ABSTRACT
Surface-enhanced Raman scattering (SERS) was first observed in1974 by Fleischmann et al. for pyridine, C5NH5, adsorbed on a silver electrode roughened by means of successive oxidation-reduction cycles. Combining SERS experiments and theoretically obtained electromagnetic (EM) field distribution around metal surfaces, the EM effect has been recognized as the dominating factor contributing to SERS in most cases, compared to the additional about 102 chemical enhancement. In the year 1997, Nie and Emory and Kneipp et al. reported SERS enhancement as large as 1014 in the experiments for single-molecule SERS. The numerical simulations confirm that the EM enhancement in the nanogaps of nanoparticle dimers can be extraordinarily high and dominate among the factors contributing to single-molecule SERS. The high EM enhancement in the nanogap between the nanowire and the nanoparticle renders single-molecule SERS to be achieved remotely from the laser illumination point.
