Biofuel Research Boosted by Discovery of How Cyanobacteria Make Energy

Biofuel Research Boosted by Discovery of How Cyanobacteria Make Energy

  10:14:00 AM    Science Lover

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A generally accepted, 44-year-old assumption about how certain kinds of bacteria make energy and synthesize cell materials has been shown to be incorrect by a team of scientists led by Donald Bryant, the Ernest C. Pollard Professor of Biotechnology at Penn State and a research professor in the Department of Chemistry and Biochemistry at Montana State University. The research, which will be published in the journal Science on Dec. 16, is expected to help scientists discover new ways of genetically engineering bacteria to manufacture biofuels -- energy-rich compounds derived from biological sources. Many textbooks, which cite the 44-year-old interpretation as fact, likely will be revised as a result of the new discovery.

Penn State scientists have scoured this cyanobacterium's
genome to discover genes that could make alternative
energy-cycle enzymes for biofuels and plastics.
(Credit: Bryant lab, Penn State)

Bryant explained that, in 1967, two groups of researchers concluded that an important energy-making cycle was incomplete in cyanobacteria -- photosynthetic bacteria formerly known as blue-green algae. This energy-producing cycle -- known as the tricarboxylic acid (TCA) cycle or the Krebs cycle -- includes a series of chemical reactions that are used for metabolism by most forms of life, including bacteria, molds, protozoa and animals. This series of chemical reactions eventually leads to the production of ATP -- molecules responsible for providing energy for cell metabolism.

"During studies 44 years ago, researchers concluded that cyanobacteria were missing an essential enzyme of the metabolic pathway that is found in most other life forms," Bryant explained. "They concluded that cyanobacteria lacked the ability to make one enzyme, called 2-oxoglutarate dehydrogenase, and that this missing enzyme rendered the bacteria unable to produce a compound -- called succinyl-coenzyme A -- for the next step in the TCA cycle. The absence of this reaction was assumed to render the organisms unable to oxidize metabolites for energy production, although they could still use the remaining TCA-cycle reactions to produce substrates for biosynthetic reactions. As it turns out, the researchers just weren't looking hard enough, so there was more work to be done."

Bryant suspected that the decades-old finding needed to be re-evaluated with a fresh set of eyes and new scientific tools. He explained that, after researchers in the 1960s concluded that cyanobacteria had an incomplete TCA cycle, that false assumption was compounded by later researchers who used modern genomics-research methods to confirm it.

"One idea we had was that the 1967 hypothesis never was corrected because modern genome-annotation methods were partly to blame," Bryant said. "Computer algorithms are used to search for strings of genetic code to identify genes. Sometimes important genes simply can be missed because of matching errors, which occur when very similar genes have very different functions. So if researchers don't use biochemical methods to validate computer-identified gene functions, they run the risk of making premature and often incorrect conclusions about what's there and what's not there."

To re-test the 1967 hypothesis, the team performed new biochemical and genetic analyses on a cyanobacterium called Synechococcus sp. PCC 7002, scouring its genome for genes that might be responsible for making alternative energy-cycle enzymes. The scientists discovered that Synechococcus indeed had genes that coded for one important alternative enzyme, succinic semialdehyde dehydrogenase, and that adjacent to the gene for this enzyme was a misidentified gene that subsequently was shown to encode a novel enzyme, 2-oxo-glutarate decarboxylase.

"As it turns out, these two enzymes work together to complete the TCA cycle in a slightly different way," Bryant said. "That is, rather than making 2-oxoglutarate dehydrogenase, these bacteria produce both 2-oxoglutarate decarboxylase and succinic semialdehyde dehydrogenase. That combination of enzymes allows these organisms to move to the next intermediate -- succinate -- and to complete the TCA cycle." Bryant also said that his team found that the genes coding for the two enzymes are present in all cyanobacterial genomes except those of a few marine species. Bryant's co-author on the Science paper is Shuyi Zhang, a graduate student in the Department of Biochemistry and Molecular Biology at Penn State.

Bryant hopes to use the findings of his research to investigate new ways of producing biofuels. "Now that we understand better how cyanobacteria make energy, it might be possible to genetically engineer a cyanobacterial strain to synthesize 1,3-butanediol -- an organic compound that is the precursor for making not just biofuels but also plastics," Bryant said.

Bryant also said that his team's discoveries about cyanobacteria show how science is an ever-evolving process, and that firm conclusions never should be drawn from studies with negative results.

"Sadly, the conclusion that cyanobacteria have an incomplete TCA cycle is written into many textbooks as fact, simply because the research teams in 1967 misinterpreted their failure to find a particular enzyme," Bryant said. "But in science there is never really an end. There always is something new to discover."

The research was supported by the Air Force Office of Scientific Research and the Genomic Science Program of the U.S. Department of Energy.

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Microwave Ovens a Key to Energy Production from Wasted Heat

Microwave Ovens a Key to Energy Production from Wasted Heat

  12:35:00 AM    Science Lover

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More than 60 percent of the energy produced by cars, machines, and industry around the world is lost as waste heat -- an age-old problem -- but researchers have found a new way to make "thermoelectric" materials for use in technology that could potentially save vast amounts of energy.

Thermoelectric generation of electricity offers a way to recapture some of the enormous amounts of wasted energy lost during industrial activities. (Credit: Graphic courtesy of Oregon State University)

And it's based on a device found everywhere from kitchens to dorm rooms: a microwave oven.

Chemists at Oregon State University have discovered that simple microwave energy can be used to make a very promising group of compounds called "skutterudites," and lead to greatly improved methods of capturing wasted heat and turning it into useful electricity.

A tedious, complex and costly process to produce these materials that used to take three or four days can now be done in two minutes.

Most people are aware you're not supposed to put metal foil into a microwave, because it will spark. But powdered metals are different, and OSU scientists are tapping into that basic phenomenon to heat materials to 1,800 degrees in just a few minutes -- on purpose, and with hugely useful results.

These findings, published in Materials Research Bulletin, should speed research and ultimately provide a more commercially-useful, low-cost path to a future of thermoelectric energy.

"This is really quite fascinating," said Mas Subramanian, the Milton Harris Professor of Materials Science at OSU. "It's the first time we've ever used microwave technology to produce this class of materials."

Thermoelectric power generation, researchers say, is a way to produce electricity from waste heat -- something as basic as the hot exhaust from an automobile, or the wasted heat given off by a whirring machine. It's been known of for decades but never really used other than in niche applications, because it's too inefficient, costly and sometimes the materials needed are toxic. NASA has used some expensive and high-tech thermoelectric generators to produce electricity in outer space.

The problem of wasted energy is huge. A car, for instance, wastes about two-thirds of the energy it produces. Factories, machines and power plants discard enormous amounts of energy.

But the potential is also huge. A hybrid automobile that has both gasoline and electric engines, for instance, would be ideal to take advantage of thermoelectric generation to increase its efficiency. Heat that is now being wasted in the exhaust or vented by the radiator could instead be used to help power the car. Factories could become much more energy efficient, electric utilities could recapture energy from heat that's now going up a smokestack. Minor applications might even include a wrist watch operated by body heat.



"To address this, we need materials that are low cost, non-toxic and stable, and highly efficient at converting low-grade waste heat into electricity," Subramanian said. "In material science, that's almost like being a glass and a metal at the same time. It just isn't easy. Because of these obstacles almost nothing has been done commercially in large scale thermoelectric power generation."

Skutterudites have some of the needed properties, researchers say, but historically have been slow and difficult to make. The new findings cut that production time from days to minutes, and should not only speed research on these compounds but ultimately provide a more affordable way to produce them on a mass commercial scale.

OSU researchers have created skutterudites with microwave technology with an indium cobalt antimonite compound, and believe others are possible. They are continuing research, and believe that ultimately a range of different compounds may be needed for different applications of thermoelectric generation.

Collaborators on this study included Krishnendu Biswas, a post-doctoral researcher, and Sean Muir, a doctoral candidate, both in the OSU Department of Chemistry. The work has been supported by both the National Science Foundation and U.S. Department of Energy.

"We were surprised this worked so well," Subramanian said. "Right now large-scale thermoelectric generation of electricity is just a good idea that we couldn't make work. In the future it could be huge." 

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Termites' Digestive System Could Act as Biofuel Refinery

Termites' Digestive System Could Act as Biofuel Refinery

  10:02:00 AM    Science Lover

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One of the peskiest household pests, while disastrous to homes, could prove to be a boon for cars, according to a Purdue University study.

Mike Scharf's work with termites has shown that the insects' digestive systems may help break down woody biomass for biofuel production. (Credit: Purdue Agricultural Communication photo/Tom Campbell)

Mike Scharf, the O. Wayne Rollins/Orkin Chair in Molecular Physiology and Urban Entomology, said his laboratory has discovered a cocktail of enzymes from the guts of termites that may be better at getting around the barriers that inhibit fuel production from woody biomass. The Scharf Laboratory found that enzymes in termite guts are instrumental in the insects' ability to break down the wood they eat.

The findings, published in the early online version of the journal PLoS One, are the first to measure the sugar output from enzymes created by the termites themselves and the output from symbionts, small protozoa that live in termite guts and aid in digestion of woody material.

"For the most part, people have overlooked the host termite as a source of enzymes that could be used in the production of biofuels. For a long time it was thought that the symbionts were solely responsible for digestion," Scharf said. "Certainly the symbionts do a lot, but what we've shown is that the host produces enzymes that work in synergy with the enzymes produced by those symbionts. When you combine the functions of the host enzymes with the symbionts, it's like one plus one equals four."

Scharf and his research partners separated the termite guts, testing portions that did and did not contain symbionts on sawdust to measure the sugars created.



Once the enzymes were identified, Scharf and his team worked with Chesapeake Perl, a protein production company in Maryland, to create synthetic versions. The genes responsible for creating the enzymes were inserted into a virus and fed to caterpillars, which then produce large amounts of the enzymes. Tests showed that the synthetic versions of the host termite enzymes also were very effective at releasing sugar from the biomass.

They found that the three synthetic enzymes function on different parts of the biomass.

Two enzymes are responsible for the release of glucose and pentose, two different sugars. The other enzyme breaks down lignin, the rigid compound that makes up plant cell walls.

Lignin is one of the most significant barriers that blocks the access to sugars contained in biomass. Scharf said it's possible that the enzymes derived from termites and their symbionts, as well as synthetic versions, could be more effective at removing that lignin barrier.

Sugars from plant material are essential to creating biofuels. Those sugars are fermented to make products such as ethanol.

"We've found a cocktail of enzymes that create sugars from wood," Scharf said. "We were also able to see for the first time that the host and the symbionts can synergistically produce these sugars."

Next, Scharf said his laboratory and collaborators would work on identifying the symbiont enzymes that could be combined with termite enzymes to release the greatest amount of sugars from woody material. Combining those enzymes would increase the amount of biofuel that should be available from biomass.

The U.S. Department of Energy and Chesapeake Perl funded the research.

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Inkjet Printing Could Change the Face of Solar Energy Industry

Inkjet Printing Could Change the Face of Solar Energy Industry

  9:33:00 AM    Science Lover

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Inkjet printers, a low-cost technology that in recent decades has revolutionized home and small office printing, may soon offer similar benefits for the future of solar energy.

Solar cell. This scanning electron microscope, 
cross-sectional image shows the various compounds 
of a new chalcopyrite solar cell only a few microns
thick, which can be created much less expensively with
inkjet printing. (Credit: Oregon State University)

Engineers at Oregon State University have discovered a way for the first time to create successful "CIGS" solar devices with inkjet printing, in work that reduces raw material waste by 90 percent and will significantly lower the cost of producing solar energy cells with some very promising compounds.

High performing, rapidly produced, ultra-low cost, thin film solar electronics should be possible, scientists said.

The findings have been published in Solar Energy Materials and Solar Cells, a professional journal, and a patent applied for on the discovery. Further research is needed to increase the efficiency of the cell, but the work could lead to a whole new generation of solar energy technology, researchers say.

"This is very promising and could be an important new technology to add to the solar energy field," said Chih-hung Chang, an OSU professor in the School of Chemical, Biological and Environmental Engineering. "Until now no one had been able to create working CIGS solar devices with inkjet technology."

Part of the advantage of this approach, Chang said, is a dramatic reduction in wasted material. Instead of depositing chemical compounds on a substrate with a more expensive vapor phase deposition -- wasting most of the material in the process -- inkjet technology could be used to create precise patterning with very low waste.

"Some of the materials we want to work with for the most advanced solar cells, such as indium, are relatively expensive," Chang said. "If that's what you're using you can't really afford to waste it, and the inkjet approach almost eliminates the waste."



One of the most promising compounds and the focus of the current study is called chalcopyrite, or "CIGS" for the copper, indium, gallium and selenium elements of which it's composed. CIGS has extraordinary solar efficiency -- a layer of chalcopyrite one or two microns thick has the ability to capture the energy from photons about as efficiently as a 50-micron-thick layer made with silicon.

In the new findings, researchers were able to create an ink that could print chalcopyrite onto substrates with an inkjet approach, with a power conversion efficiency of about 5 percent. The OSU researchers say that with continued research they should be able to achieve an efficiency of about 12 percent, which would make a commercially viable solar cell.

In related work, being done in collaboration with Greg Herman, an OSU associate professor of chemical engineering, the engineers are studying other compounds that might also be used with inkjet technology, and cost even less.

Some approaches to producing solar cells are time consuming, or require expensive vacuum systems or toxic chemicals. OSU experts are working to eliminate some of those roadblocks and create much less costly solar technology that is also more environmentally friendly. New jobs and industries in the Pacific Northwest could evolve from such initiatives, they say.

If costs can be reduced enough and other hurdles breached, it might even be possible to create solar cells that could be built directly into roofing materials, scientists say, opening a huge new potential for solar energy.

"In summary, a simple, fast, and direct-write, solution-based deposition process is developed for the fabrication of high quality CIGS solar cells," the researchers wrote in their conclusion. "Safe, cheap, and air-stable inks can be prepared easily by controlling the composition of low-cost metal salt precursors at a molecular level."

This work was supported by the Daegu Gyeongbuk Institute of Science and Technology, the U.S. Department of Energy and OSU's University Venture Development Fund, which helps donors receive tax benefits while sponsoring projects that will bring new technology, jobs and economic growth to Oregon.

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Modeling the bizarre: Quantum superfluids

Modeling the bizarre: Quantum superfluids

  10:46:00 PM    Science Lover

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More than 100 years since superconductivity was discovered, a comprehensive description for the behavior of a broad class of fundamental physical systems that exhibit the bizarre properties of superconductivity and superfluidity has been developed. Superconductivity and superfluidity are quantum mechanical phenomena in systems composed of a very large number of microscopic particles that can be observed with the "naked eye." Remarkable features of these systems include electrical flow with no resistance, or special fluids that creep up the sides of a container and overflow with no external influence.

The time-dependent SLDA (superfluid local density
approximation) provides a scalable and robust
mathematical framework to study the highly
nonlinear microscopic dynamics of Fermi systems.
Fermionic vortex crossings and exchanges are
shown as time progresses in an excited system of
cold atoms in an elongated trap. The process is
reminiscent of DNA recombination and indicative
of the onset of quantum turbulence. The dynamics
of quantum turbulence in Fermi systems may provide
insight into the pinning and de-pinning vortex
mechanisms in neutron stars, for example

When a superfluid is rotated or swirled, it develops cylinder-like vortices. In their paper featured in the June 10 issue of the journal Science, a team of scientists, including Pacific Northwest National Laboratory's Kenneth Roche, describes how these vortices form and evolve microscopically at very low temperatures in fermionic gas systems. They also describe the quantized vortices as they cross and reconnect. The team's simulations show that, in many instances, the system remains superfluid even when stirred at supercritical speeds, in contrast to a decades-old hypothesis that predicts the system would lose its superfluid properties under these circumstances.

The methods developed will open new avenues of research both in nuclear physics and astrophysics, as well as in condensed-matter and related fields. These methods can now be used to study various properties of atomic nuclei, ultra-cold gases in traps and optical lattices, induced nuclear fission, vortices within a neutron star's crust, the onset of quantum turbulence and high-temperature superconductivity.



The team developed an extension of the time-dependent density functional theory (DFT)—a method originally used in quantum chemistry and physics to study the electronic properties of molecules—for fermionic systems. Unlike a bosonic superfluid, the new mathematical framework needed for a fermionic superfluid is about a hundred thousand times more complex. To evaluate this extremely complex formulation, the research team turned to one of the world's fastest supercomputers, the Jaguar PF, a Cray XT5 system at the Department of Energy's Oak Ridge National Laboratory in Tennessee. Roche led the effort to develop software that allowed Jaguar to run the team's challenging calculations.

The team is studying the onset of quantum turbulence, the pinning and de-pinning mechanism of vortices on "defects" in a real-time dynamics, and the dynamics of exotic pairing mechanisms such as the Fulde-Ferrell-Larkin-Ovchinnikov phase. For nuclei, the team plans to study induced gamma and neutron induced fission processes and to lay the foundation for extending the deterministic superfluid DFT to a stochastic quantization of the theory amenable to many-body collective tunneling. These calculations will only be possible on exascale and beyond computing platforms.

More information: Aurel Bulgac, Yuan-Lung Luo, Piotr Magierski, Kenneth Roche, Yongle Yu. "Real-Time Dynamics of Quantized Vortices in a Unitary Fermi Superfluid."

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Superatoms With Magnetic Shells Discovered

Superatoms With Magnetic Shells Discovered

  4:49:00 PM    Science Lover

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A team of Virginia Commonwealth University scientists has discovered a new class of 'superatoms' -- a stable cluster of atoms that can mimic different elements of the periodic table -- with unusual magnetic characteristics.

A proposed assembly of FeMg₈ magnetic superatoms 
where the directions of magnetic moment is indicated 
by arrows. (Credit: Image courtesy of Victor Medel/VCU)

The superatom contains magnetized magnesium atoms, an element traditionally considered as non-magnetic. The metallic character of magnesium along with infused magnetism may one day be used to create molecular electronic devices for the next generation of faster processors, larger memory storage and quantum computers.

In a study published online in the Early Edition of the Proceedings of the National Academy of Sciences, the team reports that the newly discovered cluster consisting of one iron and eight magnesium atoms acts like a tiny magnet that derives its magnetic strength from the iron and magnesium atoms. The combined unit matches the magnetic strength of a single iron atom while preferentially allowing electrons of specific spin orientation to be distributed throughout the cluster.

Through an elaborate series of theoretical studies, Shiv N. Khanna, Ph.D., a Commonwealth professor in the VCU Department of Physics, and his team examined the electronic and magnetic properties of clusters having one iron atom surrounded by multiple magnesium atoms. The team included instructor J. Ulises Reveles and Victor M. Medel, a post-doctoral associate, both from VCU; A. W. Castleman Jr., Ph.D., the Evan Pugh Professor of Chemistry and Physics, and Eberly Distinguished chair in Science in the Department of Chemistry at Penn State University; and Prasenjit Sen and Vikas Chauhan from the Harish-Chandra Research Institute in Allahabad, India.

"Our research opens a new way of infusing magnetic character in otherwise non-magnetic elements through controlled association with a single magnetic atom. An important objective was to discover what combination of atoms would lead to a species that is stable as we put multiple units together," said Khanna.

"The combination of magnetic and conducting attributes was also desirable. Magnesium is a good conductor of electricity and, hence, the superatom combines the benefit of magnetic character along with ease of conduction through its outer skin," he said.

The team found that when the cluster had eight magnesium atoms it acquired extra stability due to filled electronic shells that were far separated from the unfilled shells. An atom is in a stable configuration when its outermost shell is full and far separated from unfilled shells, as found in inert gas atoms. Khanna said that such phenomena commonly occur with paired electrons which are non-magnetic, but in this study the magnetic electronic shell showed stability.

According to Khanna, the new cluster had a magnetic moment of four Bohr magnetons, which is almost twice that of an iron atom in solid iron magnets. A magnetic moment is a measure of the magnetic strength of the cluster. Although the periodic table has more than one hundred elements, there are only nine elements that exhibit magnetic character in solid form.

"A combination such as the one we have created here can lead to significant developments in the area of "molecular electronics" where such devices allow the flow of electrons with particular spin orientation desired for applications such as quantum computers. These molecular devices are also expected to help make denser integrated devices, higher data processing, and other benefits," said Reveles.

Khanna and his team are conducting preliminary studies on the assemblies of the new superatoms and have made some promising observations that may have applications in spintronics. Spintronics is a process using electron spin to synthesize new devices for memory and data processing.

This research was supported by the U.S. Department of Energy.

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Researchers Create Nanoscale Waveguide for Future Photonics

Researchers Create Nanoscale Waveguide for Future Photonics

  10:46:00 AM    Science Lover

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The creation of a new quasiparticle called the "hybrid plasmon polariton" may throw open the doors to integrated photonic circuits and optical computing for the 21st century. Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated the first true nanoscale waveguides for next generation on-chip optical communication systems.

The hybrid plasmon polariton (HPP) nanoscale 
waveguide consists of a semiconductor strip separated
from a metallic surface by a low dielectric gap. Schematic 
shows HPP waveguide responding when a metal slit at 
the guide’s input end is illuminated. (Credit: 
Courtesy of Xiang Zhang group)

"We have directly demonstrated the nanoscale waveguiding of light at visible and near infrared frequencies in a metal-insulator-semiconductor device featuring low loss and broadband operation," says Xiang Zhang, the leader of this research. "The novel mode design of our nanoscale waveguide holds great potential for nanoscale photonic applications, such as intra-chip optical communication, signal modulation, nanoscale lasers and bio-medical sensing."

Zhang, a principal investigator with Berkeley Lab's Materials Sciences Division and director of the University of California at Berkeley's Nano-scale Science and Engineering Center (SINAM), is the corresponding author of a paper published by Nature Communications that describes this work titled "Experimental Demonstration of Low-Loss Optical Waveguiding at Deep Sub-wavelength Scales." Co-authoring the paper with Zhang were Volker Sorger, Ziliang Ye, Rupert Oulton, Yuan Wang, Guy Bartal and Xiaobo Yin.

In this paper, Zhang and his co-authors describe the use of the hybrid plasmon polariton, a quasi-particle they conceptualized and created, in a nanoscale waveguide system that is capable of shepherding light waves along a metal-dielectric nanostructure interface over sufficient distances for the routing of optical communication signals in photonic devices. The key is the insertion of a thin low-dielectric layer between the metal and a semiconductor strip.

"We reveal mode sizes down to 50-by-60 square nanometers using Near-field scanning optical microscopy (NSOM) at optical wavelengths," says Volker Sorger a graduate student in Zhang's research group and one of the two lead authors on the Nature Communications paper. "The propagation lengths were 10 times the vacuum wavelength of visible light and 20 times that of near infrared."

The high-technology world is eagerly anticipating the replacement of today's electronic circuits in microprocessors and other devices with circuits based on the transmission of light and other forms of electromagnetic waves. Photonic technology, or "photonics," promises to be superfast and ultrasensitive in comparison to electronic technology.

"To meet the ever-growing demand for higher data bandwidth and lower power consumption, we need to reduce the energy required to create, transmit and detect each bit of information," says Sorger. "This requires reducing physical photonic component sizes down beyond the diffraction limit of light while still providing integrated functionality."

Until recently, the size and performance of photonic devices was constrained by the interference that arises between closely spaced light waves. This diffraction limit results in weak photonic-electronic interactions that can only be avoided through the use of devices much larger in size than today's electronic circuits. A breakthrough came with the discovery that it is possible to couple photons with electrons by squeezing light waves through the interface between a metal/dielectric nanostructure whose dimensions are smaller than half the wavelengths of the incident photons in free space.

Directing waves of light across the surface of a metal nanostructure generates electronic surface waves -- called plasmons -- that roll through the metal's conduction electrons (those loosely attached to molecules and atoms). The resulting interaction between plasmons and photons creates a quasi-particle called a surface plasmon polariton(SPP) that can serve as a carrier of information. Hopes were high for SPPs in nanoscale photonic devices because their wavelengths can be scaled down below the diffraction limit, but problems arose because any light signal loses strength as it passes through the metal portion of a metal-dielectric interface.

"Until now, the direct experimental demonstration of low-loss propagation of deep sub-wavelength optical modes was not realized due to the huge propagation loss in the optical mode that resulted from the electromagnetic field being pushed into the metal," Zhang says. "With this trade-off between optical confinement and metallic losses, the use of plasmonics for integrated photonics, in particular for optical interconnects, has remained uncertain."

To solve the problem of optical signal loss, Zhang and his group proposed the hybrid plasmon polariton (HPP) concept. A semiconductor (high-dielectric) strip is placed on a metal interface, just barely separated by a thin oxide (low-dielectric) layer. This new metal-oxide-semiconductor design results in a redistribution of an incoming light wave's energy. Instead of being concentrated in the metal, where optical losses are high, some of the light wave's energy is squeezed into the low dielectric gap where optical losses are substantially less compared to the plasmonic metal.



"With this design, we create an HPP mode, a hybrid of the photonic and plasmonic modes that takes the best from both systems and gives us high confinement with low signal loss," says Ziliang Ye, the other lead authors of the Nature Communications paper who is also a graduate student in Zhang's research group. "The HPP mode is not only advantageous for down-scaling physical device sizes, but also for delivering novel physical effects at the device level that pave the way for nanolasers, as well as for quantum photonics and single-photon all-optical switches."

The HPP waveguide system is fully compatible with current semiconductor/CMOS processing techniques, as well as with the Silicon-on-Insulator (SOI) platform used today for photonic integration. This should make it easier to incorporate the technology into low-cost, large-scale integration and manufacturing schemes. Sorger believes that prototypes based on this technology could be ready within the next two years and the first actual products could be on the market within five years.

"We are already working on demonstrating an all-optical transistor and electro-optical modulator based on the HPP waveguide system," Sorger says. "We're also now looking into bio-medical applications, such as using the HPP waveguide to make a molecular sensor."

This research was supported by the National Science Foundation's Nano-Scale Science and Engineering Center.

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Super Energy Storage: Activated Graphene Makes Superior Supercapacitors for Energy Storage

Super Energy Storage: Activated Graphene Makes Superior Supercapacitors for Energy Storage

  5:58:00 PM    Science Lover

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Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have helped to uncover the nanoscale structure of a novel form of carbon, contributing to an explanation of why this new material acts like a super-absorbent sponge when it comes to soaking up electric charge. The material, which was recently created at The University of Texas -- Austin, can be incorporated into "supercapacitor" energy-storage devices with remarkably high storage capacity while retaining other attractive attributes such as superfast energy release, quick recharge time, and a lifetime of at least 10,000 charge/discharge cycles.

Dong Su and Eric Stach use a powerful electron microscope 
to analyze samples of activated graphene at Brookhaven's 
Center for Functional Nanomaterials. Says Stach: "The 
CFN provides access to scientists around the world 
to solve cutting-edge problems in nanoscience and 
nanotechnology. This work is exactly what this 
facility was established to do." (Credit: Image 
courtesy of DOE/Brookhaven National Laboratory)

"Those properties make this new form of carbon particularly attractive for meeting electrical energy storage needs that also require a quick release of energy -- for instance, in electric vehicles or to smooth out power availability from intermittent energy sources, such as wind and solar power," said Brookhaven materials scientist Eric Stach, a co-author on a paper describing the material published in Science on May 12, 2011.

Supercapacitors are similar to batteries in that both store electric charge. Batteries do so through chemical reactions between metallic electrodes and a liquid electrolyte. Because these chemicals take time to react, energy is stored and released relatively slowly. But batteries can store a lot of energy and release it over a fairly long time.

Supercapacitors, on the other hand, store charge in the form of ions on the surface of the electrodes, similar to static electricity, rather than relying on chemical reactions. Charging the electrodes causes ions in the electrolyte to separate, or polarize, as well -- so charge gets stored at the interface between the electrodes and the electrolyte. Pores in the electrode increase the surface area over which the electrolyte can flow and interact -- increasing the amount of energy that can be stored.

But because most supercapacitors can't hold nearly as much charge as batteries, their use has been limited to applications where smaller amounts of energy are needed quickly, or where long life cycle is essential, such as in mobile electronic devices.

The new material developed by the UT-Austin researchers may change that. Supercapacitors made from it have an energy-storage capacity, or energy density, that is approaching the energy density of lead-acid batteries, while retaining the high power density -- that is, rapid energy release -- that is characteristic of supercapacitors.

"This new material combines the attributes of both electrical storage systems," said University of Texas team leader Rodney Ruoff. "We were rather stunned by its exceptional performance."

The UT-Austin team had set out to create a more porous form of carbon by using potassium hydroxide to restructure chemically modified graphene platelets -- a form of carbon where the atoms are arrayed in tile-like rings laying flat to form single-atom-thick sheets. Such "chemical activation" has been previously used to create various forms of "activated carbon," which have pores that increase surface area and are used in filters and other applications, including supercapacitors.

But because this new form of carbon was so superior to others used in supercapacitors, the UT-Austin researchers knew they'd need to characterize its structure at the nanoscale.

Ruoff had formed a hypothesis that the material consisted of a continuous three-dimensional porous network with single-atom-thick walls, with a significant fraction being "negative curvature carbon," similar to inside-out buckyballs. He turned to Stach at Brookhaven for help with further structural characterization to verify or refute this hypothesis.

Stach and Brookhaven colleague Dong Su conducted a wide range of studies at the Lab's Center for Functional Nanomaterials, the National Synchrotron Light Source, and at the National Center for Electron Microscopy at Lawrence Berkeley National Laboratory, all three facilities supported by the DOE Office of Science. "At the DOE laboratories, we have the highest resolution microscopes in the world, so we really went full bore into characterizing the atomic structure," Stach said.

"Our studies revealed that Ruoff's hypothesis was in fact correct, and that the material's three-dimensional nanoscale structure consists of a network of highly curved, single-atom-thick walls forming tiny pores with widths ranging from 1 to 5 nanometers, or billionths of a meter."

The study includes detailed images of the fine pore structure and the carbon walls themselves, as well as images that show how these details fit into the big picture. "The data from NSLS were crucial to showing that our highly local characterization was representative of the overall material," Stach said.

"We're still working with Ruoff and his team to pull together a complete description of the material structure. We're also adding computational studies to help us understand how this three-dimensional network forms, so that we can potentially tailor the pore sizes to be optimal for specific applications, including capacitive storage, catalysis, and fuel cells," Stach said.

Meanwhile, the scientists say the processing techniques used to create the new form of carbon are readily scalable to industrial production. "This material -- being so easily manufactured from one of the most abundant elements in the universe -- will have a broad range impacts on research and technology in both energy storage and energy conversion," Ruoff said.

Story Source:The above story is reprinted (with editorial adaptations) from materials provided by DOE/Brookhaven National Laboratory.

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Green Energy Advance: Tandem Catalysis in Nanocrystal Interfaces

Green Energy Advance: Tandem Catalysis in Nanocrystal Interfaces

  1:27:00 AM    Science Lover

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In a development that holds intriguing possibilities for the future of industrial catalysis, as well as for such promising clean green energy technologies as artificial photosynthesis, researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have created bilayered nanocrystals of a metal-metal oxide that are the first to feature multiple catalytic sites on nanocrystal interfaces. These multiple catalytic sites allow for multiple, sequential catalytic reactions to be carried out selectively and in tandem.

In a unique new bilyaer nanocatalyst system, single layers of metal and metal oxide nanocubes are deposited to create two distinct metal--metal oxide interfaces that allow for multiple, sequential catalytic reactions to be carried out selectively and in tandem. (Credit: Image courtesy of Yang group)

"The demonstration of rationally designed and assembled nanocrystal bilayers with multiple built-in metal-metal oxide interfaces for tandem catalysis represents a powerful new approach towards designing high-performance, multifunctional nanostructured catalysts for multiple-step chemical reactions," says the leader of this research Peidong Yang, a chemist who holds joint appointments with Berkeley Lab's Materials Sciences Division, and the University of California Berkeley's Chemistry Department and Department of Materials Science and Engineering.

Yang is the corresponding author of a paper describing this research that appears in the journal Nature Chemistry. Co-authoring the paper were Yusuke Yamada, Chia-Kuang Tsung, Wenyu Huang, Ziyang Huo, Susan Habas, Tetsuro Soejima, Cesar Aliaga and leading authority on catalysis Gabor Somorjai.

Catalysts -- substances that speed up the rates of chemical reactions without themselves being chemically changed -- are used to initiate virtually every industrial manufacturing process that involves chemistry. Metal catalysts have been the traditional workhorses, but in recent years, with the advent of nano-sized catalysts, metal,oxide and their interface have surged in importance.



"High-performance metal-oxide nanocatalysts are central to the development of new-generation energy conversion and storage technologies," Yang says. "However, to significantly improve our capability of designing better catalysts, new concepts for the rational design and assembly of metal-metal oxide interfaces are needed."

Studies in recent years have shown that for nanocrystals, the size and shape -- specifically surface faceting with well-defined atomic arrangements -- can have an enormous impact on catalytic properties. This makes it easier to optimize nanocrystal catalysts for activity and selectivity than bulk-sized catalysts. Shape- and size-controlled metal oxide nanocrystal catalysts have shown particular promise.

"It is well-known that catalysis can be modulated by using different metal oxide supports, or metal oxide supports with different crystal surfaces," Yang says. "Precise selection and control of metal-metal oxide interfaces in nanocrystals should therefore yield better activity and selectivity for a desired reaction."

To determine whether the integration of two types of metal oxide interfaces on the surface of a single active metal nanocrystal could yield a novel tandem catalyst for multistep reactions, Yang and his coauthors used the Langmuir-Blodgett assembly technique to deposit nanocube monolayers of platinum and cerium oxide on a silica (silicon dioxide) substrate. The nanocube layers were each less than 10 nanometers thick and stacked one on top of the other to create two distinct metal-metal oxide interfaces -- platinum-silica and cerium oxide-platinum. These two interfaces were then used to catalyze two separate and sequential reactions. First, the cerium oxide-platinum interface catalyzed methanol to produce carbon monoxide and hydrogen. These products then underwent ethylene hydroformylation through a reaction catalyzed by the platinum-silica interface. The final result of this tandem catalysis was propanal.

"The cubic shape of the nanocrystal layers is ideal for assembling metal-metal oxide interfaces with large contact areas," Yang says. "Integrating binary nanocrystals to form highly ordered superlattices is a new and highly effective way to form multiple interfaces with new functionalities."

Yang says that the concept of tandem catalysis through multiple interface design that he and his co-authors have developed should be especially valuable for applications in which multiple sequential reactions are required to produce chemicals in a highly active and selective manner. A prime example is artificial photosynthesis, the effort to capture energy from the sun and transform it into electricity or chemical fuels. To this end, Yang leads the Berkeley component of the Joint Center for Artificial Photosynthesis, a new Energy Innovation Hub created by the U.S. Department of Energy that partners Berkeley Lab with the California Institute of Technology (Caltech).

"Artificial photosynthesis typically involves multiple chemical reactions in a sequential manner, including, for example, water reduction and oxidation, and carbon dioxide reduction," says Yang. "Our tandem catalysis approach should also be relevant to photoelectrochemical reactions, such as solar water splitting, again where sequential, multiple reaction steps are necessary. For this, however, we will need to explore new metal oxide or other semiconductor supports, such as titanium dioxide, in our catalyst design."

This research was supported by the DOE Office of Science.

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Breakthrough in Nanocomposite for High-Capacity Hydrogen Storage

Breakthrough in Nanocomposite for High-Capacity Hydrogen Storage

  9:50:00 AM    Science Lover

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Since the 1970s, hydrogen has been touted as a promising alternative to fossil fuels due to its clean combustion -- unlike hydrocarbon-based fuels, which spew greenhouse gases and harmful pollutants, hydrogen's only combustion by-product is water. Compared to gasoline, hydrogen is lightweight, can provide a higher energy density and is readily available. But there's a reason we're not already living in a hydrogen economy: to replace gasoline as a fuel, hydrogen must be safely and densely stored, yet easily accessed. Limited by materials unable to leap these conflicting hurdles, hydrogen storage technology has lagged behind other clean energy candidates.

This schematic shows high-capacity magnesium nanocrystals encapsulated in a gas-barrier polymer matrix to create a new and revolutionary hydrogen storage composite material. (Credit: Image from Jeff Urban)

 

In recent years, researchers have attempted to tackle both issues by locking hydrogen into solids, packing larger quantities into smaller volumes with low reactivity -- a necessity in keeping this volatile gas stable. However, most of these solids can only absorb a small amount of hydrogen and require extreme heating or cooling to boost their overall energy efficiency.

Now, scientists with the U.S. Department of Energy (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a new composite material for hydrogen storage consisting of nanoparticles of magnesium metal sprinkled through a matrix of polymethyl methacrylate, a polymer related to Plexiglas. This pliable nanocomposite rapidly absorbs and releases hydrogen at modest temperatures without oxidizing the metal after cycling -- a major breakthrough in materials design for hydrogen storage, batteries and fuel cells.

"This work showcases our ability to design composite nanoscale materials that overcome fundamental thermodynamic and kinetic barriers to realize a materials combination that has been very elusive historically," says Jeff Urban, Deputy Director of the Inorganic Nanostructures Facility at the Molecular Foundry, a DOE Office of Science nanoscience center and national user facility located at Berkeley Lab. "Moreover, we are able to productively leverage the unique properties of both the polymer and nanoparticle in this new composite material, which may have broad applicability to related problems in other areas of energy research."

Urban, along with coauthors Ki-Joon Jeon and Christian Kisielowski used the TEAM 0.5 microscope at the National Center for Electron Microscopy (NCEM), another DOE Office of Science national user facility housed at Berkeley Lab, to observe individual magnesium nanocrystals dispersed throughout the polymer. With the high-resolution imaging capabilities of TEAM 0.5, the world's most powerful electron microscope, the researchers were also able to track defects -- atomic vacancies in an otherwise-ordered crystalline framework -- providing unprecedented insight into the behavior of hydrogen within this new class of storage materials.

"Discovering new materials that could help us find a more sustainable energy solution is at the core of the Department of Energy's mission. Our lab provides outstanding experiments to support this mission with great success," says Kisielowski. "We confirmed the presence of hydrogen in this material through time-dependent spectroscopic investigations with the TEAM 0.5 microscope. This investigation suggests that even direct imaging of hydrogen columns in such materials can be attempted using the TEAM microscope."

"The unique nature of Berkeley Lab encourages cross-division collaborations without any limitations," said Jeon, now at the Ulsan National Institute of Science and Technology, whose postdoctoral work with Urban led to this publication.

To investigate the uptake and release of hydrogen in their nanocomposite material, the team turned to Berkeley Lab's Energy and Environmental Technologies Division (EETD), whose research is aimed at developing more environmentally friendly technologies for generating and storing energy, including hydrogen storage.

"Here at EETD, we have been working closely with industry to maintain a hydrogen storage facility as well as develop hydrogen storage property testing protocols," says Samuel Mao, director of the Clean Energy Laboratory at Berkeley Lab and an adjunct engineering faculty member at the University of California (UC), Berkeley. "We very much enjoy this collaboration with Jeff and his team in the Materials Sciences Division, where they developed and synthesized this new material, and were then able to use our facility for their hydrogen storage research."

Adds Urban, "This ambitious science is uniquely well-positioned to be pursued within the strong collaborative ethos here at Berkeley Lab. The successes we achieve depend critically upon close ties between cutting-edge microscopy at NCEM, tools and expertise from EETD, and the characterization and materials know-how from MSD."

This research is reported in a paper titled, "Air-stable magnesium nanocomposites provide rapid and high-capacity hydrogen storage without heavy metal catalysts," appearing in the journal Nature Materials. Co-authoring the paper with Urban, Kisielowski and Jeon were Hoi Ri Moon, Anne M. Ruminski, Bin Jiang and Rizia Bardhan.

This work was supported by DOE's Office of Science.

The Molecular Foundry is one of the five DOE Nanoscale Science Research Centers (NSRCs), premier national user facilities for interdisciplinary research at the nanoscale. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE's Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit http://nano.energy.gov.

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Drilling Down to the Nanometer Depths of Leaves for Biofuels

Drilling Down to the Nanometer Depths of Leaves for Biofuels

  4:57:00 PM    Science Lover

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By imaging the cell walls of a zinnia leaf down to the nanometer scale, energy researchers have a better idea about how to turn plants into biofuels.

A xylem cell with fluorescent lignocellulose bands 
as the major feature. (Credit: Image courtesy 
of DOE/Lawrence Livermore National Laboratory)

In a paper appearing online in the journal Plant Physiology, a team from Lawrence Livermore led by Michael Thelen, in collaboration with researchers from Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, has used four different imaging techniques to systematically drill down deep into the cells of Zinnia elegans.

Zinnia is a common garden annual plant with solitary daisy like flower heads on long stems and sandpapery, lace shaped leaves. The leaves of seedlings provide a rich source of single cells that are dark green with chloroplasts and can be cultured in liquid for several days at a time. During the culturing process, the cells change in shape to resemble the tube-like cells that carry water from roots to leaves. Known as xylem, these cells hold the bulk of cellulose and lignin in plants, which are both major targets of recent biofuel research.

Using different microscopy methods, the team was able to visualize single cells in detail, cellular substructures, fine-scale organization of the cell wall, and even chemical composition of single zinnia cells, indicating that they contain an abundance of lignocellulose.

"The basic idea is that cellulose is a polymer of sugars, which if released by enzymes, can be converted into alcohols and other chemicals used in alternative fuel production," Thelen said. "But for this to happen efficiently, we need to find ways to see how this is proceeding at several spatial scales."

To get at the sugars is no easy task. The team had to find ways to overcome the hydrophobic protection of crystalline cellulose provided by lignin in the cell wall. The two polymers, collectively called lignocellulose, are very insoluble, resistant to common chemicals and mechanical breakage, and are a superior substance for providing strength and structure to plants.

The detailed three-dimensional molecular cell wall structure of plants remains poorly understood.

"The capability to image plant cell surfaces at the nanometer scale, together with the corresponding chemical composition, could significantly enhance our understanding of cell wall molecular architecture," said Alex Malkin, a member of the LLNL team who is an expert in atomic force microscopy. "A high resolution structural model is crucial for the successful implementation of new approaches for conversion of biomass to liquid fuels."

To make fuels from plant biomass requires a thorough understanding of the organization of cell walls before determining the best methods for cell wall deconstruction into its components. Catherine Lacayo, a postdoctoral scientist working with Thelen and Malkin, has taken the first steps toward a comprehensive approach.

She came up with techniques that reveal the inner structure of cell walls in these single xylem cells, which represent about 70 percent of the cellulose in plants that can be used in fuel processing. "This approach will be useful for evaluating the responses of plant material to various chemical and enzymatic treatments, and could accelerate the current efforts in lignocellulosic biofuel production."

The research is supported by the Department of Energy Genome Sciences Program through the Office of Biological and Environmental Research, and the DOE's BioEnergy Research Centers in Emeryville and Oak Ridge. It will appear in the September issue of Plant Physiology.

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Origins of Multicellularity: All in the Family

Origins of Multicellularity: All in the Family

  6:25:00 PM    Science Lover

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One of the most pivotal steps in evolution-the transition from unicellular to multicellular organisms-may not have required as much retooling as commonly believed, found a globe-spanning collaboration of scientists led by researchers at the Salk Institute for Biological Studies and the US Department of Energy's Joint Genome Institute.

This is Volvox carteri. (Credit: Courtesy of 
Dr. David Kirk, Washington University, St. Louis)

A comparison of the genomes of the multicellular algae Volvox carteri and its closest unicellular relative Chlamydomonas reinhardtii revealed that multicellular organisms may have been able to build their more complex molecular machinery largely from the same list of parts that was already available to their unicellular ancestors.

"If you think of proteins in terms of lego bricks Chlamydomonas already had a great lego set," says James Umen, Ph.D., assistant professor in the Plant Molecular and Cellular Biology Laboratory at the Salk Institute. "Volvox didn't have to buy a new one, and instead could experiment with what it had inherited from its ancestor."

Altogether the findings, published in the journal Science, suggest that very limited protein-coding innovation occurred in the Volvox lineage. "We expected that there would be some major differences in genome size, number of genes, or gene families sizes between Volvox and Chlamydomonas," says Umen. "Mostly that turned out not to be the case."

The evolution of multicellularity occurred repeatedly and independently in diverse lineages including animals, plants, fungi, as well as green and red algae. "This transition is one of the great evolutionary events that shaped life on earth," says co-first author Simon E. Prochnik, Ph.D., a Computationial Scientist at the DOE Joint Genome Institute. "It has generated much thought and speculation about what makes multicellular organisms different or more complex than their unicellular ancestors."

In most cases the switch from a solitary existence to a communal one happened so long ago-over 500 million years-that the genetic changes enabling it are very difficult to trace. An interesting exception to the rule are volvocine green algae. For them, the transition to multicellularity happened in a series of small, potentially adaptive changes, and the progressive increase in morphological and developmental complexity can still be seen in contemporary members of the group (see slide show).

Volvox, the most sophisticated member of the lineage, is believed to have evolved from a Chlamydomonas-like ancestor within the last 200 million years, making the two living organisms an appealing model to study the evolutionary changes that brought about multicellularity and cellular differentiation.

To gather data for the comparative genomic analysis, the researchers sequenced the 138 million base pair Volvox genome using a whole genome shotgun strategy. The genome itself is 17% larger than the previously sequenced genome of Chlamydomonas and the sequence divergence between the two is comparable to that between human and chicken.

Despite the modest increase in genome size, the number of predicted proteins turned out to be very similar for the two organisms (14,566 in Volvox vs. 14,516 in Chlamydomonas) and no significant differences could be identified in the repertoires of protein domains or domain combinations. Protein domains are parts of proteins that can evolve, function, and exist independently of the rest of the protein chain.

"This was somewhat unexpected," explains Umen, "since innovation at the domain level was previously thought to play a role in the evolution of multicellularity in the plant and animal lineages."

In contrast to the overall lack of innovation, protein families specific to volvocine algae, such as extracellular matrix proteins, were enriched in Volvox compared to Chlamydomonas. Each mature Volvox colony is composed of numerous flagellated cells similar to Chlamydomonas, which are embedded in the surface of a spheroid of elaborately patterned extracellular matrix (ECM) that is clearly related to the Chlamydomonas cell wall. Maybe not surprisingly, the difference in size and complexity between the Volvox extracellular matrix and Chlamydomonas cell wall is mirrored by a dramatic increase in the number and variety of Volvox genes for two major ECM protein families, pherophorins and VMPs.

Additionally, Umen and his collaborators identified an increase in the number of cyclin D proteins in Volvox, which govern cell division and may be necessary to ensure the complex regulation of cell division during Volvox development. Last but not least, Volvox adapted a few of its existing genes to acquire novel functions. Members of the pherophorin family, for one, not only help build the extracellular matrix; some subtypes evolved into a diffusible hormonal trigger for sexual differentiation.

Researchers who also contributed to this work include Alan Kuo, Uffe Hellsten, Jarrod Chapman, Astrid Terry, Jasmyn Pangilinan, Asaf Salamov, Harris Shapiro, Erika Lindquist, Susan Lucas, Igor V Grigoriev, Harris Shapiro and Daniel S. Rokhsar at U.S. Department of Energy Joint Genome Institute in Walnut Creek, Patrick Ferris at the Salk Institute for Biological Studies, Aurora Nedelcu at the University of New Brunswick in Fredericton, Canada, Arman Hallmann at the University of Bielefeld, Germany, Stephen M. Miller at the University of Maryland, Baltimore, Ichiro Nishii at the Nara Women's University in Nara-shi, Japan, Lillian K. Fritz-Laylin at the Center for Integrative Genomics, Berkeley, Oleg Simakov at the EMBL in Heidelberg, Germany, Stefan A. Rensing at the University of Freiburg, Germany, Vladimir Kapitonov and Jerzy Jurka at the Genetic Information Research Institute in Mountain View, Jeremy Schmutz at the HudsonAlpha Institute in Huntsville, Rüdiger Schmitt at the University of Regensburg, Germany and David Kirk at Washington University in St. Louis.

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