#Researchers grind nanotubes to get nanoribbons (w/video) A simple way to turn carbon nanotubes into valuable graphene nanoribbons may be to grind them,
is to mix two types of chemically modified nanotubes. When they come into contact during grinding,
The research by Ajayan and his international collaborators appears in Nature Communications("Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes".
the new process is still a chemical reaction that depends on molecules purposely attached to the nanotubes, a process called functionalization.
The most interesting part to the researchers is that a process as simple as grinding could deliver strong chemical coupling between solid nanostructures
but this work is entirely solid state, he said. ur question is this: If we can use nanotubes as templates,
functionalize them and get reactions under the right conditions, what kinds of things can we make with a large number of possible nanostructures and chemical functional groups?
The process should enable many new chemical reactions and products, said Mohamad Kabbani, a graduate student at Rice and lead author of the paper. sing different functionalities in different nanoscale systems could revolutionize nanomaterials development,
he said. Highly conductive graphene nanoribbons, thousands of times smaller than a human hair, are finding their way into the marketplace in composite materials.
The nanoribbons boost the materialselectronic properties and/or strength. ontrolling such structures by mechano-chemical transformation will be the key to find new applications,
said co-author Thalappil Pradeep, a professor of chemistry at the Indian Institute of technology Chennai. oft chemistry of this kind can happen in many conditions,
contributing to better understanding of materials processing. In their tests, the researchers prepared two batches of multi-walled carbon nanotubes, one with carboxyl groups and the other with hydroxyl groups attached.
When ground together for up to 20 minutes with a mortar and pestle, the chemical additives reacted with each other,
triggering the nanotubes to unzip into nanoribbons, with water as a byproduct. hat serendipitous observation will lead to further systematic studies of nanotubes reactions in solid state,
including ab initio theoretical models and simulations, Ajayan said. his is exciting. The experiments were duplicated by participating labs at Rice
at the Indian Institute of technology and at the Lebanese American University in Beirut. They were performed in standard lab conditions as well as in a vacuum, outside in the open air and at variable humidity, temperatures, times and seasons.
The researchers who carried out the collaboration on three continents still don know precisely what happening at the nanoscale. t is an exothermic reaction,
so the energy enough to break up the nanotubes into ribbons, but the details of the dynamics are difficult to monitor,
Kabbani said. here no way we can grind two nanotubes in a microscope and watch it happen.
Not yet anyway. But the results speak for themselves. don know why people haven explored this idea,
that you can control reactions by supporting the reactants on nanostructures, Ajayan said. hat wee done is very crude,
but it a beginning and a lot of work can follow along these lines. n
#Researchers develop the first flexible phase-change random access memory (Nanowerk News) Phase change random access memory (PRAM) is one of the strongest candidates for next-generation nonvolatile memory for flexible and wearable electronics.
In order to be used as a core memory for flexible devices, the most important issue is reducing high operating current.
The effective solution is to decrease cell size in sub-micron region as in commercialized conventional PRAM.
However, the scaling to nano-dimension on flexible substrates is extremely difficult due to soft nature and photolithographic limits on plastics,
thus practical flexible PRAM has not been realized yet. Recently a team led by Professors Keon Jae Lee
and Yeon Sik Jung of the Department of Materials science and engineering at KAIST has developed the first flexible PRAM enabled by self-assembled block copolymer (BCP) silica nanostructures with an ultralow current operation (below one quarter
of conventional PRAM without BCP) on plastic substrates. BCP is the mixture of two different polymer materials,
which can easily create self-ordered arrays of sub-20 nm features through simple spin-coating and plasma treatments.
BCP silica nanostructures successfully lowered the contact area by localizing the volume change of phase-change materials
and thus resulted in significant power reduction. Furthermore the ultrathin silicon-based diodes were integrated with phase-change memories (PCM) to suppress the inter-cell interference,
which demonstrated random access capability for flexible and wearable electronics. Their work was published in the March issue of ACS Nano("Flexible One Diode-One Phase change Memory Array Enabled by Block copolymer Self-Assembly".
"Low-power nonvolatile PRAM for flexible and wearable memories enabled by (a) self-assembled BCP silica nanostructures and (b) self-structured conductive filament nanoheater.
Image: KAIST) Another way to achieve ultralow-powered PRAM is to utilize self-structured conductive filaments (CF) instead of the resistor-type conventional heater.
The self-structured CF nanoheater originated from unipolar memristor can generate strong heat toward phase-change materials due to high current density through the nanofilament.
This ground-breaking methodology shows that sub-10 nm filament heater, without using expensive and non-compatible nanolithography,
achieved nanoscale switching volume of phase change materials, resulted in the PCM writing current of below 20 ua, the lowest value among top-down PCM devices.
This achievement was published in the June online issue of ACS Nano("Self-Structured Conductive Filament Nanoheater for Chalcogenide Phase transition".
"In addition, due to self-structured low-power technology compatible to plastics, the research team has succeeded recently in fabricating a flexible PRAM on wearable substrates.
Professor Lee said, "The demonstration of low power PRAM on plastics is one of the most important issues for next-generation wearable and flexible nonvolatile memory.
Our innovative and simple methodology represents the strong potential for commercializing flexible PRAM.""In addition, he wrote a review paper regarding the nanotechnology-based electronic devices in the June online issue of Advanced Materials entitled"Performance Enhancement of Electronic and Energy Devices via Block copolymer Self-Assembly
#Squid inspires camouflaging smart materials The researchers have shown the artificial skin, made from electroactive dielectric elastomer, a soft,
compliant smart material, can effectively copy the action of biological chromatophores. Chromatophores are pigmented small cells embedded on cephalopods skin
which can expand and contract and that work together to change skin colour and texture. The system achieves the dynamic pattern generation by using simple local rules in the artificial chromatophore cells,
so that they can sense their surroundings and manipulate their change. By modelling sets of artificial chromatophores in linear arrays of cells, the researchers explored
The researchers found that it is possible to mimic complex dynamic patterning seen in real cephalopods such as the Passing Cloud display,
Aaron Fishman, Visiting Fellow in Engineering Mathematics, said:""Our ultimate goal is to create artificial skin that can mimic fast acting active camouflage
"The cloaking suit could be used to blend into a variety of environments, such as in the wild.
"The researchers investigated making bio-inspired artificial skin embedded with artificial chromatophores using thin sheets (five to ten millimetre) of dielectric elastomer-a soft,
#Hematite're-growth'smoothes rough edges for clean energy harvest (Nanowerk News) Finding an efficient solar water splitting method to mine electron-rich hydrogen for clean
power has been thwarted by the poor performance of hematite. But by'regrowing'the mineral's surface, a smoother version of hematite doubled electrical yield, opening a new door to energy harvesting artificial photosynthesis,
according to a report published online today in the journal Nature Communications("Enabling Unassisted Solar Water Splitting by Iron Oxide and Silicon").
"Re-grown hematite proved to be a better power generating anode, producing a record low turn-on voltage that enabled the researchers to be the first to use earth-abundant hematite
and silicon as the sole light absorbers in artificial photosynthesis, said Boston College associate professor of chemistry Dunwei Wang,
a lead author of the report. Water splitting combines sunlight and water in a chemical reaction in order to harvest clean hydrogen energy.
By smoothing the surface of hematite, a team of researchers led by Boston College chemist Dunwei Wang achieved'unassisted'water splitting using the abundant rust-like mineral and silicon to capture and store solar energy within hydrogen gas.
NPG) The new hydrogen harvesting process achieved an overall efficiency of 0. 91 percent, a'modest'mark in and of itself,
but the first'meaningful efficiency ever measured by hematite and amorphous silicon, two of the most abundant elements On earth,'the team reported.'
'By simply smoothing the surface characteristics of hematite, this close cousin of rust can be improved to couple with silicon,
which is derived from sand, to achieve complete water splitting for solar hydrogen generation, 'said Wang,
whose research focuses on discovering new methods to generate clean energy.''This unassisted water splitting, which is very rare,
'Wang said the findings represent an important step toward realizing the potential performance theoretical models have predicted for hematite, an iron oxide similar to rust.'
which included researchers from Boston College, UC Berkeley and China's University of Science and Technology, decided to focus on hematite's surface imperfections,
The team reevaluated hematite surface features using a synchrotron particle accelerator at the Lawrence Berkeley National Laboratory.
The team reported that further modifications to the new hematite-silicon method make it amenable to large-scale utilization.
Furthermore, the're-growth'technique may be applicable to other materials under study for additional breakthroughs in artificial photosynthesis.'It is a delight to see that a simple re-growth treatment can do so much to improve the performance of hematite,
'Due to its prior poor performance, hematite has been pronounced'dead'by many leading researchers in the field.
#Transparent, stretchable conductors with a nano-accordion structure design (Nanowerk News) Researchers from North carolina State university have created stretchable, transparent conductors that work because of the structures nano-accordion design
such as flexible electronics, stretchable displays or wearable sensors. The dimensions of each ridge directly affect the transparent conductors stretchability.
a Ph d. student in mechanical and aerospace engineering at NC State and lead author of a paper describing the work.
The researchers begin by creating a three-dimensional polymer template on a silicon substrate. The template is shaped like a series of identical
The template is coated with a layer of aluminum-doped zinc oxide, which is the conducting material,
and an elastic polymer is applied to the zinc oxide. The researchers then flip the whole thing over
zinc oxide ridges on an elastic substrate. Because both zinc oxide and the polymer are clear, the structure is transparent.
And it is stretchable because the ridges of zinc oxide allow the structure to expand and contract,
like the bellows of an accordion. Video of the conductor in action We can also control the thickness of the zinc oxide layer
and have done extensive testing with layers ranging from 30 to 70 nanometers thick, says Erinn Dandley,
a Ph d. student in chemical and biomolecular engineering at NC State and co-author of the paper.
This is important because the thickness of the zinc oxide affects the structures optical, electrical and mechanical properties.
The 3-D templates used in the process are engineered precisely, using nanolithography, because the dimensions of each ridge directly affect the structures stretchability.
The taller each ridge is, the more stretchable the structure. This is because the structure stretches by having the two sides of a ridge bend away from each other at the base like a person doing a split.
its overall material properties, says Chih-Hao Chang, an assistant professor of mechanical and aerospace engineering at NC State and corresponding author of the paper.
#Complex, large-scale genome analysis made easier Researchers at EMBL-EBI have developed a new approach to studying the effect of multiple genetic variations on different traits.
The new algorithm, published in Nature Methods("Efficient set tests for the genetic analysis of correlated traits),
"makes it possible to perform genetic analysis of up to 500,000 individuals-and many traits-at the same time. The relationship between genes and specific traits is complicated more than simple one-to-one relationships between genes and diseases.
Genome-wide association studies (GWAS) show that many genetic factors are at play for any given trait
but scientists are just beginning to explore how, specifically, genetic variations affect health and disease. Two major statistical challenges to finding these connections involve analysing associations between many different genetic variants and multiple traits,
and making the best use of data from large cohorts that include hundreds of thousands of individuals."
"It is very challenging to identify genetic variants that underlie phenotypes, or traits, and usually we do this by analysing each phenotype
"But the simple models we use to do this are too simplistic to uncover the complex dependencies between sets of genetic variants and disease phenotypes."
until now so much computation that it would take a year to run a single complex query."
The researchers tested their algorithm on data from two studies from public repositories, and compared the results with existing state-of-the-art tools.
and can explain a larger proportion of these traits in terms of the genetics that drive them."
"What's important about this work is that it improves statistical power and provides the tools people need to analyse multiple traits in very large cohorts,
"Our algorithm can be used to study up to half a million individuals-that hasn't been possible until now.""
The new algorithm provides much-needed methods for genomics, making large-scale, complex analysis a manageable and practical endeavour."
These methods will help researchers determine which specific aspects of our biology are inherited, and uncover new insights into the genetics behind our countless biological processes
#Hooked on phonons: Researchers measure graphene vibrations (Nanowerk News) An international research group led by scientists at the National Institute of Standards
and Technology's (NIST) Center for Nanoscale Science and Technology has developed a method for measuring crystal vibrations in graphene.
Tunneling electrons from a scanning tunneling microscope tip excites phonons in graphene. The image shows the graphene lattice with blue arrows indicating the motion direction of that carbon atoms for one of the low energy phonon modes in graphene.
"Carbon atoms in graphene sheets are arranged in a regularly repeating honeycomb-like latticea two-dimensional crystal. Like other crystals,
when enough heat or other energy is applied, the forces that bond the atoms together cause the atoms to vibrate
and spread the energy throughout the material, akin to how the vibration of a violin's string resonates throughout the body of the violin when played.
And just like every violin has its own unique character, each material vibrates at unique frequencies.
The collective vibrations, which have frequencies in the terahertz-range (a billion billion oscillations per second),
take out or move energy around inside a material. In particular, finding effective ways to remove heat energy is vital to the continued miniaturization of electronics.
One way to measure these tiny vibrations is to bounce electrons off the material and measure how much energy the electrons have transferred to the vibrating atoms.
But it's difficult. The technique, called inelastic electron tunneling spectroscopy, elicits only a small blip that can be hard to pick out over more raucous disturbances."
"Unlike a violin that sounds at the lightest touch, according to Natterer, phonons have a characteristic threshold energy.
unless they get just the right amount of energy, such as that supplied by the electrons in a scanning tunneling microscope (STM).
the unwanted signals also varied in energy, but the phonons remained fixed at their characteristic frequency.
The high purity graphene device was fabricated by NIST researcher Y. Zhao in the Center for Nanoscale Science and Technology's Nanofab, a national user facility available to researchers from industry, academia and government t
"says Jim Ciston, a staff scientist with the National Center for Electron microscopy (NCEM) at the Molecular Foundry, a DOE Office of Science User Facility."
"Although surface atoms represent a minuscule fraction of the total number of atoms in a material, these atoms drive a large portion of the material's chemical interactions with its environment."
"Other co-authors are Hamish Brown, Adrian D'Alfonso, Pratik Koirala, Colin Ophus, Yuyuan Lin, Yuya Suzuki, Hiromi Inada, Yimei Zhu, Les Allen,
ranging from the catalysts used for the generation of energy-dense fuels from sunlight and carbon dioxide, to how bridges and airplanes rust."
"In essence, the surface of every material can act as its own nanomaterial coating that can greatly change its chemistry and behavior,
but typically provides information only about topology at nanoscale resolution. A highly promising new version of scanning electron microscopy, called"high-resolution scanning electron microscopy,
and causing atoms in the material to emit energy in the form of electrons rather than photons.
progress in materials science applications has been slow due to an inability to directly interpret the surface and bulk components of HRSEM images independently,
"We started this work by investigating a well-studied material, but new technique is so powerful that we had to revise much of was thought already to be well-known,
Co-author Allen, a scientist with Melbourne University in Australia, who led the theoretical and modeling aspects of the new imaging technique,
adds:""we now have sophisticated a understanding of what the images mean"."Perhaps the first target for applying this new HRSEM surface analytic technique will be the study of surface structures on the facets of nanoparticles.
The surface structures of nanoparticle facets are extremely challenging to image in the plan view (seen from above) using electron microscopy,
a deficit that needs to be corrected as Ciston explains.""Plan view geometry is important because surface structures will often develop multiple domains,
since scanning probe techniques cannot usually address nanoparticle surfaces at atomic resolution, and surface X-ray diffraction requires large, single crystal surfaces."
"Says co-author Marks, a professor of materials science and engineering at Northwestern University, "We are excited also quite by the possibilities of applying these to corrosion problems.
The cost to industry and the military of corrosion is enormous, and we need to understand everything that is taking place to produce materials
#New NMR tool helps scientists study elusive battery reaction (Nanowerk News) When working on a unique lithium-germanide battery with colleagues from the National University of Singapore,
scientists at Pacific Northwest National Laboratory encountered a catch-22: They knew an exciting reaction was occurring inside the battery that increased its energy storage capacity dramatically
-but they could not observe the reaction. The researchers needed to understand the process, but taking the battery apart caused the reaction to stop.
PNNL scientist Jian Zhi Hu displays a tiny experimental battery mounted in NMR apparatus used to observe the chemical reaction inside.
To solve the problem, the PNNL scientists encapsulated the battery cell in a plastic holder to allow magnetic waves to penetrate it
and developed a powerful nuclear magnetic resonance (NMR) technique to"see "and understand the electrochemical reactions taking place inside.
lithium-germanide battery and demonstrated how their unique NMR"camera"can be used to examine it
and gather data about reactions that can be observed only as they are happening inside a battery("Probing Lithium Germanide Phase Evolution and Structural Change in a Germanium-in-Carbon nanotube Energy storage system").
"Why It Matterslithium-ion batteries have many uses besides powering cell phones and laptops. Developing safer, more powerful cells with longer life is a worldwide challenge,
Germanium can take on more lithium during the reaction than other materials-making it a promising component for delivering higher battery capacity and superior discharge speeds,
but high battery performance resulting from its favorable uptake of lithium may be a factor in making lithium-germanide batteries attractive in the marketplace.
Scientists can create high-energy density batteries by using lithium with a number of different materials.
the volume of the electrode expands dramatically. It can break down and reduce battery life and storage capacity.
By using the NMR process to look inside the battery and observe this reaction as it happened,
the scientists found a way to protect the germanium from expanding and becoming ineffective after it takes on lithium.
This technique significantly stabilizes battery performance. Without embedding germanium in carbon tubes, a battery performs well for a few charging-discharging cycles,
but fades rapidly after that. Using the"core-shell"structure, however, the battery can be discharged and charged thousands of times.
What's Next? Scientists are testing many different materials, including sulfur, cobalt, magnesium, manganese and others, to use with lithium in making batteries.
Many of these materials are potentially useful, but only those that are safe to use
and offer high performance and long storage life will succeed in the marketplace. The NMR technique used to enhance the performance of the lithium-germanide reaction may prove useful to scientists working on other types of batteries
if internal reactions can be observed only where they happen.""It's all about how to engineer the battery to make it safer
and more powerful with a longer life,"said Jian Zhi Hu of PNNL, the lead NMR investigator and a collaborator in the project with Kian Ping Loh,
the leader of the team at the National University of Singapore where the battery was developed."
you have to understand the electrochemistry in the battery. Using NMR to understand hard-to-observe battery reaction phases is useful
when they exist only inside the battery. The procedure could lead to additional opportunities to collaborate with other researchers
#First solar cell made of highly ordered molecular frameworks (Nanowerk News) Researchers at KIT have developed a material suited for photovoltaics.
For the first time, a functioning organic solar cell consisting of a single component has been produced on the basis of metal-organic framework compounds (MOFS.
The material is highly elastic and might also be used for the flexible coating of clothes and deformable components.
High Efficiency as a result of an Indirect Electronic Band gap?"."Organic solar cells made of metal-organic frameworks are highly efficient in producing charge carriers.
Figure: Wll/KIT) We have opened the door to a new room, says Professor Christof Wll, Director of KIT Institute of Functional Interfaces (IFG).
This new application of metal-organic framework compounds is the beginning only. The end of this development line is far from being reached,
the physicist emphasizes. Metal-organic frameworks, briefly called MOFS, consist of two basic elements, metal node points and organic molecules,
Computations made by the group of Professor Thomas Heine from Jacobs University Bremen, which is involved also in the project,
suggest that the excellent properties of the solar cell result from an additional mechanism the formation of indirect band gaps that plays an important role in photovoltaics.
Nature uses porphyrines as universal molecules e g. in hemoglobin and chlorophyll, where these organic dyes convert light into chemical energy.
A metal-organic solar cell produced on the basis of this novel porphyrine-MOF is presented now by the researchers in the journal Angewandte Chemie (Applied Chemistry.
high efficiency resulting from an indirect electronic band gap?.The clou is that we just need a single organic molecule in the solar cell,
Wll says. The researchers expect that the photovoltaic capacity of the material may be increased considerably in the future by filling the pores in the crystalline lattice structure with molecules that can release
and take up electric charges. By means of a process developed at KIT, the crystalline frameworks grow in layers on a transparent,
and also allows for the coating of larger plastic carrier surfaces, Wll says. Thanks to their mechanical properties, MOF thin films of a few hundred nanometers in thickness can be used for flexible solar cells or for the coating of clothing material or deformable components.
While the demand for technical systems converting sunlight into electricity is increasing, organic materials represent a highly interesting alternative to silicon that has to be processed at high costs before it can be used for the photoactive layer of a solar cell l
#Chemists devise technology that could transform solar energy storage (Nanowerk News) The materials in most of todays residential rooftop solar panels can store energy from the sun for only a few microseconds at a time.
A new technology developed by chemists at UCLA is capable of storing solar energy for up to several weeks an advance that could change the way scientists think about designing solar cells.
The findings are published June 19 in the journal Science("Long-lived photoinduced polaron formation in conjugated polyelectrolyte-fullerene assemblies".
"The scientists devised a new arrangement of solar cell ingredients, with bundles of polymer donors (green rods) and neatly organized fullerene acceptors (purple, tan.
The new design is inspired by the way that plants generate energy through photosynthesis. Biology does a very good job of creating energy from sunlight,
said Sarah Tolbert, a UCLA professor of chemistry and one of the senior authors of the research.
Plants do this through photosynthesis with extremely high efficiency. In photosynthesis, plants that are exposed to sunlight use carefully organized nanoscale structures within their cells to rapidly separate charges pulling electrons away from the positively charged molecule that is left behind,
and keeping positive and negative charges separated, Tolbert said. That separation is the key to making the process so efficient.
To capture energy from sunlight conventional rooftop solar cells use silicon, a fairly expensive material. There is currently a big push to make lower-cost solar cells using plastics, rather than silicon,
but todays plastic solar cells are relatively inefficient, in large part because the separated positive and negative electric charges often recombine before they can become electrical energy.
Modern plastic solar cells dont have well-defined structures like plants do because we never knew how to make them before,
Tolbert said. But this new system pulls charges apart and keeps them separated for days,
or even weeks. Once you make the right structure you can vastly improve the retention of energy.
The two components that make the UCLA-developed system work are a polymer donor and a nanoscale fullerene acceptor.
The polymer donor absorbs sunlight and passes electrons to the fullerene acceptor; the process generates electrical energy.
The plastic materials, called organic photovoltaics, are organized typically like a plate of cooked pasta a disorganized mass of long, skinny polymer spaghetti with random fullerene meatballs.
But this arrangement makes it difficult to get current out of the cell because the electrons sometimes hop back to the polymer spaghetti
and are lost. The UCLA technology arranges the elements more neatly like small bundles of uncooked spaghetti with precisely placed meatballs.
Some fullerene meatballs are designed to sit inside the spaghetti bundles, but others are forced to stay on the outside.
The fullerenes inside the structure take electrons from the polymers and toss them to the outside fullerene
which can effectively keep the electrons away from the polymer for weeks. When the charges never come back together,
the system works far better, said Benjamin Schwartz, a UCLA professor of chemistry and another senior co-author.
This is the first time this has been shown using modern synthetic organic photovoltaic materials. In the new system, the materials self-assemble just by being placed in close proximity.
We worked really hard to design something so we dont have to work very hard,
Tolbert said. The new design is also more environmentally friendly than current technology, because the materials can assemble in water instead of more toxic organic solutions that are used widely today.
Once you make the materials you can dump them into water and they assemble into the appropriate structure because of the way the materials are designed,
So theres no additional work. The researchers are already working on how to incorporate the technology into actual solar cells.
Yves Rubin, a UCLA professor of chemistry and another senior co-author of the study, led the team that created the uniquely designed molecules.
We dont have these materials in a real device yet; this is all in solution, he said.
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