Modelling Core-Shell Plasmonic Nanoparticles as Homogenous Systems: An Effective Refractive Index Approach

Core-shell plasmonic nanoparticles have attracted significant interest for use in a vast number of applications such as optoelectronics, solar energy, and drug delivery. However, modeling core-shell nanoparticles as two distinct regions, namely the core and the shell leads to computational complexity, especially in large systems. Additionally, most metallic plasmonic nanoparticles develop a self-limiting oxide shell, creating in effect, a metal- metal oxide core-shell system. Effective medium theories have emerged as a technique to study core-shell nanoparticles as a single homogenous system. However, current effective medium theories are limited due to their low accuracy, especially for larger core and shell thicknesses (>50nm). Here, we present a novel method that enables accurate representation of core-shell nanoparticles as a homogeneous particle using a single set of refractive indices, for a vast range of core and shell radii, and material compositions; thus allowing for quick and efficient simulations with accuracy similar to that of the analytical solutions obtained based on Mie Theory. We hope that this technique will enable rapid and accurate calculations for core-shell plasmonic applications.