Department of Chemistry, University of Illinois at Urbana-Champaign, CLSL A, 601 South Goodwin Avenue, Urbana, Illinois 61801, USA.
Department of Physics, University of Illinois at Urbana-Champaign, Loomis Laboratory, 1110 West Green Street, Urbana, Illinois 61801, USA.
Nat Commun. 2017 Feb 20;8:14514. doi: 10.1038/ncomms14514.
Super-ionic solids, which exhibit ion mobilities as high as those in liquids or molten salts, have been employed as solid-state electrolytes in batteries, improved thermoelectrics and fast-ion conductors in super-capacitors and fuel cells. Fast-ion transport in many of these solids is supported by a disordered, 'liquid-like' sub-lattice of cations mobile within a rigid anionic sub-lattice, often achieved at high temperatures or pressures via a phase transition. Here we show that ultrasmall clusters of copper selenide exhibit a disordered cationic sub-lattice under ambient conditions unlike larger nanocrystals, where Cu ions and vacancies form an ordered super-structure similar to the bulk solid. The clusters exhibit an unusual cationic sub-lattice arrangement wherein octahedral sites, which serve as bridges for cation migration, are stabilized by compressive strain. The room-temperature liquid-like nature of the Cu sub-lattice combined with the actively tunable plasmonic properties of the CuSe clusters make them suitable as fast electro-optic switches.
具有类液体或熔融盐中离子迁移率的超离子固体已被用作电池中的固态电解质、改进的热电材料和超级电容器和燃料电池中的快速离子导体。在许多这些固体中，快速离子传输由无序的、“类液体”的阳离子亚晶格支持，这些阳离子在刚性阴离子亚晶格中移动，通常通过相变在高温或高压下实现。在这里，我们表明，硒化亚铜的超小团簇在环境条件下表现出无序的阳离子亚晶格，而不像较大的纳米晶体那样，其中 Cu 离子和空位形成类似于体相固体的有序超结构。团簇表现出一种不寻常的阳离子亚晶格排列，其中八面体位作为阳离子迁移的桥梁，通过压缩应变稳定。Cu 亚晶格在室温下的类液态性质与 CuSe 团簇的可主动调谐等离子体性质相结合，使它们适合用作快速电光开关。
