NIST Study Suggests Light May Be Skewing Lab Tests on Nanoparticles’ Health Effects


NIST 580303_10152072709285365_1905986131_nTruth shines a light into dark places. But sometimes to find that truth in the first place, it’s better to stay in the dark. That’s what recent findings* at the National Institute of Standards and Technology (NIST) show about methods for testing the safety of nanoparticles. It turns out that previous tests indicating that some nanoparticles can damage our DNA may have been skewed by inadvertent light exposure in the lab.

Nanoparticles made of titanium dioxide are a common ingredient in paint, and they also are considered safe for use both on the body (in sunscreen, where they help block ultraviolet light) and even within it (in foodstuffs such as salad dressings to make them appear whiter). It is well known that in the presence of light and water, these particles can form dangerous, highly reactive chemicals called free radicals that can damage DNA. Because light does not reach the human body’s interior, scientists have long accepted that these nanoparticles would not damage cells by forming free radicals from light activation.

nanoparticle containing items
Titanium dioxide nanoparticles are widely used not only in paints but in sunscreen and even salad dressing.
Credit: © GoodMood,Photo-Gabriele,Maltini-renamarie:Fotolia.com

However, some recent studies using cells suggest that titanium dioxide can damage DNA even in darkness—a disturbing possibility. Because such findings could have major health implications, the NIST team set out to determine whether light was indeed required for the nanoparticles to cause DNA damage.

“We didn’t set out to test the safety of the particles themselves—that’s for someone else to determine,” says NIST’s Elijah Petersen. “Our main concern is to ensure that scientists have enough knowledge to make accurate measurements. That way, tests will give accurate representations of reality.”

The NIST team exposed samples of DNA to titanium dioxide nanoparticles under three different conditions: Some samples were exposed in the presence of visible or ultraviolet light while others were kept carefully and intentionally in complete darkness from the moment of exposure to the time the DNA damage was measured. The team found that only when exposed to laboratory or ultraviolet light did the DNA form base lesions, a form of DNA damage associated with attack by radicals. Their conclusion? The culprit in earlier studies may be ambient light from the laboratory that inadvertently caused DNA damage.

“The results suggest that titanium dioxide nanoparticles do not damage DNA when kept in the dark,” Petersen says. “These findings show that experimental conditions, such as lighting, must be carefully controlled before drawing conclusions about nanoparticle effects on DNA.”

*E.J. Petersen, V. Reipa, S.S. Watson, D.L. Stanley, S.A Rabb and B.C. Nelson. The DNA damaging potential of photoactivated P25 titanium dioxide nanoparticles. Chemical Research in Toxicology, October 2014 issue, DOI: 10.1021/tx500340v.

UMD and NIST Announce the Creation of the Joint Center for Quantum Information and Computer Science


NIST 580303_10152072709285365_1905986131_n Center researchers aim to understand how quantum systems can store, transport, process information

The University of Maryland (UMD) and the U.S. Department of Commerce’s National Institute of Standards and Technology (NIST) announced today the creation of the Joint Center for Quantum Information and Computer Science (QuICS), with the support and participation of the Research Directorate of the National Security Agency/Central Security Service (NSA/CSS). Scientists at the center will conduct basic research to understand how quantum systems can be effectively used to store, transport and process information.

This new center complements the fundamental quantum research performed at the work of the Joint Quantum Institute (JQI), which was established in 2006 by UMD, NIST and the NSA. Focusing on one of JQI’s original objectives to fully understand quantum information, QuICS will bring together computer scientists—who have expertise in algorithm and computational complexity theory and computer architecture—with quantum information scientists and communications scientists.

“This new endeavor builds on an already successful and fruitful collaboration at JQI,” said Acting Under Secretary of Commerce for Standards and Technology and Acting Director of NIST Willie May. “The new center will be a venue for groundbreaking basic research that will help to build our capacity for quantum research and train the next generation of researchers.”

UMD and NIST have a shared history of collaboration and cooperation in education, research and public service. They have long cooperated in building collaborative research consortia and programs that have resulted in extensive personal, professional and institutional relationships.

“By deepening our partnership with NIST, we now have all the ingredients in place to make major advances in quantum science,” said UMD President Wallace Loh. “This superb, world-class quantum program will team some of the best minds in physics, computer science and engineering to overcome the limitations of current computing systems.”

Dianne O’Leary, Distinguished University Professor Emerita in computer science at UMD, and Jacob Taylor, a NIST physicist and JQI Fellow, will serve as co-directors of the new center. Like the JQI, QuICS will be located on the UMD campus in College Park, Md.

The capabilities of today’s embedded and high-performance computer architectures have limited advances in critical areas, such as modeling the physical world, improving sensors and securing communications. Quantum computing could enable us to break through some of these barriers.

QuICS’ objectives will be to:

  • Develop a world-class research center that will build the scientific foundation for quantum information science to enable understanding of the relationships between information theory, computational complexity theory and nature, as well as the advances in computer science necessary to support potential quantum computing and communication devices and systems;
  • Maintain and enhance the nation’s leading role in quantum information science by expanding an already-powerful collaboration between UMD, NIST and NSA/CSS; and
  • Establish a unique, interdisciplinary center for the interchange of ideas among computer scientists, physicists and quantum information researchers.

Some of the topics QuICS researchers will initially examine include understanding how quantum mechanics informs computation and communication theories, determining what insights computer science can shed on quantum computing, investigating the consequences of quantum information theory for fundamental physics, and developing practical applications for theoretical advances in quantum computation and communication.

QuICS is expected to train scientists for future industrial and academic opportunities and provide U.S. industry with cutting-edge research results. By combining the strengths of UMD and NIST, QuICS will become an international center for excellence in quantum computer and information science.

QuICS will be the newest of 16 centers and labs within the University of Maryland Institute for Advanced Computer Studies (UMIACS). The center will bring together researchers from UMIACS; the UMD Departments of Physics and Computer Science; and the UMD Applied Mathematics & Statistics, and Scientific Computation program with NIST’s Information Technology and Physical Measurement laboratories.

About the University of Maryland

NIST Spin Rods 14CNST004_nanorod_LR_1The University of Maryland is home to three quantum science research centers: the Joint Center for Quantum Information and Computer Science, the Joint Quantum Institute, and the Quantum Engineering Center. UMD has nation-leading computer science, physics and math departments, with particular strengths in the areas relevant to quantum science research.

In the 2015 Best Graduate Schools ranking by U.S. News & World Report, UMD’s Department of Physics ranked 14th, the Department of Computer Science ranked 15th, and Department of Mathematics ranked 17th. The atomic/molecular/optical physics specialty ranked 6th, the quantum physics specialty ranked 8th, and the applied math specialty ranked 10th. Visit UMD’s website to learn more.

About NIST

As a non-regulatory agency of the U.S. Department of Commerce, NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life. Visit NIST’s website for more information.

Improving Rechargeable Batteries: Could Novel New Sodium-Conducting Material be the Answer?


1-novelsodiumcx250Rechargeable battery manufacturers may get a jolt from research performed at NIST and several other institutions, where a team of scientists has discovered a safe, inexpensive, sodium-conducting material that significantly outperforms all others in its class.

The team’s discovery is a sodium-based, complex metal hydride, a material with potential as a much cheaper alternative to the lithium-based conductors used in many rechargeable batteries. Because lithium is a comparatively rare commodity near the earth’s surface, the industry would prefer to build reusable batteries out of common ingredients that are both economical and inexhaustible.

1-novelsodiumcx250

The novel hydride—which has the formula Na2B10H10—might fit the bill, and not only because it is formed of the three easily obtainable elements of sodium, boron and hydrogen. There are other practical reasons as well: It is a stable inorganic solid, meaning it would pose fewer of the risks carried by many flammable liquids in traditional batteries, such as the potential for leaking or exploding. And compared to other sodium-based solids, it can enable more power output.

This last advantage stems from its unusual ability to conduct sodium ions exceptionally well when heated. At room temperature, the hydride’s atoms are tightly packed together. But when heated to near water’s boiling point, they repack to create numerous corridors through which the sodium ions can flow easily. Because charged ions are what carry electricity in a battery, this “phase change,” as physicists call it, allows the team’s material to outperform others.

“It’s more than 20 times better at doing its job than other known sodium-based complex hydrides in this temperature range,” says Terrence Udovic of the NIST Center for Neutron Research (NCNR). “It’s also as good as the best solid lithium-based hydride that has been measured, so it’s quite promising.”NIST 580303_10152072709285365_1905986131_n

Udovic had been exploring metal hydride materials as candidates for hydrogen storage, and while this particular compound performed poorly at that task, he hit upon the idea of testing it as an ion conductor. NCNR research hinted at its abilities, but clarifying them took an international effort among collaborators from Japan’s Tohoku Univ., Russia’s Institute of Metal Physics, the Univ. of Maryland and Sandia National Laboratories.

Udovic says that future work will involve chemically tweaking the hydride’s properties in order to optimize its performance. At this point, it would be necessary to operate a battery above the phase transition temperature, so one goal will be to bring the transition temperature down to as close to room temperature as possible—a goal he is confident is within reach.

“You could probably use this material in a battery right now,” he says. “But the lower the temperature required to make it work, the more useful it will be.”

Source: NIST

Nanotechnology Could Provide Important Societal and Economic Benefits: Study Suggests 6 Million People Working in Nanomaterials by 2020


Rice Cancer 50167Considered by some to be the next frontier of global economic development, nanotechnology has the potential to revolutionize industries like healthcare, information technology and energy systems.

A new study provides investors and stakeholders with a comprehensive guide to this nascent, rapidly growing industry. The study indicates that nanotechnology could provide important societal and economic benefits along with substantial financial rewards for investors.

ElectrodeBarrier“Already, nanotechnology has realized scientific success. Its next phase could lead to revolutionary advancements for treating diseases, purifying water and addressing environmental issues,” said Jon Lukomnik, IRRCi executive director.NIST 580303_10152072709285365_1905986131_n

“Most industries either are already incorporating nanomaterials into products or conducting research based on nanotechnology. This means companies should tell investors how they are using nanotechnology and taking appropriate precautions,” Si2 Executive Director Heidi Welsh added.

Nanotechnology is an emerging field that focuses on the understanding and control of matter at near-atomic scale. It crosses scientific disciplines and has the potential to affect virtually every aspect of daily life and every economic sector. At least 1,600 consumer products have entered the marketplace in the last eight years, and this is just a sliver of the products and processes already in use and under development. Applications-of-Nanomaterials-Chart-Picture1

By 2020, six million people worldwide may work with nanomaterials. Corporations now provide about half the funding for research on nano frontiers, catching up with governments led by the United States and 60 other countries such as Germany, France, Japan, Korea and China.

“NIST on a Chip”? NIST Quantum Probe Enhances Electric Field Measurements: Radar, Wireless Communications & Medical Applications


1-NIST 50258Abstract:
Researchers at the National Institute of Standards and Technology (NIST) and the University of Michigan have demonstrated a technique based on the quantum properties of atoms that directly links measurements of electric field strength to the International System of Units (SI).*

NIST quantum probe enhances electric field measurements

Boulder, CO | Posted on October 8th, 2014

The new method could improve the sensitivity, precision and ease of tests and calibrations of antennas, sensors, and biomedical and nano-electronic systems and facilitate the design of novel devices.

Conventional electric field probes have limited frequency range and sensitivity, often disturb the field being measured, and require laboratory calibrations that are inherently imprecise (because the reference field depends on the geometry of the source). Furthermore, linking these measurements to SI units, the highest level of calibration, is a complex process.NIST 580303_10152072709285365_1905986131_n

NIST’s new electric-field probe spans enormous ranges. It can measure the strength of fields from 1 to 500 gigahertz, including the radio, microwave, millimeter-wave and sub-terahertz bands. It can measure fields up to 100 times weaker than conventional methods can (as weak as 0.8millivolts per meter, the SI unit of measure). Researchers used the new method to measure field strengths for a wide range of frequencies, and the results agreed with both numerical simulations and calculations.

Importantly, the new method can calibrate itself, as well as other instruments, because it is based on predictable quantum properties: vibrations in atoms as they switch between energy levels. This self-calibration feature improves measurement precision and may make traceable calibrations possible in the millimeter and sub-terahertz bands of the spectrum for the first time.

“The exciting aspect of this approach is that an atom is rich in the number of transitions that can be excited,” NIST project leader Chris Holloway says. “This results in a broadband measurement probe covering a frequency range of 1 to 500 gigahertz and possibly up to 1 terahertz.”

The NIST instrument currently is tabletop sized, but researchers are working on miniaturizing it using photonic structures.

The basic method has already been demonstrated for imaging applications.** Briefly, researchers use a red and a blue laser to prepare atoms contained in a cylinder to high-energy (“Rydberg”) states, which have novel properties such as extreme sensitivity and reactivity to electromagnetic fields. An antenna or other source generates an electric field, which, depending on its frequency, affects the spectrum of light absorbed by the atoms. By measuring this effect, researchers can calculate the field strength. Various atoms can be used—NIST uses rubidium or cesium—to measure field strength in different parts of the frequency spectrum.

Among possible applications, the NIST probe may be suitable for measuring and optimizing compatibility in densely packaged electronics that include radar and wireless communications and control links, and for integration into endoscopic probes with medical applications such as investigating implants in the body. The technique might also be included in a future “NIST on a chip” offering multiple measurement methods and standards in a portable form.

Importantly, the technique also enables, for the first time, calibrated measurements of frequencies above 100 GHZ, in the millimeter wave and sub-terahertz bands.*** This capability will be crucial for the development of advanced communications systems and climate change research, among other applications.

Five co-authors of the new paper are with the University of Michigan, which provided the blue laser and aided in the experiments. The project is funded in part by the Defense Advanced Research Projects Agency.

* C.L. Holloway, J.A. Gordon, S. Jefferts, A. Schwarzkopf, D. A. Anderson, S.A. Miller, N. Thaicharoen and G. Raithelet. Broadband Rydbergatom-based electric-field probe: From self-calibrated measurements to sub-wavelength imaging. IEEE Trans. on Antennas and Propagation. 99. Accepted for publication. DOI: 10.1109/TAP.2014.2360208.

** See 2014 NIST Tech Beat article, “NIST Technique Could Make Sub-wavelength Images at Radio Frequencies,” at http://www.nist.gov/pml/electromagnetics/subwave-061714.cfm.

*** J.A. Gordon, C.L. Holloway, A. Schwarzkopf, D. A. Anderson, S. Miller, N. Thaicharoen and G. Raithel. Millimeter wave detection via Autler-Townes splitting in rubidium Rydberg atoms. Applied Physics Letters, 2014. Vol. 105, Issue 2.DOI:10.1063/1.4890094.

Finding the ‘Holy Grail’ for Solar Energy “Are We (almost) There Yet?”


QDOT images 6

*** “Throw-Back Thursdays” – Maybe not so much! Today’s Post(s) are a compilation of some of 2014’s LATEST advances in making Solar Renewable Energy an Affordable, Efficient and Commercially Viable Energy Source.Quote, “Solar-cell technology has advanced rapidly, as hundreds of groups around the world pursue more than two dozen approaches using different materials, technologies, and approaches to improve efficiency and reduce costs.

Universities and Organizations such as the University of California, University of Sheffield, University of Electro-Communications, Okinawa Institute of Science and Technology Graduate University, MIT, University of Toronto, NREL, NIST, NRL … ALL are seeking new discoveries, new methods of application-processes … to achieve the actualization and implementation of “Abundant, Cheap, Renewable Energy”. In this Compilation:

  • Singlet Fission – For Increased Efficiencies – 2014-07
  • Spray-On Solar Cells –  2014-08
  • Pervoskites – A New (LOW COST) Semiconductor Material for Solar Cells – 2014-09
  • ‘Dark’ Spin-Triplet Excitons – 2014-10
  • Self-Organized Indium Arsenide Quantum Dots for Solar Cells – 2014-09
  • A New Breed of “Quantum Dot” Solar Cells – 2014-05

 

Solar Energy Boost: ‘Singlet Fission’ Could Increase Efficiency by as much as 30%

Jul 08, 2014

1-solarenergyg

A perspective article published last month by University of California, Riverside chemists in the Journal of Physical Chemistry Letters was selected as an Editors Choice—an honor only a handful of research papers receive. The perspective reviews the chemists’ work on “singlet fission,” a process in which a single photon generates a pair of excited states. This 1->2 conversion process, as it is known, has the potential to boost solar cell efficiency by as much as 30 percent.

Applications of the research include more energy-efficient lighting and photodetectors with 200 percent efficiency that can be used for night vision. Biology may use singlet fission to deal with high-energy solar photons without generating excess heat, as a protective mechanism.

Currently, work by absorbing a , which generates an , which subsequently separates into an electron-hole pair. It is these electrons that become solar electricity. The efficiency of these solar cells is limited to about 32 percent, however, by what is called the “Shockley-Queisser Limit.” Future solar cells, also known as “Third Generation” solar cells, will have to surpass this limit while remaining inexpensive, requiring the use of new physical processes. Singlet fission is an example of such a process.

“Our research got its launch about ten years ago when we started thinking about and what new types of photophysics this might require,” said Christopher Bardeen, a professor of chemistry, whose lab led the research. “Global warming concerns and energy security have made an important subject from society’s point-of-view. More efficient solar cells would lead to wider use of this clean energy source.”

Research details

When a photon is absorbed, its energy takes the form of an exciton inside the material. Bardeen explained that excitons come in two “flavors,” defined by the electron spins in them. One flavor is singlet, where all spins are paired. The other flavor is triplet, where two electrons are unpaired. In organic semiconductors, these two types of excitons have different energies.

“If a triplet exciton has half the energy of a singlet, then it is possible for one singlet exciton, generated by one photon, to split into two triplet excitons,” Bardeen said. “Thus, you could have a 200 percent yield of excitons—and hopefully, electrons—per absorbed photon.”

He explained that the Shockley-Queisser Limit involves photon absorption to create an exciton, which is basically a bound electron (- charge) and hole (+ charge) pair. In order to get useful electron flow (photocurrent), these excitons must be dissociated. Ideally, one exciton produces one electron (hole) and thus current to run, say, a light bulb.

“To absorb a photon, the photon energy has to be greater than the bandgap of the semiconductor, so you already miss part of the solar spectrum,” Bardeen said. “But if you absorb a photon with energy higher than the bandgap, it has too much energy, and that excess energy is usually wasted as heat. The trick is to take that high energy exciton and split the into two excitons, rather than dissipating it as heat.”

Bardeen explained that the singlet exciton spontaneously splits into the two triplets, through a mechanism that is still under active investigation.

“The exact mechanism is unknown, but it does happen quickly—at the sub-nanosecond timescale—and with high efficiency,” he said. “Our work has shown that it is very sensitive to the alignment and position of the two molecules—at least two are required, since we have two excitons—involved in singlet fission. Recent work at MIT has already demonstrated an organic photovoltaic cell with more than 100 percent external quantum efficiency based on this effect. It may be possible to integrate this effect with inorganic semiconductors and use it to raise their efficiencies.”

Next, Bardeen’s lab will look for new materials that exhibit , figure out how to take the triplet excitons and turn them into photocurrent efficiently, and look at how the spin properties of the electrons affect the exciton dynamics.

Explore further: Two for one in solar power

2- sprayon solar scientistsdeScientists develop pioneering new spray-on solar cells

Aug 01, 2014

A team of scientists at the University of Sheffield are the first to fabricate perovskite solar cells using a spray-painting process – a discovery that could help cut the cost of solar electricity.

Published on Mar 4, 2013

A robot spray-coating glass with the polymer to create a solar cell. The technology could one day be used on glass in buildings and cars. For more information about our solar cell research visit http://www.sheffield.ac.uk/physics

Experts from the University’s Department of Physics and Astronomy and Department of Chemical and Biological Engineering have previously used the spray-painting method to produce solar cells using organic semiconductors – but using perovskite is a major step forward.

Efficient organometal halide perovskite based photovoltaics were first demonstrated in 2012. They are now a very promising new material for solar cells as they combine high efficiency with low materials costs.

The spray-painting process wastes very little of the perovskite material and can be scaled to high volume manufacturing – similar to applying paint to cars and graphic printing.

Lead researcher Professor David Lidzey said: “There is a lot of excitement around perovskite based photovoltaics.

“Remarkably, this class of material offers the potential to combine the high performance of mature solar cell technologies with the low embedded energy costs of production of organic photovoltaics.”

While most solar cells are manufactured using energy intensive materials like silicon, perovskites, by comparison, requires much less energy to make. By spray-painting the perovskite layer in air the team hope the overall energy used to make a solar cell can be reduced further.

Professor Lidzey said: “The best certified efficiencies from are around 10 per cent. “Perovskite cells now have efficiencies of up to 19 per cent. This is not so far behind that of silicon at 25 per cent – the material that dominates the world-wide solar market.”

He added: “The perovskite devices we have created still use similar structures to organic cells. What we have done is replace the key light absorbing layer – the organic layer – with a spray-painted perovskite. “Using a perovskite absorber instead of an organic absorber gives a significant boost in terms of efficiency.”

The Sheffield team found that by spray-painting the perovskite they could make prototype with efficiency of up to 11 per cent.

Professor Lidzey said: “This study advances existing work where the perovskite layer has been deposited from solution using laboratory scale techniques. It’s a significant step towards efficient, low-cost solar cell devices made using high volume roll-to-roll processing methods.”

Solar power is becoming an increasingly important component of the world-wide renewables energy market and continues to grow at a remarkable rate despite the difficult economic environment.

Professor Lidzey said: “I believe that new thin-film photovoltaic technologies are going to have an important role to play in driving the uptake of solar-, and that perovskite based cells are emerging as likely thin-film candidates. “

Explore further: A new stable and cost-cutting type of perovskite solar cell

1-newsolarcellNew “Dirt Cheap” Solar Cells

Sep 24, 2014

One of the most common complaints about solar power is solar panels are still too expensive to be worth the investment. Many researchers have responded by making solar cells, the tile-like components of solar panels that absorb and transfer energy, more efficient and longer lasting. But even the longest living solar cells that most effectively convert sunlight to energy will not become common if they are prohibitively expensive.

Therefore, Professor Yabing Qi, the head of the Energy Materials and Surface Sciences Unit at the Okinawa Institute of Science and Technology Graduate University, has a different idea: make solar cells using a type of semiconductor called perovskite materials, which are, in Qi’s words, “dirt cheap.” If solar cells are cheap enough, Qi reasons that people will want to use them for the immediate payback in energy savings.

Now Professor Qi and members of his research unit have developed a new method for making perovskite solar cells worthy of attention, and The Royal Society of Chemistry published their findings September 5, 2014 in their journal, Energy & Environmental Science.

Qi’s new method uses what he calls hybrid deposition to create , made from a mixture of inexpensive organic and inorganic raw materials. In addition, his solar cell is about a thousand times thinner than a silicon solar cell, and therefore uses far less material.

Qi estimates that for the same price, he could either buy raw materials to build 1000 square meters of his solar cell, or he could buy about 20 wafers of crystallized silicon, to build 0.16 square meters of traditional . “Silicon is not rare,” Qi explains, “but processing silicon requires expensive equipment and sophisticated steps demanding high temperature, vacuum, or high pressure, and that makes crystallized silicon very expensive.”

In contrast, the hybrid deposition process uses less energy to produce a solar cell at a far lower temperature. In fact, Qi envisions manufacturing the new solar cells using a low-cost printing process. The process would deposit the materials onto thin sheets of PET plastic very quickly to make large quantities of cheap solar cells. Qi does not yet know the limits of his hybrid cells, but optimists in his field hope that they could reach 20% efficiency. This means that that the solar cells will convert 20% of the energy they absorb from the sun into usable energy, which is comparable to the best silicon solar panels on the market.

The extremely thin perovskite cell that Qi and his lab designed measures merely 135 nanometers and reaches an efficiency of 9.9%. Because these films are semitransparent, Qi hopes to use them on windows, as a sort of lightweight set of blinds. “It will be a window and at the same time it will be a solar cell,” he says. “Some of the light could go through and the rest will be absorbed. Then, a certain percentage of the absorbed light will be converted to electricity.”

If solar cells are cheap enough, consumers will reap almost immediate benefits even if the are not the most efficient, because their savings on air conditioning and electricity will offset the expense.  “If it’s so cheap that it is like wallpaper, then you might as well use it,” said Qi. “It’s like a free gift. It’s an investment with a lot of payback.”

Explore further: Researchers use liquid inks to create better solar cells

1- solarhybridmateriHybrid Materials could Smash the Solar Efficiency Ceiling

October 9, 2014

A new method for transferring energy from organic to inorganic semiconductors could boost the efficiency of widely used inorganic solar cells.

Researchers have developed a new method for harvesting the energy carried by known as ‘dark’ spin-triplet excitons with close to 100% efficiency, clearing the way for hybrid solar cells which could far surpass current efficiency limits.

The team, from the University of Cambridge, have successfully harvested the energy of triplet excitons, an excited electron state whose energy in harvested in solar cells, and transferred it from organic to inorganic semiconductors. To date, this type of energy transfer had only been shown for spin-singlet excitons. The results are published in the journal Nature Materials.

In the natural world, excitons are a key part of photosynthesis: light photons are absorbed by pigments and generate excitons, which then carry the associated energy throughout the plant. The same process is at work in a solar cell.

In conventional semiconductors such as silicon, when one photon is absorbed it leads to the formation of one free electron that can be extracted as current. However, in pentacene, a type of organic semiconductor, the absorption of a photon leads to the formation of two electrons. But these electrons are not free and they are difficult to pin down, as they are bound up within ‘dark’ triplet exciton states.

Excitons come in two ‘flavours’: spin-singlet and spin-triplet. Spin-singlet excitons are ‘bright’ and their energy is relatively straightforward to harvest in solar cells. Triplet-spin excitons, in contrast, are ‘dark’, and the way in which the electrons spin makes it difficult to harvest the energy they carry.

“The key to making a better solar cell is to be able to extract the electrons from these dark triplet excitons,” said Maxim Tabachnyk of the University’s Cavendish Laboratory, the paper’s lead author. “If we can combine materials like pentacene with conventional semiconductors like silicon, it would allow us to break through the fundamental ceiling on the efficiency of solar cells.”

Using state-of-art femtosecond laser spectroscopy techniques, the team discovered that triplet excitons could be transferred directly into inorganic semiconductors, with a transfer efficiency of more than 95%. Once transferred to the inorganic material, the electrons from the triplets can be easily extracted.

“Combining the advantages of organic semiconductors, which are low cost and easily processable, with highly efficient inorganic , could enable us to further push the efficiency of inorganic solar cells, like those made of silicon,” said Dr Akshay Rao, who lead the team behind the work.

The team is now investigating how the discovered transfer of spin-triplet excitons can be extended to other organic/inorganic systems and are developing a cheap organic coating that could be used to boost the power conversion of silicon .

3-selforganizeSelf-Organized Indium Arsenide Quantum Dots for Solar Cells

Sep 25, 2014

Kouichi Yamaguchi is internationally recognized for his pioneering research on the fabrication and applications of ‘semiconducting quantum dots’ (QDs). “We exploit the ‘self-organization’ of semiconducting nanocrystals by the ‘Stranski-Krasnov (SK) mode of crystal growth for producing ordered, highly dense, and highly uniform quantum dots,” explains Yamaguchi. “Our ‘bottom-up’ approach yields much better results than the conventional photolithographic or ‘top-down’ methods widely used for the fabrication of nano-structures.”

Notably, electrons in quantum dot structures are confined inside nanometer sized three dimension boxes. Novel applications of ‘‘—including lasers, biological markers, qubits for quantum computing, and photovoltaic devices—arise from the unique opto-electronic properties of the QDs when irradiated with light or under external electromagnetic fields.

“Our main interest in QDs is for the fabrication of high efficiency ,” says Yamaguchi. “Step by step we have pushed the limits of ‘self-organization’ based growth of QDs and succeeded in producing highly ordered, ultra-high densities of QDs.”

The realization of an unprecedented QDs density of 5 x 1011 cm-2 in 2011 was one of the major milestones in the development of ‘‘ based semiconducting QDs for solar cells by Yamaguchi and his colleagues at the University of Electro-Communications (UEC). “This density was one of the critical advances for achieving high efficiency quantum dot based photo-voltaic devices,” says Yamaguchi.

Specifically, Yamaguchi and his group used molecular beam epitaxy (MBE) to grow a layer of InAs QDs with a density of 5 x 1011 cm-2 on GaAsSb/GaAs (100) substrates. Importantly, the breakthrough that yielded this high density of highly ordered QDs was the discovery that InAs growth at a relatively low substrate temperature of 470 degrees Celsius on Sb-irradiated GaAs layers suppressed coalescence or ‘ripening’ of InAs QDs that was observed at higher temperatures. Thus the combination of the Sb surfactant effect and lower growth temperature yielded InAs QDs with an average height of 2.02.5 nm.

Self-organized indium arsenide quantum dots for solar cells
                                              InAs QD density: 1.0×1012 cm-2

The potential for photovoltaic device applications was examined by sandwiching a single layer of InAs QDs in a pin-GaAs cell structure. The resulting external quantum efficiency of these solar cell structures in the 900 to 1150 nm wavelength range was higher than devices with the QD layer.

“Theoretical studies suggest QDs solar cells could yield conversion efficiencies over 50%,” explains Yamaguchi. “This is a very challenging target but we hope that our innovative approach will be an effective means of producing such QD based high performance solar cells. We have recently achieved InAs QDs with a density of 1 x 1012 cm-2.”

Self-organized indium arsenide quantum dots for solar cells

Variation of power conversion efficiency with quantum dot density (calculated results). Enlarge

3-QD Solar PhotoV improvinganeQuantum Dot Photovoltaics: A New Breed of Solar Cells: Setting New Records for Efficiency

May 28, 2014

Solar-cell technology has advanced rapidly, as hundreds of groups around the world pursue more than two dozen approaches using different materials, technologies, and approaches to improve efficiency and reduce costs.

Now a team at MIT has set a new record for the most efficient quantum-dot cells—a type of solar cell that is seen as especially promising because of its inherently low cost, versatility, and light weight.

While the overall efficiency of this cell is still low compared to other types—about 9 percent of the energy of sunlight is converted to electricity—the rate of improvement of this technology is one of the most rapid seen for a solar technology. The development is described in a paper, published in the journal Nature Materials, by MIT professors Moungi Bawendi and Vladimir Bulović and graduate students Chia-Hao Chuang and Patrick Brown.

The new process is an extension of work by Bawendi, the Lester Wolfe Professor of Chemistry, to produce quantum dots with precisely controllable characteristics—and as uniform thin coatings that can be applied to other materials. These minuscule particles are very effective at turning light into electricity, and vice versa. Since the first progress toward the use of quantum dots to make , Bawendi says, “The community, in the last few years, has started to understand better how these cells operate, and what the limitations are.”

The new work represents a significant leap in overcoming those limitations, increasing the current flow in the cells and thus boosting their overall efficiency in converting sunlight into electricity.

Many approaches to creating low-cost, large-area flexible and lightweight solar cells suffer from serious limitations—such as short operating lifetimes when exposed to air, or the need for high temperatures and vacuum chambers during production.

By contrast, the new process does not require an inert atmosphere or high temperatures to grow the active device layers, and the resulting cells show no degradation after more than five months of storage in air.

Bulović, the Fariborz Maseeh Professor of Emerging Technology and associate dean for innovation in MIT’s School of Engineering, explains that thin coatings of quantum dots “allow them to do what they do as individuals—to absorb light very well—but also work as a group, to transport charges.” This allows those charges to be collected at the edge of the film, where they can be harnessed to provide an electric current.

The new work brings together developments from several fields to push the technology to unprecedented efficiency for a quantum-dot based system: The paper’s four co-authors come from MIT’s departments of physics, chemistry, materials science and engineering, and electrical engineering and computer science. The solar cell produced by the team has now been added to the National Renewable Energy Laboratories’ listing of record-high efficiencies for each kind of solar-cell technology.

The overall efficiency of the cell is still lower than for most other types of solar cells. But Bulović points out, “Silicon had six decades to get where it is today, and even silicon hasn’t reached the theoretical limit yet. You can’t hope to have an entirely new technology beat an incumbent in just four years of development.” And the new technology has important advantages, notably a manufacturing process that is far less energy-intensive than other types.

Chuang adds, “Every part of the cell, except the electrodes for now, can be deposited at room temperature, in air, out of solution. It’s really unprecedented.”

The system is so new that it also has potential as a tool for basic research. “There’s a lot to learn about why it is so stable. There’s a lot more to be done, to use it as a testbed for physics, to see why the results are sometimes better than we expect,” Bulović says.

A companion paper, written by three members of the same team along with MIT’s Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering, and three others, appears this month in the journal ACS Nano, explaining in greater detail the science behind the strategy employed to reach this efficiency breakthrough.

The new work represents a turnaround for Bawendi, who had spent much of his career working with quantum dots. “I was somewhat of a skeptic four years ago,” he says. But his team’s research since then has clearly demonstrated ‘ potential in solar cells, he adds.

Arthur Nozik, a research professor in chemistry at the University of Colorado who was not involved in this research, says, “This result represents a significant advance for the applications of quantum-dot films and the technology of low-temperature, solution-processed, quantum-dot photovoltaic cells. … There is still a long way to go before quantum-dot solar cells are commercially viable, but this latest development is a nice step toward this ultimate goal.”

NIST: Technology – Entrepreneurship Showcase


NIST 580303_10152072709285365_1905986131_nAre you an inventor, entrepreneur, product developer, angel investor, scientist, engineer or post-doc in search of your future? Is your company looking for technology solutions to improve your products? Spend the day at the NIST Boulder Lab learning about new innovations and the resources available to help build businesses around them.

This event brings together innovative technologies, licensable inventions, research and engineering facilities, small business support resources at the Federal and state levels, and sources of funding—all under one roof, and all available for networking. This showcase is sponsored by the National Institute of Standards and Technology (NIST), National Oceanic and Atmospheric Administration (NOAA), the Colorado Manufacturers’ Edge (Manufacturing Extension Partnership) and the Colorado Office of Economic Development and International Trade.

The format of the showcase will include opening remarks by Congressman Jared Polis, brief morning presentations of NIST and NOAA research capabilities and commercially-viable inventions. Speakers will be available following their presentations as their time permits for networking with interested attendees to explore licensing and collaboration opportunities—no appointments necessary. For those identifying collaboration opportunities, NIST’s and NOAA’s CRADA and licensing experts will be available to advise and demystify the process of collaborating with Federal agencies. Over lunch and into the afternoon, showcase sponsors will introduce the wide variety of resources available to support small and start-up businesses in the greater Denver-Boulder area and will also be available for ad hoc networking and consultation.

Start-ups as well as small and medium sized firms will:

  • Get clarity on rights to intellectual property that arises under government collaborations.
  • Gain insight on how interdisciplinary science and engineering can create new innovations.
  • Learn how local resources can connect you with the business, financing and manufacturing support you need to grow your business.

Agenda:

Security Instructions:

If you are not registered, you will not be allowed on site. Registered attendees will receive security and campus instructions prior to the workshop.

Effective July 21, 2014, under the REAL ID Act of 2005, federal agencies, including NIST, can only accept a state-issued driver’s license or identification card for access to federal facilities if issued by states that are REAL ID compliant or have an extension. Driver’s licenses from the following states and territories are not compliant with the Real ID Act of 2005 and will not be accepted as identification: Alaska, Arizona, Oklahoma, Louisiana, Massachusetts, Maine, and American Samoa. For more information, please visit this page >>

NON U.S. CITIZENS PLEASE NOTE: All foreign national visitors who do not have permanent resident status and who wish to register for the above meeting must supply additional information. Failure to provide this information prior to arrival will result, at a minimum, in significant delays (up to 24 hours) in entering the facility. Authority to gather this information is derived from United States Department of Commerce Department Administrative Order (DAO) number 207-12. When registration is open, the required NIST-1260 form will be available as well.

Details:

Start Date: Thursday, October 9, 2014
Location: Building 1, NIST Boulder, 325 Broadway, Boulder, CO 80305
Audience: Industry, Government, Academia
Format: Other

Sponsor(s):

 NIST logo

Registration:

$26 registration fee. Registration will close COB October 6, 2014. All attendees must be pre-registered to gain entry to the NIST campus. Photo identification must be presented at the main gate to be admitted to the conference. International attendees are required to present a passport. Attendees must wear their conference badge at all times while on the campus. There is no on-site registration for meetings held at NIST.

Registration Contact:

Teresa Vicente, 301-975-3883

Accommodations:

Technical Contact:

Jack Pevenstein, 301-975-5519

Scientists improve microscopic batteries with homebuilt imaging analysis


Nano forest nistscientisIn a rare case of having their cake and eating it too, scientists from the National Institute of Standards and Technology (NIST) and other institutions have developed a toolset that allows them to explore the complex interior of tiny, multi-layered batteries they devised. It provides insight into the batteries’ performance without destroying them—resulting in both a useful probe for scientists and a potential power source for micromachines.

The microscopic lithium-ion batteries are created by taking a silicon wire a few micrometers long and covering it in successive layers of different materials. Instead of a cake, however, each finished looks more like a tiny tree.NIST 580303_10152072709285365_1905986131_n

The analogy becomes obvious when you see the batteries attached by their roots to and clustered together by the million into “nanoforests,” as the team dubs them.

But it’s the cake-like layers that enable the batteries to store and discharge electricity, and even be recharged. These talents could make them valuable for powering autonomous MEMS – microelectromechanical machines – which have potentially revolutionary applications in many fields.

With so many layers that can vary in thickness, morphology and other parameters, it’s crucial to know the best way to build each layer to enhance the battery’s performance, as the team found in previous research.** But conventional (TEM) couldn’t provide all the details needed, so the team created a new technique that involved multimode scanning TEM (STEM) imaging. With STEM, electrons illuminate the battery, which scatters them at a wide range of angles. To see as much detail as possible, the team decided to use a set of electron detectors to collect electrons in a wide range of scattering angles, an arrangement that gave them plenty of structural information to assemble a clear picture of the battery’s interior, down to the nanoscale level.

NIST scientists improve microscopic batteries with homebuilt imaging analysis
                                   A STEM image of an individual battery. Credit: Oleshko/NIST

The promising toolset of techniques helped the researchers to home in on better ways to build the tiny batteries. “We had a lot of choices in what materials to deposit and in what thicknesses, and a lot of theories about what to do,” team member Vladimir Oleshko says. “But now, as a result of our analyses, we have direct evidence of the best approach.

NIST scientists improve microscopic batteries with homebuilt imaging analysis
     A colorized 3D side view of a same battery showing the metallized silicon core and its        

outer layers. Credit: Oleshko/NIST

“MEMS manufacturers could make use of the batteries themselves, a million of which can be fabricated on a square centimeter of a silicon wafer. But the same manufacturers also could benefit from the team’s analytical toolset. Oleshko points out that the young, rapidly emerging field of additive manufacturing, which creates devices by building up component materials layer by layer, often needs to analyze its creations in a noninvasive way. For that job, the team’s approach might take the cake.

Explore further: Toward making lithium-sulfur batteries a commercial reality for a bigger energy punch

More information: V.P. Oleshko, T. Lam, D. Ruzmetov, P. Haney, H.J. Lezec, A.V. Davydov, S.Krylyuk, J.Cumings and A.A. Talin. “Miniature all-solid-state heterostructure nanowire Li-ion batteries as a tool for engineering and structural diagnostics of nanoscale electrochemical processes.” Nanoscale, DOI: 0.1039/c4nr01666a, Aug. 15, 2014.

JILA Team Finds First Direct Evidence of ‘Spin Symmetry’ In Atoms: NIST Tech


NIST Atom Spin 14PML029_spin_symmetry_LRJust as diamonds with perfect symmetry may be unusually brilliant jewels, the quantum world has a symmetrical splendor of high scientific value.

Confirming this exotic quantum physics theory, JILA physicists led by theorist Ana Maria Rey and experimentalist Jun Ye have observed the first direct evidence of symmetry in the magnetic properties—or nuclear “spins”—of atoms. The advance could spin off practical benefits such as the ability to simulate and better understand exotic materials exhibiting phenomena such as superconductivity (electrical flow without resistance) and colossal magneto-resistance (drastic change in electrical flow in the presence of a magnetic field).

spin symmetry

Illustration of symmetry in the magnetic properties—or nuclear spins—of strontium atoms. JILA researchers observed that if two atoms have the same nuclear spin state (top), they interact weakly, and the interaction strength does not depend on which of the 10 possible nuclear spin states are involved. If the atoms have different nuclear spin states (bottom), they interact much more strongly, and, again, always with the same strength.
Credit: Ye and Rey groups and Steve Burrows/JILA
View hi-resolution image

The JILA discovery, described in Science Express,* was made possible by the ultra-stable laser used to measure properties of the world’s most precise and stable atomic clock.** JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder.NIST 580303_10152072709285365_1905986131_n

“Spin symmetry has a very strong impact on materials science, as it can give rise to unexpected behaviors in quantum matter,” JILA/NIST Fellow Jun Ye says. “Because our clock is this good—really it’s the laser that’s this good—we can probe this interaction and its underlying symmetry, which is at a very small energy scale.”

The global quest to document quantum symmetry looks at whether key properties remain the same despite various exchanges, rotations or reflections. For example, matter and antimatter demonstrate fundamental symmetry: Antimatter behaves in many respects like normal matter despite having the charges of positrons and electrons reversed.

To detect spin symmetry, JILA researchers used an atomic clock made of 600 to 3,000 strontium atoms trapped by laser light. Strontium atoms have 10 possible nuclear spin configurations (also referred to as angular momentum), which influences magnetic behavior. In a collection of clock atoms there is a random distribution of all 10 states.

The researchers analyzed how atom interactions—their collisions—at the two electronic energy levels used as the clock “ticks” were affected by the spin state of the atoms’ nuclei. In most atoms, the electronic and nuclear spin states are coupled, so atom collisions depend on both electronic and nuclear states. But in strontium, the JILA team predicted and confirmed that this coupling vanishes, giving rise to collisions that are independent of nuclear spin states.

In the clock, all the atoms tend to be in identical electronic states. Using lasers and magnetic fields to manipulate the nuclear spins, the JILA researchers observed that, when two atoms have different nuclear spin states, no matter which of the 10 states they have, they will interact (collide) with the same strength. However, when two atoms have the same nuclear spin state, regardless of what that state is, they will interact much more weakly.

“Spin symmetry here means atom interactions, at their most basic level, are independent of their nuclear spin states,” Ye explains. “However, the intriguing part is that while the nuclear spin does not participate directly in the electronic-mediated interaction process, it still controls how atoms approach each other physically. This means that, by controlling the nuclear spins of two atoms to be the same or different, we can control interactions, or collisions.”

The new research adds to understanding of atom collisions in atomic clocks documented in previous JILA studies.*** Further research is planned to engineer specific spin conditions to explore novel quantum dynamics of a large collection of atoms.

JILA theorist Ana Maria Rey made key predictions and calculations for the study. Theorists at the University of Innsbruck in Austria and the University of Delaware also contributed. Funding was provided by NIST, the National Science Foundation, the Air Force Office of Scientific Research, and the Defense Advanced Research Projects Agency.

*X. Zhang, M. Bishof, S.L. Bromley, C.V. Kraus, M.S. Safronova, P. Zoller, A.M. Rey, J. Ye. Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism. Science Express. Published online Aug. 21, 2104.
**See Jan. 22, 2014, Tech Beat article, “JILA Strontium Atomic Clock Sets New Records in Both Precision and Stability,” at www.nist.gov/pml/div689/20140122_strontium.cfm.
***See 2011 NIST news release “Quantum Quirk: JILA Scientists Pack Atoms Together to Prevent Collisions in Atomic Clock,” at www.nist.gov/pml/div689/jila-020311.cfm; and 2009 NIST news release “JILA/NIST Scientists Get a Grip on Colliding Fermions to Enhance Atomic Clock Accuracy,” at www.nist.gov/pml/div689/fermions_041609.cfm.

Genesis Nanotech Headlines Are Out!


Organ on a chip organx250Genesis Nanotech Headlines Are Out! Read All About It!

https://paper.li/GenesisNanoTech/1354215819#!headlines

Visit Our Website: www.genesisnanotech.com

Visit/ Post on Our Blog: https://genesisnanotech.wordpress.com

 

SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA

Chairman Terry: “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development.”

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:

“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”

 

 

electron-tomography

“Great Things from Small Things!” … We Couldn’t Agree More!