Department of Chemistry and Materials Engineering, Shinshu University 4-17-1, Wakasato, Nagano, 380-0928, Japan.
Chem Rec. 2018 Jul;18(7-8):829-839. doi: 10.1002/tcr.201700071. Epub 2017 Dec 29.
We overview the entire surface coverage of amorphous silica with layered silicates (smectite-like) using the direct crystallization technique under hydrothermal conditions. Various shapes (e. g., microspheres, fibers, microcapsules) have been available as the silica substrates, which involve partial dissolution triggered by the hydrolysis of urea for supplying a source of the layered silicates. Other sources (e. g., Li , Mg , Al ) have been supplied from aqueous solutions, participating the heterogeneous nucleation of the layered silicates. Because of partial dissolution of the silica substrates, the original shape has been preserved after the hydrothermal reactions. Cation exchange reactions, usually observed for conventional smectite systems, occurred by replacing the interlayer cations in the silicates with metal (a rare-earth ion) and organic (a quaternary long-chain alkylammonium, methylene blue, and a tris-chelated complex) cations. We have discussed the mechanism of the crystallization and displayed some applications of the hybrids (e. g., chiral discrimination, filtering, and magnetic recovery).
我们使用水热条件下的直接结晶技术，概述了无定形二氧化硅与层状硅酸盐（类蒙脱石）的整个表面覆盖。各种形状（例如微球、纤维、微胶囊）都可用作二氧化硅基质，这涉及到由尿素水解引发的部分溶解，以提供层状硅酸盐的来源。其他来源（例如 Li、Mg、Al）来自水溶液，参与了层状硅酸盐的异质成核。由于二氧化硅基质的部分溶解，水热反应后保留了原始形状。通常在常规蒙脱石体系中观察到的阳离子交换反应是通过用金属（稀土离子）和有机（季铵长链烷基、亚甲蓝和三螯合配合物）阳离子取代硅酸盐中的层间阳离子来实现的。我们讨论了结晶的机制，并展示了一些混合物的应用（例如手性识别、过滤和磁性回收）。
