Wetting behavior on graphene nanosheets and their application in capacitive deionization were discussed in this research. By altering the hydrophilicity of graphene nanosheets (GNS) through controlled introduction of sulphonic groups, the water contact angle of GNS is much reduced, indicating a better wettability. Meanwhile, the sulphonated GNS showed better dispersion and higher specific surface area, probably due to the negatively charged -SO3- acting as a repellent on the surface to prevent serious aggregation. As a result, a salt removal efficiency of 83.4% and specific electrosorptive capacity of 8.6 mg/g, indicating an increase of 109% comparing with the unmodified GNS. (C) 2012 Elsevier B. V. All rights reserved.