Photoelectric Conversion System Composed of Gene-Recombined Photosystem I and Platinum Nanoparticle Nanosheet.

Photosynthesis is one of the most vital processes in nature, which consists of two main photoreaction centers called photosystem I and photosystem II. The high quantum yield of photosystem I (PSI) makes it attractive for bioelectronic applications. However, the native PSI (N-PSI) loses its robust photochemical properties once fabricated into devices. This property degradation results from the difficulty in controlling the orientation of PSI. With the optimal orientation of PSI, photoexcited electrons can easily reach the electrode, yielding good photoelectric conversion efficiency. We developed a novel photoelectrode by integrating a newly designed gene-recombined PSI (G-PSI) with platinum nanoparticles (PtNPs) on substrates using a simple stacking method, which can control the orientation of PSI on the electrode. The target orientation of the attached G-PSI toward the substrate was confirmed by the absorption spectra of polarized light. An approximately 2-fold increase in the internal quantum yield (IQY) was observed for the G-PSI-attached electrode under 680 nm irradiation compared with that of the N-PSI-modified electrode. In addition, a 4-fold enhancement of the IQY was detected for cytochrome c (Cyt c) stacking on the G-PSI because of the electrostatic interaction, suggesting that Cyt c successfully secured the electron-transfer pathway.