July 11, 2011
University of Toronto researchers have derived inspiration from the
photosynthetic apparatus in plants to engineer a new generation of
nanomaterials that control and direct the energy absorbed from light.
Their findings are reported in
Nature Nanotechnology, released on July 10, 2011.
The U of T researchers, led by Professors
Shana Kelley and
Ted Sargent, report the construction of what they term “artificial molecules.”
“Nanotechnologists
have for many years been captivated by quantum dots – particles of
semiconductor that can absorb and emit light efficiently, and at
custom-chosen wavelengths,” explained co-author Kelley, a Professor at
the Leslie Dan Faculty of Pharmacy, the Department of Biochemistry in
the Faculty of Medicine, and the Department of Chemistry in the Faculty
of Arts & Science. “What the community has lacked – until now – is a
strategy to build higher-order structures, or complexes, out of
multiple different types of quantum dots. This discovery fills that
gap.”
The team combined its expertise in DNA and in
semiconductors to invent a generalized strategy to bind certain classes
of nanoparticles to one another.
“The credit for this remarkable
result actually goes to DNA: its high degree of specificity – its
willingness to bind only to a complementary sequence – enabled us to
build rationally-engineered, designer structures out of nanomaterials,”
said Sargent, a Professor in The Edward S. Rogers Sr. Department of
Electrical & Computer Engineering at the University of Toronto, who
is also the Canada Research Chair in Nanotechnology. “The amazing thing
is that our antennas built themselves – we coated different classes of
nanoparticles with selected sequences of DNA, combined the different
families in one beaker, and nature took its course. The result is a
beautiful new set of self-assembled materials with exciting properties.”
Traditional antennas increase the amount of an electromagnetic
wave – such as a radio frequency – that is absorbed, and then funnel
that energy to a circuit. The U of T nanoantennas instead increased the
amount of light that is absorbed and funneled it to a single site within
their molecule-like complexes. This concept is already used in nature
in light harvesting antennas, constituents of leaves that make
photosynthesis efficient. “Like the antennas in radios and mobile
phones, our complexes captured dispersed energy and concentrated it to a
desired location. Like the light harvesting antennas in the leaves of a
tree, our complexes do so using wavelengths found in sunlight,”
explained Sargent.
“Professors Kelley and Sargent have invented a
novel class of materials with entirely new properties. Their insight
and innovative research demonstrates why the University of Toronto leads
in the field of nanotechnology,” said Professor Henry Mann, Dean of the
Leslie Dan Faculty of Pharmacy.
“This is a terrific piece of
work that demonstrates our growing ability to assemble precise
structures, to tailor their properties, and to build in the capability
to control these properties using external stimuli,” noted Paul S.
Weiss, Fred Kavli Chair in NanoSystems Sciences at UCLA and Director of
the California NanoSystems Institute.
Kelley explained that the
concept published in
Nature Nanotechnology is a broad one
that goes beyond light antennas alone.
“What this work shows is
that our capacity to manipulate materials at the nanoscale is limited
only by human imagination. If semiconductor quantum dots are artificial
atoms, then we have rationally synthesized artificial molecules from
these versatile building blocks.”
Also contributing to the paper
were researchers
Sjoerd Hoogland and
Armin Fischer of The Edward S.
Rogers Sr. Department of Electrical & Computer Engineering, and
Grigory Tikhomirov and P. E. Lee of the Leslie Dan Faculty of Pharmacy.
The
publication was based in part on work supported by the Ontario Research
Fund Research Excellence Program, the Natural Sciences and Engineering
Research Council of Canada (NSERC), Canada Research Chairs program and
the National Institutes of Health (NIH).
Find out more about their work in the following selection of stories:
AZnanoBioScholar NewsIEEE SpectrumGeekoSystemNanowerk Nanotechweb Popular Science Science Daily
