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Wetting experiments show pure graphene to be weakly hydrophilic, but its contact angle (CA) also reflects the character of the supporting material. Measurements and Molecular Dynamics simulations on suspended and supported graphene often reveal a CA reduction due to the presence of the supporting substrate. A similar reduction is consistently observed when graphene is wetted from both sides. The effect has been attributed to transparency to molecular interactions across the graphene sheet, however, the possibility of substrate-induced graphene polarization has also been considered. Computer simulations of CA on graphene have so far been determined by ignoring the material’s conducting properties. We improve the graphene model by incorporating its conductivity according to the Constant Applied Potential Molecular Dynamics. Using this method, we compare the wettabilities of suspended graphene and graphene supported by water by measuring the CA of cylindrical water drops on the sheets. The inclusion of graphene conductivity and concomitant polarization effects lead to a lower CA on suspended graphene but the CA reduction is significantly bigger when the sheets are also wetted from the opposite side. The stronger adhesion is accompanied by a profound change in the correlations among water molecules across the sheet. While partial charges on water molecules interacting across an insulator sheet attract charges of the opposite sign, apparent attraction among like charges is manifested across the conducting graphene. The change is associated with graphene polarization, as the image charges inside the conductor attract equally signed partial charges of water molecules on both sides of the sheet. Additionally, by using a non-polar liquid (diiodomethane), we affirm a detectable wetting translucency when liquid-liquid forces are dominated by dispersive interactions. Our findings are important for predictive modeling toward a variety of applications including sensors, fuel cell membranes, water filtration, and graphene-based electrode materials in high-performance supercapacitors.
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This content will become publicly available on April 21, 2026
Tuning partial charges of alkyl alcohols to improve simulated fluid properties
Standard simulation interaction parameters sometimes predict liquid properties at variance with experiment, especially for polar liquids. In this work, we systematically scaled the partial charges of three alkyl alcohols to evaluate whether adjusting the partial charges, and thus the electrostatic interactions, can improve agreement with experimental values of key liquid properties, including the dielectric constant, vapor pressure, density, and self-diffusion coefficient. Changing the partial charges also affects liquid structures, which are evaluated through a hydrogen bond analysis. We found that modest adjustment factors applied to all partial charges improve values for computed properties, but too large an adjustment causes string-like aggregation of molecular dipoles and inhibits system dynamics.
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- Award ID(s):
- 2404048
- PAR ID:
- 10651921
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 162
- Issue:
- 15
- ISSN:
- 0021-9606
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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