posted on 2008-04-03, 00:00authored byPrashant K. Jain, Mostafa A. El-Sayed
Recently, we showed that the plasmon resonance coupling between two interacting metal nanoparticles decays
with the interparticle separation (in units of particle size) with the same universal trend independent of particle
size or shape, metal type, or medium. This universal scaling behavior has been shown to apply to
lithographically fabricated nanoparticle pairs, the metal nanoshell, plasmonic dielectric sensors, and the plasmon
ruler useful in determining intersite distances in biological systems. In this article, we use electrodynamic
simulations to examine the general applicability of this universal scaling behavior to more complex nanostructure
geometries, for example, head-to-tail dimers of elongated particles of different aspect ratios and curvatures
and a trimer of nanospheres. We find that the plasmon coupling between two elongated nanoparticles interacting
head-to-tail decays according to the same universal law if the interparticle separation is scaled by the particle
long-axis dimension. The absolute plasmon coupling strength, however, depends on the particle shape (i.e.,
aspect ratio and curvature), without affecting the universal scaling behavior. We also show that universal
scaling is valid in a system of three interacting nanospheres, a first step toward extending this model to
chains/arrays/assemblies of metal nanoparticles.