Single-Molecule Super-Resolution Microscopy Reveals How Light Couples to a Plasmonic Nanoantenna on the Nanometer Scale

The greatly enhanced fields near metal nanoparticles have demonstrated remarkable optical properties and are promising for applications from solar energy to biosensing. However, direct experimental study of these light-matter interactions at the nanoscale has remained difficult due to the limitations of optical microscopy. Here, we use single-molecule fluorescence imaging to probe how a plasmonic nanoantenna modifies the fluorescence emission from a dipole emitter. We show that the apparent fluorophore emission position is strongly shifted upon coupling to an antenna and that the emission of dyes located up to 90 nm away is affected by this coupling. To predict this long-ranged effect, we present a framework based on a distance-dependent partial coupling of the dye emission to the antenna. Our direct interpretation of these light-matter interactions will enable more predictably optimized, designed, and controlled plasmonic devices and will permit reliable plasmon-enhanced single-molecule nanoscopy.