Defense Date

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Julio Alvarez

Abstract

Single entity electrochemistry (SEE) detects changes in current or potential when collisions of individual particles at an ultramicroelectrode (UME) are linked with an electrochemical event. One phenomenon that has been explored is redox flux blocking when insulating analytes adsorb to or bounce from the UME. SEE thus far has detected only those analytes which make direct contact with the UME. The current response generated by the analyte is also complicated due to increased redox flux at the edge compared to the center of UMEs. In this work, we observed the typical adsorption and bounce events using budding yeast Saccharomyces cerevisiae with increasing redox concentration and electrode size. Through COMSOL Multiphysics simulation, we monitored the current response while manipulating the 3-dimensional position of an insulating sphere to represent the yeast cell. We were able to quantitatively model a sensing threshold as a result of partial blocking of redox flux even when the cells are significantly far from the UME surface. Some of the events we were able to attribute to yeast cells entering this sensing threshold, disturbing the redox flux, and leaving before ever contacting the UME directly. To analyze the role of the particle landing location, increasing size particles were placed at the edge and center of the UMEs in COMSOL. We found that using a particle ~32% smaller than the UME produced equal edge and center current responses. Based on this finding, for any monodisperse analyte there will be an electrode size at which landing position can be ignored.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-12-2022

Available for download on Tuesday, May 11, 2027

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