Functionalities of a nanoporous crystal 12CaO•7Al2O3 originating from the incorporation of active anions
Functionalities of a nanoporous crystal 12CaO•7Al2O3 originating from the incorporation of active anions
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DOI：
10.1246/bcsj.80.872
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发表时间：
2007-05-15
影响因子：
4
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Hayashi, Katsuro;Hirano, Masahiro;Hosono, Hideo
在12 CaO中心点7Al（2）O（3）（Cl 2A 7）的带正电荷的晶格框架中形成的笼状结构被用于引入和释放化学不稳定的阴离子，赋予该材料化学和电子活性。高浓度的氧自由基阴离子，即O-和O2（-），在这些笼中有效地形成在高氧活性条件下。O-离子是所有活性氧物种中最强的氧化剂，可以通过施加电场和热辅助从笼中提取到外部真空中。相反，氢还原过程允许在笼中形成氢化物（H-）离子。掺入H离子的C12 A7在紫外光或电子束照射下表现出持久的绝缘体-导体转换。在实验和第一性原理理论计算的基础上，讨论了辐照诱导转换机制和电子输运特性。从H-离子释放的电子被笼捕获，并且随后的电子的笼间跳跃负责导电。此外，一个严重的还原环境，使我们能够取代电子几乎完全的笼中的阴离子，形成一个稳定的无机氧化物。最后，这些活性阴离子在这种材料中的形成检查的电子结构，热力学和笼的结构特征。
A cage structure formed in a positively charged lattice framework of 12CaO center dot 7Al(2)O(3) (Cl2A7) is utilized to incorporate and release chemically unstable anions, imparting chemical and electronic activities to this material. High concentrations of oxygen radical anions, i.e. O- and O2(-), are formed efficiently in these cages under a high oxygen activity condition. The O- ion, which is the strongest oxidant among all the reactive oxygen species, can be extracted from the cages into an external vacuum by applying an electric field with thermal assistance. In contrast, hydrogen-reduction processes allow the formation of hydride (H-) ions in the cage. H- ion-incorporated C12A7 exhibits a persistent insulator-conductor conversion upon irradiation with ultraviolet-light or electron-beam. The irradiation-induced conversion mechanism and electronic transport characteristics are discussed on the basis of experimental evidence and first-principle theoretical calculations. Electrons released from the H- ions are trapped by the cages and subsequent inter-cage hopping of the electrons is responsible for the electrical conduction. Furthermore, a severe reducing environment enables us to substitute electrons almost completely for anions in the cages, forming a stable inorganic electride. Finally, the formation of these active anions in this material is examined in terms of electronic structures, thermodynamics, and structural features of the cage.