Dissertations / Theses on the topic 'Surface chemistry of zwitterion'
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Ghisolfi, Alessio. "Applications of functionnal diphosphines quinonoid zwietterions to coordination chemistry and surface functionalization." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF016/document.
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Le but de ce travail de thèse était de développer de nouvelles familles de ligands polyfonctionnels pour étudier, dans un premier temps, leur chimie de coordination vis-à-vis de métaux de transition et, dans un second temps, en fonction des espèces formées, leurs propriétés physiques (magnétiques par exemple) et/ou catalytiques. L’évaluation de leur potentiel pour la formation de nouveaux matériaux ou la fonctionnalisation de supports métalliques faisait également partie intégrante des objectifs de cette thèse. De ce fait, chaque ligand a été fonctionnalisé avec des groupements adaptés à l’ancrage sur surfaces, comme des fonctions zwitterioniques ou des thio-éthersThe aim of this thesis was to develop new families of polyfunctional ligands to study their coordination chemistry towards transition metals and, depending on the products formed, to investigate their physical (e.g. magnetic) and / or catalytic properties. The evaluation of their potential for the formation of new materials as well as for the functionalization of metal surfaces was also part of the objective of this thesis. Therefore, each ligand has been functionalized with groups suitable for the anchoring on metallic surfaces, such as zwitterionic or thioethers moieties
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Pu, Yuzhou. "Synthesis and functionalization of hybrid plasmon-semiconductor nanoparticles for cancer phototherapy." Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLS031.
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Les nanoparticules d'or possèdent une grande section efficace d'absorption de la lumière grâce à leur effet de résonance plasmonique de surface localisée. Cela en fait des photosensibilisateurs prometteurs pour diverses applications biomédicales. En particulier, les nano-bâtonnets d'or (AuNRs) peuvent absorber efficacement la lumière dans le proche infrarouge (NIR), la fenêtre optimale pour la pénétration de la lumière dans les tissus. Par conséquent, les AuNRs présentent un potentiel important comme photosensibilisateurs.Lorsque les AuNRs absorbent la lumière, ils génèrent des électrons « chauds », à haute énergie au sein de leur structure. Ces électrons chauds peuvent convertir directement l'énergie absorbée en chaleur, ce qui entraîne une augmentation de la température dans l'environnement. Cet effet de chauffage localisé peut tuer efficacement les cellules cancéreuses. Alternativement, les électrons chauds peuvent réagir avec l'eau ou les molécules de dioxygène, ce qui produit des espèces réactives d’oxygène cytotoxiques. Ces espèces peuvent induire la mort cellulaire programmée. Cependant, les défis actuels des photothérapies réalisées par des AuNRs concernent la faible efficacité de la conversion et de l'utilisation de l'énergie plasmonique. Une solution possible pour relever ce défi consiste à combiner les AuNRs avec des semi-conducteurs. Cette combinaison permet le transfert de l'énergie lumineuse absorbée par les AuNR vers le semi-conducteur, soit par injection d'électrons chauds, soit par transfert d'énergie.Nous avons synthétisé des nanoparticules hybrides en forme d'haltères composées d’AuNR et de dioxyde de titane (TiO2) appelées AuNR/TiO2. Dans cette hétérostructure, les électrons chauds générés au sein des AuNR sont injectés dans la bande de conduction du TiO2. Ce transfert permet aux électrons chauds d'avoir une durée de vie prolongée, et de réagir efficacement avec les molécules de dioxygène dans l'environnement pour générer des radicaux hydroxyles. Pour assurer la stabilité de ces nanoparticules dans un environnement physiologique, nous avons fonctionnalisé les nanoparticules hybrides AuNR/TiO2 avec des ligands polymères de polyéthylène glycol-phosphonate. La densité de ces ligands polymères à la surface des nanoparticules joue un rôle crucial dans l'obtention d'une photoactivité optimale. Nous avons démontré l'efficacité de ces nanoparticules hybrides pour la photothérapie in vitro sur des cellules cancéreuses en les irradiant dans le proche infrarouge.De plus, nous avons synthétisé des nanoparticules hybrides AuNRs avec des matériaux semi-conducteurs tels que le sulfure d'argent et le sulfure de cuivre. Dans ces systèmes, l'énergie plasmonique présente dans les AuNRs peut être transférée aux matériaux semi-conducteurs. Ce processus conduit à la création d'excitons dans les semi-conducteurs, qui peuvent ensuite générer des espèces réactives d'oxygène. Pour améliorer l'efficacité de ce transfert d'énergie et empêcher une recombinaison indésirable entre les électrons et les trous excités, nous avons introduit une couche de silice isolante à l'interface entre l'or et le semi-conducteur. Nous avons également évalué la photoactivité de ces nanoparticules hybrides sous illumination infrarouge.Enfin, l'efficacité thérapeutique des nanoparticules est souvent compromise par une mauvaise biodistribution, la majorité des nanoparticules injectées étant captées par les macrophages. Pour relever ce défi, nous avons testé différents polymères zwitterioniques pour fonctionnaliser différentes nanoparticules inorganiques et éviter leur capture par les macrophages. Leurs interactions avec les protéines et les macrophages ont été étudiées in vitro. De plus, nous avons mené des études pharmacocinétiques sur des AuNRs fonctionnalisées avec différents types de polyzwitterions, afin d’évaluer leur temps de circulation in vivoGold nanoparticles possess high light absorption cross sections due to their localized surface plasmon resonance, making them promising photosensitizers for various biomedical applications. Among them, gold nanorods (AuNRs), can effectively absorb light in the near-infrared range, which is the optimal window for light penetration into the human body. As a result, AuNRs hold significant potential as photosensitizers for phototherapy.When AuNRs absorb light, they generate high-energy “hot” electrons within their structure. These hot electrons can directly convert the absorbed energy into heat, leading to a temperature increase in the surrounding environment. This localized heating can effectively kill cancer cells. Alternatively, hot electrons can react with water or dioxygen in the environment, generating cytotoxic reactive oxygen species. These reactive oxygen species can induce programmed cell death. However, current challenges in phototherapies involving AuNRs revolve around the low efficiency of plasmonic energy conversion and utilization, limiting their further clinical trials. One possible solution to address this challenge is to combine AuNRs with specific semiconductors. This combination allows for the transfer of light energy absorbed by AuNRs to the semiconductor material, either through hot electron injection or energy transfer mechanisms.We synthesized hybrid dumbbell-shaped nanoparticles consisting of gold nanorods (AuNRs) and titanium dioxide (TiO2), AuNR/TiO2. In this heterostructure, hot electrons generated within the AuNRs could be directly injected into the conduction band of TiO2. This transfer extends the lifetime of energetic electrons, enabling them to effectively react with dioxygen in the environment and generate hydroxyl radicals. To ensure the stability of these nanoparticles in a physiological environment, we functionalized them with polyethylene glycol-phosphonate polymer ligands. The density of these polymer ligands on the nanoparticle surface plays a crucial role in achieving optimal photoactivity. We then evaluated the potential of these hybrid nanoparticles for photodynamic therapy in vitro on cancer cells after irradiation with near-infrared (NIR) light.We also explored the combination of AuNRs with semiconductor materials such as silver sulfide and copper sulfide, resulting in the formation of core-shell hybrid nanostructures. In these hybrid systems, the plasmon energy present in the AuNRs is transferred to the semiconductor materials through dipole-dipole interactions. This energy transfer process leads to the creation of exciton pairs within the semiconductors, which can further generate reactive oxygen species. To enhance the efficiency of this energy transfer and prevent undesired recombination between excited electrons and holes, we introduced an insulating silica layer at the interface between the gold and semiconductor components. We also assessed the photoactivity of these hybrid nanoparticles under continuous-wave NIR illumination.Lastly, the therapeutic efficacy of nanoparticles is often compromised by their poor biodistribution, as the majority of injected nanoparticles are recognized and captured by macrophages. To address this challenge, we tested the ability of different zwitterionic polymer ligands to avoid nanoparticle capture by macrophages. Semiconductor quantum dots, iron oxide and gold nanoparticles decorated with polyzwitterions were synthesized. Their interactions with proteins and macrophages were investigated in vitro to assess their potential for improved biocompatibility and reduced macrophage uptake. Furthermore, we conducted pharmacokinetic studies on AuNRs functionalized with different types of polyzwitterions. These studies aimed to evaluate the behavior of these functionalized nanoparticles within the body and gain insights into their distribution and clearance pathways
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Dragota, Simona Olimpia. "Contributions to the chemistry of higher-coordinate Silicon synthesis, structure, and stereodynamics of new Silicon(IV) complexes with SiO2N2C, SiO4C, or SiO6 skeletons /." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978743571.
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Bishop, Alexander James. "Actinide surface chemistry." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54193/.
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The surface reactivity of thorium and uranium, and how this links to the 5f electrons, has been investigated under UHV conditions using X-ray photoelectron spectroscopy (XPS), ultra violet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES). Water and ammonia adsorption on a polycrystalline thorium surface has been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The surfaces after adsorption at both temperatures proved to be unstable when exposed to the low energy electron gun utilised in IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH2 species at 298 K, and nitride, NH2, and physisorbed ammonia at 100 K. Upon reaction only the mononitride ThN is formed, the metallic nature of which was confirmed by UPS and IPES. The surface was unstable under the low energy electron gun utilised in IPES, with the ThN species being converted to the non-metallic Th3N4. Water and ammonia adsorption on a polycrystalline uranium surface has also been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The rate of reaction of water with uranium is substantially reduced in the presence of residual oxygen on the surface. The small band-gap of semi-conducting UO2 can be observed directly with UPS and IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH2 species at 100 and 298 K.
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Cooper, Philip Andrew. "Surface chemistry of foams." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335544.
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Brown, Ken D. "The surface chemistry of beryllium." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333978.
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Sirbu, Elena. "Surface chemistry of cellulose nanocrystals." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33308/.
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Chemical surface modification of cellulose nanocrystals has had a fast development and increased interest from the scientific community as cellulose is the most abundantly available renewable polymer with many advantages such as nanoscale dimensions, high specific strength and modulus, high surface area, unique optical properties and the extraordinary modification potential to increase the application field. This thesis is aimed at expanding and improving upon the current knowledge in order to unlock new applications. Four esterification techniques were applied to the formation of cellulose nanocrystal esters of acrylic acid and methacrylic acid. The degree of surface substitution reached two to three surface hydroxyl groups (the maximum number) available for functionalization and this degree of substitution is very much dependent on the chosen esterification methodology. Two new fluorescently modified cellulose esters based on carbazole-9-yl-acetic acid and coumarin-3-carboxylic acid were synthesised using p-toluenesulfonyl chloride/pyridine and carbodiimide esterifications methods. Absorption and fluorescent properties were also measured and showed fluorescence proportional to the extent of surface functionalization. The maximum theoretically attainable degree of substitution could be reached while still maintaining the crystal structure of cellulose. Cationic cellulose nanocrystals were produced with a high positive surface charge when compared with the literature. The synthesis procedure was attempted in two steps and in a single step. The degree of modification for pyridinium acetate cellulose and methyl imidazolium acetate cellulose was found to depend significantly on the selected pathway. The cationic nature of the modifications was verified using zeta potential measurements and through adsorption of an anion dye. Synthesised cellulose acrylates and methacrylates were used in Thiol-Ene click reactions in which very mild and environmentally friendly reaction conditions proved to work from 10 min reaction times. Four different thiols were added, with and without hexylamine catalyst. In addition, an amidine functionalised cellulose nanocrystal was synthesised based on previously click-modified cellulose in a 2-hour reaction. Furthermore, the switchable behaviour of the synthesised nanoparticles was demonstrated by reverse bubbling with CO2 and Ar.
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Zhao, Jun. "Surface Raman spectroscopy : instrumentation and application in surface and corrosion sciences /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487948807588245.
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Lu, Jian Ren. "The surface chemistry of emulsion breakdown." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384850.
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McElroy, Daniel. "Grain surface chemistry in molecular clouds." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602462.
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This work ia a study of chemistry in molecular clouds. I begin by describing the improvements made to gas phase chemical reaction data in the recent release of the UMIST database for astrochemistry (Rate 12). Improvements to the reaction network include the addition of anions, new reaction rate coefficient and branching rate measurements across all reactions types and newly calculated photodissociation and photoionisation rates.
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Daud, A. R. "The surface chemistry of pitting corrosion." Thesis, University of Surrey, 1985. http://epubs.surrey.ac.uk/770155/.
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The use of XPS and AFS technique has been explored in the stLrly of the surface chemistry of a whole electrode surface (XPS) and the surface chemistry of natural pits (AFS). EDXA and to a snall extend SIMS were also used in the investigation of the individual pits. A high resolution Auger electron microscope which has an analytical resolution as snall as 0.1 .un enables a nevly formed pit of less than 2 .un in diameter to be investigated. By using a Cl/Mg ratio an attempt had been made to correlate the surface chemistry of whole electrodes exposed at different potentials in 1M MgCl2 solution to the surface chemistry of individual pits naturally produced qy means of a simulated metal to metal crevice made of cammercial stainless steels (SS316 and SS304) immersed in 1M MgCl2 solution. '!he correlation was fomd to be good and within the expected limit of the data produced by XPS and AFS. The estimated val ue of potentials of the surface of pit and its immediate vicinity was based on a theoretical model of variation of potential aromd a pit by Melville and also on the potential-current curve of the steel sample in the test sol ution. The Q/Mg ratio was shown to be useful in determining the activity of pits. In repassivated pits in the crevice mouth zone magnesiun was a dominant species relative to chlorine, this is in contrast to the pits in the central part of the crevice which were (ii) engulfed in general corrosion. Active pits in the area between the two regions have higher value of Cl./Mg ratio in their surface than that in the surface in their immediate vicinity. The role of chraniun in pitting corrosion is suggested to counter the pitting attack by the fonnation of chramiun oxide and oxy-chloride on the surface of pit. Molybdenun when present, also concentrates on the surface of pit. The type of corrosion attacks on sulphide inclusions in stainless steel depend on the copper content of the inclusions. Pitting will be likely to take place on pure MnS incl usions but not on copper enriched-MnS inclusions. The fonnation of copper sulphide is suggested to be important in reducing the amount of active species of sulphur on the corroded inclusions.
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Szczepankiewicz, Steven Henry Hoffmann Michael R. "Surface chemistry of titanium dioxide photocatalysts /." Diss., Pasadena, Calif. : California Institute of Technology, 2001. http://resolver.caltech.edu/CaltechETD:etd-05232006-094537.
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Wu, Xin 1967. "Probing colloidal forces with surface collisions." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40469.
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The principal objectives of this thesis are to introduce a new method, colloidal particle scattering (CPS), to measure colloidal and surface forces, and to demonstrate various applications of this method. CPS determines particle-particle interaction forces through creating particle collisions and extracting the interaction forces from the degree of asymmetry of the collision trajectories. Since the force to deflect a micron-sized particle is much smaller than that to deform a macroscopic spring or cantilever used in a commercial force apparatus, this new technique increases the resolution of force determination by four orders of magnitude.Based on the CPS principles, we have built a force apparatus called "microcollider". It successfully determined the van der Waals forces and the electrostatic force between two 5 $ mu$m latex spheres at different salt concentrations. A "hairy" latex model was introduced to explain the measured van der Waals forces which are weaker than those predicted by theory assuming smooth latex surfaces. This is consistent with other experimental findings about the surfaces of latex particles.
A similar "hairy" model was applied to determine the adsorption layer thicknesses of two triblock copolymers adsorbed on latex particles. The results show that the configuration of the buoy block composed of polyethylene oxide (PEO) is more extended than a random PEO coil, which agrees with theoretical predictions. Moreover, excellent quantitative agreement between the adsorption layer thicknesses determined by CPS and other methods has been found.
Dynamic steric interactions between two high molecular weight PEO adlayers have also been studied. Both the elastic modulus and the adsorption layer thickness were determined. The results show that a thick layer has a lower elastic modulus than a thin one composed of the same polymer. This implies that an extended loop/tail structure in a thick layer is less stiff than a flat compact one in a thin layer, which is consistent with theory.
In addition, the microcollider can accurately determine particle-wall interactions as well. A rather weak electrokinetic lift force was measured. The results are in good agreement with the solutions rigorously derived from two new theories.
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Hamilton, Douglas W. "The effects of surface topography and surface chemistry on chondrocyte behaviour." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368577.
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Andersson, Olof. "Imaging surface plasmon resonance." Doctoral thesis, Linköpings universitet, Sensorvetenskap och Molekylfysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-14923.
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The central theme of this thesis is the use of imaging Surface Plasmon Resonance (iSPR) as a tool in the characterization of surfaces with laterally varying properties. Within the scope of this work, an instrument for iSPR analysis was designed and built. SPR is a very sensitive technique for monitoring changes in optical properties in the immediate vicinity of a sensor surface, which is very useful in biosensing and surface science research. We have employed SPR in the Kretschmann configuration, wherein surface plasmons are excited by means of an evanescent field arising from total internal reflection from the backside of the sensor surface. In iSPR, the signal is the reflectivity of TM-polarized light which is measured using an imaging detector, typically a CCD camera. Advantages of this technique include extreme surface sensitivity and, because detection is done from the backside, compatibility with complex samples. In addition, SPR is a non-labeling technique, and in imaging mode, a lateral resolution in the µm range can be attained. The imaging SPR instrument could be operated in either wavelength interrogation mode or in intensity mode. In the former case, the objective is to find the SPR wave-length, λSPR, which is the wavelength at which the reflected intensity is at a minimum. In intensity mode, a snapshot of the intensity reflectance is taken at a fixed wavelength hand incidence angle. In biosensor science, the use of an imaging technique offers a major advantage by enabling parallelization and thereby increasing throughput. We have, for example, used iSPR in biochemical interaction analysis to monitor immobilization and specific binding to protein and synthetic polypeptide micro arrays. The primary interest has been the study of soft matter surfaces that possess properties interesting in the field of biomimetics or for applications in biosensing. Specifically, the surfaces studied in this thesis include patterned self-assembled monolayers of thiolates on gold, a graft polymerized poly(ethylene glycol) (PEG) based hydrogel, a dextran hydrogel, and a polyelectrolyte charge gradient. Our results show that the PEG-based hydrogel is very well suited for use as a platform in protein immobilization in an array format, owing to the very low unspecific binding. In addition, well defined microarray templates were designed by patterning of hydrophobic barriers on dextran and monolayer surfaces. A polypeptide affinity microarray was further designed and immobilized on such a patterned monolayer substrate, in order to demonstrate the potential of analyte quantification with high sensitivity over a large dynamic range. Furthermore, iSPR was combined with electrochemistry to enable laterally resolved studies of electrochemical surface reactions. Using this combination, the electrochemical properties of surfaces patterned with self assembled monolayers can be studied in parallel, with a spatial resolution in the µm regime. We have also employed electrochemistry and iSPR for the investigation of potential and current density gradients on bipolar electrodes. The imaging SPR instrument could be operated in either wavelength interrogation mode or in intensity mode. In the former case, the objective is to find the SPR wave-length, λSPR, which is the wavelength at which the reflected intensity is at a minimum. In intensity mode, a snapshot of the intensity reflectance is taken at a fixed wavelength hand incidence angle.In biosensor science, the use of an imaging technique offers a major advantage by enabling parallelization and thereby increasing throughput. We have, for example, used iSPR in biochemical interaction analysis to monitor immobilization and specific binding to protein and synthetic polypeptide micro arrays. The primary interest has been the study of soft matter surfaces that possess properties interesting in the field of biomimetics or for applications in biosensing. Specifically, the surfaces studied in this thesis include patterned self-assembled monolayers of thiolates on gold, a graft polymerized poly(ethylene glycol) (PEG) based hydrogel, a dextran hydrogel, and a polyelectrolyte charge gradient. Our results show that the PEG-based hydrogel is very well suited for use as a platform in protein immobilization in an array format, owing to the very low unspecific binding. In addition, well defined microarray templates were designed by patterning of hydrophobic barriers on dextran and monolayer surfaces. A polypeptide affinity microarray was further designed and immobilized on such a patterned monolayer substrate, in order to demonstrate the potential of analyte quantification with high sensitivity over a large dynamic range.Furthermore, iSPR was combined with electrochemistry to enable laterally resolved studies of electrochemical surface reactions. Using this combination, the electrochemical properties of surfaces patterned with self assembled monolayers can be studied in parallel, with a spatial resolution in the µm regime. We have also employed electrochemistry and iSPR for the investigation of potential and current density gradients on bipolar electrodes.
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Crivat, Georgeta. "Surface Optochemical Sensors." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/582.
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The objective of my research is to develop new surface optochemical sensors for studying cellular processes by investigating techniques to modify surface properties. The spectral characteristics of the modified surfaces and coatings are designed to show remarkable changes after interaction with analytes from biological fluids and cells. My studies focused on pancreatic cells and addressed the need for improved techniques to measure zinc release from pancreatic cells (chapter 3, 4) and to measure the metastasis potential of cancerous pancreatic cells (chapter 5). Chapter 3 describes the development of zinc sensing glass slides by conjugating a carboxylmodified ZnAF-2 to an amino functionalized glass surface. The sensor was used for the measurement of glucose-stimulated zinc ion release from cultured beta pancreatic cells with impact in diabetes research. In chapter 4 is described conjugation of the carboxyl-modified ZnAF-2 to antibody molecules (A2B5) that specifically recognize pancreatic cells. This enabled for the first time the use of targeted zinc sensors to monitor zinc release events from pancreatic cells. Chapter 5 describes development for the first time of a fluorescence sensor to measure the proteolysis activity of pancreatic cancer cells in microfluidic systems. The sensor was fabricated using a Layer by layer (LbL) deposition of polyelectrolyte. The sensor was based on Fluorescence Resonance Energy Transfer (FRET) between luminescent quantum dots (serve as donors) and rhodamine molecules (serve as acceptors) that are separated by multi-layers of polyelectrolytes. The microfluidic platform enables precise delivery of reactants to assemble the sensor and facilitate unique cellular assays of enzymatic activity and enzymatic expression on pancreatic cancer cells.
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McKay, Hayley. "Fundamental studies of surface reaction mechanisms." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252213.
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Martínez, Esaín Jordi. "The surface chemistry of metal fluoride nanocrystals." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/665606.
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Primerament, la síntesis de quinze tipus de nanocristalls inorgànics i la tendència general dels nanocristalls de fluorurs metàl·lics ha estat satisfactòriament desentranyada. Utilitzant el mètode de la coprecipitació, es reporta la fàcil, ràpida i reproduïble síntesis de nanocristalls de LnF3 i el detallat estudi mecanístic de les diferents condicions sintètiques.
Mitjançant el complert estudi de la química de superfície, un nou tipus de self-assembly iònic en sistemes col·loidals ha estat proposat. Utilitzant mètodes experimentals i simulacions de dinàmica molecular, es postula aquest mecanisme de self-assembly aplicable a diversos sistemes i no només en el sistema estudiat. També s’han obtingut nanocristalls patchy utilitzant un mètode fàcil, ràpid i reproduïble. El comportament d’aquests nanocristalls patchy ha estat investigat en detall utilitzant mètodes experimentals i simulacions de dinàmica molecular. Els nostres resultats revelen la espontània i selectiva coordinació de cations i anions en les diferents cares exposades, com també interaccions selectives amb el solvent.
Avançant en la temàtica de nanocristalls patchy, hem demostrat que les diferents cares dels nanocristalls obtinguts poden ser modificades selectivament. Els cations i anions poden ser modificats mitjançant l’addició de nous lligands que continguin un grup amina o carboxílic. També, utilitzant una molècula zwitterionica podem aconseguir la homogeneïtzació de la superfície eliminant al mateix temps cations i anions. Addicionalment s’han estudiat diferents processos de creixement per millorar les partícules obtingudes, permetent la obtenció de nanocristalls més grans i definits al mateix temps que modifiquem l’estabilitzant orgànic.
La tècnica de EGA-MS ha estat també provada per a simplificar el complex camí de la completa caracterització en sistemes col·loidals. Hem demostrat que utilitzant una única tècnica experimental, la completa caracterització de sistemes col·loidals es possible comparat amb els nostres estudis previs en les mateixes partícules.
Aquesta tesis està basada principalment en el estudi mecanístic de la síntesis i el comportament de la química de superfície de nanocristalls de LnF3. Conseqüentment, aquest coneixement permetrà el control i la manipulació del pont que hi ha entre la síntesis i les aplicacions, actualment anomenat química de superfície. Finalment, algunes aplicacions son presentades com a diferents rutes a seguir després d’aquest treball, essent aquestes excel·lents candidats en ciència de materials i medicina.Starting from the synthesis of fifteen different types of inorganic nanocrystals, the general trends of metal fluoride nanocrystals have been successfully unravelled. Using the co-precipitation method, we reported the easy, fast and reproducible synthesis of LnF3 nanocrystals and the detailed mechanistic studies of different synthetic conditions. Through the complete study of the surface chemistry, a new kind of ionic self-assembly in colloidal systems has been proposed. Using experimental techniques and molecular dynamics simulations, we postulated this self-assembly mechanism not only specific for the studied case but also applicable to other kind of systems. In addition, thermodynamically stable patchy nanocrystals have been also obtained using an easy, fast and reproducible method. The behaviour of these patchy nanocrystals has been investigated in detail using this dual approximation, from experimental techniques to all-atomistic molecular dynamics simulations. Our results revealed the spontaneous and selective attachment of cations and anions in their different exposed faces, as well as, selective solvent interactions. Going one step further in patchy nanocrystals, we demonstrated that the different facets of the obtained nanocrystals can be modified selectively. Cations and anions can be removed from nanocrystal surface via the addition of a new molecule containing an amino group or a carboxylate respectively. Likewise, using a zwitterionic molecule, the homogenisation of the surface was possible releasing at same time cations and anions. Additionally, some growing process were carried out to enhance the obtained particles, allowing bigger hexagonal-faceted nanocrystals while trying to modify the organic stabilisers. In addition, EGA-MS technique has been tested to simplify the complex pathway to full-characterise colloidal systems. We demonstrated that using a simple experimental technique, the full characterisation of a colloidal system is possible, comparing the results with our previous characterisations. This thesis is mainly based on the mechanistic understanding of the synthesis and the final behaviour of the surface of LnF3 nanocrystals. In consequence, this knowledge will allow the control and manipulation of the bridge between synthesis and applications, currently called surface chemistry. Finally, some initial applications will be presented as different pathways emerged from the manipulation of the unravelled systems, being promising candidates for material science and medical fields.
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René-Boisneuf, Laetitia. "Probing Surface Chemistry at the Nanoscale Level." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20453.
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Studies various nanostructured materials have gained considerable interest within the past several decades. This novel class of materials has opened up a new realm of possibilities, both for the fundamental comprehension of matter, but also for innovative applications. The size-dependent effect observed for these systems often lies in their interaction with the surrounding environment and understanding such interactions is the pivotal point for the investigations undertaken in this thesis. Three families of nanoparticles are analyzed: semiconductor quantum dots, metallic silver nanoparticles and rare-earth oxide nanomaterials.
The radical scavenging ability of cerium oxide nanoparticles (CeO2) is quite controversial since they have been labeled as both oxidizing and antioxidant species for biological systems. Here, both aqueous and organic stabilized nanoparticles are examined in straightforward systems containing only one reactive oxygen species to ensure a controlled release. The apparent absence of their direct radical scavenging ability is demonstrated despite the ease at which CeO2 nanoparticles generate stable surface Ce3+ clusters, which is used to explain the redox activity of these nanomaterials. On the contrary, CeO2 nanoparticles are shown to have an indirect scavenging effect in Fenton reactions by annihilating the reactivity of Fe2+ salts.
Cadmium selenide quantum dots (CdSe QD) constitute another highly appealing family of nanocolloids in part due to their tunable, size-dependent luminescence across the visible spectrum. The effect of elemental sulfur treatment is investigated to overcome one of the main drawbacks of CdSe QD: low fluorescence quantum yield. Herein, we report a constant and reproducible quantum yield of 15%. The effect of sulfur surface treatment is also assessed following the growth of a silica shell, as well as the response towards a solution quencher (4-amino-TEMPO). The sulfur treated QD is also tested for interaction with pyronin Y, a xanthene dye that offers potential energy and electron transfer applications with the QD. Interaction with the dye molecule is compared to results obtained with untreated quantum dots, as well as CdSe/ZnS core shell examples.
In another chapter of this thesis, the catalytic potential of silver nanoparticles is addressed for the grafting of polyhydrosiloxane polymer chains with various alkoxy groups. A simple one-pot synthesis is presented with silver salts and the polymer. the latter serves as a mild reducing agent and a stabilizing ligand, once silver nanoparticles are formed in-situ. We evaluate the conversion of silane into silyl ethers groups with the addition of several alcohols, whether primary, secondary or tertiary, and report the yields of grafting under the mildest conditions: room temperature, under air and atmospheric pressure.
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Furman, Scott Anthony. "Surface chemistry of iodine on platinum (111)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ36639.pdf.
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Tasker, Simon. "The surface chemistry of polymeric bioseparation materials." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5333/.
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The aim of this thesis was to test existing theories concerning biocompatibility of polymeric materials, and in the process to try and identify the major factors which pertain to their use as bioseparation matrices. The surface chemistry of cellulose and poly(tetrafluoroethyIene) based bioseparation materials have been examined. We have been able to demonstrate a direct link in the case of the cellulose materials between the crystallinity and the accessibility of the hydroxyl groups which are the primary sites of functionalization. In addition, the effect of processing conditions on the pore structure of an amorphous cellulose matrix was demonstrated and this has been shown to have a direct consequence for the protein binding characteristics of the material. The functionalisation of PTFE has been achieved by reaction with sodium naphthalenide, which lead to the defluorination of the PTFE surface and the formation of a unsaturated carbonised layer containing oxygenated functionalities. The reaction has also been shown to alter the morphology of PTFE membranes as evidenced by AFM analysis. In the case of powdered PTFE we observed the formation of a microporous layer, however this was found to revert back to a fluorinated layer with gentle heating. A novel insight in to the defluorination reaction was obtained using the bombardment of PTFE and PVDF with a Na atom beam under ultra-high vacuum conditions. This demonstrated the single valence electron mechanism of the reaction and also showed the formation of NaF at the surface of the polymer. The formation of CF(_3) groups was attributed to the nucleophilic attack of fluoride ions from molecular NaF species formed at the initial stages of the reaction.
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Adriaens, D. A. "Theoretical investigations of surface chemistry in space." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18506/.
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In this Thesis, computational models for carbonaceous dust grains were examined and compared to known experimental data. Different formation routes of molecules, important to the astrochemical evolution of the universe, have been investigated and their relative energies were analysed with respect to the harsh conditions in interstellar dark clouds of extremely low pressure (10‐17 bar) and temperature (10 – 20 K). Dust grains are present in the universe, and evidence shows they are siliceous or carbonaceous, possible with an icy mantle surrounding the core. In this research, only carbonaceous surfaces were examined. Two models were used to represent polycyclic, aromatic carbonaceous surfaces: coronene, C24H12, representing a relatively small hydrocarbon, and graphene – a single graphite sheet – which represents an extended carbonaceous surface. The main aims of this Thesis were to examine the validity of computationally modelled astrochemical reactions and to investigate the catalytic effect of dust grain surfaces on these reactions. Several formation reactions were examined, including water, methanol and carbonyl sulfide formation. The abundance of these molecules in dark molecular clouds cannot be explained by solely considering gas phase type reactions, and the influence that the carbonaceous surfaces have on these reactions was investigated in order to examine any catalytic effect that they may have.
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Goodwin, Julian A. S. "Surface chemistry in the activated sludge process." Thesis, University of Birmingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365891.
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Michalak, David Jason Gray Harry B. "Physics and chemistry of silicon surface passivation /." Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-05082006-074414.
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Larson, Alyssa Maxine. "Antiviral polymeric drugs and surface coatings." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82315.
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Thesis (Ph. D. in Biological Chemistry)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references.
Viruses are a major cause of human morbidity and mortality in the world. New effective approaches to stop their spread are paramount. Herein, two approaches toward this goal are explored: (i) developing multivalent therapeutics (multiple copies of an antiviral agent covalently attached to a polymeric chain) with superior potency against their viral targets, and (ii) creating antiviral surface coatings that detoxify aqueous solutions containing various viruses on contact. By harnessing the power of multivalency we endeavored to improve the potency of influenza inhibitors, as well as resurrect the potency of two FDA-approved influenza inhibitors for which widespread drug resistance now exists. In the former direction of research, we attached multiple copies of bicyclic naphthoquinone-like monomeric inhibitors to polymeric chains. When tested against the Wuhan strain of influenza, these multivalent conjugates were up to 240- fold more potent inhibitors than their monomeric predecessors. However, this improvement in potency was strain-dependent, as two other serotypically-different influenza strains were not inhibited nearly as well by multivalent inhibitors. This strategy was also employed to restore inhibition for the adamantane class of influenza inhibitors against drug-resistant strains. The chemical modifications to the adamantane scaffold necessary for polymer attachment imposed deleterious steric constraints which resulted in poorer inhibitory effect. Even despite these drawbacks, however, the drug-polymer conjugates were up to 30-fold more potent against drug-resistant strains than their monomeric counterparts. These efforts made strides toward the ultimate goal of recovery of influenza virus inhibition for the adamantanes. To diminish transmission of viral infections, we explored the action of antimicrobial PEIbased (PEI = polyethylenimine) hydrophobic polycations against both enveloped and nonenveloped viruses. When solutions containing herpes simplex viruses (both 1 and 2) were brought in contact with NN-dodecyl,methyl-PEI coated on either polyethylene slides or latex condoms, they could be disinfected by up to 6-logs of viral titers. Our hydrophobic polycation also could be formulated into a suspension to disinfect herpes simplex virus-containing solutions, suggesting potential utility in a therapeutic modality. We also investigated whether these findings were applicable to non-enveloped viruses, namely poliovirus and rotavirus. Aqueous solutions containing them indeed could be drastically disinfected by our hydrophobic polycation-coated slides; subsequent mechanistic studies suggested that this disinfection was due to adsorption of the viruses onto the coated surfaces from solution.
by Alyssa Maxine Larson.
Ph.D.in Biological Chemistry
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Kay, Ronald Dale. "Trajectory studies of diatom-surface scattering /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487668215808291.
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Wright, Kierra D. "Chiral polymer surface-cell interaction: understanding the role of chirality & surface topography on polymer-cell interactions." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2012. http://digitalcommons.auctr.edu/dissertations/436.
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Understanding surface-cell interactions is essential to fabricating a successful biomaterial. In vivo, cells interact with asymmetric features on the micro- and nanoscale. Some of these features, described as valleys, ridges, and spheres, are random, but methodically placed. There are many techniques used to duplicate the topographical features that cells encounter, many of which rely on precision and are labor intensive. Alternatively, the synthetic poly(2-methoxystyrene) (P2MS) homopolymer selfassembled into desirable features, was easily processed and produced the random surface preferred by cells. The features achieved with P2MS were the result of secondary and tertiary conformations confirmed by circular dichroism. The features were also a consequence of the optical activity revealed by polarimetry. Advanced microscopy verified that the features were indeed biomimetic and measured between 150—600 nm in depth and height. Polymers were synthesized using free radical and anionic techniques; some involved the use of a chiral initiator. Spin-casting and solvent annealing were employed to create polymer films for substrate-cell studies. Reaction conditions and molecular weight were varied to achieve different topographical features and thermal profiles. In showing that the films were able to be sterilized, the films were further subjected to cytotoxicity studies involving both Escherichia coli and Bacillus cereus. The results of turbidity measurements and colony counting revealed increased cell viability. The gram positive bacteria, B. cereus, showed increased adhesion through hydrophobic interactions, the same type of interactions proteins rely on for deposition prior to cell adhesion. The cell adhesion study used the human epithelial carcinoma (HeLa) cell line, and showed increased adhesion on chiral initiated P2MS. As a result, this work verified that topographical features can influence cell behavior without the presence of biochemical cues and that P2MS may provide a viable option for tissue engineering applications.
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Das, Ujjal. "Electronic structure studies of semiconductor surface chemistry and aluminum oxide cluster chemistry." [Bloomington, Ind.] : Indiana University, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3344570.
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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2008.Title from PDF t.p. (viewed Oct. 7, 2009). Source: Dissertation Abstracts International, Volume: 70-02, Section: B, page: 1054. Adviser: Krishnan Raghavachari.
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Shukla, Nisha. "Surface spectroscopic studies of coadsorbed molecules and surface reactions at single crystal metal surfaces." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275212.
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Jackson, Stuart Thomas. "Surface analysis of polymer blends." Thesis, University of Sheffield, 1993. http://etheses.whiterose.ac.uk/14740/.
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Ghahremaninezhad, Gharelar Ahmad. "The surface chemistry of chalcopyrite during electrochemical dissolution." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42830.
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Hydrometallurgy may be an alternative to the currently practiced smelting process for
copper extraction from chalcopyrite (CuFeS₂). However, the low temperature
hydrometallurgical processes for chalcopyrite continue to face challenges, mostly relating to
their slow dissolution rates or high sulfuric acid production. The slow dissolution rate of the
mineral is strongly linked to the formation of the passive film on its surface. However,
despite 40 years of research on this topic, there is still not a complete agreement between
researchers about the composition and stability of chalcopyrite’s passive film in sulfuric acid
solutions. In this work, the nature of chalcopyrite’s passive film and its stability were studied
by application of a variety of electrochemical techniques. Additionally, the electrochemical
results of the chalcopyrite study were compared to those obtained for a pyrrhotite electrode
(Fe₁₋xS), as pyrrhotite electrochemistry represents a simplified case of the chalcopyrite
system. X-ray photoelectron spectroscopy (XPS) was used to analyze the composition of the
product layers formed on the surface.
It is shown that the chalcopyrite electrode is passive for potentials up to 0.90 VSHE.
Above this potential, transpassive dissolution occurs. Results of XPS studies have suggested
that a metal-deficient sulfide film (Cu₁₋xFe₁₋yS₂₋z) is the most plausible copper and iron
containing sulfide phase which passivates the surface of chalcopyrite. In addition, an outer
layer of iron oxyhydroxide (FeOOH) forms on the passive film. FeOOH forms via oxidation
of the passive film’s ferrous sulfide phases. The thickness of the sulfide passive film was
calculated to be approximately 6.7 nm. It is demonstrated that the transpassive dissolution of
chalcopyrite is significantly linked to oxidation of sulfur (from sulfide in the passive film to
elemental sulfur and maybe sulfur species with higher oxidation states, e.g. thiosulfate). No
elemental sulfur or polysulfide species were detected on the surface for potentials below 0.90
VSHE.
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Alvarez, Silva Mayeli. "Surface chemistry study on the pentlandite- serpentine system." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97112.
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Interaction with MgO-minerals is one mechanism suspected to reduce selectivity in flotation of pentlandite from ultramafic ore. Understanding the surface chemistry of the minerals involved will lead to improved flotation conditions that maximize flotation selectivity. The first part of the thesis compares isoelectric point (i.e.p.) and point of zero charge (p.z.c.) determined using Mular-Roberts [M-R] titration technique of MgO-minerals chlorite, serpentine and talc. The M-R technique was unsuccessful with talc, attributed to Mg2+ acting as potential determining ion. For serpentine and chlorite, respectively, p.z.c. was pH 4.3 and 4.6 and i.e.p. pH 3.2 and <3. Dispersion index (DI) for chlorite suggested that aggregation/dispersion is controlled by both; serpentine remained dispersed, possibly due to hydration effects.The second part determines surface properties of pentlandite and serpentine isolated from an ultramafic ore. Zeta potential measurements were made on minerals alone and as mixtures with either indifferent electrolyte or supernatant derived from an ore suspension as background. Individual mineral results anticipated interaction due to electrostatic attraction. This was confirmed in the mixed mineral case, with Mg(OH)2 precipitate interaction as an additional factor. Scanning electron microscopy validated the findings.Aggregation/dispersion was determined by turbidimetry using a light scattering technique and optical microscopy. The effect of selected factors on aggregation/dispersion of pentlandite and serpentine was investigated by a design of experiment (DOE). Concentration of carboxymethyl cellulose, CMC, and the interaction between CMC and pH were the important factors. Contact angle measurements explored effects of several factors on pentlandite hydrophobicity and, using a DOE, small-scale flotation was used to investigate effects on pentlandite floatability. The pH was the most important factor, acidic pH increasing both hydrophobicity and floatability. Copper activation enhanced both properties, as well; magnesium affected hydrophobicity at alkaline pH, but it did not show significant effect on floatability; serpentine was detrimental to the process; and CMC was capable of partially restoring the hydrophobicity and floatability of pentlandite depressed with serpentine.L'interaction de la pentlandite avec des minéraux d'oxide de magnésium (MgO-) est soupçonnée d'être à l'origine de la sélectivité réduite de la pentlandite dans les procédés de flottation de minerais ultrabasiques. Une meilleure compréhension de la chimie de surface des minéraux impliqués devrait mener à l'amélioration des conditions de flottation qui en maximisent la sélectivité. La première partie de la thèse compare le point isoélectrique (p.i.e) et le point de charge nulle (p.c.n), déterminés à l'aide de la technique de titrage Mular-Roberts [M-R], de minéraux d'oxide de magnésium tels que la chlorite, la serpentine et le talc. Dans le cas du talc, la technique M-R a échoué, probablement dû aux ions Mg2+ qui jouent le rôle d'ions déterminateurs de potentiel. Dans le cas de la serpentine et de la chlorite, les p.c.n. ont été déterminés à pH 4,3 et 4,6 respectivement et les p.i.e à pH 3,2 et <3 respectivement. Des tests de décantations ont suggéré que l'agrégation/dispersion observée pour la chlorite était contrôlée à la fois par le p.c.n et le p.i.e ; la serpentine au contraire est restée dispersée, possiblement dû à des effets d'hydratation. La deuxième partie détermine les propriétés de surface de la pentlandite et de la serpentine isolées à partir d'un minerai ultrabasique. Des mesures du potentiel zêta ont été effectuées sur les minéraux seuls et mélangés en présence d'un électrolyte, indifférent dans un cas et surnageant dans l'autre cas, préparé à partir d'une suspension de minerai utilisée comme milieu d'étude. Les résultats relatifs aux minéraux individuels et en particulier les forces d'attraction électrostatique observables ont permis d'anticiper leur interaction. Cette hypothèse a été confirmée dans le cas des minéraux mélangés, étant après avoir pris en compte l'interaction de précipités de Mg(OH)2 comme facteur additionnel. Des observations au microscope électronique à balayage ont permis de valider les résultats. L'agrégation/dispersion a été déterminée par décantation en utilisant des techniques de lumière diffuse et de microscopie optique. L'effet de certains facteurs sur l'agrégation/dispersion de la pentlandite et de la serpentine a été étudié sur la base d'un plan d'expériences (PE). Entre autres, la concentration en carboxymethyl cellulose (CMC) et l'interaction entre le CMC et le pH ont été considérés comme des facteurs importants. Des mesures d'angle de contact ont permis d'explorer l'hydrophobicité de la pentlandite et, à l'aide d'un PE, une étude de flottation à petite échelle a été réalisée pour investiguer la flottabilité de la pentlandite. Les résultats ont montrés que le pH était le facteur le plus important, un pH acide ayant pour effet d'augmenter à la fois l'hydrophobicité et la flottabilité. L'ajout de cuivre a également permis de renforcer ces deux propriétés par un effet d'activation; la présence de magnésium au contraire a affecté l'hydrophobicité de la pentlandite à pH alcalin mais n'a pas eu d'effet significatif sur ses propriétés de flottabilité; la présence de serpentine s'est trouvée être préjudiciable au procédé mais l'utilisation de CMC a pu être utilisée afin de restaurer partiellement l'hydrophobicité et la flottabilité de la pentlandite diminuées par la présence de la serpentine.
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Roe, Gerard. "Surface and catalytic chemistry of Ni/Sm systems." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282064.
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Perera, S. P. "Gas chromatography and surface chemistry of porous polymers." Thesis, Brunel University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376652.
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Bennett, Andrew Michael. "Properties, processes and surface chemistry at diamond interfaces." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434867.
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Shin, Nae Chul. "Controlling semiconductor nanowire crystal structures via surface chemistry." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52966.
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This thesis introduces a new route to control the structure of semiconductor nanowires using surface chemistry. Specifically, in Au-catalyzed Si nanowire growth using hydride species (Si₂H₆) as growth precursors, we demonstrate that the surface hydrogen existing on the nanowires sidewalls affects the growth morphology. First, we show the spectroscopic evidence of atomic hydrogen bonded to sidewall surface of Si nanowires in real-time in situ during growth and correlate their relative change with different growth orientations and planar defect generation. By introducing additional atomic hydrogen during the <111>-oriented nanowire growth with intrinsically low hydrogen concentration, we confirm that the growth orientation changes from <111> to <112> orientation. We also show that the transient change in the nanowire growth conditions (i.e., substrate temperature and precursor pressure) can rationally induce the planar defects such as twin boundary or stacking fault in Si nanowires at user-defined position. These findings provide important insight into the vapor-liquid-solid technique for nanowire growth and identify new possibilities for systematically controlling their structures in general.
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Stewart, Karen. "The chemistry layer of the surface of wool." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317119.
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Hart, Nicholas. "Surface chemistry of oxygenates over model platinum catalysts." Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431657.
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Marshall, Robert. "Preparation of bimetallic catalysts by surface organometallic chemistry." Thesis, Open University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265345.
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Rostam, Hassan Muhammad. "The impact of surface chemistry on macrophage polarisation." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39797/.
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Background: Antigen presenting cells (APCs) such as macrophages play a crucial role in orchestrating immune responses against foreign materials. The activation status of macrophages can determine the outcome of an immune response following implantation of synthetic materials, towards either healing or inflammation. A large range of biomaterials are used in the fabrication of implantable devices and drug delivery systems. These materials will be in close contact with APCs and characteristics such as surface chemistry may have a critical role in polarising macrophages towards pro- or anti-inflammatory immune phenotype. Each phenotype can be characterised by their cytokine profile, transcription factors, surface markers or even morphology. Objectives: The overall objective of this study was identifying novel chemistries that are able to induce differentiation of human monocytes towards macrophages with distinct pro or anti-inflammatory phenotypes. To achieve this, a combination of different surface chemistries has been generated using oxygen plasma etching as well as acrylate and acrylamide polymer libraries. Methods: Fluorescent microscopy, real time-PCR, multiplex assay, ELISA, macrophage phagocytic activity were used for macrophage phenotype identification. Libraries of acrylates and acrylamide polymer microarrays (first generation microarray of 141 polymers and second generation of 442 polymers), and oxygen plasma etching of polystyrene used as two different techniques for making different surface chemistries. CellProfiller software was used for analysing images and was used for machine learning for phenotype identification. Results: polystyrene with highly hydrophobic surfaces are shown to suppress expression of M1-associated surface markers and cytokines while promoting M2-associated markers. However, highly hydrophilic surfaces seem to have the opposite effect as evidenced by promoting M1-associated marker expression and pro-inflammatory cytokine production while suppressing M2-associated marker expression and anti-inflammatory cytokine production. Also, the protein thickness was proportional with the hydrophilicity of the surface, which had impact on cell polarisation. Furthermore, co-polymers 157 from the second generation array was the most M2 biased polymer among the first and second generation of microarray polymers by induction of MR (M2 marker) cell expression, while co-polymers 217 and 123 from the second generation had impact to increase calprotectin (M1 marker). Also, cell adherence and morphology were affected by polymers surface chemistry. Conclusion: Surface chemistry without using polarising cytokine can polarise macrophage towards pro-inflammatory and anti-inflammatory phenotypes.
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Goetting, Laura Bridget 1970. "Electrochemistry and surface chemistry of self-assembled monolayers." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85240.
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Farhan, Tamer. "Controlling surface topography & chemistry of polymer films." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612867.
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Haley, Roger David. "Surface chemistry of the vinyl acetate catalytic system." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/272089.
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Duckenfield, Kea U. "Laboratory oxide coatings: Physical form and surface chemistry." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539616635.
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The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component phases and natural sedimentary materials. Goethite (alpha-FeOOH) was coated onto quartz and kaolinite grains. Coating method and thickness were varied. Physical properties of the coated solids were probed using multipoint N2 (g) adsorption and desorption analysis (BET), The morphology of the particles was studied by scanning electron microscopy (SEM), and the uniformity of oxide distribution on the grain surfaces was assessed by energy-dispersive X-ray (EDS) analysis. Chemical properties were investigated via batch Cu(II) adsorption/desorption experiments. Goethite physical form was found to vary with coating method and substrate mineralogy. Cu(II) sorption (uptake and release of dissolved Cu from goethite-coated particles) depended on the coating method, substrate, and thickness of the coating. Analysis of these variations indicated physical changes in the form of the coating, interactions between goethite and substrate, and changes in the surface chemical properties of one or both solid phases (goethite and substrate). The combined physical and chemical alterations in the properties of the solids produced distinct behavior in each of the laboratory-prepared solids studied. A parallel set of experiments was conducted on three geologically related sedimentary materials. Several physical and chemical differences were observed between crude kaolin and a cleaned reference kaolinite. One laboratory-prepared goethite coating matched a surface soil at precipitation-dominated Cu loadings, and another coated solid matched a subsurface material at all Cu loading ranges sampled. These results suggest that more complex laboratory-prepared sorbent phases may better reflect trace metal sorption properties of environmental particles.
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Da, Silva Rodrigues Rafael Alexandre. "Dynamic covalent chemistry at the solution: Surface interface." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/200450/1/Rafael_Da%20Silva%20Rodrigues_Thesis.pdf.
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Mechanically interlocked architectures have shown great promise in applications such as catalysis, sensing and drug delivery. They have also been developed as the basis of molecular machinery. However, the use such systems often requires their incorporation to surfaces or solid supports for amplified concerted action and reusability. This research investigated new methods for the attachment of rotaxanes to polymer resins. By adopting a dynamic covalent approach to surface attachment, great improvements in proportion of rotaxanes, when compared to kinetic by-products, were achieved on polymer resins.
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Singireddy, Soujanya. "SURFACE REACTIVITY OF IRON, MANGANESE MINERALS AND THEIR ENVIRONMENTAL IMPLICATIONS." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/225394.
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ChemistryPh.D.
The focus of the thesis research was to investigate the surface reactivity of three different minerals, pyrite (FeS2), an ordered form of ferrihydrite (an iron oxyhydroxide phase), and birnessite (MnO2), toward environmentally relevant aqueous reactants. In particular, research was carried out with the goals of 1) understanding the redox chemistry of nitrite (NO2-) and nitrate (NO3-) on pyrite and 2) understanding the redox (photo) chemistry of arsenite (AsO2-, As(III)) on ordered ferrihydrite and birnessite. A motivation for all these studies stemmed in part from the recognition that NO2-, NO3-, and As(III) are all environmental pollutants when they are present at sufficiently high concentration in the environment. The removal of these species or conversion of each of them on mineral surfaces to more benign chemical species is of importance in the realm of environmental chemistry. In the case of NO2- and NO3- on pyrite, an additional and primary motivation for the research was that it has been hypothesized in the "origin-of-life" community that the reaction of NO2- and NO3- with iron sulfide (e.g., pyrite) may have played a role in the production of ammonia (NH3) on early Earth. Such prebiotic chemistry had been hypothesized to an essential step in the production of biomolecules that included proteins. With regard to the NO2- reaction with pyrite, results detailed in this thesis showed that ammonia in µmol/kg quantities could be produced by reacting NO2- in the presence of pyrite under anaerobic conditions. The concentration of NH3 (detected as ammonium, NH4+, in solution) was a strong function of the reaction temperature. At the lower temperatures studied (22oC and 70oC), a small amount of NH4+ was formed, but µmol.kg-1 amounts of NH4+ were formed at a reaction temperature of 120oC. Only about 5% of the initial NO2- concentration was converted to NH4+. In the NO3-/pyrite system, the NO3- reactant concentration remained unchanged at all the three reaction temperatures studied, consistent with the low amounts of NH4+ formed in these experiments. Finally, it was shown using in situ infrared spectroscopy that surface-bound NO formed on pyrite during the conversion of the nitrogen oxides to ammonia. Overall, it was shown that the kinetics of NH4+ formation was slower for NO3- than that observed for NO2-. Studies presented in this thesis that focused on the surface reactivity of As(III) on ordered ferrihydrite and birnessite nano particles showed that As(III) could be oxidized to arsenate (referred to as As(V)) in the presence of simulated solar radiation. In the ordered ferrihydrite circumstance the adsorption of As(III) and photo-induced oxidation to As(V) was compared to the same reaction on the more disordered and smaller ferrihydrite particles (known as "2-line" ferrihydrite). A comparison of the adsorption rate of As(III) on the two surfaces in the presence of light after normalizing for differences in surface area showed that the ordered ferrihydrite exhibited a higher arsenic adsorption rate. Also, the oxidation rate of As(III) to As(V) in the presence of light on the ordered ferrihydrite showed a strong dependence on the amount of dissolved oxygen in solution while the oxidation rate on the more disordered form showed no such dependence. It was proposed that differences in the rates of the heterogeneous oxidation rate of ferrous iron with dissolved oxygen on the two surfaces were the reason for this behavior. Finally, the photo-induced oxidation of As(III) to As(V) on Na- and K-birnessite at solution pHs of 5.0 and 7.4 was investigated. It was shown that the oxidation rate of As(III) to As(V) occurred at a faster rate on birnessite in the presence of light when compared to the same system in the dark. Mn(II) formed during the reductive dissolution of birnessite during the oxidation of As(III) was experimentally observed at pH 5.0, but not at pH 7.4. Experiments were also conducted that investigated the reductive dissolution of Na- and K-birnessite (having different sizes and average oxidation states) by As(III) under more alkaline conditions. These experiments were conducted at pH 8.5 and the post-reaction samples were analyzed with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was shown under these alkaline conditions using X-ray diffraction that structural changes occurred in/on both the Na- and K-birnessite during the As(III) oxidation reaction.
Temple University--Theses
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Combs, J. Dale. "Study of a Model alpha-Helix Peptide's Surface Properties by Langmuir Monolayer Techniques and Surface FTIR." Thesis, Middle Tennessee State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10146886.
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Cell membranes have been shown to be able to change the conformation of proteins/peptides. However, the structure of the cell membrane is complicated and has been divided to three regions: the hydrophobic region containing alkyl chains, the hydrophilic head group, and the hydration layer, or lipid-water interface, which exists between the hydrophilic head group and the bulk water solution, but with lower dielectric constant compared with fully hydrated water. The air-water interface has been used to mimic the structure of the hydration layer because of their similar dielectric constant.1,2 Some proteins were found to form a stable Langmuir monolayer and accumulate at the air-water interface. For example, ?-synclein, a membrane protein containing 140 amino acids, is unstructured in aqueous solution but changes its conformation to α-helix at the air-water interface. This incites interest to investigate short motifs of α-helix to form a stable Langmuir monolayer at the air-water interface. In this thesis, a peptide with sequence of YAAAA(KAAAA)4 (referred as Pep25 hereafter) was used as a model peptide of α-helix to spread at the air-water interface, because our group has determined the conformation of Pep25 in residue level by the 13C isotope-edited FTIR. Langmuir monolayer technique together with IRRAS showed that Pep25 does not form a typical Langmuir monolayer at the interface. Potential plans to make Pep25 to form a stable monolayer are also discussed in this thesis.
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Hausner, Douglas B. "Surface Science Investigations: Calcite Surface Reconstruction and Ferrihydrite Reactivity." Diss., Temple University Libraries, 2009. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/44342.
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ChemistryPh.D.
On surfaces and within interfaces occur some of the most important reactions in chemistry, from world changing industrial reactions to critical environmental processes. It is even hypothesized that the chiral nature of life arose from reactions occurring on chiral mineral surfaces. In any case adsorption typically plays a key role. Adsorption can occur on rapid time scales, particularly in catalytic systems, and it can be the precursor to highly stable surface interaction mechanisms such as surface precipitation. Surface adsorption can have a dramatic affect on the resulting surface increasing or decreasing the propensity for further reactivity or adsorption. In order to understand the processes occurring on a surface both the surface and the adsorbate must be understood. This includes a surface with any prior adsorbates. This is why many catalytic studies are done in UHV environments where clean surfaces are prepared for each experiment. The same is true with environmental surfaces, but obtaining pristine surfaces can be problematic, and systems are often extremely complicated involving organic, inorganic, and biological components. Often research is focused on just one component. A significant portion of this dissertation is focused on the adsorption of organic and inorganic species on pristine mineral surfaces. While there is significant research done on environmental surfaces, often times the surface used in studies is not well characterized. In essence lesser attention is paid to the substrate then the adsorbate. This is particularly true of infrared studies similar to the type presented in chapter 5 where carbonate is shown to exist in significant quantity on all ferrihydrite surfaces. Furthermore, chapter 4 highlights the potential for ion mobility on calcite surfaces under ambient conditions and the effect the adsorbates in chapter 3 have on the mobility process. The principal of this dissertation is to characterize fundamental surface processes which occur on calcite and ferrihydrite surfaces under ambient conditions. The hope is that this can lay the ground work for future studies where native adsorption and restructuring is taken into account on mineral surfaces during experimental studies.
Temple University--Theses
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Brewer, Scott Harmon. "Solution and Surface Characterization of DNA and Proteins." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-11292004-160406/.
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A variety of experimental spectroscopic techniques complemented by theoretical calculations when appropriate were used to investigate DNA adlayers on surfaces and proteins in solution. The formation and characterization of DNA adlayers on gold and indium tin oxide surfaces were characterized along with subsequent surface DNA hybridization. Prior to the modification of indium tin oxide surfaces with DNA, the optical and electronic properties of this metal oxide, fluorine doped tin oxide and iridium oxide were investigated. The detection of DNA hybridization on indium tin oxide surfaces utilized gold nanoparticle labeled target ssDNA. Further work on gold surfaces was performed using infrared spectroscopy to detect sugar binding to a phenylboronic acid terminated self-assembled monolayer. The binding properties and stability of gold nanoparticles were investigated by characterizing citrate and bovine serum albumin binding to gold surfaces and the stability of particles stabilized by these molecules. The stability and folding kinetics of the three helix bundle protein, villin headpiece subdomain was also investigated in addition to a theoretical investigation of the vibrational Stark effect. Finally, a time resolved step scan FTIR spectrometer was implemented with five microsecond time resolution.
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Hand, Michael Robert. "Theoretical studies of molecule-surface scattering." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316521.
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