Recent advances on plasmonic nanocavities for single-molecule spectroscopy

Plasmonic nanocavities are able to engineer and confine electromagnetic fields into subwavelength volumes. In the past decade, they have enabled a large set of applications, in particular for sensing, optical trapping, as well as the investigation of physical and chemical phenomena at a few or single-molecule levels. This extreme sensitivity is possible thanks to the highly confined local field intensity enhancement, which depends on the geometry of the plasmonic nanocavities. Indeed, properly designed structures providing engineered local optical fields lead to enhanced optical sensing based on different phenomena like surface enhanced Raman scattering, fluorescence, and Förster Resonant Energy Transfer. In this mini-review, we illustrate the most recent results on plasmonic nanocavities, with specific emphasis on the detection of single molecules.