Nanoparticle agglomeration and assembly in confined spaces

为了设计特定的复合材料，我们建议通过实验和模拟来研究受限条件下胶体颗粒的团聚。萨尔布吕肯团队已经建立了基本的实验方法：将直径约为10 nm的颗粒引入乳液的分散相中，然后缓慢蒸发。适当的表面活性剂可防止皮克林乳液的形成，并迫使颗粒留在液滴内。在这些条件下，粒子的行为让人想起金属原子。它们形成能量最小的“伦纳-琼斯”团簇，具有可预测几何形状的超粒子。该过程是一个技术上有前途的路线，明确的微观结构和一个很好的实验平台，以研究和调整agglomeration.In这里提出的项目，我们希望建立一个理论上的理解，有序团聚的限制和扩展的过程中，技术相关的颗粒混合物。纳米颗粒的混合物将在乳液中组装。根据粒子的相互作用和过程动力学，液滴中的粒子可以相分离成“Janus”超粒子，组装成规则的二元晶体，导致“片状”超粒子或形成无序的“混合”超粒子。我们建议通过单粒子水平的模拟来分析组装过程。为了预测哪种粒子、配体和工艺条件可以产生哪种形态，我们将在卢森堡大学进行模拟，其中粒子相互作用和限制几何形状将系统地变化。在有限的边界条件下寻找最佳的二元Lennard Jones团簇的问题将通过一个盆地跳跃的方法来解决。一旦找到了最小势能构型，我们还将使用我们最近开发的计算自由能的方法来解决它们的热稳定性。在INM，我们将根据模拟结果选择颗粒混合物和工艺条件，并通过实验评估预测的结构是否形成。金属和氧化物纳米颗粒将被混合、乳化并组装成超颗粒。组装将通过时间分辨光学透射光谱和光散射原位观察。电子显微镜将产生粒子的真实空间结构，光散射和X射线光谱将告诉我们结构是否均匀和稳定。如果我们成功地从不同极性的粒子中创造出Janus簇，我们将分析它们作为表面活性剂的行为。

We propose to study the agglomeration of colloidal particles in confinement by means of experiments and simulations with the aim to design specific composites.The basic experimental method has already been established in the group in Saarbrücken: Particles with diameters of around 10 nm are introduced into the dispersed phase of an emulsion, which is then slowly evaporated. Appropriate surfactants prevent the formation of Pickering emulsions and force the particles to remain inside the droplets. Under these conditions, the particles' behavior is reminiscent of metal atoms. They form minimum-energy "Lennard-Jones" clusters, supraparticles with predictable geometries. The process is a technologically promising route to well-defined microstructures and an excellent experimental platform to study and tune agglomeration.In the project proposed here, we want to establish a theoretical understanding of ordered agglomeration in confinement and extend the process to technologically relevant particle mixtures. Mixtures of nanoparticles will be assembled inside emulsions. Depending on the particles' interactions and the process kinetics, the particles in the droplets may phase-separate into "Janus" supraparticles, assemble into regular binary crystals that lead to "patchy" supraparticles or form disordered "mixed" supraparticles. We propose to analyze the assembly process by means of simulation at the single particle level. To predict which particles, ligands and process conditions can yield which morphology, we will perform simulations where particle interactions and confining geometries will be systematically varied.The simulations will be carried out at the university of Luxembourg. The problem of finding optimal binary Lennard Jones clusters under confining boundary conditions will be addressed by means of a basin hopping approach. Once the minimum potential energy configurations will have been found, we will also address their thermal stability using a method to calculate free energies that we have recently developed. At INM, we will select particle mixtures and process conditions according to the simulation results and assess experimentally whether the predicted structures form. Metal and oxide nanoparticles will be mixed, emulsified, and assembled into supraparticles. The assembly will be observed in situ through time-resolved optical transmission spectroscopy and light scattering. Electron microscopy will yield real-space structures of the particles, light scattering and x-ray spectroscopy will inform us whether the structures are homogeneous and stable. If we succeed in creating Janus clusters from particles of different polarity, we will analyze their behavior as surfactants.