Stability of soluble bulk nanobubbles: Many-body dissipative particle dynamics analysis

Bulk nanobubbles (bNBs) have attracted considerable research attention due to their broad application prospects. Numerous experiments have demonstrated the stability of nanobubbles (NBs) in solution, but further investigation is needed to determine their stability mechanism. This paper investigates the properties of bNBs using mesoscopic simulations based on many-body dissipative particle dynamics (MDPD). Based on the standard insoluble bubble model, the soluble bubble model is developed by modifying the attraction amplitude between gas and liquid. This modification determined the range of soluble bubble parameters. The new surface tension calculation model indicates that reducing the surface tension is helpful to the stability of soluble bubbles. In contrast, surface tension changes do not affect the stability of insoluble bubbles. The two bubble models follow the Young-Laplace equation to analyze further the internal density, pressure, gas diffusion, and other characteristics of bNBs. The results show that the gas in bNBs has a high density and pressure. In addition, as the size of the bNBs decreases, the gas density and pressure in the bNBs also increase. In the soluble bubble, the gas density is not uniform, and the gas in the soluble bubble forms a density peak at the gas-liquid interface. The density peak in the bNBs delays the outward diffusion of the gas to maintain its stability. This study aims to provide a method to simulate bNBs, reveal their characteristics, and explore the influence of non-uniform density in bNBs on diffusion.