NSF-DFG: Nonequilibrium thermal processing of nanoparticles: Laser melting and fragmentation in liquid

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Laser fragmentation in liquids (LFL) and laser melting in liquids (LML) are nonequilibrium thermal processing techniques to fabricate highly pure nanoparticles (NPs) for catalysis, optics, and biomedicine. However, the underlying NP formation mechanisms are still poorly understood. The twofold objective of the proposed NSF-DFG-funded joint computational and experimental study is (1) to deepen the understanding of the fundamental mechanisms of the laser-induced modification of NPs in liquid and (2) to facilitate the advancement of the NP synthesis techniques guided by an understanding of the processes that control the sizes, shapes, and structures of NPs produced by LFL and LML. Pt, Au, and PtAu alloy NPs are chosen as model materials and computational prediction and experimental verification of the particle´s elemental composition and defect density are used as major readouts. An advanced computational model for the realistic simulation of the NP fragmentation dynamics during LFL and LML will be developed and verified in experiments using a continuous-flow flat jet laser processing setup that ensures precise control over the pulse number and laser fluence exposure of dispersed NPs. Transient optical properties will be calculated for NPs undergoing laser-induced melting and disintegration to facilitate the connections to the results of time-resolved experimental optical probing (pump-probe) and to reveal optimum conditions for the energy-efficient NP processing also in a double-pulse (pump-pump) irradiation strategy.