Chiral R aman and Single Molecule Spectroscopy

Abstract

Abstract Chiral Raman spectroscopy, widely known as Raman optical activity (ROA) , is a vibrational tool, which besides information on structure and folding of molecules, provides information on their chirality. This tool has been employed since the early 1970 s; however, it has been limited to very few groups within the vibrational spectroscopy community, because using this tool several requirements for the instrumentation as well as the sample condition and detection have to be fulfilled. Although the first requirement concerns full control of the polarization state of the light, simultaneously for the right‐ and left‐circular polarization states, the latter requirement concerns high concentration of the sample. Consequently and because of the signal collection involving subtraction of the left‐ and right scattered light, the ROA signal is much weaker than the Raman, thus requires much longer acquisition times. After the discovery of the surface‐enhanced Raman scattering (SERS) effect in 1974, the hope of combining SERS with ROA (into surface‐enhanced Raman optical activity (SEROA)) grew high, in that the giant signal provided by SERS was thought to enable much faster ROA measurements and for much lower concentration, even down to the single molecule level. Nevertheless, three decades passed before SEROA studies began to appear in the literature. In spite of the fact that these studies are not yet at the single molecule level, they do provide SEROA from very low concentration (below μM). Here, we introduce SEROA's historical background, theory, instrumentation, and the recent results, achieved by the authors' research groups.