Mechanistic insights into plasmon-driven hot electron transfer from silver nanoclusters to PFAS: interplay of size and electronic structure

Plasmonic metal nanoclusters (NCs) are widely explored in photocatalysis due to their ability to generate excess energy carriers or hot carriers (HCs) that can transfer to nearby molecules and drive otherwise challenging chemical reactions. In this study, we investigate the efficiency of HC transfer from silver (Ag) NCs of varying sizes to two perfluoroalkyl substances (PFAS), namely, perfluorooctanoic acid and perfluorooctanesulfonic acid. Using real-time time-dependent density functional theory, we present the real-time dynamics of plasmon formation, HC generation, and HC transfer from Ag NCs to PFAS. Our findings reveal that although the probability of direct hot electron transfer (DHET) decreases with increasing NC size, the net amount of electron transfer does not exhibit a simple size-dependent trend. Instead, it is governed by the interplay between the electronic structures of the NC and the PFAS molecules. Specifically, smaller NCs exhibit Rabi-type oscillations in charge transfer, indicating back-and-forth electron transfer between Ag nanoclusters and PFAS molecules. In contrast, larger NCs support more unidirectional and stable electron transfer. These findings offer mechanistic insights into size- and electronic structure-dependent HC generation and transfer to PFAS, and provide design principles for more efficient plasmon-driven degradation strategies of PFAS and other related environmental contaminants.