Observing Intermediates of a Single-molecule Deoxygenation Reaction in a Plasmonic STM Junction

In this study, the deoxygenation reaction of a 5-membered cyclic ether on a Ag substrate was investigated at the single-molecule level. By positioning a Ag tip over the molecule and illuminating it with laser light (wavelengths 405–532 nm), we successfully monitored a two-step C–O dissociation process in real space and real time. Through STM measurements combined with density functional theory (DFT) calculations, we identified three distinct intermediate configurations and characterized five discrete reaction pathways based on ~300 single-molecule reaction events. In addition, DFT-based electronic structure analysis, together with pulse-induced reaction measurements, revealed that the reaction is driven by hot-carrier injection rather than direct photoexcitation. These findings provide the first single-molecule characterization of multiple intermediates and pathways in a plasmon-induced reaction. This work offers a comprehensive understanding of the reaction pathway and excitation mechanism in a plasmon-induced C–O dissociation process, providing design principles for efficient plasmonic catalysts in deoxygenation for biomass upgrading.

1. E. Kazuma, et al. Science. 360, 521–526 (2018)
2. E. Kazuma, et al. Angew. Chem. Int. Ed. 59, 7960–7966 (2020)
3. Y. Park, et al. Nat. Commun. 15, 6709 (2024)