NREL: Semiconducting Single-Walled Carbon Nanotubes in Solar Energy Harvesting


National Renewable Energy Laboratory, Golden, Colorado 

Semiconducting single-walled carbon nanotubes (s-SWCNTs) represent a tunable model one-dimensional system with exceptional optical and electronic properties. 

High-throughput separation and purification strategies have enabled the integration of s-SWCNTs into a number of optoelectronic applications, including photovoltaics (PVs). In this Perspective, we discuss the fundamental underpinnings of two model PV interfaces involving s-SWCNTs. 

We first discuss s-SWCNT–fullerene heterojunctions where exciton dissociation at the donor–acceptor interface drives solar energy conversion. Next, we discuss charge extraction at the interface between s-SWCNTs and a photoexcited perovskite active layer. 

In each case, the use of highly enriched semiconducting SWCNT samples enables fundamental insights into the thermodynamic and kinetic mechanisms that drive the efficient conversion of solar photons into long-lived separated charges. 

These model systems help to establish design rules for next-generation PV devices containing well-defined organic semiconductor layers and help to frame a number of important outstanding questions that can guide future studies.

New chemical method could revolutionize Graphene: U of Illinois – Chicago




“The distinction of our chemistry will enable integration of graphene with almost anything, while retaining its properties.”

University of Illinois at Chicago scientists have discovered a new chemical method that enables graphene to be incorporated into a wide range of applications while maintaining its ultra-fast electronics.

 

Graphene, a lightweight, thin, flexible material, can be used to enhance the strength and speed of computer display screens, electric/photonics circuits, solar cells and various medical, chemical and industrial processes, among other things. It is comprised of a single layer of carbon atoms bonded together in a repeating pattern of hexagons.

 

Isolated for the first time 15 years ago by a physics professor at the University of Manchester in England, it is so thin that it is considered two-dimensional and thought to be the strongest material on the planet.

 

Vikas Berry, associate professor and department head of chemical engineering, and colleagues used a chemical process to attach nanomaterials on graphene without changing the properties and the arrangement of the carbon atoms in graphene. 





By doing so, the UIC scientists retained graphene’s electron-mobility, which is essential in high-speed electronics.

 

The addition of the plasmonic silver nanoparticles to graphene also increased the material’s ability to boost the efficiency of graphene-based solar cells by 11 fold, Berry said.

Instead of adding molecules to the individual carbon atoms of graphene, Berry’s new method adds metal atoms, such as chromium or molybdenum, to the six atoms of a benzoid ring. 

Unlike carbon-centered bonds, this bond is delocalized, which keeps the carbon atoms’ arrangement undistorted and planar, so that the graphene retains its unique properties of electrical conduction.

 

The new chemical method of annexing nanomaterials on graphene will revolutionize graphene technology by expanding the scope of its applications, Berry said.

 

“It’s been a challenge to interface graphene with other nano-systems because graphene lacks an anchoring chemistry,” he said. “And if graphene’s chemistry is changed to add anchors, it loses its superior properties. 

The distinction of our chemistry will enable integration of graphene with almost anything, while retaining its properties.

 We envision that our work will motivate a worldwide move towards ‘ring-centered’ chemistries to interface graphene with other systems.”

 

Source and top image: University of Illinois at Chicago

Rice U: New Lithium metal battery prototype boasts 3X the capacity of current lithium-ions ~ Dendrite Problem Solved?


graphene-nanotube-lithium-battery-4

Could a new material involving a carbon nanotube and graphene hybrid put an end to the dendrite problem in lithium batteries? (Credit: Tour Group/Rice University)

The high energy capacity of lithium-ion batteries has led to them powering everything from tiny mobile devices to huge trucks. But current lithium-ion battery technology is nearing its limits and the search is on for a better lithium battery. But one thing stands in the way: dendrites. If a new technology by Rice University scientists lives up to its potential, it could solve this problem and enable lithium-metal batteries that can hold three times the energy of lithium-ion ones.

Dendrites are microscopic lithium fibers that form on the anodes during the charging process, spreading like a rash till they reach the other electrode and causing the battery to short circuit. As companies such as Samsung know only too well, this can cause the battery to catch fire or even explode.

“Lithium-ion batteries have changed the world, no doubt,” says chemist Dr. James Tour, who led the study. “But they’re about as good as they’re going to get. Your cellphone’s battery won’t last any longer until new technology comes along.”

Rice logo_rice3So until scientists can figure out a way to solve the problem of dendrites, we’ll have to put our hopes for a higher capacity, faster-charging battery that can quell range anxiety on hold. This explains why there’s been no shortage of attempts to solve this problem, from using Kevlar to slow down dendrite growth to creating a new electrolyte that could lead to the development of an anode-free cell. So how does this new technology from Rice University compare?

For a start, it’s able to stop dendrite growth in its tracks. Key to it is a unique anode made from a material that was first created at the university five years ago. By using a covalent bond structure, it combines a two-dimensional graphene sheet and carbon nanotubes to form a seamless three-dimensional structure. As Tour explained back when the material was first unveiled:

“By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material.”

Close-up of the lithium metal coating the graphene-nanotube anode (Credit: Tour Group/Rice University)

 

Envisioned for use in energy storage and electronics applications such as supercapacitors, it wasn’t until 2014, when co-lead author Abdul-Rahman Raji was experimenting with lithium metal and the graphene-nanotube hybrid, that the researchers discovered its potential as a dendrite inhibitor.

“I reasoned that lithium metal must have plated on the electrode while analyzing results of experiments carried out to store lithium ions in the anode material combined with a lithium cobalt oxide cathode in a full cell,” says Raji. “We were excited because the voltage profile of the full cell was very flat. At that moment, we knew we had found something special.”

Closer analysis revealed no dendrites had grown when the lithium metal was deposited into a standalone hybrid anode – but would it work in a proper battery?

To test the anode, the researchers built full battery prototypes with sulfur-based cathodes that retained 80 percent capacity after more than 500 charge-discharge cycles (i.e. the rough equivalent of what a cellphone goes through in a two-year period). No signs of dendrites were observed on the anodes.

How it works

The low density and high surface area of the nanotube forest allow the lithium metal to coat the carbon hybrid material evenly when the battery is charged. And since there is plenty of space for the particles to slip in and out during the charge and discharge cycle, they end up being evenly distributed and this stops the growth of dendrites altogether.

According to the study, the anode material is capable of a lithium storage capacity of 3,351 milliamp hours per gram, which is close to pure lithium’s theoretical maximum of 3,860 milliamp hours per gram, and 10 times that of lithium-ion batteries. And since the nanotube carpet has a low density, this means it’s able to coat all the way down to substrate and maximize use of the available volume.

“Many people doing battery research only make the anode, because to do the whole package is much harder,” says Tour. “We had to develop a commensurate cathode technology based upon sulfur to accommodate these ultrahigh-capacity lithium anodes in first-generation systems. We’re producing these full batteries, cathode plus anode, on a pilot scale, and they’re being tested.”

The study was published in ACS Nano.

Source: Rice University

 

EV Maker Fisker Tweets More Details About the Upcoming EMotion Electric Sedan – Use of Hybrid Graphene Batteries Yet 2 Come ~ A Challenge for Tesla?


 

Fisker-EMotion-TwitterSays graphene batteries won’t go into production yet

Henrik Fisker, initiator of a project to start an electric car company relying on a long-range battery that uses graphene, recently stated that the company’s upcoming electric luxury sedan will use lithium-ion batteries to power the car rather than the graphene battery technology currently under development for future models.

EMotion is slated to officially debut on August 17, 2017 with a tentative release in 2019. Pricing starts at $129,900, placing it in the same range as Tesla Model S. It will be interesting to see at what point, if at all, graphene-based batteries will be used in these cars.

Fisker says the EMotion will still offer 400+ miles of electric range. Quick charging can return 100 miles of range to the battery in nine minutes using what the company calls UltraCharger technology.

“Very proud of what we are creating!” Fisker said via Twitter recently.

His EMotion EV features dramatic suicide-butterfly doors and its sporty wheels are made from aluminum and carbon fiber. Other high-tech features include a lidar sensor recessed in the front bumper to be used for autonomous driving.

Fisker-EV-graphene-battery-img_assist-400x225The EMotion also boasts a Lipik Electrochromic glass roof and rear passenger windows, which can be tinted by the touch of a button.

EMotion is slated to officially debut on August 17, 2017 with a tentative release in 2019. Pricing starts at $129,900, placing it in the same range as Tesla Model S. Pre-orders are open now at www.fiskerinc.com.

Graphene 2017 ImageForArticle_4454(1)See Our Related Article:

The Coming Battery Revolution: Graphene and Batteries 

 

 

The Coming Battery Revolution: Graphene and Batteries 



Graphene 2017 ImageForArticle_4454(1)Graphene and Batteries 

** Re-Posted from earlier article from Graphene Info

Graphene , a sheet of carbon atoms bound together in a honeycomb lattice pattern, is hugely recognized as a “wonder material” due to the myriad of astonishing attributes it holds. It is a potent conductor of electrical and thermal energy, extremely lightweight chemically inert, and flexible with a large surface area. It is also considered eco-friendly and sustainable, with unlimited possibilities for numerous applications.

In the field of batteries, conventional battery electrode materials (and prospective ones) are significantly improved when enhanced with graphene. Graphene can make batteries that are light, durable and suitable for high capacity energy storage, as well as shorten charging times.

It will extend the battery’s life-time, which is negatively linked to the amount of carbon that is coated on the material or added to electrodes to achieve conductivity, and graphene adds conductivity without requiring the amounts of carbon that are used in conventional batteries.

Graphene can improve such battery attributes as energy density and form in various ways. Li-ion batteries can be enhanced by introducing graphene to the battery’s anode and capitalizing on the material’s conductivity and large surface area traits to achieve morphological optimization and performance.

It has also been discovered that creating hybrid materials can also be useful for achieving battery enhancement. A hybrid of Vanadium Oxide (VO2) and graphene, for example, can be used on Li-ion cathodes and grant quick charge and discharge as well as large charge cycle durability.

In this case, VO2 offers high energy capacity but poor electrical conductivity, which can be solved by using graphene as a sort of a structural “backbone” on which to attach VO2 – creating a hybrid material that has both heightened capacity and excellent conductivity.

Another example is LFP ( Lithium Iron Phosphate) batteries, that is a kind of rechargeable Li-ion battery. It has a lower energy density than other Li-ion batteries but a higher power density (an indicator of of the rate at which energy can be supplied by the battery).

Enhancing LFP cathodes with graphene allowed the batteries to be lightweight, charge much faster than Li-ion batteries and have a greater capacity than conventional LFP batteries.

 

In addition to revolutionizing the battery market, combined use of graphene batteries and supercapacitors could yield amazing results, like the noted concept of improving the electric car’s driving range and efficiency.

Battery Basics

Batteries serve as a mobile source of power, allowing electricity-operated devices to work without being directly plugged into an outlet.
While many types of batteries exist, the basic concept by which they function remains similar: one or more electrochemical cells convert stored chemical energy into electrical energy. A battery is usually made of a metal or plastic casing, containing a positive terminal (an anode), a negative terminal (a cathode) and electrolytes that allow ions to move between them.

A separator (a permeable polymeric membrane) creates a barrier between the anode and cathode to prevent electrical short circuits while also allowing the transport of ionic charge carriers that are needed to close the circuit during the passage of current.

Finally, a collector is used to conduct the charge outside the battery, through the connected device.



Eneloop battery design

When the circuit between the two terminals is completed, the battery produces electricity through a series of reactions. The anode experiences an oxidation reaction in which two or more ions from the electrolyte combine with the anode to produce a compound, releasing electrons. At the same time, the cathode goes through a reduction reaction in which the cathode substance, ions and free electrons combine into compounds. Simply put, the anode reaction produces electrons while the reaction in the cathode absorbs them and from that process electricity is produced.

The battery will continue to produce electricity until electrodes run out of necessary substance for creation of reactions.

Battery types and characteristics

Batteries are divided into two main types: primary and secondary. Primary batteries (disposable), are used once and rendered useless as the electrode materials in them irreversibly change during charging. Common examples are the zinc-carbon battery as well as the alkaline battery used in toys, flashlights and a multitude of portable devices.

Secondary batteries (rechargeable), can be discharged and recharged multiple times as the original composition of the electrodes is able to regain functionality. Examples include lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics.

Batteries come in various shapes and sizes for countless different purposes. Different kinds of batteries display varied advantages and disadvantages.


Nickel-Cadmium (NiCd)
batteries are relatively low in energy density and are used where long life, high discharge rate and economical price are key. They can be found in video cameras and power tools, among other uses. NiCd batteries contain toxic metals and are environmentally unfriendly.


Nickel-Metal hydride
batteries have a higher energy density than NiCd ones, but also a shorter cycle-life. Applications include mobile phones and laptops.


Lead-Acid
batteries are heavy and play an important role in large power applications, where weight is not of the essence but economic price is. They are prevalent in uses like hospital equipment and emergency lighting.

Lithium-Ion (Li-ion) batteries are used where high-energy and minimal weight are important, but the technology is fragile and a protection circuit is required to assure safety. Applications include cell phones and various kinds of computers.


Lithium Ion Polymer (Li-ion polymer)
batteries are mostly found in mobile phones. They are lightweight and enjoy a slimmer form than that of Li-ion batteries.
They are also usually safer and have longer lives. However, they seem to be less prevalent since Li-ion batteries are cheaper to manufacture and have higher energy density.

Batteries and supercapacitors

While there are certain types of batteries that are able to store a large amount of energy, they are very large, heavy and release energy slowly.

Capacitors, on the other hand, are able to charge and discharge quickly but hold much less energy than a battery.

The use of graphene in this area, though, presents exciting new possibilities for energy storage, with high charge and discharge rates and even economical affordability.
Graphene-improved performance thereby blurs the conventional line of distinction between supercapacitors and batteries.

Li-Polymer battery vs Supercapacitor structure


Commercial Graphene-enhanced battery products

Graphene-based batteries have exciting potential and while they are not commercially available yet, R&D is intensive and will hopefully yield results in the future.

In November 2016, Huawei unveiled a new graphene-enhanced Li-Ion battery that can remain functional at higher temperature (60° degrees as opposed to the existing 50° limit) and offers a longer operation time – double than what can be achieved with previous batteries.

To achieve this breakthrough, Huawei incorporated several new technologies – including an anti-decomposition additives in the electrolyte, chemically stabilized single crystal cathodes – and graphene to facilitate heat dissipation. Huawei says that the graphene reduces the battery’s operating temperature by 5 degrees.



In June 2014, US based Vorbeck Materials
announced the Vor-Power strap, a lightweight flexible power source that can be attached to any existing bag strap to enable a mobile charging station (via 2 USB and one micro USB ports). the product weighs 450 grams, provides 7,200 mAh and is probably the world’s first graphene-enhanced battery.

In May 2014, American company Angstron Materials rolled out several new graphene products. The products, said to become available roughly around the end of 2014, include a line of graphene-enhanced anode materials for Lithium-ion batteries. The battery materials were named “NANO GCA” and are supposed to result in a high capacity anode, capable of supporting hundreds of charge/discharge cycles by combining high capacity silicon with mechanically reinforcing and conductive graphene.

Developments are also made in the field of graphene batteries for electric vehicles. Henrik Fisker, who announced its new EV project that will sport a graphene-enhanced battery, unveiled in November 2016 what is hoped to be a competitor to Tesla. Called EMotion, the electric sports car will reportedly achieve a 161 mph (259 kmh) top speed and a 400-mile electric range.

Graphene Nanochem and Sync R&D’s October 2014
plan to co-develop graphene-enhanced Li-ion batteries for electric buses, under the Electric Bus 1 Malaysia program, is another example.

In August 2014, Tesla suggested the development of a “new battery technology” that will almost double the capacity for their Model S electric car. It is unofficial but reasonable to assume graphene involvement in this battery.

UK based Perpetuus Carbon Group and OXIS Energy agreed in June 2014 to co-develop graphene-based electrodes for Lithium-Sulphur batteries, which will offer improved energy density and possibly enable electric cars to drive a much longer distance on a single battery charge.

Another interesting venture, announced in September 2014 by US based Graphene 3D Labs, regards plans to print 3D graphene batteries. These graphene-based batteries can potentially outperform current commercial batteries as well as be tailored to various shapes and sizes.

Other prominent companies which declared intentions to develop and commercialize graphene-enhanced battery products are: Grafoid, SiNode together with AZ Electronic Materials, XG Sciences, Graphene Batteries together with CVD Equipment and CalBattery.

Fisker-EMotion-TwitterRead More: The Fisker EV Sedan “EMotion”

EV Maker Fisker and Tesla Rival Plans to Use Graphene in Batteries to Extend Range – Improve Consumer Experience

A Holey Graphene Electrode framework that enables highly efficient charge delivery – Making Better Batteries for the Future


Holey Graphene II grapheneThis visualisation shows layers of graphene used for membranes. Credit: University of Manchester

A team of researchers affiliated with institutions in the U.S., China and the Kingdom of Saudi Arabia has developed a new type of porous graphene electrode framework that is capable of highly efficient charge delivery. In their paper published in the journal Science, the group describes how they overcame traditional conflicts arising between trade-offs involving density and speed to produce an electrode capable of facilitating rapid ion transport. Hui-Ming Cheng and Feng Li with the Chinese Academy of Sciences offer a Perspective piece on the work done by the team in the same journal issue, and include some opinions of their own regarding where such work is likely heading.

In a perfect world, batteries would have unlimited energy storage delivered at speeds high enough to power devices with unlimited needs. The phaser from Star Trek, for example, would require far more power and speed than is possible in today’s devices.

While it is unlikely that such technology will ever come about, it does appear possible that batteries of the future will perform much better than today, likely due to nano-structured materials—they have already shown promise when used as material due to their unique properties. Unfortunately, their use has been limited thus far due to the ultra-thin nature of the resulting electrodes and their extremely low mass loadings compared to those currently in use. In this new effort, the researchers report on a new way to create an electrode using that overcomes such limitations.

The electrode they built is porous, which in this case means that it has holes in it. Those holes, as Cheng and Li note, allow better charge transport while also offering improved capacity retention density. The graphene framework they built, they note, offers a superior means of electron transport and its porous nature allows for a high ion diffusion rate—the holes force the ions to take shortcuts, reducing diffusion.

Cheng and Li suggest the new work is likely to inspire similar designs in the search for better electrode materials, which they further suggest appears likely to lead to new electrodes that are not only practical, but have high mass loadings.

Explore further: New graphene framework bridges gap between traditional capacitors, batteries

More information: Hongtao Sun et al. Three-dimensional holey-graphene/niobia composite architectures for ultrahigh-rate energy storage, Science (2017). DOI: 10.1126/science.aam5852

Abstract
Nanostructured materials have shown extraordinary promise for electrochemical energy storage but are usually limited to electrodes with rather low mass loading (~1 milligram per square centimeter) because of the increasing ion diffusion limitations in thicker electrodes.

We report the design of a three-dimensional (3D) holey-graphene/niobia (Nb2O5) composite for ultrahigh-rate energy storage at practical levels of mass loading (>10 milligrams per square centimeter). The highly interconnected graphene network in the 3D architecture provides excellent electron transport properties, and its hierarchical porous structure facilitates rapid ion transport.

By systematically tailoring the porosity in the holey graphene backbone, charge transport in the composite architecture is optimized to deliver high areal capacity and high-rate capability at high mass loading, which represents a critical step forward toward practical applications.

 

“Holey” graphene improves battery electrodes – May be ‘The Holy Grail’ of Next Generation Batteries 



May 12, 2017

Electrodes containing porous graphene and a niobia composite could help improve electrochemical energy storage in batteries. This is the new finding from researchers at the University of California at Los Angeles who say that the nanopores in the carbon material facilitate charge transport in a battery.

By fine tuning the size of these pores, they can not only optimize this charge transport but also increase the amount of active material in the device, which is an important step forward towards practical applications.


Niobia and holey graphene composite with tailored nanopores

Batteries and supercapacitors are two complementary electrochemical energy-storage technologies. They typically contain positive and negative electrodes with the active electrode materials coated on a metal current collector (normally copper or aluminium foil), a separator between the two electrodes, and an electrolyte that facilitates ion transport.

The electrode materials actively participate in charge (energy) storage, whereas the other components are passive but nevertheless compulsory for making the device work.

Batteries offer high energy density but low power density while supercapacitors provide high power density with low energy density.

Although lithium-ion batteries are the most widely employed batteries today for powering consumer electronics, there is a growing demand for more rapid energy storage (high power) and higher energy density. Researchers are thus looking to create materials that combine the high-energy density of battery materials with the short charging times and long cycle life of supercapacitors.

Such materials need to store a large number of charges (such as Li ions) and have an electrode architecture that can quickly deliver charges (electrons and ions) during a given charge/discharge cycle.

Increasing the mass loading of niobia in electrodes

Nanostructured materials fit the bill here, but unfortunately only for electrodes with low areal mass loading of the active materials (around 1 mg/cm2). “This is much lower than the mass of the passive components (around 10 mg/cm2 or greater),” explains team leader Xiangfeng Duan. “As a result, in spite of the high intrinsic capacity or rate capability of these new nanostructured materials, the scaled area capacity or areal current density of nanostructured electrodes rarely exceeds those of today’s Li-ion batteries.

Thus, these electrodes have not been able to deliver their extraordinary promise in practical commercial devices.

“To take full advantage of these new materials, we must increase the mass loading to a level comparable to or higher than the mass of the passive components. To satisfy the energy storage requirement of an electrode with 10 times higher mass loading requires the rapid delivery of 10 times more charge over a distance that is 10 times greater within a given time. This is a rather challenging task and has proven to be a critical roadblock for new electrode materials.

“We have now addressed this very issue of how we can increase the mass loading of niobia (Nb2O5) in electrode structures without compromising its merit for ultrahigh-rate energy storage,” he continues. “Electrodes with intrinsically high capacity or high rate capability in practical devices require a new architecture that can efficiently deliver sufficient electrons or ions.

We have designed a 3D holey-graphene-Nb2O5 composite with excellent electron and ion transport properties for ultrahigh-rate energy storage at practical levels of mass loading (greater than 10 mg/cm2).”

Porous structure facilitates rapid ion transport

“The highly interconnected graphene network in the 3D architecture provides excellent electron transport properties and its hierarchical porous structure facilitates rapid ion transport,” he adds. “What is more, by systematically tailoring the porosity in the holey graphene backbone, we optimize charge transport in the composite architecture to simultaneously deliver areal capacity and high-rate capability at practical levels of mass loading – something that is a critical step forward towards commercial applications.”

The researchers made their mechanically strong 3D porous composites in a two-step synthesis technique. “We uniformly decorate Nb2O5

Decreasing the fraction of inactive materials

The in-plane pores in the holey graphene sheet function as ion transport “shortcuts” in the hierarchical porous structure to facilitate rapid ion transport throughout the entire 3D electrode and so greatly improve ion transport kinetics and access to ions on the surface of the electrode, Duan tells nanotechweb.org.

Spurred on by these results, the researchers say they will now try to incorporate high-capacity active materials such as silicon and tin oxide to further increase output energy levels in electrochemical cells. “Extremely high mass-loaded electrodes (for example, five times that of practical mass loading, or 50 mg/cm2) could also help decrease the fraction of inactive materials in a device and so simplify the process to make these cells.”


So What’s Next?

Team GNT writes: For the Researchers to take ‘the next step’ further exploration of best outcome and integration of new structured  materials must be completed. And then …

  • Proof of Concept
  • Proof of Scalability 
  • Competitive Market Integration Analysis
  • Manufacturing Platform and Market Distribution 

A lot of hard work! But work that will be well worth the effort if the emerging technology can meet all of the required. Milestones! The current rechargeable battery market is a $112 Billion Market!



The research is detailed in Science DOI: 10.1126/science.aam5852.
Belle Dumé is contributing editor at nanotechweb.org

Chemically tailored graphene advances Potential for use in Semiconductors


Graphene chemicallytaSection of a graphene network with chemically bound hydrogen atom: the spectral vibrational signature of the single carbon-carbon bonds adjacent to the bound hydrogen atom is highlighted in different colors. Credit: Frank Hauke, FAU

Graphene is considered as one of the most promising new materials. However, the systematic insertion of chemically bound atoms and molecules to control its properties is still a major challenge. Now, for the first time, scientists of the Friedrich-Alexander-Universität Erlangen-Nürnberg, the University of Vienna, the Freie Universität Berlin and the University Yachay Tech in Ecuador succeeded in precisely verifying the spectral fingerprint of such compounds in both theory and experiment. Their results are published in the scientific journal Nature Communications.

Two-dimensional consists of single layers of carbon atoms and exhibits intriguing properties. The transparent material conducts electricity and heat extremely well. It is at the same time flexible and solid. Additionally, the electrical conductivity can be continuously varied between a metal and a semiconductor by, e.g., inserting chemically bound atoms and molecules into the graphene structure – the so-called functional groups. These unique properties offer a wide range of future applications as e.g. for new developments in optoelectronics or ultrafast components in the semiconductor industry. However, a successful use of graphene in the semiconductor industry can only be achieved if properties such as the conductivity, the size and the defects of the graphene structure induced by the functional groups can already be modulated during the synthesis of graphene.

In an international collaboration scientists led by Andreas Hirsch from the Friedrich-Alexander-Universität Erlangen-Nürnberg in close cooperation with Thomas Pichler from the University of Vienna accomplished a crucial breakthrough: using the latter’s newly developed experimental set-up they were able to identify, for the first time, vibrational spectra as the specific fingerprints of step-by-step chemically modified graphene by means of light scattering. This spectral signature, which was also theoretically attested, allows to determine the type and the number of in a fast and precise way. Among the reactions they examined, was the chemical binding of hydrogen to graphene. This was implemented by a controlled chemical reaction between water and particular compounds in which ions are inserted in graphite, a crystalline form of carbon.

Additional benefits

“This method of the in-situ Raman spectroscopy is a highly effective technique which allows controlling the function of graphene in a fast, contact-free and extensive way already during the production of the material,” says J. Chacon from Yachay Tech, one of the two lead authors of the study. This enables the production of tailored graphene-based materials with controlled electronic transport properties and their utilisation in .

Explore further: Low-cost and defect-free graphene

More information: Philipp Vecera et al. Precise determination of graphene functionalization by in situ Raman spectroscopy, Nature Communications (2017). DOI: 10.1038/ncomms15192

 

World’s first images of electric currents in Graphene released: Applications for Next Generation Electronics, Quantum Computing, Energy Storage (batteries), Flexible Displays & Bio-Chem Sensors.



Artist’s impression of a diamond quantum sensor. The ‘spotlight’ represents light passing through the diamond defect and detecting the movement of electrons. Electrons are shown as red spheres, trailed by red threads that reveal their path through graphene (a single layer of carbon atoms). Credit: David A. Broadway/cqc2t.org


Researchers at the University of Melbourne are the first in the world to image how electrons move in two-dimensional graphene, a boost to the development of next-generation electronics.

Capable of imaging the behaviour of moving electrons in structures only one atom in thickness, the new technique overcomes significant limitations with existing methods for understanding electric currents in devices based on ultra-thin materials.

“Next-generation electronic devices based on ultra-thin materials, including quantum computers, will be especially vulnerable to contain minute cracks and defects that disrupt current flow,” said Professor Lloyd Hollenberg, Deputy Director of the Centre for Quantum Computation and Communication Technology (CQC2T) and Thomas Baker Chair at the University of Melbourne.

A team led by Hollenberg used a special quantum probe based on an atomic-sized ‘colour centre’ found only in diamonds to image the flow of electric currents in graphene. The technique could be used to understand electron behaviour in a variety of new technologies.

“The ability to see how electric currents are affected by these imperfections will allow researchers to improve the reliability and performance of existing and emerging technologies. We are very excited by this result, which enables us to reveal the microscopic behaviour of current in quantum computing devices, graphene and other 2D materials,” he said.

graphenehydrWatch the video:

The Diamond Quantum Sensor is controlled by lasers.

Artist’s impression of a diamond quantum sensor. The ‘spotlight’ represents light passing through the diamond defect and detecting the movement of electrons. Electrons are shown as red spheres, trailed by red threads that reveal their path through graphene (a single layer of carbon atoms). Credit: David A. Broadway/cqc2t.org

“Next-generation electronic devices based on ultra-thin materials, including quantum computers, will be especially vulnerable to contain minute cracks and defects that disrupt current flow,” said Professor Lloyd Hollenberg, Deputy Director of the Centre for Quantum Computation and Communication Technology (CQC2T) and Thomas Baker Chair at the University of Melbourne.
We are very excited by this result, which enables us to reveal the microscopic behaviour of current in quantum computing devices, graphene and other 2D materials,” he said.

“Researchers at CQC2T have made great progress in atomic-scale fabrication of nanoelectronics in silicon for quantum computers. Like graphene sheets, these nanoelectronic structures are essentially one atom thick.
The success of our new sensing technique means we have the potential to observe how electrons move in such structures and aid our future understanding of how quantum computers will operate.”
In addition to understanding nanoelectronics that control quantum computers, the technique could be used with 2D materials to develop next generation electronics, energy storage (batteries), flexible displays and bio-chemical sensors.

“Our technique is powerful yet relatively simple to implement, which means it could be adopted by researchers and engineers from a wide range of disciplines,” said lead author Dr Jean-Philippe Tetienne from CQC2T at the University of Melbourne.

“Using the magnetic field of moving electrons is an old idea in physics, but this is a novel implementation at the microscale with 21st Century applications.”

The work was a collaboration between diamond-based quantum sensing and graphene researchers. Their complementary expertise was crucial to overcoming technical issues with combining diamond and graphene.

img_0118-1
Seeing is believing: Diamond quantum sensor reveals current flows in next-gen materials. An image of the current flow in graphene, obtained using a diamond quantum sensor. The colour reveals where defects lie by showing the current intensity i.e. the number of electrons passing through each second. Credit: University of Melbourne/cqc2t.org

“No one has been able to see what is happening with electric currents in graphene before,” said Nikolai Dontschuk, a graphene researcher at the University of Melbourne School of Physics.

“Building a device that combined graphene with the extremely sensitive nitrogen vacancy colour centre in diamond was challenging, but an important advantage of our approach is that it’s non-invasive and robust – we don’t disrupt the current by sensing it in this way,” he said.

Tetienne explained how the team was able to use diamond to successfully image the current. “Our method is to shine a green laser on the diamond, and see red light arising from the colour centre’s response to an electron’s magnetic field,” he said. “By analysing the intensity of the red light, we determine the magnetic field created by the electric current and are able to image it, and literally see the effect of material imperfections.”
The current-imaging results were published today in the journal Science Advances.

More information: “Quantum imaging of current flow in graphene,” Science Advances (2017). DOI: 10.1126/sciadv.1602429 , advances.sciencemag.org/content/3/4/e1602429

Provided by: Centre for Quantum Computation & Communication Technology

 

Turning Saltwater N2 Clean drinking Water ~ Graphene Could Solve the World’s Water Crisis: Video


Graphene Desal 1-simulationsp

Published on Apr 29, 2017

Turning  saltwater into clean drinking water is an expensive, energy-intensive process, but could the wonder material graphene make it more accessible?
New Discovery Could Unlock Graphene’s Full Potential

Watch the Video: