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Antwort auf Beitrag Nr.: 47.514.574 von Popeye82 am 14.08.14 12:55:47
Ingenuity Lab "has sights set on 'revolutionary health advances' " - NW - Jul 4, 2014
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Antwort auf Beitrag Nr.: 47.514.664 von Popeye82 am 14.08.14 13:01:18
"Layered nanosheet membranes for 'ultrafast molecule separation' " - NW - Jun 17, 2014

"The atomically thin, porous graphene membranes represent a new class of ideal molecular sieves, where transport occurs through pores which have a thickness and diameter on the atomic scale. These characteristics make graphene an ideal material for creating a separation membrane because it is durable and yet doesn’t require a lot of energy to push molecules through it.
Simulations point to graphene oxide frameworks' great potential in water purification and researchers already have used Individual graphene sheets and their functionalized derivatives to remove metal ions and organic pollutants from water (read more: "Nanotechnology water remediation with bulky graphene materials") and simulations

More recently, researchers have begun exploring analogues of graphene, i.e. other two-dimensional (2D) layered materials such as boron and molybdenum oxides (read more: "Two-dimensional nanotechnology materials beyond graphene").

"Although tens of novel 2D layered materials are found, the separation membranes made of them are rather scarce, except recently for MoS2 and graphene oxide nanosheets," Xinsheng Peng, a Professor in the State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering at Zhejiang University, tells Nanowerk. "Like graphene and its derivatives, layered transition-metal dichalcogenides have also desirable mechanical properties and could be assembled into lamellar thin films. Therefore, they are expected to be used to construct novel high-performance lamellar separation membranes."

In new work, Peng and his collaborators have developed a new separation membrane with 2D layered transition metal dichalcogenides (tungsten disulfide) for size-selective separation of small molecules of about 3 nm. As they reported in ACS Nano ("Ultrafast Molecule Separation through Layered WS2 Nanosheet Membranes"), as-prepared WS2 membranes exhibit 5 times higher water permeance than graphene oxide membranes with similar rejection.

- Schematics of the nanostrand-channeled WS2 membrane. (Reprinted with permission by American Chemical Society) -

The team assembled their separation membrane from chemically exfoliated WS20 nanosheets by filtration. As prepared, this 300-500 nm thick membrane demonstrates a water permeance of 450 L/m2•h•bar with over 90% rejection for 3 nm molecules (Evans Blue). To further improve the water permeance, they employed ultrathin metal hydroxide nanostrands to create more fluidic channels while keeping the rejection rate of specific molecules unchanged. This more than doubled the membrane performance to 930 L/m2•h•bar.
Peng points out that a well calibrated thickness is crucial for a highly efficient separation membrane to balance water flux and rejection rate: "A too thick membrane has low water flux despite high rejection rate, while a thinner membrane usually presents higher flux but worse rejection and suffers mechanical problems."

When testing their membranes under pressure, the team found that the as-prepared WS2 membrane linearly depends on pressure, as was expected. The nanostrand-channeled WS2 membrane however displays a rather different pressure-dependent water flux.

"At lower pressure range, similar to the as-prepared membranes, the water flux increases linearly with external pressure," Peng describes the results. "However, at 0.3 MPa, we observed a transition of water flux with respect to pressure. The flux at the external pressure above 0.3 MPa is fitted with a straight line with larger slope. The transition implies a geometry evolution of the nanochannels during the pressure loading on the channeled membranes beyond 0.3 MPa."

The team speculated that the larger water flux at higher pressure may be attributed to the formation of new fluidic channels.

"Our pressure loading-unloading tests suggests that the channels arising from ultrathin nanostrands are cracked between 0.3 and 0.4 MPa," explains Peng. "These cracks produce new fluidic nanochannels that further results in water flux 4 times that of the as-prepared WS2 membrane without degradation of the rejection performance."

He notes, though, that the ratio of WS2 suspension and ultrathin nanostrands needs to be carefully adjusted. An excess of nanostrands will result in their overlapping, which produces larger channels in the membranes, leading to worse separation performance.

Overall, the results suggest that WS2 membranes hold promising potential for use in applications for ultrafast small organic molecule separation for water purification.

The development of more 2D-layered materials will also expand the family of 2D-layered material separation membranes," concludes Peng. "Due to their individual unique surface states in combination with different preparation strategies, these novel membranes will exhibit different water permeation behavior and separation performances. In our opinion, the challenge likely comes from how to model the new 2D-layered materials in a proper way."

By Michael Berger. Copyright © Nanowerk "
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Antwort auf Beitrag Nr.: 47.514.943 von Popeye82 am 14.08.14 13:23:19
DNA sequencing reaches new lengths - NW/UoW/NBT, WASHINGTON - Jul 17, 2014

"Sequencing technologies have made it cheaper and faster to read the sequence of bases on a strand of DNA. A promising technology to take these advances further is nanopore sequencing. Individual strands of DNA are moved through a nanopore gap not much wider than the DNA itself. As the DNA passes through the nanopore, continuous information is gained about the sequence of individual bases – the A, C, G and Ts that make up DNA. So far the technology has been used for sequencing relatively short fragments of DNA around 100 bases long.

“One reason why people are so excited about nanopore DNA sequencing is that the technology could possibly be used to create ‘tricorder’-like devices for detecting pathogens or diagnosing genetic disorders rapidly and on-the-spot,” commented Andrew Laszlo, a researcher in nanopore technology at the University of Washington.

Researchers from the University of Washington’s Departments of Physics and Genome Sciences have developed a nanopore sequencing technique reaching read lengths of several thousand :eek: :eek: :eek: bases. The result is the latest in a series of advances in nanopore technology developed at the university.

The team, led by Jens Gundlach, published their findings in Nature Biotechnology as an advanced online publication on June 25, 2014 ("Decoding long nanopore sequencing reads of natural DNA").

- Depiction of DNA (green) passing through a polymerase (white) followed by the nanopore protein MspA (yellow/red) embedded in a lipid bilayer (cyan). University of Washington researchers use this system to identify the sequences of individual strands of DNA. (Image: Ian Derrington, University of Washington) -

This is the first time anaaaaaaaaaaaaaaayone :eek: has shown that nanopores can be used to generate interpretable signatures corresponding to very long DNA sequences from real-world genomes,” said co-author Jay Shendure, an associate professor in Genome Sciences, “It’s a major step forward.

The idea for nanopore sequencing originated in the 90s: a lipid membrane, similar to the material that makes up the cell wall, acts as a barrier separating two liquids. Inserted into the membrane is a tiny gap, just nanometers across, called a nanopore. By applying a voltage difference across the barrier, ions in the liquid try to move between the two sides of the barrier and the only way to do this is to flow through the nanopore. The movement of the charged molecules between the two liquids is a current, just like electrons moving along a wire in an electrical circuit, and can be recorded.

Any DNA in the system is also pulled towards the other side of the barrier by the voltage difference, since DNA is negatively charged, and just like the ions it has to pass through the nanopore. The difference is that the DNA is much bigger than the ions and partially blocks the nanopore, making it harder for the smaller molecules to pass through. As the ions are blocked by the DNA, there is a measurable difference in the current flowing across the membrane which is dependent on the DNA base passing through the nanopore. By measuring the changing current, information can be gained on the bases passing through.

The researchers created the nanopore by inserting a single protein called Mycobacterium smegmatis porin A, or MspA, in the membrane. MspA is normally found lining the membrane of a species of bacteria, controlling the intake of nutrients.

One challenge the researchers faced was the control of the DNA passing through the nanopore. Normally, the DNA would zip through the MspA nanopore too fast to detect the changes in the current. The researchers slowed the DNA movement through the pore using a second protein called phi29 DNA polymerase (DNAP), which captures DNA and slows its movement through the pore.

The shape of the protein MspA meant that several bases passed through the nanopore at one time and the current changes were the result of a combination of those bases. This presented another challenge. Since several bases passed through the nanopore at one time, the researchers needed a way to decipher what the current changes meant. To do this, they first made a library of DNA sequences that contains all possible combinations of 4 nucleotides (for the mathematically inclined, the library is 44 = 256 bases long – a string of 4 bases with 4 possible choices for each DNA base). The library, whose sequence was already known, was run though the nanopore first to find the current associated with each set of DNA base combinations. They combined the library measurements with known genome sequences to generate a set of expected current changes that could be compared to experimental measurements.

The researchers tested their approach by sequencing the entire genome of bacteriophage Phi X 174, a virus that infects bacteria and is used as a benchmark for evaluating new sequencing technologies. The impressive feat here is the length of the genome they sequenced – the Phi X 174 genome is 4,500 bases long. Other nanopore technologies have been limited to sequencing DNA fragments that were much shorter.

Despite the remaining hurdles, our demonstration that a low-cost device can reliably read the sequences of naturally occurring DNA and can interpret DNA segments as long as 4,500 nucleotides in length represents a major advance in nanopore DNA sequencing,” explained Gundlach.

By Dr Richard Muscat (on Twitter: @RAMuscat), Molecular Engineering and Sciences Institute, University of Washington "
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Antwort auf Beitrag Nr.: 47.515.033 von Popeye82 am 14.08.14 13:30:29
'Molecular shuttle' "speeds up hydrogen production" - NW/NIM/LMU/NM/SolTech, MUNICH - Aug 14, 2014

"A Ludwig-Maximilians-University (LMU) team affiliated with the Nanosystems Initiative Munich (NIM) has achieved a breakthrough in light-driven generation of hydrogen with semiconductor nanocrystals, by using a novel molecular shuttle to enhance charge-carrier transport.

The amount of solar radiation that reaches the Earth in a year exceeds our current annual energy needs more than 10,000-fold. However, it is not yet possible to store sufficiently high amounts of solar energy in an efficient way. A promising approach is to utilize incoming solar radiation for the photocatalytic generation of molecular hydrogen (H2) from water. Hydrogen gas is an excellent energy source, with the product of its combustion being again water, thereby making it free of greenhouse gases.

In their latest experiments with semiconductor nanocrystals as light absorbers, physicists led by Professor Jochen Feldmann (LMU Munich), in collaboration with a team of chemists under the direction of Professor Andrey Rogach (City University of Hong Kong), have succeeded in significantly increasing the yield of hydrogen produced by the photocatalytic splitting of water. The crucial innovation, reported in the latest issue of the journal Nature Materials ("Redox shuttle mechanism enhances photocatalytic H2 generation on Ni-decorated CdS nanorods"), is the use of a so-called molecular shuttle to markedly improve the mobility of charge carriers in their reaction system.

- Photocatalytic hydrogen production on nanocrystals. -

One photon, two charges, two roles

The basic principle behind photocatalysis seems to be quite simple. When a quantum of light (a “photon”) with sufficient energy excites a semiconductor nanocrystal, it produces a negative charge (electron) and a positive charge (hole). Photocatalytic synthesis of hydrogen gas from water requires the transfer of electrons to the hydrogen, while the holes interact with the oxygen or are scavenged by other molecules. However, before any of this can happen, the photogenerated electrons and holes must be quickly separated from each other. If the semiconducting nanocrystals are decorated with nanoparticles of a metal catalyst – such as the precious metal platinum – the electron can rapidly transfer to the metal and hydrogen production ensues. But unless the positively charged holes are effectively removed, they will accumulate and eventually bringing H2 synthesis to a halt.

One problem for an efficient removal of holes is the need of polar molecules being attached to the nanocrystals as surface ligands in order to make the nanocrystals water-soluble. By doing so, however, the resulting “ligand forest” of the attached polar molecules makes it difficult for the holes to interact with water or larger scavenger molecules.

A shuttle service :eek: , for molecules :eek: :eek:

One can compare this to the problem of delivering airline passengers to their final destination :eek: . Spatial constraints obviously make it impossible for the aircraft to convey its passengers directly to their hotels in town. Instead, smaller and more maneuverable carriers, such as the shuttle buses, are used for the short last stage of the trip.

In a similar way, the research teams in Munich and Hong Kong hit on the idea of using one of the smallest constituents of their system – the hydroxyl ion formed by the dissociation of water – to penetrate the ligand forest, collect the holes from the surface of the crystals and transport them to a larger acceptor molecule. Moreover, the concentration of this molecular shuttle in the system can be easily controlled by altering the pH of the solution. Indeed, raising the pH of the solution drastically increases the rate of hydrogen production.

“I was amazed the first time I tried it. As soon as I increased the pH I could see, with the naked eye, bubbles of hydrogen rising to the surface.” says Thomas Simon, a PhD student at Professor Feldmann’s chair.

A stable and cost-effective system

The new system also has other advantages. First of all, its long-term stability could be markedly improved. Furthermore, it turns out that the costly platinum catalyst can be replaced by nickel, a far less expensive metal. “The discovery of this new mechanism could lead to entirely new approaches to the photocatalytic production of hydrogen.” adds Dr. Jacek Stolarczyk, who heads the Photocatalysis group at the chair of Photonics and Optoelectronics (PhOG) at LMU.

Chair holder Professor Jochen Feldmann, who also serves as Director of the NIM Cluster of Excellence, emphasizes the crucial role of the close collaboration between the different research groups involved in the project: “Our work could only be successful by being a product of an interdisciplinary team, and with the generous support by the NIM cluster and the Bavarian Research Network ’Solar Technologies go Hybrid‘ (SolTech).”

Source: Nanosystems Initiative Munich "
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'Superhydrophobic nonwovens, from naturally occurring polymers' - MV - Aug 14, 2014

"Superhydrophobicity can be found in nature, as can be seen in the way water droplets roll off a lotus leaf, or adhere strongly to a rose petal. Such unique wetting properties have been artificially reproduced by using synthetic materials with a rough surface. However, although there is no doubt that leaves and flowers are mainly composed of biopolymers, there has been little research done on superhydrophobic materials made of natural-occurring materials.

Now, a Japanese/German collaboration has succeeded in synthesising a biodegradable, hydrophobic polymer by modifying a naturally-occurring poly(amino acid) with a hydrophobic amino acid. the modified polymer is then subjected to electrospinning, a versatile technique for producing nanofibers from various polymer solutions, which creates a nonwoven material with a rough surface. These resultant nonwovens show a water contact angle of more than 150o - they are superhydrophobic. This new class of biodegradable, superhydrophobic materials opens up new possibilites in the fields of environmental chemistry and biomedical engineering – they will become a new functional material resource which meets at least some of the criteria for green chemistry. "
Antwort auf Beitrag Nr.: 47.143.744 von Popeye82 am 12.06.14 15:58:32
Zitat von Popeye82: Cypress Development - Drills "up to" 175 feet of 12% Zinc +121 g/t Silver, @Gunman Project in Nevada - Jun 12, 2014

Cypress Samples "up to" 35% Zinc +11% Copper, in Phase2 Exploration @Gunman Zinc-Silver Project, Nevada - Aug 14, 2014
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Antwort auf Beitrag Nr.: 47.515.186 von Popeye82 am 14.08.14 13:42:34
$20.000.000 grant to support developing eco-friendly plastics NW/CU - Aug 13, 2014

"A five-year, $20 million National Science Foundation grant will allow chemists from Cornell and other institutions to study new ways to make plastics more sustainable.

The award establishes one of eight NSF Centers for Chemical Innovation, and is based at the University of Minnesota. Grant co-investigators include Cornell’s Geoffrey Coates, professor of chemistry and chemical biology and a Tisch University Professor; William Dichtel, associate professor in the same department; and Anne LaPointe, senior research associate in chemistry. Marc Hillmyer of the University of Minnesota is director of the Center for Sustainable Polymers (CSP) and the project’s lead; University of California, Berkeley, scientists are also involved.

Work in the CSP will be aimed at technologically competitive, cost-effective, environmentally sustainable materials made from polymers. Research is already underway to convert abundant, sustainable, plant-derived biomass into plastics by combining new methods in synthetic chemistry with novel processing techniques. The goal is to develop next-generation plastics that are nontoxic, biodegradable and recyclable, and attractive to consumers in cost and performance.

At Cornell, of particular importance to the center’s mission will be the polymer science laboratory led by Coates, who studies how efficient catalytic chemistry can convert biomass molecules into polymer precursors that have been traditionally prepared from petroleum. Coates is also studying whether plastics could be created from carbon dioxide. Coates’ polymer research formed the basis for his startup company, Novomer.

“This NSF Center for Chemical Innovation is unique in that it focuses not only on polymer synthesis and structure, but also on the development of new monomers from renewable feedstocks,” Coates said. “We will particularly benefit from the theoretical expertise in the center that will help guide reaction development, as well as researchers with expertise in materials processing and properties.”

More than three dozen graduate students and postdoctoral researchers will be involved in research projects at the center, as well as education and outreach activities. Each senior investigator will also mentor undergraduates during summer research programs.

Source: By Anne Ju, Cornell University "
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Antwort auf Beitrag Nr.: 47.516.110 von Popeye82 am 14.08.14 14:58:59
Carbon dioxide 'sponge' " "could" ease transition, to cleaner energy" - NW/UoL - Aug 10, 2014

"A sponge-like plastic that sops up the greenhouse gas carbon dioxide (CO2) might ease our transition away from polluting fossil fuels and toward new energy sources, such as hydrogen. The material — a relative of the plastics used in food containers — could play a role in President Obama's plan to cut CO2 emissions 30 percent by 2030, and could also be integrated into power plant smokestacks in the future.

The report on the material is one of nearly 12,000 presentations at the 248th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, taking place through Thursday.

- Plastic that soaks up carbon dioxide could someday be used in plant smokestacks. (Image: ACS) -

"The key point is that this polymer is stable, it's cheap, and it adsorbs CO2 extremely well. It's geared toward function in a real-world environment," says Andrew Cooper, Ph.D. "In a future landscape where fuel-cell technology is used, this adsorbent could work toward zero-emission technology."

CO2 adsorbents are most commonly used to remove the greenhouse gas pollutant from smokestacks at power plants where fossil fuels like coal or gas are burned. However, Cooper and his team intend the adsorbent, a microporous organic polymer, for a different application — one that could lead to reduced pollution.

The new material would be a part of an emerging technology called an integrated gasification combined cycle (IGCC), which can convert fossil fuels into hydrogen gas. Hydrogen holds great promise for use in fuel-cell cars and electricity generation because it produces almost no pollution. IGCC is a bridging technology that is intended to jump-start the hydrogen economy, or the transition to hydrogen fuel, while still using the existing fossil-fuel infrastructure. But the IGCC process yields a mixture of hydrogen and CO2 gas, which must be separated.

Cooper, who is at the University of Liverpool, says that the sponge works best under the high pressures intrinsic to the IGCC process. Just like a kitchen sponge swells when it takes on water, the adsorbent swells slightly when it soaks up CO2 in the tiny spaces between its molecules. When the pressure drops, he explains, the adsorbent deflates and releases the CO2, which they can then collect for storage or convert into useful carbon compounds.

The material, which is a brown, sand-like powder, is made by linking together many small carbon-based molecules into a network. Cooper explains that the idea to use this structure was inspired by polystyrene, a plastic used in styrofoam and other packaging material. Polystyrene can adsorb small amounts of CO2 by the same swelling action.

One advantage of using polymers is that they tend to be very stable. The material can even withstand being boiled in acid, proving it should tolerate the harsh conditions in power plants where CO2 adsorbents are needed. Other CO2 scrubbers — whether made from plastics or metals or in liquid form — do not always hold up so well, he says. Another advantage of the new adsorbent is its ability to adsorb CO2 without also taking on water vapor, which can clog up other materials and make them less effective. Its low cost also makes the sponge polymer attractive. "Compared to many other adsorbents, they're cheap," Cooper says, mostly because the carbon molecules used to make them are inexpensive. "And in principle, they're highly reusable and have long lifetimes because they're very robust."

Cooper also will describe ways to adapt his microporous polymer for use in smokestacks and other exhaust streams. He explains that it is relatively simple to embed the spongy polymers in the kinds of membranes already being evaluated to remove CO2 from power plant exhaust, for instance. Combining two types of scrubbers could make much better adsorbents by harnessing the strengths of each, he explains.

Title: Swellable, water-tolerant polymer sponges for carbon dioxide capture


To impact carbon emissions, new materials for carbon capture must be inexpensive, robust, and able to adsorb CO2 specifically from a mixture of other gases. In particular, materials must be tolerant to the water vapor and to the acidic impurities that are present in gas streams produced by using fossil fuels to generate electricity. We show that a porous organic polymer has excellent CO2 capacity and high CO2 selectivity under conditions relevant to precombustion CO2 capture. Unlike polar adsorbents, such as Zeolite 13x and the metal-organic framework, HKUST-1, the CO2 adsorption capacity for the hydrophobic polymer is hardly affected by the adsorption of water vapour. The polymer is even stable to boiling in concentrated acid for extended periods, a property that is matched by few microporous adsorbents. The polymer adsorbs CO2 in a different way from rigid materials by physical swelling, much as a sponge adsorbs water. This gives rise to a higher CO2 capacities and much better CO2 selectivity than for other water-tolerant, non-swellable frameworks, such as activated carbon and ZIF-8. The polymer has superior function as a selective gas adsorbent, even though its constituent monomers are very simple organic feedstocks, as would be required for materials preparation on the large industrial scales required for carbon capture.

Source: American Chemical Society "
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Antwort auf Beitrag Nr.: 47.516.242 von Popeye82 am 14.08.14 15:07:43
New catalyst converts carbon dioxide, to fuel - NW/UoI/NC, CHICAGO - Jul 30, 2014

"Scientists from the University of Illinois at Chicago have synthesized a catalyst that improves their system for converting waste carbon dioxide into syngas, a precursor of gasoline and other energy-rich products, bringing the process closer to commercial viability.

Amin Salehi-Khojin, UIC professor of mechanical and industrial engineering, and his coworkers developed a unique two-step catalytic process that uses molybdenum disulfide and an ionic liquid to “reduce,” or transfer electrons, to carbon dioxide in a chemical reaction. The new catalyst improves efficiency and lowers cost by replacing expensive metals like gold or silver in the reduction reaction.

The study was published in the journal Nature Communications on July 30 ("Robust ccarbon dioxide reduction on molybdenum disulphide edges").

- Amin Salehi-Khojin, assistant professor of mechanical/industrial engineering. -

The discovery is a big step toward industrialization, said Mohammad Asadi, UIC graduate student and co-first author on the paper.

“With this catalyst, we can directly reduce carbon dioxide to syngas without the need for a secondary, expensive gasification process,” he said. In other chemical-reduction systems, the only reaction product is carbon monoxide. The new catalyst produces syngas, a mixture of carbon monoxide plus hydrogen. The high density of loosely bound, energetic d-electrons in molybdenum disulfide facilitates charge transfer, driving the reduction of the carbon dioxide, said Salehi-Khojin, principal investigator on the study.

“This is a very generous material,” he said. “We are able to produce a very stable reaction that can go on for hours.”

“In comparison with other two-dimensional materials like graphene, there is no need to play with the chemistry of molybdenum disulfide, or insert any host materials to get catalytic activity,” said Bijandra Kumar, UIC post-doctoral fellow and co-first author of the paper.

“In noble metal catalysts like silver and gold, catalytic activity is determined by the crystal structure of the metal, but with molybdeneum disulfide, the catalytic activity is on the edges,” said graduate student Amirhossein Behranginia, a coauthor on the paper. “Fine-tuning of the edge structures is relatively simple. We can easily grow the molybdenum disulfide with the edges vertically aligned to offer better catalytic performance.”
The proportion of carbon monoxide to hydrogen in the syngas produced in the reaction can also be easily manipulated using the new catalyst, said Salehi-Khojin.

Our whole purpose is to move from laboratory experiments to real-world applications,” he said. “This is a real breakthrough that can take a waste gas — carbon dioxide — and use inexpensive catalysts to produce another source of energy at large-scale, while making a healthier environment.
Artem Baskin, Nikita Repnin, Davide Pisasale, Patrick Philips, Robert Klie, Petr Kral and Jeremiah Abiade of UIC; Brian Rose and Richard Haasch of the University of Illinois at Urbana-Champaign; and Wei Zhu of Dioxide Materials in Champaign, Illinois, are also coauthors on the paper.

The study was supported by UIC’s Chancellor Innovation Fund; by the American Chemical Society Petroleum Research Fund grant #53062-ND6; and the Herbert E. Paaren Graduate Fellowship. This work was carried out in part in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois. The acquisition of the UIC JEOL JEM-ARM200CF is supported by a MRI-R2 grant from the National Science Foundation (DMR-0959470). The research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231; and computational resources of the Extreme Science and Engineering Discovery Environment, which is supported by National Science Foundation grant No. OCI-1053575.

Source: University of Illinois at Chicago "
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Antwort auf Beitrag Nr.: 47.516.485 von Popeye82 am 14.08.14 15:26:09

Chemists develop MRI technique, for peeking inside supercapacitors- NW/UoC/UoNY/NC, CAMBRIDGE/NEW YORK - Aug 11, 2014

"A team of chemists from New York University and the University of Cambridge has developed a method for examining the inner workings of battery-like devices called supercapacitors, which can be charged up extremely quickly and can deliver high electrical power. Their technique, based on magnetic resonance imaging (MRI), establishes a means for monitoring and potentially enhancing the performance of such devices.

The work, which appears in the latest issue of the journal Nature Communications ("Multinuclear in situ magnetic resonance imaging of electrochemical double-layer capacitors"), focuses on electric double-layer capacitors (EDLCs), a type of so-called supercapacitor. These are excellent options for powering systems where fast charging and power delivery are crucial, such as in regenerative braking (for use in trains and buses), camera flashes, and in backup computer memory.

"The MRI method really allows us to look inside a functioning electrical storage device and locate molecular events that are responsible for its functioning," explains Alexej Jerschow, a professor in NYU's Department of Chemistry and one of the paper's senior authors.

"The approach allows us to explore electrolyte concentration gradients and the movement of ions within the electrode and electrolyte, both ultimately a cause of poor rate performance in batteries and supercapacitors," adds co-author Clare Grey, a professor in the Department of Chemistry at the University of Cambridge.

The other authors included Andrew Ilott, a post-doctoral researcher in NYU's Department of Chemistry, and Nicole Trease, a post-doctoral researcher at Stony Brook University.

Capacitors are designed to store electric charge, but their storage capabilities are limited. In recent years, advances have been made to address this shortcoming. Among these has been the creation of supercapacitors, which can store more electrical charge than their predecessors. This is due to an electrical double layer formed at the electrolyte-electrode interface—the process by which energy is stored—which serves to more effectively trap energy than can standard capacitors.

However, the exact nature of this charge process in supercapacitors remains a subject of debate. Previous research has attempted to understand this process through the synthesis of new electrode materials, simulations of the charging process, and by spectroscopy—rather than by direct imaging of a complete functioning device.

In the Nature Communications work, Jerschow, Grey, and their co-authors explored a novel approach to understanding how these devices function: the use of MRI technology, which serves as a looking glass into supercapacitors' energy storage activity.

This method has a precedent from the same research team. In work published by Nature Materials in 2012, the NYU-Cambridge team developed a method, based on MRI, to look inside a battery without damaging it. Their technique provided a method for helping to improve battery performance and safety by serving as a diagnostic of its internal workings.

In the supercapacitor work, the researchers found that MRI could pinpoint the location and estimate the amount of both positively and negatively charged electrolyte ions—data that are crucial to understanding the energy storage mechanism.

The technique has the potential to analyze functioning devices at different states of charge, and thus to provide information on the microscopic processes which are ultimately responsible for the storage and power capacity of a device.

With this non-invasive method, the researchers say, one could rapidly test the properties of different capacitor materials and thus elucidate their effectiveness in enhancing device performance. They add that techniques could also be useful in assessing factors that affect the longevity of the devices, or the conditioning or "breaking-in" of devices during first use.
The team next plans to investigate how different ions interact with other molecules in the electrolyte mixture, which may be a key to enhanced performance.

Source: New York University "

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