McMaster University: Researchers resolve problem holding back a Technology Revolution – Smaller, Nimbler Semiconductors that are expected to Replace Silicon – Carbon Nanotubes


 

mcmasterrese carbon nanotubes 081916Artistic rendition of a metallic carbon nanotube being pulled into solution, in analogy to the work described by the Adronov group. Credit: Alex Adronov, McMaster University

Imagine an electronic newspaper that you could roll up and spill your coffee on, even as it updated itself before your eyes.

It’s an example of the that has been waiting to happen, except for one major problem that, until now, scientists have not been able to resolve.

Researchers at McMaster University have cleared that obstacle by developing a new way to purify nanotubes – the smaller, nimbler semiconductors that are expected to replace silicon within computer chips and a wide array of electronics.

“Once we have a reliable source of pure nanotubes that are not very expensive, a lot can happen very quickly,” says Alex Adronov, a professor of Chemistry at McMaster whose research team has developed a new and potentially cost-efficient way to purify carbon nanotubes.

Carbon nanotubes – hair-like structures that are one billionth of a metre in diameter but thousands of times longer – are tiny, flexible conductive nano-scale materials, expected to revolutionize computers and electronics by replacing much larger silicon-based chips.

A major problem standing in the way of the new technology, however, has been untangling metallic and semiconducting carbon nanotubes, since both are created simultaneously in the process of producing the microscopic structures, which typically involves heating carbon-based gases to a point where mixed clusters of nanotubes form spontaneously as black soot.

Only pure semiconducting or metallic carbon nanotubes are effective in device applications, but efficiently isolating them has proven to be a challenging problem to overcome. Even when the nanotube soot is ground down, semiconducting and metallic nanotubes are knotted together within each grain of powder. Both components are valuable, but only when separated.

Researchers around the world have spent years trying to find effective and efficient ways to isolate carbon nanotubes and unleash their value.

While previous researchers had created polymers that could allow semiconducting carbon nanotubes to be dissolved and washed away, leaving metallic nanotubes behind, there was no such process for doing the opposite: dispersing the metallic nanotubes and leaving behind the semiconducting structures.Nanotubes images

Now, Adronov’s research group has managed to reverse the electronic characteristics of a polymer known to disperse semiconducting nanotubes – while leaving the rest of the polymer’s structure intact. By so doing, they have reversed the process, leaving the nanotubes behind while making it possible to disperse the metallic nanotubes.

The researchers worked closely with experts and equipment from McMaster’s Faculty of Engineering and the Canada Centre for Electron Microscopy, located on the university’s campus.

“There aren’t many places in the world where you can to this type of interdisciplinary work,” Adronov says.

The next step, he explains, is for his team or other researchers to exploit the discovery by finding a way to develop even more efficient polymers and scale up the process for commercial production.

The research is described in the cover story of Chemistry – A European Journal.

Explore further: Carbon nanotube ‘ink’ may lead to thinner, lighter transistors and solar cells

 

GNT Thumbnail Alt 3 2015-page-001

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McMaster University Develops Lightweight, High Density (Power) and Faster Recharging Nano- Cellulose Material: Applications in Wearable Devices, Portable Power Sources and Hybrid Vehicles


McMaster Cellulose 151006132027_1_540x360McMaster University: Summary: New work demonstrates an improved three-dimensional energy storage device constructed by trapping functional nanoparticles within the walls of a foam-like structure made of nanocellulose. The foam is made in one step and can be used to produce more sustainable capacitor devices with higher power density and faster charging abilities compared to rechargeable batteries. This development paves the way towards the production of lightweight, flexible, and high-power electronics for application in wearable devices, portable power sources and hybrid vehicles.

McMaster Engineering researchers Emily Cranston and Igor Zhitomirsky are turning trees into energy storage devices capable of powering everything from a smart watch to a hybrid car.

The scientists are using cellulose, an organic compound found in plants, bacteria, algae and trees, to build more efficient and longer-lasting energy storage devices or supercapacitors. This development paves the way toward the production of lightweight, flexible, and high-power electronics, such as wearable devices, portable power supplies and hybrid and electric vehicles.

“Ultimately the goal of this research is to find ways to power current and future technology with efficiency and in a sustainable way,” says Cranston, whose joint research was recently published in Advanced Materials. “This means anticipating future technology needs and relying on materials that are more environmentally friendly and not based on depleting resources.

Cellulose offers the advantages of high strength and flexibility for many advanced applications; of particular interest are nanocellulose-based materials. The work by Cranston, an assistant chemical engineering professor, and Zhitomirsky, a materials science and engineering professor, demonstrates an improved three-dimensional energy storage device constructed by trapping functional nanoparticles within the walls of a nanocellulose foam.

The foam is made in a simplified and fast one-step process. The type of nanocellulose used is called cellulose nanocrystals and looks like uncooked long-grain rice but with nanometer-dimensions. In these new devices, the ‘rice grains’ have been glued together at random points forming a mesh-like structure with lots of open space, hence the extremely lightweight nature of the material. This can be used to produce more sustainable capacitor devices with higher power density and faster charging abilities compared to rechargeable batteries.

Lightweight and high-power density capacitors are of particular interest for the development of hybrid and electric vehicles. The fast-charging devices allow for significant energy saving, because they can accumulate energy during braking and release it during acceleration.

“I believe that the best results can be obtained when researchers combine their expertise,” Zhitomirsky says. “Emily is an amazing research partner. I have been deeply impressed by her enthusiasm, remarkable ability to organize team work and generate new ideas.”


Story Source:

The above post is reprinted from materials provided by McMaster University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Xuan Yang, Kaiyuan Shi, Igor Zhitomirsky, Emily D. Cranston. Cellulose Nanocrystal Aerogels as Universal 3D Lightweight Substrates for Supercapacitor Materials. Advanced Materials, 2015; DOI: 10.1002/adma.201502284

McMaster University: From trees to power: McMaster Engineers Build a Better Energy Storage Device (Capacitors)


McMasters fromtreestopMcMaster Engineering researchers Emily Cranston and Igor Zhitomirsky are turning trees into energy storage devices capable of powering everything from a smart watch to a hybrid car.

The scientists are using cellulose, an organic compound found in plants, bacteria, algae and trees, to build more efficient and longer-lasting or capacitors. This development paves the way toward the production of lightweight, flexible, and high-power electronics, such as wearable devices, portable power supplies and hybrid and electric vehicles.

“Ultimately the goal of this research is to find ways to power current and with efficiency and in a sustainable way,” says Cranston, whose joint research was recently published in Advanced Materials. “This means anticipating future technology needs and relying on materials that are more environmentally friendly and not based on depleting resources.

Cellulose offers the advantages of high strength and flexibility for many advanced applications; of particular interest are nanocellulose-based materials. The work by Cranston, an assistant chemical engineering professor, and Zhitomirsky, a materials science and engineering professor, demonstrates an improved three-dimensional device constructed by trapping functional nanoparticles within the walls of a nanocellulose foam.

The foam is made in a simplified and fast one-step process. The type of nanocellulose used is called cellulose nanocrystals and looks like uncooked long-grain rice but with nanometer-dimensions. In these new devices, the ‘rice grains’ have been glued together at random points forming a mesh-like structure with lots of open space, hence the extremely lightweight nature of the material. This can be used to produce more sustainable capacitor devices with higher power density and faster charging abilities compared to rechargeable batteries.

Lightweight and high-power density capacitors are of particular interest for the development of hybrid and . The fast-charging devices allow for significant energy saving, because they can accumulate energy during braking and release it during acceleration.

“I believe that the best results can be obtained when researchers combine their expertise,” Zhitomirsky says. “Emily is an amazing research partner. I have been deeply impressed by her enthusiasm, remarkable ability to organize team work and generate new ideas.”

Explore further: Engineers craft new material for high-performing ‘supercapacitors’

More information: Cellulose Nanocrystal Aerogels as Universal 3D Lightweight Substrates for Supercapacitor Materials, DOI: 10.1002/adma.201502284

Breakthrough in Nanotechnology is a BIG DEAL for Electronics


201306047919620University of Akron researchers have developed new materials that function on a nanoscale, which could lead to the creation of lighter laptops, slimmer televisions and crisper smartphone visual displays.

 

Known as “giant surfactants” – or surface films and liquid solutions – the researchers, led by Stephen Z.D. Cheng, dean of UA’s College of Polymer Science and Polymer Engineering, used a technique known as nanopatterning to combine functioning molecular nanoparticles with polymers to build these novel materials.

The giant surfactants developed at UA are large, similar to macromolecules, yet they function like molecular surfactants on a nanoscale, Cheng says. The outcome? Nanostructures that guide the size of electronic products.

More efficient designs possible Nanopatterning, or self-assembling molecular materials, is the genius behind the small, light and fast world of modern-day gadgetry, and now it has advanced one giant step thanks to the UA researchers who say these new materials, when integrated into electronics, will enable the development of ultra-lightweight, compact and efficient devices because of their unique structures.

During their self-assembly, molecules form an organized lithographic pattern on semiconductor crystals, for use as integrated circuits. Cheng explains that these self-assembling materials differ from common block copolymers (a portion of a macromolecule, comprising manyunits, that has at least one feature which is not present in the adjacent portions) because they organize themselves in a controllable manner at the molecular level.

“The IT industry wants microchips that are as small as possible so that they can manufacture smaller and faster devices,” says Cheng, who also serves as the R.C. Musson and Trustees Professor of Polymer Science at UA.

He points out that the current technique can produce the spacing of 22 nanometers only, and cannot go down to the 10 nanometers or less necessary to create tiny, yet mighty, devices. The giant surfactants, however, can dictate smaller-scale electronic components.

“This is exactly what we are pursuing – self-assembling materials that organize at smaller sizes, say, less than 20 or even 10 nanometers,” says Cheng, equating 20 nanometers to 1 /4,000th the diameter of a human hair.

Team work has commercial applications

An international team of experts, including George Newkome, UA vice president for research, dean of the Graduate School, and professor of polymer science at UA; Er-Qiang Chen of Peking University in China; Rong-Ming Ho of National Tsinghua University in Taiwan; An-Chang Shi of McMaster University in Canada; and several doctoral and postdoctoral researchers from Cheng’s group, have shown how well-ordered nanostructures in various states, such as in thin films and in solution, offer extensive applications in nanotechnology.

The team’s study is highlighted in a pending patent application through the University of Akron Research Foundation and in a recent journal article, “Giant surfactants provide a versatile platform for sub-10-nm nanostructure engineering” published in Proceedings of the National Academy of Sciences of the United States of America (110, 10078-10083, 2013).

“These results are not only of pure scientific interest to the narrow group of scientists, but also important to a broad range of industry people,” says Cheng, noting that his team is testing real-world applications in nanopatterning technologies and hope to see commercialization in the future.

Gadget Genius: Nanotechnology Breakthrough Is Big Deal for Electronics


201306047919620July 26, 2013 — University of Akron researchers have developed new materials that function on a nanoscale, which could lead to the creation of lighter laptops, slimmer televisions and crisper smartphone visual displays

Known as “giant surfactants” — or surface films and liquid solutions — the researchers, led by Stephen Z.D. Cheng, dean of UA’s College of Polymer Science and Polymer Engineering, used a technique known as nanopatterning to combine functioning molecular nanoparticles with polymers to build these novel materials.

The giant surfactants developed at UA are large, similar to macromolecules, yet they function like molecular surfactants on a nanoscale, Cheng says. The outcome? Nanostructures that guide the size of electronic products.

More efficient designs possible

Nanopatterning, or self-assembling molecular materials, is the genius behind the small, light and fast world of modern-day gadgetry, and now it has advanced one giant step thanks to the UA researchers who say these new materials, when integrated into electronics, will enable the development of ultra-lightweight, compact and efficient devices because of their unique structures.

During their self-assembly, molecules form an organized lithographic pattern on semiconductor crystals, for use as integrated circuits. Cheng explains that these self-assembling materials differ from common block copolymers (a portion of a macromolecule, comprising manyunits, that has at least one feature which is not present in the adjacent portions) because they organize themselves in a controllable manner at the molecular level.

“The IT industry wants microchips that are as small as possible so that they can manufacture smaller and faster devices,” says Cheng, who also serves as the R.C. Musson and Trustees Professor of Polymer Science at UA.

He points out that the current technique can produce the spacing of 22 nanometers only, and cannot go down to the 10 nanometers or less necessary to create tiny, yet mighty, devices. The giant surfactants, however, can dictate smaller-scale electronic components.

“This is exactly what we are pursuing — self-assembling materials that organize at smaller sizes, say, less than 20 or even 10 nanometers,” says Cheng, equating 20 nanometers to 1 /4,000th the diameter of a human hair.

Team’s work has commercial applications

An international team of experts, including George Newkome, UA vice president for research, dean of the Graduate School, and professor of polymer science at UA; Er-Qiang Chen of Peking University in China; Rong-Ming Ho of National Tsinghua University in Taiwan; An-Chang Shi of McMaster University in Canada; and several doctoral and postdoctoral researchers from Cheng’s group, have shown how well-ordered nanostructures in various states, such as in thin films and in solution, offer extensive applications in nanotechnology.

The team’s study is highlighted in a pending patent application through the University of Akron Research Foundation and in a recent journal article, “Giant surfactants provide a versatile platform for sub-10-nm nanostructure engineering” published in Proceedings of the National Academy of Sciences of the United States of America (110, 10078-10083, 2013).

“These results are not only of pure scientific interest to the narrow group of scientists, but also important to a broad range of industry people,” says Cheng, noting that his team is testing real-world applications in nanopatterning technologies and hope to see commercialization in the future.

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

Read more: http://www.nanowerk.com/spotlight/spotid=31211.php#ixzz2ZJxaQ2C7