Plasmonic percolation: plasmon-manifested dielectric-to-metal transition

Area of Science:

• Nanotechnology
• Materials Science
• Plasmonics

Background:

• Percolation describes abrupt property changes in bicomponent systems near a threshold.
• Traditionally observed in macroscopic systems, often focusing on electrical properties.
• Plasmonic properties of nanomaterials are sensitive to their environment and composition.

Purpose of the Study:

• To investigate and report the observation of plasmonic percolation in gold nanorod core-palladium shell nanostructures.
• To understand the underlying mechanism of plasmonic percolation in these core-shell systems.
• To explore the influence of shell composition on plasmonic behavior and refractive index sensitivity.

Main Methods:

• Fabrication of gold nanorod core-palladium shell nanostructures.
• Spectroscopic analysis (UV-Vis) to observe plasmon resonance shifts.
• Scattering measurements on individual core-shell nanostructures.
• Theoretical modeling using quasistatic theory and numerical simulations.

Main Results:

• Observed a distinct plasmonic percolation phenomenon in Au-Pd core-shell nanostructures.
• A red-to-blue shift in plasmon resonance occurred as palladium volume fraction approached ~70%.
• Plasmonic percolation was linked to a transition in the real part of the shell's dielectric function.
• The effect was independent of the specific metal used in the shell.
• Core-shell structures showed enhanced refractive index sensitivity compared to bare gold nanorods.

Conclusions:

• Plasmonic percolation is a viable phenomenon in nanoscale core-shell systems.
• The dielectric properties of the shell play a critical role in inducing plasmonic percolation.
• Au-Pd core-shell nanostructures offer potential for enhanced sensing applications due to increased refractive index sensitivity.