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

液体激光破碎(LFL)和激光熔融(LML)是制备高纯纳米粒子的非平衡热加工技术，用于催化、光学和生物医学等领域。然而，NP的潜在形成机制仍然知之甚少。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NPs激光诱导修饰的基本机理的理解和(2)促进NP合成技术的进步，该技术以对LFL和LML产生的NPs的尺寸、形状和结构的控制过程的理解为指导。以铂、金和铂合金纳米颗粒为模型材料，以粒子S的元素组成和缺陷密度的计算预测和实验验证为主要读数。建立了一个先进的计算模型，用于真实模拟LFL和LML过程中的NP破碎动力学，并在实验中得到验证，该装置使用连续流动平板喷射激光加工装置，确保对分散的NP的脉冲数量和激光通量曝光进行精确控制。我们将计算经历激光诱导熔化和解体的NPs的暂态光学性质，以便于与时间分辨实验光学探测(泵浦-探测)的结果相联系，并揭示在双脉冲(泵浦)辐照策略下也可以进行高能效的NP处理的最佳条件。

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.