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Rodney S. Ruoff & Sungjin Park
talk with ScienceWatch.com and answer a few questions
about this month's New Hot Papers in the field of Materials
Science. The authors have also sent along images of their
work.
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Professor Rodney Ruoff (center) is flanked
by post-docs Weiwei Cai (left, a physicist)
and Sungjin Park (right, a chemist) in
front of the reactor where they are
producing carbon-13 labeled graphite, that
allows for studies of carbon-13 labeled
graphene, a single-atom thick layer of
carbon atoms.
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Article Title: Aqueous Suspension and Characterization
of Chemically Modified Graphene Sheets
Authors: Park, S;An, JH;Piner, RD;Jung,
I;Yang, DX;Velamakanni, A;Nguyen, ST;Ruoff,
RS
Journal: CHEM MATER
Volume: 20
Issue: 21
Page: 6592-6594
Year: NOV 11 2008
* Univ Texas Austin, Dept Mech Engn, 1 Univ Stn C2200, Austin,
TX 78712 USA.
* Univ Texas Austin, Dept Mech Engn, Austin, TX 78712
USA.
* Northwestern Univ, Dept Chem, Evanston, IL 60208
USA.
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Why do you think your paper is highly
cited?
Colloidal suspensions of
graphene platelets and
chemically modified graphene platelets are of interest for both fundamental
and practical reasons. Colloids have a wide range of uses, such as in
electrical energy storage, paints, inks, composites, paper materials, and
so on.
Also, there are fascinating fundamental issues about how graphene-based
platelets disperse in liquids. One might guess that those citing our work
are also expanding the borders of knowledge on graphene-based materials,
and are finding this paper relevant to their work.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
We explain how reduced graphene oxide platelets—these are atom-thick
platelets with the basic "graphene" skeletal framework and some chemical
groups attached to that framework—can be dispersed in water. If such
platelets immediately agglomerate, clump together, etc., then certain sorts
of studies, as well as final product materials, cannot be made.
Would you summarize the significance of your paper
in layman’s terms?
Dispersing chemically modified graphene platelets and graphene platelets in
solvents is very important for many potential industrial end uses. There is
also the fascinating fundamental science of how atom-thick platelets that
are microns in diameter—and thus often have aspect ratios of over
1,000—behave in liquids.
How did you become involved in this research, and
were there any problems along the way?
Ruoff: Shortly after the reports on carbon nanotubes that appeared in the
early 1990s, I began to think about graphene, a single layer of graphite,
and (conceptually) a nanotube "unrolled." In 1998, I led my team to invent
and use methods to pattern graphite to create "pillars" that could then be
separated into very thin layers of material.
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An atomic force microscopy (AFM) image of dried-down
deposits from an aqueous suspension, deposited onto a mica
substrate, showing exfoliation of individual hKMG
platelets.
View/download three accompanying figures and
descriptions.
 PDF
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The papers we published in 1999 included one entitled "Tailoring graphite
with the goal of achieving single sheets," Lu XK, et al.,
Nanotechnology 10: 269-72, 1999. But such top-down approaches will
never yield the thousands of metric tons of very thin platelets needed for
many exciting applications.
Colloidal suspensions of graphene were something I became interested in,
and I had the objective of exfoliating graphite itself to achieve
individual layers. I hired a postdoctoral fellow, Dr. Sasha Stankovich, and
we set about attempting to do that.
It turns out to be non-trivial, and is still not solved for significant
scale-up, although progress on the fundamental science of exfoliation of
graphite to yield "pristine" graphene is progressing.
Sasha and I, along with Professor SonBinh T. Nguyen of Northwestern
University, faced with the lack of any significant success with graphite
itself, turned to making and exfoliating graphite oxide, which readily
disperses in water to yield individual "graphene oxide" platelets.
Einstein is quoted as having said, "I have little respect for that type of
scientist who is always drilling through the thinnest piece of the wood."
So—if one is doing significant work, it is going to be "hard going"
most of the time.
There are always problems to overcome. We greatly value the hard work of
students and postdocs who try to achieve something significant every day
they go into the laboratory! There are challenges, constantly, and of
course sometimes our expectations are not met simply because our hypotheses
were wrong.
This is actually one of the great joys of science: to be confronted with
how nature really is, versus how we guessed it might be, and to find out
how nature really is through good experiments, data acquisition, and
open-minded analysis.
Park: When I joined Prof. Ruoff's group and I was
co-advised by Prof. Nguyen at Northwestern University, I had a background
in the area of synthetic chemistry.
Although graphene is a fantastic material, production of homogeneous
colloidal suspensions of graphene platelets was a great challenge. I think
that chemical modification of graphene platelets is a highly promising
route for this goal, based on the variety of possible chemical interactions
between chemically modified graphene platelets and solvent molecules.
When we pursued this goal, the most difficult problem was a lack of
information about chemical structures of chemically modified graphenes,
especially graphite oxide and thus graphene oxide, which is one precursor
for making a variety of chemically modified graphenes. Helping to pioneer
this new area as well as developing new methods using chemistry was of
great interest.
Where do you see your research leading in the
future?
My team and I are engrossed in studies of graphene-based and carbon
nanotube-based materials. In graphene-based materials, our thrusts are
essentially twofold.
One area is in large-area synthesis and properties of pristine mono- and
n-layer graphene, for both fundamental science and technology transition in
transparent conductive electrodes, nanoelectronics, and other areas.
The other thrust is in colloids with chemically modified or pristine
graphene platelets. These are two rather distinct thrust areas, but there
is a process of learning from within each area that helps with the other.
In the more distant future, and on a personal level, I am interested in
topics related to human and universal consciousness, at the intersection of
reductionist science with holistic approaches, acknowledging the existence
of psi phenomena, and so on. (Psi topics have been of interest to physical
scientists such as Lord Kelvin, Einstein, and many others.)
The interested reader might consider books such as Entangled Minds:
Extrasensory Experiences in a Quantum Reality and The Conscious
Universe: The Scientific Truth of Psychic Phenomena, both by Dean
Radin, Stanislav Grof's When the Impossible Happens: Adventures in
Non-Ordinary Reality, Upton Sinclair's Mental Radio (the
preface is written by Albert Einstein), and so on.
Do you foresee any social or political
implications for your research?
I expect that graphene-based materials will find use in a wide variety of
applications useful to society. There are significant social implications
for this material, as it will engage society in a variety of ways.
As to politics...scientists ideally should be truth seekers, although truth
seems to be at odds with politics a significant fraction of the
time—at least in my opinion. I believe in freedom, and of science
without borders.
Graphene is a material of interest to scientists, engineers, and
technologists, in all parts of this world. Perhaps its use in transparent
conductive electrodes and nanoelectronics will mean even greater
proliferation of the internet and thus of independent sources of
information and news that are not entirely tainted by monied interests.
Prof. Rodney S. Ruoff
Cockrell Family Regents Chair
Department of Mechanical Engineering and the Texas Materials
Institute
The University of Texas at Austin
Austin, TX, USA
Web
Sungjin Park
Postdoctoral fellow
Department of Mechanical Engineering and the Texas Materials
Institute
The University of Texas at Austin
Austin, TX, USA
KEYWORDS: EXFOLIATED GRAPHITE OXIDE; FILMS; DISPERSIONS; NANOSHEETS;
REDUCTION.
Additional information:
