Nanomanufacturing: path to implementing nanotechnology


carbon-nanotube(Nanowerk News) If the promise of nanotechnology is to be fulfilled, then research programs must leapfrog to new nanomanufacturing processes. That’s the conclusion of a review of the current state of nanoscience and nanotechnology to be published in the International Journal of Nanomanufacturing (“Nanomanufacturing: path to implementing nanotechnology”).
Khershed Cooper of the Materials Science and Technology Division, at the Naval Research Laboratory, in Washington, DC and Ralph Wachter of the Division of Computer and Network Systems, at the National Science Foundation, in Arlington, Virginia, USA, explain how research in nanoscience and the emerging applications in nanotechnology have led to new understanding of the properties of matter as well producing many novel materials, structures and devices.
Indeed, the list of possible applications of nanotechnology continues to grow: water filtration and purification, engineered composite materials with modified mechanical properties controlled electrical behaviour and corrosion resistance. There are nano-based materials being used as sealants, anti-fogging and abrasion resistant coatings for glass and other materials, conductive resins, paints and electromagnetic shielding as well as sensors, self-healing materials, super-hydrophobic surfaces, solar cells and ultracapacitors for energy storage as well as materials for armour and protection against bullets and bombs.
The team’s own research has focused on developing tools and techniques to make scalable processes for nanomanufacturing. They are investigating massively parallel techniques, masks and maskless processes for making 3D structures with nanoscopic features. However, they also suggest that several obstacles must be surmounted for nanotechnology to thrive as a future industrial endeavour. In particular, the team believes that research and development should be directed in the following areas:
  • – Multi-scale design, modelling and simulation of nanosystems.
  • – Component integration within large-scale systems.
  • – Integration across physical scales.
  • – Qualification, certification, verification and validation.
  • – Cyber-enabled manufacturing systems.
“Looking ahead, nanotechnology is slated to move into complex, multi-functional, multi-component nanosystems, e.g., nano-machines and nano-robots,” the team concludes. “These nanosystems will be adaptive, responsive to external stimuli, biomimetic, intelligent, smart and autonomous. Nanomanufacturing R&D will be needed to develop the knowledge base for the reliable production of these complex nanosystems.”
Source: Inderscience

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New unique nanostructure to target drug-delivery treatment of cancer cells


Human BodyA unique nanostructure developed by a team of international researchers, including those at the University of Cincinnati, promises improved all-in-one detection, diagnoses and drug-delivery treatment of cancer cells.

 

The first-of-its-kind nanostructure is unusual because it can carry a variety of cancer-fighting materials on its double-sided (Janus) surface and within its porous interior. Because of its unique structure, the nano carrier can do all of the following:

  • Transport cancer-specific detection nanoparticles and biomarkers to a site within the body, e.g., the breast or the prostate. This promises earlier diagnosis than is possible with today’s tools.
  • Attach fluorescent marker materials to illuminate specific cancer cells, so that they are easier to locate and find for treatment, whether drug delivery or surgery.
  • Deliver anti-cancer drugs for pinpoint targeted treatment of cancer cells, which should result in few drug side effects. Currently, a cancer treatment like chemotherapy affects not only cancer cells but healthy cells as well, leading to serious and often debilitating side effects.

This research, titled “Dual Surface Functionalized Janus Nanocomposites of Polystyrene//Fe304@Si02 for Simultaneous Tumor Cell Targeting and pH-Triggered Drug Release,” will be presented as an invited talk on Oct. 30, 2013, at the annual Materials Science & Technology Conference in Montreal, Canada. Researchers are Feng Wang, a former UC doctoral student and now a postdoc at the University of Houston; Donglu Shi, professor of materials science and engineering at UC’s College of Engineering and Applied Science (CEAS); Yilong Wang of Tongji University, Shanghai, China; Giovanni Pauletti, UC associate professor of pharmacy; Juntao Wang of Tongji University, China; Jiaming Zhang of Stanford University; and Rodney Ewing of Stanford University.

This recently developed Janus nanostructure is unusual in that, normally, these super-small structures (that are much smaller than a single cell) have limited surface. This makes is difficult to carry multiple components, e.g., both cancer detection and drug-delivery materials. The Janus nanocomponent, on the other hand, has functionally and chemically distinct surfaces to allow it to carry multiple components in a single assembly and function in an intelligent manner.

“In this effort, we’re using existing basic nano systems, such as carbon nanotubes, graphene, iron oxides, silica, quantum dots and polymeric nano materials in order to create an all-in-one, multidimensional and stable nano carrier that will provide imaging, cell targeting, drug storage and intelligent, controlled drug release,” said UC’s Shi, adding that the nano carrier’s promise is currently greatest for cancers that are close to the body’s surface, such as breast and prostate cancer.

If such nano technology can someday become the norm for cancer detection, it promises earlier, faster and more accurate diagnosis at lower cost than today’s technology. (Currently, the most common methods used in cancer diagnosis are magnetic resonance imaging or MRI; Positron Emission Tomography or PET; and Computed Tomography or CT imaging, however, they are costly and time consuming to use.)

In addition, when it comes to drug delivery, nano technology like this Janus structure, would better control the drug dose, since that dose would be targeted to cancer cells. In this way, anticancer drugs could be used much more efficiently, which would, in turn, lower the total amount of drug administered.

Source: University of Cincinnati

Nanotechnology techniques can improve cardiovascular implant devices


Electronics-research-001(Nanowerk News) Jeong-Yeol Yoon, associate professor of agricultural and biosystems engineering, and Dr. Marvin Slepian, professor of cardiology and biomedical engineering, collaborated to test how nanotechnology-based techniques can be used to better facilitate adhesion between tissue and implanted devices.
“When we created the nanotexture surface, we thought it could be used as a sticky surface for the implants,” Yoon says.
Cell-substrate adhesion involves the interplay of mechanical properties, surface topographic features, electrostatic charge and biochemical mechanisms. By working at the nanoscale level, Yoon was able to maximize the physical properties of the underlying substrate in promoting adhesion.
But beyond simply creating a sticky surface, the researchers’ goal was to create a selectively sticky surface, favoring endothelial cell attachment, without favoring platelet attachment, Slepian says.
The connection between Yoon, a specialist in biosensors and nanotechnology from the College of Agriculture and Life Sciences, and Slepian, co-founder and chief scientific officer of artificial-heart manufacturer SynCardia, came about by chance. A graduate student in Yoon’s lab met Slepian through their shared interest in bicycling.
“It’s very rare for the agriculture people to work with the cardiovascular people in the medical school,” Yoon says.
But their research specialties clicked.
One particular challenge to overcome in cardiovascular implants is the potential for devices – such as stents placed inside coronary arteries – to become detached as a result of blood flow, Yoon says.
“We’re particularly focused on the cardiovascular applications because there’s a blood flow involved and our system is very good when there’s a flow situation,” Yoon says.
The results of the study, published in the journal Advanced Healthcare Materials (“Nanowell-Trapped Charged Ligand-Bearing Nanoparticle Surfaces: A Novel Method of Enhancing Flow-Resistant Cell Adhesion”), reveal that the researchers’ strategy leads to enhanced endothelial cell adhesion under both static and flow conditions.
The adhesive properties derive from optimized surface texturing, electrostatic charge and cell adhesive ligands (molecular binding substances) that are uniquely assembled on the substrata surface as an ensemble of nanoparticles trapped in nanowells.
“There are lot of other people out there who use nanotechnology for improving the implants, but this is stronger than other adhesive methods using nanotechnology,” Yoon says.
“Obviously it can be used for everything else – lungs, digestive track and other systems. There are lots of other opportunities we haven’t explored,” he says.
The research is a perfect fit for Advanced Healthcare Materials, a new journal that spun off from the longstanding Advanced Materials journal.
“The use of the materials for the health care applications is probably the hottest area in materials science and engineering,” Yoon says. “We believe the journal will become even stronger than the mother journal.”
Just as the new journal marks an exciting intersection of disciplines, Yoon says the environment at the UA encourages such interdisciplinary approaches.
“I joined the University of Arizona because there are so many interdisciplinary activities going on. I see a lot of collaboration between departments in the same college at other universities, but at the University of Arizona, the environment is more open and you see collaboration across colleges,” Yoon says.
Slepian agreed, saying the pair has already filed grant applications for future work together.
“It has been fun and exciting to have an interdisciplinary collaborator,” he says.
Source: University of Arizona

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Origami Form and Nanotechnology combine to advance batteries


Nanotubes images(Nanowerk News) A combination of nanotechnology and the  traditional art of paper folding, known as origami, could be a key to a  significant step toward improved battery technologies.
Arizona State University engineers have constructed a  lithium-ion battery using paper coated with carbon nanotubes that provide  electrical conductivity.
Using an origami-folding pattern similar to how maps are folded,  they folded the paper into a stack of 25 layers, producing a compact, flexible  battery that provides significant energy density – or the amount of energy  stored in a given system or space per unit of volume of mass.
foldable battery
The  above image illustrates the architecture of a foldable lithium-ion battery ASU  engineers have constructed using paper coated with carbon nanotubes. They began  with a porous, lint-free paper towel, coated it with polyvinylidene difluoride  to improve adhesion of carbon nanotubes and then immersed the paper into a  solution of carbon nanotubes. Powders of lithium titanate oxide and lithium  cobalt oxide – standard lithium battery electrodes – are sandwiched between two  sheets of the paper. Thin foils of copper and aluminum are placed above and  below the sheets of paper to complete the battery.
Their research paper in the journal Nano Letters (“Folding Paper-Based Lithium-Ion Batteries for  Higher Areal Energy Densities”) has drawn attention from websites that focus  on news of technological breakthroughs.
The researchers have also developed a new process to incorporate  a polymer binder onto the carbon nanotube-coated paper. The polymer binder  improves adhesion of the structure’s active materials.
The achievements open up possibilities of using the origami  technique to create new forms of paper-based energy storage devices, including  batteries, light-emitting diodes, circuits and transistors, says Candace Chan,  who led the research team.
Chan is an assistant professor of materials science and  engineering in the School for Engineering of Matter, Energy and Transport, one  of ASU’s Ira A. Fulton Schools of Engineering.
Fellow ASU engineering faculty members, associate professor  Hanqing Jiang and assistant professor Hongyu Yu, have played leading roles in  the work.
We have also covered this work in our Nanowerk Spotlight series  here: Nanotechnology  researchers fabricate foldable Li-ion batteries.
Source: Arizona State University

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Solar Cell Breakthrough – 3D Graphene


072613solarThe cost of spray-on solar power could be much lower in the future after a breakthrough in dye-sensitised solar technology by a scientist at Michigan Technological University.

Yun Hang Hu, the Charles and Caroll McArthur Professor of Materials Science and Engineering, has discovered a way to replace the rare and expensive platinum normally used in dye sensitized solar cells (DSSC) with a three-dimensional form of graphene; one of the thinnest and most conductive materials in existence – without losing power generating capacity.

Hu and his team knew of graphene’s applications in solar power technology and believed that by utilising the nanomaterial’s conductive similarity to platinum, they could synthesise a version in 3D.

Hu created a chemical reaction by combining lithium oxide with carbon monoxide to form lithium carbonate (Li2CO3). When this compound was applied to standard atom-thick two-dimensional version, a honeycomb-like structure was formed. An acid is used to remove any traces of LiC203, leaving a perfect 3D structure demonstrating high conductive and catalytic activity.

The researchers then replaced the platinum counter electrode in a dye-sensitised solar cell with one made of the 3D honeycomb graphene. The cell achieved a power efficiency of 7.8 percent.

The average efficiency level of standard dye-sensitised solar cells is around 8 percent; but the promise of the technology lies in its low cost of manufacture and the ability to be sprayed or printed onto glass or ceramic surfaces.

Hu was this year awarded the McArthur Professor chair for his groundbreaking research on the use of graphene in photovoltaic systems. He says synthesising the 3D honeycomb graphene was neither expensive nor difficult and making it into a semiconductor for a solar cell posed no special challenges.

A paper describing the MTU team’s work was published in the journal Angewandte Chemie, International Edition.

Water 2.0 2013 Water Management And Nano Energy Summit


Water 2.0 open_img

2013 Water Management And Nano Energy Summit : November 13 & 14, 2013

Rice University – Shell Auditorium Jones Graduate School of Business Rice University 6100 Main Street Houston, Texas 77005

THE SUMMIT is a gathering of the world’s leading experts who are generating cutting-edge technological solutions for challenges in the water and energy sectors.

Produced in partnership with the Water Innovations Alliance, WATER 2.0, the NanoBusiness Commercialization Association, the Rice Alliance, and the Smalley Institute at Rice University, THE SUMMIT will feature prominent speakers from industry, government, finance and academia. THE SUMMIT will address state-of-the-art innovative solutions to decades-old problems in the water and oil and gas sectors. These pioneering technologies are emerging rapidly into the market thanks to revolutionary breakthroughs in material science, nanoscience and computational power.

For Full Details, Sponsors, Presenters and Exhibitors, go here: http://www.nanoevent.org/

 

 

 

Since 2009, Vincent Caprio’s Blog EVOLVING INNOVATIONS has addressed issues on Science & Technology.

About The Water Innovations Alliance Foundation The Water Innovations Alliance Foundation is focused on educating the public and key stakeholders as to new developments in fresh and waste water technologies. The Foundation works to gather data, develop reports, standards, economic analysis, and model training programs for advancing the development and deployment of new water technologies.

The Water Innovations Alliance Foundation is located in Cambridge, MA and Shelton, CT. It is a 501(c)(3) organization that works in conjunction with the Water Innovations Alliance. The Foundation was launched in Spring 2009. It is undertaking a series of initiatives to advance the understanding of new opportunities, technologies, and best practices for the water field.

To learn more about the Foundation and its membership, contact Vincent Caprio, vince@waterinnovationsfoundation.org

3D Graphene: Is It the Key to Efficeint, Low Cost Solar?


3adb215 D BurrisOne of the most promising types of solar cells has a few drawbacks. A scientist at Michigan Technological University may have overcome one of them.

Dye-sensitized solar cells are thin, flexible, easy to make and very good at turning sunshine into electricity. However, a key ingredient is one of the most expensive metals on the planet: platinum. While only small amounts are needed, at $1,500 an ounce, the cost of the silvery metal is still significant.
Yun Hang Hu, the Charles and Caroll McArthur Professor of Materials Science and Engineering, has developed a new, inexpensive material that could replace the platinum in solar cells without degrading their efficiency: 3D graphene.
Regular graphene is a famously two-dimensional form of carbon just a molecule or so thick. Hu and his team invented a novel approach to synthesize a unique 3D version with a honeycomb-like structure. To do so, they combined lithium oxide with carbon monoxide in a chemical reaction that forms lithium carbonate (Li2CO3) and the honeycomb graphene.
The Li2CO3 helps shape the graphene sheets and isolates them from each other, preventing the formation of garden-variety graphite.  Furthermore, the Li2CO3 particles can be easily removed from 3D honeycomb-structured graphene by an acid.
The researchers determined that the 3D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion.
So they replaced the platinum counter electrode in a dye-sensitized solar cell with one made of the 3D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.
The cell with the 3D graphene counter electrode converted 7.8 percent of the sun’s energy into electricity, nearly as much as the conventional solar cell using costly platinum (8 percent).
Synthesizing the 3D honeycomb graphene is neither expensive nor difficult, said Hu, and making it into a counter electrode posed no special challenges.
The research has been funded by the American Chemical Society Petroleum Research Fund (PRF-51799-ND10) and the National Science Foundation (NSF-CBET-0931587).
The article describing the work, “3D Honeycomb-Like Structured Graphene and Its High Efficiency as a Counter-Electrode Catalyst for Dye-Sensitized Solar Cells,” coauthored by Hu, Michigan Tech graduate student Hui Wang, Franklin Tao of the University of Notre Dame, Dario J. Stacchiola of Brookhaven National Laboratory and Kai Sun of the University of Michigan, was published online July 29 in the journal Angewandte Chemie, International Edition.
Michigan Technological University (www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 130 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.

“Programmable Matter” using Nanocrystals


When University of Pennsylvania nano-scientists created beautiful, tiled patterns with flat nano-crystals, they were left with a mystery: why did some sets of crystals arrange themselves in an alternating, herringbone style, even though it wasn’t the simplest pattern? To find out, they turned to experts in computer simulation at the University of Michigan and the Massachusetts Institute of Technology.

7-pennresearch

These transmission electron microscope images show the two different patterns the nano-crystals could be made to pack in. 

The result gives nanotechnology researchers a new tool for controlling how objects one-millionth the size of a grain of sand arrange themselves into useful materials, it gives a means to discover the rules for “programming” them into desired configurations.

The study was led by Christopher Murray, a professor with appointments in the Department of Chemistry in the School of Arts and Sciences and the Department of Materials Science and Engineering in the School of Engineering and Applied Sciences. Also on the Penn team were Cherie Kagan, a chemistry, MSE and electrical and systems engineering professor, and postdoctoral researchers Xingchen Ye, Jun Chen and Guozhong Xing. 

They collaborated with Sharon Glotzer, a professor of chemical engineering at Michigan, and Ju Li, a professor of nuclear science and engineering at MIT.

Their research was featured on the cover of the journal Nature Chemistry.

“The excitement in this is not in the herringbone pattern,” Murray said, “It’s about the coupling of experiment and modeling and how that approach lets us take on a very hard problem.”

Previous work in Murray’s group has been focused on creating and arranging them into larger crystal . Ultimately, researchers want to modify patches on in different ways to coax them into more complex patterns. The goal is developing “programming matter,” that is, a method for designing based on the properties needed for a particular job.

“By engineering interactions at the nanoscale,” Glotzer said, “we can begin to assemble target structures of great complexity and functionality on the macroscale.”

Glotzer introduced the concept of nanoparticle “patchiness” in 2004. Her group uses computer simulations to understand and design the patches.

Recently, Murray’s team made patterns with flat nanocrystals made of heavy metals, known to chemists as lanthanides, and fluorine atoms. Lanthanides have valuable properties for solar energy and medical imaging, such as the ability to convert between high- and low-energy light.

They started by breaking down chemicals containing atoms of a lanthanide metal and fluorine in a solution, and the lanthanide and fluorine naturally began to form crystals. Also in the mix were chains of carbon and hydrogen that stuck to the sides of the crystals, stopping their growth at sizes around 100 nanometers, or 100 millionths of a millimeter, at the largest dimensions. By using lanthanides with different atomic radii, they could control the top and bottom faces of the hexagonal crystals to be anywhere from much longer than the other four sides to non-existent, resulting in a diamond shape.

To form tiled patterns, the team purified the nano-crystals and mixed them with a solvent. They spread this mixture in a thin layer over a thick fluid, which supported the crystals while allowing them to move. As the solvent evaporated, the crystals had less space available, and they began to pack together.

The diamond shapes and the very long hexagons lined up as expected, the diamonds forming an argyle-style grid and the hexagons matching up their longest edges like a foreshortened honeycomb. The hexagons whose sides were all nearly the same length should have formed a similar squashed honeycomb pattern, but, instead, they lined up in an alternating herringbone style.

“Whenever we see something that isn’t taking the simplest pattern possible, we have to ask why,” Murray said.

They posed the question to Glotzer’s team.

“They’ve been world leaders in understanding how these shapes could work on nanometer scales, and there aren’t many groups that can make the crystals we make,” Murray said. “It seemed natural to bring these strengths together.”

Glotzer and her group built a computer model that could recreate the self-assembly of the same range of shapes that Murray had produced. The simulations showed that if the equilateral hexagons interacted with one another only through their shapes, most of the crystals formed the foreshortened honeycomb pattern, not the herringbone.

“That’s when we said, ‘Okay, there must be something else going on. It’s not just a packing problem,'” Glotzer said. Her team, which included graduate student Andres Millan and research scientist Michael Engel, then began playing with interactions between the edges of the particles. They found that that if the edges that formed the points were stickier than the other two sides, the hexagons would naturally arrange in the herringbone pattern.

The teams suspected that the source of the stickiness was those carbon and hydrogen chains. Perhaps they attached to the point edges more easily, the team members thought. Since experiment doesn’t yet offer a way to measure the number of hydrocarbon chains on the sides of such tiny particles, Murray asked MIT’s Ju Li to calculate how the chains would attach to the edges at a quantum mechanical level.

Li’s group confirmed that, because of the way that the different facets cut across the lattice of the metal and fluorine atoms, more hydrocarbon chains could stick to the four edges that led to points than the remaining two sides. As a result, the particles become patchy.

“Our study shows a way forward making very subtle changes in building block architecture and getting a very profound change in the larger self-assembled pattern,” Glotzer said. “The goal is to have knobs that you can change just a little and get a big change in structure, and this is one of the first papers that shows a way forward for how to do that.”

 

 

 

 

Ordered intermetallic core-shell nanocatalysts are promising designs for fuel cells


201306047919620(Nanowerk Spotlight) The Proton Exchange Membrane Fuel  Cells (PEMFC) are certainly promising as energy efficient devices to run  vehicles in a less polluted way. They can burn fuel in such a clean way that the  exhaust would contain nothing but water and dissipated heat.

If fuel cells are  such cool devices empowering next generation automotives then why have they not  yet been commercialized?   The problem lies at the heart of the chemical reactions taking  place inside a fuel cell and unfortunately, they are inherently sluggish. We  need catalysts to make these reactions happen faster.

Platinum, even today, is  being thought of as a wonder catalyst. But such an idea is nothing but  impractical. Simply because platinum metal is scarce, overly expensive and  despite using it in a fuel cell the reactions are still slow.

Fuel cells would  still be expensive, even if we replace big chuncks of platinum metal with an  assemblage of tiny platinum nanoparticles. Hence, a real practical solution  needs to be found in terms of designing nanocatalysts that not just accelerate  the reactions much faster compared to platinum but, are cheaper and durable.  

With this principal motivation, we – researchers at the  Department of Materials Science and Engineering, McMaster University, Canada –   collaborated with Dr. Christina Bock (National Research Council, Ottawa, Canada)  in characterizing platinum-iron alloy nanocatalysts that were found to have the  best catalytic activity among other similar systems reported so far. The work  has been published in the June 17, 2013 online edition of ACS Nano (“Strained Lattice with Persistent Atomic Order in  Pt3Fe2 Intermetallic Core–Shell Nanocatalysts”).

Iron is substantially cheaper than platinum. So, how about  substituting platinum with iron in such a way that in addition to making these  catalysts significantly cheaper, we also achieve a much better activity and  catalytic durability? With this idea, Dr. Bock looked beyond disordered systems  that were reported in the past and synthesized them in a very different way so  as to make them ordered.

About 10,000 electrochemical cycles were run to assess  their activity and it was found that they were not just very active compared to  pure platinum but, remained highly durable during these cycles. But why? We were  puzzled by these results and wanted to explore the reason at an atomic-level.   We studied this using one of the most advanced electron  microscopes in the world, hosted at the Canadian Center for Electron Microscopy (CCEM), McMaster  University.

“This microscope is so powerful that we can easily identify  individual atoms, measure their chemical state, and even probe the electrons  that bind them together,” says Dr. Gianluigi Botton, the scientific director of  CCEM and the senior author of the paper. “When we observed the as-prepared  catalysts – average size of 3.19 nm – under the microscope we found that they  had an ordered intermetallic core encapsulated within a bilayer thick platinum  rich shell.”

intermetallic coreshell nanocatalyst Left:  STEM-HAADF image of Pt3Fe2 intermetallic coreshell (IMCS) nanocatalyst showing  alternating bright and dark intensities for Pt and Fe atomic columns,  respectively, at the core. Right: Three-dimensional model of a typical IMCS  nanocatalyst. Pt and Fe atoms are represented by gray and yellow, respectively.  (Reprinted with permission from American Chemical Society)  

These are the newest members to platinum-iron alloy  nanocatalysts with such intermetallic core-shell (IMCS) design. Furthermore, on  characterizing them after 10,000 cycles we still found them to retain their  structural ordering at the core while the platinum shell got thicker and  thicker.   Such a static core-dynamic shell (SCDS) regime is being reported  for the first time. While the observed enhancement in the activity is attributed  to their strained lattice, our findings on the degradation kinetics establish  that their extended catalytic durability is attributable to a sustained atomic  order.

Although our work was specific to platinum-iron IMCS designs,  the findings carry much broader implications to understand why and how an  ordered IMCS design is better and cost-efficient compared to disordered  core-shell nanocatalysts.

In summary, ordered intermetallic core-shell nanocatalysts are  highly promising designs to realize future fuel cell vehicles and fine-tuning  them at an atomic-scale is a great leap forward.                     

By Sagar Prabhudev, Microscopy of Nanoscale Materials Research Group, McMaster  University

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Graphene on its way to conquer Silicon Valley


QDOTS imagesCAKXSY1K 8Nanowerk News) The remarkable material graphene  promises a wide range of applications in future electronics that could  complement or replace traditional silicon technology. Researchers of the  Electronic Properties of Materials Group at the University of Vienna have now  paved the way for the integration of graphene into the current silicide based  technology. They have published their results in the new open access journal of  the Nature Publishing group, Scientific Reports (“Controlled assembly of graphene-capped nickel, cobalt and iron  silicides”).
graphene layers
The  above images were taken with the spectroscopy method ARPES while NiSi was formed  under the graphene layer. In the final image (d) scientists can identify a  particular spectrum (the linear Dirac-like spectrum of grapheme electrons)  indicating that the graphene interacts only weakly with the metal silicides and  therefore preserves its unique properties.
The unique properties of graphene such as its incredible  strength and, at the same time, its little weight have raised high expectations  in modern material science. Graphene, a two-dimensional crystal of carbon atoms  packed in a honeycomb structure, has been in the focus of intensive research  which led to a Nobel Prize of Physics in 2010. One major challenge is to  successfully integrate graphene into the established metal-silicide technology.  Scientists from the University of Vienna and their co-workers from research  institutes in Germany and Russia have succeeded in fabricating a novel structure  of high-quality metal silicides all nicely covered and protected underneath a  graphene layer. These two-dimensional sheets are as thin as single atoms.
Following Einstein’s footsteps
In order to uncover the basic properties of the new structure  the scientists need to resort to powerful measurement techniques based on one of  Einstein’s brilliant discoveries – the photoelectric effect. When a light  particle interacts with a material it can transfer all its energy to an electron  inside that material. If the energy of the light is sufficiently large, the  electron acquires enough energy to escape from the material. Angle-resolved  photoemission spectroscopy (ARPES) enables the scientists to extract valuable  information on the electronic properties of the material by determining the  angle under which the electrons escape from the material.
“Single-atom thick layers and hybrid materials made thereof  allow us to study a wealth of novel electronic phenomena and continue to  fascinate the community of material scientists. The ARPES method plays a key  role in these endeavours”, say Alexander Grueneis and Nikolay Verbitskiy, members of the  Electronic Properties of Materials Group at the University of Vienna and  co-authors of the study.
Graphene keeping its head up high
The graphene-capped silicides under investigation are reliably  protected against oxidation and can cover a wide range of electronic materials  and device applications. Most importantly, the graphene layer itself barely  interacts with the silicides underneath and the unique properties of graphene  are widely preserved. The work of the research team, therefore, promises a  clever way to incorporate graphene with existing metal silicide technology which  finds a wide range of applications in semiconductor devices, spintronics,  photovoltaics and thermoelectrics.
The work on graphene related materials is financed by a Marie  Curie fellowship of the European commission and an APART fellowship of the  Austrian Academy of Sciences.
Source: University of Vienna

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