Electrical and Mechanical Properties of Freestanding Membranes Consisting of Organically Cross-Linked Metal Nanoparticles: The Effect of Order and Disorder

独立式纳米膜是一种典型厚度约为1-100纳米的二维材料，它不附着在固体基底上。由于各种各样的潜在应用，从柔性电子和新型传感器或MEMS元件到高效过滤器和生物医学产品，这种膜在过去几年中受到了极大的关注。本课题将制备并表征由共价交联金纳米颗粒组成的导电纳米膜。由于这些膜中的电荷传输依赖于邻近纳米粒子之间的载流子隧穿，粒子间距离的细微变化应该会导致这些材料的电导率发生重大变化。因此，通过简单的电阻测量，应能以极高的灵敏度检测到膜的张力。然而，考虑到以往的研究结果，预计电荷输运对应变的敏感性取决于粒子的有序程度。至于作为MEMS元件和传感元件的潜在应用，我们将研究有序和无序在多大程度上控制这些膜的机械和机电性能。为此，我们将开发一种新方法，使我们能够制备高度有序和共价交联的纳米颗粒膜。在这些膜中需要共价交联来提供材料足够的强度和耐久性。之后，将通过静、动态挠度试验分析膜的力学性能和机电转导。为了将结果与相关的结构特征联系起来，我们将通过原位SAXS测量来表征颗粒有序程度及其在应力下的扰动和重组。最后，生成的数据集将用于评估交联纳米颗粒膜作为高灵敏度机电换能器和新型MEMS元件的应用潜力。

Freestanding nanomembranes are 2D-materials with typical thicknesses of ca. 1-100 nm, which are not attached to a solid substrate. Due to the broad variety of potential applications, ranging from flexible electronics and novel sensors or MEMS elements to highly efficient filters and biomedical products, such membranes have received significant attention, during the past few years. In this project electrically conductive nanomembranes consisting of covalently cross-linked gold nanoparticles will be prepared and characterized. Because the charge transport in these membranes relies on tunneling of charge carriers between neighboring nanoparticles, already subtle variations of the interparticle distances should cause significant changes in the conductivity of these materials. Thus, straining the membrane should be detectable with extremely high sensitivity by simple resistance measurements. However, taking into account the results of previous studies, it is expected that the sensitivity of the charge transport to strain is dictated by the degree of ordering of the particles. With respect to potential applications as MEMS components and sensing elements we will investigate to what extent order and disorder control the mechanical and mechano-electrical properties of these membranes. For this purpose we will develop a new method allowing us to prepare highly ordered and covalently crosslinked nanoparticle membranes. In these membranes covalent cross-linking is needed to provide the material with sufficient strength and durability. Thereafter, the mechanical properties and mechanoelectrical transduction of the membranes will be analyzed by static and dynamic deflection tests. In order to correlate the results with relevant structural features we will characterize the degree of particle ordering and its perturbation and reorganization under stress by in situ SAXS measurements. Finally, the generated datasets will be used to evaluate the potential of cross-linked nanoparticle membranes for applications as highly sensitive mechanoelectrical transducers ond novel MEMS elements.