Self-Limiting Shell Formation in Cu@Ag Core-Shell Nanocrystals during Galvanic Replacement.,The Journal of Physical Chemistry Letters

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Self-Limiting Shell Formation in Cu@Ag Core-Shell Nanocrystals during Galvanic Replacement.
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2020-06-12 , DOI: 10.1021/acs.jpclett.0c01551
Gaurav A Kamat _{1,

2} , Chang Yan _{2,

3} , Wojciech T Osowiecki _{2,

3} , Ivan A Moreno-Hernandez ₂ , Marc Ledendecker ₄ , A Paul Alivisatos _{2,

3,

5,

6}

Affiliation

The understanding of synthetic pathways of bimetallic nanocrystals remains limited due to the complex energy landscapes and dynamics involved. In this work, we investigate the formation of self-limiting Cu@Ag core–shell nanoparticles starting from Cu nanocrystals followed by galvanic replacement with Ag ions. Bulk quantification with atomic emission spectroscopy and spatially resolved elemental mapping with electron microscopy reveal distinct nucleation regimes that produce nanoparticles with a tunable Ag shell thickness, but only up to a certain limiting thickness. We develop a quantitative transport model that explains this observed self-limiting structure as arising from the balance between entropy-driven interdiffusion and a positive mixing enthalpy. The proposed model depends only on the intrinsic physical properties of the system such as diffusivity and mixing energy and directly yields a high level of agreement with the elemental mapping profiles without requiring additional fit parameters.

中文翻译：

在电流置换过程中，Cu @ Ag核壳纳米晶体中的自限壳形成。

由于涉及复杂的能量图景和动力学，对双金属纳米晶体的合成途径的理解仍然受到限制。在这项工作中，我们研究了从Cu纳米晶体开始形成自限Cu @ Ag核壳纳米颗粒，然后用Ag离子进行电取代。原子发射光谱的大量定量分析和电子显微镜的空间分辨元素图谱揭示了独特的成核机制，该机制产生了具有可调节的Ag壳厚度，但仅达到一定极限厚度的纳米颗粒。我们开发了一个定量传输模型，该模型解释了这种观察到的自我限制结构，这种结构是由熵驱动的互扩散与正混合焓之间的平衡引起的。

更新日期：2020-06-12

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