New Giant Molecule Created

Source:

http://www.sciencedaily.com/releases/2007/10/071005214924.htm

Science Daily — Ulrich Kortz, Professor of Chemistry at Jacobs University, and his team successfully synthesized a polyoxometalate with 100 Tungsten and 20 Cerium atoms that has a molar mass of about 30 kilo Dalton. With a maximum diameter of 4.2 nm the inorganic molecule is comparable in size to large complex bio-molecules or even small viruses.

Polyoxometalates are anionic metal-oxygen clusters of large structural diversity with chemical properties, which make them especially interesting for applications in catalysis, but also in materials science and nanotechnology.
Ulrich Kortz and his co-workers now achieved the synthesis of the tungstogermanate*, which belongs to the polyoxometalates, by condensation of the precursors [α-GeW9O34]10- and Cerium(III) ions in aqueous solution.
With about 600 atoms in total, amongst them 100 atoms of the heavy metal Tungsten, the new compound is the third largest molecular polytungstate ever synthesized. In addition it contains the largest number of atoms of the Rare Earth Cerium ever incorporated in such a compound.
„A single molecule of our new giant tungstate has many catalytically active centers and therefore a very high catalytic potential, which normally applies only to biological catalyst molecules. Being a lot less temperature and oxidatively sensitive than bio-catalysts though and in crystalline form applicable as a heterogenic solid catalyst in liquid phase reactions our new tungstogermanate is predestined for industrial purposes,“ says Ulrich Kortz about the possible applications of the newly created molecule.
“In addition our successful synthesis allows very good inferences about the mechanism of formation by stepwise self-assembly of the simple precursors in a classic one-pot synthesis, which is vitally important for the development of other so-called ‘molecular machines’, large molecules designed to have very specific functions,“ the Jacobs chemist concludes.
*Tungstogermanate [Ce20Ge10W100O376(OH)4(H2O)30]56-
The reaction conditions and the molecular structure were published in Angewandte Chemie (doi: 10.1002/anie.200701422).
Note: This story has been adapted from material provided by Jacobs University.

Fausto Intilla

www.oloscience.com

What Makes Quantum Dots Blink?

Source:

http://www.sciencedaily.com/releases/2007/10/071004165602.htm

Science Daily — In order to learn more about the origins of quantum dot blinking, researchers from the U.S. Department of Energy's Argonne National Laboratory, the University of Chicago and the California Institute of Technology have developed a method to characterize it on faster time scales than have previously been accessed.

Nanocrystals of semiconductor material, also known as quantum dots, are being intensively investigated for applications such as light-emitting diodes, solid-state lighting, lasers, and solar cells. They are also already being applied as fluorescent labels for biological imaging, providing several advantages over the molecular dyes typically used, including a wider range of emitted colors and much greater stability.
Quantum dots have great promise as light-emitting materials, because the wavelength, or color, of light that the quantum dots give off can be very widely tuned simply by changing the size of the nanoparticles. If a single dot is observed under a microscope, it can be seen to randomly switch between bright and dark states.
This flickering, or blinking, behavior has been widely studied, and it has been found that a single dot can blink off for times that can vary between microseconds and several minutes. The causes of the blinking, though, remain the subject of intense study.
The methods developed by Matt Pelton of Argonne's Center for Nanoscale Materials and his team of collaborators has revealed a previously unobserved change in the blinking behavior on time scales less than a few microseconds. This observation is consistent with the predictions of a model for quantum-dot blinking previously developed by Nobel Laureate Rudolph Marcus, contributor to this research, and his co-workers. In this model, the blinking is controlled by the random fluctuation of energy levels in the quantum dot relative to the energies of trap states on the surface of the nanocrystal or in the nearby environment.
The results of this research provide new insight into the mechanism of quantum-dot blinking, and should help in the development of methods to control and suppress blinking. Detailed results of this work have been published in a paper in the Proceedings of the National Academy of Sciences.
Argonne's Center for Nanoscale Materials work for this research was funded by the U.S. Department of Energy's Office of Basic Energy Science.
Note: This story has been adapted from material provided by DOE/Argonne National Laboratory.

Fausto Intilla

www.oloscience.com

Nature Leads The Way For The Next Generation Of Paints, Cosmetics And Holograms

Source:

http://www.sciencedaily.com/releases/2007/10/071003100546.htm

Science Daily — A plant-like micro-organism mostly found in oceans could make the manufacture of products, from iridescent cosmetics, paints and fabrics to credit card holograms, cheaper and 'greener.'

The tiny single-celled 'diatom', which first evolved hundreds of millions of years ago, has a hard silica shell which is iridescent -- in other words, the shell displays vivid colours that change depending on the angle at which it is observed. This effect is caused by a complex network of tiny holes in the shell which interfere with light waves.
UK scientists have now found an extremely effective way of growing diatoms in controlled laboratory conditions, with potential for scale-up to industrial level. This would enable diatom shells to be mass-produced, harvested and mixed into paints, cosmetics and clothing to create stunning colour-changing effects, or embedded into polymers to produce difficult-to-forge holograms.
Manufacturing consumer products with these properties currently requires energy-intensive, high-temperature, high-pressure industrial processes that create tiny artificial reflectors. But farming diatom shells, which essentially harnesses a natural growth process, could provide an alternative that takes place at normal room temperature and pressure, dramatically reducing energy needs and so cutting carbon dioxide emissions. The process is also extremely rapid -- in the right conditions, one diatom can give rise to 100 million descendants in a month.
This ground-breaking advance has been achieved by scientists at the Natural History Museum and the University of Oxford, with funding from the Engineering and Physical Sciences Research Council (EPSRC). The project involved a range of experts from disciplines including biology, chemistry, physics, engineering and materials science.
"It's a very efficient and cost-effective process, with a low carbon footprint," says Professor Andrew Parker, who led the research. "Its simplicity and its economic and environmental benefits could in future encourage industry to develop a much wider range of exciting products that change colour as they or the observer move position. What's more, the shells themselves are completely biodegradable, aiding eventual disposal and further reducing the environmental impact of the process life cycle."
The new technique basically lets nature do the hard work. It involves taking a diatom or other living cells such as those that make iridescent butterfly scales, and immersing them in a culture medium -- a solution containing nutrients, hormones, minerals etc that encourage cell subdivision and growth. By changing the precise make-up of the culture medium, the exact iridescent properties of the diatoms or butterfly scales (and therefore the final optical effects that they create) can be adjusted. The researchers estimate that up to 1 tonne/day of diatoms could be produced in the laboratory in this way, starting from just a few cells. Within as little as two years, an industrial-scale process could be operational.
"It's a mystery why diatoms have iridescent qualities," says Professor Parker. "It may have something to do with maximising sunlight capture to aid photosynthesis in some species; on the other hand, it could be linked with the need to ensure that sunlight capture is not excessive in others. Whatever the case, exploiting their tiny shells' remarkable properties could make a big impact across industry. They could even have the potential to be incorporated into paint to provide a water-repellent surface, making it self-cleaning."
The 12-month research project 'Optics via Cell Culture' received EPSRC funding of just over £104,000. The research took place at the Natural History Museum in London and at the University of Oxford.
About diatoms :
Diatoms are classified as eukaryotic algae and represent one of the commonest types of phytoplankton. Each diatom is encased in a silica frustule, or cell wall. Although usually microscopic, some species of diatom may grow to as much as 2mm long. As well as oceans, diatoms can be found in freshwater and in damp soils. In the oceans, they represent an important link in the food chain.
When light strikes a diatom's shell, tiny holes in the shell's structure cause multiple reflections, resulting in interference to the light waves. This affects the shell's colour, as seen by an observer. The precise interference effect depends on the angle at which light strikes the shell (i.e. the angle of observation), hence the shell appears to change colour as it or the observer moves position. This is the same sort of phenomenon that occurs when light reflects from a film of oil on the surface of water -- viewed from different angles, the oil's colours seem to change. While some light is reflected, however, certain wavelengths are transmitted into the cell. The device acts like a 'photonic crystal.'
Note: This story has been adapted from material provided by Engineering and Physical Sciences Research Council.

Fausto Intilla

www.oloscience.com

Stopping Atoms

Source:

http://www.sciencedaily.com/releases/2007/10/071003081905.htm

Science Daily — With atoms and molecules in a gas moving at thousands of kilometres per hour, physicists have long sought a way to slow them down to a few kilometres per hour to trap them.

A paper, published October 4 in the Institute of Physics' New Journal of Physics, demonstrates how a group of physicists from The University of Texas at Austin, US, have found a way to slow down, stop and explore a much wider range of atoms than ever before.
Inspired by the coilgun that was developed by the University's Center for Electromechanics, the group has developed an "atomic coilgun" that slows and gradually stops atoms with a sequence of pulsed magnetic fields.
Dr. Mark Raizen and his colleagues in Texas ultimately plan on using the gun to trap atomic hydrogen, which he said has been the Rosetta Stone of physics for many years and is the simplest and most abundant atom in the universe.
Work on slowing and stopping atoms has been at the forefront of advancement in physics for some time. In 1997, there were three joint-winners for the Nobel Prize in Physics for their combined contribution to laser cooling - a method using laser light to cool gases and keep atoms floating or captured in "atom traps".
These important advances had limited use because they only applied to atoms with 'closed two-level transition', excluding important elements such as hydrogen, iron, nickel and cobalt. In contrast, nearly all elements and a wide range of molecules are affected by magnetic forces, or are paramagnetic, which means that this latest research has much wider applicability.
Professor Raizen said, "Of particular importance are the doors being opened for our understanding of hydrogen. Precision spectroscopy of hydrogen's isotopes, deuterium and tritium, continues to be of great interest to both atomic and nuclear physics. Further study of tritium, as the simplest radioactive element, also serves as an ideal system for the study of Beta decay. "
Having successfully designed and used an 18-coil device to slow a supersonic beam of metastable neon atoms, the team is now developing a 64-stage device to further slow and stop atoms.
Note: This story has been adapted from material provided by Institute of Physics.

Fausto Intilla

www.oloscience.com

New Plastic Is Strong As Steel, Transparent

Source:

http://www.sciencedaily.com/releases/2007/10/071004143114.htm

Science Daily — By mimicking a brick-and-mortar molecular structure found in seashells, University of Michigan researchers created a composite plastic that's as strong as steel but lighter and transparent.

It's made of layers of clay nanosheets and a water-soluble polymer that shares chemistry with white glue.
Engineering professor Nicholas Kotov almost dubbed it "plastic steel," but the new material isn't quite stretchy enough to earn that name. Nevertheless, he says its further development could lead to lighter, stronger armor for soldiers or police and their vehicles. It could also be used in microelectromechanical devices, microfluidics, biomedical sensors and valves and unmanned aircraft.
Kotov and other U-M faculty members are authors of a paper on this composite material, "Ultrastrong and Stiff Layered Polymer Nanocomposites," published in the Oct. 5 edition of Science.
The scientists solved a problem that has confounded engineers and scientists for decades: Individual nano-size building blocks such as nanotubes, nanosheets and nanorods are ultrastrong. But larger materials made out of bonded nano-size building blocks were comparatively weak. Until now.
"When you tried to build something you can hold in your arms, scientists had difficulties transferring the strength of individual nanosheets or nanotubes to the entire material," Kotov said. "We've demonstrated that one can achieve almost ideal transfer of stress between nanosheets and a polymer matrix."
The researchers created this new composite plastic with a machine they developed that builds materials one nanoscale layer after another.
The robotic machine consists of an arm that hovers over a wheel of vials of different liquids. In this case, the arm held a piece of glass about the size of a stick of gum on which it built the new material.
The arm dipped the glass into the glue-like polymer solution and then into a liquid that was a dispersion of clay nanosheets. After those layers dried, the process repeated. It took 300 layers of each the glue-like polymer and the clay nanosheets to create a piece of this material as thick as a piece of plastic wrap.
Mother of pearl, the iridescent lining of mussel and oyster shells, is built layer-by-layer like this. It's one of the toughest natural mineral-based materials.
The glue-like polymer used in this experiment, which is polyvinyl alcohol, was as important as the layer-by-layer assembly process. The structure of the "nanoglue" and the clay nanosheets allowed the layers to form cooperative hydrogen bonds, which gives rise to what Kotov called "the Velcro effect." Such bonds, if broken, can reform easily in a new place.
The Velcro effect is one reason the material is so strong. Another is the arrangement of the nanosheets. They're stacked like bricks, in an alternating pattern.
"When you have a brick-and-mortar structure, any cracks are blunted by each interface," Kotov explained. "It's hard to replicate with nanoscale building blocks on a large scale, but that's what we've achieved."
Collaborators include: mechanical engineering professor Ellen Arruda; aerospace engineering professor Anthony Waas; chemical, materials science and biomedical engineering professor Joerg Lahann; and chemistry professor Ayyalusamy Ramamoorthy. Kotov is a professor of chemical engineering, materials science and engineering, and biomedical engineering.
The nanomechanical behavior of these materials is being modeled by professor Arruda's group; Waas and his group are working on applications in aviation.
Note: This story has been adapted from material provided by University of Michigan.

Fausto Intilla

www.oloscience.com

New Particles Get A Mass Boost

Source:

http://www.sciencedaily.com/releases/2007/10/071001152838.htm

Science Daily — A sophisticated, new analysis has revealed that the next frontier in particle physics is farther away than once thought. New forms of matter not predicted by the Standard Model of particle physics are most likely twice as massive as theorists had previously calculated, according to a just-published study.
The discovery is noteworthy because experimental improvements of this magnitude rarely occur more often than once in a decade.
To see the infinitely small bits of matter that make up our universe, physicists build ever more powerful accelerators, which are the microscopes they use to see matter. But while the trend is to more powerful accelerators, the precision achieved by some less powerful ones can pinpoint the best places to look for never-before-seen particles.
Scientists at the Department of Energy's Thomas Jefferson National Accelerator Facility combined data from experiments in which electrons were used to precisely probe the nucleus of the atom. The experiments were designed to study the weak nuclear force, one of the four forces of nature. The effects of the weak force on the building blocks of the proton, up and down quarks, were determined precisely from this data and were found to be in agreement with predictions.
But when this new analysis was combined with other measurements, it raised the predicted mass scale for the discovery of new particles to about one Tera-electron-volts (1 TeV) - more than a factor of two higher than previously thought, according to Jefferson Lab scientists who published the result in Physical Review Letters.
Searches for new particles can take the form of direct production of new particles by high-energy interactions or by lower-energy, extremely precise measurements of experimental observables, which are sensitive to the existence of new particles beyond the ability of existing theories to predict.
Note: This story has been adapted from material provided by DOE/Thomas Jefferson National Accelerator Facility.

Fausto Intilla
www.oloscience.com

Physicist Defends Einstein's Theory And 'Speed Of Gravity' Measurement

Source:

http://www.sciencedaily.com/releases/2007/10/071003130816.htm

Science Daily — Scientists have attempted to disprove Albert Einstein's theory of general relativity for the better part of a century. After testing and confirming Einstein's prediction in 2002 that gravity moves at the speed of light, a professor at the University of Missouri-Columbia has spent the past five years defending the result, as well as his own innovative experimental techniques for measuring the speed of propagation of the tiny ripples of space-time known as gravitational waves.
Sergei Kopeikin, associate professor of physics and astronomy in the College of Arts and Science, believes that his latest article, "Gravimagnetism, causality, and aberration of gravity in the gravitational light-ray deflection experiments" published along with Edward Fomalont from the National Radio Astronomical Observatory, arrives at a consensus in the continuing debate that has divided the scientific community.
An experiment conducted by Fomalont and Kopeikin five years ago found that the gravity force of Jupiter and light travel at the same speed, which validates Einstein's suggestion that gravity and electromagnetic field properties, are governed by the same principle of special relativity with a single fundamental speed. In observing the gravitational deflection of light caused by motion of Jupiter in space, Kopeikin concluded that mass currents cause non-stationary gravimagnetic fields to form in accordance with Einstein's point of view.
Einstein believed that in order to measure any property of gravity, one has to use test particles. "By observing the motion of the particles under influence of the gravity force, one can then extract properties of the gravitational field," Kopeikin said. "Particles without mass -- such as photons -- are particularly useful because they always propagate with constant speed of light irrespectively of the reference frame used for observations."
"The property of gravity tested in the experiment with Jupiter also is called causality. Causality denotes the relationship between one event (cause) and another event (effect), which is the consequence (result) of the first. In the case of the speed of gravity experiment, the cause is the event of the gravitational perturbation of photon by Jupiter, and the effect is the event of detection of this gravitational perturbation by an observer.
"The two events are separated by a certain interval of time which can be measured as Jupiter moves, and compared with an independently-measured interval of time taken by photon to propagate from Jupiter to the observer. The experiment found that two intervals of time for gravity and light coincide up to 20 percent. Therefore, the gravitational field cannot act faster than light propagates."
Other physicists argue that the Fomalont-Kopeikin experiment measured nothing else but the speed of light. "This point of view stems from the belief that the time-dependent perturbation of the gravitational field of a uniformly moving Jupiter is too small to detect," Kopeikin said. "However, our research article clearly demonstrates that this belief is based on insufficient mathematical exploration of the rich nature of the Einstein field equations and a misunderstanding of the physical laws of interaction of light and gravity in curved space-time."
The research paper that discusses the gravimagnetic field appears in the October edition of Journal of General Relativity and Gravitation.
Note: This story has been adapted from material provided by University of Missouri-Columbia.

Fausto Intilla
www.oloscience.com