New transistor for plastic electronics exhibits the best of both worlds

In the quest to develop flexible plastic electronics, one of the stumbling blocks has been creating transistors with enough stability for them to function in a variety of environments while still maintaining the current needed to power the devices. Online in the journal Advanced Materials, researchers from the Georgia Institute of Technology describe a new method of combining top-gate organic field-effect transistors with a bilayer gate insulator. This allows the transistor to perform with incredible stability while exhibiting good current performance. In addition, the transistor can be mass produced in a regular atmosphere and can be created using lower temperatures, making it compatible with the plastic devices it will power.

The research team used an existing semiconductor and changed the gate dielectric because transistor performance depends not only on the semiconductor itself, but also on the interface between the semiconductor and the gate dielectric.

"Rather than using a single dielectric material, as many have done in the past, we developed a bilayer gate dielectric," said Bernard Kippelen, director of the Center for Organic Photonics and Electronics and professor in Georgia Tech's School of Electrical and Computer Engineering.

The bilayer dielectric is made of a fluorinated polymer known as CYTOP and a high-k metal-oxide layer created by atomic layer deposition. Used alone, each substance has its benefits and its drawbacks.

CYTOP is known to form few defects at the interface of the organic semiconductor, but it also has a very low dielectric constant, which requires an increase in drive voltage. The high-k metal-oxide uses low voltage, but doesn't have good stability because of a high number of defects on the interface.

So, Kippelen and his team wondered what would happen if they combined the two substances in a bilayer. Would the drawbacks cancel each other out?

"When we started to do the test experiments, the results were stunning. We were expecting good stability, but not to the point of having no degradation in mobility for more than a year," said Kippelen.

The team performed a battery of tests to see just how stable the bilayer was. They cycled the transistors 20,000 times. There was no degradation. They tested it under a continuous biostress where they ran the highest possible current through it. There was no degradation. They even stuck it in a plasma chamber for five minutes. There was still no degradation.

The only time they saw any degradation was when they dropped it into acetone for an hour. There was some degradation, but the transistor was still operational.

No one was more surprised than Kippelen.

"I had always questioned the concept of having air-stable field-effect transistors, because I thought you would always have to combine the transistors with some barrier coating to protect them from oxygen and moisture. We've proven ourselves wrong through this work," said Kippelen.

"By having the bilayer gate insulator we have two different degradation mechanisms that happen at the same time, but the effects are such that they compenstate for one another," explains Kippelen. "So if you use one it leads to a decrease of the current, if you use the other it leads to a shift of the thereshold voltage and over time to an increase of the current. But if you combine them, their effects cancel out."

"This is an elegant way of solving the problem. So, rather than trying to remove an effect, we took two processes that compliment one another and as a result you have a result that's rock stable."

The transistor conducts current and runs at a voltage comparable to amorphous silicon, the current industry standard used on glass substrates, but can be manufactured at temperatures below 150°C, in line with the capabilities of plastic substrates. It can also be created in a regular atmosphere, making it easier to fabricate than other transistors.

Applications for these transistors include smart bandages, RFID tags, plastic solar cells, light emitters for smart cards -- virtually any application where stable power and a flexible surface are needed.

In this paper the tests were performed on glass substrates. Next, the team plans on demonstrating the transistors on flexible plastic substrates. Then they will test the ability to manufacture the bilayer transistors with ink jet printing technologies.

Story Source:

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

Journal Reference:

Do Kyung Hwang, Canek Fuentes-Hernandez, Jungbae Kim, William J. Potscavage, Sung-Jin Kim, Bernard Kippelen. Top-Gate Organic Field-Effect Transistors with High Environmental and Operational Stability. Advanced Materials, 2011; DOI: 10.1002/adma.201004278

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.

Nanowires exhibit giant piezoelectricity

Gallium nitride (GaN) and zinc oxide (ZnO) are among the most technologically relevant semiconducting materials. Gallium nitride is ubiquitous today in optoelectronic elements such as blue lasers (hence the blue-ray disc) and light-emitting-diodes (LEDs); zinc oxide also finds many uses in optoelectronics and sensors.

In the past few years, though, nanostructures made of these materials have shown a plethora of potential functionalities, ranging from single-nanowire lasers and LEDs to more complex devices such as resonators and, more recently, nanogenerators that convert mechanical energy from the environment (body movements, for example) to power electronic devices. The latter application relies on the fact that GaN and ZnO are also piezoelectric materials, meaning that they produce electric charges as they are deformed.

In a paper published online in the journal Nano Letters, Horacio Espinosa, the James N. and Nancy J. Farley Professor in Manufacturing and Entrepreneurship at the McCormick School of Engineering and Applied Science at Northwestern University, and Ravi Agrawal, a graduate student in Espinosa's lab, reported that piezoelectricity in GaN and ZnO nanowires is in fact enhanced by as much as two orders of magnitude as the diameter of the nanowires decrease.

"This finding is very exciting because it suggests that constructing nanogenerators, sensors and other devices from smaller nanowires will greatly improve their output and sensitivity," Espinosa said.

"We used a computational method called Density Functional Theory (DFT) to model GaN and ZnO nanowires of diameters ranging from 0.6 nanometers to 2.4 nanometers," Agrawal said. The computational method is able to predict the electronic distribution of the nanowires as they are deformed and, therefore, allows calculating their piezoelectric coefficients.

The researchers' results show that the piezoelectric coefficient in 2.4 nanometer-diameter nanowires is about 20 times larger and about 100 times larger for ZnO and GaN nanowires, respectively, when compared to the coefficient of the materials at the macroscale. This confirms previous computational findings on ZnO nanostructures that showed a similar increase in piezoelectric properties. However, calculations for piezoelectricity of GaN nanowires as a function of size were carried out in this work for the first time, and the results are clearly more promising as GaN shows a more prominent increase.

"Our calculations reveal that the increase in piezoelectric coefficient is a result of the redistribution of electrons in the nanowire surface, which leads to an increase in the strain-dependent polarization with respect to the bulk materials," Espinosa said.

The findings by Espinosa and Agrawal may have important implications for the field of energy harvesting as well as for fundamental science. For energy harvesting, where piezoelectric elements are used to convert mechanical to electrical energy in order to power electronic devices, these results point to an advantage in reducing the size of the piezoelectric elements down to the nanometer scale. Energy harvesting devices built from small-diameter nanowires should in principle be able to produce more electrical energy from the same amount of mechanical energy than their bulk counterparts.

In terms of fundamental science, these results further previous conclusions that matter at the nanoscale has different properties. It is clear now that by tailoring the size of nanostructures, their mechanical, electrical and thermal properties can be tuned as well.

"Our focus remains on understanding the fundamental principles governing the behavior of nanostructures as a function of their size," Espinosa and Agrawal say. "One of the most important issues that needs to be addressed is to obtain experimental confirmation of these results, and establish up to what size the giant piezoelectric effects remain significant."

Espinosa and Agrawal hope their work will spur new interest in the electromechanical properties of nanostructures, both from theoretical and experimental standpoints, in order to clear the path for the design and optimization of future nanoscale devices.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Northwestern University.

Journal Reference:

Ravi Agrawal, Horacio D. Espinosa. Giant Piezoelectric Size Effects in Zinc Oxide and Gallium Nitride Nanowires. A First Principles Investigation. Nano Letters, 2011; : 110111090244079 DOI: 10.1021/nl104004d

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.

Scientists model tiny rotors, key to future nanomachines

"This is no cartoon. It's a real molecule, with all the interactions taking place correctly," said Anatoly Kolomeisky as he showed an animation of atoms twisting and turning about a central hub like a carnival ride gone mad.

Kolomeisky, a Rice University associate professor of chemistry, was offering a peek into a molecular midway where atoms dip, dive and soar according to a set of rules he is determined to decode.

Kolomeisky and Rice graduate student Alexey Akimov have taken a large step toward defining the behavior of these molecular whirligigs with a new paper in the American Chemical Society's Journal of Physical Chemistry C. Through molecular dynamics simulations, they defined the ground rules for the rotor motion of molecules attached to a gold surface.

It's an extension of their work on Rice's famed nanocars, developed primarily in the lab of James Tour, Rice's T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science, but for which Kolomeisky has also constructed molecular models.

Striking out in a different direction, the team has decoded several key characteristics of these tiny rotors, which could harbor clues to the ways in which molecular motors in human bodies work.

The motion they described is found everywhere in nature, Kolomeisky said. The most visible example is in the flagella of bacteria, which use a simple rotor motion to move. "When the flagella turn clockwise, the bacteria move forward. When they turn counterclockwise, they tumble." On an even smaller level, ATP-synthase, which is an enzyme important to the transfer of energy in the cells of all living things, exhibits similar rotor behavior -- a Nobel Prize-winning discovery.

Understanding how to build and control molecular rotors, especially in multiples, could lead to some interesting new materials in the continuing development of machines able to work at the nanoscale, he said. Kolomeisky foresees, for instance, radio filters that would let only a very finely tuned signal pass, depending on the nanorotors' frequency.

"It would be an extremely important, though expensive, material to make," he said. "But if I can create hundreds of rotors that move simultaneously under my control, I will be very happy."

The professor and his student cut the number of parameters in their computer simulation to a subset of those that most interested them, Kolomeisky said. The basic-model molecule had a sulfur atom in the middle, tightly bound to a pair of alkyl chains, like wings, that were able to spin freely when heated. The sulfur anchored the molecule to the gold surface.

While working on a previous paper with researchers at Tufts University, Kolomeisky and Akimov saw photographic evidence of rotor motion by scanning tunneling microscope images of sulfur/alkyl molecules heated on a gold surface. As the heat rose, the image went from linear to rectangular to hexagonal, indicating motion. What the pictures didn't indicate was why.

That's where computer modeling was invaluable, both on the Kolomeisky lab's own systems and through Rice's SUG@R platform, a shared supercomputer cluster. By testing various theoretical configurations -- some with two symmetrical chains, some asymmetrical, some with only one chain -- they were able to determine a set of interlocking characteristics that control the behavior of single-molecule rotors.

First, he said, the symmetry and structure of the gold surface material (of which several types were tested) has a lot of influence on a rotor's ability to overcome the energy barrier that keeps it from spinning all the time. When both arms are close to surface molecules (which repel), the barrier is large. But if one arm is over a space -- or hollow -- between gold atoms, the barrier is significantly smaller.

Second, symmetric rotors spin faster than asymmetric ones. The longer chain in an asymmetric pair takes more energy to get moving, and this causes an imbalance. In symmetric rotors, the chains, like rigid wings, compensate for each other as one wing dips into a hollow while the other rises over a surface molecule.

Third, Kolomeisky said, the nature of the chemical bond between the anchor and the chains determines the rotor's freedom to spin.

Finally, the chemical nature of rotating groups is also an important factor.

Kolomeisky said the research opens a path for simulating more complex rotor molecules. The chains in ATP-synthase are far too large for a simulation to wrangle, "but as computers get more powerful and our methods improve, we may someday be able to analyze such long molecules," he said.

The Welch Foundation, the National Science Foundation and the National Institutes of Health funded the research.

An animation of a rotor simulation: http://www.youtube.com/watch?v=GJJxSs6AkeM

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Rice University.

Journal Reference:

Alexey Akimov, Anatoly B. Kolomeisky. Dynamics of Single-Molecule Rotations on Surfaces that Depend on Symmetry, Interactions, and Molecular Sizes. The Journal of Physical Chemistry C, 2011; 115 (1): 125 DOI: 10.1021/jp108062p

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.

Scientists synthesize long-sought-after anticancer agent

A team of Yale University scientists has synthesized for the first time a chemical compound called lomaiviticin aglycon, leading to the development of a new class of molecules that appear to target and destroy cancer stem cells.

Chemists worldwide have been interested in lomaiviticin's potential anticancer properties since its discovery in 2001. But so far, they have been unable to obtain significant quantities of the compound, which is produced by a rare marine bacterium that cannot be easily coaxed into creating the molecule. For the past decade, different groups around the world have been trying instead to synthesize the natural compound in the lab, but without success.

Now a team at Yale, led by chemist Seth Herzon, has managed to create lomaiviticin aglycon for the first time, opening up new avenues of exploration into novel chemotherapies that could target cancer stem cells, thought to be the precursors to tumors in a number of different cancers including ovarian, brain, lung, prostate and leukemia. Their discovery appears online in the Journal of the American Chemical Society.

"About three quarters of anticancer agents are derived from natural products, so there's been lots of work in this area," Herzon said. "But this compound is structurally very different from other natural products, which made it extremely difficult to synthesize in the lab."

In addition to lomaiviticin aglycon, Herzon's team also created smaller, similar molecules that have proven extremely effective in killing ovarian stem cells, said Gil Mor, M.D., a researcher at the Yale School of Medicine who is collaborating with Herzon to test the new class of molecules' potential as a cancer therapeutic.

The scientists are particularly excited about lomaiviticin aglycon's potential to kill ovarian cancer stem cells because the disease is notoriously resistant to Taxol and Carboplatin, two of the most common chemotherapy drugs. "Ovarian cancer has a high rate of recurrence, and after using chemotherapy to fight the tumor the first time, you're left with resistant tumor cells that tend to keep coming back," Mor explained. "If you can kill the stem cells before they have the chance to form a tumor, the patient will have a much better chance of survival -- and there aren't many potential therapies out there that target cancer stem cells right now."

Herzon's team, which managed to synthesize the molecule in just 11 steps starting from basic chemical building blocks, has been working on the problem since 2008 and spent more than a year on just one step of the process involving the creation of a carbon-carbon bond. It was an achievement that many researchers deemed impossible, but while others tried to work around having to create that bond by using other techniques, the team's persistence paid off.

"A lot of blood, sweat and tears went into creating that bond," Herzon said. "After that, the rest of the process was relatively easy."

Next, the team will continue to analyze the compound to better understand what's happening to the stem cells at the molecular level. The team hopes to begin testing the compounds in animals shortly.

"This is a great example of the synergy between basic chemistry and the applied sciences," Herzon said. "Our original goal of synthesizing this natural product has led us into entirely new directions that could have broad impacts in human medicine."

Other authors of the paper include Liang Lu, Christina M. Woo and Shivajirao L. Gholap, all of Yale University.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Yale University, via EurekAlert!, a service of AAAS.

Journal Reference:

Seth B. Herzon, Liang Lu, Christina M. Woo, Shivajirao L. Gholap. 11-Step Enantioselective Synthesis of (-)-Lomaiviticin Aglycon. Journal of the American Chemical Society, 2011; 110131110847001 DOI: 10.1021/ja200034b

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

Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of ScienceDaily or its staff.

Mussel power: Universal solvent no match for new self-healing sticky gel

Scientists can now manufacture a synthetic version of the self-healing sticky substance that mussels use to anchor themselves to rocks in pounding ocean surf and surging tidal basins. A patent is pending on the substance, whose potential applications include use as an adhesive or coating for underwater machinery or in biomedical settings as a surgical adhesive or bonding agent for implants.

Inspiring the invention were the hair-thin holdfast fibers that mussels secrete to stick against rocks in lakes, rivers and oceans. "Everything amazingly just self-assembles underwater in a matter of minutes, which is a process that's still not understood that well," said Niels Holten-Andersen, a postdoctoral scholar with chemistry professor Ka Yee Lee at the University of Chicago.

Holten-Andersen, Lee and an international team of colleagues are publishing the details of their invention this week in the Proceedings of the National Academy of Sciences Early Edition. Holten-Andersen views the evolution of life on Earth as "this beautiful, amazingly huge experiment" in which natural selection has enabled organisms to evolve an optimal use of materials over many millions of years.

"The mussels that live right on the coast where the waves really come crashing in have had to adapt to that environment and build their materials accordingly," he said.

Many existing synthetic coatings involve a compromise between strength and brittleness. Those coatings rely on permanent covalent bonds, a common type of chemical bond that is held together by two atoms that share two or more electrons. The bonds of the mussel-inspired material, however, are linked via metals and exhibit both strength and reversibility.

"These metal bonds are stable, yet if they break, they automatically self-heal without adding any extra energy to the system," Holten-Andersen said.

A key ingredient of the material is a polymer, which consists of long chains of molecules, synthesized by co-author Phillip Messersmith of Northwestern University. When mixed with metal salts at low pH, the polymer appears as a green solution. But the solution immediately transforms into a gel when mixed with sodium hydroxide to change the pH from high acidity to high alkalinity.

"Instead of it being this green solution, it turned into this red, self-healing sticky gel that you can play with, kind of like Silly Putty," he said. Holten-Andersen and his colleagues found that the gel could repair tears within minutes.

"You can change the property of the system by dialing in a pH," said Ka Yee Lee, a professor in chemistry at UChicago and co-author of the PNAS paper. The type of metal ion (an electrically charged atom of, for example. iron, titanium or aluminum) added to the mix provides yet another knob for tuning the material's properties, even at the same pH.

"You can tune the stiffness, the strength of the material, by now having two knobs. The question is, what other knobs are out there?" Lee said.

This week's PNAS study reports the most recent in a series of advances related to sticky mussel fibers that various research collaborations have posted in recent years. A 2006 PNAS paper by Haeshin Lee, now of the Korea Advanced Institute of Technology, Northwestern's Phillip Messersmith and UChicago's Norbert Scherer demonstrated an elusive but previously suspected fact. Using atomic-force microscopy, they established that an unusual amino acid called "dopa" was indeed the key ingredient in the adhesive protein mussels use to adhere to rocky surfaces.

Last year in the journal Science, scientists at Germany's Max Planck Institute documented still more details about mussel-fiber chemical bonds. The Max Planck collaboration included Holten-Andersen and Herbert Waite of the University of California, Santa Barbara. Holten-Andersen began researching the hardness and composition of mussel coatings as a graduate student in Waite's laboratory.

"Our aspiration is to learn some new design principles from nature that we haven't yet actually been using in man-made materials that we can then apply to make man-made materials even better," he said.

Being able to manufacture green materials is another advantage of drawing inspiration from nature. "A lot of our traditional materials are hard to get rid of once we're done with them, whereas nature's materials are obviously made in a way that's environmentally friendly," Holten-Andersen said.

Citation: "pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli," by Niels Holten-Andersen, Matthew J. Harrington, Henrik Birkedal, Bruce P. Lee, Phillip B. Messersmith, Ka Yee C. Lee, and J. Herbert Waite, Proceedings of the National Academy of Sciences Early Edition, Jan. 24, 2011.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Chicago.

Journal Reference:

N. Holten-Andersen, M. J. Harrington, H. Birkedal, B. P. Lee, P. B. Messersmith, K. Y. C. Lee, J. H. Waite. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1015862108

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.

New solar cell self-repairs like natural plant systems

Researchers are creating a new type of solar cell designed to self-repair like natural photosynthetic systems in plants by using carbon nanotubes and DNA, an approach aimed at increasing service life and reducing cost.

"We've created artificial photosystems using optical nanomaterials to harvest solar energy that is converted to electrical power,"said Jong Hyun Choi, an assistant professor of mechanical engineering at Purdue University.

The design exploits the unusual electrical properties of structures called single-wall carbon nanotubes, using them as "molecular wires in light harvesting cells," said Choi, whose research group is based at the Birck Nanotechnology and Bindley Bioscience centers at Purdue's Discovery Park.

"I think our approach offers promise for industrialization, but we're still in the basic research stage," he said.

Photoelectrochemical cells convert sunlight into electricity and use an electrolyte -- a liquid that conducts electricity -- to transport electrons and create the current. The cells contain light-absorbing dyes called chromophores, chlorophyll-like molecules that degrade due to exposure to sunlight.

"The critical disadvantage of conventional photoelectrochemical cells is this degradation," Choi said.

The new technology overcomes this problem just as nature does: by continuously replacing the photo-damaged dyes with new ones.

"This sort of self-regeneration is done in plants every hour," Choi said.

The new concept could make possible an innovative type of photoelectrochemical cell that continues operating at full capacity indefinitely, as long as new chromophores are added.

Findings were detailed in a November presentation during the International Mechanical Engineering Congress and Exhibition in Vancouver. The concept also was unveiled in an online article (http://spie.org/x41475.xml?ArticleID=x41475) featured on the Web site for SPIE, an international society for optics and photonics.

The talk and article were written by Choi, doctoral students Benjamin A. Baker and Tae-Gon Cha, and undergraduate students M. Dane Sauffer and Yujun Wu.

The carbon nanotubes work as a platform to anchor strands of DNA. The DNA is engineered to have specific sequences of building blocks called nucleotides, enabling them to recognize and attach to the chromophores.

"The DNA recognizes the dye molecules, and then the system spontaneously self-assembles," Choi said

When the chromophores are ready to be replaced, they might be removed by using chemical processes or by adding new DNA strands with different nucleotide sequences, kicking off the damaged dye molecules. New chromophores would then be added.

Two elements are critical for the technology to mimic nature's self-repair mechanism: molecular recognition and thermodynamic metastability, or the ability of the system to continuously be dissolved and reassembled.

The research is an extension of work that Choi collaborated on with researchers at the Massachusetts Institute of Technology and the University of Illinois. The earlier work used biological chromophores taken from bacteria, and findings were detailed in a research paper published in November in the journal Nature Chemistry (http://www.nature.com/nchem/journal/v2/n11/abs/nchem.822.html).

However, using natural chromophores is difficult, and they must be harvested and isolated from bacteria, a process that would be expensive to reproduce on an industrial scale, Choi said.

"So instead of using biological chromophores, we want to use synthetic ones made of dyes called porphyrins," he said.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Purdue University. The original article was written by Emil Venere.

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.

Superhalogens: New class of magic atomic clusters discovered

An international team of researchers has discovered a new class of magnetic superhalogens -- a class of atomic clusters able to exhibit unusual stability at a specific size and composition, which may be used to advance materials science by allowing scientists to create a new class of salts with magnetic and super-oxidizing properties not previously found.

The discovery, which was published Feb. 10 in the Early View issue of the international chemistry journal Angewandte Chemie International Edition, was based on theoretical work by researchers from Virginia Commonwealth University, McNeese State University, and Peking University in China, and experimental work at Johns Hopkins University.

Unlike conventional superhalogens that are composed of a metal atom at the core and surrounded by halogen atoms, the magnetic superhalogens discovered by this team are composed of stoichiometric metal-halogen moieties at the core to which an additional halogen is attached.

The new chemical species known as magnetic superhalogens mimic the chemistry of halogens which are a class of elements from the periodic table, namely, iodine, astatine, bromine, fluorine and chlorine. The word halogen means "salt-former," and when one of the elements above combines with sodium, they can form a salt.

Specifically, the cluster is MnxCl2x+1, where x = 1, 2, 3, and so on, have manganese and chlorine atoms as a core to which only one chlorine atom is attached. The manganese atoms carry a large magnetic moment and therefore make these superhalogens magnetic.

"One can now design and synthesize yet unknown magnetic superhalogens by changing the metal atom from manganese to other transition metal atoms and changing chlorine to other halogen atoms. In addition to their use as oxidizing agents, being magnetic opens the door to the synthesis a new class of salts," said lead investigator Puru Jena, Ph.D., distinguished professor of physics at VCU.

According to Jena, superhalogens are like halogens, in the sense they form negative ions, but their affinity to attract electrons is far greater than those of any halogen atoms. Negative ions are useful as oxidizing agents, for purification of air and in serotonin release for uplifting mood.

"Superhalogens can do the same thing as halogens can do, only better," said Jena. "The ability of superhalogens to carry large quantities of fluorine and chlorine can be used for combating biological agents as well."

"In addition, superhalogens, due to their large electron affinity, can involve inner core electrons of metal atoms in chemical reaction, thus fundamentally giving rise to new chemistry," said Jena.

In October, Jena and his colleagues reported the discovery of a new class of highly electronegative chemical species called hyperhalogens, which use superhalogens as building blocks around a metal atom. The chemical species may have application in many industries.

Jena collaborated with researchers Qian Wang, Ph.D., with the Department of Physics at VCU; Kiran Boggavarapu, Ph.D., with the Department of Chemistry at McNeese State University, and Anil K. Kandalam, Ph.D., with the Department of Physics at McNeese State University; Qiang Sun, Ph.D., and graduate student, Miao Miao Wu, with VCU's Department of Physics at Peking University; and Haopeng Wang and Yeon Jae Ko, both graduate students, and Kit H. Bowen, Ph.D., all with the Department of Chemistry at Johns Hopkins University.

The work was supported in part by the federal Defense Threat Reduction Agency and the Department of Energy.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Virginia Commonwealth University.

Journal Reference:

Miao Miao Wu, Haopeng Wang, Yeon Jae Ko, Qian Wang, Qiang Sun, Boggavarapu Kiran, Anil K. Kandalam, Kit H. Bowen, Puru Jena. Manganese-Based Magnetic Superhalogens. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201007205

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.