Graphene quantum dots for single electron transistors ~ Application for Future Electronics


The schematic structure of the devices

Scientists from Manchester University, the Ulsan National Institute of Science & Technology and the Korea Institute of Science and Technology have developed a novel technology, which combines the fabrication procedures of planar and vertical heterostructures in order to assemble graphene-based single-electron transistors.

In the study, it was demonstrated that high-quality graphene quantum dots (GQDs), regardless of whether they were ordered or randomly distributed, could be successfully synthesized in a matrix of monolayer hexagonal boron nitride (hBN).

Here, the growth of GQDs within the layer of hBN was shown to be catalytically supported by the platinum (Pt) nanoparticles distributed in-between the hBN and supporting oxidised silicon (SiO2) wafer, when the whole structure was treated by the heat in the methane gas (CH4). It was also shown, that due to the same lattice structure (hexagonal) and small lattice mismatch (~1.5%) of graphene and hBN, graphene islands grow in the hBN with passivated edge states, thereby giving rise to the formation of defect-less quantum dots embedded in the hBN monolayer.

Such planar heterostructures incorporated by means of standard dry-transfer as mid-layers into the regular structure of vertical tunnelling transistors (Si/SiO2/hBN/Gr/hBN/GQDs/hBN/Gr/hBN; here Gr refers to monolayer graphene and GQDs refers to the layer of hBN with the embedded graphene quantum dots) were studied through tunnel spectroscopy at low temperatures (3He, 250mK).

The study demonstrated where the manifestation of well-established phenomena of the Coulomb blockade for each graphene quantum dot as a separate single electron transmission channel occurs.

‘Although the outstanding quality of our single electron transistors could be used for the development of future electronics, “This work is most valuable from a technological standpoint as it suggests a new platform for the investigation of physical properties of various materials through a combination of planar and van der Waals heterostructures.” as explained study co-author Davit Ghazaryan, Associate Professor at the HSE Faculty of Physics, and Research Fellow at the Institute of Solid State Physics (RAS)

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What Happens when Graphene is “twisted” into spirals—researchers synthesize helical nanographen – demonstrates outstanding charge and heat transport properties


Heli grapheneThis visualisation shows layers of graphene used for membranes. Credit: University of Manchester

It’s probably the smallest spring you’ve ever seen. Researchers from Kyoto University and Osaka University report for the first time in the Journal of the American Chemical Society the successful synthesis of hexa-peri-hexabenzo[7]helicene, or helical nanographene. These graphene constructs previously existed only in theory, so successful synthesis offers promising applications including nanoscale induction coils and molecular springs for use in nanomechanics.

Graphene, a hexagonal lattice of single-layer carbon atoms exhibiting outstanding charge and heat transport properties, has garnered extensive research and development interest. Helically twisted graphenes have a spiral shape. Successful synthesis of this type of  could have major applications, but its model compounds have never been reported. And while past research has gotten close, resulting compounds have never exhibited the expected properties.

“We processed some basic chemical  through step-by-step reactions, such as McMurry coupling, followed by stepwise photocyclodehydrogenation and aromatization,” explains first author Yusuke Nakakuki. “We then found that we had synthesized the foundational backbone of helical graphene.”

The team confirmed the helicoid nature of the structure through X-ray crystallography, also finding both clockwise and counter-clockwise nanographenes. Further tests showed that the electronic structure and photoabsorption properties of this compound are much different from previous ones. “This helical nanographene is the first of its kind,” concludes lead author Kenji Matsuda. “We will try to expand their surface area and make the helices longer. I expect to find many new physical properties as well.”

The paper, titled “Hexa-peri-hexabenzo[7]helicene: Homogeneously π-Extended Helicene as a Primary Substructure of Helically Twisted Chiral Graphenes,” appeared 19 March 2018 in the Journal of the American Chemical Society.

(From Phys.org)

 Explore further: Synthesis of a water-soluble warped nanographene and its application for photo-induced cell death

More information: Yusuke Nakakuki et al, Hexa-peri-hexabenzo[7]helicene: Homogeneously π-Extended Helicene as a Primary Substructure of Helically Twisted Chiral Graphenes, Journal of the American Chemical Society (2018). DOI: 10.1021/jacs.7b13412

Graphene Research and the World’s 5 Biggest Problems: From Clean Water and Healthcare to Energy and Infastructure – Solutions based in Graphene may Hold the Key


In September 2015, world leaders gathered at a historic UN summit to adopt the Sustainable Development Goals (SDGs). These are 17 ambitious targets and indicators that help guide and coordinate governments and international organizations to alleviate global problems. For example, SDG 3 is to “ensure healthy lives and promote well-being for all at all ages.” Others include access to clean water, reducing the effects of climate change, and affordable healthcare.

If you think these goals might be difficult to meet, you’re right. Reports show progress is lacking in many of the 17 categories, implying they may not be met by the target date of 2030. However, paired with progress in social and political arenas, advances in science and technology could be a key accelerant to progress too.

Just one example? Graphene, a futuristic material with a growing set of potential applications.

Graphene is comprised of tightly-knit carbon atoms arranged into a sheet only one atom thick. This makes it the thinnest substance ever made, yet it is 200 times stronger than steel, flexible, stretchable, self-healing, transparent, more conductive than copper, and even superconductive. A square meter of graphene weighing a mere 0.0077 grams can support four kilograms. It is a truly remarkable material—but this isn’t news to science and tech geeks.

Headlines touting graphene as the next wonder material have been a regular occurrence in the last decade, and the trip from promise to practicality has felt a bit lengthy.

But that’s not unexpected; it can take time for new materials to go mainstream. Meanwhile, the years researching graphene have yielded a long list of reasons to keep at it.

Since first isolated in 2004 at the University of Manchester—work that led to a Nobel Prize in 2010— researchers all over the world have been developing radical ways to use and, importantly, make graphene. Indeed, one of the primary factors holding back widespread adoption has been how to produce graphene at scale on the cheap, limiting it to the lab and a handful of commercial applications. Fortunately, there have been advances toward mass production.

Last year, for example, a team from Kansas State University used explosions to synthesize large quantities of graphene. Their method is simple: Fill a chamber with acetylene or ethylene gas and oxygen. Use a vehicle spark plug to create a contained detonation. Collect the graphene that forms afterward. Acetylene and ethylene are composed of carbon and hydrogen, and when the hydrogen is consumed in the explosion, the carbon is free to bond with itself, forming graphene. This method is efficient because all it takes is a single spark.

Whether this technique will usher in the graphene revolution, as some have claimed, remains to be seen. What’s more certain is there will be no shortage of problems solved when said revolution arrives. Here’s a look at the ways today’s research suggests graphene may help the UN meet its ambitious development goals.

Clean Water

SDG 6 is to “ensure availability and sustainable management of water and sanitation for all.” As of now, the UN estimates that “water scarcity affects more than 40 percent of the global population and is projected to rise.”

Graphene-based filters could very well be the solution. Jiro Abraham from the University of Manchester helped develop scalable graphene oxide sieves to filter seawater. He claims, “The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes.”

Furthermore, researchers from Monash University and the University of Kentucky have developed graphene filters that can filter out anything larger than one nanometer. They say their filters “could be used to filter chemicals, viruses, or bacteria from a range of liquids. It could be used to purify water, dairy products or wine, or in the production of pharmaceuticals.”

Carbon Emissions

SDG 13 focuses on taking “urgent action to combat climate change and its impacts.”

Of course, one of the main culprits behind climate change is the excessive amount of carbon dioxide being emitted into the atmosphere. Graphene membranes have been developed that can capture these emissions.

Researchers at the University of South Carolina and Hanyang University in South Korea independently developed graphene-based filters that can be used to separate unwanted gases from industrial, commercial, and residential emissions. Henry Foley at the University of Missouri has claimed these discoveries are “something of a holy grail.”

With these, the world might be able to stem the rise of CO2 in the atmosphere, especially now that we have crossed the important 400 parts per million threshold.

Healthcare

Many around the world do not have access to adequate healthcare, but graphene may have an impact here as well.

First of all, graphene’s high mechanical strength makes it a perfect material for replacing body parts like bones, and because of its conductivity it can replace body parts that require electrical current, like organs and nerves. In fact, researchers at the Michigan Technological University are working on using 3D printers to print graphene-based nerves, and this team is developing biocompatible materials using graphene to conduct electricity.

Graphene can also be used to make biomedical sensors for detecting diseases, viruses, and other toxins. Because every atom of graphene is exposed, due to it being only one atom thick, sensors can be far more sensitive. Graphene oxide sensors, for example, could detect toxins at levels 10 times less than today’s sensors. These sensors could be placed on or under the skin and provide doctors and researchers with vast amounts of information.

Chinese scientists have even created a sensor that can detect a single cancerous cell. Further, scientists at the University of Manchester report graphene oxide can hunt and neutralize cancer stem cells.

Infrastructure

SDG 9 is to “build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation.” Graphene-enhanced composites and other building materials could bring us closer to meeting this goal.

Recent research shows that the more graphene is added, the better the composite becomes. This means graphene can be added to building materials like concrete, aluminum, etc., which will allow for stronger and lighter materials.

Resins are also getting better thanks to the addition of graphene. Research by Graphene Flagship, the EU’s billion-euro project to further graphene research, and their partner Avanzare suggests “graphene enhances the functionality of the resin, combining graphene’s electrical conductivity and mechanical strength with excellent corrosion resistance.” Some uses for this are making pipes and storage tanks corrosion-resistant, and making stronger adhesives.

Energy

SDG 7 is to “ensure access to affordable, reliable, sustainable and modern energy for all.” Because of its light weight, conductivity, and tensile strength, graphene may make sustainable energy cheaper and more efficient.

For example, graphene composites can be used to create more versatile solar panels. Researchers at MIT say, “The ability to use graphene…is making possible truly flexible, low-cost, transparent solar cells that can turn virtually any surface into a source of electric power.”

We’ll also be able to build bigger and lighter wind turbines thanks to graphene composites.

Further, graphene is already being used to enhance traditional lithium-ion batteries, which are the batteries commonly found in consumer electronics. Research is also being done into graphene aerogels for energy storage and supercapacitors. All of these will be essential for large-scale storage of renewable energy.

Over the next decade, graphene is likely to find more and more uses out in the real world, not only helping the UN and member states meet the SDGs, but enhancing everything from touch screens to MRI machines and from transistors to unknown uses as a superconductor.

New research is being published and new patents being filed regularly, so keep an eye out for this amazing material.

Manchester University: Photon-friendly graphene membranes mimic photosynthesis to produce hydrogen


Graphene membranes that mimic photosynthesis to produce hydrogen by harvesting solar energy could be developed following the discovery of a new effect.

Researchers at Manchester University have discovered that the rate at which graphene conducts protons increases 10 fold when it is illuminated with sunlight.

Dubbed the “photo-proton” effect, the finding could lead to graphene membranes being used to produce hydrogen from artificial photosynthesis, as well as for light-induced water splitting, photo-catalysis and in photodetectors.

Graphene – a one atom-thick sheet of carbon – is already known to be an extremely good conductor of electrons, and can absorb light of all wavelengths.

But it has also recently been found to be permeable to thermal protons, the nuclei of hydrogen atoms.

To discover how light affects the behaviour of these protons, the researchers fabricated graphene membranes and decorated them on one side with platinum nanoparticles.

When they illuminated the membrane with sunlight, they found the proton conductivity increased by 10 times, according to Dr Marcelo Lozada-Hidalgo, who led the research alongside Prof Sir Andre Geim.

“This is a new effect, it can only be found in graphene, there are no other materials that can use light to produce an enhancement in proton transport,” said Lozada-Hidalgo. “Scientifically this is a new physical phenomenon, which is quite remarkable.”

What’s more, when the researchers measured the photoresponsivity of the membrane using electrical measurements and mass spectrometry, they discovered that around 5,000 hydrogen molecules were being formed in response to every light particle. Existing photovoltaic devices need thousands of photons to produce a single hydrogen molecule.

“To put this in context, people have been developing silicon photodiodes for the best part of 50 years, while we did not expect this material to be responsive to light in the first place, and found that it outperforms pretty much everything that is out there,” said Lozada-Hidalgo.

The researchers have published their findings in Nature Nanotechnology. They now plan to investigate the addition of catalysts to the membrane, to enable it to split water molecules. This would allow it to act as a complete artificial leaf, said Lozada-Hidalgo.

“The goal of this project is to make an artificial leaf, to split water molecules and then use the protons to generate hydrogen,” he said. “What we’re missing is the bit to break the water in the first place, and for that we need another catalyst.”

Graphene has potential as cell membrane modelling surface


lipid-nanoparticleResearchers at Manchester University have demonstrated that membranes can be  directly ‘written’ on to a graphene surface using Lipid Dip-Pen Nanolithography  (L-DPN).

The researchers at Manchester University – led by Dr Aravind Vijayaraghavan,  and Dr Michael Hirtz at the Karlsruhe Institute of Technology (KIT) – describe  their work in Nature Communications.

The human body contains 100 trillion cells, each of which is enveloped in a  cell membrane that have a plethora of proteins, ion channels and other molecules  embedded in them, each performing vital functions.

Understand these systems will enable their application in areas such as  bio-sensing, bio-catalysis and drug-delivery. Considering that it is difficult  to accomplish this by studying live cells inside the human body, scientists have  developed model cell membranes on surfaces outside the body, to study the  systems and processes under more convenient and accessible conditions.

Dr Vijayaraghavan’s team at Manchester and their collaborators at KIT have  shown that graphene is a suitable new surface on which to assemble these model  membranes, and is claimed to bring many advantages compared to existing  surfaces.

In a statement, Dr Vijayaraghavan said: ‘Firstly, the lipids spread uniformly  on graphene to form high-quality membranes. Graphene has unique electronic  properties; it is a semi-metal with tuneable conductivity.

‘When the lipids contain binding sites such as the enzyme called biotin, we  show that it actively binds with a protein called streptavidin. Also, when we  use charged lipids, there is charge transfer from the lipids into graphene which  changes the doping level in graphene. All of these together can be exploited to  produce new types of graphene/lipids based bio-sensors.’

Dr. Michael Hirtz (KIT) said: ‘The [L-DPN] technique utilises a very sharp  tip with an apex in the range of several nanometres as a means to write lipid  membranes onto surfaces in a way similar to what a quill pen does with ink on  paper.

‘The small size of the tip and the precision machine controlling it allows of  course for much smaller patterns, smaller than cells, and even right down to the  nanoscale.

‘By employing arrays of these tips multiple different mixtures of lipids can  be written in parallel, allowing for sub-cellular sized patterns with diverse  chemical composition.’

 

Read more:  http://www.theengineer.co.uk/medical-and-healthcare/news/graphene-has-potential-as-cell-membrane-modelling-surface/1017291.article#ixzz2hhu6QkMK

Nanoco (Quantum Dot Nano-Materials Manufacture) Ready to Roll


QDOTS imagesCAKXSY1K 8Quantum dots developer’s Dow deal a game-changer for digital displays.

The Manchester University spin-off develops and makes quantum dots, tiny, fluorescent semiconductors used to make next-generation electronics. Nanoco’s IP-protected manufacturing method avoids cadmium, a heavy metal banned in many countries, and its trademarked NanoDot technology is used in several applications; solid state lighting, solar panels, even some medical devices.

As we originally predicted, it is in digital displays where the biggest breakthrough has come thanks to a landmark global licensing deal with US giant Dow Chemical (DOW:NYSE) at the start of the year (23 Jan). Quantum dot LED (QLED) displays are set to become the next big trend in consumer electronics.

NANOCO GROUP - Comparison Line Chart (Rebased to first)

Market potential

A report in March from technology analyst Wintergreen Research predicts the QLED display market will hit $6.4 billion by 2019 from a standing start just a couple of years back. The report backs up our theory that once manufacturers learn to integrate quantum dots into products they will be falling over themselves to do so thanks to the technology’s lower energy use and cheaper manufacturing cost.

According to Wintergreen, Samsung (005930:KS) reckons QLED displays could cost half as much as LCD or organic LED (OLED) panels. It also estimates 80% better energy efficiency, for thinner devices with a sharper display.

TVs are a starting point, but expect QLED in smartphones and tablets too as device manufacturers desperately seek ways to defend market share in high margin top-of-the-range products.

As analysts at house broker Canaccord Genuity point out, an increasing number of industry participants share Dow Chemical’s and Nanoco’s confidence that quantum dots are on the cusp of widespread adoption in a $100 billion display market.

Sony (6758:T) already has launched the world’s first quantum dot TV using cadmium-based technology from Nanoco’s privately owned rival QD Vision. But since sales will be barred in many major markets, the US and European Union, mass market products look destined to follow the cadmium-free technology route. Nanoco is already expanding its factory in Runcorn, Cheshire from an annual 25kg capacity to 70kg, beyond initial plans to expand it to 40kg. It is rumoured to be eyeing a brand new set-up in Asia post the Dow deal, with Korea the hot tip.

Liberum sees year to July royalty-based revenues of £4 million rising to £4.6 million in 2014, before the really exciting sales flood in, hitting over £100 million inside five years from a licensing/royalty business model similar to that of UK chip champ ARM (ARM). That would imply over £90 million pre-tax profit thanks to 88% operating margins.

With cash burn running at around £5.5 million a year, its £12.5 million of cash pile should mean Nanoco is unlikely to tap investors for fresh funds. Liberum sees the shares hitting 260p over the next year, while Canaccord is even more optimistic, setting a 275p target price. That could be just scratching the surface of the shares’ longer-term profits potential.

 

Graphene Commercialisation and Applications: Global Industry and Academia Summit


QDOTS imagesCAKXSY1K 8(Nanowerk News) From its high electrical conductivity  and structural strength, graphene has been cited as a “wonder material” with the  potential to revolutionize materials engineering in many different industrial  sectors. While the number of commercial applications for graphene is potentially  unlimited, production scalability must first be established and R&D activity  properly directed to ensure graphene moves out of the lab and into the market.

The Graphene Commercialisation & Applications:  Global Industry & Academia Summit 2013, (25th-26th June, 2013, London),  is the first forum of its kind aimed at establishing the real, commercially  viable industrial applications of graphene, and expediting its role as a  game-changing technology.

With trailblazing companies such as Nokia, Head, Samsung,  Philips, BAE Systems, Sony and Thales, as well as leading academic and research  institutions such as Manchester University, UCLA, Chalmers University, Seoul  National University and Fraunhofer IPA, coming together for the first time to  present their views, this exciting event is a timely opportunity for relevant  stakeholders to evaluate specific industry requirements for graphene, as well as  understanding its’ material capabilities and real world applications.

Senior Business And Scientific Leaders Speaking At The Summit  Include

  • – Jari Kinaret, Professor, Chalmers University and Director, Graphene Flagship  Consortium
  • – James Baker, Managing Director, BAE Systems Advanced Technology Centre
  • – Jani Kivioja, Research Leader, Nokia
  • – Ralf Schwenger, Director R&D Raquetsports, Head Sport
  • – Seungmin Cho, Principal Research Engineer and Group Leader, Samsung Techwin
  • – Byung Hee Hong, Associate Professor, Seoul National University
  • Richard Kaner, Professor of Chemistry, UCLA
  • – Paolo Bondavalli, Head of Nanomaterial Topic, Thales Group
  • – Marcello Grassi, Head of Technology, Spirit AeroSystems Europe
  • – Nuno Lourenco, Head of Technology, UTC Aerospace
  • – York Haemisch, Senior Director Corporate Technologies, Philips Research
  • – Peter Fischer, CTO, Plastic Logic
  • – Antonio Avitabile, Head of Strategic Technology Partnerships, Sony
  • – Ivica Kolaric, Department Head, Fraunhofer IPA
  • – Pradyumna Goli – Research Associate, A.A. Ballandin Nano-Device Laboratory, UC  Riverside
  • – Rahul Nair, Lead Researcher, University of Manchester
  • – Craig Poland, Research Scientist, Institute of Occupational  Medicine

Day One of the Summit will establish graphene’s commercially  viable applications across multiple sectors and the commercialisation roadmap.

Day Two illustrates supply and cost projections as well as  production scalability steps.

Download The Full Agenda And Speaker Faculty  HereThis forum will provide a unique and invaluable opportunity to  gain insights into the opportunities and hindrances presented by graphene. It  will also provide the framework for industry, research and academia to  collaborate in making this revolutionary technological development a market  reality.

Click Here To Register, Saving £200 Per Person By  19th AprilIf you would like more information about joining the exhibition  showcase or require information on group registration discounts, then please  contact the team on +44 (0) 800 098 8489 or email  info@london-business-conferences.co.uk

Read more: http://www.nanowerk.com/news2/newsid=29721.php#ixzz2OfsdEfsv