Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

Abstract

Dependence of the localized surface plasmon resonance of noble metal quasispherical nanoparticles on their crystallinity-related morphologies This paper develops a novel method for simultaneously determining the plasma frequency x P and the damping constant c f ree in the bulk damped oscillator Drude model, based on experimentally measured real and imaginary parts of the metal refractive index in the IR wavelength range, lifting the usual approximation that restricts frequency values to the UV-deep UV region. Our method was applied to gold, silver, and copper, improving the relative uncertainties in the final values for x p (0.5%-1.6%) and for c f ree (3%-8%), which are smaller than those reported in the literature. These small uncertainties in x p and c f ree determination yield a much better fit of the experimental complex dielectric function. For the case of nanoparticles (Nps), a series expansion of the Drude expression (which includes x p and c f ree determined using our method) enables size-dependent dielectric function to be written as the sum of three terms: the experimental bulk dielectric function plus two size corrective terms, one for free electron, and the other for bound-electron contributions. Finally, size distribution of nanometric and subnanometric gold Nps in colloidal suspension was determined through fitting its experimental optical extinction spectrum using Mie theory based on the previously determined dielectric function. Results are compared with size histogram obtained from Transmission Electron Microscopy (TEM). V C 2014 AIP Publishing LLC.

Size-dependent complex dielectric function of Ni, Mo, W, Pb, Zn and Na nanoparticles. Application to sizing

“…In this work we determine for the first time the Drude model parameters γ free and ω p for Ni, Mo, W, Pb, Zn and Na employing a method developed by Mendoza Herrera et al [26], which lifts the restriction free ω γ . It will be shown that the so obtained γ free and ω p allow a much more accurate fitting of the experimental bulk dielectric function discrete values in a wider wavelength range, beyond the visible and extending to the FIR depending of the metal.…”

Engineering a Localized Surface Plasmon Resonance Platform for Molecular Biosensing

“…For nanoparticles, the scattering parameter has inherent contributions of the intrinsic properties of the material as well as from interface scattering, and therefore, it can be described as γ = γ bulk + γ scat . Interface scattering becomes significant when the effective electron path length L eff is larger than to the nanoparticle itself [31]. The effective path length for convex shapes particles, as sphere, rods, cubes etc, is expressed as L eff = 4V/S where V is the volume and S is the particle surface area [30].…”

High Tunability of Size Dependent Optical Properties of ZnO@M@Au (M = SiO2, In2O3, TiO2) Core/Spacer/Shell Nanostructure

“…Introducing the real ( ) and imaginary parts ( ), ̃ may be written as [25] ̃= + 26 The real part of refractive index of an ensemble consisting ZnO@M@Au spherical and cylindrical core shell embedded in host matrix which have dielectric function ℎ = 2.25 is analysed using Eq. (25) and (26). and 1000 .…”

“…Decreasing the size of a nanoparticle will eventually cause the thickness to become less than the bulk mean free path, and electron scattering from the surfaces of the particle will have decreasing effect thus broadening its plasmon resonance peaks. If the electron mean free path depends on size of the nanoparticles, a correction is available for the nanoshells and in this case, can be modified to [26], [27], [28]…”