Infrared Spectral and Dynamical Properties of Water Confined in Nanobubbles at Hybrid Interfaces of Diamond and Graphene: A Molecular Dynamics Study

Abstract

In this work, we have studied the behavior of water molecules confined in nanobubbles at the hybrid interfaces of graphene and diamond surfaces at varying temperatures. We have performed molecular dynamics simulations to investigate different spectral and dynamical properties of the confined water. The confined water molecules are characterized through calculations of their vibrational spectral properties. The spectral features are found to change significantly with variation of temperature and density of the nanobubbles. The calculated vibrational spectral results are found to be in reasonably good agreement with available experiments. Furthermore, we have looked at the dynamical properties of water molecules in the graphene nanobubbles. The current results reveal the presence of strong heterogeneity in the dynamical properties in nanobubbles at supercritical temperature. Water molecules that are confined in small nanobubbles at high density are found to possess very slow relaxation time scales because of stronger hydrogen bonding and spatial constraints. These water molecules can be considered as essentially irrotational water molecules. In other cases, water molecules confined in nanobubbles at lower density at supercritical temperature are found to show very fast relaxation time scales as the thermal energy dominates the dynamics of water molecules in these cases.