The Daily Bulletin Archive

Please join the Chemistry Department for the online seminar "Analyzing Droplets and Microbial Cells One at a Time Using Electrochemistry," presented by Julio C. Alvarez, Ph.D., associate professor of chemistry at Virginia Commonwealth University, on Thursday, November 30, at 12:30 p.m. A link to join the seminar will be sent on Wednesday. This online seminar is part of the Chemistry Fall 2023 Seminar Series.

Abstract
In the last decade, single-entity electrochemistry has emerged as a highly sensitive technique able to interrogate one entity at a time, spanning from single proteins to microparticles. The direct electrolysis mode entails a single electroactive particle impinging a polarized electrode where reducer R oxidizes to oxidant O (R = O + e-). For example, a single Ag nanoparticle oxidizing to Ag+ + e-, or a redox mediator R dissolved inside a colliding microdroplet. Prior to impact, the current-time(i-t) profile reflects the low background current from the non-electroactive electrolyte. As a result, the high baseline current due to R = O + e- undergoes a sudden step decrease marking the impact and adsorption of the particle. These two modes of single-entity electrochemistry have been applied to proteins, viruses, nanobeads, nanoparticles, liposomes, microdroplets, bacteria, cancer cells, blood cells, and more. In this seminar, Dr. Alvarez will present data from two types of microparticles. The first example describes efforts to determine hydrogen bonding effects on the electrochemical response of individual toluene droplets emulsified in water. Additionally, Dr. Alvarez and his team compare the signal output between droplet adsorption and collisions to evaluate sensing efficiency. The second example illustrates the effect of bacterial size on their arrival velocity as they collide and adsorb on the electrode. This research aims to establish particle properties and mechanisms using the signals from individual impacts with UMEs. In the case of droplets, they seek to investigate processes that control size like coalescence and self- division, whereas in cells, they want to uncover correlations of signal with biological function.