Combination of in situ functionalization and transient ultrashort-time spectroscopy for the mechanistic elucidation of laser fragmentation mechanisms and the associated growth kinetics of colloidal gold nanoparticles (Ultra frag)

基于激光的高纯度胶体金属、合金和氧化物纳米颗粒的合成及其随后在支架上的静电吸附使得柔性材料设计在生物医学、能源技术、催化和增材制造中具有广泛的应用。在一项由UDE和KIT结合实验实验室和同步加速器方法的联合研究中，对液体激光烧蚀过程中超短时间尺度上粒子形成和生长机制的基本见解已经得到了发展。因此，广泛的粒度分布是一个已知的问题，在激光烧蚀归因于内在的，几乎不可避免的机制。脉冲激光破碎是唯一已知的基于激光的方法，可以获得粒径远低于3nm的高纯度纳米颗粒，其重要性迫在眉睫。然而，相变、破碎、热传递和随后的碎片生长在叠加中进行，时间尺度从超短到微秒甚至更长的时间尺度，这抑制了可预测性。因此，基于激光的材料合成仍然严重依赖于经验配方。提出了不同的破碎机制。然而，由于叠加破碎和纳米颗粒成熟的分层能量和时间尺度，它们的验证仍然是一个挑战。在申请人的初步研究中，在选定的激光强度范围内，用脉冲x射线衍射（100 ps）分别研究了单脉冲破碎和破碎后金胶体的成熟。本项目现在打算独立地跟踪和绘制碎片化机制和随后的成熟情况。为此，将结合瞬态结构分析，瞬态光谱学和扩散延迟原位生长抑制碎片。确定的膨胀过程将与机制预测相关联，并进行定量建模。基于确定的激光照射与胶体稳定性的相互作用机制，本研究将最终为未来应用中高通量、高能效的激光纳米颗粒合成提供指导。

The laser-based synthesis of high-purity colloidal metal, alloy, and oxide nanoparticles and their subsequent electrostatic adsorption on supports allows a flexible material design with a wide range of applications in biomedicine, energy technology, catalysis, and additive manufacturing. In a joint study by UDE and KIT combining experimental laboratory and synchrotron methods, fundamental insights into the particle formation and growth mechanism occurring on ultra-short time scales during laser ablation in liquids have been developed. Therefrom, the broad particle size distribution that is a known issue during laser ablation was attributed to intrinsic, hardly avoidable mechanisms.With pulsed laser fragmentation being the only known laser-based method to access high-purity nanoparticles with particle sizes well below 3 nm its importance is imminent. Yet, phase transitions, fragmentation, heat transfer and subsequent growth of the fragments proceeds in superposition and on timescales ranging from ultrashort to microsecond and longer timescales, inhibiting predictability. Accordingly, laser-based material synthesis still relies heavily on empirical recipes. Various fragmentation mechanisms were proposed. Yet, their verification is still a remaining challenge due to the hierarchical energy and time scales of the superimposed fragmentation and nanoparticle ripening.In a preliminary study by the applicants the single-pulse fragmentation and subsequent ripening of gold colloids after fragmentation were separately investigated with pulsed X-ray diffraction (100 ps) for a selected range of laser intensities. The present project now intends to follow up and map the fragmentation mechanisms and subsequent ripening independently. To that end, transient structure analysis, transient optical spectroscopy, and diffusion-delayed in-situ growth suppression of the fragments will be combined. Identified swell processes will be correlated with predictions of mechanisms and modeled quantitatively. Based on the identified mechanistic interplay of the laser irradiation and colloidal stability this study will ultimately provide a guideline for high-throughput and energy-efficient laser-based nanoparticle synthesis in future applications.