Heather Cecile Allen (born 1960) is a research chemist, who leads the Allen Group at

Ohio State University The Ohio State University, commonly called Ohio State or OSU, is a public land-grant research university in Columbus, Ohio. A member of the University System of Ohio, it has been ranked by major institutional rankings among the best publ ...

. Allen's research focuses on interfacial phenomena, particularly those involving water and air. Her work has broad application ranging from medicine to climate change. She also develops nonlinear optical spectroscopy and microscopy instruments for the examination of interfacial surfaces. Allen has published more than 120 journal papers, and is reported to have an

H-index The ''h''-index is an author-level metric that measures both the productivity and citation impact of the publications, initially used for an individual scientist or scholar. The ''h''-index correlates with obvious success indicators such as ...

of 43 as of August 2019. She has received a number of awards, including the 2014 Alexander von Humboldt Research Award. Allen's work on the structure of water was mentioned in ''

Science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

'' magazine's list of the top ten breakthroughs of 2004.

Education

Heather Allen enrolled at

Saddleback College Saddleback College (Saddleback) is a public community college in Mission Viejo, California. It is part of the California Community College system and awards over 300 associate degrees, academic certificates, and occupational skills awards in 1 ...

, a community college, as an adult student at age 28. Interested in environmental science, she won a Science Scholarship Foundation Fellowship, enabling her to transfer to the

University of California, Irvine The University of California, Irvine (UCI or UC Irvine) is a public land-grant research university in Irvine, California. One of the ten campuses of the University of California system, UCI offers 87 undergraduate degrees and 129 graduate and p ...

to earn a chemistry or chemical engineering degree. She received her B.S. degree in Chemistry from the University of California, Irvine in 1993, working as a research assistant with Frank Sherwood Rowland and Donald R. Blake. She received her Ph.D. in

physical chemistry Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistica ...

in 1997, working with John C. Hemminger and Barbara J. Finlayson-Pitts. The topic of her Ph.D. thesis was ''Fundamental surface processes in heterogeneous atmospheric chemistry: Applications to sea-salt (NaCl) and oxide particulate chemistry.'' She received several awards and postdoctoral fellowships, and did postdoctoral work with Geraldine L. Richmond at the

University of Oregon The University of Oregon (UO, U of O or Oregon) is a public research university in Eugene, Oregon. Founded in 1876, the institution is well known for its strong ties to the sports apparel and marketing firm Nike, Inc, and its co-founder, billion ...

Career

Heather Allen joined

in 2000, as an assistant professor of environmental chemistry. She went on to become a full professor in the Department of Chemistry and Biochemistry and in the Department of Pathology. She leads the Allen Group at Ohio State University.

Interfacial phenomena

Her research focuses on fundamental interfacial phenomena, the molecular organization and orientation at interfaces between

gases Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

and

liquids A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

, gases and

solids Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

, and liquids and solids. She is particularly interested in understanding the activities of

ions An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

and molecules in aqueous surface structures. Understanding molecular organization is essential to understanding the ways in which surfaces will react. Her studies of chemical reaction mechanisms have examined

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

, and

fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an B ...

, among others. Her work has relevance to a wide variety of fields, from

medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

. Medically, aqueous surface structures are particularly relevant in the understanding of cell membranes and skin surfaces, which function as gateways to the cell and the body. As a Beckman Young Investigator, Allen studied the biophysics of the lung as a barrier mediating

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

transport, and the importance of pulmonary surfactants. Air, lipids, and water are all involved at the surface of the lung. Molecules of the alveolar lining were found to be important in the efficiency with which the lung could function. Allen has also examined the development of biomembranes with particular application to the detection of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

margins. Her team is working on the development of infrared

biomarkers In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, pa ...

and molecular level diagnostics for the use of cancer surgeons. Allen's studies of interfacial phenomena are also relevant to

geophysics Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' so ...

geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the ...

and

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

. Her work includes studies of how ions and minerals interact at surfaces where they are involved in

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

and the interactions of

pollutants A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like o ...

with

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

. The effect of particles at surfaces is important in understanding the behavior of air and water at ocean surfaces, and the health of oceans. Recent research indicates that accumulated ions are present in the ocean's surface layers. Using highly accurate laser beams, researchers were able to see the structures formed by halogen ions, or

halides In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...

, and surrounding molecules of water in the interfacial area. Halides such as

iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine de ...

and

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant ...

were found close to the surface, a result which challenged "conventional wisdom" on the subject.

Chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride sa ...

ions were found lower down. Iodide and bromide are unstable and tend to combine with other chemicals to form ozone. This means that fog and ocean spray are more chemically reactive than was previously believed by scientists. Allen's results may cause atmospheric chemists to revise their models of ozone activity and climate change. The behavior of atmospheric aerosols, particulate matter suspended in the atmosphere, is also related to climate change. Heather Allen is part of a national multidisciplinary group of researchers involved in the Center for Aerosol Impacts on Climate and the Environment (CAICE) who study the effects of atmospheric aerosols. Allen studies the surfaces of cloud systems and their electric fields, to better understand thunderstorms, lightning strikes and the effects of microdroplets on clouds and fogs. With Lisa Van Loon, she has examined the behavior of sulfuric acid and methanol, found as aerosols in the upper atmosphere. Together they can form

methyl sulfate Methyl bisulfate is a chemical compound with the molecular formula CH4O4S. This compound is the mono-methyl ester of sulfuric acid. The significance of methyl bisulfate is that it is an intermediate in the hydrolysis of the important reagent dime ...

, a compound that attracts water droplets and supports cloud formation. While sulfuric acid can reflect light and heat, clouds tend to trap light and heat in the atmosphere. The interplay between sulfuric acid and atmospheric temperature change is therefore more complex than originally thought.

Instrumentation

Heather Allen and the Allen Group are involved in the design of nonlinear optical spectroscopy and microscopy instruments for scientific research. These include vibrational sum frequency generation (VSFG) spectroscopy, and broad-bandwidth sum frequency generation (BBSFG) spectroscopy, used for investigating gas-liquid and solid interfaces. Laser technology uses ultra-fast femtosecond and picosecond laser pulses to examine molecular-level interfaces and observe the orientation and structure of the chemical species within the surface regime, the surface signature. Other techniques used and studied include polarized Raman and

infrared spectroscopy Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or function ...

techniques, Brewster angle microscopy, and

differential optical absorption spectroscopy In atmospheric chemistry, differential optical absorption spectroscopy (DOAS) is used to measure concentrations of trace gases. When combined with basic optical spectrometers such as prisms or diffraction gratings and automated, ground-based observa ...

Awards

* 2001, Research Innovation Award from

Research Corporation Research Corporation for Science Advancement (RCSA) is an organization in the United States devoted to the advancement of science, funding research projects in the physical sciences. Since 1912, Research Corporation for Science Advancement has id ...

* 2002, NSF CAREER Award * 2003,

Beckman Young Investigators Award The Beckman Young Investigators Award was established by Mabel and Arnold Beckman in 1991, and is now administered by the Arnold and Mabel Beckman Foundation. The Beckman Young Investigator (BYI) Program is intended to provide research support to p ...

* 2005,

Alfred P. Sloan Research Fellowship The Sloan Research Fellowships are awarded annually by the Alfred P. Sloan Foundation since 1955 to "provide support and recognition to early-career scientists and scholars". This program is one of the oldest of its kind in the United States. ...

* 2006, Camille Dreyfus Teacher-Scholar Award * 2012, Fellow of the American Association for the Advancement of Science (AAAS) * 2013, ACS Award for Encouraging Women into Careers in the Chemical Sciences, supported by

The Camille and Henry Dreyfus Foundation The Camille and Henry Dreyfus Foundation is a New York City-based foundation founded in 1946 by chemist and investor Camille Dreyfus in honour of his brother, Henry Dreyfus. The two men invented the acetate yarn Celanese, and Henry Dreyfus was ...

* 2014, Alexander von Humboldt Research Award (Germany) * 2015, University Distinguished Scholar Awards, Ohio State University

References

{{DEFAULTSORT:Allen, Heather C. 1960 births Living people American women chemists 21st-century American chemists Ohio State University faculty Saddleback College alumni University of California, Irvine alumni American women academics 21st-century American women scientists