Mechanisms of Electron Transfer between Metal Clusters and Molecules in Plasmonic Junctions

Surface plasmons can localize the optical field and energy at the nanoscale, significantly enhancing various light-matter interactions, such as in photocatalysis. The hot electrons generated by plasmon decay play a crucial role in driving chemical reactions. To better understand the mechanisms behind electron transfer, we have developed a polarizability bond model to visualize how the electron transfer influences bond polarization. In this study, we examine molecule-metal coupled systems, where the molecules of varying dimensions are embedded between metal clusters. Our findings show that electron transfer is significantly enhanced when the molecular component is directly excited. The efficiency of electron transfer decreases as the cavity gap widens. Distinct electron transfer behaviors are observed across different molecule-metal coupled systems with the most pronounced enhancement occurring between one-dimensional molecules and metal clusters. Further analysis reveals that the atoms in the first and second layers of the metal clusters are critical in facilitating interfacial polarization. Intramolecular bond polarization is particularly strong when electron excitation originates from the molecular component, and bonds near the cavity center or those aligned with near-field polarization are more easily polarized by plasmon excitation. This study reveals the atomic-level electron transfer mechanisms and provides a theoretical basis for optimizing plasmon-mediated catalytic reactions.