Surface-localized plasmon resonance in a system of randomly arranged gold nanorods on a dielectric substrate

Gold-nanorod arrays of a quasi-hexagonal shape are successfully obtained with electrochemical deposition method and their optical properties are investigated. The optical response of a two-layer structure, in which the first layer is a nanocomposite consisting of Au nanorods and the second one is a thin indium tin oxide film on a glass substrate, has been analyzed. Dependences of absorption cross-section of Au nanorods on the light wavelength at different eccentricities are modelled using electrostatic approximation. It is shown that longitudinal plasmon resonance prevails over other resonances for the Au nanorods deposited on glass substrates. A Maxwell−Garnett theory and a matrix method are used to predict the optical characteristics of the whole structure. We have demonstrated that it is possible to estimate the concentration of nanorods on the surface using the appropriate simulation results. In addition, efficient absorption properties can be obtained at a given wavelength by changing the geometry of nanorods. In particular, there is a shift of the absorption peak towards near-infrared region whenever the nanorods become high enough and smaller in diameter.