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Topic Name: Researchers found "shrink-wrapping" is the key; buckyballs start life as distorted
Category: Organic electronics
Research persons: Huang, Boris I. Yakobson, Ph.D.
Location: Sandia National Laboratory, United States
Details
The birth secret of buckyballs -- hollow spheres of carbon no wider than a
strand of DNA -- has been caught on tape by researchers at Sandia
National Laboratory and Rice University.
An electron microscope video and computer simulations show that
"shrink-wrapping" is the key; buckyballs start life as distorted,
unstable sheets of graphite, shedding loosely connected threads and chains until
only the perfectly spherical buckyballs remain.
The research is available online and slated to appear in an upcoming issue of
Physical Review Letters (PRL). It is among a small number of PRL papers chosen
as an "Editors' Suggestion."
Buckyballs were discovered at Rice in 1985, but understanding the intimate
details their formation has vexed scientists. Buckyballs form at high
temperatures, and one long-standing theory of their genesis is the "hot
giant" hypothesis, which suggests that the carbon atoms first assemble by
the thousands in flat graphite sheets. Heat distorts the sheets, "shrink
wrapping" them into ever-smaller shapes, and buckyballs survive thanks to
their perfect symmetry.
"This 'hot evolution' is so rapid that it was nearly impossible to prove or
disprove it by experimental observation," said study co-author Boris
Yakobson, professor of mechanical engineering and materials science at Rice.
"Sandia's Jianyu Huang solved this problem by creating an ingenious,
controllable heat bath inside a 10-nanometer-wide nanotube. That allowed him to
capture video of giant fullerenes gradually shrinking."
Huang, who performed the experiments while at Boston College and analyzed the
data at Sandia, said the results constitute the first experimental evidence for
the 'shrink-wrapping' and 'hot-giant' fullerene birth mechanisms.
Huang captured the high-resolution images using a transmission electron
microscope (TEM). The video shows a large fullerene, with an estimated 2,000
atoms of carbon gradually shrinking. It confirmed predictions about the atomic
mechanisms that Yakobson's team at Rice had made based on detailed computer
simulations.
"If heat is sustained, as it was when we took these images, the fullerenes
undergo a further shrinking and vanish," Huang said. "This confirms an
aspect of 'shrink wrapping' theory that was predicted by Rice's Rick Smalley and
Bob Curl made shortly after they discovered fullerenes."
Huang and Yakobson said it may be possible to exploit the findings to control
the fullerene formation process and tailor fullerenes for a variety of
applications.
Co-authors of the research include research scientist Feng Ding and graduate
student Kun Jiao, both of Rice. The research was funded by the Office
of Naval Research and the Department of
Energy's Center for Integrated Nanotechnologies.
Note for Transmission electron microscopy
Transmission electron microscopy (TEM) is an imaging technique whereby a beam
of electrons is transmitted through a specimen, then an image is formed,
magnified and directed to appear either on a fluorescent screen or layer of
photographic film (see electron microscope), or to be detected by a sensor such
as a CCD camera. The first practical transmission electron microscope was built
by Albert Prebus and James Hillier at the University of Toronto in 1938 using
concepts developed earlier by Max Knoll and Ernst Ruska.
The TEM is used heavily in both material science/metallurgy and the
biological sciences. In both cases the specimens must be very thin and able to
withstand the high vacuum present inside the instrument.
For biological specimens, the maximum specimen thickness is roughly 1 micrometre.
To withstand the instrument vacuum, biological specimens are typically held at
liquid nitrogen temperatures after embedding in vitreous ice, or fixated using a
negative staining material such as uranyl acetate or by plastic embedding.
Typical biological applications include tomographic reconstructions of small
cells or thin sections of larger cells and 3-D reconstructions of individual
molecules via Single Particle Reconstruction.
Note for Shrinkwrap
Shrinkwrap, also shrink wrap or shrink film, is a material made up of polymer
plastic film. When heat is applied to this material it shrinks tightly over
whatever it was covering.
Shrinkwrap is commonly used as an overwrap on many types of packaging: CDs, DVDs,
cartons, books, beverage cans, large appliances, pallet loads, etc. It can be
the primary covering for some foods such as cheese and meats. It is also used to
cover boats after manufacture and for winter storage.
Heat-shrink tubing is used to seal electric wiring.
Shrink bands are applied over parts of packages for tamper resistance or labels.
It can also combine two packages or parts.
The most commonly used shrink wrap is polyolefin. It is available in a variety
of thicknesses, clarities, strengths and shrink ratios. The two primary films
are either crosslinked, or non crosslinked. Other shrink films include PVC and
several other compositions.
Coextrusions and laminations are available for specific mechanical and barrier
properties for shrink wrapping food.
Current trends are to improve film properties which may lead to reduced caliper
(source reduction) and to improve process efficiency (cost and energy savings).
About Sandia National Laboratories
Sandia National Laboratories, which is managed and operated by the Sandia
Corporation (a wholly owned subsidiary of Lockheed Martin Corporation), is a
major United States Department of Energy research and development national
laboratory with two locations, one in Albuquerque, New Mexico and the other in
Livermore, California. Its primary mission is to develop, engineer, and test the
non-nuclear components of nuclear weapons. Its main secured campus is ~4.4
square miles (11 km²) and is located on Kirtland Air Force Base. Sandia is a
National Nuclear Security Administration laboratory.
It is Sandia's mission to maintain the reliability and surety of nuclear weapon
systems, conduct research and development in arms control and nonproliferation
technologies, and investigate methods for the disposal of the US's nuclear
weapons program's hazardous waste. Other missions include research and
development in energy and environmental programs, as well as the surety of
critical national infrastructures. In addition, Sandia is home to a wide variety
of research including computational biology, mathematics (through its Computer
Science Research Institute), materials science, alternative energy, psychology,
and cognitive science initiatives. Sandia formerly hosted ASCI Red, one of the
world's fastest supercomputers until its recent decommission, and now hosts ASCI
Thor's Hammer. Sandia is also home to the Z Machine. The Z Machine is the
largest X-ray generator in the world and is designed to test materials in
conditions of extreme temperature and pressure. It is operated by Sandia
National Laboratories to gather data to aid in computer modeling of nuclear
weapons.
About Office of Naval Research
The U.S. Office of Naval Research (ONR), headquartered in Arlington, Virginia (Ballston), is the office within the U.S. Department of the Navy that coordinates, executes, and promotes the science and technology programs of the U.S. Navy and Marine Corps through schools, universities, government laboratories, and nonprofit and for-profit organizations.
ONR, as it is frequently referred to, reports to the U.S. Secretary of the Navy through the Assistant Secretary of the Navy for Research, Development and Acquisition. It executes its mission through:
Science & Technology Departments
ONR Corporate Programs
Naval Research Laboratory (NRL)
ONR Global Office
In 2007, a Naval S&T Strategic Plan was developed to describe how ONR will enable the future operational concepts of the Navy and the Marine Corps. By design, it is a broad strategy that provides strong direction for the future, but it also retains sufficient flexibility and freedom of action to allow ONR to meet emerging challenges or alter course as directed by senior Naval leadership.
About Center for Integrated Nanotechnologies
The Center for Integrated Nanotechnologies is one of five Nanoscale Science Research Centers the United States Department of Energy sponsors. The Center's "core facility" is located in Albuquerque, New Mexico.
About Researcher:
Boris I. Yakobson, Ph.D.
Professor in Materials Science
Computational Materials Science
PH.D. (1982)
Russian Academy of Sciences
Professor Yakobson's research interests are in theory and modeling of
structure, kinetics, and properties of materials, derived from both macroscopic
and fundamental molecular interactions. Computational methods and simulation are
used to visualize and enhance the understanding of underlying physics and to
identify the efficient degrees of freedom in complex systems, especially in
connecting different length scales of description. He is an editorial board
member of the Journal of Nanoparticle Research and a member of the American
Physical Society and the Electrochemical Society.
Contact Information
biy@rice.edu www.ruf.rice.edu/~biy
Office: 201 MEB
713.348.3572
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