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Water Treatment Catalyst Microwavesid37351Water treatment technologies to remove contaminants from waste water can be made more efficient by incorporating nanomembranes or catalytic nanoparticles (get more insights into how nanotechnology is applied to water treatment).

 

 

 

Compared to conventional treatment techniques, the use of catalysts, especially nanoparticle catalysts, can shorten treatment time, target recalcitrant substances, and selectively transform wastes into valuable products for instance by recovering carbon, nitrogen and phosphorus.   By . Copyright © Nanowerk

An issue with these systems is the expense associated with the initial investment and subsequent replenishment of catalysts. The reason for the high cost of catalytic water treatment is the use of expensive noble metals such as platinum and palladium for catalyzing the degradation of environmental contaminants. In the quest to find equally effective – in some cases even more effective – yet less expensive catalyst alternatives, researchers have developed bimetallic alloys by blending a noble metal nanoparticles with cheaper promoter metals such as copper and nickel. The blending ratio of these metals is an important parameter that controls the reactivity of alloy nanocatalysts. The challenge with this approach is how to find the composition of alloy nanoparticles that show the greatest catalytic reactivity for a contaminant of interest. Doing this requires the synthesis of a series of different nanoparticles which then each needs to be screened for their catalytic activity. Researchers at the University of Notre Dame now have successfully synthesized suspended platinum/nickel nanoalloys using a cycle-controlled microwave-assisted polyol reduction method.

The metal alloy nanoparticles synthesized by this method have a dynamic structure. For example, in the synthesis of platinum (Pt) and nickel (Ni) nanoalloy, a Pt core forms first, which then catalyzes the reduction of Ni2+. Ni then blends with Pt, giving a Pt/Ni alloy shell. After platinum is exhausted, the new shell is completely made of nickel. The team, led by Chongzheng Na, an Assistant Professor in the Department of Civil and Environmental Engineering and Earth Sciences, reported their findings in the August 7, 2014 online edition of Applied Catalysis B: Environmental (“Microwave-assisted optimization of platinum-nickel nanoalloys for catalytic water treatment”).

formation of nanoalloyFormation of the dynamic Pt/Ni nanoalloy under microwave irradiation and the volcano plot of the catalytic rate and surface compositions. (Image: Na group, University of Notre Dame)

“Our one-pot method creates nanoparticles with a range of surface compositions without much change of the particle size,” Hanyu Ma, a Ph.D. student in Na’s group, tells Nanowerk. “The varied surface compositions permit the rapid determination of the optimal Pt/Ni composition to be used as an effective nanoalloy for reducing the model water contaminant p-nitrophenol.” As Na and his team point out, the adoption of this facile synthesis method in catalyst designs may permit the rapid screening of nanoalloys for other water contaminants. Given the compositional dynamics of this technique, a series of nanoalloys with different surface compositions can be quickly synthesized using a single starting solution and the optimal metal ratio experimentally determined to find the best catalytic reactivity for degrading the pollutant. Ma explains that the structure-activity relationship of alloys is often linked to the averaged composition of an entire particle.

“As we have shown in our paper, the average composition could misrepresent the real composition on surface, where reactions occur,” he says. “With active control of the surface composition, we now can ensure that the reactivity is linked to the correct composition of a nanoalloy.” The researchers note that when the precursors of a noble metal and a transition metal react with a mild reactant such as polyol solvents, their difference in redox potential plays an important role, controlling which metal is reduced and which is not. “As far as we know, this has not been discussed explicitly in the past, particularly when microwave irradiation is used,” adds Ma. “At the beginning of the synthesis, the solvent absorbs microwaves and thus is heated to an above-ambient temperature.

At this temperature, polyol can only reduce noble metal cations so noble metal nanoparticles are formed. Once the nanoparticles are formed, they absorbs microwaves themselves – more than the solvent does – giving to a localized elevated temperature and forming nano hot spots around the nanoparticles. At the elevated temperature, transition metal cations can now be reduced so an alloy mixture is deposited on surface.” The surface composition is controlled by the availability of noble and transition metal precursors in solution.

According to the researchers, two factors play critical roles in establishing the compositional dynamics: the difference of redox potentials between noble and transition metals; and the difference of microwave absorptivity between metal nanoparticles and polyol solvent. Whereas in this present paper Na’s team demonstrated the usefulness of microwave-assisted polyol reduction for synthesizing binary nanoalloys with varied surface compositions, they hope to extend its application to the synthesis of ternary, quaternary, and even more sophisticated nanoalloys.

R to R Printing id37388Electrochromic materials exhibit reversible optical change in the visible region when they are subjected to an electric charge. These switchable materials can be used for ‘smart’ windows in buildings, cars and airplanes as well as in information displays and eye wear. An electrochromic device is one of the most attractive candidates for paper-like displays, so called electronic paper, which will be the next generation display, owing to attributes such as thin and flexible materials, low-power consumption, and fast switching times.

By Michael Berger. Copyright © Nanowerk

Electrochromic devices (ECDs) generally consist of a structure where certain material layers, among them an electrolyte, are sandwiched together. A major limitation until now has been the necessity to use the very expensive indium tin oxide (ITO) as transparent electrodes. ITO’s brittleness makes it unsuitable for flexible device applications and its fabrication process – vacuum-coating, high-temperature annealing – is incompatible with plastic-based substrates. “ECD structure and manufacturing is to a wide extent challenged by the electrolyte component,” Frederik C. Krebs, a professor and head of section of Energy Conversion and Storage at the Technical University of Denmark, tells Nanowerk. “As it remains common practice to employ a semisolid adhesive gel electrolyte, fabrication of devices is limited to separately coating of the two electrodes before finalizing the device in a lamination step; a technical challenge in a simple roll-to-roll (R2R) process and an impossibility in advanced R2R processes with 2D registration requirements.” In new work, reported in the September 5, 2014 online edition of Advanced Materials (“From the Bottom Up – Flexible Solid State Electrochromic Devices”), Krebs and first author Dr. Jacob Jensen describe solid state electrochromic devices, manufactured by sequentially stacking layers in one direction using flexographic printing and slot-die coating methods.

 

LundStructure and coating of a solid state electrochromic device. The individual layers are successively coated in the A to F direction. All the layers, except the top electrode (F), are slot die coated as depicted in the upper left picture. The electrolyte layer (D) is slot-die coated followed by in-situ photo-curing as depicted in lower right picture. The top silver-grid electrode (F) is deposited by flexographic printing as depicted in the upper right picture. The structure of the primary electrochromic polymer is shown in the lower left side of the figure. (Reprinted with permission by Wiley-VCH Verlag)

 

The novelty of this bottom-up printing process for electrochromic device fabrication is the use of printed grid structures in combination with printable electrolytes that can be crosslinked in such a way that many layers can be printed on top of each other. Whereas previous processes have employed the lamination of two separately prepared films, this new method provides the ability to constitute multilayer structures with functionality through printing layers consecutively on top of each other. “We show how – using a specially developed ‘curing chamber’ mounted on a mini roll coater – solid state electrochromic devices can be manufactured continuously in one direction, i.e., from the bottom and up, using slot-die coating and flexographic printing,” says Krebs. “This technique eliminates the need for a lamination step and enables fully additive roll-to-roll processes.” This considerably simplified process constitutes an important step towards R2R manufacturing of ECDs without having to employ brittle materials such as ITO.

This new paper extends the team’s previous reports on ECD manufacture such as “Fast Switching ITO Free Electrochromic Devices” in Advanced Functional Materials and “Manufacture and Demonstration of Organic Photovoltaic-Powered Electrochromic Displays Using Roll Coating Methods and Printable Electrolytes” in the Journal of Polymer Science. The ability to cheaply mass-produce ECDs will find applications ranging from light management and shading to large area/low cost displays such as billboards.

Basically, it is a simple way of printing thin, very low cost and low power consumption display devices. The compromises that need to be made with this process are slow switching speed and relatively poor contrast. Both can be improved, notes Krebs, but since these devices rely on a chemical reaction taking place when changing color there are limits to the switching speed that can be reached. Krebs points out that the current version of his team’s ITO- and vacuum-free grid electrodes still require further optimization to achieve the same optical transmission as the brittle ITO.

Graphene Chips id36806PEN Inc. confirmed the closing of the previously announced combination of Applied Nanotech Holdings, Inc. (Applied Nanotech) and NanoHoldings, Inc., the parent company of Nanofilm, Ltd. (Nanofilm), to form the new publicly traded company. Scott Rickert, the CEO of Nanofilm, is now the CEO and Chairman of the Board of Directors of PEN.

 

 

PEN creates one of the country’s leading companies focused on developing and commercializing advanced-performance products enabled by nanotechnology. The new company unites staff and resources in nanotechnology research and development and experience in specialty product commercialization.

Nanofilm Ltd, and Applied Nanotech will continue as wholly owned subsidiaries of PEN. The company has applied to trade under a new symbol. Until it is approved, the stock will continue to trade on the OTCQB under the symbol APNT.

“My vision for PEN is to harness the vast potential of nanotechnology to create innovative, breakthrough products for a global marketplace,” said Scott Rickert. “In PEN, there’s both R&D expertise and commercialization experience to drive the growth strategy.” PEN will focus product efforts in three areas: safety, health and sustainability. “PEN will be tackling big problems that require the solutions nanotechnology makes possible,” noted Rickert.

Dr. Rickert added, “The PEN I envision will have the human capital, the scientific knowledge and the financial resources to match our ambitious goals. I know everyone on the team is ready to move forward, excited to begin a new era focused on nanotechnology-enabled performance products and company growth.”

PEN also announced a newly constituted board of directors. In addition to Dr. Rickert, new directors are Jeanne Rickert, Douglas Holmes, and James Sharp. Robert Ronstadt, Howard Westerman and Ronald Berman, who were members of the Applied Nanotech board, will remain as directors of PEN.

The new company will be headquartered in Deerfield Beach, Florida. Applied Nanotech operations will continue in Austin, Texas, and Nanofilm operations will remain in Valley View, Ohio.

Source: Applied Nanotech Holdings, Inc.

Mcnutt_carbon_anodex250When Orlando Rios first started analyzing samples of carbon fibers made from a woody plant polymer known as lignin, he noticed something unusual. The material’s microstructure—a mixture of perfectly spherical nanoscale crystallites distributed within a fibrous matrix—looked almost too good to be true.

 

 

“I thought, this looks like a material that people would go through a lot of work modifying graphite to make it look this way,” said Rios, a materials scientist at the U.S. Dept. of Energy (DOE)’s Oak Ridge National Laboratory (ORNL). “It had a really distinct microstructure from any other graphite I’d seen.”

Rios and his colleagues soon realized the lignin fiber’s unique structure could make it useful as a battery anode, potentially improving upon graphitic materials found in most lithium-ion batteries. Lignin, a low-cost byproduct of the pulp, paper and biofuels industries, could be transformed into a cheaper version of highly engineered graphite through a simple and industrially scalable manufacturing process.

Mcnutt_carbon_anodex250

Researchers at ORNL and the Univ. of Tennessee are studying the structure of plant-based battery materials by combining neutron experiments and supercomputer simulations. The molecular model pictured above shows the battery anode’s composition: amorphous carbon (blue), crystalline carbon (green) and hydrogen (white.)

“We start with the fibers when they’re in a polymer state and then fuse them together by essentially melting and burning them,” Rios said. “Then you have a structure that looks like a mat or piece of paper. You can take this material, place it in a battery and you’re done. It’s ready to go.”

Initial testing of the lignin-derived battery showed promising results in terms of capacity and cycling stability, but the researchers wanted to understand how and why the material behaved so differently from other graphites. Rios began collaborating with the Univ. of Tennessee’s Computational Materials Group, led by David Keffer, to further examine the fibers’ structure and behavior.

“There aren’t many techniques we can use to study these unique materials made of crystalline domains within an amorphous matrix,” said UT’s Nicholas McNutt, a graduate student in Keffer’s group. “We wanted to tie together some of Oak Ridge National Lab’s best resources—neutrons and computers—and see what we could do.”

The team ran neutron scattering experiments at ORNL’s Spallation Neutron Source (SNS) to analyze how lignin-based fiber samples reacted with lithium. The SNS is a DOE Office of Science user facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development.

Using the neutron data, the team developed computational models and ran simulations on supercomputers including the Oak Ridge Leadership Computing Facility’s (OLCF) Titan, supported by DOE’s Office of Science, and UT’s Kraken, supported by the National Science Foundation. The team detailed its approach in the Journal of Applied Crystallography.

“Our models allow us to take experimental neutron scattering data and predict things about the local atomic structure,” McNutt said. “We are using computation to understand experimental data in a way that you couldn’t do before.”

The initial combination of neutron experiments and simulation gave the UT-ORNL team a first glimpse into how the material’s structure affects its overall performance. Now that they have confirmed their model’s accuracy, the researchers plan on applying the technique to how the material’s structure changes with and without added lithium, mimicking the charging and discharging cycles of a real battery.

“The most useful aspect of simulation is that we can see exactly what the lithium is doing in these structures,” McNutt said. “If we can see where it’s stored, how much of it is stored, what area of the structure it diffuses through, we can basically figure out all the reasons that make these low-cost materials high-performance. Once we know that, we can help guide the manufacturing process.”

Source: Oak Ridge National Laboratory

advancedmoleResearchers from the University of Cambridge have developed advanced molecular ‘sieves’ which could be used to filter carbon dioxide and other greenhouse gases from the atmosphere.

Newly-developed synthetic membranes provide a greener and more energy-efficient method of separating gases, and can remove and other from the atmosphere, potentially reducing the cost of capturing carbon dioxide significantly.

The synthetic membranes, made of materials known as polymers of intrinsic microporosity (PIMs), mimic the hourglass-shaped protein channels found in biological membranes in cells. The tiny openings in these molecular ‘sieves’ – just a few billionths of a metre in size – can be adjusted so that only certain molecules can pass through. Details are published in the journal Nature Communications.

advancedmole

Polymer molecular sieves with interconnected pores (in green) for rapid and selective transport of molecules. Credit: Qilei Song 

Current methods for separating gases are complex, expensive and energy-intensive. Additionally, conventional polymers, while reliable and inexpensive, are not suitable for large scale applications, as there is a trade-off between low permeability levels and a high degree of selective molecular separation.

Researchers are attempting to develop new methods of energy-efficient and environmental-friendly membrane-separation technology, which is an essential process in everything from water purification to controlling gas emissions.

The team from the University’s Cavendish Laboratory, working with researchers from Kyoto University, has developed an alternative approach to generating polymer membranes, ‘baking’ them in the presence of oxygen, a process known as thermal oxidation.

Inducing a thermal oxidation reaction in the PIMs causes the loosely-packed long chains of polymer molecules to form into a cross-linked network structure, with hourglass-shaped cavities throughout. This structure not only results in a membrane which is more selective to gas molecules, but also the size of necks and cavities can be tuned according to what temperature the PIMs are ‘baked’ at.

“The secret is that we introduce stronger forces between polymer chains,” said Dr Qilei Song of the Cavendish Laboratory, the paper’s lead author. “Heating microporous polymers using low levels of oxygen produces a tougher and far more selective membrane which is still relatively flexible, with a gas permeability that is 100 to 1,000 times higher than conventional polymer membranes.”

The cross-linked structure also makes these membranes more stable than conventional solution-processed PIMs, which have a twisted and rigid structure – like dried pasta – that makes them unable to pack efficiently. Thermal oxidation and crosslinking reinforces the strength of channels while controlling the size of the openings leading into the cavities, which allows for higher selectivity.

The new is twice as selective for separation carbon dioxide as conventional polymer membranes, but allows carbon dioxide to pass through it a few hundred times faster. These thermally modified PIMs membranes are among molecular sieves with the highest combinations of gas permeability and selectivity. In addition to possible uses for separating carbon dioxide from flue gas emitted from coal-fired power plants, the membranes could also be used in air separation, natural gas processing, hydrogen gas production, or could help make more efficient combustion of fossil fuels and power generation with much lower emissions of air pollutants.

“Basically, we developed a method for making a polymer that can truly contribute to a sustainable environment,” said Professor Easan Sivaniah from Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS).

“This new way of modifying PIMs brings the prospect of large-scale, energy-efficient separation a step closer,” said Professor Peter Budd, from the University of Manchester, one of the inventors of PIMs materials.

Explore further: Catching greenhouse gases with advanced membranes

More information: “Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes.” Qilei Song, et al. Nature Communications 5, Article number: 4813 DOI: 10.1038/ncomms5813

September 16, 2014:

Note to Readers: This is a Re-Blog from the Nanosys “dot-color” Blog Site: http://www.nanosysinc.com/dot-color/

3D Printing dots-2Resolution is only a small part of the UHD story.

That was my takeaway from Europe’s massive late summer consumer electronics and broadcast trade shows IFA and IBC.

UHD” is already a bit of a murky term but it has always been about resolution. Originally, it only meant 8K but marketers have evolved it to encompass just about any resolution beyond 1080P including true 4K and 3840×2160. That’s about to change again and the definition is expanding this time to include not just more but better pixels.

Display makers seem to have recognized that while consumers will appreciate the benefits of 4K resolution, especially when checking out a new TV up close on the showroom floor, it is just not enough to deliver a truly blow-away visual experience.

Hisense%20Quantum%20Dot%20ULED

Hisense dynamic backlit, Quantum Dot “ULED” LCDs (right) take the Pepsi challenge with OLED at IFA 2014 in Berlin.

Walking the halls at IFA 2014 in Berlin, I saw tons of UHD sets from display makers of all types from Samsung to Sony to Hisense. What I did not see were nearly any plain vanilla flat panel displays pushing UHD resolution as a defining feature. Instead, there was a tremendous amount of innovation and differentiation around form factor with curved sets, high dynamic range with dynamic backlighting, wide color gamut with Quantum Dots and higher frame rates.

Content providers and creators have gotten the message as well. Speaking at IBC 2014 in Amsterdam, Paul Grey, director of European research for DisplaySearch said, “Broadcasters know consumers can barely see the difference between HD and 4K if you do nothing more than change the resolution, and this is well based in solid trials methodology. It isn’t just a bit of prejudice. The higher numbers are good for marketing, but not much else.”

When we say “UHD” we increasingly mean “next generation TV” and that encompasses a whole range of new features that will change how we watch TV whether it’s wide color gamut, high dynamic range or even curved form factors.

start-up-pitch-1f121f3

By Eric Rice

Founder & CEO at TrepScore

Much like baseball, building a business starts with a pitch. Whether it’s explaining to your boss (or your family) why you’re quitting or convincing someone to join your team, you are pitching your business idea. Considering how important it is, I’m astounded at how many entrepreneurs neglect to craft and practice their startup pitch and do it poorly.

I have been crafting pitches for years, hundreds of them, and I’ve come to learn a few approaches that work very well.

Respect the formula:

Every pitch has very distinct parts to it. For investors, there are popular ten slide templates, which are great, but here are the three that matter: 1) the problem that you are solving; 2) your solution; and 3) the market that it relates to. And you need to really refine the market (no one likes hearing about 2 trillion dollar markets)

Keep your startup pitch simple:

This goes for all of your pitches but it is especially critical to state the problem and your solution as simply as possible. You frame the entire pitch, and the ensuing conversation, at that moment. If you get that point across and it resonates, you can fill all the details later. Trust me, there will be time. Albert Einstein said it best, “if you can’t explain it simply, you don’t know it well enough”

Convey your idea visually:

Remember the old cartoon with the cat and the mouse, Tom and Jerry? In each episode Tom (the cat) would construct a plan to capture and eat Jerry (the mouse). What does that have to do with pitching? Well, Tom was a master ideator but he could also create a one page blueprint that would clearly show what he was planning and how he was going to achieve his goal. Though he never got to eat Jerry, Tom certainly did catch him quite often. Tom showed his entire business plan on one sheet of paper and humans ranging from age 3 up got it in an instant.

Begin your startup pitch journey with this simple goal; try to illustrate your business in pictures. People understand and love images, use them to your advantage.

Let personality and passion show:

A pitch can convey to potential investors that you have a great idea that solves big problem in a big market. But after that is established, investors look for reasons to NOT do a deal, like evaluating the entrepreneur to see if he or she truly enjoys what they are doing. Make sure your pitch reflects your personality and passion, which mostly involves remembering why you started the business in the first place business. If you aren’t passionate about what you do, no one else will be either.

Take Batting Practice:

Never forget the power of practice. Just like a baseball player takes warm-up swings before a game, an entrepreneur should practice ways to pitch their idea every day. Grab a co-worker, a team member, a cab driver, a co-founder and give them the pitch as often as possible when you aren’t pitching in front of actual investors. You should also just pitch yourself, recording or filming some of your practice pitches. It will help more than you can imagine.

You must be able to convey your idea verbally, in writing, and even visually. Apply these 5 simple tips, improve your pitch, and become the Startup CEO or Co-Founder an investor wants to work with.

U of Alberta 140618-emerald-awards-ualberta-sign-teaserIf two heads are better than one, three heads will no doubt be revolutionary. That is what University of Alberta professors Carlo Montemagno, Thomas Thundat and Gane Wong are aiming for.
“The path to discovery lies beyond conventional thinking and the siloed approaches that have hampered our progress thus far,” says Ingenuity Lab Director, Carlo Montemagno, PhD. “By acknowledging the interconnectedness of our systems and facilitating better research integration and the cross pollination of ideas, we give ourselves, and society as a whole, a much better chance of success.”
Whether it is in the oil patch or in the operating room, these heavy hitters will be merging their expertise and research together in the areas of single cell genomics research in breast and prostate cancer and novel physical, chemical and biological detection using micro- and nano- mechanical sensors.
“The purpose of an accelerator is to bring the right people together at the right time,” explains Thundat. “In doing so, we leverage unique knowledge and expertise and significantly boost our ability to develop tangible solutions to the world’s most complex challenges.”
The 10-year provincially funded initiative was launched in November 2013 and is attracting the best and brightest minds from around the world. With a research agenda focused on the province’s most pressing environmental, industrial and health challenges, Ingenuity Lab is a partnership with the University of Alberta and Alberta Innovates Technology Futures and is expected to reach over $100M in funds leveraged from industry partners over the next decade.vnDpjc0OLw.JPG
“Our hope is that this partnership will help reduce the existing gap between research and development, and end user application,” says Wong. “For example, we have a unique opportunity to engineer and equip industries with next generation tools and resources that will far surpass those currently available.”
The dynamic partnership promises to facilitate deeper learning, critical thinking and enhance networking opportunities. It will also contribute to our province’s competitive advantage by maximising the utility of local resources and channelling existing expertise towards shared goals.
“We are fortunate to have such a dynamic team of influential leaders in our midst,” says Dr. Lorne Babiuk, Vice President of Research at the University of Alberta. “These outstanding individuals have made remarkable progress in their fields and continue to champion leading-edge research, teaching, and learning across our campus and beyond.”
Profiles
Carlo Montemagno, PhD, is the Director of Ingenuity Lab, Professor in the Department of Chemical and Materials Engineering at the University of Alberta, AITF Strategic Chair of Bionanotechnology, Canada Research Chair in Intelligent Nanosystems and Program Lead of Biomaterials at the National Institute for Nanotechnology (NINT), and is a world-renowned expert in nanotechnology and is responsible for creating groundbreaking innovations in the areas of informatics, agriculture, chemical refining, transportation, energy, and healthcare. He is Canada Research Chair in Intelligent Nanosystems; named a Bill & Melinda Gates Grand Challenge Winner; and has been recognized with many other prestigious awards including the Feynman Prize; the Earth Award Grand Prize; and the CNBC Business Top 10 Green Innovator award.
Thomas Thundat, PhD, has a wealth of experience in novel physical, chemical and biological detection using micro- and nano- mechanical sensors. His research is contributing to the development of sustainable techniques for oil sands recovery and he currently serves as Canada Excellence Research Chair (CERC) in Oil Sands Molecule Engineering. Thundat is one of just 26 professors across Canada holding CERC honors and has authored over 285 publications in refereed journals, 48 book chapters, and has more than 30 patents to his credit.
Gane Wong, PhD, holds joint appointments in the Department of Biological Sciences and the Department of Medicine at the University of Alberta, and is the Alberta Innovates Technology Futures/AITF Strategic Chair in Biosystems Informatics. He specializes in genomics and bioinformatics and is best known for starting the world’s largest DNA sequencing organization in 1999. Based in China, BGI-Shenzhen has grown to include more than 5000 people to date and is poised to expand even further. Wong has an impressive portfolio of collaborators around the globe and wealth of experience in agriculture, neuroscience, infectious disease, and cancer research.
Source: Ingenuity Lab

nist-atom-spin-14pml029_spin_symmetry_lrJust as diamonds with perfect symmetry may be unusually brilliant jewels, the quantum world has a symmetrical splendor of high scientific value.

Confirming this exotic quantum physics theory, JILA physicists led by theorist Ana Maria Rey and experimentalist Jun Ye have observed the first direct evidence of symmetry in the magnetic properties—or nuclear “spins”—of atoms. The advance could spin off practical benefits such as the ability to simulate and better understand exotic materials exhibiting phenomena such as superconductivity (electrical flow without resistance) and colossal magneto-resistance (drastic change in electrical flow in the presence of a magnetic field).

 

spin symmetry

Illustration of symmetry in the magnetic properties—or nuclear spins—of strontium atoms. JILA researchers observed that if two atoms have the same nuclear spin state (top), they interact weakly, and the interaction strength does not depend on which of the 10 possible nuclear spin states are involved. If the atoms have different nuclear spin states (bottom), they interact much more strongly, and, again, always with the same strength.
Credit: Ye and Rey groups and Steve Burrows/JILA
View hi-resolution image

The JILA discovery, described in Science Express,* was made possible by the ultra-stable laser used to measure properties of the world’s most precise and stable atomic clock.** JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.NIST 580303_10152072709285365_1905986131_n

“Spin symmetry has a very strong impact on materials science, as it can give rise to unexpected behaviors in quantum matter,” JILA/NIST Fellow Jun Ye says. “Because our clock is this good—really it’s the laser that’s this good—we can probe this interaction and its underlying symmetry, which is at a very small energy scale.”

The global quest to document quantum symmetry looks at whether key properties remain the same despite various exchanges, rotations or reflections. For example, matter and antimatter demonstrate fundamental symmetry: Antimatter behaves in many respects like normal matter despite having the charges of positrons and electrons reversed.

To detect spin symmetry, JILA researchers used an atomic clock made of 600 to 3,000 strontium atoms trapped by laser light. Strontium atoms have 10 possible nuclear spin configurations (also referred to as angular momentum), which influences magnetic behavior. In a collection of clock atoms there is a random distribution of all 10 states.

The researchers analyzed how atom interactions—their collisions—at the two electronic energy levels used as the clock “ticks” were affected by the spin state of the atoms’ nuclei. In most atoms, the electronic and nuclear spin states are coupled, so atom collisions depend on both electronic and nuclear states. But in strontium, the JILA team predicted and confirmed that this coupling vanishes, giving rise to collisions that are independent of nuclear spin states.

In the clock, all the atoms tend to be in identical electronic states. Using lasers and magnetic fields to manipulate the nuclear spins, the JILA researchers observed that, when two atoms have different nuclear spin states, no matter which of the 10 states they have, they will interact (collide) with the same strength. However, when two atoms have the same nuclear spin state, regardless of what that state is, they will interact much more weakly.

“Spin symmetry here means atom interactions, at their most basic level, are independent of their nuclear spin states,” Ye explains. “However, the intriguing part is that while the nuclear spin does not participate directly in the electronic-mediated interaction process, it still controls how atoms approach each other physically. This means that, by controlling the nuclear spins of two atoms to be the same or different, we can control interactions, or collisions.”

The new research adds to understanding of atom collisions in atomic clocks documented in previous JILA studies.*** Further research is planned to engineer specific spin conditions to explore novel quantum dynamics of a large collection of atoms.

JILA theorist Ana Maria Rey made key predictions and calculations for the study. Theorists at the University of Innsbruck in Austria and the University of Delaware also contributed. Funding was provided by NIST, the National Science Foundation, the Air Force Office of Scientific Research, and the Defense Advanced Research Projects Agency.

*X. Zhang, M. Bishof, S.L. Bromley, C.V. Kraus, M.S. Safronova, P. Zoller, A.M. Rey, J. Ye. Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism. Science Express. Published online Aug. 21, 2104.
**See Jan. 22, 2014, Tech Beat article, “JILA Strontium Atomic Clock Sets New Records in Both Precision and Stability,” at www.nist.gov/pml/div689/20140122_strontium.cfm.
***See 2011 NIST news release “Quantum Quirk: JILA Scientists Pack Atoms Together to Prevent Collisions in Atomic Clock,” at www.nist.gov/pml/div689/jila-020311.cfm; and 2009 NIST news release “JILA/NIST Scientists Get a Grip on Colliding Fermions to Enhance Atomic Clock Accuracy,” at www.nist.gov/pml/div689/fermions_041609.cfm.

MIT Comp Chips 2-physicistsfiWhen moving through a conductive material in an electric field, electrons tend to follow the path of least resistance—which runs in the direction of that field.

But now physicists at MIT and the University of Manchester have found an unexpectedly different behavior under very specialized conditions—one that might lead to new types of transistors and electronic circuits that could prove highly energy-efficient.

They’ve found that when a sheet of —a two-dimensional array of pure carbon—is placed atop another two-dimensional material, instead move sideways, perpendicular to the electric field. This happens even without the influence of a magnetic field—the only other known way of inducing such a sideways flow.

What’s more, two separate streams of electrons would flow in opposite directions, both crosswise to the field, canceling out each other’s electrical charge to produce a “neutral, chargeless current,” explains Leonid Levitov, an MIT professor of physics and a senior author of a paper describing these findings this week in the journal Science.

MIT Comp Chips 2-physicistsfi

Credit: Christine Daniloff/MIT

The exact angle of this current relative to the can be precisely controlled, Levitov says. He compares it to a sailboat sailing perpendicular to the wind, its angle of motion controlled by adjusting the position of the sail.

Levitov and co-author Andre Geim at Manchester say this flow could be altered by applying a minute voltage on the gate, allowing the material to function as a transistor. Currents in these materials, being neutral, might not waste much of their energy as heat, as occurs in conventional semiconductors—potentially making the new materials a more efficient basis for computer chips.

“It is widely believed that new, unconventional approaches to information processing are key for the future of hardware,” Levitov says. “This belief has been the driving force behind a number of important recent developments, in particular spintronics”—in which the spin of electrons, not their electric charge, carries information.

The MIT and Manchester researchers have demonstrated a simple transistor based on the new material, Levitov says.

“It is quite a fascinating effect, and it hits a very soft spot in our understanding of complex, so-called topological materials,” Geim says. “It is very rare to come across a phenomenon that bridges materials science, particle physics, relativity, and topology.”

In their experiments, Levitov, Geim, and their colleagues overlaid the graphene on a layer of boron nitride—a two-dimensional material that forms a hexagonal lattice structure, as graphene does. Together, the two materials form a superlattice that behaves as a semiconductor.

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This superlattice causes electrons to acquire an unexpected twist—which Levitov describes as “a built-in vorticity”—that changes their direction of motion, much as the spin of a ball can curve its trajectory.

Electrons in graphene behave like massless relativistic particles. The observed effect, however, has no known analog in particle physics, and extends our understanding of how the universe works, the researchers say.

Whether or not this effect can be harnessed to reduce the energy used by computer chips remains an open question, Levitov concedes. This is an early finding, and while there is clearly an opportunity to reduce energy loss to heat locally, other parts of such a system may counterbalance those gains. “This is a fascinating question that remains to be resolved,” Levitov says.

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Francisco Guinea, a research professor at Spain’s Instituto de Ciencia de Materiales de Madrid, who was not connected with this research, calls the approach taken by this team “novel and imaginative. … The characterization of these currents in graphene is a very important advance in the understanding of .”

The work has great potential, Guinea adds, because “two-dimensional materials with special topological properties are the basis of new technologies for the manipulation of quantum information.”

Explore further: New species of electrons can lead to better computing

More information: ‘Detecting topological current in graphene superlattices” by R. V. Gorbachev, J. C. W. Song, G. L. Yu, A. V. Kretinin, F. Withers, Y. Cao, A. Mishchenko, I. V. Grigorieva, K. S. Novoselov, L. S. Levitov, A. K. Geim’, Science Sep 11, 2014.


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