Controlling Plasmonic Chemistry Pathways through Specific Ion Effects

Abstract Plasmon‐driven dehalogenation of brominated purines has been recently explored as a model system to understand fundamental aspects of plasmon‐assisted chemical reactions. Here, it is shown that divalent Ca²⁺ ions strongly bridge the adsorption of bromoadenine (Br‐Ade) to Ag surfaces. Such ion‐mediated binding increases the molecule's adsorption energy leading to an overlap of the metal energy states and the molecular states, enabling the chemical interface damping (CID) of the plasmon modes of the Ag nanostructures (i.e., direct electron transfer from the metal to Br‐Ade). Consequently, the conversion of Br‐Ade to adenine almost doubles following the addition of Ca²⁺. These experimental results, supported by theoretical calculations of the local density of states of the Ag/Br‐Ade complex, indicate a change of the charge transfer pathway driving the dehalogenation reaction, from Landau damping (in the lack of Ca²⁺ ions) to CID (after the addition of Ca²⁺). The results show that the surface dynamics of chemical species (including water molecules) play an essential role in charge transfer at plasmonic interfaces and cannot be ignored. It is envisioned that these results will help in designing more efficient nanoreactors, harnessing the full potential of plasmon‐assisted chemistry.