Author ORCID Identifier

https://orcid.org/my-orcid?orcid=0000-0002-8023-3191

Defense Date

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Julio C. Alvarez

Abstract

Single Entity Electrochemistry (SEE) is an emerging electrochemical technique that has been used to characterize discrete entities by measuring the change in current or potential during individual stochastic events (collision or adsorption) of an entity with an ultramicroelectrode (UME) of similar dimensions. The shape and magnitude of the SEE signal depend on the underlying mechanism of interaction with the UME surface. There is a critical need for quantitative models that correlate the SEE signal with properties of the entity-UME system, including effects of acquisition instrumentation, to prevent misinterpretation of data.

This research focused on integrated experiments and simulations to quantify the effects of the interaction dynamics (collision and adsorption) of the microparticle and UME to deduce the properties of liquid droplets (diameter, contact radius, droplet redox mechanism) and bacteria (size, landing orientation, arrival pace). Chapter 1 introduces the SEE technique and the signals that appeared in the current vs. time graphs relevant to this dissertation. Chapter 2 compares the signal efficiency of adsorption versus bouncing collisions of emulsified ferrocene-trapped toluene droplets (~1 µm) with a disk UME of ~ 5 µm in diameter. Chapter 3 describes the size determination and adsorption orientation for three bacilli of variable length (~1, ~2, and ~5 µm).

Comments

Electroanalytical chemistry is entering a digital era with the introduction of SEE, where the signal has on and off properties similar to binary coding used in computers. For ensemble electrochemistry, the current signals do not change rapidly with respect to time due to trillions or more electroactive analytes undergoing simultaneous electron-transfer reactions on the electrode surface. While in SEE, the signal is generated once an individual analyte particle collides and/or adsorbs on the electrode surface, thus, gaining a time-dependent profile. In my view, one needs to think innovatively to deconvolute the physicochemical properties related to these transient signals. Particularly, a better understanding of the particle interaction dynamics with UME with the effect of signal acquisitions on the resulting SEE signals is necessary to extract the properties correctly. This dissertation advanced these understandings in terms of microparticle analysis.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-11-2022

Available for download on Thursday, May 11, 2023

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