Numerical Study of Coupling Effect on the Optical Properties of Two Assembled Gold Nanorods Coated with Stimuli-Responsive Polymers

Abstract

Grafting stimuli-responsive polymers to gold nanorods (GNRs) is a convenient way to render them responsive to changes in environmental conditions such as pH and temperature. With a water-soluble polymer ligand tethered to the surface of GNRs, a stable dispersion in water can be obtained. Recent studies found that if the polymer chains become insoluble due to either a temperature change or a pH change, aggregation of GNRs can occur, resulting in a reduced optical transmittance of the solution and a shift of the surface plasmon resonance (SPR) mainly as a result of closer distances between the surfaces of GNRs. In this paper a model based on the finite element method (FEM) is developed to investigate the optical properties of GNRs dimer coated with stimuli-responsive polymeric shells. The study is performed for various possible configurations of two core/shell GNRs when they are aggregating in dielectric medium, to know; the side-to-side (parallel-shape) and end-to-end association. The numerical results that we have obtained show that the absorption spectrum of assembled GNRs is depending on the: polymer shell thickness, its dielectric permittivity and aspect ratio of the gold core nanorods.