Exfoliation mechanisms of 2D materials and their applications

Abstract

Due to the strong in-plane but weak out-of-plane bonding, it is relatively easy to separate nanosheets of two-dimensional (2D) materials from their respective bulk crystals. This exfoliation of 2D materials can yield large 2D nanosheets, hundreds of micrometers wide, that can be as thin as one or a few atomic layers thick. However, the underlying physical mechanisms unique to each exfoliation technique can produce a wide distribution of defects, yields, functionalization, lateral sizes, and thicknesses, which can be appropriate for specific end applications. The five most commonly used exfoliation techniques include micromechanical cleavage, ultrasonication, shear exfoliation, ball milling, and electrochemical exfoliation. In this review, we present an overview of the field of 2D material exfoliation and the underlying physical mechanisms with emphasis on progress over the last decade. The beneficial characteristics and shortcomings of each exfoliation process are discussed in the context of their functional properties to guide the selection of the best technique for a given application. Furthermore, an analysis of standard applications of exfoliated 2D nanosheets is presented including their use in energy storage, electronics, lubrication, composite, and structural applications. By providing detailed insight into the underlying exfoliation mechanisms along with the advantages and disadvantages of each technique, this review intends to guide the reader toward the appropriate batch-scale exfoliation techniques for a wide variety of industrial applications.

Molybdenum disulfide, exfoliation methods and applications to photocatalysis: a review

“…Cathodic exfoliation is typically performed in organic solvents such as dimethyl sulfoxide (DMSO). 18–64 El Garah et al presented a rapid (<1 hour) electrochemical exfoliation method for molybdenum disulfide (MoS 2 ) using lithium-ion intercalation, with a lithium chloride solution in DMSO as the electrolyte. Their results pave the way for a rapid and ambient condition preparation of MoS 2 nanoflakes with an average lateral size of about 0.8 μm, suitable for low-cost electronic (optoelectronic) devices.…”

Progress in photodetector devices utilizing transition metal dichalcogenides

“…Photodetectors (PDs) that convert light energy into electrical signals are one of the major components in advanced multifunctional technologies. [1][2][3][4][5][6] The developed PD technologies have so far covered a wide range of applications that have a significant impact on our daily lives such as visible light detection for video imaging and digital cameras, ultraviolet (UV) radiation for cell inspection and lithography, X-ray radiation for biomedical imaging, wide-range infrared (IR) detection for night vision, environmental monitoring, optical communication, and quality testing spectroscopy, among others. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] PDs are categorized using several key figures-of-merit such as photogain, quantum efficiency, detectivity, responsivity and others.…”

Hexagonal boron nitride exfoliation and dispersion

“…A variety of reviews have now been published on the functionalization and applications of boron nitride nanomaterials, [50][51][52][53] and others have broadly looked at liquid-phase exfoliation of various 2D materials, including hBN. [54][55][56][57][58][59] Last year, two reviews were also published on exfoliation mechanisms for 2D materials including hBN 60 and another specifically on environmental applications of hBN. 61 This review will stand apart from others by providing an indepth analysis of the experimental exfoliation and dispersion approaches for hBN and how they have progressed over time toward improved exfoliation (i.e.…”