A flexible, transparent memory chip created by researchers at Rice University. Courtesy Tour Lab/Rice University
Tour revealed today in a talk at the national meeting and exposition of the American Chemical Society in San Diego that the new type of memory could combine with the likes of transparent electrodes developed at Rice for flexible touchscreens and transparent integrated circuits and batteries developed at other labs in recent years.

Details of the Rice breakthrough will be published in an upcoming paper, Tour said. “Generally, you can’t see a bit of memory, because it’s too small,” said Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. “But silicon itself is not transparent. If the density of the circuits is high enough, you’re going to see it.”
Rice’s transparent memory is based upon the 2010 discovery that pushing a strong charge through standard silicon oxide, an insulator widely used in electronics, forms channels of pure silicon crystals less than 5 nanometers wide. The initial voltage appears to strip oxygen atoms from the silicon oxide; lesser charges then repeatedly break and reconnect the circuit and turn it into nonvolatile memory. A smaller signal can be used to poll the memory state without altering it.

http://news.rice.edu/2012/03/27/transparent-memory-chips-are-coming-2/

Graphene’s star is rising as a material that could become essential to efficient, environmentally sound oil production. Rice University researchers are taking advantage of graphene’s outstanding strength, light weight and solubility to enhance fluids used to drill oil wells.

The Rice University lab of chemist James Tour and scientists at M-I SWACO, a Texas-based supplier of drilling fluids and subsidiary of oil-services provider Schlumberger, have produced functionalized graphene oxide to alleviate the clogging of oil-producing pores in newly drilled wells.

The patented technique took a step closer to commercialization with the publication of new research this month in the American Chemical Society journal Applied Materials and Interfaces. Graphene is a one-atom-thick sheet of carbon that won its discoverers a Nobel Prize last year.

Rice’s relationship with M-I SWACO began more than two years ago when the company funded the lab’s follow-up to research that produced the first graphene additives for drilling fluids known as muds. These fluids are pumped downhole as part of the process to keep drill bits clean and remove cuttings. With traditional clay-enhanced muds, differential pressure forms a layer on the wellbore called a filter cake, which both keeps the oil from flowing out and drilling fluids from invading the tiny, oil-producing pores.

When the drill bit is removed and drilling fluid displaced, the formation oil forces remnants of the filter cake out of the pores as the well begins to produce. But sometimes the clay won’t budge, and the well’s productivity is reduced.

The Tour Group discovered that microscopic, pliable flakes of graphene can form a thinner, lighter filter cake. When they encounter a pore, the flakes fold in upon themselves and look something like starfish sucked into a hole. But when well pressure is relieved, the flakes are pushed back out by the oil.

All that was known two years ago. Since then, Tour and a research team led by Dmitry Kosynkin, a former Rice postdoctoral associate and now a petroleum engineer at Saudi Aramco, have been fine-tuning the materials.

They found a few issues that needed to be dealt with. First, pristine graphene is hard to disperse in water, so it is unsuitable for water-based muds. Graphene oxide (GO) turned out to be much more soluble in fresh water, but tended to coagulate in saltwater, the basis for many muds.

The solution was to “esterify” GO flakes with alcohol. “It’s a simple, one-step reaction,” said Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. “Graphene oxide functionalized with alcohol works much better because it doesn’t precipitate in the presence of salts. There’s nothing exotic about it.”

In a series of standard American Petroleum Institute tests, the team found the best mix of functionalized GO to be a combination of large flakes and powdered GO for reinforcement. A mud with 2 percent functionalized GO formed a filter cake an average of 22 micrometers wide — substantially smaller than the 278-micrometer cake formed by traditional muds. GO blocked pores many times smaller than the flakes’ original diameter by folding.

Aside from making the filter cake much thinner, which would give a drill bit more room to turn, the Rice mud contained less than half as many suspended solids; this would also make drilling more efficient as well as more environmentally friendly. Tour and Andreas Lüttge, a Rice professor of Earth science and chemistry, reported last year that GO is reduced to graphite, the material found in pencil lead and a natural mineral, by common bacteria.

“The most exciting aspect is the ability to modify the GO nanoparticle with a variety of functionalities,” said James Friedheim, corporate director of fluids research and development at M-I SWACO and a co-author of the research. “Therefore we can ‘dial in’ our application by picking the right organic chemistry that will suit the purpose. The trick is just choosing the right chemistry for the right purpose.”

“There’s still a lot to be worked out,” Tour said. “We’re looking at the rheological properties, the changes in viscosity under shear. In other words, we want to know how viscous this becomes as it goes through a drill head, because that also has implications for efficiency.”

Muds may help graphene live up to its commercial promise, Tour said. “Everybody thinks of graphene in electronics or in composites, but this would be a use for large amounts of graphene, and it could happen soon,” he said.

Friedheim agreed. “With the team we currently have assembled, Jim Tour’s group and some development scientists at M-I SWACO, I am confident that we are close to both technical and commercial success.”

Other authors of the paper are Rice graduate student Gabriel Ceriotti, former Rice research associates Kurt Wilson and Jay Lomeda, and M-I SWACO researchers Jason Scorsone and Arvind Patel.

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Read the abstract at http://pubs.acs.org/doi/abs/10.1021/am2012799

An image is available for download at http://www.media.rice.edu/images/media/NEWSRELS/1207_starfish.jpg

CAPTION:

Microscopic, star-shaped flakes of functionalized graphene oxide plug holes in pores in a test of the material’s ability to serve as a filter cake in fluids used to drill oil wells. The single-atom-thick flakes of treated carbon are pliable but among the strongest materials known. (Credit Tour Group/Rice University)

BY MIKE WILLIAMS
Rice News staff

The future brightened for organic chemistry when researchers at Rice University found a highly controllable way to attach organic molecules to pristine graphene and make the miracle material suitable for a range of new applications.

The Rice lab of chemist James Tour, building upon a set of previous finds in the manipulation of graphene, discovered a two-step method that turned what was a single-atom-thick sheet of carbon into a superlattice for use in organic chemistry. The work could lead to advances in graphene-based chemical sensors, thermoelectric devices and metamaterials.

Making a superlattice with patterns of hydrogenated graphene is the first step in making the material suitable for organic chemistry. The process was developed in the Rice University lab of chemist James Tour.

The work appeared this week in the online journal Nature Communications.

Graphene alone is inert to many organic reactions and, as a semimetal, has no band gap; this limits its usefulness in electronics. But the project led by the Tour Lab’s Zhengzong Sun and Rice graduate Cary Pint, now a researcher at Intel, demonstrated that graphene, the strongest material there is because of the robust nature of carbon-carbon bonds, can be made suitable for novel types of chemistry.

Until now there was no way to attach molecules to the basal plane of a sheet of graphene, said Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. “They would mostly go to the edges, not the interior,” he said. “But with this two-step technique, we can hydrogenate graphene to make a particular pattern and then attach molecules to where those hydrogens were.

“This is useful to make, for example, chemical sensors in which you want peptides, DNA nucleotides or saccharides projected upward in discrete places along a device. The reactivity at those sites is very fast relative to placing molecules just at the edges. Now we get to choose where they go.”

Researchers at Rice printed Owls, the university’s mascot, in hydrogen atoms on a graphene substrate, turning it into a graphane superlattice suitable for organic chemistry. As proof, they “lit up” the Owls by coating them with a fluorophore and viewing them through fluorescence quenching microscopy. Graphene quenches fluorescence, but the molecules shine brightly when attached to the superlattice.

The first step in the process involved creating a lithographic pattern to induce the attachment of hydrogen atoms to specific domains of graphene’s honeycomb matrix; this restructure turned it into a two-dimensional, semiconducting superlattice called graphane. The hydrogen atoms were generated by a hot filament using an approach developed by Robert Hauge, a distinguished faculty fellow in chemistry at Rice and co-author of the paper.

The lab showed its ability to dot graphene with finely wrought graphane islands when it dropped microscopic text and an image of Rice’s classic Owl mascot, about three times the width of a human hair, onto a tiny sheet and then spin-coated it with a fluorophore. Graphene naturally quenches fluorescent molecules, but graphane does not, so the Owl literally lit up when viewed with a new technique called fluorescence quenching microscopy (FQM).

FQM allowed the researchers to see patterns with a resolution as small as one micron, the limit of conventional lithography available to them. Finer patterning is possible with the right equipment, they reasoned.

In the next step, the lab exposed the material to diazonium salts that spontaneously attacked the islands’ carbon-hydrogen bonds. The salts had the interesting effect of eliminating the hydrogen atoms, leaving a structure of carbon-carbon sp3 bonds that are more amenable to further functionalization with other organics.

“What we do with this paper is go from the graphene-graphane superlattice to a hybrid, a more complicated superlattice,” said Sun, who recently earned his doctorate at Rice. “We want to make functional changes to materials where we can control the position, the bond types, the functional groups and the concentrations.

“In the future — and it might be years — you should be able to make a device with one kind of functional growth in one area and another functional growth in another area. They will work differently but still be part of one compact, cheap device,” he said. “In the beginning, there was very little organic chemistry you could do with graphene. Now we can do almost all of it. This opens up a lot of possibilities.”

The paper’s co-authors are graduate students Daniela Marcano, Gedeng Ruan and Zheng Yan, former graduate student Jun Yao, postdoctoral researcher Yu Zhu and visiting student Chenguang Zhang, all of Rice.

The work was supported by the Air Force Office of Scientific Research, Sandia National Laboratory, the Nanoscale Science and Engineering Initiative of the National Science Foundation and the Office of Naval Research MURI graphene program.

A decade ago, nobody had ever heard of graphene. Now the single-atom-thick sheet of carbon is the focus of intense research at labs all over the world, nowhere more than at Rice University.

The Rice lab of Professor James Tour finds itself among the most highly regarded graphene labs in the world with three of the top eight places on a ranking of the previous month’s most-read papers in the prestigious American Chemical Society journal, ACS Nano.

At No. 2 on the hit parade is the paper titled “Growth of Graphene from Food, Insects and Waste” by Tour, the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science; and Gedeng Ruan, Zhengzong Sun and Zhiwei Peng, all graduate students in Tour’s lab. The paper sprang from a visit earlier this year by a local troop of Girl Scouts who took part in an experiment to turn a box of Girl Scout Cookies into graphene. They determined that at current rates, a box of cookies could produce graphene worth $15 billion.

At No. 3 is “Growth of Bilayer Graphene on Insulating Substrates.” The authors are Tour, graduate students Peng, Sun, Zheng Yan, former graduate student Jun Yao, postdoctoral research associates Yu Zhu and Zheng Lio and Pulickel Ajayan, Rice’s Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry.

At No. 8 is “Direct Growth of Bilayer Graphene on SiO2 Substrates by Carbon Diffusion Through Nickel.” Tour, Peng, Yan and Sun are co-authors.

Papers from Rice have proven popular with the journal’s readers over the past year. A 12-month ranking of most-read papers has five, led by four Rice professors, among the top 20. They are:

No. 4: “Improved Synthesis of Graphene Oxide” by the Tour Group.

No. 5: “Growth of Graphene from Food, Insects and Waste” by the Tour Group.

Rice University researchers have created a solid-state, nanotube-based supercapacitor that promises to combine the best qualities of high-energy batteries and fast-charging capacitors in a device suitable for extreme environments.

A paper from the Rice lab of chemist Robert Hauge, to be published in the journal Carbon, reported the creation of robust, versatile energy storage that can be deeply integrated into the manufacture of devices. Potential uses span on-chip nanocircuitry to entire power plants.

Standard capacitors that regulate flow or supply quick bursts of power can be discharged and recharged hundreds of thousands of times. Electric double-layer capacitors (EDLCs), generally known as supercapacitors, are hybrids that hold hundreds of times more energy than a standard capacitor, like a battery, while retaining their fast charge/discharge capabilities.

But traditional EDLCs rely on liquid or gel-like electrolytes that can break down in very hot or cold conditions. In Rice’s supercapacitor, a solid, nanoscale coat of oxide dielectric material replaces electrolytes entirely.

The researchers also took advantage of scale. The key to high capacitance is giving electrons more surface area to inhabit, and nothing on Earth has more potential for packing a lot of surface area into a small space than carbon nanotubes.

When grown, nanotubes self-assemble into dense, aligned structures that resemble microscopic shag carpets. Even after they’re turned into self-contained supercapacitors, each bundle of nanotubes is 500 times longer than it is wide. A tiny chip may contain hundreds of thousands of bundles.

For the new device, the Rice team grew an array of 15-20 nanometer bundles of single-walled carbon nanotubes up to 50 microns long. Hauge, a distinguished faculty fellow in chemistry, led the effort with former Rice graduate students Cary Pint, first author of the paper and now a researcher at Intel, and Nolan Nicholas, now a researcher at Matric.

The array was then transferred to a copper electrode with thin layers of gold and titanium to aid adhesion and electrical stability. The nanotube bundles (the primary electrodes) were doped with sulfuric acid to enhance their conductive properties; then they were covered with thin coats of aluminum oxide (the dielectric layer) and aluminum-doped zinc oxide (the counterelectrode) through a process called atomic layer deposition (ALD). A top electrode of silver paint completed the circuit.

“Essentially, you get this metal/insulator/metal structure,” said Pint. “No one’s ever done this with such a high-aspect-ratio material and utilizing a process like ALD.”

Hauge said the new supercapacitor is stable and scaleable. “All solid-state solutions to energy storage will be intimately integrated into many future devices, including flexible displays, bio-implants, many types of sensors and all electronic applications that benefit from fast charge and discharge rates,” he said.

Pint said the supercapacitor holds a charge under high-frequency cycling and can be naturally integrated into materials. He envisioned an electric car body that is a battery, or a microrobot with an onboard, nontoxic power supply that can be injected for therapeutic purposes into a patient’s bloodstream.

Pint said it would be ideal for use under the kind of extreme conditions experienced by desert-based solar cells or in satellites, where weight is also a critical factor. “The challenge for the future of energy systems is to integrate things more efficiently. This solid-state architecture is at the cutting edge,” he said.

Co-authors of the paper include graduate student Zhengzong Sun; James Tour, the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science, and Howard Schmidt, adjunct assistant professor of chemical and biomolecular engineering, all of Rice; Sheng Xu, a former graduate student at Harvard; and Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry at Harvard University, who developed ALD.

The research was supported by T.J. Wainerdi and Quantum Wired, in coordination with the Houston Area Research Council; the Office of Naval Research MURI program; the Wright Patterson Air Force Laboratory and the National Science Foundation.

FROM RICE NEWS STAFF REPORTS

A Russian cargo ship carrying an experiment from Rice University was lost after launch from Kazakhstan Aug. 24.

On the eve of Rice NASAversary, silicon oxide memory chips developed at the university were bound for the International Space Station (ISS). According to NASA, Russian officials reported an “off-nominal” situation with the rocket’s third and final stage minutes after launch, and the ship did not reach its intended orbit. The ship reportedly crashed in an unpopulated area of eastern Siberia in the Russian Republic of Altai, near China.

The experiments were launched from Kazakhstan as part of Progress 44, with docking at the ISS expected two days later. The Progress capsule was carrying nearly three tons of food, water and other cargo to the station. Russian cargo ships use the same launch system as manned Soyuz missions.

The chips developed at Rice University in the labs of chemist James Tour, physicist Douglas Natelson and electrical and computer engineering professor Lin Zhong were to have spent two years aboard the ISS to see how the chips’ memories would stand up to radiation.

They were part of a larger NASA experiment called HiMassSEE, in which various electronic components were to be evaluated after exposure to primary and secondary ionizing radiation. Read more about the experiment here.

Rice graduate student Jun Yao developed the chips. He discovered that sending a current through silicon oxide, an insulator, could create a conductive pathway of silicon crystals. Electrical pulses could then repeatedly break and reconnect the pathway. That can be read as zero or one, the basic element of computer memory.

“it is a shame that the launch was unsuccessful, but I’m glad that it resulted in no human loss,” said Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. “It took Jun two weeks of 14-hour days, six days a week, to make the chips that were lost, but we can certainly recover.

“Hopefully, NASA will grant us another opportunity to place our chips on a future flight, and we will be ready. The setback is discouraging, and it underscores that space flight is never easy. But as always, humans will press on.”

Steven Koontz, the ISS system manager for space environments with whom Rice collaborated on the experiment, informed those who contributed to the range of components that were part of HiMassSEE that nearly all the materials needed for a duplicate payload are in place, and a “re-flight” is already in the works.

“As Winston Churchill is reported to have said (many times), ‘Never ever, ever, ever, ever quit,’” Koontz wrote.

Rice NASAversary, a celebration of the university’s connection to the 50-year-old Johnson Space Center (JSC) and its work with the nation’s space program, started Sept. 9 with the Rice Space Strategy Workshop and continued Sept. 10 with NASA day at Rice Stadium, in conjunction with the Rice-Purdue football game. Rice’s Susanne M. Glasscock School of Continuing Studies will offer a short course with astronauts on the history of JSC, and on Sept. 14, Norman Augustine, who led two White House reviews of the space program, will speak at Duncan Hall.

Scientists can make graphene out of just about anything with carbon — even Girl Scout Cookies.

Graduate students in the Rice University lab of chemist James Tour proved it when they invited a troop of Houston Girl Scouts to their lab to show them how it’s done.

The work is part of a paper published online today by ACS Nano. Rice scientists described how graphene — a single-atom-thick sheet of the same material in pencil lead — can be made from just about any carbon source, including food, insects and waste.

The cookie gambit started on a dare when Tour mentioned at a meeting that his lab had produced graphene from table sugar.

“I said we could grow it from any carbon source — for example, a Girl Scout cookie, because Girl Scout Cookies were being served at the time,” Tour recalled. “So one of the people in the room said, ‘Yes, please do it. … Let’s see that happen.’”

Members of Girl Scouts of America Troop 25080 came to Rice’s Smalley Institute for Nanoscale Science and Technology to see the process. Rice graduate students Gedeng Ruan, lead author of the paper, and Zhengzong Sun calculated that at the then-commercial rate for pristine graphene — $250 for a two-inch square — a box of traditional Girl Scout shortbread cookies could turn a $15 billion profit.

“That’s a lot of cash!” said an amazed Sydney Shanahan, a member of the troop.

A sheet of graphene made from one box of shortbread cookies would cover nearly 30 football fields, Sun said.

The experiment was a whimsical way to make a serious point: that graphene — touted as a miracle material for its toughness and conductivity since its discovery by Nobel Prize-winning scientists Andre Geim and Konstantin Novoselov in 2004 — can be drawn from many sources.

To demonstrate, the researchers subsequently tested a range of materials, as reported in the new paper, including chocolate, grass, polystyrene plastic, insects (a cockroach leg) and even dog feces (compliments of lab manager Dustin James’ miniature dachshund, Sid Vicious).

In every case, the researchers were able to make high-quality graphene via carbon deposition on copper foil. In this process, the graphene forms on the opposite side of the foil as solid carbon sources decompose; the other residues are left on the original side. Typically, this happens in about 15 minutes in a furnace flowing with argon and hydrogen gas and turned up to 1,050 degrees Celsius.

Tour expects the cost of graphene to drop quickly as commercial interests develop methods to manufacture it in bulk. Another new paper by Tour and his Rice colleagues described a long-sought way to make graphene-based transparent electrodes by combining graphene with a fine aluminum mesh. The material may replace expensive indium tin oxide as a basic element in flat-panel and touch-screen displays, solar cells and LED lighting.

The experiment the Girl Scouts witnessed “has a lot to do with current research topics in academia and in industry,” said Tour, Rice’s T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science. “They learned that carbon — or any element — in one form can be inexpensive and in another form can be very expensive.”

Diamonds are a good example, he said. “You could probably get a very large diamond out of a box of Girl Scout Cookies.”

Zhiwei Peng a graduate student in Tour’s group, is a co-author of the paper.

Sandia National Laboratory, the Air Force Office of Scientific Research and the Office of Naval Research MURI program funded the research.