#181 from R&D
Innovator Volume 4, Number 10
A Lesson in
Dr. Mirkin is
associate professor of chemistry at Northwestern University,
Evanston, Illinois. Dr.
McDevitt is associate professor of chemistry at the University of
Texas, Austin. This
article is written from Mirkin's vantage point.
How would it be
to have inexpensive, hand-held magnetic resonance imaging
equipment in every hospital and doctor‘s office, powerful
supercomputers on your desktop, and easily accessible mobile
telephone stations in every town?
The secret to constructing many of these devices relies on
understanding how to effectively use and process superconducting
materials--ones that exhibit zero resistivity below a critical
applications based on superconductors were, a decade ago, thought
to be impractical because of the need to cool the materials to
temperatures close to absolute zero (-273°C), the recent
discovery of high-temperature superconductors has opened up the
possibility for a number of important applications.
Mother nature was kind to reveal her secrets that allowed
scientists to make materials that conduct electricity with zero
resistance, at temperatures close to those achievable with
relatively simple refrigeration methods.
But she wasn’t kind in terms of the challenges that need
to be surmounted to make practical devices from these
My collaborator, John T. McDevitt, and I have made a
discovery that could hasten the development of high-temperature
superconducting materials and devices for various applications.
The genesis of
the idea arose from a 1994 Office of Naval Research review meeting
organized by our program officer, John C. Pazik.
These meetings are typically long, grueling sessions where
each participant is evaluated for past accomplishment and
potential future contributions to the program.
The purpose of these meetings is not only to update the
sponsors as to each lab’s progress, but also to stimulate
collaborative efforts between participating scientists.
Naturally, everyone wants to continue to be considered for
future funding allocations, so there’s a fair bit of pressure,
and the scientists are constantly thinking of ways to impact the
program through their research endeavors.
At the end of
each day, many of the participants congregate in the local bar and
discuss what they have heard.
I happened to end up across a table from John McDevitt, and
we began to discuss each others' projects.
Our group's expertise, as synthetic chemists, lies in
preparing and characterizing chemically modified interfaces, while
John works on the inorganic chemistry, electrochemistry, and
corrosion reactivity of superconductors.
solid-state inorganic and synthetic chemists don’t have a lot to
talk about with regard to interests in science.
So after a few minutes into the conversation, after we had
exhausted common areas of scientific interest, we began thinking
about ways to merge the two important fields and the ramifications
of doing so. I asked
John if anyone had tried to chemically modify the surface of
superconductors with molecule-based reagents.
Trying to covalently attach molecules to superconductors
seemed like a reasonable thing to do since the other important
classes of electronic materials, metals, semiconductors, and
insulators, had been extensively studied in this regard.
He told me that although there had been numerous ways to
chemically modify the solid-state materials through
ion-substitution reactions (e.g., substituting Ca2+
methods for covalently attaching molecules to this class of ionic
materials were, at the time, unrealized.
As it turned out,
both of us had independently considered the possibilities that
would arise from chemically modifying high-temperature
superconductors; but each group was missing one of the two key
materials to carry out the necessary studies: the appropriate
molecules and the superconducting substrates.
John, who had
recently written a comprehensive review article, was familiar with
some of the prior unsuccessful attempts to modify superconductor
surfaces, and relayed the disappointing details to me as we each
tossed down another beer. A
few drinks later, the obstacles seemed significantly less
daunting, and we began to discuss plans to attack the problem in a
systematic manner. Through
the evening and following day, we continued discussing all of the
marvelous things that could be done with superconductors, provided
that methods for controlling their surface properties could be
developed. Like many
good ideas that are catalyzed by liquor and small talk at
conferences, they were quickly filed away after leaving the
Upon returning to
our universities, neither of us acted on any of these ideas.
However, about two months later, John invited me to Texas
to give a seminar. After
the seminar, the topic of
chemically modifying superconductors came up again.
We decided that, with the molecules we had synthesized for
other studies and the superconducting substrates John routinely
prepares in his laboratory, we could quickly probe and determine
the coordination chemistry of the superconductor.
Because our molecules are all redox-active and the
superconductor is a metal at room temperature and can be used as
an electrode, we decided that we could easily probe the efficiency
of the adsorption process (if it occurred) by electrochemistry.
I soon received a
package from John with several superconducting substrates.
I asked my postdoctoral associate, Kaimin Chen, to go to
the shelf and collect every redox-active molecule that could
possibly bind to Y, Ba, Cu, or O in the superconductor.
Being inorganic coordination chemists, we first tried N-
and S-containing reagents that we expected would bind to Cu in the
tried an initial reaction between a superconducting substrate and
a redox-active ferrocenylamine.
He came to me the following day with a big smile on his
face, and exclaimed, "It worked!"
He showed me the data.
It was significantly better than what we expected.
The molecules attached to the surface in a very efficient
manner to form a stable monolayer film.
I quickly called
John to tell him the good news and to discuss our next steps.
We decided that it was important to determine whether or
not the superconducting properties of the chemically modified
material remained intact; so the samples were sent back to Texas,
and John and his co-workers confirmed that the Tc
for the superconductor had not changed as a result of its chemical
Later, I found
out that John was initially skeptical of the discovery, as it
happened too fast and seemed too good to be true, but after
receiving and testing a small amount of the sample
compound for himself, the "doubting Thomas" (his
true middle name) became convinced that the chemistry worked.
This all happened in about a week, and we were all
overwhelmed with the possibilities for this chemistry.
of modifying the superconductor with the monolayers of redox-active
agents was its resistance to corrosion.
Copper oxide superconductors normally corrode in air via a
reaction with water to form barium hydroxide, which reacts further
with carbon dioxide to form barium carbonate.
Having studied the mechanism of corrosion of high-Tc
systems, John and his coworkers were equipped to study the
influence of the monolayers on the corrosion reaction.
We thought that the monolayer might be acting as a barrier
layer that inhibited the corrosion reaction, and we decided that
there may be ways to enhance this corrosion resistance by
designing and synthesizing molecules that pack better on the
superconductor surface than the molecules chosen for our initial
We decided to try
linear hydrocarbons and fluorocarbons because they’re known to
form densely packed structures on other types of surfaces. Furthermore, we thought that the fluorinated hydrocarbons
would form a water-resistant layer comparable to Teflon polymers.
several molecules, used them to modify superconducting substrates,
and sent them to John for corrosion analysis.
Again, the results were spectacular.
We were able to show that the modified substrates, under
conditions that quickly corroded the unmodified substrates, are
resistant to corrosion.
"industrial process" written all over it, so we
immediately contacted our respective technology-transfer offices
and filed a patent application.
Since our initial discovery, we’ve shown that
superconducting substrates can be tailored with this monolayer
chemistry to improve adhesion between polymeric materials and the
superconductor, pattern organic conducting polymers on the surface
of the superconductor, and control etching of the superconductor.
The substrates can also make insulating barrier layers of
controlled thickness, which may be useful to prepare more
sensitive SQUID devices for detecting magnetic fields (these have
applications in the human health industry for cardiovascular
assessment, and in the petroleum industry for detecting large oil
deposits in the earth's crust).
As with many
important scientific discoveries, this one involved the
combination of two disciplines that in the past have had very
little overlap. It’s
a lesson in collaboration and persistence.
It has opened up exciting personal opportunities for us, as
we have recently begun to work with several superconductor
start-up companies to help them develop their high-performance
products. We currently are searching for additional funding to
develop this important area of research.