Solution-processable GO/rGO: Preparation, functionalization, self-assembly and applications in smart information devices

Abstract

Graphene, as a kind of nano and mesoscopic molecule which consists of one-atom-thick planar sheet comprising sp2-bonded carbon structure with exceptionally high crystal and electronic quality, shows hierarchical different physical and chemical properties and has been emerged as a rapidly rising star in the field of material science. Graphene has caused much concern in many areas of science and technology due to its remarkable properties. These properties include extraordinary mechanic performances, high specific surface areas and electron transport capabilities. These unique physicochemical properties suggest that graphene has great potential for providing new approaches and critical improvements in the field of information devices. In recent years, many reviews focusing on graphene and related materials have been published. In addition, several reviews with particular emphasis on information devices based on graphene related materials have been reported. One specific branch of graphene research deals with graphene oxide (GO) and reduced graphene oxide (rGO). GO can be considered as a precursor to graphene synthesis by either chemical or thermal/light reduction processes. GO consists of a single-layer of graphite oxide and is usually produced by the chemical treatment of graphite through oxidation, with subsequent dispersion and exfoliation in water or suitable organic solvents. With respect to its structure, there have been several structural models proposed over the years. These assume the presence of various oxygen functional groups in the GO. The oxygen functional groups have been identified as mostly in the form of hydroxyl and epoxy groups on the basal plane, with smaller amounts of carboxyl, carbonyl, phenol, lactone, and quinone at the sheet edges. The chemical reduction of graphene oxide is a promising route towards the large scale production of graphene for commercial applications. The electrical conductivity of the functionalized graphene has been observed to decrease significantly compared to pure graphene, moreover, the surface area of the functionalized graphene prepared by covalent and non-covalent techniques decreases significantly due to the destructive chemical oxidation of flake graphite followed by sonication, functionalization and chemical reduction. However, complementary to the inherent properties of graphene, functionalization or hybridization from GO and rGO can substantially improve the performance of these materials in the information devices. The functionalization of graphene can be performed by covalent and noncovalent modification techniques. In both cases, surface modification and chemical selective reduction of graphene oxide have been carried out to obtain solution-processable graphene related materials. It has been found that both the covalent and noncovalent modification techniques are very effective in the preparation of solution-processable graphene related materials. In this review, we outline the developments of GO/rGO related chemical reactions, functionalization routes and self-assembled methods in the viewpoint of hierarchical chemistry. The dispersibility and interactions of nanosheets involved in thin film technology are summarized here to better understanding the GO/rGO ink formula, film forming and nanostructure. Finally, the applications of GO/rGO related soluble processed materials in smart information devices such as information display, information storage and neuromorphic are discussed as well as the current challenges and several possible future research directions.