Materials World Network (MWN) for Particle-mediated Control Over Crystallization: From the Pre-nucleation Stage to the Final Crystal

将建立一个材料世界网络(MWN)来研究粒子介导的结晶机制，通过它来产生介晶--在介观尺度上结构的晶体。在生物矿物系统中，分子晶体的形成是一种普遍的现象，由生物分子介导，并导致与这些材料通常相关的层次化组织。我们的最终目标是从机制上理解这一过程，并制定一套原则来指导仿生策略来创造层次化组织的材料(如生物陶瓷、光子固体、能量收集材料)。国际合作增加的价值是，它将化学和介晶生长方面的专业知识与高分辨率原位成像、相互作用测量、结构确定以及从原子到介观尺度的建模和模拟能力相结合，从而促进了这一目标。利用碳酸钙、氧化铁和水合硅酸钙(C-S-H)体系与聚合物相结合，该项目将进行三次推进，围绕关键科学问题进行：推力1：预成核阶段、初级纳米颗粒和中间相的成核-将使用离子电势测量、滴定和超速离心法确定预成核团簇的性质。它们的溶液相互作用动力学将通过液室电子显微镜来探索。推力2：纳米晶体和介晶形成的有机介体之间的相互作用力-负责粒子共取向和重新取向的相互作用将通过动态力光谱(DFS)和建模相结合来确定。DFS将提供与取向相关的晶体-晶体和聚合物相互作用的自由能的直接测量。实验测量得到了分子模型的支持，它使我们能够确定有效相互作用的分子细节，并为推力中的相场计算提供参数。3.推力3：成核后粒子聚集和共取向-粒子聚集的动力学，聚集粒子的结晶取向随时间的变化，以及介晶聚集的结构演变将用液胞电子显微镜和非原位HRTEM进行研究。重点将侧重于区分定向附着和随机聚集后的定向附着，无论是通过全粒子旋转还是原子尺度成熟。这些数据将与利用推力2中确定的相互作用能的介晶组装的相场模型进行比较。

A Materials World Network (MWN) will be formed to investigate mechanisms of particle-mediated crystallization through which mesocrystals — crystals structured on the mesoscale — are created. In biomineral systems, mes-ocrystal formation is a widespread phenomenon mediated by biomolecules and leading to the hierarchical organization commonly associated with these materials. Our ultimate goal is a mechanistic understanding of this process and a set of principles to guide biomimetic strat-egies to create hierarchically organized materials (e.g. bioceramics, photonic solids, energy harvesting materials). The value added by the international collaboration is that it facilitates this goal by combining expertise in chemistry and growth of mesocrystals with capabilities in high-resolution in situ imaging, measurement of interactions, determination of structure, and modeling and simulation from the atomic to mesoscale. Using the calcium carbonate, iron oxide and calcium-silicate hydrate (C-S-H) systems combined with polymers, the project will pursue three thrusts, structured around the key scientific questions: Thrust 1: The pre-nucleation stage, nucleation of primary nanoparticles and intermediate phases - The nature of pre-nucleation clusters will be determined using ion potential measurements, titration and ultracentrifugation. Their solution interaction dynamics will be probed through liquid cell TEM. Thrust 2: Interactions forces between nanocrystals and organic mediators of mesocrystal formation – The interactions responsible for particle co-orientation and reorientation will be determined through a combination of dynamic force spectroscopy (DFS) and modeling. DFS will provide a direct measure of the free energy of the orientation dependent crystal-crystal and -polymer interactions. Experimental measurements are supported by molecular model-ing, which allows us to determine molecular details of the effective interactions and provides parameters for the phase field calculations in Thrust 3. Thrust 3: Post-nucleation particle ag-gregation and co-orientation – The kinetics of particle aggregation, crystallographic orienta-tions of the aggregating particles as a function of time, and structural evolution of mesocrys-talline 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 mesocrystal assembly that utilize the interaction energies determined in Thrust 2.