Silver-silver oxide core-shell nanoparticles fabricated by ultrashort laser ablation. Analysis of size by optical extinction spectroscopy

D. C. SCHINCA; L. B. SCAFFARDI; G. A. TORCHIA; P. MORENO; L. ROSO

Kobe, Japan

Congreso; The 5th International Congress on Laser Advanced Materials Processing LAMP 2009; 2009

JLPS- Japan Laser Processing Society, Japan

A great amount of research has been directed toward a multitude of actual and potential uses of silver nanoparticles (Nps) smaller than 10 nm by engineering their properties through control of their size. The properties for functionalization depend of the metallic core, shell thickness and the requirements for specific applications.  Ultrashort pulse laser ablation methods tend to produce in general, bare-core silver nanostructures. However, depending on the surrounding media, in some cases, it is possible to grow a silver oxide coating around a silver core.    This work studies the influence of a silver oxide coating on the optical properties of the spherical core-shell nanostructures. Optical extinction spectra can be used to size both core mean radius and shell mean thickness by analyzing the FWHM of the plasmon resonance together with wavelength maximum. Since silver oxide is not a dielectric, it has a complex refractive index. When this fact is taken into account for the coating dielectric function in the expression of the polarizability in the electrostatic approximation, calculation results show that very small thicknesses of silver oxide coating produces a red shift of the plasmon peak and a broader FWHM which are compatible with experimental extinction spectra. Comparison with TEM analysis of the same samples shows good agreement.