Department of Chemistry, ‡The James Franck Institute, §Department of Physics, The University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.
ACS Nano. 2016 Sep 27;10(9):8947-55. doi: 10.1021/acsnano.6b04965. Epub 2016 Sep 7.
A central challenge in nano- and mesoscale materials research is facile formation of specific structures for catalysis, sensing, and photonics. Self-assembled equilibrium structures, such as three-dimensional crystals or ordered monolayers, form as a result of the interactions of the constituents. Other structures can be achieved by imposing forces (fields) and/or boundary conditions, which Whitesides termed "self-organization". Here, we demonstrate contact line pinning on locally curved surfaces (i.e., a self-assembled monolayer of SiO2 colloidal particles) as a boundary condition to create extended arrays of uniform rings of Au nanoparticles (NPs) on the SiO2 colloids. The mechanism differs from the well-known "coffee-ring" effect; here the functionalized NPs deposit at the contact line and are not driven by evaporative transport. Thus, NP ring formation depends on the hydrophobicity and wetting of the SiO2 colloids by the chloroform solution, ligands on the NPs, and temperature. The NP rings exhibit size scaling behavior, maintaining a constant ratio of NP ring-to-colloid diameter (from 300 nm to 2 μm). The resultant high-quality NP ring structures are expected to have interesting photonic properties.
在纳米和介观材料研究中，一个核心挑战是为催化、传感和光子学方便地形成特定结构。自组装平衡结构，如三维晶体或有序单层，是由于组成部分的相互作用而形成的。其他结构可以通过施加力（场）和/或边界条件来实现，Whitesides 将其称为“自组织”。在这里，我们展示了在局部弯曲表面（即 SiO2 胶体颗粒的自组装单层）上固定接触线作为边界条件，在 SiO2 胶体上创建均匀的 Au 纳米颗粒（NPs）环的扩展阵列。该机制不同于众所周知的“咖啡环”效应；在这里，功能化的 NPs 在接触线处沉积，而不是由蒸发传输驱动。因此，NP 环的形成取决于 SiO2 胶体对氯仿溶液的疏水性和润湿性、NP 上的配体和温度。NP 环表现出尺寸缩放行为，保持 NP 环与胶体直径的恒定比值（从 300nm 到 2μm）。预期所得的高质量 NP 环结构具有有趣的光子特性。
