Photosystem I/molecular wire/metal nanoparticle bioconjugates for the photocatalytic production of H₂

Photosystem I (PS I) is a robust photosynthetic complex that adeptly captures photons to create a charge-separated state with a quantum efficiency that approaches 1.0. This charge-separated state is stable for ∼100 ms, and the low-potential reductant that is produced is poised at a redox potential favorable for H₂ evolution. PS I has been covalently linked to Pt and Au nanoparticle surfaces by 1,6-hexanedithiol which serves as a molecular wire to both connect PS I to the particles and transfer electrons from the terminal electron transfer cofactor of PS I, F_B, to the nanoparticle. Illumination of these Photosystem I/molecular wire/nanoparticle bioconjugates is able to catalyze the reaction: 2H⁺ + 2e^- → H₂. Transfer of the electrons from PS I to the nanoparticle through the molecular wire is not rate-limiting for H₂ evolution. Supplying the system with more efficient donor-side electron donating species results in a 5-fold increase in the rate of H₂ evolution.