Linear optical properties of a linear chain of interacting gold nanoparticles

Abstract

In a Drude-like model for the conduction electrons of Metal Nanoparticles (MNPs) in a periodic linear chain, considering dipole-dipole interactions of adjacent particles, an analytical expression is derived for each particle permittivity for two different polarizations of incident light: parallel with and perpendicular to the chain line. A numerical analysis is carried out for a chain including 10 identical gold Nanoparticles (NPs) for two different sizes of NPs and two different host media of air and glass. It is shown that in the parallel case of polarization, interaction of NPs leads to a substantial increase in the extinction cross section and the red-shift of the Surface Plasmon Resonance (SPR) wavelength. In comparison with the linear properties of a single NP, the second and penultimate particles have the most increase in the extinction cross section and SPR wavelength displacement while the first and last particles experience the least variations due to the mutual interactions. For the perpendicular polarization, inversely, the dipolar coupling causes the decrease in extinction cross section of all particles and the blue-shift of SPR wavelength. For the parallel polarization, the absolute values of the real and imaginary parts of complex permittivity of each MNP decrease in comparison with the single particle case while they increase for the perpendicular state of polarization.

Linear optical properties of 2d assembly of interacting gold nanoparticles: analytical approach in dipole approximation

“…n NP , using the equation (19) where the parameters of ξ and γ are not determined yet. In light of our recent study [24], using experimental data of extinction cross section of individual gold NP, we have specified them. The values of the free parameters ξ and γ in the permittivity of small gold NPs ranged from 4 nm to 5.4 nm and for the large gold NPs ranged from 20 nm to 100 nm are suggested.…”

“…Such a primitive model is commonly used for the cases in which the particles are not very close to each other and their characteristic dimension is very less than the incident light wavelength. In some recent studies, by such a manner, we could theoretically extract some linear and nonlinear aspects of 1-D chains of MNPs [21][22][23][24]. In the linear regime, the measurable parameter which is a complicated function of the permittivity is the extinction cross section of particles which indicates the absorption and scattering of light, thus, we calculate it for an MNP of array.…”