Long-Range Surface Plasmon Field-Enhanced Raman Scattering Spectroscopy Based on Evanescent Field Excitation

Abstract

The purpose of this paper is to enhance Raman signals in the evanescent field by using the excitation of long-range surface plasmons (LRSPs). A four-phase Kretschmann LRSP resonance (LRSPR) setup composed of a K9 prism/MgF₂ film/silver film/water configuration was constructed. Incident angle-dependent surface-enhanced Raman scattering (SERS) spectra were measured in the evanescent field on this four-phase configuration. The SERS signal obtained under the evanescent field excitation at the LRSPR angle was 15 times higher than that collected based on the conventional SPR configuration. The experimental result also proved that the LRSPs in this evanescent field-enhanced SERS spectroscopy possessed at least 500 nm in the electric field penetration depth, which is longer than the electric field penetration depth of conventional surface plasmons