Lin Yingzheng, Cao Yitao, Yao Qiaofeng, Xie Jianping
Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University Binhai New City Fuzhou 350207 P. R. China.
Department of Chemical and Biomolecular Engineering, National University of Singapore 4 Engineering Drive 4 Singapore 117585 Singapore
Chem Sci. 2022 Mar 25;13(16):4598-4607. doi: 10.1039/d1sc06296d. eCollection 2022 Apr 20.
Alloy nanoparticles represent one of the most important metal materials, finding increasing applications in diverse fields of catalysis, biomedicine, and nano-optics. However, the structural evolution of bimetallic nanoparticles in their full composition spectrum has been rarely explored at the molecular and atomic levels, imparting inherent difficulties to establish a reliable structure-property relationship in practical applications. Here, through an inter-particle reaction between [Au(SR)] and [Ag(SR)] nanoparticles or nanoclusters (NCs), which possess the same number of metal atoms, but different atomic packing structures, we reveal the composition-dependent structural evolution of alloy NCs in the alloying process at the molecular and atomic levels. In particular, an inter-cluster reaction can produce three sets of Au Ag NCs in a wide composition range, and the structure of Au Ag NCs evolves from Ag-rich [Au Ag (SR)] ( = 1-12), to evenly mixed [Au Ag (SR)] ( = 19-24), and finally to Au-rich [Au Ag (SR)] ( = 40-43) NCs, with the increase of the Au/Ag atomic ratio in the NC composition. In addition, leveraging on real-time electrospray ionization mass spectrometry (ESI-MS), we reveal the different inter-cluster reaction mechanisms for the alloying process in the sub-3-nm regime, including partial decomposition-reconstruction and metal exchange reactions. The molecular-level inter-cluster reaction demonstrated in this study provides a fine chemistry to customize the composition and structure of bimetallic NCs in their full alloy composition spectrum, which will greatly increase the acceptance of bimetallic NCs in both basic and applied research.
合金纳米颗粒是最重要的金属材料之一，在催化、生物医学和纳米光学等不同领域的应用越来越广泛。然而，双金属纳米颗粒在其整个组成范围内的结构演变在分子和原子水平上很少被探索，这给在实际应用中建立可靠的结构-性能关系带来了固有的困难。在这里，通过具有相同金属原子数但不同原子堆积结构的[Au(SR)]和[Ag(SR)]纳米颗粒或纳米团簇（NCs）之间的颗粒间反应，我们在分子和原子水平上揭示了合金化过程中合金NCs的组成依赖性结构演变。特别是，团簇间反应可以在很宽的组成范围内产生三组Au-Ag NCs，并且随着NC组成中Au/Ag原子比的增加，Au-Ag NCs的结构从富Ag的[Au-Ag(SR)]（=1-12）演变为均匀混合的[Au-Ag(SR)]（=19-24），最后演变为富Au的[Au-Ag(SR)]（=40-43）NCs。此外，利用实时电喷雾电离质谱（ESI-MS），我们揭示了亚3纳米范围内合金化过程的不同团簇间反应机制，包括部分分解-重构和金属交换反应。本研究中展示的分子水平团簇间反应提供了一种精细的化学方法来定制双金属NCs在其整个合金组成范围内的组成和结构，这将大大提高双金属NCs在基础研究和应用研究中的接受度。
