物理化学学报 >> 2018, Vol. 34 >> Issue (7): 770-775.doi: 10.3866/PKU.WHXB201711061

所属专题: 原子水平上精确控制纳米簇和纳米粒子

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巯基保护的中空金纳米球

许文武,高嶷*()   

  • 收稿日期:2017-10-11 发布日期:2018-03-26
  • 通讯作者: 高嶷 E-mail:gaoyi@sinap.ac.cn
  • 基金资助:
    国家自然科学基金(11504396);国家自然科学基金(21773287)

Thiolate-Protected Hollow Gold Nanospheres

Wenwu XU,Yi GAO*()   

  • Received:2017-10-11 Published:2018-03-26
  • Contact: Yi GAO E-mail:gaoyi@sinap.ac.cn
  • Supported by:
    the National Natural Science Foundation of China(11504396);the National Natural Science Foundation of China(21773287)

摘要:

基于全统一模型和密度泛函理论(DFT)计算,我们提出了具有高对称性和稳定性的巯基保护的中空金纳米球Au60(SR)20的原子结构。Au60(SR)20由一个二十面体Au50富勒烯中空笼子(由20个四面体Au4融合构成)和10个[―RS―Au―SR―]订书针结构组成,并遵循“分离和保护”规则。DFT计算表明,这种空心Au60(SR)20纳米球具有大的带隙(1.3 eV)以及在笼中心的核独立化学位移(NICS)为负值(−5),表明其高度的化学稳定性。此外,四面体Au4单元中心的NICS值远大于空心笼中心的NICS值,表明Au60(SR)20的总体稳定性可能来自每个四面体Au4单元的局部稳定性。正的谐波振动频率说明Au60(SR)20纳米球至少是势能表面的局部最小值。另外,我们还通过融合四面体Au4层设计了双层中空金纳米球,表明调整中空金纳米球壳层厚度是可行的。最后,我们还介绍了更大的中空金纳米球Au180(SR)60的设计。这项工作提供了可控设计中空金纳米球的新策略。

关键词: 巯基保护的中空金纳米球, 密度泛函理论, 全统一模型, “分离和保护”规则, 核独立化学位移

Abstract:

We present the atomic structure of thiolate-protected hollow Au nanosphere (HAuNS), Au60(SR)20, with high symmetry and stability based on the grand unified model (GUM; Nat. Commun. 2016, 7, 13574) and density-functional theory (DFT) calculations. Using C20 fullerene (with Ih symmetry) as a template, 20 tetrahedral Au4 units were used to replace the C atoms of C20, and three Au atoms of each Au4 were fused with three neighboring Au4 units by sharing one Au atom to form an icosahedral Au50 fullerene cage as the inner core. Subsequently, the unfused Au atom in each Au4 was bonded with the [―RS―Au―SR―] staple to form the completely hollow Au60(SR)20 nanosphere. Therefore, the Au60(SR)20 is composed of an icosahedral Au50 fullerene hollow cage (constructed by fusing 20 tetrahedral Au4 units) with 10 [―RS―Au―SR―] staples, obeying the "divide and protect" rule. Each Au4 unit has 2e valence electrons, namely, the tetrahedral Au4(2e) elementary block in the grand unified model. The DFT calculations showed that this hollow Au60(SR)20 nanosphere had a large HOMO–LUMO (HOMO: the highest occupied molecular orbital; LUMO: the lowest unoccupied molecular orbital) gap (1.3 eV) and a negative nucleus-independent chemical shift (NICS) value (−5) at the center of the hollow cage, indicating its high chemical stability. Furthermore, the NICS values in the center of the tetrahedral Au4 units were much more negative than that in the center of the hollow cage, revealing that the overall stability of Au60(SR)20 likely stemmed from the local stability of each tetrahedral Au4 unit. The harmonic vibrational frequencies were all positive, suggesting that the HAuNS corresponded to the local minimum of the potential energy surface. In addition, the bilayer HAuNS was designed by fusing the tetrahedral Au4 layers, indicating the feasibility of tuning the thickness of the shell of HAuNS. In bilayer HAuNS, each tetrahedral Au4 unit in the first layer shared four Au atoms, while those in the second layer shared one Au atom. The other three Au atoms of each tetrahedral unit bonded with the SR groups, demonstrating that each tetrahedral Au4 unit has 2e valence electrons (namely the tetrahedral Au4(2e) elementary block in GUM). The HOMO-LUMO gap of the bilayer Au140(SH)60 nanosphere is 1.5 eV, indicating its chemical stability. The thicknesses of the shells in monolayer and bilayer HAuNS are about 0.2 and 0.4 nm, respectively. This process could be easily understood in terms of the local stabilities of the tetrahedral Au4(2e) elementary block in GUM. Finally, the design of larger HAuNS, Au180(SR)60, has also been presented. The HOMO-LUMO gap of Au180(SH)60 was 0.9 eV, which showed that it was also a stable HAuNS. This work provides a new strategy to controllably design the HAuNS.

Key words: Thiolate-protected hollow Au nanosphere, Density-functional theory, Grand unified model, "Divide and protect" rule, Nucleus-independent chemical shift

MSC2000: 

  • O641