Nobel Prize in Chemistry 2023: Discovery and Synthesis of Quantum Dots

This note covers the Nobel Prize in Chemistry 2023: who won it, what quantum dots are, how three scientists discovered and learned to make these light-emitting nanoparticles, how the work developed over four decades, why it matters for screens, lamps and medicine, and quick facts for exams.

What was the Nobel Prize in Chemistry 2023 awarded for?

The official citation reads: "for the discovery and synthesis of quantum dots". In plain words, the three laureates found a brand new way that very tiny particles behave, and then worked out how to build those particles reliably in a laboratory.

A quantum dot is a crystal so small, usually just a few nanometres across, that it is made of only a few thousand atoms.

At this size, ordinary chemistry rules bend: the particle's colour and other properties change simply because of its size, not because its chemical formula changes.

A big crystal of a substance and a tiny quantum dot of the exact same substance can glow in completely different colours.

The prize is formally called the Nobel Prize in Chemistry, awarded by the Royal Swedish Academy of Sciences. The 2023 prize was announced on 4 October 2023, with a total prize amount of 11,000,000 Swedish kronor shared equally among the three winners.

Who are the laureates?

Moungi Bawendi

Moungi G. Bawendi was born in 1961 in Paris, France. At the time of the award he was a professor at the Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. He received one third of the prize.

In 1993, Bawendi revolutionised the chemical production of quantum dots, developing a method that produced almost perfect particles with smooth, even surfaces and a well-defined size. This quality was essential before quantum dots could be used in any real-world application.

Louis Brus

Louis E. Brus was born in 1943 in Cleveland, OH, USA, and died on 11 January 2026 in New York, NY, USA. At the time of the award he was affiliated with Columbia University, New York, NY, USA. He received one third of the prize.

In 1983, while working at Bell Laboratories, Brus was the first scientist to show that quantum effects depend on size in particles floating freely in a liquid (a solution), rather than trapped inside a solid block of glass.

Aleksey Yekimov

Aleksey Yekimov was born in 1945 in Leningrad, USSR (now St. Petersburg, Russia). At the time of the award he was affiliated with Nanocrystals Technology Inc., New York, NY, USA, as its former Chief Scientist. He received one third of the prize.

In the early 1980s, Yekimov managed to create quantum effects that depended on particle size in coloured glass, using nanoparticles of copper chloride, and showed that their size affected the colour of the glass through quantum effects.

What problem were the laureates trying to solve?

Every student of chemistry learns that an element's properties, such as its colour or how it reacts, are governed mainly by how many electrons it has. This is the logic behind the periodic table.

But physicists had long suspected something extra: that if you made matter small enough, down to nanometre dimensions, a different set of rules, called quantum effects, would start to govern its properties, purely because of its size.

The theoretical seed for this idea goes back to 1937, when physicist Herbert Fröhlich explored what the Schrödinger equation predicts for very small particles. When a particle shrinks, there is less room for its electrons, and squeezing electrons together in this way should change the material's behaviour drastically.

For decades this stayed a purely theoretical prediction. Researchers could do the maths, but they could not actually sculpt matter at such a tiny scale, with the right crystal structure and clean surfaces, to test the idea.

Even a successful experiment in the 1970s, using molecular-beam methods to make ultra-thin coated layers, needed an extremely strong vacuum and temperatures near absolute zero, far too demanding for everyday use.

The real breakthrough came from an unexpected direction: an ancient craft, the making of coloured glass.

How did Yekimov and Brus discover quantum dots?

Colour in glass that puzzled chemists

Glassmakers had known for thousands of years that adding substances such as gold, silver or cadmium compounds could colour glass.

Oddly, the same substance could produce different colours depending on how the glass was heated and cooled, something that made no obvious chemical sense, since a pure pigment should always give the same colour.

Aleksey Yekimov, working at the S.I. Vavilov State Optical Institute in the then Soviet Union, investigated this puzzle using optical methods borrowed from semiconductor physics.

He systematically heated glass containing copper chloride at temperatures between 500°C and 700°C for times from 1 to 96 hours, then examined it.

He found that tiny crystals of copper chloride, ranging from about 2 to 30 nanometres, had formed inside the glass, and crucially, the colour of light absorbed by the glass shifted depending on the crystal size: smaller crystals absorbed bluer light.

Yekimov correctly attributed this to a size-dependent quantum effect, publishing his finding in a Soviet journal in 1981.

Confirming the effect in free particles

Louis Brus, at Bell Laboratories in the USA, was unaware of Yekimov's work, which was hard to access across the Iron Curtain. Brus was experimenting with cadmium sulphide particles in solution, aiming to use light to drive chemical reactions.

He noticed the particles' optical properties changed after sitting on the lab bench, because they had slowly grown larger.

To test this, in 1983 Brus compared freshly made particles of about 4.5 nanometres with older, larger particles of about 12.5 nanometres. The larger particles behaved like ordinary bulk cadmium sulphide, but the smaller ones absorbed light shifted towards blue.

Brus had become the first researcher to prove the quantum size effect in particles floating freely in a fluid, rather than locked inside solid glass.

1. Prepare cadmium sulphide particles in a solution, kept small using a copolymer to stop them clumping together.
2. Measure a freshly made, small batch (about 4.5 nanometres) using absorption and Raman scattering.
3. Let a separate batch age so the particles grow larger (to about 12.5 nanometres).
4. Compare the light absorbed by the small and large particles.
5. Observe that smaller particles absorb more blue-shifted light, confirming a size-dependent quantum effect.

Draw two boxes of particles of the same substance, one with large crystals and one with small crystals.

Show the large crystal emitting red-tinted light and the small crystal emitting blue-tinted light, with an arrow labelled "particle size decreases" pointing from the red box to the blue box.

Why does particle size change the colour?

The explanation lies in how electrons behave when confined. An electron, like light, behaves partly as a wave.

When it sits inside a large material, its wave has plenty of room and can take on a wide range of energy states, close together.

When the same electron is confined inside a tiny crystal, barely a few nanometres across, its wave gets squeezed, and the allowed energy states become more spread apart and size-dependent.

This effect can be pictured as a "particle in a box": the smaller the box, the more widely spaced the electron's allowed energy levels.

In a quantum dot, this means the energy gap between the material's lowest empty and highest filled electron states grows larger as the dot shrinks.

Since the colour of light absorbed or emitted depends directly on this energy gap, smaller dots absorb and emit bluer light, while larger dots absorb and emit redder light.

This is a big conceptual shift. A chemist choosing a new material usually thinks about which atoms to combine and in what structure.

Quantum dots added a completely new knob to turn: size itself, without changing the chemical formula at all.

The same semiconductor, say cadmium selenide, can be tuned across almost the whole visible light spectrum just by growing the crystal bigger or smaller.

How did Bawendi make quantum dots good enough to use?

Discovering the quantum effect was one thing; manufacturing quantum dots of consistent, reliable quality was another problem entirely.

The particles Brus and others could make in the 1980s were of unpredictable quality: different sizes mixed together, and often containing defects, which blurred their useful optical properties. Sorting particles by size after making them was slow and difficult.

Moungi Bawendi, who began postdoctoral work in Brus's laboratory in 1988, took on this challenge. After moving to MIT as a research leader, his breakthrough came in 1993.

1. Heat a carefully chosen solvent to a high temperature.
2. Rapidly inject the chemical precursors needed to form the nanocrystals.
3. Let tiny crystal "embryos" form simultaneously as the solution becomes supersaturated.
4. Dynamically vary the solution's temperature to control how the crystals grow to a chosen size.
5. Allow the solvent to help smooth and even out the growing crystal's surface.

This approach, known as hot injection synthesis, produced batches of quantum dots that were almost all the same size and nearly free of defects. Because the method was relatively easy to reproduce, it quickly spread through chemistry labs worldwide, and more researchers began exploring applications of quantum dots.

Draw a flask of hot solvent with an arrow showing precursor chemicals being injected in, followed by a row of small dots growing bigger over time as temperature is adjusted, ending in a set of evenly-sized crystals.

How did the discovery unfold?

Why does this discovery matter?

Quantum dots are now, as the Nobel Committee for Chemistry noted, of great importance to nanotechnology. Johan Åqvist, Chair of the Nobel Committee for Chemistry, said: "Quantum dots have many fascinating and unusual properties. Importantly, they have different colours depending on their size."

Today quantum dots light up QLED television and computer screens, where "Q" stands for quantum dot: blue light from energy-efficient diodes is converted by quantum dots into red and green to create the three primary colours a screen needs.

They also fine-tune the light from some LED lamps, making it warmer or cooler as desired.

In medicine and biology, quantum dots can be attached to biomolecules to map cells and tissue, and doctors have begun exploring their use to help surgeons see and remove tumour tissue. Chemists also use quantum dots' catalytic properties to drive chemical reactions.

Looking ahead, the Nobel committee's press release stated that researchers believe quantum dots could in future contribute to bendable electronics, miniature sensors, slimmer solar cells and secure quantum communication, adding that exploration of their potential has only just begun.

How does this connect to what you study?

Quantum dots build directly on ideas met in school chemistry and physics: the periodic table and electron configuration, and the basic quantum mechanics idea that electrons behave as both particles and waves.

The "particle in a box" model used to explain quantum dots is a simplified version of the same wave mechanics that explains why atoms have discrete energy levels and why elements absorb and emit light at specific colours.

Seeing how size alone can change a material's colour is a vivid, concrete example of quantum theory having real, everyday consequences, from the screen you may be reading this on to lamps in your home.

The idea that a substance's electrons govern its colour, its ability to conduct electricity, and its ability to catalyse chemical reactions connects to several strands of a school chemistry course at once. A student who has learned that elements differ because of how many electrons they have can extend that idea to see how, at nanometre scale, the sheer size of a crystal becomes a second variable alongside composition.

This also links to practical physics topics such as light, colour and the electromagnetic spectrum: the wavelength of light absorbed or emitted by a quantum dot shifts systematically as its size changes, giving a concrete numerical example of how energy and wavelength are related.

Students interested in materials science or nanotechnology as a future field of study can see, in this prize, how a fairly simple laboratory technique, heating a solvent and injecting chemicals, can translate a theoretical prediction from 1937 into a technology found in millions of television screens today.

Quick facts for exams

The Nobel Prize in Chemistry 2023 was awarded jointly to Moungi G. Bawendi, Louis E. Brus and Aleksey Yekimov for the discovery and synthesis of quantum dots, announced on 4 October 2023 by the Royal Swedish Academy of Sciences.

Quantum dots are nanometre-sized crystals whose colour and other properties depend on their size because of quantum effects, not on their chemical formula alone.

Yekimov first observed the effect in coloured glass in the early 1980s, Brus confirmed it in free-floating solution particles in 1983, and Bawendi developed a reliable, high-quality manufacturing method in 1993.

The three laureates shared the prize equally, each receiving one third. Their work underpins technologies such as QLED screens, LED lighting and biomedical imaging.

Note: Source. The prize facts in this note are from the Nobel Prize's official site, nobelprize.org.

Glossary

• Quantum dot — a nanometre-sized crystal whose optical and electronic properties depend on its size because of quantum effects.
• Nanotechnology — the science and engineering of materials and devices at the scale of nanometres, millionths of a millimetre.
• Quantum effect — a behaviour of matter that only appears because of the rules of quantum mechanics, often visible when particles become extremely small.
• Bandgap — the energy gap between a material's filled and empty electron states, which governs what colour of light it absorbs or emits.
• De Broglie wavelength — the wave-like length associated with a moving particle, such as an electron, under quantum mechanics.
• Semiconductor — a material whose ability to conduct electricity lies between that of a conductor and an insulator, and whose bandgap can often be tuned.
• Colloid — tiny particles of one substance spread evenly through a liquid without fully dissolving, as quantum dots are in solution.
• Hot-injection synthesis — Bawendi's method of rapidly injecting precursor chemicals into a hot solvent to grow uniform nanocrystals.
• QLED — a display technology that uses quantum dots to produce the primary colours needed on a screen.
• Exciton — a bound pair of an electron and the "hole" it leaves behind, whose behaviour in small particles helps explain quantum size effects.
• Ostwald ripening — a process where smaller particles in a solution dissolve and redeposit onto larger ones, causing average particle size to grow over time.
• Molecular-beam epitaxy — a technique for depositing extremely thin, precisely controlled layers of material under high vacuum.

Common errors and misconceptions

• Misconception: Quantum dots change colour because they are made of different chemicals. Correct: The same chemical substance can glow in different colours purely because the crystal's size changes, due to quantum effects.
• Misconception: Yekimov, Brus and Bawendi worked together as a team from the start. Correct: Yekimov and Brus made their discoveries independently in the early 1980s, unaware of each other's work; Bawendi later worked in Brus's laboratory before developing his own method at MIT.
• Misconception: The prize rewards only a theoretical discovery. Correct: The citation specifically credits both the discovery and the synthesis, meaning both the scientific finding and the practical method for making quantum dots reliably.
• Misconception: Quantum dots are only used in television screens. Correct: They are also used in LED lamps, biomedical imaging, mapping tumour tissue, and are being researched for solar cells and quantum communication.
• Misconception: Smaller quantum dots absorb redder light. Correct: It is the opposite: smaller particles absorb and emit light shifted towards blue, while larger particles shift towards red.
• Misconception: Yekimov's quantum dots in glass were immediately usable in devices. Correct: His particles were "frozen" inside glass and not suitable for further processing, which is part of why Brus's and Bawendi's later work mattered.

Exam-style questions with model answers

Q1. State the official citation for the Nobel Prize in Chemistry 2023. [1 mark]

1. "for the discovery and synthesis of quantum dots".

Q2. What is a quantum dot? [2 marks]

1. A quantum dot is a nanometre-sized crystal, typically only a few nanometres across and made of just a few thousand atoms, whose optical and electronic properties are determined by its size rather than only by its chemical composition, because of quantum effects.

Q3. When was the Nobel Prize in Chemistry 2023 announced, and by which body? [2 marks]

1. It was announced on 4 October 2023 by the Royal Swedish Academy of Sciences, which awards the Nobel Prize in Chemistry each year.

Q4. Name the three laureates and their affiliations at the time of the award. [3 marks]

1. Moungi G. Bawendi was affiliated with the Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. Louis E. Brus was affiliated with Columbia University, New York, NY, USA. Aleksey Yekimov was affiliated with Nanocrystals Technology Inc., New York, NY, USA. Each received one third of the prize.

Q5. Explain why the colour of a quantum dot changes with its size. [4 marks]

1. Electrons behave partly as waves. In a large piece of material, electrons have plenty of space, so their allowed energy levels are close together. When a crystal shrinks to nanometre size, the electron waves are squeezed into a tiny "box", spreading the allowed energy levels further apart. This widens the gap between the material's filled and empty electron states. Since the colour of light absorbed or emitted depends on this energy gap, smaller quantum dots absorb and emit bluer light, while larger ones shift towards red, even though the chemical substance is unchanged.

Q6. Describe Yekimov's experiment with coloured glass and what it showed. [4 marks]

1. Aleksey Yekimov heated glass doped with copper chloride at temperatures between 500°C and 700°C for times ranging from 1 to 96 hours, then examined the cooled glass. He found tiny crystals of copper chloride, ranging from about 2 to 30 nanometres, had formed inside the glass. The wavelength of light absorbed by the glass shifted towards blue as the crystal size decreased. He correctly identified this as a size-dependent quantum effect, publishing the discovery in 1981, making it the first deliberate production of quantum dots.

Q7. Outline the steps Moungi Bawendi used in his 1993 hot-injection method. [4 marks]

1. Bawendi's group heated a carefully chosen solvent to a high temperature. They then rapidly injected the chemical precursors needed to form nanocrystals, causing many tiny crystal embryos to form at once as the solution became supersaturated. By dynamically varying the solution's temperature afterwards, they controlled how large the crystals grew. The solvent also helped smooth and even out each crystal's surface, giving nearly perfect, evenly-sized quantum dots that were suitable for real applications.

Q8. Discuss how the work of Yekimov, Brus and Bawendi together led to the modern field of quantum dot technology. [6 marks]

1. The three laureates' discoveries built on each other across more than a decade. In the early 1980s, Aleksey Yekimov, working in the Soviet Union, showed that copper chloride nanoparticles grown inside glass displayed size-dependent quantum effects, proving that quantum theory's old prediction about nano-sized matter was real, though his particles were frozen in glass and could not be processed further. Unaware of this, Louis Brus in the United States confirmed the same basic effect in 1983, but in particles floating freely in a solution rather than fixed inside glass, opening the door to practical chemical manipulation of quantum dots. However, the particles made by Brus and others were of inconsistent size and quality, which limited their usefulness. Moungi Bawendi, who had worked in Brus's laboratory, solved this production problem in 1993 at MIT by developing the hot-injection synthesis method, in which precursor chemicals are rapidly injected into a hot solvent and the temperature is then carefully controlled to grow nearly perfect, evenly-sized crystals. Because this method was relatively simple and reproducible, it allowed quantum dots to move from a scientific curiosity to a technology that could be manufactured reliably and at scale, underpinning today's applications in displays, lighting and biomedical imaging.

Key takeaways

• The Nobel Prize in Chemistry 2023 went to Bawendi, Brus and Yekimov for discovering and synthesising quantum dots.
• Quantum dots are nanometre-sized crystals whose colour depends on their size, not just their chemical formula.
• Yekimov first showed this effect in copper chloride crystals grown inside glass in the early 1980s.
• Brus confirmed the effect in particles floating freely in solution in 1983, independently of Yekimov.
• Bawendi's 1993 hot-injection method made it possible to produce high-quality, consistently sized quantum dots.
• Smaller quantum dots emit bluer light; larger ones emit redder light, for the same chemical substance.
• Quantum dots are used in QLED screens, LED lamps, and to map biological tissue.
• The prize amount of 11 million Swedish kronor was shared equally among the three laureates.

Test yourself

Who discovered quantum effects in coloured glass, and when?

Aleksey Yekimov, in the early 1980s, publishing his discovery in 1981, using copper chloride nanoparticles in glass.

What change in colour happens as a quantum dot gets smaller?

Its absorbed and emitted light shifts towards blue; larger particles shift towards red.

Which laboratory did Brus work at when he proved quantum effects in free-floating particles?

Bell Laboratories in the USA, where he studied cadmium sulphide particles in solution in 1983.

What method did Bawendi develop in 1993?

Hot-injection synthesis, injecting precursor chemicals into a hot solvent and controlling temperature to grow near-perfect, evenly sized nanocrystals.

Name some everyday uses of quantum dots mentioned by the Nobel committee.

QLED television and computer screens, and some LED lamps; also mapping biological tissue and tracking tumour tissue.

What prize amount did the 2023 Chemistry laureates share?

11,000,000 Swedish kronor, shared equally among the three laureates.

Why could Yekimov's original quantum dots in glass not be used in devices?

They were "frozen" inside the glass and not suitable for further chemical processing or manipulation.