Layer-stacked graphene oxide (GO) membranes, in which unique two-dimensional (2D) water channels are formed between two neighboring GO nanosheets, have demonstrated great potential for aqueous phase separation. Subjects of crucial importance are to fundamentally understand the interlayer spacing (i.e. channel height) of GO membranes in an aqueous environment, elucidate the mechanisms for water transport within such 2D channels, and precisely control the interlayer spacing to tune the membrane separation capability for targeted applications. In this investigation, we used an integrated quartz crystal mass balance (QCM-D) and ellipsometry to experimentally monitor the interlayer spacing of GO, reduced GO and crosslinked GO in aqueous solution and found that crosslinking can effectively prevent GO from swelling and precisely control the interlayer spacing. We then used molecular dynamics simulations to study the mass transport inside the 2D channels and proved that the chemical functional groups on the GO plane dramatically slow down water transport in the channels. Our findings on GO structure and water transport provide a necessary basis for further tailoring and optimizing the design and fabrication of GO membranes in various separation applications.

中文翻译：

---

二维水氧化石墨烯通道

在两个相邻的GO纳米片之间形成独特的二维（2D）水通道的层堆叠氧化石墨烯（GO）膜已证明具有巨大的水相分离潜力。至关重要的主题是从根本上了解中间层间距（即GO膜在水环境中的通道高度），阐明了在此类2D通道内进行水传输的机制，并精确控制层间间距以调整膜分离能力以用于目标应用。在这项研究中，我们使用集成的石英晶体质量平衡（QCM-D）和椭圆偏振法来实验监测水溶液中GO的层间距，还原的GO和交联的GO，并发现交联可以有效防止GO溶胀并精确控制夹层间距。然后，我们使用分子动力学模拟研究了二维通道内的质量传输，并证明了GO平面上的化学官能团极大地减慢了通道中的水传输。