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.
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,” explains coauthor 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,” says 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,”
explains 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,” says 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,” notes
Paul S. Weiss, Fred Kavli Chair in NanoSystems Sciences at UCLA and director of
the California NanoSystems Institute.
Kelley explains that the concept published in the Nature Nanotechnology paper 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.”
