Two pyrrolo[2,3-d]pyrimidines and a nucleoside analogue have been prepared. The nucleobases were obtained by spontaneous cyclisation of 4-aminopyrimidyl-acetaldehydes as an acetal. The adenosine analogue has been made by glycosylation of a suitable sugar derivative with the corresponding heterocyclic base. This nucleoside can be converted into fluorescently-labeled chain-terminating substrates for DNA polymerase after subsequent triphosphorylation and coupling to through-bond energy transfer systems. Fluorescein-based donor components to be incorporated into through-bond energy transfer systems have been prepared. The synthesis of 5-ethynylfluorescein-(5-tert-butoxycarbonyl)-pentyl ester has been executed in five steps from 1,3-dihydroxybenzene and phthalic anhydride. The donor fluorescein carboxylate has been alkylated with the tert-butyl ester of 6-bromohexanoic acid to provide a handle for attachment to biomolecules. In the context of regioisomerically pure halofluoresceins, besides the synthesis of pure regioisomers of bromofluorescein derivatives, 5-iodosulfofluorescein and pure regioisomers of 5-nitrofluorescein diacetate, as an intermediate in the synthesis of 5-iodofluoresceins, have been synthesized. New rhodamine-based acceptor components with extended aromatic systems have been prepared from an affordable starting material, tetralin. The attempts to isolate them via repeated recrystallizations and flash chromatography have been unsuccessful. However, these pyrylium cations are expected to fluoresce at longer wavelengths.

Luminescent properties of the dye molecules can be influenced by the environments as well as intermolecular interactions. Suitable control the aggregation can be useful for optoelectronic device applications. In this thesis, we investigate the spectroscopic properties of dye molecule, DiI_C18, in solutions. Solvents and concentrations are used to control the degree of aggregation. Absorption and emission are used to probe the properties. We use water, methanol, and ethylene glycol as key solvents to control the aggregation effects, especially the methanol solution mixing with water. As the concentration increased, the change of the absorption spectra are observed, which is caused by the aggregation between molecules. Two types of aggregations: head-to-tail structure and parallel structure, are proposed. Head-to-tail structure behaves red-shifted spectrum, and a corresponding shorter decay lifetime. On the contrary, parallel structure aggregation exhibits blue-shifted absorption spectrum and a longer fluorescence lifetime. Both structures are observed at different period after mixing. Only monomer exists in the methanol solution, even at high concentration. However, after missing with water, parallel structure aggregates are formed. Head-to-tail structure aggregates are formed after a much longer period, usually several hours after the mixing. These aggregates not only have different photo-physical properties. After high light intensity illumination, parallel structures are easier to turn into non-fluorescent structures, while head-to-tail structures last a longer period. Monomer structures exhibit the longest period. This provides additional evidence for the formation of different structures in the mixing solutions.

Thesis (Ph.D.)--Northwestern University, 2008. / Adviser: Hupp, Joseph T. Includes bibliographical references.

Dye sensitized solar cells (DSSCs) have received extensive attention among solar cells in recent years as the production cost is comparatively low and photovoltaic performance is good. Apart from TiO2, SnO2-based DSSCs are of great interest since SnO2 has a wide band gap and high mobility. Though the conversion efficiency of SnO2-based DSSCs is still not comparable to TiO2-based DSSCs, there is room for improvement to fabricate an efficient device. In this study, different commercial SnO2 nanoparticles have been compared. The number of SnO2 layers and paste formulation have been optimized. The effects of TiCl4 and TTIP treatments have been investigated. In order to further optimize the performance of SnO2-based DSSCs, different strategies have been adopted to increase dye loading, facilitate electron transport and enhance photon absorption. Different dopants (Zn, Mg and Ag) have been introduced to SnO2 pastes. It is found that cells with Zn dopants perform the best with increased dye uptake. SnO2 nanorods have been synthesized and mixed with SnO2 nanoparticles. More nanorods result in faster electron transport and hence increase the conversion efficiency. In addition, different gold nanostructures (nanostars, nanorods and nanocubic Au) have been synthesized and incorporated into SnO2 photoanodes to study the plasmonic effects. It can be observed that nanocubic Au demonstrates the largest improvement in conversion efficiency. The obtained results will be discussed in detail. / published_or_final_version / Physics / Master / Master of Philosophy

No description available.

No description available.

Diazotisation and aso=coupling reactions have been studied and the results are reported. A kinetic study of the acid catalysed diazotisation of various aniline derivatives has been made. The substrates considered were 2,4-dinitro-aniline, 4-nitroaniline, sulphanilaraide (aniline-4-sulphonamide) and sulphanilic acid (aniline-4-sulphonic acid). A new pK(_a) value of l.4 is reported for sulphanilamide. A study of the diazotisation of sulphanilic acid and sulphanilamide in the presence of Cl¯, Br¯, SCN¯, and SC(NH(_2))(_2) shows that the general catalytic trend Cl¯ < Br¯, SCN¯ < SC(NH(_2))(_2) is followed; whereas for the corresporaing nitrosating agents the general reactivity trend NOCl > NOBr >; NOSCN >NOS(^+)C(NH(_2))(_2) is followed. No catalysis was observed in the case of 2,4=dinitroaniline and this has-been interpreted in terms of a rapid reversible nitrosation in which the rate of the denitrosation step is greater than the rate of decomposition of the intermediate nitrosammonium ion. The bimolecular rate constants obtained for sulphanilic acid and sulphanilamide approach the diffusion controlled limit for this process in the case of NOCl and NOBr, Also reported is a study of the diazotisation of two heteroaromatic amines: 2-amino-5-nitrothiazole and 3-amino-l,2,4-triazoleo Catalysis by acid and the nucleophiles Cl¯ and SCN¯ has been observed. The catalytic and reactivity trends described above have been noted for reaction of these heteroaroraaticso The Pk(_a) value for 2-amino—5-nitrothiazole has-been determined and agrees well with the literature values. In addition to the above studies of diazotisation mechanisms, results are reported of a study of the leaving abilities of various electrofugal leaving groups X during ipso=coupling of 4=nitroaniline with 4-X,N- dimethylanilineso The sequence of leaving abilities has been determined by product yield studies. Rate constants for attack of ArN(^+)(_2) have also been determined. It is suggested that a substrate molecule (X-Ar-NMe(_2)) acts as a base in removing the group X from the Wheland intermediate.

Thèse--Toulouse. / Bibliography: p. [17]-21.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 81-87) Also available in print.