Electromagnetic enhancement of one-dimensional plasmonic hotspots along silver nanowire dimer examined by ultrafast surface enhanced fluorescence

Abstract

We investigated the spectral properties of electromagnetic (EM) enhancement of one-dimensional hotspots (1D HSs) generated between silver nanowire (NW) dimers. The EM enhancement spectra were directly derived by dividing the spectra of ultrafast surface-enhanced fluorescence (UFSEF) from single NW dimers with UFSEF obtained from large nanoparticle aggregates, which aggregate-by-aggregate variations in the UFSEF spectra were averaged out. Some NW dimers were found to exhibit EM enhancement spectra that deviated from the plasmon resonance Rayleigh scattering spectra, indicating that their EM enhancement was not generated by superradiant plasmons. These experimental results were examined by numerical calculation based on the EM mechanism by varying the morphology of the NW dimers. The calculations reproduced the spectral deviations as the NW diameter dependence of EM enhancement. Phase analysis of the enhanced EM near fields along the 1D HSs revealed that the dipole-quadrupole coupled plasmon, which is a subradiant mode, mainly generates EM enhancement for dimers with NW diameters larger than ~80 nm, which was consistent with scanning electron microscopic measurements.

46 pages, 10 figures

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• Surface-enhanced Raman scattering and fluorescence near metal nanoparticles
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Cited by in corpus (3)

• Plasmon-enhanced two photon excited emission from edges of one-dimensional plasmonic hotspots with continuous-wave laser excitation
• Ultrabroad resonance of localized plasmon on a nanoparticle coupled with surface plasmon on a nanowire enabling two-photon excited emission via continuous-wave laser
• Electromagnetic coupling between subradiant plasmons and dye molecular excitons analyzed by spectral changes in ultrafast surface-enhanced fluorescence