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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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    Development of a new cathode for aqueous rechargeable batteries : 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, 2015) Mortensen, Kelsey Leigh
    The demand for low/cost energy storage is a current issue. Existing batteries are unable to meet this constraint due to the high raw material prices, in particular the metal content. The risk of fluctuating metal prices and future availability will not meet the market demand and therefore alternative materials need to be considered. The focus of this project was to develop a non/metal based battery electrode specifically for stationary battery systems. This study presents fundamental concepts required to form a rechargeable electrochemical storage device utilising hydrogen peroxide as the electroactive species. This involved two key aspects: immobilisation of hydrogen peroxide in order to prevent self/discharge and catalytic regeneration of hydrogen peroxide from hydroxide ions. Although the construction of the device was not within the scope of this project, the chemical and electrochemical analysis of potential compounds were evaluated at a molecular level. In particular, the synthesis and molecular behaviour of a urea/ based ’binder‘ that will immobilise hydrogen peroxide, and an oxoammonium ’catalyst‘ to reform hydrogen peroxide during recharge of the battery. Additionally, the attachment of these compounds to a surface was also evaluated. Analysis of the interactions between substituted ureas (‘binder’) and hydrogen peroxide proved challenging. Although these findings suggest that adduct formation is occurring, the methods undertaken were not able to determine the equilibrium constant or strength of binding. They did however give an indication of the quantity of hydrogen peroxide in the synthesised adducts and this methodology can be applied to the range of hydrogen peroxide adducts. Additionally, functionalisation of surfaces with a diazonium/containing substituted urea was achieved and is a viable method for attaching the ‘binder’ to the electrode substrate material. The second key step is to incorporate a rechargeable aspect to the battery system. An oxoammonium cation was proposed to act as a ‘catalyst’ to replenish H2O2 during charging. Details regarding the synthetic methodology for synthesis of nitroxide/containing compounds, incorporating diazonium functionalities for attachment to a surface, were obtained. Of particular interest was the amido/ TEMPO structure that was electrochemically attached to a carbon surface electrode. Evaluation of its ability to form H2O2 was achieved using a bi/potentiostat where a current density of 0.21 A m/2 was observed. This novel idea shows promise and demonstrates the ability for the catalyst to replenish H2O2 in an aqueous battery system.