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Simple composite dipole model for the optical modes of strongly-coupled plasmonic nanoparticle aggregates

Simple composite dipole model for the optical modes of strongly-coupled plasmonic nanoparticle aggregates
Simple composite dipole model for the optical modes of strongly-coupled plasmonic nanoparticle aggregates
Self-assembled strongly coupled plasmonic aggregates exhibit optical spectra which show complex plasmonic resonances. To understand the optics of such systems, we introduce an effective composite dipole model extending previous effective models of aggregates into the plasmonic domain. The ingredients in this model are found by comparing the time-resolved extinction of self-assembling growing aggregates of gold nanoparticles spaced by rigid sub-nm gaps to recent rigorous electromagnetic simulations of this geometry. The highly reproducible spectral signatures from experiments match our simulations, confirming that the electromagnetic response of such fractal plasmonic clusters can be well-understood in terms of embedded straight chains of plasmonically coupled nanoparticles surrounded by an optically decoupled halo of dimers. We show how to derive simple analytical formulas that lead to rapid extraction of key parameters from such experimental spectra and which properly account for the long-wavelength lineshapes. In particular, we find these effective parameters describe the extent of plasmon delocalization along such chains, the eccentricity of these optically dominant cores, and the fraction of nanoparticles active within them. This underpins applications which depend on spectral selectivity and field enhancements in such tightly coupled plasmonic systems.
1932-7447
25044-25051
Taylor, Richard W.
14b4e086-50e8-4161-8314-7de98f1ef695
Esteban, Rubén
9c440ac5-9a06-48a1-aae9-53d7dd0ef84a
Mahajan, Sumeet
b131f40a-479e-4432-b662-19d60d4069e9
Coulston, Roger
61f128ea-d9e0-4d7a-b4e8-b28a6776ff70
Scherman, Oren A.
4889711e-5279-4211-b6ae-bbe70846e1ef
Aizpurua, Javier
17705349-38e3-4089-adba-547d02449095
Baumberg, Jeremy J.
51423b5f-bdb8-4851-8d50-472253ceb12c
Taylor, Richard W.
14b4e086-50e8-4161-8314-7de98f1ef695
Esteban, Rubén
9c440ac5-9a06-48a1-aae9-53d7dd0ef84a
Mahajan, Sumeet
b131f40a-479e-4432-b662-19d60d4069e9
Coulston, Roger
61f128ea-d9e0-4d7a-b4e8-b28a6776ff70
Scherman, Oren A.
4889711e-5279-4211-b6ae-bbe70846e1ef
Aizpurua, Javier
17705349-38e3-4089-adba-547d02449095
Baumberg, Jeremy J.
51423b5f-bdb8-4851-8d50-472253ceb12c

Taylor, Richard W., Esteban, Rubén, Mahajan, Sumeet, Coulston, Roger, Scherman, Oren A., Aizpurua, Javier and Baumberg, Jeremy J. (2012) Simple composite dipole model for the optical modes of strongly-coupled plasmonic nanoparticle aggregates. The Journal of Physical Chemistry C, 116 (47), 25044-25051. (doi:10.1021/jp308986c).

Record type: Article

Abstract

Self-assembled strongly coupled plasmonic aggregates exhibit optical spectra which show complex plasmonic resonances. To understand the optics of such systems, we introduce an effective composite dipole model extending previous effective models of aggregates into the plasmonic domain. The ingredients in this model are found by comparing the time-resolved extinction of self-assembling growing aggregates of gold nanoparticles spaced by rigid sub-nm gaps to recent rigorous electromagnetic simulations of this geometry. The highly reproducible spectral signatures from experiments match our simulations, confirming that the electromagnetic response of such fractal plasmonic clusters can be well-understood in terms of embedded straight chains of plasmonically coupled nanoparticles surrounded by an optically decoupled halo of dimers. We show how to derive simple analytical formulas that lead to rapid extraction of key parameters from such experimental spectra and which properly account for the long-wavelength lineshapes. In particular, we find these effective parameters describe the extent of plasmon delocalization along such chains, the eccentricity of these optically dominant cores, and the fraction of nanoparticles active within them. This underpins applications which depend on spectral selectivity and field enhancements in such tightly coupled plasmonic systems.

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More information

Published date: 2 November 2012

Identifiers

Local EPrints ID: 350066
URI: http://eprints.soton.ac.uk/id/eprint/350066
ISSN: 1932-7447
PURE UUID: cf49419e-9445-4376-bc06-f2db41484f23
ORCID for Sumeet Mahajan: ORCID iD orcid.org/0000-0001-8923-6666

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Date deposited: 18 Mar 2013 13:42
Last modified: 09 Nov 2021 03:16

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Contributors

Author: Richard W. Taylor
Author: Rubén Esteban
Author: Sumeet Mahajan ORCID iD
Author: Roger Coulston
Author: Oren A. Scherman
Author: Javier Aizpurua
Author: Jeremy J. Baumberg

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