Interaction of high-power laser pulses with monodisperse gold particles

The interaction of repetitive nanosecond laser pulses with near-spherical gold nanoparticles, dispersed in an aqueous ambient and having various mean sizes, was studied for two different wavelengths 355 and 532 nm and various energies per pulse. From the in situ surface plasmon (SP), extinction measurements combined with ex situ TEM studies of the irradiated hydrosols, we conclude that the process of laser-induced fragmentation is cumulative with increasing number of subsequent pulses. Interestingly, irradiation of all parent hydrosols having different mean particle sizes (except of that one containing nanoparticles with the mean diameter of 5 nm) with laser pulses of the 532 nm wavelength and the same energy per pulse absorbed in the hydrosol resulted into hydrosols containing nanoparticles of very similar reduced mean sizes and size distributions. On the other hand, for the parent nanoparticle hydrosol with the initial mean particle diameter below 5 nm, a small increase of the mean particle size has been detected after irradiation with pulses of the same wavelength. The mean sizes of Au nanoparticles fragmented by 355 nm pulses were generally smaller than those fragmented at 532 nm.