Role of supercontinuum in the fragmentation of colloidal Gold nanoparticles in solution

摘要

In this work we have studied the fragmentation of gold nanoparticles (NPs) after generation by femtosecond laser ablation of a solid target in deionized water. The fragmentation process was carried out using two different types of radiation: direct ultra-fast pulses and super-continuum radiation focused in the colloidal solution. In the former case, IR pulses were applied both in low and high fluences regime, while in the latter, super-continuum was generated by an external sapphire crystal. In this last case, to assess the effects of the different spectral bands present in the super-continuum for fragmentation, we have determined different efficiency regions. From the analysis of optical extinction spectra and Transmission Electron Microscopy (TEM) histograms we can conclude that the main mechanism is linear absorption in the visible region. Likewise, the super-continuum generated in water during fragmentation resulted more efficient than that obtained externally by the sapphire crystal. This fact can be attributed to the broadening of the water continuum band originated due to large intensity used for generation. TEM and Small Angle X-ray Scattering (SAXS) measurements support the results found from optical extinction spectroscopy.