Exploiting new ways for a more efficient orientation and wiring of PSI to electrodes: A fullerene C70 approach

For successful production of photobioelectrodes two major aspects have to be addressed: The proper orientation of the photo-active biomolecules on the electrode surface and a good electrical connection with the electrode. In this work a step-by-step procedure for the successful construction of a photosystem I (PSI)-based photobioelectrode is shown. First, the orientation of PSI on a ruthenium hexamine-thiol-modified gold surface is improved: Here, positively charged ruthenium hexamine complexes allow for a better and a more directed assembly of PSI with the luminal side to the electrode. In a second step, an improved electrical communication of the PSI reaction center with the electrode is achieved by employing carboxy-modified C₇₀-fullerenes. Due to the outstanding electrical properties of the small fullerene nanoparticles and their accessibility towards the PSI's reaction center and the electrode, the system shows an enhanced magnitude of the cathodic photocurrent (15 μA cm⁻² at U = - 0.300 V vs. Ag/AgCl) and a positive onset potential of the cathodic photocurrent generation (U_onset = + 0.157 V vs. Ag/AgCl). In conclusion, it can be stated that this study demonstrates alternative approaches in meeting key demands for the construction of PSI-based photobioelectrodes resulting in relatively high IQE values (ca. 10%) and turnover frequencies (ca. 228 e⁻ s⁻¹).