Tip-Enhanced Raman Imaging and Nanospectroscopy: Sensitivity, Symmetry, and Selection Rules

Abstract

The fundamental mechanisms of tipenhanced Raman spectroscopy (TERS) have been investigated, including the role of the plasmonic excitation of the metallic tips, the nature of the optical tip-sample coupling, and the resulting local-field enhancement and confinement responsible for ultrahigh resolution imaging down to just several nanometers. Criteria for the distinction of near-field signature from far-field imaging artifacts are addressed. TERS results of molecules are presented. With enhancement factors as high as 10 9 , single-molecule spectroscopy is demonstrated. Spatially resolved vibrational mapping of crystalline nanostructures and determination of crystallographic orientation and domains is discussed making use of the symmetry properties of the tip scattering response and the intrinsic Raman selection rules.

Tip-enhanced Raman spectroscopy: principles and applications

“…Electrochemical etching methods have been implemented by different research groups to obtain sharp and smooth metal tips [38][39][40]. For example, in the electrochemical etching of gold tips, a gold wire acts as the anode and a second electrode (gold or platinum) acts as the cathode (as shown schematically in Fig.…”

“…Williams and D. Roy [38,39] used hydrochloric acid as the etchant for etching gold wires according to the following equations…”

Tip enhanced Raman scattering: plasmonic enhancements for nanoscale chemical analysis

“…TERS has also been used for nano-crystallography [102,103]. Many crystalline materials present interesting challenges associated with the large far-field signal observed.…”

Gold Nanoparticles as Probes for Nano-Raman Spectroscopy: Preliminary Experimental Results and Modeling

“…As underlined above, particular optical properties of noble metals can significantly increase Raman scattering. There is a large variety of technical possibilities to elaborate metallic probes and several report efficient probes for TERS spectroscopy [19,[34][35][36][37]. The most frequently used are the electrochemical etching of solid metal rods and the thermal evaporation technique to deposit metal on sharp tips.…”