Growth mechanism of monodisperse spherical particles under nanosecond pulsed laser irradiation

It is well-known that the colloidal nanoparticles irradiated by laser can be reduced in size. Recently, we demonstrated that at particular experimental conditions, colloidal nanoparticles of different materials can grow under pulse laser irradiation, finally transforming to the near monodisperse submicron spheres. To date, the detailed mechanism of this process was not revealed. In this work, we explore the mechanism of particle growth by applying the particle heating-melting-evaporation model. Our investigations show that the process of particle growth can be divided into two stages. At the initial stage, particle agglomeration is the dominant factor for the fast particle growth. Then, the process continues as long as the particles can be melted. The final particle diameter is determined by the value of laser fluence, because the laser fluence determines the maximum diameter of the particle which can be melted. Good agreement between the experimental results and results of calculation was obtained.