The generation of colloidal solutions of chemically clean nanoparticles through pulsed laser ablation in liquids (PLAL) has evolved into a thriving research field that impacts industrial applications. Large-scale atomistic simulations have yielded important insights into the fundamental mechanisms of ultrashort (femtoseconds to tens of picoseconds) PLAL [1-5] and provided a plausible explanation of the origin of the experimentally observed bimodal nanoparticle size distributions. Recently, the

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... tomistic simulations were extended to longer (hundreds of picoseconds to nanoseconds) laser pulses, enabling a detailed analysis of the effect of the pulse duration on the mechanisms responsible for the generation of nanoparticles [6]. In these simulations, three distinct nanoparticle generation mechanisms operating at different stages of the ablation process and in different parts of the emerging cavitation bubble were identified. The coexistence of the three distinct mechanisms of the nanoparticle formation at the initial stage of the ablation process can be related to the broad nanoparticle size distributions commonly observed in nanosecond PLAL experiments. The generation of broad size distributions presents an obstacle for direct use of the colloids in advanced photonic, catalytic, and biomedical applications. To alleviate this limitation of PLAL, a complementary technique for laser processing of colloidal solutions of nanoparticles, the laser fragmentation in liquid (LFL) has been developed. In this technique larger nanoparticles are fragmented to produce a population of smaller nanoparticles with a narrow size distribution. First atomistic simulations of LFL of Au nanoparticles reveal the mechanisms that control the sizes, shapes and structure of the fragmentation products [7], as well as an important role the formation of a nanobubble around the irradiated nanoparticle plays in the pragmentation process. Figure 1. Density profiles and a snapshot of fragmentation products colored by nanoparticle size predicted in a simulation of LFL of a 20 nm Au particle irradiated by a 10 ps laser pulse in water [7]. [1] C.-Y. Shih, C. Wu, M. V. Shugaev, and L. V. Zhigilei, Atomistic modeling of nanoparticle generation in short pulse laser ablation of thin metal films in water, J. Colloid Interface Sci. 489, 3, 2017. [2] C.-Y. Shih, M. V. Shugaev, C. Wu, L. V. Zhigilei, Generation of subsurface voids, incubation effect, and formation of nanoparticles in short pulse laser interactions with bulk metal targets in liquid: Molecular dynamics study,