Elucidating Mechanisms of Diffusion-Based Calcium Carbonate Synthesis Leads to Controlled Mesocrystal Formation
Elucidating Mechanisms of Diffusion-Based Calcium Carbonate Synthesis Leads to Controlled Mesocrystal Formation
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DOI：
10.1002/adfm.201201742
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发表时间：
2013-04-19
影响因子：
19
通讯作者：
Meldrum, Fiona C.
中科院分区：
文献类型：
--
作者：
Ihli, Johannes;Bots, Pieter;Meldrum, Fiona C.
基于聚集的晶体生长通常产生具有复杂形态的晶体，其不能通过经典生长过程产生。尽管如此，对该机制的理解相当差，特别是当存在有机添加剂或无定形前体相时。在这项工作中，优势是采取的观察，聚集为基础的增长碳酸钙，实际上许多其他矿物，是最经常观察到使用基于扩散的合成方法。通过充分表征广泛使用的氨扩散法（ADM），这是目前使用的黑箱的解决方案和过饱和条件下，伴随着碳酸钙沉淀使用这种方法被确定和洞察力获得的成核和生长过程中产生的方解石介晶。这表明ADM的区别特征在于初始成核爆发仅消耗少量的可用离子，然后过饱和度保持相对恒定，并且远高于无定形碳酸钙（ACC）的溶解度，直到反应几乎完成。因此，在整个沉淀过程中产生新的材料，这似乎是形成复杂的，基于聚集的形态的基本特征。最后，证明了这种理解的重要性，使用确定的碳酸盐和过饱和配置文件，完美地复制碳酸钙介晶通过缓慢添加试剂的散装溶液。这种方法克服了ADM的许多固有的问题，提供了良好的再现性，使这种碳酸钙结构的合成在大规模和连续流动的系统，并最终促进原位研究的组装为基础的结晶机制。
Aggregation-based crystal growth often gives rise to crystals with complex morphologies which cannot be generated via classical growth processes. Despite this, understanding of the mechanism is rather poor, particularly when organic additives or amorphous precursor phases are present. In this work, advantage is taken of the observation that aggregation-based growth of calcium carbonate, and indeed many other minerals, is most often observed using diffusion-based synthetic methods. By fully characterizing the widely used ammonia diffusion method (ADM)which is currently used as a black boxthe solution and supersaturation conditions which accompany CaCO3 precipitation using this method are identified and insight is gained into the nucleation and growth processes which generate calcite mesocrystals. This reveals that the distinguishing feature of the ADM is that the initial nucleation burst consumes only a small quantity of the available ions, and the supersaturation then remains relatively constant, and well above the solubility of amorphous calcium carbonate (ACC), until the reaction is almost complete. New material is thus generated over the entire course of the precipitation, a feature which appears to be fundamental to the formation of complex, aggregation-based morphologies. Finally, the importance of this understanding is demonstrated using the identified carbonate and supersaturation profiles to perfectly replicate CaCO3 mesocrystals through slow addition of reagents to a bulk solution. This approach overcomes many of the inherent problems of the ADM by offering excellent reproducibility, enabling the synthesis of such CaCO3 structures in large-scale and continuous-flow systems, and ultimately facilitating in situ studies of assembly-based crystallization mechanisms.