Stuckert Rouven, Lüders Anton, Wittemann Alexander, Nielaba Peter
Colloid Chemistry, Department of Chemistry, University of Konstanz, Universitaetsstrasse 10, D-78464 Konstanz, Germany.
Statistical and Computational Physics, Department of Physics, University of Konstanz, Universitaetsstrasse 10, D-78464 Konstanz, Germany.
Soft Matter. 2021 Jul 14;17(27):6519-6535. doi: 10.1039/d1sm00635e.
The structure formation and the phase behaviour of monolayers of dumbbell-shaped colloids are explored. For this, we conduct Langmuir-Blodgett experiments at the air/water interface and conventional Brownian dynamic simulations without hydrodynamic interactions. Using Voronoi tessellations and the probability density of the corresponding shape factor of the Voronoi cells p(ζ), the influence of the area fraction φ on the structure of the monolayers is investigated. An increase of the area fraction leads to a higher percentage of domains containing particles with six nearest neighbours and a sharper progression of p(ζ). Especially in dense systems, these domains can consist of aligned particles with uniform Voronoi cells. Thus, the increase of φ enhances the order of the monolayers. Simulations show that a sufficient enhancement of φ also impacts the pair correlation function which develops a substructure in its first maxima. Furthermore, we find that reducing the barrier speed in the Langmuir-Blodgett experiments enhances the final area fraction for a given target surface pressure which, in turn, also increases the percentage of particles with six nearest neighbours and sharpens the progression of p(ζ). Overall, the experiments and simulations show a remarkable qualitative agreement which indicates a versatile way of characterising colloidal monolayers by Brownian dynamics simulations. This opens up perspectives for application to a broad range of nanoparticle-based thin film coatings and devices.
研究了哑铃状胶体单层的结构形成和相行为。为此，我们在空气/水界面进行了朗缪尔-布洛杰特实验，并进行了无流体动力学相互作用的传统布朗动力学模拟。使用沃罗诺伊镶嵌和沃罗诺伊单元相应形状因子的概率密度p(ζ)，研究了面积分数φ对单层结构的影响。面积分数的增加导致包含具有六个最近邻粒子的区域百分比更高，并且p(ζ)的进展更陡峭。特别是在密集系统中，这些区域可以由具有均匀沃罗诺伊单元的排列粒子组成。因此，φ的增加增强了单层的有序性。模拟表明，φ的充分增加也会影响对关联函数，该函数在其第一个最大值处形成子结构。此外，我们发现降低朗缪尔-布洛杰特实验中的屏障速度会提高给定目标表面压力下的最终面积分数，这反过来也会增加具有六个最近邻粒子的百分比，并使p(ζ)的进展更尖锐。总体而言，实验和模拟显示出显著的定性一致性，这表明通过布朗动力学模拟表征胶体单层是一种通用的方法。这为应用于广泛的基于纳米颗粒的薄膜涂层和器件开辟了前景。
