Nanoclast iconNanoclast

Nanowire Circuit Guides Both Electricity and Light on the Same Wire

The field of plasmonics—the use surface plasmons generated when photons hit a metal structure—might enable photonic circuits that could do what electronic ICs do, but do it much faster—at the speed of light.  Without plasmonics, photonic circuits would be too large, because they need to accommodate wavelength of light.

In a step toward that goal, a joint research team from the University of Rochester and the Swiss Federal Institute of Technology in Zurich have developed a primitive circuit consisting of a silver nanowire and single-layer flake of molybdenum disulfide (MoS2). This simple circuit can efficiently guide both electricity and light along the same wire.

In the experiment, which was published in the journal Optica, a laser was used to trigger the plasmons on the surface of the wire. The plasmons coming off the nanowire triggered a photoluminescence in the MoS2, which is a two-dimensional material like graphene but has an inherent band gap. Excitons—basically energized electrons bound to positively charged holes that form when light hits a semiconductor—form in the MoS2, and decay into the nanowire plasmons. So, the international team demonstrated that the nanowire serves the dual purpose of exciting the MoS2 via plasmons and recollecting the decaying exciton as nanowire plasmons.

“We have found that there is pronounced nanoscale light-matter interaction between plasmons and atomically thin material that can be exploited for nanophotonic integrated circuits,” said Nick Vamivakas, assistant professor at the University of Rochester, in the press release.

The combination of subwavelength light guidiance and strong nanoscale light-matter interaction they demonstrated could help lead to compact and efficient on-chip optical processing, the researchers believe.

The next step in their research will be to demonstrate the primitive circuit with light emitting diodes.

Carbon Nanotubes Make a Comeback in Photovoltaics

Carbon nanotubes (CNTs) have had a bit of a hard time of it lately. A few years back the National Institute of Standards and Technology (NIST) reported that CNTs have a major reliability problem when applied to electronics. In photovoltaics the prognosis hasn’t been much better. Despite efforts from some research teams to use CNTs instead of silicon as the basic element for converting light to energy for a solar cell, they simply haven’t proven themselves to be very efficient in energy conversion.

Now researchers at Northwestern University may have turned around the fortunes of CNTs, at least for photovoltaic applications, by demonstrating that they can make solar cells based on CNTs that are twice as efficient at energy conversion than its predecessors.

"The field had been hovering around 1 percent efficiency for about a decade; it had really plateaued," said Mark Hersam, a professor at Northwestern, in a news release. "But we've been able to increase it to over 3 percent. It's a significant jump."

Read More

Nanoparticles Enable New Levels of Holographic Optical Data Storage

By exploiting the same properties of nanoparticles that made the Lycurgus Cup change colors depending on the light hitting it, researchers at the University of Cambridge have used nanoparticles to create holograms that could store twice as much information as today’s digital optical devices.

In research published in the journal Proceedings of the National Academy of Sciences,  the UK team used a thin film of silver nanoparticles to produce multicolor holograms.The nanoparticles create interference that allows the holograms to go beyond the normal limits of diffraction.

The nanoparticles are able to go beyond the normal diffraction limits by exploiting plasmonics, which takes advantage of oscillations in the density of electrons that are generated when photons hit a metal surface. Plasmonics has a number of potential applications, including transmitting data on computer chips and producing high-resolution lithography.

“This technology will lead to a new range of applications in the area of photonics, as conventional optical components simply cannot achieve this kind of functionality,” said Yunuen Montelongo, a PhD student from the Cambridge engineering department, who led the research, in a press release. “The potential of this technology will be realized when they are mass produced and integrated into the next generation of ultra-thin consumer electronics.”

In the device, each nanoparticle scatters light into varying colors depending on its size and shape. The scattered light from all the nanoparticles interacts and combines with each other to produce an image.

Among some of the unusual effects that can be produced by this device is its ability to display different images when illuminated with different color light and its ability to produce a multi-color image when multiple light sources are focused on it.

“This hologram may find a wide range of applications in the area of displays, optical data storage, and sensors,” said PhD student Calum Williams, a co-author of the paper. “However, scalable approaches are needed to fulfill the potential of this technology.”

Graphene Drumheads Could Lead to New Sensors for Mobile Phones

Just over two years ago, we reported on research out of the National Institute of Standards and Technology (NIST) and the University of Maryland that discovered graphene could be manipulated to act like a drumhead giving it electromechanical properties.

Following along this line of research, a team of scientists at the TU Delft’s Kavli Institute of Nanoscience in the Netherlands has demonstrated that using this drumhead principal for graphene could lead to new types of sensors for mobile phones, or even quantum memory used in quantum computing.

Read More

Nanoscale Material Enables Cheap, Emission-free Hydrogen Production

When it comes to separating hydrogen from the water molecule, it’s like the old Neil Sedaka song said: “Breaking up is hard to do.” It is so difficult, in fact, that the production of hydrogen gas has been one of the main obstacles in the deployment of fuel cellbased vehicles.

Now researchers at Stanford University have developed a nanoscale material that makes it possible to split water cheaply using just a 1.5-volt "AAA" battery, and they claim it can be done without producing any emissions. 

We've previously reported on the work done by Hongjie Dai, who has spent years working on developing better catalysts for fuel cells, including some employing carbon nanotubes. But this time, instead of focusing on the fuel cell itself, Dai has turned his eye towards ways of generating the hydrogen to feed the fuel cells.

Dai’s previous work, which examined how carbon nanotubes could replace more expensive catalysts used in oxidizing the hydrogen at the anode within the fuel cell, indirectly came into play here. Since the process inside the fuel cell is the mirror opposite of what is needed to split water, this latest work, which was published in the journal Nature Communications, is somewhat along the same lines. It involves using an inexpensive nanomaterial made from nickel and iron in place of platinum as the catalyst in the water-splitting reaction.

“Using nickel and iron, which are cheap materials, we were able to make the electrocatalysts active enough to split water at room temperature with a single 1.5-volt battery," said Dai, in a press release. "This is the first time anyone has used non-precious metal catalysts to split water at a voltage that low. It's quite remarkable, because normally you need expensive metals, like platinum or iridium, to achieve that voltage."

Dai further describes the water-splitting device and its implications in the video below.

While there has been much research into using nanomaterials for hydrogen separation, previous efforts to produce hydrogen gas on an industrial scale without first generating hot steam in an energy-intensive process with carbon dioxide as a byproduct were unsuccessful.

"It's been a constant pursuit for decades to make low-cost electrocatalysts with high activity and long durability," Dai says. "When we found out that a nickel-based catalyst is as effective as platinum, it came as a complete surprise."

A surprise indeed. In fact, the Stanford researchers don’t even understand the science that makes the novel nickel-metal/nickel-oxide nanomaterial perform the way it does.

However, the researchers do know that it works.

One area where continued research might yield improvement is durability. The material, say the Stanford engineers, doesn’t last as long as hoped, and certainly not long enough for an industrial application.

"The electrodes are fairly stable, but they do slowly decay over time," said Ming Gong, the graduate student who discovered the material, in a press release. "The current device would probably run for days, but weeks or months would be preferable. That goal is achievable based on my most recent results"

Dai added: "We're very glad that we were able to make a catalyst that's very active and low cost. This shows that through nanoscale engineering of materials we can really make a difference in how we make fuels and consume energy."

A close up look at a pile of multicolor rubber bands of many sizes.

Graphene and Rubber Bands Could Revolutionize Health Monitoring

One of graphene’s most attractive properties is its flexibility. It’s this property that has led researchers to consider using it to replace for indium tin oxide (ITO) in the electrodes of organic solar cells. Researchers at the University of Surrey and Trinity College may have found another use for that flexibility—adding graphene to rubber bands to give elastics electronic properties and using the combination for health monitoring.

In research published in the journal ACS Nano,  the researchers explain a simple process for infusing graphene into elastic bands such that they become extremely sensitive strain sensors.

The researchers claim that the sensors are extremely cheap to produce and could be used as wearable sensors for monitoring a patient's breathing, heart rate, or irregular movements.

Read More
terahertz imaging reveals defects in graphene

Novel Sensing Technique Developed for Graphene Electronics Manufacturing

Researchers at Rice and Osaka universities have developed a method for detecting impurities in graphene using terahertz waves. The joint research team believes that the method could provide a relatively simple way for anyone trying to use graphene for electronic applications to identify problems with the material early in the manufacturing process.

The new technique can identify a single foreign molecule on graphene. This is critically important in electronic applications where a single foreign molecule in graphene can corrupt its electrical properties. Before this work, in order to test those electrical properties you needed to attach contacts to the material, which itself could damage the graphene.

Read More

Silicene's Suicidal Tendencies Can Be Overcome

Early this year, research indicated that silicene—essentially two-dimensional (2-D) silicon—had “suicidal tendencies”. As soon as you tried to layer silicene it would revert back to the crystal structure of silicon instead of maintaining its honeycomb structure.

Now an international team of researchers claims to have proven the stability of silicene under these circumstances,  paving the way for it to compete in the growing world of 2-D materials.

The research, which was published in the journal 2D Materials,  demonstrated for the first time that thick, multilayer silicene films can be stable in air for at least 24 hours. While 24 hours doesn’t seem like a long time, it should give researchers a window of opportunity to perform more tests on the material to reveal its capabilities.

Read More

"Holey" Graphene Boosts Energy Density of Supercapacitors

Image: California NanoSystems Institute/UCLA

A research team at the California NanoSystems Institute (CNSI) at UCLA has developed what they call a “holey graphene framework” that they claim can significantly boost the energy density of supercapacitors.

Graphene has been held out by some as a silver bullet for enabling supercapacitors to combine the quick recharge and large bursts of energy of capacitors with the high storage capacity of electrochemical batteries. But so far using graphene as a replacement for activated carbon on the electrodes of supercapacitors has fallen short of expectations. It seems that graphene-based electrodes don’t enable energy storage much better than activated carbon, but because they can operate a higher frequencies than most supercapacitors they can be applied in novel ways, such as being used as part of filtering circuits in AC rectifiers.

Read More


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
Rachel Courtland
New York City
Load More