Surface-Enhanced Raman Spectroscopy (SERS)

In 1974 Fleischmann et al. observed a strong enhancement of Raman scattering when molecules were in contact or proximity to the surface of nanostructured coin metal surfaces. The “Surface-Enhanced Raman Scattering” (SERS) has attracted significant attention in many scientific research fields as a powerful spectroscopic tool and has been the subject of extensive research since then. This chapter will give an overview about applications of SERS but will also focus on the investigation of the contributions to the SE effect. Different techniques will be introduced including special arrangements like the so-called Kretschmann setup. In the discussion of the fundamentals of SERS, two main mechanisms play an important role, electromagnetic and chemical enhancement. These mechanisms have been studied by many researchers where most concentrated on the electromagnetic mechanism. The main goal was obtaining a bigger enhancement factor and several groups have reported high enhancement ratios, reaching up to 1012. The chemical or electronic SE mechanism on the other hand still is not completely understood. However, its contribution to SERS must not be neglected since it is based on a direct coupling between the electronic systems of metal and chemisorbed molecules, which results in changes of the Raman spectral features. The chapter will discuss results obtained from investigations of this mechanism. The results summarized in this chapter will help to use SERS as a reliable and robust tool in modern science.