Cyclic Voltammetry, Surface Enhanced Raman Spectroscopy and SHell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) have been used to investigate two types of heterogeneously catalysed hydrogenation reactions – hydrogenation of selected alkynes and the Orito reaction. Using a spectro-electrochemical flowcell, which is designed and built in-house, the selectivity and reactivity of the reactions on platinum surfaces have been truly discovered. By studying hydrogenation of a range of alkyne molecules, including 2-butyne-1,4-diol, 2-pentyne, 4-octyne, propargyl alcohol and 2-methyl-3-butyn-2-ol, on different platinum surfaces, it was found that alkyne adsorption on Pt defect sites produces a long-lived di-sigma/pi- alkene complex which may undergo further hydrogenation to produce alkane. This complex may form on different surfaces with various orientations. However, depending on the specific molecules, the intermediate may not survive on some surfaces due to the steady state conditions arising from the catalytic reaction whereby adsorption of alkyne and hydrogenative desorption of reaction intermediates determines the overall surface coverage of intermediate as a function of potential. Alkene selectivity can be increased by blocking defect sites, using polyvinylpyrrolidone or bismuth, leaving only platinum{111} terraces available for catalysis. By studying ethyl pyruvate (EP) adsorption on different surfaces of platinum and palladium, it was found that EP half-hydrogenated state (HHS) is a critical intermediate of the hydrogenated product which only forms on the step sites of the platinum surface at the hydrogen evolution reaction potential. However, another new intermediate adsorbate, which is believed to be a η1 species and is believed to be a precursor of the HHS only forms on the terraces of the surface. By studying the surface intermediates formed during hydrogenation of EP at palladium modified platinum single crystal electrodes, it was found that there was no unequivocal evidence for bands pertaining to EP adsorption on palladium could be identified under hydrogenating conditions due to the reconstruction of the palladium adlayer to reveal Pt subsurface sites.

The determination of pesticides and related materials in food and environmental samples is important and presents an enduring challenge to analytical chemists. For practicality it is important that as many pesticides as possible are compared using a common technique. Mass spectrometry is the method of choice for multi-residue detection techniques, because of its sensitivity and specificity. This thesis comprises a detailed analysis and critical review of the mass spectrometric behaviour of over 600 commonly encountered pesticides and related compounds. The work described in this thesis was undertaken in two tranches, one old and one new. The former experimental work was performed during the author’s employment at the Ministry of Agriculture, Fisheries & Food (Harpenden, Hertfordshire, UK) and at Unilever Research (Colworth House, Sharnbrook, Bedfordshire, UK). The data helped underpin the analytical work of the UK national pesticide residues monitoring surveillance team and the pesticide formulations safety team. Qualitative and quantitative aspects were both important, e.g. for identification and characterisation of active ingredients, contaminants and degradation products in technical pesticide formulations, as well as unambiguous detection and/or confirmation of residue levels in UK fruit and vegetables. The latter experimental work was undertaken recently (2015) at the Cardiff School of Chemistry during the preparation of this thesis. The newly acquired data helped confirm the validity and robustness of the original data, and helped to better understand them. Understanding the complex and sometimes unexpected behaviour of molecules during their extraction/analysis is essential, especially when performing trace analysis at the parts per billion level. Rationalisation of the mass spectrometric fragmentation pathways of these compounds was undertaken in order to better understand the fundamental processes taking place in the mass spectrometer. This improved understanding was essential in order to ensure the quality and validity of the data generated using these techniques. For comparison, some additional data are included, e.g. for chemical warfare agents, using literature data. Mass spectrometry was chosen because of its power as an analytical technique. General approaches and specific precautions which should be taken when using mass spectrometry for pesticide analysis are discussed and explained in this document and literature data were critically reviewed. It is hoped that these data and recommendations will find continued and future use as an adjunct to the plethora of literature data and MS instrument manufacturer databases.

In this thesis, the structure and reactivity of Pd, Au and Au-Pd structures on TiO2(110) single crystals has been investigated with surface science techniques, including X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), Auger electron spectroscopy (AES) and temperature programmed desorption (TPD). Sputtering a clean titania single crystal resulted in reduction of the surface. The surface was partially re-oxidised by annealing in UHV and further oxidised by annealing in O2. Pd growth on TiO2(110) was found to be Volmer Weber (3D island growth) regardless of the preparation and condition of the titania – whether it was heavily sputtered, sputtered then annealed or annealed in oxygen. On annealing the Pd/TiO2(110) to temperatures above 723K, an SMSI effect was observed between the Pd nanoparticles and the TiO2 support – the Pd is encapsulated by the reduced titania support. This was found to be affected by the oxidation state of the titania – SMSI occurred at a higher temperature for an oxidised surface than for a reduced surface. Au did not show an SMSI effect and is not encapsulated by the titania support, even when annealing to temperatures of 873K. The Au film only sinters and forms nanoparticles. Pd and Au were deposited sequentially on to TiO2(110). They are proposed to form bimetallic Au-Pd core-shell structures on annealing. After continued annealing to higher temperatures an SMSI effect is once again seen. This appears to be diminished with a greater amount of Au present in the bimetallic structure. The reactivity of TiO2(110) towards several small organic molecules was studied with TPD when clean and when deposited with Pd and Au, both separately and combined. Titania showed similar reactivity to that found in the literature – ethanol decomposed primarily to ethene and acetaldehyde, formic acid gave both CO and H2O, and CO2 and H2, and acetic acid gave ketene, CO and CO2. Au was found to be unreactive. Pd was found to reduce the reactivity of the titania. Pd-Au were, in most cases, found to be more reactive than their component metals.

A novel crosslinking agent, 2,4-diallyloxy-6-diethylaminotriazine, was used for the cure of unsaturated polyester resins based on maleic anhydride. The aim of this investigation was to analyse the chemical structure of these cured resins. The analysis of thermosets is difficult because once cured the resin is both insoluble and infusible. An analytical strategy was devised to overcome these difficulties by using several different approaches. Spectroscopy formed an important part of this investigation. Both NMR and FT-IR were used to characterise the precursor materials and FT-IR spectroscopy for the final products. This technique was also used to monitor the curing reaction in conjunction with DSC studies. These studies showed that other chemical changes were taking place as well as the expected loss of the carbon double bonds. The extent of cure of these resins is usually determined by a solvent extraction method and this was followed by C,H,N analysis of both the soluble and insoluble (gel) fraction. An HPLC method was developed to measure the amount of unreacted monomer in the extract. Further information on the cured structure could only be obtained by destructive methods and both chemical and thermal degradation methods were examined. The attempt to release the crosslinking chain from the cured polyester by alkaline hydrolysis was unsuccessful because the cyanurate links were found to be more susceptible to hydrolysis than the phthalate and maleate links. Pyrolysis of the resins gave an extremely complex mixture of products. Many of the products identified for the resins were also identified when a homopolymer of 2,4- diallyloxy-o-diethylaminotriazine was pyrolysed. These included aromatic and other ring structures. This evidence in conjunction with the spectroscopic studies suggested that the monomer did not produce linear crosslinking chains but that several monomer units were linked together to form a three-dimensional structure which acted as a crosslinking junction for the linear polyester chains and that this structure was likely to involve some fused rings. A further aim of this research was to review the methods currently available for the analysis of thermosets and make recommendations based on this study and the literature search to other analysts dealing with this class of materials. There have been major developments in spectroscopic techniques which mean that far more data can now be obtained on these systems than previously. FT-IR spectroscopy is probably the most applicable method. There are also major developments in the use of pyrolysis with GC and/or MS, but interpretation of these results with respect to the original structure requires care. Development of chemical modification methods are continuing, particularly on the small scale for identification of components by GC. In the case of structural analysis, once an appropriate method for cleaving the structure has been obtained, then spectroscopic analysis of the products can provide a great deal of information, particularly NMR spectroscopy.

No description available.

This project focused on the comparison of conventional liquid chromatography and superheated water chromatography. It examined the differences in efficiency and retention of a range of different stationary phases. Alkyl aryl ketones and eight aromatic compounds were separated on PBD-zirconia, Xterra™ RP 18, Luna™ C18(2) and Oasis HLB™ columns using conventional LC and superheated water chromatography system. The retention indices were determined in the different eluents. On changing the organic component of the eluent from methanol to acetonitrile to superheated water considerable improvements were found in the peak shapes and column efficiencies on the PBD-zirconia and Oasis HLB™ columns.

Luminescent nanoprobes have been widely researched for applications in areas such as biological imaging, sensing and photonics. Developing a nanoprobe that adopts the properties of a molecular probe has great difficulty due to quenching of the luminescence of the probe upon attachment to the nanoparticle. Luminescent polypyridyl ruthenium complexes were efficiently labelled on gold nanoparticles to produce a nanoprobe with enhanced photophysical properties compared to the molecular probe. Gold nanoparticles with diameter 13, 50 and 100 nm were employed to investigate the effect of the size of the nanoparticle and it was found that this has no effect on the photophysical properties of the nanoprobe. The distance between the photoactive ruthenium centre and nanoparticle surface was varied through an organic chain to investigate the effect of distance and it was found that increasing the distance increases the photophysical enhancement. Ruthenium molecular probes with optimised photophysical properties were designed and synthesised for development of further enhanced nanoprobes. Upon attaching a bis-phenanthroline ruthenium probe (RuphenS12) to gold nanoparticles, a luminescent lifetime of 1.7 μs was demonstrated. This is competitive with tris-phenanthroline ruthenium complexes seen in the literature. The molecular probes and nanoprobes were investigated in applications for Dye Sensitized Solar Cells.

Analytical methods based on LC-ESI-MS/MS or LC-APPI-MS/MS were developed and/or validated for the separation and determination of BDE-209 and TBBP-A, in addition to HBCD diastereomers, enantiomers and degradation products in a wide range of samples including air, dust, diet, simulated GIT fluid, human serum and breast milk. The obtained concentrations were used to estimate the exposure of adults, toddlers and nursing infants to the target BFRs via inhalation, dust ingestion and diet using different exposure scenarios and the relative importance of each exposure pathway was assessed for the studied age groups. Causes of variability in concentrations of HBCDs in indoor dust were elucidated and forensic microscopy techniques were used to study the mechanisms of transfer of BDE-209 and HBCDs to indoor dust. A colon-enhanced physiologically based extraction model was developed and applied for the first time to study the bioaccessibility of target BFRs from human GIT. Exposure via dust ingestion, but not diet, correlated significantly (p<0.01) with ΣHBCDs in serum of 16 adults. The levels of target BFRs were reported for the first time in 28 human milk samples from the UK. The relationship between adult intake of BFRs and the observed body burdens was studied using a pharmacokinetic model. Although no enantioselective enrichment was detected in either dust or diet, enrichment of (-)-α-HBCD was observed in both human serum and milk which may be attributable to enantioselective absorption, metabolism and/or excretion.

Mass spectrometry imaging (MSI) enables two- and three-dimensional overviews of hundreds of unlabelled molecular species including drugs, metabolites, lipids and proteins in complex samples such as intact tissue. In this research, a new extensible software platform is presented, suitable for spectral preprocessing, multivariate analysis and visualisation of large MSI datasets from all major MSI vendors. Principal component analysis (PCA) has been widely used in the unsupervised processing of MSI data. Standard implementations of PCA require the entire dataset to be stored in memory, necessitating a compromise between the number of pixels and the number of peaks to include. In this research a new method which has no limitation on the number of pixels is developed. Hierarchical composition of data has been shown as an efficient method of capturing the information present within images in other fields. An adaptation of these ideas to MSI data is described. The way in which imaging data are presented can have a significant impact on the perceived structure, especially when using false colour to display images. The research presented in this thesis has resulted in new recommendations for presentation of MS images. Finally, the software and algorithms presented were used to analyse MSI data from a traumatic brain injury model. Manual exploration and use of multivariate analysis methods such as PCA did not reveal any differences between the injured hemisphere of the brain and the control hemisphere, however the hierarchical composition algorithms identified multiple ion images which appear elevated in the injured hemisphere.

Within this thesis the use of linear dichroism (LD) spectroscopy was utilised as a new platform for the development of diagnostic sensors. To develop a novel diagnostic sensor in combination with LD spectroscopy a particle with a high aspect ratio is need. Such a particle is M13 bacteriophage, this micron long molecular scaffold is easily alignable in shear flow generating a large LD signal. Using LD spectroscopy, it was possible to demonstrate the successful detection of multiple DNA targets, and that the sensor can also discriminate between DNA sequences differing in length, with a limit of detection (LOD) of 2 M, competitive with the current non amplification methods of DNA detection. The reversibility and regeneration of the sensor were also investigated. Finally, the development of an M13 bacteriophage sensor for the detection of proteins was designed in an unprecedented plug-and-play format. The assay was designed to detect thrombin, which is important in the monitoring of blood clotting disorders. LD spectroscopy enabled the detection of thrombin with a LOD of 10 pM and with a dynamic range from 10 pM to 47 nM.