Wang Qian, Wang Zongpeng, Li Zhe, Xiao Junyan, Shan Hangyong, Fang Zheyu, Qi Limin
Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry, Peking University, Beijing 100871, China.
State Key Laboratory for Mesoscopic Physics, Collaborative Innovation Center of Quantum Matter, School of Physics, Peking University, Beijing 100871, China.
Sci Adv. 2017 Oct 27;3(10):e1701183. doi: 10.1126/sciadv.1701183. eCollection 2017 Oct.
Self-assembly of colloidal nanocrystals into complex superstructures offers notable opportunities to create functional devices and artificial materials with unusual properties. Anisotropic nanoparticles with nonspherical shapes, such as rods, plates, polyhedra, and multipods, enable the formation of a diverse range of ordered superlattices. However, the structural complexity and tunability of nanocrystal superlattices are restricted by the limited geometries of the anisotropic nanoparticles available for supercrystal self-assembly. We show that uniform gold nanoarrows (GNAs) consisting of two pyramidal heads connected by a four-wing shaft are readily synthesized through controlled overgrowth of gold nanorods. The distinct concave geometry endows the GNAs with unique packing and interlocking ability and allows for the shape-directed assembly of sophisticated two-dimensional (2D) and 3D supercrystals with unprecedented architectures. Net-like 2D supercrystals are assembled through the face-to-face contact of the GNAs lying on the pyramidal edges, whereas zipper-like and weave-like 2D supercrystals are constructed by the interlocked GNAs lying on the pyramidal {111} facets. Furthermore, multilayer packing of net-like and weave-like 2D assemblies of GNAs leads to non-close-packed 3D supercrystals with varied packing efficiencies and pore structures. Electromagnetic simulation of the diverse nanoarrow supercrystals exhibits exotic patterns of nanoscale electromagnetic field confinement. This study may open new avenues toward tunable self-assembly of nanoparticle superstructures with increased complexity and unusual functionality and may advance the design of novel plasmonic metamaterials for nanophotonics and reconfigurable architectured materials.
胶体纳米晶体自组装成复杂的超结构为制造具有非凡特性的功能器件和人工材料提供了显著机会。具有非球形形状的各向异性纳米粒子，如棒状、片状、多面体和多脚状纳米粒子，能够形成各种有序的超晶格。然而，纳米晶体超晶格的结构复杂性和可调性受到可用于超晶体自组装的各向异性纳米粒子有限几何形状的限制。我们表明，由通过四翼轴连接的两个锥头组成的均匀金纳米箭头（GNA）可通过金纳米棒的可控过度生长轻松合成。独特的凹面几何形状赋予GNA独特的堆积和互锁能力，并允许以形状导向方式组装具有前所未有的结构的复杂二维（2D）和三维（3D）超晶体。网状二维超晶体通过位于锥边的GNA面对面接触组装而成，而拉链状和编织状二维超晶体则由位于锥{111}晶面的互锁GNA构建而成。此外，GNA的网状和编织状二维组件的多层堆积导致具有不同堆积效率和孔结构的非密堆积三维超晶体。对各种纳米箭头超晶体的电磁模拟展示了纳米级电磁场限制的奇异模式。这项研究可能为具有更高复杂性和非凡功能的纳米粒子超结构的可调自组装开辟新途径，并可能推动用于纳米光子学的新型等离子体超材料和可重构结构材料的设计。
