Structure, Dynamics, and Electronic Spectrum of N,N‘-Diethyl-p-nitroaniline at Water Interfaces. A Molecular Dynamics Study

The adsorption of N,N‘-diethyl-p-nitroaniline (DEPNA)a common chromophore probe of liquid polarityat the water liquid/vapor interface and at the water/1,2-dichloroethane (DCE) interface is studied using molecular dynamics computer simulations. The adsorption energetics, orientation, and reorientation dynamics are examined. The electronic absorption line shapes at the two interfaces, in bulk DCE, and in bulk water are calculated and are found to be in reasonable agreement with experimental results. Including many-body polarizable liquid potentials in the calculations at the water/DCE interface is found to improve the results. The role of surface roughness is examined by repeating the calculations for an artificially smooth water/DCE interface.