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Electromagnetic interactions of dye molecules surrounding a nanosphere

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journal contribution
posted on 15.07.2020 by Baptiste Auguié, Brendan Darby, Eric Le Ru
Enhanced interaction between light and molecules adsorbed on metallic nanoparticles is a cornerstone of plasmonics and surface-enhanced spectroscopies. Recent experimental access to the electronic absorption spectrum of dye molecules on silver colloids at low molecular coverage has revealed subtle changes in the spectral shape that may be attributed to a combination of factors, from a chemical modification of the molecule in contact with a metal surface to electromagnetic dye–dye and dye–metal interactions. Here we develop an original model to rigorously address the electromagnetic effects. The dye molecules are described as coupled anisotropic polarisable dipoles and their interaction with the core metal particle is described using a generalised Mie theory. The theory is readily amenable to numerical implementation and yields far-field optical cross-sections that can be compared to experimental results. We apply this model to specific adsorption geometries of practical interest to highlight the effect of molecular orientation on predicted spectral shifts and enhancement factors, as a function of surface coverage. These are compared to experimental results and reproduce the measured spectral changes as a function of concentration. These results have direct implications for the interpretation of surface selection rules and enhancement factors in surface-enhanced spectroscopies, and of orientation and coverage effects in molecular/plasmonic resonance coupling experiments.

History

Preferred citation

(2019). Electromagnetic interactions of dye molecules surrounding a nanosphere. Nanoscale, 11(25), 12177-12187. https://doi.org/10.1039/C9NR01304K

Journal title

Nanoscale

Volume

11

Issue

25

Publication date

01/01/2019

Pagination

12177-12187

Publisher

The Royal Society of Chemistry

Publication status

Published

Online publication date

01/01/2019

ISSN

2040-3364

eISSN

2040-3372

Language

en

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