Abstract
Despite significant progresses made on mass production of chemically exfoliated graphene, the quality, cost and environmental friendliness remain major challenges for its market penetration. Here, we present a fast and green exfoliation strategy for large scale production of high quality water dispersible few layer graphene through a controllable edge oxidation and localized gas bubbling process. Mild edge oxidation guarantees that the pristine sp2 lattice is largely intact and the edges are functionalized with hydrophilic groups, giving rise to high conductivity and good water dispersibility at the same time. The aqueous concentration can be as high as 5.0 mg mL−1, which is an order of magnitude higher than previously reports. The water soluble graphene can be directly spray-coated on various substrates, and the back-gated field effect transistor give hole and electron mobility of ~496 and ~676 cm2 V−1 s−1, respectively. These results achieved are expected to expedite various applications of graphene.
Highlights
Weak oxidation or oxidation-free process is very helpful in preserving graphene’s lattice integrity, retaining its performance advantages
Compared with generally reported Hummers or modified Hummers, as shown in Supplementary Table 1, we employed less oxidant, low temperature and very short reaction time, which results in lower oxygen content and higher C/O ratio of 5.34, as shown in the X-ray photoelectron spectroscopy (XPS) of oxidized graphite data in Supplementary Fig. S1
The oxygen content from XPS is 15.7 at.%, which is double confirmed by CHN elemental analysis
Summary
Weak oxidation or oxidation-free process is very helpful in preserving graphene’s lattice integrity, retaining its performance advantages. 20 L aqueous dispersion of water-dispersable graphene with the concentration of 2.5 mg mL−1 was obtained with the reaction setup in Supplementary Fig. S7.
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