Influence of Oxidation Degrees on the a-b Structures and Conductivity of Graphene Oxide Samples

The graphene oxide samples with different oxidation degree were prepared by modified Hummers method followed ultrasonic stripping and subsequent processing. 'The evolution of oxygen-containing functional groups, structure, surface characteristics and electrical conductivity of the samples were carried out by XPS, XRD, AVM, UV-Vis and four-point probe method. The results show that monolayer graphene oxide with the thickness of 1.4 nm can be dispersed in the condition of water phase by ultrasonic. The monolayer graphene oxide reconfigured stacked along the c axis under the action of hydrogen bond force, led the layered condensate with better ordering to forrn. With the dosage of KMnO4 increasing, the oxygen-containing functional groups in the carbon basal plane keep increasing. Especially the adding of hydroxyl group (C-OH) led the maximal basal spacing along the a-b axis (d(100) and d(110)) to continue increasing, and the values of d(100) and d(110) reach the maximum with the 3.0 g of KMnO4. The values of d(100) and d(110) slightly reducing with the 4.0 g of KMnO4 are due to the hydrolysis of partial C-OH. The increasing content of the oxygen-containing functional groups, especially the increasing content of C-O-C, led to the increasing of the energy gap and the conductivity dropping.