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Title: Electrochemical and spectroscopic studies of graphene nanoflakes with functionalised edges
Author: Lounasvuori, M. M.
ISNI:       0000 0004 8498 8377
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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The influence of surface functional groups on the electrochemical performance of carbon electrodes was studied by using graphene nanoflakes (GNF), a well-defined carbon nanomaterial. After characterisation with different techniques, GNF were used to modify a boron-doped diamond (BDD) electrode and the influence of different edge terminations on various redox probes was investigated using cyclic voltammetry (CV). The outer-sphere redox probe ferrocenemethanol (FcMeOH) was found to be unaffected by the presence of GNF at the electrode surface, confirming that GNF do not inhibit electron transfer. When proton-coupled electron transfer was investigated, it was shown that the acid-terminated GNF acted as a non-solution proton source and sink. The [Fe(CN6)]3−/4− redox couple was found to be quasi-reversible and independent of electrolyte pH at clean BDD and BDD modified with amide-terminated GNF. When GNF were decorated with COOH functionalities, the reaction became less reversible and pH-dependent. The reaction was also directly influenced by the electrolyte concentration, with low concentrations causing the reaction to become more irreversible. Potential-induced dissociation of the carboxylic acid edge groups on GNF was investigated with in situ spectroelectrochemistry combining potentiostatic control with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Applying a negative electrode potential led to the deprotonation of both electrode-immobilised groups and species in solution. Acid dissociation was driven by an increase in interfacial cation activity at the electrode surface that lowered the apparent pKa of all species at or near the electrode. Different methods of GNF attachment on the electrode surface were explored, including direct attachment to gold via thiol edge groups and EDC-mediated amidation reaction to form covalent bonds with a self-assembled monolayer (SAM) on gold. Scanning tunnelling microscopy (STM) was used to verify the presence and probe the orientation of GNF at the surface.
Supervisor: Holt, K. B. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available