Explaining the Colorful Quantum Discoveries That Earned the Nobel Prize in Chemistry

Moungi Bawendi, Louis Brus and Alexei Ekimov won the award for their work developing tiny “quantum dots” that light TV displays and enable medical imaging

the winners of the chemistry nobel prize, Moungi Bawendi, Louis Brus and Alexei Ekimov, appear on a tv screen with five vials of glowing colors in front
The winners of the 2023 Nobel Prize in Chemistry are displayed on a screen at the Royal Swedish Academy of Sciences in Stockholm during the award announcement on October 4. At the front are five vials filled with glowing quantum dots. JONATHAN NACKSTRAND / AFP via Getty Images

The Nobel Prize in Chemistry was awarded today to a trio of scientists whose work helped bring tiny particles called “quantum dots” into wide use—now, these colorful, glowing specks illuminate TV screens, and one day, they might enable more efficient solar panels.

Working separately, the laureates Alexei Ekimov, Louis Brus and Moungi Bawendi each made pivotal discoveries about these tiny nanoparticles—pieces of matter that measure between 1 and 100 billionths of a meter—and the way they emit light.

“These achievements represent an important milestone in nanotechnology, and today there are numerous applications of quantum dots, ranging from QLED screens to imaging in biochemistry and medicine,” Johan Åqvist, chair of the Nobel committee for chemistry, said during the award announcement.

A quantum dot is a tiny crystal made of just a few thousand atoms. Packed into a small space only a handful of nanometers long, the atoms’ electrons get squeezed together, resulting in changes to the material’s properties, such as its color or melting point. For context: The size difference between a quantum dot and a soccer ball is roughly equal to the difference between a soccer ball and planet Earth.

Importantly, the dots absorb light that hits them, then re-emit that light in a specific color based on their size. Smaller quantum dots glow in blue, while the larger ones emit more red or orange light—even if they are made of exactly the same material.

five vials with glowing matter inside. from left to right: red, orange, green, and two shades of blue
The vials filled with matter glowing red and orange have quantum dots of larger sizes, while those emitting green and blue light contain smaller quantum dots. JONATHAN NACKSTRAND / AFP via Getty Images

The theory that quantum dots could exist dates back to the 1930s. But for the next 50 years, actually producing these objects seemed impossible to scientists.

In the early 1980s, however, Ekimov proved it could be done. He showed how changing the size of tiny nanoparticles of copper chloride suspended in glass affected the color of the glass. Brus repeated this effect a few years later, demonstrating the same change in color with quantum dots of cadmium sulfide, floating freely in a fluid instead of in glass.

Though it was impressive the scientists had achieved this, quantum dots were still not ready for practical use. In 1993, Bawendi fine-tuned the production of these miniscule particles so they could be a “very specific size and very high quality,” as Åqvist said at the announcement.

“The theoretical frameworks provided by Brus and Ekimov were made into a reality with Bawendi’s seminal paper in 1993, from which this now mature science sprung,” says Mark Green, a physicist at King’s College London, to Nature News’ Katharine Sanderson and Davide Castelvecchi. “It’s an amazing result for the quantum dot community.”

Quantum dots are already used in TV displays and LED lights—the dots, manufactured in a powder form, are backlit by blue light in some television screens, leading them to glow in various colors according to their size, writes CNN’s Christian Edwards, Katie Hunt and Ed Upright. In medicine, doctors use them in probes that illuminate cancerous tumors.

In the future, quantum dots could even contribute to solar panels that are up to twice as efficient as those we have today.

“This isn’t just esoteric science,” Judith Giordan, president of the American Chemical Society, tells the New York Times’ Emma Bubola and Katrina Miller. “This is meant to help people.”

The prize announcement came after an unexpected mishap—early Wednesday morning, details about the winners were leaked from the Royal Swedish Academy of Sciences, which awards the physics and chemistry Nobel prizes. Swedish media published an email from the academy with the names of the recognized chemists about four hours before the public unveiling of the winners took place.

Åqvist told Reuters that the email had been a “mistake,” and at that time, “the winners [had] not been selected.” However, when the official announcement was made, the honorees matched those in the leaked message.

The laureates, for their part, did not know about the controversy as it happened, because it occurred so early in the morning. Bawendi learned of his award in a phone call from the committee, then went on to teach a 9 a.m. class at MIT. Ekimov was reached by the committee while on a trip to Mexico, writes the Guardian’s Hannah Devlin. Brus could not be contacted until after the official announcement, but he later said “it’s a great honor, and it’s recognition for the field.”

On Monday, Katalin Karikó and Drew Weissman won the Nobel Prize in Physiology or Medicine for their past work with mRNA that enabled the development of life-saving Covid-19 vaccines. Tuesday, the Nobel Prize in Physics went to Pierre Agostini, Ferenc Krausz and Anne L’Huillier, who created and refined a way to produce ultra-fast pulses of light that can illuminate the tiny and rapid movements of electrons.

With the chemistry award announced, the Nobel Prizes are halfway through—the literature prize will be awarded Thursday, followed by the peace prize on Friday and economics on Monday.

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