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Mostafa A. El-Sayed () is an Egyptian-American physical chemist, nanoscience researcher, member of the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
and US National Medal of Science laureate. He is known for the spectroscopy rule named after him, the ''El-Sayed rule''.


Early life and academic career

El-Sayed was born in Zifta, Egypt and spent his early life in Cairo. He earned his B.Sc. in chemistry from
Ain Shams University Ain Shams University () is a public university located in Cairo, Egypt. Founded in 1950, the university provides education at the undergraduate, graduate and post-graduate levels. History Ain Shams University was founded in July 1950, the third ...
Faculty of Science,
Cairo Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
in 1953. El-Sayed earned his doctoral degree in chemistry from
Florida State University Florida State University (FSU or Florida State) is a Public university, public research university in Tallahassee, Florida, United States. It is a senior member of the State University System of Florida and a preeminent university in the s ...
working with Michael Kasha, the last student of the legendary G. N. Lewis. While attending graduate school he met and married Janice Jones, his wife of 48 years. He spent time as a post-doctoral researcher at
Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...
,
Yale University Yale University is a Private university, private Ivy League research university in New Haven, Connecticut, United States. Founded in 1701, Yale is the List of Colonial Colleges, third-oldest institution of higher education in the United Stat ...
and the
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
before joining the faculty of the
University of California at Los Angeles The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the Ca ...
in 1961. In 1994, he retired from UCLA and accepted the position of Julius Brown Chair and Regents Professor of Chemistry and Biochemistry at the
Georgia Institute of Technology The Georgia Institute of Technology (commonly referred to as Georgia Tech, GT, and simply Tech or the Institute) is a public university, public research university and Institute of technology (United States), institute of technology in Atlanta, ...
. He led th
Laser Dynamics Lab
there until his full retirement in 2020. El-Sayed is a former editor-in-chief of the '' Journal of Physical Chemistry'' (1980–2004).


Research

El-Sayed's research interests include the use of
steady-state In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p'' ...
and ultra fast laser spectroscopy to understand relaxation, transport and conversion of energy in
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 solids, in
photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...
systems, semiconductor
quantum dots Quantum dots (QDs) or semiconductor nanocrystals are semiconductor particles a few nanometres in size with optical and electronic properties that differ from those of larger particles via quantum mechanical effects. They are a central topic i ...
and metal nanostructures. The El-Sayed group has also been involved in the development of new techniques such as magnetophotonic selection, picosecond
Raman spectroscopy Raman spectroscopy () (named after physicist C. V. Raman) is a Spectroscopy, spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Ra ...
and phosphorescence microwave double resonance spectroscopy. A major focus of his lab is currently on the optical and chemical properties of
noble metal A noble metal is ordinarily regarded as a metallic chemical element, element that is generally resistant to corrosion and is usually found in nature in its native element, raw form. Gold, platinum, and the other platinum group metals (ruthenium ...
nanoparticles A nanoparticle or ultrafine particle is a particle of matter 1 to 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At ...
and their applications in nano
catalysis Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
, nanophotonics and nanomedicine. His lab is known for the development of the gold nanorod technology. As of 2021, El-Sayed has produced over 1200 publications in refereed journals in the areas of
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 ...
,
molecular dynamics Molecular dynamics (MD) is a computer simulation method for analyzing the Motion (physics), physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a fixed period of time, giving a view of the dynamics ( ...
and nanoscience, with over 130,000 citations.


Honors

For his work in the area of applying
laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
spectroscopic techniques to study of properties and behavior on the nanoscale, El-Sayed was elected to the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
in 1980. In 1989 he received the Tolman Award, and in 2002, he won the Irving Langmuir Award in Chemical Physics. He has been the recipient of the 1990 King Faisal International Prize ("Arabian Nobel Prize") in Sciences,
Georgia Tech The Georgia Institute of Technology (commonly referred to as Georgia Tech, GT, and simply Tech or the Institute) is a public research university and institute of technology in Atlanta, Georgia, United States. Established in 1885, it has the lar ...
's highest award, "The Class of 1943 Distinguished Professor", an honorary doctorate of philosophy from the
Hebrew University The Hebrew University of Jerusalem (HUJI; ) is an Israeli public research university based in Jerusalem. Co-founded by Albert Einstein and Chaim Weizmann in July 1918, the public university officially opened on 1 April 1925. It is the second-ol ...
, and several other awards including some from the different
American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all ...
local sections. He was a Sherman Fairchild Distinguished Scholar at the
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
and an Alexander von Humboldt Senior U.S. Scientist Awardee. He served as editor-in-chief of the '' Journal of Physical Chemistry'' from 1980 to 2004 and has also served as the U.S. editor of the ''International Reviews in Physical Chemistry''. He is a Fellow of the
American Academy of Arts and Sciences The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...
, a member of the
American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion 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 ...
and the Third World Academy of Science. Mostafa El-Sayed was awarded the 2007 US
National Medal of Science The National Medal of Science is an honor bestowed by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral science, behavior ...
"for his seminal and creative contributions to our understanding of the electronic and
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
properties of
nanomaterials Nanomaterials describe, in principle, chemical substances or materials of which a single unit is sized (in at least one dimension) between 1 and 100 nm (the usual definition of nanoscale). Nanomaterials research takes a materials science ...
and to their applications in nano
catalysis Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
and nanomedicine, for his
humanitarian Humanitarianism is an ideology centered on the value of human life, whereby humans practice benevolent treatment and provide assistance to other humans to reduce suffering and improve the conditions of humanity for moral, altruistic, and emotiona ...
efforts of exchange among countries and for his role in developing the scientific leadership of tomorrow." Mostafa was also announced to be the recipient of the 2009
Ahmed Zewail Ahmed Hassan Zewail (February 26, 1946 – August 2, 2016) was an Egyptian-American chemist, known as the "father of femtochemistry". He was awarded the 1999 Nobel Prize in Chemistry for his work on femtochemistry and became the first Egyptian a ...
prize in molecular sciences. In 2011, he was listed #17 in Thomson-Reuters listing of the Top Chemists of the Past Decade. Professor El-Sayed also received the 2016
Priestley Medal The Priestley Medal is the highest honor conferred by the American Chemical Society (ACS) and is awarded for distinguished service in the field of chemistry. Established in 1922, the award is named after Joseph Priestley, one of the discoverers of ...
, the
American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry. Founded in 1876 at New York University, the ACS currently has more than 155,000 members at all ...
’s highest honor, for his decades-long contributions to chemistry.


The El-Sayed rule

This rule pertains to
phosphorescence Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
and similar phenomena. Electrons vibrate and resonate around molecules in different
modes Mode ( meaning "manner, tune, measure, due measure, rhythm, melody") may refer to: Arts and entertainment * MO''D''E (magazine), a defunct U.S. women's fashion magazine * ''Mode'' magazine, a fictional fashion magazine which is the setting fo ...
(
electronic state A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The t ...
), usually depending on the energy of the system of electrons. This law states that constant-energy flipping between two electronic states happens more readily when the vibrations of the electrons are preserved during the flip: any change in the
spin Spin or spinning most often refers to: * Spin (physics) or particle spin, a fundamental property of elementary particles * Spin quantum number, a number which defines the value of a particle's spin * Spinning (textiles), the creation of yarn or thr ...
of an electron is compensated by a change in its orbital motion ( spin-orbit coupling).
Intersystem crossing Intersystem crossing (ISC) is an isoenergetic radiationless process involving a transition between the two electronic states with different spin multiplicity. Excited singlet and triplet states When an electron in a molecule with a singlet grou ...
(ISC) is a photophysical process involving an isoenergetic radiationless transition between two
electronic state A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The t ...
s having different multiplicities. It often results in a vibrationally excited molecular entity in the lower electronic state, which then usually decays to its lowest
molecular vibration A molecular vibration is a Periodic function, periodic motion of the atoms of a molecule relative to each other, such that the center of mass of the molecule remains unchanged. The infrared spectroscopy correlation table, typical vibrational fre ...
al level. ISC is forbidden by rules of conservation of
angular momentum Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity – the total ang ...
. As a consequence, ISC generally occurs on very long time scales. However, the El-Sayed rule states that the rate of intersystem crossing, e.g. from the lowest
singlet state In quantum mechanics, a singlet state usually refers to a system in which all electrons are paired. The term 'singlet' originally meant a linked set of particles whose net angular momentum is zero, that is, whose overall spin quantum number s=0. A ...
to the triplet manifold, is relatively large if the radiationless transition involves a change of
molecular orbital In chemistry, a molecular orbital is a mathematical function describing the location and wave-like behavior of an electron in a molecule. This function can be used to calculate chemical and physical properties such as the probability of finding ...
type. For example, a (π,π*) singlet could transition to a (n,π*)
triplet state In quantum mechanics, a triplet state, or spin triplet, is the quantum state of an object such as an electron, atom, or molecule, having a quantum spin ''S'' = 1. It has three allowed values of the spin's projection along a given axis ''m''S = � ...
, but not to a (π,π*) triplet state and vice versa. Formulated by El-Sayed in the 1960s, this rule found in most
photochemistry Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 Nanometre, nm), visible ligh ...
textbooks as well as the
IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
Gold Book The International Union of Pure and Applied Chemistry (IUPAC) publishes many books which contain its complete list of definitions. The definitions are divided initially into seven IUPAC Colour Books: Gold, Green, Blue, Purple, Orange, White, and R ...
. The rule is useful in understanding
phosphorescence Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance will glow, absorbing the light and reemitting it at a longer wavelength. Unlike fluor ...
, vibrational relaxation,
intersystem crossing Intersystem crossing (ISC) is an isoenergetic radiationless process involving a transition between the two electronic states with different spin multiplicity. Excited singlet and triplet states When an electron in a molecule with a singlet grou ...
,
internal conversion Internal conversion is an atomic decay process where an excited nucleus interacts electromagnetically with one of the orbital electrons of an atom. This causes the electron to be emitted (ejected) from the atom. Thus, in internal conversion (o ...
and lifetimes of excited states in molecules.


Notes


References

* El-Sayed, M.A., Acc. Chem. Res. 1968,1,8. * Lower, S.K.; El-Sayed, M.A., Chem. Rev. 1966,66,199 * Mostafa Amr El-Sayed (8 May 1933 – Egyptian-American, b. Zifta, Egypt) * Biographical References: McMurray, Emily J. (ed.), Notable Twientieth-Century Scientists, Gale Research, Inc.: New York, 1995.


External links


Faculty web page at Georgia Tech

Laser Dynamics Lab
at Georgia Tech

* ttps://web.archive.org/web/20110525080621/http://www.us4arabs.com/content/view/952/31 Mostafa El-Sayed praised for contributions to nanotechnology {{DEFAULTSORT:Sayed, Mostafa Biochemists Egyptian chemists Egyptian Muslims American Muslims Egyptian inventors Egyptian emigrants to the United States Harvard University staff Members of the United States National Academy of Sciences Florida State University alumni Georgia Tech faculty Living people 1933 births National Medal of Science laureates Ain Shams University alumni American physical chemists Fellows of the American Physical Society Arab chemists