‘Butterfly’ molecule could build sensors, photoenergy devices


U of FLA Sensors bmaExciting new work by a Florida State University research team has led to a novel molecular system that can take your temperature, emit white light, and convert photon energy directly to mechanical motions.

And, the molecule looks like a butterfly.

Biwu Ma, associate professor in the Department of Chemical and Biomedical Engineering in the FAMU-FSU College of Engineering, created the molecule in a lab about a decade ago, but has continued to discover that his creation has many other unique capabilities.

U of FLA Sensors bma

For example, the molecular butterfly can flap its “wings” and emit both blue and red light simultaneously in certain environments. This dual emission means it can create white light from a single molecule, something that usually takes several luminescent molecules to achieve.

And, it is extremely sensitive to temperature, which makes it a thermometer, registering temperature change by emission color.

“This work is about basic, fundamental science, but also about how we can use these unique findings in our everyday lives,” Ma said.

Among other things, Ma and his team are looking at creating noninvasive thermometers that can take better temperature readings on infants, and nanothermometers for intracellular temperature mapping in biological systems. They are also trying to create molecular machines that are operated simply by sunlight.

“These new molecules have shown very interesting properties with a variety of potential applications in emerging fields,” Ma said. “I have been thinking of working on them for quite a long time. It is so wonderful to be able to make things really happen with my new team here in Tallahassee.”

The findings are laid out in the latest edition of the academic journal Angewandte Chemie. Other authors for this publication are Mingu Han, Yu Tian, Zhao Yuan and Lei Zhu from the Chemistry and Biochemistry Department. Florida State has also filed a patent application on the work.

Ma came to Florida State in 2013 from the Lawrence Berkeley National Laboratory as part of a strategic push by the university to aggressively recruit and hire up-and-coming researchers in energy and materials science.

In addition to the faculty hires, the university has invested in top laboratory space and other resources needed to help researchers make technology breakthroughs.

“This type of research is why we continue to invest in materials science and recruit faculty like Biwu Ma to Florida State,” said Vice President for Research Gary K. Ostrander. “Making this area of research a priority shows why FSU is a preeminent institution, and we look forward to what Biwu and our other scientists can accomplish in the years to come.”

Space Elevators? Super Strong Materials? All from Diamonds Ultra-Thin Nanothreads


Nano Diamonds 201409229914891For the first time, scientists have discovered how to produce ultra-thin “diamond nanothreads” that promise extraordinary properties, including strength and stiffness greater than that of today’s strongest nanotubes and polymers. A paper describing this discovery by a research team led by John V. Badding, a professor of chemistry at Penn State University, will be published in the 21 September 2014 issue of the journal Nature Materials. “From a fundamental-science point of view, our discovery is intriguing because the threads we formed have a structure that has never been seen before,” Badding said.

The core of the nanothreads that Badding’s team made is a long, thin strand of carbon atoms arranged just like the fundamental unit of a diamond’s structure — zig-zag “cyclohexane” rings of six carbon atoms bound together, in which each carbon is surrounded by others in the strong triangular-pyramid shape of a tetrahedron. “It is as if an incredible jeweler has strung together the smallest possible diamonds into a long miniature necklace,” Badding said. “Because this thread is diamond at heart, we expect that it will prove to be extraordinarily stiff, extraordinarily strong, and extraordinarily useful.”

The team’s discovery comes after nearly a century of failed attempts by other labs to compress separate carbon-containing molecules like liquid benzene into an ordered, diamondlike nanomaterial. “We used the large high-pressure Paris-Edinburgh device at Oak Ridge National Laboratory to compress a 6-millimeter-wide amount of benzene — a gigantic amount compared with previous experiments,” said Malcolm Guthrie of the Carnegie Institution for Science, a coauthor of the research paper. “We discovered that slowly releasing the pressure after sufficient compression at normal room temperature gave the carbon atoms the time they needed to react with each other and to link up in a highly ordered chain of single-file carbon tetrahedrons, forming these diamond-core nanothreads.” Nano Diamond 2 201409229914890

Badding’s team is the first to coax molecules containing carbon atoms to form the strong tetrahedron shape, then link each tetrahedron end to end to form a long, thin nanothread. He describes the thread’s width as phenomenally small, only a few atoms across, hundreds of thousands of times smaller than an optical fiber, enormously thinner that an average human hair. “Theory by our co-author Vin Crespi suggests that this is potentially the strongest, stiffest material possible, while also being light in weight,” he said.

The molecule they compressed is benzene — a flat ring containing six carbon atoms and six hydrogen atoms. The resulting diamond-core nanothread is surrounded by a halo of hydrogen atoms. During the compression process, the scientists report, the flat benzene molecules stack together, bend, and break apart. Then, as the researchers slowly release the pressure, the atoms reconnect in an entirely different yet very orderly way. The result is a structure that has carbon in the tetrahedral configuration of diamond with hydrogens hanging out to the side and each tetrahedron bonded with another to form a long, thin, nanothread.

“It really is surprising that this kind of organization happens,” Badding said. “That the atoms of the benzene molecules link themselves together at room temperature to make a thread is shocking to chemists and physicists. Considering earlier experiments, we think that, when the benzene molecule breaks under very high pressure, its atoms want to grab onto something else but they can’t move around because the pressure removes all the space between them. This benzene then becomes highly reactive so that, when we release the pressure very slowly, an orderly polymerization reaction happens that forms the diamond-core nanothread.”

The scientists confirmed the structure of their diamond nanothreads with a number of techniques at Penn State, Oak Ridge, Arizona State University, and the Carnegie Institution for Science, including X-ray diffraction, neutron diffraction, Raman spectroscopy, first-principle calculations, transmission electron microscopy, and solid-state nuclear magnetic resonance (NMR). Parts of these first diamond nanothreads appear to be somewhat less than perfect, so improving their structure is a continuing goal of Badding’s research program. He also wants to discover how to make more of them. “The high pressures that we used to make the first diamond nanothread material limit our production capacity to only a couple of cubic millimeters at a time, so we are not yet making enough of it to be useful on an industrial scale,” Badding said. “One of our science goals is to remove that limitation by figuring out the chemistry necessary to make these diamond nanothreads under more practical conditions.”

The nanothread also may be the first member of a new class of diamond-like nanomaterials based on a strong tetrahedral core. “Our discovery that we can use the natural alignment of the benzene molecules to guide the formation of this new diamond nanothread material is really interesting because it opens the possibility of making many other kinds of molecules based on carbon and hydrogen,” Badding said. “You can attach all kinds of other atoms around a core of carbon and hydrogen. The dream is to be able to add other atoms that would be incorporated into the resulting nanothread. By pressurizing whatever liquid we design, we may be able to make an enormous number of different materials.”

Potential applications that most interest Badding are those that would be vastly improved by having exceedingly strong, stiff, and light materials — especially those that could help to protect the atmosphere, including lighter, more fuel-efficient, and therefore less-polluting vehicles. “One of our wildest dreams for the nanomaterials we are developing is that they could be used to make the super-strong, lightweight cables that would make possible the construction of a “space elevator,” which so far has existed only as a science-fiction idea,” Badding said.

In addition to Badding at Penn State and Guthrie at the Carnegie Institution, other members of the research team include George D. Cody at the Carnegie Institution, Stephen K. Davidowski, at Arizona State, and Thomas C. Fitzgibbons, En-shi Xu, Vincent H. Crespi, and Nasim Alem at Penn State. Penn State affiliations include the Department of Chemistry, the Materials Research Institute, the Department of Physics, and the Department of Materials Science and Engineering. This research received financial support as part of the Energy Frontier Research in Extreme Environments (EFree) Center, and Energy Frontier Research Center funded by the U.S. Department of Energy (Office of Science award #DE-SC0001057).

Source: Penn State

JILA Team Finds First Direct Evidence of ‘Spin Symmetry’ In Atoms: NIST Tech


NIST Atom Spin 14PML029_spin_symmetry_LRJust as diamonds with perfect symmetry may be unusually brilliant jewels, the quantum world has a symmetrical splendor of high scientific value.

Confirming this exotic quantum physics theory, JILA physicists led by theorist Ana Maria Rey and experimentalist Jun Ye have observed the first direct evidence of symmetry in the magnetic properties—or nuclear “spins”—of atoms. The advance could spin off practical benefits such as the ability to simulate and better understand exotic materials exhibiting phenomena such as superconductivity (electrical flow without resistance) and colossal magneto-resistance (drastic change in electrical flow in the presence of a magnetic field).

spin symmetry

Illustration of symmetry in the magnetic properties—or nuclear spins—of strontium atoms. JILA researchers observed that if two atoms have the same nuclear spin state (top), they interact weakly, and the interaction strength does not depend on which of the 10 possible nuclear spin states are involved. If the atoms have different nuclear spin states (bottom), they interact much more strongly, and, again, always with the same strength.
Credit: Ye and Rey groups and Steve Burrows/JILA
View hi-resolution image

The JILA discovery, described in Science Express,* was made possible by the ultra-stable laser used to measure properties of the world’s most precise and stable atomic clock.** JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.NIST 580303_10152072709285365_1905986131_n

“Spin symmetry has a very strong impact on materials science, as it can give rise to unexpected behaviors in quantum matter,” JILA/NIST Fellow Jun Ye says. “Because our clock is this good—really it’s the laser that’s this good—we can probe this interaction and its underlying symmetry, which is at a very small energy scale.”

The global quest to document quantum symmetry looks at whether key properties remain the same despite various exchanges, rotations or reflections. For example, matter and antimatter demonstrate fundamental symmetry: Antimatter behaves in many respects like normal matter despite having the charges of positrons and electrons reversed.

To detect spin symmetry, JILA researchers used an atomic clock made of 600 to 3,000 strontium atoms trapped by laser light. Strontium atoms have 10 possible nuclear spin configurations (also referred to as angular momentum), which influences magnetic behavior. In a collection of clock atoms there is a random distribution of all 10 states.

The researchers analyzed how atom interactions—their collisions—at the two electronic energy levels used as the clock “ticks” were affected by the spin state of the atoms’ nuclei. In most atoms, the electronic and nuclear spin states are coupled, so atom collisions depend on both electronic and nuclear states. But in strontium, the JILA team predicted and confirmed that this coupling vanishes, giving rise to collisions that are independent of nuclear spin states.

In the clock, all the atoms tend to be in identical electronic states. Using lasers and magnetic fields to manipulate the nuclear spins, the JILA researchers observed that, when two atoms have different nuclear spin states, no matter which of the 10 states they have, they will interact (collide) with the same strength. However, when two atoms have the same nuclear spin state, regardless of what that state is, they will interact much more weakly.

“Spin symmetry here means atom interactions, at their most basic level, are independent of their nuclear spin states,” Ye explains. “However, the intriguing part is that while the nuclear spin does not participate directly in the electronic-mediated interaction process, it still controls how atoms approach each other physically. This means that, by controlling the nuclear spins of two atoms to be the same or different, we can control interactions, or collisions.”

The new research adds to understanding of atom collisions in atomic clocks documented in previous JILA studies.*** Further research is planned to engineer specific spin conditions to explore novel quantum dynamics of a large collection of atoms.

JILA theorist Ana Maria Rey made key predictions and calculations for the study. Theorists at the University of Innsbruck in Austria and the University of Delaware also contributed. Funding was provided by NIST, the National Science Foundation, the Air Force Office of Scientific Research, and the Defense Advanced Research Projects Agency.

*X. Zhang, M. Bishof, S.L. Bromley, C.V. Kraus, M.S. Safronova, P. Zoller, A.M. Rey, J. Ye. Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism. Science Express. Published online Aug. 21, 2104.
**See Jan. 22, 2014, Tech Beat article, “JILA Strontium Atomic Clock Sets New Records in Both Precision and Stability,” at www.nist.gov/pml/div689/20140122_strontium.cfm.
***See 2011 NIST news release “Quantum Quirk: JILA Scientists Pack Atoms Together to Prevent Collisions in Atomic Clock,” at www.nist.gov/pml/div689/jila-020311.cfm; and 2009 NIST news release “JILA/NIST Scientists Get a Grip on Colliding Fermions to Enhance Atomic Clock Accuracy,” at www.nist.gov/pml/div689/fermions_041609.cfm.

Researchers’ at Rice University Find Acid-Free Approach Leads to Strong Conductive Carbon Threads


Rice Carbon Threads 25-researchersaThe very idea of fibers made of carbon nanotubes is neat, but Rice University scientists are making them neat—literally.

Why It Matters: To create strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.

The single-walled carbon in new fibers created at Rice line up like a fistful of uncooked spaghetti through a process designed by chemist Angel Martí and his colleagues.

The tricky bit, according to Martí, whose lab reported its results this month in the journal ACS Nano, is keeping the densely packed nanotubes apart before they’re drawn together into a fiber.

Rice Carbon Threads 25-researchersa

Rice University scientists are making carbon nanotube solutions that act as liquid crystals as a precursor to pulling them into strong, conductive fibers. Credit: Martí Group 

Left to their own devices, carbon nanotubes form clumps that are perfectly wrong for turning into the kind of strong, conductive fibers needed for projects ranging from nanoscale electronics to macro-scale power grids.

Earlier research at Rice by chemist and chemical engineer Matteo Pasquali, a co-author on the new paper, used an acid dissolution process to keep the nanotubes separated until they could be spun into fibers. Now Martí, Pasquali and their colleagues are producing “neat” fibers with the same mechanical process, but they’re starting with a different kind of feedstock.

“Matteo’s group used chlorosulfonic acid to protonate the surface of the nanotubes,” Martí said. “That would give them a positively charged surface so they would repel each other in solution. The technique we use is exactly the opposite.”

Researchers’ acid-free approach leads to strong conductive carbon threads
Fiber of pure carbon nanotubes has potential for use in small-scale electronics and large scale power applications. Credit: Jeff Fitlow

A process revealed last year by Martí and lead authors Chengmin Jiang, a graduate student, and Avishek Saha, a Rice alumnus, starts with negatively charging carbon nanotubes by infusing them with potassium, a metal, and turning them into a kind of salt known as a polyelectrolyte. They then employ cage-like crown ethers to capture the potassium ions that would otherwise dampen the nanotubes’ ability to repel one another.

Put enough nanotubes into such a solution and they’re caught between the repellant forces and an inability to move in a crowded environment, Martí said. They’re forced to align—a defining property of liquid crystals—and this makes them more manageable.

The tubes are ultimately forced together into fibers when they are extruded through the tip of a needle. At that point, the strong van der Waals force takes over and tightly binds the nanotubes together, Martí said.

But to make macroscopic materials, the Martí team needed to pack many more nanotubes into the solution than in previous experiments. “As you start increasing the concentration, the number of nanotubes in the liquid crystalline phase becomes more abundant than those in the isotropic (disordered) phase, and that’s exactly what we needed,” Martí said.

The researchers discovered that 40 milligrams of nanotubes per milliliter gave them a thick gel after mixing at high speed and filtering out whatever large clumps remained. “It’s like a centrifuge together with a rotary drum,” Martí said of the mixing gear. “It produces unconventional forces in the solution.”

Carbon nanotubes extruded into a pure fiber are the product of an acid-free process invented at Rice University. Credit: Martí Group

Feeding this dense nanotube gel through a narrow needle-like opening produced continuous fiber on the Pasquali lab’s equipment. The strength and stiffness of the neat fibers also approached that of the fibers previously produced with Pasquali’s acid-based process. “We didn’t make any modifications to his system and it worked perfectly,” Martí said.

The hair-width fibers can be woven into thicker cables, and the team is investigating ways to improve their electrical properties through doping the nanotubes with iodide. “The research is basically analogous to what Matteo does,” Martí said. “We used his tools but gave the process a spin with a different preparation, so now we’re the first to make neat of pure electrolytes. That’s very cool.”

Pasquali said that the spinning system worked with little need for adaptation because the setup is sealed. “The nanotube electrolyte solution could be protected from oxygen and water, which would have caused precipitation of the nanotubes,” he said.

“It turns out that this is not a showstopper, because we want the nanotubes to precipitate and stick to each other as soon as they exit the sealed system through the needle. The process was not hard to control, adapt and scale up once we figured out the basic science.”

Explore further: Carbon nanotube fibers outperform copper

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Could Hemp Batteries be a Reality?


Colorado-WeedResearchers have found a way to boost the energy density of supercapacitors through the use of more sophisticated electrodes. These electrodes are composed of hemp fibers, and they have a high energy storage capacity.

The development breakthrough has been made by a Canadian start-up company, led by Dr. David Mitlin. The idea arose from some applied thinking, when Mitlin’s group decided to see if they could make graphene-like carbons from hemp bast fibers.

From Mitlin’s research, it seems that hemp fibers can hold as much energy and power as graphene, the current favored material for supercapacitors. Supercapacitors are energy storage devices that have huge potential to transform the way future electronics are powered. Unlike batteries, which store energy chemically in the material of their electrodes, a capacitor stores energy physically, on the electrodes’ surfaces.

Mitlin’s group discovered that when hemp fibers were heated for 24 hours at a little over 350 degrees Fahrenheit this would exfoliated the material into carbon nanosheets. From the reformed material, the group constructed supercapacitors using the hemp-derived carbons as electrodes and an ionic liquid as the electrolyte. In tests, the devices performed far better than commercial supercapacitors. This was assessed by examining for energy density and across a range of temperatures. The hemp-based devices yielded energy densities as high as 12 Watt-hours per kilogram, which is two to three times higher than currently available commercial systems.

Interviewed by Phys.Org, Mitlin expands on the success so far: “Our device’s electrochemical performance is on par with or better than graphene-based devices. The key advantage is that our electrodes are made from biowaste using a simple process, and therefore, are much cheaper than graphene.”

The parallels with graphene are a reference to the considerable research that has gone into to new variant of carbon. Graphene is a single-layer mesh of carbon atoms. Graphene is considered the new “wonder material,” due its durability and lightness. Graphene can be described as a one-atom thick layer of graphite.

Mitlin’s new research could trigger the electronic industry to move in a new direction. The research group are currently preparing the hemp-based prototype supercapacitor for small-scale manufacturing.

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Scientists “clone” carbon nanotubesto unlock electronic potential


Scientists “clone” carbon nanotubesto unlock electronic potential
Wed, 11/14/2012 – 1:14pm
The heart of the computer industry is known as “Silicon Valley” for a reason. Integrated circuit computer chips have been made from silicon since computing’s infancy in the 1960s. Now, thanks to a team of USC researchers, carbon nanotubes may emerge as a contender to silicon’s throne. Scientists and industry experts have long speculated that carbon nanotube transistors would one day replace their silicon predecessors.In 1998, Delft University built the world’s first carbon nanotube transistors—carbon nanotubes have the potential to be far smaller,faster, and consume less power than silicon transistors.
A key reason carbon nanotubes are not in your computer right now isthat they are difficult to manufacture in a predictable way. Scientists have had a difficult time controlling the manufacture of nanotubes to the correct diameter, type and ultimately chirality, factors that control nanotubes’ electrical and mechanical properties. Think of chirality like this: if you took a sheet of notebook paper and rolled it straight up into a tube, it would have a certain chirality. If you rolled that same sheet up at an angle,it would have a different chirality. In this example, the notebook paper represents a sheet of latticed carbon atoms that are rolled-up to create a nanotube. 
A team led by Professor Chongwu Zhou of the USC Viterbi School of Engineering and Ming Zheng of the National Institute of Standards and  Technology in Maryland solved the problem by inventing a system that consistently produces carbon nanotubes of a predictable diameter and chirality. Zhou worked with his group members Jia Liu, Chuan Wang, Bilu Liu,Liang Chen, and Ming Zheng and Xiaomin Tu of the National Institute of Standards and Technology in Maryland. “Controlling the chirality of carbon nanotubes has been a dream for many researchers.
Now the dream has come true.” said Zhou. The team has already patented its innovation, and its research will be published Nov. 13 in Nature Communications. Carbon nanotubes are typically grown using a chemical vapor deposition (CVD) system in which a chemical-laced gas is pumped intoa chamber containing substrates with metal catalyst nanoparticles,upon which the nanotubes grow. It is generally believed that the diameters of the nanotubes are determined by the size of the catalytic metal nanoparticles. However, attempts to control the catalysts in hopes of achieving chirality-controlled nanotube growth have not been successful. The USC team’s innovation was to jettison the catalyst and instead plant pieces of carbon nanotubes that have been separated and pre-selected based on chirality, using a nanotube separation technique developed and perfected by Zheng and his coworkers at NIST. Usingthose pieces as seeds, the team used chemical vapor deposition toextend the seeds to get much longer nanotubes, which were shown to have the same chirality as the seeds.. The process is referred to as “nanotube cloning.” The next steps in the research will be to carefully study the mechanism of the nanotubeg rowth in this system, to scale up the cloning process to get large quantities of chirality-controlled nanotubes, and to use those nanotubes for electronic applications. Funding of the USC team for this research came from the Semiconductor Research Corporation’s Focus Research Program Functional Engineered Nano Architectonics center and the Office of Naval Research.

The potentially world-changing research that no one knows about


Foresight Nanotech Institute Logo

 

Imagine that there exists a two-dimensional (single-layer) crystal that is made of a commonly available element, is stronger than steel yet lighter weight and flexible, displays ballistic electron mobility (for comparison, two orders of magnitude greater mobility than silicon, at room temperature), and is sufficiently optically active to see with the naked eye (though far more practically, using an optical microscope). Prospective applications include flexible, high-speed electronic devices and new composite materials for aircraft.

 

Would this sound like a potentially world-changing substance worthy of scientific attention and funding?

That substance is graphene, a single layer of graphite with hexagonally arranged carbon atoms (visualized as chicken wire).

 

Now imagine that the mechanical properties of this substance aren’t measured yet, as was the case for graphene before 2009. Imagine further that there is no way to grow or isolate the single-layer crystals in their free state, as was the case for graphene before 2004. Stepping back in time yet further, imagine that the theoretical work predicting massless charge carrier behavior hasn’t been carried out yet, as was the case for graphene before 1984.

 

Peeling back these milestones, we can see that if the scientific question being asked is “What can be realized from here?” then the graphene timeline played out characteristically, with major advancements coming primarily from opportunity-based research. In other words, over 50+ years, from the initial theoretical work on graphene in 1947 until stable monolayers were achieved in 2004, there was limited vision of what end-goals might be achievable and limited drive to get there.

 

What happens when a different question is asked, specifically “What can be realized according to physical law?” This is the key premise of the exploratory engineering approach, a methodology proposed by Eric Drexler for assessing the capabilities of future technologies. He points out, for example, that the principles of space flight had been worked out long before science and industry advanced enough to get to actual launch.

 

For initial space flight development, the answers to the two questions above were dramatically different: what could be done in practice was far behind what had been established as theoretically possible, and there was no defined path between them. By identifying what was achievable according to physical law, the longer-term goal of space flight entered the consciousness of physicists, engineers, and politicians, bringing great minds and great resources to the challenge.

 

With the benefit of similarly future-focused knowledge, perhaps graphene might have received far more attention far sooner. Consider this: the groundbreaking experimental work that sparked the field as we know it today was the discovery that single-layer graphene could be extracted from a piece of graphite by (essentially) pressing cellophane tape against it and peeling it away. In other words, a decades-long roadblock to achievements in graphene research was not a matter of inadequate supporting technology but one of limited scientific attention.

 

Here graphene serves as a useful illustration of how progress could potentially be hindered when opportunity-based research is relied upon exclusively. Scientific advancement could benefit significantly from deliberate, exploratory engineering. Perhaps there are numerous other ‘graphenes’ right now, going unnoticed or under-prioritized, because we are failing to ask: what can be realized according to physical law?

 

English: Graphene layer. Français : Couche de ...

 

Effort to mass-produce flexible nanoscale electronics


Case Western Reserve University researchers have won a $1.2 million grant to develop technology for mass-producing flexible electronic devices at a whole new level of small.

As they’re devising new tools and techniques to make wires narrower than a particle of smoke, they’re also creating ways to build them in flexible materials and package the electronics in waterproofing layers of durable plastics.

The team of engineers, who specialize in different fields, ultimately aims to build flexible electronics that bend with the realities of life: Health-monitoring sensors that can be worn on or under the skin and foldable electronic devices as thin as a sheet of plastic wrap. And, further down the road, implantable nerve-stimulating electrodes that enable patients to regain control from paralysis or master a prosthetic limb.

Thinking bigger, the team believes the technology could be used to crank out rolls of thin-film solar panels that stand up to decades in the elements. Current thin-film panels are plagued with short life spans due to seepage between layers.

“The commercial development of nanoelectromechanical systems is limited by access to low-cost, high output—we call it ‘throughput’—processing tools,” says Christian Zorman, an associate professor of electrical engineering and computer science and lead researcher on the grant. “We’re trying to address that bottleneck.”

With this four-year National Science Foundation Scalable Nanomanufacturing Program grant, Zorman and his colleagues will push alternative technologies they’ve created to make wires and other metal structures less than 100 nm.

Currently, devices that combine electronic and mechanical functions are being made this small using electron beam lithography. But electron beams are too energetic to use on flexible plastics and require very high vacuum, which significantly limits throughput, is costly, and very time-consuming—all impediments to mass production.

Using inkjet printers to build small devices has proven cheap and effective, but getting down into the nanometers has been difficult.

Philip Feng, an assistant professor of electrical engineering and computer science, specializes in nanofabrication and devices. Joao Maia, an associate professor of macromolecular science and engineering, is an expert at making nanolayered polymers.

R. Mohan Sankaran, an associate chemical engineering professor, developed the technology to use microplasmas as a manufacturing tool. Zorman spent the last two decades developing techniques used to build microelectromechanical devices for harsh environments and biomedical applications.

When Feng and Zorman saw Sankaran’s work “we realized this could revolutionize nanoscale manufacturing,” Zorman says.

A plasma is a state of matter similar to a gas but a portion is ionized, that is particles are gaining or losing electrons and becoming charged. A spark is an example of a plasma, but it’s hot and uncontrollable.

Sankaran makes a controllable microplasma by ionizing argon gas as it is pumped out of a tube a hair-width across. “The plasma is like a pencil,” Sankaran says, “You can use it to draw a line or any pattern you want.”

To get down to nanometers, Feng must make stencils of nano-sized wires, circuits, and other desired forms. He’ll use a durable silicon carbide material Zorman has developed.

“To get to 100 nm or less,” Feng says, “we must study the laws of scaling, the materials used, and reactions that a microplasma can induce, such as the reactions on the surface of a polymer and inside the polymer, and to compare this process side-by-side with the electron beam lithography.”

As they scale down, Maia will focus on sealing the electronics from moisture.

“A lot of people are working on flexible electronics, but the problem is the product’s lifetime is short because moisture enters and decreases resistivity, shorts out or corrodes the electronics,” Maia says. “If you have to change out your flexible device every two weeks or two months, that’s not such a good thing.”

Maia will make sheets of polymers that include a nanolayer embedded with metal salts, such as silver nitride or gold chloride. These are the precursors of the wires and metallic structures needed to make the electronics.

The sheet will roll through a production line and pause under stencils. A set of microplasmas above the stencils will fire.

In preliminary tests on a stationary piece of film, electrons from the microplasma travel through the stencil and into the polymer where they turn the metal salts into conductive chains of metal particles that form wires and structures, like spray paint and a stencil form letters and numbers.

The sheet can then be dipped in a solution to dissolve the unexposed metal salts, to be recycled.

More layers or combinations of layers will be added to make the sheet watertight.

If multiple devices or packaging layers are needed, the sheets can be looped back through the process.

Feds enlist Rice for nanocarbon project


Rice News

National Institute of Standards and Technology grant supports measurement and characterization of nanomaterials

The nascent industry of carbon-based nanomanufacturing will benefit from a new cooperative venture between scientists at Rice University and its Richard E. Smalley Institute for Nanoscale Science and Technology and scientists at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md.

NIST announced a $2.7 million, five-year cooperative research agreement to study how nanoparticles – particularly fullerenes (aka buckyballs), nanotubes and graphene – operate and interact with other materials at the molecular, even atomic, scale.

“The payoff will be grand,” said Rice engineering professor Matteo Pasquali, the principal investigator of the new cooperative agreement to advance methods of measurement and characterization of nanomaterials. The goal is to enable the manufacture of high-end products that incorporate carbon-based nanomaterials for enhanced optical, electrical, mechanical and thermal properties.

“With this agreement, we’re building and expanding on several successful years of collaboration between NIST and Rice,” said Pasquali, a professor of chemical and biomolecular engineering and of chemistry at Rice. “Up to now, the research has focused primarily on the separation, spectroscopy and rheology of carbon nanotubes, but we will now go further to enable products and devices to be manufactured that include many types of carbon nanomaterials.”

“A lot of the research we’ve already done we can map onto the long-term goal of benefiting U.S. manufacturing,” he said.

The range of products that could benefit from advanced nanomaterials is vast, Pasquali said. The new research will help kick start advances in energy, health care, materials science and national security.

“We look forward to leveraging our combined scientific, engineering and standards leadership in nanomaterials to help the U.S. lead in the race toward commercialization and manufacturing,” said Kalman Migler, leader of the Complex Fluids Group of the Materials Science and Engineering Division at NIST.

“The opportunity to work closely with Rice faculty will quicken the pace of realizing carbon-based nanoelectronics,” said Angela Hight Walker, project leader in the Semiconductor and Dimensional Metrology Division at NIST.

Migler and Hight Walker are technical leads from NIST on the joint project.

The Rice grant will be administered by Pasquali and his colleagues, Vice Provost for Research Vicki Colvin, the Kenneth S. Pitzer-Schlumberger Professor of Chemistry and a professor of chemical and biomolecular engineering, and Junichiro Kono, a professor of electrical and computer engineering and of physics and astronomy.

The agreement builds on two earlier cooperative research agreements and a series of NIST workshops at which industry, government and academic researchers were polled about obstacles that remain in the path of efficient manufacturing with nanoscale carbon, from production of components to integration.

The agreement allows Rice to hire a team of postdoctoral associates and researchers who will study ways to disperse and characterize nanomaterials for specific uses, control and measure nano-network structures and create systems for in-line measurements during manufacturing. The new team will be primarily based at NIST headquarters in Maryland, where they will work closely with NIST scientists while also drawing on Rice expertise as they develop new methods.

Carbon at the nanoscale has become one of the most-studied materials by labs around the world since the discovery of the buckyball at Rice in 1986, which brought the Nobel Prize to Rice’s Richard Smalley and Robert Curl. Since then, nanocarbon has taken on new forms with the discovery of the carbon nanotube in the late ’90s and graphene, the single-atomic-layer form of carbon that won a Nobel for its discovers two years ago.

Pasquali’s lab has deep experience working on the dispersal and characterization of carbon nanotubes and graphene, which group members are working toward extruding into fibers that could become essential components in the advanced energy grid envisioned by Smalley.

Kono’s lab focuses on the physics and applications of carbon nanomaterials, with recent breakthroughs on the fabrication of devices based on aligned carbon nanotubes and graphene to control terahertz waves. “We’ve been working closely with NIST scientists Ming Zheng, Jeffery Fagan and Angela Hight Walker on the chirality separation and spectroscopy of single-wall carbon nanotubes,” Kono said. “Their successful enrichment of armchair carbon nanotubes has led to a significant advancement in our understanding of the electronic and optical properties of these one-dimensional metals.”

Colvin’s group has expertise in how nanoparticles interact with the environment and living systems and has recently demonstrated nano-based technology to remove arsenic from drinking water in Mexico.

 

Light might prompt graphene devices on demand


MIKE WILLIAMS

 – OCTOBER 10, 2012

Rice University researchers find plasmonics show promise for optically induced electronics

Rice University researchers are doping graphene with light in a way that could lead to the more efficient design and manufacture of electronics, as well as novel security and cryptography devices.

Graphene circuitry

Nanoscale plasmonic antennas called nonamers placed on graphene have the potential to create electronic circuits by hitting them with light at particular frequencies, according to researchers at Rice University. The positively and negatively doped graphene can be prompted to form phantom circuits on demand.

Manufacturers chemically dope silicon to adjust its semiconducting properties. But the breakthrough reported in the American Chemical Society journal ACS Nano details a novel concept: plasmon-induced doping of graphene, the ultrastrong, highly conductive, single-atom-thick form of carbon.

That could facilitate the instant creation of circuitry – optically induced electronics – on graphene patterned with plasmonic antennas that can manipulate light and inject electrons into the material to affect its conductivity.

The research incorporates both theoretical and experimental work to show the potential for making simple, graphene-based diodes and transistors on demand. The work was done by Rice scientists Naomi Halas, Stanley C. Moore Professor in Electrical and Computer Engineering, a professor of biomedical engineering, chemistry, physics and astronomy and director of the Laboratory for Nanophotonics; and Peter Nordlander, professor of physics and astronomy and of electrical and computer engineering; physicist Frank Koppens of the Institute of Photonic Sciences in Barcelona, Spain; lead author Zheyu Fang, a postdoctoral researcher at Rice; and their colleagues.

“One of the major justifications for graphene research has always been about the electronics,” Nordlander said. “People who know silicon understand that electronics are only possible because it can be p- and n-doped (positive and negative), and we’re learning how this can be done on graphene.

“The doping of graphene is a key parameter in the development of graphene electronics,” he said. “You can’t buy graphene-based electronic devices now, but there’s no question that manufacturers are putting a lot of effort into it because of its potential high speed.”

Researchers have investigated many strategies for doping graphene, including attaching organic or metallic molecules to its hexagonal lattice. Making it selectively – and reversibly – amenable to doping would be like having a graphene blackboard upon which circuitry can be written and erased at will, depending on the colors, angles or polarization of the light hitting it.

Nonamers

Nonamers in the drawings at top and in the photos at bottom are arrays of nine gold nanoparticles deposited on graphene and tuned to particular frequencies of light. When illuminated, the plasmonic particles pump electrons into the graphene, according to researchers at Rice University who say the technology may lead to the creation of on-demand circuitry for electronic devices.

The ability to attach plasmonic nanoantennas to graphene affords just such a possibility. Halas and Nordlander have considerable expertise in the manipulation of the quasiparticles known as plasmons, which can be prompted to oscillate on the surface of a metal. In earlier work, they succeeded in depositing plasmonic nanoparticles that act as photodetectors on graphene.

These metal particles don’t so much reflect light as redirect its energy; the plasmons that flow in waves across the surface when excited emit light or can create “hot electrons” at particular, controllable wavelengths. Adjacent plasmonic particles can interact with each other in ways that are also tunable.

That effect can easily be seen in graphs of the material’s Fano resonance, where the plasmonic antennas called nonamers, each a little more than 300 nanometers across, clearly scatter light from a laser source except at the specific wavelength to which the antennas are tuned. For the Rice experiment, those nonamers – eight nanoscale gold discs arrayed around one larger disc – were deposited onto a sheet of graphene through electron-beam lithography. The nonamers were tuned to scatter light between 500 and 1,250 nanometers, but with destructive interference at about 825 nanometers.

At the point of destructive interference, most of the incident light energy is converted into hot electrons that transfer directly to the graphene sheet and change portions of the sheet from a conductor to an n-doped semiconductor.

Arrays of antennas can be affected in various ways and allow phantom circuits to materialize under the influence of light. “Quantum dot and plasmonic nanoparticle antennas can be tuned to respond to pretty much any color in the visible spectrum,” Nordlander said. “We can even tune them to different polarization states, or the shape of a wavefront.

“That’s the magic of plasmonics,” he said. “We can tune the plasmon resonance any way we want. In this case, we decided to do it at 825 nanometers because that is in the middle of the spectral range of our available light sources. We wanted to know that we could send light at different colors and see no effect, and at that particular color see a big effect.”

Nordlander said he foresees a day when, instead of using a key, people might wave a flashlight in a particular pattern to open a door by inducing the circuitry of a lock on demand. “Opening a lock becomes a direct event because we are sending the right lights toward the substrate and creating the integrated circuits. It will only answer to my call,” he said.

Rice co-authors of the paper are graduate students Yumin Wang and Andrea Schlather, research scientist Zheng Liu, and Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry.

The research was supported by the Robert A. Welch Foundation, the Office of Naval Research, the Department of Defense National Security Science and Engineering Faculty Fellows program and Fundacio Cellex Barcelona.