Professor Heather Allen
Professor Heather Allen
Department of Chemistry & Biochemistry
Ohio State University
Host: Professor Renee Frontiera
Interfacial Aqueous Organization and Electric Fields Generated from Chemical Composition
Marine and continental atmospheric aerosol, ocean surfaces, surfaces of the lung, biomembranes, and aqueous interfaces of materials, these interfaces have one thing in common - WATER. This unique molecule plays an important role in the structure of environmental, biological, and material interfaces, and can drive interfacial chemistry in sometimes subtle ways. Water at the air-water interface organizes and facilitates the surface adsorption of other molecular and ionic species. In studies presented, the hydration of surface molecules is evident by spectroscopic signatures using vibrational sum frequency generation (SFG) and infrared reflection absorption (IRRA) spectroscopies. Brewster angle microscopy (BAM) is also used to study macroscopic aggregation, and surface potentiometry is used to reveal the inherent electric field and net dipole perpendicular to and at the water’s surface. I will present studies of salts and lipids, interfacial binding and inherent structure of aqueous interfaces, prior and recent work in our lab. Water has preferred orientations such that free OH oscillators are persistent at the surface, breaking the hydrogen bonding structure of the 3D liquid. Complexation and binding motifs are driven by different rules at the liquid water-vapor interface. Studies on guanidinium surface-anchored receptor binding with phosphate, sulfate, and chloride will be presented. I’ll also present our newest work on applied electric fields to control organization of alcohols, fatty acids, sodium dodecyl sulfate, and ions such as potassium thiocyanate.
Professor Allen
Professor Allen received her bachelor's degree in chemistry from Saddleback, and her doctorate in physical chemistry from the University of California, Irvine. She continued her post-doctoral studies at the University of Oregon. She began her professorial career at Ohio State in 2000, and has since been recognized for many research accomplishments: Research Innovation Award from Research Corp., National Science Foundation CAREER Award, Beckman Young Investigator Award, Alfred P. Sloan Research Fellow Award, Camille Dreyfus Teacher-Scholar Award, Fellow of the American Association for the Advancement of Science, Ohio State Distinguished Scholar Award, and the Alexander von Humboldt Research Award from Germany. In addition, Professor Allen has been recognized for several mentoring awards over the years including the Ohio State Office of Minority Affairs Mentor Award, an Empowered Woman Award from the City of Columbus, and the American Chemical Society National Award for Encouraging Women into Careers in the Chemical Sciences.
Professor Allen's research specialization is in molecular organization, ion pairing, and hydration at aqueous interfaces. Aqueous surfaces are of particular interest with emphasis on understanding surface structure. Investigations of molecular organization and orientation, and chemical reaction mechanisms at gas - liquid, gas - solid, and liquid - solid interfaces are of interest. Cell membranes, atmospheric aerosols, cloud microdroplets, and geochemical systems are interfacial systems that can be studied using vibrational spectroscopic methods, and the Allen research group utilizes and designs optical spectroscopic instruments to this end. To understand the molecular-level details of an interface, state-of-the-art nonlinear optical technologies that utilize ultra-fast femto and picosecond laser pulses are necessary. Surface vibrational sum frequency generation spectroscopy, broadband and scanning technologies, are used by Professor Allen's researchers to elucidate interfacial chemistry.
