Zhang, BoWan, Ruixuan2025-10-022025-10-022025-10-022025Wan_washington_0250E_28786.pdfhttps://hdl.handle.net/1773/53940Thesis (Ph.D.)--University of Washington, 2025This dissertation explores novel advances in single-entity electrochemistry, with a focus on understanding nanoscale electrochemical processes and developing innovative sensing platforms. Chapter 2 investigates the electrocatalytic behavior of individual Pt nanoparticles on electrode-solution interface using a single-nanoparticle collision approach. The study reveals that molecular adsorption and dynamic changes in the local chemical environment critically influence catalytic responses. Furthermore, the observed steady-state currents are found to be governed by either chemical kinetics or mass transport limitations, providing key mechanistic insights into single-nanoparticle electrochemistry. In Chapter 3, a glass microbulb (GMB) nanopore is employed to study the transient bipolar electrochemical behavior of single metal nanoparticles. The design of GMB enables high-throughput recording of translocation events with minimal clogging. The ionic current response exhibits biphasic signals at low voltages and oscillatory behavior at higher potentials, suggesting the formation of transient nanobubbles on moving nanoparticles. These findings advance the development of ultrasensitive biosensors based on single-entity bipolar electrochemistry. Chapters 4 and 5 focus on the development of optical imaging techniques for single-entity electrochemical detection. Chapter 4 explores the use of electrogenerated chemiluminescence (ECL) to image gold nanoparticle translocations, identifying key challenges such as nanoparticle residence time, faradaic efficiency, and optical sensitivity. Chapter 5 introduces a novel dark-field microscopy (DFM) platform based on closed-bipolar electrochemistry, enabling real-time optical monitoring of electrochemical reactions. This system demonstrates quantitative detection capabilities, serving as a promising optical reporter for transient single-entity electrochemistry. Collectively, this work advances fundamental understanding and practical applications of single-entity electrochemistry, paving the way for next-generation biosensing, nanoscale electroanalysis, and high-throughput single-particle studies.application/pdfen-USnoneClosed-bipolar electrochemistryElectrochemical imagingNanoparticle collisionNanopore sensingSingle-entity electrochemistryChemistryNanotechnologyAnalytical chemistryChemistryThesis