Spiers Memorial Lecture : Recent experimental advances in studies of liquid/liquid interfaces (original) (raw)
Related papers
A molecular theory of liquid interfaces
Physical Chemistry Chemical Physics, 2005
We propose a site-site generalization of the Lovett-Mow-Buff-Wertheim integro-differential equation for the one-particle density distributions to polyatomic fluids. The method provides microscopic description of liquid interfaces of molecular fluids and solutions. It uses the inhomogeneous site-site direct correlation function of molecular fluid consistently constructed by nonlinear interpolation between the homogeneous ones. The site-site correlations of the coexisting bulk phases are obtained from the reference interaction site model (RISM) integral equation with our closure approximation. For illustration, we calculated the structure of the planar liquid-vapor as well as liquid-liquid interfaces of n-hexane and methanol at ambient conditions.
Physical Chemistry Chemical Physics, 2004
The orientational statistics of water molecules at the vicinity of the water/CCl 4 liquid-liquid interface is analyzed at different levels of statistics on the basis of a Monte Carlo computer simulation. Profiles describing the average orientation of various molecule-fixed vectors relative to the interface along the interface normal axis, monovariate distributions of parameters describing these orientations, as well as the bivariate joint probability distribution of two independent orientational parameters in different water layers are determined. It is demonstrated that a complete description of the orientational preferences of the entire water molecule can only be given by the bivariate joint probability distribution of two independent orientational parameters. Two co-existing preferred orientations of the water molecules have found: in the first orientation, present at the entire interfacial region, the water molecule lays in a plane parallel with the interface, whereas in the second preferred orientation, present only among the water molecules penetrated deepest into the nonpolar phase, the plane of the water molecule is perpendicular to the interface and one of its O-H bonds points straight toward the nonpolar phase. This latter orientation corresponds to the orientation expected for a hydrogen bonded neighbor, located toward the nonpolar phase, of a water molecule which lays parallel with the interface.
A molecular dynamics study of a liquid–liquid interface: structure and dynamics
Fluid Phase Equilibria, 2004
The liquid-liquid (L/L) interface between two partially miscible model Lennard-Jones fluids is investigated in the temperature range 100 K ≤ T ≤ 138 K using molecular dynamics computer simulations. The equilibrium compositions in the two phases agree reasonably well with recent results from DFT theory. The structure of the L/L interface is characterized in terms of partial density profiles of the two components and the interfacial tensions are computed for all temperatures using the virial method. The self-diffusion coefficients are determined as a function of temperature and distance from the interface and are compared to the ones of the pure liquids under identical conditions. A slight anisotropy is found in the interfacial system. It is restricted to the regions of strong variations of the partial density profiles and is due to an enhancement of the tangential components of the self-diffusion coefficients compared to the components D s,N normal to the interface.
Molecular dynamics of the water liquid-vapor interface
The Journal of Physical Chemistry, 1987
The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C, , molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 f 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.
Applications of Molecular Dynamics Techniques and Spectroscopic Theories to Aqueous Interfaces
Her love and patience seem to have no end. The unwavering support she has offered, and her belief in me, has been a true source of joy and inspiration in my life. Words cannot express how grateful I am, and I only hope that my support for her continues to be as meaningful as what she has given to me. I truly love you with all of my heart. I would especially like to express my appreciation to my parents, John and Dianna Green, as well as Grandma, Gramps, Aunt Barb, and my extended family and friends whose love, support, and encouragement has been never ending. I could never have gotten this far without any of you. From the bottom of my heart, thank you.
Spectroscopic studies of molecular interaction at the liquid–liquid interface
Analytical and Bioanalytical Chemistry, 2009
New experimental results are reported on molecular interactions in the n-ethylamines and 2-nitropropane (2-NP)/n-ethylamine mixtures studied by Raman spectroscopy under pressure in a diamond anvil cell (0-50 GPa) and, at ambient pressure, by infrared spectroscopy. Modifications of the infrared spectra in 2-NP in presence of triethylamine (TEA) or diethylamine (DEA) have been observed at ambient pressure and interpreted as a specific molecular interaction. High-pressure fluorescence in the vicinity of the liquid-solid phase transition of the 2-NP/DEA and 2-NP/monoethylamine mixtures, is highlighted and discussed.
Journal of Molecular Liquids, 2013
Molecular dynamics simulations of the water-CCl 4 interface have been done in two different ways. In the first simulation the CCl 4 phase has been frozen in an equilibrium configuration, and only the water molecules have been allowed to move, whilst in the other one no such artificial freezing has been done. This way the effect of the fluid-like structure and fluid-like dynamics of the CCl 4 phase on the surface properties of the aqueous phase could be investigated separately. Due to the separate thermostatting of the two types of molecules in the simulations all the differences seen between the interfacial properties of water in the two systems can indeed be attributed to the rigid vs. fluid nature of the organic phase, and not to the thermal contact with a phase of zero temperature. The obtained results reveal that the rigidity of the opposite phase introduces an ordering both in the layering structure and orientation of the surface water molecules. The enhanced orientational ordering leads to a stronger lateral hydrogen bonding structure of the molecules within the subsequent molecular layers beneath the surface, and hence also to a slower exchange of the water molecules between the surface and the bulk aqueous phase.