Abstract
A wide variety of two-dimensional layered materials are synthesized by liquid-phase exfoliation. Here we examine exfoliation of MoS2 into nanosheets in a mixture of water and isopropanol (IPA) containing cavitation bubbles. Using force fields optimized with experimental data on interfacial energies between MoS2 and the solvent, multimillion-atom molecular dynamics simulations are performed in conjunction with experiments to examine shock-induced collapse of cavitation bubbles and the resulting exfoliation of MoS2. The collapse of cavitation bubbles generates high-speed nanojets and shock waves in the solvent. Large shear stresses due to the nanojet impact on MoS2 surfaces initiate exfoliation, and shock waves reflected from MoS2 surfaces enhance exfoliation. Structural correlations in the solvent indicate that shock induces an ice VII like motif in the first solvation shell of water.
Highlights
Liquid-phase exfoliation (LPE)[1,2,3,4,5,6,7] is a highly promising approach to large-scale production and dispersion of a wide variety of layered materials (LMs)
A wide variety of transition metal dichalcogenides (TMDCs), metal oxides, and perovskites have been exfoliated into 2D layers by electrochemical, sonication and shear methods[1,6]
The motivation for the joint experimental and simulation work reported in the paper is to unveil the atomic mechanism of liquid-phase exfoliation and facilitate the synthesis of atomically thin layered materials (LMs)
Summary
Liquid-phase exfoliation (LPE)[1,2,3,4,5,6,7] is a highly promising approach to large-scale production and dispersion of a wide variety of layered materials (LMs). It affords facile processing of individual nanosheets, which can be deposited on surfaces or combined into free-standing films[6], and vertical or horizontal stacks. We have performed molecular dynamics (MD) simulations[17,18] in which a MoS2 crystal is suspended in a solvent of water and isopropanol (IPA) containing a cavitation bubble. We have performed LPE experiment with IPA and DI water, which verify the conclusion from the simulations
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