Selective Functionalization of the Nanogap of a Plasmonic Dimer

We report a self-developing anisotropic gold/polymer hybrid nanosystem that precisely places dye molecules at the plasmonic hotspot of metal nanostructures for sensing and photonics applications. Unlike conventional molecule–particle configurations, the anisotropic hybrid nanosystem (AHN) introduces an anisotropic spatial distribution of dye-containing active medium. This allows us to precisely overlap the near-field spatial distribution with the active medium and rule out the contribution from the background molecules. This overlap effect selectively highlights the optical response of the molecules of interest, that is, molecules located at the hotspots. Our AHN consists of gold nanodimers whose gaps have been filled with methylene blue molecules. They have been studied by plasmon-enhanced Raman spectroscopy as a probing tool. The AHN opens new doors not only for fundamental studies and photonics applications of molecule–particle interactions, but also for molecular trapping methods at the nanoscale.