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

DAVID MUÑETÓN ARBOLEDA; JESICA M. J. SANTILLÁN; LUIS J. MENDOZA HERRERA; DIEGO MURACA; DANIEL C. SCHINCA; LUCÍA B. SCAFFARDI

JOURNAL OF PHYSICS - D (APPLIED PHYSICS)

IOP PUBLISHING LTD

Lugar: Londres; Año: 2016 vol. 49 p. 75302 - 75312

0022-3727

This work determines the size dependent metal nanoparticle (NP) dielectric function from a "top-down" approach using the bulk experimental refractive index as a starting point. Free-electron damping constant (𝛾𝑓𝑟𝑒𝑒) and plasma frequency (𝜔𝑝) parameters in the Drude model are calculated for nickel (Ni), molybdenum (Mo), tungsten (W), lead (Pb), zinc (Zn) and sodium (Na) using a method developed in our group. Determined 𝛾𝑓𝑟𝑒𝑒 and 𝜔𝑝 parameters allow to develop an expression that improves the accuracy in reproducing the discrete metal bulk dielectric function in a wide wavelength range (UV-FIR). The bulk dielectric function is modified for describing the nanometric case by adding size corrective terms for free and bound electrons contributions. As an application of this study we characterize Ni spherical NPs synthesized by ultrafast laser ablation of a solid target in water. Using Mie theory together with the size-dependent dielectric function, we theoretically reproduce its experimental extinction spectrum. From this fitting, composition and size distribution of the particles in the colloidal suspension may be derived. Transmission ElectronMicroscopy (TEM) results agree with the sizes and structure derived from Optical Extinction Spectroscopy (OES).