NSF-DFG Confine: Reacting precursor/solvent microdroplets in confined 2-D microflows for tailored nanomaterials synthesis

该项目是通过“受限空间中的化学和运输（NSF-DFG Confine）”机会获得的，这是一个涉及美国国家科学基金会和德国研究共同体（DFG）的合作征集。通常，这些材料是能源和资源可持续利用的关键。它们的应用实例包括催化组件、电池、电极、复合材料、气体传感器、流动剂、3D打印和人造炉渣系统。在大多数应用中对每单位质量的高表面积和快速传质的需求需要使用具有大外表面积的非常小的颗粒。成功的方法是通过生产和使用这种纳米颗粒，主要是氧化物的形式，通常具有特定的成分，化学计量和多材料相互作用。 它们的自下而上的合成涉及反应、成核、表面生长、凝聚、聚结，并且通常涉及结晶。 提出了一种新型的微反应器，涉及燃烧微滴合成纳米粒子的定制的化学组成和晶体结构中的可扩展的，均匀的，一致的方式。 该项目的成功结果将揭示基本过程并改善实际过程控制，以弥合功能性火焰合成纳米颗粒的实验室研究与工业大规模和高速率制造之间的差距。 该项目联合了来自美国（罗格斯大学）和德国（不莱梅大学）的研究人员的能力，他们是新兴的纳米材料火焰合成领域的公认专家。课程将开发为一个综合的，多学科的研究和教育项目，以培养未来的纳米制造劳动力。通过联合博士学位/工商管理硕士课程的技术创业，将评估基于该项目知识产权的新商业风险。拟议计划的目标是通过利用反应多相二维微流系统，利用受控的单独燃烧液体前体/在精确可调的气体成分和温度环境中的溶剂液滴。限定沿着微滴路径的工艺条件应允许在连续系统中制造高质量和定制的纳米颗粒的无与伦比的能力，该连续系统的输出可被引导到用于复合材料的在线加工或其他用途的另一系统中。我们的微流体几何形状和可用的操作参数允许对在其他宏观系统中难以辨别的各种现象进行基本和孤立的研究。微反应器中的微液滴可以经历大的加热和冷却速率，从而在远离平衡的条件下影响详细的化学和运输。 可以使用温度控制（加热或冷却）的壁进行单个液滴研究以维持燃烧或淬灭反应，其中可以表征液滴和所产生的纳米材料（例如，通过取样离线使用色谱法）在不同位置（与不同停留时间相关），从而测量反应动力学和纳米材料演变。 燃烧液滴可以与相同或不同前体的燃烧/非燃烧液滴合并。燃烧微滴移动通过透明微流体反应器（Hele-Shaw细胞）的设置适合于许多原位诊断，包括基于激光的光谱学、高速成像、干涉颗粒成像和彩虹折射法。将进行非原位表征和计算建模，以了解，优化和指导实验。也许在常规燃烧合成中迄今未见，在所提出的设置中均匀液滴的组合和直接操纵可以产生各种纳米颗粒，例如有机、无机、混合和复合纳米颗粒，其具有对尺寸、尺寸分布、形态、组成、该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的评估支持影响审查标准。

This project was awarded through the “Chemistry and Transport in Confined Spaces (NSF-DFG Confine)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).Ubiquitously, our daily life involves the use of high surface-area materials. Frequently, these materials are the key to the sustainable use of energy and resources. Examples of their applications include catalytic components, batteries, electrodes, composite materials, gas sensors, flowing agents, 3D printing, and artificial slag systems. The demand for high surface area per unit mass and fast mass transfer in most applications requires using very small particles with a large external surface area. The way to success is by producing and using such nanoparticles, mostly in the form of oxides and often with specific composition, stoichiometry, and multi-material interactions. Their bottom-up synthesis involves reaction, nucleation, surface growth, coagulation, coalescence, and often crystallization. A novel microreactor involving combusting microdroplets is proposed to synthesize nanoparticles of tailored chemical composition and crystal structure in a scalable, uniform, and consistent fashion. Successful results of this project will reveal fundamental processes and improve practical process control to bridge the current gap between laboratory studies and industrial large-scale and high-rate manufacturing of functional flame-synthesized nanoparticles. This project unites the capabilities of researchers from the U.S.A. (Rutgers University) and Germany (University of Bremen), who are recognized specialists in the emerging field of flame synthesis of nanomaterials. Curricula will be developed as an integrated, multidisciplinary research and education project to train a future nano-manufacturing workforce. Through a joint Ph.D./MBA curriculum on technology entrepreneurship, new business ventures based on the IP from this project will be assessed.The proposed program’s objective focuses on investigating the mechanisms of droplet-to-particle conversion (DPC) and gas-to-particle conversion (GPC) in a confined environment by utilizing a reactive multiphase 2D microflow system with controlled individual burning liquid precursor/solvent droplets in precisely adjustable gas composition and temperature environments. Defining process conditions along a microdroplet’s path should allow unparalleled ability to fabricate high-quality and tailored nanoparticles in a continuous system whose output can be directed into another system for inline processing of composite materials or other uses. Our microfluidic geometry and available operational parameters allow basic and isolated studies of various phenomena hardly discernable in other macroscopic systems. The microdroplets in the microreactor can experience large heating and cooling rates, affecting detailed chemistry and transport in far-from-equilibrium conditions. Individual droplet investigation can be conducted using temperature-controlled (heated or cooled) walls to sustain combustion or quench reactions, where the droplets and as-produced nanomaterials can be characterized (e.g., offline using chromatography by sampling) at different locations (correlating to different residence times), thereby measuring reaction kinetics and nanomaterials evolution. Burning droplets can coalesce with burning/non-burning droplets of the same or different precursors. The setup of burning microdroplets moving through a transparent microfluidic reactor (Hele-Shaw cell) is amenable to a host of in-situ diagnostics, including laser-based spectroscopy, high-speed imaging, interferometric particle imaging, and rainbow refractometry. Ex-situ characterization and computational modeling will be conducted to understand, optimize, and guide the experiments. Perhaps hitherto unseen in conventional combustion synthesis, the combinations and direct manipulation of uniform droplets in the proposed setup can produce a variety of nanoparticles, such as organic, inorganic, hybrid, and complex nanoparticles, with exceptional control of size, size distribution, morphology, composition, and crystallinity.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.