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Graphene, as an intermediate phase between fullerene and carbon nanotube, has aroused much interests among the scientific community due to its outstanding electronic, mechanical, and thermal properties. With excellent electrical conductivity of 6000 S/cm, which is independent on chirality, graphene is a promising material for high-performance nanoelectronics, transparent conductor, as well as polymer composites. On account of its Young’s Modulus of 1 TPa and ultimate strength of 130 GPa, isolated graphene sheet is considered to be among the strongest materials ever measured. Comparable with the single-walled carbon nanotube bundle, graphene has a thermal conductivity of 5000 W/(m·K), which suggests a potential application of graphene in polymer matrix for improving thermal properties of the graphene/polymer composite. Furthermore, graphene exhibits a very high surface area, up to a value of 2630 m2/g. All of these outstanding properties suggest a wide application for this nanometer-thick, two-dimensional carbon material. This review article presents an overview of the significant advancement in graphene research: preparation, functionalization as well as the properties of graphene will be discussed. In addition, the feasibility and potential applications of graphene in areas, such as sensors, nanoelectronics and nanocomposites materials, will also be reviewed.

Recently, much work has focused on the exfoliation of graphene through a combination of oxidation and sonication procedures, followed by reduction through chemical methods. We demonstrated that the individual graphene oxide sheets can be readily reduced by using phenolphthalin as both reducing agent and stabilizer. The obtained non-covalently functionalized chemically reduced graphene oxide (CRG) can be dispersed in organic solvents very well, such as alcohol, N,N-dimethylformamide, N,N-Dimethylacetamide, N-methyl-2-pyrrolidone, etc., which can give practical applications in large scale production of oil dispersible graphene and have a potential in polymer nanocomposites fabrication.

Graphene oxide (GO) reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers in the presence of GO sheets dispersed in N,N-Dimethylacetamide (DMAc). The functional groups (e.g., hydroxyl, epoxide, and carboxyl groups) associated with the GO make GO excellent dispersion in the organic solvent, which benefits the subsequent in situ polymerization. This process enabled uniform dispersion of GO sheets in the polymer matrix. The resultant GO-polyimide nanocomposite films were studied by tensile test, TGA and SEM. The results showed that the GO sheets incorporated in the polymer matrix exhibited a layer-aligned structure without destruction of the thermal stability of the polymer matrix, and a loading of GO (10 wt%) resulted in a significant enhancement in elastic modulus (86.4%).

In this paper, we have reported that paper-like graphene-Ag composite films could be prepared by a facile and novel chemical reduction method at a large scale. Using ascorbic acid as a reducing agent, graphene oxide films dipped in Ag+ aqueous solutions can be easily reduced along with the decoration of different sizes of Ag particles distributed uniformly. The results reveal that the obtained films exhibit improved mechanical properties with the enhancement of tensile strength and Young's modulus by as high as 82% and 136%, respectively. The electrical properties of graphene-Ag composite films were studied as well, with the sheet resistance of which reaching lower than approximately 600 Ω/□. The graphene-Ag composite films can be expected to find interesting applications in the area of nanoelectronics, sensors, transparent electrodes, supercapacitors, and nanocomposites.

Here we present a useful ammonia (NH3) gas sensor based on reduced graphene oxide (RGO)–polyaniline (PANI) hybrids. PANI nanoparticles were successfully anchored on the surface of RGO sheets by using RGO–MnO2 hybrids as both of the templates and oxidants for aniline monomer during the process of polymerization. The resultant RGO–PANI hybrids were characterized by transmittance electron microscopy, infrared spectroscopy, Raman spectroscopy, UV-Vis spectroscopy, and scanning electron microscopy. The NH3 gas sensing performance of the hybrids was also investigated and compared with those of the sensors based on bare PANI nanofibers and bare RGO sheets. It was revealed that the synergetic behavior between both of the candidates allowed excellent sensitivity and selectivity to NH3 gas. The RGO–PANI hybrid device exhibited much better (3.4 and 10.4 times, respectively, with the concentration of NH3 gas at 50 ppm) response to NH3 gas than those of the bare PANI nanofiber sensor and bare graphene device. The combination of the RGO sheets and PANI nanoparticles facilitated the enhancement of the sensing properties of the final hybrids, and pave a new avenue for the application of RGO–PANI hybrids in the gas sensing field.

A facile route for the large scale production of graphene oxide (GO) papers and their mechanical enhancement has been presented in this work. The novel paper-like GO made from individual GO sheets in aqueous suspension can be achieved in large scale by a simple drop casting method on hydrophobic substrates. Significant enhancement in mechanical stiffness (341%) and fracture strength (234%) of GO paper have been achieved upon modification with a small amount (less than 10 wt%) of glutaraldehyde (GA). The cross-linking reaction takes place between hydroxyl groups on the surface of GO and aldehyde groups of GA, through forming hemiacetal structure, which can result in distinct mechanical enhancement of the GO papers.