How to assemble nanostructures

There are two main approaches to the creation of structures in the nanometer scale: self-assembly and positional.

When positional assembly of researchers using any device, like a miniature robotic arm or other microscopic tools for assembling molecules one by one manually.

On the other hand, is much less laborious self, because it uses the natural tendency of certain molecules to find each other. For samosobirayuschihsya components, all that is required of the person - it is enough to put them in the tube and allow them to automatically come to the right konfiruratsii according to their natural properties. Construction of a complex system requires nanorobotnoy production technology in which the molecular structures arranged with the help of a computer model of diamond mechanosynthesis (DMS). DMS - this is controlled addition of carbon atoms on the surface of the diamond lattice in a vacuum. Covalent chemical bonds are formed sequentially as the result of positionally attached mechanical effort in a programmed sequence.

Magnetic Nanoparticles Assembled Into Long Chains

ScienceDaily (Oct. 23, 2005) — Chains of 1 million magnetic nanoparticles have been assembled and disassembled in a solution of suspended particles in a controlled way, scientists at the National Institute of Standards and Technology (NIST) report. Such particles and structures, once their properties are more fully understood and can be manipulated reliably, may be useful in applications such as medical imaging and information storage.

Colorized transmission electron micrograph showing chains of cobalt nanoparticles. (Image credit: G. Cheng, A.R. Hight Walker/NIST)

The NIST work, scheduled to be featured on the cover of an upcoming issue of Langmuir* (an American Chemical Society journal), is the first to demonstrate the formation and control of centimeter-long chains of magnetic nanoparticles of a consistent size and quality in a solution. The researchers spent several years learning how to make cobalt particles with controllable size and shape, and they hope to use this knowledge to eventually "build" useful structures.

The researchers induce the nanoparticles to form linear chains by subjecting them to a weak magnetic field--about the same strength as a refrigerator magnet. The particles line up because the nanoparticles act like tiny bar magnets, all facing the same direction as the applied field. Once this alignment occurs, the attraction between particles is so strong that reversing the direction of the applied magnetic field causes the whole chain to rotate 180 degrees. When the magnetic field is turned off, the chains fold into three-dimensional coils. When the solution is lightly shaken, the chains fall apart into small rings. NIST scientists used optical and transmission electron microscopes to characterize these structures.

Magnetic particles have already been used in medical imaging and information storage, and nano-sized particles may offer unique or improved properties. For example, magnetic nanoparticle dyes may improve contrast between healthy and diseased tissue in magnetic resonance imaging (MRI), a possibility under study by a different NIST research group. The authors of the Langmuir paper are now developing methods to improve the biocompatibility of these magnetic nanoparticles.

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*G. Cheng, D. Romero, G.T. Fraser, and A.R. Hight Walker. 2005. Magnetic-field-induced assemblies of cobalt nanoparticles. Langmuir. December. Posted online Oct. 12.

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Adapted from materials provided by National Institute of Standards and Technology, via EurekAlert!, a service of AAAS.

Sophisticated Nano-structures Assembled With Magnets

ScienceDaily (Feb. 19, 2009) — What do Saturn and flowers have in common?

New nano-structures. (Credit: Duke University)

As shapes, both possess certain symmetries that are easily recognizable in the natural world. Now, at an extremely small level, researchers from Duke University and the University of Massachusetts have created a unique set of conditions in which tiny particles within a solution will consistently assemble themselves into these and other complex shapes.

By manipulating the magnetization of a liquid solution, the researchers have for the first time coaxed magnetic and non-magnetic materials to form intricate nano-structures. The resulting structures can be "fixed," meaning they can be permanently linked together. This raises the possibility of using these structures as basic building blocks for such diverse applications as advanced optics, cloaking devices, data storage and bioengineering.

Changing the levels of magnetization of the fluid controls how the particles are attracted to or repelled by each other. By appropriately tuning these interactions, the magnetic and non-magnetic particles form around each other much like a snowflake forms around a microscopic dust particle.

"We have demonstrated that subtle changes in the magnetization of a fluid can create an environment where a mixture of different particles will self-assemble into complex superstructures," said Randall Erb, fourth-year graduate student. He performed these experiments in conjunction with another graduate student Hui Son, in the laboratory of Benjamin Yellen, assistant professor of mechanical engineering and materials science and lead member of the research team.

The results of the Duke experiments appear in Feb. 19 issue of the journal Nature.

The nano-structures are formed inside a liquid known as a ferrofluid, which is a solution consisting of suspensions of nanoparticles composed of iron-containing compounds. One of the unique properties of these fluids is that they become highly magnetized in the presence of external magnetic fields. The unique ferrofluids used in these experiments were developed with colleagues Bappaditya Samanta and Vincent Rotello at the University of Massachusetts.

"The key to the assembly of these nano-structures is to fine-tune the interactions between positively and negatively magnetized particles," Erb said. "This is achieved through varying the concentration of ferrofluid particles in the solution. The Saturn and flower shapes are just the first published examples of a range of potential structures that can be formed using this technique."

According to Yellen, researchers have long been able to create tiny structures made up of a single particle type, but the demonstration of sophisticated structures assembling in solutions containing multiple types of particles has never before been achieved. The complexity of these nano-structures determines how they can ultimately be used.

"It appears that a rich variety of different particle structures are possible by changing the size, type and or degree of magnetism of the particles," Yellen said.

Yellen foresees the use of these nano-structures in advanced optical devices, such as sensors, where different nano-structures could be designed to possess custom-made optical properties. Yellen also envisions that rings composed of metal particles could be used for antenna designs, and perhaps as one of the key components in the construction of materials that display artificial "optical magnetism" and negative magnetic permeability.

In the Duke experiments, the nano-structures were created by applying a uniform magnetic field to a liquid containing various types of magnetic and non-magnetic colloidal particles contained between transparent glass slides to enable real-time microscopic observations of the assembly process. Because of the unique nature of this "bulk" assembly technique, Yellen believes that the process could easily be scaled up to create large quantities of custom-designed nano-structures in high-volume reaction vessels. However, the trick is to also be able to glue the structures together, because they will fall apart when the external field is turned off, he said.

"The magnetic forces assembling these particles are reversible," Yellen said. "We were able to lock these nano-structures in their intended shapes both by using chemical glues and by simple heating."

The Duke team plans to test different combinations of particles and ferrofluids developed by the University of Massachusetts team to create new types of nano-structures. They also want to try to make even smaller nano-structures to find the limitations of the assembly process, and study the interesting optical properties which are expected from these structures.

"While we have shown that we can get small magnetic particles to form complex and beautiful structures, we believe that based on theory and the results of preliminary experiments, we should be able manipulate even smaller particles by using other magnetic particles and ferrofluids," Yellen said.

The research was supported by the National Science Foundation.

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Adapted from materials provided by Duke University.

Magnetic Nano-'shepherds' Organize Cells

ScienceDaily (Mar. 31, 2009) — The power of magnetism may address a major problem facing bioengineers as they try to create new tissue -- getting human cells to not only form structures, but to stimulate the growth of blood vessels to nourish that growth.

The process of forming cell chains using magnetic particles. (Credit: Duke University/Case Western Reserve University/University of Mass. Amherst)

A multidisciplinary team of investigators from Duke University, Case Western Reserve University and the University of Massachusetts, Amherst created an environment where magnetic particles suspended within a specialized solution act like molecular sheep dogs. In response to external magnetic fields, the shepherds nudge free-floating human cells to form chains which could potentially be integrated into approaches for creating human tissues and organs.

The cells not only naturally adhere to each other upon contact, the researchers said, but the aligned cellular configurations may promote or accelerate the creation and growth of tiny blood vessels.

"We have developed an exciting way of using magnetism to manipulate human cells floating freely in a solution containing magnetic nanoparticles" said Randall Erb, fourth-year graduate student in the laboratory of Benjamin Yellen, assistant professor of Mechanical Engineering and Materials Science, at Duke University's Pratt School of Engineering. "This new cell assembly process holds much promise for tissue engineering research and offers a novel way to organize cells in an inexpensive, easily accessible way."

Melissa Krebs, third-year biomedical engineering graduate student at Case Western and Erb's sister, co-authored a paper appearing online in advance of the May publication of Nano Letters, a journal published by the American Chemical Society.

"The cells have receptors on their surfaces that have an affinity for other cells," Krebs said. "They become sticky and attach to each other. When endothelial cells get together in a linear fashion, as they did in our experiments, it may help them to organize into tiny tubules."

The iron-containing nanoparticles used by the researchers are suspended within a liquid known as a ferrofluid. One of the unique properties of these ferrofluids is that they become highly magnetized in the presence of external magnetism, which allows researchers to readily manipulate the chain formation by altering the strength of the magnetic field.

At the end of the process, the nanoparticles are simply washed away, leaving a linear chain of cells. That the cells remain alive, healthy and relatively unaltered without any harmful effects from the process is one of the major advances of the new approach over other strategies using magnetism.

"Others have tried using magnetic particles either within or on the surface of the cells," Erb said. "However, the iron in the nanoparticles can be toxic to cells. Also, the process of removing the nanoparticles afterward can be harmful to the cell and its function."

The key ingredient for these studies was the synthesis of non-toxic ferrofluids by colleagues Bappaditya Samanta and Vincent Rotello at the University of Massachusetts, who developed a method for coating the magnetic nanoparticles with bovine serum albumin (BSA), a protein derived from cow blood. BSA is a stable protein used in many experiments because it is biochemically inert. In these experiments, the BSA shielded the cells from the toxic iron.

"The other main benefit of our approach is that we are creating three-dimensional cell chains without any sophisticated techniques or equipment," Krebs said. "Any type of tissue we'd ultimately want to engineer will have to be three-dimensional."

For their experiments, the researchers used human umbilical vein endothelial cells. Others types of cells have also been used, and it appears to the researchers that this new approach can work with any type of cell.

"While still in the early stages, we have shown that we can form oriented cellular structures," said Eben Alsberg, assistant professor of Biomedical Engineering and Orthopedic Surgery at Case Western and senior author of the paper. "The next step is to see if the spatial arrangement of these cells in three dimensions will promote vascular formation. A major hurdle in tissue engineering has been vascularization, and we hope that this technology may help to address the problem."

The research was supported by the National Institutes of Health, the National Science Foundation and Case Western.

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Adapted from materials provided by Duke University.

New Process For Making Much-sought Iron Nanospheres

ScienceDaily (Feb. 20, 2007) — Using a process that creates bubbles as hot as the surface of the sun, chemists are reporting development of a new method for making hollow hematite (iron oxide) nanospheres.

The University of Illinois at Urbana-Champaign's Kenneth S. Suslick and Jin Ho Bang describe the synthesis of these iron nanoparticles in a report scheduled for the Feb. 28 issue of the Journal of the American Chemical Society, a weekly publication.

Hollow nanospheres of metals and other inorganic materials are generating great interest because of their unusual properties and potential applications in drug delivery, electronic components, catalysts and other products.

"We believe that this procedure will be easily extended to prepare other hollow inorganic materials," the researchers note. In the past, production of hollow hematite nanospheres required a time-consuming process and use of toxic hydrofluoric acid.

The new process uses sonochemistry, in which high-frequency sound waves are focused into a solution containing an iron compound and carbon nanoparticles. Those sound waves create tiny bubbles in the liquid. The collapse of those bubbles causes intense local heating with temperatures estimated at 9,000 F, which is nearly as hot as the surface of the sun. The sonochemical process forms iron spheres around the carbon nanoparticles. On exposure to air, the iron rapidly oxidizes, which burns away the carbon core, leaving hematite spheres one thousandth the diameter of a red blood cell.

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Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Nanomaterial - not wet, even under water

Chemists at the University of Zurich have developed a new fabric that does not namokaet even with full immersion in water for two and a half months.
This nanotkan made from polyester yarn coated with a layer of 40 nanometer pointed nanovolokon. Nanovolokna forced to collect water drops on a cloth and provide a permanent layer of air on its surface.

In addition, this fabric will never become wet or dirty, it also reduces friction in the water - which involves the manufacture of a sporting bathing suits.

In Japan, designed the first "nanobrain"

In Japan, scientists have developed a «nanobrain» - molecular structure, which allows to manage nanorobotami. As part of the experiment, with the help of «nanobrain» Various nanomashiny able to perform simple commands. While nanoroboty has not yet been invented, but scientists have invented the use of their developments. «Nanobrain» can be used in the creation of supercomputers.

The International Center for Young Scientists in Tsukuba (Japan) Somobrata Aharya and Anirban Bandiopadya created a complex molecular structure, which enables you to control multiple nanomashinami. Researchers put the experiment, which proved that the structure of the 17 molecules DRQ operates similarly to the processor, performs 16 teams in a single stroke.

17 DRQ molecules can be formed into a molecular machine that is able to encode more than 4 billion different combinations. The amount received by the molecular structure - only 2 nanometers. This is the world's first working model of «nanobrain».

It is assumed that «nanobrain» can be used when creating nanorobotov projects which are still under development. Nanoroboty can be widely used for medical purposes. In particular, the nanorobotov placed hope in the delivery of drugs - they would bring drugs to the places the human body that need them. However nanoroboty require monitoring, and to lay them in a program, you need «nanobrain».

Scientists hope that nanoroboty not yet invented, the development can be derived for creating high-performance processor for today's computers. Scientists have developed a much larger sample of «nanobrain», which could serve as a basis for future processors.

By foreign media.

Inorganic nanokompozit as antiseptic

The researchers from the Madrid Institute of Materials (ICMM) developed the technology, which contains the fine silver nanoparticles. The powder of this glass with silver nanoparticles is a powerful antibacterial and antifungal agent, inorganic, in the structure of nanoparticles which are included in the fiber sepiolita, clay with magnesium silicate.

The structure of glass allows silver nanoparticles to act very quickly, leaving a small amount of money provides a fast, safe and complete disinfection. Scientists explain this synergistic effect of the action of calcium ions that are leached from the glass.


The amount of silver leached from the glass powder during all types of bactericidal tests (with the gram-positive bacteria, gram-negative bacteria and yeast) was very low, about 28 parts per million, far below the acceptable level of toxicity. This formulation can be applied in many fields, including medicine, agriculture and food industry.


Currently scientists are working on understanding the processes of interaction resulting synergies and the development of possible combinations of types of glass-metal.

Hollow Gold Nanospheres Show Promise For Biomedical And Other Applications

ScienceDaily (Mar. 28, 2009) — A new metal nanostructure developed by researchers at the University of California, Santa Cruz, has already shown promise in cancer therapy studies and could be used for chemical and biological sensors and other applications as well.

Partial view of a gold nanosphere (shown), magnified by a factor of one billion, as seen through an electron microscope. The darker ring shows the "wall" of the nanosphere, while the lighter area to the right of the ring shows the interior region of the shell. (Credit: Adam Schwartzberg, Ph.D.; Jin Zhang, Ph.D.)

The hollow gold nanospheres developed in the laboratory of Jin Zhang, a professor of chemistry and biochemistry at UCSC, have a unique set of properties, including strong, narrow, and tunable absorption of light. Zhang is collaborating with researchers at the University of Texas M. D. Anderson Cancer Center, who have used the new nanostructures to target tumors for photothermal cancer therapy. They reported good results from preclinical studies earlier this year (Clinical Cancer Research, February 1, 2009).

Zhang will describe his lab's work on the hollow gold nanospheres in a talk on Sunday, March 22, at the annual meeting of the American Chemical Society in Salt Lake City.

"What makes this structure special is the combination of the spherical shape, the small size, and the strong absorption in visible and near infrared light," Zhang said. "The absorption is not only strong, it is also narrow and tunable. All of these properties are important for cancer treatment."

Zhang's lab is able to control the synthesis of the hollow gold nanospheres to produce particles with consistent size and optical properties. The hollow particles can be made in sizes ranging from 20 to 70 nanometers in diameter, which is an ideal range for biological applications that require particles to be incorporated into living cells. The optical properties can be tuned by varying the particle size and wall thickness.

In the cancer studies, led by Chun Li of the M. D. Anderson Cancer Center, researchers attached a short peptide to the nanospheres that enabled the particles to bind to tumor cells. After injecting the nanospheres into mice with melanoma, the researchers irradiated the animals' tumors with near-infrared light from a laser, heating the gold nanospheres and selectively killing the cancer cells to which the particles were bound.

Cancer therapy was not the goal, however, when Zhang's lab began working several years ago on the synthesis and characterization of hollow gold nanospheres. Zhang has studied a wide range of metal nanostructures to optimize their properties for surface-enhanced Raman scattering (SERS). SERS is a powerful optical technique that can be used for sensitive detection of biological molecules and other applications.

Adam Schwartzberg, then a graduate student in Zhang's lab at UCSC, initially set out to reproduce work reported by Chinese researchers in 2005. In the process, he perfected the synthesis of the hollow gold nanospheres, then demonstrated and characterized their SERS activity.

"This process is able to produce SERS-active nanoparticles that are significantly smaller than traditional nanoparticle structures used for SERS, providing a sensor element that can be more easily incorporated into cells for localized intracellular measurements," Schwartzberg, now at UC Berkeley, reported in a 2006 paper published in Analytical Chemistry.

The collaboration with Li began when Zhang heard him speak at a conference about using solid nanoparticles for photothermal cancer therapy. Zhang immediately saw the advantages of the hollow gold nanospheres for this technique. Li uses near-infrared light in the procedure because it provides good tissue penetration. But the solid gold nanoparticles he was using do not absorb near-infrared light efficiently. Zhang told Li he could synthesize hollow gold nanospheres that absorb light most efficiently at precisely the wavelength (800 nanometers) emitted by Li's near-infrared laser.

"The heat that kills the cancer cells depends on light absorption by the metal nanoparticles, so more efficient absorption of the light is better," Zhang said. "The hollow gold nanospheres were 50 times more effective than solid gold nanoparticles for light absorption in the near-infrared."

Zhang's group has been exploring other nanostructures that can be synthesized using the same techniques. For example, graduate student Tammy Olson has designed hollow double-nanoshell structures of gold and silver, which show enhanced SERS activities compared to the hollow gold nanospheres.

The ability to tune the optical properties of the hollow nanospheres makes them highly versatile, Zhang said. "It is a unique structure that offers true advantages over other nanostructures, so it has a lot of potential," he said.

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Adapted from materials provided by University of California - Santa Cruz, via EurekAlert!, a service of AAAS.

Carbon Dioxide Forms Polymeric Materials Under High Pressure

ScienceDaily (Mar. 25, 2009) — Carbon dioxide is a molecular gas at ambient conditions and an important constituent of the Earth’s atmosphere. It is also a likely component in the Earth’s mantle, and it plays an important role in the life cycle. But at high pressure, carbon dioxide can transform to a solid.

As the pressure increases and temperature varies, the intra- and inter-molecular interactions of carbon dioxide change dramatically and this results in different crystal structures in polymeric dense phases with interesting physical properties, such as “super-hardness”. (Credit: Image courtesy of Ruhr-Universitaet-Bochum)

The commonly known solid-state form of carbon dioxide is the so called “dry ice”, which is a molecular crystal and has many important applications, e.g. food production and storage, artificial fog in theatre and artificial rainfall, etc.

Even more interesting, as the pressure increases and temperature varies, the intra- and inter-molecular interactions of carbon dioxide change dramatically and this results in different crystal structures in polymeric dense phases with interesting physical properties, such as “super-hardness”. Thus carbon dioxide has become an extremely hot topic in science in the last decade.

Recently, a collaborative study between the research groups in Canada, Germany, Slovakia, Italy and USA achieved progress on this highly interested compound. Using  a novel computer-based simulation method called metadynamics combined with accurate quantum mechanical calculations, they found that a molecular solid called CO₂-II transfers to a layered polymeric structure at a pressure of 60 GPa (1 GPa is approximately 10000 atmospheres) and temperature at 600 Kelvin. Based on the good agreement between their calculated Raman spectra and X-ray diffraction patterns and the previous experimental values, a new interpretation of a previous experimental result is given.

A recently identified dense phase VI found in experiment, assumed to be disordered stishovite-like structure, is instead interpreted as the result of an incomplete transformation from the molecular phase into a final layered polymeric structure. In addition, a new α-cristobalite-like CO₂ as found in silicon dioxide, is predicted to be formed from CO₂-III via an intermediate structure at 80 GPa and temperature lower than room temperature. Defects in the crystals increase with temperature and CO₂ transforms to an amorphous form when temperature is higher than room temperature, consistent with previous experiments.

These results obtained from fully dynamical simulations reveal hitherto unknown microscopic transformation mechanisms, and illustrate the transformation from a molecular solid characterized by only intra-molecular bonding to a polymerized structure. The transformation takes place at pressures within the range found in the Earth’s mantle, where a significant amount of oxidized carbon is thought to be present, either in the form of carbonates or as a fluid. The large and abrupt changes in the bonding properties of CO₂ reported here hint to possible discontinuities in the carbon chemistry of the mantle.

Their article by Dr. Jian Sun et al. is soon to be (has been) published in the journal - Proceedings of the National Academy of Sciences USA.

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Journal reference:

1. Jian Sun, Dennis D. Klug, Roman Martonak, Javier Antonio Montoya, Mal-Soon Lee, Sandro Scandolo and Erio Tosatti.High-pressure polymeric phases of carbon dioxide.PNAS, DOI: 10.1073_pnas.0812624106

Adapted from materials provided by Ruhr-Universitaet-Bochum, via AlphaGalileo.

To Fight Drug Addiction, Researchers Target The Brain With Nanoparticles

Scientists in UB's Institute for Lasers, Photonics and Biophotonics and UB's Department of Medicine have developed a stable nanoparticle that delivers short RNA molecules in the brain to "silence" or turn off a gene that plays a critical role in many kinds of drug addiction.

The UB team's in vitro findings were published online the week of March 23 in the Proceedings of the National Academy of Sciences.

"These findings mean that in the future, we might be able to add a powerful pharmaceutical agent to the current arsenal of weapons in order to more effectively fight a whole range of substance addictions," said Paras N. Prasad, Ph.D., executive director of the UB Institute for Lasers, Photonics and Biophotonics and SUNY Distinguished Professor in the departments of Chemistry, Physics, Electrical Engineering and Medicine, who led the UB team.

The new approach developed by the UB researchers also may be applicable to treating Parkinson's disease, cancer and a range of other neurologic and psychiatric disorders, which require certain drugs to be delivered to the brain.

At the same time, the study's co-authors in the UB Department of Medicine say this highly translational research strongly suggests that the nanoparticles would be applicable to other diseases. They will soon begin to study their use in treating AIDS dementia, prostate cancer and asthma.

"The findings of this study tell us that these nanoparticles are both a safe and very efficient way of delivering to a variety of tissues highly sophisticated new drugs that turn off abnormal genes," said Stanley A. Schwartz, M.D., Ph.D., professor in the UB departments of Medicine, Pediatrics and Microbiology, director of the Division of Allergy, Immunology and Rheumatology in the UB School of Medicine and Biomedical Sciences, and a co-author on the study.

The PNAS paper describes the development of an innovative way to silence DARPP-32, a brain protein, understood to be a central "trigger" for the cascade of signals that occurs in drug addiction.

DARPP-32 is a protein in the brain that facilitates addictive behaviors. Silencing of the DARPP-32 gene with certain kinds of ribonucleic acid (RNA), called short interfering RNA (siRNA), can inhibit production of this protein and thus, could help prevent drug addiction.

"When you silence this gene, the physical craving for the drug should be reduced," said Adela C. Boniou, Ph.D., a post-doctoral researcher in the Institute for Lasers, Photonics and Biophotonics in the UB Department of Chemistry in the College of Arts and Sciences, and a co-author.

The drawback has been in finding a way to safely and efficiently deliver the siRNA, which is not stable by itself.

The UB researchers were successful when they combined the siRNA molecules with gold nanoparticles shaped like rods, called nanorods.

This may be the first time that siRNA molecules have been used with gold nanorods.

"What is unique here is that we have applied nanotechnology to therapeutic concepts directed at silencing a gene in the brain, using RNA techniques," said Supriya D. Mahajan, Ph.D., research assistant professor in the UB Department of Medicine in the School of Medicine and Biomedical Sciences.

In addition to their biocompatibility, the gold nanorods developed by the UB researchers are advantageous because they are rod-shaped rather than spherical, thus allowing for more siRNA molecules to be loaded on to their surface. This further increases their stability and allows for better penetration into cells.

"We have demonstrated that we can use these gold nanorods to stabilize the siRNA molecules, take them across the blood-brain barrier and silence the gene," said Indrajit Roy, Ph.D., deputy director for biophotonics at the institute. "The nanorods nicely address all three of these requirements."

The nanorods delivered 40 percent of the silencing RNA molecules across the blood-brain barrier model, significantly higher than the amounts that have previously been achieved in other experiments.

In the next stage of the research, the UB scientists will conduct similar experiments in vivo.

The researchers are active participants in the strategic strength in Integrated Nanostructured Systems identified in the UB 2020 planning process, which brings together researchers in the life sciences, medicine and engineering to promote interdisciplinary advancements.

Additional co-authors on the paper are Earl J. Bergey, Ph.D., research associate professor in chemistry; Rui Hu, senior research support specialist, and Hong Ding, Ph.D., Ken-Tye Yong, Ph.D., and Rajiv Kumar, Ph.D., all postdoctoral associates in the Institute for Lasers, Photonics and Biophotonics.

Funding for this research was provided by the National Cancer Institute, the Kaleida Health Foundation, the John R. Oishei Foundation, the Air Force Office of Scientific Research and UB's New York State Center of Excellence in Bioinformatics and Life Sciences.

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Journal reference:

1. Adela C. Bonoiu, Supriya D. Mahajan, Hong Ding, Indrajit Roy, Ken-Tye Yong, Rajiv Kumar, Rui Hu, Earl J. Bergey, Stanley A. Schwartz, and Paras N. Prasad.Nanotechnology approach for drug addiction therapy: Gene silencing using delivery of gold nanorod-siRNA nanoplex in dopaminergic neurons. Proceedings of the National Academy of Sciences, 2009; DOI:10.1073/pnas.0901715106

Adapted from materials provided by University at Buffalo.

New Surface Material That Resists Biofilm Growth Created

ScienceDaily (Mar. 27, 2009) — This is the tale of two biological substances-cells from mammals and bacteria. It's a story about the havoc these microscopic entities can wreak on all manner of surfaces, from mighty ships to teeth and medical devices, and how two Syracuse University researchers are discovering new ways to prevent the damage.

Yan-Yeung Luk, assistant professor of chemistry in SU's College of Arts and Sciences, and Dacheng Ren, assistant professor of biomedical engineering in SU's L.C. Smith College of Engineering and Computer Science created a surface material on which they could manipulate and confine biofilm growth four times longer than current technologies. (Credit: Image courtesy of Syracuse University)

Under moist conditions, bacteria form what scientists call biofilms-a sticky, slimy buildup on almost any kind of surface. Biofilms can corrode the hulls of ships, produce green slime on rocks, pollute drinking water systems, form plaque on teeth and stick to medical devices implanted in humans, resulting in infection or rejection.

It's critically important, therefore, for scientists to gain a better understanding of how biofilms are formed and use that knowledge to develop surfaces that will resist such biofouling. In an unusual, interdisciplinary collaboration, SU researchers have found that if you can prevent protein from sticking to a surface, you can prevent both bacteria and mammalian cells from doing likewise. In the process, they developed a novel surface technology that scientists can use to study biofilms in ways that were not previously possible.

In a series of experiments, Yan-Yeung Luk, assistant professor of chemistry in SU's College of Arts and Sciences, and Dacheng Ren, assistant professor of biomedical engineering in SU's L.C. Smith College of Engineering and Computer Science, created a surface material on which they could manipulate and confine biofilm growth four times longer than current technologies. By further manipulating the chemical makeup of the surface, the scientists uncovered how mammalian cells and bacteria adhere to surfaces.

Luk and Ren began collaborating about three years ago, when they discovered a common thread in their individual research efforts-the desire to chemically modify surfaces to prevent biofouling. They went on to create a surface that seems to repel both bacteria and mammalian cells when the molecule is chemically applied to a surface. The surface used in the laboratory is a thin film of gold coated on a glass slide.

They explain their research in terms of land, soil and plants. "You start with a glass surface (the land); apply a thin film of gold to that surface, about 20 nanometers or five atoms thick (the soil); then top the gold with the molecules we created in the laboratory (the trees)," Luk says. "The goal is to see if the special molecules (trees) can resist or prevent protein from sticking to the overall surface. Put another way, do the trees provide an inhospitable environment for birds (the biofilm) and therefore prevent them from roosting en masse?"

The surface the researchers created in the laboratory was able to confine the growth of bacteria to surface patterns of desired, two-dimensional shapes. In other words, the researchers were able to control the growth of the biofilm with the surface material, allowing the biofilm to form in some places and restricting its growth in others. Additionally, the scientists found that when confined in two dimensions, the biofilm grew in a vertical direction.

In other experiments, the scientists discovered important differences in the way mammalian cells and bacteria attach to a surface. "Our surfaces are able to reveal that mammalian cell adhesion requires the existence of an anchor, while bacteria can adhere to almost any sticky surface," Luk says.

The researchers' discoveries and the surface technology they developed can be used to answer critical questions that previously eluded scientists and may lead to the development of improved medical implants and to new ways to prevent biofouling.

"This level of surface control has never before been achieved," Ren says. "We hope that what we have learned in the laboratory will help answer other fundamental questions in surface materials research and lead to the production of new materials for use in medicine and industry."

Their work, which is supported by grants from the National Science Foundation, was reported in the Feb. 4 online version of ChemComm, the journal of the Royal Society of Chemistry (forthcoming in print) and in the Jan. 9 online version ofLangmuir, published by the American Chemical Society (forthcoming in print).

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Adapted from materials provided by Syracuse University.

How To Make Polymeric Micro- And Nanoparticles

ScienceDaily (July 11, 2007) — Researchers in the College of Engineering at UC Santa Barbara have discovered how to make polymeric micro- and nanoparticles in a wide variety of different shapes and sizes using commonly-available lab chemicals and equipment. Knowing how to create these particles in the average laboratory environment will facilitate further discovery, as the particles are essential to understanding the role of shape in particle function. 

Researchers have discovered how to make polymeric micro- and nanoparticles in a wide variety of different shapes and sizes using commonly-available lab chemicals and equipment. (Credit: Image courtesy of University of California - Santa Barbara)

Polymeric micro- and nanoparticles are used in a wide range of applications including medical imaging, drug delivery, and beauty and personal care products. These applications typically use spherical particles. While making particles in other shapes could be extremely useful, fabricating shapes other than spheres has been technically challenging.

The research team, led by Samir Mitragotri, a professor of chemical engineering, with Julie Champion, a graduate student, and Yogesh Katare, a post-doctoral researcher, used spherical polystyrene beads as a starting point. In one approach, the beads were liquefied by heat or solvents and then stretched. In the second, the beads were embedded in a polyvinyl alcohol film and the film was stretched to create voids around the beads. These voids were then filled by liquefying the beads using heat or solvent. From these two simple techniques, more than 20 different shapes were formed, ranging from simple rods and eggs to lenses, diamonds, food-shaped ravioli and tacos.

The methods used to create the potpourri of micro- and nanoparticles allow the researchers to control the size and shape of the particles created, a crucial factor in the development of nonspeherical particles in a variety of fields, including drug delivery, microbiology, advanced materials and rheology. This research was funded by the NIH program of excellence in nanotechnology.

 Their research is published in the online edition of the Proceedings of the National Academy of Sciences.

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Adapted from materials provided by University of California - Santa Barbara, via EurekAlert!, a service of AAAS.

Nano Breach: When Particles Are So Small That They Seep Right Through Skin

ScienceDaily (Oct. 1, 2008) — Scientists are finding that particles that are barely there – tiny objects known as nanoparticles that have found a home in electronics, food containers, sunscreens, and a variety of applications – can breach our most personal protective barrier: The skin.

Quantum dot nanoparticles are visible as fluorescing green dots in the skin. (Credit: Image courtesy of University of Rochester Medical Center)

The particles under scrutiny by Lisa DeLouise, Ph.D., are almost unfathomably tiny. The particles are less than one five-thousandth the width of a human hair. If the width of that strand of hair were equivalent to the length of a football field, a typical nanoparticle wouldn't even belly up to the one-inch line.

In the September issue of the journal Nano Letters, a team led by DeLouise at the University of Rochester Medical Center published a paper showing that nanoparticles pass through the skin of a living organism, a type of mouse commonly used as a model to study the damaging effects of sunlight.

It's the strongest evidence yet indicating that some nanoparticles are so small that they can actually seep through skin, especially when the skin has been damaged.

The health implications of nanoparticles in the body are uncertain, said DeLouise, an assistant professor of Dermatology and Biomedical Engineering and an expert on the properties of nanoparticles. Other scientists have found that the particles can accumulate in the lymph system, the liver, the nervous system, and in other areas of the body. In her study, she found that the particles accumulate around the hair follicles and in tiny skin folds.

DeLouise, a chemist, points out that her study did not directly address the safety of nanoparticles in any way. "We simply wanted to see if nanoparticles could pass through the skin, and we found that they can under certain conditions," she said.

DeLouise's work is part of a broad field known as nanomedicine that is a strategic area at the University of Rochester Medical Center. The area includes research, like hers, looking at the properties of nanoparticles, as well as possibilities like new forms of drug delivery and nano-sensors that can immediately identify microbes and other threats to our health.

While nanoparticles are becoming widely used in the manufacture of consumer products, they are also under a great deal of study in research labs, and there are some processes – including ordinary candle flames – that produce them naturally. Some of the particles are so small, less than 10 nanometers wide (a nanometer is one-millionth of a millimeter), that they are nearly as small as the natural gaps between some skin cells.

In its paper in Nano Letters, the team studied the penetration of nanoparticles known as quantum dots that fluoresce under some conditions, making them easier to see and track compared to other nanoparticles. The scientists looked at the distribution of quantum dots in mice whose skin had been exposed to about the same amount of ultraviolet light as might cause a slight sunburn on a person. The team showed that while the nanoparticles were able to breach the skin of all the mice, the particles passed more quickly through skin that had been damaged by ultraviolet light.

Part of the explanation likely lies with the complex reaction of skin when it's assaulted by the Sun's rays. In response to ultraviolet light, cells proliferate, and molecules in the skin known as tight-junction proteins loosen so that new cells can migrate to where they're needed. Those proteins normally act as gatekeepers that determine which molecules to allow through the skin and into the body, and which molecules to block. When the proteins loosen up, they become less selective than usual, possibly giving nanoparticles an opportunity to pass through the barrier.

In the future, DeLouise plans to study titanium dioxide and zinc oxide, two materials that are widely used in sunscreens and other cosmetic products to help block the damaging effects of ultraviolet light. In recent years the size of the metal oxide particles used in many consumer products has become smaller and smaller, so that many now are nanoparticles. The effects of the smaller particle size are visible to anyone who takes a walk on the beach or stops by the cosmetics counter at a department store: The materials are often completely transparent when applied to skin. A transparent lip gloss that protects against UV light, for example, or a see-through sunscreen may contain nanoparticles, DeLouise says.

"A few years ago, a lifeguard at the swimming pool wearing sunscreen might have had his nose completely covered in white. Older sunscreens have larger particles that reflect visible light. But many newer sunscreens contain nanoparticles that are one thousand times smaller, that do not reflect visible light," said DeLouise, who noted that many people apply sunscreens after their skin has been damaged by sunlight.

Initial funding from two sources allowed the team to gather the evidence necessary to expand the project dramatically. DeLouise's project was first funded by the University's Environmental Health Sciences Center, which supported graduate student Luke Mortensen during his research. The University's Clinical and Translational Science Institute has also awarded $100,000 to the team, and DeLouise has just received $394,000 from the National Science Foundation to expand the project for the next three years. She will be working with dermatologist Lisa Beck, M.D., who is an expert in allergic skin disorders.

In addition to DeLouise and Mortensen, authors of the paper include Günter Oberdörster, Ph.D., professor of Environmental Medicine and a widely recognized authority on the bio-effects of nanoparticles. Oberdörster is director of the Particulate Matter Center, funded by the Environmental Protection Agency, where scientists study the link between tiny air particles we breathe every day and our cardiovascular health. Dermatologist Alice Pentland, M.D., professor and chair of the Department of Dermatology and an expert on how sunlight brings about skin cancer, was also an author.

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Adapted from materials provided by University of Rochester Medical Center.

Nanoparticles In Cosmetics, Personal Care Products May Have Adverse Environmental Effects

ScienceDaily (Mar. 27, 2009) — Using aquatic microbes as their "canary-in-a-cage," scientists from Ohio today reported that nanoparticles now being added to cosmetics, sunscreens, and hundreds of other personal care products may be harmful to the environment.

This is a magnification of E. coli exposed to a low concentration (10 mg/L) of titanium dioxide nanoparticles. Cells with compromised membranes are stained red. (Credit: University of Toledo)

Their report was part of symposia that included almost two dozen papers at the 237th National Meeting of the American Chemical Society where scientists grappled to understand the environmental and human health effects of nanotechnology. Hundreds of products utilizing these microscopic particles — 1/5,000th the diameter of a human hair — already are on the market. With many more poised for debut, scientists are seeking to avoid unwanted health and environmental effects in advance.

The study by Cyndee Gruden, Ph.D. and Olga Mileyeva-Biebesheimer focused on nano-titanium dioxide (nano-TiO2) particles found in cosmetics, sunscreens, and other personal care products. The particles are added to those products for their highly beneficial effects in blocking ultraviolet light in sunlight. Excess exposure can cause premature aging of the skin and skin cancer.

Gruden, who is with the University of Toledo, explained that the particles are washed down the drain in homes as people bathe and end up in municipal sewage treatment plants. From there, they can enter lakes, rivers, and other water sources where microorganisms serve essential roles in maintaining a healthy environment.

"When they enter a lake, what happens?" Gruden asked. "Would they enter an organism or bind to it? Maybe they kill it — or have nothing to do with it at all. These are important questions for determining the effects that nanoparticles may have on the environment. Right now, we're not really sure of the answers."

Gruden studied survival of Escherichia coli (E. coli) bacteria when exposed in laboratory cultures to various amounts of nano-TiO2. She found surprisingly large reductions in survival in samples exposed to small concentrations of the nanoparticles for less than an hour. "How fast the impact was surprised me," she said. The findings open the door to future research, including studies to determine whether the same effects occur in the natural environment.

Gruden's method for pinpointing damage from nanoparticles uses fluorescence to identify when the cell membrane in microbes undergo damage. When membranes — a crucial part of the microbe — are damaged, the cells emit a faint red glow. "Methods based upon fluorescence allow us to obtain results faster, maybe with greater sensitivity," she said, adding that this approach could speed scientific efforts to understand the threshold at which nanoparticles become toxic to microbes.

In a second study on nanotoxicity at the ACS National Meeting, scientists from Utah described development of a new biosensor that flashes like a beacon upon detecting nanoparticles in the environment.

Anne Anderson and colleagues at Utah State University and the University of Utah have inserted genes into a strain of Pseudomonas putida (P. putida) — a beneficial soil microbe — so that it emits light upon contact with nanoparticles of heavy metals. They are with Utah State University. The bacteria glow brightly when it is in its normal healthy state. The glow dims upon exposure to toxic substances.

"The novelty of the biosensor is we're able to get responses very, very quickly," she said, "and we can get those answers in the absence of other factors that could bind the challenging compounds." Anderson noted that traditional approaches in measuring bacterial cell growth may take two days. "At the snap of your finger you can see some of these things take place."

Anderson's group discovered that P. putida cannot tolerate silver, copper oxide and zinc oxide nanoparticles. Toxicity occurred at levels as low as micrograms per liter. That's equivalent to two or three drops of water in an Olympic-sized swimming pool. Anderson warns it could spell danger for aquatic life. "If you look up the Environmental Protection Agency's risk level of Copper to fish and other aquatic organisms, you are at that point of toxicity."

There's much debate in the science community about nanoparticle toxicity, Anderson said. Some scientists believe that nanoparticles in nature will aggregate together or bind onto silt and/or other organic matter, greatly reducing their toxicity. "We don't know if that's true or not," she said. So other members of this Utah research group currently are investigating that aspect of the issue.

Although the public is ultimately responsible for understanding the risks of consumer products, Gruden said, science plays a large role in highlighting possible hazards. "It is the scientist's job to perform good research and let the findings speak for themselves," she said. And so far the promises of nanotechnology need more evaluation. "To date, it's unclear whether the benefits of nanotech outweigh the risks associated with environmental release and exposure to nanoparticles."

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Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Carbon Nanotubes Are Superior To Metals For Electronics, According to Engineers

ScienceDaily (Mar. 20, 2009) — In the quest to pack ever-smaller electronic devices more densely with integrated circuits, nanotechnology researchers keep running up against some unpleasant truths: higher current density induces electromigration and thermomigration, phenomena that damage metal conductors and produce heat, which leads to premature failure of devices.

Research conducted by Cemal Basaran may make metal an obsolete component of electronics. (Credit: Image courtesy of University at Buffalo)

But University at Buffalo researchers who study electronics packaging recently made a pleasant discovery: that's not the case with Single-Walled Carbon Nanotubes (SWCNTs).

"Years ago, everyone thought that the problem of cooling for electronics could be solved," said Cemal Basaran, Ph.D., professor in the UB Department of Civil, Structural and Environmental Engineering and director of the Electronics Packaging Lab in UB's School of Engineering and Applied Sciences. "Now we know that's not true. Electronics based on metals have hit a wall. We are done with metals."

Single Walled Carbon Nanotubes are extremely thin, hollow cylinders, measuring no thicker than a single atom. Thousands of times stronger than metals, they are expected to one day replace metals in millions of electronic applications.

Basaran and his doctoral student Tarek Ragab have spent the past four years performing quantum mechanics calculations, which prove that in carbon nanotubes, higher current density does not lead to electromigration and thermomigration; it also produces just one percent of the heat produced by traditional metals, such as copper.

Basaran will present the findings in November when he delivers a keynote lecture at the American Society of Mechanical Engineers (ASME) International Mechanical Engineering Congress and Exposition in Orlando.

The findings demonstrate yet another tantalizing property of CNTs, he said.

"It has been assumed that for carbon nanotubes, the electrical heating process would be governed by Joules law, where resistance in a circuit converts electric energy into heat," said Basaran. "We are the first to show mathematically, from a quantum mechanics point of view, that carbon nanotubes do not follow Joules law."

According to Basaran, this essential difference between metals and carbon nanotubes lies in the way they conduct electricity.

"Even though carbon nanotubes are conductive, they do not have metallic bonds," he said. "As a result, they do not conduct electricity the way that traditional metals do."

In conventional metals, he explained, conduction causes a scattering of electrons within the lattice of the material so that, when electrons move during conduction, they bump into atoms. This creates friction and generates heat, the same way a household iron works.

"On the other hand, in carbon nanotubes, electric conduction happens in a very different, one-dimensional 'ballistic' way," he said. "The electrons are fired straight through the material, so that the electrons have very little interference with the atoms."

He drew an analogy, using the difference between a conventional railroad train and a magnetically levitated train.

"In the conventional train, you have friction between the wheels and the track," said Basaran. "Through the generation of heat, that friction causes a loss of energy. But with a magnetically levitated train, the wheels and track are not in direct contact. Without that friction, they can travel much faster."

The minimal amount of friction gives carbon nanotubes a tremendous advantage over conventional metals, said Basaran. The unique properties of carbon nanotubes will allow engineers to realize a host of smaller, faster and more powerful new devices that right now cannot exist because of the limitations of conventional metals.

"When an electric car finally is manufactured, its batteries probably will be based on carbon nanotubes," said Basaran. "You can't use traditional metals in the engines because they run so hot."

Much of Basaran's $1 million-plus funding at UB comes from sources like the U.S. Navy, which is interested in sophisticated electronics systems that could operate under very demanding conditions, such as the electric ship the Navy is building.

Basaran's unique perspective comes from decades of research, which has fundamentally changed what is known about the high current density performance properties of metals and their limitations.

He also sounded a cautionary note, pointing out that current research and development expenditures on carbon nanotubes in the U.S. electronics industry are very small when compared to those of our Asian competitors.

"If the industry continues this way, when carbon nanotube-based electronics become a reality, U.S. electronics manufacturers may be in a position similar to U.S. car manufacturers today, because they have failed to keep up with advances in engineering," he said.

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Adapted from materials provided by University at Buffalo.

Nanotech Batteries For A New Energy Future

In order to save money and energy, many people are purchasing hybrid electric cars or installing solar panels on the roofs of their homes. But both have a problem -- the technology to store the electrical power and energy is inadequate.

Battery systems that fit in cars don't hold enough energy for driving distances, yet take hours to recharge and don't give much power for acceleration. Renewable sources like solar and wind deliver significant power only part time, but devices to store their energy are expensive and too inefficient to deliver enough power for surge demand.

Researchers at the Maryland NanoCenter at the University of Maryland have developed new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available. The results of their research are available in a recent issue of Nature Nanotechnology.

"Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded," said Gary Rubloff, director of the University of Maryland's NanoCenter. "Conventional devices to store and deliver electrical energy -- batteries and capacitors -- cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future."

Researchers working with Professor Rubloff and his collaborator, Professor Sang Bok Lee, have developed a method to significantly enhance the performance of electrical energy storage devices.

Using new processes central to nanotechnology, they create millions of identical nanostructures with shapes tailored to transport energy as electrons rapidly to and from very large surface areas where they are stored. Materials behave according to physical laws of nature. The Maryland researchers exploit unusual combinations of these behaviors (called self-assembly, self-limiting reaction, and self-alignment) to construct millions -- and ultimately billions -- of tiny, virtually identical nanostructures to receive, store, and deliver electrical energy.

"These devices exploit unique combinations of materials, processes, and structures to optimize both energy and power density -- combinations that, taken together, have real promise for building a viable next-generation technology, and around it, a vital new sector of the tech economy," Rubloff said.

"The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power)," he continued.

Electrical energy storage devices fall into three categories. Batteries, particularly lithium ion, store large amounts of energy but cannot provide high power or fast recharge. Electrochemical capacitors (ECCs), also relying on electrochemical phenomena, offer higher power at the price of relatively lower energy density. In contrast, electrostatic capacitors (ESCs) operate by purely physical means, storing charge on the surfaces of two conductors. This makes them capable of high power and fast recharge, but at the price of lower energy density.

The Maryland research team's new devices are electrostatic nanocapacitors which dramatically increase energy storage density of such devices - by a factor of 10 over that of commercially available devices - without sacrificing the high power they traditionally characteristically offer. This advance brings electrostatic devices to a performance level competitive with electrochemical capacitors and introduces a new player into the field of candidates for next-generation electrical energy storage.

Where will these new nanodevices appear? Lee and Rubloff emphasize that they are developing the technology for mass production as layers of devices that could look like thin panels, similar to solar panels or the flat panel displays we see everywhere, manufactured at low cost. Multiple energy storage panels would be stacked together inside a car battery system or solar panel. In the longer run, they foresee the same nanotechnologies providing new energy capture technology (solar, thermoelectric) that could be fully integrated with storage devices in manufacturing.

This advance follows soon after another accomplishment, the dramatic improvement in performance (energy and power) of electrochemical capacitors (ECC's), thus 'supercapacitors,' by Lee's research group, published recently in the Journal of the American Chemical Society. Efforts are under way to achieve comparable advances in energy density of lithium (Li) ion batteries but with much higher power density.

"The University of Maryland's successes are built upon the convergence and collaboration of experts from a wide range of nanoscale science and technology areas with researchers already in the center of energy research," Rubloff said.

The Research Team

Gary Rubloff is Minta Martin Professor of Engineering in the materials science and engineering department and the Institute for Systems Research at the University of Maryland's A. James Clark School of Engineering. Sang Bok Lee is associate professor in the Department of Chemistry and Biochemistry at the College of Chemical and Life Sciences and WCU (World Class University Program) professor at KAIST (Korea Advanced Institute of Science and Technology) in Korea. Lee and Rubloff are part of a larger team developing nanotechnology solutions for energy capture, generation, and storage at Maryland. Their collaborators on electrical energy storage include Maryland professors Michael Fuhrer (physics), associate director of the Maryland Nanocenter Reza Ghodssi (electrical and computer engineering), John Cumings (materials science engineering), Ray Adomaitis (chemical and biomolecular engineering), Oded Rabin (materials science and engineering), Janice Reutt-Robey (chemistry), Robert Walker (chemistry), Chunsheng Wang (chemical and biomolecular engineering), Yu-Huang Wang (chemistry) and Ellen Williams (physics), director of the Materials Research Science and Engineering Center at the University of Maryland.

This work was partially supported by the Laboratory for Physical Sciences and by the university's Materials Research Science and Engineering Center under a grant from the National Science Foundation

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Adapted from materials provided by University of Maryland, College Park.

An Improved Fluorescent Sensor Material For Detecting Explosives Developed

ScienceDaily (May 29, 2007) — Scientists in the United States and China are reporting development of a new type of fluorescent sensing material that could lead to innovative devices for rapid detection of explosives in security screening, criminal investigations, and other applications. 

In the study, Southern Illinois University's Ling Zang and colleagues at the University of Illinois at Urbana-Champaign and the Chinese Academy of Sciences point out that fluorescent-based sensors signal the presence of explosives by losing their glow. Such existing devices, however, have serious limitations, which created the need for a new generation of sensor materials.

The new fluorescent film, made from nanofibrils, overcomes those disadvantages. In laboratory tests, it sensed the presence of vapors from TNT and a related explosives compound with greater effectiveness than existing materials. After sensing the compounds and losing its fluorescence, the material recovered its ability to fluoresce repeatedly during the tests. The experiments suggested that sensors made from the material would resist deterioration from exposure to sunlight, another drawback with existing sensor materials.

Their report is scheduled for the June 20 issue of the Journal of the American Chemical Society, a weekly publication. 

Article: "Detection of Explosives with a Fluorescent Nanofibril Film"

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Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.