O presente trabalho descreve a síntese, a caracterização e o estudo das propriedades de materiais híbridos nanoestruturados constituídos de sílica e do grupo orgânico 1,4- diazabiciclo[2,2,2]octano (dabco). A síntese desses materiais foi realizada pelo método solgel, partindo-se de precursores organosilanos desenvolvidos em nosso laboratório. Foram sintetizados materiais híbridos contendo o grupo orgânico covalentemente ligado à estrutura da sílica na forma pendente, contendo uma carga positiva (1-aza-4-azoniabiciclo[2,2,2] octano) e também materiais contendo o grupo orgânico na forma duplamente carregada, constituindo pontes (1,4-diazoniabiciclo[2,2,2]octano). Para o híbrido que apresenta o grupo orgânico na forma de pontes, foram sintetizadas amostras variando-se o conteúdo orgânico. Nas amostras com baixo conteúdo orgânico (até 3 %) observou-se que o diâmetro dos microporos está relacionado com o tamanho da cadeia desse grupo. Nas amostras com maior conteúdo orgânico a análise por difração de raios X evidenciou uma organização nanoestrutural que apresentou espaçamentos interplanares impostos pelo grupo orgânico positivamente carregado. A presença de birrefringência óptica nos materiais confirmou a existência de organização estrutural anisotrópica. Adicionalmente, as amostras mostraram-se transparentes e termicamente estáveis. A presença do contra-íon cloreto nos híbridos permitiu seu uso como trocadores aniônicos na adsorção de Cr (IV) de soluções aquosas. Adicionalmente, foi possível imobilizar espécies eletroativas aniônicas, tais como o hexacianoferrato e o corante amarelo brilhante. Foram preparados eletrodos de pasta de carbono modificados com essas amostras e realizados estudos de voltametria cíclica, onde foi observado que essas espécies eletroativas encontram-se fortemente adsorvidas nos poros. O eletrodo de pasta de carbono modificado com uma amostra de híbrido contendo sílica/titânia e corante amarelo brilhante foi utilizado como mediador na eletroxidação do ácido ascórbico, possibilitando o desenvolvimento de um sensor para vitamina C. Na perspectiva de estudar fatores que afetam as características morfológicas e texturais de materiais resultantes de sínteses em sistemas híbridos, apresenta-se também, a preparação de xerogéis microporosos de sílica, com área superficial elevada, acima de 800 m2g-1. Esses xerogéis foram obtidos estudando-se alguns parâmetros experimentais como a temperatura de gelificação, solvente e catalisadores, sendo que a presença do ácido acético mostrou-se o fator primordial. / The present work describes the synthesis, the characterization and the study of properties of the hybrid nanostructured materials constituted by silica and the organic group 1,4-diazabicycle[2,2,2]octane (dabco). The synthesis of the materials was performed using the sol-gel method, starting from organosilane precursors developed in our laboratory. Hybrid materials with the organic group covalently bonded to silica structure in the pendant form were prepared, containing one positive charge (1-aza-4-azoniabicycle[2,2,2]octane), and also hybrid materials with the organic group in the double charged form, forming bridges (1,4- diazoniabicycle[2,2,2]octane). For the hybrid presenting the organic group in the bridged form, samples varying the organic content were prepared. In the samples with low organic content (up to 3 %) it was observed that the diameter of the micropores was related to the chain length of the organic group. In the samples with high organic content the X-ray diffraction analysis showed nanostructural organization with interplanar distances imposed by the positively charged organic group. The presence of optical birefringence in the materials confirmed the existence of anisotropic structural organization. Additionally the samples were transparent and thermally stable. The presence of chloride contra-ions in the hybrids afforded their use as anionic exchangers in the adsorption of Cr (VI) from aqueous solutions. Additionally, it was possible to immobilize anionic electroactive species like hexacyanoferrate and brilliant yellow dye. Modified carbon paste electrodes were prepared with these samples and cyclic voltammetry studies were performed. It was observed that these electroactive species are strongly adsorbed in the pores. The carbon paste electrode modified with a hybrid containing silica/titania and brilliant yellow dye was used as mediator in the electroxidation of ascorbic acid, enabling the development of a sensor for vitamin C. In the perspective to study the factors that affect morphological and textural characteristics of materials resulting from syntheses in hybrid systems, it was also presented the preparation of silica microporous xerogels with high surface area, above 800 m2 g-1. These xerogels were obtained studying some experimental parameters as gelation temperature, solvent and catalyst, being that the presence of acetic acid was significant.

Os compostos amônio quaternários (CAQ) e as nanopartículas de prata (AgNPs) são extensamente conhecidos por suas atividades antibacterianas. Neste contexto o silsesquioxano iônico contendo o grupo catiônico 1,4-diazôniabiciclo[2,2,2]octano (SiDb(NO3)2) foi utilizado como agente estabilizante de AgNPs em meio aquoso, possibilitando a obtenção de nanopartículas de prata estáveis na forma esféricas com diâmetros médios inferiores a 10 nm. Mesmo em concentrações baixas de prata (1.1 μg.mL-1), o sistema AgNPs/SiDb(NO3)2 apresenta excelente atividade antibacteriana contra as bactérias E. coli e S. aureus, como também baixa citotoxicidade. Também foram produzidos filmes finos, sobre substratos de vidro, com o sistema AgNPs/SiDb(NO3)2. Os filmes de AgNPs apresentaram excelentes atividades bacteriostática e bactericida contra as bactérias E. coli e S. aureus. Portanto, o sistema AgNPs/SiDb(NO3)2 é muito promissor para ser aplicado como agente antibacteriano na forma de dispersão aquosa ou de filme fino. / The quaternary ammonium compounds (QAC) and silver nanoparticles (AgNPs) are widely known for their antibacterial activities. In this context, the ionic silsesquioxane containing the cationic group 1,4- diazoniabicyclo [ 2,2,2 ] octane and the nitrate group as counter ion (SiDb(NO3)2) was used as a stabilizing agent of AgNPs in aqueous medium, making possible to obtain stable silver nanoparticles with spherical shape and average diameters below 10 nm. Even at low silver concentration (1.1 μg.mL-1), the AgNPs/SiDb(NO3)2 system shows excellent antibacterial activity against E. coli and S. aureus bacteria, as well as low cytotoxicity. Thin films of AgNPs/SiDb(NO3)2 system were made on glass substrates. The films of AgNPs showed excellent bacteriostatic and bactericidal activity against E. coli and S. aureus bacteria. Therefore, the AgNPs/SiDb(NO3)2 system is very promising to be applied as antibacterial agent as water dispersion or film form.

Ces travaux de thèse portent sur le développement d'un revêtement multifonctionnel issu de la voie sol-gel pour la protection anticorrosion et anti-usure de pièces de pompes. Le matériau d'étude est un acier laminé non allié DC04, très sensible à la corrosion et de topographie irrégulière. Il a été démontré la faisabilité du développement d'un revêtement hybride architecturé nanocomposite, densifié en extrême surface et élaboré par voie sol-gel sur l'acier DC04. L'architecture est basée sur un gradient de concentration de couches hybrides non chargées et chargées de nanoparticules de zircone. La bicouche primaire, qui est non chargée et d'une épaisseur de 5 microns, est adhérente, couvrante, nivelante et présente de très bonnes propriétés anticorrosion, jusqu'à 1000 heures lors de l'immersion dans l'eau de ville à 60°C. L'introduction de nanoparticules de zircone dans le sol hybride permet d'obtenir une couche supérieure plus épaisse de l'ordre d'une dizaine de microns dont la surface a été densifiée par traitement laser. Les systèmes architecturés ont été caractérisés par une méthode innovante qui combine les tests d'usure Taber, les observations microstructurales et la spectroscopie d'impédance électrochimique. Des analyses spectroscopiques par RMN des noyaux 13C, 29Si et 27Al ont mis en évidence l'importance de contrôler les réactions de polymérisation inorganique et organique pour l'obtention de revêtements performants en anticorrosion. La modification de la structure de la matrice hybride organique- inorganique permettant l'insertion d'une plus grande quantité de cérium sans détériorer les propriétés anticorrosion du revêtement. / This thesis focuses on the development of a multifunctional sol-gel coating for corrosion and wear protection of pump parts. The studied material is a DC04 laminated carbon steel, very sensitive to corrosion and with an uneven topography. Feasibility of the development of an architectured hybrid coating, densified on the extreme surface and prepared by the sol-gel route on the DC04 steel has been demonstrated. The architecture is based on a gradient of concentration of zirconia nanoparticles imbedded in an aluminosilicated hybrid matrix. The resulting bilayered primer in the range 5-6 microns is adherent, covering, leveling and presents high-performance anticorrosion properties, up to 1000 hours when immersed in tap water at 60 ° C. The introduction of zirconia nanoparticles in the hybrid sol allows to obtain a thicker upper layer, in the range 8-10 microns, which surface has been densified by laser treatment for few nm in deep. Architectured systems were assessed by an innovative method which combines Taber wear tests, microstructural observations and analysis by electrochemical impedance spectroscopy. 13C, 29Si and 27Al NMR spectroscopies have highlighted the importance of controlling both the organic and inorganic polymerisation reactions to obtain efficient anticorrosion coatings. Moreover, these results demonstrate that the modification of the organic-inorganic hybrid matrix structure allows the introduction of a higher amount of cerium, as corrosion inhibitor, without damage for the anticorrosive properties of the coating.

Li, Yuefang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 46-48). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgement --- p.iii / Table of contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Introduction to protein crystallization --- p.1 / Chapter 1.1.1 --- Principles of protein crystallization --- p.2 / Chapter 1.1.2 --- Classical methods to crystallize protein --- p.4 / Chapter 1.2 --- Crystal growth in unique environments: the pursuit of better crystals --- p.6 / Chapter 1.2.1 --- Protein crystallization in space --- p.6 / Chapter 1.2.2 --- Crystallization in gel and capillary --- p.7 / Chapter 1.3 --- Microfluidic methods for protein crystallization: high through-put screenings --- p.9 / Chapter 1.3.1 --- Valve-controlled methods --- p.10 / Chapter 1.3.2 --- Droplet-based methods --- p.11 / Chapter 1.3.3 --- Microwell-based methods --- p.11 / Chapter 1.4 --- Objective of the project --- p.13 / Chapter Chapter 2 --- Rehydratable hydrogel in nanoliter microwells --- p.15 / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Experimental --- p.17 / Chapter 2.2.1 --- Fabrication of SU-8 mould --- p.17 / Chapter 2.2.2 --- Fabrication of the PDMS device --- p.19 / Chapter 2.2.3 --- Liquid dispensing in PDMS device --- p.20 / Chapter 2.2.4 --- Polymerization of PA gel --- p.21 / Chapter 2.2.5 --- Drying and Rehydration of PA gel --- p.22 / Chapter 2.3 --- Results and discussions --- p.23 / Chapter 2.3.1 --- Preparation of PA gel in PDMS device --- p.23 / Chapter 2.3.2 --- Immobilization of PA gel in microwells --- p.25 / Chapter 2.3.3 --- Dehydration and Rehydration of PA gel --- p.25 / Chapter 2.3.4 --- Liquid dispensing in the gel-preloaded microwells --- p.29 / Chapter 2.4 --- Conclusion --- p.31 / Chapter Chapter 3 --- Protein crystallization by gel-based FID --- p.32 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Experimental --- p.34 / Chapter 3.2.1 --- Conditions used for crystallize proteins --- p.34 / Chapter 3.2.2 --- Protein crystallization by microbatch method --- p.34 / Chapter 3.2.3 --- Protein crystallization in microchip --- p.35 / Chapter 3.3 --- Results and discussions --- p.35 / Chapter 3.3.1 --- Crystallization in microplate --- p.36 / Chapter 3.3.2 --- Crystallization in microwells --- p.38 / Chapter 3.4 --- Conclusion --- p.41 / Chapter Chapter 4 --- Conclusions --- p.43 / Chapter 4.1 --- Summary of the work --- p.43 / Chapter 4.2 --- Future perspectives --- p.44 / Reference --- p.46

Orientador: Renata Marques de Melo Marinho / Coorientador: Tiago Moreira Bastos Campos / Banca: Altair Antoninha Del Bel Cury / Banca: Marco Antonio Bottino / Banca: Paulo Francisco César / Banca: Guilherme de Siqueira Ferreira Anzaloni Saavedra / Resumo: O objetivo do estudo foi avaliar os efeitos de diferentes infiltrações de sílica pelo método sol-gel realizado com a presença de catalisadores nas propriedades mecânicas, microestrutura, características de superfície de uma zircônia Y-TZP, e na resistência de união entre a zircônia e um cimento resinoso, bem como avaliar a energia interfacial (tenacidade à fratura) na união de zircônia infiltrada por sílica ou vidro ao cimento resinoso. O estudo foi segmentado em duas partes, na parte A foram confeccionados 210 discos de Zircônia Y-TZP e divididos em 6 grupos, infiltrados por ácido silícico obtido por TEOS, infiltrados por ácido silícico obtido por metassilicato de sódio (Na2SiO3): sem catalisador, com catalisador, com duas e três imersões, e o grupo não infiltrado (controle). Os discos foram caracterizados com DRX, FT-IR e MEV, e depois foram submetidos ao ensaio de resistência à flexão biaxial. Os dados foram analisados com a estatística descritiva, ANOVA 1-fator e Teste de Tukey (95%), e também com a Análise de Weibull para determinar a homogeneidade estrutural. Adicionalmente foram produzidos espécimes retangulares de zircônia, que foram divididos da mesma forma que os grupos citados acima, para a realização do teste de resistência de união. Os espécimes infiltrados foram tratados com ácido fluorídrico 2% por 10 segundos e depois silanizados. Uma matriz de silicone foi adaptada com cera sobre as superfícies tratadas da zircônia e o cimento resinoso foi inserido dentro da ... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Das Ziel dieser Arbeit ist neben der Synthese von Sol-Gel-Funktionsschichten auf der Basis von transparent leitfähigen Oxiden (transparent conducting oxides, TCOs) die umfassende infrarotoptische und elektrische Charakterisierung sowie Modellierung dieser Schichten. Es wurden sowohl über klassische Sol-Gel-Prozesse als auch über redispergierte Nanopartikel-Sole spektralselektive Funktionsschichten auf Glas- und Polycarbonat-Substraten appliziert, die einen möglichst hohen Reflexionsgrad im infraroten Spektralbereich und damit einhergehend einen möglichst geringen Gesamtemissionsgrad sowie einen niedrigen elektrischen Flächenwiderstand aufweisen. Zu diesem Zweck wurden dotierte Metalloxide, nämlich einerseits Zinn-dotiertes Indiumoxid (tin doped indium oxide, ITO) und andererseits Aluminium-dotiertes Zinkoxid (aluminum doped zinc oxide, AZO)verwendet. Im Rahmen dieser Arbeit wurden vertieft verschiedene Parameter untersucht, die bei der Präparation von niedrigemittierenden ITO- und AZO-Funktionsschichten im Hinblick auf die Optimierung ihrer infrarot-optischen und elektrischen Eigenschaften sowie ihrer Transmission im sichtbaren Spektralbereich von Bedeutung sind. Neben der Sol-Zusammensetzung von klassischen Sol-Gel-ITO-Beschichtungslösungen wurden auch die Beschichtungs- und Ausheizparameter bei der Herstellung von klassischen Sol-Gel-ITO- sowie -AZO-Funktionsschichten charakterisiert und optimiert. Bei den klassischen Sol-Gel- ITO-Funktionsschichten konnte als ein wesentliches Ergebnis der Arbeit der Gesamtemissionsgrad um 0.18 auf 0.17, bei in etwa gleichbleibenden visuellen Transmissionsgraden und elektrischen Flächenwiderständen, reduziert werden, wenn anstelle von (optimierten) Mehrfach-Beschichtungen Einfach-Beschichtungen mit einer schnelleren Ziehgeschwindigkeit anhand des Dip-Coating-Verfahrens hergestellt wurden. Mit einer klassischen Sol-Gel-ITO-Einfach-Beschichtung, die mit einer deutlich erhöhten Ziehgeschwindigkeit von 600 mm/min gedippt wurde, konnte mit einem Wert von 0.17 der kleinste Gesamtemissionsgrad dieser Arbeit erzielt werden. Die Gesamtemissionsgrade und elektrischen Flächenwiderstände von klassischen Sol-Gel-AZOFunktionsschichten konnten mit dem in dieser Arbeit optimierten Endheizprozess deutlich gesenkt werden. Bei Neunfach-AZO-Beschichtungen konnten der Gesamtemissionsgrad um 0.34 auf 0.50 und der elektrische Flächenwiderstand um knapp 89 % auf 65 Ω/sq verringert werden. Anhand von Hall-Messungen konnte darüber hinaus nachgewiesen werden, dass mit dem optimierten Endheizprozess, der eine erhöhte Temperatur während der Reduzierung der Schichten aufweist, mit N = 4.3·1019 cm-3 eine etwa doppelt so hohe Ladungsträgerdichte und mit µ = 18.7 cm2/Vs eine etwa drei Mal so große Beweglichkeit in den Schichten generiert wurden, im Vergleich zu jenen Schichten, die nach dem alten Endheizprozess ausgehärtet wurden. Das deutet darauf hin, dass bei dem optimierten Heizschema sowohl mehr Sauerstofffehlstellen und damit eine höhere Ladungsträgerdichte als auch Funktionsschichten mit einem höheren Kristallisationsgrad und damit einhergehend einer höheren Beweglichkeit ausgebildet werden. Ein Großteil der vorliegenden Arbeit behandelt die Optimierung und Charakterisierung von ITO-Nanopartikel-Solen bzw. -Funktionsschichten. Neben den verwendeten Nanopartikeln, dem Dispergierungsprozess, der Beschichtungsart sowie der jeweiligen Beschichtungsparameter und der Nachbehandlung der Funktionsschichten, wurde erstmals in einer ausführlichen Parameterstudie die Sol-Zusammensetzung im Hinblick auf die Optimierung der infrarot-optischen und elektrischen Eigenschaften der applizierten Funktionsschichten untersucht. Dabei wurde insbesondere der Einfluss der verwendeten Stabilisatoren sowie der verwendeten Lösungsmittel auf die Schichteigenschaften charakterisiert. Im Rahmen dieser Arbeit wird dargelegt, dass die exakte Zusammensetzung der Nanopartikel-Sole einen große Rolle spielt und die Wahl des verwendeten Lösungsmittels im Sol einen größeren Einfluss auf den Gesamtemissionsgrad und die elektrischen Flächenwiderstände der applizierten Schichten hat als die Wahl des verwendeten Stabilisators. Allerdings wird auch gezeigt, dass keine pauschalen Aussagen darüber getroffen werden können, welcher Stabilisator oder welches Lösungsmittel in den Nanopartikel-Solen zu Funktionsschichten mit kleinen Gesamtemissionsgraden und elektrischen Flächenwiderständen führt. Stattdessen muss jede einzelne Kombination von verwendetem Stabilisator und Lösungsmittel empirisch getestet werden, da jede Kombination zu Funktionsschichten mit anderen Eigenschaften führt. Zudem konnte im Rahmen dieser Arbeit erstmals stabile AZO-Nanopartikel-Sole über verschiedene Rezepte hergestellt werden. Neben der Optimierung und Charakterisierung von ITO- und AZO- klassischen Sol-Gel- sowie Nanopartikel-Solen und -Funktionsschichten wurden auch die infrarot-optischen Eigenschaften dieser Schichten modelliert, um die optischen Konstanten sowie die Schichtdicken zu bestimmen. Darüber hinaus wurden auch kommerziell erhältliche, gesputterte ITO- und AZO-Funktionsschichten modelliert. Die Reflexionsgrade dieser drei Funktionsschicht-Typen wurden einerseits ausschließlich mit dem Drude-Modell anhand eines selbstgeschriebenen Programmes in Sage modelliert, und andererseits mit einem komplexeren Fit-Modell, welches in der kommerziellen Software SCOUT aus dem erweiterten Drude-Modell, einem Kim-Oszillator sowie dem OJL-Modell aufgebaut wurde. In diesem Fit-Modell werden auch die Einflüsse der Glas-Substrate auf die Reflexionsgrade der applizierten Funktionsschichten berücksichtigt und es können die optischen Konstanten sowie die Dicken der Schichten ermittelt werden. Darüber hinaus wurde im Rahmen dieser Arbeit ein Ellipsometer installiert und geeignete Fit-Modelle entwickelt, anhand derer die Ellipsometer-Messungen ausgewertet und die optischen Konstanten sowie Schichtdicken der präparierten Schichten bestimmt werden können. / The aim of this thesis is on the one hand the synthesis of sol-gel functional layers on the basis of transparent conducting oxides (TCOs) and on the other hand a comprehensive infrared-optical and electrical characterization as well as modeling of these layers. Spectrally selective coatings have been prepared with the classical sol-gel route as well as with redispersed nanoparticle sols on glass and polycarbonate substrates and these coatings should have a reflectance in the infrared spectral range which is as high as possible and therefore a total emittance and an electrical sheet resistance which are as small as possible. For this purpose tin doped indium oxide (ITO) and aluminum doped zinc oxide (AZO) have been used as doped metal oxides. Within this thesis several parameters have been investigated in-depth which play a decisive role in the preparation of ITO and AZO low emissivity coatings, in order to prepare such coatings with optimized infrared-optical and electrical properties as well as visual transmittances. Besides the composition of the classical sol-gel ITO coating solutions, also the parameters of the coating as well as the heating processes have been characterized and optimized in the manufacture of classical sol-gel ITO and AZO functional layers. As a significant result the total emittance of classical sol-gel ITO functional layers could be reduced by 0.18 to 0.17 while the visual transmittance and electrical sheet resistances stay approximately the same, if just one-layered coatings are applied with a higher withdrawal speed with the dip coating technique instead of (optimized) multi-layered coatings. With a classical sol-gel ITO single coating, which has been produced with a withdrawal speed of 600 mm/min, the smallest total emittance of this work could be realized with 0.17. The total emittances and electrical sheet resistances of classical sol-gel AZO functional layers were reduced drastically in this work by using the optimized final heating process. The total emittance could be reduced by 0.34 to 0.50 and the electrical sheet resistance by 89 % to 65Ω/sq with a coating which consists of nine single layers. On the basis of Hall measurements it has been shown that coatings which were treated with the optimized heating process (which exhibits a higher temperature during the reducing treatment of the coatings) show a higher charge carrier density as well as a higher mobility than those coatings treated with the old heating process. With the optimized heating process the ninelayered coatings exhibit a charge carrier density of N = 4.3·1019 cm-3 which is approximately twice as high and a mobility of µ = 18.7 cm2/Vs which is about three times higher than the values of coatings which have been heated with the old process. This indicates that with the optimized heating process more oxygen vacancies and, associated therewith a higher charge carrier density as well as a higher crystallinity of the layer and thus a higher mobility are generated. One focus of the presented work lies on the optimization and characterization of ITO redispersed nanoparticle sols and functional layers respectively. In addition to the used nanoparticles, the dispersion process, the coating type with the respective coating parameters and post-treatments of the functional layers also a detailed parameter study has been done. This parameter study examined the composition of the nanoparticle sols with a view to the optimization of the infrared-optical and electrical properties of the applied coatings. The coating properties have been studied in particularly with regard to the influence of the used stabilizers and solvents respectively. In this work it will be shown, that the accurate composition of the nanoparticle sols plays a decisive role and the choice of the used solvents has a bigger impact on the coating properties than the choice of the used stabilizers. However, it will also be shown, that no general statements can be made which stabilizers or which solvents within the sols lead to coatings which have small total emittances and small electrical sheet resistances. Instead each combination of used stabilizer and used solvent has to be empirically tested since each combination leads to coatings with different properties. Furthermore stable AZO nanoparticle sols based on several formulas have been developed for the first time. Besides the optimization and characterization of ITO and AZO classical sol-gel as well as nanoparticle sols and functional layers, also the infrared-optical properties of these coatings have been modeled in order to determine the optical constants as well as the coating thicknesses. Furthermore also commercially available sputtered ITO and AZO coatings have been modeled. The reflectances of these three types of coatings have been modeled on the one hand by using only the Drude model within a self-written program in the software Sage. On the other hand these coatings have been modeled with more complex fitting models within the commercially available software called SCOUT. These more complex fitting models consist of the extended Drude model, a Kim oscillator and an OJL model and they also take the influence of the glass substrates on the reflectances of the applied coatings into account. By using these fitting models, the optical constants of the applied coatings and the coating thicknesses can be obtained. In addition an Ellipsometer has been installed as part of this work and suitable fitting models have been developed. These models can be used for analyzing the Ellipsometer measurements in order to determine the optical constants and the coating thicknesses of the coatings applied.

Sample preparation is a key step in chemical analysis, and includes isolation of target analytes, removal of interferences, preconcentration, and/or modification of target analytes (if needed). Sample preparation is also the most time-consuming and error-prone step in the whole analytical process. Traditional sample preparation techniques involve hazardous solvents. Considering the environmental and health safety, it is desirable to reduce or eliminate organic solvents in sample preparation. Solid phase microextraction (SPME) was introduced as a solvent free sample preparation technique. Capillary microextraction (CME) is one of the formats of SPME that can be easily coupled to high performance liquid chromatography (HPLC). In SPME and CME a solvent free sample preparation is accomplished by using a sorbent coating instead of hazardous organic solvents commonly used in conventional extraction techniques. This research is focused on the development and systematic examination of novel niobia-, titania- and silica-based organic-inorganic hybrid sol-gel sorbents for CME. Conventionally silica and titania based precursors were used in organi-inorganic hybrid sol-gel sorbents for CME, here novel niobia based precursor was used in creating organic-inorganic hybrid sol-gel sorbents. Poly tetrahydrofuran (polyTHF) as well as electrically neutral and charged organic ligands were used to prepare the sorbents for CME coupled to HPLC. Characterization of created sol-gel sorbents, evaluation of extraction performance, and enrichment of environmentally and biomedically important analytes including organophosphorus compounds were performed. CME performances of the created sorbents were characterized by specific extraction (SE) (a measure of extraction efficiency) and desorption efficiency (DE) (a measure of completeness desorption of extracted analytes). Scientific findings of this research has shown that sol-gel niobia-polyTHF sorbent provides 60 to 70 % higher SE values for different environmentally important analytes compared to analogously prepared silica-polyTHF sorbent. This superior extraction performance can be attributed to the presence of surface Lewis acid sites undergoing Lewis acid-base interactions with analytes representing Lewis bases. The prepared sorbents also have the ability to undergo van der Waals interactions due to the presence of polyTHF. Absence of Lewis acid sites on silica surface resulted in inferior extraction efficiency compared to niobia-polyTHF sorbents. Extraction efficiency of the created sol-gel based niobia-polyTHF was also explored in the enrichment of organophosphorus pesticides and compared with that of the state-of-the-art titania-based sorbent. Sol-gel niobia-polyTHF sorbent has provided 40 to 50 % higher SE values in the enrichment of organophosphorus pesticides compared to sol-gel titania-polyTHF sorbent which can be attributed to the presence of bronsted acid sites on niobia surface (but lacking on titania) along with Lewis acid sites. To explore relative contributions of electrostatic, Lewis acid-base and van der Waals interactions between sol-gel sorbents and analytes, two sol-gel sorbents, one containing a positively charged octadecyl ligand and the other a neutral octadecyl ligand were created. Positive charge was imparted by using N-octadecyldimethyl [3-(trimethoxysilyl) propyl] ammonium chloride (C18 (+ve)) as ligand bearing co-precursor. Similarly N-octadecyl trimethoxysilane was used to impart a neutral C18 ligand in sol-gel coating. Experimental results have shown that sol-gel Nb2O5-C18 (+ve) sorbent has superior extraction efficiency compared to sol-gel based Nb2O5-C18 and purely inorganic Nb2O5 sorbents in enrichment of organophosphorus compounds (nucleotides and organophosphorus pesticides). Electrostatic interactions between the positive charge of organic ligand (C18 (+ve)) and negative charge of phosphate group has contributed to the higher extraction performance of sol-gel based Nb2O5-C18 (+ve) sorbent. TiO2-C18 (+ve) sorbent was also created to compare with the novel sol-gel niobia based sorbents, since titania-based sorbents are considered as the state-of-the-art extraction material in the enrichment of organophosphorus compounds. Established research results has shown that sol-gel based Nb2O5-C18 (+ve) sorbent has provided 40 to 50 % higher specific extraction values for organophosphorus compounds compared to sol-gel based TiO2-C18 (+ve) sorbent. Desorption efficiency of sol-gel Nb2O5-C18 (+ve) and TiO2-C18 (+ve) sorbents were 96% vs 90%. This superior DE of sol-gel Nb2O5-C18 (+ve) sorbent can be attributed the higher Lewis acid strength of titania than nioiba. The developed sol-gel niobia based sorbents have also shown high pH stability compared to traditional sol-gel silica based sorbents. The created sol-gel sorbents were characterized by less than 5% run to run RSD values and also less than 5% capillary to capillary RSD values which indicated the high reproducibility of developed method. The developed sol-gel niobia sorbents are applicable to sample preparation in different fields including biomedical, environmental, forensic, defense etc.

Titania-based photocatalysts have been extensively studied for the oxidative photodestruction of organic pollutants in wastewaters, releasing non-toxic substances such as CO2, HCl, and water. However, commercial exploitation of this process is limited by the fact that titania is only active under UV irradiation (wavelength below about 388 nm), which is only less than 5% of solar light energy. Sol-gel synthesised catalyst specimens were characterised to determine the correlation between preparation conditions on morphology (XRD, SEM), optical (bandgap energy level) and physicochemical properties (BET surface area, pore volume, acid site density, acid site strength and type) of the photocatalysts. These spesific properties would then be linked to their photoactivity using aqueous aliphatic and aromatic model pollutants. This study has demonstrated that sol-gel synthesised doped titania photocatalysts, especially Pt/TiO2, may be used to effectively degrade non-volatile acids (DL-malic acid, dichloroacetic acid, and p-hydroxybenzoic acid) under visible light and UV irradiation with significant photoactivity suitable for the solar light application of photocatalytic wastewater treatment. A significant drop in band-gap energy was found for all titania sol-gel catalysts doped with Pt, Co, and Ce with values between 1.41 to 1.78 eV. The BET areas of the photocatalysts were also higher (65-117 m2/g) than that of Degussa P25 (50 m2/g). The visible-light photomineralisation of the three pollutants with Pt-TiO2 specimen were further extended to evaluate the effects of major variables in a bubble-column photoreactor on the photodegradation activities. Those major variables were lamp intensity, oxygen concentration, initial pH, catalyst dosage, and inital pollutant concentration. All the three pollutants seemed to follow the Langmuir-Hinselwood model with dual adsorption sites which implicated a bimolecular surface rate-limiting step probably between the adsorbed organic substrate and a surface hydroxyl (or peroxy) radical. A study of the CeyCoxTi(1-x)O3+d perovskite was conducted to investigate the influence of metal composition and pH on the intrinsic optophysical attributes as well as p-hydroxybenzoic acid degradation under UV irradiation. The perovskite UV photoactivities were lower than that of pure TiO2 likely due to excessive loading (metal content) creating new oxide phases act as electron-hole recombination center, regardless better physicochemical attributes of some of the perovskite samples. The role of aging time and calcination temperature on the sol-gel synthesised TiO2 was also explored. Higher calcination temperature (from 250 to 700 0C) resulted in TiO2 photocatalysts with better crystallinity, which is important for OH group formation as active sites for photodegradation. Despite of some advantages from higher temperature preparation, some detrimental effects such as decreased acidity attributes, surface area, and pore volume were also observed. The significant red-shift of sol-gel synthesized TiO2 into visible light, especially for 250 0C specimen since 600 or 700 0C had extremely low activities, has promising implications that this specimen might be used for solar application to substitute Pt-doped TiO2 in order to produce a more cost effective photocatalyst. Aging period (1 to 14 days) did not have any discernible effect on the band-gap value and acid-site density. Even so, the highest acid site strength was obtained with an aging time of 10 days. From the overall perspective, aging time longer than 3 days did not bring noticeable benefits to both catalyst attributes and photoactivities.

Cellulosic biomass is the major organic matter produced in the biosphere. The biodegradation of this cellulosic material is achieved by enzymatic activities of the cellulose degrading microorganisms. These organisms usually express a complex extracellular or a membrane bound cellulolytic system comprising combination of several cellulase enzymes. Cellulases are the group of hydrolytic enzymes capable of hydrolysing insoluble cellulose to glucose. Phlebia gigantea is an aggressive white rot basidiomycete with ability to tolerate resinous extracts on freshly cut wood and higher growth rate. This helps the fungus to colonise the sapwood preventing other fungi from becoming established. Early research on the cellulase system of this organism reported the presence of a cellulase system composed of P-glucosidase, endoglucanase and a cellobiohydrolase. Based on these unpublished studies, our aim was to obtain a complete sequence of putative cellobiohydrolase I (CbhI) from this organism. Attempts to identify and isolate the cellulase gene resulted in an incomplete cDNA sequence of I 154 bp. To understand the cellulase system, expression and regulation of the cellulase enzymatic activity was examined for incubation of P. gigantea on substrates glucose, xylose, Avicel, carboxymethyl cellulose and cellobiose. The pH, total protein and biomass production results indicated that the capacity of P. gigantea to degrade cellulose is dependent upon the nature of the carbon source and the regulation of the cellulase synthesis is repressed in the presence of simple sugars like glucose and xylose. The study employed the highly effective method of purification by affinity adsorption and purified cellulase complex in large quantity. Characterisation of the kinetic properties of this cellulase complex revealed that the rate of cellulase catalysis were optimum at pH 5.0 and temperature 50GC. The purified complex was comprised of multiple proteins and demonstrated significant CMCase and CBHase activity on zymogram analysis. The purified cellulase complex was characterised by 2D gel electrophoresis and by peptide mass finger printing using MALDI-TOF massspectrometry analysis. The 2D gel analysis of the purified cellulase complex showed 15 spots within the range of pI 3.5 to pI 7 and the molecular weight between 20KDa to 100KDa. Three protein spots were selected based on the IEF and SDS zymogram and identified using MALDI-TOF MS analysis. These proteins were identified based on the peptide mass data belonging to the 6-phospho-a-glucosidase, p-glucosidase and glycosyl hydrolase family 13 a-amylase or pullulanases, suggesting the divergent evolution of specific cellulase proteins. This study showed P. gigantea as a potential cellulase source and the cellulase complex secreted by the induction of substrate, comprises a variety of enzymes related to hydrolysis of cellulose biomass. It is evident from this and previous studies that P. gigantea cellulase complex comprises of a specific set of enzymes that possess the ability to degrade crystalline cellulose and is one of the first organisms to colonise freshly cut wood. Further studies on the cellulase system of this primary colonist may open up the prospects to utilise this organism as the potential onsite bioreactor agent, pre-treating the biomass and increasing the economic feasibility of the industrial bioenergy processes.

Ce travail concerne l'étude du phénomène de décharges partielles dans les matériaux isolants utilisés en électronique de puissance. En utilisant des méthodes de détection électrique et optique, le mécanisme de décharge partielle sur des substrats d'AlN dans l'huile silicone a été étudié sur un grand nombre d'échantillons. La variation de la nature du substrat (AlN, Al2O3 et composite verre/époxy) et du matériau d'encapsulation (huile silicone, huile de colza, huile minérale de transformateur, liquide d'imprégnant du condensateur Jarylec et Ugilec) met en évidence l'origine des décharges partielles de l'ensemble substrat - encapsulant. Les décharges partielles sur les substrats céramiques frittés ne dépendent pas du passivant, et se produisent dans le volume du substrat. L'évolution temporelle de la lumière émise dans les liquides en configuration pointe - plan et sur le substrat dans différents liquides montre que l'émission de lumière est un phénomène très complexe influencé par de nombreux paramètres : électroluminescence du solide, de l'encapsulant, décharges partielles, absorption des matériaux. Le phénomène d'électroluminescence du liquide est activé par une illumination extérieure. Les mesures de spectroscopie diélectrique haute tension n'apportent pas d'information supplémentaire sur le phénomène de décharges partielles, car les pertes correspondantes sont très faibles.