Heather Allen

Heather Allen

Heather Allen

Dow Professor, Ohio State Distinguished Scholar



3105 Newman & Wolfrom Laboratory
100 W 18th Ave
Columbus, OH 43210

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Areas of Expertise

  • Physical

Divisional Affiliation: Physical, Analytical, Biochemistry, Chemical Physics, Environmental



Professor Heather C. Allen attended Saddleback College from 1989-1992, completing much of her undergraduate science and general education coursework before transferring to the University of California, Irvine in 1992. After her second year at Saddleback, she focused on the sciences, targeting chemistry as her major, winning a Saddleback College Science Scholarship Award to continue advancement toward her chemistry degree.  She received her B.S. degree in Chemistry in 1993, and Ph.D. in Physical Chemistry in 1997 at the University of California Irvine working with Nobel Laureate F. S. Rowland, and Professors D. Blake, J. Hemminger, and B. Finlayson-Pitts. She continued her postdoctoral studies in 1997 at the University of Oregon advised by Professor G. L. Richmond. Following the Saddleback Science Scholarship, as a student and postdoctoral researcher, she was also recognized with other scholarships and fellowships: Fannie and John Hertz Fellowship, EPA, NSF Traineeship, and a NOAA Post-Doctoral Fellowship in Climate and Global Change. 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., 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, the Alexander von Humboldt Research Award from Germany, and the 2022 American Chemical Society Irving Langmuir Award in Chemical Physics. In addition, Dr. 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. She is a Full Professor in the Department of Chemistry and Biochemistry, and in the Department of Pathology.  Her research specialization is in molecular organization, ion pairing, and hydration at aqueous interfaces.

Research Overview

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.


A complete list of Allen Group's publications is available.

(Selected Publications)

Sodium Drives Interfacial Equilibria for Semi-Soluble Phosphoric and Phosphonic Acids of Model Sea Spray Aerosol Surfaces, ACS Earth and Space Chemistry, J. F. Neal, M. M. Rogers, M. A. Smeltzer, K. A. Carter-Fenk, A. J. Grooms, M. M. Zerkle, H. C. Allen; https://doi.org/10.1021/acsearthspacechem.0c00132 (2020).

Thermodynamic Signatures of the Origin of Anti-Hofmeister Selectivity for Phosphate at Aqueous Interfaces, A. J. Grooms, J. F. Neal, K. C. Ng, W. Zhao, A. H. Flood, H. C. Allen; J. Phys. Chem. A (2020)124, No27, July 9.

Iron(III) Speciation Observed at Aqueous and Glycerol Surfaces: Vibrational Sum Frequency and X-Ray,   L. Lin, J. Husek, Jakub; S. Biswas, S. Baumler, T. Adel, K. C. Ng, L. R. Baker, H. C. Allen; J. Am. Chem. Soc. (2019) 141, 34, 13525-13535.

Hydration of Ferric Chloride and Nitrate in Aqueous Solutions: Water-mediated Ion Pairing Revealed by Raman Spectroscopy, S. M. Baumler, W. H. Hartt V, H.C. Allen; Phys. Chem. Chem. Phys. (2019) DOI: 10.1039/C9CP01392J.

Molecular-level origin of the carboxylate head group response to divalent metal ion complexation at the air-water interface, J.K. Denton, P. J. Kelleher, M. D. Baer, S. M. Kathmann, C. J. Mundy, B. A. Wellen Rudd, H. C. Allen, T. H. Choi, K D.ordan, and M. A. Johnson; Proc. Natl. Acad. Sci. USA (2019), V116 (30), 14874-14880.

Interfacial Supramolecular Structures of Amphiphilic Receptors Drive Aqueous Phosphate Recognition; J. F. Neal, W. Zhao, A. J. Grooms, M. A. Smeltzer, B. M. Shook, A. H. Flood, H. C. Allen;   J. Am. Chem. Soc.  (2019) V141, 7876-7886 10.1021/jacs.9b02148 .

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


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