▎ 摘　　要

In this work we use a chemical approach based on supra-molecular and non-covalent interactions between graphene and 1-pyrenesulfonic acid sodium salt (Py-1SO(3)) to obtain a stable dispersion of graphene by using only water as solvent. The material has been characterized by a combination of spectroscopic and microscopic techniques. In particular, an extensive Raman analysis shows that we have similar to 70% few-graphene layers (<7). We also show that the exfoliation efficiency strongly depends on the number of functional groups by comparing suspensions obtained by Py-1SO(3) and 1,3,6,8-pyrenetetrasulfonic acid (Py-4SO(3)). A strong decrease in the exfoliation yield has been observed by using pyrene with 4 sulphonic groups (Py-4SO(3)), as compared to one sulphonic group (Py-1SO(3)). Being completely water-based, these suspensions can be used as inks for printable tattoo-based electro-chemical sensors. (C) 2012 Elsevier Ltd. All rights reserved.