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

激光液相裂解（LFL）和激光液相熔化（LML）是一种非平衡热处理技术，用于制备用于催化、光学和生物医学的高纯纳米颗粒（NPs）。然而，潜在的NP形成机制仍然知之甚少。拟议的NSF-DFG资助的联合计算和实验研究的双重目标是（1）加深对液体中纳米粒子激光诱导改性的基本机制的理解，以及（2）通过理解控制LFL和LML产生的纳米粒子的尺寸，形状和结构的过程，促进纳米粒子合成技术的进步。选择Pt、Au和Pt Au合金纳米颗粒作为模型材料，并将颗粒的元素组成和缺陷密度的计算预测和实验验证用作主要读数。一个先进的计算模型，在LFL和LML的NP碎裂动力学的现实模拟将开发和验证实验中使用的连续流平面射流激光加工设置，确保精确控制脉冲数和激光能量密度曝光的分散NP。瞬态光学性质将计算纳米粒子进行激光诱导熔化和解体，以促进连接的时间分辨实验光学探测（泵浦探测）的结果，并揭示最佳条件的能量效率的NP处理也在双脉冲（泵浦泵浦）照射策略。

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.