Reversible state transition in nanoconfined aqueous solutions

Zhao, L., Wang, C., Liu, J., Wen, B., Tu, Y., Wang, Z. and Fang, H. (2014) Reversible state transition in nanoconfined aqueous solutions. Physical Review Letters, 112. 078301. ISSN 0031-9007 doi: 10.1103/PhysRevLett.112.078301

Abstract/Summary

Using molecular dynamics simulations, we find a reversible transition between the dispersion and aggregation states of solute molecules in aqueous solutions confined in nanoscale geometry, which is not observed in macroscopic systems. The nanoscale confinement also leads to a significant increase of the critical aggregation concentration (CAC). A theoretical model based on Gibbs free energy calculation is developed to describe the simulation results. It indicates that the reversible state transition is attributed to the low free energy barrier (of order kBT) in between two energy minima corresponding to the dispersion and aggregation states, and the enhancement of the CAC results from the fact that at lower concentrations the number of solute molecules is not large enough to allow the formation of a stable cluster in the confined systems.