School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore.
Langmuir. 2011 Aug 2;27(15):9174-81. doi: 10.1021/la201230k. Epub 2011 Jun 29.
Graphene oxide (GO) can be viewed as an amphiphilic soft material, which form thin films at organic solvent-water interfaces. However, organic solvent evaporation provides little driving force, which results in slow GO transfer in aqueous phase, thus dawdling GO film formation processes for various potential applications. We present an ethanol-assisted self-assembly method for the quick formation of GO or GO-based composite thin films with tunable composition, transmittance, and surface resistivity at pentane-water interface. The thickness of pure GO and reduced GO (rGO) films ranging from ~1 nm to more than 10 nm can be controlled by the concentration of GO in bulk solution. The transmittance of rGO films can be tuned from 72% to 97% at 550 nm while the surface resistivity changes from 8.3 to 464.6 kΩ sq(-1). Ethanol is essential for achieving quick formation of GO thin films. When ethanol is injected into GO aqueous dispersion, it serves as a nonsolvent, compromising the stability of GO and providing driving force to allow GO sheets aggregate at the water-pentane interface. On the other hand, neither the evaporation of pentane nor the mixing between ethanol and water provides sufficient driving forces to allow noteworthy amount of GO sheets to migrate from the bulk aqueous phase to the interface. This method can also be extended to prepare GO-based composites thin films with tunable composition, such as GO/single walled carbon nanotube (SWCNT) composite thin films investigated in this work. Reduced GO/SWCNT composite films show much lower surface resistivity compared to pure rGO thin films. This ethanol-assisted self-assembly method opens opportunities to design and fabricate new functional GO-based hybrid materials for various potential applications.
氧化石墨烯（GO）可视为一种两亲性软物质，其在有机溶剂-水界面形成薄膜。然而，有机溶剂的蒸发提供的驱动力很小，导致 GO 在水相中的转移缓慢，从而拖延了各种潜在应用的 GO 薄膜形成过程。我们提出了一种乙醇辅助的自组装方法，用于在戊烷-水界面快速形成具有可调组成、透光率和表面电阻率的 GO 或基于 GO 的复合薄膜。通过改变 GO 在本体溶液中的浓度，可以控制纯 GO 和还原氧化石墨烯（rGO）薄膜的厚度，范围从~1nm 到 10nm 以上。rGO 薄膜的透光率可以从 550nm 处的 72%调谐到 97%，而表面电阻率可以从 8.3kΩ sq(-1)变化到 464.6kΩ sq(-1)。乙醇对于实现 GO 薄膜的快速形成是必不可少的。当乙醇注入 GO 水溶液中时，它作为非溶剂，破坏 GO 的稳定性并提供驱动力，使 GO 片在水-戊烷界面聚集。另一方面，戊烷的蒸发或乙醇与水的混合都不能提供足够的驱动力，使大量的 GO 片从本体水相向界面迁移。这种方法也可以扩展到制备具有可调组成的基于 GO 的复合材料薄膜，如本工作中研究的 GO/单壁碳纳米管（SWCNT）复合材料薄膜。还原氧化石墨烯/单壁碳纳米管复合薄膜的表面电阻率远低于纯 rGO 薄膜。这种乙醇辅助的自组装方法为设计和制备各种潜在应用的新型功能性 GO 基杂化材料提供了机会。
