Yi Min, Zhang Wen, Shen Zhigang, Zhang Xiaojing, Zhao Xiaohu, Zheng Yiting, Ma Shulin
Beijing Key Laboratory for Powder Technology Research and Development, Beijing University of Aeronautics and Astronautics, Beijing, 100191 China ; Plasma Laboratory, Ministry-of-Education Key Laboratory of Fluid Mechanics, Beijing University of Aeronautics and Astronautics, Beijing, 100191 China.
J Nanopart Res. 2013;15(8):1811. doi: 10.1007/s11051-013-1811-2. Epub 2013 Jul 2.
Though chemical modification of graphene based on Hummers method has been most widely used to tailor its properties and interfacial characteristics, a method which could achieve definitive and controllable groups and properties is still highly required. Here, we demonstrate a high-vacuum oxidation strategy by atomic oxygen (AO) and investigate the AO induced functionalization and wettability transition in films made from basal-defect- and oxide-free graphene dispersions. These graphene-based films are neither graphene nor graphite, but graphene blocks constituted by numerous randomly stacked graphene flakes. It is found that AO induced functionalization of these films through the formation of epoxy groups, sp configuration, ether, and double and triple C-O groups. The films turn to be hydrophilic after exposed to AO. The contact angle increases with AO exposure time. This phenomenon is attributed to the lower surface roughness induced by collision and/or edge erosion of energetic ions to the film surface and is further explained by the Wenzel model. The demonstrated strategy can overcome limitations of Hummers method, provide possibility to gain functionalization and wettability transition in liquid-phase exfoliated basal-defect- and oxide-free graphene in the dry environment, and may extend the study and application of this material in spacecraft in low earth orbit.
尽管基于Hummers法的石墨烯化学修饰已被最广泛地用于调整其性能和界面特性，但仍然迫切需要一种能够实现确定且可控的基团和性能的方法。在此，我们展示了一种通过原子氧（AO）进行的高真空氧化策略，并研究了AO诱导的由无基底缺陷和无氧化物的石墨烯分散体制备的薄膜中的功能化和润湿性转变。这些基于石墨烯的薄膜既不是石墨烯也不是石墨，而是由大量随机堆叠的石墨烯薄片构成的石墨烯块。研究发现，AO通过形成环氧基团、sp构型、醚以及碳氧双键和三键诱导这些薄膜发生功能化。薄膜在暴露于AO后变为亲水性。接触角随AO暴露时间增加。这种现象归因于高能离子与薄膜表面碰撞和/或边缘侵蚀导致的较低表面粗糙度，并且温泽尔模型对此进行了进一步解释。所展示的策略可以克服Hummers法的局限性，为在干燥环境中实现液相剥离的无基底缺陷和无氧化物的石墨烯的功能化和润湿性转变提供可能性，并且可能扩展这种材料在近地轨道航天器中的研究和应用。
