A molecular dynamics study on the wettability property of modified hydrophilic quartz (001) surface with hydrophobic nanoparticles

In this study, molecular dynamics simulation was used to investigate the modification of quartz surface with adsorption of polystyrene and graphene nanoparticles. The simulations were performed on the super-hydrophilic quartz (001) surface. Polystyrene nanoparticles in three different percentages of surface coverage (5, 7, and 10) and one, two, four, and six layers’ graphene nano-sheets were created and adsorbed on the quartz surface. Then, contact angle, dipole moments, and intermolecular and intermolecular interactions between different nano-particles, quartz surface as a super hydrophilic substrate, and water molecules in the nano droplets were measured as the indicators of surface wettability. Analysis of the simulation results showed that the net and uncovered surface of quartz tolerates a high and asymmetric distribution of partial charge, causing a severe surface stress and intense hydrophilic behavior of the mineral surface. However, with the adsorption of polystyrene and graphene nanoparticles, the wettability behavior of the surface was changed to hydrophobic. Besides, changes in the surface energy due to nanoparticle adsorption, led to extensive changes in the dipole moment arrangement of water molecules on the quartz surface.