Morphological instability of core-shell metallic nanoparticles
Morphological instability of core-shell metallic nanoparticles
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DOI：
10.1103/physrevb.87.165435
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发表时间：
2013-04-24
影响因子：
3.7
通讯作者：
Ferrando, Riccardo
中科院分区：
文献类型：
--
作者：
Bochicchio, Davide;Ferrando, Riccardo
具有核-壳结构的双金属纳米颗粒(通常称为纳米合金)在光学、催化、磁性和生物医学等领域具有特殊的应用价值。尽管这些纳米粒子的应用受到了广泛的关注，但稳定其结构的物理因素在很大程度上仍不清楚，尤其是几何结构与化学有序模式之间的关系。这里进行了全局优化搜索，以挑选出与最重要的几何结构相对应的最稳定的化学有序化模式，用于一系列弱互溶体系，包括AgCu、AgNi、AgCO和AuCo。计算表明：(I)纳米合金的整体几何结构与其内核的形状和位置是严格相关的；(Ii)在二十面体纳米粒子中可以获得中心核，但在晶体或十面体纳米粒子中不能获得中心核，形成不对称的准Janus形貌；(Iii)在二十面体纳米粒子中，当核超过临界尺寸时，会产生一种新的形态不稳定性，使核不对称并向纳米粒子表面延伸；(Iv)在多二十面体纳米合金中可以获得多中心图案。讨论了二十面体纳米合金中的核不稳定性与薄膜生长中的斯特兰基-克拉斯塔诺夫不稳定性之间的相似和区别。所有这些问题对于设计战略以实现有效的岩芯涂层至关重要。DOI：10.1103/PhysRevB.87.165435
Bimetallic nanoparticles (often known as nanoalloys) with core-shell arrangement are of special interest in several applications, such as in optics, catalysis, magnetism, and biomedicine. Despite wide interest in applications, the physical factors stabilizing the structures of these nanoparticles are still unclear to a great extent, especially for what concerns the relationship between geometric structure and chemical ordering patterns. Here global-optimization searches are performed in order to single out the most stable chemical ordering patterns corresponding to the most important geometric structures, for a series of weakly miscible systems, including AgCu, AgNi, AgCo, and AuCo. The calculations show that (i) the overall geometric structure of the nanoalloy and the shape and placement of its inner core are strictly correlated; (ii) centered cores can be obtained in icosahedral nanoparticles but not in crystalline or decahedral ones, in which asymmetric quasi-Janus morphologies form; (iii) in icosahedral nanoparticles, when the core exceeds a critical size, a new type of morphological instability develops, making the core asymmetric and extending it towards the nanoparticle surface; (iv) multicenter patterns can be obtained in polyicosahedral nanoalloys. Analogies and differences between the instability of the core in icosahedral nanoalloys and the Stranski-Krastanov instability occurring in thin-film growth are discussed. All these issues are crucial for designing strategies to achieve effective coatings of the cores. DOI: 10.1103/PhysRevB.87.165435