Molecular-Level Understanding of the Enhanced Stability of Single Bulk Nanobubbles

Abstract

In this study, we employed molecular dynamics simulations and classical bubble stability theory to investigate the relationship between bubble stability and various thermophysical parameters. Our findings indicate that, in contrast to small nanobubbles, large nanobubbles exhibit a longer lifespan in water and a smaller inner pressure. Specifically, nanobubbles with radii of 14 Å, 18 Å and 22 Å have pressures of 820 atm, 673 atm and 525 atm, respectively. The calculations reveal that smaller bubbles exhibit a more stretched state than larger bubbles, which is confirmed by the radial density distributions. Our findings show that larger nanobubbles exhibit reduced mobility and greater friction when undergoing brownian motion. We have also substantiated the classical theory for nanobubbles, confirming the calculated solubility of nanobubbles using Henry's law to be in accordance with simulation outcomes. The surface tension predicted by Young's equation at the calculated plane corroborates with the simulation findings. However, we observed an inconsistency in the theoretical value of the surface tension for the calculated highly curved interface, which was opposite to experimental observations. Overall, our results provide new insights into the design of stable nanobubbles generation for various applications.

Keywords: nanobubbles, Molecular Dynamics, Thermodynamic stability, Bubble dynamics