Electrons, Molecules, and the Bigger Pictures

By Sarah Plumridge

Courtesy: Science in Society (Northwestern University)

Mark Ratner, chair of Northwestern University’s chemistry department, Dumas University Professor of Chemistry, and co-director of the Initiative for Sustainability and Energy at Northwestern (ISEN), talked to Medill Reports about molecular electronics, what it means to be a theoretical chemist, and the gratification that comes with science.

Mark Ratner, chair of Northwestern University’s chemistry department

How would you describe what you do as a theoretical chemist?
I am a chemist that studies molecules, and I happen to study them using computations and models rather than doing experiments. I research how electrons move through molecules.

Why is this important?
Fundamentally I am interested in how nature works, but secondarily and very importantly I am interested in what you can do with that knowledge once you have it. For example, those green leaves out there are capturing energy and they are turning it into chemical energy, [but] they do it very inefficiently. How do you make that better? Well, you make that better by studying how molecules absorb light and what they do with light.

How does the work you are doing fit into a bigger picture?
All molecular electronics have to do with energy in one way or another – light energy, heat energy, displays, photovoltaics, capturing electricity, photo fuels, etc. It is all a part of the energy problem, which is one of the problems, if not the major problem, that is confronting us at the moment with sustainability and climate change. So chemistry has a big part to play in this.

What is your favorite lesson when you are teaching?
There is a series of laws of thermodynamics. The first one is the concept of conservation of energy. If I take this [a pen] and drop it, the energy that was gravitational energy becomes kinetic energy and then becomes heat energy and sound energy. Do it again and it becomes work, so energy and work are related and conserved.

The second one is much more interesting. It says there is also an addition to work and energy, a second component and that is disorder. It is called “entropy,” and the way equilibrium systems are governed is a competition between energy and disorder. That is the second law of thermodynamics. You could argue that it is the most important truth that science knows. If you don’t know much about the second law of thermodynamics, then you don’t know much about science.

Can you tell me about the moment you knew you wanted to be a chemist?
Everybody says it was because of my chemistry set when I was a kid. You could get these little bottles and see reactions of color and smoke and flames, and it was really fun. But that is only part of it. I mean it is a mystery. It’s how these things work.

What has been the best thing that has happened in your career?
The rewards of science are delayed gratification – let’s put it that way. You can’t arrange for high-five moments, even when things go well. I had a conference with one of my [postdoctoral fellows] yesterday who just did something wonderful, and we did the high-five thing. Those are the things you live for, the moments when it all works – when you get some new idea that works, [or] you get an experiment that works.

What do you do outside of studying chemistry?
Anything having to do with water. I like to swim in it, I like to fish in it, I like to canoe in it, I like to kayak on it, I like to sail on it, I like to hike along it and I like to ski on it. You go out to this little river, and you don’t think about anything but you and the river – it’s good. The only time I don’t think about science is when I’m fishing.

– Sarah Plumridge

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