Nanoconfinement of salty water results in complex effects

Researchers have spent decades studying the properties of water and how they change under various perturbations. Research on the topic has a wide range of applications from biochemical systems to water desalination.

Rozsa et al. studied how the structure and electronic properties of liquid water can be affected by the presence of ions and nanoconfinement. They employed first-principle simulations to search for signs of these perturbations.

“The effect of perturbations from nanoconfinement may greatly alter the properties of water, which must be understood in order to enable rational molecular engineering of a variety of confined water technologies,” said author Giulia Galli.

For comparison, the authors performed their simulations for water inside semiconducting nanotubes with diameters of 1.1 and 1.5 nm respectively.

They discovered that due to the nanoconfinement, there are competing effects of broken hydrogen bond and water-carbon interaction on the molecular polarizability. They identified polarizability as the “fingerprint” of ion and nanoconfinement perturbation.

“The molecular polarizabilities displayed a competing balance between reductions from structure breaking and enhancements at the interface from the nanotube,” said author Tuan Pham.

This work can be extended to understand the effect of anions or divalent ions on confined water. In the future, the authors hope to research how the competing effects on molecular polarizability are influenced by other solvated ions and in different degrees of confinement.

Source: “Molecular polarizabilities as fingerprints of perturbations to water by ions and confinement,” by Viktor Rozsa, Tuan Anh Pham, and Giulia Galli, Journal of Chemical Physics (2020). The article can be accessed at https://doi.org/10.1063/1.5143317 .