Pyridine−Ag₂₀Cluster:  A Model System for Studying Surface-Enhanced Raman Scattering

Abstract

This work presents a detailed analysis of enhanced Raman scattering of the pyridine-Ag(20) model system using time-dependent density functional theory. A consistent treatment of both the chemical and electromagnetic enhancements (EM) is achieved by employing a recently developed approach based on a short-time approximation for the Raman cross section. A strong dependence of the absolute and relative intensities on the binding site and excitation wavelength is found. The analysis of the Raman scattering cross sections shows the importance of different contributions to the enhancements, including static chemical enhancements (factor of 10), charge-transfer enhancements (10(3)), and EM enhancements (10(5)). The largest enhancement found (10(5)-10(6)) is due to the EM mechanism, with a small contribution from the chemical interaction. This suggests that the enhanced Raman scattering due to atomic clusters is comparable to findings on single nanoparticles. A combination of information about the vibrational motion and the local chemical environment provides a simple picture of why certain normal modes are enhanced more than others.

Nanowire-supported plasmonic waveguide for remote excitation of surface-enhanced Raman scattering

“…[38][39][40] One of the most promising applications of SPPs, especially localized SPPs, is surface-enhanced Raman scattering (SERS), which has been studied both theoretically and experimentally for many decades. [12][13][14][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] As an optical fingerprint, Raman spectra, which could be used to analyze chemical structures, are widely used in scientific investigations and material analysis. However, as a weak process, the small Raman scattering cross-section makes the detection of a small number of molecules a problem even after the laser power is increased.…”

“…12,52,58 In addition, the charge transfer processes, which are the electronic structure variation of molecules adsorbed on metal surfaces, also play an important role in the SERS effect. [45][46][47][48]54 The area where the highest EM field enhancement is generated in a nanostructure is called a 'hot spot', such as the nanogap between the nanoparticle dimer and the gaps between nanoparticles and wires. The Raman signals in most SERS experiments are obtained at the tiny hot spots.…”

Raman and DFT Study of the Reaction of Hydrazine and Hypophosphite on a Cu Surface in the Electroless Deposition Process

“…5, the surface model was the tetrahedral cluster model made up of 20 Cu atoms. 20 All parameters of adsorbing system are optimized, including the cluster structure and molecular structure. Figure 5 indicates that hydrazine exhibits electrostatic interaction with hypophosphite on the surface.…”

State-by-State Investigation of Destructive Interference in Resonance Raman Spectra of Neutral Tyrosine and the Tyrosinate Anion with the Simplified Sum-over-States Approach

“…To simulate the resonant Raman spectra with a reduced computational burden while obtaining insight into the influence of the electronic structure on the Raman intensities, we utilized the simplified sum-over-states approach that some of us introduced in Rappoport et al 29 [33][34][35][36] and NWCHEM 37 . A similar approach is implemented in Orca.…”