Molecular Simulation of MoS2 Exfoliation

Guoqing Zhou; Pankaj Rajak; Sandhya Susarla; Pulickel M Ajayan; Rajiv K Kalia; Aiichiro Nakano; Priya Vashishta

doi:10.1038/s41598-018-35008-z

Molecular Simulation of MoS₂ Exfoliation

Sci Rep. 2018 Nov 13;8(1):16761. doi: 10.1038/s41598-018-35008-z.

Authors

Guoqing Zhou¹, Pankaj Rajak², Sandhya Susarla³, Pulickel M Ajayan³, Rajiv K Kalia^{4

5

6}, Aiichiro Nakano^{1

2

7}, Priya Vashishta^{1

2

7}

Affiliations

¹ Collaboratory of Advanced Computing and Simulation, Department of Physics and Astronomy, University of Southern California, Los Angeles, USA.
² Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, USA.
³ Department of Materials Science and Nanoengineering, Rice University, Houston, Texas, 77005, USA.
⁴ Collaboratory of Advanced Computing and Simulation, Department of Physics and Astronomy, University of Southern California, Los Angeles, USA. rkalia@usc.edu.
⁵ Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, USA. rkalia@usc.edu.
⁶ Department of Computer Science, University of Southern California, Los Angeles, California, 90089, USA. rkalia@usc.edu.
⁷ Department of Computer Science, University of Southern California, Los Angeles, California, 90089, USA.

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.