NSF-DFG: Nonequilibrium Thermal Processing of Nanoparticles via Laser Melting and Fragmentation in Liquid

纳米颗粒在制造用于催化和生物医学的先进纳米材料方面的广泛和迅速扩大的使用要求开发能够满足全球需求急剧增长的纳米颗粒制造技术。激光加工纳米粒子胶体溶液是一种独特的绿色化学技术，在室温和常压下工作，不需要任何化学添加剂或反应物，节省资源，最大限度地减少浪费。为了充分释放这种可扩展纳米制造技术的潜力，该奖项支持基础研究，通过紧密集成的计算机建模和实验，揭示液体环境中激光诱导纳米颗粒修饰的基本机制。这些对纳米颗粒形成机制的见解促进了纳米颗粒制造技术的进步，这些纳米颗粒的尺寸和结构特征满足了催化和生物医学未来发展的高需求。该研究的多学科性质以及与德国杜伊斯堡埃森大学的国际合作促进了新一代研究人员的专业准备，他们准备在快速扩展的激光先进制造和科学计算领域的前沿工作。该项目的影响是通过首次在美国举办关于先进纳米颗粒生成和液体中激光激发的国际会议，以及扩大美国学生在威尼斯国际材料科学激光学校的参与，来增强的。液体激光碎裂和液体激光熔融是制备化学清洁纳米颗粒的两种非平衡热加工技术，可用于催化和生物医学。然而，人们对纳米颗粒的形成机制知之甚少。该项目通过结合多尺度和多物理场建模、时间分辨光学探测以及纳米颗粒相组成和缺陷密度的非原位表征，解决了探测短脉冲激光照射引发的快速高度非平衡过程的挑战。建立了一种用于研究纳米颗粒破碎和熔化动力学的先进计算模型，并在使用连续流平面射流激光处理装置的实验中进行了验证，该装置可确保精确控制分散纳米颗粒的脉冲数和激光辐照量。通过计算纳米粒子在激光诱导下熔化和解体的瞬态光学特性，将其与时间分辨实验光学探测（泵浦探测）的结果联系起来，并揭示在新型双脉冲辐照策略下高能效纳米粒子加工的最佳条件。这些最佳条件是更好的纳米颗粒尺寸，形状和结构控制，以及进一步升级的关键。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The widespread and rapidly expanding use of nanoparticles in the manufacturing of advanced nanomaterials for applications in catalysis and biomedicine calls for the development of nanoparticle manufacturing techniques capable of meeting the sharp rise in global demand. Laser processing of colloidal solutions of nanoparticles is a unique green chemistry technique, working at room temperature and ambient pressure without the need for any chemical additives or reactants, saving resources and minimizing waste. To fully unleash the potential of this scalable nanomanufacturing technique, this award supports fundamental research to reveal, through tightly integrated computer modeling and experiments, the fundamental mechanisms of the laser-induced modification of nanoparticles in a liquid environment. These insights into mechanisms of nanoparticle formation foster the advancement of manufacturing techniques for environment-friendly and energy-efficient generation of nanoparticles with sizes and structural characteristics that meet the high demand of future developments in catalysis and biomedicine. The multidisciplinary nature of the research and the international collaboration with the University of Duisburg Essen, Germany facilitate the professional preparation of a new generation of researchers ready for work at the forefront of the rapidly expanding fields of laser-based advanced manufacturing and scientific computing. The impact of the project is augmented by bringing an established International Conference on Advanced Nanoparticle Generation and Excitation by Lasers in Liquids to the US for the first time and broadening participation of US students in the Venice International School on Lasers in Materials Science.Laser fragmentation in liquids and laser melting in liquids are two nonequilibrium thermal processing techniques to fabricate chemically clean nanoparticles for catalysis and biomedicine. However, the underlying nanoparticle formation mechanisms are poorly understood. This project tackles the challenge of probing the rapid highly nonequilibrium processes triggered by short pulse laser irradiation by combining multiscale and multiphysics modeling, time-resolved optical probing, and ex situ characterization of nanoparticle phase composition and defect density. An advanced computational model for investigation of the nanoparticle fragmentation and melting dynamics is 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 nanoparticles. Transient optical properties are calculated for nanoparticles 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 nanoparticle processing in a novel double-pulse irradiation strategy. These optimum conditions are key for better nanoparticle size, shape, and structure control, as well as for further upscaling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.