Chirality-independent plasmon damping at nanoparticle interfaces

Area of Science:

• Plasmonics and Nanophotonics
• Surface Chemistry
• Biophysical Chemistry

Background:

• Chemical interface damping (CID) is a critical plasmon decay mechanism in plasmonic systems.
• Understanding CID's interplay with chiral molecular adsorption is vital for advanced spectroscopic techniques and biosensors.
• Small biomolecules on plasmonic nanoparticles present unique challenges for studying CID.

Purpose of the Study:

• To systematically investigate the influence of molecular chirality on Chemical Interface Damping (CID).
• To elucidate the mechanistic interplay between chiral adsorption and CID on plasmonic nanoparticles.
• To determine the dominant factors modulating CID in metal nanoparticle-biomolecule systems.

Main Methods:

• Single-particle dark-field spectroscopy was employed to monitor CID responses.
• Experiments focused on L/D-cysteine enantiomers adsorbed onto gold nanorods.
• Density functional theory (DFT) calculations were performed to analyze interfacial interactions.

Main Results:

• L-cysteine and D-cysteine enantiomers exhibited nearly identical adsorption kinetics and CID variations.
• DFT identified competing mechanisms: enantiomer-specific dipole moments and chirality-insensitive electron redistribution.
• Electron transfer at the gold-molecule interface was found to be the dominant factor in CID modulation.

Conclusions:

• CID modulation in this system is primarily driven by electron transfer, not molecular chirality.
• The intrinsic electronic effects dominate over weaker dipolar effects related to chirality.
• CID is an intrinsic process independent of molecular chirality for gold nanoparticle-cysteine systems.