Spatial, Spectral, and Coherence Mapping of Single-Molecule SERS Active Hot Spots via the Discrete-Dipole Approximation

摘要: The electromagnetic scattering properties of Ag nanoparticle aggregates known to be antennas for single-molecule surface-enhanced Raman are investigated from a continuum electrodynamics perspective. High-resolution mappings the spatial, spectral, and polarization dependence volumes aggregate’s hot spots reveal multiple active regions enhanced activity by molecular chromophores. Further analysis these using maps surface-charge density shows that some due collective phase-coherent excitation localized surface-plasmon resonances, whereas others derive interfering plasmonic excitations resulting gaps surfaces. latter still capable generating intense local fields at certain energies, former tend provide most spatially delocalized high electromagnetic-field strength.