G.K. Jennings, M. Robinson, F. Mwambutsa, E. Gizzie, M. Armbruster, C. Simons, D. Cliffel
Keywords: Photosystem I, PSI, nanoscale photocatalytic protein
Summary:Photosystem I (PSI) is a nanoscale photocatalytic protein complex within the chloroplast granum of photosynthetic organisms that converts incident solar radiation to transfer electrons across the thylakoid membrane with nearly perfect internal quantum efficiency. PSI is extracted from green plants and has been successfully employed by several groups across the world as the active photosensitizer within a host of low-cost electrochemical and solid-state photovoltaic architectures. This presentation explores our recent advances to prepare coatings in which spinach-extracted PSI is integrated with other materials, including semiconductors, graphene oxide, conducting polymers, and natural dyes. These composite assemblies address limitations of PSI, including structural scaffolding, conductivity, and light absorbance. Composite coatings of PSI with conducting polymers can be prepared by either electrochemical co-polymerization from a bath of PSI and aniline or a vapor-phase Friedel-Crafts grafting procedure, whereby dispersed Fe(III) catalyzes rapid growth of conducting polymer from aromatic moieties inherent to PSI. The latter technique avoids the requirements of high temperature and solvent exposure inherent to the fabrication of bulk heterojunctions in organic photovoltaics and can be employed using a library of conjugated monomers with high vapor pressures. The group has recently reported two prototype solid-state devices in which PSI or its composite coatings are deployed between energetically appropriate electrodes. In general, the move toward more effective integration of PSI within these composite, biohybrid coatings has greatly enhanced the turnover frequency of the individual proteins, yielding more efficient utilization of nature’s renewable, mass-produced photodiode.