Gas-Induced Drying of Nanopores*

Drying of nanopores - formation of the vapor phase from the liquid phase in nano-confinement - plays a fundamental role in many different scenarios spanning from biology where ionic currents through ion channels can be blocked by the formation of a bubble inside them, to technology where, e.g., devices for mechanical energy storage can be based on drying properties of nanoporous materials. The presence of hydrophobic solutes in the liquid phase can dramatically modify the kinetics of the drying process. We investigate the role of a dilute hydrophobic gas on the phase behavior of water confined in hydrophobic cylindrical nanopores with diameter 14 Å [1]. With advanced molecular dynamics simulations we characterize the drying free-energy landscape of the systems and we show that a single hydrophobic atom inside the nanopore can decrease and in some cases totally abate the drying free-energy barrier causing the instantaneous drying of the whole nanopore. The identified mechanism provides a possible explanation for the action of volatile anesthetics and strategy for the design of efficient technological devices.
[1] G. Camisasca, A. Tinti, A. Giacomello. Gas-Induced Drying of Nanopores. JPCL 11 (2020), 9171-9177