Quantum Dots New Nobel Laureate Describes Development of These Nanoparticles from Basic Research to Industrial Applications

The 2023 Nobel Prize in Chemistry was awarded to three scientists for the discovery and synthesis of quantum dots. The Conversation Weekly podcast caught up with one of the trio, physical chemist Louis Bruce, who did groundbreaking work discovering that the properties of these nanoparticles depend on their size. Bruce’s phone was switched off when Nobel representatives called to tell him the good news, but now many people have switched to congratulations and advice. Below are edited excerpts from the podcast.

When you were working at Bell Labs in the 1980s and discovered quantum dots, it was something of an accident. You were studying semiconductor particle solutions. And when you pointed lasers at these solutions, called colloids, you noticed that the colors they emitted were not constant.

The first day we prepared the colloid, sometimes the spectrum was different. The second and third day was normal. There was certainly a surprise when I first saw this change in the spectrum. And so I started trying to figure out what was going on with it.

I noticed that the properties of the particle itself began to change in very small amounts.

What you found was a quantum dot; a type of nanoparticle that absorbs light and emits it at a different wavelength. Importantly, the color of these particles changes depending on the actual size of the particle. How do you even see a crystal of quantum dots when one of them is only a few hundred thousandths the width of a human hair?

Well, you can’t see them with an optical microscope because they are smaller than the wavelength of light. There are also ways to see them using other types of special microscopes, such as an electron microscope. And a common way to display them is to line up a series of brightly colored glass flasks, each containing a solution of quantum dots of different sizes.

A quantum dot is a crystal that often consists of only a few thousand atoms. In terms of size, it has the same relationship to a soccer ball as a soccer ball has to the size of the Earth.
Johan Jarnestad / Royal Swedish Academy of Sciences, CC BY-ND

One of your laureates, Alexei Yekimov, was a Russian scientist and had actually observed quantum dots in colored glass, but you were not aware of his findings at the time.

Yes, that’s right. It was the Cold War at the time, and he published in Russian literature. And he was not allowed to travel to the West to speak about his work.

I asked all the physicists if there was any work on small particles. I was trying to build a model of quantum size effects. And they told me no, no one is really working on this. Most of his articles were not seen by anyone.

I was part of the US chemistry community doing synthetic chemistry in the lab. He was in the glass industry in the Soviet Union, working on industrial technologies.

When I finally found his articles in the technological literature, I wrote a letter to the Soviet Union with my papers to say hello to Ekimov and his colleagues. When the letter arrived, the KGB came to talk to the Russian scientists, trying to understand why they had communicated with anyone in the West. But in reality they had never spoken to me or anyone in the West when my letter arrived in the mail.

Have you met him since then?

Yes, they were able to get out of the Soviet Union during Glasnost, this would be the late 1980s. Theres Ekimov, and then his theoretical partner Sasha Efros, who now works at the US Naval Research Laboratory. I met them when I came to the US

Listen to an interview with Louis Bruce on The Conversation Weekly podcast. Every week, academic experts tell us about the fascinating discoveries they’re making to understand the world and the big questions they’re still trying to answer.

One of the problems with quantum dots was how to actually produce them and keep them stable. Then, in the 1990s, your laureate Mungi Bawendi realized it. What do you think is the most remarkable thing you’ve seen using quantum dots so far?

Usually, when a new substance is invented, it takes a long time to figure out what it’s really good for. Research scientists, they have ideas, you can use it for this, you can use it for that. But then, if you talk to people in real industry who deal with manufacturing problems every day, these ideas are often not very good.

But the knowledge we have acquired, scientific principles can be used to design new devices.

As for the first applications, people started trying to use them in biological imaging. Biochemists attach quantum dots to other molecules to help map cells and organs. They have even been used to detect tumors and guide surgeons during operations.

7 shiny bottles
Quantum dot particles have been continuously improved so that they reliably emit very specific colors.
Tayfun Ruzgar/iStock via Getty Images Plus

And as scientists continued to work toward synthesizing quantum dots, the quality of the particles continued to improve. They emitted pure colors, not a distribution of light like maybe red with a little green, or maybe red with some pink. When you get a better particle, it would be pure red, for example.

So people came into contact with computer screens and television screens in the display industry. In this application, you want to convert electricity into three colors: red, green, and blue. You can create any kind of image starting with just those three colors in different proportions.

It takes a lot of courage. You have to invest a lot of money to develop the technology and maybe in the end it is not good enough and it will not replace what you already have. And there’s a lot of credit in Japan thanks to the Samsung Corporation. Hundreds of billions of dollars have been invested in these particle technologies to get them to the point where they can start producing displays and flat-screen TVs using quantum dots.

Your work is an example of the importance of basic research, of being curious, of trying to solve mysteries without any particular endpoint or industrial application. What message would you have for a young chemist starting to work on such fundamental research today?

The world is a huge place and you can do basic research in a huge number of different areas. You want to pick a problem where, if you’re spectacularly lucky and actually discover something interesting, it might have some application in the world.

For better or worse, you have to make a choice first, and for that you need some intuition.

A good way to do this is for you to pick a subject that you know is important to technology, but currently have no idea about science. It’s a complete black box. Nobody understands the basic principles. A problem like this, you can start breaking it down and see what the main steps are.

What changes for you now that you have won the Nobel Prize?

Well, this Nobel Prize, for better or for worse, has a special meaning in the minds of people all over the world. Yesterday when the postman came I happened to be at the front door and he recognized me because my face was in the local paper. And he said: I have never shaken hands with a Nobel laureate.

For better or for worse, this is where I am now, in a special category whether I like it or not. I still have my office at the university, but I don’t have a research group. I try to leave it to the young people. So this recognition probably means less to my research than it would if I were 40 years old.

I have received e-mail congratulations from a number of people who have won the award in previous years. Their main advice is that you should learn to say no. People will ask you to do all kinds of crazy things, and your time will be completely taken up with these honorary campus visits and little speeches. To have a real life and be productive, you must say no to all these unnecessary invitations.

elaborate stage ceremony
The Nobel Prize ceremony in Stockholm is a black tie affair.
Pascal Le Segretain/Getty Images

And they also told me to have fun in Sweden. Schedule of events for the week in December when this award ceremony will take place. Too luxurious. American culture, the culture of physics is different, if you win an award from the American Physical Society, it’s a very low profile event. You just appear in the hall. Even wearing a suit is not mandatory.

So I will take my family, my grandchildren to Sweden and try to enjoy this as a great vacation.

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