Understanding the SERS Effects of Single Silver Nanoparticles and Their Dimers, One at a Time

This Perspective article highlights recent development in a class of surface-enhanced Raman scattering (SERS) experiments that aim to correlate SERS enhancement factors with the physical parameters of metal nanostructures. In a typical study, the SERS substrate is fabricated by depositing colloidal nanoparticles on a silicon wafer, to obtain individual particles isolated from each other or small aggregates such as dimeric units. With the help of registration marks, the same nanoparticle, or dimer of nanoparticles, can be quickly located under a Raman microscope (for SERS spectra) and a scanning electron microscope (for structural characterization). The nanoscale characterization achieved by these,studies has, resulted in unparalleled investigations into the nature of polarization dependency for SERS, the hot. spot nature of single nanoparticles and dimers, and the manipulation Of hot spots through shape-controlled synthesis and self-assembly;. We discuss the new insights that these studies have offered and the future progress that they can deliver to the advancement of SERS.