A simple method for graphene production based on exfoliation of graphite in water using 1-pyrenesulfonic acid sodium salt

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–1SO3) 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 ∼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–1SO3 and 1,3,6,8-pyrenetetrasulfonic acid (Py–4SO3). A strong decrease in the exfoliation yield has been observed by using pyrene with 4 sulphonic groups (Py–4SO3), as compared to one sulphonic group (Py–1SO3). Being completely water-based, these suspensions can be used as inks for printable tattoo-based electro-chemical sensors.