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.

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Researchers Intoduce an Electric Field to Enhance Solar Cell Performance


 

Electrical Field pic1Researchers at the Kavli Energy Nanosciences Institute, the University of California at Berkeley and the Lawrence Berkeley National Lab, have succeeded in boosting the performance of a new type of solar cell by simply applying an electric field to it. The device (made of low cost zinc phosphide and graphene) is novel in its design in that it lacks a junction between the two p- and n-type semiconductors that make it up – which is a first. The cell might be ideal for use in areas where the intensity of sunlight changes a lot over the course of the year.

The device and experimental results

“Our solar cell does not need to be doped, nor does it require high-quality heterojunctions, which are challenging and expensive to fabricate,” says team member Oscar Vazquez-Mena. “Our work is a novel and promising approach for making photovoltaics with low-cost and abundant materials such as certain phosphides and sulphides that are easy to synthesize and which are environmentally friendly.”

Beside expensive light absorbers like silicon, there are semiconductors like zinc phosphide, copper zinc tin sulphide, cuprous oxide and iron sulphide that are much cheaper. However, for these materials to efficiently convert sunlight into energy, they need to be doped to form homojunctions, or require complementary emitter materials to form high-quality p-n heterojunctions.

A team led by Alex Zettl, Harry Atwater, Ali Javey and Michael Crommie has now overcome this problem by making a simple junction with graphene rather than a semiconductor. A voltage applied to a gate over the junction can tune the energy barrier between the graphene and an adjoining layer of zinc phosphide to boost how efficiently solar cells made from these materials convert light into energy.

The devices are relatively simple to fabricate, says Vazquez-Mena. “Jeff Bosco from Harry Atwater’s team at Caltech makes high-quality zinc phosphide films and in our lab at UC Berkeley, we are experts at growing graphene on copper substrates. Basically, we transfer the graphene from the copper onto the zinc phosphide film to form a graphene- zinc phosphide junction. We then add an insulator layer on top of the graphene, prepared by our colleagues in Ali Javey’s team, also at UC Berkeley. Finally we add a thin top gate to the structure.”

Barrier is like a dam

Conventional solar cells normally contain two bulk semiconductors, with their electrons at different energy levels. These semiconductors are brought into contact to form an electric barrier between them that separates the electrons from each side. “This barrier can be likened to the dam in a hydroelectric power plant that separates two reservoirs of water at different heights,” explains Vazquez-Mena. “In a solar cell, the electric charges are the water in the dam and we use energy from the Sun to make the charges jump over the barrier.”

In the new device, the researchers used a layer of graphene in place of one of the semiconductors and added a top gate to it. “Why? Because it is easy to control the energy level of electrons in graphene by doing this,” Vazquez-Mena tells nanotechweb.org. “Such a thing is difficult to do in a bulk semiconductor.”

The top gate can regulate the barrier between graphene and the zinc phosphide, needed for the solar cell to work, he adds. “This is critical for the performance of the device and allows us to optimize the energy extracted from it. Going back to the dam analogy, it is as if we would be controlling the height of the dam.”

The fact that we can manipulate the barrier height in this way means that, in principle, we could make graphene junctions with many other materials, he says.

Modifying the barrier

In bulk semiconductor solar cells, the barrier height depends on the intrinsic properties of the materials making up the barrier. So, once you put the materials together, there is not much you can do to change the barrier, explains Vazquez-Mena.

“Our device is very different in that we can modify this barrier by simply applying an electric field to the top gate and adjusting the strength of the field applied for different materials and light conditions to optimize energy conversion. Our device, which is just a basic graphene-zinc phosphide solar cell, normally has an efficiency of 1% without any applied gate voltage, but we have doubled this to 2% by increasing the gate voltage to 2V. We have thus been able to boost its performance beyond the intrinsic properties of the material it is made up of.”

This type of solar cell might be ideal in climes where the sunlight varies a lot, he says – thanks to the fact that we can adjust the barrier to optimize energy conversion.

The California researchers say that they are looking to improve the efficiency of their devices and improving the quality of the graphene-zinc phosphide junction so that it produces a higher photocurrent. “We also want to apply our technology to other low-cost and readily available materials,” says Vazquez-Mena. “For example, the device we have made can be improved by using graphene itself or a transparent conductor like indium-tin oxide as the top gate.”

The team, reporting its work in Nano Letters, says that it will also test copper zinc tin sulphide, cuprous oxides and copper sulphide. “These materials are less harmful to the environment compared with commonly used solar cell materials like cadmium telluride and are cheaper than pure silicon. We definitely have many ideas to try but we also hope that other research groups will be inspired by our experiments and develop similar strategies to keep improving the efficiencies of alternative photovoltaic materials.”

SiNode and Merck’s AZ Electronic Materials to co-develop graphene-based materials for Li-Ion batteries



SiNode-Systems-graphene-silicon-anode-materialSiNode Systems signed a joint-development agreement with Merck’s AZ Electronic Materials with an aim to commercialize graphene-based materials for lithium-ion batteries. The two companies will develop electrode materials that deliver high energy density and improved rate capabilities – to enable Li-Ion batteries that last longer and charge faster.

SiNode, established in 2013 to commercialize a novel anode Li-ion battery technology developed at Northwestern University, developed a composite material of silicon nano-particles and graphene in a layered structure. The company says that their material will enable 10 times higher battery capacity and a tenfold decrease in charging time compared with current technology. The company is now expanding its R&D and pilot manufacturing facility in Chicago.

AZ has exclusive worldwide rights to the high yield preparation methods of graphene oxide invented at Rice University. Pairing this GO materials with SiNode’s electrode materials technology will enable a significant improvement in cell level performance.

SiNode Systems wins Rice University’s business-plan competition, price valued at over $900,000

SiNode Systems was chosen as the top startup company in the 2013 Rice Business Plan Competition (which they say is the largest business plan competition in the world). SiNode’s prize is valued at $911,400, and incldues $700,000 in equity investments, $110,000 in additional cash prizes and $101,400 of business services (including office space, marketing support and business mentoring|).
Rice U Silicon Oxide 49797

 

SiNode, established in 2013 to commercialize a novel anode Li-ion battery technology developed at Northwestern University, developed a composite material of silicon nano-particles and graphene in a layered structure. The company says that their material will enable 10 times higher battery capacity and a tenfold decrease in charging time compared with current technology.

Source: Rice University

Source: SiNode Systems

Dateline Australia: World’s First Technology Breakthrough In Using Graphene For Micro Devices


Aus francesca-iacopi

Next month, Dr. Iacopi will travel to Seattle in the US to address the 4th International Symposium on Graphene Devices.

 

 

 

 

Dr. Francesca Iacopi

Researchers are claiming world-first technology developed at Griffith University will harness the remarkable properties of graphene and could launch the next generation of mass produced, low-cost micro-devices.

Dr. Francesca Iacopi’s novel micro-fabrication process enables production-scale manufacturing of a material companies can use to commercially produce sensor devices which are biocompatible, chemically resistant and highly sensitive.

graphene_cover_orange_highres

“We believe this process will change the way we live by providing the ultimate in device miniaturisation,” says Dr Iacopi, from Griffith University’s Queensland Micro- and Nanotechnology Centre.

“It will influence a lot of different sectors because many modern applications relying on micro and nano-devices will be able to advance by incorporating this technology,” says Dr Iacopi, from Griffith University’s Queensland Micro and Nanotechnology Centre.

“For example, medicine is just one area where this technology can be applied. Someone with diabetes could have a nanochip sitting on their skin -– mass produced with the help of our micro-fabrication process — continuously monitoring their blood, and any changes can be relayed directly to a doctor.”

First isolated in the laboratory about a decade ago, graphene is pure carbon and one of the thinnest, lightest and strongest materials known.

A supreme conductor of electricity and heat, much has been written about its mechanical, electrical, thermal and optical properties and the possibilities with the fabrication of new and advanced micro-devices.

However, progress so far has been slow due to the difficulty in synthesising high quality graphene on to Silicon wafers, which would enable cost-effective mass production of such devices.

That problem has now been overcome.

Working with three PhDs, a postdoctorate, national and international collaborators Dr Iacopi has developed:

  • a low temperature process to synthesise graphene by using a metal alloy catalyst which produces a continuous, high quality, controllable graphene film;
  • a strategy for patterning graphene in such a way that it will grow only on a pre-patterned Silicon Carbide (SiC) layer on Silicon.

“Until now, high quality graphene was restricted to the use of expensive SiC wafers or the use of complicated transfer procedures to Silicon wafers. A cheaper substrate and a simpler methodology was badly needed to ensure the micro-devices would be cost-competitive,” says Dr Iacopi.

“At Griffith, we were the first develop a method for depositing a very high quality thin layer of SiC on to 300mm Si wafers.

“This work is still very early but the prospects are very exciting and broad-ranging.”

Dr Iacopi and her team have already begun seeking industry partners to leverage the technology in an industrial product.

 

Translating Science into Business: The Business of Organic Semiconductors


 

KAUST karl

“There are many things which can go wrong when starting a company; but the worst thing that can go wrong is to not do it,” said Prof. Karl Leo, Director of KAUST’s Solar & Photovoltaics Engineering Research Center, when speaking at an Entrepreneurship Center speaker series event this past spring. Wearing the dual hats of scientist and entrepreneur, Prof. Leo is the author of 440 publications, holds more than 50 patents, and has co-created 8 companies which have generated over 300 jobs.

A physicist by training, Prof. Leo highlighted the point that he is primarily a scientist who stumbled onto business by chance. “For me it’s always started with and been about the science,” he says. All his spin-off companies came about as a result of basic research he and his group conducted on organic semiconductors. Speaking specifically to the young KAUST researchers hoping to emulate his success as academics and entrepreneurs, Prof. Leo said: “The message I want to pass along is if you really want to do things, just be curious. Don’t say I want to do research to make a company. Do very basic research and the spin-off ideas will come along.”

The Growing Influence of Organic Semiconductors

Prof. Karl Leo started doing research on organic semiconductors about 20 years ago. He has since been passionate about this field’s developments and future potential. Despite his early skepticism resulting from the ephemeral lifetime of organic semiconductors in the ’90s, the performance levels of LED devices for instance have gone from just a few minutes of useful life then to virtually not aging today. “In the long-term, as in 20 to 30 years from now, almost everything will be organics,” he believes. “Silicon has dominated electronics for a long time but organic is something new.” Organic products have evolved into a variety of applications such as: small OLED displays, OLED televisions, OLED lighting, OPV and organic electronics.

Organics, as opposed to traditional silicon-based semiconductors, are by nature essentially lousy semiconductors. Mobility, or the speed at which electrons move on these materials, is a really important property. However, when looking at the electronic properties of semiconductors, carbon offers interesting developments for the performance of organics. For instance, graphene, which is a carbon-based organic material, has even higher mobility than silicon.

Organic Semi untitled

One of the companies Prof. Karl Leo co-founded and began operating out of Dresden, Germany in 2003, Novaled, became a leader in in organic light-emitting diode (OLED) field. OLEDs are made up of multiple thin layers of organic materials, known as OLED stacks. They essentially emit light when electricity is applied to them. Novaled became a pioneer in developing highly efficient and long-lifetime OLED structures; and it currently holds the world record in power efficiency. They key to Novaled’s success, as Prof. Leo explains, is “the simple discovery that you can dope organics.” This was a major breakthrough achieved simply adding a very little amount of another molecule.

This organic conductivity doping technology, used to enhance the performance of OLED devices, was the main factor leading to the company being purchased by Samsung in 2013.

Organic Photovoltaics: Technology of the Future

Following the successful commercial penetration of OLED displays in the consumer electronics market, Prof. Karl Leo has since turned his focus on organic photovoltaics. “I think organic PV is something that can change the world,” said Leo. Among the many advantages of organic photovoltaics are that they are thin organic layers which can be applied on flexible plastic substrates. They consume little energy, can be made transparent, and are compatible with low-cost large-area production technologies. Because they are transparent, they can be made into windows for instance, and also be manufactured in virtually any color. All these characteristics make organic PV ideal for consumer products.

Again based on basic research conducted by his group, Prof. Leo also started a company, Heliatek, which is now a world-leader in the production of organic solar film. Heliatek has developed the current world record in the efficiency of transparent solar cells. The company also holds the record for efficiency of opaque cells at 12 percent. Leo believes that it’s possible to achieve up to 20 percent efficiency in the near future, which will be necessary to compete with silicon and become commercially viable.

Don’t Believe Business Plans

Prof. Leo explained that the experience he and his team gained from launching a successful company like Novaled helped them to both define the objectives and obtain funding from investors for his solar cell company, Heliatek. “Once you create a successful company, things get much easier,” he said. But Leo also cautioned the budding entrepreneurs in the audience to be willing to adapt as they present and implement their ideas.

“If you have a good idea and you are convinced you have a good idea, never give up,” he said. But being able to adapt to market needs is also crucial. For instance, Leo’s original business plan for Novaled focused on manufacturing displays. But the realities of the market, and the prohibitive cost of manufacturing displays, convinced his team that the smarter way to go was to supply materials. At the end of the day, what really succeeded in getting a venture capital firm’s attention, after haven been told no 49 times, was his team’s ability to demonstrate the value of the technology.

“Business plans are useful but they must not be overestimated,” said Prof. Leo. Business plans are a good indicator of how entrepreneurs are able to structure their thoughts, identify markets and create a roadmap, but “nobody is able to predict the future in a business plan; it’s not possible.”

 

Definition of Organic Semi-Conductors: Background

An organic semiconductor is an organic material with semiconductor properties, that is, with an electrical conductivity between that of insulators and that of metals. Single molecules, oligomers, and organic polymers can be semiconductive. Semiconducting small molecules (aromatic hydrocarbons) include the polycyclic aromatic compounds pentacene, anthracene, and rubrene. Polymeric organic semiconductors include poly(3-hexylthiophene), poly(p-phenylene vinylene), as well as polyacetylene and its derivatives.

There are two major overlapping classes of organic semiconductors. These are organic charge-transfer complexes and various linear-backbone conductive polymers derived from polyacetylene. Linear backbone organic semiconductors include polyacetylene itself and its derivatives polypyrrole, and polyaniline.

At least locally, charge-transfer complexes often exhibit similar conduction mechanisms to inorganic semiconductors. Such mechanisms arise from the presence of hole and electron conduction layers separated by a band gap.

Although such classic mechanisms are important locally, as with inorganic amorphous semiconductors, tunnelling, localized states, mobility gaps, and phonon-assisted hopping also significantly contribute to conduction, particularly in polyacetylenes. Like inorganic semiconductors, organic semiconductors can be doped. Organic semiconductors susceptible to doping such as polyaniline (Ormecon) and PEDOT:PSS are also known as organic metals

 

Further Information

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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!

 

Quantum Dots may turn House Windows into Solar Panels


 

New-QD-Solar-Cell-id35756-150x150A house window that doubles as a solar panel could be on the horizon, thanks to recent quantum-dot work by researchers at Los Alamos National Laboratory in the US in collaboration with scientists from University of Milano-Bicocca (UNIMIB) in Italy.

Their work, published earlier this year in Nature Photonics, demonstrates that superior light-emitting properties of quantum dots can be applied in solar energy by helping more efficiently harvest sunlight.

“The key accomplishment is the demonstration of large-area luminescent solar concentrators that use a new generation of specially engineered quantum dots,” said lead researcher Victor Klimov of the Center for Advanced Solar Photophysics at Los Alamos. Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry.

A luminescent solar concentrator (LSC) is a photon-management device, representing a slab of transparent material that contains highly efficient emitters such as dye molecules or quantum dots. Sunlight absorbed in the slab is re-radiated at longer wavelengths and guided toward the slab edge equipped with a solar cell.

Quantum dots are embedded in the plastic matrix and capture sunlight to improve solar-panel efficiency.
Courtesy Los Alamos Lab.
 
LUMINESCENT SOLAR CONCENTRATOR AS LIGHT HARVESTER

Sergio Brovelli, a faculty member at UNIMIB and a co-author of the paper, explained, “The LSC serves as a light-harvesting antenna which concentrates solar radiation collected from a large area onto a much smaller solar cell, and this increases its power output. LSCs are especially attractive because in addition to gains in efficiency, they can enable new interesting concepts such as photovoltaic windows that can transform house facades into large-area energy-generation units.”

Because of highly efficient, color-tunable emission and solution processability, quantum dots are attractive materials for use in inexpensive, large-area LSCs. To overcome a nagging problem of light reabsorption, the Los Alamos and UNIMIB researchers developed LSCs based on quantum dots with artificially induced large separation between emission and absorption bands, known as a large Stokes shift.

These “Stokes-shift-engineered” quantum dots represent cadmium selenide/cadmium sulfide (CdSe/CdS) structures in which light absorption is dominated by an ultra-thick outer shell of CdS, while emission occurs from the inner core of a narrower-gap CdSe.

Los Alamos researchers created a series of thick-shell (so-called “giant”) CdSe/CdS quantum dots, which were incorporated by their Italian partners into large slabs (sized in tens of centimeters across) of polymethylmethacrylate. While being large by quantum dot standards, the active particles are still tiny, only about hundred angstroms across.

QUANTUM DOTS USED FOR NEW DISPLAYS

Quantum dots are ultra-small bits of semiconductor matter that can be synthesized with nearly atomic precision via modern methods of colloidal chemistry.

Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100%.3D Printing dots-2

These properties have recently become the basis of a new technology — quantum-dot displays — employed, for example, in the newest generation of the Kindle Fire e-reader.

In a new SPIE.TV video, Lawrence Berkeley National Lab director Paul Alivisatos demonstrates the Kindle Fire quantum-dot display.

 

DOI: 10.1117/2.4201407.10

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

‘Bricks-and-Mortar’ Assembly of New Molecular Structures Demonstrated by Chemists at Indiana University


 

Bricks and Mortar chemistsdemoChemists at Indiana University Bloomington have described the self-assembly of large, symmetrical molecules in bricks-and-mortar fashion, a development with potential value for the field of organic electronic devices such as field-effect transistors and photovoltaic cells.

 

Their paper, “Anion-Induced Dimerization of 5-fold Symmetric Cyanostars in 3D Crystalline Solids and 2D Self-Assembled Crystals,” has been published online by Chemical Communications, a journal of the Royal Society of Chemistry. It is the first collaboration by Amar Flood, the James F. Jackson Associate Professor of Chemistry, and Steven L. Tait, assistant professor of chemistry. Both are in the materials chemistry program in the IU Bloomington Department of Chemistry, part of the College of Arts and Sciences.

The article will appear as the cover article of an upcoming issue of the journal. The cover illustration was created by Albert William, a lecturer in the media arts and science program of the School of Informatics and Computing at Indiana University-Purdue University Indianapolis. William specializes in using advanced graphics and animation to convey complex scientific concepts.

Bricks and Mortar chemistsdemo

This artwork will appear on the cover of Chemical Communications. It depicts the cyanostar molecules moving in solution, ordering on the surface, and stacking by anion binding. Imaging of the surface structure is performed by scanning. 

Lead author of the paper is Brandon Hirsch, who earned the cover by winning a poster contest at the fall 2013 meeting of the International Symposium on Macrocyclic and Supramolecular Chemistry. Co-authors, along with Flood and Tait, include doctoral students Semin Lee, Bo Qiao and Kevin P. McDonald and research scientist Chun-Hsing Chen.

The researchers demonstrate the self-assembly and packing of a five-sided, symmetrical molecule, called cyanostar, that was developed by Flood’s IU research team. While researchers have created many such large, cyclic , or macrocycles, cyanostar is unusual in that it can be readily synthesized in a “one pot” process. It also has an unprecedented ability to bind with large, negatively charged anions such as perchlorate.

“This great piece of work, with state-of-the-art studies of the assembly of some beautiful compounds pioneered by the group in Indiana, shows how anions can help organize molecules that could have very interesting properties,” said David Amabilino, nanomaterials group leader at the Institute of Materials Science of Barcelona. “Symmetry is all important when molecules pack together, and here the supramolecular aspects of these compounds with a very particular shape present tantalizing possibilities. This research is conceptually extremely novel and really interdisciplinary: It has really unveiled how anions could help pull molecules together to behave in completely new ways.”

The paper describes how cyanostar molecules bind with anions in 2-to-1 sandwich-like complexes, with anions sandwiched between two saucer-shaped cyanostars. The study shows the packing of the molecules in repeating patterns reminiscent of the two-dimensional packing of pentagons shown by artist Albrecht Durer in 1525. It further shows the packing to take place not only at but away from the surface of materials.

The future of organic electronics will rely upon packing molecules onto electrode surfaces, yet it has been challenging to get packing of the molecules away from the surface, Tait and Flood said. With this paper, they present a collaborative effort, combining their backgrounds in traditionally distinct fields of , as a new foray to achieve this goal using a bricks-and-mortar approach.

The paper relies on two complementary technologies that provide high-resolution images of molecules:

  • X-ray crystallography, which is being celebrated worldwide for its invention 100 years ago, can provide images of molecules from analysis of the three-dimensional crystalline solids.
  • Scanning tunneling microscopy, or STM, developed in 1981, shows two-dimensional packing of molecules immobilized on a surface.

The results are distinct, with submolecular views of the star-shaped molecules that are a few nanometers in diameter. (A human hair is about 100,000 nanometers thick).

Explore further: Two teams pave way for advances in 2D materials

 

 

Dye-sensitized solar cell absorbs a broad range of visible and infrared wavelengths: Increases Efficiencies


 

Phy Org Dye Solar dyesensitizeDye-sensitized solar cells (DSSCs) rely on dyes that absorb light to mobilize a current of electrons and are a promising source of clean energy. Jishan Wu at the A*STAR Institute of Materials Research and Engineering and colleagues in Singapore have now developed zinc porphyrin dyes that harvest light in both the visible and near-infrared parts of the spectrum1. Their research suggests that chemical modification of these dyes could enhance the energy output of DSSCs.

DSSCs are easier and cheaper to manufacture than conventional silicon , but they currently have a lower efficiency. Ruthenium-based dyes have been traditionally used in DSSCs, but in 2011 researchers developed a more efficient dye based on a zinc atom surrounded by a ring-shaped molecule called a porphyrin. Solar cells using this new dye, called YD2-o-C8, convert visible light into electricity with an efficiency of up to 12.3 per cent. Wu’s team aimed to improve that efficiency by developing a zinc porphyrin dye that can also absorb .

The most successful dyes developed by Wu’s team, WW-5 and WW-6, unite a zinc porphyrin core with a system of fused carbon rings bridged by a nitrogen atom, known as an N-annulated perylene group. Solar cells containing these dyes absorbed more infrared light than YD2-o-C8 and had efficiencies of up to 10.5 per cent, matching the performance of an YD2-o-C8 cell under the same testing conditions (see image).

Phy Org Dye Solar dyesensitize

Zinc porphyrin dyes were used to create solar cells that can absorb both visible and near-infrared light. Credit: A*STAR Institute of Materials Research and Engineering 

Theoretical calculations indicate that connecting the porphyrin and perylene sections of these dyes by a carbon–carbon triple bond, which acts as an electron-rich linker, improved the flow of electrons between them. This bond also reduced the light energy needed to excite electrons in the molecule, boosting the dye’s ability to harvest infrared light.

Adding bulky chemical groups to the dyes also improved their solubility and prevented them from aggregating—something that tends to reduce the efficiency of DSSCs.

However, both WW-5 and WW-6 are slightly less efficient than YD2-o-C8 at converting visible light into electricity, and they also produce a lower voltage. “We are now trying to solve this problem through modifications based on the chemical structure of WW-5 and WW-6,” says Wu.

Comparing the results from more perylene–porphyrin should indicate ways to overcome these hurdles, and may even extend light absorption further into the infrared. “The top priority is to improve the power conversion efficiency,” says Wu. “Our target is to push the efficiency to more than 13 per cent in the near future.”

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More information: Luo, J., Xu, M., Li, R., Huang, K.-W., Jiang, C. et al. N-annulated perylene as an efficient electron donor for porphyrin-based dyes: Enhanced light-harvesting ability and high-efficiency Co(II/III)-based dye-sensitized solar cells. Journal of the American Chemical Society 136, 265–272 (2014). DOI: 10.1021/ja409291g

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