Are Hot Spots between Two Plasmonic Nanocubes of Silver or Gold Formed between Adjacent Corners or Adjacent Facets? A DDA Examination.

Of all the plasmonic solid nanoparticles, single Ag or Au nanocubes are known to be plasmonic nanoparticles with strong plasmonic fields, which are concentrated around their corners. However, when nanoparticles aggregate, they do so in a face-to face arrangement. The formation of hot spots between plasmonic nanoparticles in close proximity to each other is known to greatly enhance their plasmonic fields which are important in the field of imaging. Thus, what is the structural development of hot spots between two nanocubes in a dimer? Do they form between the corners or are they between the adjacent facets, and what does this depend on? A detailed discrete dipole approximation (DDA) simulation of Au-Au and Ag-Ag dimers suggests that there is a competition between their formation in these two locations, which depends on the polarization direction of the exciting light (with respect to the interparticle axis in the dimer), its intensity and the wavelength as well as the interparticle separation of the dimer.