Dichroic Calcite Reveals the Pathway from Additive Binding to Occlusion
Dichroic Calcite Reveals the Pathway from Additive Binding to Occlusion
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DOI：
10.1021/acs.cgd.1c00068
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发表时间：
2021-06-18
影响因子：
3.8
通讯作者：
Meldrum, Fiona C.
中科院分区：
文献类型：
--
作者：
Green, David C.;Darkins, Robert;Meldrum, Fiona C.
有机添加剂在控制碳酸钙在环境、工业和生物中的沉淀方面起着关键作用，它们可以指导多晶型，改变晶体形态，有时甚至被封闭，改变整体性质。然而，重要的问题仍然是关于从吸附在晶体表面上的闭塞的途径。在这里，在染料刚果红的存在下生长的方解石晶体的光学性质用于表征晶体内的添加剂的组织。补充通过原位原子力显微镜（AFM），分子模拟和晶体形态的变化的表面吸附分析，我们表明，闭塞的染料分子是随机取向的快速生长条件下，但缓慢的生长产生有序的岛屿内的染料，其方向是由染料/梯田相互作用自由能。这些岛随后被过度生长，使得它们的内部结构被保留。这些结果表明，有机大分子进入方解石的闭塞可以理解的热力学操作在吸附阶段。这种新的见解将最终使添加剂的设计能够赋予特定的材料特性。
Organic additives play key roles in controlling the precipitation of calcium carbonate in the environment, industry, and biology, where they can direct polymorphism, alter crystal morphologies, and sometimes even become occluded, modifying bulk properties. However, significant questions remain regarding the pathway from adsorption on crystal surfaces to occlusion. Here, the optical properties of calcite crystals grown in the presence of the dye Congo red are used to characterize the organization of the additives within the crystal. Complemented by the analysis of surface adsorption through in situ atomic force microscopy (AFM), molecular simulations, and changes in crystal morphologies, we show that the occluded dye molecules are randomly oriented under fast growth conditions, but that slow growth engenders ordering of the dye within islands, whose orientation is determined by the dye/terrace interaction free energy. The islands are subsequently overgrown such that their internal structure is preserved. These results reveal that the occlusion of organic macromolecules into calcite can be understood by thermodynamics operating at the adsorption stage. This new insight will ultimately enable the design of additives to give specific material properties.