A screen shows Moungi Bawendi, Louis Brus and Alexei Ekimov during announcement of the 2023 Nobel Prize in chemistry.

The formal announcement of the winners followed a leak earlier in the day.Credit: Jonathan Nackstrand/AFP via Getty

Three chemists who predicted and were first to make quantum dots — nanoscale crystals that interact with light in unusual ways — have been awarded the Nobel Prize in Chemistry.

Moungi Bawendi at the Massachusetts Institute of Technology in Cambridge, Louis Brus at Columbia University in New York City and Alexei Ekimov at New York City-based company Nanocrystals Technology will each receive one-third of the 11-million-Swedish-krona (US$1-million) prize.

“It’s an amazing result for the quantum-dot community,” says Mark Green, a physicist at King’s College London. “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.”

Quantum dots are semiconductor crystals consisting of just a few thousand atoms, which have some properties of single atoms. This allows them to be tuned so they can emit specific wavelengths of light. Very small quantum dots of cadmium selenide, for example, can emit blue light, but bigger crystals of the same compound emit red light. Quantum dots are used in applications that need specific wavelengths of light, from bright television displays to biological imaging.

The names of the winners were leaked a few hours before the official announcement, when a press release was accidentally emailed to Swedish media. At a press conference after the announcement, Bawendi said that he had been “sound asleep”, and therefore unaware of the leak. He was woken by a call from the Nobel committee, and felt “very surprised, sleepy, shocked” and “very honoured” to learn that he had won the prize. “I didn’t think it would be me that would get this prize, because we’re all working together on this,” he said. “There’s still a lot of exciting work to be done in this field.”

Joining the dots

Ekimov was first to report observing size-dependent light effects, in coloured glass doped with copper chloride particles, in 19811. The following year, Brus described making quantum dots in a solution, while looking at semiconducting particles for solar-energy applications2. “It was Brus who made the link between semiconductors and particle size,” says Green. But “it would have remained a relatively inaccessible and poorly developed materials system until Bawendi developed the chemistry”.

Bawendi discovered a way to make quantum dots in specific sizes, combining inorganic and organometallic techniques for precise control3. The method involved injecting the chemical ingredients into a hot solvent until it became saturated, causing crystals to form suddenly. When the mixture was removed from the heat, the growth of the crystals slowed down. The resulting dots were all of the same size and quality.

Laboratory flasks in a darkened room, the contents glowing red, orange, green and two shades of blue.

The Nobel committee demonstrated the optical properties of quantum dots using flasks containing particles of various sizes under ultraviolet light.Credit: Jonathan Nackstrand/AFP via Getty

“If you want every atom to count and to be able to do it in a scalable manner, then a chemist’s approach is a very valuable one,” says Christopher Murray, a chemist at the University of Pennsylvania in Philadelphia who was a PhD student working with Bawendi at the time and is a co-author of the 1993 paper. He says he was really happy to hear the news, having woken up oblivious to the controversy over the leak.

He explains that the quantum effects that give the particles their name come from how electrons and their quantum energy levels change when particles get smaller and smaller. As quantum dots reach the nanoscale, the electrons start to be confined by the size of their surroundings. Once that size becomes smaller than the natural volume that an electron can move around in, the electrons respond by changing their energy levels. This in turn changes how those systems interact with light.

Nanotech milestone

“For a long time, nobody thought you could ever actually make such small particles. But this year’s laureates succeeded,” said Johan Åqvist, chair of the Nobel committee for chemistry at the Royal Swedish Academy of Sciences in Stockholm, during the announcement. “This achievement represents an important milestone in nanotechnology.”

Quantum dots have now made it into the mainstream, and are used in television displays in a multimillion-dollar industry. When he and Bawendi started their work, Murray says, there was scepticism around whether it was worth funding efforts to control materials on such a small level using chemistry. “It’s nice to see a significant return on that investment,” he says.

Now that producing quantum dots has become a fairly straightforward chemical process, they can find more applications, Murray says. Being able to tune how a particle interacts with light could help engineers to develop low-cost optical detectors and sensors — an important component of autonomous transport, for example. It is also possible to integrate quantum dots into materials with unique shapes, textures and densities.

A similar concept has been adopted as a platform for quantum computing, which aims to harness quantum phenomena to perform calculations that would be impossible with an ordinary computer. Researchers can fabricate devices with the properties of quantum dots on a silicon chip, and then manipulate the spin of individual electrons trapped in them. “Both types of quantum dots are small, and confinement of electrons in the quantum dots leads to quantized orbitals, like in atoms,” says Lieven Vandersypen, a physicist at Delft University of Technology in the Netherlands.

‘Nationality does not matter’

In late August, the Nobel Foundation announced that it would be inviting ambassadors from Russia and Belarus to the Nobel prize award ceremony in December. Days later, it reversed the decision, following an angry public reaction. When asked whether Russian-born Ekimov will be able to accept his award in person, Hans Ellegren, secretary-general of the Royal Swedish Academy of Sciences, told the press conference that when it comes to selecting for the Nobel prize, “we simply follow the procedure of identifying the most important discoveries. Having done that, we identify the most important contributors to those findings.”

“That means nationality does not matter here.”