New plastics can conduct electricity

 

(PhysOrg.com) -- A newly discovered technique makes it possible to create a whole new array of plastics with metallic or even superconducting properties.

Plastics usually conduct electricity so poorly that they are used to insulate electric cables but, by placing a thin film of metal onto a plastic sheet and mixing it into the polymer surface with an ion beam, Australian researchers have shown that the method can be used to make cheap, strong, flexible and conductive plastic films.

The research has been published in the journal ChemPhysChem by a team led by Professor Paul Meredith and Associate Professor Ben Powell, both at the University of Queensland, and Associate Professor Adam Micolich of the UNSW School of Physics. This latest discovery reports experiments by former UQ Ph.D. student, Dr Andrew Stephenson.

Ion beam techniques are widely used in the microelectronics industry to tailor the conductivity of semiconductors such as silicon, but attempts to adapt this process to plastic films have been made since the 1980s with only limited success – until now.

"What the team has been able to do here is use an ion beam to tune the properties of a plastic film so that it conducts electricity like the metals used in the electrical wires themselves, and even to act as a superconductor and pass electric current without resistance if cooled to low enough temperature," says Professor Meredith.

To demonstrate a potential application of this new material, the team produced electrical resistance thermometers that meet industrial standards. Tested against an industry standard platinum resistance thermometer, it had comparable or even superior accuracy.

"This material is so interesting because we can take all the desirable aspects of polymers - such as mechanical flexibility, robustness and low cost - and into the mix add good electrical conductivity, something not normally associated with plastics," says Professor Micolich. "It opens new avenues to making plastic electronics."

Andrew Stephenson says the most exciting part about the discovery is how precisely the film’s ability to conduct or resist the flow of electrical current can be tuned. It opens up a very broad potential for useful applications.

"In fact, we can vary the electrical resistivity over 10 orders of magnitude – put simply, that means we have ten billion options to adjust the recipe when we're making the plastic film. In theory, we can make plastics that conduct no electricity at all or as well as metals do – and everything in between,” Dr Stephenson says.

These new materials can be easily produced with equipment commonly used in the microelectronics industry and are vastly more tolerant of exposure to oxygen compared to standard semiconducting polymers.

Combined, these advantages may give ion beam processed polymer films a bright future in the on-going development of soft materials for plastic electronics applications – a fusion between current and next generation technology, the researchers say.

Provided by University of New South Wales (news : web)

 

Residual dipolar couplings unveil structure of small molecules

 German chemists at the Technische Universitaet Muenchen and the Karlsruhe Institute of Technology introduced a new method for identifying chemical compounds. The approach they used is an improvement on nuclear magnetic resonance measurements -- for decades one of the most successful methods for determining the chemical structure of organic molecules. The results now published in the scientific journal Angewandte Chemie show a handy approach to structural data when classical methods of analysis fail.

The team of Professor Burkhard Luy from KIT and Junior Professor Stefan F. Kirsch from the TUM has now shown for the first time that certain NMR parameters, the so-called residual dipolar couplings (RDCs), can make a significant contribution towards determining the constitution of chemical compounds when traditional methods fail. To do this they embedded molecules of the compound in a gel which slightly constricts their mobility. By stretching the gel, the molecules can be aligned along a preferred orientation. While residual dipolar couplings average out in solution, they become measurable in such partially aligned samples and provide valuable structural information that can be used to build a model of the molecule.

To test this new approach to chemical structure determination the scientists examined a molecule whose atomic composition was known, but not the precise connectivities of the individual atoms in the molecule. The molecule was obtained using a unique reaction, so there were no precedents for its structure. Classical methods of analysis failed because of the compactness of the molecule. In this particular case it was only possible to determine the structure by means of residual dipolar couplings, so that the newly acquired knowledge could be used to draw conclusions about the formation of the molecule – something that in the past could only be speculated about.

"This type of analysis will not be suitable for all structures in the future," said scientists Luy and Kirsch. "There will still be molecules whose structures will defy all attempts at unraveling, in spite of tremendous efforts and cutting-edge technologies. But this new method provides us with one further tool to help us unravel the structural mysteries of nature."

More information: Grit Kummerlöwe, Benedikt Crone; Manuel Kretschmer, Stefan F. Kirsch und Burkhard Luy: Residual Dipolar Couplings as a Powerful Tool for Constitutional Analysis: The Unexpected Formation of Tricyclic Compounds. Angewandte Chemie International Edition, scheduled to go online 17 or 18 February 2011. DOI:10.1002/anie.2010007305

Provided by Technische Universitaet Muenchen

Researchers discover a new class of magic atomic clusters called superhalogens

February 11, 2011 This image illustrates MnxCl2x+1clusters - new class of magnetic superhalogens.The violet and green spheres represent Mn and Cl atoms, respectively. Image courtesy of Puru Jena, Ph.D./VCU, and Anil Kandalam, Ph.D./McNeese State University.

(PhysOrg.com) -- 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.

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Science review casts doubt on 2001 anthrax case (Update 2)

There was insufficient scientific evidence to support the FBI's assertion that anthrax sent to politicians and journalists in the wake of the September 11 attacks originated in Ivins' lab, said the National Academy of Sciences.

"It is not possible to reach a definitive conclusion about the origins of the B. anthracis in the mailings based on the available scientific evidence alone," said the NAS report.

The anthrax mailings, which killed five people and injured 17, rattled an already jittery American public just days after Al-Qaeda militants hijacked passenger jets and plunged them into the World Trade Center and the Pentagon.

The review found that anthrax contained in a flask, known as RMR-1029, in Ivins' lab shared genetic similarities with spores in the mailed letters but "was not the immediate source of spores used in the letters."

"One or more derivative growth steps would have been required to produce the anthrax in the attack letters," the report said, adding that the letters sent to Washington had different characteristics than those sent to New York.

"They have enough physical and chemical differences between the two that they must have come from separate batches," said lead author of the report Alice Gast.

The FBI concluded that the mailed anthrax must have come from a single flask of parent spores that Ivins had created and which he alone had maintained.

The type of anthrax contained in the letters, mailed to NBC anchor Tom Brokaw, the New York Post and senators Tom Daschle and Patrick Leahy, was correctly identified as the Ames strain of B. anthracis, which originated from a cow in Texas in 1981 and was shared with labs worldwide, the report said.

But a key problem arose from the way the FBI attempted to narrow down the source of the anthrax by creating a repository of potential samples provided by the labs that maintain them.

The repository was incomplete, leaving the possibility that other sources could remain unexamined, and also relied on scientists to provide their own samples, allowing for manipulation by potential suspects.

"Standards of custody of evidence would dictate that agents of the FBI should have obtained the samples," the report said.

"The sender could have been the instigator and may not have complied with instructions, as the FBI alleges with respect to Dr. Ivins."

Ivins, a bio-defense researcher at the US Army's Medical Research Institute of Infectious Diseases, committed suicide by taking drugstore medications in July 2008 as FBI agents were about to bring charges against him.

Investigators began focusing on Ivins in 2007 after new forensic scientific methods traced the anthrax back to him.

The NAS report was delayed in November 2010 when the FBI, which had just received the final draft for security review, decided to release more, previously classified information for the panel to consider.

FBI investigators had looked at anthrax evidence from "an undisclosed overseas site at which a terrorist group's anthrax program was allegedly located," the report said.

"The information indicates that there was inconsistent evidence of Ames strain DNA in some of these samples, but no culturable B. anthracis," it said, adding that the late-arriving information "deserves a more thorough scientific review."

The NAS reviewers also noted that their analysis of evidence was limited to "the biological, physical, and chemical sciences," and did not consider other traditional forensic science methods.

The FBI, which commissioned the NAS report, highlighted the panel's assertion that a definitive conclusion based on science alone "was not possible" and said a combination of factors led investigators to Ivins.

"The FBI has long maintained that while science played a significant role, it was the totality of the investigative process that determined the outcome of the anthrax case," it said in a statement.

Some lawmakers called for a new, independent probe of the government's response.

"The National Academy of Sciences report released today shows that the science is not necessarily a slam dunk," said Senator Chuck Grassley.

"There are no more excuses for avoiding an independent review and assessment of how the FBI handled its investigation in the anthrax case."

Congressman Rush Holt said he was re-introducing a 2008 bill to establish a legislative commission to investigate.

Scientists find a new way insulin-producing cells die

The death of insulin-producing beta cells in the pancreas is a core defect in diabetes. Scientists in Italy and Texas now have discovered a new way that these cells die — by toxic imbalance of a molecule secreted by other pancreatic cells.

"Our study shows that neighboring cells called alpha cells can behave like adversaries for beta cells. This was an unexpected finding," said Franco Folli, M.D., Ph.D., professor of medicine/diabetes at The University of Texas Health Science Center at San Antonio. He is co-lead author on the study with Carla Perego, Ph.D., assistant professor of physiology at the University of Milan.

Balance needed to control sugars

Alpha and beta cells are grouped in areas of the pancreas called the islets of Langerhans. Alpha cells make glucagon, the hormone that raises blood sugar during fasting. In the same environment the beta cells make insulin, the hormone that lowers sugars after a meal. Imbalance ultimately leads to diabetes.

"We found that glutamate, a major signaling molecule in the brain and pancreas, is secreted together with glucagon by alpha cells and affects beta cell integrity," Dr. Folli said. "In a situation where there is an imbalance toward more alpha cells and fewer beta cells, as in Type 1 and Type 2 diabetes, this could result in further beta cell destruction."

Role of alpha cells

Glutamate toxicity is a new mechanism of beta cell destruction not previously known, Drs. Perego and Folli said. It has not been typically thought that alpha cells could themselves be a cause of beta cell damage, they said.

The study also found a protection for beta cells, namely, a protein called GLT1 that controls glutamate levels outside the beta cells. "GLT1 is like a thermostat controlling the microenvironment of beta cells with respect to glutamate concentration," Dr. Perego said.

Early warning

A diagnostic test for glutamate toxicity in the islets of Langerhans is being developed by the authors, Dr. Folli said. Eventually an intervention to slow the process could follow.

Glutamate poisoning is a new candidate mechanism for beta cell destruction in diabetes. Others are high glucose, buildup of a protein called amyloid, and free fatty acids, which are found in patients with type 2 diabetes.

"The vicious cycle in diabetes is that there are several substances that have been shown, also by us, to be toxic to beta cells," Dr. Folli said. "And now we have found a new one, glutamate."

More information: The Journal of Biological Chemistry published the study online this week.

Provided by University of Texas Health Science Center at San Antonio

Alchemy is making a comeback.

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Feb 24, 2011 | 4.8 / 5 (10) | 7 |

(PhysOrg.com) -- A newly discovered technique makes it possible to create a whole new array of plastics with metallic or even superconducting properties.

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