Coupling effect of gas solubility in a solvent and substrate structure on performance in nanobubble morphological changes

Abstract

The distribution morphologies of nanobubbles on Highly Oriented Pyrolytic Graphite (HOPG) surfaces prepared using the alcohol-water exchange test method were observed using atomic force microscopy. In situ observation revealed the distinct growth evolution behavior of nanobubble morphology. Molecular dynamics simulation was employed to replicate the experimental test and investigate the influence of the coupling effect of gas solubility and substrate structure on the morphological features of nanobubble distribution in alcohol-water exchange experiments. The results demonstrate that gas solubility plays a pivotal role in the nucleation of surface nanobubbles during alcohol-water exchange. Specifically, stable surface nanobubbles form only when the solubility exceeds 0.02535. Furthermore, under conditions where gas solubility satisfies the nucleation criteria, the surface potential energy of concave and defective structures exhibits concave characteristics, giving rise to the nucleation of cap-shaped nanobubbles. In contrast, the step structure, characterized by the smallest average surface potential energy, results in relatively flat properties in the lowest area, with nanobubble nucleation taking the form of layer-shaped features. yields relatively uniform characteristics at the lowest level, where nanobubble nucleation manifests in the form of layered features. As time progresses, cap-shaped nanobubbles coalesce, leading to the escape of gas molecules and subsequent dissipation, whereas the layer-shaped nanobubbles adsorb gas molecules from the solution, prompting their expansion.