Peer Reviewed: Pushing Down the Limits of Detection: Molecular

Report

Because liquid iquid surfaces and interfaces play a central role in many of the surfaces, and interchemical and physical processes in our lives. Exchange of molecules and faces play a central ions across liquid or membrane surfaces is prevalent in biological processes. Many important chemical separole in everyday life, environmentally ration processes are based on the partiof solute molecules across the inunderstanding their tioning terface between two immiscible liquids. in the lungs of living organstructure and dynam- Respiration isms occurs across lipid surfactant monoThe ordering of organic molecules ics on the molecular layers. at liquid interfaces to form supramolecular structures UDon transfer to a solid is level is important. being used in molecular recognition catal-

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ysis and nonlinear optical applications Understanding such processes requires a knowledge of the structure and dynamics of these liquid interfaces on a molecular level. Our knowledge of the properties of these interfaces has come primarily from theoretical studies and experimental measurements of a more macroscopic nature. Development of several experimental techniques has recently advanced our knowledge about molecular structure at liquid-air interfaces. Neutron (1) and X--ay (2) )iffraation and reflection studies have provided structural details on an angstrom level about molecular packing at the liquid-air interface From optical techniques such as Fourier transform-IR (3) Brewster rcoL-CllCc IIllClOaCOJjy \0), (SFVS) sUIIl ITtlJllCllCy vibrational snectrosconv (6-8) and second harmonic Feneration (SHO (8-1 f\ information aho t the phase he U

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