Silver nanoparticles: generation and fragmentation by using femtosecond ablation inside of deionised water solution

G. A. TORCHIA; F. VIDELA; D. SCHINCA ; L.B. SCAFFARDI

Foz do Iguaçu

Workshop; 19th INTERNATIONAL LASER PHYSICS WORKSHOP; 2010

Instituto de Física de São Carlos, Universidade de São Paulo

  In this work we present the generation and fragmentation of silver nanoparticles (Nps) by using femtosecond (fs) laser ablation focusing on the solid target inside a solution of deionised water. In order to do these experiments, we have used a Spectra Physics Chirped Pulse Amplification (CPA) Ti: Sapphire system lasing at 800 nm, 120 fs pulse width, 1 KHz repetition rate and it can deliver up to 1 mJ of energy per pulse. The generation and fragmentation of silver Nps were conducted by means of different strategies. First of all, silver colloidal solution in desionised water was obtained by using a direct laser ablation at fundamental wavelength. On the other hand in order to obtain a reduced size for the mean average radii corresponding to the silver Nps in the water solution, we have conducted the ablation process by using the Second Harmonic (SH) radiation. It was obtained after pass the fundamental fs pulse trough a BBO non linear crystal. By focusing the SH on the silver target inside the water solution, we obtained the smallest silver Nps solution. This fact can be explained by taking into account the following points i) the location of the resonance plasmon corresponding to the fresh silver Nps, which coincides with SH wavelength thus linear and non linear absorption can be responsible of the particle reduction by Coulomb repulsion (nano-ablation); 2) the super-continuum radiation generated in water by blue radiation and then lineally absorbed by the fresh silver Nps can deliver ablated Nps. In order to identify the particles sizes distribution, optical extinction spectroscopy was used to fit all optical spectra. In order to do that, we additionally have taken into account the oxidation (core-shell structures) for the resultant silver Nps solution. TEM picture were also used to explore the shape, morphology and sizes of the Nps obtained in work.