Greater Cycle Life Lithium-Sulfur Batteries Using Nitrogen-Doped Carbon Nanotubes


L Io Batts id36790Sulfur is a very intriguing solution for the design of high energy density storage devices. The lithium-sulfur battery theoretically delivers energy density of 2600 Wh kg-1, which is 3-5 times higher than traditional lithium-ion batteries.

Copyright Michael Berger

 

Unfortunately, several obstacles so far have prevented the practical demonstration of sulfur-based cathodes for Li-S batteries. Among them, the most important one is the rapid capacity fading. “The fast capacity decay of lithium-sulfur battery is ascribed to multifaceted aspects,” Dr. Qiang Zhang, an associate professor at Department of Chemical Engineering at Tsinghua University, tells Nanowerk. “One of the most widely accepted reasons is assigned to the intermediate polysulfides.” Polysulfides are a variety of transition forms of partially lithiated sulfur, which is highly polar and soluble in organic electrolytes. During discharge, they dissolve in the electrolyte, diffuse from cathode to anode, and react with the lithium anode.

“The active materials lose in this way, undoubtedly causing capacity fading,” says Zhang. “While considerable research endeavor is dedicated to solving this problem, what we are interested in is another rarely addressed issue regarding the capacity fading: the dynamic fluctuation of affinity between different sulfur species and conductive host materials.” He continues to explain that, because of the multi-electron-transfer process, sulfur species vary from the initial elemental sulfur, intermediate polysulfides, and final discharge product of lithium sulfides. “Sulfur is unpolar, thus exhibits highest affinity to conventional carbon hosts,” he says. “But polysulfides and lithium sulfides are highly polar, weakening the interaction between them and carbon.

Due to this poor interaction, they easily detach from the carbon host and contribute no capacity. As a result, the performance of a lithium-sulfur battery deteriorates rapidly when only pure carbon hosts is employed.” Consequently, he concludes, the key issue lies in how to choose an ideal host material with high affinity to both unpolar sulfur and polar polysulfides, as well as lithium sulfides.

In new work published in the July 24, 2014 online edition of Advanced Materials Interfaces (“Strongly Coupled Interfaces between a Heterogeneous Carbon Host and a Sulfur-Containing Guest for Highly Stable Lithium-Sulfur Batteries: Mechanistic Insight into Capacity Degradation”), Zhang and his collaborators developed a novel strategy towards highly stable Li-S batteries by building a strongly coupled interface between surface- mediated carbon hosts and various sulfur-containing guests.

Schematic illustration of strongly coupled interfaces between N-doped carbon host and S-containing guest for highly stable Li-S batterySchematic illustration of strongly coupled interfaces between N-doped carbon host and S-containing guest for highly stable Li-S battery. (Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)

In this work, the team used nitrogen-doped carbon nanotubes as host material for the sulfur cathode: Nitrogen atoms with higher electronegativity are incorporated into the graphitic lattices of pristine carbon nanotubes, thereby providing a capability to tune their electronic structure and surface properties.

How do the doping nitrogen atoms affect the electrochemical behavior when nitrogen-doped carbon nanotubes are applied to lithium-sulfur battery? Hong-Jie Peng, a graduate student in Zhang’s group and the paper’s first author, answers this question:

“Firstly, we conducted a density functional theory (DFT) study and designed three molecular models to illustrate pure carbon, carbon with nitrogen at the edge – which we called pyridinic nitrogen – and carbon with nitrogen substituting the central carbon atom, which we called quaternary nitrogen.” “Through theoretical calculations, we found that nitrogen-doped carbon nanotubes exhibited stronger interaction with polysulfides and lithium sulfides,” he continues. “This is attributed to the adsorption of these polar sulfur species on the negatively charged nitrogen-doped sites.

It revealed that nitrogen-doped carbon nanotubes might be worth trying as host materials.” In their experiments, the team then prepared nitrogen-doped carbon nanotube/sulfur composites and assembled batteries to check if their theoretical results were reliable. “We were very happy to see that the electrochemical experiment matched our theoretical prediction very well,” says Peng.

“Compared to pristine carbon nanotubes-based host materials, the cycling life was significantly enhanced by six times.” In conclusion, this work highlights the importance of a stable dynamic interface between carbon hosts and sulfur-containing guests and sheds new light on the lithium-sulfur battery decay mechanism. “In fact” says Zhang, “the concept of building heterogeneous cathode scaffold won’t stop here. More advanced host materials satisfying the demand of amphiphilicity to both unpolar and polar sulfur species need to be explored.

Nanomaterials Give Boost to Immune Cells to Fight Cancer


immunecellsg(Phys.org) —Scientists at Yale University have developed a novel cancer immunotherapy that rapidly grows and enhances a patient’s immune cells outside the body using carbon nanotube-polymer composites; the immune cells can then be injected back into a patient’s blood to boost the immune response or fight cancer.

As reported Aug. 3 in Nature Nanotechnology, the researchers used bundled carbon nanotubes (CNTs) to incubate cytotoxic T cells, a type of white blood cell that is important to . According to the researchers, the topography of the CNTs enhances interactions between cells and long-term cultures, providing a fast and effective stimulation of the cytotoxic T cells that are important for eradicating cancer.

The researchers modified the CNTs by chemically binding them to polymer nanoparticles that held Interleukin-2, a cell signaling protein that encourages T cell growth and proliferation. Additionally, in order to mimic the body’s methods for stimulating cytotoxic T cell proliferation, the scientists seeded the surfaces of the CNTs with molecules that signaled which of the patient’s cells were foreign or toxic and should be attacked.

immunecellsg

A high-resolution, scanning electron microscope image of the carbon nanotube-polymer composite. The bundled CNTs appear as spaghetti-like structures.

Over the span of 14 days, the number of T cells cultured on the composite nanosystem expanded by a factor of 200, according to the researchers. Also, the method required 1,000 times less Interleukin-2 than conventional culture conditions. A magnet was used to separate the CNT-polymer composites from the T cells prior to injection.

“In repressing the body’s , tumors are like a castle with a moat around it,” says Tarek Fahmy, an associate professor of biomedical engineering and the study’s principal investigator. “Our method recruits significantly more cells to the battle and arms them to become superkillers.”

According to Fahmy, previous procedures for boosting antigen-specific T cells required exposing the patient’s harvested to other cells that stimulate activation and proliferation, a costly procedure that risks an adverse reaction to foreign cells. The Yale team’s use of magnetic CNT-polymer composites eliminates that risk by using simple, inexpensive magnets.

“Modulatory nanotechnologies can present unique opportunities for promising new therapies such as T cell immunotherapy,” says Tarek Fadel, lead author of the research and a Yale postdoc who is currently a staff scientist with the National Nanotechnology Coordination Office. “Engineers are progressing toward the design of the next generations of nanomaterials, allowing for further breakthrough in many fields, including cancer research.”

Explore further: New ‘doping’ method improves properties of carbon nanotubes

Researchers Unveil New Solar Cell: Carbon Nanotubes that Convert Sunlight into MORE Power


CNT Solar 1-researchersuA team of researchers with members from several research facilities in the U.S. has unveiled a new type of solar cell based on single walled carbon nanotubes (SWCNTs). In their paper published in the journal Nano Letters, the team claims they have overcome limitations with such technology resulting in a solar cell that is two times as good at converting sunlight into power as other SWCNT based cells.

Scientists would like to use carbon nanotubes in solar cells because it would mean lighter panels, lower costs and easier to make products. They’ve been hampered, however, by the limited amount of power that such cells are able to generate. In this new effort the research team claims they’ve overcome the limitations of prior generations of SWCNTs by adding more chiralities to the nanotubes. Chiralities describe the way atoms are arranged in their hexagonal patterns—different patterns allow for absorbing different portions of the . Most prior efforts have used just one. This new team has added what they call polychiral SWCNTs to their cells which allows for capturing much more of the solar spectrum—most notably, in the near infrared, which other don’t make use of at all.

CNT Solar 1-researchersu

The researchers also added an ability to control the interface between the underlying hole-transport layer and the active photovoltaic layer, allowing the electron and hole pair (excitons) to recombine more efficiently. Taken together the two improvements serve to allow for both higher current and voltage, resulting in record high power conversion efficiency. They report that The National Renewable Energy Laboratory has already certified (by verifying) the performance claimed by the team. But the team isn’t done just yet. They want to improve the even more and may do so by testing new materials not used in any other cell.

Scientists would like to use carbon nanotubes in solar cells because it would mean lighter panels, lower costs and easier to make products. They’ve been hampered, however, by the limited amount of power that such cells are able to generate. In this new effort the research team claims they’ve overcome the limitations of prior generations of SWCNTs by adding more chiralities to the nanotubes. Chiralities describe the way atoms are arranged in their hexagonal patterns—different patterns allow for absorbing different portions of the . Most prior efforts have used just one. This new team has added what they call polychiral SWCNTs to their cells which allows for capturing much more of the solar spectrum—most notably, in the near infrared, which other don’t make use of at all.

The researchers also added an ability to control the interface between the underlying hole-transport layer and the active photovoltaic layer, allowing the electron and hole pair (excitons) to recombine more efficiently. Taken together the two improvements serve to allow for both higher current and voltage, resulting in record high power conversion efficiency. They report that The National Renewable Energy Laboratory has already certified (by verifying) the performance claimed by the team. But the team isn’t done just yet. They want to improve the even more and may do so by testing new materials not used in any other cell.

While it could be awhile before a product is made for sale based on what the team has wrought, their research might cause others in the field to take notice, which could conceivably result in a resurgence of interest in carbon based in general—interest has lagged in recent years as researchers began to doubt they could make them both useful and profitable. Hopefully so, because it would mean less expensive (and lighter) that produce as much power as conventional panels or even more—leading perhaps to a major move from greenhouse gas emitting coal fired to something much cleaner.

Explore further: Inexpensive flexible fiber perovskite solar cells

More information: Polychiral Semiconducting Carbon Nanotube–Fullerene Solar Cells, Nano Lett., Article ASAP, DOI: 10.1021/nl5027452

Abstract
Single-walled carbon nanotubes (SWCNTs) have highly desirable attributes for solution-processable thin-film photovoltaics (TFPVs), such as broadband absorption, high carrier mobility, and environmental stability. However, previous TFPVs incorporating photoactive SWCNTs have utilized architectures that have limited current, voltage, and ultimately power conversion efficiency (PCE). Here, we report a solar cell geometry that maximizes photocurrent using polychiral SWCNTs while retaining high photovoltage, leading to record-high efficiency SWCNT–fullerene solar cells with average NREL certified and champion PCEs of 2.5% and 3.1%, respectively. Moreover, these cells show significant absorption in the near-infrared portion of the solar spectrum that is currently inaccessible by many leading TFPV technologies.

 

 

Carbon Nanotubes to Improve Coatings


image descriptionResin coatings are widely used in various sectors, like the aeronautical and automotive sectors, and in the structural components of aircraft and vehicles, in particular. Research by the UPV/EHU-University of the Basque Country has used carbon nanotubes to improve the properties of these coatings.

The research has been conducted within the POCO European project and seeks to come up with strategies to spread carbon nanotubes properly throughout different polymers. Carbon nanotubes improve the conductivity of these coatings, repair any scratches they may have and have excellent mechanical properties: they are tough and rigid and, what is more, conduct electricity. Epoxy resins, by contrast, are insulating materials. So if these nanotubes are added to them, the coatings are also turned into conductors. “However, to transmit or enhance these properties better, the carbon nanotubes must be properly spread throughout the material,” pointed out the UPV/EHU chemist Galder Kortaberria. But this advantage turns into a problem for the nanotubes because they tend to form clusters and often group together. So they cause problems when it comes to being expanded across a matrix. So for that very reason strategies or methods are needed to help the carbon nanotubes spread as much as possible within the polymer matrix.

image description

A new development: the use of copolymers

Different strategies are used to spread the carbon nanotubes across the polymer matrix. Firstly, electric and magnetic fields. Since carbon nanotubes are conductors, they position and align themselves in the desired direction when they come up against an electric field. What is more, the surface of these nanotubes can be changed by means of chemical treatments until a specific affinity or compatibility is achieved with the epoxy. Finally, this UPV/EHU research team has put forward a new strategy: the use of copolymers, in other words, blocks of two different polymers joined to each other by means of chemical bonds. In this case, the styrene-butadiene-styrene copolymer was used.

The first step was to chemically transform one of the blocks of the copolymer (the butadiene in this case), to make it compatible with the epoxy resin matrix. The other block, by contrast, was divided, but as it has a covalent bond with the butadiene, the division was on a nanometric scale and nanostructures were produced. “That way the carbon nanotubes disperse much better across the epoxy matrix, without forming clusters,” pointed out Kortaberria. In general, “all the coatings we prepared were more stable than the ones based on the epoxy alone. The most stable coating is the one that has 0.2% of carbon nanotubes,” he added. The research team saw that the coating properties could be improved by varying the quantities of copolymers and nanotubes, thermal stability and behaviour, in particular, when handling temperature, and that coatings suitable for industry could be designed.

“The spread of the nanotubes has improved considerably with the use of copolymers, and the properties of the epoxy resin-based coatings are maintained; in some cases they have even improved,” asserted Kortaberria. “All this makes it possible to produce coatings suitable for industry with enhanced characteristics,” he added.

Source: nanoBasque

Oklahoma Nanotechnology Company Secures $2.7M to Expand Manufacturing Capacity


 

Food and NT 4153936-3x2-340x227A Norman-based technology company has secured $2.7 million in financing to add staff and expand its production capacity.

SouthWest NanoTechnologies Inc. produces carbon nanotube materials used in printed electronics, energy storage and composites applications.

“We need to add to our capacity to meet the demand for our specialty multi-wall products driven by our strategic partnerships and distribution agreements,” company President Dave Arthur said in a news release.

“This additional funding will also be used for (research and development) to develop additional carbon nanotube materials and inks that meet customer specifications.”

SouthWest NanoTechnologies will use its new funding to expand its Norman plant and fill about eight available positions for scientists, engineers and technical support personnel.

Arthur said the company’s Norman plant has only one shift of workers, but he hopes to increase that to three by the end of the year to churn out more nanotubes.

“We’re shipping as much of that material as we can make,” he said.

The company is getting $1.7 million as part of a $4 million round of convertible notes.

The other $1 million is from a venture debt transaction.

Arthur said the company also intends to invest in ramping up its catalyst operations, which provide the feedstock to make nanotubes.

SouthWest NanoTechnologies has licensed its catalyst to an Asian nanotube manufacturer to serve that market, he said.

Such deals could be expanded to include manufacturers around the world as the technology becomes more widespread.

Dave Arthur w300-97e212016cc04a09d6d1ac403be54d47

               

Dave Arthur, SouthWest NanoTechnologies Inc. president

 

 

 

Arthur said in the next five years or so carbon nanotubes could be used to enhance cement and asphalt, reducing infrastructure costs and making it easier to detect cracks.

Graphene (Oxide) for New Solar Cells: Stronger, Cheaper .. Better?


Graphene Solar Cells 9138062484_ca590547c3_kThere remains a lot to learn on the frontiers of solar power research, particularly when it comes to new advanced materials which could change how we harness energy.

Under the guidance of Canada Research Chair in Materials Science with Synchrotron Radiation, Dr. Alexander Moewes, University of Saskatchewan researcher Adrian Hunt spent his PhD investigating graphene , a cutting-edge material that he hopes will shape the future of technology.

To understand graphene oxide, it is best to start with pure graphene, which is a single-layer sheet of carbon atoms in a honeycomb lattice that was first made in 2004 by Andre Geim and Kostya Novoselov at the University of Manchester – a discovery that earned the two physicists a Nobel Prize in 2010.

“It is incredibly thin, therefore it is incredibly transparent. It also has extremely high conductivity, it’s much better than copper, and it’s extremely strong, its tensile strength is even stronger than steel,” Hunt said.

“Air doesn’t damage it. It can’t corrode, it can’t degrade. It’s really stable.”

All of this makes graphene a great candidate for . In particular, its transparency and conductivity mean that it solves two problems of solar cells: first, light needs a good conductor in order to get converted into usable energy; secondly, the cell also has to be transparent for light to get through.CNT multiprv1_jpg71ec6d8c-a1e2-4de6-acb6-f1f1b0a66d46Larger

Most solar cells on the market use with a non-conductive glass protective layer to meet their needs.

“Indium is extremely rare, so it is becoming more expensive all the time. It’s the factor that will keep solar cells expensive in the future, whereas graphene could be very cheap. Carbon is abundant,” said Hunt.

Although graphene is a great conductor, it is not very good at collecting the electrical current produced inside the solar cell, which is why researchers like Hunt are investigating ways to modify graphene to make it more useful.

Graphene oxide, the focus of Hunt’s PhD work, has oxygen forced into the carbon lattice, which makes it much less conductive but more transparent and a better charge collector. Whether or not it will solve the solar panel problem is yet to be seen, and researchers in the field are building up their understanding of how the new material works.

Using X-ray scattering techniques at the REIXS and SGM beamlines at the Canadian Light Source, as well as a Beamline 8.0.1 at the Advanced Light Source, Hunt set out to learn more about how oxide groups attached to the graphene lattice changed it, and how in particular they interacted with charge-carrying graphene atoms.

“Graphene oxide is fairly chaotic. You don’t get a nice simple structure that you can model really easily, but I wanted to model graphene oxide and understand the interplay of these parts.”

Previous models had seemed simplistic to Hunt, and he wanted a model that would reflect graphene oxide’s true complexity.

Each different part of the graphene oxide has a unique electronic signature. Using the synchrotron, Hunt could measure where electrons were on the graphene, and how the different oxide groups modified that.

He showed that previous models were incorrect, which he hopes will help improve understanding of the effects of small shifts in oxidization.

Moreover, he studied how graphene oxide decays. Some of the oxide groups are not stable, and can group together to tear the lattice; others can react to make water. If graphene oxide device has water in it, and it is heated up, the water can actually burn the and produce carbon dioxide. It’s a pitfall that could be important to understand in the development of long-lasting solar cells, where sun could provide risky heat into the equation.

More research like this will be the key to harnessing graphene for solar power, as Hunt explains.

“There’s this complicated chain of interreactions that can happen over time, and each one of those steps needs to be addressed and categorized before we can make real progress.”

Explore further: Super-stretchable yarn is made of grapheme

Read more at: http://phys.org/news/2014-08-stronger-solar-cells-graphene-cusp.html#jCp

Genesis Nanotech Headlines Are Out!


Organ on a chip organx250Genesis Nanotech Headlines Are Out! Read All About It!

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Visit Our Website: www.genesisnanotech.com

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SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA

Chairman Terry: “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development.”

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:

“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”

 

 

electron-tomography

“Great Things from Small Things!” … We Couldn’t Agree More!

 

Subcommittee Examines Breakthrough Nanotechnology Opportunities for America


Applications-of-Nanomaterials-Chart-Picture1SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA
July 29, 2014

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on “Nanotechnology: Understanding How Small Solutions Drive Big Innovation.” Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is approximately 1 to 100 nanometers (one nanometer is a billionth of a meter). This technology brings great opportunities to advance a broad range of industries, bolster our U.S. economy, and create new manufacturing jobs. Members heard from several nanotech industry leaders about the current state of nanotechnology and the direction that it is headed.UNIVERSITY OF WATERLOO - New $5 million lab

“Just as electricity, telecommunications, and the combustion engine fundamentally altered American economics in the ‘second industrial revolution,’ nanotechnology is poised to drive the next surge of economic growth across all sectors,” said Chairman Terry.

 

 

Applications of Nanomaterials Chart Picture1

Dr. Christian Binek, Associate Professor at the University of Nebraska-Lincoln, explained the potential of nanotechnology to transform a range of industries, stating, “Virtually all of the national and global challenges can at least in part be addressed by advances in nanotechnology. Although the boundary between science and fiction is blurry, it appears reasonable to predict that the transformative power of nanotechnology can rival the industrial revolution. Nanotechnology is expected to make major contributions in fields such as; information technology, medical applications, energy, water supply with strong correlation to the energy problem, smart materials, and manufacturing. It is perhaps one of the major transformative powers of nanotechnology that many of these traditionally separated fields will merge.”

Dr. James M. Tour at the Smalley Institute for Nanoscale Science and Technology at Rice University encouraged steps to help the U.S better compete with markets abroad. “The situation has become untenable. Not only are our best and brightest international students returning to their home countries upon graduation, taking our advanced technology expertise with them, but our top professors also are moving abroad in order to keep their programs funded,” said Tour. “This is an issue for Congress to explore further, working with industry, tax experts, and universities to design an effective incentive structure that will increase industry support for research and development – especially as it relates to nanotechnology. This is a win-win for all parties.”

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Professor Milan Mrksich of Northwestern University discussed the economic opportunities of nanotechnology, and obstacles to realizing these benefits. He explained, “Nanotechnology is a broad-based field that, unlike traditional disciplines, engages the entire scientific and engineering enterprise and that promises new technologies across these fields. … Current challenges to realizing the broader economic promise of the nanotechnology industry include the development of strategies to ensure the continued investment in fundamental research, to increase the fraction of these discoveries that are translated to technology companies, to have effective regulations on nanomaterials, to efficiently process and protect intellectual property to ensure that within the global landscape, the United States remains the leader in realizing the economic benefits of the nanotechnology industry.”

James Phillips, Chairman & CEO at NanoMech, Inc., added, “It’s time for America to lead. … We must capitalize immediately on our great University system, our National Labs, and tremendous agencies like the National Science Foundation, to be sure this unique and best in class innovation ecosystem, is organized in a way that promotes nanotechnology, tech transfer and commercialization in dramatic and laser focused ways so that we capture the best ideas into patents quickly, that are easily transferred into our capitalistic economy so that our nation’s best ideas and inventions are never left stranded, but instead accelerated to market at the speed of innovation so that we build good jobs and improve the quality of life and security for our citizens faster and better than any other country on our planet.”

Chairman Terry concluded, “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development. I believe the U.S. should excel in this area.”

– See more at: http://energycommerce.house.gov/press-release/subcommittee-examines-breakthrough-nanotechnology-opportunities-america#sthash.YnSzFU10.dpuf

Carbyne: Carbon-Atom Chain Goes from Metal to Semiconductor: Useful in Many Applications


Carbyne 140721124028-largeApplying just the right amount of tension to a chain of carbon atoms can turn it from a metallic conductor to an insulator, according to Rice University scientists.

 

Stretching the material known as carbyne — a hard-to-make, one-dimensional chain of carbon atoms — by just 3 percent can begin to change its properties in ways that engineers might find useful for mechanically activated nanoscale electronics and optics.

The finding by Rice theoretical physicist Boris Yakobson and his colleagues appears in the American Chemical Society journal Nano Letters.

Carbyne 140721124028-large

Carbyne chains of carbon atoms can be either metallic or semiconducting, according to first-principle calculations by scientists at Rice University. Stretching the chain dimerizes the atoms, opening a band gap between the pairs.

Until recently, carbyne has existed mostly in theory, though experimentalists have made some headway in creating small samples of the finicky material. The carbon chain would theoretically be the strongest material ever, if only someone could make it reliably.

The first-principle calculations by Yakobson and his co-authors, Rice postdoctoral researcher Vasilii Artyukhov and graduate student Mingjie Liu, show that stretching carbon chains activates the transition from conductor to insulator by widening the material’s band gap. Band gaps, which free electrons must overcome to complete a circuit, give materials the semiconducting properties that make modern electronics possible.

In their previous work on carbyne, the researchers believed they saw hints of the transition, but they had to dig deeper to find that stretching would effectively turn the material into a switch.

Each carbon atom has four electrons available to form covalent bonds. In their relaxed state, the atoms in a carbyne chain would be more or less evenly spaced, with two bonds between them. But the atoms are never static, due to natural quantum uncertainty, which Yakobson said keeps them from slipping into a less-stable Peierls distortion.

“Peierls said one-dimensional metals are unstable and must become semiconductors or insulators,” Yakobson said. “But it’s not that simple, because there are two driving factors.”

One, the Peierls distortion, “wants to open the gap that makes it a semiconductor.” The other, called zero-point vibration (ZPV), “wants to maintain uniformity and the metal state.”

Yakobson explained that ZPV is a manifestation of quantum uncertainty, which says atoms are always in motion. “It’s more a blur than a vibration,” he said. “We can say carbyne represents the uncertainty principle in action, because when it’s relaxed, the bonds are constantly confused between 2-2 and 1-3, to the point where they average out and the chain remains metallic.”

But stretching the chain shifts the balance toward alternating long and short (1-3) bonds. That progressively opens a band gap beginning at about 3 percent tension, according to the computations. The Rice team created a phase diagram to illustrate the relationship of the band gap to strain and temperature.

How carbyne is attached to electrodes also matters, Artyukhov said. “Different bond connectivity patterns can affect the metallic/dielectric state balance and shift the transition point, potentially to where it may not be accessible anymore,” he said. “So one has to be extremely careful about making the contacts.”

“Carbyne’s structure is a conundrum,” he said. “Until this paper, everybody was convinced it was single-triple, with a long bond then a short bond, caused by Peierls instability.” He said the realization that quantum vibrations may quench Peierls, together with the team’s earlier finding that tension can increase the band gap and make carbyne more insulating, prompted the new study.

“Other researchers considered the role of ZPV in Peierls-active systems, even carbyne itself, before we did,” Artyukhov said. “However, in all previous studies only two possible answers were being considered: either ‘carbyne is semiconducting’ or ‘carbyne is metallic,’ and the conclusion, whichever one, was viewed as sort of a timeless mathematical truth, a static ‘ultimate verdict.’ What we realized here is that you can use tension to dynamically go from one regime to the other, which makes it useful on a completely different level.”

Yakobson noted the findings should encourage more research into the formation of stable carbyne chains and may apply equally to other one-dimensional chains subject to Peierls distortions, including conducting polymers and charge/spin density-wave materials.

The Robert Welch Foundation, the U.S. Air Force Office of Scientific Research and the Office of Naval Research Multidisciplinary University Research Initiative supported the research. The researchers utilized the Data Analysis and Visualization Cyberinfrastructure (DAVinCI) supercomputer supported by the NSF and administered by Rice’s Ken Kennedy Institute for Information Technology.


Story Source:

The above story is based on materials provided by Rice University. The original article was written by Mike Williams. Note: Materials may be edited for content and length.

NANOTECHNOLOGY – On the Horizon and in the Far Future: Video


 

 

 

What is Nanotechnology?

 
A basic definition: Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced.

 

 
In its original sense, ‘nanotechnology’ refers to the projected ability to construct items from the bottom up, using techniques and tools being developed today to make complete, high performance products.

Nanotechnology (sometimes shortened to “nanotech”) is the manipulation of matter on an atomic and molecular scale. The earliest, widespread description of nanotechnology referred to the particular technological goal of precisely manipulating atoms and molecules for fabrication of macroscale products, also now referred to as molecular nanotechnology.

A more generalized description of nanotechnology was subsequently established by the National Nanotechnology Initiative, which defines nanotechnology as the manipulation of matter with at least one dimension sized from 1 to 100 nanometers. This definition reflects the fact that quantum mechanical effects are important at this quantum-realm scale, and so the definition shifted from a particular technological goal to a research category inclusive of all types of research and technologies that deal with the special properties of matter that occur below the given size threshold.

It is therefore common to see the plural form “nanotechnologies” as well as “nanoscale technologies” to refer to the broad range of research and applications whose common trait is size. Because of the variety of potential applications (including industrial and military), governments have invested billions of dollars in nanotechnology research.

Through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars. The European Union has invested 1.2 billion and Japan 750 million dollars