For better batteries, just add water

For better batteries, just add water

  12:29:00 AM    Science Lover

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A new type of lithium-ion battery that uses aqueous iodide ions in an aqueous cathode configuration provides twice the energy density of conventional lithium-ion batteries.

A new type of lithium-ion battery that uses aqueous iodide ions
in an aqueous cathode configuration provides twice the energy
density of conventional lithium-ion batteries.

Lithium-ion batteries are now found everywhere in devices such as cellular phones and laptop computers, where they perform well. In automotive applications, however, engineers face the challenge of squeezing enough lithium-ion batteries onto a vehicle to provide the desired power and range without introducing storage and weight issues. Hye Ryung Byon, Yu Zhao and Lina Wang from the RIKEN Byon Initiative Research Unit have now developed a lithium-iodine battery system with twice the energy density of conventional lithium-ion batteries.

Byon's team is involved in alternative energy research and, specifically, improving the performance of lithium-based battery technologies. In their research they turned to an 'aqueous' system in which the organic electrolyte in conventional lithium-ion cells is replaced with water. Such aqueous lithium battery technologies have gained attention among alternative energy researchers because of their greatly reduced fire risk and environmental hazard. Aqueous solutions also have other advantages, which include an inherently high ionic conductivity.

For their battery system, the researchers investigated an 'aqueous cathode' configuration (Fig. 1), which accelerates reduction and oxidation reactions to improve battery performance. Finding suitable reagents for the aqueous cathode, however, proved to be a tricky proposition. According to Byon, water solubility is the most important criterion for screening new materials, since this parameter determines the battery's energy density. Furthermore, the redox reaction has to take place in a restricted voltage range in order to avoid water electrolysis. An extensive search led the researchers to produce the first-ever lithium battery involving aqueous iodine—an element with high water solubility and a pair of ions, known as the triiodide/iodide redox couple, that readily undergo aqueous electrochemical reactions.

The team constructed a prototype aqueous cathode device and found the energy density to be nearly double that of a conventional lithium-ion battery, thanks to the high solubility of the triiodide/iodide ions. Their battery had high and near-ideal power storage capacities and could be successfully recharged hundreds of times, avoiding a problem that plagues other alternative high-energy-density lithium-ion batteries. Microscopy analysis revealed that the cathode collector remained untouched after 100 charge/discharge cycles with no observable corrosion or precipitate formation.

Byon and colleagues now plan to develop a three-dimensional, microstructured current collector that could enhance the diffusion-controlled triiodide/iodide process and accelerate charge and discharge. They are also seeking to raise energy densities even further by using a flowing-electrode configuration that stores aqueous 'fuel' in an external reservoir—a modification that should make this low-cost, heavy metal-free design more amenable to electric vehicle specifications.
More information: 1.Zhao, Y., Wang, L. & Byon, H. R. High-performance rechargeable lithium-iodine batteries using triiodide/iodide redox couples in an aqueous cathode. Nature Communications 4, 1896 (2013). dx.doi.org/10.1038/ncomms2907

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More data storage? Here's how to fit 1,000 terabytes on a DVD

More data storage? Here's how to fit 1,000 terabytes on a DVD

  1:17:00 AM    Science Lover

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We live in a world where digital information is exploding. Some 90% of the world's data was generated in the past two years. The obvious question is: how can we store it all?

Using nanotechnology, researchers have developed a technique to increase the data storage capacity of a DVD from a measly 4.7GB to 1,000TB. Credit: Nature Communications

In Nature Communications today, we, along with Richard Evans from CSIRO, show how we developed a new technique to enable the data capacity of a single DVD to increase from 4.7 gigabytes up to one petabyte (1,000 terabytes). This is equivalent of 10.6 years of compressed high-definition video or 50,000 full high-definition movies.

So how did we manage to achieve such a huge boost in data storage? First, we need to understand how data is stored on optical discs such as CDs and DVDs.

The basics of digital storage

Although optical discs are used to carry software, films, games, and private data, and have great advantages over other recording media in terms of cost, longevity and reliability, their low data storage capacity is their major limiting factor.

The operation of optical data storage is rather simple. When you burn a CD, for example, the information is transformed to strings of binary digits (0s and 1s, also called bits). Each bit is then laser "burned" into the disc, using a single beam of light, in the form of dots.

The storage capacity of optical discs is mainly limited by the physical dimensions of the dots. But as there's a limit to the size of the disc as well as the size of the dots, many current methods of data storage, such as DVDs and Blu-ray discs, continue to have low level storage density.

To get around this, we had to look at light's fundamental laws.
On the basis of this law, the diameter of a spot of light, obtained by focusing a light beam through a lens, cannot be smaller than half its wavelength – around 500 nanometres (500 billionths of a metre) for visible light.

And while this law plays a huge role in modern optical microscopy, it also sets up a barrier for any efforts from researchers to produce extremely small dots – in the nanometre region – to use as binary bits.

In our study, we showed how to break this fundamental limit by using a two-light-beam method, with different colours, for recording onto discs instead of the conventional single-light-beam method.

Both beams must abide by Abbe's law, so they cannot produce smaller dots individually. But we gave the two beams different functions:

• The first beam (red, in the figure right) has a round shape, and is used to activate the recording. We called it the writing beam
• The second beam – the purple donut-shape – plays an anti-recording function, inhibiting the function of the writing beam

The two beams were then overlapped. As the second beam cancelled out the first in its donut ring, the recording process was tightly confined to the centre of the writing beam.

This new technique produces an effective focal spot of nine nanometres – or one ten thousandth the diameter of a human hair.

The technique, in practical terms

Our work will greatly impact the development of super-compact devices as well as nanoscience and nanotechnology research.

The exceptional penetration feature of light beams allow for 3D recording or fabrication, which can dramatically increase the data storage – the number of dots – on a single optical device.

The technique is also cost-effective and portable, as only conventional optical and laser elements are used, and allows for the development of optical data storage with long life and low energy consumption, which could be an ideal platform for a Big Data centre.

As the rate of information generated worldwide continues to accelerate, the aim of more storage capacity in compact devices will continue. Our breakthrough has put that target within our reach.

 

More information: www.nature.com/ncomms/2013/130619/ncomms3061/full/ncomms3061.html 

 

Story from: http://phys.org/news/2013-06-storage-terabytes-dvd.html#ajTabs

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Etch-a-sketch with superconductors

Etch-a-sketch with superconductors

  10:26:00 AM    Science Lover

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Reporting in Nature Materials this week, researchers from the London Centre for Nanotechnology and the Physics Department of Sapienza University of Rome have discovered a technique to 'draw' superconducting shapes using an X-ray beam. This ability to create and control tiny superconducting structures has implications for a completely new generation of electronic devices.

In future, X-ray beams could be used to write superconducting circuits, such as those depicted in the image. Here, solid lines indicate electrical connections while semicircles denote superconducting junctions, whose states are indicated by red arrows. Credit: UCL Press Office

Superconductivity is a special state where a material conducts electricity with no resistance, meaning absolutely zero energy is wasted.

The research group has shown that they can manipulate regions of high temperature superconductivity, in a particular material which combines oxygen, copper and a heavier, 'rare earth' element called lanthanum. Illuminating with X-rays causes a small scale re-arrangement of the oxygen atoms in the material, resulting in high temperature superconductivity, of the type originally discovered for such materials 25 years ago by IBM scientists. The X-ray beam is then used like a pen to draw shapes in two dimensions.

A well as being able to write superconductors with dimensions much smaller than the width of a human hair, the group is able to erase those structures by applying heat treatments. They now have the tools to write and erase with high precision, using just a few simple steps and without the chemicals ordinarily used in device fabrication. This ability to re-arrange the underlying structure of a material has wider applications to similar compounds containing metal atoms and oxygen, ranging from fuel cells to catalysts.



Prof. Aeppli, Director of the London Centre for Nanotechnology and the UCL investigator on the project, said: "Our validation of a one-step, chemical-free technique to generate superconductors opens up exciting new possibilities for electronic devices, particularly in re-writing superconducting logic circuits. Of profound importance is the key to solving the notorious 'travelling salesman problem', which underlies many of the world's great computational challenges. We want to create computers on demand to solve this problem, with applications from genetics to logistics. A discovery like this means a paradigm shift in computing technology is one step closer."

Prof Bianconi, the leader of the team from Sapienza, added: "It is amazing that in a few simple steps, we can now add superconducting 'intelligence' directly to a material consisting mainly of the common elements copper and oxygen."

More information: The X-ray experiments were performed at the Elettra (Trieste) synchrotron radiation facility. The work is published in Nature Materials, 21 August 2011 (doi:1038/nmat3088) and follows on from previous discovery of fractal-like structures in superconductors (doi:10.1038/nature09260).

Provided by University College London

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'Quantum magic' without any 'spooky action at a distance'

'Quantum magic' without any 'spooky action at a distance'

  8:55:00 PM    Science Lover

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The quantum mechanical entanglement is at the heart of the famous quantum teleportation experiment and was referred to by Albert Einstein as "spooky action at a distance". A team of researchers led by Anton Zeilinger at the University of Vienna and the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences used a system which does not allow for entanglement, and still found results which cannot be interpreted classically. Their findings were published in the latest issue of the renowned scientific journal Nature.

The central part of the optical setup used to demonstrate
that even a system which does not allow entanglement
exhibits features commonly attributed to this phenomenon.
Credit: IQOQI; Jacqueline Godany 2011

Asher Peres, a pioneer of quantum information theory once remarked jokingly in a letter to a colleague (Dagmar Bruß): Entanglement is a trick 'quantum magicians' use to produce phenomena that cannot be imitated by 'classical magicians'. When two particles are entangled, measurements performed on one of them immediately affect the other, no matter how far apart the particles are. What if, in an experiment, one considers a system that does not allow for entanglement? Will the quantum magicians still have an advantage over the classical magicians?

Quantum physics beyond magic

This is the question the team of quantum physicists led by Anton Zeilinger from the Faculty of Physics at the University of Vienna and from the IQOQI of the Austrian Academy of Sciences addressed in their experiment. The physicists used a "qutrit" – a quantum system consisting of a single photon that can assume three distinguishable states. "We were able to demonstrate experimentally that quantum mechanical measurements cannot be interpreted in a classical way even when no entanglement is involved," Radek Lapkiewicz explains. The findings relate to the theoretical predictions by John Stewart Bell, Simon B. Kochen, and Ernst Specker.

Quantum world versus everyday life



Quantum physics is in stark contrast with what we perceive and experience in our everyday lives and what we understand as "classical physics". Let us, for example, examine a globe: from a given point of view we can only see one respective hemisphere at any given time. When spinning the globe once around its axis we are able to construct a meaningful and "true" picture of our planet assuming that the shape of the continents stays the same, even when we cannot see them.

Therefore, by means of our experience and the assumptions made in classical physics, we can assign certain properties to a system without actually observing it. This is no longer the case if one pictures a "quantum globe". Contrary to a globe where –due to the assumptions of classical properties– the various pieces fit together as they do in a puzzle, the pictures of the quantum globe do not fit together. Yet the pattern is not random: it is possible to predict by how much the individual parts will differ from each other after an observation.

More information: Experimental non-classicality of an indivisible quantum system, Radek Lapkiewicz, Peizhe Li, Christoph Schaeff, Nathan K. Langford, Sven Ramelow, Marcin Wiesniak and Anton Zeilinger, Nature, June 23, 2011. DOI: 10.1038/nature10119

Provided by University of Vienna

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Extreme Darkness: Carbon Nanotube Forest Covers Ultra-Dark Detector

Extreme Darkness: Carbon Nanotube Forest Covers Ultra-Dark Detector

  10:46:00 AM    Science Lover

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Harnessing darkness for practical use, researchers at the National Institute of Standards and Technology (NIST) have developed a laser power detector coated with the world's darkest material -- a forest of carbon nanotubes that reflects almost no light across the visible and part of the infrared spectrum.

This is a colorized micrograph of the world's darkest 
material -- a sparse "forest" of fine carbon nanotubes -- 
coating a NIST laser power detector. Image shows a 
region approximately 25 micrometers across. 
(Credit: Aric Sanders, NIST)

NIST will use the new ultra-dark detector, described in a new paper in Nano Letters, to make precision laser power measurements for advanced technologies such as optical communications, laser-based manufacturing, solar energy conversion, and industrial and satellite-borne sensors.

Inspired by a 2008 paper by Rensselaer Polytechnic Institute (RPI) on "the darkest man-made material ever," the NIST team used a sparse array of fine nanotubes as a coating for a thermal detector, a device used to measure laser power. A co-author at Stony Brook University in New York grew the nanotube coating. The coating absorbs laser light and converts it to heat, which is registered in pyroelectric material (lithium tantalate in this case). The rise in temperature generates a current, which is measured to determine the power of the laser. The blacker the coating, the more efficiently it absorbs light instead of reflecting it, and the more accurate the measurements.

The new NIST detector uniformly reflects less than 0.1 percent of light at wavelengths from deep violet at 400 nanometers (nm) to near infrared at 4 micrometers (μm) and less than 1 percent of light in the infrared spectrum from 4 to 14 μm. The results are similar to those reported for the RPI material and in a 2009 paper by a Japanese group. The NIST work is unique in that the nanotubes were grown on pyroelectric material, whereas the other groups grew them on silicon. NIST researchers plan to extend the calibrated operating range of their device to 50 or even 100 micrometer wavelengths, to perhaps provide a standard for terahertz radiation power.

NIST previously made detector coatings from a variety of materials, including flat nanotube mats. The new coating is a vertical forest of multiwalled nanotubes, each less than 10 nanometers in diameter and about 160 micrometers long. The deep hollows may help trap light, and the random pattern diffuses any reflected light in various directions. Measuring how much light was reflected across a broad spectrum was technically demanding; the NIST team spent hundreds of hours using five different methods to measure the vanishingly low reflectance with adequate precision. Three of the five methods involved comparisons of the nanotube-coated detector to a calibrated standard.

Carbon nanotubes offer ideal properties for thermal detector coatings, in part because they are efficient heat conductors. Nickel phosphorous, for example, reflects less light at some wavelengths, but does not conduct heat as well. The new carbon nanotube materials also are darker than NIST's various Standard Reference Materials for black color developed years ago to calibrate instruments.

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Roller Coaster Superconductivity Discovered

Roller Coaster Superconductivity Discovered

  10:17:00 AM    Science Lover

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Superconductors are more than 150 times more efficient at carrying electricity than copper wires. However, to attain the superconducting state, these materials have to be cooled below an extremely low, so-called transition temperature, at which point normal electrical resistance disappears. Developing superconductors with higher transition temperatures is one of physics' greatest quests.

This graphic shows the crystal structure of three-
layered bismuth oxide. (Credit: Xiao-Jia Chen)

Now, researchers at the Carnegie Institution's Geophysical Laboratory, with colleagues, have unexpectedly found that the transition temperature can be induced under two different intense pressures in a three-layered bismuth oxide crystal referred to as "Bi2223." The higher pressure produces the higher transition temperature. They believe this unusual two-step phenomena comes from competition of electronic behavior in different kinds of copper-oxygen layers in the crystal.

The work is published in the August 19, 2010, issue of Nature.

Until now, copper-laden materials called cuprates have been the only superconductors whose transition temperatures are higher than the liquid nitrogen boiling point at -321°F (77 K). Whether researchers can make transition temperatures higher in such materials remains a challenge.

"Bi2223 is like a layered cake," explained lead author Xiao-Jia Chen at Carnegie. "On the top and bottom there are insulating bismuth-oxide layers. On the inside of those, come layers of strontium oxide. Next, are layers of copper oxide, then calcium, and finally the middle is another copper-oxide layer. Interestingly, the outermost and inner layers of copper oxide have different physical properties resulting in an imbalance of electric charge between the layers."

One way scientists have found to increase the transition temperature of superconducting materials is to "dope" them by adding charged particles.

Under normal pressure, the optimally doped Bi2223's transition temperature is -265°F (108K). The scientists subjected doped crystals of the material to a range of pressures up to 359,000 times the atmospheric pressure at sea level (36.4 Giga Pascal), the highest pressure yet for magnetic measurements in cuprate superconductors. The first higher transition temperature happened at 100,666 atmospheres (10.2 GPa).

"After that, increasing pressures ended up with lower transition temperatures," remarked Chen. "Then to our complete surprise at about 237,000 atmospheres (24 GPa) the superconducting state reappeared. Under even more pressure, 359,000 atmospheres, the transition temperature rose to -215°F (136K). That was the highest pressure our measuring system could detect."

Other research has shown that some multilayered superconducting materials like this one exhibit different electronic and vibrational behaviors in different layers. The researchers think that 237,000 atmospheres might be a critical point where pressure suppresses one behavior and enhances superconductivity.

"The finding gives new perspectives on making higher transition temperature in multilayer cuprate superconductors. The research may offer a promising way of designing and engineering superconductors with much higher transition temperatures at ambient conditions," concluded coauthor Viktor Struzhkin also of Carnegie.

The research was supported by the U. S. Department of Energy, Carnegie Canada, and the National Natural Science Foundation of China.

This work was conducted in collaboration with researchers at the South China University of Technology and Max Plank Institute for Solid State Research in Germany.

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Superconducting Hydrogen

Superconducting Hydrogen

  7:02:00 PM    Science Lover

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Physicists have long wondered whether hydrogen, the most abundant element in the universe, could be transformed into a metal and possibly even a superconductor -- the elusive state in which electrons can flow without resistance.

Periodic table detail of hydrogen. (Credit: iStockphoto/David Freund)

 

They have speculated that under certain pressure and temperature conditions hydrogen could be squeezed into a metal and possibly even a superconductor, but proving it experimentally has been difficult. High-pressure researchers, including Carnegie's Ho-kwang (Dave) Mao, have now modeled three hydrogen-dense metal alloys and found there are pressure and temperature trends associated with the superconducting state -- a huge boost in the understanding of how this abundant material could be harnessed.

The study is published in the January 25, 2010, early, on-line edition of the Proceedings of the National Academy of Sciences.

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Nanotubes Weigh A Single Atom

Nanotubes Weigh A Single Atom

  5:49:00 PM    Science Lover

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How can you weigh a single atom? European researchers have built an exquisite new device that can do just that. It may ultimately allow scientists to study the progress of chemical reactions, molecule by molecule.

A diagram (above) and real-life image (inset) of a carbon nanotube.
(Credit: CARDEQ Project (www.cardeq.eu)

Carbon nanotubes are ultra-thin fibres of carbon and a nanotechnologist’s dream.

They are made from thin sheets of carbon only one atom thick – known as graphene – rolled into a tube only a few nanometres across. Even the thickest is more than a thousand times thinner than a human hair.

Interest in carbon nanotubes blossomed in the 1990s when they were found to possess impressive characteristics that make them very attractive raw materials for nanotechnology of all kinds.

“They have unique properties,” explains Professor Pertti Hakonen of Helsinki University of Technology. “They are about 1000 times stronger than steel and very good thermal conductors and good electrical conductors.”

Hakonen is coordinator of the EU-funded CARDEQ project (http://www.cardeq.eu/) which is exploiting these intriguing materials to build a device sensitive enough to measure the masses of atoms and molecules.

Vibrating strings

A carbon nanotube is essentially an extremely thin, but stiff, piece of string and, like other strings, it can vibrate. As all guitar players know, heavy strings vibrate more slowly than lighter strings, so if a suspended carbon nanotube is allowed to vibrate at its natural frequency, that frequency will fall if atoms or molecules become attached to it.

It sounds simple and the idea is not new. What is new is the delicate sensing system needed to detect the vibration and measure its frequency. Some nanotubes turn out to be semiconductors, depending on how the graphene sheet is wound, and it is these that offer the solution that CARDEQ has developed.

Members of the consortium have taken the approach of building a semiconducting nanotube into a transistor so that the vibration modulates the current passing through it. “The suspended nanotube is, at the same time, the vibrating element and the readout element of the transistor,” Hakonen explains.

“The idea was to run three different detector plans in parallel and then select the best one,” he says. “Now we are down to two. So we have the single electron transfer concept, which is more sensitive, and the field effect transistor concept, which is faster.”

Single atoms

Last November, CARDEQ partners in Barcelona reported that they had sensed the mass of single chromium atoms deposited on a nanotube. But Hakonen says that even smaller atoms, of argon, can now be detected, though the device is not yet stable enough for such sensitivity to be routine. “When the device is operating well, we can see a single argon atom on short time scales. But then if you measure too long the noise becomes large.”

CARDEQ is not alone in employing carbon nanotubes as mass sensors. Similar work is going on at two centres in California – Berkeley and Caltech – though each has adopted a different method to measuring the mass.

All three groups have announced they can perform mass detection on the atomic level using nanotubes, but CARDEQ researchers provided the most convincing data with a clear shift in the resonance frequency.

But a single atom is nowhere near the limit of what is possible. Hakonen is confident they can push the technology to detect the mass of a single nucleon – a proton or neutron.

“It’s a big difference,” he admits, “but typically the improvements in these devices are jump-like. It’s not like developing some well-known device where we have only small improvements from time to time. This is really front-line work and breakthroughs do occur occasionally.”

Biological molecules

If the resolution can be pared down to a single nucleon, then researchers can look forward to accurately weighing different types of molecules and atoms in real time.

It may then become possible to observe the radioactive decay of a single nucleus and to study other types of quantum mechanical phenomena.

But the real excitement would be in tracking chemical and biological reactions involving individual atoms and molecules reacting right there on the vibrating nanotube. That could have applications in molecular biology, allowing scientists to study the basic processes of life in unprecedented detail. Such practical applications are probably ten years away, Hakonen estimates.

“It will depend very much on how the technology for processing carbon nanotubes develops. I cannot predict what will happen, but I think chemical reactions in various systems, such as proteins and so on, will be the main applications in the future.”

The CARDEQ project received funding from the FET-Open strand of the EU’s Sixth Framework Programme for ICT research.

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