Plasmonic couplings in Ag-Au heterodimers

Area of Science:

• Plasmonics
• Nanotechnology
• Materials Science

Background:

• Plasmonic coupling between dissimilar metal nanoparticles (e.g., silver and gold) is crucial for advanced optical applications.
• Understanding polarization-dependent interactions is key to controlling nanoparticle behavior.
• Localized Surface Plasmon Resonance (LSPR) in metal nanoparticles dictates their optical properties.

Purpose of the Study:

• To investigate the plasmonic coupling between silver (Ag) and gold (Au) nanoparticles under various polarization modes.
• To analyze the influence of coupling on extinction, absorption, and near-field spectra.
• To elucidate the origin of Fano profiles and near-field enhancements in Ag-Au heterodimers.

Main Methods:

• Utilized the discrete dipole approximation (DDA) to model nanoparticle interactions.
• Developed an in-house postprocessing code to calculate extinction, absorption, and near-field spectra.
• Employed dielectric particle (DP) models to further investigate Fano profiles and near-field phenomena.

Main Results:

• Observed distinct spectral shifts and intensity changes in Ag-Au heterodimers compared to individual nanoparticles.
• Demonstrated reabsorption of scattered light by Au NPs from Ag NPs, particularly at the Ag LSPR region.
• Identified the appearance and masking of Fano profiles based on nanoparticle material and dielectric environment.

Conclusions:

• Ag-Au nanoparticle coupling significantly modifies their individual plasmonic responses.
• The observed phenomena, including Fano profiles and enhanced near-fields, are explained by interband transitions and dielectric properties.
• This research offers a deeper understanding of plasmonic interactions in hybrid nanoparticle systems.