Novel self-assembly can tune the electronic properties of graphene

Novel self-assembly can tune the electronic properties of graphene

In what could prove to be a significant advance in fabricating new technologies, scientists discovered a new self-assembly mechanism that surprisingly drives negatively charged molecules to clump together to form islands when graphene is supported by an electrical insulator. Under these conditions, different charge interactions are not diminished, as they are when graphene is supported by a metallic substrate. At low concentrations, individual adsorbed molecules repel each other, but with increasing concentration, the molecules form two-dimensional islands. It was determined by theory that the flow of extra electrons into the islands from graphene keeps the molecules together. The electronic driving forces and stabilization energies are sufficient to overcome the repulsion between the negative charges.

This self-assembly mechanism can be used to tune the electronic properties of graphene layers in devices and control how electrons flow through the graphene. This mechanism permits atomic-scale patterning of electronic properties, which cannot be achieved with conventional lithographic techniques currently being used in the semiconductor industry.

Silicon has been successful because it is an electronically tunable semiconductor material that can be used in electronic devices. Graphene has distinct advantages over silicon for many applications due to its higher electron mobility and a very stable crystal structure, but it can be difficult to precisely tune. One way to tune the electronic properties of graphene is to adsorb molecules onto its surface. For example, negatively charged molecules on a graphene surface pull electrons from the graphene layer, changing its electronic properties. However, efforts to controllably assemble such negatively charged molecules have been limited because negatively charged species repel each other. Now scientists led by the University of California-Berkeley and Lawrence Berkeley National Laboratory have discovered that this repulsion can be overcome and two-dimensional islands can be controllably formed by negatively charged molecules on graphene supported by an insulator. Through microscopy and theoretical modeling, they determined that the underlying insulator was key to altering the nature of the interactions between the negatively charged molecules and graphene. These molecules are known to extract electrons from its substrate. At low surface concentrations, the negatively charged molecules separately accept electrons from the underlying graphene and repel each other, as expected because like charges repel each other.

Remarkably and counterintuitively, at higher concentrations, these charged molecules clump together to form ordered islands. This usual behavior is explained by theory as the donation of extra electrons to the islands of molecules by the graphene when compared to the donation to a single molecule. This extra charge makes it energetically more favorable to form islands. Surprisingly, this behavior observed on graphene substrate supported by an insulator does not occur when graphene is supported by a metal. This molecular self-assembly provides a possible alternative to patterning graphene using conventional lithographic techniques. Atomic-scale tuning of the properties of graphene layers could enable the fabrication of new devices based on graphene that cannot be made using silicon.

Explore further: 2D islands in graphene hold promise for future device fabrication

More information: Hsin-Zon Tsai et al. Molecular Self-Assembly in a Poorly Screened Environment: FTCNQ on Graphene/BN, ACS Nano (2015). DOI: 10.1021/acsnano.5b05322

Journal reference: ACS Nano

Graphene Nanostructures Heal Damaged Muscles

Iranian researchers used graphene to synthesize a scaffold to treat damaged muscles TEHRAN (INIC)- Iranian researchers from Stem Cell Technology Research Center, Tarbiat Modarres University and Sharif University of Technology produced polymeric nanofibers and used graphene to synthesize a scaffold with optimized properties. Continue reading

How to make continuous rolls of graphene

How to make continuous rolls of graphene

Graphene is a material with a host of potential applications, including in flexible light sources, solar panels that could be integrated into windows, and membranes to desalinate and purify water. But all these possible uses face the same big hurdle: the need for a scalable and cost-effective method for continuous manufacturing of graphene films.

That could finally change with a new process described this week in the journal Scientific Reports by researchers at MIT and the University of Michigan. MIT mechanical engineering Associate Professor A. John Hart, the paper’s senior author, says the new roll-to-roll manufacturing process described by his team addresses the fact that for many proposed applications of graphene and other 2-D materials to be practical, “you’re going to need to make acres of it, repeatedly and in a cost-effective manner.”

Making such quantities of graphene would represent a big leap from present approaches, where researchers struggle to produce small quantities of graphene — often pulling these sheets from a lump of graphite using adhesive tape, or producing a film the size of a postage stamp using a laboratory furnace. But the new method promises to enable continuous production, using a thin metal foil as a substrate, in an industrial process where the material would be deposited onto the foil as it smoothly moves from one spool to another. The resulting sheets would be limited in size only by the width of the rolls of foil and the size of the chamber where the deposition would take place.

Because a continuous process eliminates the need to stop and start to load and unload materials from a fixed vacuum chamber, as in today’s processing methods, it could lead to significant scale-up of production. That could finally unleash applications for graphene, which has unique electronic and optical properties and is one of the strongest materials known.

The new process is an adaptation of a chemical vapor deposition method already used at MIT and elsewhere to make graphene — using a small vacuum chamber into which a vapor containing carbon reacts on a horizontal substrate, such as a copper foil. The new system uses a similar vapor chemistry, but the chamber is in the form of two concentric tubes, one inside the other, and the substrate is a thin ribbon of copper that slides smoothly over the inner tube.

Gases flow into the tubes and are released through precisely placed holes, allowing for the substrate to be exposed to two mixtures of gases sequentially. The first region is called an annealing region, used to prepare the surface of the substrate; the second region is the growth zone, where the graphene is formed on the ribbon. The chamber is heated to approximately 1,000 degrees Celsius to perform the reaction.

The researchers have designed and built a lab-scale version of the system, and found that when the ribbon is moved through at a rate of 25 millimeters (1 inch) per minute, a very uniform, high-quality single layer of graphene is created. When rolled 20 times faster, it still produces a coating, but the graphene is of lower quality, with more defects.

Some potential applications, such as filtration membranes, may require very high-quality graphene, but other applications, such as thin-film heaters may work well enough with lower-quality sheets, says Hart, who is the Mitsui Career Development Associate Professor in Contemporary Technology at MIT.

So far, the new system produces graphene that is “not quite [equal to] the best that can be done by batch processing,” Hart says — but “to our knowledge, it’s still at least as good” as what’s been produced by other continuous processes. Further work on details such as pretreatment of the substrate to remove unwanted surface defects could lead to improvements in the quality of the resulting graphene sheets, he says.

The team is studying these details, Hart adds, and learning about tradeoffs that can inform the selection of process conditions for specific applications, such as between higher production rate and graphene quality. Then, he says, “The next step is to understand how to push the limits, to get it 10 times faster or more.”

Hart says that while this study focuses on graphene, the machine could be adapted to continuously manufacture other two-dimensional materials, or even to growing arrays of carbon nanotubes, which his group is also studying.

“This is high-quality research that represents significant progress on the path to scalable production methods for large-area graphene,” says Charlie Johnson, a professor of physics and astronomy at the University of Pennsylvania who was not involved in this work. “I think that the concentric tube approach is very creative. It has the potential to lead to significantly lower production costs for graphene, if it can be scaled to larger copper-foil widths.”

The research team also included Erik Polsen and Daniel McNerny of the University of Michigan and postdocs Viswanath Balakrishnan and Sebastian Pattinson of MIT. The work was supported by the National Science Foundation and the Air Force Office of Scientific Research.

NanoXplore Montreal Graphene Manufacturing Plant Fully Operational

MONTREAL, CANADA–(Marketwired – Feb 19, 2015) – Group NanoXplore Inc., a Montreal-based company specialising in the production and application of graphene and its derivative materials, announced today that its graphene production facility is in full operation with a capacity of 3 metric tonnes per year. This is the largest graphene production capacity in Canada and, outside of China, one of the 5 largest in the world.

NanoXplore’s production process is unique and the core of the company’s competitive advantage. The proprietary process gently and efficiently creates pristine graphene from natural flake graphite without creating the crystalline defects that can limit performance. The process also functionalises the graphene material during production making subsequent mixing with a broad range of industrial materials simple and efficient. NanoXplore’s facility is routinely producing several standard grades of graphene as well as derivative products such as a unique graphite-graphene composite suitable for anodes in Li-ion batteries.

“I am very pleased to announce the successful launch of our production facility. The simplicity and robustness of our production technology has enabled this achievement and positions NanoXplore as a leading graphene company”, said Dr. Soroush Nazarpour, President and CEO of NanoXplore. “Our customers have been very pleased with the high quality of the material being produced. Our stringent quality control ensures both the highest levels of graphene performance and batch-to-batch consistency.”

About Group NanoXplore Inc.

NanoXplore is a privately held advanced materials company focused on the large-scale production of high quality graphene and the integration of graphene into real world industrial products. NanoXplore achieves significant improvements in performance for its customers with very low levels of graphene because its material is of high quality (few defects, highly dispersible), because the production process can easily tune the dimensions of the graphene platelets, and because NanoXplore has specific expertise in dispersing graphene in a broad range of industrial materials. NanoXplore partners with its customers to integrate graphene into their products and processes, providing them with innovative products and a strong competitive advantage.

For more information about NanoXplore, please visit www.nanoxplore.ca.

Canadian Government Announces Significant Investments in Clean Technologies

TORONTO, Feb. 20, 2015 /CNW/ – The Honourable Greg Rickford, Canada’s Minister of Natural Resources, along with Jane Pagel, Acting CEO of Sustainable Development Technology Canada (SDTC), today announced seven clean technology projects in Ontario receiving investments totalling over $26.8 million, supporting jobs, economic growth and the environment.

These development projects will help reduce emissions, protect the environment and generate high-quality jobs:

  • Grafoid Inc. in Ottawa will receive $8,121,000 to develop low-cost, environmentally sustainable, high-quality graphene with a minimal environmental footprint.
  • OTI Lumionics in Toronto will receive $5,700,000 to implement a pilot production line capable of producing high volumes of organic light-emitting diode (OLED) lighting panels.
  • Ranovus Inc. in Ottawa will receive $4,250,000 for commercializing technology that streamlines data through data centres reducing energy consumption four-fold.
  • Kelvin Storage in Toronto will receive $2,800,000 to develop a Thermal Matrix Energy Storage (TMES) system to reduce greenhouse gas emissions produced by industrial facilities worldwide.
  • Polar Sapphire in Mississauga will receive $2,650,000 for an energy-efficient process to produce high-purity alumina, used in the production of synthetic sapphire.
  • GaN Systems in Ottawa will receive $2,188,000 to maximize the efficiency of electric vehicle chargers connecting to the power grid, reducing wasted heat and cutting power losses while batteries charge.
  • Ionada in Concord will receive $1,100,000 to produce a cost-effective, energy-efficient marine scrubber to remove sulphur oxides from ship exhaust.

On February 18th, SDTC announced that the SD Tech and Natural Gas Funds have re-opened to new applications from the next wave of clean technology entrepreneurs.

Quick Facts

  • Canada possesses one of the cleanest electricity mixes in the world with just under two-thirds of its electricity coming from renewable sources — the highest in the G7.
  • In 2013, Canada was the second-fastest growing clean energy market in the G20.
  • Canada’s per-capita GHG emissions are now among their lowest level since tracking began.
  • In 2013, the Canadian Government announced $325 million over eight years in support for SDTC for advanced research projects resulting in a cleaner environment.
  • SDTC’s SD Tech Fund™ has supported 269 projects with $684 million allocated by the federal government.
  • 57 of the more mature companies supported by SDTC have received $2.5 billion in follow-on financing as of December 2013, meaning that for every dollar invested by Canada in these companies, the marketplace has responded with $14 of private capital.
  • The SD Tech Fund™ supports projects that address climate change, air quality, clean water and clean soil, providing solutions to key Canadian industries that increase efficiency and enhance environmental responsibility.

Quotes

“Our government is investing in advanced clean energy technologies that create well-paying jobs and generate economic opportunities. Today’s announcement contributes to economic prosperity and a cleaner environment in Ontario and across Canada.”

The Honourable Greg Rickford
Canada’s Minister of Natural Resources

“The projects announced today are great examples of the Canadian clean tech initiatives and true entrepreneurship that drive SDTC’s portfolio. By supporting these innovative technologies, SDTC is investing in efficiency and environmental performance — which translates into a cleaner environment. We look forward to working with these companies to get their products closer to commercialization.”

Jane Pagel
Acting CEO of Sustainable Development Technology Canada (SDTC)

“Grafoid Inc., a complete solutions graphene company and Canada’s graphene standard bearer in global markets, is very pleased and grateful to the Government of Canada and SDTC for their $8.2-million contribution in support of our development of an automated production method for our proprietary MesoGraf™ graphene process. We see SDTC’s funding commitment as a tacit recognition by the Government of Canada of Grafoid’s leading science as we advance the commercialization of graphene — a material with the potential to benefit humanity.”

Gary Economo
Co-founder and Chief Executive Officer, Grafoid Inc.

Grafoid

Grafoid is a Canadian graphene research, development and investment company partnered with Focus Graphite Inc., owner of the high grade Lac Knife, Quebec graphite deposit. They invest in, manage, and develop markets for processes that produce economically scalable, pristine graphene for polymer and non-polymer, energy storage and other applications. Grafoid claims to have a technology for inexpensive exfoliation of graphene at a stage that is very close to the raw ore, which would really be a game changer. The technology is still secret, and a patent has been filed in November 2012 (expect publication mid-2014). Focus Graphite holds a 40% stake in Grafoid and is listed on several stock markets (TSX VENTURE:FMS, OTCQX:FCSMF, FRANKFURT:FKC).

http://www.graphenetracker.com/companies/165/grafoid/

UK Researchers Debut the First Flexible Graphene Display

UK Researchers Debut the First Flexible Graphene Display

UK researchers have taken a step forward in making flexible displays, debuting a warping screen that uses graphene as its electronic material.

Like many of the screens that we view today, the new Cambridge invention uses an electrophoretic display that rearranges particles suspended in a solution by means of an electric field. However, in contrast to most displays the screen is made of flexible plastic and its pixel electronics, also known as backplane, replace the traditional metal electrode with one built from graphene.

According to Cambridge researchers, “Graphene is more flexible than conventional ceramic alternatives like indium-tin oxide (ITO) and more transparent than metal films.” What’s more the 2-dimensional carbon material is also processed and printed very easily making the display simple to produce.

Currently, the Cambridge consortium’s display is only capable of a 150 pixel per inch resolution, however, that may change in short order. Researchers believe they can build a flexible OLED or LCD screen that can project a full color HD image. Looking further into the future the UK team also believes that using graphene-based backplanes might allow them to embed sensors in the displays, making them more capable of interacting with their viewers.

“We are happy to see our collaboration with Plastic Logic resulting in the first graphene-based electrophoretic display exploiting graphene in its pixels’ electronics,” said Professor Andrea Ferrari, Director of the Cambridge Graphene Centre. “This is a significant step forward to enable fully wearable and flexible devices.”

While graphene’s potential has been known since it was first discovered, industries have been slow to leverage its unique abilities. This Cambridge display should do wonders for the development of process engineering for graphene and in the end it might just dazzle us with beautiful, flexible moving images.

Growing graphene – blue sky research attempts to replicate nature

Growing graphene – blue sky research attempts to replicate nature

A ground-breaking experiment at The University of Nottingham could herald the production of high-purity, large-area graphene and boron nitride layers in a controlled way. If successful this research could unlock the full potential of graphene in electronics and optoelectronics.

Ten years after the discovery of graphene by the Nobel Prize winning research team at The University of Manchester, Sergei Novikov, Professor of Physics and his co-investigators at Nottingham secured funding to build a custom made Molecular Beam Epitaxy (MBE) machine capable of the high temperatures required to grow graphene and boron nitride layers on an industrial scale.

Over £2m from the Engineering and Physical Sciences Research Council, The University of Nottingham and the Leverhulme Trust, has been invested in the design, purchase and running costs of the world’s hottest MBE machine. The new facility in the School of Physics and Astronomy will be officially opened at 11am on Thursday 8 January 2015.