Ground state depletion microscopy for imaging interactions between gold nanowires and fluorophore-labeled ligands.

Ground state depletion with individual molecule return (GSDIM) is used to interrogate the location of individual fluorescence bursts from fluorophore-labelled DNA molecules on gold nanowire surfaces. Carboxytetramethyl rhodamine (TAMRA)-labelled double-stranded DNA molecules were bound to the surface of gold nanowires via gold-thiol linkages. Individual fluorescence bursts were spatially localized using point spread function fitting and used to reconstruct the image of the underlying nanowire. While the reconstructed images reproduce the size and shape of the nanowire structures, plasmonic coupling between the nanowire and fluorophore is observed, indicating that the location of the observed fluorescence may not precisely correlate with the location of the emitting fluorophore. Thus, plasmonic coupling is an important factor when using super-resolution imaging techniques to study plasmonic nanostructures.