The Nature of Plasmonically Assisted Hot -Electron Transfer in a Donor-Bridge-Acceptor Complex

This work provides a mechanistic understanding of hot-electron-based catalysis on Au nanoparticles (NPs) induced under plasmonic excitation. Plasmon excitation-induced hot-electron transfer from an Au NP (donor) to a ferricyanide anion (acceptor) was studied as a function of the donor acceptor distance set by a thiolate-based self-assembled monolayer (SAM). Hot-electron-transfer rates and activation barrier heights were measured as a function of the donor acceptor distance, up to 20 A. Hot-electron transfer was found to be longer range than anticipated. The distance-dependent kinetics reveal that the hot-electron transfer takes place via multistep hopping in a "wire-like" manner across the insulating ligands, quite unlike the tunneling-dominated electron transfer known to take place across SAMs in the absence of plasmonic excitation. Field-assisted electron hopping may play a crucial role in hot-electron extraction and catalysis involving plasmon-excited NPs.