Optical properties of a metalo-dielectric nanocomposite: small gold spherical nanoparticles in a cylindrical di-block copolymer

Abstract

In this paper, the well-known effective medium approximation (EMA) and coupled dipole approximation (CDA) methods are employed to study the optical properties of a metal nanoparticle-block copolymer (MNP-BCP) nanocomposite. This approach is applied to study a system consisting of small gold spherical nanoparticles randomly distributed in the cylindrical micelles of a di-BCP. At first, the EMA method is used to obtain the effective dielectric function of a semi-metallic cylinder. Then, the extinction spectrum of the hexagonal 2D-array of semi-metallic cylinders is obtained by the CDA method. This procedure makes it possible to study simultaneously both the electromagnetic extinction of MNPs and incident light scattering from the 2D-array of polymeric cylinders. This work investigates the effect of different parameters such as filling fraction of MNPs, inter-cylinder distances, polarization and direction of the incident light and the difference between the refractive indices of the BCP blocks on the optical properties of the MNP-BCP nanocomposite system.