Sponsored by the ACS Division of Colloid & Surface Chemistry
When Kenneth B. Eisenthal looks at satellite images of planet Earth, instead of just admiring the greens and blues, he sees surfaces where chemical reactions occur. More than two-thirds of Earth’s surface, after all, is covered by ocean—a vast air-water interface. Much of the rest is covered with plants whose cell surfaces host molecular interactions crucial to life.
Eisenthal, the Mark Hyman Professor of Chemistry at Columbia University, has made a career of studying the orientation and dynamics of molecules at these interfaces. And he is one of a handful of pioneers to develop nonlinear optical techniques that scientists now use routinely to explore these phenomena. He takes home this year’s award for these contributions to the advancement of surface science.
In the 1980s, when Eisenthal first began applying nonlinear optical techniques to surfaces, only one other scientist—Yuen-Ron Shen of the University of California, Berkeley—was doing the same. “I heard him give a talk at a meeting,” Eisenthal recalls. “He had measured the orientation of molecules on a silica surface.” Filled with excitement, Eisenthal rushed back to his lab at Columbia to confirm that nonlinear optical methods worked for liquid surfaces too.
Fast-forward to today, and scads of scientists are applying nonlinear optical techniques to a multitude of interfaces, publishing thousands of papers per year, says Franz M. Geiger, a physical chemist at Northwestern University. “Ken’s ability to inspire new generations of scientists is an important reason why the field is now more productive and thriving than ever,” Geiger says.
Without Eisenthal, scientists might not have realized that nonlinear optical techniques such as second harmonic generation (SHG) and sum frequency generation (SFG) could probe the orientation and dynamics of molecules on the surfaces of particles. Prior to the mid-1990s, researchers believed that these methods worked only on flat, asymmetric surfaces and assumed that spherical particles weren’t capable of producing SHG or SFG optical signals. Eisenthal, though, captured SHG signals from polystyrene microparticles coated in an organic dye in 1996 (Chem. Phys. Lett., DOI: 10.1016/0009-2614(96)00707-5).
“With Ken’s invention, it became possible to use nonlinear optics to look at molecular adsorption on colloids” and cell surfaces, says Dana D. Dlott, a chemist at the University of Illinois, Urbana-Champaign.
Eisenthal also realized that charged molecules at water-based interfaces could be coaxed to produce an enhanced SHG signal, a technique he’s since used to measure acid-base equilibria at interfaces (Chem. Phys. Lett. 1993, DOI: 10.1016/0009-2614(93)90082-c) and even electric signals traveling through nerve cells. Many in the field now call this phenomenon the “Eisenthal χ(3) method.”
Although he entered New York’s Brooklyn College in 1950 as a premed student, Eisenthal fell in love with hard science and graduated in 1954 with a bachelor’s degree in chemistry. He obtained a master’s degree in physics in 1957 and a Ph.D. in chemical physics in 1959, both from Harvard University. After brief stints working at Aerospace Corp., in El Segundo, Calif., and IBM Research Laboratory, in San Jose, Calif., he joined the faculty at Columbia in 1975.
“I’ve just followed what I love to do,” Eisenthal says of his success. “And I’ve been lucky enough to get away with it.”
Eisenthal will present the award address before the Division of Colloid & Surface Chemistry.