氧化程度对氧化石墨烯a-b轴结构及电学性能的影响

采用改进的Hummers法及超声分散等后续处理制备不同氧化程度的氧化石墨烯样品。用XPS、XRD、AFM、UV-Vis及四探针测试仪对样品官能团变化规律、结构、形貌特征以及电学性能进行表征分析。结果表明,氧化石墨烯在超声波的作用下水相条件下可达单层分散,单层氧化石墨烯厚度约为1.4 nm:成膜过程中,在氢键力的作用下氧化石墨烯片层沿c轴重叠形成层状凝聚体,结构有序度较好;随氧化剂(KMn O4)用量增加,碳层平面上含氧官能团含量持续增加,特别是羟基官能团(C-OH)含量的增加,使a-b轴方向最大底面间距(d100和d110)一直增大,直至KMn O4用量达4.0 g时,部分C-OH水解,导致d100与d110略有减小;碳层平面上含氧官能团尤其是环氧官能团(C-O-C)含量的增加,使样品带隙宽度逐渐增大,导电性能越来越差。

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, AFM, 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 form. 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 (d₁₀₀ and d₁₁₀) to continue increasing, and the values of d₁₀₀ and d₁₁₀ reach the maximum with the 3.0 g of KMnO_4. The values of d₁₀₀ and d₁₁₀ 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.