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 AND L. ROSO

Kobe, japón

Conferencia; The 5th International Congress on Laser Advanced Materials processing,; 2009

A great amount of research has been focused to 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 on the metallic core, shell thickness and the requirements for specific applications. Ultrashort pulsed 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 the silver core. This work studies the influence of the silver oxide coating on the optical properties of the spherical core-shell nanostructures. Optical extinction spectra can be used to measure both the 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 dielectric function of the coating in the electrostatic approximation, calculation results show that very small thicknesses of silver oxide coating should give rise to a red shift of the plasmon peak and a broader FWHM which are compatible with our experimental extinction spectra. Comparison with TEM analysis of the same samples shows good agreement as well.