A simple and low-cost method of sulfur functionalization and aqueous dispersion of graphene driven by gas-liquid non-thermal plasma discharge

Graphene is a 2D nanomaterial that has received increasing attention due to its remarkable properties, such as high electric and thermal conductivity and good mechanical properties. The insertion of heteroatoms onto graphene enables the control of various properties of the material, such as dispersion, catalysis and band gap. Among the heteroatoms studied, sulfur is attractive due to its versatility, being part of functional groups that enhance dispersion and enable further modification. Various methods of sulfur functionalization were studied, and non-thermal plasma distinguishes itself due to its energy efficiency, ease of operation, and low heating of the treated material. However, existing non-thermal plasma methods are limited due to the expense of the equipment, energy consumption due to vacuum conditions and limited treated mass. In this work, we present a brand new simple, low-cost method for sulfur functionalization of graphene by argon non-thermal plasma discharged over an aqueous medium containing potassium thiocyanate, operating at ambient pressure and temperature. The modified graphene obtained was analyzed by Raman, XPS, FTIR, zeta potential and thiol quantification. The results showed an increase in graphene dispersion in water caused by the insertion of sulfonic acid and thiol functional groups onto the graphene structure, while maintaining the pristine qualities of the starting material.