120th General Meeting of the KCS

Type Oral Presentation
Area Oral Presentation for Young Scholars in Physical Chemistry
Room No. Room 208+209+210
Time THU 09:30-:
Code PHYS.O-4
Subject A Mechanism at a Molecular Level for the Shear Exfoliation of Nanoplates
Authors Inhyuk Jang, Bong June Sung*
Department of Chemistry, Sogang University, Korea
Abstract Graphene is one of promising materials with various potential applications due to its unique properties. One of stumbling blocks to the application of graphene would be that it is difficult to prepare a large amount of single layer graphene from graphite without worsening its desired properties. Recent studies suggested that when a shear force was introduced to the graphene nanosheets, quite a monodisperse distribution of graphene could be prepared. However, scientific questions still remain: how the shear would be delivered effectively to the graphite and how the shear would be sufficient to overcome the strong van der Waals interactions between layers of graphene. In this work, we perform extensive non-equilibrium molecular dynamics simulations to answer those scientific questions. We employ a simple model for two layers of nanoplates to mimic the graphene with an explicit solvent model. A steady shear experiment is realized in our simulations by confining solvent molecules and nanoplates between two walls and moving an upper wall at a constant velocity. We find that the interaction between solvent molecules and nanoplates matters: as the interaction becomes more attractive, a larger shear would be required for the exfoliation. We construct a pseudo-phase diagram for the exfoliation as a function of the shear rate and intermolecular interaction. We also find that the shear exfoliation process consists of several steps, each of which corresponds to the barrier crossing in the free energy profile. This suggests that the shear exfoliation is not a single step that overcomes a huge van der Waals energy barrier but is a complicated process that follows the minimum path along the free energy landscape. A detailed molecular mechanism will be also discussed in this talk.
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