Multifunctional membranes of graphene oxide and titania nanocrystals: Electrical, mechanical, and electromechanical properties tuned via photocatalytic reduction

在这个项目中，我们研究了部分还原氧化石墨烯（rGO/GO）和二氧化钛纳米棒或纳米板的独立纳米膜。在这些膜中，石墨烯成分提供导电性。此外，（氧化石墨烯/氧化石墨烯）薄片是非常坚固但具有高度柔韧性的材料，它们以保形包裹并粘合二氧化钛纳米晶体，从而形成极其坚固的纳米复合材料。二氧化钛纳米晶体提供了两个重要的附加功能：首先，它们提供光催化活性，我们利用它来调节氧化石墨烯的还原程度，从而调整膜的各种物理和化学性质。其次，二氧化钛纳米晶体非常坚硬。根据它们的大小、形状和面密度，它们可以形成叠瓦状或干草堆状的形态，这可以强烈地增强所得到的纳米膜。本项目的主要重点是这些纳米膜的机械和响应机电特性，通过原子力显微镜膨胀试验结合原位电荷输运测量来研究这些特性。此外，这些膜被用于制造静电驱动的致动器和谐振器，我们探索了它们的性能如何受到各种环境参数的影响。该项目产生了全面的数据集，这将能够可靠地评估这些材料作为机电传感器和执行器的应用潜力，例如作为新型可打印微机电系统（MEMS）的组件。

In this project we study freestanding nanomembranes of partially reduced graphene oxide (rGO/GO) and TiO2-nanorods or -nanoplates. In these membranes the graphene component provides electrical conductivity. Further, (rGO/GO)-sheets are very strong but highly flexible materials, which conformally wrap around and agglutinate the TiO2-nanocrystals resulting in extremely robust nanocomposites. The TiO2-nanocrystals provide two important additional functions: First, they provide photocatalytic activity, which we utilize to adjust the degree of graphene oxide reduction and, thereby, to tune various physical and chemical properties of the membranes. Second, TiO2-nanocrystals are very stiff. Depending on their size, shape, and areal density they can form assemblies of imbricative or haystack-like morphology, which can strongly reinforce resulting nanomembranes. The main focus of this project is on the mechanical and responsive electromechanical properties of these nanomembranes, which are studied by AFM-bulge tests combined with in situ charge transport measurements. Further, the membranes are used for the fabrication of electrostatically driven actuators and resonators, and we explore how their properties are affected by various environmental parameters. This project generates comprehensive sets of data, which will enable a reliable evaluation of the potential of these material for applications as electromechanical sensors and actuators, e.g. as components in novel types of printable microelectromechanical systems (MEMS).