Metal oxide simulations could help green technology

The new paradigm could lead to a better understanding of corrosion and how toxic minerals leach from rocks and soil. It could also help in the development of “green” technology: new types of batteries, for example, or catalysts for splitting water to produce hydrogen fuel.

“This is a global change in how people should view these processes,” said William Casey, UC Davis professor of chemistry and co-author of the study with James Rustad, a former geology professor at UC Davis who now works as a scientist at Corning Inc. in New York.

Previously, when studying the interactions of water with clusters of metal oxides, researchers tried to pick and study individual atoms to assess their reactivity. But “none of it really made sense,” Rustad said.

Using computer simulations developed by Rustad, and comparing the resulting animations with lab experiments by Casey, the two found that the behavior of an atom on the surface of the cluster can be affected by an atom some distance away.

Instead of moving through a sequence of transitional forms, as had been assumed, metal oxides interacting with water fall into a variety of “metastable states” — short-lived intermediates, the researchers found.

For example, in one of Rustad’s animations, a water molecule approaches an oxygen atom on the surface of a cluster. The oxygen suddenly pulls away from another atom binding it into the middle of the cluster and leaps to the water molecule. Then the structure collapses back into place, ejecting a spare oxygen atom and incorporating the new one.

Provided by UC Davis (news : web)

Metal oxide simulations could help green technology

 University of California, Davis, researchers have proposed a radical new way of thinking about the chemical reactions between water and metal oxides, the most common minerals on Earth.

Their work appears in the current issue of the journal Nature Materials.

The new paradigm could lead to a better understanding of corrosion and how toxic minerals leach from rocks and soil. It could also help in the development of "green" technology: new types of batteries, for example, or catalysts for splitting water to produce hydrogen fuel.

"This is a global change in how people should view these processes," said William Casey, UC Davis professor of chemistry and co-author of the study with James Rustad, a former geology professor at UC Davis who now works as a scientist at Corning Inc. in New York.

Previously, when studying the interactions of water with clusters of metal oxides, researchers tried to pick and study individual atoms to assess their reactivity. But "none of it really made sense," Rustad said.

Using computer simulations developed by Rustad, and comparing the resulting animations with lab experiments by Casey, the two found that the behavior of an atom on the surface of the cluster can be affected by an atom some distance away.

Instead of moving through a sequence of transitional forms, as had been assumed, metal oxides interacting with water fall into a variety of "metastable states" -- short-lived intermediates, the researchers found.

For example, in one of Rustad's animations, a water molecule approaches an oxygen atom on the surface of a cluster. The oxygen suddenly pulls away from another atom binding it into the middle of the cluster and leaps to the water molecule. Then the structure collapses back into place, ejecting a spare oxygen atom and incorporating the new one.

The U.S. Department of Energy and the National Science Foundation sponsored the research.

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The above story is reprinted from materials provided by University of California - Davis.

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Journal Reference:

James R. Rustad, William H. Casey. Metastable structures and isotope exchange reactions in polyoxometalate ions provide a molecular view of oxide dissolution. Nature Materials, 2012; DOI: 10.1038/nmat3203

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

Functionalized graphene oxide plays part in next-generation oil-well drilling fluids

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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The above story is reprinted from materials provided by Rice University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Dmitry V. Kosynkin, Gabriel Ceriotti, Kurt C. Wilson, Jay R. Lomeda, Jason T. Scorsone, Arvind D. Patel, James E. Friedheim, James M. Tour. Graphene Oxide as a High-Performance Fluid-Loss-Control Additive in Water-Based Drilling Fluids. ACS Applied Materials & Interfaces, 2011; : 111213103240001 DOI: 10.1021/am2012799

Emerging new properties at oxide interfaces

 Dr. Ariando of the National University of Singapore discovered a collective electronic state not seen before in the bulk of either two individual insulating oxides, thus demonstrating that electrons at their interface can now exhibit ferromagnetism.

In many ionic materials, including the oxides, surfaces created along specific directions can become electrically charged. By the same token, such electronic charging, or 'polarisation', can also occur at the interface of two connecting materials.

Theoretically, this could lead to the build-up of an ever increasing voltage in the materials in certain systems, a situation known as a 'polarity catastrophe'. Certainly this cannot occur in practical systems, for energy sake, and Nature deals with this situation by reconstructing the electronic configuration of the interface via a shifting of charges across the interface, or by structural reconstructions, namely, the displacement of atoms.

With oxide materials, a unique consequence of these reconstructions is that it provides a means to create novel electronic phases, stabilised by the interface, and which cannot exist in the bulk.

Dr. Ariando from the National University of Singapore's (NUS) Department of Physics and NUS Nanoscience and Nanotechnology-NanoCore, along with his co-workers, showed that at this interface, a remarkable combination of strong diamagnetism (superconductor like), paramagnetism and ferromagnetism can co-exist with the quasi two-dimensional electron gas when prepared under a more oxidising condition.

Past studies had shown that two-dimensional conducting planes, in the form of quasi two-dimensional electron gas, could emerge between otherwise non-magnetic insulating oxide, Lanthanum Alumniate (LaAlO3) and Strontium Titanate (SrTiO3).

Interestingly, Dr. Ariando's team had also shown that the ferromagnetic phase was stable even above room temperature and the diamagnetism below a relatively high temperature of 60 K.

Industrial applications

The results also indicate that the free surface of SrTiO3 could well be responsible for all these fascinating phenomena. The SrTiO3 resembles Silicon. This will have a significant impact on industry since Silicon has been used in semiconductor technology -- silicon has been the workhorse for oxide-based devices and electronics.

These multiple electronic and magnetic phases at oxide interfaces could yield interesting technological applications. That a variety of magnetic states can be produced close to the surface (< 10 nm) by changing the external stimulus to the SrTiO3 or the interface of LaAlO3/SrTiO3, be it change in oxygen pressure or magnetic field, thus proves that this is a very active interface, and that it can yield strong responses to external stimuli.

One could well consider building novel sensors out of these interfaces that could be used as, say, oxygen sensors, or even magnetic sensors. Still, where these applications are concerned, there is a need to further understand these phenomena and optimise the device configuration.

The research of Dr. Ariando and his co-workers in the oxide interface field is reminiscent of the times when two-dimensional electron gas in the semiconductor heterostructures first became available, and the quantum Hall effect and fractional quantum Hall effect were discovered, both resulting in Nobel prizes.

The physics of the oxide material systems is however richer, involving much stronger interaction between the electrons, mutually and within the crystal lattice. There is great interest in exploring these interfaces in the quest for new nano-electronic devices.

Story Source:

The above story is reprinted from materials provided by National University of Singapore, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Ariando, X. Wang, G. Baskaran, Z. Q. Liu, J. Huijben, J. B. Yi, A. Annadi, A. Roy Barman, A. Rusydi, S. Dhar, Y. P. Feng, J. Ding, H. Hilgenkamp, T. Venkatesan. Electronic phase separation at the LaAlO3/SrTiO3 interface. Nature Communications, 2011; 2: 188 DOI: 10.1038/ncomms1192

Patent application for innovative film - possible Indium Tin Oxide replacement

On Nov. 5, Iroh filed a provisional patent application with the U.S. Patent Office for a polymer-based film with remarkable properties. The film is highly transparent and electrically conductive. It has potential uses in energy, including applications in solar and fuel cell technology. It is economical, easily processed, durable, flexible, and heat resistant.

"Because of its properties, this film is very flexible," Iroh said. "I can envision a very thin solar panel that can be unrolled and applied, perhaps to an automobile, while the sun is shining, then peeled off and stored."

More importantly, Iroh's innovative film has the potential to replace a substance known as ITO, an abbreviation for Indium Tin Oxide. While the acronym may be unfamiliar to most consumers, ITO's uses are not. ITO is behind most touch-screen devices like smart phones and video kiosks. It appears in flat panel displays, electronic inks, and organic light-emitting diodes (LEDs).

ITO is also expensive and rare. It is fragile, lacks flexibility, and it is requires complicated processes to apply. All the major sources of Indium lie outside the United States, lending a strategic value to a suitable replacement for ITO.

Development of the new film grew out of Iroh's work on coatings.

"My initial focus was in composites, particularly laminated composites," he said. "It was for that work that I received my first patents."

After earning his Ph.D. from the University of Connecticut in 1990 and a Post-doctoral stint at Temple University, Iroh accepted a position at the University of Cincinnati as an assistant professor on September 1, 1991. His research attracted the attention of the Office of Naval Research, which asked him to look into coatings to protect metal. Iroh's projects earned acclaim from the Office of Naval Research, and he was named an ONR Young Investigator for 1995-1999. This honor was followed by others. Iroh was selected as the Sigma Xi Young Investigator at the University of Cincinnati for 2001, and was named a Resident Senior Research Associate at the Air Force Research Laboratory for 2002-2003. In 2004 he was elected as a Fellow of the Society for the Advancement of Materials and Process Engineering, SAMPE.

For the naval work, Iroh adapted a laminating process to apply coatings to steel.

"I was using what was then a new class of polymer, intrinsically conducting polymer, and applying it for corrosion prevention measures," he said.

Over the years, Iroh has tackled substantial problems related to coating materials. For example, adding trace amounts of various substances can improve corrosion prevention, but these "dopants" can be lost due to weather, defeating the purpose of the coating. Other coatings are very effective, but must be cured at high temperatures.

"We have found methods to reduce curing temperatures by more than 100 degrees Celsius," Iroh said. "That is very significant."

Effective coatings must meet a wide range of requirements, Iroh said. Cost is a factor, as is ease of application, environmental safety, ability to adhere and impact resistance.

The impact resistance of nanocomposite coatings has opened a fruitful partnership between Iroh's laboratory and Jackson State University, a historically black university in Mississippi. Funded by the Office of Naval Research, Jackson State students are working with Iroh's lab on low temperature systems for high-impact epoxy coatings.

"I would hope to see some of these students return here one day as graduate student," he said.

As Iroh gained more insight into the function of various substances as coatings, it occurred to him that these coating had useful properties, even if they were not coating something.

"A coating is essentially a film. What properties does this film possess?" Iroh said.

It was the question that led to the development of the highly transparent, electrically conductive, polymer-based nanocomposite film.

"This breakthrough will give us a unique place in the broader field of composites and energy research," he said. "This is an exciting development, and I am glad that my research group is very well positioned to continue to make a significant impact in this area."

Provided by University of Cincinnati (news : web)

Giant flakes make graphene oxide gel: Discovery could boost metamaterials, high-strength fibers

Giant flakes of graphene oxide in water aggregate like a stack of pancakes, but infinitely thinner, and in the process gain characteristics that materials scientists may find delicious.

A new paper by scientists at Rice University and the University of Colorado details how slices of graphene, the single-atom form of carbon, in a solution arrange themselves to form a nematic liquid crystal in which particles are free-floating but aligned.

That much was already known. The new twist is that if the flakes -- in this case, graphene oxide -- are big enough and concentrated enough, they retain their alignment as they form a gel. That gel is a handy precursor for manufacturing metamaterials or fibers with unique mechanical and electronic properties.

The team reported its discovery online this week in the Royal Society of Chemistry journal Soft Matter. Rice authors include Matteo Pasquali, a professor of chemical and biomolecular engineering and of chemistry; 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; postdoctoral research associate Dmitry Kosynkin; and graduate students Budhadipta Dan and Natnael Behabtu. Ivan Smalyukh, an assistant professor of physics at the University of Colorado at Boulder, led research for his group, in which Dan served as a visiting scientist.

"Graphene materials and fluid phases are a great research area," Pasquali said. "From the fundamental point of view, fluid phases comprising flakes are relatively unexplored, and certainly so when the flakes have important electronic properties.

"From the application standpoint, graphene and graphene oxide can be important building blocks in such areas as flexible electronics and conductive and high-strength materials, and can serve as templates for ordering plasmonic structures," he said.

By "giant," the researchers referred to irregular flakes of graphene oxide up to 10,000 times as wide as they are high. (That's still impossibly small: on average, roughly 12 microns wide and less than a nanometer high.) Previous studies showed smaller bits of pristine graphene suspended in acid would form a liquid crystal and that graphene oxide would do likewise in other solutions, including water.

This time the team discovered that if the flakes are big enough and concentrated enough, the solution becomes semisolid. When they constrained the gel to a thin pipette and evaporated some of the water, the graphene oxide flakes got closer to each other and stacked up spontaneously, although imperfectly.

"The exciting part for me is the spontaneous ordering of graphene oxide into a liquid crystal, which nobody had observed before," said Behabtu, a member of Pasquali's lab. "It's still a liquid, but it's ordered. That's useful to make fibers, but it could also induce order on other particles like nanorods."

He said it would be a simple matter to heat the concentrated gel and extrude it into something like carbon fiber, with enhanced properties provided by "mix-ins."

Testing the possibilities, the researchers mixed gold microtriangles and glass microrods into the solution, and found both were effectively forced to line up with the pancaking flakes. Their inclusion also helped the team get visual confirmation of the flakes' orientation.

The process offers the possibility of the large-scale ordering and alignment of such plasmonic particles as gold, silver and palladium nanorods, important components in optoelectronic devices and metamaterials, they reported.

Behabtu added that heating the gel "crosslinks the flakes, and that's good for mechanical strength. You can even heat graphene oxide enough to reduce it, stripping out the oxygen and turning it back into graphite."

Co-authors of the paper are Angel Martinez and Julian Evans, graduate students of Smalyukh at the University of Colorado at Boulder.

The Institute for Complex Adaptive Matter, the Colorado Renewable and Sustainable Energy Initiative, the National Science Foundation, the Air Force Research Lab, the Air Force Office of Scientific Research, the Welch Foundation, the U.S. Army Corps of Engineers Environmental Quality and Installation Program and M-I Swaco supported the research.

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The above story is reprinted from materials provided by Rice University.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Budhadipta Dan, Natnael Behabtu, Angel Martinez, Julian S. Evans, Dmitry V. Kosynkin, James M. Tour, Matteo Pasquali, Ivan I. Smalyukh. Liquid crystals of aqueous, giant graphene oxide flakes. Soft Matter, 2011; DOI: 10.1039/C1SM06418E

How nitrous oxide is decomposed: Researchers identify structure of enzyme that breaks down potent greenhouse gas

Nitrous oxide (N2O) is a harmful climate gas. Its effect as a greenhouse gas is 300 times stronger than that of carbon dioxide. Nitrous oxide destroys the ozone layer. In industrial agriculture, it is generated on excessively fertilized fields when microorganisms decompose nitrate fertilizers. Decomposition of nitrous oxide frequently is incomplete and strongly depends on environmental conditions. Researchers from Freiburg, Constance, and KIT have now identified the structure of the enzyme that decomposes nitrous oxide and the decomposition mechanism.

Their results are published in the journal Nature.

The study demonstrated that the N2O-reductase enzyme possesses active centers made up of four copper atoms and two sulfur atoms. "Surprisingly, we found that microbiologists all over the world have assumed an incorrect structure so far," explains Professor Oliver Einsle, group leader at the Institute of Organic Chemistry and Biochemistry of the University of Freiburg. Scientists have assumed a single sulfur atom only and have not been able to completely identify the nitrous oxide decomposition mechanism. Based on the new data, the reaction sequence of the enzyme can be modeled much better. Future investigations are to provide further details and help understand which influence environmental conditions have on the process.

"It was of decisive importance that all steps of our investigation were executed in the absence of air oxygen," emphasizes Walter G. Zumft, retired professor of Karlsruher Institute of Technology. In contact with oxygen, parts of the enzyme react and the enzyme changes its structure. Together with Dr. Anja Pomowski from the University of Freiburg, the bacteria were cultivated under an oxygen-free atmosphere, the enzymes were isolated on a large scale, crystallized, and the structure was analyzed using X-rays. The team of four authors was completed by Professor Peter Kroneck from the University of Constance.

"The current study provides interesting and complementary insight into the nitrogen cycle," says Dr. Ralf Kiese from the KIT Institute of Meteorology and Climate Research. Nitrous oxide and nitrogen production on fields, pastures, and in forests depends on a multitude of often opposing effects. Last year, a KIT study demonstrated that animal husbandry may lead to less nitrous oxide unter certain conditions (doi:10.1038/nature08931). Detailed knowledge of microbial processes and their dependence on environmental conditions might help to better model the nitrous oxide contribution to the climate. In the long term, it might even be feasible to use the knowledge in order to prevent nitrous oxide from being released into the atmosphere, for example, by additives in fertilizers that preserve the functioning of N2O-reductase or by optimized processes in sewage treatment plants.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Karlsruhe Institute of Technology.

Journal References:

Anja Pomowski, Walter G. Zumft, Peter M. H. Kroneck, Oliver Einsle. N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase. Nature, 2011; DOI: 10.1038/nature10332Benjamin Wolf, Xunhua Zheng, Nicolas Brüggemann, Weiwei Chen, Michael Dannenmann, Xingguo Han, Mark A. Sutton, Honghui Wu, Zhisheng Yao, Klaus Butterbach-Bahl. Grazing-induced reduction of natural nitrous oxide release from continental steppe. Nature, 2010; 464 (7290): 881 DOI: 10.1038/nature08931

Climate change and ozone destruction hastened with nitrous oxide used in agriculture

Researchers have discovered a new binding site for nitrous oxide (N2O). Nitrous oxide reductase, an enzyme containing copper, plays a key role in the biochemical process by reducing N2O to N2. This enzyme is highly sensitive to oxygen and is often precipitated in the reaction chain, meaning large amounts of N2O are released by fertilised fields in the farming industry.

Nitrous oxide (N2O) harms Earth's climate in two ways. First, N2O is a colourless and odourless greenhouse gas that is 300 times stronger than carbon dioxide (CO2). Second, under the effect of cosmic radiation, it contributes to the destruction of the ozone layer, like halocarbons, or chlorofluorocarbons (CFCs).

N2O is therefore probably the most critical greenhouse gas of the 21st century and is an unwanted by-product of industrial farming. Nitrous oxide reductase, an enzyme containing copper, plays a key role in the biochemical process by reducing N2O to N2. This enzyme is highly sensitive to oxygen and is often precipitated in the reaction chain, meaning large amounts of N2O are released by fertilised fields in the farming industry.

The functionality and mechanisms of this important enzyme had not been thoroughly researched until Dr Anja Pomowski successfully clarified the structure of a N2O reductase, primed under the strict exclusion of dioxygen (O2). Dr Pomowski belongs to the research group headed by Prof Dr Oliver Einsle, a professor at the Institute of Organic Chemistry and Biochemistry of the University of Freiburg and a member of the BIOSS Cluster of Excellence. Together with Prof Dr Walter Zumft from the Karlsruhe Institute of Technology and Prof Dr Peter Kroneck from the University of Konstanz, the team of researchers is presenting their results in the current issue of the journal Nature.

The newly discovered structure shows first that the ratio and amount of substances in the metal centre of the enzyme have only been described incompletely thus far, and that they contain an additional sulphur atom. Second, the team also identified the binding of the N2O substrate to the metal centre. This binding site was a surprise to the scientists, and it has encouraged them to re-evaluate the mechanisms of the enzyme, whose molecular properties Prof Dr Oliver Einsle's group will continue to research in the future.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Albert-Ludwigs-Universität Freiburg.

Journal Reference:

Anja Pomowski, Walter G. Zumft, Peter M. H. Kroneck, Oliver Einsle. N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase. Nature, 2011; DOI: 10.1038/nature10332