Research On Preparation And Properties Of Graphene By Oxidation-reduction Method

With the unique two-dimensional structure, graphene has larger specific surface area,excellent electrical conductivity, good mechanical property, especially good transparencyand unique quantum hall effect. It is expected to achieve wide application in theoptoelectronic device field with the unique electronic structure and these excellentproperties of graphene. At present, graphene are commonly prepared by the mechanicalexfoliation method, oxidation-reduction method, chemical vapor deposition method,heating SiC method, graphite intercalating method, cutting carbon nanotube method and soon. In this paper, graphene is prepared by oxidation-reduction method and characterized bydifferent means. The effect of reducing agents on synthetic product is also investigated.Moreover, graphene film is prepared by the spin-coating method and the relation betweenluminousness and electrical conductivity is studied.Graphene is prepared by the improved Hummers method and characterized by meanssuch as x-ray diffraction (XRD), fourier transform infrared spectrometry (FT-IR),thermogravimetry-differential scanning calorimetry (TG-DSC) and scanning electronmicroscopy (SEM). The results show that graphite oxide containing a large number ofpolar functional groups such as-OH、-COOH、C-O-C、C=O and has good hydrophilic.Graphene oxide colloid solution is acquired by the ultrasonic dispersion and centrifugaltreatment. By adding the reducing agents of N2H4, NaBH4, VC, HI, N2H4+VC andNaBH4+VC to remove the oxygen-containing functional groups, the graphene oxide hashigh electrical conductivity with the morphology unchanged. With the XRD, FT-IR,TG-DSC, SEM, XPS and Raman, the structure and morphology of the samples arecharacterized and the effect of different reducing agent is analyzed. It is shown that theoxygen-containing functional groups are largely reduced after the samples are reduced. The reduced samples are nearly not dissolved in water and become a state of precipitation. Thethermal stability of graphene is obviously higher than that of graphite oxide and is a kindof excellent thermal stability of nano materials. The effect of different reducing agents isnot the same. The reducing effect is improved with two-step reduction after analysis and itshows that the minimum interplanar spacing of graphene can be up to0.344nm and theC/O ratio is around6.Graphene oxide film and graphene film are prepared by the spin-coating method andby adjusting the concentration of dispersion or the rotate speed, the controllablepreparation of thin film thickness is achieved. At the same time, the dispersingperformance of graphene in different dispersion solvent is discussed through thedispersibility characterization by the UV-Vis and it is proved that graphene has gooddispersion stability in the N, N-dimethyl formamide (DMF). The luminousness andelectrical conductivity of the graphene film are tested with the UV-Vis and four point probeinstrument. The results show that the graphene film prepared with the precursor ofgraphene is better than the one with the precursor of graphene oxide. The probable reasonis that the reduction contact area of graphene oxide film is small in the process of reductionand the degree of reduction is not completely. The luminousness and electrical conductivityof the graphene film prepared by the two-step reduction are better than the one prepared bythe single reducing agent. The luminousness can be achieved to70%when the squareresistance of the film is~5746/sq and it provides an experimental basis of graphene forthe application in the electronic devices field.