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

Abstract

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 21 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.

Synthesis of few layer graphene by direct exfoliation of graphite and a Raman spectroscopic study

“…AFM is considered as one of the direct methods for estimating the thickness of graphene sheets. 26 AFM images of dispersions coated on Si substrates are shown in Fig. 2(a) to 2(e).…”

One-pot sustainable preparation of sunlight active ZnS@graphene nano-composites using a Zn containing surface active ionic liquid

“…24 The low value of I D /I G , (0.46) indicates that exfoliated graphene sheets are of good quality with low defect content in comparison to literature reports for graphene (I D /I G $ 0.27-2.0) prepared by the liquid-phase exfoliation method. 16,20,25 The I D /I G value for exfoliated graphene is also lower than that observed for graphene oxide prepared by Hummer's method (I D /I G ¼ 1.1-1.5). 26 The shiing of the position of the G band from 1584.8 cm À1 to 1581.7 cm À1 while going from graphite to graphene is assigned to the interaction of the hydrophobic part of [C 16 mim][ZnCl 3 ] with the graphene sheets.…”

Bile salts and derivatives: Rigid unconventional amphiphiles as dispersants, carriers and superstructure building blocks

“…In particular, a comparative analysis of the interaction of NaC, NaDC and NaTC with (6,5) SWCNTs, showed that NaDC forms the thickest interfacial layer on the CNT surface, and NaTC the most densely packed [45]. On the other hand, NaC and NaDC were used as dispersant of graphene nanosheets, and the absence of an OH group at the centre of the steroidal skeleton in NaDC was found to offer a flat and hydrophobic surface towards the graphene, which helps in the formation of uniform bilayer micelles on the carbon surface, thus making the exfoliation process more efficient [46]. Investigations on the competition of NaC and phenanthrene in the adsorption on graphene highlight the ability of NaC in adsorbing on the graphene surface and its effectiveness in promoting the exfoliation via sonication [47].…”

“…The facial amphiphilic structure makes the BSs particularly suitable to exfoliate and disperse the latter nanostructures, avoiding aggregation and reboundling due to the strong π-π interactions among different nanotubes or graphene sheets. Some studies demonstrated that the packing density of natural BSs on specific types of single-walled CNTs (SWCNTs) [45] and their efficiency in exfoliating graphene [46] are dependent on the number of hydroxyl groups of the steroidal skeleton, highlighting their crucial role in the dispersion process. In particular, a comparative analysis of the interaction of NaC, NaDC and NaTC with (6,5) SWCNTs, showed that NaDC forms the thickest interfacial layer on the CNT surface, and NaTC the most densely packed [45].…”