Forster J.D.,Molecular Foundry |
Harris S.J.,Lawrence Berkeley National Laboratory |
Urban J.J.,Molecular Foundry
Journal of Physical Chemistry Letters | Year: 2014
We demonstrate confocal Raman microscopy as a general, nonperturbative tool to measure spatially resolved lithium ion concentrations in liquid electrolytes. By combining this high-spatial-resolution technique with a simple microfluidic device, we are able to measure the diffusion coefficient of lithium ions in dimethyl carbonate in two different concentration regimes. Because lithium ion transport plays a key role in the function of a variety of electrochemical devices, quantifying and visualizing this process is crucial for understanding device performance. This method for detecting lithium ions should be immediately useful in the study of lithium-ion-based devices, ion transport in porous media, and at electrode-electrolyte interfaces, and the analytical framework is useful for any system exhibiting a concentration-dependent Raman spectrum. © 2014 American Chemical Society.
But building nanostructures is difficult. And creating a large quantity of nanostructures with the same trait, such as millions of nanotubes with identical diameters, is even more difficult. This kind of precision manufacturing is needed to create the nanotechnologies of tomorrow. Help could be on the way. As reported online the week of March 28 in the journal Proceedings of the National Academy of Sciences, researchers at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered a family of nature-inspired polymers that, when placed in water, spontaneously assemble into hollow crystalline nanotubes. What's more, the nanotubes can be tuned to all have the same diameter of between five and ten nanometers, depending on the length of the polymer chain. The polymers have two chemically distinct blocks that are the same size and shape. The scientists learned these blocks act like molecular tiles that form rings, which stack together to form nanotubes up to 100 nanometers long, all with the same diameter. "This points to a new way we can use synthetic polymers to create complex nanostructures in a very precise way," says Ron Zuckermann, who directs the Biological Nanostructures Facility in Berkeley Lab's Molecular Foundry, where much of this research was conducted. Several other Berkeley Lab scientists contributed to this research, including Nitash Balsara of the Materials Sciences Division and Ken Downing of the Molecular Biophysics and Integrated Bioimaging Division. "Creating uniform structures in high yield is a goal in nanotechnology," adds Zuckermann. "For example, if you can control the diameter of nanotubes, and the chemical groups exposed in their interior, then you can control what goes through—which could lead to new filtration and desalination technologies, to name a few examples." The research is the latest in the effort to build nanostructures that approach the complexity and function of nature's proteins, but are made of durable materials. In this work, the Berkeley Lab scientists studied a polymer that is a member of the peptoid family. Peptoids are rugged synthetic polymers that mimic peptides, which nature uses to form proteins. They can be tuned at the atomic scale to carry out specific functions. For the past several years, the scientists have studied a particular type of peptoid, called a diblock copolypeptoid, because it binds with lithium ions and could be used as a battery electrolyte. Along the way, they serendipitously found the compounds form nanotubes in water. How exactly these nanotubes form has yet to be determined, but this latest research sheds light on their structure, and hints at a new design principle that could be used to build nanotubes and other complex nanostructures. Diblock copolypeptoids are composed of two peptoid blocks, one that's hydrophobic one that's hydrophilic. The scientists discovered both blocks crystallize when they meet in water, and form rings consisting of two to three individual peptoids. The rings then form hollow nanotubes. Cryo-electron microscopy imaging of 50 of the nanotubes showed the diameter of each tube is highly uniform along its length, as well as from tube to tube. This analysis also revealed a striped pattern across the width of the nanotubes, which indicates the rings stack together to form tubes, and rules out other packing arrangements. In addition, the peptoids are thought to arrange themselves in a brick-like pattern, with hydrophobic blocks lining up with other hydrophobic blocks, and the same for hydrophilic blocks. "Images of the tubes captured by electron microscopy were essential for establishing the presence of this unusual structure," says Balsara. "The formation of tubular structures with a hydrophobic core is common for synthetic polymers dispersed in water, so we were quite surprised to see the formation of hollow tubes without a hydrophobic core." X-ray scattering analyses conducted at beamline 7.3.3 of the Advanced Light Source revealed even more about the nanotubes' structure. For example, it showed that one of the peptoid blocks, which is usually amorphous, is actually crystalline. Remarkably, the nanotubes assemble themselves without the usual nano-construction aids, such as electrostatic interactions or hydrogen bond networks. "You wouldn't expect something as intricate as this could be created without these crutches," says Zuckermann. "But it turns out the chemical interactions that hold the nanotubes together are very simple. What's special here is that the two peptoid blocks are chemically distinct, yet almost exactly the same size, which allows the chains to pack together in a very regular way. These insights could help us design useful nanotubes and other structures that are rugged and tunable—and which have uniform structures." More information: Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1517169113
Home > Press > Polar vortices observed in ferroelectric: New state of matter holds promise for ultracompact data storage and processing Abstract: The observation in a ferroelectric material of "polar vortices" that appear to be the electrical cousins of magnetic skyrmions holds intriguing possibilities for advanced electronic devices. These polar vortices, which were theoretically predicted more than a decade ago, could also "rewrite our basic understanding of ferroelectrics" according to the researchers who observed them. A team of scientists with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have recorded the first ever observations of rotating topologies of electrical polarization that are similar to the discrete swirls of magnetism known as "skyrmions." If these smoothly rotating vortex/anti-vortex topologies prove to be electrical skyrmions, they could find potential applications in ultracompact data storage and processing, and could also lead to the production of new states of matter and associated phenomena in ferroic materials. "It has long been thought that rotating topological structures are confined to magnetic systems and aren't possible in ferroelectric materials, but through the creation of artificial superlattices, we have controlled the various energies of a ferrolectric material to promote competition that lead to such new states of matter and polarization arrangements," says Ramamoorthy Ramesh, Berkeley Lab's Associate Laboratory Director for Energy Technologies and the co-principal investigator for this study. He also holds UC Berkeley's Purnendu Chatterjee Endowed Chair in Energy Technologies. "Ferroelectric materials such as the materials used in this work have produced a number of exciting emergent properties over the years, but these smoothly-rotating polar vortex structures really are different," says Lane Martin, a faculty scientist with Berkeley Lab's Materials Sciences Division and Associate Professor in UC Berkeley's Department of Materials Science and Engineering, who is this study's co-principal investigator. "I think if you surveyed the community many would shake their heads in disbelief at such structures, but it turns out there really is a tendency for vortex states to form in nature even in these polar systems. And, when one looks more broadly, vortex structures can occur across huge length scales - from galaxies and weather systems all the way down to 10s of atoms as in our case." Ramesh and Martin are the corresponding authors of a Nature paper describing this study in detail. The paper is titled "Observation of Polar Vortices in Oxide Superlattices." The lead researchers on this work are Ajay Yadav, Christopher Nelson, and Anoop Damodaran who also hold joint appointments with Berkeley Lab and UC Berkeley. (Full list of authors below.) Ferroic materials display unique electrical or magnetic properties - or both in the case of multiferroics. For example, the electrical field of a ferroelectric material can be polarized in favor of either a positive or negative charge with the application of an external electrical field. In a ferromagnetic material, the application of an external magnetic field aligns the spin of their charged particles, resulting in the material becoming a permanent magnet. In recent years, it was discovered that the application of an external magnetic field can also produce atom-sized cyclones of skyrmions, which act like baryon particles and can be moved coherently over macroscopic distances. These properties make skyrmions excellent candidates for spintronic applications. "We believe the polar vortices we observed in ferroelectrics, when fully explored, have the potential to be topological states of matter that are similar to magnetic skyrmions," Ramesh says. "The fact that our polar vortices can display emergent behavior in their electronic, optical, magnetic and other properties suggests that heretofore unexplored applications and functionalities could be possible." Ramesh, Martin and their collaborators worked with what has become a canonical system in the community, ultrafine layered structures built from lead titanate and strontium titante compounds controlled down to a few unit cells each, in which each unit cell is approximately 0.4 nanometers thick. They created superlattices that harbored a three-way competition between elastic, electrostatic and gradient energies within the layers of lead titanate and strontium titanate. This unique three-way competition gives rise to the polar vortices. "As we tune the period lengths of our superlattices, we can tune the relative importance of these three energy scales," Martin says. "Although rather exotic things can occur if one changes the superlattice period to be both smaller and bigger than we studied here, we really found the 'sweet-spot' in this work that produced these polar vortices which are an entirely new phenomenon." A combination of scanning transmission electron microscopy (STEM) and X-ray diffraction studies were used observe and characterize the polar vortices. The STEM work was carried out at Berkeley Lab's Molecular Foundry, a DOE Office of Science User Facility, on TEAM 0.5, the world's most powerful transmission electron microscope. The X-ray diffraction work was carried out at the Advanced Photon Source, another DOE Office of Science User Facility, which is hosted by DOE's Argonne National Laboratory. "Our study is really indicative of how DOE-funded research programs can bring together a diverse range of expertise, including atomically-controlled materials synthesis and cutting-edge research facilities, and materials theory to enable foundational discoveries that really change the way we think about exotic materials and the possibilities for using them," says Ramesh. "This is just the beginning for the study of polar vortices in ferroelectric materials," Martin says. "We're observing a new state of matter and we have our work cut out for us in mapping and understanding how it evolves. We can imagine adding a magnetic spin component to similar superlattices and thus potentially paving a pathway to fundamentally demonstrate electric-field control of magnetism." ### Other co-authors of the Nature paper were Shang-Lin Hsu, Zijian Hong, James Clarkson, Christian Schlepüetz, Anoop Damodaran, Padraic Shafer, Elke Arenholz, Liv Dedon, Deyang Chen, Ashvin Vishwanath, Andrew Minor, Long-Qing Chen and Jason Scott. This research was primarily funded by the DOE Office of Science. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Home > Press > Revealing the fluctuations of flexible DNA in 3-D: First-of-their-kind images by Berkeley Lab-led research team could aid in use of DNA to build nanoscale devices Abstract: An international team working at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) has captured the first high-resolution 3-D images from individual double-helix DNA segments attached at either end to gold nanoparticles. The images detail the flexible structure of the DNA segments, which appear as nanoscale jump ropes. This video shows techniques that scientists used to produce 3-D reconstructions of shape fluctuations in double-helix DNA segments attached to gold nanoparticles. Credit: Lei Zhang, Dongsheng Lei, Jessica M. Smith, Meng Zhang, Huimin Tong, Xing Zhang, Zhuoyang Lu, Jiankang Liu, A. Paul Alivisatos & Gang "Gary" Ren These views compare the various shape fluctuations obtained from different samples of the same type of double-helix DNA segment (DNA renderings in green, 3-D reconstructions in purple) connected to gold nanoparticles (yellow). Credit: Berkeley Lab This unique imaging capability, pioneered by Berkeley Lab scientists, could aid in the use of DNA segments as building blocks for molecular devices that function as nanoscale drug-delivery systems, markers for biological research, and components for computer memory and electronic devices. It could also lead to images of important disease-relevant proteins that have proven elusive for other imaging techniques, and of the assembly process that forms DNA from separate, individual strands. The shapes of the coiled DNA strands, which were sandwiched between polygon-shaped gold nanoparticles, were reconstructed in 3-D using a cutting-edge electron microscope technique coupled with a protein-staining process and sophisticated software that provided structural details to the scale of about 2 nanometers, or two billionths of a meter. "We had no idea about what the double-strand DNA would look like between the nanogold particles," said Gang "Gary" Ren, a Berkeley Lab scientist who led the research. "This is the first time for directly visualizing an individual double-strand DNA segment in 3-D," he said. The results were published in the March 30 edition of Nature Communications. The method developed by this team, called individual-particle electron tomography (IPET), had earlier captured the 3-D structure of a single protein that plays a key role in human cholesterol metabolism. By grabbing 2-D images of the same object from different angles, the technique allows researchers to assemble a 3-D image of that object. The team has also used the technique to uncover the fluctuation of another well-known flexible protein, human immunoglobulin 1, which plays a role in our immune system. For this latest study of DNA nanostructures, Ren used an electron-beam study technique called cryo-electron microscopy (cryo-EM) to examine frozen DNA-nanogold samples, and used IPET to reconstruct 3-D images from samples stained with heavy metal salts. The team also used molecular simulation tools to test the natural shape variations, called "conformations," in the samples, and compared these simulated shapes with observations. Ren explained that the naturally flexible dynamics of samples, like a man waving his arms, cannot be fully detailed by any method that uses an average of many observations. A popular way to view the nanoscale structural details of delicate biological samples is to form them into crystals and zap them with X-rays, though this does not preserve their natural shape and the DNA-nanogold samples in this study are incredibly challenging to crystallize. Other common research techniques may require a collection of thousands near-identical objects, viewed with an electron microscope, to compile a single, averaged 3-D structure. But this 3-D image may not adequately show the natural shape fluctuations of a given object. The samples in the latest experiment were formed from individual polygon gold nanostructures, measuring about 5 nanometers across, connected to single DNA-segment strands with 84 base pairs. Base pairs are basic chemical building blocks that give DNA its structure. Each individual DNA segment and gold nanoparticle naturally zipped together with a partner to form the double-stranded DNA segment with a gold particle at either end. The samples were flash-frozen to preserve their structure for study with cryo-EM imaging, and the distance between the two gold particles in individual samples varied from 20-30 nanometers based on different shapes observed in the DNA segments. Researchers used a cryo-electron microscope at Berkeley Lab's Molecular Foundry for this study. They collected a series of tilted images of the stained objects, and reconstructed 14 electron-density maps that detailed the structure of individual samples using the IPET technique. They gathered a dozen conformations for the samples and found the DNA shape variations were consistent with those measured in the flash-frozen cryo-EM samples. The shapes were also consistent with samples studied using other electron-based imaging and X-ray scattering methods, and with computer simulations. While the 3-D reconstructions show the basic nanoscale structure of the samples, Ren said that the next step will be to work to improve the resolution to the sub-nanometer scale. "Even in this current state we begin to see 3-D structures at 1- to 2-nanometer resolution," he said. "Through better instrumentation and improved computational algorithms, it would be promising to push the resolution to that visualizing a single DNA helix within an individual protein." The technique, he said, has already excited interest among some prominent pharmaceutical companies and nanotechnology researchers, and his science team already has dozens of related research projects in the pipeline. In future studies, researchers could attempt to improve the imaging resolution for complex structures that incorporate more DNA segments as a sort of "DNA origami," Ren said. Researchers hope to build and better characterize nanoscale molecular devices using DNA segments that can, for example, store and deliver drugs to targeted areas in the body. "DNA is easy to program, synthesize and replicate, so it can be used as a special material to quickly self-assemble into nanostructures and to guide the operation of molecular-scale devices," he said. "Our current study is just a proof of concept for imaging these kinds of molecular devices' structures." ### The Molecular Foundry is a DOE Office of Science User Facility. In addition to Berkeley Lab scientists, other researchers contributing to this study were from UC Berkeley, the Kavli Energy NanoSciences Institute at Berkeley Lab and UC Berkeley, and Xi'an Jiaotong University in China. This work was supported by the National Science Foundation, DOE Office of Basic Energy Sciences, National Institutes of Health, the National Natural Science Foundation of China, Xi'an Jiaotong University in China, and the Ministry of Science and Technology in China. About Berkeley Lab Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov. DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. 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In a breakthrough for energy-efficient computing, UC Berkeley engineers have shown for the first time that magnetic chips can actually operate at the lowest fundamental energy dissipation theoretically possible under the laws of thermodynamics. The findings, published in the peer-reviewed journal Science Advances, mean that dramatic reductions in power consumption are possible — down to as little as one-millionth the amount of energy per operation used by transistors in modern computers. This is critical for mobile devices, which demand powerful processors that can run for a day or more on small, lightweight batteries. On a larger, industrial scale, as computing increasingly moves into “the cloud,” the electricity demands of the giant cloud data centers are multiplying, collectively taking an increasing share of the country’s — and world’s — electrical grid. “We wanted to know how small we could shrink the amount of energy needed for computing,” said senior author Jeffrey Bokor, a UC Berkeley professor of electrical engineering and computer sciences and a faculty scientist at the Lawrence Berkeley National Laboratory. “The biggest challenge in designing computers and, in fact, all our electronics today is reducing their energy consumption.” Lowering energy use is a relatively recent shift in focus in chip manufacturing after decades of emphasis on packing greater numbers of increasingly tiny and faster transistors onto chips. “Making transistors go faster was requiring too much energy,” said Bokor, who is also the deputy director the Center for Energy Efficient Electronics Science, a Science and Technology Center at UC Berkeley funded by the National Science Foundation. “The chips were getting so hot, they’d just melt.” Researchers have been turning to alternatives to conventional transistors, which currently rely upon the movement of electrons to switch between 0s and 1s. Partly because of electrical resistance, it takes a fair amount of energy to ensure that the signal between the two states is clear and reliably distinguishable, and this results in excess heat. Magnetic computing emerged as a promising candidate because the magnetic bits can be differentiated by direction, and it takes just as much energy to get the magnet to point left as it does to point right. “These are two equal energy states, so we don’t throw energy away creating a high and low energy,” said Bokor. Bokor teamed up with UC Berkeley postdoctoral researcher Jeongmin Hong, UC Berkeley graduate student Brian Lambson and Scott Dhuey at the Berkeley Lab’s Molecular Foundry, where the nanomagnets used in the study were fabricated. They experimentally tested and confirmed the Landauer limit, named after IBM Research Lab’s Rolf Landauer, who in 1961 found that in any computer, each single bit operation must expend an absolute minimum amount of energy. Landauer’s discovery is based on the second law of thermodynamics, which states that, as any physical system is transformed, going from a state of higher concentration to lower concentration, it gets increasingly disordered. That loss of order is called entropy, and it comes off as waste heat. Landauer developed a formula to calculate this lowest limit of energy required for a computer operation. The result depends on the temperature of the computer; at room temperature, the limit amounts to about 3 zeptojoules, or one-hundredth the energy given up by a single atom when it emits one photon of light. The UC Berkeley team used an innovative technique to measure the tiny amount of energy dissipation that resulted when they flipped a nanomagnetic bit. The researchers used a laser probe to carefully follow the direction that the magnet was pointing as an external magnetic field was used to rotate the magnet from “up” to “down” or vice versa. They determined that it only took 15 millielectron volts of energy — the equivalent of 3 zeptojoules — to flip a magnetic bit at room temperature, effectively demonstrating the Landauer limit. This is the first time that a practical memory bit could be manipulated and observed under conditions that would allow the Landauer limit to be reached, the authors said. Bokor and his team published a paper in 2011 that said this could theoretically be done, but it had not been demonstrated until now. While this paper is a proof of principle, he noted that putting such chips into practical production will take more time. But the authors noted in the paper that “the significance of this result is that today’s computers are far from the fundamental limit and that future dramatic reductions in power consumption are possible.” The National Science Foundation and the U.S. Department of Energy supported this research.