A New Coupling Mechanism of Gold and Silver Nanoparticles at Short Separation Distances in Their Hvbrid-Dimers

Abstract

Using theoretical calculation, we investigated near-field coupling properties changes between two excited Au and Ag 35 nm nanoparticles in a face-to-face hybrid dimer configuration at different separation distances. A detailed calculation of the near-field coupling behavior strongly suggests that a new plasmon mode generated as the departure distance below 4 nm. The reason is that the plasmonic field distributions of the pair of Au and Ag nanoparticles separated by distances smaller than 4 nm, resulting in the electrostatic coupling between the oscillating dipoles at the adjacent facets of the nanoparticles. At separations larger than 4 nm, the distributions of the plasmonic dipoles along the facets of the adj acent monomers control the plasmonic spectra and the distance dependent optical properties of the dimer, which obey the noted “plasmon ruler equation”. The research paved the road for study the hybrid NPs coupling even the utilizing of the plasmonic NPs in cancer therapeutics, biological thermal-imaging and sensing.