School of Life Science and Technology, and State Key Laboratory of Natural Medicines, China Pharmaceutical University , Nanjing 210009, P. R. China.
School of Food Science and Technology, State Key Lab of Food Science and Technology, Jiangnan University , Wuxi, Jiangsu 214122, P. R. China.
J Am Chem Soc. 2017 Nov 22;139(46):16630-16639. doi: 10.1021/jacs.7b07838. Epub 2017 Nov 10.
The ability of semiconductor nanoparticles (NPs) to self-assemble has been known for several decades. However, the limits of the geometrical and functional complexity for the self-assembled nanostructures made from simple often polydispersed NPs are still continuing to amaze researchers. We report here the self-assembly of primary ∼2-4 nm FeSe NPs with puck-like shapes into either (a) monocrystalline nanosheets ∼5.5 nm thick and ∼1000 nm in lateral dimensions or (b) mesoscale hedgehogs ∼550 nm in diameter with spikes of ∼250 nm in length, and ∼10-15 nm in diameter, the path of the assembly is determined by the concentration of dodecanethiol (DT) in the reaction media. The nanosheets represent the constitutive part of hedgehogs. They are rolled into scrolls and assembled around a single core with distinct radial orientation forming nanoscale "needles" approximately doubling its fractal dimension of these objects. The core is assembled from primary NPs and nanoribbons. The size distribution of the mesoscale hedgehogs can be as low as 3.8%, indicating a self-limited mechanism of the assembly. Molecular dynamics simulation indicates that the primary FeSe particles have mobile edge atoms and asymmetric basal surfaces. The top-bottom asymmetry of the puck-like NPs originates from the Fe-rich/Se-rich stripes on the (011) surface of the orthorhombic FeSe crystal lattice, displaying 2.7 nm periodicity that is comparable to the lateral size of the primary NPs. As the concentration of DT increases, the NPs bind to additional metal sites, which increases the chemical and topographic asymmetry and switches the assembly pathways from nanosheets to hedgehogs. These results demonstrate that the self-assembly of NPs with non-biological surface ligands and without any biological templates results in morphogenesis of inorganic superstructures with complexity comparable to that of biological assemblies, for instance mimivirus. The semiconductor nature of FeSe hedgehogs enables their utilizations in catalysis, drug delivery, optics, and energy storage.
半导体纳米粒子（NPs）自组装的能力已经被人们知晓了几十年。然而，由简单的、通常是多分散的 NPs 自组装而成的纳米结构在几何和功能复杂性方面的极限，仍然让研究人员感到惊讶。我们在这里报告了具有 puck 形状的初级 ∼2-4nmFeSe NPs 自组装成单晶纳米片，厚度约为 5.5nm，横向尺寸约为 1000nm，或者自组装成介观刺猬，直径约为 550nm，刺长约为 250nm，直径约为 10-15nm，组装的路径由反应介质中二已基硫醇（DT）的浓度决定。纳米片是刺猬的组成部分。它们被卷成螺旋状，并围绕单个核心组装，核心具有明显的径向取向，形成纳米级的“针”，使其分形维数增加一倍左右。核心由初级 NPs 和纳米带组装而成。介观刺猬的尺寸分布可以低至 3.8%，表明组装具有自限制机制。分子动力学模拟表明，初级 FeSe 颗粒具有可移动的边缘原子和不对称的基面。 puck 形状 NPs 的上下不对称性源于正交 FeSe 晶格（011）表面上的富 Fe/富 Se 条纹，显示出 2.7nm 的周期性，与初级 NPs 的横向尺寸相当。随着 DT 浓度的增加， NPs 结合到更多的金属位点，这增加了化学和地形的不对称性，并将组装途径从纳米片切换到刺猬。这些结果表明，具有非生物表面配体且没有任何生物模板的 NPs 的自组装导致具有与生物组装相当复杂性的无机超结构的形态发生，例如 mimivirus。FeSe 刺猬的半导体性质使其能够在催化、药物输送、光学和储能等方面得到应用。
