Finite Element Investigation of the Plasmonic Properties of Hexagonally Arranged Gold Nanoparticles

In this work, a localized surface plasmon resonance (LSPR) sensor based on hexagonally arranged ellipsoidal gold nanoparticles is designed and investigated by finite element method (FEM) via COMSOL Multiphysics. The wave optics module was used to investigate the relationship between the geometrical properties of the nanoparticle arrangement and their refractive index sensitivity. Three different particle arrangements with different interparticle distances between the hexagonally arranged ellipsoidal nanoparticles were investigated, all with periodic and nonperiodic boundary conditions as well. The latter results were compared with boundary element method (BEM) simulations, performed with the MNPBEM Matlab Toolbox. Although the FEM and BEM approaches resulted in well-comparable extinction spectra and bulk refractive index sensitivity values for the non-periodic conditions, applying periodic boundary conditions in the FEM model resulted in consistently lower sensitivities for the investigated arrangements.