Surface plasmon coupling between wide-field SPR microscopy and gold nanoparticles

Area of Science:

• Nanophotonics
• Plasmonics
• Optical Microscopy

Background:

• Surface plasmon resonance (SPR) is crucial for sensing and imaging.
• Gold nanoparticles (AuNPs) exhibit unique optical properties due to SPR.
• Wide field surface plasmon microscopy (WF-SPRM) enables visualization of plasmonic phenomena.

Purpose of the Study:

• Investigate the coupling behavior of WF-SPRM with single, two, and multiple gold nanoparticles (AuNPs) of varying sizes.
• Understand the signal intensity dependence on AuNP size and interparticle interactions.
• Validate theoretical models with experimental WF-SPRM data.

Main Methods:

• Theoretical calculations and numerical simulations (finite element method).
• Experimental investigations using WF-SPRM.
• Analysis of Rayleigh scattering theory and discrete particle models for SPR.
• Application of Maxwell-Garnet equations for effective media representation.

Main Results:

• Signal intensity of single AuNPs increases with size (40-80 nm), consistent with Rayleigh scattering.
• A discrete particle model accurately predicts single AuNP intensity profiles.
• Superposition of surface plasmon waves from two AuNPs creates observable interference patterns.
• Plasmonic scattering from multiple AuNPs can be modeled as an effective medium.

Conclusions:

• WF-SPRM effectively characterizes plasmonic coupling in AuNPs.
• Particle size and arrangement significantly influence plasmonic interactions and scattering.
• Theoretical and simulation models provide accurate predictions of experimental observations.
• The effective medium approximation is suitable for describing multi-particle plasmonic systems.