Shaping nanoparticles with laser light: a multi-step approach to produce nanoparticle ensembles with narrow shape and size distributions

In this paper we present a multi-step laser tailoring process in order to narrow the size distribution of self-assembled supported metal nanoparticles. The method exploits the shape and size dependent optical absorption coefficients of metal particles. Silver nanoparticles were prepared by deposition of atoms on dielectric substrates followed by diffusion and nucleation. This results in ensembles of oblate nanoparticles with broad size and shape distributions. Post-growth irradiation allows tailoring the average size of the nanoparticles by laser-induced surface diffusion and evaporation of surface atoms of the nanoparticles. This makes it possible to shrink large particles to the desired size and remove all nanoparticles that are too small. We demonstrate here that the size distribution of silver nanoparticles can be narrowed significantly by subsequently applying different laser wavelengths.