In this work, thermosensitive hydrogels having tunable thermo-mechanical properties were synthesized. Generally the thermal transition of thermosensitive hydrogels is based on either a lower critical solution temperature (LCST) or critical micelle concentration/ temperature (CMC/ CMT). The temperature dependent transition from sol to gel with large volume change may be seen in the former type of thermosensitive hydrogels and is negligible in CMC/ CMT dependent systems. The change in volume leads to exclusion of water molecules, resulting in shrinking and stiffening of system above the transition temperature. The volume change can be undesired when cells are to be incorporated in the system. The gelation in the latter case is mainly driven by micelle formation above the transition temperature and further colloidal packing of micelles around the gelation temperature. As the gelation mainly depends on concentration of polymer, such a system could undergo fast dissolution upon addition of solvent. Here, it was envisioned to realize a thermosensitive gel based on two components, one responsible for a change in mechanical properties by formation of reversible netpoints upon heating without volume change, and second component conferring degradability on demand. As first component, an ABA triblockcopolymer (here: Poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PEPE) with thermosensitive properties, whose sol-gel transition on the molecular level is based on micellization and colloidal jamming of the formed micelles was chosen, while for the additional macromolecular component crosslinking the formed micelles biopolymers were employed. The synthesis of the hydrogels was performed in two ways, either by physical mixing of compounds showing electrostatic interactions, or by covalent coupling of the components. Biopolymers (here: the polysaccharides hyaluronic acid, chondroitin sulphate, or pectin, as well as the protein gelatin) were employed as additional macromolecular crosslinker to simultaneously incorporate an enzyme responsiveness into the systems. In order to have strong ionic/electrostatic interactions between PEPE and polysaccharides, PEPE was aminated to yield predominantly mono- or di-substituted PEPEs. The systems based on aminated PEPE physically mixed with HA showed an enhancement in the mechanical properties such as, elastic modulus (G′) and viscous modulus (G′′) and a decrease of the gelation temperature (Tgel) compared to the PEPE at same concentration. Furthermore, by varying the amount of aminated PEPE in the composition, the Tgel of the system could be tailored to 27-36 °C. The physical mixtures of HA with di-amino PEPE (HA·di-PEPE) showed higher elastic moduli G′ and stability towards dissolution compared to the physical mixtures of HA with mono-amino PEPE (HA·mono-PEPE). This indicates a strong influence of electrostatic interaction between –COOH groups of HA and –NH2 groups of PEPE. The physical properties of HA with di-amino PEPE (HA·di-PEPE) compare beneficially with the physical properties of the human vitreous body, the systems are highly transparent, and have a comparable refractive index and viscosity. Therefore,this material was tested for a potential biological application and was shown to be non-cytotoxic in eluate and direct contact tests. The materials will in the future be investigated in further studies as vitreous body substitutes. In addition, enzymatic degradation of these hydrogels was performed using hyaluronidase to specifically degrade the HA. During the degradation of these hydrogels, increase in the Tgel was observed along with decrease in the mechanical properties. The aminated PEPE were further utilised in the covalent coupling to Pectin and chondroitin sulphate by using EDC as a coupling agent. Here, it was possible to adjust the Tgel (28-33 °C) by varying the grafting density of PEPE to the biopolymer. The grafting of PEPE to Pectin enhanced the thermal stability of the hydrogel. The Pec-g-PEPE hydrogels were degradable by enzymes with slight increase in Tgel and decrease in G′ during the degradation time. The covalent coupling of aminated PEPE to HA was performed by DMTMM as a coupling agent. This method of coupling was observed to be more efficient compared to EDC mediated coupling. Moreover, the purification of the final product was performed by ultrafiltration technique, which efficiently removed the unreacted PEPE from the final product, which was not sufficiently achieved by dialysis. Interestingly, the final products of these reaction were in a gel state and showed enhancement in the mechanical properties at very low concentrations (2.5 wt%) near body temperature. In these hydrogels the resulting increase in mechanical properties was due to the combined effect of micelle packing (physical interactions) by PEPE and covalent netpoints between PEPE and HA. PEPE alone or the physical mixtures of the same components were not able to show thermosensitive behavior at concentrations below 16 wt%. These thermosensitive hydrogels also showed on demand solubilisation by enzymatic degradation. The concept of thermosensitivity was introduced to 3D architectured porous hydrogels, by covalently grafting the PEPE to gelatin and crosslinking with LDI as a crosslinker. Here, the grafted PEPE resulted in a decrease in the helix formation in gelatin chains and after fixing the gelatin chains by crosslinking, the system showed an enhancement in the mechanical properties upon heating (34-42 °C) which was reversible upon cooling. A possible explanation of the reversible changes in mechanical properties is the strong physical interactions between micelles formed by PEPE being covalently linked to gelatin. Above the transition temperature, the local properties were evaluated by AFM indentation of pore walls in which an increase in elastic modulus (E) at higher temperature (37 °C) was observed. The water uptake of these thermosensitive architectured porous hydrogels was also influenced by PEPE and temperature (25 °C and 37 °C), showing lower water up take at higher temperature and vice versa. In addition, due to the lower water uptake at high temperature, the rate of hydrolytic degradation of these systems was found to be decreased when compared to pure gelatin architectured porous hydrogels. Such temperature sensitive architectured porous hydrogels could be important for e.g. stem cell culturing, cell differentiation and guided cell migration, etc. Altogether, it was possible to demonstrate that the crosslinking of micelles by a macromolecular crosslinker increased the shear moduli, viscosity, and stability towards dissolution of CMC-based gels. This effect could be likewise be realized by covalent or non-covalent mechanisms such as, micelle interactions, physical interactions of gelatin chains and physical interactions between gelatin chains and micelles. Moreover, the covalent grafting of PEPE will create additional net-points which also influence the mechanical properties of thermosensitive architectured porous hydrogels. Overall, the physical and chemical interactions and reversible physical interactions in such thermosensitive architectured porous hydrogels gave a control over the mechanical properties of such complex system. The hydrogels showing change of mechanical properties without a sol-gel transition or volume change are especially interesting for further study with cell proliferation and differentiation. / In der vorliegenden Arbeit wurden thermosensitive Hydrogele mit einstellbaren thermo-mechanischen Eigenschaften synthetisiert. Im Allgemeinen basiert der thermische Übergang thermosensitiver Gele auf einer niedrigsten kritischen Löslichkeitstemperatur (LCST) oder kritischer Mizellkonzentration bzw. –temperatur(CMC/ CMT). Der temperaturabhängige Übergang von Sol zu Gel mit großer Volumenänderung wurde im ersten Fall bei thermosensitiven Hydrogelen beobachtet und ist vernachlässigbar für CMC/ CMT abhängige Systeme. Die Änderung des Volumens führt zum Ausschluss von Wassermolekülen, was zum Schrumpfen und Versteifen des Systems oberhalb der Übergangstemperatur führt. Die Volumenänderung kann unerwünscht sein, wenn Zellen in das Gel eingeschlossen werden sollen. Die Gelierung im zweiten Fall beruht hauptsächlich auf der Mizellbildung oberhalb der Übergangstemperatur und weiterem kolloidalem Packen von Mizellen im Bereich der Gelierungstemperatur. Weil die Gelierung hauptsächlich von der Polymerkonzentration abhängt, kann sich das Gel bei Zugabe von Lösungsmittel leicht wieder lösen. Hier sollten thermosensitive Gele entwickelt werden, die auf zwei Komponenten beruhen. Eine Komponente sollte aus einem ABA-Triblockcopolymer mit thermosensitiven Eigenschaften bestehen, dem Poly(ethylen glycol)-b-Poly(propylenglycol)-b-Poly(ethylen glycol) (PEPE), dessen Sol-Gel-Übergang auf Mizellierung und kolloidalem Jamming der gebildeten Mizellen basiert, und einer weiteren makromolekularen Komponente, einem Biopolymer, dass die Mizellen vernetzt. Auf diese Weise sollten thermosensitive Gele realisiert werden, die keine oder nur eine kleine Volumenänderung während der Änderung der mechanischen Eigenschaften zeigen, die stabiler gegenüber Verdünnung sein sollten als klassische Hydrogele mit einem CMC-basierten Übergang und die jedoch gezielt abgebaut werden können. Die Hydrogele wurden auf zwei Arten vernetzt, entweder durch physikalisches Vermischen, bei dem die Vernetzung durch elektrostatische Wechselwirkungen erfolgte, oder durch kovalente Kopplung der beiden Komponenten. Als makromolekulare Komponente zur Vernetzung der Mizellen wurden Biopolymere (hier: die Polysaccharide Hyaluronsäure (HA), Chondroitinsulfat oder Pektin oder das Protein Gelatin) verwendet, um die Hydrogele enzymatisch abbaubar zu gestalten. Um eine starke ionische/elektrostatische Wechselwirkung zwischen dem PEPE und den Polysachariden zu erzielen, wurde PEPE aminiert, um hauptsächlich monoaminiertes bzw. diaminiertes PEPE einsetzen zu können. Die Gele, die auf der physikalischen Mischung von aminierten PEPE mit HA bestehen, zeigten im Vergleich zu PEPE bei gleicher Konzentration eine Zunahme der mechanischen Eigenschaften, wie beispielsweise dem elastischem Modulus (G′) und dem Viskositätsmodulus (G′′) bei gleichzeitiger Abnahme der Gelierungstemperatur (Tgel). Durch Variation des Gehalts an aminierten PEPE-, konnte die Tgel in einem Bereich von 27-36 °C eingestellt werden. Interessanterweise zeigten die physikalischen Mischungen mit diaminierten PEPE (HA·di-PEPE) höhere mechanische Eigenschaften (elastischer Modulus G′) und eine höhere Stabilität gegenüber Verdünnungseffekten als Mischungen mit monoaminiertem PEPE (HA·mono-PEPE). Dies zeigt den starken Einfluss der elektrostatischen Wechselwirkungen zwischen der Carboxylgruppe der HA und der Amingruppe von PEPE. Die physikalischen Eigenschaften HA·di-PEPE sind vergleichbar mit den physikalischen Eigenschaften des Glaskörpers im Auge hinsichtlich Transparenz, Brechungsindex und Viskosität. Deswegen wurde das Material hinsichtlich seiner biologischen Anwendung getestet und zeigte sich sowohl im Überstand als auch im direkten Kontakt als nichtzytotoxisch. Zukünftig wird dieses Material in weiteren Untersuchungen bezüglich seiner Eignung als Glaskörperersatz geprüft werden. Zusätzlich konnte der enzymatische Abbau der Hydrogele mit Hyaluronidase gezeigt werden, die spezifisch HA abbaut. Beim Abbau der Hydrogele stieg Tgel bei gleichzeitiger Abnahme der mechanischen Eigenschaften. Aminiertes PEPE wurde zusätzlich zur kovalenten Bindung unter Verwendung von EDC als Aktivator an Pektin und Chondroitinsulfat eingesetzt. Tgel konnte auf 28 – 33 °C eingestellt werden durch Variation der Pfropfungsdichte am Biopolymer bei gleichzeitiger Zunahme der thermischen Stabilität. Die Pec-g-PEPE Hydrogele waren enzymatisch abbaubar, was zu einer leichten Erhöhung von Tgel und zu einer Abnahme von G′ führte. Die kovalente Bindung der aminierten PEPE an HA erfolgte unter Verwendung von DMTMM als Aktivator, der sich in diesem Fall als effektiver als EDC herausstellte. Die Reinigung mittels Ultrafiltration führte zu einer deutlich besseren Aufreinigung des Produkts als mittels Dialyse. Die gegrafteten Systeme waren in Nähe der Körpertemperatur bereits im Gelstadium und zeigten eine Erhöhung der mechanischen Eigenschaften bereits bei sehr geringen Konzentrationen von 2.5Gew.%. Die höheren mechanischen Eigenschaften dieser Hydrogele erklären sich durch die Kombination der Mizellbildung (physikalische Wechselwirkung) des PEPE und der Bildung kovalenter Netzpunkte zwischen PEPE und HA. PEPE bzw. entsprechende physikalische Mischungen derselben Komponenten zeigten kein thermosensitives Verhalten bei einer Konzentration unterhalb von 16 Gew%. Diese thermosensitiven Hydrogele zeigten auch eine Löslichkeit auf Abruf durch enzymatischen Abbau. Das Konzept der Thermosensitivität wurde in 3D strukturierte, poröse Hydrogele (TArcGel)eingeführt, bei dem PEPE kovalent an Gelatin gebunden wurde und mit LDI vernetzt wurde. Das gepfropfte PEPE führte zu einer Erniedrigung der Helixbildung der Gelatinketten. Nach Fixierung der Gelatinketten durch Vernetzung zeigte das System eine Erhöhung der mechanischen Eigenschaften bei Erwärmung (34-42 °C). Dieses Phänomen war reversibel beim Abkühlen. Eine mögliche Erklärung der reversiblen Änderungen bezüglich der mechanischen Eigenschaften sind die starken physikalischen Wechselwirkungen zwischen den Mizellen des PEPE, die kovalent an Gelatin gebunden wurden. Ferner wurde durch AFM Untersuchungen festgestellt, dass bei Temperaturerhöhung (37 °C) die örtlichen elastischen Moduli (E) der Zellwände zugenommen haben. Zusätzlich wurde die Wasseraufnahme der TArcGele durch PEPE und die Temperatur (25 °C und 37 °C) beeinflusst und zeigte eine niedrigere Wasseraufnahme bei höherer Temperatur und umgekehrt. Durch die niedrigere Wasseraufnahme bei hohen Temperaturen erniedrigte sich die Geschwindigkeit des hydrolytischen Abbaus im Vergleich zu dem strukturierten Hydrogel aus reiner Gelatin. Diese temperatursensitiven ArcGele könnten bedeutsam sein für Anwendungen im Bereich Stammzellkultivierung, Zelldifferenzierung und gerichteter Zellmigration. Zusammenfassend konnte bei den thermosensitiven Hydrogelen gezeigt werden, dass die Vernetzung von Mizellen mit einem makromolekularen Vernetzer die Schermoduli, Viskosität und Löslichkeitsstabilität im Vergleich zu reinen ABATriblockcopolymeren mit CMC-Übergang erhöht. Dieser Effekt konnte durch kovalente und nichtkovalente Mechanismen, wie beispielsweise Mizell- Wechselwirkungen, physikalische Interaktionen von Gelatinketten und physikalische Interaktionen von Gelatinketten und Mizellen, realisiert werden. Das Pfropfen von PEPE führte zu zusätzlichen Netzpunkten, die die mechanischen Eigenschaften der thermosensitiven architekturisierten, porösen Hydrogele beeinflussten. Insgesamt ermöglichten die physikalischen und chemischen Bindungen und die reversiblen physikalischen Wechselwirkungen in den strukturierten, porösen Hydrogelen eine Kontrolle der mechanischen Eigenschaften in diesem sehr komplexen System. Die Hydrogele, die eine Veränderung ihrer mechanischen Eigenschaften ohne Volumenänderung oder Sol-Gel-Übergang zeigen sind besonders interessant für Untersuchungen bezüglich Zellproliferation und –differenzierung.

Darbo tikslas yra pagaminti La2O3 sluoksnius, atkaitinant prie aukštų temperatūrų nenaudojant vakuumo ir ištirti gautų sluoksnių Rentgeno fotoelektronų spektrus. Darbe aprašyti Rentgeno fotoelektronų spektroskopijos (RFS) (XPS - X-ray photoelectron spectroscopy) metodo, naudojamo įvairių medžiagų paviršių cheminei sudėčiai nustatyti, pagrindai. Pirmajame skyriuje aprašytas Rentgeno fotoelektroninės spektroskopijos metodas, pagrindinė RFS aparatūra bei teorinė dalis. Antrajame skyriuje aprašyti: La2O3 oksidiniai junginiai ir jų tyrimų metodika, plonų nanostruktūrizuotų medžiagų sluoksnių nusodinimo iš dujų fazės (plazmos) metodas- magnetroninis dulkinimas (magnetron sputtering), aparatūra ir zolis – gelis metodas. Trečiasis skyrius yra skirtas Rentgeno fotoelektroninių spektrų matavimų, naudojant spektrometrą XSAM 800 (Kratos Analytical, Didžioji Britanija) ypatumams ir bandinių gamybos metodikai aptarti. Pateiktas išsamus La2O3 sintezės zolių-gelių metodu technologijos aprašymas. Ketvirtajame skyriuje pateikiami eksperimentiniai rezultatai gauti, matuojant La2O3 Rentgeno fotoelektronų spektrus. Darbo pabaigoje yra pateikiamos išvados, kurios galėtų būti naudingos, tobulinant La2O3 bandinių gamybos technologiją. Gautas rezultatas: nustatyta, kad zolių – gelių technologija leidžia paprastais metodais, nenaudojant sudėtingos aparatūros,bei vakuuminės įrangos susintetinti La2O3. / The aim of presented work was to synthesis by using sol-gel technology and investigate the X- ray photoelectron spectra (XPS) of La2O3 thin films in the annealed high temperature and without using vacuum installation. In the present work we described the essentials of the method of X-ray photoelectron spectroscopy, used to determine chemical composition of various materials. In the first part describes the X- ray photo-electronic spectroscopy method, basic XPS equipment and theoretical part. The second part are described: La2O3 oxide compounds and the methods of their production from the gas phase – magnetron sputtering and sol – gel method. In the third part we discussed the peculiarities and methodology of spectrometer XSAM 800 (Kratos Analytical, Great Britain) samples production while measuring X-ray photoelectron spectra. The thorough description of the technology by synthesis of La2O3 sol-gel method was provided. The fourth part presents the experimental results obtained by measuring the La2O3X-ray photoelectron spectra. In the end of the work conclusions are produced that could be useful in improving production technology of La2O3 samples. Obtained results: we identified that sol-gel technology allows synthesizing La2O3 by simple methods, without using sophisticated equipment and vacuum installation.

The interaction between metal nanoparticles and small molecules has been investigated by FTIR and UV-visible absorption spectroscopy. Electrospray deposition into an argon matrix was chosen as the initial method. An electrospray metal source was tested in development stage. Both the formation of a stable corona discharge as well as a stable Taylor cone were successfully completed. Problems arose when the entire system was tested. It was determined that the vacuum was insufficient for the length of the flight path. Focus then shifted to nanoparticles in more conventional environments. Sol-gel encapsulated nanoparticles were generated, in the form of both monoliths as well as thin film coatings on silicon wafers. The gels were exposed to 1atm of carbon monoxide in a gas cell. The method encountered problems due to spectral interference from the matrix. The next attempt consisted of solution stabilized nanoparticles. The solution was exposed to various amounts of both ammonium sulphate and diethylamine. There was again the problem of solvent interference, even when attempting to observe the system using Raman spectroscopy. Finally, surface stabilized nanoparticles were generated, using 3-mercaptopropyltrimethoxysilane to adhere the particles to glass slides. While the coating was successfully applied to the glass slides, as confirmed with Raman spectroscopy, it was not possible to get the nanoparticles to adhere. Future outlook for this project is briefly reviewed. / Thesis (Master, Chemistry) -- Queen's University, 2009-06-26 10:30:58.295

Zolis-gelis procesas, kuris turi potencialiai didelę technologinę vertę, leidžia sukurti medžiagas, kurių unikalios struktūros ir savybės yra retai gaunamos naudojant kitus metodus. Šio darbo užduotis- pagaminti Vanadžio-Titano-hidrochinono oksidinę bronzą panaudojant zolis-gelis technologiją bei ištirti vanadžio ir titano jonų valentingumą juose naudojant Rentgeno fotoelektronų spektroskopijos metodą. Darbe aprašoma Zolio-Gelio technologijos pagrindai, Rentgeno fotoelektronų spektroskopija ir jos spinduliuotės prietaisai, bei matavimo metodika. Aprašyti eksperimentiniai bronzos ir vanadžio – titano- hidrochinono kserogelio Rentgeno Fotoelektronų spektrai. Darbe pateikti ir lyginami grafikai buvo braižomi paisnaudojus įvairiomis programomis (SDP, XPS ir Origin). Apibendrinant šio darbo rezultatus, galima teigti, jog Vanadžio- Titano- hidrohinono kserogelyje vanadis yra V5+, V4+ ir V3+ būsenose, o deguonies jonai surišti su vanadžiu, hidroksilinėmis grupėmis ir molekuliniu vandeniu. Vanadžio- Titano- hidrochinono kserogelio kaitinimas aplinkos atmosferoje iki 580K leidžia visiškai pašalinti iš kserogelio chemiškai surišta vandenį, tai yra pereiti nuo kserogelio prie bronzos. / Sol-gel process, which has a potentially high technological value, allows you to create materials with unique structure and properties are reraly generated using other methods. This work made the task – Vanadium-Titanium-hydroquinone oxidic bronze using the sol-gel technology and study of vanadium and titanium ion valence them using X- ray photoelectron spectroscopy. The paper describes the sol-gel technology basics, X-ray photoelectron spectroscopy radiation devices, and measurement techniques. Describe the experimental and vanadium - titanium - hydroquinone xerogels and bronze X-ray photoelectron spectra. The paper presents and compares graphs were drawn from this various programs (SDP, XPS and Original). Summing up the results, one can argue that the vanadium-titanium in xerogel is V5+, V4+ and V3+ states and the oxygen ions are bound to vanadium hydroxyl groups and molecular water. Vanadium- titanium-hydroquinone xerogels heating in the atmosphere to 580K allows to completely remove from the xerogels chemically bound water which is the transition from xerogels to bronze. Vanadium and titanium ions in the bronze are in stable V5+ and Ti4+ states respectively.

Titanium dioxide is a well-studied and popular photocatalyst, but a number of factors still prevent its widespread use in a number of commercial applications. In this thesis we explored the synthesis of titanium dioxide nanoparticles via the sol-gel method, with the goal of creating a viable catalyst for the visible-light degradation of wastewater dyes. A number of different synthetic pathways were explored and developed, and the products categorised with respect to nanoparticle size, shape and crystallinity as well as electronic and photocatalytic properties.

This dissertation addresses three research areas in the sol-gel synthesis of functionalmaterials. The first is the kinetics of hydrolysis and condensation of variousorganoalkoxysilanes. Two mathematical models are developed for the sol-gel reaction inbasic conditions with and without nearest-neighbor effects. Effects on reactivity aremeasured with systematic changes in the organic group structure. Replacing onemethoxy group on the precursor with a methyl group decelerates hydrolysis under basicconditions, but accelerates condensation under acidic conditions. Replacing two methylfunctionalprecursors with one ethylene-bridged precursor accelerates hydrolysis in base,but decelerates condensation in acid. Replacing an ethylene bridge with a hexylenebridge always decelerates the sol-gel reactions. Adding an amine into the hexylenebridge always accelerates the sol-gel reactions. These trends show inductive effectsplaying a role only under basic conditions, while steric effects play a role at all pHvalues. The second topic of this thesis is the synthesis of organic-inorganic materialswith bridging or non-bridging organics. The structure of the organic-inorganic hybrids ispartially correlated with the kinetics of the precursors, but the trends indicate anadditional structural role of siloxane cyclization. The third topic of this thesis is thesynthesis of surfactant-templated nanoporous particles. The key to preparing orderedhybrid materials is found to be encouraging aggregation with a surfactant whilediscouraging random condensation of silanes independent of the surfactants. Ahomologous series of cationic pyridinium chloride fluorinated surfactants with varyingchain length are used as pore templates. Typical pore structures such as hexagonal closepackedcylinders are synthesized, as well as new pore structures including random meshphase pores and vesicular silica particles with bilayer or multilayer shells.Fluorosurfactants enable the formation of unusually small pores (1.6 nm) and poresformed from discs or bilayers. In the presence of ethanol, spherical particles with radiallyoriented pores are shown by TEM to form by precipitation of disordered silica-surfactantparticles followed by assembly into organized structures. High-capacity hollow particleswith ordered mesoporous shells are prepared by dual latex / surfactant templating.Finally, we load amine-functionalized mesoporous silica with highly dispersedsuperparamagnetic iron oxide nanoparticles.

Surface modification is an extensively researched approach in order to overcomethe limitations, and improve the performance of orthopedic and dental implants. It is atthe surface of the implant materials that the initial interactions of tissues or body fluidstake place. Therefore, surface properties of biomaterials are the important factors that cancontrol these biological responses. Molecular imprinting is a surface modificationtechnique that creates specific recognition sites on the surface of biomaterials. Todevelop the recognition sites, a functional monomer is assembled with templatebiomolecule and then crosslinked. After removal of the template, the surface can rebindthe molecules. Therefore, desired reactions can be initiated at the interface between tissueand implants by modifying surfaces to selectively bind certain types of biomolecules,such as proteins. The objective of this project was to observe the potential of molecularimprinting technique for creating biomaterials that can recognize specific biomolecules.Fluorescently labeled lysozyme or RNase A was used as a template biomolecule and theprotein-imprinted scaffolds were fabricated by sol-gel processing. To interpret the densityof binding sites created, the quantity of surface-accessible protein was determined. Theamount of protein available on the surface was proportional to the amount loaded.Protein-imprinted scaffolds were evaluated for their ability to selectively recognize thetemplate biomolecule. Further, for these selectivity studies, a combination of theimprinted protein and a competitor protein were rebound to the polysiloxane scaffolds.The template protein rebound to the surface was measured more than twice as much ascompetitor. These scaffolds were then tested to understand their interaction with cells.The results of DNA and alkaline phosphatase activities indicate that the scaffolds thusdeveloped support growth and adhesion of osteoblastic cells. These initial selectivity andcytocompatibility studies show the potential of molecular-imprinted polysiloxanescaffolds to be used as tissue engineered materials for stable and controlled interactions atthe tissue-implant interface.

Molecular imprinting, a common method used in separations and chromatography to isolate specific molecules via surface binding, has been adapted for applications in biomaterials and related sciences. The objective of this study was to determine the effectiveness of different approaches to molecular imprinting by testing for preferential binding of protein on polysiloxane scaffold surfaces. To test preferential rebinding, the scaffolds were exposed to a mixture of the template protein and a competitor protein with similar size but different chemistry. Lysozyme-imprinted polymers rebound 8.13 0.99% of lysozyme without any competition and 5.1 0.3% of the protein during competition. Lysozyme C peptide was imprinted into polysiloxane scaffolds to investigate the epitope approach to molecular imprinting. Without competition, 8.95 11.53% of the lysozyme preferentially bound to the scaffolds, while under competition 1.85 9.47% bound to the scaffolds. Lastly, bone morphogenetic protein 2 (BMP-2) was imprinted into the polymer scaffolds. Results revealed that BMP-2 imprinted scaffolds bound 10.09 6.625% under noncompetitive conditions and a very small 0.65 4.55% during competition. Trends of preferential binding via peptide imprinting and BMP-2 imprinting can be seen, and show promise in future tissue engineering material applications and biomaterial compatibility.

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.

Nanomaterials are currently attracting billions of dollars in research funding and are entering such diverse fields as the computing, communications, life science and energy sectors. The growing popularity of nanomaterials demands a comprehensive understanding of the means by which such materials can be produced including the effects of physical and chemical factors. One method of forming inorganic nanomaterials is the sol-gel process; a low temperature process combining the benefits of glass and plastics technology. Whilst the research community has ascertained that gravity is important and appears to affect the sol-gel process, no coherent picture of the role of gravity on the sol-gel process has been proposed. The flexibility of the sol-gel process, and the promise it holds for creating products as diverse as hydrogen fuel cell membranes through to protective coatings for space vehicles, make it an important area of study. This thesis addressed a fundamental gap in the scientific knowledge concerned with the sol-gel process: how and why does gravity affect the sol-gel process? The nanomaterial chosen for study was a xerogel, a dense compound with a high surface area which finds applications in high temperature ceramics, energy saving coatings, molecular filtration and thin film sensors. The xerogel was produced from an acid catalysed sol. 2ml samples of the sol were subjected to reduced, normal and high gravity levels, and the resultant xerogels were characterised through liquid and solid state NMR and nitrogen adsorption/desorption techniques. Viscosity and pH measurements were also recorded. Reduced gravity conditions were provided by NASA’s KC-135 aircraft which is capable of creating a 25 second window of 1x10−2 gravities. A centrifuge was utilised to simulate increased gravity environments and xerogels were formed between 2 and 70 gravities. Analysis of the results led to two major contributions to this field of scientific endeavour. It was concluded that (1) gravity affected the reaction pathways of the sol-gel process and (2) gravity directly altered the molecular structure of xerogels The second contribution was determined through the NMR studies, where it was shown that a reduction in gravity resulted in a molecular structure composed of extended branches of cyclic compounds. Due to a decrease in convection in reduced gravity the molecular structure of the sample was dominated by cyclisation. In terrestrial and high gravity the molecular structure grew through both bimolecularisation and cyclisation reactions. Thus the gravity level also determined the reaction pathway available within the sol by creating a more or less convective environment. This created a structure composed of cyclics (rings) and chains. As gelation and drying of the sol occurred there was a loss in Q4 group amount. Chains, having a higher energy configuration than rings, underwent repolymerisation. Short chains formed which reacted end-to-end to form small, stable rings. The rings packed together more closely within the liquid sol and delayed the formation of a spanning cluster. The greater the gravity level, the greater the extent of bimolecularisation reactions contributing to chain formation, in turn allowing a greater degree of repolymerisation of the molecular structure. Thus gel times increased as the gravity level increased. Again gravity directly affected the reaction pathway of the sol-gel process. In reduced gravity the sol gelled very quickly due to the formation of a cyclic structure which was not capable of repolymerisation. The final contribution of this thesis was the proposal of a mechanistic model. The model depicted the ffect of gravity on the formation of the molecular structure of a xerogel.