Bioinspired Engineering of Programmable Proton-Coupled Electron Transfer in Gold Nanoclusters

The development of programmable, rapid electron transfer (ET) reactions in fluorescent probes represents a significant advancement in fluorescence sensing technologies. In this study, we engineered the ET pathway in red-emissive gold nanoclusters (NCs), drawing inspiration from proton-coupled ET (PCET) mechanisms found in redox enzymes. By mimicking proton transfer in the metal catalytic center, we precisely substituted chitosan with carboxylated chitosan as the secondary ligand. This modification transformed the pure ET process of photoexcited Au₉(DTT)₄ (DTT: dithiothreitol) NCs into a concerted PCET process. The transition reduced the energy barrier and enhanced the controllability, resulting in a 15-fold increase in the ET rate and significant photoluminescence quenching. As a consequence, the system achieved a more than 90-fold higher sensitivity and improved selectivity for mitomycin C detection. Our work introduces a novel strategy to overcome the limitations of conventional ET-based fluorescent probes and provides valuable insights for designing next-generation bioinspired sensing technologies.