Surfactant assisted liquid phase exfoliation of graphite rod in the production of stable colloidal graphene-surfactant solution

Abstract

Surfactant assisted Liquid Phase Exfoliation (LPE) was reported to be the most promising strategy to produce high quality stable colloidal graphene solution. In this study, surfactant assisted LPE was carried out in a two electrode system, using surfactants namely sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB). The study was carried out at concentrations of surfactant below critical micelle concentration (CMC) which are 0.01M SDS and 0.001M CTAB. The electrochemical process was carried out for 5 hours, at several intercalation potentials of 6V, 7V and 8V with a sequence of intercalation of surfactant onto the graphite anode followed by exfoliation of the surfactant-intercalated graphite electrode when the anode was treated as cathode. The graphene-surfactant suspension was characterized by Optical microscopy, UV-Visible spectroscopy, Nuclear magnetic resonance (NMR) and Raman spectroscopy. UV-Visible spectroscopic analysis indicated an increase in graphene production with increased in intercalation potential while Optical microscope images shows that graphene-SDS was more dispersed than graphene-CTAB at the various intercalation potential employed.  The presence of shielding in ¹H NMR spectroscopy indicates the interaction of graphene with surfactant. Raman spectra of both graphene-SDS and graphene-CTAB obtained show typical exfoliated graphene band shape affected by the attachment of surfactant molecules confirmed the graphitic configuration. Three peaks in the Raman spectra shown by graphene-surfactant are the D band around 1350 cm^-1, the G band 1590 cm^-1 and the 2D band around 2700 cm^-1. The study concluded that graphene-SDS results is a more stable colloidal graphene-surfactant solution compared to graphene-CTAB.