Zernike Institute for Advanced Materials and the Materials Innovation Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Nanoscale. 2013 Jun 21;5(12):5375-83. doi: 10.1039/c3nr00565h.
Nowadays bimetallic nanoparticles (NPs) have emerged as key materials for important modern applications in nanoplasmonics, catalysis, biodiagnostics, and nanomagnetics. Consequently the control of bimetallic structural motifs with specific shapes provides increasing functionality and selectivity for related applications. However, producing bimetallic NPs with well controlled structural motifs still remains a formidable challenge. Hence, we present here a general methodology for gas phase synthesis of bimetallic NPs with distinctively different structural motifs ranging at a single particle level from a fully mixed alloy to core-shell, to onion (multi-shell), and finally to a Janus/dumbbell, with the same overall particle composition. These concepts are illustrated for Mo-Cu NPs, where the precise control of the bimetallic NPs with various degrees of chemical ordering, including different shapes from spherical to cube, is achieved by tailoring the energy and thermal environment that the NPs experience during their production. The initial state of NP growth, either in the liquid or in the solid state phase, has important implications for the different structural motifs and shapes of synthesized NPs. Finally we demonstrate that we are able to tune the alloying regime, for the otherwise bulk immiscible Mo-Cu, by achieving an increase of the critical size, below which alloying occurs, closely up to an order of magnitude. It is discovered that the critical size of the NP alloy is not only affected by controlled tuning of the alloying temperature but also by the particle shape.
如今，双金属纳米粒子（NPs）已经成为纳米等离激元学、催化、生物诊断和纳米磁学等重要现代应用中的关键材料。因此，控制具有特定形状的双金属结构基元为相关应用提供了越来越多的功能和选择性。然而，生产具有良好控制结构基元的双金属 NPs 仍然是一个艰巨的挑战。因此，我们在这里提出了一种在气相中合成具有独特结构基元的双金属 NPs 的通用方法，这些结构基元在单个颗粒水平上从完全混合的合金到核壳、洋葱（多壳），最后到 Janus/dumbbell，其整体颗粒组成相同。这些概念以 Mo-Cu NPs 为例进行了说明，通过调整 NPs 在生产过程中经历的能量和热环境，可以精确控制具有不同化学有序度的双金属 NPs，包括从球形到立方体的不同形状。NP 生长的初始状态，无论是在液态还是固态，对合成 NPs 的不同结构基元和形状都有重要影响。最后，我们证明，我们能够通过实现合金化临界尺寸的大幅增加（在该尺寸以下发生合金化），来调节原本不互溶的 Mo-Cu 的合金化范围，其增加幅度接近一个数量级。发现 NP 合金的临界尺寸不仅受到合金化温度的控制调节的影响，还受到颗粒形状的影响。
