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O: Fachverband Oberflächenphysik

O 13: 2D Materials (joint session CPP/O)

O 13.2: Vortrag

Montag, 16. März 2020, 11:45–12:00, ZEU 255

Solvent interactions with two-dimensional materials: A computational investigation of the dispersion of graphene monolayers in commonly-used solvents. — •Urvesh Patil and Nuala Caffrey — School of Physics & CRANN, Trinity College, Dublin 2

Maintaining stable dispersions of two-dimensional (2D) materials is a prerequisite for several applications. The stability of dispersion, i.e., the ability of a solvent to maintain an adequate concentration of suspended flakes over time, depends strongly on the interaction between the 2D material and the chosen solvent. In order to identify the optimal solvent for a particular 2D material it is imperative to determine this interaction on the atomic scale. Here, we use density functional theory (DFT) combined with solvent models and molecular dynamics (MD) to study the interaction of graphene and MoS2 with solvent molecules such as NMP, cyclopentanone and toluene. Using DFT, we show that isolated solvent molecules interact via a van der Waals (vdW) interaction with pristine monolayers, with negligible charge transferred between them. MD calculations show that distinct solvation shells form around the 2D layer; the first solvation shell is formed as a result of vdW interaction irrespective of the polarity of solvent. This then interacts with rest of the solvent via a combination of both electrostatic and vdW forces. We show that the formation of this solvation shell is always favourable, and determine the relationship between the free energy of interaction and the experimental concentration of graphene in solution. Finally, we suggest a simple rule for mixing solvents that can be used to improve the 2D layer concentration in solution.