Loh Guan Chee
Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore, 138632, Singapore.
Chemphyschem. 2016 Apr 18;17(8):1180-94. doi: 10.1002/cphc.201501131. Epub 2016 Feb 19.
With the rise of 2D materials, such as graphene and transition metal dichalcogenides, as viable materials for numerous experimental applications, it becomes more necessary to maintain fine control of their properties. One expedient and efficacious technique to regulate their properties is surface functionalization. In this study, DFT calculations are performed on triangular MoS2 quantum dots (QDs) either partially or completely doped with nanoparticles (NPs) of the noble metals Au, Ag, and Pt. The effects of these dopants on the geometry, electronic properties, magnetic properties, and chemical bonding of the QDs are investigated. The calculations show that the structural stability of the QDs is reduced by Au or Ag dopants, whereas Pt dopants have a contrasting effect. The NPs diminish the metallicity of the QD, the extent of which is contingent on the number of NPs adsorbed on the QD. However, these NPs exert distinctly disparate charge transfer effects-Ag NPs n-dope the QDs, whereas Au and Pt NPs either n- or p-dope. The molecular electrostatic potential maps of the occupied states show that metallic states are removed from the doping sites. Notwithstanding the decrease of magnetization in all three types of hybrid QD, the distribution of spin density in the Pt-doped QD is inherently different from that in the other QDs. Bond analyses using the quantum theory of atoms in molecules and the crystal orbital Hamilton population suggest that bonds between the Pt NPs and the QDs are the most covalent and the strongest, followed by the Au-QD bonds, and then Ag-QD bonds. The versatility of these hybrid QDs is further examined by applying an external electric field in the three orthogonal orientations, and comparing their properties with those in the absence of the electric field. There are two primary observations: 1) dopants at the tail, head and tail, and in the fully encased configuration are most effective in modifying the distribution of metallic states if the electric field is absent, and 2) the metallic states in these aforementioned QDs are generally insensitive to the electric field. Conversely, the asymmetric electric effects on the charge transfer in these QDs have to be carefully monitored to allow finer control of their structural stability. This study aptly demonstrates the value of noble metal dopants for manipulating the properties of MoS2 QDs, and shows the versatility of these hybrid QDs as tunable nanodevices. This notably extends the functionality of these nanostructures for applications such as catalysis and nanoelectronics.
随着二维材料（如石墨烯和过渡金属二卤化物）作为众多实验应用的可行材料的兴起，对其性质进行精细控制变得更加必要。一种调节其性质的便捷且有效的技术是表面功能化。在本研究中，对部分或完全掺杂有贵金属金、银和铂纳米颗粒（NP）的三角形二硫化钼量子点（QD）进行了密度泛函理论（DFT）计算。研究了这些掺杂剂对量子点的几何结构、电子性质、磁性和化学键的影响。计算结果表明，金或银掺杂剂会降低量子点的结构稳定性，而铂掺杂剂则有相反的效果。纳米颗粒降低了量子点的金属性，其程度取决于吸附在量子点上的纳米颗粒数量。然而，这些纳米颗粒产生明显不同的电荷转移效应——银纳米颗粒对量子点进行n型掺杂，而金和铂纳米颗粒则进行n型或p型掺杂。占据态的分子静电势图表明，金属态从掺杂位点移除。尽管所有三种类型的混合量子点的磁化强度都有所降低，但铂掺杂量子点中的自旋密度分布与其他量子点本质上不同。使用分子中原子的量子理论和晶体轨道哈密顿布居进行的键分析表明，铂纳米颗粒与量子点之间的键是最具共价性且最强的，其次是金 - 量子点键，然后是银 - 量子点键。通过在三个正交方向上施加外部电场并将其性质与无电场时的性质进行比较，进一步研究了这些混合量子点的多功能性。有两个主要观察结果：1）如果没有电场，位于尾部、头部和尾部以及完全包裹构型的掺杂剂在改变金属态分布方面最有效；2）上述量子点中的金属态通常对电场不敏感。相反，必须仔细监测这些量子点中电荷转移的不对称电效应，以便更精细地控制其结构稳定性。本研究恰当地证明了贵金属掺杂剂在操纵二硫化钼量子点性质方面的价值，并展示了这些混合量子点作为可调谐纳米器件的多功能性。这显著扩展了这些纳米结构在催化和纳米电子学等应用中的功能。
