Role of the Crystal Structure in Cation Exchange Reactions Involving Colloidal Cu(2)Se Nanocrystals.
Role of the Crystal Structure in Cation Exchange Reactions Involving Colloidal Cu(2)Se Nanocrystals.
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DOI：
10.1021/jacs.7b03706
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发表时间：
2017-07-19
影响因子：
15
通讯作者：
Manna L
中科院分区：
文献类型：
--
作者：
Gariano G;Lesnyak V;Brescia R;Bertoni G;Dang Z;Gaspari R;De Trizio L;Manna L
化学计量的 Cu2Se 纳米晶体以立方或六方（亚稳态）晶体结构合成，并用作与 Pb2+ 离子的阳离子交换反应的主体材料。即使在这两种情况下交换的最终产物都是岩盐 PbSe 纳米晶体，我们在这里表明起始纳米晶体的晶体结构对交换途径有很大的影响。将立方 Cu2Se 纳米晶体暴露于 Pb2+ 阳离子导致 PbSe 在主体纳米晶体的整个表面上无选择性地初始形成，产生 Cu2Se@PbSe 核@壳纳米异质结构。这种中间体的形成归因于主晶格内 Pb2+ 离子的低扩散率以及立方 Cu2Se 中缺乏优选的进入点。另一方面，在六方 Cu2Se 纳米晶体中，Pb2+ 离子的进入产生了“夹在”六方 Cu2Se 域之间的 PbSe 条纹。这些奇特的异质结构是由于 Pb2+ 离子通过六方 Cu2Se 结构的特定 (a, b) 平面优先扩散而形成的，其特征是几乎空的八面体位点。我们的研究结果表明，部分阳离子交换反应形成的纳米异质结构的形态不仅与NC主体材料密切相关，而且与其晶体结构密切相关。
Stoichiometric Cu2Se nanocrystals were synthesized in either cubic or hexagonal (metastable) crystal structures and used as the host material in cation exchange reactions with Pb2+ ions. Even if the final product of the exchange, in both cases, was rock-salt PbSe nanocrystals, we show here that the crystal structure of the starting nanocrystals has a strong influence on the exchange pathway. The exposure of cubic Cu2Se nanocrystals to Pb2+ cations led to the initial formation of PbSe unselectively on the overall surface of the host nanocrystals, generating Cu2Se@PbSe core@shell nanoheterostructures. The formation of such intermediates was attributed to the low diffusivity of Pb2+ ions inside the host lattice and to the absence of preferred entry points in cubic Cu2Se. On the other hand, in hexagonal Cu2Se nanocrystals, the entrance of Pb2+ ions generated PbSe stripes “sandwiched” in between hexagonal Cu2Se domains. These peculiar heterostructures formed as a consequence of the preferential diffusion of Pb2+ ions through specific (a, b) planes of the hexagonal Cu2Se structure, which are characterized by almost empty octahedral sites. Our findings suggest that the morphology of the nanoheterostructures, formed upon partial cation exchange reactions, is intimately connected not only to the NC host material, but also to its crystal structure.
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