Highly-repeatable generation of very small nanoparticles by pulsed-laser ablation in liquids of a high-speed rotating target.

By irradiating a cylindrical silver target rotated at a high-speed within the range 300-2400 rpm (lateral speed 0.16-1.25 m s-1) in pure water, we prepare ligand-free Ag nanoparticles (NPs) with a size of 4 ± 2 nm which are likely to be primary particles. Usually, the generation of NPs showing such a small size requires either a laser post-treatment and/or chemical additives. As the rotation rate of the target is increased, calculated 3D flow patterns revealed different hydrodynamic regimes which clearly influence the ablation rate and repeatability of the process as well as the colloidal properties. In addition to revealing the importance of fluid dynamics in pulsed-laser ablations in liquids, this study provides a way for producing in one step pure NPs with sizes below 5 nm which are suitable for applications in catalysis.