A Two-Dimensional Polyimide-Graphene Heterostructure with Ultra-fast Interlayer Charge Transfer.

Two-dimensional polymers (2DPs) are a class of atomically/molecularly thin crystalline organic 2D materials. They are intriguing candidates for the development of unprecedented organic-inorganic 2D van der Waals heterostructures (vdWHs) with exotic physicochemical properties. In this work, we demonstrate the on-water surface synthesis of large-area (cm2 ), monolayer 2D polyimide (2DPI) with 3.1-nm lattice. Such 2DPI comprises metal-free porphyrin and perylene units linked by imide bonds. We further achieve a scalable synthesis of 2DPI-graphene (2DPI-G) vdWHs via a face-to-face co-assembly of graphene and 2DPI on the water surface. Remarkably, femtosecond transient absorption spectroscopy reveals an ultra-fast interlayer charge transfer (ca. 60 fs) in the resultant 2DPI-G vdWH upon protonation by acid, which is equivalent to that of the fastest reports among inorganic 2D vdWHs. Such large interlayer electronic coupling is ascribed to the interlayer cation-π interaction between 2DP and graphene.

Glial cell responses on tetrapod-shaped graphene oxide and reduced graphene oxide 3D scaffolds in brain in vitro and ex vivo models of indirect contact.

Brain implants are promising instruments for a broad variety of nervous tissue diseases with a wide range of applications, e.g. for stimulation, signal recording or local drug delivery. Recently, graphene-based scaffold materials have emerged as attractive candidates as neural interfaces, 3D scaffolds, or drug delivery systems due to their excellent properties like flexibility, high surface area, conductivity, and lightweight. To date, however, there is a lack of appropriate studies of the foreign body response, especially by glial cells, towards graphene-based materials. In this work, we investigated the effects of macroscopic, highly porous (>99.9%) graphene oxide (GO) and reduced graphene oxide (rGO) (conductivity ∼1 S m-1) scaffolds with tailorable macro- and microstructure on human astrocyte and microglial cell viability and proliferation as well as expression of neuroinflammation and astrogliosis associated genes in an indirect contact approach. In this in vitro model, as well as ex vivo in organotypic murine brain slices, we could demonstrate that both GO and rGO based 3D scaffolds exert slight effects on the glial cell populations which are the key players of glial scar formation. These effects were in most cases completely abolished by curcumin, a known anti-inflammatory and anti-fibrotic drug that could in perspective be applied to brain implants as a protectant.

Carbon Nanoparticles' Impact on Processability and Physical Properties of Epoxy Resins-A Comprehensive Study Covering Rheological, Electrical, Thermo-Mechanical, and Fracture Properties (Mode I and II).

A trade-off between enhancement of physical properties of the final part and the processability during manufacturing always exists for the application of nanocarbon materials in thermoset-based composites. For different epoxy resins, this study elaborates the impact of nanocarbon particle type, functionalization, and filler loading on the resulting properties, i.e., rheological, electrical, thermo-mechanical, as well as the fracture toughness in mode I and mode II loading. Therefore, a comprehensive set of carbon nanoparticles, consisting of carbon black (CB), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), few layer graphene (FLG), and electrochemically expanded graphite (ExG), in purified or functionalized configuration was introduced in various epoxy resins, with different molecular weight distributions. A novel technique to introduce sharp cracks into single-edge notched bending (SENB) fracture toughness specimens led to true values. SWCNT show highest potential for increasing electrical properties without an increase in viscosity. Functionalized MWCNT and planar particles significantly increase the fracture toughness in mode I by a factor of two.