Abstract
Graphene, a two-dimensional (2D) carbon nanomaterial, has attracted worldwide attention owing to its fascinating properties. One of critical bottlenecks on some important classes of applications, such as printed electronics, conductive coatings, and composite fillers, is the lack of industrial-scale methods to produce high-quality graphene in the form of liquid suspensions, inks, or dispersions. Since 2008, when liquid-phase exfoliation (LPE) of graphene via sonication was initiated, huge progress has been made in the past decade. This review highlights the latest progress on the successful preparation of graphene in various media, including organic solvents, ionic liquids, water/polymer or surfactant solutions, and some other green dispersants. The techniques of LPE, namely sonication, high-shear mixing, and microfluidization are reviewed subsequently. Moreover, several typical devices of high-shear mixing and exfoliation mechanisms are introduced in detail. Finally, we give perspectives on future research directions for the development of green exfoliation media and efficient techniques for producing high-quality graphene. This systematic exploratory study of LPE will potentially pave the way for the scalable production of graphene, which can be also applied to produce other 2D layered materials, such as BN, MoS2, WS2, etc.
Highlights
Graphene is a new type of two-dimensional (2D) carbon nanomaterial, which exists as a single layer of carbon atoms that are tightly arranged in a honeycomb lattice
Since graphene was first prepared by Novoselov and Geim using micromechanical exfoliation of graphite [2], which is called the ‘Scotch tape’ method [3], it has been fascinating to many researchers
The high surface tension of pure water, 72.8 mJ m−2, can be reduced by the addition of suitable surfactants so that water/surfactant system has potential to apply to the exfoliation and stabilization of graphene
Summary
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