Posts belonging to Category nanowire

Cheap, Robust Catalyst Splits Water Into Hydrogen And Oxygen

Splitting water into hydrogen and oxygen to produce clean energy can be simplified with a single catalyst developed by scientists at Rice University and the University of Houston. The electrolytic film produced at Rice and tested at Houston is a three-layer structure of nickel, graphene and a compound of iron, manganese and phosphorus. The foamy nickel gives the film a large surface, the conductive graphene protects the nickel from degrading and the metal phosphide carries out the reactionRice chemist Kenton Whitmire and Houston electrical and computer engineer Jiming Bao and their labs developed the film to overcome barriers that usually make a catalyst good for producing either oxygen or hydrogen, but not both simultaneously.

A catalyst developed by Rice University and the University of Houston splits water into hydrogen and oxygen without the need for expensive metals like platinum. This electron microscope image shows nickel foam coated with graphene and then the catalytic surface of iron, manganese and phosphorus

Regular metals sometimes oxidize during catalysis,” Whitmire said. “Normally, a hydrogen evolution reaction is done in acid and an oxygen evolution reaction is done in base. We have one material that is stable whether it’s in an acidic or basic solution.

The discovery builds upon the researchers’ creation of a simple oxygen-evolution catalyst revealed earlier this year. In that work, the team grew a catalyst directly on a semiconducting nanorod array that turned sunlight into energy for solar water splittingElectrocatalysis requires two catalysts, a cathode and an anode. When placed in water and charged, hydrogen will form at one electrode and oxygen at the other, and these gases are captured. But the process generally requires costly metals to operate as efficiently as the Rice team’s catalyst.

The standard for hydrogen evolution is platinum,” Whitmire explained. “We’re using Earth-abundant materials — iron, manganese and phosphorus — as opposed to noble metals that are much more expensive.

The robust material is the subject of a paper in Nano Energy.


New Solar System Produces 50 Percent More Energy

A concentrating photovoltaic system (CPV) with embedded microtracking can produce over 50 percent more energy per day than standard silicon solar cells in a head-to-head competition, according to a team of engineers who field tested a prototype unit over two sunny days last fall.

Solar cells used to be expensive, but now they’re getting really cheap,” said Chris Giebink, Charles K. Etner Assistant Professor of Electrical Engineering, Penn State. “As a result, the solar cell is no longer the dominant cost of the energy it produces. The majority of the cost increasingly lies in everything else — the inverter, installation labor, permitting fees, etc. — all the stuff we used to neglect.

This changing economic landscape has put a premium on high efficiency. In contrast to silicon solar panels, which currently dominate the market at 15 to 20 percent efficiency, concentrating photovoltaics focus sunlight onto smaller, but much more efficient solar cells like those used on satellites, to enable overall efficiencies of 35 to 40 percent. Current CPV systems are large — the size of billboards — and have to rotate to track the sun during the day. These systems work well in open fields with abundant space and lots of direct sun.

What we’re trying to do is create a high-efficiency CPV system in the form factor of a traditional silicon solar panel,” said Giebink.


Nanoscale Memory Cell

Developing a superconducting computer that would perform computations at high speed without heat dissipation has been the goal of several research and development initiatives since the 1950s. Such a computer would require a fraction of the energy current supercomputers consume, and would be many times faster and more powerful. Despite promising advances in this direction over the last 65 years, substantial obstacles remain, including in developing miniaturized low-dissipation memory.

Researchers at the University of Illinois at Urbana-Champaign have developed a new nanoscale memory cell that holds tremendous promise for successful integration with superconducting processors. The new technology, created by Professor of Physics Alexey Bezryadin and graduate student Andrew Murphy, in collaboration with Dmitri Averin, a professor of theoretical physics at State University of New York at Stony Brook, provides stable memory at a smaller size than other proposed memory devices.

The device comprises two superconducting nanowires, attached to two unevenly spaced electrodes that were “written” using electron-beam lithography. The nanowires and electrodes form an asymmetric, closed superconducting loop, called a nanowire ‘SQUID’ (superconducting quantum interference device). The direction of current flowing through the loop, either clockwise or counterclockwise, equates to the “0” or “1” of binary code.

This is very exciting. Such superconducting memory cells can be scaled down in size to the range of few tens of nanometers, and are not subject to the same performance issues as other proposed solutions,” comments Bezryadin.

Murphy adds, “Other efforts to create a scaled-down superconducting memory cell weren’t able to reach the scale we have. A superconducting memory device needs to be cheaper to manufacture than standard memory now, and it needs to be dense, small, and fast.”


Super Efficient Nanowires shape the future of electronics

A group of researchers at the Basque Excellence Research Center into Polymers (POLYMAT), the University of the Basque Country (UPV/EHU), the University of Barcelona, the Institute of Bioengineering of Barcelona (IBEC), and the University of Aveiro, and led by Aurelio Mateo-Alonso, the Ikerbasque research professor at POLYMAT, have developed a new suite of molecular wires or nanowires that are opening up new horizons in molecular electronics.

The growing demand for increasingly smaller electronic devices is prompting the need to produce circuits whose components are also as small as possible, and this is calling for fresh approaches in their design.

Molecular electronics has sparked great interest because the manufacture of electronic circuits using molecules would entail a reduction in their size. Nanowires are conducting wires on a molecular scale that carry the current inside these circuits. That is why the efficiency of these wires is crucially important.

In fact, one of the main novelties in this new suite of nanowires developed by the group led by Aurelio Mateo lies in their high efficiency, which constitutes a step forward in miniaturizing electronic circuits.
The findings have been published today in the journal Nature Communications.


All Carbon Spin Transistor Is Quicker And Smaller

A researcher with the Erik Jonsson School of Engineering and Computer Science at UT Dallas has designed a novel computing system made solely from carbon that might one day replace the silicon transistors that power today’s electronic devices.

The concept brings together an assortment of existing nanoscale technologies and combines them in a new way,” said Dr. Joseph S. Friedman, assistant professor of electrical and computer engineering at UT Dallas who conducted much of the research while he was a doctoral student at Northwestern University.

The resulting all-carbon spin logic proposal, published by lead author Friedman and several collaborators in the June 5 edition of the online journal Nature Communications, is a computing system that Friedman believes could be made smaller than silicon transistors, with increased performance.

Today’s electronic devices are powered by transistors, which are tiny silicon structures that rely on negatively charged electrons moving through the silicon, forming an electric current. Transistors behave like switches, turning current on and off.

In addition to carrying a charge, electrons have another property called spin, which relates to their magnetic properties. In recent years, engineers have been investigating ways to exploit the spin characteristics of electrons to create a new class of transistors and devices called “spintronics.”

Friedman’s all-carbon, spintronic switch functions as a logic gate that relies on a basic tenet of electromagnetics: As an electric current moves through a wire, it creates a magnetic field that wraps around the wire. In addition, a magnetic field near a two-dimensional ribbon of carbon — called a graphene nanoribbon — affects the current flowing through the ribbon. In traditional, silicon-based computers, transistors cannot exploit this phenomenon. Instead, they are connected to one another by wires. The output from one transistor is connected by a wire to the input for the next transistor, and so on in a cascading fashion.


Cellulose-based Ink For 3D Printing

Empa (Switzerland) researchers have succeeded in developing an environmentally friendly ink for 3D printing based on cellulose nanocrystals. This technology can be used to fabricate microstructures with outstanding mechanical properties, which have promising potential uses in implants and other biomedical applications.

Cellulose, along with lignin and hemicellulose, is one of the main constituents of wood. The biopolymer consists of glucose chains organized in long fibrous structures. In some places the cellulose fibrils exhibit a more ordered structure.

In order to produce 3D microstructured materials for composite applications, for instance, Empa researchers have been using a 3D printing method called “Direct Ink Writing” for the past year. During this process, a viscous substance – the printing ink – is squeezed out of the printing nozzles and deposited onto a surface, pretty much like a pasta machine. Empa researchers Gilberto Siqueira and Tanja Zimmermann from the Laboratory for Applied Wood Materials have now succeeded, together with Jennifer Lewis from Harvard University and André Studart from the ETH Zürich, in developing a new, environmentally friendly 3D printing ink made from cellulose nanocrystals (CNC).
The places with a higher degree of order appear in a more crystalline form. And it is these sections, which we can purify with acid, that we require for our research“, explains Siqueira. The final product is cellulose nanocrystals, tiny rod-like structures that are 120 nanometers long and have a diameter of 6.5 nanometers. And it is these nanocrystals that researchers wanted to use to create a new type of environmentally friendly 3D printing ink.They have now succeeded that  their new inks contain a full 20 percent CNC.

The biggest challenge was in attaining a viscous elastic consistency that could also be squeezed through the 3D printer nozzles“, says Siqueira. The ink must be “thick” enough so that the printed material stays “in shape” before drying or hardening, and doesn’t immediately melt out of shape again.


‘Spray-On’ Memory for Paper, Fabric, Plastic

USB flash drives are already common accessories in offices and college campuses. But thanks to the rise in printable electronics, digital storage devices like these may soon be everywhere – including on our groceries, pill bottles and even clothingDuke University researchers have brought us closer to a future of low-cost, flexible electronics by creating a new “spray-on digital memory device using only an aerosol jet printer and nanoparticle inks. The device, which is analogous to a 4-bit flash drive, is the first fully-printed digital memory that would be suitable for practical use in simple electronics such as environmental sensors or RFID tags. And because it is jet-printed at relatively low temperatures, it could be used to build programmable electronic devices on bendable materials like paper, plastic or fabric.


Duke University researchers have developed a new “spray-on” digital memory (upper left) that could be used to build programmable electronics on flexible materials like paper, plastic or fabric. They used LEDS to demonstrate a simple application.

We have all of the parameters that would allow this to be used for a practical application, and we’ve even done our own little demonstration using LEDs,” said Duke graduate student Matthew Catenacci, who describes the device in a paper published online in the Journal of Electronic Materials. At the core of the new device, which is about the size of a postage stamp, is a new copper-nanowire-based printable material that is capable of storing digital information.

Memory is kind of an abstract thing, but essentially it is a series of ones and zeros which you can use to encode information,” said Benjamin Wiley, an associate professor of chemistry at Duke and an author on the paper.


Clean Renewable Source Of Hydrogen Fuel For Electric Car

Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.

anode RiceA photo shows an array of titanium dioxide nanorods with an even coating of an iron, manganese and phosphorus catalyst. The combination developed by scientists at Rice University and the University of Houston is a highly efficient photoanode for artificial photosynthesis. Click on the image for a larger version

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. An oxygen-evolution  catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.

The Rice team came up with a way to combine three of the most abundant metalsiron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it. To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.

The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.


Cheap, Non-Toxic, Super Efficient Solar Cell

In the future, solar cells can become twice as efficient by employing a few smart little nano-tricks. Researchers are currently developing the environment-friendly solar cells of the future, which will capture twice as much energy as the cells of today. The trick is to combine two different types of solar cells in order to utilize a much greater portion of the sunlight.


These are going to be the world’s most efficient and environment-friendly solar cells. There are currently solar cells that are certainly just as efficient, but they are both expensive and toxic. Furthermore, the materials in our solar cells are readily available in large quantities on Earth. That is an important point,” says Professor Bengt Svensson of the Department of Physics at the University of Oslo (UiO) and Centre for Materials Science and Nanotechnology (SMN) in Norway.

Using nanotechnology, atoms and molecules can be combined into new materials with very special properties. The goal is to utilize even more of the spectrum of sunlight than is possible at present. Ninety-nine per cent of today’s solar cells are made from silicon, which is one of the most common elements on Earth. Unfortunately, silicon solar cells only utilize 20 per cent of the sunlight. The world record is 25 per cent, but these solar cells are laced with rare materials that are also toxic. The theoretical limit is 30 per cent. The explanation for this limit is that silicon cells primarily capture the light waves from the red spectrum of sunlight. That means that most of the light waves remain unutilized.

The new solar cells will be composed of two energy-capturing layers. The first layer will still be composed of silicon cells. “The red wavelengths of sunlight generate electricity in the silicon cells in a highly efficient manner. We’ve done a great deal of work with silicon, so there is only a little more to gain.” The new trick is to add another layer on top of the silicon cells. This layer is composed of copper oxide and is supposed to capture the light waves from the blue spectrum of sunlight.


Nano-Implant Could Restore Sight

A team of engineers at the University of California San Diego (UC San Diego)  and La Jolla-based startup Nanovision Biosciences Inc. have developed the nanotechnology and wireless electronics for a new type of retinal prosthesis that brings research a step closer to restoring the ability of neurons in the retina to respond to light. The researchers demonstrated this response to light in a rat retina interfacing with a prototype of the device in vitro. The technology could help tens of millions of people worldwide suffering from neurodegenerative diseases that affect eyesight, including macular degeneration, retinitis pigmentosa and loss of vision due to diabetes.

Despite tremendous advances in the development of retinal prostheses over the past two decades, the performance of devices currently on the market to help the blind regain functional vision is still severely limited—well under the acuity threshold of 20/200 that defines legal blindness.

cortical neuronsPrimary cortical neurons cultured on the surface of an array of optoelectronic nanowires. Note the extensive neurite outgrowth and network formation

We want to create a new class of devices with drastically improved capabilities to help people with impaired vision,” said Gabriel A. Silva, one of the senior authors of the work and professor in bioengineering and ophthalmology at UC San Diego. Silva also is one of the original founders of Nanovision.

Power is delivered wirelessly, from outside the body to the implant, through an inductive powering telemetry system developed by a team led by Cauwenberghs.

The device is highly energy efficient because it minimizes energy losses in wireless power and data transmission and in the stimulation process, recycling electrostatic energy circulating within the inductive resonant tank, and between capacitance on the electrodes and the resonant tank. Up to 90 percent of the energy transmitted is actually delivered and used for stimulation, which means less RF wireless power emitting radiation in the transmission, and less heating of the surrounding tissue from dissipated power. For proof-of-concept, the researchers inserted the wirelessly powered nanowire array beneath a transgenic rat retina with rhodopsin P23H knock-in retinal degeneration.

The findings are published in a recent issue of the Journal of Neural Engineering.



Semiconductors As Thin As An Atom

A two-dimensional material developed by physicist Prof. Dr. Axel Enders (Bayreuth University  in Germany) together with international partners could revolutionize electronicsSemiconductors that are as thin as an atom are no longer the stuff of .  Thanks to its semiconductor properties, this material could be much better suited for high tech applications than graphene, the discovery of which in 2004 was celebrated worldwide as a . This new material contains carbon, boron, and nitrogen, and its chemical name is “Hexagonal Boron-Carbon-Nitrogen (h-BCN)”. The new development was published in the journal ACS Nano.

2D material Bayreuth University

Our findings could be the starting point for a new generation of electronic transistors, circuits, and sensors that are much smaller and more bendable than the electronic elements used to date. They are likely to enable a considerable decrease in power consumption,” Prof. Enders predicts, citing the CMOS technology that currently dominates the electronics industry. This technology has clear limits with regard to further miniaturization. “h-BCN is much better suited than graphene when it comes to pushing these limits,” according to Enders.

Graphene is a two-dimensional lattice made up entirely of carbon atoms. It is thus just as thin as a single atom. Once scientists began investigating these structures more closely, their remarkable properties were greeted with enthusiasm across the world. Graphene is 100 to 300 times stronger than steel and is, at the same time, an excellent conductor of heat and electricity.


Nano Printing Heralds NanoComputers Era

A new technique using liquid metals to create integrated circuits that are just atoms thick could lead to the next big advance for electronics. The process opens the way for the production of large wafers around 1.5 nanometres in depth (a sheet of paper, by comparison, is 100,000nm thick). Other techniques have proven unreliable in terms of quality, difficult to scale up and function only at very high temperatures – 550 degrees or more.

Professor Kourosh Kalantar-zadeh, from RMIT’s School of Engineering in Australia , led the project with  colleagues from RMIT and researchers from CSIRO, Monash University, North Carolina State University and the the University of California, He observed that the electronics industry had “hit a barrier.

nano printing

The fundamental technology of car engines has not progressed since 1920 and now the same is happening to electronics. Mobile phones and computers are no more powerful than five years ago. That is why this new 2D printing technique is so important – creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costsIt will allow for the next revolution in electronics.

Benjamin Carey, a researcher with RMIT and the CSIRO, said creating electronic wafers just atoms thick could overcome the limitations of current chip production. It could also produce materials that were extremely bendable, paving the way for flexible electronics. “However, none of the current technologies are able to create homogenous surfaces of atomically thin semiconductors on large surface areas that are useful for the industrial scale fabrication of chips.  Our solution is to use the metals gallium and indium, which have a low melting point.  These metals produce an atomically thin layer of oxide on their surface that naturally protects them. It is this thin oxide which we use in our fabrication method,”  explains Carey.

By rolling the liquid metal, the oxide layer can be transferred on to an electronic wafer, which is then sulphurised. The surface of the wafer can be pre-treated to form individual transistors.  We have used this novel method to create transistors and photo-detectors of very high gain and very high fabrication reliability in large scale,” he adds.

The paper outlining the new technique has been published in the journal Nature Communications.