<p>Fabrication of microarrays using sol-gel immobilization has been utilized as an approach to develop high density biosensors. Microarray fabrication using various printing techniques including pin-printing and piezoelectric ink jet printing methods has been demonstrated. However, only limited characterization to understand the encapsulated biomolecule-material interface has been reported. Herein, Chemical characterization using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) on pin-printed microarrays of sol-gel derived acetylcholinesterase (AChE) microarrays is reported. Furthermore, the <em>in situ</em> fabrication of microarrays following the sol-gel process using piezoelectric ink jet printing methods was explored. Through techniques measuring solution viscosity, surface tension and particle size, important aspects of bio-ink formulation for piezoelectric ink jet printing were identified. Combined, a greater understanding towards the fabrication and characterization of sol-gel derived microarrays was achieved through this exploratory research.</p> / Master of Science (MSc)

Bipolar electrochemistry is an interesting concept for high throughput screening techniques due to the ability to induce gradients in a range of materials and their properties, such as composition, particle size, or dopant levels, among many others. One of the key advantages of the method is the ability to test, create or modify materials without the need for a direct electrical connection. In this thesis, the viability of this method has been explored for a range of possible applications, such as metal recycling, nanoparticle modification and corrosion analysis. In the initial part of the work a process to electrodeposit gradients in metal composition was evaluated, with a view to applying the technique to the extraction and recycling of metals from fly ash. Compositional gradients in the metals under study could be readily obtained from controlled reference solutions, although the spatial resolution of the metals was not sufficient to perform separation. Only copper could be easily deposited from the fly ash solution. Bipolar electrodeposition was also successfully used to modify the particle size across substrates decorated with gold nanoparticles. The approach was demonstrated both for surfaces possessing either a uniform particle density or a gradient in particle density. In the latter case samples with simultaneous, orthogonal gradients in both particle size and density were obtained. A combination of the bipolar approach with rapid image analysis was also evaluated as a method for corrosion screening, using quantitative analysis of gradients in pitting corrosion damage on stainless steels in HCl as a model system. The factors affecting gradient formation and the initiation of corrosion were thoroughly investigated by the use of a scanning droplet cell (SDC) technique and hard x-ray photoelectron spectroscopy (HAXPES). The ability to screen arrays of different materials for corrosion properties was also investigated, and demonstrated for stainless steel and Ti-Al alloys with pre-formed compositional gradients. The technique shows much promise for further studies and for high throughput corrosion screening applications.

This thesis is concerned with furthering our understanding of the basis of visible region photocatalytic activity exhibited by doped TiO2-based materials. A range of experimental techniques including high resolution X-ray photoemission spectroscopy and diffuse reflectance spectroscopy are used to investigate electronic structure and an attempt is made to link these results to the observed photocatalytic activity. Both anionic (N) and cationic (Rh and Sn) dopants are investigated. [See pdf file for full abstract].

<p>A fundamental understanding of heterogeneous catalysis requires analysis of model catalytic surfaces in tandem with complex technical catalysts. This work was divided in three areas, 1- preparation and characterization of model surfaces synthesized by vapor deposition techniques, 2- kinetic evaluation of model catalysts for formic acid decomposition and dry methane reforming, 3- characterization and kinetic evaluation of technical catalysts for the water gas shift reaction.</p> <p>In the first project, model PdZn intermetallic surfaces, a relevant catalyst for propane dehydrogenation, were prepared using an ALD approach. In this work, model surfaces were synthesized by exposing Pd(111) and Pd(100) surfaces to diethylzinc at ca. 10^-6mbar. Several different surface structures were identified by careful control of the deposition temperature of the substrate. Modifications in the adsorption properties of these surfaces towards carbon monoxide and propylene coincided with the structure of the PdZn surface layer. </p> <p>In the second project, formic acid decomposition kinetics were evaluated on model Pt catalysts. Formic acid decomposition was found to be structure-insensitive on Pt(111), Pt(100), and a polycrystalline foil under standard reaction conditions. CO selectivity remained < 1% for conversions <10%. Additionally, inverse Pd-Zr model catalysts were prepared by ALD of zirconium-t-butoxide (ZTB). Depending on treatment conditions, either ZrO_xH_y or ZrO₂ overlayers or Zr as sub-nanometer clusters could be obtained. The activity of the model catalyst surface towards dry reforming of methane if the initial state of the zirconium is metallic. </p> <p>In the third project, Au/Fe₃O₄ heterodimer catalysts were characterized for their thermal stability. In-situ TEM and XPS characterization demonstrates that the gold nanoparticles transform into gold thin films that wet the Fe₃O₄ surface as the reduction of the oxide proceeds. DFT calculations show that the adhesion energy between the Au film is increased on a partially reduced Fe₃O₄ surface. Additionally, Pt/Nb₂CT_x catalysts were characterized and kinetics evaluated for the water gas shift reaction. XPS and TEM characterization indicates that a Pt-Nb surface alloy is formed under moderate reduction temperatures, 350^OC. Water-gas shift reaction kinetics reveal that the alloy-MXene interface exhibit high H₂O activation ability compared to a non-reducible support or bulk niobium carbide. </p>

Given the wide range of properties and applications of intermetallic compounds, it is important to achieve a detailed understanding of their structure and bonding. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) were used to study the electronic structure of several types of pnictides (compounds containing Pn = P, As). ZrAs2, forming a PbCl2-type structure, has been established to be a genuine binary phase that is strictly stoichiometric. At 900 °C, it supports extensive solubility of Ge to form the ternary extension Zr(GexAs1−x)As (0 ≤ x ≤ 0.4). XPS analysis and band structure calculations confirmed that the Ge and As atoms are anionic in character and that the substitution of Ge for As is driven by a depopulation of anion–anion antibonding states. ZrCuSiPn and REMAsO are important representatives of ZrCuSiAs-type materials. The small magnitudes of the binding energy shifts in the XPS spectra of ZrCuSiPn suggest significant covalent character in the Zr–Si, Zr–Pn, and Cu–Pn bonds, consistent with a three-dimensional structure. On progressing from ZrCuSiP to ZrCuSiAs, the charge transfer from metal to Pn atoms becomes less pronounced, as indicated by changes in the intensity of the Cu K-edge and Zr K, L-edge XANES spectra. Binding energy shifts and satellite features of the XPS spectra of REMAsO indicated that bonding in the [REO] layer is ionic, whereas bonding in the [MAs] layer is strongly covalent. Altering the electronic structure of one layer (by M or RE substitution) does not affect the electronic structure of the other layer, consistent with a two-dimensional structure in REMAsO. Metal-rich phosphides M2P (forming Cr2P-, Fe2P-, and Co2P-type structures) and M3P (forming Ni3P-type structures) were examined by XPS and XANES. The P 2p3/2 binding and P K-edge absorption energies decrease with greater ionic character of the M−P bonding and indicate the presence of anionic phosphorus. Interatomic effects play a more important role in affecting the energy shifts in these metal-rich phosphides than in the monophosphides, becoming more pronounced with higher metal concentration. Surprisingly, intraatomic effects dominate in mixed-metal phosphides (Ni1-xMx)2P despite evidence of metal-to-metal charge transfer from the Ni XANES spectra and Ni 2p XPS satellite features.

The main objective for the work described in this PhD thesiswas to formulate a friction model to characterize thefrictional behavior of paper. More specifically, the modelshould explain a phenomenon that is typical for paper grades,viz.: that the level of paper-to-paper friction is dependent onthe direction and the number of previous slides. The modelshould also explain the lubricating effect oflow-molecular-mass lipophilic compounds (LLC) that occur inpaper on paper-to-paper friction. Furthermore, the model shoulddescribe the types of forces that influence paper-to-paperfiction and explain the mechanism by which the LLC decreasepaper-to-paper friction. This thesis consists of a literature review of the basicconcepts of tribology and a summary of the main results andconclusions from four studies on the frictional characteristicsof paper and a study on the friction and adhesion of cellulosesurfaces together with some unpublished material. The purpose of the investigation described in the firstpaper was to explain a phenomenon that is typical for papergrades, viz.: the level of paper-to-paper friction is dependenton the direction and the number of previous slides. Thisbehavior is called“friction hysteresis”by theauthors, and it has its origin in the reorientation of thefibers on the surface of a paper and their alignment relativeto the sliding direction. The second paper describes a study that was aimed atidentifying lubricants that occur natively in paper. Filterpapers were impregnated with model compounds representing woodextractives, i.e. low-molecular-weight lipophilic compounds,which are present in wood, pulp and paper, and thepaper-to-paper friction was determined. The results of thatstudy show that a wood extractive must fulfill severalstructural criteria in order to lubricate a paper surface: Itmust have a hydrophilic group that can attach to the papersurface and a linear hydrocarbon backbone of sufficientlength. Although it is not specifically stated in the second paper,the authors proposed a type of lubrication by which woodextractives decrease paper-to-paper friction that is, ineffect, boundary lubrication. The purpose of the investigationdescribed in the third paper was to clarify whether woodextractives and other low-molecular-mass lipophilic compoundsthat occur in paper can act as boundary lubricants on papersurfaces. The main objective of that study was to investigatethe role of chemical structure of LLC for their orientationrelative to the paper surface, which is an important criterionfor boundary lubrication. Filter papers were impregnated withmagnesium salts of different lipophilic acids, which were usedfor model compounds for the LLC. The deposited layers ofmagnesium salts were characterized by X-ray photoelectronspectroscopy (XPS) and contact angle goniometry and thefriction of the impregnated paper sheets was determined. Theresults show that the degree of lubrication and the resistanceto wear of the layers of a magnesium salt increased withincreasing chain length and increasing degree of linearity ofthe lipophilic acid. Based on the results of that study and ofearlier studies, it is concluded that boundary lubrication isthe type of lubrication by which low-molecular-mass lipophiliccompounds that occur natively in paper decreasepaper-to-paper-friction. In boundary lubrication, surfaces are covered withmonolayers of lubricant molecules that comprise an active headgroup that can attach to the surface, e.g. a carboxyl group,and an inert linear backbone, such as a long saturatedhydrocarbon chain. Such compounds form ordered monolayers onsurfaces, so that the backbone points vertically out of planeof the surface. The friction is then determined by theinteractions between the monolayers, which are weaker than theinteractions between the clean surfaces and this gives a lowerfriction. The fourth paper describes a study on the origin of thedifferences in friction levels between different linerboardsbased on recycled fiber (old corrugated container, OCC). Thesheets were subjected to two extraction stages and analyzedwith respect to surface roughness and their content oflow-molecular-mass lipophilic compounds (LLC). The resultsshowed that a high amount of LLC in the sheets lead to lowfriction, due to lubrication. The fifth paper describes a study that was aimed atdetermining the types of forces that influence the frictionbetween the surfaces of hydrophilic polymers and explaining themechanism by which boundary lubricants decrease the friction.The adhesion and the friction of model systems was measuredwith atomic force microscopy (AFM) using regenerated cellulosefilms and functionalised AFM tips and the effect of fatty acidsand humidity was investigated. The friction significantlyincreased with increasing humidity and that there was a strongcorrelation between the ability of a fatty acid to form ahydrophobic surface and its lubricating performance. Measuredadhesion forces at high humidity were well predicted bytheoretical models that took into account the effect of theLaplace pressure acting in a water meniscus formed aroundcontact regions due to capillary condensation. The resultsindicated that the degree of capillary condensation may beeffectively suppressed by increasing the hydrophobicity of thecontacting surfaces, causing adhesion and friction to decrease.These results suggest that friction between paper surfacesunder ambient conditions is greatly influenced by the degree ofcapillary condensation. Furthermore, lubrication by fatty acidsis achieved by the formation of a vertically oriented,hydrophobic monolayer that can withstand the stresses duringsliding and increase the hydrophobicity of the paper surfaceand thereby suppress capillary condensation. <b>Keywords:</b>Friction, paper-to-paper friction, frictionhysteresis, fibers, orientation, sliding direction, woodextractives, low-molecular-mass lipophilic compounds, boundarylubrication, adhesion, capillary condensation, Laplacepressure, surface forces, JKR theory, gas chromatography-massspectroscopy, X-ray photoelectron spectroscopy, contact angle,atomic force microscopy

Allyl methacrylate, AMA was polymerized by chemical initiator and by &amp / #947 / -radiation under different conditions. The polymer obtained is mostly gel type with some soluble fractions at lower conversions. Arrhenius activation energy is 82.3 kJ/mol for chemical initiated polymerization. The polymer was characterized by FT-IR, NMR, DSC, TGA, XPS, XRD, DLS, and MS methods. It was found that about 98-99% of allyl side groups retained as pendant even after completion of the polymerization, while 1-2% may give crosslinking and/or cyclization that yields lactones and anhydrides. The spectroscopic and thermal results of the work showed that the reaction is not cyclopolymerization, but may have end group cyclization. Molecular weight of 1.1x106 was measured by DLS. Therefore, insolubility is due to the high molecular weight of polymer, even in the early stage of polymerization rather than crosslinking. The Tg of PAMA was observed as 94&ordm / C before curing, upon curing at 150-200&ordm / C, Tg increased to 211&ordm / C as measured by DSC. The thermal treatment of polymer at about 350&ordm / C gave anhydride by linkage type degradation, following side group cyclization. The XPS analysis showed the presence of radical fragments of AIBN and CCl4 associated with oligomers. The MS and TGA thermograms showed two or three stage degradations depending on solubility. The first stage was mostly linkage type degradation for the fragmentation of pendant allyl groups at 225-350&ordm / C. In the second stage, at 395-515&ordm / C, the degradation is random scission and depolymerization.

DC and RF magnetron co-sputtering techniques are one of the most suitable techniques in fabrication of thin films with different compositions. In this work, Al2O3 and Si/Al2O3 thin films were fabricated by using magnetron co-sputtering technique. For Al2O3 films, the stoichiometric, optical and crystallographic analyses were performed. For Si contained Al2O3 films, the formation conditions of Si nanocrystals were investigated. To do so, these thin films were sputtered on Si (100) substrates. Post annealing was done in order to clarify the evolution of Al2O3 matrix and Si nanocrystals at different temperatures. Crystallographic properties and size of the nanocrystals were investigated by X-ray diffraction (XRD) method. The variation of the atomic concentrations and bond formations were investigated with X-ray photoelectron spectroscopy (XPS). The luminescent behaviors of Si nanocrystals and Al2O3 matrix were investigated with photoluminescence (PL) spectroscopy. Finally, the characteristic emissions from the matrix and the nanocrystals were separately identified.

<p>The main objective for the work described in this PhD thesiswas to formulate a friction model to characterize thefrictional behavior of paper. More specifically, the modelshould explain a phenomenon that is typical for paper grades,viz.: that the level of paper-to-paper friction is dependent onthe direction and the number of previous slides. The modelshould also explain the lubricating effect oflow-molecular-mass lipophilic compounds (LLC) that occur inpaper on paper-to-paper friction. Furthermore, the model shoulddescribe the types of forces that influence paper-to-paperfiction and explain the mechanism by which the LLC decreasepaper-to-paper friction.</p><p>This thesis consists of a literature review of the basicconcepts of tribology and a summary of the main results andconclusions from four studies on the frictional characteristicsof paper and a study on the friction and adhesion of cellulosesurfaces together with some unpublished material.</p><p>The purpose of the investigation described in the firstpaper was to explain a phenomenon that is typical for papergrades, viz.: the level of paper-to-paper friction is dependenton the direction and the number of previous slides. Thisbehavior is called“friction hysteresis”by theauthors, and it has its origin in the reorientation of thefibers on the surface of a paper and their alignment relativeto the sliding direction.</p><p>The second paper describes a study that was aimed atidentifying lubricants that occur natively in paper. Filterpapers were impregnated with model compounds representing woodextractives, i.e. low-molecular-weight lipophilic compounds,which are present in wood, pulp and paper, and thepaper-to-paper friction was determined. The results of thatstudy show that a wood extractive must fulfill severalstructural criteria in order to lubricate a paper surface: Itmust have a hydrophilic group that can attach to the papersurface and a linear hydrocarbon backbone of sufficientlength.</p><p>Although it is not specifically stated in the second paper,the authors proposed a type of lubrication by which woodextractives decrease paper-to-paper friction that is, ineffect, boundary lubrication. The purpose of the investigationdescribed in the third paper was to clarify whether woodextractives and other low-molecular-mass lipophilic compoundsthat occur in paper can act as boundary lubricants on papersurfaces. The main objective of that study was to investigatethe role of chemical structure of LLC for their orientationrelative to the paper surface, which is an important criterionfor boundary lubrication. Filter papers were impregnated withmagnesium salts of different lipophilic acids, which were usedfor model compounds for the LLC. The deposited layers ofmagnesium salts were characterized by X-ray photoelectronspectroscopy (XPS) and contact angle goniometry and thefriction of the impregnated paper sheets was determined. Theresults show that the degree of lubrication and the resistanceto wear of the layers of a magnesium salt increased withincreasing chain length and increasing degree of linearity ofthe lipophilic acid. Based on the results of that study and ofearlier studies, it is concluded that boundary lubrication isthe type of lubrication by which low-molecular-mass lipophiliccompounds that occur natively in paper decreasepaper-to-paper-friction.</p><p>In boundary lubrication, surfaces are covered withmonolayers of lubricant molecules that comprise an active headgroup that can attach to the surface, e.g. a carboxyl group,and an inert linear backbone, such as a long saturatedhydrocarbon chain. Such compounds form ordered monolayers onsurfaces, so that the backbone points vertically out of planeof the surface. The friction is then determined by theinteractions between the monolayers, which are weaker than theinteractions between the clean surfaces and this gives a lowerfriction.</p><p>The fourth paper describes a study on the origin of thedifferences in friction levels between different linerboardsbased on recycled fiber (old corrugated container, OCC). Thesheets were subjected to two extraction stages and analyzedwith respect to surface roughness and their content oflow-molecular-mass lipophilic compounds (LLC). The resultsshowed that a high amount of LLC in the sheets lead to lowfriction, due to lubrication.</p><p>The fifth paper describes a study that was aimed atdetermining the types of forces that influence the frictionbetween the surfaces of hydrophilic polymers and explaining themechanism by which boundary lubricants decrease the friction.The adhesion and the friction of model systems was measuredwith atomic force microscopy (AFM) using regenerated cellulosefilms and functionalised AFM tips and the effect of fatty acidsand humidity was investigated. The friction significantlyincreased with increasing humidity and that there was a strongcorrelation between the ability of a fatty acid to form ahydrophobic surface and its lubricating performance. Measuredadhesion forces at high humidity were well predicted bytheoretical models that took into account the effect of theLaplace pressure acting in a water meniscus formed aroundcontact regions due to capillary condensation. The resultsindicated that the degree of capillary condensation may beeffectively suppressed by increasing the hydrophobicity of thecontacting surfaces, causing adhesion and friction to decrease.These results suggest that friction between paper surfacesunder ambient conditions is greatly influenced by the degree ofcapillary condensation. Furthermore, lubrication by fatty acidsis achieved by the formation of a vertically oriented,hydrophobic monolayer that can withstand the stresses duringsliding and increase the hydrophobicity of the paper surfaceand thereby suppress capillary condensation.</p><p><b>Keywords:</b>Friction, paper-to-paper friction, frictionhysteresis, fibers, orientation, sliding direction, woodextractives, low-molecular-mass lipophilic compounds, boundarylubrication, adhesion, capillary condensation, Laplacepressure, surface forces, JKR theory, gas chromatography-massspectroscopy, X-ray photoelectron spectroscopy, contact angle,atomic force microscopy</p>

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