Role of deoxy group on the high concentration of graphene in surfactant/water media

Graphene nanosheets have been successfully dispersed via surfactant-assisted exfoliation of graphite using sodium cholate (SC) and sodium deoxycholate (SDC) surfactants in aqueous media. The concentration of SC and SDC surfactants and saturated graphite concentration have been well optimized to highly disperse graphene in water. The concentration of dispersed graphene in water has been estimated to be 0.52 and 2.58 mg mL(-1) for SC and SDC respectively. The absence of an oxygen molecule at the centre aromatic ring of SDC offers a flat and hydrophobic surface that helps to form uniform bilayer micelles on graphitic surfaces and facilitates efficient exfoliation of graphene in a short duration of sonication. The discrepancy in the electrostatic interaction of SC-G over SDC-G dispersions and its re-aggregation stability were compared by zeta potential measurements. The thermal analysis of surfactant covered graphene powders exhibit weak bonding of surfactants with graphitic surfaces through electrostatic interactions. FESEM and AFM images demonstrate the successful exfoliation of few layer graphene with uniform dispersion. Crystalline quality and the stacking of graphene sheets in SC-G and SDC-G dispersions were analyzed using micro-Raman scattering and photoluminescence spectra.