School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
J Am Chem Soc. 2010 Jun 23;132(24):8378-84. doi: 10.1021/ja101083v.
The superatom model for nanoparticle structure is shown to be inadequate for the prediction of the thermodynamic stability of gold nanoparticles. The observed large HOMO-LUMO gaps for stable nanoparticles predicted by this model are, for sulfur-stabilized gold nanoparticles, attributed to covalent interactions of the metal with thiyl adsorbate radicals rather than ionic interactions with thiolate adsorbate ions, as is commonly presumed. In particular, gold adatoms in the stabilizing layer are shown to be of Au(0) nature, subtle but significantly different from the atoms of the gold core owing to the variations in the proportion of gold-gold and gold-sulfur links that form. These interactions explain the success of the superatom model in describing the electronic structure of both known and informatory nanoparticle compositions. Nanoparticle reaction energies are, however, found not to correlate with the completion of superatom shells. Instead, local structural effects are found to dominate the chemistry and in particular the significantly different chemical properties of gold nanoparticle and bulk surfaces. These conclusions are drawn from density-functional-theory calculations for the Au(102)(p-mercaptobenzoic acid)(44) nanoparticle based on the X-ray structure (Jadzinsky, P. D.; et al. Science 2007, 318, 430), as well calculations for the related Au(102)(S(*)-CH(3))(44) nanoparticle, for the inner gold-cluster cores, for partially and overly reacted cores, and for Au(111) surface adsorbates.
该模型表明，纳米粒子结构的超原子模型不足以预测金纳米粒子的热力学稳定性。观察到的稳定纳米粒子的大 HOMO-LUMO 间隙由该模型预测，这归因于金属与硫醇吸附物自由基的共价相互作用，而不是通常假设的与硫醇化物吸附物离子的离子相互作用。特别是，稳定层中的金原子是 Au(0)性质的，由于形成的金-金和金-硫键的比例不同，与金核原子微妙但显著不同。这些相互作用解释了超原子模型在描述已知和信息纳米粒子组成的电子结构方面的成功。然而，发现纳米粒子反应能与超原子壳的完成无关。相反，发现局部结构效应主导了化学性质，特别是金纳米粒子和体相表面的显著不同的化学性质。这些结论是基于 X 射线结构（Jadzinsky，PD；等。Science 2007，318，430）对 Au(102)(p-巯基苯甲酸)(44)纳米粒子的密度泛函理论计算得出的，以及对相关的 Au(102)(S(*)-CH(3))(44)纳米粒子、内金核芯、部分和过度反应的核芯以及 Au(111)表面吸附物的计算得出的。
