This thesis describes the synthesis of macrocyclic trinuclear ruthenium(II) “bowls” that incorporated 9-methyladenine, 9-benzyl-9H-purin-6-amine, 9-ethyladenine and 9-(4-methoxybenzyl)-9H-purin-6-amine as ligands with good yields and high purities. Their binding to a variety of anion guests was investigated through nuclear magnetic resonance as well as electrochemical studies. These macrocycles possess extremely interesting binding affinity:1H-NMR investigations revealed selectivity in the macrocycles-host binding, particularly with medium sized halide anions, namely chloride and bromide, being most strongly bound. Generally, electrochemistry-based titrations showed good agreement with the NMR host-guest titrations results, with potential shifts being dependent on binding affinities -although there are some specific differences in the results with fluoride and iodide. In the case of nuclear magnetic resonance we found that the fluoride ion is too small in size to be suitable for the macrocycle cavity to bind strongly, whilst in the case of electrochemistry titrations larges shifts are seen after addition of fluoride due to the high charge density of this ion. It was found that more complex oxo-anions also bound to the host and affected the RuII based oxidations. However, in general, the binding affinities for these more complex anions were lower than the highest values for halide guests. Again electrochemical potential shifts generally correlated with binding affinity. Studies also revealed that the electrochemical response to addition of anion guest was complex, as the guest induced shifts of the three RuII oxidations of the bowls were not always the same.

A fluorimeter was constructed which utilises solid state components. The novel arrangement of these components meant that an inexpensive, sensitive, robust and portable fluorimeter was feasible. If the optical components ofthe instrument were selected for a specific assay, a dedicated fluorimeter with comparable sensitivity to a research grade fluorimeter resulted. The construction and evaluation of such a fluorimeter is described. Nile Red is a hydrophobic phenoxazine fluorescent dye, which has an emission in the long wavelength region of the spectrum (600 - 1000 nm). Assays based on fluorescence measurements in this spectral region have the advantage oflower background, reduced scattering and decreased photodecompostion when compared with conventional fluorescence utilising UVNis wavelengths. Nile Red is also a solvatochromic dye, which means it emission wavelength is strongly dependant on its molecular environment. The property is utilised here in the development of a novel assay for the protein ~-lactoglobulin. As the fluorescence properties of the Nile Red:Protein complex differ form those ofthe unbound Nile Red molecule, the fluorescence intensity can be related to concentration of the protein present. The feasibility and development of such an assay is presented as one possible application for the fluorimeter described.

Unsaturated lipids exist in carton-board and can be the precursors of odorous compounds. Two unsaturated lipids that can be present are oleic acid (cis 9-octadecenoic acid) and linoleic acid (cis, cis 9,12-octadecadienoic acid). These lipids can be present in the free acid form, as alkyl ester derivatives and in the triglyceride form. These lipids are able to undergo oxidation. Such oxidation leads to the formation of a number of odorous compounds. Oxidation proceeds via hydroperoxide intermediates to produce aldehydes, ketones, alcohols, furans, lower fatty acids, alkenes and alkanes, the majority of which are odorous. The aldehydes, in particular, have very low odour and taste detection thresholds, needing to be present only in very small amounts in a packaging material to cause a taint problem. Typically, taints associated with these compounds are described as 'rancid', 'pungent', 'soapy' and 'green'. Static headspace GC/MS analyses have identified a number of odorous compounds formed from oxidation reactions, within standard samples of wood pulp obtained from carton-board manufacturers. These oxidation reactions are affected to various extents, by a number of factors such as the temperature, the nature of the fatty acids, the presence of oxidation catalysts such as transition metal ions, the availability of oxygen, the humidity and the presence of photosensitising agents. Breakdown pathways and reaction schemes are presented in context as are kinetic details of odorous product formation. UV curable inks are commonly used in the printing of carton-board packaging materials. These inks contain photoinitiators which have the potential to affect the oxidation rate and extent of formation of unsaturated lipids, resulting in the formation of odorous compounds within the carton-board matrix. Static headspace analysis, dynamic headspace analysis and vacuum extraction procedures have identified a number of volatile components, that are odorous, in the inks and varnishes. These compounds, which include by-products arising from photoinitiators, amine photoactivators and residual solvents, have the potential to cause 'ink', 'varnishy', 'plasticy' taints in a packaged food system if these components are able to migrate from the carton.

This thesis is composed of two parts: Part I is focused on studying how quantum dot (QD) surface small-molecule capping ligands affect its Förster resonance energy transfer (FRET) with a fluorescent protein (FP); Part II is focused on developing an ultrasensitve DNA sensing technology by combining magnetic nanoparticle (MNP) and enzymatic signal amplification. Part I The FRET between a CdSe/ZnS core/shell QD capped with three different small-molecule ligands and a hexa-histidine (His6)-tagged FP (mCherry) has been studied. Results show that small-molecule ligands strongly affect the FRET behaviours between QD and FP. The QD-FP self-assembly process is fast (complete in minutes at low nM concentration), strong (with Kd ~ 1 nM), suggesting that the QD-His6-tagged biomolecule self-assembly is an effective approach for making compact QD-bioconjugates which may have a wide range of sensing and biomedical applications. PART II I have developed a facile, rapid, and sensitive DNA sensor by combining the efficient MNP-based target capture with the highly efficient signal amplification power of enzymes to achieve ultra-sensitivity. This sensor works efficiently in both pure buffer and complex media (such as 10% human serum in buffer). Moreover, this developed approach is able to quantitate two distinct DNA strands in a homogenous phase at the same time with a detection limit of ~5 pM. Second, I have developed a novel, highly sensitive and selective approach for label-free DNA detection and single-nucleotide polymorphism (SNP) discrimination by combining target-recycled ligation (TRL), MNP assisted target capture/ separation, and efficient enzymatic amplification. This approach possesses a detection limit of 600 fM unlabelled DNA targets and offers exquisitely high discrimination ratio (up to > 380 fold) between a perfect-match mutant and its single-base mismatch DNA target. Furthermore, it can quantitate the rare cancer mutant in large excesses of coexisting wildtype DNA down to 0.75%.

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Generic methods were developed using different columns for analysis and purification of hydrophilic compounds by hydrophilic interaction chromatography (HILIC). Mobile phases were investigated in detail, and across each column chemistry tested (BEH Amide, Atlantis bare silica, ZIC-HILIC and Cogent Hydride), salt-buffered mobile phase offered good to excellent peak shape for acids, bases and neutral solutes with a range of hydrophilicities. Additionally, cation exchange occurred on the bare silica column even when rubidium nitrate was added to the mobile phase, which should block all cation exchange sites. Measurement of mobile phase pH in hydroorganic solvent (ACN-water mixture with buffer) better represented the environment solutes experience on column than fully-aqueous pH measurement. The performance of HILIC with Charged Aerosol Detection (CAD) was evaluated with a hydrophilic acid, a hydrophobic base and a hydrophilic neutral solute; limits of detection and quantitation were 1-3 ng and 5-9 ng on column, respectively. This compared favourably to literature values for other universal detectors. HILIC-CAD was further investigated by flow injection analysis (FIA) using 29 solutes containing acids, bases and neutrals. HILIC and CAD had excellent compatibility: peak areas were double compared to reversed-phase conditions, response was reasonably uniform for 21 non-volatile solutes considering the solutes’ diversity. HILIC-CAD was viable for retention and detection of highly hydrophilic species without chromophores: salts, sugars and amino acids. Salts travelled down the column as independent cations and anions. Resolution of sugars and amino acids was challenging and was incomplete due to project time constraints. Generic methods were developed on an analytical system in the labs of the industrial collaborator and applied to purifications on wide-bore columns at scaled-up flow rates (21mm id, 20mL/min prep vs. 4.6mm id 1 mL / min analytical analytical). A standard prep system was capable of usable productivity using HILIC with 1mL injections (22 mg of crude purified per hour) and use of At-Column Dilution enhanced this around 10-fold with scope for 4mL injections (223 mg of crude purified per hour).

Electrochemical promotion of catalysis (EPOC) is a result of backspillover phenomena which involves the migration of backspillover (oxygen ionic) species through the tpb onto the catalyst surface under the influence of electrical potential application. The present work studies the occurrence and the role of the backspillover species and also the mechanisms of the related processes including factors controlling this phenomenon in a Pt/YSZ system which utilises a model catalyst or sputtered patterned electrodes. In comparison to the electrodes prepared by painting the commercially available Pt catalysts on YSZ, the geometric characteristics and the type and amount of impurities on the Pt surface should not vary significantly among the samples except the tpb length (of the 3rd batch samples). Therefore, the electrochemical processes at the tpb can be studied systematically and the electrochemical data should be reproducible which are not the case when electrodes prepared by using the commercially available catalysts are involved. The variability in the electrochemical behaviour (charge transfer reaction) of the Pt/YSZ system, as depicted by CV results under a nonreactive condition at 400 oC, of the Pt electrodes prepared by using the commercially available catalysts is demonstrated in the first part of the study. The three commercially available catalysts provided by ESL, Heraeus and Metalor are shown to contain different type and amount of impurities and to have different Pt surface morphology. The impurities were analysed by ICP-OES while the surface morphology was investigated by SEM. In the second part of the study, the focus was on the Pt/YSZ system utilising the patterned electrodes where the correlations between the oxygen charge transfer (oxygen activity) and the tpb length were investigated by CV, EIS and current overpotential experiments under a nonreactive condition at temperatures between 300 oC and 450 oC .The term oxygen activity in this thesis refers to the kinetics of the oxygen charge transfer reaction. A proportional relationship between the oxygen charge transfer and the tpb length was not observed and this is explained by the changes in Pt surface morphology throughout the experimental works and most important the formation of surface oxides at the tpb which blocks the charge transfer processes. However, the changes in the oxygen activity at the tpb can be observed from the correlation between the current density and the peak current from the CV results. Another interesting observation is the appearance of additional peak in CV after exposure to hydrogen which can be associated with either the decomposition of impurity oxides or ii Pt oxides of different oxidation state at the binary interface. In the third part of the study, the catalytic and electrochemical behaviour of the system utilising the patterned electrodes was investigated during CO oxidation at temperatures between 300 oC and 450 oC. The Pt/YSZ system was found to exhibit (i) EPOC at 0.10 V, 0.20 V and 1.0 V, (ii) permanent EPOC and (iii) permanent poisoning effect. The backspillover species was found not only to enhance the catalytic rate but also to stop the open circuit rate oscillations and, at a high pO2, to restore the rate due to the permanent poisoning effect. Furthermore, five types of oxygen species are suggested to present at the tpb and on the Pt surface during the experimental works where the coverage of these species controls the amount of oxygen ionic species which can migrate through the tpb onto the Pt surface.

The ability to utilise new knowledge of biomarkers from genomic and proteomic data will have a great impact on molecular diagnosis. Biomarker detection could be achieved by utilising a capture molecule that associates specifically with the target biomarker. The work described in this thesis focuses on a platform comprising a lysozyme binding aptamer and an amperometric electrode (an electrochemical aptasensor). To couple the binding reaction to a change in current, the aptamer is modified with a redox group, ferrocene. Two types of signalling aptamer were constructed, one comprised the aptamer self-assembled on gold and hybridised to a short complementary oligonucleotide carrying a ferrocene group. The second incorporated the binding sequence into a molecular beacon, one end of which self-assembled onto the electrode, the other end carried the ferrocene group. Both of these showed a lysozyme dependent change in current on a gold electrode. Further characterisation of the first aptasensor suggested that the nucleic acid formed a multilayer structure on the electrode surface and that lysozyme binding induced conformational change moved ferrocene close to the surface, increasing the current. In contrast, the second aptamer usually showed a decrease in current in the presence of lysozyme suggesting that the binding resulted in the ferrocene moving away from the surface. In order to evaluate the possible use of these aptasensors for continuous in vivo measurement, needle shaped microelectrodes arrays were produced and the beacon aptamer immobilised on the surface. These electrodes had high impedance which resulted in low sensitivity, however lysozyme binding could still be detected using electrochemical impedance spectroscopy with ferrocyanide in solution. These microspike arrays could also be used for glucose sensing following modification with glucose oxidase.