Effect of non-soluble gases on the evaporation of water in extreme hydrophobic confinement*

We hereby report on the use of Restrained Molecular Dynamics [1] to investigate the effect of the presence of small concentrations of hydrophobic gases on the phase behaviour of water confined in hydrophobic nanopores [2].

Metastability, and thus rare events, are a typical feature of water in extreme hydrophobic confinement: nanopores can either be wet or occupied by vapor with the relative stability of the two states depending on the size and hydrophobicity of the porous material [3].

Our results show that the presence of even a single hydrophobic gas atom within the pore can dramatically accelerate evaporation and alter the relative stability of the wet and vapor-filled states.

These findings might shed a light on a possible unspecific mechanism of action of volatile anaesthetic gases on certain ion channels, whose ionic currents may be block by vapour bubbles, and on the control of undesired bubble formation in artificial nanopores for sensing and chromatography.

[1] Maragliano, L., & Vanden-Eijnden, E., (2006). Chem.Phys.Letters 426.1-3
[2] Camisasca, G., Tinti, A., & Giacomello, A. (2020). JPCL 11
[3] Tinti, A., Giacomello, A., Grosu, Y., & Casciola C.M. (2017). PNAS 114.48