Weizmann Institute of Science, Department of Structural Biology, Rehovot 76100, Israel.
J Am Chem Soc. 2010 Sep 29;132(38):13208-11. doi: 10.1021/ja106883c.
Silicate ions increase the thermal stability of the unstable amorphous calcium carbonate (ACC). This effect was observed first by comparing ACC from two different species of cystoliths, small calcified bodies formed in the leaves of some plants. The temperature of crystallization to calcite in the silicate-rich cystoliths from M. alba is 100 °C higher than that of the silicate-poor cystoliths from F. microcarpa. The stabilizing effect is confirmed in vitro with synthetic samples differing in their silicate content. With increasing silicate concentration in ACC, the crystallization temperature to calcite also increases. A mechanism of geometric frustration is suggested, whereby the presence of the tetrahedral silicate ion in the flat carbonate lattice prevents organization into crystalline polymorphs.
硅酸盐离子提高了不稳定的无定形碳酸钙（ACC）的热稳定性。这一效应最初是通过比较两种不同种属的囊泡中的 ACC 而观察到的，囊泡是一些植物叶片中形成的小型钙化体。富含硅酸盐的囊泡来自 M. alba，其方解石结晶温度比富硅酸盐的囊泡来自 F. microcarpa 高 100°C。体外实验用不同硅酸盐含量的合成样品证实了这种稳定效应。随着 ACC 中硅酸盐浓度的增加，结晶至方解石的温度也随之升高。提出了一种几何受挫的机制，其中四面体硅酸盐离子在平坦的碳酸盐晶格中的存在阻止了其组织成晶态多晶型物。
