Surface plasmon resonance of gold and silver nanoparticle monolayers: effect of coupling and surface oxides

Abstract

Material properties are described by some physical parameters such as temperature or pressure. Optical properties of materials are very important for applications where is light as electromagnetic wave dominant. Behavior of the light in interaction with materials depends on refractive indices. These indices are same for various sizes of materials, but in nanoscale dimensions, they depend on some phenomena. Herein, we present the study of the silver (Ag) nanoparticle (NP) monolayer film and its dielectric properties. The aim of the study is to explain phenomenon why it is necessary to use effective material properties for Ag NPs, where these properties are size-dependent. The plasmonic properties of NP have been investigated by the finite domain time difference (FDTD) simulation methods. Although the good agreement of plasmonic resonances was found for gold (Au) NP film, a significant mismatch in the resonance energy for Ag NP film was observed. The deviation was assigned to the presence of silver oxide (Ag 2 O) in Ag NPs as a surface layer. This real structure of Ag NPs can be replaced by structure with suitable effective material properties. Results depict importance of the effective material properties in Ag NP film for reason of the presence of silver oxide. The Ag NPs with surface oxide exhibits linear tendency in the deviation of the effective dielectric function, which agrees with the experimental observations.