Pattern Formation in Binary Colloidal Assemblies: Hidden Symmetries in a Kaleidoscope of Structures
Pattern Formation in Binary Colloidal Assemblies: Hidden Symmetries in a Kaleidoscope of Structures
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DOI：
10.1021/acs.langmuir.8b01411
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发表时间：
2018-07-03
期刊：
影响因子：
3.9
通讯作者：
Zambelli, Tomaso
中科院分区：
文献类型：
--
作者：
Lotito, Valeria;Zambelli, Tomaso
在这项研究中，我们详细地研究了两种不同尺寸的颗粒在空气/水界面自组装形成的二元胶体结构的形态，其尺寸比使得较大的颗粒在二元组装中不保持六方排列。虽然保存了这种六方有序的二元混合物的结构和对称性已经被彻底地研究过了，但由于很难找到适合于识别看似无定形和无序排列中隐藏的对称性的分析工具，在不保持六方有序的情况下的二元胶体还没有得到同样详细的研究。为此，我们求助于基于计算几何和计算拓扑的不同分析工具的组合，以获得组件的形态的全面图像。通过对小粒子相对于大粒子的不同浓度的二元组装体进行广泛的研究，我们确定了明显无序的组装体中共存的主要图案，并检测到随着小粒子数量的增加对称性的转变。随着小颗粒浓度的增加，大颗粒的排列变得更加稀薄，发生了从六方对称到菱形和方形对称的转变，同时伴随着小颗粒簇的增加；每种特定对称的相对重量可以通过改变组件的组成来控制。证明了通过改变实验条件来控制表面无序的二元胶体组装体的形态的可能性，并定义了研究无序组装体的路线，这对于未来研究复杂的胶体模式、了解自组装机制和定制胶体组装体的物理性质是重要的。
In this study, we present a detailed investigation of the morphology of binary colloidal structures formed by self-assembly at air/water interface of particles of two different sizes, with a size ratio such that the larger particles do not retain a hexagonal arrangement in the binary assembly. While the structure and symmetry of binary mixtures in which such hexagonal order is preserved has been thoroughly scrutinized, binary colloids in the regime of non-preservation of the hexagonal order have not been examined with the same level of detail due also to the difficulty in finding analysis tools suitable to recognize hidden symmetries in seemingly amorphous and disordered arrangements. For this purpose, we resorted to a combination of different analysis tools based on computational geometry and computational topology to get a comprehensive picture of the morphology of the assemblies. By carrying out an extensive investigation of binary assemblies in this regime with variable concentration of smaller particles with respect to larger particles, we identify the main patterns that coexist in the apparently disordered assemblies and detect transitions in the symmetries upon increase in the number of small particles. As the concentration of small particles increases, large particle arrangements become more dilute and a transition from hexagonal to rhombic and square symmetries occurs, accompanied also by an increase in clusters of small particles; the relative weight of each specific symmetry can be controlled by varying the composition of the assemblies. The demonstration of the possibility to control the morphology of apparently disordered binary colloidal assemblies by varying experimental conditions and the definition of a route for the investigation of disordered assemblies are important for future studies of complex colloidal patterns to understand self-assembly mechanisms and to tailor the physical properties of colloidal assemblies.