Electrochemical characterization of bimetallic thin films and semiconductor interfaces for advanced sensing applications
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[EMBARGOED UNTIL 08/01/2026] This dissertation focuses on the design, fabrication, characterization, and understanding of the fundamental electrochemical properties of advanced electrode materials that could have a significant impact on electrocatalytic research and chemical and biosensing applications. This dissertation centers on the design and characterization of bimetallic thin films (Pd/Au and Pt/Au) and a wide-bandgap semiconductor electrode material, silicon carbide (SiC). Multiple analytical techniques, including electrochemical quartz crystal microbalance (E-QCM), cyclic voltammetry (CV), chronoamperometry (CA), and surface-limited redox replacement (SLRR) techniques, are employed to characterize the electrode/electrolyte interfacial phenomena to obtain a molecular-level understanding of the processes and properties at the interface. These fundamental understandings are essential for utilizing these electrode materials for electrocatalysis and chemical/biochemical sensing applications. This dissertation presents the systematic design and characterization of noble metal and semiconductor materials-based electrodes since they have significant applications in chemical and biosensing. Many electrochemical studies focus on the modified electrode materials, but there is very limited understanding of how the substrate electrode properties affect the metal thin film deposited on the substrate electrode. Among them, gold (Au) and Palladium (Pd) are the most used electrode materials due to their inertness and biocompatibility. In the first project, E-QCM was employed to investigate the influence of Au substrate crystallinity and anodic potential range on Pd oxide formation and hydrogen uptake in Pd/Au thin films. Results revealed that substrate structure and oxidative pre-treatment significantly modulate PdOx layer characteristics and hydrogen incorporation, as observed through distinct shifts in E-QCM responses. In the second project, cathodic underpotential deposition (UPD) and bulk deposition of lead ions (Pb²â º) on polycrystalline Au electrode were studied in nitric acid to understand the effects of hydrogen evolution reactions in the Pb deposition and stripping processes. Using CA and QCM, the deposition dynamics were investigated, and two protocols, sequential deposition and regenerative stripping, were designed to differentiate reversible Pb-UPD on Au from irreversible growth. In the third study, we further evaluated hydrogen-related interference on Pb-UPD using Pt- and Pd-modified Au electrodes fabricated via the SLRR technique. Electrochemical responses were examined under varying conditions, including ambient and deoxygenated environments, highlighting the influence of hydrogen adsorption, hydrogen evolution reaction (HER), and lattice strain on Pb-UPD behavior and redox signatures. Finally, in the fourth study, we demonstrated the selective detection of dopamine (DA) using nitrogen-doped 4H-SiC single-crystal electrodes. The engineered 4H-SiC interface, rich in silicon (Si) vacancies, exhibited excellent electrochemical performance, with tunable surface charge and favorable interaction with charged neurotransmitter species. Collectively, these investigations contribute to advancing the design of robust, high-performance materials for electrochemical sensing, catalysis, and interfacial characterization in complex environments.
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Ph. D