Mammen Nisha, Malola Sami, Honkala Karoliina, Häkkinen Hannu
Department of Physics, Nanoscience Center, University of Jyväskylä, Jyväskylä-40014, Finland.
Nanoscale. 2020 Dec 8;12(46):23859-23868. doi: 10.1039/d0nr07366k.
Atomically precise metal nanoclusters, stabilized and functionalized by organic ligands, are emerging nanomaterials with potential applications in plasmonics, nano-electronics, bio-imaging, nanocatalysis, and as therapeutic agents or drug carriers in nanomedicine. The ligand layer has an important role in modifying the physico-chemical properties of the clusters and in defining the interactions between the clusters and the environment. While this role is well recognized from a great deal of experimental studies, there is very little theoretical information on dynamical processes within the layer itself. Here, we have performed extensive molecular dynamics simulations, with forces calculated from the density functional theory, to investigate thermal stability and dynamics of the ligand layer of the meta-mercaptobenzoic acid (m-MBA) protected Au68 and Au144 nanoclusters, which are the first two gold nanoclusters structurally solved to atomic precision by electron microscopy [Azubel et al., Science, 2014, 345, 909 and ACS Nano, 2017, 11, 11866]. We visualize and analyze dynamics of three distinct non-covalent interactions, viz., ligand-ligand hydrogen bonding, metal-ligand O[double bond, length as m-dash]C-OHAu interaction, and metal-ligand Ph(π)Au interaction. We discuss their relevance for defining, at the same time, the dynamic stability and reactivity of the cluster. These interactions promote the possibility of ligand addition reactions for bio-functionalization or allow the protected cluster to act as a catalyst where active sites are dynamically accessible inside the ligand layer.
由有机配体稳定并功能化的原子精确金属纳米团簇是新兴的纳米材料，在等离子体激元学、纳米电子学、生物成像、纳米催化以及作为纳米医学中的治疗剂或药物载体等方面具有潜在应用。配体层在改变团簇的物理化学性质以及定义团簇与环境之间的相互作用方面起着重要作用。虽然从大量实验研究中已经充分认识到了这一作用，但关于该层本身内部动力学过程的理论信息却非常少。在这里，我们进行了广泛的分子动力学模拟，使用从密度泛函理论计算得到的力，来研究间巯基苯甲酸（m-MBA）保护的Au68和Au144纳米团簇的配体层的热稳定性和动力学，这是通过电子显微镜首次在原子精度上解析结构的前两个金纳米团簇[阿祖贝尔等人，《科学》，2014年，345卷，909页；《美国化学会纳米》，2017年，11卷，11866页]。我们可视化并分析了三种不同的非共价相互作用的动力学，即配体-配体氢键、金属-配体O[双键，长度为m破折号]C-OHAu相互作用以及金属-配体Ph(π)Au相互作用。我们讨论了它们对于同时定义团簇的动态稳定性和反应性的相关性。这些相互作用促进了生物功能化的配体加成反应的可能性，或者使受保护的团簇能够作为催化剂，其中活性位点在配体层内部是动态可及的。
