The work presented in this thesis involves the use of room temperature ionic liquids (RTILs) as solvents in electrochemical experiments for the detection of hydrogen sulfide. The fundamentals of electrochemistry are presented, followed by an overview of RTILs in terms of their properties, applications and their behaviour as electrochemical solvents compared to conventional solvents. This is followed by an outline of electrochemical detection of various gases in aqueous, organic and ionic solvents. The results of 8 original studies are then presented as follows: <ul><li>The study of the electrochemical window of twelve different room temperature ionic liquids using cyclic voltammetry vs. an internal redox couple for two defined current densities, and observation of water uptake of different ionic liquids under different conditions using a Karl Fischer titrator.</li><li>The reduction of hydrogen sulfide in various room temperature ionic liquids at a platinum electrode, measured using cyclic voltammetry. Also, solubilities and diffusion coefficients of hydrogen sulfide determined by potential step chronoamperometry.</li><li>The oxidation of hydrogen sulfide in various room temperature ionic liquids at a platinum electrode measured using cyclic voltammetry and the simulation of the electrochemical signal using experimentally defined parameters.</li><li>The disproportionation of N,N-dimethyl-p-phenylenediamine (DMPD) in room temperature ionic liquids using cyclic voltammetry, and computational simulation of the voltammetry of DMPD using experimentally defined parameters to elucidate kinetic and thermodynamic data. DMPD was examined as a mediating species for hydrogen sulfide detection.</li><li>The oxidation of catechol and dopamine in ionic liquids using cyclic voltammetry and observing adsorption effects when varying solvent anion. Catechol was examined as a mediating species for hydrogen sulfide detection.</li><li>The electrochemical oxidation of NADH in ionic liquids using cyclic voltammetry and observing the ”switching on or off” of the electrochemical signal when varying the solvent anion. NADH was examined as a mediating species for hydrogen sulfide detection.</li><li>The mediated detection of hydrogen sulfide utilizing various mediating species in several ionic liquids using cyclic voltammetry, and the elucidation of the mediating mechanism of hydrogen sulfide in 3,5-tert-butyl-o-benzoquinone.</li><li>The observation of the diffusion of ferrocene in an ionic liquid at ring-recessed disc microelectrode arrays in generator-collector mode using potential step chronoamperometry.</li><ul> The results presented show that room temperature ionic liquids perform well as solvents in gas sensors, and could be viable alternatives to traditional organic solvents. Ionic liquids have also been observed to be tuneable in their reactions with analytes depending on the constituent cations and, in particular, anions. This tuneability is advantageous as specific combinations of cations and anions can be chosen to suit particular experiments.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:526497 |
| Date | January 2010 |
| Creators | O'Mahony, Aoife Maria |
| Contributors | Compton, Richard Guy |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:6f3dcf36-b06c-4d98-ba8f-824f4b72c145 |
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