Nanoscience research could prove a breakthrough in electronics

05 August 2013

Electronic ink

 

Electronic touch pads that cost just a few dollars and solar cells that cost the same as roof shingles are one step closer to reality today.
Researchers in the University of Minnesota’s College of Science and Engineering and the National Renewable Energy Laboratory in Golden, Colo., have overcome technical hurdles in the quest for inexpensive, durable electronics and solar cells made with non-toxic chemicals.

 
The research team discovered a novel technology to produce a specialized type of ink from non-toxic nanometer-sized crystals of silicon, often called “electronic ink.” This “electronic ink” could produce inexpensive electronic devices with techniques that essentially print it onto inexpensive sheets of plastic.

 

 
“This process for producing electronics is almost like screen printing a number on a softball jersey,” said Lance Wheeler, a University of Minnesota mechanical engineering Ph.D. student and lead author of the research.

 

 
But it’s not quite that easy. Wheeler, Kortshagen and the rest of the research team developed a method to solve fundamental problems of silicon electronic inks.
First, there is the ubiquitous need of organic “soap-like” molecules, called ligands, that are needed to produce inks with a good shelf life, but these molecules cause detrimental residues in the films after printing. This leads to films with electrical properties too poor for electronic devices. Second, nanoparticles are often deliberately implanted with impurities, a process called “doping,” to enhance their electrical properties.

 
Researchers used a new method to use an ionized gas, called nonthermal plasma, to not only produce silicon nanocrystals, but also to cover their surfaces with a layer of chlorine atoms. This surface layer of chlorine induces an interaction with many widely used solvents that allows production of stable silicon inks with excellent shelf life without the need for organic ligand molecules.

 

 
In addition, the researchers discovered that these solvents lead to doping of films printed from their silicon inks, which gave them an electrical conductivity 1,000 times larger than un-doped silicon nanoparticle films. The researchers have a provisional patent on their findings.

 

 

This story is reprinted from material from University of Minnesota, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

Plastic electronics made easy

(Nanowerk News)  Scientists have discovered a way to  better exploit a process that could revolutionise the way that electronic  products are made.

The scientists from Imperial College London say improving the  industrial process, which is called crystallisation, could revolutionise the way  we produce electronic products, leading to advances across a whole range of  fields; including reducing the cost and improving the design of plastic solar  cells.

The process of making many well-known products from plastics  involves controlling the way that microscopic crystals are formed within the  material. By controlling the way that these crystals are grown engineers can  determine the properties they want such as transparency and toughness.  Controlling the growth of these crystals involves engineers adding small amounts  of chemical additives to plastic formulations. This approach is used in making  food boxes and other transparent plastic containers, but up until now it has not  been used in the electronics industry.

The team from Imperial have now demonstrated that these  additives can also be used to improve how an advanced type of flexible circuitry  called plastic electronics is made.

The team found that when the additives were included in the  formulation of plastic electronic circuitry they could be printed more reliably  and over larger areas, which would reduce fabrication costs in the industry.

The team reported their findings this month in the journal  Nature Materials (“Microstructure formation in molecular and polymer  semiconductors assisted by nucleation agents”).

Dr Natalie Stingelin, the leader of the study from  the Department of Materials and Centre of Plastic Electronics at Imperial, says:

“Essentially, we have demonstrated a simple way to gain control  over how crystals grow in electrically conducting ‘plastic’ semiconductors. Not  only will this help industry fabricate plastic electronic devices like solar  cells and sensors more efficiently. I believe it will also help scientists  experimenting in other areas, such as protein crystallisation, an important part  of the drug development process.”

Dr Stingelin and research associate Neil Treat looked at two  additives, sold under the names IrgaclearÒ XT 386 and MilladÒ 3988, which are  commonly used in industry. These chemicals are, for example, some of the  ingredients used to improve the transparency of plastic drinking bottles. The  researchers experimented with adding tiny amounts of these chemicals to the  formulas of several different electrically conducting plastics, which are used  in technologies such as security key cards, solar cells and displays.

The researchers found the additives gave them precise control  over where crystals would form, meaning they could also control which parts of  the printed material would conduct electricity. In addition, the  crystallisations happened faster than normal. Usually plastic electronics are  exposed to high temperatures to speed up the crystallisation process, but this  can degrade the materials. This heat treatment treatment is no longer necessary  if the additives are used.

Another industrially important advantage of using small amounts  of the additives was that the crystallisation process happened more uniformly  throughout the plastics, giving a consistent distribution of crystals.  The team  say this could enable circuits in plastic electronics to be produced quickly and  easily with roll-to-roll printing procedures similar to those used in the  newspaper industry. This has been very challenging to achieve previously.

Dr Treat says: “Our work clearly shows that these additives are  really good at controlling how materials crystallise. We have shown that printed  electronics can be fabricated more reliably using this strategy. But what’s  particularly exciting about all this is that the additives showed fantastic  performance in many different types of conducting plastics. So I’m excited about  the possibilities that this strategy could have in a wide range of materials.”

Dr Stingelin and Dr Treat collaborated with scientists from the  University of California Santa Barbara, and the National Renewable Energy  Laboratory in Golden, US, and the Swiss Federal Institute of Technology on this  study. The team are planning to continue working together to see if subtle  chemical changes to the additives improve their effects – and design new  additives.

They will be working with the new Engineering and Physical  Sciences Research Council (EPSRC)-funded Centre for Innovative Manufacturing in  Large Area Electronics in order to drive the industrial exploitation of their  process. The £5.6 million of funding for this centre, to be led by researchers  from Cambridge University, was announced earlier this year. They are also  exploring collaborations with printing companies with a view to further  developing their circuit printing technique.

Controlling crystals

Here are some of the technologies that could benefit from Drs  Treat and Stingelin’s research:

Improving drugs

Most drugs work by blocking or activating proteins in our  bodies. To develop better drugs, scientists must understand what these proteins  look like. The work carried out by the Imperial team could enable researchers in  the future to develop more accurate models of proteins, by converting them into  a crystalline form.

More efficient solar technology

Solar cells are made from a solid mixture of electrically  conducting crystalline chemicals. Currently these cells only convert about 10%  of the Sun’s energy into electricity. Dr Treat and Stingelin’s additives may  provide a way of improving crystal growth in solar cells, which could improve  the amount of energy they convert.

New flexible electronics

Flexible semiconductor films can be made by methods such as  inkjet printing. Using additives that control how inkjet-printed droplets of  semiconductors crystallise will mean they crystallise in evenly distributed  patterns that conduct electricity efficiently. This means industry can produce  these printed electronics more easily and cheaply.

Source: By Joshua Howgego, Imperial College London

Read more: http://www.nanowerk.com/news2/newsid=31181.php#ixzz2YPLhjKF8

NREL’s Keith Emery Awarded Prestigious Cherry Award: Efficiency of Solar Cells

Top PV award goes to researcher who brought credibility to testing of solar cells and modules

June 19, 2013

An engineer from the Energy Department’s National Renewable Energy Laboratory (NREL) whose testing and characterization laboratory brings credibility to the measurement of efficiency of solar cells and modules has been awarded the prestigious William R. Cherry Award by the Institute of Electrical and Electronics Engineers (IEEE).

Keith Emery, a principal scientist at NREL, received the award at the 39th IEEE’s Photovoltaic Specialists Conference in Tampa Bay.

“Accredited measurements from Emery’s laboratories are considered the gold standard by the U.S. and international PV communities,” said NREL colleague Pete Sheldon, Deputy Director of the National Center for Photovoltaics on the NREL campus in Golden, CO. “His leadership in the development of cell and module performance measurement techniques and the development of standards, has set the foundation for the PV community for the last 25 years.”

The award is named in honor of William R. Cherry, a founder of the photovoltaic community. In the 1950s, Cherry was instrumental in establishing solar cells as the ideal power source for space satellites and for recognizing, advocating and nurturing the use of photovoltaic systems for terrestrial applications. The purpose of the award is to recognize an individual engineer or scientist who devoted a part of their professional life to the advancement of the science and technology of photovoltaic energy conversion.

Emery is the third consecutive Cherry Award winner from NREL. In 2011, Jerry Olson, who developed the multi-junction solar cell, won the award. Last year, Sarah Kurtz, who helped Olson develop the multi-junction cell and now is a global leader in solar module reliability, won the award. Three other NREL scientists won the Cherry Award previously – Paul Rappaport (1980), Larry Kazmerski (1993), and Tim Coutts (2005).

Emery says he was floored by the award, considered among the top one or two annual awards globally in the photovoltaic community.

Others aren’t surprised, citing his work to bring iron-clad certainty to the claims made by solar companies about the efficiency of their photovoltaic cells and modules – not to mention the 320 scientific publications he was able to write.

He has spent his career building the capabilities of that testing and characterization lab, making it one of a handful of premier measurement labs in the world – and the only place in the United States that calibrates primary terrestrial standards for solar-cell characterization.

Unbelievable claims of high efficiency would be out in the literature without any independent verification. “We decided that independent verification was critical for credibility,” Emery said.

“We have to thank DOE for this,” Emery said. “They’ve funded it. We’ve been able to offer the service to all terrestrial PV groups in the U.S. from national labs to universities to low-budget startups. They all get the same quality of service.”

The readily available service is so researchers and companies have equal access to the resources needed for independent efficiency measurement, he said. “We provide the same playing field for everyone.”

Emery spent the first 25 years of his life in Lansing, Michigan, attending public schools, then going on to Lansing Community College and Michigan State University where he earned his bachelor’s and master’s degrees. From there he went to Colorado State University to fabricate and test ITO on silicon solar cells, and then was hired at NREL. At NREL, in the 1980s, Emery developed the test equipment and put together the data-acquisition system for characterizing and measuring the efficiency of solar cells.

Emery gives much of the credit to the colleagues who work in his lab and who have on average about 16 years at NREL. “Take my team away and I wouldn’t have gotten this award – it’s that simple.”

Sheldon said Emery’s work “brings scientific credibility to the entire photovoltaic field, ensuring global uniformity in cell and module measurements. His getting the award is certainly well deserved.”

NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by the Alliance for Sustainable Energy, LLC.

###

Visit NREL online at www.nrel.gov

Why quantum dots can join every aspect of everyday life

Nanotechnology is often confined to niche products, but quantum dots are so versatile they could be used in everything from light bulbs to laptops.

 

 

 

 

Tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable properties that scientists think they will soon be used in everything from light bulbs to the design of ultra-efficient solar cells. Photograph: Science Photo Library

The properties of a material were once thought to be defined only by its chemical composition. But size matters too, especially for semiconductors. Make crystals of silicon small enough – less than 10 nanometres – and their tiny dimensions can start to dictate how the atoms behave and react in the presence of other things.

These tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable, novel properties that scientists think they will soon be used in everything from light bulbs to imaging of cancer cells or in the design of ultra-efficient solar cells.

Semiconductors such as silicon or indium arsenide are chosen to build electronic circuits because of the discrete energy levels at which they can give off electrons or photons. This makes them useful in building switches, transistors and other devices. It was once thought these energy levels – known as band gaps – were fixed. But shrinking the physical size of the semiconductor material to quantum-dot level seems able to change the band gaps, altering the wavelengths of light the material can emit or changing the energy it takes to change a material from an insulator to a conductor.

Instead of looking for brand new materials to build different devices, then, quantum dots make it possible to use a single type of semiconductor to produce a range of different characteristics. Researchers could tune dots made from silicon to emit a range of different colours in different situations, for example, instead of having to use a range of materials with different chemical compositions.

“The main application for quantum dots at the moment is biological tagging of cells,” says Paul O’Brien, a professor of inorganic materials at the University of Manchester and co-founder of Nanoco Technologies a quantum dot manufacturer also based in Manchester. They are used in the same way as fluorescent dyes, to label agents, he says, but with the advantage that a single laser source can be used to illuminate many different tags each with a specific wavelength.

By attaching different types of quantum dots to proteins that target and attach to specific cell types in the body, these bits of semiconductor can be used by doctors to monitor different kinds of cells. When a laser is then directed on to tagged cells, doctors can see what colour they glow.

The ability to shine also makes quantum dots well suited to produce white light. Existing white bulbs based on low energy light emitting diode (LED) technology tend to produce a garish and bluish form of light that notoriously feels cold, says O’Brien. This is because these LEDs use a phosphor that produces an artificial white light that contains less red wavelengths than natural white light. By embedding quantum dots into a film that is placed over a bulb containing blue LEDs, it is possible to get a much warmer colour of white light. The blue light  from the LED stimulates the quantum dots which, in turn, emit light in a range of colours. Provided you have chosen your dots carefully, these will combine to form white light.

The first of these quantum dot lights hit the market in 2010, a partnership between QD Vision, an MIT spinout in Lexington, Massachusetts, and Nexxus Lighting of Charlotte, North Carolina.

Backlights for laptops, tablets and mobile devices are next in line, and they should appear in products before the end of 2012 says VJ Sahi, head of corporate development at materials design company Nanosys of Palo Alto, California. Besides the colour advantages, quantum-dot-based backlights can be three times more efficient than traditional backlights.

Eventually, says Sahi, quantum dots will do more than just light up displays. The long-term aim is use them to create each red, green and blue sub-pixel that makes up a coloured display. This should produce much brighter colours and consume less power than LCD or even the latest state-of-the-art organic LED (OLED) displays. They should also have no problems with viewing angles, he adds.

The interesting properties of quantum dots come from the fact that they behave like tuning forks for photons, a result of a phenomenon called confinement. At less than 10 nanometres in size – about 50 atoms – they fall within the dimensions of a critical quantum characteristic of the material known as the exciton Bohr radius. The energy levels of electrons within the material’s atoms are constrained and, when a photon or electron hits an atom and excites it, the atom re-emits the energy as a photon of a very specific energy level.

Quantum dots also have another trick up their sleeve. Besides converting photons of one energy into photons of another, they can also be used to release electrons and create electrical currents: in other words they can be used to make solar cells. Arthur Nozik at the National Renewable Energy Laboratory in Boulder, Colorado, says that quantum-dot solar cells would be much more efficient at converting the energy from photons and therefore boost the amount of power they can produce.

Sun Plus Nanotechnology: Can Solar Energy Get Bigger by Thinking Small?

Patrick J. Kiger

For National Geographic News

Published April 28, 2013

“Advances in nanotechnology will lead to higher efficiencies and lower costs, and these can and likely will be significant,” explains Matt Beard, a senior scientist for the U.S. Department of Energy‘s National Renewable Energy Laboratory (NREL). “In fact, nanotechnology is already having dramatic effects on the science of solar cells.”

 

Nearly 60 years after researchers first demonstrated a way to convert sunlight into energy, science is still grappling with a critical limitation of the solar photovoltaic cell.

It just isn’t that efficient at turning the tremendous power of the sun into electricity.

And even though commercial solar cells today have double to four times the 6 percent efficiency of the one first unveiled in 1954 by Bell Laboratories in New Jersey, that hasn’t been sufficient to push fossil fuel from its preeminent place in the world energy mix.

But now, alternative energy researchers think that something really small—nanotechnology, the engineering of structures a fraction of the width of a human hair—could give a gigantic boost to solar energy. (Related Quiz: “What You Don’t Know About Solar Power“)

“Advances in nanotechnology will lead to higher efficiencies and lower costs, and these can and likely will be significant,” explains Matt Beard, a senior scientist for the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL). “In fact, nanotechnology is already having dramatic effects on the science of solar cells.”

Of course, the super-expensive solar arrays used in NASA’s space program are far more efficient than those installed on rooftops. (Related: “Beam It Down: A Drive to Launch Space-Based Solar“) And in the laboratory, scientists have achieved record-breaking efficiencies of more than 40 percent. But such contests are a testament to the gap between solar potential and the mass market cells of today.

 

The light glinting off the surface of this solar photovoltaic cell signifies lost efficiency. Scientists are looking to nanotechnology to boost solar power, including by reducing the amount of sunlight that silicon wastes through reflection.

The power output of the Sun that reaches the Earth could provide as much as 10,000 times more energy than the combined output of all the commercial power plants on the planet, according to the National Academy of Engineering. The problem is how to harvest that energy.

Today’s commercial solar cells, usually fashioned from silicon, are still relatively expensive to produce (even though prices have come down), and they generally manage to capture only 10 to 20 percent of the sunlight that strikes them. This contributes to the high cost of solar-generated electricity compared to power generated by conventional fossil-fuel-burning plants. By one comparative measure, the U.S. Energy Information Administration estimated the levelized cost of new solar PV as of 2012 was about 56 percent higher than the cost of generation from a conventional coal plant.

Nanotechnology may provide an answer to the efficiency problem, by tinkering with solar power cells at a fundamental level to boost their ability to convert sunlight into power, and by freeing the industry to use less expensive materials. If so, it would fulfill the predictions of some of nanotechnology’s pioneers, like the late Nobel physicist Richard Smalley, who saw potential in nanoscale engineering to address the world’s energy problems. (See related: “Nano’s Big Future“) Scientists caution that there’s still a lot of work ahead to overcome technical challenges and make these inventions ready for prime time. For example, more research is needed on the environmental, health, and safety aspects of nano-materials, said the National Academy of Sciences in a 2012 report that looked broadly at nanotechnology, not at solar applications in particular. (Related Pictures: “Seven Ingredients for Better Car Batteries.”)

But Luke Henley, a University of Illinois at Chicago chemistry professor who received a 2012 National Science Foundation grant to develop a solar-related nanotechnology project, predicts there will be major advances over the next five to 10 years. “It’s potentially a game changer,” he says. Here are five intriguing recent nanotechnology innovations that could help to boost solar power.

Billions of Tiny Holes

To reduce the amount of sunlight that is reflected away from silicon solar cells and wasted, manufacturers usually add one or more layers of antireflective material, which significantly boosts the cost. But late last year, NREL scientists announced a breakthrough in the use of nanotechnology to reduce the amount of light that silicon cells reflect. It involves using a liquid process to put billions of nano-sized holes in each square inch of a solar cell’s surface. Since the holes are smaller than the light wavelengths hitting them, the light is absorbed rather than reflected. The new material, which is called “black silicon,” is nearly 20 percent more efficient than existing silicon cell designs. (Related photos: “Spanish Solar Energy“)

The “Nano Sandwich”

Organic solar cells, made from elements such as carbon, nitrogen, and oxygen that are found in living things, would be cheaper and easier to make than current silicon-based solar cells. The tradeoff, until now, is that they haven’t been as efficient. But a team of Princeton University researchers, led by electrical engineer Stephen Chou, has been able to nearly triple the efficiency of solar cells by devising a nanostructured “sandwich” of metal and plastic. In technical lingo, their invention is called a plasmodic cavity with subwavelength hole array, or PlaSCH. It consists of a thin strip of plastic sandwiched between a top layer made from an incredibly fine metal mesh and a bottom layer of the metal film used in conventional solar cells.

All aspects of the solar cell’s structure—from its thickness to the spacing of the mesh and diameter of the holes—are smaller than the wavelength of the light that it collects. As a result, the device absorbs most of the light in that frequency rather than reflecting it. “It’s like a black hole for light,” Chou explained in a Princeton press release in December. “It traps it.” Another plus: researchers say the PlaSCH cells can be manufactured cost-effectively in sheets, using a process developed by Chou years ago that embosses the nanostructures over a large area, similar to the way newspapers are printed.

Mimicking Evolution

One of the big difficulties in coming up with more energy-efficient solar cells is the limitations of the researchers’ own imaginations. But in a January 2013 article published in Scientific Reports, Northwestern University mechanical engineering professor Wei Chen and graduate student Cheng Sun introduced a method that might be superior to human brainstorming. Using a mathematical search algorithm based on natural biological evolution, they took dozens of design elements and then “mated” them over a series of 20 generations, in a process that mimicked the evolutionary principles of crossover and genetic mutation.

“Our approach is based upon the biologically evolutionary process of survival of the fittest,” Chen explained in an article on Northwestern University’s website.

The result: An evolution-inspired organic solar cell—that is, one that uses carbon-based materials rather than silicon crystals–in which light first enters a 100-nanometer-thick scattering layer with an unorthodox geometric pattern. The researchers say this should enable it to absorb light more efficiently. The U.S. Department of Energy’s Argonne National Laboratory will fabricate an actual working version of the new cell for testing.

Tiny Antennae

We’re used to thinking of solar energy as something that we collect with panels. But even the latest-generation silicon panels can take in light from only a relatively narrow range of frequencies, amounting to about 20 percent of the available energy in the sun’s rays. The panels then require separate equipment to convert the stored energy to useable electricity. But researchers at the University of Connecticut and Penn State  are working on an entirely new approach, using tiny, nanoscale antenna arrays, which would take in a wider range of frequencies and collect about 70 percent of the available energy in sunlight. Additionally, the antenna arrays themselves could convert that energy to direct current, without need for additional gear.

Scientists have been thinking about using tiny antennae for a while, but until recently, they lacked the technology make them work, since such a setup would require electrodes that were just one or two nanometers apart—about 1/30,000 the width of a human hair. Fortunately, University of Connecticut engineering professor Brian Willis has developed a fabrication technique called selective area atomic-layer deposition, which makes it possible to coat the electrodes with layers of individual copper atoms, until they are separated by just 1.5 nanometers. “This new technology could get us over the hump and make solar energy cost-competitive with fossil fuels,” Willis explained in February. “This is brand new technology, a whole new train of thought.”

Solar-Collecting Paint

No matter what sort of solar energy-collecting technology you employ, there’s still the problem of building a bunch of the devices and hooking them up in places with sun exposure. But University of Southern California chemistry professor Richard L. Brutchey and postdoctoral researcher David H. Webber have devised a technology that could turn a building into a solar collector.

They’ve created a stable, electricity-conducting liquid filled with solar-collecting nanocrystals, which can be painted or printed like an ink onto surfaces such as window glass or plastic roof panels. The nanocrystals, made of cadmium selenide instead of silicon, are about four nanometers in size—about 250 billion of them could fit on the head of a pin—so they are capable of floating in a liquid solution.  (Related Pictures: “A New Hub for Solar Tech Blooms in Japan“)

Brutchey’s and Webber’s secret to getting the technology to work? Finding an organic molecule that could attach to the nanocrystals and stabilize them and prevent them from sticking together, without hindering their ability to conduct electricity.

The researchers aim to work on nanocrystals built from materials other than cadmium, a toxic metal. “While the commercialization of this technology is still years away, we see a clear path forward toward integrating this into the next generation of solar cell technologies,” Brutchey says. (Related video: “Toxic Land Generates Solar Power“)

Quantum Dots that Assemble Themselves

A paper on the new technology, “Self-assembled Quantum Dots in a Nanowire System for Quantum Photonics,” appears in the current issue of the scientific journal Nature Materials. Quantum dots are tiny crystals of semiconductor a few billionths of a meter in diameter. At that size they exhibit beneficial behaviors of quantum physics such as forming electron-hole pairs and harvesting excess energy.

The scientists demonstrated how quantum dots can self-assemble at the apex of the gallium arsenide/aluminum gallium arsenide core/shell nanowire interface. Crucially, the quantum dots, besides being highly stable, can be positioned precisely relative to the nanowire’s center. That precision, combined with the materials’ ability to provide quantum confinement for both the electrons and the holes, makes the approach a potential game-changer.

Electrons and holes typically locate in the lowest energy position within the confines of high-energy materials in the nanostructures. But in the new demonstration, the electron and hole, overlapping in a near-ideal way, are confined in the quantum dot itself at high energy rather than located at the lowest energy states. In this case, that’s the gallium-arsenide core. It’s like hitting the bulls-eye rather than the periphery.

The quantum dots, as a result, are very bright, spectrally narrow and highly anti-bunched, displaying excellent optical properties even when they are located just a few nanometers from the surface – a feature that even surprised the scientists. “Some Swiss scientists announced that they had achieved this, but scientists at the conference had a hard time believing it,” said NREL senior scientist Jun-Wei Luo, one of the co-authors of the study. Luo got to work constructing a quantum-dot-in-nanowire system using NREL’s supercomputer and was able to demonstrate that despite the fact that the overall band edges are formed by the gallium Arsenide core, the thin aluminum-rich barriers provide quantum confinement both for the electrons and the holes inside the aluminum-poor quantum dot. That explains the origin of the highly unusual optical transitions.

Several practical applications are possible. The fact that stable quantum dots can be placed very close to the surface of the nanowires raises a huge potential for their use in detecting local electric and magnetic fields. The quantum dots also could be used to charge converters for better light-harvesting, as in the case of photovoltaic cells.

The team of scientists working on the project came from universities and laboratories in Sweden, Switzerland, Spain, and the United States.

More information: http://www.nature.com/nmat/journal/vaop/ncurrent/fig_tab/nmat3557_F4.htmlJournal reference: Nature Materials Provided by National Renewable Energy Laboratory

Read more at: http://phys.org/news/2013-04-team-quantum-dots.html#jCp

Why quantum dots can join every aspect of everyday life

Nanotechnology is often confined to niche products, but quantum dots are so versatile they could be used in everything from light bulbs to laptops.

 

The properties of a material were once thought to be defined only by its chemical composition. But size matters too, especially for semiconductors. Make crystals of silicon small enough – less than 10 nanometres – and their tiny dimensions can start to dictate how the atoms behave and react in the presence of other things.

These tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable, novel properties that scientists think they will soon be used in everything from light bulbs to imaging of cancer cells or in the design of ultra-efficient solar cells.

Semiconductors such as silicon or indium arsenide are chosen to build electronic circuits because of the discrete energy levels at which they can give off electrons or photons. This makes them useful in building switches, transistors and other devices. It was once thought these energy levels – known as band gaps – were fixed. But shrinking the physical size of the semiconductor material to quantum-dot level seems able to change the band gaps, altering the wavelengths of light the material can emit or changing the energy it takes to change a material from an insulator to a conductor.

Instead of looking for brand new materials to build different devices, then, quantum dots make it possible to use a single type of semiconductor to produce a range of different characteristics. Researchers could tune dots made from silicon to emit a range of different colours in different situations, for example, instead of having to use a range of materials with different chemical compositions.

Tiny bits of semiconductor crystals – so-called quantum dots – have such remarkable properties that scientists think they will soon be used in everything from light bulbs to the design of ultra-efficient solar cells. Photograph: Science Photo Library

“The main application for quantum dots at the moment is biological tagging of cells,” says Paul O’Brien, a professor of inorganic materials at the University of Manchester and co-founder of Nanoco Technologies a quantum dot manufacturer also based in Manchester. They are used in the same way as fluorescent dyes, to label agents, he says, but with the advantage that a single laser source can be used to illuminate many different tags each with a specific wavelength.

By attaching different types of quantum dots to proteins that target and attach to specific cell types in the body, these bits of semiconductor can be used by doctors to monitor different kinds of cells. When a laser is then directed on to tagged cells, doctors can see what colour they glow.

The ability to shine also makes quantum dots well suited to produce white light. Existing white bulbs based on low energy light emitting diode (LED) technology tend to produce a garish and bluish form of light that notoriously feels cold, says O’Brien. This is because these LEDs use a phosphor that produces an artificial white light that contains less red wavelengths than natural white light. By embedding quantum dots into a film that is placed over a bulb containing blue LEDs, it is possible to get a much warmer colour of white light. The blue light  from the LED stimulates the quantum dots which, in turn, emit light in a range of colours. Provided you have chosen your dots carefully, these will combine to form white light.

The first of these quantum dot lights hit the market in 2010, a partnership between QD Vision, an MIT spinout in Lexington, Massachusetts, and Nexxus Lighting of Charlotte, North Carolina.

Backlights for laptops, tablets and mobile devices are next in line, and they should appear in products before the end of 2012 says VJ Sahi, head of corporate development at materials design company Nanosys of Palo Alto, California. Besides the colour advantages, quantum-dot-based backlights can be three times more efficient than traditional backlights.

Eventually, says Sahi, quantum dots will do more than just light up displays. The long-term aim is use them to create each red, green and blue sub-pixel that makes up a coloured display. This should produce much brighter colours and consume less power than LCD or even the latest state-of-the-art organic LED (OLED) displays. They should also have no problems with viewing angles, he adds.

The interesting properties of quantum dots come from the fact that they behave like tuning forks for photons, a result of a phenomenon called confinement. At less than 10 nanometres in size – about 50 atoms – they fall within the dimensions of a critical quantum characteristic of the material known as the exciton Bohr radius. The energy levels of electrons within the material’s atoms are constrained and, when a photon or electron hits an atom and excites it, the atom re-emits the energy as a photon of a very specific energy level.

Quantum dots also have another trick up their sleeve. Besides converting photons of one energy into photons of another, they can also be used to release electrons and create electrical currents: in other words they can be used to make solar cells. Arthur Nozik at the National Renewable Energy Laboratory in Boulder, Colorado, says that quantum-dot solar cells would be much more efficient at converting the energy from photons and therefore boost the amount of power they can produce.

Such applications are many years from becoming commercial reality. But they serve to demonstrate that no material technology stands still; sometimes all you have to do is cut it down to size.

 For More on How “Nanotechnology” and “Quantum Dots” Will Impact the Future, Go To:

10 Ways Nano-Manufacturing Will Alter Industry

https://genesisnanotech.wordpress.com/2013/03/30/10-ways-nanomanufacturing-will-alter-industry/

10 Ways Nanomanufacturing Will Alter Industry

By Robert Lamb

Do you remember your childhood building blocks? You probably started out with large, wooden cubes and turned to increasingly smaller blocks as you grew older and the structures you created became more complex. That miniature version of the space shuttle wouldn’t have been nearly as accurate (or cool) with big bricks, right?

The building blocks get even smaller in the real world — so much so that even an optical microscope won’t reveal them. They exist at the nanoscale of things, where a single-walled carbon nanotube is scarcely 1 nanometer thick. To put that in relatable terms, you’d have to line up 100,000 of these nanotubes side by side in order to equal the 100-micrometer diameter of a single strand of hair .

     

Nanomaterials occur naturally all around us, but it wasn’t until the 1930s that scientists developed the tools to see and manipulate such minuscule building blocks as individual molecules and atoms. By directing matter at the nanoscale, scientists achieve greater control over a material’s properties, ranging from its strength and melting point to its fluorescence and electrical conductivity. We call this field nanotechnology, and it involves such diverse disciplines as chemistry, biology and physics.

Currently, more than 800 commercial products rely on nanomaterials, according to the U.S. National Nanotechnology Initiative. To capitalize on nanotechnology, however, we need to mass-produce at the nanoscale. So we enter the world of nanomanufacturing. Here are 10 ways it will change the landscape of industry forever.

10. Rise of the Super Drugs

Nanotechnology allows us to mess with matter molecularly, which is great news for the pharmaceutical industry. After all, every profitable brand-name medication ultimately breaks down to a particular, and often synthetic, molecular structure. This structure interacts with molecules in the human body, and that’s where the profitable magic happens.

Just consider the botulinum toxin in Botox treatments. The bacteria’s muscle-weakening abilities aid in the treatment of muscle pain, in addition to smoothing wrinkles. Doctors typically inject Botox into the target tissue since it can’t pass through the skin. Researchers at the University of Massachusetts Lowell Nanomanufacturing Center, however, aim to create a topical Botox cream. Their secret? Simply attach the toxin to a nanoparticle, allowing it to hitch a ride through the skin.

 

Meanwhile, other drugs suffer from poor solubility, resulting in inadequate or delayed absorption into the human body and, consequently, a need for greater dosage levels. Yet if we reduce the size of the drug particles to the nanoscale, then absorption rates increase and dosage levels decrease.

Finally, nanotechnology enables scientists to knit together tiny drug fragments into single “super-molecules” — such as the proposed morphine-cannabis painkiller. Envisioned by the University of Kentucky College of Medicine, this pharmaceutical tag team would consist of a morphine molecule and a THC molecule (THC being the intoxicating part of marijuana) joined by a single linking particle. Once in the body, the linking bit would break free, releasing the morphine and THC in equal, targeted doses.

Mass production at the nanoscale will enable pharmaceutical companies to create increasingly effective medication.

9. Drug Delivery Goes Nano

Nanomanufacturing will change far more than the medications we take; it also will alter the nature of drug delivery. Researchers at Northwestern University are developing drug devices made from nano-diamonds, which prevent medicine from releasing too swiftly into the body. With this technology, doctors will be able to implant months’ worth of medication directly into the affected tissue area.

But nano-manufacturing will provide far more than mere convenience — it will save lives. Just consider today’s anticancer drugs. Chemotherapy treatments often damage healthy cells as well as cancerous ones, leading to the full array of side effects typically associated with cancer treatments. By studying the inner workings of cell-seeking viruses, scientists hope to engineer nanostructures capable of delivering medication directly to targeted tissue.

Both of these nanoscale biomedical technologies enable smarter and minimally invasive treatment. Just imagine a day when chemotherapy doesn’t wipe out the entire body and when implanted nanostructures administer your daily medication for you.

8. Fresh-grown Organs All Around

Modern organ transplant technology continues to save lives, but emerging biomedical nanotechnology aims to streamline the process. In some cases, it even eliminates the need for an organ donor. Why worry about harvesting a new heart from a fresh cadaver when we can grow a new one instead?

By using a patient’s own stem cells, researchers have successfully grown human bladders and even hearts. In 2011, doctors made history by transplanting a bio-artificial trachea into a cancer patient . The key is to have accurate, organ-shaped scaffolding for the cells to grow on — such as a collagen “ghost heart” (a donor heart stripped of its cells) or a glass replica of the patient’s trachea.

Nanotechnology introduces even more exciting possibilities here, such as the use of nano-engineered gel to help nerve cells re-grow around spinal injuries. As for growing new organs wholesale, the future is also bright. Researchers at Rice University and the MD Anderson Cancer Center in Houston, Texas, have developed an organ sculpting technique that employs metal nanoparticles suspended in a magnetic field. This 3-D environment encourages the suspended cells to grow more naturally and may enable the development of complex, 3-D systems such as the heart or lung.

In the future, researchers hope to program detailed magnetic fields tailored to specific organs. So imagine a future where human organs aren’t merely harvested but custom-manufactured to fit the patient.

7. The World’s Smallest Laboratory

State-of-the-art medical diagnostic technology helps physicians save countless lives. There’s one catch: Much of this equipment requires a modern laboratory and a highly trained staff to operate it. Take this sort of diagnostic tool out of an air-conditioned, sterile and electrically stable environment and transport it to a distant outpost in the developing world, and guess what happens?

 

That’s right: The technology fails to function. Luckily, nanotechnology comes to the rescue with so-called lab-on-a-chip (LOC) technology. Such nanodevices would boast high-tech laboratory functions on a single, tiny chip capable of processing extremely small fluid volumes. Through lasers and electrical fields, scientists hope to manipulate these fluids and tiny particles of bacteria, viruses and DNA for analysis. The possible applications range from swift blood analysis during the initial outbreak of an epidemic to improved food safety screenings.

It all comes down to nano-manufacturing, however, as such technology would only provide a significant advantage if cheap and plentiful. A single application of a disease vaccine, after all, won’t fight off an epidemic. You need doses for multiple patients in several locations. Likewise, an LOC-enabled health scanner would only make a difference if it were standard issue in the field.

6. Honey, the Walls Are Bleeding Again

Even the most devoted horror movie fan would probably shy away from a house that oozes blood whenever you scratch the wall or suffer a mild earthquake. Yet this is exactly the sort of reality nanotechnology can bring into the world. And if nano-manufacturing makes the fruits of this technology available globally, then you may very well spend your retirement years in a bleeding house of your own.

In this case, however, bleeding walls are a good thing. Just as blood from a cut clots into a sealing scab, proposed nano-polymer particles in a house’s walls will liquefy when squeezed by an earthquake or structural collapse. This liquid will then flow into any cracks and transform back to a solid state.

The University of Leeds’ Nano-Manufacturing Institute plans to build a prototype on a Greek mountainside — with an estimated price tag of $15 million . The technology is too costly and too “bleeding-edge” (get it?) to make an impact on the construction industry just yet, but nano-manufacturing techniques could allow buildings around the world to benefit from this amazing self-healing technology.

5. Super-strong Materials

When it comes to nanotechnology, there’s no denying the abundant applications for carbon nanotubes, or carbon sealed up into cylindrical tubes. Materials forged from these tubes are both lightweight and incredibly strong, since the carbon atoms in each tube are so tightly bonded.

The applications are endless. Virtually any synthetic structure could be made lighter and more durable. In addition to improving existing structures, carbon nanotubes could make impossible structures a reality. Just consider the premise of a space elevator: a direct, physical connection between the surface of the Earth and a satellite tethered in geosynchronous orbit. Such a structure would enable humans to transport large payloads into space without explosive rocketry and costly heavy-lift vehicles.

Operating space elevators would be a game changer for not only the space exploration industry but also the energy industry. Imagine an orbital solar collector that wires energy right back down to the planet’s surface. Although the necessary carbon nanotube technology is already within grasp, the ability to cheaply mass-produce the material would move such a massive project even closer to reality .

4. Will Nano-bots Clean Up the Mess?

Nanomanufacturing will revolutionize the oil industry, enabling stronger pipelines and more effective pollution detectors as well. Plus, in the event of an oil spill or leak, tiny nanobots might just come to the rescue, “feeding” on oil as part of the cleanup effort.

Researchers at the Massachusetts Institute of Technology are currently working on a pack of autonomous, solar-powered robots called the Seaswarm. While this 16-foot (5-meter) long technology is hardly nano in scale, it does implement nanotechnology. Each Seaswarm, which already exists in prototype form, will use a conveyor belt lined with oil-absorbing nanowire fabric. The unique, hydrophobic, meshed structure of the fabric grabs the oil molecules but not the water molecules. These properties allow the fabric to absorb a reported 20 times its weight in oil, which can then be released when the fabric is heated .

How much difference will the mass-production of such nanotechnology make in the event of an oil spill? A swarm of oil-absorbing robots potentially could clean up a disaster involving millions of barrels worth of fossil fuels within a single month .

3. Tiny Oil Hunters

Speaking of oil, if you want to send a robot into an oil reservoir, you’re going to have to think small — nanorobotics small. After all, fossil fuel deposits don’t occur in large, spacious underground caverns but in the pores of solid rock. The oil travels through tiny pore throats that are tinier than the average germ . So, if you want to build a robot petite enough to explore an oil reservoir, you’ll need to design it at the nanoscale.

Scientists and oil companies envision a day when trillions of minuscule, water-soluble carbon clusters can be injected deep underground and then pulled back to the surface. Geologists would then be able to note changes in the chemical makeup of the carbon clusters to decipher such details as temperature and pressure in the oil reserve. Other, more advanced plans even call for nano-robots capable of transmitting their findings back to the surface.

2. Nano-empowered Batteries and Solar Panels

Whether facing the battery death of a beloved smartphone or the limitations of solar technology, nano-manufacturing will eventually solve your problem. Not only will nanotechnology enable the production of longer-lasting batteries and more efficient solar sails, it will also do it cheaply.

The limitations of both batteries and solar panels tend to boil down to the materials used in the electrode portion of a battery. This material is the conductor through which an electric current enters or leaves a solution in a battery. Typical electrode materials can only transmit a limited electrical charge. Nanotechnology, however, gives scientists the ability to enlarge the surface area of the electrode material at the nanoscale without increasing the material size. The trick is to boost the complexity of the material at the nanoscale.

 

For example, imagine two blocks of cheese of equal size: one solid cheddar and the other Swiss cheese riddled with pores and holes. Due to the interior walls of the holes, the Swiss cheese benefits from greater surface area than the solid cheddar.

Scientists have drawn inspiration for such technology from marine sponges, which assemble their complex, crystalline structures at the molecular level. And it’s that sort of assembly that factors into the last item on our list.

1. Some Self-assembly Required

All of these nano-manufacturing and nanotechnology advancements will undoubtedly change the face of industry forever, but the biggest game changer of them all will come in the form of self-assembly. The smaller the building blocks become, the closer we get to the molecular-scale building techniques of nature itself.

Earlier applications of nanotechnology implemented a top-down approach, in which scientists use instruments such as the atomic force microscope to manipulate matter at the nanoscale. The bottom-up approach, however, actually builds at the molecular level. The difference between the two approaches is not unlike that between Victor Frankenstein’s stitching together body parts to make a new human and nature simply growing one up from genetic material.

In the future, nano-manufacturing will take place entirely at a scale invisible to the naked eye, as nano-bots construct everything from delicate fabrics and super-strong steel to computing components.

 

The future of industry all comes down to the size and complexity of the building blocks.

 

New Energy Technologies, Inc. and NREL Launch 2nd Phase of SolarWindow Project

On March 6th, 2013, New Energy Technologies Inc. (Columbia, Maryland, US) announced that it has entered into the second phase of its cooperative research and development agreement (CRADA) with the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) to advance the development of its SolarWindow technology, capable of generating electricity on glass.

For more information on the Company’s technologies go here:

http://www.newenergytechnologiesinc.com/

Under the terms of the agreement, New Energy and NREL will work to advance SolarWindow technology by enhancing performance, processing, and lifetime. Additionally, researchers will work towards optimizing the deposition of various coatings on flexible surfaces; these layers allow for solar power to be generated on surfaces such as see-through and tinted plastics.

 Researchers will work towards layers which allow for solar power to be generated on surfaces such as see-through and tinted plastics

On track to commercially valuable building integrated photovoltaic products

“This second phase of the CRADA emphasizes the company’s active commitment to develop the SolarWindow see-through electricity-generating coatings into commercially valuable building integrated PV products, with the assistance of world-class research teams at NREL,” stated J. Patrick Thompson, vice president, business and technology development for New Energy Technologies.

New Energy Principal Scientist Dr. Scott Hammond and NREL research scientists will make use of intellectual property brought into and developed under the CRADA in order to work towards specific product development goals.

See-through glass generating electricity

“Company and NREL scientists jointly developed this CRADA to maintain focus on SolarWindow power production, large area and high speed coating equipment and methods, improving reliability and performance, and commercialization,” New Energy Technologies President and Chief Executive Officer (CEO) John A. Conklin stated.

Conklin added: “As we work towards commercialization, the market potential of deploying a readily-available and affordable see-through glass window capable of generating electricity continues to aggressively drive our product development efforts.”

Currently under development for eventual commercial deployment in commercial buildings and homes in America, SolarWindow technology is the subject of 12 patent filings and is the world’s first-of-its-kind see-through technology capable of generating electricity on glass windows.

 

High-Efficiency Quantum Dot Solar Cells Developed

Oct. 26, 2012 — Research shows newly developed solar powered cells may soon outperform conventional photovoltaic technology. Scientists from the National Renewable Energy Laboratory (NREL) have demonstrated the first solar cell with external quantum efficiency (EQE) exceeding 100 percent for photons with energies in the solar range. (The EQE is the percentage of photons that get converted into electrons within the device.)

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The researchers will present their findings at the AVS 59th International Symposium and Exhibition, held Oct. 28 — Nov. 2, in Tampa, Fla.

While traditional semiconductors only produce one electron from each photon, nanometer-sized crystalline materials such as quantum dots avoid this restriction and are being developed as promising photovoltaic materials. An increase in the efficiency comes from quantum dots harvesting energy that would otherwise be lost as heat in conventional semiconductors. The amount of heat loss is reduced and the resulting energy is funneled into creating more electrical current.

By harnessing the power of a process called multiple exciton generation (MEG), the researchers were able to show that on average, each blue photon absorbed can generate up to 30 percent more current than conventional technology allows. MEG works by efficiently splitting and using a greater portion of the energy in the higher-energy photons. The researchers demonstrated an EQE value of 114 percent for 3.5 eV photons, proving the feasibility of this concept in a working device.

Joseph Luther, a senior scientist at NREL, believes MEG technology is the right direction. “Since current solar cell technology is still too expensive to completely compete with non-renewable energy sources, this technology employing MEG demonstrates that the way in which scientists and engineers think about converting solar photons to electricity is constantly changing,” Luther said. “There may be a chance to dramatically increase the efficiency of a module, which could result in solar panels that are much cheaper than non-renewable energy sources.”