Gebauer Denis, Völkel Antje, Cölfen Helmut
Max Planck Institute of Colloids and Interfaces, Research Campus Golm, Am Mühlenberg 1, D-14424 Potsdam, Germany.
Science. 2008 Dec 19;322(5909):1819-22. doi: 10.1126/science.1164271.
Calcium carbonate forms scales, geological deposits, biominerals, and ocean sediments. Huge amounts of carbon dioxide are retained as carbonate ions, and calcium ions represent a major contribution to water hardness. Despite its relevance, little is known about the precipitation mechanism of calcium carbonate, and specified complex crystal structures challenge the classical view on nucleation considering the formation of metastable ion clusters. We demonstrate that dissolved calcium carbonate in fact contains stable prenucleation ion clusters forming even in undersaturated solution. The cluster formation can be characterized by means of equilibrium thermodynamics, applying a multiple-binding model, which allows for structural preformation. Stable clusters are the relevant species in calcium carbonate nucleation. Such mechanisms may also be important for the crystallization of other minerals.
碳酸钙形成水垢、地质沉积物、生物矿物质和海洋沉积物。大量二氧化碳以碳酸根离子的形式留存，钙离子是水硬度的主要贡献因素。尽管其具有重要意义，但关于碳酸钙的沉淀机制却知之甚少，特定的复杂晶体结构对基于亚稳离子簇形成的经典成核观点提出了挑战。我们证明，溶解的碳酸钙实际上包含即使在不饱和溶液中也会形成的稳定的预成核离子簇。可以通过应用允许结构预形成的多重结合模型，借助平衡热力学来表征簇的形成。稳定的簇是碳酸钙成核中的相关物种。这种机制对于其他矿物质的结晶可能也很重要。
