Far Field Optical Properties of a Monolayer of SiO2 Spheres and Small Au Nanoparticles

Abstract

Here, we present a numerical study of the far field optical response of a monolayer composed by an hexagonal closed packed array of SiO2 spheres with a single Au NP at each interstitial position. The Optical Efficiencies, Reflection, Transmission and Absorption at normal incidence, were calculated using Discrete Dipole Approximation model extended to periodic targets. In order to consider different amounts of loads of Au NPs per unit of area in the monolayer, we have fixed the diameter of Au NPs (9 nm) and varied the diameter of the SiO2 spheres. The numerical calculations indicate that Au-SiO2 composite monolayers can absorb and scatter the incident electromagnetic wave, as the load of Au NPs increases the monolayer becomes less transparent to light and the spectra are red-shifted. The profile of the absorption spectrum of the Au-SiO2 composite monolayer is very similar to that of a Au NPs monolayer (composite monolayer without the Silica spheres) but less intense, presumably because the Silica spheres screen the coupling of the Localized Surface Plasmons of Au NPs.

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“…Herein, we place attention to DDA's extended version, proposed by Draine and Flatau, for modeling R and T of infinite 2D periodic systems [24]. Recently, DDA was employed to study R and T of periodic arrays of dielectric and metal spheres [25].…”

Theoretical and Experimental Study on the Functionalization Effect on the SERS Enhancement Factor of SiO2-Ag Composite Films

“…In particular, Discrete Dipole Approximation (DDA) is a flexible integral equation method that allows to study the optical response of targets with a size smaller or similar to that of the incident wavelength. With this method is possible to study isolated or periodic targets with arbitrary shapes [15,16]. On the other hand, this method has been widely used to study the absorbed and scattered light by several systems as nanoparticles, bacteria, films, red blood cells, among others [17,18].…”