Tag Archives: China

LEGO2NANO, a UK-China initiative

LEGO2NANO is a ‘summer’ school being held in China sometime during September 2015 (I could not find the dates). The first summer school, held last year, featured a prototype functioning atomic force microscope made of Lego bricks according to an Aug. 25, 2015 news item on Nanowerk,

University College London students from across a range of disciplines travel to China to team up with students from Beijing, Boston (USA) and Taipei (Taiwan) for an action-packed two-week hackathon summer school based at Tsinghua University’s Beijing and Shenzhen campuses.

LEGO2NANO aims to bring the world of nanotechnology to school classrooms by initiating projects to develop low-cost scientific instruments such as the Open AFM—an open-source atomic force microscope assembled from cheap, off-the-shelf electronic components, Arduino, Lego and 3D printable parts.

Here’s an image used to publicize the first summer school in 2014,

LEGO2NANO – a summer school about making nanotechnology, 6–14 September 2014, Beijing, China LEGO2NANO关于纳米技术暑期学校2014年9月6-14日

LEGO2NANO – a summer school about making nanotechnology, 6–14 September 2014, Beijing, China
LEGO2NANO关于纳米技术暑期学校2014年9月6-14日

An August 20, 2015 University College of London press release, which originated the news item, provides more detail about the upcoming two-week session,

The 2015 LEGO2NANO challenge is focused on developing a range of innovative imaging and motion-sensitive instruments based on optical pick-up units available in any DVD head.

Aside from the intense, daily making sessions, the programme is packed with trips and visits to local Chinese schools, university laboratories, the Chinese Academy of Sciences, Beijing’s electronics markets, Shenzhen’s Open Innovation Laboratory (SZOIL)  and SEEED Studio. The students will also have daily talks and presentations from international experts on a variety of subjects such as the international maker movement, the Chinese education system, augmented reality and DIY instrumentation.

You can find more information about LEGO2NANO here at openafm.com and here at http://lego2nano.openwisdomlab.net/.

Pancake bounce

What impact does a droplet make on a solid surface? It’s not the first question that comes to my mind but scientists have been studying it for over a century. From an Aug. 5, 2015 news item on Nanowerk (Note: A link has been removed),

Studies of the impact a droplet makes on solid surfaces hark back more than a century. And until now, it was generally believed that a droplet’s impact on a solid surface could always be separated into two phases: spreading and retracting. But it’s much more complex than that, as a team of researchers from City University of Hong Kong, Ariel University in Israel, and Dalian University of Technology in China report in the journal Applied Physics Letters, from AIP Publishing (“Controlling drop bouncing using surfaces with gradient features”).

An Aug. 4, 2015 American Institute of Physics news release (also on EurekAlert), which originated the news item, describes the impact in detail,

“During the spreading phase, the droplet undergoes an inertia-dominant acceleration and spreads into a ‘pancake’ shape,” explained Zuankai Wang, an associate professor within the Department of Mechanical and Biomedical Engineering at the City University of Hong Kong. “And during the retraction phase, the drop minimizes its surface energy and pulls back inward.”

Remarkably, on gold standard superhydrophobic–a.k.a. repellant–surfaces such as lotus leaves, droplets jump off at the end of the retraction stage due to the minimal energy dissipation during the impact process. This is attributed to the presence of an air cushion within the rough surface.

There exists, however, a classical limit in terms of the contact time between droplets and the gold standard superhydrophobic materials inspired by lotus leaves.

As the team previously reported in the journal Nature Physics, it’s possible to shape the droplet to bounce from the surface in a pancake shape directly at the end of the spreading stage without going through the receding process. As a result, the droplet can be shed away much faster.

“Interestingly, the contact time is constant under a wide range of impact velocities,” said Wang. “In other words: the contact time reduction is very efficient and robust, so the novel surface behaves like an elastic spring. But the real magic lies within the surface texture itself.”

To prevent the air cushion from collapsing or water from penetrating into the surface, conventional wisdom suggests the use of nanoscale posts with small inter-post spacings. “The smaller the inter-post spacings, the greater the impact velocity the small inter-post can withstand,” he elaborated. “By contrast, designing a surface with macrostructures–tapered sub-millimeter post arrays with a wide spacing–means that a droplet will shed from it much faster than any previously engineered materials.”

What the New Results Show

Despite exciting progress, rationally controlling the contact time and quantitatively predicting the critical Weber number–a number used in fluid mechanics to describe the ratio between deforming inertial forces and stabilizing cohesive forces for liquids flowing through a fluid medium–for the occurrence of pancake bouncing remained elusive.

So the team experimentally demonstrated that the drop bouncing is intricately influenced by the surface morphology. “Under the same center-to-center post spacing, surfaces with a larger apex angle can give rise to more pancake bouncing, which is characterized by a significant contact time reduction, smaller critical Weber number, and a wider Weber number range,” according to co-authors Gene Whyman and Edward Bormashenko, both professors at Ariel University.

Wang and colleagues went on to develop simple harmonic spring models to theoretically reveal the dependence of timescales associated with the impinging drop and the critical Weber number for pancake bouncing on the surface morphology. “The insights gained from this work will allow us to rationally design various surfaces for many practical applications,” he added.

The team’s novel surfaces feature a shortened contact time that prevents or slows ice formation. “Ice formation and its subsequent buildup hinder the operation of modern infrastructures–including aircraft, offshore oil platforms, air conditioning systems, wind turbines, power lines, and telecommunications equipment,” Wang said.

At supercooled temperatures, which involves lowering the temperature of a liquid or gas below its freezing point without it solidifying, the longer a droplet remains in contact with a surface before bouncing off the greater the chances are of it freezing in place. “Our new surface structure can be used to help prevent aircraft wings and engines from icing,” he said.

This is highly desirable, because a very light coating of snow or ice–light enough to be barely visible–is known to reduce the performance of airplanes and even cause crashes. One such disaster occurred in 2009, and called attention to the dangers of in-flight icing after it caused Air France Flight 447 flying from Rio de Janeiro to Paris to crash into the Atlantic Ocean.

Beyond anti-icing for aircraft, “turbine blades in power stations and wind farms can also benefit from an anti-icing surface by gaining a boost in efficiency,” he added.

As you can imagine, this type of nature-inspired surface shows potential for a tremendous range of other applications as well–everything from water and oil separation to disease transmission prevention.

The next step for the team? To “develop bioinspired ‘active’ materials that are adaptive to their environments and capable of self-healing,” said Wang.

Here’s a link to and a citation for the paper,

Controlling drop bouncing using surfaces with gradient features by Yahua Liu, Gene Whyman, Edward Bormashenko, Chonglei Hao, and Zuankai Wang. Appl. Phys. Lett. 107, 051604 (2015); http://dx.doi.org/10.1063/1.4927055

This paper appears to be open access.

Finally, here’s an illustration of the pancake bounce,

Droplet hitting tapered posts shows “pancake” bouncing characterized by lifting off the surface of the end of spreading without retraction. Credit- Z.Wang/HKU

Droplet hitting tapered posts shows “pancake” bouncing characterized by lifting off the surface of the end of spreading without retraction. Credit- Z.Wang/HKU

There is also a pancake bounce video which you can view here on EurekAlert.

Replacing metal with nanocellulose paper

The quest to find uses for nanocellulose materials has taken a step forward with some work coming from the University of Maryland (US). From a July 24, 2015 news item on Nanowerk,

Researchers at the University of Maryland recently discovered that paper made of cellulose fibers is tougher and stronger the smaller the fibers get … . For a long time, engineers have sought a material that is both strong (resistant to non-recoverable deformation) and tough (tolerant of damage).

“Strength and toughness are often exclusive to each other,” said Teng Li, associate professor of mechanical engineering at UMD. “For example, a stronger material tends to be brittle, like cast iron or diamond.”

A July 23, 2015 University of Maryland news release, which originated the news item, provides details about the thinking which buttresses this research along with some details about the research itself,

The UMD team pursued the development of a strong and tough material by exploring the mechanical properties of cellulose, the most abundant renewable bio-resource on Earth. Researchers made papers with several sizes of cellulose fibers – all too small for the eye to see – ranging in size from about 30 micrometers to 10 nanometers. The paper made of 10-nanometer-thick fibers was 40 times tougher and 130 times stronger than regular notebook paper, which is made of cellulose fibers a thousand times larger.

“These findings could lead to a new class of high performance engineering materials that are both strong and tough, a Holy Grail in materials design,” said Li.

High performance yet lightweight cellulose-based materials might one day replace conventional structural materials (i.e. metals) in applications where weight is important. This could lead, for example, to more energy efficient and “green” vehicles. In addition, team members say, transparent cellulose nanopaper may become feasible as a functional substrate in flexible electronics, resulting in paper electronics, printable solar cells and flexible displays that could radically change many aspects of daily life.

Cellulose fibers can easily form many hydrogen bonds. Once broken, the hydrogen bonds can reform on their own—giving the material a ‘self-healing’ quality. The UMD discovered that the smaller the cellulose fibers, the more hydrogen bonds per square area. This means paper made of very small fibers can both hold together better and re-form more quickly, which is the key for cellulose nanopaper to be both strong and tough.

“It is helpful to know why cellulose nanopaper is both strong and tough, especially when the underlying reason is also applicable to many other materials,” said Liangbing Hu, assistant professor of materials science at UMD.

To confirm, the researchers tried a similar experiment using carbon nanotubes that were similar in size to the cellulose fibers. The carbon nanotubes had much weaker bonds holding them together, so under tension they did not hold together as well. Paper made of carbon nanotubes is weak, though individually nanotubes are arguably the strongest material ever made.

One possible future direction for the research is the improvement of the mechanical performance of carbon nanotube paper.

“Paper made of a network of carbon nanotubes is much weaker than expected,” said Li. “Indeed, it has been a grand challenge to translate the superb properties of carbon nanotubes at nanoscale to macroscale. Our research findings shed light on a viable approach to addressing this challenge and achieving carbon nanotube paper that is both strong and tough.”

Here’s a link to and a citation for the paper,

Anomalous scaling law of strength and toughness of cellulose nanopaper by Hongli Zhu, Shuze Zhu, Zheng Jia, Sepideh Parvinian, Yuanyuan Li, Oeyvind Vaaland, Liangbing Hu, and Teng Li. PNAS (Proceedings of the National Academy of Sciences) July 21, 2015 vol. 112 no. 29 doi: 10.1073/pnas.1502870112

This paper is behind a paywall.

There is a lot of research on applications for nanocellulose, everywhere it seems, except Canada, which at one time was a leader in the business of producing cellulose nanocrystals (CNC).

Here’s a sampling of some of my most recent posts on nanocellulose,

Nanocellulose as a biosensor (July 28, 2015)

Microscopy, Paper and Fibre Research Institute (Norway), and nanocellulose (July 8, 2015)

Nanocellulose markets report released (June 5, 2015; US market research)

New US platform for nanocellulose and occupational health and safety research (June 1, 2015; Note: As you find new applications, you need to concern yourself with occupational health and safety.)

‘Green’, flexible electronics with nanocellulose materials (May 26, 2015; research from China)

Treating municipal wastewater and dirty industry byproducts with nanocellulose-based filters (Dec. 23, 2014; research from Sweden)

Nanocellulose and an intensity of structural colour (June 16, 2014; research about replacing toxic pigments with structural colour from the UK)

I ask again, where are the Canadians? If anybody has an answer, please let me know.

There’s more than one black gold

‘Black gold’ is a phrase I associate with oil, signifying its importance and desirability. These days, this analogic phrase can describe a material according to a July 24, 2015 news item on Nanowerk,

If colloidal gold [gold in solution] self-assembles into the form of larger vesicles, a three-dimensional state can be achieved that is called “black gold” because it absorbs almost the entire spectrum of visible light. How this novel intense plasmonic state can be established and what its characteristics and potential medical applications are is explored by Chinese scientists and reported in the journal Angewandte Chemie …

A July 24, 2015 Wiley (Angewandte Chemie) press release, which originated the news item, provides more details,

Metal nanostructures can self-assemble into superstructures that offer intriguing new spectroscopic and mechanical properties. Plasmonic coupling plays a particular role in this context. For example, it has been found that plasmonic metal nanoparticles help to scatter the incoming light across the surface of the Si substrate at resonance wavelengths, therefore enhancing the light absorbing potential and thus the effectivity of solar cells.

On the other hand, plasmonic vesicles are the promising theranostic platform for biomedical applications, a notion which inspired Yue Li and Cuncheng Li of the Chinese Academy of Science, Hefei, China, and the University of Jinan, China, as well as collaborators to prepare plasmonic colloidosomes composed of gold nanospheres.

As the method of choice, the scientists have designed an emulsion-templating approach based on monodispersed gold nanospheres as building blocks, which arranged themselves into large spherical vesicles in a reverse emulsion system.

The resulting plasmonic vesicles were of micrometer-size and had a shell composed of hexagonally close-packed colloidal nanosphere particles in bilayer or, for the very large superspheres, multilayer arrangement, which provided the enhanced stability.

“A key advantage of this system is that such self-assembly can avoid the introduction of complex stabilization processes to lock the nanoparticles together”, the authors explain.

The hollow spheres exhibited an intense plasmonic resonance in their three-dimensionally packed structure and had a dark black appearance compared to the brick red color of the original gold nanoparticles. The “black gold” was thus characterized by a strong broadband absorption in the visible light and a very regular vesicle superstructure. In medicine, gold vesicles are intensively discussed as vehicles for the drug delivery to tumor cells, and, therefore, it could be envisaged to exploit the specific light-matter interaction of such plasmonic vesicle structures for medical use, but many other applications are also feasible, as the authors propose: “The presented strategy will pave a way to achieve noble-metal superstructures for biosensors, drug delivery, photothermal therapy, optical microcavity, and microreaction platforms.” This will prove the flexibility and versatility of the noble-metal nanostructures.

Here’s a link to and a citation for the paper,

Black Gold: Plasmonic Colloidosomes with Broadband Absorption Self-Assembled from Monodispersed Gold Nanospheres by Using a Reverse Emulsion System by Dilong Liu, Dr. Fei Zhou, Cuncheng Li, Tao Zhang, Honghua Zhang, Prof. Weiping Cai, and Prof. Yue Li. Angewandte Chemie International Edition Article first published online: 25 JUN 2015 DOI: 10.1002/anie.201503384

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

There is an image illustrating the work but, sadly, the gold doesn’t look black,

BlackGold

© Wiley-VCH

That’s it!

Nanoscale device emits light as powerfully as an object 10,000 times its size

The potential application in the field of solar power is what most interests me in this collaborative research from the University of Wisconsin-Madison (US) and Fudan University in China. From a July 13, 2015 news item on ScienceDaily,

University of Wisconsin-Madison engineers have created a nanoscale device that can emit light as powerfully as an object 10,000 times its size. It’s an advance that could have huge implications for everything from photography to solar power.

In a paper published July 10 [2015] in the journal Physical Review Letters, Zongfu Yu, an assistant professor of electrical and computer engineering, and his collaborators describe a nanoscale device that drastically surpasses previous technology in its ability to scatter light. They showed how a single nanoresonator can manipulate light to cast a very large “reflection.” The nanoresonator’s capacity to absorb and emit light energy is such that it can make itself — and, in applications, other very small things — appear 10,000 times as large as its physical size.

A July 13, 2015 University of Wisconsin-Madison news release (also on EurekAlert) by Scott Gordon, which originated the news item, expands on the theme,

“Making an object look 10,000 times larger than its physical size has lots of implications in technologies related to light,” Yu says.

The researchers realized the advance through materials innovation and a keen understanding of the physics of light. Much like sound, light can resonate, amplifying itself as the surrounding environment manipulates the physical properties of its wave energy. The researchers took advantage of this by creating an artificial material in which the wavelength of light is much larger than in a vacuum, which allows light waves to resonate more powerfully.

The device condenses light to a size smaller than its wavelength, meaning it can gather a lot of light energy, and then scatters the light over a very large area, harnessing its output for imaging applications that make microscopic particles appear huge.

“The device makes an object super-visible by enlarging its optical appearance with this super-strong scattering effect,” says Ming Zhou, a Ph.D. student in Yu’s group and lead author of the paper.

Much as a very thin string on a guitar can absorb a large amount of acoustic energy from its surroundings and begin to vibrate in sympathy, this one very small optical device can receive light energy from all around and yield a surprisingly strong output. In imaging, this presents clear advantages over conventional lenses, whose light-gathering capacity is limited by direction and size.

“We are developing photodetectors based on this technology and, for example, it could be helpful for photographers wanting to shoot better quality pictures in weak light conditions,” Yu says.

Given the nanoresonator’s capacity to absorb large amounts of light energy, the technology also has potential in applications that harvest the sun’s energy with high efficiency. In addition, Yu envisions simply letting the resonator emit that energy in the form of infrared light toward the sky, which is very cold. Because the nanoresonator has a large optical cross-section — that is, an ability to emit light that dramatically exceeds its physical size — it can shed a lot of heat energy, making for a passive cooling system.

“This research opens up a new way to manipulate the flow of light, and could enable new technologies in light sensing and solar energy conversion,” Yu says.

Here’s a link to and a citation for the paper,

Extraordinarily Large Optical Cross Section for Localized Single Nanoresonator by Ming Zhou, Lei Shi, Jian Zi, and Zongfu Yu. Phys. Rev. Lett. 115, 023903  DOI: http://dx.doi.org/10.1103/PhysRevLett.115.023903 Published 10 July 2015

This paper is behind a paywall.

Your tires generate energy that can be harvested

One day, this new work from the University of Wisconsin-Madison could help cut gas expenditures for your car and other motorized vehicles dependent on fossil fuels. A June 29, 2015 news item on Nanowerk describes the research (Note: A link has been removed),

A group of University of Wisconsin-Madison engineers and a collaborator from China have developed a nanogenerator that harvests energy from a car’s rolling tire friction.

An innovative method of reusing energy, the nanogenerator ultimately could provide automobile manufacturers a new way to squeeze greater efficiency out of their vehicles.

The researchers reported their development, which is the first of its kind, in a paper published May 6, 2015, in the journal Nano Energy (“Single-electrode triboelectric nanogenerator for scavenging friction energy from rolling tires”).

A June 29, 2015 University of Wisconsin-Madison news release (also on EurekAlert), which originated the news item, provides more details (Note: Links have been removed),

Xudong Wang, the Harvey D. Spangler fellow and an associate professor of materials science and engineering at UW-Madison, and his PhD student Yanchao Mao have been working on this device for about a year.

The nanogenerator relies on the triboelectric effect to harness energy from the changing electric potential between the pavement and a vehicle’s wheels. The triboelectric effect is the electric charge that results from the contact or rubbing together of two dissimilar objects.

Wang says the nanogenerator provides an excellent way to take advantage of energy that is usually lost due to friction.

“The friction between the tire and the ground consumes about 10 percent of a vehicle’s fuel,” he says. “That energy is wasted. So if we can convert that energy, it could give us very good improvement in fuel efficiency.”

The nanogenerator relies on an electrode integrated into a segment of the tire. When this part of the tire surface comes into contact with the ground, the friction between those two surfaces ultimately produces an electrical charge-a type of contact electrification known as the triboelectric effect.

During initial trials, Wang and his colleagues used a toy car with LED lights to demonstrate the concept. They attached an electrode to the wheels of the car, and as it rolled across the ground, the LED lights flashed on and off. The movement of electrons caused by friction was able to generate enough energy to power the lights, supporting the idea that energy lost to friction can actually be collected and reused.

“Regardless of the energy being wasted, we can reclaim it, and this makes things more efficient,” Wang says. “I think that’s the most exciting part of this, and is something I’m always looking for: how to save the energy from consumption.”

The researchers also determined that the amount of energy harnessed is directly related to the weight of a car, as well as its speed. Therefore the amount of energy saved can vary depending on the vehicle-but Wang estimates about a 10-percent increase in the average vehicle’s gas mileage given 50-percent friction energy conversion efficiency.

“There’s big potential with this type of energy,” Wang says. “I think the impact could be huge.”

Here’s a link to and a citation for the paper,

Single-electrode triboelectric nanogenerator for scavenging friction energy from rolling tires by Yanchao Mao, Dalong Geng, Erjun Liang, & Xudong Wang. Nano Energy Volume 15, July 2015, Pages 227–234 doi:10.1016/j.nanoen.2015.04.026

This paper is behind a paywall.

Convergence at Canada’s Perimeter Institute: art/science and physics

It’s a cornucopia of convergence at Canada’s Perimeter Institute (PI). First, there’s a June 16, 2015 posting by Colin Hunter about converging art and science in the person of Alioscia Hamma,

In his professional life, Hamma is a lecturer in the Perimeter Scholars International (PSI) program and an Associate Professor at China’s Tsinghua University. His research seeks new insights into quantum entanglement, quantum statistical mechanics, and other aspects of the fundamental nature of reality.

Though he dreamed during his boyhood in Naples of one day becoming a comic book artist, he pursued physics because he believed – still believes – it is our most reliable tool for decoding our universe.

“Mathematics is ideal, clean, pure, and meaningless. Natural sciences are living, concrete, dirty, and meaningful. Physics is right in the middle, like the human condition,” says Hamma.

Art too, he says, resides in the middle ground between the world of ideals and the world as it presents itself to our senses.

So he draws. …

Perimeter Institute has provided a video where Hamma shares his ideas,

This is very romantic as in literature-romantic. If I remember rightly, ‘truth is beauty and beauty is truth’ was the motto of the romantic poets, Byron, Keats, and Shelley. It’s intriguing to hear similar ideas being applied to physics, philosophy, and art.

H/t to Speaking Up For Canadian Science regarding this second ‘convergence at PI‘. From the Convergence conference page on the Perimeter Institute website,

Convergence is Perimeter’s first-ever alumni reunion and a new kind of physics conference providing a “big picture” overview of fundamental physics and its future.

Physics is at a turning point. The most sophisticated experiments ever devised are decoding our universe with unprecedented clarity — from the quantum to the cosmos — and revealing a stunning simplicity that theory has yet to explain.

Convergence will bring together many of the world’s best minds in physics to probe the field’s most exciting ideas and chart a course for 21st century physics. The event will also celebrate, through commemorative lectures, the centenaries of two defining discoveries of the 20th century: Noether’s theorem and Einstein’s theory of general relativity.

Converge with us June 20-24. [Registration is now closed]

Despite registration being closed it is still possible to attend online,

CONVERGE ONLINE

Whether you’re at Convergence in person or joining us online, there are many ways to join the conversation:

You can find PI’s Convergence blog here.

A race to find substitutes for graphene?

I have two items concerning research which seeks to replace graphene in one application or other.

Black phosporus and the École Polytechniqe de Montréal

A June 2, 2015 news item on Nanotechnology Now features work on developing a two-dimensional black phosphorus material, 2D phosphane,

A team of researchers from Universite de Montreal, Polytechnique Montreal and the Centre national de la recherche scientifique (CNRS) in France is the first to succeed in preventing two-dimensional layers of black phosphorus from oxidating. In so doing, they have opened the doors to exploiting their striking properties in a number of electronic and optoelectronic devices. …

Black phosphorus, a stable allotrope of phosphorus that presents a lamellar structure similar to that of graphite, has recently begun to capture the attention of physicists and materials researchers. It is possible to obtain single atomic layers from it, which researchers call 2D phosphane. A cousin of the widely publicized graphene, 2D phosphane brings together two very sought-after properties for device design.

A June 2, 2015 École Polytechniqe de Montréal news release, which originated the news item, expands on why 2D phosphane is an appealing material,

First, 2D phosphane is a semiconductor material that provides the necessary characteristics for making transistors and processors. With its high-mobility, it is estimated that 2D phosphane could form the basis for electronics that is both high-performance and low-cost.

Furthermore, this new material features a second, even more distinctive, characteristic: its interaction with light depends on the number of atomic layers used. One monolayer will emit red light, whereas a thicker sample will emit into the infrared. This variation makes it possible to manufacture a wide range of optoelectronic devices, such as lasers or detectors, in a strategic fraction of the electromagnetic spectrum.

The news release goes on to describe an important issue with phosphane and how the scientists addressed it,

Until now, the study of 2D phosphane’s properties was slowed by a major problem: in ambient  conditions, very thin layers of the material would degrade, to the point of compromising its future in the industry despite its promising potential.

As such, the research team has made a major step forward by succeeding in determining the physical mechanisms at play in this degradation, and in identifying the key elements that lead to the layers’ oxidation.

“We have demonstrated that 2D phosphane undergoes oxidation under ambient conditions, caused jointly by the presence of oxygen, water and light. We have also characterized the phenomenon’s evolution over time by using electron beam spectroscopy and Raman spectroscopy,” reports Professor Richard Martel of Université de Montréal’s Department of Chemistry.

Next, the researchers developed an efficient procedure for producing these very fragile single-atom layers and keeping them intact.

“We were able to study the vibration modes of the atoms in this new material. Since earlier studies had been carried out on heavily degraded materials, we revealed the as-yet-unsuspected effects of quantum confinement on atoms’ vibration modes,” notes Professor Sébastien Francoeur of Polytechnique’s Department of Engineering Physics.

The study’s results will help the world scientific community develop 2D phosphane’s very special properties with the aim of developing new nanotechnologies that could give rise to high-performance microprocessors, lasers, solar cells and more.

Here’s a link to and a citation for the paper,

Photooxidation and quantum confinement effects in exfoliated black phosphorus by Alexandre Favron, Etienne Gaufrès, Frédéric Fossard, Anne-Laurence Phaneuf-L’Heureux, Nathalie Y-W. Tang, Pierre L. Lévesque, Annick Loiseau, Richard Leonelli, Sébastien Francoeur, & Richard Martel. Nature Materials (2015)  doi:10.1038/nmat4299 Published online 25 May 2015

This paper is behind a paywall.

Now. for the second item about replacing graphene.

China’s new aerogel, a rival to graphene aerogels?

A June 2, 2015 American Institute of Physics news release (also on EurekAlert) describes research into an alternative to expensive graphene aerogels,

The electromagnetic radiation discharged by electronic equipment and devices is known to hinder their smooth operation. Conventional materials used today to shield from incoming electromagnetic waves tend to be sheets of metal or composites, which rely on reflection as a shielding mechanism.

But now, materials such as graphene aerogels are gaining traction as more desirable alternatives because they act as electromagnetic absorbers. They’re widely expected to improve energy storage, sensors, nanoelectronics, catalysis and separations, but graphene aerogels are prohibitively expensive and difficult to produce for large-scale applications because of the complicated purification and functionalization steps involved in their fabrication.

So a team of researchers in China set out to design a cheaper material with properties similar to a graphene aerogel–in terms of its conductivity, as well as a lightweight, anticorrosive, porous structure. In the journal Applied Physics Letters, from AIP Publishing, the researchers describe the new material they created and its performance.

Aming Xie, an expert in organic chemistry, and Fan Wu, both affiliated with PLA University of Science and Technology, worked with colleagues at Nanjing University of Science and Technology to tap into organic chemistry and conducting polymers to fabricate a three-dimensional (3-D) polypyrrole (PPy) aerogel-based electromagnetic absorber.

They chose to concentrate on this method because it enables them to “regulate the density and dielectric property of conducting polymers through the formation of pores during the oxidation polymerization of the pyrrole monomer,” explained Wu.

And the fabrication process is a simple one. “It requires only four common chemical reagents: pyrrole, ferric chloride (FeCl3), ethanol and water — which makes it cheap enough and enables large-scale fabrication,” Wu said. “We’re also able to pour the FeCl3 solution directly into the pyrrole solution — not drop by drop — to force the pyrrole to polymerize into a 3-D aerogel rather than PPy particles.”

In short, the team’s 3-D PPy aerogel is designed to exhibit “desirable properties such as a porous structure and low density,” Wu noted.

Beyond that, its electromagnetic absorption performance — with low loss — shows great promise. “We believe a ‘wide’ absorption range is more useful than high absorption within one frequency,” Wu said. Compared with previous works, the team’s new aerogel has the lowest adjunction and widest effective bandwidth — with a reflection loss below -10 decibels.

In terms of applications, based on the combination of low adjunction and a “wide” effective bandwidth, the researchers expect to see their 3-D PPy aerogel used in surface coatings for aircraft.

Another potential application is as coatings within the realm of corrosion prevention and control. “Common anticorrosion coatings contain a large amount of zinc (70 to 80 percent by weight), and these particles not only serve as a cathode by corroding to protect the iron structure but also to maintain a suitable conductivity for the electrochemistry process,” Wu pointed out. “If our 3-D PPy aerogel could build a conductivity network in this type of coating, the loss of zinc particles could be rapidly reduced.”

The team is now taking their work a step further by pursuing a 3-D PPy/PEDOT-based (poly(3,4-ethylenedioxythiophene) electromagnetic absorber. “Our goal is to grow solid-state polymerized PEDOT particles in the holes of the 3-D PPy aerogel formed by PPy chains,” Wu added.

Here’s a link to and a citation for the paper,

Self-assembled ultralight three-dimensional polypyrrole aerogel for effective electromagnetic absorption by Aming Xie, Fan Wu, Mengxiao Sun, Xiaoqing Dai, Zhuanghu Xu, Yanyu Qiu, Yuan Wang, and Mingyang Wang. Appl. Phys. Lett. 106, 222902 (2015); http://dx.doi.org/10.1063/1.4921180

This paper is open access.

Alternative to rare earth magnets synthesized at Virginia Commonwealth University (US)

There’s a lot of interest in finding alternatives to rare earths given that China has been restricting exports (this Nov. 25, 2010 post describes the situation which hasn’t changed much, as far as I know). Should the research at the Virginia Commonwealth University highlighted in a June 1, 2015 news item on Nanotechnology Now present a viable alternative to rare earths the geopolitical situation should undergo some interesting changes,

A team of scientists at Virginia Commonwealth University has synthesized a powerful new magnetic material that could reduce the dependence of the United States and other nations on rare earth elements produced by China.

“The discovery opens the pathway to systematically improving the new material to outperform the current permanent magnets,” said Shiv Khanna, Ph.D., a commonwealth professor in the Department of Physics in the College of Humanities and Sciences.

A June 1, 2015 Virginia Commonwealth University news release by Brian McNeill (also on EurekAlert), which originated the news item, describes the achievement in more detail,

The new material consists of nanoparticles containing iron, cobalt and carbon atoms with a magnetic domain size of roughly 5 nanometers. It can store information up to 790 kelvins with thermal and time-stable, long-range magnetic order, which could have a potential impact for data storage application.

When collected in powders, the material exhibits magnetic properties that rival those of permanent magnets that generally contain rare earth elements. The need to generate powerful magnets without rare earth elements is a strategic national problem as nearly 70 to 80 percent of the current rare earth materials are produced in China.

Permanent magnets, specifically those containing rare earth metals, are an important component used by the electronics, communications and automobile industries, as well as in radars and other applications.

Additionally, the emergence of green technology markets – such as hybrid and electric vehicles, direct drive wind turbine power systems and energy storage systems – have created an increased demand for permanent magnets.

However, China is the main supplier of world rare earth demands and has tried to impose restrictions on their export, creating an international problem.

The current paper is a joint experimental theoretical effort in which the new material was synthesized, characterized and showed improved characteristics following the theoretical prediction.

“This is good science along with addressing a problem with national importance,” said Ahmed El-Gendy, a former postdoctoral associate in the Department of Chemistry in the College of Humanities and Sciences and a co-author of the paper.

Here’s a link to and a citation for the paper,

Experimental evidence for the formation of CoFe2C phase with colossal magnetocrystalline-anisotropy by Ahmed A. El-Gendy, Massimo Bertino, Dustin Clifford, Meichun Qian, Shiv N. Khanna, and Everett E. Carpenter. Appl. Phys. Lett. 106, 213109 (2015); http://dx.doi.org/10.1063/1.4921789

This is an open access paper.

‘Green’, flexible electronics with nanocellulose materials

Bendable or flexible electronics based on nanocellulose paper present a ‘green’ alternative to other solutions according to a May 20, 2015 American Chemical Society (ACS) news release (also on EurekAlert),

Technology experts have long predicted the coming age of flexible electronics, and researchers have been working on multiple fronts to reach that goal. But many of the advances rely on petroleum-based plastics and toxic materials. Yu-Zhong Wang, Fei Song and colleagues wanted to seek a “greener” way forward.

The researchers developed a thin, clear nanocellulose paper made out of wood flour and infused it with biocompatible quantum dots — tiny, semiconducting crystals — made out of zinc and selenium. The paper glowed at room temperature and could be rolled and unrolled without cracking.

(h’t Nanotechnology Now, May 20, 2015)

There’s no mention in the news release or abstract as to what material (wood, carrot, banana, etc.) was used to derive the nanocellulose. Regardless, here’s a link to and a citation for the paper,

Let It Shine: A Transparent and Photoluminescent Foldable Nanocellulose/Quantum Dot Paper by Juan Xue, Fei Song, Xue-wu Yin, Xiu-li Wang, and Yu-zhong Wang. ACS Appl. Mater. Interfaces, 2015, 7 (19), pp 10076–10079 DOI: 10.1021/acsami.5b02011 Publication Date (Web): May 4, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.