Heather Cecile Allen is a research chemist and Professor of Chemistry, who leads the Allen Group at The

Ohio State University The Ohio State University (Ohio State or OSU) is a public university, public Land-grant university, land-grant research university in Columbus, Ohio, United States. A member of the University System of Ohio, it was founded in 1870. It is one ...

. 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 150 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 success indicators such as winning t ...

of 53 as of May 2024. She has received a number of awards including the 2022 American Chemical Society Irving Langmuir Award in Chemical Physics, and in 2014 the

Alexander von Humboldt Research Award The Humboldt Research Award (), also known informally as the Humboldt Prize, is an award given by the Alexander von Humboldt Foundation of Germany to internationally renowned scientists and scholars who work outside of Germany in recognition of t ...

. Allen's work on the structure of water was mentioned in ''

Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...

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

Education

Heather Allen enrolled at

Saddleback College Saddleback College 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 190 programs. ...

, 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 university, public Land-grant university, land-grant research university in Irvine, California, United States. One of the ten campuses of the University of California system, U ...

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 Nobel Laureate

Frank Sherwood Rowland Frank Sherwood "Sherry" Rowland (June 28, 1927 – March 10, 2012) was an American Nobel laureate and a professor of chemistry at the University of California, Irvine. His research was on atmospheric chemistry and chemical kinetics. His b ...

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, statistical mech ...

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 university, public research university in Eugene, Oregon, United States. Founded in 1876, the university is organized into nine colleges and schools and offers 420 undergraduate and gra ...

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 a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such ...

and

liquids Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

, gases and

solids Solid is a state of matter where molecules are closely packed and can not slide past each other. Solids resist compression, expansion, or external forces that would alter its shape, with the degree to which they are resisted dependent upon the ...

, 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 convent ...

and

molecules A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry ...

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 is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

lipids Lipids are a broad group of organic compounds which include fats, waxes, sterols, fat-soluble vitamins (such as vitamins Vitamin A, A, Vitamin D, D, Vitamin E, E and Vitamin K, K), monoglycerides, diglycerides, phospholipids, and others. The fu ...

, and

fatty acids In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

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

medicine Medicine is the science and Praxis (process), practice of caring for patients, managing the Medical diagnosis, diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, ...

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

. 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 The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

as a barrier mediating

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

and

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

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 Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...

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, p ...

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 property, properties of Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists conduct i ...

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 e ...

and

climate Climate is the long-term weather pattern in a region, 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 meteoro ...

. 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 engine ...

and the interactions of

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

with

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

. 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 fluo ...

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

iodide An iodide ion is 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 deficiency ...

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-retard ...

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

Chloride The term chloride refers to a compound or molecule that contains either a chlorine anion (), which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond (). The pr ...

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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

and

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

, found as aerosols in the upper atmosphere. Together they can form methyl sulfate, 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 Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectro ...

and

microscopy Microscopy is the technical field of using microscopes to view subjects too small to be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of microscopy: optical mic ...

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 A femtosecond is a unit of time in the International System of Units (SI) equal to 10 or of a second; that is, one quadrillionth, or one millionth of one billionth, of a second. A femtosecond is to a second, as a second is to approximately 31.6 ...

and

picosecond A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10−12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 ...

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 functio ...

techniques, Brewster angle microscopy, and differential optical absorption spectroscopy.

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 ...

* 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 The American Association for the Advancement of Science (AAAS) is a United States–based international nonprofit with the stated mission of promoting cooperation among scientists, defending scientific freedom, encouraging scientific responsib ...

(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,

(Germany) * 2015, University Distinguished Scholar Awards, Ohio State University * 2022, American Chemical Society (ACS) Irving Langmuir Award in Chemical Physics

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 21st-century American academics 21st-century American women scientists