Rationally Designed Surfactants for Few-Layered Graphene Exfoliation: Ionic Groups Attached to Electron-Deficient π-Conjugated Unit through Alkyl Spacers

Mass production of graphene with low cost and high throughput is very important for practical applications of graphene materials. The most promising approach to produce graphene with low defect content at a large scale is exfoliation of graphite in an aqueous solution of surfactants. Herein, we report a molecular design strategy to develop surfactants by attaching ionic groups to an electron-deficient pi-conjugated unit with flexible alkyl spacers. The molecular design strategy enables the surfactant molecules to interact strongly with both the graphene sheets and the water molecules, greatly improving graphene dispersion in water. As the result, a few-layered graphene concentration as high as 1.2-5.0 mg mL(-1) is demonstrated with the surfactant, which is much higher than those (<0.1 mg mL(-1)) obtained with normal aromatic or nonaromatic surfactants. Moreover, the surfactant can be easily synthesized at large scale. The superior performance and convenient synthesis make the surfactant very promising for mass production of graphene.