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Determination of the Excitation and Coupling Rates Between Light Emitters and Surface Plasmon Polaritons
Published on: July 21, 2018
Plasmon coupling in nanorod assemblies: optical absorption, discrete dipole approximation simulation, and
Prashant K Jain1, Susie Eustis, Mostafa A El-Sayed
1Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400, USA.
The Journal of Physical Chemistry. B
|September 15, 2006
Summary
Gold nanorod assembly influences plasmon coupling, causing distinct spectral shifts. End-to-end assembly red-shifts the longitudinal plasmon band, while side-by-side assembly blue-shifts it, offering insights into nanostructure interactions.
Area of Science:
- Nanotechnology
- Plasmonics
- Optical Spectroscopy
Background:
- Nanoparticle shape anisotropy dictates assembly modes (end-to-end, side-by-side).
- Previous studies noted red-shifts in end-to-end gold nanorod assembly due to plasmon coupling.
- Understanding plasmon coupling in assembled nanorods is crucial for optical properties and applications.
Purpose of the Study:
- To investigate the distinct optical absorption spectral shifts in gold nanorods assembled side-by-side versus end-to-end.
- To simulate and understand the underlying plasmon coupling mechanisms responsible for these spectral shifts.
- To compare nanorod plasmon coupling with molecular exciton coupling theory.
Main Methods:
- Experimental observation of optical absorption spectra for assembled gold nanorods.
- Numerical simulation of plasmon coupling using the discrete dipole approximation (DDA) method.
- Analysis of spectral shifts in relation to nanorod assembly orientation, distance, aspect ratio, and number.
Main Results:
- Side-by-side assembly induces a blue-shift in the longitudinal plasmon band and a red-shift in the transverse band.
- End-to-end assembly results in a red-shift of the longitudinal plasmon band.
- Plasmon coupling strength increases with decreasing inter-nanorod distance and increasing nanorod number and aspect ratio.
- Simulations of dissimilar aspect ratios or nonparallel orientations lead to dual blue- and red-shifted components in the longitudinal resonance.
Conclusions:
- The observed plasmon coupling behaviors in assembled nanorods are consistent with molecular exciton coupling theory.
- Coupled nanorod plasmons can be viewed as electromagnetic analogs of molecular orbitals.
- Investigating nanorod assembly-induced plasmon coupling aids in characterizing optical excitations and plasmon propagation.
- Surface plasmon resonance shifts from nanorod assembly present opportunities for advanced analyte-sensing assays.
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