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Laser-Driven "Bubble Pen" Patterns Nanoparticles

Lasers have been used inside microscopes for many years to trap and move objects floating around in solution. 

Now Linhan Lin, a postdoctoral researcher in Yuebing Zheng’s group at the University of Texas in Austin and colleagues have developed a new strategy for drawing those particles down to the surface, where they can be arranged at will.

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Flexible Nanocomposite Film Could Yield Handheld Cancer Detector

This past September, we reported on research out of Vanderbilt University, in Nashville, in which nanowires were used to create the first integrated circularly polarized light (CPL) detector on a silicon chip that could ultimately lead to portable sensors for drug screening—or even enable quantum computers.

Now, researchers at the University of Michigan, in Ann Arbor, have continued this miniaturization of CPL detectors by developing a flexible nanocomposite circularly polarized-light detector that they claim could lead to the development of a cellphone-size cancer detector.

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Stable Superoxide Could Usher in New Class of Lithium-Air Batteries

Researchers at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory have added a twist to lithium-oxygen batteries (Li–O2) by successfully demonstrating for the first time the ability to stabilize crystalline lithium-superoxide (LiO2) which could usher in an entirely new class of batteries.

In research published in the journal Nature,  the Argonne researchers were able to produce the stable lithium-superoxide by using a graphene-based cathode. This approach avoids the presence of lithium peroxide (Li2O2), a solid precipitate that clogs the pores of the electrode in lithium-oxygen (aka lithium-air) batteries.

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Potential of Graphene Nanoribbons in Electronics Gets a Boost

If graphene is going to make a splash in electronics, it more than likely is going to be in the form of nanoribbons.  What makes them attractive is that their width determines their electronic properties: Narrow ones are semiconductors, while wider ones act as conductors. This essentially provides a simple way to engineer a band gap into graphene.

Last summer, this blog reported on news that a bottom-up approach to manufacturing graphene nanoribbons (GNRs) had been developed that is both compatible with current semiconductor manufacturing methods and can be scaled up.

Okay, so, GNRs have the properties you need for electronics and you can manufacture the material in bulk. But what can you do with it once you’ve made it? An international team of researchers at Tohoku University's Advanced Institute of Materials Research (AIMR) in Japan has demonstrated the ability to interconnect GNRs end to end using molecular assembly that forms elbow structures which are essentially interconnection points. The researchers believe that this development provides the key to unlocking GNRs’ potential in high-performance and low-power-consumption electronics.

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"Printing Press" Method Stamps Out Gold Nanoparticles With New Properties

Gold nanoparticles have become a de facto do-it-all substance, with applications including cancer treatment and a number of electronics applications. If gold nanoparticles have become the go-to nanomaterial for myriad applications, then DNA has to be considered a key tool for generating patterns upon which effective nanomaterial designs are based. 

Now researchers at McGill University, in Montreal, Canada, have brought gold nanoparticles and DNA together in a new process that serves as a kind of printing press that makes it easier to replicate such designs.

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Graphene Flakes Make Laser Neuron Superfast

Tiny flakes of graphene may hold the key to building computer chips that can process information similar to the way the human brain does—only far faster—potentially leading to everything from better image recognition to control systems for hypersonic aircraft.

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Nanotech Could Raise Incandescents From The Dead

Love energy-efficient LED lights, but miss the warm glow of incandescent bulbs? A new nanotech-enabled design by MIT researchers just might breathe new life into incandescent lighting. It promises to increase the efficiency of incandescent light sources by twenty times, surpassing that of LED bulbs.

Incandescents are thermal emitters: they heat up a tungsten filament to such high temperatures that it glows. Only a very small fraction of energy is emitted as visible light. Most of it is lost as infrared radiation. So the luminous efficiency of a typical incandescent is a paltry 2.5 percent compared to 5-10 percent for compact fluorescents and 14-15 percent for state-of-the-art compact LED bulbs.

It is possible to tailor the thermal radiation of a light source so that it emits more visible light and less infrared. This involves putting specially designed periodic nanostructures on the emitter’s surface, says Ognjen Ilic, a postdoctoral researcher in physics at MIT. The structures resonate at specific wavelengths of light, allowing only those wavelengths to be emitted.

However, the approach only works for room temperature light sources. The temperature of tungsten filaments reaches up to 3000 K. “Those nanostructures are delicate and would start degrading at those temperatures,” Ilic says.

So Ilic and his colleagues designed a resonating nanostructure that would surround the filament. They used numerical optimization techniques to design the structure, which is a stack of materials of different refractive indices and nanometer thicknesses. The structure lets through visible wavelengths but reflects infrared light back at the tungsten filament to be reabsorbed.

The researchers built a proof-of-principle device based on the scheme. This reincarnated incandescent source, reported in the journal Nature Nanotechnology, doesn’t look much the long coiled tungsten wire in traditional light bulbs. Here, the filament is a flat, wavy 1-square-centimeter piece of tungsten laser-machined from a thin tungsten sheet. The researchers sandwiched it between two 2-cm2 resonators.

In theory, the scheme should allow a luminous efficiency of 40 percent, Ilic says. But the prototype just is 6.6 percent efficient.That would require a complex stack consisting of 300 layers of four different materials: oxides of silicon, aluminum, tantalum, and titanium. For now, the researchers built a simpler resonator containing a 90-layer stack made of silicon dioxide and tantalum pentoxide. 

So, what’s keeping nanotech-enabled incandescents from becoming  the next best thing in efficient lighting? “The materials involved are cheap and abundant and the manufacturing process is scalable,” Ilic says. But the nanolayer production costs will have to be brought down before this reincarnated incandescent could compete with LED light bulbs.

“But beyond lighting, another really interesting avenue to use this would be for energy conversion,” he says. Tailoring thermal emission to match the absorption spectrum of photovoltaic cells, he adds, could boost the efficiency of thermo-photovoltaic systems, which combine solar thermal and photovoltaics to achieve extremely high light-to-electricity efficiencies.

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Little Dripper Builds Better Electrodes for Touch-Screens

The key factors in touch-screen displays are conductivity and transparency. Touch-screen displays need electrodes that are excellent conductors so the electronics react quickly to a touch on the screen. The electrodes also need to be transparent so they they don’t detract from the clarity of the screen image.

The industry standard for producing these transparent electrodes has been indium tin oxide (ITO)—a relatively scarce resource with a price tag commensurate with its scarcity. As a result, a veritable cavalcade of nanomaterials have been experimented with as an alternative, including carbon nanotubes, graphene, and recently a material called correlated metals.

Now researchers at ETH Zurich in Switzerland have not only thrown new materials into the ring in the form of gold or silver nanoparticles, but they’ve also come up with a new way to produce the electrodes on touch-screens with a 3-D printer dubbed the Nanodrip.

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Graphene Filter Could Change the Game in Nuclear Power Costs

Ever since Andre Geim and Konstantin Novoselov won the 2010 Nobel Prize in Physics for their production and study of graphene, Geim has dedicated a significant amount of his research efforts to the use of graphene as a filtering medium in various separation technologies such as water desalination and gas separation.

This focus makes sense because graphene possesses qualities such as large surface area, variability of pore size and adhesion properties—traits that have marked it for greatness as a filter medium for years now.

Now Geim and his colleagues at the University of Manchester have found that graphene filters are effective at cleaning up the nuclear waste produced at nuclear power plants.  This application could make one of the most costly and complicated aspects of nuclear power generation ten times less energy intensive and therefore much more cost effective.

In research published in the journal Science, the Manchester researchers used the graphene as a sieve to sort protium, the lightest stable isotope of hydrogen, from deuterium, which, unlike protium, contains a neutron in its nucleus. Deuterium appears in larger amounts in so-called heavy water, which is an essential component of some types of nuclear reactors. Though it’s not radioactive like tritium, the heaviest hydrogen isotope, in high enough concentrations, it can cause cell dysfunction and death. Deuterium is also widely used in analytical and chemical tracing technologies.

The Manchester researchers experimented to see if the nuclei of deuterium, deuterons, could pass through the two-dimensional (2-D) materials graphene and boron nitride. The existing theories seemed to suggest that the deuterons would pass through easily. But to the surprise of the researchers, not only did the 2-D membranes sieve out the deuterons, but the separation was also accomplished with a high degree of efficiency.

“This is really the first membrane shown to distinguish between subatomic particles, all at room temperature,” said Marcelo Lozada-Hidalgo, a post-doctoral researcher at the University of Manchester and first author of the paper, in a press release. “Now that we showed that it is a fully scalable technology, we hope it will quickly find its way to real applications.”

Irina Grigorieva, another member of the research team, added: “It is a really simple set up. We hope to see applications of these filters not only in analytical and chemical tracing technologies but also in helping to clean nuclear waste from radioactive tritium.”

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Polymer Embedded With Metallic Nanoparticles Enables Soft Robotics

Nanomaterials are increasingly viewed as important ingredients in artificial muscles meant to power different types of robots. Carbon nanotubes have been proposed as well as graphene

Now researchers at North Carolina State University (NCSU), in Raleigh, have developed a technique for embedding nanoparticles of magnetite—an iron oxide—into a polymer so that when the material comes near a magnetic field the polymer moves. The researchers believe that the nanoparticle-studded polymer could lead to a method of remotely controlling so-called “soft robots” whose flexible components allow them to move around in tight spaces in a manner reminiscent of octopodes.

In research described in a paper published in the journal Nanoscale, the NCSU researchers describe a process that starts with dispersing the nanoparticles in a solvent. Next, a polymer is dissolved into the mixture and the resulting fluid is poured into a mold. Then a magnetic field is applied that arranges the magnetite nanoparticles into parallel chains. Once the solution dries in the mold, the chains of nanoparticles are locked into place.

“Using this technique, we can create large nanocomposites, in many different shapes, which can be manipulated remotely,” said Sumeet Mishra, lead author of the paper, in a press release. “The nanoparticle chains give us an enhanced response, and by controlling the strength and direction of the magnetic field, you can control the extent and direction of the movements of soft robots.”

You can see the movement of the polymer under the influence of a magnetic field in the video below.

The phenomenon that causes the polymer to react so strongly to the magnetic field is something called magnetic anisotropy; it makes the material’s magnetic properties directionally dependent. This is achieved by assembling the nanoparticles into chains.

“The key here is that the nanoparticles in the chains and their magnetic dipoles are arranged head-to-tail, with the positive end of one magnetic nanoparticle lined up with the negative end of the next, all the way down the line,” said Joe Tracy, an associate professor at NCSU and corresponding author of the paper, in the press release. “When a magnetic field is applied in any direction, the chain re-orients itself to become as parallel as possible to the magnetic field, limited only by the constraints of gravity and the elasticity of the polymer.”

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
Contributor
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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