School of Engineering, Institute for Molecular and Nanoscale Innovation, Brown University, Providence, Rhode Island, USA.
Environ Sci Technol. 2012 Jul 17;46(14):7717-24. doi: 10.1021/es301377y. Epub 2012 Jul 3.
Many environmental technologies rely on containment by engineered barriers that inhibit the release or transport of toxicants. Graphene is a new, atomically thin, two-dimensional sheet material, whose aspect ratio, chemical resistance, flexibility, and impermeability make it a promising candidate for inclusion in a next generation of engineered barriers. Here we show that ultrathin graphene oxide (GO) films can serve as effective barriers for both liquid and vapor permeants. First, GO deposition on porous substrates is shown to block convective flow at much lower mass loadings than other carbon nanomaterials, and can achieve hydraulic conductivities of 5 × 10(-12) cm/s or lower. Second we show that ultrathin GO films of only 20-nm thickness coated on polyethylene films reduce their vapor permeability by 90% using elemental mercury as a model vapor toxicant. The barrier performance of GO in this thin-film configuration is much better than the Nielsen model limit, which describes ideal behavior of flake-like fillers uniformly imbedded in a polymer. The Hg barrier performance of GO films is found to be sensitive to residual water in the films, which is consistent with molecular dynamics (MD) simulations that show lateral diffusion of Hg atoms in graphene interlayer spaces that have been expanded by hydration.
许多环境技术依赖于工程屏障来阻止有毒物质的释放或迁移。石墨烯是一种新型的原子级薄二维片状材料，其纵横比、耐化学性、柔韧性和不渗透性使其成为下一代工程屏障的候选材料。在这里，我们表明超薄氧化石墨烯 (GO) 薄膜可用作液体和蒸气渗透物的有效屏障。首先，我们发现 GO 沉积在多孔基底上可以在比其他碳纳米材料低得多的质量负载下阻止对流流动，并且可以达到 5×10(-12) cm/s 或更低的水力学电导率。其次，我们发现仅 20nm 厚的超薄 GO 薄膜涂覆在聚乙烯薄膜上可以使元素汞模型蒸气毒剂的蒸气透过率降低 90%。GO 在这种薄膜结构中的阻隔性能远远优于尼尔森模型极限，尼尔森模型极限描述了均匀嵌入聚合物中的片状填充剂的理想行为。GO 薄膜的 Hg 阻隔性能对薄膜中的残留水敏感，这与分子动力学 (MD) 模拟结果一致，模拟结果表明，在水合作用下扩展的石墨烯层间空间中，Hg 原子的横向扩散。
