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Three-Dimensional Mesoscale Heterostructures of ZnO Nanowire Arrays Epitaxially Grown on CuGaO2 Nanoplates as Individual Diodes

Three-Dimensional Mesoscale Heterostructures of ZnO Nanowire Arrays Epitaxially Grown on CuGaO2 Nanoplates as Individual Diodes | Research | Scoop.it

A three-dimensional (3D) mesoscale heterostructure composed of one-dimensional (1D) nanowire (NW) arrays epitaxially grown on two-dimensional (2D) nanoplates is reported. Specifically, three facile syntheses are developed to assemble vertical ZnO NWs on CuGaO2 (CGO) nanoplates in mild aqueous solution conditions. The key to the successful 3D mesoscale integration is the preferential nucleation and heteroepitaxial growth of ZnO NWs on the CGO nanoplates. Using transmission electron microscopy, heteroepitaxy was found between the basal planes of CGO nanoplates and ZnO NWs, which are their respective (001) crystallographic planes, by the observation of a hexagonal Moiré fringes pattern resulting from the slight mismatch between the c planes of ZnO and CGO. Careful analysis shows that this pattern can be described by a hexagonal supercell with a lattice parameter of almost exactly 11 and 12 times the a lattice constants for ZnO and CGO, respectively. The electrical properties of the individual CGO–ZnO mesoscale heterostructures were measured using a current-sensing atomic force microscopy setup to confirm the rectifying p–n diode behavior expected from the band alignment of p-type CGO and n-type ZnO wide band gap semiconductors. These 3D mesoscale heterostructures represent a new motif in nanoassembly for the integration of nanomaterials into functional devices with potential applications in electronics, photonics, and energy.

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Graphene and related materials promise cheap, flexible printed cameras

Graphene and related materials promise cheap, flexible printed cameras | Research | Scoop.it

The vision is to create a technology for cheap flexible cameras that can be printed or stamped on plastic or paper. "For example it might eventually be possible to embed these printed, flexible optoelectronic devices into clothes, packaging, wall papers, posters, touch screens or even buildings. Everybody with a printer at home will be able to print their own "artificial eye" and physically stick it to a flexible mobile phone" Felice said.

The goal of the 18 month project is to design, develop and characterize inkjet printed 2D crystal-based flexible photodetectors and study their integration with commercial electronics.

“Photodetectors are needed in cameras, automotive applications, sensing and telecommunications, medical devices and security” he says. “If these could be made flexible they could be integrated in clothes, rolled up or printed over any irregular surface substantially increasing the quality of printed and flexible electronics.”

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Self-cooling solar cells boost power, last longer

Self-cooling solar cells boost power, last longer | Research | Scoop.it

Scientists may have overcome one of the major hurdles in developing high-efficiency, long-lasting solar cells—keeping them cool, even in the blistering heat of the noonday Sun.

By adding a specially patterned layer of silica glass to the surface of ordinary solar cells, a team of researchers led by Shanhui Fan, an electrical engineering professor at Stanford University in California has found a way to let solar cells cool themselves by shepherding away unwanted thermal radiation. The researchers describe their innovative design in the premiere issue of The Optical Society's (OSA) new open-access journal Optica.

Solar cells are among the most promising and widely used renewable energy technologies on the market today. Though readily available and easily manufactured, even the best designs convert only a fraction of the energy they receive from the Sun into usable electricity.

Part of this loss is the unavoidable consequence of converting sunlight into electricity. A surprisingly vexing amount, however, is due to solar cells overheating.

Under normal operating conditions, solar cells can easily reach temperatures of 130 degrees Fahrenheit (55 degrees Celsius) or more. These harsh conditions quickly sap efficiency and can markedly shorten the lifespan of a solar cell. Actively cooling solar cells, however—either by ventilation or coolants—would be prohibitively expensive and at odds with the need to optimize exposure to the Sun.

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The Next Big Thing in Computer Memory

The Next Big Thing in Computer Memory | Research | Scoop.it

A novel type of computer memory could, in theory, let you to store tens or even hundreds of times as much data on your smartphone. Researchers at Rice University have demonstrated a more practical way to manufacture it.

The type of memory in question, resistive random access memory (RRAM), is being developed by several companies, but fabrication usually requires high-temperatures or voltages, making production difficult and expensive. The Rice researchers have shown a way to make RRAM at room temperature and with far lower voltages.

Like flash memory, RRAM can store data without a constant supply of power. Whereas flash memory stores bits of information in the form of charge in transistors, RRAM stores bits using resistance. Each bit requires less space, increasing the amount of information that can be stored in a given area.

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Nano-scale gold particles are good candidates for drug delivery

Nano-scale gold particles are good candidates for drug delivery | Research | Scoop.it

A special class of tiny gold particles can easily slip through cell membranes, making them good candidates to deliver drugs directly to target cells.

A new study from MIT materials scientists reveals that these nanoparticles enter cellsby taking advantage of a route normally used in vesicle-vesicle fusion, a crucial process that allows signal transmission between neurons. In the July 21 issue of Nature Communications, the researchers describe in detail the mechanism by which these nanoparticles are able to fuse with a membrane.

The findings suggest possible strategies for designing nanoparticles—made from gold or other materials—that could get into cells even more easily.

"We've identified a type of mechanism that might be more prevalent than is currently known," says Reid Van Lehn, an MIT graduate student in materials science and engineering and one of the paper's lead authors. "By identifying this pathway for the first time it also suggests not only how to engineer this particular class of nanoparticles, but that this pathway might be active in other systems as well."

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So It Begins: Darpa Sets Out to Make Computers That Can Teach Themselves

So It Begins: Darpa Sets Out to Make Computers That Can Teach Themselves | Research | Scoop.it

The Pentagon’s blue-sky research agency is readying a nearly four-year project to boost artificial intelligence systems by building machines that can teach themselves — while making it easier for ordinary schlubs like us to build them, too.

When Darpa talks about artificial intelligence, it’s not talking about modeling computers after the human brain. That path fell out of favor among computer scientists years ago as a means of creating artificial intelligence; we’d have to understand our own brains first before building a working artificial version of one. But the agency thinks we can build machines that learn and evolve, using algorithms — “probabilistic programming” — to parse through vast amounts of data and select the best of it. After that, the machine learns to repeat the process and do it better.

But building such machines remains really, really hard: The agency calls it “Herculean.” There are scarce development tools, which means “even a team of specially-trained machine learning experts makes only painfully slow progress.” So on April 10, Darpa is inviting scientists to a Virginia conference to brainstorm. What will follow are 46 months of development, along with annual “Summer Schools,” bringing in the scientists together with “potential customers” from the private sector and the government.

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Spin Memory Shows Its Might

Spin Memory Shows Its Might | Research | Scoop.it

The read head of a hard-disk drive might seem an unlikely place to hunt for the future of memory technology. But TDK-Headway Technologies, in Milpitas, Calif., is betting that the lowly magnetic tunnel junction—the device it makes to read data off hard-disk platters—could be redesigned and repackaged to create a new way of storing information.

Magnetoresistive random-access memory, or MRAM, has undergone a few incarnations already. But TDK-Headway and a number of other companies are now converging on a scheme they say could upend the memory business. Dubbed spin-transfer torque (STT) MRAM, it promises speed and reliability comparable to that of static random-access memory, or SRAM—the quick-access memory embedded inside microprocessors—along with the “nonvolatility” of flash, the storage of smartphones and other portables.

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An anti-glare, anti-reflective display for mobile devices

An anti-glare, anti-reflective display for mobile devices | Research | Scoop.it

If you’ve ever tried to watch a video on a tablet on a sunny day, you know you have to tilt it at just the right angle to get rid of glare or invest in a special filter. But now scientists are reporting in the journal ACS Applied Materials & Interfaces that they’ve developed a novel glass surface that reduces both glare and reflection, which continue to plague even the best mobile displays today.

Valerio Pruneri and colleagues note that much effort has been poured into anti-reflective and anti-glare technology. In the highly competitive digital age, any bonus feature on a device gives it an edge. But for the most part, that hasn’t included an integrated anti-glare, anti-reflective display. Users still typically have to dish out extra cash for a filter or film — some of questionable effectiveness — to lay on top of their glass screens so they can use the devices in bright light. One of the most promising developments involves layering anti-reflective nano-structures on top of an anti-glare surface. But the existing technique doesn’t work well with glass, the material of choice for many electronic displays, so Pruneri’s team at ICFO (The Institute of Photonic Sciences) in collaboration with Prantik Mazumder’s team at Corning Incorporated set out to find a new method.

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New materials for future green tech devices

New materials for future green tech devices | Research | Scoop.it

 From your hot car to your warm laptop, every machine and device in your life wastes a lot of energy through the loss of heat. But thermoelectric devices, which convert heat to electricity and vice versa, can harness that wasted heat, and possibly provide the green tech energy efficiency that's needed for a sustainable future.

Now, a new study shows how porous substances can act as thermoelectric materials—pointing the way for engineering the use of such materials in thermoelectric devices of the future.

About 70 percent of all the energy generated in the world is wasted as heat, said Dimitris Niarchos of the National Center for Scientific Research Demokritos in Athens, Greece. He and Roland Tarkhanyan, also of NCSR Demokritos, have published their analysis in the journal APL Materials, from AIP Publishing.

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Laser physics upside down

Laser physics upside down | Research | Scoop.it

At the Vienna University of Technology a system of coupled lasers has been created which exhibits truly paradoxical behaviour: An increase in energy supply switches the lasers off, reducing the energy can switch them on.

Sound waves fade, water waves ebb, light waves are dissipated by a wall. The absorption of waves is a very common phenomenon. But only recently have physicists realized that amazing new possibilities are opened up, when this energy loss, rather than being seen as an annoying nuisance, is actually considered a desired effect. At the Vienna University of Technology, a system of two coupled lasers has been created, in which wave dissipation leads to a behaviour completely contrary to intuition: additional energy can switch it off; a reduction of energy may switch it on. This way, logical circuits can be built using light. The experiment has now been presented in the journal Nature Communications.

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Scientists characterize carbon for batteries

Scientists characterize carbon for batteries | Research | Scoop.it

Lithium-ion batteries could benefit from a theoretical model created at Rice University and Lawrence Livermore National Laboratory that predicts how carbon components will perform.

The model is based on intrinsic characteristics of materials used as battery electrodes. These include limitations on quantum capacitance (the ability of the material to absorb charge) and the material's absolute Fermi level, which determines how many lithium ions may bond to the electrodes.

Subtle changes in the structure, chemistry and shape of an electrode will alter how strongly lithium ions bond to it and affect a battery's capacity, voltage and energy density. In fact, the researchers found what they called a "universal" linear relationship between the lithium binding energy and the "states-filling work" (determined by the quantum capacitance and the Fermi level of the material) that should allow scientists to fine-tune electrodes.

The research appears in the journal Physical Review Letters. Lawrence Livermore scientist Brandon Wood and Rice theoretical physicist Boris Yakobson led the study.

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A narrower spectrum for a wider view of matter

A narrower spectrum for a wider view of matter | Research | Scoop.it

Condensed matter physicists, who study the physics of solids and liquids, often use a technique called "inelastic scattering," in which they bounce photons or neutrons of selected energy off a material and measure the energy loss to examine the collective vibrations of atoms in that material. The technique helps researchers understand the dynamics of energy transfers that occur in trillionths of a second (picoseconds) over distances of billionths of a meter (nanometers).

There are, however, gaps in the resolutions of these techniques—distances of one nanometer to a few hundredths of a nanometer and time scales from a few picoseconds to approximately 100 picoseconds. Unfortunately, a key physical phenomenon takes place within that gap: the liquid-glass transition. The details of how a material transforms from liquid to glass is one of the great mysteries of condensed matter physics, and understanding it could not only provide new theoretical insights, but also help pharmaceutical researchers make drugs that are more easily absorbed in the body.

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Arrays of electrons could form the basis for future scalable quantum computers

Arrays of electrons could form the basis for future scalable quantum computers | Research | Scoop.it

A single electron trapped in a semiconductor nanostructure can form the most basic of building blocks for a quantum computer. Before practical quantum computers can be realized, however, scientists need to develop a scalable architecture that allows full control over individual electrons in computational arrays.

Matthieu Delbecq and colleagues from the RIKEN Center for Emergent Matter Science, in collaboration with researchers from Purdue University in the United States, have now demonstrated the scalability of quantum dot architectures by trapping and controlling four electrons in a single device1.

Electrons have a property known as spin that can be either 'up' or 'down'. This is the same binary coding as used in conventional computing, but electrons can also be linked at the quantum level to form quantum bits, or 'qubits', that can have many more usable states, providing dramatic improvements in computational performance.

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Rice's silicon oxide memories catch manufacturers' eye

Rice's silicon oxide memories catch manufacturers' eye | Research | Scoop.it

Rice University's breakthrough silicon oxide technology for high-density, next-generation computer memory is one step closer to mass production, thanks to a refinement that will allow manufacturers to fabricate devices at room temperature with conventional production methods.

First discovered five years ago, Rice's silicon oxide memories are a type of two-terminal, "resistive random-access memory" (RRAM) technology. In a new paper available online in the American Chemical Society journal Nano Letters, a Rice team led by chemist James Tour compared its RRAM technology to more than a dozen competing versions.

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Technique simplifies the creation of high-tech crystals

Technique simplifies the creation of high-tech crystals | Research | Scoop.it

Highly purified crystals that split light with uncanny precision are key parts of high-powered lenses, specialized optics and, potentially, computers that manipulate light instead of electricity. But producing these crystals by current techniques, such as etching them with a precise beam of electrons, is often extremely difficult and expensive.

Now, researchers at Princeton and Columbia universities have proposed a new method that could allow scientists to customize and grow these specialized materials, known asphotonic crystals, with relative ease.

"Our results point to a previously unexplored path for making defect-free crystals using inexpensive ingredients," said Athanassios Panagiotopoulos, the Susan Dod Brown Professor of Chemical and Biological Engineering and one of the paper's authors. "Current methods for making such systems rely on using difficult-to-synthesize particles with narrowly tailored directional interactions."

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New etching process builds custom nanostructures for X-ray optics

New etching process builds custom nanostructures for X-ray optics | Research | Scoop.it

Scientists at the Department of Energy's SLAC National Accelerator Laboratory have invented a customizable chemical etching process that can be used to manufacture high-performance focusing devices for the brightest X-ray sources on the planet, as well as to make other nanoscale structures such as biosensors and battery electrodes.

"The tools researchers use to manipulate X-rays today are very limited," said Anne Sakdinawat, an associate staff scientist at SLAC's Stanford Synchrotron Radiation Lightsource (SSRL) who developed the new "V-MACE" process with Chieh Chang, an SSRL research associate.

"Our new technique for fabricating high performance X-ray optics involves just a few chemicals in a simple, easy-to-implement, one-step technology," Sakdinawat said. "It offers significant advantages in many far-ranging applications." The patent-pending technique is detailed in the June 27 edition of Nature Communications.

Focusing X-rays, particularly higher-energy or "hard" X-rays, is particularly challenging at the nanoscale, though it is key to the success of many scientific studies at two of SLAC's DOE Office of Science user facilities, SSRL and the Linac Coherent Light Source (LCLS) X-ray laser.

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Liquid bits could brim with data in future computers

Liquid bits could brim with data in future computers | Research | Scoop.it

Don't drink that, it's my hard drive! A future form of computing could see information stored on clusters of microscopic particles suspended in liquid.

Clusters of spheres can arrange themselves around a central sphere in a limited number of ways, similar to how a Rubik's cube can only be twisted in certain ways around the central point. Sharon Glotzer at the University of Michigan and her team realised these states could represent information.

To test the idea, the team created a cluster of five spheres in a liquid and watched them naturally switch between two states, like the 0s and 1s of traditional computing bits. "It's really just the first baby steps," says Glotzer. Next, they plan to create clusters that can be locked into a particular state to store a bit of data, and unlocked again to rewrite it, using a central sphere made from gel that can swell and shrink.

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Tiny laser sensor heightens bomb detection sensitivity

Tiny laser sensor heightens bomb detection sensitivity | Research | Scoop.it

New technology under development at the University of California, Berkeley, could soon give bomb-sniffing dogs some serious competition.

A team of researchers led by Xiang Zhang, UC Berkeley professor of mechanical engineering, has found a way to dramatically increase the sensitivity of a light-based plasmon sensor to detect incredibly minute concentrations of explosives. They noted that it could potentially be used to sniff out a hard-to-detect explosive popular among terrorists.

Their findings are to be published Sunday, July 20, in the advanced online publication of the journal Nature Nanotechnology.

They put the sensor to the test with various explosives – 2,4-dinitrotoluene (DNT), ammonium nitrate and nitrobenzene – and found that the device successfully detected the airborne chemicals at concentrations of 0.67 parts per billion, 0.4 parts per billion and 7.2 parts per million, respectively. One part per billion would be akin to a blade of grass on a football field.

The researchers noted that this is much more sensitive than the published results to date for other optical sensors.

"Optical explosive sensors are very sensitive and compact," said Zhang, who is also director of the Materials Science Division at the Lawrence Berkeley National Laboratory and director of the National Science Foundation Nanoscale Science and Engineering Center at UC Berkeley. "The ability to magnify such a small trace of an explosive to create a detectable signal is a major development in plasmon sensor technology, which is one of the most powerful tools we have today."

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New material puts a twist in light

New material puts a twist in light | Research | Scoop.it

Scientists at The Australian National University (ANU) have uncovered the secret to twisting light at will. It is the latest step in the development of photonics, the faster, more compact and less carbon-hungry successor to electronics.

A random find in the washing basket led the team to create the latest in a new breed of materials known as metamaterials. These artificial materials show extraordinary properties quite unlike natural materials.

The work is published in Nature Communications.

"Our material can put a twist into light – that is, rotate its polarisation – orders of magnitude more strongly than natural materials," said lead author Mingkai Liu, a PhD student at the ANU Research School of Physics and Engineering (RSPE).

"And we can switch the effect on and off directly with light," said Mr Liu .

Electronics is estimated to account for two per cent of the global carbon footprint, a figure which photonics has the potential to reduce significantly. Already light carried by fibre optics, has replaced electricity for carrying signals over long distances. The next step is to develop photonic analogues of electronic computer chips, by actively controlling the properties of light, such as its polarisation.

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First ab initio method for characterizing hot carriers

First ab initio method for characterizing hot carriers | Research | Scoop.it

One of the major road blocks to the design and development of new, more efficient solar cells may have been cleared. Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) have developed the first ab initio method – meaning a theoretical model free of adjustable or empirical parameters – for characterizing the properties of "hot carriers" in semiconductors. Hot carriers are electrical charge carriers - electrons and holes – with significantly higher energy than charge carriers at thermal equilibrium.

"Hot carrier thermalization is a major source of efficiency loss in solar cells, but because of the sub-picosecond time scale and complex physics involved, characterization of hot carriers has long been a challenge even for the simplest materials," says Steven Louie, a theoretical physicist and senior faculty scientist with Berkeley Lab's Materials Sciences Division (MSD). "Our work is the first ab initio calculation of the key quantities of interest for hot carriers - lifetime, which tells us how long it takes for hot carriers to lose energy, and the mean free path, which tells us how far the hot carriers can travel before losing their energy."

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'Nanocamera' takes pictures at distances smaller than light's own wavelength

'Nanocamera' takes pictures at distances smaller than light's own wavelength | Research | Scoop.it

Researchers at the University of Illinois at Urbana-Champaign have demonstrated that an array of novel gold, pillar-bowtie nanoantennas (pBNAs) can be used like traditional photographic film to record light for distances that are much smaller than the wavelength of light (for example, distances less than ~600 nm for red light). A standard optical microscope acts as a "nanocamera" whereas the pBNAs are the analogous film.

"Unlike conventional photographic film, the effect (writing and curing) is seen in real time," explained Kimani Toussaint, an associate professor of mechanical science and engineering, who led the research. "We have demonstrated that this multifunctional plasmonic film can be used to create optofluidic channels without walls. Because simple diode lasers and low-input power densities are sufficient to record near-field optical information in the pBNAs, this increases the potential for optical data storageapplications using off-the-shelf, low-cost, read-write laser systems."

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Fundamental Chemistry Findings Could Help Extend Moore’s Law

Fundamental Chemistry Findings Could Help Extend Moore’s Law | Research | Scoop.it

Over the years, computer chips have gotten smaller thanks to advances in materials science and manufacturing technologies. This march of progress, the doubling of transistors on a microprocessor roughly every two years, is called Moore’s Law. But there’s one component of the chip-making process in need of an overhaul if Moore’s law is to continue: the chemical mixture called photoresist. Similar to film used in photography, photoresist, also just called resist, is used to lay down the patterns of ever-shrinking lines and features on a chip. 

Now, in a bid to continue decreasing transistor size while increasing computation and energy efficiency, chip-maker Intel has partnered with researchers from the U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab) to design an entirely new kind of resist. And importantly, they have done so by characterizing the chemistry of photoresist, crucial to further improve performance in a systematic way. The researchers believe their results could be easily incorporated by companies that make resist, and find their way into manufacturing lines as early as 2017. 

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Researchers demonstrate novel, tunable nanoantennas

Researchers demonstrate novel, tunable nanoantennas | Research | Scoop.it

A research team from the University of Illinois at Urbana-Champaign has developed a novel, tunable nanoantenna that paves the way for new kinds of plasmonic-based optomechanical systems, whereby plasmonic field enhancement can actuate mechanical motion.

"Recently, there has been a lot of interest in fabricating metal-based nanotextured surfaces that are pre-programmed to alter the properties of light in a specific way after incoming light interacts with it," explained Kimani Toussaint, an associate professor of mechanical science and engineering who led the research. "For our approach, one can take a nanoarray structure that was already fabricated and further reconfigure the plasmonic, and hence, optical properties of select antennas. Therefore, one can decide after fabrication, rather than before, how they want their nanostructure to modify light."

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First "Buckyball" Molecules Created from Boron

First "Buckyball" Molecules Created from Boron | Research | Scoop.it

Just in time for the World Cup final, researchers have succeeded in building the first ‘buckyballs’  made entirely from boron atoms. Unlike true, carbon-based buckyballs, the boron molecules are not shaped exactly like soccer balls.  But this novel form of boron might lead to new nanomaterials and could find uses in hydrogen storage.

Robert Curl, Harold Kroto and Richard Smalley found the first buckyball — or buckminsterfullerene — in 1985. The hollow cage, made of 60 carbon atoms arranged in pentagons and hexagons like a soccer ball, got its name from the US architect and engineer Richard Buckminster Fuller, who used the same shapes in designing his domes. The discovery opened the flood gates for creating more carbon structures with impressive qualities, such as carbon nanotubes and the single-atom-thick graphene. Since then, material scientists have also searched for buckyball-like structures made of other elements.

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New simple setup for X-ray phase contrast

New simple setup for X-ray phase contrast | Research | Scoop.it

X-ray phase-contrast imaging is a method that uses the refraction of X-rays through a specimen instead of attenuation resulting from absorption. The images produced with this method are often of much higher quality than those based on absorption. The scientists in the team of Prof. Franz Pfeiffer are particularly interested in developing new approaches for biomedical X-ray imaging and therapy – including X-ray phase-contrast imaging. One main goal is to make this method available for clinical applications such as diagnosis of cancer or osteoporosis in the future.

In their new study, the scientists have now developed an extremely simple setup to produce X-ray phase-contrast images. The solution to many of their difficulties may seem counter-intuitive: Scramble the X-rays to give them a random structure. These speckles, as they are called in the field, encode a wealth of information on the sample as they travel through it. The scrambled X-rays are collected with a high-resolution X-ray camera, and the information is then extracted in a post-measurement analysis step.

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Work on 'singlet fission' can increase solar cell efficiency by as much as 30 percent

Work on 'singlet fission' can increase solar cell efficiency by as much as 30 percent | Research | Scoop.it

A perspective article published last month by University of California, Riverside chemists in the Journal of Physical Chemistry Letters was selected as an Editors Choice—an honor only a handful of research papers receive. The perspective reviews the chemists' work on "singlet fission," a process in which a single photon generates a pair of excited states. This 1->2 conversion process, as it is known, has the potential to boost solar cell efficiency by as much as 30 percent.

Applications of the research include more energy-efficient lighting and photodetectors with 200 percent efficiency that can be used for night vision. Biology may use singlet fission to deal with high-energy solar photons without generating excess heat, as a protective mechanism.

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