Department of Chemistry and Biochemistry, University of Mississippi , Oxford, Mississippi 38677, United States.
Department of Chemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States.
J Am Chem Soc. 2017 Nov 1;139(43):15450-15459. doi: 10.1021/jacs.7b08651. Epub 2017 Oct 9.
We report the discovery of an unprecedentedly large, 2.2 nm diameter, thiolate protected gold nanocrystal characterized by single crystal X-ray crystallography (sc-XRD), Au(SPh-tBu) named Faradaurate-279 (F-279) in honor of Michael Faraday's (1857) pioneering work on nanoparticles. F-279 nanocrystal has a core-shell structure containing a truncated octahedral core with bulk face-centered cubic-like arrangement, yet a nanomolecule with a precise number of metal atoms and thiolate ligands. The AuS geometry was established from a low-temperature 120 K sc-XRD study at 0.90 Å resolution. The atom counts in core-shell structure of Au follows the mathematical formula for magic number shells: Au@Au@Au@Au@Au, which is further protected by a final shell of Au. Au core is protected by three types of staple motifs, namely: 30 bridging, 18 monomeric, and 6 dimeric staple motifs. Despite the presence of such diverse staple motifs, AuS structure has a chiral pseudo-D symmetry. The core-shell structure can be viewed as nested, concentric polyhedra, containing a total of five forms of Archimedean solids. A comparison between the Au and Au cuboctahedral superatom model in shell-wise growth is illustrated. F-279 can be synthesized and isolated in high purity in milligram quantities using size exclusion chromatography, as evidenced by mass spectrometry. Electrospray ionization-mass spectrometry independently verifies the X-ray diffraction study based heavy atoms formula, AuS, and establishes the molecular formula with the complete ligands, namely, Au(SPh-tBu). It is also the smallest gold nanocrystal to exhibit metallic behavior, with a surface plasmon resonance band around 510 nm.
我们报告了一种前所未有的大尺寸、2.2nm 直径的硫醇保护金纳米晶体的发现，该晶体通过单晶 X 射线晶体学（sc-XRD）进行了表征，被命名为 Faradaurate-279（F-279），以纪念迈克尔·法拉第（Michael Faraday）（1857 年）在纳米颗粒方面的开创性工作。F-279 纳米晶体具有核壳结构，包含一个具有体心立方状排列的截断八面体核，但却是一个具有精确数量金属原子和硫醇配体的纳米分子。AuS 几何结构是通过低温 120K sc-XRD 研究在 0.90Å 分辨率下确定的。核壳结构中的原子数符合魔术数壳的数学公式：Au@Au@Au@Au@Au，进一步由最后一层 Au 保护。Au 核由三种类型的钉扎基序保护，即：30 个桥接、18 个单体和 6 个二聚体钉扎基序。尽管存在如此多样的钉扎基序，但 AuS 结构具有手性拟 D 对称性。核壳结构可以看作是嵌套的、同心的多面体，包含总共五种阿基米德固体形式。Au 和 Au 二十面体超原子模型在壳层生长方面的比较如图所示。F-279 可以使用尺寸排阻色谱法以毫克级的量合成和分离，得到高纯度的产物，质谱法证明了这一点。电喷雾电离质谱法独立验证了 X 射线衍射研究中基于重原子的公式 AuS，并建立了具有完整配体的分子公式，即 Au(SPh-tBu)。它也是表现出金属行为的最小金纳米晶体，其表面等离子体共振带约为 510nm。
