Open Access

ARTICLE

Simulation and Modeling of Wetting and Adsorption Phenomena Associated with Nanomaterials

Prabhakar Misra¹, Silvina Gatica¹, Daniel Casimir¹

1 Department of Physics & Astronomy, Howard University, Washington, DC 20059, USA. E-mail: pmisra@howard.edu

Structural Longevity 2012, 7(3), 135-142. https://doi.org/10.3970/sl.2012.007.135

Abstract

Atomic Force Microscopy of hydrophobic material surfaces in water shows the presence of closely spaced soft domains. The radii of curvature of these features are of the order of 100 nm and their heights above the substrate are in the range 20-30 nm. The consensus interpretation of these features is that they are nanosized gas bubbles formed on the substrate following immersion. A recent study on interfacial wetting at epitaxial graphene, with its combined use of experimental and computational approaches, showed that the macroscopic contact angle of water on epitaxial graphene layers is correlated with the number of layers. Based on these results, the small amount of the epitaxial buffer layer of bi-layer graphene that makes direct contact with water helps explain its macroscopic contact angle being close to the value for bulk graphite, that is ∼ 93◦ ±3◦ . This contact angle value for bulk graphite, independent of the number of graphene layers, n, was also obtained after it was found that the water-exposure coverage of Gn (n-layer graphene) was close to unity. These results agree with ours reported previously,specifically the room temperature contact angle value of water on graphite. On another front, we note that recent studies involving permeation of water through single wall nanotubes via Molecular Dynamics (MD) simulations is an alternate means of showing phase transitions not manifested on the macroscopic scale because of confinement effects of matter at the nanometer scale of gases. We illustrate this effect with several MD simulations.

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