The confinement-induced phase separation of water-alcohol binary mixture is significant in the field of chemical engineering, medicinal chemistry, and industrial chemistry. Therefore, a microscopic understanding of the structure and dynamics of aqueous alcohol in crowded environments becomes necessary. Although neat water under nanoconfinement was studied extensively in the past, a comprehensive study is missing in the case of aqueous binary mixture. In confined water, two factors influence the properties: (i) water-water interaction and (ii) water-surface interaction. The situation becomes more complex in a confined binary mixture with the additional set of liquid-liquid, liquid-surface, and cross interactions. Thus, it becomes an interesting exercise to explore the unique dynamical properties of aqueous binary mixture placed inside confinements. We observe by computer simulations a remarkable long-distance rare but repetitive exchange of ethanol and DMSO molecules between the two parallel graphene surfaces in nanoconfined water-ethanol and water-DMSO solutions, respectively. Interestingly, the observed exchange phenomenon is coupled with the orientational motion of the molecules. This observation leads us to construct a two-dimensional free energy surface and allows us to estimate the exchange rate by employing Kramers’ theory. Furthermore, we explore the dynamics of ions in the confined aqueous binary mixture, which unveils various exciting features. Although ions motion in water is widely studied, relatively few studies have been carried out in an aqueous binary mixture. The water-DMSO mixture is known to exhibit anomalies, often attributed to transient liquid-liquid phase separation. In the present study, we explore the size- and composition-dependent diffusion of ions by varying the size of the ions and the composition of the mixture. Later, we formulate a mode-coupling theory (MCT) approach to capture various aspects exhibited by ions in the aqueous binary mixture.

Ion diffusion in aqueous binary mixtures and effect of hydrophobic confinement

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.