Design, development and characterization of nanostructured electrochemical sensors

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Juska, Vuslat B.
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University College Cork
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This is a publication-based thesis which focuses on the study of electrochemical microbiosensors for glucose detection. It investigates applications of a series of microfabricated gold electrodes based on several nanostructures in electrochemical biosensing technologies, embracing three major methodologies: direct electro-catalytic detection, enzymatic detection and dual-enzyme cascade detection. The study is described over five main chapters with a sixth providing a summary of the material presented and perspectives for the future. Chapter 1 provides an introduction to the field of the electrochemical biosensors with a specific focus on the chosen nanostructures and miniaturized systems, as well as a brief history of the biosensor. Chapter 2 presents results published in ACS Applied Nanomaterials, 2019, 2, 9, 5878-5889. It demonstrates the enzyme free detection of glucose via a direct electro-catalytic reaction. The miniaturized band array electrodes with specific width, length and inter-electrode-distance were integrated with homogeneously distributed copper foam nano dendrites. Such foam deposits presented for the first time at the micro scale were achieved using the in-situ hydrogen bubble template method. The resulting very high electroactive surface area of the porous foam deposits was one of the major advantages in terms of achieving superior performance from each micro band foam electrode towards glucose detection. Moreover, both sensors also showed a strong resistance to the poisoning effects of chloride ions and displayed excellent stability over a period of three months.Chapter 3 presents the first of t wo sets of results for the enzymatic detection of glucose, results published in Elsevier Electrochimica Acta, 2019, 293, 307-317. Chapter 4 then presents the second set of results on this topic which is published in and Elsevier Electrochimica Acta, 2019, 298, 97-105. The aim of these two chapters is to discuss the effect of miniaturization on the enzymatic biosensor performance which was studied in the presence of a carbon quantum dot (CQD) and gold nanoparticle nanohybrid system. CQDs, are a new class of carbon-based materials and have been used here for the first time as a matrix component integrated onto microfabricated gold electrode surfaces for enzyme immobilization and further miniaturization. The biosensors developed were studied by electrochemistry to investigate the analytical performance of each device. By scaling down the surface area of the biosensor, a 13-times increase in sensitivity was achieved towards glucose. Moreover both sensors-planar, micro disk array- exhibited excellent reproducibility, reusability and operational stability in terms of the performance of biosensors. Chapter 5 presents results published in RSC Analyst, 2020 (DOI: 10.1039/C9AN01664C). It demonstrates the operation of a dual-enzyme cascade which was constructed onto a micro band array electrode based on glucose oxidase and horseradish peroxidase enzymes. To achieve a very high surface area, a porous gold-foam was electrodeposited onto surface and then a second electrodeposition layer of chitosan and multi walled carbon nanotube nano-bio-composite. The micro band cascade scheme developed exhibited the highest sensitivity towards glucose detection in comparison to other systems reported in the literature. Chapter 6 provides an insight into the field of electrochemical biosensing with the support of the achievements presented in this thesis. Thus, by taking advantage of the available system, this chapter discusses the possible future applications of the electrochemical biosensors. The thesis then ends with section 7 which presents some Appendices.
Biosensors , Electrochemical detection , Chemical sensors , Electrochemistry , Nanomaterials , Microfabrication , Miniaturisation
Juska, V. B. 2020. Design, development and characterization of nanostructured electrochemical sensors. PhD Thesis, University College Cork.