Single-molecule fluorescence is a powerful tool for imaging structures below the standard diffraction limit of light. The resolution gain comes from fitting the emission of isolated fluorophores, and localization accuracy improves with
number of photons detected. Here, we control single-molecule emission by coupling fluorescence to gold nanoparticle local plasmon resonances. These strongly localized electromagnetic modes are generated by the interaction of light with particles smaller than the incident wavelength. We discuss the effects of this plasmonic mode coupling on the fluorescence intensity and lifetime of dye molecules and quantum dots.
In this work, we use evaporated gold nanoparticle films (GNPFs) as substrates for plasmon-enhanced imaging of two fluorescent proteins (FPs): mCherry and YFP. Through single-molecule epifluorescence microscopy, we show enhancement of single FP emission in the presence of GNPFs. The gold-coupled FPs demonstrate emission up to four times brighter and seven times longer lived, yielding order-of-magnitude enhancements in total photons detected. Ultimately, this results in increased localization accuracies for single-molecule imaging. Furthermore, we introduce preliminary results for enhancement of mCherry-labeled TcpP membrane proteins inside live Vibrio cholerae cells coupled to GNPFs. Our work indicates that plasmonic substrates are uniquely advantageous for super-resolution imaging and that plasmon-enhanced imaging is a promising technique for improving live cell single-molecule microscopy.