Chirality-independent plasmon damping at nanoparticle interfaces.

Abstract

Chemical interface damping (CID), a plasmon decay mechanism arising from interfacial chemical perturbations, has become a crucial design parameter in surface-enhanced spectroscopic techniques and single-molecule biosensor development. Despite its significance, the mechanistic interplay between chiral molecular adsorption and CID remains poorly understood, especially for small biomolecules on plasmonic nanoparticles. In this study, we systematically investigated the CID responses of L/D-cysteine enantiomers on gold nanorods using single-particle dark-field spectroscopy. Our experiments revealed nearly identical adsorption kinetics and CID variations between the enantiomers. Density functional theory (DFT) analyses identified two competing mechanisms: (i) enantiomer-specific dipole moment disparities and (ii) chirality-insensitive electron density redistribution at gold-molecule interfaces. Our results suggest that electron transfer plays a dominant role in CID modulation, effectively overshadowing the weaker dipolar effects. This dominance of electronic effects implies that CID is an intrinsic process, independent of molecular chirality, in specialized metal nanoparticle-L/D-cysteine enantiomer systems.