Photosynthesis is used by plants, algae and bacteria to convert solar energy into stable chemical energy. The initial stages of this process—where light is absorbed and energy and electrons are transferred—are mediated by reaction centres composed of chlorophyll and carotenoid complexes1. It has been previously shown that single small molecules can be used as functional components in electric2,3,4,5,6 and optoelectronic circuits7,8,9,10, but it has proved difficult to control and probe individual molecules for photovoltaic11,12,13 and photoelectrochemical applications14,15,16. Here, we show that the photocurrent generated by a single photosynthetic protein—photosystem I—can be measured using a scanning near-field optical microscope set-up. One side of the protein is anchored to a gold surface that acts as an electrode, and the other is contacted by a gold-covered glass tip. The tip functions as both counter electrode and light source. A photocurrent of ∼10 pA is recorded from the covalently bound single-protein junctions, which is in agreement with the internal electron transfer times of photosystem I.
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This work was supported by the DFG via SPP 1243 (grants HO 3324/2 and RE 2592/2), COST-Phototech, the China Scholarship Council, the Nanosystems Initiative Munich (NIM), the Munich Center for Advanced Photonics (MAP), ERC Advanced Grant MolArt (no. 47299) and the Center of NanoScience (CeNS) in Munich. The authors thank A. Brenneis for technical assistance.
The authors declare no competing financial interests.
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Gerster, D., Reichert, J., Bi, H. et al. Photocurrent of a single photosynthetic protein. Nature Nanotech 7, 673–676 (2012). https://doi.org/10.1038/nnano.2012.165
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