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Graphene Enables First Example of a Textile Electrode

Wearable electronics has been a hotly pursued research area for years now, but there has been precious little to show for all that effort in terms of electronic garments appearing on people’s backs. The reason for this is not entirely clear. Maybe it’s because the technologies that would enable fabric makers to weave in electronic components have been unwieldy, or maybe people just don’t feel that compelled to wear their electronic devices.

In any case, researchers have recently been able to leverage the properties of graphene to bring the long-promised future of wearable electronics closer to the present. We’ve already seen graphene woven into a yarn-like material that acts as a supercapacitor to power wearable electronics both here and here.

Now, an international research team from the University of Exeter in the U.K. and the Institute for Systems Engineering and Computers, Microsystems and Nanotechnology (INESC-MN) in Lisbon, the Universities of Lisbon and Aveiro in Portugal and the Belgian Textile Research Centre (CenTexBel) has managed to coat textile fibers with graphene in a way that turns them into electrodes.

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Perovskite Transistors Made for First Time

The last couple of years have seen the emergence of a new “wonder material” in photovoltaics: perovskite. Recently, we’ve seen that perovskite’s wonders are not limited to just solar cells; they can create 100-percent efficient lasers and can be manipulated to carry both electric and magnetic polarization.

Even without any particular manipulation, perovskites are a class of material with attractive PV properties such as high charge-carrier mobility, long diffusion lengths, and low cost. With these as motivation, research has pushed perovskite energy conversion efficiency up from 5 percent to 20 percent in just a few years.

Despite its spectacular development in photovoltaics, there has been no way to directly measure perovskits charge-transport properties for other applications. Now a team of researchers from both Wake Forest University and the University of Utah has overcome this limitation. The researchers have shown that it’s possible to make a field-effect transistor (FET) out of perovskite, showing for the first time that anyone can directly measure the material’s electronic properties at room temperature.

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2-D Materials Produce Optically Active Quantum Dots for First Time

Tungsten diselenide (WSe2), which belongs to a class of 2-D crystals known as transition metal dichalcogenides, is proving to be an attractive platform for producing solid-state quantum dots for emitting light.

While graphene has become increasingly used for optoelectronic applications, researchers at the University of Rochester claim that the work they have done with tungsten diselenide represents the first time that 2-D materials have produced optically active quantum dots.

The researchers believe that this research, details of which were published in the journal Nature Nanotechnology, could serve as a basis for integrating quantum photonics with solid-state electronics. The result could be a new way to produce so-called integrated photonics.

In the research, the Rochester team laid atomically thin sheets of the semiconductor tungsten diselenide one on top of the next, creating defects in the semiconducting material. These defects are what create the quantum dots: nanoscale semiconductor crystals that are sometimes described as “artificial atoms” because, like atoms, when they absorb the right amount of energy they subsequently give off energy as colored light.

The researchers discovered that the quantum dots they created by engineering the tungsten diselenide defects did not impact the electrical or optical performance of the semiconductor. Further, they found that they could control the electrical and optical properties of the quantum dots by applying either an electrical or magnetic field.

In this way, the researchers were able to control the brightness of the quantum dot’s light emissions simply by applying a voltage. In future iterations of the technology, the researchers believe they will also be able to tune the color of the emitted photons using a voltage, which will open up these quantum dots to applications including nanophotonic devices.

Another possibility opened up by the quantum dots having been produced in this way is a potential use in “spintronics,” where the spin of an electron is used to encode information rather than a charge.

"What makes tungsten diselenide extremely versatile is that the color of the single photons emitted by the quantum dots is correlated with the quantum dot spin," said Chitraleema Chakraborty, one of the authors of the Nature Nanotechnology paper, in a press release.

The researchers believe that the easy interaction between the spin and the photons should make them attractive for quantum information applications.

Light Reveals the Spin of Electrons

Spintronics—in which the spin of electrons is used to encode information rather than chargeis the foundational technology for the read heads in the hard drives of our computers and is the focus of extensive research in creating the logic devices based on the spin of electrons that could lead to quantum computing.

While there has been some recent research in which electric fields are used to manipulate the spin of electrons, the predominant way to read the spin of an electron is to use extremely powerful magnetic fields.

Now researchers at the London Centre for Nanotechnology (LCN) have put aside both magnetic and electrical fields and have demonstrated that it’s possible to read the spin of an electron with a laser.

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Novel Process Promises Atomically Thin Semiconductors for Electronics

Researchers at Cornell University have developed a process for producing transition metal dichalcogenides (TMDs) with spatial uniformity—a key attribute for thin films in electronics—on wafers. This development could ultimately translate into atomically thin semicondutor layers that could pave the way for atomic-scale minutarization of electronics.

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“Holey” Graphene Improved as an Electrode Material

Researchers at the University of California San Diego (UCSD) have developed a method for increasing the amount of electric charge that graphene can store as an electrode material in supercapacitors.  The key to what the researchers have done is making the graphene “holey.”

The UCSD team is not the first to recognize the merits of “holey” graphene. Last year, researchers at the California NanoSystems Institute (CNSI) at UCLA developed what they termed a “holey graphene framework;” they claimed that it significantly boosted the energy density of supercapacitors.  The CNSI researchers concluded that an energy density of a fully packaged device stack based on the holey-graphene framework is capable of energy densities as high as 35 watt-hours per kilogram, which compares favorably to today’s upper average supercapacitor, which can get around 28 Wh/kg.

The UCSD team told IEEE Spectrum that in their latest research, they created "holes" that are of the order of 1 nanometer in size, while the work from the UCLA paper reports pores that are 1000 times larger. Consequently, there are more holes in the UCSD samples, implying greater charge density per unit area or volume of material.

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Graphene Could Enable Holographic 3-D Imaging on a Mobile Device

Last year, we covered research that was promising to bring new life to 3-D TV by eliminating the need for special glasses to see the 3-D effect.

That work proposed at the University of Central Florida (UCF) was going to pursue nanoprinting techniques that would turn polymers into 3-D holographic displays that functioned much like Princess Leia’s message in Star Wars. In theory, the proposed technology would involve a stationary table projecting the holograms.

Now researchers at Swinburne University of Technology in Australia are leveraging graphene to get a similar effect with a mobile device. 

“Our technique can be leveraged to achieve compact and versatile optical components for controlling light,” said Min Gu, director of Swinburne’s Centre for Micro-Photonics, in a press release. “We can create the wide angle display necessary for mobile phones and tablets.”

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3-D Printed Graphene Aerogels Could Improve Sensors and Batteries

Aerogels have long been one of those ‘gee whiz’ materials that gets people to take notice—watching a solid float on air tends to do that. To accomplish their remarkable feats, aerogels are essentially a gel in which the liquid component of the gel has been replaced with gas. We’ve seen them used in applications from “invisibility cloaks” to oil spill remediation.

Now researchers at Lawrence Livermore National Laboratory (LLNL) have produced an aerogel out of graphene that could have applications ranging from electronics to energy storage. Boosting the ‘gee whiz’ factor: the new material is produced through 3-D printing.

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New Material Can Change Its Color and Texture Like a Cuttlefish

Nanomaterials have offered scientists a variety of ways to pursue biomimicry. We’ve seen nanorods used in polymers to mimic the ability of amphibians to grow back lost limbs or to duplicate the adhesive properties used by geckos when they walk on ceilings.

Now researchers at the University of Nebraska-Lincoln (UNL) have looked at the camouflage capabilities of the cuttlefish to develop a structure than can change both its color and texture within seconds of being exposed to pulses of light.

"Changing color is relatively easy; a TV can do that,” said Li Tan, an associate professor a UNL, in a press release. “Changing texture is harder. We wanted to combine the two."

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Molybdenum Disulfide Gets a Boost as a Li-ion Electrode Material

While the prospect of aluminum-ion batteries may have received a lift recently, the workhorse battery for both our handheld electronic devices and our electric vehicles remains the ubiquitous lithium-ion (Li-ion) battery.

And now, researchers at Kansas State University (KSU) have taken a fresh look at the venerable Li-ion battery: Using the two-dimensional material molybdenum disulfide (MoS2) on its electrodes, they say, may dramatically boost its storage capacity. What they have come up with is a hybrid material that combines MoS2 with silicon carbonitride (SiCN); it can store double the charge of electrodes using MoS2 on its own.

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

Dexter Johnson
Madrid, Spain
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