Ko Myoungjae, Choi Hee Jae, Kim Jin Yong, Kim In Ho, Kim Sang Ouk, Moon Myeong Hee
Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.
Department of Materials Science and Engineering, KAIST, Daejeon 34141, Republic of Korea.
J Chromatogr A. 2022 Oct 11;1681:463475. doi: 10.1016/j.chroma.2022.463475. Epub 2022 Sep 5.
Graphene oxide (GO)-a chemical derivative of graphene with numerous oxygen functional groups on its surface-has attracted considerable interest because of its intriguing properties in relation to those of pristine graphene. In addition to the inherent wide lateral size distribution of GO sheets arising from the typical oxidative exfoliation of graphite, control of the lateral size of GO is critical for desired GO-based applications. Herein, flow/hyperlayer field-flow fractionation (flow/hyperlayer FFF) is optimized to separate GO sheets by lateral dimensions. Optimized fractionation is achieved by investigating the influences of carrier solvent, channel thickness, and flow rate conditions on the steric/hyperlayer separation of GO sheets by flow FFF. Due to the strong hydrodynamic lift forces of extremely thin GO sheets, a thick flow FFF channel (w = 350 μm) and a very low field strength are required to retain the GO sheets within the channel. GO sheets with narrow size fractions are successfully collected from two different graphite sources during flow/hyperlayer FFF runs and are examined to verify the size evolution. Considering the average lateral diameter of the GO fraction calculated on the basis of the assumption of a circular disk shape, the retention of the GO sheets is 2.2-5.0 times faster than that of spherical particles of the same diameter. This study demonstrates that through flow/hyperlayer FFF, the size distribution of GO sheets can be determined and narrow size fractions can be collected (which is desirable for GO-based applications), which are commonly influenced by the GO lateral dimension.
氧化石墨烯（GO）是石墨烯的一种化学衍生物，其表面带有大量氧官能团，因其与原始石墨烯相比具有引人关注的特性而备受瞩目。除了由典型的石墨氧化剥离产生的GO片层固有的横向尺寸分布较宽之外，控制GO的横向尺寸对于基于GO的理想应用至关重要。在此，对流动/超层场流分级法（flow/hyperlayer FFF）进行了优化，以按横向尺寸分离GO片层。通过研究载液、通道厚度和流速条件对流动场流分级法中GO片层的空间/超层分离的影响，实现了优化分级。由于极薄的GO片层具有强大的流体动力升力，需要一个较厚的流动场流分级通道（w = 350μm）和非常低的场强，以将GO片层保留在通道内。在流动/超层场流分级运行过程中，成功地从两种不同的石墨源收集到了尺寸窄分布的GO片层，并对其进行了检查以验证尺寸演变。基于圆盘形状假设计算出的GO级分的平均横向直径，GO片层的保留速度比相同直径的球形颗粒快2.2至5.0倍。这项研究表明，通过流动/超层场流分级法，可以确定GO片层的尺寸分布，并收集窄尺寸级分（这对于基于GO的应用是理想的），而这些通常受GO横向尺寸的影响。
