Featured Scientist Interview
Essential Science IndicatorsSM from
Reuters, the work of Professor Jonathan
Coleman ranks in the top 1% in both Chemistry and Materials
Science. His full record in the database includes 97 papers
cited a total of 3,019 times between January 1, 1999 and
August 31, 2009.
Professor Coleman is Director of Postgraduate Studies,
Associate Professor of Physics, and a Principal
Investigator of CRANN, the Centre for Research on Adaptive
Nanostructures and Nanodevices, all at Trinity College in
In the interview below, ScienceWatch.com correspondent Gary
Taubes talks with Professor Coleman about his highly cited work.
How did you get into nanotechnology research and
how did that in turn bring you to your highly cited 2003 research on
super-tough carbon-nanotube fibers?
I started working in nanotechnology in the area of polymer nanotube
composites back in 1995-96. If you add nanotubes to polymers, you get
plastics in composite form that are much stronger and stiffer. So we
learned to make these stiff strong plastics.
Then in 2002, I was working in Dallas as a visiting researcher with Ray
Baughman. His group was trying to make composite fibers with polymers and
nanotubes. That was my background and so I was able to contribute to that
work, but I want to make it absolutely clear that I was not the lead author
on that work or the lead researcher. Professor Baughman was the undisputed
leader of that work.
Ray had a DARPA project to develop artificial muscles, and one of the
things we needed for that was fibers that would have a very high
stiffness—this was the goal driving that work. This was very focused
research. They were making fibers, and although we knew they were good
fibers, they were just not stiff enough. It was a matter of going to the
books, the literature, to see what we could learn.
Then Joe Razal, a student in the lab, came to me and said, "Look, I think
this is good for something else." He showed me a paper on the toughness of
spider silk, which is fantastically tough material. People had been trying
to make fibers as tough as that for a long, long time, without a lot of
success. This student said, "I think our fibers are quite tough," and we
calculated the toughness and they were much tougher than spider silk.
How do you calculate toughness?
You measure the stretch-strain curve. You stretch it and measure the force
by which it pulls back. So you're measuring the force as a function of
expansion, of how much you stretched it to begin with. Then you calculate
the quantity called toughness from the area under the curve.
So how tough is spider silk is and how much
tougher were the fibers made in Professor Baughman's
"When you work on a new field like
you're apt to get very, very excited."
I can't be precise, because there are many different spiders and they make
different types of silk with different mechanical properties. But tough
spider silk would be around 150 megajoules per gram and our material was
about 500. Ergo, ours was something like a factor of three tougher. So
these polymer nanotube composite fibers were pretty strong and pretty
tough—they were the toughest materials known to man at the time. And
that was the work we published in Nature, the highly cited paper,
"Super-tough carbon-nanotube fibres—these extraordinary composite
fibres can be woven into electronic textiles," (Dalton AB, et al.,
423: 703, 12 June 2003).
What did you do after you measured it and realized
how tough it was?
I think we went to the pub. Well, okay, we also had to reproduce
it—that was key. We spent a lot of time rebuilding and improving the
apparatus so we could make the stuff reproducibly. That took a lot of time.
That was the not-very-exciting part of the research: when you have
something interesting but you have to turn it from a one-off result to a
Did you expect the paper to have the impact it did
or was that a surprise?
We certainly knew we had something, and well, Ray Baughman made the
decision that we would submit it to Nature. With submissions to
Nature, you know you have only a very small chance of being
successful. We knew with this one that there was a good chance it would be
accepted. To be honest, I think when most people submit to a journal like
Nature, all they're thinking about is getting it accepted. They
don't think too far beyond that—citations, etc. We were just excited
about having something we knew had a real chance of getting into the top
Your second most-cited article is the 2006
Advanced Materials paper, "Mechanical reinforcement of
polymers using carbon nanotubes," (Coleman JN, Khan U, Gun'ko YK,
18: 689-706, 17 March 2006). What prompted you to write that paper
and why do you think it's been so highly cited?
That's a review paper, an invited review paper. I had done quite a lot of
work on reinforcing polymers with carbon nanotubes. We had really published
a number of papers on this—maybe 10—so we were well known in
the area. Out of the blue I was invited to write this review with a
collaborator, and it was the sort of thing that when you agree to do it,
you don't really realize what you're getting into. It was a huge amount of
work; it ruined my life for about three months. All I did was read
literally hundreds of papers trying to digest them all and distill the
information. But the thing about a review is that you know if you do it
right, you're going to get a lot of citations. I did put a lot of effort
into that and I think I got it right and it's been quite highly cited.
Now that it's three years later, is there anything
you would go back and change?
I think I captured a pretty good snapshot of where the field was at the
time. One thing, though, is that paper had a page limit. There were things
I would have liked to do with the data that I didn't have the space for.
You can always do a better job within an infinite amount of space. Still
it's cited a lot, and I meet people that mention it to me. I'm quite happy
How has the field itself evolved in the three
years since you wrote that review?
Well, real progress is starting to be made. I've noticed a number of papers
lately where the mechanical properties of composites have really started to
get places. One of the things we suggested in that review, and many people
knew this, is that the chemical treatment of nanotubes to make them bond
better to polymers was really the way to go. Recently a number of papers
have reported doing that and it has worked. People have shown they can make
really, really strong composites.
What are you working on now?
Well I don't really work on that stuff at all. What we're doing a lot of
work on now is graphene.
Graphene is a single carbon layer and it was shown around 2004 that it had
these phenomenal properties. But people couldn't make it in any large-scale
way. The way people have made it is they take a single layer of graphene
off a graphite crystal, and they do it one flake at a time. Last year, we
were able to show that we could make graphene in liquids—very, very
high yield, and very, very large throughput. We can make a billion layers
in parallel at the same time in solution. That's quite a big advantage.
This work was published in Nature Nanotechnology in 2008
("High-yield production of graphene by liquid-phase exfoliation of
graphite," Hernandez Y, et al., 3: 563-8, September 2008).
Since then it's had more than 50 citations. That's quite a lot for one
year. This for me is where my future is, so I'm not really doing much
nanotube work anymore.
What's the next step then, for your graphene
"...the thing about a review is that you know if you do
it right, you're going to get a lot of citations."
Right now the graphene flakes we make are limited to about one micrometer
in size. We'd like to have them bigger. We want to make graphene flakes
that are really quite large.
Do you have a strategy for doing that?
Well, yes and no. We've found out what controls the size. Once you know
that then you at least have some hope of getting around it, but we
certainly don't have a successful strategy yet.
Other than making bigger flakes, what do you
consider the biggest challenge or obstacle in the graphene
I think it's having self discipline. When you work on a new field like
graphene, you're apt to get very, very excited. You think you're doing
something new and you're going to change the world and get lots of
high-impact papers. It's very easy to get carried away. But that's not what
science is about. It should be about really doing good work and keeping
your head down and making sure you're doing things right, making sure what
you're doing is reproducible and measuring things again and again, just
doing good science. I'm not saying you forget how to do that, but it's easy
to get carried away because of how exciting you tell yourself your work is.
It's always important to keep your feet on the ground. That's what I very
consciously have to do.
What unexpected or serendipitous events arose in
the course of your research?
I'm not sure we've had any truly serendipitous moments but we've had some
surprising results, not amazing in the scientific sense, but interesting,
almost amusing. One of my students found out that graphene can be dissolved
and exfoliated using a chemical, a liquid that turned out to be liquid
ecstasy. We got little bit of a surprise there. We knew what molecules
worked, and we were just choosing molecules with a similar structure from a
catalog. We tried to order this material and we got some serious emails
back, asking us to explain exactly why it was we needed this chemical. I
wondered why, so I asked a chemist—I'm a physicist, I don't know what
these chemicals are—and this chemist said, "My God, that's liquid
ecstasy. Why do you need that?"
Which of your professional achievements brings you
the most satisfaction?
Exfoliating of graphene. There's no doubt about that and I can tell you
why. We were trying to exfoliate carbon nanotubes, because we knew we could
make better composites that way. Nanotubes tend to stick together. That's
their problem. If we can separate them from one another, we should have
better composites. At some point, I said, "Hold the composites, and let's
solve this problem of nanotubes sticking together."
We worked quite hard on that for quite some time, and we found we could
only unstick these nanotubes by using special solvents. We had done some
theory work as well as experiments, and we found solvents that worked and
they did so—and I'm going to get technical here for a
moment—because their surface energy matched the surface energy of the
nanotube. And if that's the case, we thought, well, graphene has the same
surface energy as nanotubes, so it should also work for graphene.
We went off and bought this new material, graphite. We'd never worked with
it before, but simply on the basis of this prediction from this theoretical
model, we tried it and it worked the first time. It really illustrated the
value of really understanding what you're doing, understanding the theory,
and then making connections with other things. I think that is science in a
Prof. Jonathan N. Coleman, FTCD
School of Physics
Trinity College Dublin
Jonathan Coleman's current most-cited paper in
Essential Science Indicators, with 372
Dalton AB, et al., "Super-tough carbon-nanotube fibres—these
extraordinary composite fibres can be woven into electronic textiles,"
Nature 423(6941): 703, 12 June 2003. Source: Essential Science
Indicators from Clarivate Analytics.
KEYWORDS: CARBON NANOTUBES, COMPOSITE FIBERS, ELECTRONIC TEXTILES, POLYMER
NANOTUBE COMPOSITES, SPIDER SILK, GRAPHENE, GRAPHITE, FLAKE SIZE.