Shifting of surface plasmon resonance due to electromagnetic coupling between graphene and Au nanoparticles

TL;DR

This study investigates how the surface plasmon resonance wavelength shifts due to electromagnetic coupling between graphene and gold nanoparticles, revealing a complex behavior with initial blue shift, subsequent red shift, and saturation.

Contribution

It provides new insights into the tunability of plasmon resonance via spacer thickness, combining experimental results with the plasmon ruler model.

Findings

Blue shift of 29 nm with spacer increase from 0 to 15 nm

Red shift of 17 nm when spacer exceeds 20 nm

Coupling strength decays exponentially with spacer thickness

Abstract

Shifting of the surface plasmon resonance wavelength induced by the variation of the thickness of insulating spacer between single layer graphene and Au nanoparticles is studied. The system demonstrates a blue shift of 29 nm as the thickness of the spacer layer increases from 0 to 15 nm. This is due to the electromagnetic coupling between the localized surface plasmons excited in the nanoparticles and the graphene film. The strength of the coupling decays exponentially with a decay length of d/R=0.36, where d is the spacer layer thickness and R is the diameter of the Au nanoparticles. The result agrees qualitatively well with the plasmon ruler equation. Interestingly, a further increment of the spacer layer thickness induces a red shift of 17 nm in the resonance wavelength and the shift saturates when the thickness of the spacer layer increases above 20 nm.