Unveiling the Competition among Surface Damping Pathways in Single Gold Nanorods Immobilized on Graphene Using Amine Derivatives as Adsorbates.

Understanding plasmon damping in gold nanorods (AuNRs) is crucial for optimizing their use in photochemical processes and biosensing. This study used dark-field microscopy and spectroscopy to explore plasmon damping in single AuNRs on graphene monolayers (AuNR@GL) with pyridine derivatives as adsorbates. The Au-graphene heterostructure caused a Fermi-level downshift, making graphene a dominant electron acceptor. Hot electrons transferred from AuNR to graphene, leading to a redshift and broadening of the LSPR spectrum. Pyridine adsorption at the AuNR-graphene interface induced a redshift and LSPR line width narrowing due to competing surface damping pathways involving graphene and adsorbate molecules (chemical interface damping, CID). The electron-donating groups of pyridine derivatives on AuNR@1GL caused further LSPR narrowing and decreased plasmon dephasing time. Additionally, thicker graphene layers suppressed electron transfer, highlighting a dominant CID effect. This study, therefore, provides detailed insights into controlling competing plasmon decay mechanisms at the adsorbate-AuNR-graphene interface at the single-particle level.