Pitt Researchers Make Breakthrough in Nanotechnology by
Uncovering Conductive Property of Carbon-based Molecules
Newfound ability of organic
molecules to conduct electricity opens door to smaller, cheaper,
and more powerful technologies
PITTSBURGH-University of
Pittsburgh researchers have discovered that certain organic-or
carbon-based-molecules exhibit the properties of atoms under
certain circumstances and, in turn, conduct electricity as well
as metal. Detailed in the April 18 edition of “Science,” the
finding is a breakthrough in developing nanotechnology that
provides a new strategy for designing electronic materials,
including inexpensive and multifunctional organic conductors
that have long been considered the key to smaller, cheaper, and
faster technologies.
The Pitt team found that the hollow, soccer-ball-shaped carbon
molecules known as fullerenes can hold and transfer an
electrical charge much like the most highly conductive atoms,
explained project head Hrvoje Petek, a professor of physics and
chemistry in Pitt's School of Arts and Sciences and codirector
of Pitt's Petersen Institute for NanoScience and Engineering.
The research was performed by Pitt post-doctoral associates Min
Feng and Jin Zhao.
When an electron was introduced into a fullerene molecule, the
shape of the electron distribution mimicked that of a hydrogen
atom or an atom from the alkali metal group, which includes
lithium, sodium, and potassium. Moreover, when two fullerenes
were placed next to each other on a copper surface, they showed
the electron distribution of their chemical bond and appeared as
H2, a hydrogen molecule. The assembly exhibited metal-like
conductivity when the team extended it to a wire
1-molecule-wide.
“Our work provides a new perspective on what determines the
electronic properties of materials,” Petek said. “The
realization that hollow molecules can have metal-like
conductivity opens the way to develop novel materials with
electronic and chemical properties that can be tailored by shape
and size.”
Although the team worked with fullerenes, the team's results
apply to all hollow molecules, Petek added, including carbon
nanotubes-rolled, 1-atom-thick sheets of graphite 100,000 times
smaller than a human hair.
The team's research shows promise for the future of electronics
based on molecular conductors. These molecule-based devices
surpass the semiconductor and metal conductors of today in terms
of lower cost, flexibility, and the ability to meld the speed
and power of optics and electronics. Plus, unlike such inorganic
conductors as silicon, molecule-based electronics can be
miniaturized to a 1-dimensional scale (1-molecule-wide), which
may enable them to conduct electricity with minimal loss and
thus improve the performance of an electronic device.
Traditionally, the problem has been that organic conductors have
not conducted electrical current very well, Petek said. The Pitt
team's discovery could enable scientists to finally overcome
that problem, he added.
“Metal-like behavior in a molecular material-as we have found-is
highly surprising and desirable in the emerging field of
molecular electronics,” he said.
“Our work is a unique example of how nanoscale materials can be
used as atom-sized building blocks for molecular materials that
could replace silicon and copper in electronic devices,
luminescent displays, photovoltaic cells, and other
technologies.”
To view the paper, visit the “Science” Web site at
www.sciencemag.org.
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4/15/08/tmw
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Inspired by
Etch A SketchTM Toy, Pitt-Led Team Invents Technique for
Switching Electrical Properties at Nanometric Scales
Metallic features can be written and erased
at scales that approach atomic dimensions, with wide-ranging
potential for information technologies, as reported online in
“Nature Materials”
PITTSBURGH-A
University of Pittsburgh-led research team developed a process
wherein the ability to conduct electricity can be turned on and
off at nanoscale dimensions. This capability holds promise for
more powerful and compact information technologies including
ultra-high density information storage, reconfigurable logic
devices, single-electron devices, and quantum computers. These
findings were published online March 2 in “Nature Materials”
with the print version scheduled for April.
Led by Jeremy Levy, a professor of Physics and Astronomy in
Pitt's School of Arts and Sciences, the researchers discovered
how to switch, at will, the interface of two readily formed
insulating materials from an electrical conductor to an
insulator and back. The research's considerable technological
applications stem from this adjustability, Levy said.
The process works like a microscopic Etch A SketchTM, Levy
explained, referencing the drawing toy of his youth that
inspired his idea. The interface lies between a crystal of
strontium titanate and a 1.2 nanometer-thick layer of lanthanum
aluminate, both of which are insulators. Using the sharp
conducting probe of an atomic-force microscope, the team created
wires less than 4 nanometers wide at the interface of the two
materials. These conducting nanostructures can subsequently be
erased with a reverse voltage or with light, rendering the
interface an insulator once more.
“This work is not only potentially useful for technological
applications, but also fascinating from a fundamental
perspective,” Levy said. “The prospect of making both logic and
memory devices with the same material is very intriguing, and at
this small of a scale, it's almost unheard of.”
The physical model still needs tested in crucial ways, but
provides an important framework for future research directions,
Levy said. For example, the interface also acted as a
transistor-an essential part of electronic devices that
regulates electron flow-when the atomic-force probe served as a
gate; further research will include creating devices that
utilize single electrons for logic or storage.
The idea originated from a visit Levy made to the University of
Augsburg in Germany where coauthors Jochen Mannhart and his
student Stefan Thiel showed Levy how the entire interface could
be switched between a conducting and insulating state. Levy
thought of adapting the process to nanoscale dimensions and his
student, Cheng Cen, the paper's first author, brought the idea
to fruition. Research by C. Stephen Hellberg from the Naval
Research Laboratory contributed to the theoretical understanding
of the project. The work was supported by the Defense Advanced
Research Projects Agency and the National Science Foundation.
Levy has worked in the field of oxide electronics for the last
decade, and has been recognized by Pitt with the Chancellor's
Distinguished Teaching Award in 2007 and the Chancellor's
Distinguished Research Award in 2004.
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2/27/08/tmw
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Pitt Receives $1 Million Grant
to Research Ultrafast Time-Resolved Microscopy of Nanostructured
Electronic Materials
Researchers will develop
revolutionary method to probe molecular structures
PITTSBURGH-The University of
Pittsburgh received a $1 million grant from the W.M. Keck
Foundation to develop a groundbreaking method that will
significantly advance nanoscale science and technology by
allowing scientists to observe, probe, and control molecules.
The revolutionary technique involves probing molecular structure
with femtosecond-a billionth of a millionth of a second-temporal
and atomic spatial resolution, leading to new knowledge on
activating and harnessing matter at its most fundamental level.
The principal investigator for this research is Hrvoje Petek, a
professor of physics and chemistry in Pitt's School of Arts and
Sciences and codirector of the Petersen Institute of NanoScience
and Engineering. Petek is an expert in the fields of surface
femtochemistry and ultrafast microscopy. He invented
ITR-PEEMtime-resolved photoemission electron microscopy, the
enabling technique for this study.
“In pursuit of this grail, several leading physics and chemistry
research groups around the world are exploring different ways to
combine the spatial resolution of electron microscopy with
temporal resolution of femtosecond laser spectroscopy,” Petek
said. “ Our goal is to develop methods for interacting with
single molecules in order to observe and control how they
respond to stimulation by light or electrons to undergo chemical
reactions or specific mechanical motion.”
Based in Los Angeles, the W.M. Keck Foundation is one of the
nation's largest philanthropic organizations. Established in
1954 by the late William Myron Keck, founder of The Superior Oil
Co., the foundation focuses primarily on medical research,
science, and engineering.
Since 1988, the W.M. Keck Foundation has donated more than $4
million to support research in medicine, engineering, and
science at Pitt. The latest grant is part of the University's
“Building Our Future Together” campaign, the most successful
fundraising campaign in the history of both the University and
Southwestern Pennsylvania. To date, the campaign has raised more
than $1.2 billion.
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2/6/08/tmw
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Model for the Assembly of
Advanced, Single-Molecule-Based Electronic Components Developed
at Pitt
Template for creating
one-molecule-wide wires for crafting molecular level organic
semiconductors published in the Journal of the American Chemical
Society
PITTSBURGH—Researchers based at
the University of Pittsburgh have created the best method so far
of assembling wire-like structures only a single molecule wide,
a significant step in science’s increasing attempts to reduce
the circuitry size of electronic devices to the single molecule
scale and provide smaller, faster, and more energy efficient
electronics. The findings were published online Sept. 26 in the
Journal of the American Chemical Society (JACS).
The project presents a template for assembling molecules over
troughs that are only as wide as a single atom of copper, but
extend with faultless uniformity over distances corresponding to
several hundred copper atoms. These ultra-thin wires are
one-dimensional, which may enable them to conduct electricity
with minimal loss and thus improve the performance of an
electronic device, said project leader Hrvoje Petek, a professor
of physics and chemistry in Pitt’s School of Arts and Sciences
and codirector of Pitt’s Petersen Institute for NanoScience and
Engineering (PINSE).
The published research pertains to organic—or
carbon-based—soccer ball-shaped carbon molecules known as
fullerenes, but the method can serve as a template for creating
the molecule-scale wires from a broad range of organic
molecules, Petek said. The merits of these wire-like structures
can only be fully realized with organic molecules. Materials
used in contemporary electronics—such as silicon—are inorganic
and cannot be miniaturized to be truly one-dimensional, Petek
said.
The project was conceived by Junseok Lee of the University of
Virginia’s chemistry department and executed by Min Feng, a
research associate in Pitt’s physics and astronomy department.
Research associate Jin Zhao of Pitt’s physics and astronomy
department served as the project’s theoretician. The template
was developed with the chemistry group of Pitt emeritus
professor John T. Yates Jr., now of the chemistry department at
the University of Virginia and an advisor to PINSE.
The research was sponsored by grants from the Keck Foundation,
the American Chemical Society Petroleum Research Fund, and the
U.S. Department of Energy.
The paper is on the JACS Web site at pubs.acs.org/journals/jacsat/.
September 27, 2007
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People With Asthma Could Breathe Easier Anywhere With Hand-Held
Pitt Nano-Sensor That Indicates Oncoming Attacks and Helps
Monitor Symptoms
Portable, affordable
nanotube sensor detects spikes in nitric oxide before an
attack's onset, Pitt researchers report in journal
“Nanotechnology”
PITTSBURGH-A sensor developed at
the University of Pittsburgh could strip the element of surprise
from some asthma attacks by detecting one before its onset.
Fitted in a hand-held device, the tiny sensor provides people
who have asthma with a simple and affordable means of keeping
tabs on their condition by measuring their breath for high
levels of a specific gas associated with asthma inflammation.
Researchers led by Alexander Star, a chemistry professor in
Pitt's School of Arts and Sciences, created a sensor reactive to
even minute amounts of nitric oxide, a gas prevalent in the
breath of asthmatics, as they describe in the Aug. 22 online
edition of the journal “Nanotechnology.” Star also will present
his research at the American Chemical Society's 234th National
Meeting slated for Aug. 19-23 in Boston. The sensor consists of
a carbon nanotube-a rolled, one-atom thick sheet of graphite
100,000 times smaller than a human hair-coated with a
polyethylene imine polymer.
Star cased the sensor in a hand-held device that people blow
into to determine the nitric oxide content of their breath. The
nitric oxide level in the breath of a person with asthma spikes
as the airways grow more inflamed. High levels-perhaps
two-thirds over normal-may precede an attack by one to three
weeks, but possibly earlier depending on the asthma's severity,
said Jigme Sethi, a Pitt assistant professor in the School of
Medicine's Division of Pulmonary, Allergy, and Critical Care
Medicine and a clinician at UPMC Montefiore, who plans to
clinically test Star's sensor.
Besides detecting attacks early on, Star's device also provides
an easy, portable method for patients and their doctors to
regularly monitor their symptoms and tailor treatment
accordingly, Sethi said. Physicians use nitric oxide readings to
help diagnose and gauge the severity of asthma, but the current
method of measuring it requires expensive machines available
only in outpatient clinics, Sethi said. Star's invention could
allow people with asthma to watch their nitric oxide levels as
easily as people with diabetes check their blood sugar with
hand-held glucose monitors, Sethi said.
Star specializes in using carbon nanotubes-which were widely
introduced to science in the early 1990s-as chemical sensors and
in hydrogen fuel cells. In the case of sensors, a nanotube's
extreme thinness renders it extremely sensitive to small changes
in their chemical environment, which makes for an excellent
detector, Star said.
August 22, 2007
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Dr. Jin Zhao, Postdoctoral Fellow of
Physics, Receives M.T. Thomas Award for Outstanding Postdoctoral
Achievement from the Environmental Molecular Sicences Laboratory
(EMSL) of the Pacific Northwestern National Laboratory (PNNL)
Dr. Jin Zhao
|
Jin Zhao, University
of Pittsburgh, has been selected as the 2006
recipient of the
M.T. Thomas Award for Outstanding Postdoctoral
Achievement. This award is in recognition of her
seminal contributions to the theory of the
unoccupied electronic structure and dynamics of
solid-adsorbate interfaces, which are of fundamental
importance to geochemistry, atmospheric science, and
energy related interfacial phenomena.
Dr. Zhao is a
post-doctoral research associate in Professor Hrvoje
Petek's group in the Physics and Astronomy
Department at the University of Pittsburgh.
According to Petek, "Jin, as the lone theorist, has
been the cornerstone of all surface science research
done in my experimental group for the last 3 years.
I could only provide a stream of questions, and a PC
to connect to the world, while it was up to her, and
she did it brilliantly, to find the theoretical
resources and support to chart several new
directions in surface science theory." Zhao
submitted her first EMSL user proposal in 2005 and
was awarded 75,000 hours on EMSL's supercomputer.
Zhao's
accomplishments include theoretical description and
assignment of partially solvated electronic states
at the protic solvent/metal oxide interfaces (H2O)/TiO2
and CH3OH/TiO2). Her
theoretical discovery of the so-called "wet electron
state" paves the way to understanding how the
specific molecule-surface and molecule-molecule
interactions define the properties of acceptor
states in nonadiabatic electron transfer processes,
such as photoinduced charge transfer excitation.
Moreover, her theoretical interpretation of the
deuterium isotope effect on interfacial electron
transfer provides deep insight in proton-coupled
electron transfer that is likely to have an
important role specifically in the area of surface
photocatalysis.
Another area of
Zhao's theoretical analysis includes the description
of the electronic structure of excess electrons at O
atoms vacancy defects, which control the chemical
and electronic properties of TiO2
surfaces. As TiO2 has important
applications in catalysis, photocatalysis, sensors,
and light switchable amphiphilic films, the
understanding of how surface defects affect chemical
reactivity is an important step in the understanding
and expanding of these applications. Zhao has shown
that when describing the electronic structure of
metal oxides, ad hoc treatments of self-interaction
effects can easily lead to incorrect conclusions
concerning the extent of electron localization. By
constraining her theory with high quality atomic
resolution images of the excess electron charge on
reduced TiO2 surfaces, she has been able
to explore the range of validity of hybrid
functional techniques for describing the electronic
properties of metal oxide surfaces.
Zhao's work also
includes the development of a simple, yet profound,
broadly applicable phenomenological theory that
explains the period-independent, interfacial
electronic structure of alkali atoms. Her work has
been the key to understanding the universal binding
energy of Li-Cs chemisorbed on copper and silver; it
is applicable to and has the potential to provide
insight into the design of future molecular
electronics devices.
Dr. Zhao obtained her
Ph.D. in computational condensed matter physics from
the University of Science and Technology of China,
Hefei, Anhui, China in 2003. Dr. Zhao has been a
post-doctoral research associate in Professor Hrvoje
Petek's group in the Physics and Astronomy
Department at the University of Pittsburgh since
2004.
The 2006 M.T. Thomas
Award will be presented to Dr. Zhao at a ceremony
following a presentation of her work (tentatively
scheduled for May 24, 2007). A reception in her
honor will follow.
Publications
resulting, in part, due to the use of EMSL's
supercomputer:
- Jin Zhao,
Bin Li, Ken Onda, Min Feng and Hrvoje Petek,
"Solvated Electrons on Metal Oxide Surfaces",
Chem. Rev. 106, 4402
(2006).
- Jin Zhao,
Bin Li, Kenneth D. Jordan, Jinlong Yang and
Hrvoje Petek, "Interplay between Hydrogen
Bonding and Electron Solvation on Hydrated TiO2(110)",
Phys. Rev. B 73,
195309 (2006).
- Taketoshi
Minato, Jin Zhao, Yasuyuki
Sainoo, Yousoo Kim, Hiroyuki S. Kato, Maki
Kawai, Ken-ichi Aika, Jinlong Yang, and Hrvoje
Petek, "Correlation between the Lattice
Distortion and the Local Electronic Structure at
an Atom Vacancy Defect on Titanium Dioxide (110)
Surface", Phys. Rev. Lett., submitted.
- Jin Zhao,
Niko Pontius, Aimo Winklemann, Vahit Sametoglu,
Atsushi Kubo, Andrei G. Borisov, Daniel Sanchez
Portal, V. M. Silkin, Engene V. Chulkov, Pedro
Echenique, and Hrvoje Petek, "The universal
electronic structure of alkali atom/metal
interface", Science, submitted.
<Source:
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The Research of
Dr. Sanford Asher, Professor of Chemistry, Highlighted in the
March 19, 2007 Issue of Chemical & Engineering News
Spectroscopic method offers
large signal enhancements but
until now was expensive and
complicated
DO THINGS a
little differently from the
way they're usually done,
and the results might turn
out surprisingly well. By
modifying familiar recipes,
chefs sometimes produce
masterpieces. By altering
their daily routes,
commuters may shave minutes
off their travel times. Even
spectroscopists stand to
gain by trying something
different.
|
Mitch Jacoby/C&EN
JUST A HANDFUL! Hug
shows off a small,
low-cost deep-UV laser from
Photon
Systems that may help boost
the
popularity of UV-Raman
spectroscopy
|
A case in point is Raman
spectroscopy, an analytical
technique in which samples
are most often probed with
light in the visible and
near-infrared regions (about
400 to 700 nm). In the past
several years, UV-Raman
aficionados have pushed to
capitalize on the benefits
of carrying out a variant of
the technique using
ultraviolet light (typically
200 to 300 nm). Exciting
samples deep in the UV
region can enhance signal
intensities by a factor of 1
million or more compared
with conventional Raman
spectroscopy. UV light also
offers a method for probing
certain functional groups
selectively. In addition,
moving to shorter excitation
wavelengths can avoid
interference from
fluorescence, which
sometimes obliterates
standard Raman spectra.
Attendees of Pittcon earlier
this month in Chicago
learned about some of the
most recent advances in the
UV-Raman field.
Practitioners and instrument
makers gathered at a
symposium to report on
applications in biochemistry
and catalysis and to discuss
commercialization of
UV-Raman instrumentation.
"It can be argued that the
single most important issue
in biology today is
understanding how proteins
fold into their native
states." That assertion was
made by University of
Pittsburgh chemistry
professor
Sanford A. Asher, a
pioneer of UV-Raman
methodology. Asher explained
that conformational
variations (misfoldings)
that cause proteins to adopt
structures that differ from
normal protein geometries
have been fingered as key
factors in Alzheimer's,
Huntington's, and several
other diseases.
|
ANGULAR DEPENDENCE Folding and coiling geometries
in peptides and proteins are specified by amide Ψ and Φ
dihedral angles.
|
"If we understood the
mechanism through which
proteins fold or misfold, we
would have an opportunity to
intervene chemically," he
said. So Asher's group has
been probing protein-folding
processes with UV-Raman
spectroscopy, a method that,
he argued, is particularly
well-suited to studying
dilute solutions.
The nuances of a protein's
folding and coiling
geometry, which collectively
are known as a protein's
secondary structure, are
dictated in large part by
hydrogen-bonding
interactions along the
molecule's peptide backbone.
As Asher pointed out, it's
known from X-ray
crystallography studies and
other types of analyses that
proteins often adopt a
combination of common
secondary structural motifs,
including the so-called
random coil, which is
reminiscent of cooked
spaghetti, and the more
orderly α-helix and β-sheet
arrangements.
The particular conformation
adopted by a peptide chain
is determined by rotations
about C-C and C-N amide
bonds and the resulting
dihedral angles, known as
the Ramachandran Ψ and Φ
angles, respectively. These
angles are named for the
Indian biophysicist G. N.
Ramachandran, who began
studying them in the 1960s.
To get a spectroscopic
handle on the secondary
structure, Asher's group
analyzed UV-Raman data from
a number of proteins and
peptides with known
secondary structures and
determined how amide
vibrational bands correlate
with the various geometries.
Then they calculated basis
spectra, which represent the
Raman signals that would be
measured from proteins that
adopt only a single
structural motif-for
example, pure α-helix. Next,
they showed that measured
spectra could be modeled by
the sum of appropriately
weighted basis spectra,
thereby providing a way to
determine secondary
structures of previously
uncharacterized peptides and
proteins.
|
Asher
Stair
Mitch Jacoby/C&EN (both)
|
THOSE RESULTS
set the stage for a number
of follow-up studies and key
findings. For example, the
Pittsburgh group observed
that as polyglutamic acid is
heated, it undergoes a
structural transition
(melts) from the α-helix
conformation to a random
coil. As the conformation
evolves, a large change
occurs in the Ψ angle, which
in turn causes a large
change in the frequency of
one of the amide vibrational
bands known as the amide III3
band. In contrast, the
researchers found that the
band depends only weakly on
the Φ angle.
Following other UV-Raman
studies, Alexander V.
Mikhonin, a graduate student
in Asher's group, developed
a method for determining Ψ
angles from spectra measured
under various experimental
conditions. That development
is noteworthy, Asher argued,
because the Ψ angle serves
as a textbook-type reaction
coordinate for evolution of
protein and peptide
secondary structures. As
such, the researchers
uncovered a way to
experimentally monitor
secondary structures as they
evolve.
The team then used that
methodology to interrogate
α-helix melting in a number
of samples, including a
21-residue peptide known as
AP, which consists mainly of
alanine units. Some of the
main findings of that
investigation are that AP
melts at a significantly
higher temperature than
previously reported and that
other types of conformations
melt before the α-helices
unfold. Furthermore, in the
melted state, AP's structure
closely resembles that of
polyproline II, which
consists of left-handed
helices with three residues
per helical turn. (J.
Am. Chem. Soc.
2006, 128, 13789).
MOVING A STEP
closer to a detailed
understanding of secondary
structure, the Pittsburgh
group recently showed that
the distribution of Ψ angles
can be used to calculate
energy landscapes associated
with peptide conformations.
The plots dictate which
structures are energetically
favored and which are
blocked by energy barriers.
|
Courtesy
of Sanford A. Asher
MELTDOWN Analysis via UV-Raman spectroscopy
reveals molecular details of the process by which this
coiled 21-residue peptide (left) unfolds (melts).
|
Switching gears,
Northwestern University
chemistry professor Peter C.
Stair lauded the ability of
UV-Raman spectroscopy to
probe reactions occurring at
the surfaces of
heterogeneous catalysts.
"There is virtually no other
technique that can see the
catalyst and the molecules
[reactants and products] in
a single measurement and
under reaction conditions,"
Stair declared. He added
that before the development
of UV-Raman methods,
researchers' efforts were
often thwarted by
fluorescence signals that
buried the Raman data.
Drawing on results of an
investigation of butane
dehydrogenation on supported
vanadia catalysts, Stair
demonstrated that UV-Raman
analysis sheds light on
several experimental
parameters. For example, the
results show that at a
catalyst loading
(concentration on the
support material) of roughly
one vanadium atom per square
nanometer, which corresponds
to an active form of the
catalyst, vanadia consists
of roughly equal proportions
of monomeric and polymeric
forms of V=O. At higher
loadings, the polymeric form
prevails and the catalyst is
inactive. The method also
indicates that while the
catalyst is active, it's
coated with a carbonaceous
(coke) layer that resembles
polystyrene. In contrast,
layers composed of coronene,
pyrene, and other polycyclic
aromatic hydrocarbons with
2-D sheetlike structures
poison the catalyst.
Despite the strengths of
UV-Raman spectroscopy, the
method is not practiced in
many labs today. William F.
Hug, president of
Photon Systems, a
Covina, Calif., maker of
low-cost UV lasers and other
equipment, remarked that
widely used analytical
instruments such as
UV-visible spectrometers are
easy to operate, are rugged,
require little or no
servicing, and are
relatively inexpensive (in
the $15,000 to $80,000
range). UV-Raman
instruments, in sharp
contrast, are used strictly
by specialists, and systems
with high-end deep-UV lasers
can cost well over a
half-million dollars, he
said.
The good news, according to
Hug, is that the past
several years have seen
"tremendous progress" in
lowering the costs of UV
lasers, detectors, lenses,
mirrors, and other
components of UV-Raman
systems. Hug's presentation
touched off an impromptu
discussion of
analytical-method
limitations that culminated
with symposium organizer
Michael W. Blades of the
University of British
Columbia declaring that
"nothing is really holding
back UV-Raman anymore." He
added, "We should expect
more of these sessions and
better attendance in the
future."
-
<Source:
Chemical & Engineering
News, March 19,
2007 (Volume 85, Number
12) pp. 59-60.>
-
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Pitt
Professor
Scores
Science Double-header
By
Allison M.
Heinrichs
TRIBUNE-REVIEW
Friday, November 17, 2006
Anna Balazs is becoming a Science celebrity.
The University of Pittsburgh engineering professor
published her second article of the month in the international
weekly magazine Science -- a peer-reviewed journal in which
scientists strive to get their work published.
"We are a selective journal. We only publish about
8 percent of the papers that are sent to us," said Katrina Kelner,
a deputy editor at Science. "Although I wouldn't say we've never
(had an author publish two articles in less than a month) before,
it certainly isn't common."
Balazs is lead author on an article titled "Nanoparticle
Polymer Composites: Where Two Small Worlds Meet" in today's issue
of Science. She co-authored an article about pulsating gels in the
Nov. 3 issue.
Both articles tackle subjects in the field of
materials engineering.
Balazs and co-authors Todd Emrick and Thomas
Russell, professors at the University of Massachusetts in Amherst,
review the latest research in incorporating nanoparticles with
flexible, easy-to-mold plastics. Nanoparticles are inorganic
particles 1,000 times smaller than the width of a human hair that
are prized for their electrical, optical and mechanical
properties.
Plastics and nanoparticles "both have very
desirable properties and when you integrate the two, the sum is
better than the parts," said Balazs, who works in Pitt's
department of chemical and petroleum engineering. "When you
combine the two you get a material that is tough, but also stiff."
For example, if an automobile company wants to make
a lightweight but strong car, the company could create a material
that suits its needs, rather than adapting the car design to
available materials, such as steel, aluminum and plastic.
In her earlier article, Balazs and postdoctoral
student Victor Yashin explored "pulsating gels," polymer gels that
expand and contract like a beating heart when put in a chemical
solution.
Scientists have known about the gels for a
half-century, but Balazs and Yashin developed a mathematical model
to explain how their shapes change as they pulsate. This gives
people experimenting with the gels -- which could be useful as
muscles in robots -- a "recipe" to follow.
"It's like telling someone how to bake a cake,"
Balazs said. "If they follow your directions, the cake should come
out perfectly."
In the case of pulsating gels, experimentalists
confirmed that the recipe, in this case a mathematical model, is
correct.
"That's such an amazing high," Balazs said. "It's
just an incredibly joyous feeling -- it's validation for all your
hard work."
Balazs, who has been with Pitt since 1987, spreads
that "high" to her colleagues and students, said professor Bob
Enick, chairman of the department.
"She has the enthusiasm of a young child opening a
gift, and it's contagious," Enick said. "She sets an example for
the rest of us."
Allison M. Heinrichs can be reached at
aheinrichs@tribweb.com or (412) 380-5607.
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Electrons ‘In Limbo’ Seen for First Time
Two recent papers by Pitt
physicist offer a deeper understanding of how electrons behave on
surfaces, with applications in electronics and energy
PITTSBURGH—Hrvoje Petek,
University of Pittsburgh professor of physics and codirector of
Pitt’s Gertrude E. and John M. Petersen Institute of NanoScience
and Engineering (PINSE), has published two papers in recent weeks
that literally illuminate how electrons behave on various
surfaces.
In the first paper, Petek and Miroslav Nyvlt of Charles University
in Prague explored the properties of metals under intense light—a
situation “where the classical physics of electron emission from
metals emerges from its quantum roots,” says Petek. They found
that when light of a certain energy and intensity is shone onto a
metal surface, a few electrons in the metal become stuck on the
surface (that is, they are neither emitted from nor reabsorbed
into the metal). As Petek puts it, the electrons are “in limbo.”
These electrons undergo the process of “total internal
reflection”—a process well known for light, but observed by Petek
and Nyvlt for the first time in electrons.
These findings, published in the March 3 issue of Physical Review
Letters (PRL), could lead to the ability to transmit electrons,
without scattering, over larger distances than previously
possible. For example, electrons on the surface of carbon
nanotubes could be excited to make “very small and very fast”
transistors, Petek says.
“We anticipate that these elusive electrons will provide exquisite
probes for how photons and electrons interact with metal
surfaces,” he adds.
In Petek’s second paper, published in the current issue of
Science, he and Pitt Professor of Chemistry Kenneth Jordan, a
PINSE researcher, make new progress toward extracting hydrogen
from water using titanium dioxide as a catalyst.
In a May 2005 Science paper, Petek and Jordan presented their
findings on the properties of water on the surface of titanium
dioxide. In their current experiment, they used methanol instead
of water, because they discovered that excited electrons last
longer in methanol than in water, allowing chemical reactions to
be observed.
This research shows how protons in methanol molecules move in such
a way that they control the reabsorption of electrons into the
titanium dioxide. Such motion, correlated between protons and
electrons, is needed to convert light into chemical energy on
solid surfaces, as well as by light-harvesting proteins.
PINSE is an integrated, multidisciplinary organization that brings
coherence to the University’s research efforts and resources in
the fields of nanoscale science and engineering. More information
about PINSE can be found at www.nano.pitt.edu.
The work for the PRL paper was performed at the Max Planck
Institute of Microstructure Physics in Halle, Germany, where Petek
was an Alexander von Humboldt Senior Scholar and Nyvlt was the
group leader. Other authors on the paper are Francesco Bisio, now
at the University of Genoa; Jirka Franta, now at Charles
University; and Jurgen Kirschner, director of the Max Planck
Institute.
That work was supported by the Alexander von Humboldt Foundation,
the U.S. National Science Foundation, the Italian National
Research Council, and the Czech Ministry of Education.
In addition to Petek and Jordan, authors on the Science paper are
postdoctoral fellows Jin Zhao and Ken Onda and graduate student
Bin Li, all of Pitt's Department of Physics and Astronomy, and
Jinlong Yang of the University of Science and Technology of China.
The work was supported by the U.S. Department of Defense
Multidisciplinary University Research Initiative program, the New
Energy Development Organization of Japan, and the National Science
Foundations of the United States and China.
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University of Pittsburgh Announces $5 Million Gift to Advance
Nanoscale Science and Engineering Research
Gift from John M. and Gertrude E.
Petersen for Pitt's Institute of NanoScience and Engineering gives
the University a competitive edge as an international leader in a
new and potentially revolutionary field
Big research push from matter as small as one eighty-thousandth of
the width of a human hair
PITTSBURGH-The University of
Pittsburgh has received a $5 million gift from alumnus John M.
Petersen and his wife, Gertrude, to create an endowment supporting
research in nanoscale science and technology at Pitt's Institute
of NanoScience and Engineering, now the Gertrude E. and John M.
Petersen Institute of NanoScience and Engineering.
Nanoengineering and nanotechnology use atoms and molecules as
basic blocks to build minute machines, create new materials, and
perform new molecular tasks. In a major push to advance the
frontiers of the promising nanoscience field, which has energized
researchers worldwide, Pitt enjoys a competitive edge through its
newly endowed Petersen Institute. Pitt researchers in the
institute, founded in 2002, focus at the “essentially nano” level
(less than 10 nanometers, each nanometer approximately one
eighty-thousandth of the width of a human hair), where the
greatest breakthroughs in nanoscience are expected to occur,
offering the potential for previously unimagined progress in a
wide variety of areas. Work already done by institute researchers
has resulted in the development of color-shifting paints, a
contact lens-embedded sensor with the potential for noninvasive
glucose-level monitoring for diabetes, and scaffolding to heal
damaged hearts.
Within the last three years, Pitt-developed nanotechnology has
been licensed to three start-up companies and one major
corporation. The National Science Foundation predicts that the
market for nanotech products and services will reach $1 trillion
by the year 2015.
John Petersen, the retired president and chief executive officer
of the Erie Insurance Group in Erie, Pa., earned the Bachelor of
Business Administration degree at Pitt in 1951. He was among the
first students to live on campus at Pitt, where he earned varsity
athletics letters as a member of the swimming and diving team. The
Petersens have maintained a strong relationship with the
University through their support of a variety of University
programs, including their gift to name Pitt's John M. and Gertrude
E. Petersen Events Center, home of what is considered the nation's
premier on-campus basketball arena. Both avid fans of Pitt
athletics, the Petersens recently continued their longstanding
support of the Department of Athletics with a gift of $600,000 to
support baseball and swimming scholarships.
“John and Gertrude Petersen have been extraordinarily loyal and
generous to the University over the years. Their gift to support
the construction of the Petersen Events Center helped elevate both
our men's and women's basketball programs to remarkable new
heights and also gave us the chance to hold commencement on campus
and to host such special events as the National Senior Olympics
and the Jeopardy! College Championship,” said Pitt Chancellor Mark
A. Nordenberg. “Their more recent gift to support our
nanotechnology initiatives positions the newly named Petersen
Institute to be an international leader in the field, to solve
complex scientific and engineering challenges, and to develop new
technologies with the potential for commercial applications.”
The scientists and engineers who make up Pitt's Petersen Institute
are experts in designing, characterizing, and fabricating
nanoscale materials, devices, and systems. The researchers, drawn
from the University's Schools of Arts and Sciences, Engineering,
and the Health Sciences, form flexible, cross-disciplinary teams
to investigate major questions in nanoscience and engineering.
Fall 2006 will mark the opening of Pitt's 4,000-square-foot
nanoscale fabrication and characterization facility, located in
Benedum Hall, which will house the best available technology in a
single location and allow researchers to observe and manipulate
materials at the atomic level.
“Exciting advances are on the horizon through the study of
phenomena at length scales of only a few nanometers,” said Pitt
Provost James V. Maher. “The increased scientific understanding we
gain will lead to technological breakthroughs, and the resulting
improved technology will allow us to deepen our understanding of
the science. This gift greatly enhances the sizeable commitment
that Pitt is making to position ourselves as a leader in this
field.”
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Pitt nanotech researcher devises versions of building blocks on a
molecular scale
Sweating the very small stuff
Monday, November 21, 2005
By Byron Spice, Pittsburgh
Post-Gazette
Nanotechnology is a buzzword that
often brings to mind images of microscopic gears and springs
etched into silicon wafers.
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Tony Tye, Post-Gazette
Christian Schafmeister
of the University of Pittsburgh has developed a system for
building nanodevices using molecular building blocks.
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But if you really want to build
nanomachines, ones measured in billionths of meters, or
nanometers, it makes sense to consider the nanomachines of nature
-- proteins.
That's what
Christian Schafmeister did.
"We've got 40,000 of these machines
in our bodies that make us what we are," explained the University
of Pittsburgh chemist. Proteins digest our food, move our arms and
transport materials. And the beauty of it is that all are made
from about 20 different types of building blocks, called amino
acids.
Taking this cue from nature, Dr.
Schafmeister and his students have spent the last five years
concocting their own set of 14 building blocks -- the molecular
equivalent of Lego pieces.
By his estimation, that's enough to
make roughly 140 trillion structures. So creating different shapes
is no longer the challenge; rather, "it's finding those sequences
that do interesting things," he said.
New types of pharmaceuticals,
chemical catalysts and sensors are all among the possibilities.
"We haven't made a big splash with
this yet," acknowledged Dr. Schafmeister, an assistant professor
of chemistry and a researcher at Pitt's
Institute of
NanoScience and Engineering. But that should change once
applications are identified, something he hopes will occur within
the next year.
Even so, the work already has drawn
attention within the nanotech community. Last month, the Foresight
Nanotech Institute, a nanotechnology think tank, awarded its
Feynman Prize for experimental work to Dr. Schafmeister and its
Distinguished Student Award to one of his graduate students,
Christopher Levins, who developed one of the building blocks.
"It's the most impressive work
we've seen on the pathway to building useful three-dimensional
structures with atomic precision," said Christine Peterson,
Foresight's founder and vice president for public policy. "The
biggest payoffs across the board in nanotechnology . . . are from
reaching the ultimate goal of atomic precision."
Controlling the position of each
atom within a molecule would be difficult to achieve simply by
trying to build molecules out of the same amino acids used so
skillfully by nature.
Trouble is, as good as humans may
be with their hands, they still lack the intellectual dexterity
needed to build machines with amino acids. Arrange a set of amino
acids one way and you've made an enzyme; rearrange the same amino
acids and you've got a muscle component.
The reason for these dramatically
different functions lies in what's called the protein folding
problem. Proteins are more than just long, floppy chains of amino
acids; their function depends in large part on their shape, how
they fold themselves up. And the rules that govern that folding
procedure are only dimly understood.
During four years of graduate
school at the University of California, San Francisco, Dr.
Schafmeister designed his own protein, called 4HB1, with 180 amino
acids. "It's a molecular doorstop," he said wistfully, gazing at
its structure on his computer monitor. "It doesn't do anything.
But it is well-folded."
So he reasoned that to control the
shape of his molecules -- and thus increase the chances of
designing a molecule that does something -- he would need to
eliminate the folding problem. And that meant developing molecular
building blocks with rigid connections between them.
Rigid connections
Amino acids connect to each other with single
bonds, creating chains with all of the rigidity of a string of
plastic beads. He and his students devised blocks with a pair of
bonds, creating rigid connections between the molecules much like
those between Lego blocks.
Most of the blocks have been
processed from 4-hydroxyproline, a form of the amino acid proline
obtained commercially from chicken feathers; two are processed
from the amino acid tyrosine. Making the building blocks "is
boring chemistry, pedestrian chemistry," he said, and
intentionally so. Though he and his students now make their own
building blocks, he hopes that someday they will be churned out in
large quantities by industry.
The building blocks each have a
different shape, though they are not as simple as pieces of an
Erector set -- no straight sections, or right angles. All twist a
bit in three dimensions, but can be assembled to form a number of
shapes.
Simply repeating the same building
block will form something roughly rod-shaped. Alternating a block
with a mirror-image block will form a horseshoe- or ring-shaped
molecule. Dr. Schafmeister has devised a software program that can
show a designer the options available for shaping a molecule with
each of the available building blocks.
"You can sculpt almost anything,"
said William A. Goddard III, director of the Materials and Process
Simulation Center at the California Institute of Technology.
"Proteins are like a piece of string, but his structure is like
having a wide ribbon" that can be used to build all sorts of
three-dimensional objects.
This "bottom-up" approach to
building nanotech devices still must be further developed, but
eventually will be essentially for building nanomachines, he
suggested.
The "top-down" approach,
particularly that used by the semiconductor industry, may soon
reach its limits, Dr. Goddard explained. Computer chip makers, who
etch transistors and wires into silicon wafers, now are preparing
to build devices measuring 130 nanometers and have begun to
struggle with 90 nanometer devices.
Increasingly smaller component
sizes have been the key to "Moore's Law," the concept that chip
capabilities roughly double every year or so. On the horizon are
45- and 32-nanometer components. But within 10 years, he said,
continued progress may depend on switching over from a top-down to
a bottom-up strategy.
"There's a good chance that by
2015, this might be the only solution to maintaining Moore's Law,"
he added.
Dr. Schafmeister envisions using
his building blocks, each measuring about half a nanometer, to
build little boxes with lids that could serve as sensors; when a
molecule of interest enters the box, the lid would shut and send a
signal. The blocks might also be used as scaffolding to construct
customized catalysts, which promote certain chemical reactions, or
to build artificial antibodies.
He also is exploring the use of his
building blocks for devising multivalent drugs -- drugs that bind
to multiple receptors on the surface of cells, thus blocking
toxins, such as cholera. Unlike the floppy molecules that now
carry sugars designed to bind with these receptors, Dr.
Schafmeister's rigid molecules could hold the sugars at the same
precise distance as the spacing of the receptors on the cell.
"I have so many applications I want
to try," he said. Though it's not clear which one is likely to
prove itself first, he has encountered few limitations to the
underlying building blocks themselves.
"If there are walls," he said, "we
haven't hit them yet."
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Pitt
Professor, Student Win Nanotechnology Prize for Work on "Molecular
Lego(r) Set"
Molecules promising as nanoscale
parts for atomically precise machines
PITTSBURGH-A University of Pittsburgh researcher has been
awarded a prestigious prize from the Foresight Nanotech Institute
for his work in developing a "molecular Lego(r) set" that will
enable, for the first time, the quick manufacture of sturdy,
predictable nanostructures.
Christian Schafmeister, assistant professor of chemistry at the
University of Pittsburgh and a researcher in the University's
Institute of NanoScience and Engineering (INSE), was awarded the
2005
Foresight Institute Feynman Prize for experimental work, named in
honor of pioneer physicist Richard Feynman. He received the award
at a banquet Oct. 26.
Schafmeister has designed 14 small molecules, each about 0.5
nanometers across. Each includes two removable molecular caps.
Controlled chemical reactions strategically strip the caps away,
causing the molecules to link together in predictable ways with
pairs of stiff bonds-similar to Lego(r) blocks. He has snapped
together 2.5-nanometer rods and 1.5-nanometer crescents, and has
developed software that can aid in the construction of a wide
variety of shapes.
With this method of nanofabrication, which he calls "a completely
new field," Schafmeister is using his blocks to craft hinged,
molecular traps that attract specific molecules, snap shut, and
light up, serving as perfect chemical sensors-just one of an
almost infinite number of possible uses. Molecules with customized
cavities could serve as catalysts or biomedical agents. Because
the molecules are
large enough to have interesting functions and rigid, designed
shapes, they hold great promise as nanoscale parts for future
atomically precise nanoscale machines.
"We're developing a new programming language for matter," said
Schafmeister, "and we're writing, 'Hello, world.'"
Schafmeister's student Christopher Levins, a doctoral candidate in
chemistry, received the Foresight Distinguished Student Award for
work that he did within the umbrella of Schafmeister's research.
"Chris
made some of the first breakthroughs-building blocks and larger
structures-in our research," said Schafmeister.
"We're proud to see Dr. Schafmeister and his student awarded for
nanotechnology research," said University Provost James V. Maher.
"Pitt's program in nanoscience is focused on platform
technologies,
like Dr. Schafmeister's, that will have a great affect on future
research and applications."
The Foresight Nanotech Institute is the leading think tank and
public interest organization focused on nanotechnology. Founded in
1986, its mission is to ensure the beneficial implementation of
nanotechnology.
The INSE is an integrated, multidisciplinary organization that
brings coherence to the University's research efforts and
resources in the fields of nanoscale science and engineering.
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New Nanofabrication Capability Makes Pitt Unique in United
States
PITTSBURGH-The University of Pittsburgh recently became the
only institution in the United States and only the second in the
world to have a unique nanofabrication capability. Eight
researchers in Pitt's Institute of NanoScience and Engineering (INSE)
have just completed a week of training on the new Raith electron
beam Lithography and Nano Engineering (eLiNE) workstation.
The eLiNE system allows researchers to create nanometer-scale
structures using an electron beam that is focused to less than two
nanometers. A unique feature of this instrument is an electron
beam-induced deposition and etching capability that allows metals,
insulators, and semiconductors to be added or removed, using the
electrons as a nanocatalyst. This new capability only recently has
become commercially available.
Pitt students and faculty from various disciplines, including
electrical engineering, biomedical engineering, physics, and
chemistry, are scheduled for training.
“In a sense, it's like having a machine shop, only a million times
smaller,” said Jeremy Levy, Pitt professor of physics and
astronomy and the faculty member in charge of training new users
and maintaining the instrument.
“What is exciting is that researchers have come to the initial
training session with some precursory ideas about what they want
to do, but after seeing all of the capabilities, their outlooks
change; completely new approaches now seem possible,” Levy added.
The eLiNE system is the first of three major pieces of
instrumentation available at INSE. The other two instruments, a
focused ion beam system and a transmission electron microscope,
are scheduled for delivery in early 2006.
The INSE is an integrated, multidisciplinary organization that
brings coherence to the University's research efforts and
resources in the fields of nanoscale science and engineering.
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UCLA Scientist to Present
Provost Lecture on "Nano Meccano" Oct. 7 at Science2005
The research of this third-most-cited chemist has led to
breakthroughs in product synthesis and nanotechnology
PITTSBURGH--An internationally recognized pioneer in the field
of supramolecular chemistry--the chemistry beyond the
molecule-from the University of California, Los Angeles (UCLA),
will present the Provost Lecture at the University of
Pittsburgh's fifth annual showcase of science and technology,
Science2005: The New Research Ecology.
J. Fraser Stoddart, the Fred Kavli Chair of NanoSystems Sciences
and director of the California NanoSystems Institute at UCLA,
will speak at 11 a.m. Friday, Oct. 7, in the 7th floor
auditorium of Alumni Hall at the University of Pittsburgh. The
title of his lecture is "Nano Meccano: An Integrated
Systems-Oriented Approach to Molecular Electronics."
Stoddart's work focuses on elucidating the natural processes of
molecular recognition and self-assembly and applying that
dynamic to directed activities in both the life and materials
sciences, leading to a number of breakthroughs in product
synthesis and nanotechnology. According to the Institute for
Scientific Information, Stoddart is currently the third most
cited chemist in academia.
Stoddart's research has given scientists a much better
understanding of the information and instructions stored in the
covalent frameworks of supramolecular architectures. By learning
from existing supramolecular systems that use weak noncovalent
bonding to undergo self-organization, Stoddart has developed
unique mechanical interlocked molecules, often involving
interlocking rings and dumbbells that function as molecular
switches on the nanoscale. (A nanometer is one-billionth of a
meter, or
10,000 times smaller than the thickness of a human hair.) These
molecules are not only useful in and of themselves, but they
represent the beginning of a series of developments that may
give researchers
unprecedented control over the structural and dynamic
organization of matter.
"Building artificial molecular machines and getting them to
operate is where airplanes were a century ago," said Stoddart.
"We have come a long way in the last decade, but we have a very,
very long way to go yet to realize the full potential of
artificial molecular machines." However, a number of
futuristic-sounding concepts and materials already have been
inspired by his work, including nanofibers that can improve
sensor response, an artificial molecular machine that can move
up and down between two levels like an elevator, and a
molecule-trapping nanovalve that could potentially be used as a
drug delivery system.
Stoddart received the Ph.D. and D.Sc. degrees from Edinburgh
University in Scotland. In 1997, he arrived at UCLA as the Saul
Winstein Professor of Chemistry. Stoddart has published more
than 725 scientific papers. He is an associate editor of Organic
Letters and is currently on the international advisory boards of
numerous journals, including Angewandte Chemie and the Journal
of Organic Chemistry. Among his many honors are the Carnegie
Centenary Professorship at the Universities of Scotland (2005),
the Nagoya Gold Medal in Organic Chemistry (2004), the American
Chemical Society's Cope Scholar Award (1999), and the
International Izatt-Christensen Award in Macrocyclic Chemistry
(1993). Stoddart was elected to fellowship in the Royal Society
of London in 1994 and to
membership in the German Academy of Natural Sciences Leopoldina
in 1999.
The Provost Lecture is presented by Pitt's Office of the
Provost. "The University is keenly interested in nanotechnology,
and the provost has allocated considerable resources to this
exciting new venture," said George Klinzing, Pitt vice provost
for research.
Science2005 will explore some of today's leading areas of
research at the University of Pittsburgh and throughout the
region that are characterized by increasingly interrelated
disciplines working together
to shed light on new pathways to discovery. The free, public
program, which will take place Oct. 6-7 in Alumni Hall, will
feature keynote lectures by some of America's leading scientists
and symposium sessions on timely research topics as diverse as
neuroimaging, whole genome analysis, nanoscience, the science of
aging, structural biology, Einsteinian principles, and more. For
more information or advance registration, go to
www.science2005.pitt.edu.
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"Wet"
Electrons Provide Easiest Way to Transport Charge,
Pitt Researchers Find
Technology
has potential to produce clean fuel "if we could make it
more efficient"
PITTSBURGH- The
task of transporting electrical charges between metal-oxide and
water phases is critical in such technologies as catalysis, sensors,
and electrochemistry. In a paper published in this week's issue
of the journal Science, University of Pittsburgh researchers report
that "wet"electrons afford the lowest energy pathway
for transporting electrons between solid and liquid states.
In their paper,
titled "Wet electrons at the H2O/TiO2(110) Surface,"
Hrvoje Petek, Pitt professor of physics and codirector of Pitt's
Institute of NanoScience and Engineering, and Kenneth Jordan,
professor and chair of Pitt'ss Department of Chemistry, extend
Jordan's previous work on the structure of electrons in small
water clusters, which was named one of the top 10 breakthroughs
of 2004 by Science.
Wet electrons,
which occur on metal oxide surfaces, represent a transition point
for electrons between solid and liquid states of matter. A tiny
amount of water from the atmosphere sticks to the surfaces of
the oxides and forms hydroxide molecules, which then act like
"molecular-scale Velcro" said Petek. In the presence
of energy, their positively charged hydrogen atoms attract negatively
charged electrons. Those so-called "wet" electrons then
determine how other molecules interact with the surfaces of metal
oxides.
The researchers
gave the electrons sufficient energy to achieve the wet state
by directing short bursts of laser light at titanium dioxide.
Titanium dioxide was used because it is a photocatalyst: Exposure
to light excites its electrons, which split water molecules into
hydrogen and oxygen. Because of this potential for making hydrogen
from water, it is possible that titanium dioxide could be used
to make a clean fuel-but the process remains inefficient, said
Petek. "If we could find out how to make it more efficient
by observing how electrons interact with hydrogen atoms, it would
have a huge economic impact," he added.
Petek's research could also illuminate the interaction between
protons and electrons in such biological processes as photosynthesis,
in which the light energy is converted to chemical energy through
correlated transport of protons and electrons, which Petek calls
similar to a wet electron system "on a fundamental level."
Petek plans
to continue research on the properties of other oxide materials.
In their paper, the researchers note that conditions exist to
support similar states on all oxide surfaces in contact with water
or with a humid atmosphere.
The paper's
other authors are Ken Onda, Bin Li, and Jin Zhao, graduate students
and postdoctoral researchers in Pitt's Department of Physics and
Astronomy, and Jinlong Yang, a professor at the University of
Science and Technology of China.
This research
was supported by the U.S. Department of Defense Multidisciplinary
University Research Initiative program, the New Energy and Industrial
Technology Development Organization (Japan), and the National
Science Foundation.
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Pitt
Researcher, Colleagues Create Self-Assembling Nanoparticle/Polymer
Mixtures
New findings represent significant advance toward
manufacture of nanodevices, researchers announce in Nature
PITTSBURGH ---- A University of Pittsburgh
researcher and her colleagues announced today in the journal Nature
that they have created self-assembling mixtures of nanoparticles
and polymer layers that spontaneously assume different orientations.
Their findings have applications in such areas as chemical sensing,
data storage, and photonic materials.
In a paper titled "Self-Directed Self-Assembly of Nanoparticle/Copolymer
Mixtures," Anna Balazs, Robert Von der Luft Professor in
the Department of Chemical and Petroleum Engineering in Pitt's
School of Engineering and a researcher in Pitt's Institute for
NanoScience and Engineering, Thomas Russell of the University
of Massachusetts Amherst, and their colleagues described a method
with significant advantages over previous research.
While self-assembling processes are common in biological systems,
such multiple-step processes are difficult to engineer synthetically.
Previous research required intervention at each step of the process,
but Balazs and her colleagues created a two-step process that
only requires one intervention.
"What is unique about this study is that it has two interlocking
self-assembling steps," said Balazs. "This is one-stop
shopping."
The researchers began with thin films of copolymers-two types
of polymer joined together-spread onto a surface. When equal amounts
of each polymer are present, the copolymers arrange themselves
int
