Tech Briefs Magazine - July 2021 - 34

Manufacturing &
Prototyping
The optical tweezers act as a lightbased
" tractor beam " that can assemble
nanoscale semiconductor materials precisely
into larger structures. There are
no chamber surfaces involved in the
manufacturing process, which minimizes
the formation of strain or other
defects. All of the components are suspended
in solution and the size and
shape of the nanostructure can be controlled
as it is assembled piece by piece.
Using the technique in an organic
solvent allows work with components
that would otherwise degrade or corrode
on contact with water or air.
Organic solvents also help to superheat
the material, allowing control of material
transformations.
To demonstrate the approach, the
researchers used the optical tweezers to
build a novel nanowire heterostructure
- a nanowire consisting of distinct sections
comprised of different materials.
The starting materials for the nanowire
heterostructure were shorter nano rods
of crystalline germanium, each just a few
hundred nanometers long and tens of
nanometers in diameter. Each is capped
with a metallic bismuth nanocrystal.
The researchers then used the lightbased
tractor beam to grab one of the
germanium nanorods. Energy from the
beam also superheats the nanorod, melting
the bismuth cap. They then guide a
second nanorod into the tractor beam
and - thanks to the molten bismuth
cap at the end - solder them end-toend.
They could then repeat the process
until they had assembled a patterned
nanowire heterostructure with repeating
semiconductor-metal junctions that was
five to ten times longer than the individual
building blocks.
Nanowires that contain junctions
between materials - such as the germanium-bismuth
junctions - may eventually
be a route to creating topological
qubits for applications in quantum computing.
The nanosoldering approach
could enable additive manufacturing of
nanoscale structures with different sets
of materials for other applications.
For more information, contact James
Urton at jurton@uw.edu; 206-543-2580.
Green Method for Producing Hydrogen Peroxide
This portable method could enable hospitals to make their own supply of the disinfectant
on demand and at lower cost.
University of California, San Diego
ydrogen peroxide has made headlines
as researchers and medical
centers around the country have been
testing its viability in decontaminating
N95 masks to deal with shortages amid
the COVID-19 pandemic. While results
so far are promising, some researchers
worry that the chemical's poor shelf life
could make such decontamination ef -
forts costly.
H
The main problem is that hydrogen
peroxide is not stable; it starts breaking
down into water and oxygen even before
the bottle has been opened. It breaks
down even more rapidly once it is
exposed to air or light. And because it
decomposes so quickly, shipping and storing
it become very expensive.
Researchers have developed a quick,
simple, and inexpensive method to generate
hydrogen peroxide in-house using
just a small flask, air, an off-the-shelf electrolyte,
a catalyst, and electricity.
The goal was to create a portable setup
that can be simply plugged in so that hospitals
and even households have a way to
generate hydrogen peroxide on demand.
Another advantage is that the method is
less toxic than industrial pro cesses.
The method is based on a chemical
reaction in which one molecule of oxygen
combines with two electrons and two
protons in an acidic electrolyte solution
to produce hydrogen peroxide. This type
of reaction is known as the two-electron
34
Cov
The H-cell setup for developing the hydrogen peroxide production method.
oxygen reduction reaction and it is userfriendly
because it can produce dilute
hydrogen peroxide with the desired concentration
on demand.
The key to making this reaction happen
is a special catalyst that the team
developed. It is made up of carbon
nano tubes that have been partially oxidized,
meaning that oxygen atoms have
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been attached to the surface. The oxygen
atoms are bound to tiny clusters of
three to four palladium atoms. These
bonds between the palladium clusters
and oxygen atoms are what enable the
reaction to occur with a high selectivity
and activity due to its optimal binding
energy of the key intermediate during
the reaction.
Tech Briefs, July 2021
http://www.techbriefs.com http://www.abpi.net/ntbpdfclicks/l.php?202107TBNAV
Tech Briefs Magazine - July 2021

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