Carbon Dots as Versatile Photosensitizers for Solar-Driven Catalysis with Redox Enzymes

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• 作者：Georgina A. M. Hutton ; Bertrand Reuillard ; Benjamin C. M. Martindale ; Christine A. Caputo ; Colin W. J. Lockwood ; Julea N. ButtErwin Reisner
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：December 28, 2016
• 年：2016
• 卷：138
• 期：51
• 页码：16722-16730
• 全文大小：670K
• ISSN：1520-5126

文摘

Light-driven enzymatic catalysis is enabled by the productive coupling of a protein to a photosensitizer. Photosensitizers used in such hybrid systems are typically costly, toxic, and/or fragile, with limited chemical versatility. Carbon dots (CDs) are low-cost, nanosized light-harvesters that are attractive photosensitizers for biological systems as they are water-soluble, photostable, nontoxic, and their surface chemistry can be easily modified. We demonstrate here that CDs act as excellent light-absorbers in two semibiological photosynthetic systems utilizing either a fumarate reductase (FccA) for the solar-driven hydrogenation of fumarate to succinate or a hydrogenase (H₂ase) for reduction of protons to H₂. The tunable surface chemistry of the CDs was exploited to synthesize positively charged ammonium-terminated CDs (CD-NHMe₂⁺), which were capable of transferring photoexcited electrons directly to the negatively charged enzymes with high efficiency and stability. Enzyme-based turnover numbers of 6000 mol succinate (mol FccA)⁻¹ and 43,000 mol H₂ (mol H₂ase)⁻¹ were reached after 24 h. Negatively charged carboxylate-terminated CDs (CD-CO₂^–) displayed little or no activity, and the electrostatic interactions at the CD–enzyme interface were determined to be essential to the high photocatalytic activity observed with CD-NHMe₂⁺. The modular surface chemistry of CDs together with their photostability and aqueous solubility make CDs versatile photosensitizers for redox enzymes with great scope for their utilization in photobiocatalysis.