Distinct metal-exchange pathways of doped Ag25 nanoclusters
Distinct metal-exchange pathways of doped Ag25 nanoclusters
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DOI：
10.1039/c6nr06353e
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发表时间：
2016-01-01
期刊：
影响因子：
6.7
通讯作者：
Bakr, Osman M.
中科院分区：
文献类型：
--
作者：
Bootharaju, Megalamane S.;Sinatra, Lutfan;Bakr, Osman M.
原子精密金属纳米团簇（NCs）包含一种以上类型的金属原子（即掺杂或合金），由于协同效应，为NCs的催化和光学特性的工程设计开辟了新的途径，这是同金属NCs无法做到的。不幸的是，如何在纳米碳管中可控地引入多金属掺杂剂，了解掺杂剂的位置、机制和协同效应仍然是一个主要的挑战。为了克服这些挑战，我们设计了一种金属交换方法，其中nc作为分子模板，金属离子作为传入掺杂剂的来源。特别合成了两种结构相似的单掺杂富银纳米材料[MAg24(SR)(18)](2-) （M = Pd/Pt和SR：硫代酸盐）作为模板，研究了它们在金原子引入后的转化机理。通过高分辨率质谱、光谱学和元素分析，Au原子在MAg24框架中的可控结合有助于阐明不同的掺杂途径。有趣的是，金取代了[PdAg24(SR)(18)]（2-）团簇的中心Pd原子，产生了主要的双金属[AuAg24(SR)(18)]（-）团簇和少量的[Au2Ag23(SR)(18)]（-）团簇。相反，在[PtAg24(SR)(18)]（2-）簇中，中心Pt原子保持完整，金取代了非中心Ag原子形成三金属[AuxPtAg24-x(SR)(18)](2-) NCs，其中x = 1-2，保留了一部分起始[PtAg24(SR)(18)](2-) NCs。这项研究揭示了一些不寻常的掺杂纳米碳化物的金属交换途径，以及初始金属掺杂在指导第二掺杂在最终产物中的位置方面所起的重要作用。
Atomically precise metal nanoclusters (NCs) containing more than one type of metal atom (i.e., doped or alloyed), due to synergistic effects, open new avenues for engineering the catalytic and optical properties of NCs in a manner that homometal NCs cannot. Unfortunately, it is still a major challenge to controllably introduce multimetallic dopants in NCs, understanding the dopants' positions, mechanism, and synergistic effects. To overcome these challenges, we designed a metal-exchange approach involving NCs as molecular templates and metal ions as the source of the incoming dopant. In particular, two structurally similar monodoped silver-rich NCs, [MAg24(SR)(18)](2-) (M = Pd/Pt and SR: thiolate), were synthesized as templates to study their mechanistic transformation in response to the introduction of gold atoms. The controllable incorporation of Au atoms into the MAg24 framework facilitated the elucidation of distinct doping pathways through high-resolution mass spectrometry, optical spectroscopy and elemental analysis. Interestingly, gold replaced the central Pd atom of [PdAg24(SR)(18)](2-) clusters to produce predominantly bimetallic [AuAg24(SR)(18)](-) clusters along with a minor product of an [Au2Ag23(SR)(18)](-) cluster. In contrast, the central Pt atom remained intact in [PtAg24(SR)(18)](2-) clusters, and gold replaced the noncentral Ag atoms to form trimetallic [AuxPtAg24-x(SR)(18)](2-) NCs, where x = 1-2, with a portion of the starting [PtAg24(SR)(18)](2-) NCs remaining. This study reveals some of the unusual metal-exchange pathways of doped NCs and the important role played by the initial metal dopant in directing the position of a second dopant in the final product.