Electromagnetic enhancement spectra of one-dimensional plasmonic hotspots along silver nanowire dimer derived via surface-enhanced fluorescence

Tamitake Itoh; Yuko S Yamamoto

doi:10.1063/5.0179985

Electromagnetic enhancement spectra of one-dimensional plasmonic hotspots along silver nanowire dimer derived via surface-enhanced fluorescence

J Chem Phys. 2024 Jan 14;160(2):024703. doi: 10.1063/5.0179985.

Authors

Tamitake Itoh¹, Yuko S Yamamoto²

Affiliations

¹ Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Takamatsu, Kagawa 761-0395, Japan.
² School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), Nomi, Ishikawa 923-1292, Japan.

PMID: 38189611
DOI: 10.1063/5.0179985

Abstract

We developed a spectroscopic method for directly obtaining the spectra of electromagnetic (EM) enhancement of plasmonic hotspots (HSs). The method was applied to one-dimensional (1D) HSs generated between silver nanowire (NW) dimers. The EM enhancement spectra were derived by dividing the spectra of surface-enhanced fluorescence (SEF) from single NW dimers with SEF obtained from large nanoparticle aggregates, where aggregate-by-aggregate variations in the SEF 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 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.