In order to gain an understanding of the interaction of probe molecules with NaCh aggregates, steady-state and time-resolved photophysical methods were used. By employing several probe molecules, an understanding of how the structure of the probe affected binding to the two distinct sites in the aggregates was investigated. The first half of the thesis examined the reactivity of benzophenone (Bp) and 4,4-dimethylbenzophenone (DMBp) with NaCh aggregates by studying the kinetics of both the ketone triplet excited states and the ketone ketyl radicals. There were three species of triplet excited states observed in the presence of primary aggregates. One of the ketone triplet excited state species was located within the primary aggregate, and it reacted to form ketyl radicals. Other triplet states included in the primary aggregate were found to be long-lived, while a third species of triplet states was present in the aqueous phase. At higher bile salt concentrations, and in the presence of secondary aggregates, a layer of complexity was added. The binding dynamics for the triplet excited state with the secondary binding sites were much faster than those observed for the primary binding site. Hydrogen abstraction did not compete with other deactivation pathways in the presence of secondary aggregates, and thus only self-quenching and exit of the excited state probe from the secondary site were observed. Ketyl radical recombination took place in water and in the secondary sites. The second half of the research focused on the study a series of naphthalene (Np) derivatives in order to look at the effects of shape and hydrophobicity of probe molecules on the interactions between these probes and the host NaCh aggregates. 1-Ethylnaphthalene, 2-ethylnaphthalene, 1-acetonaphthone, 2-acetonaphthone, 1-naphthyl-1-ethanol and 2-naphthyl-1-ethanol were studied. 1-Ethylnaphthalene and 2-ethylnaphthalene were Ethylnaphthalene, 2-ethylnaphthalene, 1-acetonaphihone, 2-acetonaphthone, 1-naphthyl- 1-ethanol and 2-naphthyl-1-ethanol were studied. I-Ethylnaphthalene and 2- ethylnaphthalene were contained within the primary binding site, while 1-naphthyl-1-ethanol, 2-naphthyl-1-ethanol, 1-acetonaphthone and 2-acetonaphthone were contained within the secondary binding site. The effect of the position of the substituent was only noticed when the probe molecules formed weak interactions with the outside of the primary aggregate, and not when the probe was complexed to one of the binding sites present in the NaCh system. The naphthalene probe molecules were also used to study the effect of ionic strength on NaCh aggregate formation. It was found that primary aggregation occurred at lower NaCh concentration as the ionic strength was increased. No effect of ionic strength was observed on the formation of secondary aggregates. All the findings in this study are consistent with an aggregation model in which two distinct binding sites are present. The shape of the probe as well as its hydrophobicity are critical to its interaction with the NaCh aggregates. From these dynamic studies it was found that only a small number of NaCh monomers (6-13) are needed to define both the primary and secondary binding sites. / Graduate

Activated carbons have been modif fed using reactive chemicals to produce adsorbents of enhanced hydrophobic character which will also be resistant to surface oxidation that results from exposure to humid air ("ageing"). The intention was that modification would not disrupt the carbon pore structure. The adsorptive properties of the modified carbons have been investigated using probe molecules Including nitrogen, water, hexane, and chloropicrin, and the ageing characteristics of the carbons, and the factors controlling the adsorption of a model hydrophobic vapour from high humidity air have been studied. Directly fluorinated carbons were unstable, probably due to weakly adsorbed fluorine. Treatment of these adsorbents with other chemicals indicated the potential of the technique for Introducing specific functional groups onto the carbon surface. Carbons modified using selective fluorinating reagents (hexafluoropropene and 1,1-difluoroethene) were more hydrophobic, and adsorbed hydrophobic vapours more efficiently from humid air in comparison to controls. These adsorbents aged, but at a reduced rate in comparison to control carbon. Carbons modified using chlorinating reagents (carbonyl chloride and chlorine) and treated with solvents to remove adsorbed reagent and/or reaction products were of improved hydrophobic character, and adsorbed hydrophobic vapours from humid air at least as efficiently as the control samples. More importantly, these carbons offered resistance to ageing effects. A study of the factors controlling the efficiency with which hydrophobic vapours; are adsorbed from humid air revealed that the surface chemistry of the carbon is important, but that under typical conditions of use, filter performance was limited by the rate at which water displaced by the organic vapour could be carried away by the airstream. The results illustrate that filters containing chemically modified activated carbon offer advantages when volatile hydrophobic contaminant vapours are present, and where ageing effects are an important mechanism by which filtration efficiency is degraded.

Afin d'étudier la granulo- et la morpho-dépendance des propriétés d'énergies de surface de solides divisés, plusieurs lots de TiO2 anatase ont été synthétisés. Une série de matériaux parfaitement définis avec des morphologies allant de sphéroïdale à facettée, dans des gammes de tailles allant de 4 à 20 nm a été obtenue grâce aux modifications de conditions de pH et la présence d'acides organiques. La combinaison de différentes molécules sonde a permis de déterminer l'hétérogénéité énergétique superficielle de ces matériaux, aux interfaces solide/gaz et solide/liquide. La volumétrie de quasi-équilibre à basse pression (N2/Ar) couplée à la méthode de modélisation DIS et la microcalorimétrie à écoulement de gaz (NH3) ont mis en évidence les contributions des différentes faces cristallographiques et les effets de la cristallinité. Ces mêmes propriétés ont été analysées grâce à la titration potentiométrique en milieu aqueux (H+/OH-), couplée à la procédure TDIS (détermination du PCN et des distributions d'affinité de protons). Cette stratégie a permis une étude complète des propriétés superficielles énergétiques et géométriques des nanomatériaux. / In order to study the relationships between the particle size, the morphology and the surface energy properties of divided solids, several batches of TiO2 anatase were synthesized. A series of materials with morphologies ranging from spheroidal to well faceted, with particle sizes ranging from 4 to 20 nm were obtained by adjusting the pH conditions and the presence of organic acids. The surface heterogeneity of these materials, at solid/gas and solid/liquid interfaces, was studied by combining various molecular probes. The low pressure quasi-equilibrium adsorption volumetry (N2/Ar) coupled with the DIS modeling approach and the flow adsorption microcalorimetry (NH3) have evidenced the various contributions of crystallographic faces and the effect of the crystallinity. These properties have also been analyzed using potentiometric titration in aqueous medium (H+/OH-), coupled with the TDIS procedure, to determine PZC and proton affinity distributions. Such a strategy has led to a complete study of the energetic and geometric surface properties of these nanomaterials.

Acid/Base characterizations of metal oxide surfaces are often used to explain their catalytic behavior. However, the vast majority of these studies have been performed on powders or supported oxides, and there is very little information available in the literature on the interaction of acid/base probe molecules with well-defined oxide surfaces of known coordination geometry and oxidation state. The well-defined, single crystal surfaces of Cu₂O (111), SnO₂ (110), and Cr₂O₃ (101̲2) were investigated for their acid/base properties by the interactions between the probe molecules and the well-defined surface features. The adsorption of NH₃ at cation sites was used to characterize the Lewis acidity of SnO₂ (110) and Cu₂O (111) surfaces. The adsorption of CO₂, a standard acidic probe molecule, was used to characterize the Lewis basicity of the oxygen anions on SnO₂ (110), Cu₂O (111) , and Cr₂O₃ (101̲2) surfaces. BF₃, while not a standard probe molecule, has been tested as a probe of the Lewis basicity of the oxygen anions on SnO₂ (110) and Cr₂O₃ (101̲2). By studying probe molecules on well-defined metal oxide surfaces with known coordination geometry and oxidation state, an overall evaluation of NH₃, CO₂, and BF₃ as probe molecules can be made using the surfaces studied. NH₃ probed differences in Lewis acidity of Sn cations on SnO₂ (110), which had differences in coordination environments and oxidation states. But, NH₃ adsorption failed to provide any direct information on differences in Lewis acidity of Cu cations in different local coordination geometries on Cu₂O (111). CO₂ is a poor probe of the Lewis basicity of oxygen anions on the metal oxide surfaces studied here. CO₂ does not strongly adsorb to either SnO₂ (110) or Cu₂O (111). On Cr₂O₃ (101̲2), CO₂ does interact with oxygen sites but in two different coordinations, which vary with surface condition, making a comparison of basicity difficult. In the cases studied here, CO₂ either does not adsorb, or it does not provide a clear set of results that can be related simply to Lewis basicity. BF₃ seems to be a much better probe of the Lewis basicity than CO₂ for the well-defined metal oxide surfaces studied here. On SnO₂ (110) and Cr₂O₃ (101̲2), the boron atom of BF₃ directly interacts with oxygen sites by accepting their electrons. BF₃ thermal desorption seems to provide a direct measure of the Lewis basicity of different surface oxygen species as long as they are thermally-stable in vacuum. / Ph. D.