Institute of Functional Nano and Soft Materials (FUNSOM), Collaborative Innovation Center for Suzhou Nano Science and Technology (NANO-CIC), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Soochow University , Suzhou, Jiangsu 215123, People's Republic of China.
Wheeler High School , Marietta, Georgia 30068, United States.
Nano Lett. 2017 May 10;17(5):3270-3275. doi: 10.1021/acs.nanolett.7b00958. Epub 2017 May 1.
The shape anisotropy of nanoparticle building blocks is of critical importance in determining their packing symmetry and assembly directionality. While there has been extensive research on the effect of their overall geometric shapes, the importance of nanometer morphology details is not well-recognized or understood. Here we draw on shape-anisotropic gold triangular nanoprism building blocks synthesized based on a method we recently developed; besides the "large-scale" triangular prism shape (79.8 nm in side length and 22.0 nm in thickness), the prisms are beveled with their sides convexly enclosed by two flat {100} facets. We engineer the balance between electrostatic repulsion and entropically driven depletion attraction in the system to generate self-assemblies without or with the effect of the nanoscale beveling detail. A conventional, planar honeycomb (p-honeycomb) lattice forms with the triangular basal planes packed on the same plane at low depletion attraction, whereas an unexpected interlocking honeycomb (i-honeycomb) lattice and its "supracrystal" forms are assembled with additional close-paralleling of side facets at high depletion attraction. The i-honeycomb lattice renders all the metallic surfaces in close proximity and leads to a surface-enhanced Raman scattering signal nearly 5-fold higher than that in the p-honeycomb lattice and high sensitivity for detecting the model molecule Rhodamine 6G at a concentration as low as 10 M. Our study can guide future work in both nanoparticle synthesis and self-assembly; nanoscale geometrical features in anisotropic nanoparticles can be used as an important handle to control directional interactions for nonconventional ordered assemblies and to enrich diversity in self-assembly structure and function.
纳米粒子结构单元的形状各向异性对于确定其堆积对称性和组装方向性至关重要。尽管已经有大量关于其整体几何形状影响的研究，但纳米形貌细节的重要性尚未得到很好的认识或理解。在这里，我们借鉴了最近开发的方法合成的基于形状各向异性的金三角纳米棱镜结构单元；除了“大规模”三角棱镜形状（边长 79.8nm，厚度 22.0nm）之外，这些棱镜还带有斜面，其侧面由两个平面{100}面凸面封闭。我们在系统中平衡静电排斥和熵驱动的耗尽吸引，以在没有或有纳米级斜面细节的情况下产生自组装。在低耗尽吸引下，三角形基面在同一平面上堆积形成常规的平面蜂窝（p-蜂窝）晶格，而在高耗尽吸引下，会组装出意想不到的互锁蜂窝（i-蜂窝）晶格及其“超晶格”形式，同时还会使侧面更加平行。i-蜂窝晶格使所有金属表面都非常接近，导致表面增强拉曼散射信号比 p-蜂窝晶格高近 5 倍，并且对浓度低至 10M 的模型分子 Rhodamine 6G 具有高灵敏度。我们的研究可以指导纳米粒子合成和自组装的未来工作；各向异性纳米粒子中的纳米级几何特征可用作控制非常规有序组装中定向相互作用的重要手段，并丰富自组装结构和功能的多样性。
