Exfoliation and re-aggregation mechanisms of black phosphorus: A molecular dynamics study

I Benabdallah and A Kara and M Benaissa, APPLIED SURFACE SCIENCE, 507, 144826 (2020).

DOI: 10.1016/j.apsusc.2019.144826

We used molecular dynamics simulations to extensively investigate the influence of the solvent molecule's self-diffusion, morphology/size and interaction energies on the exfoliation/re-aggregation mechanisms of black phosphorous (BP). For such a purpose, eight solvents, with a Hildebrand solubility parameter close to that of BP, are tested and then classified as a function of their planarity. In terms of exfoliation ease, planar molecules are found to require less energy than non-planar ones due to their high self-diffusion and strong interaction with phosphorene sheets. This exfoliation process gives rise to a suspension where each phosphorene sheet is surrounded by a surface-molecular dense layer. Then, the stability of this phosphorene suspension is found to be governed by the formation of a confined molecular layer. The energy balance of this confined layer, with respect to that of the surface- molecular layer, is of central importance. When the solvent molecules cohesion energy becomes weaker, with respect to the adhesion energy between phosphorene and molecules, a confined layer is favored then trapped between the phosphorene sheets forming therefore a stabilized system. The higher is the energy interaction of the confined layer, the favorable re-aggregation process is. In this context, non-planar molecules are found unfavorable neither for a stable phosphorene suspension nor for an easy exfoliation process.

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