Graphene exfoliation in organic solvents and switching solubility in aqueous media with the aid of amphiphilic block copolymers

Abstract

The successful exfoliation of graphite to graphene sheets in liquid phase via tip sonication was achieved. A number of solvents were examined for several time periods and it was found that o-dichlorobenzene (o-DCB) and N-methyl-1,2-pyrolidone (NMP) are ideal solvents to exfoliate graphite and produce stable dispersions of graphene. The exfoliated graphene dispersions were characterized by complementary techniques including AFM, DLS, TGA and Raman. Furthermore, treatment of stable dispersions of exfoliated graphene sheets in NMP with poly[styrene-b-(2-vinylpyridine)] block copolymer, under acidic conditions, resulted on aqueous solubilization of graphene. Similar results were obtained, i.e. transfer of graphene from the organic to the aqueous phase, when poly(isoprene-b-acrylic acid) block copolymer was added on exfoliated graphene in NMP.

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

“…10 The concentration of graphene in solvent against the exfoliation time plot is shown in the inset Figure 1. The concentration of the synthesized graphene sheets also increased remarkably with the increasing sonication time.…”

“…The synthesis was only based on sonication and the sonication time was varied up to 5 hours. Skaltsas et al 10 have exfoliated graphene in o-DCB and N-methyl-1,2-pyrolidone via tip sonication for various exfoliation time up to 1 hour. Hamilton et al 16 have demonstrated the production of graphene dispersions from synthetic graphite, HOPG and expanded graphite in o-DCB by cup-horn sonication for 30 minutes.…”

“…Several liquids were used to create stable dispersions of graphene such as surfactants in aqueous media, ionic liquids and organic solvents. [10][11][12][13][14][15] The organic solvent ortho-dichlorobenzene (o-DCB), being aromatic, is able to interact with graphene via π -π stacking. o-DCB has a surface tension of 36.6 mJ/m 2 , which is very close to the proposed range (40-50 mJ/m 2 ).…”

Supramolecular Approaches to Graphene: From Self‐Assembly to Molecule‐Assisted Liquid‐Phase Exfoliation

“…It has been shown recently that the exfoliated graphene in NMP can be stabilized with an acidic solution of the poly(isopreneb-acrylic acid) (PI-b-PAA) or poly[styrene-b-(2-vinylpyridine)] (PS-b-P2VP) block copolymers [197] (Figure 10). Unfortunately, the thickness of graphitic flakes amounts to 44 nm and 2.5 nm respectively, implying that the PI-b-PAA-and/or PS-b-P2VP-assisted UILPE protocol needs to be further optimized.…”

“…Over the past years, it has been proven that graphene can be dispersed in water by using a wide range of polymers acting as DSAs, [14,195,197,198,[215][216][217][223][224][225][226][227][228][229][230][231][232] such as cellulose acetate (CA), [233] ethyl cellulose (EC), [229] polyvinylpyrrolidone (PVP), [224] lignin, [230] gum arabic (GA), [225,226] gelatin derived from animal skin and bones, [227] and even more complex systems such as bovine serum albumin (BSA), [223] hyaluronan (PyHA) [216] and DNA [198] functionalized with pyrene head-groups.…”