Building smaller greener electronics In the drive to get small, Robert Wolkow and his lab at the University of Alberta are taking giant steps forward.
The digital age has resulted in a succession of smaller, cleaner and less power-hungry technologies since the days the personal computer fit atop a desk,
replacing mainframe models that once filled entire rooms. Desktop PCS have given since way to smaller and smaller laptops, smartphones and devices that most of us carry around in our pockets.
But as Wolkow points out, this technological shrinkage can only go so far when using traditional transistor-based integrated circuits.
That's why he and his research team are aiming to build entirely new technologies at the atomic scale."
"Our ultimate goal is to make ultra-low-power electronics because that's what is demanded most by the world right now,
"said Wolkow, the icore Chair in Nanoscale Information and Communications technology in the Faculty of science.""We are approaching some fundamental limits that will stop the 30-yearlong drive to make things faster, cheaper, better and smaller;
this will come to an end soon.""An entirely new method of computing will be necessary.""Wolkow and his team in the U of A's physics department and the National Institute for Nanotechnology are working to engineer atomically precise technologies that have practical, real-world applications.
His lab already made its way into the Guinness Book of World records for inventing the world's sharpest object microscope tip just one atom wide at its end.
They made an earlier breakthrough in 2009 when they created the smallest-ever quantum dots single atom of silicon measuring less than one nanometre widesing a technique that will be awarded a U s. patent later this month.
Quantum dots Wolkow says, are vessels that confine electrons, much like pockets on a pool table. The dots can be spaced
so that electrons can be in two pockets at the same time, allowing them to interact and share electrons level of control that makes them ideally suited for computer-like circuitry."
"It could be as important as the transistor, "says Wolkow.""It lays the groundwork for a whole new basis of electronics,
and in particular, ultra-low-power electronics.""Wolkow and his team have built upon their earlier successes, modifying scanning tunnelling microscopes with their atom-wide microscope tip,
which emits ions instead of light at superior resolution. Like the needle of a record player, the microscopes can trace out the topography of silicon atoms, sensing surface features on the atomic scale.
In a new paper published in Physical Review Letters, postdoctoral fellow Bruno Martins together with Wolkow and other members of the team,
observed for the first time how an electrical current flows across the skin of a silicon crystal and also measured electrical resistance as the current moved over a single atomic step.
Wolkow says silicon crystals are mostly smooth except for these atomic staircaseslight imperfections with each step being one atom high.
and being able to record the magnitude of resistance paves the way to design superior nanoelectronic devices,
In another first, this time led by Phd student Marco Taucer, the research team observed how single electrons jump in and out of the quantum dots,
and devised a method of monitoring how many electrons fit in the pocket and measuring the dot's charge.
give scientists the ability to monitor the charge of quantum dots. They've also found a way to create quantum dots that function at room temperature,
meaning costly cryogenics is not necessary.""That's exciting because, suddenly, things that were thought of as exotic,
QSI plans to demonstrate the potential of these"extremely green"circuits that can make use of smaller, longer-lasting batteries.
"We have this nice connection where we have a training ground for students and highly academic ambitions for progress,
"Much of their efforts initially will focus on creating hybrid technologiesdding atom-scale circuitry to conventional electronics such as GPS devices
"It has the potential to totally change the world's electronic basis. It's a trillion-dollar prospect. l
#Designing ultra-sensitive biosensors for early personalised diagnostics A new type of high-sensitivity and low-cost sensors,
called plasmonic biosensors, could ultimately become a key asset in personalised medicine by helping to diagnose diseases at an early stage.
Personalised medicine is one of the new developments that is deemed to revolutionise health care. A key component is the detection of biomarkers, proteins in blood or saliva, for example,
whose presence or abnormal concentration is caused by a disease. Biomarkers can indicate the presence of diseases long before the appearance of symptoms.
However, currently the detection of these molecules still requires specialised laboratories and is costly. Thanks to the EU-funded research project called NANOANTENNA
completed in March 2013, physicists joined forces with chemists, nanotechnologists and biomedical researchers with the aim of developing a so-called plasmonic nanobiosensor for the detection of proteins.
It consisted of nanoantennas, tiny gold rods about 100 to 200 nanometres long and 60 to 80 nm wide.
By shining light onto such a nanoantenna, the electrons inside start moving back and forth, amplifying the light radiation in hot spots regions of the antenna,
explains Pietro Giuseppe Gucciardi, a physicist at the Institute for Chemical-Physical Processes, affiliated with the Italian National Research Council CNR, in Messina,
Sicily.""The aim of the project was to deliver a proof of concept, "says Gucciardi.
During the 1990s'researchers found that plasmons, tiny waves of electrons in metallic surfaces that appear
when such surfaces are illuminated, also amplify the light in an area close to that surface. In biosensors, protein molecules are identified by irradiating them with infrared light
If these molecules are close to nanoparticles, the plasmons in the nanoparticles enhance the Raman signal coming from the molecules that have to be detected with several orders of magnitude.
The nanoantennas developed in this project only enhance the emitted Raman signal if the biomolecules are close to the hot spots Therefore,
the molecules have to be trapped to be detected. To do so, the researchers attached bioreceptors, fragments of DNA engineered to recognise specific proteins, to the nanoantennas.
When the nanoantennas studded with the bioreceptors are incubated in a solution that contains the biomarkers to be detected,
the latter become attached to the nanoantennas. When, subsequently, these nanoantennas are illuminated with light, they show the Raman fingerprints of both the bioreceptor and the biomarker,
as Gucciardi points out. One expert comments that health-care programmes are quickly moving to prevention
and early detection of diseases, done in point-of-care (POC) or bed-side conditions."
"It is important to fund this research because it will be a component of future medicine,
"says Alexandre Brolo, professor of chemistry specialised in nanotechnology research, who has been developing plasmonic biosensors at the University of Victoria, British columbia, Canada.
He also believes that such approach will make medical care more cost effective.""You want something that is very cheap
and is not going to put a big burden on the health care system, "says Brolo. Another expert agrees."
"Small, compact and autonomous devices with the same features in terms of sensitivity and robustness as current commercial instrumentation based on plasmonics are needed still,
"says Maria Carmen Estévez, a researcher at the Catalan Institute of Nanoscience and Nanotechnology in Bellaterra, Spain.
The"end-users"of these biosensors have to understand that the development of these devices by researchers in many disciplines is a long process, notes Estévez.
She adds that these biosensors will need to be integrated with optical components, with electronics for reading out the measurements, software to process all data,
and rely on the use of microfluidics to prepare and process the sample p
#Simple inexpensive fabrication procedure boosts light-capturing capabilities of tiny holes carved into silicon wafers Increasing the cost-effectiveness of photovoltaic devices is critical to making these renewable energy sources competitive with traditional fossil fuels.
One possibility is to use hybrid solar cells that combine silicon nanowires with low-cost, photoresponsive polymers. The high surface area and confined nature of nanowires allows them to trap significant amounts of light for solar cell operations.
Unfortunately, these thin, needle-like structures are very fragile and tend to stick together when the wires become too long.
Now, findings by Xincai Wang from the A*STAR Singapore Institute of Manufacturing Technology and co-workers from Nanyang Technological University could turn the tables on silicon nanowires by improving the manufacturing of silicon'nanoholes'arrow cavities carved into silicon wafers
that have enhanced mechanical and light-harvesting capabilities. Nanoholes are particularly effective at capturing light because photons can ricochet many times inside these openings until absorption occurs.
Yet a practical understanding of how to fabricate these tiny structures is still lacking. One significant problem, notes Wang, is control of the initial stages of nanohole formation crucial period that can often induce defects into the solar cell.
Instead of traditional time-consuming lithography, the researchers identified a rapid, 'maskless'approach to producing nanoholes using silver nanoparticles.
First, they deposited a nanometer-thin layer of silver onto a silicon wafer which they toughened by annealing it using a rapid-burst ultraviolet laser.
Careful optimization of this procedure yielded regular arrays of silver nanospheres on top of the silicon surface,
with sphere size and distribution controlled by the laser annealing conditions. Next, the nanosphereilicon complex was immersed into a solution of hydrogen peroxide and hydrofluoric acid mixture that eats away at silicon atoms directly underneath the catalytic silver nanospheres.
Subsequent removal of the silver particles with acid produced the final, nanohole-infused silicon surface (see image).
The team analyzed the solar cell activity of their nanohole interfaces by coating them with a semiconducting polymer and metal electrodes.
Their experiments revealed a remarkable dependence on nanohole depth: cavities deeper than one micrometer showed sharp drops in power conversion efficiency from a maximum of 8. 3 per cent due to light scattering off of rougher surfaces and higher series resistance effects."
"Our simple process for making hybrid silicon nanohole devices can successfully reduce the fabrication costs
which impede the solar cell industry, "says Wang.""In addition, this approach can be transferred easily to silicon thin films to develop thin-film siliconolymer hybrid solar cells with even higher efficiency. e
#Making dreams come true: Making graphene from plastic? Graphene is gaining heated attention dubbed a wonder material with great conductivity flexibility and durability.
However graphene is hard to come by due to the fact that its manufacturing process is complicated and mass production not possible.
Recently a domestic research team developed a carbon material without artificial defects commonly found during the production process of graphene
while maintaining its original characteristics. The newly developed material can be used as a substitute for graphene in solar cells and semiconductor chips.
Further the developed process is based on the continuous and mass-produced process of carbon fiber making it much easier for full-scale commercialization.
In recognition of the innovative approach the research was introduced on the cover of Nanoscale a high impacting peer-reviewed journal in the field of nano science.
The research team led by Dr. Han-Ik Joh at KIST along with Dr. Seok-In Na at Chonbuk National University and Dr. Byoung Gak Kim at KRICT synthesized carbon nanosheets similar to graphene using polymer
and directly used the transparent electrodes for organic solar cells. The research outcome was introduced in Nanoscale a journal of Royal Society of Chemistry in the UK under the title of One-step Synthesis of Carbon Nanosheets Converted from a Polycylic Compound
and Their Direct Use as Transparent Electrodes of ITO-free Organic solar cells and was selected as a cover story in the January 21st edition in recognition for this innovative and superb research findings.
To manufacture high quality graphene in large volume the CVD (chemical vapor deposition)* method is used widely.
However this method requires intensive postprocessing (transfer process) as it has to remove used metal after the manufacturing process
and move the manufactured graphene to another board such as a solar cell substrate. In this process the quality quickly degrades as it is prone to wrinkles or cracks.
CVD (Chemical Vapor Deposition: It is a method of manufacturing graphene on the board of metal film that serves as a catalyst.
After it is done the metal has to be removed and graphene has to be transported to another board.
The research team developed carbon nanosheet in a two-step process which consists of coating the substrate with a plymer solution and heating.
In addition the new method can be used directly as solar cell without any additional process. The research team synthesized a polymer with a rigid ladder structure namely PIM-1 (Polymer of intrinsic microporosity-1) to form the#through the simpole process
which is spin-coated on the quarts substrates using PIM-1 solution with light green color
The carbon nanosheet can be mass-produced in a simpler process while having high quality since the new process bypasses the steps that are prone to formation of defects such as elimination of the metal substrate or transfer of graphene to another board.
since this process is based on the continuous and mass-produced process of carbon fiber. Explore further:
#Shrinky Dinks close the gap for nanowires How do you put a puzzle together when the pieces are too tiny to pick up?
Engineers at the University of Illinois at Urbana-Champaign are using Shrinky Dinks, plastic that shrinks under high heat,
to close the gap between nanowires in an array to make them useful for high-performance electronics applications.
Nanowires are extremely fast, efficient semiconductors, but to be useful for electronics applications, they need to be packed together in dense arrays.
Researchers have struggled to find a way to put large numbers of nanowires together so that they are aligned in the same direction and only one layer thick."
"Chemists have done already a brilliant job in making nanowires exhibit very high performance. We just don't have a way to put them into a material that we can handle,
"said study leader Sungwoo Nam, a professor of mechanical science and engineering at the U. of I."With the shrinking approach,
people can make nanowires and nanotubes using any method they like and use the shrinking action to compact them into a higher density."
"The researchers place the nanowires on the Shrinky Dinks plastic as they would for any other substrate,
but then shrink it to bring the wires much closer together. This allows them to create very dense arrays of nanowires in a simple, flexible and very controllable way.
The shrinking method has added the bonus of bringing the nanowires into alignment as they increase in density.
Nam's group demonstrated how even wires more than 30 degrees off-kilter can be brought into perfect alignment with their neighbors after shrinking."
"There's assembly happening at the same time as the density increases, "Nam said, "so even if the wires are assembled in a disoriented direction we can still use this approach."
"The plastic is clamped before baking so that it only shrinks in one direction, so that the wires pack together
The researchers also can control how densely the wires pack by varying the length of time the plastic is heated.
They also are exploring using lasers to precisely shrink the plastic in specific patterns. Nam first had the idea for using Shrinky Dinks plastic to assemble nanomaterials after seeing a microfluidics device that used channels made of shrinking plastic.
He realized that the high degree of shrinking and the low cost of plastic could have a huge impact on nanowire assembly and processing for applications."
"I'm interested in this concept of synthesizing new materials that are assembled from nanoscale building blocks, "Nam said."
"You can create new functions. For example, experiments have shown that film made of packed nanowires has properties that differ quite a bit from a crystal thin film."
"One application the group is now exploring is a thin film solar cell, made of densely packed nanowires,
that could harvest energy from light much more efficiently than traditional thin-film solar cells s
#Chemists seek state-of-the-art lithium-sulfur batteries When can we expect to drive the length of Germany in an electric car without having to top up the battery?
Chemists at the NIM Cluster at LMU and at the University of Waterloo in Ontario, Canada, have synthesized now a new material that could show the way forward to state-of-the-art lithium-sulfur batteries.
Whether or not the future of automotive traffic belongs to the softly purring electric car depends largely on the development of its batteries.
The industry is currently placing most of its hopes in lithium-sulfur batteries, which have a very high storage capacity.
Moreover, thanks to the inclusion of sulfur atoms, they are cheaper to make and less toxic than conventional lithium-ion power packs.
However the lithium-sulfur battery still presents several major challenges that need to be resolved until it can be integrated into cars.
For example, both the rate and the number of possible charge-discharge cycles need to be increased before the lithium-sulfur battery can become a realistic alternative to lithium-ion batteries.
Lots of pores for sulfur The chemists Professor Thomas Bein (LMU), Coordinator of the Energy conversion Division of the Nanosystems Initiative Munich, Professor Linda Nazar (University of Waterloo, Waterloo Institute
of Nanotechology) and their colleagues have succeeded now in producing a novel type of nanofiber whose highly ordered and porous structure gives it an extraordinarily high surface-to-volume ratio.
Thus, a sample of the new material the size of a sugar cube presents a surface area equivalent to that of more than seven tennis courts."
"The high surface-to-volume ratio, and high pore volume is important because it allows sulfur to bind to the electrode in a finely divided manner, with relatively high loading.
Together with its easy accessibility, this enhances the efficiency of the electrochemical processes that occur in the course of charge-discharge cycles.
And the rates of the key reactions at the sulfur electrode-electrolyte interface, which involve both electrons
To synthesize the carbon fibers, the chemists first prepare a porous, tubular silica template, starting from commercially available,
but nonporous fibers. This template is filled then with a special mixture of carbon, silicon dioxide and surfactants,
which is heated then at 900°C. Finally the template and the Sio2 are removed by an etching process.
During the procedure, the carbon nanotubes and thus the pore size shrink to a lesser extent than they would in the absence of the confining template
and the fibers themselves are correspondingly more stable.""Nanostructured materials have great potential for the efficient conversion
and storage of electrical energy,"says Thomas Bein.""We in the NIM Cluster will continue to collaborate closely with our colleagues in the Bavarian Soltech Network
#Chirality-controlled growth of single-walled carbon nanotubes Recently, Professor Li Yan's research team developed a novel strategy to produce single-walled carbon nanotubes with specific chirality by applying a new family of catalysts,
"We need to use structure specific carbon nanotubes for real applications. The structure controlled growth has been a dream of our field for about 20 years.
Recent work by Professor Yan Li at Peking University shows that it is realized finally. I believe her idea to use W-based catalyst is the landmark of growth of carbon nanotubes.
We expect a plenty of very useful applications of carbon nanotubes based on her new discovery, "said Professor Shigeo Maruyama from The University of Tokyo,
who also serves the president of Fullerene, Carbon nanotubes, and Graphene research Society of Japan. Single-walled carbon nanotube (SWNT
which can be considered as a seamlesscylinder formed by rolling a piece of graphene, may be either metallic
or semiconducting depending on the manner of rolling denoted as (n m)( or the'chirality').'Relying on the fantastic structure and property, especially the extremely high mobility for both electrons and holes,
SWNTS has shown great potential in various fields such as nanoelectronics. In 2009, the International Technology Roadmap for Semiconductors (ITRS) selected carbon-based nanoelectronics to include carbon nanotubes
and graphene for additional resources and detailed road mapping for ITRS as promising technologies targeting commercial demonstration in the next 10-15 year horizon.
However, it has been a big challenge for over 20 years to realize the chirality-selective synthesis of SWNTS.
As stated by Dr. Avouris in his review article published in Nature Nanotechnology (V. 2 P. 605"
the main hurdle (of carbon-based electronics) is our current inability to produce large amounts of identical nanostructureshere is no reliable way to directly produce a single CNT type such as will be needed in a large integrated system."
"Inspiringly, Professor Li and her collaborators have made a breakthrough on this issue. The catalysts, tungsten-based bimetallic alloy nanoparticles of non-cubic symmetry, have high melting points
and consequently are able to maintain their crystal structure during the chemical vapor deposition (CVD) process,
to regulate the chirality of the grown SWNTS. The (12,6) SWNTS are synthesized directly at an abundance of>92%by using W6co7 catalysts.
Experimental evidence and theoretical simulation reveal that the good structural match between the carbon atom arrangement around the nanotube circumference
and the arrangement of the atoms in one of the planes of the nanocrystal catalyst facilitates the (n,
m) preferential growth of SWNTS. This method is also valid for other tungsten-based alloy nanocatalysts to grow SWNTS of various designed chirality."
"Employing tungsten-based alloy nanocrystals with unique structure as catalysts paves a way for the ultimate chirality control in SWNT growth.
This may accumulate the development in SWNT applications, for example, carbon-based nanoelectronics",said Li. The work was evaluated highly by Professor Jie Liu at Duke university,
"The chirality-specific growth of single-walled carbon nanotubes is the most challenging and important issue in the field,
which has not been solved for many years. Prof. Yan Li at Peking University first shows that the controlled growth is possible.
This development is very important for the applications of carbon nanotubes in many fields especially nanoelectronics. c
#Lab unzips nanotubes into ribbons by shooting them at a target (Phys. org) Carbon nanotubes unzipped into graphene nanoribbons by a chemical process invented at Rice university are finding use in all kinds of projects
but Rice scientists have now found a chemical-free way to unzip them. The Rice lab of materials scientist Pulickel Ajayan discovered that nanotubes that hit a target end first turn into mostly ragged clumps of atoms.
But nanotubes that happen to broadside the target unzip into handy ribbons that can be used in composite materials for strength
and applications that take advantage of their desirable electrical properties. The Rice researchers led by graduate student Sehmus Ozden reported their finding in the American Chemical Society journal Nano Letters.
The result was a surprise Ozden said. Until now we knew we could use mechanical forces to shorten and cut carbon nanotubes.
This is the first time we have showed carbon nanotubes can be unzipped using mechanical forces. The researchers fired pellets of randomly oriented multiwalled carbon nanotubes from a light gas gun built by the Rice lab of materials scientist Enrique Barrera with funding from NASA.
The pellets impacted an aluminum target in a vacuum chamber at about 15000 miles per hour. When they inspected the resulting carbon rubble they found nanotubes that smashed into the target end first
or at a sharp angle simply deformed into a crumpled nanotube. But tubes that hit lengthwise actually split into ribbons with ragged edges.
Hypervelocity impact tests are used mostly to simulate the impact of different projectiles on shields spacecraft
and satellites Ozden said. We were investigating possible applications for carbon nanotubes in space when we got this result.
The effect was confirmed through molecular simulations. They showed that when multiwalled tubes impact the target the outer tube flattens hitting the inside tubes
and unzipping them in turn. Single-wall nanotubes do just the opposite; when the tube flattens the bottom wall hits the inside of the top wall
which unzips from the middle out to the edges. Ozden explained that the even distribution of stress along the belly-flopping nanotube which is many times longer than it is wide breaks carbon bonds in a line nearly simultaneously.
The researchers said 70 to 80 percent of the nanotubes in a pellet unzip to one degree or another.
Ozden said the process eliminates the need to clean chemical residues from nanoribbons produced through current techniques.
One-step chemical-free clean and high-quality graphene nanoribbons can be produced using our method. They're potential candidates for next-generation electronic materials he said.
Explore further: Scientists shoot carbon nanotubes out of high-speed gun (w/video) More information: Unzipping Carbon nanotubes at High Impact.
Sehmus Ozden Pedro A s. Autreto Chandra Sekhar Tiwary Suman Khatiwada Leonardo Machado Douglas S. Galvao Robert Vajtai Enrique V. Barrera
and Pulickel M. Ajayan. Nano Letters Article ASAP. DOI: 10.1021/nl501753 3
#Diamond plates create nanostructures through pressure not chemistry You wouldn't think that mechanical forcehe simple kind used to eject unruly patrons from bars,
shoe a horse or emboss the raised numerals on credit cardsould process nanoparticles more subtly than the most advanced chemistry.
Yet, in a recent paper in Nature Communications, Sandia National Laboratories researcher Hongyou Fan and colleagues appear to have achieved a start toward that end.
Their newly patented and original method uses simple pressure kind of high-tech embossingo produce finer and cleaner results in forming silver nanostructures than do chemical methods,
which are not only inflexible in their results but leave harmful byproducts to dispose of. Fan calls his approach"a simple stress-based fabrication method"that,
when applied to nanoparticle arrays, forms new nanostructures with tunable properties.""There is a great potential market for this technology,
"he said.""It can be readily and directly integrated into current industrial manufacturing lines without creating new expensive and specialized equipment."
"Said Sandia co-author Paul Clem, "This is a foundational method that should enable a variety of devices,
including flexible electronics such as antennas, chemical sensors and strain detectors.""It also would produce transparent electrodes for solar cells and organic light-emitting diodes,
Clem said. The method was inspired by industrial embossing processes in which a patterned mask is applied with high external pressure to create patterns in the substrate,
Fan said.""In our technology, two diamond anvils were used to sandwich nanoparticulate thin films. This external stress manually induced transitions in the film that synthesized new materials,
"he said. The pressure, delivered by two diamond plates tightened by four screws to any controlled setting, shepherds silver nanospheres into any desired volume.
Propinquity creates conditions that produce nanorods, nanowires and nanosheets at chosen thicknesses and lengths rather than the one-size-fits-all output of a chemical process, with no environmentally harmful residues.
While experiments reported in the paper were performed with silverhe most desirable metal because it is the most conductive,
stable and optically interesting and becomes transparent at certain pressureshe method also has been shown to work with gold,
platinum and other metallic nanoparticles Clem said the researchers are now starting to work with semiconductors.
Bill Hammetter, manager of Sandia's Advanced Materials Laboratory, said, "Hongyou has discovered a way to build one structure into another structure capability we don't have now at the nanolevel.
Eight or nine gigapascal he amount of pressure at which phase change and new materials occurre not difficult to reach.
Any industry that has embossing equipment could lay a film of silver on a piece of paper
A coating of nanoparticles that can build into another structure has a certain functionality we don't have right now.
but could be done today with the same equipment used by anyone who makes credit cards.""The method can be used to configure new types of materials.
For example, under pressure, the dimensions of ordered three-dimensional nanoparticle arrays shrink. By fabricating a structure in
which the sandwiching walls permanently provide that pressure, the nanoparticle array will remain at a constant state,
able to transmit light and electricity with specific characteristics. This pressure-regulated fine-tuning of particle separation enables controlled investigation of distance-dependent optical and electrical phenomena.
At even higher pressures, nanoparticles are forced to sinter, or bond, forming new classes of chemically
and mechanically stable nanostructures that no longer need restraining surfaces. These cannot be manufactured using current chemical methods.
Depending on the size composition and phase orientation of the initial nanoparticle arrays, a variety of nanostructures or nanocomposites and 3-D interconnected networks are achievable.
The stress-induced synthesis processes are simple and clean. No thermal processing or further purification is needed to remove reaction byproducts r
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