Correlated Rod-like Nanostructures: One Rule to Rule Them All

Abstract

Plasmonic aspects of anisotropic nanostructures have been a subject of considerable interest over the proposition of electromagnetic scattering theories in the past century. Since an accurate description is not possible in the polar coordinates, Gans modified Mie scattering theory for metal spheres assuming the shape of a rod-like scatterer as an approximated case of infinitely elongated ellipsoid (R ≪ L) so that the contributions of end-caps can be neglected. Due to prudent sophistication in the nanoscale synthetic strategies, a plethora of correlated rod-like nanostructures with diverse end-cap geometries have been synthesized. Experimental measurements have elucidated that a seemingly minor change in end-cap morphology of the nanorods imbues distinctly different optical characteristics; therefore, the consideration of adequate contributions is obvious to the electromagnetic modeling of realistic geometry of the nanorods. Since the basic philosophy of science is to dissect similar observations into diverse magnification, we focus to enumerate the pragmatic change in shape toward scattering characteristics employing topology as a general description of the realistic rod-like nanostructures. Two widely different structures, nanodumbbells (extreme case of dogbone-like nanorods) and nanobars have been considered as the two extremities of rod-like geometries. The geometries have been described through proper functional assignment of their shape functions that have been adopted for electromagnetic simulations. These methodologies lead to achieve a general solution to substantiate the observed plasmonic response of the realistic rod-like nanostructures.