School of Physics, Trinity College Dublin, Dublin 2, Ireland.
ACS Nano. 2010 Jun 22;4(6):3155-62. doi: 10.1021/nn1005304.
A method is presented to produce graphene dispersions, stabilized in water by the surfactant sodium cholate, at concentrations up to 0.3 mg/mL. The process uses low power sonication for long times (up to 400 h) followed by centrifugation to yield stable dispersions. The dispersed concentration increases with sonication time while the best quality dispersions are obtained for centrifugation rates between 500 and 2000 rpm. Detailed TEM analysis shows the flakes to consist of 1-10 stacked monolayers with up to 20% of flakes containing just one layer. The average flake consists of approximately 4 stacked monolayers and has length and width of approximately 1 mum and approximately 400 nm, respectively. These dimensions are surprisingly stable under prolonged sonication. However, the mean flake length falls from approximately 1 mum to approximately 500 nm as the centrifugation rate is increased from 500 to 5000 rpm. Raman spectroscopy shows the flake bodies to be relatively defect-free for centrifugation rates below 2000 rpm. The dispersions can be easily cast into high-quality, free-standing films. The method extends the scope for scalable liquid-phase processing of graphene for a wide range of applications.
本文提出了一种方法，可将表面活性剂胆酸钠稳定在水中的石墨烯分散体浓度提高至 0.3mg/mL。该过程使用低功率超声长时间（长达 400 小时）处理，然后通过离心得到稳定的分散体。分散体的浓度随超声时间的增加而增加，而在 500 至 2000rpm 的离心速率下可获得最佳质量的分散体。详细的 TEM 分析表明，这些薄片由 1-10 层堆叠的单层组成，其中多达 20%的薄片仅包含一层。平均薄片由大约 4 个堆叠的单层组成，长度和宽度分别约为 1μm 和大约 400nm。这些尺寸在长时间超声下非常稳定。然而，随着离心速率从 500rpm 增加到 5000rpm，平均薄片长度从大约 1μm 下降到大约 500nm。拉曼光谱表明，在低于 2000rpm 的离心速率下，薄片体相对无缺陷。这些分散体可以很容易地浇铸成高质量的、独立的薄膜。该方法扩展了适用于广泛应用的石墨烯的可扩展液相处理的范围。
