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    SEIRAS of functionalised graphene nanomaterials : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nanoscience at Massey University, Manawatū, New Zealand
    (Massey University, 2017) Fisher, Ewan
    Graphene exhibits many excellent properties, but many next-generation devices require post chemical treatment to introduce structural confirmations, defects or a particular impurity to obtain functionality. The understanding of these defects and the manifestation of desirable properties using chemical modification is a fundamental problem with low defect graphene as the small number of functional groups provides insufficient signal intensity for many characterisation techniques. Metallic nanoparticles are at the centre of plasmonics for enhancing optical signals. This work is a unique undertaking for the examination of novel Steglich esterification chemistry that is performable on graphene as well as providing insight into the native edge structure of as-produced graphene flakes using surface enhanced infrared reflection absorption spectroscopy (SEIRAS) to characterise covalently functionalised graphene materials. Two methods of producing graphene flakes that are relatively low or high in defects have been developed to contrast the effect that inherent defects have on the macroscopic physical and spectroscopic properties. Ultraviolet-visible spectroscopy in conjunction with Raman, electron and atomic force microscopy was used to elucidate the origins and density of defects to draw conclusions on how graphene’s macroscopic properties manifest from atomic level defects. Discussions of infrared vibrational spectroscopy are carried out before an extension to SEIRAS where the use of near-field plasmon and phonon modes are attributed to observed optical enhancements. The experimental preparation is focused towards understanding the role nanoparticles play in SEIRAS of graphene and is discussed such that other graphene researchers can recreate SEIRAS for their graphene research. TEM is used to characterise the variety of nanoparticle shapes and geometries as well as provide topological insights on nanoparticles adsorbed to flakes of graphene. SEIRAS probes the defects native to graphene which confirms the presence of oxygen functionality. Steglich esterification reactions were utilised to successfully prepare a range of graphene materials with novel covalently bound functional groups as confirmed by SEIRAS. Covalent chemistry was extended to introduce a redox-active ferrocene derivative where SEIRAS was used to observe in real-time, the effect of interconversion of ferrocene to the ferrocenium cation. The foundations for the development of graphene-based solid state solar cells was the final focus of this work. Development and production of a potential photo-active layer was explored with Cl-BODIPY as the basis chromophore. Production of a flexible, electrically conductive substrate from graphene flakes was carried out, and tunnelling electron microscopy (TEM) was used to characterise topological and morphological surface features. The focus here was on covalent and physical absorption to graphene flakes. SEIRAS was used to confirm nucleophilic substitution (covalent) modification while STEM was used to confirm the uniformity of BODIPY on the substrate and chlorine atomic mapping to confirm physisorption.
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    The synthesis and spectroscopy of dipyrrins and their metal complexes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry, Massey University
    (Massey University, 2012) McLean, Tracey Maree
    Dipyrrin ligands can be considered as ‘half-porphyrins’. They absorb light in the visible region due to a strongly allowed π-π* transition. With the energy crisis being one of the most important issues of our time, the strong absorption in the visible region endows dipyrrinato complexes with promise in solar energy conversion applications. The focus of this project was to undertake some fundamental synthesis and spectroscopy of dipyrrin ligands and dipyrrinato complexes for their applications in photochemical devices. The well-known characteristics of Ru(II)-bipyridine chemistry were combined with the light absorbing properties and synthetic versatility of dipyrrin ligands to prepare and test a range of Ru(II)-dipyrrinato-bipyridine complexes as dyes for applications in dye-sensitised solar cells. The preliminary results of the solar cell measurements show evidence that the Ru(II)-dipyrrinato-bipyridine complexes show promise as light harvesters in solar energy conversion applications. A series of Re(I)-dipyrrinato complexes has also been designed and prepared for potential applications as catalysts in carbon dioxide reduction. Metallodipyrrin complexes also exhibit strong exciton coupling. A library of transition metal dipyrrinato complexes has been prepared to investigate the exciton interactions in dipyrrin systems. Understanding the exciton interactions in dipyrrin systems and the ability to control the exciton interactions are desirable for improving the solar energy conversion efficiency of dye-sensitised solar cells containing Ru(II)-dipyrrinato-bipyridine complexes as the dye. Raman spectroscopy and more specifically resonance Raman, as a technique for probing the excited state of dipyrrinato complexes, has largely been overlooked in the literature. Therefore the spectroscopy aspect of this thesis has a central focus on the Raman spectroscopy of dipyrrins, including the first full characterisation of dipyrrin ligands by Raman spectroscopy at a variety of wavelengths (visible and near infrared). Strong resonance enhancement was observed for the dipyrrin ligands, which lays the foundation for fundamental single-molecule SERS studies but also for a broad range of bioanalytical applications.
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    Porphyrins for surface modification : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Palmerston North, New Zealand
    (Massey University, 2001) Campbell, Wayne Mason
    The controlled synthesis of a variety of benzoic acid porphyrins ranging from monomers to arrays for the modification of TiO2 and GaAs semiconductors, and sulfur functionalised porphyrin monomers for attachment to GaAs and Au surfaces was achieved. A semi-quantitative study of the photosensitisation of TiO2 by the porphyrin acids was carried out. The syntheses of β-styryl linked porphyrin benzoic acids and some meso-substituted benzoic acid porphyrins was successfully carried out employing Wittig chemistry and classical porphyrin-forming condensation reactions with appropriate formyl methyl esters. Hydrolysis of the resulting porphyrin esters provided a facile and reliable acid synthesis, particularly where multi-step reactions were necessary. It was also demonstrated that acid functionality on porphyrins could be generated from aldehydes via esters, even though direct oxidation of the aldehydes to acids could not be achieved. The syntheses of "dipole" and "collinear" diporphyrins were achieved, providing two different porphyrin light harvesting arrays for evaluation on semiconductor surfaces. As a result of the synthesis of a new linear diporphyrin Building Block C, an alternative pathway to the controlled syntheses of mixed-metal and mixed-porphyrin arrays was achieved. This provided an alternative strategy for the controlled placement of three different metals into three different porphyrins of a linear triporphyrin, pentaporphyrin and a larger star-shaped nonaporphyrin. The exploitation of the stepwise controlled synthesis of the triporphyrin systems was expanded to include mixed-porphyrin systems synthesised with a unique tetraester porphyrin phosphonium salt. This phosphonium salt afforded mixed-diporphyrin and mixed-triporphyrin arrays, which were hydrolysed to give "sticky" mixed-diporphyrin and triporphyrin acid arrays. An alternative milder and higher yielding stepwise Wittig method was developed for the synthesis of a star shaped TXP pentaporphyrin. This new method involving milder base conditions gives advantages over the traditional acid catalysed approach developed in these laboratories. It is now possible to build these arrays in a stepwise manner with acid labile metals present in the porphyrin moieties. Access to the controlled synthesis of "sticky" mixed-pentaporphyrin arrays was then achieved using this new methodology. With the synthesis of a variety of unique benzoic acid functionalised porphyrin monomers and multiporphyrin array systems, evaluation of their performance in the dye-sensitised TiO2 Grätzel cell was carried out. The development of a reliable solar cell testing apparatus and procedures required to assess the solar cell performance of these chromophores is presented. None of the conditions employed have been optimised, but insights into the significance of the porphyrin photoelectrochemical cell variables has been obtained. It was determined that the porphyrin acids are better photosensitisers than their salts, and that Zn(II) metalloporphyrins performed best as dyes. The results also suggest that Cu(II) metalloporphyrins are worth pursuing in future where long term stability of the chromophores is required in solar cells. It was also found that adsorption solvent choice, electrolyte composition and dye concentrations are all critical to cell performance, and should all be optimised in future studies. The tetraaryl β-substituted monoporphyrin acids were found to have a significant advantage over the multiporphyrin arrays and other monoporphyrins synthesised and examined in this work. A variety of new disulfide porphyrins and some new 2- and 3-thienylporphyrins were successfully synthesised. A new class of terthiophene-appended porphyrins was also synthesised. Using a combination of Wittig chemistry and classical condensation reactions, β-substituted, and bis- and tetra-meso-porphyrin variants were synthesised and characterised. Both the bis- and tetraterthienylpoprhyrins were isolated as mixtures of atropisomers.