Although oriented aggregation of particles is a widely recognized mechanism of crystal growth, the impact of many fundamental parameters, such as crystallographically distinct interfacial structures, solution composition, and nanoparticle morphology, on the governing mechanisms and assembly kinetics are largely unexplored. Thus, the collective dynamics of systems exhibiting OA has not been predicted. In this context, we investigated the structure and dynamics of boehmite aggregation as a function of solution pH and ionic strength. Cryogenic transmission electron microscopy shows that boehmite nanoplatelets assemble by oriented attachment on (010) planes. The coagulation rate constants obtained from dynamic light scattering during the early stages of aggregation span 7 orders of magnitude and cross both the reaction-limited and diffusion-limited regimes. Combining a simple scaling analysis with calculations for stability ratios and rotational/translational diffusivities of irregular particle shapes, the effects of orientation for irregular-shaped particles on the early stages of aggregation are understood via angular dependencies of van der Waals, electrostatic, and hydrodynamic interactions. Using Monte Carlo simulations, we found that a simple geometric parameter, namely, the contact area between two attaching nanoplatelets, presents a useful tool for correlating nanoparticle morphologies to the emerging larger-scale aggregates, hence explaining the unusually high fractal dimensions measured for boehmite aggregates. Our findings on nanocrystal transport and interactions provide insights toward the predictive understanding of nanoparticle growth, assembly, and aggregation, which will address critical challenges in developing synthesis strategies for nanostructured materials, understanding the evolution of geochemical reservoirs, and addressing many environmental problems.

中文翻译：

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溶液化学和颗粒各向异性对定向聚集体集体动力学的影响

尽管粒子的定向聚集是公认的晶体生长机制，但许多基本参数（例如晶体学上不同的界面结构，溶液组成和纳米粒子形态）对控制机制和组装动力学的影响尚待探索。因此，尚未预测到表现出OA的系统的集体动力学。在这种情况下，我们研究了勃姆石聚集体的结构和动力学随溶液pH和离子强度的变化。低温透射电子显微镜显示勃姆石纳米片通过在（010）平面上定向附着而组装。从聚集早期的动态光散射获得的凝结速率常数跨越7个数量级，并且跨越了反应受限和扩散受限机制。将简单的比例分析与不规则颗粒形状的稳定性比和旋转/平移扩散率的计算相结合，可以了解不规则形状颗粒的取向对聚集早期的影响通过范德华力，静电和流体动力相互作用的角度依赖性。使用蒙特卡洛模拟，我们发现一个简单的几何参数，即两个附着的纳米片之间的接触面积，提供了一个有用的工具，可以将纳米颗粒的形态与新兴的大规模聚集体相关联，从而解释了勃姆石聚集体的异常高分形维数。我们对纳米晶体的运输和相互作用的发现提供了对纳米颗粒生长，组装和聚集的预测性理解的见识，这将解决开发纳米结构材料的合成策略，理解地球化学储层的演化以及解决许多环境问题方面的重大挑战。