Surface-Enhanced Raman Excitation Spectroscopy: An Overview

In this chapter, we described the SERS and enhancement mechanisms very briefly in the introduction part. Further Surface-enhanced Raman excitation spectroscopy is defined and next the instrumentation and sampling for experiments are described. Surface-enhanced Raman excitation spectroscopy is basically by definition to trace the profile of the intensity of a particular Raman band in SERS excited with the different excitation wavelengths obtained by a tunable laser source. This profile generally provides the extinction spectrum of complex structures (adsorbed molecules on the SERS substrate). In the foremost section of the chapter, various examples of surface-enhanced Raman excitation profiles (SEREP) are discussed along with corresponding conclusions. In SEREPs examples, mainly plasmon-scanned excitation profiles (PSEPs), and wavelength-scanned excitation profiles (WSEPs) are discussed. In PSEPs, the intensity (or intensity ratio wrt to a reference) of SERS bands versus plasmon wavelengths or cluster size of nanoparticles have explained and shown that the electromagnetic model is suitable for the trend of enhancement of Raman bands in SERS and also shown that the maximum contribution of enhancement is due to electromagnetic enchantment. In wavelength-scanned excitation profiles (WSEPs), the intensity (or intensity ratio wrt to a reference) of SERS bands versus excitation wavelengths for SERS have been explained. The excitation profile of SERS is very precise about information that what extent of the particular enhancement mechanisms e.g. electromagnetic (LSPR), charger-transfer resonance, and molecular electronic resonance are involved and how these play the roles effectively in the enhancement of Raman bands in SERS.