organisms. Mesoporous silica nanoparticles (MSNs) are highly biocompatible and safe for biological applications and may provide the solution. Therefore, this project focused on the synthesis of dye-doped mesoporous silica nanoparticles, coupling them with various bioactive carbohydrate molecules, and investigation of these nanoparticles for their potential biological applications in microorganisms. Rhodamine B, fluorescein, and methylene blue dyes were employed for doping into amine modified mesoporous silica matrix through covalent and non-covalent approaches. The results revealed that all dyes were successfully doped into the silica matrix and showed bright fluorescence. In the next stage, methylene blue encapsulated amine grafted mesoporous silica nanoparticles (MB AMSNs) were utilized for coupling with carbohydrates- glucose, maltose, ribose, and raffinose by employing N, N'-carbonyldiimidazole as a coupling agent. The chemical and physical characterization showed the successful conjugation of carbohydrates onto amine-modified silica surface. Finally, glucose conjugated methylene blue doped mesoporous silica nanoparticles (Glu-MB MSN) were used in bioimaging and toxicity assessments. The as-synthesized nanoparticles were investigated in E.Coli and B.Subtilis bacterial samples. The characteristic results revealed bright fluorescence in bacteria like formations via confocal microscopy. Therefore, Glu-MB MSN may be useful for bioimaging purposes. SEM images showed bacterial aggregation after treatment with nanoparticles. This interaction is relatively higher in the case of B.Subtilis. Moreover, the bacterial cell structure appeared unaltered after incubation with the nanoparticles. This suggested that the nanoparticles were not toxic to these specific bacteria. However, more studies need to be performed to confirm these results.

Phlogopite is a mineral found in the Phalaborwa complex, which is mined in abundance and has little to no industrial use. Phlogopite in its raw form consists of between 40 50% silicon. Previous studies have yielded various forms of silica through acid leaching of phlogopite. The aim is to leach phlogopite with aqua regia to obtain mesoporous silica with the maximum specific surface area possible. Interest in mesoporous silica utilization has greatly increased in areas such as catalysis, polymer reinforcement, adsorption and medical uses. Phlogopite is leached in a temperature controlled batch reactor with aqua regia, nitric acid and hydrochloric acid to recover the remaining silicon product. The leaching conditions are varied in order to obtain the silicon oxide with the largest specific surface area. The leaching conditions such as acid concentration, nitrate ratio, leaching time, temperature, solid to liquid ratio, stirring speed and particle size are varied to determine the effects on the surface area. With aqua regia as leaching agent the maximum specific surface area of 99.41% silica achieved was 515 m²/g at acid concentration of 8.40 M, nitrate ratio of 0.64, leaching time of 12 hrs and leaching temperature at 50 ?C. This experiment provided mesoporous silica with average pore width of 2.62 nm and average pore volume of 0.36 cm³/g. Similar specific surface area values were achieved with 6.33 M nitric acid, leaching time of 6 hrs and leaching temperature at 60 ?C. A regression (R²= 0.90) was developed which can accurately estimate the specific surface area of the recovered silica with the known acid concentration, nitrate ratio, leaching time and temperature.
Dissertation (MEng)--University of Pretoria, 2015.
tm2016
Chemical Engineering
MEng
Unrestricted

Zeolites and mesoporous silica were used as drug delivery systems for the loading and release of small drug molecules, aspirin and 5-fluorouracil. Different parameters were varied such as aluminum content in the zeolite, effect of distribution of functional groups and the method of surface modification in case of mesoporous silica. The effect of the aforementioned variables was studied on drug loading and release from these microporous and mesoporous systems. The drug loaded materials were extensively characterized using various physical techniques such as powder X-ray diffraction, nitrogen isotherms, infrared spectroscopy, solid state NMR and thermogravimetric analysis. Quantum calculations and molecular dynamics simulations were performed in order to validate the experimental data and also to obtain a molecular level insight of the drugs inside the pores of the host materials. Drug templated synthesis of mesoporous silica was also carried out in the presence of aspirin as the template. The aspirin templated material was characterized by aforementioned techniques and showed a sustained drug release profile.

The aim of this PhD work was to develop and characterize all physicochemical aspects of this new CRT for CTZ and AKS using OMS until the introduction onto the market. The first part comprehends the characterization of different OMS synthesized and commercially available; the study of different incorporation techniques based on hydrophilicity/hydrophobicity of API; the characterization of the new impregnated OMS. Consequently, the work is oriented on the interaction details of API on silica surfaces. A closer look is given to the big questions of OMS-drug phenomena: mobility, solubility, bioavailability, etc. Therefore, all the scCO2 incorporation parameters have been studied, highlighting the differences between OMS and the spatial assembly of drug inside the mesoporous channels. Thus, the patented CRT has been developed for AKS describing all the main aspect of the innovative semisolid formulation. In-vitro and ex-vivo release test has been produced and characterized, revealing the functionality of the OMS reservoir effect. Finally, the same DDS have been developed for CTZ. Both the DDS have been compared with commercially available creams.

ROS (Reactive Oxygen Species), such as H2O2, HO● and O2-●, are naturally produced by the metabolism of living beings. However, they can appear in large quantities in the case of certain diseases (Alzheimer's, Parkinson's, sclerosis, cancer). Overproduction of ROS leads to higher cell mortality. Some microorganisms have an Mn-based enzyme capable of catalyzing the disproportionation reaction of H2O2 into O2 and H2O. Several molecules have been synthesized to reproduce this process, however very few of them are active in aqueous environment. Recently, polynuclear synthetic Mn species have been introduced into mesoporous silica to protect them from the environment. Thus, these complexes of Mn are stable and even see their catalytic activity increase. In order to persevere in this way, this thesis presents new compounds of formula [Mn(bpy)(AntCO2)2]n and [{Mn(bpy)(AntCO2)}2(µ-AntCO2)2(µ-OH2)] for MnII (chain and dinuclear respectively) and [Mn4O2(AntCO2)6(bpy)2(ClO4)2] for MnIII (tetranuclear) based on this concept. These compounds have two types of ligands, 2,2'-bipyridine, commonly found for similar compounds and 9-anthracene carboxylate, a fluorescent ligand added for theragnostic purposes. The resolution of the crystal structure of the MnII dinuclear compound shows a compression along the axis on the direction of the monodentate anthracene carboxylate. Moreover, by hydrolysis the one- dimensional system can be converted to the dinuclear compound. In the synthesis of the Mn(III) compound some oxidation of the anthracene is observed and two organic compounds are obtained, an anthraquinone and an ester formed by reaction between the quinone and the carboxylate. The manganese compounds were inserted into silica nanoparticles (NPs), resol (a polyphenol resin) -silica and carbon-silica hybrids in order to allow their vectorization and to study the compatibility of hybrid NPs with this type of system. This work explores the magnetic properties of the complexes and the luminescent properties of the coordination compounds and materials. The Mn(II) compounds show weak antiferromagnetic interaction, and the best way to differentiate these compounds is by EPR spectroscopy: the chain shows a unique band at g~2 while for the dinculear compound the spectrum is more complex, with several features at low fields. Magnetic properties of the Mn(III) compound confirms that it is a tetranuclear with butterfly type geometry with stronger antiferromagnetic interaction between the central ions than between central-terminal ions. The study of the porosity of the materials and the quantification of the presence of manganese inside the materials shows a good incorporation rate of the compounds. However it seems that the compounds are not present homogenously inside the support and that they are broken into smaller units. This is confirmed with the study of the magnetic properties of the hybrid [Mn]@NPs materials. In addition, fluoresecence measurement show that both the support and the compounds are luminescent but that both emission are strongly quenched when the compounds are inside the nanoparticles. The study of the optic properties of the materials show that a large amount of the compounds is released when the loaded silica and carbon-silica nanoparticles are redispersed in ethanol. However, resol-silica nanoparticles seem a lot more efficient to retain the complexes inside and apparently do not need further functionalization to achieve this goal. Finally, some preliminary test of disproportionation of H2O2 catalyzed by the manganese systems show low to moderate activity of Mn compounds in acetonitrile and paves the way for optimizing hybrid systems in aqueous media.

Les ROS (Reactive Oxygen Species), tels H2O2, HO● et O2-●, sont produites naturellementpar le métabolisme des êtres vivants. Cependant, elles peuvent apparaître en trop grandesquantités dans le cas de certaines maladies (Alzheimer, Parkinson, scléroses, cancers). Lasurproduction de ROS conduit à une mortalité des cellules plus élevée.Certains micro-oragnismes possèdent une enzyme à base de Mn capable de catalyser laréaction de dismutation du H2O2 en O2 et H2O. Plusieurs molécules ont été synthétisées pourreproduire ce procédé, cependant très peu d'entre elle sont actives en environnement aqueux.Récemment, des espèces synthétiques du Mn ont été introduites dans des silicesvoient même leur activité catalytique augmenter. Afin de perséverer dans cette voie, cettethèse présente de nouveaux composés de MnII (dinucléaire et chaîne) et MnIII(tetranucléaire) basés sur ce concept. Ils sont dotés de ligands fluorescents, ajoutés pour desfin théragnostiques. Ces composés ont été insérés dans des nanoparticules (NPs) de silice ethybrides carbone-silice afin, de permettre leur vectorisation et d'étudier la compatibilité desNPs hybrides avec ce type de système.Le travail fourni explore les propriétés magnétiques des complexes, les propriétésluminescentes des composés et matériaux et montre la bonne insertion des composés dans lesNPs hybrides, ne nécessitant pas, contrairement aux NPs de silice pure, de fonctionnalisationsupplémentaire pour la rétention des complexes. Il met aussi en évidence l'activité descomposés du Mn dans l'acétonitrile et ouvre des pistes pour une optimisation des systèmeshybrides en milieu aqueux.Le travail fourni explore les propriétés magnétiques des complexes, les propriétésluminescentes des composés et matériaux et montre la bonne insertion des composés dans lesNPs hybrides, ne nécessitant pas, contrairement aux NPs de silice pure, de fonctionnalisationsupplémentaire pour la rétention des complexes. Il met aussi en évidence l'activité descomposés du Mn dans l'acétonitrile et ouvre des pistes pour une optimisation des systèmeshybrides en milieu aqueux
ROS (Reactive Oxygen Species), such as H2O2, HO● and O2-●, are naturally produced by themetabolism of living beings. However, they can appear in large quantities in the case of certaindiseases (Alzheimer's, Parkinson's, sclerosis, cancer). Overproduction of ROS leads to highercell mortality.Some microorganisms have an Mn-based enzyme capable of catalyzing the disproportionationreaction of H2O2 into O2 and H2O. Several molecules have been synthesized to reproduce thisprocess, however very few of them are active in aqueous environment. Recently, synthetic Mn species have been introduced into mesoporous silica to protect themfrom the environment. Thus, these complexes of Mn are stable and even see their catalyticactivity increase. In order to persevere in this way, this thesis presents new compounds ofMnII (dinuclear and chain) and MnIII (tetranuclear) based on this concept. They havefluorescent ligands (9-anthracene carboxylate), added for theragnostic purposes. Thesecompounds were inserted into silica nanoparticles (Nps), resol (a polyphenol resin) -silica andcarbon-silica hybrids in order to allow their vectorization and to study the compatibility ofhybrid NPs with this type of system.This work explores the magnetic properties of the complexes, the luminescent properties of thecompounds and materials and shows the good insertion of the compounds into the hybrid NPs,not requiring, in contrast to pure silica NPs, additional functionalization for the retention of thecomplexes. It also highlights the activity of Mn compounds in acetonitrile and paves the wayfor optimizing hybrid systems in aqueous media

This thesis describes the synthesis and characterization of various polyamidoamine (PAMAM) dendrimer moieties supported on amorphous mesoporous and periodic mesoporous silica supports. The surface characteristics of the supports are investigated using various methods and found to be intricately involved in the success of the dendrimer synthesis. The dendrimers are phophinomethylated and complexed with either palladium or rhodium and used as catalysts for carbonylation reactions. The palladium complexed C6-PAMAM dendrimers supported on aminopropyl silica gel are recyclable catalysts for the hydroesterification of olefins and turnover numbers (TON) of up to 1200 are possible. C2-PAMAM dendrimers supported on LPMCM-41 and Davisil are complexed with rhodium and used as catalysts for the hydroformylation reaction of olefins. These catalysts show how the pore geometry influences the activity and recyclability of the catalysts. The dendrimer-rhodium complexes supported on LPMCM-41 exhibit very high activity and a TOF of up to 1800 h-1 are observed for the hydroformylaton of 1-octene. These catalysts can be recycled effectively by simple filtration. A negative dendrimer effect is observed with the higher generations exhibiting lower activity than the lower generations. The dendrimer-rhodium complexes supported on Davisil also exhibit very high activity and a TOF of up to 1700 h-1 are observed for the hydroformylation of 1-octene. The activity of these catalysts are less dependent on the generation than the LPMCM-41 dendrimers, and excellent activity is observed up to the third generation for the hydroformylation reaction of 1-octene.

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.