Quantitative evaluation of electromagnetic enhancement in surface-enhanced resonance Raman scattering from plasmonic properties and morphologies of individual Ag nanostructures

Abstract

The electromagnetic ͑EM͒ enhancement in surface-enhanced resonance Raman scattering ͑SERRS͒ is quantitatively evaluated for rhodamine molecules adsorbed on Ag nanostructures. Polarization dependence of the plasma resonance ͑plasmon resonance͒ and the SERRS spectra from single isolated Ag nanostructures was evaluated to determine one-to-one relationship between optical anisotropy of plasma resonance, that of SERRS, and the morphology of the nanostructures. Experimental observations were compared with finitedifference time-domain calculations of the EM field induced by plasma resonance using individual morphology of the nanostructures. The experimental enhancement factor of SERRS ϳ10 9 was consistent with that of the calculations within a factor of ϳ2 for three excitation wavelengths. We conclusively fortify the indispensible importance of SERRS-EM theory with our results to design metal nanostructures generating strong EM enhancement.

Analysis of Blinking SERS by a Power Law with an Exponential Function

“…A similar interference pattern appears despite changing the mesh sizes in the FDTD calculations [17,18]. The metastable state in the optical trapping potential well due to the periodic EM field may not be strong enough to emit SERS light, because the optical trapping potential and the SERS enhancement factor are proportional to the square and fourth power of the EM field, respectively, because of twofold enhancement of SERS [63,64,73].…”

“…In the case of amorphous carbon formed by photo-and thermo-degradation, sharp peaks are observed at random [47][48][49][50][51][52]. In this case, however, it was thought that the heat of the molecule adsorbed on the junction because of the enhanced EM field is quickly transferred to the Ag nanoaggregate [62,63]. Indeed, the anti-Stokes to Stokes intensity ratios for the SERS peaks were estimated not by a Boltzmann distribution at high temperature, but by the selective enhancement of the SERS peaks that are close to the LSPR band [64].…”

Recent progress and frontiers in the electromagnetic mechanism of surface-enhanced Raman scattering

“…The prediction is then confirmed by experiments using a silver colloidal solution along with an aqueous solution of rhodamine 6G (R6G) dye molecules. Yoshida et al experimentally validated the EM enhancement in SERS [32]. They compared with the plasmonic properties of the silver NP aggregates and SERS spectra of R6G molecules individually detected from each NP aggregate, then found the results conclusively demonstrated the indispensable effect of the EM mechanism in SERS ( Fig.…”

“…Currently, the simplest and most successful theory for the EM mechanism of SERS comprises the two-fold EM enhancement by plasmons [22,23,28,32]. As described in Section 2.1, the study of the EM enhancement mechanism was dramatically advanced with the discovery of the single-molecule (SM) SERS condition; thus, Reprinted from Ref.…”

“…They also indicated that the EM mechanism is critical in the case of R6G molecules between silver nano-crevasses, i.e., hotspots, in SM-SERS systems. This study verified a simple expression for the EM enhancement, called the "two-fold EM mechanism" [32]. A detailed description of the twofold EM mechanism is provided herein, in Section 2.2.…”