Organic contaminants and atmospheric nitrogen at the graphene–water interface: a simulation study

Abstract

Formation of hydrocarbon monolayers at the graphene–water interface can be predicted from the concentration in ambient air and the free energies of hydration, adsorption from the aqueous phase, and subsequent integration into the monolayer phase.

Interfacial layering of hydrocarbons on pristine graphite surfaces immersed in water

“…These distances are not consistent with other possible constituents such as polyaromatic compounds, which exhibit smaller interlayer distances. 17,20 The results indicated that hydration layers were initially formed on a pristine graphite surface. However, those layers were replaced over time by 2-3 layers of alkane-like hydrocarbons likely originating from the air.…”

“…While MD simulations have indicated that distances of 0.45 nm are characteristic of well-ordered straightchain alkane layers, small amounts of branching, heteroatom substitution, or cyclic moieties led to slightly larger interlayer distances of 0.47-0.52 nm. 17,20 Furthermore, the simulations revealed that the tails of straight-chain alkanes sometimes extend out-of-plane, forming defects in the layer that disrupt the structure of layers above and slightly increase the interlayer distance. Hence, defects in the lower layers cumulatively make the third layer more disordered and d 2 slightly larger than d 1 .…”

“…(d) Free energy as a function of distance between the center of mass of an isolated alkane molecule and an alkane monolayer at the graphite-water interface. For efficiency, this quantity was calculated using our previously developed 20 coarse-grain model. By convention, the free energy of the gas phase is considered zero.…”

“…In the past few years, the interfacial liquid water structure on graphite-like surfaces was described in terms of three different molecular species: water, [5][6][7][8][9] dissolved gases [10][11][12][13][14][15] and hydrocarbons. [16][17][18][19] Recently some experimental 17 and theoretical 20 results have ruled out the existence of layers made from dissolved gas (N 2 ) molecules. High-spatial resolution images of graphite and 2D materials surfaces immersed in water revealed the presence of 1-3 alkane layers.…”

Design of Peptides that Fold and Self-Assemble on Graphite

“… 48 Our simulations have also predicted that water molecules in this first solvation layer exhibit a mild tendency to orient parallel to the graphene sheet. 47 Therefore, the solvation structure around the planar β-sheet is quite different from a regular β-sheet in solution. Figure 11 A shows regions of high water density around the peptide CHP1404.…”