(325e) Electropolymerization of Conductive Biopolymers By Photosystem I

The Photosystem I (PSI) protein complex found in all photosynthetic organisms is known for its impressive redox capabilities. PSI has two photoactive redox sites, the oxidizing P₇₀₀ chlorophyll pair and the reducing F_B iron-sulfur cluster, with more than 1.1 V of potential difference between them. We are investigating the use of these active sites to perform photo-driven, nanomaterials chemistry directly at the protein surface. The wide range of reduction potentials places PSI in a position to photooxidatively electropolymerize conductive polymers and photoreduce metal ions into nanoparticles. This presentation will focus on the preparation of PSI-conducting polymer conjugates and films. A reduction potential of 0.48 V vs. Ag/AgCl at the P₇₀₀ site makes PSI a promising candidate for oxidative polymerization of certain monomers. Because PSI is a renewable and readily available material, electropolymerization via PSI is a sustainable and low-cost alternative to produce conductive polymers, including polypyrrole and polyaniline. Polymerization occurs with the addition of protein and monomer in an acidic aqueous solution. The protein-polymer dispersion is then separated, yielding a powder that contains conducting polymer mixed with PSI protein. The powder can be pressed into pellets or cast into thin films. Surrounding PSI with a conductive polymer matrix results in a photoactive polymer film that could be utilized in solar energy conversion systems. We have examined the effect of monomer to protein ratio, polymerization time, and solution environment on the resulting polymer-protein conjugates. Successful polymerization of a conductive polymer by the protein is confirmed by four-point probe conductivity measurements, UV-vis spectra, and IR spectra.