Two-dimensional graphene has been at the center of a significant research effort due to its high thermal conductivity, high Young's modulus, charge/hole mobility, fracture strength, specific Brunauer-Emmett-Teller surface area, and the quantum Hall effect. Similar to the functionalization of fullerenes, by using covalent or non-covalent modification methods, some organic functional groups, small molecules and polymers have been covalently grafted to the graphene surface or non-covalently doped into the graphene system to form a larger number of graphene derivatives designed for optoelectronics, photonics and biologies. Molecular computation using graphene as the data storage medium has ignited the revolution in information technology industries, making it possible to store more data in less space and with less energy. The data storage performance, stability and reliability of the graphene memories have advanced significantly towards practical information storage applications. A number of essential strategies can be employed to control and optimize the switching characteristics of graphene memories. In this comprehensive review, recent research progress on the graphene-based functional materials, including graphene, graphene oxide(GO), reduced graphene oxide (RGO), chemically modified GO/RGO, graphene/GO/RGO-based composites, and others, as active materials for information storage, has been systematically summarized and discussed. The key problems that need to be solved urgently in the materials design and device fabrication and the future development of this area have also been pointed out.

Contents
1 Introduction
2 Graphene-based information storage devices
2.1 Intrinsic graphene prepared by chemical vapor deposition (CVD)
2.2 Intrinsic graphene prepared by mechanical exfoliation
2.3 Graphene nanoribbons
2.4 Graphene oxide (GO)
2.5 Reduced graphene oxide (RGO)
2.6 Nitrogen-doped RGO (N-RGO)
3 Covalent modified GO/RGO-based information storage devices
3.1 Conjugated polymer-functionalized GO/RGO
3.2 Non-conjugated polymer-functionalized GO/RGO
3.3 Small molecule-functionalized GO/RGO
3.4 Metal nanoparticle-functionalized GO/RGO
4 Graphene/GO/RGO composites-based information storage devices
4.1 Polymer-graphene/GO/RGO composites
4.2 Small molecule-graphene/GO/RGO composites
4.3 Polymer-graphene quantum dot composites
5 Graphene(GO, RGO)/inorganics heterojunction-based information storage devices
5.1 Graphene/inorganics
5.2 GO(RGO)/inorganics
6 Graphene and RGO-based electrodes for information storage
6.1 Graphene electrodes
6.2 RGO electrodes
7 Summary and outlook