Colloidal synthesis of alloyed multimetallic nanocrystals with precise composition control remains a challenge and a critical missing link in theory-driven rational design of functional nanomaterials. Liquid phase transmission electron microscopy (LP-TEM) enables directly visualizing nanocrystal formation mechanisms that can inform discovery of design rules for colloidal multimetallic nanocrystal synthesis, but it remains unclear whether the salient chemistry of the flask synthesis is preserved in the extreme electron beam radiation environment during LPTEM. Here we demonstrate controlled in situ LP-TEM synthesis of alloyed AuCu nanoparticles while maintaining the molecular structure of electron beam sensitive metal thiolate precursor complexes. Ex situ flask synthesis experiments showed that nearly equimolar AuCu alloys formed from heteronuclear metal thiolate complexes, while gold-rich alloys formed in their absence. Systematic dose rate-controlled in situ LP-TEM synthesis experiments established a range of electron beam synthesis conditions that formed alloyed AuCu nanoparticles with similar alloy composition, random alloy structure, and particle size distribution shape as those from ex situ flask synthesis, indicating metal thiolate complexes were preserved under these conditions. Reaction kinetic simulations of radical-ligand reactions revealed that polymer capping ligands acted as effective hydroxyl radical scavengers during LP-TEM synthesis and prevented metal thiolate oxidation at low dose rates. In situ synthesis experiments and ex situ atomic scale imaging revealed that a key role of metal thiolate complexes was to prevent copper atom oxidation and facilitate formation of prenucleation cluster intermediates. This work demonstrates that complex ion precursor chemistry can be maintained during LP-TEM imaging, enabling probing nanocrystal formation mechanisms with LP-TEM under reaction conditions representative of ex situ flask synthesis.

中文翻译：

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可视化配体介导的双金属纳米晶体形成途径与原位液相传输电子显微镜合成

具有精确的成分控制的合金多金属纳米晶体的胶体合成仍然是功能性纳米材料的理论驱动合理设计中的一个挑战和关键的缺失环节。液相透射电子显微镜（LP-TEM）可以直接观察纳米晶体的形成机理，从而可以告知胶体多金属纳米晶体合成设计规则的发现，但仍不清楚在极端的电子束辐射环境下烧瓶合成的显着化学性质是否得到保留在LPTEM期间。在这里，我们证明了合金化的AuCu纳米粒子的受控原位LP-TEM合成，同时保持了电子束敏感的金属硫醇盐前体复合物的分子结构。异位烧瓶合成实验表明，几乎等摩尔的AuCu合金是由异核金属硫醇盐络合物形成的，而富金合金则在不存在的情况下形成。系统剂量率控制的原位LP-TEM合成实验建立了一系列电子束合成条件，形成了合金化的AuCu纳米粒子，其合金成分，无规合金结构和粒度分布形状与异位烧瓶合成中的相似，表明金属硫醇盐复合物在这些条件下被保存。自由基-配体反应的反应动力学模拟表明，在LP-TEM合成过程中，聚合物封端配体可作为有效的羟基自由基清除剂，并在低剂量率下防止金属硫醇盐的氧化。原位合成实验和原位原子尺度成像显示，金属硫醇盐配合物的关键作用是防止铜原子氧化并促进预成核簇中间体的形成。这项工作表明，在LP-TEM成像过程中可以保持复杂的离子前驱体化学，从而能够在代表异位烧瓶合成的反应条件下用LP-TEM探测纳米晶体的形成机理。