Dissertations / Theses on the topic 'Surface chemistry'
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1
Bishop, Alexander James. "Actinide surface chemistry." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54193/.
Abstract:
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.
2
Cooper, Philip Andrew. "Surface chemistry of foams." Thesis, University of Hull, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335544.
3
Cole, D. J. "Surface chemistry and adhesive properties of oxidised Si surfaces." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597835.
Abstract:
I have used density functional theory and classical molecular dynamics to study the chemistry of the native oxide layer on the Si(100) surface. Surface oxidation is accompanied by the development of tensile surface stress and by formation of Si species with a range of oxidation states. Total energy calculations of P and B substitution into the oxide layer and first principles molecular dynamics simulations of oxide growth on the doped surface both indicate a surface oxidation mechanism whereby impurities remain trapped at the Si/SiOx interface. A new two- and three-body classical potential is developed to simulate the hydroxylated, natively oxidised Si surface in contact with water solutions and biological molecules. The potential parameters are chosen to reproduce the structure, charge distribution, tensile stress and interactions with single water molecules of a natively oxidised Si surface previously obtained by ab initio simulations. I apply this classical potential to study the atomic-level processes that determine the mutual adhesion between hydrophilic Si wafers during room temperature bonding. Moreover, I have investigated the adhesion mechanisms of proteins such as collagen and human serum albumin, which mediate the interactions between cells and implanted Si-based devices.
4
Brown, Ken D. "The surface chemistry of beryllium." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333978.
5
Sirbu, Elena. "Surface chemistry of cellulose nanocrystals." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33308/.
Abstract:
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.
6
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.
7
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.
8
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.
Abstract:
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.
9
Daud, A. R. "The surface chemistry of pitting corrosion." Thesis, University of Surrey, 1985. http://epubs.surrey.ac.uk/770155/.
Abstract:
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.
10
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.
11
Tidwell, Caren Diana. "Endothelial cell interactions with model surfaces : effect of surface chemistry, surface mobility, and the adsorbed protein layer /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8004.
12
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.
13
Martínez, Esaín Jordi. "The surface chemistry of metal fluoride nanocrystals." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/665606.
Abstract:
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.
14
René-Boisneuf, Laetitia. "Probing Surface Chemistry at the Nanoscale Level." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20453.
Abstract:
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.
15
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.
16
Tasker, Simon. "The surface chemistry of polymeric bioseparation materials." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5333/.
Abstract:
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.
17
Adriaens, D. A. "Theoretical investigations of surface chemistry in space." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18506/.
Abstract:
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.
18
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.
19
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.
20
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.
Abstract:
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.
21
Andrews, Marilyn Mockus 1958. "Characterization of the surface acidity of passivated iron particles by flow microcalorimetry." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276614.
Abstract:
The characteristics of passivated iron particles have been examined with flow microcalorimetry to determine the acidic nature of the surface sites. The molar heat of adsorption of pyridine from hexane was measured with a FMC and a differential refractive index detector, at 23 and 40°C. The adsorption data were found to obey the assumptions of the Freundlich isotherm. The adsorption densities at different temperatures were used to calculate the isosteric heat of adsorption. The molar heat of adsorption of triethylamine from hexane was also measured and combined with the data for pyridine in order to calculate the Drago constants for the iron particles. A static adsorption method was used for the adsorption of pyridine from hexane onto the iron particles, for comparison with the dynamic method. The heat of wetting for the iron particles, with hexane, has also been measured. The iron particles were examined with X-ray diffraction. Mossbauer spectroscopy, XPS, SEM, TEM, and electrophoresis to characterize the surface layer. These techniques have revealed that the iron particles are coated with ferric oxide and this surface is amphoteric in aqueous solutions.
22
Poirier, Jason S. "Polymer Templating in Surfactant Monolayers." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/PoirierJS2004.pdf.
23
Young, Aidan Gerard, and n/a. "Chemistry at cadmium sulfide surfaces." University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080806.164202.
Abstract:
Probing the surface chemistry of thiol ligand binding to cadmium chalcogenide nanoparticles is important to clarify factors involved in quantum dot stability and surface functionalisation. This research is a spectroscopic investigation aimed at gaining a better understanding of the interaction/bonding of various ligands to CdS, with respect to the use of CdS in biological imaging. The findings of this research are important to the more general field of cadmium chalcogenide materials as biological imaging agents.
Deposited CdS nanoparticle films were used in this work as model quantum dot surfaces for ligand adsorption studies. The adsorption of the monothiol-containing ligands, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol, to CdS thin films were studied in situ using attenuated total reflectance infrared spectroscopy. The absence of an S-H stretch absorption for the adsorbed species showed that adsorption occurred via the deprotonated thiol group.
The adsorption of the dithiol-containing ligands α-lipoic acid, dihydrolipoic acid, and dithiothreitol to CdS nanoparticle films was investigated. The adsorption of dihydrolipoic acid and dithiothreitol was found to occur via both thiol functional groups and an additional interaction between the carboxylate group and the CdS surface. The adsorption of α-lipoic acid to CdS in the presence of light proceeded with photo-oxidation of the CdS surface and reductive cleavage of the disulfide bond of α-lipoic acid to produce some adsorbed dihydrolipoic acid and thiosulfate. The adsorption of α-lipoic acid to CdS in the absence of visible light showed no photo-oxidation, and suggested adsorption occurred via retention of the disulfide bond.
The kinetics of adsorption and desorption of oxalic acid on deposited anatase TiO₂ films were studied to investigate the feasibility of extracting molecular information from attenuated total reflectance infrared spectroscopic kinetic data of ligand processes on deposited particle films. Oxalic acid adsorbed on anatase TiO₂ is a well-studied example and is reported to result in three different surface species. The profile of the desorption data indicated contributions from three different components. Different component contributions were unable to be obtained from the adsorption data which is attributed to adsorption occurring much faster than desorption and thus being relatively insensitive to the presence of different adsorbed species.
The kinetics of adsorption and desorption of mercaptoacetic acid on CdS were investigated. The desorption data profile indicated the presence of two adsorbed species with different affinities for the CdS surface, the exact chemical nature of which can only be speculated upon given the absence of distinguishing IR spectral features.
Ligand exchange reactions at the surface of oleate and trioctylphosphine oxide-capped CdS quantum dot films were investigated. Adsorbed oleate was coordinated to the CdS in a chelating bidentate manner through the carboxylate functional group, while adsorbed trioctylphosphine oxide was coordinated though the P=O functional group. Ligand exchange reactions on the oleate and trioctylphosphine-capped CdS films were studied, and exchange with monothiol-containing ligands was observed only at solution pH where the exchanging ligand was uncharged.
Avidin-biotin bioconjugation reactions were carried out on CdS films, which involved the sequential adsorption of mercaptoacetic acid, the protein avidin, and the subsequent binding of the ligand biotin. The spectral data suggested that avidin underwent a conformational change upon adsorption to the CdS surface. This conformation appeared to be perturbed again upon binding of biotin, and it is speculated that the conformation partially reverted back to the native solution conformation.
24
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.
25
Barch, Mariya. "Molecular fluorescent reporters for force and smart surfaces for sensing cell-surface interaction." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55089.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-130).
Molecular sensors are powerful because they make it possible to adapt the measurement to the sample instead of a sample to an instrument. Many reporter are available for measuring the chemical properties of a sample, but no purpose-built molecular sensors exist to report a sample's mechanical properties. To address recent interest in the mechanical coordinate of molecular interactions, we developed a prototype molecular sensor, calibrated its force-fluorescence relationship, and adapted the sensor to a cell adhesion assay. This thesis focuses on the considerations for combining force measurement with the environmental and distance sensitivity offered by fluorescence to measure cell-surface adhesion. We showed that DNA can be used as a scaffold to build a sensor molecule, that fluorescence can be used as a reporter of a threshold force, and that introducing cells to the sensor molecules changes the fluorescence properties. Because Cy3 experiences an enhanced intensity sensitivity when conjugated to DNA, the reporter's FRET signal was occluded and we instead activated the sensor complex as a novel, all-fluorescent means of reporting cell-surface proximity. This method for reporting cell-surface separation is significant because it simplifies measurements in thicker and more complex materials interesting to cell-substrate interaction studies.
by Mariya Barch.
Ph.D.
26
Ingram, Jani Cheri. "Surface-enhanced Raman scattering and electron spectroscopic studies of copper and silver surfaces." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185153.
Abstract:
The overall goal of this research is to investigate the enhancement mechanisms associated with the surface enhanced Raman scattering (SERS) phenomenon. The approach taken in these investigations is to directly compare the SERS abilities of Cu and Ag surfaces using both SERS and electron spectroscopy. One set of experiments has been directed toward studying the contribution of the charge transfer (CT) mechanism to the SERS of pyridine adsorbed on Cu and Ag electrodes. These studies involve modifying the electrodes by depositing submonolayer amounts of Pb which serves to quench the SERS. By using a variety of excitation energies, the resulting quenching profiles track the CT process. Additionally, other electrochemical/SERS experiments have been pursued in order to probe the contribution of the CT mechanism. The second set of experiments involved measuring the optical properties of the Pb-modified Cu and Ag surfaces using electron energy loss spectroscopy in the reflection mode (REELS). Based on electromagnetic (EM) theory, the enhancement is, to a rough approximation, indirectly proportional to ε₂, the imaginary part of the dielectric constant. Thus, the goal of these studies is to determine the changes in ε₂ as a function of Pb coverage in order to determine the contribution of the EM mechanism to the SERS quenching profile. It was necessary to develop a method to determine optical constants from REELS data. A number of pure metals (Al, Cu, Ag, Au, Ti, V, Fe, Co, and Ni) were chosen to test the method. In all cases, our results compare well to the literature values with a relative standard deviation of 20% or less. Having established the method, the next step was to apply it to the Pb-modified Cu and Ag surfaces. Due to instrumental limitations, only semi-quantitative optical constants could be determined. From these values, it was found that the relative changes in the ε₂ values were larger for submonolayer coverages of Pb on Ag compared to Cu. The EM enhancements determined from these results did not predict the SERS-quenching behavior suggesting that other mechanisms must be considered.
27
Adamkiewicz, Malgorzata. "Self-assembled monolayers on silicon : deposition and surface chemistry." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3938.
Abstract:
Fabrication of surfaces with versatile functional groups is an important research area. Hence, it is essential to control and tune the surface properties in a reliable manner. Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for tailoring of surface properties. Here a synthetic route for the preparation of vinyl-terminated trichlorosilane self-assembling molecules: 9-decenyltrichlorosilane (CH₂=CH-(CH₂)₈-SiCl₃), 10-undecenyltrichlorosilane (CH₂=CH-(CH₂)₉-SiCl₃), and 14-pentadecenyltrichlorosilane (CH₂=CH-(CH₂)₁₃-SiCl₃) is presented. These molecules were used for the preparation of SAMs in either liquid or vapour phase processes. Commercially available methyl-terminated self-assembling molecules: decyltrichlorosilane (CH₃-(CH₂)₉-SiCl₃) and octadecanetrichlorosilane (CH₃-(CH₂)₁₇-SiCl₃) were used as controls. The resultant films were characterised by X-ray photoelectron spectroscopy (XPS), contact angle analysis, ellipsometry, and atomic force microscopy (AFM). Well defined, vinyl-terminated SAMs were further chemically modified with carbenes (:CCl₂, :CBr₂, :CF₂) and hexafluoroacetone azine (HFAA). The reactions were performed in the liquid or the vapour phase. The resulting SAMs were characterised using the same methods as for the vinyl-terminated monolayers. Successful modification was confirmed by the appearance of new signals in the XPS spectrum, with simultaneous changes in water contact angle values and unchanged thickness values. Methyl-terminated SAMs were also exposed to carbenes and HFAA as a control system. These are the first examples of C-C bond formation on SAMs in the vapour phase.
28
Yan, Liling. "Effects of surface topography on hydrophobicity of surfaces with spherical micro-protusions." Thesis, The University of Sydney, 2005. https://hdl.handle.net/2123/27892.
Abstract:
The water repellency of a surface is principally governed by a combination of its
chemical nature (i.e. surface energy) and topographical microstructure. The surface
energy is an intrinsic property of a material that can be controlled by chemical
modification, and other factors that can affect wettability, especially the surface
topography were investigated. In particular, the study of topographical factors
influencing the wettability of solid films is very important in View of production of
surfaces with tailored properties and functions.
The main objective of this research was to investigate the effect of surface
topography on surface hydrophobicity. Particular emphasis was given to those
surfaces with a particulate-like structure, which is one of the most popular surface
features in natural and man-made superhydrophobic surfaces. Surfaces with
particulate-like structure from both real superhydrophobic surface and model
surfaces were characterized.
29
Ghahremaninezhad, Gharelar Ahmad. "The surface chemistry of chalcopyrite during electrochemical dissolution." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42830.
Abstract:
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.
30
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.
Abstract:
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.
31
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.
32
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.
33
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.
34
Shin, Nae Chul. "Controlling semiconductor nanowire crystal structures via surface chemistry." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52966.
Abstract:
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.
35
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.
36
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.
37
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.
38
Rostam, Hassan Muhammad. "The impact of surface chemistry on macrophage polarisation." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/39797/.
Abstract:
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.
39
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.
40
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.
41
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.
42
Duckenfield, Kea U. "Laboratory oxide coatings: Physical form and surface chemistry." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539616635.
Abstract:
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.
43
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.
Abstract:
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.
44
Greene, George W. IV. "Surface modification of sintered porous polyethylene membrane." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/20126.
45
Khan, Suleman Manawar. "Surface active lanthanide complexes for sensing applications on silica and gold surfaces." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5726/.
Abstract:
The work presented in this thesis investigates the use of new luminescent lanthanide bis-amide DTPA complexes, both in solution and bound to gold and silica surfaces. The bis-amide arms have been modified with surface attachment groups consisting of disulphides, thioacetates and silyl ethers. Both sensitising and non-sensitising bisamides arms were attached to DTPA in order to develop the best lanthanide based sensor. When these visible and NIR emitting lanthanide complexes are bound to the surface they can be used to detect various small analytesm including benzoic acid, phthalic acid, isophthalic acid, picolinic acid, dipicolinic acid, quinaldic acid, dibenzoyl methane and curcumin. The detection of analytes was performed on surfaces and in solution allowing for comparisons between the two techniques to be made. Lanthanide complexes were attached to silica microparticles and they were used for detection of analytes under flow conditions; these studies were compared to surface and solution analyte detection. The lanthanide-based silica microparticles were developed further to show the advantages of bimodal luminescent silica microparticles. The development of self-assembled monolayers of the lanthanide complexes on gold were studied using surface plasmon resonance and ellipsometry.
46
Parker, Emily M. "Surface active polymers as anti-infective and anti-biofouling materials." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:54e462df-b64c-499c-94ce-55d624be9a69.
Abstract:
This thesis is concerned with the chemical modification of polymers in the preparation of a library of materials which exhibit altered surface properties as a result of the surface chemical functionality, with particular emphasis on the development of materials that control biofouling and are antibacterial. Chemical modification of crosslinked polystyrene, in film and microsphere form, was carried out by carbene insertion followed by diazonium coupling. This provided access to a collection of materials with varying surface chemistry, whilst the bulk properties of the polystyrene substrates were maintained. Synthesis of the diaryldiazo and the diazonium salts used to perform the surface modifications is described, as well as the preparation and characterisation of the materials. Analysis of the ability of the materials to adsorb and bind the protein bovine serum albumin (BSA) is presented with data obtained from two methods of observation. Quartz Crystal Microbalance with Dissipation (QCM-D) and a protein assay based on the change in optical density of a BSA/PBS solution are used to demonstrate how the specific surface chemistry of the materials influences the ability to adsorb and bind protein. The behaviour of the materials was time dependent and was rationalised with respect to the surface water contact angle and the calculated parameters polar surface area and % polar surface area of the functional groups added to the surfaces. Finally, penicillin loaded materials were prepared and their antibacterial activity was tested against E. coli and S. aureus, demonstrating that the antibiotic is still active from within the polystyrene scaffold.
47
Li, Qiang. "Surface Chemistry of Hexacyclic Aromatic Hydrocarbons on (2x1) and Modified Surfaces of Si(100)." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/1263.
Abstract:
Room-temperature chemisorption of hexacyclic aromatic hydrocarbons on the 2x1, sputtered, oxidized and H-terminated Si(100) surfaces, as well as those upon post treatments of hydrogenation, oxidization and electron irradiation have been investigated by using thermal desorption spectrometry (TDS), Auger electron spectroscopy (AES) and low energy electron diffraction (LEED). This work focuses on the effects of the functional groups (phenyl, methyl, vinyl, heteroatom, and H atom) in the chemisorbed aromatic hydrocarbons (benzene, toluene, xylene isomers, styrene and pyridine) on organic functionalization of the Si(100) surface, particularly on such surface processes as cycloaddition, dative adsorption, hydrogen abstraction, desorption, dissociation, diffusion, and condensation polymerization. Unlike the earlier notion that hydrogen evolution in the hydrocarbon/Si(100) systems is the result of hydrocarbon dissociation (into smaller hydrocarbon fragments and H atoms) on the surface, condensation polymerization of the adsorbed aromatic hydrocarbons is proposed in the present work, in order to explain the higher-temperature hydrogen evolution feature in the toluene/Si(100) system. This hypothesis is supported by our TDS results for other hydrocarbon adsorbates, especially in the pyridine/Si(100) system where electron-induced condensation polymerization has been observed at room temperature. The improved techniques in the TDS experiments developed in the present work have enabled us to observe condensation polymerization and the effect of H on the surface processes (via surface reconstruction) on Si(100) for the first time. New analysis methods have also been developed to determine the adsorption coverage from the AES data, and this work has not only improved the accuracy of the elemental-coverage evaluation, but also provided a means to estimate the rate and the order of chemisorption. By using the density functional theory with the Gaussian 98 program, the adsorption geometries and the corresponding adsorption energies of various adsorption phases have been calculated. These computational results have provided useful insights into the chemisorption structures on the Si(100) surface. The present work also presents the development of three kinetics models for hydrogen evolution in the aforementioned aromatic-hydrocarbon systems on Si(100). Based on a modified collision theory with consideration of diffusion, these theoretical models have proven to be quite successful in simulating the observed TDS profiles and in estimating the kinetic parameters for the analysis of condensation polymerization in 2-dimensional diffusion systems. The present work illustrates that TDS experiments can be used effectively with quantum computation and theoretical kinetics modelling to elucidate the intricate nature of organosilicon surface chemistry.
48
Park, Jung Hwa. "The role of surface chemistry and wettability of microtextured titanium surfaces in osteoblast differentiation." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44732.
Abstract:
Biomaterial surface energy, chemical composition, charge, wettability and roughness all play an important role in determining the degree of the direct bone-to-implant interface, termed osseointegration. Surface chemistry, which is influenced by surface energy, wettability, and composition, is another factor that determines osteoblast phenotype and regulates osteoblast maturation. Increased surface energy is desirable for bone implants due to enhanced interaction between the implant surface and the biological environment. The extent of bone formation in vivo is also increased with increasing water wettability of implants.
The physiological role of implant surface chemistry is important in determining the success of implant osseointegration because of molecular rearrangements, surface reactions, contamination, and release of toxic or biologically active ions that are determined by the starting chemistry. However, the role of surface chemistry on osteoblast response is not fully studied.
Therefore, the overall goal of this dissertation is to understand how the surface chemistry, including wettability, chemical composition, and charge density, of titanium biomaterials impacts osteoblast maturation (in vitro). This study focuses on the general hypothesis that modifications of surface chemistry of titanium surfaces with sterilization or polyelectrolyte coating on titanium surfaces regulate osteoblast response.
49
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.
Abstract:
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.
50
Golding, Randy Dale. "Synthesis and application of alkyl dihydrochlorosilanes: A new approach to the surface modification of porous silica." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184427.
Abstract:
Three alkyldihydrochlorosilanes were synthesized; ethyldihydrochlorosilane, octyldihydrochlorosilane and octadecyldihydrosilane. Ethyldihydrochlorosilane was produced by the reaction of ethylsilane with mercuric chloride and the other two chlorosilanes were produced by the reaction of the alkyl Grignard reagent with dichlorosilane. Each alkyldihydrochlorosilane was reacted with porous silica in an attempt to discover the extent of reaction or the highest surface concentration of bonded groups attainable. The reaction between these alkydihydrochlorosilanes and porous silica was compared to the reaction between silica and the analogous alkyldimethylchlorosilane. The rate of reaction of both type of chlorosilane was found to be essentially the same. The maximum surface concentration of bonded surface groups attainable by alkyldihydrochlorosilanes was found to be approximately 1.3 #moles/m² greater than that attainable by alkyldimethylchlorosilanes. This increased surface coverage seemed to depend very little on the chain length of the alkyl group and was attributed to the decrease in steric hindrance of the bonding silicon atom of the silane. Surface bound silyl hydrides could be oxidized selectively and sequentially to form silane silanols. Surface silanes also appeared to reduce chloroplatinic acid, but were not observed to add efficiently to olefins. The chromatographic properties of silica modified with alkyldihydrochlorosilanes were compared to those of equivalent silicas modified with alkyldimethylchlorosilanes and alkyltrichlorosilanes before and after the surface silanes were oxidized. Both normal and reversed-phase liquid chromatographic studies were conducted. In general, it was found that alkyldihydrochlorosilanes yielded the most polar modified silicas. This greater surface polarity was attributed to an increase in the activity of water in the near surface region of the bonded phase.