Models of primary production require parameters to describe photosynthesis as a function of irradiance, such as the saturation irradiance (Ek, ?mol photons m-2 s-1). However, this parameter varies in both time and space, is expensive to measure, and its variability in the oceans is not well described. A novel fluorescence-based approach is presented to determine an empirical parameter (EFT, ?mol photons m-2 s-1), which is strongly correlated with Ek. This correlation provides evidence to use EFT as a proxy for Ek. Using an autonomous profiling instrument package (SeaHorseTM, located on the Scotian Shelf) and an autonomous oceanographic observational buoy (Land/Ocean Biogeochemical Observatory, located in the Northwest Arm, N.S., Canada), the variability of EFT was examined on three time scales: hours, days, and seasons. Studying variations of EFT with these autonomous instruments provided insights to its variability on time scales relevant to models of primary production.

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The objective of this thesis was to synthesize N2-modified guanosines (N2G) in order to introduce fluorescent and chelating ligands, such as diphenylamino, 2,2’-dipridylamino, 2-(2’-pyridyl)benzimidazolyl and p-pyrenylphenyl functionalities. Their photophysical properties were examined in order to gain further knowledge about the effect of guanine modification on its electronic structure. The impact of N2-modification was first studied in terms of self-assembly of the luminescent guanosines in solution and gas phase. Extensive NMR and ESI MS studies provided evidence that these N2-modified guanosines self-assemble exclusively into octamers with high-fidelity, in the presence of Group 1 and Group 2 metal ions. In addition, the first example of “empty” G-octamer (free of metal cations) was identified by ESI MS. Experimental results suggested that N2-substituents provide additional electronic and steric effects which drive the diastereoselectivity of self-assembly and provide additional stability. Hydrogen bonding of N2Gs with cytidine was monitored using fluorescence and NMR. In addition to GC base pair formation, the G-quartet-to-GC base pair structural transformation was studied using CD, fluorescence, and NMR spectroscopy. Due to the luminescent and chelating nature of some of the N2G derivatives, their interactions with a number of metal ions, such as Zn2+, Cd2+, Hg2+, La3+, Tb3+ and Eu3+ ions, were probed by using various spectroscopic methods. The overall optical response in the presence of metal ions was highly dependent on the nature of N2-substituent, and it varied from “turn-on” to “turn-off” response, clearly indicating that the modification at the N2-site of guanosine can be used to finely tune the optical response of these nucleosides. Finally, synthesis of a phosphorescent N2-arylguanosine containing the Ru2+ metal center was achieved and its photophysical and electrochemical properties were examined. / Thesis (Ph.D, Chemistry) -- Queen's University, 2009-09-22 16:02:20.934

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The opening section describes the development of the instrument from an existing Raman spectrometer operating in the visible region with Ar-ion laser excitation. In the first part of this section the steps carried out to improve the performance of the visible Raman system are outlined. In the second part, the development of the near-IR Raman system is described. The near-IR region was used because the radiation in this region has insufficient energy to induce a molecular transition to an electronically excited state and hence cause fluorescence. The system comprised of a Nd-YAG laser as a source in conjunction with a Ge detector. In the third part, the computer programs written to increase the capabilities of the data manipulation software are described. In the second section, a comparison is made of the near-IR system with Fourier Transform Raman spectroscopy, this being the most widely used technique used today to overcome the fluorescence problem. A wide range of samples were investigated and conclusions drawn concerning the future applicability of the near-IR dispersive technique. The third section describes the applications of the dispersive system: (a) to study the complexing of BBr₃ with (i) PBr₃ and (ii) P₄S₃; (b) to study, in conjunction with IR spectroscopy, the complexing of Me₂SnCl₂ with a range of pyridine and quinoline derivatives.

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Study of structure and interface morphology of magnetic thin films is crucial in obtaining a better understanding of the coupling mechanisms in such systems. In this thesis various x-ray scattering techniques are applied to a series of Co/Cr trilayers, Cu/Co multilayers and spin valve structures. It is demonstrated that modifications to the distorted wave Born approximation allow the modelling of grazing incidence diffuse scatter originating from graded systems such as Co/Cr. Grazing incidence scattering techniques are also employed to investigate the out of plane correlations of lateral roughness in Cu/Co multilayers, as well as in miscible trilayer structures. The use of soft x-rays in the investigation of 3d transition metal multilayers is also presented. Such experiments are sensitive to the component of magnetisation aligned with the direction of the incident beam. In a series of magnetisation experiments, the dependence of the x-ray scatter sensitive to this component of magnetisation are analysed. For the first time evidenced is found for correlated magnetic roughness, which has lateral correlation lengths far greater than the structural roughness length scales. This magnetic roughness is measured in detail, and the correlation length is found to vary with applied field direction. Grazing incidence x-ray fluorescence is applied to two spin valve structures. These experiments provide a direct measure of buried layer thicknesses which is not possible by other x-ray scattering techniques. This novel method for the determination of the copper layer thickness in spin valves shows the versatility of non-destructive x-ray methods for the characterisation of magnetic metallic multilayers.

Luminescent complexes of lanthanide ions are of growing interest because the long lifetime of emission allows time-resolved detection procedures to be employed. A key step in the development of such systems lies in the preparation of highly luminescent complexes which display high stability in aqueous solution. A series of ligands based on 1,4,7,10-tetraazacyclododecane have been prepared, in which the nitrogen atoms are appended with coordinating phosphinate or amide groups, or a combination of both. The compounds obtained are octadentate ligands which form water-soluble lanthanide complexes of high stability. Complexes incorporating aryl groups in the pendent arms have been prepared and some display intense metal luminescence following excitation into the organic chromophores. A back energy transfer process occurs in the terbium complexes containing naphthyl or quinohnone groups. Measurements of the luminescence lifetimes in H(_2)O and H(_2)O show diat diere are no metal-bound water molecules in the tetrabenzylphosphinate complexes. Those incorporating one amide and three phosphinate groups display hydration states between 0 and 1. An attempt has been made to correlate this information with that obtained from an analysis of the nuclear magnetic resonance dispersion profiles of related gadolinium complexes. The complexes incorporating secondary amide groups display an additional deactivation pathway for the metal excited state involving energy transfer into N-H bonds. The luminescence behaviour of four macrocyclic tetraamide ligands incorporating naphthyl fluorophores has been studied. These compounds exhibit distinctive changes in luminescence in the presence of quenching (eg. Pb(^2+), Cu(^2+) and Ni(^2+)) and non- quenching ions (eg. Cd(^2+) and Zn(^2+)). This behaviour extends to non-aqueous solution. The protonated tetranaphthyl ligand forms an intramolecular excimer in which the excimer emission displays a sensitive dependence on the polarity of die solvent.