Category Archives: Chemistry
Origin of Photosynthesis Revealed
Schematic of Cyanophora paradoxa. (Credit: Courtesy of Bhattacharya Lab.)
Atmospheric oxygen really took off on our planet about 2.4 billion years ago during the Great Oxygenation Event. At this key juncture of our planet’s evolution, species had either to learn to cope with this poison that was produced by photosynthesizing cyanobacteria or they went extinct. It now seems strange to think that the gas that sustains much of modern life had such a distasteful beginning.
So how and when did the ability to produce oxygen by harnessing sunlight enter the eukaryotic domain, that includes humans, plants, and most recognizable, multicellular life forms? One of the fundamental steps in the evolution of our planet was the development of photosynthesis in eukaryotes through the process of endosymbiosis.
This crucial step forward occurred about 1.6 billion years ago when a single-celled protist captured and retained a formerly free-living cyanobacterium. This process, termed primary endosymbiosis, gave rise to the plastid, which is the specialized compartment where photosynthesis takes place in cells. Endosymbiosis is now a well substantiated theory that explains how cells gained their great complexity and was made famous most recently by the work of the late biologist Lynn Margulis, best known for her theory on the origin of eukaryotic organelles.
Story continues -> http://www.sciencedaily.com/releases/2012/02/120221125409.htm
New ‘Diamond?’ New Form of Superhard Carbon Is as Strong as a Diamond
Carbon is the fourth-most-abundant element in the universe and takes on a wide variety of forms, called allotropes, including diamond and graphite. Scientists have now discovered a new form of carbon, which is capable of withstanding extreme pressure stresses that were previously observed only in diamond. (Credit: © adimas / Fotolia)
Carbon is the fourth-most-abundant element in the universe and takes on a wide variety of forms, called allotropes, including diamond and graphite. Scientists at Carnegie’s Geophysical Laboratory are part of a team that has discovered a new form of carbon, which is capable of withstanding extreme pressure stresses that were previously observed only in diamond.
his breakthrough discovery will be published in Physical Review Letters.
The team was led by Stanford’s Wendy L. Mao and her graduate student Yu Lin and includes Carnegie’s Ho-kwang (Dave) Mao, Li Zhang, Paul Chow, Yuming Xiao, Maria Baldini, and Jinfu Shu. The experiment started with a form of carbon called glassy carbon, which was first synthesized in the 1950s, and was found to combine desirable properties of glasses and ceramics with those of graphite. The team created the new carbon allotrope by compressing glassy carbon to above 400,000 times normal atmospheric pressure.
This new carbon form was capable of withstanding 1.3 million times normal atmospheric pressure in one direction while confined under a pressure of 600,000 times atmospheric levels in other directions. No substance other than diamond has been observed to withstand this type of pressure stress, indicating that the new carbon allotrope must indeed be very strong.
However, unlike diamond and other crystalline forms of carbon, the structure of this new material is not organized in repeating atomic units. It is an amorphous material, meaning that its structure lacks the long-range order of crystals. This amorphous, superhard carbon allotrope would have a potential advantage over diamond if its hardness turns out to be isotropic — that is, having hardness that is equally strong in all directions. In contrast, diamond’s hardness is highly dependent upon the direction in which the crystal is oriented.
Story Continues -> New ‘Diamond?’ New Form of Superhard Carbon Is as Strong as a Diamond
‘Quasicrystals’ Once Thought Impossible Have Changed Understanding of Solid Matter
Aperiodic mosaics, such as those found in the medieval Islamic mosaics of the Alhambra Palace in Spain (shown above), have helped scientists understand what quasicrystals look like at the atomic level. In those mosaics, as in quasicrystals, the patterns are regular — they follow mathematical rules — but they never repeat themselves. (Credit: © cbomers / Fotolia)
The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Chemistry for 2011 to Daniel Shechtman of the Technion — Israel Institute of Technology in Haifa, Israel, for the discovery of quasicrystals: non-repeating regular patterns of atoms that were once thought to be impossible.
A remarkable mosaic of atoms
In quasicrystals, we find the fascinating mosaics of the Arabic world reproduced at the level of atoms: regular patterns that never repeat themselves. However, the configuration found in quasicrystals was considered impossible, and Daniel Shechtman had to fight a fierce battle against established science. The Nobel Prize in Chemistry 2011 recognizes a breakthrough that has fundamentally altered how chemists conceive of solid matter.
On the morning of April 8, 1982, an image counter to the laws of nature appeared in Daniel Shechtman’s electron microscope. In all solid matter, atoms were believed to be packed inside crystals in symmetrical patterns that were repeated periodically over and over again. For scientists, this repetition was required in order to obtain a crystal.
Shechtman’s image, however, showed that the atoms in his crystal were packed in a pattern that could not be repeated. Such a pattern was considered just as impossible as creating a football using only six-cornered polygons, when a sphere needs both five- and six-cornered polygons. His discovery was extremely controversial. In the course of defending his findings, he was asked to leave his research group. However, his battle eventually forced scientists to reconsider their conception of the very nature of matter.
Aperiodic mosaics, such as those found in the medieval Islamic mosaics of the Alhambra Palace in Spain and the Darb-i Imam Shrine in Iran, have helped scientists understand what quasicrystals look like at the atomic level. In those mosaics, as in quasicrystals, the patterns are regular — they follow mathematical rules — but they never repeat themselves.
Story Continues -> ‘Quasicrystals’ Once Thought Impossible Have Changed Understanding of Solid Matter
Making Complex Composite Materials to Order
A sample of a co-continuous polymer composite material produced in the lab by a team including MIT postdoctoral researcher Lifeng Wang. Device in background is used to test the strength of the material. (Credit: Melanie Gonick)
A team of researchers at MIT has found a way to make complex composite materials whose attributes can be fine-tuned to give various desirable combinations of properties such as stiffness, strength, resistance to impacts and energy dissipation.
composites is a “co-continuous” structure of two different materials with very different properties, creating a material combining aspects of both. The co-continuous structure means that the two interleaved materials each form a kind of three-dimensional lattice whose pieces are fully connected to each other from side to side, front to back, and top to bottom.
The research — by postdoc Lifeng Wang, who worked with undergraduate Jacky Lau and professors Mary Boyce and Edwin Thomas — was published in April in the journal Advanced Materials.
The initial objective of the research was to “try to design a material that can absorb energy under extreme loading situations,” Wang explains. Such a material could be used as shielding for trucks or aircraft, he says: “It could be lightweight and efficient, flexible, not just a solid mantle” like most present-day armor.
In most conventional materials — even modern advanced composites — once cracks start to form they tend to propagate through the material, Wang says. But in the new co-continuous materials, crack propagation is limited within the microstructure, he says, making them highly “damage tolerant” even when subjected to many crack-producing events.
Some existing composite materials, such as carbon-carbon composites that use fibers embedded in another material, can have great strength in the direction parallel to the fibers, but not much strength in other directions. Because of the continuous 3-D structure of the new composites, their strength is nearly equal in all dimensions, Wang says.
Story Continues -> Making Complex Composite Materials to Order
Biodegradeable products may be more harmful to the environment
by Emma Woollacott
Think you’re doing the right thing by using biodegradeable products? Think again. Research from North Carolina State University shows that they’re actually doing more harm than good, by releasing a powerful greenhouse gas as they break down.
“Biodegradable materials, such as disposable cups and utensils, are broken down in landfills by microorganisms that then produce methane,” says Dr Morton Barlaz. “Methane can be a valuable energy source when captured, but is a potent greenhouse gas when released into the atmosphere.”
The US Environmental Protection Agency (EPA) estimates that only about a third of municipal solid waste goes to landfills that capture methane for energy use. Another third is captured and burned off-site, and the rest allowed to escape.
“In other words,” Barlaz says, “biodegradable products are not necessarily more environmentally friendly when disposed in landfills.”
Story Continues -> Biodegradeable products may be more harmful to the environment
A Car Battery at Half the Price
Battery prototype: Two sludge-like electrode materials are fed into the device shown here. The anode material flows into the top half, and the cathode flows into the bottom. Lithium ions pass from one material to the other, and electrons flow through the black and red leads. Credit: Yet-Ming Chiang
A startup hopes to commercialize a novel design that features a liquid electrolyte.
Last year, the battery startup A123 Systems spun out another company, called 24M, to develop a new kind of battery meant to make electric vehicles go farther and cost less. Now a research paper published in Advanced Energy Materials reveals the first details about how that battery would work. It also addresses the challenges in bringing the battery to market.
A big problem with the lithium-ion batteries used in electric vehicles and plug-in hybrids is that only about 25 percent of the battery’s volume is taken up by materials that store energy. The rest is made up of inactive materials, such as packaging, conductive foils, and glues, which make the batteries bulky and account for a significant part of the cost.
24M intends to greatly reduce the inactive material in a battery. According to estimates in the new paper, its batteries could achieve almost twice the energy densities of today’s vehicle battery packs. Batteries with a higher energy density would be smaller and cheaper, which means electric and hybrid cars would be less expensive. The paper estimates that the batteries could cost as little as $250 per kilowatt hour—less than half what they cost now.
A conventional battery pack is made up of hundreds of cells. Each cell contains a stack of many thin, solid electrodes. These electrodes are paired with metal foil current collectors and separated from each other by plastic films. Increasing the energy storagerequires adding more layers of electrode material—which in turn requires more layers of metal foil and plastic film.
24M’s design makes it possible to increase energy storage without the extra metal foil and plastic film. The key difference is that the electrodes are not solid films stacked in a cell, but sludge-like materials stored in tanks—one for the positive electrode material and another for the negative electrode.
The materials are pumped from the tanks into a small device, where they move through channels carved into blocks of metal. As this happens, ions move from one electrode to the other through the same kind of separator material used in a conventional battery. Electrons make their way out of the material to an external circuit. In this design, increasing energy storage is as simple as increasing the size of the storage tanks—the device that allows the electrodes to interact stays the same size. The design also does away with the need to wire together hundreds of cells to achieve adequate energy storage.
Story Continues -> A car battery at half the price
Particle Trap Paves Way for Personalized Medicine
Scientists were able to trap a single particle between four microelectrodes, paving the way for a faster and cheaper way to sequence DNA. (Credit: Weihua Guan and Mark Reed/Yale University)
Sequencing DNA base pairs — the individual molecules that make up DNA — is key for medical researchers working toward personalized medicine. Being able to isolate, study and sequence these DNA molecules would allow scientists to tailor diagnostic testing, therapies and treatments based on each patient’s individual genetic makeup.
But being able to isolate individual molecules like DNA base pairs, which are just two nanometers across — or about 1/50,000th the diameter of a human hair — is incredibly expensive and difficult to control. In addition, devising a way to trap DNA molecules in their natural aqueous environment further complicates things. Scientists have spent the past decade struggling to isolate and trap individual DNA molecules in an aqueous solution by trying to thread it through a tiny hole the size of DNA, called a “nanopore,” which is exceedingly difficult to make and control.
Now a team led by Yale University researchers has proven that isolating individual charged particles, like DNA molecules, is indeed possible using a method called “Paul trapping,” which uses oscillating electric fields to confine the particles to a space only nanometers in size. (The technique is named for Wolfgang Paul, who won the Nobel Prize for the discovery.) Until now, scientists have only been able to use Paul traps for particles in a vacuum, but the Yale team was able to confine a charged test particle — in this case, a polystyrene bead — to an accuracy of just 10 nanometers in aqueous solutions between quadruple microelectrodes that supplied the electric field.
Their device can be contained on a single chip and is simple and inexpensive to manufacture. “The idea would be that doctors could take a tiny drop of blood from patients and be able to run diagnostic tests on it right there in their office, instead of sending it away to a lab where testing can take days and is expensive,” said Weihua Guan, a Yale engineering graduate student who led the project.
Story Continues -> Particle Trap Paves Way for Personalized Medicine
Spongy carbon an energy storage breakthrough?
Posted on May 18th 2011 by Caleb Denison, EarthTechling
Scientific efforts to create new high performance, efficient energy storage technologies may be taking a pretty big leap forward according to researchers at The University of Texas.
The research team, led by Professor Rodney S. Ruoff, has created a new porous, three-dimensional carbon they say can be used like a “greatly enhanced supercapacitor.”
In a statement, the team likens a supercapacitor to a sprinter. It can discharge a bunch of energy very quickly, but also runs out of energy quickly because of its limited storage potential.
Comparatively, a battery is more like a marathon runner which can store a lot more energy but, because of the way batteries store energy, they are slower to discharge it.
The team believes that the continuous, three-dimensional porous network that is created within their new sponge-like carbon is an optimum electrode material for supercapacitors because, apparently, it is an excellent conductor of electricity and the massive amount of surface area it offers within a very small space will allow supercapacitors to store much more energy.
To put this new carbon’s attributes into perspective, Professor Ruoff explains that just one gram of the material contains 3,100 square meters of surface area. Two grams of the material have roughly as much surface area as a football field.
Eric Stach, a material’s scientist at the U.S. Department of Energy’s Brookhaven National Laboratory and co-author of a paper about the material that will be published in Science magazines online publication, believes the enhanced storage capacity combined with a supercapacitor’s existing attributes of rapid discharge and lengthy life-cycle 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.”
Professor Ruoff says the process used to make the material is readily scalable to industrial levels, which would suggest the new carbon can be quickly implemented into new energy storage devices which are used in everything from energy grids to electric cars and even consumer electronics.
New Water-Splitting Catalyst: Researchers Expand List of Potential Electrode Materials That Could Be Used to Store Energy
Daniel Nocera. (Credit: Photo by Donna Coveney/MIT)
Expanding on work published two years ago, MIT’s Daniel Nocera and his associates have found yet another formulation, based on inexpensive and widely available materials, that can efficiently catalyze the splitting of water molecules using electricity. This could ultimately form the basis for new storage systems that would allow buildings to be completely independent and self-sustaining in terms of energy: The systems would use energy from intermittent sources like sunlight or wind to create hydrogen fuel, which could then be used in fuel cells or other devices to produce electricity or transportation fuels as needed.
Nocera, the Henry Dreyfus Professor of Energy and Professor of Chemistry, says that solar energy is the only feasible long-term way of meeting the world’s ever-increasing needs for energy, and that storage technology will be the key enabling factor to make sunlight practical as a dominant source of energy. He has focused his research on the development of less-expensive, more-durable materials to use as the electrodes in devices that use electricity to separate the hydrogen and oxygen atoms in water molecules. By doing so, he aims to imitate the process of photosynthesis, by which plants harvest sunlight and convert the energy into chemical form.
Nocera pictures small-scale systems in which rooftop solar panels would provide electricity to a home, and any excess would go to an electrolyzer — a device for splitting water molecules — to produce hydrogen, which would be stored in tanks. When more energy was needed, the hydrogen would be fed to a fuel cell, where it would combine with oxygen from the air to form water, and generate electricity at the same time.
An electrolyzer uses two different electrodes, one of which releases the oxygen atoms and the other the hydrogen atoms. Although it is the hydrogen that would provide a storable source of energy, it is the oxygen side that is more difficult, so that’s where he and many other research groups have concentrated their efforts. In a paper in Science in 2008, Nocera reported the discovery of a durable and low-cost material for the oxygen-producing electrode based on the element cobalt.
Now, in research being reported in the journal Proceedings of the National Academy of Science (PNAS), Nocera, along with postdoctoral researcher Mircea Dincă and graduate student Yogesh Surendranath, report the discovery of yet another material that can also efficiently and sustainably function as the oxygen-producing electrode. This time the material is nickel borate, made from materials that are even more abundant and inexpensive than the earlier find.
Even more significantly, Nocera says, the new finding shows that the original compound was not a unique, anomalous material, and suggests that there may be a whole family of such compounds that researchers can study in search of one that has the best combination of characteristics to provide a widespread, long-term energy storage technology.
“Sometimes if you do one thing, and only do it once,” Nocera says, “you don’t know — is it extraordinary or unusual, or can it be commonplace?” In this case, the new material “keeps all the requirements of being cheap and easy to manufacture” that were found in the cobalt-based electrode, he says, but “with a different metal that’s even cheaper than cobalt.”
But the research is still in an early stage. “This is a door opener,” Nocera says. “Now, we know what works in terms of chemistry. One of the important next things will be to continue to tune the system, to make it go faster and better. This puts us on a fast technological path.” While the two compounds discovered so far work well, he says, he is convinced that as they carry out further research even better compounds will come to light. “I don’t think we’ve found the silver bullet yet,” he says.
Already, as the research has continued, Nocera and his team have increased the rate of production from these catalysts a hundredfold from the level they initially reported two years ago. In addition, while the earlier paper and the new report focus on electrodes on the oxygen-producing side, originally the other electrode, which produced hydrogen, included the use of a relatively expensive platinum catalyst. But in further work, “we have totally gotten rid of the platinum of the hydrogen side,” Nocera says. “That’s no longer a concern for us,” he says, although that part of the research has not yet been formally reported.
The original discovery has already led to the creation of a company, called Sun Catalytix, that aims to commercialize the system in the next two years. And his research program was recently awarded a major grant from the U.S. Department of Energy’s Advanced Research Projects Agency — Energy.
Funding was provided by the National Science Foundation and the Chesonis Family Foundation.
Story Source:
Adapted from materials provided by Massachusetts Institute of Technology. Original article written by David L. Chandler, MIT News Office.
Journal Reference:
- M. Dinca, Y. Surendranath, D. G. Nocera. Nickel-borate oxygen-evolving catalyst that functions under benign conditions. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1001859107
http://www.sciencedaily.com/releases/2010/05/100512141953.htm
Renewable Energy: Inexpensive Metal Catalyst Can Effectively Generate Hydrogen from Water
From left, Jeffrey Long, Christopher Chang and Hemamala Karunadasa have discovered an inexpensive metal that can generate hydrogen from neutral water, even if it is dirty, and can operate in sea water. (Credit: Photo by Roy Kaltschmidt, Berkeley Lab Public Affairs)
Hydrogen would command a key role in future renewable energy technologies, experts agree, if a relatively cheap, efficient and carbon-neutral means of producing it can be developed. An important step towards this elusive goal has been taken by a team of researchers with the U.S. Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley. The team has discovered an inexpensive metal catalyst that can effectively generate hydrogen gas from water.
“Our new proton reduction catalyst is based on a molybdenum-oxo metal complex that is about 70 times cheaper than platinum, today’s most widely used metal catalyst for splitting the water molecule,” said Hemamala Karunadasa, one of the co-discoverers of this complex. “In addition, our catalyst does not require organic additives, and can operate in neutral water, even if it is dirty, and can operate in sea water, the most abundant source of hydrogen on earth and a natural electrolyte. These qualities make our catalyst ideal for renewable energy and sustainable chemistry.”
Karunadasa holds joint appointments with Berkeley Lab’s Chemical Sciences Division and UC Berkeley’s Chemistry Department. She is the lead author of a paper describing this work that appears in the April 29, 2010 issue of the journal Nature, titled “A molecular molybdenum-oxo catalyst for generating hydrogen from water.” Co-authors of this paper were Christopher Chang and Jeffrey Long, who also hold joint appointments with Berkeley Lab and UC Berkeley. Chang, in addition, is also an investigator with the Howard Hughes Medical Institute (HHMI).
Hydrogen gas, whether combusted or used in fuel cells to generate electricity, emits only water vapor as an exhaust product, which is why this nation would already be rolling towards a hydrogen economy if only there were hydrogen wells to tap. However, hydrogen gas does not occur naturally and has to be produced. Most of the hydrogen gas in the United States today comes from natural gas, a fossil fuel. While inexpensive, this technique adds huge volumes of carbon emissions to the atmosphere. Hydrogen can also be produced through the electrolysis of water — using electricity to split molecules of water into molecules of hydrogen and oxygen. This is an environmentally clean and sustainable method of production — especially if the electricity is generated via a renewable technology such as solar or wind — but requires a water-splitting catalyst.
Nature has developed extremely efficient water-splitting enzymes — called hydrogenases — for use by plants during photosynthesis, however, these enzymes are highly unstable and easily deactivated when removed from their native environment. Human activities demand a stable metal catalyst that can operate under non-biological settings.
Metal catalysts are commercially available, but they are low valence precious metals whose high costs make their widespread use prohibitive. For example, platinum, the best of them, costs some $2,000 an ounce.
“The basic scientific challenge has been to create earth-abundant molecular systems that produce hydrogen from water with high catalytic activity and stability,” Chang says. “We believe our discovery of a molecular molybdenum-oxo catalyst for generating hydrogen from water without the use of additional acids or organic co-solvents establishes a new chemical paradigm for creating reduction catalysts that are highly active and robust in aqueous media.”
The molybdenum-oxo complex that Karunadasa, Chang and Long discovered is a high valence metal with the chemical name of (PY5Me2)Mo-oxo. In their studies, the research team found that this complex catalyzes the generation of hydrogen from neutral buffered water or even sea water with a turnover frequency of 2.4 moles of hydrogen per mole of catalyst per second.
Long says, “This metal-oxo complex represents a distinct molecular motif for reduction catalysis that has high activity and stability in water. We are now focused on modifying the PY5Me ligand portion of the complex and investigating other metal complexes based on similar ligand platforms to further facilitate electrical charge-driven as well as light-driven catalytic processes. Our particular emphasis is on chemistry relevant to sustainable energy cycles.”
This research was supported in part by the DOE Office of Science through Berkeley Lab’s Helios Solar Energy Research Center, and in part by a grant from the National science Foundation.
Story Source:
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory.
Journal Reference:
- Hemamala I. Karunadasa, Christopher J. Chang, Jeffrey R. Long. A molecular molybdenum-oxo catalyst for generating hydrogen from water. Nature, 2010; 464 (7293): 1329 DOI: 10.1038/nature08969
http://www.sciencedaily.com/releases/2010/04/100430154902.htm
