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Promising steps towards large scale production of graphene nanoribbons for electronics

Posted By Graphene Council, The Graphene Council, Thursday, January 31, 2019
Two-dimensional sheets of graphene in the form of ribbons a few tens of nanometers across have unique properties that are highly interesting for use in future electronics. Researchers have now for the first time fully characterised nanoribbons grown in both the two possible configurations on the same wafer with a clear route towards upscaling the production.

Graphene in the form of nanoribbons show so called ballistic transport, which means that the material does not heat up when a current flow through it. This opens up an interesting path towards high speed, low power nanoelectronics. The nanoribbon form may also let graphene behave more like a semiconductor, which is the type of material found in transistors and diodes. The properties of graphene nanoribbons are closely related to the precise structure of the edges of the ribbon. Also, the symmetry of the graphene structure lets the edges take two different configurations, so called zigzag and armchair, depending on the direction of the long respective short edge of the ribbon.

The nanoribbons were grown in two directions along ridges on the substrate. This way both the zigzag- and armchair-edge varieties form and can be studied at the same time. The positions of the atoms in the graphene layer as well as the zig zag edge can be seen from the scanning tunneling microscopy image (Å stands for Ångström, 0.1 nanometers).

The nanoribbons were grown on a template made of silicon carbide under well controlled conditions and thoroughly characterised by a research team from MAX IV Laboratory, Technische Universität Chemnitz, Leibniz Universität Hannover, and Linköping University. The template has ridges running in two different crystallographic directions to let both the armchair and zig-zag varieties of graphene nanoribbons form. The result is a predictable growth of high-quality graphene nanoribbons which have a homogeneity over a millimeter scale and a well-controlled edge structure.

One of the new findings is that the researchers were able to show ballistic transport in the bulk of the nanoribbon. This was possible due to extremely challenging four probe experiments performed at a length scale below 100 nm by the group in Chemnitz, says Alexei Zakharov, one of the authors.

The electrical characterization also shows that the resistance is many times higher in the so called armchair configuration of the ribbon, as opposed to the lower resistance zig-zag form obtained. This hints to a possible band gap opening in the armchair nanoribbons, making them semiconducting. The process used for preparing the template for nanoribbon growth is readily scalable. This means that it would work well for development into the large-scale production of graphene nanoribbons needed to make them a good candidate for a future material in the electronics industry.

So far, we have been looking at nanoribbons which are 30–40 nanometers wide. It’s challenging to make nanoribbons that are 10 nanometers or less, but they would have very interesting electrical properties, and there´s a plan to do that. Then we will also study them at the MAXPEEM beamline, says Zakharov.

The measurements performed at the MAXPEEM beamline was done with a technique not requiring X-rays. The beamline will go into its commissioning phase this spring and will start welcoming users this year.

Tags:  2d materials  Graphene  graphene production 

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Open-source automated chemical vapor deposition system for the production of two-dimensional nanomaterials

Posted By Graphene Council, The Graphene Council, Wednesday, January 30, 2019
Updated: Tuesday, January 29, 2019
A research group at Boise State University led by Assistant Professor David Estrada of the Micron School of Materials Science and Engineering has released the open-source design of a chemical vapor deposition (CVD) system for two-dimensional (2D) materials growth, an advance which could lower the barrier of entry into 2D materials research and expedite 2D materials discovery and translation from the benchtop to the market.

2-dimensional materials are a class of materials that are one to a few atoms thick. The pioneering work of Nobel Laureates Andre Geim and Konstantin Novoselov in isolating and measuring the physical properties of graphene – a 2D form of carbon arranged in a hexagonal crystal structure - ignited the field of 2D materials research

While 2D materials can be obtained from bulk van der Waals crystals (e.g. graphite and MoS2) using a micromechanical cleavage approach enabled by adhesive tapes, the community quickly realized that unlocking the full potential of 2D materials would require advanced manufacturing methods compatible with the semiconductor industry’s infrastructure.

Chemical vapor deposition is a promising approach for scalable synthesis of 2D materials – but automated commercial systems can be cost prohibitive for some research groups and startup companies. In such situations students are often tasked with building custom furnaces, which can be burdensome and time consuming. While there is value in such endeavors, this can limit productivity and increase time to degree completion.

A recent trend in the scientific community has been to develop open-source hardware and software to reduce equipment cost and expedite scientific discovery. Advances in open-source 3-dimensional printing and microcontrollers have resulted in freely available designs of scientific equipment ranging from test tube holders, potentiostats, syringe pumps and microscopes. Estrada and his colleagues have now added a variable pressure chemical vapor deposition system to the inventory of open-source scientific equipment.

“As a graduate student I was fortunate enough that my advisor was able to purchase a commercial chemical vapor deposition system which greatly impacted our ability to quickly grow carbon nanotubes and graphene. This was critical to advancing our scientific investigations,” said Estrada. “When I read scientific articles I am intrigued with the use of the phrase “custom-built furnace” as I now realize how much time and effort graduate students invest in such endeavors.”

The design and qualification of the furnace was accomplished by lead authors Dale Brown, a former Micron School of Materials Science and Engineering graduate student, and Clinical Assistant faculty member Lizandra Godwin, with assistance from the other co-authors. The results of their variable pressure CVD system have been published in PLoS One ("Open-source automated chemical vapor deposition system for the production of two- dimensional nanomaterials") and include the parts list, software drivers, assembly instructions and programs for automated control of synthesis procedures. Using this furnace, the team has demonstrated the growth of graphene, graphene foam, tungsten disulfide and tungsten disulfide – graphene heterostructures.

“Our goal in publishing this design is to alleviate the burden of designing and constructing CVD systems for the early stage graduate student,” said Godwin. “If we can save even a semester of time for a graduate student this can have a significant impact on their time to graduation and their ability to focus on research and advancing the field.”

“We hope others in the community can improve on our design by incorporating open-source software for automated control of 2D materials synthesis,” said Estrada. “Such an improvement could further reduce the barrier to entry for 2D materials research.”

Tags:  2D materials  Boise State University  CVD  Graphene 

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Nanotech Energy, the UCLA Energy Incubator and Holder of First Patent for Graphene Announces Profound Achievement in Production of High Quality Graphene Based Materials

Posted By Graphene Council, The Graphene Council, Tuesday, January 29, 2019
Updated: Tuesday, January 29, 2019
Nanotech Energy, a leading supplier of graphene, graphene oxide and graphene super batteries, announced today that it has cleared a monumental hurdle in the production of high-quality graphene-based materials. The first patent for Graphene, now exclusively licensed to Nanotech Energy, was filed in 2002 by Dr. Richard Kaner, Nanotech co-founder and UCLA professor of Chemistry and of Materials Science and Engineering.

Through its proprietary technology, Nanotech Energy is now able to produce graphene with an unsurpassed surface area of over 2,500 meters squared per gram, almost the theoretical limit. A second version of graphene with a surface area of 2,000 to 2,200 meters squared per gram, measured by methylene blue adsorption is available for purchase based on downstream application, while the other version of over 2,500 meters squared per gram is being used only for Nanotech’s downstream products.

Graphene is a single layer of carbon with a theoretical surface area limit of slightly over 2,600 meters squared per gram. The surface area determines how many electrons can be stored and, in turn, how much energy can be stored in batteries and supercapacitors. Without the large surface area, graphene loses most of its superlatives and behaves just like graphite.

Jack Kavanaugh, Nanotech founder and CEO said, ”Nanotech Energy has created a remarkable technology that reaches the boundaries of superior energy density, power density, cycle life and, most importantly, safety. It’s an exciting time for the company and the industry.”

Dr. Maher El-Kady added “it’s widely accepted that the properties of graphene vary depending on the number of layers. The high surface area of our graphene has potential to dramatically transform the graphene industry. We already produce super-batteries, supercapacitors, conductive inks and conductive epoxies with unprecedented performance and have responsibly extended our leads in each of those arenas by making them all safer.”

Dr. Kaner further added, “After tests have demonstrated that almost all graphene sold today is really thin layer graphite and not graphene, this is a major step forward to be able to scale real graphene with a surface area (over 2500 m 2 /g) that approaches the theoretical limit.”

Tags:  Batteries  Graphene  graphene oxide  Nanotech Energy 

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Properties of ‘wonder material’ graphene change in humid conditions

Posted By Graphene Council, The Graphene Council, Tuesday, January 29, 2019
Updated: Friday, January 25, 2019

The ‘wonder material’, which is made from carbon and was discovered in 2004, is hailed for many of its extraordinary characteristics including being stronger than steel, more conductive than copper, light, flexible and transparent.

This study, published in the journal Physical Review B, shows that in bi-layer graphene, which is two sheets of one atom thick carbon stacked together, water seeps between the layers in a humid environment.

The properties of graphene significantly depend on how these carbon layers interact with each other and when water enters in between it can modify the interaction.

The researchers found the water forms an atomically thin layer at 22 per cent relative humidity and separates graphene layers at over 50 per cent relative humidity.

This suggests that layered graphene could exhibit very different properties in a humid place such as Manchester, UK, where average relative humidity is over 80 per cent every month of the year, compared to a dry place such as Tucson, Arizona, where relative humidity is 13 per cent on afternoons in May but rises to 65 per cent on January mornings. So, in Tucson the properties will vary according to the time of the year.

Graphene, both layered and single layer, potentially has a huge number of uses but the results of this study could impact how the material can be used in real-life applications.

Humidity needs to be recorded

Lead author Dr Yiwei Sun, from Queen Mary's School of Engineering and Materials Science, said: “The critical points, 22 per cent and 50 per cent relative humidity, are very common conditions in daily life and these points can be easily crossed. Hence, many of the extraordinary properties of graphene could be modified by water in between graphene layers.”

He added: “Some graphene-based devices may function to their full capability in dry places while others may do so in humid places. We suggest all experiments on 2D materials should in future record the relative humidity.”

The researchers suggest humidity is also likely to have an impact on other layered materials such as boron nitride (sheets made of boron and nitrogen) and Molybdenum disulphide (sheets made of molybdenum and sulphur).

The study was carried out because it was known that graphite, a material also made from carbon, loses its excellent lubricating ability in low humidity conditions, such as aboard aeroplanes at high altitude, which was reported during the Second World War, or in outer space, as reported by NASA in the 1970s.

It was believed that the water in between layers of graphite is crucial to its behaviour and now the same effect has been shown to affect layered graphene.  

Tags:  2D  Bi-layer graphene  Graphene  water  Yiwei Sun 

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Creating a roadmap for 2-D materials

Posted By Graphene Council, The Graphene Council, Monday, January 28, 2019
Updated: Monday, January 28, 2019

The rapid growth of research on 2-D materials – materials such as graphene and others that are a single or few atoms thick – is fueled by the hope of developing better performing sensors for health and environment, more economical solar energy, and higher performing and more energy efficient electronics than is possible with current silicon electronics.

Technical roadmaps, such as the International Technology Roadmap for Semiconductors (ITRS), first published in 1998, serve as guides for future advances in a particular field and provide a means for organizations to plan for investments in new technology.

An invited article in the December online edition of the journal 2-D Materials provides a roadmap for the synthesis of electronic-grade two-dimensional materials for future electronic and sensing applications. Led by Penn State, with contributions from five additional universities and national laboratories, the roadmap addresses the grand challenges in 2-D materials with useful electronic or photonic properties, and the outlook for U.S. advances in the field.

"This article is a review of where we currently are in regard to the synthesis of 2-D materials and our thoughts on the top research priorities that need to be addressed to achieve electronic grade 2-D materials," said Joshua Robinson, associate professor of materials science and engineering, whose Ph.D. students Natalie Briggs and Shruti Subramanian are co-lead authors on the report titled "A Roadmap for Electronic Grade 2-Dimensional Materials," published online today, Jan. 17.

The authors divided the paper into four parts: Grand Challenges, which are the technology drivers, such as the internet of things; Synthesis, the techniques and theories required to grow close to perfect 2-D materials; Materials Engineering, which is fine tuning the properties of 2-D and composite materials; and finally, Outlook, which is the future of electronic devices when silicon technology reaches an inevitable roadblock.

"To put our roadmap together, we reached out to experts in various subfields, such as different synthesis approaches, defect engineering and computational theory," said Briggs of the two-year project. "We asked them to talk about the key fundamental challenges and the steps required to address these challenges in their area of expertise."

Robinson added, "This is the first roadmap focused on 2-D synthesis for electronic applications and there are still a lot of open questions. We want to bring some of those topics into the light."

A list of the twenty authors and their affiliations can be found online in the open access article in 2-D Materials.

Tags:  2D materials  Graphene  International Technology Roadmap for Semiconductor 

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Graphene and related materials safety: human health and the environment

Posted By Graphene Council, The Graphene Council, Monday, January 28, 2019
Updated: Friday, January 25, 2019

As the drive to commercialise graphene continues, it is important that all safety aspects are thoroughly researched and understood. The Graphene Flagship project has a dedicated Work Package studying the impact of graphene and related materials on our health, as well as their environmental impact. This enables safety by design to become a core part of innovation.

Researches and companies are currently using a range of materials such as few layered graphene, graphene oxide and heterostructures. The first step to assess the toxicology is to fully characterise these materials. This work overviews the production and characterisation methods, and considers different materials, which biological effects depend on their inherent properties.

"One of the key messages is that this family of materials has varying properties, thus displaying varying biological effects. It is important to emphasize the need not only for a systematic analysis of well-characterized graphene-based materials, but also the importance of using standardised in vitro or in vivo assays for the safety assessment," says Bengt Fadeel, lead author of this paper working at Graphene Flagship partner Karolinska Institutet, Sweden.

"This review correlates the physicochemical characteristics of graphene and related materials to the biological effects. A classification based on lateral dimensions, number of layers and carbon-to-oxygen ratio allows us to describe the parameters that can alter graphene's toxicology. This can orient future development and use of these materials," explains Alberto Bianco, from Graphene Flagship partner CNRS, France and deputy leader of the Graphene Flagship Work Package on Health and Environment.

The paper gives a comprehensive overview of all aspects of graphene health and environmental impact, focussing on the potential interactions of graphene-based materials with key target organs including immune system, skin, lungs, cardiovascular system, gastrointestinal system, central nervous system, reproductive system, as well as a wide range of other organisms including bacteria, algae, plants, invertebrates, and vertebrates in various ecosystems.

"One cannot draw conclusions from previous work on other carbon-based materials such as carbon nanotubes and extrapolate to graphene. Graphene-based materials are less cytotoxic when compared to carbon nanotubes and graphene oxide is readily degradable by cells of the immune system," comments Fadeel.

Andrea C. Ferrari, Science and Technology Officer of the Graphene Flagship and Chair of its Management Panel added that "understanding any potential Health and Environmental impacts of graphene and related materials has been at the core of all Graphene Flagship activities since day one. This review provides a solid guide for the safe use of these materials, a key step towards their widespread utilization as targeted by our innovation and technology roadmap."

Tags:  Graphene  graphene oxide  Healthcare  The Graphene Flagship 

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Drilling speed increased by 20% – yet another upgrade in the oil & gas sector made possible by graphene nanotubes

Posted By Graphene Council, The Graphene Council, Friday, January 25, 2019
Updated: Friday, January 25, 2019

56% of drilling tool failures in the oil extraction industry are caused by low durability of the rubber stator – one of the most important elements in a screw drill. In China, annual losses from the failure of drilling tools are estimated to be more than $40,000 per oil well. Equipment manufacturers are thus always looking for ways to improve the rubber used in screw drilling tools, to reduce these financial losses for oil-extracting companies.

One of the largest Chinese producers of PDM drilling tools, Orient Energy & Technology Ltd., has completed laboratory testing of nitrile butadiene rubber (NBR) containing TUBALL graphene nanotubes, produced by OCSiAl. Just 1.7 wt.% of graphene nanotube concentrate introduced into NBR was found to increase the tensile modulus by 30%.

“Improving the modulus of elasticity is the most valuable advantage of graphene nanotubes in our industry, because that leads to a 30% increase in output torque of our products. With that, the drilling speed can also be increased by more than 20%, resulting in a shortened drilling cycle, reduced energy consumption and less environmental pollution, greatly improving China’s drilling technology,” said Mr. Hu, a rubber engineer at Orient Energy & Technology. At the same time, the graphene nanotubes result in a reduction of abrasion by 20% without increasing the Mooney viscosity of rubber, whereas other additives such as multi wall carbon nanotubes increase viscosity, which is unacceptable for injecting.

Graphene nanotubes are one of the allotropic forms of carbon, where each tube can be considered to be a rolled-up sheet of graphene. This universal additive is already on duty protecting the oil & gas industry, where it is widely applied as a conductive additive in fiberglass pipes for permanent and uniform conductivity, as well as 15% reinforcement. Another example is anti-static fiberglass tanks for storing and transporting easily combustible materials, where these nanotubes ensure permanent and stable resistivity of less than 10^6 Ω·cm, without “hot spots” and independent of humidity.

Orient Energy & Technology is continuing to test TUBALL graphene nanotubes, in particular by studying their effects on other types of rubber, such as HNBR and FKM. Meanwhile, the first industrial prototype of a TUBALL-enhanced NBR stator for a screw drill is undergoing industrial trials.

Tags:  Carbon Nanotubes  Graphene  TUBALL 

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Gratomic to Launch New Graphene Ultra Efficient Tires

Posted By Graphene Council, The Graphene Council, Thursday, January 24, 2019
Updated: Thursday, January 24, 2019

Gratomic Inc. a vertically integrated graphite to graphenes, advanced materials company is pleased to announce the development of Gratomic's new Graphene Ultra Fuel Efficient Tires (GUET) with certification and terrain testing targeted for completion in Q3, 2019.

"Purely from a demand perspective, we have been pulled into a market which represents a very large opportunity for Gratomic. Simply put, our customers want what we have; high quality graphene. Not only are Hybrid Graphene enhanced tires fuel efficient, but they can also demonstrate better handling and longer life" commented Gratomic's Chairman and Co-CEO Sheldon Inwentash. "The GUET tire market represents a very large vertical for Gratomic which the Company will be vigorously pursuing in 2019, and beyond."

Gratomic recognizes the automotive tire market is large and is expected to grow to 2.5 billion tires by 2022. Gratomic looks to penetrate and disrupt the traditional means of tire production by providing graphene enabled GUET tires. To date, the global tire market has recognized that employing graphenes within tire treads, walls and the inner linings can make tires lighter, provide better grip and reduce rolling resistance to an extent that is not possible with existing tire compounds. On average, this would require 20 to 25 grams of graphene per tire. However, for the Industry, specification consistency and scaleability of supply have been limiting factors and to date have been the biggest constraints in commercializing Graphene.

Attributed to the right combination of geology at the mine and our processing partner, Gratomic strongly believes it can satisfy the supply demand of quality graphenes required for what the Company believes is the growing market demand for a new age economy tire. Gratomic is confident in its ability to deliver consistent quality and quantities of Graphenes to end users.

Gratomic has been able to achieve this through a unique collaboration agreement with its development partner Perpetuus Carbon Technologies who currently supplies substantial quantities of surface modified graphenes on a monthly basis to the tire industry through its Patented Plasma Process.

Ian Walters Director - Perpetuus Carbon Technologies Limited stated:

"Perpetuus' investigative analysis and characterization has concluded that the Graphenes derived from the Gratomic mine are highly friable, more so than any other graphite tested for purpose by the Perpetuus Labs. The liberated graphenes when functionalized have demonstrated excellent processability. Initial application in a host of end uses has demonstrated excellent suitability for a range of products. Most noteworthy are the excellent results generated when the Hybrid Graphenes are included in elastomers for tire construction. Perpetuus looks forward to working with Gratomic to launch probably the first range of Graphene enabled ultra fuel efficient tires."

Employing its dedicated facility for the patented Perpetuus plasma method Gratomic post plasma processing produces graphenes (less than 10 layers) of a high purity (CK 99.10%) derived from its Graphite Mine in Namibia.

Tags:  Automotive tyres  Graphene  Gratomic  Perpetuus  Tires 

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Graphene Technology to Deice Aircraft Enters $1.30 Billion Deicing Market, Time Saving, More Efficient & Less Toxic

Posted By Graphene Council, The Graphene Council, Wednesday, January 23, 2019

Mr. Tom Donaldson, President, Signet International Holdings, Inc., the parent company of Signet Graphene Technologies, Inc. (SGT), announced recently that the company has executed a contract with Florida International University (FIU) to further the development and commercialization of a new deicing technology enhanced by graphene, the revolutionary carbon-based nanotechnology.

Adhesion of ice to the surfaces of aircraft in inclement weather severely compromises aircraft aerodynamic performance. Time-consuming airport deicing operations are performed for safety, causing extensive flight delays for travelers and a heavy financial burden for the airline industry. Airport Lifestyle magazine notes that the average cost of deicing a passenger aircraft is over $7,000 per coating.

A team of engineers at Florida International University headed up by Professor Arvind Agarwal, PhD, Chair of Mechanical and Materials Engineering and his team in Plasma Forming Laboratory: Ms Jenniffer Bustillos, Dr. Cheng Zhang and Dr. Benjamin Boesl have developed a graphene foam−polymer composite with superior deicing efficiency and strength. A patent for the technology will be issued on Jan. 22, 2019.

The graphene-foam polymer composite provides lightweight coatings and free-standing components with heating abilities, with exceptional thermal stability. The graphene reinforcement also increases the tensile strength of the polymer coating on the aircraft and reduces the impact of nasty toxic chemical runoff seeping into the ground and water.

The patent application entitled, “Three Dimensional Graphene Foam Reinforced Composite Coating & Deicing Systems Therefrom,” was a result of research conducted by a grant from the U.S. Army Research Office. Signet Graphene Technologies, Inc., intends to further develop the technology and make it ready for mass production. This invention is expected to have a major impact on the aircraft deicing market, which, according to Opus Materials Technologies, the U.S. spends over $1.30 billion in deicing fluids alone.

“This contract marks the first of an exciting ongoing relationship with FIU,” says Donaldson. “This invention is the solution to a very practical problem in air transportation. Critically low temperature conditions are the reasons delays are imminent, costing the airlines and travelers time and money. Although our focus is on time and safety in the airline industry, we are discovering an abundance of uses for this technology. In fact, we are exploring applied applications in solving icing conditions from icy steps; turbine blades and their mechanics, helicopter rotor blades; even private home uses and other subzero problems.”

“It is a pleasure to be associated with FIU,” says Ernest Letiziano, CEO, SIGN. “We were looking for applied use of graphene that can be made available to the public quickly; this invention is the answer to efficiency and toxic waste. The Army Grant technology has been achieved; we will take it from here.”

Tags:  Florida International University  Graphene  Signet Graphene Technologies 

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The ‘Holey graphene’ membrane has been elected ‘Molecule of the year 2018’ by the C&EN journal

Posted By Graphene Council, The Graphene Council, Wednesday, January 16, 2019
Updated: Wednesday, January 16, 2019

Readers of the journal of the American Chemical Society have elected this graphene membrane with pores controlled at the atomic scale as the best molecule of 2018. This structure was presented in Science in a joint article by researchers from the ICN2, the CiQUS and the DIPC.

The porous graphene membrane synthesized by researchers from the Institut Català de Nanociència i Nanotecnologia (ICN2, a center of BIST and CSIC), the Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS) and The Donostia International Physics Center (DIPC) has been elected as the molecule of the year by the readers of C&EN magazine of the American Chemical Society with 58% of the votes among 8 international candidates.

Science magazine published this milestone in April in a work directed by the ICN2 Group Leader ICREA Prof. Aitor Mugarza and CiQUS IP Dr. Diego Peña. The article explained the potential of this precious material for applications in electronics, filters and sensors. The results of this study, whose first author is Dr. César Moreno from the ICN2, conducted with the molecule synthesized at CiQUS by Dr. Manuel Vilas Varela made possible the application for a patent.

The presence of pores in graphene pores whose size, shape and density can be tuned with atomic precision at the nanoscale can modify its basic structure and make it suitable as a selective filter for extremely small substances, from greenhouse gases to salt, to biomolecules. In addition, graphene becomes a semiconductor when the space between pores is reduced to a few atoms, opening the door for its use in electronic applications, where it could be used to replace the bulkier, more rigid silicon components used today.

Applied in conjunction, these two properties are predicted to allow the development of combined filter and sensor devices which will not only sort for specific molecules, but will alternatively block or monitor their passage though the nanopores using an electric field.

The resulting graphene exhibits electrical properties akin to those of silicon which can also act as a highly-selective molecular sieve. Applied in conjunction, these two properties are predicted to allow the development of combined filter and sensor devices which will not only sort for specific molecules, but will alternatively block or monitor their passage though the nanopores using an electric field.

Tags:  Graphene 

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