Braxton, Emily (2021) Investigation and optimisation of electrochemical electron paramagnetic resonance spectroscopy experiments. PhD thesis, University of Warwick.

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Abstract

Investigation and optimisation of electrochemical electron paramagnetic resonance spectroscopy experiments

Electrochemically generated hydroxyl radicals (HO˙) is thought to be the most prevalent and powerful species exploited in the areas of electrosynthesis and electrochemical advanced oxidative processes. The electrochemical generation of HO˙ requires an electrode material which only exhibits a very weak interaction with HO˙ such as boron doped diamond. HO˙ is directly generated through the electrochemical oxidation of water which is a high dielectric solvent; the use of high dielectric solvents in electron paramagnetic resonance spectroscopy can be problematic. Since free radicals are highly reactive and therefore have a short lifetime, the role of a spin trap is necessary for their detection. However, there are many intricacies when using a spin trap like 5,5-dimethyl-1-pyrroline N-oxide (DMPO) such as the artefactual generation of spin adducts due to inverted spin trapping and the Forrester-Hepburn mechanism. In this thesis, the optimal conditions of EPR spectrometer for the detection of spin trapped free radicals in aqueous media are investigated. Additionally, the generation of false positive spin adduct species from inverted spin trapping was thoroughly studied, as well as the consequences of electrochemical oxidation of DMPO. Finally, the optimised conditions and information learned about inverted spin trapping in electrochemical systems was applied to a real-life system. In this case, probing the mechanism behind non-contact electrochemical etching of sp2 carbon to create diamond membranes.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Electron paramagnetic resonance spectroscopy, Hydroxyl group, Electrochemistry, Carbon -- Etching, Free radicals (Chemistry)
Official Date:	November 2021
Dates:	Date Event November 2021 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Molecular Analytical Science Centre for Doctoral Training
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Macpherson, Julie V.
Sponsors:	University of Warwick. Molecular Analytical Science Centre for Doctoral Training ; Engineering and Physical Sciences Research Council ; Pfizer Ltd. ; AstraZeneca (Firm)
Format of File:	pdf
Extent:	xxiv, 25-189 leaves : illustrations
Language:	eng

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