Dielectric Medium Effects on Collective Surface Plasmon Coupling Interactions in Oligothiophene-Linked Gold Nanoparticles

The near-field coupling interactions between surface plasmon modes of neighboring metal nanoparticles (NPs) are investigated in thin films of oligothiophene-linked Au NPs. The oligothiophene linker facilitates near-field coupling between adjacent NPs, and disruption of the conjugation in the oligothiophene by chemical oxidation leads to a decrease in surface plasmon resonance (SPR) coupling between neighboring particles. The SPR coupling between NPs was found to be highly dependent on the dielectric constant of the medium that the films are exposed to, where a higher dielectric medium leads to weaker coupling. The dependence of the SPR coupling on the dielectric constant of the medium is explained using electrodynamic theory.