Probing local electromagnetic field enhancements on the surface of plasmonic nanoparticles

Noble metal nanoparticles have attracted significant research interest due to their ability to support localized surface plasmons. Plasmons not only give the nanoparticles a characteristic color, but they also enhance electromagnetic fields at the nanoparticle surface, often by many orders of magnitude. The enhanced electromagnetic fields are the basis for a host of surface-enhanced spectroscopies, such as surface-enhanced Raman scattering (SERS), but characterizing how the enhanced electromagnetic fields are distributed on the surface of the nanoparticles is an experimental challenge due to the small size of the nanoparticles (∼20-200 nm) relative to the diffraction limit of light. This Progress Highlight will discuss methods for characterizing local electromagnetic field enhancements with < 5 nm resolution, including electron energy loss spectroscopy, cathodoluminescence, and super-resolution optical imaging.