The frequency at which droplets emerge is controlled by an acoustic trigger, which can be tuned so that each droplet containing a protein or virus meets an incoming pulse of x-rays. |
A
newly developed carbon nanotube material could help lower the cost of
fuel cells, catalytic converters and similar energy-related technologies
by delivering a substitute for expensive platinum catalysts.
The
precious metal platinum has long been prized for its ability to spur
key chemical reactions in a process called catalysis, but at more than
$1,000 an ounce, its high price is a limiting factor for applications
like fuel cells, which rely on the metal.
In
a search for an inexpensive alternative, a team including researchers
from the Department of Energy’s Oak Ridge National Laboratory turned to
carbon, one of the most abundant elements. Led by Stanford University’s
Hongjie Dai, the team developed a multi-walled carbon nanotube complex
that consists of cylindrical sheets of carbon.
Once
the outer wall of the complex was partially “unzipped” with the
addition of ammonia, the material was found to exhibit catalytic
properties comparable to platinum. Although the researchers suspected
that the complex’s properties were due to added nitrogen and iron
impurities, they couldn’t verify the material’s chemical behavior until
ORNL microscopists imaged it on an atomic level.
“With
conventional transmission electron microscopy, it is hard to identify
elements,” said team member Juan-Carlos Idrobo of ORNL. “Using a
combination of imaging and spectroscopy in our scanning transmission
electron microscope, the identification of the elements is
straight-forward because the intensity of the nanoscale images tells you
which element it is. The brighter the intensity, the heavier the
element. Spectroscopy can then identify the specific element.”
ORNL
microscopic analysis confirmed that the nitrogen and iron elements were
indeed incorporated into the carbon structure, causing the observed
catalytic properties similar to those of platinum. The next step for the
team is to understand the relationship between the nitrogen and iron to
determine whether the elements work together or independently.
An oxygen reduction electrocatalyst based on carbon nanotube-graphene complexes
Source: Oak Ridge National Laboratory
