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Professor Allen received her B.S. degree in Chemistry in 1993 and Ph.D. in Physical Chemistry in 1997 at the University of California Irvine. Her advisors as an undergraduate, graduate, and postgraduate were Nobel Laureate F. S. Rowland, D. Blake, J. C. Hemminger, B. J. Finlayson-Pitts, and G. L. Richmond respectively. As a student and postdoctoral researcher she was awarded several fellowships including Fannie and John Hertz, EPA, an NSF Traineeship, and a NOAA Post-Doctoral Fellowship in Climate and Global Change. At Ohio State since 2001 to present she has been recognized for many research accomplishments: Research Innovation Award from Research Corp., NSF 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 (AAAS), Ohio State Distinguished Scholar Award, and the Alexander von Humboldt Research Award from Germany. Dr. Allen has also been recognized for several mentoring awards over the years including the Ohio State OMA 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. She is a Full Professor in the Department of Chemistry and Biochemistry and in the Department of Pathology, and her research specialization is in molecular organization at interfaces.
Molecular Organization at Interfaces: Atmospheric Aerosols - Air/Water Interfaces, Geochemical Interfaces, Biophysics of Lung Surfactant and Model Biomembranes, and Nonlinear-Optical Spectroscopy and Microscopy
Research in the Allen group encompasses the characterization of fundamental interfacial phenomena. 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. Laboratory experiments are designed to further understand organization of solvated ions and molecules such as water, lipids, and fatty acids at surfaces and interfaces of biological and environmental relevance.
Cell membranes, atmospheric aerosols, cloud microdroplets, and geochemical systems are interfacial systems that can be studied using vibrational spectroscopic methods. The Allen group utilizes and designs optical spectroscopic instruments to this end. The applications to this work drive the fundamental investigations. For example, in the atmosphere heterogeneous chemistry of liquid aerosols plays a critical role in thunderstorm and lightening production. In biology, cell membranes are dynamic barriers and gateways to the cell interior as is skin on a more macroscopic level. The lung lining is a uniquely dynamic barrier that is critical for oxygen and carbon dioxide transport to and from biological tissues. In geochemistry, water-solvated ions and ion pairs and minerals interact at surfaces and the interaction strength is key to the mechanisms of adsorption and transport. Cancer margin detection (collaborators Coe, Magliery, Hitchcock, Martin, Povoski) is focused on methodology and technology development.
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. Hence, surface vibrational sum frequency generation (VSFG) spectroscopy, broadband and scanning technologies, are used to elucidate interfacial chemistry. VSFG is inherently interface-selective and provides molecular-level interfacial information that includes relative orientation and structure of the surface species, i.e. the surface signature. An array of analytical optical spectroscopic and interfacial methods is incorporated to fully understand the heterogeneous chemical processes at an interface, for example, polarized Raman and infrared spectroscopies and microscopies, broadband VSFG, specular reflection infrared spectroscopy, and Brewster angle microscopy for biological and environmental applications.
Current Research Funding: National Science Foundation - Chemistry Division; Department of Energy - Basic Energy Sciences; National Institute of Health
Previous Allen group members have positions in industry, national laboratories, and academia: PPG Technologies in Pittsburgh, KLA Tencor; Batelle Corporation (Analytical and Aerosol Divisions); Chemical Abstracts Service; Canadian Synchotron Facility; Spartan Chemical; OSU Surface Science Facility; Syngenta, Switzerland; Pacific Northwest National Laboratory; professor positions at Bowdoin College-Maine and Herbei University in Baoding, China.
> Dr. Allen is accepting new graduate students that have interest in studying ion and molecular processes at aqueous surfaces using laser technology, specifically applying and learning vibrational sum frequency generation spectroscopy. Graduate students from any of the chemistry, biochemistry, biophysics, or chemical physics divisions are encouraged to request a meeting to discuss this project. Detailed research information can be found on the Allen Group website: http://research.chemistry.ohio-state.edu/allen/
Complete Publication list can be found at:
W. Hua, X. Chen, H.C. Allen; Phase-Sensitive Sum Frequency Revealing Accommodation of Bicarbonate Ions, and Charge Separation of Sodium and Carbonate Ions within the Air/Water Interface, J. Phys. Chem. A 2011, 115, 6233-6238; (Memorial Issue for Victoria Buch). pdf
C. Y. Tang, Z. Huang, H. C. Allen; Interfacial Water Structure and Effects of Mg2+ and Ca2+ Binding to the COOH Headgroup of Palmitic Acid Monolayer Studied by Vibrational Sum Frequency Generation Spectroscopy, J Phys Chem B. 2011 Jan 13;115(1):34-40. pdf
X. Chen, W. Hua, Z. Huang, H. Castada, H. C. Allen; Reorganization and Caging of DPPC, DPPE, DPPG, and DPPS Mono layers Caused by Dimethylsulfoxide Observed Using Brewster Angle Microscopy, Langmuir, 2010, 26 (24), pp 18902-18908. pdf
M. R. Sierra-Hernandez and H. C. Allen, Incorporation and Exclusion of Long Chain Alkyl Halides in Fatty Acid Monolayers at the Air-Water Interface, Langmuir, 2010, 26 (24), pp 18806-18816. pdf
X. Chen and H. C. Allen, Water Structure at Aqueous Solution Surfaces of Atmospherically Relevant Dimethyl Sulfoxide and Methanesulfonic Acid Revealed by Phase Sensitive Sum Frequency Spectroscopy, J. Phys. Chem. B, 2010, 114 (46), pp 14983-14988. pdf
PCCP Perspective: Shedding Light on Water Structure at Air-Aqueous Interfaces: Ions, Lipids, and Hydration; H. C. Allen, N. N. Casillas-Ituarte, M. R. Sierra-Hernandez, X. Chen, C. Y. Tang; Phys. Chem. Chem. Phys., 2009, 11, 5521-5852. pdf
Ionic Binding of K+ and Na+ to the Carboxylic Acid Head Group of Palmitic Acid in Monolayers using Vibrational Sum Frequency Spectroscopy; C. Y. Tang, H. C. Allen; J. Phys. Chem. A, 2009, 113, 7383-7393. -Benny Gerber Festschrift Issue- pdf
Surface Residence and Uptake of Methyl Chloride and Methyl Alcohol at the Air/Water Interface Studied by Vibrational Sum Frequency Spectroscopy and Molecular Dynamics; K. Harper, B. Minofar, M. R. Sierra-Hernandez, N. N. Casillas-Ituarte, M. Roeselova, H.C. Allen; J. Phys. Chem. A, 2009, 113, 2015-2024 -Max Wolfsberg Festschrift Issue- pdf
Dangling OD Confined in a Langmuir Monolayer, G. Ma, X. Chen, H. C. Allen*, J. Am. Chem. Soc., 2007; 129(45); 14053-14057. pdf
Observation of hydronium ions at the air-aqueous acid interface: Vibrational spectroscopic studies of aqueous HCl, HBr, and HI, L. M. Levering, M. R. Sierra-Hernández, H. C. Allen*, 2007, J. Phys. Chem. C, 111 (25), 8814-8826. pdf
Oxidation of oleic acid at air/liquid interfaces, Voss, L. F., M. F. Bazerbashi, C. P. Beekman, C. M. Hadad, and H. C. Allen*, J. Geophys. Res., 2007, 112, D06209, doi:10.1029/2006JD007677. pdf
New Insights into Lung Surfactant Monolayers using Vibrational Sum Frequency Generation Spectroscopy; G. Ma and H. C. Allen*; Photochemistry and Photobiology, 2006, V82, 1517-1529. pdf
DPPC Langmuir monolayer at the air-water interface: probing the tail and head groups by vibrational sum frequency generation spectroscopy, G. Ma & H.C. Allen*, 2006, Langmuir; 22(12); 5341-5349. pdf
Vibrational Spectroscopic Studies of Aqueous Interfaces: Salts, Acids, and Nanodrops, S. Gopalakrishnan, D. Liu, and H. C. Allen* and M. Kuo and M. J. Shultz*, Chemical Reviews, 2006, 106(4), 1155-1175. pdf
Air-Liquid Interfaces of Aqueous Solutions Containing Ammonium and Sulfate: Spectroscopic and Molecular Dynamics Studies, S. Gopalakrishnan, P. Jungwirth, D. J. Tobias, H. C. Allen*, J. Phys. Chem. B, 2005, V109 (18), 8861 - 8872. pdf
Unified Molecular Picture of the Surfaces of Aqueous Acid, Base, and Salt Solutions; M. Mucha, T. Frigato, L. M. Levering, H. C. Allen, D. J. Tobias, L. X. Dang, P. Jungwirth; J. Phys. Chem. B, 2005, 109, 7617 - 7623. pdf