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

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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).