Slow water dynamics at the surface of macromolecular assemblies of different morphologies

Abstract

In this contribution we, for the first time, explore the slow dynamical states of confined water molecules in lamellar structures of AOT with various degrees of hydration using a picosecond resolved fluorescence spectroscopic technique using coumarin-500 as the fluorophore. A comparison of slow dynamics between AOT lamellar structures and AOT RMs have been made by preparing RMs that have a diameter the same as the interplanar water layer thickness of lamellar structures and the same number of water molecules in lamellar structures in order to understand the effect of morphology and hydration on the relaxation dynamics of water molecules in these nanoconfining systems. The relaxation time scales obtained in the lamellar systems differ to those of the RM systems and the difference of the timescales has been explained as a interplay between two opposing factors arising out of the morphology and interlayer distance, respectively. The geometrical restriction of the probe at the lamellar interface is determined by measuring time-resolved rotational anisotropy. The hydrogen bond energy of the water molecules residing at the lamellar interface is measured applying the Arrhenius type barrier crossing model.