This dissertation investigates the photophysics of bis(diarylamino)biphenyl (TPD) and silver nanoparticles (AgNP). A main goal of this work was to develop an understanding of the relaxation pathways involved in the deactivation of photoexcited TPD chromophores in close proximity to silver nanoparticles. The TPD chromophores were attached to the silver nanoparticle core via an alkylthiol group. The TPD-AgNP systems were synthesized and characterized using Transmission Electron Microscopy (TEM), UV-visible absorption, infrared spectroscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy, Inductively Coupled Plasma - Emission Spectroscopy (ICP-ES) and Thermogravimetric Analysis (TGA). Time-resolved photophysical processes in these systems were studied using femtosecond transient absorption spectroscopy. Initial studies of the interaction of the TPD and AgNP addressed the linker length dependence of the dye excited state decay kinetics, wherein alkyl linker chains of 3, 4, 8 and 12 carbon atoms were used. These results showed that an ultrafast deactivation of the excited state of the TPD chromophore, which is three orders of magnitude faster than that of the free chromophore in solution, occurred in all of the systems. However, an unexpected new transient species was observed for the systems with three and four carbon linker chains. Further studies showed this species to be spectroscopically very similar to the TPD radical cation, suggesting a charge separation pathway in the excited state relaxation. Possible pathways for formation of the cation-like state were examined through comparisons to the photophysics of alkyl substituted TPD in solution and in solid films, investigation of the pulse energy and TPD surface coverage dependence of the yield of the cation-like TPD species, transient absorption anisotropy decay dynamics, and kinetic modeling studies. Taken together, these investigations provide support for exciton-exciton annihilation being responsible for the formation of cation-like species. The packing of the TPD chromophores is concluded to be of critical importance in the generation of the cation like species but it is also possible that proximity to the silver nanoparticle plays a role in facilitating charge separation as well.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Kinetics investigations of the thermal Cope rearrangement of meso-and d1-3,4-diphenylhexa-1,5-dienes were undertaken in order to gain information about the transition states for these reactions by determining the appropriate enthalpies and entropies of activation. Of particular interest were the activation parameters for the meso compounds' rearrangement as it represents the only known example in which both four-and six-centered transition states are of comparable energy. Kinetics of the dl isomers' rearrangement in the temperature range 90-110⁰were determined using 5 X 10¯⁵M solutions of the olefin in heptane contained within sealed Pyrex ampules. Extents of reaction were determined from UV absorbance measurements at 256 nm. Product instability, becoming pronounced after 85-90% reaction, was observed. Two rate constants were calculated covering 0-85% and 0-98% reaction respectively, from each set of data. Evaluations of enthalpies of activation from the two sets of rate constants gave, respectively, 23.8 and 23.9 kcal/mole, indicating that inclusion of the increasingly erratic kinetics data collected after 85% reaction had little effect upon this activation parameter. The corresponding entropies of activation at 100⁰were -12.9 and -12.6 eu. Both activation parameters are consistent with those for other Cope rearrangements indicating that the thermal isomerization of dl-3,4-diphenylhexa-1,5-diene in the temperature range 90-110⁰is normal in every respect. Kinetics studies of the more interesting meso-diene were precluded by the failure to locate means of controlling product decomposition, which would be expected to become more severe at the higher temperature required (140-160⁰). Additionally, alumina-catalyzed isomerizations first observed accidently for the d1-diene, and subsequently verified for both meso--and d1-olefins, were examined. In contact with 100 times its weight of very active alumina at room temperature the d1 isomer was found to undergo conversion in the extent of 40% during a two-hour period to trans, trans-1,6-diphenylhexa-1,5-diene.meso--3,4-Diphenylhexa-1 ,5-diene underwent structural reorganization more slowly; after 70 hours over alumina a 15% conversion to a 9:1 mixture of cis-trans and trans,trans-1,6-diphenylhexa-1,5-dienes was noted. The stereo specificities observed for these unusual catalyzed rearrangements parallel those of their thermally-induced counterparts. Modifications in the syntheses of meso- and d1-1, 6--dibromo-3,4-diphenylhexanes, and meso--and dl-3,4-diphenylhexa-1,5-dienes, are also presented.

No description available.

This thesis is a continuation of a study of molecular moments begun by Joseph T. Fielder. In his paper he discussed the theory and the equipment necessary for such a study. It is the purpose of this paper to set forth modifications of his equipment, to present data obtained with this modified equipment, and to interpret this data.

No description available.

The interest in biosensors can be attributed to the first described enzyme containing sensor used to detect levels of glucose in 1962. Although research into biosensors was initially slow to pick up, the field has become increasingly popular and research has been widespread for the last 20 years. The continuing research into biosensors is crucial as this will improve current devices to become smaller, faster and more economical and yield new biosensors. This thesis is mostly concerned with the development of an integral component of a biosensor, the redox mediator. Complexes of ruthenium incorporating electron rich sulfur-donor ligands such as naphthalenedithiol should possess interesting redox qualities which could be used to produce better mediators. A second area covered in this thesis is in the structural studies of a series of iridium and rhodium complexes. Two classes of ruthenium complexes with sulfur-donor ligands have been prepared. The first class incorporates the ruthenium bis-bipyridine moiety while the second contains pentamethylcyclopentadienyl ruthenium. Most complexes synthesised exhibited reversible oxidation waves in the region of -0.1 to 0.2 V vs. Ag/Ag⁺. Their possible use as redox mediators was hindered by several factors, particularly difficulties in purification. They also exhibited oxygen sensitivity and low stability when in solution.The second area covered in this thesis is to further understand the bonding of the ligands used in the above study. A series of pentamethylcyclopentadienyl iridium and rhodium complexes were synthesised with three different dithiolato ligands. Two of the three ligands studies produced structures that included more than one metal centre leading to straining of the ligand. In order to study the monomeric form, the clusters were opened with a neutral phosphine ligand. Both the Ir…S and Rh…S bond lengths of all the complexes were within expected parameters.

Bifenilas Policloradas (PCB) são compostos orgânicos clorados altamente tóxicos e também são considerados poluentes orgânicos persistentes. Sua alta estabilidade térmica e química é responsável pela sua difícil degradação, e quando estas substâncias são liberadas no meio ambiente, sua acumulação nos ecossistemas incorpora-se na cadeia alimentar, exibindo biomagnificação. Deve-se ressaltar a importância para o meio ambiente do tratamento de resíduos com PCB. Considerando que a Convenção de Estocolmo sobre poluentes orgânicos persistentes (POP) estabeleceu a eliminação do uso de PCB em equipamentos, por exemplo, transformadores e capacitores elétricos, até 2025. O objetivo deste trabalho foi estudar a remoção de PCB pelos processos de extração usando fluido supercrítico e a extração convencional (Soxhlet) no tratamento de materiais contaminados com PCB. Assim foi desenvolvida uma ferramenta computacional para correlacionar os dados de solubilidade de PCB em CO₂ supercrítico, usando a equação de estado de Peng-Robinson com parâmetros ajustados. O procedimento de cálculo foi inicialmente usado para uma série de compostos aromáticos (naftaleno, antraceno, fenantreno e bifenil), a fim de testar a abordagem. Os parâmetros binários para a regra de mistura quadrática clássica (vdW2) foram sistematicamente estimados, juntamente com um novo conjunto de dados de pressão de vapor, a fim de descrever a dependência da temperatura e alcançar incertezas experimentais. Finalmente, foram utilizados os parâmetros estimados para simular valores de solubilidade dos principais congêneres constituintes das misturas comerciais reais de PCB, como função das condições de operação de extração com uma solução simultânea das equações de equilíbrio para cada composto. A modelagem termodinâmica demonstrou ser viável para a análise de processos. / Polychlorinated Biphenyls (PCB) are chlorinated organic compounds which are highly toxic and are also considered persistent organic pollutants. The high thermal and chemical stability of PCB are responsible for their hard degradation, and when these substances are liberated in the environment, their accumulation in ecosystems leads to their incorporation in the food chain, exhibiting biomagnification. It should be emphasized the environmental importance for treating wastes with PCB. Considering that, Stockholm Convention on persistent organic pollutants (POP) established the elimination of the use of PCB in equipments, e.g. electrical transformers and capacitors, by 2025. The objective of this work was to study the removal of PCB by the processes of extractions using supercritical fluid and conventional (Soxhlet) extraction method in the treatment of contaminated materials with PCB. As well was the formulation of a computational tool to correlate solubility data of PCB in supercritical CO₂, using Peng-Robinson equation of state with fitted parameters. The calculation procedure was initially used for a series of aromatic compounds (naphthalene, anthracene, phenanthrene and biphenyl) in order to test the approach. The binary parameters for the classical quadratic mixing rule (vdW2) were systematically estimated, together with a new set of vapor pressure in order to describe the temperature dependence and achieve experimental uncertainties. Finally, the estimated parameters were used to simulate solubility values of the major constituent congeners of commercial and real mixtures of PCB, as function of the operational conditions of extraction by a simultaneous solution of the equilibrium equations for each compound. The thermodynamic modeling demonstrated to be feasible for process analysis and design.

Polychlorinated biphenyls (PCBs) are a group of 209 persistent organic pollutants, whose documented carcinogenic, neurological and respiratory toxicities are expansive and growing. Existing inhalation estimates demonstrate ubiquitous exposure to World Health Organization (WHO) indicator PCBs and limited other PCB congeners in North America and Europe. However, inhalation exposure estimates of most lower-chlorinated congeners are lacking, and continuing release of PCBs from urban areas demands location-specific assessments of PCB exposure in ambient air and contaminated environments. Using paired indoor and outdoor airborne PCB measurements and activity questionnaires from the AESOP Study, we assess congener-specific exposure rates for adolescent children and their mothers in East Chicago, Indiana and Columbus Junction, Iowa. Our cohorts of 129 (EC) and 135 (CJ) and our detection of 202 individual congeners and coelutions allows unprecedented quantification of congener-specific inhalation exposure, which we compare to dietary exposure using Total Diet Survey PCB concentrations. ∑PCB inhalation is greater for children than for their mothers in both locations, and is greater for East Chicago mothers and children than for Columbus Junction mothers and children, respectively. Schools attended by AESOP Study children have higher indoor PCB concentrations than do homes, and contribute to more than half of children's inhalation PCB exposure. Inhalation of the potentially neurotoxic congeners PCB 11, 40/41/71, and 51 was apparent among individuals at each location. Additional, congener-specific and biological inferences are possible via comparison with sera-based PCB concentrations for these cohorts.