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For example, they have studied the abalone shell
for its high-performance, super-resistant, composite mineral structure.
Now they are now looking to learn new
biotechnological routes to make high performance electronic and
optical materials.
"We are now learning how to harness the
biomolecular mechanism that directs the nanofabrication of silica in
living organisms," says Morse. "This is to learn to direct the
synthesis of photovoltaic and semiconductor nanocrystals of titanium
dioxide, gallium oxide and other semiconductors –– materials with
which nature has never built structures before."
Most recently, Morse and his students have made
advances in copying the way marine sponges construct skeletal glass
needles at the nanoscale. The research group is using nature's example
to produce semiconductors and photovoltaic materials in an
environmentally benign way –– as they report in a recent issue of the
journal Chemistry of Materials.
"Sponges are abundant right here off-shore and they
provide a uniquely tractable model system that opens the paths to the
discovery of the molecular mechanism that governs biological synthesis
from silicon," says Morse. "This sponge produces copious quantities of
fiberglass needles made from silicon and oxygen."
Morse directs the new Institute for Collaborative
Biotechnologies, a UCSB-led initiative funded by a grant of $50
million from the Army Research Office, which operates in partnership
with MIT and Caltech. He also directs the Marine Biotechnology Center
of UCSB's Marine Science Institute.
The work is particularly exciting, according to
Morse, because silicon has been called the most important element on
the planet technologically –– silicon chips are fundamental components
of computers, telecommunications devices, and in combination with
oxygen forms fiber optics and drives other high-tech applications.
He explains that his research group discovered that
the center of the sponge's fine glass needles contains a filament of
protein that controls the synthesis of the needles. By cloning and
sequencing the DNA of the gene that codes for this protein, they
discovered that the protein is an enzyme that acts as a catalyst, a
surprising discovery. Never before had a protein been found to serve
as a catalyst to promote chemical reactions to form the glass or a
rock-like material of a biomineral. From that discovery, the research
group learned that this enzyme actively promotes the formation of the
glass while simultaneously serving as a template to guide the shape of
the growing mineral (glass) that it produces.
"Most recently in this research, which is supported
by the National Oceanic and Atmospheric Administration's Sea Grant
Program and the Department of Energy, we've discovered that these
activities can be applied to the synthesis of valuable semiconductors,
metal oxides such as titanium and gallium that have photovoltaic and
semiconductor properties," says Morse. The group is using a synthetic
mimic of the enzymes found in marine sponges.
These discoveries are significant because they
represent a low temperature, biotechnological, catalytic route to the
nanostructural fabrication of valuable materials. The research group
is now translating these discoveries into practical engineering.
Currently these materials are produced at very high
temperatures in high vacuums, using caustic chemicals. With these
latest discoveries, scientists have found that nanotechnology can copy
nature and produce materials in a much more environmentally friendly
way than the current state-of-the-art. |
