Composites are combinations of materials that produce properties
inaccessible in any one material. A classic example of a composite
is fiberglass - plastic fibers woven with glass to add strength to
hockey sticks or the hull of a boat. Unlike the well-established
techniques for producing fiberglass and other macroscale
composites, however, there aren't general schemes available for
making nanoscale composites.
Now, researchers at Berkeley Lab's Molecular Foundry, in
collaboration with researcher at the University of California,
Berkeley, have shown how nanocomposites with desired properties can
be designed and fabricated by first assembling nanocrystals and
nanorods coated with short organic molecules, called ligands. These
ligands are then replaced with clusters of metal chalcogenides,
such as copper sulfide. As a result, the clusters link to the
nanocrystal or nanorod building blocks and help create a stable
nanocomposite. The team has applied this scheme to more than 20
different combinations of materials, including close-packed
nanocrystal spheres for thermoelectric materials and vertically
aligned nanorods for solar cells.
"We're just starting to understand how combining materials on
the nanoscale can open up new possibilities for electronic
properties and efficient energy technologies," said Delia Milliron,
Director of the Inorganic Nanostructures Facility at the Molecular
Foundry. "This new process for fabricating inorganic nanocomposites
gives us unprecedented ability to tune composition and control
morphology."
The researchers anticipate demand from users seeking this latest
addition to the Foundry's arsenal of materials synthesis
capabilities, as this mix-and-match approach to nanocomposites
could be used in an infinite list of applications, including
materials for such popular uses as battery electrodes,
photovoltaics and electronic data storage.
"The beauty of our method is not just the flexibility of
compositions that can be achieved, but the ease with which this can
be done. No specialized equipment is required, a variety of
substrates can be used and the process is scalable," said
Ravisubhash Tangirala, a Foundry post-doctoral researcher working
with Milliron.
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