Osowiecki Wojciech T, Ye Xingchen, Satish Pratima, Bustillo Karen C, Clark Ezra L, Alivisatos A Paul
Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
Department of Chemistry , University of California , Berkeley , California 94720 , United States.
J Am Chem Soc. 2018 Jul 11;140(27):8569-8577. doi: 10.1021/jacs.8b04558. Epub 2018 Jun 29.
The ability to predict and control the formation of bimetallic heterogeneous nanocrystals is desirable for many applications in plasmonics and catalysis. Here, we report the synthesis and characterization of stable, monodisperse, and solution-processed Cu-Ag bimetallic nanoparticles with specific but unusual elemental arrangements that are consistent with a recently developed thermodynamic model. Using air-free scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, the distribution of Cu and Ag positions was unambiguously identified within individual nanocrystals (NCs), leading to the discovery of a Cu-Ag nanocrescent shape. A simple yet versatile thermodynamic model was applied to illustrate how the interplay between surface and interface energies determines the particle morphology. It is found that there exists a range of surface-to-interface energy ratios under which crescent-shaped nanocrystals are the thermodynamically favored products, with the morphology tunable by adjusting the Ag content. We further show the conversion of Cu-Ag nanocrescents into Ag@CuO upon mild oxidation, whereas fully core-shell Cu@Ag NCs are robust against oxidation up to 100 °C. The plasmonic and interband absorptions of Cu-Ag NCs depend on the composition and the degree of Cu oxidation, which may find application in light-driven catalysis.
对于等离子体激元和催化领域的许多应用而言，能够预测和控制双金属异质纳米晶体的形成是非常必要的。在此，我们报道了具有特定但不寻常元素排列的稳定、单分散且可溶液加工的铜 - 银双金属纳米粒子的合成与表征，这些排列与最近开发的热力学模型一致。使用配备能量色散X射线光谱仪的无空气扫描透射电子显微镜，明确确定了单个纳米晶体（NCs）内铜和银的位置分布，从而发现了一种铜 - 银纳米新月形状。应用了一个简单但通用的热力学模型来说明表面能与界面能之间的相互作用如何决定颗粒形态。研究发现，存在一系列表面与界面能之比，在此比例下新月形纳米晶体是热力学上更有利的产物，其形态可通过调整银含量来调节。我们进一步表明，在温和氧化条件下，铜 - 银纳米新月会转化为Ag@CuO，而完全核壳结构的Cu@Ag NCs在高达100°C 的温度下对氧化具有抗性。铜 - 银NCs的等离子体激元和带间吸收取决于组成以及铜的氧化程度，这可能在光驱动催化中得到应用。
