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Eli Fahrenkrug

Assistant Professor

Biography:

Eli received his B.S. in Chemistry from The Evergreen State College in 2011. His fascination with electrochemistry and materials science started while he was an engineer at Hummingbird Scientific. There he contributed to some of the first commercial instrumentation that would allow researchers to visualize electrochemical reactions at the atomic scale. He was hooked.

He channeled his interests into research at the University of Michigan where he obtained his PhD in 2016. There he helped pioneer an electrochemical strategy for preparing semiconductor crystals at liquid metal electrodes. His work spurred a new technology that allows cheap and energy efficient preparation of photovoltaic materials like Si, Ge, and GaAs directly at room temperature in water. Mixing science with a bit of wanderlust, Eli ventured to Beijing to serve as a visiting scientist at the Institute of Semiconductors at the Chinese Academy of Sciences. Beyond the lab he also found refuge for his other interest in brewing chemistry by helping construct one of the world’s highest microbreweries at 11,500 ft. on the Tibetan plateau.

He joined the faculty at Colorado College as Assistant Professor of Analytical Chemistry in the fall of 2017. The general scope of his research centers on developing new platforms by which the practice and interpretation of chemical diagnostics can be made broadly accessible to all people. His pedagogical interests focus on the creation of contemporary case studies as vehicles for conveying analytical chemistry concepts through the mediums of environmental justice, power, and equity.

Eli Fahrenkrug's CV

Research Projects:

Developing a sub-$1, Simple, and Open-Source Sensor for Heavy Metals in Drinking Water

In low-resource settings, meeting the need for high-quality environmental chemical testing requires overcoming challenges of harsh transportation and storage conditions, non-technically trained users, limited infrastructure for support and maintenance, and an economy that cannot afford expensive solutions. We aim to develop and employ new bipolar electrochemical sensors for truly simple, open-source, high-quality, low-cost water quality diagnostics. The sensors combine aspects of conventional anodic stripping voltammetry, wireless bipolar electrochemistry, and light-emitting reactions to quantitate aqueous heavy metals in water. This project has thus far produced the first demonstration of a closed-cell BPE sensor utilizing a cathodic electrochemiluminescent reaction scheme for optical readout. With initial sensor development, a novel device fabrication technology based on simple laser ablation of commercial conductive glass substrates was also introduced. The current sensor transduction scheme has also been extended to include an all solid-state optical readout that provides performance metrics of sub-ppb detection limits, device precision (n = 10) of ~1%, and per sensor costs of less than $1.

Eli Photo 1 2019 Plating Stripping

The Fountain Valley Water Project: A Local Citizen-Science Chemical Contamination Initiative

PFAS (poly- and perfluoroalkyl substances) are a family of nearly 5000 human-made compounds which persist in most environments without breaking down. Their distinctive chemical structures make them especially useful in hydraulic fluids, in carpets and textiles, in firefighting foams, as well as in everyday products like Teflon pans, waterproof clothing, cosmetics, and oil-resistant food packaging. The few epidemiological studies conducted thus far correlate long-term human exposure with kidney cancer, testicular cancer, and cognitive development issues. Since 1970, the Peterson Air Force Base in Southeast Colorado Springs has dispensed an unknown volume of PFAS (poly- and perfluoroalkyl substance)-containing foam used in firefighting drills into the surrounding soil which leeched into the Widefield Aquifer, a key source of drinking water for the over 70,000 residents. This project puts forth a complementary community-centered citizen-science study of the fate and transport of a suite of PFAS compounds in the affected area. This non-partisan longitudinal research project aims for complete and total transparency by making all results publicly available and accessible, with the interpretation and discussion of project results oriented towards the needs of a community audience.  

Eli Photo 2 2019 FV

Molecular Crystallization within the Electrical Double Layer

In pharmaceutical drugs, molecules can often crystallize in several different arrangements called polymorphs. Even when the molecular identity remains the same, simple differences in the packing motif can dramatically affect drug solubility and downstream bioactivity in patients. Controlling molecular polymorphism typically requires crystal seeding or electrostatic influence with exogenous salts, both of which can serve as contamination sources, are difficult to implement at scale, and ultimately impose downstream cost to the consumer. Recent molecular dynamics simulations have indicated molecular nucleation to be sensitive to large external electric fields, yet little is known about the molecular-scale interactions. This project investigates how supersaturated solutions of model molecular systems like paracetamol (i.e. Tylenol) nucleate and crystallize within the electrical double layer (i.e. metal/solution interfaces) where electric fields can exceed ~109 V m-1.

Eli Photo 3 2019 cell scheme

Publications

Selected Publications:

*Undergraduate co-authors

Fahrenkrug, E., Gu, J. & Maldonado, S. Electrodeposition of Crystalline GaAs on Liquid Gallium Electrodes in Aqueous Electrolytes. J. Am. Chem. Soc. 135, 330-339 (2012).

Gu J, Fahrenkrug E, Maldonado S. Direct Electrodeposition of Crystalline Silicon at Low Temperatures. J. Am. Chem. Soc. 135, 1684-1687 (2013).

Fahrenkrug E, Gu J, Jeon S, Veneman PA, Goldman RS, Maldonado S. Room-Temperature Epitaxial Electrodeposition of Single-Crystalline Germanium Nanowires at the Wafer Scale from an Aqueous Solution. Nano Lett. 14, 847-852 (2014).

Ma, L.; Gu, J.; Fahrenkrug, E.; Maldonado, S., Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Ge Nanowires as a Function of Ga Nanodroplet Size. J. Electrochem. Soc. 161, D3044-D3050 (2014).

Fahrenkrug, E., Gu, J. & Maldonado, S. Electrochemically-Gated Alloy Formation of Crystalline InAs Thin Films at Room Temperature in Aqueous Electrolytes. Chem. Mat., 26, 4535-4543 (2014).

Gu J, Fahrenkrug E, Maldonado S. Analysis of the Electrodeposition and Surface Chemistry of CdTe, CdSe, and CdS Thin Films through Substrate-Overlayer Surface-Enhanced Raman Spectroscopy. Langmuir 30, 10344-10353 (2014).

DeMuth, J.; Ma, L.; Fahrenkrug, E, Maldonado, S. Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Gallium Antimonide. Electrochim. Acta, 197, 353-362 (2016).

Lee S., Fahrenkrug E., Maldonado S. Synthesis of photoactive ZnSnP2 semiconductor nanowires. J. Mater. Res. 30, 2170-2178 (2015).

Zhang, T., Fahrenkrug, E., Maldonado, S., Electrochemical Liquid-Liquid-Solid Growth of Crystalline Ge at Hg Microdroplet Ultramicroelectrodes. J. Electrochem. Soc. 163, D500-D505 (2016).

Fahrenkrug E., *Biehl J., Maldonado S. Electrochemical Liquid–Liquid–Solid Crystal Growth of Germanium Microwires on Hard and Soft Conductive Substrates at Low Temperature in Aqueous Solution. Chem. Mater. 27, 3389-3396 (2015).

Fahrenkrug E, Maldonado S. Electrochemical Liquid–Liquid–Solid (ec-LLS) Crystal Growth: A Low-Temperature Strategy for Covalent Semiconductor Crystal Growth. Acc. Chem. Res. 48, 1881-1890 (2015).  

Lee S., Bielinski, A., Fahrenkrug E., Dasgupta, N., Maldonado S. Macroporous p-GaP Photocathodes Prepared by Anodic Etching and Atomic Layer Deposition Doping. ACS Appl. Mater. Inter. 8, 16178-16185 (2016).

Fahrenkrug, E., Alsem, D. H., Salmon, N., Maldonado, S., Electrochemical Measurements in In Situ TEM Experiments. J. Electrochem. Soc., 164, H358-H364 (2016).

DeMuth, J., Fahrenkrug E., Maldonado S. Liquid Metal-Mediated Semiconductor Synthesis: Dependence of Liquid Metal Thickness, Temperature, and Flux on Semiconductor Crystal Growth. Cryst. Gorwth Des., 16, 7130-7138 (2016).

Ma, L., Fahrenkrug, E., *Gerber, E., Maldonado, S., High-Performance Ge Microwire Li-ion Battery Anodes As-Prepared by the Electrochemical Liquid-Liquid-Solid Deposition Process. ACS Energy Letters, 2, 238-243 (2017).

Fahrenkrug E., DeMuth, J., Ma, L., Maldonado, S., Electrochemical Liquid Phase Epitaxy (ec-LPE): A New Methodology for the Synthesis of Crystalline Group IV Semiconductor Epifilms. J. Am. Chem. Soc., 139, 6960-6968 (2017).

Fahrenkrug E., *Rafson, J., Lancaster, M., Maldonado, S., Concerted Electrodeposition and Alloying of Antimony on Indium Electrodes for Selective Formation of Crystalline Indium Antimonide. Langmuir, (2017) ASAP.

Bower, N., Brasuel, M., Fahrenkrug, E., Cooney, M., Insights into Geographic and Temporal Variation in Fatty Acid Composition of Croton Nuts using ATR-FTIR. Int. J. Anal. Chem., 1-8, (2018).