The aim of this work has been to make use of surface scattering techniques to study soft matter at interfaces. The work presented herein is composed of two distinct bodies of work. The first comprises a fundamental study of the physical and structural properties of Langmuir monolayers composed of sulfobetaine surfactants. Physiochemical properties of the films have been investigated through the use of Langmuir trough techniques. This has been used to support x-ray and neutron reflectometry data, from which structural parameters were derived. The second body of work involves attempts to find and/or characterize novel ways of aligning proteins at interfaces. Soluble proteins at lipid interfaces have been characterized in terms of their interactions with functionalized lipid monolayers. Specific interactions have been utilized to adsorb protein layers at the interface through interactions with His-tag chelating lipids within the monolayer. These have been characterized using neutron reflectometry and quartz crystal microbalance studies. Work has also been completed to design a suitable system for the adsorption of membrane proteins. This has involved aligning phospholipid bilayer nanodiscs at the lipid interface and subsequent characterization through neutron reflectometry.

<p>Abstract to“Interfacial colloidal particle films andtheir structure formation”; a licentiate thesis, whichwill be presented by Sandra Rödner in Q2, 29 November 2002at 13.00.</p><p>Colloidal particles can be made to organise themselves intoordered arrays. These colloidal structures acquire interestingand useful properties, not only from their constituentmaterials but also from the spontaneous emergence of mesoscopicorder that characterises their internal structure. Orderedarrays of colloidal particles, with lattice constants rangingfrom a few nanometers to a few microns, have potentialapplications as optical computing elements and chemicalsensors, and also has an important influence on the mechanicalproperties and optical appearance of paint films and papercoatings.</p><p>The control of colloidal structure formation starts with theparticle interactions (attractive or repulsive) and colloidaldynamics, which is the topic of this thesis. To enable adetailed understanding of the different factors that controlthe formation of dense 2D colloidal films, a method forstructural characterisation was developed. The degree of orderin the hexagonal close-packed structure, displayed by thecolloidal films, was characterised by the size of ordereddomains and by the distribution of pore sizes. The size ofordered domains was obtained from the pair distributionfunction, and the distribution of pores from a Delaunaytriangulation procedure. These methods are based on theparticle positions in the film, which were determined by lightmicroscopy and processed digital images.</p><p>The two methods were used to study the effect of particleinteractions on the structure of colloidal monoparticulatefilms, formed at the air-liquid interface. The size of theordered domains decreased exponentially with increasing bondstrength, while the pore density increased. The transfer andsubsequent drying of the formed film on a solid substrateinduced structural changes; the capillary forces transformedsmall pores into triangular order while some of the largervoids and cracks increased in size.</p><p>The structural features of colloidal monolayers, formed bydrying a dilute silica suspension on a substrate, wereinvestigated. Addition of small amounts of salt resulted indrastic changes of the particle film structure. The size of theordered domains decreased exponentially with increasing amountsof added salt (0-2.9% NaCl/Silica ratio), with a simultaneousincrease of the concentration of large defects. This suggeststhat loss of colloidal stability and onset of particle adhesionto the substrate inhibit rearrangement and ordering. Theevaporation rate was controlled by varying the relativehumidity during drying. Colloidal monolayers with the largestordered domains and the lowest concentration of stacking faultswere formed at an intermediate humidity (55% RH).</p><p>The rearrangement process during drying of dilute silicasuspensions was followed in detail by studying the changes inthe structural features during growth of colloidal monolayers.Low crystal growth rate promoted the transition of squarelattice domains to a hexagonal close-packed structure. Additionof salt to the electrostatically stabilised dispersionincreased the formation of square structured regions at thecrystal-suspension interface, due to increasing adhesion to thesubstrate. The loss of colloidal stability inhibited therearrangement process, resulting in higher concentrations ofsquare lattice domains at large distances from the crystal edgecompared to systems without added salt.</p>

Although phosphatidylinositol (PI) and phosphoinositides (PIPs) only comprise a small percentage of the inner leaflet of the plasma membrane, they mediate a large variety of signaling events. In previous studies, we have observed the absence of macroscopically discernible domains in mixtures of PI/PC and PI(4,5)P2/PC. The addition of cholesterol to these mixtures results in condensation of the monolayer and hence domain formation. To better mimic the ionic conditions and hydrogen bonding properties of the inner leaflet plasma membrane, we investigated in this study the effect of common inner leaflet plasma membrane lipids like phosphatidylethanolamine (PE), phosphatidylserine (PS) and PI, on phosphoinositide domain behavior in the presence of cholesterol and/or bivalent cations.

We described the synthesis of multilayer organic thin films prepared by sequential vapor-phase coupling of monomers. The reactions were carried out at room temperature and atmospheric pressure. Films prepared using up to six sequential coupling reactions are reported. Homobifunctionalized monomers, such as hexamethylenediamine, react primarily via a single endgroup rather than cross coupling to the reactive surface via both reactive groups. We synthesized bifunctionalized polyamidoamine (PAMAM) dendrimers having both quaternary ammonium groups and primary amines on their periphery were prepared. The high positive charge on the surface of these dendrimers prevents agglomeration, and the unquanternized amine groups provide a reactive handle for immobilizing the dendrimer-encapsulated nanoparticles onto surfaces. We prepared highly monodisperse, 1-2 nm diameter Au nanoparticles using bifunctionalized PAMAM dendrimers as templates. The synthesis is carried out in water, takes less than 30 min, and requires no subsequent purification. The high monodispersity is a function of the template synthesis, which avoids size variations arising from random nucleation and growth phenomena, and the use of magic number equivalent ratios of AuCl4-/dendrimer. We investigated the electrochemical properties of Au, Pd and PdAu monolayer-protected clusters (MPCs), prepared by dendrimer-templating and subsequent extraction, are described. Purification of the extracted Au, Pd and PdAu nanoparticles was not required to obtain well-defined differential pulse voltammetry peaks arising from quantized double-layer charging. The calculated sizes of the nanoparticles were essentially identical to those determined from the electrochemical data. The capacitance of the particles was independent of the composition of core metal.

Preliminary work towards the development of novel biosensing interfaces for EMPAS (ElectroMagnetic Piezoelectric Acoustic Sensor) is presented in this manuscript. This method involves the use of unprecedented thiosulfonate-based linkers to construct robust and durable SAMs (Self-Assembling Monolayer) onto piezoelectric quartz crystals, which can chemoselectively immobilize thiol-containing biomolecules under aqueous conditions in a single, straightforward, reliable and coupling-free manner. Initial efforts are devoted to the construction of SAMs and the subsequent immobilization of thiol-containing biomolecules, and then characterization by CAMs (Contact Angle Measurement) and ARXPS (Angle-Resolved X-ray Photoelectron Spectroscopy). This method is then implemented into the construction of biosensing interfaces dedicated to the detection of avidin. With the incorporation of OEG (Oligo(Ethylene Glycol)) backbone and diluent in the method, 14-fold difference in signal response of EMPAS was observed between biotinylated and unfunctionalized SAMs.

Preliminary work towards the development of novel biosensing interfaces for EMPAS (ElectroMagnetic Piezoelectric Acoustic Sensor) is presented in this manuscript. This method involves the use of unprecedented thiosulfonate-based linkers to construct robust and durable SAMs (Self-Assembling Monolayer) onto piezoelectric quartz crystals, which can chemoselectively immobilize thiol-containing biomolecules under aqueous conditions in a single, straightforward, reliable and coupling-free manner. Initial efforts are devoted to the construction of SAMs and the subsequent immobilization of thiol-containing biomolecules, and then characterization by CAMs (Contact Angle Measurement) and ARXPS (Angle-Resolved X-ray Photoelectron Spectroscopy). This method is then implemented into the construction of biosensing interfaces dedicated to the detection of avidin. With the incorporation of OEG (Oligo(Ethylene Glycol)) backbone and diluent in the method, 14-fold difference in signal response of EMPAS was observed between biotinylated and unfunctionalized SAMs.

Today, optimizing well stimulation techniques to obtain maximum return of investment is still a challenge. Hydraulic fracturing is a typical application to improve ultimate recovery from oil and gas reservoirs. Proppant fracturing has become one of the most widely considered alternatives for application in carbonate reservoirs. Especially in areas that have high closure stress, the non-smoothly etched surface created by acid fracturing may not remain open upon closing, resulting in decrease in fracture conductivity and unsuccessful stimulation treatment. In early years, because of the increase in the success of proppant fracturing, proppant partial monolayer has been put forward as a method that helps generate the maximum fracture conductivity from proppant fracturing treatment. However, this method was not widely successful because of proppant crushing and proppant embedment problems that result in losing conductivity. The ability to transport propping agents in available fracturing fluid was also poor and resulted in difficulties and failures to obtain proppant partial monolayer placement. For carbonate formations, acid fracturing is another effective stimulation method. Simpler operation and lower cost made the technique attractive in the field with plenty of successful experiences. The heterogeneity feature of carbonate formation brings a challenge to create sufficient conductivity. In cases of high closure formation, fracture conductivity is hard to sustain. This factor limited the applications of acid fracturing sometimes. In this study, laboratory tests were carried out using low concentrations of ultralightweight proppant to obtain partial monolayer proppant. Because of low specific gravity property of this proppant, it was claimed to help improve proppant transport inside the fracture. In this experimental study, the partial monolayer technique was examined with particular emphasis upon the impact of acid in possibly improving fracture conductivity of carbonate rocks. The technique is referred as "closed fracture acidizing". After obtaining a partial monolayer distribution on the fracture face, gelled acid was injected through the fracture face. Fracture conductivity before and after acid injection were evaluated. Experimental results showed clearly that acid injection does not enhance fracture conductivity of partial monolayer proppant fracturing. The more the volume of acid injection, the more rapidly fracture conductivity declines.

We examine the electrochemical properties of SAM of alkanethiols terminated with biferrocenyl group (complex 7) to understand the interactions between metal surface and molecules. The cyclic voltammogram of complex 8 shows two successive reversible one-electron redox waves corresponding to the oxidation of the biferrocenyl moiety and all peak-to-peak separations are smaller than 59 mV (ideal value of one electron transfer with diffusing controlling). In addition, the peak currents are linear to scan rate, i.e., i£\V. This observation is corresponding to the electrochemical property of SAM, and we would like to suggest that the electron transfer process in the electrochemical measurements is direct controlling. Furthermore, we synthesized a nano-material by using of redox stable biferrocenylalkanethiol attached to gold cluster (complex 10). The clusters are stable in air, soluble in nonpolar organic solvents and the characters could be examining by traditional chemical instruments such as NMR, IR, UV/Vis, TEM. The cyclic voltammogram shows that the electron transfer process in the electrochemical measurements is also direct controlling. Finally, the well-known mechanism of intramolecular electron transfer in mixed-valence biferroceniums and the stable biferrocene on Au (111) surface and on gold clusters let to the more advanced concept. We believe that the microstructure of biferrocene assembled on an electrode surface or on gold clusters might enable to carry out a particular function extraordinarily well, for example, optical switch.

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