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low natural abundance and quadrupolar nature. “The signal
enhancement that DNP provides, allows for detection of
17
O without enrichment,” said Pruski. “The detection of
17
O
nuclei was among our key targets early on, because oxygen is
one of the most ubiquitous elements in materials.”
Frédéric Perras, Pruski’s colleague and Ames Laboratory’s
Spedding Postdoctoral Fellow, used DNP to hyper-polarize
1
H nuclei, and subsequently transferred
1
H polarization to
17
O, cleverly using a scheme called PRESTO, which was
published over 10 years ago and then nearly forgotten in the
NMR community. Perras has since used DNP-enhanced
17
O solid-state NMR to characterize mesoporous silica
nanoparticles (MSNs) and metal organic frameworks
(MOFs) without expensive isotope enrichment (shown in
the figures on page 13).
Pruski and his team, which also includesAmes Laboratory
scientist Takeshi Kobayashi, use DNP-enhanced spectra of
other nuclei, such as
15
N,
29
Si,
27
Al,
195
Pt, and
207
Pb, to make
key characterizations of a variety of other materials prepared
at Ames Laboratory.
They collaborate with Aaron Sadow’s and Igor Slowing’s
research groups on the design and testing of new types of
supported catalysts, as well as new polarizing agents that
may offer even more improvement in DNP measurements.
They also work together with Vitalij Pecharsky and co-
workers on understanding the solid-state transformations
in complex metal hydrides. The ‘DNP contingent’ has been
further strengthened by Aaron Rossini, who recently joined
the Ames Laboratory as a faculty scientist. Rossini’s interests
include DNP characterizations of novel materials as well as
DNP method development.
“Hardly a week passes where we don’t get a contact
from other researchers about DNP, and the instrument is
operated practically non-stop,” said Pruski. “Our external
collaborations include Iowa State University, Argonne
National Laboratory, Northwestern University, Washington
University, University of Delaware, University of Lille (Lille,
France), University of Wisconsin and Purdue University,
and the list continues to grow.”
One important next step is enhancing the capabilities of
DNP by designing new pulse sequences, instrumentation,
highly efficient polarizing agents and improved sample
formulations, in order to open new doors to even faster,
detailed measurements of materials’ properties. Pruski’s
team is engaged in this effort.
“DNP was invented by physicists and then first widely
used by researchers to characterize biological systems, but
I think many would agree that the primary beneficiaries of
DNP are materials scientists and chemists,” he said. “The
technique is particularly well suited for studying the surfaces
of materials. But, it’s still early and much work is needed to
improve the technique.”
Ames Laboratory scientist Marek Pruski, left,
and Ames Laboratory postdoc and Spedding Fellow
Frédéric Perras stand next to the DNP NMR equipment.
Hardly a week passes
where we don’t get
a contact from other
researchers about DNP, and
the instrument is operated
non-stop ...
Takeshi Kobayashi, left, looks on while Frédéric Perras
loads a sample into the DNP NMR equipment.