The Solar Energy Conversion Group has developed and maintains unique, advanced electron paramagnetic resonance (EPR) facilities at Argonne for the analysis of the structure and function of artificial and natural photosynthetic assemblies, catalytically active transition metal complexes, biohybrid complexes, organic photovoltaic materials, and metallo-organic frameworks.

Electron paramagnetic resonance (EPR) spectroscopy is only sensitive to systems containing unpaired electron spins. This makes EPR an indispensable technique for research into the chemical, biochemical and catalytical reactions where these radicals play a vital role. Another related field of application is in photochemistry, where chemical reactions are initiated by light.

After light absorption, the first step of transformation involves a charge separation process, which create both a negatively charged electron and a positively charged hole. Both of these posses unpaired spins and can be detected, characterized and followed by EPR. Furthermore, open-shell transition metals which are at the center of many catalytic reactions can also be studied in detail by EPR spectroscopy.

The research at the Advanced EPR Facility is focused on the following fields:

• Understanding the fundamental mechanisms of photochemical energy conversion in natural photosynthesis. These mechanisms are responsible for water splitting, oxygen production, and conversion of solar energy to the energy of chemical bond.

• Characterization of biohybrids and biomimetic supramolecular architectures for artificial photosynthesis that are designed to achieve light-induced water splitting and solar fuel production similar to natural photosynthesis.

• Understanding the mechanism of light-induced charge separation as well as charge recombination processes in organic photovoltaic systems. This is crucial for designing the next generation solar cells that will efficiently convert solar energy to electrical potential.

• Resolving electronic structure and catalytic steps of molecular catalysts for photochemical solar energy transformation. This research is focused to design of stable, efficient, and cheap catalysts whose performance can rival the best performance on natural enzymes.