Electroanalysis of solid particles

Lin, Q

Abstract:: This thesis reports theoretical and experimental work with the primary aim of developing new electrochemical methods to detect and characterise solid particles at the micron scale, specifically alumina (aluminium oxide) particles and graphene nanoplatelets, as representative of insulating and conductive particles, respectively.

The fundamentals of thermodynamics, kinetics and mass transport in electrochemistry are introduced in Chapter 1, with the elaboration of electrodes, voltamme...
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APA Style

Lin, Q. (2017). Electroanalysis of solid particles [PhD thesis]. University of Oxford.

MLA Style

Lin, Q. Electroanalysis of Solid Particles. University of Oxford, 2017.

Chicago Style

Lin, Q. 2017. “Electroanalysis of Solid Particles.” PhD thesis, University of Oxford.
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Files:: QLin_DPhil_Thesis_single.pdf

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Authors

+ Lin, Q More by this author

Division:: MPLS
Department:: Chemistry
Sub department:: Physical & Theoretical Chem
Department:: University of Oxford
Role:: Author

Contributors

+ Gonçalves, L

Department:: Faculdade de Ciências da Universidade do Porto
Role:: Contributor

+ Lima, C

Department:: Faculdade de Ciências da Universidade do Porto
Role:: Contributor

+ Lin, C

Department:: University of Oxford
Role:: Contributor

+ Li, Q

Department:: University of Oxford
Role:: Contributor

+ Batchelor-McAuley, C

Department:: University of Oxford
Role:: Contributor

More contributors...

DOI:: 10.5287/ora-dewzrpge9
Type of award:: DPhil
Level of award:: Doctoral
Awarding institution:: University of Oxford

UUID:: uuid:1b2868bf-4fa6-47e8-8a6e-8a7172af812d
Deposit date:: 2018-04-10

Related item:: Quantifying Adsorption on Single Alumina Particles via Impact Voltammetry and Current Transient Analysis
Description:: Particle impacts are used to quantify the adsorption of catechol on single alumina particles. In these experiments, particles suspended in solution impact a microelectrode held at a suitable potential for the oxidation or reduction of the adsorbed species and the resulting current/time transient “spikes” associated with individual impacts measured. Using theory for charge diffusion over the surface of a sphere, the individual impact spikes arising from the electro-oxidation of adsorbed catechol can be modelled to derive the diffusion coefficient of charge transfer over the surface of alumina as (2.5 ± 0.5) × 10^(−6) cm^2 s^(−1). The coverage of catechol on the surface of alumina is found to be (5.9 ± 1.9) × 10^(−10) mol cm^(−2).
Related item:: Two-Electron, Two-Proton Oxidation of Catechol: Kinetics and Apparent Catalysis
Description:: The study of proton-coupled electron transfer reactions is of great current interest. In this work, the catechol redox process was studied voltammetrically in the pH range from 1.0 to 14.0 using a glassy carbon electrode. Analysis of the peak potentials and currents together with Tafel analysis allowed the inference of the likely transition states and electrode reaction mechanism. Modification of the glassy carbon electrode surface with sparse coverages of alumina particles was shown to lead to strong apparent catalysis of the catechol redox process at low pH. A possible mechanism for this is proposed.
Related item:: Altered Electrochemistry at Graphene- or Alumina-Modified Electrodes: Catalysis vs Electrocatalysis in Multistep Electrode Processes
Description:: The voltammetric behaviour of glassy carbon electrodes modified with either submonolayer quantities of alumina or graphene is examined with respect to the two-electron, two-proton reaction of catechol (1,2-dihydroxybenzene) in aqueous solution. While the voltammetric behaviour superficially hints at a change of electron transfer rate, an alternative explanation in terms of the changed thermodynamics of the intermediate species is advanced and rationalised.
Related item:: Impacts Reveal and Quantify Monolayer Adsorption on Single Alumina Particles
Description:: A particle impact method is used to quantify adsorption of redox active species on single insulating particles by simulation of individual spike transient, circumventing the complexity of measurements with ensembles of particles. For catechol, anthraquinone and chloranil molecules and the ferrocene moiety of poly(vinylferrocene) adsorbed on alumina, the surface coverages are found to be (3.0 ± 0.9), (1.5 ± 1.4), (2.7 ± 1.7) and (2.1 ± 0.7) × 10^(−10) mol cm^(−2), and the charge diffusion coefficients are found as (2.5 ± 0.5), (7.9 ± 4.0), (0.4 ± 0.2) and (2.4 ± 0.8) × 10^(−6) cm^2 s^(−1), respectively.
Related item:: Stochastic detection and characterisation of individual ferrocene derivative tagged graphene nanoplatelets
Description:: Graphene nanoplatelets (GNPs) are ‘tagged’ with 1-(biphen-4-yl)ferrocene. Chronoamperometry is then utilised to observe single particle impacts when GNPs suspended in solution collide with a carbon fibre micro wire electrode held at an oxidising potential, resulting in current/time transient “spikes”. The impacts are associated with two types of charge transfer: Faradaic due to oxidation of the ‘tag’ and capacitative due to disruption of the double layer. Analysis of the spikes suggests approximate monolayer coverage of 1-(biphen-4-yl)ferrocene on the GNP surfaces, with a surface coverage of (2.2 ± 0.3) × 10^(−10) mol cm^(−2). In contrast non-derivatised ferrocene does not exhibit any significant adsorption on the GNP material.
Related item:: Catalytic Single-Particle Nano-Impacts: Theory and Experiment. Poly(vinylferrocene)-Modified Graphene Nanoplatelet Mediated L‐Cysteine Oxidation
Description:: The theory of catalytic nano-impacts is developed specifically for the case of a single particle in contact with an electrode for a short period of time in which it mediates electron transfer to or from a species in homogeneous solution. The theory is applied to impacts of chemically modified graphene nanoplatelets in which the immobilized ferrocene/ferrocenium couple is used to mediate the oxidation of L-cysteine in aqueous solution. Theory and experiment are in good agreement, and the catalytic rate constant is found to be (2.4 ± 1.2) × 10^3 M^(−1) s^(−1).
Related item:: Nanoimpacts Reveal the Electron-Transfer Kinetics of the Ferrocene/Ferrocenium Couple Immobilised on Graphene Nanoplatelets
Description:: The kinetics of the ferrocene/ferrocenium (Cp2Fe/Cp2Fe+) redox couple immobilised on graphene nanoplatelets (GNPs) in aqueous solution are evaluated by using the nanoimpacts method. Single GNPs modified with poly(vinylferrocene) are allowed to impact a microelectrode. For the duration (ca. 10– 100 ms) of the impacts, the GNP adopts the potential of the electrode and acts as a “chemically modified nanoelectrode”. The study of individual impacts facilitates the resolution of fast electron-transfer kinetics that, for the Cp2Fe/Cp2Fe+ couple, is shown to be at least 3 ± 1 s^(−1).

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Electroanalysis of solid particles

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