Vibrational Sum Frequency Spectroscopy and Molecular Dynamics Simulation of the Carbon Tetrachloride−Water and 1,2-Dichloroethane−Water Interfaces

Abstract

Vibrational sum frequency (VSF) spectra calculated using molecular dynamics (MD) simulations are compared with VSF experimental spectra to gain a clearer picture of water structure and bonding at the carbon tetrachloride-water (CCl 4 -H 2 O) and the 1,2-dichloroethane-water (DCE-H 2 O) liquid-liquid interfaces. The VSF spectral response from interfacial water at the CCl 4 -H 2 O interface contains spectral features similar to the resonant VSF response of the vapor-water interface and alkane-water interfaces, while the VSF spectrum from the DCE-H 2 O interface has a low signal with no distinguishing OH stretch spectral features. These MD based spectral calculations show how different bonding interactions at the DCE-H 2 O interface lead to spectral broadening, frequency shifting, and spectral interferences that are responsible for the difference in the experimentally measured DCE-H 2 O and CCl 4 -H 2 O spectra. The computational results show that weak H 2 O-H 2 O interactions are perturbed by the presence of DCE, leading to increased water penetration into the more organic-rich portion of the interfacial region and strong orientation of these penetrating water molecules relative to the CCl 4 -H 2 O interface. Strong H 2 O-H 2 O interactions at the interface are not significantly impacted by the presence of DCE.

An Investigation of the Influence of Chain Length on the Interfacial Ordering of l-Lysine and l-Proline and Their Homopeptides at Hydrophobic and Hydrophilic Interfaces Studied by Sum Frequency Generation and Quartz Crystal Microbalance

“…38 The SFG spectrum of the d 8 -PS/buffer interface is quite similar to the dichloromethane/water interface that has been studied by Richmond and coworkers. 39,40 They determined that the water structure is a consequence of increased water penetration in the organic phase (something that is not likely here) 40 and general disorder at the interface.…”

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

“…Ultimately, it is the intermolecular forces between neighboring molecules that govern surfactant packing at the interface, and this depends on its molecular structure (10), the organic phase (14), and the electrostatics of the interface (15). The studies described herein are aided by prior work at neat oil-water interfaces as examined by vibrational sumfrequency spectroscopy (VSFS) and computational studies on planar interfaces (16)(17)(18). What has been learned from these and related studies is that weak bonding interactions between interfacial water and various hydrophobic oils is a general trait for these oilwater systems, which results in significant molecular ordering and structuring of both solvent phases near the interfacial region.…”

Ordered polyelectrolyte assembly at the oil–water interface

“…We know, for example, that weak bonding interactions between interfacial water and various hydrophobic oils is a general trait for these oil-water systems, resulting in significant molecular orientational ordering and structuring of both phases near the interfacial region (13)(14)(15). The existence of an interfacial electric field created by this structuring has been shown to facilitate the adsorption of simple electrolyte ions at the interface (15), surfactant adsorption, and also the penetration of oriented water into the organic phase (16).…”