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.

Thesis (Ph.D.)--Oklahoma State University, 2006. / Adviser: Allen Apblett. Includes bibliographical references.

No description available.

This thesis describes the synthesis and application of three types of selectively functionalized mesoporous materials. In the first section, periodically ordered mesoporous organosilicas (PMOs) are prepared that have the axially chiral bidentate phosphine ligand 2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) embedded in the wall structure. Asymmetric hydrogenation of β-ketoesters under high-pressure hydrogen gas and hydrogen transfer reduction were carried out using Ru catalysts resulting from these materials. In the next chapter, our new methodology to selectively functionalize the internal/external surface of SBA-15, a mesoporous silica whose pore diameter is ~8 nm, by blocking the pore surface with reloaded Pluronic P123® micelles is presented. Multiple tests were attempted to validate the efficiency of the methodology including nitrogen adsorption, quantitative analysis by solid state NMRs, fluorescence measurements, elemental analysis and XPS. Eventually SS NMR proved to be the most appropriate. Finally, chapter four describes ordered organic materials in catalysis, namely star-shaped polymers containing chiral core-gels synthesized from chiral 1,1’- binaphthalene-2,2’-diol (BINOL) and 1,1’-binaphthalene-2,2’-diamine (BINAM). The kinetic resolution of 1-phenyl ethanol was carried out expecting to see differential affinity of the chiral core-gel to one enantiomer of the substrate in hydrogen transfer oxidation reaction. / Thesis (Ph.D, Chemistry) -- Queen's University, 2013-02-25 12:08:40.27

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment for the degree of Master of Science in Chemistry. Johannesburg 2016. / In the current study, different platinum-hollow carbon sphere catalysts were synthesized for use as electrocatalysts in low temperature fuel cells such as proton exchange membrane fuel cells (PEMFCs). The support material was synthesized via a hard templating method using mesoporous silica (synthesized using a modified Stöber method) as a sacrificial template. In fuel cells, one aim is to ensure that as much platinum as possible is present on a given electrode while keeping the entirety of the catalytic layer as thin as possible (i.e. with the minimum amount of carbon). One approach to achieving this was to make the hollow carbon spheres as small as possible, starting of course with the templating material. It was found that tailoring the molar ratios between the two co-solvents (that is water and ethanol) during Stöber synthesis was the key to achieving particles as small as approximately 150 nm with a uniform shape, size, and significant yields of up to 5.00 g. Another focal point in terms of the template material was achieving a silica structure that consisted of a solid core, and a distinctly mesoporous shell. Two different surfactants were explored in order to fabricate these structures; namely octadecyltrimethoxysilane (C18TMS) and cetyltrimethylammonium bromide (CTAB). It was found that of the two, the C18TMS resulted in more distinctly formed mesoporous silica layers with higher measured specific surface areas. Because the type of support material greatly influences the catalytic behaviour of the loaded catalysts, two different carbonization techniques were explored; namely the bubbling method using toluene as a carbon source, and a nanocasting method where resorcinol formaldehyde (RF) was the carbon source. The toluene-synthesized hollow carbon spheres had advantages over their RF-synthesized counterparts in that they were more thermally stable and had a more graphitic crystalline carbon framework. The RF-synthesized carbon, however, possessed a pseudo-capacitance due to surface carbon-oxygen groups, as well as a higher specific surface area, which resulted in the RF-carbon cyclic voltammetry profile spanning a larger current range in microampere per square centimetre. The effect of the size of the support materials was also explored; comparing 350 nm and 150 nm hollow carbon spheres. Besides the type of carbon, the metal precursor used to synthesize the catalyst nanoparticles was also explored, with either platinum(II)chloride (PtCl2) or platinum(II)acetylacetonate [Pt(acac)2] being used as the platinum source. It is also known that achieving high metal yields using conventional methods is quite difficult, and so an easier, quicker and less wasteful method was also explored; comparing the traditional wet-impregnation (WI) method with a chemical vapour deposition (CVD) method. Ultimately, it was found that platinum loaded on top of small-sized toluene-synthesized hollow carbon spheres using the CVD method and Pt(acac)2 as the metal precursor was the better catalyst in terms of oxygen reduction (determined using linear sweep voltammetry measurements); outperforming even commercial Pt/C catalysts as a result of improved mass transfer afforded by the voided cores of the hollow carbon spheres. The ability of a catalyst to withstand the reaction conditions present in a PEM fuel cell (i.e. oxygen-rich environments) was also considered. The stability of the catalysts was tested using chronoamperometry measurements in an oxygen-saturated perchloric acid solution. It was evident that the platinum loaded on the inner shells of the hollow carbon spheres showed far superior stability to those loaded on the outside surface. This was attributed to the qualities bestowed by the carbon shell around the platinum nanoparticles, protecting said platinum against the consequences of support corrosion due to the oxygenated environment; consequences such as metal sintering and interaction with surrounding carbon supports for example. These encapsulated catalysts, however, displayed a decrease in electrocatalytic activity compared to the catalysts with top-loaded platinum. In conclusion, the study of different platinum-carbon catalysts studied in the current work revealed that (a) loading platinum on top of small sized toluene-synthesized hollow carbon spheres using a CVD method and Pt(acac)2 as a metal precursor resulted in a highly active oxygen reduction catalyst, while (b) loading platinum on the inside surface of the hollow carbon spheres under the dame conditions resulted in a more electrocatalytically stable catalyst. / LG2017

Li, Li = 多功能介孔微米球 / 李麗. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 97-111). / Abstracts in English and Chinese. / Li, Li = Duo gong neng jie kong wei mi qiu / Li Li. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.v / Table of Contents --- p.vii / List of Figures --- p.x / Chapter 1 --- Introduction / Chapter 1.1 --- Multifunctional microspheres --- p.1 / Chapter 1.1.1 --- Preparations --- p.3 / Chapter 1.1.2 --- Applications --- p.8 / Chapter 1.2 --- Photophysical properties of rare earth ions --- p.13 / Chapter 1.3 --- Outline of thesis --- p.20 / Chapter 2 --- Preparation of Mesostructured Microspheres by Spray Pyrolysis / Chapter 2.1 --- Nanomaterials prepared by spray pyrolysis --- p.22 / Chapter 2.2 --- Our spray pyrolysis system --- p.29 / Chapter 3 --- Luminescent Mesostructured Titania Microspheres / Chapter 3.1 --- Rare earth-doped titania nanomaterials --- p.32 / Chapter 3.2 --- Experimental --- p.34 / Chapter 3.3 --- Results and discussion --- p.35 / Chapter 3.3.1 --- As-prepared undoped mesostructured titania microspheres --- p.35 / Chapter 3.3.2 --- Thermally-treated undoped mesostructured titania microspheres / Chapter 3.3.3 --- Rare earth-doped nanocrystalline titania microspheres --- p.43 / Chapter 3.3.4 --- Nanocrystalline titania microspheres co-doped with europium and samarium --- p.54 / Chapter 3.4 --- Conclusion --- p.55 / Chapter 4 --- Luminescent Mesostructured Silica Microspheres / Chapter 4.1 --- Rare earth complex-doped mesostructured silica matrices --- p.57 / Chapter 4.2 --- Experimental --- p.61 / Chapter 4.3 --- Results and discussion --- p.62 / Chapter 4.3.1 --- Rare earth complex-doped mesostructured silica microspheres --- p.62 / Chapter 4.3.2 --- Rare earth-doped mesostructured silica microspheres --- p.70 / Chapter 4.4 --- Conclusion --- p.72 / Chapter 5 --- Magnetic Luminescent Mesostructured Silica Microspheres / Chapter 5.1 --- Multifunctional microspheres containing magnetic components --- p.73 / Chapter 5.2 --- Experimental --- p.74 / Chapter 5.3 --- Results and discussion --- p.76 / Chapter 5.3.1 --- Magnetic mesostructured silica microspheres --- p.76 / Chapter 5.3.2 --- Magnetic luminescent mesostructured silica microspheres --- p.80 / Chapter 5.4 --- Conclusion --- p.83 / Chapter 6 --- Magnetic Photosensitive Mesostructured Silica Microspheres / Chapter 6.1 --- Mesostructured composite materials for optical applications --- p.84 / Chapter 6.2 --- Experimental --- p.87 / Chapter 6.3 --- Results and discussion --- p.89 / Chapter 6.3.1 --- Photosensitive mesostructured silica microspheres --- p.89 / Chapter 6.3.2 --- Magnetic photosensitive mesostructured silica microspheres --- p.91 / Chapter 6.4 --- Conclusion --- p.92 / Chapter 7 --- Summary --- p.94 / References --- p.97

In this research, cetyltrimethylammonium bromide (CTAB) is used as organic template and hydrous tin chloride (SnCl4) is used as inorganic precursor to prepare mesostructured SnO2 powder. The synthesis is carried out in the room temperature using NH3(aq) as pH-modifier. The changing variables in the synthesis process include: the mixing sequence of CTAB(aq), SnCl4(aq) and NH3(aq), the molar ratio of CTAB/SnCl4 (R), the pH value of the mixture and the aging time of the mixture. The X-ray diffraction (XRD) results show that the pH value of the mixture is the determining factor for the successful synthesis of mesoporous powder. On the other hand, the mixing sequence is of no consequence on the formation of the mesostructure. For solutions of pH<1 and R=0.2, 0.5 or 1, a crystalline phase of organic-inorganic complex is found in the final products, which hinders the hydrolysis and condensation of the inorganic precursor and hence the formation of mesoporous structure. For powders derived from the solutions of pH=2~5, the diffraction peak of mesoporous structure appears and becomes more intense with increasing pH value. For solutions of pH>7, mesoporous powders are obtained constantly. As mesoporous powder is also obtained from solution of R=0.01, it is concluded that the formation of surfactant cylinders and the subsequently packed hexagonal arrays are not fulfilled during the cooperation assembly process of organic and inorganic moleculars because the concentration of CTAB is far below the critical concentration for rod micelle (~10wt0/0). On the other hand, surfactant rod micelles instead of mesoporous structure is found in the powder derived from the basic solution of R=10 (CTAB: 5 g, SnCl4: 0.5 g). This implies that in spite of the formation of CTAB rod micelles, the mesostructured SnO2 powder can not be obtained without sufficient amount of Sn-precursor . According to the model of mesostructure synthesis, in current work, surfactant ions (S+), inorganic ions (I+) and counter ions (X-) are connected in the form of S+X-I+ through the electrostatic attraction and their cooperation assembly results in mesoporous structure. As pH valueincreases instantly as NH3(aq) is added into CTAB(aq), it is concluded that CTA+OH- does not exist and X- is Br- or Cl- instead of OH-. Finally, the mesostructure obtained in this work collapse after a calcination of 5000C for two hours. Therefore, a great deal needs to be done to improve the thermal stability in the future.

The zirconia is one of the transition metal oxides with a wide band-gap, showing many good mechanical and physical properties. This study concentrates on the preparation of the polystyrene template and the characterization of the ordered mesoporous zirconia thus prepared. The polystyrene (PS) templates have been prepared by the emulsifier-free emulsion polymerization of styrene monomer (SM) in mixed solution of K2S2O8 and H2O, without any cross-linking agent. The PS spheres so prepared have diameters ranging from 50 ¡V 400 nm. These spheres are then arranged in array by sedimentation method; then the infiltration of zirconia sol solution is followed. After the sol has been transformed to the gel, calcinations under high temperature are proceeded to remove the PS template to obtain the ordered mesoporous zirconia with various pore sizes. Doping of the zirconia also is conducted by applying an AgNO3 solution to the mesoporous zirconia. Results from SEM indicate that with a fixed ratio of K2S2O8/styrene = 5.98 wt¢H, the PS size decreases with the SM concentration; PS as small as 66 nm can be obtained when SM/H2O = 0.05¢H by volume. The PS spheres forms a hexagonal close packing when using a solution of H2O/ethanol = 3¡G7 by wt during sedimentation. Shrinkage ranging from 60 ¡V 80% of the original PS size happens when the PS template is removed from the calcined zirconia. Results from XRD indicate the same tetragonal crystalline structure of zirconia after calcinations at 500oC, regardless of the different pore sizes. BET measurements show the specific surface area of the zirconia from 6.05 - 42.61m2/g. For Ag-doped zirconia under hydrogen atmosphere, it is found from EDS mapping that the AgNO3 can be reduced to the metallic silver without particles aggregation but random distribution on the pore walls or surfaces, while the tetragonal crystalline structure of zirconia remains unaltered.

In our study, 3D interconnection channels of mesoporous silica MCM-48 was used as template. We try to fill the channels with the metal precussor by ¡§incipient wetness¡¨ technique. After the reduction with H2, the composites containning metal Pd and MCM-48 could be obtained. Then, Pd nanowire network was obtained through HF etching. The mesoporous palladium nanoparticles are obtained and we try to use it as the catalyst in the Heck coupling reaction of £\-methylstyrene and p-bromoacetophenone. We find that our catalyst have different effect in this Heck reaction. The terminal and internal (E/Z form) isomer ratio variated in the reaction. In the future, we will attempt to apply our mesoporous Palladium nanoparticles as organic molecule storage. The MCM-48 and mesoporous Palladium nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution nitrogen adsorption.We used NMR and GC to trace the reaction. Heck reaction was performed as a test reaction to compare catalytic performances of the meosoporous Palladium nanoparticles and the catalyst of refrence.

The impregnation of mesoporous carbon cloth with alumina has been studied. The most successful method of impregnation resulted from preparation of the alumina phase by a sol/gel route. This method involves a boehmite intermediate, and the heating environment for the thermal transition of boehmite to the final alumina was investigated. Heat treatment of the boehmite intermediate under flowing N2, flowing air and vacuum was found to give a different pore size distribution for the final alumina than did still air heat treatment. For the former environments the transition from boehmite to alumina was not accompanied by the usual increase in pore size. Alumina/carbon composites were made by dipping pieces of mesoporous carbon cloth in a boehmite sol. The distribution of boehmite about the carbon cloth was found to be improved by pre-wetting the carbon cloth and by the use of ultrasonic dispersion during boehmite impregnation. Dried boehmite/carbon composites, with loading levels of up to 180wt.%, were heated under vacuum to 5000 C. In this manner alumina/carbon composites of up to 60wt.% alumina were fabricated. The distribution of the alumina phase about the carbon cloth was investigated by electron microscopy and by gas adsorption techniques. Nitrogen isotherm data indicated that the mesopores of the carbon cloth were not blocked by the deposited alumina, rather the pore volume of the carbon cloth was increased by the clustering of porous alumina about the pore entrances of the carbon cloth. Water isotherms were determined for the composite materials. The water activity of the composite, particularly at low relative pressures, was found to be significantly greater than that of the carbon cloth as a result of the presence of alumina. CO2 activity of the composites was investigated by a gas chromatographic technique. The CO2 activity of the composite material was found to be up to 500 times greater than that of virgin carbon cloth.