Poly (glycerol-sebacate) (PGS) is a synthetic bioelastomer with a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. This biodegradable polymer is biocompatible (in vitro and in vivo), tough, elastic, inexpensive, and flexible, and finds potential applications in tissue engineering and regenerative medicine. Due to the slow rate of step-growth polymerisation, the synthesis of PGS prepolymer requires 24-48 h. A batch and a continuous process, if developed, could address the inherent deficiencies (eg. long residence time, venting) associated with the large-scale synthesis of such bioelastomers. However, in order to assess whether this particular system may be adapted to continuous processes, such as reactive extrusion, studies on kinetics of controlled condensation reactions are of vital importance. FT-Raman spectroscopy was used to study the kinetics of the step-growth reactions between glycerol (G) and sebacic acid (SA) at three molar ratios (G:SA= 0.6,0.8,1.0) and three temperatures (120, 130, 140 ˚C). The rate curves followed first-order kinetics with respect to sebacic acid concentration in the kinetics regime. An increase in the molar ratio (G : SA) of the reactants decreased the average functionality of the system and the crosslinking density, resulting in the lowering of the activation energy and pre-exponential factor. The average functionality of the system had a profound effect on the crosslinking density, mechanical properties, and the reaction kinetics of the system. Three different PGS oligomers and films (PGS 0.6, PGS 0.8, PGS 1.0) were thoroughly characterised using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and contact angle measurements. FTIR spectra of PGS oligomers confirmed the formation of ester bonds (1740 cm -1). Quantification of various functional groups in PGS films using XPS was in agreement with the theoretical values of the proposed structure. WAXS results indicated that PGS system with a higher average functionality possesses a higher degree of crystallinity. Crystallisation exotherms and melting endotherms of PGS systems revealed that the average functionality influences the density of crosslinking, degree of crystallinity, and the network structure of bioelastomers. Contact angle studies confirmed that an increase in the average functionality of PGS system increases hydrophilicity, and the surface treatment through aminolysis further increases the hydrophilicity of the films. Batch studies were performed on a Brabender Plasticorder®. The samples collected over a reaction period of 5 h were characterised using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The number-average molecular weight (Mn) and the weight-average molecular weight (Mw) of the oligoesters were determined using matrix-assisted laser desroption/ionization time-of-flight spectroscopy (MALDI-TOF) and compared with the corresponding values from the benchtop synthesis. It was found that due to higher shear-mixing and better orientation of functional groups, the degree of polymerisation at any stage of the reaction was higher in the Brabender than in the benchtop process. The gel-point of the reaction was determined from the crossover point of storage and loss moduli, and the reaction rate constant was calculated using the torque vs time data of the rheometer. The kinetics rate constant and the extent of the reaction in the Brabender were found to be higher than the corresponding values obtained from the conventional benchtop process by a factor of 2. PGS was found to be thermo-mouldable and adaptable to high-shear mixing, and hence is a better candidate for making thermoplastic elastomers using reactive extrusion. The challenges and possibilities in scaling up a batch process to a continuous process were investigated. The use of a wiped film reactor or a disk reactor along with reactive extrusion and batch-mixing (as a post-extrusion operation) is a commercially viable method to synthesise PGS oligomers. Such a continuous process will boost the production of bioelastomers for tissue engineering application by addressing the constraints in step-growth polymerisation. Finally, the effect of PGS substrate stiffness and surface treatment (aminolysis, hydrolysis, layer-by-layer deposition) on the morphology and lineage of mesenchymal stem cells – which have a capacity to differentiate themselves into cartilage, adipose, tendon, and muscle tissues – was analysed using fluorescence microscopy and DNA and protein assays. Stiffness of the PGS surface and the method of treatment influenced the cell attachment and spreading on different surfaces. However, cells did not differentiate into definite phenotypes at the end of 14 d time-point, indicating that higher time-points are needed to be considered to study the effect of matrix stiffness and surface treatment on cell attachment and phenotype differentiation.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 132-140).

Catalytic combustion is an environmentally benign technologywhich has recently reached the stage of commercialization.Palladium is the catalyst of choice when considering gasturbines fuelled with natural gas because of its superioractivity for methane oxidation. Several fundamental issues arestill open and their understanding would result in animprovement of the technology. Hence, the work presented inthis thesis aims at the identification of some of theparameters which govern the combustion activity ofpalladium-based catalysts. The first part of this work gives a background to catalyticcombustion and a brief comparison with other existingtechnologies. Paper I reviews some of the issues related tomaterial development and combustor design. The second part of this thesis consists of an experimentalinvestigation on palladium-based catalysts. The influence ofthe preparation method onthe properties of these catalystmaterials is investigated in Paper II. Paper III examines theactivity of the following catalysts: Pd/Al2O3, Pd/Ba-Al2O3 andPd/La-Al2O3. Specific attention is given to the metal-supportinteraction which strongly affects the combustion activity ofpalladium. The effect of doping of the support by addition ofcerium is reported in Paper IV. Finally, the deactivation of combustion catalysts isconsidered. The various deactivation processes which may affecthigh temperature combustion catalysts are reviewed in Paper V.Paper VI focuses on the poisoning of supported palladiumcatalysts by sulphur species. Palladium exhibits a higherresistance to sulphur poisoning than transition metals.Nevertheless, the nature of the support material plays animportant role and may entail a severe loss of activity whensulphur is present in the fuel-air mixture entering thecombustion chamber. <b>Keywords</b>: catalytic combustion, gas turbine, methane,palladium, alumina, barium, lanthanum, oxidation, preparation,temperature-programmed oxidation (TPO), decomposition,reoxidation, X-ray photoelectron spectroscopy (XPS),metal-support interaction, deactivation, sulphur, poisoning.The cover illustration is a TEM picture of a 100 nm palladiumparticle supported on alumina

In this thesis, firstly, carbon-supported platinum nanoparticle catalysts have been prepared by using PtCl4 and H2PtCl6 as starting materials and 1-hexanethiol, and tert-octanethiol, as surfactants for the first time. Secondly, these prepared catalysts were heated to 200 &deg / C, 300 &deg / C, and 400 &deg / C for 4 h under argon gas. Lastly, PtRu/C catalysts, which have different atomic percent ratios of Pt and Ru (Pt/Ru: 0.8, 2.1 and 3.5), were prepared using PtCl4 and RuCl3 as starting materials and tert-octanethiol as a surfactant. Each was characterized by X-ray diffraction, transmission electron microscopy, energy dispersive analysis, X-ray photoelectron spectroscopy, cyclic voltammetry, and elemental analysis, and their activities were determined toward the methanol oxidation reaction. It has been found that all prepared catalysts are more active toward methanol oxidation reaction compared to the commercial catalysts. It was also found that increasing the temperature during the heat treatment process results in an enlargement of platinum particle size and a decrease in catalytic activity in the methanol oxidation reaction. Transmission electron microscopy shows that platinum nanoparticles are homogeneously dispersed on the carbon support and exhibited a narrow size distribution with an average particle size of about 2-3 nm in diameter. X-ray photoelectron spectra of all catalysts indicated that most of the platinum nanoparticles (&gt / 70 %) have an oxidation state of zero and rest (&lt / 30 %) have a +4 oxidation state with (Pt 4f7/2) binding energies of 71.2-72.2 and 74.3-75.5 eV, respectively.

The work of this thesis comprises extensive Noncontact Atomic Force Microscopy (NC-AFM) characterization of clean metal-oxide (YSZ(100)/(111) and MgO(100)) and graphitic (HOPG) supports as templates for the novel, photochemically induced nucleation of cobalt oxide nanostructures, particularly Cobalt (III) Oxide. The nanostructure-support surfaces were also studied by X-ray Photoelectron Spectroscopy (XPS) to verify the nature of the supported cobalt oxide and to corroborate the surface topographic and phase NC-AFM data. Heteroepitaxial growth of Co2O3 nanostructures proves to exhibit a variety of different growth modes based on the structure of the support surface. On this basis, single-crystal support surfaces ranging from nonpolar to polar and atomically flat to highly defective and reactive were chosen, again, yielding numerous substrate-nanostructure interactions that could be probed by high-performance surface science techniques.

In this thesis, carbon supported platinum nanoparticle catalysts were prepared using PtCl4 and H2PtCl6 as starting materials and 1-heptanethiol, tert-nonyl mercaptan, 1-hexadecanethiol, 1-octadecanethiol as surfactants. These new catalysts were employed for methanol oxidation reaction which are used for direct methanol fuel cells. Tert-nonyl mercaptane was used for the first time in this type of reaction and the other surfactants were used for comparison of the catalysts performance. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used in order to determine the nature of the catalysts. The average platinum crystallite particle sizes of all prepared catalysts were determined by both X-ray diffraction and transmission electron microscopy. It was found that platinum crystallizes in face-centered cubic structure and the surfactant play an important role on the size of platinum nanoparticles, branch surfactant, such as tert-nonyl mercaptane, causes an increase in the size of platinum nanoparticles, about 3 nm, compared to linear surfactant, such as 1-heptanethiol, about 2 nm. The oxidation states of platinum and their ratios were determined by XPS technique. These results indicated that platinum has two different oxidation states, zero and +4, and Pt(0) to Pt(IV) ratio is about 7.5 to 2.5. In addition to this, O 1s region of XPS was also examined and found that the surface of all of the catalysts covered by adsorbed hydroxide except the catalyst which was prepared by PtCl4 and tert-nonyl mercaptane (Catalyst IIa), where adsorption of water were observed and the catalyst which was prepared by H2PtCl6 and tert-nonyl mercaptane (Catalysts IIb), where adsorption of 65% of hydroxide and 35% of water were identified. Electrochemical studies indicated that Catalyst IIa has the maximum activity (&amp / #61566 / 342 A/gPt at 0.612 V) towards methanol oxidation reaction while Catalyst IIIb (H2PtCl6 and 1-hexanethiol were used to prepare this catalyst) has the minimum activity (&amp / #61566 / 91A/gPt at 0.580V). XRD, TEM and XPS results indicated that the optimum catalyst for methanol oxidation reaction contains about 3 nm of platinum nanoparticles, adsorbed hydroxide and water on the surface of catalyst, but sulphur. These results are in agreement with the proposed mechanism.

This study focuses on various aspects of nanocrystals embedded in a dielectric matrix. In the first part of this work, a new approach with the use of Fourier Transform Infrared spectroscopy (FTIR) in the nanocrystal analysis was developed and presented. Si and Ge nanocrystals embedded in SiO2 matrix were mainly studied. This new approach is based on the analysis of structural variations of SiO2 matrix during the formation of semiconductor nanocrystlas. It is shown that the chemical and structural variations of the host matrix are directly related to the precipitation of nanocrystals in it. This correlation provides valuable information about the presences of nanocrystals in the matrix. In the second part of this work, fabrication of SiC films with and without Si nanocrystals inclusions was studied. With this aim, stoichiometric SiC and Si rich SiC thin films were fabricated by using magnetron co-sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques. For SiC films, the structural and optical analyses were performed. For Si rich SiC films, the formation conditions of Si nanocrystals were investigated. Post annealing studies were carried out to track the evolution of the SiC matrix and formation of Si nanocrystals at different temperatures. Chemical and structural properties of the SiC host matrix were investigated with FTIR spectroscopy. Optimum conditions for the fabrication of stoichiometric SiC layers were determined. The crystallography of the nanocrystals was investigated by X-Ray Diffraction (XRD). The variation of the atomic concentrations and bond formations were investigated with X-Ray Photoelectron Spectroscopy (XPS). Raman spectroscopy and Transmission Electron Microscopy (TEM) were used to verify the formation of Si nanocrystals. We have shown that both single and multilayer Si nanocrystals can be fabricated in the amorphous SiC matrix for applications such as light emitting diodes and solar cells.

In this work, two groups of carbon supported Pt-Pd catalysts have been prepared in order to investigate the effect of Pd, as a second metal, and surfactants on the catalytic activity towards methanol and ethanol oxidation reactions used in the direct methanol and ethanol fuel cells. In the first group (group a), 1- hexanethiol was used as a stabilizing agent while in the second group (group b), 1,1 dimethyl hexanethiol was utilized. Cyclic voltammetry (CV), chronoamperometry (CA), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used in order to determine the nature of the catalysts. The average crystalline size of the metal particles in the catalysts was explored by XRD and TEM. TEM results revealed the uniform distribution of the metal nanoparticles on carbon support with a narrow size distribution in the range of 3.0 to 3.7 nm and the average crystalline sizes of metal particles for group &ldquo / b&rdquo / catalysts were larger than that of group &ldquo / a&rdquo / catalysts which can be explained by the surfactant effect. These results were in good agreement with XRD data. The oxidation states of platinum (Pt(0) and Pt(IV)) and palladium (Pd(0) and Pd(II)) and their ratios were investigated by XPS and for the most active catalyst, catalyst Ib, these ratios were found to be as 6.94 and 13.7, respectively. Electrochemical activities of the catalysts towards methanol and ethanol oxidation reactions were recorded and compared with that of Pt/C and the commercial Pt (ETEK 20 %wt) catalysts. The results indicated that the group &lsquo / b&rsquo / catalyst has greater catalytic activities than that of group &lsquo / a&rsquo / catalysts. Catalyst Ib comes into prominence as the most active catalyst due to its superior characteristics that it possess such as highest extent of alloying with respect to the palladium amount used, active surface area, CO-tolerance, stability and Pt (0) to Pt (IV) and Pd (0) to Pd (II) ratios.

<p>Catalytic combustion is an environmentally benign technologywhich has recently reached the stage of commercialization.Palladium is the catalyst of choice when considering gasturbines fuelled with natural gas because of its superioractivity for methane oxidation. Several fundamental issues arestill open and their understanding would result in animprovement of the technology. Hence, the work presented inthis thesis aims at the identification of some of theparameters which govern the combustion activity ofpalladium-based catalysts.</p><p>The first part of this work gives a background to catalyticcombustion and a brief comparison with other existingtechnologies. Paper I reviews some of the issues related tomaterial development and combustor design.</p><p>The second part of this thesis consists of an experimentalinvestigation on palladium-based catalysts. The influence ofthe preparation method onthe properties of these catalystmaterials is investigated in Paper II. Paper III examines theactivity of the following catalysts: Pd/Al2O3, Pd/Ba-Al2O3 andPd/La-Al2O3. Specific attention is given to the metal-supportinteraction which strongly affects the combustion activity ofpalladium. The effect of doping of the support by addition ofcerium is reported in Paper IV.</p><p>Finally, the deactivation of combustion catalysts isconsidered. The various deactivation processes which may affecthigh temperature combustion catalysts are reviewed in Paper V.Paper VI focuses on the poisoning of supported palladiumcatalysts by sulphur species. Palladium exhibits a higherresistance to sulphur poisoning than transition metals.Nevertheless, the nature of the support material plays animportant role and may entail a severe loss of activity whensulphur is present in the fuel-air mixture entering thecombustion chamber.</p><p><b>Keywords</b>: catalytic combustion, gas turbine, methane,palladium, alumina, barium, lanthanum, oxidation, preparation,temperature-programmed oxidation (TPO), decomposition,reoxidation, X-ray photoelectron spectroscopy (XPS),metal-support interaction, deactivation, sulphur, poisoning.The cover illustration is a TEM picture of a 100 nm palladiumparticle supported on alumina</p>

Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the <110> substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T > 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T < 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the <110> substrate orientations, whereas above 283 K a regularly ordered 1D phase arises with a +10° rotation off these high-symmetry axis. XPS reveals a structural transformation triggered by a thermally activated deprotonation of the zwitterionic ammonium group. On Ag(111), tyrosine self-assembles above a critical temperature into linear structures primarily following the substrate crystalline symmetry. A zwitterionic non-covalent molecular dimerization is demonstrated, NEXAFS data providing evidence of a non-flat adsorption of the phenyl ring. This recalls the geometrical pattern of methionine on Ag(111) and supports a universal self-assembling scheme for amino acids on close-packed noble metal surfaces, the different mesoscopic ordering being determined by the side chain reactivity.