Exhibition on Lasers, Optics & Photonics

Surface Enhanced Spectroscopy (SES)

Surface-enhanced Raman scattering (SERS) or Surface-enhanced Raman spectroscopy is a surface sensitive technique which enhances Raman scattering by the molecules adsorbed on the rough metal surfaces or by the nanostructures such as plasmonic magnetic silica nanotubes and the enhancement factor can be as much as 1010 to 1011, which means the technique may detect single molecules. The mechanism of enhancement effect of SERS is a matter of debate in the literature. There are two primary theories and their mechanisms differ substantially, distinguishing them experimentally has not been forthright. The electromagnetic theory recommends the excitation of localized surface Plasmon’s, and then the chemical theory recommends the formation of charge transfer complexes. The chemical theory applies only for the species that have formed a chemical bond with surface. So it cannot explain the observed signal enhancement in all the cases, whereas electromagnetic theory can put on even in those cases where the specimen is physically absorbed only to the surface. It has been shown lately that SERS enhancement can occur even when excited molecule is relatively far apart from the surface which swarms metallic nanoparticles enabling surface Plasmon phenomena.