Department of Chemistry and Biochemistry

Organic/Inorganic/Materials Seminar Series

Professor Jeffrey Dick, Purdue University 

Hosted by CBGReAT

Droplet Like It’s Hot: Understanding Curious Chemistry in Multiphase Microenvironments with Nanoelectrochemistry

Over the past decade, several reports have emerged demonstrating chemistry depends on the reaction volume in which it is occurring. This surprising finding has been observed across fields of measurement, from fluorimetry to mass spectrometry. This talk will detail our group’s efforts in developing new nanoelectrochemical tools to probe curious chemistry in sub-femtoliter volumes [1]. We will answer the question: Are biochemical reactions as studied in beakers representative of reactions presently occurring within our cells? [2] In the pursuit of an answer, we will show that the famous Michaelis-Menten equation requires modification in confined volumes. We will demonstrate that electroactive molecules are spontaneously produced in suspended droplets. [3] The previous work [1-3] is performed on aqueous nanodroplets suspended in a non-aqueous phase. However, many studies detailing microdroplet curious chemistry come from droplets suspended in air, where the liquid|air boundary is the dominant interface (as opposed to the water|organic boundary). Electrochemistry in air is rather difficult. This difficulty comes from the strict requirement of needing two electrodes to make an electrochemical measurement. We will go on a journey of discovery through developing electrochemical measurement tools to probe reactivity in a bubble wall. [4] We have recently demonstrated that this experiment allows the electrochemical interrogation of single micrometer-sized liquid aerosol droplets, where a majority of the interface is the liquid|air boundary. [5] This interface accelerates enzyme reactions beyond the water|organic interface, a truth of nature that has broad implications on the genesis and propagation of life. 

[1] Lu, S.; Vannoy, K. J.; Dick, J. E.*; Long, Y. T.* Multiphase Chemistry under Nanoconfinement: An Electrochemical Perspective, Journal of the American Chemical Society, 2023 145, 25043 – 25055.
[2] Vannoy, K. J.; Lee, I.; Sode, K.; Dick, J. E.* Electrochemical Quantification of Accelerated FADGDH Rates in Aqueous Nanodroplets, Proceedings of the National Academy of Sciences USA, 2021, 118, e2025726118. 
[3] Krushinski, L. E.; Dick, J. E.* Direct Electrochemical Evidence Suggests that Aqueous Microdroplets Spontaneously Produce Hydrogen Peroxide, Proceedings of the National Academy of Sciences USA, 2024, Accepted, DOI: doi.org/10.1073/pnas.2321064121 
[4] Vannoy, K. J.; Tarolla, N. E.; Kauffmann, P. J.; Clark, R. B.; Dick, J. E.* Detecting Methamphetamine in Aerosols by Electroanalysis in a Soap Bubble Wall, Analytical Chemistry, 2022, 94, 6311 – 6317. 
[5] Krushinski, L. E.; Vannoy, K. J.; Dick, J. E.* Single Liquid Aerosol Microparticle Electrochemistry on a Suspended Ionic Liquid Film, Small, 2024, 2308637.