Particle Size-Dependent Onset of the Tunneling Regime in Ideal Dimers of Gold Nanospheres.

We report on the nanoparticle-size-dependent onset of quantum tunneling of electrons across the subnanometer gaps in three different sizes (30, 50, and 80 nm) of highly uniform gold nanosphere (AuNS) dimers. For precision plasmonics, the gap distance is systematically controlled at the level of single C-C bonds via a series of alkanedithiol linkers (C-C). Parallax-corrected high-resolution transmission electron microscope (HRTEM) imaging and subsequent tomographic reconstruction are employed to resolve the nm to subnm interparticle gap distances in AuNS dimers.