Super continuum effects in gold nanoparticles fragmentation irradiated by ultra-short laser pulses

G.A. TORCHIA; F. VIDELA; D. SCHINCA; L.B. SCAFFARDI; P. MORENO; L. ROSO, ; L. GIOVANETTI ; J. RAMALLO LÓPEZ

Foz do Iguaçu

Workshop; 19th INTERNATIONAL LASER PHYSICS WORKSHOP,2010; 2010

Instituto de Física de São Carlos, Universidade de São Paulo

In work we present the effects of super-continuum radiation of the fragmentation process on colloidal gold nano-particles (Nps) solutions by two step procedure. In the first stage the gold Nps were obtained by focusing ultra-short pulses onto solid target inside on deionised water. The second was performed by irradiating the Nps solution with infrared and external super continuum radiation obtained by using a Sapphire crystal. In both cases, low fluences were used for fragmentation. Also super-continuum can be delivered by infrared focused in water. In particular in this paper we have studied the influence the spectral response for fragmentation. For this, by means of the function defined  as the product the optical extinction against the super continuum spectra, we recognize three different efficiency regions. We conclude that the visible was the most import to perform the gold fragmentation. Likewise, we stated that the super-continuum obtained in water was more efficiency that one applied externally. This fact can attributed to the extra blue broadening shown in the first case due to large intensity reached at focus on the water. SAXS experiments and optical extinction measurements were conducted to size the average radii of gold Nps solutions. Besides, TEM was used in order to test the shape and morphology as complementary technique.