Correlated Rod-like Nanostructures: One Rule to Rule\nThem All

Abstract

Plasmonic\naspects of anisotropic nanostructures have been a subject\nof considerable interest over the proposition of electromagnetic scattering\ntheories in the past century. Since an accurate description is not\npossible in the polar coordinates, Gans modified Mie scattering theory\nfor metal spheres assuming the shape of a rod-like scatterer as an\napproximated case of infinitely elongated ellipsoid (<i>R</i> ≪ <i>L</i>) so that the contributions of end-caps\ncan be neglected. Due to prudent sophistication in the nanoscale synthetic\nstrategies, a plethora of correlated rod-like nanostructures with\ndiverse end-cap geometries have been synthesized. Experimental measurements\nhave elucidated that a seemingly minor change in end-cap morphology\nof the nanorods imbues distinctly different optical characteristics;\ntherefore, the consideration of adequate contributions is obvious\nto the electromagnetic modeling of realistic geometry of the nanorods.\nSince the basic philosophy of science is to dissect similar observations\ninto diverse magnification, we focus to enumerate the pragmatic change\nin shape toward scattering characteristics employing topology as a\ngeneral description of the realistic rod-like nanostructures. Two\nwidely different structures, nanodumbbells (extreme case of dogbone-like\nnanorods) and nanobars have been considered as the two extremities\nof rod-like geometries. The geometries have been described through\nproper functional assignment of their shape functions that have been\nadopted for electromagnetic simulations. These methodologies lead\nto achieve a general solution to substantiate the observed plasmonic\nresponse of the realistic rod-like nanostructures.