Do You Know Nano?

The Project on Emerging Nanotechnologies is a fast-paced science policy group within the Woodrow Wilson International Center for Scholars in Washington, DC. The Project serves as a neutral, nonpartisan forum for study, discussion, and debate of the issues surrounding nanotechnology policy. The Project has become a reference point for information and analysis of these issues as it strives to bring the voices of policymakers, industry, and academia together to promote a fair and rational consideration of the risks and benefits of nanotechnology.

The Project is seeking qualified interns for Fall/Winter 2009. The Project’s internship program provides graduate and undergraduate level students an exciting opportunity to work the world of science policy and learn about the rapidly expanding field of nanotechnology. Past interns have worked with former officials of the EPA, FDA, and NIOSH on analyses of research and regulatory priorities at those agencies, and helped coordinate focus groups and national polls, prepare congressional testimony, compile the largest and most comprehensive database available of consumer products containing nanotechnologies—and worked on many other projects. For more information on the internship program at the Project on Emerging Nanotechnologies, please see the Intern Position Announcement. Questions? Email nano@wilsoncenter.org with Intern in the subject line. Applications are due by August 22, 2009.

findNano App Puts Nanotech in Your Pocket

WASHINGTON – The Project on Emerging Nanotechnologies (PEN) has developed findNano, an application for Apple’s iPhone and iPod Touch that lets users discover and determine whether consumer products are nanotechnology-enabled. Nanotechnology, the emerging technology of using materials by engineering them at an incredibly small scale, has applications ranging from consumer electronics to improved drug delivery systems.

findNano allows users to browse an inventory of more than 1,000 nanotechnology-enabled consumer products, from sporting goods to food products and electronics to toys, using the iPhone and iPod Touch. Using the built-in camera, iPhone users can even submit new nanotech products to be included in future inventory updates.

The new application makes PEN’s unique Consumer Products Inventory more accessible for today’s consumers. The inventory, which was launched in 2006, is the leading source of information on manufacturer-identified nanotechnology consumer products around the world.

“The Consumer Products Inventory provides valuable insight into the world of nanotech consumer products, and now it’s even easier to access because of findNano,” says PEN Research Associate Patrick Polischuk. “This innovative tool satisfies the needs of citizen scientists, tech-savvy consumers, and those who are merely curious about whether products contain nanomaterials.”

The number of nanotech products in the inventory has risen from approximately 200 in 2006 to more than 1,000 today. But this is most likely an underestimate of the number of products using nanotechnology available worldwide. To help develop better estimates of the number of nano-based products in commerce, the iPhone app allows users to submit information on new products, including product name and where the product can be purchased.

Using findNano, users can take or select a photo of a possible nanotech product and submit it for inclusion in the PEN inventory. This feature will help consumers, researchers, and policymakers determine how—and where—nanotechnologies are entering the marketplace.

findNano is available as a free download for the iPhone and iPod Touch, and can be found in the iTunes App Store or at nanotechproject.org/iphone.

Reinventing Technology Assessment for the 21st Century

WASHINGTON—A new report from the Science and Technology Innovation Program at the Woodrow Wilson International Center for Scholars defines the criteria for a new technology assessment function in the United States. The report, Reinventing Technology Assessment: A 21st Century Model, emphasizes the need to incorporate citizen-participation methods to complement expert analysis. Government policymakers, businesses, non-governmental organizations, and citizens need such analysis to capably navigate the technology-intensive world in which we now live.

The U.S. Congress set a global precedent in 1972 when it created an Office of Technology Assessment (OTA), but then reversed course in 1995 by shutting down the OTA. In the meantime, 18 European Technology Assessment agencies are flourishing and have pioneered important new methods, including Participatory Technology Assessment (pTA). By educating and engaging laypeople, pTA is unique in enabling decision-makers to learn their constituents’ informed views regarding emerging developments in science and technology. pTA also deepens the social and ethical analysis of technology. European pTA methods have been adapted, tested, and proven in the U.S. at least 16 times by university-based groups and independent nonprofit organizations.

“We style ourselves as living in a ‘technological society’ and an ‘information age,’” notes report author Dr. Richard Sclove, “yet we lack adequate information about – of all things! – the broad implications of science and technology.”

As the pace of technological change quickens and the Obama Administration moves forward on its Open Government Initiative, the time is ripe to institutionalize a robust national TA capability incorporating both expert and participatory TA methods. The Internet and social networking capacities make it possible to organize such an endeavor on a distributed, agile and open basis, harnessing collaborative efficiencies and supporting broad public engagement.

“In the 15 years since OTA was closed, TA has progressed significantly in Europe. It is time for the U.S. to institutionalize a serious, continuous and nonpartisan capability to assess the broad social, ethical, legal, and economic impacts of emerging science and technology in areas such as nanotechnology, biotechnology, and earth systems engineering,” said David Rejeski, who directs the Wilson Center program.

In the report, Dr. Sclove recommends creating a nationwide Expert & Citizen Assessment of Science & Technology (ECAST) network that will combine the skills of nonpartisan policy research organizations with the research strengths of universities and the public outreach and education capabilities of science museums. Founding partners in ECAST include the Science and Technology Innovation Program at the Wilson Center,, the Boston Museum of Science, Arizona State University, ScienceCheerleader, and the Loka Institute.

Report author Richard Sclove, Ph.D. is founder and senior fellow of the Loka Institute, a nonprofit organization dedicated to making science and technology responsive to democratically decided priorities.

The report can be downloaded at http://www.wilsoncenter.org/techassessment

Nanotech-enabled Consumer Products Top the 1,000 Mark

Over 1,000 nanotechnology-enabled products have been made available to consumers around the world, according to the Project on Emerging Nanotechnologies (PEN). The most recent update to the group’s three-and-a-half-year-old inventory reflects the increasing use of the tiny particles in everything from conventional products like non-stick cookware and lighter, stronger tennis racquets, to more unique items such as wearable sensors that monitor posture.

“The use of nanotechnology in consumer products continues to grow rapidly,” says PEN Director David Rejeski. “When we launched the inventory in March 2006 we only had 212 products. If the introduction of new products continues at the present rate, the number of products listed in the inventory will reach close to 1,600 within the next two years. This will provide significant oversight challenges for agencies like the Food and Drug Administration and Consumer Product Safety Commission, which often lack any mechanisms to identify nanotech products before they enter the marketplace.”

Health and fitness items continue to dominate the PEN inventory, representing 60 percent of products listed. More products are based on nanoscale silver—used for its antimicrobial properties—than any other nanomaterial; 259 products (26 percent of the inventory) use silver nanoparticles. The updated inventory represents products from over 24 countries, including the US, China, Canada, and Germany. This update also identifies products that were previously available, but for which there is no current information.

The release of the updated inventory coincides with a public hearing on the agenda and priorities of the Consumer Product Safety Commission (CPSC) where project director David Rejeski testified. The CPSC, with a staff of fewer than 400 employees, oversees the safety of 15,000 types of consumer products.

Andrew Maynard, chief science advisor for PEN, noted that “the CPSC deserves credit for focusing on nanotechnologies. The resources available to the agency to address health and safety issues are negligible compared to the over $1.5 billion federal investment in nanotechnology research and development.”

The inventory is available at http://www.nanotechproject.org/inventories/consumer/

The PEN consumer products inventory includes products that have been identified by their manufacturer or a credible source as being nanotechnology-based. This update identifies products that were previously sold, but which may no longer be available. It remains the most comprehensive and widely used source of information on nanotechnology-enabled consumer products in the world.

Download project director David Rejeski’s testimony before the CPSC here.

nanoscience and nanotechnology

Nanoscience, nanotechnology, or nanotech, are all used to describe the same dynamic new field of applied science. Simply put, nanotechnology is the study and development of components measuring 100 nanometers (one billionth of a meter) or less. At these dimensions, matter begins to exhibit different characteristics. Aluminum explodes on contact with the air. Carbon can become a one-dimensional material, and conduct electricity better than copper.

The concept of nanoscience was first broached by Dr. Richard Feynman, a Nobel Prize-winning physicist who helped develop the atom bomb and did much to make physics popularly comprehensible through a series of lectures and books. In a 1959 speech that speculated on the immense potential of a conflux between biology and manufacturing, Dr. Feynman described the intricacy with which biological cells manufacture substances in natural bodies, and challenged his audience to “consider the possibility that we, too, can make a thing very small, which does what we want—that we can manufacture an object that maneuvers at that level.”

The actual word “nanotechnology” was coined by Tokyo Science University Professor Norio Taniguchi in 1974, to describe the manufacture of materials with at the level of a billionth of a meter. The term was popularized by controversial researcher Dr. K. Eric Drexler in a book that proposed the idea of manufacturing an “assembler” of nanoscale matter.

The applications of nanotechnology have been both expansive and prosaic. The implications, however, are still under scrutiny. While it is exciting to see products of startling efficiency and low cost result from this technology, and to speculate on the near possibility of cures for cancer, further research is essential to development this emergent technology in its most beneficial form possible.

Biotechnology Companies

Biotechnology is a practice as simple, and as ancient, as brewing beer or making cheese. In a practical sense, biotechnology is nothing more than humans putting to use the natural activity of microorganisms. But in the last twenty years, biotechnology has become one of the world’s most rapidly growing industries, as researchers dig out the ever unfolding capabilities of a single cell.

The preponderance of biotechnology companies are focused on medical science. These corporations not only produce medication, but also do heavy research into the environmental and genetic factors for disease. Their focus on disease prevention powers them forward in the medical business, and the top biotechnology companies may well outpace their pharmaceutical counterparts in as little as five years.

Biotechnology companies also plays a part in environmental science. By manipulating materials at the cellular level, solar energy companies produce receptors that will in time eliminate the need for fuel-based electricity. Similarly, genetic engineering has produced oil-utilizing microorganisms that can be spread over the surface of oceanic oil spills, simplifying the clean-up and the restoration of the ecosystem. Biofertilizers and disease-resistant plants are being developed to replace the toxic chemical pesticides used in conventional agriculture.

The intricacy of cellular function also serves as a model for improving existing industrial processes. Biotechnology has been the key to streamlining chemical manufacturing, decreasing water usage and waste generation in industry, and finding uses for traditional industrial waste.

Nanotechnology in Medicine

Nanoscience has, since its conception, been intertwined with medical research. The science is based on the replication and substance manufacturing of cells. Nanotechnology began as an endeavor to mimic the cell’s amazing self-sufficiency, and has since become an industry that strives to improve existing products in every sector through the manipulation of matter on the cellular level. This is most poignantly seen in the application of nanotechnology back to the medical field, where it began.

In one such application, nanoparticles of substances such as heat, light, or drugs, are engineered to have an attraction to diseased cells. This allows for direct treatment of diseased cells with minimal damage to healthy cells.

There is ongoing research, testing the efficacy of delivering chemotherapy drugs via nanoparticles directly to cancer cells.

Another example is the activation of nanoparticles by x-rays, to generate cancer-destroying electrons. This application would replace radiation therapy and circumvent its disastrous effects on the body’s healthy tissue.

Other developments include the use of nanoparticles to stimulate the production of cartilage in damaged joints, or the immune response against viruses.

Disease prevention is another important use of nanotechnology in medicine. Quantum Dots, an application still in its testing phase, may be used for finding cancerous tumors and for performing diagnostic tests. Nanocrystalline silver is one of the earliest forms of medical nanotechnology, used as an antimicrobial wound treatment.

Finally, nanotechnology is making vast improvements in the tools that physicians and medical scientists depend upon. From high-powered microscopes and imaging technology, to refined surgery implements, nanotechnology makes for cleaner, faster and more precise medicine.

Nanotechnology Investment

“Long-term, nanotech has the potential to be as significant as the steam engine, the transistor and the Internet.” (Tom Kalil, former Deputy Assistant to President Clinton for Technology and Economic Policy)

Since its conceptual debut in 1959, nanotechnology has promised an amazing wealth of potential. The possibilities it suggests for uses as noble as space travel, to as mundane as car manufacturing, make it a front-running candidate for public and private investment.

The practical similarities of nanotechnology to biotechnology mirror their commercial paths, as nanotechnology allows similar strategies toward commercialization and investment opportunities.

In only the last ten years, initiatives such as the National Nanotechnology Initiative and the European Union Framework for Nanotechnology set the precedent in the western world for government funding in nanotechnology research. According to a study completed by Lux Research in 2004, the United States is putting more money into nanotechnology than any other country.

However, Asian companies are close behind, with such countries as Taiwan and South Korea bending their efforts toward the development of actual products improved by nanotechnology, such as magnetoresistive RAM, and display consoles for computer and television lighted by carbon nanotubes. Indeed, nanotechnology has launched a new friendly competition among nations, similar to the international space race of the middle 20th century.

Investing in Nanotechnology

“Long-term, nanotech has the potential to be as significant as the steam engine, the transistor and the Internet.” (Tom Kalil, former Deputy Assistant to President Clinton for Technology and Economic Policy)

Since its conceptual debut in 1959, nanotechnology has promised an staggering wealth of potential. The possibilities it suggests for uses as noble as space travel, to as mundane as car manufacturing, make it a front-running candidate for investment.

There are a variety of ways to invest in nanotechnology including stocks of individual research companies, mutual funds weighted toward nanotechnology, and more recently an ETF which also seeks to track the value of the nanotechnology sector. Each of these investment vehicles is different and you are encouraged to research them to find the one that best fits your strategy.

The exciting trajectory and the spectrum of possibilities for nanotechnology has inspired a great number of small companies, who capitalize on the United States government’s interest in leading the world in this field. Additionally, many large companies are spawning smaller ones in an effort to focus their expertise onto manageable projects.

In itself, nanotechnology is an intriguing opportunity for the investor. However, But its particular incarnations require thoughtful research into not only their potential, but also for the implications of their work.

New Biotech Companies

One of the hard hits of the recent economic recession has been the slow-down of private funding for biotechnology research and development. With a general haze of uncertainty hovering in the economic climate, comes an apprehensive attitude toward emergent industry. As consumers tighten their hold on limited resources, they adopt a wary approach toward what they view as unproven technology. And as the consumer goes, so also goes the venture capitalist. Consequently, sources of funding, especially for start-up and early-stage companies, have grown scarce in recent years.

Companies that persist in the face of this economic adversity have proven their creativity in avoiding the need for large amounts of capital. They have sought out standardized form licensing, with pre-established economic terms, to reduce the obstacles between technological discovery and the launch of research. Additionally, established biotech companies are beginning to partner with fledgling developers, licensing out a concept for development by the smaller company, which allows both companies to benefit from the resultant technology.

Finally, companies have focused on bringing prototypes of their technology only to the stage where it will attract the interest of large investors. This involves focusing efforts on the development of a specific, marketable product. The result of this focused development is exemplified in new biotech companies such as Allylix, a tiny firm in San Diego, CA that engineers fragrances at the molecular level to produce sought-after tastes and fragrances for beverages and perfumes at a fraction of the cost. The future will reveal companies, which will focus on treatments for cancer, infections, autoimmune diseases and new techniques in immunogen development.

Innovative solutions such as these are a benefit to the industry as a whole, as biotech companies set themselves to doing one thing well, rather than spreading their efforts unprofitably wide.

Biotech Companies

In the last twenty years, biotechnology has become one of the world’s most rapidly growing industries, as researchers dig out the ever unfolding capabilities of a single cell.

The preponderance of biotechnology companies are focused on medical science. Corporations such as
Amgen, Gilead Sciences, and Merck & Co. are the leaders in development of medicine production, refining synthetic therapeutics to greater effectiveness and reduced cost.

Other biotech companies, such as Geron and Heal Corporation, are primarily dedicated to investigating the environmental and genetic factors for disease.

It has been speculated that the top biotechnology companies may well outpace their pharmaceutical counterparts in as little as five years.

Biotech companies also play a part in repairing the environment and improving existing industrial processes. With innovations in solar energy, chemical manufacturing, agriculture, and waste repurposing, biotech companies put the intricacies of the natural cell to astonishing practical use.

Nanotechnology

Nanoscience, nanotechnology, or nanotech, are all used to describe the same dynamic new field of applied science. Simply put, nanotechnology is the study and development of components measuring 100 nanometers (one billionth of a meter) or less. At these dimensions, matter begins to exhibit different characteristics. Aluminum explodes on contact with the air. Carbon can become a one-dimensional material, and conduct electricity better than copper.

The applications of nanotechnology have been both expansive and prosaic. Nanocrystal quantum dots are being developed to provide efficient emission of laser light, which could pave the way for startling efficiency of computing, communications and remote sensing. One of the first commerical practices of nanotechnology was the development of nanocatalysts for important chemical reactions. Nanocatalysts are being developed with 100% selectivity, extremely high activity, low energy consumption, and long lifetimes, to replace expensive and frangible catalysts and speed the forward motion of scientific research.

In the more prosaic realm, nanotechnology has been applied to the automotive industry to produce cars with improved engine efficiency, lighter but stronger body materials, reduced environmental impact, even self-repairing materials for better economies.

The result of nanotechnology is already apparent on store shelves–we already see pants, shirts and bedsheets with nanostructure textile coatings that make them wrinkle-proof or stain-repellent.

Nanotechnology Companies Stock

The emergent industry of nanotechnology has grown exponentially in the past ten years, and the stock market has struggled to keep up. As nanotech companies proliferate, there is some confusion over what constitutes a nanotech stock.

For example, the ISE-CCM Nanotechnology Index defines a nanotech stock like this:

“Companies involved in the science and technology of building electronic circuits and devices from single atoms and molecules. Applications involve the intended ability to manipulate materials to fundamentally improve processes, materials, and devices on an ‘atomic’ scale.”
Meanwhile, Merrill Lynch states in its documentation:

“Our new criteria for inclusion in the index is companies that indicate in public documents that nanotechnology initiatives represent a significant component of their future business strategy. We believe this definition, although still subjective, is more objective than our previous criteria that companies must have a significant percentage of future profits tied to nanotech.”
The problem with any attempt at defining a nanotech stock is that one must start with defining the nanotech industry. Nanoscience affects many scientific fields, industries, markets and products.
A “pure” nanotech stock for instance would be a company that manufactures nanoparticles, and nothing else. But as nanotechnology is an applied science, the plurality of nanotech companies have a particular product in development toward which their technology is directed. For instance, chemical giants BASF or DuPont produce nanomaterials–should they not as easily qualify as a nanotech stock, as a nanobiotech company like Geron or Amgen? Or companies that take “pure” nanomaterials and use them to make parts for end products that are not nanotech-specific, such as stain-resistant fabric or enhanced computer displays.

In the end, it must be decided what percentage of a company’s revenues should come from nanotech before they become a nanotech stock?

The volatile state of the three major exchange-quoted nanotechnology stock indices reflects this uncertainty.
Starting in late 2005, all three would have outperformed the Dow Jones Industrial Average. But in June of 2006, stocks dropped by 5-10%, with no clear reason for the sudden reversal.

As might be expected by a new industry whose primary funding is directed into research and prototype development, it is best to look into nanotech stock as a long-term investment. Growth over the next several years is likely, but there are equally likely to be bumps along the way.

Nanotechnology Companies

Simply put, nanotechnology is the study and development of components measuring 100 nanometers (one billionth of a meter) or less. At these dimensions, matter begins to exhibit different characteristics. Aluminum explodes on contact with the air. Carbon can become a one-dimensional material, and conduct electricity better than copper.

In the past ten years, the applied sciences field has been proliferated with companies devoted to the research of nanotechnology’s potential, and the development of products that showcase its capabilities to improve upon natural matter. Large chemical and manufacturing concerns have established nanotechnology arms to refine their production and remain competitive in their market. Smaller entities, with the eager help of public funding, have proven themselves strong with focused, product-specific innovations that prove nanotechnology’s value under the scrutiny of investors.

Nonetheless, it should be unsurprising that the stock market’s reflection of the nanotech industry should be unsteady. Between the relative novelty of the nanotech field, the number of start-ups represented among nanotech companies, and the nearly worldwide economic recession, a fair amount of ebb and flow in the longevity of individual companies is a reasonable expectation.

But with so much still to be grasped, and with such staggering innovations as nanotech companies have already generated in common products–self-regenerating car paint, stain-resistant fabrics, chemotherapy treatments that target diseased cells in the human body–it is best to look into nanotech companies as a long-term investment in an undeniably burgeoning field.

Researchers create new high-performance fiber

Working in a multidisciplinary team that includes groups from other universities and the MER Corporation, Horacio Espinosa, James N. and Nancy J. Farley Professor in Manufacturing & Entrepreneurship at the McCormick School of Engineering and Applied Science, and his group have created a high performance fiber from carbon nanotubes and a polymer that is remarkably tough, strong, and resistant to failure. Using state-of-the-art in-situ electron microscopy testing methods, the group was able to test and examine the fibers at many different scales — from the nano scale up to the macro scale — which helped them understand just exactly how tiny interactions affect the material's performance. Their results were recently published in the journal ACS Nano.

"We want to create new-generation fibers that exhibit both superior strength and toughness," said Espinosa said. "A big issue in engineering fibers is that they are either strong or ductile — we want a fiber that is both. The fibers we fabricated show very high ductility and a very high toughness. They can absorb and dissipate large amounts of energy before failure. We also observed that the strength of the material stays very, very high, which has not been shown before. These fibers can be used for a wide variety of defense and aerospace applications."

The project is part of the Department of Defense's Multidisciplinary University Research Initiative (MURI) program, which supports research by teams of investigators that intersect more than one traditional science and engineering discipline. Espinosa and his collaborators received $7.5 million from the U.S. Army Research Office for the study of disruptive fibers, which could be used in bulletproof vests, parachutes, or composite materials used in vehicles, airplanes and satellites.

To create the new fiber, researchers began with carbon nanotubes —cylindrical-shaped carbon molecules, which individually have one of the highest strengths of any material in nature. When you bundle nanotubes together, however, they lose their strength — the tubes start to laterally slip between each other.

Working with the MER Corporation and using the corporation's CVD reactor, the team added a polymer to the nanotubes to bind them together, and then spun the resulting material into yarns. Then they tested the strength and failure rates of the material using in-situ SEM testing, which uses a powerful microscope to observe the deformation of materials under a scanning electron beam. This technology, which has only been available in the past few years, allows researchers to have extremely high resolution images of materials as they deform and fail and allows researchers to study materials on several different scales. They can examine individual bundles of nanotubes and the fiber as a whole.

"We learned on multiple scales how this material functions," said Tobin Filleter, a postdoctoral researcher in Espinosa's group. "We're going to need to understand how molecules function at these nanometer scales to engineer stronger and tougher fibers in the future."

The result is a material that is tougher than Kevlar — meaning it has a higher ability to absorb energy without breaking. But Kevlar is still stronger — meaning it has a higher resistance to failure. Next, researchers hope to continue to study how to engineer the interactions between carbon nanotube bundles and between the nanotubes within the bundle itself.

"Carbon nanotubes, the nanoscale building blocks of the developed yarns, are still 50 times stronger than the material we created," said Mohammad Naraghi, a postdoctoral researcher in Espinosa's group. "If we can better engineer the interactions between bundles, we can make the material stronger."

The group is currently looking at techniques — like covalently crosslinking tubes within bundles using high-energy electron radiation – to help better engineer those interactions.

Filleter and Naraghi said this work wouldn't have been possible without the interdisciplinary team that includes merging academia with industry.

"To work in an environment where we can trade information back and forth is a unique opportunity that will push the technology farther," Naraghi said. "MER has given us a unique raw material and a commercial perspective on the project. In turn, we provide the fundamental scientific understanding."

NASA engineers develop 'blacker than black' nanotubes (w/ Video)

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Principal Investigator John Hagopian developed a new nanotech-based material that is 10 times more effective than black paint used by instrument developers to absorb stray light, which can contaminate scientific data. The sample on the left is black paint typically used to suppress errant light in instruments; the sample on the right is the new nanotube material. Credit: Chris Gunn/NASA

The nanotech-based material now being developed by a team of 10 technologists at the NASA Goddard Space Flight Center in Greenbelt, Md., is a thin coating of multi-walled carbon nanotubes — tiny hollow tubes made of pure carbon about 10,000 times thinner than a strand of human hair. Nanotubes have a multitude of potential uses, particularly in electronics and advanced materials due to their unique electrical properties and extraordinary strength. But in this application, NASA is interested in using the technology to help suppress errant light that has a funny way of ricocheting off instrument components and contaminating measurements.

Better than Paint

"This is a technology that offers a lot of payback," said engineer Leroy Sparr, who is assessing its effectiveness on the Ocean Radiometer for Carbon Assessment (ORCA), a next-generation instrument that is designed to measure marine photosynthesis. "It's about 10 times better than black paint" typically used by NASA instrument designers to suppress stray light, he said.

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Multi-walled carbon nanotubes are tiny hollow tubes made of pure carbon about 10,000 times thinner than a strand of human hair. NASA is investigating their use to help suppress errant light that ricochets off instrument components and contaminates measurements. Credit: NASA

The technology works because of its super-absorption abilities. The nanotubes themselves are packed vertically much like a shag rug. The tiny gaps between the tubes absorb 99.5 percent of the light that hits them. In other words, very few photons are reflected off the carbon-nanotube coating, which means that stray light cannot reflect off surfaces and interfere with the light that scientists actually want to measure. The human eye sees the material as black because only a small fraction of light reflects off the material.

The team began working on the technology in 2007. Unbeknownst to the group, the New York-based Rensselaer Polytechnic Institute also had initiated a similar effort and announced in 2008 that its researchers had developed the darkest carbon nanotube-based material ever made — more than three times darker than the previous record.

"Our material isn't quite as dark as theirs," said John Hagopian, the principal investigator leading the development team. "But what we're developing is 10 times blacker than current NASA paints that suppress system stray light. Furthermore, it will be robust for space applications," he said.

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NASA's Goddard Space Flight Center has a team of scientists testing micro and nanotechnology to use on spacecraft. The goal is to reduce the reflection off the surface of instruments satellites so that the data does not get polluted by the scattered light. The carbon nanotubes that the team grows have proven to be 10 times better than the NASA Z306 paint, currently used on spacecraft instruments.

That is an important distinction, said Carl Stahle, assistant chief of technology for Goddard's Instrument Systems and Technology Division. Not all technology can be used in space because of the harsh environmental conditions encountered there. "That's the real strength of this effort," Stahle said. "The group is finding ways to apply new technology and fly it on our instruments."

Big Breakthrough

The breakthrough was the discovery of a highly adhesive underlayer material upon which to grow the carbon nanotubes, which are just a few tens of nanometers in diameter. To grow carbon nanotubes, materials scientists typically apply a catalyst layer of iron to an underlayer on the silicon substrate. They then heat the material in an oven to about 750° C (1,382° F). While heating, the material is bathed in carbon-containing feedstock gas.

Stephanie Getty, the materials scientist on Hagopian's team, varied the underlayer as well as the thickness of the catalyst materials to create carbon nanotubes that not only absorb light, but also remain fixed to the material upon which they are grown. As a result, they are more durable and less likely to scratch off. The team also has grown durable nanotube coatings on titanium, a better structural material for space use. The team now is fine-tuning production techniques to assure consistent quality and light-suppression capabilities, Hagopian said.

New Capabilities Added

Should the team prove the material's suitability in space, the material would provide real benefits to instrument developers, Hagopian added.

Currently, instrument developers apply black paint to baffles and other components to reduce stray light. Because reflectance tests have shown the coating to be more effective than paint, instrument developers could grow the carbon nanotubes on the components themselves, thereby simplifying instrument designs because fewer baffles would be required. To accommodate larger components, the team now is installing a six-inch furnace to grow nanotubes on components measuring up to five inches in diameter. And under a NASA R&D award, the team also is developing a separate technique to create sheets of nanotubes that could be applied to larger, non-conforming surfaces.

In addition to simplifying instrument design, the technology would allow scientists to gather hard-to-obtain measurements because of limitations in existing light-suppression techniques or to gather information about objects in high-contrast areas, including planets in orbit around other stars, Hagopian said.

The ORCA team, which is fabricating and aligning an instrument prototype, is the first to actually apply and test the technology. The instrument is the front-runner for the proposed Aerosol/Cloud/Ecosystems (ACE) mission and requires robust light-suppression technologies because more than 90 percent of the light gathered by the instrument comes from the atmosphere. Therefore, the team is looking for a technique to suppress the light so that it doesn't contaminate the faint signal the team needs to retrieve.

"It's been an issue with all the (ocean sensors) we've flown so far," said ORCA Principal Investigator Chuck McClain.

Working with the ORCA team, Hagopian's group grew the coating on a slit, the conduit through which all light will pass on ORCA. "Having an efficient absorber is critical and the nanotubes could provide the solution," McClain said. "Right now, it looks promising," Sparr added. "If I can support them and they can continue advancing the technology so that it can be applied to other spacecraft components, it could be a very important development for NASA."

Goddard Chief Technologist Peter Hughes agrees, and, in fact, selected Hagopian and his team to receive his organization’s 2010 "Innovator of the Year" award. "Our job is to develop and advance new technology that will ultimately result in better scientific measurements. Goddard has a well-deserved reputation for creating technologies that enhance instrument performance because we are adept at quickly infusing emerging technology for specific spaceflight applications. John’s team demonstrated that key strength. And in doing so, he’s leading the way in NASA’s quest to bring about a new level of scientific discovery," Hughes said.

Light touch brightens nanotubes (w/ Video)

Single-walled carbon nanotubes treated with ozone incorporate oxygen atoms that shift and intensify the nanotubes' near-infrared fluorescence emission. The discovery by Rice University scientists should lead to new uses of nanotubes in biomedicine and materials science. (Credit: Bruce Weisman/Rice University)

The Rice lab of researcher Bruce Weisman, a pioneer in nanotube spectroscopy, found that adding tiny amounts of ozone to batches of single-walled carbon nanotubes and exposing them to light decorates all the nanotubes with oxygen atoms and systematically changes their near-infrared fluorescence.

Chemical reactions on nanotube surfaces generally kill their limited natural fluorescence, Weisman said. But the new process actually enhances the intensity and shifts the wavelength.

He expects the breakthrough, reported online in the journal Science, to expand opportunities for biological and material uses of nanotubes, from the ability to track them in single cells to novel lasers.

Best of all, the process of making these bright nanotubes is incredibly easy -- "simple enough for a physical chemist to do," said Weisman, a physical chemist himself.

He and primary author Saunab Ghosh, a graduate student in his lab, discovered that a light touch was key. "We're not the first people to study the effects of ozone reacting with nanotubes," Weisman said. "That's been done for a number of years.

"But all the prior researchers used a heavy hand, with a lot of ozone exposure. When you do that, you destroy the favorable optical characteristics of the nanotube. It basically turns off the fluorescence. In our work we only add about one oxygen atom for 2,000-3,000 carbon atoms, a very tiny fraction."

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Ghosh and Weisman started with a suspension of nanotubes in water and added small amounts of gaseous or dissolved ozone. Then they exposed the sample to light. Even light from a plain desk lamp would do, they reported.

Most sections of the doped nanotubes remain pristine and absorb infrared light normally, forming excitons, quasiparticles that tend to hop back and forth along the tube -- until they encounter oxygen.

"An exciton can explore tens of thousands of carbon atoms during its lifetime," Weisman said. "The idea is that it can hop around enough to find one of these doping sites, and when it does, it tends to stay there, because it's energetically stable. It becomes trapped and emits light at a longer (red-shifted) wavelength.

"Essentially, most of the nanotube is turning into an antenna that absorbs light energy and funnels it to the doping site. We can make nanotubes in which 80 to 90 percent of the emission comes from doped sites," he said.

Lab tests found the doped nanotubes' fluorescent properties to be stable for months.

Weisman said treated nanotubes could be detected without using visible light. "Why does that matter? In biological detection, any time you excite at visible wavelengths, there's a little bit of background emission from the cells and from the tissues. By exciting instead in the infrared, we get rid of that problem," he said.

The researchers tested their ability to view doped nanotubes in a biological environment by adding them to cultures of human uterine adenocarcinoma cells. Later, images of the cells excited in the near-infrared showed single nanotubes shining brightly, whereas the same sample excited with visible light displayed a background haze that made the tubes much more difficult to spot.

His lab is refining the process of doping nanotubes, and Weisman has no doubt about their research potential. "There are many interesting scientific avenues to pursue," he said. "And if you want to see a single tube inside a cell, this is the best way to do it. The doped tubes can also be used for biodistribution studies.

"The nice thing is, this isn't an expensive or elaborate process," Weisman said. "Some reactions require days of work in the lab and transform only a small fraction of your starting material. But with this process, you can convert an entire nanotube sample very quickly."

Revealing the secrets of chemical bath deposition

November 26, 2010 By Mark Wolverton

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Photo above: Drexel University Ph.D. student Kevin McPeak prepares the microreactor for XANES spectroscopy at the MR-CAT 10-ID beamline. Inset: Scanning electron micrograph of ZnO nanowire array and in situ, time-resolved Zn K-edge XANES spectra of ZnO nanowire growth at 90 ?C showing transition from Zn(H2O)62+ to ZnO.

X-ray absorption near-edge structure (XANES) spectroscopy is well known as a versatile and powerful technique for examining the microstructure of everything from crystalline solids to amorphous materials, even liquids. Its extreme sensitivity also makes it an ideal tool for probing the kinetics of various chemical reactions in situ.

Experimenters utilizing the U.S. Department of Energy Office of Science’s Advanced Photon Source at Argonne recently demonstrated a new wrinkle for XANES that has opened a window on a poorly-understood technique for deposition of materials. These insights will encourage the development of better-controlled and more precise chemical synthesis techniques for semiconductor and other nanomaterial applications, and are valuable as a demonstration of the extension of XANES spectroscopy into other realms of experimentation.

While chemical bath deposition (CBD) is widely used in the laboratory and industry for the creation of thin films and nanostructures for semiconductors and photovoltaics, its actual molecular workings have remained something of a mystery. This has somewhat limited its utility, because precise tailoring of CBD products is not possible without a clear understanding and thus control of CBD mechanics. Scientists from Drexel University and the University of Notre Dame have obtained the first detailed look at how CBD operates at the molecular level, using XANES spectroscopy to witness in situ the formation of zinc oxide nanowires. The work was published in October 2010 in Chemistry of Materials.

CBD begins with a water solution with chemical precursors containing the components from which the desired film structure will be formed. But because the precursor chemical species tend to be very dilute within the solution, identifying and isolating them to monitor their activity during the deposition process has been a daunting challenge. “It’s very difficult to find experimental techniques that will allow you to assess the different things that you need to measure,” said principal investigator Jason Baxter of Drexel University. “This has led to some criticism of CBD for being too recipe-based, where it can be difficult to take one set of conditions and say what might happen elsewhere.” XANES proved to be the ideal window into the CBD process. “It gives you very high sensitivity so you can measure species that are very dilute,” Baxter said. “So we were able to look at CBD with a degree of accuracy that people could not achieve before.”

The researchers subjected a solution of zinc nitrate and HMTA (hexamethylenetetramine) to different temperatures and pressures inside a custom-built microreactor device to induce ZnO nanowire growth, observing the reactions with XANES spectroscopy at the Materials Research Collaborative Access Team (MR-CAT) beamline 10-ID at the Advanced Photon Source. Baxter points out a particular advantage of XANES for the current work: “It also has good enough time resolution that we could actually watch the reaction proceeding in time. Every minute we could take a new set of data and look at the kinetics of the reaction.”

One open question the researchers sought to address was the specific role of HMTA in the ZnO CBD process. Previous work had suggested that HMTA might break down into intermediate forms that provided the raw materials for the ZnO film, perhaps even binding to zinc ions in the solution, or that it might act simply as a pH buffer to facilitate the reactions.

This first in situ view afforded by the XANES technique demonstrated that HMTA decomposes slowly under heating, releasing hydroxide ions that react with zinc ions in the formation of ZnO. This slow release of hydroxides also has the effect of minimizing ZnO saturation and thus controlling the solution pH.

“HMTA releases the hydroxide at the appropriate rate, just at the borderline where you’re primarily growing zinc oxide on the substrate with minimal precipitation,” says Baxter.

The team observed the growth of ZnO nanowires from zinc nitrate and HMTA precursors at 90° C after two hours, with typical hexagonal cross-sections and diameters of 300-500 nm.

They also employed principal component analysis (PCA) techniques to obtain quantitative data on the observed species during the CBD process. This showed that the ZnO nanowire growth occurred through direct crystallization from the precursor materials without any long-lived intermediates. The pH buffering provided by the HMTA helps to avoid overabundant precipitation of ZnO in the solution, allowing the controlled growth of the nanowire structures.

These new insights into the mechanisms of CBD will encourage the development of better-controlled and more precise chemical synthesis techniques for semiconductor and other nanomaterial applications.

The work is also valuable as a demonstration of the extension of XANES spectroscopy into other realms.

“I think the more widely useful part of this paper is actually in the application of XANES spectroscopy to a new type of system,” said Baxter.

He and his team plan to extend their work to study other CBD chemistries and processes. “You can actually see what’s happening as it is growing,” he said. “It gives one a lot of information about the process. I think that’s the exciting part.”

More information: Bruce A. Bunker2, and Jason B. Baxter1, “In Situ X-ray Absorption Near-Edge Structure Spectroscopy of ZnO Nanowire Growth During Chemical Bath Deposition,” Chem. Mater. 22, 6162 (2010). DOI:10.1021/cm102155m

Provided by Argonne National Laboratory (news : web)

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A greener way to grow carbon nanotubes

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Graphic: Christine Daniloff

Given their size, strength and electrical properties, carbon nanotubes — tiny, hollow cylinders made of carbon atoms — hold promise for a range of applications in electronics, medicine and other fields. Despite industrial development of nanotubes in recent years, however, very little is known about how they form or the environmental impacts of their manufacture.

It turns out that one process commonly used to produce carbon nanotubes, or CNTs, may release several hundred tons of chemicals, including greenhouse gases and hazardous air pollutants, into the air each year. In a paper published last week on the ACS Nano website, the researchers report that in experiments, removing one step in that process — a step that involves heating carbon-based gases and adding key reactive “ingredients” — reduced emissions of harmful by-products at least tenfold and, in some cases, by a factor of 100. It also cut the amount of energy used in the process by half.

“We were able to do all of this and still have good CNT growth,” says Desiree Plata, who led the research between 2007 and 2009 as a doctoral student in MIT’s joint program with the Woods Hole Oceanographic Institution. Now a visiting assistant professor in MIT’s Departments of Aeronautics and Astronautics and Civil and Environmental Engineering (CEE), Plata collaborated on the paper with several MIT and University of Michigan researchers, including Philip Gschwend, Ford Professor of Engineering in CEE, and John Hart, a mechanical engineering professor at the University of Michigan. The study is part of a long-term effort to change the approach to material development so that environmental chemists work with the young CNT industry to develop methods to prevent or limit undesirable environmental consequences.

In their study, Plata and her colleagues analyzed a common CNT manufacturing process known as catalytic chemical vapor deposition. In this method, manufacturers combine hydrogen with a “feedstock gas,” such as methane, carbon monoxide or ethylene. They then heat the combination in a reactor that contains a metal catalyst like nickel or iron, which then forms CNTs. The problem is that once the CNTs form, unreacted compounds (up to 97 percent of the initial feedstock) are often released into the air.

Turning off the heat

In a custom-made laboratory-scale reactor, the researchers heated hydrogen and ethylene, which is commonly used in high-volume CNT manufacturing, and then delivered it to a metal catalyst. They found that more than 40 compounds formed, including greenhouse gases like methane and toxic air pollutants like benzene.

The researchers suspected that not all of those compounds were essential for growing CNTs, and they knew that heating the feedstock gas plays a critical role in creating the dangerous compounds. So they combined unheated ethylene and hydrogen with several of the 40 compounds, one by one, to see which combination of compounds led to the best growth. They observed that certain alkynes, or molecules that have at least two carbon atoms stuck together with three distinct bonds, produced the best growth, while other compounds that are undesirable by-products, such as methane and benzene, did not.

Plata and her colleagues accomplished their dramatic reduction in both harmful emissions and energy consumption by impinging room-temperature alkynes, with ethylene and hydrogen, directly onto the metal catalyst, without heat. They also learned that they could reduce the amount of ethylene and hydrogen used by about 20 and 40 percent, respectively, and still achieve the same rate and quality of CNT growth. Plata says that while the results of lab experiments are hard to generalize, in a market that is expected to reach several billion dollars within several years, these changes could translate into “significant cost savings” for manufacturers.

Industry reaction

Although it’s too soon for manufacturers to adopt the method presented in the paper, David Lashmore, vice president and chief technology officer of Concord, N.H.-based Nanocomp Technologies, says the method is something his company is willing to try as it looks for ways to minimize the environmental effects of its production process. “This is of high interest to us and could have a broad impact on our process economics,” he says.

Plata points out that the MIT study analyzed only one of several feedstock gases used to make CNTs, and that the same analysis needs to be done for the others. But for her own part, she is now focusing on how CNTs form, trying to determine the precise interaction of the metal catalyst and the hydrocarbons in this process. Knowing the catalyst’s role could help researchers manipulate CNTs’ formation atom by atom — much more precisely than they can now, she says.
This story is republished courtesy of MIT News (http://web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Provided by Massachusetts Institute of Technology (news : web)

Scientists imitate nature to engineer nanofilms

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a, Schematic of PPX nanofilm deposition by OAP. b, Electron microscope cross-section of PPX nanofilm (insets show top view and high-resolution cross-section micrographs). c, Picture of the anisotropic adhesive wetting surface with water drops. d, Water adhesion and release in three configurations of the nanofilm. Schematics illustrate the nanorod inclination at each tilt angle and correspond to photographs showing the anisotropic wetting behaviour of the nanofilm. (Credit: Nature Materials)

In nature, water striders can walk on water, butterflies can shed water from their wings, and plants can trap insects and pollen. Scientists at the Naval Research Laboratory are part of a research team working to engineer surfaces that imitate some of these water repellency features found in nature.

This technology offers the possibility of significant advances for producing new generations of coatings that will be of great value for military, medical, and energy applications. The research is published in the December 2010 issue of Nature Materials.

Dr. Walter Dressick from NRL, working with Professor Melik Demirel of Penn State and Dr. Matthew Hancock of MIT, have collaborated to create an engineered water-repellant thin film. What sets this development apart from earlier technologies is that this newest film has the ability to control the directionality of liquid transport.

In this system, parylene nanorods are deposited on the surface by a simple, straightforward vapor deposition method. The single step usually takes less than 60 minutes, compared with the more complex, multi-step lithography processes often used in previous systems. This is the first time this kind of surface has been engineered at the nanoscale.

In the newly created surface, the nanorods that form the film are smooth on a micron scale. This size and smoothness in the posts means that when droplets are placed on the surface, they move without being distorted in any way. Also, they can be moved without pumps or optical waves. Previous systems caused the water droplets to be distorted, which could rupture, spill, or destroy the cargo in the droplet when used in medical or microassembly applications. As they continue the research, the team will focus on optimizing the droplet transport mechanism and tuning the preparation method.

Looking to the future, researchers are hopeful that this film could be used as a coating on the hull of ships where it would reduce the drag and slow the fouling. In industry applications, the film might have uses in directional syringes and fluid diodes, pump-free digital fluidic devices, increased efficiency of thermal cooling for microchips, and tire coatings.

Secrets of nanohair adhesion un-peeled by UA polymer scientists

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Fine hairs on the soles of gecko feet allow the lizards to climb vertical surfaces with ease. UA polymer researchers have discovered a synthetic glue (carbon nanotubes) with nearly four times the adhesion power of gecko hairs. Now the scientists reveal why the mimic version offers its remarkable staying power.

Not long after Dr. Ali Dhinojwala, chairman of The University of Akron Department of Polymer Science, unpeeled the secret (fine, clingy hairs) behind the remarkable adhesion of gecko feet, he and fellow researchers came up with a synthetic replica: carbon nanotubes. Now, five years after that initial discovery, the basis of the success of these nanotubes is published in the Oct. 12, 2010, issue of the American Chemical Society’s Nano Letters.

While the story of nanotubes is one of success, not all carbon nanotubes are equal, nor is the individual adhesion performance of each strand, according to Dhinojwala. Although Dhinojwala and UA polymer science graduate student Liehui Ge determined that these 8-nanometer-diameter carbon hairs — each 2,000 times smaller than the diameter of a human hair — adhere powerfully to glass and similar substrates, they furthered their research to learn why some strands have a firmer grip than others.

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Getting a grip on adhesion

Findings by the UA scientists, in collaboration with Lijie Ci and Anubha Goyal, researchers with the Department of Mechanical Engineering and Materials Science at Rice University; Rachel Shi, UA Research Experience for Undergraduates (REU) intern; and L. Mahadevan, professor of applied mathematics and professor of organismic and evolutionary biology at Harvard University, reveal that the softer the nanotube, the greater its adhesion.

Using a combination of mechanics, electrical resistance and scanning electron microscopy (SEM) to study the contact between hairs of a large number of vertically aligned carbon nanotubes with glass or silicon substrates, the researchers found that soft nanotubes clasp and curve when pressure is applied, contributing to their adhesive strength.

“We found out that the diameter of the tubes is an important parameter for adhesion because we have to balance the adhesion and bending rigidity of the tubes,” Ge says. “Also, if you apply a high pressure, the tubes bend and buckle and make a larger contact area with the surface, which is the reason for higher adhesion.”

The dry adhesive, unlike liquid glue counterparts, promises successful use in extreme atmospheric and temperature conditions and in other applications that present challenges.

“The carbon nanotube-based gecko adhesives are going to open up opportunities to using these materials on robots, to climb vertical walls, and could actually be used in outer space (vacuum condition) because these materials stick without any liquid glue,” Dhinojwala says.

Provided by University of Akron

New possibilities for solar energy with molecular 'stencils'

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This film of block copolymers shows the material's characteristic tendency to separate into distinct regions.

Scientists at the U.S. Department of Energy’s Argonne National Laboratory have begun to use molecular "stencils" to pave the way to new materials that could potentially find their way into future generations of solar cells, catalysts and photonic crystals.

Researchers at Argonne’s Center for Nanoscale Materials and Energy Systems Division have developed a technique known as sequential infiltration synthesis (SIS), which relies on the creation of self-assembled nanoscale chemical domains into which other materials can be grown. In this technique, a film composed of large molecules called block copolymers acts as a template for the creation of a highly-tunable patterned material.

This new method represents an extension of atomic layer deposition (ALD), a popular technique for materials synthesis that is routinely used by Argonne scientists. Instead of just layering two-dimensional films of different nanomaterials on top of one another, however, SIS allows scientists to construct materials that have much more complex geometries.

“This new technique allows us to create materials that just weren’t possible with ALD or block copolymers alone,” said Seth Darling, an Argonne nanoscientist who helped to develop SIS in collaboration with Argonne chemist Jeff Elam. “Having the ability to control the geometry of the material we’re making as well as its chemical composition opens the door to a whole universe of new materials.”

According to Darling, the success of the technique relies on the unique chemistry of block copolymers. Every block copolymer is composed of two chemically distinct subunits; for instance, one subunit might have an affinity for water while the other might repel water. In such a case, like would seek out like, creating a heterogeneous matrix of interspersed homogenous regions.

“You can think of a block copolymer as like a pair of molecular Siamese twins where one likes to talk and one likes to read quietly,” Darling said. “If you put a bunch of these twins together in a room, the talkative ones are going to try to be near the talkative ones and the readers are going to try to be near the readers, but they can’t simply all separate themselves to either side of the room, and it’s this action that gives us the geometries we’re looking for.”

Depending on the initial substrate, the block copolymers, and the processing that materials scientists use, regions can form that have many different shapes, from spherical to cylindrical to planar. While there are many types of block copolymers, in general they cannot serve as wide an array of purposes as inorganic materials. The challenge, according to Darling, is to bring the self-assembly of block copolymers together with the functionality of inorganic materials.

The physical and chemical properties of a material generated using SIS depend on how block copolymer chemistry and morphology interact with the chemistry of ALD techniques. “We can tailor our materials synthesis efforts in a much more precise way than we ever could before,” Darling said.

Darling and Elam have spent most of their careers at Argonne focused on the development of new types of materials, including the development of solar cells that combine organic and inorganic components. They believe that the types of materials that SIS can generate will drive fundamental solar energy technologies to greater efficiencies and lower cost.

“Our solar energy future does not have a one-size-fits-all solution,” Elam said. “We need to investigate the problem from many different angles with many different materials, and SIS will give researchers like us many new routes of attack.”

Provided by Argonne National Laboratory

DNA can act like Velcro for nanoparticles

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Argonne researcher Byeongdu Lee has determined that different shapes of gold nanoparticles, above and below, will self-assemble into different configurations when attached to single strands of DNA.

DNA can do more than direct how bodies our made -- it can also direct the composition of many kinds of materials, according to a new study from the U.S. Department of Energy’s Argonne National Laboratory.

Argonne researcher Byeongdu Lee and his colleagues at Northwestern University discovered that strands of DNA can act as a kind of nanoscopic "Velcro" that binds different nanoparticles together. "It’s generally difficult to precisely control the assembly of these types of nanostructures," Lee said. "By using DNA, we’re borrowing nature's power."

The "Velcro" effect of the DNA is caused by the molecule’s "sticky ends," which are regions of unpaired nucleotides — the building blocks of DNA — that are apt to bond chemically to their base-pair partners, just like in our genes. When sufficiently similar regions contact each other, chemical bonds form a rigid lattice. Scientists and engineers believe these complex nanostructures have the potential to form the basis of new plastics, electronics and fuels.

In 2008, Lee and his colleagues attached DNA to spherical nanoparticles made of gold, hoping to control the way the particles arrange themselves into compact, ordered crystals. This process is called nanoparticle "packing," and Lee believed that by affixing DNA to the nanoparticles, he could control how they packed together. "Materials that are packed differently — even if they are made from the same substance — have been shown to exhibit dramatically different physical and chemical properties," Lee said.

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While the 2008 experiment showed that DNA appeared to control that instance of nanosphere packing, it was not known whether the effect would occur with different nanoparticle geometries. The more recent experiment looked at different shapes of nanoparticles to determine whether their contours affected how they packed.

According to Lee, the spherical nanoparticles in the earlier experiment tended to arrange themselves into one of two separate types of cubic crystals: a face-centered cube (a simple cube with nanospheres at each vertex and additional ones located in the middle of each face) or a body-centered cube (a simple cube with an additional nanosphere located in the middle of the cube itself). The type of lattice that the nanoparticles formed was determined by how the "sticky ends" attached to the nanoparticles paired together.

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In the more recent experiment, the particles' shape did change the material's final structure, but only insofar as it altered how the DNA "sticky ends" attached to each other. In fact, the study showed that dodecahedral (12-sided) nanoparticles arranged into a face-centered cubic configuration while octahedral (8-sided) nanoparticles formed body-centered cubes — even when the nanoparticles were attached to identical strands of DNA. "We may be able to make all different types of nanoparticle packing structures, but the structure that will result will always be the one that maximizes the amount of binding," he said.

"The face-centered cubic structure is the most compact way for the nanoparticles to arrange themselves, while the body-centered cubic is slightly less compact. The DNA binding is really the true force controlling the construction of the lattice," he added.

More information: A paper based on the research, "DNA-nanoparticle superlattices formed from anisotropic building blocks", appeared in the October 3 issue of Nature Materials.

Provided by Argonne National Laboratory (news : web)

A new twist for nanopillar light collectors

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On the left a schematic of a germanium nanopillar array embedded in an alumina foil membrane; on the right are cross-sectional SEM images of a blank alumina membrane with dual-diameter pores; inset shows germanium nanopillars after growth. (Images courtesy of Ali Javey)

Sunlight represents the cleanest, greenest and far and away most abundant of all energy sources, and yet its potential remains woefully under-utilized. High costs have been a major deterrant to the large-scale applications of silicon-based solar cells. Nanopillars – densely packed nanoscale arrays of optically active semiconductors – have shown potential for providing a next generation of relatively cheap and scalable solar cells, but have been hampered by efficiency issues. The nanopillar story, however, has taken a new twist and the future for these materials now looks brighter than ever.

“By tuning the shape and geometry of highly ordered  nanopillar arrays of germanium or cadmium sulfide, we have been able to drastically enhance the optical absorption properties of our nanopillars,” says Ali Javey, a chemist who holds joint appointments with the Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley.

Javey, a faculty scientist with Berkeley Lab’s Materials Sciences Division and a UC Berkeley professor of electrical engineering and computer science, has been at the forefront of nanopillar research. He and his group were the first to demonstrate a technique by which cadmium sulfide nanopillars can be mass-produced in large-scale flexible modules. In this latest work, they were able to produce nanopillars that absorb light as well or even better than commercial thin-film solar cells, using far less semiconductor material and without the need for anti-reflective coating.

“To enhance the broad-band optical absorption efficiency of our nanopillars we used a novel dual-diameter structure that features a small (60 nanometers) diameter tip with minimal reflectance to allow more light in, and a large (130 nanometers) diameter base for maximal absorbtion to enable more light to be converted into electricity,” Javey says. “This dual-diameter structure absorbed 99-percent of incident visible light, compared to the 85 percent absorbtion by our earlier nanopillars, which had the same diameter along their entire length.”

Theoretical and experimental works have shown that 3-D arrays of semiconductor nanopillars – with well-defined diameter, length and pitch – excel at trapping light while using less than half the semiconductor material required for thin-film solar cells made of compound semiconductors, such as cadmium telluride, and about one-percent of the material used in solar cells made from bulk silicon. But until the work of Javey and his research group, fabricating such nanopillars was a complex and cumbersome procedure.

Javey and his colleagues fashioned their dual diameter nanopillars from molds they made in 2.5 millimeter-thick alumina foil. A two-step anodization process was used to create an array of one micrometer deep pores in the mold with dual diameters – narrow at the top and broad at the bottom. Gold particles were then deposited into the pores to catalyze the growth of the semiconductor nanopillars.

“This process enables fine control over geometry and shape of the single-crystalline nanopillar arrays, without the use of complex epitaxial and/or lithographic processes,” Javey says. “At a height of only two microns, our nanopillar arrays were able to absorb 99-percent of all photons ranging in wavelengths between 300 to 900 nanometers, without having to rely on any anti-reflective coatings.”

The germanium nanopillars can be tuned to absorb infrared photons for highly sensitive detectors, and the cadmium sulfide/telluride nanopillars are ideal for solar cells. The fabrication technique is so highly generic, Javey says,  it could be used with numerous other semiconductor materials as well for specific applications. Recently, he and his group demonstrated that the cross-sectional portion of the nanopillar arrays can also be tuned to assume specific shapes – square, rectangle or circle – simply by changing the shape of the template.

“This presents yet another degree of control in the optical absorption properties of nanopillars,” Javey says.

Javey’s dual-diameter nanopillar research was partially funded through the National Science Foundation’s Center of Integrated Nanomechanical Systems (COINS) and through Berkeley Lab LDRD funds.

More information: A paper describing this research appears on-line in the journal NANO Letters under the title “Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption.” Co-authoring the paper with Javey were Zhiyong Fan, Rehan Kapadia, Paul Leu,Xiaobo Zhang, Yu-Lun Chueh, Kuniharu Takei, Kyoungsik Yu, Arash Jamshidi, Asghar Rathore, Daniel Ruebusch and Ming Wu.

Provided by Lawrence Berkeley National Laboratory (news : web)

Fluorographene: The world's thinnest insulator

Kostya Novoselov and Andre Geim, working at the University of Manchester, UK, first isolated graphene in 2004. It was a tricky task, as one would expect if a Nobel Prize is among the rewards, even if it did involve using humble adhesive tape to peel away surfaces one layer at a time. They found graphene to be the thinnest and strongest form of carbon, and that it could conduct heat better than any other known material. As a conductor of electricity, it performs just as well as copper. Their most recent endeavours have led to a new derivative material that is just as strong and even more stable than the original graphene, but that does not conduct electricity at all: so-called fluorographene.

Graphene itself is a single atomic layer of the material graphite, commonly found in pencils. On a molecular level, it has a flat honeycomb structure of connecting hexagons with carbon atoms at the vertices. Clouds of electrons spread across the top and bottom surfaces, which is why the material conducts electricity so well.

The current achievement of the Manchester group, working closely with international collaborators, is to place a fluorine atom at every single carbon atom, thereby destroying the electron cloud and preventing electricity from flowing under normal conditions, but not impinging on the structural integrity of the carbon framework. In previous work, they had added hydrogen atoms instead of fluorine, but found the resulting material to be unstable at high temperatures.

The latest breakthrough is published this week in the journal Small. Rahul Raveendran-Nair is a postgraduate researcher at the University of Manchester and responsible for the publication. He describes fluorographene as “the thinnest possible insulator, made by attaching fluorine atoms to each of the carbon atoms in graphene. It is the first stoichiometric chemical derivative of graphene and it is a wide-gap semiconductor. Fluorographene is a mechanically strong and chemically and thermally stable compound. Properties of this new material are very similar to Teflon and we call this material 2D Teflon.”

Developing a suitable method for making this 2D Teflon was not simple. “Fluorine is a highly reactive element, and it reacts with all most everything. So the major challenge was to fully fluorinate graphene without damaging the graphene and its supporting substrates. Our fluorination of single-layer graphene membranes on chemically inert support grid and bulk graphene paper at elevated temperature overcomes this technical problem,” explains Raveendran-Nair.

The authors envisage that fluorographene will be used in electronics, but acknowledge that “for realistic electronic applications the electronic quality has to be improved. We hope this can be achieved very soon. Some possible electronic applications of fluorographene are its use as a tunnel barrier and as a high-quality insulator or barrier material for organic electronics.” Other fields of application are also possible. For example, as a wide-gap semiconductor that is fully transparent to visible light, fluorographene could well find use in LEDs (light-emitting diodes) and displays.

The Manchester group was not the only one involved, and collaborators from China (Shenyang National Laboratory for Materials Science), The Netherlands (Radboud University of Nijmegen), Poland (Institute of Electronic Materials Technology), and Russia (Nikolaev Institute of Inorganic Chemistry) added their expertise. According to Raveendran-Nair, having such a large team helped undertake a thorough investigation of fluorographene; “All of us worked very hard to make this project successful. We used a large variety of characterisation techniques and very detailed studies to understand the properties of this new material.”

During the course of the project the leaders were named as Nobel Laureates, but apparently life working in the group has not changed very much. “Even in their new busy life both professors still work very closely with all those in the group and are very much involved in the day-to-day research”, says Raveendran-Nair. “Working under them is a great inspiration. It is both a rewarding and enjoyable place to undertake research.”

Transparent conductive material could lead to power-generating windows

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Top: Scanning electron microscopy image and zoom of conjugated polymer (PPV) honeycomb. Bottom (left-to-right): Confocal fluorescence lifetime images of conjugated honeycomb, of polymer/fullerene honeycomb double layer and of polymer/fullerene honeycomb blend. Efficient charge transfer within the whole framework is observed in the case of polymer/fullerene honeycomb blend as a dramatic reduction in the fluorescence lifetime.

(PhysOrg.com) -- Scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and Los Alamos National Laboratory have fabricated transparent thin films capable of absorbing light and generating electric charge over a relatively large area. The material, described in the journal Chemistry of Materials, could be used to develop transparent solar panels or even windows that absorb solar energy to generate electricity.

The material consists of a semiconducting polymer doped with carbon-rich fullerenes. Under carefully controlled conditions, the material self-assembles to form a reproducible pattern of micron-size hexagon-shaped cells over a relatively large area (up to several millimeters).

"Though such honeycomb-patterned thin films have previously been made using conventional polymers like polystyrene, this is the first report of such a material that blends semiconductors and fullerenes to absorb light and efficiently generate charge and charge separation," said lead scientist Mircea Cotlet, a physical chemist at Brookhaven's Center for Functional Nanomaterials.

Furthermore, the material remains largely transparent because the polymer chains pack densely only at the edges of the hexagons, while remaining loosely packed and spread very thin across the centers. "The densely packed edges strongly absorb light and may also facilitate conducting electricity," Cotlet explained, "while the centers do not absorb much light and are relatively transparent."

"Combining these traits and achieving large-scale patterning could enable a wide range of practical applications, such as energy-generating solar windows, transparent solar panels, and new kinds of optical displays," said co-author Zhihua Xu, a materials scientist at the CFN.

"Imagine a house with windows made of this kind of material, which, combined with a solar roof, would cut its electricity costs significantly. This is pretty exciting," Cotlet said.

The scientists fabricated the honeycomb thin films by creating a flow of micrometer-size water droplets across a thin layer of the polymer/fullerene blend solution. These water droplets self-assembled into large arrays within the polymer solution. As the solvent completely evaporates, the polymer forms a hexagonal honeycomb pattern over a large area.

"This is a cost-effective method, with potential to be scaled up from the laboratory to industrial-scale production," Xu said.

The scientists verified the uniformity of the honeycomb structure with various scanning probe and electron microscopy techniques, and tested the optical properties and charge generation at various parts of the honeycomb structure (edges, centers, and nodes where individual cells connect) using time-resolved confocal fluorescence microscopy.

The scientists also found that the degree of polymer packing was determined by the rate of solvent evaporation, which in turn determines the rate of charge transport through the material.

"The slower the solvent evaporates, the more tightly packed the polymer, and the better the charge transport," Cotlet said.

"Our work provides a deeper understanding of the optical properties of the honeycomb structure. The next step will be to use these honeycomb thin films to fabricate transparent and flexible organic solar cells and other devices," he said.

Structure of new form of super-hard carbon identified

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Views along [100]/[001], and [010] directions of 2x2x2 supercell of bct-Carbon,the dotted-dashed in (b) indicate the perpendicular graphene-like structure of bct-Carbon. Image credit: Xiang-Feng Zhou, http://arxiv.org/PS_cache/arxiv/pdf/1003/1003.1569v4.pdf

(PhysOrg.com) -- An experiment in 2003 formed what was believed to be a new form of carbon, but the findings were controversial. Now two teams of scientists have used different means to identify a three-dimensional network structure called "bct-carbon," which they say could have been the structure formed in 2003.

Pure carbon exists in a variety of structures, including graphite and diamond. The new structure, body-centered tetragonal carbon or bct-carbon, is unexpectedly simple and consists of sheets of squares of four carbon atoms each, joined by “short” bonds perpendicular to the sheets. This form of carbon is created when graphite is exposed to high pressure at normal temperatures.

It has been known for nearly 50 years that graphite subjected to cold compression (high pressure at ambient temperatures) undergoes a transformation that is reversible, and in 2003 researchers at Stanford University compressed graphite in a diamond anvil press, while simultaneously obtaining the x-ray diffraction pattern to help them study the bonds within the structure. They found that when the pressure exceeded 17 gigapascals (GPa) (170,000 atmospheres) the carbon atoms in the normally soft graphite formed a material hard enough to crack diamond, but its structure remained unclear.

Now a team of scientists led by Hui-Tian Wang of Nankai University at Tianjin, China, have shown through computer simulations that the super-hard carbon may be at least partly composed of bct-carbon, since this takes the least energy to form. Bct-carbon has a structure part-way between diamond’s cubes of carbon atoms and graphite’s linked sheets of carbon atoms in a hexagonal lattice. Bct-carbon consists of sheets of four-atom carbon rings linked together by strong bonds.

The team studied 15 possible structures and found the transparent bct-carbon not only required lower energies to form but that its shear strength is 17 percent greater than diamond’s. If the results are confirmed, this means it may be possible to produce a material stronger than diamond at normal temperatures.

Another group of scientists, including Renata Wentzcovitch of the University of Minnesota and Takashi Miyake from the National Institute of Advanced Industrial Science and Technology in Japan, came to similar conclusions earlier this year, but by a different method. This group analyzed the proposed bct-carbon structure using quantum mechanical simulations. They found bct-carbon was more stable than graphite at 18.6 GPa, and that when mixed with M-carbon it would produce an x-ray diffraction pattern closely matched to that found in 2003. (M-carbon is a structure consisting of layers of carbon in rings of five and seven members.)

The paper from Hui-Tian Wang’s team was published in the journal Physical Review B, while the US/Japan research was reported in Physical Review Letters in March this year.

Berkeley lab scientists generate low-cost, hybrid thermoelectrics

November 8, 2010 by Aditi Risbud

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Using simple water-based chemistry to wrap a polymer that conducts electricity around a nanorod of tellurium, this composite nanoscale thermoelectric is easily spin cast or printed into a film.

Although climate-controlled car seats don't spring to mind when you think of energy efficiency, the latest technology underpinning this luxury automobile feature is based on thermoelectrics—materials that convert electricity directly into heating or cooling. Conversely, thermoelectrics can also funnel excess heat from energy inefficient systems, such as car engines or power plants, by recovering this 'waste heat' and turning it into electricity. As a result, these materials offer a potentially clean source of energy to reduce fuel consumption and CO2 emissions.

Currently, this thermal energy is converted with high-efficiency, expensive thermoelectric materials. In automotive exhaust systems, for example, solid-state thermoelectrics recover waste heat that can result in fuel savings of up to five percent, but their high cost bars them from being used in smaller-scale settings. Boosting these savings through lower-cost materials could make a significant impact in power generation for batteries or electronic components in computers.

Now, Lawrence Berkeley National Laboratory (Berkeley Lab) scientists are tackling this challenge by “changing the budget for thermal energy management,” said Jeff Urban, Deputy Director of the Inorganic Nanostructures Facility at the Molecular Foundry, a nanoscience user facility.

“Historically, high-efficiency thermoelectrics have required high-cost, materials-intensive processing,” said Urban. “By engineering a hybrid of soft and hard materials using straightforward flask chemistry in water, we’ve developed a route that provides respectable efficiency with a low cost to production.”

In their approach, Urban and colleagues constructed a nanoscale composite material by wrapping a polymer that conducts electricity around a nanorod of tellurium—a metal coupled with cadmium in today’s most cost-effective solar cells. This composite material is easily spin cast or printed into a film from a water-based solution. Along with its ease of manufacture, this hybrid material also has a thermoelectric figure of merit thousands of times greater than either the polymer or nanorod alone—a crucial factor in boosting device performance.

“In recent years, we’ve seen tremendous gains in thermoelectric efficiency, but there is a need for low-cost, moderate efficiency materials that are easy to process and pattern over large areas,” said Rachel Segalman, a faculty scientist at Berkeley Lab and professor of Chemical and Biomolecular Engineering at University of California, Berkeley. “We had a lot of intuition about what would work using polymers and nanocrystals, and will now explore materials space to optimize these systems and switch to more earth-abundant materials.”

More information: A paper reporting this research titled, “Water-processable polymer-nanocrystal hybrids for thermoelectrics,” appears in Nano Letters and is available to subscribers online. Co-authoring the paper with Urban and Segalman were Kevin See, Joseph Feser, Cynthia Chen and Arun Majumdar.

Provided by Lawrence Berkeley National Laboratory (news : web)

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Water could hold answer to graphene nanoelectronics

October 26, 2010

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Researchers at Rensselaer Polytechnic Institute developed a new method for using water to tune the band gap of the nanomaterial graphene, opening the door to new graphene-based transistors and nanoelectronics. In this optical micrograph image, a graphene film on a silicon dioxide substrate is being electrically tested using a four-point probe. Credit: Rensselaer/Koratkar

Researchers at Rensselaer Polytechnic Institute developed a new method for using water to tune the band gap of the nanomaterial graphene, opening the door to new graphene-based transistors and nanoelectronics.

By exposing a graphene film to humidity, Rensselaer Professor Nikhil Koratkar and his research team were able to create a band gap in graphene – a critical prerequisite to creating graphene transistors. At the heart of modern electronics, transistors are devices that can be switched "on" or "off" to alter an electrical signal. Computer microprocessors are comprised of millions of transistors made from the semiconducting material silicon, for which the industry is actively seeking a successor.

Graphene, an atom-thick sheet of carbon atoms arranged like a nanoscale chain-link fence, has no band gap. Koratkar's team demonstrated how to open a band gap in graphene based on the amount of water they adsorbed to one side of the material, precisely tuning the band gap to any value from 0 to 0.2 electron volts. This effect was fully reversible and the band gap reduced back to zero under vacuum. The technique does not involve any complicated engineering or modification of the graphene, but requires an enclosure where humidity can be precisely controlled.

"Graphene is prized for its unique and attractive mechanical properties. But if you were to build a transistor using graphene, it simply wouldn't work as graphene acts like a semi-metal and has zero band gap," said Koratkar, a professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer. "In this study, we demonstrated a relatively easy method for giving graphene a band gap. This could open the door to using graphene for a new generation of transistors, diodes, nanoelectronics, nanophotonics, and other applications."

Results of the study were detailed in the paper "Tunable Band gap in Graphene by the Controlled Adsorbtion of Water Molecules," published this week by the journal Small.

In its natural state, graphene has a peculiar structure but no band gap. It behaves as a metal and is known as a good conductor. This is compared to rubber or most plastics, which are insulators and do not conduct electricity. Insulators have a large band gap – an energy gap between the valence and conduction bands – which prevents electrons from conducting freely in the material.

Between the two are semiconductors, which can function as both a conductor and an insulator. Semiconductors have a narrow band gap, and application of an electric field can provoke electrons to jump across the gap. The ability to quickly switch between the two states – "on" and "off" – is why semiconductors are so valuable in microelectronics.

"At the heart of any semiconductor device is a material with a band gap," Koratkar said. "If you look at the chips and microprocessors in today's cell phones, mobile devices, and computers, each contains a multitude of transistors made from semiconductors with band gaps. Graphene is a zero band gap material, which limits its utility. So it is critical to develop methods to induce a band gap in graphene to make it a relevant semiconducting material."

The symmetry of graphene's lattice structure has been identified as a reason for the material's lack of band gap. Koratkar explored the idea of breaking this symmetry by binding molecules to only one side of the graphene. To do this, he fabricated graphene on a surface of silicon and silicon dioxide, and then exposed the graphene to an environmental chamber with controlled humidity. In the chamber, water molecules adsorbed to the exposed side of the graphene, but not on the side facing the silicon dioxide. With the symmetry broken, the band gap of graphene did, indeed, open up, Koratkar said. Also contributing to the effect is the moisture interacting with defects in the silicon dioxide substrate.

"Others have shown how to create a band gap in graphene by adsorbing different gasses to its surface, but this is the first time it has been done with water," he said. "The advantage of water adsorption, compared to gasses, is that it is inexpensive, nontoxic, and much easier to control in a chip application. For example, with advances in micro-packaging technologies it is relatively straightforward to construct a small enclosure around certain parts or the entirety of a computer chip in which it would be quite easy to control the level of humidity."

Based on the humidity level in the enclosure, chip makers could reversibly tune the band gap of graphene to any value from 0 to 0.2 electron volts, Korarkar said.

Gold nanoparticles that make leaves glow in the dark

October 25, 2010 by Lin Edwards Image credit: Nanoscale, DOI:10.1039/C0NR00330A . For more details, please see the original publication.

Light-emitting diodes (LEDs) are much more energy efficient than traditional light globes, but researchers in Taiwan led by Yen Hsun Su and colleagues at Academia Sinica in Taipei and the National Cheng Kung University in Tainan wanted to find a way of making LEDs that were even more efficient than those currently available. They succeeded by synthesizing gold nanoparticles and implanting them into leaves of the Bacopa caroliniana plant to induce bio-luminescence in them.

Bacopa caroliniana is a perennial aquatic or semi-aquatic creeping herb commonly used as an aquarium plant. The color of the leaves varies in proportion to the amount of light, turning bronze to almost red when exposed to high light levels.

The green pigment in leaves, chlorophyll, is bioluminescent when exposed to high wavelength (400 nanometers (nm)) ultra violet excitation, but the wavelength is much shorter for the photoluminescence of gold nanoparticles, and they emit light at 400 nm. The light is localized at a nanoscale and the nanoparticles made by the Taiwan team suppresses emission blinking, which is a problem already known in gold nanoparticles. Using their sea-urchin-shaped nanoparticles (dubbed nano-sea-urchins or NSUs), Su was able to excite chlorophyll in the leaves to emit red light.

Su said the bio-LEDs (light emitting diodes) might eventually be used to make trees lining roads luminescent at night, and since the light causes the chloroplast to conduct photosynthesis no energy source is needed and the plant will absorb CO2 for the process, which does not normally occur at night.

Su and his colleagues are looking at applying the same technique to other plant molecules and on trying to improve the efficiency of the process. Their work was reported in the journal Nanoscale.

Birth of nanoparticles seen by Argonne scientists for the first time

October 14, 2010 By Louise Lerner

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These silver nanoplates are decorated with silver oxy salt nanoparticles along the edges. These nanostructures were grown under irradiation of high-energy x-rays, which allowed scientists to "watch" them grow in real time. The image is from a scanning electron microscope.

A team of scientists at the U.S. Department of Energy's Argonne National Laboratory and the Carnegie Institution of Washington has succeeded in "watching" nanoparticles grow in real time.

The revolutionary technique allows researchers to learn about the early stages of nanoparticle generation, long a mystery due to inadequate probing methods, and could lead to improved performance of the nanomaterials in applications including solar cells, sensing and more.

"Nanocrystal growth is the foundation of nanotechnology," said lead researcher Yugang Sun, an Argonne chemist. "Understanding it will allow scientists to more precisely tailor new and fascinating nanoparticle properties."

The way that nanoparticles look and behave depends on their architecture: size, shape, texture and surface chemistry. This, in turn, depends very much on the conditions under which they are grown.

"Accurately controlling nanoparticles is very difficult," Sun explained. "It's even harder to reproduce the same nanoparticles from batch to batch, because we still don't know all the conditions for the recipe. Temperature, pressure, humidity, impurities—they all affect growth, and we keep discovering more factors."

In order to understand how nanoparticles grow, the scientists needed to actually watch them in the act. The problem was that electron microscopy, the usual method for seeing down into the atomic level of nanoparticles, requires a vacuum. But many kinds of nanocrystals have to grow in a liquid medium—and the vacuum in an electron microscope makes this impossible. A special thin cell allows a tiny amount of liquid to be analyzed in an electron microscope, but it still limited the researchers to a liquid layer just 100 nanometers thick, which is significantly different from the real conditions for nanoparticle synthesis.

To solve this conundrum, Sun found he needed to use the very high-energy X-rays provided at Sector 1 of Argonne’s Advanced Photon Source (APS), which adjoins the laboratory’s Center for Nanoscale Materials, where he works. The pattern of X-rays scattered by the sample allowed the researchers to reconstruct the earliest stages of nanocrystals second-by-second.

"This technique yields a treasure trove of information, especially on the nucleation and growth steps of the crystals, that we had never been able to get before," said Sun.

The intensity of the X-rays does affect the growth of the nanocrystals, Sun said, but the effects only became significant after an especially long reaction time. "Getting a clear image of the growth process will allow us to control samples to get better results, and eventually, new nanomaterials that will have a wide range of applications,” Sun explained.

The nanomaterials could be used in photovoltaic solar cells, chemical and biological sensors and even imaging. For example, noble metal nanoplates can absorb near-infrared light, so they can be used to enhance contrast in images. In one possible case, an injection of specially tailored nanoparticles near a cancer patient's tumor site could increase the imaging contrast between normal and cancerous cells so that doctors can accurately map the tumor.

"The key to this breakthrough was the unique ability for us to work with scientists from the Advanced Photon Source, the Center for Nanoscale Materials and the Electron Microscopy Center—all in one place," Sun said.