2021 Priestley Medalist A. Paul Alivisatos helped introduce the world to the nanocrystal. Photo Gabriela Hasbun for C&EN.
Some scientists make discoveries that trigger a tidal wave of research. Some inspire so many others to join their scientific endeavor that a new field of research is born. But few people do the kind of extreme-impact work that helps morph a scientific term into everyday language.
That’s what A. Paul Alivisatos (Ph.D. '86, Chem) of the University of California, Berkeley, has done—and the term, actually a prefix, is nano.
Priestley Medal address 2021: The growth of the nanocrystal--a little coming-of-age story
Nanotechnology, nanoscience, nano this, and nano that. Twenty-five years ago, the word hardly appeared in everyday use. Almost overnight, nano words began appearing throughout mainstream media and popular culture.
Nanoscience skyrocketed because of the efforts of many people—physicists, biologists, engineers, and others. But Alivisatos, a chemist, is credited with developing the now-widely-used solution-phase colloidal chemistry methods for synthesizing and precisely controlling the fundamental components—the nanocrystals—that underpin much of nanotechnology. Today, nanotechnology’s applications appear in medical diagnostics, electronic displays, and solar panels.
At UC Berkeley, Alivisatos, 61, is the Samsung Distinguished Professor of Nanoscience and Nanotechnology, the executive vice chancellor and provost, and a professor of chemistry and materials science and engineering. He is also director emeritus of Lawrence Berkeley National Laboratory, the founding editor in chief of Nano Letters, and the next president of the University of Chicago, a position he will assume Sept 1. Both Nano Letters and C&EN are published by the American Chemical Society.
For “foundational contributions to the chemistry of nanoscience, development of nanocrystals as nanotechnology building blocks and leadership in the chemistry and nanoscience communities,” ACS has bestowed its highest honor upon Alivisatos, naming him the 2021 Priestley Medalist. Read his Priestly Medal address here.
“Paul demonstrated that nanocrystals are a new class of macromolecule that can be grown with precision and complexity, modified through well-defined chemical principles and mechanisms, and assembled into functional materials,” says Georgia Institute of Technology’s Mostafa A. El-Sayed, a physical chemist. He adds that Alivisatos’s publications have led to “fundamental understanding and chemical tools that are used by thousands of researchers and by companies worldwide.” Alivisatos’s discoveries benefit human health, improve electronic technology, and promote energy efficiency, he says.
A. Paul Alivisatos and coworkers developed microscopy methods for probing nanocrystal nucleation (yellow cubes) by trapping droplets of solution in nanosized graphene blisters. Credit: Alivisatos, Lee, and Zettl Research Groups/LBNL and KAIST.
Outside the lab, Alivisatos has also served as a prominent leader and representative of the scientific community. “Paul has been a national and global advocate for science that addresses the greatest challenges faced by humanity and for education that is accessible to all, regardless of income or background or national or ethnic origin,” says Geraldine Richmond, a chemistry professor at the University of Oregon.
She adds that “it is altogether rare for an actively practicing scientist of such continued high accomplishment to also be involved at this level of impact in the service of the science community and humanity.”
Alivisatos’s name is synonymous with nanocrystals, especially the large family of semiconductor nanomaterials, which includes zinc sulfide, cadmium selenide, various tellurides, and others. Since the early 1990s, he and his coworkers have been studying the chemistry, physics, and biology of these materials—determining how to make them, customize their properties, and use them in disparate applications.
For example, Alivisatos and colleagues demonstrated that semiconductor nanocrystals, also known as quantum dots, could be used as highly fluorescent probes for monitoring drug uptake and metabolism and for other types of medical diagnostics. They also showed that the tiny bits of matter shine brightly when used in light-emitting diodes, and they harvest sunlight efficiently in low-cost solar cells.
These advances weren’t just academic feats. Alivisatos and coworkers started Quantum Dot Corporation to make the materials available for probing DNA, analyzing tumors, and other applications. Now a brand under Fisher Scientific, Quantum Dot provides nanocrystal products worldwide to biomedical research groups and hospital pathology labs. These kinds of nanocrystals are also used commercially in a seemingly unrelated business area—high-end electronic displays and quantum dot televisions.
Growing up in Chicago
Although nano enthusiasts can look at Alivisatos’s scientific track record and tick off a slew of important breakthroughs, the path that his childhood took featured some major challenges and setbacks.
As a young boy, Alivisatos was an inquisitive student and curious about science. But family tragedy upended his happy-go-lucky home life and left him transplanted in a foreign country where people spoke a language he did not know. The chaotic experience could have turned him away from school, but it didn’t. He eventually made his way back to the US—starting in the Midwest and then moving from one coast to the other as he advanced his scientific career and progressed through some of the finest US academic institutions and centers of research and discovery.
Alivisatos’s story begins in the 1960s on the north side of Chicago, not far from Northwestern University. The time and setting were ideal for capturing young people’s imagination with the boundless possibilities of space exploration.
“I remember vividly being greatly enamored by the Apollo space program,” Alivisatos says. As a second grader, his enthusiasm was pushed into high gear when a Northwestern student, “an impossibly tall young man,” visited Alivisatos’s class and talked to the students about the solar system and space travel. “I just loved all that stuff,” Alivisatos recalls with a wide smile.
He also remembers being fascinated with the Time Life series of books his parents gave him about the solar system, planets, galaxies, and stars. “I built models of all the rockets and lunar landers and hung them up in my room,” he says with a warm laugh, proudly reflecting on these long-ago accomplishments.
And like many future chemists of his era, Alivisatos experimented with a chemistry set as a kid. He also built a radio from a kit and remembers tinkering with other electronics, assembling circuits that lit up or sounded an alarm.
Suddenly moving overseas
Alivisatos sits near the Parthenon in Athens, Greece, at age 11. (Photo couresty A. Paul Alivisatos)
Then tragedy struck the Chicago family, and the young boy’s experiences took a sudden turn. “My life changed dramatically at age 10, when my mother died from a brain tumor,” Alivisatos says. As he explains, his father didn’t have the wherewithal to raise children alone. So he sent Alivisatos and his 14-year-old sister to Greece, from which his father had emigrated, to live in boarding schools—one for boys, and one for girls. Alivisatos remained in Greece until age 17.
“I didn’t speak a word of Greek when I went over there,” Alivisatos says. People were nice to him, but the new life that was thrust upon him presented numerous challenges. To begin with, the language in which the students conversed—a common spoken form of Greek—differed from the formal version in textbooks and classroom instruction; he understood neither version at first. Furthermore, schools there were a little more advanced in terms of content than ones in the US, Alivisatos says. So he constantly felt that he was falling behind his peers in class.
“So there I was, already behind in school, regardless of the language issue. Then on top of that, I had to deal with a different language and a different culture, and my family life was completely disrupted.”
Alivisatos pauses. Then with an easygoing laugh that makes it seem as though he’s talking about the life of a character in an interesting novel—not his own life—he adds, “I was pretty well out of commission in terms of academics, and it was not going to be easy to do well in school.”
It took a while to learn the language and acclimate to his new surroundings. “My challenge was with myself. I knew I wasn’t going to be the best student in the class. That wasn’t an option.” Yet he was resilient, and the experience taught him to become independent. Alivisatos says he eventually caught up.
Another factor that complicated his new life in Greece was the country’s political turmoil. By the time he was a teenager, demonstrators protested regularly against the right-wing military dictatorship that ran Greece. Alivisatos says he and his classmates used to climb over the walls of the boarding school to get an up-close view of the demonstrations, which the military endeavored to quash violently. Eventually, after much bloodshed, the dictatorship fell in 1974, when Alivisatos was 14. “It was a period of enormous tumult,” he recalls.
Returning to the U.S.
Working against the odds, Alivisatos managed to do well in school in Greece. But he longed to return to the US, and he did so for his final year of high school. It was then that his math teacher advised him to apply to the University of Chicago.
But the path leading him to nanoscience had one more challenge for him to overcome. “My family, especially my father, really wanted me to become a doctor,” Alivisatos says. The elder Alivisatos had studied medicine in Athens and wanted his children to stay in Greece and do the same. He was a professor at the Chicago Medical School, where he taught biochemistry and physiology. (Paul’s sister, Regina Alivisatos, is a medical doctor.)
“I spent a lot of my youth trying to escape becoming a physician,” Alivisatos says, laughing. In bargaining with his father to be allowed to attend UChicago, Alivisatos agreed to return to Greece first and take the entrance exam for medical school. He sat for the exam and passed, but he returned to the US anyway and thrived at UChicago, where he became a chemistry major and fell in love with physical chemistry.
Alivisatos says one experiment in particular sparked his interest and convinced him that this type of chemistry is what he wanted to pursue. The experiment involved growing a tiny metal wire from vapor-phase metal atoms. The neat thing about the process is that the metal atoms can land anywhere on the growing wire, Alivisatos explains, but they diffuse to the tip, making the wire longer and longer. “I thought it was so cool that you could infer this level of detail from a lab experiment. That was like wow!” Alivisatos says he really enjoyed physical chemistry but acknowledges he wasn’t the top student in the class. “What matters more than how well you perform on an exam is what captures your imagination. I found what I really liked,” he says.
Enter the nanocrystal
Alivisatos in the 1980s at Berkeley. (Photo courtesy A. Paul Alivisatos)
From UChicago, Alivisatos made his way to UC Berkeley, an institution with a long history of excellence in physical chemistry. While working on a PhD, he began thinking about nanosized chunks of matter.
His thesis work involved understanding how energy is transferred from molecules, which are composed of relatively few atoms, to solids, which have essentially an infinite number of atoms. The phenomenon was difficult to analyze because the language scientists used for describing molecules was quite different from that for solids, making the physical chemistry of the two hard to reconcile. That challenge led Alivisatos to wonder about the properties of entities that lie between tiny molecules and enormous solids—nanosized flecks of material, or nanocrystals.
He pursued the study of nanosized matter as a postdoctoral researcher at Bell Labs in New Jersey, working with Louis Brus, now of Columbia University. Alivisatos explored electronic, optical, and other properties of semiconductor nanocrystals and began developing methods for synthesizing and functionalizing them.
After 2 years at Bell Labs, Alivisatos accepted a faculty position in UC Berkeley’s Chemistry and Materials Science and Engineering Departments. He wanted to start a research group to continue investigating the fundamental properties of nanocrystals and ways to use them in applications. Alivisatos says the topic was so obscure at that time—around 1990—that people stared blankly when he described his work, and at first, he had difficulty securing research funding. But things soon began to change—the topic sparked people’s interest, and Alivisatos built a research program that led him and his team to many discoveries of nanosized materials. For example, they discovered the size-dependent nature of nanocrystals’ melting temperatures, an unexpected quantum effect. They also showed that nanocrystals can reversibly undergo structural transformations with large volume changes without fracturing, a property that researchers are now studying for application in lithium-ion batteries. And the team also developed high-resolution microscopy methods for tracking the growth of nanocrystals by confining droplets of precursors in graphene bubbles.
A. Paul Alivisatos received the National Medal of Science at a ceremony in 2016. From left: his daughter Stephanie; his wife, Nicole; President Barack Obama; Alivisatos; and his daughter Clara.
Mentor and leader
While uncovering new insights in nanocrystals, Alivisatos also assembled a research group of talented scientists who looked up to him and learned from his approach to research and laboratory management.
“He is so easy to get along with,” says Harvard University’s Hongkun Park, who was a postdoc with Alivisatos from 1996 to 1999. “He was an ideal adviser for me, always supportive and patient and gave me the freedom to explore things that interested me.” Park says in terms of the way he interacts with his own students, “I try to emulate Paul.”
Jennifer Dionne of Stanford University worked with Alivisatos as a postdoc from 2009 to 2010. She remembers her mentor as “thoughtful, creative, and very accessible to his students.” She, too, tries to follow his example in running a group and conducting research. She says she learned from Alivisatos to “aim high,” meaning pursue high-risk, high-reward science. She also learned from Alivisatos to “leave no stone unturned,” because following up on unexpected results can lead to the most important discoveries.
The attribute of Alivisatos that impresses Vida Jamali the most is his “incredible time management.” Since 2017, Jamali has been a postdoc in the Alivisatos group. Even though Alivisatos is the university provost and incredibly busy, she says, he meets with his group members several times a week.
Working with Alivisatos has been a wonderful learning experience, she says. “He teaches you how to pose a question that is fundamentally important yet technologically relevant. I hope to do the same when I run a research group.”
Forty years after leaving UChicago, Alivisatos is heading back to his alma mater. At the end of February, UChicago announced that Alivisatos would be the university’s next president, a role he will assume in September.
Some scientists at Alivisatos’s level might find large management jobs, like running a university or national lab, distracting, leaving no time for research. Not Alivisatos. “I find these kinds of jobs deeply satisfying,” he says. Each interaction with bright, innovative people “infuses me with new energy and creativity. It’s not a distraction. It has made me a better scientist.”
Asked whether he plans to set up a lab and continue doing research in his new location, Alivisatos answers without hesitation. “Absolutely. For me, doing research is not a job. It’s who I am. It’s part of my life.”