Graphene 2.0

Yep, I’m going to be lazy just cop part of the title of this release, well really more of an article than an out-and-out press release. Sounds like a pretty cool graphene transistor with potential real world applications.

The release:

Graphene 2.0: a new approach to making a unique material

June 30, 2010

Since its discovery, graphene—an unusual and versatile substance composed of a single-layer crystal lattice of carbon atoms—has caused much excitement in the scientific community. Now, Nongjian (NJ) Tao, a researcher at the Biodesign Institute at Arizona State University has hit on a new way of making graphene, maximizing the material’s enormous potential, particularly for use in high-speed electronic devices.

Along with collaborators from Germany’s Max Planck Institute, the Department of Materials Science and Engineering, University of Utah, and Tsinghua University, Beijing, Tao created a graphene transistor composed of 13 benzene rings.

The molecule, known as a coronene, shows an improved electronic band gap, a property which may help to overcome one of the central obstacles to applying graphene technology for electronics. Tao is the director of the Biodesign Institute’s Center for Bioelectronics and Biosensors and electrical engineering professor in the Ira A. Fulton Schools of Engineering. The group’s work appears in the June 29 advanced online issue of Nature Communications.

Eventually, graphene components may find their way into a broad array of products, from lasers to ultra-fast computer chips; ultracapacitors with unprecedented storage capabilities; tools for microbial detection and diagnosis; photovoltaic cells; quantum computing applications and many others.

As the name suggests, graphene is closely related to graphite. Each time a pencil is drawn across a page, tiny fragments of graphene are shed. When properly magnified, the substance resembles an atomic-scale chicken wire. Sheets of the material possess exceptional electronic and optical properties, making it highly attractive for varied applications.

“Graphene is an amazing material, made of carbon atoms connected in a honeycomb structure,” Tao says, pointing to graphene’s huge electrical mobility—the ease with which electrons can flow through the material. Such high mobility is a critical parameter in determining the speed of components like transistors.

Producing usable amounts of graphene however, can be tricky. Until now, two methods have been favored, one in which single layer graphene is peeled from a multilayer sheet of graphite, using adhesive tape and the other, in which crystals of graphene are grown on a substrate, such as silicon carbide.

In each case, an intrinsic property of graphene must be overcome for the material to be suitable for a transistor. As Tao explains, “a transistor is basically a switch—you turn it on or off. A graphene transistor is very fast but the on/off ratio is very tiny. ” This is due to the fact that the space between the valence and conduction bands of the material—or band gap as it is known—is zero for graphene.

In order to enlarge the band gap and improve the on/off ratio of the material, larger sheets of graphene may be cut down to nanoscale sizes. This has the effect of opening the gap between valence and conductance bands and improving the on/off ratio, though such size reduction comes at a cost. The process is laborious and tends to introduce irregularities in shape and impurities in chemical composition, which somewhat degrade the electrical properties of the graphene.  “This may not really be a viable solution for mass production,” Tao observes.

Rather than a top down approach in which sheets of graphene are reduced to a suitable size to act as transistors, Tao’s approach is bottom up—building up the graphene, molecular piece by piece. To do this, Tao relies on the chemical synthesis of benzene rings, hexagonal structures, each formed from 6 carbon atoms. “Benzene is usually an insulating material, ” Tao says. But as more such rings are joined together, the material’s behavior becomes more like a semiconductor.

Using this process, the group was able to synthesize a coronene molecule, consisting of 13 benzene rings arranged in a well defined shape. The molecule was then fitted on either side with linker groups—chemical binders that allow the molecule to be attached to electrodes, forming a nanoscale circuit. An electrical potential was then passed through the molecule and the behavior, observed. The new structure displayed transistor properties, showing reversible on and off switches.

Tao points out that the process of chemical synthesis permits the fine-tuning of structures in terms of ideal size, shape and geometric structure, making it advantageous for commercial mass production. Graphene can also be made free of defects and impurities, thereby reducing electrical scattering and providing material with maximum mobility and carrier velocity, ideal for high-speed electronics.

In conventional devices, resistance is proportional to temperature, but in the graphene transistors by Tao et al., electron mobility is due to quantum tunneling, and remains temperature independent—a signature of coherent process.

The group believes they will be able to enlarge the graphene structures through chemical synthesis to perhaps hundreds of rings, while still maintaining a sufficient band gap to enable switching behavior. The research opens many possibilities for the future commercialization of this uncommon material, and its use in a new generation of ultra high-speed electronics.

Written by Richard Harth
Biodesign Institute Science Writer

Molecular nanobots

Via KurzweilAI.net — very cool! As always, I’ve included the entire KurzweilAI post. This one is a bit longer than usual.

How to make a molecular nanobot

KurzweilAI.net, May 13, 2010 Scientists have programmed an autonomous molecular nanorobot made out of DNA to start, move, turn, and stop while following a DNA track. (Paul Michelotti) The development could ultimately lead to molecular systems that could be used for medical therapeutic devices and molecular-scale reconfigurable robots—robots made of many simple units that can reposition or even rebuild themselves to accomplish different tasks. Molecular robots, in theory, could be programmed to sense their environment (say, the presence of disease markers on a cell), make a decision (that the cell is cancerous and needs to be neutralized), and act on that decision (deliver a cargo of cancer-killing drugs). Or they could be programmed to assemble complex molecular products. “In normal robotics, the robot itself contains the knowledge about the commands, but with individual molecules, you can’t store that amount of information, so the idea instead is to store information on the commands on the outside,” says Nils G. Walter, professor of chemistry and director of the Single Molecule Analysis in Real-Time (SMART) Center at the University of Michigan in Ann Arbor. And you do that by “imbuing the molecule‘s environment with informational cues,” says Milan N. Stojanovic, a faculty member in the Division of Experimental Therapeutics at Columbia University. “We were able to create such a programmed or ‘prescribed’ environment using DNA origami,” explains Hao Yan, professor of chemistry and biochemistry at Arizona State University. DNA origami is a type of self-assembledstructure made from DNA that can be programmed to form nearly limitless shapes and patterns. Exploiting the sequence-recognition properties of DNA base pairing, DNA origami are created from a long single strand of DNA and a mixture of different short synthetic DNA strands that bind to and “staple” the long DNA into the desired shape. The origami used in the Nature study was a rectangle that was 2 nanometers (nm) thick and roughly 100 nm on each side. The researchers constructed a trail of molecular “bread crumbs” on the DNA origami track by stringing additional single-stranded DNA molecules, or oligonucleotides, off the ends of the staples. These represent the cues that tell the molecular robots what to do—start, walk, turn left, turn right, or stop, for example—akin to the commands given to traditional robots. To build the 4-nm-diameter molecular robot, the researchers started with a common protein called streptavidin, which has four symmetrically placed binding pockets for a chemical moiety called biotin. Each robot leg is a short biotin-labeled strand of DNA, “so this way we can bind up to four legs to the body of our robot,” Walter says. “It’s a four-legged spider,” quips Stojanovic. Three of the legs are made of enzymatic DNA, which is DNA that binds to and cuts a particular sequence of DNA. The spider also is outfitted with a “start strand”—the fourth leg—that tethers the spider to the start site (one particular oligonucleotide on the DNA origami track). “After the robotis released from its start site by a trigger strand, it follows the track by binding to and then cutting the DNA strands extending off of the staple strands on the molecular track,” Stojanovic explains. “Once it cleaves,” adds Yan, “the product will dissociate, and the leg will start searching for the next substrate.” In this way, the spider is guided down the path laid out by the researchers. Finally, explains Yan, “the robot stops when it encounters a patch of DNA that it can bind to but that it cannot cut,” which acts as a sort of flypaper. Using atomic force microscopy and single-molecule fluorescence microscopy, the researchers were able to watch spiders crawling over the origami, showing that they were able to guide their molecular robots to follow four different paths. More info: Caltech news and Molecular robots guided by prescriptive landscapes

Providing disadvantages along with advantages helps nanotech acceptance

One of my more popular all time posts is “Nanotechnology does have drawbacks” from September 2008 so that tells me people regularly search for the negative side of nanotech. The topic is something that heads toward higher level science and the term gets tossed around a lot — and a lot of the time incorrectly as far as that goes — so people are naturally curious about exactly what is nanotechnology and how is it good and bad.

This survey, not surprisingly, found that providing information about the risks of nanotech increases public support among those who have heard of the field. Of course it also found support decreased among those who’d never heard the term once they were frightened by the potential drawbacks. I’m guessing scientific fact that sounds like scientific fiction can be pretty scary to someone who’s not familiar with what it can, and might, do both positive and negative.

From the second link, the release:

Survey: Hiding Risks Can Hurt Public Support For Nanotechnology

Release Date: 05.04.2010

A new national survey on public attitudes toward medical applications and physical enhancements that rely on nanotechnology shows that support for the technology increases when the public is informed of the technology’s risks as well as its benefits – at least among those people who have heard of nanotechnology. The survey, which was conducted by researchers at North Carolina State University and Arizona State University (ASU), also found that discussing risks decreased support among those people who had never previously heard of nanotechnology – but not by much.

“The survey suggests that researchers, industries and policymakers should not be afraid to display the risks as well as the benefits of nanotechnology,” says Dr. Michael Cobb, an associate professor of political science at NC State who conducted the survey. “We found that when people know something about nanotechnologies for human enhancement, they are more supportive of it when they are presented with balanced information about its risks and benefits.”

The survey was conducted by Cobb in collaboration with Drs. Clark Miller and Sean Hays of ASU, and was funded by the Center for Nanotechnology in Society at ASU.

However, talking about risks did not boost support among all segments of the population. Those who had never heard of nanotechnology prior to the survey were slightly less supportive when told of its potential risks.

In addition to asking participants how much they supported the use of nanotechnology for human enhancements, they were also asked how beneficial and risky they thought these technologies would be, whether they were worried about not getting access to them, and who should pay for them – health insurance companies or individuals paying out-of-pocket. The potential enhancements addressed in the survey run the gamut from advanced cancer treatments to bionic limbs designed to impart greater physical strength.

One segment of participants was shown an image of an unrealistic illustration meant to represent a nanoscale medical device. A second segment was shown the image and given a “therapeutic” framing statement that described the technology as being able to restore an ill person to full health. A third segment was given the image, along with an “enhancement” framing statement that described the technology as being able to make humans faster, stronger and smarter. Two additional segments were given the image, the framing statements and information about potential health risks. And a final segment of participants was not given the image, a framing statement or risk information.

The survey found that describing the technology as therapeutic resulted in much greater public support for the technology, as well as a greater perception of its potential benefits. The therapeutic frame also resulted in increased support for health insurance coverage of nanotech treatments once they become available, and increased concerns that people wouldn’t be able to afford such treatments without insurance coverage.

“These findings suggest that researchers, policymakers and industries would be well advised to focus their research efforts on developing therapeutic technologies, rather than enhancements, because that is the area with the greatest public support,” Cobb says.

The use of the nanotech image did not have a significant overall impact on participants’ support, but did alarm people who were not previously familiar with nanotechnology – making them less likely to support it.

The survey was conducted by Knowledge Networks between April 2-13. The survey included 849 participants, and has a margin of error of plus or minus 3.3 percent.

NC State’s Department of Political Science is part of the university’s College of Humanities and Social Sciences.

This illustration was used to represent a nanoscale medical device in the national survey on public attitudes towards the use of nanotechnology for human enhancement.

Going beyond radio in the search for ET

I’ve been a longtime supporter of SETI’s efforts, but I also welcome any new ideas in the search for extraterrestrial intelligence. These ideas from Paul Davies sound worthwhile.

The release

Widening the search for extraterrestrial intelligence

The Search for Extraterrestrial Intelligence (SETI) has been dominated for its first half century by a hunt for unusual radio signals. But as he prepares for the publication of his new book The Eerie Silence: Are We Alone?, Paul Davies tells Physics World readers why bold new innovations are required if we are ever to hear from our cosmic neighbours.

Writing exclusively in March’s Physics World, Davies, director of BEYOND: Center for Fundamental Concepts in Science at Arizona State University in the US, explains why the search for radio signals is limited and how we might progress.

As Davies writes, “speculation about SETI is bedevilled by the trap of anthropocentrism – a tendency to use 21st-century human civilisation as a model for what an extraterrestrial civilisation would be like… After 50 years of traditional SETI, the time has come to widen the search from radio signals.”

Questioning the idea of an alien civilisation beaming radio signals towards Earth, Davies explains that even if the aliens were, say, 500 light years away (close by SETI standards), the aliens would be communicating with Earth in 1510 – long before we were equipped to pick up radio signals.

While SETI activity has been concentrated in radio astronomy, from Frank Drake’s early telescope to the more recent Allen Telescope Array, astronomers have only ever been met with an (almost) eerie silence.

Davies suggests that there may be more convincing signs of intelligent alien life, either here on Earth in the form of bizarre microorganisms that somehow found their way to Earth, or in space, through spotting the anomalous absence of, for example, energy-generating particles that an alien life form might have harvested.

“Using the full array of scientific methods from genomics to neutrino astrophysics,” Davies writes, “we should begin to scrutinise the solar system and our region of the galaxy for any hint of past or present cosmic company.”

Following the publication of his book, The Eerie Silence, Davies will be giving a Physics World webinar at 4pm (BST) on Wednesday 31 March. You can view the webinar live at http://www.physicsworld.com or download it afterwards.

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Also in the March edition:

• Getting intimate with Mars – robotic rovers are starting to unravel the secrets of the red planet but, according to one NASA expert, we would discover so much more if we brought samples back to Earth.
• The Hollywood actor Alan Alda, star of M*A*S*H and The West Wing, who has a deep and passionate interest in science, is now part of an innovative US project to help scientists to communicate.

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Testing graphene for potential applications

Graphene is proving to be one of the most, if not the most, exciting nanotech discovery of the last few years. The material has a lot of promise in terms of applications in medicine, electronics and who know what else.

Here’s some measurement and testing on putting the nanomaterial to actual use in the market.

The release:

Material world: graphene’s versatility promises new applications

July 09, 2009

Since its discovery just a few years ago, graphene has climbed to the top of the heap of new super-materials poised to transform the electronics and nanotechnology landscape. As N.J. Tao, a researcher at the Biodesign Institute of Arizona State University explains, this two-dimensional honeycomb structure of carbon atoms is exceptionally strong and versatile. Its unusual properties make it ideal for applications that are pushing the existing limits of microchips, chemical sensing instruments, biosensors, ultracapacitance devices, flexible displays and other innovations.

In the latest issue of Nature Nanotechnology Letters, Tao describes the first direct measurement of a fundamental property of graphene, known as quantum capacitance, using an electrochemical gate method. A better understanding of this crucial variable should prove invaluable to other investigators participating in what amounts to a gold rush of graphene research.

Although theoretical work on single atomic layer graphene-like structures has been going on for decades, the discovery of real graphene came as a shock.  “When they found it was a stable material at room temperature,” Tao says,  “everyone was surprised.” As it happens, minute traces of graphene are shed whenever a pencil line is drawn, though producing a 2-D sheet of the material has proven trickier.  Graphene is remarkable in terms of thinness and resiliency. A one-atom thick graphene sheet sufficient in size to cover a football field, would weigh less than a gram. It is also the strongest material in nature—roughly 200 times the strength of steel. Most of the excitement however, has to do with the unusual electronic properties of the material.

Graphene displays outstanding electron transport, permitting electricity to flow rapidly and more or less unimpeded through the material. In fact, electrons have been shown to behave as massless particles similar to photons, zipping across a graphene layer without scattering. This property is critical for many device applications and has prompted speculation that graphene could eventually supplant silicon as the substance of choice for computer chips, offering the prospect of ultrafast computers operating at terahertz speeds, rocketing past current gigahertz chip technology. Yet, despite encouraging progress, a thorough understanding of graphene’s electronic properties has remained elusive. Tao stresses that quantum capacitance measurements are an essential part of this understanding.

Capacitance is a material’s ability to store energy. In classical physics, capacitance is limited by the repulsion of like electrical charges, for example, electrons. The more charge you put into a device, the more energy you have to expend to contain it, in order to overcome charge repulsion. However, another kind of capacitance exists, and dominates overall capacitance in a two-dimensional material like graphene. This quantum capacitance is the result of the Pauli exclusion principle, which states that two fermions—a class of common particles including protons, neutrons and electrons—cannot occupy the same location at the same time. Once a quantum state is filled, subsequent fermions are forced to occupy successively higher energy states. As Tao explains, “it’s just like in a building, where people are forced to go to the second floor once the first level is occupied.”

In the current study, two electrodes were attached to graphene, and a voltage applied across the material’s two-dimensional surface by means of a third, gate electrode. Plots of voltage vs. capacitance can be seen in fig1. In Tao’s experiments, graphene’s ability to store charge according to the laws of quantum capacitance, were subjected to detailed measurement. The results show that graphene’s capacitance is very small. Further, the quantum capacitance of graphene did not precisely duplicate theoretical predictions for the behavior of ideal graphene. This is due to the fact that charged impurities occur in experimental samples of graphene, which alter the behavior relative to what is expected according to theory.

Tao stresses the importance of these charged impurities and what they may mean for the development of graphene devices. Such impurities were already known to affect electron mobility in graphene, though their effect on quantum capacitance has only now been revealed. Low capacitance is particularly desirable for chemical sensing devices and biosensors as it produces a lower signal-to-noise ratio, providing for extremely fine-tuned resolution of chemical or biological agents. Improvements to graphene will allow its electrical behavior to more closely approximate theory. This can be accomplished by adding counter ions to balance the charges resulting from impurities, thereby further lowering capacitance.  

The sensitivity of graphene’s single atomic layer geometry and low capacitance promise a significant boost for biosensor applications. Such applications are a central topic of interest for Tao, who directs the Biodesign Institute’s Center for Bioelectronics and Biosensors. As Tao explains, any biological substance that interacts with graphene’s single atom surface layer can be detected, causing a huge change in the properties of the electrons.

One possible biosensor application under consideration would involve functionalizing graphene’s surface with antibodies, in order to precisely study their interaction with specific antigens. Such graphene-based biosensors could detect individual binding events, given a suitable sample.  For other applications, adding impurities to graphene could raise overall interfacial capacitance. Ultracapacitors made of graphene composites would be capable of storing much larger amounts of renewable energy from solar, wind or wave energy than current technologies permit.

Because of graphene’s planar geometry, it may be more compatible with conventional electronic devices than other materials, including the much-vaunted carbon nanotubes. “You can imagine an atomic sheet, cut into different shapes to create different device properties,” Tao says.

Since the discovery of graphene, the hunt has been on for similar two-dimensional crystal lattices, though so far, graphene remains a precious oddity.

 Advanced Online Publication: http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2009.177.html

 -Written by Richard Harth
Science Writer
Biodesign Institute

Aliens amonst us

Yep, this is a total release dump and there’s one more to come. I couldn’t resist because a slew of very cool news came out of the 2009 AAAS Annual Meeting today.

The release:

Cosmologist Paul Davies explores notion of ‘alien’ life on Earth

CHICAGO – Astrobiologists have often pondered “life as we do not know it” in the context of extraterrestrial life, says Paul Davies, an internationally acclaimed theoretical physicist and cosmologist at Arizona State University. “But,” he asks, “has there been a blind spot to the possibility of ‘alien’ life on Earth?”

Davies will challenge the orthodox view that there is only one form of life in a lecture titled “Shadow Life: Life As We Don’t Yet Know It” on Feb. 15 at the annual meeting of the American Association for the Advancement of Science. His presentation is part of the symposium “Weird Life.”

“Life as we know it appears to have had a single common ancestor, yet, could life on Earth have started many times? Might it exist on Earth today in extreme environments and remain undetected because our techniques are customized to the biochemistry of known life?” asks Davies, who also is the director of the BEYOND Center for Fundamental Concepts in Science at Arizona State University in the College of Liberal Arts and Sciences.

In the lecture, Davies will present, challenge and extend some of the conclusions from a July 2007 report by the National Research Council. That report looked at whether the search for life should include “weird life” – described by the Council as “life with an alternative biochemistry to that of life on Earth.”

“If a biochemically weird microorganism should be discovered, its status as evidence for a second genesis, as opposed to a new branch on our own tree of life, will depend on how fundamentally it differs from known life,” wrote Davies in the Nov. 19, 2007, issue of Scientific American.

Davies and other pioneers who speculate that life on Earth may have started many times are wondering “why we have overlooked this idea for so long?”

The concept of a shadow biosphere, according to Davies, “is still just a theory. If someone discovers shadow life or weird life it will be the biggest sensation in biology since Darwin. We are simply saying, ‘Why not let’s take a look for it?’ It doesn’t cost much (compared to looking for weird life on Mars, say), and, it might be right under our noses.”

Davies, whose research is steeped in the branches of physics that deal with quantum gravity – an attempt to reconcile theories of the very large and the very small – is a prolific author (27 books, both popular and specialty works) and is a provocative speaker (he delivered the 1995 Templeton Prize address after receiving the prestigious award for initiating “a new dialogue between science and religion that is having worldwide repercussions”).

Among his books are: “How to Build a Time Machine,” “The Origin of Life,” “The Big Questions,” “The Last Three Minutes,” “The Mind of God,” “The Cosmic Blueprint” and his most recent book “The Goldilocks Enigma: Why is the universe just right for life?” published in the United States under the title “Cosmic Jackpot.”

He is putting the finishing touches on “The Eerie Silence,” to be published in 2010 to coincide with the 50th anniversary of the SETI Institute. According to Davies, the book is “a comprehensive fresh look at the entire SETI enterprise.”

 

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Arizona State University
College of Liberal Arts and Sciences
Tempe, Arizona USA
www.asu.edu

3D DNA nantubes

Pretty cool research here.

The release:

The gold standard: Biodesign Institute researchers use nanoparticles to make 3-D DNA nanotubes

DNA nanotubes may soon find their way into a new generation of ultra-tiny electronic and biomedical innovations

		VIDEO: 5-nm size gold nanoparticles wrap around the perimeter of a DNA nanotube in a spiral pattern. The 3-D structures have been recreated from cryoelectron tomographic imaging. Click here for more information.

Arizona State University researchers Hao Yan and Yan Liu imagine and assemble intricate structures on a scale almost unfathomably small. Their medium is the double-helical DNA molecule, a versatile building material offering near limitless construction potential.

In the January 2, 2009 issue of Science, Yan and Liu, researchers at ASU’s Biodesign Institute and faculty in the Department of Chemistry and Biochemistry, reveal for the first time the three-dimensional character of DNA nanotubules, rings and spirals, each a few hundred thousandths the diameter of a human hair. These DNA nanotubes and other synthetic nanostructures may soon find their way into a new generation of ultra-tiny electronic and biomedical innovations.

Yan and Liu are working in the rapidly proliferating field of structural DNA nanotechnology. By copying a page from nature’s guidebook, they capitalize on the DNA molecule’s remarkable properties of self-assembly. When ribbonlike strands of the molecule are brought together, they fasten to each other like strips of Velcro, according to simple rules governing the pairing of their four chemical bases, (labeled A, C, T and G). From this meager alphabet, nature has wrung a mind-bending multiplicity of forms. DNA accomplishes this through the cellular synthesis of structural proteins, coded for by specific sequences of the bases. Such proteins are fundamental constituents of living matter, forming cell walls, vessels, tissues and organs. But DNA itself can also form stable architectural structures, and may be artificially cajoled into doing so.

		VIDEO: In this DNA nanotube configuration, again using 5-nm size gold nanoparticles, the nanoparticles form stacked rings around the DNA. Click here for more information.

In his research, Yan has been much inspired by nanoscale ingenuity in the natural world: “Unicellular creatures like oceanic diatoms,” he points out, “contain self-assembled protein architectures.” These diverse forms of enormous delicacy and organismic practicality are frequently the result of the orchestrated self-assembly of both organic and inorganic material.

Scientists in the field of structural DNA nanotechnology, including Dr. Yan’s team, have previously demonstrated that pre-fab DNA elements could be induced to self-assemble, forming useful nanostructural platforms or “tiles.” Such tiles are able to snap together—with jigsaw puzzle-piece specificity—through base pairing, forming larger arrays.

Yan and Liu’s work in Science responds to one of the fundamental challenges in nanotechnology and materials science, the construction of molecular-level forms in three dimensions. To do so, the team uses gold nanoparticles, which can be placed on single-stranded DNA, compelling these flexible molecular tile arrays to bend away from the nanoparticles, curling into closed loops or forming spring-like spirals or nested rings, roughly 30 to 180 nanometers in diameter.

The gold nanoparticles, which coerce DNA strands to arc back on themselves, produce a force known as “steric hindrance,” whose magnitude depends on the size of particle used. Using this steric hindrance, Yan and Liu have shown for the first time that DNA nanotubules can be specifically directed to curl into closed rings with high yield.

When 5 nanometer gold particles were used, a milder steric hindrance directed the DNA tiles to curl up and join complementary neighboring segments, often forming spirals of varying diameter in addition to closed rings. A 10 nanometer gold particle however, exerted greater steric hindrance, directing a more tightly constrained curling which, produced mostly closed tubules. Yan stresses that the particle not only participates in the self-assembly process as the directed material, but also as an active agent, inducing and guiding formation of the nanotube.

		VIDEO: Using 10-nm-size gold nanoparticles, the DNA nanotubes form a split branch structure, with both the spiral tube splitting into two smaller stacked rings. Click here for more information.

With the assistance of Anchi Cheng and Jonanthan Brownell at the Scripps Research Institute, they have used an imaging technique known as electron cryotomography to provide the first glimpses of the elusive 3-D architecture of DNA nanotubules. “You quickly freeze the sample in vitreous ice,” he explains, describing the process. “This will preserve the native conformation of the structure.” Subsequent imaging at various tilted angles allows the reconstruction of the three-dimensional nanostructure, with the gold particles providing enough electron density for crisp visualization. (see movies)

DNA nanotubules will soon be ready to join their carbon nanotube cousins, providing flexible, resilient and manipulatable structures at the molecular level. Extending control over 3-D architectures will lay the foundation for future applications in photometry, photovoltaics, touch screen and flexible displays, as well as for far-reaching biomedical advancements.

“The ability to build three-dimensional structures through self-assembly is really exciting, ” Yan says. “It’s massively parallel. You can simultaneously produce millions or trillions of copies.”

Yan and Liu believe that controlled tubular nanostructures bearing nanoparticles may be applied to the design of electrical channels for cell-cell communication or used in the construction of various nanoelectrical devices.

 

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About the Biodesign Institute at ASU

The Biodesign Institute at Arizona State University pursues research to create personalized medical diagnostics and treatments, outpace infectious disease, clean the environment, develop alternative energy sources, and secure a safer world. Using a team approach that fuses the biosciences with nanoscale engineering and advanced computing, the Biodesign Institute collaborates with academic, industrial and governmental organizations globally to accelerate these discoveries to market. For more information, go to: www.biodesign.asu.edu

More on nanotech and public perception

Man, this study is producing a lot of press releases. I’ve blogged here and here so far, and now here’s more food for thought.

The release:

New studies reveal differing perceptions of nature-altering science

Religion and culture shape views of nanotechnology

Two new National Science Foundation (NSF)-sponsored research studies say public acceptance of the relatively new, nature-altering science of nanotechnology isn’t a foregone conclusion. Instead, the studies indicate continued concern.

Researchers at Yale University say that when people learn about this novel technology they become sharply divided along cultural lines, while a separate study led by researchers at the University of Wisconsin-Madison and Arizona State University says nanotechnology seems to be failing the moral litmus test of religion.

Federal entities are looking into safety and public acceptance issues surrounding nanotechnology because of its ability to alter matter on an atomic and molecular scale. The potential societal benefits of using nanotechnology to create new materials and devices for medicine, electronics and energy production could be huge. But the idea of creating them through molecular manipulation leaves some people apprehensive.

“Evidence shows that there is much room for improvement in efforts to communicate about the environmental, health, and safety impacts of nanotechnology,” said Robert E. O’Connor, NSF program manager for decision, risk and management sciences.

The Yale study, part of their Cultural Cognition Project, surveyed 1,500 Americans, the majority of whom were unfamiliar with nanotechnology. Researchers gave participants balanced information about its risks and benefits. Upon seeing it, study participants became highly divided on the technology’s safety compared to a group that was not shown the same information.

According to Dan Kahan, the Elizabeth K. Dollard Professor at Yale Law School and lead author of the study, people’s cultural values determined how they responded. “People who had more individualistic, pro-commerce values, tended to infer that nanotechnology is safe,” said Kahan. People more worried about economic inequality saw the same information as implying that nanotechnology is likely to be dangerous.

The finding is consistent with other Cultural Cognition Project studies that show people’s cultural values influence their perceptions of environmental and technological risks. Kahan notes, “When respondents learned about this new technology, they matched their views of its risks with previously held cultural values.”

A separate study conducted in the United States and Europe indicates that people with religious views see nanotechnology as less morally acceptable, compared with people who live in more secular societies.

According to the study, the United States and a few European countries where religion plays a larger role, notably Italy, Austria and Ireland see the potential of nanotechnology to alter living organisms or inspire synthetic life as less morally acceptable. In more secular European societies such as France and Germany, people are less likely to see nanotechnology as morally suspect.

“What we captured is nano-specific,” said Dietram Scheufele, University of Wisconsin-Madison professor of life sciences communication. “But it is also representative of a larger attitude toward science and technology. It raises a big question about what’s really going on in our public discourse where science and religion often clash.”

“Our findings show that the public no longer just turns to scientists for answers about the science, but also for answers about its social implications,” he said. “In other words, they want to know not only what can be done, but also what should be done. The more prepared scientists are to answer both questions, the more credible their societal leadership will be on issues like nanotechnology,” said Scheufele, who co-authored the study with Elizabeth Corley, School of Public Affairs at Arizona State.

According to O’Connor, both studies highlight the need for specific public education strategies that consider citizens’ values and predispositions. “Understanding that people make decisions about technology through the prisms of their personal values will be important to take into account if we are to accurately communicate the risks and benefits of innovations like nanotechnology to the public,” said O’Connor.

“There is still plenty of time to develop risk-communication strategies that make it possible for persons of diverse values to understand the best evidence on nanotechnology’s risks,” said Kahan. “The only mistake would be to assume that such communication strategies aren’t necessary.”

It’s estimated that nanotechnology will be a $3.1 trillion global industry by 2015. Both studies can be found in the Dec. 7, 2008, issue of the journal Nature Nanotechnology.

 

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DNA-based nanotech

From KurzweilAI.net — This is interesting nanotechnology news. Using cells to create DNA-based nanostructures inside a cell.

Using living cells as nanotechnology factories

PhysOrg.com, Oct. 8, 2008 Arizona State University and New York University researchers are using cells as factories to make DNA-based nanostructures inside a living cell. They are using a phagemid, a virus-like particle that infects a bacteria cell. Once inside the cell, the phagemid uses the cell just like a photocopier machine. By theoretically starting with just a single phagemid infection, and a single milliliter of cultured cells, they found that the cells could churn out trillions of the DNA junction nanostructures.   Read Original Article>>

Looking inside aerogels

Aerogels are pretty amazing substances with many uses. This press release covers using X-ray diffraction to get a 3D nanoscale look inside aerogels.

The full release and two of the provided images:

X-Ray Diffraction Looks Inside Aerogels in 3-D

A multi-institutional team of scientists has used beamline 9.0.1 at the Advanced Light Source to perform high-resolution x‑ray diffraction imaging of an aerogel for the first time, revealing its nanoscale three-dimensional bulk lattice structure down to features measured in nanometers, billionths of a meter.

Aerogels, sometimes called “frozen smoke” or “San Francisco fog,” are nanoscale foams: solid materials whose sponge-like structure is riddled by pores as small as nanometers across and whose strength is surprising, given their low density. Many porous materials are extraordinary for their properties as insulators, filters, and catalysts; they are used to produce clean fuels, to insulate windows and even clothing, to study the percolation of oil through rock, as drug-delivery systems, and even to cushion the capture of high-velocity comet fragments in outer space.

“The smallest pore size is the key to the strength of porous materials and what they can do,” says Stefano Marchesini, an ALS scientist at Berkeley Lab, who led the research. “Seeing inside bulk porous materials has never been done before at this resolution, making this one of the first applications of x-ray diffractive microscopy to a real problem.” 

Team members from Lawrence Livermore National Laboratory, the University of California at Davis, Arizona State University, Argonne National Laboratory, and Berkeley Lab performed the x‑ray diffraction imaging and have published their results online in Physical Review Letters, available to subscribers at http://link.aps.org/abstract/PRL/v101/e055501.

Seeing inside foam

One way to study aerogels and other nanofoams is with electron microscopy, which can image only thin, two-dimensional slices through the porous structure of the material. Another method is straightforward x-ray microscopy, using zone plates as “lenses”; microscopy can penetrate a sample but has difficulty maintaining resolution at different depths in the material. Small-angle x‑ray scattering (SAXS) can also gather limited structural information from finely powdered aerogels, but SAXS cannot provide full three-dimensional information. None of these techniques can capture the 3-D internal structure of nanofoam samples measured in micrometers, a few millionths of a meter across.

X-ray diffraction approaches the problem differently. A laser-like x-ray beam passes all the way through the sample and is diffracted onto a CCD detector screen; diffraction patterns are repeatedly stored while the sample is moved and rotated. A typical series requires approximately 150 views in all.

The individual diffraction patterns are then processed by a computer. The way the photons in the beam are redirected from each component of the structure is different for each orientation, and comparing their intensities serves to position that component precisely in three-dimensional space. Thousands of iterations are required – in the present study, team member Anton Barty of Livermore led the solution of almost 100 million measured intensities, as opposed to the 100 thousand or so typical of, say, protein crystallography – but the end result is a 3‑D image of the tiny sample at nanometer-scale resolution.

Foam-like structures are described in terms of interconnecting lattice beams and the nodes where they intersect. These elements became vividly apparent in the reconstructed 3-D images of the aerogel used in the imaging at the ALS, which was made of tantalum ethoxide (Ta₂O₅), a ceramic material proposed for cladding capsules of hydrogen isotopes for inertial-confinement fusion experiments being pursued at Livermore.

“The strength and stiffness of foam-like structures are expected to scale with their density, relating the density of individual elements like beams and nodes to the overall density,” Marchesini says. “But below about 10 percent density, the strength of aerogels like the ones we tested – on the order of 1 percent density – is orders of magnitude less than expected.”

Of the theories that seek to explain this phenomenon, one is the “percolation” model, in which fragments become detached from the load-bearing structure and add mass without contributing to strength. The alternate “heterogeneities” model proposes that the structure is increasingly riddled with defects like micron-sized holes and buckles more easily.

A third theory is the “diffusion-limited cluster aggregation” model: blobs of material accumulate that are connected by thin links, instead of sturdy beams between nodes.

“The high resolution we achieved allowed us to see which of these models more accurately described the actual observed structure,” Marchesini says. By seeing the foam from the inside, the team was able to see exactly how it was structured, and the shape and dimensions of each component. “The structure was far more complex than anything we’d seen in earlier images obtained using this technique.”

What the team observed in their 3-D images of the tantalum ethoxide aerogel was a “blob-and-beam” structure consistent with the third model, that of diffusion-limited cluster aggregation. The observed structure explained the relative weakness of the low-density material and also suggested that changes in methods of preparing aerogels might improve their strength.

Into the future

“We’d like to use x-ray diffraction to study a range of porous materials and nanostructures in general, for example porous polymers developed at the Molecular Foundry for storing hydrogen as fuel – and at even higher resolutions,” Marchesini says. “To do so, David Shapiro, who built the end station we used for this work, is working with us to overcome some obstacles.”

One is time. At present, each sample takes months of work. After preparation, the experiment first requires one or two days of mounting, rotating, and exposing the sample to the x-ray beam, about a minute per view – because of a slow detector – for 150 views. There follow weeks of computation time. “And after all this, you can find out the sample was no good, so you have to start over,” Marchesini says.

Improved sample handling, faster detectors, and a beamline dedicated to x-ray diffraction are principal goals. The Coherent Scattering and Diffraction Microscopy (COSMIC) facility, a top priority in the ALS strategic plan, will provide intense coherent x-rays with full polarization control.

“We are also collaborating with Berkeley Lab’s Computational Research Division to develop efficient and robust algorithms to speed up the time needed to construct the 3-D image from the individual rotated views,” Marchesini says. “This will open an entire spectrum of possibilities for new ways of seeing the very small – not just aerogels but virtually any unknown object, from nanostructures to biological cells.”

This work was principally supported by the Department of Energy through a variety of grants, by Laboratory Directed Research and Development programs at Livermore, and additionally by the National Science Foundation.

Additional information

• “Three-dimensional coherent X-ray diffraction imaging of a ceramic nanofoam: determination of structural deformation mechanisms,” by A. Barty, S. Marchesini, H. N. Chapman, C. Cui, M. R. Howells, D. A. Shapiro, A. M. Minor, J. C. H. Spence, U. Weierstall, J. Havsky, A. Noy, S. P. Hau-Riege, A. B. Artyukhin, T. Baumann, T. Willey, J. Stolken, T. van Buuren, and J. H. Kinney, appears in Physical Review Letters online publication and is available to subscribers at http://link.aps.org/abstract/PRL/v101/e055501.
• More about beamline 9.0.1 at the Advanced Light Source

Silicon aerogel acting as an insulator

 

A 500-nanometer cube of aerogel from the interior of the 3-D volume, reconstructed by x-ray diffraction. The foam structure shows globular nodes that are interconnected by thin beam- like struts. Approximately 85 percent of the total mass is associated with the nodes; relatively little of the mass is in the load-bearing links.

Nanotrees and nanomotors

From KurzweilAI.net, nanotrees are a new type of nanowire and Arizona State researchers have created the fastest nanomotor.

Spiraling nanotrees offer new twist on growth of nanowires

PhysOrg.com, May 1, 2008 University of Wisconsin-Madison researchers have discovered a new way of growing nanowires that leads to “nanopines”–elaborate pine-tree-shaped nanowires–caused by a “screw” dislocation, or defect, in their crystal structure. Dislocations are fundamental to the growth and characteristics of all crystalline materials, but this is the first time they’ve been shown to aid the growthof one-dimensional nanostructures. Engineering these dislocations may allow scientists to create more elaborate nanostructures, and to investigate the fundamental mechanical, thermal and electronic properties of dislocations in materials.   Read Original Article>>

 

Revving up the world’s fastest nanomotor

PhysOrg.com, May 1, 2008 Arizona State University researchers have developed a new generation of nanomotors with an average speed of 60 micrometers per second. Tracks left by various types of speeding nanomotors (American Chemical Society) Existing catalytic nanomotors–made with gold and platinum nanowires and fueled with hydrogen peroxide–have top speeds of about 10 micrometers per second. The new design adds carbon nanotubes to the platinum (boosting the average speed) and spikes the hydrogenperoxide fuel with hydrazine to increase the nanomotor’s top speed to 200 nanometers per second.   Read Original Article>>

Synthetic DNA new nanotech building block

From KurzweilAI.net:

Scientists make chemical cousin of DNA for use as new nanotechnology building block

PhysOrg.com, April 29, 2008 Arizona State University’s Biodesign Institute scientist John Chaput and his research team have made the first synthetic self-assembled nanostructures, composed entirely of glycerol nucleic acid (GNA), a synthetic analog of DNA. (Biodesign Institute at Arizona State University) With GNA, the five carbon sugar commonly found in DNA (deoxyribose) is substituted by glycerol, which contains just three carbon atoms. Unlike DNA and proteins, which have evolved to exist only as right-handed, the GNA structures are “enantiomeric” molecules (both left and right-handed). The ability to make mirror image structures opens up new possibilities for making nanostructures.   Read Original Article>>