Zubarev wins rare NSF Special Creativity Award
Courtesy of Rice News
for ounce, gold nanorods that are commercially available cost about
7,000 times more than bulk gold, but that may change, thanks to an
award-winning research program in the laboratory of Rice University
chemist Eugene Zubarev.
chemist Eugene Zubarev (right) with graduate student Paul Derry.
Zubarev won a rare two-year grant funding extension for "special
creativity" from the National Science Foundation for his research on the
synthesis and self-assembly of gold nanorods.
Zubarev won a three-year grant from the National Science Foundation
(NSF) in 2011 to develop new methods for large-scale synthesis and
self-assembly of gold nanorods; based on his early progress, the NSF
awarded Zubarev one of its most rare honors — a two-year funding
extension for “special creativity.”
Just how rare are “special creativity” grant award extensions? Out of
more than 43,000 active NSF grants in 2013, only 30 were chosen for the
extensions, and NSF has awarded fewer than 700 creativity extensions
since the program began in 1995.
“We published 25 papers with the original funding, and some of our results were reported
in Chemical & Engineering News,” Zubarev said. “Program managers
pay attention to that, as well as to the impact factor of the journals
where results are published.”
Zubarev's team is refining new methods for tightly packing millions of gold nanorods into 3-D "supercrystals."
Zubarev becomes the fourth member of Rice’s faculty to receive an NSF
creativity extension for work done at Rice. Other winners are physicist
Bruce Johnson, chemist Gustavo Scuseria and biochemist Michael Stern.
Engineering Dean Ned Thomas won three creativity extensions prior to
Zubarev said the additional two years of funding will allow his group
to continue their efforts to develop methods for large-scale production
and processing of gold nanorods. The nanoparticles, which are typically
about 75 nanometers long and 25 nanometers wide, have been studied for
possible use in medical diagnostics and photothermal therapy of cancer,
solar cells, sensors, metamaterials and optical devices.
Prior work in Zubarev’s lab led to a 2008 patent
that was licensed by a company that now manufactures most of the
commercially available gold nanorods (sold through Sigma-Aldrich). But
Zubarev said further advances are needed if gold nanorods are to find
widespread commercial success.
Eugene Zubarev's research group includes (clockwise from left)
postdoctoral fellow Min Wang, Zubarev, graduate student Paul Derry,
postdoctoral fellow Anton Liopo and graduate student Stella Keck.
“If you look at existing synthetic methods, the yield of the reaction
is extremely low, and the quantity you can make in one batch is also
very small, usually a fraction of a milligram,” Zubarev said. “If we
want to talk about real-life applications, we have to discover new
methods that can generate much more than that.”
To address the problem, Zubarev’s team began by examining current
batch processes to see whether they could produce more nanorods simply
by changing the speed of chemical reduction and the nature of reducing
“The reaction takes place in water and at room temperature,” Zubarev
said. “Essentially, we take gold chloride and reduce it with ascorbic
acid. In order to produce nanorods from the reaction, one must first
introduce ‘seed particles’ of pure gold. Once that is done, a
characteristic dark brown color will appear in solution, indicating that
small seed particles are getting bigger and bigger and becoming
gold nanorods are longer than they are wide, 3-D nanorod supercrystals
have "anisotropic" properties, which means they have a different
response to external fields in one direction than another.
One problem in scaling up the reaction is the incomplete
understanding of how it occurs. For example, the seeds are tiny gold
spheres, and it is unclear why the reaction forms elongated gold
nanorods rather than a uniform batch of large gold spheres.
“It’s been almost 20 years since this method was discovered, and
people are still debating the actual mechanism of the reaction,” he
said. “One interesting thing people have found is that adding a small
amount of silver ions will allow you to produce more rods and fewer
spheres. But once again, why that happens in the presence of silver and
not any other metal is still unknown.”
Zubarev said his team has taken a systematic approach to tackling the
scale-up problem, and they hope to publish significant new findings in
the coming months.
In addition to the issue of high-yield synthesis of nanorods the NSF
grant is also supporting research into new processing methods to
incorporate nanorods into metamaterials, man-made materials with unique
properties that blur the line between material and machine. For example,
Zubarev’s team is refining new methods for creating gold nanorod 3-D
“supercrystals” that contain many millions of nanorods that are tightly
packed in uniform arrangements. Because the rods are longer than they
are wide, the supercrystals have “anisotropic” plasmonic and electronic
properties, which means they have a different response to external
fields in one direction than another.