Materials World Network: Particle-Mediated Control Over Crystallization: From the Pre-Nucleation Stage to the Final Crystal

技术概述：通过纳米颗粒的相互作用和附着形成有层次组织的结晶固体，现在被认为是环境、生物和合成结晶系统中普遍存在的现象。这个项目的目标是对这些所谓的中晶是如何通过粒子介导的生长过程产生的机制进行理解。为了实现这一目标，中晶生长方面的专业知识将与高分辨率原位透射电子显微镜（TEM）和原子力显微镜（AFM）成像、纳米颗粒相互作用的动态力谱（DFS）、原子结构的测定以及从原子到中尺度的建模和模拟能力相结合。使用碳酸钙、氧化铁和水合硅酸钙（SCH）结合聚合物作为实验系统，该项目将围绕关键科学问题进行三个重点研究。预成核团簇的性质将通过离子电位测量、滴定和超离心来确定，它们的溶液相互作用动力学将通过液池透射电镜来探测。将DFS和建模相结合，确定粒子共取向和重取向的相互作用。实验测量将得到分子模拟模拟的支持，这将用于确定有效相互作用的分子细节，并为相场计算提供参数。利用液池TEM和原位HRTEM研究了颗粒聚集动力学、聚集颗粒的结晶取向和中晶聚集体的结构演变。重点将放在区分定向附着和定向后随机聚集或通过全粒子旋转或原子尺度成熟。这些数据将与利用实验确定的相互作用能量的装配相场模型进行比较。结果将是一套指导合成策略的原则，用于创建分层组织的材料，如生物陶瓷，光子固体，能量收集材料。非技术总结：在美国国家科学基金会材料研究部的支持下，将形成一个材料世界网络，以研究通过纳米颗粒的相互作用和附着产生复杂晶体结构（称为介晶）的机制。本研究的目标是建立对这一过程的机械理解，并建立一套指导合成策略的原则，以创建分层组织的材料，如生物陶瓷，光子固体和能量收集材料。这项工作将通过将计算机模拟和化学分析与一套强大的原位显微镜工具相结合来进行，这些工具可以提供有关纳米颗粒附着过程和颗粒之间相互作用力的实时分子尺度信息。要研究的材料包括与生物材料研究相关的材料，如碳酸钙，以及与能源和环境系统相关的材料，如氧化铁。结果将是一套物理原理，既可以应用于理解自然材料在环境中形成的过程，也可以应用于能源、生物医学和结构应用的分层材料合成。该项目的成功得益于四所美国和德国大学之间的国际合作，每所大学都为项目带来了一套独特的技能和知识。此外，此次合作将通过美国和德国实验室之间的国际交流，为参与研究的研究生和本科生提供独特的学习体验。最后，该项目将包括开发一个关于中晶形成的模块，该模块将通过nsf资助的纳米非正式科学教育网络提供给公众。

TECHNICAL SUMMARY:The formation of hierarchically organized crystalline solids through nanoparticle interaction and attachment is now recognized as a widespread phenomenon in environmental, biological and synthetic crystallization systems. The goal of this project is to develop a mechanistic understanding of how these so-called mesocrystals are created through particle-mediated growth processes. To achieve that goal, expertise in growth of mesocrystals will be combined with capabilities in high-resolution in situ transmission electron microscopy (TEM) and atomic force microscopy (AFM) imaging, dynamic force spectroscopy (DFS) of nanoparticle interactions, determination of atomic structure, and modeling and simulation from the atomic to mesoscale. Using calcium carbonate, iron oxide and calcium-silicate hydrate (SCH) combined with polymers as the experimental systems, the project will pursue three thrusts, structured around the key scientific issues. The nature of pre-nucleation clusters will be determined using ion potential measurements, titration and ultracentrifugation and their solution interaction dynamics will be probed through liquid cell TEM. The interactions responsible for particle co-orientation and reorientation will be determined through a combination of DFS and modeling. Experimental measurements will be supported by molecular modeling simulations, which will be used to determine molecular details of the effective interactions and provide parameters for phase field calculations. The kinetics of particle aggregation, crystallographic orientations of the aggregating particles, and structural evolution of mesocrystalline aggregates will be investigated by liquid cell TEM and ex situ HRTEM. Emphasis will be placed on distinguishing between oriented attachment and orientation following random aggregation either through whole-particle rotation or atomic-scale ripening. These data will be compared to phase-field models of assembly that utilize the experimentally determined interaction energies. The outcome will be a set of principles to guide synthetic strategies for creating hierarchically organized materials such as bioceramics, photonic solids, energy harvesting materials.NON-TECHNICAL SUMMARY:Through support from the NSF Division of Materials Research, a Materials World Network will be formed to investigate mechanisms by which complex crystalline structures, known as mesocrystals, are created through the interaction and attachment of nanoparticles. The goal of this research is to establish a mechanistic understanding of this process and a set of principles to guide synthetic strategies for creating hierarchically organized materials such as bioceramics, photonic solids, and energy harvesting materials. The work will be carried out by combining computer simulations and chemical analyses with a powerful set of in situ microscopy tools that provide real-time molecular-scale information about both nanoparticle attachment processes and the interaction forces between the particles. The materials to be investigated include those of relevance to biomaterials research, such as calcium carbonate, as well as those of relevance in energy and environmental systems such as iron oxide. The outcome will be a set of physical principles that can be applied both to understanding the processes responsible for formation of natural materials in the environment and to synthesis of hierarchical materials for energy, biomedical, and structural applications. Success of the project is enabled by an international collaboration between four US and German Universities, each of which brings a unique set of skills and knowledge to the project. Moreover, this collaboration will provide a unique learning experience for the graduate and undergraduate students involved in the research through international exchanges between the US and German labs. Finally, the project will include development of a module on mesocrystal formation for the public outreach programs to be made available through the NSF-funded Nanoscale Informal Science Education network.