America’s National Laboratories – 75 Breakthroughs We’ve Made that You May Not have Read About

America’s National Laboratories have been changing and improving the lives of millions of people for more than 75 years. Born at a time when the world faced a dire threat, the laboratories came together to advance science, safeguard the nation and protect our freedoms for generations to come. This network of Department of Energy Laboratories has grown into 17 facilities, working together as engines of prosperity and invention. As this list of breakthroughs attests, Laboratory discoveries have spawned industries, saved lives, generated new products, fired the imagination and helped to reveal the secrets of the universe. Rooted in the need to serve the public good and support the global community, the National Laboratories have put an American stamp on the last century of science. With equal ingenuity and tenacity, they are now engaged in innovating the future.

Download and read 75 Breakthroughs by America’s National Laboratories.

75 Breakthroughs

At America’s National Laboratories, we’ve …

Advanced supercomputing

The National Labs operate some of the most significant high performance computing resources available, including 32 of the 500 fastest supercomputers in the world. These systems, working at quadrillions of operations per second, model and simulate complex, dynamic systems – such as the nuclear deterrent – that would be too expensive, impractical or impossible to physically demonstrate. Supercomputers are changing the way scientists explore the evolution of our universe, climate change, biological systems, weather forecasting and even renewable energy.

Decoded DNA 

In 1990, the National Labs joined with the National Institutes of Health and other laboratories to kick off the Human Genome Project, an international collaboration to identify and map all of the genes of the human genome.

Brought the web to the United States 

National Lab scientists, seeking to share particle physics information, were first to install a web server in North America, kick-starting the development of the worldwide web as we know it.

Put eyes in the sky 

Vela satellites, first launched in 1963 to detect potential nuclear detonations, transformed the nascent U.S. space program. The satellites featured optical sensors and data processing, logic and power subsystems designed and created by National Labs.

Revolutionized medical diagnostics and treatment 

Researchers at the National Labs helped to develop the field of nuclear medicine, producing radioisotopes to diagnose and treat disease, designing imaging technology to detect cancer and developing software to target tumors while sparing healthy tissue.

Powered NASA spacecraft 

The National Labs built the enclosure for the radioisotope thermoelectric generators that fuel crafts such as Cassini and have begun producing plutonium-238 for future NASA missions.

Harnessed the power of the atom 

National Lab scientists and engineers have led the world in developing safe, efficient and emissions-free nuclear power. Starting with the first nuclear reactor to generate electricity, National Labs have been the innovation engine behind the peaceful use of nuclear energy. Today’s labs are supporting the next generation of nuclear power that will be available for the nation and world.

Brought safe water to millions 

Removing arsenic from drinking water is a global priority. A long-lasting particle engineered at a National Lab can now do exactly that, making contaminated water safe to drink. Another technology developed at a National Lab uses ultraviolet light to kill water-borne bacteria that cause dysentery, thus reducing child mortality in the developing world.

Filled the Protein Data Bank 

National Lab X-ray facilities have contributed a large portion of more than 100,000 protein structures in the Protein Data Bank. A protein’s structure reveals how it functions, helping scientists understand how living things work and develop treatments for disease. Almost all new medications that hit the market start with these data bank structures.

Invented new materials 

National Labs provide the theory, tools and techniques that offer industry revolutionary materials such as strong, lighter-weight metals and alloys that save fuel and maintenance costs and enable cleaner, more efficient engines.

Found life’s mystery messenger 

National Lab scientists discovered how genetic instructions are carried to the cell’s protein manufacturing center, where all of life’s processes begin. Subsequent light source research on the genetic courier, called messenger RNA, has revealed how the information is transcribed and how mistakes can cause cancer and birth defects.

Mapped the universe — and the dark side of the moon

Credit for producing 3D maps of the sky — and 400 million celestial objects — goes to National Lab scientists, who also developed a camera that mapped the entire surface of the moon.

Shed light on photosynthesis 

Ever wonder how plants turn sunlight into energy? National Lab scientists determined the path of carbon through photosynthesis, and today use X-ray laser technology to reveal how each step in the process is triggered by a single particle of light. This work helps scientists explore new ways to get sustainable energy from the sun.

Solved cultural mysteries 

The works of ancient mathematician Archimedes — written over by medieval monks and lost for millennia — were revealed to modern eyes thanks to the X-ray vision and light-source technology at National Labs. These studies also have revealed secrets of masterpiece paintings, ancient Greek vases and other priceless cultural artifacts.

Revolutionized accelerators 

A National Lab built and operated the first large-scale accelerator based on superconducting radio frequency technology. This more efficient technology now powers research machines for exploring the heart of matter, examining the properties of materials and providing unique information about the building blocks of life.

Revealed the secrets of matter 

Protons and neutrons were once thought to be indivisible. National Lab scientists discovered that protons and neutrons were made of even smaller parts, called quarks. Over time, experimenters identified six kinds of quarks, three types of neutrinos and the Higgs particle, changing our view of how the material world works.

Confirmed the Big Bang and discovered dark energy

National Lab detectors aboard a NASA satellite revealed the birth of galaxies in the echoes of the Big Bang. Dark energy — the mysterious something that makes up three-quarters of the universe and causes it to expand at an accelerating rate — also was discovered by National Lab cosmologists.

Discovered 22 elements 

The periodic table would be smaller without the National Labs. To date the National Labs have discovered: technetium, promethium, astatine, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, lawrencium, rutherfordium, dubnium, seaborgium, flerovium, moscovium, livermorium, tennessine and oganesson.

Made refrigerators cool 

Next-generation refrigerators will likely put the freeze on harmful chemical coolants in favor of an environmentally friendly alloy, thanks to National Lab scientists.

Got the lead out 

Removing hazardous lead-based solders from the environment is a reality thanks to a lead-free alloy of tin-silver-copper developed at a National Lab. The lead-free solder has been licensed by more than 60 companies worldwide.

Invented a magic sponge to clean up oil spills

National Lab scientists used a nano technique to invent a new sponge that can absorb 90 times its own weight in oil from water. It can be wrung out to collect the oil and reused hundreds of times — and it can collect oil that has sunk below the surface, something previous technology couldn’t do.

Added the punch to additive manufacturing 

High-pressure gas atomization processing pioneered at a National Lab made possible the production of titanium and other metal-alloy powders used in additive manufacturing and powder metallurgy.

 

Created inexpensive catalysts 

Low-cost catalysts are key to efficient biomass refining. National Lab scientists created catalysts that are inexpensive and stable for biomass conversion. 

Created high-tech coatings to reduce friction 

National Lab scientists created ways to reduce wear and tear in machines from table fans to car engines all the way up to giant wind turbines, such as a diamond-like film that rebuilds itself as soon as it begins to break down — so that engines last longer and need fewer oil additives.

Put the jolt in the Volt 

Chevy’s Volt would not be able to cruise on battery power were it not for the advanced cathode technology that emerged from a National Lab. The same technology is sparking a revival of America’s battery manufacturing industry.

Cemented a new material 

National Lab scientists have developed a novel and versatile material that blends properties of ceramic and concrete to form a non-porous product that can do everything from seal oil w ells to insulate walls with extra fire protection. It even sets in cold weather.

Pioneered efficient power lines 

New kinds of power lines made from superconductors can carry electric current with no energy loss. Now deployed by National Lab scientists, these prototypes could usher in a new era of ultra-efficient power transmission.

Made early universe quark soup 

National Lab scientists used a particle collider to recreate the primordial soup of subatomic building blocks that last existed shortly after the Big Bang. The research is expanding scientists’ understanding of matter at extreme temperatures and densities.

Levitated trains with magnets 

Say goodbye to traffic jams. National Lab scientists developed a technology that uses the attractive and repulsive forces of magnets to levitate and propel trains. Maglev trains now ferry commuters in Japan and China and will be operational in other countries soon.

Developed efficient burners 

National Lab researchers developed cleaner-combusting oil burners, saving consumers more than $25 billion in fuel costs and keeping more than 160 megatons of carbon dioxide out of Earth’s atmosphere.

Improved automotive steel

A company with National Lab roots is pioneering a metal that weighs significantly less than regular steel, retains steel’s strength and malleability and can be fabricated without major modifications to the automotive manufacturing infrastructure.

Looked inside weapons

National Lab researchers created a device that could identify the contents of suspicious chemical and explosive munitions and containers, while minimizing risk to the people involved. The technology, which quickly identifies the chemical makeup of weapons, has been used to verify treaties around the world.

Pioneered nuclear safety modeling 

National Lab scientists began developing the Reactor Excursion and Leak Analysis Program (RELAP) to model nuclear reactor coolant and core behavior. Today, RELAP is used throughout the world and has been licensed for both nuclear and non-nuclear applications, including modeling of jet aircraft engines and fossil-fuel power plant components.

Identified good and bad cholesterol 

The battle against heart disease received a boost in the 1960s when National Lab research unveiled the good and bad sides of cholesterol. Today, diagnostic tests that detect both types of cholesterol save lives.

Unmasked a dinosaur killer 

Natural history’s greatest whodunit was solved in 1980 when a team of National Lab scientists pinned the dinosaurs’ abrupt extinction on an asteroid collision with Earth. Case closed.

Pitted cool roofs against carbon dioxide 

National Lab researchers and policy experts led the way in analyzing and implementing cool roofing materials, which reflect sunlight, lower surface temperature and slash cooling costs.

Squeezed fuel from microbes 

In a milestone that brings advanced biofuels one step closer to America’s gas tanks, National Lab scientists helped develop a microbe that can produce fuel directly from biomass.

Tamed hydrogen with nanoparticles 

To replace gasoline, hydrogen must be safely stored and easy to use, which has proven elusive. National Lab researchers have now designed a new pliable material using nanoparticles that can rapidly absorb and release hydrogen without ill effects, a major step in making fuel-cell powered cars a commercial reality.

Exposed the risk 

You can sleep easier thanks to National Lab research that quantified the health risk posed by radon gas in parts of the country. Subsequent EPA standards, coupled with radon detection and mitigation measures pioneered by a National Lab research team, prevent the naturally occurring gas from seeping into basements, saving thousands of lives every year.

Created a pocket-sized DNA sampler 

A tool that identifies the microbes in air, water and soil samples is fast becoming a workhorse in public health, medical and environmental cleanup projects. Developed by National Lab scientists, the credit-card-sized device pinpoints diseases that kill coral reefs and catalogs airborne bacteria over U.S. cities. It also was used to quickly categorize the oil-eating bacteria in the plumes of the Deepwater Horizon spill.

Fabricated the smallest machines

The world’s smallest synthetic motors — as well as radios, scales and switches that are 100,000 times finer than a human hair — were engineered at a National Lab. These and other forays into nanotechnology could lead to life-saving pharmaceuticals and more powerful computers.

Preserved the sounds of yesteryear 

National Lab scientists engineered a high-tech way to digitally reconstruct aging

sound recordings that are too fragile to play, such as Edison wax cylinders from the late 1800s. Archivists estimate that many of the millions of recordings in the world’s sound archives, including the U.S. Library of Congress, could benefit from the technology.

Exposed explosives 

A credit-card sized detector developed by National Lab scientists can screen for more than 30 kinds of explosives in just minutes. The detector, called ELITE, requires no po wer and is widely used by the military, law enforcement and security personnel.

Toughened airplanes 

A National Lab and industry technique for strengthening metal by bombarding it with laser pulses has saved the aircraft industry hundreds of millions of dollars in engine and aircraft maintenance expenses.

Simulated reality 

Trains, planes and automobiles — and thousands of other objects — are safer, stronger and better-designed thanks to computer simulation software, DYNA 3D, developed by National Lab researchers.

Detected the neutrino 

Starting with the Nobel-Prize winning discovery of the neutrino in 1956 by Fred Reines and Clyde Cowan Jr., National Lab researchers have made numerous contributions to neutrino physics and astrophysics.

Discovered gamma ray bursts

Sensors developed at the National Labs and placed aboard Vela satellites were used in the discovery of gamma-ray bursts (GRBs) in 1973. GRBs are extremely energetic explosions from distant galaxies. Scientists believe that most of these bursts consist of a narrow beam of intense radiation released when a rapidly rotating, high-mass star collapses to form a neutron star, a quark star or a black hole.

Created the first 100-Tesla magnetic field 

National Lab scientists achieved a 100.75-Tesla magnetic pulse in March 2012, setting a world record. The pulse was nearly 2 million times more powerful than Earth’s magnetic field. The 100-Tesla multi-shot magnet can be used over and over again without being destroyed by the force of the field it creates, and produces the most powerful non-destructive magnetic field in the world.

Froze smoke for hot uses 

National Labs researchers perfected aerogels, known as frozen smoke. They are one of the lightest solids ever made and have the highest heat resistance of any material tested. They also are fireproof and extraordinarily strong — able to support more than a thousand times their own weight. As a result of their heat resistance, aerogels are outstanding candidates for insulation in buildings, vehicles, filters and appliances.

Invented the cell sorter 

During the 1960s, a National Lab physicist invented a “cell sorter” — a novel device that works much like an ink jet printer, guiding a tiny flow of cell-containing droplets so cells of interest can be deflected for counting and study. Cell sorters are a vital tool for studying the biochemistry behind many diseases, including cancer and AIDS.

Ushered a domestic energy renaissance 

National Lab research jump-started the shale gas revolution by pointing the way to key technologies and methodologies for cost efficient extraction. An estimated $220 million in research and development expenditures on unconventional gas R&D from 1976 to 1992 have resulted in an estimated $100 billion in annual economic activity from shale gas production alone.

Enabled space exploration 

National Labs invented Laser-Induced Breakdown Spectroscopy (LIBS), the backbone of the device that allowed the Curiosity Rover to analyze material from Mars. Lab researchers also found the right combination of materials to make high-efficiency solar cells for spacecraft.

Sharply curtailed power plant air emissions 

National Lab scientists introduced some 20 innovative technologies — such as low nitrogen oxide (NOx) burners, flue gas desulfurization (scrubbers) and fluidized bed combustion — through the Clean Coal Technology Development Program that have deeply penetrated the marketplace, substantially controlled harmful power plant emissions and benefited energy production and air quality.

Made wind power mainstream 

Increasing wind turbine efficiency with high efficiency airfoils has reduced the cost of wind power by more than 80 percent over the last 30 years. Now deployed in wind farms nationwide, these turbines owe their existence to National Lab research.

Engineered smart windows 

National Lab scientists have created highly insulated windows that change color to modulate interior temperatures and lighting. If broadly installed, they could save about 5 percent of the nation’s total energy budget.

Delivered troops safely 

National Lab researchers have developed computer models that effectively manage the complex logistical tasks of deploying troops and equipment to distant destinations.

Channeled chips and hips 

Integrated circuits and artificial hips owe their success to a National Lab discovery that revealed how to change a material by injecting it with charged atoms, called ions. Ion channeling is now standard practice in industry and science.

Made 3D printing bigger and better 

A large-scale additive manufacturing platform developed by a National Lab and an industry partner printed 3D components 10 times larger and 200 times faster than previous processes. So far, the system has produced a 3D-printed sports car, SUV, house, excavator and aviation components.

Purified vaccines

National Lab researchers adapted nuclear separations technology to develop a zonal centrifuge used to purify vaccines, which reduces or eliminates unwanted side effects. Commercial centrifuges based on the invention produce vaccines for millions of people.

Built a better building 

A National Lab has built one of the world’s most energy efficient office buildings. The facility, operating as a living laboratory at a lab site, uses 50 percent less energy than required by commercial codes and only consumes energy produced by renewable power on or near the building.

Improved airport security 

Weapons, explosives, plastic devices and other concealed tools of terrorists are easier to detect thanks to technology developed at a National Lab and now installed in airports worldwide.

Improved grid resiliency 

A National Lab created an advanced battery that can store large amounts of energy from intermittent renewable sources — such as wind and solar — onto the power grid, while also smoothing over temporary disruptions to the grid. Several companies have licensed the technology and offer it as a commercial product.

Solved a diesel dilemma 

A National Lab insight into how catalysts behave paved the way for a new, “lean-burn” diesel engine that met emissions standards and improved fuel efficiency by 25 percent over conventional engines.

Harvested energy from air 

A miniature device — commercialized by private industry after a National Lab breakthrough — generates enough power from small temperature changes to power wireless sensors or radio frequency transmitters at remote sites, such as dams, bridges and pipelines.

Gone grid friendly 

Regulating the energy use of household appliances — especially at peak times — could slash energy demand and avoid blackouts. A National Lab appliance-control device senses grid stress and responds instantly to turn off machines and reduce end-use demand, balancing the system so that the power stays on.

Put the digital in DVDs 

The optical digital recording technology behind music, video and data storage originated at a National Lab nearly 40 years ago.

Locked nuclear waste in glass 

Disposal of U.S. Cold War waste is safer thanks to National Lab scientists who developed and deployed a process to lock it into glass to keep it from leaching into the environment.

Cleaned up anthrax 

Scientists at a National Lab developed a non-toxic foam that neutralizes chemical and biological agents. This foam was used to clean up congressional office buildings and mail rooms exposed to anthrax in 2001.

Removed radiation from Fukushima seawater 

After a tsunami damaged the Fukushima Daiichi nuclear power plant in 2011, massive amounts of seawater cooled the reactor. A molecular sieve engineered by National Lab scientists was used to extract radioactive cesium from tens of millions of gallons of seawater.11

Sped up Ebola detection 

In 2014, researchers from a National Lab modeled the Liberian blood sample transport system and made recommendations to diagnose patients quicker. This minimized the amount of time people were waiting together, reducing the spread of Ebola.

Prevented unauthorized use of a nuclear weapon 

In 1960, National Lab scientists invented coded electromechanical locks for all U.S. nuclear weapons. The switch blocks the arming signal until it receives the proper presidential authorization code.

Launched the LED lighting revolution 

In the 1990s, scientists at a National Lab saw the need for energy-efficient solid-state lighting and worked with industry to develop white LEDs. Today, white LEDs are about 30 percent efficient, with the potential to reach 70 percent to 80 percent efficiency. Fluorescent lighting is about 20 percent efficient and incandescent bulbs are 5 percent.

Mastered the art of artificial photosynthesis 

National Lab scientists engineered and synthesized multi-layer semiconductor structures in devices that directly convert sunlight to chemical energy in hydrogen by splitting water at efficiencies greater than 15 percent. This direct conversion of sunlight to fuels paves the way for use of solar energy in applications beyond the electrical grid.

Advanced fusion technology

From the first fusion test reactor to briefly produce power at the megawatt scale, and the world’s largest and most energetic laser creating extreme conditions mimicking the Big Bang, the interiors of planets and stars and thermonuclear weapons, to the international experiment to generate industrial levels of fusion energy from burning plasmas, fusion science and applications are advancing because of the National Labs.

Made the first molecular movie 

National Lab scientists have used ultrafast X-rays to capture the first molecular movies in quadrillionths-of-a-second frames. These movies detail the intricate structural dances of molecules as they undergo chemical reactions.

The National Laboratory System: Protecting America Through Science and Technology

For more than 75 years, the Department of Energy’s National Laboratories have solved important problems in science, energy and national security. This expertise keeps our nation at the forefront of science and technology in a rapidly changing world. Partnering with industry and academia, the laboratories also drive innovation to advance economic competitiveness and     ensure our nation’s future prosperity.

Oak Ridge National Laboratory – Demystifying Quantum Dot Conundrums – A ‘Titan’ Task at Lawrence Berkeley National Laboratory

Complete atomistic model of the colloidal lead sulfide nanoparticle, also known as a quantum dot, passivated with oleic acid, oleyl amine and hydroxyl ligands.

Berkeley researchers use Titan to seek solutions to decades-old nanocrystal mysteries

Since their discovery over two decades ago [ Rice – Smalley – Curly Institute – “Buckyballs” ] they have gone relatively unnoticed until recently. Now they are showing up in our TVs, smart phones, solar panels, and even our bodies. For something so small, we are beginning to see them everywhere.

Nanocrystals (NCs) are making a significant impact in materials sciences, resulting in better, more energy-efficient products, and in many cases at lower costs. This is because small is different; in other words, at nanoscale the relevant material properties and phenomena behave in interesting and useful ways—differently from how they behave at a scale, say, visible to the human eye.

The benefits of NC technologies are well known; however, on the atomic level, many of the characteristics and behaviors that make them so beneficial remain a mystery.

But thanks to the high-performance computing resources at the Oak Ridge Leadership Computing Facility (OLCF), they’re becoming less mysterious with the help of the Titan supercomputer, a Cray XK7 capable of 27 petaflops, or 27 quadrillion calculations per second. After completing a 3-year project, researchers from Lawrence Berkeley National Laboratory (LBNL) recently published two articles in the journal Science, revealing new insights into the NC atomic structure.

“Understanding more of the fundamental physics in different nanosystems, like how they grow, how the electrons behave, or how different molecules affect the system, allows us to utilize some control,” said lead investigator Lin-Wang Wang, a senior staff scientist at LBL. “And if we can control things like the crystal’s size and shape, we will be able to further advance their usefulness.”

The crystal soup concoction

When thinking about NCs, mind the scale—nanoscale is crazy small.

Picture a strand of hair: 1 nanometer is approximately 100,000 times smaller. Furthermore, each atom inside the crystals—arranged in a repeating, orderly 3D pattern—is 10 times smaller still. The structures Wang and his researchers deal with are typically about 5 nanometers, units with about 2,000 atoms each, called quantum dots (QDs).

It sounds intimidating, but surprisingly, synthesizing QDs is relatively simple; controlling their structure, however, is not.

“We call it a chemical cocktail,” Wang said. “Traditionally, laboratory experimentalists add ingredients like salt and acid [precursors] to organic solvents, or ‘soup,’ which, done under the right conditions, will cause the crystals to grow.”

Once that process is performed, within a matter of minutes a new crystal is formed. But saying “new crystal,” however, isn’t entirely accurate. NCs have the innate ability to regenerate. That is, if an NC is cut into smaller pieces, those smaller pieces will in fact grow back to their original shape during synthesis. Another way of describing it would be to say that once an NC reaches approximately 5 nanometers, growth in some cases abruptly stops.

But why do they do that? How do they do that? What’s happening on the NC surface that we can’t see? Are other molecules playing a role we don’t know about?

“At the atomic level, these were questions no one really had any answers to,” Wang said. “So the details of the atomic structure during passivation have for many, many years been like a black box.”

And according to him, a better understanding of what goes on during passivation is the key to opening that box.

“Imagine it like this,” said Danylo Zherebetskyy, a postdoctoral researcher in Wang’s group. “During passivation, organic molecules act like builders delivering bricks [atoms] to the particles’ surfaces. The molecules form extensions from the crystal’s center, almost like hairs that guide the atoms where to land, growing the crystal brick by brick.”

Those hairs are known as ligands, and not only are they responsible for growth, but they also influence how QDs interact with light, electrical charges, and other materials. And learning how to control ligand passivation, Zherebetskyy said, is critical in advancing nanotech applications.

Dissecting dots

Through an allocation from the OLCF’s Innovative and Novel Computational Impact on Theory and Experiment program, Wang and his team sought to answer those questions via a series of simulations, using Titan to calculate the surface energies and passivation patterns of lead sulfide and platinum nanocrystals.

Whereas laboratory experiments and various imaging methods could offer only hypotheses, for the first time Titan gave researchers precise predictions about NC surface development. Using the density functional theory codes VASP, LS3DF, and PEtot—quantum mechanics-based applications used to calculate the electronic and structural properties of molecules in many-body systems—researchers were able to develop an accurate, testable model, revealing an up-close examination of how each atom arranges itself within the system and how each of those molecules binds with other elements during passivation.

Because NC growth happens layer by layer, outward from the center, understanding the strange, abrupt stoppage in growth required the team to work from the outside in by slicing off sections of the NC surfaces. This process creates additional surfaces, each having different molecular arrangements and energies.

Wang explained: “For simplicity’s sake, let’s just look at two different surfaces. According to the old theory, based on principles in thermodynamics, the surface with the higher energy should grow the most because a higher energy means it’s more active, giving us an energetics picture. But what we find is just the opposite.”

As it turns out, the real secret to NC growth, Titan found, is ligand mobility.

“It takes a certain level of energy to displace a ligand on the surface, and that energy defines the ligand’s mobility,” Zherebetskyy said. “And the more energy it costs to displace the ligand, the more immobile it becomes.”

For growth to happen, he said, once a builder lays a brick, that ligand has to move out of the way so another atom can land next to it. Titan’s simulations made it clear, showing surfaces with lower energies facilitating the process, whereas higher energies actually create such a strong bond between the NC surface and the ligand molecules that passivation becomes completely blocked. Hence, NC growth abruptly stops.

“People have suspected this to be the case,” Wang said, “but until Titan, they never had the evidence to confirm that kinetic processes play a more important role than previously believed.”

The not-so-mysterious molecule

“I talk about size changing or controlling the properties, but the shape can also change the properties,” Wang said. “Different shapes will have different electronic structures and therefore will have different surfaces. Likewise, different surfaces require different methods of passivation.

“For almost 20 years we have been synthesizing inorganic [lead sulfide] quantum dots. But nevertheless, on the atomic level, no one has been able to figure out how the molecules attach to the particles’ surfaces.”

The reason, he explained, is that during passivation, a myriad of chemical reactions are taking place, making it impossible for physical testing or even advanced microscopy methods to identify every actor involved.

This was evidenced when the team placed a lead sulfide NC particle—recognized for its natural symmetry and its ability to form distinct facets—passivated with Oleic acid under Titan’s microscope to focus on unmasking unknown agents. By simulating the experiment, researchers can easily add or remove various molecules such as hydrogen and oxygen to observe their effects on passivation.

Consequently, because hydrogen and oxygen are two key ingredients of the Earth’s most valuable resource, it wasn’t entirely surprising when Titan revealed water to be the masked culprit behind the scenes of so many molecular mysteries. It was thought not possible because part of the synthesis process requires heating the precursor to 110°C (230°F), presumably eliminating any trace of water.

They found that water molecules occur as a byproduct of decomposition during crystal synthesis. Titan showed that water molecules, previously thought to exist only as a free-floating molecule within the soup, actually were a vital component in surface passivation.

“In the past, different experiments have revealed different features about surface passivation, from the amount of ligand molecules to the lead and sulfur atom ratios, but no one had ever put them together to agree with a single atomic model,” Wang said. “This is the first time all those observations actually fit.”

Truth be told

Titan’s findings subsequently aided the team in reproducing their experiments in the lab, giving them the physical confirmation needed to disprove several controversial theories.

The team produced large amounts of data by parallelizing their codes to take advantage of a significant number of Titan’s approximately 300,000 cores. Generated data sets were efficiently managed by routing them through the OLCF’s High Performance Storage System, a tape-based archiving tool.

“Without Titan our calculations would have taken forever, if not been outright impossible,” Zherebetskyy said.

“Our ability to simulate research has become a very powerful technique,” Wang added. “If you cannot do a simulation to get your result, then you probably still don’t fully understand your problem.”

Thanks to Titan and the many resources offered at the OLCF, a US Department of Energy Office of ScienceUser Facility, the team was able to combine computations with various methods of physical testing to produce groundbreaking results in the advancement of new nanomaterials studies.

“I think these projects are just the beginning,” Wang said. “We now have a complete model. So that, I think, will open the door for future investigations into the surface states for more realistic calculations for the QD.”

—Jeremy Rumsey

Oak Ridge National Laboratory is supported by the US Department of Energy’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Oakridge National Laboratory: Using New Graphene Technology to Desalinate Water

Given that less than 1 percent of the water on the planet is drinkable, a process to remove minerals, like salt, from water could help to alleviate many problems for the global community.

In the U.S., a research group based at the Department of Energy’s Oak Ridge National Laboratory have been working on a low-energy efficient desalination process. The newly devised method deploys a porous membrane made of graphene.

Graphene is a very strong, low weight material. It is 100 times stronger than steel and it conducts heat and electricity with great efficiency. The material is being investigated for many potential applications, including water purification.

The graphene membrane is, according to the researchers, more effective and uses less energy compared with current polymeric membranes, which work on the basis of reverse osmosis. With reverse osmosis an applied pressure is used to overcome osmotic pressure; this allows water to pass through a membrane whilst at the same time particles are retained.

With the new method the most important aspect is making the pores in the graphene. The size here is important: large enough to allow water molecules to pass through but sufficiently small to stop salt molecules from traversing the mesh.

The reason that the graphene process is more energy efficient comes down to the size of the mesh. Graphene is considerably thinner (just one atom in thickness) than the plastic polymers and the result of this is that less energy is required to push the fluid through.

The graphene structure was manufactured by passing methane gas through a tube furnace at 1,000 degrees C over a copper foil. This decomposed the methane into carbon and hydrogen. The carbon then assembled into a hexagonal configuration of one atom thick molecules. The graphene was then mounted onto a silicon nitride support. Small pores in the graphene are created using a plasma (an ionized gas.) Pores were created at the rate of one pore for every 100 square nanometers of graphene.

In experimental runs the graphene filter was used to remove salt from sea water in order to create water of drinking water quality. The test runs were effective with almost 100 percent of the salt removed.

The research has been published in the journal Nature Nanotechnology. The title of the paper is “Water Desalination Using Nanoporous Single-Layer Graphene.”

Read more: http://www.digitaljournal.com/science/graphene-technology-used-to-desalinate-water/article/429594#ixzz3Y4AR4wTh

Oak Ridge National Laboratory: Controlling the Properties of Nanomaterials

Scientists at the US Department of Energy’s Oak Ridge National Laboratory are learning how the properties of water molecules on the surface of metal oxides can be used to better control these minerals and use them to make products such as more efficient semiconductors for organic light emitting diodes and solar cells, safer vehicle glass in fog and frost, and more environmentally friendly chemical sensors for industrial applications.

The behavior of water at the surface of a mineral is determined largely by the ordered array of atoms in that area, called the interfacial region. However, when the particles of the mineral or of any crystalline solid are nanometer-sized, interfacial water can alter the crystalline structure of the particles, control interactions between particles that cause them to aggregate, or strongly encapsulate the particles, which allows them to persist for long periods in the environment. As water is an abundant component of our atmosphere, it is usually present on nanoparticle surfaces exposed to air.

A great scientific challenge is to develop ways to look closely at the interfacial region and understand how it determines the properties of nanoparticles. The ORNL researchers are taking advantage of two of the lab’s signature strengths—neutron and computational sciences—to reveal the influence of just a few monolayers of water on the behavior of materials.

In a set of papers published in the Journal of the American Chemical Society and the Journal of Physical Chemistry C, the team of researchers studied cassiterite (SnO2, a tin oxide), representative of a large class of isostructural oxides, including rutile (TiO2). These minerals are common in nature, and water wets their surfaces. The behavior of water confined on the surface of metal oxides readily relates to applications in such diverse areas as heterogeneous catalysis, protein folding, environmental remediation, mineral growth and dissolution, and light-energy conversion in solar cells, to name just a few.

Pictured at the NOMAD instrument at Oak Ridge National Laboratory’s Spallation Neutron Source are David Wesolowski of the Chemical Sciences Division, Thomas Proffen of SNS, Hsiu-Wen Wang of JINS, and NOMAD instrument scientist Mikhail Feygenson. Wang and Feygenson are holding the NOMAD sample-mounting wand. Credit: Jason Richards

When metal oxide nanoparticles are produced, they spontaneously adsorb water from the atmosphere, bonding it to their surface, explained Hsiu-Wen Wang, a research scientist currently at the ORNL–University of Tennessee Joint Institute for Neutron Sciences who performed this research while conducting a postdoctoral fellowship in the Chemical Sciences Division (CSD) at ORNL.

This water can interfere with the function of SnO2-containing products in surprising ways that are hard to predict. Wang’s team used neutron scattering at ORNL’s Spallation Neutron Source (SNS) to help understand the role that bound water plays in the stability of SnO2 nanoparticles and to learn more about the bound water’s structure and dynamics. Wang said neutrons are perfect for studying light elements such as the hydrogen and oxygen that make up water, and molecular dynamics simulations are an ideal tool to reinforce the observations. In fact, hydrogen is essentially invisible to X-ray and electron beams but scatters neutrons strongly, making neutron diffraction and inelastic scattering the ideal tools for probing the properties of water and other hydrogen-bearing species.
“When we drive all the water off the surface of the nanoparticles, this destabilizes the structure of the nanoparticles, and they grow larger,” said David J. Wesolowski, a co-author and Wang’s supervisor when she worked in CSD.

“The lifetime of engineered nanoparticles in the environment is an important environmental safety and health issue,” Wesolowski said. “We show that water sorbed on the nanoparticles, which naturally happens when they are exposed to normal humid air, prolongs their lifetimes as nanomaterials, thus prolonging their potential environmental impacts. In addition, the high surface area of nanoparticles is desirable. If the particles grow, which happens as they are heated and dehumidified, their surface area drops rapidly.”

To remove sorbed water, the nanoparticles are heated under vacuum. Water dissipation begins at around 250°C (nearly 500°F, or about as hot as you can set your kitchen’s oven). Much energy is required to drive off the water completely from the nanoparticles, which stay stable to these relatively high temperatures precisely because of the presence of the bound water. Once the water begins to dissipate, destabilization begins. Before completing this study, researchers did not know to what degree the removal of water would cause destabilization.

“It may be that the surfaces without water have different and useful chemical properties, but because water is everywhere in the environment, it is very important to know that the surfaces of oxide nanoparticles are likely to be already covered with a few molecular layers of water,” Wesolowski said.

Researchers used SNS’s Nanoscale-Ordered Materials Diffractometer (NOMAD) instrument to determine the structure of water on cassiterite nanoparticle surfaces, as well as the structure of the particles themselves. NOMAD is dedicated to local structure studies of various materials from liquids to nanoparticles, using the neutron scattering pattern produced during experiments, said Mikhail Feygenson, NOMAD instrument scientist.

“The combination of the high neutron flux of SNS and the wide detector coverage of NOMAD enables rapid data collection on very small samples, like our nanoparticles,” Feygenson said. “NOMAD is much faster than similar instruments around the world. In fact, the measurements of our samples that took about 24 hours of NOMAD time could have required as much as a full week on a similar instrument at another lab.”

The second step of the study took place at SNS on the Fine-Resolution Fermi Chopper Spectrometer (SEQUOIA), which allows for forefront research on dynamical processes in materials. “This part of the study focuses on the role of surface hydrogen bonds and the surface water vibrational properties,” said Alexander Kolesnikov, SEQUOIA instrument scientist.

The NOMAD and SEQUOIA studies enabled the research team to validate computational models they created to fully capture the structural ordering of the surface-bound water on the SnO2 nanocrystals. Integrating neutron scattering experiments with classical and first principles molecular dynamics simulations provided evidence that strong hydrogen bonds—as strong as in water under ultrahigh pressure of >500,000 atm—drive water molecules to dissociate at the interfaces and result in a weak interaction of the hydrated SnO2 surface with additional water layers.

“The results are significant in demonstrating many new features of surface-confined water that can provide general guidance into tuning of surface hydrophilic interactions at the molecular level,” said Jorge Sofo, professor of physics at Pennsylvania State University.

Explore further: Mixed nanoparticle systems may help purify water and generate hydrogen

More information: H.-W. Wang, M. DelloStritto, N. Kumar, A. I. Kolesnikov, P. R. C. Kent, J. D. Kubicki, D. J. Wesolowski, and J. O. Sofo, “Vibrational density of states of strongly H-bonded interfacial water: Insights from inelastic neutron scattering and theory.” The Journal of Physical Chemistry C, 118, 10805–1083 (2014); DOI: dx.doi.org/10.1021/jp500954v

A Self-Correcting Crystal May Unleash the Next Generation of Advanced Communications

Researchers from the National Institute of Standards and Technology (NIST) have joined with an international team to engineer and measure a potentially important new class of nanostructured materials for microwave and advanced communication devices.

 

Based on NIST’s measurements, the new materials—a family of multilayered crystalline sandwiches—might enable a whole new class of compact, high-performance, high-efficiency components for devices such as cellular phones.*

Not a brick wall. Electron microscope image of a cross section of the newly characterized tunable microwave dielectric clearly shows the thick layers of strontium titanate “bricks” separated by thin “mortar lines” of strontium oxide that help promote the largely defect-free growth of the bricks. Credit: TEM image courtesy David Mueller. Color added for clarity by Nathan Orloff. high resolution version

“These materials are an excellent example of what the Materials Genome Initiative refers to as ‘materials-by-design’,” says NIST physicist James Booth, one of the lead researchers. “Materials science is getting better and better at engineering complex structures at an atomic scale to create materials with previously unheard-of properties.”

The new multilayer crystals are so-called “tunable dielectrics,” the heart of electronic devices that, for example, enable cell phones to tune to a precise frequency, picking a unique signal out of the welter of possible ones.

Tunable dielectrics that work well in the microwave range and beyond—modern communications applications typically use frequencies around a few gigahertz—have been hard to make, according to NIST materials scientist Nathan Orloff. “People have created tunable microwave dielectrics for decades, but they’ve always used up way too much power.” These new materials work well up to 100 GHz, opening the door for the next generation of devices for advanced communications.

Modern cellphone dielectrics use materials that suffer from misplaced or missing atoms called “defects” within their crystal structure, which interfere with the dielectric properties and lead to power loss. One major feature of the new materials, says Orloff, is that they self-correct, reducing the effect of defects in the part of the crystal where it counts. “We refer to this material as having ‘perfect faults’,” he says. “When it’s being grown, one portion accommodates defects without affecting the good parts of the crystal. It’s able to correct itself and create perfect dielectric bricks that result in the rare combination of high tuning and low loss.”

The new material has layers of strontium oxide, believed to be responsible for the self-correcting feature, separating a variable number of layers of strontium titanate. Strontium titanate on its own is normally a pretty stable dielectric—not really tunable at all—but another bit of nanostructure wizardry solves that. The sandwich layers are grown as a thin crystalline film on top of a substrate material with a mismatched crystal spacing that produces strain within the strontium titanate structure that makes it a less stable dielectric—but one that can be tuned. “It’s like putting a queen-sized sheet on a king-sized bed,” says Orloff. “The combination of strain with defect control leads to the unique electronic properties.”

One key discovery by the research team was that, in addition to adding strain to the crystal sandwich, adding additional layers of strontium titanate in between the strontium oxide layers increased the room-temperature “tunability” performance of the structure, providing a new mechanism to control the material response. The material they reported on recently in the journal Nature has six layers of strontium titanate between each strontium oxide layer.

The new sandwich material performs so well as a tunable dielectric, over such a broad range of frequencies, that the NIST team led by Booth had to develop a new measurement technique—an array of test structures fabricated on top of the test film—just to measure its electronic characteristics. “We were able to characterize the performance of these materials as a function of frequency running from 10 hertz all the way up to 125 gigahertz. That’s the equivalent of measuring wavelengths from kilometers down to microns all with the same experimental set-up,” says Orloff, adding, “This material has a much lower loss and a much higher tunability for a given applied field then any material that we have seen.”

An international team of researchers contributed to the recent paper, representing, in addition to NIST, Cornell University, the University of Maryland, Pennsylvania State University, the Institute of Physics ASCR (Czech Republic), Universitat Politècnica de Catalunya (Spain), the Kavli Institute at Cornell for Nanoscale Science, Oak Ridge National Laboratory, the Leibniz Institute for Crystal Growth (Germany), The University of Texas at Austin and Temple University.

Contact: Michael Baum 301-975-2763

For additional perspective, see the Cornell University news story, “Tunable antenna could end dropped cell phone calls” at www.news.cornell.edu/stories/2013/10/tunable-antenna-could-end-dropped-cell-phone-calls. For more on the MGI at NIST, see www.nist.gov/mgi/index.cfm.

Neutrons, electrons and theory reveal secrets of natural gas reserves

OAK RIDGE, Tenn., Oct. 28, 2013 – Gas and oil deposits in shale have no place to hide from an Oak Ridge National Laboratory technique that provides an inside look at pores and reveals structural information potentially vital to the nation’s energy needs.

The research by scientists at the Department of Energy laboratory could clear the path to the more efficient extraction of gas and oil from shale, environmentally benign and efficient energy production from coal and perhaps viable carbon dioxide sequestration technologies, according to Yuri Melnichenko, an instrument scientist at ORNL’s High Flux Isotope Reactor.

Scanning electron microscope image illustrating mineralogy and texture of unconventional gas reservoir. Note that nanoporosity is not resolvable with this image. SANS and USANS analysis is required to quantify pore size distribution and interconnectivity.          (hi-res image)

Melnichenko’s broader work was emboldened by a collaboration with James Morris and Nidia Gallego, lead authors of a paper recently published in Journal of Materials Chemistry A and members of ORNL’s Materials Science and Technology Division.

Researchers were able to describe a small-angle neutron scattering technique that, combined with electron microscopy and theory, can be used to examine the function of pore sizes.

Using their technique at the General Purpose SANS instrument at the High Flux Isotope Reactor, scientists showed there is significantly higher local structural order than previously believed in nanoporous carbons. This is important because it allows scientists to develop modeling methods based on local structure of carbon atoms. Researchers also probed distribution of adsorbed gas molecules at unprecedented smaller length scales, allowing them to devise models of the pores.

“We have recently developed efficient approaches to predict the effect of pore size on adsorption,” Morris said. “However, these predictions need verification – and the recent small-angle neutron experiments are ideal for this. The experiments also beg for further calculations, so there is much to be done.”

While traditional methods provide general information about adsorption averaged over an entire sample, they do not provide insight into how pores of different sizes contribute to the total adsorption capacity of a material. Unlike absorption, a process involving the uptake of a gas or liquid in some bulk porous material, adsorption involves the adhesion of atoms, ions or molecules to a surface.

This research, in conjunction with previous work, allows scientists to analyze two-dimensional images to understand how local structures can affect the accessibility of shale pores to natural gas.

“Combined with atomic-level calculations, we demonstrated that local defects in the porous structure observed by microscopy provide stronger gas binding and facilitate its condensation into liquid in pores of optimal sub-nanometer size,” Melnichenko said. “Our method provides a reliable tool for probing properties of sub- and super-critical fluids in natural and engineered porous materials with different structural properties.

“This is a crucial step toward predicting and designing materials with enhanced gas adsorption properties.”

Together, the application of neutron scattering, electron microscopy and theory can lead to new design concepts for building novel nanoporous materials with properties tailored for the environment and energy storage-related technologies. These include capture and sequestration of man-made greenhouse gases, hydrogen storage, membrane gas separation, environmental remediation and catalysis.

Other authors of the paper, titled “Modern approaches to studying gas adsorption in nanoporous carbons,” are Cristian Contescu, Matthew Chisholm, Valentino Cooper, Lilin He, Yungok Ihm, Eugene Mamontov, Raina Olsen, Stephen Pennycook, Matthew Stone and Hongxin Zhang. The research, funded by DOE’s Office of Basic Energy Sciences, utilized the following DOE Office of Science user facilities:

ORNL’s Spallation Neutron Source (http://neutrons.ornl.gov/faciliities/SNS/) is a one-of-a-kind research facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development.

HFIR (http://neutrons.ornl.gov/facilities/HFIR/) at ORNL is a light-water cooled and moderated reactor that is the United States’ highest flux reactor-based neutron source.

The ShaRE User Facility (http://web.ornl.gov/sci/share/) makes available state-of-the-art electron beam microcharacterization facilities for collaboration with researchers from universities, industry and other government laboratories.

As a national resource to enable scientific advances to support the missions of DOE’s Office of Science, the National Energy Research Scientific Computing Center (http://www.nersc.gov), annually serves approximately 3,000 scientists throughout the United States.

UT-Battelle manages ORNL for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of the time. For more information, please visit science.energy.gov.

Superconducting wire with unprecedented performance

Just add nanocolumn defects

 

The ability to control nanoscale imperfections in superconducting wires results in materials with unparalleled and customized performance, according to a new study from the Department of Energy’s Oak Ridge National Laboratory.

Applications for superconducting wires, which carry electricity without resistance when cooled to a critical temperature, include underground transmission cables, transformers and large-scale motors and generators. But these applications require wires to operate under different temperature and magnetic field regimes.

A team led by ORNL’s Amit Goyal demonstrated that superconducting wires can be tuned to match different operating conditions by introducing small amounts of non-superconducting material that influences how the overall material behaves. Manipulating these nanoscale columns — also known as defects — allows researchers to exert control over the forces that regulate the wires’ superconducting performance. The team’s findings are published in Nature Publishing Group’s Scientific Reports.

“Not only can we introduce these nanocolumn defects within the superconductor and get enhanced performance, but we can optimize the performance for different application regimes by modifying the defect spacing and density,” Goyal said.

A wire sample grown with this process exhibited unprecedented performance in terms of engineering critical current density, which measures the amount of current the wire can carry per unit cross-sectional area. This metric more accurately reflects the real-world capabilities of the material because it takes into account the wire’s non-superconducting components such as the substrate and the buffer and stabilizer layers, Goyal said.

“We report a record performance at 65 Kelvin and 3 Tesla, where most rotating machinery applications like motors and generators are slated to operate,” he said.

The paper reports a minimum engineering critical current density at all applied

magnetic field orientations of 43.7 kiloamperes/cm², which is more than twice the performance level needed for most applications. This metric assumes the presence of a 50-micron-thick copper stabilizer layer required in applications. Generating defects in the superconductor is accomplished through an ORNL-developed self-assembly process, which enables researchers to design a material that automatically develops the desired nanoscale microstructure during growth.

The mechanism behind this process, which adds very little to the production cost, was the subject of a recently published study by a team led by Goyal in Advanced Functional Materials. “When you’re making the wires, you can dial-in the properties because the defects self-assemble,” Goyal said. “You change the composition of the superconductor when you’re depositing the tape.” Goyal, who has collaborated with multiple superconducting technology companies, hopes the private sector will incorporate the team’s findings to improve upon existing products and generate new applications.

The study is published as “Engineering nanocolumnar defect configurations for optimized vortex pinning in high temperature superconducting nanocomposite wires.” Co-authors are ORNL’s Sung Hun Wee and Claudia Cantoni and the University of Tennessee’s Yuri Zuev.

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

Nanoparticles Harness Powerful Radiation Therapy for Cancer

Posted: May 17th, 2013

Nanoparticle harnesses powerful radiation therapy for cancer

(Nanowerk News) Researchers at the University of Missouri have demonstrated the ability to create a multi-layered harness nanoparticle that can safely encapsulate powerful alpha-emitting radioisotopes and target tumors. The resulting nanoparticles not only offer the possibility of delivering tumor-killing alpha emitters to tumors, but also sparing healthy tissue from radiation damage. J. David Robinson and his colleagues published their findings in the journal PLoS One (“Gold Coated Lanthanide Phosphate Nanoparticles for Targeted Alpha Generator Radiotherapy”).Typically, when radiation treatment is recommended for cancer patients, doctors are able to deliver radiation from a source outside the body or they might inject one of several radiopharmaceuticals that emit low-energy radiation known as beta particles. For years, scientists have been studying how to use “alpha emitters,” which are radioactive elements that release high-energy alpha particles that would more effectively damage cancer cells and trigger cell death. The challenge to using alpha emitters is that the decay elements, the so-called daughters, are themselves highly toxic and difficult to contain in the vicinity of the tumor, thus causing significant damage to healthy tissues.”If you think of beta particles as slingshots or arrows, alpha particles would be similar to cannon balls,” said Dr. Robertson. He explains that recent work has shown that alpha particles can be effective in treating cancer in specific instances. “For example, a current study using radium-223 chloride, which emits alpha particles, has been fast-tracked by the U.S. Food and Drug Administration because it has been shown to be effective in treating bone cancer. However, it only works for bone cancer because the element, radium, is attracted to the bone and stays there. We believe we have found a solution that will allow us to target alpha particles to other cancer sites in the body in an effective manner.”In their studies, Dr. Robertson and colleagues from Oak Ridge National Laboratory and the School of Medicine at the University of Tennessee in Knoxville used the isotope actinium-225, an element that when it decays produces a high-energy alpha particle and radioactive daughter elements, which are also capable of emitting alpha particles. Efforts to contain the daughter elements using traditional molecular constraints proved fruitless because the emitted alpha particles broke the chemical bonds necessary to hold the daughter elements in place.The Missouri team solved this problem by sequestering actinium-225 in the core of a gold-coated magnetic nanoparticle. The magnetic layer, comprised of gadolinium phosphate, serves to increase retention of the daughter elements while simplifying particle purification and the gold coating provides a surface to which tumor-targeting molecules can be attached. In the experiments described in their current publication, the researchers used an antibody that targets a receptor found on the surface of lung tumors.”Holding these alpha emitters in place is a technical challenge that researchers have been trying to overcome for 15 years,” Dr. Robertson said. “With our nanoparticle design, we are able to keep more than 80 percent of the element inside the nanoparticle 24 hours after it is created.” While alpha particles are extremely powerful, they do not travel very far, so when the nanoparticles get close to the targeted cancer cells, the alpha particles are more selective at damaging cancer cells but not surrounding cells.

Read more: http://www.nanowerk.com/news2/newsid=30558.php#ixzz2TiEg009k

New Material Promises Better Solar Cells

Researchers at the Vienna University of Technology show that a recently discovered class of materials can be used to create a new kind of solar cell.

 

Elias Assmann (left) and Karsten Held (right) demonstrate the idea behind the new solar cell: Light is absorbed by a layered structure, free charge carrieres are produced and electric current starts to flow.

Sunlight is converted into electrical current in a layered structure.

Single atomic layers are combined to create novel materials with completely new properties. Layered oxide heterostructures are a new class of materials, which has attracted a great deal of attention among materials scientists in the last few years. A research team at the Vienna University of Technology, together with colleagues from the USA and Germany, has now shown that these heterostructures can be used to create a new kind of extremely efficient ultra-thin solar cells.

Discovering New Material Properties in Computer Simulations “Single atomic layers of different oxides are stacked, creating a material with electronic properties which are vastly different from the properties the individual oxides have on their own”, says Professor Karsten Held from the Institute for Solid State Physics, Vienna University of Technology. In order to design new materials with exactly the right physical properties, the structures were studied in large-scale computer simulations. As a result of this research, the scientists at TU Vienna discovered that the oxide heterostructures hold great potential for building solar cells.

Turning Light into Electricity The basic idea behind solar cells is the photoelectric effect. Its simplest version was already explained by Albert Einstein in 1905: when a photon is absorbed, it can cause an electron to leave its place and electric current starts to flow. When an electron is removed, a positively charged region stays behind – a so called “hole”. Both the negatively charged electrons as well as the holes contribute to the electrical current.

“If these electrons and holes in the solar cell recombine instead of being transported away, nothing happens and the energy cannot be used”, says Elias Assmann, who carried out a major part of the computer simulations at TU Vienna. “The crucial advantage of the new material is that on a microscopic scale, there is an electric field inside the material, which separates electrons and holes.” This increases the efficiency of the solar cell.
Two Isolators Make a Metal The oxides used to create the material are actually isolators. However, if two appropriate types of isolators are stacked, an astonishing effect can be observed: the surfaces of the material become metallic and conduct electrical current. “For us, this is very important. This effect allows us to conveniently extract the charge carriers and create an electrical circuit”, says Karsten Held. Conventional solar cells made of silicon require metal wires on their surface to collect the charge carriers – but these wires block part of the light from entering the solar cell.

Not all photons are converted into electrical current with the same efficiency. For different colors of light, different materials work best. “The oxide heterostructures can be tuned by choosing exactly the right chemical elements”, says Professor Blaha (TU Vienna). In the computer simulations, oxides containing Lanthanum and Vanadium were studied, because that way the materials operate especially well with the natural light of the sun. “It is even possible to combine different kinds of materials, so that different colors of light can be absorbed in different layers of the solar cell at maximum efficiency”, says Elias Assmann.

Putting Theory into Practice The team from TU Vienna was assisted by Satoshi Okamoto (Oak Ridge National Laboratory, Tennessee, USA) and Professor Giorgio Sangiovanni, a former employee of TU Vienna, who is now working at Würzburg University, Germany. In Würzburg, the new solar cells will now be build and tested. “The production of these solar cells made of oxide layers is more complicated than making standard silicon solar cells. But wherever extremely high efficiency or minimum thickness is required, the new structures should be able to replace silicon cells”, Karsten Held believes.