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A schematic of graphene nanoribbon field-effect transistor with palladium contacts (S,D) on a 10 nm thick insulating silicon dioxide surface (purple). Beneath the Si02 layer is a highly conductive silicon layer (G). Credit: Stanford University.

Stanford chemists have developed a new way to make transistors out of carbon nanoribbons. The devices could someday be integrated into high-performance computer chips to increase their speed and generate less heat, which can damage today’s silicon-based chips when transistors are packed together tightly.

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Stanford chemists have developed a new way to make transistors out of carbon nanoribbons. The devices could someday be integrated into high-performance computer chips to increase their speed and generate less heat, which can damage today’s silicon-based chips when transistors are packed together tightly. For the first time, a research team led by Hongjie Dai, the J. G. Jackson and C. J. Wood Professor of Chemistry, has made transistors called “field-effect transistors”—a critical component of computer chips—with graphene that can operate at room temperature. Graphene is a form of carbon derived from graphite. Other graphene transistors, made with wider nanoribbons or thin films, require much lower temperatures.

“For graphene transistors, previous demonstrations of field-effect transistors were all done at liquid helium temperature, which is 4 Kelvin [-452 Fahrenheit],” said Dai, the lead investigator. His group’s work is described in a paper published online in the May 23 issue of the journal Physical Review Letters.

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Microcantilever actuators made from carbon nanotube (CNT)-polymer composites could dramatically improve the performance of microelectromechanical systems, according to scientists in Taiwan. The researchers from National Tsing Hua University have developed an easy to actuate material that rapidly suppresses unwanted oscillations thanks to a low quality factor.

“Lightweight and highly flexible CNT-composites provide fast electrothermo-actuation at low power,” Weileun Fang told nanotechweb.org. “Moving the actuator from its original position to its pull-in position can be employed to define two different states such as 0/1 or on/off, which suits many applications in communications and displays.”

The group’s nanocomposite device has a pull-in voltage of just 50?V for a full deflection of 560?µm. As Fang explains, this value is very low compared with existing microcantilevers, which can demand at least 500?V to achieve a similar displacement. The researchers believe that CNT-based field amplification is responsible for the low pull-in voltage.

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Carbon cages can hold super-dense volumes of nearly metallic hydrogen. Hydrogen could be a clean, abundant energy source, but it’s difficult to store in bulk.

In new research, materials scientists at Rice University have made the surprising discovery that tiny carbon capsules called buckyballs are so strong they can hold volumes of hydrogen nearly as dense as those at the center of Jupiter.

The research appears on the March 2008 cover of the American Chemical Society’s journal Nano Letters.

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Mark Jacobson, professor of civil and environmental engineering, has released a study showing direct links between an increase in carbon dioxide emissions and an increase in resulting deaths, a particularly relevant finding in light of the December decision by the EPA denying California and other states the right to set their own limits on carbon dioxide emissions.

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Bypassing decades-old conventions in making computer chips, Princeton engineers developed a novel way to replace silicon with carbon on large surfaces, clearing the way for new generations of faster, more powerful cell phones, computers and other electronics.

The electronics industry has pushed the capabilities of silicon — the material at the heart of all computer chips — to its limit, and one intriguing replacement has been carbon, said Stephen Chou, professor of electrical engineering. A material called graphene — a single layer of carbon atoms arranged in a honeycomb lattice — could allow electronics to process information and produce radio transmissions 10 times better than silicon-based devices.

Until now, however, switching from silicon to carbon has not been possible because technologists believed they needed graphene material in the same form as the silicon used to make chips: a single crystal of material 8 or 12 inches wide. The largest single-crystal graphene sheets made to date have been no wider than a couple millimeters, not big enough for a single chip. Chou and researchers in his lab realized that a big graphene wafer is not necessary, as long they could place small crystals of graphene only in the active areas of the chip. They developed a novel method to achieve this goal and demonstrated it by making high-performance working graphene transistors. 

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New technology could enable new cancer treatment techniques and antibacterial coatings

Troy, NY — Researchers at Rensselaer Polytechnic Institute have developed a new way to seek out specific proteins, including dangerous proteins such as anthrax toxin, and render them harmless using nothing but light. The technique lends itself to the creation of new antibacterial and antimicrobial films to help curb the spread of germs, and also holds promise for new methods of seeking out and killing tumors in the human body.

Scientists have long been interested in wrapping proteins around carbon nanotubes, and the process is used for various applications in imaging, biosensing, and cellular delivery. But this new study at Rensselaer is the first to remotely control the activity of these conjugated nanotubes. Details of the project are outlined in the article “Nanotube-Assisted Protein Deactivation” in the December issue of Nature Nanotechnology.

A team of Rensselaer researchers led by Ravi S. Kane, professor of chemical and biological engineering, has worked for nearly a year to develop a means to remotely deactivate protein-wrapped carbon nanotubes by exposing them to invisible and near-infrared light. The group demonstrated this method by successfully deactivating anthrax toxin and other proteins.

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