Graphene oxide (GO) sheets prepared by Hummers' method have been separated into two portions with large (f1) or small (f2) lateral dimensions from their aqueous dispersion. This method is based on the selective precipitation of GO sheets with lateral dimensions mostly (>90%) larger than 40 μm(2) at a pH value of 4.0 because of their larger hydrophobic planes and fewer hydrophilic oxygenated groups. The hydrazine reduced Langmuir-Blodgett (LB) films of f1 showed much higher conductivities than those of f2. Furthermore, the thin film of f1 prepared by filtration exhibited a smaller d-space and much higher tensile strength and modulus than those of f2 films. The one-step size fractionation method reported here is simple, cheap, efficient, and environmentally friendly, which can be used for the size fractionation of GO sheets in large scale.

This review summarizes the recent advancements in the synthesis and applications of graphene materials for flexible graphene devices related to energy conversion and storage.

A gram-scale, low-cost and sustainable synthesis of single-crystalline graphene quantum dots derived from biomass waste.

This review details recent progress in the conversion of technical lignins to multi-functional, high-value, and promising carbon fiber materials, and discusses their applications.

Composite films of chitosan and reduced graphene oxide (RGO) sheets with nacre-like layered structure have been prepared by vacuum filtration of the stable aqueous mixture of both components. The film containing 6 wt% RGO is electrically conductive with a conductivity of 1.2 S m À1 . Furthermore, it is mechanically strong and ductile; its Young's modulus, tensile strength and elongation at break were measured to be 6.3 AE 0.2 GPa, 206 AE 6 MPa and 6.5 AE 0.6%, respectively. These values partly exceed those of nacre. The high mechanical and electrical properties of chitosan/ RGO composite films are mainly attributed to the uniform dispersion of RGO nanofillers in the polymer matrices to form a compact layered structure.

A metal-free and flexible supercapacitor was prepared based on redox-active lignosulfonate functionalized graphene hydrogels.

Graphene nanomeshes (GNMs) which can be cheaply produced on a large scale and processed through wet approaches are important materials for various applications, including catalysis, composites, sensors and energy related systems. Here, we report a method for large scale preparation of GNMs by refluxing reduced graphene oxide sheets in concentrated nitric acid solution (e.g., 8 moles per liter). The diameters of nanopores in GNM sheets can be readily modulated from several to hundreds nanometers by varying the time of acid treatment. The porous structure increased the specific surface areas of GNMs and the transmittances of GNM-based thin films. Furthermore, GNMs have large number of carboxyl groups at the edges of their nanopores, leading to good dispersibility in aqueous media and strong peroxidase-like catalytic activity.

Pristine graphene and chemically modified graphenes (CMGs, e.g., graphene oxide, reduced graphene oxide and their derivatives) can react with a variety of chemical substances. These reactions have been applied to modulate the structures and properties of graphene materials, and to extend their functions and practical applications. This perspective outlines the chemistry of graphene, including functionalization, doping, photochemistry, catalytic chemistry, and supramolecular chemistry. The mechanisms of graphene related reactions will be introduced, and the challenges in controlling the chemical reactions of graphene will be discussed.