Driven diffusion in nanoscaled materials

这个新成立的项目旨在研究液体中的扩散以及在几nm到几μm范围内的固液界面、孔洞和受挫液晶层中的扩散。实验上设想了两种方法，即单示踪剂扩散(通过光学技术)和在纳米室中的自扩散(通过场梯度核磁共振)。这两种方法之间的联系是基于详细的数据评估和理论建模。我们将涵盖非常广泛的时间范围，从10 ns到几分钟。中心目标是研究由于空间限制和物理化学性质的特定界面相互作用而产生的限制效应。主要挑战之一是比较来自单个量子物体观测和整体实验的数据，因为它们允许比较时间和系综平均，从而研究纳米尺度系统的遍历性。出于这个原因，所有类别的设想材料都必须能够通过这两种实验方法获得。将特别强调由外部梯度驱动的运动，例如化学势和电场或磁场的梯度。化学势的梯度将被用来通过核磁共振研究纳米孔中的冻结前沿，相比之下，通过表面附着的分子转子的旋转动力学来研究。作为一个附加的受限纳米系统，我们将研究受挫液晶薄膜中的扩散动力学。单个近晶液晶层的“受挫”将由外加电场或磁场与固-液界面的物理化学势之间的竞争控制。理论上具有挑战性的任务是这类非均质系统中的张量类扩散和纳米尺度环境中的相变。

The newly formed project aims at the investigation of diffusion in liquids and in thin liquid crystal layers at solid-liquid interfaces, in pores and in frustrated liquid crystal layers in the range between a few nm and a few μm. Experimentally two approaches are envisaged, namely single tracer diffusion (via optical techniques) and self-diffusion in nano-compartments (via field gradient NMR). The link between these two approaches is based on elaborated data evaluation and theoretical modeling. We will cover an extremely broad time range from 10 ns to several minutes. The central goal is the investigation of confinement effects due to spatial restrictions and specific interface interactions of physico-chemical nature. One of the major challenges is the comparison of data from single quantum object observations and bulk experiments, since they allow for a comparison of time and ensemble averaging and thus the investigation of ergodicity of nanoscaled systems. For this reason it is mandatory that all classes of envisaged materials should be accessible by both experimental approaches. Special emphasis will be on motion driven by external gradients such as gradients of the chemical potential and electric or magnetic fields. Gradients of the chemical potential will be used to study the freezing front in nanopores via NMR and, in comparison, via rotational dynamics of surface attached molecular rotors. As an additional restricted nanosystem we will study diffusion dynamics in frustrated liquid crystal films. The “frustration” of individual smectic liquid crystal layers will be controlled by the competition between applied external electric or magnetic fields and the physicochemical potentials at the solid-liquid interface. Theoretically challenging tasks are the tensor-like diffusion in such heterogeneous systems and the occurrence of phase transitions in nanoscaled environments.