Self-construction of core-shell and hollow zeolite analcime icositetrahedra: A reversed crystal growth process via oriented aggregation of nanocrystallites and recrystallization from surface to core
Self-construction of core-shell and hollow zeolite analcime icositetrahedra: A reversed crystal growth process via oriented aggregation of nanocrystallites and recrystallization from surface to core
复制标题
核壳和中空沸石方沸石二十面体的自构建：通过纳米微晶的定向聚集和从表面到核心的再结晶的逆晶体生长过程
DOI：
10.1021/ja074834u
复制
发表时间：
2007-10-31
影响因子：
15
通讯作者：
He, Heyong
中科院分区：
文献类型：
--
作者：
Chen, Xueying;Qiao, Minghua;He, Heyong
在乙胺和Raney Ni存在下，采用一锅水热法合成了具有核壳结构和中空二十面体结构的沸石方解石。对不同制备阶段样品的详细研究表明，复杂单晶几何结构的生长并不遵循经典的晶体生长路线，即具有高度对称性的晶体(如多面体)通常是通过原子或离子附着到原子核上来生长的。通过纳米晶的定向聚集和表面再结晶，观察到了反向晶体生长过程。整个过程可以用以下四个连续的步骤来描述。(1)初生方解石纳米小片定向聚集，形成铁饼状颗粒。(2)这些圆盘进一步组装成多晶微球。(3)较大的血小板通过消耗较小的血小板而长成纳米棒，同时微球的表面通过Ostwald熟化重新结晶成薄的单晶二十碳四面体外壳。(4)再结晶以牺牲纳米棒为代价从表面向核心继续进行，单晶壳的厚度不断增加，直到所有纳米棒被消耗殆尽，导致中空的单晶二十面体。本工作为理解沸石分子筛的生长机理提供了新的有用信息。
Zeolite analcime with a core-shell and hollow icositetrahedron architecture was prepared by a one-pot hydrothermal route in the presence of ethylamine and Raney Ni. Detailed investigations on samples at different preparation stages revealed that the growth of the complex single crystalline geometrical structure did not follow the classic crystal growth route, i.e., a crystal with a highly symmetric morphology (such as polyhedra) is normally developed by attachment of atoms or ions to a nucleus. A reversed crystal growth process through oriented aggregation of nanocrystallites and surface recrystallization was observed. The whole process can be described by the following four successive steps. (1) Primary analcime nanoplatelets undergo oriented aggregation to yield discus-shaped particles. (2) These disci further assemble into polycrystalline microspheres. (3) The relatively large platelets grow into nanorods by consuming the smaller ones, and meanwhile, the surface of the microspheres recrystallizes into a thin single crystalline icositetrahedral shell via Ostwald ripening. (4) Recrystallization continues from the surface to the core at the expense of the nanorods, and the thickness of the monocrystalline shell keeps on increasing until all the nanorods are consumed, leading to hollow single crystalline analcime icositetrahedra. The present work adds new useful information for the understanding of the principles of zeolite growth.