Super-Resolving the Actual Position of Single Fluorescent Molecules Coupled to a Plasmonic Nanoantenna

Plasmonic nanoparticles (NPs) enhance the radiative decay rate of adjacent dyes and can significantly increase fluorescence intensity for improved spectroscopy. However, the NP nanoantenna complicates super-resolution imaging by introducing a mislocalization between the emitter position and its super-resolved emission position. The mislocalization magnitude depends strongly on the dye/NP coupling geometry. It is therefore crucial to quantify mislocalization to recover the actual emitter position in a coupled system. Here, we super-resolve in two and three dimensions the distance-dependent emission mislocalization of single fluorescent molecules coupled to gold NPs with precise distance tuning via double-stranded DNA. We develop an analytical framework to uncover detailed spatial information when direct 3D imaging is not accessible. Overall, we demonstrate that by taking measurements on a single, well-defined, and symmetric dye/NP assembly and by accounting explicitly for artifacts from super-resolution imaging, we can measure the true nanophotonic mislocalization. We measure up to 50 nm mislocalizations and show that smaller separation distances lead to larger mislocalizations, also verified by electromagnetic calculations. Overall, by quantifying the distance-dependent mislocalization shift in this gold NP/dye coupled system, we show that the actual physical position of a coupled single emitter can be recovered.