Contribution of Subradiant Plasmon Resonance to Electromagnetic Enhancement in Resonant Raman with Fluorescence Examined by Single Silver Nanoparticle Dimers

We investigate the spectral relationships between electromagnetic (EM) enhancement and surface-enhanced resonant Raman scattering (SERRS) with surface-enhanced fluorescence (SEF), which is observed as background emission of SERRS, in the context of light-matter interactions between subradiant plasmons and molecular excitons, using single silver nanoparticle dimers as a model system. We focus on the lowest-energy (superradiant) plasmon in far-field scattering to examine EM enhancement. We classify the spectral relationships into two types: those in which the spectral envelopes of SERRS with SEF have spectral shapes similar to those of plasmon resonance and those in which the spectral envelopes of SERRS with SEF exhibit higher energy shifts than the plasmon resonance. By examining these results, we aim to determine the degree of morphological asymmetry in the dimers based on an EM mechanism. Our analysis of the two types of spectral relationships reveals that dipole-dipole and dipole-quadrupole-coupled plasmon resonance (subradiant resonance) are responsible for EM enhancement.

Automated summary

In this study, we investigate the spectral relationships between electromagnetic enhancement, surface-enhanced resonant Raman scattering (SERRS), and surface-enhanced fluorescence (SEF) by using single silver nanoparticle dimers as a model system. We focus on the lowest-energy plasmon in far-field scattering and classify the spectral relationships into two types. Based on our analysis, we find that dipole-dipole and dipole-quadrupole-coupled plasmon resonance are responsible for the electromagnetic enhancement.