Going beyond photochemistry to drive innovations in energy and medicine

Discover the Research: Article 3 - Nobuhiro Yanai, Faculty of Engineering

Going beyond photochemistry to drive innovations in energy and medicine

Light—whether from the sun or a manmade power source, we hardly notice the many different kinds of light around us. Associate Professor Nobuhiro Yanai of the Faculty of Engineering focuses on the power of light in his research, studying how to apply it in energy, medicine, quantum science, and other fields. We asked Yanai what he loves about photochemistry and how it can be applied in other fields.

The interview was held in March 2024. The original Japanese version of the interview can be found here.

Even tiny is mighty when small energy sources are combined

Can you tell us about your research?

I specialize in photochemistry, which refers to the branch of chemistry concerned with light. Photochemistry covers a broad range of areas, but our laboratory focuses on two major types of research.
The first is wavelength conversion. When you shine light on an object, it reflects light. I am studying this phenomenon, specifically materials that reflect light in somewhat odd ways. Did you know that the color of light corresponds to differences in energy? Let’s look at an example. Which color of light do you think has the greatest energy: green, red, or blue?

Is it red?

Unfortunately, no (laughs). Red has the least energy, followed by green, and blue has the most. Generally speaking, when a material absorbs light and gains energy, it emits light as it sheds some of that energy. In contrast, we are studying a process called “upconversion” in which we create materials that reflect light with greater energy than the light shined on them. Materials like these are uncommon in the natural world.

That seems to violate the law of conservation of energy.

Yes, it does, at first glance. It may seem counterintuitive that a material would emit higher-energy blue light when we shine lower-energy green light on it. Of course, there is a reason and mechanism behind this—when we combine multiple materials that have absorbed energy, we create greater energy. In the manga “Dragon Ball,” the main characters use fusion to combine forces and form a stronger entity. The same phenomenon can occur on a molecular level.

What can this light be used for?

We expect to find applications for the light we produce in many fields, such as energy and medicine. In past studies on energy, for example, electricity has been generated from sunlight, and hydrogen has been produced from sunlight and water. Technologies that utilize sunlight currently focus on visible light. However, by applying upconversion to harness infrared or other forms of invisible light—which have been largely unusable due to their lower energy—we could significantly enhance the efficiency of sunlight-based technologies.

What are the potential applications in the field of medicine?

When you hold your hand up to the sun, you can see through it, and the light is red. This is because only red light reaches your eyes, even though blue, green, and other colors are also in the mix. This demonstrates that red, infrared, and other low-energy light can pass through our bodies. If low-energy light can be upconverted inside the body to produce higher-energy light, we should be able to administer drugs to target areas or facilitate treatment of areas considered too difficult to operate on, such as cranial nerves.

Harnessing the power of light to enhance the sensitivity of medical devices

Can you talk about your other research interest?

We use light to enhance the sensitivity of medical and analytical devices, such as magnetic resonance imaging (MRI) machines and nuclear magnetic resonance (NMR) instruments. MRI machines are important medical devices. They scan the body and provide images, or "slices," that reveal the shape and condition of the brain or injured areas. However, a major challenge with MRI right now is that the sensitivity is quite low.

I’m no expert, but what you can see with MRI looks pretty detailed.

It does, doesn’t it? It may look elaborate, but what you see with MRI is only the vast amount of water and fat in the body. MRI doesn’t show us biomolecules, which are very important. That means we cannot see proteins, DNA, metabolites, and many other things. MRI can show us the shape of a tumor, for example, but not detailed information about what is happening inside the tumor or with the molecules. If we can enhance the sensitivity of MRI to show us molecules and other substances in detail, then we can use it to diagnose diseases and study things like how proteins and drugs interact.

How do you enhance the sensitivity of MRI?

MRI has such low sensitivity because it involves using strong magnets and electromagnetic waves to visualize the nuclear spins of molecules. These nuclear spins are like tiny magnets in the nuclei of the molecules, and most of them cancel each other out in the process. There are many nuclear spins in the body, but all we see with MRI are the ones that do not cancel each other out. In our research, we are working to enhance sensitivity by creating molecules that absorb light and become excited. This process increases the difference in the remaining electron spins, which are then transferred to the nuclear spins of the molecules we aim to detect.

New possibilities await discovery beyond chemistry

What sets your laboratory apart from others?

Many people are working on enhancing the sensitivity of MRI in their own fields. However, not many laboratories are involved in quantum physics or MRI sensitivity from the viewpoint of chemistry. Our laboratory’s stance is to jump into different fields—namely quantum physics and chemistry—to find out what new things we can do there.

Is it fair to say you are involved in research projects across different fields?

In the area of physics, the common practice is to use materials that are available at the time, but there are limitations to this approach. If we apply what we know about chemistry, the research can go beyond the limits of physics and connect to other fields, including medicine, biology, and drug discovery. We call this “jumping” into different fields rather than “fusion,” so it’s a little different from “Dragon Ball” (laughs).

Studying other fields must be quite challenging.

As we continue to venture into previously uncharted territory, we encounter problems that we cannot solve in our laboratory alone. For example, we are not equipped to conduct experiments using mice or cells, so when we want to do research in the field of life sciences, we collaborate with researchers who specialize in those areas. We each bring our expertise and learn from each other in the course of joint research.

True enjoyment underpins success in research

Did you always want to be a researcher?

When I started university, I wasn’t thinking about becoming a researcher at all. Back then, I chose my laboratory purely because it sounded impressive and intriguing. But once I started my research, I enjoyed it so much! It made me want to become a researcher, as long as it continued to be enjoyable. At the time, I was researching materials with holes, called "porous metal complexes," in a laboratory at the leading edge of the field worldwide. It was still an emerging research area, so I was thrilled to realize that my ideas, shaped through discussions with my friends and professors, could potentially compete with the world's leading experts. That was how I got started as a researcher.

It seems like a student’s laboratory can end up having an immense impact on their career.

When I was a student, my lab gave me the freedom to explore whatever I wanted and taught me the joys of research. Now that I’m in a position to teach, I want to provide a place like that for my students. That is why I don’t tell students what to do on a given day or give them detailed assignments. Of course, I give them research topics to start out, but then I ask them to come up with their own ideas, and they do! The most important thing is for students to discover ideas that seem interesting to them so that they feel enthusiastic and genuinely enjoy their research.

You treat your students as full-fledged researchers.

Of course! There are limits to what I can think of on my own. I routinely ask my students to share their opinions, and they regularly come up with novel perspectives that would not have occurred to me, or we generate new ideas together.

What kind of people do you want your students to become?

They alone must choose what kind of job they get and what they do after they graduate. My hope is that they find a sense of meaning in their lives. To get there, they cannot merely follow in somebody else's footsteps. They must use their abilities to blaze their own trails and forge their own paths. In my laboratory, they experience jumping into new fields, which I think helps them develop a mindset to try new things.

What are your goals and outlook for the future?

I think quantum technology will receive a lot of attention in the next 20 or 30 years. My goal is to figure out how I can contribute as a chemist. That said, the word “quantum” covers many areas, including quantum computers, quantum communication, and quantum sensing. For example, if researchers like myself, who are able to create new materials, can develop innovative sensors in quantum sensing with unprecedented levels of sensitivity, it could open up new areas for chemists to explore.

Follow your values and challenge yourself, and you will find your way

I understand you are also involved in outreach work to promote the allure of chemistry.。

I’m part of “Pikari Kagaku,” a team of volunteer teachers and students from Kyushu University that promotes the joy of chemistry to teenagers not just in Kyushu but across Japan. We mainly give lectures at middle schools and high schools, but we also plan to interview researchers working at the forefront of chemistry and share content on our website and other platforms.
We started doing outreach because we believe there is a massive gap between the chemistry taught in middle schools and high schools and the research we carry out in pursuit of our interests. Of course, students learn the basics of chemistry at that age, but it may not be enough to give them an idea of what they will study at university. We hope our activities get middle school and high school students interested in chemistry and encourage them to study it at university. We want them to experience the joys of chemistry and hope that they consider joining us in some capacity in the future.

Finally, do you have any advice for middle school and high school students who may be unsure of what to do next?

Today, you can try many different things from a young age and start over as many times as you like. If there's a problem you want to address or a contribution you want to make, you should be proactive and give it a try. On the other hand, if you’re still unclear about what you want to do, it might be good to explore fields that seem somewhat interesting to you. There are many things about learning and research that you won’t understand until you try them, but if you challenge yourself based on the things you value, I’m sure you will find your way.

Visit Yanai Lab for more information about his research.