Sub-ambient water wettability of hydrophilic and hydrophobic SiO₂ surfaces.

This article focuses on the wettability of silicon dioxide (SiO₂) surfaces, specifically examining water contact angles on hydrophilic and hydrophobic SiO₂ at temperatures between 220 and 300 K through experimental measurements and molecular dynamics (MD) simulations. The study finds that hydroxyl density on SiO₂ surfaces is the primary factor influencing water contact angles, with fully hydroxylated (Q3) surfaces exhibiting near-complete wetting and fully dehydroxylated (Q4) surfaces showing hydrophobic behavior; the distribution of hydroxyl groups and droplet size have lesser or negligible effects. Temperature variations within the studied range do not significantly affect contact angles, although hydrogen bond density between water and SiO₂ increases at lower temperatures, enhancing water affinity but slowing precursor film spreading. The research validates the use of both droplet wetting and capillary bridge wetting MD methods, providing insights relevant to natural and industrial processes involving water phase transitions on SiO₂ surfaces.