SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746, Republic of Korea.
ACS Appl Mater Interfaces. 2011 Feb;3(2):360-8. doi: 10.1021/am100977p. Epub 2011 Jan 5.
In this study, we present a facile means of fabricating graphene thin films via layer-by-layer (LbL) assembly of charged graphene nanosheets (GS) based on electrostatic interactions. To this end, graphite oxide (GO) obtained from graphite powder using Hummers method is chemically reduced to carboxylic acid-functionalized GS and amine-functionalized GS to perform an alternate LbL deposition between oppositely charged GSs. Specifically, for successful preparation of positively charged GS, GOs are treated with an intermediate acyl-chlorination reaction by thionyl chloride and a subsequent amidation reaction in pyridine, whereby a stable GO dispersibility can be maintained within the polar reaction solvent. As a result, without the aid of additional hybridization with charged nanomaterials or polyelectrolytes, the oppositely charged graphene nanosheets can be electrostatically assembled to form graphene thin films in an aqueous environment, while obtaining controllability over film thickness and transparency. Finally, the electrical property of the assembled graphene thin films can be enhanced through a thermal treatment process. Notably, the introduction of chloride functions during the acyl-chlorination reaction provides the p-doping effect for the assembled graphene thin films, yielding a sheet resistance of 1.4 kΩ/sq with a light transmittance of 80% after thermal treatment. Since the proposed method allows for large-scale production as well as elaborate manipulation of the physical properties of the graphene thin films, it can be potentially utilized in various applications, such as transparent electrodes, flexible displays and highly sensitive biosensors.
在这项研究中，我们提出了一种通过层层（LbL）组装基于静电相互作用的带电石墨烯纳米片（GS）制造石墨烯薄膜的简便方法。为此，使用 Hummers 方法从石墨粉中获得的氧化石墨（GO）通过亚硫酰氯的中间酰氯化反应和吡啶中的酰胺化反应被化学还原为羧酸官能化的 GS 和胺官能化的 GS，以在带相反电荷的 GS 之间进行交替的 LbL 沉积。具体而言，为了成功制备带正电荷的 GS，GO 先用亚硫酰氯进行中间酰氯化反应，然后在吡啶中进行酰胺化反应，从而可以在极性反应溶剂中保持稳定的 GO 分散性。结果，无需额外与带电纳米材料或聚电解质杂交，带相反电荷的石墨烯纳米片可以通过静电组装在水相环境中形成石墨烯薄膜，同时可以控制薄膜的厚度和透明度。最后，通过热处理过程可以增强组装的石墨烯薄膜的电性能。值得注意的是，在酰氯化反应过程中引入氯官能团为组装的石墨烯薄膜提供了 p 掺杂效应，经热处理后，其方阻为 1.4 kΩ/sq，透光率为 80%。由于所提出的方法允许大规模生产以及对石墨烯薄膜的物理性质进行精细操作，因此它可以在各种应用中得到利用，例如透明电极、柔性显示器和高灵敏度生物传感器。
