Mild sonochemical exfoliation of bromine-intercalated graphite: a new route towards graphene

Abstract

A method to produce suspensions of graphene sheets by combining solution-based bromine intercalation and mild sonochemical exfoliation is presented. Ultrasonic treatment of graphite in water leads to the formation of suspensions of graphite flakes. The delamination is dramatically improved by intercalation of bromine into the graphite before sonication. The bromine intercalation was verified by Raman spectroscopy as well as by x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations show an almost ten times lower interlayer binding energy after introducing Br2 into the graphite. Analysis of the suspended material by transmission and scanning electron microscopy (TEM and SEM) revealed a significant content of few-layer graphene with sizes up to 30 µm, corresponding to the grain size of the starting material.

Chemically Derived Graphene Oxide: Towards Large‐Area Thin‐Film Electronics and Optoelectronics

“…It should be clarified that in this Review, we define GO as graphene oxide and not graphite oxide. CDG has become a generic term for describing reduced GO (rGO) and its derivatives, while other forms derived from fluorinated [37] or brominated [38] graphite can also be included in this category. rGO is also referred to as functionalized graphene, chemically modified graphene, chemically converted graphene, or reduced graphene.…”

Structure and functionality of bromine doped graphite

“…This may indicate an increase in the band conductivity along the c-direction of graphite, which is not observed experimentally. 13 This band conductivity is due to the alignment of the Br atoms along the c-direction, which arises from the periodicity of our model. For that, we built a larger supercell containing two of the original supercells repeated in the c-direction.…”

“…13 The presence of atomic Br plus the evidence from the band structure provide the explanation of the supermetallic in-plane conductivity observed in experiments. 12 Whereas, the increase in the resistivity along the c-direction 12 can be explained by the increase in the separation between the intercalated layers of graphite and the flat bands along the k z direction of the disordered supercell (Fig.…”

“…The charge transfer from the bromine molecule to the carbon atoms is reported to range from 0.01 to 0.08 electrons for different intercalation concentration. 13 The charge transfer from graphene to a single Br atom is found to be much more substantial compared with that of a Br 2 molecule. 11 In this study, we use first principles numerical simulations to investigate the properties of low-and high-concentration bromine doped graphite.…”

“…It should be mentioned that since the experimental discovery of graphene in 2004, and with the fascination with its exceptionally high crystal and electronic quality, GICs are used as intermediates for the exfoliation of graphite to form graphene in solutions, [13][14][15] where the intercalant pushes the graphite layers apart from each other and significantly reduces the inter-layer binding energy. 13 Both theoretical and computational communities show great interest in single-layer and few-layer graphene systems because of their exotic electronic structure. Recently, the adsorption of halogen diatomic molecules on graphene was studied using density functional theory (DFT) with the self-consistent inclusion of van der Waals interactions.…”