Enhanced Photocurrent Production by Photosystem I Multilayer Assemblies

The long-term success of photosynthetic organisms has resulted in their global superabundance, which is sustained by their widespread, continual mass-production of the integral proteins that photocatalyze the chemical processes of natural photosynthesis. Here, a fast, general method to assemble multilayer films composed of one such photocatalytic protein complex, Photosystem I (PSI), onto a variety of substrates is reported. The resulting films, akin to the stacked thylakoid structures of leaves, consist of a protein matrix that is permeable to electrochemical mediators and contain a high concentration of photoelectrochemically active redox centers. These multilayer assemblies vastly outperform previously reported monolayer films of PSI in terms of photocurrent production when incorporated into an electrochemical system, and it is shown that these photocatalytic properties increase with the film thickness. These results demonstrate how the assembly of micron-thick coatings of PSI on non-biological substrates yields a biohybrid ensemble that manifests the photocatalytic activity of the film's individual protein constituents, and represent significant progress toward affordable, biologically-inspired renewable energy conversion platforms.