Tuesday, July 5, 2011

Pinpointing the origin of corpses, fingering fake cheese and more -- with 'isoscapes'

An emerging field of science termed "isoscapes" is making it possible to pinpoint the geographical origins of illegal drugs, trafficked endangered animals, dismembered human body parts at crime scenes, and even pricey scotch whiskey and cheese, according to an article in the current edition of Chemical & Engineering News (C&EN), the American Chemical Society's weekly newsmagazine.

In the article, Sarah Everts, C&EN European correspondent, explains how isoscapes has even led to development of one of the newest and most unusual maps of the world. It is a map showing the isotope contours of the world, which scientists and others are using in tracking the geographical origins of objects, and even in research on global climate change. Isoscape is a combination of the words "isotope" and "landscapes," where are atoms of an element that differ slightly in the number of subatomic particles called neutrons that they possess.

Identification by isoscapes is based on the discovery that the tissue in a person's body and composition of drugs, whiskey, and other objects contains a distinctive isotope ratio "fingerprint." That fingerprint stems from the isotope ratios of food, water, and air where the person, whiskey and other objects originated. And those isotope ratios vary with geography that can be plotted on a map. The article explains how the isotope-based map can help convict murderers and authenticate the origins of fancy foods.

More information: “Isotopes Impart Geographical Clues”: http://pubs.acs.or … 926sci1.html

Provided by American Chemical Society (news : web)

'Super sand' for better purification of drinking water (Update)

Scientists have developed a way to transform ordinary sand -- a mainstay filter material used to purify drinking water throughout the world -- into a "super sand" with five times the filtering capacity of regular sand. The new material could be a low-cost boon for developing countries, where more than a billion people lack clean drinking water, according to the report in the ACS journal Applied Materials & Interfaces.

Researchers at Rice University are spinning a bit of nano-based magic to create "coated sand" that has enhanced properties for water purification. The breakthrough may benefit where more than a billion people lack .

Beds of sand are commonly used throughout the world to filter . The particle size of sand and surface modifications determine the efficiency of sand in removing contaminants from water.

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Beds of sand are commonly used throughout the world to filter drinking water. The particle size of sand and surface modifications determine the efficiency of sand in removing contaminants from water. Researchers at Rice University are spinning a bit of nano-based magic to created "coated sand" that has enhanced properties for purification. The breakthrough may benefit developing countries where more than a billion people lack clean drinking water.

The Rice researchers’ technique makes use of graphite oxide, a product in the chemical exfoliation process of graphite (aka pencil lead) that leads to single-atom sheets known as graphene via subsequent reduction.
A team from the Rice lab of Professor Pulickel Ajayan published a report in the American Chemical Society journal and Interfaces describing a process to coat coarse grains of sand in graphite oxide; the resulting material is several times more efficient at removing contaminants than sand alone.

Nanosheets of graphite oxide can be tailored to have hydrophobic (water-hating) and hydrophilic (water-loving) properties. When mixed in a solution with sand, they self-assemble into coatings around the grains and keep the hydrophilic parts exposed. Adding aromatic thiol molecules to the coatings enhances their ability to sequester water-soluble contaminants.

Ajayan, a Rice professor in mechanical engineering and materials science and of chemistry, and his collaborators from Australia and Georgia conducted experiments to compare this coated sand with plain sand and activated carbon granules used by municipalities and in-home systems.

The researchers ran two model contaminants -- mercury (at 400 parts per billion) and Rhodamine B dye (10 parts per million) -- through sand and coated sand placed into filtration columns. They found coarse sand's adsorption capacity of mercury was saturated within 10 minutes.

The coated sand continued removing mercury for more than 50 minutes and resulted in filtered water with less than one part per billion. (The Environmental Protection Agency's maximum contaminant level goal for mercury in drinking water is two parts per billion.)

Results for water treated with Rhodamine B dye were similar.

The researchers found coated sequestered contaminants just as well as the commercially available active carbon filtration systems they tested.

The lab is looking at ways to further functionalize graphite oxide shells to enhance contaminant removal. "By attaching different functional moieties onto graphite oxide, we could engineer some form of a 'super sand' to target specific contaminants species, like arsenic, trichloroethylene and others," said Rice graduate student Wei Gao, primary author of the paper.

More information: "Engineered Graphite Oxide Materials for Application in Water Purification" ACS Appl. Mater. Interfaces, 2011, 3 (6), pp 1821–1826
DOI: 10.1021/am200300u

Retaining the inherent hydrophilic character of GO (graphite-oxide) nanosheets, sp2 domains on GO are covalently modified with thiol groups by diazonium chemistry. The surface modified GO adsorbs 6-fold higher concentration of aqueous mercuric ions than the unmodified GO. “Core–shell” adsorbent granules, readily useable in filtration columns, are synthesized by assembling aqueous GO over sand granules. The nanostructured GO-coated sand retains at least 5-fold higher concentration of heavy metal and organic dye than pure sand. The research results could open avenues for developing low-cost water purification materials for the developing economies.

Provided by American Chemical Society (news : web)

Unearthing the appearance of ancient animals: X-ray technique for determining fossil pigmentation patterns

An international team including University of Pennsylvania paleontologists is unearthing the appearance of ancient animals by using the world's most powerful X-rays. New research shows how trace metals in fossils can be used to determine the pigmentation patterns of creatures dead for more than a hundred million years.

The research was conducted by an international team working with Phillip Manning, an adjunct professor in the School of Arts and Sciences' Department of Earth and Environmental Science, and Peter Dodson, a professor in both the Department of Earth and Environmental Science and the School of Veterinary Medicine's Department of Animal Biology. They collaborated with Roy Wogelius of the University of Manchester, Uwe Bergmann of Stanford University's SLAC National Accelerator Laboratory and other researchers.

Their work will be published in the journal Science on July 1.

Manning and Dodson have long studied fossils of the earliest birds, including Confuciusornis sanctus, which lived 120 million years ago and was one of many evolutionary links between dinosaurs and birds, and Gansus yumenensis, which is considered the oldest modern bird and lived more than 100 million years ago. Their partnership with researchers from Manchester and Stanford, however, has opened a new avenue of investigation.

"Every once in a while we are lucky enough to discover something new, something that nobody has ever seen before," said Wogelius, a geochemist and the paper's lead author.

The team's discovery is rooted in a new technique, using technology based on synchrotron radiation to identify copper-bearing molecules in the fossilized feathers of these ancient birds.

"There is an intimate relationship between trace metals and organics. When you're getting a good suntan, melanin forms in your skin. There are many forms of melanin, and some are found in the dark feathers of birds, but copper is always bound into its structure," Manning said. "You can see this in living animals, but it's only since we've been using a synchrotron -- a vast accelerator that generates intense X-rays a hundred million times brighter than the sun -- that we can see the chemical detail in fossils and show that the copper complexes we found were originally part of the animal."

Metallic compounds can survive in these fossils for hundreds of millions of years because they are unpalatable to microorganisms. But to distinguish the copper that was bound in melanin with copper that might have been geochemically produced requires the precision that only a tool like the synchrotron can provide. By measuring the energy released by atoms when they are bombarded with high-powered X-rays, researchers can get an accurate picture of the molecules in which they reside.

"We're able to map absolute quantities, to parts-per-million levels in discrete biological structures, which we compare with living organisms and see they are comparable," Manning said.

The new technique paints a richer picture of the lives of these ancient creatures.

"While our work doesn't yet allow you to diagnose color, you can get the concentration and distribution of pigments," Dodson said. "In other words, you can work out monochrome patterns, which may tell us something about camouflage or other traits relevant to natural selection of the species."

"If we could eventually give colors to long extinct species, that in itself would be fantastic," said co-author Uwe Bergmann, deputy director of the Linac Coherent Lightsource at SLAC. "But synchrotron radiation has revolutionized science in many fields, most notably in molecular biology. It is very exciting to see that it is now starting to have an impact in paleontology, in a way that may have important implications in many other disciplines,"

The team is confident that further research with this technique will enable them to fully diagnose color via fossil chemistry, and they also believe that this is only one of many applications the technique will have.

"This synchrotron research is really important as it gives us the first clue to really understanding what happens with organic debris when you bury it in the ground," Manning said. "For example, there are huge implications for understanding the mass transfer of buried waste; trace metals can be bad if you get too much of them, so we can spatially map and give images of exact loadings of these metals in both living and extinct organisms. No one else can do this. It's not just contributing to a field, it's creating a whole new discipline."

In addition to Wogelius, Manning, Dodson and Bergmann, the research was conducted by Holly Barden, Nick Edwards and William Sellers, of Manchester University; Peter Larson of Manchester University and the Black Hills Institute of Geological Researc, Inc.; Kevin Taylor of Manchester Metropolitan University; Sam Webb of the SLAC National Accelerator Laboratory; Hai-lu You of the Chinese Academy of Geological Sciences; and Li Da-qing of the Gansu Geological Museum.

Support for this research was provided by the United Kingdom's National Environmental Research Council and an anonymous private donor.

Fossil samples were provided by the Black Hills Institute Museum and the Museum für Naturkunde, Humboldt University, Berlin. The Stanford Synchrotron Radiation Lightsource at SLAC is a Department of Energy Office of Science national user facility which provides synchrotron radiation for research in chemistry, biology, physics and materials science to more than a thousand users each year.

Story Source:

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

Journal Reference:

R. A. Wogelius, P. L. Manning, H. E. Barden, N. P. Edwards, S. M. Webb, W. I. Sellers, K. G. Taylor, P. L. Larson, P. Dodson, H. You, L. Da-Qing, U. Bergmann. Trace Metals as Biomarkers for Eumelanin Pigment in the Fossil Record. Science, 2011; DOI: 10.1126/science.1205748

Natural gases as a therapy for heart disease?

 An understanding of the interaction between hydrogen sulphide (the 'rotten eggs' gas) and nitric oxide, both naturally occurring in the body, could lead to the development of new therapies and interventions to treat heart failure.

Research carried out by scientists from the Peninsula Medical School at the University of Exeter and the National University of Singapore has analysed the complex 'cross talk' between hydrogen sulphide (H2S ) and nitric oxide (NO), both gasses that occur naturally in the body, and found that the interaction may offer potential strategies in the management of heart failure.

The research is published in the leading international journal Antioxidants and Redox Signaling.

Both gases interact naturally with each other within the body and the balance between the two and other chemical compounds has influence on health. The research team found that by modulating how H2S and NO interact, a positive affect was produced for heart health.

The two gases were found to interact together to form a thiol-sensitive compound (linked to the sulphur in H2S) which produces inotropic (muscular contraction) and lusitropic (muscular relaxation) effects in the heart. This crosstalk suggests that there is the potential to produce a molecule that may be of benefit to the heart and which could be the basis of a new drug therapy based on elements that occur naturally in the body.

The study also offers a new perspective on gaseous neurotransmitters, in which the function of cells is influenced by the interaction of the two gases.

Prof. Matt Whiteman, joint author from the Peninsula Medical School, commented: "Our findings are potentially very exciting and offer a novel insight into understanding how and why the heart fails. This could lead to new treatment and management strategies of heart failure, such as molecules which release H2S. By altering the ratio of H2S and NO, two naturally occurring physiological gases in the heart and perhaps the rest of the cardiovascular system, we have the potential to manipulate heart and vascular function. There is huge potential in the continued development of H2S delivery systems either through pharmacological means or through dietary intervention."

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by The Peninsula College of Medicine and Dentistry.

Journal Reference:

Qian-Chen Yong, Jia Ling Cheong, Fei Hua, Lih-Wen Deng, Yok Moi Khoo, How-Sung Lee, Alexis Perry, Mark Wood, Matthew Whiteman, Jin-Song Bian. Regulation of Heart Function by Endogenous Gaseous Mediators—Crosstalk Between Nitric Oxide and Hydrogen Sulfide. Antioxidants & Redox Signaling, 2011; 14 (11): 2081 DOI: 10.1089/ars.2010.3572

New technique makes artificial bones more natural

A new technique for producing artificial bone implants has been developed by Korean researchers. By mimicking natural bone, it is hoped the implant material will better complement the natural regeneration process.

A new technique for producing artificial bone has been developed by Korean researchers. Published in the journal Science and Technology of Advanced Material (STAM), the technique combines two methods to approximate both types of . By mimicking natural bone, it is hoped the implant material will better complement the natural regeneration process.

Most previous studies have focussed on producing cancellous bone, which has a spongy, honeycombed structure. However, artificial bones for practical applications must also imitate , the hard, strong tissue found on the outer layers of bone. Cortical bone is less porous than cancellous bone, but contains canals through which the for flow. By developing a process to imitate this canal structure, the researchers made significant advances in the fabrication of artificial bones.

Bundles of polymer-based * were wrapped around 0.3mm diameter steel wires by the method of “electrospinning”, whereby fine fibres of material are drawn out by electric charge. These bundles were used to cover a scaffold of cancellous bone structure, made by the standard “sponge replica method” out of zirconia (ZrO2) and biphasic calcium phosphate (BCP). Removal of the steel wires resulted in interconnected structures mimicking small human bones.

The resulting structure had a high strength and a porosity of approximately 70%—similar to natural bone. Tests confirmed the artificial bone structure had a high degree of biocompatibility which is critical for real-world applications. However, more research is needed to evaluate the biological properties of this material both in vitro and in vivo.

The rapid ageing of the population makes bone loss and fracture a major worldwide problem and stimulates bone regeneration research. Biomimetic approaches to making artificial implants have attracted much attention, but the dependence of the healing process on interaction with the implant material requires close mimicry of the architecture of natural bone. This paper marks a significant advance in the development of materials and processing technology for the fabrication of artificial bone structures.

*HAp-loaded PMMA-PCL, or polymethylmethacrylate-polycaprolactone-hydroxyapatite

More information: Yang-Hee Kim and Byong-Taek Lee, Novel approach to the fabrication of artificial small bone using a combination of sponge replica and electrospinning methods, Science and Technology of Advanced Materials 12 (2011) 035002. http://dx.doi.org/ … /12/3/035002

Provided by National Institute for Materials Science

New surface nonlinear spectroscopy capability: Picosecond-femtosecond broadband sum frequency generation system

In Dr. Hongfei Wang's spectroscopy laboratory at the end of EMSL's main hallway, the lights are always off. Because the instrumental capability his team has built uses lasers as its main weapon, light interference would hinder scientific results. So Wang, postdoctoral researcher Dr. Luis Velarde, and visiting scientist Dr. Xianyi Zhang constantly wear headlamps in the lab, giving them the appearance of old-time coal miners. But instead of coal, they are using the new surface nonlinear spectroscopy capability to dig up never-before-seen data on molecular interactions at interfaces. Early in 2011, they struck a vein that could lead scientists in many fields to research gold.

When the first high resolution vibrational spectrum of the air/DMSO interface appeared on the screen (DMSO is Dimethyl sulfoxide, a very common and important solvent), Wang immediately began to celebrate: after shaking hands with the others and taking a few pictures with his phone, he burst into the hallway to show the evidence to whoever happened to be around. After six months of system design and configuration, and another six months of delivery, installation, and seemingly endless testing, it was finally up and running: the picosecond-femtosecond broadband sum frequency generation system was ready to provide a new generation of surface vibrational and imaging.

"I was very relieved," he said. "We expected it to happen, and it happened. Now we know we have something that is truly unique—the SFG community has been waiting for this, and many scientific fields will benefit."

Back in the lab, Velarde hadn't started celebrating yet. He wanted to make sure everything was just as they expected it would be, and that the spectrum was genuine proof of the system's capability. When he was satisfied, he finally let himself enjoy the moment as well.

For Wang, the milestone was more than a successful project at work; it confirmed his decision to leave his home nation and a job at the Chinese Academy of Sciences in 2009.

"EMSL is the perfect place to develop this capability. Not many places offer an environment like this, and surface chemistry is crucial to all three of EMSL's science themes." He added, "After we generated the first spectrum, I called my wife to tell her: the decision to move here has been validated."

Sum frequency generation (SFG) is a highly specialized surface nonlinear spectroscopy technique scientists use to analyze at surfaces and interfaces of all kinds. It is an important, crosscutting technique that can unlock new discoveries in several energy, environmental, and health-related research areas. While the technique has been pioneered by Professor Ron Shen at Berkeley in the 1980s, there is a very small community worldwide that can perform these very difficult experiments to understand the one or few layers of molecules at various interfaces. As for resolution, strength, and efficiency of this capability, this recent "Moment" demonstrates that Wang and his team now stand alone. Previous techniques forced researchers to choose between signal strength and resolution, and carry out time-intensive examinations of each specific data point.

The new system in EMSL for the first time synchronizes two powerful lasers with completely different characteristics. Namely, one has very short pulses (35fs, 1fs=10-15 second) which provides the ultrafast time resolution, and another has very long pulses (100ps, 1ps=10-12 second) which provides the high spectral resolution. This offers the best of both worlds: reliable data is gathered in a few seconds or minutes, at more than ten times the best previously documented spectral resolution with the similar systems. Specifically, they achieved 0.7cm-1 spectral resolution, versus>15cm-1 resolution. With these gains, the tool is ready to reveal detailed molecular conformation and interactions at the molecular interface.

The capability is best shown by example: imagine a team of researchers who want to examine a sample with a liquid-liquid interface: oil and water. This is an example of a "buried interface"—a difficult case for many experimental techniques. SFG specializes in this problem. Experimentalists like Wang interrogate the sample by shooting two pulsed lasers through the oil and water so they meet at the liquid-liquid interface at an exact time (on the scale). If done correctly, the signal the sample sends back is "surface sensitive"—which means it selects only information about the interface (the two-atom-wide molecular interaction the scientists care about), clearing away the background noise. The resulting spectra allow researchers to piece together what is truly happening on a molecular level—such as how these molecular groups are oriented. In the case of where oil and water meet, deeper fundamental information can provide new insights for environmental cleanup. In addition, the use of lasers causes far less damage to the sample (as opposed to bombarding it with ions) and allows scientists to perform in situ experiments that replicate true environmental conditions.

Wang is often invited to give talks around the world on surface nonlinear spectroscopy. On March 16, 2011, he gave a seminar of his latest findings at Oregon State University in Corvallis, Oregon, and he will do the same at Rice University in October 2011.

Like all of EMSL's experimental and computational tools, the new surface nonlinear spectroscopy capability is available at no cost to the global scientific community through EMSL's user proposal process.

Provided by Environmental Molecular Sciences Laboratory (news : web)

Splitsville for boron nitride nanotubes

For Hollywood celebrities, the term "splitsville" usually means "check your prenup." For scientists wanting to mass-produce high quality nanoribbons from boron nitride nanotubes, "splitsville" could mean "happily ever after."

Scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, working with scientists at Rice University, have developed a technique in which boron nitride nanotubes are stuffed with atoms of potassium until the tubes split open along a longitudinal seam. This creates defect-free boron nitride nanoribbons of uniform lengths and thickness. Boron nitride nanoribbons are projected to display a variety of intriguing magnetic and electronic properties that hold enormous potential for future devices.

Nanoribbons are two-dimensional single crystals (meaning only a single atom in thickness) that can measure multiple microns in length, but only a few hundred or less nanometers in width. Graphene nanoribbons, which are made from pure carbon, carry electrons at much faster speeds than silicon, and can be used to cover wide areas and a broad assortment of shapes. Boron nitride nanoribbons offer similar advantages plus an additional array of electronic, optical and magnetic properties.

"There has been a significant amount of theoretical work indicating that, depending on the ribbon edges, boron nitride nanoribbons may exhibit ferromagnetism or anti-ferromagnetism, as well as spin-polarized transport which is either metallic or semi-conducting," says physicist Alex Zettl, one of the world's foremost researchers into nanoscale systems and devices who holds joint appointments with Berkeley Lab's Materials Sciences Division (MSD) and the Physics Department at UC Berkeley, where he is the director of the Center of Integrated Nanomechanical Systems (COINS).

"The unique properties of boron nitride nanoribbons are of great fundamental scientific interest and also have implications for applications in technologies that include spintronics and optoelectronics," Zettl says. "However, the facile, scalable synthesis of high quality boron nitride nanoribbons has been a significant challenge."

Zettl and members of his research group met this challenge using the chemical process known as "intercalation," whereby atoms or molecules of one type are inserted between atoms and molecules of another type. James Tour at Rice University and his research group had demonstrated that the intercalation of potassium atoms into carbon nanotubes promotes a longitudinal splitting of the tubes. This prompted Zettl and Tour to collaborate on a study that used the same approach on boron nitride nanotubes, which are very similar in structure to nanotubes made from carbon.

Zettl and Tour reported the results of this study in the journal Nano Letters.  Co-authoring the paper were Kris Erickson, Ashley Gibb, Michael Rousseas and Nasim Alem, who are all members of Zettl's research group, and Alexander Sinitskii, a member of Tour's research group.

"The likely mechanism for the splitting of both carbon and boron nitride nanotubes is that potassium islands grow from an initial starting point of intercalation," Zettl says. "This island growth continues until enough circumferential strain results in a breakage of the chemical bonds of the intercalated nanotube. The potassium then begins bonding to the bare ribbon edge, inducing further splitting."

Alex Zettl holds joint appointments with Berkeley Lab and UC Berkeley where he directs the Center of Integrated Nanomechanical Systems.

This synthesis technique yields boron nitride nanoribbons of uniform widths that can be as narrow as 20 nanometers. The ribbons are also at least one micron in length, with minimal defects within the plane or along the edges. Zettl says the high quality of the edges points to the splitting process being orderly rather than random. This orderliness could explain why a high proportion of the boron nitride nanoribbons display the coveted zigzag or armchair-shaped edges, rather than other edge orientations.

Edges are critical determinants of a nanoribbon's properties because the electrons along the edge of one ribbon edge can interact with the electrons along the edge of another ribbon, resulting in the type of energy gap that is crucial for making devices. For example, zigzagged edges in graphene nanoribbons have been shown to be capable of carrying a magnetic current, which makes them candidates for spintronics, the computing technology based on the spin rather than the charge of electrons.

Kris Erickson, who was the lead author on the Nano Letters paper, says that, "Given the significant dependence upon boron nitride nanoribbon edges for imbuing particular electronic and magnetic properties, the high likelihood of synthesizing ribbons with zigzag and armchair edges makes our technique particularly suitable for addressing theoretical predictions and realizing proposed applications."

Erickson also says it should be possible to functionalize the edges of the boron nitride nanoribbons, as these edges are terminated with chemically reactive potassium atoms following synthesis and with reactive hydrogen atoms following exposure to water or ethanol.

"The potassium-terminated edge could easily be replaced with a species other than hydrogen," Erickson says. "Different chemicals could be used for quenching to impart other terminations, and, furthermore, hydrogen could be replaced after quenching by either utilizing established boron nitride functionalization routes, or by devising new routes unique to the highly reactive nanoribbon edge."

Zettl and his research group are now investigating alternative syntheses using different boron nitride nanotube precursors to increase yields and improve the purification process. They are also attempting to functionalize the edges of their nanoribbons and they are in the process of determining if the various predicted edge states for these nanoribbons can be studied.

"What we really need most right now is a better source of boron nitride nanotubes," Zettl says.

This work was supported by the U.S. Department of Energy's Office of Science, with additional support from the National Science Foundation through the Center of Integrated Nanomechanical Systems (COINS), the Office of Naval Research, and the Air Force Research Laboratory.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Kris J. Erickson, Ashley L. Gibb, Alexander Sinitskii, Michael Rousseas, Nasim Alem, James M. Tour, Alex K. Zettl. Longitudinal Splitting of Boron Nitride Nanotubes for the Facile Synthesis of High Quality Boron Nitride Nanoribbons. Nano Letters, 2011; : 110524125655048 DOI: 10.1021/nl2014857

Specialized seeds can really float your boat

A new artificial surface inspired by floating seeds, which could provide an alternative to the toxic paints currently used to prevent fouling on ship hulls, has been developed by German scientists.

Scientists from the Biomimetics-Innovation-Centre have developed a new anti-fouling surface based on a seed from a species of palm tree. "These have which are dispersed by the . As it is an advantage for these seeds to remain free of fouling to allow them to disperse further, we guessed they might have specialised surfaces we could mimic," explains Katrin Mühlenbruch, a PhD researcher who is presenting this work at the Society for Experimental Biology Annual Conference in Glasgow on the 4th of July 2011.

The researchers floated seeds from 50 species in the North Sea for 12 weeks. The seeds of 12 species showed no fouling at all. "We then began by examining the micro-structure of the seeds' surfaces, to see if we could translate them into an artificial surface. The seeds we chose to mimic had a hairy-like structure," says Ms. Mühlenbruch. "This structure might be especially good at preventing fouling because the fibres constantly move, preventing marine organisms from finding a place to settle."

Using a silicone base the scientists created an artificial surface similar to the seeds, with fibres covering the surface. Currently the new surface is being trialled by floating it in the sea. "Initial results are quite good," says Ms. Mühlenbruch. "But we still have a long way to go"

Fouling by seaweeds and marine animals is a problem for the shipping industry, resulting in increased fuel costs. Currently the only solutions are highly toxic and environmentally damaging marine paints which are specifically designed to leach biocides to prevent organisms settling on the hull. "Our aim is to provide a new toxin-free and bio-inspired ship coating," says Ms. Mühlenbruch. "This would prevent environmental damage while allowing ships to operate efficiently."

Future work will include analysing the chemical composition of the seeds' , to find out whether this adds to their anti-fouling properties.

Provided by Society for Experimental Biology

Molecular glue sticks it to cancer

University of Toronto Mississauga researchers have developed a "molecular glue" that sticks cancer-promoting proteins to a cell's membrane -- shutting off a cancer cell's growth.

Imagine dropping dish soap into a sink full of greasy water. What happens? As soon as the soap hits the water, the grease recoils—and retreats to the edges of the sink.

Now, what if the sink was a cell, the globs of grease were cancer-promoting proteins and the dish soap was a potential drug? According to new research from the University of Toronto Mississauga, such a drug could force the proteins to the cell's membrane (a.k.a., the edge of the sink)—and make the cancer cell more vulnerable to chemotherapy.

"This is a totally new approach to cancer therapy," says Professor Patrick Gunning of the Department of Chemical and Physical Sciences. "Everything prior to this has targeted functionally relevant binding sites. Our approach inhibits the mobility of cancer-promoting proteins within —essentially, it's like molecularly targeted glue."

The "glue" is shaped like a dumbbell: at one end is an anchor that sticks to the membrane, and at the other is a molecule that binds to the cancer-promoting proteins. The anchor is a cholesterol molecule that is well known to chemists for sticking to cell membranes. The recognition molecule is fairly picky about what it will bind to, reducing the risk of drug-related side effects.

Gunning says that by sticking the target proteins to the cell membrane, the glue-like substance interferes with how they cause to multiply out of control. However, on a normal cell, the new therapy should have little effect.

"We are really excited about the potential for this type of drug," says Gunning, who developed the concept along with Professor Claudiu Gradinaru at U of T Mississauga and Professor James Turkson at the University of Central Florida. "This is ready to move to preclinical studies, and this treatment could slow or stop the explosive growth of cancerous tumours. And for patients, this might reduce the need for really powerful chemotherapy, which can be very hard to tolerate."

The study appears on the cover of the latest issue of the journal Angewandte Chemie.

Provided by University of Toronto (news : web)

Researchers image graphene electron clouds, revealing how folds can harm conductivity

 A research team led by University at Buffalo chemists has used synchrotron light sources to observe the electron clouds on the surface of graphene, producing a series of images that reveal how folds and ripples in the remarkable material can harm its conductivity.

The research, scheduled to appear June 28 in Nature Communications, was conducted by UB, the National Institute of Standards and Technology (NIST), the Molecular Foundry at Lawrence Berkeley National Laboratory (Berkeley Lab), and SEMATECH, a global consortium of semiconductor manufacturers.

Graphene, the thinnest and strongest material known to man, consists of a single layer of carbon atoms linked in a honeycomb-like arrangement.

Graphene's special structure makes it incredibly conductive: Under ideal circumstances, when graphene is completely flat, electric charges speed through it without encountering many obstacles, said Sarbajit Banerjee, one of the UB researchers who led the study in Nature Communications.

But conditions are not always optimal.

The new images that Banerjee and his colleagues captured show that when graphene is folded or bent, the electron cloud lining its surface also becomes warped, making it more difficult for an electric charge to travel through.

"When graphene is flat, things just kind of coast along the cloud. They don't have to hop across anything. It's like a superhighway," said Banerjee, an assistant professor of chemistry. "But if you bend it, now there are some obstacles; imagine the difference between a freshly paved highway and one with construction work along the length forcing lane changes.

"When we imaged the electron cloud, you can imagine this big fluffy pillow, and we saw that the pillow is bent here and there," said Banerjee, whose National Science Foundation CAREER award provided the primary funding for the project.

To create the images and understand the factors perturbing the electron cloud, Banerjee and his partners employed two techniques that required use of a synchrotron: scanning transmission X-ray microscopy and near edge X-ray absorption fine structure (NEXAFS), a type of absorption spectroscopy. The experiments were further supported by computer simulations performed on computing clusters at Berkeley Lab.

"Using simulations, we can better understand the measurements our colleagues made using X-rays, and better predict how subtle changes in the structure of graphene affect its electronic properties," said David Prendergast, a staff scientist in the Theory of Nanostructures Facility at the Molecular Foundry at Berkeley Lab. "We saw that regions of graphene were sloped at different angles, like looking down onto the slanted roofs of many houses packed close together."

Besides documenting how folds in graphene distort its electron cloud, the research team discovered that contaminants that cling to graphene during processing linger in valleys where the material is uneven. Such contaminants uniquely distort the electron cloud, changing the strength with which the cloud is bound to the underlying atoms.

Graphene's unusual properties have generated excitement in industries including computing, energy and defense. Scientists say that graphene's electrical conductivity matches that of copper, and that graphene's thermal conductivity is the best of any known material.

But the new, UB-led study suggests that companies hoping to incorporate graphene into products such as conductive inks, ultrafast transistors and solar panels could benefit from more basic research on the nanomaterial. Improved processes for transferring flat sheets of graphene onto commercial products could greatly increase those products' efficiency.

"A lot of people know how to grow graphene, but it's not well understood how to transfer it onto something without it folding onto itself," Banerjee said. "It's very hard to keep straight and flat, and our work is really bringing home the point of why that's so important."

"Graphene is going to be very important in electronics," said PhD candidate Brian Schultz, one of three UB graduate students who were lead authors on the Nature Communications paper. "It's going to be one of the most conductive materials ever found, and it has the capability to be used as an ultrahigh-frequency transistor or as a possible replacement for silicon chips, the backbone of current commercial electronics.

"When graphene was discovered, people were just so excited that it was such a good material that people really wanted to go with it and run as fast as possible," Schultz continued. "But what we're showing is that you really have to do some fundamental research before you understand how to process it and how to get it into electronics."

Other research partners offered the following insight into the significance of the findings:

Dan Fischer, NIST Material Measurement Laboratory, leader, Synchrotron Methods Group: "The NEXAFS results indicating that performance-damaging contaminants cling to graphene during processing highlights the importance of chemically sensitive advanced synchrotron measurement method developments for promoting innovation and industrial competiveness in commercial applications of nanotechnology."Pat Lysaght, SEMATECH Front End Processes, senior member technical staff: "We place a premium on the power of collaboration, and this is a great example of the benefits associated with that philosophy. The unique expertise of each of the four collaborative entities has come together to forge a new understanding of subtle functionalization variations of surface graphene atoms. Our findings represent another important step toward potential industrial applications such as low-cost broadband radio frequency (RF) devices, and correlation of NEXAFS with Raman spectroscopy which may enhance monitoring capabilities for graphene as a replacement for large area organic LED displays."

Synchrotron imaging was conducted at the Canadian Light Source in Saskatchewan in Canada and at the National Synchrotron Light Source (NSLS ) at Brookhaven National Laboratory in New York State. NEXAFS was measured at the NIST soft X-ray beamline of the NSLS.

Story Source:

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

Journal Reference:

Brian J. Schultz, Christopher J. Patridge, Vincent Lee, Cherno Jaye, Patrick S. Lysaght, Casey Smith, Joel Barnett, Daniel A. Fischer, David Prendergast, Sarbajit Banerjee. Imaging local electronic corrugations and doped regions in graphene. Nature Communications, 2011; 2: 372 DOI: 10.1038/ncomms1376

Inkjet printing could change the face of solar energy industry

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.

Engineers at Oregon State University have discovered a way for the first time to create successful "CIGS" 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 on a substrate with a more expensive 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 .

"In summary, a simple, fast, and direct-write, solution-based deposition process is developed for the fabrication of high quality CIGS ," 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."

Provided by Oregon State University (news : web)

Pistachios make healthy decafs

 If caffeine gets your blood pumping more than it should, here's a piece of good news: when roasted appropriately, pistachios can become a tasty and healthier substitute for coffee, with all the aromas and flavour and none of the undesirable effects.

Fresh , as they are picked from bushes in high-altitude , are nothing like the finished product that fuels millions of lives across the world. The reassuring smell of and its familiar taste only after a fair share of roasting.

Roasting triggers the aroma thanks to the release of that exist as vapours, known as volatiles. Volatiles come with complicated names, but some are linked to very familiar aromas. Limonene smells of citrus, alpha-pinene gives a pine/turpentine scent and 5-methylfurfural is better described as a bouquet of caramel and burnt sugar.

'Not all of the volatiles are responsible for aroma even if they are present in a high concentration,' says Mustafa Özel, a chemist based at the University of York. 'However some of the volatiles give a strong aroma even at a very low concentration – it just depends on which compound it is.'

If aroma depends on volatiles, is it possible to make two different things smell and taste similar?

Pistachio beans have many culinary uses. They can be eaten as snacks, added to bread recipes or used as cooking oil. In Turkey pistachios are sometimes roasted and ground to be used as a coffee substitute. Özel and his colleagues decided to explore what makes pistachios so like coffee.

'Roasting time and roasting temperature really affect the production of many volatile compounds,' explains Özel. 'As some particular compounds are mainly responsible for the characteristic aroma of the roasted product, you can manipulate which ones appear by altering the roasting time and temperature.'

The team took six handfuls of pistachios and roasted them on a frying pan at 200 degrees Celsius for different periods of time, from 5 to 25 minutes. One set of pistachios was left uncooked as a control. Then they grounded the beans to fit through a 1mm sieve and analysed the samples' chemical composition.

The idea was to see which volatiles are released at various stages of roasting and what is the ideal roasting time to produce the best aroma while keeping undesirable products to a minimum.

The results, published in Food Chemistry, show that pistachios tend to produce the most volatiles after 20 minutes in a pan; after that the effect decreases. But most importantly, the pan-roast produces furans, furanones, benzene derivatives, pyrazines and other volatiles typical of coffee and flavour.

The beans might be very different when raw but after roasting pistachios and coffee have indeed similar bouquets. This suggests that pistachios 'may provide an alternative for use in the coffee industry,' says Özel.

And a healthier one as well: 'There are lots of important anti-oxidants in pistachios, which are beneficial to health and they don't contain caffeine,' he adds. 'Therefore pistachio coffee could be said to be healthier than conventional coffee.'

The findings have interesting industrial applications. 'If the are processed to remove the excess oil, then they can be ground to a smaller size and commercialized as coffee substitutes more broadly,' Özel concludes.
This story is republished courtesy of Planet Earth online, a free, companion website to the award-winning magazine Planet Earth published and funded by the Natural Environment Research Council (NERC).

More information: Gogus, F., Özel, M.Z., Kocak, D., Hamilton, J.F., Lewis, A.C., Analysis of roasted and unroasted Pistacia terebinthus volatiles using direct thermal desorption-GCxGC-TOF/MS, Food Chemistry (2011), doi: 10.1016/j.foodchem.2011.05.003

Provided by PlanetEarth Online (news : web)

Breaking Kasha's rule: Scientists find unique luminescence in tetrapod nanocrystals

 Observation of a scientific rule being broken can sometimes lead to new knowledge and important applications. Such would seem to be the case when scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) created artificial molecules of semiconductor nanocrystals and watched them break a fundamental principle of photoluminescence known as "Kasha's rule."

Named for chemist Michael Kasha, who proposed it in 1950, Kasha's rule holds that when light is shined on a molecule, the molecule will only emit light (fluorescence or phosphorescence) from its lowest energy excited state. This is why photoluminescent molecules emit light at a lower energy than the excitation light. While there have been examples of organic molecules, such as azulene, that break Kasha's rule, these examples are rare. Highly luminescent molecular systems crafted from quantum dots that break Kasha's rule have not been reported -- until now.

"We have demonstrated a semiconductor nanocrystal molecule, in the form of a tetrapod consisting of a cadmium-selenide quantum dot core and four cadmium sulfide arms, that breaks Kasha's rule by emitting light from multiple excited states," says Paul Alivisatos, director of Berkeley Lab and the Larry and Diane Bock Professor of Nanotechnology at the University of California (UC) Berkeley. "Because this nanocrystal system has much higher quantum yield and is relatively more photostable than organic molecules, it holds promising potential for optical sensing and light emission-based applications, such as LEDs and imaging labels."

Alivisatos, an internationally recognized authority on nanochemistry, is one of two corresponding authors, along with Sanjeevi Sivasankar of DOE's Ames Laboratory and Iowa State University, on a paper describing this work in the journal Nano Letters. The paper is titled "Spatially Indirect Emission in a Luminescent Nanocrystal Molecule." Co-authoring the paper were Charina Choi, Prashant Jain and Andrew Olson, all members of Alivisatos' research group, plus Hui Li, a member of Sivasankar's research group.

Semiconductor tetrapods make exceptionally good subjects for the study of electronically coupled nanocrystals as Charina Choi, lead author of the Nano Letters paper, explains.

"For the study of nanocrystal molecules, it is important to be able to grow complex nanocrystals in which simple nanocrystal building blocks are connected together in well-defined ways," Choi says. "Although there are many versions of electronically coupled nanocrystal molecules, semiconductor tetrapods feature a beautiful symmetry that is analogous to the methane molecule, one of the fundamental units of organic chemistry."

In this study, Choi, Alivisatos and their co-authors designed a cadmium-selenide (CdSe)and cadmium-sulfide (CdS) core/shell tetrapod whose quasi-type-I band alignment results in high luminescence quantum yields of 30- to 60-percent. The highest occupied molecular orbital (HOMO) of this tetrapod involves an electron "hole" within the cadmium-sulfide core, while the lowest unoccupied molecular orbital (LUMO) is centered within the core but is also likely to be present in the four arms as well. The next lowest unoccupied molecular orbital (LUMO+1) is located primarily within the four CdS arms.

Through single particle photoluminescence spectroscopy carried out at Ames, it was determined that when a CdSe/CdS core/shell tetrapod is excited, not only is a photon emitted at the HOMO-LUMO energy gap as expected, but there is also a second photon emitted at a higher energy that corresponds to a transition to the HOMO from the LUMO+1.

"The discovery that these CdSe/CdS core/shell tetrapods emit two colors was a surprise," Choi says. "If we can learn to control the frequency and intensity of the emitted colors then these tetrapods may be useful for multi-color emission technologies."

For example, says co-author Prashant Jain, "In the field of optical sensing with light emitters, it is impractical to rely simply on changes in emission intensity as emission intensity can fluctuate significantly due to background signal. However, if a molecule emits light from multiple excited states, then one can design a ratiometric sensor, which would provide more accurate readouts than intensity magnitude, and would be more robust against fluctuations and background signals."

Another promising possibility for CdSe/CdS core/shell tetrapods is their potential application as nanoscale sensors for measuring forces. Previous work by Alivisatos and Choi showed that the emission wavelengths of these tetrapods will shift in response to local stress on their four arms.

"When a stress bends the arms of a tetrapod it perturbs the electronic coupling within the tetrapod's heterostructure, which in turn changes the color of the emitted light, and also likely alters the ratio of emission intensity from the two excited states," Choi says. "We are currently trying to use this dependence to measure biological forces, for example, the stresses exerted by a beating heart cell."

By adjusting the length of a CdSe/CdS core/shell tetrapod's arms, it is possible to tune band alignment and electronic coupling within the heterostructure. The result would be tunable emissions from multiple excited states, an important advantage for nano-optic applications.

"We've demonstrated that the oscillator strength of LUMO+1 to HOMO light emissions can be tuned by changing the arm length of the tetrapod," Choi says. "We predict that the lifetime and energy of the emissions can also be controlled through appropriate structural modifications, including arm thickness, number of arms, chemical composition and particle strain."

This research was primarily supported by DOE's Office of Science.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Charina L. Choi, Hui Li, Andrew C. K. Olson, Prashant K. Jain, Sanjeevi Sivasankar, A. Paul Alivisatos. Spatially Indirect Emission in a Luminescent Nanocrystal Molecule. Nano Letters, 2011; 110519123339093 DOI: 10.1021/nl2007032