Droplet-Based EPR Spectroscopy

Thomas Moragues and colleagues in the Department of Chemistry at ETH Zurich have developed a droplet-based microfluidic platform for real-time monitoring of liquid-phase catalytic reactions using electron paramagnetic resonance (EPR) spectroscopy. Conventional methods for EPR spectroscopy in the liquid-phase are unable to properly control reaction residence time, consume large volumes of reagents and are ill-suited to studying fast kinetic processes. By encapsulating solid and dissolved species within nanoliter droplets, Moragues’ platform engenders precise control over mass transport whilst consuming miniscule amounts of reagent. This in turn allows EPR to be probe the kinetics of solid catalyst-based systems.

The utility of the platform is showcased by monitoring dynamic ligand exchange processes and redox kinetics using commercial EPR instruments, with a focus on the oxidation of ascorbic acid by copper (II) catalysts in both homogeneous and heterogeneous formats. Results reveal that homogeneous copper catalysts are more efficient at consuming ascorbyl radicals than their heterogeneous counterparts, highlighting the importance of catalyst design when optimizing reactions.  Such a droplet-based approach not only enhances the understanding of catalytic mechanisms but also sets a new standard for in situ EPR measurements, paving the way for advancements in both homogeneous and heterogeneous catalysis.

Written by Andrés Rocha Tapia

Read the published article here.