Alvarez [View Image]

Julio Alvarez, Ph.D.

Graduate Program Director,
Associate Professor
jcalvarez2@vcu.edu
(804) 828-3521
Oliver Hall 4025

Education

B.S., Universidad del Tolima, Ibague, Colombia, 1989
M.S., Universidad del Valle, Cali, Colombia, 1996
Ph.D., University of Miami, Coral Gables, FL., 2000
Postdoctoral Research, Texas A&M University, College Station, TX, 2000-2004


Honors and awards

National Science Foundation Career Award 2007
Excellence in Scholarship Award, College of Humanities and Sciences, VCU, 2007
Outstanding Graduate Student Award, University of Miami, 2000


Research interests

Research in our lab revolves around using various methodologies to address specific problems in bioanalytical and physical electrochemistry. Students gain experience in electroanalytical techniques to characterize molecular and particulate entities for sensing applications or to elucidate complex electrochemical mechanisms. Other methodologies that are used in our lab depending on the project may include: UV-Vis/Fluorescence Spectroscopy, Electron Microscopy, XPS, NMR, Mass Spectrometry, cell-culturing techniques, ultramicroelectrode fabrication, and simulations with commercial software packages like DigiSim, MatLab and COMSOL Multiphysics. Currently we are pursuing projects in the following areas (representative publications included):

Single-Entity Electrochemistry


We aim to develop electrochemical methods that measure size, charge, and shape of cells (microbial and human) for biological cytometric applications. In this vein, we also study emulsion droplets as cell models because their size and charge can be easily controlled for fundamental investigations connecting structure with electrochemical signal. To this end, we employ Single Entity Electrochemistry, a recently developed approach for characterizing microscopic particles using micrometer-size electrodes. The signal in this case arises from stochastic collision or adsorption events of the particle at the electrode surface, thereby allowing single-particle resolution due to the low noise and comparable size of ultramicroelectrodes.

Ahmed, J.U., Lutkenhaus, J.A., Alam, M.S., Marshall, I., Paul, D.K., Alvarez, J.C., “Dynamics of Collisions and Adsorption in the Stochastic Electrochemistry of Emulsion Microdroplets”, Anal. Chem., 2021, 93, 7993-8001.

Paul, D., Meng, K., Omanovic, D., Alvarez, J.C.; “Hydrogen Bonding and Proton Transfer in Aqueous Toluene Microdroplets Studied by Particle Collision Electrochemistry”, ChemElectroChem, 2018, 5, 2528-2533.

Reaction Mechanisms of Complex Redox Reactions

Our goal is to investigate structure-reactivity principles that govern the concerted transfer of protons and electrons (proton-coupled electron transfer or PCET) in reactions that produce electrochemical energy. In living systems, PCET reactions are responsible for biochemical energy production (i.e. photosynthesis, respiration, etc.) and are believed to follow a concerted pathway as a way to maximize kinetic and thermodynamic efficiency. Currently there is no recipe for recreating the molecular conditions or designing a catalyst that elicit the dominance of the concerted PCET pathway with enough efficiency to produce renewable electrochemical energy cheaply. We aim to elucidate how pKa and redox potential determine the rate and dominance of the concerted pathway in comparison to the sequential routes at different thermodynamic gradients. For this purpose, we work with model systems that allow systematic variation of pKa and redox potential in different conditions.

Meng, K., Medina-Ramos, J., Yibeltal-Ashenafi, E., Alvarez, J.C.; “Interplay of Proton and Electron Transfer to Determine Concerted Behavior in the Proton-Coupled Electron Transfer of Glutathione Oxidation”, Phys. Chem. Chem. Phys., 2018, 20, 17666 – 17675. (Selected as part of the hot article list of 2018 by the journal)

Medina-Ramos, J., Oyesanya, O., Alvarez, J. C.; “Buffer Effects in the Kinetics of Concerted Proton-Coupled Electron Transfer: The Electrochemical Oxidation of Glutathione Mediated by [IrCl6]2−at Variable Buffer pKa and Concentration”, J. Phys. Chem. C, 2013, 117, 902-912

Sensing with Streaming Potentials

The surface of microchannels is used as charge-sensing element for detecting adsorbing molecules or particles on the surface by monitoring the streaming potential. This is a spontaneous ion gradient generated when solutions move through a microchannel by pressure-driven flow. At the microscopic interface between the liquid and the surface, the forward liquid flow creates a downstream excess of surface counterions which is manifested as a potential difference along the flow axis and can be detected by two electrodes located at the outlets of the microchannel. Adsorption processes can be detected by measuring the polarity and magnitude of the potential, which is also proportional to the liquid pressure and the Z-potential of the microchannel surface.

Wu, J., Zhang, Y., Zhao, L., Zou, L., Alvarez, J. C., Pu, Q.; “Towards Robust Biosensors Based on Pulsed Streaming Potentials in Microfluidic Channels: Online Correction and Output Signal Selection”, Sens. Actuact. B, 2012, 174, 18-23

Luna-Vera, F., Ferguson, J. D., Alvarez, J.C, “Real Time Detection of Lysozyme by Pulsed Streaming Potentials Using Polyclonal Antibodies Immobilized on a Renewable Nonfouling Surface Inside Plastic Microfluidic Channels”, Anal. Chem., 2011, 83, 2012-2019.

 

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