Liquid-Phase Exfoliation of Graphite into Single- and Few-Layer Graphene with α-Functionalized Alkanes

Abstract

Graphene has unique physical and chemical properties, making it appealing for a number of applications in optoelectronics, sensing, photonics, composites, and smart coatings, just to cite a few. These require the development of production processes that are inexpensive and up-scalable. These criteria are met in liquid-phase exfoliation (LPE), a technique that can be enhanced when specific organic molecules are used. Here we report the exfoliation of graphite in N-methyl-2-pyrrolidinone, in the presence of heneicosane linear alkanes terminated with different head groups. These molecules act as stabilizing agents during exfoliation. The efficiency of the exfoliation in terms of the concentration of exfoliated single- and few-layer graphene flakes depends on the functional head group determining the strength of the molecular dimerization through dipole-dipole interactions. A thermodynamic analysis is carried out to interpret the impact of the termination group of the alkyl chain on the exfoliation yield. This combines molecular dynamics and molecular mechanics to rationalize the role of functionalized alkanes in the dispersion and stabilization process, which is ultimately attributed to a synergistic effect of the interactions between the molecules, graphene, and the solvent.

Simple Technique of Exfoliation and Dispersion of Multilayer Graphene from Natural Graphite by Ozone-Assisted Sonication

“…The most common methods are liquid phase exfoliation, the reduction of graphene oxide, micromechanical exfoliation, chemical vapor deposition, and the exfoliation of graphite intercalation compounds in organic solvents [8,9,10,11,12]. Among these methods, the liquid phase exfoliation of graphite is the most promising way to produce graphene at a very low cost [13,14,15]. However, almost all reported methods have used surfactants, organic solvents, strong acids, and chemical reagents in order to exfoliate and stabilize in the specific medium [16,17,18].…”

Thermo-responsive graphene dispersions by liquid phase exfoliation of graphite aided by an alkylated Percec monodendron

“…Thus, the much larger SD/SG of G-ds compared to that of graphite can be mainly ascribed to the effect of sonication. Compared to the samples obtained by the LPE method at the presence of linear SRs [13][14][15], this SD/SG value is smaller, which indicates a reduced number of defect sites and again highlights the advantage of using 1 as the SR for the exfoliation of graphite. The 2D peak is known to contain important information about the number of graphene layers [23].…”

“…An alternative way to improve cg is to use stabilizing reagents (SRs) [13][14][15][16][17]. This strategy can also greatly expand the range of solvents used for the exfoliation of graphite, even in aqueous solutions [18].…”

“…This strategy can also greatly expand the range of solvents used for the exfoliation of graphite, even in aqueous solutions [18]. Typical SRs include alkylated compounds with different functional groups [13][14][15], polymers [16] and porphyrin derivatives [17]. For the alkylated compounds attempted up to now, the molecular structures are limited, i.e., only molecule bearing one aliphatic chain has been tried.…”

Structural Optimization of Alkylbenzenes as Graphene Dispersants

“…Octylbenzene is a type of alkylbenzene; however, in their research, other molecules were not investigated. It has been under the argument that the alkyl chain [23][24][25][26][27] or aromatic moiety [28][29][30][31][32][33][34][35][36] contributes to the graphene dispersion. To make clear the role of the alkyl chain and the aromatic moiety of the dispersant, we synthesized a series of alkylbenzenes and evaluated their graphene dispersing abilities.…”