Nov. 10,
2004
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Gold
Nano Anchors Put Nanowires in Their Place
Researchers
at the National Institute of Standards and Technology (NIST)
have demonstrated a technique for growing
well-formed,
single-crystal nanowires in place—and
in a predictable orientation—on
a commercially important substrate.
The method
uses nanoparticles of gold arranged in rows on a sapphire surface
as starting points for growing horizontal semiconductor "wires"
only 3 nanometers (nm) in diameter. Other methods produce semiconductor
nanowires more than 10 nm in diameter. NIST chemists' work was
highlighted in the Oct. 11 issue of Applied Physics Letters.*
Part of
the vision of nanotechnology is the possibility of building
powerful, extraordinarily compact sensors and other devices
out of atomic-scale components. So-called “nanowires”—long
thin crystals of, e.g., a semiconductor—
could
not only link nanoelectronic devices like conventional wire
but also function as devices themselves, tipped with photodetector
or light-emitting elements, for example.
An obvious
stumbling block is the problem of working with components so
small that only the most sophisticated measurement instruments
can even track them. To date, the most successful nanowire alignment
method involved growing large numbers of the rod-like crystals
on a suitable base like blades of grass, shearing them off,
mixing them in a solvent, and forcing them to align by either
flow or surface confinement on the test substrate to orient
most of the crystals in a specific horizontal direction. Further
photolithography steps are required to ensure that nanowires
are positioned correctly.
In contrast,
the NIST technique grows arrays of nanowires made of zinc
oxide,
a semiconductor widely used in optoelectronics,
with precise alignments. The gold "anchors" are placed
with a chemical etching step and the orientation of the wires—horizontal,
vertical or at a 60 degree angle from the surface—is
determined by tweaking the size of the gold particles.
Media
Contact:
Michael
Baum, michael.baum@nist.gov,
(301) 975-2763
*B. Nikoobakht,
C.A. Michaels, S.J. Stranick, M. Vaudin, Applied Physics
Letters, Oct. 11, 2004, Vol. 85, Issue 15, pp. 3244-3246.
Designing
an Ultrasensitive 'Optical Nose' for Chemicals
A
laser-based method for identifying a single atom or molecule
hidden among 10 trillion others soon
may find its way from the laboratory to the
real world.
 |
NIST
physicist Jun Ye in his laboratory.
© Geoffrey
Wheeler
To receive a high-resolution version of this image,
contact Gail Porter. |
Developed
by physicists at the National Institute of Standards and
Technology (NIST),
the technique is believed to be more
than 1,000 times more sensitive than conventional methods.
Vescent Photonics of Denver, Colo., hopes to commercialize
the method as an "optical nose" for atmospheric
monitoring. The portable sensors would rapidly identify chemicals
in a gas sample based on the frequencies of light they absorb.
Other applications eventually may include detection of chemical
weapons and land mines, patient breath analysis for medical
diagnosis or monitoring, and industrial detection of leaks
in subterranean pipes or storage tanks, the company says.
Vescent
recently signed a Cooperative Research and Development Agreement
with NIST. The company will work with NIST physicist Jun Ye
(co-developer of the technology) to apply the public domain
"optical nose" technique to detecting and quantifying
trace quantities of atmospheric gases. Ye works at JILA, a
joint institute of NIST and the University of Colorado at
Boulder.
The technique is a product of years of work and several
innovations by NIST scientists. A gas sample is placed in
an optical cavity containing two highly reflective mirrors.
An infrared laser beam is directed into the cavity, where
the light bounces back and forth many times. The repeated
reflections increase the path length on which laser light
will interact with gas molecules in the sample. In addition,
the laser frequency is quickly and systematically varied
in a way that enables scientists to observe and subtract
background noise from the signal.
The approach allows analysis of gases that are present in
minute concentrations and at very low pressures, which may
enable identification of compounds such as explosives that
are difficult to detect by other means.
Media
Contact:
Laura
Ost, laura.ost@nist.gov, (301) 975-4034
Research
Effort Seeks A’s to Gene Expression Q’s
The
National Institute of Standards and Technology (NIST) has
launched a new $6.25 million, five-year program to explore
and address
challenges in measurement, validation and quality control
for the rapidly growing field of gene expression profiling.
Enormous
quantities of gene-sequence data are pouring out of labs
thanks to
dramatic gains in DNA sequencing technology,
but that’s only a start. The real question is how genetic
information translates into biological activity. Gene expression—the
complex process by which some genes are turned on, others
off—is
an essential part of the functioning of an organism. It also
can indicate, or be a factor in, many diseases.
The mechanisms of gene regulation are poorly understood—recent
research, for example, suggests that a great deal of gene
regulation information may be encoded in long stretches of
DNA previously written off as “junk.”
Gene
expression measurements impact everything from basic bioresearch
to drug development and clinical diagnostics.
The most powerful tool for studying gene expression is the
microarray, a device that uses many thousands
of DNA probes to make massively parallel measurements of
gene activity.
But the technology is beset by large uncertainties and unexplained
variability in measurement. One experiment using three different
microarray systems to measure the same sample found that
under the most stringent criteria the three agreed on only
four out of 275 genes identified.
NIST’s
multidisciplinary Metrology for Gene Expression Program seeks
to improve the quality, reliability and comparability of gene
expression measurements with microarrays. Working with instrument
developers and users, the program will evaluate sources of
error and variability in measurement, and will develop reference
data, reference materials and measurement methods to enable
quality assurance for the chemistry, detection methods and
information processing used in microarray analysis.
A key partnership that helped inspire the program is the
External RNA Control Consortium, a group of almost 50 organizations
from industry, academic labs, federal agencies and other
key stakeholders.
Open
Source Software Driver Can Improve PDA Security
The
National Institute of Standards and Technology (NIST), working
with Renesas Technology America Inc., has developed a software
driver that will help improve the security of personal digital
assistants—commonly known as PDAs. The new driver will enable
PDAs to use special postage stamp-sized multimedia cards, which
have all the security functions of a smart card and more storage
capacity built-in, but are easier and less cumbersome to use than
traditional credit card-sized smart cards.
PDAs are
relatively inexpensive and highly portable and can store
documents, spreadsheets, databases and many other resources
usually associated with a laptop or desktop computer. One problem
has been that if they are lost or stolen, it is relatively
easy to bypass security mechanisms and gain access to their
contents. Smart cards, which have an embedded computer chip
with its own protected operating system, programs and data,
can provide formidable PDA security. However, they also require
a card reader, which can be nearly the size of the PDA, as
well as the means to connect the reader to the PDA, such as
a device expansion sleeve or a communications cord. As a result,
traditional smart cards are seldom used as a security device
for PDAs or other handheld devices.
Most current
PDAs have multimedia card slots. The new software driver
controls the functions of the card when it is inserted
into the slot, following standard specifications for secure
multimedia cards recently drafted by the MultiMediaCard Association.
NIST worked with Renesas, a member of the MMC Association,
to develop the driver which is
now available to researchers and others at http://www.musclecard.com/sourcedrivers.html (scroll
to "Renesas XMC Mobile Card"), an open source repository of
Linux and Unix smart card development tools.
Media
Contact:
Jan
Kosko, janice.kosko@nist.gov,
(301) 975-2767
NIST
Requests Comments on Draft Federal ID Standard
The
National Institute of Standards and Technology
(NIST) is looking for comments on a draft
Federal Information Processing Standard (FIPS)
for a smart-card based form of identification
that all federal government agencies will
issue to its employees and contractors. On
Aug. 27, 2004, President Bush issued a
directive calling for the mandatory, government-wide
standard (www.whitehouse.gov/news/releases/2004/08/20040827-8.html).
The directive noted that adopting a uniform
format for government ID badges will eliminate
the wide variations in the quality and security
of forms of identification used to gain access
to federal facilities and non-national security
systems.
The
draft standard specifies the framework, architecture
and technical requirements for
the personal identity verification (PIV) card,
including cryptographic, biometric and card
reader specifications. The requirements are graduated,
from least secure to most secure, to ensure flexibility
in selecting the appropriate level of security
for each application. All PIV cards will include
biometric information, including a photo and
two fingerprints. The framework also incorporates
other technical and operational standards necessary
to achieve interoperability among identification
cards, electronic card readers, communication
systems and access control systems interfaces.
The standard includes processes for issuing and
managing cards, including application and approval
and card maintenance and termination.
Personal
Identity Verification (PIV) for Federal
Employees and Contractors (FIPS PUB 201)
is available at http://csrc.nist.gov/piv-project/index.html. Comments
on this draft may be sent to DRAFTFIPS201@nist.gov or
Chief, Computer Security Division, Information
Technology Laboratory, Attention: Comments
on Draft FIPS 201, 100 Bureau Drive - Stop
8930,
National Institute of Standards and Technology,
Gaithersburg, MD 20899-8930. Comments must
be received on or before Dec. 23, 2004.
NIST
expects the standard to become effective Feb.
25, 2005.
Quick
Links
Scientific
American Dubs Jin 'Research Leader of the
Year'
Scientific
American magazine has selected physicist Deborah
S. Jin, of the National Institute of Standards
and Technology (NIST) as its "Research Leader
of the Year." Jin is a fellow of JILA, a joint
institute of NIST and the University of Colorado
at Boulder. Jin is honored as part of the "Scientific
American 50." The magazine's list recognizes "contributions
to science and technology during 2003-2004 that
promise a better future." The list honors
the achievements of individuals, organizations
and institutions, named by the magazine as research,
policy and business leaders in science and technology
categories ranging from Computing and Medical Treatments
to Aerospace and Energy.
Jin was
selected for her "unprecedented success
at creating a peculiar new state of matter called
a 'Fermi condensate' that promises someday to enhance
superconductivity technology."
The "Scientific
American 50" appears in the December issue of magazine,
which
hits newsstands on Nov. 23, and may be simultaneously
accessed at www.sciam.com.
Gebbie
Honored as a AAAS Fellow
Katharine
Blodgett Gebbie, director of the Physics Laboratory
of the National Institute of Standards and Technology
(NIST), has been elected as a fellow of the American
Association for the Advancement of Science (AAAS),
an honor bestowed upon members by their peers.
The AAAS is the world's largest general scientific
society and publisher of the journal Science.
Gebbie
was cited for her "inspired directorship
of the NIST Physics Laboratory, which is a world
leader in the fields of atom cooling and trapping,
nanotechnology, quantum metrology, and quantum
computation."
This
year AAAS recognized 308 members as fellows, "whose
efforts on behalf of the advancement of science or
its applications are scientifically or socially distinguished."
New fellows will be honored on Feb. 19, at the Fellows
Forum during the 2005 AAAS Annual Meeting in Washington,
D.C. For the full list of the newly elected AAAS Fellows,
see www.aaas.org/news/releases/2004/1101fellows.shtml.
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