nanotehnoloogia, nanoteknologia, nanotechnologija, nanotehnologijas, nanoteknologija,
nanotechnologii, nanotecnologia, nanotehnologijo, nanoteknik
A first: Hydrogen atoms manipulated
below surface of palladium crystal
the first time, scientists have manipulated hydrogen
atoms into stable sites beneath the surface of a
palladium crystal, creating a structure predicted
to be important in metal catalysts, in hydrogen storage
and in fuel cells. The research will be published
in the Dec. 13 issue of the journal Proceedings of
the National Academy of Science.
Observations of the effects of the resulting subsurface hydrides -- hydrogen
atoms with a partial negative charge -- confirmed the existence of the stable
sites, which had been predicted but previously had neither been deliberately
assembled nor directly observed. The research was led by Paul S. Weiss, distinguished
professor of chemistry and physics at Penn State.
After moving absorbed hydrogen atoms to just below the crystal surface, the
researchers were able to observe how the presence of the hydride in specific
sites within a metal crystal affects the chemical, physical and electronic
properties of the metal. Understanding these effects could advance efforts
to improve chemical reactions involving metal catalysts. In addition, the subsurface
hydride may provide a model material for application in hydrogen storage and
fuel cells. The ability to prepare the subsurface hydride provides an important
research tool for these applications.
Weiss pointed out that hydrogen atoms just below the surface of the metal have
been thought to be important in a number of chemical reactions. "Indirect experimental
data have shown that chemically reactive hydrogen atoms were located at such
sites, but there was no way to test them," said Weiss. "This material will
allow us to test the predictions and to apply data from direct observation."
The researchers carried out the experiments in a low-temperature scanning tunneling
microscope (STM) under ultrahigh vacuum by exposing the crystal to a hydrogen
atmosphere. They removed excess hydrogen from the surface by cycles of exposure
to heat and oxygen. After the surface had been cleaned, the researchers were
able to use electrons from the STM tip to move hydrogen atoms that had been
absorbed into the bulk metal up into the stable subsurface sites. As the hydride
formed underneath the surface of the material, Weiss and his team observed
that the surface of the crystal distorted, the positive charge of palladium
atoms above them increased, and interactions occurred with hydrogen atoms on
the surface of the palladium crystal. "One of the most interesting aspects
of the research was the ability to move atoms beneath the surface," Weiss said. "The
observation of the effects of the populated sites, such as surface distortion,
confirmed the existence of the stable sites and the theoretical predictions
of the physical and electrical properties of the hydrides."
Years ago, Weiss was the first on an IBM team to manipulate xenon atoms on
a metal surface. His coworkers later moved atoms to spell out their corporate
logo. By extending the ability to manipulate atoms beyond the surface of a
material, this research is expected to advance the understanding and control
of important chemical reactions in a variety of commercial applications. In
addition, this ability has potential as a model system of a technologically
This research was funded by the Air Force Office of Scientific Research, with
additional support from the Army Research Office, the National Science Foundation
and the Office of Naval Research.
story has been adapted from a news release
Diese Meldung basiert auf einer Pressemitteilung -
tekst is gebaseerd op een nieuwsbericht -
the wave ?
some news ?
click on archive photo
how about joining us
contacting us ?